JPH0444332B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical disk having an air sandwich structure used as a high-density information storage medium such as a video disk or a digital code disk.

[Conventional technology]

Currently, many optical disks with an air sandwich structure are used. This involves coating a substrate such as glass or plastic with a thin film of recording material, and in the case of double-sided writing, the two substrates are glued together via spacers at the inner and outer peripheries so that the recording films face each other. It has a structure that is Further, a disk is also known in which a spacer portion is provided on one or both sides of both substrates to form an integrated structure. Among these optical disks, for those with an outer diameter of about 130 mm, polycarbonate resin is usually used as the substrate and spacer material. Conventionally, optical disks with such an air sandwich structure have used spacers with an outer diameter of 40 mm or less at the inner circumference.

[Problem that the invention seeks to solve]

As for the dynamic characteristics of optical disks, there are limits to disk surface runout and surface runout acceleration due to the servo performance of the optical head, and although this has not been standardized,
For example, for an optical disk with an outer diameter of 130 mm, the surface runout is ±300μm (<500Hz), and the surface runout acceleration is 20m/
A value such as sec ² or less is set as a standard.

In the above optical disc, when it is put into an information recording/reproducing device (hereinafter referred to as a drive),
Usually 200 optical discs are driven by a spindle motor.
Rotate at a speed of ~3600rpm. In this case, depending on the type and quality of the drive, or the usage environment, if the optical disk is subjected to vibrations from the spindle motor, etc., and the resonance point of the optical disk matches the vibration frequency of the drive, resonance may occur. There is. Therefore, in some cases, the surface runout or surface runout acceleration exceeds standard values and exceeds the servo control range of the optical head, making it impossible to read or write information. In our study, we found that the resonance frequency is 800 to 1000Hz.
It has been found that such a problem is likely to occur when the outside diameter is within the range of 130 mm, and such a phenomenon is likely to occur in an optical disk that uses polycarbonate resin as the substrate material and has an outer diameter of 130 mm.

The purpose of the present invention is to provide a drive with an outer diameter made of highly reliable polycarbonate resin, which is highly suitable for drives that can perform stable and highly accurate information processing even if there is some vibration from a spindle motor, etc. on the drive side. Our goal is to provide 130mm optical discs.

[Means to solve the problem]

The present invention has an air sandwich structure in which two polycarbonate resin substrates are integrated through an inner circumferential spacer portion and an outer circumferential spacer portion, and has an outer diameter of approximately 130 mm.
The present invention provides an optical disc characterized in that the inner peripheral spacer portion has an outer diameter of 45 to 70 mm.

The present invention has found that by setting the outer diameter of the inner circumferential spacer portion of the optical disk having the air sand arch structure to a range of 45 to 70 mm, the above-mentioned problem can be solved and a more reliable optical disk can be manufactured. It is something that

The present invention will be explained in detail below.

The material of the substrate of the optical disk used in the present invention is polycarbonate resin, for example, aromatic polycarbonate (polycarbonate made from bisphenol A, etc.), aromatic polycarbonate as a main component, and styrene-N-alkylmaleimide. modified aromatic polycarbonate blended, blocked or grafted with a styrene polymer such as methyl methacrylate-styrene copolymer, etc., and those with good transparency and low birefringence are used.

As shown in FIGS. 1 and 2, the structure of the optical disk according to the present invention consists of two polycarbonate resin substrates 1 each having a recording medium layer 2 formed on one side of the inner and outer spacers. This is an air sandwich structure in which the spacer part 3 is integrated with the spacer part 3 on one side of one or both of the substrates and the spacer part 3 is placed on the inside.

Furthermore, the center of the disk has a so-called hub-attached disk structure, in which a hub 4 is provided as shown in FIG. 2 to fit a magnetic clamp in addition to a hole that fits a mechanical clamp. It's okay.

The outer circumference of the optical disk of the present invention is approximately 130 mm,
On the other hand, the inner circumference of a disc with a hub is 15 mm according to general standards, but it may be less than this.

The outer diameter of the inner peripheral spacer portion of the optical disk of the present invention is in the range of 45 to 70 mm, more preferably 50 to 60 mm. If it exceeds 70 mm, the recording area of the disk will be reduced, which is undesirable, while if it is less than 45 mm, the effects of the present invention will not be achieved.

