JP2002063740A - Optical information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical information recording medium consisting of two disks laminated by adhering with a small amount of an adhesive and having little warpage and a small radial tilt angle. SOLUTION: The optical information recording medium consists of a disk 12 and a disk 14 laminated on the disk 12. The disk 12 is prepared by forming a recording layer region containing a dye recording layer 20 in the region within a specified radius on a transparent substrate 18 having a center hole 16 in the center and by coating the recording layer region with a light reflection layer 22. The disk 14 is laminated with the disk 12 in such a manner that at least a region along the inner circumference part of the disk 12 and a region along the outer circumference part are adhered with an adhesive 26 and that a notch 28 is formed in the region along the outer circumference part to connect the non-adhering part to the outside.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium, and more particularly, to an optical information recording medium formed by bonding two disks.

[0002]

2. Description of the Related Art With the recent development of short wavelength lasers, DVDs capable of higher density recording and reproduction have been put to practical use.
This DVD employs a structure in which two disks are bonded together. The two disks are bonded together using a hot-melt adhesive, an ultraviolet-curable adhesive, a thermosetting adhesive, a double-sided adhesive sheet, or the like. It is done by. Here, as described in Japanese Patent Application Laid-Open No. H10-149580 and the like, the two disks are adhered by applying an adhesive to almost the entire surface thereof, leaving a slight margin area in the peripheral area of the center hole. .

[0003]

However, a large amount of adhesive is required to apply the adhesive to substantially the entire surface of the disk and to bond the two disks together. The bonded disk may warp due to the thermal expansion of air bubbles held in the disk, or may be located in a specific area on the axis perpendicular to the reference plane (specific surface on the disk perpendicular to the axis) and the light incident surface of the disk. There has been a problem that the radial tilt angle, which is an angle between the axis and a perpendicular axis, increases.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide a disk having two disks bonded together with a small amount of adhesive and having a small tilt and a radial tilt angle. Is to provide an optical information recording medium having a small size.

[0005]

In order to achieve the above object, an optical information recording medium according to the present invention has a recording layer region formed in a region within a predetermined radius on a substrate having a hole formed in the center. A first disk whose recording layer area is covered with a light reflecting layer, and at least a first area along an inner peripheral edge and a second area along an outer peripheral edge of the first disk are formed of an adhesive. The first region is bonded to at least one of the first region and the second region so that the non-bonded portion between the first region and the second region communicates with the outside.
And a second disc bonded to the disc.

As described above, in the present invention, it is sufficient that at least the area along the inner peripheral edge and the area along the outer peripheral edge of the first disk are bonded with the adhesive, and the adhesive is applied to the entire surface. There is no need to use a small amount of adhesive.

Further, if air-sealed portions are present in the non-adhesive portions, the thermal expansion causes the warpage and the radial tilt angle to increase, but the air passage is provided in at least one of the first region and the second region. Is provided, and by bonding the two disks so that a non-adhesive portion between the first region and the second region is communicated with the outside, an air-sealed portion does not occur, An optical information recording medium having a small warp and a small radial tilt angle can be obtained.

[0008] In the above optical information recording medium, it is preferable that 25 to 80% of the surface of the first disk is bonded with an adhesive, and 30 to 75% of the area is bonded with an adhesive. Is more preferable.

The area ratio of the first region to the second region is preferably 20 to 60%, more preferably 25 to 55%. The first area on the inner circumference side and the second area on the outer circumference side
If the area ratio of the region is extremely biased, that is, if the area ratio of the first region to the second region is too large or too small, the internal stress accumulated in the bonding region is too small. Since the difference is large, the disk is likely to be warped or slightly distorted.

[0010]

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

The optical information recording medium according to the present embodiment is:
As shown in FIG. 1, a DVD-R type having a recording layer only on one side where a disk 12 having a recording layer region mainly composed of a dye recording layer formed on a substrate and a disk 14 composed of only the substrate are bonded together. Optical information recording medium.

