JP2001121710A - Ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly accurate ink jet head wherein a quantity of ejected ink is not varied depending upon a using environment or a temperature at the using time. SOLUTION: This ink jet head comprises a pair of opposing substrates 2, 3 and an ink chamber 5 which is enclosed by a plurality of partition walls 4 provide in parallel to the substrates 2, 3. At least one of the pair of substrates 2, 3 is formed from cordierite ceramic.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet head for forming a print and an image by discharging ink droplets from fine nozzle holes.

[0002]

2. Description of the Related Art In recent years, with the spread of multimedia, a non-impact method has been proposed as an interface for printing various types of small and lightweight information suitable for use in a small number of types and with no need for a printing plate. Various printing apparatuses have been developed, and among them, ink jet heads are rapidly spreading because of easy multi-gradation and colorization and low running cost.

[0003] In general, the ink-jet head includes:
An ink chamber surrounded by a pair of substrates and a partition, and a nozzle plate formed on one end surface of the ink chamber and having a nozzle hole formed therein, and ejects ink droplets from the nozzle hole. is there.

FIG. 3 is an exploded perspective view showing an example of a specific structure of such an ink jet head. An ink jet head 50 is composed of a pair of opposing substrates 51 and
A plurality of partitions 54, 54 are arranged in parallel between 52 to form an ink chamber 55. The ink chamber 55 is filled with ink, and the ink chamber 55 is deformed by the piezoelectric ceramic formed in the ink chamber 55. Alternatively, the ink is heated and foamed by a heater to cause volume expansion, and the ink chamber 55
By generating an internal pressure inside, ink droplets are ejected through nozzles 57 of a nozzle plate 56 provided on the side surface of the ink chamber 55.

In FIG. 3, a partition wall 54 is formed of piezoelectric ceramics, and a potential difference is applied to a pair of electrodes 58 formed on the side surfaces of the piezoelectric ceramics to deform the piezoelectric ceramics in a shear mode. According to this structure, it has been proposed that an ink jet head having a simple structure that can be increased in density, can be used without limiting the kind of ink, and has excellent responsiveness can be manufactured.

Conventionally, in such an ink jet head, it has been known that the substrates 51 and 52 are formed of glass, alumina, or a non-polarized piezoelectric ceramic sintered body. For example, in Japanese Patent Application Laid-Open No. 7-60962, The partition walls are formed of piezoelectric ceramics, and a fixed height from the substrate side of the partition walls is formed of the same non-piezoelectric ceramic material as the substrate. It is disclosed that the deformation amount of the body ceramic can be controlled to be constant.

[0007]

However, according to the ink jet head in which the above-mentioned conventional substrate is formed of glass or alumina, the dimensions of the substrate change due to the use environment or heat during operation of the ink jet head, and the volume of the ink chamber is reduced. There is a problem that the amount of ink ejected due to variation varies.

Further, when the substrate is formed of a non-polarized piezoelectric ceramic sintered body, there is a problem that a so-called crosstalk occurs, which is slightly displaced due to the influence of a voltage applied to an adjacent partition wall.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and an object of the present invention is to provide a high-precision ink jet head in which the amount of ink ejected does not change due to a use environment or heat during use. .

[0010]

Means for Solving the Problems As a result of intensive studies in view of the above problems, the present inventors have found that the volume change of the ink chamber due to the temperature change can be suppressed by forming at least one substrate from cordierite ceramics. From the above, it was found that an ink jet head in which the amount of ejected ink does not change was obtained, and the present invention was reached.

That is, an ink jet head according to the present invention includes an ink chamber surrounded by a pair of opposed substrates and a plurality of partitions arranged in parallel between the substrates. At least one of the pair of substrates is made of cordierite ceramics.

Here, it is preferable that at least a part of the partition is made of cordierite ceramics, and at least a part of the partition is made of piezoelectric ceramics.

The piezoelectric ceramic may be polarized in one direction substantially parallel to the direction perpendicular to the substrate, or one end and the other end of the piezoelectric ceramic may be substantially parallel to the direction perpendicular to the substrate. It is characterized by being polarized in two opposite directions.

