JPS62202740A - Ink jet recorder - Google Patents

Abstract

PURPOSE:To make the perfect removal of the clogging of a nozzle top part due to the solidification of ink possible, by a method wherein a heating unit is provided to a part of the wall of a pressure generating room and at the same time, an interconnecting opening is established between the pressure generation room and an ink supply room. Then, the heating unit is heated according to a recording signal and the ink is jetted. CONSTITUTION:A penetrating hole is provided to the thermal element 2 of a thermal head 1. A fluid resistance layer 4 is provided to its rear and a pressure generation room 5 is formed. The liquid tank 6 feeding pressure generating liquid is established to the back thereof. The recession interconnected to the penetrating hole 3 on the substrate 8 side of the thermal head 1 is covered with a plate 9. Then, an ink supply room 10 is formed and an ink jetting hole 11 is provided on the wall opposed to the penetrating hole 3. When a thermal element 2 is heated by applying voltage, bubbles 23 are generated on the contact surface of the liquid in the pressure generation room 5 and the thermal element. Liquid 25 is discharged from the penetrating hole 3 by those bubbles 23 and ink 26 is discharged from the jetting hole 9 to be flown. Because the ink jetting hole 11 part is filled with liquid after end of recording, despite operation shutdown for a long time, the clogging of the jetting hole does not occur.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to an inkjet recording device.

[Technical background of the invention and its problems]

BACKGROUND OF THE INVENTION The inkjet method has been one of the various recording techniques that have been extensively researched and developed for recording on plain paper. This means that the only consumable item is ink, that since ink is a liquid, it is easy to transport the ink to the recording head, that the recording energy requires only the energy required to move the ink, and that solid ink has a phase change. This is because it has the advantage of requiring less recording energy because it is not a recording method that utilizes , and it has attracted attention as a recording method suitable for printers because it can perform high-speed recording and instantaneous recording. .

However, despite these excellent features, this recording technology has not yet become widespread because it is difficult to manufacture inexpensive, high-density multi-heads that have actually been used, and also because the nozzle tips that eject ink are difficult to manufacture. This is because the biggest drawback of this method is that the ink solidifies when the device is stopped, causing nozzle clogging, making it impossible to always perform stable recording.

In '7, the valve jet method is used for density multi-head (Picture A, IEICE 63rd Research Conference Lecture Proceedings 8l-04-
5) has been announced. In this method, nozzles are installed on thermal elements arranged at high density at the tips of the nozzles, and the ink is ejected from each nozzle by utilizing the bumping of the ink itself as the temperature of the heating elements increases. This multi-head requires high-precision manufacturing technology to manufacture the head by providing a high-density thermal element at the tip of the head and pasting the multi-nozzle onto the thermal element in the bracket, making it expensive. Ta.

Furthermore, like the conventional inkjet method, no countermeasures were taken against clogging.

This was an attempt to solve the problem of clogging.

Electrostatic acceleration type slit jet method (Transactions of Institute of Electronics and Communication Engineers V, L J -68-CNa21985 P93), method using manual pump (Nikkei Electronics 1985
(February 11, 2015 issue, p. 153). In the former, many nozzles are combined into one slit to function as a nozzle.

This is an attempt to reduce clogging.

However, since this method requires a slit width similar to that of conventional nozzles (80 microns), the latter does not completely eliminate nozzle clogging.

This method uses a manual pump to eject the ink that is causing the clogging, eliminates the ink ejection failure, and restores the nozzle function. However, if some of the nozzles in the multi-nozzle were clogged, the pressure from the single manual pump would leak to the unclogged nozzles, making it impossible to completely eject the clogged ink.

For the above reasons, an inexpensive, stable, and high-density inkjet head has not yet been developed, and the nozzle tip becomes clogged due to ink coagulation.

There is no known method to completely remove it.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned drawbacks, and an object thereof is to provide an inexpensive and stable multi-head for inkjet without clogging.

[Summary of the invention]

In the present invention, the pressure generation chamber and the ink supply chamber are separated, a heating element is provided on a part of the wall of the pressure generation chamber, and a connection port is provided at nn between the pressure generation chamber and the ink supply chamber.

The heating element generates heat in accordance with a recording signal to generate pressure and eject ink.

〔Effect of the invention〕

According to this invention, because of the double cavity system in which the pressure generation chamber and the ink supply chamber are separated, there is little pressure loss and high-speed, high-efficiency recording is possible.

Furthermore, since a liquid other than water with a low heat of vaporization or a liquid with a low boiling point can be used as the pressure generating liquid, there is an advantage that highly efficient recording can be performed.

