JP2002137384A - Ink jet recording head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recording head in which ink drop ejection interval can be shortened without enlarging the size of the head. SOLUTION: The ink jet recording head 20 comprises a channel member 1 provided with ink channels 3 by juxtaposing a plurality of barrier walls 2 of piezoelectric ceramics, a frame body 11 provided on the side of the channel member 1 to form ink chambers 14 communicating with the ink channels 3, drive electrodes 4 formed on the side face of respective barrier walls 2, and a nozzle plate 10 bonded to the top face of each barrier wall 2 to cover at least the plurality of channels 3 and provided with ink ejection holes 9 communicating with the respective ink channels 3 wherein a relation 2h<=H is satisfied, assuming the distance from the top face of the barrier wall 2 to the bottom face of the channel 3 is h and the distance from the top face of the barrier wall 2 to the bottom face of the ink chamber 14 is H.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to various printers and recorders for recording characters and images by ejecting ink droplets from ink ejection holes, facsimile machines, and recording machines used for pattern formation in the printing and ceramic fields. And the like.

[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 an 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.

FIGS. 7A and 7B show an example of an ink jet recording head used in a recording apparatus utilizing an ink jet system. As shown in FIG. A plurality of grooves, both ends of which are open, are juxtaposed on one main surface (the widest surface) of the processed piezoelectric ceramic plate, and each groove is used as an ink flow path 83, and a wall separating each groove is formed by a partition wall. 82, a driving electrode 84 formed on the lower half of the side surface of each partition 82, and a top surface of each partition 82 so as to cover each flow channel 83. Nozzle plate 85 having ink ejection holes 86 communicating with 83
And a sealing member 88 joined to the ends of the flow path member 81 and the nozzle plate 85 to form an ink chamber 87 communicating with the flow paths 83, and an ink supply provided in each of the sealing members 88. When current is applied between the driving electrodes 84 formed on both side surfaces of the partition wall 82, the piezoelectric ceramics forming the partition wall 82 undergo shear mode deformation, and the partition wall 82 is restricted vertically. From "ku"
The ink in the flow path 83 is pressurized by the displacement of the partition wall 82 to eject ink droplets from the ink ejection holes 86.

The ink jet recording head 10
0 can supply the ink into each of the ink chambers 87 from the ink supply holes 89 provided in the sealing members 88 provided on both sides, so that the time until the ink is replenished in the flow path 83 is shortened. As a result, it is possible to reduce the time until the next ink ejection is possible. Reference numeral 90 denotes a lead wire of the driving electrode 84 (see Japanese Patent Application Laid-Open No. 9-94952).

[0006]

FIG. 7 (a)
In the conventional head 100 shown in (b), the height M of the ink chamber 87 (the distance from the top surface of the partition wall 82 to the bottom surface of the ink chamber 87) is equal to the height m of the flow path 83 (flow from the top surface of the partition wall 82). Road 83
The distance N from the end face of the partition 82 to the inner wall surface of the sealing member 88 is short when the ink in the flow path 83 is pressurized. The pressure wave generated toward the open end side is reflected on the inner wall surface of the sealing member 88 and returns to the inside of the flow path 83.
In this case, if the synchronization with the pressure wave generated for the next ink ejection is not properly achieved, the ink droplet ejection speed becomes unstable or unnecessary ink droplets are ejected. Therefore, in order to perform stable ejection of ink droplets, it is necessary to wait for the reflected wave reflected on the inner surface of the sealing member 88 to return to the inside of the flow path 83 and generate the ink for the next ink ejection. It suffices to synchronize with the pressure wave, but there is a problem in that it takes time for the reflected wave to return to the inside of the flow path 83, and the interval between ink droplet ejections cannot be shortened.

On the other hand, if the distance N from the end surface of the partition wall 82 to the inner wall surface of the sealing member 88 is increased, when the ink in the flow channel 83 is pressurized, the ink is generated toward the open end of the flow channel 83. Can be attenuated in the ink chamber 87, the ink in the flow path 83 can be immediately pressurized and ejected as soon as the replenishment of the ink in the flow path 83 is completed. Although the ejection interval of the droplets can be shortened, in this case, there is an inconvenience that the length of the head 100 is increased and the size cannot be reduced.
In particular, in recent years, in order to obtain clear color image quality, three, five, or even more different colors of ink are used. However, unless a plurality of heads are mounted on a printing apparatus according to the number of inks, However, as a result, one head 100
Is large, the recording apparatus cannot be downsized.

