JP2002248769A - Ink jet recording head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent ink from remaining in the vicinity of a discharge opening. SOLUTION: An ink jet recording head has a plurality of electrothermal conversion elements 51 for foaming the ink, a plurality of discharge openings 52 for discharging the ink, a pressure chamber 55 in which the electrothermal conversion elements 51 are stored and which forms a space for heating and foaming the ink, a plurality of ink channels 83 for supplying the ink to the discharge openings 52, and a common liquid chamber 54 for supplying the ink to the plurality of ink channels 83. One ink channel 83 is set to one electrothermal conversion element 51 and is disposed so that a center line is positioned with an offset to a center line of the electrothermal conversion element 51. Moreover, the center of the discharge opening 52 is arranged to a position offset in a direction opposite to the common liquid chamber 54 from the center of the electrothermal conversion element 51.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an ink jet recording head for recording an image on a recording medium by discharging a recording liquid such as ink from a discharge port.

[0002]

2. Description of the Related Art An ink jet recording apparatus is a recording apparatus of a so-called non-impact recording method, and has a feature that almost no noise is generated at the time of recording, and high-speed recording and recording on various recording media are possible. ing. For this reason, the ink jet recording apparatus has been widely adopted as an apparatus having a recording mechanism such as a printer, a copying machine, a facsimile, and a word processor.

As a typical ink ejection method for a recording head mounted on such an ink jet recording apparatus, a method using an electromechanical transducer such as a piezo element or the like is used. In addition, there is known a device that discharges ink droplets by the action of this heat generation, or a device that heats ink by an electrothermal conversion element having a heating resistor and discharges the ink droplet by the effect of film boiling.

Among these, an ink jet recording head using an electrothermal conversion element is provided with an electrothermal conversion element in a recording liquid chamber, and supplies an electric pulse, which is a recording signal, to the recording liquid chamber to generate heat. Which performs recording on a recording medium by discharging ink liquid from minute discharge ports using bubble pressure at the time of bubbling (at the time of boiling) of the recording liquid caused by a phase change of the recording liquid at that time. It is. An ink jet recording head using an electrothermal transducer generally has a nozzle having an opening for discharging ink droplets, an ink flow path for supplying ink to the nozzle, and a common liquid chamber. I have.

[0005] Such an ink jet recording head is
Usually, it is mounted on a carriage of the printing apparatus main body. The recording apparatus main body has a conveying unit that conveys the recording medium so as to pass through a position facing the ejection opening surface of the ink jet recording head mounted on the carriage. The carriage is configured to be movable in a direction intersecting the transport direction of the recording medium.

[0006] The printing operation of such a printing apparatus is performed by repeatedly performing a main scan for discharging ink at a predetermined cycle while moving an ink jet print head and a sub-scan for conveying a print medium by a predetermined width. Will be

FIG. 8 is a schematic view showing a nozzle portion of a conventional ink jet recording head. FIG. 3A is a plan view showing the discharge port forming member in a see-through state, and FIG.
Shows a sectional view taken along the line PP ′ of FIG.

[0008] The ink jet recording head shown in FIG.
It has a common liquid chamber 154 connected to the ink supply port 156. On both sides of the common liquid chamber 154, an electrothermal conversion element 151 that foams and discharges ink and an electrothermal conversion element 15 that houses the electrothermal conversion element 151 are provided.
A plurality of circular pressure chambers 155 centered on one center are provided side by side. An ink flow path 153 is provided between the common liquid chamber 154 and each of the pressure chambers 155. A discharge port 152 is opened at a position facing the electrothermal conversion element 151.

In this ink jet recording head, the positions of the adjacent ejection ports 152 and the electrothermal transducers 151 in the printing direction (carriage moving direction) are determined by the carriage (not shown) during the drive timing shift time between the respective drive blocks. Are displaced by an offset corresponding to the moving distance. FIG. 8 shows four nozzles for each nozzle for simplicity.
5 shows an ink jet recording head to which three drive blocks are assigned, and the arrangement of the ejection ports 152 in the printing direction is periodically changed every four nozzles in the direction in which the ejection ports are arranged.

