Electric heating – Metal heating – By arc
Reexamination Certificate
2000-11-28
2004-06-08
Dunn, Tom (Department: 1725)
Electric heating
Metal heating
By arc
Reexamination Certificate
active
06747244
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a laser working apparatus, a laser working method, a method for producing an ink jet recording head utilizing such laser working apparatus or method, and an ink jet recording head produced by such producing method, and more particularly to a laser working apparatus and a laser working method capable of ablation working of a work article and of fine working of a complex material and a complex structure such as of a micromachine, an IC and a hybrid IC device.
2. Related Background Art
In case of forming a fine structure directly on a work article by laser light, there is generally employed a harmonic wave of an excimer laser or a YAG laser, but, since the energy density of the laser light in the oscillated pulse is limited to the order of 100 megawatts at maximum, the laser working is difficult in materials of high thermal conductivity such as metals, ceramics or minerals (such as silicon) or those of low light absorbance such as quartz or glass, and can only be applied for the sublimation ablation working principally of organic resinous materials. Because of such drawbacks, in case of fine working of a compound material including or composed of the aforementioned metals, ceramics, minerals or glass, the desired structure can only be formed by a lithographic process requiring steps of resist coating, resist patterning by exposure, resist development, etching utilizing the resist pattern and resist ashing for each of the different materials.
Also in the manufacture of an ink jet recording head which is generally provided, in the ink discharge mechanism, with an ink discharge orifice for discharging ink, a liquid chamber containing ink to be supplied to the ink discharge orifice, an ink flow path connecting the ink discharge orifice and the liquid chamber, an energy generating element provided in a part of the ink flow path for generating energy for ink discharge and an ink supply aperture for ink supply to the liquid chamber from the exterior, it is being tried to form the ink discharge orifice in a compound material including a laminated metal film in order to provide the plate bearing the ink discharge orifice (hereinafter called orifice plate) with a function not achievable with a resinous material only. In such case there is applied press working process or lithographic pattern etching process, but the press working is limited in the precision and is unsuitable for fine working. Also the etching process is disadvantageous in cost because of the complex working process, and also in the significant investment required for the production facility, in consideration of the process tact time.
As explained in the foregoing, there is generally required a complex working process such as the lithographic process, in order to form a fine structure in the work article.
Therefore, the present applicant already proposed, for example in the Japanese Patent Applications Nos. 2000-187464, 2000-188333 and 2000-187146, means utilizing so-called femtosecond laser described for example in the “Next Generation Optotechnology Review” (published 1992 by Optronics Co.; Part 1 Elementary Technology; Generation and compression of ultra short light pulse, pp.24-31) and executing irradiation with the laser light in plural pulses of a high energy density in space and in time, emitted from a laser oscillator having a pulse emission time not exceeding 1 picosecond, in concentrated manner with a predetermined energy density, thereby achieving sublimation ablation working before the laser light is diffused as thermal energy in the work article. With such means, since the energy density in time is drastically increased (a pulse emission time not exceeding 150 femtoseconds and an optical energy exceeding 500 microjoules per pulse being achievable in the commercially available femtosecond lasers, thus providing an energy density of about 3 gigawatts in the oscillated pulse of the emitted laser light), and since the laser irradiation time is very short, the sublimation ablation working process can be completed before the laser light is diffused as thermal energy in the work article. Such phenomenon may be scientifically interpreted that the optical energy is not converted into thermal energy but directly functions as the lattice cleaving energy because the photons require a time of about 1 picosecond for conversion into phonons or thermal quantum particles by absorption in the electrons.
Such phenomenon allows to concentrate energy even in materials of high thermal conductivity such as metals, ceramics or minerals (for example silicon) thereby easily achieving the working by a multi-photon absorbing process, and the working becomes possible even in materials of low light absorbance such as glass, quartz or optical crystals as long as they have an absorbance of 0.1 to 1%, since, even in such materials, the optical energy density reaches a gigawatt level which is more than 100 times higher than that achievable with the excimer laser.
Consequently the optical ablation working, utilizing the high output femtosecond laser capable of emitting a high power laser light with a pulse emission time not exceeding 1 picosecond, is highly promising as the fine working process not limited in the material, and is therefore actively developed in recent years.
However, the above-mentioned laser oscillation system, capable of emitting the laser light with a pulse emission time not exceeding 1 picosecond, generally employs vertical mode synchronization for oscillation, and the compression of the laser pulse in time is realized by the vertical mode synchronization, which requires adjustment of an optical member in the laser system in the order of a micrometer. For this reason, the system is very sensitive to the thermal expansion or contraction of the members constituting the system, and, if the repeated oscillation state of the laser is changed for example by a burst oscillation or a modulation of the repeated oscillation frequency, the thermal equilibrium in the laser oscillator is perturbed to cause instability of the temperature therein, whereby the support member for the optical members causes thermal expansion or contraction to disrupt the optical adjustment of the micrometer order, thereby resulting in a variation in the oscillated pulse duration and the output energy of the laser light. In order to avoid such drawbacks, the above-mentioned laser oscillation system is operated under temperature control of the order of 0.1° C. for the portions of laser oscillation and amplification, but such temperature control is still insufficient and it is still desirable to operate the system in a continuous pulse oscillation mode in a stationary state.
On the other hand, in case of using such continuous pulse oscillation mode for actual working process, a light intercepting device or a light intensity attenuating device has to be provided in the optical path of the continuously emitted laser light, but such device, if simply provided in the laser oscillator, results in the following drawbacks.
As explained in the foregoing, since the laser emission of the extremely short pulse emission time is achieved by the vertical mode synchronization, the optical members in the laser oscillation system have to be positioned with a precision of the order of a micrometer, and the entire laser oscillator is precisely controlled in temperature with a precision of the order of 0.1° C. If a light intercepting device or a light intensity attenuating device is simply provided in the main body of such laser oscillator, such device absorbs or emits the energy of the laser, whereby the temperature in the laser oscillator is elevated by the absorption of the optical energy and the laser oscillation itself becomes extremely unstable.
Also, for achieving optimum fine working with a higher precision, it is not sufficient to merely consider the influence on the temperature control of the entire laser oscillating portion, in providing the light intercepting device or the like there
Canon Kabushiki Kaisha
Dunn Tom
Johnson Jonathan
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