JPH0281634A - Ink jet recording apparatus - Google Patents

Abstract

PURPOSE:To make the title apparatus nozzleless and to enhance the reliability to clogging by constituting a slitlike emitting part for simultaneously emitting a plurality of liquid droplets, the heating means provided in an ink chamber and the electric field generating means for generating an electric field provided at the position opposed to the heating means. CONSTITUTION:Recording paper 11 is moved between a ground electrode plate 5 and a bias electrode 7. In such a state that there is no printing signal, ink constitutes a meniscus between ground electrodes to be held. When the printing signal is applied to a heater, the sudden gasifying phenomenon of the ink by the quick heating of the surface of the heater is generated to form an air bubble 12. The air bubble 12 is further expanded by this gasifying phenomenon and, when no electric field is applied to the bias electrode 7 at this time, no flight of the ink is generated. When the electric field due to the bias electrode 7 is applied, the expanded ink becomes a stringing state and flies at last to be adhered to recording paper 11. Subsequently, the air bubble is contracted by the extinction of the printing signal to become an extinction state.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inkjet recording device, and more particularly, to a full-line multi-ink on-demand inkjet head, which is applicable to printing devices such as printers.

BACKGROUND ART Conventionally, in inkjet recording apparatuses, an electrostatic suction method that uses electrostatic force and a bubble jet method that uses a vaporization phenomenon are known.

On the other hand, recent digital recording image devices are becoming more and more dense6. For example, laser printers have a
0dpi, 300-360dp for thermal printers
i is being commercialized.

If this is configured with a full line multi-head, A4
(210aa width), 300dpi is 248
For 0 dots and 400 dpi, a head count of 3300 dots is required. In addition, in a DOD head for high-resolution printing of 300 to 400 dpi, droplets are formed from a nozzle diameter of about 30 to 50 μm at a flying speed of about 3 to 5 m/s, so the kinetic energy of the droplets is small. Due to slight ink adhesion to the nozzle, dryness, adhesion of dust, etc.
The jetting direction became unstable and the image quality (white stripes) was unreliable. Furthermore, when left unused for long periods of time, it was necessary to deal with clogging of heads with thousands of nozzles, and reliability was an issue that remained with high resolution and full multiplication.Furthermore, with conventional static In the electric attraction method, images are produced using a bias voltage (or accelerating voltage) of several kilovolts and switching of several hundred volts, so a high-voltage switching circuit and
The high resolution and multi-head design required multi-channel circuits, which had the disadvantage of increasing production costs.

■--The present invention was made in view of the above-mentioned circumstances.
In particular, when putting the high-density full-line on-demand inkjet system into practical use, a slit-shaped opening is used to create a drive unit (ink droplet generation and trigger for flight) that responds to the image signal.
Utilizes the ink vaporization phenomenon that can be divided and driven even with a power supply voltage of about 24V, similar to the thermal head, and the high-cost high-voltage switching circuit can be configured with one circuit for multiple heads as a bias voltage, and furthermore, it is stable. The purpose of this invention is to provide a driving method for ejecting ink.

In order to achieve the above object, the present invention includes a slit-shaped ejection section for ejecting a plurality of droplets simultaneously, an ink chamber provided in communication with the ejection section, and an ink chamber provided within the ink chamber. and an electric field generating means for generating an electric field provided at a position facing the heating means. This device is characterized by supplying a plurality of pulse signals to the heat generating means. Hereinafter, the present invention will be explained based on examples.

FIG. 1 is a partially cutaway overall configuration diagram for explaining one embodiment of the present invention, and FIG. 2 is a partially enlarged view.
is the base, 2 is the substrate, and 3 is the heater surface.

4 is a separator, 5 is a ground electrode plate, 6 is a spacer,
7 is a bias electrode, 8 is a high voltage power supply, 9 is an ink supply tube,
Reference numeral 10 indicates an arrow indicating the direction of movement of the recording paper.A heater surface 3 and a pattern for arranging it are formed on a substrate 2 mounted on a base 1.

Additionally, since it is a multi-head device, a driver chip can be placed on the board and driven. Since the driving waveform is short, for example, about 5 μs, divided driving can be performed to reduce the number of driver chips. Form a separator 4 for dividing between each heater, for example, 300 d
The diameter of the heater surface of pi is 55 μm, and a separator is arranged so as to surround the circumference, and a band-shaped notch of about 10 μm is provided. The height is 0.5 to 2 of the diameter of the heater surface.
It is composed of about twice as much. If a photosensitive resin is used as the material for the separator, microfabrication can be performed. A ground electrode plate 5 is placed on the upper surface of the substrate via a spacer 6, and the spacer 6 forms a band-shaped ink reservoir surrounding the heater array.

