JPH07314687A - Ink-jet recording head - Google Patents

Abstract

PURPOSE:To obtain an ink-jet head enabling high speed recording by an inexpensive constitution, by providing an air holding chamber possessing an air producing heating resistor and having a gas-liquid interface to absorb a pressure change in a common liquid chamber part in the rear of a nozzle. CONSTITUTION:A heating resistor 112 is formed on a board, Ti and Al are metallized continuously, a heat acting part 111 is made by preparing a pattern and at the same time, the heating resistor 112 is manufactured on a part becoming an air holding chamber 208. Then SiO2, Ta2O5 and Ta are accumulated continuously, which are made into a protective film by performing patterning, a dry film is laminated and a nozzle 201, a part of a common liquid chamber 204 and an air holding chamber 208 becoming a gas-liquid interface are manufactured by a photolithographic process. The air holding chamber 208 is arranged on a position corresponding to a common liquid chamber 204 on the rear of a nozzle 201. Then a dry film is laminated to glass having an engraved part becoming a part of the common liquid chamber 204 and a through hole becoming an ink supply port and patterning is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a droplet ejection head for forming flying droplets by ejecting a liquid from an orifice and performing recording using the flying droplets, particularly an ink jet recording head utilizing thermal energy. Regarding

[0002]

2. Description of the Related Art Ink jet recording method is to eject ink (recording liquid) from an orifice provided in a recording head,
This is a recording method in which recording is performed by adhering this to a recording material such as paper, and noise generation is extremely low, high-speed recording is possible, and there is no need to use a specially configured recording paper. And various types of recording heads have been developed.

Among them, the recording head of the type in which thermal energy is applied to the ink and ejected from the orifice is
It has advantages such as good responsiveness to a recording signal and easy arrangement of a large number of orifices at high density.

However, in spite of the so-called bubble jet recording head having such advantages, various problems have occurred while the recent demand for higher speed recording has increased.

FIG. 8 shows a schematic perspective view of a bubble jet recording head. An orifice (202) provided for ejecting ink to form flying droplets and the orifice (2
02) for communicating ink with the nozzle (20)
1), a thermal action part (111) for ejecting ink to form flying droplets, a common liquid chamber (204) communicating with the nozzle, and ink is supplied to the common liquid chamber (204). It is composed of an ink supply port (206).

The recording principle of such a bubble jet head will be described below (FIG. 4).

The ink is rapidly heated by the heat acting portion (111), and the ink in the vicinity of the heat acting portion exceeds the overheating limit and is vaporized (FIG. 4-b). The ink is pushed out to the orifice side and the common liquid chamber side by the pressure increase at that time. The ink extruded from the orifice side forms an ink column in a columnar shape. After that, the ink column separates from the ink in the nozzle (202), becomes a flying droplet, and jumps toward the recording material. The ink in the nozzle forms a meniscus and gradually returns due to the capillary force (FIGS. 4-e, f). This one cycle ends and the next cycle starts.

In order to perform high-speed recording on a bubble jet head having such a recording principle, a method of increasing the number of nozzles, increasing the response frequency of the head, or adopting both of them is adopted. Has been taken.

Increasing the response frequency of the head is achieved by reducing the amount of receding of the ink meniscus and increasing the speed at which the ink meniscus returns by the capillary force. As a method for reducing the receding amount of the ink meniscus, an improvement is made by mounting a fluid diode behind the nozzle. Further, as a method of increasing the speed at which the ink meniscus returns by the capillary force, the length of the nozzle is shortened. However, in reality, these two methods are often used together to perform high-speed recording.

Here, a method of driving the bubble jet head will be described. The heat pulse used for heating the bubble jet head is usually several μs to several tens μs, and the maximum instantaneous current flowing at that time is several tens of milliamps to several hundreds of milliamps. Also, the number of nozzles is usually several tens to several thousands, and if all nozzles are driven at once, the current that flows will become too large.Therefore, a method of dividing all nozzles into several blocks and driving them in time Taken (time division drive). Figure 5
Shows the state of the pulse applied to each block.
Normally, the number of nozzles belonging to the same block is determined so that the currents flowing simultaneously are about several amperes.

