Patent Application
20190263124
The present invention relates to a liquid ejection head substrate that ejects liquid droplets such as ink through ejection orifices as well as to a method for producing the liquid ejection head substrate.
In recent years, there has been demand for higher print quality and there is strong demand for improvement in ejection performance of liquid ejection head substrates such as ink jet recording substrates adapted to eject ink using an ink jet technique. For example, if ink attaches to a neighborhood of ejection orifices provided in an ink jet recording substrate, a traveling direction of the ejected ink may become unsettled. Therefore, water repellent treatment is applied to a liquid droplet ejection surface of a nozzle plate in which ejection orifices are formed.
According to Japanese Patent Application Laid-Open No. 2009-107314, a diamond-like carbon (hereinafter also referred to as “DLC”) film that has excellent wear resistance and high resistance against acid solutions and alkaline solutions is formed on the liquid droplet ejection surface of a nozzle plate and projections and depressions are formed on a surface of the DLC film by a rubbing or other technique. The projections and depressions formed on the surface of the DLC film structurally act to exhibit water repellency. Consequently, it is supposed that the nozzle plate disclosed in Japanese Patent Application Laid-Open No. 2009-107314 can maintain stable water repellency for an extended period of time.
A liquid ejection head substrate according to the present invention comprises a nozzle plate provided with nozzle holes adapted to eject liquid droplets; and a projection/depression pattern made up of minute projections and minute depressions disposed alternately at predetermined spacing on a liquid droplet ejection surface of the nozzle plate.
That is, the present invention provides a liquid ejection head substrate comprising a nozzle plate provided with an ejection orifice adapted to eject liquid droplets, wherein: a projection/depression pattern is provided on a liquid droplet ejection surface of the nozzle plate, the projection/depression pattern being made up of a plurality of projections and depressions, the projections being separated by depressions 1 μm or less in depth and disposed at predetermined spacing 10 μm or less in length; and the projection/depression pattern includes a part having water repellency due to lotus effect.
Also, according to another aspect of the present invention, there is provided a method for producing a liquid ejection head substrate that includes a nozzle plate provided with an ejection orifice adapted to eject liquid droplets, the method comprising emitting a linearly-polarized laser to a liquid droplet ejection surface of the nozzle plate at irradiation intensity in a neighborhood of a processing threshold and thereby forming a projection/depression pattern in a self-organizing manner on the liquid droplet ejection surface of the nozzle plate, the projection/depression pattern being made up of projections and depressions disposed alternately at predetermined spacing.
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.
A liquid droplet ejection surface of a nozzle plate of an ink jet recording substrate gradually decreases in water repellency with use due to chemical impact caused by contact with ink or due to physical wear caused by wiping of adherent ink droplets. When a water-repellent layer is formed by the method described in Japanese Patent Application Laid-Open No. 2009-107314, spacing and depth of a projection/depression structure formed by rubbing are irregular. Therefore, the extent of decrease in water repellency with the use of the ink jet recording substrate varies with the place on the nozzle plate. Consequently, there is a problem in that unintended variations occur in water repellency on the nozzle plate, making a liquid droplet ejection direction unsettled.
The present invention has been made in view of the conventional technique described above and has an object to provide a liquid ejection head substrate on which spacing and depth of a projection/depression structure on a liquid droplet ejection surface of a nozzle plate are uniform as well as to provide a method for producing the liquid ejection head substrate.
An ink jet head 102 includes an ink jet recording substrate 300 and a substrate perimeter sealant serving as a sealing member 111 provided around a base 5, which is part of the ink jet recording substrate. The ink jet recording substrate 300 includes the base 5 provided with plural energy generating elements 6 adapted to generate energy used to eject a liquid and an ejection orifice member 109 provided with ejection orifices 9 corresponding to the elements. Furthermore, a flow path 113 is provided by being communicated with the ejection orifices 9. The ink jet recording substrate 300 is supported and fixed by a supporting member 105. Also, the sealing member 111 is provided on an outer periphery of the base 5 in contact with at least part of end faces, which are side faces of the substrate. This enables preventing a liquid or the like from coming into contact with the end faces, which are the side faces of the substrate. Also, the sealing member 111 is in contact with the supporting member 105. The ink jet recording substrate 300 and an electric wiring member 101 are connected with each other via lead wires 106 and the lead wires 106 are sealed by a lead sealing member 112.
On the base 5, energy generating elements 6 used to foam ink and a drive circuit (not shown) adapted to drive the energy generating elements 6 are formed on a silicon substrate using semiconductor producing technology. Also, to communicate between that surface on the base 5 on which the energy generating elements 6 are formed and an undersurface on the opposite side, a supply port 7 is formed penetrating the base 5. Furthermore, the ejection orifices 9 used to eject ink supplied from an underside of the substrate by a nozzle forming member 8 are formed above the energy generating elements 6. The ink is foamed by driving the energy generating elements 6 corresponding to the ejection orifices 9, and using pressure of the foaming, ink is ejected to do printing. Whereas
Next, a method for producing the ink jet recording substrate according to the present embodiment will be described.
The base 5 is made up of various layers formed on a substrate 10 of silicon or the like and the energy generating elements 6 corresponding to the ejection orifices 9 are formed thereon. The nozzle forming member 8 is also referred to as a nozzle plate 21. A projection/depression pattern 22 made up of plural projections separated by depressions 1 μm or less in depth and disposed at predetermined spacing 10 μm or less in length is formed on a liquid droplet ejection surface, which is an outermost surface of the nozzle plate 21. Also, the projection/depression pattern includes a part having water repellency due to lotus effect.
Steps of producing the ink jet recording substrate will be described below with reference to
First, the base 5 such as shown in
Next, as shown in
Any publicly-known material can be used for the nozzle plate 21, but desirably the material is an inorganic material processible by plasma CVD. Also, the nozzle plate 21 is not limited to a single layer, and may be multi-layered. In particular, desirably the liquid droplet ejection surface designed to become the outermost surface of the nozzle plate is made of a water-repellent material.
For example, as shown in
The layer designed to become the nozzle plate 21 can be formed on the coating layer 18 and on any protective layer 19 as well by being extended on top of the mold 20. Note that the nozzle plate is a nozzle forming member in which ejection orifices are formed. Desirably thickness of the nozzle plate on the mold 20 is between 1 μm and 100 μm (both inclusive). More desirably, the thickness is 2 μm or above, and still more desirably 5 μm or above. The nozzle plate is prepared in this way.
Next as shown in
When the projection/depression pattern is made up of grooves 32 serving as depressions such as shown in
Also, the spacing of projections in the projection/depression pattern 22 can be controlled by an angle formed by a laser beam and nozzle plate surface. That is, when the laser beam is emitted at right angles to the nozzle plate surface, a period of the projection/depression pattern 22 (projection spacing) is the shortest and approximately coincides with wave length of the laser. When the laser beam is emitted at an inclined angle to the nozzle plate surface, the period of the projection/depression pattern 22 increases, and the larger the inclined angle (the smaller the angle of incidence to the substrate surface), the longer the period of the projection/depression pattern 22. The use of this phenomenon enables providing a region in which the period of the projection/depression pattern 22 on the nozzle plate changes stepwise or continuously using a laser beam of the same wave length. As shown in
Upon reaching the nozzle plate, each ink droplet moves on the nozzle plate by kinetic energy possessed by the ink droplet itself, inertial force generated by movement of the recording head, airflow produced by paper feed, and other forces. When the entire surface of the nozzle plate has high water repellency, because of small contact area between the ink droplets and nozzle plate, ink droplets will get detached from the nozzle plate, and attach to a printing object, presumably deteriorating print quality. Thus, as described above, the period of the projection/depression pattern is configured to be the shortest in the neighborhood of the ejection orifices and to increase with increasing distance from the ejection orifices. Consequently, if high water repellency is maintained by lotus effect in a region (which is referred to as a high-repellency region) in which adhesion of ejected ink droplets is desired to be inhibited and water repellency is reduced in another region (which is referred to as a low-repellency region), a moving direction of ink droplets can be kept at a fixed direction. That is, the ink droplets moving on the nozzle plate by being attached to the high-repellency region can be caught in the low-repellency region. With this configuration, any ink droplets attached to the neighborhood of ejection orifices do not stay there for a long time and can be caught in the low-repellency region that do not affect the ejection direction. As a result, the ink droplets that will affect the ejection direction by being located in the neighborhood of ejection orifices move quickly and are caught in the low-repellency region with limited impact on the ejection direction and without attaching to the printing object, which enables inhibiting deterioration in print quality.
In this way, desirably the spacing of those projections in the projection/depression pattern that are formed up to a predetermined distance from the ejection orifice is smaller than the spacing of those projections in the projection/depression pattern that are formed beyond the predetermined distance from the ejection orifice. As shown in
Note that actually, the contour of the high-repellency region 41 does not need to have a shape similar to the contour of the ejection orifice 9 and may extend in a direction irrelevant to movement of ink droplets. In
Next, as shown in
Next, the supply port 7 used to supply ink to the flow path is formed in the substrate 10. The supply port 7 is formed, for example, by irradiating the substrate 10 with laser or by anisotropically etching the substrate 10. Also, as shown in
An ink jet recording substrate that achieves the advantageous effects of the present invention can be produced whenever the projection/depression pattern 22 may be formed without being limited to the above step as long as the projection/depression pattern 22 is formed not before a film formation step for the layer designed to become the nozzle plate 21. However, desirably the step of forming the projection/depression pattern 22 and the step of removing the mold 20 are carried out in this order. This is because if one attempts to form the projection/depression pattern 22 after removing the mold 20, the coating layer 18 or protective layer 19 provided on the heat generating resistor 17 will also be irradiated with laser, which may affect ink droplet ejection characteristics.
The ink jet recording substrate according to the present embodiment shown in
The liquid ejection head substrate according to the present invention has a projection/depression pattern with even spacing and depth on the nozzle plate surface. Therefore, even if water repellency decreases with use, unintended variations in water repellency are less likely to occur on the nozzle plate. This enables preventing a liquid droplet ejection direction from wobbling, and thereby enables inhibiting deterioration in print quality more greatly than the conventional technique.
The ink jet recording substrate according to the embodiment of the present invention will be described concretely below with reference to examples. The present invention is not limited to these examples.
A production process according to Example 1 of the present invention will be described below with reference to
On a silicon substrate 10 on which driving elements such as transistors were provided, a thermally-oxidized layer 11 was formed to a thickness of 1 μm by thermally-oxidizing part of the substrate 10, and an aluminum layer was further formed as a sacrifice layer 14 in a location where a supply port was to be formed. Next, a heat accumulating layer 12 made of a silicon oxide film was formed to a thickness of 1 μm by plasma CVD. On the heat accumulating layer 12, a resistor layer 15 made of TaSiN (sheet resistance: 300 Ω/sq) and a film of aluminum alloy (Al—Cu; 1 μm) lower in resistance than the resistor layer 15 were formed continuously by a sputtering process. The resistor layer 15 and aluminum alloy were patterned by dry etching, forming an interconnect layer. Furthermore, aluminum alloy was removed by wet etching from a region designed to become the heat generating resistor 17 and a pair of electrode layers 16 were formed. By supplying a voltage between the pair of electrode layers 16, that part of the resistor layer 15 which was located between the pair of electrode layers 16 would be caused to generate heat and used as the heat generating resistor 17. Covering the heat generating resistor 17 and the pair of electrode layers 16, a 400-nm coating layer 18 made of SiN was deposited on an entire surface of a wafer by plasma CVD. Furthermore, a 300-nm tantalum film was formed by a sputtering process, covering the heat generating resistor 17 and patterned by dry etching, forming the protective layer 19. The structure shown in
Next, polyimide was spin-coated to a thickness of 20 μm, covering the heat generating resistor 17. Resist made of a photosensitive resin was applied to the formed polyimide film, exposed, and developed, forming a mask. Using the resist mask, the polyimide was etched by RIE, forming the mold 20 designed to become a pattern for the flow path 27. Next, a 10-μm layer of the nozzle plate 21 made of fluoridated DLC was formed by plasma CVD, covering the mold 20 from above. The structure shown in
Next, a surface of the layer designed to become the nozzle plate 21 was irradiated with a linearly-polarized femtosecond laser at energy density in the neighborhood of the processing threshold, thereby forming a grating-shaped projection/depression pattern 22.
