Micro-injecting device and method for manufacturing the same

Abstract: A micro-injecting device and a method for manufacturing the device are disclosed in which a main operational part of a membrane (20) is structured to have two regions: an impact film (24) region having high expansion and contraction delivery characteristics, for example, a nickel film region, and an organic film (21) region having high expansion and contraction, for example, a polyimide film region. Each of the two regions serves as an impact delivery medium for efficiently pushing ink upward, a prompt initialization medium, and a hinge for dispersing and eliminating a stress, to thereby prevent deformation, for example, wrinkling, of a membrane. In addition, a membrane having such enhanced main operation part can endure stress and react well during operation. As a result, significantly enhanced injecting performance can be obtained.

Description: The present invention relates to the field of micro-injecting devices and inkjet printheads, and more particularly, to membrane-containing micro-injecting devices. The present invention also relates to a method for manufacturing such micro-injecting devices. Generally, a micro-injecting device refers to a device which is designed to provide printing paper, a human body or motor vehicles with a predetermined amount of liquid, for example, ink, pharmaceutical liquid or petroleum using a method in which a predetermined amount of electric or thermal energy is applied to the above-mentioned liquid, yielding a volumetric transformation of the liquid. This method allows the application of a small quantity of liquid to a specific object. Recently, developments in electrical and electronic technology have enabled rapid development of such micro-injecting devices. Thus, micro-injecting devices are being widely used in daily life. One example of the use of micro-injecting devices in daily life is the inkjet printer. The inkjet printer is a form of micro-injecting device which differs from conventional dot printers in the capability of performing print jobs in various colours by using cartridges. Additional advantages of inkjet printers over dot printers are lower noise and enhanced quality of printing. For these reasons, inkjet printers are gaining immensely in popularity. An inkjet printer generally includes a printer head having nozzles with a minute diameter. In such an inkjet printhead, the ink which is initially in the liquid state is transformed and expanded to a bubble state by turning on or off an electric signal applied from an external device. Then, the ink so bubbled is injected so as to perform a print job on a print paper. Examples of the construction and operation of several ink jet print heads of the conventional art are seen in the following US Patents. US Patent No 4,490,728, to Vaught et al, entitled Thermal Ink Jet Printer , describes a basic print head. US Patent No 4,809,428 to Aden et al, entitled Thin Film Device For An Ink Jet Printhead and Process for Manufacturing Same and US Patent No 5,140,345, to Komuro, entitled Method of manufacturing a Substrate For a Liquid Jet Recording Head and Substrate Manufactured By The Method , describe manufacturing methods for ink-jet printheads. US Patent No 5,274,400, to Johnson et al, entitled Ink Path Geometry For High Temperature Operation Of Ink-Jet Printheads , describes altering the dimensions of the ink-jet feed channel to provide fluidic drag. US Patent No 5,420,627, to Keefe et al, entitled Ink Jet Printhead , shows a particular printhead design. In such a conventional inkjet printhead, a high temperature which is generated by a heating resistor layer is employed so as to eject ink. Here, if the ink contained in a liquid chamber is exposed to high temperature for a considerable time, thermal changes in the constituent parts of the ink may significantly reduce the lifespan of the device. Recently, to overcome the above-mentioned problem, there has been proposed a method in which a substrate-shaped membrane is caused by the vapour pressure of a working liquid that fills a heating chamber. Thus, the ink contained in the liquid chamber is smoothly discharged. In this case, direct contact between the ink and heating resistor layer can be avoided, since a membrane is inserted between the liquid chamber and the heating resistor layer. Thus, thermal changes in the ink can be minimised. Examples of this type of printhead are disclosed in US-A-4,480,259, and in EP-A-0 841 166. In the above-described membrane-containing inkjet printhead, a membrane is expanded and contracted by a vapour pressure delivered from working liquid contained in a heating chamber, and is thus transformed in volume. Subsequently, an impact having a predetermined size is delivered to ink contained in a liquid chamber so that the ink can be ejected to external printing paper. Here, the above-described transformation in volume of the membrane occurs simultaneously all over the membrane. Because the membrane is frequently transformed in volume during operation, if the membrane is made of nickel, due to the impact delivery or operational resilience (that is, the restoring force to the original state) characteristics of nickel, a weak part of the membrane may be wrinkled. In particular, this may occur in the portion of the membrane not supported by the structure of the heating chamber. Moreover, the part which is not supported by the structure of the heating chamber, mentioned above, is a main operational part of the membrane which pushes ink upward. Therefore, if wrinkling occurs in such a main operational part, the mechanical