JP2014177092A - Liquid droplet discharge device and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a temperature distribution of the whole head without making the head larger in size nor higher in cost, and to suppress deterioration in image quality.SOLUTION: It is determined whether a liquid in a pressurized liquid chamber is discharged from a nozzle hole based upon a detected temperature difference of each temperature detection means without performing a liquid droplet discharging operation. When a detected temperature difference of each temperature detection means becomes equal to or larger than a desired temperature difference, a liquid in a common liquid chamber is sent to the pressurized liquid chamber to be discharged from the nozzle hole and the liquid in the pressurized liquid chamber is sucked from the nozzle hole without performing any liquid droplet discharging operation. Then the heated liquid in the pressurized liquid chamber is replaced with an unheated liquid.

Description

  The present invention relates to a droplet discharge device including a droplet discharge head that discharges droplets from nozzle holes, and an image forming apparatus that forms an image by discharging a recording liquid agent onto a medium from the droplet discharge head. .

  This type of droplet discharge apparatus is used as an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a plotter. The image forming apparatus here forms an image on a recording material, but the material of the recording material is not limited to paper, and is a thread, fiber, fabric, leather, metal, plastic, glass, It means an apparatus for forming an image by discharging a liquid onto any recording material such as wood or ceramics. Image formation not only applies an image having a meaning such as a character or a figure to a recording material, but also applies an image having no meaning such as a pattern to the recording material (simply ejects a droplet). ) Also means. The liquid ejected as droplets is not limited to so-called ink, and is not particularly limited as long as it becomes liquid when ejected, and includes, for example, DNA samples, resists, pattern materials, and the like. It is.

  As a driving method of the droplet discharge head in such an image forming apparatus, an electromechanical conversion method using a piezoelectric element composed of a common electrode, a piezoelectric layer, and an individual electrode is mainly used at present. In this droplet discharge head, the bottom portion of the pressurizing fluid chamber is configured by converting the deformation of the piezoelectric element into a pressure change in the pressurizing fluid chamber via a vibration plate constituting the ceiling portion of the pressurizing fluid chamber. Droplets are ejected from nozzle holes provided in the nozzle plate. When the droplet discharge head is driven in this way, the temperature of the head and ink rises due to heat generation of the piezoelectric element, heat generation of the driver IC that performs drive control, and heat generation due to wiring resistance in each wiring.

  In a droplet discharge head having a plurality of nozzle holes, the temperature rise is not the same across the entire nozzle array. Depending on the print data, heat is concentrated in the pressurized liquid chamber that communicates with nozzles that are frequently ejected, and thus a temperature distribution may occur in the head. If there is such a temperature distribution over the entire nozzle array of the droplet discharge head, there is a problem that a difference occurs in the ink discharge characteristics for each nozzle hole, resulting in a decrease in print quality. As a method for solving this problem, among the pressurized liquid chambers having a temperature difference, the ink in the low temperature pressurized liquid chamber is heated by a heating means such as a heater to substantially uniform the temperature between the pressurized liquid chambers. There is a way. However, when the heater is mounted, there is a problem that the cost is increased and the size is increased. A device disclosed in Patent Document 1 is known as a droplet discharge device that substantially equalizes the temperature between pressurized liquid chambers without mounting a heater. In the droplet discharge device of Patent Document 1, a fine drive waveform that is a drive waveform in which liquid is not discharged from a nozzle hole is applied to a piezoelectric element. Thereby, the temperature of the ink in the pressurized liquid chamber can be increased without using the heater and preventing the droplets from being discharged. Therefore, the temperature between the pressurized liquid chambers can be made substantially uniform and the viscosity of the ink in all the pressurized liquid chambers can be made substantially uniform to a desired viscosity without increasing the size of the head and increasing the cost.

  However, in the droplet discharge device of Patent Document 1, when the temperature difference of the ink between the pressurized liquid chambers is large, the desired temperature can be obtained only by stirring the ink in the pressurized liquid chamber using the fine driving waveform. There is a possibility that heating cannot be completed, and there is a problem that the temperature distribution in the entire head cannot be reduced.

  The present invention has been made in view of the above-described problems, and the object thereof is a liquid that can reduce the temperature distribution in the entire head and suppress deterioration in image quality without increasing the size and cost of the head. To provide a droplet discharge device and an image forming apparatus.

  In order to achieve the above object, a first aspect of the present invention provides a common liquid that supplies a plurality of nozzle holes for discharging droplets, a pressurized liquid chamber communicating with each nozzle hole, and a liquid to each pressurized liquid chamber. And a diaphragm having an electromechanical conversion element formed in a part of the chamber and a pressurized liquid chamber, and applying the driving voltage to the electromechanical conversion element to deform the electromechanical conversion element, A plurality of temperature detecting means for detecting a liquid temperature in each of the pressurizing liquid chambers; Based on the detected temperature difference between the liquid discharge means for discharging the liquid in the pressurized liquid chamber from the nozzle hole and the temperature detecting means, it is determined whether or not the liquid in the pressurized liquid chamber is discharged from the nozzle hole. And a drainage hand based on the judgment result of the judgment means and the judgment means. And control means for controlling is characterized in that it comprises a.

