JPH053664B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a method for manufacturing a double-sided optical disc that performs recording and reproduction using light.

<Prior Art> In recent years, optical storage devices have been actively developed as memory media with high density, large capacity, and high-speed access, especially so-called optical disks, which record information at high density by irradiating a disk-shaped memory medium with laser light. It is carried out in

The structure of these optical disks generally involves forming a recording medium on one side of an optically transparent substrate by some method, irradiating the recording medium with a laser beam through the substrate, and the interaction between the laser beam and the recording medium. Information is recorded by causing some kind of change in the state of the recording medium.

Such optical disks are generally manufactured by the following manufacturing method.

First, a disk-shaped substrate is manufactured from optically transparent glass, synthetic resin, or the like. Spiral or concentric grooves (guide tracks) are formed on the surface of this substrate for servo control of the optical spot.

Next, a recording medium having characteristics that allow optical recording and reproduction is formed on the surface of this substrate, that is, the surface on which the guide drag is formed, by a method such as vacuum evaporation or sputtering.

Next, in order to prevent this recording medium from deteriorating due to moisture and oxygen in the air, the two substrates are bonded together with the surfaces on which the recording medium is formed inside each other.

For bonding, an outer circumference reference method is used in which the outer circumference of one substrate is made to coincide with the outer circumference of the other substrate, or an inner circumference reference method is used in which the inner circumferences of center holes provided in the center of the substrates are made to coincide with each other.

Next, a part called a center hub is attached to the center of both sides of the bonded substrate to form an optical disk. This is because the density of the recording tracks of the optical disk is extremely high, and when the optical disk is rotated, it is necessary to reduce the wobbling of the tracks, and the optical disks are mounted with high precision concentricity with the guide track. That is, this center hub is attached to the other surface of the optical disk on which the guide track is not formed so that the center of the guide track and the rotation reference axis of the center hub coincide.

Next, a method for recording and reproducing information using the optical disk thus manufactured will be explained with reference to FIG.

Reference numeral 1 denotes a double-sided optical disk used for recording and reproduction, in which a substrate 2 and a substrate 3 are bonded together with the recording layer facing inward, and center hubs 6 and 5 are attached to the substrates 2 and 3, respectively. ing.
The rotation reference axis of the center hub 5 is installed so as to coincide with the center of the guide track of the base plate 3, and the rotation reference value of the center hub 6 is installed so as to coincide with the center of the guide track of the base plate 2. The optical disk 1 is mounted on a turntable 7 via a center hub 5, and is rotated by a motor 8 rotating the turntable 7. Recording and reproduction of information on the substrate 3 of the optical disk 1 is performed by a pickup 9.

Now, in this type of device, generally in order to prevent the optical disc 1 from coming off the turntable 7, as shown in FIG. is being forced upon. The structure of this presser 10 is as shown in FIG. 6a. That is, the conical portion at the tip of the vertically movable presser metal fitting 10a is inserted into the center hole 6a of the center hub 6 by the coil spring 10b, and presses the center hub 6 downward.
The presser metal fitting 10a can freely rotate by a bearing 10c, and rotates together with the rotation of the optical disk 1. Note that, as shown in FIG. 6b, a presser metal fitting 10'a having a spherical tip may be used.

However, when the apparatus shown in FIGS. 5 and 6 a and b is used, the following phenomenon may occur. That is, the center hub 6 of the board 2
and the center hub 5 of the board 3 are not concentric. This is because the substrates 2 and 3 are bonded together based on the outer periphery or the inner periphery.
Due to the manufacturing process, it is difficult to manufacture the guide tracks with high precision concentricity with the inner and outer peripheries of the substrates 2 and 3, and the concentricity usually has an error of about ±0.1 mm. Therefore, when the substrate 2 and the substrate 3 are bonded based on the outer circumference or the inner circumference, the concentricity of the guide tracks has an error of the same degree, and therefore the center hubs 5 and 6 attached concentrically with the guide tracks have an error of the same degree. There will also be an error of that degree in concentricity. As a result, the center hub 6 on which the optical disk 1 rotates wobbles, and at the same time, the presser metal fittings 10a and 10'a inserted into the center hole 6a of the center hub 6 also wobble, and as a result, the coil spring 10
b. Bearing 10c and its mounting part (not shown)
Vibrations are generated from the above, which not only causes noise, but also causes wear on the center hub 6 and shortens the lifespan of the turntable 7 and motor 8.

<Object of the Invention> The present invention aims to accurately control the concentricity of the guide track and center hub of the two substrates when manufacturing a so-called double-sided optical disk by gluing two disk-shaped substrates together. It is an object of the present invention to provide a method for manufacturing an optical disk that can be adjusted.

<Structure of the Invention> In order to achieve the above object, the present invention has a recording area on a part or the entire surface of one side, and a guide track for servo control and a guide track concentric with the guide track on the part or the entire surface. two optically transparent disc-shaped substrates having concentric tracks;
The method for manufacturing an optical disk is characterized in that the concentric tracks are fitted together so as to coincide with each other in the radial direction.