characteristics of the membrane are significantly impaired or altered. On the other hand, if a membrane is made of polyimide, for example, in consideration of the stress or adhesion (to the heating chamber or liquid chamber) characteristics of this material, then the main operational part of the membrane is capable of remaining ductile and can endure deformation, for example, wrinkling, to some extent. However, the impact delivery characteristics and operational resilience are extremely weak for polyimide. Thus, the main part of the membrane cannot rapidly respond to generation of vapour pressure from the heating chamber, thereby disturbing the smooth operation of ink ejection. Thus, the overall printing performance of the inkjet printhead is significantly lowered. It is therefore an object of the present invention to provide an improved micro-injecting device. It is a further object of the invention to provide a micro-injecting device with improved injection performance. It is a still further object of the invention to provide a micro-injecting device in which damage to the membrane is avoided. It is a yet further object of the invention to provide a micro-injecting device in which the mechanical characteristics of the membrane are improved. Accordingly, a first aspect of the present invention provides a micro-injecting device, comprising: a substrate; a protection film formed on said substrate; a heating resistor layer formed on a portion of said protection film, for heating a heating chamber; an electrode layer formed on said protection film and which contacts said heating resistor layer, for transmitting an electric signal to said resistor layer; a heating chamber barrier layer formed on said electrode layer and defining a heating chamber enclosing said heating resistor layer, said heating chamber having an axis, said heating chamber for holding a working liquid; a membrane formed on the heating chamber barrier layer for transmitting volume changes of the liquid in the heating chamber, said membrane comprising: an organic film formed over the entire heating chamber barrier layer and covering the heating chamber; and an impact film formed on a portion of said organic film, said impact film centred on the axis of the heating chamber; a liquid chamber barrier layer formed on a portion of the membrane and defining a liquid chamber, said liquid chamber being coaxial with said heating chamber and the centre of said impact film; and a nozzle plate formed on said liquid chamber barrier layer, said nozzle plate having a nozzle coaxial with said liquid chamber. To achieve the above objects and other advantages of the present invention, the main operational part of a membrane is structured to have two regions: an impact film region having high impact delivery and operational resilience characteristics, for example, a nickel film region; and an organic film region having high expansion and contraction characteristics, for example, a polyimide film region. The above two regions serve as an impact delivery medium for strongly pushing up ink, a rapid initialisation medium, and a hinge for dispersing and eliminating stress, to thereby prevent wrinkling of the membrane. In addition, a membrane having such an enhanced main operational part can endure stress and react well during operation. As a result, a significantly enhanced injecting performance can be obtained. Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a perspective view showing an inkjet printhead of a first embodiment of the present invention. Figure 2 is a cross-sectional view of an inkjet printhead taken along II-II in figure 1; Figure 3 is a plan view of a membrane according to the first embodiment of the present invention; Figure 4 is a cross-sectional view showing a first operation of an inkjet printhead of the first embodiment of the present invention; Figure 5 is a cross-sectional view showing a first operation of a membrane according to the first embodiment of the present invention; Figure 7 is a cross-sectional view showing a second operation of a membrane according to the first embodiment of the present invention; Figure 8 is a perspective view showing an inkjet printhead according to a second embodiment of the present invention; Figures 9a to 9d are cross-sectional views showing a process for manufacturing an inkjet printhead according to a third embodiment of the present invention; Figures 10a to 10d are cross-sectional views showing a process for manufacturing a membrane according to a third embodiment of the present invention; Figures 11a and 11b are cross-sectional views showing a process for manufacturing a membrane according to a fourth embodiment of the present invention; and Figures 12a to 12e are cross-sectional views showing a process for manufacturing a membrane according to a fifth embodiment of the present invention. As shown in figures 1 and 2, in an inkjet printhead of the present invention, a protection film 2 made of SiO 2 is formed on a substrate 1 made of Si, and a heating resistor layer 11 to be heated by electric energy applied from an external device is formed on the protection film 2, and an electrode layer 3 for supplying the electric energy applied from an external device to the heating resistor layer is formed on the heating resistor layer 11. The electrode layer 3 is connected to a common electrode 12, and the electric energy supplied from the electrode layer 3 is converted to thermal energy by the heating resistor layer 11. Meanwhile, a heating chamber 4 bordered by a heating chamber barrier layer 5 is formed on the electrode layer 3 so as to cover the heating resistor layer 