Further, the cordierite ceramic has a coefficient of thermal expansion of 1 ppm / ° C. or less at 10 to 40 ° C., a Young's modulus of 90 to 140 MPa, and a porosity of the cordierite ceramic of 4% or less. It is desirable.

In the ink jet head according to the present invention, since at least one of the substrates is made of cordierite ceramics having a low coefficient of thermal expansion, the change in the volume of the ink chamber with respect to the temperature change is reduced. Ink-jet with no change in ink amount.

Further, by forming a part of the partition wall of the piezoelectric ceramics as a driving portion and using the cordierite ceramics for the other non-driving portions of the partition walls, the driving portion is formed. If the area where the electrode formed on the side surface covers the piezoelectric ceramic part,
Even if the deposition area in the non-driving portion of the electrode varies for each partition, the amount of displacement of the piezoelectric ceramic can be controlled to be constant, and a constant internal pressure can be generated in the ink chamber. And the dielectric constant is lower than when the non-driven portion of the partition other than the piezoelectric ceramic is made of the same material as the non-polarized piezoelectric ceramic. It is possible to reduce the power consumption and heat generation of the non-driving part due to the application, and it is possible to suppress the change in the viscosity of the ink. Furthermore, crosstalk between adjacent ink chambers can be eliminated.

Also, lead zirconate titanate (PZT),
Young's modulus (about 130 GPa) of piezoelectric ceramics such as lead titanate, barium titanate, and tungsten bronze, and Young's modulus (14
0 GPa), a part of the partition is made of piezoelectric ceramics to form a driving part, and the other part of the partition is made of cordierite ceramics which is a non-driving part. Compared to the case where a part of the partition wall is made of glass (about 75 GPa of Young's modulus) or alumina (about 350 GPa of Young's modulus), when the grinding process is performed with a slicer or the like, the grinding resistance is similar, and thus the workability is improved. This improves the yield and prevents the partition walls from being chipped or cracked and the slicer disk or the like from being damaged, thereby enabling good grinding with high yield.

Further, the cordierite ceramics can bend with the displacement of the piezoelectric ceramics, a large displacement can be instantaneously obtained with a small applied voltage, and the interface between the piezoelectric ceramics and the cordierite ceramics can be obtained. In addition, stress concentration at the interface between the partition wall of the cordierite ceramic and the substrate can be reduced, and a long-term stable and highly reliable inkjet head can be obtained.

Further, if the partition walls are formed of piezoelectric ceramics polarized in two directions, and a voltage is applied to each of them to drive them, a predetermined amount of displacement can be caused by a small applied voltage. Temperature rise can be suppressed.

[0019]

FIG. 1 is a schematic perspective view and FIG. 2 is a schematic sectional view of an example of an ink jet head according to the present invention.

The ink-jet head 1 shown in FIGS. 1 and 2 has an ink chamber 5 surrounded by a pair of opposed substrates 2 and 3 and a plurality of partitions 4 and 4 arranged in parallel between the substrates 2 and 3. And

According to the present invention, it is a major feature that at least one of the substrates 2 and 3 is made of cordierite ceramics having a low coefficient of thermal expansion, whereby a change in volume of the ink chamber with respect to a change in temperature is reduced. Therefore, an ink jet in which the amount of ink ejected in response to a temperature change does not change is obtained. Further, since the dielectric constant of the substrates 2 and 3 is low, the power consumption of the substrates 2 and 3 can be reduced, and crosstalk between the partition walls of the substrates can be prevented. In FIGS. 1 and 2, both the substrates 2 and 3 are formed of cordierite ceramics. Furthermore, the shape is 5 to 400 mm in width and 1 to 50 in the longitudinal direction of the partition wall.
mm and a plate-like body having a thickness of 0.05 to 5 mm.

According to FIGS. 1 and 2, about half of the partition wall 4 is a driving portion 7 made of a ceramic piezoelectric material on the bonding surface side of the substrate 2 and about half of the partition wall 4 on the bonding surface side of the substrate 3 as the remaining portion. A non-driving section 8 made of the same cordierite ceramic as the substrate 3 is formed.

