JP7047514B2 - Liquid discharge head control device and liquid discharge device - Google Patents

Description

The present invention relates to a control device for a liquid discharge head and a liquid discharge device.

An inkjet recording device (liquid ejection device) used as an image recording device or an image forming device such as a printer, a facsimile or a copying device is a nozzle for ejecting ink droplets and a pressure chamber (ink flow path, addition) through which the nozzles communicate. Also referred to as a pressure chamber, a pressurizing chamber, a discharge chamber, or a liquid chamber), an electromechanical conversion element such as a piezoelectric element that pressurizes ink in the pressure chamber, an electrothermal conversion element such as a heater, and an ink flow path. A recording head (liquid discharge head) including an energy generating means including a vibrating plate forming a wall surface of the above and an electrode facing the vibrating plate. Then, the recording head pressurizes the ink in the pressure chamber with the energy generated by the energy generating means to eject ink droplets from the nozzle. There are two types of inkjet recording heads: one that uses an electromechanical conversion actuator in the longitudinal vibration mode that expands and contracts in the axial direction of the electromechanical conversion element, and one that uses an electromechanical conversion actuator in the deflection vibration mode. Is already known. As for the actuator using the deflection vibration mode, for example, a uniform electromechanical conversion film is formed over the entire surface of the vibrating plate by the film forming technique, and the electromechanical conversion film is formed into a shape corresponding to the pressure chamber by the lithography method. It is known that the electromechanical conversion element is formed independently for each pressure chamber by cutting it. When the vector component of the spontaneous polarization axis of the electromechanical conversion film coincides with the electric field application direction, expansion and contraction due to the increase / decrease in the electric field application strength occurs effectively, and a large electromechanical conversion constant can be obtained. It is most preferable that the spontaneous polarization axis of the film and the electric field application direction completely coincide with each other.

In such a recording head, as the electromechanical conversion element is repeatedly driven, the displacement amount of the electromechanical conversion element fluctuates, and a phenomenon occurs in which the droplet ejection characteristics such as the droplet ejection amount and the droplet ejection speed are not stable. It has been known. In particular, the displacement amount of the electromechanical conversion element may fluctuate significantly in the initial stage when the drive operation is started. In order to solve this, for example, an aging process in which a drive signal with a higher voltage and frequency than in actual use is driven by applying a pulse to the electromechanical conversion element a predetermined number of times (focusing on the polarization state, "polarization processing"). The technology to carry out (sometimes called) is already known. Further, a technique for suppressing fluctuation by introducing a voltage waveform different from the actual drive voltage waveform when actually used is already known. Further, a technique for suppressing fluctuations in the droplet ejection characteristics by adjusting the actual drive voltage waveform is already known.

In order to suppress the decrease in the droplet ejection characteristics as described above, a technique for correcting the bias voltage based on the drive information is disclosed in order to suppress the decrease in the displacement amount of the piezoelectric element due to repeated driving. Patent Document 1).

However, since the bias voltage correction by the technique described in Patent Document 1 is performed based only on the drive information, an excessive load is superimposed on the electromechanical conversion element, and as a result, the droplet ejection characteristics are deteriorated. There is a problem that fluctuations will increase.

The present invention has been made in view of the above, and is a control device for a liquid ejection head capable of suppressing a decrease in droplet ejection characteristics while reducing a load on an electromechanical conversion element with respect to repeated driving. And to provide a liquid discharge device.

In order to solve the above-mentioned problems and achieve the object, in the present invention, the nozzle plate on which the nozzle is formed, the substrate on which the liquid chamber is formed, and the vibrating plate forming one surface of the liquid chamber are laminated in this order. A liquid discharge head having a body and further having a common electrode, an electromechanical conversion element, and an individual electrode to which a drive waveform voltage for driving the electromechanical conversion element is applied to drive the vibrating plate. In the control device of the above , the bias voltage applied to the common electrode is corrected so as to cancel the fluctuation of the displacement amount of the electromechanical conversion element due to the shift from the coercive electric field in the initial state of the electromechanical conversion element. A voltage correction unit that corrects the voltage applied between the individual electrode and the common electrode for driving the electromechanical conversion element, a voltage of the drive waveform applied to the individual electrode, and the voltage correction unit. It is provided with the bias voltage applied to the common electrode corrected by the above, and a voltage command unit for sending a command for applying the applied voltage determined by The voltage correction unit is characterized in that the bias voltage is corrected so that the ratio of the coercive electric field to the bias voltage becomes constant .

According to the present invention, it is possible to suppress a decrease in droplet ejection characteristics while reducing the load on the electromechanical conversion element with respect to repeated driving.

FIG. 1 is a diagram showing an example of the overall structure of the inkjet recording apparatus according to the embodiment. FIG. 2 is a diagram showing an example of a cross-sectional configuration of the inkjet recording apparatus according to the embodiment. FIG. 3 is a cross-sectional view of a main part of the recording head according to the embodiment. FIG. 4 is a cross-sectional view for explaining the individual electrodes and the common electrodes of the recording head according to the embodiment. FIG. 5 is a diagram illustrating a holding substrate in the recording head according to the embodiment. FIG. 6 is a diagram showing an example of the configuration of the polarization processing device. FIG. 7 is a diagram showing an example of the state of the polarization processing for the electromechanical conversion element. FIG. 8 is a diagram illustrating a state in which the coercive electric field shifts. FIG. 9 is a diagram showing an example of the hardware configuration of the inkjet recording device according to the embodiment. FIG. 10 is a diagram showing an example of a hardware configuration of a main part of an inkjet recording device according to an embodiment. FIG. 11 is a diagram showing an example of a functional block configuration of the inkjet recording device according to the embodiment. FIG. 12 is a diagram showing an example of a drive waveform and a bias voltage of the inkjet recording apparatus according to the embodiment. FIG. 13 is a diagram showing an example of a drop control signal and a drive waveform for ejecting a large drop of ink. FIG. 14 is a diagram showing an example of a drop control signal and a drive waveform for ejecting a medium drop ink drop. FIG. 15 is a diagram showing an example of a drop control signal and a drive waveform for ejecting a small drop of ink. FIG. 16 is a diagram showing an example of a drop control signal and a drive waveform for causing a fine drive operation. FIG. 17 is a diagram showing an example of a correction table used by the inkjet recording device according to the embodiment for correcting the bias voltage. FIG. 18 is a flowchart showing an example of the printing operation of the inkjet recording apparatus according to the embodiment. FIG. 19 is a diagram showing an example of a correction table used by the inkjet recording device according to the first modification of the embodiment for correcting the bias voltage. FIG. 20 is a diagram showing an example of a correction table used by the inkjet recording device according to the second modification of the embodiment for correcting the bias voltage. FIG. 21 is a cross-sectional view of a main part of the recording head according to the third modification of the embodiment. FIG. 22 is a graph showing a comparison result of the rate of change of the ink ejection speed. FIG. 23 is a diagram showing an example of a correction table used by the inkjet recording device according to Comparative Example 2 for correcting the bias voltage.

Hereinafter, embodiments of the liquid discharge head control device and the liquid discharge device according to the present invention will be described in detail with reference to the drawings. Further, the present invention is not limited to the following embodiments, and the components in the following embodiments include those easily conceived by those skilled in the art, substantially the same, and so-called equivalent ranges. Is included. Further, various omissions, substitutions and changes of components can be made without departing from the gist of the following embodiments.

(Overall configuration of inkjet recording device)
FIG. 1 is a diagram showing an example of the overall structure of the inkjet recording apparatus according to the embodiment. FIG. 2 is a diagram showing an example of a cross-sectional configuration of the inkjet recording apparatus according to the embodiment. The overall configuration of the inkjet recording apparatus 1 according to the present embodiment will be described with reference to FIGS. 1 and 2.

As shown in FIGS. 1 and 2, the inkjet recording apparatus 1 according to the present embodiment includes a carriage 11 that can move in the main scanning direction, a recording head 12 that ejects ink mounted on the carriage 11, and the recording head. A printing mechanism unit 10 including an ink cartridge 13 for supplying ink to 12 is provided. Further, the inkjet recording device 1 has a paper feed cassette 23 that can load a large number of sheets 22 from the front side in the lower portion and can be freely inserted and removed, and a manual feed that can be opened and closed to manually feed the paper 22. A tray 24 and a paper ejection tray 21 for ejecting the paper 22 fed from the paper feed cassette 23 or the manual feed tray 24 to the rear surface side after a predetermined image is printed are provided.

The carriage 11 is slidably held in the main scanning direction by a main guide rod 31 and a slave guide rod 32, which are guide members laid horizontally in the main scanning direction. The recording head 12 is mounted on the carriage 11, ejects ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (BK), and is arranged in a direction intersecting the main scanning direction. Moreover, it is a liquid ejection head having a plurality of ink ejection ports (nozzles) formed so that the ejection direction is downward. The ink cartridge 13 is replaceably mounted on the carriage 11 in order to supply ink of each color to the recording head 12. Further, the ink cartridge 13 has an air port that communicates with the atmosphere formed above, a supply port that supplies ink to the recording head 12 formed below, and a porous body filled with ink held inside. And have. This porous body keeps the ink supplied to the recording head 12 by the capillary force at a slight negative pressure. The recording head 12 may be formed of a plurality of heads that eject ink droplets for each of a plurality of colors, or may be formed of one head having a plurality of nozzles that eject ink droplets of each color. It may be the one that is.

Further, the inkjet recording device 1 includes a main scanning motor 33, a drive pulley 34 that is rotationally driven by the rotation of the main scanning motor 33, a driven pulley 35 that is paired with the drive pulley 34, and a drive pulley 34 and a driven pulley. It has a timing belt 36 stretched between the 35 and the timing belt 36. The carriage 11 is fixed to the timing belt 36 and reciprocates in the main scanning direction by the forward / reverse rotation of the main scanning motor 33.

Further, the inkjet recording device 1 includes a paper feed roller 41, a friction pad 42, a guide member 43, a transfer roller 44, a transfer roller 45, a tip roller 46, and a sub-scanning motor 47.