Further, in the conventional head 100 shown in FIGS. 7A and 7B, since the ink supply hole 89 is opened on the extension of the flow path 83, the ink supplied from the ink supply hole 89 can be removed. Due to the flow, there is a difference between the flow of ink in the flow path 83 and the propagation velocity of the pressure wave between the flow path 83 located near the ink supply hole 89 and the flow path 83 located at a position distant from the ink supply hole 89. In such a case, the ejection performance of the ink droplets ejected from each ink ejection hole 86 may be adversely affected.

[0009]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention provides a flow path member in which a plurality of piezoelectric ceramic partition walls are juxtaposed, and an ink flow path is provided between the partition walls. Are provided on the sides of the frame, and form a frame body that forms an ink chamber that communicates with the flow path, driving electrodes formed on the side surfaces of the partition walls, and the above-described respective electrodes so as to cover at least the plurality of flow paths. A nozzle plate that is joined to the top surface of the partition wall and has an ink discharge hole that communicates with each of the flow paths; a distance from the top surface of the partition wall to the bottom surface of the flow path is h; When the distance to the bottom of the ink chamber is H, 2
The ink jet recording head is configured so as to satisfy the relationship of h ≦ H.

In particular, the distance h from the top surface of the partition to the bottom surface of the flow path and the distance H from the top surface of the partition to the bottom surface of the ink chamber may satisfy the relationship of 4h ≦ H. preferable.

[0011]

Embodiments of the present invention will be described below.

FIGS. 1A and 1B are views showing an example of an ink jet recording head according to the present invention. FIG. 1A is a perspective view with a part thereof cut away, and FIG. 1B is a sectional view taken along line XX of FIG. FIG.
(A) and (b) are cross-sectional views for explaining the driving principle of the inkjet recording head according to the present invention.

The ink jet recording head 20 (hereinafter, simply referred to as a head) is made of insulating ceramics or glass, and has a rectangular cross-section on a side surface of a rectangular prism 15 along a longitudinal direction and a height direction. A plurality of partition walls 2 made of piezoelectric ceramics polarized in parallel are arranged at predetermined intervals, and a flow path member 1 having an ink flow path 3 between the partition walls 2 is provided on both sides of the main surface of the prism 15. A frame 11 that is provided and forms an ink chamber 14 that communicates with each of the flow paths 3; and a top surface of each partition 2 and a top surface of each frame 11 that cover each flow path 3 and each ink chamber 14. Each of the partition walls 2 is formed with a nozzle plate 10 having an ink discharge hole 9 communicating with each of the flow paths 3.

The frame body 11 is configured so that its cross-sectional shape is substantially U-shaped. One side of the frame body 11 is joined to the main surface of the prism 15 and the other side has a top. The surface is
An ink supply hole 12 for supplying ink into the ink chamber 14 is formed at an end of the frame 11 at the same height as the top surface of the partition 2.

The bottom surface of the ink chamber 14 formed by the frame 11 is such that the distance from the top surface of the partition 2 is larger than the distance from the top surface of the partition 2 to the bottom surface of the flow path 3. The distance from the top surface of the partition 2 to the bottom surface of the ink chamber 14 is H, and the distance from the top surface of the partition 2 to the bottom surface of the flow path 3 is h.
, It is configured to satisfy the relationship of 2h ≦ H.

Further, the nozzle plate 10 includes a lid 5 having an ink guide hole 6 communicating with each flow path 2 and a nozzle hole 8 communicating with the ink guide hole 6 and having a smaller diameter than the ink guide hole 6. The ink guide hole 6 and the nozzle hole 8 are combined to form an ink discharge hole 9.

Reference numeral 13 denotes a lead line of the driving electrode 4 formed on one main surface of the prism 17. Although not shown, the driving electrode 4 and the lead 13 of the driving electrode 4 are covered on the side surface of the partition wall 2 forming the flow path 3, the side surface of the prism 15, and the main surface of the prism 15. A protective film such as silicon nitride is applied to prevent the drive electrode 4 and the lead wire 13 from being corroded by the ink.

