JP7389961B2 - Liquid ejection head, liquid ejection unit, and device that ejects liquid - Google Patents

Description

The present invention relates to a liquid ejection head, a liquid ejection unit, and a device for ejecting liquid.

Conventionally, a plurality of nozzles for discharging liquid, a plurality of pressure chambers communicating with each of the plurality of nozzles, a plurality of diaphragms forming part of a wall of each of the plurality of pressure chambers, and a plurality of diaphragms forming part of the wall of each of the plurality of pressure chambers, 2. Description of the Related Art A liquid ejection head is known that includes a plurality of electromechanical transducers each formed on a diaphragm.

For example, in Patent Document 1, ink droplets are ejected from each nozzle by varying the thickness of a vibrating membrane (diaphragm) between the nozzles in a nozzle row in which a plurality of nozzles are arranged side by side in a predetermined arrangement direction. Inkjet heads (liquid ejection heads) with different amounts (ejected liquid amounts) are described.

However, in conventional liquid ejection heads equipped with nozzles that eject different amounts of liquid, when a small droplet ejection nozzle becomes non-ejecting due to nozzle clogging, etc., the small droplet ejecting nozzle (non-ejecting nozzle) It has been difficult to eject large droplets of liquid from closely arranged large droplet ejection nozzles to complement dots to be formed by non-ejecting nozzles.

In order to solve the above problems, the present invention includes a plurality of nozzles that discharge liquid, a plurality of pressure chambers communicating with each of the plurality of nozzles, and a part of the wall of each of the plurality of pressure chambers. A liquid ejection head comprising a plurality of diaphragms and a plurality of electromechanical transducers respectively formed on the diaphragms, in which two or more nozzles are arranged side by side along a predetermined arrangement direction. The plurality of nozzle groups are composed of nozzles that eject the same liquid, and each of the mutually adjacent nozzle groups in the plurality of nozzle groups and the size of the corresponding pressure chamber and the thickness of the corresponding diaphragm so that the nozzle opening area is the same and the amount of liquid discharged is different between nozzles that are located close to each other. are characterized by being different .

According to the present invention, when a small droplet discharging nozzle becomes in a non-discharging state due to nozzle clogging or the like, large droplets are ejected from a large droplet discharging nozzle located close to the small droplet discharging nozzle (non-discharging nozzle). It becomes easy to eject liquid to complement dots to be formed by non-ejecting nozzles.

FIG. 2 is an explanatory diagram showing an example of a layer structure of a piezoelectric element of a liquid ejection head in an embodiment. FIG. 7 is an explanatory diagram showing another example of a structure in which each of the lower electrode layer and the upper electrode layer has a multilayer structure. FIG. 1 is an explanatory diagram showing main parts of a liquid ejection head according to an embodiment. A graph showing an example of the results of θ-2θ measurement using X-ray diffraction method for PZT. (a) is a cross-sectional explanatory view schematically showing a state in which an insulating protective film and lead-out wiring are produced for the piezoelectric element of the embodiment. (b) is an explanatory plan view of the same figure (a). FIG. 3 is an explanatory cross-sectional view along a direction perpendicular to the nozzle arrangement direction of a liquid ejection head using the same piezoelectric element. FIG. 3 is an enlarged cross-sectional explanatory view of the main parts of the liquid ejection head. FIG. 3 is an explanatory cross-sectional view of the main parts of the liquid ejection head along the nozzle arrangement direction. (a) is an explanatory plan view schematically showing a substrate of the liquid ejection head. (b) is a cross-sectional explanatory diagram schematically showing a cross section taken along the line A-A' in FIG. (a) is an explanatory diagram showing the waveform of a drive signal for ejecting one small droplet of ink in an example of the conventional art. (b) is an explanatory diagram showing the waveform of a drive signal for ejecting one large droplet of ink in a conventional example. (a) is an explanatory diagram showing the waveform of a drive signal for ejecting one small droplet of ink in another conventional example. (b) is an explanatory diagram showing the waveform of a drive signal for ejecting one large droplet of ink in another conventional example. (a) is an explanatory diagram showing the waveform of a drive signal for ejecting one small droplet of ink in the embodiment. (b) is an explanatory diagram showing the waveform of a drive signal for ejecting one large droplet of ink in the embodiment. FIG. 7 is an explanatory plan view schematically showing another example of the substrate of the liquid ejection head in the embodiment. 14 is an explanatory plan view showing four nozzle rows in the example of FIG. 13. FIG. FIG. 7 is an explanatory plan view schematically showing still another example of the substrate of the liquid ejection head in the embodiment. FIG. 2 is a cross-sectional explanatory diagram schematically showing a liquid ejection head having a nozzle row in which a plurality of nozzles are arranged. FIG. 1 is a perspective explanatory diagram showing an inkjet recording apparatus according to an embodiment. FIG. 3 is an explanatory side view of a mechanism section of the inkjet recording apparatus. FIG. 6 is an explanatory plan view of main parts of an inkjet recording apparatus of this modification. FIG. 6 is an explanatory side view of a main part of an inkjet recording apparatus of this modification. FIG. 2 is a plan view of the main parts of the liquid ejection unit. FIG. 3 is a front explanatory view of the liquid ejection unit.

An embodiment of a liquid ejection head according to the present invention will be described below.
FIG. 1 is an explanatory diagram showing an example of the layer structure of a piezoelectric element 100 as an electromechanical transducer of a liquid ejection head in this embodiment.
As shown in FIG. 1, the piezoelectric element 100 in this embodiment has a lower electrode layer 103 forming a lower electrode, a piezoelectric film 104, and an upper electrode on a substrate 101 and a diaphragm layer 102 forming a diaphragm. A constituting upper electrode layer 105 is formed.

The lower electrode layer 103 and the upper electrode layer 105 of the piezoelectric element 100 are required to have sufficient electrical resistance. On the other hand, in order for the piezoelectric element 100 to perform well as an actuator for displacing the diaphragm layer 102, it is required that the displacement and the like decrease less when continuously driven. If it is difficult to obtain the lower electrode layer 103 and the upper electrode layer 105 that satisfy both of these requirements, the lower electrode layer 103 and the upper electrode layer 105 may have a multilayer structure.

FIG. 2 is an explanatory diagram showing another example of the structure in which the lower electrode layer 103 and the upper electrode layer 105 each have a multilayer structure.
The piezoelectric element 100 of this configuration example has a first lower electrode layer 103A and a first upper electrode layer 105A made of metal layers that provide sufficient electrical resistance, and a displacement etc. when continuously driven. It is provided with a second lower electrode layer 103B and a second upper electrode layer 105B which are made of a conductive oxide electrode layer for suppressing a decrease in .

As the substrate 101 on which the piezoelectric element 100 is formed, it is preferable to use a silicon single crystal substrate, and it is preferable to have a thickness of 100 [μm] or more and 600 [μm] or less. Among the three types of plane orientations, (100), (110), and (111), substrates with (100) and (111) plane orientations, which are generally widely used in the semiconductor industry, are preferable. As the substrate 101 of this embodiment, a silicon single crystal substrate having a (100) plane orientation is used.

FIG. 3 is an explanatory diagram showing the main parts of the liquid ejection head 110 of this embodiment.
The liquid ejection head 110 of this embodiment has a pressure chamber 111 formed on the back surface (the surface opposite to the piezoelectric element 100) of the substrate 101 on which the piezoelectric element 100 described above is formed, and a nozzle 112a. A nozzle plate 112 is joined and configured. The liquid ejection head 110 applies pressure to the liquid filled in the pressure chamber 111 by driving the piezoelectric element 100 and displacing the diaphragm layer 102, and ejects the liquid from the nozzle 112a.

When producing the pressure chamber 111, the substrate 101 made of a silicon single crystal substrate is processed using etching, and anisotropic etching is generally used as the etching method in this case. Anisotropic etching utilizes the property that the etching rate differs depending on the plane orientation of the crystal structure. For example, in anisotropic etching by immersion in an alkaline solution such as KOH, the etching rate for the (111) plane is about 1/400 of that for the (100) plane. Therefore, with the plane orientation (100), a structure having an inclination of about 54° can be produced, whereas with the plane orientation (110), a deep groove can be cut. Therefore, since it is possible to increase the arrangement density while maintaining more rigidity, it is also possible to use a silicon single crystal substrate with a (110) plane orientation as the substrate 101 of this embodiment. However, in this case, the mask material SiO ₂ may also be etched, so this point must also be kept in mind when using the method.

The diaphragm layer 102 is deformed and displaced in response to the force generated by the piezoelectric film 104 of the piezoelectric element 100, causing the liquid in the pressure chamber 111 to be discharged from the nozzle 112a. Therefore, it is preferable that the diaphragm layer 102 has a predetermined strength that can withstand the deformation and displacement. The diaphragm layer 102 can be manufactured using, for example, Si, SiO ₂ , or Si ₃ N ₄ as a material by a CVD method.

