JPH0454586B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in ink recording heads that utilize electroosmotic phenomena.

This type of ink recording head has already been proposed by one of the inventors of the present invention.

The basis of this is that it has an array of grooves extending to one edge of a dielectric support substrate, and a liquid ink permeable electrode is passed through a porous material onto the dielectric support substrate in which recording electrodes are installed in the grooves. A recording voltage is applied between the recording electrode and the liquid ink permeable electrode, and the liquid ink is pumped and sucked into the groove by electroosmosis of the liquid ink into the porous body due to this voltage. The ink recording head has an exposed part in which the liquid ink to be recorded is controlled by the pressure feeding and suction and selectively adheres to a recording medium such as paper according to an image signal, the exposed part is provided on one edge of the dielectric support substrate. This type of recording head has the advantage that good ink recording can be performed by bringing a recording medium such as paper into contact with the one edge and transferring the ink.

However, since the liquid ink to be transferred moves within the groove of the exposed part by pressure feeding and suction from the ink modulating part, unless the length of movement is shortened, the ink will be damaged by the viscous resistance of the liquid ink. It has been found that it becomes difficult to control the movement up to the one edge side groove opening, which directly contributes to printing, which causes a decrease in recording speed, recording density, etc.

The present invention is intended to remedy this problem and to enable multiplex operation by electrically controlling the movement of liquid ink within the grooves of the exposed portion.

To explain the present invention more specifically, in the ink recording head, at least the inner surface of the groove in the exposed portion is configured to be electroosmotic to the liquid ink, and the tip of the recording electrode is formed at the one edge. an edge of the dielectric support substrate where the inner surface of the groove on the one edge side or the groove opening on the one edge side is located, which An auxiliary electrode is installed on at least one of the end faces, and a voltage is applied between the recording electrode and the auxiliary electrode to electroosmotically control the liquid ink in the groove through the inner surface of the groove. It is.

An embodiment of the present invention will be described in detail below.

FIG. 1 is a diagram showing a perspective partial structure and power supply system of an ink recording head according to the present invention. In the figure, 1 is a plate-shaped dielectric support substrate made of a plastic plate such as cellulose acetate or polyimide phenolic resin, a glass plate, or a porcelain plate such as alumina; 2
is made of plastic materials such as cellulose acetate and cellulose nitrate, glass materials, and porcelain materials such as alumina, etc., and has pores with an average diameter of about 0.1 to 10 μm that penetrate continuously in the thickness direction with the same average gap. A film-like or plate-like porous body with a thickness of about 20 to 200 μm is provided, and 3 is an electrode through which oil-based or water-based liquid ink 4 supplied from the outside passes.
For example, in a phosphor bronze plate or stainless steel plate with a thickness of about 20 to 200 μm, the through holes 3a have a density of about 100 to 400 meshes (i.e., 100 to 400 meshes).
to form a mesh electrode. 5 is for example
Cr or Ni-Cr alloy is deposited thinly to a thickness of about 0.1 to 0.3 μm, and then Au, etc. is deposited on top of it to a thickness of about 1 to 3 μm.
This is a recording electrode.

This recording electrode 5 is formed by photo-etching, cutting, or molding on a dielectric support substrate in order to form a gap between the electrode surface 5' and the porous body surface 2' through which the liquid ink 4 can move. 1 provided on the surface 1', for example, with a depth of 10 to 50 μm and a width αp (however,
α<1) in the groove 6.

For example, p is 125~250μm (i.e. 8 lines/mm~
4 pieces/mm), and α is selected to be around 0.2 to 0.8.

One edge 2'' of the porous body 2 is positioned about 50 to 1000 μm inside the edge 1'' of the dielectric support substrate 1 to form an exposed portion 7.

One edge 3' of the liquid ink permeable electrode 3 is located approximately 50 to 100 μm inside the edge 2'' of the porous body 2 in order to prevent dielectric breakdown.

