Incremental printing of symbolic information – Light or beam marking apparatus or processes
Reexamination Certificate
2000-06-28
2004-02-17
Pham, Hai (Department: 2861)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
C347S065000
Reexamination Certificate
active
06693656
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a laser processing method. More particularly, the invention relates to a method of manufacture that uses such laser processing, for example, to manufacture an ink jet recording head for enabling ink droplets to fly and adhere to a recording medium, and also, relates to an ink jet recording head manufactured by such method of manufacture.
2. Related Background Art
Conventionally, there has been known the laser processing method that uses ultraviolet laser in order to precisely process a structural object that requires minute structures formed in high precision.
As an example of such precise processing, there is such one as processing ink flow paths or ink discharge ports of an ink jet head.
In the specification of Japanese Patent Application Laid-Open No. 2-121842 or 2-121845, is disclosed the high precision processing of ink flow paths or ink discharge ports using excimer layer, the typical ultraviolet laser.
In other words, the excimer laser can oscillate ultraviolet rays of short pulses (15 to 35 ns) by the discharge excitation of a mixed gas of rare gas and halogen. The oscillation energy thereof is 100 mJ/pulse, and pulse repetition frequency is 10 to 500 Hz. Then, when the highly bright ultraviolet rays, such as the excimer layer, are radiated on the surface of resin polymer, the ablative photodecompotion (APD) process occurs to decompose such portion to be scattered instantaneously with plasma emission and impact noises, thus making it possible to perform the so-called laser ablation process of polymer resin.
With the YAG laser which has been generally in use as a laser processing, edge faces tend to become rough, although drilling is possible. Also, the CO
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laser, which is infrared, has a drawback that crater is made on the circumference of each hole. Here, the laser processing of the kind is the so-called laser heat process, which is executed by transforming light energy into thermal energy. As a result, the processed shape is liable to be collapsed to make precise processing difficult. In contrast, the ablation process that uses excimer laser performs sublimation etching by means of the photochemical reaction that cuts the covalent binding of carbon atoms. Therefore, processed shape is not easily collapsed, hence making it possible to execute an extremely precise processing.
Here, the ablation process means a method for performing sublimation process by use of laser without conditioning any liquid phase.
Particularly, in the field of ink jet technologies and techniques, the practical use of laser ablation process has remarkably developed in recent years as fresh in the memory of those skilled in the art.
Further, while practicing the laser process using excimer laser, the following has been found: in other words, the oscillating pulses of radiated laser is approximately several tens of nano seconds per pulse for the excimer layer, that is, the aforesaid ultraviolet laser, while the ultraviolet harmonic oscillation of YAG laser is approximately 100 pico seconds to several nano seconds. However, the light energy of the laser beams radiated on a work piece is not necessarily used all for cutting the covalent binding of atoms.
Then, because of the existence of light energy which is not used for cutting the covalent binding of atoms, the laser processed portion of a work piece is scattered before being completely decomposed. Thus, a by-product is created on the circumference of the processed portion.
Also, a part of light energy which is not used for cutting the covalent binding of atoms is converted into thermal energy.
The energy density of excimer laser reaches only a 100-megawatt level at the maximum in terms of oscillating pulses. Therefore, it becomes difficult to process. metal, ceramics, and minerals (such as silicon) having high ratio of heat transfer, and quartz and glass having low light absorptance. Mainly, organic resin materials can be processed by use of sublimating ablation.
These have been unavoidable phenomena that may take place when using excimer laser. Therefore, various processing techniques have been proposed so that these phenomena do not produce unfavorable influences on the recording heads to be used actually.
For example, if an ink jet recording head is assembled with the aforesaid by-product yet to be eliminated, it may cause clogging of discharge ports. Here, a processing step should be provided additionally in order to remove the by-product.
Also, with a part of light energy being converted into thermal energy, a work piece may be caused to expand while it is processed or there is a fear that the work piece tends to be partly fused. Therefore, a material having a high glass transition point or a material having a lower processing pitch should be used.
Nevertheless, as described above, no fundamental solution has been given to any one of these techniques. The actuality is, therefore, that various restrictions should be imposed upon laser processing.
On the other hand, for the ink jet recording head described above, it has been required to provide highly precise images in recent years. For that matter, whereas the arrangement density of 300 to 400 dpi should be good enough conventionally, it is now demanded to provide that of 600 dpi or as high as 1,200 dpi in recent years.
Under the circumstances, the arrangement intervals of discharge ports and recording liquid flow paths should be processed in higher precision at extremely small intervals of 50 &mgr;m or less or in the extremely small diameter of 20 &mgr;m or less.
However, since the phenomena observable for the excimer laser processing as described above become more conspicuous as the process intervals or process diameters become smaller, there has begun a limit in using it for manufacturing a head of such a highly precise type as described earlier.
In this respect, the inventors hereof have recognized that the aforesaid phenomena are brought about by the laser ablation processing using the ultraviolet laser which is typically represented by the excimer laser, and assiduously made studies from the new point of view completely free from the conventional art. As a result, the fundamental solution has been found to eliminate these phenomena, and a revelational laser ablation processing technique has been found, which can deal with the microprocessing that makes further progress from now on, and which contributes to enhancing the versatility of such technique.
SUMMARY OF THE INVENTION
The present invention is designed with a view to solving the technical problems discussed above. It is an object of the invention to provide a laser processing method capable of performing a highly precise processing without creating by-product, while preventing fundamentally the thermal energy converted during the operation of laser processing from being accumulated on a work piece, such as resin, without fusing the work piece or causing thermal expansion, and also to provide a method for manufacturing an ink jet recording head using such laser processing method, as well as an ink jet recording head manufactured by such method of manufacture.
It is another object of the invention to provide a laser processing method capable of performing processing with simple and easy steps when processing a precise structural member formed by materials of plural kinds to be provided for a work pieces, and also, to provide a method for manufacturing an ink jet recording head using such laser processing method, as well as an ink jet recording head manufactured by such method of manufacture.
Also, it is still another object of the invention to provide a laser processing method which makes it possible to simplify the alignment step, and also, implement to increase the positional precision of the inner structural member or the like, while reducing the costs of manufacture, among some others, and also, to provide a method for manufacturing an ink jet recording head using such laser processing method, as well as an ink jet recording head manufactu
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