JPH08187850A - Ink jet recorder - Google Patents

Abstract

PURPOSE: To realize stable flight of an ink drop without any cross talk by simple manufacture by a method wherein an ink jet head is arranged on a substrate forming an ink chamber, which is composed of a piezoelectric material a part of which is not fixed to the substrate, and that part is displaced. CONSTITUTION: A plurality of piezoelectric materials 26 are arranged on a substrate 24 according to each recessed part 21. The piezoelectric material 26 is composed of, for example, PZT piezoelectric ceramic, and fitted along the recessed part 21 under a state wherein a little clearance is formed between both side faces of the recessed part 21. Further, an individual electrode 27 is provided on an upper surface of the piezoelectric material opposed to a bottom surface of the recessed part 21, and besides a common electrode 28 is set on a lower surface on the substrate 24 side. A polarization direction [the arrow (b) direction] of the piezoelectric material 26 is arranged parallel to a direction of an electric field formed by impressing voltage to the individual electrode 27 and the common electrode 28.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus having an on-demand type ink jet head for recording on a recording medium such as paper by ejecting ink droplets according to an image signal.

[0002]

2. Description of the Related Art Conventionally, a voltage is applied to a piezoelectric body in response to an image signal, and ink is pressed based on the deformation of the piezoelectric body to eject ink droplets from a nozzle, thereby recording on a recording medium such as paper. On-demand type inkjet heads are used in recording devices such as printers.

As an ink jet head of this system,
For example, the one shown in FIG. 18 is known from Japanese Patent Laid-Open No. 62-56150. This inkjet head 60
Has a piezoelectric member 62 in which a plurality of recesses 61 are formed and a cover plate 63 that covers the plurality of recesses 61, and an ink chamber 64 is formed inside the recess 61. Also,
A convex portion 65 is formed on the bottom surface of each concave portion 61, and the upper surface of the convex portion 65 and the convex portion 65 on the rear surface of the piezoelectric member 62 are formed.
Electrodes 66 and 67 are installed at the positions corresponding to, respectively. Inkjet head 6 configured in this way
At 0, a voltage is applied between the electrodes 66 and 67 to deform the convex portion 65 of the piezoelectric member 62, so that the ink chamber 64
By changing the volume of the ink and pressurizing the ink filled in the ink chamber 64, an ink droplet is ejected from the nozzle.

[0004]

However, in the above ink jet head 60, it is necessary to form a groove having a complicated sectional shape on the piezoelectric member 62, which not only increases the manufacturing cost but also increases the density. In case of recess 6
Since the width of the groove sandwiched between the side wall 1 and the convex portion 65 is several μm, there is a problem that the processing is substantially difficult.

Further, since the partition walls that partition the ink chambers 64 are made of a piezoelectric material like the convex portions 65, both electrodes 6 are formed.
The partition wall itself is displaced due to the electric field flowing between the electrodes 6 and 67, and in addition, depending on the pattern of the image signal, up to the convex portion 65 to which no voltage is applied between the electrodes 66 and 67, the adjacent convex portion 65. The displacement of (1) propagates through the piezoelectric member 62, resulting in interlocking displacement. For this reason, ink droplets are ejected from the ink chamber 64 that does not want to eject ink, or the flow of ink is disturbed in the ink chamber 64 even when the ink droplets are not ejected, and the ink droplet diameter is reduced in the next ink ejection. There is a problem that non-uniformity occurs, that is, so-called crosstalk, which causes mutual interference of ink ejection characteristics, and print quality deteriorates.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an ink jet recording apparatus which solves the above problems, is simpler to manufacture than the conventional example, and can realize stable ink droplet flight without crosstalk.

[0007]

In order to achieve the above object, an ink jet recording apparatus according to the present invention comprises an ink jet head having piezoelectric bodies arranged in a plurality of ink chambers, and an ink chamber in which the piezoelectric bodies are displaced. In an ink jet recording apparatus provided with a voltage applying means for applying a voltage to the piezoelectric body according to an image signal so as to pressurize and discharge the ink filled in the ink jet head, the ink jet head has a plurality of groove-shaped concave portions. A piezoelectric member, a substrate that covers each recess and forms an ink chamber inside the recess, and a piezoelectric body that is disposed on the substrate corresponding to each recess and at least a portion of which is not fixed to the substrate, The piezoelectric element is designed to displace an unfixed portion.

Further, one end of the piezoelectric body may be fixed to the substrate and the other end may not be fixed. In this case, if the total length of the piezoelectric body is l and the length of the fixed region is s,
It is preferable that 0.2l≤s≤0.9l, and 0.3l
It is more preferable that ≦ s ≦ 0.7 l.

Furthermore, by applying a voltage to the piezoelectric body, the unfixed portion of the piezoelectric body may be displaced in the direction away from the substrate, or conversely, in the direction toward the substrate. It may be displaced.