On the other edge 2 side of the porous body 2, the surface of the porous body is sealed to the surface of the recording electrode 5 in the groove 6 by a sealant 8 to prevent the liquid ink 4 from flowing out. The other parts of the dielectric support substrate 1 except for the groove 6 are
The surface of the porous body is adhered to the surface 1' using a sealing agent 8'.

The area from the sealing agent 8 to the edge 2'' of the porous body 2 constitutes the ink modulating section 9, and its length L is selected to be, for example, about 2 cm to 10 cm.

External liquid ink 4 to recording head 100
The ink container 10 is supplied as illustrated in the figure.
It is supplied to the porous body 2 via the electrode 3 and impregnated therein by capillary action of the sponge body 11 .

The recording electrode tip 5'' may be located within the ink modulation section 9, but preferably, as illustrated in the figure, the recording electrode tip 5'' is located 50 to 200 μm closer to the exposed portion 7 side than the porous body edge 2''.
Configure it so that it shows the degree.

The recording electrodes 5 are divided into groups of even numbers, in this case four electrodes, as e _a1 ... e _a4 , e _b1 ... e _b4 , and are arranged in groups according to the arrangement order within the group, e.g. e _a1 and e _b1 , e _a2 and e _b2 . . . are connected in parallel, and connected to the recording signal voltage source 20, to which the recording voltage V _S and off voltage V _pff are selectively applied.

As shown in FIG. 2, on the edge surface 1a of the dielectric support substrate 1, corresponding to the recording electrodes e _a1 ... e _a4 , e _b1 ... e _b4 , there are located at least the opening ends 6' of the grooves 6. Mutually insulated auxiliary electrodes e _A , e _B . This auxiliary electrode
e _A , e _B ... are recording electrodes e _a1 ... via the groove inner surface 6a.
…e _a4 , e _b1 …e _b4 are formed so as to face the electrode tips 5″, and between them, an auxiliary voltage V _t is applied via switches S _a , S _b ……, respectively. Ru.

The electrodes e _A , e _B . . . are provided extending to the back surface of the substrate 1, as shown in e _c in the figure, and are connected to the switches S _a , S _{b .} . . on the back surface side.

Furthermore, in order to prevent wear damage to the electrodes e _A , e _B , . . . , etc., it is preferable to sputter deposit a wear-resistant material such as SiC to cover these electrodes e _A , e _B and the edge 1a.

Ink adhesion record 12 on recording medium 30 such as paper
For example, the recording medium 30 is brought into light contact with the edge 1'' of the dielectric support substrate using a rubber roller 31,
This is done by moving the recording medium 30 in the direction of the arrow 32 in the figure.

The ink recording head 100 is driven by applying a constant amplitude voltage V _pff to the liquid ink permeable electrode 3 and the odd-numbered and even-numbered recording electrodes 5 alternately, as shown in the figure.
(However, amplitude |V _pff |≧O) and a recording voltage V _S modulated by an input signal for ink recording are added, and these are alternately switched to record one line divided into two.
The recording medium 30 is intermittently fed in the direction of the arrow 32 in synchronization with this recording.

The liquid ink 4 can be formed by dissolving ionic dyes, direct dyes, etc. in an aqueous solvent such as water or alcohol, or by dissolving an ionic dye or direct dye in an aqueous solvent such as water or alcohol, or a non-aqueous or oil-based solvent such as xylene or γ-methacryloxypropyltrimethoxysilane. An oil-based ink is formed by dissolving oil-soluble dyes, etc. in
The porous body 2 is configured to have electroosmotic properties by dissolving a surfactant, a charge control agent, and a vehicle material.

These inks 4 preferably have a resistivity of 10 ³ Ωcm or more, a viscosity of 10 cp or less, and a surface tension of 15
It has a value of ~40dyne/cm.

From the viewpoint of dielectric strength, it is preferable to use an oil-based ink with a specific resistance of 10 ⁷ Ωcm or more.

The electroosmotic polarity of the liquid ink 4 is determined by the porous body 2,
Depending on the material relationship with the dielectric support substrate 1, either the negative potential direction or the positive potential direction can be selected.

