JPH1148473A - On demand type multinozzle ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of a second drop by bonding a laminated piezoelectric element to a diaphragm using an elastic material exhibiting a bonding function lower than a specified hardness of A or D scale thereby reducing mutual interference and preventing the ink drop jetting characteristics from deteriorating. SOLUTION: An orifice, a chamber, restrictor plates 12, 11 and 10, a diaphragm 3 and a support 13 are bonded and further bonded integrally to common ink supply path plates A, B and a common ink supply path plate cover bonded together before being bonded with a head board fixing plate. When it is fixed to the forward end of a laminated piezoelectric element 4 on a head board 6 by applying an elastic material 9, the laminated piezoelectric element 4 is bonded to a diaphragm 3 corresponding to one pressure chamber. A silicone resin exhibiting a bonding function lower than Shore hardness of 80 deg. on scale A or Shore hardness of 30 deg. on scale D is employed as the elastic material 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material property of an adhesive layer for connecting and fixing a diaphragm and a laminated piezoelectric element in an on-demand type ink jet head using the laminated piezoelectric element.

[0002]

2. Description of the Related Art In an ink jet recording system, an on-demand system in which ink is ejected only when a recording signal is input is currently mainstream. A thermal jet method using bubbles generated on the surface and a piezo method in which ink is ejected from nozzles by driving a piezoelectric element (piezo element) are widely known.

In particular, in the piezo method, it is necessary to improve the coupling between the piezoelectric element and the diaphragm to efficiently transmit the displacement of the piezoelectric element to the pressurizing chamber.
As described in Japanese Patent Application Laid-Open No. 2-79352, if a piezoelectric element used for ejecting ink droplets and a diaphragm are bonded by an adhesive layer having a Shore hardness of 40 degrees or more on a D scale, the piezoelectric element It has been shown that mechanical deformation can be efficiently transmitted to the ink in the ink flow path via the diaphragm, and a highly reliable inkjet head in ejecting ink droplets can be provided.

FIG. 2 shows the conventional head structure described above.

[0005] A substrate 19 having a groove corresponding to the flow path and a vibration plate 20 are joined to form an ink flow path 21 and a nozzle 22, and a metal is interposed through a conductive adhesive layer 23 of the vibration plate 20. The plate 24 is adhered, and an adhesive layer 23, a piezo vibrator 25, a thin film electrode 26, and a solder bump 9 are sequentially formed.

The printing is performed by applying a driving voltage V0 to the piezo vibrator 25 from a power supply 29 between the solder bump 27 and the metal plate 24 via a switch 28 via a switch 28, and generating the mechanical voltage generated on the piezo vibrator 25 and the metal plate 24. The deformation is performed by sequentially transmitting the ink to the adhesive layer 23, the vibration plate 20, and the ink 30, extruding the ink 30, and ejecting the ink droplet 31 in the ejection direction 32 from the nozzle 22. After the printing, the deformation of the piezoelectric vibrator 25 is recovered, and the shortage of the ejected ink is supplied from the ink supply port 33 in the supply direction 34.

A head having such a structure is generally called a Kaiser type ink jet head. When a piezoelectric element and a vibration plate are bonded with a soft adhesive, the vibration of the piezoelectric element is absorbed by the adhesive, and ink is ejected. Is not possible.

[0008]

However, a plurality of laminated piezoelectric elements are arranged in a row on a substrate to form a nozzle.
In the ink jet head for ejecting ink d ₃₃ direction of displacement of the multilayer piezoelectric element of each nozzle, the diaphragm and the piezoelectric element is bonded by the adhesive layer of the above Shore hardness of 40 degrees by D scale, ink from adjacent nozzles droplets When the ink is ejected, the individual meniscus vibrations cannot be sufficiently attenuated and interact with each other to reduce the ink droplet speed. There is a problem that a second drop is ejected, and all of them cause a decrease in print quality.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to reduce meniscus vibrations promptly after a desired ink droplet is ejected, thereby reducing mutual interference in which driving conditions between adjacent nozzles affect each other, and thereby reducing ink droplets. It is an object of the present invention to provide a multi-nozzle ink jet head that can prevent a drop in ejection characteristics and can prevent a second drop from being caused by residual vibration of a meniscus.

[0010]

According to the present invention, in order to solve the above-mentioned problems, a pressurized chamber for storing ink, a laminated piezoelectric element for generating pressure fluctuation in the pressurized chamber by applying an electric signal, a pressurized chamber A diaphragm that forms at least a part of the wall surface of the, a restrictor that is a flow path that supplies ink to the pressurizing chamber, a common ink supply path that supplies ink to the restrictor, and an ink droplet that flows from the pressurizing chamber. In an on-demand type multi-nozzle inkjet head which arranges a plurality of nozzles composed of orifices for ejecting in a row and presses a pressure chamber with a displacement of a laminated piezoelectric element in the d33 direction in each nozzle to eject ink. An elastic material having an adhesive function of bonding the laminated piezoelectric element to the vibration plate with a Shore hardness of less than 80 degrees on A scale or 30 degrees on D scale. It was configured to perform. Here, the value obtained by converting the Shore hardness of A scale of 80 degrees to the Shore hardness of D scale is 30 degrees of Shore hardness. The elastic material having such a small adhesive function applied in the present invention is preferably a silicon-based resin.

