Patent Application
20100149260
1. Field of the Invention
The present invention relates to an ink jet head and a method of manufacturing the ink jet head.
2. Description of the Related Art
In general, ink jet heads used for ink jet recording methods (liquid-ejecting recording methods) in which recording liquids are ejected to perform recording include ink passages, substrates including energy-generating elements for ejecting ink droplets placed in portions of the ink passages, and fine ink discharge ports (referred to as “orifices”) for ejecting the ink droplets in the ink passages with the energy generated from the energy-generating elements.
U.S. Pat. No. 6,143,190 discloses a method of forming a supply port for supplying ink to energy-generating elements by anisotropic etching. In this method, when a {100} plane of a silicon wafer with a {100} orientation is etched, etching proceeds such that a {111} plane which is inclined at an angle of 54.7 degrees to an etching start surface and which is tapered in the thickness direction is obtained. Among crystal planes of silicon, the {111} plane is unlikely to be etched with a solution.
On the other hand, in the case of setting the area of a front surface aperture of a supply port to a predetermined value, the area of a back surface aperture of the supply port is greater than the area of the front surface aperture of the supply port. Since the back surface of a substrate is a junction with a member for supporting the substrate, the back surface of the substrate needs to have a portion with an area sufficient to form a good bond therebetween.
A supply port can be formed in a substrate with a {100} orientation by a dry etching process so as to have a wall perpendicular to the substrate. However, it is difficult to form the supply port in a {111} plane of the substrate because the {111} plane thereof is resistant to etching.
The present invention provides an ink jet head which can be securely bonded to a support substrate for supporting the ink jet head and which includes a supply port having walls highly resistant to liquids. Furthermore, the present invention provides a method of readily manufacturing such an ink jet head.
An ink jet head according to an embodiment of the present invention includes a Si substrate with a surface having a {100} orientation; a passage holding ink on the Si substrate; an ink discharge port which is communicatively connected to the passage and through which ink is ejected; and a supply port which extends through the Si substrate, which is communicatively connected to the passage, and which supplies ink to the passage. The supply port has walls having two {111} planes facing each other.
According to the present invention, the following head can be obtained: an ink jet head which includes an ink supply port having walls having {111} planes highly resistant to ink, which has high adhesion to a support substrate bonded to the ink jet head, and which has high reliability.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
A method of manufacturing an ink jet head according to an embodiment of the present invention will now be described in detail with reference to the attached drawings.
In this step, a photodegradable positive resist layer 3 is formed on a substrate 1 as shown in
The substrate 1 is made of Si and carries energy-generating elements (not shown) for ejecting ink. Examples of the energy-generating elements include, but are not limited to, electric heat-generating elements and piezoelectric elements. When the energy-generating elements are electric heat-generating elements, a protective layer (not shown) may be formed over the electric heat-generating elements for the purpose of reducing the impact caused by bubbling, the purpose of preventing damage caused by ink, and/or the like.
Examples of a photodegradable positive resist used to form the photodegradable positive resist layer 3 include, but are not limited to, common resists, such as poly(methyl isopropenyl ketone) (PMIPK) and poly(vinyl ketone), sensitive to light with a wavelength of about 290 nm and methacrylate unit-containing polymers, such as poly(methyl methacrylate) (PMMA), sensitive to light with a wavelength of about 250 nm.
After the photodegradable positive resist layer 3 is formed, a predetermined region is removed from the photodegradable positive resist layer 3 by a photolithographic process including an exposure step and a development step, whereby ink passage patterns (structures) 4 is formed as shown in
The photodegradable positive resist layer 3 is irradiated with an ionizing radiation through a quartz mask 2 having the same pattern as each ink passage pattern 4. The ionizing radiation used has a wavelength which is close to about 250 or 290 nm and to which the photodegradable positive resist used herein is sensitive. This allows a region of the photodegradable positive resist layer 3 that is irradiated with the ionizing radiation to be degraded to selectively increase the solubility of this region in a developing liquid. Therefore, the structures 4, which are used to form ink passages 20, can be formed above the substrate 1 by developing the photodegradable positive resist layer 3 irradiated with the ionizing radiation.
The developing liquid is not particularly limited and may be a solvent that does not dissolve an unexposed region but dissolves an exposed region increased in solubility.
