JP2000099996A - optical disk - Google Patents

Abstract

(57) [Problem] To provide an optical disk in which it is difficult to physically copy information recorded as a fine unevenness (pit). SOLUTION: It is composed of two substrates 1 and 5 having bonding surfaces 1a and 5a, respectively, and a pit row of a fine pattern and reflection layers 2 and 4 are formed on at least one surface of these bonding surfaces 1a and 5a. It has a substrate surface, and these bonding surfaces 1
a and 5a are bonded by using an adhesive layer 6, and are at least 5 m from the outer periphery of the disk.
m, the reflective layers 2 and 4 are not formed on the inner side and the adhesive layer 6
Is provided at least 5 mm from the reflective layers 2 and 4 to the outer peripheral side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk capable of preventing illegal duplication of a bonded optical disk such as a digital versatile disk (DVD).

[0002]

2. Description of the Related Art In recent years, optical disks such as compact disks (CDs) and DVDs capable of recording a large amount of information have become remarkably popular. In particular, read-only optical discs in which information such as music, video, databases, and computer programs are recorded as fine concave and convex patterns (so-called pits) on a substrate can be mass-produced at low cost, so that a huge number of discs are manufactured. Widespread.

[0003]

However, as optical disks become more widespread, malicious third parties copy information recorded on these optical disks and duplicate or use illegal optical disks for sale or sale. The problem of so-called pirated disks has become more serious. In particular, in the last few years, pirated discs such as CD-DAs (compact discs for digital audio) and CD-ROMs, which contain music and computer programs and are exclusively for reproduction, have been circulating in considerable quantities and have been damaged by legitimate rights holders. Is enormous.

[0004] There have been devised several optical disks having a function of preventing duplication against such illegal copying and recording / reproducing apparatuses for the optical disks. For example, JP-A-2-17941, JP-A-8-55370, and JP-A-9-128812 disclose an arbitrary picture which can be viewed on a disk surface on which an information signal is recorded without affecting reproduction of the recorded signal. And a technology having characters. It has been invented that such a technique is applied to visually discriminate a genuine product from a pirate product. However, in this method, although it is possible to discriminate between a genuine product and a pirated product, it is possible to reproduce even a pirated disk, and there is no prevention effect for a person who uses the product as a pirated product.

Japanese Unexamined Patent Publication No. Hei 6-73100 discloses that a pirated disk creator obtains recorded information from a signal obtained by reproducing a genuine product for the purpose of making a duplicate disk, and also obtains the signal. However, there is also disclosed a technology that cannot be reproduced even if a pirate disk is produced. There is disclosed a technique for preventing illegal duplication by including information, signals, and processing methods that cannot be obtained only by reproducing a genuine disc in the information and signals recorded in this way.

[0006] However, even in such a technique, if the pirated disk creator physically duplicates the entire fine irregularities (pits) recorded on the genuine disk, it is recorded on the genuine disk. All the same information can be copied.

[0007] For example, a method of physically copying a whole fine pits and pits recorded on a read-only CD as an example will be described below.

As shown in FIG. 2, a CD usually has a metal reflective layer 2 such as aluminum and a protective layer 3 such as an ultraviolet-curable resin laminated on a transparent substrate 1 on which information is recorded as fine irregularities (pits). It has a disc structure. Therefore, in order to duplicate the pits, the protective layer 3 must be removed to expose the uneven surface 1a of the substrate 1. Protective layer 3
The method of removing the protective layer 3 is to remove the protective layer 3 from the disk (substrate 1) by bringing an adhesive tape into close contact with the protective layer 3 and pulling it vigorously with the tape. Thus, the protective layer 3 on the entire surface of the disk is removed, and the uneven surface 1a on which the signal is recorded is formed.
To expose.