<Examples> The present invention will be described in detail below with reference to illustrated examples.

FIG. 1 is an overall view of a disk-shaped substrate 13. As shown in FIG. A recording medium is formed on the surface of the substrate 13 by vacuum deposition or the like to form a recording area 14, and signals are recorded and reproduced in this recording area 14. A guide track (not shown) is formed in the recording area 14 at the same time as the recording medium for servo control of the optical spot. Reference numeral 15 denotes a perfectly circular concentric determining track, which is fabricated outside the recording area 14. The concentricity determining track 15 is fabricated at the same time by the same method as the guide track provided in the recording area 14, and therefore has extremely good concentricity with the guide track. The number of concentric determination tracks 15 may be one or more.

An example of a method for bonding substrates on which guide tracks and concentric tracks 15 have been formed in this manner will be described with reference to FIG. FIG. 2 is a sectional view of the bonding device, showing two substrates 13 and 1.
7 is placed on the turntable 21 with the recording areas 14 and 18 facing each other and overlapped with a UV adhesive (ultraviolet curable adhesive) 16 interposed therebetween. At this time, the side surfaces of the lower substrate 13 are held down by set screws 19 and 20 and fixed to the turntable 21. The turntable 21 is designed to rotate around a rotating shaft 22, but at this time, the substrates 13, 17
Concentric tracks 15 and 2 formed in the faces of
4 can be observed using a microscope 34.

If the centers of the guide tracks of the substrates 13 and 17 are aligned, if you observe the concentric tracks 15 and 24 within the field of view of the microscope 34, you will see that when the turntable 21 is rotated, it will extend around the entire circumference. Concentric tracks 15 and 24 appear to overlap. If the centers of both guide tracks are shifted, when the turntable 21 is rotated, there will be a portion where the concentric tracks 15 and 24 appear to be shifted.

In such a case, micrometers 25, 25, .
and 24 will appear to overlap. The micrometers 25, 25, . The substrate 17 can be positioned at any desired position while rotating. In this way, the positioning is completed, and the concentric track 1 is moved around the circuit board 13, 17.
5 and 24 appear to overlap, the surface of the substrate 17 is irradiated with ultraviolet rays generated by the ultraviolet generator 26 using the light guide 27 to harden the layer of UV adhesive 16 and bond the substrate 13 and Glue 17.

By producing the substrates 13 and 17 having concentric tracks 15 and 24 in this manner, it is possible to produce a double-sided optical disk 12 in which the tracks have good concentricity. If the center hubs (not shown) are attached concentrically to the tracks on each side of the double-sided optical disk 12, the center hubs on both sides will also be attached concentrically, allowing recording and playback. As shown in Figure 5, even when the presser metal is pressed from the opposite direction to the turntable, the center hub swings less, so the presser metal swings less, and noise and vibration are less likely to occur. The effect of less is obtained.

As another example of application, a pickup 28 may be arranged on the opposite side of the turntable 7, as shown in FIG. In this case as well, if the double-sided optical disk 12 manufactured according to the present invention has good concentricity between tracks, the amount of whirling of the guide tracks will be reduced, so that good tracking can be achieved. , the degree of freedom in device design can be increased.

Further, as another example of application, as shown in FIG. 4, two pickups 32 and 33 are arranged on both sides of the double-sided optical disk 12. At this time as well, since the guide track swings around less, good tracking can be achieved.

Although an example has been given here in which the concentric tracks are formed outside the recording area, the present invention is not limited to this, and the concentric tracks may be formed inside the recording area.

<Effects of the Invention> As explained above, according to the present invention, since the guide track and the concentric concentric track are fitted together so as to coincide with each other in the radial direction, the concentricity of the guide track and center hub of both boards can be accurately determined. This prevents the center hub and presser metal from swinging around, reducing vibration and
It is possible to prevent the generation of noise, prevent wear of the center hub, and enable accurate tracking.

[Brief explanation of drawings]

FIG. 1 is an overall front view of a substrate according to an embodiment of the present invention, FIG. 2 is a sectional view of an optical disk and a bonding device according to the above embodiment, and FIGS. 3 and 4 are examples of applications of the above embodiment. FIG. 5 is a diagram showing the configuration of the recording/reproducing apparatus, and FIGS. 6a and 6b are diagrams showing the presser fittings, respectively. 12... Optical disk, 13, 17... Substrate, 14,
18... Recording area, 15, 24... Concentric determination track.

Claims (1)

[Claims] 1. Two optically transparent disc-shaped discs having a recording area on a part or the entire surface of one side, and having a guide track for servo control and a concentric determination track concentric with the guide track on the part or the entire surface. A method for manufacturing an optical disk, characterized in that the substrates are laminated together so that the concentric tracks coincide with each other in the radial direction.