The disk 12 has a disk-shaped transparent substrate 18 having a center hole 16 formed in the center, a dye recording layer 20 containing an organic dye, and a light reflection layer 22 made of a light-reflective material having a high reflectance to laser light. , And a protective layer 24 for physically and chemically protecting the dye recording layer. On the transparent substrate 18 of the disk 12, a spiral pre-groove is formed in a region within a predetermined radius range excluding the peripheral portion of the center hole 16 and the outer peripheral edge of the transparent substrate 18, and this pre-groove is formed. The dye recording layer 20 is provided on the region thus formed to form a recording layer region. A light reflection layer 22 is formed on the dye recording layer 20 so as to cover the dye recording layer, and a protective layer 24 is formed on the light reflection layer 22 so as to cover the light reflection layer. Note that the transparent substrate 18 transmits light of a predetermined wavelength used as recording light and reproduction light.

The disk 14 has the same size as the transparent substrate 18 and is formed by forming a protective layer 23 on a disk-shaped transparent substrate 19 in which a center hole 25 of the same size is formed at the same position as the transparent substrate 18. However, the protective layer 23 may not be formed, or the protective layer 23 may be formed via a reflective layer. Note that no groove is formed on the transparent substrate 19.

The disk 14 is formed of the protective layer 2 of the disk 14.
3 and the protective layer 24 of the disk 12 are overlapped so as to face each other, and are bonded together with an adhesive 26 interposed therebetween. As shown in FIG. 2, the disk 12 and the disk 14 are bonded by bonding an area along the inner peripheral edge and an area along the outer peripheral edge of the disk 12 with an adhesive 26. The layer made of the adhesive 26 is provided with a notch 28 as an air passage, and the notch 28 allows a non-adhesive portion to communicate with the outside. That is, a layer made of the adhesive 26 is formed substantially continuously along the inner peripheral edge and the outer peripheral edge of the disk 12 except for the notched portion, thereby forming a ring-shaped adhesive region.

If the area bonded by the adhesive 26 is too large, the warpage and radial tilt increase, and if the area is too small, the bonding strength decreases.
It is preferable that the region of 80% is bonded by the adhesive 26, and it is more preferable that the region of 30% to 75% is bonded by the adhesive 26.

The area ratio of the area along the inner peripheral edge to the area along the outer peripheral edge of the area bonded by the adhesive 26 is preferably 20 to 60%, and more preferably 25 to 55%.
Is more preferred. Even if the area ratio of the first region to the second region is extremely large or extremely small,
Since the difference in internal stress accumulated in the bonding area increases, the disk is likely to be warped or minutely distorted.

Further, it is desirable that the notch 28 as an air passage is smaller so as not to deform the shape of the substrate.

As a material used for the transparent substrate 18 and the transparent substrate 19, glass, polycarbonate, acrylic resin, epoxy resin and the like can be used. Among them, polycarbonate is preferable in terms of moisture resistance, dimensional stability, cost, and the like.

The pregroove formed on the transparent substrate 18 is preferably formed directly on the substrate when the resin material is injection-molded or extruded. The track pitch of the pre-groove is preferably 0.8 μm or 0.74 μm, the depth of the pre-groove is preferably in the range of 80 to 300 nm, and the half width is preferably in the range of 0.2 to 0.9 μm.

The dye recording layer 20 is prepared by preparing a coating solution by dissolving a dye having predetermined optical properties in a solvent, if desired, with an anti-fading agent and a binder, and then applying the coating solution to the pre-groove of the transparent substrate 18. Can be formed by spin-coating or the like on the surface on which is formed and drying the coating film. As the solvent, 2,2,3,3-
Fluorinated solvents such as tetrafluoropropanol are preferred. As the anti-fading agent, known anti-fading agents described in JP-A-2-300288 can be used. As the binder, a natural organic polymer substance such as gelatin or a cellulose derivative, or a synthetic organic polymer such as polyethylene or polyvinyl chloride can be used. The thickness of the dye recording layer 20 is generally in the range of 20 to 500 nm, preferably in the range of 50 to 300 nm.

The material of the light reflecting layer 22 is Cr, N
i, Pt, Cu, Ag, Au, Al and stainless steel, or alloys thereof are used. Light reflection layer 22
Can be formed on the recording layer by vapor deposition, sputtering or ion plating of these materials. The thickness of the light reflection layer 22 is generally 10 to 80.
It is in the range of 0 nm, preferably in the range of 20-500 nm.

