JPH07186403A - Double liquid chamber head - Google Patents

Abstract

PURPOSE:To improve a printing quality and make reproducibility of density gradation favorable, by a method wherein a solution which is in the first flow path and does not contain a coloring matter and a solution which is in the second flow path and contains the coloring matter are mixed up with each other and the mixed solutions are discharged at a time. CONSTITUTION:A solution obtained by mixing up a coloring matter such as the coloring matter or a pigment with a solvent is foamed or antifoamed every pixel. Out of the mixed solution, which is foamed or antifoamed, only the solution, which is in front of a bubble, is emitted to a medium by making use of an on-demand type ink-jet head and a letter or an image is made printable. On this occasion, the first flow path possesses a discharge device comprised of a heating resistor, the second flow path is opened in the vicinity of the first flow path, at the time of discharge, the solution which does not contain a coloring matter and is in the first flow path and the solution which contains the coloring matter and is in the second flow path are mixed up with each other by changing quantities of them. As for the solution containing the coloring matter, positive water head pressure is applied to the solution containing the coloring matter, the solution containing the coloring matter is supplied to the discharge part by a method wherein a device comprised of the heating resistor is provided in the second flow path.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an ink jet head and an apparatus using the same, and more particularly, to improvement of ink jet head characteristics and improvement of an ink jet apparatus capable of printing multi-valued images.

[0002]

2. Description of the Related Art The ink jet method (that is, the bubble jet method) described in U.S. Pat. No. 4,723,129 and U.S. Pat. No. 4,740,796 is capable of high-speed, high-density, high-definition and high-quality recording. In addition, it is suitable for colorization and compactness, and has recently attracted attention. In a typical example of an apparatus using this method, since ink (recording liquid or the like) is ejected by using thermal energy, there is a heat acting portion that applies heat to the ink. That is, a heating resistor having a heat acting portion is provided corresponding to the ink path, the heat energy generated from the heating resistor is used to rapidly heat the ink to cause foaming, and the ink is ejected by this foaming. Is.

Further, as disclosed in Japanese Patent Publication No. 61-58312, a liquid to be heated is vaporized and ejected toward a material to be printed, and also a liquid for recording is ejected, and Japanese Patent Publication No. 57-57-. An ink jet device using a pump, such as 189857, which mixes a low density ink and a high density ink and flies the material to be printed has been proposed.

This ink discharge mechanism is different from the conventional so-called ink jet head structure in that heat is applied to an object, that is, the heat acting part is in direct contact with the ink, or the heat acting part causes foaming of the ink. It is exposed to mechanical impact (cavitation erosion) due to repeated defoaming, and the heat acting part is 10 ^-1 to 10 μsec.
The fundamental technology is greatly different from the inkjet device using a piezoelectric device in that it is exposed to a temperature rise and fall of about 1000 degrees in an extremely short time of the order. Therefore, it goes without saying that the inkjet technology using piezoelectric cannot be directly applied to the bubble jet technology. Also, in the inkjet device that vaporizes and flies the heating liquid described above, all vaporized liquid flies, so there is no mechanical shock due to repeated foaming and defoaming as described above. I can't.

As described above, the thermal ink jet device using the electrothermal converter is said to be the mainstream of the ink jet printing device in the future because of its superior running cost and printing speed.

Further, in the case of performing multi-valued printing in a conventional ink jet device, the nozzle shape is made small and one pixel is formed by a plurality of small points, and the nozzle shape is made to be a shade by the black / white area ratio. There is a method of reducing the density and changing the density by printing at the same point multiple times.

[0007]

In the above-mentioned ink jet head, in the case of thermal ink jet, the ink is overheated to generate blisters, and the momentum is used. Disassembly causes charring on the heater, which reduces the amount of ejected ink and lowers the printing quality. To avoid this, the dye concentration of the ejected ink is only 2 to 5%. The ink cannot be mixed and does not dry immediately when the ink reaches the printing object, which causes a problem such as insufficient bleeding density.

Further, in the general ink jet apparatus, when the printing interval is long, the ink stays at the ejection port for a long time, and water having a low boiling point such as water and organic solvent in the ink evaporates to increase the viscosity of the ink. However, there is a problem that printing becomes impossible the next time you try to print, and as a method to solve this, put a cap (lid) on the discharge port when not in use or suck ink at regular intervals (from the discharge port). A method of drawing ink with a negative pressure), a method of printing by mixing the above-described low-concentration ink and high-concentration ink, and filling the ejection port with the low-concentration ink after printing is disclosed. . However, although this method is used in the ink jet device using piezoelectric as described above, in the bubble jet device such as the present invention, the reduction of the ejection efficiency due to the accumulation of the charred dye on the heater and the reduction of the print quality are solved. It doesn't. Further, even with low-concentration ink, the problem that the concentration of the dye rises and remains fixed (discharging impossible) if the ink stays at the ejection port for a long time has not been solved. Therefore, according to this method, it is necessary to provide a device irrelevant to printing such as closing the ejection port with a cap, which causes a problem of high cost.

