Patent Application
20120222308
The present invention relates to a method for processing a silicon substrate and a method for manufacturing a substrate for a liquid ejection head.
As one representative example of a liquid ejection head ejecting a liquid, there may be mentioned an ink jet recording head applied to an ink jet recording method which performs recording by ejecting ink to a recording medium. In general, a liquid ejection head represented by the ink jet recording head includes flow paths, energy generating portions provided in the respective flow paths, and minute ejection ports for ejecting a liquid by energy generated in the energy generating portion. For manufacturing this liquid ejection head, a lithographic method using photosensitive materials is frequently employed in view of microfabrication and the like.
In the method disclosed in Japanese Patent Laid-Open No. 2006-044237 (Patent Literature 1), a patterned layer of molds for flow paths is formed using a photo-sensitive material on a substrate having ejection energy generating portions, and subsequently, a covering layer formed into a flow path wall forming member is provided on the patterned layer. After openings used as ejection ports are formed in the covering layer on the patterned layer of molds for flow paths and at positions facing energy generating surfaces of the energy generating portions, the patterned layer is removed, so that rooms each functioning as a flow path are formed.
However, when the liquid ejection head is manufactured using the method disclosed in Patent Literature 1, the following may unfavorably arise in some cases.
For example, since being formed along the patterned layer of molds for flow paths, the covering layer is liable to be influenced by the shape of the patterned layer. Hence, the thickness of the covering layer in the vicinity of the central portion of the patterned layer may be different from the thickness of the covering layer in the vicinity of the end portion of the patterned layer, and as a result, the distribution in thickness of the covering layer may be generated. In addition, when solvent coating of a liquid photo-sensitive resin is performed on a silicon wafer to form the covering layer, while a solvent of the photosensitive resin evaporates, the photosensitive resin spreads so as to get over the patterned layer. Hence, the thickness of the covering layer located at a central side of the wafer is unfavorably different from the thickness of the covering layer located along an outer peripheral portion of the wafer.
Since the thickness of the covering layer on the patterned layer determines the length of a liquid path of an ejection port portion, when the variation in thickness of the covering layer occurs, the distance between the ejection port surface and the energy generating surface of the energy generating portion (element) may vary. Since this distance is a factor having a strong influence on the amount of a liquid to be ejected, when the above variation occurs, it becomes difficult to stably eject liquid droplets having uniform liquid volumes. This is a serious problem in the field of an ink jet recording method by the following reasons.
In the field of an ink jet recording method, further improvement in image quality has been increasingly demanded year by year.
Hence, an ejected liquid droplet is required to be minimized, and the liquid ejection head is also increasingly required to satisfy the above requirement.
PTL 1: Japanese Patent Laid-Open No. 2006-044237
The present invention provides a method for manufacturing a liquid ejection head with good yield, the liquid ejection head being capable of suppressing variation in liquid volume of ejected liquid droplets and of stably and repeatedly ejecting liquid droplets having uniform liquid volumes.
According to one aspect of the present invention, there is provided a method for manufacturing a liquid ejection head which has ejection ports each ejecting a liquid and flow paths communicating with the ejection ports, comprising:
a first step of preparing a substrate on which a first layer and a second layer are evenly laminated in this order; a second step of forming members (A) for forming the ejection ports from the second layer; a third step of forming molds for forming the flow paths from the first layer; a fourth step of providing a third layer so as to cover the molds and so as to come into close contact with the members (A); and a fifth step of removing the molds to form the flow paths.
According to the present invention, a liquid ejection head which can suppress the variation in liquid volume of ejected liquid droplets and which can stably and repeatedly eject liquid droplets having uniform liquid volumes can be manufactured with good yield.
Hereinafter, the present invention will be described with reference to the drawings.
A liquid ejection head can be mounted on an apparatus such as a printer, a copying machine, a facsimile machine having a communication system, a word processor having a printer unit, and also an industrial recording apparatus integrally combined with various processing devices. The liquid ejection head can also be used, for example, for biochip production, printing of electronic circuits, and spraying of chemicals.
