Liquid ejection head and method for manufacturing liquid ejection head

A liquid ejection head and a method of forming the same. The liquid ejection head includes a substrate, an ejection port, a liquid channel, and a supply port. The substrate has, above one side thereof, an energy generating element configured to generate energy used to eject liquid. The ejection port, from which a liquid is ejected, is located at a position corresponding to the energy generating element. The liquid channel communicates with the ejection port and penetrates the substrate from the one side to another side of the substrate. The supply port communicates with the liquid channel. The substrate has a projecting layer extending inward of an inner peripheral portion of an opening in the supply port in the one side, and the projecting layer and the energy generating element are formed of the same material.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid ejection head that is able to eject a liquid from ejection ports and a method for manufacturing the liquid ejection head.

2. Description of the Related Art

Side shooter liquid ejection heads are known as common liquid ejection heads. The side shooter liquid ejection head has an energy generating element that allows droplets to be ejected perpendicularly to a surface of the head on which the energy generating element is located.

A side shooter liquid ejection head has been proposed which has an electric control circuit built into a substrate to drive the energy generating element. In the liquid ejection head, the electric control circuit is formed inside the substrate using a semiconductor manufacturing technique. A method for manufacturing such a side shooter ink jet head has been disclosed in Japanese Patent Laid-Open No. 09-011479 (1997). According to the method for manufacturing a side shooter ink jet head, disclosed in Japanese Patent Laid-Open No. 09-011479 (1997), the head is manufactured as follows. A substrate formed of silicon is provided, and a silicon anisotropic etching technique is used to form a liquid supply port in the silicon substrate. An ejection port forming layer is then joined to the silicon substrate. A liquid ejection head is thus manufactured.

FIGS. 12,13A, and13B show another method for manufacturing a side shooter liquid ejection head. According to the method for manufacturing the side shooter liquid ejection head, at first a liquid supply port formed in the silicon substrate is separated from a liquid channel formed in the ejection port forming layer by a layer formed of a thermal oxide film, an interlayer insulating film, and a protective film. In this state, the layer formed of the thermal oxide film, interlayer insulating film, and protective film is removed, by etching, from an area I shown inFIG. 12forming the liquid supply port. This allows the liquid supply port to communicate with the liquid channel.

This type of liquid ejection head has been demanded to stabilize frequency properties in order to improve print quality in association with high-speed printing. To stabilize the frequency properties, it is necessary to stabilize a liquid refilling capability with which a liquid is supplied to the liquid channel between the energy generating element and the ejection port after droplets have been ejected from the liquid ejection head. In recent years, in order to improve image quality, the size of droplets has been reduced to increase printing density. Thus, in particular, the refilling capability has been demanded to be stabilized. The liquid refilling capability depends on the opening width of the liquid supply port as well as the distance from the opening end of the liquid supply port to the energy generating element.

However, when the liquid ejection head is manufactured in accordance with the method for manufacturing the ink jet head in Japanese Patent Laid-Open No. 09-011479 (1997), the liquid supply port is formed in the silicon substrate by etching. Consequently, the positional accuracy for the liquid supply port depends on the processing accuracy of the etching. However, for the etching of the silicon substrate, etching rate varies depending on the dissolvability of silicon with respect to an etchant. The dissolvability of the silicon substrate with respect to the etchant varies depending on the position on the silicon substrate. Furthermore, the silicon substrate may contain crystal defects or impurities. Consequently, the etching rate of the silicon substrate varies depending on the position on the silicon substrate. Thus, the positional accuracy of the opening end of the liquid supply port is not fixed; the opening end is not stably formed at the same position. Since the position of the opening end of the liquid supply port is not fixed, a part of the liquid supply port which is in communication with the liquid channel does not have a fixed opening width. Furthermore, the distance from the opening end of the liquid supply port to the energy generating element is not fixed. This prevents droplets ejected from the ejection ports from being stably supplied to print media. Thus, since the liquid supply port is formed in the silicon substrate by etching, a variation occurs in the accuracy of the opening width of the liquid supply port and in the accuracy of the distance from the opening end of the liquid supply port to the energy generating element.