In order to eject ink droplets from the head 20, first, an ink such as a pigment-type aqueous ink, an oil-based ink, an aqueous dye ink, or an ultraviolet-curable ink is supplied from an ink tank (not shown) to an ink supply hole 1.
2 to fill the ink chamber 10 and each flow path 3 with ink. In this state, for example, as shown in FIG. 2A, the negative electrodes are applied to the driving electrodes 4b and 4c and the driving electrodes 4h and 4i, and the positive voltages are applied to the driving electrodes 4a, 4d, 4g and 4j. Is applied, the piezoelectric ceramics forming the partition walls 2a and 2b undergo shear mode deformation, and the partition walls 2a and 2b can be bent and displaced toward the flow path 3a because the upper and lower walls are restrained, respectively. The piezoelectric ceramics forming the partition wall 2d and the partition wall 2e also undergo shear mode deformation, and since the partition walls 2d and 2e are respectively restrained up and down, they can be bent and displaced toward the flow channel 3d. The ink filled in 3d is pressurized, and ink droplets are ejected from the ink ejection holes 9.

Next, the driving electrodes 4a to 4d, 4g to 4
When the current to j is cut off, the partition walls 2a,
2b, 2d, 2e return to the original shape by the elastic action, and as a result the pressure inside the flow paths 3a, 3d is reduced. As a result, the introduction of ink from the ink supply hole 12 is started, and the above-mentioned driving lightning pole When a voltage is applied to 4a to 4d and 4g to 4j by reversing the positive and negative, as shown in FIG.
2b is bent outwardly with respect to the flow path 3a,
Since the partitions 2d and 2e are bent and displaced outward with respect to the ink flow path 3d, the pressure in the flow paths 3a and 3d is further reduced, and the ink is filled. Then, each driving electrode 4a
4d, 4g to 4j, the partition walls 2a, 2b, 2d, 2e, which have been bent and displaced, return to the original shape by the elastic action and enter the next ink ejection stage. By repeating these operations sequentially, ink droplets are continuously discharged from the ink discharge holes 9.

According to the present invention, the distance H from the top surface of the partition wall 2 to the bottom surface of the ink chamber 14 and the distance h from the top surface of the partition wall 2 to the bottom surface of the flow path 3 satisfy 2h ≦ H. The relationship is satisfied, so that when the ink in the flow path 3 is pressurized in order to eject ink droplets, the ink chamber 1
4 can be diffused and attenuated in the direction of the bottom surface of the ink chamber 14, the distance L from the end of the partition 2 to the inner wall surface of the frame 11 can be reduced.
Can be prevented from being reflected on the inner wall surface of the frame 11 even if the length of the head 20 is shortened, and the head 20 can be significantly reduced in size. As described above, the pressure wave generated in the flow path 3 is
Since the ink is not reflected by the inner wall surface of the ink, the next ink droplet can be ejected immediately after the ink is filled in the flow path 3, and the ejection interval of the ink droplet can be greatly reduced.

In addition, the head 20 shown in FIG. 1 is also provided with ink chambers 14 on both sides of the flow path 3, and each ink chamber 14 is provided with an ink supply hole 12 for supplying ink. The time for refilling the ink into the ink droplets 3 can be shortened, and the interval between ink droplet ejections can be further reduced.

Therefore, the use of the head 20 makes it possible to reduce the size of the recording device and to provide a recording device capable of high-speed printing.

According to the head 20 of the present invention, the prism 15 constituting the bottom surface of the flow path 3 is made of insulating ceramics or glass, and only the partition 2 to be displaced is made of piezoelectric ceramic. Unlike the conventional head 100 shown in (a) and (b), the dielectric loss can be greatly reduced unlike the case where the bottom surface of the flow path 83 is formed of piezoelectric ceramics. Power consumption can be reduced, and the partition wall 2 can be displaced with less power.
, The heat generation of the ink droplets can be suppressed, and it is possible to prevent the deterioration of the ink and the adverse effect on the ejection of the ink droplets.

Further, according to the head 20 of the present invention, the ink supplied from the ink supply hole 12 is made to flow by opening the ink supply hole 12 in the region formed by the frame 11 and the prism 15. The ink can be supplied uniformly into each flow path 3 without obstructing the flow of the ink in the flow path 3. Drops can be ejected.

