JPH0572876B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an image forming method for forming an image on a recording member by jetting ink.

"Prior Art" Various types of output devices have been developed for the purpose of outputting image signals processed by computers, word processors, etc.

Among these, those that directly form an image on a recording member such as recording paper have the following reasons: the recording device itself can be made smaller, and it is inexpensive.
It is considered to be optimal as an output device for small computers that have become widespread in recent years.

As such output devices, wire dot type and ink jet type are well known.

In the wire dot method, an ink ribbon coated with pressure-sensitive wax and recording paper are layered together.
The ink is transferred by hitting it with a metal wire and recording is performed.

In the inkjet method, recording is performed by storing ink in a sealed container, applying a pressure pulse to the container, and ejecting the ink from an orifice in the container.

"Problems to be Solved by the Invention" While all of these methods are effective in achieving miniaturization, they have the following problems.

First, the wire dot method generates noise because the wire hits the ink ribbon. Furthermore, in order to maintain its mechanical strength, the wire diameter cannot be reduced beyond a certain level. Therefore, it has been difficult to increase the image density (the number of pixels per unit area), and it has been difficult to achieve high resolution.

On the other hand, in the inkjet method, the ink ejection mechanism cannot be made smaller due to its operating mechanism. Therefore,
In order to perform printing with the required image density, it was necessary to mechanically scan the ink ejection device. Therefore,
This resulted in a slowdown in recording speed. In addition, due to insoluble substances contained in the ink and solidification of the ink itself,
Another disadvantage was that the ink discharge ports were easily clogged.

The present invention has been made focusing on the above points,
It is an object of the present invention to provide an image forming method that can directly record an image at high image density on a recording member and does not cause problems such as ink clogging.

"Means for Solving the Problems" The image forming method of the present invention involves forming a conductive hot-melt ink layer on an insulating support, and disposing a recording electrode composed of a plurality of unit electrodes on the upper surface of the conductive heat-melting ink layer. Further, a counter electrode is disposed on the same surface, facing the recording electrode at a predetermined distance, and electrically contacting the heat-melting ink layer, and sandwiching the recording electrode and the counter electrode. , a recording member is arranged to face the heat-melting ink layer, and a voltage is selectively applied between each of the unit electrodes and the counter electrode in correspondence with the image signal to be recorded, The method is characterized in that the ink of the ink layer is ejected toward the recording medium to record an image on the recording medium.

Here, the unit electrode is divided into mutually electrically independent electrode groups connected by a common wire, and the conductive support facing each electrode group is similarly electrically divided, and each of the electrodes is divided into electrically independent electrode groups. It is preferable to record an image by applying a voltage to each unit electrode constituting the group at different timings.

"Operation" As described above, in the present invention, the ink in the heat-melting ink layer is caused to fly by applying a voltage between the unit electrode and the counter electrode. Since this ink is conductive, this voltage will be applied between the ink that is in electrical contact with the counter electrode and the unit electrode placed on its upper surface. As a result, spark discharge occurs between this ink and the unit electrode.

In this way, this ink is locally melted, flies toward the recording member, and adheres to the surface of the recording member in the form of dots. This dot becomes one recording pixel.

The unit electrodes are arranged in parallel in a row so that each electrode records one pixel. By selectively applying a voltage to these unit electrodes according to the image signal and simultaneously sub-scanning the recording member in a direction perpendicular to the row of unit electrodes, an image can be recorded thereon.

Here, if the unit electrode is divided into a predetermined number of electrode groups and the timing of applying voltage to each unit electrode making up the electrode group is shifted from each other, so-called time division driving is performed, the power supply can be made smaller. be able to.

"Embodiment" (Outline of Recording Apparatus) FIG. 1 is a schematic configuration diagram of a recording apparatus suitable for implementing the present invention.

This device has a heat-melting ink layer 2 on a support 1.
A recording electrode 5 in which a plurality of unit electrodes 3 are arranged in an insulating spacer 4 is disposed above the recording electrode 5, and a recording member 6 is further disposed in an overlapping manner above the recording electrode 5.

Further, a counter electrode 10 is provided to face the recording electrode 5 at a predetermined interval.
is attached to and supported by the lower surface of the end of the insulating spacer 15.

This counter electrode 10 is placed in contact with the upper surface of the heat-fusible ink layer 2 and sandwiched between the heat-fusible ink layer 2 and the recording member 6 together with the insulating spacer 15 .