11; the thermal energy generated by the heating resistor layer 11 is delivered to the heating chamber 4. The heating chamber 4 is filled with working liquid from which a vapour pressure is easily generated. In operation, the working liquid is rapidly vaporised by the thermal energy delivered from the heating resistor layer 11. In addition, the vapour pressure generated by the vaporisation of the working liquid is delivered to a membrane 20 formed on the heating chamber barrier layer 5. Then, a liquid chamber 9 bordered by a liquid chamber barrier layer 7 and positioned coaxially with the heating chamber layer 4 is formed on the membrane 20 and is filled with a relevant amount of ink. Here, a nozzle 10 is formed on the liquid chamber barrier layer 7 so as to cover the liquid chamber 9 and serves as a jet gate for ink droplet discharge. The nozzle 10 is formed penetrating through a nozzle plate 8 so as to be positioned coaxially with the heating chamber 4 and liquid chamber 9. In the above-described structure, the membrane 20 has a deposited layered structure in which an organic film 21 is formed over the entire heating chamber barrier layer 5 so as to cover the heating chamber 4, an adhesion film 23 to be positioned coaxially with the heating chamber 4 is formed on the organic film 21 so as to correspond to a region where the heating chamber 4 is formed, and an impact film 24 is formed on the adhesion film 23. That is, the impact film 24 is positioned in a main operational part of the membrane 20, corresponding to the position of heating chamber 4. The organic film 21 to which the impact film 24 adheres forms the lower portion of the membrane 20. During operation, the impact film 24 is rapidly transformed in volume and serves to deliver a strong impact to ink contained in the liquid chamber 9 formed thereon. At the same time, the organic film 21 is rapidly transformed in volume with excellent expansion and contraction characteristics, to thereby disperse and remove stress on the impact film 24. Preferably, the organic film 21 is made of a polyimide having excellent expansion, contraction and ductility. Here, the organic film 21 adheres to the liquid chamber barrier layer 7 formed on the membrane 20. In general, the liquid chamber barrier layer 7 is made of polyimide having a strong tolerance to ink. As described above, the organic film 21 is made of the same polyimide as that of liquid chamber barrier layer 7. Therefore, a strong adhesion between the organic film 21 and the liquid chamber barrier layer 7 can be obtained. Preferably, the impact film 24 is made of nickel having excellent restoring force characteristics. Thus, the impact film 24 made of nickel rapidly reacts to the vapour pressure generated by a vaporisation of working liquid, and is thus rapidly transformed in volume. Then, ink contained in the liquid chamber 9 can be promptly expelled toward the nozzle 10. The adhesion film 23 for promoting an adhesive force is formed between the organic film 21 and the impact film 24. Thus, the organic film 21 and the impact film 24, which are made of different materials, can adhere strongly to each other. Preferably, the adhesion film 23 is made of vanadium, titanium, or chromium. In the prior art, if the membrane is made of nickel, wrinkling has occurred in a main operational part of the membrane, thereby significantly lowering mechanical characteristics of the membrane. On the other hand, if the membrane is made of polyimide, a main operation part of the membrane cannot rapidly react to a vapour pressure generated from a heating chamber, thereby lowering significantly the overall printing performance. To overcome these problems, in the present invention, both nickel and polyimide are employed as a main operational part of the membrane 20. That is, as shown in figure 3, the impact film 24 having an excellent restoring force is formed in the main operational part of the membrane 20. In this manner, stress in the impact film 24, generated by a vapour pressure of the heating chamber 4, is delivered to the organic film 21 which has excellent expansion and contraction, and the stress is then dispersed and removed. Thus, the membrane 20 can rapidly react, without any wrinkling, to the vapour pressure of working liquid. As a result, overall printing quality is greatly enhanced. As shown in figure 4, when an electric signal is applied to the electrode layer 3 from an external power source, the heating resistor layer 11 that contacts the electrode layer 3 is provided with the electric energy and thus is rapidly heated to a high temperature of 500°C or higher. In this process, the electric energy is converted to a thermal energy of approximately 500°C to 550°C. Subsequently, this thermal energy is delivered to the heating chamber 4 that contacts the heating resistor layer 11. Then, the working liquid that fills the heating chamber 4 is rapidly vaporized so as to generate a vapour pressure having a predetermined size. Then, the vapour pressure is delivered to the membrane 20 on the heating chamber barrier layer 5, thus an impact power P having a predetermined size is applied to the membrane 20. In this case, as shown in figure 4, the membrane 20 is rapidly expanded as indicated in arrow 70 and bent to a round shape. Accordingly, a strong impact is delivered to ink 100 contained in the liquid chamber 9, and the ink 100 is bubbled by the impact and ready to be discharged. As described above, the membrane 20 of the present invention is made up of two regions, and includes the impact film 24 having an excellent impact delivery characteristic and the organic film 21 for