In the projection/depression pattern 22 formed in this way, the spacing of the projections was approximately 700 nm and the depth of the depressions was approximately 200 nm. The structure shown in
Next, the ejection orifices 9 adapted to eject ink were formed in the layer designed to become the nozzle plate 21, and thus the nozzle plate 21 was formed (
The ink jet recording substrate created as described above was set on “MAXIFY (registered trademark) MB5330” (brand name) printer made by Canon, and 150000-sheet printing endurance test was conducted using A4-size sheets. As a result, no deterioration in print quality was recognized. Note that during the printing endurance test, wiping was done after every two sheets.
Next, Example 2 of the present invention will be described. In Example 1, the material itself of the nozzle plate 21 had water repellency. As shown in
In Example 2, the substrate layer 23 of the nozzle plate 21 was formed by forming a film of silicon carbonitride (SiCN) 15 μm in thickness by plasma CVD. SiCN was not water-repellent. Next, a fluoridated DLC film 2 μm in thickness was formed as the water-repellent layer 24 on the substrate layer 23 by sputtering, and then as with Example 1, a surface of the water-repellent layer 24 was irradiated with a linearly-polarized femtosecond laser at energy density in the neighborhood of the processing threshold, thereby forming a grating-shaped projection/depression pattern 22. In the projection/depression pattern 22, the spacing of the projections was approximately 700 nm and the depth of the depressions was approximately 200 nm. This configuration allows a projection/depression pattern 22 with a water-repellent material on the outermost surface thereof to be formed on the surface of the nozzle plate 21 even when the material itself of the nozzle plate 21 does not have water repellency. Subsequently, the ink jet recording substrate was produced in the same manner as Example 1, and the structure shown in
The ink jet recording substrate created as described above was subjected to a printing endurance test in the same manner as Example 1, and almost no deterioration in print quality was recognized.
Next, Example 3 of the present invention will be described. In Example 2, the projection/depression pattern 22 was formed by irradiating the water-repellent layer 24 formed on the substrate layer 23 with laser. Example 3 differed from Example 2 only in that a water-repellent layer 26 was formed after projections and depressions were formed on the substrate layer 25 itself. The rest of the configuration and production method were similar to those of Example 2, and thus description thereof will be omitted.
First, steps up to the step of forming the mold 20 of
In the projection/depression pattern 22, the spacing was approximately 700 nm and the depth was approximately 200 nm. Next, a fluorine resin was spray-coated onto the projection/depression pattern 22, thereby forming a water-repellent layer 26 with a thickness of 5 nm. Regarding the fluorine resin, one that can form a monomolecular film is used suitably, and grooves are not buried when surplus resin adhering along the projection/depression pattern, i.e., resin other than the monomolecular film, is removed by washing or the like. This configuration allows a projection/depression pattern 22 with a water-repellent material on the outermost surface thereof to be formed on the surface of the nozzle plate 21 even when the substrate layer (material for forming the substrate layer) itself of the nozzle plate 21 does not have water repellency. Subsequently, the ink jet recording substrate was produced in the same manner as Example 1, and the structure shown in
The ink jet recording substrate created as described above was subjected to a printing endurance test in the same manner as Example 1, and almost no deterioration in print quality was recognized.
Next, Example 4 of the present invention will be described. In this example, description will be given of how deterioration in print quality is affected by an angle (hereinafter referred to as θ) formed by a direction of grooves in the projection/depression pattern 22 formed on the nozzle plate 21 and the wiping direction for wiping ink droplets attached to the surface of the nozzle plate 21 during use. The direction of grooves in the projection/depression pattern 22 can be controlled by a polarization direction of the laser. This example differed from Example 3 only in the polarization direction of the laser used to form the projection/depression pattern 22. The rest of the configuration and production method were similar to those of Example 3, and thus description thereof will be omitted.
In Example 4, ink jet recording substrates with θ of between 0 and 90 degrees were created by varying the polarization direction of the laser for irradiation.
The ink jet recording substrate created as described above was subjected to a printing endurance test in the same manner as Example 1. When the angle θ was from 0 degrees to 45 degrees, almost no deterioration in print quality was recognized even after 150000 sheets of printing. When the angle θ was 60 degrees or 75 degrees, almost no deterioration in print quality was recognized after 100000 sheets of printing, but deterioration in print quality was recognized after 150000 sheets of printing. Also, when the angle θ was 90 degrees, deterioration in print quality was recognized before reaching 100000 sheets of printing. When the head was analyzed after the test, it was found that the water-repellent layer decreased with increases in the angle θ. Results of the test are summarized in Table 1.
