JPH0255142A - Ink jet recorder - Google Patents

Abstract

PURPOSE:To reduce a recording voltage for a discharge by generating bubbles in a liquid chamber between a pair of electrodes provided in the chamber having a section communicating with a discharge port and a different area, and then so applying a voltage as to vary the volume of the bubbles by discharging. CONSTITUTION:When a voltage Vp1 is applied between electrodes 1 and 2, Joule heat of W=Vp /R by a resistance R of conductive ink itself. However, in this case, since the volume of the passage of a liquid chamber 9 is small, the ink is boiled simultaneously upon application of the voltage, and bubbles 10 are generated. As the bubbles are grown, a current value is decreased, and when the bubbles block the passages, it becomes an OFF state. Here, when a voltage Vp2 is applied between the electrodes 1 and 2, a large electric field is generated between both the inks interposed at the bubble 10. When it arrives at a breakdown voltage, a discharge is generated, the generated bubble 10 is exploded, and liquid droplets 11 is splashed from an injection port by the energy.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to various recording apparatuses, and more particularly, to a head section of an inkjet recording apparatus.

PRIOR ART Conventionally, various inkjet recording apparatuses that eject ink using the emission phenomenon have been proposed.
The inkjet recording device described in U.S. Patent No. 3,179,042 has a heater for preheating the ink, and an electrode near the ejection orifice for energizing the ink to destroy it. The ink is heated by the heater to preheat the ink so that it has certain characteristics, and then the ink is sent to the head through the flow path, where the ink between the electrodes is heated by energizing the opposing electrodes. It ionizes, vaporizes, etc. to generate a sudden force, which causes the ink to be ejected. However, this method requires additional equipment such as providing a preheating section, has a large electric power f1'1 cost, and requires a high-voltage switching circuit, resulting in high costs.In particular, multiplication is difficult, and electrode breakage occurs. There are disadvantages such as problems in durability such as .

Furthermore, the inkjet recording device described in Japanese Patent Application Laid-Open No. 58-36462 applies a pulse voltage between a first electrode that is in contact with ink in a container and a second electrode that is disposed outside a nozzle. This method excites the meniscus and generates a current in the ink inside the nozzle, which releases a spray consisting of multiple ink particles to print dots. This also utilizes the phenomenon of discharge. Since the discharge is generated through the conductive ink, the voltage pulse is as high as 3000V, and there is one disadvantage in terms of cost.

Purpose The present invention was made in view of the above-mentioned circumstances.
In particular, this was done for the purpose of reducing the recording voltage for ejection 41f in an inkjet recording apparatus that ejects small droplets from an orifice to record by utilizing the explosive energy generated by the discharge phenomenon.

In order to achieve the above object, the present invention provides a discharge port for discharging a liquid, a liquid chamber communicating with the discharge port and having portions having different areas, and a liquid chamber provided within the liquid chamber. a pair of electrodes;
The apparatus is characterized by comprising a voltage applying means for applying a voltage so as to generate bubbles in the liquid in the liquid chamber between the pair of electrodes and then change the volume of the bubbles by discharge.

Hereinafter, the present invention will be explained based on examples.

FIG. 1 is a partially cutaway perspective view for explaining one embodiment of the present invention, in which 1 is a recording electrode, 2 is a common electrode, 3 is an upper plate, 4 is a lower plate, and 5 is an ink jetting electrode. port, 6 is the ink supply port,
7 is a partition wall, 8 is a recording signal, and 9 is a liquid chamber. The liquid chamber 9 partitioned by the partition wall 7 communicates with the ink supply port 6 to constitute a head. Each liquid chamber 9 has a recording electrode 1. It has a common electrode 2 and one nozzle 5, the ink nozzle 5 is arranged on an extension of each electrode, and a voltage (Vp) according to the print information is applied to the recording electrode 1. Ru.