  In the present invention, for example, when the detected temperature difference is greater than or equal to a desired temperature difference in the liquid temperature in each pressurized liquid chamber detected by each temperature detecting means, the liquid in the pressurized liquid chamber is discharged from the nozzle hole. In addition, the drainage means is controlled by the control means. Specifically, the liquid in the common liquid chamber is fed to the pressurized liquid chamber, or the liquid in the pressurized liquid chamber is sucked from the nozzle hole. That is, the heated liquid in the pressurized liquid chamber is replaced with an unheated liquid. As a result, the heat of the liquid in the pressurized liquid chamber can be quickly released. Thereby, the temperature of the ink in the pressurized liquid chamber can be lowered in a short time. Therefore, it is possible to reduce the temperature distribution in the entire head in a short time without increasing the size of the head and increasing the cost, and a specific effect is obtained in that deterioration of image quality can be suppressed.

1 is a perspective view illustrating a configuration of an ink jet recording apparatus according to an embodiment. It is a side view of the mechanism part of the inkjet recording device of this embodiment. It is sectional drawing of the droplet discharge head of this embodiment. It is a partial top view of the actuator part of the droplet discharge head of this embodiment. It is process sectional drawing which shows the manufacturing process of the droplet discharge head of this embodiment. It is process sectional drawing which shows the manufacturing process of the droplet discharge head of this embodiment. It is a perspective view showing a droplet discharge head in a state where a common liquid chamber substrate is laminated on a protective substrate. It is a top view of the whole droplet discharge head. It is the figure which showed typically the electrical wiring inside a droplet discharge head. It is the figure which showed typically the inside of a common liquid chamber and a pressurized liquid chamber. 6 is a flowchart showing Example 1 of liquid chamber temperature adjustment processing in the droplet discharge head of the present embodiment. It is the schematic which shows the liquid feeding means using the recovery apparatus which consists of a cap member and a suction pump. 6 is a flowchart showing Example 2 of liquid chamber temperature adjustment processing in the droplet discharge head of the present embodiment. It is a top view of the whole droplet discharge head divided into blocks of ch. It is a wave form diagram which shows a fine drive waveform and a drive waveform. It is a top view which shows the modification of the droplet discharge head of this embodiment.

First, the configuration of an ink jet recording apparatus which is an example of a liquid droplet ejection apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a configuration of an ink jet recording apparatus according to the present embodiment, and FIG. 2 is a side view of a mechanism portion of the ink jet recording apparatus according to the present embodiment.
The ink jet recording apparatus 100 of this embodiment shown in FIGS. 1 and 2 includes a carriage 101 that can move in the main scanning direction inside the apparatus main body. In addition, a droplet discharge head 1 mounted on the carriage 101 and a printing mechanism 103 including an ink cartridge 102 that supplies ink to the droplet discharge head 1 are stored. A paper feed cassette (or a paper feed tray) 104 on which a large number of recording sheets P can be stacked is detachably attached to the lower part of the apparatus main body from the front side. Further, it has a manual feed tray 105 that is opened to manually feed the recording paper P, and takes in the recording paper P fed from the paper feed cassette 104 or the manual feed tray 105. Then, after a required image is recorded by the printing mechanism unit 103, the image is discharged to a discharge tray 106 mounted on the rear side.

  The printing mechanism 103 holds the carriage 101 slidably in the main scanning direction with a main guide rod 107 and a sub guide rod 108 which are guide members horizontally mounted on left and right side plates (not shown). The carriage 101 has a plurality of ink discharge ports (nozzles) for a droplet discharge head 1 for discharging ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (Bk). They are arranged in the sub-scanning direction orthogonal to the main scanning direction. Furthermore, the droplet discharge head 1 is mounted on the carriage 101 with the ink droplet discharge direction facing downward. In addition, each ink cartridge 102 for supplying ink of each color to the droplet discharge head 1 is replaceably mounted on the carriage 101.

  The ink cartridge 102 is provided with an air opening communicating with the atmosphere above, and a supply opening for supplying ink to the droplet discharge head 1 below, and has a porous body filled with ink inside. The ink supplied to the droplet discharge head 1 is maintained at a slight negative pressure by the capillary force of the porous body. Further, although the droplet discharge head is used for each color as the droplet discharge head 1, one droplet discharge head having nozzles for discharging ink droplets of each color may be used.

  Here, the carriage 101 is slidably fitted to the main guide rod 107 on the rear side (downstream side in the paper conveyance direction) and slidable on the front guide rod 108 on the front side (upstream side in the paper conveyance direction). It is placed. In order to move and scan the carriage 101 in the main scanning direction, a timing belt 112 is stretched between a driving pulley 110 and a driven pulley 111 that are rotationally driven by a main scanning motor 109a. The timing belt 112 is fixed to the carriage 101, and the carriage 101 is reciprocally scanned by forward and reverse rotation of the main scanning motor 109a.

  On the other hand, the recording paper P set in the paper feed cassette 104 is conveyed to the lower side of the droplet discharge head 1. For this purpose, a paper feed roller 113 and a friction pad 114 for separating and feeding the recording paper P from the paper feeding cassette 104 and a guide member 115 for guiding the recording paper P are provided. Furthermore, a conveyance roller 116 that reverses and conveys the fed recording paper P, a conveyance roller 117 that is pressed against the circumferential surface of the conveyance roller 116, and a leading edge that defines a feeding angle of the recording paper P from the conveyance roller 116. It has a roller 118. The conveyance roller 116 is rotationally driven via a gear train by the sub-scanning motor 109b.

  In addition, a printing receiving member 119 that is a paper guide member is provided to guide the recording paper P fed from the transport roller 116 below the droplet discharge head 1 in accordance with the moving range of the carriage 101 in the main scanning direction. ing. A conveyance roller 120 and a spur 121 that are rotationally driven to send the recording paper P in the paper discharge direction are provided on the downstream side of the printing receiving member 119 in the paper conveyance direction. Further, a paper discharge roller 123 and a spur 124 for feeding the recording paper P to the paper discharge tray 106, and guide members 125 and 126 for forming a paper discharge path are provided.

  When recording with the inkjet recording apparatus 100, the droplet discharge head 1 is driven in accordance with the image signal while moving the carriage 101, thereby discharging ink onto the stopped recording paper P to record one line. Thereafter, after the recording paper P is conveyed by a predetermined amount, the next line is recorded. Upon receiving a recording end signal or a signal that the trailing edge of the recording paper P reaches the recording area, the recording operation is terminated and the recording paper P is discharged.

  A recovery device 127 for recovering the ejection failure of the droplet ejection head 1 is disposed at a position outside the recording area on the right end side in the movement direction of the carriage 101. Each of the recovery devices 127 includes a cap unit, a suction unit, and a wiping unit (not shown). During printing standby, the carriage 101 is moved to the recovery device 127 side, and the droplet discharge head 1 is capped by the capping unit to keep the discharge port portion in a wet state, thereby preventing discharge failure due to ink drying. Further, by ejecting ink that is not related to recording during recording or the like, the ink viscosity of all the ejection ports is made constant and stable ejection performance is maintained.

  Further, when a discharge failure occurs, the discharge port (nozzle) of the droplet discharge head 1 is sealed with a capping unit, and bubbles and the like are sucked out from the discharge port through the tube with a suction unit. Subsequently, ink, dust or the like adhering to the discharge port surface is removed by wiping the discharge port surface with a wiping means, and the discharge failure is recovered. Further, the sucked ink is discharged to a waste ink reservoir (not shown) installed at the lower part of the main body and absorbed and held by an ink absorber inside the waste ink reservoir.

  As described above, since the ink jet recording apparatus 100 includes the liquid droplet ejection head having the actuator unit, stable ink droplet ejection characteristics can be obtained, and the image quality can be improved.

  FIG. 3 is a cross-sectional view of the droplet discharge head of this embodiment. FIG. 4 is a partial plan view of the actuator portion of the droplet discharge head of this embodiment. The droplet discharge head 1 shown in FIG. 1 mainly has a laminated structure in which a nozzle substrate 10, a liquid chamber substrate 20, a vibration plate 30, and a protective substrate 40 are stacked. Nozzle holes 11 are formed in the nozzle substrate 10 by pressing and polishing a SUS (Steel Use Stainless) substrate having a thickness of 30 to 50 [μm]. The nozzle hole 11 communicates with the pressurized liquid chamber of the liquid chamber substrate. The liquid chamber substrate 20 is an SOI substrate in which silicon is bonded to a silicon substrate via a silicon oxide film. The diaphragm 30 is formed with a silicon oxide film on the surface of the Si layer of the SOI substrate by applying a pyro-oxidation method. On the diaphragm 30, the actuator unit has a multilayer structure of a platinum film that becomes the lower electrode 51 that is a common electrode, a piezoelectric layer (PZT) 52, and a platinum film that becomes the upper electrode 53 that is an individual electrode. Such an actuator portion is formed in a region facing the pressurized liquid chamber 12 formed by etching silicon.

  The lower electrode 51 and the upper electrode 53 are drawn out by the wiring member 54 and are electrically connected to the lower electrode pad portion 57 and the upper electrode pad portion 58, respectively. Further, an interlayer insulating film 55 disposed between the lower electrode 51 and the wiring member 54 and between the upper electrode 53 and the wiring member 54, and a passivation film as a moisture resistant layer for protecting the wiring member 54, respectively. 56 is arranged so as to cover the upper surface and the side surface of the actuator portion. In addition, a diaphragm filter 60 having a plurality of supply holes is provided in a portion of the diaphragm that serves as a flow path for supplying ink from the common liquid chamber of the protective substrate 40 to the pressurized liquid chamber of the liquid chamber substrate 20. . The protective substrate 40 includes a groove serving as an ink flow path as a common liquid chamber, a piezoelectric element protection space for preventing the piezoelectric element from being protected and displaced, and a column for supporting the entire liquid chamber by increasing the rigidity of the flow path partition wall. Is a substrate formed.

Next, the manufacturing method of the droplet discharge head of this embodiment will be described with reference to FIGS. 5 and 6 which are process cross-sectional views showing the manufacturing process.
First, as shown in FIG. 5A, a silicon oxide film 202 is bonded to a surface of a <100> silicon substrate 201 having a thickness of 400 [μm], and silicon is bonded to 2.0 [μm]. An SOI substrate is used. A silicon oxide film of 0.3 [μm] is formed on the surface of the SOI substrate by a pyro oxidation method, and this is used as a diaphragm layer. Thereafter, a platinum (Pt) layer 203 to be a lower electrode of the piezoelectric element is formed on the diaphragm layer by sputtering, and is patterned. Further, as shown in FIG. 5C, a piezoelectric layer 204 is formed by 2 [μm] on the platinum layer 203 serving as a lower electrode by a sol-gel method, and further a platinum (Pt) layer 205 serving as an upper electrode. Is formed to a thickness of 0.1 [μm]. Thereafter, the upper electrode and the piezoelectric layer are patterned by a lithoetch method. As will be described later, a resistance temperature detector as a temperature detecting means is formed at the same time in the patterning process of the platinum layer serving as the upper electrode. This resistance temperature detector can also use the platinum layer of the lower electrode.

