JP2001246745A - Ink-jet recording head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink-jet recording head which can stably discharge ink drops and print at a higher speed by eliminating effects by the reflection of a pressure wave generated in a channel when discharging ink drops. SOLUTION: This ink-jet recording head 20 has a plurality of diaphragms 1 of piezoelectric ceramics arranged side by side on an insulating substrate 4. Between the diaphragms 1 is made an ink channel 2. An electrode for driving is set to a side face of each diaphragm 1. The ink-jet recording head further includes a channel member 16 having ink reservoirs 6 and 7 communicating with each channel 2 set to both sides of each diaphragm 1, and a nozzle plate 14 joined to an upper part of the channel member 16 to cover each channel 2 and the ink reservoirs 6 and 7 and having ink discharge openings 13 each communicating with the channel 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in various printers and recorders for printing characters and images by discharging ink droplets from fine ink discharge holes, in facsimile machines, and in pattern formation in the printing and ceramic fields. The present invention relates to an inkjet recording head mounted on a recording device such as a printing machine.

[0002]

2. Description of the Related Art In recent years, with the spread of multimedia, a non-impact type recording device using an ink jet system or a thermal transfer system has been developed in place of the impact type recording device. It is expanding in the home sector.

[0003] Among such non-impact type printing apparatuses, a printing apparatus using an ink jet system has attracted attention for its future potential because it is easy to increase the number of gradations and colors and the running cost is low.

Conventionally, as an ink jet recording head mounted on a recording apparatus using an ink jet system, for example, as shown in FIG. 4, a plurality of grooves having one end closed on a piezoelectric ceramic plate are provided side by side. Each groove is provided with an ink flow path 6
1, and a flow path member 63 having a partition wall 60 as a partition wall for each flow path 61, and joined to an upper portion of the flow path member 63;
A top plate 64 having an ink supply hole 65 for supplying ink to each flow channel 61, a nozzle plate 66 having an ink discharge hole 67 joined to the open end of the flow channel member 63 and communicating with each flow channel 61, In some cases, a driving electrode 62 was formed on the upper half of the side surface of each partition wall 60. In FIG. 4, arrows indicate the polarization direction of the piezoelectric ceramics forming the partition wall 60 (see Japanese Patent Application Laid-Open No. 7-276648).

The ink jet recording head 5
When a voltage is applied to the driving electrode 62 from the driver IC 69 mounted on the closed portion of the flow path member 63 through the lead wire 68 to discharge the ink droplet from 0, the piezoelectric ceramic forming the partition wall 60 is deformed in the shear mode. When the partition wall 60 whose upper and lower sides are constrained is bent and displaced in a substantially “U” shape, a pressure wave is generated in the ink in the flow channel 61, and this pressure wave propagates to the ink ejection hole 67. Ink ejection hole 67
Ink droplets were ejected more.

In the ink jet recording head 50 (hereinafter simply referred to as a head) shown in FIG.
It is difficult to further narrow the pitch of 1 and arrange the ink ejection holes 67 at a high density.
Two heads 50 are arranged and used so that one ink ejection hole 67 of the other head 50 is located between two ink ejection holes 67 of one head 50.

However, when two heads 50, 50 are provided side by side, there is a disadvantage that when the head 50 is mounted on the recording apparatus, the proportion occupied by the head 50 increases.

Therefore, an ink jet recording head 90 as shown in FIG. 5 has been proposed as one corresponding to high-density recording.

The head 90 is formed by arranging two rows of piezoelectric ceramic plates having a plurality of open grooves at both ends, and joining sealing members 81 to both open ends of each groove to form both ends of each groove. A channel member 73 having two rows of channel groups in which each groove serves as an ink flow channel 71 and a wall separating each groove serves as a partition 70, and is joined to an upper portion of the flow channel member 73;
A lid 74 provided with an ink guide hole 76 and an ink supply hole 77 communicating with each flow path 71, and joined on the lid 74;
A nozzle plate 80 comprising a nozzle portion 78 having an ink ejection hole 79 communicating with the ink guide hole 76,
Some of the side walls of each partition wall 70 had a driving electrode 72 formed thereon. A concave portion is formed in the lid portion 74, an ink supply hole 77 is opened in the bottom surface of the concave portion, and an ink passage 75 is formed by the concave portion of the lid portion 74 and the nozzle portion 78. In addition, the flow paths 71 provided in the two rows of flow path groups are obliquely arranged side by side with respect to the end surface of the flow path member 73, and are provided between two ink ejection holes 79 corresponding to one flow path group. It is configured such that one ink ejection hole 79 corresponding to the other flow path group is located (see Japanese Patent Application Laid-Open No. 7-76083).