In the head 20 shown in FIG. 1, two ink supply holes 12 communicating with the ink chambers 14 provided on both sides of the flow path 3 are shown. For example, one of the ink supply holes 12 is provided. The ink recovery hole may be used, and the ink may be supplied from the other ink supply hole 12 to the flow channel 3 to recover the ink from the ink recovery hole. With such a structure, the pressure in the flow channel 3 is reduced. Even when air flows in from the ink ejection holes 9 and bubbles are generated in the flow path 3,
Since bubbles can be removed by circulating in the flow path 3, when the ink in the flow path 3 is pressurized, the pressure wave is attenuated by the deformation of the bubbles, and the discharge speed and discharge amount of the ink droplets decrease. Can be prevented.

By the way, in order to shorten the interval between ink droplets while miniaturizing the head 20, the distance H from the top surface of the partition 2 to the bottom surface of the ink chamber 14 and the distance H from the top surface of the partition 2 to the flow path 3 It is important that the distance h to the bottom surface satisfies the relationship of 2h ≦ H. That is, if the relationship between the distance H from the top surface of the partition wall 2 to the bottom surface of the ink chamber 14 and the distance h from the top surface of the partition wall 2 to the bottom surface of the flow path 3 is 2h> H, ink droplets are ejected. Therefore, even if the pressure wave generated in the direction of the ink chamber 14 when the ink in the flow path 3 is pressurized is diffused in the direction of the bottom surface of the ink chamber 14, it cannot be sufficiently attenuated in the ink chamber 14. Since the pressure wave is reflected on the inner wall surface of the frame body 11 and the reflected wave returns to the inside of the flow path 3, it is necessary to synchronize with the pressure wave generated for the next ink ejection. This is because the ejection interval of the droplet cannot be shortened. In addition, more preferably, the partition 2
The distance h from the top surface to the bottom surface of the flow path 3 and the distance H from the top surface of the partition wall 2 to the bottom surface of the ink chamber 14 may satisfy the relationship of 4h ≦ H.

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

First, a prism 15 having a rectangular cross section made of insulating ceramics or glass mainly composed of alumina, zirconia, forsterite, zircon, cordierite or the like is prepared.

On the side surface of the prism 15, a long piezoelectric material mainly composed of lead zirconate titanate, lead lanthanum titanate zirconate, lead magnesium niobate, or a mixture thereof is polarized. Functional ceramic plates are joined with an epoxy adhesive.

Next, after the end face of the piezoelectric ceramic plate is cut off to form a trapezoidal side surface by surface grinding, the piezoelectric ceramic plate is extended by a diamond blade in a direction perpendicular to the main surface of the prism 15. The grooves are arranged at regular intervals along the longitudinal direction of the prism 15, and the flow path member 1 is formed in which each groove is used as an ink flow path 3 and a wall that partitions between the grooves is a partition 2.

The material for forming the prism 15 is as follows.
When it is not necessary to consider power consumption or the like so much, a piezoelectric ceramic having lead zirconate titanate, lead zirconate lanthanum titanate, lead magnesium niobate or a mixture thereof as a main component may be used. In the case of using piezoelectric ceramics, the prism 15 is subjected to a polarization treatment in a direction perpendicular to the side surface, and the longitudinal end surface on one side surface of the prism 15 is cut out by plane grinding to form a tapered surface. Prismatic prism 15 with surface formed
The channel member 1 may be formed by arranging grooves extending in a direction perpendicular to the main surface with a diamond blade at equal intervals along the longitudinal direction of the prism 15 on the side surfaces of the prism.

Next, the upper half of the side wall of each of the partition walls 2 and the side surface of the prism 15 (the bottom surface of the flow path 3) and one main surface of the prism 15 are formed on the main surface of the prism 15 by vapor deposition, sputtering, ion plating, CVD, or the like. Aluminum,
A metal film made of palladium, nickel, gold, copper, or the like is deposited, and the metal film formed on the upper half of the side surface of the partition wall 2 is used as the driving electrode 4 and communicates with the driving electrode 4 to form a side surface of the prism 15. After the metal film formed on one main surface of the prism 15 from the (bottom of the flow path 3) is used as the lead 13 of the driving electrode 4, the flow is further covered so as to cover the driving electrode 4 and the lead 13. The side surfaces of the partition walls 2 and the side surfaces of the prisms 15 and the one main surface of the prisms 15 constituting the path 3 are made of silicon nitride or the like by a film forming means such as an evaporation method, a sputtering method, an ion plating method, and a CVD method. A protective film (not shown) is applied.