The material of the protective layers 23 and 24 is SiO
₂ , inorganic substances such as MgF ₂ , SnO ₂ , and Si ₃ N _4; and organic substances such as a thermoplastic resin, a thermosetting resin, and a UV-curable resin can be used. In the case of an inorganic substance, the protective layers 23 and 24 can be formed by a method such as vacuum deposition, sputtering, or coating. In the case of an organic substance, the protective layers 23 and 24 can be formed by lamination of a plastic film, application and drying of a coating solution dissolved in a solvent, or the like. it can. The thickness of the protective layers 23 and 24 is generally in the range of 0.1 to 100 μm.

As the adhesive 26, a hot melt adhesive, an ultraviolet curable adhesive, a thermosetting adhesive, or the like can be used. Depending on the type of the adhesive 26, a method such as roll coating, spin coating, or screen printing is used.
It is applied to the adhesive surface of one of the disks. Adhesive 26
Is generally in the range of 5.0 to 50 μm,
The range is preferably from 0 to 40 μm, and particularly preferably around 20 μm.

In the optical information recording medium of the present embodiment, the area along the inner peripheral edge and the area along the outer peripheral edge of the disk are adhered and adhered with an adhesive. Only a small amount is needed. In addition, since two discs are bonded to each other so that a non-adhesive portion is communicated with the outside by providing a cutout in the adhesive layer, no air-sealed portion is generated, and warpage occurs due to thermal expansion. No increase in radial tilt angle. In addition, since bonding is performed with a small amount of adhesive, unevenness in the amount of adhesive applied and entrapped air bubbles in the adhesive layer are unlikely to occur, and the occurrence of warpage and an increase in the radial tilt angle are further suppressed.

In the above-described embodiment, an example has been described in which only the area along the inner peripheral edge and the area along the outer peripheral edge of the disc are bonded by bonding with an adhesive, but other portions are bonded with an adhesive. The two disks may be bonded together by bonding. However, from the viewpoint of reducing the amount of the adhesive, the significance of providing the adhesive region between the region along the inner peripheral edge and the region along the outer peripheral edge is small.

For example, as shown in FIG. 3A, the adhesive 2 is formed radially from the center axis of the disc so as to connect the area along the inner peripheral edge and the area along the outer peripheral edge of the disc.
6 can be applied and the two disks can be bonded together, and as shown in FIG.
6 can be applied and two disks can be bonded together. It is also a preferable embodiment to apply and bond an adhesive while leaving a slight margin area in the peripheral area of the center hole. It is necessary to appropriately provide an air passage (for example, a notch 28) communicating with the outside so that an air-sealed portion does not occur in the non-adhesive portion.

In the above embodiment, a DVD-R type optical information recording medium having a dye recording layer on only one side using a disk composed of a substrate and a protective layer on one side is described. Can be widely applied to optical information recording media formed by laminating, for example, discs having a recording layer region formed on a substrate such that the side on which each recording layer region is formed is on the inside. By sticking together, a DVD-R type optical information recording medium having recording layers on both sides can be obtained.

[0028]

[Example 1] A polycarbonate substrate having a spiral pre-groove formed on its surface by injection molding (thickness: 0.6 mm, outer diameter: 120 mm, inner diameter: 15 mm,
A product name “Panlite AD5503” manufactured by Teijin Limited was produced.

1 g of the following cyanine dye was added to 2,2,3,3
-Dissolved in 100 ml of tetrafluoro-1-propanol, and the obtained coating solution was applied on the surface of the polycarbonate substrate on the pre-groove side at a rotation speed of 300 rpm to 30 rpm.
Coating by spin coating while changing to 00 rpm, drying, and dye recording layer (thickness in pre-groove:
(About 200 nm).