According to the method for manufacturing the liquid ejection head shown inFIGS. 12,13A, and13B, the opening in that part of the liquid supply port which is in communication with the liquid channel is also formed by etching. Consequently, with this method, the processing accuracy of the opening width of the liquid supply port also depends on the processing accuracy of the etching of the liquid supply port, as is the case with the method for manufacturing the liquid ejection head in Japanese Patent Laid-Open No. 09-11479. Thus, the positional accuracy of the opening end of the liquid supply port in the manufactured liquid ejection head is not fixed; the opening end is not stably formed at the same position. The distance from the center of the energy generating element to the opening end of the liquid supply port is denoted by E inFIG. 13Aand by F inFIG. 13B. As shown inFIGS. 13A and 13B, the distance from the opening end of the liquid supply port, formed by etching, to the energy generating element varies between E and F; the variation amounts to about 10 to 30 μm. This is due to a variation in silicon dissolvability and in the rate of the etching of the silicon substrate, depending on the area to be etched.

SUMMARY OF THE INVENTION

The present invention is directed to a liquid ejection head with high dimensional accuracy of the opening width of an opening in a liquid supply port, allowing a liquid refilling capability to be stabilized, as well as a method for manufacturing the liquid ejection head. The present invention is also directed to a liquid ejection head with high dimensional accuracy of the distance from the opening end of the liquid supply port to the energy generating element to allow the liquid refilling capability to be stabilized, as well as a method for manufacturing the liquid ejection head.

The liquid ejection head can be mounted on printers, copying machines, facsimiles with a communication system and word processors with a printer unit, and also on industrial printing devices used in combination with a variety of processing devices. By using this liquid ejection head, it is possible to print on a variety of print media, such as paper, threads, fibers, cloth, leather, metal, plastics, glass, wood, and ceramics. Word “print” in this specification means imparting to print media not only images having significance or meaning such as letters and figures, but also images with no meaning such as patterns.

The words “ink” or “liquid” should be interpreted in a broad sense and thus the ink, by being applied on the printing media, shall mean a liquid to be used for forming images, designs, patterns and the like, processing the printing medium or processing inks. Processing the printing medium or processing inks include coagulation or encapsulation of coloring materials in the inks to be applied to the printing media for the purpose of improvement of fixing, printing quality, coloring and endurance of images, for example.

According to an aspect of the present invention, a liquid ejection head includes a substrate, an ejection port, a liquid channel, and a supply port. The substrate has, above one side thereof, an energy generating element configured to generate energy used to eject liquid. The ejection port, from which a liquid is ejected, is located at a position corresponding to the energy generating element. The liquid channel communicates with the ejection port and penetrates the substrate from the one side to another side of the substrate. The supply port communicates with the liquid channel. The substrate has a projecting layer extending inward of an inner peripheral portion of an opening in the supply port in the one side, and the projecting layer and the energy generating element are formed of the same material. The projecting layer projecting inward of the inner peripheral portion of the opening in that part of the liquid supply port which is in communication with the liquid channel is disposed on the substrate. The accurately formed liquid flow adjusting layer appropriately controls the flow rate of the liquid. This enables the liquid refilling capability of the liquid ejection head to be stabilized. The frequency properties of the liquid ejection head are thus stabilized.

The method for manufacturing the liquid ejection head in accordance with the present invention enables the projecting layer to be accurately manufactured. This allows the appropriate control of the flow rate of the liquid ejected from the ejection ports.

DESCRIPTION OF THE EMBODIMENTS

First Embodiment

FIG. 1shows a perspective view of an ink jet print head1as a liquid ejection head in accordance with a first embodiment of the present invention.FIG. 2shows a schematic sectional view of the ink jet print head1inFIG. 1, taken along line II-II inFIG. 1.FIG. 3is an enlarged view of area G in the sectional view inFIG. 2. An ink tank (not shown) containing ink is connected to the ink jet print head1to supply ink to an ink supply port (liquid supply port)4in the ink jet print head1via a communication path (not shown). The ink jet print head1is constructed by joining an ejection port forming layer2, what is called an orifice plate, to a front surface of a substrate3.

