JPS6117551Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an optical information disk equipped with a protection plate used in an optical information recording/reproducing device, which eliminates deformation of the disk due to temperature expansion and contraction of the protection plate, and is resistant to temperature changes. The object of the present invention is to provide an optical information disc that can perform good recording and reproduction. For example, an optical information recording/reproducing device records information by replacing the information signal with the strength of a laser beam using an optical modulator.
Modulated laser light is transmitted using optical means to approximately 1 μm.
The light is focused on a minute spot of m and irradiates the optical recording material. Optical recording materials are changed by the thermal energy of laser light and can record information. For reproduction, a weak laser beam is irradiated onto the information track, and the intensity of the reflected or transmitted light is extracted as an information signal and reproduced. In this way, the information track is 1μ
It has a fine shape of about 1.5 m in size, and if dust in the air adheres to the surface of the recording material, information will be lost at that location during recording and reproduction, that is, a dropout will occur. For this reason, optical information recording and reproducing devices require dust-proof measures.
As a measure against dust, optical information disks have heretofore been devised in which a protective plate is provided to prevent dust from adhering to the surface of the optical recording material. An example of a conventional optical information disk having this protective plate will be explained with reference to FIG. In FIG. 1, 1 is a cylindrical inner metal fitting having a flange, and 2 is a disc-shaped disk base material, one surface 2a of which is coated with an optical recording material. 3 is a disc-shaped transparent protection plate, and 4 is a ring having a flange. The disc base material 2 and the transparent protection plate 3 are adhesively fixed by an inner metal fitting 1 and a ring 2, so that the optical recording material surface 2a of the disc base material 2 is completely isolated from the outside. Further, the transparent protection plate 3 is provided at a certain distance from the disk base material 2 by the inner fitting 1 and the flange of the ring 4, and an air layer is formed between the disk base material 2 and the transparent protection plate 3. Since the thermal conductivity of air is much lower than that of the transparent protection plate 3, the thermal energy of the recording laser beam is less diffused compared to when the transparent protection plate 3 is brought into close contact with the optical recording material surface 2a, and the laser can be made smaller. This is because it can be done.

The material of the disk base material 2 requires surface precision.
Glass is generally used. In addition, the material of the transparent protective plate 3 is required to be hard to break and highly transparent in consideration of safety, and a transparent plastic such as acrylic, which is different from the material of the disk base material, is used. In the configuration shown in FIG. 1, when metal is used for the inner fitting 1 and ring 4, glass is used for the disk base material 2, and plastic is used for the transparent protection plate 3, the coefficient of thermal expansion of plastic is that of glass. Because the temperature is much higher than that of metal, the disk deforms due to temperature changes. That is, if the temperature is higher than that at the time of assembly, compressive stress due to thermal expansion is applied to the transparent protection plate 3, causing the transparent protection plate 3 to bend and come into contact with the recording material surface 2a, making recording and reproduction impossible. Furthermore, if the temperature is lower than that at the time of assembly, tensile stress will be applied between the transparent protection plate 3 and the ring 4, and there is a risk that the adhesive will peel off.

The present invention aims to provide a dust-proof optical information disk that eliminates the above-mentioned drawbacks caused by temperature changes. Embodiments of the present invention will be described below based on the drawings.

In FIG. 2, 5 is a cylindrical inner metal fitting having a flange, 6 is a disc-shaped disk base material made of glass, and an optical recording material is coated on the surface 6a. Reference numeral 7 denotes a disc-shaped transparent protection plate made of transparent plastic. The disk base material 6 and the transparent protection plate 7 are each adhesively fixed to the inner fitting 5. Reference numeral 8 denotes a ring having a flange and is bonded to the outer circumference of the disk base material 6. Reference numeral 9 denotes a holding ring having a dustproof pad 10 made of an elastic body. This presser ring 9 is adhered to the ring 8 at its outer circumference, and a groove 11 extending in the radial direction of the transparent protection plate 7 is formed between the dustproof pad 10 and the ring 8. The outer peripheral portion of the transparent protection plate 7 is inserted into this groove portion 11 . The width of the groove portion 11 is set to be slightly narrower than the thickness of the transparent protection plate 7, and to a width that does not prevent sliding of the transparent protection plate 7 when a strong force is applied thereto. Further, the depth of the groove portion 11 (in the radial direction of the transparent protection plate 7) is set to such a depth that even if the transparent protection plate 7 thermally expands and its diameter increases, the grooves 11 do not come into contact with each other. In such a configuration, when a temperature change occurs in the disk, strong stress is applied to the transparent protection plate 7 because it can slide in the radial direction within the groove formed by the holding ring 9 and the ring 8 at the tip of the transparent protection plate 7. It can be expanded and contracted without adding. Therefore, the transparent protection plate 7 is free from distortion and can maintain the same precision as when assembled, allowing good recording and reproduction. Furthermore, since the transparent protection plate 7 and the dustproof pad 10 are always in close contact with each other, external dust does not enter and adhere to the optical recording material surface 6a.

As described above, the optical information disk according to the present invention has a dust-proof structure and a structure that does not deform the disk shape due to temperature changes. Excellent recording and playback can be performed without being affected by this.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of a conventional optical information disk, and FIG. 2 is a side sectional view of an embodiment of the optical information disk of the present invention. 5...Inner metal fitting, 6...Disc base material, 6a...
Coated surface of recording material, 7...transparent protection plate, 8...ring, 9...pressing ring, 10...elastic dustproof pad, 11...groove.

Claims (1)

[Scope of utility model registration request] a disc-shaped disk base material having an information recording surface on one surface; a disc-shaped transparent protective material having a different coefficient of thermal expansion from that of the disc base material; and an information recording surface of the disc base material and the transparent protective material. an optical information disk having a ring that connects the disk base material and the transparent protective material so as to form an air layer separated from the outside by extending the ring at a certain distance, the ring being fixed to the outer periphery of the disk base material. An optical information disk characterized in that the transparent protective material is pressed and held by an elastic body inside the ring with a pressure that does not prevent sliding when the transparent protective material expands and contracts due to temperature changes.