Further, in the case of an ink jet head in which the heating liquid is vaporized and ejected and the recording liquid is ejected onto the printing material, the vaporized heating liquid must be ejected together with the recording liquid. Since it is necessary to shorten the distance between the heater for heating and the discharge port due to the structure (for example, 20 μm or less), it is very difficult to provide a supply port for supplying the recording liquid.

Further, in the method of performing multi-valued printing, the method of producing light and shade depending on the area at a plurality of points requires a longer printing time than the conventional printing because printing is performed a plurality of times to form one pixel.
Alternatively, there is a method of shortening the printing cycle in order to make the printing time equal to that of the conventional one, but there is a problem that the heating resistor is exposed to a higher temperature than before and the life is shortened.

Further, in the method of printing the same point a number of times to obtain the light and shade, there is a problem that it is difficult to realize the density gradation with good reproducibility because the number of times of printing and the increase of the density are not uniform.

[0012] The problem to be solved by the present invention is to take measures to prevent ejection failure due to increase in ink density even when the ejection port is not closed with a cap even when it is not used for a long time. It is possible to improve the printing quality by making it possible to use the ink that dries as soon as the ink arrives, and to realize the density gradation with good reproducibility.

[0013]

That is, the present invention uses a solution in which a dye such as a dye or a pigment is mixed in a solvent, foams and defoams this solution for each pixel, and only the solution in front of the bubble is flown. For an on-demand type ink jet head that enables printing of characters and images by arriving on the printing material and for a solution that does not contain a pigment that leads to an ink ejection unit that can eject a solution that does not contain a pigment and a solution that contains a pigment. And a second channel for the dye-containing solution,
The first flow path has a discharge means composed of a heating resistor,
The second flow path opens near the discharge part of the first flow path, and when discharging, the amount of the dye-free solution of the first flow path and the dye-containing solution of the second flow path are changed. An inkjet head is provided which is characterized in that it is mixed. In the present invention, as an example of a solution containing no dye, DEG20 is used.
%, Ethanol 5%, water 75% solution is used. The solution containing the dye is obtained by adding 2 to 50% of the dye to this solution. In the inkjet head of the present invention,
The dye-containing solution is supplied to the discharge part by the following methods. 1) Apply positive head pressure to the dye-containing solution. 2) Discharge means including a heating resistor is provided in the second flow path of the dye-containing solution. 3) The opening of the second flow path is provided closer to the discharge port than the discharge means of the first flow path, and the force of returning the ink to the ink supply side after discharge is used. Further, the present invention uses the above inkjet head,
An ink jet device that ejects only a solution containing no dye when the print signal is not energized to the head for a certain period or longer.
Further, the present invention provides an ink jet device that enables multi-valued printing by changing the print density by changing the mixing ratio of the dye-containing solution and the dye-free solution.

In the present invention, only the ink is ejected by repeating foaming and defoaming, and the generated heater remains in the discharge nozzle with a relatively long distance between the heater and the discharge port (50 μm).
m or more) to make it easier to supply the dye-containing solution to the discharge part, and to mix the dye-free solution such as a dye pigment with the dye-containing solution near the discharge port. The density is adjusted by changing the mixing ratio, and when the ink is not ejected for a certain period of time, a solution containing no pigment is ejected in advance, and the pigment concentration is fixed in the vicinity of the ejection port (ejection due to an increase in ink concentration). Impossible). Furthermore, the present invention is a dye, a pigment by discharging a mixed solution of a solution containing a dye and a solution containing a dye on the discharge port side from a heating heater by applying heat energy only to a solution containing no dye and foaming the solution. It is possible to provide stable discharge by reducing the charring that adheres to the heater.

According to the present invention, a first flow path for introducing a solution containing no dye such as a dye pigment and a second flow path for introducing a solution containing a dye are provided, and both solutions are mixed in the vicinity of the discharge port, and the mixture is mixed. By making it possible to change the concentration depending on the ratio, and when the ejection is not performed for a certain time or more, only the solution containing no dye is ejected and the vicinity of the ejection port is filled with only the solution containing no dye or pigment. It is possible to realize a head that prevents sticking due to an increase in dye concentration.

