Recorders – Record receivers and/or driving means therefor – Laminated – impregnated – or coated bases
Patent
1984-06-26
1986-05-20
Goldberg, E. A.
Recorders
Record receivers and/or driving means therefor
Laminated, impregnated, or coated bases
369283, 369284, 427162, 427402, 428913, 430495, 430945, 430961, G01D 1534, G11B 724, G03C 504
Patent
active
045904936
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an optical disc comprising a resin disc, as its substrate, with a metal film on the surface of, e.g. optical reproduction discs which utilizes laser or other light sources.
Such a disc has a protective coating on the metal film. The present invention provides an optical disc having on the metal film two layers of film--a protective film which is highly cohesive to the metal and a hard coating--and a hard coating on the opposite surface of the resin disc, which is improved with respect to susceptibility to warpage or injury and which features ease of handling.
BAKCGROUND ART
The optical disc generally represented by a digital audio disc is being manufactured by forming by way of sputtering or vapor-deposition a film of aluminum, etc., on the signal side surface of an acrylic resin disc or polycarbonate resin disc into which signals have been written by injection molding or photo polymerization. Because such a disc is susceptible to injury, the provision a protective film for the metal film and the provision a protective material for the resin surface have been desired; however, no particular structure, for such a film has been devised.
Thus in order to have excellent adhesion the metal film, normally, acrylate monomers having phosphate radicals and with small molecular weights are added or primers are mixed. Such a method, however, has raised the problem of increasing the acidity (pH) of the coating material or causing electrolysis of aluminum film. However, for the improved adhesion on metal attained by phosphate radical, acrylates of novel molecular structure were desired. Because the audio disc utilizes laser beams, without using a needle, the disc and the optical pick-up do not make contact. However, since dust adhering on the disc disperses the beams, the cleaning of its surface e.g. by wiping it with a cloth is necessary, but may cause injury. Such injury, if large, would scatter the laser beams, thus interfering with inputting of signals.
The present inventors have noted that when coating urethane coating material or acrylate material, if the protective film is too thick, a disc with smooth surface cannot be obtained or, if the protective film is hard and thick, warping of substrate occurs, problems of warpage and impairment of surface flatness have been experienced.
Thus it is desired to have an optical disc on which a protective film excellent in cohesion to metal film and a hard coating excellent in cohesion to the protective film and the resin substrate (polycarbonate substrate, in particular) are formed to such thickness that they do not cause development of warpage.
DISCLOSURE OF THE INVENTION
The present invention has achieved an optical disc comprising a resin disc, a metal film formed on at least one of the surfaces of the resin disc, a protective film formed on this metal film and a hard coating formed on the resin disc or on the protective film and having a bridging density which is higher than that of the aforementioned protective film, said optical disc being of a structure such that not only the metal film is protected from scratching, but also corrosion prevention is improved by forming a protective film on the metal film and, further, an adherent hard coating on the protective film. This permits high transmission of laser beams and provides improved protection of the disc of a resin such as polycarbonate, etc., from scratching.
FIG. 1 is a plan view of an optical disc, an embodiment of this invention;
FIG. 2 is a section view on line A--A; and
FIG. 3 is an enlarged section view of the part of B shown in FIG. 2.
THE MOST PREFERRED MODE OF EXERCISING THE INVENTION
In the following, an embodiment of this invention is described with reference to the accompanying drawings and experiment result tables. FIG. 1 is a plan view of an optical disc of this invention, which is an extrusion molded polycarbonate substrate with 120 dia. and having a hollow for cassette at the center. FIG. 2 gives a section view on line A--A of FIG. 1. Numeral
REFERENCES:
patent: 4340655 (1982-07-01), Hollister et al.
patent: 4360820 (1982-11-01), Forster et al.
patent: 4458004 (1984-07-01), Tanikawa
Inoue Takao
Yoshimura Munehiro
Goldberg E. A.
Matsushita Electric - Industrial Co., Ltd.
Preston Gerald E.
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