JP2013116590A - Liquid droplet ejection head and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid droplet ejection head with a high joining reliability by decreasing the nozzle down caused by breakage of a filter pillar.SOLUTION: In a liquid droplet ejection head 20 that has a plurality of nozzles 21a that eject the droplets; a pressurized liquid chamber 22 that communicates to each nozzle 21a; a driving means that pressurizes the liquid in the pressurized liquid chamber 22; and an ink supply passage 24 that supplies the liquid to each of a plurality of pressurized liquid chambers 22 respectively, wherein the ink supply passage 24 has at least one pillar-shaped projection 36a as a filter 36 for removal of the foreign body, the length of the pillar-shaped projection 36a is formed shorter than the height of the pressurized liquid chamber 22.

Description

  The present invention relates to a droplet discharge head that discharges a liquid such as an ink droplet from a hole such as a nozzle hole.

  An inkjet head in an inkjet recording apparatus used as an image forming apparatus such as a printer, a facsimile machine, a copying apparatus, or a plotter includes a nozzle that ejects ink droplets, a pressurized liquid chamber that communicates with the nozzle, Actuator means for generating energy for pressurizing the ink, and driving the actuator means to pressurize the ink in the pressurized liquid chamber and eject ink droplets from the nozzle, only when recording is required Ink-on-demand systems that eject ink droplets are the mainstream, and are roughly classified into several systems depending on the type of actuator means for ejecting ink droplets.

  For example, as described in “Patent Document 1”, a part of the wall of the liquid chamber is formed as a thin diaphragm, and a piezoelectric element as an electromechanical conversion element is arranged corresponding to this, and is generated when a voltage is applied. Piezo type that discharges ink droplets by changing the pressure in the pressurized liquid chamber by deforming the diaphragm by the deformation of the piezoelectric element, and the heating element is placed inside the pressurized liquid chamber to generate heat by energization A bubble jet (registered trademark) system in which bubbles are generated by heating the body and ink droplets are ejected by the pressure of the bubbles is generally well known. In addition to these, as described in, for example, “Patent Document 2”, a diaphragm that forms the wall surface of the pressurized liquid chamber, and an individual electrode outside the pressurized liquid chamber that is disposed to face the diaphragm. Ink droplets are ejected from the nozzles by changing the pressure / volume in the pressurized liquid chamber by deforming the diaphragm by an electrostatic force generated by applying an electric field between the diaphragm and the electrode. An electrostatic type has been proposed.

  Further, in the piezoelectric type, those using a longitudinal vibration mode piezoelectric actuator that expands and contracts in the axial direction of the piezoelectric element and those using a flexural vibration mode piezoelectric actuator are put into practical use. In the former, the volume of the pressurized liquid chamber can be changed by bringing the end of the piezoelectric element into contact with the diaphragm of the ink jet surface that discharges, and a head suitable for high-density printing can be manufactured. The manufacturing process is complicated because it requires a difficult process of dividing the element into a comb-teeth shape in accordance with the arrangement pitch of the nozzle openings and an operation for positioning and fixing the divided piezoelectric element in the pressurized liquid chamber. There's a problem. On the other hand, in the latter case, a piezoelectric element can be formed on the diaphragm by a relatively simple process of attaching a green sheet of piezoelectric material in accordance with the shape of the pressurized liquid chamber and firing it. There is a problem that a certain amount of area is required in order to use vibration, and that high-density arrangement is difficult.

  In order to eliminate the inconvenience of the latter recording head, for example, in “Patent Document 3”, a uniform piezoelectric material layer is formed over the entire surface of the vibration plate by a film forming technique, and this piezoelectric material layer is formed into a pressurized liquid by a lithography method. A device in which a piezoelectric element is formed so as to be separated into shapes corresponding to chambers and independent for each pressurized liquid chamber has been proposed. This eliminates the need to attach the piezoelectric element to the diaphragm, and not only can the piezoelectric element be created by a precise and simple technique called a lithography method, but also the piezoelectric element can be reduced in thickness and driven at high speed. There is an advantage that it becomes possible.

  By the way, regardless of the driving method, the ink jet head is composed of a nozzle formed with a size of several tens of μm and a pressurized liquid chamber, so that the entry of minute foreign matter clogs the nozzle and causes discharge failure. Become. Ink jet heads are required to increase the number of nozzles in response to the recent increase in speed, and accordingly, there is an increasing need to improve foreign matter removing means for removing foreign matters that cause ejection defects. Conventionally, a configuration has been adopted in which a filter is provided in an ink supply system for supplying ink from an ink cartridge to a nozzle to remove foreign matters and bubbles. However, since fine foreign matters floating in the air also become a problem, it is not easy to remove foreign matters mixed in the inkjet head assembly process or the ink supply path assembly process. In order to prevent contamination by foreign matter, it is preferable to install the filter as soon as possible in a place as close to the inkjet head as possible.

  Therefore, several inkjet heads having a filter function in a part of the component parts have been proposed. For example, in “Patent Document 4”, the filter column is placed in the flow path for the purpose of filtering foreign substances and obtaining a desired acoustic impedance. The technique to form in is disclosed. In addition, “Patent Document 5” discloses an ink jet head in which columnar protrusions are formed by etching in a common liquid chamber and used as a filter for the purpose of reducing the size of the head and reducing the number of parts.

However, in recent years, the liquid chamber width of the pressurized liquid chamber tends to be narrow and the height is increased with the increase in density and integration of the individual liquid chambers in the ink jet head. For this reason, when a plurality of filter columns are provided as filters for removing foreign substances in the pressurized liquid chamber, as in the techniques disclosed in “Patent Document 4” and “Patent Document 5”, each filter column is one by one. Becomes long and thin, and the mechanical strength becomes low. For this reason, when joining an actuator and a nozzle board | substrate, the filter column will be broken by the pressure received at the time of joining, and there exists a problem that the broken piece will clog a nozzle.
An object of the present invention is to solve the above-described problems, provide a droplet discharge head with high bonding reliability, and reduce nozzle down due to filter column breakage.

  The invention according to claim 1 is a plurality of nozzles for discharging droplets, a pressurized liquid chamber communicating with each of the nozzles, a driving means for pressurizing a liquid in the pressurized liquid chamber, and a plurality of the pressurized liquids An ink supply path for supplying a liquid to each chamber, and the ink supply path has at least one columnar protrusion as a foreign matter removing filter unit, and the length of the columnar protrusion is the pressure liquid chamber It is characterized by being shorter than the height.

  According to the present invention, the mechanical strength of the columnar protrusion is increased by making the length of the columnar protrusion shorter than the height of the pressurized liquid chamber. As a result, it is possible to provide a liquid droplet ejection head in which the columnar protrusion is less likely to be broken by the pressure received when the driving means and the nozzle substrate are joined, and the joining reliability is high and the nozzle down is less likely to occur due to breakage of the filter portion. .

1 is a schematic perspective view of an ink jet recording apparatus to which an embodiment of the present invention can be applied. 1 is a schematic front sectional view of an ink jet recording apparatus to which an embodiment of the present invention can be applied. It is a schematic front view of the inkjet head used for one Embodiment of this invention. It is a schematic side view of the inkjet head used for one Embodiment of this invention. It is a schematic plan view of the inkjet head used for one Embodiment of this invention. It is a schematic front view of the conventional inkjet head. It is a schematic side view of the conventional inkjet head. It is the schematic explaining the manufacturing method of the inkjet head used for one Embodiment of this invention. It is the schematic explaining the manufacturing method of the inkjet head used for one Embodiment of this invention. It is the schematic explaining the manufacturing method of the inkjet head used for one Embodiment of this invention. It is the schematic explaining the manufacturing method of the inkjet head used for one Embodiment of this invention. It is the schematic explaining the manufacturing method of the inkjet head used for one Embodiment of this invention. It is the schematic explaining the manufacturing method of the inkjet head used for one Embodiment of this invention. It is the schematic explaining the manufacturing method of the inkjet head used for one Embodiment of this invention. It is the schematic explaining the manufacturing method of the inkjet head used for one Embodiment of this invention. It is the schematic explaining the manufacturing method of the inkjet head used for one Embodiment of this invention. It is the schematic explaining the manufacturing method of the inkjet head used for one Embodiment of this invention. It is the schematic explaining the manufacturing method of the inkjet head used for one Embodiment of this invention. It is the schematic explaining forming a columnar projection using the difference in the etching rate in one embodiment of the present invention.

  An example of an ink jet recording apparatus equipped with an ink jet head according to an embodiment of the present invention will be described with reference to FIGS. 1 is a schematic perspective view of the ink jet recording apparatus, and FIG. 2 is a schematic side view of a mechanism portion of the ink jet recording apparatus. The ink jet recording apparatus includes a carriage 93 that can move in the main scanning direction inside the apparatus main body 81, a recording head 94 that is an ink jet head that implements the present invention mounted on the carriage 93, and an ink cartridge that supplies ink to the recording head 94. 95, etc. is housed, and a paper feed cassette (or a paper feed tray) 84 on which a large number of sheets 83 can be stacked from the front side is detachable in the lower part of the apparatus main body 81. It can be mounted, and the manual feed tray 85 for manually feeding the paper 83 can be raised and lowered. The paper 83 fed from the paper feed cassette 84 or the manual feed tray 85 is taken in, and the printing mechanism section 82 is loaded. After recording a required image, the paper is discharged to a paper discharge tray 86 mounted on the rear side.

