JPS58137146A - Optical recording and reproducing disc - Google Patents

Abstract

PURPOSE:To eliminate the uneven film thickness in the outside circumferential part of an optical recording and reproducing disc and the defective recording and reproducing near the outside circumference and to improve commodity value without generating cracking of the film, etc., in the stage of applying a hard film treatment on said disc, by chamfering the outside circumferential end part of the disc. CONSTITUTION:In the stage of forming cured protective films 3 on both surfaces of an optical recording and reproducing disc wherein an acrylic plate 1 or the like is used, and optical recording and reproducing layers 2 are provided thereon and further another acrylic plates 7, etc. are superposed thereon by spin-coating a mixture contg. crosslinkable monomers such as dipentaerythtol hexaacrylate, epoxy acrylate, trimethylolpropane acrylate or the like and curing the coating, the outside circumferential part A of such disc is chamfered at 5-60 deg. angle alpha so that the width l in the part where the film thickness of the end part increases is made <=1mm.. Said part is chamfered to a semicircular shape wherein the radius R is 1/2-4/5 the thickness (t) of the disc and the films 3 are formed. The uneven film thicknesses are thus eliminated in the outside circumferential part.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical recording and reproducing disc, and in particular provides a disc in which a hard coating is formed on the disc surface and the coating is uniform at the outer peripheral edge.

Conventionally, optical recording disks have been produced by forming a recording layer that can be optically recorded and reproduced on a circular plastic plate, and then layering other plastic plates as necessary to protect the recording layer. It was common to do so. The problem with this conventional method is that the plastic plate used to protect the recording layer also has marks on its surface due to contact with dust or foreign matter during manufacturing. This has also become a problem for optical recording and reproducing discs that use laser light. That is,
The problem was that this appeared as noise in recorded and reproduced signals. In response, the inventors coated and cured the coating compositions disclosed in JP-A-56-22364 and JP-A-66-135626 on optical recording discs manufactured by conventional methods, thereby forming a transparent hard coating. It has been found that by forming a , a remarkable effect of preventing chafing appears. However, the viscosity of the coating material after spin drying becomes high, and the surface tension also increases, so that the difference in film thickness at the edge of the disc is large, sometimes reaching 100 μm or more. This not only results in a small film thickness t at the edge of the disc, which impairs its aesthetic appearance, but also causes problems such as cracks in the film and abnormal refraction of light during recording and reproduction near the outer periphery.

The present invention solves the above-mentioned drawbacks and provides an optical recording disk in which the film thickness t5 at the outer peripheral edge of the disk after spinner coating and curing is eliminated.

One embodiment will be described below with reference to FIGS. 1 to 3.

The optical recording/reproducing disk substrate used in the present invention consists of three main layers as shown in FIG.

That is, a recording layer 2 necessary for optical recording and reproduction is placed between two acrylic plates 1 each having a diameter of 210 mm and having a hole in the center.
is formed. More specifically, this recording layer 2 utilizes the principle of causing a phase transition by irradiation with laser light and changing the reflectance of the layer.

2 and 3 are partially enlarged cross-sectional views of section A in FIG. 1, showing a state in which the hardened coating 3 is applied to the disk shown in FIG. 1. The corners of the outer edge of the disk in Figure 2 are chamfered,
Figure 3 shows each circular chamfer.

The coating device and method used in the present invention are the method described in Japanese Patent Application No. 142062/1987 previously filed by the present inventors, namely, dip rotation speed 5 Orpm, spinner rotation speed 200O.
The coating was applied under constant conditions of 75 rpm rotation speed during ultraviolet irradiation.

The material used for coating was 40 parts by weight of dipentaerythritol hexaacrylate.

A composition composed of 10 parts by weight of epoxy acrylate, 60 parts by weight of trimethylolpropane triacrylate, and 10 parts by weight of hydroethyl methacrylate, in which 3 parts by weight of benzoin isobutyl ether was added to 100 parts by weight of the above composition, was mixed with isopropyl alcohol and methyl It is a mixed solvent with isobutyl ketone and has a viscosity of 16 cps (26°C).

Under the above conditions, the results shown in Tables 1 and 2 below were obtained using a chamfer angle of 62 and a circular chamfer radius of H.

Table 1 Table 2 (Substrate disk φ210. Acrylic plate) If the chamfer angle α is larger than 600, the width l of the thick part of the film will be large, and if no chamfering is performed,
Some cases where l exceeds 1 crn have appeared.

Therefore, the chamfer angle α is preferably 60 degrees or less, more preferably 6 degrees to 46 degrees. Although 6 degrees cannot be generalized due to the relationship with the recording area, it should be a sufficient angle to reach the recording layer, and the plane chamfered portion in FIG. 2 may be circular.

Figure 3 shows the edge of the disk with a semicircular chamfer,
The radius R is 1/2 to 4/6 times the disk thickness, preferably 1/2 to 315 times.

As described above, according to the present invention, when applying a hard coating treatment to an optical recording/reproducing disk, chamfering or circular chamfering on the outer circumferential edge of the disk eliminates the film thickness t' on the outer circumference, and as a result, the outer circumference This has the effect of not only eliminating near recording and reproduction defects, but also increasing the product value.

[Brief explanation of the drawing]

FIG. 1 shows optical recording in one embodiment of the present invention. The side view of the reproduced disk, FIGS. 2 and 3 are partial cross-sectional views of the outer peripheral end of one embodiment and another embodiment of the same disk, respectively. 1... Acrylic board, 3... Cured film. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure IIa

Claims (3)

[Claims] (1) A circular plastic plate, a recording layer provided on the plastic plate and capable of optical recording/reproduction, and a circular plastic plate provided on the recording layer that protects the recording layer. An optical recording/reproducing disk, which is made of a plastic plate, has chamfers or circular chamfers formed on the corners of the outer peripheral edge, and is further provided with a hardened coating. (2) The optical recording/reproducing disk according to claim 1, wherein the corner of the outer peripheral end of the disk is chamfered at an angle of 6 degrees to 60 degrees with respect to the plane of the disk. (3) The radius of the circular chamfer at the corner of the outer peripheral end of the disk is equal to the thickness of the disk! A~415 Optical recording/reproducing disk 0 according to claim 1