  Next, as shown in FIG. 5D, an interlayer insulating film 206 is formed in a thickness of 0.3 [μm] by a plasma CVD (Chemical Vapor Deposition) method, and a via hole 207 for making a wiring contact by a lithoetch method is formed. Form. The interlayer insulating film 206 patterns a conductive portion 208 between a wiring member and an upper electrode to be formed next, a conductive portion 209 to the bypass wiring member, and a through portion 210 that becomes an ink supply hole. Further, as shown in FIG. 5E, an extraction electrode 211 is formed of an aluminum material. Since the lead electrode 211 receives stress due to vibration of the diaphragm driven by the piezoelectric body, the lead electrode 211 is made of a soft aluminum material and has a thickness of about 1 [μm] so as not to be disconnected by vibration.

  Next, as shown in FIG. 5F, a silicon nitride film 212 of 2 [μm] is formed by plasma CVD as a passivation film for protecting the aluminum wiring and patterned. Then, the portion 213 to be the ink supply hole of the diaphragm is etched in advance. Rather than simply opening the ink supply holes, a plurality of supply holes smaller than the inner diameter of the nozzle holes are formed in the member of the diaphragm. By simply changing the mask for forming the supply hole, the manufacturing process is the same as that for forming a large opening. Therefore, a diaphragm filter that prevents foreign matter from entering can be manufactured without increasing costs. In order to form the opening of this embodiment, it is convenient to use inductively coupled plasmas (ICP) dry etching which has no directivity for processing. Thereafter, as shown in FIG. 6A, gold is laminated by a plating method to form the upper electrode pad portion 214 and the lower electrode pad portion 215 at the same time. By forming the upper electrode pad portion 214 and the lower electrode pad portion 215 with gold, electrical connection with a driver IC (not shown) is connected by low-temperature wire bonding. Also, gold has a low resistance value, and has a great effect of lowering the resistance values of the upper electrode and the lower electrode. The driver IC (not shown) is mounted not by wire bonding but by flip chip mounting, and the driver IC chip (not shown) is flip-chip mounted on the pad portion. Furthermore, the lower electrode pad portion 215 may be formed separately from the upper electrode pad portion 214 and the formation process may be performed, and copper, aluminum, or the like may be used as a material for the pad portion. In this case, the upper electrode pad part 214 that is not protected from the outside may require a protective layer that protects against corrosion.

  Thereafter, as shown in FIG. 6B, a protective substrate 216 in which a column is separately formed on a glass substrate by blasting is bonded to the liquid chamber substrate side, and the liquid chamber substrate is protected as shown in FIG. 6C. The surface opposite to the substrate bonding surface is polished to a desired thickness. The protective substrate 216 may be a silicon substrate obtained by processing a recess by a lithoetch method, or may be a silicon substrate processed by wet etching using an alkaline etching solution such as TMAH or KOH. Further, it may be a molded part such as a resin mold or a metal injection mold. Further, when the driver circuit is integrally formed on the actuator substrate, an oxide film formed by a pyro-oxidation method is formed by a LOCOS (Local Oxidation of Silicon) oxidation method, and a region for forming the oxide film is selected. Can also be formed on the same substrate. Thereafter, as shown in FIG. 6C, concave portions to be the pressure liquid chamber 218, the fluid resistance portion 219, and the ink supply portion 220 are formed on the opposite surface of the liquid chamber substrate 217, which is a silicon substrate, by ICP dry etching. Finally, as shown in FIG. 6 (d), the nozzle substrate 222 having the nozzle holes 221 formed thereon is bonded to the flow channel partition surface of the liquid chamber substrate 217, and the aluminum connected to the upper and lower electrodes of the piezoelectric element. A droplet discharge head is completed by connecting the wiring portion to the drive circuit. The nozzle substrate is separately manufactured by pressing and polishing a SUS substrate having a thickness of 30 to 50 [μm].

  FIG. 7 is a perspective view showing a droplet discharge head in a state where a common liquid chamber substrate is laminated on a protective substrate. In the liquid droplet ejection head 300 shown in the figure, the nozzle hole row has a four-row configuration. The common liquid chamber substrate 301 is manufactured by pressing a SUS plate. An ink supply path is formed on the common liquid chamber substrate 301 by joining a damper member and a frame member (not shown). In the common liquid chamber substrate 301, the installation position of the supply port 302 into which ink flows is shown. The four common liquid chambers 303 each have a gradually decreasing cross-sectional area toward the end of the pressurizing liquid chamber row, thereby ensuring the ink flow rate at the time of filling. From the ink flow, in the common liquid chamber 303, the location of the supply port 302 is upstream, and the location of the end of the pressurized liquid chamber row is downstream. The connection portion 304 side with the external circuit is downstream of the common liquid chamber 303.

  FIG. 8 is a plan view of the entire droplet discharge head, and FIG. 9 schematically shows electrical wiring inside the droplet discharge head. In the liquid droplet ejection head shown in FIGS. 8 and 9, external connection pad portions 308 are produced for the individual wiring 307 drawn from the upper electrode 306 of each piezoelectric element 305, and the driver IC 309 is directly flip-chip mounted. . The driver IC 309 connects two rows in series, and the driver IC 309 controls the piezoelectric elements 305 on both sides. When a pressurized liquid chamber is arranged at a high density with a thin-film piezo-type droplet discharge head, the electrical wiring is also high in density, and it is difficult to take out from the pad portion that becomes a three-dimensional wiring. Flip chip mounting is advantageous for such high-density wiring, but since the driver IC 309 is in close contact with the liquid chamber substrate 310, the heat generated by the driver IC 309 is easily transmitted to the ink in the pressurized liquid chamber. In the liquid droplet ejection head shown in FIGS. 8 and 9, temperature measuring resistors 311a, 311b, and 311c are provided in the head as three temperature detecting means. The temperature measuring resistor 311a is installed near the ink supply port (upstream) in the common liquid chamber, and the temperature measuring resistors 311b and 311c are installed at both ends (downstream) in the common liquid chamber. As described above, the resistance temperature detector 311 was manufactured at the same time using the process of forming the upper electrode. Costs can be reduced because only the mask pattern needs to be changed.