[0016]

EXAMPLES The present invention will be described in detail below with reference to examples.

(Embodiment 1) FIG. 1 is a perspective view of an embodiment of an ink jet head of the present invention. 2 is shown in FIG.
2 is a sectional view taken along line AA ′ of FIG. 1, in which 1 is a substrate, 2 is a resistance layer, 3 is a wiring conductor, 4 is a heating resistor protective film, and 5 is a cavitation resistant film.

A method of manufacturing the ink jet head of the present invention will be described with reference to FIGS. Sequentially sputtered HfB ₂ 2, Ti, Al @ 3 on the Si wafer 1 with a thermal oxide film,
A resist pattern is formed by the photolithography method, and Al is etched with a nitric acid / phosphoric acid-based etching solution. Then
After peeling off the Al resist, HfB ₂ resist is formed. The HfB ₂ is etched by dry etching using RIE. After removing the resist by ashing, Si ₃ N ₄ 4 and Ta 5 are sequentially sputtered as a film for protecting the resistor from cavitation that occurs when the heating resistor 2 is oxidized at high temperature and ink bubbles disappear. First, a resist pattern for etching the upper Ta film is formed.

Next, a resist pattern is formed to open a through hole 21 for connecting the wiring 3 under the protective film to the outside, and Si ₃ N ₄ is etched.
The ink flow path 10 is formed by first welding the dry film 6 in this wafer state, exposing the nozzle pattern, and then removing unnecessary portions by development. The dry film 8 is welded to the flow path side of the first top plate 7 for blocking the ink flow path to form the flow path upper wall 8 for making the distance b + a from the ejection port 11 to the liquid chamber 12 accurate. A dry film 13 is welded to the opposite side of this wall to form a chamber (liquid chamber) 14 for storing the dye-containing solution. Then, a second top plate 9 is further welded to align these parts so as to close their upper parts, and the positions thereof are aligned, and then the second top plate 9 is bonded to a heater board having a wiring part formed thereon.
Then, a filter (not shown) for preventing dust in the ink or dust in the head formation process is attached, cut and adhered to an ink supply system (not shown) to complete the head according to the present invention.

The dye-containing solution of the present invention passes through the second flow path 16 shown in FIG. 2- (B) and is guided to the heater section 18 on the first flow path 17 of the solution containing no dye. In the case of discharging, the bubble 20 closes the opening of the flow path 10, and the ink mixed before that discharges toward the paper. After that, the generated bubbles cause a decrease in volume with a decrease in temperature and pull the surrounding ink (solution). At this time, the dye-containing solution flows into the ejection portion by the positive head pressure, and the dye-containing solution and the solution containing no dye are mixed to form the ink for the next ejection.

When the head is not used for a while (more than a certain period of time), the pressure of the dye-containing solution chamber is set to a negative pressure so that the dye-containing solution does not flow into the ejection portion, and then the dye is not contained. When only the solution is ejected, the ejection portion is filled with the solution containing no pigment, and it is possible to prevent non-ejection or sticking of the head due to an increase in viscosity due to an increase in pigment concentration.

(Embodiment 2) FIG. 3 is a sectional view of another embodiment of the present invention, that is, an example in which a discharge means is also provided on the dye-containing solution side. The wiring conductor, 4 is a heating resistor protective film, and 5 is a cavitation resistant film.

The inkjet head of the present invention will be described with reference to the drawings.
Explain how to create. H on Si wafer with thermal oxide film
fB₂ , Ti, Al are sputtered one after another and the photolithography method is used.
More resist pattern is formed, Al is nitric acid, phosphoric acid type
Etching with etching solution. Then Al resist
After peeling off HfB₂ Forming resist. HfB ₂ 
Is dry etched using RIE.
U After removing the resist by ashing, the resistance
Is generated when the ink fluff disappears due to oxidation at high temperature.
Si is used as a film to protect resistance from pitting.₃ N_Four 
And Ta are sequentially sputtered. First, etch the Ta film on top
Forming a resist pattern to be patterned.