The ink supply port4is formed to penetrate the substrate3. In the present embodiment, the ink supply port4is formed so that the opening width of the ink supply port4decreases from a back surface of the substrate3, that is, from an upstream side of an ink supply path, toward the front surface, that is, the surface on which the ejection port forming layer2is located.

A plurality of ejection ports5are formed in a surface of the ejection port forming layer2which is to be located opposite a print medium. The ejection port forming layer2and the substrate3define an ink chamber6A having an ink channel (liquid channel)6that is in communication with ejection ports5and the ink supply port4. The ink chamber6A has an opening width larger than that of an opening7in the ink supply port4.

The substrate3is produced by sequentially forming a thermal oxide film8, an interlayer insulating film9, a protective film10, and an adhesion improving layer11on a silicon base3A. The thermal oxide film8also serves as a stop layer that stops an etching step described below. The interlayer insulating film9is a layer that electrically insulates the substrate3from wires connected to heater elements12described below. The protective film10is formed of SiN (silicon nitride) in order to compensate for the insufficient rigidity of the substrate3and each of the layers arranged on the substrate3. The adhesion improving layer11is located to improve the adhesion between the substrate3and the ejection port forming layer2. The adhesion improving layer11is formed of a thermoplastic resin. The thermal oxide film8is formed by partly oxidizing the substrate3and thus does not increase the thickness of the substrate3. The thermal oxide film8is also formed on the back surface of the substrate3.

The heater elements12are arranged on the substrate3in two rows at predetermined pitches; the heater elements12are energy generating elements which generate energy used to eject ink and generate heat when energized. Although not shown in the present embodiment, the actual ink jet print head1has wires connected to the heater elements12and driving elements that drive the heater elements12, and soon. The ejection ports5are formed in the ejection port forming layer2in association with the heater elements12on the substrate3.

A cavitation resistant layer13is located on the respective heater elements12. The heater elements12are in a harsh environment; the heater elements12may be exposed to a temperature rise and a temperature drop of several hundreds degrees Celsius in a short time, and subjected to a mechanical shock by cavitation resulting from the repetition of bubbling and debubbling. To protect the heater elements12from the harsh environment, the cavitation resistant layer13, formed of, for example, tantalum (Ta), a mechanically stable metal, is located on the heater elements12.

A water repellent layer14is formed on a surface of the ejection port forming layer2which is to be located opposite a print medium, so as to cover the entire surface.

In the present embodiment, a projecting layer15is formed on the substrate3so as to extend inward of an inner peripheral portion of the opening7in the ink supply port4. Specifically, the projecting layer15is formed of the protective film10, second heater elements16, and second cavitation resistant layers17. Here, the second heater elements16formed of the same material as that of the heater elements12are located between the protective film10and the substrate3. The second cavitation resistant layer17formed of the same material as that of the cavitation resistant layer13is located at positions corresponding to the second heater elements16on the protective film10.

As shown inFIG. 2, when the opening width of the ink supply port4is defined as A and the opening width of an ink flow rate adjusting opening18formed by the projecting layer15is defined as B, the relationship A>B is satisfied. The layers of the projecting layer15are formed in an area in which the layers are in contact with ink. Thus, the projecting layer15has ink resistance.

FIG. 4is a plan view showing the ink jet print head1inFIG. 2from which the ejection port forming layer2has been removed for illustration. As shown inFIG. 4, the ink supply port4and the ink flow rate adjusting opening18are formed like rectangles each having short and long sides. When the opening width of the ink supply port4in a short side direction is defined as A and the opening width of the ink flow rate adjusting opening18in the short side direction is defined as B, the relationship A>B is satisfied, as well as shown inFIG. 2.

Now, description will be given of the method for manufacturing the ink jet print head1in accordance with the present embodiment.

In the present embodiment, silicon with a crystal orientation <100> is used as the base3A, constituting the material of the substrate3. However, the crystal face orientation is not limited to this. Other crystal orientations may be used.