The paper feed roller 41 and the friction pad 42 separately supply the paper 22 from the paper feed cassette 23 in order to convey the paper 22 set in the paper feed cassette 23 to the lower side of the recording head 12. The guide member 43 guides the paper 22 separately supplied by the paper feed roller 41 and the friction pad 42 to the transport roller 44. The transport roller 44 reverses the fed paper 22 and transports it to the lower side of the recording head 12. The transport roller 45 presses the paper 22 against the peripheral surface of the transport roller 44. The tip roller 46 defines the feeding angle of the paper 22 conveyed from the conveying roller 44 to the lower side of the recording head 12. The sub-scanning motor 47 rotationally drives the paper feed roller 41 via the gear train.

Further, the inkjet recording device 1 has a stamp receiving unit 48, a transfer roller 49, a spur 50, a paper ejection roller 51, a spur 52, and guide members 53 and 54.

The imprint receiving unit 48 is a guide member that guides the paper 22 sent out from the paper feed roller 41 corresponding to the movement range of the carriage 11 in the main scanning direction on the lower side of the recording head 12. The transport roller 49 and the spur 50 are members provided on the downstream side of the printing receiving unit 48 in the paper transport direction and rotationally driven to feed the paper 22 in the paper discharge direction. The paper ejection roller 51 and the spur 52 are members that are rotationally driven to feed the paper 22 fed by the transport roller 49 and the spur 50 to the paper ejection tray 21. The guide members 53 and 54 are members that form a paper ejection path.

Further, the inkjet recording device 1 is arranged at a position outside the recording area on the end side of the carriage 11 in the moving direction, and includes a recovery device 61 for recovering a ejection defect of the recording head 12. The recovery device 61 has a capping means, a suction means, and a cleaning means. The carriage 11 moves to the recovery device 61 side while waiting for printing, the recording head 12 is capped by the capping means, and the wet state of the nozzle portion is maintained. As a result, ejection defects due to drying of the ink are suppressed. Further, the recording head 12 ejects ink that is not related to recording to keep the viscosities of the inks of all the nozzles constant and maintain stable ejection performance.

Further, in the recording head 12, when a ejection failure occurs, the nozzle is sealed by the capping means, air bubbles or the like are sucked out from the nozzle through the tube by the suction means, and the ink and the like adhering to the vicinity of the nozzle are sucked by the cleaning means. Dust and the like are removed, and ejection defects are recovered. Further, the sucked ink is discharged into a waste ink reservoir (not shown) installed in the lower part of the main body of the inkjet recording device 1, and is absorbed and held by an ink absorber inside the waste ink reservoir.

At the time of recording (printing), the inkjet recording apparatus 1 as described above drives the recording head 12 according to the image data while moving the carriage 11 to eject ink onto the stopped paper 22. The lines are recorded, and after the predetermined amount of paper 22 is conveyed in the sub-scanning direction, the next line is recorded. Further, the inkjet recording apparatus 1 ends the recording operation and ejects the paper 22 by receiving the recording end signal or the signal that the rear end of the paper 22 reaches the recording area.

(Recording head configuration)
FIG. 3 is a cross-sectional view of a main part of the recording head according to the embodiment. FIG. 4 is a cross-sectional view for explaining the individual electrodes and the common electrodes of the recording head according to the embodiment. FIG. 5 is a diagram illustrating a holding substrate in the recording head according to the embodiment. The configuration of the recording head 12 of the inkjet recording apparatus 1 according to the present embodiment will be described with reference to FIGS. 3 to 5.

As shown in FIG. 3, the recording head 12 according to the present embodiment is layered in the order of individual electrode 501, electromechanical conversion element 502, common electrode 503, diaphragm 504, pressure chamber substrate 505, and nozzle plate 507 from the upper side. It is configured in. The "laminated body" of the present invention corresponds to an object configured in a layered manner in the order of a diaphragm 504, a pressure chamber substrate 505, and a nozzle plate 507. In the recording head 12, after the individual electrodes 501, the electromechanical conversion element 502, and the common electrode 503 are etched so as to have a desired shape, an insulating protective film (see FIG. 4) is produced, and a pressure chamber substrate 505 (substrate) is formed. A pressure chamber 506 (liquid chamber) for ejecting ink is created by etching from the nozzle side of the. In the recording head 12, it is necessary to increase the rigidity of the electromechanical conversion element 502, the diaphragm 504, and the insulating protective film in order to secure the ejection performance at high frequencies, and it is necessary to secure a high Young's modulus and further thicken the film. There is. In particular, the diaphragm 504 is formed of a plurality of layers made of SiO ₂ , Si ₃ N ₄ , and poly-Si materials in order to ensure high-frequency ejection performance, and has a film thickness of 1 [μm] or more. It is desirable that the product is produced at 3 [μm] or less, and the Young's modulus is 75 [GPa] or more and 95 [GPa] or less.

It is desirable that a silicon single crystal substrate is used for the pressure chamber substrate 505, and it is desirable that the pressure chamber substrate 505 has a thickness of 100 to 600 [μm]. There are three types of plane orientations, (100), (110), and (111). In the semiconductor industry, (100) and (111) are generally widely used, and the pressure chamber of the present embodiment is widely used. In the substrate 505, for example, a single crystal substrate having the plane orientation of (100) is mainly used. Further, when the pressure chamber 506 as shown in FIG. 3 is produced in the pressure chamber substrate 505, the silicon single crystal substrate is processed by using etching. In this case, the etching method is, for example, anisotropic. Etching is used. Here, anisotropic etching utilizes the property that the etching rate differs with respect to the plane orientation of the crystal structure. For example, in anisotropic etching in which the surface is immersed in an alkaline solution such as KOH, the etching rate of the (111) surface is about 1/400 of that of the (100) surface. Therefore, in the plane orientation (100), a structure having an inclination of about 54 ° can be produced, whereas in the plane orientation (110), a deep groove can be dug, so that the arrangement density can be maintained while maintaining higher rigidity. Can be raised. Therefore, as the pressure chamber substrate 505, it is also possible to use a single crystal substrate having the plane orientation of (110). However, in this case, SiO ₂ which is a mask material also has a property of being etched, so it is necessary to keep this point in mind when using it.

The width of the pressure chamber 506 is preferably 50 [μm] or more and 70 [μm] or less, and more preferably 55 [μm] or more and 65 [μm] or less. If it is larger than this value, the residual vibration becomes large and it becomes difficult to secure the ejection performance at a high frequency. If it is smaller than this value, the displacement amount decreases and sufficient ejection performance cannot be secured.

The diaphragm 504 is deformed and displaced by receiving a force generated by the electromechanical conversion element 502, and the ink in the pressure chamber 506 is ejected as ink droplets from the nozzle 508 of the nozzle plate 507 formed in the lower part of the pressure chamber substrate 505. Let me. Therefore, it is desirable that the diaphragm 504 has a predetermined strength. Examples of the manufacturing method include a method of manufacturing Si, SiO ₂ , or Si ₃ N ₄ or the like by a CVD (Chemical Vapor Deposition) method. Further, as the diaphragm 504, it is desirable to select a material having a coefficient of linear expansion close to that of the electromechanical conversion element 502 and the common electrode 503 as shown in FIG. In particular, since PZT is generally used as a material for the electromechanical conversion element 502, a linear expansion coefficient close to 8 × 10 ^-6 [1 / K] is used, and 5 × for the vibrating plate 504. A material having a coefficient of linear expansion of ^10-6 to 10 × ^10-6 [1 / K] is desirable, and a material having a coefficient of linear expansion of 7 × ^10-6 to 9 × ^10-6 [1 / K] is more desirable. The material is more desirable.

Specific materials for the vibrating plate 504 include aluminum oxide, zirconium oxide, iridium oxide, ruthenium oxide, tantalum oxide, hafnium oxide, osmium oxide, rhenium oxide, rhodium oxide, palladium oxide, and compounds thereof. The diaphragm 504 is manufactured by a spin coater using the above-mentioned substance and a sputtering method or a sol-gel method. The film thickness of the diaphragm 504 is preferably 1 to 3 [μm], and more preferably 1.5 to 2.5 [μm]. If it is smaller than this range, it becomes difficult to process the pressure chamber 506 in the pressure chamber substrate 505 as shown in FIG. 3, and if it is larger than this range, the diaphragm 504 is less likely to be deformed and displaced, and ink droplet ejection becomes unstable. Become.

The individual electrode 501 and the common electrode 503 are electrodes that deform and displace the electromechanical conversion element 502 by applying a voltage to the electromechanical conversion element 502 arranged between them. As the individual electrode 501 and the common electrode 503, for example, platinum having high heat resistance and low reactivity is used. However, since it may not be possible to say that it has a sufficient barrier property against lead, a platinum group element such as iridium or platinum-rhodium, or an alloy film thereof may be used. Further, when platinum is used as the individual electrode 501 and the common electrode 503, the adhesion to the diaphragm 504 (particularly SiO ₂ ) is poor, so that Ti, TIO ₂ , Ta, Ta ₂ O ₅ , and Ta It is preferable to stack ₃ N ₅ and the like first. Examples of the manufacturing method include a method of manufacturing by vacuum film formation such as a sputtering method or vacuum vapor deposition. The film thickness of the individual electrode 501 and the common electrode 503 is preferably 0.05 to 1 [μm], and more preferably 0.1 to 0.5 [μm].

Further, an oxide electrode film made of SrRuO ₃ or LaNiO ₃ may be formed between the individual electrode 501 and the common electrode 503 and the electromechanical conversion element 502. In particular, regarding the oxide electrode film between the common electrode 503 and the electromechanical conversion element 502, since it affects the orientation control of the electromechanical conversion element 502 manufactured on the oxide electrode film, the material selected according to the orientation in which the orientation is to be prioritized. Is different. For example, when the electromechanical conversion element 502 is formed of PZT, a seed layer such as LaNiO ₃ , TiO ₂ or PbTiO ₃ is formed on the common electrode 503 in order to preferentially orient it to (100), and then a PZT film. The electromechanical conversion element 502 may be formed.

