JPH1142782A - Liquid-jet recording head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid-jet recording head which improves bubble exclusion efficiency and remarkably reduces the frequency of image quality defects due to bubbles. SOLUTION: A common liquid chamber 8 and a channel to be an individual channel are formed on a channel substrate, heat generating elements 4 are formed on a heater substrate 1, thick film resin layers 3 are formed on the elements 4, and the part of a bypass channel 7 for making pits 6 in the upper parts of the elements 4, the liquid chamber 8, and the individual channel 5 communicate with each other is removed. One or more nozzles in the end part of the liquid chamber 8 are made dummy nozzles, the pit 6 is connected directly with the bypass channel 7 in the corresponding dummy individual channel, and a resin is removed so that the bypass channel 7 is extended into the dummy individual channel. In this way, the channel resistance of the dummy individual channel is reduced, and bubbles staying in the end part of the common liquid chamber 8 are discharged outside efficiently to reduce image quality defects.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid jet recording head for jetting a liquid from a nozzle and attaching the liquid to a recording medium to perform recording, and more particularly to a liquid jet recording head having a dummy nozzle which does not jet a liquid. It concerns the head.

[0002]

2. Description of the Related Art Conventionally, as a liquid jet recording head of a liquid jet recording system, for example, a piezoelectric liquid jet recording head in which a pressure chamber is mechanically deformed by a piezoelectric material and a liquid is ejected from a nozzle by a generated pressure, There is known a thermal type liquid jet recording head which energizes a heater disposed in a liquid flow path, vaporizes the liquid, and jets the liquid from a nozzle at the pressure.

[0003] As a known liquid jet recording head, there is one described in Japanese Patent Application Laid-Open No. 5-138888.
7 is an external view of an example of a conventional liquid jet recording head, FIG. 8 is a plan view of the same heater substrate, and FIG. 9 is a sectional view of the same C. In the figure, 1 is a heater substrate, 2 is a channel substrate, 3 is a thick resin layer, 4 is a heating element, 5 is an individual channel, 6
Is a pit, 7 is a bypass channel, 8 is a common liquid chamber, 9 is a nozzle, 10 is a bubble, 11 is a droplet, 12 is a heat sink,
3 is a bonding wire.

The channel substrate 2 is formed with a common liquid chamber 8, a groove serving as an individual flow path 5, and the like. When silicon is used as the channel substrate 2, the common liquid chamber 8, the groove serving as the individual flow path 5, and the like can be formed by, for example, anisotropic etching. As a method for forming these common liquid chambers 8 and grooves serving as the individual flow paths 5 by anisotropic etching, Japanese Unexamined Patent Application Publication Nos. Hei.
As described in Japanese Patent Publication No. 2 (1993), after an etching mask is patterned on a silicon wafer having a (100) crystal plane on its surface, heated potassium hydroxide (KOH)
The etching may be performed using an aqueous solution or the like. The common liquid chamber 8 formed by using the anisotropic etching, the groove serving as the individual flow path 5, and the like have a shape having a predetermined angle.

[0005] On the heater substrate 1, a plurality of heating elements 4 for discharging liquid are arranged. Here, the heating element 4 is used as the liquid ejecting element, but an energy conversion element for discharging another liquid such as a piezoelectric element can be used. In addition to the heating element 4 on the heater substrate 1,
A drive circuit and the like (not shown) are formed, and a thick resin layer 3 is provided thereon. As shown in FIG. 8, the thick resin layer 3 is removed from the heating element 4 to form a pit 6. The pits 6 limit the growth region of bubbles generated by driving the heating element 4, and the pressure at the time of bubble growth can be efficiently used for ejecting liquid. Among the plurality of pits 6 shown in FIG. 8, the heating elements 4 are not provided in every two pits 6 arranged at both ends of the heater substrate 1. This is a dummy pit that forms part of a dummy liquid flow path that communicates with a dummy nozzle that does not eject liquid. As shown in FIG. 8, the thick film resin layer 3 has a bypass flow path 7 for supplying a liquid from the common liquid chamber 8 to the individual flow path 5.
Are also removed. In FIG. 8, the bypass flow path 7 is formed as a concave portion common to all the individual flow paths 5 (including the dummy liquid flow path), but is formed as a groove communicating with the common liquid chamber 8 for each individual flow path 5. It may be done.