[0010] When the drive blocks are numbered in ascending order from the one that is driven earlier, in the example shown in FIG. 8, the discharge port 152 is located at the upper right and is separated from the nozzle 152 by an integer multiple of 4 to the left. The drive block 1 is allocated to the discharge port 152, the drive block 2 is disposed on the discharge port 152 on the left side, the drive block 3 is disposed on the discharge port 152 on the left side, and the drive block 4 is disposed on the discharge port 152 on the left side.
Is assigned. With such a configuration,
The drive blocks 1 to 4 are sequentially driven in ascending order to discharge ink, and the ink discharged from these discharge ports 152 can land on the recording medium in a line.

In the nozzle having the configuration shown in FIG. 8, since the center line of the ink flow path 163 coincides with the center line of the electrothermal conversion element 151, the common liquid chamber 154
The flow of the ink toward the pressure chamber 155 through the pressure chamber 155 occurs line-symmetrically with respect to the center line of the electrothermal conversion element 151. Therefore, bubbles generated by heating the ink by the electrothermal conversion element 151 stably disappear on the electrothermal conversion element 151 symmetrically with respect to the center line. In some cases, the defoaming positions may be dispersed at the corners (four places in total) of the heat generating area of the electrothermal conversion element 151, but even in such a case, the defoaming positions are constant.

At the time of bubble erasure, an impact force is generated due to cavitation collapse. In the nozzle configuration in which the defoaming position is stable as in the conventional example, a specific portion of the electrothermal transducer 151 receives an impact force due to cavitation, so that the electrothermal transducer 151 is easily damaged and has a long life. There is a problem that becomes shorter.

Therefore, an ink jet recording head having a nozzle configuration shown in FIG. 9 has been proposed in order to disperse the bubble erasing positions. FIG. 9 is a schematic view showing a nozzle portion of another conventional inkjet recording head. FIG. 3A is a plan view showing the discharge port forming member in a see-through state, and FIG. 3B is a cross-sectional view taken along line BB ′ of FIG. In this figure, the same parts as those in FIG. 8 are denoted by the same reference numerals, and description thereof will be omitted.

In this ink jet recording head, an ink flow path 183 is provided between the electrothermal transducer 151 and the pressure chamber 155 which are arranged so that the center is located on the vertical line of the center of the ejection port 152. Are arranged at positions offset from the center line of the electrothermal conversion element 151.

In this prior art, by arranging the ink flow path 183 in this manner, a rotating flow component is generated in the flow of ink refilling at the time of defoaming. Is intended to reduce the effect of this. This will be described with reference to FIG. 10 showing the defoaming step. FIG. 10 is a schematic plan view of the nozzle, and FIG.
(A) to (f) of FIG.

FIG. 10A shows the maximum foaming time when the bubble 187 becomes the maximum size, and the defoaming starts at this time. Then, as shown in FIG. 10B, the flow of the ink from the common liquid chamber 154 is generated together with the defoaming, and the bubble 187 becomes smaller such that the portion protruding into the ink flow path 183 is retracted.

When the ink flow reaches the pressure chamber 155,
Since the space in the center direction of the pressure chamber 155 is suddenly widened, the flow velocity becomes slow. As a result, the flow of the ink is
Bend toward the center of 55. As a result, as shown in FIGS. 10C and 10D, the bubbles 187 become smaller as they are pushed by the ink in the ink flow direction.

In the process of further reducing the size of the bubble 187, the bubble 187 is swept away by the flow of the ink to a position in the pressure chamber 155 that is deviated to the left in FIG. At this time, the flowing ink has a momentum in the direction from the common liquid chamber 154 to the pressure chamber 155, that is, the upward direction in FIG. 10, so that the flow flowing under the pressure chamber 155 is small. For this reason, the bubble 187 seems to extend long downward, and the bubble 187 immediately before the defoaming.
Has a crescent shape extending vertically long as shown in FIG. Then, the final defoaming step shown in FIG. 10F occurs in such a vertically long region.

As described above, in the ink jet recording head of this conventional example, since a rotating component is generated in the ink flow in the pressure chamber 155 during bubble erasing, it is fluidly unstable and the bubble erasing position tends to fluctuate. In addition, since the defoaming is generated by being dispersed in a vertically long area, the cavitation impact is also widely dispersed in the continuous area. As a result, the cavitation impact does not concentrate on one point, and the electrothermal conversion element 151
Impact force is reduced.

