Abrading – Machine – Sandblast
Reexamination Certificate
2000-08-04
2002-04-09
Hail, III, Joseph J. (Department: 3723)
Abrading
Machine
Sandblast
C451S038000, C451S039000, C451S040000, C451S087000
Reexamination Certificate
active
06368195
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a plastic abrasive for sandblasting; a method for sandblast processing a plasma display panel substrate using the same; and a method for treating waste matters generated during sandblast processing. More particularly, it relates to a plastic abrasive which is used in sandblast processing for forming cellular or linear structures composed of barrier ribs and/or priming ribs in a plasma display panel substrate; a method for sandblast processing a plasma display panel substrate using the plastic abrasive; and a method for treating waste matters generated during the sandblast processing.
BACKGROUND OF THE INVENTION
Sandblast processing has been known as a processing method to be used in surface-patterning glasses, marbles, plastics, ceramics, leathers, woods, etc. In this method, patterns are drawn by forming a sandblast resist on the surface of a material to be processed, and spraying an abrasive or the like onto the exposed portions of the resist to selectively grind the resist. In particular, fine processing can be achieved by using a sandblasting-resistant photosensitive resin as the sandblasting resist, forming a sandblasting mask pattern by means of photolithography and then spraying an abrasive or the like onto the exposed portions. This technique is applied to the formation of circuit substrates in which metal patterns and insulating patterns are present in admixture, in particular, metal wiring patterns and insulating patterns made of ceramics, luminophors, etc. in plasma display panel (hereinafter referred to simply as “PDP”).
PDPs are prepared by forming a cellular or linear structure comprising barrier ribs and priming ribs on a substrate such as glass, providing an electrode and a luminophor layer within the cellular structure or between the linear structures, and introducing a discharge gas thereinto to give a display device. As proposed, for example, by JP-A-2-301934 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”), the cellular or linear structure can be formed by applying on a substrate a composition containing an inorganic powder (e.g., a glass frit having a low melting point) and an appropriate vehicle and drying it to thereby form a paste layer, forming a sandblast-resistant photosensitive resin composition layer thereon, forming a mask pattern for the cell drawing by a lithographic means, effecting sandblasting via the mask pattern to peel off and remove the sandblast-resistant photosensitive resin composition layer, and baking.
The abrasives used in this sandblast processing are those comprising inorganic fine particles having a particle size of 2 to 500 &mgr;m such as glass beads, SiC, SiO
2
, Al
2
O
3
and ZrO
2
.
However, the use of these abrasives comprising inorganic fine particles in the sandblast processing results in a large amount of powders of ground electrodes, luminophors, barrier ribs and priming ribs, as well as the fine particles of the abrasives, which are mixed together. The mixture is discarded as wastes as such, since it is difficult to classify the particles in the mixture. This brings about a serious problem in terms of environment.
Under these circumstances, the present inventors have conducted extensive studies, and found out that when specific plastic particles are used as an abrasive in sandblast processing, not only an excellent sandblasting performance can be achieved but also the abrasive in the sandblasting waste matters can be easily removed. This makes it possible to reuse the sandblasting waste matters and to avoid the environmental problem associating the disposal of the sandblasting waste matters. The present invention has been completed based on such findings.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a plastic abrasive for sandblasting which has excellent performance in sandblasting and enables the reuse of waste matters generated in sandblasting.
Another object of the present invention is to provide a method for sandblast processing a PDP substrate using the above-mentioned plastic abrasive.
A further object of the present invention is to provide a method for treating waste matters generated during sandblast processing.
In order to achieve the above objects, the present invention provides a plastic abrasive for sandblasting which is soluble in an organic solvent or a mixture of water and an organic solvent and comprises plastic particles having an average particle size of 5 to 100 &mgr;m;
a method for sandblast-processing a plasma display panel substrate, which comprises applying a paste composition on a plasma display panel substrate, drying the same to form a paste layer, forming a sandblasting-resistant photosensitive resin composition layer thereon, selectively irradiating the photosensitive resin composition layer with actinid rays to form an exposed pattern, effecting development to form a mask pattern for sandblasting and then grinding exposed portions with the plastic abrasive for sandblasting; and
a method for treating sandblasting waste matters which comprises treating waste matters generated during sandblast processing with an organic solvent or a mixture of water and an organic solvent to thereby remove the plastic abrasive.
DETAILED DESCRIPTION OF THE INVENTION
As described above, the plastic abrasive for sandblasting of the present invention is required to not only be easily soluble in an organic solvent or a mixture of water and an organic solvent but also be comparable in sandblasting performance to those comprising inorganic particles. Any plastic particles are usable as long as they satisfy the above requirements, but plastic particles of acrylonitrile /polyethylene chloride/styrene resin are preferred. The average particle size of the plastic particles preferably ranges from 5 to 100 &mgr;m, though it can be determined appropriately depending on the processing accuracy, thickness, etc. of the material to be processed. When the average particle size is less than 5 &mgr;m, a long time is needed for the sandblast processing. When it exceeds 100 &mgr;m, on the other hand, fine processing becomes difficult in some cases. From a practical viewpoint, it is preferable to use plastic particles containing at least 80% by weight of particles of not more than about 100 &mgr;m in particle size. The particle size of such plastic particles can be adjusted by conditions of grinding such as impact grinding and air current grinding.
As the organic solvent or mixture of water/organic solvent in which the plastic particles are soluble, ketone solvents, ester solvents, and water/alcohol solvents are preferred in terms of the cost and handling properties. More specifically, preferred examples of the solvent include acetone, methyl ethyl ketone, ethyl acetate, water/methanol, water/ethanol and water/isopropyl alcohol.
In order to improve the cutting properties in the sandblast processing, a material can be once ground with the plastic particles having a large particle size within the range as specified above and then finished with plastic particles having a smaller particle size.
As described above, the plastic abrasive of the present invention is easily soluble in an organic solvent or a mixture of water and an organic solvent. After the completion of the sandblast processing, therefore, inorganic components such as barrier ribs and/priming ribs, electrodes and luminophors can be easily recovered and reused, since the water/organic solvent mixture thus recovered are free from contaminants. As a result, there arises no environmental problem due to the disposal of the sandblasting waste matters.
Now, a concrete example of the sandblast processing method by using the plastic abrasive of the present invention will be illustrated.
This method involves the following steps: (i) the step of applying onto a PDP substrate (e.g., glass) a paste composition comprising an inorganic powder and an appropriate vehicle by screen printing and the like, and drying the same to form a paste layer; (ii)
Obiya Hiroyuki
Oshio Kiminori
Hail III Joseph J.
McDonald Shantese
Sughrue & Mion, PLLC
Tokyo Ohka Kogyo Co. Ltd.
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