JPH07201083A - Optical disk and its manufacture - Google Patents

Abstract

PURPOSE:To straighten the warpage of an optical disk. CONSTITUTION:In a disk in which a substrata 101 is warped in a convex shape to a laser incidence plane 104, ultraviolet-curing resin with hardening contraction ratio larger than that of a protective film 103 and that of an adhesive 107 for hub mounting is used as the material of the hard coating film 105 when the mounting contact plane of the substrate 101 with a hub 106 is located on the protective film 103 formed on the upper plane of a reflecting film 102, etc., as the shape of the hub. High stress 108 in a warpage straightening direction can be generated on a hard coating plane side by thickening the film thickness of the hard coating film 105, making that of the protective film 103 thin, and reducing the quantity of hub mounting adhesive, which straightens the warpage. The thickness of each film and the quantity of adhesive to be applied can be adjusted depending on the degree of warpage of the disk and the hardening constraction ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk and a method for manufacturing the same, and more particularly to a structure of a single-disk optical disk having no warp and a method for manufacturing the same.

[0002]

2. Description of the Related Art Generally, a transparent synthetic resin substrate such as polycarbonate (PC) or acrylic (PMMA) is used as a substrate of an optical disk. This is because the synthetic resin substrate is superior in mass productivity to the glass substrate and is low in cost. However, in the production process of an optical disc using a synthetic resin substrate, there is always a warp in each process of production such as a warp when the substrate is molded and injected, a warp due to the stress of the optical recording medium film, a warp due to the stress of the protective film and the like. Likely to happen.

This warp makes tracking and focusing of the optical disk difficult. In order to eliminate the warp of the substrate, it is necessary to adjust the manufacturing conditions (injection molding conditions, sputter rate conditions, curing shrinkage conditions of the protective film, etc.) in each process of production to reduce the warp. Conventionally, for example, the warpage of a substrate during injection molding has been corrected by laminating the substrates. A method for preventing the warp due to the stress of the optical recording medium film is disclosed in JP-A-4-67.
332 etc.

[0004]

However, products using a single plate as a substrate (3.5-inch optical disc, CD
Etc.), the conventional straightening method by laminating cannot be applied to the warp of the substrate at the time of injection molding and the warp generated in other steps of production. That is, in the conventional production of a single-plate optical disc, there was no means other than adjusting the conditions so as to prevent warpage in each of the above-mentioned production steps, and there was no means for correcting the warp of the substrate.

The present invention is intended to solve the above problems, and an object thereof is to provide a structure and a correction method for an optical disk of a single plate, which is capable of correcting a warp generated during injection molding or other manufacturing steps. To provide.

[0006]

In order to achieve the above object, in the present invention, attention is paid to the curing shrinkage action of an ultraviolet curable resin, and the cured resin is applied onto the optical disc and the amount thereof is adjusted to adjust the optical disc. I found to correct the warp.

A method of manufacturing an optical disk according to a first aspect of the present invention aims to prevent oxidative corrosion of a recording layer, a reflective layer, and the two films on one surface (a surface opposite to a laser light incident surface) of a synthetic resin substrate. In addition to providing an ultraviolet curable resin film, an ultraviolet curable resin film is provided on the back surface (laser light incident surface) of the substrate for the purpose of strengthening the hardness of the substrate and preventing dust adhesion due to electrification. In an optical disc provided with a hub in which is intervened as an adhesive, by utilizing the curing shrinkage action of the ultraviolet curable resin at the above three locations,
The warp of the optical disc is generated by generating a stress for correcting the warp of the optical disc.

According to a second aspect of the present invention, in the optical disc manufacturing method according to the first aspect, the amount of the ultraviolet curing resin is adjusted to adjust the stress generated by the curing shrinkage.
It is characterized by controlling the correction amount.

The invention according to claim 3 is the invention according to claim 1 or 2.
In the method for producing an optical disc described above, in the optical disc which is warped concavely with respect to the laser light incident surface of the optical disc substrate by using the curing shrinkage action of the ultraviolet curable resin film for the purpose of preventing oxidative corrosion of the recording layer and the reflective layer. The warp of the disk is corrected by generating a stress that corrects the concave warp.

The invention according to claim 4 is the invention according to claim 1 or 2.
In the method for producing an optical disc described above, a convex shape is applied to the laser incident surface of the optical disc substrate by using the curing shrinkage action of the ultraviolet curable resin for the purpose of strengthening the hardness of the laser light incident face of the optical disc substrate and preventing dust adhesion due to charging. In the optical disc having a warp, the warp is corrected by generating a stress for correcting a convex warp.

The invention according to claim 5 is the invention according to claim 1 or 2.
In the method for producing an optical disc described above, particularly in an optical disc which is convexly warped with respect to an adhesive surface between an optical disc substrate and a hub by using a curing shrinkage action of an ultraviolet curable resin interposed as an adhesive between the optical disc substrate and the hub, It is characterized in that the warp is corrected by generating a stress for correcting the convex warp.

According to a sixth aspect of the present invention, in the optical disc manufacturing method according to the third, fourth or fifth aspect, the warp of the optical disc is corrected by combining the curing shrinkage action of the ultraviolet curable resin at the three locations. Is characterized by.

According to a seventh aspect of the present invention, in the optical disc manufacturing method according to the sixth aspect, the ultraviolet curable resin on the opposite surface is cured as a material of the ultraviolet curable resin provided on the surface for generating the stress for correcting the warp. It is characterized by using a material having a curing shrinkage ratio larger than the shrinkage ratio.

The optical disk according to claim 8 is an ultraviolet curable resin for the purpose of preventing oxidative corrosion of the recording layer, the reflective layer and the two films on one surface (the surface opposite to the laser light incident surface) of the synthetic resin substrate. In addition to providing a film, an ultraviolet curable resin film is provided on the back surface (laser light incident surface) of the substrate for the purpose of strengthening the hardness of the substrate and preventing dust adhesion due to electrification. In the optical disc provided with the hub interposed as above, by utilizing the curing and contracting action of the ultraviolet curable resin at the above-mentioned three places, a stress for correcting the warp is generated for the warp of the optical disc, and the warp of the optical disc is corrected. Is characterized by.

A protective film (recording layer,
A film for preventing oxidation and corrosion of the recording layer, etc. and a hard coat film (film for preventing scratches on the substrate and laser light incident surface).
UV curable resin is mainly used as a material for the adhesive for attaching the hub and the anti-static effect).

These ultraviolet curable resins have a contracting action simultaneously with curing by ultraviolet rays. For example, when the ultraviolet curable resin is applied to a substrate having no warp and cured, the substrate warps. Therefore, it is also possible to utilize the curing and contracting action of the ultraviolet curable resin as a means for flattening the warped substrate.

Generally, the greater the curing shrinkage of the UV curable resin, the greater the amount of warp correction. As a method of controlling the warp correction amount, it is possible to change the correction amount by using several kinds of ultraviolet curable resins having different curing shrinkage rates, but this is not practical in production.

Therefore, in the present invention, as a more realistic method, a method of controlling the correction amount by the amount of the ultraviolet curing resin was devised. That is, generally, when the amount of the ultraviolet curable resin is large, the stress generated between the substrate and the substrate due to curing contraction is large and the correction amount is large, and conversely, when the amount is small, the correction amount is small. [Table 1] shows the relationship between the film thickness and the warp of the two kinds of ultraviolet curable resins. Since the two UV curable resins have different cure shrinkage rates, the amount of warpage is different, but the thicker the film thickness, the greater the warpage.
It can be seen that the correction amount increases.

[0019]

[Table 1]

Next, the method of straightening by curing shrinkage of the respective UV curable resins used for the protective film, the hard coat film and the hub mounting adhesive will be specifically described.

In FIG. 1, the substrate 101 has a laser beam incident surface 104.
On the other hand, it is an example in which it is warped in a concave shape. In the case of the above example, the curing shrinkage action of the protective film 103 causes the substrate to generate a stress 108 in the direction of correcting the warp as shown in the figure, and corrects the warp.

FIG. 2 shows an example in which the substrate 101 is warped in a convex shape with respect to the laser light incident surface 104. in this case,
Due to the hardening and shrinking action of the hard coat film 105, stress 108 in the direction of correcting the warp is generated in the substrate to correct the warp.

Further, FIGS. 3 and 4 show examples in which the bonding surface between the substrate 101 and the hub 106 has a warp. In the case of the hub 106 as shown in FIG. 3, a stress 108 for correcting the warp as shown in the figure is generated by the curing and shrinking action of the adhesive 107, and it is possible to correct the substrate warped in a concave shape with respect to the laser light incident surface 104. is there. Further, in the case of the hub 106 as shown in FIG. 4, the substrate having a convex warp with respect to the laser light incident surface 104 can be corrected by the same action. In an actual disc, the correction amounts of the protective film, the hard coat film and the hub mounting adhesive are adjusted by combining the curing and shrinking actions of the hub mounting adhesive so that the disc is not warped finally. 3 and 4, 102 is a reflective film, 109 is a central hole, and 110 is a metal plate.

[0024]

EXAMPLES Next, the present invention will be described in more detail with reference to examples. Example 1 A method of correcting warpage by a protective film, a hard coat film, and a hub mounting adhesive in a disk in which a substrate warps in a convex or concave shape with respect to the laser light incident surface 104 will be described. Note that the shape of the hub is, for example, a case where there is a mounting contact surface between the hub 106 and the substrate 101 on the protective film 103 side as shown in FIG. When the disk is warped in a convex shape, the hard coat film 105 is made of an ultraviolet curable resin having a higher curing shrinkage than any of the protective film 103 and the hub mounting adhesive 107. By increasing the film thickness of the hard coat film 105, decreasing the film thickness of the protective film 103, and decreasing the amount of the hub mounting adhesive, a large stress 108 in the warp correction direction is generated on the hard coat surface side. , Warp can be corrected. The coating amount of each film and the adhesive is adjusted by the warp amount of the disk and the curing shrinkage ratio. If the disc is concave, the warp can be corrected by reversing the above conditions.
It should be noted that a 3.5-inch magneto-optical disk or the like having no warp can be manufactured by the above method.