The defoaming position shown in FIG. 10 is a position where an Al electrode (not shown) for supplying electric power to the electrothermal transducer 151 is connected to the electrothermal transducer 151. This portion is step-shaped from the Al electrode toward the electrothermal transducer 151 and is a structurally weak portion. It was confirmed that the durability was remarkably increased only by forming a shallow crack.

[0021]

However, in the conventional ink jet recording head shown in FIG. 8, as described above, the center line of the ink flow path 163 coincides with the center line of the electrothermal transducer 151. The common liquid chamber 154
The flow of the ink from the ink jet head to the pressure chamber 155 through the ink flow path 163 is generated symmetrically with respect to the center line of the electrothermal conversion element 151. Therefore, bubbles generated by heating the ink by the electrothermal conversion element 151 stably disappear on the electrothermal conversion element 151 symmetrically with respect to the center line.

As a result, microdroplets are generated from the meniscus surface of the ink on the center line of the ink flow path 163 by the impact force due to the cavitation at the time of the defoaming. Since many of these fine droplets are generated substantially at the center of the ejection port 152, the ejection port 152 is stably provided without being blocked by the edge of the ejection port 152.
Will be discharged.

On the other hand, the following phenomenon occurs in the ink jet recording head shown in FIG.

FIG. 11 shows the manner in which ink droplets are ejected from the nozzles of the ink jet recording head shown in FIG. 9 in the order of FIGS. 2A is a plan view showing the discharge port forming member in a see-through state, and FIG. 2B is a cross-sectional view taken along the line CC ′ in FIG. I have.

FIG. 11 (I) shows a state immediately after bubbles generated on the electrothermal transducer 151 have disappeared. The main droplet and the satellite droplet following it are ejected from the ejection port 152 along the ejection port center axis. As mentioned above,
Since the center line of the ink flow path 183 is offset from the center line of the electrothermal transducer 151 and the pressure chamber 155, and the nozzle shape is asymmetric with respect to the center line of the ink flow path 183, the defoaming occurs. This is performed in the defoaming area indicated by the dotted line in FIG. Then, fine droplets are generated above the defoaming region. The generated microdroplets are located at the ejection port 15
2, it flies near the edge of the discharge port 152 as shown in FIG. 11 (II).

In such an asymmetric nozzle, since the defoaming position tends to fluctuate, the ejection direction of the minute droplet is unstable. For this reason, as shown in FIG. 11 (III), there is a case where the ink is discharged through the discharge port 152, but in many cases, the discharge is performed.
The ink collides with the edge of No. 2 and adheres to the outer surface near the ejection port to form an ink reservoir.

When an ink pool is formed on the outer surface near the discharge port, and the size of the ink pool exceeds a certain level, the ink pool interferes with ink droplets discharged from the discharge port and affects the discharge state of the ink droplets.

FIG. 12 shows how ink droplets are ejected from the nozzles of the ink jet recording head shown in FIG. 9 in a state where an ink reservoir is formed on the outer surface near the ejection port, from FIG. (III). 2A is a plan view showing the discharge port forming member in a see-through state, and FIG. 2B is a cross-sectional view taken along the line CC ′ in FIG. I have.

FIG. 12I shows that the minute droplets
This shows a state in which an ink pool is formed by adhering to a nearby outer surface.

FIG. 12 (II) shows a state in which ink droplets are about to be ejected in a state where an ink pool is formed on the outer surface near the ejection port 152. If an ink pool is formed near the discharge port 152, the ink droplet contacts the ink pool when discharged from the discharge port 152, and is drawn toward the ink pool by surface tension. Then, the ink droplets are ejected in a direction shifted from the ejection port central axis.

FIG. 12 (III) shows a state in which the formation of the ink droplets is completed thereafter, and the main droplets and the satellite droplets fly in a direction deviated from the central axis of the discharge port. When the ejection operation is performed in a state where the ink reservoir is formed near the ejection port 152, not only the ejection direction of the ink droplet is shifted, but also the ejection speed and the ejection amount are decreased at the same time. easy. As a result, the landing position of the ink droplet on the recording medium is deviated from the original position, causing "streaks" or "unevenness" in the recorded image, and the quality of the recorded image is degraded. Was.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ink jet recording head which can prevent an ink pool from being generated in the vicinity of a discharge port and can maintain an ideal discharge state of ink droplets.