When _SrRuO3 is used as the oxide electrode film between the individual electrode 501 and the electromechanical conversion element 502, the film thickness is preferably 20 [nm] to 80 [nm], preferably 30 [nm] to 30 [nm]. 50 [nm] is more desirable. If it is thinner than this film thickness range, sufficient characteristics for initial displacement and displacement deterioration characteristics cannot be obtained. On the other hand, if it is thicker than this film thickness range, the withstand voltage of the PZT (electromechanical conversion element 502) formed thereafter becomes very poor, and the current leakage becomes large.

The electromechanical conversion element 502 is a piezoelectric element formed between the individual electrodes 501 and the common electrode 503 that causes bending and deformation, and is an element that deforms and deforms when a voltage is applied to both electrodes. As the electromechanical conversion element 502, for example, PZT is used as described above. PZT is a solid solution of lead zirconate (PbTIO ₃ ) and lead titanate (PbTiO ₃ ), and its characteristics differ depending on the ratio thereof. In general, a composition exhibiting excellent piezoelectric properties has a ratio of PbZrO ₃ to PbTiO ₃ of 53:47, and is expressed as Pb (Zr _0.53 Ti _0.47 ) O ₃ in the chemical formula. , Generally represented as PZT (53/47). Examples of the composite oxide other than PZT as the material of the electromechanical conversion element 502 include barium titanate. In this case, barium alkoxide or a titanium alkoxide compound is used as a starting material and dissolved in a common solvent to prepare a barium titanate precursor. It is also possible to make a body solution. However, when the (100) plane of PZT is preferentially oriented, the composition ratio of Zr / Ti is preferably 0.45 or more and 0.55 or less when expressed in Ti / (Zr + Ti). , 0.48 or more and 0.52 or less is more desirable. In the present embodiment, it is desirable to preferentially orient the (100) plane of PZT, and the degree of orientation of the crystal is represented by the following formula (1).

ρ (hkl) = I (hkl) / ΣI (hkl) ... (1)
[Ρ (hkl): (hkl) degree of orientation of plane orientation, I (hkl): peak intensity of arbitrary orientation, ΣI (hkl): sum of each peak intensity]

Using the above equation (1), it is calculated based on the ratio of the peak intensities of each orientation when the sum of the peak intensities obtained by the θ-2θ measurement of the X-ray diffraction method is 1. (100). The degree of orientation of the plane orientation is preferably 0.75 or more, and more preferably 0.85 or more. When the degree of orientation is equal to or less than the above value, the piezoelectric strain cannot be sufficiently obtained and the displacement amount cannot be sufficiently secured. Materials such as lead zirconate (PbTiO ₃ ) and lead titanate (PbTiO ₃ ) described above are described by the general formula ABO ₃ and have A = Pb, Ba, Sr, B = Ti, Zr, Sn, Ni, Zn. , Mg, Nb as the main components of the composite oxide. As a specific description thereof, it is expressed as (Pb _1-x Ba _x ) (Zr, Ti) O ₃ , (Pb _1-x Sr _x ) (Zr, Ti) O ₃ , which is one of Pb of A site. This is the case when the parts are replaced with Ba or Sr. Such substitution is possible if it is a divalent element, and its effect is to compensate for the deterioration of characteristics due to evaporation of lead during heat treatment. As a manufacturing method, it is manufactured by a spin coater using a sputtering method or a sol-gel method. In that case, since patterning is required, a desired pattern can be obtained by photolithography etching or the like.

When PZT is prepared by the sol-gel method, a PZT precursor solution is prepared by using lead acetate, zirconate alkoxide, and a titanium alkoxide compound as starting materials and dissolving them in methoxyethanol as a common solvent to obtain a uniform solution. Since the metal alkoxide compound is easily hydrolyzed by moisture in the atmosphere, an appropriate amount of a stabilizer such as acetylacetone, acetic acid, or diethanolamine may be added to the precursor solution as a stabilizer. Further, when a PZT film is obtained on the entire surface of the base surface, it is obtained by forming a coating film by a solution coating method such as spin coating and performing heat treatments of solvent drying, thermal decomposition, and crystallization. Since the transformation from the coating film to the crystallized film involves volume shrinkage, it is necessary to adjust the precursor concentration so that a film thickness of 100 [nm] or less can be obtained in one step in order to obtain a crack-free film. become. The film thickness of the electromechanical conversion element 502 is preferably 1 to 3 [μm], and more preferably 1.5 to 2.5 [μm]. If the film thickness is smaller than this range, it becomes difficult to process the pressure chamber 506 as shown in FIG. 3, and if it is larger than this range, the substrate is less likely to be deformed and displaced, and ink droplet ejection becomes unstable.

Further, as shown in FIG. 4A, the recording head 12 according to the present embodiment is formed so as to cover the exposed upper surfaces of the individual electrode 501, the electromechanical conversion element 502, and the common electrode 503 shown in FIG. A first insulating protective film 511, an individual electrode 509 arranged on the first insulating protective film 511 and conducting with the individual electrode 501, and an individual electrode 509 arranged on the first insulating protective film 511 and conducting with the common electrode 503. Further, it has a common electrode 510, an individual electrode 509, a common electrode 510, and a second insulating protective film 512 formed so as to cover the upper surface of the first insulating protective film 511.

As shown in FIG. 4B, the first insulating protective film 511 is provided with the same number of contact holes 509a as the individual electrodes 501, and the individual protective films 511 are arranged on the first insulating protective film 511. The electrode 509 is in contact (conducting) with the individual electrode 501 via the contact hole 509a. Further, a contact hole 510a is bored in the first insulating protective film 511, and the common electrode 510 arranged on the first insulating protective film 511 passes through the contact hole 510a to the common electrode 503. Is in contact (conduction) with.

Further, as shown in FIG. 4A, the second insulating protective film 512 is partially opened so that a part of the individual electrode 509 and the common electrode 510 are exposed. The portion exposed through the opening of the individual electrode 509 forms the individual electrode pad 509b as shown in FIG. 4 (b). A voltage based on a drive waveform for deforming and displacementing the diaphragm 504 is applied to the individual electrodes 501 and 509 via the individual electrode pads 509b, as will be described later.

Further, the portion exposed through the opening of the common electrode 510 forms the common electrode pad 510b as shown in FIG. 4 (b). A bias voltage described later is applied to the common electrode 503 and the common electrode 510 via the common electrode pad 510b.

Further, as shown in FIG. 5, the recording head 12 is held on the carriage 11 by the holding substrate 531. As shown in FIG. 5, the holding substrate 531 has a step on the lower surface for joining to the joint surface step 525 formed between the electromechanical conversion elements 502. The joint surface step 525 is formed between the electromechanical conversion elements 502, that is, at a position facing the partition wall 506a of the pressure chamber 506. As shown in FIG. 5, a plurality of pressure chambers 506 are formed in the pressure chamber substrate 505, and each is defined by a partition wall 506a. The joint surface step 525 includes a first insulating protective film 521 formed on the portion of the common electrode 503 facing the partition wall 506a of the pressure chamber 506, a metal wiring 523 installed on the first insulating protective film 521, and a metal wiring 523. , Formed by a second insulating protective film 522 covering the metal wiring 523. As described above, the joint surface step 525 is not provided in the active portion of the electromechanical conversion element 502 and is formed at a position facing the partition wall 506a of the pressure chamber 506, so that the diaphragm 504 is deformed. It does not affect the displacement.

(Polarization treatment for electromechanical conversion element)
FIG. 6 is a diagram showing an example of the configuration of the polarization processing device. FIG. 7 is a diagram showing an example of the state of the polarization processing for the electromechanical conversion element. The polarization processing for the electromechanical conversion element will be described with reference to FIGS. 6 and 7.

The polarization processing device 1000 shown in FIG. 6 is an example of a device for performing polarization processing on an electromechanical conversion element. The polarization processing apparatus 1000 includes a corona electrode 1001, a grid electrode 1002, and a sample stage 1003.

The corona electrode 1001 is an electrode for generating a corona discharge by applying a high voltage from the corona power supply 1001a. The grid electrode 1002 is a mesh-shaped electrode, and by applying a voltage from the grid power supply 1002a, charged ions and the like generated by the corona discharge of the corona electrode 1001 are efficiently poured onto the lower sample stage 1003. It is an electrode for doing. The sample stage 1003 is a stage for mounting a wafer 1011 which is an electromechanical conversion element to be polarized, and has, for example, a temperature control function capable of applying a temperature of up to 350 degrees. It makes it possible to perform the polarization treatment on the wafer 1011 while applying an appropriate temperature. The sample stage 1003 is connected to ground to allow polarization processing.

In the polarization processing apparatus 1000 having the above-described configuration, the voltage applied to the corona electrode 1001 or the grid electrode 1002, or the distance between both electrodes and the sample stage 1003 is adjusted to cause corona discharge from the corona electrode 1001. You can adjust the strength of.

FIG. 7 shows the states of the hysteresis of the electric field strength E and the polarization P when the polarization processing is performed on the electromechanical conversion element using the polarization processing device 1000 as described above. Specifically, the hysteresis loop is measured by applying an electric field strength of ± 150 [kV / cm].

First, the polarization at the time of the first 0 [kV / cm] is set to Pini, then a voltage having an electric field strength of +150 [kV / cm] is applied, and then the voltage is returned to the electric field strength of 0 [kV / cm]. When the polarization is Pr, the value of Pr-Pini is defined as the polarizability. Then, the polarization state of the electromechanical conversion element is determined from this polarizability. The polarizability Pr-Pini is preferably 10 [μC / cm ² ] or less, and more preferably 5 [μC / cm ² ] or less. If it is less than this value, it is not possible to sufficiently specify the displacement deterioration after continuous driving as the electromechanical conversion element of PZT.

In order to obtain the desired polarizability Pr-Pini, the voltage applied to the corona electrode 1001 or the grid electrode 1002 or the distance between both electrodes and the sample stage 1003 is adjusted in the polarization processing apparatus 1000 shown in FIG. It can be achieved by. The electromechanical conversion element subjected to the above polarization treatment is applied as the electromechanical conversion element 502 shown in FIG.

