JPS60210462A - Inkjet recorder - Google Patents

Abstract

PURPOSE:To enable the separating and flying of ink accurately and uniformly at the electrode corresponding to image information by applying a high voltage pulse according to image information to an ink adapted decrease in the surface tension responding to the intensity of electric field to form ink drops separately. CONSTITUTION:When a high voltage pulse is applied, the surface tension of an ink decreases to 1/2-1/3 between electrodes 16. With such a decrease in the surface tension of the ink, ink is constricted between the electrodes 16 as it tends to be spherical at the portion of a nozzle 2 not subjected to this decrease in the surface tension. As the constriction of the ink grows, ink drops 7 forms and are about to be discharged from the nozzle 2 by an ink pressure of a space 17. Upon the discharge of the ink drops 7 from the nozzle 2, the positively charged ink drops 7 fly toward an opposed electrode 19 by an electric field between an electrode 15 for accelerating electric field and the opposed electrode 19 to print a recording paper 18.

Description

Detailed Description of the Invention [Technical Field] The present invention facilitates accurate separation and formation of ink droplets by applying a high-voltage pulse corresponding to one image information to ink whose surface tension decreases according to electric field strength. The present invention relates to an inkjet recording device.

[Background technology]

For example, an inkjet recording apparatus shown in FIG. 1 has been proposed. This inkjet recording device includes a housing 3, which is equipped with an ink chamber 1 into which ink fed by a pressure pump is introduced from one end, a nozzle 2 which discharges ink particles 7 at the other end, and a housing 3 around the nozzle. The nozzle is provided with a heat generating section 4 that uses a laser or the like to heat the ink inside the nozzle. The heat generating section 4 is connected to a power supply section 5 that receives the supply of heat generating power.

The power supply unit 5 is connected to a control unit 6 that performs control according to print signals.

In the above configuration, when the control unit 6 controls the power supply unit 5 according to the print signal to supply one power to the heat generating unit 4 at the time of ink droplet ejection, the ink in the nozzle 2 instantaneously boils and generates bubbles. Then, ink particles 7 are generated by the bubbles and are ejected. According to this drop-on-demand type inkjet recording apparatus, the apparatus can be simplified and control can be made easier compared to the electric field control type or the charge control type.

However, according to this inkjet recording device, since the ink in the nozzle is boiled at a high temperature by the heat generating section 4,
There is a disadvantage in that it is difficult to stably obtain ink droplets of uniform particle size.

[Object and structure of the invention]

Q. The present invention has been made in view of the above.

To stably separate and fly ink droplets of uniform size with a simple configuration.

The present invention provides an inkjet recording apparatus that separates and forms ink droplets by applying high-voltage pulses in accordance with image information to ink whose surface tension decreases in accordance with electric field strength.

〔Example〕

An inkjet recording apparatus according to the present invention will be explained in detail below.

FIG. 2 shows an embodiment of the present invention, in which an ink tank 11 stores ink to be supplied to the recording head A;
A pump 12 that always supplies a constant amount of ink in an ink tank 11 to the recording door A, and an insulating upper plate 13 and a lower plate 14 forming a casing 3 that holds the supplied ink.

Insulating top plate 13. Bottom+! i, a housing 30 formed by 14;
Nozzle 2f: A full pulse voltage is applied to the ink in the space 17 of the housing 3 formed by the metal accelerating voltage raising electrode 4i 15 whose removed surface is covered and the upper and lower insulating plates 13 and 14 according to the recorded information. A pair of recording electrodes 16 facing each other, a recording paper 18 disposed and moving facing a nozzle 2 that ejects ink according to image information, and ink droplets separated and formed on the recording electrodes 16 are electrostatically accelerated. A counter electrode 19 (disposed on the back side of the recording paper 18 and connected to one of the recording electrodes 16 and to which an electric field is applied between the electrode 15 and the recording electrode 15)
a high-voltage drive circuit 20 that applies a pulse voltage to the accelerating electric field electrode 15, and a high-voltage source 21 that applies a positive electric field to the accelerating electric field electrode 15 and a negative electric field to the counter electrode 19 (the negative electrode is also connected to the other recording electrode 16). ) and #) are configured.

FIG. 3 shows an embodiment of a porous insulating upper plate 13 and a lower plate 14, which are separated and independent for each nozzle 2. The upper plate 13 is partitioned at intervals of 2 from one end, 913
a, and the lower plate 14 is partitioned from one end to position 1! 714
11, and then partitions 114a at intervals of 21, and two recording electrodes 16 between the partitions at intervals of 21 (in area 7 at one end of the lower plate 14). is provided with one recording electrode 16).

In FIG. 3(B), the upper plate 13 and the lower plate 14 are mounted facing each other, and a predetermined number of nozzles 2 are formed at regular intervals l. The space from the tip of the recording electrode 16 to the tip of the nozzle 2 was always configured to be, for example, 50 μm×50 μm×50 μm.

