Method of producing ink jet head valve, method of producing ink jet head and ink jet head produced by the method

Abstract: A method of producing an ink jet head valve for an ink jet head having a discharge port for discharging ink, an ink flow path communicated with said discharge port and an electrothermal converting member used as an energy generating means for discharging ink into said ink flow path, comprises the step of producing said ink jet head valve by a metal CVD process.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a method of producing an ink jet head. Related Background Art An ink jet recording process, so called a bubble jet recording process, in which a state change including a rapid volume change of ink (i.e., generation of bubbles) is caused to generate by imparting energy such as heat or the like to the ink, the ink is discharged from a discharge port by an active force due to this state change and the discharged ink is adhered to a medium to be recorded to perform an image formation, has been well known. In the recording device using this bubble jet recording process, as disclosed, for example, in document US-A-4,723,129, there are generally provided a discharge port for discharging ink, an ink flow path communicated with this discharge port and an electrothermal converting member used as an energy generating means for discharging ink provided in the ink flow path. According to such recording process, a high quality level image can be recorded at high speed and low noise and a discharge port for discharging ink can be provided at high density in a head in this recording process. Therefore, the recording process has a number of the advantages that a high revolution recording image and such color image could easily be obtained in a compact device. Thus, this bubble jet recording process has recently been used in various office equipment such as a printer, copy machine, facsimile and the like. Further, the recording process is used even in an industrial system such as a printing equipment etc. With the increased use of the bubble jet technology in products in many fields, the following various demands is recently increased. For example, an answer to demand of improvement of energy efficiency includes optimization of a heating element in which thickness of a protective film is controlled. This technology has an advantage in that the transmission efficiency of generated heat to liquid is enhanced. Further, to obtain a high definition image, there is provided a driving condition for imparting a liquid discharging method in which an improved ink discharge based on a stable bubble generation can be performed. Furthermore, to obtain a liquid discharge head having a high refilling speed of a discharged liquid to a liquid flow path from the viewpoint of the high speed recording, there is also provided a liquid discharge head having improved shapes of the liquid flow path. A flow path structure and a head producing method disclosed in document JP-A-63-199972, relating to the shapes of the flow path, are inventions directed to a back wave (pressure in a direction opposite to that toward a discharge port, that is pressure toward a liquid chamber) which is generated with the generation bubbles. This back wave is known as a loss energy since it is not an energy toward the discharge direction. A head disclosed in document JP-A-63-199972, has an ink jet head valve which is spaced from a bubbling area of bubbles formed by the heating element and is positioned at the opposite side to the discharge port with respect to the heating element. This valve has an initial position in a manner that it is adhered to the ceiling of the flow path by a head producing method using a plate material, and is hung down in the flow path with the generation of bubbles. This document discloses an invention in which an energy loss is controlled by controlling a part of the above-mentioned back wave with a valve. Further, to realize improvements of liquid discharge properties including control of the back wave, and of liquid supply properties, the document EP-A-0 739 734 discloses a constitution in which a movable valve member is provided facing a bubble generation area which generates bubbles, and the growth of bubbles is controlled by using displacement of the movable valve member, generated by pressure at the time of bubble generation. Fig. 4 shows a partially broken perspective view of one embodiment of a liquid discharging head provided with such an ink jet head having a moveable valve member. In the liquid discharging head in Fig. 4, a heating element 2 which allows a heat energy to act on liquid is provided on an element substrate 1 as a discharge energy generating element for discharging liquid. Liquid flow paths 7 are provided on this element substrate 1 correspondingly to the heating element 2. The liquid flow paths 7 are communicated with a discharge port 5, and are also communicated with a common liquid chamber 13 for supplying liquid to the plurality of liquid flow paths 7, thereby receiving an amount of liquid corresponding to the liquid discharged from a discharge port, from this common liquid chamber 13. On the element substrate 1 of this liquid flow paths 7 is provided an ink jet head valve in which a 1 µm thick plate-shaped movable valve member 6 having a flat surface portion, which is composed of an elastic material, such as a thin film resin, metal or the like, is provided like a cantilever beam. In Fig. 4, when