[0006] The heater substrate 1 and the channel substrate 2 are aligned and joined. Thereby, a flow path communicating from the common liquid chamber 8 to the bypass flow path 7 and the individual flow path 5 is formed,
The opening end becomes the nozzle 9. Further, a pit 6 is formed in the middle of the individual flow path 5, and the heating element 4 is arranged at the bottom of the pit 6. Liquid is common liquid chamber 8
And is supplied to the individual flow path 5 through the bypass flow path 7. In response to the driving of the heating element 4 in the individual flow channel 5, the liquid in the individual flow channel 5 is pushed out from the nozzle 9 by the pressure of the bubble grown in the pit 6, ejected as a droplet 11, and recording is performed.

The heater substrate 1 is fixed to a heat sink 12 to release heat generated by the heating element 4. A wiring board (not shown) is also formed on the heat sink 12,
Power and signals supplied from the printer body are transmitted to the heater substrate 1 via the bonding wires 13 and
Signals from various sensors provided on the heater substrate 1 are transmitted to the printer body.

In such a conventional liquid jet recording head, when the bubbles 10 remain in the common liquid chamber 8 as shown in FIG. 9, the bubbles 10 grow during use, and the bubbles 10 Road 5 may be closed. When the individual channel 5 is closed by the bubble 10, the supply of the liquid is stopped,
Since the droplets are not ejected, printing defects occur, causing image quality defects. The bubbles 10 are mixed with the liquid when the liquid is introduced, or the temperature of the liquid increases due to the heat generated by the heating element 4, the dissolved gas in the liquid precipitates, and grows in the common liquid chamber 8. What happens. In particular, the bubbles 10 remain concentrated at both ends of the common liquid chamber 8 where the flow of the liquid is small.

As a method for eliminating the air bubbles 10 remaining in the common liquid chamber 8, a method of sucking from the nozzle 9 is generally used. When the liquid is sucked from the nozzle 9, the amount of the sucked liquid is supplied from a tank (not shown). The supplied liquid spreads along the shape of the common liquid chamber 8, is guided to the individual flow path 5 side, and the bubble 10 advances to the individual flow path 5 with the flow of the liquid, and is discharged from the nozzle 9 to the outside together with the liquid. You. However, it is difficult to eliminate the air bubbles 10 staying at both ends of the common liquid chamber 8, which are the major cause of the image quality defect, because they exist in an area where the flow of the liquid is extremely small. Although it is conceivable to increase the number of times of suction, the more frequently the suction is performed, the lower the efficiency of use of the liquid used for recording, and the larger the capacity of the waste liquid tank for holding the suctioned waste liquid, the larger the overall device. There is a problem that the size is increased.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and improves the efficiency of removing bubbles without increasing the size of the apparatus, thereby greatly reducing the frequency of occurrence of image quality defects due to bubbles. It is an object of the present invention to provide a reduced liquid jet recording head.

[0011]

In the liquid jet recording head according to the present invention, in the individual flow path corresponding to the dummy nozzle, the resin is continuously removed from the bypass flow path to the inside of the individual flow path. As a result, the flow of the liquid from the bypass flow passage to the individual flow passage for the dummy nozzle becomes smooth, and it becomes easy to remove bubbles remaining in the common liquid chamber when suction is performed by the maintenance operation. If the flow path resistance corresponding to the dummy nozzle is set lower than the others, the amount of liquid suctioned from the dummy nozzle at the time of suction increases, so that the flow of the liquid becomes faster and the bubbles can be efficiently discharged from the dummy nozzle. In addition, if the dummy nozzle is disposed at the end of the common liquid chamber, air bubbles remaining at the end of the common liquid chamber can be satisfactorily discharged. In this way, air bubbles remaining in the common liquid chamber can be efficiently removed from the dummy nozzles, thereby minimizing the size of the apparatus, shortening the maintenance operation, reducing the amount of waste liquid, and causing image defects due to air bubbles remaining. Frequency can be significantly reduced, and reliability can be improved.

[0012]

FIG. 1 is a plan view of a heater substrate showing a first embodiment of a liquid jet recording head according to the present invention, FIG. 2 is a sectional view taken along the line AA, and FIG. It is -B sectional drawing. In the figure, the same parts as those in FIGS. 7 to 9 are denoted by the same reference numerals. 21 is a dummy nozzle, and 22 is a dummy individual flow path. The appearance of the first embodiment is the same as that of FIG.

