JP3097707B2 - Ink jet head and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention
The present invention relates to an ink jet recording apparatus such as a printer that forms an ink image on a recording medium such as recording paper, and more particularly to an ink jet head and a method of manufacturing the same.

[0002]

2. Description of the Related Art The structure of a conventional ink jet head disclosed in Japanese Patent Publication No. 60-8953 is arranged with a nozzle forming member having a nozzle opening and a nozzle forming member behind the nozzle forming member.
A piezoelectric transducer that comes into direct contact with the ink.

In the ink jet head having such a structure, the piezoelectric transducer vibrates as it is displaced in a direction substantially perpendicular to the nozzle forming member, and the flow path between the nozzles communicates at a short distance. The ink droplets have good stability, and can operate normally without being affected by foreign matters such as air bubbles and dust in the ink.

However, in the ink jet head having the above-described structure, the amount of expansion and contraction per unit length and the amount of expansion and contraction per unit voltage of the piezoelectric transducer are extremely small, and the ink droplet generation force is also small. Therefore, in order to obtain the flying force of ink droplets required for printing, it is necessary to lengthen the beam of the piezoelectric transducer or to apply a high voltage, which complicates the drive circuit and measures for electrical insulation. Was.

In order to solve such a problem, Japanese Patent Publication No. 63-1
As disclosed in Japanese Patent No. 25343 or the like, an ink jet head using a laminated piezoelectric transducer in which internal electrodes and piezoelectric bodies are alternately stacked and integrated has been proposed. Such a laminated piezoelectric transducer does not reduce the mechanical strength of the piezoelectric transducer by adjusting the number of layers,
The interlayer distance between the internal electrodes can be made as small as possible, and the driving voltage can be reduced.

[0006]

However, any of the above-mentioned conventional ink jet heads can be used because the piezoelectric transducer itself is in direct contact with the ink or the ink is not sufficiently shut off. Inks are limited to those having electrical insulation properties, and there is a problem that printing quality such as affinity with a recording medium, ink drying property, and the type of recording medium adapted for printing are limited.

[0007] In particular, since a metal mainly composed of silver or silver-palladium is used for the internal electrode of the laminated piezoelectric transducer, failures such as creeping discharge and trans-layer discharge due to the electromigration phenomenon occur. Cheap. These phenomena are promoted with the increase in the humidity near the internal electrodes, the temperature, and the density of the distance between the internal electrodes, regardless of whether the piezoelectric transducer is in direct contact with the ink.

[0008] That is, a laminated piezoelectric transducer is composed of a ceramic powder containing a large amount of an organic component such as a binder;
Since it is manufactured by sintering a metal paste, organic components are easily removed by sintering, and porous material including fine through holes (this hole is called a hole) is easily formed. There is a risk that not only a creeping discharge on the surface of the converter but also a trans-layer discharge may occur inside.

The present invention has been made in view of such a problem, and an object of the present invention is to reduce creeping discharge on the surface of a piezoelectric transducer and transmembrane discharge inside the piezoelectric transducer as much as possible. It is an object of the present invention to provide an ink jet head that can prevent such a problem and improve the reliability and expand the range of selection of usable ink. Another object of the present invention is to propose a method for manufacturing the above-mentioned inkjet head.

[0010]

According to the present invention, there is provided a nozzle forming member having a nozzle opening arranged to face a recording medium, and a nozzle forming member disposed behind the nozzle forming member. Having a piezoelectric transducer,
In an ink jet head configured so that ink is filled between a nozzle forming member and a piezoelectric converter, a surface of a piezoelectric material constituting the piezoelectric converter, and a hole have a carbon chain in a main chain and a side chain. An electric insulating material containing a polymer having fluorine is impregnated and solidified .

[0011]

According to the ink jet head of the present invention, the main chain impregnated in the pores generated by firing has a carbon chain,
A piezoelectric transducer is made of an electrically insulating substance containing a polymer having fluorine in the side chain and an electrically insulating substance containing a polymer having a carbon chain in the main chain applied to the surface and having a fluorine in the side chain. Has high hermetic sealing properties, suppresses electrical insulation breakdown, and improves long-term stability of vibration characteristics.

