JPS6164456A - Formation of image - Google Patents

Abstract

PURPOSE:To obtain image recording having god color reproducibility at a high speed without using a nozzle, by preliminarily applying voltage when an image is formed by the flight of ink onto recording paper and forming ink protuberances in a slit member. CONSTITUTION:When voltage is applied to electrodes 4 every other electrode from a voltage source V and the other electrodes are earthed, electric fields around the electrodes 4, to which voltage was applied, are formed. At this time, the ink 1 in a slit generates protuberances IR on the liquid surface thereof at the voltage applied electrode parts. When a slit electrode is earthed, the applied signal required in the flight of the ink usually requires 3msec or more but, when voltage of -200V was applied to the electrodes 4 of the slit member 1, protuberances of about 50mum are formed to the voltage applied electrode parts and, when opposed electrodes 6 are respectively matched with the positions accurately opposed to the aforementioned protuberances of the ink liquid surface and signal voltage comprising a rectangular wave of 500V and 300musec is applied, ink droplets fly from the protuberance parts of the ink liquid surface corresponding to the picture element with an approximate circular shape of diameter of about 150mum is formed on recording paper 8.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an image forming method, and more particularly to an image forming method in which an image is formed by ejecting ink onto recording paper according to an image signal. Regarding.

(Prior art) Image formation using ink does not require a fixing process compared to contrast xerography using powder, and the equipment used to perform it is simpler and more compact. Furthermore, compared to thermal transfer methods, it has advantages such as better color reproduction, better image quality, and less printing energy.

Currently, the mainstream image forming method using this ink is an inkjet method in which charged ink is calculated from a nozzle and controlled by a signal electric field.

This inkjet method uses a nozzle,
Nozzles can become clogged due to ink drying or foreign matter getting mixed in, and since nozzles cannot be mounted in a high density, it is necessary to scan the nozzles or the recording paper, which reduces printing speed.
Furthermore, since it has movable parts, it has the disadvantage of poor reliability.

On the other hand, a method has been proposed in which the nozzle is formed into a slit and a signal is applied to a counter electrode to induce charge in the ink for recording.

This method has the advantage that there is no need to worry about nozzle clogging, which is a problem with conventional inkjet, and the high density arrangement of electrodes eliminates the need for scanning. Pixel formation occurs through a process in which an electric charge is induced into the ink, causing the ink to bulge, and then the ink to fly, resulting in slow response and difficulty in printing at high speeds. It has its drawbacks.

In order to eliminate this drawback, we use magnetic ink with magnetic powder dispersed in it, and by placing a magnetic field in the electrode section on the ink supply side and magnetically forming a bulge of ink, we can generate a signal. A method with improved recording responsiveness has also been proposed.

Although this method improves the responsiveness of printing, it is difficult to color the magnetic ink in the desired color, making it unusable for color recording, and the stability over time is poor due to sedimentation and magnetic aggregation of dispersed magnetic powder. It has the problem of damaging the

(Object of the Invention) In view of the problems of the conventional methods described above, the present invention provides an image forming method capable of stably recording an image with good color reproducibility at high speed without using a nozzle. It also aims to provide the following.

(Structure of the Invention) The present invention provides a slit member in which first and second flat plates each having one or more electrodes are provided with a slight gap therebetween, and a slit member disposed close to an end of the slit member. A plurality of counter electrodes are provided, conductive ink is held in the gap of the slit member, and a signal is applied to the counter electrode to cause the ink to fly from the slit onto a recording paper disposed near the counter electrode. An image forming method for forming an image by applying a voltage to an electrode provided on the slit member before applying the signal to form a bulge of ink within the slit member. That is. Note that the polarity of the voltage applied to the electrode within the slit member is desirably set to be opposite to the polarity of the signal applied to the counter electrode.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a plan view showing the configuration of an image forming apparatus that implements the image forming method of the present invention.

The image forming apparatus includes a slit member 1, and this slit member 1 has first and second slit members as shown in FIG.
It is formed by holding flat plates 2.3 at intervals of 80 μm. On the inner surface of the first flat plate 2, electrodes 4' are arranged side by side in a comb-like manner at a density of 16 electrodes/fi, and on the inner surface of the second flat plate 3, electrodes 5 are provided on the entire surface. Opposing electrodes are arranged in a row at a constant distance of about 300 μm from the end of the slit member 1 and directly facing the opening 1a of the slit member 1. Counter electrode 6 is 8 pieces/m
m, and each electrode 6 is connected to a signal applying power source 7. This counter electrode 6 and the slit member 1
Recording paper 8 is placed between them.

In the gap between the slit members 1, the ink I having a conductivity of 1□-8Uall-> is normally held by its own interfacial tension in such a state that the liquid level does not reach the ends of the slit members.

In the above structure, a voltage is applied to every other electrode 4 by the power supply ■, and the other electrodes are grounded, so that the voltage is applied alternately, and at the same time, the electrode 5 is grounded. By doing so, an electric field is formed in the voltage application electrode portion of the electrode 4. At this time, the ink I in the slit forms a liquid level bulge (R) at the voltage application electrode portion. This is a phenomenon that occurs when the ink is attracted to areas with a high electric field because the relative permittivity of the ink is greater than 1.The amount of swelling depends on the magnitude of the applied electric field, the relative permittivity of the ink, and the surface Determined by tension, etc.