  As described above, in a droplet discharge head in which the ch of the piezoelectric element (ch represents the entire configuration of the droplet discharge head) is increased in density, depending on the discharge data, if the ch of the driven piezoelectric element is biased, the heat generation location Is biased, and the temperature distribution in the droplet discharge head is increased. Ink is supplied through the flow path of the common liquid chamber and the protective substrate, but the warmed ink flows along the flow line of the ink, so that even when driven uniformly, it is downstream of the common liquid chamber. The temperature rise on the side increases. Further, it was found that the external connection pad portion 308 and the individual wiring 307, which are external connection portions, also serve as heat generation sources, and the temperature rise is further increased downstream on the power supply side.

  Therefore, when three temperature measuring resistors 311a, 311b, 311c are provided in the droplet discharge head and the difference between the detected temperatures becomes equal to or higher than a predetermined temperature, printing is interrupted and the inside of the pressurized liquid chamber is stopped. Deliver liquid. Sending the liquid heated by the head temperature rise and discharging it from the pressurizing liquid chamber is very effective for radiating the temperature of the pressurizing liquid chamber. By this heat dissipation treatment, the temperature in the head can be made uniform because it approaches the state before the head temperature rises. In particular, as described above, the temperature distribution in the head tends to increase the downstream temperature along the streamline of the common liquid chamber. As shown in FIG. 10, by providing a dummy liquid chamber 322 at the downstream end of the common liquid chamber 321, the liquid of the common liquid chamber 321 is discharged from the nozzle hole of the dummy liquid chamber 322 by liquid feeding by suction or pressurization. The heated liquid is discharged. From the supply port 323, an unheated liquid flows through the common liquid chamber 321 to equalize the temperature of the ink in the common liquid chamber 321 and efficiently equalize the temperature in the head. Specifically, dummy liquid chambers 322 are provided on both ends of the row of pressurized liquid chambers 324, and the diaphragm filter 325 and a fluid resistance portion (not shown) are not provided in the dummy liquid chamber 322. For this reason, since the fluid resistance value is small, the liquid in the common liquid chamber 321 is easily discharged by pressurization or suction force.

  FIG. 11 is a flowchart showing Example 1 of the cooling sequence in the droplet discharge head of this embodiment. In FIG. 10, when a recording command is received, preparation for printing is performed as usual (step S101). Preparation for printing includes not only the removal of the head from the cap member but also the ejection before printing in which the thickened ink is ejected to the idle ejection receptacle and removed. Depending on the elapsed time of capping, etc., there may be a case where a maintenance process for removing the thickened ink is performed by the suction mechanism, but these are included. After the print preparation, the drive waveform is usually selected based on the print mode (plain paper high speed, plain paper image quality, glossy paper, etc.) and the detected temperature. A plurality of resistance thermometers are provided, and it is determined whether the temperature difference between the detected temperatures of the resistance thermometers is within a predetermined temperature (steps S102 and S103). In this embodiment, three temperature measuring resistors are provided as temperature detecting means, and it is determined whether the temperature difference between the three detected temperatures is within 5 [° C.]. As the temperature compensation, the drive waveform is switched at 2 [° C.], but if the liquid is sent frequently, the liquid consumption will be accelerated, so the predetermined temperature of 5 [° C.] for stopping the printing and sending the liquid is set wider. This is the reference temperature.

  When the temperature difference between the detected temperatures of the temperature sensors is within a predetermined temperature, the drive waveform is selected with reference to the average value of the detected temperatures, and the printing operation (ejection operation) is performed according to the image data with the selected drive waveform ( Step S104: YES, steps S105 and S106). In this embodiment, the printing operation is performed in units of one page. After printing one page, the process returns to step S102 for temperature detection, and the detected temperature difference (temperature distribution in the head) is determined and the drive waveform is selected. Although printing is performed in units of one page (the drive waveform is not changed during one page), the print unit may be changed to 1 scan, and the temperature distribution in the head may be checked every scan. If the temperature difference between the detected temperatures of each resistance temperature detector exceeds a predetermined temperature difference, it is determined that the temperature distribution in the head is large, the printing operation is interrupted, and the common liquid chamber and the pressurized liquid chamber are The liquid is fed and discharged (step S104: NO, step S108).

  As shown in FIG. 12, the liquid feeding means of the present embodiment diverts a recovery device 404 including a cap member 402 and a suction pump 403 provided in a normal droplet discharge head 400. When discharging from the nozzle hole in this way, printing is stopped by the head control unit 411 based on a control signal from the print control unit 406, and a cleaning mode for the cooling sequence is selected by the cleaning mode selection unit 407. Then, the suction control pump 403 is driven by the cleaning control means 408 via the pump control means 410, and the ink in the head covered with the cap member 402 is sucked and discharged to the drain tank 405. Since the meniscus is not maintained, it goes without saying that a meniscus is formed in the nozzle hole by wiping in order to make it possible to discharge after feeding. Since the liquid feeding process and wiping are also effective for discharging bubbles and re-forming the meniscus, it is possible to fundamentally reset a partial temperature increase caused by driving without discharging droplets. If the temperature distribution in the head does not fall within the predetermined temperature difference even after performing the liquid feeding process, the liquid feeding process is performed again. However, if the temperature distribution does not fall within the predetermined temperature difference even after a few implementations, there is a high possibility that an abnormal state has occurred, and the process proceeds to error processing, such as displaying an error and stopping. In this embodiment, the liquid is sucked from the nozzle hole and fed by the recovery device 404, but a pressurizing means may be separately provided upstream from the common liquid chamber, and the liquid may be fed under pressure. In addition, the liquid supply is not limited to being discharged from the nozzle, and the liquid may be circulated in the circulation type common liquid chamber. Furthermore, when the pressurized liquid chamber is a circulation type, it may be circulated from the common liquid chamber via the pressurized liquid chamber. This circulation type droplet discharge head is circulated for the purpose of improving the bubble discharge performance, but it is not necessarily circulated by detecting the temperature difference in the head.