Next, a resist pattern is formed in order to open a through hole for connecting the wiring under the protective film and the outside to the protective film, and Si ₃ N ₄ is etched. The ink flow path is formed by first welding a dry film in this wafer state, exposing the nozzle pattern, and then developing to remove unnecessary portions. A dry film is welded to the flow path side of the top plate for closing the ink flow path to form a flow path upper wall for accurately adjusting the distance from the ejection port to the liquid chamber. A heating resistor is formed on the side opposite to this wall as a discharging means for sending the dye-containing solution to the discharging portion. After that, a dry film is welded to the surface containing the heating resistor to form a chamber for storing the dye-containing solution. Then, a top plate is further welded to align these parts so as to close their upper parts, and the positions thereof are aligned with each other, and then they are adhered to a heater board having a wiring part formed thereon. Then, a filter for preventing dust in the ink and dust in the process of forming the head is attached, cut, and an ink supply system (not shown) is adhered to complete the head according to the present invention.

FIG. 4 shows a driving diagram of the heater (heating resistor) on the dye-containing solution side of this embodiment, a timing chart in that case, and a model of the mixture of the dye-containing solution and the solution containing no dye at that time. It was The dye-containing solution driving heater driving IC is provided with switches (ENABLE 1 to 3) having different pulse widths, and the dye-containing solution does not contain a dye by changing the opening / closing time of the switch to express the shade of color. Control the inflow to the.

When the dye-containing solution is not used for a certain period of time, the heater for the dye-containing solution is not driven and only the solution containing no dye is ejected to prevent the non-ejection or the fixation of the head as described in the first embodiment.

(Embodiment 3) FIG. 5 shows another embodiment according to the present invention, that is, an ink jet head in which a flow path opening for a dye-containing solution is provided in front of a discharge section, in which 1 is a substrate and 2 is a substrate. Is a resistance layer, 3 is a wiring conductor, 4 is a heating resistor protective film, and 5 is an anti-cavitation film.

The inkjet head of the present invention will be described with reference to the drawings.
Explain how to create. H on Si wafer with thermal oxide film
fB₂ , Ti, Al are sputtered one after another and the photolithography method is used.
More resist pattern is formed, Al is nitric acid, phosphoric acid type
Etching with etching solution. Then Al resist
After peeling off HfB₂ Forming resist. HfB ₂ 
Is dry etched using RIE.
U After removing the resist by ashing, the resistance
Is generated when the ink fluff disappears due to oxidation at high temperature.
Si is used as a film to protect resistance from pitting.₃ N_Four 
And Ta are sequentially sputtered. First, etch the Ta film on top
Forming a resist pattern to be patterned.

Next, a resist pattern is formed to open a through hole for connecting the wiring under the protective film and the outside to the protective film, and Si ₃ N ₄ is etched. The ink flow path is formed by first welding a dry film in this wafer state, exposing the nozzle pattern, and then developing to remove unnecessary portions. A dry film is welded to the flow path side of the top plate for closing the ink flow path to form a flow path upper wall for accurately adjusting the distance from the ejection port to the liquid chamber. A dry film is welded to the opposite side of the wall to form a chamber for storing the dye-containing solution. Then, a top plate is further welded to align these parts so as to close their upper parts, and the positions thereof are aligned with each other, and then they are adhered to a heater board having a wiring part formed thereon. Then, a filter for preventing dust in the ink and dust in the process of forming the head is attached, cut, and an ink supply system (not shown) is adhered to complete the head according to the present invention.

FIG. 5- (B) shows the state of each stage of ejection. The dye-containing solution of the present invention is guided to the discharge section through 16 channels. When discharging, the foam 20 forms the flow path 17.
When the ink is ejected to close the outlet of, the ink mixed before that ejects toward the paper. At this time, as shown in FIG. 6- (A), the mixed solution described in the first embodiment is a mixture of the solution β part formed by diffusion of the dye-containing solution and the solution of α containing no dye. At this time, most of the flying solution flies from the center of the heater shown in the figure to the discharge port side. Therefore, the amount of the dye with respect to the total amount of the flying solution is β / (α + β). This ratio will indicate the ink density.

On the other hand, when the solution containing the dye is introduced before the heater of Example 3, the amount γ containing no dye becomes smaller than the above α as shown in FIG. 6- (B). .
And the amount of the dye is β / (α
+ Β), so β / (α + β) <β / (α + β)
Becomes Therefore, although factors such as the content of the dye and the specific gravity and the viscosity are related, in the case of the same solution, the example 3 is
It is possible to construct a head that can eject dark color ink and can use a solution with less dye.

When the dye-containing solution is not used for a while (more than a certain period of time), the pressure in the liquid chamber of the dye-containing solution is set to a negative pressure so that the dye-containing solution does not flow into the discharge part, and then only the solution containing no dye is used. When the ink is ejected, the ejection portion is filled with a solution containing no pigment, and it is possible to prevent non-ejection or sticking of the head due to an increase in viscosity due to an increase in pigment concentration.