An ink supply pipe for supplying ink from the outside is connected to this ink reservoir. The ground electrode plate 5 opens into a slit (about 100 to 200 μm in width) when the power is turned on, and moves to close the slit when the power is turned off, functioning as a shutter to prevent ink from evaporating. . A gap of about 50 μm was created between the ground electrode plate and the separator, and the ink filled this space.
The liquid level of the ink tank is configured so that the slit-shaped opening (ground electrode plate) is O, and the upper surface of the separator is kept from being exposed even if there is a meniscus due to surface tension.

The bias electrode 7 is disposed at a position approximately 1 m above the ground electrode, and a voltage of several KV is applied from a high-voltage power supply 8 to apply a bias electric field for attracting ink droplets.

Recording paper (not shown) is fed in the direction of arrow 10 between the ground electrode and the bias electrode.

3(a) to (e) are diagrams for explaining the operation of the present invention. In each figure, 3 is a heater surface, 4 is a separator, 5 is a ground electrode plate, and 7 is a bias electrode. The shaded area is ink. Recording paper 11 moves between ground electrode plate 5 and bias electrode 7. When there is no print signal, the ink is held in a meniscus between the ground electrodes (Figure 3a). When the print signal is applied to the heater, the ink rapidly vaporizes due to the rapid heating of the heater surface. This occurs and bubbles 12 are generated (FIG. 3b).

The bubbles 12 due to this vaporization phenomenon further expand (FIG. 3(c)). At this time, if the electric field is not applied by the bias electrode 7, the ink will not fly. When the bubble is in a string state (Fig. 3d), it finally flies off and adheres to the recording paper 11.Then, as the print signal disappears, the bubble contracts and disappears (Fig. 3d). Figure 3 e).

4 to 6 explain the operation when several continuous pulses are applied as a print signal for one dot, and FIG. 4 is a waveform diagram in the case of only one pulse as described above, The pulse after 1 ms is the pulse of the next dot signal.

The phenomenon in this case is as described above, but the state of the bubbles on the heater surface 3 will be illustrated as time passes.

The result is as shown in FIG. 6(a). Instead of the pulse shown in Fig. 4, a pulse with a pulse width of 4 μs is used for 25 seconds as shown in Fig. 5.
FIG. 6(b) shows the state of bubbles on the heater surface when the gas is supplied to the heater surface at μs intervals.

The state of the meniscus at that time is shown in FIG. 6(C).

The bubble expands in about 15 μs due to the first pulse, and at this time, the applied electric field causes the ink to fly, and as the bubble contracts and disappears, rapid heating occurs due to the second pulse, causing the ink to evaporate again. Flight occurs. During several times this time (for example, the 25 μs mentioned above), the recording paper does not move much, so the flying ink caused by several pulses becomes a dot of darker ink, and by controlling the number of pulses, recording with gradation is achieved. Can be done. Furthermore, from the experimental results, 20
The meniscus could be controlled even with three consecutive pulses with an interval of μs or more.

Effects As is clear from the above description, according to the present invention, since the ink ejection opening is slit-shaped, there is no nozzle, and even a high-density full-line head can easily ensure reliability against clogging. In addition, problems such as drying, evaporation, and changes in ejection direction due to ink stains around the nozzle edges (deterioration of image streaks, etc.) do not occur, and furthermore, by controlling the number of pulses, recording with gradation is possible. be able to.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway schematic configuration diagram for explaining the present invention in detail, FIG. 2 is a detailed enlarged view of the electrode portion of FIG. 1, and FIG. 3 is an operation explanatory diagram. FIGS. 4 to 6 are explanatory diagrams of operations when the number of pulses is changed. 2... Substrate, 3... Heater surface, 5... Ground electrode plate, 7... Bias electrode, 8... High voltage power supply. Fig. 4 (Ol Fig. 6 (b-15, after its 30μs, after 35μS, after 45PS, after 6C) after us, after 80μS, 2221, knee, - 102214 = ≧ - - this: two To= Yoha. 1ha, Gohaego J℃2 Go\No〇=

Claims (1)

[Scope of Claims] 1. A slit-shaped ejection portion for ejecting a plurality of droplets simultaneously, an ink chamber provided in communication with the ejection portion, and a heat generating means provided within the ink chamber; An inkjet recording apparatus comprising an electric field generating means for generating an electric field, which is provided at a position facing the heat generating means. 2. The inkjet recording apparatus according to claim 1, wherein a plurality of pulse signals are supplied to the heating means to eject one droplet.