Further, a pair of electrodes may be installed asymmetrically on the mutually parallel side surfaces of the piezoelectric body, or the respective piezoelectric bodies may be formed in a comb-tooth shape having connected portions. .

[0011]

In the ink jet recording apparatus having the above structure, when a voltage is applied to the piezoelectric body to form an electric field, the unfixed portion of the piezoelectric body is deformed sharply. Due to this deformation, the ink filled in the ink chamber is pressurized and ejected. On the other hand, when the voltage application to the piezoelectric body is released to extinguish the electric field, the unfixed portion of the piezoelectric body returns to its original state. At this time, negative pressure is generated in the ink chamber to replenish the ink, and the next ink ejection is ready.

In this case, since the piezoelectric body and the substrate are only fixed at a part of their contact surfaces, other piezoelectric bodies are not interlocked and displaced through the substrate, and crosstalk does not occur.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 schematically shows the overall configuration of an inkjet recording apparatus that is an embodiment of the present invention. The ink jet recording apparatus 1 is roughly classified into a power supply unit 2 having a connector 2a, a drive system 3, a mechanical controller 4, a memory 5, a controller 6, an ink supply unit 7, a scan carriage 8, and a paper feed unit. It is composed of a section 9, a case 10, and an operation panel 11. The scan carriage 8 is capable of scanning in a direction orthogonal to the paper passing direction (direction of arrow a) (front and back direction of the paper surface in FIG. 1), and inside the carriage 4 is provided for each color of black, cyan, magenta and yellow. The two inkjet heads 12 are arranged along the paper passing direction, and the ink discharge nozzles are directed downward.

Next, the structure of the ink jet head 12 will be described with reference to FIGS. As shown in FIG. 2, the inkjet head 12 has a configuration in which an ink ejection unit 14, a terminal plate 15, and a connector 16 are sequentially installed on a base plate 13 from the front (lower left in FIG. 2).

The top plate 20 of the ink ejecting section 14 is composed of a plate made of a non-piezoelectric material such as alumina,
As shown in FIG. 3, a plurality of groove-shaped recesses 21 are formed on the lower surface thereof. These recesses 21 are formed at a predetermined pitch in the width direction of the top plate 20, and extend parallel to the longitudinal direction of the top plate 20, respectively.

The top plate 20 is provided on the surface of the top plate 20 where the recess 21 is formed.
Similarly, the base 24 made of a non-piezoelectric plate is bonded,
The ink chamber 2 is provided inside the recess 21 covered with the substrate 24.
3 are formed.

A plurality of piezoelectric bodies 26 are arranged on the substrate 24 so as to correspond to the recesses 21. The piezoelectric body 26 is made of, for example, PZT piezoelectric ceramic, and has a concave portion 21.
And a slight gap is formed between both side surfaces of the recess 21. An individual electrode 27 is provided on the upper surface of the piezoelectric body 26 facing the bottom surface of the recess 21, while a common electrode 28 is provided on the lower surface on the substrate 24 side. Note that, as shown in FIG. 3, the polarization direction of the piezoelectric body 26 (direction of arrow b) is the individual electrode 27 and the common electrode 28.
Are arranged so as to be parallel to the direction of the electric field formed by applying a voltage to.

As shown in FIG. 4, the piezoelectric body 26 has the substrate 2 in the region s on the rear end side (right side in FIG. 4).
4 is adhered and fixed to the conductive adhesive 4 and its front end is a free end. Thus, when a voltage is applied to the piezoelectric body 26 to form an electric field, the area of the piezoelectric body 26 located in front of the bonding area s with the substrate 24 is deformed to form an action portion that pressurizes and ejects ink. become. If the surface of the substrate 24 corresponding to the adhesive region s is cut by the thickness of the adhesive layer (several μm to several tens of μm), the gap between the front end portion of the piezoelectric body 26 and the substrate 24 is reduced. It can also be eliminated, which has the effect of reducing gap variations.

A nozzle plate 30 made of a polyimide film having a thickness of, for example, about 25 to 200 μm is adhesively fixed to the front end surface of the joined body of the top plate 20 and the substrate 24. The nozzle plate 30 has a plurality of nozzle holes 30a formed by, for example, an excimer laser.
3 and the same pitch, and the pitch is, for example, about 42.3 to 254 μm (pixel density: 600 to 100 dp
i) about the same.

As shown in FIG. 2, side plates 31 and 31 for closing both end openings of ink inlets (not shown, which will be described later) communicating with the ink chambers 23 are provided on both side surfaces of the top plate 20. A back plate 32 that is adhered and closes the rear end opening of each ink chamber 23 on the rear end surface of the top plate 20.
Are glued together. Further, a manifold 33 for supplying ink to the ink chamber 23 is adhered to the upper surface of the top plate 20, and a plurality of ink supply ports 33a are provided on the upper portion of the manifold 33 so as to project.