[0033]

As described above, the ink jet head of the present invention mixes the dye-containing solution and the dye-free solution and ejects only the dye-free solution when the dye-free solution is not used for a certain period of time or more. It is possible to prevent the non-ejection due to the rise and to obtain the concentration gradation by changing the mixing ratio of the dye-containing solution and the dye-free solution. Therefore, since it is not necessary to provide a non-ejection preventing mechanism in the printer, it is inexpensive, and the density gradation can be realized without changing the dot pitch, and the effect of being able to realize a printer with high printing quality at high speed is great. .

[Brief description of drawings]

FIG. 1 is a perspective view illustrating an embodiment of an inkjet head of the present invention, that is, an example in which a dye-containing solution is supplied to a discharge unit with a positive head pressure.

FIG. 2 is a cross-sectional view illustrating a state of the head of FIG. 1 cut in the AA ′ direction. (A) A sectional view of the head of FIG. 1.
FIG. 6B is a schematic diagram illustrating a solution supply state in the vicinity of the discharge unit.

FIG. 3 is another embodiment of the inkjet head of the present invention,
That is, it is a cross-sectional view illustrating an example in which the dye-containing solution side also has a discharging unit.

FIG. 4 is a diagram illustrating a driving diagram of a heater on the dye-containing solution side of the inkjet head of FIG. 3, a timing chart in that case, and a model of the mixing degree of the solution. (A) Dye-containing solution discharge diagram. (B) Timing chart. (C) A model showing how the solution is mixed.

FIG. 5 is another embodiment of the inkjet head of the present invention,
That is, it is a cross-sectional view illustrating an example in which a flow path opening for a dye-containing solution is provided in front of a discharge unit (heater). (A)
Sectional drawing of an inkjet head. FIG. 6B is a schematic diagram illustrating each stage of discharge in the vicinity of the discharge unit.

FIG. 6 is a schematic diagram for comparing and explaining the ink densities in Example 1 and Example 3. (A) In the case of Example 1.
(B) In the case of Example 3.

[Explanation of symbols]

1 Substrate (Si Wafer) 2 Heating Resistor 3 Wiring Conductor (Al) 4 Heating Resistor Protective Film (Si ₃ N ₄ ) 5 Cavitation Resistant Film (Ta) 6 Dry Film for Ink Flow Path 7 Top Plate for Blocking Flow Path 8 Dry film on top plate 9 Top plate 10 Ink flow path 11 Discharge port 12 Liquid chamber for solution containing no dye 13 Dry film 14 Liquid chamber for dye-containing liquid 15 Top plate 16 Flow path for dye-containing solution 17 Dye-free solution flow path 18 Heater 20 Bubble 21 Through hole

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B41J 3/04 103 X

Claims (7)

[Claims] 1. A solution prepared by mixing a dye and a dye such as a pigment into a solvent is used to foam and defoam each pixel, and only the solution in front of the bubble is made to fly to reach a printing object. In an on-demand type inkjet head capable of printing images and images, a first flow path for a dye-free solution and a dye that guides a dye-free solution and a dye-containing solution to an ink ejecting unit that can eject each A second flow path for a solution containing a liquid, and the first flow path has a discharge means composed of a heating resistor, and the second flow path is near the discharge port of the first flow path. An inkjet head that mixes a dye-free solution in a first channel with a solution containing a dye in a second channel and ejects the mixed solution at the same time when the liquid is opened and ejected. 2. The ink jet head according to claim 1, wherein the bubbling is caused by a dye-free solution by a discharge means including a heating resistor provided in the first flow path. 3. The ink jet head according to claim 1, wherein the solution containing the dye is supplied to the ink ejection section by a positive head pressure. 4. The inkjet according to claim 1, wherein the solution containing the dye is supplied to the ink discharge section of the first flow path by a discharge means including a heating resistor provided in the second flow path. head. 5. The second flow path is provided on the ejection port side of the ejection means of the first flow path, and the pigment is contained by utilizing the force of the ink returning to the ink supply side after ejection. The inkjet head according to claim 1, wherein the solution is supplied to the ink ejection unit. 6. An ink jet device using the ink jet head according to claim 1, wherein when a print signal is not transmitted to the head for a certain period or longer, only a solution containing no dye is ejected. 7. The ink jet head according to claim 1, wherein multi-value printing is enabled by changing a mixing ratio of a solution containing a dye and a solution containing no dye to change a printing density. Inkjet device.