The ink used in the present invention may be either water-based or oil-based as long as it has sufficient electrical conductivity to induce charge.

The smaller the surface tension of the ink, the larger the amplitude of the bumps, which is preferable.
/mouth), there is no problem.

In addition, the electrodes provided on the slit member l are as shown in FIGS. 1 and 2.
The shape is not limited to the one shown in the figure, and may include a shape with a notch 10 at the tip as shown in FIG. 3, or a shape with comb teeth on the two inner surfaces of the slit member 1 as shown in FIG. Any material may be used as long as it can form a bulge of ink liquid corresponding to the counter electrode.

Furthermore, as shown in FIG. 5, it is also effective to protrude the portion of the slit member 1 where the electrode 4 is provided and to assist the formation of a protuberance caused by the electric field by the interfacial tension of the ink.

Additionally, if the ink has high conductivity and there is a large amount of leakage from the slit member, it is possible to prevent the leakage without interfering with the operation by insulating or coating one of the slit electrodes with a high-resistance material. I can do it.

In the device shown in the figure, -200V is applied to the electrode 4 of the slit member 1.
When the voltage was applied, a bump of about 50 μm was formed on the voltage application electrode portion. In this state, each of the counter electrodes 6 was set at a position directly facing the above-mentioned protrusion of the ink liquid level, and the voltage was set at 500 V and 3
When a signal voltage consisting of a rectangular wave of 00 #sec is applied to the counter electrode according to the image information, ink droplets fly from the raised part of the ink liquid surface in response to the applied signal, and the recording paper 8 A substantially circular pixel with a diameter of about 150 μm was formed on the top.

Next, the voltage applied to the electrode 4 of the slit member 1 is increased by +20
When the voltage was set to 0, the same bulge as before was formed, but the ink did not fly even when a signal of 500 μ and 300 p sec was applied to the counter electrode, and in order to make the ink fly, 700 V was required. , required a 500 usec signal.

This is considered to be due to the fact that the electric field between the counter electrode and the slit became smaller and that the positive charge that had been induced in the slit electrode portion in advance was neutralized.

Furthermore, when the slit electrode was grounded, the applied signal required for the ink to fly was required to be 3 m5ec or more.

No protuberance is formed in advance on the electrode 4 portion of the slit member 1. These conditions can be broadly divided into (i) inducing charges into the ink, (i) forming ridges on the liquid surface due to electrostatic attraction applied to the induced charges, and ③ the ridges elongating, forming ink droplets and flying. Recording is performed through the process of raising the liquid level, but it is thought that the pulse width of the applied signal must be wide, mainly due to the time required for the process of raising the liquid level (i).

(Effects of the Invention) As described above, in the present invention, by forming ridges in advance in the ink inside the slit member, the duration of the applied signal required for recording can be greatly shortened, and high-speed recording can be achieved. Image formation becomes possible.

Furthermore, by applying a voltage with the opposite polarity to the signal to the electrode placed in the slit to form the protuberances in the slit, charges are already induced in the ink, which increases the speed. Not only can recording be performed, the electric field between the electrodes facing the slit is strengthened, the signal voltage applied to the facing electrode can be lowered, and the drive circuit can be simplified.
It also has the effect of being smaller and having higher reliability.

In addition, in the conventional recording method using ink, the stability of operation was impaired due to fluctuations in viscosity due to changes in temperature, etc., but in the present invention, since the ink liquid bulges are formed in advance, The effect of viscosity is small and stable recording can be performed. In this way, since there are wide restrictions on ink physical properties, it is possible to select ink materials with emphasis on color reproduction, and it is possible to obtain good images.

In addition, since the present invention retains ink within the slit member and does not use a nozzle, clogging due to ink drying or foreign matter is less likely to occur, and operation reliability is far greater than that of recording methods that use nozzles. expensive.

[Brief explanation of drawings]

1 is a plan view showing an image forming apparatus for implementing the image forming method according to the present invention; FIG. 2 is a perspective view showing the structure of a slit member in the apparatus shown in FIG. 1; FIG. FIG. 4 and FIG. 5 are diagrams showing modified examples of the slit portion. 1... Slit member, 2.3... Flat plate, 4.5...
- Electrode, 6... Counter electrode, ■... Power supply, ■... Ink, IR... Ink swell. Figure 1

Claims (2)

[Claims] (1) A slit member comprising first and second flat plates each having one or more electrodes separated by a small gap;
A plurality of counter electrodes are arranged close to the ends of the slit member, and conductive ink is held in the gap of the slit member, and a signal is applied to the counter electrode to cause the ink to be in the vicinity of the counter electrode. An image forming method in which an image is formed by ejecting ink from the slit onto a disposed recording paper, wherein a voltage is applied in advance to an electrode provided on the slit member before the signal is applied, and the inside of the slit member is An image forming method characterized by forming a mound of ink. (2) The voltage polarity applied to the electrode inside the slit member is
2. The image forming method according to claim 1, wherein the polarity of the signal applied to the counter electrode is opposite to that of the signal applied to the counter electrode.