In addition, when the device is out of service for a long period of time, the ink chamber can be filled with pressure-generating liquid that does not contain coagulated or solid matter, except for the ink from the ink supply chamber, so that clogging does not occur. In the inkjet method, the pressure generation chamber and the ink chamber were the same, and the ink itself was used for pressure generation. Therefore, it is important to remove ink from the nozzles when the device is not used for a long period of time.

When guiding ink to the nozzle during the next operation.

This method has not been put to practical use because it causes air bubbles to get mixed into the pressure generating section, making it difficult to eject ink.

[Embodiments of the invention]

Next, one embodiment of this invention will be explained. first.

The actual recording head will be explained.

As the heat generating means, a conventionally commonly used thermal head in which each heating element is provided with a through hole is used. The liquid in contact with this thermal element is brought to a boil by the temperature rise of the thermal element, and the resulting pressure causes the liquid to be ejected through the through hole to the back of the head, and the ink is ejected along with the liquid from the ink layer provided on the back of the head to perform recording. It is something to do. At this time, a fluid resistance element is provided behind the thermal element, so that the pressure generated in the fluid does not escape behind the thermal element.

After recording, the pressure-generating liquid tank and ink tank are raised and lowered, and hydrostatic pressure is applied to suck ink from the ink ejection hole into the ink tank.The ink ejection hole is then filled with pressure-generating liquid to prevent clogging. It's something I lost. This pressure-generating liquid does not contain any coagulated or solid matter, and the ink ejection holes will not be clogged even if the device is stopped for a long period of time. However, the ink ejection holes are always filled with liquid due to the hydrostatic pressure of the liquid or the surface tension of the liquid in the ink ejection holes.

When printing is resumed after the apparatus has been stopped for a long period of time, the pressure-generating liquid tank and the ink tank are moved up and down, and when the pressure-generating liquid is sucked from the ink ejection hole by hydrostatic pressure, the surrounding area is filled with ink.

A mechanical pump that generates negative pressure and positive pressure may be used to suck and inject these liquids or inks.

The above steps are automatically performed when the user turns the printer off or on.

Next, details of an apparatus according to an embodiment will be explained using the drawings. 1st Ug is a schematic cross-sectional view of the inkjet device of the present invention.

FIG. 1(a) shows an overall view of the recording section. A through hole (2) is provided in the thermal element (2) of a conventional thermal head (2), and a fluid resistance M (2) is provided behind the through hole (2) so as to seal the recessed portion in which the thermal element (2) is provided, thereby forming a pressure generating chamber (2). A liquid tank 0 for supplying pressure-generating liquid to the pressure-generating chamber (2) is installed behind it. This liquid tank ■ has a liquid inlet ■.
A liquid (not shown) that does not contain coagulates or solids is injected as a pressure-generating liquid through this inlet. On the other hand, on the substrate (C) side of the thermal head (2), a recess is provided to connect with the first through hole (2). The recess is covered by a plate 0) and forms an ink supply chamber (10). An ink ejection hole (11) is provided on the wall of the ink supply chamber (10) opposite to the through hole (2) coaxially with the through hole (2). Ink supply chamber (10
) is supplied with ink from an ink tank (13) through an ink supply path (12) provided on the substrate (2). This ink tank (13) is provided with an ink inlet (14), and ink is supplied from an external ink tank (not shown). The depth of the ink supply chamber (10) must not be too large compared to the diameter of the through hole (2).

The depth of the ink supply chamber (10) is preferably equal to or less than the diameter of the through hole (2).The reason for this restriction is as follows.
When the depth of the ink supply chamber (10) becomes larger than the diameter of the through hole (2), the rapid liquid movement within one through hole (2) or the pressure caused by the moving liquid diffuses into the ink supply chamber (10), causing the ink ejection hole ( 11) to the ink.

This is because it becomes impossible to provide sufficient ejection force.

Alternatively, the ink supply chambers (io) may be provided independently corresponding to the ink ejection holes (11).

It may be provided in common. 15 is an ink spout (11)
was set opposite to. A recording paper that receives ink droplets.

FIG. 1(b) shows an enlarged view of the area around the ink ejection holes of the recording head. On the board made of 0.2mm thick iron plate,
Depth 60μ to form ink supply chamber (1o) in advance
A recess with a width of 500 μm and an ink supply path (12) connected to this recess are etched to a depth of 0.1 nn. Next, a metal layer for heat dissipation (not shown) is vapor-deposited to a thickness of 1 micron on the opposite side of the substrate, and a further 20 μs
A thick polyimide layer (16) is formed. Next, the polyimide layer (16), the metal layer, and the substrate (c) are sequentially etched to form a through hole (2) with a diameter of 60 μs.

On the polyimide surface with the through holes created in this way,
A resistive film (1) is formed to a thickness of 5000 by sputtering, and a metal lead layer (17) is deposited on it to a thickness of 7 μs. When this lead layer is deposited, at the same time, a contact layer (not shown) is also deposited between adjacent elements. Thereafter, lead electrode patterning, etching, thermal element patterning, and etching are performed to form a thermal element and lead electrodes connected thereto. Thereafter, sputtering for waterproof protection ((18)) is performed to complete the basic process of manufacturing the recording head. The thickness of this lead layer is the pressure generation chamber (5
) becomes part of the depth. A fluid resistance layer (4) composed of a metal filter is uniformly adhered onto the protective film (18). (The thickness of the lead layer and the thickness of the adhesive layer are not shown)
is the depth of the pressure generation chamber ■. On the other hand, above the recess forming the base Fi(B) ink supply chamber (10), there is an 80I! which is larger than the through hole ■! ! A thin metal having a thickness of 60 microns and having a hole that will become the ink ejection hole (11) in a is glued so that the center of the through hole (2) and the ink ejection hole (11) are coaxial. The recording head is configured in this way.

FIG. 1(c) is a cross-sectional perspective view of this multi-recording head. The ink supply path (12) and the ink supply chamber (10) are
It is provided in common for each thermal element (2).

Further, the through holes (2) in each thermal element of the recording head may be provided in one thermal element as shown in FIG. 2-(a), or in large numbers as shown in FIG. 2-(b). It's okay to be hit.

Next, referring to FIG. 3, the process of ejecting ink by the above recording head will be explained. FIG. 3(a) shows the initial state where a voltage is applied to the thermal element (2). When the heating element generates heat and its temperature rises rapidly, bubbles (23) are generated at the contact surface between the heating element and the liquid in the pressure generating chamber (2). Due to the rapid increase in volume due to vaporization, the liquid in the pressure generation chamber 0 is prevented from flowing out behind by the liquid resistance layer (a), so it moves rapidly inside the through hole ■, causing a fast flow. will occur. This flow is extremely fast, and the depth of the ink supply chamber (10) is almost equal to the diameter of the first through hole (3), so the ink between the through hole The ink is pushed or pulled in by the flow, creating protrusions on the ink jetting port. Figure 3(b) shows
The discharge state is shown. The generated air bubbles (23) reach the maximum, causing the liquid (25) to be rapidly discharged from the first through hole (2). Due to this ejection pressure, the ink (26) is vigorously ejected from the ink ejection hole (2) and starts flying.

FIG. 3(c) shows a state in which the voltage applied to the thermal element (2) is turned off; the grown bubble (23) is cooled and begins to shrink in the direction of the arrow. At this time, the liquid MO is bubbles (23)
Negative pressure occurs due to volume reduction. On the other hand, the fluid resistance layer (to)
Therefore, the liquid according to the negative pressure is transferred from the liquid tank 0) 8■
cannot be supplied. Therefore, the liquid (25) that was being discharged is sucked into the liquid layer 0. As a result, a constriction occurs at the base of the ejection portion, and a portion of the leading portion is separated and ejected together with the ink. On the other hand, the ink (30) suddenly ejected from the ink ejection holes ejects and flies in the direction of arrow A together with the separated liquid (29).

FIG. 3(d) shows the final state in which the recording process has been completed and the thermal cord (2) has cooled. Six bubbles (23) shrink in the direction of the arrow and suck the liquid (32) into the through hole. On the other hand, the liquid is gradually replenished into the scattering layer (1) via the fluid resistance layer (1) by the generated negative pressure and hydrostatic pressure. The ink layer is also sucked by this negative pressure, forming an ink orifice (33) in the ink ejection hole. Therefore, a negative pressure is also generated in the ink layer, and the ink moves from the ink supply path in the direction of arrow (B) to be replenished. Also, the ink (34) and liquid (3) that separated and flew
5) flies in the direction of arrow A, adheres to the recording paper, and performs recording.゛The diagram used in the above explanation schematically shows the recording process, and when the pressure-generating liquid and the ink solvent are the same, the ink diffuses into the liquid at the interface and mixes together. do. Therefore, the flying ink droplets and the liquid in the ink droplets do not exist separately. Furthermore, when the liquid is sucked after ejecting the ink, the liquid and ink are mixed at the interface. Therefore, the density of the recording dots during continuous recording is determined by the amount of ink supplied to the ink layer (■) through the ink supply path and the amount of liquid supplied through the fluid resistance layer. Become.