  If the printing speed is slow, the temperature distribution in the head is unlikely to occur. However, printing of image data with extremely ubiquitous nozzle holes, such as the occurrence of temperature distribution in the head itself, is rare. What is set is that the productivity of printing as a printer is lowered. Therefore, in the case of extreme image data as in the present embodiment, it is possible to ensure the productivity as a printer by performing the equalization process. According to the present invention, productivity can be ensured, and the difference in droplet velocity and droplet volume caused by the difference in ink temperature due to the temperature distribution in the head can be suppressed. Problems such as nozzle down can be suppressed. In this embodiment, the number of resistance thermometers is three, but the number of resistance thermometers is not limited to this.

  FIG. 13 is a flowchart showing Example 2 of the cooling sequence in the droplet discharge head of this embodiment. In the figure, when a recording command is received in the figure, the above-described printing preparation is performed as usual (step S201). After the print preparation, the drive waveform is usually selected based on the print mode (plain paper high speed, plain paper image quality, glossy paper, etc.) and the detected temperature. A plurality of resistance temperature detectors are provided, and it is determined whether the temperature difference T of the detected temperatures of each resistance temperature detector is within a predetermined temperature ΔT1 = 2 [° C.] or within a predetermined temperature ΔT2 = 5 [° C.] (step S102). , S103). In this embodiment, three resistance temperature detectors are provided, and when the temperature difference T between the detected temperatures of the three resistance temperature detectors is equal to or greater than ΔT1 = 2 [° C.] and less than ΔT2 = 5 [° C.], printing is performed. Is stopped, and a fine driving waveform that is a driving waveform that does not eject droplets is applied to a low temperature portion to heat (step S104: NO, step S208: YES, step S109). Thereby, the temperature in the head is equalized. When the temperature difference T of the detection temperature of the resistance temperature detector is equal to or greater than the predetermined temperature difference ΔT2 = 5 [° C.], the temperature difference in the head is large, and it takes time to equalize the heating by fine driving. The liquid feeding process is performed. In the same manner as in the first embodiment, the liquid feeding process is performed using a cap member and a recovery device for a suction pump. Thereby, even when the temperature difference in the head is large, uniformization can be achieved quickly.

  Note that the predetermined temperature difference ΔT1 = 2 [° C.] or more is set in the case of the droplet discharge head of this embodiment when the droplet is discharged within the same drive waveform and the droplet speed is within 2 [° C.]. This is because it has been confirmed that the drop volume is within the allowable range. Actually, the drive waveform prepared for temperature compensation is switched in two steps. In this embodiment, as shown in FIG. 14, the ch of the droplet discharge head is divided into three blocks for processing according to the three resistance temperature detectors. In the case of using two resistance temperature detectors, it is described in a later-described modification. If the number of resistance temperature detectors is increased, the ch of the droplet discharge head may be blocked in a region corresponding to the resistance temperature detector. The temperature equalization processing in the head may be performed in the order of the detected temperatures, and intermediate processing may be performed, for example, by changing the frequency of fine driving stepwise from the temperature difference. Note that before resuming printing, the nozzles of the entire head are once ejected to discharge the thickened ink, and then printing is performed.

  In addition, it is suspected that the temperature difference in the head becomes large, and it is suspected that the temperature has risen partially due to insufficient heat radiation due to ejection failure such as bubble entrainment, but the liquid in the pressurized liquid chamber is also sent as in this example. The liquid treatment is also effective for bubble discharge and meniscus re-formation. As a result, it is possible to fundamentally reset a partial temperature rise due to driving without discharging droplets. Further, in the equalizing process by fine driving when the temperature difference T of the temperature sensing resistor in the head is not less than the predetermined temperature difference ΔT1 = 2 [° C.] and less than the predetermined temperature difference ΔT2 = 5 [° C.] There is a case of the above-described thin film piezo type droplet discharge head. In this case, charging / discharging to the piezo is directly related to power consumption (heat generation amount) in the driver IC. For this reason, the fine driving with a small inclination and a large voltage value as shown in FIG. 15B generates more heat from the driver IC than the fine driving with a small voltage as shown in FIG. FIG. 15C shows a discharge waveform as a reference. Therefore, when the temperature is raised by heat generated by the driver IC and it is desired to make it uniform quickly, the fine drive waveform has a small inclination (inevitably deviating from the liquid chamber resonance) as shown in FIG. It is preferable to use a large fine drive waveform.