The heater substrate 1 is manufactured by using a manufacturing apparatus and a manufacturing method of an LSI or the like. For example, a heat storage layer made of silicon oxide or the like is provided on the surface of single crystal silicon, and a liquid discharge element is formed thereon. Here, the heating element 4 is formed as a liquid ejection element. A plurality of heating elements 4 are formed, and signal lines for supplying electric power and signals are connected.
The heating element 4 generates heat by a signal given from a driving circuit or the like provided in the same chip or outside the chip. A protective film composed of a single layer or a plurality of layers of silicon oxide, nitrogen silicon, tantalum, or the like is provided on the heating element 4 to protect the heating element 4.

A thick resin layer 3 is formed thereon. The thick resin layer 3 is coated with a photosensitive resin and patterned by a photolithography process. As the photosensitive resin, for example, photosensitive polyimide can be used. The thickness of the photosensitive polyimide can be arbitrarily selected from several μm to 50 μm in accordance with the target characteristics of the liquid jet recording head. Since the photosensitive polyimide may be dissolved in the liquid as it is, for example, heat is applied to cure the polyimide so as not to dissolve in the liquid.
In addition to photosensitive polyimide, polymer materials such as non-photosensitive polyimide and dry film can be used.
At the time of patterning the thick resin layer 3, as shown in FIG. 1, the resin on the heating element 4 is removed, and pits 6 for limiting the growth area of bubbles generated by the heating of the heating element 4 are formed. . Further, the resin is also removed from the bypass flow path 7 that connects the common liquid chamber 8 to the individual flow path 5 and the portion extending from the bypass flow path 7 to the dummy individual flow path 22.

The channel substrate 2 is similar to a conventional liquid jet recording head. For example, silicon is anisotropically etched to form a common liquid chamber 8, an individual flow path 5, or a dummy individual flow path 22.
And the like. The anisotropic etching may be performed, for example, by patterning an etching mask on a silicon wafer having a (100) crystal plane on the surface and then using a heated aqueous solution of potassium hydroxide (KOH) or the like. The common liquid chamber 8, the individual flow paths 5, the grooves serving as the dummy individual flow paths 22, and the like formed using anisotropic etching have a shape having a predetermined angle.

The heater substrate 1 and the channel substrate 2 thus manufactured are aligned and joined. As a result, a liquid flow path from the common liquid chamber 8 to the nozzle 9 through the bypass flow path 7 and the individual flow path 5 is formed.
In addition, a flow path from the common liquid chamber 8 to the dummy nozzle 21 through the bypass flow path 7 and the dummy individual flow path 22 is formed as a flow path corresponding to the dummy nozzle 21.

In the flow paths corresponding to the nozzles for ejecting liquid other than the dummy nozzles 21, the pits 6 and the bypass flow paths 7 are formed on the same plane as shown in FIGS.
Are separated from each other. As mentioned above,
The pits 6 are provided to limit the growth area of bubbles generated by the vaporization of the liquid due to the heat generated by the heating element 4. In particular, the wall of the thick resin layer 3 behind the pits 6
It has the effect of pushing the liquid to the front of the nozzle. further,
By changing the distance between the wall of the thick resin layer 3 behind the pit 6 and the bypass flow path 7, the flow resistance ratio of the individual flow path 5 before and after the heating element 4 can be changed. The printing characteristics such as the frequency characteristics can be controlled. For this reason, the polyimide wall behind the pit plays an important role in the liquid flow path for discharging the liquid.

However, in the dummy individual flow channel 22, it was found that the wall of the thick film resin layer 3 at the rear of the pit becomes a resistance when the liquid flows, and reduces the effect of removing bubbles. Therefore, as shown in FIGS. 1 and 2, the thick film resin layer 3 between the pit 6 and the bypass flow path 7 is removed to directly connect the two, and the bypass flow path 7 extends into the dummy individual flow path 22. The thick resin layer 3 is patterned so as to have an existing shape. As a result, the flow of the liquid from the common liquid chamber 8 to the dummy individual flow path 22 becomes smooth. Therefore, the bubbles in the common liquid chamber 8 are removed by the dummy individual flow path 22 during suction.
It is easy to get inside. In the dummy individual flow channel 22,
Compared with the individual flow path 5 other than the dummy individual flow path 22, the flow path resistance is reduced by an amount corresponding to the removal of the thick film resin layer 3. Nozzle 9
When suction is performed from the side, the nozzles 9 are suctioned at the same pressure, so that the smaller the flow path resistance is, the larger the liquid discharge amount is. Therefore, when suction is performed, the amount of liquid discharged from the dummy nozzle 21 having a small flow path resistance increases, so that the bubbles in the common liquid chamber 8 are also easily discharged from the dummy nozzle 21 through the dummy individual flow path 22. Bubbles in the liquid chamber 8 can be efficiently eliminated.

