JPS6249190B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic fluid recording device, and provides a magnetic fluid recording device that realizes noise-free image recording by controlling recording signals according to the positional relationship of opposing electrodes. It is intended to provide.

FIG. 1 shows the configuration of the main parts of a conventionally proposed magnetic fluid recording device. In the example shown in the figure, magnetic ink 4 contained in an ink tank 5 is supplied to the tip of the needle electrode 2 through a supply path 3 made up of a magnet, thereby forming a bump due to magnetic force. A voltage pulse from a high voltage switching circuit 9 controlled by a needle electrode control circuit 10 is applied to the needle electrode 2, and the ink at the tip of the needle electrode 2 is charged. On the other hand, gate electrode 1
A voltage pulse from a high-voltage switching circuit 7 controlled by an image signal control circuit 8 is applied to the recording paper 6, and charges are induced on the surface of the recording paper 6 in contact with the gate electrode 1.

When the Coulomb force generated by the charged ink at the tip of the needle electrode 2 and the electric charge induced on the surface of the recording paper 6 exceeds a certain value that depends on the distance between the ink and the paper surface, the ink begins to fly. It reaches the surface of the paper and a recorded image is formed.

FIG. 2 shows the relationship between the gate electrode 1 and the needle electrodes 2, in which 16 needle electrodes are arranged to face one gate electrode. Usually, matrix driving is performed to simplify the driving circuit.

In the conventional configuration, the gap between the gate electrodes is
There was a problem with printing the part corresponding to SP.

In other words, as the pitch of the needle electrodes becomes finer in order to improve printing quality (resolution), the gap SP between the gate electrodes must be made smaller, and the opposing positions of the needle electrodes and the gate electrodes must also be carefully adjusted. comes out. However, in reality, due to the withstand voltage between gate electrodes and the difficulty of alignment, conventional devices of this type require the same signal to be sent to both gate electrodes when printing at the boundary between adjacent gate electrodes. By providing this, problems caused by misalignment of opposing electrodes and the size of the electrode gap have been overcome.

Therefore, as shown in FIG. 2, printing can be performed even with the needle electrode located in the gap between the gate electrodes. However, by using a special driving method when printing a portion corresponding to the gate electrode gap SP, a new problem arises in that recording noise is generated. Figure 3 shows the distribution of potential that appears on the surface of the recording paper due to the signal applied to the gate electrode. Potentials appear in a distribution shape such as 14a and 14b corresponding to the electrodes. However, as mentioned above, when printing on the boundary between two gate electrodes, signals are applied to both gate electrodes at the same time, so a combined potential distribution like 15 is formed on the surface of the recording paper. . As shown in the figure, a higher potential than usual appears near the boundary of the gate electrode, which causes crosstalk. In other words, a potential larger than normal appears in the opposite part of the needle electrode that is supposed to print, and reliable printing is performed, but on the other hand, this larger-than-normal potential has a spread, so that other non-selected needle electrodes It also generates extra Coulomb force between the If this extra Coulomb force exceeds a certain value, the ink will fly, resulting in recording noise at non-selected points, and greatly reducing print quality.

Additionally, since a larger electric field than usual is applied between the needle electrode at the selected point and the recording paper, the print density increases only in this area, resulting in striped density unevenness that matches the pattern of the gate electrode as a whole. There was also a drawback.

The present invention was made in view of the problems of recording noise and density unevenness in conventional devices as described above, and enables magnetic fluid recording without recording noise and density unevenness by performing simple signal control. The aim is to provide equipment.

An embodiment of the present invention will be described below based on the drawings. FIG. 4 shows the signal waveforms of each electrode, taking as an example the case where matrix driving is performed by sequentially scanning the needle electrode and applying an image signal to the gate electrode.

Positive _polarity pulses 16a to 16g, . On the other hand, the two gate electrodes A and B each have a peak value V
_G negative polarity image signal pulse trains 17a and 17b are applied. If the boundary region K here corresponds to the four needle electrodes near the gap between the two gate electrodes, then in this region A,
An image signal is applied to both B gate electrodes at the same time.

One way to prevent noise generation in this boundary area is to reduce the peak value of the gate image signal pulse when printing the boundary area K, so that the image signal on the surface of the recording paper synthesized by the two gate signals is This is a method of making the potential equal to the normal potential. However, it is necessary to apply a high-voltage pulse signal of several hundred volts to the gate electrode, and dynamically controlling the peak value of such a high-voltage pulse is difficult and impractical from a circuit configuration standpoint. .

In the present invention, printing density and ink flying are
Focusing on the fact that on/off depends on the energy of the signal pulse, that is, the product of the pulse peak value and the pulse width, this system is characterized by dynamically controlling the pulse width while keeping the pulse peak value constant. .

