JPH10772A - Method for driving piezoelectric member for inkjet recording head and piezoelectric member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve jetting efficiency of ink drops by deforming a piezoelectric member so as to squeeze out an ink and superimposing timings of pressure waves generated by deformation of each region of the piezoelectric member. SOLUTION: In a method for driving a piezoelectric member 15 for an inkjet recording head, the driving is performed in a manner that deformation of the above described piezoelectric member 15 when an electric potential is applied successively becomes max. from a region A being a part separated from a nozzle 14 to a region C being a part close toward the nozzle by deviation of time. This method for driving is achieved by a method wherein an electrode 30 and an electrode 31 facing to this are provided on the piezoelectric member 15 and the electrode 31 consists of a plurality of electrode parts 32, 33 and 34 arranged toward the nozzle 14 and resistances 35 and 36 which electrically connect these electrode parts and an electric potential is applied on the electrode part 32 being farthest apart from the nozzle in this electrode 31 by means of a driver 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drop-on-demand (DOD) for recording an image by causing an ink drop to fly in response to an image signal and attaching the ink drop to a recording medium such as recording paper.
The present invention relates to a piezoelectric member used for an ink jet recording head of a system.

[0002]

2. Description of the Related Art Conventionally, there has been known an ink jet recording head which ejects ink by deformation of a piezoelectric member. FIG. 10 shows an example of an ink jet recording head using such a piezoelectric member. As shown in FIG. 10, the inkjet recording head 51 includes a channel plate 52 made of resin, metal, or the like. A plurality of recesses are formed in the channel plate 52 by a method such as molding or etching, and a partition wall 53 made of a thin film of resin, metal, or the like is adhered so as to cover the recess formation surface. The ink channels 55 and the ink supply chambers 58 are respectively provided inside the recesses covered by the partition walls 53.
And an inlet 57 that connects each ink channel 55 and the ink supply chamber 58 are formed. In addition, a plurality of nozzles 60 communicating with the ends of the ink channels 55 are formed in the channel plate 52. The ink channels 55 and the inlet 5
The nozzles 7 and the nozzles 60 are formed at an equal pitch along the depth direction (a direction perpendicular to the drawing) in FIG.

A spacer member 6 is provided below the partition wall 53.
The substrate 54 is fixed via the first and the second 62. A plurality of piezoelectric members 63 are adhesively fixed between the partition wall 53 and the substrate 54 below the ink channel 55 so as to face each ink channel 55 via the partition wall 53. Electrode layers 64 and 65 are formed on the upper and lower surfaces of the piezoelectric member 63, respectively, and a voltage is applied to the piezoelectric member 63 via the electrode layers 64 and 65.

In the ink jet recording head 51 having the above-described structure, when a voltage is applied to the piezoelectric member 63, as shown by a broken line in FIG. 10, the piezoelectric member 63 suddenly moves in the thickness direction, that is, in the direction in which the partition wall 53 and the substrate 54 face each other. It expands and deforms, and pushes up the partition wall 53 to the ink channel 55 side.
As a result, the ink in the ink channel 55 is momentarily pressurized, and the ink drop flies from the nozzle 60.

[0005]

The pressure wave generated in the ink channel 55 due to the deformation of the piezoelectric member 63 propagates in the ink at a speed slightly lower than the speed of sound, reaches the nozzle 60 end, and drops the ink. It becomes the ejection power of the flight.

However, the length L of the ink channel 55 is usually about 1 to 10 mm, and the corresponding piezoelectric member 63 has substantially the same length. Further, since the piezoelectric member 63 to which the voltage is applied is deformed substantially uniformly in the longitudinal direction (the left-right direction in FIG. 10), the piezoelectric member 6
The pressure waves are simultaneously generated in the respective regions in the ink channel 55 corresponding to No. 3. Therefore,
The pressure wave generated in the region near the nozzle 60 in the ink channel 55 and the pressure wave generated in the region farthest from the nozzle 60 have a difference in arrival time to the nozzle 60. Specifically, the speed of the pressure wave is set to 1500 m / s
ec, the length L of the ink channel 55
The shift of the pressure wave arrival time corresponding to (1 to 10 mm) is 0.7 to 7 μs (microsecond). Such a time lag means that the peak of the pressure wave does not concentrate at the time of ink ejection. Therefore, there has been a problem that a sufficient ink ejection efficiency has not been obtained and a load is imposed on a driver circuit.