There is Kane's law regarding electroosmotic polarity.
When the dielectric constants of the solid material and the liquid material are larger than the latter, the liquid material electroosmoses in the positive potential direction, and when the former is smaller than the latter, the liquid material electroosmoses in the negative potential direction. electroosmotic.

In the figure, a case is illustrated in which the liquid ink 4 electroosmoses in the negative potential direction.

Such electroosmosis is achieved by, for example, forming the liquid ink 4 by dissolving 2 to 5 percent by weight of an azo dye as a coloring material in a non-aqueous (oil-based) solvent consisting of γ-methacryloxypropyltrimethoxysilane. The body 2 is made of cellulose acetate, and the dielectric support substrate 1 is made of soda lime glass or borosilicate glass.

The recording voltage V _S is selected to have such a polarity that it is osmotic and pressure-transferred from the electrode 3 side through the porous body 2 to the recording electrode 5' side by electroosmosis in the thickness direction of the porous body 2 as indicated by the circle mark 14 in the figure. In this example, a negative voltage is applied to V _S .

The off-voltage V _pff is determined by electroosmosis in the thickness direction of the porous body 2, which causes the liquid ink 4 on the recording electrode surface 5' to pass through the porous body 2, as shown by circle mark 13 in the figure. The polarity is selected so that it is sucked up to the electrode 3 side, and in this example, a positive voltage is applied to V _pff .

The amplitude of the recording voltage V _S |V _S | has a value in the range of O to |V _po | (however, |V _po | > 1V _pff ), the polarity of V _S is opposite to V _pff , and the polarity of V _S is superimposed on V _pff , so V _S has a value in the range from V _pff to V _po .

In the figure, the off-voltage V _pff , that is, the recording voltage
V _S = V _pff applied e _a1 , e _b1 , e _a2 , e _b2 , e _a4 ,
e At the part _b4 , the recording electrode tip 5'' and the groove inner surface 6 of the exposed part 7 are
The liquid ink 4 located at point a travels along the recording electrode surface 5' in the groove 6 as shown by the solid arrow 15 and is sucked up to the electrode 3 side via the porous body 2 forming the ink modulation section 9, so that the recording medium No ink deposits 12 can occur on 30.

However, when a negative voltage of V _S = V _po was applied,
In the areas of the recording electrode 5 such as e _a3 and e _b3 , recording in the groove 6 is performed as indicated by the solid arrow 16, contrary to the above, by osmotic pressure feeding as indicated by the ○× mark 14 according to the voltage amplitude or pulse width. The ink 4 is transmitted along the electrode surface 5', exceeds the recording electrode tip 5'', and is supplied to the groove opening end 6', forming a controlled liquid ink portion 4'.
Ink deposits 12 may occur on the recording medium 10.

In this case, as described above, the dielectric support substrate 1 for the liquid ink 4, and thus the recording electrode gap surface 1b at least in the exposed portion 7 of the substrate surface 1'.
When the electroosmotic polarity of the porous body 2 is selected to be the same as that of the porous body 2, that is, in the negative potential direction in this example, the liquid ink pumped as shown by the arrow 16 corresponds to the potential difference V _S −V _pff in the exposed portion 7. electrode gap surface 1b
Because the ink is focused in the groove 6 due to the ink focusing action based on surface direction electroosmosis as shown by the arrow 18,
Dotted ink adhesion 12 corresponding to the cross-sectional shape of the groove 6
can be obtained.

Such an ink focusing effect is extremely effective for high-resolution ink recording, and for this purpose, it is necessary to position the recording electrode tip 5'' so as to protrude toward the exposed portion 7 side, as in this embodiment. .

Thus, under the above operating conditions, a positive voltage V _t =V _p is applied to the auxiliary electrode e _A as the auxiliary voltage V _t by turning the switch S _a to the terminal b side. In this state, the recording electrode tip 5'' has a potential difference V _po − with respect to the auxiliary electrode e _a
A negative potential is formed by V _p .

