JPS61114855A - Ink jet recorder - Google Patents

Abstract

PURPOSE:To make the realization of a compact drive circuit consuming low electric consumption possible by decreasing a drive voltage of an ink jet recorder. CONSTITUTION:A pulse voltage corresponding to a pixel is applied to a multinozzle ink jet recorder utilizing static power. Then the pulse voltage corresponding to an image signal is applied to an independent electrode provided near each ink discharging port. The figure shows a voltage waveform (a) applied to a common electrode and a voltage waveform (b) of one of the independent electrodes as an example. Experiments were conducted based on the voltage of the voltage pulse represented by Vpd=-350V and the pulse width by Pwb=50mus. Consequently it was found that even if a signal voltage V to be applied to the independent electrode were decreased to 300V, the response and gradation are favorably comparable to those of the conventional recorder.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an inkjet recording apparatus for recording character images and the like by ejecting ink from minute openings.

Conventional configurations and their problems As multi-nozzle inkjet recording mounting using electrostatic force, Japanese Patent Laid-Open Nos. 57-120452 and 1982
There is an inkjet recording device that utilizes air flow and electrostatic force, which is described in Japanese Patent No. 220758 and the like.

FIG. 1 shows a multi-nozzle inkjet recording device that utilizes air flow and electrostatic force.

In FIG. 1, air discharge ports 1-1 to 1-4 are perforated at equal intervals in an insulating air nozzle plate 2, and at least one surface including the periphery of the air discharge ports 1-1 to 1-4 is perforated. A common electrode 12 is provided for both. An insulating thin plate 14 is installed parallel to the air nozzle plate 2 and on the opposite side from the electrode 12, and ink discharge ports 4-1 to 4-4 are arranged opposite to the air discharge ports 1-1 to 1-4. 4 is perforated. The insulating thin plate 14 and the body member 13 form a common ink chamber 10, which communicates with the ink discharge ports 4-1 to 4-4 and to the ink reservoir via the ink supply path 6. . Further, electrodes 15-1 to 16-1 are independently and separately arranged around the ink discharge ports 4-1 to 4-4 facing the ink chamber 1o.
4 is provided. Air nozzle plate 2 and body member 13
An air flow flows into the air chamber 9 formed by the air chamber 9 via the air supply path 8, and this air flow flows through the air layer 7 formed by the air nozzle plate 2 and the insulating thin plate 14, and then flows through the air discharge port 1. -1 to 1-4, each flows out with a sharp bend. On the other hand, a constant pressure is applied to the ink in the ink chamber 10, and the pressure is adjusted so that the meniscus of the ink is stably maintained in each of the ink discharges 04-1 to 4-4 when the inkjet recording device is not driven. There is.

The electrodes 15-1 to 16-4 are connected to signal sources 5-1 to 5-, respectively.
4, and a potential difference can be independently generated between the electrode 12 and the electrode 12 commonly connected to the signal sources 6-1 to 5 to 4. When a potential difference occurs between the electrodes 15-1 to 15-4 and the electrode 12, the ink ejection ports 4-1 to 4-4 are
The ink liquid is ejected and flies through the air ejection ports 1-1 to 1-4. The configuration shown in FIG. 1 is an example in which there are four ink discharge ports or air discharge ports, but it is obvious that it is possible to have other number of ink discharge ports (n). Moreover, since the ejection of ink liquid from each ink ejection port can be controlled independently, it is possible to create a sickle at n times the speed.

Signal source 5- of the inkjet recording apparatus shown in FIG.
The signal formats generated from signals 1 to 6-4 are as shown in FIG. In FIG. 2, the vertical axis shows the electrode 12,
The potential difference between the electrodes 15-1 to 15-4 is shown, and the horizontal axis shows time. Electrode 12 and electrode 15-
A bias voltage Vb is constantly applied between 1 and 16-4. The value of this bias voltage vb is
The size is set within a range that does not allow the fly to fly while the meniscus that occurs in the fly is maintained. In addition, when an image signal is input, correspondingly, the signal voltage ① is applied superimposed on the bias voltage vbK, and the ink ejection port 4
A potential difference V is generated that enables the ink liquid to be ejected.

The pulse width Pw of the signal voltage v8 needs to be a value equal to or greater than the minimum pulse width 2wm that allows ejection of ink liquid. This minimum pulse width Pwm serves as a guideline for responsiveness, and is usually 50 to 1 ooμB.

In addition, inkjet recording devices that have good responsiveness and are capable of ejecting ink with a small pulse width perform pulse width modulation by setting the recording time for one pixel to be larger than the minimum pulse width Pwm, and produce images with shading. can be recorded.

FIG. 3 shows an example of density recording when pulse width modulation is performed, where the recording time for one pixel is set as Po, and the pulse width of the signal voltage is varied from Pwfn to P. This is an example of reproduction of the recording reflection degree obtained when changing the degree to . One of the reasons why shading can be reproduced over such a wide range is that the suction method using electrostatic force can form small dots relative to the diameter of the ink ejection opening. ``When recording at 8 dots/# with wm, a very light dark gray recording with an optical density change of about 0.06 was made.

However, inkjet recording devices that use electrostatic force generally have the disadvantage of high driving voltage.
Even in the recording device shown in the figure, the signal voltage is 300 to 5
It is ooV. Furthermore, there is a tendency that a signal with a high signal voltage has a good response.

Such a high signal voltage increases the size of the drive circuit and increases power consumption. This problem becomes more pronounced as the number of nozzles increases, and has been a major obstacle in realizing a multi-nozzle inkjet recording apparatus.