[0007]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problems, and a driving method of a piezoelectric member according to a first invention is arranged corresponding to an ink channel containing ink. In a piezoelectric member for an ink jet recording head that pressurizes ink in the ink channel based on a deformation at the time of applying a voltage and causes an ink drop to fly from a nozzle, a deformation of the piezoelectric member is from a portion away from the nozzle to a portion close to the nozzle. Are driven so as to become maximum sequentially with a time lag.

A piezoelectric member for an ink jet recording head according to a second aspect of the present invention is arranged corresponding to an ink channel for storing ink, and pressurizes the ink stored in the ink channel based on deformation when a voltage is applied to the ink channel. A piezoelectric member for an ink jet recording head that causes an ink drop to fly from a nozzle communicating with the first member, wherein the piezoelectric member includes a first electrode and a second electrode opposed to the electrode with the first member interposed therebetween. Is composed of a plurality of electrode portions arranged toward the nozzle and a resistor for electrically connecting these electrode portions. The electrode portion of the first electrode farthest from the nozzle and the second electrode are connected to each other. It is connected to voltage application means.

[0009]

According to the driving method of the piezoelectric member of the first invention, when a voltage is applied to the piezoelectric member, first, a voltage is applied to the piezoelectric member.
The portion near the end of the piezoelectric member farthest from the nozzle shows the largest deformation, and the pressure wave generated in the ink of the ink channel due to the deformation of this portion propagates toward the nozzle.
Then, with a time lag, the deformation of the portion of the piezoelectric member located closer to the nozzle than the above portion is maximized. The pressure wave generated by the deformation of this portion overlaps with the pressure wave generated in the vicinity of the end portion and propagates in the nozzle direction. Such deformation is performed up to the nozzle side end of the piezoelectric member, and the pressure waves generated in each portion are sequentially overlapped, so that the peak of the pressure wave can be adjusted at the time of discharging the ink drop, and the discharge efficiency of the ink drop can be improved. Can be raised.

Further, according to the piezoelectric member for an ink jet recording head of the second invention, the driving method of the first invention can be realized. That is, for the first electrode of the piezoelectric member, a voltage is applied to the electrode portion farthest from the nozzle by the voltage applying unit. By this voltage application, first, the portion of the piezoelectric member farthest from the nozzle shows the maximum deformation amount according to the applied voltage. Subsequently, since the voltage of the electrode portion adjacent to the resistor is connected via the resistor,
The maximum voltage value is obtained with a time lag from the voltage application, and the portion of the piezoelectric member where this electrode portion is located, that is, the portion closer to the nozzle, indicates the maximum deformation amount according to the voltage value. As described above, the voltage applied to each part of the piezoelectric member reaches its maximum value with a time lag from the resistance, and the deformation of each part of the piezoelectric member sequentially becomes maximum toward the nozzle side. Thus, the timing at which the pressure wave generated in the ink channel due to the deformation of each part of the piezoelectric member reaches the vicinity of the nozzle can be adjusted at the time of ink ejection, and the ejection efficiency of the ink drop can be increased.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 and 2 show an ink jet recording head 1 using a piezoelectric member according to a first embodiment of the present invention. The inkjet recording head 1 has a first head unit 10 and a second head unit 20. The first and second head portions 10 and 20 are integrally formed by the channel plate 2, the partition wall 3, and the substrate 4, and are configured symmetrically with respect to the center cross section X of the head 1. Only the head unit 10 will be described.

The channel plate 2 is made of a flat plate made of resin, metal, or the like.
A plurality of recesses are formed by fine processing such as photoresist or electroforming. The partition 3 is made of a thin film of metal, resin, or the like, and is adhered so as to cover the concave surface of the channel plate 2. An ink channel 11, an inlet 12, and an ink supply chamber 13 are formed inside each concave portion of the channel plate 2 covered by the partition 3.

The plurality of ink channels 11 are arranged in parallel at an equal pitch. Each ink channel 11 receives ink from an ink supply chamber 13 via a corresponding inlet 12. In addition, the channel plate 2 includes each ink channel 1.
The plurality of nozzles 14 communicating with each other in the vicinity of one end
Are formed on two straight lines. The nozzle 14 has a tapered circular cross section having a large diameter on the ink channel 11 side and a small diameter on the discharge side facing the outside.

The channel plate 2 and the partition 3 are
It is fixed to a substrate 4 made of a highly rigid material such as ceramic via spacer members 6, 7, 8. A plurality of piezoelectric members 15 are fixed on the substrate 4 so as to face the ink channels 11 with the partition walls 3 interposed therebetween. The piezoelectric member 15 is a pressurizing unit that pressurizes the ink in the ink channel 11 via the partition 3 based on the deformation at the time of applying a voltage, and causes the ink drop to fly from the nozzle 14.

