JP3888705B2 - Optical disc bonding method and bonded optical disc - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a large-capacity optical recording medium, and more particularly to a whole-bonding type optical disc capable of recording, reproducing, or erasing information and a method for bonding the same.
[0002]
[Prior art]
Several optical disks using laser beams have already been put into practical use as large-capacity memories. However, it is desired to develop an optical disc having a larger recording capacity due to an increase in the amount of information, and various methods for increasing the recording capacity have been developed. For example, since the recording capacity is inversely proportional to the laser beam diameter during recording and / or reproduction, a method of reducing the beam diameter by using a short wavelength laser or a high NA objective lens has been proposed. When a high NA objective lens is used, aberration due to deformation of the substrate increases. This problem can be avoided by reducing the thickness of the substrate, for example, about 0.6 mm. However, since the mechanical strength of the medium is reduced when the thickness of the substrate is reduced, a medium in which two substrates are bonded to each other has been proposed. At the time of bonding, it is required that the adhesive layer does not leave bubbles, the adhesive does not protrude from the center hole, and that the innermost peripheral portion is also neatly bonded concentrically.
[0003]
Laser disks, magneto-optical disks, and the like are available on the market as disks having two substrates bonded together, and various methods have been proposed for bonding methods. Laser discs are usually bonded using a hot melt adhesive, but the hot melt adhesive is inferior in heat resistance, and for example, heat resistance at 85 ° C is required for use in an in-house company. Does not meet heat resistance requirements.
[0004]
An ultraviolet curable resin has been proposed as an adhesive having excellent heat resistance. In a bonded disc provided with an air gap, a narrow spacer is bonded to the outside of the innermost peripheral portion and the outermost recording support portion. An ultraviolet curable resin may be used for bonding the spacer. It is known. In the adhesion of the spacer, the adhesion area is very small and no bubbles remain in the adhesion layer. Further, since the amount of the adhesive to be applied is minimal, there is almost no protrusion from the bonded portion.
[0005]
The UV curable resin is a one-component, fast-curing, low-viscosity resin that is excellent in workability. However, when the entire disk-shaped substrate having a hole in the center is bonded, an adhesive made of the UV curable resin from the center hole. It is very difficult to stick the whole surface without protruding and without bubbles. For example, if an adhesive is applied to the entire surface and bonded together, bubbles remain. Therefore, a method has been proposed in which adhesive is partially applied and bonded, the weight of the substrate or a load is applied to spread the adhesive over the entire surface, and excess adhesive is spun off from the outer peripheral edge by rotating the substrate. . However, even in this method, it is very difficult to spread the adhesive uniformly in a concentric manner by a load, and there is a problem that a part of the adhesive protrudes from the center hole of the substrate.
[0006]
[Problems to be solved by the invention]
In order to solve the above-mentioned problems, the present inventors diligently studied various conditions for laminating an optical disk using an ultraviolet curable resin, and completed the present invention.
[0007]
[Means for Solving the Problems]
That is, the present invention includes (1) a substrate having a central hole and having a recording support surface on one side, and an ultraviolet curable resin having a viscosity of 150 to 800 centipoise at 25 ° C. with the recording support surface on the inside. the bonded, except the excess UV curing resin and air bubbles by rotating the substrate, then UV rays are irradiated, characterized that you cure, recording, reproduction, of one or more optical disc capable of erasing Bonding method, (2) Bonding method of optical disk according to (1) using UV curable resin having a viscosity of 300 to 650 centipoise at 25 ° C., (3) Groove or concave shape on innermost circumference of record carrying surface (1) or (2) optical disk laminating method using a substrate having a step, (4) a substrate having a groove or concave step at the innermost peripheral portion having a width of 5.5 mm or less and a depth of 0.2 mm or less. (3) optical disc laminating method used, (5 Has a central hole, to a substrate having a recording bearing surface on one side, and the recording carrier surface on the inside, a viscosity at 25 ° C. bonding the entire surface of 150 to 800 centipoises of the ultraviolet curable resin, the substrate is rotated The optical disk is made by removing excess UV curable resin and bubbles, and then cured by irradiating with UV light, and can be used for one or more of recording, reproduction and erasing. (6) Viscosity at 25 ° C is 300 to 650 centipoise (5) or (7) bonded using a substrate having a groove or a concave step on the innermost peripheral portion of the recording support surface. The optical disk according to 6) and (8) the optical disk according to (7), wherein the innermost peripheral groove or concave step is bonded using a substrate having a width of 5.5 mm or less and a depth of 0.2 mm or less. .
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The substrate having a central hole used in the present invention and having a recording support surface on one side is a transparent film having a thickness of about 0.8 to 0.4 mm, a diameter of the central hole of about 15 mm, and an outer diameter of about 130 to 80 mm. It is a resin substrate. Then, on one side of the transparent resin substrate, in the case of a read-only optical disc, information is formed by pits when forming the substrate, forming a record carrying surface, and a reflective layer is formed thereon, as with a compact disc. Has been. In the case of a recordable optical disk, a groove is formed on the substrate surface, and a recording layer made of a known dye, or a phase change recording layer made of an inorganic alloy or a magneto-optical recording layer is formed thereon. Thus, a recording support surface is formed, and a dielectric layer and a reflective layer are formed on these recording layers. Further, if necessary, a protective layer may be formed, but the adhesive layer of the ultraviolet curable resin or the bonded substrate may not be used as the protective layer.