Further, as the material for the diaphragm layer 102, it is preferable to select a material having a coefficient of linear expansion close to that of the lower electrode layer 103 and the piezoelectric film 104. In particular, since PZT is used for the piezoelectric film 104 of this embodiment, its linear expansion coefficient is close to 8×10 ⁻⁶ [1/K], specifically, 5× A material having a linear expansion coefficient of 10 ⁻⁶ to 10×10 ⁻⁶ is preferable, and a material having a linear expansion coefficient of 7×10 ⁻⁶ to 9×10 ⁻⁶ is more preferable.

Specific materials for the diaphragm layer 102 include aluminum oxide, zirconium oxide, iridium oxide, ruthenium oxide, tantalum oxide, hafnium oxide, osmium oxide, rhenium oxide, rhodium oxide, palladium oxide, and compounds thereof. can. The diaphragm layer 102 can be made of these materials using a spin coater using a sputtering method or a Sol-gel method.

The thickness of the diaphragm layer 102 is preferably within the range of 0.1 [μm] or more and 10 [μm] or less, and more preferably within the range of 0.5 [μm] or more and 3 [μm] or less. If it is smaller than this range, it will be difficult to process the pressure chamber 111, and if it is larger than this range, the diaphragm layer 102 will be difficult to deform and displace, making the discharge of liquid unstable.

Platinum (Pt), which has high heat resistance and low reactivity among metal materials, is generally used as the material for the first lower electrode layer 103A and the first upper electrode layer 105A in the configuration example shown in FIG. . However, when using platinum (Pt), it may not have sufficient barrier properties against lead, so even if platinum group elements such as iridium or platinum-rhodium or alloy films of these are used. good. Furthermore, when platinum is used as the first lower electrode layer 103A _, it has poor adhesion to the underlying diaphragm layer 102 (particularly the SiO ₂ diaphragm layer 102). A layer of ₂ O ₅ , Ta ₃ N ₅ or the like may be interposed. As a method for producing this layer, vacuum film formation such as sputtering or vacuum evaporation is generally used. The thickness of this layer is preferably 0.05 [μm] or more and 1 [μm] or less, more preferably 0.1 [μm] or more and 0.5 [μm] or less.

As a material for the second lower electrode layer 103B and the second upper electrode layer 105B in the configuration example shown in FIG. 2, for example, SrRuO ₃ or LaNiO ₃ is used. Since the second lower electrode layer 103B can also affect the orientation control of the PZT piezoelectric film 104 produced thereon, the material selected usually differs depending on the direction in which the orientation is desired to be prioritized.

In this embodiment, it is desired to preferentially align PZT (100) regardless of the material or structure of the lower electrode layer 103 or the second lower electrode layer 103B, which may also affect the orientation control of the PZT piezoelectric film 104. , a seed layer having an amorphous structure may be formed on the lower electrode layer 103 or the second lower electrode layer 103B. The material for this seed layer is preferably PbTiO ₃ or PZT.

Further, when using a PbTiO ₃ seed layer, the composition ratio Pb/Ti of Pb and Ti is preferably 0.7 or more and 1.5 or less, and more preferably 1.0 or more and 1.2 or less. . Outside this range, the (100) orientation rate of PZT constituting the piezoelectric film 104 decreases.

Further, when a PZT seed layer is used, its composition ratio Pb/(Ti+Zr) is preferably 0.7 or more and 1.5 or less, and more preferably 1.0 or more and 1.2 or less. Outside this range, the (100) orientation rate of PZT constituting the piezoelectric film 104 decreases. Further, the composition ratio of Ti/(Zr+Ti) is preferably 0.3 or more, more preferably 0.4 or more. Outside this range, the (100) orientation rate of PZT constituting the piezoelectric film 104 decreases.

The thickness of the seed layer in this embodiment is preferably 3 [nm] or more and 15 [nm] or less, and more preferably 6 [nm] or more and 12 [nm] or less. Outside this range, the (100) orientation rate of PZT constituting the piezoelectric film 104 decreases.

In this embodiment, it is preferable that PZT constituting the piezoelectric film 104 be preferentially oriented in (100), and the crystal orientation is expressed by the following formula.
ρ(hkl) = I(hkl)/ΣI(hkl)
Note that "ρ(hkl)" is the orientation degree of the (hkl) plane orientation, "I(hkl)" is the peak intensity of any orientation, and "ΣI(hkl)" is the sum of each peak intensity. It is.

The degree of orientation of the (100) orientation is calculated based on the ratio of the peak intensity of each orientation when the sum of the peak intensities obtained by θ-2θ measurement by X-ray diffraction is set to 1. In the piezoelectric film 104 of this embodiment, the degree of orientation of the (100) orientation is preferably 0.99 or more, and more preferably 0.995 or more. When it is less than this, sufficient piezoelectric strain cannot be obtained and a sufficient amount of displacement cannot be secured, so variations in the crystal orientation of the piezoelectric film 104 become large, causing ejection variations in the liquid ejection head 110.

PZT is used for the piezoelectric film 104 of this embodiment. PZT is a solid solution of lead zirconate (PbZrO ₃ ) and lead titanate (PbTiO ₃ ), and its properties change depending on the ratio. Generally, the composition exhibiting excellent piezoelectric properties has a ratio of PbZrO ₃ and PbTiO ₃ of 53:47, which is represented by the chemical formula Pb(Zr _0.53 , Ti _0.47 )O ₃ , and PZT( 53/47).

Examples of complex oxides other than PZT used as the piezoelectric film 104 include barium titanate. In this case, barium alkoxide and titanium alkoxide compounds are used as starting materials and dissolved in a common solvent to form a barium titanate precursor. It is also possible to create solutions.

The composition ratio of Pb/(Zr+Ti) of PZT constituting the piezoelectric film 104 is preferably 0.9 or more and 1.3 or less, and more preferably 1.0 or more and 1.2 or less. If it falls below this range, Pb will be insufficient and a sufficient amount of displacement will not be ensured. Moreover, if it exceeds this range, dielectric breakdown is likely to occur due to excessive Pb.

The composition ratio of Zr and Ti in PZT constituting the piezoelectric film 104 is preferably 0.40 or more and 0.55 or less, and 0.45 or more and 0.53 when expressed as Ti/(Zr+Ti). It is more preferable that it is as follows. By adjusting these composition ratios, the peak position and peak asymmetry of the PZT (200) plane differ in the θ-2θ measurement as shown in FIG. 4. When the composition ratio of Ti/(Zr+Ti) is out of the above range, the amount of displacement accompanied by rotational strain decreases when it is smaller than that range, and the amount of displacement due to piezoelectric strain decreases when it exceeds that range. , it becomes impossible to secure a sufficient amount of displacement.

When producing PZT by the Sol-gel method, a PZT precursor solution is produced by using lead acetate, zirconium alkoxide, and titanium alkoxide compounds as starting materials and dissolving them in methoxyethanol as a common solvent to obtain a homogeneous solution. Since metal alkoxide compounds are easily hydrolyzed by atmospheric moisture, an appropriate amount of a stabilizer such as acetylacetone, acetic acid, diethanolamine, etc. may be added to the PZT precursor solution.

The thickness of the piezoelectric film 104 is preferably 0.5 [μm] or more and 5 [μm] or less, more preferably 1 [μm] or more and 2 [μm] or less. If it is smaller than this range, sufficient displacement cannot be generated, and if it is larger than this range, the number of layers to be laminated increases, which increases the number of steps and increases the process time.

FIGS. 5A and 5B are explanatory diagrams showing a state in which insulating protective films 113 and 115 and lead-out wirings 114 and 116 are formed on the piezoelectric element 100.
The first insulating protective film 113 has a contact hole 113a, and the upper electrode layer 105 and the individual lead-out wiring 114 are electrically connected to each other. Further, the first insulating protective film 113 has a contact hole 113b, and the lower electrode layer 103 and the common lead wire 116 are electrically connected.

A second insulating protective film 115 is formed on these lead wires 114 and 116. A part of the second insulating protective film 115 is provided with an opening through which the lead wirings 114 and 116 are exposed, and these openings are configured as electrode pads 114a and 116a.

As the first insulating protective film 113, it is necessary to prevent damage to the piezoelectric element 100 due to film formation and etching processes, and to select a material that is difficult for atmospheric moisture to pass through, so a dense inorganic material should be used. is preferred. This is because organic materials require a thick film in order to obtain sufficient protection performance. If the first insulating protection film 113 is made thick, it will inhibit the vibrational displacement of the diaphragm layer 102, which will cause a decrease in the ejection performance of the liquid ejection head 110.

In order to obtain the first insulating protective film 113 that is thin and has high protective performance, it is preferable to use an oxide, nitride, or carbide film, but the adhesion to the underlying electrode material, piezoelectric material, and diaphragm material It is necessary to select materials with high properties. Furthermore, it is necessary to select a film forming method that does not damage the piezoelectric element 100. That is, a plasma CVD method in which a reactive gas is turned into plasma and deposited on a substrate, and a sputtering method in which a film is formed by colliding plasma with a target material and causing it to fly are not preferred. Examples of preferable film forming methods include vapor deposition, ALD, etc., and ALD is preferable because it allows a wide selection of usable materials.