FIG. 4 shows an embodiment of the lower plate 14 in which the planar shape of the recording electrode 16 is U1 cow-shaped in order to ensure the separation of ink droplets. Since the shape of the recording electrode 16 facilitates the separation and formation of ink droplets, ink droplets can be formed accurately even if the partition 14m is omitted.

In the above configuration, the ink tank 11 is filled with ink to a certain level and is supplied by the pump 12 to the space 17 for the recording head. A high voltage drive circuit 2 is connected to the recording electrode 16.
Voltage 7 KV, pulse width 50 depending on recording information
A high voltage pulse of 0 μsec is applied. Further, a voltage of -3 KV was applied between the accelerating electric field electrode 15 and the counter electrode 190, and an aqueous ink mixed with 20% ethanol was used as an ink having the following characteristics.

Relative permittivity = 20 ~ 80 Electrical conductivity = lQ-LIQ-8 (Ω・required) -1 surface tension crab
20 to 30 (dyne/crn) When the high voltage pulse is applied, the surface tension of the ink increases between the electrodes 16 at V2 to IA.
decreased to

The formation of the ink droplets 7 will be explained below in FIGS. When the surface tension of the ink decreases to 1/2 to IA between the electrodes 16, the ink in the part of the nozzle 2 where the surface tension has not decreased tries to become spherical, causing a constriction in the ink between the electrodes 16 ((Fig. 5). (4)) As the constriction grows, an ink droplet 7 is formed, and the ink droplet 7 is about to be ejected from the nozzle 2 due to the ink pressure in the space 17 (Fig. 5 (B)). Then, the positively charged ink droplets 7 fly toward the counter electrode 19 due to the electric field between the accelerating electric field electrode 15 and the counter electrode 19, and are printed on the recording paper 16.

FIG. 6 shows another embodiment of the present invention, in which ink droplets with different particle sizes are generated by arranging a plurality of recording electrodes in parallel,
Although this is an embodiment in which gradation recording is possible, parts that are the same as those in FIG. 2 are indicated by the same reference numerals, so redundant explanation will be omitted. For example, three rows of recording electrodes 16a are arranged parallel to the ink jetting direction on the insulating upper plate 13 and the lower plate 14.

16b, 16c, and the recording electrodes 16a, 16
b.

A switching circuit 62 (with switches 1, 2.3) is provided for applying a high voltage pulse to 16c and selecting the particle size of the ink droplets.

In the above configuration, when the switch 1.2 or 3 of the switching circuit 62 is turned on depending on the particle size of the ink droplet and a high voltage pulse is applied from the high voltage drive circuit 20 according to the recorded information, as explained in FIG. An ink droplet is formed as shown in FIG. It goes without saying that when switch 1 is turned on, ink droplets with the smallest size are formed, when switch 3 is turned on, ink droplets with the largest size are formed, and when switch 2 is turned on, ink droplets with an intermediate size are formed. of ink droplets are formed. In this example, recording electrodes were arranged in three rows to form ink droplets with three levels of particle size, but by further increasing the number of electrodes, it is possible to increase the number of levels of particle size as appropriate.

〔Effect of the invention〕

As explained above, according to the inkjet recording apparatus of the present invention, ink droplets are separated and formed by applying nine high voltage pulses according to image information to the ink whose surface tension decreases according to the electric field strength, so that it is easy to form ink droplets. With this configuration, it is possible to reliably and uniformly separate and fly ink on the electrode portion according to image information.

Explanatory diagram showing one embodiment of the present invention, FIG. 3(A) (EO
4 is a perspective view of a recording head section to which the present invention is applied, FIG. 4 is a plan view of a recording electrode section to which the present invention is applied, and FIG. 5 (B)
(di is an explanatory diagram showing the ink droplet formation stage, and FIG. 6 is an explanatory diagram of a double-row recording electrode. Explanation of symbols 1... Ink chamber, 2... Nozzle, 3... Housing, 4
... Heat generating part, 5... Power supply part, 6... Control part, 7
...Ink particles, 11...Ink tank, 12...
・Pump, 13... Upper plate, 14... Lower plate, 15...
- Accelerating electric field electrode, 16... Recording electrode, 17...
Housing space (ink chamber), 18...recording paper, 19...
Counter electrode, 20... High voltage drive circuit, 21... High voltage power supply, 31... Groove, 61... Recording electrode array, 6
2...Switching circuit.

Figure 4 Figure 5

Claims (1)

[Scope of Claims] An inkjet recording apparatus including a recording electrode that applies a voltage according to recording information to ink in an ink chamber having an ink discharge nozzle. The recording electrode is provided at a position corresponding to the particle size of the ink droplet from the tip of the nozzle. An inkjet recording apparatus characterized in that the ink is ejected from the nozzle as ink droplets after the surface tension of the ink is reduced by application of the voltage.