[0033]

In order to achieve the above object, an ink jet recording head according to the present invention comprises: a plurality of electrothermal transducers for foaming and discharging ink; a plurality of ink discharge ports for discharging ink; A pressure chamber that houses the electrothermal transducer and forms a space for heating and bubbling the ink, a plurality of ink flow paths for supplying ink to the ink ejection ports, and a plurality of the ink flow paths A common liquid chamber for supplying ink, wherein one ink flow path is provided for one electrothermal conversion element, and a center line of the ink flow path is offset from a center line of the electrothermal conversion element. In the ink jet recording head, the center of the ink ejection port is arranged to be offset from the center of the electrothermal transducer. To.

According to the above-described ink jet recording head of the present invention, when the discharge port is arranged at a position far from the defoaming area which is the energy source of the fine droplet, the fine droplet is discharged from the discharge port. Can be prevented, or
When the discharge port is arranged almost directly above the defoaming region, it becomes possible to discharge the minute droplet without being blocked by the edge of the discharge port. Therefore, by arranging the center of the ink ejection port so as to be offset from the center of the electrothermal conversion element, it is possible to prevent the occurrence of ink accumulation in the vicinity of the ejection port. As a result, it is possible to maintain an ideal ejection state of the ink droplet.

The center of the ink ejection port is arranged at a position offset from the center of the electrothermal transducer in the direction opposite to the common liquid chamber, so that the ink ejection port is minute. Since the liquid droplets are arranged at a position farther from the defoaming region which is the energy source of the droplets, the minute droplets collide with the wall surface of the discharge port and are not discharged out of the discharge port. As a result, it is possible to prevent the accumulation of ink near the ejection port.

Alternatively, the center of the ink discharge port is arranged at a position offset from the center of the electrothermal transducer in the direction opposite to the center line of the ink flow path. Since the discharge port is arranged almost directly above the defoaming region, the minute droplet is discharged without being blocked by the edge of the discharge port. As a result, it is possible to prevent the accumulation of ink near the ejection port.

Further, the center of the ink discharge port is arranged at a position offset from the center of the electrothermal transducer in the direction opposite to the common liquid chamber, and the center of the electrothermal transducer is A configuration may be adopted in which the ink flow path is arranged at a position offset in a direction opposite to the center line of the ink flow path.

Further, the amount of the offset is 1 to 10 μm.
m is preferable.

Further, the electrothermal transducer may be arranged so that the center of the electrothermal transducer is offset from the center of the pressure chamber. Accordingly, it is possible to set a large offset amount between the center of the discharge port and the center of the electrothermal transducer while keeping the offset amount of the center of the discharge port from the center of the pressure chamber small. As a result, it is possible to prevent ink from being formed on the outer surface in the vicinity of the ejection port while achieving appropriate maintenance of the ejection direction of the ink droplets and suppression of bubble accumulation generated in the pressure chamber, thereby preventing the recording image from being formed. The quality can be kept higher.

Further, it is preferable that the direction of offset of the ink flow path from the center line of the electrothermal transducer is the same for the plurality of ink flow paths arranged in a line. . With this configuration, even if the formation positions of the members that form the ink flow paths and the pressure chambers deviate from their original positions due to manufacturing variations, the relative positions of the ink flow paths with respect to the electrothermal conversion elements and the ejection openings Is similarly shifted by a plurality of nozzles, so that a shift in the ink discharge amount and the ink discharge direction between the plurality of nozzles can be prevented, and a bad influence on a formed image can be prevented.

Similarly, the ink flow paths are formed in two rows so as to face each other with the common liquid chamber interposed therebetween, and the electric heat flow of the ink flow paths belonging to the opposed ink flow path rows is formed. It is preferable that the offset direction from the center line of the conversion element be a line-symmetrical direction with respect to a line parallel to the direction in which the opposed ink flow channel rows are arranged.

[0042]

Next, embodiments of the present invention will be described with reference to the drawings.