The structures 4 are coated with a negative resist layer 5 for forming the walls of the ink passages 20 as shown in
A negative resist used to form the negative resist layer 5 may be, but is not limited to, one based on a reaction such as cationic or radical polymerization. For example, a negative resist based on cationic polymerization is cured in such a manner that molecules of a cationically polymerizable monomer or polymer contained in this negative resist are polymerized or cross-linked by cations generated from a cationic photoinitiator contained in this negative resist. Examples of the cationic photoinitiator include aromatic iodonium salts and aromatic sulfonium salts and, in particular, include photoinitiators, SP-170™ and SP-150™, commercially available from Adeka Corporation.
Suitable examples of the cationically polymerizable monomer or polymer include, but are not limited to, those containing an epoxy group, a vinyl ether group, or an oxetane group.
The negative resist layer 5 is can be formed in such a manner that the negative resist is applied to the structure 4 by a spin coating process, a direct coating process, a laminate transfer process, or another process.
An ink-repellent layer (not shown) is formed on the negative resist layer 5 as required. The ink-repellent layer, as well as the negative resist, is preferably cross-linkable and sensitive to light. It is important that the ink-repellent layer is incompatible with the negative resist. The ink-repellent layer can be formed by a spin coating process, a direct coating process, a laminate transfer process, or another process.
Ink discharge ports 6 is formed in predetermined portions of the negative resist layer 5 as shown in
In this operation, the negative resist layer 5 is cured in such a manner that a region other than portions for forming the ink discharge ports 6 is irradiated with light and the portions for forming the ink discharge ports 6 are shielded from light. The ink-repellent layer is cured together with the negative resist layer 5 and the resulting ink-repellent layer and negative resist layer 5 are developed, whereby the ink discharge ports 6 are formed. The following liquid is most suitable for the negative resist layer 5 and the ink-repellent layer: a developing liquid which is incapable of dissolving an exposed portion but is capable of completely dissolving off an unexposed portion and which does not dissolve the photodegradable positive resist (the structure 4), which is disposed under the negative resist layer 5. Examples of the developing liquid include methyl isobutyl ketone and a solvent mixture of methyl isobutyl ketone and xylene. The reason for why it is important that the photodegradable positive resist is not dissolved in this operation is as described below. In usual, a plurality of heads are provided on a single wafer and the wafer is cut into ink jet heads. Therefore, a photodegradable positive resist for forming ink passage patterns is preferably dissolved off subsequently to the cutting of the wafer for waste reduction.
The ink passages 20 and the ink discharge ports 6 may be formed after ink supply ports 8 below is formed. In this case, the formed ink supply ports 8 may be filled with resin or ink passages formed in different substrates may be attached to each other.
A step of forming the ink supply ports 8 is described below.
Silicon substrates with surfaces having a corresponding one of a {100} orientation, a {110} orientation, and a {111} orientation are often selected. If a silicon substrate having a surface with an orientation other than the {100} orientation is used and MOS transistors are formed on the silicon substrate, the field-effect mobility of electrons and holes in the silicon substrate is nonuniform in the in-plane direction. This causes in-plane dependence and differences in properties. Since interfacial properties thereof are unsatisfactory, good gate insulating layers are unlikely to be formed and therefore failures such as leakage currents are likely to be caused. In the field of microelectromechanical systems (MEMS) in which driving circuits are configured on surfaces, substrates with surfaces having a {100} orientation are suitable. The thickness of the substrates is selected in consideration of the strength required for substrates for ink jet heads.
Examples of a process of forming the ink supply ports 8 include, but are not limited to, anisotropic etching, laser processing, and dry etching.
The following procedure is usually used to form the ink supply ports 8 in consideration of tact efficiency because portions with a large volume are removed from the substrate 1: an etching mask is formed on the substrate 1 and the substrate 1 is then anisotropically etched. In the procedure, the ink supply ports 8 formed in the substrate 1 have a quadrangular pyramid shape. In order to form the ink supply ports 8 such that the ink supply ports 8 have a target aperture area at an etching end surface, the aperture area (W) of each ink supply port 8 at an etching start surface needs to be set to be large as shown in
The ink supply ports 8 can be densely provided in such a manner that the ink supply ports 8 are formed by dry etching so as to have a vertically rectangular shape, because the aperture area of the back surface need not be large. In the case of using a substrate with a surface having in a {100} orientation, walls of the ink supply ports 8 are perpendicular to the {100} plane and are parallel to the {110} plane and therefore such a substrate has low reliability against ink. In order to form the ink supply ports 8 such that walls of the ink supply ports 8 are perpendicular to the {111} plane, the substrate 1 needs to have a surface with a {110} orientation. This can cause in-plane dependence and differences in properties as described above because the field-effect mobility of electrons and holes in a silicon substrate is nonuniform in the in-plane direction thereof in the case of forming MOS transistors or the like on the silicon substrate. Since interfacial properties thereof are unsatisfactory, good gate insulating layers are unlikely to be formed and therefore failures such as leakage currents are likely to be caused.