In the head 90 as well, when a voltage is applied to the driving electrode 72, the piezoelectric ceramics forming the partition wall 70 undergoes shear mode deformation, and the partition wall 70 whose upper and lower sides are constrained is substantially shaped like a square. The ink in the flow path 71 is pressurized by the bending displacement, and the ink ejection holes 79 are pressed.
Ink droplets were ejected more.

Also, since one ink ejection hole 79 corresponding to the other flow path group is located between two ink ejection holes 79 corresponding to one flow path group, The interval between ink droplets ejected from one head 90 can be narrowed, and the dot density of printing can be increased.

[0012]

However, the ink jet recording head 50 shown in FIG.
5 is closed, and the ink jet recording head 90 shown in FIG. 5 has a structure in which both ends of the flow path 71 are closed. Therefore, when the partition walls 60 and 70 are displaced, the flow path 61 is closed. , 71 are reflected at the respective ends and return as reflected waves, which have an adverse effect on the ejection of the next ink droplet. Since the next ink droplet must be ejected at a cycle corresponding to the wave, there has been a problem that it takes time to eject the next ink droplet. The loss of time in one ejection is a very serious problem when viewed over the entire time required for printing.

The heads 50 and 90 shown in FIGS.
Since the entire flow path members 63 and 73 are formed of piezoelectric ceramic, the number of the ink ejection holes 67 and 79 is increased and the flow path members 63 and 73 are increased in order to improve the printing speed. There is also a problem that variations in piezoelectric characteristics of the piezoelectric ceramics forming the path members 63 and 73 become apparent, and the characteristics of ink droplet ejection from the ink ejection holes 67 and 73 become unstable.

[0014]

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a plurality of partitions made of piezoelectric ceramics on an insulating substrate, and a space between the partitions as an ink flow path. And a flow path member having an ink reservoir communicating with each flow path at both ends of each partition wall, and joined to an upper portion of the flow path member so as to cover the flow path and the ink reservoir. In addition, the ink jet recording head comprises a nozzle plate having ink discharge holes communicating with the respective flow paths.

It is preferable that the volume of each ink reservoir is 1.0 times or more and 10.0 times or less of the sum of the volumes of the respective flow paths.

Further, according to the present invention, a plurality of partitions made of piezoelectric ceramics are juxtaposed on an insulating substrate, and a plurality of rows are formed at intervals with a group of channels having ink channels between the partitions. A flow path having a driving electrode on a side surface of the partition wall forming the flow path group, and ink reservoirs respectively communicating with the flow paths of the flow path groups at both end sides of the partition wall forming the flow path group. An ink jet recording head is constituted by a member and a nozzle plate which is joined to an upper portion of the flow path member so as to cover the flow path and the ink reservoir and has an ink discharge hole communicating with each flow path.

It is preferable that the volume of each ink reservoir be 1.0 times or more and 10.0 times or less the total of the volumes of the flow paths in each flow path group.

[0018]

Embodiments of the present invention will be described below.

FIG. 1 is a view showing an ink jet recording head according to the present invention, wherein FIG.
(B) is a front view of (a).

The ink jet recording head 20 includes a flow path member 16, a nozzle plate 14 joined to an upper part of the flow path member 16, and a container 17 joined to a lower part of the flow path member 16.

The flow path member 16 includes a plurality of partition walls 1 made of piezoelectric ceramics subjected to a polarization process, which are bonded on the insulating substrate 4 by bonding, and a frame body 5 surrounding each partition wall 1 is bonded by bonding. The space between the plurality of partitions 1 is used as an ink flow path 2, the concave portions formed by both ends of each partition 1 and the frame 5 are used as ink reservoirs 6 and 7, respectively, An ink supply hole 8 is formed in the insulating substrate 4 forming the bottom of the reservoir 6, and an insulating substrate 4 forming the bottom of the other ink reservoir 7.
Are provided with ink recovery holes 9 respectively.

The nozzle plate 14 is made of molybdenum or Ni-Fe.
A lid portion 10 made of a metal such as a base alloy, and a nozzle portion 12 made of a resin such as a polyimide resin. The lid portion 10 has an ink guide hole 11 communicating with each flow path 2,
The nozzle portion 12 has an ink ejection hole 13 communicating with each ink guide hole 11. And this nozzle plate 1
Numeral 4 is bonded to the top surface of each partition wall 1 of the flow channel member 16 and the top surface of the frame 5 so as to cover each flow channel 2 and the ink reservoirs 6 and 7.