(First Embodiment) FIG. 1 is a schematic view showing a nozzle portion in a first embodiment of the ink jet recording head of the present invention. FIG. 3A is a plan view showing the discharge port forming member in a see-through state, and FIG. 3B is a cross-sectional view taken along line BB ′ of FIG.

In the ink jet recording head of this embodiment, the ink flow path 83 has a center line
1, and the discharge port 52 is positioned such that the center of the discharge port 52 is offset from the center of the electrothermal conversion element 51 in the direction opposite to the common liquid chamber 54. It is arranged to be located. Other configurations of the ink jet recording head of the present embodiment are the same as those of the ink jet recording head shown in FIG.

FIG. 2 shows the manner in which ink droplets are ejected from the nozzles of the ink jet recording head shown in FIG. 1 in the order of FIGS. 2A is a plan view showing the discharge port forming member in a see-through state, and FIG. 2B is a cross-sectional view taken along the line CC ′ in FIG. I have.

FIG. 2I shows a state immediately after bubbles generated on the electrothermal transducer 51 have disappeared. The main droplet and the satellite droplet following it are ejected from the ejection port 52 along the ejection port central axis.

As described above, since the center of the discharge port 52 is offset from the center of the electrothermal conversion element 51 in the direction opposite to the common liquid chamber 54, the discharge port 52 is a source of energy for microdroplets. Is disposed at a position offset in that direction relative to the defoaming area (see FIG. 7A). Therefore, as compared with the case described with reference to FIG. 9, the relative distance between the center of the discharge port 52 and the defoaming position is longer. Therefore, at the time of defoaming, the meniscus surface slightly rises slightly near the wall surface of the discharge port tapered portion (nozzle) as shown by the arrow A in FIG. Disappears. Further, even when a minute droplet is generated, the discharge port taper portion becomes narrower toward the front in the discharge direction. It does not lead to.

As described above, in the recording head of the present embodiment, the minute droplet does not collide with the edge of the ejection port 52,
No ink pool is formed on the outer surface near the discharge port 52.
Therefore, unlike the case described with reference to FIG. 12, the ink droplet does not come into contact with the ink reservoir when ejected from the ejection port 52 and is not drawn toward the ink reservoir due to surface tension. Therefore, the ink droplet discharged from the discharge port 52 flies straight and stably along the central axis of the discharge port as shown in FIGS. 2 (II) and 2 (III). It is possible to stably maintain the quality of the recorded image at a high level.

When the offset amount X (see FIG. 1) of the center of the discharge port with respect to the center of the electrothermal transducer is smaller than 1 μm,
The relative distance between the center of the discharge port 52 and the defoaming position is shortened, and there is a high possibility that the minute liquid droplet is discharged out of the discharge port 52 without colliding with the wall surface of the discharge port taper portion. On the other hand, if the offset amount X is larger than 10 μm, the direction of action of the discharge pressure during bubbling is greatly inclined from the center axis of the discharge port, which adversely affects the discharge direction of ink droplets. Therefore, this offset amount X is 1 μm ≦ X ≦ 1
It is preferably in the range of 0 μm.

(Second Embodiment) FIG. 3 is a schematic diagram showing a nozzle portion of an ink jet recording head according to a second embodiment of the present invention. FIG. 2A is a plan view showing the discharge port forming member in a see-through state, and FIG. 2B is a cross-sectional view taken along line CC ′ of FIG.

In the ink jet recording head of this embodiment, the ink flow path 83 has a center line
1, and the ejection port 52 is arranged such that its center is offset from the center of the electrothermal conversion element 51 in the direction opposite to the center line of the ink flow path 83. It is arranged so that it may be located in the position where it did. Other configurations of the ink jet recording head of this embodiment are the same as those of the ink jet recording head shown in FIG.

FIG. 4 shows the manner in which ink droplets are ejected from the ink jet recording head shown in FIG. 3 in the order of FIGS. 2A is a plan view showing the discharge port forming member in a see-through state, and FIG. 2B is a cross-sectional view taken along the line CC ′ in FIG. I have.

FIG. 2I shows a state immediately after bubbles generated on the electrothermal transducer 51 have disappeared. The main droplet and the satellite droplet following it are ejected from the ejection port 52 along the ejection port central axis.