  FIG. 16 is a plan view showing a modification of the droplet discharge head of this embodiment. In this modification, a temperature measuring resistor 311d as temperature detecting means is provided in the upstream portion near the ink supply port, and a temperature measuring resistor 311e is provided in the downstream portion on the power supply side. In order to accurately measure the temperature distribution (temperature gradient) in the head, it is preferable to increase the number of resistance thermometers. However, because the head area increases due to the routing of wiring and the increase in the number of pads, it is small. This is not preferable from the viewpoint of cost reduction and cost reduction. In order to measure the temperature distribution in the head (at least the temperature gradient), at least two resistance temperature detectors are required. The arrangement of the two resistance temperature detectors is preferably upstream of the ink supply streamline, that is, near the supply port, and downstream of the power supply side, that is, near the end of the common liquid chamber on the external wiring pad side. Since the head generates heat by driving, the temperature of the head flow path is higher than that of the ink, and the ink is stored while passing through it. For this reason, the longer the streamline, the higher the head temperature.

  Furthermore, in such a high-density head, heat generated in the wiring and the externally connected power supply path itself cannot be ignored. For this reason, the common liquid chamber end on the power supply side has a high rate of temperature rise in this head. It has been confirmed that the temperature rise in this part is the largest when driven uniformly. Conversely, since new ink flows in the vicinity of the ink supply port, there is little heat storage of the ink, and the temperature does not easily rise. In other words, since the temperature difference stochastically becomes the largest in the upstream portion near the ink supply port and the downstream portion on the power supply side, the number of temperature measuring resistors is reduced to reduce the temperature distribution in the head ( This arrangement is preferred for detecting (temperature gradient). Since it is necessary to block ch, it is preferable that the temperature measuring resistor in the vicinity of the supply port (upstream) is provided at a position slightly moved from the supply port to the opposite side of the power supply unit.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
(Aspect 1)
A plurality of temperature detecting means for detecting the liquid temperature in each pressurized liquid chamber, a drain means for discharging the liquid in the pressurized liquid chamber from the nozzle hole, and a pressurized liquid based on the detected temperature difference between each temperature detecting means A determination unit that determines whether or not to discharge the liquid in the chamber from the nozzle hole, and a control unit that controls the drainage unit based on the determination result of the determination unit. According to this, as described in Example 1 of the above embodiment, when the detected temperature difference of each temperature detecting means such as the resistance temperature detectors 311a to 311e becomes equal to or larger than the desired temperature difference, the droplet discharge The liquid in the pressurized liquid chamber is discharged from the nozzle hole without moving. Specifically, the liquid in the common liquid chamber is fed to the pressurized liquid chamber, or the liquid in the pressurized liquid chamber is sucked from the nozzle hole. That is, the heated liquid in the pressurized liquid chamber is replaced with an unheated liquid. As a result, the heat of the liquid in the pressurized liquid chamber can be quickly released. Thereby, the temperature of the ink in the pressurized liquid chamber can be lowered in a short time. Therefore, the temperature distribution in the entire head can be reduced in a short time without increasing the size of the head and increasing the cost, and image deterioration can be prevented.
(Aspect 2)
In (Aspect 1), when the detected temperature difference between the temperature detection temperatures is larger than the predetermined first temperature difference ΔT1 and smaller than the predetermined second temperature difference ΔT2 (> ΔT1), the droplet discharge is stopped. If the detected temperature difference is larger than the predetermined second temperature difference ΔT2 by applying a voltage of a driving waveform that does not discharge droplets to the pressurized liquid chamber having a low temperature to stir the liquid in the pressurized liquid chamber, Perform a cooling sequence. According to this, as explained in Example 2 of the above embodiment, the temperature in the head is made uniform by heating by fine driving according to the degree of the temperature difference in the head, and the temperature in the head by liquid feeding. By separating the case where the difference is equalized, it can be recovered quickly.
(Aspect 3)
In (Aspect 1) or (Aspect 2), the temperature detecting means is located at a position corresponding to upstream and downstream in the liquid flow line of the common liquid chamber in each pressurized liquid chamber to which a voltage having a common driving waveform is applied. Is provided. According to this, as described in Example 2 of the above embodiment, the ink heated by the driving operation flows into the common liquid chamber and the temperature distribution is likely to occur. For this reason, in order to detect a temperature difference in the head, it is preferable to provide temperature detection means such as resistance temperature detectors 311a to 311e along the flow line of the common liquid chamber.
(Aspect 4)
In (Aspect 1) or (Aspect 2), the drainage means includes a cap member that covers the head portion, and a suction pump 403 that sucks the liquid in the pressurized liquid chamber through the cap member 402 and the nozzle hole. According to this, as described in the above embodiment, an additional configuration is not required by diverting the recovery device including the cap member 402 and the suction pump 403 provided in the normal device. Up can be suppressed.
(Aspect 5)
In (Aspect 1) or (Aspect 2), the supply port for supplying the liquid to the common liquid chamber is the upstream side, and a dummy liquid chamber smaller than the fluid resistance of the pressurized liquid chamber is provided at the downstream end of the common liquid chamber. When the cooling sequence is formed, the liquid in the common liquid chamber is discharged from the nozzle hole of the dummy liquid chamber. According to this, as described in the above embodiment, it is easy to discharge the liquid downstream of the common liquid chamber, which is likely to rise in temperature, from the nozzle hole of the dummy liquid chamber, and the temperature of the common liquid chamber can be efficiently and quickly adjusted. It can be made uniform.
(Aspect 6)
In (Aspect 1) or (Aspect 2), the temperature detection means is provided at least on the power supply wiring side. According to this, as described in the above embodiment, the power supply wiring is also a heat generation source, and therefore, it is provided on the downstream side where the wiring is concentrated rather than the upstream side where there are few wirings. The temperature difference in the head can be detected with high accuracy.
(Aspect 7)
In (Aspect 1), the electromechanical conversion element is a piezoelectric element having a laminated structure including a piezoelectric layer fired with an electrode layer sandwiched on a diaphragm. According to this, as described in the above embodiment, since the so-called thin-film piezo-type electromechanical conversion element has a large electric field strength and strain, the element itself easily generates heat and a temperature distribution is easily generated in the head. For this reason, it is effective to reduce the temperature distribution by discharging the liquid in the pressurized liquid chamber from the nozzle hole by the drainage means.
(Aspect 8)
In (Aspect 7), the temperature detecting means is formed by patterning an electrode layer sandwiching the piezoelectric layer or a part of the electrode layer. As described in the above embodiment, the upper electrode layer or the lower electrode layer in the so-called thin film piezoelectric electromechanical conversion element forms a noble metal layer such as platinum. By patterning this noble metal layer, it becomes possible to form a resistance temperature detector represented by a change in resistance value due to the temperature of the platinum resistor. Thereby, the temperature detection means can be formed without increasing the number of processes.
(Aspect 9)
In (Aspect 1), at least one of the determination unit and the control unit is flip-chip mounted on the substrate on which the electromechanical conversion element is formed. According to this, as described in the above embodiment, since the heat generation of the driver IC causes the temperature distribution in the head, the temperature distribution is reduced by discharging the liquid in the pressurized liquid chamber from the nozzle hole. It is effective for.
(Aspect 10)
An image is formed by discharging a recording liquid onto a medium by a droplet discharge head provided in any of the droplet discharge apparatuses according to (Aspect 1) to (Aspect 9). According to this, as described in the above embodiment, the discharge characteristics are excellent and stable image formation can be performed.

