Plastic and nonmetallic article shaping or treating: processes – Direct application of electrical or wave energy to work – Injection molding
Reexamination Certificate
2002-02-26
2004-11-02
Lechert, Jr., Stephen J. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Direct application of electrical or wave energy to work
Injection molding
C264S494000, C264S297200, C425S542000
Reexamination Certificate
active
06811736
ABSTRACT:
TECHNICAL FIELD
The present invention relates primarily to a method of producing a plastic product having at least one outer surface assigned a microstructure, utilising an arrangement for moulding plastic products.
This arrangement for producing plastic products has at least two mould parts movable towards and away from each other, a predetermined volume or quantity of a viscous polymerisable plastic material being supplied to a first cavity formed between the mould parts.
By the expression “polymerisable plastic materials” is meant a plastic material having a viscosity equivalent to that of water or thinly fluid syrup.
The method in accordance with the invention is designed for use in both die-casting and compression moulding.
In the case of die-casting the mould parts assume a co-operating position in relation to each other and a cavity formed between the mould parts has a shape conforming to an outer shape of the plastic product, viscous plastic material being pressed into the cavity and being permitted to polymerise there.
In the case of compression moulding the mould parts shall be able to assume an almost fully united position in order to allow a predetermined volume or quantity of a viscous polymerisable plastic material to be supplied to a first cavity formed between the mould parts.
The method in accordance with the invention is thus based on the mould parts being subsequently compressed to a fully united position and said viscous plastic material being distributed under a positive pressure within a smaller second cavity corresponding to the shape of the final plastic product, the outer form of which will conform to the internal shape of the second cavity formed by the mould parts.
The defining inner surfaces of the second cavity will thus correspond to the outer defining surfaces for the final product. However, each microstructured surface portion of the final product will have its corresponding microstructured surface portion in the second cavity.
Polymerisation of the viscous plastic material is then performed, with the mould parts in fully united position and, after said polymerisation of the plastic material, the mould parts are caused to move apart from each other to allow removal of a finished plastic product from the second cavity formed by the mould parts.
In this context it should be mentioned that by the expression “polymerisable plastic material” is meant a plastic which is supplied in thinly fluid form to a first cavity formed between the mould parts and which is distributed in its thinly fluid form within a second cavity by the movement of the mould parts towards each other, thereby filling out and penetrating into the surface portions of the microstructure in one or more mould parts, whereafter measures are taken to cure or polymerise the plastic material in the second cavity.
Polymerisation of the plastic material may be carried out by means of various known methods.
For instance an addition curing component may be added to the plastic material used, a so-called two-component system, or a plastic material may be chosen that is cured when subjected to light such as UV (ultraviolet) light, a plastic material curable when subjected to heat, or a plastic material with catalytic properties for polymerising, etc.
Thus the invention is not based primarily on the use of such viscous thermoplastic materials with which a desired curing shall occur by a hot plastic material being introduced under a positive pressure between fully united mould parts forming said second cavity and where the curing occurs by cooling of the mould parts and the inner structure of the second cavity.
The invention relates secondly to an arrangement for producing plastic products, designed to enable performance of the method in accordance with the invention.
Although the invention may be applied in the die-casting technology the significant properties of the invention will be illustrated in the following in the compression moulding technology, utilising a viscous polymerisable plastic material.
BACKGROUND ART
Various methods have been proposed for producing a plastic product with microstructured surface portions, utilising an arrangement for producing plastic products.
Considering the application so significant for the present invention, namely the prime object of providing a method and an arrangement for producing plastic products for the manufacture of plastic discs containing information, such as CD discs, DVD discs or, in a wider application, micromechanical discs of various types, a plurality of methods and arrangements are known.
Microfluids fall within the latter application, where a fluid shall pass through channels in the disc formed by means of micromechanics, for measuring various entities. Open channels in the surface may here be covered by a lid in order to form closed channels in the surface.
A more specific application is to allow winding channels to be formed on a disc in order to separate different DNA molecules with electrophoresis. A voltage forces the molecules forward and an optical detector registers when they arrive.
The microstructure of CD discs and storage of information currently has a height of 0.1 &mgr;m and a breadth (elevation and depression) of 0.7 &mgr;m.
The microstructure useful in microfluids for flow handling and optics may have a height of 10-100 &mgr;m and a channel breadth of 20-100 &mgr;m.
For information storage it is known to produce CD discs with high or extremely high storage capacity.
In this context it should be mentioned that CD discs of the type under discussion have been given various designations for the relevant storage capacity, such as DVD
5
, DVD
8
(Digital Versatile Disc), where the figure stated indicates the storage capacity in Gbyte.
An arrangement for producing plastic products which is currently extremely useful for producing such CD discs is the use of an injection moulding machine for thermoplastics where two mould parts used shall assume a position fully co-operating with each other and where the mould parts form said second cavity.
In this co-operating position a heated thermoplastic compound, in the form of a plastic composite, is pressed through a fixed mould part to a space or a second cavity formed between the two mould parts, for die-casting of a flat plastic component with microstructured surface portions.
The movable mould part is then moved away from the fixed mould part and the formed flat moulded plastic component or the CD disc is removed from the movable mould part.
In this application curing of the thermoplastic material occurs through a considerable drop in temperature, usually in the order of 100° C. The drop in temperature stated here applies to the difference between the temperature of the feeding screw and of the plastic product upon removal from the mould parts.
The ambition to maintain a high rate of manufacture demands a temperature in the mould parts and the second cavity that has a cooling and curing effect on the thermoplastic material supplied, with reduction of the replication ability as regards the microstructured surface section.
However, the present invention is also based on an, albeit, previously known method of producing a plastic product and an arrangement for producing plastic products which, as a result of the thermoplastic-based manufacturing method described has been pushed aside since, with current technology and demands, it has been considered too expensive and too slow. This method with an arrangement for producing plastic products has therefore only be used to a limited extent for producing genuine, complete plastic products with one or more microstructured surfaces.
The method and the arrangement for producing plastic products from which the present invention can be deemed to emanate are shown and described in more detail in the publication “High Density CD and Industrial approach”, publication number ISBM 90-80 2001-2-3, particularly pages 77-79.
The method and arrangement for producing plastic products from which the present invention has been developed are described in more de
Lundbladh Lars Rune
Ohman Per Ove
Birch & Stewart Kolasch & Birch, LLP
Gyros AB
Lechert Jr. Stephen J.
LandOfFree
Method of producing a plastic product and an arrangement for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of producing a plastic product and an arrangement for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of producing a plastic product and an arrangement for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3344545