dispersing and removing a stress on the impact film 24. Therefore, deformations which have occurred in a conventional membrane, for example, wrinkling, can be eliminated. The impact film 24 made of nickel preferably has weight per unit area which is larger than that of the organic film 21 made of polyimide. Thus, as shown in FIG 6, the impact film 24 is capable of delivering a strong impact to the ink contained in the liquid chamber 9 according to the equation P=mΔV where P is the impact, m is weight of the film, and ΔV is volume displaced by the film during expansion). In addition, the organic film 21 is preferably made of polyimide which has better expansion and contraction characteristics than that of the impact film 24 made of nickel. As shown in FIG 6, a stress δ2 on the impact film 24 can be absorbed into a stress δ1 so as to be dispersed and removed. When, as shown in figure 5, the electric signal applied from an external power source is cut off and the heating resistor layer 11 rapidly cools down, the vapour pressure in the heating chamber 4 rapidly decreases. Then, the inside of the heating chamber 4 rapidly becomes a vacuum. Subsequently, the vacuum applies a strong buckling power B corresponding to the above-described impact to the membrane 20, to thereby contract the membrane 20 to the initial state. As shown in figure 5, the membrane 20 is rapidly contracted in the direction indicated in arrows 72 so as to deliver a strong buckling power to the inside of the liquid chamber 4. Then, the ink 100 ready to be expelled by the expansion of the membrane 20 is transformed, due to its own weight, to oval and then circular shapes in turn, and is ejected onto printing paper. As a result, rapid printing can be realised on the print paper. The membrane 20 of the present invention consists of the impact film 24 having excellent impact delivery characteristics, and the organic film 21 having excellent expansion and contraction characteristics for dispersing and removing stress on the impact film 24. Therefore, deformations, for example, wrinkling, which can occur in a conventional membrane can be prevented. In addition, the membrane 20 can be rapidly initialised toward the heating chamber 4 and an excellent operational reaction can be obtained. The organic film 21 made of polyimide has better expansion and contraction characteristics than that of the impact film 24 made of nickel. As shown in FIG 7, the organic film 21 makes a stress δ4 absorbed into a stress δ3 on the impact film 24 and disperses and remove this stress. As shown in figure 8, in an inkjet printhead according to another embodiment of the present invention, an auxiliary organic film 22 that contacts a side surface of the impact film 24 and which overlaps an upper edge of the heating chamber 4 is further formed on the organic film 21 of the membrane 20. In this case, the auxiliary organic film 22 serves to further strengthen expansion and contraction of the organic film 21. Therefore, the organic film 21 can remove more smoothly the stress on the impact film 24. In this configuration of this embodiment, the auxiliary organic film 22 further formed on the organic film 21 adheres to the liquid chamber barrier layer 7 formed on the membrane 20. Here, like the organic film 21, the auxiliary organic film 22 is made of the same polyimide as that of the liquid chamber barrier layer 7. As a result, the auxiliary organic film 22 can be further strongly adhered to the liquid chamber barrier layer 7. Now, a first method for manufacturing an inkjet printhead of the present invention will be explained in more detail. The first method consists of three independent processes. Parts manufactured through the three processes, for example, a heating resistor layer 11 and heating chamber barrier layer 5 assembly, membrane 20, and a nozzle plate 8 and liquid chamber barrier layer 7 assembly, etc are assembled to each other at a relevant position through an alignment process which will be performed later. As a result, a complete inkjet printhead can be obtained. At the first method, as a first process, as shown in FIG 9a, metal, for example, polysilicon, is deposited on the silicon-substrate 1 on which the protection film 2 made of SiO 2 is formed. Subsequently, the polysilicon is etched using a pattern film (not shown) so that the protection film 2 can be partially exposed, thereby forming the heating resistor layer 11 on the protection film 2. Metal, for example, aluminium, is then deposited on the protection film 2 so as to cover the heating resistor layer 11. Subsequently, the aluminium is etched using a pattern film so that a centre surface of the heating resistor layer 11 can be exposed, thereby forming the electrode layer 3 which contacts both side surfaces of the heating resistor layer 11. Then, organic material, for example, polyimide, is deposited on the electrode layer 3 so as to cover heating resistor layer 11. The polyimide is then etched using a pattern film so that a partial surface of the heating resistor layer 11 and the electrode layer 3 can be exposed, thereby forming the heating chamber barrier layer 5 that defines an area for the formation of the heating chamber 4. This ends the first process. Then, a second process for forming a membrane shown in figure 9b is performed. The second process will be explained in more detail with reference to figures 10a to 10d. As shown in figure 10a, organic material, preferably polyimide, is deposited on a silicon-substrate 200 on which a protection film 201 made of SiO 2 is formed, thereby forming the organic film 21. Preferably, the organic film 21 is deposited by a