As a result, if the electrode 6 to be formed on the side surface of the partition wall 4 to be described later covers the piezoelectric ceramic which is the driving portion 7, for example, the cordierite ceramics where the electrode 6 is the non-driving portion 8 Even if the formation area varies for each partition, the amount of displacement of the piezoelectric ceramic of the drive unit 7 can be controlled to be constant, and a constant internal pressure can be generated in the ink chamber 5. ,
The amount of ink to be ejected can be made constant, and printing without printing unevenness becomes possible.

Further, since the dielectric constant of cordierite ceramics is lower than the case where the non-driving portion 8 of the partition wall 4 is formed of a non-polarized piezoelectric ceramic sintered body, the non-driving portion 8 in Power consumption and heat generation can be reduced. Furthermore, crosstalk between the adjacent ink chambers 5 can be eliminated.

Further, since the Young's modulus of the piezoelectric ceramics and the Young's modulus of the cordierite ceramics are close to each other, the workability of the grinding using a slicer or the like is improved, and good grinding can be performed.

Further, the cordierite ceramics can bend with the displacement of the piezoelectric ceramics, and a large displacement can be obtained efficiently and instantaneously with a small applied voltage, and the piezoelectric ceramics and the cordierite ceramics can be obtained. There is no stress concentration at the interface between the substrate 3 and the interface between the cordierite ceramic partition wall 4 and the substrate 3, and the structure can be stably maintained for a long period of time.

If the upper and lower halves in the height direction of the partition wall 4 are formed in two directions in which the polarization directions are opposite to the height direction of the partition wall, a predetermined displacement can be obtained efficiently with a small applied voltage. As a result, power consumption can be reduced, and heat generation due to voltage application can be suppressed.

As the above-mentioned ceramic piezoelectric material, specifically, lead zirconate titanate, lead titanate and the like can be suitably used, and if necessary, a known additive for enhancing the piezoelectricity, for example, , Ba, Ca, Sr, Nb and the like. Furthermore, the shape is 100 μm wide
Hereinafter, it is a roughly rib shape having a height of 200 to 400 μm and a length of 1 to 8 mm, and a pitch of the partition walls 4 and 80 to 300 μm
Are arranged in a plurality of stripes.

In addition, cordierite ceramics
Against _{2MgO · 2Al 2 O 3 · SiO} 2, the transition metal and the periodic table group 3a metal may be added. In view of the above, the thermal expansion coefficient at 10 to 40 ° C., which is the use environment temperature, is 1 ppm / ° C. or less, and the Young's modulus is 90 to 150 MPa.
a, It is desirable that the dielectric constant is 5 or less, and the three-point bending strength is 100 MPa or more.

Further, in order to prevent chipping or the like at the time of processing, the porosity of cordierite ceramics is set to 4%.
% Is desirable.

The electrode 6 is formed of a conductive material such as at least one of gold, silver, copper, platinum, nickel, tungsten, chromium, and aluminum, and has a thickness of 0.5 to 10 μm.

Electrodes 6 and 6 are formed on both side walls of the partition 4 at a predetermined height from the joint surface of the partition 4 with the substrate 2, preferably at a height almost half the height of the partition. An extraction electrode (not shown) formed on an end face side of the chamber 5 opposite to a side on which the nozzle plate 11 described later is provided, and further, a chip element (not shown) formed outside thereof, a lead terminal, and wiring. It is connected via a circuit or the like, and controls the voltage applied to the electrodes 6 by the chip element.

A nozzle plate 11 having a nozzle 10 communicating with the ink chamber 5 is formed on one side of the ink chamber 5 by bonding.

Further, an ink inlet 13 for introducing ink from an ink tank (not shown) into the ink jet head 1 is formed in a part of the substrate 2, and each ink chamber 5 of the ink jet head 1 is formed. To supply ink.