From the above viewpoint, preferable materials for the first insulating protective film 113 include oxide films used in ceramic materials such as Al ₂ O ₃ , ZrO ₂ , Y ₂ O ₃ , Ta ₂ O ₃ , and TiO ₂ . Particularly, when the first insulating protective film 113 is manufactured by ALD using these materials, a thin film with extremely high film density can be manufactured, and damage during the process can be suppressed.

The thickness of the first insulating protective film 113 needs to be thick enough to ensure the protection performance of the piezoelectric element 100, and at the same time, it must be as thin as possible so as not to inhibit the displacement of the diaphragm layer 102. There is a need to. The preferred thickness of the first insulating protective film 113 is 20 [nm] or more and 100 [nm] or less. If it is thicker than 100 [nm], the displacement of the diaphragm layer 102 decreases, which reduces the ejection efficiency of the liquid ejection head 110. On the other hand, if it is thinner than 20 [nm], the function as a protective layer of the piezoelectric element 100 will be insufficient, and the performance of the piezoelectric element 100 will deteriorate.

It is also possible to form the first insulating protective film 113 into two layers. In this case, it is preferable that the second insulating protective film be thicker and have an opening near the upper electrode layer 105 so as not to inhibit the vibrational displacement of the diaphragm layer 102. At this time, any oxide, nitride, carbide, or composite compound thereof can be used as the second insulating protective film, but it is preferable to use _SiO2, which is commonly used in semiconductor devices. be.

Any method can be used to form the first insulating protective film 113, such as a CVD method or a sputtering method. It is preferable to use a CVD method that can form a film isotropically.

The first insulating protective film 113 needs to have a sufficient thickness to prevent dielectric breakdown due to the voltage applied to the lower electrode layer 103 and the individual lead wires 114. That is, it is necessary to set the electric field strength applied to the first insulating protective film 113 within a range that does not cause dielectric breakdown. Considering the surface properties and pinholes of the base of the first insulating protective film 113, the thickness of the first insulating protective film 113 needs to be 200 [nm] or more, and more preferably 500 [nm] or more. .

The lead wires 114 and 116 are preferably made of a metal electrode material made of any one of Ag alloy, Cu, Al, Au, Pt, and Ir. As a manufacturing method, a sputtering method or a spin coating method is used for manufacturing, and then a desired wiring pattern is obtained by photolithography etching or the like. The thickness of the lead wirings 114 and 116 is preferably 0.1 [μm] or more and 20 [μm] or less, and more preferably 0.2 [μm] or more and 10 [μm] or less. If it is smaller than this range, the electrical resistance value will increase, making it impossible to flow a sufficient current through the electrodes, resulting in unstable ejection. On the other hand, if it is larger than this range, the process time will become longer.

Further, it is preferable that the contact resistance in the contact holes 113a and 113b of 10 [μm]×10 [μm] is 10 [Ω] or less in the common lead-out wiring 116 and 1 [Ω] or less in the individual lead-out wiring 114, More preferably, the resistance is 5 [Ω] or less for the common lead-out wiring 116 and 0.5 [Ω] or less for the individual lead-out wiring 114. If this range is exceeded, it will not be possible to supply sufficient current and problems will occur during ejection.

The second insulating protective film 115 functions as a passivation layer that functions as a protective layer for the individual lead-out wiring 114 and the common lead-out wiring 116. As shown in FIG. 5, the second insulating protective film 115 covers the individual lead wires 114 and the common lead wires 116, except for the individual electrode pads 114a and the common electrode pads 116a. Therefore, as the material for these lead wires 114 and 116, inexpensive Al or an alloy material containing Al as a main component can be used. As a result, a low-cost and highly reliable liquid ejection head 110 can be obtained.

Any inorganic or organic material can be used as the material for the second insulating protective film 115, but a material with low moisture permeability is preferable. Examples of inorganic materials include oxides, nitrides, carbides, etc., and examples of organic materials include polyimide, acrylic resin, urethane resin, etc. However, in the case of an organic material, it is necessary to increase the film thickness, so it is not suitable for patterning the second insulating protective film 115. Therefore, the material for the second insulating protective film 115 is preferably an inorganic material that is a thin film and can exhibit a wiring protection function. In particular, when the lead wires 114 and 116 are made of Al, it is preferable to use Si ₃ N ₄ as the material for the second insulating protective film 115 because it is a proven technology in semiconductor devices.

The thickness of the second insulating protective film 115 is preferably 200 [nm] or more, more preferably 500 [nm] or more. If the film thickness is small, a sufficient passivation function cannot be achieved, and wire breakage occurs due to corrosion of the wiring material, reducing the reliability of the liquid ejection head 110.

Further, it is preferable that openings be formed in the second insulating protection film 115 above the piezoelectric element 100 and above the diaphragm layer 102 surrounding the piezoelectric element 100. This is to prevent the displacement of the diaphragm layer 102 from being inhibited, similar to the above-mentioned thinning of the portion of the first insulating protection film 113 corresponding to the pressure chamber 111.

FIG. 6 is an explanatory cross-sectional view of the liquid ejection head 110 along a direction perpendicular to the nozzle arrangement direction.
FIG. 7 is an enlarged cross-sectional view of the main part of the liquid ejection head 110.
FIG. 8 is an explanatory cross-sectional view of the main part of the liquid ejection head 110 along the nozzle arrangement direction.

The liquid ejection head 110 includes a nozzle plate 112, a substrate 101 serving as a channel plate, a diaphragm layer 102, a piezoelectric element 100, a holding substrate 50, and a second wiring board 121 that is a wiring member such as an FPC. It includes a common liquid chamber member 70 and a cover member 45. Here, a portion constituted by the substrate 101, the diaphragm layer 102, and the piezoelectric element 100 becomes the actuator substrate 20.

A plurality of nozzles 112a that eject liquid are formed on the nozzle plate 112. Here, the configuration is such that four nozzle rows are arranged in which nozzles 112a are arranged. The substrate 101 constituting the flow path plate, together with the nozzle plate 112 and the diaphragm layer 102, includes a pressure chamber 111 serving as an individual liquid chamber through which the nozzle 112a communicates, a fluid resistance section 7 that communicates with the pressure chamber 1116, and a liquid chamber through which the fluid resistance section 7 communicates. An introduction section 8 is formed. This liquid introducing portion 8 communicates with a common liquid chamber 10 formed by a common liquid chamber member 70 via an opening 9 in the diaphragm layer 102 and an opening 51 serving as a flow path in the holding substrate 50.

The diaphragm layer 102 forms a vibration region 30 as a deformable diaphragm that forms part of the wall surface of the pressure chamber 111 . A piezoelectric element 100 is provided integrally with the vibration region 30 on the surface of the vibration plate layer 102 opposite to the pressure chamber 111, and the vibration region 30 and the piezoelectric element 100 constitute a piezoelectric actuator. Ru.

A lower electrode layer 103 serving as a common electrode for the plurality of piezoelectric elements 100 is connected to a common lead wire 116. Note that the lower electrode layer 103 is one electrode layer formed across all piezoelectric elements 100 in the nozzle arrangement direction.

Further, the upper electrode layer 105 serving as an individual electrode of the piezoelectric element 100 is connected to a drive IC (hereinafter referred to as "driver IC") 500 that is a drive circuit section via an individual lead-out wiring 114. The individual lead-out wiring 114 and the like are covered with a second insulating protective film 115. The driver IC 500 is mounted on the actuator substrate 20 by a method such as flip-chip bonding so as to cover the area between the rows of piezoelectric elements. A wiring pattern provided on the second wiring board 121 is electrically connected to the driver IC 500, and the other end side of the second wiring board 121 is connected to a printed circuit board via the first wiring board, and further connected to the device main body side. connected to the control unit.

A holding substrate 50 covering the piezoelectric element 100 on the actuator substrate 20 is bonded to the diaphragm layer 102 side of the actuator substrate 20 with an adhesive. The holding substrate 50 is provided with a common liquid chamber 10, an opening 51 that becomes part of a flow path leading to the pressure chamber 111, a recess 52 that accommodates the piezoelectric element 100, and an opening 53 that accommodates the driver IC 500. It is being The opening 51 is a slit-shaped through hole extending in the nozzle arrangement direction, and here constitutes a part of the common liquid chamber 10.

