JPS63113827A - Optical information recording disk - Google Patents

Abstract

PURPOSE:To reduce a stress applied to a base plate, and to reduce its double refraction by constituting the titled disk so that a bulge having an expansion coefficient or a longitudinal elastic modulus of the same degree as that of the base plate is interposed between a disk substrate and a center fittings. CONSTITUTION:Two pieces of disk base plate 1 having a recording sensitized material 2 for recording the information are stuck to each other by an adhesive agent layer 3, and two pieces of bulges having a projection 6 fitted to its center hole, and a center fittings are stuck to the outside of the substrate 1. The substrate 1 and the bulge 5 are made of the same polycarbonate, and also, constituted so that they have a linear expansion coefficient and a linear moisture absorption expansion coefficient of the same degree, or a longitudinal elastic modulus of the bulge 5 at a room temperature takes a value being near that of the substrate. In such a way, stress and strain applied to the substrate 1 by the bulge 5 are reduced, therefore, a double refraction of the substrate can be reduced.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to the structure of an optical information recording disk.

(Prior Art) Some optical information recording discs are magnetically clamped by a center metal fitting when mounted on an optical information recording/reproducing device. In this case, the basic structure of the conventional optical information recording disk is shown in Figure 4.The material is plastic such as acrylic resin or polycarbonate, and the recording surface is used to record information on one or both sides. It is composed of a portion where a disk substrate 1 having a material 2 is bonded together with an adhesive layer 3, and a center metal fitting 4 attached to the outside of the inner peripheral portion of the disk substrate 1.

(Problems to be Solved by the Invention) In the conventional structure, the plastic disk substrate 1 deforms due to moisture absorption and dehumidification, whereas the center metal fitting 4 maintains a constant dimension, which causes large stress and strain to be applied to the disk substrate 1. , the birefringence will increase. Furthermore, since there is a difference in linear expansion coefficient between the disk substrate 1 and the center fitting 4, a similar phenomenon occurs due to temperature fluctuations.

The present invention relates to the structure of an optical information recording disk that reduces stress and strain caused by moisture absorption/dehumidification or temperature fluctuations.

(Means for Solving the Problems) The structure of the present invention uses a polymeric material having a coefficient of linear expansion and linear hygroscopic expansion comparable to that of the disk substrate and/or The disk substrate is characterized by having a bulge made of a polymer material whose longitudinal elastic modulus at room temperature is less than the value of the material of the disk substrate.

Suitable polymer materials for the bulge include glasstex, rubber, etc., such as polycarbonate, polymethyl methacrylate, and compound resins of modified polystyrene and polycarbonate, which are generally used for disk substrates.

The range of linear expansion coefficient and linear hygroscopic expansion coefficient of bulge is preferably from twice to twice that of the disk substrate, and the lower limit of the longitudinal elastic modulus is that if the center metal fitting is too flexible, the center metal fitting will not be able to be fixed to the disk substrate, so the disk Preferably, it is up to twice the size of the substrate.

The bulge may be separate from the disk substrate and integrated with the disk substrate by hot melt adhesion or ultrasonic welding, or as shown in Figure 3, it may be integrated with the disk substrate by injection molding or the like. It may be molded.

The thicker the thickness of the bulge, the thicker the effect (it is better to set it to 1, On or more, but if it is too thick, it may not be possible to attach it to the playback device, or it may deform due to its own weight). arise.

(Example) Example 1 As shown in Fig. 1, the flat ring-shaped center metal fitting 4 is made of polycarbonate, and has an inner diameter of φ15ue and an outer diameter of φ1.
30,1. 1.5mm thick, single or double sided Kfll
A disk substrate 1 having a recording sensitive material 2 for recording information.
are bonded together with an adhesive layer 3, and the disk substrate l
The outside of the inner circumference is made of polycarbonate, with an inner diameter of φ4.
11 + outer diameter φ32B.

Thickness 2.111! and a bulge 5 having a protrusion 6 for fitting into the center hole of the disk substrate 1 on the outside of the inner circumference for easy attachment to the disk substrate 1 is joined by ultrasonic welding. The center metal fitting 4 and the bulge 5 are bonded with hot melt adhesive.

The above embodiment was compared with the conventional one shown in FIG. 4, which has the same basic size. That is.

A disk substrate l made of polycarbonate, with an inner diameter of 1511 mm, an outer diameter of 130 mm, and a thickness of 1.5 mm, and has a recording material 2 for recording information on one or both sides.
A conventional optical information recording disk in which a center metal fitting 4 is attached to the outside of the inner circumference of the part bonded with an adhesive layer 3 and that of the above embodiment were heated at 60° C. and 90% RH (relative humidity). ) After saturated moisture absorption in the environment, the birefringence was measured. As a result, the birefringence of Example 1 was about 10 nm (double pass) smaller than that of the conventional optical information recording disk.

Embodiment 2 As shown in FIG. 2, a disk substrate l having a flat ring-shaped center fitting 4 and a recording material 2 made of polycarbonate for recording information on one or both sides.
are bonded together with an adhesive layer 3, and the disk substrate l
on the outside of the inner periphery of.

The material is polycarbonate, and the inner diameter is the same as that of the disk substrate 1, and the bulge 5 is bonded with an adhesive.The center metal fitting 4 and the bulge 5 are bonded with an adhesive.

Embodiment 3 As shown in FIG. 3, a disk substrate 1 has a flat ring-shaped center fitting 4 and a recording material 2 made of polycarbonate for recording information on one or both sides.
are bonded together with an adhesive layer 3, and the disk substrate 1
on the outside of the inner periphery of.

The center fitting 4 and the bulge 5 are joined together with an adhesive.

(Effect) By providing a bulge in the structure of the information recording disk where it is joined to the center metal fitting of the disk substrate, this bulge causes stress to be applied to the disk substrate.

Because it plays the role of a buffer layer that reduces strain, it has become possible to reduce birefringence compared to conventional materials.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of one embodiment of the present invention, Fig. 2 is a sectional view of another embodiment, Fig. 3 is a sectional view of yet another embodiment, and Fig. 4 is a conventional optical information recording circle. FIG. 3 is a cross-sectional view of the plate. DESCRIPTION OF SYMBOLS 1... Disk substrate, 2... Recording sensitive material, 3... Adhesive layer, 4... Center metal fitting, 5... Swelling, 6
... Protrusion patent applicant Asahi Kasei Corporation Figure 1 Figure 21! !

Claims (1)

[Claims] In the structure of an information recording disk that is magnetically clamped to an optical information recording/reproducing device, the center metal fitting and the part that joins the center metal fitting are made of a polymer material having a coefficient of linear expansion and linear hygroscopic expansion comparable to that of the disk substrate. An optical information recording disk comprising: a disk substrate having a bulge made of a polymeric material whose longitudinal elastic modulus at room temperature is less than the value of the material of the disk substrate;