The piezoelectric member 15 is made of a piezoelectric material such as lead zirconate or lead titanate, and is formed in a rectangular parallelepiped having a length and width slightly smaller than the ink channel 11. As shown in FIG. 3, electrodes 30 and 31 extending along the same longitudinal direction as the ink channel 11 and facing each other via the piezoelectric member 15 are formed on the upper and lower surfaces of each piezoelectric member 15 by a sputtering method. And are formed by a plating method or the like. Among them, the upper electrode 30 is grounded via the conductive partition wall 3 that comes into contact with the upper electrode 30.

On the other hand, the lower electrode 31 comprises three electrode portions 32, 33, 34 arranged toward the nozzle 14, and resistors 35, 36 for electrically connecting these electrode portions 32, 33, 34. ing. These resistors 35, 36
Can be simultaneously formed for each piezoelectric member 15 by applying a resistive material by printing to a region masked when the lower electrode 31 is formed by sputtering or the like. Hereinafter, the respective portions of the piezoelectric member 15 bordering the respective central portions of the resistors 35 and 36 will be referred to as regions A, B, and C in order from the side away from the nozzle 14. As shown in FIG. 2, the electrode portion 32 in this area A is electrically connected to an individual lead 37 printed on the substrate 4. The individual lead wires 37 are formed corresponding to the respective piezoelectric members 15 and connected to the driver 9 from the side of the substrate 4. The individual lead wires 37, the driver 9, and the partition wall 3 that grounds the electrode 30 constitute voltage applying means for applying a voltage to the piezoelectric member 15.

The ink channels 11, 11, the inlets 12, 12, and the piezoelectric member 1 of each of the heads 10, 20 are provided.
5 and 15 are formed in the same size. The nozzles 14, 14 are also formed to have the same diameter. The sizes of the ink channel 11, the inlet 12, the piezoelectric member 15, the nozzle 14, and the like may be different for each head, and ink droplets having different diameters may be ejected from each head.

Next, the driving method of the piezoelectric member 15 and the ink discharging operation in the ink jet recording head 1 having the above-described configuration will be described. Each of the above ink channels 1
1 stores the ink supplied from the ink supply chamber 13. In this state, the driver 9 applies a predetermined voltage to the electrode portion 32 of the lower electrode 31 to drive the piezoelectric member 15. FIG. 4 is a graph showing the transition of the voltage value of each of the electrode portions 32, 33, and 34 of the lower electrode 31 for each of the regions A, B, and C corresponding thereto. In this graph, time t is plotted on the horizontal axis, and voltage value V is plotted on the vertical axis. As shown in this graph, the voltage in the region A has the same waveform as the voltage applied by the driver 9. That is, it has a predetermined rising gradient and reaches the maximum voltage value V ₁ at t ₁ . On the other hand, the voltage in the region B is equal to the time constant at which the capacitance (capacitor) component of the piezoelectric member in the region B is charged by the current temporarily flowing through the electrode 31 passing through the resistor 35. The rising gradient becomes gentler than the voltage of A. Therefore, in the region B, reaches t ₂ at the maximum voltage value V ₁ also temporally slightly later than the region A. Similarly, the voltage of the region C, the presence of the resistor 36 reach t ₃ at the maximum voltage value V ₁ and further delayed than the area B.

As described above, each region A,
The voltages of B and C reach the maximum voltage value V ₁ with a time lag. Therefore, as shown in FIG. 5, first, the area A of the piezoelectric member 15 has the maximum deformation amount Δ (delta) corresponding to the voltage value V ₁ . The partition 3 is momentarily pushed up into the ink channel 11 by the deformation of the area A, and a pressure wave is generated in the ink. This pressure wave spreads in the ink channel 11 and propagates toward the nozzle 14 (left side in FIG. 5). Subsequently, the maximum deformation amount Δ of the portion of the piezoelectric member 15 in the region B is slightly delayed. This area B
The pressure wave generated by the deformation of the portion propagates toward the nozzle 14 so as to overlap the pressure wave generated in the region A. Then, even slightly later, the area C of the piezoelectric member 15
Is the maximum deformation amount Δ, and the pressure wave generated in the area C overlaps the pressure wave to reach the vicinity of the nozzle 14, and the ink drop is ejected from the nozzle 14.