As shown in FIG. 2, the piezoelectric body 26 extends rearward beyond the back plate 32 adhered to the rear end of the top plate 20. The individual electrode 27 at the rear end of each piezoelectric body 26 is connected to a plurality of conductors 15a installed on the upper surface of the terminal plate 15 by wire bonding, and further via the driving IC 17, the conductor 15b, and the connector 16. It is connected to the controller 6 shown in FIG. On the other hand, since the rear end side surface 24a of the substrate 24 is electrically conductive with the common electrode 28 of each piezoelectric body 26 via the conductive adhesive, the rear end side surface 24a of the substrate 24 and the base plate 13 are formed.
When the conductor 13a installed above is connected by wire bonding or the like at one place, each common electrode 28 is connected to the controller 6 via the connector 16.

Next, a manufacturing process of the ink jet head 12 having the above structure will be described with reference to FIGS. First, as shown in FIG.
The Au / Ni film or Au / (Ni, Cr) sputtered film of 10 μm to 0.1 μm formed by electroless plating on the upper and lower surfaces of the PZT plate 40, which is the material of FIG. Are bonded to the substrate 24 using a conductive adhesive. In this case, the bonding area s is only on the rear end side (right side in FIG. 5A) of the PZT plate 40, and the front end side is in a non-bonding state.

Then, as shown in FIG. 5B, the PZT plate 4 is formed by using the automatic dicing saw 39.
0 is slitted, and the piezoelectric bodies 26 are formed at a predetermined pitch as shown in FIG. After that, in order to prevent the displacement when the voltage is applied to the piezoelectric body 26 from decreasing due to the permeation of the ink, the entire surface of the piezoelectric body 26 is
For example, a polyimide resin may be applied by spin coating,
Bake at 0 ° C for 1 hour for overcoating. However, when a piezoelectric material having a high ink resistance is used for the piezoelectric body 26, this step may be omitted.

On the other hand, as shown in FIG. 6, the top plate 20 uses a ceramic plate 41 such as alumina,
A plurality of recesses 21 to be the ink chambers 23 are formed at the same pitch as the piezoelectric bodies 26 by dicing. The width of these recesses 21 is set so that the piezoelectric body 26 can be loosely fitted.
Form to larger dimensions. Further, a groove-shaped ink inlet 42 that is orthogonal to the recess 21 and communicates with all the recesses 21 is formed on the surface opposite to the surface where the recesses 21 are formed by dicing.

Subsequently, as shown in FIG. 7, the top plate 20 is superposed on the substrate 24, and the contact surface is adhered and fixed, and
The nozzle plate 30 is bonded to the front end surface of the joined body of the top plate 20 and the substrate 24 so that the nozzle hole 30 a is located at the center of the ink chamber 23.

Then, as shown in FIG. 8, the manifold 33 is adhered and fixed on the ink inlet 42, and the side plate 3 for closing the opening portions on both sides of the ink inlet 42.
The assembling of the ink ejecting portion 14 is completed by bonding the backing plate 32 that closes the rear end opening of the ink chamber 23 to the top plate 20.

Further, as shown in FIG. 9, the ink ejecting portion 14, the driving IC 17 and the conductor 15a on the upper surface,
The terminal plate 15 provided with 15b and the connector 16 are bonded and fixed to the upper surface of the base plate 13 provided with the conductor 13a. Then, the individual electrode 27 of the piezoelectric body 26 and the conductor 15
a, the rear end side surface 24a of the substrate 24 that conducts to the common electrode 28 of each piezoelectric body 26 and the conductor 13a on the base plate 13
Are electrically connected to each other, and the conductors 15b and 13a are electrically connected to the terminal 16a of the connector 16, whereby the assembly of the inkjet head 12 is completed. Thereafter, as shown by the dotted line in FIG. 9, if the outer surface is integrally resin-molded, more rational fixing becomes possible.

Next, the ink jet head 1 of this embodiment
The ink ejection operation in No. 2 will be described. Ink is supplied from the ink supply unit 7 (see FIG. 1) to the manifold 33.
The ink chamber 23 in the top plate 20 is filled with the ink supplied from the ink supply port 33a. When a pulsed voltage as shown in FIG. 10A is applied to the individual electrode 27 and the common electrode 28 in accordance with the image signal, the piezoelectric body 26 has a polarization direction (direction of arrow b in FIGS. 12 and 13). An electric field is formed in parallel. Then, when the piezoelectric body 26 is adhered and fixed on the entire surface of the substrate 24 (adhesion region s ₁ ), like the inkjet head of the conventional example, as shown by the dotted line in FIG. 11, the piezoelectric body 26 is expanded and displaced by Δy in the y direction. At the same time, it was slightly contracted and displaced in the x direction and the depth direction (the front and back directions of the paper surface in FIG. 11). However, when the bonding area s ₂ is a part of the contact surface with the substrate 24 and one end side of the piezoelectric body 26 is a free end as in the configuration of this embodiment, as shown by the dotted line in FIG. It was confirmed that the free end was deformed so as to warp with a curvature in the direction away from the substrate, and the displacement ΔY in the y direction at this time was 100 times or more as compared with Δy when the same voltage was applied.