First, as shown inFIG. 5A, the thermal oxide film8is formed on each of the front and back surfaces of the base3A. Then, as shown inFIG. 5B, the interlayer insulating film9is located on the thermal oxide film8. The heater elements12are arranged on the interlayer insulating film9, and the second heater elements16are arranged on the thermal oxide film8, at the same time. Once the heater elements12and the second heater elements16are arranged, the protective film10is located on the top surfaces of the heater elements12, second hater materials16, and a part of the interlayer insulating film9as shown inFIG. 5C. Then, as shown inFIG. 5D, the cavitation resistant layer13is placed on appropriate parts of the top surface of the protective film10. The second cavitation resistant layer17is also arranged on appropriate parts of the top surface of the protective film10, at the same time. A layer forming the projecting layer15is thus located on the base3A. At this time, the layers forming the projecting layer15are formed and patterned into a desired shape by photolithography, respectively. This enables the projecting layer15to be accurately positioned. Then, as shown inFIG. 5E, the adhesion improving layer11is formed on the top surface of the protective film10and patterned into a desired shape by photolithography. The thermal oxide film8, the interlayer insulating film9, the protective film10, and the adhesion improving layer11are thus formed on the base3A. In this case, as described below in a fifth embodiment, a second adhesion improving layer formed of the same material as that of the adhesion improving layer11may be formed on the top surface of the second cavitation resistant layer17of the projecting layer15by patterning. In present embodiment, the thermal oxide film8is defined as an inorganic layer.

Then, as shown inFIG. 5F, a dissolvable resin layer is located on the top surface of the base3A via the projecting layer15and other layers so as to constitute an area corresponding to an ink channel6and an ink chamber6A later. The substrate3is thus formed. Then, as shown inFIG. 5G, in this state, the ejection port forming layer2is formed on the substrate3via the adhesion improving layer11and other layers. The ejection port forming layer2can be polymerized and cured by receiving light or thermal energy and then adheres tightly to the substrate3. The water repellent layer14is formed on a print medium-side surface of the ejection port forming layer2.

Once the ejection port forming layer2is cured, the ejection ports5are formed in the ejection port forming layer2as shown inFIG. 5H. The ejection ports5are accurately positioned on the ejection port forming layer2by photolithography. Then, as shown inFIG. 5I, the ejection port forming layer2is coated with a coating material27such as wax or cyclization rubber so as to be protected from a solution used for etching for forming the ink supply port4.

Then, as shown inFIG. 5J, a method such as wet etching using BHF solution or dry etching using CF4is executed to remove that area of the thermal oxide film8on the back surface of the substrate3in which the ink supply port4is to be formed. Here, the thermal oxide film8on the back surface of the substrate3subsequently functions as a mask for an etching step for forming the ink supply port4.

Then, anisotropic etching is performed using a strong alkali solution such as TMAH (tetra methyl ammonium hydroxide) or KOH (potassium hydroxide). The anisotropic etching is performed on that area of the back surface of the substrate3from which the thermal oxide film8has been removed until the substrate3is penetrated. Upon reaching the thermal oxide film8on the front surface of the substrate3, the etching is stopped. The thermal oxide film8as the inorganic layer thus functions as an etching stop layer. Thus, as shown inFIG. 5K, the ink supply port4is formed in the substrate3.

The layers formed on the substrate3so as to constitute the projecting layer15offers alkali resistance. This is because even when the projecting layer15is already accurately positioned, the projecting layer15may be corroded by a strong alkali solution during etching and thus have deviated dimensions of the ink flow rate adjusting opening18.

Then, as shown inFIG. 5L, a method such as plasma dry etching using CF4is applied to the area corresponding to the substrate front surface-side opening in the ink supply port4to remove the corresponding area of the thermal oxide film8to allow the ink supply port4to communicate with the ink channel6. In this case, the cavitation resistant layer13and second cavitation resistant layer17of the projecting layer15are constructed so as to contain metal such as Ta. Consequently, even with the application of the method such as plasma dry etching, the projecting layer15can be selectively left by adjusting an amount of etching gas, instead of being eliminated.

