JPH0469828A - Production of optical disk substrate - Google Patents

Abstract

PURPOSE:To smoothly perform degassing for molding to improve the birefringence and the transferability by forming a ruggedness on the outside of an optical disk area on a stamper which forms pits and grooves on the resin material of an optical disk substrate. CONSTITUTION:The gap between a stamper 9 and a stamper retaining ring 10 in a part A is used for escape of air and gas. Since pits and grooves are provided even on the inside of the stamper retaining ring 10, air and gas can be driven out along pits and grooves even if the stamper retaining ring 10 is brought into contact with the stamper 9. Consequently, the resin formed base material is molded in a uniform condition especially in the outer peripheral part because the stamper 9 is freely expanded and contracted. Thus, the birefringence and the transferability in the outer peripheral part are improved, and the resin material is easy to flow in by the existence of pits and grooves.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method of manufacturing an optical disk substrate, such as an optical disk or magneto-optical disk (typified by an optical disk), which is mainly used as an optical information recording medium. .

2. Description of the Related Art Optical disk devices, like magnetic disk devices, are used as storage devices for computers and the like, and also for optical video disks and the like. The optical disk substrate used in this optical disk device is made of transparent plastic such as acrylic resin or polycarbonate resin, or a disk made of glass, and the surface thereof is coated with aluminum (A1), palladium (Pd), selenium (Se). A typical example is one in which a metal film such as tellurium (Te) is formed as a recording layer (reflective film layer). When the base material of the optical disk substrate is plastic, it is an ultraviolet curing type or a similar type of base material (protective plate) that does not have a reflective film layer through an adhesive such as a hot melt agent, or
By laminating a substrate with a reflective film layer similar to that described above, it can be used as a single-sided or double-sided optical disk substrate.

Hereinafter, a typical manufacturing method of an optical disk substrate that has been put into practical use will be described with reference to the drawings.

5 to 8 are diagrams showing a conventional method of manufacturing an optical disk substrate. 1 in Fig. 5 is a resin molding base material that can be used for molding methods such as injection molding, compression molding, and casting.
Δ~l A stamper with a fine pit diameter, groove width, and groove depth of 20 OA is set in a part of the mold, and a transparent resin is injected. 2 in FIG. 6 is a reflective film layer, which is coated on the signal surface (pit and groove molding surface) of the resin molded base material 1.
1. A metal film of tellurium, selenium, aluminum, etc. is formed by a method such as sputtering or vapor deposition.

3 in FIG. 7 is an adhesive layer, and reflective films N2 a, 2b
The resin molded base materials 1a and lb formed with the above are bonded together. Adhesive P! 3, when the resin molded base materials 1a and 1b both form reflective films N2a and 2b, a thermosetting adhesive is used, and one side is simply a resin molded base material that does not form a reflective film layer. If so, an ultraviolet curing type adhesive is used. 4 in Figure 8 is an adhesive layer using a hot melt agent as an adhesive, and 5 is an outer coating layer, which is used to improve bonding strength and life characteristics, and is an ultraviolet curing type adhesive. This is done through a process of coating the outer periphery with a chemical agent. In Fig. 9, the shaded part 6 is the resin molded base material I.
This is a schematic representation of the area occupied by the pits and grooves formed in the IE1.
No pits or grooves are formed on the outermost peripheral end surface.

As described above, in the conventional manufacturing of optical disk substrates, the reflective film layer 2 is formed on the resin molded base material l on which pits and grooves are not formed on the outermost edge surface, and when both sides are used, the same process is performed. An optical disk substrate is manufactured by bonding the reflective film N2 formed through the process and, in the case of single-sided use, a simple resin molded base material 1 on which no reflective film layer 2 is formed via an adhesive layer 3. Ru.

Problems to be Solved by the Invention However, in the production of the above-mentioned optical disk substrate, pits and grooves are not formed up to the outermost peripheral end surface of the resin molding base material. Since the unevenness that forms the grooves is formed only in an area smaller than the outer shape of the resin molded base material, when molding the resin molded base material, it is difficult for debris to escape from the stamper side, resulting in transfer and birefringence near the outer periphery. There are issues that can get worse.

In addition, when the adhesive layer is a hot melt agent as shown in the conventional example shown in FIG.
After the reflective film layer is formed on the resin molded base material, the surface of the reflective film becomes convex and warps, so in the conventional laminating method of applying a photo-melt agent and then laminating with a press, adhesion at the outer periphery is difficult to straighten. Therefore, in terms of life, the bonding surface of the outer peripheral end surface may open, and the electrical characteristics (C/N characteristics, etc.) may deteriorate due to moisture absorption. Therefore, at present,
It has been put into practical use by adding a process of coating only the outer peripheral end face with an ultraviolet curing type adhesive.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for manufacturing an optical disc that solves such conventional problems.

