method of producing perforations in a solid material in sheet fo

Details method of producing perforations in a solid material in sheet fo method of producing perforations in a solid material in sheet fo

1988-01-25

1990-09-11

Ryan, Patrick

Stock material or miscellaneous articles

Structurally defined web or sheet

Including aperture

428220, 428412, 428480, 428515, 428520, 20415715, 321234, 2504923, 156625, B32B 300

Patent

active

049562193

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a method of producing perforations in a solid material in sheet form, an irradiation device for working the method and the resulting perforated material.
It is already known to obtain perforations in a solid material in sheet form, in a first phase by producing traces of damage to the material, using particles which adversely affect the material along their trajectories, and in a second phase by chemical treatment for selectively attacking or corroding the material along the damaged traces (Physical Review, volume 133a, No. 5a, 1964, pages 1443 ff, Science, volume 149, No. 3682, 1965, pages 383 ff).
A number of variants of this method have been proposed. U.S. Pat. No. 3,303,085 describes the production of perforations having a transverse dimension (diameter) between 5 and 20,000 .ANG. in a mica sheet 100 microns thick. The mica sheet is placed in a reactor and bombarded by .alpha. particles or oxygen ions and then chemically treated with a solution of hydrofluoric acid. U.S. Pat. No. 3,493,751 describes the production of perforations in a sheet of cellulose nitrate about 0.02 mm thick. The cellulose nitrate sheet is bombarded with .alpha. particles having an energy of about 4.5 Mev, then chemically treated with a 6N aqueous solution of sodium hydroxide at between 60.degree. and 70.degree. C. for 30 seconds. U.S. Pat. No. 3,612,871 describes the production of perforations in a sheet of synthetic resin, inter alia polycarbonate. The polycarbonate sheet is irradiated in a nuclear reactor then subjected to electromagnetic radiation at a wavelength below 4,000 .ANG. and having an energy of at least 1.5 Mev and finally chemically treated with an aqueous solution of sodium hydroxide at about 60.degree. C. for 20 seconds. GB PS No. 1 375 204 describes the production of perforations in a film of non-conductive material by irradiation with sufficiently heavy, energetic ions followed by chemical treatment for widening the traces left by the ions. The materials under consideration are polyethylene terephthalate, polytetrafluoroethylene, polycarbonate, glass and vinyl polychloride. The ion bombardment energy is between 5 Mev and 20 Mev. The ions under consideration are ions of argon, chlorine and iron. The bombardment density is between 5.10.sup.12 and 9.10.sup.13 traces per square inch. After being bombarded, the membrane can be stretched or heated.
Other variant processes are considered in the prior art (U.S. Pat. Nos. 3713,921, 3,852,134 and 3,677,844 and French PS No. 2181215).
As is clear from the known state of the art, the main aim hitherto has been to define the physical and chemical conditions for the process under consideration, rather than the conditions for industrial operation so as to obtain, under acceptable economic conditions and in a sufficiently simple process, inter alia continuous, a strip material formed with perforations and of good quality, inter alia with regard to the uniformity and dimensional regularity of the perforations. Hitherto the process has mainly been worked by using nuclear reactors rather than particle accelerators. The use of a particle accelerator and the associated irradiation device poses a number of problems which, if not solved, may limit the use of accelerators or result in perforations of inadequate quality.
More particularly, continuous treatment of a strip material is difficult because of the intense vacuum in the associated irradiation device downstream of the accelerator, and the inadequate speed of chemical treatment. Also, the beam of particles produced by the accelerator is such that the resulting distribution of perforations in the material is usually insufficiently homogeneous and therefore unacceptable for certain applications. Finally the beam, if intense, can produce directly adjacent impacts in the material, and after chemical treatment the impacts result in multiple perforations made up of a number of elementary perforations (two or even three perforations). The result is a decrease in the dimensional regularity of the perforations, w

REFERENCES:
patent: 3303085 (1967-02-01), Price et al.
patent: 3493751 (1970-02-01), Davies et al.
patent: 3612871 (1971-10-01), Humphrey, Jr. et al.
patent: 3677844 (1972-07-01), Fleischer et al.
patent: 3713921 (1973-01-01), Fleischer et al.
patent: 3852134 (1974-12-01), Bean
patent: 4115303 (1978-09-01), Marchand et al.
Flerov et al., "Practical Applications of Heavy Ion Beams", Sov. Phys.-Usp., Mar.-Apr. 1975, pp. 783-793, Copyright 1975 American Institute of Physics.
Fischer et al., "Production and Use of Nuclear Tracks: Imprinting Structure on Solids", Reviews of Modern Physics, vol. 55, No. 4, Oct. 1983; Copyright 1983, The American Physical Society.
Physical Review, vol. 133, No. 5A, 3-2-64, pp. A 1443-1449.
Science, Jul. 23, 1965, vol. 149, No. 3682, pp. 383-392.

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