According to the above structure, the meniscus vibration is attenuated immediately after the desired ink droplet is ejected, the mutual interference of the driving conditions between adjacent nozzles is reduced, and the meniscus is caused by the residual vibration of the meniscus. Second drop can be prevented.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing the structure of a nozzle portion of a multi-nozzle ink jet head as an example of the present invention. This head can perform recording by ejecting ink according to an input signal.

[0014] 1 orifice, 2 pressure chamber, 3 the diaphragm, the multilayer piezoelectric element Takasei to utilize d ₃₃ displacement 4, 5a and 5b is the signal input terminal, the head substrate 6, 7
Is a restrictor that connects the ink flow path 8 to the pressure chamber 2 and controls the flow of ink into the pressure chamber 2, 8 is an ink flow path, 9 is an elastic material that connects the vibration plate 3 and the piezoelectric element 4, Reference numeral 10 denotes a restrictor plate that forms the restrictor 7, 11 denotes a chamber plate that forms the pressurizing chamber 2, and 12 denotes an orifice plate that forms the orifice 1. The ink flows in the order of the ink flow path 8, the restrictor 7, the pressurizing chamber 2, and the orifice 1. The piezoelectric element 4 expands when a positive potential is applied to the signal input terminal 5a, and returns to the state before expansion if there is no potential difference between the signal input terminals 5a and 5b, and does not deform.

Here, the diaphragm 3, the restrictor plate 10, and the chamber plate 11 are made of, for example, stainless steel, and the orifice plate 12 is made of nickel. The head substrate 6 is made of an insulating material such as ceramics or polyimide, and has electrodes formed thereon by a conductive paste or solder plating.

The elastic material 9 is made of, for example, an adhesive made of a silicon resin, and specifically, 3-6611 manufactured by DOW CORNING Co., Ltd. having a Shore hardness of 72 degrees at A scale at room temperature, or a Shore at A scale. Hardness is 7
One example is SE1701 manufactured by Toray Dow Corning.

A method for manufacturing the multi-nozzle ink jet head of the present invention will be described below with reference to FIG.

FIG. 3 is an exploded view showing the order of assembling the plates of the ink jet head of this embodiment.
Two laminated piezoelectric element rods each having a length of 36 mm are arranged on the head substrate 6 at a predetermined interval, and an epoxy-based adhesive is applied to a mounting surface of the laminated piezoelectric element rods and fixed to the head substrate 6. Thereafter, the laminated piezoelectric element rod is cut with a dicing saw or a wire saw so that the width of the laminated piezoelectric element serving as a driving source of one nozzle is 0.2 mm and the nozzle pitch is 0.51 mm, and 32 pieces are divided into one row. The laminated piezoelectric element thus formed is formed. At this time, each of the divided laminated piezoelectric elements corresponds to one of the pressure chambers.

Next, the orifice plate 12, the chamber plate 11, the restrictor plate 10, the diaphragm 3, and the support plate 13 are bonded together. This combination is called a laminated plate A. Further, the three plates of the common ink supply path plate A14, the common ink supply path plate B15, and the common ink supply path plate cover 16 are adhered together, and this combination is called a laminated plate B. A combination of the laminated plate A and the laminated plate B integrally bonded and then bonded and fixed to the head substrate mounting plate 17 is referred to as a laminated plate C.

The above-described elastic material is applied to the tip of the laminated piezoelectric element of the head substrate 6 to form a laminated plate C
Then, the laminated piezoelectric elements are bonded to the vibration plates corresponding to the respective pressure chambers with an elastic material. Further, when the peripheral portion of the head substrate 6 that contacts the head substrate mounting plate 17 is fixed with an adhesive (for example, an ultraviolet curable adhesive or an epoxy-based adhesive), the multi-nozzle inkjet head having the above-described head structure of FIG. Is produced.

In FIG. 3, the heater 18 is adhered to the common ink supply path plate cover 16. This is because a hot melt ink which is solid at room temperature as ink but is heated and melted at the time of jetting is used. In this case, it is assumed that the ink is used, and when the liquid ink is used at room temperature, it is not necessary to attach the heater 18.

FIG. 4 shows the nozzle surface of the ink jet head of the present invention, in which 32 nozzles are arranged in one row, and a total of 64 nozzles are formed in two rows.

Table 1 shows the results of an investigation on the ejection characteristics of the ink jet head having the above-described structure by changing the elastic material having an adhesive function of connecting and fixing the vibration plate 3 and the laminated piezoelectric element 4. The material was selected from one-part adhesives and two-part adhesives and examined.

[0024]

[Table 1]

In Table 1 above, the driving conditions are as follows: pulse width: 8 μs, driving frequency: 2 kHz, ink droplet speed: 13
m / s. The ink is hot melt ink, and the head is heated to 130 ° C. by a heater.