The partition wall 1 is formed of a piezoelectric ceramic mainly containing lead zirconate titanate, lead zirconate lanthanum titanate, lead magnesium niobate or a mixture thereof, and has a trapezoidal side surface. As shown in FIG. 2, it is polarized in the direction of the arrow. Further, a driving electrode 3 is formed on the upper half of the side surface of each partition wall 1, and an electric field is generated in a direction perpendicular to the polarization direction of the piezoelectric ceramics forming the partition wall 1 by energizing the driving electrode 3. Then, the piezoelectric ceramics undergo shear mode deformation, so that the partition 1 can be displaced. S is a protective film made of silicon nitride or the like that is applied to the side surface of the partition wall 1 and the bottom surface of the flow channel 2 so as to cover the driving electrode 3, and prevents the driving electrode 3 from being eroded by ink. It is.

The drive electrodes 3 are energized by connecting the leads 3a of each drive electrode 3 wired on the insulating substrate 4 to the frame 5
It is connected to a driver IC 15 mounted on the outer insulating substrate 4, and the driver IC 15 controls the energization of each driving electrode 3.

Further, an ink supply passage 18 for guiding ink to the ink supply hole 8 and an ink collection passage 19 for collecting ink from the ink collection hole 9 are provided in a container 17 joined to a lower portion of the insulating substrate 4. The ink supplied from an ink tank (not shown) to the ink supply passage 18 of the container 17 is supplied from the ink supply hole 8 to one of the ink reservoirs 6.
To the other ink reservoir 7 through the inside of the flow path 2, and can be collected from the ink collection hole 9 to the ink collection passage 19.

As described above, by generating and circulating a minute flow of ink in the flow path 2, the head 2
To prevent bubbles or foreign matter in the ink from entering the flow path 2 due to the malfunction of the ink ejection hole 13, thereby lowering the ink droplet ejection performance or causing the ink ejection hole 13 to be clogged. Can be prevented.

In order to eject ink droplets from the ink jet recording head 20, first, an ink such as a pigment type oil-based ink, a water-based dye ink, or an ultraviolet curable ink is supplied to the container 17 by a circulation mechanism (not shown). The ink is supplied to the passage 18, sent to the ink reservoir 6, the channel 2, and the ink reservoir 7 through the ink supply hole 8, and then circulated so as to be recovered from the ink recovery hole 9 to the ink recovery passage 19. In this state, for example, as shown in FIG. 2A, a positive voltage is applied to the driving electrodes 3b, 3c and the driving electrodes 3h, 3i, and a negative voltage is applied to the driving electrodes 3a, 3d, 3g, 3j. Then, the partition 1a and the partition 1b are connected to the flow path 2a.
And the partition walls 1d and 1e are connected to the flow path 2d.
Because of the bending displacement to the side, the ink filled in the flow paths 2a and 2d can be pressurized and ink droplets can be ejected from the ink ejection holes 9. Next, each of the driving electrodes 3a to 3d,
When the power supply to 3g to 3j is cut off, the partition walls 1a, 1b, 1d, 1e that have been bent and displaced return to their original shapes by the elastic action, and the pressure in the flow paths 2a, 2d is reduced. When the voltage is applied with the polarity of the driving electrodes 3a to 3d and 3g to 3j reversed, as shown in FIG. 2B, the partition walls 1a and 1b flow. Since the partition walls 1d and 1e are bent and displaced outward with respect to the flow path 2d while being bent outward with respect to the path 2a, the pressure inside the flow paths 2a and 2d is further reduced and the ink is filled. Then, the driving electrodes 3a to 3d
When the energization of 3d, 3g to 3j is cut off, the partition walls 1a, 1b, 1d, 1e, which have been bent and displaced, return to their original shapes by the elastic action, and enter the stage of discharging the next ink droplet. By sequentially repeating these operations, it is possible to continuously discharge ink droplets.

According to the ink jet recording head 20 of the present invention, both ends of each flow path 2 are opened, and each flow path 2
Since the ink reservoirs 6 and 7 communicating with the ink are provided, the partition wall 1 is bent and displaced in order to discharge the ink droplets. Even if a pressure wave is generated in the direction, since both ends of the flow path 2 are open, they are not reflected at both ends of the flow path unlike the conventional head, and the pressure waves are attenuated by the ink reservoirs 6 and 7. Can be done. That is, upon ejection of ink droplets,
There is no need to consider reflected waves. Therefore, according to the head 20 of the present invention, it is possible to always generate a pressure wave in accordance with the displacement of the partition 1, so that stable ejection of ink droplets is possible, and in ejection of the next ink droplet, Since the ink droplets can be ejected at an arbitrary timing, the ejection interval of the ink droplets ejected from one ink ejection hole 13 can be shortened, and higher-speed printing can be realized.