Due to this warp deformation, the free end of the piezoelectric body 26 is abruptly displaced in the direction away from the substrate 24 from the normal position shown by the dotted line in FIG. As a result, the pressurized ink is ejected and ejected as droplets from the nozzle holes 30a and adheres to the recording paper (not shown).

When the voltage application between the individual electrode 27 and the common electrode 28 is released and the electric field disappears, the piezoelectric body 26 returns to its normal position. At this time, since a negative pressure is generated in the ink chamber 23, the ink is replenished in the ink chamber 23 through the manifold 33 and the ink inlet 42, and the next ink ejection can be prepared.

However, at the time of ink replenishment, as shown in FIG.
When the voltage is instantaneously set to zero and the piezoelectric body 26 is restored based on its elasticity as shown in (a), an excessive negative pressure is generated in the ink chamber 23 and air bubbles are sucked into the ink chamber 23 from the nozzle hole 30a. When the next pulse voltage is applied, the bubbles may absorb the pressure and hinder the ink ejection. For this reason, as shown in FIG. 10B, the piezoelectric body 26 has an inclination in the pulse shape of the voltage at the time of the restoring operation so that the piezoelectric body 26 returns to the earliest in a range where bubble suction does not occur,
It is desirable to prevent this.

The ink discharge operation as described above is independently performed for each ink chamber 23 according to the image signal, so that an image for one line is drawn and this is repeated in synchronization with the movement of the recording paper. As a result, an image corresponding to the image signal is drawn on the recording paper.

As described above, in the ink jet head 12 of this embodiment, the bonding area s ₁ between the piezoelectric body 26 and the substrate 24 is
Is made a part of the entire length of the piezoelectric body 26, so that the interlocking displacement caused by the vibration of the piezoelectric body 26 when a voltage is applied is propagated to the adjacent piezoelectric body 26 through the substrate 24 is completely suppressed. We were able to. Therefore, there is no unnecessary ink ejection or crosstalk such as turbulence of the ink flow in the ink chamber 32, and the ink ejection can be performed very stably, and as a result, the printing quality can be significantly improved. It became possible.

Further, since the piezoelectric body 26 is partially bonded, a large displacement amount can be obtained at the same voltage as compared with the conventional example, and the displacement amount is substantially proportional to the applied voltage. Have a relationship. Therefore, an extremely low voltage is sufficient to secure the same ink discharge amount and flight speed as in the conventional case, and the driver cost can be reduced, and the applied voltage is controlled to adjust the displacement amount of the piezoelectric body 26. As a result, the diameter of the flying ink droplets can be changed arbitrarily, and as a result, it has become possible to reproduce halftones in the color of the image drawn on the recording paper.

Further, if the length of the bonding area s of the piezoelectric body 26 is increased to the maximum value at which the adjacent piezoelectric body 26 does not cause the interlocking displacement, the force generated when the free end portion of the piezoelectric body 26 is displaced becomes strong. It was This makes it possible to achieve highly efficient ink flight with a stable ink droplet diameter and improve high-frequency response, and as a result, increase printing speed. In addition, in order to prevent the interlocking displacement of the adjacent piezoelectric bodies 26 and to prevent the reduction of the adhesive strength to the substrate 24, the length s of the adhesive region is 0.2l ≦ s when the total length of the piezoelectric bodies 26 is 1. It is preferable that ≦ 0.9 l. This is because if the volume is 0.2 l or less, the piezoelectric body 26 becomes fragile and is easily damaged during processing and assembly, and if the volume is 0.9 l or more, the interlocking displacement leading to crosstalk increases. Also,
The range of 0.3 l ≦ s ≦ 0.7 l is more preferable.

By the way, in the above embodiment, the pulse is applied to the piezoelectric body 26 so that the piezoelectric body 26 is deformed in the direction away from the substrate 24 to eject the ink and the ink is replenished when the piezoelectric body 26 is restored. Contrary to the above, FIG.
Alternatively, the pulse shown in (d) may be applied to deform the piezoelectric body 26 in the direction toward the substrate 24 to replenish the ink, and then the ink may be ejected when the piezoelectric body 26 is restored. For that purpose, it is necessary to secure a gap below the free end of the piezoelectric body 26, but in reality, this gap is several μm.
It is sufficient that the thickness is about m to several tens of μm, and the height of the adhesive layer between the piezoelectric body 26 and the substrate 24 is sufficient. Here, FIG. 10 (d)
The reason why the rising portion of the pulse is inclined is the same as in the case of FIG.

