Metal working – Method of mechanical manufacture – Fluid pattern dispersing device making – e.g. – ink jet
Reexamination Certificate
2000-06-27
2004-07-13
Tugbang, A. Dexter (Department: 3729)
Metal working
Method of mechanical manufacture
Fluid pattern dispersing device making, e.g., ink jet
C219S121600, C219S121610, C219S121690, C219S121760, C347S047000, C355S067000
Reexamination Certificate
active
06760973
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a laser working method, for example, a method for producing with such laser working method an ink jet recording head for discharging ink droplets and depositing such ink droplets on a recording medium, an ink jet recording head or a micromachine produced with such method, and a laser working method capable of fine working of complex material or complex shape such as an IC or a hybrid IC.
2. Related Background Art
For fine working of a structured article requiring a fine structure and high precision, there has been employed a laser working method employing an ultraviolet laser.
Such fine working can be exemplified by working of ink flow paths and ink discharge ports of an ink jet recording head.
The Japanese Patent Application Laid-Open No. 2-121842 and No. 2-121845 disclose high precision working of forming ink flow paths and ink discharge ports with an excimer laser which is a representative ultraviolet laser. The excimer laser is capable of emitting ultraviolet light of a short pulse (15 to 35 ns) by discharge excitation of mixed gas of rare gas and halogen gas, with an oscillation energy of several hundred mJ/pulse and a pulse repeating frequency of 10 to 500 Hz. When the surface of polymer surface is irradiated with a short-pulsed ultraviolet light of such high intensity, there is generated an ablative photodecomposition (APD) process in which the irradiated portion instantaneously decomposes and scatters with a plasma light emission and an impact sound, whereby so-called laser ablation working of polymer resin is made possible.
Among the conventional lasers employed for such working, the widely employed YAG laser can form a hole but generates a coarse edge face, while the CO
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laser emitting infrared light is associated with a drawback of generating a crater around the formed hole. Such laser working methods are laser thermal working in which the working is achieved by converting optical energy into thermal energy, so that the shape of the workpiece (the object to be worked) is often destructed and fine working is difficult to achieve. On the other hand, the laser ablation working utilizing the excimer laser, based on sublimation etching by a photochemical reaction breaking the covalent bond of carbon atoms, does not easily destruct the shape of the workpiece and can therefore achieve working of very high precision.
The laser ablation working method means a working method by sublimation, not through a liquid phase, by a laser.
Particularly in the field of ink jet technology, it is well known that the technology has undergone a remarkable progress to the present state by the adoption of the laser ablation working technology utilizing such excimer laser.
With the practical adoption of such laser working technology with excimer laser, there have been found the following phenomena.
The pulse oscillation time of the irradiating laser is about several ten nanoseconds in case of the excimere laser which is an ultraviolet laser or about 100 picoseconds to several nanoseconds in case of an ultraviolet laser of high frequency oscillation of the YAG laser, but all the laser beam falling on the workpiece is not consumed for cleaving the covalent bonds of the atoms.
Because of the presence of such optical energy not consumed in cleaving the covalent bonds of the atoms, the laser worked portion of the workpiece scatters before being completely decomposed, thereby forming by-products around the working area.
Also a part of the optical energy not consumed in cleaving the covalent bonds of the atoms is converted into thermal energy.
Also, as the energy density of the excimer laser remains at the level of 100 megawatts at maximum in the oscillation pulse, the subliming ablation working is not easily applicable to the materials of high thermal conductivity such as metals, ceramics or mineral substances (such as silicon) or materials of low light absorption such as quartz or glass but can principally employed for organic resins.
These phenomena are unavoidable in using the excimer laser, and various technologies have been proposed to avoid the influences of these phenomena on the actual ink jet head.
For example, a step of removing the by-products is conducted, since the ink discharge ports may be clogged if the ink jet recording head is assembled while such by-products still remain.
Also, as the conversion of a part of optical energy into thermal energy may cause thermal expansion or partial fusion of the workpiece in the course of working, there is employed a material of a high glass transition point or a reduced working pitch.
Besides, since these technologies do not fundamentally resolve these phenomena, there are practically encountered various limitations in conducting the laser working.
On the other hand, a higher definition in the image quality is being requested for the ink jet recording head, and the density of arrangement of the ink discharge ports or the ink flow paths, conventionally in a range of 300 to 400 dpi, is now requested to be elevated to 600 dpi or even 1200 dpi.
Therefore, there is requested a method capable of forming the discharge ports and the ink flow paths with a small pitch or a small dimension, such as an arrangement pitch of 50 &mgr;m or less and a working diameter of 20 &mgr;m or less, with a high precision. However the above-mentioned phenomena associated with the exciver laser become more conspicuous as the working pitch or the working diameter becomes smaller, and are posing limitations in producing the ink jet head of high precision as mentioned above.
In consideration of the foregoing, the present inventor, having recognized that the aforementioned phenomena are based on the laser ablation working utilizing the ultraviolet laser exemplified by the excimer laser, and have made intensive investigations not restricted in the field of the conventional technologies and have reached a novel laser ablation technology that is capable of fundamentally resolving these phenomena, also adapting to the fine working technologies ever advancing hereafter and also expanding the adaptability to various applications.
SUMMARY OF THE INVENTION
In consideration of the foregoing, an object of the present invention is to provide a laser working method free from generation of by-products and fundamentally avoiding accumulation of thermal energy, generated in the course of laser working, in the workpiece such as a resin, thereby achieving highly precise working without fusion or thermal expansion of the workpiece, a method for producing an ink jet recording head utilizing such laser working method, and an ink jet recording head produced by such producing method.
Another object of the present invention is to provide a laser working method capable of forming a fine structure in a workpiece composed of plural materials by a simple working step, a method for producing an ink jet recording head utilizing such laser working method, and an ink jet recording head produced by such producing method.
Still another object of the present invention is to provide a laser working method capable of simplifying an alignment step, improving the precision such as the positional precision of an internally structured member and reducing the manufacturing cost, a method for producing an ink jet recording head utilizing such laser working method, and an ink jet recording head produced by such producing method.
Still another object of the present invention is to provide a laser working method capable of improving the working efficiency by constructing the workpiece so as to absorb the radiation energy of laser, a method for producing an ink jet recording head utilizing such laser working method, and an ink jet recording head produced by such producing method.
Still another object of the present invention is to provide a laser working method capable of preventing speckle interference and reducing the damage by the laser beam on the mask, thereby enabling the working of a workpiece by projection of a large-area patter
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Tugbang A. Dexter
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