The liquid ejection head of the present invention shown in
A flow-path wall member 4 which forms walls of the flow paths 6 communicating with the respective ejection ports 5 from the supply port 3 is integrally formed with an ejection port member in which the ejection ports 5 are provided.
Next, a first embodiment of a method for manufacturing a liquid ejection head of the present invention will be described with reference to
As shown in
Molds 10 for flow paths are formed from the first layer 7, and ejection port forming members (A)9 are formed from the second layer 8. Since each of the molds 10 on the substrate 1 is finally removed, the first layer 7 can be formed from a material which can be easily removed by using a solvent. By the reason described above, the first layer 7 can be formed from a positive type photosensitive resin. Although through-holes used as the ejection ports are provided in the ejection port forming members (A)9, the through-holes can be formed by a photolithographic method to have minute dimensions with high positional accuracy. In addition, the ejection port forming members (A)9 are each required to have a mechanical strength as a structural member. By the reason described above, the second layer 8 can be formed from a negative type photosensitive resin.
As the positive type photosensitive resin used for the first layer, for example, a poly(methyl isopropenyl ketone) and a copolymer of methacrylic acid and a methacrylate may be mentioned as a suitable resin. The reasons for this are that the above compound can be easily removed by a commonly used solvent and that since the above compound has a simple composition, constituent components thereof have only a small influence on the second layer 8.
As the negative type photosensitive resin used for the second layer 8, for example, a composition containing a resin having an epoxy group, an oxetane group, a vinyl group, or the like and a polymerization initiator corresponding to the above resin may be mentioned as a suitable composition. The reason for this is that since a resin having the above functional group has high polymerization reactivity, the member (A)9 can be obtained to have a high mechanical strength.
The thickness of the first layer 7 and the thickness of the second layer 8 can be appropriately and separately determined. When an ejection port which ejects a minute liquid droplet having a several picoliters and a liquid flow path corresponding to the above ejection port are formed, the thickness of the first layer 7 is preferably set in a range of 3*10−6 m to 15*10−6 m, and the thickness of the second layer 8 is preferably set in a range of 3*10−6 m to 10*10−6 m.
In this case, a photosensitive liquid repellent material may be provided on a predetermined surface of the second layer 8 for the purpose of imparting a liquid repellent function to the surface in which the ejection ports are provided.
Next, the ejection port forming members (A)9 are formed from the second layer 8 (second step). First, as shown in
Since the first step and the second step are performed in this order, when the surface of the first layer is flat before being machined into the molds for flow paths, the members (A)9 can be obtained from the second layer 8 to have substantially no variation in thickness. As shown in
In addition, when a liquid repellent material is applied on the surface of the second layer 8, the upper surface of each of the members (A)9 (surface of each member (A)9 opposite to the substrate 1 side) has liquid repellence, and it is convenient since liquids, such as ink, do not adhere to the upper surface of the member (A)9. When an ink including a pigment or a dye is assumed as an ejection liquid, it is believed that liquid repellence at a water advance contact angle of approximately 80 degrees or more is sufficient. A water advance contact angle of approximately 90 degrees or more is more preferable since the adhesion of the liquid to the member (A)9 can be further suppressed.
Subsequently, the mold 10 which has the shape of the flow path is formed from the first layer 7 (third step). As shown in
Subsequently, as shown in
By the reason described above, when the first layer 7 has a thickness of 3*10−6 m to 15*10−6 m, and the second layer 8 has a thickness of 3*10−6 m to 10*10−6 m, the third layer 11 is formed to have a thickness of more than 3*10−6 m from the energy generating surface. In addition to that described above, in consideration of the intensity of stress generated inside the third layer 11, the thickness of the third layer 11 is preferably set to 40*10−6 m or less.
As for the thickness of the third layer 11, the upper surface position thereof may be higher (larger) than, may be equivalent to, or may be lower (smaller) than the position of an upper surface 13 of the member (A)9. For example, as shown in
Next, as shown in
Subsequently, as shown in
Next, as shown in
Subsequently, as shown in
Subsequently, a liquid repellent function may be imparted to the opening surface 14 of the ejection port 5.