However, even if the time-division driving is performed by using the high-speed recording head as described above, the expected effect is not always obtained. FIG. 6 shows the meniscus recovery time of the high-speed head driven in this manner. In FIG. 6, the horizontal axis represents the nozzle position (block NO), and the vertical axis represents the time from when the heating pulse is applied until the retracted meniscus is restored. As described above, when the driving order is delayed, the time required for the meniscus to be restored becomes long.

The reason why the bubble jet head shown in FIG. 8 exhibits the characteristics shown in FIG. 6 will be described. When the first block is driven, the ink is rapidly heated and vaporized, and the pressure increase at that time pushes the ink toward the orifice side and the common liquid chamber side, forming flying droplets and retracting the meniscus. And the meniscus tries to recover by the capillary force. After that, when the second block is driven and the ink is rapidly heated, the ink is vaporized, and the pressure increase at that time causes the ink to be uniformly pushed out to the orifice side and the common liquid chamber side. At this time, as described above, the nozzle of the first block is when the meniscus is about to return,
The ink pushed out to the common liquid chamber side of the second block is the first
Helps block return to meniscus. In the vicinity of the second block, the pressure of the common liquid chamber decreases, and the time required for the meniscus to recover becomes longer than that in the first block. Next, when the third block and the fourth block are driven, the number of nozzles whose meniscus is returning is increasing. Therefore, the ink pushed toward the common liquid chamber is directed toward the nozzle whose meniscus is returning. Flowing. For this reason, the backward movement of the meniscus is greater in the block driven later than in the block driven previously. Further, at this time, ink flows from the common liquid chamber toward the nozzle where the meniscus is returning, and the pressure in the common liquid chamber decreases. For these two reasons, it takes a long time for the meniscus to return to the block driven later. It is known that such a pressure fluctuation in the common liquid chamber is absorbed by the air layer, but the present inventor confirmed by experiments that the degree of the effect varies depending on the position of the air layer. The most effective place is behind the nozzle, and if there is an air layer here, high-speed driving is possible even in time-divisional driving regardless of the size of the heating resistor and the size of the common liquid chamber. . However, it is not easy to stably retain the air in this place, and there is a problem that the air disappears due to the recovery operation for preventing the clogging of the nozzle.

Further, it has been attempted to solve the above problems by introducing air into the common liquid chamber from the orifice side. However, in this method, the air introduced from the orifice side is not fixed in the common liquid chamber and can move freely, so it often enters the nozzle and does not discharge, or the air that has been put in is discharged. There is a problem of being lost.

Further, it has been proposed to hold air above the common liquid chamber to prevent an instantaneous pressure drop in the common liquid chamber. However, depending on the size of the common liquid chamber, the size of the heat-generating resistor that heats the ink, and the like, a perfect effect is not always exhibited.

[0015]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an ink jet head capable of high-speed recording with an inexpensive structure. .

[0016]

An ink jet head capable of high speed recording with an inexpensive structure can be achieved by the following structure.

An orifice provided for ejecting the recording liquid to form flying droplets, and a heat acting portion which is in communication with the orifice and is a portion where thermal energy for forming the droplets acts on the liquid. In an ink jet recording head provided with a nozzle that is a part of the configuration and a common liquid chamber that communicates with the nozzle and supplies the recording liquid, a pressure fluctuation is applied to a portion of the corresponding common liquid chamber behind the nozzle. An ink jet recording head having an air holding chamber having a gas-liquid interface for absorbing and having a heating resistor for generating air.

[0018]

According to the present invention, an air holding chamber having a gas-liquid interface for absorbing pressure fluctuation is provided in the corresponding common liquid chamber portion behind the nozzle, and the air is stably present. In addition, by providing the heating resistor for air generation in the air holding chamber, high speed recording is possible.