[0012]

FIG. 1 is a perspective view of a main part of an ink jet head according to an embodiment of the present invention. The piezoelectric transducer 10
A piezoelectric body 11 such as a piezoelectric ceramic and a conductive material 12a,
12b (hereinafter, referred to as internal electrodes 12a and 12b)
Each has a multilayer structure stacked alternately. Further, the piezoelectric transducer 10 is formed with conductive materials 13a and 13b (hereinafter, referred to as external electrodes 13a and 13b). The external electrode 13a is an internal electrode 12a, and the external electrode 13b is an internal electrode 12b. Are electrically conductive. Further, the piezoelectric transducer 10 is joined on the base member 14.

The piezoelectric transducer 10 has a pore formed by sintering having a carbon chain in a main chain and an electric insulating material containing a polymer having a fluorine bond in a side chain. Is coated with an electrically insulating substance containing a polymer having a carbon chain in the main chain and a fluorine bond in a side chain.

FIG. 2 is a sectional view showing the structure of an ink jet head using the piezoelectric transducer 10. As shown in FIG. Ink 2
Reference numeral 0 denotes a plate-shaped nozzle forming member 21 having a nozzle opening 22 (hereinafter, referred to as a nozzle plate 21), and five members including frames 23a and 23b, a base member 14, and an elastic plate 24 on which a projection 25 is formed. The ink is supplied to the space between the projection 25 and the nozzle plate 21 by the capillary force of the ink 20.

With this configuration, the flexible substrate 27
When a drive signal is input to the piezoelectric converter 10 through the interface and an electric field is applied, the piezoelectric converter 10 contracts in a direction orthogonal to the nozzle plate 21. When this electric field is released, pressure is applied to the ink 20 between the projection 25 and the nozzle plate 21 by the elastic restoring force of the piezoelectric converter 10, and an ink droplet is ejected from the nozzle opening 22. Even when an electric field is applied in this manner, the pores are impregnated with an electrically insulating substance containing a polymer having a carbon chain in the main chain and a fluorine-bonded side chain, and the surface has a main chain. Since an electrically insulating substance having a carbon chain and containing a polymer having a fluorine bond in a side chain is applied thereto, the piezoelectric material and the internal electrodes of the piezoelectric transducer 10 are reliably shut off from the outside air, so that dielectric breakdown or the like occurs. Is reliably prevented.

FIGS. 3A to 3F show an embodiment of a method of manufacturing an ink jet head according to the present invention. Acetone, methyl ethyl ketone, dimethylformamide, dimethylacetamide, etc.
) Is prepared. This solution contains a polymer having a carbon chain in the main chain and fluorine in the side chain.

First, an adhesive 31 is applied to both or any one of the piezoelectric conversion plate 30 and the base member 14. After that, the piezoelectric conversion plate 30 and the base member 14 are bonded and positioned. Pressing at the specified temperature, time and load conditions,
The adhesive 31 is cured to form a single plate 32 (FIG. 3A).

After the adhesive 31 is applied, the adhesive 3
When the pressure reduction of 1 is performed, bubbles in the adhesive 31 are removed, which is extremely effective in stabilizing the bonding strength.

Although not shown in FIG. 3, the piezoelectric conversion plate 3
At the time of joining the base member 14 to the base member 14, conductive particles are kneaded in the adhesive 31, so that mechanical joining and electric joining are simultaneously obtained.

The plate 32 integrally formed as described above is
Groove processing is performed using a rotating grindstone blade 34 that rotates at a high speed or a metal wire that runs at a high speed to form a piezoelectric converter module 33. When a slit reaching the surface of the base member 14 is inserted at a predetermined interval, one end of the slit is
4 and a plurality of cantilever-shaped piezoelectric transducers 10 whose other ends are free ends are formed (FIG. 3B).