A second embodiment of the present invention will be described with reference to
Steps from the start to the step (first step) shown in
As shown in
Subsequently, as shown in
Next, the mold 10 is formed in a manner similar to that of the method described with reference to
Since liquid repellence is imparted to the opening surface 14 at which the ejection port 5 of the member (A)9 is open, an ejection liquid 30 filled in the flow path does not stay on the opening surface 14 (see
A third embodiment of the present invention will be described with reference to
First, the steps shown in
Subsequently, in the step (third step) of forming the molds for flow paths, as shown in
When the exposed portions of the first layer 7 are removed by development, as shown in
Since the member (A)9 which is in contact with the first layer 7 is used as a shade mask, the alignment accuracy therebetween can be improved. In addition, the first layer is suppressed from being exposed by light diffracted by the shade mask.
Subsequently, the third layer 11 is provided so that the thickness thereof is higher than the upper surface of the mold 10 (fourth step). Next, as shown in
Hereinafter, the present invention will be described in more detail with reference to Examples.
With reference to
First, the substrate 1 (6-inch wafer) provided with the first layer 7 and the second layer 8 was prepared (
Next, a composition shown in Table 1 was applied on the first layer 7 using a spin coating and was dried at 90 degrees centigrade for 3 minutes, so that the second layer 8 was formed. The average thickness of the second layer 8 was 5*10−6 m, and the standard deviation of the thickness thereof within the substrate (6-inch wafer) was 0.2*10−6 m (350 positions in the 6-inch wafer were measured).
Next, the second layer 8 was exposed using a mask aligner MPA-600 Super (product name) manufactured by CANON KABUSHIKI KAISHA (
Subsequently, postbake and development were performed on the second layer 8, so that the members (A)9 were formed. In addition, the exposure dose was 1 J/cm2, a mixed liquid of methyl isobutyl ketone/xylene at a ratio of 2/3 was used as a developing solution, and xylene was used as a rinse agent after development.
Next, the first layer 7 was irradiated at 10 J/cm2 with deep-UV light (wavelength of 220 nm to 400 nm) using a mask aligner UX-3000SC (product name) manufactured by Ushio, Inc. (
Subsequently, after development of the first layer 7 was performed using methyl isobutyl ketone, the first layer 7 was rinsed with isopropyl alcohol, and the exposed portions of the first layer 7 were removed, so that the molds 10 for flow paths were formed (
Next, the composition shown in Table 1 was applied on the members (A)9 and the molds 10, so that the third layer 11 was formed (
Subsequently, after exposure was performed on the third layer 11 (exposure dose=1 J/cm2) by MPA-600 Super (product name: manufactured by CANON KABUSHIKI KAISHA) (
By using a tetramethylammonium hydroxide aqueous solution at 80 degrees centigrade as an etching solution, anisotropic etching was performed on the substrate 1 of silicon, so that the supply port 3 was formed (
Then, the molds 10 on the substrate 1 were dissolved by methyl lactate and were removed, so that the ejection ports 5 each having a diameter of 12*10−6 m were formed (
Within the substrate (6-inch wafer), the average distance D was 12*10−6 m, and the standard deviation thereof was 0.25*10−6 m. Incidentally, 350 ejection ports in the wafer were evenly selected from the center to the end of the wafer, and the distance D was obtained from each ejection port by measurement.
Finally, the 6-inch wafer was cut by a dicing saw, and one liquid ejection head was obtained.
Example 2 will be described with reference to
Different points of Example 2 from Example 1 were as follows. The thickness of the second layer 8 from the upper surface of the first layer 7 was set to 10*10−6 m, and the third layer 11 was formed so that the height of the upper surface of a portion thereof provided on the first layer 7 was set to 5*10−6 m from the upper surface of the first layer 7. As described above, the third layer 11 was provided so that the upper surface thereof was located lower than the upper surface of the member (A)9. The others points of this example were performed in a manner similar to that in Example 1.
Within the substrate (6-inch wafer), the average distance D was 17*10−6 m, and the standard deviation of the distance D was 0.25*10−6 m. In addition, as in Example 1, 350 ejection ports in the wafer (6-inch wafer) were evenly selected from the center to the end of the wafer, and the distance D of each ejection port was measured.
A method for forming a liquid ejection head according to a comparative example will be described with reference to
After ODUR-1010 (trade name, manufactured by Tokyo Ohka Kogyo Co., Ltd.) was applied on a silicon substrate 101 (6-inch wafer) provided with energy generating elements 102, drying was performed, so that a layer 103 of a positive type photo-sensitive resin having a thickness of 7*10−6 m was formed on the substrate 101 (
Subsequently, exposure and following development were performed on the layer 103 of a positive type photosensitive resin, so that a mold 104 for a flow path was formed (
Next, the composition shown in Table 1 of Example 1 was applied on the mold 104 using a spin coating method, followed by performing drying at 90 degrees centigrade for 3 minutes, so that a covering layer 105 was formed. The covering layer 105 was formed so that a portion thereof provided on the upper surface of the mold 104 had a thickness of 7*10−6 m (
Subsequently, exposure was performed on the covering layer 105 using a mask 110, and an exposed portion 106 was cured (
Non-exposed portions of the covering layer 105 were removed by development, so that a member 111 forming walls of the flow paths and ejection ports 107 each having a diameter of 12*10−6 m were formed (
Next, after a supply port 109 was formed in the substrate 101, the mold 104 was removed, so that a flow path 108 was formed (
Next, the 6-inch wafer was cut by a dicing saw, and one liquid ejection head unit was separated.
In the liquid ejection head thus obtained, the average value of a distance h from the energy generating surface of the energy generating element 102 of the substrate 101 to the ejection port 107 was 12*10−6 m. In addition, the standard deviation of the distance h was 0.6*10−6 m. Incidentally, 350 ejection ports in the wafer were evenly selected from the center to the end of the wafer, and the distance h was obtained from each ejection port by measurement.
It is found that the standard deviation of the distance D of the liquid ejection head according to each of Examples 1 and 2 is significantly different from the standard deviation of the distance h of the liquid ejection head according to Comparative Example 1.
The reason the standard deviation of the distance D was as small as 0.25*10−6 m is believed that the members (A)9 having a significantly small variation in thickness can be obtained from the second layer 8 which is evenly formed.
On the other hand, one reason the standard deviation of the distance h was as large as 0.6*10−6 m is believed that the height of the upper surface of the covering layer 105 under which the mold 104 is provided is different from that under which the mold 104 is not provided. In addition, as another reason the standard deviation of the distance h was large in Comparative Example 1 is believed as follows. Since no mold 104 is provided at a position outside the mold 104 which is provided at an outermost peripheral portion of a 6-inch wafer, the height of the upper surface of the covering layer 105 at the peripheral portion of the wafer is formed relatively lower than that at the central portion thereof.
Test recording was performed using the liquid ejection heads of Examples 1 and 2 and Comparative Example 1. The recording was performed using a plurality of liquid ejection heads cut out from the same 6-inch wafer. In addition, a liquid ink containing pure water/diethylene glycol/isopropyl alcohol/lithium acetate/black dye food black 2 at a ratio of 79.4/15/3/0.1/2.5 was used, and the recording was performed at an ejection volume Vd of 1 picoliter and an ejection frequency f of 15 kHz.
When the image obtained by recording was observed, it was found that a very high quality recording image was obtained when recording was performed using the liquid ejection heads of Examples 1 and 2. In addition, the images formed by a plurality of liquid ejection heads obtained from the same 6-inch wafer were equally high quality. On the other hand, when the recording was performed using the liquid ejection head of Comparative Example 1, the recorded image was non-uniform as compared to that of each of Examples 1 and 2. In addition, when the recorded images obtained by using a plurality of liquid ejection heads formed from the same 6-inch wafer were compared to each other, the degree of non-uniformity was slightly different from each other. The reason for this is believed that since the standard deviation of the distance D described above is smaller than that of the distance h, the variation in volume of ink ejected from the liquid ejection head of each of Examples 1 and 2 is smaller than the variation in volume of ink ejected from the liquid ejection head of Comparative Example 1.
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. 2009-258192, filed Nov. 11, 2009, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-258192 | Nov 2009 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2010/006474 | 11/2/2010 | WO | 00 | 5/2/2012 |