The inventors have made intensive investigations and have found that openings having a desired aperture area can be formed in the front surface and openings having a small aperture area can be formed in the back surface in such a manner that the ink supply ports 8 are formed so as to have a rectangular or slit shape in a direction parallel to the {111} plane. Four walls of each ink supply port 8 are all {111} planes and the ink supply port 8 has one or more pairs of parallel surfaces; hence, the back openings can be more greatly reduced in aperture area than conventional ones having a quadrangular pyramid shape as shown in
Therefore, the ink jet head can be manufactured so as to include the ink supply ports 8 each surrounded by {111} planes resistant to ink. The ink jet head has high reliability because the bonding area (S) between the substrate 1 and the support substrate is large and therefore failures such as the leakage of ink are prevented. Since each ink supply port 8 has a reduced aperture area (W) at the back surface, the ink jet head can be manufactured such that the density of nozzle passages is larger than that of conventional nozzle passages. The ink jet head can be designed to be shrunk. The ink supply ports 8 can be readily arranged to be independent of each other; hence, the ink passages 20 can be formed such that ink is circulated through the ink passages 20.
An exemplary procedure for forming the ink supply ports 8 having a rectangular or slit shape in parallel to the {111} plane is described below.
The negative resist layer 5 having surface discharge ports is protected with a protective layer 7 with etching resistance as shown in
The substrate 1 is drilled from the back surface toward front surface thereof in directions substantially parallel to {111} planes 60 by a dry process such that the aperture area at the front surface is traced, whereby the ink supply ports 8 can be formed as shown in
A Si substrate with a front surface that is a {100} plane has four {111} planes which are not parallel to each other. Therefore, rectangular or slit-shaped ink supply ports can be formed so as to have pairs of walls composed of two {111} planes substantially parallel to each other in such a manner that the Si substrate is drilled in the direction parallel to one of the four {111} planes. Alternatively, ink supply ports can be formed so as to have slits arranged in descending order of length in such a manner that openings in the front surface are fixed and the drilling direction of the Si substrate is shifted with respect to one {111} plane other than a pair of {111} planes substantially parallel to each other.
Rectangular or slit-shaped ink supply ports can be formed so as to each have two pairs of {111} planes substantially parallel to each other in such a manner that the Si substrate is drilled in the direction parallel to the boundary between adjacent two of the four {111} planes. The ink supply ports each have two pairs of {111} planes substantially parallel to each other and all the four walls of each ink supply port are surrounded by {111} planes; hence, the dissolution of Si in ink is reduced. This is preferable.
A laser used to form the ink supply ports in the Si substrate needs to emit light which has a wavelength absorbed by Si and which has intensity sufficient to process Si. Examples of the laser include, but are not limited to, commercially available laser beam machines such as CO2 ultraviolet lasers and solid YAG lasers, which have sufficient absorption intensity with respect to Si and therefore can be used to process Si, including fundamental lasers, second-harmonic lasers, third-harmonic lasers, and similar lasers. Gas and/or plasma may be used to increase the processing accuracy and processing efficiency of the laser. Furthermore, an assist technique, such as aqueous treatment, for removing heat and/or debris (dust) generated during processing may be used.
Examples of dry etching, used to form the ink supply ports in the Si substrate, for removing Si include, but are not limited to, dry etching processes, such as Bosch processes and DRIE, capable of performing directional deep drilling. In a substrate with a surface having a {100} orientation, there are four directions having two pairs of {111} planes as shown in
Another embodiment of the present invention is described below with reference to
Rectangular ink supply ports each having four {111} planes can be formed in a substrate with a surface having a {100} orientation in four directions. This allows these ink supply ports to intersect with each other in this substrate as shown in
The protective layer 7 is removed from the negative resist layer 5 and the negative resist for forming the ink passage patterns 4 are removed, whereby the ink passages 20 are formed so as to be connected to the ink discharge ports 6 as shown in
In this step, the negative resist forming the ink passage patterns 4 is irradiated with an ionizing radiation so as to be degraded, whereby the solubility of the negative resist in a remover is increased. The ionizing radiation may the same as that used to pattern the photodegradable positive resist layer 3. Since an object of this step is to form the ink passages 20 by removing the ink passage patterns 4, the ionizing radiation can be applied to the whole of the negative resist without using a mask. The negative resist forming the ink passage patterns 4 can be completely removed with substantially the same developing liquid as that used to pattern the photodegradable positive resist layer 3. In this step, the following solvent can be used without consideration of patternability: a solvent which is capable of dissolving the negative resist and which has no influence on the negative resist layer 5 or the ink-repellent layer. The ink jet head can be manufactured through the above steps.