In addition, the pixel density during continuous printing is different from the pixel density after stopping. In other words, the pixel density after the image is still is increased by the amount of ink diffused into the liquid. This difference can be solved by performing dummy injection after a long-term stop or after setup, but before starting the printing operation.

If the pressure-generating liquid and the ink solvent are incompatible, the two will be clearly separated at the interface, and the ink will not diffuse into the liquid.

In this case, the density within the image point tends to be uneven, so
Care must be taken in selecting the solvent.

FIG. 4 shows the state of the liquid and ink in the print head when the printing apparatus is stopped after printing is completed.

FIG. 4(a) shows the state of liquid and ink in recording during use, with the liquid in liquid layer 0 and the ink layer (1
0) The ink inside exists with the through hole (2) of the thermal element as a boundary. Figure 4(b) shows the state of the liquid and ink when the apparatus is stopped after recording, and the ink layer (41) is completely replaced with liquid, and the ink ejection hole (11) is also filled with liquid. has been done. Therefore, even if the printer is stopped for a long time, the liquid only evaporates, the ink does not evaporate, and the ink ejection holes do not become clogged. Ink is completely drained from the ink passage in the recording head through the ink supply path (12) and replaced with liquid. The ink is removed using the hydrostatic pressure of the ink tank (not shown) by lowering the ink tank below the recording head section, and the liquid is removed from the ink layer by raising the liquid tank (not shown) to the top. supply inside. The above operations may also be performed using a pump.When the device is stopped for a long period in this way,
Contrary to the above process.

The liquid for pressure generation is passed from the ink ejection hole (11) to the through hole■
At the same time, the ink layer (10) is filled with ink to start recording.

According to the present invention, it is possible to manufacture an inkjet recording head using substantially the same manufacturing process as that of a thermal head manufactured in a conventional mass-produced manner, and it is possible to supply an inexpensive and stable inkjet recording head. In addition, when the recording device is at rest, all ink is removed from the ink ejection holes, and the ink ejection holes can be filled with liquid that does not contain coagulates or solids, so there is no need to worry about clogging. Since the liquid and ink were the same, it was not possible to remove the ink from the nozzle during rest because it was necessary to prevent air bubbles from entering the pressure generating section. In addition, in this inkjet method, the pressure generation chamber and ink supply chamber are separated, so there is little pressure loss, and a liquid other than water with a low boiling point and low heat of vaporization can be used as the pressure generation liquid, resulting in high speed and high efficiency recording. is possible.

The present invention is not limited to the above example, but includes a pressure generation chamber in which the heating element is part of the wall, and an ink supply chamber,
A recording method in which both chambers are connected by a connecting path, a liquid containing no solids or coagulated substances is supplied to the pressure generating chamber, and the ink in the ink chamber is caused to fly by the pressure generated within the pressure generating chamber is beyond the scope of the document. It is included in this invention to the extent that it does not.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional diagram ρ of an inkjet device according to an embodiment of the present invention, FIG. 2 is a schematic diagram showing the arrangement of through holes of a thermal element, and FIG. 3 is a diagram showing the steps up to ink flying. ,
FIG. 4 is a diagram showing the state inside the print head when the printing apparatus is inactive. DESCRIPTION OF SYMBOLS 1...Thermal head 2...Thermal element 3...Through hole 11...Ink ejection hole 4...Fluid resistance layer 6...Liquid tank 12...Ink supply path 13... Ink tank 23... air bubbles
5...Liquid layer 10...Ink layer Agent Patent attorney Nori Chika Ken Yudo Kikuo Takehana

Claims (3)

[Claims] (1) A pressure generating chamber in which the heating element is part of the wall, an opening for ejecting ink on one side, and an opening connected to the pressure generating chamber on the other opposing side; an ink supply chamber in which two openings are located coaxially; a connection path connecting the pressure generation chamber and the ink supply chamber and having a cross-sectional area smaller than those of the pressure generation chamber and the ink supply chamber, which face each other; An inkjet comprising means for supplying ink to the pressure generation chamber and the ink supply chamber, and a heating element driving means for causing the heating element to generate heat in accordance with a recording signal to generate pressure in the pressure generation chamber. Recording device. (2) The inkjet recording apparatus according to claim 1, characterized in that only a pressure-generating liquid that does not contain or precipitate solids is supplied to the pressure-generating chamber. (3) The inkjet recording apparatus according to claim 2, further comprising means for replacing ink in the ink supply chamber with a pressure-generating liquid.