JPH10255327A - Sticking type optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce camber in a sticking type optical disk for which two substrates are stuck together with an adhesive applied only on the data area. SOLUTION: Substrates 11a, 11b are each provided, in the clamp area 32, with an annular projected part 18, which is provided with a hole 31 in the center and is concentric with the entire clamp area 32. The substrate 11a, a functional film 2a and a protective film 3a comprise the first disk 15a, while the substrate 11b, a functional film 2b and a protective film 3b comprise the second disk 15b; this first 15a and the second disk 15b form an optical disk 21, with their protective films 3a, 3b bonded together by an adhesive 4. The height of the annular projected part 18 is roughly one half of the thickness of the adhesive 4, and becomes nearly the same thickness by sticking two substrates together.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk in which two disks are bonded, and more particularly, to a reduction in warpage of the bonded optical disks.

[0002]

2. Description of the Related Art Optical disks for recording and reproducing information by irradiating a laser beam include magneto-optical disks, various write-once optical disks, digital audio disks (so-called compact disks), and optical video disks (so-called laser disks). And other various media have been put to practical use. Each of these optical discs has a configuration in which a recording portion made of a functional film such as a recording layer or a reflective film is formed on a transparent substrate made of plastic such as polycarbonate resin or glass.

[0003] In addition, from the usage method, a ROM (R) such as a compact disk or a laser disk that performs only reproduction is used.
an optical disk (hereinafter, simply referred to as a "ROM disk") like a head-only memory, and a RAM (Random Access Memory) for recording and reproducing information like a magneto-optical disk or various write-once optical disks.
ry) -like optical disk (hereinafter simply referred to as “RAM disk”)
Described).

[0004] In the reproduction of a ROM optical disk, irregular pre-pits are formed on a transparent substrate at a depth of about 1/4 wavelength of the reproduction laser beam, and a reflection film is formed so as to cover the pre-pits. This is performed by detecting a change in reflectance due to the generated light interference.

On the other hand, in a RAM optical disk, for example, in the case of a phase-change disk, recording is performed by changing the recording pits from a crystalline state to an amorphous state in accordance with the recording information, and reproducing is performed by detecting the accompanying change in the reflectance. In the recording part of the conventional phase change disk, both sides of the GeSbTe film, which is a phase change film, are made of a transparent dielectric film, for example, ZnS—
It has a four-layer structure covered with an SiO ₂ film or the like and further covered with an Al reflection film.

[0006] Recently, a digital video disc has been developed in which a single movie is stored on a disc having a diameter of 120 mm, which is the same as a compact disc, with image quality comparable to that of a current television. Since the digital video disk needs to increase the recording capacity to 6 to 8 times that of the compact disk, a laser of 635 to 650 nm shorter than the current laser wavelength of 780 nm is used for recording and reproduction, and the thickness is 0.6 mm. (Nikkei Electronics, February 27, 1995, No. 630) has been devised.

A read-only ROM disk has an SD-10 type disk having recording surfaces formed on both sides of the disk,
There has been proposed an SD-5 type disc on which a dummy disc having only one recording face and the other face having no recording face is bonded. Also, there are a type that can record on both sides of a recordable RAM disk and a type that can record on only one side.

As a transparent substrate used for these optical disks, resins such as polycarbonate, acrylic, epoxy and the like are used in addition to glass. Among them, moldability,
Polycarbonate resins are most often used because of their excellent dimensional stability and low water absorption. In addition, lamination of disks formed of these materials is generally performed using a hot-melt adhesive, an ultraviolet-curable adhesive, a thermosetting adhesive, a double-sided adhesive sheet, or the like.

In the above-described digital video disk or the like, a laser beam is irradiated from the read head toward the disk recording surface, and the intensity of the laser light reflected from the recording surface and returned is detected to detect information. Reading is being performed. Therefore, if the warp of the disk is large, the amount of returning light cannot be sufficiently obtained, and it becomes difficult to read information accurately. Therefore, the warpage of the disk must be within a predetermined range. In particular, since the recording density of a digital video disk is higher than that of a conventional CD or the like, it is necessary to manage the warpage more strictly. is there. It has been proposed that the range of the warp is, for example, within ± 6 to ± 12 mrad (ISOM / ODS96Hawa).
i).

Next, a conventional bonded optical disk will be described with reference to FIGS. FIG. 5 is a schematic plan view of the optical disk, and FIG. 6 is an enlarged view of a cross section taken along line AA of FIG. FIG. 7 is a schematic sectional view of a conventional bonded optical disk, and FIG. 8 shows measured values of warpage of the conventional bonded optical disk.