(Shifting of coercive field)
FIG. 8 is a diagram illustrating a state in which the coercive electric field shifts. As shown in FIG. 8, the electromechanical conversion element 502 is repeatedly driven from the hysteresis loop of the electric field strength E and the polarization P in the initial state to the electromechanical conversion element 502 (in the example of FIG. 8, 10 ¹⁰ times of drive). As a result, the coercive electric field has the property of shifting to the negative side of the electric field strength E. Here, the coercive electric field means the electric field strength when the sign of polarization is inverted (as shown in FIG. 8, there are positive and negative coercive electric fields). With such a shift in the coercive electric field, the output (displacement amount) of the electromechanical conversion element 502 changes, so that the ink droplet ejection characteristics of the recording head 12 also change. Therefore, in the inkjet recording apparatus 1 according to the present embodiment, as will be described later, fluctuations in ejection characteristics are suppressed by performing correction processing for the bias voltage applied to the common electrode 503 based on the shifting coercive electric field. It is supposed to be. In this embodiment, attention is paid to the negative electric field among the positive and negative electric fields.

(Hardware configuration of inkjet recording device)
FIG. 9 is a diagram showing an example of the hardware configuration of the inkjet recording device according to the embodiment. FIG. 10 is a diagram showing an example of a hardware configuration of a main part of an inkjet recording device according to an embodiment. The hardware configuration of the inkjet recording apparatus 1 according to the present embodiment will be described with reference to FIGS. 9 and 10.

As shown in FIG. 9, the inkjet recording apparatus 1 according to the present embodiment includes an image processing board 300, a main control board 100, and a head relay board 200.

The image processing board 300 is a circuit board that performs image processing on the input image data. As shown in FIG. 9, the image processing board 300 includes an image processing circuit 310 that executes image processing on image data.

Based on the image-processed image data, the main control board 100 determines the generation of the drive waveform for driving the electromechanical conversion element 502 for ejecting ink droplets for printing on the paper, and the bias voltage. It is a substrate (control device) that commands the application of a voltage for driving the electromechanical conversion element 502 to the head relay substrate 200. As shown in FIG. 9, the main control board 100 includes a CPU (Central Processing Unit) 101, an FPGA (Field-Programmable Gate Array) 102, a RAM (Random Access Memory) 103, and a ROM (Read Only Memory) 104. , NVRAM (Non-Volatile RAM) 105, a motor driver 106, and a drive waveform generation circuit 107.

The CPU 101 is an arithmetic unit that controls the overall operation of the inkjet recording device 1. The CPU 101 uses the RAM 103 as a work area and outputs control commands for controlling various operations in the inkjet recording device 1 by executing various control programs stored in the ROM 104. While communicating with the FPGA 102, the CPU 101 cooperates with the FPGA 102 to perform various operation controls in the inkjet recording device 1.

The FPGA 102 is an integrated circuit that controls various operations in the inkjet recording device 1 in cooperation with the CPU 101. The FPGA 102 includes a CPU control unit 111, a memory control unit 112, an I2C control unit 113, a sensor processing unit 114, a motor control unit 115, and a recording head control unit 116.

The CPU control unit 111 has a function of communicating with the CPU 101. The memory control unit 112 has a function of accessing the RAM 103 and the ROM 104. The I2C control unit 113 has a function of accessing the NVRAM 105.

The sensor processing unit 114 processes sensor signals from various sensors 130. The various sensors 130 are a general term for sensors that detect various states in the inkjet recording device 1. The various sensors 130 include an encoder sensor, a paper sensor that detects the passage of paper (recording paper), a cover sensor that detects the opening of the cover member, a temperature / humidity sensor that detects environmental temperature and humidity, and an operation of a lever that fixes the paper. It includes a paper fixing lever sensor that detects the state, a remaining amount detection sensor that detects the remaining amount of ink in the cartridge, and the like. Further, the analog sensor signals output from the various sensors 130 are converted into digital signals by, for example, an AD converter mounted on the main control board 100 or the like and input to the FPGA 102.

The motor control unit 115 controls various motors 140. Various motors 140 are a general term for motors included in the inkjet recording device 1. The various motors 140 include a main scanning motor 33 for operating the carriage 11, a sub-scanning motor 47 for transporting paper (recording paper) in the sub-scanning direction, a paper feed motor for feeding paper, and the like. Is included.

Here, the operation control of the main scanning motor 33 will be taken as an example, and a specific example of the control by the cooperation between the CPU 101 and the motor control unit 115 of the FPGA 102 will be described. First, the CPU 101 notifies the motor control unit 115 of the movement speed and the movement distance of the carriage 11 together with the operation start instruction of the main scanning motor 33. Upon receiving this instruction, the motor control unit 115 generates a drive profile based on the information on the movement speed and the movement distance notified from the CPU 101, and compares it with the encoder value of the encoder sensor acquired from the sensor processing unit 114. , The PWM command value is calculated and output to the motor driver 106. When the motor control unit 115 finishes the predetermined operation, the motor control unit 115 notifies the CPU 101 of the end of the operation. Although the example in which the motor control unit 115 generates the drive profile has been described here, the configuration may be such that the CPU 101 generates the drive profile and instructs the motor control unit 115. The CPU 101 also counts the number of prints, counts the number of scans of the main scanning motor 33, and the like.

The recording head control unit 116 sends the head drive data, the discharge synchronization signal LINE, and the discharge timing signal CHANGE stored in the ROM 104 to the drive waveform generation circuit 107, and causes the drive waveform generation circuit 107 to generate the drive waveform signal Vcom. The drive waveform signal Vcom generated by the drive waveform generation circuit 107 is output to the recording head driver 210 mounted on the head relay board 200 described later.

Next, with reference to FIG. 10, the hardware configuration of the main part of the inkjet recording apparatus 1 will be further described.

When the recording head control unit 116 receives the trigger signal Trig that triggers the discharge timing, the recording head control unit 116 outputs the discharge synchronization signal LINE that triggers the generation of the drive waveform to the drive waveform generation circuit 107. The recording head control unit 116 further outputs a discharge timing signal CHANGE indicating a delay amount from the discharge synchronization signal LINE to the drive waveform generation circuit 107.

The drive waveform generation circuit 107 uses the waveform data read from the ROM 104 to generate a drive waveform signal Vcom at a timing based on the discharge synchronization signal LINE and the discharge timing signal CHANGE.

Further, the recording head control unit 116 receives the image data SD'after image processing from the image processing circuit 310 shown in FIG. 9, and ejects ink droplets from each nozzle of the recording head 12 based on the image data SD'. A mask control signal MN for selecting a predetermined waveform of the drive waveform signal Vcom according to the magnitude of is generated. This mask control signal MN is a signal whose timing is synchronized with the discharge timing signal CHANGE. Then, the recording head control unit 116 transmits the image data SD', the synchronous clock signal SCK, the latch signal LT instructing the latch of the image data SD', and the generated mask control signal MN to the recording head driver 210. do.

As shown in FIG. 10, the recording head driver 210 includes a shift register 211, a latch circuit 212, a gradation decoder 213, a level shifter 214, and an analog switch 215.

The shift register 211 inputs the image data SD'transmitted from the recording head control unit 116 and the synchronization clock signal SCK. The latch circuit 212 latches each resist value of the shift register 211 by the latch signal LT transmitted from the recording head control unit 116.

The gradation decoder 213 outputs a logic level voltage signal obtained by decoding the value (image data SD') latched by the latch circuit 212 and the mask control signal MN. The level shifter 214 converts the logic level voltage signal of the gradation decoder 213 into a level at which the analog switch 215 can operate.

The analog switch 215 is a switch that is turned on / off by the logic level voltage signal of the gradation decoder 213 given via the level shifter 214. The analog switch 215 is provided for each nozzle included in the recording head 12, and is connected to the individual electrode 501 of the electromechanical conversion element 502 corresponding to each nozzle. Further, the analog switch 215 inputs the drive waveform signal Vcom from the drive waveform generation circuit 107. Further, as described above, the timing of the mask control signal MN is synchronized with the timing of the drive waveform signal Vcom. Therefore, the analog switch 215 is switched on / off at an appropriate timing according to the logic level voltage signal of the gradation decoder 213 given via the level shifter 214, so that the drive waveform signal Vcom is composed of the drive waveforms. The waveform (drive waveform) applied to the electromechanical conversion element 502 corresponding to each nozzle is selected. As a result, the voltage of the drive waveform is applied to the individual electrode 501 corresponding to the electromechanical conversion element 502, and the size of the ink droplets ejected from the nozzle is controlled.

The hardware configuration of the inkjet recording device 1 shown in FIGS. 9 and 10 is an example, and it is not necessary to include all the components shown in FIGS. 9 and 10, or other components. May include.

(Functional block configuration of inkjet recording device)
FIG. 11 is a diagram showing an example of a functional block configuration of the inkjet recording device according to the embodiment. FIG. 12 is a diagram showing an example of a drive waveform and a bias voltage of the inkjet recording apparatus according to the embodiment. FIG. 13 is a diagram showing an example of a drop control signal and a drive waveform for ejecting a large drop of ink. FIG. 14 is a diagram showing an example of a drop control signal and a drive waveform for ejecting a medium drop ink drop. FIG. 15 is a diagram showing an example of a drop control signal and a drive waveform for ejecting a small drop of ink. FIG. 16 is a diagram showing an example of a drop control signal and a drive waveform for causing a fine drive operation. FIG. 17 is a diagram showing an example of a correction table used by the inkjet recording device according to the embodiment for correcting the bias voltage. The functional block configuration of the inkjet recording apparatus 1 according to the present embodiment will be described with reference to FIGS. 11 to 17.

As shown in FIG. 11, the inkjet recording apparatus 1 according to the present embodiment includes an image processing unit 600, a control unit 700, a temperature measuring unit 750, a head driving unit 800 (driving unit), a recording head 12, and the recording head 12. including.

The image processing unit 600 is a functional unit that executes image processing including gradation processing and image conversion processing on the input image data and converts the input image data into image data in a format that can be processed by the recording head control unit 116. As shown in FIG. 11, the image processing unit 600 includes an interface unit 601, a gradation processing unit 602, an image conversion unit 603, and an image data storage unit 604. The image processing unit 600 is realized by the image processing circuit 310 shown in FIG.

