1. Field of the Invention
The present invention relates to a liquid ejection head for ejecting a liquid such as an ink to conduct recording.
2. Description of the Related Art
An ink jet recording system is generally known as a recording system that a liquid is ejected to conduct recording. This ink jet recording system includes a method utilizing a heating resistor element (heater) as an ejection energy-generating element used for ejecting a liquid such as an ink and a method utilizing a piezoelectric element (piezo). Both elements permit controlling the ejection of the liquid by an electric signal. In a recording head using the heating resistor element of these, thermal energy is applied to a liquid from the heating resistor element by supplying an electric pulse which is a recording signal to the heating resistor element to bring film boiling (bubbling) to the liquid. A bubble pressure generated at this time is utilized to eject the liquid from a minute opening, thereby conducting recording on a recording medium.
In addition,
Since the ejection orifice forming member 12 is equipped with the hollow portions such as the liquid flow paths 17 and the common liquid chamber 18, the member is a member brittle against external force. Therefore, a beam-like structure (hereinafter referred to as a beam 20) having a plurality of reinforcing ribs 20a is provided at a position of the common liquid chamber 18 facing the liquid supply port 13 in the ejection orifice forming member 12, thereby improving the rigidity of the ejection orifice forming member 12. The beam 20 and the reinforcing ribs 20a are formed in the form of a projecting line and brought into close contact with the substrate 11.
In addition, the reinforcing ribs 20a extend with a fixed thickness in the vicinity of an inlet of an optional liquid flow path 17 from the beam 20. At this time, the reinforcing ribs 20a are each formed on a line extending from a center line Y passing through a center of a flow path width d of the liquid flow path 17.
The fact that the beam 20 and the reinforcing ribs 20a are formed for improving the rigidity of the ejection orifice forming member 12 as described above is disclosed in Japanese Patent Application Laid-Open No. 2007-283501.
In the construction illustrated in
A cause for this is as follows. Since a center line of the reinforcing rib 20a conforms to a center line Y of the liquid flow path 17 as understood from
In addition, the end portion in the longitudinal direction of the reinforcing rib 20a is arranged in the vicinity of the inlet of the liquid flow path 17, so that a flow resistance in the vicinity of the inlet of the liquid flow path 17 becomes high, and the force of the liquid flowing into the liquid flow path 17 becomes weak.
For the reason described above, the bubble generated in the vicinity of the end wall of the pressure chamber 15 is hard to be discharged from the pressure chamber 15. In addition, when the bubble stays in the pressure chamber 15, the growth of a bubble upon bubbling of the liquid is inhibited, and so stable bubbling cannot be conducted, and there is a possibility that ejection failure may be caused.
The present invention provides a liquid ejection head comprising a substrate, an ejection orifice forming member joined to the substrate, in which ejection orifices ejecting a liquid have been formed, a plurality of energy generating elements arranged in a row on the surface of the substrate, to which the ejection orifice forming member has been joined, and generating energy for ejecting the liquid, and a liquid supply port formed in the substrate and having an opening portion at said surface, wherein the ejection orifice forming member is formed face to face with the plural energy generating elements, and which further comprises a plurality of pressure chambers respectively communicating with the ejection orifices, a plurality of liquid flow paths supplying the liquid to the plural pressure chambers, a common liquid chamber communicating the plural flow paths with the liquid supply port and a reinforcing rib formed in the common liquid chamber and extending from a position facing the liquid supply port toward an inlet of each of the liquid flow paths, wherein an end portion in a longitudinal direction of the reinforcing rib is arranged in the vicinity of the inlet of the liquid flow path and formed in such a manner that a center line of the reinforcing rib deviates in an arranging direction of the ejection orifices from a center line passing through the center of the liquid flow path in the arranging direction.
The present invention also provides a liquid ejection head comprising an energy generating element generating energy utilized for ejecting a liquid, a liquid supply port provided at a surface on which the energy generating element is provided for supplying the liquid to the energy generating element, a liquid flow path for supplying the liquid to the energy generating element from the liquid supply port and a rib extending from the liquid supply port toward an inlet of the liquid flow path, wherein an end portion of the rib on the side of the liquid flow path is provided at a position deviated from a center line of the liquid flow path.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Preferred embodiments of the present invention will now be described in detail in accordance with the accompanying drawings.
The ejection orifice forming member 12 joined to the first surface of the substrate 11 is composed of a photosensitive resin member. Pressure chambers 15 arranged accordingly to the respective heating resistor elements 14, a plurality of liquid flow paths 17 for supplying a liquid such as an ink to the plural pressure chambers 15, a common liquid chamber 18 collectively communicating the plural liquid flow paths 17 with one liquid supply port 13 and ejection orifices 19 communicating with the respective pressure chambers 15 are formed in the ejection orifice forming member 12.
The pressure chambers 15, the liquid flow paths 17, the common liquid chamber 18 and the ejection orifices 19 are formed by working gloves or holes in a surface of a photosensitive resin layer by a photolithographic process. Incidentally, another material than the resin member may also be used to form the ejection orifice forming member 12 having elements such as the pressure chambers 15. In addition, the pressure chamber is also called a bubbling chamber in the ejection system utilizing the heating resistor element.
The respective ejection orifices 19 are provided at positions corresponding to the respective heating resistor elements 14. Therefore, an ejection orifice array composed of the plural ejection orifices 19 is formed in the ejection orifice forming member 12, and the arranging direction of the ejection orifices 19 is along a longitudinal direction of the rectangular opening portion of the liquid supply port 13. The length of the ejection orifice array is, for example, about 0.43 inch.
A beam (beam-like projection) 20 having a plurality of reinforcing ribs 20a and columns (columnar projections) 21 which are plural columnar members is provided within the common liquid chamber 18 which is a hollow portion of the ejection orifice forming member 12, whereby the rigidity of the ejection orifice forming member 12 is improved. The beam 20, the reinforcing ribs 20a and the columns 21 are integrally formed in a state projected toward the first surface of the substrate 11 from the ejection orifice forming member 12 and joined to the substrate 11.
The beam 20 is arranged over the longitudinal direction of the opening portion of the liquid supply port 13 rectangularly opened to the first surface. Both ends in the longitudinal direction of the beam 20 is brought into close contact with the substrate 11 across the liquid supply port 13 (not illustrated). A groove (hereinafter referred to as a slit 16) is formed along the longitudinal direction of the beam 20 at the center of the beam 20.
The thicknesses (heights from the first surface of the substrate 11) of the beam 20 and the ejection orifice forming member 12 are the same as each other and 26 μm. The depth of the slit 16 is equal to the thickness of a portion of the ejection orifice forming member 12, at which the pressure chambers 15 and the liquid flow paths 17 have been formed and 10 μm. The width of the beam 20 is 62.5 μm including the slit 16. The width of the slit 16 is 14 μm.
The column 21 is arranged in the vicinity of the inlet of each liquid flow path 17 communicating with the pressure chamber 15 for the purpose of preventing dust from reaching the ejection orifice 19. In addition, the reinforcing ribs 20a are formed within the common liquid chamber and extend in a direction intersecting an extending direction of the beam 20 located at a position facing the liquid supply port 13 from both side wall portions of the beam 20. A tip portion in a longitudinal direction of each reinforcing rib 20a is arranged in the vicinity of the inlet of each liquid flow path 17. The thickness (the width in a direction orthogonally intersecting an extending direction of the reinforcing rib 20a and parallel with the first surface of the substrate 11) of the reinforcing rib 20a is equal to the diameter of the column 21. The thicknesses of the reinforcing rib 20a and the column 21 are equal to the thickness of the ejection orifice forming member 12 and 26 μm.
In case of the first embodiment, the reinforcing rib 20a and the column 21 are arranged at every liquid flow path 17, and the column 21 and the reinforcing rib 20a are alternately arranged along the arranging direction of the ejection orifices 19. In addition, the reinforcing rib 20a and the column 21 arranged in the vicinity of the inlet of each liquid flow path 17 are located at positions deviated in opposite directions to each other from the line extending from the center line Y. Further, the reinforcing rib 20a and the column 21 are formed on a line deviated in the arranging direction of the ejection orifices 19 from the center line Y passing through the center of the flow path width d of the liquid flow path 17.
Incidentally, since the ejection orifice forming member 12 is comprised of the resin, it swells with a solvent contained in an ink when the ink is used as the liquid ejected from the ejection orifice. When the ejection orifice forming member 12 swells as illustrated in
An ejection operation in case where the liquid ejection head according to this embodiment is applied to an ink jet recording head for ejecting an ink on a recording medium such as paper or a resin sheet to record an ink image will now be described. The ink is supplied to the pressure chamber 15 passing through the liquid flow path 17 through the liquid supply port 13 and the common liquid chamber 18 from an ink supply section (not illustrated), and the ejection orifice 19 is filled with the ink. When a printing signal is transmitted to an ejection control section of the ink jet recording head from a printer (not illustrated), an optional heating resistor element 14 is selected according to an image intended to be printed, and a current is applied to the heating resistor element 14. The ink is heated by the heating resistor element 14 and film-boiled (bubbled) on the heating resistor element 14. An ink droplet is ejected from the ejection orifice by the bubbling to form an image on a recording medium (not illustrated).
Incidentally, the liquid ejection head according to this embodiment is not limited to the use for recording like the ink jet recording head and may also be applied to a head for ejecting a liquid such as an ink containing an electroconductive nanoparticle such as gold, silver or copper, a resist, a UV-curable resin, a protein or a special liquid according to the ink jet system.
The action and effect brought by the liquid ejection head according to this embodiment will now be described.
As illustrated in
Therefore, with respect to a flow speed of the liquid supplied to the liquid flow path 17, as illustrated in
That is, the flow of the liquid within the pressure chamber 15 becomes, for example, a swirled flow, and so the movement of the bubble within the pressure chamber 15 can be promoted. The bubble is thereby moved on the heating resistor element 14 without attaching to the end wall of the pressure chamber 15 as illustrated in
When the liquid ejection head according to the present invention is utilized as an ink jet recording head using the heating resistor element in particular, a bubbling operation for ejecting an ink is stabilized, so that recording quality on a recording medium is not lowered.
For comparing with this embodiment,
In the reinforcing rib 20a illustrated in
The second embodiment will now be described. The same components as the components of the liquid ejection head according to the first embodiment are described with the same signs.
In the first embodiment, the reinforcing rib 20a and the column 21 have been arranged in each of the plural liquid flow paths 17. However, the liquid ejection head according to the second embodiment may also have a construction that the reinforcing rib 20a and the column 21 are arranged at every other liquid flow path 17 as illustrated in
According to such the construction, the flow of the liquid supplied to the liquid flow path 17 is not hindered in the liquid flow path 17 at which the 2 columns are arranged because no reinforcing rib 20a is arranged, and so the liquid can be supplied to the pressure chamber at a speed sufficient to move a bubble within the pressure chamber 15. In addition, the number of the reinforcing ribs 20a is lessened compared with the first embodiment, whereby a flow resistance from the liquid supply port 13 to each pressure chamber 15 of the ejection orifice forming member 12 can be lowered, and so a refill speed of the liquid to the whole ejection orifice array can be raised.
Quite naturally, this embodiment is not limited to the arrangement of the reinforcing rib 20a at every other liquid flow path 17 among the plural liquid flow paths 17 as described above, and the reinforcing rib 20a may also be arranged at every several liquid flow paths 17 (for example, at every 3 liquid flow paths) among the plural liquid flow paths 17.
In addition, with respect to the liquid flow path 17 at which the reinforcing rib 20a has been arranged, a speed of the liquid supplied to the pressure chamber 15 varies over the flow path width d of the liquid flow path 17. The shape of a trailing portion of the liquid at the time the liquid has been ejected from the ejection orifice 19 is deflected in the arranging direction of the ejection orifices 19. As a result, an ejecting direction of the liquid varies between adjoining ejection orifices 19, which may lower the impact accuracy of the liquid at a target position on an ejection object. The term “trailing” means a phenomenon that the liquid leaves a trail backward when the liquid is ejected from the ejection orifice 19.
In order to suppress the deflection of such a shape of the trailing portion of the liquid upon the liquid ejection as described above, 2 projections 19a facing each other are formed on an inside surface of each ejection orifice 19 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. 2014-112183, filed May 30, 2014, which is hereby incorporated by reference herein in its entirety.
Number | Date | Country | Kind |
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2014-112183 | May 2014 | JP | national |