JPS61214241A - Optical disc - Google Patents

Abstract

PURPOSE:To align an inside peripheral spacer and a disc substrate easily and accurately by providing light and dark gratings in center junction parts of the inside peripheral spacer and the disc substrate and utilizing the moire which is generated when they are put one over the other. CONSTITUTION:A light and dark drating 14 is formed on concentric circles having a center hole 7 as the center on the outside peripheral part of an inside peripheral spacer 1, and a light and dark grating 15 having the same diameter as the light and dark grating 14 is formed near the center through hole of a transparent disc substrate 4. When two light and dark gratings 14 and 15 are put on over the other in case of disc assembling, minute inclination angles of the spacer 1 and the disc substrate 4 are grasped as a macroscopical variance of moire interference fringes. Thus, these inter-ference fringes are used to align the spacer 1 and the substrate 4 easily and accurately with the naked eyes.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical disc on which information is recorded or from which recorded information is reproduced, and particularly relates to an inner circumference flat disc.

[Conventional technology]

FIG. 7 is a sectional view showing an example of a conventional double-sided recording type optical disc. As shown in the figure, two disks 3 are fixed so as to face each other with an inner circumferential spacer 1 and an outer circumferential spacer 2 interposed therebetween. This disk 3 is composed of a transparent disk substrate 4 and a recording layer 5 provided on one side of the substrate.
are formed, and the two disks 3 are arranged so that the recording layers 5 face each other.

On the other hand, the inner spacer 1 is made of a wear-resistant material such as metal, and a spindle (not shown) of a drive device is inserted into the center of the inner spacer 1 to position the optical disc within the device. A center hole 7 is provided for this purpose. 8 in the diagram is two disks 3
An air gap is formed between the two.

Figures 8 to 10 show the manufacture of this optical disc.
$Jj】-1, +--+@uotsrq-'Fly/F
%Ifn+w1-t-+,-? The O1-dtMi1+1 transmission method will be explained.

First, as shown in FIG. 8, an uncured ultraviolet curing resin 11 having fluidity is dropped onto a stamper 10 having a large number of concentric grooves 9 corresponding to the pre-groups 6 on its surface. Then, the disk substrate 4 is pressed onto the resin 11 in a slightly curved state so that the center portion thereof is downward, and
Gradually lower the peripheral portion onto the stamper 10. When the disk substrate 4 is pressed onto the stamper 10 in this way,
Between the two 4.10, the ultraviolet curing resin 11 does not contain any air bubbles (it is pushed outward in the outer circumferential direction and is also filled into each of the grooves 9).

Thereafter, as shown by the arrow in FIG. 9, ultraviolet rays 12 are irradiated from above the disk substrate 4 to harden the ultraviolet curing resin 11. Next, when the disk substrate 4 is peeled off from the stamper 10, the cured resin film is also separated from the stamper 10 together with the disk substrate 4, and as a result, the pregroup 6
The recording layer 5 is formed with the following. In this way, the replica process is completed. There is also a method of injection molding molten resin into a mold to form the disk substrate 4 and the recording layer 5 at the same time.

Next, a recording film is formed on the recording layer 5 by vapor deposition or the like. The material of this recording film is an optically recordable and reproducible substance such as T e s and its alloy, TeOx, an organic monolayer film, G
Examples include dTbFe.

Next, the center position of the disk substrate 4 is optically determined using the pre-group 6, and based on this, a central through hole 13 is provided in the disk substrate 4 as shown in FIG. By adhering and combining the outer circumferential spacers 2, an optical disk as shown in FIG. 7 is produced.

[Problem that the invention seeks to solve]

However, in this conventional technique, it is difficult to center the disc substrate 4 and the inner circumferential spacer 1 when they are assembled, and there are problems in terms of reliability and poor productivity.

That is, since the disk substrate 4 needs to be transparent for writing and reading information, polycarbonate resin, epoxy resin, glass, or the like is used, for example. On the other hand, since the optical disk is repeatedly attached to and detached from the device, the inner circumferential spacer l is required to have wear resistance, and is generally made of metal. In this way, the thermal expansion coefficients of the disk substrate 4 made of synthetic resin or glass and the metal inner spacer 1 are significantly different on the order of 10 times, and as a result, the disk substrate 4 is deformed due to the thermal expansion of the inner circumference spacer 1. A slight clearance is provided between the disk substrate 4, the inner circumferential spacer 1, and the fitting portion in order to prevent the disk substrate 4 from being damaged. This clearance is also necessary to facilitate fitting of the disk substrate 4 and the inner spacer 1. If there is such a clearance, relative positional deviation, that is, center deviation, tends to occur when the disk substrate 4 and the inner spacer 1 are combined.