After Step 2 is performed to form the ink supply ports 8, Step 1 may be performed to form the ink passages 20 and the ink discharge ports 6. In this case, the substrate 1 has the ink supply ports 8; hence, Step 1 can be performed in such a manner that the ink supply ports 8 are filled with resin or another substrate having ink passages is bonded to the substrate 1.
In the case of bonding the substrate having the ink passages is bonded to the substrate 1 having the ink supply ports 8, there is an advantage in that the ink supply ports 8 can be formed by the dry process so as to extend through the substrate 1 without consideration of influence on walls of the ink passages and therefore conditions of the dry process need not be precisely controlled. However, the following steps are additionally required: a step of correcting the misalignment of the ink passages and a step of removing a treating agent remaining in the ink supply ports 8. Therefore, the bonding of these substrates can be selected depending on the processing load and accuracy of the ink passages and the ink supply ports 8.
Examples of the present invention will now be described. The present invention is not limited to the examples.
In this example, an ink jet head was manufactured by the method according to the above embodiment.
A substrate 1 made of silicon was prepared as shown in
The following solution was applied to the substrate 1 by a spin coating process: a solution containing 20% by weight of poly(methyl isopropenyl ketone), ODUR-1010™, available from Tokyo Ohka Kogyo Co., Ltd. The substrate 1 was pre-baked at 120° C. for three minutes on a hot plate and then 150° C. for 30 minutes in an oven filled with nitrogen, whereby a photodegradable positive resist layer 3 with a thickness of 15 μm was formed as shown in
A negative resist was applied over the structures 4, whereby a negative resist layer 5 was formed as shown in
In particular, the resist solution applied over the structures 4 by a spin coating process and the substrate 1 was pre-baked at 90° C. for three minutes on a hot plate, whereby the negative resist layer 5. The negative resist layer 5 had a thickness of 20 μm and was flat. An ink-repellent layer (not shown) was formed on the negative resist layer 5 by a laminating process. The ink-repellent layer was made from a resin composition containing 35 mass parts of EHPE-3150™ available from Daicel Chemical Industries Ltd., 25 mass parts of 2,2-bis(4-glycidyloxyphenyl)hexafluoropropane, 25 mass parts of 1,4-bis(2-hydroxyhexafluoroisopropyl)benzene, 16 mass parts of 3-(2-perfluorohexyl)ethoxy-1,2-epoxypropane, four mass parts of A-187™ available from Nihon Unicar Co., Ltd., 1.5 mass parts of SP170™ available from Adeka Corporation, and 200 mass parts of diethylene glycol monoethyl ether.
The ink-repellent layer was exposed to light at a dose of 3,000 mJ/cm2 through a mask having a pattern of ink discharge ports 6 shown in
The ink-repellent layer and the negative resist layer 5 were subjected to post-exposure baking (PEB) at 90° C. for 180 seconds, developed with a solvent mixture of methyl isobutyl ketone and xylene, the ratio of methyl isobutyl ketone to xylene in the solvent mixture being 2:3, and then rinsed with xylene, whereby the ink discharge ports 6 were formed as shown in
OBC™ available from Tokyo Ohka Kogyo Co., Ltd. was applied over the ink-repellent layer, whereby a protective layer 7 was formed as shown in
Holes for forming ink supply ports 8 were formed in the back surface of the substrate 1 with a laser. In particular, a laser beam was applied to the substrate 1 in parallel to a {111} plane using a pico-second laser, Hyper Rapid™, available from Lumera in such a manner that the laser beam was inclined at an angle of 54.7 degrees to a {100} plane and a {110} plane. The laser beam was scanned in the X-Y direction and depth direction of the substrate 1 while being inclined to the substrate 1, whereby rectangular ink supply port forms were formed in the substrate 1 in parallel to the {111} plane. The ink supply port forms were processed toward arbitrary portions of the ink passage patterns (structures 4) and then communicatively connected to each other. In this operation, as shown in
After the protective layer 7 was removed with xylene, the structures 4 forming the ink passage patterns were exposed to light at a dose of 7,000 mJ/cm2 through the ink-repellent layer using a deep UV exposure system, UX-3000™, available from Ushio Inc., whereby the structures 4 were solubilized. The structures 4 were immersed in methyl lactate and ultrasonic waves were applied to the structures 4, whereby the structures 4 were removed as shown in
An ink jet head was manufactured through substantially the same steps as those described in Example 1 except that a step of forming ink supply ports 8 in the back surface of a substrate 1 was as described below.
