JPH0462268B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention is characterized in that liquid ink is ejected by an electric field to form dots on a recording medium, and images such as characters and figures are formed by the combination of these dots. The present invention relates to printing devices.

Conventional technology Conventionally, so-called inkjet printers, which form images on a recording medium by ejecting liquid ink droplets from a nozzle, have been known to produce less noise during printing and to perform multicolor printing compared to other printing methods. Many inventions have been made and improvements have been made for reasons such as being advantageous in terms of running costs and the like. However, countermeasures against nozzle clogging due to ink evaporation are not sufficient and have become a practical problem.

In order to eliminate the occurrence of such nozzle clogging, a type of printer using liquid ink that is different from the above-mentioned inkjet printer is being considered.

First, to give an example, as described in JP-A-56-170 and JP-A-56-4467, a slit-shaped opening is formed instead of a nozzle that is prone to clogging. However, an electric field is applied between opposing electrodes facing this opening to cause the ink to fly.

This type of ink has a problem in that the structure for releasing ink droplets from the slit-shaped opening is delicate and lacks stability.

In addition, as for other methods, JP-A-54-
As seen in Japanese Patent Application Laid-open No. 23534 and Japanese Patent Application Laid-open No. 159355/1983, ink is guided to the tip of a needle-like member along its outer periphery, and the ink is caused to fly by an electric field.

In this type of product, magnetic ink must be used to guide the ink to the tip of the needle-like member, and this magnetic ink has a high degree of freedom in color selection due to the ground color of the magnetic powder contained in it. The disadvantage is that there is no

Problems to be Solved by the Invention In order to solve the disadvantages of the above-mentioned inkjet printer using liquid ink while maintaining its features, it is necessary to avoid clogging in the part where the ink is ejected. That is absolutely necessary.

Furthermore, the use of magnetic ink as the liquid ink is undesirable due to its color, and it must be possible to print with normal ink.

In order to solve these problems, the present applicant invented a printing device of the type shown in FIG. 7, and
A patent application has been filed. First, an ink container 2 for storing ordinary liquid ink 1 is provided, and a needle-shaped recording electrode 3 having electrical conductivity and ink-impregnating property is provided inside the ink container 2 and immersed in the ink 1. The tip 4 of the electrode 3 is exposed from the ink container 2. A counter electrode 6 is provided at the tip 4 of the recording electrode 3 with a recording paper 5 interposed therebetween. , 9 are connected. Then, the switching circuit 7
A control circuit 10 that generates a control signal according to an image signal is connected to.

The following recording electrodes 3 are used as the above-mentioned recording electrodes 3.

(1) Metal granules formed by casting without losing air permeability. (2) Conductive granules such as transition metal oxides sintered. (3) Conductive particles mixed with carbon fine particles. Breathable foam molded plastics Among these, (1) and (2) are a collection of irregularly shaped particles, and the pores formed between the particles communicate three-dimensionally. In addition, (3) also has a substantially similar structure.

Therefore, the ink 1 always reaches the tip 4 of the recording electrode 3, and the switching circuit 7 operates according to the image signal to generate an electric field between the recording electrode 3 and the counter electrode 6, and the tip reaches the tip 4. 4, the ink 1 is ejected toward the recording paper 5.

Printing is performed according to this principle, but since the tip 4 of the recording electrode 3 is exposed to the outside, the ink 1 in that part dries, but the ink container 2
Since the degree of fluid communication with the ink 1 inside is high, the concentration of the ink 1 can be uniformized well, and no slag of the ink 1 is generated at the tip 4.

In this way, this type of printing device is a dramatic advance over conventional technology, but in order to increase the printing speed, it is necessary to reduce the amount of ink 1 supplied without the risk of droplets. This is something that needs to be increased. That is, it is desirable that the recording electrode 3 has a high ability to retain the ink 1 and has low fluid resistance.

Means for Solving the Problems A recording electrode of a printing device is formed by a through-hole thin tube in which a large number of through-holes are formed along the longitudinal direction.

Function The ink flows in the length direction of the recording electrode, and the presence of many through holes provides an abundant supply of ink to the tip of the recording electrode. Further, clogging due to ink evaporation does not occur.

Embodiment A first embodiment of the present invention will be described based on FIGS. 1 to 4. Components that are the same as those described in connection with FIG. 7 are designated by the same reference numerals, and description thereof will be omitted. First, the printer 11 has two (first
Guide shaft 1 (only one is shown in the figure)
2 is provided horizontally, and a carrier 13 is attached to this guide shaft 12 so as to be able to reciprocate from side to side. A printing head 14 is placed on this carrier 13. Further, in the center of the printer 11, a counter electrode 6 facing the printing head 14 is horizontally attached. Behind this counter electrode 6 is a tractor 1 that feeds recording paper 5 as a recording medium.
5 is provided. An operating knob 16 projecting outward is coupled to the tractor 15.

The printing head 14 is similar to that shown in FIG. 7, but the recording electrode 17 has a different structure as will be described later. The upper surface of the ink container 2 is covered with a printed wiring board 18, and the recording electrode 17 is held at the tip of a wire 19 that is electrically connected and fixed to the printed wiring board 18. Further, the printed wiring board 18 is connected to a connector 20,
This connector 20 is connected to a switching circuit 21.