Thereafter, a frame 11 having a substantially U-shaped cross section is disposed on both sides of the main surface of the prism 15, and the top of one side of the frame 11 is flush with the top of the partition 2. After being positioned so as to be positioned above, the other side of the frame 11 is air-tightly bonded to the main surface of the prism 15 with an epoxy-based or silicon-based adhesive to form the frame 11 and the prism 15 together. Is defined as an ink chamber 14.

The material for forming the frame 11 is as follows.
Although not particularly limited, resins such as polycarbonate, polyimide, and polysulfone are suitable in terms of cost and workability, and metals and ceramics may be used.

Next, the nozzle plate 10 is joined to the top surface of the partition wall 2 and the top surface of the frame body 11. First, metals such as stainless steel, nickel-based alloy, molybdenum, alumina, zirconia, forsterite, zircon A thin plate-shaped lid 5 made of ceramics containing cordierite or the like as a main component, or a resin such as glass, polycarbonate, polyimide, or polysulfone is positioned such that the ink guide hole 6 of the lid 5 is located at the center of the flow path 3. After the alignment, the lid 5 is joined to the top surface of the partition wall 2 and the top surface of the frame body 11 via an epoxy-based or silicon-based adhesive, and further, polyimide, polysulfone, or the like is placed on the lid 5. After joining the thin plate-shaped nozzle portion 7 made of the above resin with an epoxy-based or silicon-based adhesive, the nozzle portion 7 is laser-processed with an excimer laser or the like. Can be obtained head 20 shown in FIG. 1 by a nozzle hole 8 communicating with an ink guide hole 6 of the lid 5 is opened to form ink discharge holes 9.

Next, another embodiment of the ink jet recording head according to the present invention will be described.

The head 20 shown in FIG. 3 has two walls 2a and 2a made of piezoelectric ceramics which are polarized in the height direction.
The partition walls 2 are brought into contact with each other so that their polarization directions are opposed to each other, and are joined with an epoxy-based or silicon-based adhesive to form the partition walls 2, and the driving electrodes 4 are formed on the entire side surfaces of the partition walls 2. Except for this, the head has the same structure as the head 20 shown in FIG. 1.
When the drive electrode 4 is energized, the two walls 2a and 2b forming the partition wall 2 can be deformed in the shear mode, respectively, and the joint between the two walls 2a and 2b is formed of an adhesive layer that is easily elastically deformed. In addition, compared with the head 20 shown in FIG. 1, the partition wall 2 can be largely bent and displaced, and the discharge speed and the discharge amount of the ink droplet can be increased.

The head 20 shown in FIG. 4 has the side top surface of the frame 11 of the head 20 shown in FIG. 1 slightly lower than the top surface of the partition wall 2, and the top surface of the partition wall 2 and the side portion of the frame body 11. When the nozzle plate 10 is joined to the top surface, the end of the nozzle plate 10 is curved,
The structure is such that the center of the nozzle plate 10 having the ink discharge holes 9 protrudes. With such a structure,
Even if the recording paper comes into contact with the nozzle plate 10, the recording paper can be smoothly fed, so that a paper jam can be effectively prevented.

The head 21 shown in FIG. 5 is prepared by preparing two flow path members 1 of the head 20 shown in FIG. 1, and making the main surfaces of the flow path members 1 on which the lead-out lines 13 are not formed face each other. 22 and a frame 23 having a U-shaped cross section is disposed above the spacer 22.
A space formed by the two flow path members 1 is defined as an ink chamber 24, and a substantially U-shaped frame 11 is formed on the main surface of the two flow path members 1 where the lead lines 13 are formed. The space formed by the frame body 11 and the flow path member 1 is joined to form an ink chamber 14, and the top surface of the partition wall 2 and the top surface of the frame body 11 cover the flow paths 3 and the ink chambers 14 and 24. The nozzle plate 10 is formed with ink discharge holes 9 communicating with the respective flow paths 3 formed in the two flow path members 1.