As described above, the liquid ink 4 is electroosmotic into the inner surface of the groove 6a in the negative potential direction similarly to the porous body 2. Therefore, in the groove inner surface 6a of the electrode e _a3 , the dotted line arrow 15a
Because of the electroosmosis of liquid ink 4,
The ink is pumped by electroosmosis as shown by the solid arrow 16 corresponding to V _S = V _po from the auxiliary electrode e _A side to the recording electrode.
e It is pushed back to the tip 5″ side of _a3 . Therefore, V _S
= Even if a recording voltage of V _po is applied, the potential difference
As long as V _po -V _t is negative, the liquid ink 4 located on the opening end 6' side decreases due to the deceleration and push-back effect based on reverse electroosmosis on the groove inner surface 6a, and the concentration of the ink deposit 12 decreases. If V _t =V _p as in this example, the ink adhesion 12 is prevented by strong reverse electroosmosis 15a.

On the other hand, switch S _b is turned to the a terminal side, and a negative voltage V _t is applied to the auxiliary electrode _{e B such} that its amplitude |V _o | is |V _o |>|V _po | , V _t −V _po is negative, that is, the opening end 6' forms a negative potential with respect to the electrode tip 5''.Therefore, the electroosmosis of the groove inner surface 6a is as shown by the dotted arrow 16a.
Since it is in the forward direction of the ink pressure feeding 16, the liquid ink 4 by the ink pressure feeding 16 is electrically accelerated on the groove inner surface 6a, contrary to the case of e _a3 described above.

Due to the acceleration based on this forward electroosmosis 16a, even if the length M of the exposed portion 7 is large, ink deposition 12 can be obtained efficiently and at high speed, unlike conventional ink recording heads. .

Therefore, according to the above-mentioned selection of the auxiliary voltage V _t by the switches S _a and S _b , the applied recording voltage V _S = limited to the recording electrode groups e _b1 , e _b2 , e _b3 , e _b4 Since ink recording 12 can be performed in correspondence with V _po , groups e _b1 ... e _b4 are connected to terminals T ₁ , T ₂ , T ₂ , T ₄
For recording, odd numbered electrodes e _b1 , e _b3 and even numbered electrodes e _b2 ,
After alternately switching off voltage V _pff and recording voltage V _S to e _{and b4} to perform two-split ink recording, next
Add signal voltage for group e _a1 ... e _a4 recording to T ₁ ... T ₄ , and connect S _b to terminal b and S _a to terminal a.
By switching V _{t and} sequentially switching switches S _a and S _b to perform ink recording at e _a1 , e _a2 , e _a3 , and e _a4 , line-sequential ink recording can be performed in a time-sharing manner by so-called multiplexing. .

In this case, as shown in the figure, each group of recording electrodes 5
If the number of electrodes is selected as an even number, the off-voltage V _pff is always applied to the recording electrodes 5 on both sides even between groups, and there is an advantage that ink focusing by the surface direction electroosmosis 18 can be utilized.

The electrode spacing between the electrode tip 5″ and the auxiliary electrodes e _A and e _B ,
In this example, the length of the groove inner surface 6a is the length M of the exposed portion 7,
Considering the position of the recording electrode tip 5″, for example, 50~
Select within the range of about 800μm.

When an oil-based ink with a specific resistance of 10 ⁷ Ωcm or more is used as the liquid ink 4, each voltage such as V _pff , V _po , V _t etc. has a maximum electric field strength of 2×
It can be selected as appropriate within the range of about 10 ⁴ V/cm.

In addition, in the figure, the recording electrodes 5 are divided into groups,
We have explained the multiplex operation in which the auxiliary electrodes are divided into e _A and e _B , but when recording simply in the bisecting line sequence without performing multiplex operation, the auxiliary electrodes are provided continuously without being divided. Reverse electroosmosis 1 by changing the amplitude and polarity of V _t
It can be used for fine adjustment of the ink recording density by the method 5a, and for improving the recording speed and recording density by the forward electroosmosis 16a.