The recording electrode 17 is formed by kneading fine powder of alumina (A1 ₂ O ₃ ) with a binder, extruding it by a special method, and then sintering it to form a through hole having a large number of through holes 22 in the longitudinal direction. This is due to the pore capillary tube 23. That is, the diameter φ along its length
It is a cylindrical member with a diameter of about 0.8 mm and a length of 10 mm, having a large number of through holes 22 with a diameter of about 50 μm, and its tip 4 is machined into a conical shape with an apex angle of 60° and an R of 0.15. has been done. Although not particularly shown in the drawings, the surface of the through-hole thin tube 23 is provided with a thin metal film of chromium to provide conductivity. A ceramic member having such a large number of through holes 22 is supplied by Pilot Precision Co., Ltd. under the name "ceramic through hole tube," and was published in the Nikkan Kogyo Shimbun on May 20, 1980. There is also an article about this.

Further, if a similar shape is manufactured using metal powder or carbon powder instead of such non-conductive alumina powder, there is no need to attach a metal thin film to provide conductivity.

In such a configuration, the printing operation is similar to that described with reference to FIG. supply

Next, FIG. 5 shows a second embodiment of the present invention, in which a large number of recording electrodes 17 are arranged in parallel. In this case, each recording electrode 17
An independent switching circuit 7 is connected to the control circuit 10, and a control circuit 10 performs a switching operation corresponding to the image signal.

Next, a third embodiment of the present invention will be described based on FIG. The difference from the first embodiment shown in FIG. 1 is that the ink container 2 is of a sealed type, and a pressure device is connected to a connection hole 24 formed on the top surface of the ink container 2 to increase the pressure inside the ink container 2. Static pressure higher than atmospheric pressure is applied. As a result, through hole 2
Even if the fluid resistance of the ink container 2 is somewhat high, the ink 1 can flow out smoothly because the internal pressure of the ink container 2 is high. In particular, it is desirable to apply an appropriate pressure depending on the porosity of the through-hole thin tube 23 and the printing speed.

Note that the ink 1 may be supplied under pressure from an external ink supply pump instead of using air pressure.

Note that the recording electrode 17 described above is extremely inexpensive, so the printing head 14 is made into a unit and used as a disposable unit, and the printing head 14 is replaced with a new one when the ink 1 in the ink container 2 is used up. Is possible.

Effects of the Invention As described above, the recording electrode facing the counter electrode with the recording medium interposed therebetween is formed by a through-hole thin tube having a large number of through holes in the longitudinal direction. At the same time, the ink can flow smoothly, and as a result, the ink supply to the tip of the recording electrode is plentiful, and high print quality can be obtained even during high-speed printing, and the ink at the tip is plentiful. Since there are many through holes through which ink flows out, clogging due to ink drying does not occur, and the recording electrode can be made conductive by making the through hole capillary itself conductive or by attaching a thin metal film. This is possible by a simple means.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal side view showing a first embodiment of the present invention, FIG. 2 is a perspective view of the printer, FIG. 3 is a side view of the recording electrode, FIG. 4 is a rear view thereof, and FIG. 5 is a booklet. FIG. 6 is a longitudinal side view showing the second embodiment of the invention, FIG. 6 is a longitudinal side view showing the third embodiment of the invention, and FIG. 7 is a longitudinal side view showing the already proposed printing method of the invention. FIG. 1... Ink, 4... Tip, 5... Recording paper (recording body), 6... Counter electrode, 17... Recording electrode,
22...Through hole, 23...Through hole thin tube.

Claims (1)

[Scope of Claims] 1. A recording electrode with ink attached to the tip thereof and a counter electrode are arranged facing each other with a recording body interposed therebetween, and an electric field between these recording electrodes and the counter electrode exceeds a predetermined value. In a printing device in which ink sometimes flies from the tip of the recording electrode to form an image on the recording medium, the recording electrode is formed by a through-hole thin tube having a large number of through holes formed in the length direction. A printing device featuring: 2. The printing device according to claim 1, wherein the recording electrode has a conical tip. 3. The printing device according to claim 1, wherein the recording electrode is formed of a sintered compact made of a conductive material such as metal or carbon. 4. The recording electrode according to claim 1, characterized in that the recording electrode is formed by a through-hole thin tube made of sintered metal oxide, and a metal thin film is attached to the surface of the through-hole thin tube to impart conductivity. Printing device. 5. A recording electrode with ink attached to its tip and a counter electrode are arranged facing each other with a recording body interposed therebetween, and when the electric field between these recording electrodes and the counter electrode exceeds a predetermined value, the tip of the recording electrode In a printing device in which ink is ejected from a portion of the recording body to form an image on the recording medium, a condition in which only the tip of a through-hole capillary tube in which a large number of through holes are formed in the length direction of the recording electrode is exposed. 1. A printing device characterized in that the ink container is housed in an airtight ink container, and a static pressure equal to or higher than atmospheric pressure is applied to the inside of the ink container.