Next, a stamper for mass-producing duplicates is manufactured based on the disc with the uneven surface 1a as a signal surface exposed. In this method, a conductive layer is provided on a signal uneven surface by a sputtering method or an electroless plating method on a disk having an exposed signal surface, and a stamper is manufactured by an electrolytic plating method. By making a substrate 1 on which signal pits are transferred by injection molding or 2P molding from the produced stamper, and further providing a reflective layer 2 and a protective layer 3, a duplicate product having exactly the same information as a regular product can be produced. Noh.

In the case of a disk such as a CD in which signal pits (irregular surface 1a) are covered with a very thin protective layer 3 of about 10 μm, it is relatively easy to expose the irregular surface 1a having a signal. As long as the surface 1a can be exposed, a pirated disc can be produced by the subsequent duplication step following substantially the same process as that for manufacturing a CD.

Next, a DVD having a structure in which substrates are bonded together
An example of a method of physically replicating the entire shape of the fine irregularities (pits) recorded is described below. As shown in FIG. 3, a read-only DVD is usually composed of two substrates 1, 2 provided with a metal reflection layer 2, 4 of aluminum or the like on transparent substrates 1, 5 on which information is recorded as fine irregularities (pits).
5 are adhered to each other with an adhesive layer 6 interposed therebetween.

In the case of a disc having such a structure, a method of exposing the pit by exfoliating the protective layer 3 with an adhesive tape as in the case of the CD cannot be used. Therefore, in the case of a disc having a laminated structure, exposing the pits is considerably more difficult than that of a CD. However, even with such a disc, a sharp cutter knife 7 is used to attach 1-2 mm to the substrate bonding portion a on the outer peripheral portion as shown in FIG.
It is possible to make a small cut b. Commercially available D
In some VD disks, the substrates 1 and 5 stuck together can be separated into two just by making such a cut. In some disks, the substrates 1 and 5 cannot be peeled off only by inserting the notch b. In this case, after the notch b is formed, the disk is immersed in an aqueous solution of acid or alkali to form the aluminum reflective layer 2. , 4 gradually begin to dissolve, and the reflection layers 2, 4 can be completely removed by leaving them for several hours to several days.
When this happens, the two substrates 1, which have lost their adhesion at the interface,
It becomes extremely easy to peel 5. It is relatively easy to manufacture a stamper for duplication and a duplicate substrate from the substrates 1 and 5 with the pits exposed in the same manner as described for the CD.

As described above, in the case where information is recorded in fine irregularities, even if the duplication is prevented by software or electric signals, it can be prevented by physically copying the fine irregularities as they are. No effect. That is, once the fine uneven surface is exposed, it is possible to physically copy the fine unevenness to produce a pirated disk. SUMMARY OF THE INVENTION In view of such conventional problems, an object of the present invention is to provide an optical disc in which it is difficult to physically copy information recorded as fine irregularities (pits).

[0014]

In order to solve the above-mentioned problems, the present invention provides the following optical disks (1) to (3).

(1) As shown in FIG. 1, the joining surfaces 1a,
5a, and at least one of the joining surfaces 1a and 5a has a substrate surface on which a pit array of fine patterns and the reflective layers 2 and 4 are formed. An optical disk constructed by bonding surfaces 1a and 5a using an adhesive layer 6, wherein no reflective layers 2 and 4 are formed at least 5 mm or more inward from the outer periphery of the disk, and the adhesive layer 6 is An optical disk provided at least 5 mm from the outer periphery of the optical disk;

(2) The optical disk according to claim 1, wherein the substrate is a thermoplastic polymer compound.

(3) The optical disk according to claim 1 or 2, wherein an adhesive for dissolving a thermoplastic polymer compound is used for the adhesive layer 6.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a specific embodiment of the optical disk of the present invention will be described by taking a read-only optical disk as an example. In addition to the read-only optical disk recorded as a pattern, a read-only part in which part of the information is recorded in advance as a fine uneven pattern, and a write-once part where information can be recorded only once, or Having a rewritable type part that can be rewritten,
So-called hybrid optical disks are also included.

