Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1997-10-29
2001-06-26
Johnstone, Adrienne C. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C065S017300, C156S235000, C445S024000
Reexamination Certificate
active
06251208
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a method for manufacturing a structure which has fine ribs or projections arranged in a stripe, lattice or honeycomb pattern on its surface. The structure is used as a component part of a plasma display panel or of a chemical reaction apparatus. The invention also relates to a method for manufacturing a mold used for manufacturing the structure.
Attention is now being paid to a plasma display panel as an image display apparatus which is thin and has a big screen. The rear or front panel of the plasma display panel has fine ribs which constitute barrier walls and are arranged in a predetermined pattern. In the case of, for example, the rear panel, ribs with a width of about 50 &mgr;m and a height of about 100 &mgr;m are arranged at regular intervals in a stripe pattern.
Further, in a chemical apparatus, a structure with fine ribs (whose arrangement patterns depend upon their functions) is used as a filter for classifying fine particles; a catalyst; or a catalyst carrier for accelerating burning, synthesis, decomposition, etc.; a micro organism, or a polar plate.
These ribs are required to have a highly precise configuration and dimension. In the conventional art, such ribs are manufactured by various methods such as multiplex printing, pressure molding, etching, sand blast, an electrolytic treatment, an electric spark machining, etc.
As described above, structures with fine ribs are manufactured by various methods according to their respective configurations, purposes or properties required. These methods, however, have the following problems concerning precision in configuration or dimension, manufacturing cost, etc.:
a) In the case of multiplex printing, ribs are formed by repeating screen printing and curing ten or more times. Accordingly, the ribs have side surfaces of low flatness, and hence show a low precision in configuration and position. Further, the process of the manufacture of the ribs requires a great amount of time, which results in a high manufacturing cost.
b) In the case of etching, if the rate of etching is increased to shorten the manufacturing time, the precision in configuration and position of each barrier wall inevitably decreases, with the result that the tips or bottom corners of the ribs cannot have desired configurations. In light of this, the etching rate cannot be increased, which means that a great amount of time and a high manufacturing cost are required. Moreover, the material of the ribs is limited to a chemically corrodable one. In addition, if the material of the ribs has a large crystal grain size, the ribs cannot have a high configuration precision, a high profile regularity, and cross sections which satisfy their specification.
c) In the case of the sand blast, it is not easy to enhance the configuration precision since the cutting rate is greatly influenced by changes in working conditions. In particular, it is difficult to control the height of each rib with a high precision. Moreover, during working, a great amount of cutting particles or fine dust may occumulate, thereby contaminating the working environment or requiring additional labor for waste disposal.
BRIEF SUMMARY OF THE INVENTION
It is the object of the invention to provide a method for manufacturing, in a relatively short time and at a low cost, a structure having fine ribs on its surface, formed with a high precision in configuration and position.
According to a first aspect of the invention, there is provided a method for manufacturing a structure with fine ribs, which comprises the steps below.
(a) To prepare a composite sheet which comprises an elastic surface layer and a base layer with a higher rigidity than the surface layer. The surface layer has grooves of a predetermined cross section arranged in a two-dimensional pattern.
(b) To fill the grooves of the composite sheet with a paste material.
(c) To cure the paste material to form ribs by evaporating solvent or chemical action.
(d) To laminate a substrate on the composite sheet, and press the composite sheet against the substrate from the base layer side, thereby compressing the ribs and adhering them to the substrate.
(e) To remove the ribs and the substrate from the composite sheet. As the result, the structure with fine ribs on the substrate is obtained.
Preferably, the surface layer is formed of rubber. More preferably, the surface layer is formed of a material with a low adhesive surface, such as silicone rubber.
Preferably, the base layer is formed of a thin steel sheet.
Typical conditions for manufacturing the rear panel or the front panel of a plasma display panel are explained below
The surface layer is made of rubber and has a thickness falling within a range of 0.3 mm-1 mm. The base layer is formed of a metal sheet and has a thickness falling within a range of 0.2 mm-0.5 mm. The ribs have a width of not less than 20 &mgr;m and not more than 100 &mgr;m, and a height of not less than 20 &mgr;m and not more than 200 &mgr;m.
Further preferably, the grooves each have a surface portion which is wider than a deeper portion thereof. By virtue of this structure, that base portion of each rib which is adhered to the substrate is formed in the surface portion of a corresponding groove when the grooves are filled with the paste material.
Also preferably, the composite sheet is vibrated from the base layer side at the time of filling the grooves with the paste material, to accelerate the flow of the paste material into the grooves.
Where the paste material contains a solvent, it is preferable that at the time of curing the material, evaporation of the solvent is accelerated by reducing pressure around the surface layer and heating the surface layer.
If necessary, the surface of the substrate or the ribs is coated with an adhesive before the ribs are adhered to the substrate.
A structure consisting of only the ribs can be formed by removing the ribs from the substrate after removing the ribs and the substrate from the composite sheet.
Moreover, a structure, which comprises a plurality of layers laminated on one another and each including ribs, can be formed by repeating the step of adhering the ribs on the substrate.
The method of the invention enables manufacturing of a structure with fine ribs in a smaller number of process steps than the case of using the conventional method. The ribs formed by the method of the invention have a high precision in side surface regularity, configuration and position.
According to a second aspect of the invention, there is provided a method for forming grooves, arranged in a two-dimensional pattern, on an elastic body constituting the surface layer of the composite sheet. To form such grooves, a mold is used. This mold is produced by electroforming, electric spark machining, etching, etc.
In the case of the electroforming, the mold is produced in a manner as below.
First, an inverse mold which has first grooves arranged in a predetermined pattern in a surface thereof is formed using a cutting or grinding tool. Then, using the inverse mold, an electroformed mold which has projections corresponding to the first grooves is formed. As a result, an electroformed mold with a high precision in configuration and position is obtained.
If necessary, part of the projections from the electroformed mold is removed after forming the electroformed mold, thereby obtaining projections arranged in a pattern corresponding to a partially modified one of the arrangement pattern of the first grooves. This means that the inverse mold used for forming a composite sheet with a complicated surface pattern can be produced relatively easily.
In the case of using the electric spark machining, the mold is formed in a manner as below.
First, a cylindrical electrode is prepared, which is supported such that it can rotate about an axis thereof, and has a plurality of grooves formed in an outer periphery thereof and extending circumferential.
Then, the electrode is relatively moved along a surface of an item to be worked, thereby subjecting the item to an electric sp
Hasegawa Yutaka
Hosoi Haruji
Nakamura Hiromi
Serizawa Shogo
Johnstone Adrienne C.
Pillsbury & Winthrop LLP
Toshiba Machine Co. Ltd.
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