According to the ink jet head 1, the ink is filled into the ink chamber 5 from the ink tank through the ink tank inlet 13, and a voltage is applied to the electrode 6 to cause the piezoelectric ceramic 7 to deform. In this way, ink is ejected from the nozzle holes 10 by applying pressure to the ink chamber 5.

The above-mentioned ink may be a pigment or / and / or
In addition, dyes and water-based solvents such as water and alcohol, or non-aqueous solvents such as hexane and toluene as main components are applicable.

Further, in FIG. 1, the nozzle plate 11 is disposed on the end surface of the side wall of the partition wall 4 of the ink chamber 5. However, the present invention is not limited to this, and the communication between the substrate 3 and the nozzle 10 is established. The nozzle plate 11 may be provided on the side wall surface of the substrate 3 by providing holes.

Next, an example of a method for manufacturing the ink jet head shown in FIGS. 1 and 2 will be described. First, a polarization process is performed in the thickness direction of the plate by forming a conductor layer on the upper and lower surfaces of the plate made of the above-described piezoelectric ceramic material and applying a voltage to the conductor layers.

On the other hand, magnesia, alumina, and silica powder having an average particle diameter of 10 μm or less were mixed with 2MgO.2Al ₂ O ₃ .S
After mixing to obtain iO ₂ , adding the above-described additives thereto, and adding an organic binder and a solvent as desired, the plate is formed by a conventionally known press molding method, extrusion molding method, or tape molding method. A shaped body is produced.

After subjecting the molded body to a binder removal treatment, the molded body is fired at about 1100 to 1450 ° C. to produce a plate made of cordierite ceramics.

The electrode 6 is formed after the obtained piezoelectric ceramics having been subjected to the polarization treatment are bonded to the surface of the obtained cordierite ceramic plate by an adhesive.

Specifically, for example, a conductive material such as gold, silver, copper, platinum, nickel, tungsten, chromium, or aluminum having a thickness of 0.5 to 10 μm is formed on both wall surfaces of the partition wall 4. An electrode 6 is formed. Means for forming the electrode 6 include, for example, a sputtering method, an evaporation method,
The electrode 6 is formed on the wall surface of the partition wall 4 including the distal end surface of the partition wall 4 by an ion plating method, a vapor phase method such as a CVD method, a plating method, or the like, and the electrode portion formed on the distal end surface of the partition wall 4 is polished. A short-circuit between the electrodes 6 on both wall surfaces can be prevented by removing a part by irradiating a laser or the like. In addition, it is also possible to mask the tip of the partition wall 4 before forming the electrode 6 and remove the masking after the electrode 6 is formed.

Here, in the case where the partition wall 4 is polarized in one direction by the above-mentioned polarization processing, the electrode 6 is preferably located at the upper end of the wall surface of the partition wall 4, preferably, in order to drive the partition wall 4 efficiently. It is desirable to form up to half the height from the tip. The electrodes 6 formed on both surfaces of the partition 4
Is also formed on the end face of the partition wall 4 in the longitudinal direction, and a central portion of the end face of the partition wall 4 can be removed by the above-described laser irradiation or the like to obtain an extraction electrode.

When the partition wall 4 is formed by joining two piezoelectric ceramics whose polarization directions are opposite to each other in the height direction of the partition wall 4, the piezoelectric members polarized in two directions opposite to each other in the height direction are used. A body ceramic can be formed in the partition wall 4. In this case, the electrode 6 is formed over the partition wall height of the partition wall 4.

Further, after applying an adhesive such as an epoxy resin to the leading end surface of the partition wall 4 by a known printing method such as screen printing or gravure printing, the other substrate 2 is bonded.
Grinding is performed if desired. According to the present invention, workability can be improved as described above.

The nozzle hole 10 having a diameter of 10 to 30 μm is formed on one end surface of the partition wall 4 in the longitudinal direction by laser processing or the like.
Are bonded together. Nozzle plate 11
The plastic, metal, ceramics and the like can be used, for example, polyethylene terephthalate and polyimide, polyether imide, polyether ketone, polyether sulfone, polycarbonate, plastics such as cellulose acetate, or stainless steel or chromium molybdenum steel, Metals such as aluminum, and ceramics such as alumina, zirconia, lead zirconate titanate, cordierite and the like can be cited. In particular, a plastic plate made of polyethylene terephthalate or polyimide can be suitably used from the viewpoint of ease of processing.