According to the head 21, although a large number of ink ejection holes 9 can be formed in the nozzle plate 9 while being small, many characters and images can be formed at once, and the printing time can be reduced. Since the length can be reduced and the dot interval can be narrowed, a head having a high pixel density can be obtained.

The head 31 shown in FIG. 6 corresponds to the frame 11 shown in FIG.
Are prepared, and each of the flow path members 1 is joined to each other via a spacer 32 so as to integrally cover the flow path 3 and the ink chamber 14 of each of the flow path members 1. Nozzle plate 9
Are joined to the top surface of the partition wall 2 of each flow path member 1 and the top surface of the frame body 11, and the nozzle plate 10 has ink ejection holes communicating with the flow paths 3 formed in each flow path member 1. 9 is formed.

According to this head 31, since each flow path member 1 provided with the frame 11 is independent, each flow path member 1
By filling the flow path 3 and the ink chamber 14 with inks of different colors, it is possible to eject four types of inks in a small size, and to obtain a head capable of color printing.
Also, if the same color ink is filled in the flow path 3 and the ink chamber 14 of each flow path member 1, a large number of characters and images can be formed at once, and the printing time can be reduced. be able to.

Although the embodiments of the present invention have been described above, the present invention is not limited to these structures. For example, an example in which the nozzle plate 9 is formed by joining the lid 5 and the nozzle 7 respectively. However, it is needless to say that it may be formed of a single substance of ceramics, metal, glass, or resin, and may be changed or improved without departing from the gist of the present invention.

[0044]

(Embodiment 1) Hereinafter, a specific example of the head 20 shown in FIG. 1 will be described.

First, a prism 15 made of alumina ceramic of 50 mm × 10 mm × 2 mm was prepared, and 11 mm × 2 m was placed on the side (50 mm × 2 mm) of the prism 15.
Four piezoceramic plates, each composed of lead zirconate titanate having a plate shape of mx 0.5 mm and polarized in the thickness direction, are arranged in a straight line in the same polarization direction, and the epoxy adhesive is used. Then, the end face of the piezoelectric ceramic plate was cut out with a surface grinder to form a taper surface having an angle of 45 ° with the side surface of the prism 15, so that the side surface shape was trapezoidal. The upper surface of the piezoelectric ceramic plate was ground so that the height became 0.45 mm.

Next, using a diamond blade having a thickness of 70 μm, a depth of 0.45
A flow path member 1 was formed in which 284 grooves having a pitch of 0.141 mm were formed and each groove was used as a flow path 3 for the ink, and a wall separating each groove was a partition wall 2.

Next, an aluminum metal film is applied to the upper half of the side surface of each partition 2 by vacuum evaporation to form the driving electrode 4, and aluminum is formed on the main surface and side edges of the prism 15 by vacuum evaporation. After forming the lead lines 13 of the driving electrode 4 by depositing the metal film described above, a protective film S of silicon nitride covering the driving electrode 4 and the lead lines 13 was deposited.

Next, the cross-sectional shape is substantially U-shaped, the thickness is 0.3 mm, the radius of curvature of the inner diameter is 0.7 mm, and the height of one side (from the bottom surface to the top surface of the ink chamber 14). Distance)
Is 5 mm, the height of the other side (the distance from the bottom surface to the top surface of the ink chamber 14) is 3.5 mm, the length is 50 mm, and a polysulfone frame 11 is prepared. The height is 5 m.
m is positioned such that the top surface of the side portion of the m is located on the same plane as the top surface of the partition wall 2, and the side portion having a height of 3.5 mm is
5 is airtightly bonded to the main surface with an epoxy-based adhesive,
The space formed by 1 and the prism 15 was defined as an ink chamber 10.

The distance h from the top surface of the partition wall 2 of the head 20 to the bottom surface of the flow path 2 is 0.4 as described above.
5 mm, and the distance H from the top surface of the partition 2 to the bottom surface of the ink chamber 14 is 5 mm, so that the relationship of 2h <H is satisfied.