spin coating method in which the thickness of thin film can be easily controlled. Preferably, the organic film 21 is deposited to a thickness in the range of approximately 2 µm to 2.5 µm. Subsequently, the organic film 21 is heat-treated approximately two times, at temperatures of, preferably, in the range of approximately 130°C to 290°C, at regular intervals. As a result, the organic film 21 has an excellent toughness all over the surface, which allows the adhesion film 23 to be firmly fixed. More preferably, the heat treatment on the organic film 21 is performed at temperatures of approximately 150°C and 280°C respectively. As shown in figure 10b, a metallic substance, preferably, vanadium, titanium, or chromium etc is deposited on the organic film 21 by a sputtering method, to thereby form the adhesion film 23. Preferably, the adhesion film 23 is formed to a thickness in the range of approximately 0.1 µm to 0.2 µm. Subsequently, metallic material, preferably nickel, is deposited on the adhesion film 23 by a sputtering method, to thereby form the impact film 24. Preferably, the impact film 24 is formed to a thickness in the range of approximately 0.2 µm to 0.5 µm. Preferably, the impact film 24 is annealed at a temperature in the range of approximately 150°C to 180°C. This annealing is for providing the impact film 24 with excellent toughness and mechanical tolerance. Then, a pattern film 30 is formed partially on the surface of the impact film 24 so as to complete the impact film 24/adhesion film 23 structure. Subsequently, the impact film 24/adhesion film 23 is etched using the pattern film 30 as a mask, and the residual pattern film 30 is removed by chemicals. Thus, the organic film 21 is partially exposed so as to thereby complete the membrane 20 shown in figure 10c. As another embodiment of the first method for manufacturing an inkjet printhead of the present invention, a step for strengthening expansion and contraction of the organic film 21 can be added to the above-described step where the impact film 24/adhesion film 23 is etched to partially expose the organic film 21. In the added step, as shown in FIG 11a, an organic substance, preferably, a polyimide 22' is deposited on the organic film 21 by a chemical vapor deposition method so as to thereby cover the impact film 24/adhesion film 23. As shown in figure 11b, the polyimide is etched back until a surface of the impact film 24 is exposed, to thereby complete the auxiliary organic film 22 that contacts both side surface of the impact film 24/adhesion film 23. The auxiliary organic film 22 so formed adheres firmly onto the organic film 21 so as to thereby improve the overall expansion and contraction of the membrane 20. When the membrane 20 is completed through the processes explained above, as shown in figure 10d, the complete membrane 20 is tripped away from the substrate 200 on which the protection film 201 is formed, using chemicals, for example, hydrogen fluoride (HF). This ends the second process. Now, a third process of the first method for manufacturing an inkjet printhead of the present invention will be explained. In the third process, as shown in figure 9c, metallic substance, for example, nickel, is deposited by electroplating method on a silicon-substrate 300 on which a protection film 301 made of SiO 2 is formed. Then, the nickel is etched using a pattern film so as to partially expose the protection film 301. Thus, the nozzle plate 8 is formed to define an area in which the nozzle 10 will be formed. Subsequently, organic material, for example, polyimide, is deposited on the nozzle plate 8 so as to cover the protection film 301. Then, the polyimide is etched using a pattern film so as to partially expose the protection film 301 and the nozzle plate 8. Thus, the liquid chamber barrier layer 7 is formed to define an area in which the liquid chamber 9 will be formed. When the nozzle plate 8/liquid chamber barrier layer 7 assembly is completed through the processes explained above, the complete nozzle plate 8/liquid chamber barrier layer 7 assembly is stripped away from the substrate 300 on which the protection film 301 is formed, using chemicals, for example, hydrogen fluoride (HF). This ends the third process. When the above-described first to third processes are all completed, the assemblies manufactured in each process are then assembled to form a single assembly. That is, the membrane 20 formed through the second process is assembled onto the heating resistor layer 11/heating chamber barrier layer 5 assembly formed through the first process, and the nozzle plate 8/liquid chamber barrier layer 7 assembly formed through the third process is assembled onto the membrane. Here, the impact film 24/adhesion film 23 structure of the membrane 20 is aligned to the position where the heating resistor layer 11/heating chamber barrier layer 5 assembly is also positioned. The nozzle 10 in the nozzle plate 8/liquid chamber barrier layer 7 is aligned to the position where the heating chamber 4 and the impact film 24/adhesion film 23 are also positioned. The assemblies manufactured through the first to third processes are assembled to form a single assembly by the process of alignment and assembling. As a result, a complete inkjet printhead shown in FIG 9d can be obtained. Alternatively, an inkjet printhead of the present can be manufactured by a second method different from the above-described first one. As compared to the first method, the second method which will be explained hereinafter aligns at the same time a plurality of impact film 24/adhesion film 23 and a plurality of heating chambers to the