Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Patent
1991-02-12
1994-03-08
Bowers, Jr., Charles L.
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
430495, 430945, 430270, 3401351, 369284, 369283, G11B 724, G03C 100
Patent
active
052926168
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to an optical card, that is, an optical recording card in which information is optically written in an optical recording section in or on the card, and the written information is optically read and, more particularly, to an optical card of closed type in which an optical recording section, onto which information is recorded, is isolated from the outside environment.
BACKGROUND ART
Generally, an optical card has extremely high information recording density as compared with other recording cards such as a magnetic card, and IC card and so on. The optical card has an optical recording section on one side of a substrate. Information is recorded onto the optical recording section by an optical energy, chiefly, a laser light. Based on the difference in optical reflectivity between a recorded portion and an unrecorded portion, the recorded information is optically read back.
The general background of the optical card constructed as described above is disclosed in U.S. Pat. No. 4,680,460 or U.S. Pat. No. 4,673,626, for example. As will be seen from these patents, the optical card is broadly divided into two categories. One of them is an read only optical card in which a user performs only reading-out, that is, an optical card of ROM (Read Only Memory) type. The other is an additional recording optical card in which the user performs also writing, that is, an optical card of WO (Write Once) type.
A first characteristic required for a recording material in the optical card of WO type is a writing characteristic. In view of this, a recording material of pitted type is preferable which is comprised of a low-melting-point metal such as tellurium, bismuth or the like or its alloy. Conversely, however, the more superior the writing characteristic, the more the recording material tends to be influenced by the outside environment, negatively affecting other characteristics such as durability and so on.
As a method of improving the environmental resistance, means are known for isolating the optical recording section made of pitted type recording material, from the outside environment. For example, an optical recording section of an optical disks is enclosed between a pair of substrates of the optical disc while providing an air gap. Here, the air gap is provided for recording material that is melted due to heat, in order to prevent the writing characteristic from being deteriorated.
A technique is also known in which the closing method having an air gap is applied to an optical card (Japanese Patent Provisional Publication No. SHO 61-96539). It cannot be said, however, that the technique is suitable for wide usage such as carrying or the like of the optical card, because it is believed that the air gap causes disadvantages such as reducing compactness and strength of the card.
DISCLOSURE OF THE INVENTION
It is an object of this invention to provide a new or novel technique of an optical card construction in which, in spite of the fact that the card is of a closed construction and thereby superior in environmental resistance, the optical card also being superior in writing characteristics and other card characteristics.
This invention is widely applicable to various kinds of optical cards of WO type of construction in which an optical recording section is closed. Methods of closing the optical recording section include entirely covering the optical recording section on one side of a light transmittive substrate by a protective layer, or enclosing the optical recording section between a pair of card substrates in a sandwich fashion, or a method wherein a substrate supporting the optical recording section is made of a flexible sheet, or where the optical recording section on the sheet is enclosed between a pair of reinforcing substrates together with the sheet in a sandwich fashion, or the like.
This invention is also directed to an optical card using any one of the aforementioned enclosing methods. In either case, a sensitizing layer made of a self-oxidizable or thermoplastic resi
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Fujita Minoru
Fukushima Yoichi
Kakinuma Yuji
Angebranndt Martin
Bowers Jr. Charles L.
Kyodo Printing Co., Ltd.
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