The interface unit 601 is an image data input / output unit and is a communication interface with the control unit 700 (CPU 101 and FPGA 102).

The gradation processing unit 602 is a functional unit that performs gradation processing on the multi-valued image data input by the interface unit 601 and converts it into low-value image data. The small value image data is image data having a gradation number equal to the type of droplet (large droplet, medium droplet, small droplet) ejected by the recording head 12. Then, the gradation processing unit 602 stores the converted image data on the image data storage unit 604 for one band or more. The image data for one band refers to image data corresponding to the maximum width in the sub-scanning direction that can be printed by the recording head 12 in one scan in the main scanning direction.

The image conversion unit 603 is a functional unit that converts image data for one band on the image data storage unit 604 in units of images output by one scan (one scan) in the main scanning direction. .. Specifically, the image conversion unit 603 configures the recording head 12 according to the information of the print order and the print width (width in the sub-scanning direction of image printing per scan) received from the CPU 101 via the interface unit 601. Convert according to.

The printing order and printing width may be one-pass printing in which an image is formed by scanning the recording medium in one main scanning direction, or by the same nozzle group or different nozzle groups for the same area of the recording medium. Multi-pass printing may be used in which an image is formed by scanning a plurality of times in the main scanning direction. Further, the heads may be arranged in the main scanning direction and the same area may be separated by different nozzles. These recording methods can be used in combination as appropriate. Here, the print width indicates the width in the sub-scanning direction of the image recorded by one scan (one scan) of the recording head 12 in the main scanning direction. In this embodiment, the print width is set by the CPU 101.

Then, the image conversion unit 603 outputs the converted image data SD'to the control unit 700 via the interface unit 601.

The control unit 700 generates a drive waveform for driving the electromechanical conversion element 502 that ejects ink droplets for printing on paper (recording medium) based on the image data image-processed by the image processing unit 600. It is a functional unit that determines the bias voltage and commands the head drive unit 800 to apply a voltage for driving the electromechanical conversion element 502. As shown in FIG. 11, the control unit 700 includes an input unit 701, an application time measurement unit 702 (measurement unit), a voltage correction unit 703, a drive waveform generation unit 704, a bias voltage command unit 705, and a storage unit. 706 and. The control unit 700 is realized by the main control board 100 shown in FIG.

The input unit 701 is a functional unit for inputting image data SD'that has been image-processed by the image processing unit 600. The input unit 701 is realized by a program executed by the CPU 101 shown in FIG. 9 or an FPGA 102.

When the voltage of the drive waveform generated by the drive waveform generation unit 704 is applied from the head drive unit 800 to the recording head 12 (individual electrode 501), the application time measurement unit 702 has an intermediate potential among the voltages of the drive waveform. It is a functional unit that measures (integrates) the applied time. Here, the intermediate potential is a voltage that is raised by a predetermined amount from 0 [V], and is a reference when the voltage fluctuates as in the example of the drive waveform shown in FIG. 12 for ejecting ink. It shall mean the voltage. Further, as shown in FIG. 12, the intermediate potential in this embodiment is set to a voltage higher than the bias voltage which is a DC voltage. In the example shown in FIG. 12, the voltage is an intermediate potential except when the voltage of the drive waveform fluctuates when the ink is ejected (in FIG. 12, an example in which the voltage drops and returns to the intermediate potential is shown). The applied time measuring unit 702 is realized by a program executed by the CPU 101 shown in FIG. 9 or by the FPGA 102.

The voltage correction unit 703 estimates the shift amount of the coercive electric field of the electromechanical conversion element 502 from the application time of the intermediate potential measured by the application time measurement unit 702, and applies it to the common electrode 503 from the shift amount of the coercive electric field. This is a functional unit that obtains a shift amount of the bias voltage to be applied and corrects the bias voltage according to the shift amount. Specifically, the voltage correction unit 703 directly obtains the shift amount of the bias voltage corresponding to the application time of the intermediate potential by referring to the correction information 713 stored in the storage unit 706, which will be described later, and the bias voltage is based on the shift amount. Is corrected so that the bias voltage shifts by the amount of the shift of the coercive electric field. However, the voltage correction unit 703 makes the corrected bias voltage a value smaller than the absolute value of the coercive electric field. In this case, the voltage correction unit 703 may store the corrected bias voltage information in the storage unit 706. Further, the correction of the bias voltage applied to the common electrode 503 by the voltage correction unit 703 results in a correction for the applied voltage between the individual electrodes 501 and the common electrode 503.

Here, as an example of the correction information 713, the correction table 901 is shown in FIG. The correction table 901 is information relating the application time of the intermediate potential (corresponding to the correction timing shown in FIG. 17) and the shift amount (correction amount) of the bias voltage. In the correction table 901 shown in FIG. 17, for example, when the correction timing (application time of the intermediate potential) is 200,000 [sec], it is shown that the shift amount of the bias voltage is 0.25 [V].

The correction table 901 shown in FIG. 17 is information in a table format, but the information is not limited to this, and if the application time of the intermediate potential and the shift amount of the bias voltage can be managed in relation to each other. The information may be in any format. Further, the shift amount of the bias voltage specified in the correction table 901 may be, for example, a shift amount from the reference voltage (for example, the initial bias voltage), or a shift amount from the current bias voltage. May be good.

The voltage correction unit 703 is realized by a program executed by the CPU 101 shown in FIG. 9 or by the FPGA 102.

The drive waveform generation unit 704 applies the reference waveform information 711 stored in the storage unit 706 to the individual electrodes 501 of the recording head 12 based on the image data SD'or the like input by the input unit 701. This is a functional unit that generates a voltage drive waveform (corresponding to the drive waveform signal Vcom shown in FIG. 10). Further, the drive waveform generation unit 704 uses, for example, the temperature information 712 stored in the storage unit 706, which will be described later, to generate a drive waveform according to a change in the characteristics depending on the temperature of the ink. The drive waveform generation unit 704 transmits the generated drive waveform to the head drive unit 800.

The drive waveform generation unit 704 generates, for example, a drive waveform as shown in FIG. 12. As shown in FIG. 12, the drive waveform is a voltage waveform for ejecting ink droplets from the nozzle of the recording head 12 by raising and lowering the voltage with reference to the above-mentioned intermediate potential. Next, with reference to FIGS. 13 to 16, drive waveforms for ejecting ink droplets of various sizes will be described. FIG. 13 shows an example of a drive waveform for ejecting a large drop of ink from the recording head 12 and a drop control signal that defines the timing of applying a voltage according to the drive waveform. The drop control signal is a signal indicating that a voltage is applied by a drive signal while the signal level is in the High state. That is, as shown in FIG. 13, the drive waveform for ejecting a large drop of ink is a waveform that goes up and down with reference to the intermediate potential when the drop control signal is in the High state. By applying a voltage to the individual electrodes 501 according to the drive waveform shown in FIG. 13, a large drop of ink is ejected from the nozzle of the recording head 12 to the recording medium.

FIG. 14 shows an example of a drive waveform for ejecting a medium drop of ink from the recording head 12 and a drop control signal that defines the timing of applying a voltage according to the drive waveform. As shown in FIG. 14, the drive waveform for ejecting the ink of the middle drop has an intermediate potential in two sections (one section in the first half and one section in the second half in the time axis direction) in which the drop control signal is in the High state. It is a waveform that goes up and down as a reference. By applying a voltage to the individual electrodes 501 according to the drive waveform shown in FIG. 14, medium drops of ink are ejected from the nozzle of the recording head 12 to the recording medium.

FIG. 15 shows an example of a drive waveform for ejecting a small drop of ink from the recording head 12 and a drop control signal that defines the timing of applying a voltage according to the drive waveform. As shown in FIG. 15, the drive waveform for ejecting a small drop of ink is a waveform that goes up and down with reference to an intermediate potential in the middle section in the time axis direction in which the drop control signal is in the High state. By applying a voltage to the individual electrodes 501 according to the drive waveform shown in FIG. 15, small drops of ink are ejected from the nozzle of the recording head 12 onto the recording medium.

FIG. 16 shows an example of a drive waveform for finely driving the ink in the vicinity of the nozzle of the recording head 12 and a drop control signal that defines the application timing of the voltage according to the drive waveform. As shown in FIG. 16, the drive waveform for finely driving the ink in the vicinity of the nozzle is a waveform that moves up and down with reference to the intermediate potential in the initial section in the time axis direction in which the drop control signal is in the High state. .. By applying a voltage to the individual electrodes 501 according to the drive waveform shown in FIG. 16, the ink in the vicinity of the nozzle is finely driven. Such a drive waveform for finely driving the ink is not for ejecting ink droplets to the recording medium, but is a voltage waveform for suppressing ejection defects due to drying of the ink in the vicinity of the nozzle of the recording head 12.

As described above, the drop control signal shown in FIGS. 13 to 16 described above corresponds to the mask control signal MN for selecting a predetermined waveform of the drive waveform signal Vcom according to the size of the ink droplet to be ejected. Is.

The drive waveform generation unit 704 is realized by, for example, the drive waveform generation circuit 107 and the recording head control unit 116 shown in FIG.

The bias voltage command unit 705 is a functional unit that transmits a command for applying the bias voltage corrected by the voltage correction unit 703 to the common electrode 503 of the recording head 12 to the head drive unit 800. The bias voltage command unit 705 is realized by, for example, the drive waveform generation circuit 107 and the recording head control unit 116 shown in FIG.

The "voltage command unit" of the present invention corresponds to the drive waveform generation unit 704 and the bias voltage command unit 705. In FIG. 11, the drive waveform generation unit 704 and the bias voltage command unit 705 are shown as separate functional units, but they are conceptually separate functional units for the sake of explanation, and have the same functions in terms of mounting. It may constitute a part.