A laser beam was applied to the substrate 1 in parallel to a {111} plane using a pico-second laser, Hyper Rapid™, available from Lumera in such a manner that the laser beam was inclined at an angle of 54.7 degrees to a {100} plane and a {110} plane. The laser beam was scanned in the X-Y direction and depth direction of the substrate 1 while being inclined to the substrate 1, whereby tabular supply port forms were formed in the substrate 1 in parallel to the {111} plane. In this operation, as shown in
An ink jet head was manufactured through substantially the same steps as those described in Example 1 except that a step of forming ink supply ports 8 in the back surface of a substrate 1 was as described below.
A laser beam was applied to the substrate 1 in parallel to a {111} plane using a pico-second laser, Hyper Rapid™, available from Lumera in such a manner that the laser beam was inclined at an angle of 54.7 degrees to a {100} plane and a {110} plane. The laser beam was scanned in the X-Y direction and depth direction of the substrate 1 while being inclined to the substrate 1, whereby rectangular supply port forms were formed in the substrate 1 in parallel to the {111} plane. In this operation, as shown in
An ink jet head was manufactured through substantially the same steps as those described in Example 1 except that a step of forming ink supply ports 8 in the back surface of a substrate 1 was as described below.
A laser beam was applied to the substrate 1 in parallel to a {111} plane using a pico-second laser, Hyper Rapid™, available from Lumera in such a manner that the laser beam was inclined at an angle of 54.7 degrees to a {100} plane and a {110} plane. The laser beam was scanned in the X-Y direction and depth direction of the substrate 1 while being inclined to the substrate 1, whereby rectangular supply port forms were formed in the substrate 1 in parallel to the {111} plane. In this operation, as shown in
An ink jet head was manufactured through substantially the same steps as those described in Example 1 except that a step of forming ink supply ports 8 in the back surface of a substrate 1 was as described below.
The substrate 1 was dry-etched in parallel to a {111} plane using a dry etching system, Pegasus™, available from Sumitomo Precision Products Co., Ltd. in such a manner that the substrate 1 was inclined at an angle of 54.7 degrees to a {100} plane and a {110} plane. Rectangular supply port forms were anisotropically etched in such a manner that the substrate 1 was immersed in an 80° C. aqueous solution of tetramethylammonium hydroxide, whereby the ink supply ports 8 were formed so as to each have four {111} planes as shown in
The ink jet heads manufactured in Examples 1 to 5, ink tanks, and other components were assembled into ink jet units. Each ink jet unit was mounted on a printer and then evaluated for ejection and recording. This showed that printing was performed stably and obtained prints had high quality.
In order to confirm advantages of the present invention, an ink jet head for comparison was manufactured as described below. In this comparative example, the ink jet head included a substrate 1 identical to that described in Example 1 and a common supply port disposed in the back surface of the substrate 1. In a step of forming the common supply port in the back surface of the substrate 1, OBC™ available from Tokyo Ohka Kogyo Co., Ltd. was applied over an ink-repellent layer, whereby a protective layer 7 was formed. An etching mask with a slit was formed on the back surface of the substrate 1 using a polyether amide resin, HIMAL™, available from Hitachi Chemical Co., Ltd. The substrate 1 was immersed in an 80° C. aqueous solution of tetramethylammonium hydroxide, whereby the substrate 1 was anisotropically etched, resulting in the formation of the common supply port. The shape of the etching mask was adjusted at an etching start surface such that a form including openings formed at an etching end surface in Example 1 was obtained.
After OBC™, that is, the protective layer 7 was removed with xylene, an ink-repellent layer was entirely exposed to light at a dose of 7,000 mJ/cm2 through using a deep UV exposure system, UX-3000™, available from Ushio Inc. This allowed a negative resist for forming ink passage patterns to be solubilized. The ink passage patterns were removed in such a manner that the ink passage patterns were immersed in methyl lactate and ultrasonic waves were applied to the ink passage patterns, whereby the ink jet head was obtained.
In the ink jet head manufactured as described above, ink leakage was observed when the substrate 1 was bonded to a support substrate. This is probably because an etching start surface has an opening with a large area and therefore the adhesion between the substrate 1 and the support substrate is insufficient.
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 modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2008-318510 filed Dec. 15, 2008, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-318510 | Dec 2008 | JP | national |