After that, the outer dimensions are 50 mm × 7 mm ×
It has a plate shape of 0.07 mm and has a diameter of 6 communicating with each flow path 3.
A lid 5 made of a nickel-iron alloy having an ink guide hole 6 of about 0 μm is joined to the top surface of the partition wall 2 and the top surface of the frame 11 with an epoxy-based adhesive.
A nozzle section 7 made of polyimide resin having a plate shape of mx 6 mm x 0.04 mm is joined with an epoxy adhesive, and then a nozzle hole 8 communicating with each ink guide hole 6 is opened by an excimer laser. The head 20 was manufactured.

The ink discharge holes 9 of the head 20
The head 20 is mounted on the recording apparatus so that the row of the recording medium is in the main scanning direction, and the recording paper is fed in the sub-scanning direction while ejecting ink droplets. Then, a predetermined single-color test pattern composed of lines, a lattice pattern, characters, and the like was recorded on the recording paper.

More specifically, an area of 100 cm ² was extracted from the test pattern recorded on the recording paper, and the diameters of all the ink droplets in the measurement area were measured using a dimensional measuring device utilizing image recognition. The average value and the standard deviation of the diameters of the ink droplets were calculated, and at the time of the above measurement, recording failure spots based on the ink droplet ejection failure were observed, and the number thereof was counted.

The results are as shown in Table 1.

In order to ensure accuracy in measuring the diameter of ink droplets, the recording paper used was a roll-form coated paper having a width of 45 mm having a surface layer coated with silica and an organic binder. The signal voltage applied to the driving electrode 4 formed on the partition 2 is set at a frequency of 20 kHz so that the pattern is recorded at a pixel density of 360 dpi in the sub-scanning direction, and the recording is performed in synchronization with the feeding speed of the recording paper. Was done.

As a comparative example, the distance H from the top surface of the partition wall 2 to the bottom surface of the ink chamber 14 was set to 0.8 mm, and 2 h
A similar experiment was conducted by preparing a head having a relationship of> H.

[0056]

[Table 1]

As a result, in the head of the comparative example, the relationship between the distance H from the top of the partition 2 to the bottom of the ink chamber 14 and the distance h from the top of the partition 2 to the bottom of the flow path 3 is 2h> H, and the distance L from the end face of the partition wall 2 to the inner wall surface of the frame 11 is as small as 1.4 mm, so that the ink chamber generated when the ink in the flow path 3 is pressurized in order to eject the ink. Since the pressure wave in the 14 direction cannot be attenuated in the ink chamber 14, if the ink droplet is ejected in 5 μsec,
The ejection of the next ink droplet was adversely affected by the influence of the reflected wave reflected on the inner wall surface of the frame 11, the average diameter and standard deviation of the ink droplet were large, and the number of defective recordings was large.

On the other hand, in the head 20 of the present invention, the distance L from the end face of the partition wall 2 to the inner wall surface of the frame 11 is 1.4 m.
m, the distance H from the top surface of the partition wall 2 to the bottom surface of the ink chamber 14 and the distance h from the top surface of the partition wall 2 to the bottom surface of the flow path 3 have a relationship of 2h ≦ H. Even if a pressure wave in the direction of the ink chamber 14 is generated when the ink in the flow path 3 is pressurized to discharge
The average diameter and standard deviation of the ink droplets are small even when the ink droplets are ejected at a speed of 5 μsec, and the number of defective recording locations can be extremely small, so that the ink droplets can be stably formed. It can be seen that ejection can be performed. (Embodiment 2) Therefore, in the head 20 in Embodiment 1, the relationship between the distance H from the top surface of the partition wall 2 to the bottom surface of the ink chamber 14 and the distance h from the top surface of the partition wall 2 to the bottom surface of the flow path 3. And the same experiment as in Example 1 was performed.

The results are as shown in Table 2.

[0060]

[Table 2]

As a result, the sample No. Partition wall 2 as in 1
And the distance H from the top surface of the ink chamber 14 to the bottom surface of the ink chamber 14.
(H / h) from the distance h from the top surface to the bottom surface of the flow path 3
Is less than 2, the average diameter and standard deviation of the ink droplets are large, and the number of defective recording locations is as large as 200 or more.