As shown in FIG. 1, the optical disk according to the present invention has a cross-sectional structure in which metal reflective layers 2, 4 such as aluminum are provided on transparent substrates 1, 5 on which information is recorded as fine irregularities (pits). It has a structure in which two substrates 1 and 5 are adhered and adhered via an adhesive layer 6. The same components as those described above have the same reference numerals allotted, and description thereof will not be repeated. Then, reflection layers 2 and 4 are provided on the transparent substrates 1 and 5 on which information is recorded as pits. At this time, the reflection layers 2 and 4 are provided at least 5 mm or more inward from the outer circumference. Preferably, the reflection layers 2 and 4 are formed only on the portion A where information is recorded as pits, and the reflection layers 2 and 4 are formed on the outer peripheral portion X thereafter.
It is desirable not to provide 4.

Although the above-described bonded optical disk has been described in which pits are formed on two substrates 1 and 5, respectively, other than this, although not shown here, it is bonded to one substrate 1 (5). The other substrate 5 (1) to be combined may be a transparent substrate only and not provided with a reflective layer. The two substrates 1 and 5 are bonded with an adhesive. At this time, the adhesive layer 6 is provided at least to the outer periphery of the reflective layers 2 and 4 by 5 mm or more. Preferably, the adhesive layer 6 is provided on the entire surface of the disk.

It is difficult to peel off the two substrates 1 and 5 of the optical disk having such a structure at the bonding surfaces 1a and 5a and expose all the pit surfaces on which information is recorded without any damage. In particular, the greater the number of portions where the bonded substrates 1 and 5 are in direct contact with the adhesive layer 6 without passing through the reflective layers 2 and 4, the more difficult it becomes. Further, when the adhesive used for bonding is a type of adhesive that dissolves the substrates 1 and 5 used, the bonding surface is not flat due to the dissolution of the substrates 1 and 5 and becomes complicated. As the adhesive force of the metal is increased, it becomes difficult to make a sharp cut with the cutter knife 7, and the effect of preventing the penetration of chemicals such as acids and alkalis that dissolve the metal reflective layers 2, 4 such as aluminum on the inner peripheral side is improved. I do.

The transparent substrates 1 and 5 used in the present invention are substrates using a thermoplastic polymer compound, and are not particularly limited, but may be polycarbonate, polystyrene, polycarbonate / polystyrene copolymer, polymethyl methacrylate, polyvinyl Synthetic resins such as chloride, alicyclic polyolefin, and polymethylpentene; quartz glass; soda-lime glass; and chemically strengthened soda-aluminosilicate glass. Particularly preferred are polycarbonate, polymethyl methacrylate, and alicyclic polyolefin.

The metal reflective layers 2 and 4 are not particularly limited, but are preferably metals, such as aluminum, gold, silver, and nickel, and alloys thereof, which are generally used for optical disks.

Examples of the adhesive forming the adhesive layer 6 include an adhesive dissolving a thermoplastic polymer compound, for example, an ultraviolet curable resin such as epoxy acrylate, urethane acrylate, and ultraviolet curable unsaturated polyester; Examples include a two-part epoxy adhesive, an anaerobic adhesive, a primer-curable adhesive, and a cyanoacrylate adhesive. Among them, it is preferable to use an adhesive capable of dissolving the substrates 1 and 5 used. For example, when polycarbonate is used for the substrate, an acrylate-based ultraviolet curable resin is suitable.

The method of bonding the two substrates 1 and 5 with an adhesive is not particularly limited, but examples thereof include a spin coating method, a hot melt method, a screen coating method, and a sheet bonding method.

EXAMPLE An exfoliation experiment was performed on an optical disk having the structure shown in FIG. 1 while changing the positions where the reflection layers 2 and 4 were provided. X in the drawing indicates the length from the outer periphery of the portion where the reflective layer is not provided.