The piezoelectric converter module 33 thus configured and the above-mentioned solution 35a are accommodated in a pressure vessel 36, and the pressure in the pressure vessel 36 is reduced. Immerse in the PVDF-containing solution 35a. Then, the pressure vessel 36 is opened to the atmosphere, the pores of the piezoelectric transducer 10 are sealed with the PVDF-containing solution 35a by the atmospheric pressure, and the surface is coated with the PVDF-containing solution 35a (FIG. 3C).

In particular, since it is necessary to infiltrate the pores of the piezoelectric transducer 10 generated by sintering with the PVDF-containing solution 35a, P
The viscosity of the VDF-containing solution 35a is at most 500 [m · Pa
S] or less, preferably 100 [m · Pa · s] or less. More preferably, it is 20 [m · Pa · s] or less. As the immersion method, in addition to the above-described method, the piezoelectric transducer 10
May be subjected to a reduced pressure treatment after immersion in the PVDF-containing solution 35a. In this case, preferably, when the state changes from the depressurized state to the pressurized state, the PVDF-containing solution 35a surely penetrates into the fine pores even if the piezoelectric transducer 10 is hardly wet. Sealing is ensured. In addition, although a method of immersing only at atmospheric pressure without performing a pressure operation is also possible, the density of the piezoelectric transducer is low due to the natural penetration of the PVDF-containing solution 35a and the wettability to the PVDF-containing solution 35a. Is high, and only when the viscosity of the PVDF-containing solution 35a is extremely low.

The piezoelectric converter module 33 impregnated with the PVDF-containing solution 35a in the above-described process is gradually heated to evaporate the solvent 37 of the filled PVDF-containing solution 35a, and the PVDF A film of the resin 16 is formed (FIG. 3D).

Next, the degassed PVDF-containing solution 3
The piezoelectric transducer module 33 described above is immersed in 5b, pulled up, heated and dried to form a PVDF resin 16 film (FIGS. 3E and 3F).

Then, the piezoelectric transducer module 33 is connected to the PV
When immersion in the DF-containing solution 35b and heating and drying are alternately repeated a plurality of times, coating film defects such as pinholes due to volatilization of the solvent 37 are eliminated, and the gas barrier properties of the entire piezoelectric transducer 10 is improved.

Then, the solid concentration of the PVDF-containing solution 35b used in the second step is adjusted to the P concentration used in the first step.
When the height is set higher than the VDF-containing solution 35a, coating film defects on the surface of the piezoelectric transducer 10 such as pinholes generated by coating with the PVDF-containing solution 35a in the first step can be surely repaired.

Blocking the piezoelectric transducer 10 from the outside is important for preventing the electrical insulation resistance of the piezoelectric transducer 10 from deteriorating and improving reliability such as stability of vibration characteristics, and is difficult to obtain by the conventional method. Met. On the other hand, according to the present embodiment, the electric insulating substance 16 containing a polymer having a carbon chain in the main chain and a fluorine bond in the side chain is used for the piezoelectric transducer 1.
The reliability of the piezoelectric transducer 10 could be improved by forming it on the surface of 0 and the holes.

Furthermore, a solution 35 containing the polymer
a is first filled and solidified, and then immersed in a solution 35b containing the polymer and solidified, thereby complementarily covering a coating defect portion such as a pinhole of the electrically insulating substance 16 containing the polymer. Therefore, a protective layer of the piezoelectric transducer 10 having extremely excellent water absorption and gas barrier properties can be formed.

In this embodiment, the substance containing PVDF is used in the form of a solution. However, the present invention is not limited to the solution, and it is also possible to use dispersion, powder, organosol, or thermal dissolution. Also, acrylic, epoxy, silicone,
A substance having a carbon chain in the main chain and having fluorine in a side chain, such as a urethane-based or phenol-based resin, can also be used.

In the above-described embodiment, a vinylidene fluoride polymer is used as a polymer having a carbon chain in the main chain and fluorine in the side chain. However, a tetrafluoroethylene polymer (PTFE) -based polymer is used. Or fluoroethylene vinyl ether copolymer (FEVE), ethylene trifluorochloride copolymer (PCTFE), vinyl fluoride polymer (PVF),
Ethylene tetrafluoride / ethylene copolymer (ETFE),
Ethylene tetrafluoride / propylene hexafluoride copolymer (FE
P) -based materials, ethylene tetrafluoride / verfluoroalkylvinyl ether copolymer (PFA) -based materials, and ethylene trifluoride-ethylene / ethylene copolymer (ECTFE) -based materials can be used.