When the disk substrate 4 and the inner circumferential spacer 1 are bonded together with the center misaligned in this way, the disk substrate 4 and the inner circumferential spacer 1 are attached to a recording/reproducing device, and the writing or reading spacer 1 is fitted onto the spindle, thereby causing damage inside the device. Since the positioning is performed at , the pre-group 6 on the recording layer 5 rotates in an eccentric state with respect to the rotation center of the optical disc, making accurate tracking impossible and causing problems in terms of authenticity. Particularly in recent years, with the trend toward higher density recording, the pitch of the pregroups 6 has become extremely small, about 1.6 μm, so that the effects of track deviation as described above directly appear on the characteristics.

In order to prevent this from happening, when bonding the disk substrate 4 and the inner circumferential spacer 1, each step is performed while observing the positional relationship between the two using a microscope, which reduces productivity. It had some drawbacks such as very poor performance.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical disc that eliminates the drawbacks of the prior art described above and allows easy and accurate alignment of the inner circumferential spacer and the disc substrate.

[Means for solving problems]

When two sets of bright and dark grids are superimposed, bright and dark stripes appear that are much larger than the original grid spacing. This is called a moiré interference fringe, and if the lattice spacing is d, the inclination of the two sets of bright and dark gratings is θ, and the interval between the moiré interference fringes is D, then D”d/sin θ−−−−−−−−− --------(1
It becomes 1. From this equation (+1), it can be seen that as θ becomes smaller, D becomes larger, and therefore, the slight inclination of the two sets of bright and dark gratings can be macroscopically known by the moiré interference fringes. The same thing can be said when the bright and dark stripes are concentric arcs.

The present invention utilizes such moiré interference fringes to achieve the above object, and for this purpose, light and dark gratings are provided at the joint portions of the inner spacer and the disk substrate, and when these light and dark gratings are superimposed, the The feature is that the eccentricity between the inner spacer and the disk substrate is detected using moiré interference fringes.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of an optical disc according to an embodiment of the present invention;
FIG. 2 is a plan view of an inner circumferential spacer provided on the optical disk, FIG. 3 is a plan view of a disk substrate provided on the optical disk, and FIG. 4 is an enlarged sectional view of the joint portion of these inner circumferential spacers and the disk substrate. FIG. 5 is an explanatory diagram of the light-dark grid, 14 and 15 are light-dark grids, 16 is an adhesive, and parts corresponding to those in FIG. 7 are given the same reference numerals.

In FIG. 1, the optical disc is composed of an inner spacer 11, an outer spacer 2, and a disc 3, which are manufactured by basically the same process as the prior art described above. That is, two disks 3 each consisting of a transparent disk substrate 4 and a recording layer 5 and a recording film provided on one side thereof are fixed so as to face each other with an inner circumferential spacer 1 and an outer circumferential spacer 2 in between. .

As shown in FIG. 2, light and dark gratings 14 are formed at a plurality of locations (four locations in the embodiment) on the outer periphery flange la of the inner periphery spacer 1 on concentric circles with the center hole 7 as the center of rotation. On the other hand, the central through hole 13 of the disk substrate 4
As shown in Figure 3, there is a light and dark grid around the entire circumference near
5 is formed. As shown in Fig. 5, these light and dark grids 14 and 15 have light and dark stripes that repeat alternately at minute intervals, and these can be created by printing materials with different reflectances or by etching fine irregularities. is formed. Further, one of the bright and dark gratings 14 is formed in two concentric circles with the center hole 7 of the inner spacer 1 as the center 0, and the other bright and dark grating 15 is formed in a concentric circle with the center O coincident with the concentric pre-group 6 of the disk substrate 4. It is formed in the shape of

Inner circumferential spacer 1 and outer circumferential spacer 2 configured in this way
In order to manufacture an optical disk by combining the discs 3 and 3, the inner circumferential spacer l and the outer circumferential spacer 2 are integrated with both disk substrates 4 using an adhesive, as in the prior art described above. At this time, since bright and dark gratings 14 and 15 are formed in the overlapping parts of the inner spacer 1 and the disk substrate 4, the inner spacer 1
The center alignment between the disk substrate 4 and the disk substrate 4 can be easily performed. Specifically, as the inclination angle of both light and dark gratings 14 and 15 approaches zero, the interval between moiré interference fringes increases, so if the interval between moire interference fringes is adjusted to be as large as possible, The relative positional shift of the substrate 4 is reduced.