This holding substrate 50 is interposed between the actuator substrate 20 and the common liquid chamber member 70 and forms a part of the wall surface of the common liquid chamber 10. The common liquid chamber member 70 forms a common liquid chamber 10 that supplies liquid to each pressure chamber 111. Note that the common liquid chamber 10 is provided corresponding to each of the four nozzle rows. Further, a liquid of a desired color is supplied to the common liquid chamber 10 through a supply port communicating with the liquid supply member. A damper member 150 is joined to the common liquid chamber member 70. The damper member 150 includes a deformable damper 151 that forms a part of the wall surface of the common liquid chamber 10 and a damper plate 152 that reinforces the damper 151.

The common liquid chamber member 70 is bonded to the outer periphery of the nozzle plate 112 and the holding substrate 50 with an adhesive, houses the actuator substrate 20 and the holding substrate 50, and forms a head frame. A cover member is provided to cover the peripheral edge of the nozzle plate 112 and a part of the outer peripheral surface of the common liquid chamber member 70.

In this liquid ejection head 110, by applying a driving voltage between the upper electrode layer 105 and the lower electrode layer 103 of the piezoelectric element 100 from the driver IC 500, the piezoelectric element 100 expands in the electrode stacking direction, that is, in the electric field direction. It contracts in a direction parallel to the vibration region 30. As a result, tensile stress is generated on the lower electrode layer 103 side of the vibration region 30, the vibration region 30 is bent toward the pressure chamber 111, and the liquid inside the pressure chamber 111 is pressurized, causing the liquid to be discharged from the nozzle 112a. Ru.

Next, the characteristic parts of the liquid ejection head 110 in this embodiment will be explained.
FIG. 9A is an explanatory plan view schematically showing the substrate 101, which is a channel plate of the liquid ejection head 110 in this embodiment.
FIG. 9(b) is an explanatory cross-sectional view schematically showing a cross section taken along the line AA′ in FIG. 9(a).
Two nozzle rows N1 and N2 are illustrated in FIGS. 9(a) and 9(b). Nozzles 112a1 and 112a2 forming the same nozzle row communicate with pressure chambers 111-1 and 111-2 that are supplied with ink from the same common liquid chamber 10. In the nozzle rows N1 and N2 of this embodiment, as shown in FIG. They are arranged in a staggered manner along the sub-scanning direction (horizontal direction in FIG. 9(a)). However, the arrangement of the pressure chambers 111-1 and 111-2 is not limited to this, and may be arranged in a straight line, for example.

In the liquid ejection head 110 of this embodiment, the amount of ejected liquid is smaller between the nozzles 112a1 and 112a2 that belong to the first nozzle row N1 and the second nozzle row N2 that are adjacent to each other and are arranged close to each other. are configured differently. Specifically, the nozzles 112a1 constituting the first nozzle row N1 are large droplet ejection nozzles that eject large droplets of liquid (ink), and the nozzles 112a2 constituting the second nozzle row N2 are nozzles for ejecting large droplets of liquid (ink). This is a small droplet ejection nozzle that ejects small droplets of liquid (ink) in a smaller amount than that of a small droplet.

Here, the droplet ejection nozzle 112a2 may become in a non-ejecting state due to nozzle clogging or the like. In this case, by performing complementary control in the control unit, a large droplet is ejected from any nozzle located close to the small droplet ejection nozzle 112a2 that is in the non-ejecting state, and the large droplet is formed by the non-ejecting nozzle. You can complete the dots that should be done.

A method of implementing such complementary control is to eject large droplets of ink from another small droplet ejection nozzle 112a2 adjacent to the small droplet ejection nozzle 112a2 in the same nozzle row that is in a non-ejecting state. can be mentioned. This method controls the amount of ink to be ejected by differentiating the drive signal applied to the piezoelectric element 100 in a conventional general liquid ejection head in which the configuration is the same between nozzles. This is to switch between.

However, in this method, the drive signal for ejecting one droplet of ink consists of an ejection waveform for one pulse and a damping waveform for one pulse (inside the nozzle), as shown in FIG. 10(a), for example. (a waveform for suppressing vibrations of ink). On the other hand, the drive signal for ejecting one large droplet of ink is composed of a combination of the ejection waveform for two pulses and the above-mentioned basic ejection waveform, as shown in FIG. 10(b), for example. Therefore, the cycle of the drive signal required to eject a large droplet of ink (the drive signal wavelength λ1' shown in FIG. 10(b)) is different from the cycle of the drive signal required to eject a small droplet of ink (the drive signal wavelength λ1' shown in FIG. 10(a)). The drive signal wavelength λ2) shown in FIG. Therefore, it is necessary to reduce the ejection frequency when performing supplementary control using large droplets of ink, resulting in a problem that the productivity of the liquid ejection head decreases.

Furthermore, conventionally, by varying the thickness of the diaphragm layer (thickness of the diaphragm layer 102 in the vibration region 30 portion) between adjacent nozzles in the same nozzle row, the amount of ink droplets ejected from each nozzle can be varied. A liquid ejection head is known (Patent Document 1). By varying the thickness of the diaphragm layer in this way, it is possible to vary the ejection characteristics between the nozzles, so compared to the method described above that ejects large droplets by varying only the drive signal, it is possible to eject large droplets. It is possible to shorten the period of the drive signal used when ejecting ink.

Specifically, when the thickness of the diaphragm layer 102 in the vibration region 30 changes, the period (natural period) of the drive signal suitable for ejecting ink changes, and the amount of ink droplets ejected (the amount of ejected liquid) changes. Change. Therefore, by changing the thickness of the diaphragm layer 102, it is possible to eject a large drop of ink using a basic ejection waveform having an ejection waveform of one pulse as shown in FIG. 11(b), for example. The method described above in which large droplets of ink are ejected by varying only the drive signal requires ejection waveforms for multiple pulses, as shown in FIG. 10(b). In the example shown in , a basic ejection waveform having one pulse worth of ejection waveform is sufficient. Therefore, the cycle of the drive signal (drive signal wavelength λ1'' shown in FIG. 11(b)) required to eject a large droplet of ink is different from the cycle of the drive signal (drive signal wavelength λ1'' shown in FIG. 10(b)). ), it is possible to improve the ejection frequency when performing complementary control using large droplet ink, and to suppress a decrease in productivity of the liquid ejection head.

However, in a configuration in which the thickness of the diaphragm layer 102 of the vibration region 30 is made different between adjacent nozzles within the same nozzle row, the thickness of the diaphragm layer 102 for small droplets shown in FIG. It is necessary to separately apply two types of drive signals having different cycles: a basic ejection waveform and a basic ejection waveform for large droplets shown in FIG. 11(b). As described above, applying two types of drive signals with different periods to the nozzles in the same nozzle row individually causes a problem in that the wiring configuration, drive control, etc. become complicated.

Note that even if drive signals of the same cycle are applied to nozzles with different thicknesses of the diaphragm layer 102 in the oscillating region 30, it is not possible to stably eject large droplets of ink in the required amount of ejected liquid. In other words, simply changing the thickness of the diaphragm layer 102 will change the period (natural period) of the drive signal suitable for ejecting ink, so how to adjust the thickness of the diaphragm layer 102 is important. However, with a drive signal having a cycle comparable to that of a drive signal for small droplets, it is not possible to stably eject large droplets of ink in the required amount of ejected liquid.

Therefore, in this embodiment, as shown in FIGS. 9(a) and 9(b), nozzles 112a1 and 112a2 belong to mutually adjacent nozzle rows N1 and N2 and are arranged close to each other. The thicknesses D1 and D2 of the diaphragm layer 102 in each vibration region 30-1 and 30-2 are made different between the two. Two types of drive signals are applied to the different nozzle rows N1 and N2, respectively: the basic ejection waveform for small droplets shown in FIG. 11(a) and the basic ejection waveform for large droplets shown in FIG. 11(b). In this case, the wiring configuration, drive control, etc. do not become complicated as in the case where the two types of drive signals are individually applied to the nozzles in the same nozzle row. Therefore, according to the present embodiment, it is possible to easily realize a configuration that can improve the ejection frequency when performing supplementary control using large droplets of ink and suppress a decrease in productivity of the liquid ejection head 110.

In this embodiment, the size of the ink droplet to be ejected (the amount of liquid to be ejected) is determined by the size of the ink droplet ejected from the large droplet ejection nozzle 112a1 and the small droplet that belong to each of the nozzle rows N1 and N2 and are arranged close to each other. As an example of a method of making the thicknesses different from those of the discharge nozzle 112a2, a method of making the thicknesses D1 and D2 of the diaphragm layer 102 of the vibration regions 30-1 and 30-2 different has been described as an example. Not limited. That is, the configuration is not limited to the configuration of this embodiment as long as the configuration can be changed so that the period (natural period) of the drive signal suitable for ejecting ink can be changed. Examples of such configuration changes include, for example, changing the nozzle opening area (nozzle diameter), changing the size of the pressure chamber 111, and changing the thickness of the piezoelectric element 100.

Here, if the configuration change that changes the natural period is only the thicknesses D1 and D2 of the diaphragm layer 102 in the vibration regions 30-1 and 30-2, the natural period will be different, so It is difficult to match the periods of drive signals applied to the nozzle 112a1 and the droplet ejection nozzle 112a2.

Therefore, in this embodiment, by combining two or more configuration changes that can change the natural period, the natural period between the large droplet ejection nozzle 112a1 and the small droplet ejection nozzle 112a2 can be changed from each other. The periods of the drive signals applied to each are adjusted to be close to each other or substantially the same period, and the periods of the drive signals applied to each are matched.

Specifically, in this embodiment, between the large droplet ejection nozzle 112a1 and the small droplet ejection nozzle 112a2, only the thicknesses D1 and D2 of the diaphragm layer 102 in the vibration regions 30-1 and 30-2 are used. Instead, by making the pressure chambers 111-1 and 111-2 different in size, the cycles of the drive signals applied to each are made to match. More specifically, for the large droplet discharge nozzle 112a1, the thickness D1 of the diaphragm layer 102 in the vibration region 30-1 is made thinner than the thickness D2 of the small droplet discharge nozzle 112a2 (D1<D2), and the pressure The width W1 of the chamber 111-1 (the length in the direction perpendicular to the arrangement direction of the nozzle rows) is made shorter than the width W2 of the droplet ejection nozzle 112a2 (W1<W2), and the width of the pressure chamber 111-1 is The length (length in the arrangement direction of the nozzle row) L1 is made longer than the length L2 of the droplet discharge nozzle 112a2 (L1<L2).

By combining such configuration changes, it becomes possible to adjust the natural period between the large droplet ejection nozzle 112a1 and the small droplet ejection nozzle 112a2 so that they become substantially the same period. As a result, as shown in FIG. 12(b), the period of the drive signal applied to the large droplet ejection nozzle 112a1 is the same as the period of the drive signal of the small droplet ejection nozzle 112a2 shown in FIG. 12(a). It is possible to make them almost match.

Furthermore, according to the present embodiment, not only can the period of the drive signal used by the large droplet discharge nozzle 112a1 and the small droplet discharge nozzle 112a2 be made substantially the same, but also the same drive signal waveform can be used. . That is, it is possible to use the same drive signal for the large droplet discharge nozzle 112a1 and the small droplet discharge nozzle 112a2.

In addition to the thicknesses D1 and D2 of the diaphragm layer 102, the widths W1 and W2 and the lengths L1 and L2 of the pressure chambers 111-1 and 111-2, the nozzle opening area (nozzle diameter) and the thickness of the piezoelectric element 100 are also determined. It may be adjusted.

FIG. 13 is an explanatory plan view schematically showing another example of the substrate 101 which is a flow path plate of the liquid ejection head 110 in this embodiment.
The liquid ejection head 110 shown in FIG. 13 has thicknesses D1 and D2 of the diaphragm layer 102 in the vibration areas 30-1 and 30-2 between the large droplet ejection nozzle 112a1 and the small droplet ejection nozzle 112a2. Not only the sizes of the pressure chambers 111-1 and 111-2 are made different, but also the opening areas (nozzle diameters) of the nozzles 112a1 and 112a2 are made different. In this example, the opening area (nozzle diameter) of the large droplet discharge nozzle 112a1 is made larger than that of the small droplet discharge nozzle 112a2. According to this example, it is easier to adjust the natural period between the large droplet ejection nozzle 112a1 and the small droplet ejection nozzle 112a2 so that they become substantially the same period.

FIG. 14 illustrates four nozzle rows N1, N2, N3, and N4 in the example of FIG. 13.
In the example of FIG. 14, the nozzles 112a1 and 112a3 constituting the first nozzle row N1 and the third nozzle row N3 are large droplet ejection nozzles that eject large droplets of liquid (ink), and the second nozzle row N2 and The nozzles 112a2 and 112a4 constituting the fourth nozzle row N4 are small droplet ejection nozzles that eject small droplets of liquid (ink) that are smaller in volume than the large droplets. The number of nozzle rows can be set as appropriate, and as long as there are two or more rows, it may be three rows or five or more rows.

FIG. 15 is an explanatory plan view schematically showing still another example of the substrate 101, which is the channel plate of the liquid ejection head 110 in this embodiment.
In the example of FIG. 15, the positions of the pressure chambers 111-1 and 111-2 in the sub-scanning direction (positions in the left-right direction in FIG. 15) between the nozzle rows N1 and N2 are such that the nozzle pitch The distance between the centers of adjacent nozzles in the sub-scanning direction in the row) P1, P2 (P1=P2) is shifted by half (half pitch ΔP).

Next, an example of the piezoelectric element 100 in this embodiment will be described.
In this embodiment, the substrate 101 is configured using SOI (Silicon On Insulator). SOI has a multilayer structure consisting of a substrate (Si), a Box layer (SiO ₂ ), an active layer (Si), and a surface layer (SiO ₂ ) from the bottom, and the layers from the Box layer to the surface layer are the diaphragm layer. 102.

In this example, in order to create a difference in the film thickness of the diaphragm layer 102 within the wafer plane, a partial etching process is performed up to the active layer (Si), and then an oxidation process is performed to remove the surface layer (SiO ₂ ). Formed. On this surface layer (SiO ₂ ), a Ti film (film thickness: about 20 [nm]) was formed at 350 [°C] by sputtering, and thermally oxidized at 750 [°C] by RTA (rapid thermal treatment). Subsequently, a Pt film (thickness: about 160 [nm]) was formed as the lower electrode layer 103 by sputtering at about 300 [° C.]. The TiO ₂ film obtained by thermally oxidizing the Ti film serves as an adhesion layer between the diaphragm layer 102 made of the SiO ₂ film and the lower electrode layer 103 made of the Pt film.

In this example, a seed layer was formed on the lower electrode layer 103. The seed layer was produced to have a thickness of 6 [nm].

Furthermore, three types of PZT precursor coating liquids prepared at a composition ratio of Pb:Zr:Ti=115:49:51 were prepared as materials for the PZT film (piezoelectric film 104) to be formed on the seed layer. A specific PZT precursor coating solution was synthesized as follows.

First, lead acetate trihydrate, isopropoxide titanium, and isopropoxide zirconium were used as starting materials, and the crystal water of lead acetate was dissolved in methoxyethanol and then dehydrated. Note that the amount of lead is excessive compared to the stoichiometric composition. This is to prevent a decrease in crystallinity due to so-called lead removal during heat treatment. In addition, by dissolving isopropoxide titanium and isopropoxide zirconium in methoxyethanol, proceeding with the alcohol exchange reaction and esterification reaction, and mixing it with the methoxyethanol solution in which lead acetate was dissolved, a PZT precursor coating liquid is prepared. Synthesized. The PZT concentration in the PZT precursor coating liquid was set to 0.5 [mol/l]. Note that the PT coating liquid was also synthesized in the same manner as the PZT precursor coating liquid.

Using these coating solutions, a PT layer was first formed by spin coating, and then dried at 120[° C.] using a hot plate. Thereafter, processing was carried out at the calcination temperatures listed in Table 1 above as the calcination conditions. Thereafter, three layers were formed by repeating coating → drying → calcination, and after the third layer was thermally decomposed, heat treatment (temperature 730 [° C.]) for crystallization was performed by RTA (rapid thermal treatment). The thickness of the PZT film when this heat treatment for crystallization was completed was 240 [nm]. The heat treatment steps of coating, drying, thermal decomposition, and crystallization of the PZT precursor solution were performed a total of 8 times (24 layers) to form a PZT film (piezoelectric film 104) with a film thickness of approximately 2.0 [μm]. I got it.

Next, as the upper electrode layer 105, a SrRuO film (thickness: 40 [nm]), which is an oxide film, and a Pt film (thickness: 125 [nm]), which is a metal film, were formed by sputtering. After that, a film of photoresist (TSMR8800) manufactured by Tokyo Ohka Co., Ltd. was formed using a spin coating method, and a resist pattern was formed by ordinary photolithography, and then an ICP etching system (manufactured by Samco) was used to form a film as shown in FIG. A pattern was created.

Next, as the first insulating protective film 113, a 50 [nm] Al ₂ O ₃ film was formed using the ALD method. At this time, for Al, TMA (Sigma-Aldrich) was used, and for O, O ₃ generated by an ozone generator was used, and these were alternately laminated to proceed with film formation. Then, as shown in FIG. 5, after contact holes 113a and 113b were formed by etching, an Al film was sputtered to form lead wiring lines 114 and 116, and patterned by etching. After that, a 500 [nm] Si ₃ N ₄ film was formed as a second insulating protective film 115 by plasma CVD, and the piezoelectric element 100 was manufactured.

Thereafter, the substrate 101 was excavated from the back side, and the nozzle plate 112 was joined to form pressure chambers 111-1 and 111-2. The nozzle diameter of both the large droplet discharge nozzle 112a1 and the small droplet discharge nozzle 112a2 is 24 [μm].