[0009]
When adhering the above-described substrate using a liquid ultraviolet curable resin as an adhesive, in order to prevent the adhesive from protruding from the center hole, the innermost peripheral portion of the record-carrying surface of the substrate is used to keep excess adhesive. In addition, it is preferable to provide grooves or concave steps concentrically. 1 and 2 are schematic views of the cross section of the groove or the concave step. As shown in FIG. 1, a groove 2 is provided outside the center hole 1. The groove may be U-shaped, V-shaped or the like. Further, as shown in FIG. 2, a concave step 2 ′ in which the partition wall between the center hole 1 and the groove is removed may be used.
[0010]
The position where this groove or concave step is provided is preferably within 5.5 mm from the innermost periphery of the substrate. Although the shape is not particularly limited, the width is 5.5 mm or less, preferably 3 mm or less, and the depth is 0.2 mm or less, preferably 0.15 mm or less from the mechanical strength of the substrate. Is about 0.05 mm or more. The groove or the concave step may be provided on one or both of the substrates to be bonded.
[0011]
On the other hand, the viscosity of the ultraviolet curable resin used in the present invention is important. That is, if the viscosity of the resin is too small, the resin spreads too much when the resin is applied to the substrate, and bubbles tend to remain in the adhesive layer. In order to adhere so that bubbles do not remain, it is preferable that the adhesive is applied in a mountain shape without spreading when the adhesive is applied. On the other hand, even if the viscosity of the resin is too high, bubbles are difficult to escape, and it takes a long time to shake off excess adhesive by rotating the substrate, resulting in poor productivity. From these points, the viscosity of the ultraviolet curable resin is 150 to 800 centipoise at 25 ° C., preferably 300 to 650 centipoise.
[0012]
The ultraviolet curable resin used in the present invention is not particularly limited except for the above-mentioned viscosity, and examples thereof include known radical polymerization type acrylic ultraviolet curable resins and cationic polymerization type epoxy ultraviolet curable resins.
[0013]
The bonding method of the present invention will be described more specifically. The substrate is set on a spin coater, and an adhesive is applied to the inner peripheral side of the substrate with a dispenser while rotating at a low speed. Next, the substrate to be bonded is placed on the substrate while aligning the position of the center hole. If the substrate is placed, the adhesive spreads in both the inner circumferential direction and the outer circumferential direction by the weight of the substrate. Then, when the adhesive approaches the innermost periphery of the substrate, it rotates at a high speed. At this time, a load may be further applied on the substrates to be bonded. When the substrate is rotated at a high speed, the adhesive moves in the outer peripheral direction, and excess adhesive is shaken off from the substrate. At this time, the air bubbles built in are also removed. The thickness of the adhesive layer varies depending on the amount of deformation of the substrate, but is preferably about 30 to 70 μm, and it is sufficient to continue high-speed rotation until the thickness becomes as described above. Finally, it is cured by irradiating with ultraviolet rays.
[0014]
In the present invention, the recording support surface may be provided on one or both of the substrates to be bonded.
In the present invention, the transparent resin substrate having an information carrying surface preferably has a light transmittance of 85% or more for recording and / or reproduction and a small optical anisotropy. Preferable materials used for the substrate include thermoplastic resins such as acrylic resin, polycarbonate resin, and polyolefin resin. Prepits and / or grooves are applied to the substrate. As a method of applying, known methods, for example, a method of applying the substrate by injection molding, an active energy ray-curable resin layer on the substrate, or the like. The method of providing and providing (2P method) is mentioned.
[0015]
The recording layer in the case of the above recordable optical disc includes, for example, a known organic dye such as cyanine dye, phthalocyanine dye, naphthalocyanine dye, naphthoquinone dye, azo dye, inorganic compound made of metal such as Te, FeTbCo And magneto-optical recording alloys and phase change recording alloys such as GeSbTe, AgInSbTe, and SnSbSe. These materials can be formed by a known method such as spin coating, vacuum deposition, or sputtering. In this case, an intermediate layer made of an organic or inorganic compound can be provided for various purposes between the substrate and the recording layer.
[0016]
Furthermore, examples of the material used for the reflective layer for reflecting the recording light and reproducing light of the present invention include, for example, Al, Au, Ag, Ni, Cu, Pt, compounds of these metals, and alloys containing these metals. And inorganic dielectrics such as silicon nitride, aluminum nitride, silicon oxide, aluminum oxide and zinc sulfide. The reflective layer can be formed by a usual method such as vacuum deposition or sputtering. At this time, an intermediate layer made of an organic or inorganic compound may be provided between the recording layer and the reflective layer.
[0017]
In addition, a protective layer can be provided on the surface of the optical disc made according to the present invention on which light is incident in order to prevent electrification and scratches. Also, label printing or the like can be performed on the surface opposite to the light incident surface of the optical disk or the surface to which the substrate is bonded.