The storage unit 706 is a functional unit that stores information necessary for driving the recording head 12 by the head drive unit 800. For example, as shown in FIG. 11, the storage unit 706 stores reference waveform information 711, temperature information 712, and correction information 713. The storage unit 706 is realized by, for example, at least one of the RAM 103, ROM 104, and NVRAM 105 shown in FIG.

The reference waveform information 711 is reference waveform information for generating a drive waveform by the drive waveform generation unit 704. The temperature information 712 is the temperature information inside the inkjet recording device 1 measured by the temperature measuring unit 750, and is referred to when the driving waveform generation unit 704 generates the driving waveform. The correction information 713 is information relating the application time of the intermediate potential and the shift amount of the bias voltage.

The temperature measuring unit 750 is a functional unit that measures the temperature inside the inkjet recording device 1. The temperature measuring unit 750 is realized by, for example, various sensors 130 shown in FIG.

The head drive unit 800 applies the voltage of the drive waveform received from the drive waveform generation unit 704 to the individual electrodes 501 of the recording head 12, and to the common electrode 503 of the recording head 12 based on the command received from the bias voltage command unit 705. It is a functional part that applies a bias voltage. The head drive unit 800 is realized by the recording head driver 210 shown in FIG.

It should be noted that each functional unit included in the image processing unit 600 and the control unit 700 of the inkjet recording device 1 shown in FIG. 11 conceptually shows the function, and is not limited to such a configuration. .. For example, in each of the image processing unit 600 and the control unit 700 shown in FIG. 11, a plurality of functional units shown as independent functional units may be configured as one functional unit. On the other hand, in each of the image processing unit 600 and the control unit 700 shown in FIG. 11, the functions of one functional unit may be divided into a plurality of functions and configured as a plurality of functional units.

(Printing operation of inkjet recording device)
FIG. 18 is a flowchart showing an example of the printing operation of the inkjet recording apparatus according to the embodiment. The flow of the printing operation of the inkjet recording apparatus 1 according to the present embodiment will be described with reference to FIG.

<Step S11>
The input unit 701 of the control unit 700 inputs the image data SD'that has been image-processed by the image processing unit 600. Then, the process proceeds to step S12.

<Step S12>
The drive waveform generation unit 704 of the control unit 700 uses the reference waveform information 711 stored in the storage unit 706 to the individual electrodes 501 of the recording head 12 based on the image data SD'etc. input by the input unit 701. Generates a drive waveform for the applied voltage. Then, the drive waveform generation unit 704 transmits the generated drive waveform to the head drive unit 800. Then, the process proceeds to step S13.

<Step S13>
The bias voltage command unit 705 of the control unit 700 reads out the bias voltage information stored in the storage unit 706, and transmits a command for applying the bias voltage to the common electrode 503 of the recording head 12 to the head drive unit 800. do. Then, the process proceeds to step S14.

<Step S14>
The head drive unit 800 applies the voltage of the drive waveform received from the drive waveform generation unit 704 to the individual electrodes 501 of the recording head 12, and to the common electrode 503 of the recording head 12 based on the command received from the bias voltage command unit 705. Apply a bias voltage. Then, the process proceeds to step S15.

<Step S15>
After the voltage is applied to the individual electrodes 501 and the common electrode 503 by the head drive unit 800, the application time measurement unit 702 of the control unit 700 is driven by the head drive unit 800 to the recording head 12 (individual electrode 501). Of the waveform voltage, the applied time, which is an intermediate potential, is measured (integrated). Then, the process proceeds to step S16.

<Step S16>
The recording head 12 ejects ink from a nozzle by applying a voltage to the individual electrodes 501 and the common electrode 503 by the head drive unit 800, and prints on a recording medium. Then, the process proceeds to step S17.

<Step S17>
When the recording head 12 finishes printing for a predetermined amount (for example, one scan in the main scanning direction), the head drive unit 800 ends applying voltage to the individual electrodes 501 and the common electrode 503. Then, the process proceeds to step S18.

<Step S18>
After the voltage application to the individual electrodes 501 and the common electrode 503 by the head drive unit 800 is completed, the application time measurement unit 702 of the control unit 700 ends the measurement of the intermediate potential application time. The application time measurement unit 702 stores the measured application time of the intermediate potential in, for example, the storage unit 706, and accumulates and measures the application time each time the ink ejection operation is performed by the recording head 12. Then, the process proceeds to step S19.

<Step S19>
The voltage correction unit 703 of the control unit 700 determines whether or not the application time of the intermediate potential measured by the application time measurement unit 702 has reached a predetermined time. For example, the voltage correction unit 703 determines whether or not the application time has reached the correction timing specified in the correction table 901 shown in FIG. When the arrival time of the intermediate potential reaches the predetermined time (step S19: Yes), the process proceeds to step S20, and when the arrival time of the intermediate potential has not reached (step S19: No), the process proceeds to step S21.

<Step S20>
The voltage correction unit 703 estimates the shift amount of the coercive electric field of the electromechanical conversion element 502 from the application time of the intermediate potential, and obtains the shift amount of the bias voltage applied to the common electrode 503 from the shift amount of the coercive electric field. , The bias voltage is corrected by the shift amount. Specifically, the voltage correction unit 703 refers to the correction table 901 stored in the storage unit 706, directly obtains the shift amount of the bias voltage corresponding to the application time of the intermediate potential, and corrects the bias voltage by the shift amount. do. Then, the voltage correction unit 703 stores the corrected bias voltage information in the storage unit 706. Then, the process proceeds to step S21.

<Step S21>
The control unit 700 determines whether or not all the image data SD'input by the input unit 701 has been printed. When printing is completed (step S21: Yes), the printing operation is completed, and when printing is not completed (step S21: No), the process returns to step S11.

By the above steps S11 to S21, the printing operation of the inkjet recording apparatus 1 according to the present embodiment is performed.

As described above, as the electromechanical conversion element 502 is repeatedly driven, the coercive electric field of the electromechanical conversion element 502 shifts, so that the displacement amount fluctuates and the droplet ejection characteristics of the recording head 12 become unstable. On the other hand, in the inkjet recording apparatus 1 according to the present embodiment, the bias voltage applied to the common electrode 503 is corrected based on the shift amount of the coercive electric field of the electromechanical conversion element 502, and the displacement of the electromechanical conversion element 502 is corrected. The amount is stabilized. By correcting the bias voltage in consideration of the shift amount of the coercive electric field, the load of the electromechanical conversion element 502 can be reduced with respect to repeated driving, and the droplet ejection characteristic of the recording head 12 is deteriorated. It can be suppressed.

Further, the specific fluctuation of the electromechanical conversion element 502 becomes remarkable by applying a bias voltage that exceeds the absolute value of the coercive electric field on the negative side, and this fluctuation contributes to the applied cumulative time. Therefore, in the present embodiment, more specifically, the application time of the intermediate potential is measured, and each time the application time reaches a predetermined time, the bias voltage is corrected so as to shift by the amount of the shift of the coercive electric field. It is supposed to be. As a result, it is possible to suppress the occurrence of failures such as cracks in the electromechanical conversion element 502, suppress fluctuations in the characteristics of the electromechanical conversion element 502 over time, and eventually reduce the droplet ejection characteristics of the recording head 12. Can be suppressed.

In the above description, the bias voltage is corrected by focusing on the shift amount of the negative electric field, but the bias voltage is not limited to this, and the bias voltage is corrected based on the shift amount of the positive field. You may do it.

In addition, the correction was performed based on the applied time of the measured intermediate potential, but the correction is not limited to this, and if there is information that can be used as another reference as the timing of the correction, the correction is performed based on it. May be good. For example, instead of the application time of the intermediate potential, the application time of the voltage of the drive waveform, that is, the ON time of the drop control signal shown in FIGS. 13 to 15 may be measured. Alternatively, the correction may be performed based on the number of times the drive waveform is applied. The number of times the drive waveform is applied may be, for example, counting the number of times ink droplets are ejected for each nozzle of the recording head 12 (for each electromechanical conversion element 502).

(Modification 1)
FIG. 19 is a diagram showing an example of a correction table used by the inkjet recording device according to the first modification of the embodiment for correcting the bias voltage. With reference to FIG. 19, the inkjet recording apparatus according to the first modification of the present embodiment will be described focusing on the differences from the inkjet recording apparatus 1 according to the present embodiment.

The voltage correction unit 703 of the control unit 700 of the inkjet recording device according to this modification estimates the shifted coelectric field of the electromechanical conversion element 502 from the application time of the intermediate potential measured by the application time measurement unit 702. The bias voltage is corrected so that the ratio between the coercive electric field and the bias voltage is constant. Specifically, the voltage correction unit 703 refers to the correction information 713 stored in the storage unit 706, directly obtains the shift amount of the bias voltage corresponding to the application time of the intermediate potential, and corrects the bias voltage by the shift amount. Then, the ratio between the coercive electric field and the bias voltage is made constant. However, the voltage correction unit 703 makes the corrected bias voltage a value smaller than the absolute value of the coercive electric field. In this case, the voltage correction unit 703 may store the corrected bias voltage information in the storage unit 706. Further, the correction of the bias voltage applied to the common electrode 503 by the voltage correction unit 703 results in a correction for the applied voltage between the individual electrodes 501 and the common electrode 503.

Here, as an example of the correction information 713, the correction table 902 is shown in FIG. The correction table 902 is information relating the application time of the intermediate potential (corresponding to the correction timing shown in FIG. 19) and the shift amount (correction amount) of the bias voltage so that the ratio between the coercive electric field and the bias voltage becomes constant. Is. In the correction table 902 shown in FIG. 19, for example, when the correction timing (application time of the intermediate potential) is 80,000 [sec], it is shown that the shift amount of the bias voltage is 0.25 [V].

The correction table 902 shown in FIG. 19 is information in a table format, but the information is not limited to this, and if the application time of the intermediate potential and the shift amount of the bias voltage can be managed in relation to each other. The information may be in any format. The bias voltage shift amount specified in the correction table 902 may be, for example, a shift amount from the reference voltage (for example, the initial bias voltage), or a shift amount from the current bias voltage. May be good.

The voltage correction unit 703 is realized by a program executed by the CPU 101 shown in FIG. 9 or by the FPGA 102.