The present invention will be described in more detail below.

In the present invention, when a voltage pulse is applied to the heating resistor, the temperature of the heat acting portion rises and the ink near the heat acting portion is vaporized. At this time, the air dissolved in the ink is also deposited at the same time. In the normal case, the deposited air is discharged together with the flying droplets from the orifice and remains in the nozzle without causing any adverse effect. The present invention is intended to stably retain the air that precipitates at this time.

FIG. 3 shows the shape of the heating resistor and electrodes of the present invention. A heat acting portion 111 for forming flying droplets and a heating resistor 112 provided in the air holding chamber are connected in series between the individual electrode 114 and the common electrode 113 (not common in this figure). ing. Therefore, the two heating resistors are heated at the same time when the voltage pulse is applied. However, as shown in FIG. 2, since the air is normally held in the air holding chamber, the heating resistor inside the air holding chamber does not foam. However, as described above, a recovery operation or the like for preventing clogging (usually, the thickened ink remaining in the nozzle is sucked by sucking from the orifice side).
When the air in the air holding chamber is replaced with ink, the bubbles are generated and the dissolved air is deposited. Unlike the thermal action part provided in the nozzle that forms flying droplets outside the orifice with low resistance, the heating resistor inside the air holding chamber that moves the fluid to the common liquid chamber side with high resistance foams stably. I can't. For this reason, the deposited air remains in the vicinity of the heating resistor and acts as an absorber of the pressure fluctuation generated in the heat acting portion. Therefore, according to the present invention, the air layer as the pressure fluctuation absorber can be stably created.

[0022]

EXAMPLES The present invention will be described in more detail based on the following examples.

Example 1 The ink jet head shown in FIG. 1 was manufactured as follows.

A SiO ₂ film having a thickness of 3 μm was formed by thermal oxidation of a Si wafer to obtain a substrate. HfB ₂ as a heating resistor was formed on the substrate to a thickness of 1500 angstrom by sputtering, and then Ti 5 was formed by electron beam evaporation.
0 Å and Al 6000 Å were continuously deposited.

A pattern is formed by a photolithography process,
The heat acting parts were made at a pitch of 360 DPI. At the same time, a heating resistor was produced in the portion that will become the air holding chamber. At this time, the size of the heating resistor in the heat acting portion is 28 μm.
It is a rectangle of × 110 μm, 512 heating resistors are arranged, and the size of the heating resistor in the air holding chamber is 28 μm.
m × 28 μm, similarly 512 pieces were arranged. FIG. 3 shows the wiring pattern at this time. The heating resistors are connected in series, and both heating resistors generate heat when an electric pulse is applied. Next, by sputtering again, SiO ₂ , Ta ₂ O ₅ , and Ta are each made to have a thickness of 1.5 μm.
m, 500 angstroms, 5000 angstroms were continuously deposited, and patterned by a photolithography process and a dry etching process to form a protective film.

A negative type dry film (photosensitive resin) having a thickness of 25 μm was laminated, and a nozzle, a part of the common liquid chamber and an air holding chamber to be a gas-liquid interface were prepared by a photolithography process. The air holding chamber was arranged at a position corresponding to the common liquid chamber behind the nozzle, and the opening on the common liquid chamber side was set to 20 μm as shown in FIG. 2 (FIG. 2 (b)).

Next, the engraving part (5
(0 mm x 4 mm) and a glass having a through hole to serve as an ink supply port is laminated with a negative type dry film (photosensitive resin) and then patterned by a photolithography process,
It was bonded to the above-mentioned substrate.

Next, the driver IC die-bonded on the printed board and the substrate were electrically connected by wire bonding to form an ink jet head.

The ink jet head manufactured in this manner was formed into blocks for every 64 nozzles adjacent to each other, and a total of 8 blocks were driven. FIG. 7A shows meniscus recovery times of an inkjet head having no air holding chamber and the inkjet head according to the present invention. As is clear from this figure, the inkjet head according to the present invention can be driven at a high speed, and a good printing state was exhibited even with an ejection frequency of 6 kHz.