As shown in FIG. 5, a conventional lamination type optical disc 20 has a center hole 31 for inserting a spindle motor shaft from the center, a clamp area 32 for fixing the optical disc 20 to the spindle motor, and data for recording information. There is an area 33 and a transparent outer periphery 34 of a predetermined width. The clamp area 32 and the outer peripheral portion 34 are portions that are pressed by a ring-shaped member in a sputtering apparatus when a functional film such as a recording film or a reflective film of the data area 33 is formed by sputtering. It does not adhere and remains transparent.

The cross-sectional structure of the bonded optical disk 20 will be described with reference to FIG. 6. Pits are formed on a substrate 1a made of polycarbonate having a diameter of 120 mm and having recording pits formed on one side thereof by injection molding. The functional film 2a is formed in a region, that is, the data area 33 by a method such as sputtering. This functional film 2a
For a read-only disc, a monolayer film of Al, Au or the like is used, and for a recordable disc, a multilayer film in which a dielectric film or the like is formed above and below a GeSbTe-based or AgIn-based recording layer is used. On this functional film 2a, a protective film 3a made of an ultraviolet curable resin or the like is formed for moisture prevention and corrosion prevention, and a first disk 5a is formed. Similarly, the substrate 1b, the functional film 2b,
A second disk 5b is constituted by the protective film 3b, and the first disk 5a and the second disk 5b are bonded to each other by the adhesive 4 so that the protective film 3a and the protective film 3b are bonded to each other.
Is formed. Incidentally, in FIG. 6, the functional films 2a,
Although the thickness of the protective film 2b and the thickness of the protective films 3a and 3b are shown to be thick, they are actually extremely thin with respect to the thickness of the adhesive 4.

When the adhesive 4 of the optical disk 20 is colored, such as white, the adhesive 4 is perceived when applied to the clamp area 32 and the transparent portion of the outer peripheral portion 34. The functional films 2a and 2b are applied only to a certain portion, that is, only to the data area 33. FIG. 7 is a cross-sectional view across the diameter of the optical disc 20. As can be seen from this figure, no adhesive is applied to the clamp area 32, and a cavity 35 is formed. However, the cavity 35 causes the optical disc 20 to warp, which causes a reduction in information recording / reproducing ability.

There are two types of optical disk warpage: radial warp and circumferential warp. For digital video disks, the substrate is as thin as 0.6 mm, so that radial warp occurs at the time of molding. Cheap. Particularly, in the case of a RAM disk, since recording is performed along a groove provided in advance, higher transferability is required to form this groove, so that molding at a higher temperature is required, and large warpage is likely to occur. Further, the functional film for recording has a multilayer structure of, for example, four layers, and when the film is formed by sputtering, the substrate is warped by kinetic energy of particles and heat in the film forming chamber. Further, the ultraviolet curable acrylic resin applied to the surface of the functional film for corrosion prevention shrinks at the time of curing, which causes warpage.

Further, in addition to these warpage generation factors,
In an optical disk where two substrates are bonded, no adhesive is applied to the clamp area. Therefore, when pressing is performed by pressing with a press, the plane action of the press does not work effectively due to the presence of the cavity without the adhesive. Warpage was occurring. Further, when such an optical disc is mounted on the drive device while holding down the clamp area, the pressing force may cause the cavity to bend and warp. In particular, in the case of a digital video disc having a substrate thickness of 0.6 mm, the rigidity of the substrate itself is small, so that warpage easily occurs with applied pressure.

FIG. 8 shows an example of measuring the warpage of the above-mentioned bonded optical disk. The horizontal axis is the radius of the disk (m
m), and the vertical axis is warpage (mrad). The dashed line
The solid line is the data on the opposite surface across the bonding surface,
The range is ± 3 mrad.

[0017]

SUMMARY OF THE INVENTION Therefore, the present invention reduces the warpage of a bonded optical disk in which an adhesive is applied only to the data area and the two substrates are bonded to each other, which lowers the information recording / reproducing ability. The purpose is to let them.

[0018]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been made in consideration of the above-mentioned problem, and has a recording surface comprising at least one recording layer or a reflection layer formed on one principal surface of a transparent plastic substrate. In an optical disk having a structure in which two disks are bonded with an adhesive or an optical disk having a structure in which the disk and a disk having no recording surface are bonded with an adhesive, recording is performed in an area of the central portion of the disk where the adhesive is not applied. A laminated optical disk is provided having an annular convex portion having a thickness substantially equal to the thickness of the adhesive applied below the surface.