Next, Example 5 of the present invention will be described. In Example 5, description will be given of a case in which the period of the projection/depression pattern 22 is changed on the nozzle plate 21. Note that the ink jet recording substrate used in Example 5 differed from Example 1 only in a laser irradiation method. The rest of the configuration and production method were similar to those of Example 1, and thus description thereof will be omitted.
The spacing of the projections making up the projection/depression pattern 22 can be controlled by an angle formed by the laser beam and the surface of the nozzle plate 21. That is, the spacing of the grooves is the narrowest when the laser beam is emitted at right angles to the nozzle plate 21 and approximately coincides with the wave length of the laser. When the laser beam is emitted at an inclined angle to the nozzle plate, the spacing of the grooves increases, and the larger the angle, the larger the spacing of the grooves. Using this phenomenon, in this example, by scanning a laser of the same wave length while changing an irradiation angle, the projection/depression pattern 22 was formed such that the spacing of the projections would be narrow in a neighborhood of the ejection orifices 9, increasing with increasing distance from the ejection orifices 9. More specifically, the high-repellency region 41 was formed by emitting the laser at right angles to the nozzle plate 21 in the neighborhood of the ejection orifices 9 and the low-repellency region 42 was formed by decreasing the angle of incidence of the laser with increasing distance from the ejection orifices 9. The nozzle plate surface of the ink jet recording substrate created in this way is shown in
The spacing of the projection/depression pattern 22 was classified into levels A to C as follows. At level A, a region covering the distance R corresponding to a radius R of the ejection orifice from the contour of the ejection orifice 9 was a high-repellency region 41 in which the spacing of the projections was approximately 700 nm and groove depth was approximately 200 nm. A region further away from the ejection orifice 9 was a low-repellency region 42 in which the spacing of the projections was approximately 2000 nm and groove depth was approximately 600 nm. At level B, a region covering the distance 2R corresponding to a diameter of the ejection orifice 9 from an edge of the ejection orifice 9 was a high-repellency region 41 and a region on an outer side thereof was a low-repellency region 42. At level C, the projection spacing in the neighborhood of the ejection orifice 9 was approximately 700 nm and groove depth was approximately 200 nm. The projection spacing increased gradually with increasing distance from the ejection orifice 9. At the edge of the projection/depression pattern, the projection spacing was approximately 2000 nm and groove depth was approximately 600 nm. Note that at level C, scanning was done by changing the laser irradiation angle and there was no clear boundary between the high-repellency region 41 and low-repellency region 42.
The ink jet recording substrate created as described above was subjected to a printing endurance test in the same manner as Example 1, and almost no deterioration in print quality was recognized at any of the levels. When the nozzle plate surface was observed after the printing endurance test, adhesion of ink droplets was found in locations away from the ejection orifices, but almost no adhesion of ink droplets was found in the neighborhood of the ink ejection orifices.
The printing endurance test was continued to check relative superiority among the levels, and deterioration in print quality was observed in the order: in level C, level A, and level B.
The present invention, which can form a projection/depression structure with even spacing and depth at a desired position unlike the conventional technique, enables preventing a liquid droplet ejection direction from wobbling due to variations in water repellency resulting from changes in water repellency with use. Thus, the present invention provides a liquid ejection head substrate that can inhibit deterioration in print quality more greatly than the conventional technique.
In a comparative example, a projection/depression pattern 22 on the nozzle plate 21 was formed by rubbing. The comparative example differed from Example 1 only in that the projection/depression pattern 22 on the nozzle plate 21 was formed by rubbing. The rest of the configuration was similar to that of Example 1, and thus description thereof will be omitted. Cotton velvet cloth was used for the rubbing. Compared to Example 1, the projection/depression pattern 22 was formed randomly, the spacing of projections was distributed in a range of 10 nm to 1 μm, and the depression depth was dispersed. When 100000 sheets were printed as with Example 1 using an ink jet recording substrate created in this way, there were variations in the ejection direction of ink droplets and deterioration in print quality was recognized.
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. 2018-034903, filed Feb. 28, 2018, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-034903 | Feb 2018 | JP | national |