Example 2 A 3 μm thick SiO ₂ film was formed by thermal oxidation of a Si wafer to obtain a substrate. HfB ₂ as a heating resistor was formed on the substrate to a thickness of 1500 angstroms by sputtering, and then Ti 50 angstroms and Al 6000 angstroms were successively deposited by electron beam evaporation.

A pattern is formed by a photolithography process,
The heat acting part was produced at a pitch of 200 DPI. The size of the heating resistor at this time was a rectangle of 34 μm × 150 μm, 512 heating resistors were arranged, and the size of the heating resistor in the air holding chamber was 30 μm × 30 μm.

Then, again by sputtering, SiO ₂ , T
a ₂ O ₅ and Ta were successively deposited at 1.0 μm, 500 Å and 3500 Å, respectively, and patterned by a photolithography process and a dry etching process to form a protective film.

A negative type dry film (photosensitive resin) having a thickness of 50 μm was laminated, and a nozzle, a part of the common liquid chamber, and an air holding chamber to be a gas-liquid interface were prepared by a photolithography process. The air holding chamber is arranged at a position corresponding to the common liquid chamber behind the nozzle, and the opening on the common liquid chamber side is 45
.mu.m, and a common portion for every four nozzles was provided on the opposite side of the nozzle.

Next, the engraving part (8) which is a part of the common liquid chamber
(0 mm x 4 mm) and a glass having a through hole to serve as an ink supply port is laminated with a negative type dry film (photosensitive resin) and then patterned by a photolithography process,
It was bonded to the above-mentioned substrate. Next, the driver IC die-bonded on the printed board and the substrate were electrically connected by wire bonding to form an inkjet head.

The ink jet head thus manufactured was formed into blocks for every 32 nozzles adjacent to each other, and a total of 16 blocks were driven. FIG. 7B shows the meniscus recovery time of the inkjet head having no air holding chamber and the inkjet head of the present invention. As is clear from this figure, the ink jet head provided with the air holding chamber was capable of high-speed driving, and showed a good printing state even at the ejection frequency of 4 kHz.

[0036]

According to the present invention, the air holding chamber is provided behind the common liquid chamber at a position corresponding to the nozzle, and the heating resistor for stably holding the air is provided, so that high speed driving is achieved. It is now possible to provide a possible inkjet head. Further, according to this method, the substrate size can be reduced, and a high-speed drive head can be provided at a lower cost.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a bubble jet recording head of the present invention.

2A and 2B are cross-sectional views of a specific embodiment of the present invention.

FIG. 3 is a view showing a heating resistor and an electrode pattern according to the present invention.

FIG. 4 is an explanatory diagram of a discharge principle of a bubble jet recording head.

FIG. 5 is an explanatory diagram for driving a bubble jet head.

FIG. 6 is a graph showing meniscus recovery time of a conventional bubble jet recording head.

7A and 7B are graphs showing meniscus recovery time of a bubble jet head according to the present invention.

FIG. 8 is a typical perspective view of a conventional bubble jet recording head.

[Explanation of reference numerals] 101 substrate 111 thermal action part 112 heating resistor 113 common electrode 114 individual electrode 201 nozzle 202 orifice 203 nozzle wall 204 common liquid chamber 205 top plate 206 ink supply port 207 electrical connection part 208 air holding chamber

Claims (1)

[Claims] 1. An orifice provided for ejecting a recording liquid to form flying droplets, and an orifice provided in communication with the orifice,
Inkjet recording provided with a nozzle having a heat acting portion, which is a portion where thermal energy for forming the droplet acts on the liquid, as a part of the configuration, and a common liquid chamber communicating with the nozzle and supplying a recording liquid. In the head, an air holding chamber having a gas-liquid interface for absorbing pressure fluctuation is provided in a corresponding portion of the common liquid chamber behind the nozzle, and the air holding chamber has an air generating heating resistor. An inkjet recording head comprising: