Patent Application
20180141335
The present invention relates to a liquid ejection head, a liquid ejection apparatus, and a control method. Particularly, the present invention relates to a technique for keeping, away from the heater, a component contained in ink and capable of becoming a hardly-soluble substance to thereby reduce a “koge” (meaning “scorch”) adhering to a heater, by forming an electric field in the ink to be ejected by heating the heater.
In a liquid ejection head which ejects liquid by foaming the liquid with heat generated by a heater, there is known a phenomenon in which a charged colloidal particle or the like contained in the liquid is decomposed by being exposed to high-temperature heating, changes into a hardly-soluble substance, and adheres to the surface of a heating element. This phenomenon is referred to as “kogation” (meaning “scorching”) and an adhesive material is referred to as a “koge.” Once a koge adheres to the surface of a heating element, there are cases where the heat conduction to ink may become nonuniform and foaming may become unstable.
In order to solve the problems as described above, Japanese Patent Laid-Open No. 2009-51146 describes that a heater upper electrode arranged in a vicinity of a heater as a heating element and an electrode paired with this heater upper electrode form an electric field in ink between these electrodes. Then, this formed electric field keeps a charged colloidal particle in the ink away from the heater upper electrode to thereby reduce the concentration of the charged colloidal particles in a vicinity of the heater, and suppresses the adhesion of a koge to the surface of the heater.
However, in Japanese Patent Laid-Open No. 2009-51146, depending on the arrangement of a paired electrode, there are cases where a vicinity thereof may cause stagnation in the flow of ink. Then, relatively minute bubbles present in the ink may gather in this stagnated portion to thereby become a large bubble and stay. As described above, in a case where a bubble stays in a vicinity of a paired electrode, the resistance between the heater upper electrode and the paired electrode increases since the electric conductivity of the bubble is relatively lower than that of the liquid. As the result, the amount of charged colloidal particles which move to the side of the paired electrode by the generated electric field may decrease, and thus an effect of suppressing kogation may become insufficient.
The present invention provides, in a configuration for suppressing the adhesion of a koge onto the surface of a heater by forming an electric field between an electrode in a vicinity of the heater and a paired electrode, a liquid ejection head, a liquid ejection apparatus, and a control method capable of reducing the staying of a bubble in a vicinity of the paired electrode.
In the first aspect of the present invention, there is provided a liquid ejection head comprising: a wall member for partitioning a first liquid chamber and a second liquid chamber adjacent to each other and forming the first liquid chamber and the second liquid chamber, the wall member having formed therein a void for communicating between the first liquid chamber and the second liquid chamber; a first energy generation element which is provided in the first liquid chamber and foams liquid in order to eject the liquid; a second energy generation element which is provided in the second liquid chamber and foams liquid in order to eject the liquid; a first electrode which is provided in the first liquid chamber and is arranged in a vicinity of the first energy generation element; a second electrode for forming, between the first electrode and the second electrode, an electric field in liquid inside the first liquid chamber; and a supply port which supplies liquid to the first energy generation element, wherein the wall member includes a channel wall in which the second liquid chamber, the void, and the supply port communicate, in this order, with each other via liquid, and the second electrode is arranged between the second liquid chamber and the supply port in the channel.
In the second aspect of the present invention, there is provided a liquid ejection apparatus comprising: a liquid ejection head including: a wall member for partitioning a first liquid chamber and a second liquid chamber adjacent to each other and forming the first liquid chamber and the second liquid chamber, the wall member having formed therein a void for communicating between the first liquid chamber and the second liquid chamber; a first energy generation element which is provided in the first liquid chamber and foams liquid in order to eject the liquid; a second energy generation element which is provided in the second liquid chamber and foams liquid in order to eject the liquid; a first electrode which is provided in the first liquid chamber and is arranged in a vicinity of the first energy generation element; a second electrode which is provided in the first liquid chamber and is for forming, between the first electrode and the second electrode, an electric field in liquid inside the first liquid chamber; and a supply port which supplies liquid to the first energy generation element, wherein the wall member includes a channel wall in which the second liquid chamber, the void, and the supply port communicate, in this order, with each other via liquid, and the second electrode is arranged between the second liquid chamber and the supply port in the channel; a detection unit configured to detect a bubble between the first electrode and the second electrode in the first liquid chamber; and a generation unit configured to generate, in a case where the detection unit detects a bubble, a flow of liquid moving toward the first liquid chamber via the void from the second liquid chamber.
In the third aspect of the present invention, there is provided a control method of a liquid ejection head, the liquid ejection head including: a wall member for partitioning a first liquid chamber and a second liquid chamber adjacent to each other and forming the first liquid chamber and the second liquid chamber, the wall member having formed therein a void for communicating between the first liquid chamber and the second liquid chamber; a first energy generation element which is provided in the first liquid chamber and foams liquid in order to eject the liquid; a second energy generation element which is provided in the second liquid chamber and foams liquid in order to eject the liquid; a first electrode which is provided in the first liquid chamber and is arranged in a vicinity of the first energy generation element; a second electrode for forming, between the first electrode and the second electrode, an electric field in liquid inside the first liquid chamber; and a supply port which supplies liquid to the first energy generation element, wherein the wall member includes a channel wall in which the second liquid chamber, the void, and the supply port communicate, in this order, with each other via liquid, and the second electrode is arranged between the second liquid chamber and the supply port in the channel, the method comprising the step of generating a flow of liquid which moves toward the supply port through the second electrode via the void from the second liquid chamber.
According to the above-described configuration, in the configuration for suppressing the adhesion of a koge onto the surface of a heater by forming an electric field between the electrode in a vicinity of the heater and the paired electrode, it becomes possible for a liquid ejection head to reduce the staying of a bubble in a vicinity of the paired electrode.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings.
As illustrated in
An operation unit 220 is a group of switches for receiving an instruction input by an operator, and includes: a non-illustrated power supply switch; a switch for giving an instruction of printing start; a recovery switch for giving an instruction of suction recovery start; and the like. A head driver 2040 is a driver which drives an electrothermal conversion element of the liquid ejection head 104 according to print data or the like, and is capable of ejecting ink from the ejection port of the print head 104 through this driving. The liquid ejection head 104 includes an ejection port which ejects the ink of each of four colors, namely, cyan (C), magenta (M), yellow (Y), and black (K). A motor driver 2050 is a driver which drives: a main-scanning motor mounting the head cartridge 100 provided with the liquid ejection head 104, for moving the head cartridge 100 in a main-scanning direction; a sub-scanning motor for conveying a printing medium in a sub-scanning direction.
The control system described above detects a staying state of a bubble in a liquid chamber of the liquid ejection head on the basis of the resistance between electrodes arranged in the liquid chamber, and performs the ejection control corresponding to this detection, as described later in an embodiment of the present invention.
As illustrated in these views, the liquid ejection head 104 generally includes: a substrate 1; and the liquid chamber-forming member 20 provided on this substrate. The liquid chamber-forming member 20 is provided with an ejection port 21. Furthermore, a channel wall 41 is provided as a part of the liquid chamber-forming member, and the substrate 1 is provided with a heater 2 as an energy generation element corresponding to a liquid chamber 30. In addition, the substrate 1 is provided with a supply port 12 for supplying ink as liquid to a pressure chamber which applies a foaming pressure caused by the heater 2 for each liquid chamber 30. In each liquid chamber 30, a heater upper electrode 31 is provided above the heater 2, and furthermore, in the liquid chamber 30, a paired electrode 32 is provided at a position on a side opposite to a position where this electrode 31 is provided. Namely, the paired electrode 32 is provided on a side opposite to the heater upper electrode 31 with respect to the supply port 12. In the channel wall 41 which partitions the liquid chamber 30 and the adjacent liquid chamber 30, a void 42 is provided and liquid chambers adjacent via this void communicate with each other. This void 42 is provided so as to extend generally from the surface of the substrate 1 to the inner side surface of the upper portion of the liquid chamber-forming member 20.