The dummy nozzle 21 is preferably provided at an end of the common liquid chamber 8. The example shown in FIG. 1 shows an example in which two nozzles at both ends of the common liquid chamber 8 are used as dummy nozzles 21. Of course, the number of dummy nozzles 21 is arbitrary. By providing the dummy nozzle 21 at the end of the common liquid chamber 8, air bubbles that easily stay at the end of the common liquid chamber 8 can be discharged by suction. FIG. 4 is an explanatory diagram of the flow of liquid during a suction operation in the liquid jet recording head according to the first embodiment of the present invention. As described above, the flow rate of the liquid is slow and the flow rate is small in the nozzle 9 that ejects the liquid because the flow path resistance is large. As shown in (1), the liquid flows to the end of the common liquid chamber 8, and the flow rate also increases. Therefore, the air bubbles remaining at the left and right ends in the common liquid chamber 8 are guided to the dummy individual flow paths 22 along the flow of the liquid shown in FIG.

Further, by providing the dummy nozzle 21 at the end of the common liquid chamber 8, recording can be performed without using the nozzle at the end of the common liquid chamber 8 having poor liquid ejection characteristics. Image quality can be obtained. In addition, as described above, bubbles are likely to stay at both ends of the common liquid chamber 8, but by not using the nozzles at the ends for recording, the effects of bubbles can be reduced.

In this example, the heating element 4 is not provided in the dummy individual flow path 22, but the heating element 4 may be formed. The length of the bypass channel 7 extending into the dummy individual channel 22 is arbitrary.

FIG. 5 is a sectional view showing a liquid jet recording head according to a second embodiment of the present invention. The reference numerals in FIG.
3 to FIG. FIG. 5 is a sectional view taken along line AA in FIG.
The cross section, that is, the cross section of the dummy nozzle 21 and the dummy individual flow path 22 is shown. In this example, the bypass flow path 7 and the pit 6 are directly connected to each other to extend the bypass flow path 7 into the dummy individual flow path 22, and the channel substrate 2 side corresponding to the dummy nozzle 21, as in the above-described example. The groove of the dummy individual flow path 22 and the common liquid chamber 8 are also changed.
And are connected directly.

According to such a configuration, the projecting portion of the channel substrate 2 that has separated the individual flow channel 5 corresponding to the nozzle 9 for ejecting the liquid and the common liquid chamber 8 becomes the flow channel corresponding to the dummy nozzle 21. Therefore, the bubbles can be more easily entered into the dummy individual flow path 22, the flow path resistance can be reduced, and the bubbles in the common liquid chamber 8 can be more efficiently discharged to the outside.

FIG. 6 is an explanatory diagram of a recording experiment result in the first embodiment and the second embodiment of the liquid jet recording head of the present invention. Actually, a liquid jet recording head having dummy individual flow paths 22 as shown in FIGS. 2 and 5 was prepared, and a printing experiment was performed. 7 to 9 for comparison.
The conventional liquid jet recording head shown in FIG. Specifically, a liquid jet recording head having 188 nozzles and each structure having ten nozzles at both ends as dummy nozzles was prepared.

In a conventional liquid jet recording head, 1
Each of the individual liquid flow paths corresponding to the 88 nozzles has the flow path structure shown in FIG. 3, and the flow path corresponding to the dummy nozzle also has a wall of the thick film resin layer 3 at the rear of the pit. Since all the channels have the same structure, all the channel resistances of the individual channels are the same.

In the liquid jet recording head according to the first embodiment of the present invention shown in FIGS. 1 to 3, out of the 188 nozzles, ten nozzles at both ends of each of the 188 nozzles have a thick resin layer behind the pit. The dummy nozzle has a structure in which the bypass channel is directly connected to the pit by eliminating the wall of No. 3 and the bypass channel extends into the dummy individual channel.