Further, in the head 20 of the present invention, since the bottom surface of the flow path 2 is formed of the insulating substrate 4, the dielectric loss is smaller than that in which the entire flow path member is formed of piezoelectric ceramics. Partition wall 1 necessary to discharge
In order to obtain the displacement, it is possible to suppress useless electric power and drive with low electric power.

By the way, to achieve such an effect,
It is preferable that the volume of each of the ink reservoirs 6 and 7 formed at both ends of the partition wall 1 be 1.0 times or more and 10.0 times or less of the total volume of each flow path 2.

If the volume of each of the ink reservoirs 6 and 7 is less than 1.0 times the sum of the volumes of the respective flow paths 2,
This is because it is difficult to sufficiently attenuate the pressure wave generated in the ink reservoirs 6 and 7, and conversely,
Is larger than 10.0 times the sum of the volumes of the respective flow paths 2, even if the volumes of the ink reservoirs 6 and 7 are further increased, the size of the head 20 is increased and only one ink ejection hole is formed. 13
This is because it is not possible to shorten the ejection interval of ink droplets that can be ejected from the printer. Preferably, the volume of each of the ink reservoirs 6 and 7 is set to 1.0% of the total volume of each of the flow paths 2.
It is better to be at least twice and at most 5.0 times.

For example, like the head 20 shown in FIG.
Insulating substrate 4 and nozzle plate 14 for forming ink reservoirs 6 and 7
Is installed in parallel at a fixed distance, the distance from the end face of the partition wall 1 forming the ink reservoirs 6 and 7 to the frame 5 is 0.5 times or more the length of the flow path 2; 5.0 times or less,
Preferably, the volume of each of the ink reservoirs 6 and 7 is set to 1.0 times or more and 10.0 times or less of the sum of the volumes of the respective flow paths 2 by preferably being 0.5 times or more and 2.5 times or less. be able to.

Next, a method of manufacturing the ink jet recording head 20 shown in FIG. 1 will be described.

First, a ceramic plate or a glass plate is prepared as the insulating substrate 4. Although the type of the ceramic plate is not particularly limited, for example, alumina, zirconia,
Insulating ceramics containing forsterite, zircon or the like as a main component are preferred.

The ink supply holes 8 are formed at predetermined positions on the insulating substrate 4 by laser processing such as a carbon dioxide gas laser.
Then, a piezoelectric ceramic plate polarized in the thickness direction is attached to a predetermined position on the insulating substrate 4 with an epoxy-based adhesive or the like.

Next, the piezoelectric ceramic plate is cut out using a surface grinder to form a trapezoidal side surface, and then a plurality of grooves serving as flow paths 2 are juxtaposed in the piezoelectric ceramic plate with a diamond blade. At this time, the wall that partitions the groove becomes the partition wall 1.

Then, aluminum, palladium, nickel, gold, copper, etc. are formed on the upper half of the side wall of each partition 1 and on the insulating substrate 4 by a film forming means such as a vapor deposition method, a sputtering method, an ion plating method and a CVD method. A driving electrode 3 is formed on the upper half of the side surface of the partition wall 1, and a lead 16 of the driving electrode 3 is formed on the insulating substrate 4.
Further, a protective film S such as silicon nitride is applied to the inside of the flow channel 2 by the film forming means.

Thereafter, the frame 5 is attached to the insulating substrate 4 so as to surround each partition 1, the ink supply hole 8 and the ink recovery hole 9.
It is air-tightly bonded on the top with an adhesive such as epoxy.

The cover 10 made of a metal such as a Ni—Fe alloy or molybdenum is placed on the partition wall 1 and the frame 5 so that the center of the ink guide hole 11 coincides with the center of the flow path 2 in the width direction. And a nozzle 12 made of a resin such as a polyimide resin on the lid 10 with an epoxy-based adhesive or the like.

Thereafter, the driver IC 15 is mounted on the insulating substrate 4 on which the lead wires 16 are formed outside the frame body 5 and connected through a reflow furnace. Then, the nozzle is formed by laser processing such as excimer laser. An ink discharge hole 13 communicating with each of the ink guide holes 11 is opened in the portion 12, and a container 17 having an ink supply passage 18 and an ink recovery passage 19 is formed below the insulating substrate 4 with an adhesive such as epoxy. It can be obtained by joining in an airtight manner.

Next, another embodiment of the present invention will be described.

FIGS. 3A and 3B are views showing another ink jet recording head according to the present invention, wherein FIG. 3A is a perspective view with a part thereof cut away, and FIG. 3B is a plan view of FIG.

The ink jet recording head 40 has basically the same structure as the ink jet recording head 20 shown in FIG. 1 except that two rows of flow path groups are provided on the insulating substrate 24 and a high-density printing type head is used. Things.