the heating element 2 is heated, heat is acted on liquid in a bubble generation region between the movable valve member 6 and heating element, thereby generating bubbles based on the film boiling phenomena. The pressure and bubbles based on the generation of bubbles act on the movable valve member 6 and cause the valve member 6 to displace so that the valve member is largely opened on a liquid discharge side using a fulcrum 6a as the center of rotation, whereby the pressure generated by generation of bubbles and the bubbles themselves can be led to the down stream side where the discharge port 5 is provided. Document EP-A-0 739 734 also discloses a method comprising the features according to the preamble of claim 1. According to this known method, a valve material produced by an electroforming process or the like is used to laminate the material on a substrate. When the valve material is laminated on the substrate, it is necessary to provide a space of about 1 to 20 µm between the movable valve member and heating element so as to sufficiently obtain effects of the movable valve member. Further, to laminate the valve material produced by the electroforming process or the like so that a space can be formed in the movable portions, it is necessary to form a pedestal portion on the substrate so that the pedestal portion of a valve is previously fixed onto the substrate. Further, to form the pedestal portion having for example 5 µm, which is merely the height of the space, and to prevent the pedestal portion from being corroded with ink, it is necessary to form the portion by an Au plating process or the like. To perform the Au plating, sputtering of Au and patterning thereof by the photolithography technology are needed. Further, it is necessary to provide an electroformed valve member on a surface of the Au pedestal after the Au plating, make positioning of the valve member and fix the valve by a stud bump process or the like. However, it is difficult to position the valve member with high precision. Therefore, not only the thickness control of the valve member and positioning of the valve member were difficult, but also the production steps were extremely complicated. Accordingly, the object of the present invention is to solve the above-mentioned problems and to provide an improved method of producing an ink jet head. SUMMARY OF THE INVENTION According to the invention, the above-mentioned object is achieved by the method according to claim 1. According to the present invention, positioning of a high precision valve member obtained by the photolithography steps can be realized and controlling of the valve member thickness can be easily performed, whereby simplified steps can be realized. Advantageous developments of the invention are defined in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS Figs. 1A, 1B, 1C, 1D and 1E are cross-sectional views showing the first half production steps of a method of producing an ink jet head according to the present invention; Figs. 2F, 2G, 2H, 21 and 2J are cross-sectional views showing the last half production steps of a method of producing an ink jet head valve according to the present invention; Fig. 3 is a cross-sectional view taken along the direction of liquid flow path for explaining an example of a basic structure of a liquid discharging head not according to the present invention; Fig. 4 is a partially broken perspective view of one embodiment of a liquid discharging head provided with a movable valve member according to the state of the art. Fig. 5 is a cross-sectional view of a moveable valve member of an ink jet head produced in Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail by examples hereinbelow. Example 1 Figs. 1A to 1E and Figs. 2F to 2J are cross-sectional views showing the first half and last half production steps of a method of producing an ink jet head according to the present invention, respectively. First, to form a pedestal of a valve on a substrate, an about 5 µm thick PSG film 102 is formed on a Ta film 101 used as an anti-cavitation film at a temperature of 350 °C by a plasma CVD process (Fig. 1A). Then, to perform patterning of the PSG film 102 by the photolithography process, resist is spin-coated on the PSG film 102 to form a resist film thereon. After that a predetermined portion of the resist layer is exposed and developed. In this case, as a film material for forming the pedestal of a valve, PSG was used. However, the material is not limited to PSG, other materials such as an inorganic material, for example, BPSG, or SiO or the like, or an organic material may be used, if such material is not changed in quality in a metal CVD process which will be described later. Then, the PSG film 102 is etched by a buffered hydrogen fluoride to form a desired PSG film pattern (Fig. 1B). Then, an about 5 µm thick tungsten film is formed on the obtained substrate by a selective tungsten (W) CVD process using conditions of mixed gases and the mixing ratio of WF 6 /SiH 4 /H 2 = 10/7/1000 sccm, pressure of 26.6 Pa, and temperature of 260 °C. The tungsten film is selectively formed only on an exposed Ta portion, thereby forming a pedestal 61 of a valve (Fig. 1C). Although W is selected as the material of the pedestal 61 of a valve, the material is not limited to W, Ta, Pt, Mo, Cr, Mn, Fe, Co, Ni, Cu, or the like may be used, if they have functions as the materials of the valve pedestal and the valve itself. Alternatively, the materials of the pedestal and