The height of the annular projections provided on each of the disks is distributed so that the value obtained by adding the heights of the respective annular projections is substantially equal to the thickness of the adhesive. Also, the height of the annular projection provided on each of the disks is configured to be approximately 略 of the thickness of the adhesive.

An optical disk having a structure in which two disks having at least one or more recording layers or reflective layers formed on one main surface of a transparent plastic substrate are bonded to each other with an adhesive, In an optical disc having a structure in which a disc having no surface is bonded with an adhesive, of the two discs, one disc is flat over the entire surface, and the other disc is an area in the center of the disc where no adhesive is applied. Then, a laminated optical disk is provided having an annular convex portion having a thickness substantially equal to the thickness of the adhesive applied below the recording surface.

An optical disk having a structure in which two disks having at least one recording layer or a reflective layer formed on one main surface of a transparent plastic substrate are bonded with an adhesive, In an optical disc having a structure in which a disc having no surface is bonded with an adhesive, the two discs are flat over the entire surface, and an adhesive is applied under a recording surface in an area where the adhesive is not applied in the center of the disc. A bonded optical disk is provided in which an annular member having a thickness substantially equal to the thickness of the agent is provided. The annular member has a structure in which characters and patterns are provided on the surface by printing or etching.

Further, the above-mentioned problem is solved by setting the thickness of each of the two disks to be bonded of the above-mentioned bonded type optical disk to 0.6 mm.

The hollow portion of the clamp area is filled with the annular convex portion or the annular member of the bonded optical disk of the present invention, and the strength at this portion is increased to reduce the occurrence of warpage.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic sectional view of a first embodiment of a bonded optical disk according to the present invention, FIG. 2 is a schematic sectional view of a second embodiment, and FIG. 3 is a schematic sectional view of the third embodiment. It is an outline sectional view. FIG.
Is a measured value of the warpage of the bonded optical disk of the present invention.

In the bonded optical disk of the present invention, the hollow portion of the clamp area of the optical disk is formed by an annular convex portion of the disk.
Alternatively, this is different from the conventional example in filling with an annular member (hereinafter, referred to as a “spacer”), and detailed description of the same components as the other conventional examples will be omitted.

First Embodiment An optical disc 21 according to a first embodiment will be described with reference to FIG. In the substrate 11a and the substrate 11b of this embodiment, the annular convex portions 18 are provided in the clamp area 32, respectively. The annular projection 18 has a center hole 31 at the center, and is formed concentrically over the entire area of the clamp area 32. A substrate 11a, a functional film 2a,
The first disk 15a is composed of the protective film 3a, and the second disk 15b is composed of the substrate 11b, the functional film 2b, and the protective film 3b. The first disk 15a, the second disk 15b The protective film 3a and the protective film 3b are adhered to each other by the adhesive 4, and the optical disc 21 is formed. Although the thicknesses of the functional films 2a and 2b and the protective films 3a and 3b are schematically shown in FIG. 1 as being thick, they are actually extremely thin with respect to the thickness of the adhesive 4. Hereinafter, the same applies to the second embodiment and the third embodiment.

The height of the annular convex portion 18 is approximately の of the thickness of the adhesive 4 and is approximately the same as the thickness of the adhesive by combining the two substrates. For example, the adhesive 4 is a functional film 2
A doughnut-shaped mask having windows opened only in the areas a and 2b is applied by a silk printing machine. When the thickness of the adhesive 4 after bonding is set to be about 50 μm, an annular convex The heights of the portions 18 are each 25 μm.

[0028] With reference to FIG. 2 will be described an optical disk 22 is a second embodiment the second embodiment. The substrate 12a of this embodiment is a flat plate, while the substrate 12b is provided with an annular convex portion 18 in the clamp area 32. The annular projection 18 has a center hole 31 at the center, and is formed concentrically over the entire area of the clamp area 32. The first disk 16a is composed of the substrate 12a, the functional film 2a, and the protective film 3a, and the second disk 16b is composed of the substrate 12b, the functional film 2b, and the protective film 3b.
The protective film 3a and the protective film 3b are bonded to each other by the adhesive 4 so that the optical disk 22 is formed.

The height of the annular projection 18 of the substrate 12b is substantially the same as the thickness of the adhesive 4, and as in the first embodiment, if the thickness of the adhesive 4 after bonding is about 50 μm,
The height of the annular projection 18 of b is also set to 50 μm.

[0030] With reference to FIG. 3 will be described an optical disk 23 is a third embodiment the third example embodiment. The optical disk 23 of this embodiment is obtained by filling the hollow portion 35 of the conventional optical disk 20 with the spacer 19 having the center hole 31 at the center. The thickness of the spacer 19 is substantially the same as the thickness of the adhesive 4 for bonding the first disk 5a and the second disk 5b, and the thickness of the adhesive 4 after bonding is the same as in the first embodiment. If it is about 50 μm, the height of the spacer 19 is also about 50 μm.
Set to m.

As the material of the spacer 19, for example, the same polycarbonate as the substrate, Teflon, acrylic resin or the like can be used. It is also possible to use metals such as aluminum and stainless steel, polyethylene terephthalate, polyethylene naphthalate and aramid.

Further, characters and patterns may be formed on the surface of the spacer 19 by printing, transfer by injection molding, etching, or the like so that they can be seen through the clamp area.

FIG. 4 shows an example of measuring the warpage of the bonded optical disk according to the present invention. The horizontal axis is the radius (mm) of the disk, and the vertical axis is the warpage (mra).
d) Yes. The dashed line is the data on the opposite surface across the bonding surface from the solid line, and its value is in the range of ± 0.4 mrad, which is a marked improvement over the conventional example shown in FIG. Is recognized.

Incidentally, without being limited to the above-described embodiment,
Naturally, various forms that embody the technical idea of the present invention can be adopted.

[0035]

As is clear from the above description, according to the bonded type optical disc of the present invention, it is possible to reduce the warp in the radial direction of the optical disc, and to improve the recording / reproducing performance for the optical disc and the commercial quality of the optical disc. The appearance is improved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a first embodiment of a bonded optical disc according to the present invention.

FIG. 2 is a schematic sectional view of a second embodiment of the bonded optical disk of the present invention.

FIG. 3 is a schematic sectional view of a third embodiment of the bonded optical disk of the present invention.

FIG. 4 is a measured value of the warpage of the bonded optical disk of the present invention.

FIG. 5 is a schematic plan view of an optical disc.

FIG. 6 is an enlarged view of a cross section taken along line AA of FIG. 5;

FIG. 7 is a schematic sectional view of a conventional bonded optical disk.

FIG. 8 shows measured values of warpage of a conventional bonded optical disk.

[Explanation of symbols]

1a, 1b, 11a, 11b, 12a, 12b ... substrate,
2a, 2b: functional film, 3a, 3b: protective film, 4: adhesive, 5a, 15a, 16a: first disk, 5b, 1
5b, 16b: second disk, 18: annular convex portion, 19
... spacers, 20, 21, 22, 23 ... optical disks, 3
DESCRIPTION OF SYMBOLS 1 ... Center hole, 32 ... Clamp area, 33 ... Data area, 34 ... Outer periphery, 35 ... Cavity

Claims (7)

[Claims] 1. An optical disc having a structure in which two discs each having at least one recording layer or a recording layer made of a reflective layer formed on one main surface of a transparent plastic substrate are bonded to each other with an adhesive, or An optical disk with a structure in which an adhesive is bonded to a disk that does not have a recording surface by using an adhesive. A bonded optical disk, comprising a projection. 2. The height of the annular projections provided on each of the disks is distributed so that a value obtained by adding the heights of the respective annular projections is substantially equal to the thickness of the adhesive. 2. The bonded optical disc according to claim 1, wherein 3. The bonded optical disk according to claim 1, wherein the height of the annular projection provided on each of the disks is approximately １ ／ of the thickness of the adhesive. 4. An optical disc having a structure in which two discs each having at least one recording layer or a recording surface formed of a reflective layer formed on one main surface of a transparent plastic substrate are bonded with an adhesive, or An optical disk having a structure in which a disk having no recording surface is bonded with an adhesive, of which one of the two disks is flat over the entire surface and the other disk is coated with an adhesive at the center of the disk. A bonded optical disk, wherein an annular convex portion having a thickness substantially equal to the thickness of an adhesive applied below a recording surface is provided in an area not to be recorded. 5. An optical disk having a structure in which two disks, each having at least one recording layer or a recording surface composed of a reflective layer formed on one principal surface of a transparent plastic substrate, are bonded with an adhesive, or the disk. An optical disk having a structure in which the disk and the disk having no recording surface are bonded with an adhesive, wherein the two disks are flat over the entire surface and are coated below the recording surface in an area where the adhesive is not applied in the center of the disk. A bonded optical disk, wherein an annular member having a thickness substantially equal to the thickness of the adhesive to be bonded is provided. 6. The bonded optical disk according to claim 5, wherein characters and patterns are provided on the surface of the annular member by any one of printing, injection molding, and etching. . 7. The bonded optical disk according to claim 1, wherein each of the two disks has a thickness of 0.6 mm.