Next, a modification of the piezoelectric body 26 of the above embodiment will be described with reference to FIGS. First,
As a first modification, in the above embodiment, as shown in FIG. 4, the individual electrode 27 and the common electrode 28 are formed on the upper and lower surfaces of the piezoelectric body 26.
14 were installed symmetrically over the entire length of the piezoelectric body 26.
As shown in (a) and (b), a difference in length is provided between the electrodes, or as shown in FIG.
A notch in the width direction is formed in the upper part so that the individual electrodes 27 are installed so as to enter the inside of the piezoelectric body, and the individual electrodes 27 and the common electrode 28 are asymmetrically installed by providing a difference in size of the covering area of each electrode. You may do it. The piezoelectric body 26 shown in FIG. 4 and the piezoelectric body 26 shown in FIGS. 14A, 14B, and 14C.
Table 1 below shows experimental data on the generated force and the amount of displacement at the free end of the. As is clear from Table 1, the piezoelectric body 26 of FIG. 4 <FIG. 14 (a) <FIG. 14 (b) <FIG. 14 (c).
It was confirmed that the generated force and the amount of displacement increased in the order of. Therefore, if the piezoelectric body 26 shown in FIG. 14 is used, further low voltage driving and highly efficient ink ejection are possible. The generated force in Table 1 shows the generated force per ink chamber when the displacement amount ΔY of the free end of the piezoelectric body 26 is 1 μm, and the displacement amount in Table 1 is when the applied voltage is 50V. The displacement amount ΔY of the free end portion of the piezoelectric body 26 is shown.

[0038]

Table 1 Generated force (gf) Displacement amount (μm) Piezoelectric body 26 of FIG. 4 86.5 1.0 Piezoelectric body 26 of FIG. 14 (a) 240.0 2.8 Piezoelectric body 26 of FIG. 14 (b) 693.6 8.0 Piezoelectric body 26 1020.0 11.8 of FIG.

As a second modification, as shown in FIG. 15, each piezoelectric body 26 may have a trapezoidal cross-sectional shape. In this case, the top plate 20 can be easily fitted and the piezoelectric body 26 can be easily assembled. It can be facilitated.

Then, as a third modification, in the above embodiment, as shown in FIG. 5, a flat plate-shaped piezoelectric material partially fixed to the substrate 24 in a bonded state is subjected to a dicing process to form each piezoelectric body 26. Although it is completely divided into strips, as shown in FIG. 16, a so-called comb-shaped piezoelectric member 51 may be used. In the piezoelectric member 51, each piezoelectric body 52 is divided into strips in the front area (left side in FIG. 16) including the adhesion area s with the substrate, but in the area behind the adhesion area s, the individual electrode 27 is formed. The piezoelectric bodies 52 are connected to each other via a connecting portion 53 having an upper surface that is one step lower than the upper surface of each of the piezoelectric bodies 52 in which is formed. In addition,
This connecting portion 53 is formed by making the cutting depth shallower when the plate-shaped piezoelectric material is slit by dicing and past the adhesion region s with the substrate.

With this configuration, each piezoelectric body 52
The structural strength of the inkjet head,
Improves reliability. Further, since the common electrode formed on the lower surface of each piezoelectric body 52 is connected in the rear region of the piezoelectric member 51 due to the existence of the connecting portion 53, the connection between each common electrode 28 and the driver power supply is The common electrode in this rear region and the conductor 13a on the base plate 13
Is completed by connecting at one place by wire bonding or soldering. Therefore, it is not necessary to use a conductive adhesive for adhesion to the substrate 24 as in the case where the piezoelectric body 26 is formed by separating it into strips.

Further, when a voltage is applied to the individual electrode and the common electrode, the force generated when the non-bonded regions of the piezoelectric bodies 52 push up the partition wall 22 is the force generated by the piezoelectric bodies 26 completely separated into strips. It has been experimentally confirmed to be larger than. Therefore, by forming the piezoelectric member 51 in the shape of a comb, it is possible to achieve more efficient ink flight.

Each of the above modifications may be applied to the above embodiment alone, or may be applied in an appropriate combination.
Further, in the above-described embodiment and its modification, the single-layer piezoelectric body 2 is used.
6 is used, but as shown in FIG. 17, the piezoelectric body 26 'is laminated in two or more layers, and the individual electrode 27 and / or the common electrode 28 is arranged not only on the upper and lower surfaces but also inside. By doing so, a large effective displacement can be obtained according to the number of stacked layers, so that the driving voltage can be further reduced and the driver cost can be reduced.