As can be seen from Table 1, when the Shore hardness on the A scale is 80 degrees or less, no second drop occurs. This is because the vibration of the ink meniscus was sufficiently attenuated, and the influence of the ink droplets ejected first did not remain. In addition, the Shore hardness in Table 1 is a value measured at room temperature, but all the investigated materials can be used at 130 ° C.

Next, among the silicone resin adhesives in which second drops did not occur, DOW CORNIN was used.
For one row of an inkjet head using 3-6611 (Shore hardness 72 degrees (A scale)) manufactured by Company G,
FIG. 5 shows the result of measuring the crosstalk. The driving conditions were as follows: the pulse width was 8 μs, the driving frequency was 10 kHz, all the nozzles were driven at a constant voltage of 30 V, and 16 even-numbered nozzles and 16 odd-numbered nozzles were shifted by 50 μs. The horizontal axis in the figure is the nozzle number, and the vertical axis is the value (speed ratio) obtained by dividing the speed when 32 nozzles are driven evenly and oddly by 16 nozzles by the speed when driven alone (here, 13 m / s). is there.

In the figure, it is shown that the closer the speed ratio is to 1, the smaller the effect of the ejection of the adjacent nozzle is. However, since the effect is almost equal to 1 for all the nozzles, the crosstalk in the ink jet head of the present invention is reduced. It can be understood that the influence of the above can be reduced. This is because the elastic material that bonds the vibration plate and the laminated piezoelectric element efficiently attenuates the meniscus vibration generated after ejecting the ink droplets by applying an electric signal.

As described above, in the ink jet head having the above-mentioned structure, the Shore hardness of the diaphragm and the laminated piezoelectric element on the A scale is 80 degrees, or the Shore hardness on the basis of the Shore hardness of the D scale is 30 degrees. When connected and fixed with an elastic material having a smaller hardness, stable ink droplet ejection characteristics can be obtained, and since there is no generation of second drops, good print quality can be maintained.

[0030]

According to the ink jet head of the present invention, the vibrating plate and the piezoelectric element are bonded with an elastic material having a hardness smaller than 80 degrees Shore hardness (A scale) or 30 degrees Shore hardness (D scale), so that the meniscus remains. Vibration is quickly attenuated, so that the influence of crosstalk can be reduced, the landing deviation of ink droplets can be reduced, good print quality can be obtained, and print quality degradation due to the occurrence of second drops can be eliminated.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a nozzle of an inkjet head used in the present invention.

FIG. 2 is a cross-sectional view of a nozzle of a conventional inkjet head.

FIG. 3 is a perspective view showing the assembly order of the jet pack of the present invention.

FIG. 4 is a front view of a nozzle of the multi-nozzle inkjet head used in the present invention.

FIG. 5 is a graph showing the results of measuring the crosstalk of the inkjet head of the present invention.

[Explanation of symbols]

1 is an orifice, 2 is a pressure chamber, 3 is a vibration plate, 4 is a piezoelectric element, 5a and 5b are signal input terminals, 6 is a head substrate, 7 is a restrictor, 8 is an ink flow path, 9 is silicon rubber, 1
0 is a restrictor plate, 11 is a chamber plate, 12 is an orifice plate, 13 is a support plate, 14 is a common ink supply path plate A, 15 is a common ink supply path plate B, 16 is a common ink supply path plate cover,
17 is a plate for attaching a piezoelectric element fixing plate, 18 is a heater, 19 is a substrate, 20 is a vibration plate, 21 is a flow path, 22 is a nozzle, 23 is an adhesive layer, 24 is a metal plate, 25 is a piezo oscillator, and 26 thin film Electrode, 27 is a solder bump, 28 is a switch, 29 is a power supply, 30 is ink, 31 is an ink droplet, 3
2 is an ejection direction, 33 is an ink supply port, and 34 is an ink supply direction.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuo Takano 1060 Takeda, Hitachinaka-shi, Ibaraki Pref.Hitachi Koki Co., Ltd. (72) Inventor Tokumasa Kondo 1060 Takeda, Hitachinaka-shi, Ibaraki Pref. Inventor Nobuhiro Kurosawa 1060 Takeda, Hitachinaka-shi, Ibaraki Prefecture Within Hitachi Koki Co., Ltd.

Claims (2)

[Claims] 1. A pressure chamber for increasing the pressure of ink, a laminated piezoelectric element for generating pressure fluctuation in the pressure chamber by applying an electric signal, and a diaphragm forming at least a part of a wall surface of the pressure chamber. A plurality of nozzles each including a restrictor for forming an ink supply flow path in the pressurized chamber, a common ink supply path for supplying ink to the restrictor, and an orifice for ejecting ink droplets from the pressurized chamber. and arranged in a row, in the on-demand type multi-nozzle ink jet head for ejecting the d ₃₃ direction ink pressurizing chamber is pressurized by the displacement of the multilayer piezoelectric element of each nozzle, the multilayer to the diaphragm The on-demand type multi-function device, wherein the piezoelectric element is bonded with an elastic material having a bonding function smaller than the Shore hardness of 80 degrees on the A scale or the Shore hardness of 30 degrees on the D scale. Zulu inkjet head. 2. The on-demand type multi-nozzle ink jet head according to claim 1, wherein said elastic material is a silicon resin.