(Preparation of Optical Disk) The optical disk used in this embodiment is a substrate obtained by molding a polycarbonate resin (H4000 manufactured by Mitsubishi Engineering-Plastics Co., Ltd.) to a thickness of 0.6 mm by injection molding. An aluminum film is formed to a thickness of 70 nm by a sputtering method, and an adhesive is an ultraviolet-curable acrylate resin (XR11 manufactured by Sumitomo Chemical Co., Ltd.) applied to the entire substrate by about 30 μm by a spin coating method.
m, and the two substrates were bonded together. The position where the reflective layer is provided was adjusted by masking the outer periphery with a ring during sputtering.

(Peeling Test 1) A notch of about 1 to 2 mm was cut into the entire circumference of the disc with a sharp cutter knife at the substrate bonding portion on the outer periphery, and two pieces of tweezers or the like having thin and flat tips were used. An attempt was made to peel off the substrate to pry it open.

(Peeling Test 2) A notch of about 1 to 2 mm was made in the outer peripheral portion of the substrate bonding portion in the same manner as in Peeling Test 1 over the entire circumference of the disk, and then placed in 36% concentrated hydrochloric acid for a predetermined time. Dipped at room temperature. After being immersed for a predetermined time, the disk was sufficiently washed with water, and then peeling was attempted to pry open the two substrates with tweezers or the like whose tips were thin and flat.

(Peeling Test 3) A cut of about 1 to 2 mm is made in the outer peripheral portion of the substrate to be bonded to the substrate in the same manner as in Peeling Test 1, and then cut in a saturated aqueous solution of sodium hydroxide for a predetermined time. Dipped at room temperature. After being immersed for a predetermined time, the disk was sufficiently washed with water, and then peeling was attempted to pry open the two substrates with tweezers or the like whose tips were thin and flat. FIG. 5 shows the results of (peeling test 1)-(peeling test 3) described above. In the figure, NG indicates that separation could be performed without damaging the pit of the substrate, and OK indicates that separation could not be performed. X indicates the length from the outer periphery of the portion where the reflective layer is not provided. Comparative Examples 2 and 3 are the results of performing the same experiment using commercially available DVD-ROM and DVD-R disks.

[0031]

As described above, the optical disc of the present invention
It has a strong resistance to peeling of the bonded substrate, and after exposing the pit surface where information is recorded,
There is a strong prevention effect against attempts to make a pirated disk by physically copying the entire fine irregularities (pits). Further, the effect of preventing an attempt to peel off the bonded substrate is greater than that of a conventional disk having a reflective layer formed near the outermost periphery of the disk. Further, the substrate used in the optical disc of the present invention uses a thermoplastic polymer compound and an adhesive having a property of dissolving the thermoplastic polymer compound used in the substrate, thereby further increasing the peeling prevention effect. effective.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a cross-sectional configuration of an optical disc according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a cross-sectional configuration of an optical disc.

FIG. 3 is a diagram illustrating a cross-sectional configuration of an optical disc.

FIG. 4 is a diagram illustrating a cross-sectional configuration of an optical disc.

FIG. 5 is a diagram showing the results of a peel test.

[Explanation of symbols]

 1,5 substrate 1a, 5a bonding surface 2,4 reflective layer, reflective film, metal reflective film 3 protective layer, protective film 6 adhesive layer

Claims (3)

[Claims] The present invention comprises two substrates each having a bonding surface, and at least one of these bonding surfaces has a substrate surface on which a pit row of a fine pattern and a reflective layer are formed,
An optical disc constructed by bonding these bonding surfaces using an adhesive layer, wherein no reflective layer is formed at least 5 mm inside the outer periphery of the disc, and the adhesive layer is at least 5 m from the reflective layer.
An optical disc, wherein the optical disc is provided at least to the outer circumference. 2. The optical disk according to claim 1, wherein said substrate is made of a thermoplastic polymer compound. 3. The optical disk according to claim 1, wherein an adhesive for dissolving a thermoplastic polymer compound is used for the adhesive layer.