Note that when the electroosmotic polarity of the liquid ink 4 with respect to the porous body 2, dielectric support substrate 1, and groove inner surface 6a is in the positive voltage direction, the polarities of V _pff , V _S , V _po , and V _t are different from those described above. You can choose the opposite and do the same thing.

As explained above, when the porous body 2 and the groove inner surface 6a have the same electroosmotic polarity with respect to the liquid ink 4, in the recording electrode 5 where V _S =V _pff is applied, the forward direction due to the auxiliary voltage V _t When the effect of the electroosmosis 16a is extremely large, the porous body 2 directly
Liquid ink 4 may electroosmote to the auxiliary electrode side, causing ink adhesion 12.

This improvement includes the groove inner surface 6 for the liquid ink 4.
This can be improved by selecting the electroosmotic polarity of a to be opposite to the electroosmotic polarity of the porous body 2. That is, as shown in the figure, a material that electro-osmoses the liquid ink 4 in a positive potential direction may be deposited on the groove inner surface 6a by vapor deposition, sputter deposition, or coating. For these materials, for example, a material having a higher dielectric constant than the liquid ink 4, such as a ferroelectric material such as PbTiO ₃ or PLZT, is sputter-deposited.

In this case, for example, if the auxiliary voltage V _t is zero volts, the auxiliary electrodes e _A and e _B are at a positive potential with respect to the recording electrode 5 for V _S = V _po , and the auxiliary electrodes e A and e B are at a positive potential with respect to the recording electrode 5. A forward electroosmosis 16a is obtained in which the liquid ink 4 electroosmoses the inner surface 6a of the groove.

However, for V _S =V _pff , the electrode tip 5'' side is at a positive potential, resulting in reverse electroosmosis 15a, and no ink adhesion 12 can occur.

In addition, in this case, when the polarity of the surface electroosmosis 18 on the electrode gap surface 1b is selected to be the same as the electroosmosis polarity of the porous body 2, as in _FIG . Ink focusing effects related to voltages of _S −V _pff can also be used. Therefore, high resolution, multiplex operation, high-speed recording, and electrical control of ink recording characteristics can be realized.

Thus, in the ink recording head 100 of the present invention, the relationship between the recording voltage V _S =V _po and the auxiliary voltage V _t can be generalized as follows.

The off-voltage V _pff is a voltage with a constant amplitude or pulse width, and is a voltage with a constant amplitude or pulse width.
The polarity voltage at which 3 and 15 are applied, the recording voltage V _po , is
Ink pressure feeding 1 with opposite polarity to V _pff superimposed on V _pff
4, 16 is a voltage modulated in at least one of the amplitude and pulse width, and the auxiliary voltage V _t has a polarity,
It is a voltage whose amplitude can be adjusted or switched as necessary.

Porous body 2, liquid ink 4 on groove inner surface 6a
When the electroosmotic polarities of are the same, with respect to V _po
When V _t has the same polarity and |V _t |>|V _po |, the liquid ink 4 on the inner surface of the groove 6a exhibits forward electroosmosis 16a, assisting the ink pressure feeding 16, and making the ink adhesion 12 more effective. can be done. V _po and V _t have the same polarity and O
|V _t |<|V _po |, and when V _po and V _f have opposite polarities,
Reverse electroosmosis 15a is shown, reducing ink adhesion 12 due to ink pressure feeding 16 and finally reducing ink adhesion 12.
to prevent

Porous body 2, liquid ink 4 on groove inner surface 6a
If the electroosmotic polarities of V _po and
When V _t has the same polarity, O | V _t | < | V _po , and
Obtained when V _po and V _t have opposite polarities.

The reduction and even prevention of ink adhesion 12 by ink pumping 16 by reverse electroosmosis 15a
It is obtained when V _po and V _t have the same polarity and |V _t |>|V _po |.