Further, a spacer (not shown) made of an insulator having a larger gap than the nozzle hole 10 can be interposed between the nozzle plate 11 in which the nozzle hole 10 is formed and the ink chamber 5. The rigidity of the thin nozzle plate 11 of several tens μm can be increased, and the rigidity of the entire inkjet head can be increased.

An ink inlet for introducing ink from an ink tank is formed in a part of the substrate 2.

The extraction electrode formed on the end face of the partition wall 4 forms a wiring pattern formed outside, and / or a chip element formed outside the ink chamber by a wire, a lead, TAB or the like (see FIG. (Not shown)) to form an ink jet head.

The present invention is not limited to the above-described shear mode type ink jet head.
An inkjet head such as a Kaiser type or a thermal jet type may be used. In this case, if the partition walls are formed of cordierite ceramics, the change in volume of the ink chamber can be further reduced. Further, the substrate size is not limited, and the present invention can be used for a serial type or line type ink jet head.

[0051]

(Example 1) First, an organic binder and a solvent were added to lead zirconate titanate (PZT) powder having an average particle diameter of 2 μm to prepare a slurry, and then a sheet was formed by a doctor blade method. Molded, cut and 1200
Bake at ℃, outer dimensions 0.4mm thick, 40m long
m, 20 mm wide plate-shaped lead zirconate titanate (PZ
T) A sintered body was prepared. By applying a conductor layer to both surfaces of the plate-shaped sintered body and applying a voltage, a piezoelectric ceramic polarized in the thickness direction was obtained.

On the other hand, MgO, Al having an average particle size of 2 μm
The ₂ O _3, SiO ₂ were blended so that the _{2MgO · 2Al 2 O 3 · SiO} 2, relative to this, Y ₂ O _3, by adding an organic binder, was molded by a uniaxial press molding, debinding This was treated and further baked at 1350 ° C. to produce a plate-like body made of cordierite having a thickness of 1 mm, a length of 40 mm and a width of 20 mm.

Then, the above-mentioned plate-like body and the piezoelectric ceramic were bonded with an epoxy adhesive. The sample No. As for No. 2, piezoelectric ceramics having the same thickness in two directions with opposite polarization directions were used.

Next, the surface of the piezoelectric ceramic was polished to a predetermined thickness by lapping, and a resist solution was applied to the entire surface by a spin coater and cured.

Then, a slicer equipped with a 75 μm-thick diamond blade was used to remove 1 mm from the surface on the PZT substrate side.
Slicing was performed in the substrate width direction at a pitch of 41.1 μm, and 259 partition walls having a width of 75 μm, a height of 400 μm, and a length of 12 mm were produced. Table 1 shows the ratio of the samples which could be processed favorably without chipping to 100 samples as the processing rates. The partition walls were configured as shown in Table 1 by changing the thickness of the cordierite ceramics and the thickness of the piezoelectric ceramics.

In the table, the half of the partition wall on the substrate side is defined as region 1, the tip half of the partition wall is defined as region 2, and PZT whose polarization direction is polarized toward the partition tip direction is PZT (+). Those polarized in the plane direction were described as PZT (-).

Next, after an electrode was formed at a predetermined height on the partition wall surface by electroless nickel plating, the resist mask was removed. When the height of each electrode was measured by SEM observation, the average electrode height was 160 mm and the variation was 20 μm.

Then, an epoxy resin was applied to the tip end face and side end face of the partition, and a 700 μm thick substrate made of the cordierite ceramic was bonded to the tip end of the partition. In addition, a 50 μm-thick polyimide nozzle plate was attached to the side end surface of the partition wall to produce an ink jet head.

The ink chamber of the obtained ink jet head was filled with ink, and a voltage for obtaining a predetermined amount of displacement of the partition was applied to the electrodes at 100 kHz for 30 minutes to confirm the presence or absence of a temperature rise. The results are shown in Table 1.