In addition, although it is generally preferable that the inner diameter of the inner circumferential spacer is equal to or somewhat larger than the inner diameter of the substrate, it is not limited to this and can be determined as appropriate. Furthermore, the inner and outer diameters of the outer spacer are not particularly different from those of conventional optical disks. The material of these spacers is preferably the same as that of the substrate, but is not limited thereto. The thickness of the spacer is regulated by the thickness of the substrate and the total thickness of the optical disk, but is usually in the range of 0.2 to 1 mm.

The disk of the present invention can be manufactured by basically the same manufacturing method as that of a conventional optical disk having an air sandwich structure.

〔Effect of the invention〕

Since the optical disc of the present invention has excellent vibration damping performance, it is well suited to drive devices, and the optical disc can be highly reliable.

〔Example〕

EXAMPLES The present invention will be explained in more detail with reference to Examples and Comparative Examples below, but the present invention is not limited thereto.

Example 1 As shown in Fig. 1, two substrates made of aromatic polycarbonate made from bisphenol A were prepared, each having an outer diameter of 130 mm, an inner diameter of 15 mm, and a thickness of 1.2 mm, with the recording medium layer on the inside, and a thickness of 0.5 mm and an outer diameter of 50 mm. , inner diameter 15mm inner circumference spacer and thickness 0.5mm, outer diameter 130mm, inner circumference
An optical disk was fabricated by bonding them together with a photocurable adhesive using a 123 mm outer spacer. In order to investigate the vibration damping performance of this optical disk, a focus error measuring device whose system diagram is shown in FIG. 3 was used. That is, the disk drive 5 of the measuring device
A spindle motor 10 is built into the spindle motor 10, to which an optical disk 9 is attached and rotated at a rotational speed of 1800 rpm, while outputting an optical signal of constant intensity from the optical head 6 at a position with a radius of 55 mm from the optical disk. When the error signal was measured and displayed on the oscilloscope 8 and frequency analyzed using the FFT analyzer 7, the results shown in Figure 4 were obtained, and the resonance frequency was 1360Hz.
It was confirmed that the frequency was well above 2640Hz and 1000Hz.

We also measured the resonance point and its size of this optical disk using Gen Rad's GR-2506 vibration analysis system.
Figure 5 shows the results of measuring the transfer function (inertance) between two points in the radial direction (near the inner circumference and near the outer circumference) using SDRC's modal analysis software M-PLUS. The same results as above were obtained with this measurement method. When this optical disc was driven at a rotation speed of 1800 rpm, recording and playback could be performed well over the entire surface.

Comparative example 1 As a spacer for the inner circumference, outer diameter is 35 mm and inner diameter is 15 mm.
An optical disc was produced in the same manner as in Example 1, except that the same material was used.

This optical disk was driven at a rotation speed of 1800 rpm, and the focus error signal was measured and frequency analyzed in the same manner as in Example 1. The results shown in Figure 6 were obtained, and a large resonance peak was confirmed at 920 Hz. It was done. Furthermore, when the transfer function was measured, the results shown in FIG. 7 were obtained.

In addition, when this optical disk was driven at a rotation speed of 1800 rpm for recording and playback, there were parts near the inner and outer peripheries where the focus servo was not activated and recording could not be performed.

[Brief explanation of drawings]

1 and 2 are schematic cross-sectional views of an example of the optical disk of the present invention. FIG. 3 is a block diagram of an apparatus for frequency analysis of the vibration characteristics of an optical disk.
FIGS. 4 and 6 are diagrams showing vibration characteristics due to focus error signals when optical discs in Examples and Comparative Examples are driven by a disc drive,
The vertical axis represents the output value of the FFT analyzer, and the horizontal axis represents the frequency. 5 and 7 are diagrams showing the vibration analysis results of the resonance of the optical disk in the example and the comparative example, respectively, where the vertical axis represents the transfer function and the horizontal axis represents the frequency. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Information recording thin film, 3... Spacer part, 4... Hub for magnetic clamp, 9
...Optical disk.

Claims (1)

[Claims] 1 In an optical disk with an outer diameter of approximately 130 mm, which has an air sandwich structure in which two polycarbonate resin substrates are integrated through an inner circumferential spacer portion and an outer circumferential spacer portion, the outer diameter of the inner circumferential spacer portion is 45 mm.
An optical disc characterized by ~70mm.