The operation of the other functional blocks of the inkjet recording device according to the present modification is the same as that of the inkjet recording device 1 according to the embodiment.

As described above, in the inkjet recording apparatus according to the present modification, the bias voltage applied to the common electrode 503 is corrected based on the shift amount of the coercive electric field of the electromechanical conversion element 502, and the displacement amount of the electromechanical conversion element 502. Is stabilizing. In this modification, more specifically, the application time of the intermediate potential is measured, and the bias voltage is such that the ratio between the coercive electric field and the bias voltage becomes constant each time the application time reaches a predetermined time. Is to be corrected. As a result, the load of the electromechanical conversion element 502 can be reduced with respect to repeated driving, and the deterioration of the droplet ejection characteristics of the recording head 12 can be suppressed.

(Modification 2)
FIG. 20 is a diagram showing an example of a correction table used by the inkjet recording device according to the second modification of the embodiment for correcting the bias voltage. With reference to FIG. 20, the inkjet recording apparatus according to the second modification of the present embodiment will be described focusing on the differences from the inkjet recording apparatus 1 according to the present embodiment.

The voltage correction unit 703 of the control unit 700 of the inkjet recording device according to this modification estimates the shifted coercive electric field of the electromechanical conversion element 502 from the application time of the intermediate potential measured by the application time measurement unit 702, and counteracts the voltage. The bias voltage is corrected so that the absolute value of the electric field is not exceeded and the discharge speed is maximized. Specifically, the voltage correction unit 703 refers to the correction information 713 stored in the storage unit 706, directly obtains the shift amount of the bias voltage corresponding to the application time of the intermediate potential, and corrects the bias voltage by the shift amount. Then, the discharge speed is maximized within a range that does not exceed the absolute value of the coercive electric field. In this case, the voltage correction unit 703 may store the corrected bias voltage information in the storage unit 706. Further, the correction of the bias voltage applied to the common electrode 503 by the voltage correction unit 703 results in a correction for the applied voltage between the individual electrodes 501 and the common electrode 503.

Here, as an example of the correction information 713, the correction table 903 is shown in FIG. The correction table 903 includes an intermediate potential application time (corresponding to the correction timing shown in FIG. 20) and a bias voltage shift amount (correction) that does not exceed the absolute value of the coercive electric field and maximizes the discharge speed. It is the information associated with the quantity). In the correction table 903 shown in FIG. 20, for example, when the correction timing (application time of the intermediate potential) is 400,000 [sec], it is shown that the shift amount of the bias voltage is 0.1 [V].

The correction table 903 shown in FIG. 20 is information in a table format, but the information is not limited to this, and if the application time of the intermediate potential and the shift amount of the bias voltage can be managed in association with each other. The information may be in any format. The bias voltage shift amount specified in the correction table 903 may be, for example, a shift amount from the reference voltage (for example, the initial bias voltage), or a shift amount from the current bias voltage. May be good.

The voltage correction unit 703 is realized by a program executed by the CPU 101 shown in FIG. 9 or by the FPGA 102.

The operation of the other functional blocks of the inkjet recording device according to the present modification is the same as that of the inkjet recording device 1 according to the embodiment.

As described above, in the inkjet recording apparatus according to the present modification, the bias voltage applied to the common electrode 503 is corrected based on the shift amount of the coercive electric field of the electromechanical conversion element 502, and the displacement amount of the electromechanical conversion element 502. Is stabilizing. In this modification, more specifically, the application time of the intermediate potential is measured, and each time the application time reaches a predetermined time, the absolute value of the coercive electric field is not exceeded and the discharge speed is maximum. The bias voltage is corrected so as to be. As a result, the load of the electromechanical conversion element 502 can be reduced with respect to repeated driving, and the deterioration of the droplet ejection characteristics of the recording head 12 can be suppressed (the ejection speed can be maximized).

(Modification 3)
FIG. 21 is a cross-sectional view of a main part of the recording head according to the third modification of the embodiment. With reference to FIG. 21, the configuration of the recording head 12a according to the third modification of the present embodiment will be described focusing on the differences from the recording head 12 according to the present embodiment.

As shown in FIG. 21, the recording head 12a according to this modification is layered in the order of common electrode 503a, electromechanical conversion element 502, individual electrode 501a, diaphragm 504, pressure chamber substrate 505, and nozzle plate 507 from the upper side. It is configured in.

The individual electrode 501a and the common electrode 503a are electrodes that deform and displace the electromechanical conversion element 502 by applying a voltage to the electromechanical conversion element 502 arranged between them.

The electromechanical conversion element 502 is a piezoelectric element formed between the individual electrodes 501a and the common electrode 503a, and is an element that is deformed and displaced by applying a voltage to both electrodes. As the electromechanical conversion element 502, for example, PZT is used as described above.

As described above, in the recording head 12a according to the present modification, the individual electrodes and the common electrodes are arranged upside down as compared with the recording head 12 according to the embodiment. Even with such a configuration, by applying the voltage of the drive waveform to the individual electrodes described above and applying the bias voltage to the common electrodes, the same effect as that of the inkjet recording apparatus 1 according to the present embodiment can be obtained.

(Manufacturing of recording head 12)
As the recording head 12 of the inkjet recording apparatus according to the above-described embodiment, Modified Example 1 and Modified Example 2, the one produced as follows was used to evaluate the fluctuation of the ejection speed.

SiO ₂ (thickness 600 [nm]), Si (thickness 200 [nm]), SiO ₂ (thickness 100 [nm]), SiN (thickness 150 [nm]), SiO ₂ in 6-inch silicon wear. (Thickness 1300 [nm]), SiN (Thickness 150 [nm]), SiO ₂ (Thickness 100 [nm]), Si (Thickness 200 [nm]), SiO ₂ (Thickness 600 [nm]) The vibrating plate 504 formed in the order of the above was produced. Then, a titanium film (thickness 20 [nm]) was formed as an adhesion film between the individual electrodes 501 and the common electrode 503 by a sputtering apparatus at a film forming temperature of 350 [° C.], and then RTA (Rapid Thermal Anneal: rapid heat treatment) was performed. ) Was thermally oxidized at 750 [° C.], and a platinum film (thickness 160 [nm]) was subsequently formed as a metal film by a sputtering apparatus at a film formation temperature of 400 [° C.].

Next, a solution adjusted to Pb: Ti = 1: 1 as the PbTiO ₃ layer to be the base layer and a solution adjusted to Pb: Zr: Ti = 115: 49: 51 as the electromechanical conversion film were prepared. A film was formed by the spin coating method. For the synthesis of a specific precursor coating solution, lead acetate trihydrate, isopropoxide titanium, and isopropoxide zirconium were used as starting materials. The water of crystallization of lead acetate was dissolved in methoxyethanol and then dehydrated. The amount of lead is excessive for the composition of both chemistry. This is to prevent a decrease in crystallinity due to so-called lead loss during heat treatment. A PZT precursor solution was synthesized by dissolving isopropoxide titanium and isopropoxide zirconium in methoxyethanol, proceeding with an alcohol exchange reaction and an esterification reaction, and mixing with the above-mentioned lead acetate-dissolved methoxyethanol solution. This PZT concentration was set to 0.5 [mol / liter]. The Pt solution was also prepared in the same manner as PZT, and the Pt layer was first formed by spin coating using these solutions, and after the film formation, drying was performed at 120 [° C.], and then the PZT solution was spun. A film was formed by coating, dried at 120 [° C.], and thermally decomposed at 400 [° C.]. After the thermal decomposition treatment of the third layer, a crystallization heat treatment (temperature 730 ° C.) was performed by RTA. At this time, the film thickness of PZT was 240 [nm]. This step was carried out a total of 8 times (24 layers) to obtain a PZT film thickness of about 2 [μm].

Next, an SrRuO ₃ film (thickness 40 [nm]) was formed as an oxide film of the individual electrode 509 and the common electrode 510, and a Pt film (thickness 125 [nm]) was formed as a metal film by sputtering. After that, a photoresist (TSMR8800) manufactured by Tokyo Ohka Kogyo Co., Ltd. was formed by a spin coating method, a resist pattern was formed by ordinary photolithography, and then an ICP (Inductively Coupled Plasma) etching apparatus (manufactured by SAMCO) was used. A pattern as shown in 4 was produced.

Next, as the first insulating protective film 511 _, an _Al2O3 film was formed into a 50 [nm] film using an ALD (Atomic Layer Deposition) method. At this time, as raw materials, TMA (trimethylaluminum) (Sigma-Aldrich) was alternately laminated for Al _, and O3 generated by an ozone generator for O was alternately laminated to proceed with film formation. Then, as shown in FIG. 4, contact holes 509a and 510a were formed by etching, then Al was sputter-deposited as a metal wiring, patterned by etching, and Si ₃ N ₄ was formed as a second insulating protective film 512. A 500 [nm] film was formed by plasma CVD (Chemical Vapor Deposition). The electromechanical conversion element 502 was laid out so as to be lined up in a row of 300 pieces in one chip.

After that, a polarization treatment was performed by a corona charging treatment. A tungsten wire of Φ50 [μm] was used for the corona charging treatment, and a stainless steel grid electrode having an aperture ratio of 60 [%] was used as the grid electrode. The polarization processing conditions include a processing temperature of 80 [° C.], a corona voltage of 9 [kV], a grid voltage of 1.5 [kV], a processing time of 30 [sec], a distance between the corona electrode and the grid electrode of 4 [mm], and a grid electrode. -The distance between the stages was 4 [mm].

Further, the individual electrode pads 509b and the common electrode pads 510b were formed, but the distance between the individual electrode pads 509b was set to 80 [μm]. Then, as shown in FIG. 3, Si on the back surface was etched to form a pressure chamber 506 (width 60 [μm]). At this time, in order to hold the pressure chamber 506, Si etching was performed from the back surface of the wafer after joining the holding substrate 531.

(Evaluation of fluctuation in discharge rate)
The fluctuation evaluation of the discharge speed was carried out by using the recording head 12 manufactured as described above. Specifically, the voltage of the drive waveform described in the above-described embodiment, Modification 1 and Modification 2 is applied to the individual electrodes 501, and the bias voltage is applied to the common electrode 503 to evaluate the fluctuation of the discharge speed. bottom.