same position. In the second method, like the first one, the first process shown in figure 9a is performed. That is, the heating resistor layer 11 made of polysilicon is formed on the silicon-substrate 1 on which the protection film 2 made of SiO 2 is formed. Then, the electrode layer 3 made of aluminium is formed on both side surfaces of the heating resistor layer 11. Then, the electrode layer 3 made of aluminium is formed on both side surfaces of the heating resistor layer 11. Then, the heating chamber barrier layer 5 made of polyimide is formed on the electrode layer 3 that includes the heating resistor layer 11 so as to define an area in which the heating chamber 4 will be formed. Then, second and third processes for forming a membrane will be formed. Different from those of the first method, the second and third processes for manufacturing a membrane are as follows. The organic film 21 having no impact film/adhesion film is assembled to the heating resistor layer 11/heating chamber barrier layer 5 assembly, and the impact film 24/adhesion film 23 is formed on the assembled organic film 21. The second and third processes of the second method will be explained in more detail with reference to figure 12a to figure 12e. As shown in figure 12a, organic material, preferably polymide, is deposited on the silicon-substrate 200 on which the protection film 201 made of SiO 2 is formed, to thereby form the organic film 21. Preferably, the organic film 21 is deposited by a spin coating method in which the thickness of thin film can be easily controlled. Preferably, the thickness of the organic film 21 is in the range of approximately 2 µm to 2.5 µm. Then, the organic film 21 is heat-treated approximately two times, preferably at temperatures in the range of approximately 130°C to 290°C, at regular intervals. As a result, the organic film 21 has an excellent toughness over the entire surface, which allows the adhesion film 23 to be firmly fixed. Preferably, the heat treatment on the organic film 21 is performed two times at temperatures of approximately 150°C and 280°C, respectively. As shown in figure 12b, using chemicals, for example, hydrogen fluoride, the complete organic film 21 is stripped away from the substrate 200 on which the protection film 201 is formed. Then, the organic film 21 so stripped is assembled to the heating resistor layer 11/heating chamber barrier layer 5 assembly which is completed through the first process. As shown in figure 12c metallic material, preferably, vanadium, titanium, or chromium, etc, is deposited by a sputtering method on the organic film 21 assembled onto the heating resistor layer 11/heating chamber barrier layer 5 assembly, to thereby form the adhesion film 23. Preferably, the thickness of the adhesion film 23 is in the range of approximately 0.1 µm to 0.2 µm. Subsequently, metallic material, preferably, nickel, is deposited on the adhesion film 23 by a sputtering method, to thereby form the impact film 24. Preferably, similarly to the first method, the thickness of the impact film 24 is in the range of approximately 0.2 µm to 0.5 µm. Preferably, the impact film 24 is annealed at a temperature in the range of approximately 150°C to 180° C so that the impact film 24 can have excellent toughness and mechanical tolerance. To complete the impact film 24/adhesion film 23 structure, as shown in figure 12d, a pattern film 30 is partially formed on the impact film 24, and the impact film 24/adhesion film 23 is etched using the pattern film 30 as a mask. Then, the residual pattern film 30 is removed by chemicals so that the organic film 21 can be partially exposed. As a result, the membrane having a complete structure shown in FIG 12e can be obtained. Here, the impact film 24/adhesion film 23 is formed at a position which corresponds to that where the heating chamber 4 is formed. As described above, in the second method of the present invention, the organic film 21 is assembled onto the heating chamber 4 prior to the formulation of impact film 24/adhesion film 23 structure of which position corresponds to that of the heating chamber 4. Thus, differently from the first method, when the membrane 20 is assembled onto the heating resistor layer 11/heating chamber barrier layer 5 assembly, an additional process for aligning each by each a plurality of impact film 24/adhesion film 23 and a plurality of heating chamber 4 to the relevant position can be omitted. As a result, the efficiency of the overall manufacturing process can be significantly improved. As another embodiment of the second method, similarly to the first method, a step for forming the auxiliary organic film 22 for strengthening expansion/contraction of the organic film 21 can be added to the step of etching the impact film 24/adhesion film 23 to partially expose the organic film 21. The auxiliary organic film 22 thus formed contacts both side surfaces of the impact film 24/adhesion film 23, and is firmly adhered onto the organic film 21, to thereby serve to promote overall expansion and contraction of the membrane 20. Subsequently, a fourth process of the second method is performed. In the fourth process, similarly to the first method, the process as shown in figure 9c is performed. The nozzle plate 8 made of nickel is formed on the silicon-substrate 300 on which the protection film 301 made of SiO 2 etc, is formed, so as to define an area where the nozzle 10 will be formed. Then, the liquid chamber barrier layer 7 made of polyimide is formed on the nozzle plate 8 so as to define an area where the liquid chamber 9 will be formed. When the nozzle plate 8/liquid chamber barrier layer 7 assembly is completed through the above-described processes, the nozzle plate 8/liquid chamber barrier layer 7 assembly is stripped away from the substrate 300 on which the protection film 301 is formed, using chemicals, for example, hydrogen fluoride. This ends the fourth process. When the above-described first to fourth processes are completed, the assemblies manufactured by each process are assembled to form a single assembly. In the second method, as described above, the membrane 20 is assembled onto the heating resistor layer 12/heating chamber barrier layer 5 assembly through the second and third processes, prior to assembling the parts as a single assembly. Then, all that remains is assembling the nozzle plate 8/liquid chamber barrier layer 7 assembly onto the membrane. Accordingly, the yield of an overall manufacturing process can be significantly improved. In this case, the nozzle 10 in the nozzle plate 8/liquid chamber barrier layer 7 assembly is aligned to the position which corresponds to those where the heating chamber 4 and the impact film 24/adhesion film 23 are formed. Each structure completed through the first to fourth processes is assembled to a single assembly through process of alignment and assembling. Thus, an inkjet printhead having a complete structure as shown in FIG 9d can be obtained. In the embodiments of the present invention, a membrane consists of two films: an impact film for delivering expansion and an organic film for dispersing and removing a stress on the impact film. Thus, prevention of the deformation of a main operation part of the membrane can be obtained. In addition, the main operational part of the membrane can be provided with an enhanced performance characteristic. As a result, overall performance of an inkjet printhead can be greatly improved. As described above, the embodiments of the present invention are characterised in that a main operational part of a membrane is structured to have two regions: an impact film region having high restoring force characteristics, for example, a nickel film region. The above two regions serve as an impact delivery medium for strongly pushing ink upward, a prompt initialization medium. And a hinge for dispersing and eliminating a stress, to thereby prevent deformation, for example, wrinkling, of a membrane. In addition, a membrane having such enhanced main operational part can endure stress and react well during operation. As a result, a significantly enhanced printing performance can be obtained.

Claims: A micro-injecting device, comprising: a substrate (1); a protection film (2) formed on said substrate (1); a heating resistor layer (11) formed on a portion of said protection film (2) for heating a heating chamber (4); an electrode layer (3) formed on said protection film (2) and which contacts said heating resistor layer (11), for transmitting an electric signal to said resistor layer (11); a heating chamber barrier layer (5) formed on said electrode layer (3) and defining the heating chamber (4) enclosing said heating resistor layer (11), said heating chamber (4) having an axis, said heating chamber for holding a working liquid; a membrane (20 formed on the heating chamber barrier layer (5) for transmitting volume changes of the liquid in the heating chamber (4), said membrane (20) comprising: an organic film (21) formed over the entire heating chamber barrier layer (5) and covering the heating chamber (4); and an impact film (24) formed on a portion of said organic film (21), said impact film (24) centered on the axis of the heating chamber (4); a liquid chamber barrier layer (7) formed on a portion of the membrane (20) and defining a liquid chamber (9), said liquid chamber (9) being coaxial with said heating chamber (4) and the center of said impact film (24); and a nozzle plate (8) formed on said liquid chamber barrier layer (7), said nozzle plate (8) having a nozzle (10) coaxial with said liquid chamber (9). A micro-injecting device as claimed in claim 1, said membrane further comprising: an auxiliary organic film formed of the same material as said organic film, said auxiliary organic film being formed on a portion of the organic film overlapping an upper edge of the heating chamber, a side surface of the auxiliary organic film contacting a side surface of said impact film, and said auxiliary organic film disposed between said organic film and said liquid chamber barrier layer. A micro-injecting device as claimed in either of claims 1 and 2, further comprising: an adhesion film of different material than the organic film and the impact film, said adhesion film disposed between the organic film and the impact film on the same portion of the organic film as the impact film, said adhesion film for improving the adhesion of the impact film to the organic film. A micro-injecting device of any preceding claim, in which: said organic film is formed of polyimide. A micro-injecting device of any preceding claim, in which said impact film is formed of nickel. A micro-injecting device as claimed in any preceding claim, in which: said adhesion film being formed of vanadium, titanium or chromium. A micro-injecting device as claimed in any preceding claim in which: said organic film having a thickness in the range of approximately 2.0 to 2.5 µm. A micro-injecting device as claimed in any preceding claim, in which: said impact film has a thickness in the range of approximately 0.2 to 0.5 µm. A micro-injecting device as claimed in any preceding claim, in which: said adhesion film has a thickness in the range of approximately 0.1 to 0.2 µm. A method of manufacturing a micro-injecting