In this embodiment, as shown in FIG. 9, between the nozzles 112a1 and 112a2 that belong to the first nozzle row N1 and the second nozzle row N2 that are adjacent to each other and are arranged close to each other (large droplet ejection thicknesses D1 and D2 of the diaphragm layer 102 in the vibration areas 30-1 and 30-2 and the size of the pressure chambers 111-1 and 111-2). are different.

Table 1 below shows the main production conditions, droplet size, drive signal waveform length (period), and drive frequency for Examples 1 to 3 and Comparative Examples.

As shown in FIG. 16, a liquid ejection head 110 having a nozzle row in which a plurality of nozzles 112a are arranged is manufactured, and the above-mentioned pressure applying means for applying pressure to the liquid in the pressure chamber 111 corresponding to each nozzle 112a is used. Liquid ejection evaluation was performed using the piezoelectric elements 100 of Examples 1 to 3 and Comparative Example. In this evaluation, ink whose viscosity was adjusted to 5 [cp] was used as the liquid, and the ejection status was confirmed when a drive signal of -10 [V] to -30 [V] was applied. As a result, for the droplet ejection nozzle 112a2, in both Examples 1 to 3 and the comparative example, a drive signal with a high drive frequency (100 [kHz] or more), that is, a short period (10 [μs] or less) It was possible to stably eject small droplets.

On the other hand, with respect to the large droplet ejection nozzle 112a1, in Examples 1 to 3, a desired large droplet is ejected using a drive signal with a relatively high drive frequency (66.7 [kHz] or more), that is, a short cycle (15 [μs] or less). (4 [pl] or more) could be stably discharged. However, in the comparative example, it was possible to stably eject the desired large droplets (4 [pl] or more) at a relatively low driving frequency of 33.3 [kHz], that is, a long period of 30 [μs]. This was the driving signal.

Next, an embodiment of an inkjet recording apparatus, which is an apparatus for ejecting liquid, in which the above-described liquid ejection head 110 is mounted as an inkjet head will be described.
FIG. 17 is a perspective explanatory diagram showing the inkjet recording apparatus of this embodiment.
FIG. 18 is an explanatory side view of the mechanism section of the inkjet recording apparatus.

The inkjet recording apparatus of this embodiment includes a carriage movable in the main scanning direction, an inkjet head (recording head) mounted on the carriage, an ink cartridge that supplies liquid ink to the recording head, etc. inside the apparatus main body 81. A paper feed cassette (or a paper feed tray may be used) 84, which houses the printing mechanism section 82 and the like, and which can load a large number of sheets of paper 83, can be freely inserted and removed below the main body 81 of the apparatus. In addition, a manual feed tray 85 for manually feeding paper 83 can be opened and folded, and the paper 83 fed from the paper feed cassette 84 or the manual feed tray 85 is taken in, and an image is recorded by the printing mechanism section 82. After that, the paper is discharged to the paper discharge tray 86.

The printing mechanism section 82 holds a carriage 93 slidably in the main scanning direction by a main guide rod 91 and a subordinate guide rod 92, which are guide members that are horizontally suspended between left and right side plates. A recording head 94 is mounted on the carriage 93 to eject ink of each color: yellow (Y), cyan (C), magenta (M), and black (Bk). The recording head 94 includes a nozzle row in which a plurality of nozzles 112a are arranged in a direction intersecting the main scanning direction, and is mounted on the carriage 93 so that the ink ejection direction faces downward. Further, each ink cartridge 95 for supplying ink of each color to the recording head 94 is replaceably mounted on the carriage 93.

The ink cartridge 95 has an air port communicating with the atmosphere at the top, a supply port for supplying ink to the recording head 94 at the bottom, and a porous body filled with ink inside. The ink supplied to the recording head 94 is maintained at a slight negative pressure by capillary force. Furthermore, although the recording heads 94 are provided individually for each color, they may be configured with a single recording head.

Here, the carriage 93 is slidably fitted onto the main guide rod 91 on the downstream side in the paper transport direction, and is slidably placed on the slave guide rod 92 on the upstream side in the paper transport direction. In order to move and scan the carriage 93 in the main scanning direction, a timing belt 130 is stretched between a drive pulley 98 and a driven pulley 99 that are rotationally driven by a main scanning motor 97. The carriage 93 is driven back and forth by the forward and reverse rotation of the main scanning motor 97.

On the other hand, in order to convey the paper 83 set in the paper feed cassette 84 to the lower side of the head 94, a paper feed roller 131 and a friction pad 132, which separate and feed the paper 83 from the paper feed cassette 84, and a friction pad 132 are used to guide the paper 83. A guide member 133, a conveyance roller 134 that reverses and conveys the fed paper 83, a conveyance roller 135 that is pressed against the circumferential surface of the conveyance roller 134, and a tip that defines the angle at which the paper 83 is sent out from the conveyance roller 134. A roller 136 is provided. The conveyance roller 134 is rotationally driven by a sub-scanning motor 137 via a gear train.

An impression receiving member 139 is provided as a paper guide member that guides the paper 83 sent out from the conveyance roller 134 below the recording head 94 in accordance with the moving range of the carriage 93 in the main scanning direction. On the downstream side of the print receiving member 139 in the paper transport direction, a transport roller 141 and a spur 142 which are rotatably driven to send out the paper 83 in the paper ejection direction are provided. A roller 143, a spur 144, and guide members 145 and 146 forming a paper ejection path are provided.

During recording, by driving the recording head 94 according to the image signal while moving the carriage 93, ink is ejected onto the stationary paper 83 to record one line, and after conveying the paper 83 a predetermined amount, Record the next line. By receiving a recording end signal or a signal indicating that the trailing edge of the paper 83 has reached the recording area, the recording operation is ended and the paper 83 is ejected.

Further, a recovery device 147 for recovering from an ejection failure of the recording head 94 is disposed at a position outside the recording area on the right end side in the moving direction of the carriage 93. The recovery device 147 has a cap means, a suction means, and a cleaning means. During printing standby, the carriage 93 is moved to the recovery device 147 side and the recording head 94 is capped by a capping means to keep the nozzles 112a in a wet state to prevent ejection failure due to ink drying. Further, by ejecting ink unrelated to printing during printing, etc., the ink viscosity of all nozzles 112a is made constant, and stable ejection performance is maintained.

If an ejection failure occurs, etc., the nozzle 112a of the recording head 94 is sealed with a capping means, and air bubbles and the like are sucked out together with ink from the nozzle 112a through a tube with a suction means, and the ink and dust adhering to the nozzle surface are removed by a cleaning means. , and the ejection failure is recovered. Further, the sucked ink is discharged to a waste ink reservoir installed at the bottom of the main body, and is absorbed and held by an ink absorber inside the waste ink reservoir.

As described above, since the inkjet recording apparatus of this embodiment is equipped with the recording head 94 consisting of the liquid discharge heads 110 of Examples 1 to 10 described above, ink discharge failure due to drive failure of the diaphragm layer 102 can be avoided. Therefore, stable ink ejection characteristics can be obtained and image quality can be improved.

Next, another example (modification) of the inkjet recording apparatus as an apparatus for ejecting liquid according to the present embodiment will be described with reference to FIGS. 19 and 20.
FIG. 19 is an explanatory plan view of the main parts of the inkjet recording apparatus of this modification.
FIG. 20 is an explanatory side view of the main part of the inkjet recording apparatus of this modification.

The inkjet recording device of this modification is a serial type device, and the carriage 403 is reciprocated in the main scanning direction by a main scanning movement mechanism 493. The main scanning movement mechanism 493 includes a guide member 401, a main scanning motor 405, a timing belt 408, and the like. The guide member 401 spans between the left and right side plates 491A and 491B, and movably holds the carriage 403. Then, the carriage 403 is reciprocated in the main scanning direction by the main scanning motor 405 via a timing belt 408 stretched between a driving pulley 406 and a driven pulley 407 .

This carriage 403 is equipped with a liquid ejection unit 440 that integrates a liquid ejection head 404 and a head tank 441 similar to the liquid ejection head 110 according to the embodiment described above. The liquid ejection head 404 of the liquid ejection unit 440 ejects liquid of each color, for example, yellow (Y), cyan (C), magenta (M), and black (K). Further, the liquid ejection head 404 has a nozzle array including a plurality of nozzles arranged in the sub-scanning direction perpendicular to the main scanning direction, and is mounted with the ejection direction facing downward.

A supply mechanism 494 for supplying liquid stored outside the liquid ejection head 404 to the liquid ejection head 404 supplies the liquid stored in the liquid cartridge 450 to the head tank 441 .

The supply mechanism 494 includes a cartridge holder 451, which is a filling section into which the liquid cartridge 450 is mounted, a tube 456, a liquid feeding unit 452 including a liquid feeding pump, and the like. Liquid cartridge 450 is removably attached to cartridge holder 451. Liquid is fed from the liquid cartridge 450 to the head tank 441 by a liquid feeding unit 452 via a tube 456 .

The inkjet recording apparatus of this modification includes a transport mechanism 495 for transporting paper 410. The conveyance mechanism 495 includes a conveyance belt 412 that is a conveyance means, and a sub-scanning motor 416 for driving the conveyance belt 412.

The conveyance belt 412 attracts the paper 410 and conveys it to a position facing the liquid ejection head 404 . This conveyance belt 412 is an endless belt, and is stretched between a conveyance roller 413 and a tension roller 414. Adsorption can be performed by electrostatic adsorption, air suction, or the like.

The conveyance belt 412 rotates in the sub-scanning direction by rotationally driving the conveyance roller 413 via the timing belt 417 and timing pulley 418 by the sub-scanning motor 416.

Further, a maintenance and recovery mechanism 420 that maintains and recovers the liquid ejection head 404 is arranged on one side of the carriage 403 in the main scanning direction and on the side of the conveyor belt 412.

The maintenance and recovery mechanism 420 includes, for example, a cap member 421 that caps the nozzle surface (a surface on which a nozzle is formed) of the liquid ejection head 404, a wiper member 422 that wipes the nozzle surface, and the like.

The main scanning movement mechanism 493, the supply mechanism 494, the maintenance and recovery mechanism 420, and the transport mechanism 495 are attached to a housing including side plates 491A, 491B and a back plate 491C.

In this apparatus configured in this manner, the paper 410 is fed onto the conveyor belt 412 and adsorbed, and the paper 410 is conveyed in the sub-scanning direction by the rotational movement of the conveyor belt 412.

Therefore, by driving the liquid ejection head 404 according to the image signal while moving the carriage 403 in the main scanning direction, liquid is ejected onto the stationary paper 410 to form an image.

In this way, since the inkjet recording apparatus of this modification includes the liquid ejection head of the embodiment described above, it is possible to stably form a high-quality image.

Next, another example of the liquid ejection unit in this embodiment will be described with reference to FIG. 21.
FIG. 21 is an explanatory plan view of the main parts of the liquid ejection unit.
This liquid ejection unit includes, among the members constituting the above-mentioned inkjet recording apparatus, a housing portion composed of side plates 491A, 491B and a back plate 491C, a main scanning movement mechanism 493, a carriage 403, and a liquid ejection unit. It is composed of a head 404. Note that it is also possible to configure a liquid ejection unit in which at least one of the above-mentioned maintenance and recovery mechanism 420 and supply mechanism 494 is further attached to, for example, the side plate 491B of this liquid ejection unit.

Next, still another example of the liquid ejection unit in this embodiment will be described with reference to FIG. 22.
FIG. 22 is an explanatory front view of the liquid ejection unit.
This liquid ejection unit includes a liquid ejection head 404 to which a flow path component 444, which is a liquid supply member, is attached, and a tube 456 connected to the flow path component 444. Note that the channel component 444 is arranged inside the cover 442. A head tank 441 can also be included instead of the flow path component 444. Further, a connector 443 for electrically connecting with the liquid ejection head 404 is provided on the upper part of the flow path component 444.

In the present application, the liquid to be ejected may have a viscosity or surface tension that allows it to be ejected from the head, and is not particularly limited. It is preferable that the following is true. More specifically, solvents such as water and organic solvents, coloring agents such as dyes and pigments, functional materials such as polymerizable compounds, resins, and surfactants, and biocompatible materials such as DNA, amino acids, proteins, and calcium. , edible materials such as natural pigments, etc., and these include, for example, inkjet inks, surface treatment liquids, constituent elements of electronic devices and light emitting devices, and formation of electronic circuit resist patterns. It can be used for purposes such as a liquid for use in liquids, a material liquid for three-dimensional modeling, and the like.

A "liquid ejection unit" is a liquid ejection head with functional parts and mechanisms integrated, and includes an assembly of parts related to liquid ejection. For example, the "liquid ejection unit" includes a combination of a liquid ejection head and at least one of the following structures: a head tank, a carriage, a supply mechanism, a maintenance recovery mechanism, and a main scanning movement mechanism.

Here, integration refers to, for example, a liquid ejection head, a functional component, or a mechanism fixed to each other by fastening, adhesion, engagement, etc., or one in which one is held movably relative to the other. include. Further, the liquid ejection head, the functional parts, and the mechanism may be configured to be detachable from each other.

For example, some liquid ejection units have a liquid ejection head and a head tank integrated. In addition, there are devices in which a liquid ejection head and a head tank are integrated by being connected to each other with a tube or the like. Here, a unit including a filter may be added between the head tank and the liquid ejection head of these liquid ejection units.

Further, some liquid ejection units have a liquid ejection head and a carriage integrated.

Further, some liquid ejection units have the liquid ejection head movably held by a guide member that constitutes a part of the scanning movement mechanism, so that the liquid ejection head and the scanning movement mechanism are integrated. Further, there are some in which the liquid ejection head, the carriage, and the main scanning movement mechanism are integrated.

Furthermore, some liquid ejection units have a cap member, which is part of the maintenance recovery mechanism, fixed to the carriage to which the liquid ejection head is attached, so that the liquid ejection head, the carriage, and the maintenance recovery mechanism are integrated. .

Further, some liquid ejection units have a tube connected to a liquid ejection head to which a head tank or a flow path component is attached, so that the liquid ejection head and a supply mechanism are integrated. The liquid from the liquid storage source is supplied to the liquid ejection head through this tube.

The main scanning movement mechanism also includes a single guide member. Further, the supply mechanism includes a single tube and a single loading section.

The term "device for ejecting liquid" includes a device that includes a liquid ejection head or a liquid ejection unit and drives the liquid ejection head to eject liquid. Devices that eject liquid include not only devices that are capable of ejecting liquid onto objects to which liquid can adhere, but also devices that eject liquid into air or into liquid.

The "device for discharging liquid" may include means for feeding, transporting, and discharging objects to which liquid can adhere, as well as pre-processing devices, post-processing devices, and the like.

For example, an image forming device is a device that ejects ink to form an image on paper as a “device that ejects liquid,” and an image forming device that forms layers of powder to form three-dimensional objects (three-dimensional objects). There is a three-dimensional modeling device (three-dimensional modeling device) that discharges a modeling liquid onto a powder layer.

Further, the "device for ejecting liquid" is not limited to a device that can visualize significant images such as characters and figures using ejected liquid. For example, it includes those that form patterns that have no meaning in themselves, and those that form three-dimensional images.

The above-mentioned "something to which a liquid can adhere" means something to which a liquid can adhere at least temporarily, such as something that adheres and sticks, something that adheres and penetrates, etc. Specific examples include recording media such as paper, recording paper, recording paper, film, and cloth, electronic components such as electronic boards, piezoelectric elements, powder layers, organ models, and test cells. Unless otherwise specified, it includes everything to which liquid adheres.

The material for the above-mentioned "thing to which liquid can adhere" may be paper, thread, fiber, cloth, leather, metal, plastic, glass, wood, ceramics, etc., as long as liquid can adhere thereto, even temporarily.

Further, the "device for discharging liquid" includes a device in which a liquid discharging head and an object to which liquid can be attached move relative to each other, but the present invention is not limited to this. Specific examples include a serial type device that moves a liquid ejection head, a line type device that does not move a liquid ejection head, and the like.

In addition, the "device for discharging a liquid" includes a processing liquid coating device that discharges a processing liquid onto paper in order to apply the processing liquid to the surface of the paper for the purpose of modifying the surface of the paper, etc. There is an injection granulation device that granulates fine particles of the raw material by spraying a composition liquid in which the raw material is dispersed in a solution through a nozzle.

In addition, in the terms of this application, image formation, recording, printing, imprinting, printing, modeling, etc. are all synonymous.

