JPH0440682A - Optical information recording disk - Google Patents

Abstract

PURPOSE:To suppress double refraction to be generated by stress due to screwing by superposing three disks having respectively different diameters and arranging a contact face between a hub member and a disk base in the vicinity of a center hole. CONSTITUTION:The hub members 5, 5 are constituted of cutting the insides of respective flange parts 7 so as to previously leaving proper ring-like step parts 9 on respective boss parts 6 and forming slight gaps 10 between the outsides of respective disk bases 1 and the insides of the flange parts 7. Namely, three disks having respectively different radiuses are concentrically stacked in the descending order and a concentrical hole is formed on the center part. Thus, a pair of hub members 5 are constituted of cutting off the size of the fixing face to be attached to a turn table, i.e. a part exposed to the outsides of the disk bases 1 so as to leave a part close to the center hole as much as possible and forming gaps between the insides of the flange parts 7 and outsides of the disk bases 1. Consequently, the generation of stress due to the clamping force of a screw is deviated from the recording area of each disk base and the influence of double refraction due to the stress can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to optical information recording discs such as write-once optical discs and rewritable optical discs.

[Conventional technology]

As shown in FIG. 2, an optical information recording disk consists of two transparent plastic disk substrates 1 each having a recording layer 2' made of an organic dye film, a low melting point metal film, or a magneto-optical recording film on the inner surface. ', 1' are pasted together in a sandwich shape via an inner circumferential spacer 3' and an outer circumferential spacer 4', and hub members 5', 5' made of a magnetic material are inserted into the center holes of these disk substrates 1', 1'. It is formed by sticking together,
These hub members 5', 5' are mounted on a magnetic chuck of a turntable and used for rotation.

Incidentally, ultrasonic welding, UV adhesion, solvent adhesion, etc. were once used as means for fixing the hub member to the disc substrate, but these did not have a permanent adhesive force and were difficult to attach and remove from the turntable. However, there were disadvantages such as the hub member falling off due to shocks such as sudden changes in rotational speed.

For this reason, in recent years, a pair of upper and lower hub members 5' has been used as the fixing means, instead of using adhesive as shown in FIG.

5', a screw 8' is screwed in surrounding the center hole, and the screw 8' is fixed by the tightening force of the screw 8'.

[Problem to be solved by the invention]

However, although fixing with screws is highly reliable as a means of fixing, in the case of general disk substrates made of plastic plates with a large photoelastic constant such as polycarbonate, the stress caused by tightening the screws , there is a disadvantage that the disk substrate is partially deformed and large birefringence occurs (FIG. 4). This birefringence is large at the inner periphery of the substrate, and is almost unaffected at the middle and outer periphery, but at the innermost periphery of the recording area, it is affected by a reduction in signal amplitude, a reduction in C/N, etc. It's coming.

Originally, grooves are provided on the surface of the recording layer to guide the light beam spot in order to read, add to, or rewrite information.By aligning the light beam spot along this guide groove, information can be recorded, reproduced, and rewritten. Since the guide grooves are formed concentrically or spirally at minute intervals, such as 1.6 mm, the slight deformation of the disk substrate caused by the above-mentioned But it will have a big impact.

The present invention has been made in order to eliminate such drawbacks of the conventional technology, and aims to provide a highly reliable optical information recording disk by minimizing the influence of birefringence caused by stress caused by screw fastening. purpose.

[Means to solve the problem]

In order to achieve the above object, according to the present invention, two disk substrates each having a recording layer formed on one side are bonded together with or without a spacer so that the recording layer is on the inside, and On the top and bottom outer surfaces of the disk board,
A pair of hub members made of an integral magnetic material and each having a flange portion connected to a boss portion are inserted into the center hole of a disk substrate, and the boss portions are fastened together by screwing them together with screws. In the optical information recording disk configured, the inner surface of the flange portion of these hub members that overlaps the outer surface of the disk substrate is cut leaving a moderate ring-shaped step at the base of the pre-boss portion, and a slight gap is formed between the inner surface of the flange portion and the outer surface of the disk substrate. An optical information recording disc characterized by having a gap therebetween is provided.