As described above, the piezoelectric member 1 is squeezed so as to squeeze the ink in the ink channel 11 toward the nozzle 14.
If the maximum deformation time of each of the regions A, B, and C is shifted, the pressure waves generated in the regions A, B, and C can be sequentially overlapped, and the peak of the pressure wave can be adjusted at the time of discharging the ink drop. . As a result, the ink drop ejection efficiency can be increased by about 10 to 20%, depending on the length of the ink channel 11 and the timing of overlapping pressure waves.

The voltage applied to the piezoelectric member 15 rises steeply (the above-mentioned t ₁ is about ₁ to 10 μs) or slowly (the above-mentioned t ₁ is about ₁₀ to 50 μs).
With such control, the ink ejection force can be changed without changing the circuit of the driver 9, and the size of the ink drop and the ejection speed can be adjusted.

On the other hand, when the voltage application by the driver 9 is released, the piezoelectric member 15 returns to the original state, and the negative pressure generated in the ink channel 11 from the ink supply chamber 13 through the inlet 12 at that time. The ink is replenished. The operation of restoring the piezoelectric member 15 shows a direction opposite to that of the deformation when the ink is pressed. That is, when the voltage application to the electrode portion 32 is released, first,
The area A of the piezoelectric member 15 is restored promptly, and then the area B and the area C are sequentially restored with a slight time lag. By performing such a restoring operation, ink is supplied to the ink channel 11 more slowly than when the piezoelectric member 15 is simultaneously restored over the entire length. Fluctuation of the ink in the channel 11 can be suppressed.

According to the structure of the present embodiment, since the voltage applied to each area of the piezoelectric member 15 can be maximized with a time difference by one driver, the circuit is simple and inexpensive. it can. However,
Not limited to the configuration of the present embodiment, the piezoelectric member 15 as described above
In order to more accurately control the deformation operation of the resistors 35, 3
6, the lower electrode 31 is composed of only the non-conductive electrode portions 32, 33, and 34, and a corresponding driver is connected to each of the electrode portions 32, 33, and 34. Electrode part 32,3
The application and release of the voltage may be performed with a time lag between 3, 34.

Although the piezoelectric member 15 has a single-layer structure, as shown in FIG. 6, a laminated piezoelectric member 40 having a plurality of electrodes extending in parallel along the longitudinal direction is used. You may. The piezoelectric member 40 is configured by laminating a plurality of thin piezoelectric layers 41. A common electrode portion 42 is provided on the end surface of the piezoelectric member 40 remote from the nozzle 14 (the right end surface in FIG. 6), from which the electrode portions 32, 33,
An electrode 31 consisting of 34 extends between the piezoelectric layers 41. On the other hand, a common electrode portion 43 is also provided on the end surface of the piezoelectric member 40 on the nozzle 14 side (the left end surface in FIG. 6), from which a plurality of electrodes 30 are interposed between the piezoelectric layers 41 positioned between the electrodes 31. Each extends. Each of the above electrodes 30
Are grounded via a common electrode portion 43, and a driving voltage is applied to each of the electrodes 31 via a common electrode portion. The electrodes 30 and 31 are formed so as not to conduct with each other.

When a voltage is applied to the common electrode portion 42 of the piezoelectric member 40 having the above-described configuration, the deformation operation of the regions A, B, and C is the same as that of the single-layer piezoelectric member 15. However, the laminated type piezoelectric member 40 has a higher deformation efficiency when the same voltage is applied as compared with a single-layered piezoelectric member, and a large amount of deformation can be obtained. The effect can be achieved with lower drive voltage.

Although the piezoelectric member 15 is formed to be elongated along the longitudinal direction of the ink channel 11, its shape can be variously changed corresponding to the ink channel 11. For example, the ink channel is formed in a cylindrical space, and the piezoelectric member is accordingly formed in a cylindrical shape.
A plurality of annular electrode portions 32, 33, 34 and resistors 35, 36 each having a predetermined width are concentrically arranged on one surface of the cylindrical piezoelectric member to form the electrode 31, and the other electrode is formed. An electrode 30 is formed on the entire surface. The nozzle is provided to face the center of the cylindrical piezoelectric member.

In the above configuration, if a voltage is applied to the electrode portion 32 located farthest from the nozzle, the deformation of the piezoelectric member sequentially becomes maximum with a time lag from the outer peripheral portion toward the central portion, and the peak of the pressure wave is reduced. It is possible to concentrate on the center where the nozzle is located.

In the ink jet recording head 1, the piezoelectric member 15 is separated from the ink channel 11 by the partition wall 3.
However, a moisture-proof coating may be applied to the surface of the piezoelectric member 15 or the like so that the surface directly faces the ink channel 11.