[0030]

Embedded image

Next, an A layer having a thickness of about 70 nm was formed on the dye recording layer by DC sputtering in an argon atmosphere.
The light reflection layer made of g was formed. Furthermore, on the light reflection layer,
A UV-curable resin (trade name "SD-318", manufactured by Dainippon Ink and Chemicals, Inc.) was used at a rotation speed of 60 rpm to 4000 rpm.
It was applied by spin coating while changing to rpm. After the application, the coating was irradiated with ultraviolet light from a high-pressure mercury lamp to cure the coating, thereby forming a protective layer having a thickness of 7 μm. The surface hardness was 2H as the pencil hardness. In this way, a laminate in which a dye recording layer, a light reflection layer, and a protective layer were sequentially provided on the substrate was obtained.

A disc-shaped protective substrate made of polycarbonate having only a protective layer (diameter: 120 mm, thickness: 0.6 m)
m), and as shown by hatching in FIG. 4, the inner peripheral edge is located at a radius of 20 mm to 30 mm, and the outer peripheral edge is 50 mm.
A slow-acting adhesive (cation-curable epoxy resin) “SK7000” manufactured by Sony Chemical Co., Ltd. was applied by screen printing to a position of mm to 59.5 mm. At this time, the application area of the adhesive was 40% of the substrate surface area, and the thickness of the adhesive layer was 17 μm. 1m width at one place on the outer edge
m was provided. The area ratio of the inner peripheral edge to the outer peripheral edge was 30%.
Next, the laminate obtained above and the substrate on which only the protective layer was formed were superposed and bonded so that the substrate side was inside. Through the above steps, a DVD-R type optical disk according to the present invention was manufactured.

[Embodiment 2] As shown by hatching in FIG. 5, the adhesive "SK7" is applied to the inner peripheral edge at a position of a radius of 8 mm to 30 mm and the outer peripheral edge at a position of a radius of 50 mm to 59.5 mm.
A DVD-R type optical disk according to the present invention was manufactured in the same manner as in Example 1 except that “000” was applied. The application area of the adhesive at this time is 50% of the substrate surface area. The area ratio of the inner peripheral edge to the outer peripheral edge was 50%.

Comparative Example 1 An adhesive "SK70" was applied to the entire surface of the substrate.
A DVD-R type optical disk of a comparative example was manufactured in the same manner as in Example 1 except that “00” was applied.

[Evaluation of Optical Disc] For each of the obtained CD-R discs, an optical media mechanical property evaluation tester “LM”
-100A ", the following amounts of warpage and radial tilt were measured, respectively. The results obtained are shown in Table 1 below. <Warp> This is the amount of warp in the axial direction when the disc is stationary.
The standard according to the Orange Book is within ± 400 μm. <Radial tilt> This is the angle between the axis perpendicular to the reference plane (the specific plane on the disk perpendicular to the axis) and the axis perpendicular to the specific area of the light incident surface of the disk. It is within 6 degrees.

[0036]

[Table 1]

As can be seen from Table 1, the DVD-R type optical disk according to the present invention has less warpage and a smaller radial tilt angle than the DVD-R type optical disk of the comparative example.

[0038]

According to the optical information recording medium of the present invention, two discs are adhered to each other with a small amount of adhesive, and the disc has a small warp and a small radial tilt angle.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view illustrating a cross section of a part of an optical information recording medium according to an embodiment of the present invention.

FIG. 2 is a plan view showing an adhesion area of the optical information recording medium of the present embodiment.

FIG. 3A is a plan view showing a modified example of the bonding area of the optical information recording medium, and FIG. 3B is a plan view showing another modified example of the bonding area of the optical information recording medium.

FIG. 4 is a plan view showing an adhesion area of the DVD-R type optical disk of the first embodiment.

FIG. 5 is a plan view showing an adhesion area of a DVD-R type optical disc of Example 2.

[Explanation of symbols]

 12, 14 Disc 16, 25 Center hole 18, 19 Transparent substrate 20 Dye recording layer 22 Light reflection layer 23, 24 Protective layer 26 Adhesive 28 Notch

Claims (1)

[Claims] A first disk having a recording layer region formed in a region within a predetermined radius range on a substrate having a hole formed in a center portion, wherein the recording layer region is covered with a light reflecting layer; A first area along the inner peripheral edge of the first disk and a second area along the outer peripheral edge are bonded with an adhesive, and an air passage is provided in at least one of the first area and the second area. And a second disc bonded to the first disc such that a non-adhesive portion between the first area and the second area is communicated with the outside.