[Effect]

In this invention, the size of the mounting surface to be attached to the turntable of the pair of hub members, that is, the portion exposed on the outer surface of the disk substrate, is replaced by the same size, external shape, dimensions, etc. as before. Then, cut the back side of the above part, that is, the part that is in contact with the outer surface of the disk substrate, leaving a part as close to the center hole as possible, and leave a gap between it and the outer surface of the disk substrate to reduce the tightening force of the screw. The generation of stress on the disk is kept as far away from the recording area of the disk substrate as possible, and the effects of birefringence caused by stress are prevented.
It becomes highly reliable.

〔Example〕

An embodiment of the present invention will be described with reference to FIG. 1. In the figure, 1 is a disk substrate made of a transparent plastic disc, 2 is a recording layer formed on the inner surface thereof, and 3 is an inner periphery. A spacer, 4 is an outer periphery spacer, 5, 5 is a hub member made of stainless steel (SUS43), which is a magnetic material.
0) and has a flange part 7 connected to the boss part 6,
This boss portion 6 is inserted into the center hole of the disk substrates 1, 1, and the screws 8 are inserted and tightened across the respective flanges 7, 7, and the disk substrates 1, 1 are sandwiched from above and below and fixed together. There is. The outer surfaces of the flange portions of these hub members 5, 5 are provided with engagement holes (not shown) for position fixing, as in the prior art.

Up to this point, it is the same as the conventional device shown in FIG. It has a structure in which the cut is made leaving a portion 9 and a slight gap 10 is interposed between it and the outer surface of the disk substrate 1. That is, each of the hub members 5, 5 has a shape in which three disks having different radii are stacked concentrically in descending order of size, and each has a concentric hole in the center. Then, the part corresponding to the smallest disc fits into the center hole of the disc substrates 1, 1,
The surface corresponding to the second largest disk is the disk substrate 1.1
is in contact with the surface of

The hub members 5, 5' are provided with through holes for screwing and grooves to prevent burrs, and are chamfered.

In the above configuration, the pair of upper and lower hub members 5, 5 are made in the shape of three disks having different diameters, which at first glance appear to be stacked, consisting of a boss portion 6, an annular step portion 9, and a flange portion 7, and the disk substrate 1
Since the pressure contact with the outer surface is made as a local contact only by the annular step 9, the tightening force of the screw 8 is limited to the periphery of the center hole outside the recording area of the disk substrate 1 via the annular step 9, and furthermore, Even if there is a slight imbalance in the tightening of the screws 8 and the pair of upper and lower hub members 5, 5 are tilted relative to each other,
The inclination of the flange portion 7 having a predetermined diameter, which is the mounting surface for the turntable, is absorbed by the gap 1o, and there is no risk of deformation of the disk substrate 1°1.

As a result, the birefringence at the innermost circumference of the recording area becomes small as shown in FIG. 3, and the drop in signal amplitude is extremely reduced.

〔Effect of the invention〕

According to the present invention, the hub member has a shape in which three discs with different diameters are stacked, each consisting of a boss part, an annular step part, and a flange part, so that the contact surface between the hub member and the disc substrate is as close to the center hole as possible. Because it is limited to.

Birefringence that occurs due to stress caused by screwing is suppressed, and the drop in signal amplitude can be minimized.

Therefore, an optical information recording disc with improved reliability can be provided.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of an optical information recording disk according to an embodiment of the present invention, FIG. 2 is a vertical cross-sectional view of a conventional optical information recording disk, and FIG. 3 is a hub member ( Figure 4 is a graph showing the change in birefringence that occurs in the disk substrate due to the tightening torque at a radius of 30 cm.
3 is a graph showing a change in birefringence caused in a disk substrate by a tightening torque with a radius of 30 mm. DESCRIPTION OF SYMBOLS 1... Disk substrate 2... Recording layer 5... Hub member 7... Flange portion 9... Annular step portion 6... Boss portion 8... Screw 10... Gap Patent applicant Rico Co., Ltd.

Claims (1)

[Claims] (1) Two disk substrates with a recording layer formed on one side are bonded together with or without a spacer so that the recording layer is on the inside, and an integrated magnetic A pair of hub members made of a material and having a flange portion connected to a boss portion are each inserted into a center hole of a disk substrate, and these boss portions are fastened together by screws. In optical information recording disks, the inner surface of the flange portion of these hub members that overlaps the outer surface of the disk substrate is cut leaving a moderate ring-shaped step at the base of the pre-boss portion, and a slight gap is interposed between it and the outer surface of the disk substrate. An optical information recording disc characterized by: