JPH0130625B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic fluid recording device, and an object of the present invention is to form a high-quality image on recording paper without recording noise.

First, we will explain the main structure of the conventional magnetic fluid recording device.
As shown in the figure. In FIG. 1, 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, and a bump is formed there by the magnetic force of a bump magnet 7. In FIG. A voltage pulse from a high voltage switching circuit 10 controlled by a needle electrode control circuit 11 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 8 controlled by an image signal control circuit 9 is applied to the recording paper 6, and charges are induced on the surface of the recording paper 6 which is 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 related to the distance between the ink and the paper surface, the ink stops flying. It first reaches the surface of the recording paper. 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. In order to simplify the drive circuit, matrix drive is normally used, and the needle electrodes connected in groups of 16 are sequentially scanned and an image signal is simultaneously applied to each gate electrode. 3 and 4 show voltage waveforms applied to the needle electrode and the gate electrode. Figure 3 shows the case where the recording cycle is long, that is, the image signal is not applied continuously, and the needle electrode has a voltage as shown in Figure 3A.
A pulse 12a of voltage V _S is applied to the gate electrode, while a pulse 13a of voltage -V _G shown in FIG. 3A is applied to the gate electrode. In addition, Fig. 3C shows the voltage -V _p 14a appearing on the surface of the recording paper, and when the recording cycle is long, that is, the image signal pulse 13a is not continuously applied, the charge on the recording paper is not appropriate. is being discharged. 1 shown in Figure 4 A, B, and C
2b, 13b, and 14b are the needle electrode pulse waveform, gate electrode pulse waveform, and recording paper surface voltage waveform when the recording cycle is short, that is, when the image signal is continuously applied. The voltage V _p that appears becomes larger in the negative direction with time. In other words, a large voltage in the negative direction is induced across the surface of the recording paper corresponding to the entire gate electrode, and ink also flies from unselected needle electrodes. This resulted in recording noise and degraded the quality of recorded images.

The present invention is intended to eliminate the above-mentioned drawbacks, and FIGS. 5 and 6 show waveform diagrams for explaining the invention, and FIG. 7 shows the main configuration of an embodiment. FIG. 5 shows a voltage pulse waveform 15a applied to the gate electrode and a voltage waveform 16a appearing on the surface of the recording paper when the recording period is long. The voltage applied to the gate electrode is the voltage applied to the gate electrode described in the conventional example, with a voltage V _A superimposed at the timing when the recording voltage -V _G ends.
Therefore, the voltage appearing on the surface of the recording paper can quickly return to its original state because the discharge is accelerated. On the other hand, 15b and 16b shown in Fig. 6A and _6B show the gate electrode voltage pulse waveform and the recording paper surface voltage waveform when the recording cycle is short. Discharge occurs, and the voltage on the surface of the recording paper does not increase in the negative direction, resulting in a voltage waveform similar to that when the recording cycle is long (FIG. 5). That is,
If the voltage on the surface of the recording paper is 16b, no recording noise will occur and the quality of the image can be improved.

FIG. 7 shows one embodiment of a high voltage switching circuit for generating the signal to be applied to the gate electrode. 17 is an input terminal for inputting a signal from the image signal control circuit 9, and 18 is an image signal high voltage switching terminal for insulating the image signal control circuit 9 and the high voltage switching circuit and creating an image signal of -V _G. This is an insulating means for insulating between the drive signal of the circuit 19 and a switching circuit 21 to be described later for creating a pulse called V _A , and is composed of, for example, a photocoupler. 19
20 is a delay circuit and waveform shaping circuit for delaying and shaping the image signal; 21 is a switching circuit; and 22 is an output terminal for a signal obtained by combining the output signals of 21 and 19. , is an application terminal to the gate electrode 1. With the above configuration, it is possible to superimpose the pulse V _A of the opposite polarity on the image signal created in the same way as in the prior art, that is, the output signal of the 19 image signal high voltage switching circuits. Further, by using only the waveform shaping circuit 20 and providing a delay circuit before the picture signal high voltage switching circuit 19, it is possible to superimpose a pulse V _A of opposite polarity on the leading edge of the picture signal.

With the above configuration, the waveforms 15a and 15b in FIG. 6 can be obtained as gate electrode voltage waveforms, and the potential on the surface of the recording paper can be made constant regardless of the frequency of image signals.

As is clear from the above embodiments, according to the present invention, it is possible to prevent charge from accumulating on the recording paper and keep the surface potential constant regardless of the frequency of image signals, and from the unselected needle electrodes. Since this eliminates ink flying, it is possible to obtain very high quality images without recording noise. Furthermore, it is possible to eliminate changes in recording density that occur when the surface potential of the recording paper changes to such an extent that the needles do not fly from unselected needle electrodes, making it possible to obtain images with good uniformity.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of the main parts of a conventional magnetic fluid recording device, Fig. 2 is a configuration diagram showing a gate electrode and a needle electrode, and Fig. 3 A, B, and C are voltage waveform diagrams of various parts when the recording cycle is long. Figure 4 A, B, and C are voltage waveform diagrams at various parts when the recording cycle is short; Figures 5 and 6 are for explaining an embodiment of the present invention; Voltage waveform diagram of each part when the cycle is long,
FIGS. 6A and 6B are voltage waveform diagrams of various parts when the recording cycle is short, and FIG. 7 is a diagram showing the configuration of the main parts of this embodiment. DESCRIPTION OF SYMBOLS 1... Control electrode, 2... Needle electrode, 4... Magnetic ink, 9... Image signal control circuit, 18... Photocoupler, 19... Image signal high voltage switching circuit, 2
0... Delay circuit and waveform shaping circuit, 21... Switching circuit.

Claims (1)

[Claims] 1. Magnetic ink is supplied to the tip of the needle electrode group through a supply path composed of a magnet, and a bump of the magnetic ink is formed at the tip of the needle electrode group by the magnetic force of a bump magnet, and at the same time, a bump is formed on the needle electrode group. a needle electrode drive circuit that applies a pulsed selection signal; and a control electrode drive that applies a pulsed image signal at the same time as the pulsed selection signal is applied to a control electrode group arranged opposite to the needle electrode group. a circuit, and a recording paper interposed between the needle electrode group and the control electrode group for recording the image signal with flying magnetic ink,
The control electrode drive circuit is a circuit that generates a signal to which a pulse having a polarity opposite to that of the image signal is added in a period after the period in which the image signal exists, thereby reducing the charge on the surface of the recording paper. Features of magnetic fluid recording device.