What has been described above is just an example, and each of the following aspects has its own unique effects.
[First aspect]
A first aspect includes a plurality of nozzles 112a1 and 112a2 that eject liquid (for example, ink), a plurality of pressure chambers 111-1 and 111-2 communicating with each of the plurality of nozzles, and each of the plurality of pressure chambers. A plurality of diaphragms (for example, vibration regions 30-1 and 30-2 of the diaphragm layer 102) forming a part of the wall of the diaphragm, and a plurality of electromechanical transducers (for example, A liquid ejection head 110 including a piezoelectric element 100-1, 100-2), which has a plurality of nozzle rows in which two or more nozzles are arranged side by side along a predetermined arrangement direction (for example, a sub-scanning direction). , the nozzle opening area (for example, the nozzle diameter ), the sizes of the corresponding pressure chambers (for example, widths W1, W2, lengths L1, L2), the thicknesses of the corresponding diaphragms D1, D2, and the thicknesses of the corresponding electromechanical transducers are different. It is characterized by the fact that
When a nozzle that ejects a small amount of liquid (small droplet ejection nozzle) is in a non-ejecting state due to nozzle clogging, etc., large droplets are ejected from other nozzles (large droplet ejection nozzle) located close to each other. Dots to be formed by small droplet ejection nozzles (non-ejection nozzles) may be supplemented. At this time, large droplets can be ejected from the large droplet ejection nozzle simply by making the drive signal applied to the large droplet ejection nozzle different from that of the small droplet ejection nozzle. However, in this case, the drive signal for the large droplet ejection nozzle has a longer cycle than that for the small droplet ejection nozzle, so it is necessary to reduce the ejection frequency when performing supplementary control using large droplets. As a result, the productivity of the liquid ejection head decreases.
On the other hand, conventionally, there is a liquid ejection head in which the thickness of the diaphragm is made different between adjacent nozzles in the same nozzle row, so that the amount of liquid ejected from each nozzle is made different (Patent Document 1). By varying the thickness of the diaphragm, the ejection characteristics between the nozzles can be varied, so compared to the method described above, which ejects large droplets by varying only the drive signal, it is possible to It is possible to shorten the period of the drive signal used. Therefore, it is possible to suppress a decrease in productivity of the liquid ejection head.
In the conventional liquid ejection head described above, it is possible to shorten the period of the drive signal used when ejecting large droplets, but it is possible to shorten the period of the drive signal used when ejecting small droplets. It is not possible to do so. Therefore, in the conventional liquid ejection head, it is necessary to individually apply two types of drive signals with different periods to the nozzles in the same nozzle row. As described above, applying two types of drive signals with different periods to the nozzles in the same nozzle row individually causes a problem in that the wiring configuration, drive control, etc. become complicated.
Therefore, in this embodiment, the nozzle opening area, the size of the corresponding pressure chamber, the thickness of the corresponding diaphragm, and the corresponding At least one of the thicknesses of the electromechanical transducer elements used in the nozzles is different, so that the amount of liquid ejected is different between these nozzles. This makes it possible to shorten the cycle of the drive signal used when ejecting large droplets without complicating the wiring configuration or drive control. Therefore, when the dots to be formed by the small droplet ejection nozzle (non-ejecting nozzle) are complemented by ejecting large droplets from the large droplet ejection nozzle, it is possible to do so without complicating the wiring configuration or drive control. , it is possible to suppress a decrease in productivity of the liquid ejection head.

[Second aspect]
A second aspect is characterized in that, in the first aspect, the periods of the drive waveforms applied to the electromechanical transducer elements are substantially the same between the nozzles.
According to this aspect, even when the dots to be formed by the small droplet ejection nozzle (non-ejecting nozzle) are complemented by ejecting large droplets from the large droplet ejection nozzle, the productivity of the liquid ejection head decreases. It never invites.

[Third aspect]
In a third aspect, in the first or second aspect, at least the size of the corresponding pressure chamber and the thickness of the corresponding diaphragm are different between the nozzles.
In this way, as a configuration change that can change the period (natural period) of the drive signal suitable for ejecting ink, it is possible to combine two factors: the size of the corresponding pressure chamber and the thickness of the corresponding diaphragm. This makes it easy to adjust the natural periods between the large droplet ejection nozzle and the small droplet ejection nozzle so that they are close to each other or have substantially the same period. Therefore, when dots to be formed by small droplet ejection nozzles (non-ejecting nozzles) are complemented by ejecting large droplets from large droplet ejection nozzles, it is easy to suppress the drop in productivity of the liquid ejection head. Become.

[Fourth aspect]
A fourth aspect is the third aspect characterized in that at least the nozzle opening area also differs between the nozzles.
According to this aspect, it becomes easier to adjust the natural periods between the large droplet ejection nozzle and the small droplet ejection nozzle so that they are close to each other or have substantially the same period. It becomes easier to suppress a decrease in the productivity of the liquid ejection head when dots to be formed by the ejection nozzles (non-ejection nozzles) are complemented by ejecting large droplets from the large droplet ejection nozzles.

[Fifth aspect]
A fifth aspect is that in any one of the first to fourth aspects, the nozzle array is characterized in that the corresponding pressure chambers are arranged in a staggered manner along the predetermined arrangement direction.
According to this aspect, a small liquid ejection head can be realized.

[Sixth aspect]
A sixth aspect is characterized in that, in any of the first to fifth aspects, the difference in the amount of liquid ejected between the nozzles is 4 pl or more.
According to this aspect, large droplets exceeding 4 pl can be ejected.

[Seventh aspect]
A seventh aspect is a liquid ejection unit characterized by including the liquid ejection head according to any one of the first to sixth aspects.
According to this aspect, when the small droplet discharging nozzle is in a non-discharging state due to nozzle clogging or the like, large droplets are ejected from the large droplet discharging nozzle disposed close to the small droplet discharging nozzle (non-discharging nozzle). It is possible to provide a liquid ejection unit that can easily eject liquid to complement dots to be formed by non-ejecting nozzles.

[Eighth aspect]
In an eighth aspect, in the seventh aspect, there is provided a head tank for storing liquid to be supplied to the liquid ejection head, a carriage for mounting the liquid ejection head, a supply mechanism for supplying liquid to the liquid ejection head, and a supply mechanism for supplying liquid to the liquid ejection head. The present invention is characterized in that the liquid ejection head is integrated with at least one of a maintenance and recovery mechanism that performs maintenance and recovery, and a main scanning movement mechanism that moves the liquid ejection head in the main scanning direction.
According to this aspect, when the small droplet discharging nozzle is in a non-discharging state due to nozzle clogging or the like, large droplets are ejected from the large droplet discharging nozzle disposed close to the small droplet discharging nozzle (non-discharging nozzle). Various liquid ejection units that can easily eject liquid to complement dots to be formed by non-ejecting nozzles can be provided.

[Ninth aspect]
A ninth aspect is a device for discharging liquid (for example, an inkjet recording device), which includes the liquid discharging head according to any one of the first to sixth aspects, or the liquid discharging unit according to any one of the seventh or eighth aspects. It is characterized by having at least one of the following.
According to this aspect, when the small droplet discharging nozzle is in a non-discharging state due to nozzle clogging or the like, large droplets are ejected from the large droplet discharging nozzle disposed close to the small droplet discharging nozzle (non-discharging nozzle). It is possible to provide a liquid ejecting device that can easily eject liquid to complement dots to be formed by non-ejecting nozzles.

10: Common liquid chamber 20: Actuator substrate 30: Vibration region 94: Recording head 100: Piezoelectric element 101: Substrate 102: Vibration plate layer 103: Lower electrode layer 103A: First lower electrode layer 103B: Second lower electrode layer 104 : Piezoelectric film 105 : Upper electrode layer 105A : First upper electrode layer 105B : Second upper electrode layer 110 : Liquid discharge head 111 : Pressure chamber 112 : Nozzle plate 112a : Nozzle 112a1 : Large droplet discharge nozzle 112a2 : Small droplet Discharge nozzle 112a3: Large droplet discharge nozzle 112a4: Small droplet discharge nozzle

Patent No. 3622484

Claims (7)

a plurality of nozzles that discharge liquid; a plurality of pressure chambers communicating with each of the plurality of nozzles; a plurality of diaphragms forming a part of a wall of each of the plurality of pressure chambers; and a plurality of diaphragms. A liquid ejection head comprising a plurality of electromechanical transducers respectively formed on the liquid ejection head,
It has a plurality of nozzle groups consisting of one or two or more nozzle rows in which two or more nozzles are arranged side by side along a predetermined arrangement direction,
The plurality of nozzle groups are composed of nozzles that eject the same liquid,
Nozzles belonging to adjacent nozzle groups in the plurality of nozzle groups and arranged close to each other are arranged so that the nozzle opening area is the same and the amount of liquid ejected is different . A liquid ejection head characterized in that the sizes of pressure chambers and the thicknesses of corresponding diaphragms are different. The liquid ejection head according to claim 1,
A liquid ejection head characterized in that a period of a driving waveform applied to the electromechanical transducer is substantially the same between the nozzles . The liquid ejection head according to claim 1 or 2 ,
The liquid ejection head is characterized in that the nozzle group consists of two nozzle rows in which corresponding pressure chambers are arranged in a staggered manner along the predetermined arrangement direction. The liquid ejection head according to any one of claims 1 to 3 ,
A liquid ejection head characterized in that a difference in ejected liquid amount between the nozzles is 4 pl or more. A liquid ejection unit comprising the liquid ejection head according to any one of claims 1 to 4 . The liquid ejection unit according to claim 5 ,
A head tank that stores liquid to be supplied to the liquid ejection head, a carriage that mounts the liquid ejection head, a supply mechanism that supplies liquid to the liquid ejection head, a maintenance and recovery mechanism that maintains and recovers the liquid ejection head, and the liquid. A liquid ejection unit characterized in that the liquid ejection head is integrated with at least one of a main scanning movement mechanism that moves the ejection head in a main scanning direction. Discharging a liquid characterized by comprising at least one of the liquid discharging head according to any one of claims 1 to 4 or the liquid discharging unit according to claim 5 or 6. Device.

Images