Means for Solving the Problems In the present invention, in a method for manufacturing an optical disk substrate using a resin material, a stamper for forming pits and grooves in the resin material that will become the optical disk substrate corresponds to the optical disk. This method of manufacturing an optical disk substrate is characterized in that unevenness is formed in an area beyond the area.

Effects The present invention has the above-described configuration, which allows gas to escape from the stamper surface side when molding a resin molding base material, and improves transfer and birefringence near the outer periphery. Furthermore, the life of the optical disk substrate is extended, and the outer periphery coating process can be eliminated.

Embodiments Below, embodiments of the present invention will be described with reference to the drawings. 1st
4 to 4 are diagrams for explaining the method for manufacturing an optical disk substrate according to the present invention.

FIG. 1 is a cross-sectional view of a resin molded base material 7 molded by injection molding, and FIG. 2 is a cross-sectional view of the signal surface of the resin molded base material 7, that is, pits and grooves are formed by sputtering, vapor deposition, etc. FIG. 3 is a cross-sectional view showing a reflective film N2 formed on the surface of the device. FIG. 3 shows a reflective film layer 2a formed through the process shown in FIG.
2b is a sectional view of an optical disk substrate in which resin molded base materials 7a and 7b with 2b are bonded together with an adhesive layer 8 interposed therebetween. FIG. FIG. 4 is a sectional view of the main parts of the mold when the resin molding base material 7 is obtained by injection molding, 9 is a stamper, and in the outer periphery, electricity is applied to the area outside the outer diameter of the resin molding base material 7. Forms pits and grooves for signals. 10 is a stamper holding ring, 11 is a fixed side mirror block, 12 is a movable side mirror block, and 13 is a cavity portion for obtaining the resin molded base material 7. Further, 14 indicates a movable outer cylinder, 15 indicates a fixed outer cylinder, and 16 indicates a sprue runner.

A method of manufacturing the optical disk substrate of this embodiment configured as described above will be explained.

The resin molded base material 7 shown in FIG. 1 is molded using the indexing mold shown in FIG. Depth is 500A~12
Fine pits and grooves of 0OA are formed. Conventionally used acrylic resins and polycarbonate resins are used as materials for the resin molding base material 7, but polycarbonate resins have particularly high photoelastic coefficients, poor birefringence properties at the outer periphery, and poor transferability. However, providing pits and grooves at the outermost edge according to the present invention has the advantage that the surface condition is made uniform all the way to the outermost circumference, thereby making the flow state of the resin uniform. That L,
Gas escape from the part shown in part A in FIG. 4 toward the outer periphery is improved, which is effective for improving the birefringence and transferability of the outer periphery.

Next, in forming the reflective film N2 in FIG.
Forming the reflective film layer 2 on the inner side of the outer diameter of the resin molded base material 7 is stronger in terms of bonding strength at the outer peripheral end, and is more effective in terms of the intention of the present invention.

In the process shown in Fig. 3, the two resin molded base materials 7a and 7b with the reflective film N2 are bonded together via the adhesive M8, but a hot melt agent or a thermosetting type can be used as the adhesive M8. . By the way, when a hot-melt agent is used as the adhesive layer 8, the adhesive N8 is laminated with a knive press after roll coating, but since air bubbles are mixed into the adhesive N8, the life of the properties in the weather test is significantly deteriorated. Furthermore, since the bonding strength deteriorates quickly at the outer periphery, when using a hot melt agent as the conventional adhesive N8, after going through the process shown in Figure 2, an ultraviolet curing type overcoat is applied to the surface of the reflective film layer 2. The discs are made by applying a coating agent and pasting them together. However, in the present invention, since the pits and grooves are formed up to the outermost edge, the bonding strength at the outermost edge is the same as that of the adhesive layer 8 and the resin if the adhesive N8 is a thermosetting type. The strength between the molding base materials 7a and 7b is also the adhesive layer 8.
If is a hot melt agent, the strength between the overcoat layer and the resin molded base materials 7a, 7b will be increased,
It is no longer necessary to apply the outer periphery coating on the outer periphery end face from the viewpoint of bonding strength as in the past.

In addition, when using a hot melt agent as the adhesive layer 8, the hot melt agent is applied with a roll as described above and then bonded together using a knife press. ) also has a large warpage, which must be corrected while bonding. Therefore, after lamination, internal stress remains, especially in the outer periphery, and stress remains in the direction in which the end face intersects, causing the overcoat layer and the resin molded base material 7 to separate, and moisture absorption from the outer periphery end face to occur, resulting in deterioration of life. Although this problem is easy to occur, the present invention can solve this problem.