Further, as a liquid jet recording head according to the second embodiment of the present invention, out of 188 nozzles,
Dummy nozzles having the structure shown in FIG. 5 were used for ten nozzles at each end. The dummy individual flow path has a structure in which a pit and a bypass flow path are directly connected on the heater substrate side, and a protrusion between the individual flow path on the channel substrate side and the common liquid chamber is removed. Therefore, compared to the structure shown in FIG.
Further, a channel structure in which the channel resistance of the individual liquid channel is reduced is obtained.

After injecting liquid into each liquid jet recording head and performing air bubble elimination maintenance several times, a printing experiment was performed. As a result, the frequency of occurrence of image quality defects was about 1.3% in the conventional liquid jet recording head, whereas the frequency of occurrence of image quality defects was in the liquid jet recording head shown in the first embodiment of the present invention. Decreased to 0.7%.
Thus, in the present invention, by eliminating the polyimide wall at the rear of the pit of the dummy individual flow path and extending the bypass flow path to the inside of the dummy individual flow path, air bubbles remaining in the common liquid chamber can be suctioned by maintenance operation. Efficient removal was possible, and the incidence of image quality defects was reduced.

Further, in the liquid jet recording head shown in FIG. 5 according to the second embodiment of the present invention, the frequency of occurrence of defective image quality is reduced to 0.5%. The described effects of the present invention could be further enhanced.

In each of the above embodiments, only one liquid chamber is shown in the liquid jet recording head, but the present invention is not limited to this. For example, when there are a plurality of independent common liquid chambers such as a multi-color integrated liquid jet recording head, one or a plurality of dummy nozzles are provided at the end of each common liquid chamber. 2 or a flow channel structure as shown in FIG.

[0031]

As is apparent from the above description, according to the present invention, the bubbles remaining in the common liquid chamber can be efficiently discharged to the outside from the dummy nozzle by the bubble removing operation. Therefore, the time and the number of times of the bubble elimination operation can be reduced, the amount of drainage can be reduced, and the size of the apparatus can be suppressed. Further, the frequency of occurrence of image quality defects due to remaining air bubbles can be significantly reduced, and the reliability can be improved.

[Brief description of the drawings]

FIG. 1 is a plan view of a heater substrate showing a first embodiment of a liquid jet recording head of the present invention.

FIG. 2 is a sectional view of the liquid jet recording head according to the first embodiment of the present invention, taken along line AA.

FIG. 3 is a sectional view of the liquid jet recording head according to the first embodiment of the present invention, taken along line BB.

FIG. 4 is an explanatory diagram of a liquid flow during a suction operation in the liquid jet recording head according to the first embodiment of the present invention.

FIG. 5 is a cross-sectional view illustrating a liquid jet recording head according to a second embodiment of the present invention.

FIG. 6 is an explanatory diagram of a recording experiment result in the first embodiment and the second embodiment of the liquid jet recording head of the present invention.

FIG. 7 is an external view of an example of a conventional liquid jet recording head.

FIG. 8 is a plan view of a heater substrate in an example of a conventional liquid jet recording head.

FIG. 9 shows C in an example of a conventional liquid jet recording head.
It is sectional drawing.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Heater board, 2 ... Channel board, 3 ... Thick film resin layer,
4 heating element, 5 individual flow path, 6 pit, 7 bypass path, 8 common liquid chamber, 9 nozzle, 10 air bubble, 11
... droplets, 12 heat sinks, 13 bonding wires, 21 dummy nozzles, 22 dummy individual flow paths.

Claims (4)

[Claims] 1. A plurality of nozzles arranged in a line, individual flow paths corresponding to the nozzles, a common liquid chamber common to the plurality of individual flow paths, the individual flow path and the common liquid chamber. And a liquid ejecting element that is provided in the individual flow path and urges liquid to eject liquid droplets from the nozzles, and at least a part of the individual flow path is made of resin. Formed, the bypass flow path is formed as a concave portion not provided with the resin, at least one of the nozzles is a dummy nozzle that does not discharge liquid, and the individual flow path corresponding to the dummy nozzle is continuous from the bypass flow path. Wherein the resin is removed. 2. The flow path resistance of an individual flow path corresponding to the dummy nozzle is smaller than the flow path resistance of an individual flow path corresponding to a nozzle other than the dummy nozzle that ejects a liquid. 2. The liquid jet recording head according to 1. 3. The liquid jet recording head according to claim 1, wherein the dummy nozzle is provided so as to be connected to an end of the common liquid chamber. 4. The liquid jet recording head according to claim 1, wherein the individual flow path is directly connected to the common liquid chamber.