OBJECTS OF THE INVENTION It is an object of the present invention to substantially reduce the driving voltage of an inkjet recording apparatus that uses electrostatic force, to reduce power consumption, and to realize a miniaturized driving circuit.

Structure of the Invention The present invention applies a pulse voltage corresponding to a pixel to a common electrode of a multi-nozzle inkjet recording device using electrostatic force, and applies a pulse voltage corresponding to an image signal to an independent electrode provided near each ink ejection port. The structure is such that a voltage is applied to independently control the ejection of ink from each ink ejection port.

DESCRIPTION OF EMBODIMENTS FIG. 4 shows an example of voltage waveforms when the present invention is applied to the inkjet recording head of FIG. 1. In FIG. 4, a indicates a voltage waveform applied to the common electrode 12 in FIG. shows.

The case where the voltage in FIG.
ooV, the pixel period of the image signal P0 = 300as, ink is ejected for the pulse width P-〇〇μs of the signal voltage v8, and when Pw is changed from 60μg to 300μS, the ink is ejected at 8 dots/ltm. Optical densities in the range of 0.06 to 1.3 were recalculated. However, the signal voltage V is 60
The drawback is that the voltage is extremely high at 0V, and when converting to 7 multi-nozzles, multiple driver circuits with withstand voltages of 600V or more were required. For example, in order to realize a printer that uses four 24-nozzle multi-nozzle heads and is capable of color recording using yellow, cyan, magenta, and black inks, a 96-channel driver circuit is required.

In the embodiment of the present invention, as shown in Table 1, the common electrode 1
2, a voltage pulse with a period of P0 = 3oOμB corresponding to the pixel is applied, and the voltage of this voltage pulse is vpb = -36
ov, an experiment was conducted with a pulse width of Pwb = 50μB, and even if the signal voltage v8 applied to the independent electrodes 15-1 to 16-4 was lowered to 300V, the response and gradation remained unchanged with no color loss compared to the conventional one. I was able to get sex. In other words, the minimum width pwmd, which is a measure of responsiveness, is almost the same, and in terms of gradation, the maximum recorded reflection density is slightly lower, but the optical density is 1, which poses no problem in practice. The value was above.

Table 1 Example The pulse width Pwb and voltage vpb of the voltage applied to the common electrode (hereinafter referred to as pulse bias voltage) are, of course, set so that no ink is ejected when the signal voltage vs is 0. .

The values in Table 1 are an example.
1. Also, an important point of this pulse bias voltage is that it is synchronized in correspondence with the pixels. Furthermore, by synchronizing the ink, the energy at the start of ink ejection is increased. If we look at this from a physical phenomenon, the ink meniscus occurring at the ink ejection port is
In response to the pulse bias voltage, the period P0 (=300μB
), and it can be said that the pulse of the signal voltage v8 is applied in synchronization with this imaging to eject ink.

If such vibrations of the ink meniscus are made to have too high a frequency, they will gradually accumulate and will only have the same effect as the bias voltage vb in FIG. 4.

That is, the vibration of the ink meniscus caused by the pulse bias voltage needs to be reduced after the pulse is eliminated and before the next pulse is applied.

In the experiment, the effect of pulse bias was investigated by changing the pixel period P0, and it was found that a sufficient effect is obtained if P0≧200 μs. When Po<160 μs, the effect of the pulse bias voltage was almost the same as that of the bias voltage v8, and the signal voltage V could not be lowered.

Since the minimum pulse width P6 of the inkjet recording apparatus shown in FIG. 1 is approximately 60 μs, it is preferable to set the pixel period to approximately 60 μs when performing high-speed recording. however,
The concept of the pulse bias voltage of the present invention cannot be applied to recording in such a short period.

Therefore, the present invention is particularly effective when the characteristic of ejecting with a very small pulse width is applied to pulse width modulation. This is because in pulse width modulation, in order to obtain sufficient gradation, the pixel period is set to the minimum pulse width Pwm.
This is because it needs to be several times longer.

Note that the present invention requires a new driver circuit to generate a pulse bias voltage, but since it is applied to the common electrode 12, one circuit is sufficient regardless of the number of ink ejection orifices, so multi-nozzle The circuit will not become larger due to the increased size.

Effects of the Invention As described above in detail, according to the present invention, the driving voltage of the inkjet recording device can be lowered, and the inkjet recording device can be miniaturized with low power consumption. You can experiment with drive circuits. Further, the present invention is particularly useful for an inkjet recording apparatus that revises gradations by pulse width modulation.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment of an inkjet recording apparatus to which the present invention is applied, and FIG. 2 is an actual applied voltage waveform diagram of a conventional signal form of the inkjet recording apparatus of FIG. 1-1 to 1-4...Air discharge port, 4-1 to 4-
4...Ink discharge ports, 15-1 to 16-4...
...electrode, 12...electrode. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 11 [Figure 2 Time 1Ii 3 Figure 111111] White Shichiyuki 1 Figure 4

Claims (2)

[Claims] (1) One electrode of an inkjet recording device that ejects ink by electrostatic force by creating a potential difference between an electrode provided inside the ink chamber and an electrode provided outside the ink ejection port is divided into multiple parts. A pulse voltage corresponding to an image signal is applied to the independent electrode, a pulse voltage synchronized with a pixel cycle is applied to the common electrode, and the other electrode is a common electrode. An inkjet recording device characterized in that ink is ejected in response to a pulse voltage. (2) The inkjet according to claim 1, wherein the pulse voltage applied to the independent electrode is subjected to pulse width modulation processing in which the pulse width changes in accordance with the image density. Recording device.