JP2721655B2 - Composite optical disk structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite optical disk made by laminating two single-sided disks such as an optical video disk.

[0002]

2. Description of the Related Art There is an optical disk for reading recorded information using a laser beam or the like, in which two disk substrates are bonded to each other. Examples thereof include a laser disk and a DVD. As a representative thereof, a conventional laser disk will be described below.

First, in a conventional method for manufacturing a laser disk, a mold (referred to as a stamper) in which pits serving as recording information are formed in advance is attached to a resin molding machine such as an injection molding machine. A transparent plastic disk (single-sided disk), which is a transparent plastic disk on which pits have been transferred, is formed by injection molding or pressure molding of a transparent plastic resin such as acrylic (base molding step). In the actual plastic disk (single-sided disk) produced in this base molding process, the part to be hit by the stamper clamp for fixing the stamper to the resin molding machine has a concave processing groove (hereinafter, referred to as
(Referred to as a stamper clamp groove) and remains in a ring shape.

Next, a metal such as aluminum is adhered to the pit surface of the disk by sputtering or vacuum evaporation to form a reflective film (reflective film forming step). Next, a hot-melt type protective film is applied to the surface of the reflective film by a roll coater or the like, and irradiated with ultraviolet rays to form a protective film (5 to 10 μm) for preventing scratches and corrosion (protective film). Coating process).

As described above, A to be bonded
After separately forming a pair of single-sided disks of side B and side B, a thermoplastic adhesive called hot melt is applied to the bonding surface of each single-sided disk using a roll coater or the like (coating thickness: 15 to 30 μm / double-sided) ) (Adhesive application step).

Then, a pair of single-sided disks to which the adhesive has been applied are bonded together by a method as shown in FIG. 7 (bonding step). That is, the bonding surfaces of the pair of single-sided disks 10a and 10b to which the adhesive has been applied are abutted with each other and placed on a lower pressing table 51 having a flat pressing surface. And a pair of single-sided disks 10a and 10b are pressed and pressed on the flat press surface to bond them to one laser disk.

Recently, a small-sized DVD (diameter 12c)
m, a double-sided recording type digital video disk capable of high-density recording with a single-sided disk substrate thickness of 0.6 mm) is being developed. This DVD is manufactured in the same manner as described above except that in the protective film applying step, an ultraviolet curable resin is applied to the surface of the reflective film using a spinner or the like.

[0008] Since such a composite optical disk is a high-density recording disk, it is required to minimize warpage and deformation and to make it as flat as possible. That is, a highly accurate bonding technique is required in the bonding process as well as in making the disk substrate itself flat before bonding.

As shown in the plan view of the single-sided disk shown in FIG. 4A and the cross-sectional view of the single-sided disk after the adhesive application step shown in FIG. 1a, a stamper clamp groove 2, a disc clamp area 2c between the center hole 1a and the stamper clamp groove 2, and a data recording area 3 which is an information recording area around the stamper clamp groove 2.
And a non-signal area 5 around the data recording area 3.

[0010] A protective film 6 is attached on the reflective film 4 in order to maintain the reliability (lifetime) of the reflective film 4. That is, the protective film 6 is attached to prevent the oxide film from forming on the surface of the reflective film 4 and losing gloss. In order to attach the protective film 6, a method of coating an ultraviolet curable resin or the like by a spin coating method is used.

However, in order to apply the protective film 6 to the entire recording surface of the plastic disk 1, if the protective film 6 is to be applied around the center hole 1a of the disk having a large concave portion called the stamper clamp groove 2, as shown in FIG. 5 (a), air 6a accumulates in the protective film 6 at the recessed portion, or the resin 6 unnecessarily stays 6 as shown in FIG. 5 (b).
The coating unevenness occurs due to b.

Therefore, as shown in FIG. 5 (c), in order to avoid coating unevenness due to the stamper clamp groove 2, a few millimeters before the data recording area 3 without large irregularities starts, that is, the data recording area 3 The protective film 6 was applied between the stamper clamp groove 2 and the outer periphery of the disk.

In such a coating method, the portion without the protective film 6, that is, the inner portion between the data recording area 3 and the stamper clamp groove 2 and the portion with the protective film 6 on the outer portion are formed around the center hole 1a. And the thickness t of the protective film 6
The height difference is caused as a step of several micrometers to tens of micrometers.