The support 1 is biased by a spring or the like (not shown) in the direction toward the recording electrode 5, and presses the outer surface of the conductive heat-melting ink layer 2 against the recording electrode 5.

Further, a conveying roll 7 is provided on the back side of the recording member 6, and is configured to press the recording member 6 toward the recording electrode 5 by a spring or the like (not shown). This conveyance roll 7 rotates in the direction of arrow 8 to convey the recording member 6 and performs sub-scanning thereof.

At the same time, the support 1 is also driven to rotate in the direction of arrow 9.

On the other hand, a smoothing roll 11 is disposed so as to be in circumscribed contact with the outer surface of the heat-melting ink layer 2 . This smoothing roll 11 is brought into pressure contact with the heat-fusible ink layer 2 by a spring or the like (not shown) and rotates in the direction of arrow 12. Further, a heating means (not shown) is configured to heat the smooth roll 11 to a predetermined temperature.

A resistor 13 and a first recording power source 14 that applies a pulse of negative polarity are connected in series to the counter electrode 10 .

Further, each unit electrode 3 constituting the recording electrode 5 is also connected in series with a resistor 16 and a second recording power source 17 that applies a pulse of positive polarity.

The heat-melting ink layer 2 is solid at room temperature, with carbon black, colored pigments, colored dyes, etc. dispersed in a binder such as wax or resin that dissolves and decomposes at relatively low temperatures. This ink layer 2 was prepared by adjusting the amount of carbon black,
Provided with a certain level of conductivity.

In order to explain the structure of the recording electrode, FIG. 2 shows a perspective view of the main parts of the apparatus shown in FIG. 1.

As shown in this figure, the recording electrode 5 has a structure in which a large number of needle-shaped conductors 3 (in the present invention, these are called unit electrodes) are embedded in parallel in an insulating spacer 4.

The tip of each unit electrode 3 is exposed at the end surface 41 of the spacer 4. Further, at the rear end of the unit electrode 3, the resistor 16 and the second recording power source 1 are connected.
7 are connected to each other.

On the other hand, the end surfaces of the insulating spacer 15 face each other at a predetermined distance G in parallel with the end surface 41 of the insulating spacer, and the counter electrode 10 is attached to the lower surface thereof. This distance G is between the unit electrode 3 and the counter electrode 10.
The length is selected to be long enough so that when a recording voltage is applied, an air discharge does not occur directly between the two.

(Recording Operation) The apparatus having the above configuration records an image as follows.

First, it is assumed that a pulsed voltage is simultaneously applied between the unit electrode 31 and the counter electrode 10 in FIG. 2 by the first recording power source 14 and the second recording power source 17, for example.

At this time, since the heat-fusible ink layer 2 has a certain conductivity, this pulsed voltage eventually becomes
The voltage is applied between the end face 32 of the unit electrode 3 and the heat-melting ink layer 2 directly below it. This interval is a constant, sufficiently short distance set by the thickness of the insulating spacer 4.

In this way, the heat-melting ink layer 2 and the unit electrode 3 are connected to each other through the path shown by the dashed arrow 33 in FIG.
A discharge current flows between the A part of the heat-melting ink layer 2 is melted and softened by this discharge energy,
Vaporize. The ink flies toward the surface of the recording member 6.

In this way, dots are recorded on the recording member 6.

Since the dots attached to the recording member 6 are made of wax, resin, etc. in which carbon black, pigment, dye, etc. are dispersed, their adhesion is strong and does not require any post-treatment such as pressurization and heating.

(Role of Spacer) In the above embodiment, the distance between the unit electrode 3 and the outer surface of the heat-fusible ink layer 2 has a large effect on the discharge starting voltage. That is, if this interval fluctuates randomly, the discharge that occurs during that interval will become unstable. Therefore, the heat-fusible ink layer 2 is always pressed against the spacer 4, and this distance is stably maintained.

Also, since ink gradually spreads while flying,
It is also necessary to keep the distance between the outer surface of the heat-fusible ink layer 2 and the recording member 6 constant, so that the size of the recorded dots is constant.

Furthermore, if ink enters the gap between the recording member 6 and the recording electrode 5, the shape of the recorded dots will be distorted.

Therefore, as shown in FIG. 1, the conveyance roll 7 is configured to press the recording member 6 against the spacer 4.