That is, the flow path member 36 includes a plurality of partition walls 21 made of piezoelectric ceramics on an insulating substrate 24 made of a ceramic plate or a glass plate containing alumina, zirconia, forsterite, steatite, zircon or the like as a main component. Two groups of flow channels, which are arranged side by side by bonding and have ink channels 22 between the partition walls 21, are formed at predetermined intervals in two rows, and the frame 25 is bonded to surround the flow channel group. The recess formed between the two rows of flow channel groups is an ink reservoir 26, and the recess formed by the end of each flow channel group and the frame 25 is an ink reservoir 27, 27, an ink supply hole 28 is formed in the insulating substrate 24 forming the bottom surface of the ink reservoir 26.
The ink collecting holes 29 are formed in the insulating substrate 24 which forms the bottom surface of each of the ink reservoirs 27.

A flow path 22 formed between the partition walls 21
Are inclined with respect to the short side of the insulating substrate 24 in the range of 0.8 ° to 1.0 °, the flow paths 22 of each flow path group are set at the same interval, and the flow paths 22 are positioned on the same line. It is arranged to do.

The partition wall 21 is formed of piezoelectric ceramics mainly containing lead zirconate titanate, lead zirconate lanthanum titanate, lead magnesium niobate or a mixture thereof, and has a trapezoidal side surface. 21 is polarized similarly to the partition wall 1 of FIG. A driving electrode 23 is formed on the upper half of the side surface of each partition 21, and an electric field is generated in a direction perpendicular to the polarization direction of the piezoelectric ceramics forming the partition 21 by supplying electricity to the driving electrode 23. Then, the piezoelectric ceramics undergo shear mode deformation, so that the partition 21 can be displaced.

The energization of the driving electrodes 23 is performed by connecting the lead wires 23 a of the respective driving electrodes 23 wired on the insulating substrate 24.
Is connected to a driver IC 35 mounted on the insulating substrate 24 outside the frame 25, and the driver IC 35 controls the energization of each driving electrode 23.

The nozzle plate 34 is made of molybdenum or Ni.
A lid portion 30 made of a metal such as an Fe-based alloy, and a nozzle portion 32 made of a resin such as a polyimide resin;
Is provided with an ink guide hole 31 communicating with the flow path 22 of each flow path group, and the nozzle section 32 is provided with each ink guide hole 31.
An ink discharge hole 33 communicating with the nozzle is opened. The nozzle plate 34 is connected to each flow path 22 and the ink reservoir 2.
The top surface of each partition wall 21 of the flow path member 36 and the top surface of the frame body 35 are bonded by adhesive so as to cover 6 and 27. Therefore, as shown in FIG. 3B, the ink ejection holes 33 corresponding to one flow path group are arranged between the two ink ejection holes 33 corresponding to the other flow path group. Has become.

Further, a container 37 is provided below the insulating substrate 24.
In the container 37, an ink supply passage 38 for guiding ink to the ink supply hole 28, an ink collection passage 39 for collecting ink from the ink collection hole 29,
39 are formed, and an ink tank (not shown) is
The ink supplied to the ink supply passage 38 of No. 7 is sent from the ink supply 28 to the ink reservoir 26,
2, the ink is sent to the ink reservoirs 27, 27, and can be recovered from the ink recovery holes 29, 29 to the ink recovery passages 39, 39.

The ink jet recording head 4
0, when an ink droplet is ejected, the pressure wave generated in the flow path 22 due to the displacement of the partition wall 21, especially the pressure wave in the longitudinal direction of the flow path 22 is attenuated by the ink reservoirs 26, 27, 27,
Since it is difficult to return to the inside of the flow path 22, it is possible to generate a pressure wave in accordance with the displacement of the partition 21 at all times, thereby enabling stable ejection of ink droplets, and at an arbitrary timing upon ejection of the next ink droplet. Since ink droplets can be ejected, the ejection interval of ink droplets ejected from one ink ejection hole 33 can be shortened, and higher-speed printing can be realized.

Further, since the bottom surface of the flow path 2 is formed of the insulating substrate 4, the dielectric loss can be reduced as compared with the case where the entire flow path member is formed of piezoelectric ceramics. It is possible to suppress useless electric power for obtaining a simple displacement of the partition wall 1 and to drive the partition wall 1 with low electric power.

Further, the flow path group is formed obliquely to the short side of the insulating substrate 24, and the ink discharge holes 33 corresponding to one of the flow path groups are replaced with two ink discharge holes corresponding to the other flow path group. 33, when the ink droplets are ejected from the ink ejection holes 33 corresponding to the respective flow path groups, the dot interval can be reduced without increasing the size of the head, and the recording density can be reduced. Can be increased.