A copolymer of vinylidene fluoride and ethylene trifluoride chloride, a copolymer of vinylidene fluoride and propylene hexafluoride, a copolymer of ethylene tetrafluoride and propylene, and a copolymer of vinylidene fluoride and tetrafluoroethylene Since the copolymer with ethylene fluoride is a substance having a rubber-like elasticity having a Young's modulus of 10 ⁷ [N / m] or less, the influence on the vibration characteristics of the piezoelectric transducer 10 is small. Strict management is not required, and the processing steps can be simplified.

A substance containing a polymer having a carbon chain in the main chain and fluorine in the side chain is excellent in heat resistance, chemical resistance, electric insulation, and voltage resistance. Above all, it has a feature that water absorption and gas permeability are extremely low. Therefore, by forming it on the surface of the piezoelectric transducer 10 and the pores, it is possible to reliably prevent electric breakdown due to moisture, temperature, and the like. be able to.
In the above-described embodiment, the piezoelectric transducer extending in the axial direction has been described. However, it is apparent that the same effect can be obtained by applying the present invention to a piezoelectric transducer having a laminated bimorph type or unimorph type structure. .

[0033]

As described above, according to the present invention, an electric insulating material containing a polymer having a carbon chain in a main chain impregnated in pores generated by firing and having a fluorine in a side chain, In addition, since the piezoelectric transducer has a high gas-sealing property due to an electrically insulating substance containing a polymer having a carbon chain in the main chain and fluorine in the side chain applied to the surface, the piezoelectric material has electrical insulation breakdown Vibration
Characteristics can be stabilized for a long time, and a highly reliable inkjet head can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional perspective view of a main part of an ink jet head according to the present invention.

FIG. 2 is a cross-sectional view illustrating a structure of an inkjet head according to the present invention.

FIGS. 3A to 3F are manufacturing process diagrams showing one embodiment of the manufacturing method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Piezoelectric transducer 11 Piezoelectric body 12a, b Internal electrode 13a, b External electrode 14 Base member 15 Base electrode 16 Electric insulating material containing PVDF 20 Ink 21 Nozzle plate, 22 Nozzle opening 23a, b Frame a, b 24 Elasticity Plate 25 Projection 26 Frame b 27 Flexible substrate 30 Piezoelectric conversion plate 31 Adhesive 32 Plate material integrating piezoelectric conversion plate and base member 33 Piezoelectric converter module 34 Rotating wheel blade 35a Low-viscosity solution containing PVDF 35b Contains PVDF Solution with high solids concentration 36 Pressure vessel 37 Solvent 38 Protective tape

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B41J 2/045 B41J 2/055 B41J 2/16 B41J 2/295 H01L 41/08

Claims (2)

(57) [Claims] 1. A nozzle forming member having a nozzle opening disposed to face a recording medium, and a piezoelectric converter disposed behind the nozzle forming member, wherein the nozzle forming member and the piezoelectric converter are provided. An ink jet head configured so as to be filled with ink between the surface of the piezoelectric material constituting the piezoelectric transducer, and a polymer having a carbon chain in a main chain in pores and a fluorine in a side chain. An inkjet head impregnated with an electrically insulating material and solidified . 2. A piezoelectric transducer is immersed and solidified in a first substance having a viscosity of 500 [m · Pa · s] or less, a polymer having a carbon chain in a main chain and a fluorine in a side chain. The pressure
A first step of forming an electric insulating material containing the polymer on a piezoelectric material constituting the electric converter ; and a carbon chain as a main chain in the piezoelectric converter in which the electric insulating material is formed by the first step. Poly that has fluorine in the side chain
A second step of applying and solidifying a second substance containing a polymer at a higher concentration than the first substance.