Lastly, materials and the like that can be used in the above-mentioned embodiments and modifications will be described. Material of Piezoelectric Material As the material of the piezoelectric materials 26 and 52, the following piezoelectric materials can be used. (1) Piezoelectric crystal Quartz (SiO ₂ ), Rochelle salt (RS: NaKC ₄ H
₄ O ₆・ 4H ₂ O) Ethylenediamine tartrate (ETD: C ₆ H ₁₄ N ₂ O ₆ )
, Potassium tartrate (DKT: K ₂ C ₄ H ₄ O ₆ 1 / 2H
₂ O), diammonium phosphate (ADP: NH ₄ H ₂
PO ₄ ), perovskite crystals (ex. CaTi
O ₃ , BaTiO ₃ , PLZT), tungsten bronze-based crystal (ex. Na _x WO ₃ [0.1 <x <0.2
8]), sodium barium niobate (Ba ₂ NaN
b ₅ O ₁₅ ), potassium lead niobate (Pb ₂ KNb
₅ O ₁₅ ), lithium niobate (LiNbO ₃ ), lithium tantalate (LiTaO ₃ ), sodium chlorate (NaClO ₃ ), tourmaline (Tourmalin)
e), zinc blende (ZuS), lithium sulfate (LiS)
O ₄ H ₂ O), lithium metagallate (LiGa
O ₂ ), lithium iodate (LiIO ₃ ), glycine sulfate (TGS), bismuth germanate (Bi ₁₂ G)
eO ₂₀ ), lithium germanate (LiGeO ₃ )
, Barium titanate, germanium (Ba ₂ G
Crystals such as e ₂ TiO ₃ ).

(2) Piezoelectric semiconductor Wurtzite, BeO, ZnO, CdS, CdSe
, AlN. (3) Piezoelectric ceramics Barium titanate (BaTiO ₃ ), lead zirconate titanate (PbTiO ₃ · PbZrO ₃ ),
Titanium lead (PbTiO _3), niobate barium lead _{((Ba-Pb) Nb 2} O 6). (4) The above (1) piezoelectric crystal, (2) piezoelectric semiconductor,
(3) The powder of the piezoelectric ceramic material may be dispersed and molded in plastics. (5) piezoelectric polymer polyvinylidene fluoride _{PVDF (-CH 2 -CF 2 -)} n
, Polyvinylidene fluoride / PZT, rubber / PZT
, Copolymer of trifluoroethylene and vinylidene fluoride, copolymer of vinylidene cyanide and vinyl acetate,
Polyvinylidene, etc. The above-mentioned piezoelectric materials may be polarized and then processed as a piezoelectric body, or may be processed as a piezoelectric body and then polarized.

Overcoating of Piezoelectric Material The overcoating of the piezoelectric materials 26 and 52 can be performed by the following methods (1) to (5). (1) Application of plastics Saturated polyester resin, polyamide resin, acrylic resin, aramid resin, ethylene-vinyl acetate resin,
Thermoplastic resins such as ion-crosslinked olefin copolymers (ionomers), styrene-butadiene block copolymers, polyacetals, polycarbonates, vinyl chloride-vinyl acetate copolymers, cellulose esters, polyimides and styrene resins.

Thermosetting resins such as epoxy resin, phenoxy resin, urethane resin, nylons, silicone resin, fluorosilicone resin, phenol resin, melamine resin, xylene resin, alkyd resin and thermosetting acrylic resin. Polyvinyl carpazole,
Photoconductive resins such as polyvinyl pyrene, polyvinyl anthracene, and polyvinylol.

These can be used alone or in combination. In addition, engineering plastics such as liquid crystal polymer, a mixture of plastics and powder, and whiskers may be used. Photosensitive resin, thick film photoresist resin, etc. can be used. Bakelite, fluorocarbon resin, glass / epoxy resin (glass filler mixed in epoxy) may be used. These are coating, dipping,
A known liquid application method such as a spray method may be used. Among the above, in particular, polyamide resin, aramid resin, epoxy resin, phenoxy resin, fluorosilicone resin,
The effect of fluororesin and glass / epoxy resin is excellent.

(2) Vapor Deposition of Oxidizing / Nitriding / Sulfide Metal Compounds Metal oxide compounds (SiO ₂ , SiO, CrO, Al ₂ O ₃
Etc.), metal nitride compounds (Si ₃ N ₄ , AlN, etc.), metal sulfide compounds (ZnS, etc.), or alloys thereof,
It is coated by vacuum deposition or sputtering. In addition, the above (1)
The plastic may be applied by vapor deposition, or valerin resin vapor deposition may be applied. Among the above, Al ₂ O ₃ , S
The effect of i ₃ N ₄ is excellent.

(3) Application of hydrocarbon compounds Hydrocarbons, oxygen-containing hydrocarbons, sulfur-containing hydrocarbons and other group IV element-containing hydrocarbons, nitrogen-containing hydrocarbons, silicon-containing hydrocarbons, fluorine-containing hydrocarbons, etc. Halogen-containing hydrocarbons, Group III element-containing hydrocarbons
-Apply by CVD (plasma CVD) and perform overcoat treatment. Alternatively, under these mixed gas phases, P-C
It may be applied by VD. Among the above, the effect of the fluorine-containing hydrocarbon is excellent. Note that these films need to be appropriately provided with an undercoat of a-Si (amorphous silicon), a-SiC, a-SiN, or the like according to the compatibility of the adhesiveness with the piezoelectric body. (4) Instead of coating the surface of the piezoelectric plate in the coating liquid state with the plastics of (1) above, the piezoelectric body forming portion is replaced and impregnated under reduced pressure for molding. (5) The surface of the piezoelectric plate is surface-treated with an ink repellent solvent.