In order to achieve these effects, the volume of each ink reservoir 26, 27, 27 must be the same as that of the head 20 in FIG. The total volume of the flow path is 1.0 times or more and 10.0 times or less, preferably 1.0 times or more and 5.0 times or less.

Although the embodiments of the ink jet recording head of the present invention have been described above, the present invention is not limited to only these structures.
34 may be formed of a simple substance of ceramics or metal.
4 are provided with ink supply holes 8 and 28 and ink recovery holes 9 and 29, and containers 17 and 37 provided with ink supply passages 18 and 38 and ink recovery passages 19 and 39 are provided. Although the ink is circulated constantly, the ink may be circulated only when the ejection performance of the ink droplets is reduced.

Needless to say, changes and improvements can be made without departing from the gist of the present invention.

[0056]

(Embodiment 1) The ink jet recording head 20 shown in FIG. 1 will be specifically described.

First, as the insulating substrate 4, 95 mm × 25
A 10 mm × 3 mm × 10 mm × 3 mm × 10 mm × 3 mm × 10 mm × 3 mm × 10 mm × 1.5 mm round ink supply hole 8 and an ink recovery hole 9 were formed in an insulating substrate 4 made of an alumina ceramic plate of mm × 1 mm. Four piezoelectric ceramic plates each having a plate shape of 0.5 mm and mainly composed of lead zirconate titanate polarized in the thickness direction are placed on the insulating substrate 4 between the ink supply holes 8 and the ink recovery holes 9. , And pasted with an epoxy-based adhesive. Then, the end of the piezoelectric ceramic plate is cut off with a surface grinder to form a taper with an angle of 60 ° with the insulating substrate 4. The shape was made trapezoidal, and the upper surface of the piezoelectric ceramic plate was ground so that the height became 0.45 mm.

Further, using a diamond blade having a thickness of 70 μm,
0.45mm deep on the piezoceramic plate at an angle of 1 °,
284 channels 2 were formed at a pitch of 0.14 mm.

Next, an aluminum metal film is applied to the lower half of the side surface of the partition wall 1 by vacuum evaporation to form the driving electrode 3, and the aluminum metal film is also applied to a predetermined position on the insulating substrate 4. After forming the lead wire 16 of the driving electrode 3, a protective film S of silicon nitride was further deposited on the inner wall surface of the flow channel 2 by a sputtering method.

A molybdenum frame 5 having an outer shape of 50 × 17 mm, an inner shape of 42 × 13 mm, and a thickness of 0.45 mm surrounds each partition 1, ink supply hole 8 and ink recovery hole 9. As described above, the air-tight bonding was performed on the insulating substrate 4 with an epoxy-based adhesive, and the concave portions formed by both ends of each flow path 2 and the frame body 5 were ink reservoirs 6 and 7.

On the top surface of the frame 5 and the top surface of the partition wall 1, an ink guide hole having an outer shape of 50 mm × 17 mm × 0.07 mm and having a diameter of about 60 μm communicating with each flow path 2 is provided. A molybdenum lid 10 provided with an adhesive 11 is bonded with an epoxy-based adhesive, and on the lid 10, a polyimide resin nozzle 12 having an outer shape of 50 mm × 13 mm × 0.05 mm is formed. After bonding with an epoxy-based adhesive, an ink ejection hole 13 having a diameter of about 28 μm communicating with the ink guide hole 11 was opened with an excimer laser, and the nozzle plate 14 was bonded.

Thereafter, the driver IC 15 is mounted on the lead 16 formed on the insulating substrate 4 and connected through a reflow furnace, and has an ink supply passage 18 and an ink recovery passage 19 below the insulating substrate 4. The container 17 was joined with an epoxy-based adhesive to produce the ink jet recording head 20 of the present invention shown in FIG.

Here, the row of the ink ejection holes 13 of the ink jet recording head 20 is incorporated in the recording apparatus so that it is perpendicular to the main scanning direction of the head 20.
Eject ink droplets while reciprocating in the main scanning direction,
The printing is performed by sending the printing paper in a direction perpendicular to the main scanning direction, the time required to print the predetermined information, the maximum driving frequency of the partition 1, the average diameter of the ink droplets and its variation, and the continuous driving for 30 minutes. An experiment was conducted to examine the variation in the average diameter of ink droplets ejected from the same ink ejection hole 13 and the number of average ejection failure locations per fixed area.

In this experiment, in order to ensure the accuracy in measuring the diameter of the ink droplet, A4 size ink jet paper coated with silica was used.

In measuring the time required to print the predetermined information, a 360 dpi line, a lattice pattern,
And a monochrome test pattern consisting of characters and the like was printed, and the time required for this printing was measured.