FIG. 5 shows a main part of an embodiment of a magnetic fluid recording device equipped with an image signal control circuit for performing the above control. In order to detect the timing for printing the boundary area K, the output of the clock signal generation circuit 20, which serves as a reference for the image signal, is input to the count/decode circuit 21 to obtain the position detection signal 18 shown in FIG. 4C.
The pulse width of the image signal is determined by two mono/multi circuits 2.
2a, 22b and a selection circuit 23.
The mono/multi 22a generates a pulse having a width corresponding to a normal image signal in response to a clock input.
On the other hand, the mono/multi 22b generates a pulse having a width corresponding to the image signal in the boundary area. Naturally, the pulse width of the output pulse of the mono/multi 22b is set to be shorter. These two mono/multi outputs are input to a selection circuit 23, and dynamic switching is performed using the position detection signal 18 as a control signal to obtain a pulse train 24 with an appropriate pulse width depending on the printing position. The AND circuit 26 performs an AND operation between this pulse train 24 and the image signal train 25 which is the output of the image signal control circuit 8.
Improved gate signals 19a and 19 shown in FIG.
get b.

The two mono/multi output pulse widths may be set to appropriate values to eliminate density unevenness and recording noise.

According to the configuration of the above embodiment, when printing a portion corresponding to the boundary area K, an image signal with a shorter pulse width than usual is applied, so that the pulse height value remains constant and the applied energy is approximately equal. This makes it possible to obtain high-quality printing without flying noise from non-selected points or uneven density.

Although we have shown the simplest example of switching between signals with two types of pulse widths, it is also possible to prepare signals with several types of pulse widths by inversely correcting the composite potential distribution 15 shown in Figure 3. Therefore, if more detailed control is performed depending on the printing position, it is possible to further improve printing quality.

In addition, since concentration unevenness is caused by a larger electric field being applied than usual at the selected point, it is possible to similarly correct concentration unevenness by controlling the signal pulse width on the needle electrode side. It is possible. Therefore, if the pulse width control of the present invention is performed on both the needle electrode and the gate electrode, a recording device with higher printing quality can be realized.

Furthermore, in the above embodiment, the case where the needle electrode is sequentially scanned and an image signal is applied to the gate electrode has been explained, but it is also possible to consider a driving method in which an image signal is applied to the needle electrode and the gate electrode is sequentially scanned. Can be done. In this case as well, if the pulse width is controlled by a method such as adding a cut pulse to the scanning signal on the gate electrode side at the timing of printing the joint between the gate electrodes, the same effect as in the above embodiment can be obtained. Can be done.

As described above, according to the present invention, by simply adding a simple signal control circuit, it is possible to solve the problems of recording noise and density unevenness caused by flying noise, which were very serious problems in conventional devices. This has the great effect of making it possible to realize a magnetic fluid recording device with high speed and high print quality.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of the main parts of a conventional magnetic fluid recording device, Figure 2 is an explanatory diagram showing the positional relationship between the needle electrode and the gate electrode, and Figure 3 is the distribution shape of the potential that appears on the surface of the recording paper due to the gate signal. Explanatory diagram showing 4th
The figure shows a conventional device and an embodiment of the present invention.
FIG. 5 is an explanatory diagram showing the positional relationship between the needle electrode and the gate electrode and their signal waveforms, and FIG. 5 is a configuration diagram of the main part of the magnetic fluid recording device of the present invention, which is equipped with a pulse width control circuit. DESCRIPTION OF SYMBOLS 1...Gate electrode, 2...Needle electrode, 4...Magnetic ink, 8...Picture signal control circuit, 20...Reference clock generation circuit, 21...Count/decode circuit, 22a, 22b...Mono/multi , 23...
Selection circuit, 26...AND circuit.

Claims (1)

[Claims] 1. A diagonal electrode group in which a plurality of needle electrodes are arranged, a magnet that is provided close to the needle electrode group and makes the supplied magnetic ink rise at the tip of each needle electrode, and a recording paper for the needle electrode group. a group of gate electrodes facing each other via the needle electrode group, and matrix driving is performed by applying a pulsed signal voltage of opposite polarity to the needle electrode group and the gate electrode group, and an electric field between the needle electrode and the gate electrode facing each other is used. In a magnetic fluid recording device that forms an image on recording paper by flying magnetic ink at the tip of a needle electrode, driving needle electrodes located opposite to each other near a gap between two adjacent gate electrodes of the gate electrode group. In this case, two gate electrodes forming the gap are driven simultaneously, and these two gate electrodes are driven simultaneously.
The pulse width of the signal applied to at least one of the needle electrode or gate electrode group is such that it compensates for the increase in the electric field generated between the needle electrode and two gate electrodes by driving two gate electrodes simultaneously. What is claimed is: 1. A magnetic fluid recording device characterized by comprising means for controlling to shorten the length of the magnetic fluid.