The liquid chamber-forming member 20 can be formed of a resin, a metal, or an inorganic material. The examples of the resin can include a photosensitive resin such as an epoxy resin which cure by light cationic polymerization. The examples of the metal can include a SUS plate, and the examples of the inorganic material can include SiN, SiC, SiCN, or the like. In the example illustrated in
In the substrate 1, the heater 2 is formed by a wiring layer 5 connected to a heating resistor layer 4 made of TaSiN or the like. Namely, a part of the wiring layer 5 formed on an upper part of the heating resistor layer 4 is removed to form a gap and the heating resistor layer 4 of the gap portion is exposed, thereby forming the heater 2. The wiring layer 5 is provided on the heating resistor layer 4, but in contrast, the heating resistor layer 4 may be provided on the wiring layer 5. Furthermore, in the undermost layer of the heater 2, there may be provided a heat storage layer composed of an SiO film or a BPSG film for preventing escaping of heat in contact with the substrate 1.
A protection layer 6 is provided on the heating resistor layer 4 and wiring layer 5, and functions as an insulating layer composed of an SiO film, an SiN film, or the like. An upper protection layer 31 is provided above the protection layer 6, and protects the heater 2 from chemical and physical effects associated with foaming of liquid, and in this embodiment, functions as the heater upper electrode 31 to which an electric potential is applied, in order to suppress kogation. The upper protection layer 31 includes a material to which an electric potential can be applied as the heater upper electrode, and the material which is stable particularly against heating is preferably used. Specifically, a noble metal such as Ir can be used. This upper protection layer 31 may be a single layer or even a plurality of layers stacked. In a case of stacking a plurality of layers, some of the layers may be insulating layers if an electric field formed by the heater upper electrode is not to be shielded. An electrode wiring 9 is for electrically connecting the upper protection layer 31 and an external electrode, and is formed by the use of an electrically conductive material. The electrode wiring 9 extends to an end portion of the liquid ejection head 104, and a tip thereof forms an external electrode (not illustrated) for electrically connecting to the outside. Alternatively, the electrode wiring 9 may be connected to the wiring layer 5 through a through-hole (not illustrated). The electrode wiring 9 and the upper protection layer 31 may include the same member as each other.
Although the paired electrode 32 is provided on the substrate 1, the electrode is not required to be in contact with the substrate 1 but may be provided via another layer with respect to the substrate 1. Alternatively, the paired electrode 32 may be provided in contact with the liquid chamber-forming member 20. The paired electrode 32 is paired with the heater upper electrode 31 and is used for forming an electric field between these electrodes. With this electric field, a substance such as a colloidal particle, which becomes hardly soluble due to heating of ink, can be moved from a vicinity of the heater upper electrode 31 to the paired electrode 32 side, and thus the adhesion of a koge to the heater upper electrode 31 or the like can be suppressed. This paired electrode 32 can be formed of a noble metal such as Ir. The paired electrode 32 may have a single layer or even a plurality of layers stacked, and in a case of stacking a plurality of layers, some of the layers may form insulating layers if an electric field formed between the heater upper electrode and the paired electrode is not to be shielded. The outermost layer of the paired electrode 32 preferably includes a material which does not dissolve in liquid. Note that the heater upper electrode is not necessarily required to be present above the heater 2, but may be at a position in a vicinity of the heater 2 where the heater upper electrode exhibits an effect of keeping, by an electric field formed by the heater upper electrode, a colloidal particle and the like in ink away from the heater 2. In this specification, from this viewpoint, the heater upper electrode is referred to also as a “near-element electrode.”