valve may be varied according to functions. After that, on the obtained substrate is formed an 1000 angstrom thick Ni wiring layer 103 by a sputtering process (Fig. 1D). The Ni wiring layer 103 is used for forming a valve material using a metal CVD process. In this case, the wiring layer was formed with Pd. However, other metals may be used. Then, an about 5 µm thick PSG film 104 is formed by a plasma CVD process (Fig. 1E). As the insulating film, a PSG film was used. However, the insulating material is not limited to PSG, other materials such as an inorganic material, for example, BPSG, or SiO or the like, or an organic material may be used, if such material is not changed in quality in a metal CVD process which will be described later. Then, the PSG film 104 is etched by a buffered hydrogen fluoride (HF) to form a desired PSG film pattern (Fig. 2F). Then, an about 5 µm thick tungsten film is formed on the obtained substrate by a selective tungsten (W) CVD process using conditions of mixed gases and the mixing ratio of WF 6 /SiH 4 /H 2 = 10/7/1000 sccm, pressure of 26.6 Pa, and temperature of 260 °C. The tungsten film is selectively formed only on an exposed Pd portion, thereby forming a valve 62 (Fig. 2G). Then, the PSG film 104 around the valve 62 is removed by a buffered hydrogen fluoride (Fig. 2H). After that Ni wiring layer 103 is removed by hydrogen peroxide solution (Fig. 2I). Finally, the exposed PSG film 102 is removed by the buffered hydrogen fluoride to form the pedestal 61 and the valve 62 (Fig. 2J). Example 2 In steps shown in Figs. 1A to 1E and Figs. 2F to 2J in Example 1, if stresses of the underlying wiring layer 103 and metal layer formed by a metal CVD process are controlled, a previously curved valve member 62, 103 having a cross-sectional view of Fig. 5 and not that of Fig. 2J, can be formed as the final configuration. For example, if an underlying wiring layer is formed by a compression stress of 1 × 10 9 dyn/cm 2 and the metal layer on the metal CVD side is formed by a tensile stress of 1 × 10 9 dyn/cm 2 , the valve member 62, 103 is deformed so that it is warped on the metal CVD side as shown in Fig. 5. Thus formed valve member does not require power to deform the valve during bubbling and can be moved only at the time of refilling. Therefore, the valve can reduce lost energy. Other Examples Fig. 3 is a cross-sectional view taken along the direction of liquid flow path for explaining an example of a basic structure of a liquid discharging head not according to the present invention. As shown in Fig. 3, the liquid discharging head comprises an element substrate 1 on which a plurality of heating elements 2 (only one of them are shown in Fig. 3) for imparting a bubble generating heat energy to liquid are provided in parallel, a top plate 3 connected to other member above this element substrate 1, and an orifice plate 4 connected to the front edges of the element substrate 1 and top plate 3. The element substrate 1 is formed by forming a silicon oxide film or silicon nitride film for insulation and heat accumulation on a substrate of, for example, silicon or the like, and forming a patterned electric resistance layer forming the heating element 2, and a patterned wiring, on the film. The heating element 2 is heated by applying the voltage on the electric resistance layer from this wiring and flowing current to the electric resistance layer. The top plate 3 is formed to form a plurality of liquid flow paths 7 corresponding to each of the heating elements 2 and a common liquid chamber 8 for supplying liquid to each of the liquid flow paths 7. A flow path side wall 9 extending between the heating elements from a ceiling portion is integrally provided with the top plate 3. The top plate 3 is composed of a silicon type material, and can be formed by etching the patterns of the liquid flow path 7 and common liquid chamber 8, or depositing a material of the flow path side wall 9, such as silicon nitride or silicon oxide etc., and etching the portion of the liquid flow path 7. In the orifice plate 4 is formed a plurality of discharge ports 5, each of which is communicated with the common liquid chamber 8 through each of the liquid flow paths 7. The discharge port 5 corresponds to each of the liquid flow paths 7. The orifice plate 4 is also composed of silicon type material and can be formed, for example, by planing a silicon substrate provided with a discharge port 5 to about 10 to 150 µm. The orifice plate 4 is not always a required constitution in the present invention. In place of provision of the orifice plate 4, when the liquid flow path 7 is formed in the top plate 3, a wall having substantially the same thickness as that of the orifice plate 4 is left in the top plate 3 and the discharge port 5 is formed in the wall portion, whereby a top plate with a discharge port can be formed. Further, the liquid discharging head is provided with a cantilever type movable valve member 6 positioned opposingly to the heating element 2 so that the liquid flow path 7 is divided into a first liquid flow path 7a communicated with the discharge port 5 and a second liquid flow path 7b having the heating element 2. The movable valve member is a thin film composed of a silicon type material, such as silicon nitride, silicon oxide or the like. This movable valve member 6 is provided at a position facing the heating element 2 while having a desired distance from the heating element 2 and covering it. The movable valve member 