JPH068425A - Ink jet head - Google Patents

Abstract

PURPOSE:To maintain stable printing quality for a long time by providing a dummy channel filled with elastic filler between two partition walls whose faces opposite to opposing faces of adjacent two partition walls face an ink passage channel. CONSTITUTION:Partition walls 5aa, 5ab, 5bb, 5bc... of piezoelectric raw material are fixed on a substrate 1 in parallel. A large number of slender channels formed among the partition walls are channels 2a, 2b, 2c and dummy channels 12a, 12b of an ink chamber/passage alternately. The channels 2a, 2b, 2c of the ink chamber/passage are connected to a common ink reservoir by each one end, and other ends are stuck to a nozzle plate having nozzle holes 3a, 3b.... The dummy channels 12a and 12b are filled with an elastic filler 6 so as to separate ink between the adjacent channels of the ink chamber/passage. When electric potential which is positive with respect to an electrode 4ab is applied to an electrode 14ab, ink drops are discharged from the nozzle hole 3b by deformation of a shearing mode of the partition wall 5ab. At this time, the elastic filler 6 of the dummy channel is easily deformed as the compressibility is large.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drop-on-demand (DOD) type ink jet head.

[0002]

2. Description of the Related Art Of the non-impact printers that are expanding their market today, the principle is the simplest,
Inkjet printers are also suitable for color printing, and among them, the so-called DOD type that ejects ink droplets only at the time of dot formation can be said to be the mainstream.
Typical examples of the DOD type are the Kaiser type disclosed in Japanese Patent Publication No. 53-12138 and the thermal jet type disclosed in Japanese Patent Publication No. 61-59914. Of these, the former is difficult to miniaturize, the latter says that the ink sticks because of the high heat applied to the ink.
Each has very difficult problems.

As a new method for simultaneously solving the above-mentioned defects, Japanese Patent Laid-Open No. 63-252750 has been proposed.
The shear mode type disclosed in. The structure and operating principle are shown in FIGS. FIG. 8 is a cross-sectional structure diagram when not driven, in which elongated partitions 5aa, 5ab, 5bb, 5bc made of a piezoelectric material such as PZT (lead zirconate titanate) are arranged in parallel on the substrate 1 made of glass, ceramic or plastic. Stick to. Then, the upper surface of the partition wall is flexibly adhered to the lid 8 by the elastic sealing material 7. Although the substrate 1 and the lid 8 are usually insulating members, they may be conductive members that have been subjected to an insulating coating treatment.

Here, a large number of elongated channels formed between the partition walls are alternately formed as channels 2 of the ink chamber / ink channel.
a, 2b, 2c and dummy channels 12a, 12b, 12
c and. Of these channels, one end of the channel of the ink chamber / ink channel is connected to a common ink reservoir, ink is supplied from this end, and the other end has small nozzle holes 3a, 3b, 3c. The nozzle plate is glued. On the other hand, the dummy channel has a hollow interior. The partition wall of the piezoelectric material is aligned in one direction as shown by an arrow 9 (or in the opposite direction) and polarized, and electrodes 4aa, 14aa, 14a are formed on the side surfaces thereof.
b, 4 cc, etc. are formed.

Here, the electrode 4ab is connected to the electrode 14ab shown in FIG.
If a sufficient positive potential is applied to the partition wall 5ab, the partition wall 5ab causes shear mode deformation as shown in FIG. Do the same thing
If the partition wall 5bb is also used, the cross-sectional area of the channel 2b of the ink chamber / ink flow path decreases as shown in FIGS. 8 to 9 in the initial state. That is, due to this volume decrease, the pressure of the ink filled in the channel 2b instantaneously rises,
Ink droplets fly out from the nozzle hole 3b.

[0006]

By the way, FIG. 8 and FIG.
The meaning of the dummy channel is to prevent interference between the channels 2b and 2c of the ink chamber / ink channel corresponding to the adjacent nozzle holes 3b and 3c in the case of 12b of FIG. 9, for example. That is, the function of the dummy channel is to mechanically separate the movements of the partition walls 5bb and 5bc. When the inside of the dummy channel is made hollow, the compression rate of air is large, so that the deformation of one partition wall is not transmitted to the other partition wall, and the above-mentioned function is exhibited. However, it is difficult to keep the inside of the dummy channel hollow, and this is the problem to be solved by the present invention. Hereinafter, the description will be made by chewing.

In the ink jet head, there is a strong demand for higher resolution for high quality printing, and in order to satisfy this, the distance between adjacent nozzle holes, for example, 3b and 3c in FIG.
Usually, about 0 to 300 μm is required. The dummy channel 12b only needs to have the width necessary for the mechanical separation as described above and is narrower than the channels 2b and 2c of the ink chamber / ink channel, but the elastic sealing material 7 for adhesion is nevertheless used. Must be formed with a width of several tens of μm.

Although such a fine bonding process itself is a bottleneck in manufacturing, it is a more serious problem that the formed elastic sealing material 7 is required to have a perfect sealing property. That is, if a minute defect exists in the elastic seal material 7, the dummy channel 12b is filled with ink due to the inflow of ink from the adjacent channel in the long term. In this case, since the compression rate of the ink is small,
The dummy channel 12b does not fulfill its original function, the speed of ink droplets ejected from the adjacent nozzle holes 3b and 3c varies, and ink is ejected erroneously from nozzle holes that should not be ejected. It causes serious problems.

The present invention eliminates the problems of erroneous ejection of ink droplets and variations in ejection speed due to ink flow into the dummy channel due to the structure of the conventional head, and an ink jet which can obtain highly reliable and high quality printing. It is intended to provide a head.

[0010]

[Means for Solving the Problems] To achieve the above object,
The present invention is characterized in that the inside of the dummy channel, which is conventionally hollow, is filled with the elastic filler.

[0011]

By filling the inside of the dummy channel with the elastic filler as in the present invention, the mechanical interference between the partition walls can be prevented at a level close to that when the dummy channel is made hollow. This is because the compressibility of the elastic filler is higher than that of ink. Needless to say, the inflow of ink into the dummy channel is prevented by the elastic filler, and long-term head stability is guaranteed. In addition, the vibration of the partition wall is attenuated more quickly than in the hollow state, and the important secondary effect of improving the response characteristic of the head is also produced. Further, according to this configuration, since the fine pattern formation of the elastic seal material in the conventional example can be omitted, the head manufacturing process is greatly simplified.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 shows an example of the structure of an ink jet head according to the present invention corresponding to FIG. 8 of a conventional example. here,
The difference from FIG. 8 is that the dummy channels 12a and 12b are filled with the elastic filler 6, and further, the elastic seal material 7 used in the conventional example is omitted, and the adjacent inks fulfilled by the seal material are adjacent to each other. The elastic filler 6 also has a function of separating ink between the channels of the chamber and the ink flow path. As the elastic filler, natural rubber, butyl rubber,
Any of urethane rubber, silicon rubber, acrylic rubber, fluororubber, etc. can be used. The width of the dummy channel was made narrower than that of the channel of the ink chamber / ink channel for the same reason as in the conventional example.

FIG. 2 is a sectional view of the head of the present embodiment shown in FIG. 9 in a driven state. Here, the electrode 14a
It is the same as in the case of FIG. 9 that a positive potential is applied to the electrode 4ab at b, the shear mode is deformed at the partition wall 5ab, and ink droplets are ejected from the nozzle hole 3b. At this time, since the elastic filler 6 in the dummy channel has a large compression rate, it is easily deformed, and the original function of the dummy channel is to mechanically separate the movement between the two partition walls forming the dummy channel. It is clear what can be achieved. Actually, the head of this configuration was manufactured and ink was ejected from only a single nozzle hole or a plurality of nozzle holes of various combinations, but there was no erroneous ejection at all, and there was no variation in the ejection speed of ink droplets. Was 4% or less, which was a practically negligible level.

Further, if the meniscus vibration of the ink in the nozzle hole after the ink is ejected is damped and stabilized early, the next ink droplet can be ejected in a short cycle. For this purpose, it is necessary that the vibration of the ink in the channel of the ink chamber and the ink flow path is attenuated quickly. In the case of the configuration of the present invention, the damping of the vibration by viscoelasticity of the elastic filler in the dummy channel is required. Great effect. As a result, the vibration is stabilized more quickly and the high frequency response characteristic of the head is improved, as compared with the conventional dummy channel having a gap.

(Embodiment 2) FIG. 3 is a sectional view showing a different embodiment of the present invention. Here, the substrate 3 made of piezoelectric material
1 by directly forming a groove, the partition walls 35aa, 35ab, 35
bc etc. are formed, and electrodes 3 are formed on the entire inner surface of each groove.
4a, 314a, 34b, etc. are formed. According to this configuration, there is an advantage that the partition formation and the step of fixing the partition to the substrate can be performed at one time. Of course, the electrode may be formed only on the wall surface of the partition wall, but for that purpose, it is necessary to selectively form the electrode in the groove, which is difficult to manufacture.
It was also integrally formed on the bottom as shown. By covering this with the lid 8, the groove is formed into the channel 3 of the ink chamber / ink channel.
2a, 32b, 32c and dummy channels 132a, 13
2b. The basis of the present invention is to fill the dummy channel with the elastic filler 6, and the effect of this structure is the same as that described in FIGS.
Here, both the width and the depth of the channel are smaller in the dummy channel than in the channel that also serves as the ink chamber. The width is as described with reference to FIG. 8, but the depth is intended to reduce the deformation of the substrate base of the piezoelectric material due to the leakage electric field.

FIG. 4 is a perspective view of an ink jet head according to the present invention having the structure of FIG. In this head, a plurality of grooves 32, which serve as channels of ink chambers and ink channels, and grooves 132, which are narrower and shallower than dummy channels, are formed alternately in parallel on a substrate 31 made of a piezoelectric material. The nozzle plate 33 is adhered so as to close the end of the groove, and the lid 38 covers the entire groove. The nozzle plate has a nozzle hole corresponding to the end of the groove 32, and the ink droplet 30 is ejected. The ink is supplied to the ink supply port 39.
It is introduced and supplied to the groove 32 of the ink chamber / ink flow path through a common ink reservoir 34. On the other hand, the groove 132 serving as the dummy channel is filled with the elastic filler 37, and the lid 38 is fixed to the substrate 31 by the filler. The shallow groove portion 36 formed by step processing is used for electrical connection to the outside, and the sealing plate 35 is provided to prevent the outflow of ink to the step processing portion.

The manufacturing method and specific dimensions of this head are as follows. First, thickness 1 polarized in the thickness direction
By cutting the PZT substrate 31 of mm with a dicing saw, a groove 32 of an ink chamber / ink channel having a width of 70 μm and a depth of 200 μm and a groove 132 of a dummy channel having a width of 40 μm and a depth of 120 μm are alternately formed. . The length of each groove is 10 mm. Electrodes were formed on the inner surfaces of these grooves by vapor deposition with a laminated film of chromium and gold having a total thickness of 0.8 μm. Then, the groove of the dummy channel is filled with silicone rubber which is an elastic member, and the plastic lid 38 is fixed by the elastic filling material. Also, the diameter is 35 μm
Nozzle plate 33 made of stainless steel having a nozzle hole of No. 1 was attached by an epoxy adhesive. Nozzle hole pitch is 217
μm and the number was 50.

(Embodiment 3) FIG. 5 shows another embodiment according to the present invention, which is based on the driving principle already disclosed in FIG. 2 of JP-A-63-252750. This structure essentially corresponds to FIG. 1, but a partition wall 55 made of a piezoelectric material is fixed to the substrates 51 and 58, and the polarization directions are reversed as in 9a and 9b.
The tops of a and 55b are bonded together. This structure is composed of a channel 2 serving as an ink chamber and an ink flow path, a dummy channel 12, electrodes 4 and 14, and the like, and the elastic channel is filled in the dummy channel. Further, the partition wall 55 formed integrally is different from the case of FIG. 2 in that the partition wall 55 is deformed in a V shape. However, also in this embodiment, the effect of the present invention described with reference to FIG.

(Embodiment 4) FIG. 6 is a sectional view of still another embodiment of the present invention. This structure is almost the same as that of FIG. 1, and includes a substrate 1, a partition wall 5 of a piezoelectric material polarized as shown by an arrow 9, a lid 8, a channel 2 of an ink chamber / ink channel, a dummy channel 12, electrodes 4, 14. It is composed of nozzle holes 3 and the like. Then, the dummy channel is filled with the elastic filler 6, but an important feature of the present invention is that a large number of minute voids 60 are further present in the elastic filler. The effect of doing so is that the voids are more easily deformed than the elastic filler itself, so that the effective bulk modulus of the elastic filler as a whole is further lowered, and as a result, the dummy channel is sandwiched. The mechanical interference between the partitions has become smaller.

(Embodiment 5) FIG. 7 is a perspective view of an ink jet head according to the present invention, which has a structure different from that of FIG. In this head, a large number of grooves 32, which serve as channels for ink chambers and ink channels, and grooves 132, which serve as dummy channels, are alternately formed in parallel on a substrate 31 made of a piezoelectric material, and the ends of these grooves are closed. Adhering the nozzle plate 33 in this manner is the same as in FIG. However, here, the groove is formed up to the sealing plate 35 without providing a common ink reservoir.
Then, the ink is supplied to the groove 32, which serves as a channel of each ink chamber and ink channel, from the ink supply hole 71 formed corresponding to the groove position of the ink chamber and ink channel of the lid 38. Further, a filling hole 72 is formed in the lid so as to correspond to the groove position of the dummy channel. Then, the elastic member is injected into the groove of the dummy channel through the filling hole to assemble the head. The greatest advantage of this structure is that the filling of the elastic member into the groove is significantly simplified in the head assembling process, and the head can be made stable and the yield can be improved.

[0021]

As described above, according to the structure of the present invention, the instability of the hollow dummy channel, which is one of the serious problems in the shear mode type ink jet head, can be eliminated. That is, since the inflow of ink into the dummy channel is prevented by the elastic filler, the function of the dummy channel does not deteriorate. Therefore, the interference between the adjacent nozzles can be significantly suppressed, and the variation in the ink ejection speed,
Erroneous discharge is eliminated and stable printing quality can be maintained for a long time. Further, as compared with the hollow state, the vibration of the partition wall is attenuated earlier, and the response characteristic of the head is improved, which is an important side effect. Further, according to this configuration, since the fine pattern formation of the elastic seal material in the conventional example can be omitted, the head manufacturing process is greatly simplified.

[Brief description of drawings]

FIG. 1 is an explanatory view of a first embodiment of an inkjet head according to the present invention and is a sectional view.

FIG. 2 is an explanatory diagram of the first embodiment of the inkjet head according to the present invention, and is a sectional view in a driving state.

FIG. 3 is an explanatory view of a second embodiment of the inkjet head according to the present invention and is a sectional view.

FIG. 4 is an explanatory diagram of a second embodiment of the inkjet head according to the present invention, and is a perspective view.

FIG. 5 is an explanatory view of a third embodiment of the ink jet head according to the present invention and is a sectional view.

FIG. 6 is an explanatory view of a fourth embodiment of the inkjet head according to the present invention and is a sectional view.

FIG. 7 is an explanatory diagram of a fifth embodiment of the inkjet head according to the present invention, and is a perspective view.

FIG. 8 is an explanatory diagram of a conventional technique and is a cross-sectional view.

FIG. 9 is an explanatory view of a conventional technique and is a cross-sectional view in a driving state.

[Explanation of symbols]

 1 Substrate 2a Channel for ink chamber and ink channel 3a Nozzle hole 5ab Partition wall 6 Elastic filler 8 Lid 9 Polarization direction 12a Dummy channel 30 Ink droplet 31 Substrate made of piezoelectric material 34 Common ink reservoir 60 Micro void

Claims (4)

[Claims] 1. A plurality of elongated barrier ribs made of a piezoelectric material and having electrodes on side surfaces are arranged in parallel, and the barrier ribs are deformed in a shear mode by a voltage applied between the electrodes, and are formed between the barrier ribs. In a shear mode inkjet head for ejecting ink of an ink flow channel through a nozzle hole, a surface opposite to an opposing surface of two adjacent partition walls faces the ink flow channel between the two partition walls. An ink jet head characterized in that a dummy channel filled with an elastic filler is provided. 2. The ink jet head according to claim 1, wherein the elastic filling body has a large number of minute voids. 3. An ink flow channel is formed by providing a lid covering each partition wall, forming an elastic filler in the dummy channel higher than the height of the partition wall, and fixing the lid to the elastic filler body. The ink jet head according to claim 1, which is characterized in that. 4. An elastic filling body which covers each partition wall, and is provided with a lid having a filling hole corresponding to each dummy channel, the lid is adhered and fixed to the partition wall, and an elastic member is injected from the filling hole. The inkjet head according to claim 1, wherein the inkjet head is formed.