As described above, since the center of the discharge port 52 is offset from the center of the electrothermal transducer 51 in the direction opposite to the center line of the ink flow path 83, the discharge port 52 is Is located almost directly above the defoaming region (see FIG. 1A) which is the energy generation source. for that reason,
The fine droplets generated by the cavitational impact at the time of bubble disappearance are discharged from substantially the center of the discharge port 52 along the central axis thereof.

Therefore, in the recording head of the present embodiment, the fine droplets are not blocked by the edge of the
Therefore, no ink pool is formed on the outer surface near the discharge port 52. Therefore, unlike the case described with reference to FIG. 12, the ink droplet does not come into contact with the ink reservoir when ejected from the ejection port 52 and is not drawn toward the ink reservoir due to surface tension. Therefore, the ink droplets ejected from the ejection port 52 are as shown in FIG.
As shown in (I) and (III), the ink droplet flies straight and stably along the central axis of the discharge port, so that the landing position of the ink droplet is stabilized, and the quality of the recorded image can be kept high.

Also in the present embodiment, when the offset amount X (see FIG. 3A) of the center of the discharge port with respect to the center of the electrothermal transducer is smaller than 1 μm, the relative position between the center of the discharge port 52 and the defoaming position is reduced. Therefore, there is a high possibility that the minute droplet will be ejected out of the ejection port 52 without colliding with the wall surface of the ejection port taper portion. On the other hand, when the offset amount X is 1
If it is larger than 0 μm, the direction of action of the discharge pressure during foaming will be greatly inclined from the central axis of the discharge port, which will adversely affect the discharge direction of the ink droplets. Therefore, the offset amount X is preferably in the range of 1 μm ≦ X ≦ 10 μm.

Further, in addition to offsetting the discharge port 52 as in the present embodiment, the discharge port 52 as shown in FIG.
May be further offset from the center of the electrothermal conversion element 51 in the direction opposite to the common liquid chamber 54.

(Third Embodiment) FIG. 5 is a schematic diagram showing a nozzle portion of an ink jet recording head according to a third embodiment of the present invention. FIG. 3A is a plan view showing the discharge port forming member in a see-through state, and FIG. 3B is a cross-sectional view taken along line BB ′ of FIG.

In the ink jet recording head of this embodiment, the ink flow path 83 has a center line
1 is arranged so as to be located at a position offset from the center line. Further, the discharge port 52 is arranged such that the center thereof is located at a position offset from the center of the pressure chamber 55 in the direction opposite to the common liquid chamber 54, and the electrothermal conversion element 51 is disposed at the center thereof. Are disposed at positions offset from the center of the pressure chamber 55 toward the common liquid chamber 54. The relative positional relationship between the discharge port 52 and the electrothermal conversion element 51 in the present embodiment is as follows:
It is the same as that shown in FIG. The features of this embodiment are as follows.
The center of the electrothermal conversion element 51 is offset from the center of the pressure chamber 55. Other configurations are the same as those of the ink jet recording head shown in FIG.

In the configuration shown in FIGS. 1 and 3, when the offset amount of the position of the center of the discharge port 52 with respect to the center of the pressure chamber 55 becomes excessively large, the flow resistance balance in the pressure chamber 55 is lost, and the ink droplets are lost. The problem is that the discharge direction of the pressure chamber 55 tends to change, and that the dead pace increases in the pressure chamber 55, so that the accumulation of bubbles in the pressure chamber 55 tends to occur. Here, “bubble accumulation” means that bubbles formed by the aggregation of bubbles dissolved in the ink stay.

On the other hand, according to the configuration of the present embodiment,
While keeping the amount of offset of the center of the discharge port 52 from the center of the pressure chamber 55 small, the center of the discharge port 52 and the electrothermal transducer 51
The offset amount from the center can be set large.
Therefore, according to the present embodiment, while maintaining the proper ejection direction of the ink droplets and suppressing the bubble accumulation generated in the pressure chamber, the minute droplets are discharged from the ejection port 52 as in the configuration of FIG. And the ink pool is not formed on the outer surface near the ejection port 52, and the quality of the recorded image can be kept higher.