Next, a piezoelectric member 46 according to a second embodiment will be described with reference to FIGS. As shown in FIG. 7, the piezoelectric member 46 is also of a laminated type and has substantially the same configuration as the piezoelectric member 40. Therefore, the same reference numerals are given to the same members, and the detailed description is omitted.
However, the configuration is different in that the tip of each electrode 31 is electrically connected to the common electrode 43 via the resistor 47.

When a voltage having a predetermined rising gradient is applied to the common electrode portion 42 of the piezoelectric member 46, the common electrode portion 43 is electrically connected to the grounded common electrode portion 43 through the resistor 47. A current will flow through the electrode 31. Therefore, the voltages of the electrode portions 32, 33, and 34 corresponding to the regions A, B, and C of the piezoelectric member 46 change as shown in the graph of FIG. That is, the voltage in the area A has the maximum voltage value V ₁ at t ₁ according to the same waveform as the applied voltage.
, The voltage of the region B rises slowly and reaches the maximum voltage value V ₂ lower than the above-mentioned V ₁ at t _{2 due to} the voltage drop at the resistor 35. Further, the rise of the voltage in the region C becomes more gradual, and the voltage drop at the resistor 36 causes the maximum voltage value V ₃ lower than the above-mentioned V ₂ at t _{3 due to} the voltage drop.
Reach

The deformation of the piezoelectric element 46 the voltage of each region as described above to remain, as shown in FIG. 9, first, the maximum deformation amount delta ₁ becomes the area A corresponding to the voltage value V _1, which slightly delays region Te B is the maximum amount of deformation delta ₂ becomes corresponding to the voltage value V _2, the area C is delayed further slightly the maximum deformation amount delta ₃ corresponding to the voltage value V _3. By such a stepwise deformation of the piezoelectric member 46, the pressure waves generated in the respective areas A, B, and C can be sequentially overlapped similarly to the case of the piezoelectric member 15, and
The ejection efficiency of ink drops can be increased.

[Brief description of the drawings]

FIG. 1 is a plan view of an ink jet recording head using a piezoelectric member according to the present invention.

FIG. 2 is a cross-sectional view of the head shown in FIG. 1, taken along the line II-II.

FIG. 3 is a side view of the piezoelectric member according to the first embodiment.

4 is a graph showing a transition of a voltage applied to each region of the piezoelectric member of FIG.

5 is a side view for explaining the amount of deformation in the thickness direction in each region of the piezoelectric member in FIG. 3 with time.

FIG. 6 is a side view of the laminated piezoelectric member according to the present invention.

FIG. 7 is a side view of a laminated piezoelectric member according to a second embodiment.

FIG. 8 is a graph showing a transition of a voltage in each region when a voltage is applied to the piezoelectric member of FIG. 7;

9 is a side view for explaining the amount of deformation in the thickness direction in each region of the piezoelectric member of FIG. 7 over time.

FIG. 10 is a cross-sectional view illustrating an example of a conventional ink jet recording head using a piezoelectric member.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ink jet recording head, 2 ... Channel plate, 3 ... Partition, 4 ... Substrate, 11 ... Ink channel, 1
4 Nozzle, 15 Piezoelectric member, 30 Electrode (second electrode) 31 Electrode (first electrode), 32, 33, 34 Electrode portion, 35, 36 Resistance.

Claims (2)

[Claims] 1. A piezoelectric member for an ink jet recording head, which is arranged corresponding to an ink channel containing ink and pressurizes ink in the ink channel based on a deformation at the time of applying a voltage to fly an ink drop from a nozzle. The driving method of the piezoelectric member, wherein the piezoelectric member is driven so that the deformation of the piezoelectric member sequentially becomes maximum with a time lag from a portion away from the nozzle to a portion near the nozzle. 2. An ink jet recording apparatus which is arranged corresponding to an ink channel containing ink and pressurizes the ink contained in the ink channel based on a deformation at the time of applying a voltage to fly an ink drop from a nozzle communicating with the ink channel. In the piezoelectric member for a head, the piezoelectric member includes a first electrode and a second electrode facing the electrode with the piezoelectric member interposed therebetween, and the first electrode includes a plurality of electrodes arranged toward a nozzle. An electrode portion and a resistor for electrically connecting the electrode portions; an electrode portion of the first electrode farthest from the nozzle;
A piezoelectric member for an ink jet recording head, wherein the electrodes are connected to voltage applying means.