Then, the resin layer located in an area corresponding to the ink channel6is dissolved and removed to form the ink channel6and the ink chamber6A. The coating material27such as wax or sensitized rubber is removed, which has been used for protecting the ejection port forming layer2from the solution used to form the ink supply port4. The ink jet print head1in accordance with the present embodiment, shown inFIG. 2, is thus manufactured.

The present embodiment uses the thermal oxide film8as a stop layer that ends the etching step. However, the present invention is not limited to this, and a silicon nitride film or the like may be used.

In the present embodiment, the projecting layer15is formed by photolithography while being accurately positioned by photolithography. This allows the stable setting of the opening width of the ink flow rate adjusting opening18, defined by the projecting layer15. In this case, the opening width of the ink flow rate adjusting opening18is accurately defined regardless of the etching rate of the substrate3. Consequently, the high dimensional accuracy of the opening width of the ink flow rate adjusting opening18can be fixed to stabilize the ink refilling capability. This also fixes the high dimensional accuracy of the distance from the opening end of the ink flow rate adjusting opening18to the heater elements12. This allows the appropriate control of the flow rate of ink flowing to the ink channel6through the ink flow rate adjusting opening18.

Moreover, instead of using a new material to form the projecting layer15, the present embodiment uses the same material as that of the heater elements12, the cavitation resistant layer13, or the like to form the projecting layer15when each heater element12, the cavitation resistant layer13, or the like is formed on the substrate3. Consequently, the conventional material forms and functions as the projecting layer15, making it possible to prevent an increase in the manufacturing costs of the ink jet print head1. Furthermore, the projecting layer15can be formed simultaneously with the formation of each heater element12or the cavitation resistant layer13is formed on the substrate3. This enables the manufacturing process to be achieved without the need to add new manufacturing steps to the process.

Now, description will be given of the operation of the ink jet print head1in accordance with the present embodiment. When ink is filled into the ink jet print head1, the ink is fed from the ink tank (not shown) to the ink supply port4and then to the ink channel6. The ink jet print head1performs printing by driving the heater elements12to bubble the ink filled in the ink channel6to generate pressure, thus ejecting ink droplets from the ejection ports5and landing on the print medium.

In the ink jet print head1in accordance with the present embodiment, the projecting layer15is accurately formed to stabilize the ink refilling capability. This stabilizes the amount of ink ejected and thus the frequency properties. Therefore, the print quality of the ink jet print head1is improved.

Second Embodiment

A second embodiment of the present invention will be described with reference toFIG. 6. The same components of the second embodiment as those of the first embodiment are denoted by the same reference numerals and will not be described below. Only the differences from the first embodiment will be described.

In the first embodiment, the projecting layer15is formed of the protective film10, the second heater elements16, and the second cavitation resistant layer17. In contrast, in the second embodiment, a projecting layer19is formed only of the protective film10and the second heater elements16. This embodiment is effective in case that the projecting layer19exhibits a sufficient strength even without the second cavitation resistant layer17. Thus, the present embodiment reduces the number of layers constituting the projecting layer19. Therefore, a stress generating in the projecting layer19can be reduced.

Third Embodiment

A third embodiment of the present invention will be described with reference toFIG. 7. The same components of the third embodiment as those of the first and second embodiments are denoted by the same reference numerals and will not be described below. Only the differences from the first and second embodiments will be described.

In the third embodiment, a projecting layer20is formed only of the second cavitation resistant layer17. The present embodiment uses this configuration because the projecting layer20formed only of the second cavitation resistant layer17exhibits sufficient strength. The further reduced number of layers constituting the projecting layer20. Therefore, a stress generating in the projecting layer20can be reduced. The second cavitation resistant layer17which constitutes the projecting layer20in the present embodiment contains tantalum Ta, which is mechanically stable, and particularly contains one of TaSiN (tantalum silicon nitride), TaAl (tantalum aluminum), and TaN (tantalum nitride). This enhances the strength of the projecting layer20so that the projecting layer20, formed only of the one layer, exhibits sufficient strength.

Fourth Embodiment

A fourth embodiment of the present invention will be described with reference toFIG. 8. The same components of the fourth embodiment as those of the first to third embodiments are denoted by the same reference numerals and will not be described below. Only the differences from the first to third embodiments will be described.