The ink convergence 18 at the exposed portion 7 is caused by the porous body 2;
A state in which the electroosmotic polarity of the liquid ink 4 with respect to the electrode gap surface 1b is the same and the off-voltage V _pff is applied to the adjacent recording electrode 5, that is, the recording electrode 5
It can be formed with V _pff applied to every other wire. There is no electrical effect at V _t = V _po .

Therefore, by combining the above-mentioned general conditions, it is possible to control and improve the ink recording characteristics in bipartite line sequential recording using the auxiliary voltage V _t , or to prevent or assist ink adhesion using V _t during multiplexing. A split ink recording is achieved.

Note that the installation positions of the auxiliary electrodes _eA , _eB, etc. are not limited to the example shown in the figure;
It may also be provided so that it enters from the side. Auxiliary electrode
The installation requirements for e _A , e _B, etc. are at least the bottom surface of the groove inner surface 6a facing the electrode tip 5'' and the edge where this bottom and the edge surface 1a intersect (the edge surface 1
If the ink focusing 18 is to be used, it is not preferable to be located on the electrode gap surface 1b.

However, if the electrode gap surface 1b is configured to be non-electroosmotic or ink repellent, the surface 1b and the groove inner surface 6 may include the edge 1'' or be apart from the edge 1''.
A continuous bag-shaped auxiliary electrode can be provided over the length a. This configuration has the effect of facilitating the feeding of the auxiliary voltage V _t when the auxiliary electrode is configured in a non-divided manner without multiplex operation.

As described above, the present invention is an ink recording head in which an auxiliary electrode is installed opposite the tip of the recording electrode, and by controlling the potential of the auxiliary electrode, multiplex operation and legendary control of ink recording characteristics can be achieved. The ink recording characteristics can be improved by assisting ink movement on the open surface by ink pressure feeding, and the effect is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an ink recording apparatus having an ink recording head according to an embodiment of the present invention, and FIG. 2 is a partially enlarged perspective view of the image end portion of a dielectric support substrate of the same ink recording apparatus. 1... Dielectric support substrate, 2... Porous body, 3...
...Liquid ink permeable electrode, 4...Liquid ink, 5
... Recording electrode, 6 ... Groove, 7 ... Exposed part, 8 ...
Sealing agent, 9... Ink modulation section, 12... Adhesive ink, 20... Recording signal voltage source, 30... Recording medium, 31... Pressure roller, 100... Ink recording head, e _A , e _B ... ...Auxiliary electrode, V _S , V _po , V _pff ,
V _c , V _p , _Vo ... voltage.

Claims (1)

[Scope of Claims] 1. A dielectric support substrate having an array of grooves extending to one edge of the dielectric support substrate, in which a recording electrode is installed, and liquid ink is applied to the dielectric support substrate through a porous material. installing a transparent electrode, applying a recording voltage between the recording electrode and the liquid ink permeable electrode, and force-feeding the liquid ink in the groove by electroosmosis of the liquid ink into the porous body by this voltage; In an ink recording head having an ink modulating part for suction, and an exposed part on the one edge side where the liquid ink part to be recorded is controlled by the pressure feeding and suction, at least the inner surface of the groove in the exposed part is The liquid ink is electroosmotic to the liquid ink, and one or more auxiliary electrodes are installed on one edge side surface of the dielectric support substrate opposite to the recording electrode tip. By applying an image signal voltage of a polarity that generates an electric field in a direction corresponding to the polarity of electroosmosis between the transparent electrode and the recording electrode, the liquid ink is modulated and moved in a desired direction, and the tip of the recording electrode is An ink recording head characterized in that ejection of liquid ink is controlled in accordance with the polarity of electroosmosis between the auxiliary electrode and the auxiliary electrode. 2. The recording electrodes are grouped into even-numbered units, and the recording electrodes of each group are connected in parallel according to the order within the group, and the liquid ink-permeable electrodes are alternately connected to the odd-numbered and even-numbered recording electrodes. 2. The ink recording head according to claim 1, wherein application start times of the selection signals that are sequentially applied to each of the plurality of auxiliary electrodes at the same time as the image signals are applied are different.