The maximum driving frequency of the partition 1 is measured by observing the ejection state of ink droplets by a high-speed photographing with a magnifying glass and a CCD camera with the head 20 fixed and the ink jet exclusive paper removed, and analyzing the image by image analysis. The maximum drive frequency at which ink droplets were ejected was determined.

With respect to the average diameter and variation of the ink droplets and the fluctuation of the diameter of the ink droplets during continuous printing, the diameter when the ink droplets landed on the ink jet paper was measured by a dimension measuring machine utilizing image recognition. Then, after measuring the average value and the variation, the landing state of the ink droplet after continuously driving for 30 minutes was examined, and the fluctuation state was confirmed.

Regarding the number of average ejection failure locations per fixed area, assuming that the driving frequency is 12 kHz, 360 d
A monochrome test pattern consisting of pi lines, a lattice pattern, characters, etc. is printed, and the printed test pattern is
Observed with a microscope every 0 cm ² ,
The number of locations determined to be printing defects due to ejection of ink droplets, such as significant displacement and the attachment of unnecessary ink droplets, were counted.

The results are as shown in Table 1.
For comparison, a similar experiment was performed using the conventional ink jet recording head 50 shown in FIG. However,
The conventional inkjet recording head 50 has the same diameter as the ink ejection holes 67 and the interval between the ink ejection holes 67 as the head 20 of the present invention.

[0070]

[Table 1]

As a result, the head 20 of the present invention can obtain a higher limit driving frequency than the conventional head 50 and has a small variation although the average diameter of the ink droplet is large.
In addition, even when the ink droplets were continuously driven, the fluctuation of the average diameter of the ink droplets was small, and the number of defective ink droplets was also small, so that stable ink droplet discharge was possible.

(Embodiment 2) Next, in the ink jet recording head 20 of the present invention in Embodiment 1, the distance from the end face of the partition 1 to the frame 5 and the height of the partition 1 and the frame 5 are respectively changed. To change the volume of the ink reservoirs 6 and 7, and, as in the first embodiment, a line of 360 dpi, a lattice pattern,
A monochrome test pattern consisting of a solid portion and a character is printed, and the ejection interval of ink droplets is increased or decreased so that the partition 1
An experiment was conducted to determine the average number of defective ink droplet ejections per 100 cm ² when the driving frequency was changed.

The results are as shown in Table 2.

[0074]

[Table 2]

As a result, by setting the volumes of the ink reservoirs 6 and 7 to be at least 1.0 times the sum of the volumes of the respective flow paths 2,
The longitudinal pressure waves generated in the flow path 2 are transferred to the ink reservoirs 6 and 7.
In this way, it is possible to reduce the number of defective ink droplet ejections, and to suppress the number of defective ink droplet ejections even if the driving frequency is increased to increase the ink droplet ejection speed. Especially suitable for high speed printing.

However, if the volume of each of the ink reservoirs 6 and 7 exceeds 10.0 times the sum of the volumes of the respective flow paths 2, the head 20
Became too large, which was not preferable.

As a result, it is preferable that the volumes of the ink reservoirs 6 and 7 are set within a range of 1.0 times or more and 10.0 times or less of the sum of the volumes of the respective flow paths 2. It can be seen that the volume of each of the ink reservoirs 6 and 7 should be set to 1.0 times or more and 5.0 times or less of the sum of the volumes of the respective flow paths 2 in order to achieve the above.

In this embodiment, only an example in which the ink jet recording head 20 shown in FIG. 1 is compared with the conventional ink jet recording head 50 shown in FIG. 4 is shown, but the ink jet recording head 40 of the present invention shown in FIG.
In comparison with the conventional ink jet recording head 90 shown in FIG. 5, the ink jet recording head 40 of the present invention also had better performance.

[0079]

As described above, in the ink jet recording head of the present invention, a plurality of partitions made of piezoelectric ceramic are arranged in parallel on an insulating substrate. A driving electrode is provided on the side surface of the partition wall, and a flow path member having ink reservoirs communicating with the respective flow paths at both end sides of each partition wall, and is joined to an upper portion of the flow path member so as to cover the flow paths and the ink reservoir. And the nozzle plate having ink discharge holes communicating with each flow path, it is not necessary to consider the reflected wave in the flow path when discharging ink droplets, so that it always responds to the displacement of the partition wall. Can generate stable pressure waves, thereby enabling stable ejection of ink droplets and, at the same time as discharging the next ink droplet, discharging ink droplets at an arbitrary timing. Hole Ejection interval of the ink droplets ejected can be reduced, it is possible to achieve faster printing.