(Comparative Example) The cordierite ceramics of the examples were formed from glass and alumina having the thermal expansion coefficient and Young's modulus shown in Table 1, and the lead zirconate titanate (PZT) sintered body of the example 1. Except for performing, the same procedure was performed as in the examples (samples Nos. 4 to 6), and the same evaluation was performed. The results are shown in Table 1.

[0061]

[Table 1]

From Table 1, it can be seen that Sample No. using a substrate made of cordierite ceramics was used. In Nos. 1 to 3, since the thermal expansion coefficient of the substrate is low, it is estimated that the ink ejection amount is constant regardless of the temperature change, and the dielectric constant of the substrate is low and the power consumption in the substrate can be reduced. It can be inferred that crosstalk between them can be prevented. In addition, by forming a portion of the partition wall to be processed together with the cordierite ceramic substrate and joining the substrate with the cordierite ceramic, high processing with a yield of 98% or more could be performed.

On the other hand, in the case of Sample No. in which the substrate was formed of glass or alumina, In 4 and 5, workability decreases,
Further, in the sample No. in which the non-driving portions of the substrate and the partition were formed of a lead zirconate titanate (PZT) sintered body. In 6,
By applying a voltage to the electrodes, the temperature of the ink in the ink chamber rose.

[0064]

As described in detail above, in the ink jet head of the present invention, by forming at least one of the substrates from cordierite ceramics having a low coefficient of thermal expansion, the amount of ink ejected with respect to a temperature change is reduced. Can be suppressed.

Further, by forming a part of the partition wall from a piezoelectric ceramic and making the other non-driving part of the partition wall a cordierite ceramics, it is possible to reduce the variation in the adhered area in the non-driving part of the electrode. In addition, the amount of displacement of the piezoelectric ceramic can be controlled to be constant, and since the dielectric constant is low, it is possible to reduce power consumption and heat generation of a non-drive portion due to voltage application. Furthermore, crosstalk between adjacent ink chambers can be eliminated.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing an example of an inkjet head of the present invention.

FIG. 2 is a schematic sectional view of the ink jet head of FIG.

FIG. 3 is a schematic perspective view of a conventional inkjet head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ink jet head 2, 3 Substrate 4 Partition wall 5 Ink chamber 6 Electrode 7 Driving part 8 Non-driving part 10 Nozzle 11 Nozzle plate 13 Ink introduction port

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Mizuho Ota 1-4-4 Yamashita-cho, Kokubu-shi, Kagoshima Prefecture Kyocera Research Institute (72) Inventor Kazumi Kubo 1-4-4 Yamashita-cho, Kokubu-shi, Kagoshima Kyocera Corporation F-term in Shikisha Research Laboratory (reference) 2C057 AF23 AG12 AG37 AG39 AG44 BA03 BA14

Claims (7)

[Claims] An ink jet head comprising: a pair of opposed substrates; and an ink chamber surrounded by a plurality of partitions arranged in parallel between the substrates, wherein at least one of the pair of substrates is provided. An ink jet head, wherein one substrate is made of cordierite ceramics. 2. The ink jet head according to claim 1, wherein at least a part of said partition is made of cordierite ceramics. 3. An ink jet head according to claim 1, wherein at least a part of said partition wall is made of piezoelectric ceramics. 4. An ink jet head according to claim 3, wherein said piezoelectric ceramic is polarized in one direction substantially parallel to a direction perpendicular to said substrate. 5. The ink jet head according to claim 3, wherein one end and the other end of the piezoelectric ceramic are polarized substantially in parallel to a direction perpendicular to the substrate and in two opposite directions. 6. The cordierite-based ceramic of claim 10
The inkjet head according to any one of claims 1 to 5, wherein a thermal expansion coefficient at 1 to 40 ° C is 1 ppm / ° C or less, and a Young's modulus is 90 to 150 MPa. 7. The ink jet head according to claim 1, wherein the cordierite ceramic has a porosity of 4% or less.