In the recording head 12 according to the above-described embodiment, the application time of the intermediate potential is measured, and when a predetermined timing (correction timing) is reached according to the correction table 901 shown in FIG. 17, the coercive electric field is shifted by the amount. It was decided to correct the bias voltage so that it would shift. The initial bias voltage was set to 5 [V], and the environmental temperature was set to 25 [° C]. Under the above conditions, the fluctuation evaluation of the discharge speed of the recording head 12 was carried out.

In the recording head 12 according to the above-mentioned modification 1, when the application time of the intermediate potential is measured and a predetermined timing (correction timing) is reached according to the correction table 902 shown in FIG. 19, the coercive electric field and the bias voltage are obtained. The bias voltage is corrected so that the ratio of is constant. The initial bias voltage was set to 5 [V], and the environmental temperature was set to 25 [° C]. Under the above conditions, the fluctuation evaluation of the discharge speed of the recording head 12 was carried out.

In the recording head 12 according to the above-mentioned modification 2, the application time of the intermediate potential is measured, and when a predetermined timing (correction timing) is reached according to the correction table 903 shown in FIG. 20, the absolute value of the coercive electric field is set. The bias voltage is corrected so that the discharge speed is maximized within a range that does not exceed the limit. The initial bias voltage was set to 5 [V], and the environmental temperature was set to 25 [° C]. Under the above conditions, the fluctuation evaluation of the discharge speed of the recording head 12 was carried out.

Further, as an example of comparison with the above-described embodiment, Modification 1 and Modification 2 (Comparative Example 1), the bias voltage is not corrected and a constant voltage, that is, the initial bias voltage 5 [V] is continuously applied. Then, the fluctuation evaluation of the discharge speed of the recording head 12 was carried out. The environmental temperature was 25 [° C.].

Further, as another example (Comparative Example 2) to be compared with the above-described embodiment, Modified Example 1 and Modified Example 2, the application time of the intermediate potential is measured, and the predetermined timing is determined according to the correction table 904 shown in FIG. When the correction timing) is reached, the bias voltage is lowered by a predetermined shift amount. The initial bias voltage was set to 5 [V], and the environmental temperature was set to 25 [° C]. Under the above conditions, the fluctuation evaluation of the discharge speed of the recording head 12 was carried out.

Here, the correction table 904 shown in FIG. 23 is information relating the application time of the intermediate potential (corresponding to the correction timing shown in FIG. 23) and the shift amount of the bias voltage. In the correction table 904 shown in FIG. 23, for example, when the correction timing (application time of the intermediate potential) is 10000 [sec], it is shown that the shift amount of the bias voltage is 0.4 [V].

FIG. 22 shows the results of evaluation of the rate of change in the discharge rate of the recording head 12 in the above-described embodiment, Modified Example 1, Modified Example 2, Comparative Example 1 and Comparative Example 2. The rate of change in the initial discharge rate is 100 [%].

From the evaluation results of each of the embodiment, the modified example 1 and the modified example 2, it was confirmed that the ejection speed of the droplet was changed at about 100 [%]. From this, it is possible to suppress the fluctuation of the droplet ejection characteristic by correcting the bias value by the method considering the coercive electric field described in the above-described embodiment, Modification 1 and Modification 2. Further, the correction that shifts the bias voltage by the amount of the shift of the coercive electric field as in the embodiment can make the fluctuation range of the discharge speed the smallest. Further, when the bias voltage is corrected so that the ratio of the coercive electric field and the bias voltage becomes constant as in the first embodiment, the discharge speed tends to start to decrease a little as the number of drives increases. Further, when the bias voltage is corrected so that the absolute value of the coercive electric field is not exceeded and the discharge speed is maximized as in the second embodiment, the discharge speed is slightly higher at the initial stage and the number of drives is large. It tends to start to decrease a little as it becomes. This is considered to be based on the characteristics of the electromechanical conversion element 502. That is, it is presumed that the main cause of the shift of the coercive electric field is that the polarization axes of the electromechanical conversion element 502 are aligned in the drive voltage direction. Therefore, when the number of drives increases, that is, when the polarization axes are mostly aligned in the drive voltage direction due to long drive, characteristic fluctuations occur due to other factors other than the shift of the bias voltage, and the discharge rate becomes slightly higher. Although it has decreased, the characteristic fluctuation is sufficiently suppressed.

On the other hand, in Comparative Example 1, the discharge speed is significantly reduced from the initial stage after the start of driving. Further, in Comparative Example 2, the initial discharge speed is kept relatively constant, but the discharge speed fluctuates as the number of drives increases. It is considered that this is because the bias voltage is uniformly shifted by a predetermined shift amount, so that the bias voltage exceeds the coercive electric field.

As described above, in the embodiment, the first modification and the second modification, the bias voltage setting is determined by the characteristics (value of coercive electric field) of the electromechanical conversion element 502. Further, the intermediate potential of the drive waveform was measured to measure the time until the correction timing. As a result, as shown in FIGS. 13 to 16, the drive waveform including a plurality of discharge pulses and the corresponding droplets are measured. Even a waveform that controls the size of the ejected ink droplet by the control signal can be corrected by measuring the application time of the intermediate potential.

1 Inkjet recording device 10 Printing mechanism 11 Carriage 12, 12a Recording head 13 Ink cartridge 21 Paper ejection tray 22 Paper 23 Paper feed cassette 24 Manual feed tray 31 Main guide rod 32 Secondary guide rod 33 Main scanning motor 34 Drive pulley 35 Driven pulley 36 Timing belt 41 Paper feed roller 42 Friction pad 43 Guide member 44 Conveyor roller 45 Conveyor roller 46 Tip roller 47 Sub-scanning motor 48 Imprint receiver 49 Conveyor roller 50 Acceler 51 Paper ejection roller 52 Acceler 53 Guide member 54 Guide member 61 Recovery device 100 Main control board 101 CPU
102 FPGA
103 RAM
104 ROM
105 NVRAM
106 Motor driver 107 Drive waveform generation circuit 111 CPU control unit 112 Memory control unit 113 I2C control unit 114 Sensor processing unit 115 Motor control unit 116 Recording head control unit 130 Various sensors 140 Various motors 200 Head relay board 210 Recording head driver 211 Shift register 212 Latch circuit 213 Gradation decoder 214 Level shifter 215 Analog switch 300 Image processing board 310 Image processing circuit 501, 501a Individual electrode 502 Electromechanical conversion element 503, 503a Common electrode 504 Vibration plate 505 Pressure chamber board 506 Pressure chamber 506a Partition 507 Nozzle plate 508 Nozzle 509 Individual electrode 509a Contact hole 509b Individual electrode pad 510 Common electrode 510a Contact hole 510b Common electrode pad 511 First insulation protective film 512 Second insulation protection film 521 First insulation protection film 522 Second insulation protection film 523 Metal wiring 525 Joint surface step 531 Holding board 600 Image processing unit 601 Interface unit 602 Gradation processing unit 603 Image conversion unit 604 Image data storage unit 700 Control unit 701 Input unit 702 Application time measurement unit 703 Voltage correction unit 704 Drive waveform generation Unit 705 Bias voltage command unit 706 Storage unit 711 Reference waveform information 712 Temperature information 713 Correction information 750 Temperature measurement unit 800 Head drive unit 901 to 904 Correction table 1000 Polarization processing device 1001 Corona electrode 1001a Corona power supply 1002 Grid electrode 1002a Grid power supply 1003 Stage 1011 wafer

Japanese Unexamined Patent Publication No. 2010-194834

Claims (6)

It has a laminated body in which a nozzle plate on which a nozzle is formed, a substrate on which a liquid chamber is formed, and a vibrating plate forming one surface of the liquid chamber are laminated in this order, and further, a common electrode is used to drive the vibrating plate. A control device for a liquid discharge head having an electromechanical conversion element and an individual electrode to which a voltage of a drive waveform for driving the electromechanical conversion element is applied.
The electromechanical conversion element is corrected by correcting the bias voltage applied to the common electrode so as to cancel the fluctuation of the displacement amount of the electromechanical conversion element due to the shift from the coercive electric field in the initial state of the electromechanical conversion element . A voltage correction unit that corrects the applied voltage between the individual electrode and the common electrode for driving the
The applied voltage determined by the voltage of the drive waveform applied to the individual electrode and the bias voltage applied to the common electrode corrected by the voltage correction unit is applied between the individual electrode and the common electrode. The voltage command unit that sends the command to send to the drive unit,
Equipped with
The voltage correction unit is a control device for a liquid discharge head that corrects the bias voltage so that the ratio of the coercive electric field to the bias voltage becomes constant . Further, a measuring unit for measuring the time when the voltage of the driving waveform is applied to the individual electrode by the driving unit is provided.
The control device for a liquid discharge head according to claim 1 , wherein the voltage correction unit corrects the bias voltage at a timing based on the time measured by the measurement unit. The measuring unit integrates the time that is the intermediate potential of the voltage of the driving waveform applied to the individual electrode by the driving unit and measures it as the applied time.
The control device for a liquid discharge head according to claim 2 , wherein the voltage correction unit corrects the bias voltage at a timing based on the application time measured by the measurement unit. A storage unit for storing correction information in which the applied time and the correction amount of the bias voltage are associated with each other is further provided.
The liquid discharge head according to claim 3 , wherein the voltage correction unit corrects the bias voltage by referring to the correction information and using the correction amount corresponding to the application time measured by the measurement unit. Control device. The control device for the liquid discharge head according to any one of claims 1 to 4 .
Based on the command from the voltage command unit of the control device, the drive unit that applies the applied voltage between the individual electrode and the common electrode, and the drive unit.
The liquid ejection head that ejects ink from the nozzle by the applied voltage applied by the driving unit, and the liquid ejection head.
Liquid discharge device with. The liquid discharge device according to claim 5 , wherein the electromechanical conversion element of the liquid discharge head is a piezoelectric element that bends and deforms due to the applied voltage.

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