Further, according to the present invention, a plurality of partition walls made of piezoelectric ceramics are juxtaposed on an insulating substrate, and a plurality of rows are formed at intervals with a group of flow paths having ink flow paths between the partition walls. A flow path having a driving electrode on a side surface of the partition wall forming the flow path group, and ink reservoirs respectively communicating with the flow paths of the flow path groups at both end sides of the partition wall forming the flow path group. The above-described effects are obtained by configuring an ink jet recording head from a member and a nozzle plate having an ink ejection hole communicating with each flow path, which is joined to an upper part of the flow path member so as to cover the flow path and the ink reservoir. In addition, since the ejection density of ink droplets can be increased without increasing the size of the head, a head capable of higher density printing can be obtained.

Further, in the present invention, the volume of each ink reservoir provided at both ends of each partition is set to 1.0 times or more and 10.0 times or less, preferably 1.0 time or less of the sum of the volumes of the respective flow paths. By setting the length to at least 5.0 times, it is possible to attenuate the longitudinal pressure waves generated in the flow path in each ink reservoir without increasing the size of the head. It is possible to realize a head capable of discharging droplets and printing at higher speed.

[Brief description of the drawings]

FIGS. 1A and 1B are views showing an ink jet recording head according to the present invention, wherein FIG. 1A is a perspective view with a part thereof cut away, and FIG.

FIGS. 2A and 2B are partial cross-sectional views illustrating the driving principle of an ink jet recording head according to the present invention.

3A and 3B are views showing another ink jet recording head according to the present invention, wherein FIG. 3A is a perspective view with a part thereof cut away, and FIG.
Is a plan view thereof.

FIG. 4 is a partially broken perspective view showing a conventional ink jet recording head.

FIG. 5 is a partially cutaway perspective view showing another conventional ink jet recording head.

[Explanation of symbols]

1: partition wall 2: flow path 3: drive electrode 3a: lead wire
4: Insulating substrate 5: Frame body 6, 7: Ink reservoir 8: Ink supply hole 9: Ink recovery hole 10: Lid 11: Ink guide hole 12: Nozzle 13: Ink ejection hole 14: Nozzle plate 15: Driver IC 16: flow path member 17: container
18: Ink supply path 19: Ink recovery path 20: Ink jet recording head 21: Partition wall 22: Flow path 23: Driving electrode 23a:
Lead wire 24: insulating substrate 25: frame body 26, 27: ink reservoir 28: ink supply hole 29: ink recovery hole 30: lid 31: ink guide hole 32: nozzle 3
3: Ink ejection hole 34: Nozzle plate 35: Driver IC 36: Flow path member 37: Container 38: Ink supply path 39: Ink recovery path 40: Ink jet recording head 50: Ink jet recording head 60: Partition 61: Flow path 62: Driving electrode 63: Flow path member 64: Lid plate 65: Ink supply hole 66: Nozzle plate 67: Ink ejection hole 68: Lead line 69: Driver IC 70: Partition wall 71: Flow path 7
2: drive electrode 73: flow path member 74: lid 75: ink passage 7
6: Ink guide hole 77: Ink supply hole 78: Nozzle part 79: Ink ejection hole 80: Nozzle plate 81: Sealing member 90: Ink jet recording head

Claims (4)

[Claims] 1. A plurality of partitions made of piezoelectric ceramics are juxtaposed on an insulating substrate, a space between the partitions is used as an ink flow path, a driving electrode is provided on a side surface of each of the partitions, and each partition is provided with a driving electrode. At both end sides, there is provided a flow path member having an ink reservoir communicating with each flow path, and an ink discharge hole joined to an upper portion of the flow path member so as to cover the flow path and the ink reservoir and communicating with each flow path. An ink jet recording head comprising a nozzle plate. 2. The ink jet recording head according to claim 1, wherein the volume of each ink reservoir is 1.0 times or more and 10.0 times or less of the sum of the volumes of the respective flow paths. 3. A plurality of partitions made of piezoelectric ceramics are juxtaposed on an insulating substrate, and a plurality of rows are formed at intervals with a plurality of rows of flow channels having ink channels between the partitions. A flow path member having an ink reservoir communicating with the flow path of each flow path group at both end sides of the partition walls configuring each flow path group, and a driving electrode on a side surface of the partition wall configuring the group, An ink jet recording head comprising: a nozzle plate having an ink discharge hole connected to each of the flow passages and joined to an upper portion of the flow passage member so as to cover the flow passage and the ink reservoir. 4. The ink jet recording head according to claim 3, wherein the volume of each ink reservoir is 1.0 times or more and 10.0 times or less of the sum of the volumes of the flow paths in each of the flow path groups.