The inner circumferential spacer l and the disk substrate 4, which have been centered in this manner, are adhesively fixed using an adhesive 16, as shown in the enlarged cross-sectional view of FIG. Here, if the adhesive 16 is a transparent adhesive, even if the adhesive 16 is interposed between the light-dark grid 14 of the inner spacer 1 and the light-dark grid 15 of the disk substrate 4 as shown in FIG. Moiré interference fringes can be seen through the transparent disk substrate 4 and transparent adhesive 16. Of course, both light and dark grids 14.15
If the adhesive is applied partially so that the adhesive is not interposed in the overlapping portion of Improved adhesive strength with adhesive 16
This has the effect of simplifying the application process.

In addition, in the above embodiment, moiré interference fringes are generated by overlapping the bright and dark gratings 14 formed at a plurality of locations on the inner spacer 1 and the bright and dark gratings 15 formed around the entire circumference of the disk substrate 4. As described above, these light and dark gratings 14 and 15 may be formed partially or may be formed on the entire circumference.In short, when the inner spacer 1 and the disk substrate 4 are joined It is sufficient if there is an overlapping part in 14 and 15.

Furthermore, in the above embodiment, the light/dark grating 15 was formed separately from the pre-group 6 of the recording layer 5 on the inner peripheral portion of the disk substrate 4, but when forming the pre-group 6, this was explained. The pre-groups on the inner circumference are formed by extending to the inner circumference of the disk substrate 4, and the light-dark grid 1
It is also possible to use it as 5. In this case, since the step of separately forming the bright and dark grating 15 can be omitted, the manufacturing process of the disk substrate 4 can be simplified, and the bright and dark grating 15 can be omitted.
and the center of the pre-group are formed exactly the same, so
Centering can be done more accurately.

〔Effect of the invention〕

As explained above, according to the present invention, the macroscopic moiré interference fringes that appear when the inner circumferential spacer and the disk substrate are overlapped make it possible to easily and accurately align them with the naked eye. It is possible to provide an optical disc that eliminates the drawbacks of the prior art described above.

[Brief explanation of drawings]

1 to 5 relate to one embodiment of the present invention, in which FIG. 1 is a cross-sectional view of an optical disk, FIG. 2 is a plan view of an inner spacer, FIG. 3 is a plan view of a disk substrate, and FIG. is an enlarged cross-sectional view of the joint between the inner circumferential spacer and the disk substrate, FIG. 5 is an explanatory diagram of the bright-dark grating, FIG. 6 is an explanatory diagram showing the principle of moiré interference fringes, and FIG. 7 is a cross-sectional diagram of a conventional optical disc. FIGS. 8, 9, and 10 are cross-sectional views illustrating the manufacturing process of the optical disc. 1... Inner spacer, 3... Disc, 4...
... Disc substrate, 5... Recording layer, 6... Pre-group, 7... Center hole, 13... Center through hole, 14.15... Light/dark grating, 16... ···glue. Fig. 1 1: Inner layer spacer 4: Inner spacer 5: Recording layer 7: Center hole Fig. 2 14.15: Diffraction filter Fig. 3 Fig. 4 Fig. 6 Fig. 7

Claims (2)

[Claims] (1) In an optical disc formed by integrating an inner circumferential spacer with a center hole and a transparent disk substrate provided with a recording surface with an adhesive, the bonding surfaces of the inner circumferential spacer and the disk substrate, respectively. The inner peripheral spacer is formed with a light-dark grating centered around the rotation center, and the disc substrate is formed with a light-dark grating concentric with the pre-group, and by overlapping these light-dark gratings, moiré interference fringes appear. optical disc. (2) The optical disc according to claim (1), wherein the adhesive is a transparent adhesive.