device, comprising the steps of: forming a heating resistor layer/heating chamber barrier layer assembly by the steps of: forming a heating resistor layer on a protection film on a substrate; forming an electrode layer contacting the heating resistor layer; and forming a heating chamber barrier layer, defining a heating chamber, on the heating resistor layer; forming a membrane by the steps of: depositing an organic film on a protection film of a second substrate; heat-treating the organic film; depositing an adhesion film of different material from the organic film on the organic film; depositing an impact film of different material from the adhesion film on the adhesion film; etching the adhesion film and the impact film to partially expose the organic film; and stripping the deposited and etched films as a membrane from the second substrate; forming a nozzle plate/liquid chamber barrier layer assembly by the steps of: forming a nozzle plate on a protection film on a third substrate; forming a liquid chamber barrier layer, defining a liquid chamber, on said nozzle plate; and stripping the nozzle plate/liquid chamber barrier layer assembly from the third substrate; and assembling the micro-injector by the steps of: attaching the striped membrane to the heating resistor layer/heating chamber barrier layer assembly with the organic film contacting the heating chamber barrier layer and with the impact film aligned with the heating chamber to form a first assembly; and attaching the nozzle plate/liquid chamber barrier layer assembly to the first assembly with the liquid chamber barrier layer on the membrane and with the liquid chamber aligned coaxially with the heating chamber. A method of manufacturing a micro-injecting device, comprising the steps of: forming a heating resistor layer/heating chamber barrier layer assembly by the steps of: forming a heating resistor layer on a protection film on a substrate; forming an electrode layer contracting the heating resistor layer; and forming a heating chamber barrier layer, defining a heating chamber, on the heating resistor layer; forming an organic film by the steps of: depositing an organic film on a protection film of a second substrate: heat-treating the organic film, and stripping said organic film from said second substrate; forming a first assembly by the steps of: attaching said stripping organic film to said heating resistor layer/heating chamber barrier layer assembly; depositing an adhesion film of different material than the organic film on the attached organic film; depositing an impact film of different material from the adhesion film on the adhesion film; and etching the adhesion film and the impact film to partially expose the organic film and to leave an adhesion film/impact film section aligned with the heating chamber; forming a nozzle plate/liquid chamber barrier layer assembly by the steps of: forming a nozzle plate on a protection film on a third substrate; forming a liquid chamber barrier layer, defining a liquid chamber, on said nozzle plate; and stripping the nozzle plate/liquid chamber barrier layer assembly from the third substrate; and attaching said nozzle plate/liquid chamber barrier layer assembly to the upper surface of said first assembly with the liquid chamber coaxial with the heating chamber. A method as claimed in either of claims 10 or 11, in which said step of depositing the organic film further comprising: spin-coating an organic substance on the protection film. A method as claimed in any of claims 10 to 12, in which said step of depositing the organic film further comprises: depositing a film made of a polyimide. A method as claimed in any of claim 10 to 13, in which said step of depositing the organic film further comprises: depositing the organic film to a thickness in the range of approximately 2.0 to 2.5 µm. A method as claimed in any of claims 10 to 14 in which said step of heat-treating the organic film further comprises: heat-treating the organic film at a temperature in the range of approximately 130 to 290°C. A method as claimed in any of claims 10 to 15, in which said heat-treating being performed in two steps at approximately 150 to 180°C, respectively. A method as claimed in any of claims 10 to 16, in which said step of depositing the adhesion film further comprises: depositing a film made of vanadium, titanium or chromium. A method as claimed in any of claims 10 to 17, in which said step of depositing the adhesion film further comprises: depositing the adhesion film to a thickness in the range of approximately 0.1 to 0.2 µm. A method as claimed in any 10 to 18 in which said step of depositing the impact film further comprising: depositing a film made of nickel. A method as claimed in any of claims 10 to 19 said step of forming the membrane further comprises: after depositing the impact film, annealing the impact film at a temperature in the range of approximately 150 to 180°C. A method as claimed in any of claims 10 to 20, in which said step of forming the membrane further comprises: after said etching step, depositing an auxiliary film of the same material as the organic film on the organic film so as to cover the surface of the impact film; and etching the auxiliary film to expose the impact film leaving the auxiliary film contacting the side surfaces of the impact film.

Inventors: AHN BYUNG-SUN, ALEKSANDROVICH ZUKOV ANDREY, NIKOLAEVICH DUNAEV BORIS, AHN, BYUNG-SUN, ALEKSANDROVICH, ZUKOV ANDREY, NIKOLAEVICH, DUNAEV BORIS
Applicants: SAMSUNG ELECTRONICS CO LTD, SAMSUNG ELECTRONICS CO., LTD.
Application year: 1999
Main classification: B41J2
IPC codes: B41J2