  The printing mechanism 82 holds a carriage 93 slidably in the main scanning direction by a main guide rod 91 and a sub guide rod 92 which are guide members horizontally mounted on left and right side plates (not shown). ), Cyan (C), magenta (M), black (K), and a head 94 formed of an inkjet head according to the present invention that discharges ink droplets of each color intersects a plurality of ink discharge ports (nozzles) with the main scanning direction. The ink droplets are mounted with the ink droplet ejection direction facing downward. In addition, each ink cartridge 95 for supplying ink of each color to the head 94 is replaceably mounted on the carriage 93. The ink cartridge 95 has an air port that communicates with the atmosphere above, a supply port that supplies ink to the head 94 below, and a porous body filled with ink inside. The ink supplied to the head 94 is maintained at a slight negative pressure by the capillary phenomenon. Further, although the heads 94 of the respective colors are used here as the recording heads, a single head having nozzles for ejecting ink droplets of the respective colors may be used.

  The carriage 93 is slidably fitted to the main guide rod 91 on the rear side (downstream side in the paper conveyance direction), and is slidably mounted on the sub guide rod 92 on the front side (upstream side in the paper conveyance direction). Yes. Then, in order to move and scan the carriage 93 in the main scanning direction, the timing belt 100 is wound around the driving pulley 98 and the driven pulley 99 that are rotationally driven by the main scanning motor 97, and the timing belt 100 is fixed to the carriage 93. As a result, the carriage 93 is reciprocated by forward and reverse rotation of the main scanning motor 97.

  On the other hand, in order to convey the paper 83 set in the paper feed cassette 84 to the lower side of the head 94, a paper feed roller 101 and a friction pad 102 for separating and feeding the paper 83 from the paper feed cassette 84, and a guide for guiding the paper 83 are provided. The member 103, the conveyance roller 104 that reverses and conveys the fed paper 83, the conveyance roller 105 that is pressed against the peripheral surface of the conveyance roller 104, and the leading roller 106 that defines the feeding angle of the sheet 83 from the conveyance roller 104. And are provided. The transport roller 104 is rotationally driven by a sub-scanning motor 107 through a gear train.

  Corresponding to the range of movement of the carriage 93 in the main scanning direction, there is provided a printing receiving member 109 which is a sheet guide member for guiding the sheet 83 fed from the conveying roller 104 below the head 94. A conveyance roller 111 and a spur 112 that are rotationally driven to send the paper 83 in the paper discharge direction are provided downstream of the printing receiving member 109 in the paper conveyance direction, and a paper discharge roller that sends the paper 83 to the paper discharge tray 86. 113 and a spur 114, and guide members 115 and 116 that form a paper discharge path are disposed. During recording, the head 94 is driven in accordance with the image signal while moving the carriage 93, thereby ejecting ink onto the stopped sheet 83 to record one line, and after the sheet 83 is conveyed by a predetermined amount, the next line is recorded. Record. By receiving a recording end signal or a signal that the trailing edge of the paper 83 has reached the recording area, the recording operation is terminated and the paper 83 is discharged.

  A recovery device 117 for recovering defective ejection of the head 94 is provided at a position outside the recording area on the right end side in the movement direction of the carriage 93. The recovery device 117 includes a cap unit, a suction unit, and a cleaning unit. The carriage 93 is moved to the recovery device 117 side during printing standby, and the head 94 is capped by the capping unit, and the ejection port portion is kept in a wet state to prevent ejection failure due to ink drying. Further, by discharging ink that is not related to recording in the middle of recording or the like, the ink viscosity of all the ejection ports is made constant and stable ejection performance is maintained. When ejection failure occurs, the ejection port (nozzle) of the head 94 is sealed with a capping unit, and bubbles and the like are sucked out from the ejection port with the suction unit through the tube. Is removed by the cleaning means to recover the ejection failure. The sucked ink is discharged into a waste ink reservoir (not shown) installed at the lower part of the main body and absorbed and held by an ink absorber provided inside the waste ink reservoir.

  Here, the droplet discharge head which is a feature of the present invention will be described. 3, 4 and 5 are cross-sectional views of the droplet discharge head used in the first embodiment of the present invention when viewed from three directions. The droplet discharge head used in the present embodiment is of a side shooter type that discharges ink droplets from nozzles provided on the surface of the substrate.

  An inkjet head 20 as a droplet discharge head used in the present embodiment includes a nozzle substrate 21 having a nozzle hole 21a for discharging ink, a pressurized liquid chamber 22, a fluid resistance portion 23, a groove portion 24 serving as an ink supply path, and vibration. It has a laminated structure in which three substrates, a liquid chamber substrate 27 on which an actuator unit such as a plate 25 and a piezoelectric layer 26 is formed, and a protection substrate (subframe) 29 on which a piezoelectric element protection space 28 is arranged are overlapped. .

  The liquid chamber substrate 27 is an SOI substrate in which silicon is bonded to a silicon substrate via a silicon oxide film. In addition, the diaphragm 25 forms a silicon oxide film on the surface of the Si layer of the SOI substrate by forming a silicon oxide film, and a platinum layer serving as the lower electrode 30, a piezoelectric layer (PZT) 26, and an upper electrode 31 are formed thereon. An actuator having a multilayer structure of platinum films is formed in a region facing the pressurized liquid chamber 22 formed by etching silicon. Further, an interlayer insulating film 33 disposed between the upper electrode 31 and the lead-out wiring 32 and a passivation film 34 for protecting the material of the lead-out wiring 32 are disposed so as to cover the upper surface and side surfaces of the actuator.

  The nozzle substrate 21 has a nozzle hole 21 a formed by pressing and polishing a 30 to 50 μm thick SUS substrate, and has a nozzle hole 21 a so as to communicate with the pressurized liquid chamber 22 of the liquid chamber substrate 27. doing. The protective substrate 29 forms a column for supporting the entire liquid chamber by increasing the rigidity of the groove 24 serving as an ink flow path as a common liquid chamber, the space for preventing the piezoelectric element from being protected and displaced, and the flow path partition 35. doing.

  In the present invention, as shown in FIG. 3, FIG. 4, and FIG. 5, the filter column 36a, which is a plurality of columnar projections, is formed in the flow path as the filter portion 36. The length h of 36 a is formed shorter than the height H of the pressurized liquid chamber 22. On the other hand, in the conventional inkjet head 20A shown in FIGS. 6 and 7, the length of the filter column 36b in the filter portion 36A is equal to the height of the pressurized liquid chamber 22. With this configuration, in the present invention, the length of each filter column 36a is made shorter than that of the conventional filter column 36b, thereby increasing the mechanical strength of each filter column. Therefore, it is possible to provide a droplet discharge head that is difficult to break due to the pressure received during the joining, and has high joining reliability and is unlikely to cause nozzle down due to breakage of the filter portion 36. In this embodiment, the height H of the pressurized liquid chamber 22 is 70 μm and the length h of the filter column 36a is 50 μm, but the numerical values are not limited to these.

  Next, a method for manufacturing the above-described inkjet head 20 will be described with reference to FIGS. In this embodiment, an actuator is created by forming a diaphragm material and a piezoelectric element material on a silicon substrate. First, an SOI substrate in which a silicon oxide film of 0.2 μm and silicon of 2.0 μm are bonded to the surface of a 400 μm thick silicon substrate is used, and a silicon oxide film of 0.3 μm is formed on this surface by a pyro oxidation method. This is a diaphragm layer (see FIG. 8). Thereafter, a platinum (Pt) layer serving as a lower electrode of the piezoelectric element is deposited by sputtering to pattern it (see FIG. 9). Further, a piezoelectric layer having a thickness of 2 μm is formed by a sol-gel method, and a platinum (Pt) layer as an upper electrode is further formed by a thickness of 0.1 μm. Thereafter, the upper electrode and the piezoelectric layer are patterned by a lithoetch method (see FIG. 10).

  Next, an interlayer insulating film is formed to a thickness of 0.3 μm by a plasma CVD method, and a via hole for making a wiring contact is formed by a lithoetch method. In the interlayer insulating film, a conduction portion between the lead wiring and the upper electrode to be formed next, a conduction portion to the bypass wiring, and a penetration portion serving as an ink supply hole are patterned (see FIG. 11). Further, an extraction electrode is formed from an aluminum material (see FIG. 12). Since the extraction electrode receives stress due to vibration of the diaphragm due to driving of the piezoelectric body, a soft aluminum material is used and is thickly stacked so as not to be disconnected by vibration.

  Next, as a passivation film for protecting the aluminum wiring, a silicon nitride film by a plasma CVD (Chemical Vapor Deposition) method is formed to a thickness of 2 μm and patterned (see FIG. 13). Thereafter, a portion to be an ink supply port of the diaphragm is etched in advance (see FIG. 14). Furthermore, gold is laminated by a plating method to form pad portions of individual electrodes and bypass wirings simultaneously (see FIG. 15). By forming the pad portion with gold, electrical connection with a driver IC (not shown) is connected by low-temperature wire bonding. Gold has a low resistance value, and has a great effect of reducing the common electrode resistance value as a bypass wiring. In addition, copper, aluminum, etc. can also be used as a bypass wiring material, dividing a pad part and a formation process. In that case, a protective layer may be required to protect the bypass wiring from corrosion.

  Thereafter, a protective substrate in which a column is separately formed on a glass substrate by blasting is bonded to the liquid chamber substrate (see FIG. 16), and the surface of the liquid chamber substrate opposite to the protective substrate bonding surface is polished to a desired thickness. The protective substrate may be a silicon substrate processed with a recess by a lithoetch method, or a silicon substrate processed by wet etching using an alkaline etchant such as TMAH or KOH, and may be a resin mold or a metal injection mold. Molded parts may be used. 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 the drive circuit is selected by selecting an oxide film formation region. It is also possible to form on the same substrate.

  Thereafter, in the present invention, the opposite surface of the silicon substrate is half etched by ICP (Inductively Coupled Plasma) dry etching to form a pressurized liquid chamber, a fluid resistance portion, and a recess serving as a supply portion (see FIG. 17). The filter part is formed by changing and etching again, and the pressurized liquid chamber, the fluid resistance part, and the supply part are formed to a desired depth (see FIG. 18). By using such a method, the length of the filter column becomes shorter than that of the conventional one, and thereby, a filter portion having higher mechanical strength than that of the conventional one can be provided inside the head, and the bonding reliability can be improved. A high droplet discharge head can be provided.

  Moreover, it is good also as a process of producing a filter part by one etching using the difference of an etching rate, without performing the above half etching processes. In general, when forming a recess by etching, if a recess having a narrow width and a wide recess are formed at the same time, an etching rate is relatively slower for a recess having a narrow width and a wider one is faster ( (See FIG. 19). For this reason, by narrowing the interval between the columnar protrusions to be formed, the etching rate of the pressurized liquid chamber part and the filter part is different, and the length of the columnar protrusions is made shorter than the height of the pressurized liquid chamber. Can do. By forming the filter portion by this method, the above-described filter portion can be formed without increasing the number of processes (without increasing the cost). Finally, a nozzle substrate in which nozzle holes are formed by pressing and polishing on a stainless steel substrate having a thickness of 30 to 50 μm is separately bonded to the flow channel partition surface of the liquid chamber substrate, and the upper electrode and lower electrode of the piezoelectric element 3 is connected to the drive circuit to complete the droplet discharge head shown in FIG.

  In the present embodiment, a so-called thin film piezoelectric head in which a thin film piezoelectric layer is formed on the vibration plate has been described. However, the essence of the present invention is that the length of the filter column formed in the flow path is lower than the height of the pressurized liquid chamber. Thus, since the filter portion having higher mechanical strength than the conventional one is formed, the driving means is not limited to the thin film piezoelectric head. Moreover, it is not limited to the electromechanical conversion element represented by the piezoelectric element. The image forming apparatus to which the present invention can be applied is not limited to a printer, and the present invention can also be applied to a facsimile, a copying apparatus, a plotter, and a complex machine such as these.

20 Droplet ejection head (inkjet head)
21a Nozzle hole 22 Pressurized liquid chamber 24 Ink supply part (groove part)
36 Filter part 36a Columnar projection (filter column)

Japanese Patent Laid-Open No. 10-100401 JP-A-2-289351 Japanese Patent Laid-Open No. 5-286131 JP 2005-532199 A JP-A-6-278279

Claims (4)

A plurality of nozzles for discharging liquid droplets, a pressurized liquid chamber communicating with each of the nozzles, driving means for pressurizing the liquid in the pressurized liquid chamber, and ink for supplying the liquid to the plurality of pressurized liquid chambers, respectively. In the droplet discharge head, the supply path and the ink supply path have at least one columnar protrusion as a foreign matter removal filter part.
A droplet discharge head, wherein a length of the columnar protrusion is shorter than a height of the pressurized liquid chamber. The droplet discharge head according to claim 1,
A liquid droplet ejection head, wherein the columnar protrusion is formed by half-etching. The droplet discharge head according to claim 1,
A liquid droplet ejection head, wherein the columnar protrusions are formed using a difference in etching rate.   An image forming apparatus comprising the droplet discharge head according to claim 1.

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