FIG. 2 is a cross-sectional view of a main part for explaining the operating principle of the present invention, and FIG. 3 shows the waveform of the voltage applied between the recording electrode 1 and the common electrode 2, and the current flowing between these electrodes. When the liquid chamber 9 is in a stopped state in which no voltage is applied to the electrodes 1 and 21jl, the inside of the liquid chamber 9 is in the state shown in FIG. 2(a). Here, when the voltage V P x shown in ■ in Fig. 3 (,) is applied between the electrodes 1°2, the resistance R of the conductive ink itself causes a joule of W = V p t ” / R. Generates heat.

However, at this time, since the flow path volume of the liquid chamber 9 is small, the ink boils at the same time as the voltage is applied, and bubbles 10 are generated (
Figure 2 (b)), the current waveform at that time is shown in Figure 3 (a) @
As shown in , as the bubble grows, the current value decreases,
When air bubbles block the flow path, it becomes the off state. Therefore, the relationship between the voltage application time t1 and the current flow time t1' is 11)1□'.

Here, a voltage V shown in ■ in FIG. 3(b) is applied between electrodes 1 and 2.
When P2 is applied, a large electric field is generated between the two inks that sandwich the bubble 10, and when this reaches a breakdown voltage, a discharge phenomenon occurs, and the bubble 1o generated as described above explodes, releasing its energy. The droplet 11 is ejected from the injection port (
Figure 2 (C)).

In this case, as is clear from the @current waveform in FIG. 3(b), the discharge phenomenon occurs during L12, but the voltage VPz
If t, >t,' for the application time t, the process shown in Fig. 2(b) will occur again, and if t2 is set large, one injection cycle can be obtained as many times as the pixel diameter It can be modulated and halftones are easily possible. In addition, in the above, Vp engineering 1V
Although P2 is shown individually, it is also possible that V P x ” V P 2 and 1.t2 be one pulse.

FIGS. 4 and 5 are sectional views of main parts for explaining other embodiments of the present invention, and the embodiment shown in FIG.
A protrusion 12 is provided in the channel section sandwiching the electrodes 1 and 2 to form a narrow channel section 13.
is provided, the current density is increased in this narrow passage part 13, and air bubbles are generated in this narrow passage part 13, thereby,
This is intended to improve the efficiency of bubble generation in the process shown in FIG. 2(b). Note that the narrow passage portion 13 can be formed arbitrarily in the height direction, in one width direction, or in a combination of both.6 Furthermore, in the embodiment shown in FIG. , 2 is provided to eject ink in a direction perpendicular to the ink, thereby reducing liquid resistance during ejection.

Effects As is clear from the above explanation, according to the present invention, since a discharge point is not provided in the electrode part, - damage to the electrode does not occur;
Improves durability.

- High electric field strength can be obtained by applying voltage between bubbles.

- Recording voltage decreases because air bubbles are generated by Joule heat.

Effects such as this can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view of an essential part of an inkjet recording apparatus to which the present invention is applied, FIG. 2 is a diagram for explaining the operating principle of the present invention, and FIG. A diagram showing the voltage waveform applied to and the current waveform flowing between the electrodes,
FIGS. 4 and 5 are sectional views of essential parts for explaining the present invention in detail, respectively. 1... 1st electric 14 (independent type + lFA,), 2... 2nd
Electrode (common electrode), 3...upper plate, 4...lower plate, 5...
- Ink jet port, 6... Ink supply port, 7... Partition wall, 8... Recording signal, 9... Liquid chamber, 10... Air bubble, 1
1... Droplet, 12... Protrusion, ] 3... Narrow passage, 14
...Injection port. Part ■ Group - @ Bite - Partial figure

Claims (1)

[Claims] 1. A discharge port for discharging liquid, a liquid chamber that communicates with the discharge port and has portions with different cross-sectional areas, a pair of electrodes provided within the liquid chamber, and a discharge port for discharging the liquid between the pair of electrodes. 1. An inkjet recording apparatus comprising: a voltage applying means for applying a voltage so as to generate bubbles in a liquid in a room and then change the volume of the bubbles by discharge.