When the overcoat films formed by the above methods (1) to (5) are compared, the following characteristics are observed (however, (3) has an undercoat). Strength: Strong (2), (3)> (1), (4)> (5) Weak smoothness: Good (1), (4)> (2), (3), (5) Poor adhesion ( Vibration resistance included: Strong (1), (4)> (2), (3)> (5) Weak durability (including ink resistance): Good (1), (4)> (2) , (3)> (5) Bad Others, the processing of (5) is simple and can be used as the post-processing of (1) to (4). In terms of cost, (1) and (4) are particularly inexpensive. The methods (1) to (5) described above may be appropriately combined and used depending on the piezoelectric body and the ink type.

Materials for Top Plate and Substrate Materials that can be used for the non-piezoelectric material forming the top plate 20 and the substrate 24 include the following (1) to (4). (1) Ceramics Al ₂ O ₃ , SiC, C, BaTiO ₃ , BiO ₃
.3SnO ₂ , Pb (Zr _x , Ti _1-x ) O ₃ , ZnO
, SiO ₂ , (1-x) Pb (Zr _x , Ti _1-x ) O ₃
+ (X) La ₂ O ₃ , Zn _1-x Mn _x Fe ₂ O ₃ , γ-F
e ₂ O ₃ , Sr · 6Fe ₂ O ₃ , La _1-x Ca _x CrO ₃
, SnO ₂ , transition metal oxides, ZnO-Bi ₂ O ₃
, Semiconductor BaTiO ₃ , β-Al ₂ O ₃ , stabilized zirconia, LaB ₆ , B ₄ C, diamond, Ti
N, TiC, Si ₃ N ₄ , Y ₂ O ₂ S: Eu, PL
_{ZT, ThO 2, -CaO · nSiO} 2, Ca
₅ (F, Cl) P ₃ O ₁₂ , TiO ₂ , K ₂ O.nAl ₂
O ₃ .

(2) Glasses Elemental glass = Si, Se, Te, As Hydrogen-bonded glass = HPO ₃ , H ₃ PO ₄ , SiO ₂ ,
_{B 2 O 2, P 2 O} 5, GeO 2, As 2 O 3 oxide glass _{= SbO 3, Bi 2 O 3} , P 2 O 3, V 2
O ₅ , Sb ₂ O ₅ , As ₂ O ₃ , So ₃ , ZrO ₂ Fluoride glass = BeF ₂ , Chloride glass = ZnCl ₂ Sulfide glass = GeS ₂ , As ₂ S ₃ Carbonate glass = K ₂ CO ₃ , MgCO ₃ nitrate glass = NaNO ₃ , KNO ₃ , AgNO ₃ sulfate glass = Na ₂ S ₂ O ₃ , H ₂ O, Tl ₂ SO
_4, alum silicate glass = SiO ₂ silicate alkali glass _{= Na 2 O-CaO-SiO} 2 potash lime glass _{= K 2 O-CaO-SiO} 2 soda _{= Na 2 O-CaO-SiO} 2 lead glass, barium glass Borosilicate glass.

(3) Plastics Saturated polyester resin, polyamide resin, aramid resin, acrylic resin, ethylene-vinyl acetate resin,
Thermoplastic resins such as ion-crosslinked olefin copolymers (ionomers), styrene-butadiene block copolymers, polyacetals, polycarbonates, vinyl chloride-vinyl acetate copolymers, cellulose esters, polyimides and styrene resins. Thermosetting resins such as epoxy resin, urethane resin, nylon resin, silicone resin, phenol resin, melamine resin, xylene resin, alkyd resin, thermosetting acrylic resin. Photoconductive resins such as polyvinyl carpazole, polyvinyl pyrene, polyvinyl anthracene, and polyvinylol.

The above items (1) to (3) can be used alone or in combination. In addition, engineering plastics such as liquid crystal polymer, a mixture of plastics and powder, and whiskers may be used. A photosensitive resin, a thick film photoresist resin, or the like can also be used, and bakelite, a fluororesin, or a glass / epoxy resin (a glass filler mixed in epoxy) may be used.

(4) Others When the side surface in contact with the ink is coated with an insulating film, all metals can be used. These non-piezoelectric materials are formed into a plate shape and then processed into the top plate 20, or die-molded, pattern etching, photocuring, or the like is used from the beginning.
It may be molded into a shape of 0.

Material of Adhesive As the adhesive used for assembling the ink jet head 12, the following adhesives (1) to (4) can be used. However, the adhesive used to bond the piezoelectric body 26 to the substrate 24 needs to have conductivity. (1) Thermosetting resin adhesives such as epoxy resin, phenol resin, phenoxy resin, acrylic resin, furan resin, polyurethane resin, polyimide resin, silicone resin. (2) Thermoplastic resin adhesives such as polyvinyl acetate, polyvinyl chloride, vinyl acetal, polyvinyl alcohol, and polyvinyl butyral. (3) UV curable resin adhesive. (4) Anaerobic curable adhesive.

[0058]

As is apparent from the above description, in the ink jet recording apparatus of the present invention, each piezoelectric body is fixed to the substrate in a partially adhered state, so that vibration of one piezoelectric body passes through the substrate. Thus, crosstalk can be completely suppressed without propagating to other piezoelectric bodies and being interlocked and displaced. Therefore, the ink droplets can be stably ejected from each ink chamber, and the printing quality can be improved.

Further, since the piezoelectric body is partially adhered, the displacement of the piezoelectric body when the ink is pressed becomes remarkably large. Therefore, it is possible to fly the ink to the same extent at a voltage extremely lower than that of the conventional example. Therefore, the driver cost can be reduced. At the same time, since the displacement of the piezoelectric body is increased, the amount of displacement of the piezoelectric body can be adjusted by controlling the applied voltage. As a result, the diameter of the ink droplets flying from the ink chamber can be arbitrarily changed, and halftone reproduction of the color of the image drawn on the recording paper becomes possible.

Further, by disposing a pair of electrodes asymmetrically on the mutually parallel side surfaces of the piezoelectric body or by forming each piezoelectric body in a so-called comb-like shape, further low voltage driving and highly efficient ink flying can be achieved. Can be achieved.

Moreover, since it is not necessary to process the piezoelectric body into a complicated sectional shape as in the conventional example, the manufacturing is relatively simple and the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an inkjet recording apparatus that is an embodiment of the present invention.

FIG. 2 is an overall perspective view of an inkjet head according to an embodiment.

FIG. 3 is a cross-sectional view in the width direction of a main part of the inkjet head in the example.

FIG. 4 is a longitudinal cross-sectional view of a main part of the inkjet head in the example.

FIG. 5 is a perspective view illustrating a manufacturing process of the inkjet head in the embodiment.

FIG. 6 is a perspective view illustrating a manufacturing process of the inkjet head according to the embodiment.

FIG. 7 is a perspective view illustrating the manufacturing process of the inkjet head in the embodiment.

FIG. 8 is a perspective view illustrating a manufacturing process of the inkjet head according to the embodiment.

FIG. 9 is a perspective view illustrating a manufacturing process of the inkjet head in the embodiment.

FIG. 10 is a diagram showing a pulse shape of a voltage applied to the piezoelectric body of the example.

FIG. 11 is a side view showing displacement of a piezoelectric body in a conventional inkjet head.

FIG. 12 is a side view showing the displacement of the piezoelectric body in the inkjet head of the embodiment.

FIG. 13 is a cross-sectional view of an essential part of the inkjet head in the width direction for explaining the ink ejection operation.

FIG. 14 is a side view showing a first modification of the piezoelectric body of the example.

FIG. 15 is a cross-sectional view of an essential part of an inkjet head in the width direction, showing a second modification of the piezoelectric body of the embodiment.

16A and 16B are a plan view and a side view showing a third modification of the piezoelectric body of the embodiment.

FIG. 17 is a cross-sectional view in the width direction of a main part of an inkjet head showing a laminated piezoelectric body.

FIG. 18 is a partial cross-sectional view showing an example of a conventional inkjet head.

[Explanation of symbols]

12 ... Inkjet head, 20 ... Top plate, 21 ... Recess, 23 ... Ink chamber, 24 ... Substrate, 26 ... Piezoelectric body, 27
... Individual electrodes, 28 ... Common electrodes

Claims (6)

[Claims] 1. An ink jet head having piezoelectric bodies arranged in a plurality of ink chambers, respectively, and the piezoelectric body responsive to an image signal so that the piezoelectric body is displaced to eject ink filled in the ink chamber under pressure. In an ink jet recording apparatus including a voltage applying unit that applies a voltage to a non-piezoelectric member in which the ink jet head forms a plurality of groove-shaped recesses, a substrate that covers each recess and forms an ink chamber inside the recess, Electrodes that are arranged on the substrate corresponding to the recesses and that form an electric field parallel to the polarization direction thereof are provided, and at least a part of the piezoelectric body is not fixed to the substrate. An ink jet recording apparatus, wherein an unfixed part of the device is displaced. 2. The ink jet recording apparatus according to claim 1, wherein one end side of the piezoelectric body is fixed to the substrate and the other end side is not fixed. 3. The ink jet recording according to claim 1, wherein by applying a voltage to the piezoelectric body, an unfixed portion of the piezoelectric body is displaced in a direction away from the substrate. apparatus. 4. The ink jet recording according to claim 1, wherein by applying a voltage to the piezoelectric body, an unfixed portion of the piezoelectric body is displaced in a direction toward the substrate. apparatus. 5. The ink jet recording apparatus according to claim 1, wherein the electrodes of the piezoelectric body are installed asymmetrically. 6. The ink jet recording apparatus according to claim 1, wherein each of the piezoelectric bodies is formed in a comb shape having a portion connected to each other.