300 Liquid droplet ejection head 301 Common liquid chamber substrate 302 Supply port 303 Common liquid chamber 304 Connection unit 305 Piezoelectric element 306 Upper electrode 307 Individual wiring 308 External connection pad unit 309 Driver IC
310 Liquid chamber substrate 311a Resistance temperature detector 311b Resistance temperature detector 311c Resistance temperature detector 311d Resistance temperature detector 311e Resistance temperature detector 321 Common liquid chamber 322 Dummy liquid chamber 323 Supply port 324 Pressure liquid chamber 325 Vibration plate filter 400 Droplet discharge head 401 Ink tank 402 Cap member 403 Suction pump 404 Recovery device 405 Drain tank 406 Print control means 407 Cleaning mode selection means 408 Cleaning control means 409 CL command detection means 410 Pump control means 411 Head control means

JP 2009-183866 A

Claims (10)

A plurality of nozzle holes for discharging droplets, a pressurized liquid chamber communicating with each nozzle hole, a common liquid chamber for supplying liquid to each pressurized liquid chamber, and an electric machine in a part of the pressurized liquid chamber A pressure plate configured to form a diaphragm including a conversion element, and to apply a driving voltage to the electromechanical conversion element to deform the electromechanical conversion element to change the pressure in the pressurized liquid chamber through the vibration plate; In a droplet discharge apparatus equipped with a droplet discharge head having
A plurality of temperature detecting means for detecting a liquid temperature in each pressurized liquid chamber;
Drainage means for discharging the liquid in the pressurized liquid chamber from the nozzle hole;
Determining means for determining whether or not to discharge the liquid in the pressurized liquid chamber from the nozzle hole based on the detected temperature difference between the temperature detecting means;
Control means for controlling the drainage means based on the judgment result of the judgment means;
A droplet discharge apparatus comprising: The droplet discharge device according to claim 1,
When the detected temperature difference is larger than the predetermined first temperature difference ΔT1 and smaller than the predetermined second temperature difference ΔT2 (> ΔT1), the driving is performed so as not to discharge droplets into the pressurized liquid chamber having a low temperature. When the voltage in the waveform is applied to stir the liquid in the pressurized liquid chamber and the detected temperature difference is larger than a predetermined second temperature difference ΔT2, the liquid in the pressurized liquid chamber is caused to flow by the draining means. A droplet discharge device that discharges from the nozzle hole. The liquid droplet ejection apparatus according to claim 1 or 2,
The temperature detecting means is provided in positions corresponding to upstream and downstream in a flow line of liquid in the common liquid chamber in each of the pressurized liquid chambers to which a voltage having a common driving waveform is applied. Droplet discharge device. The liquid droplet ejection apparatus according to claim 1 or 2,
The liquid discharge device includes a cap member that covers a head portion, and a suction pump that sucks the liquid in the pressurized liquid chamber through the cap member and the nozzle hole. The liquid droplet ejection apparatus according to claim 1 or 2,
A dummy liquid chamber having a fluid resistance value smaller than that of the pressurized liquid chamber is formed at the downstream end of the common liquid chamber, the supply port supplying the liquid to the common liquid chamber being upstream, and the draining means The liquid discharge apparatus according to claim 1, wherein the liquid in the common liquid chamber is discharged from a nozzle hole in the dummy liquid chamber. The liquid droplet ejection apparatus according to claim 1 or 2,
The temperature detecting means is provided at least on the power supply wiring side. The droplet discharge device according to claim 1,
The electro-mechanical conversion element is a piezoelectric element having a laminated structure including a piezoelectric layer fired with an electrode layer sandwiched on the diaphragm. In the droplet discharge device according to claim 7,
The droplet detecting apparatus, wherein the temperature detecting means is formed by patterning an electrode layer or a part of the electrode layer sandwiching a piezoelectric layer. The droplet discharge device according to claim 1,
At least one of the determination unit and the control unit is flip-chip mounted on a substrate on which the electromechanical conversion element is formed.   An image forming apparatus, wherein a recording liquid agent is ejected onto a medium by a liquid droplet ejection head provided in the liquid droplet ejection apparatus according to claim 1.

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