(Role of the smooth roll) When a voltage is applied between the unit electrode 3 and the counter electrode 10 and the ink near the surface of the heat-fusible ink layer 2 flies, unevenness occurs in that part.

The heat-melting ink layer 2 rotates together with the support 1 in the direction of arrow 9 in FIG. 1 in synchronization with the sub-scanning of the recording member 6. A smoothing roll 11 is provided to make the uneven portion smooth again.

This smoothing roll 11 can also smooth the surface of the heat-melting ink layer 2 only by its pressing force. However, if the smoothing roll 11 is heated, the smoothing process becomes easier.

This makes it possible to record dots stably for a long period of time.

(Application of recording voltage) In order to perform the above recording, the counter electrode 10
It is preferable to apply the following voltages between the unit electrode 3 and the unit electrode 3, respectively.

Note that in this embodiment, the recording electrode 5 has a thickness of
A unit electrode 3 made of nickel with a diameter of 50 μm is placed in an insulating spacer made of a 50 μm polyester film.
were buried in parallel at a density of 8 pieces per 1 mm.

In addition, as the heat-melting ink layer 2, the melting temperature is 80
A mixture of carbon black and wax at a temperature of °C was used so that its volume resistivity was 10 ³ Ω·cm.

In FIG. 3, the voltage applied to the unit electrode 3 is shown above, and the voltage applied to the counter electrode 10 is shown below.

In other words, +400V, 100μsec is applied to unit electrode 3.
A pulsed voltage of -1.6 KV and 100 μsec is applied to the counter electrode 10 at the same timing.

Distance G between unit electrode 3 and counter electrode 10 (Fig. 2)
When such a voltage was applied while setting the voltage to 100 μm to 1 mm, a good discharge occurred and dots with high density were recorded on the recording member 6.

Note that when this interval was set to 500 μm, stable discharge could be performed even when the volume resistivity of the heat-fusible ink layer 2 was increased to a high resistance of 10 ⁸ Ω·cm.

Note that here, it is also possible to set the voltage applied to the counter electrode 10 to be a constant negative voltage, that is, a DC voltage. This voltage is a voltage that does not start a discharge between the heat-fusible ink layer 2 and the unit electrode 3 as it is, and only when a pulsed voltage is applied to the unit electrode 3 does it reach a voltage that causes a discharge. Select.

Usually, a driver element made of a semiconductor is connected to each unit electrode 3, and the driver element is turned on and off in response to an image signal to be recorded, and a pulsed voltage is applied. In order to reduce the burden on the driver element, it is preferable to make this pulsed voltage sufficiently low.

Therefore, in the above embodiment, a relatively low pulsed voltage is applied to the unit electrode 3.

On the other hand, a relatively high voltage is applied to the counter electrode 10, and a pulsed voltage is applied at a constant cycle regardless of the image signal. As described above, this voltage is applied in synchronization with the pulsed voltage applied to the unit electrodes 3.

In this case, only one element is required to turn on and off the switch, so even if a high voltage withstand voltage is used, the cost will not increase significantly.

Further, as described above, if a constant voltage is applied to the counter electrode 10, this switching element becomes unnecessary.

However, in this case, erroneous discharge is likely to occur between the unit electrode to which no pulsed voltage is applied and the opposing electrode.
Furthermore, there is a possibility that the time from the start of discharge to the stop of discharge may become irregular.

From this point of view, it can be said that the method of applying a pulsed voltage to the counter electrode 10 as in the above embodiment is more superior.

Further, it is preferable that the pulse width of the pulsed voltage applied to the counter electrode 10 is slightly longer than the pulse width of the pulsed voltage applied to the unit electrode 3. The timing is shown in Figure 4.

In the present invention, as shown in FIG. 2, a discharge current flows from the unit electrode 3 toward the counter electrode 10 through a path indicated by a broken line 33.

The electrical resistance of this path remains constant as long as the heat-fusible ink layer 2 is pressed against the counter electrode 10 and the spacer 4 with a constant pressure.

Therefore, even if recording is performed continuously, recording at a constant density can be achieved by constant and stable discharge.

Furthermore, even when the distance G between the counter electrode 10 and the insulating spacer 4 is sufficiently large, the heat-fusible ink layer 2
The electrical resistance of can be selected to be relatively high, and there is a large degree of freedom in its composition.