On the other hand, the sample No. As shown in 2 to 6, the distance H from the top surface of the partition wall 2 to the bottom surface of the ink chamber 14 is shown.
If the ratio (H / h) of the distance h from the top surface of the partition wall 2 to the bottom surface of the flow path 3 (H / h) is set to 2 or more, the average diameter and the standard deviation of the ink droplets can be reduced, which is particularly problematic in appearance. It can be seen that the number of defective recording locations can be reduced. In particular, if the ratio (H / h) of the distance H from the top surface of the partition wall 2 to the bottom surface of the ink chamber 14 and the distance h from the top surface of the partition wall 2 to the bottom surface of the flow path 3 is 4 or more, recording is performed. The number of defective portions can be reduced to 100 or less, which is preferable.

[0063]

As described above, according to the ink jet recording head of the present invention, a plurality of partition walls made of piezoelectric ceramics are juxtaposed, and a flow path member having an ink flow path between the partition walls; A frame provided on a side portion of the member and forming an ink chamber communicating with the flow path, a driving electrode formed on a side surface of each of the partition walls, and at least the plurality of flow paths so as to cover the plurality of flow paths. A nozzle plate that is joined to the top surface of each partition and has an ink ejection hole that communicates with each of the flow paths, and the distance from the top surface of the partition to the bottom of the flow path is h,
When the distance from the top surface of the partition wall to the bottom surface of the ink chamber is H, the relationship of 2h ≦ H is satisfied, so that the volume of the ink chamber is secured without increasing the size of the head, The pressure wave in the direction of the ink chamber, which is generated when the ink in the ink chamber is pressurized, can be diffused and attenuated in the ink chamber, so that the ejection interval of the ink droplet can be shortened.

In particular, if the distance h from the top of the partition to the bottom of the flow path and the distance H from the top of the partition to the bottom of the ink chamber satisfy the relationship of 4h ≦ H, Since the pressure wave in the ink chamber direction generated when the ink in the flow path is pressurized can be more effectively diffused and attenuated in the ink chamber, the ejection interval of the ink droplet can be further shortened.

[Brief description of the drawings]

FIGS. 1A and 1B are views showing an inkjet recording head according to the present invention, wherein FIG. 1A is a perspective view with a part thereof cut away, and FIG. 1B is a sectional view taken along line XX of FIG.

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

FIG. 3 is a cross-sectional view illustrating another example of the inkjet recording head according to the present invention.

FIG. 4 is a cross-sectional view showing another example of the inkjet recording head according to the present invention.

FIG. 5 is a partially cutaway perspective view showing an application example of the ink jet recording head according to the present invention.

FIG. 6 is a partially broken perspective view showing another application example of the ink jet recording head according to the present invention.

FIG. 7 is a diagram showing a conventional inkjet recording head.
(A) is a perspective view with a part thereof cut away, and (b) is a cross-sectional view taken along line XX of (a).

[Explanation of symbols]

1: Flow path member 2: Partition wall 3: Flow path 4: Driving electrode
5: Lid 6: Ink guide hole 7: Nozzle 8: Nozzle 9:
Ink ejection hole 10: Nozzle plate 11: Frame 12: Ink supply hole 1
3: Leader line of drive electrode 14: Ink chamber 15: Prismatic column 20: Ink jet recording head H: Distance from top of partition to bottom of ink chamber h: Distance from top of partition to bottom of flow path L: Distance from the end face of the partition to the inner wall of the frame

Claims (2)

[Claims] A plurality of partition walls made of piezoelectric ceramics are juxtaposed, and a flow path member having an ink flow path between the partition walls is provided on a side portion of the flow path member and communicates with each of the flow paths. A frame body that forms the ink chamber, drive electrodes formed on the side surfaces of each of the partition walls, and a top surface of each of the partition walls so as to cover at least each of the flow paths, and communicate with each of the flow paths. A nozzle plate having ink ejection holes, wherein h is the distance from the top surface of the partition to the bottom surface of the flow path, and H is the distance from the top surface of the partition to the bottom surface of the ink chamber.
An ink jet recording head satisfying a relationship of ≦ H. 2. A distance h from the top surface of the partition to the bottom surface of the flow path and a distance H from the top surface of the partition to the bottom surface of the ink chamber satisfy a relationship of 4h ≦ H. The ink jet recording head according to claim 1, wherein: