JPH03281252A - Droplet discharging device - Google Patents

Abstract

PURPOSE:To simplify structure and permit fine droplets to be discharged by providing a piezo plate which has a specific dimension and causes a change in liquid pressure to take place in a pressure chamber due to its expansion and contraction. CONSTITUTION:Each of chambers 4 forming a part of a pressure chamber is so dimensioned as to be greater in depth than in width and greater in length than in depth. A piezo plate 5 has electrodes 7 and 8 at both side faces, a smaller thickness and width than the width and depth of the chamber 4 and a length 1/2-2 times that of the chamber 4. When an input signal 31 is applied to the electrodes 7 and 8 of the piezo plate 5 through electrodes 27 and 28 and lead wires 10 and 11, the piezo plate 5 is stretched lenghwise, pressure rises inside the pressure chamber 24 and fine droplets are discharged from an injection nozzle 25. Although the length of the piezo plate 5 is returned to its original length as the signal voltage drops and the pressure of the pressure chamber 24 is reduced, since the air suction of the injection nozzle 25 is hindered due to the surface tension retaining force of liquid meniscus, a liquid 30 is supplied from a liquid reservoir 16 through a filter 23 into the pressure chamber 24. By repeating this cyclic action, the function of a droplet injection head is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applied to inkjet printers that eject small droplets of liquid in response to electrical signals, control the amount of ejected liquid, and record characters, graphics, etc. on a recording medium. The present invention relates to a droplet ejection device used for recording, etc.

2. Description of the Related Art Conventionally, there is an inkjet head as an example of ejecting small droplets of liquid by utilizing the longitudinal expansion and contraction of a rectangular piezoelectric vibrator. For example, the U.S. patent cylinder 4.0 owned by Exxon Printing Systems, Inc. 646. 1
No. 06 (registered February 24, 1987) and U.S. Pat.
88,9,6 registration) is known. Hereinafter, an outline of the above conventional inkjet head will be explained with reference to the drawings.

FIG. 8 is a sectional view showing an example of a conventional inkjet head. As shown in Part 8, the housing member 101
A pressure chamber 102 and a nozzle 103 communicating with the pressure chamber 102 are formed in the housing member 101, and a diaphragm 104 forming one wall of the pressure chamber 102 is joined to the back of the housing member 101. The pressure chamber 102 has an ink supply channel 105.
One end of the ink supply channel 105 is communicated with the ink supply channel 105, and the other end of the ink supply channel 105 is communicated with an ink reservoir (not shown). Diaphragm 1
04 is joined to one end of a rectangular piezo plate 106, and the piezo plate 106 has piezo electrodes 107 and 108.

The operation of the above configuration will be described below.

When a signal voltage is applied to the piezo electrodes 107 and 108, the piezo plate 106 expands and contracts in the longitudinal direction. This results in
Diaphragm 10 forming one wall of pressure chamber 102
4, and by the amplifying action of the diaphragm 104, the ink in the pressure chamber 102 is pressurized, 5 or depressurized to eject ink droplets from the nozzle 103, or the ink supply channel is inserted into the pressure chamber 102. Ink is supplied from 105.

FIG. 9 is a sectional view showing another example of a conventional inkjet head. As shown in FIG. 9, the head body 111
A chamber member 113 is fixed to the front surface of the ink supply channel forming member 112 via an ink supply flow path forming member 112. Chamber member 11
A pressure chamber 114 is formed in the chamber member 113.
A nozzle plate 115 is fixed to the front surface of the nozzle plate 115 , and nozzles 116 formed in the nozzle plate 115 communicate with the pressure chamber 114 . A cylindrical chamber 117 is formed behind the pressure chamber 114 in the head body 111, and a cylindrical member 118 is inserted into this chamber 117, and the inner wall of the chamber 117 and the cylindrical member 118 are inserted into the chamber 117.
An elastic potting material 119 is filled in the gap between the outer wall and the outer wall. One end of an electrode surface 121 of a strip-shaped piezo plate 120 is joined to the cylindrical member 118, and the electrode surface 12
1 is joined to the rear side of the helad body 111 with a conductive epoxy adhesive 123, and a lead wire 124 is taken out from the other electrode surface 122.

The operation of the above configuration will be described below. When a signal voltage is applied between the lead wire 124 and the spacing body 4111, the piezo plate 120 expands and contracts in the longitudinal direction. Correspondingly, the cylindrical member 118 also moves back and forth, thereby amplifying the minute displacement of the piezo plate 120 and increasing the pressure chamber 1.
A pressure change is created in the ink within 14 causing a droplet of ink to be ejected from the nozzle 117 or supplying ink to the pressure chamber 114 .

Problems to be Solved by the Invention However, as in the above conventional example, the diaphragm 104,
Alternatively, if the amplifying member made of the cylindrical member 118 is used by joining them, the manufacturing process becomes complicated and the cost increases. In addition, since adhesive is used for bonding, variations in discharge voltage between nozzles 103 or 116,
When hot melt ink is used at a high temperature of around 0° C., thermal stress causes deterioration of joints.

Furthermore, since a large adhesive area cannot be secured, the reliability and life of the head are poor. Furthermore, piezo plates 106, 7
- There were problems such as difficulty in increasing the degree of nozzle integration due to limitations on the horizontal dimensions of the amplification members 120 and 104 and 118.

The present invention solves the problems of the prior art as described in -[-, and simplifies the configuration and makes it possible to generate a pressure change sufficient for discharging high viscosity liquid. We provide a droplet ejection device that reduces manufacturing costs, prevents cost burden on drive circuits by eliminating variations in characteristics between nozzles, and improves nozzle integration, heat resistance, and reliability. The purpose is to

Means for Solving the Problems 1--The technical solution of the present invention for achieving the object described above is such that the dimension in the depth direction is larger than the width, and the dimension in the length direction is larger than the depth. a pressure chamber formed at least on the front side of the chamber, a liquid supply passage communicating with the pressure chamber, a discharge nozzle formed on the front side of the pressure chamber, and a thickness and width. method is smaller than the width and depth dimensions of the chamber, and the length dimension is 1 of the length dimension of the chamber.
~2 times the size of the piezoelectric plate, electrodes are disposed on both sides parallel to the surface in the depth direction of the chamber, and the piezoelectric plate is inserted into the chamber and causes a pressure change in the liquid in the pressure chamber by expansion and contraction. It is prepared.

Alternatively, a gap is formed between the J chamber and the above-mentioned Ebizo plate 1 to be filled with liquid.

-4- The Viezo board has a thickness of 0.1 to i, omm,
It is preferable to set the dimensions to a width of 1.0 to 4.0 mm and a length of 10 to 50 r++m.

Furthermore, a notch for forming a liquid supply channel can be provided at one end of the piezo plate.

This notch has a length of 0.1 to 0.4 + nm,
Width 0.1-1.0mm (piezo board thickness), length 1-10
It is preferable to set it in the size range of mm. Further, a liquid supply port for supplying liquid to the pressure chamber is located 05 to 9.5 m from the tip of the piezo plate, facing the notch of the piezo plate.
It is preferable to place it in the position of Also, -] The width of the second room is -
Piezo plate thickness + 002 to 0.2 mm, depth Niviezo plate width + 002 to 0.2 mm, length = 1 to piezo plate length
- It is preferable to set the size range to double. In addition, the ejected liquid can be oil-based ink, hot melt ink, liquid crystal,
Using a fragrance made of various types of Nisdel, the specific resistance of the liquid is 10゜Ω or more in the liquid state (operating state) so that electrolysis and short circuits do not occur even if the piezo electrode is in direct contact with the ink. is preferable.

Therefore, according to the present invention, by using a thin and wide piezo plate and using a conductive liquid with a sufficiently high resistivity such as oil-based ink or liquid crystal, the displacement in the longitudinal direction of the piezo plate can be reduced. A pressure change sufficient to discharge high viscosity liquid can be generated in the output chamber by itself without using an amplification member. In this way, the configuration can be simplified and micro droplets can be ejected.

EMBODIMENTS Embodiments of the present invention will now be described with reference to the drawings. 3. First, a first embodiment of the present invention will be described.

Figures 1 and 5 show a droplet ejection device according to a first embodiment of the present invention, in which Figure 1 is a perspective view, Figure 2 is an exploded perspective view, and Figure 3 (a) is a longitudinal section. Figure 3(b) is an enlarged view of the X section in Figure 3(a), Figure 4 is a partial enlarged sectional view along the FIG.

As shown in FIGS. 1 to 4, the groove forming member 1 is made of a poorly conductive material, and has a plurality of grooves 2 formed in parallel. The opening on the longitudinal side of the valley groove 2 of the groove forming member 1 is closed by a lid member 3 made of a poorly conductive material, and a chamber 4 forming a part of a pressure chamber is formed. The valley groove 2, that is, each chamber 4, is set so that the dimension in the depth direction is larger than the width, and the dimension in the length direction is smaller than the depth. In particular, as is clear from FIG. 5, the piezo plate 5 has a notch 6 at the tip of one side of the first edge, and has a notch 6 on both sides parallel to the plane in the depth direction of the chamber 4 in the longitudinal direction. It has electrodes 7.8. The piezo plate 5 with the electrode 7.8 has thickness and width dimensions smaller than the width and depth dimensions of the chamber 4, and its length dimension is 72 times the length dimension of the chamber 4 (in the example shown). In this case, the chamber is longer than chamber 4).

Each piezo plate 5 is brought into contact with a piezo abutting member 9 at its rear end on the opposite side of the notch 6, and its end surface is glued with epoxy adhesive to prevent the piezo from escaping backwards when displaced. It has become so. By bonding with solder, gold, aluminum wire, etc. from the rear end of the electrode 7 and 90 of each piezo plate 5,
A lead wire f+110 and a lead wire c)11 are respectively taken out. Piezo plate 5 with electrodes 7.8 in each chamber 4
is inserted, a gap 12 is formed between the chamber 4 and the piezo plate 5, and the lower part of the piezo contact member 9 is fitted into a groove 13 formed on the upper surface of the lid member 3 and fixed. A liquid storage tank 14 is fixed to the lower side of the lid member 3, and a nozzle member 15 is fixed to the front side of the groove forming member 1 and the liquid storage tank 14. A liquid supply channel forming member 17 located on the front side of the lid member 3 is provided on the front side of the liquid reservoir 16 of the liquid storage tank 14, and a ventilation hole 18 is provided in the liquid storage tank 14 on the opposite side of the liquid channel forming member 17. is formed. A plurality of liquid supply channels 20 are formed in the liquid supply channel forming member 17 in the vertical direction by partition walls 19, and one end of the liquid supply channel 20 is communicated with the bottom of the liquid reservoir 16 via a filter 23. The other end is communicated via a liquid supply port 21 with a liquid supply channel 22 formed by the notch 6 of the piezo plate 5 and the front upper surface of the liquid storage tank 14 . A pressure chamber 24 is formed so as to straddle each chamber 4 and the nozzle member 15, and a liquid supply channel 22 is communicated with this pressure chamber 24. A discharge nozzle 25 is formed in the nozzle member 15 in front of the pressure chamber 24 .

The ends of the lead wires 10 and 11 are bonded to the electrodes 27 and 28 of the signal input terminal board 26 in the same manner as described above, and are bonded to the rear end of the groove forming member 1 and the rear end of the piezo plate 5 exposed from the chamber 4. , a piezo contact member 9, a lead wire 10.11,
The front side of the signal input terminal board 26 is adhesively coated with a silicone resin sealing member 29 having viscoelasticity. This seal member 29 prevents liquid leakage from the gap 12 between the piezo plate 5 and the chamber 4, and prevents damage to the lead wires 10 and 11.
It plays the role of stably fixing the piezo plate 5. Electrodes 27 and 28 of the signal input terminal board 26 are connected to a connector (not shown). The liquid 30 in the liquid reservoir 16 passes through the filter 23 of the liquid supply port 21 and the liquid supply channel 20.2.
2 to the pressure chamber 13 through 7 24, and the gap 12 between the chamber 4 and the piezo plate 5 forming a part of the pressure chamber 24 is filled. Each of the above components can be easily assembled using methods such as adhesion, mechanical caulking, and heat fusion.

The operation of the above configuration will be described below.

First, the input signal 31 is applied to the electrodes 27. of the signal input terminal board 26.
28, electrode 7 of piezo plate 5 via lead wire 10.11
．． 8, the piezo plate 5 expands in the length direction. Accordingly, a pressure rise occurs in the pressure chamber 24 according to the applied electric field strength, the cross-sectional area of the piezo tip, and the piezoelectric constant (d, .) of the material, and minute droplets are discharged from the discharge nozzle 25. Next, the piezo plate 5 returns to its original length in response to a drop in the signal voltage, and the pressure chamber 24 is depressurized, but the discharge nozzle 25 is prevented from inhaling air due to the surface tension retention force of the liquid meniscus. Therefore, the liquid 30 in the liquid reservoir 16 is supplied into the pressure chamber 24 through the filter 23 of the liquid supply port 21 and the liquid supply channel 20.22. By repeating the above operations, it functions as a droplet ejection head.

14 - In other words, the pressure chamber 24 is expanded and contracted by the piezo plate 5 itself.
The pressure change (volume change) is caused to occur, and minute droplets are ejected from the ejection nozzle 25 without requiring an amplification effect by other members.

In addition, since the liquid supply channel 20 is divided by the partition wall 19 as described above, mutual interference can be prevented.

Furthermore, since the gap 12 between the chamber 4 and the piezo plate 5 excluding the rear seal portion is filled with the liquid 30, the heat generated by driving the piezo plate 5 can be radiated and cooled by the liquid 30.

As a specific example, the piezo plate 5 is a piezoelectric ceramic (product name: SUMIPIEZOSPEM) manufactured by Sumitomo Special Metals ■, and is SPEM-5 (product name: SUMIPIEZOSPEM) with Ni-Au electrodes 7.8 on both sides.
:.

and SPEM-H5C, length 10-50IrI
ITl, width 1.0-4.0 mm, thickness 0.1-1.0
It is formed into a rectangular shape with a length of 1 to 10 ITI at the tip.
IT11 vertical notch portions 6 having a valence of 0.1 to 0.4 were formed.

The groove forming member 1 is a machinable ceramic manufactured by Ishihara Pharmaceutical ■.
Groove 2 is machined using a dizer in Macor (trade name), and the length of groove 2, that is, chamber 4 is 10-5
01TIm, the width is 0.02. The thickness of the Viezo board 5 is 0.02
~0.2 mm, the height (depth) is the width of the piezo plate 5 +
5U is formed into a rectangular shape of 0.02 to 0.2 mm, and has a discharge nozzle 25 at its tip with an opening area of 0.0007 to 0.003 mm and an effective length of 0.01 to 0.1 mm.
A nozzle member 15 made of S304 was joined. 1-After the call,
Place the piezo plate 5 so that the notch 6 faces F.
and position 1 of 045 to 9.5 strokes from the tip of the notch 6
The liquid supply port 21 has an opening area of 0.01 to 0.6 @FI and a length of 0.03 to 0.5 mm.
] were arranged so that they were facing each other. In these heads,
Discharge viscosity 8-15 centipoise, specific resistance 10°-1
When using a liquid of 0゛Ωcm, with the drive waveform shown in Fig. 6 (1, 2 to 5 μs, t2 2 to 1511 s, L3 25 to 200/7S), the highest response frequency at an applied voltage of 30 to 150 V. It was possible to obtain a discharge performance of 18kHz or more.

Note that the members such as the groove forming member 1 and the lid member 3 are not limited to machinable ceramics, but may also be made of poorly conductive materials such as glass or plastics that have good workability.

Next, a second embodiment of the present invention will be described.

FIG. 7 is a longitudinal cross-sectional view showing a droplet discharge device in a second embodiment of the present invention.

In this embodiment, the liquid level of the liquid 30 is set to be higher than the discharge nozzle 25. That is, the groove forming part 1, the piezo plate 5, and the nozzle member] 5 are arranged upside down, and the liquid storage tank 14 is arranged on the groove forming member 1, so that the groove forming member 1 and the bottom surface of the liquid storage tank 14 A chamber 4 is formed, a piezo contact member 9 is fixed to the groove forming member 1,
The rear end of the liquid storage tank 14, the rear end of the piezo plate 5 exposed from the chamber 4, the piezo contact member 9, the lead wires 10.11, and the front side of the signal input terminal board 26 are connected to the seal member 29. Since the other configurations, operating principles, etc. are the same as those of the first embodiment, the same parts are given the same reference numerals and the explanation thereof will be omitted.

Next, a third embodiment of the present invention will be described.

FIG. 8 is a longitudinal cross-sectional view showing a droplet discharge device in a third embodiment of the present invention.

In this embodiment, for example, liquid crystal is used as the liquid 30, and the discharge nozzle 25 is arranged downward in order to spot small droplets of a certain amount on the medium 32 to be coated, which is a glass substrate. It is.

In this case, the droplet discharge device is fixed, and the glass substrate, which is the medium 32 to be coated, moves in the X-Y direction, and droplets are discharged at a predetermined position. .

When applying liquid crystal to a glass substrate, one of the most important factors is to minimize variation in the amount of application.

Usually, in the case of liquid crystal, the viscosity at room temperature is several IQc, P. Unfortunately, when driven at room temperature, it is almost impossible to eject liquid due to the flow resistance of the fill 23, liquid supply port 21, ejection nozzle 25, and the like. For this reason, a heater holder 33 is provided adjacent to the groove forming member 1 in order to lower the viscosity to a dischargeable range and to control the discharge amount to a constant value. This holder 33 is provided with a heater insertion hole 34 and a temperature control sensor insertion hole 35, into which a heater 36 and a temperature control sensor 37 are inserted, respectively, and are controlled to a predetermined temperature by a control circuit (not shown). be done. Operating temperature is 4
The temperature is controlled within ±1°C from 0 to 70°C with respect to the set temperature.

Still keeping the liquid level position of the liquid 30 in the liquid storage tank 14 constant,
In order to eliminate variations in the discharge amount due to changes in the liquid level, liquid circulation ports 31 and 31' are provided in the liquid storage tank 14, and the liquid level position of the liquid 30 is always kept constant by a liquid circulation device (not shown). . Furthermore, since the liquid 30 is stirred by circulating the liquid 30, the temperature of the liquid 30 is made uniform.

Furthermore, by connecting a pressure regulating means 40 such as a fan or an air pump to the ventilation hole 18 provided in the liquid storage tank 14, the liquid pressure applied to the discharge nozzle 25 can be freely controlled. By setting the pressure to negative, it is possible to prevent liquid dripping during operation or non-operation, and it is possible to further suppress variations in discharge amount. It goes without saying that this pressure regulating means 40 can be applied to the embodiments of the first and second inventions.

19 ・＼−・ Effects of the Invention As described above, according to the present invention, a piezo plate with a thin plate thickness and a wide width is used, and resistivity of oil-based ink, hot melt ink, liquid crystal, esters, etc. By using an oil-based liquid having a large value, it is possible to generate a pressure change sufficient to discharge the liquid in the pressure chamber by simply displacing the piezo plate in the length direction without using an amplification member. In this way, the configuration can be simplified and micro droplets can be ejected. Therefore, it is possible to reduce manufacturing costs,
Furthermore, high integration can be achieved. In addition, since the piezo actuator variations caused by conventional variations in the adhesion of amplification members are extremely small, there is no need for an adjustment circuit to adjust the drive voltage variations between each ejection nozzle and between each head. It is possible to reduce the cost of the circuit.

In addition, since there is no bonding structure that applies stress in the direction of expansion and contraction of the piezo plate, temperature changes between room temperature and around 100℃ (
In hot-melt inkjet heads and the like that frequently undergo thermal shock, deterioration of the head can be significantly suppressed and the lifespan and reliability can be improved.

[Brief explanation of drawings]

1 to 5 show a droplet ejection device according to a first embodiment of the present invention, in which FIG. 1 is a perspective view, FIG. 2 is an exploded perspective view, and FIG. Figure 3 (bl is an enlarged view of the main part, Figure 4 is a sectional view along the L-IV line in Figure 3,
FIG. 5 is a perspective view of the piezo plate, FIG. 6 is a drive waveform diagram in the above embodiment, FIG. 7 is a longitudinal sectional view showing a droplet discharge device in a second embodiment of the present invention, and FIG. 8 is a diagram of the present invention. A vertical cross-sectional view showing a droplet ejecting device according to a third embodiment of the invention, and FIGS. 9 and 10 are cross-sectional views showing a conventional droplet ejecting head, respectively. DESCRIPTION OF SYMBOLS 1... Groove forming member, 2... Groove, 3... Lid member, 4
... Chamber, Death ... Piezo plate, 6 ... Notch, 12
... Gap, 14... Liquid storage tank, 15... Nozzle member,
20.22...Liquid supply channel, 24...Pressure chamber, 2
5...Discharge nozzle nope 29...Seal member, 31.3
1'...Liquid circulation port, 36...Heater, 37...Temperature sensor, 40...Pressure adjustment means.

Claims (8)

[Claims] (1) A chamber formed so that the depth dimension is larger than the width direction and the length direction dimension is larger than the depth, a pressure chamber formed at least in the front side of the chamber, and this pressure chamber and a discharge nozzle formed on the front side of the pressure chamber, the thickness and width of which are smaller than the width and depth of the chamber, and the length of which is the same as the length of the chamber. The size is 1/2 to 2 times the size, and electrodes are arranged on both sides parallel to the surface in the depth direction of the chamber, and are inserted into the chamber to cause pressure changes in the liquid in the pressure chamber by expansion and contraction. A droplet ejecting device equipped with a piezo plate. (2) The droplet discharge device according to claim 1, wherein a gap is formed between the chamber and the piezo plate to be filled with liquid. (3) The droplet discharge device according to claim 1 or 2, wherein the piezo plate has the following dimensions. Thickness 0.1~1.0mm Width 1.0~4.0mm Length 10~50mm (4) The droplet ejecting device according to any one of claims 1 to 3, wherein the piezo plate has a notch at one end for forming a liquid supply channel. (5) The droplet discharge device according to claim 4, wherein the cutout portion of the piezo plate has the following size range. Height: 0.1-0.4mm Width: 0.1-1.0mm (piezo plate thickness) Length: 1-10mm (6) The liquid supply port that supplies liquid to the pressure chamber is located 0.5 to 9 mm from the tip of the piezo plate, facing the notch of the piezo plate.
．． 5 mm, and the opening area of the liquid supply port is 0.01 to 0.6 mm^2, and the length is 0.03 mm.
The droplet discharge device according to claim 4 or 5, wherein the droplet discharge device has a diameter of 0.5 mm. (7) The droplet discharge device according to any one of claims 1 to 6, wherein the chamber has the following size range. Width = piezo plate thickness + 0.02 to 0.2 mm Depth = piezo plate width + 0.02 to 0.2 mm Length = piezo plate length x (0.5 to 2) mm (8) The specific resistance of the liquid is 10^5Ω in the liquid state.
The droplet ejection device according to any one of claims 1 to 7, wherein the droplet discharge device has a diameter of cm or more.