The present embodiment is not limited to the above configuration. For example, as shown in FIG. 3, the ejection port 52 is disposed such that the center thereof is located at a position offset from the center of the pressure chamber 55 in a direction opposite to the center line of the ink flow path 83. In the configuration,
The electrothermal transducer 51 may be arranged so that its center is located at a position offset from the center of the pressure chamber 55 in the direction of the center line of the ink flow path 83.

According to this configuration, the offset amount between the center of the discharge port 52 and the center of the electrothermal transducer 51 can be set large while the offset amount of the center of the discharge port 52 from the center of the pressure chamber 55 is kept small. Accordingly, while achieving proper maintenance of the ejection direction of the ink droplets and suppression of bubble accumulation generated in the pressure chamber, the minute droplets are not blocked by the edge of the ejection port 52 as in the configuration of FIG. It is possible to prevent ink from being formed on the outer surface in the vicinity of the discharge port 52 by discharging from the discharge port 52, and it is possible to further maintain the quality of the recorded image.

(Other Embodiments) As in the above embodiments, when the ink flow path 83 is arranged to be offset with respect to the center line of the electrothermal conversion element 51, the nozzle as a whole in FIG. As shown in the enlarged view of FIG.
It is preferable that the offset direction of the ink flow path 83 with respect to the center line of the electrothermal conversion element 51 be uniform for all the nozzles included in one nozzle row.

This will be described with reference to FIG. 7 which shows a plan view of the nozzle. The ink flow path 83 and the pressure chamber 55 are formed on the recording element substrate on which the electrothermal conversion element 51 is formed.
When patterning the members constituting the above, the patterning mask is displaced in the nozzle row direction, and the ink flow path 83 and the pressure chamber 55 are displaced from their original positions shown by the solid lines in FIG.
It may be formed at a position indicated by a broken line.

In such a case, as shown in FIG. 7A, if there is a nozzle having a different offset direction of the ink flow path 83 with respect to the electrothermal conversion element 51, the electrothermal conversion element 5
The positional relationship between 1 and the ink flow path 83 is shifted in different directions between the two nozzles. That is, in the nozzle on the left side of FIG. 7A, the ink flow path 83 shifts in a direction approaching the electrothermal conversion element 51, whereas in the nozzle on the right side, the ink flow path 83 moves away from the electrothermal conversion element 51. Deviate in the direction. This also applies to the positional relationship between the discharge port 52 and the ink flow path 83 which are arranged at a position facing the electrothermal conversion element 51. For this reason, a difference occurs between the two nozzles in the ink ejection characteristics, and there is a fear that the recorded image is disturbed. Further, even if the width and height of the ink flow path are adjusted so as to make the flow resistance uniform between the two nozzles, there is a fear that a difference occurs in the flow resistance between the two nozzles.

On the other hand, as shown in FIG.
When the offset direction of the ink flow path 83 with respect to the electrothermal conversion element 51 is the same, if the formation positions of the ink flow path 83 and the pressure chamber 55 are shifted, the electrothermal conversion element 51 and the ejection port 52 and the ink flow path 83 Is similarly generated in both nozzles, so that the ink ejection characteristics of both nozzles change in the same manner. Therefore, for example, even if the ejection direction and the ejection amount of the ink slightly change, a similar change occurs in a plurality of nozzles, so that the influence on the recorded image is small.

As described above, by making the offset direction of the ink flow path 83 with respect to the electrothermal conversion element 51 the same for each nozzle in one nozzle row, the influence on the recorded image due to manufacturing variations can be reduced. Similarly, when there are two nozzle rows with the common liquid chamber 54 interposed therebetween, the offset direction of the ink flow path 83 with respect to the electrothermal conversion element 51 in the two nozzle rows is the center axis 89 (parallel to the nozzle row). FIG.
Preferably, the direction is line-symmetric with respect to (b). That is, by doing so, the positional relationship between the electrothermal conversion element 51 and the ink flow path 83 due to manufacturing variations can be similarly generated between the two nozzle arrays, and the effect on the recorded image can be reduced. .