In the fourth embodiment, a projecting layer21is formed only of the second heater elements16. The present embodiment uses this configuration because the projecting layer21formed only of the second heater elements16exhibits sufficient strength as well as the third embodiment. Therefore, the projecting layer21is formed only of the one layer, enabling a reduction in a stress generating in the projecting layer21.

Fifth Embodiment

A fifth embodiment of the present invention will be described with reference toFIG. 9. The same components of the fifth embodiment as those of the first to fourth embodiments are denoted by the same reference numerals and will not be described below. Only the differences from the first to fourth embodiments will be described.

In the fifth embodiment, a projecting layer22is formed by arranging a second adhesion improving layer23, on the top surface of the second cavitation resistant layer17, the protective film10, second heater elements16, and the second cavitation resistant layer17, used in the first embodiment. In the present embodiment, the second adhesion improving layer23functions as a reinforcing layer that reinforces the projecting layer. Here, the second adhesion improving layer23is formed of the same material as that of the adhesion improving layer11. The adhesion improving layer11is formed of the thermoplastic resin to improve the adhesion between the substrate3and the ejection port forming layer2. If the projecting layer in accordance with the first embodiment has insufficient strength, the projecting layer22is formed by placing the second adhesion improving layer23on the top surface of the second cavitation resistant layer17as the present embodiment. This improves the strength of the projecting layer22, which can thus endure a harsher environment. The durability of the ink jet print head1is thus improved. Furthermore, the second adhesion improving layer23is formed simultaneously with the formation of the adhesion improving layer11, located between the substrate3and the ejection port forming layer2. This eliminates the need to add a new step for the manufacture of the ink jet print head1. However, a decrease occurs in the height in the ink channel6from the projecting layer22to the print medium side of the ejection port forming layer2.

Sixth Embodiment

A sixth embodiment of the present invention will be described with reference toFIG. 10. The same components of the sixth embodiment as those of the first to fifth embodiments are denoted by the same reference numerals and will not be described below. Only the differences from the first to fifth embodiments will be described.

In the first to fifth embodiments, the projecting layer is formed of the same material as that of part of the layers arranged on the substrate3during the manufacture of the ink jet print head1. However, the present embodiment applies a new material that forms a projecting layer24. In the present embodiment, the projecting layer24is formed by placing the second cavitation resistant layer17on the substrate3and placing a reinforcing layer25on the second cavitation resistant layer17. A reinforcing layer25is placed newly, and is formed to reinforce the second cavitation resistant layer17. The present embodiment forms the reinforcing layer25and patterns the reinforcing layer25by the photolithography technique that uses polyether amide so that the resulting reinforcing layer25has the same dimensions as those of the second cavitation resistant layer17.

The reinforcing layer25is not limited to polyether amide, and any other material may be used. However, the projecting layer24contacts the etchant during the etching step for forming the ink supply port4in the substrate3. Accordingly, the material which is not damaged even when exposed to the strong alkali solution such as TMAH or KOH, which is used as the etchant is selected to manufacture the reinforcing layer25. Furthermore, the projecting layer24is positioned in an area where the projecting layer24comes into contact with ink when the manufactured ink jet print head1is used. The projecting layer24is thus formed of an ink resistant material. That is, any material can be used to form the reinforcing layer25provided that the material has strong alkali resistance and ink resistance.

Further, the reinforced layer is not limited to the second cavitation resistant layer17. As shown inFIG. 11, a projecting layer26may be formed of the second heater elements16and the reinforcing layer25reinforcing the second heater elements16. Layers different from the second cavitation resistant layer17and the second heater elements16may be reinforced by the reinforcing layer.

Furthermore, the sixth embodiment uses the new material to form the reinforcing layer25reinforcing the projecting layer. However, the new material may solely form the projecting layer. In this case, the material forming the projecting layer is selected from materials which has strong alkali resistance and ink resistance.

This application claims the benefit of Japanese Patent Application No. 2007-013767, filed Jan. 24, 2007, which is hereby incorporated by reference herein in its entirety.