Furthermore, if the heat-melt ink layer 2 is formed sufficiently thick around the outer periphery of the support 1 (FIG. 1), there will be no need to replenish the heat-melt ink layer for a long period of time.

(Divided Driving) As described above, the above pulsed voltage is selectively applied between the unit electrodes 3 and the counter electrode 10 to cause discharge, but in the case where discharge is caused in a large number of unit electrodes 3 , so-called full-line driving requires a large amount of discharge energy.

In order to downsize the power supply circuit that supplies this discharge energy, it is preferable to perform the following divided driving.

5 to 7 show circuits and time charts for explaining the driving method.

In FIG. 5, first, the unit electrode 3 is divided into N electrode groups 51 each having M electrodes from the left in the order of arrangement.
Then, the first unit electrode of each electrode group 51 is electrically connected to the lead wire E1, and similarly, the M unit electrodes are electrically connected to the lead wires E2 to EN in order.

On the other hand, the counter electrode 10 is divided into N parts corresponding to the electrode groups 51 with a width equal to the width of each electrode group 51. These were designated as C1 to CN.

For example, if a voltage is simultaneously applied between one of the unit electrodes of the leftmost electrode group 21 and the leftmost counter electrode C1 as shown in FIG. A dot is recorded.

Here, as shown in FIG. 7, a pulsed voltage having a pulse width Δtnc is applied to the counter electrodes C1 to CN in a time-division manner, respectively.

That is, in this case, a pulsed voltage is applied to the counter electrode C1 at the timing of time t1, and similarly, a similar pulsed voltage is applied to the counter electrodes C2 to CN exclusively in sequence from time t2 to tN. is applied to

On the other hand, as for the unit electrode 3, as shown in FIG.
A pulsed voltage is simultaneously supplied from E1 to EM. This pulsed voltage corresponds to the image signal to be recorded.

As a result, during the period from t1 to tN, discharge can be caused exclusively in each electrode group 51 in order from the left to the right end of the unit electrode 3.

Note that when such split driving is performed, the counter electrode that does not contribute to discharge is not only kept at the ground potential, but also grounded via a high resistance resistor as shown in the embodiment. By doing so, it is possible to prevent current from flowing between the divided opposing electrodes. Further, when an erroneous discharge is about to occur between the counter electrode and the unit electrode to which no pulsed voltage is applied, the discharge current is limited and the discharge is suppressed.

"Modification" Almost the same recording can be performed even if the voltage applied between the unit electrode and the support is of opposite polarity to that in the example.

Furthermore, in the above embodiments, the support and the heat-fusible ink layer are formed in a concentric cylindrical shape, but any shape that can continuously supply the heat-fusible ink layer may be used; for example, an endless belt-like shape may be used. Items or sheet-like materials are acceptable.

"Effects of the Invention" According to the image forming method of the present invention described above,
Images with high image density and high quality can be recorded with a small and low-cost device.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a recording apparatus suitable for carrying out the image forming method of the present invention, FIG. 2 is a perspective view of the main parts thereof, and FIGS. 3 and 4 explain a method of applying a recording voltage. Voltage waveform diagram, Figure 5 is a connection diagram of unit electrodes and counter electrodes for split drive, Figures 6 and 7 are
The figure is a time chart of the drive. DESCRIPTION OF SYMBOLS 1...Support, 2...Thermofusible ink layer, 3...
... Unit electrode, 4 ... Spacer, 5 ... Recording electrode,
6... Recording member, 10... Counter electrode, 51... Electrode group.

Claims (1)

[Claims] 1. A conductive heat-melting ink layer is formed on a support, a recording electrode composed of a plurality of unit electrodes is arranged on the upper surface of the ink layer, and a recording electrode composed of a plurality of unit electrodes is further arranged on the same surface. disposing counter electrodes facing each other at a predetermined interval and electrically contacting the heat-melting ink layer;
and a recording member is arranged to face the heat-melting ink layer with the recording electrode and the counter electrode in between, and a recording member is arranged between each unit electrode and the counter electrode to correspond to an image signal to be recorded. An image forming method comprising: selectively applying a voltage to cause ink in the ink layer to fly toward the recording medium, thereby recording an image on the recording medium. 2. Divide the unit electrode into mutually electrically independent electrode groups connected by a common wire, and electrically divide the conductive support facing each electrode group in the same way to form each electrode group. 2. The image forming method according to claim 1, wherein a voltage is applied to each unit electrode at different timings.