JPH0344838A - Optical disk - Google Patents

Abstract

PURPOSE:To prevent the occurrence of the warpage of a disk by providing a parallel part on an inner peripheral side having a uniform sheet thickness and a tapered part which is connected to the parallel part and where the sheet thickness gradually becomes thin as it goes from the inner peripheral part to the outer peripheral part and constituting the whole as both-side symmetrical one. CONSTITUTION:As to a substrate 1, synthetic resin such as acrylic is injection molded so as to form a signal track and a signal pit, and a reflective film 2 capable of optically recording, reproducing and erasing is formed on the substrate 1 by vapor deposition, etc. A resin protective layer 3 is formed on the reflective film 2 by a spin coating method and a roll coating method, etc., and the substrate 1 has the both-side symmetrical constitution obtained by making the surfaces on which the reflective layer 2 is formed opposed and sticking them with adhesive 4 on both sides of the core 6 made of the synthetic resin such as the acrylic, shaped like a bead on an abacus. Thus, the occurrence of warping and flexure can be prevented even if there are changes in the peripheral environmental condition and in the left state.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to optical discs used for CDs, video discs, information files, etc.

Conventional technology A conventional optical disc is disclosed in Japanese Patent Application Laid-Open No. 58-6536.
As shown in Japanese Unexamined Patent Publication No. 68-108044, the structure was as shown in FIG.

In FIG. 2, 1 is a substrate made of synthetic resin such as acrylic, and signal bits are formed on one side. 2 is a reflective film made of aluminum or the like formed thereon, 3 is a resin protective layer, and 4 is an adhesive.

Problems to be Solved by the Invention However, with the above-mentioned configuration, since the overall shape is flat, warpage is likely to occur, and there is a problem that focus failure of the optical system occurs during reproduction.

In an attempt to solve the above problem, Japanese Patent Laid-Open No. 60-75672 discloses that a flat carrier having a signal recording surface and a conical carrier are pasted together with the signal recording surface of the flat carrier facing the plane of the conical carrier. An optical disc with a combined structure is shown.

The configuration of the optical disc is shown in FIG. 3. In addition to FIG. 3, 1.2.4 is the same as in FIG. 2.

6 is a conical protection substrate.

With the above configuration, the
It is possible to obtain an optical disk with small warpage and deflection and good characteristics.

However, in the configuration shown in FIG. 3, since the signal board 1 and the protection board 5 have different shapes, there is a problem in that the discs elongate differently due to moisture absorption and heat, causing warpage in the disc.

Means for Solving the Problems In order to solve the above problems, the optical disc of the present invention has a parallel part on the inner periphery where the plate thickness is uniform, and a plate thickness that gradually increases from the inner periphery to the outer periphery continuously from the parallel part. It has a tapered part that becomes thinner, and the entire structure is symmetrical on both sides.

Function The optical disc of the present invention has a solo-pan bead-like overall shape due to the above-described configuration, so that the rigidity is increased and warping and deflection can be reduced. Also, since it has a symmetrical structure on both sides, it will not warp like a bimetal even if it absorbs moisture or expands due to heat.

EXAMPLE Hereinafter, an optical disc according to an example of the present invention will be described with reference to the drawings.

In FIG. 1, 1.2 and 3.4 are the same as in FIG. 6 is a core made of synthetic resin such as acrylic and shaped like a solo bread ball.

The substrate 1 on the optical disk constructed as described above is generally formed by injection molding synthetic resin such as acrylic or polycarbonate to form signal tracks and signal pits. A reflective film 2 that can be optically recorded, reproduced, or erased is formed on the substrate 1 by vapor deposition or the like. A resin protective layer 3 is formed on the reflective film 2 by a spin coding method, a roll coating method, or the like. The substrate 1 has a reflective film 2 on both sides of the core 6.
They are bonded together with an adhesive 4 with the surfaces on which they are formed facing each other.

As described above, according to this embodiment, by pasting the same signal board on both sides of the Solo bread ball-shaped core, a highly rigid and symmetrical structure on both sides is achieved, and it does not warp or bend due to changes in the surrounding environmental conditions or the state of being left unused. Therefore, it is possible to obtain an optical disk with less surface runout and good characteristics. Furthermore, even if the disc is placed directly on a desk or the like, the overall shape is like a solo pan bead, so the surface of the signal section will not get dirty or scratched, making it extremely easy to handle.

Effects of the Invention As described above, the present invention provides an optical disc with a parallel portion at the inner circumference where the plate thickness is uniform, and a tapered portion where the plate thickness gradually becomes thinner from the inner circumference to the outer circumference following the parallel portion. By making the entire structure symmetrical on both sides, it is possible to prevent the occurrence of warping and deflection due to changes in surrounding environmental conditions and storage conditions, and it is possible to obtain optical discs with less wobbling and good characteristics. can. Furthermore, even if the disc is placed directly on a desk or the like, the overall shape is like a solo pan ball, so the surface of the signal section will not get dirty or scratched, making it extremely easy to handle.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an optical disc according to an embodiment of the present invention, and FIG. 2 is a sectional view of a conventional optical disc. FIG. 3 is a sectional view of another conventional optical disc. 1... Substrate, 2... Reflective film, 3...
...Resin protective layer, 4...Adhesive, 5...
...Protection board, 6...core.

Claims (1)

[Claims] An optical disk having a parallel portion of an inner circumferential portion having a uniform thickness, and a tapered portion continuous with the parallel portion and having a thickness that gradually decreases from the inner circumference toward the outer circumference, and the entire structure is symmetrical on both sides.