Embodiment 2 Next, a method of correcting warpage by the protective film 103 when the disk is concave with respect to the laser light incident surface 104 will be described. Also in this case, by utilizing the curing shrinkage effect of the protective film 103, the warp can be corrected by generating the stress 108 for correcting the concave warp in the substrate on the protective film 103 side. The correction amount can be controlled by the film thickness of the protective film. By the above method, a CD without warpage can be produced.

[0026]

According to the present invention, the warp can be corrected by generating a stress for correcting the warp of the optical disk on the substrate by the curing shrinkage action of the ultraviolet curable resin. That is, it is possible to manufacture a single-plate optical disk and a bonded optical disk, which are warped-free disks by correcting the warpage that occurs during the injection molding and other manufacturing steps.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view explaining a case where a warp of an optical disc is corrected by a protective film.

FIG. 2 is a schematic cross-sectional view illustrating a case where a warp of an optical disc is corrected by a hard coat film.

FIG. 3 is a schematic cross-sectional view illustrating a case where a hub mounting agent corrects a warp of an optical disc that is concavely warped with respect to a laser light incident surface.

FIG. 4 is a schematic cross-sectional view illustrating a case where a hub mounting agent corrects a warp of an optical disc that is convexly warped with respect to a laser light incident surface.

[Explanation of symbols]

 101 Substrate 102 Reflective Film 103 Protective Film 104 Laser Light Incident Film 105 Hard Coat Film 106 Hub 107 Adhesive 108 Stress 109 Center Hole 110 Metal Plate

Claims (8)

[Claims] 1. A synthetic resin substrate is provided with a recording layer, a reflection layer, and an ultraviolet-curable resin film for the purpose of preventing oxidative corrosion of the two films on one surface (the surface opposite to the laser light incident surface), and the above-mentioned substrate. A UV-curable resin film is provided on the back surface (laser light incident surface) for the purpose of strengthening the hardness of the substrate and preventing dust from adhering due to electrification. Furthermore, a hub with an UV-curable resin as an adhesive is provided in the center of the substrate. In the optical disc, a curing shrinkage effect of the ultraviolet curable resin at the above-mentioned three locations is used to generate a stress for correcting the warp of the optical disc, thereby correcting the warp of the optical disc. Method. 2. The optical disc manufacturing method according to claim 1, wherein the amount of the ultraviolet curing resin is adjusted to adjust the stress generated by the curing shrinkage, and the correction amount is controlled. . 3. The method for producing an optical disk according to claim 1, wherein the laser light incident surface of the optical disk substrate is formed by using the curing shrinkage action of the ultraviolet curable resin film for the purpose of preventing oxidative corrosion of the recording layer and the reflective layer. On the other hand, in a concavely warped optical disc, a method for producing an optical disc is characterized in that the warp of the disc is corrected by generating a stress for correcting the concave warp. 4. The optical disk manufacturing method according to claim 1, wherein the hardening and shrinking action of the ultraviolet curable resin is used for the purpose of strengthening the hardness of the laser light incident surface of the optical disk substrate and preventing dust adhesion due to charging. In the optical disc which is convexly warped with respect to the laser incident surface, the warp is corrected by generating stress for correcting the convex warp. 5. The optical disc manufacturing method according to claim 1 or 2, wherein the curing shrinkage effect of an ultraviolet curable resin interposed as an adhesive between the optical disc substrate and the hub is used to make a projection on the bonding face between the optical disc substrate and the hub. A method for producing an optical disc, which comprises correcting a warp by generating a stress for correcting a convex warp in the curved optical disc. 6. The method for producing an optical disc according to claim 3, 4 or 5, wherein the warp of the optical disc is corrected by combining the curing shrinkage action of the ultraviolet curable resin at the three locations. Method. 7. The method of manufacturing an optical disk according to claim 6, wherein the material of the ultraviolet curable resin provided on the surface for generating the stress for correcting the warp is a curing shrinkage larger than the curing shrinkage rate of the ultraviolet curable resin on the opposite surface. A method for manufacturing an optical disk, characterized in that a material having a high index is used. 8. A synthetic resin substrate is provided with a recording layer, a reflective layer, and an ultraviolet-curable resin film for the purpose of preventing oxidative corrosion of the two films on one surface (the surface opposite to the laser light incident surface), and the above-mentioned substrate. A UV-curable resin film is provided on the back surface (laser light incident surface) for the purpose of strengthening the hardness of the substrate and preventing dust from adhering due to electrification. Furthermore, a hub with an UV-curable resin as an adhesive is provided in the center of the substrate. In the optical disc, the warp of the optical disc is corrected by generating a stress for correcting the warp of the optical disc by utilizing the curing shrinkage action of the ultraviolet curable resin at the three locations.