[0069]

As described above, the ink jet recording head of the present invention is arranged so that the center of the ink ejection port is offset from the center of the electrothermal transducer, so that the vicinity of the ink ejection port is attained. In this way, it is possible to prevent the occurrence of ink pools, and to maintain an ideal ejection state of ink droplets.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a nozzle portion in a first embodiment of an ink jet recording head of the present invention.

FIG. 2 is a diagram illustrating a state where ink droplets are ejected from nozzles of the inkjet recording head illustrated in FIG. 1;

FIG. 3 is a schematic view showing a nozzle portion in a second embodiment of the ink jet recording head of the present invention.

FIG. 4 is a diagram illustrating a state in which ink droplets are ejected from nozzles of the inkjet recording head illustrated in FIG. 3;

FIG. 5 is a schematic diagram showing a nozzle portion in a third embodiment of the ink jet recording head of the present invention.

6A is a plan view of the entire nozzle portion of the inkjet recording head of the present invention, and FIG. 6B is a plan view of FIG.
It is the A section enlarged view of (a).

FIG. 7 is a plan view of a nozzle portion of the ink jet recording head of the present invention, showing a case where a formation position of a nozzle forming member is shifted.

FIG. 8 is a schematic diagram showing a nozzle portion of a conventional ink jet recording head.

FIG. 9 is a schematic diagram showing a nozzle portion of another conventional inkjet recording head.

FIG. 10 is a schematic plan view of a nozzle showing each transition state of a defoaming step.

FIG. 11 is a diagram illustrating a state in which ink droplets are ejected from nozzles of the inkjet recording head illustrated in FIG. 9;

12 is a diagram illustrating a state in which ink droplets are ejected from nozzles of the ink jet recording head illustrated in FIG. 9 in a state where an ink reservoir is formed on an outer surface near an ejection port.

[Explanation of symbols]

 51 Electrothermal conversion element 52 Discharge port 54 Common liquid chamber 55 Pressure chamber 56 Ink supply port 83 Ink flow path 89 Central axis B

(72) Inventor Kenji Yabe 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Maki Oikawa 3-30-2, Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Mineo Kaneko 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2C057 AF30 AF78 AG11 AG29 AG46 BA04 BA13

Claims (8)

[Claims] 1. A plurality of electrothermal transducers for foaming and ejecting ink, a plurality of ink ejection ports for ejecting ink, and the electrothermal transducer for housing the electrothermal transducer and heating the ink to foam the ink. A pressure chamber forming a space, a plurality of ink flow paths for supplying ink to the ink discharge ports, and a common liquid chamber for supplying ink to the plurality of ink flow paths, wherein the ink flow path is one In the inkjet recording head, one is provided for the electrothermal conversion element, and a center line thereof is arranged so as to be offset from a center line of the electrothermal conversion element. Is arranged so as to be offset from the center of the electrothermal conversion element. 2. The ink jet recording according to claim 1, wherein the center of the ink ejection port is arranged at a position offset from the center of the electrothermal transducer in a direction opposite to the common liquid chamber. head. 3. The ink jet printer according to claim 1, wherein a center of the ink discharge port is arranged at a position offset from a center of the electrothermal transducer in a direction opposite to a center line of the ink flow path. Inkjet recording head. 4. A center of the ink discharge port is arranged at a position offset from a center of the electrothermal conversion element in a direction opposite to the common liquid chamber, and from a center of the electrothermal conversion element. 2. The ink jet recording head according to claim 1, wherein the ink jet recording head is arranged at a position offset in a direction opposite to a center line of the ink flow path. 5. The ink jet recording head according to claim 2, wherein the amount of the offset is 1 to 10 μm. 6. The ink jet recording head according to claim 1, wherein the center of the electrothermal transducer is arranged so as to be offset from the center of the pressure chamber. 7. The method according to claim 1, wherein an offset direction of the ink flow path from a center line of the electrothermal transducer is the same for a plurality of the ink flow paths arranged in a line. The inkjet recording head according to any one of the above. 8. The electrothermal converter according to claim 1, wherein the ink flow paths are formed in two rows so as to face each other with the common liquid chamber interposed therebetween. 8. The ink jet recording head according to claim 1, wherein an offset direction from a center line of the element is a line-symmetric direction with respect to a line parallel to a direction in which the opposed ink flow channel rows are arranged. 9.