6 has a fulcrum 6a on the upstream side of a large flow which flows from the common liquid chamber 8 to the discharge port side through the movable valve member 6 by the discharging action of liquid, and a free end 6b on the downstream side with respect to the fulcrum 6a. The space between this heating element 2 and movable valve member 6 becomes a bubble generation region 10. When the heating element is heated, based on the above-mentioned constitution, heat is acted on the liquid of the bubble generation region 10 between the movable valve member 6 and heating element 2, thereby generating bubbles on the heating element 2 due to the film boiling phenomena and being grown. The pressure generated by the growth of the bubbles is preferentially acted on the movable valve member 6. The movable valve member 6 is displaced so that it is greatly opened or pivoted on the discharge port 5 side keeping the fulcrum 6a as the center, as shown in Fig. 3 by a broken line. By the displacement of the movable valve member 6 or the state of the displaced thereof, propagation of pressure due to the generation of bubbles and grown bubbles themselves are led to the discharge port 5 side, whereby liquid is discharged from the discharge port 5. Namely, by providing the movable valve member 6 having the fulcrum 6a on the upstream side (common liquid chamber 8 side) of the liquid flow in the liquid flow path 7 and the free end 6b on the downstream side (discharge port 5 side), on the bubble generation region 10, the bubble pressure propagation direction is led to the downstream side and the bubble pressure directly and efficiently contributes to the discharge of liquid. Further, the bubble growth direction itself is also led to the downstream side as in the pressure propagation direction, whereby bubbles are further largely grown in the downstream than in the upstream. Thus, by controlling the bubble growth direction itself with the movable member and controlling the bubble pressure propagation direction, fundamental discharge properties such as discharge efficiency, discharge output, or discharge speed etc., can be improved. On the other hand, when bubbles are in a bubble vanishing step, the bubbles are rapidly vanished by a multiplier effect of elasticity of the movable valve member 6, and the movable valve member 6 is finally returned to the original position as shown in Fig. 3 by a solid line. In this case, to compensate the shrinkage volume of bubbles in the bubble generation region 10 and to compensate the amount for the volume of discharged liquid, liquid is flown from the upstream side, that is the common liquid chamber 8 side to refill liquid into the liquid flow path 7. This refilling of the liquid can be efficiently, reasonably and stably performed by the return action of the movable valve member 6. According to the present invention, positioning a valve member with a high precision can be realized by the photolithography steps and controlling of the valve member thickness can be easily performed, whereby simplified steps can be realized. Further, according to the present invention, the moveable valve member of the ink jet head valve can be produced in a curved shape by the stress control of an underlying metal layer and the CVD stress control.

Claims: A method of producing an ink jet head having a discharge port (5) for discharging ink, an ink flow path (7) communicated with said discharge port (5), an electrothermal converting member (2) used as an energy generating means for discharging ink into said ink flow path (7), a movable valve member (62, 103) positioned opposingly to the electrothermal converting member (2), and a pedestal portion (61) for supporting said valve member (62, 103), the method comprising the steps of: preparing a substrate (1) provided with said electrothermal converting member (2) and having a conducting portion (101) on the surface of said substrate; and forming a first masking layer (102) for forming said pedestal portion (61) on said substrate surface; the method being characterized by comprising the following steps: etching a portion of said first masking layer (102), said portion being a portion where said pedestal portion (61) is formed; forming said pedestal portion (61) by metal CVD process and forming a conducting layer (103) on said pedestal portion (61) and on said first masking layer (102); forming a second masking layer (104) on said conducting layer (103) and etching a portion of said second masking layer (104), said portion being a portion where said movable member (62) is formed; forming said movable member (62) on said conducting layer (103) by metal CVD process; and thereafter removing said first and second masking layers (102, 104). The method of producing an ink jet head according to claim 1, wherein said movable member (62) and/or said pedestal portion (61) is/are produced by using Ta, W, Pt, Mo, Cr, Mn, Fe, Co, Ni, or Cu. The method of producing an ink jet head according to claim 1 or 2, wherein said conducting layer (103) is formed by compression stress and said movable member (62) is formed by tensile stress.

Inventors: HIROKI TOMOYUKI, IKEDA MASAMI, IMANAKA YOSHIYUKI, ISHINAGA HIROYUKI, KUBOTA MASAHIKO, OGAWA MASAHIKO, OZAKI TERUO, SAITO ICHIRO, HIROKI, TOMOYUKI, IKEDA, MASAMI, IMANAKA, YOSHIYUKI, ISHINAGA, HIROYUKI, KUBOTA, MASAHIKO, OGAWA, MASAHIKO, OZAKI, TERUO, SAITO, ICHIRO
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1998
Main classification: B41J2
IPC codes: B41J2