In this state, when the adhesive 7 is applied to the disk by means of a roll coater or the like, the thickness of the coating film of the adhesive 7 is uniformly applied over the entire surface of the disk.
The adhesive 7 having a uniform thickness is placed on the step d, and the bonding is performed in a state where the step d by the protective film 6 remains.

[0015]

However, in the above-mentioned conventional composite optical disc, a gap S is formed in a portion where the steps are adhered while the step d due to the protective film 6 remains, as shown in FIG. As the bonding accuracy is reduced,
As shown in (b), it is difficult to stably produce a high-precision bonded disc with little warpage or deformation, as one disk base is deformed or deformed so as to follow the other disk base. There was a problem.

Generally, in the case of a small bonded disc having a small diameter, most of the flat disc portion from the center hole 1a of the disc to the information recording start area is used as a clamp zone of the player. The flat portion functions as a reference surface for the optical system when the disc is placed on the turntable of the player and held by the clamper.

In particular, a small-sized, high-density recording disk such as a DVD uses an optical system having a large numerical aperture (NA), and therefore has a small depth of focus. The signal will be significantly degraded. There is a problem that the load on the pickup servo for preventing this deterioration by the pickup servo becomes too large. Therefore, in particular, since the warpage or deformation of the disk in the clamp zone directly affects the reference surface for the optical system, it is desired to flatten with high precision.

Accordingly, an object of the present invention is to provide a composite optical disc structure which is less warped or deformed and is suitable for high-density recording.

[0019]

In order to achieve the above object, in the composite optical disk structure of the present invention, a reflective film is provided on an information recording area formed on one surface of an optical disk substrate having a center hole. In a composite optical disc in which a pair of single-sided optical discs provided with a protective film on a reflective film and these protective films are bonded and integrated with the protective films facing each other, the bonding surface of the single-sided optical disc is the surface of the protective film and the protective film. A translucent disc base surface between the film and the center hole, and a step having a depth such that the translucent disc base surface and the protective film surface between the protective film and the center hole are flush with each other. But,
It is characterized by being provided on each of the single-sided optical discs.

[0020]

In the composite optical disc structure of the present invention having the above-mentioned structure, a step having a depth such that the surface of the protective film is flush with the bonded surface without the protective film is provided on the bonding surface of the composite optical disk. Therefore, after applying a protective film on the reflective film, the surface of the protective film and the bonding surface where the protective film is not applied are flush with each other and have the same height. In addition, a compressive force acts evenly over almost the entire surface of the single-sided disk, so that there is no gap or deformation between the bonding surfaces.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the optical disk structure according to the present invention will be described below with reference to the accompanying drawings. FIG.
(A) is a cross-sectional view of a plastic disk which is a part of the composite optical disk according to one embodiment, (b) is a cross-sectional view of forming a protective film on the plastic disk of (a), (c) is (b) FIG. 3 is a cross-sectional view showing an adhesive formed on the plastic disk of FIG. FIG. 2 is a sectional view of a mold used for molding a plastic disk.

This mold 20 has a stamper 21 having a data recording area transfer portion 23 for transferring pits to the data recording area 3 of the plastic disk 1, and the data recording area 3 is mainly formed by attaching the stamper 21. The first mold part 22 is provided with a second mold part 25 which forms the mold 20 in cooperation with the first mold part 22 and mainly forms an adhesive-coated surface. The stamper 21 is attached to the second mold part 25 by the first mold part 2.
A stamper clamp 26 sandwiched and held between the plastic disk 1 and the stamper clamp 26 protrudes, and the stamper clamp 26 forms a stamper clamp groove 2 in the plastic disk 1.

Further, a depth corresponding to the thickness t of the protective film 6 is provided between the surface of the stamper 21 which becomes the molding surface 24 of the first mold component 22 and the molding surface 27 of the second mold component 25. Is formed. Accordingly, as shown in FIG. 1A, the molded plastic disk 1 has a protective film 6 on the outer upper surface 1b and the inner upper surface 1c of the stamper clamp groove 2.
A step d having a depth corresponding to the thickness of is formed. Further, a reflection film 4 is formed on the pit portion transferred to the upper surface 1b outside the stamper clamp groove 2 by a reflection film forming step. As the reflection film 4, for example, a metal film such as aluminum, nickel, and gold, or a dielectric film such as silicon nitride and silicon oxide can be used.

A protective film 6 is formed on the reflective film 4 as shown in FIG. The protective film 6 is formed by coating an ultraviolet curable resin or the like by a spin coating method. Here, as described above, since the surface 1b on which the protective film 6 is formed has the step portion D which is formed lower by the step d in advance than the surface 1c on which the protective film 6 is not formed, this protective film 6 is formed.
The adhesive application surface 6a on the upper surface and the adhesive application surface 1c inside the stamper clamp groove 2 of the plastic disk 1 have the same height and are flush. Then, a bonding surface is constituted by the protective film surface 6a and the plastic disk surface 1c between the protective film 6 and the center hole 1a.

The single-sided disk manufactured as described above is coated with an adhesive 7 by a roll coater as shown in FIG. The adhesive 7 includes an upper surface of the protective film 6 and
It is applied with a uniform thickness on the upper surface of the plastic disk 1 without the protective film 6.

FIG. 3 is a sectional view showing a state before and after laminating disks. As shown in the upper diagram of FIG. 3, the single-sided disk described above is arranged with the protective film 6 side facing the same. When a pressure is applied in this state, the surface of the protective film 6 which is the bonding surface and the bonding surface of the plastic disk 1 without the protective film 6 are flush with each other. Is transmitted uniformly over substantially the entire surface, and warping and deformation after bonding can be prevented.

Since the warpage and deformation can be prevented only by providing a step having a depth equal to the thickness of the protective film on the disk side, it is only necessary to change the shape of the mold. Conventional manufacturing equipment can be used.

In the above embodiment, the step is formed inside and outside the stamper clamp groove, and the protective film is attached from the outer edge of the stamper clamp groove. For example, the outer edge of the stamper clamp groove and the inner edge of the data recording area are formed. A step d may be provided on the upper surface 1b between the first and second steps, and the position where the protective film starts to be attached may be used as the step.

[0029]

As is apparent from the above description, according to the composite optical disk structure of the present invention, a reflective film is provided on an information recording area formed on one surface of an optical disk substrate having a center hole. In a composite optical disc in which a pair of single-sided optical discs having a protective film provided thereon and these protective films are bonded and integrated with each other so as to face each other, the bonding surface of the single-sided optical disc has the surface of the protective film and the protective film. A translucent disc substrate surface between the center hole and a step having a depth to make the translucent disc substrate surface and the protective film surface between the protective film and the central hole flush with each other, Since each of the single-sided optical discs is provided, there is no gap or deformation between the bonding faces when bonding a pair of optical discs at the time of manufacturing. It has the effect of providing a disk.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a main part showing a single-sided disk of a composite optical disk according to an embodiment of the present invention in the order of manufacturing steps;
(A) is a cross-sectional view of a plastic disk which is a part of the composite optical disk according to one embodiment, (b) is a cross-sectional view of forming a protective film on the plastic disk of (a), (c) is (b) FIG. 3 is a cross-sectional view showing an adhesive formed on the plastic disk of FIG.

FIG. 2 is an enlarged sectional view of a main part of a mold used for molding a plastic disk of the composite optical disk of one embodiment.

FIG. 3 is an enlarged sectional view of a main part showing before and after bonding of the composite optical disc of one embodiment.

4A is a plan view of a single-sided disk, and FIG. 4B is a cross-sectional view of the single-sided disk after an adhesive application step is completed.

5A and 5B are enlarged cross-sectional views of a main part for explaining a conventional state of application of a protective film, in which FIG. 5A is a diagram showing air pockets in the protective film, and FIG. FIG. 3C is a diagram showing a step of the protective film.

FIGS. 6A and 6B are enlarged cross-sectional views of a main part showing a bonded state of a conventional composite optical disk, wherein FIG. 6A is a view showing a state in which a gap is formed between the bonded disks, and FIG. FIG. 4 is a diagram showing a state in which the disk has been deformed.

FIG. 7 is a view for explaining a bonding step.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plastic disk (translucent disk base) 1a Center hole 1c Lamination surface 3 Information recording area (data recording area) 4 Reflective film 6 Protective film 6a Lamination surface 7 Adhesive D Step d Step

Claims (1)

(57) [Claims] 1. A pair of single-sided optical discs having a reflective film provided on an information recording area formed on one surface of an optical disc substrate having a center hole, and a protective film provided on the reflective film. In a composite optical disk in which the single-sided optical disk is bonded and bonded to face each other, the bonding surface of the single-sided optical disk is composed of the protective film surface and a light-transmitting disk substrate surface between the protective film and the center hole. A composite optical disc structure, characterized in that the single-sided optical disc is provided with a step having a depth between the protective film and the center hole, the surface being made flush with the surface of the translucent disc substrate and the surface of the protective film. .