FIG. 4 shows an injection mold for molding the resin molding base material 7 of FIG. 1. A movable outer cylinder 14 includes a movable mirror surface 12 to which a stamper 9 for forming signal pits and grooves on the outermost edge of the optical disc substrate is attached, and a stamper holding ring 10 for determining the outer diameter of the resin molded base material 7. It is inserted into the molding machine and attached to the movable side (moving side). On the other hand, the fixed side mirror surface 11 is inserted into the fixed side outer cylinder 15 and attached to the fixed side of the molding machine. Fixed side outer cylinder 15 and movable side outer cylinder 1
4 and 20 or more high-pressure mold clamping is performed to form a cavity 13 in which the resin molded base material 7 is formed. A molten resin with excellent optical properties, such as polycarbonate resin or acrylic resin, is filled into this cavity 13 from a sprue runner 16 at high pressure and high speed, and is solidified into the resin molding base material 7.
is obtained. The center hole of the resin molded base material 7 is punched out during molding together with the sprue runner I6.

When injection molding is performed using this method, the opening gap between the stamper 9 and the stamper holding ring 10 at the entrance is originally
Since it is used as an air and gas escape, it is extremely difficult to manage the gap.

In other words, if the gap is too large, it will become loose, and if it is too small, the stamper 9 will be pressed against the stamper holding ring 10, causing distortion in the expansion and contraction of the stamper 9 due to heat during injection, increasing birefringence, and causing pits and grooves to form. Transfer becomes shallow,
Furthermore, it may cause multiple transcription. However, in the present invention, the pits and grooves, which are examples of irregularities formed on the stamper 9, are provided to the inside of the stamper holding ring 10, that is, they are provided to the outside beyond the corresponding area of the resin molded base material 7. Therefore, even if the stamper holding ring 10 is in contact with the stamper 9, air and gas can be expelled through the pits and grooves. Therefore, air and gas escape is better compared to the case where the stamper holding ring contacts the mirror surface of the conventional Sudan bar, and as a result, the stamper 9 can be expanded and contracted freely. It becomes easier to mold under uniform conditions. Therefore, the birefringence and transferability at the outer periphery are also improved compared to the prior art. Furthermore, the presence of the pits and grooves makes it easier for the resin material to flow.

Note that the present invention is not limited to a type in which two resin molded substrates are bonded together, but is also applicable to an optical disk substrate having a single-plate structure that does not have a bonded structure.

Effects of the Invention As described above, the present invention is characterized in that the unevenness is formed in the outer area beyond the area corresponding to the optical disk of the stamper that forms pits and grooves in the resin material that becomes the optical disk substrate. , degassing occurs smoothly during molding,
As a result, birefringence and transferability are improved.

Furthermore, since the bonding strength at the outermost periphery is increased, the outer periphery application step of building up the outer periphery end face with adhesive, which was conventionally performed, is eliminated.

Further, there are effects such as less deterioration of life characteristics due to moisture absorption from the outer peripheral end surface.

[Brief explanation of the drawing]

1 to 3 are diagrams showing an embodiment of the method for manufacturing an optical disk substrate according to the present invention, in which FIG. 1 is a cross-sectional view of a resin molded base material, and FIG. 2 is a cross-sectional view of a resin molded base material with a reflective film layer. 3 is a sectional view of the optical disk substrate, FIG. 4 is a partial sectional view of a mold for molding the resin molding base material of the present invention, and FIG. 5 is a sectional view of the material.
7 and 8 are diagrams showing a conventional method for manufacturing an optical disk substrate, and FIG. 5 is a cross-sectional view of a resin molded base material, and FIG.
The figures are cross-sectional views of a resin molded base material with a reflective film layer, Figures 7 and 8.
The figure is a sectional view of an optical disk substrate, and FIG. 9 is a plan view showing areas of pits and grooves formed in a conventional optical disk substrate. 1, 1a, 1b, 7.7a, 7b---resin molding base material, 2.2a, 2b---reflective film layer, 3.4.8...
・Adhesive layer, 5... Outer coating layer, 9... Stamper,
lO... Stamper holding ring, 11... Fixed side mirror surface, 12... Movable side mirror surface, 13... Cavity. Agent Patent Attorney Matsu 1) Tadashi Road Diagram Figure 4] 1 Fixed side mirror surface 12 Movable g! Mirror surface diagram Figure 9

Claims (4)

[Claims] (1) In a method for manufacturing an optical disk substrate using a resin material, unevenness is formed in an area beyond the area corresponding to the optical disk of a stamper that forms pits and grooves in the resin material that becomes the optical disk substrate. 1. A method of manufacturing an optical disc substrate, characterized in that: (2) The method for manufacturing an optical disk substrate according to claim 1, wherein the unevenness of the stamper is formed in the same manner as the unevenness forming the pits and grooves. (3) The optical disc according to claim 1, characterized in that when forming a reflective film on the resin molded base material obtained by molding, the reflective film is formed inside the outer diameter of the resin molded base material. Substrate manufacturing method. (4) The method for manufacturing an optical disk substrate according to claim 1, 2, or 3, characterized in that the pair of resin molded substrates, at least one of which has a reflective film, are bonded together using a hot-melt adhesive.