The electrode wiring 9 is for electrically connecting the paired electrode 32 and an external electrode, and is formed by the use of an electrically conductive material, as with the heater upper electrode 31 described above. The electrode wiring 9 extends to an end portion of the liquid ejection head 104, and the tip thereof serves as an external electrode (not illustrated) for electrically connecting to the outside. Alternatively, the electrode wiring 9 may be connected to the wiring layer 5 through a through-hole (not illustrated). The electrode wiring 9 and paired electrode 32 may include the same member as each other.
The supply port 12 in the substrate 1 can be formed by dry etching, wet etching by TMAH, KOH or the like, laser processing, and the like. Ink supplied via the supply port 12 from an ink tank foams by a thermal energy generated by the heater 2, and the ink is ejected from the ejection port 21 due to the foaming pressure. Note that the number of supply ports corresponding to one heater may be one or may be plural. In a case where the number of supply ports corresponding to one heater is an even number, the supply ports are preferably arranged so as to sandwich the energy generation element since the liquid is equally supplied.
Note that the arrangement of the paired electrode 32 in the liquid chamber 30 is not limited to the above-described example. The paired electrode 32 may be at a distance at which an electric field formed between the heater upper electrode 31 and the paired electrode 32 exhibits an effect of reducing the concentration of charged particles in the ink in a vicinity of the heater 2 and at a position where a bubble present in a vicinity of the paired electrode 32 can be removed by the flow of ink from the void 42. In the configuration illustrated in
In the above-described example, the number of the paired electrodes 32 present in the same liquid chamber as the one heater upper electrode 31 is one, but is not limited thereto and may be plural. Alternatively, one paired electrode 32 may correspond to a plurality of heater upper electrodes 31. In addition, the void 42 is not required to be present at all the channel walls 41, and may be present at, for example, every other channel walls 41. Namely, the void 42 may be formed at at least one of two channel walls corresponding to one liquid chamber.
The paired electrode 32 may be arranged in the inside of the void 42 which is narrower than the liquid chamber 30. More specifically, at least a part of the paired electrode 32 may be arranged in the area where the void 42 of the upper part of the substrate 1 is provided. In other words, at least a part of the paired electrode 32 may be arranged in a communicating portion of the adjacent liquid chamber 30.When the paired electrode 32 is provided at such a position, the speed of the ink flow from the adjacent liquid chamber via the void 42 becomes quicker in the inside of the void 42 than the liquid chamber 30. Therefore, a bubble moves easily. As a result, the staying of a bubble is reduced in the vicinity of the paired electrode.
In the second embodiment, between the paired electrode 32 and the supply ports 12, there is provided a backflow prevention unit (backflow prevention member) 43 whose size is narrowed in the horizontal direction from the paired electrode 32 toward the supply port 12. Although the direction in which ink flows is reversed between at the time of ejection and at the time of refill, the backflow prevention unit 43 can suppress the reverse flow of the ink from the supply port 12 toward the paired electrode 32, thereby making a bubble difficult to flow backward to the paired electrode 32 side. Accordingly, the scorching to the surface of the heater upper electrode can be further reduced as compared with the first embodiment.
In the second embodiment, there is provided a backflow prevention unit whose size is narrowed in the horizontal direction from the paired electrode 32 toward the supply port 12, whereas in the third embodiment, there is provided a backflow prevention unit 43a whose size is narrowed in the vertical direction from the paired electrode 32 toward the supply port 12. As with the second embodiment, the backflow prevention unit 43a can suppress the reverse flow of the ink from the supply port 12 toward the paired electrode 32, thereby making a bubble difficult to flow backward to the paired electrode 32 side.
In the first embodiment, the channel wall 41 has a uniform thickness in the horizontal direction in
In the first embodiment, among the liquid chamber-forming members 20 partitioning the liquid chamber, a member adjacent to the void 42 and extending in the arrangement direction of the paired electrode 32 has a uniform thickness. In contrast, in this embodiment, a partition 40 serving as a convex portion toward the paired electrode 32 is formed as a part of the liquid chamber-forming member 20, for each liquid chamber 30. Since the liquid chamber 30 between the void 42 and the paired electrode 32 is partitioned by the partition 40 in this way, the adjacent cavities 42 do not directly connect to each other in terms of channel. Accordingly, most of the flow of ink via the void 42 from the adjacent liquid chamber 30 does not go directly toward the void 42 on the opposite side, but passes through the liquid chamber 30 of a section in which the paired electrode 32 and the supply port 12 are present. As the result, a bubble in a vicinity of the paired electrode 32 can be easily moved to the supply port 12. In this embodiment, the shape of the partition 40 is rounded in a concave shape. Therefore, the flow of liquid via the void 42 from the adjacent liquid chamber 30 can flow without losing the strength thereof and also so as not to cause stagnation in the flow, and thus a bubble can be more easily moved.
In the positional and size-wise relationships between the partition 40 and the paired electrode 32, preferably, the area of the partition 40 on the paired electrode 32 is made as small as possible, or a gap is formed between the paired electrode 32 and the partition 40.
A sixth embodiment of the present invention relates to a configuration for controlling ejection from an ejection port corresponding to the liquid chamber 30 in accordance with staying of a bubble in the liquid chamber. Since the electric conductivity of a bubble is relatively lower than that of liquid such as ink, the resistance between the heater upper electrode 31 and the paired electrode 32 increases in a case where a bubble stays in a vicinity of the paired electrode as compared with a case where it does not stay.
In this embodiment, an electric-current measurement circuit is provided in an external electrode connected to the wiring layer of each heater upper electrode 31, and the degree of staying and the degree of removal of the bubble 36 between the heater upper electrode 31 and the paired electrode 32 are measured through a change in a resistance to be measured. Accordingly, as to the liquid chamber 30 in which staying of the bubble 36 is detected, the control is performed so as not to allow ejection from the ejection port of this liquid chamber 30, but so as to allow ejection from the ejection port of the adjacent liquid chamber 30. Specifically, the ejection from the adjacent ejection port is repeated until the above-described resistance value becomes equal to or less than a predetermined threshold at which it can be assumed that a bubble has been removed from the liquid chamber by the measurement of the above-described resistance value. Note that detection of the staying of a bubble in each of the plurality of consecutive liquid chambers 30 and ejection not from an ejection port of a liquid chamber but from an ejection port of a liquid chamber adjacent to the liquid chamber are performed sequentially from an end ejection port of an ejection port array. Furthermore, the electric-current measurement circuit may be provided in the wiring layer of the heater upper electrode 31 to measure a change in resistance, or an electric-current measurement unit may be provided in the wiring layer of the paired electrode 32 or in an external electrode connected to the wiring layer of the paired electrode 32 to measure a change in resistance.
A bubble staying in the liquid chamber 30 becomes unlikely to inhibit the electric-potential control effect, by control of the liquid ejection head 104 as described above.
Note that, although a bubble is detected via a change in resistance in the sixth embodiment, a bubble may be detected by optically determining the presence or absence of a bubble through the liquid chamber-forming member 20 from the outside of the liquid ejection head 104. Alternatively, a bubble may be detected by measurement of the speed of a liquid ejected to the outside of the liquid ejection head 104 through the supply port 12 and by utilization of a decrease in the speed of the ejected liquid resulting from a deterioration of the ejection efficiency due to staying of a bubble.
In the sixth embodiment, the driving timings between the heater 2 of the liquid chamber 30 and the heater 2 of the adjacent liquid chamber 30 are shifted from each other to thereby not allow simultaneous ejection from the ejection port 21 of the adjacent liquid chamber 30, and a bubble is removed by utilization of a flow of ink which is generated via the void 42 at the time of ejection of the adjacent liquid chamber 30. In contrast, in the seventh embodiment, as illustrated in
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2016-225312, filed Nov. 18, 2016, which is hereby incorporated by reference wherein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-225312 | Nov 2016 | JP | national |