[0018]
【Example】
Examples of the present invention will be described below.
[Example 1]
Reflection made of 80nm Al by sputtering method on the surface with pit of polycarbonate resin substrate with diameter 120mm and 0.6mm thickness with central hole with diameter 15mm having information on one side made by normal injection molding The medium on which the layer is formed is set on a spin coater with the reflective layer surface facing up, and an adhesive made of an ultraviolet curable resin having a viscosity of 350 centipoise at 25 ° C., mainly composed of epoxy acrylate, is rotated at 30 rpm. A 3 g coating was applied to the outside of the stamper groove on the inner periphery of the substrate with a dispenser, and a polycarbonate resin substrate having a diameter of 120 mm and a thickness of 0.6 mm having a central hole with a diameter of 15 mm was placed on the substrate. After about 2 seconds, the adhesive spread to the innermost periphery, so the rotational speed was set to 2500 rpm and rotated for 5 seconds. Next, the adhesive was cured by irradiating 300 mj / cm ² of ultraviolet rays. The adhesive layer contained no bubbles and was bonded from a position about 2 mm from the innermost periphery of the disk. However, the innermost peripheral portion of the adhesive layer was not a beautiful circle and was somewhat disturbed, but there was no problem in terms of disk characteristics. The film thickness of the adhesive was an average of 45 μm from the weight measurement.
[0019]
[Example 2]
Example 1 except that the substrate (FIG. 1) provided with a groove 1 mm wide and 0.15 mm deep 1 mm from the center hole of the substrate in Example 1 and an ultraviolet curing agent having a viscosity of 600 centipoise as an adhesive The same method as in No. 1 was used to make an optical disc. Bubbles were not included in the adhesive layer, and the innermost peripheral portion of the disk was more clearly bonded in a circular shape than in Example 1.
[0020]
[Example 3]
Has a groove on one side and a polycarbonate resin substrate (Fig. 2) with a diameter of 120 mm and a thickness of 0.6 mm, with a central hole with a diameter of 15 mm and a concave step with a depth of 0.15 mm from the center hole to the outside of 2 mm. A cyanine dye (NK-97: Nippon Sensitive Dye Research Laboratories) solution was spin-coated on the surface to form a 120 nm recording layer. A reflective layer made of 90 nm gold was formed on the recording layer by sputtering. This medium was bonded in the same manner as in Example 1 to produce a write-once optical disc. The adhesive layer contained no bubbles, and the innermost periphery of the disk was also adhered in a concentric manner.
[0021]
[Comparative Example 1]
Lamination was performed in the same manner as in Example 1 except that an ultraviolet curable resin having a viscosity of 100 centipoise was used as an adhesive, but many bubbles remained in the adhesive layer. Further, the adhesive partially protruded from the center hole at the innermost peripheral portion.
[0022]
【The invention's effect】
In the manufacture of optical discs by bonding two substrates together with UV curable resin, a groove or a concave step is provided on the innermost periphery of the substrate, and the adhesive is used by using a resin with a viscosity of 150 to 800 centipoise. No air bubbles remain in the layer, and it can be adhered to the innermost periphery.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an example of a cross section of a groove or a concave step of the present invention. FIG. 2 is a schematic diagram showing an example of a cross section of a groove or a concave step of the present invention.
1 Center hole 2 Groove 2 'concave step

Claims (8)

 A substrate with a central hole and a recording support surface on one side is bonded to the entire surface with an ultraviolet curable resin with a viscosity of 150 to 800 centipoise at 25 ° C with the recording support surface inside, and the substrate is rotated at high speed An optical disk laminating method capable of at least one of recording, reproduction, and erasing, characterized in that excess ultraviolet curable resin and bubbles are removed by curing, and then cured by irradiating with ultraviolet rays.  The method for laminating optical disks according to claim 1, wherein an ultraviolet curable resin having a viscosity at 25 ° C of 300 to 650 centipoise is used.  3. The method of laminating an optical disk according to claim 1, wherein a substrate having a groove or a concave step is used on the innermost peripheral portion of the recording support surface.  4. The method of laminating an optical disk according to claim 3, wherein the innermost peripheral groove or concave step is a substrate having a width of 5.5 mm or less and a depth of 0.2 mm or less. A substrate with a central hole and a recording support surface on one side is bonded to the entire surface with an ultraviolet curable resin with a viscosity of 150 to 800 centipoise at 25 ° C with the recording support surface inside, and the substrate is rotated at high speed. It is to remove excess ultraviolet curable resin and a bubble that causes, by curing and thereafter irradiated with ultraviolet rays, recording, reproducing, the optical disc capable of one or more of the erase.  6. The optical disk according to claim 5, wherein the optical disk is bonded using an ultraviolet curable resin having a viscosity at 25 ° C. of 300 to 650 centipoise.  The optical disk according to claim 5 or 6, wherein the optical disk is laminated by using a substrate having a groove or a concave step on the innermost peripheral portion of the record carrying surface.  The optical disk according to claim 7, wherein the innermost peripheral groove or concave step is bonded using a substrate having a width of 5.5 mm or less and a depth of 0.2 mm or less.

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