JPH11277578A - Mold for molding thin-walled disc and manufacture of thin-walled disc - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent occurrence of a thickness difference of a disc base plate in inner and outer circumferential directions by specifying a thickness of a minimum plate at a center of both fixed and movable side mold bodies for holding both fixed and movable side mirror surfaces for receiving an inner pressure to pressurize a resin. SOLUTION: A melted plastic resin is injected in a disc formed by clamping fixed and movable side mold bodies 3, 4, an information pit of a stamper 9 is transferred to the resin, and a disc base plate 15 is molded. A mold in which a minimum plate thickness X thinned in a thickness of the body 3 is set to 50 mm or more by a sprue bush 7 installed on the body 3 fixed to a fixed side platen 1 and a minimum plate thickness X thinned in thickness of the body 4 fixed to a movable side platen 2 is set to 50 mm or more is used. Thus, a thickness difference in a circumferential direction is set to 5 μm or less to obtain a uniform disc base plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for forming a thin disk, and a method of manufacturing a thin disk using the same. More specifically, by providing a disk molding die having a large recording area and a small thickness difference of the thin disk as a thin disk molded product for recording, and a method of manufacturing a thin disk using the same, the warpage of the disk substrate, An object of the present invention is to provide a disk substrate having excellent surface deflection during rotation and excellent mechanical characteristics.

[0002]

2. Description of the Related Art Conventionally, as one method of forming a disk such as a thin-walled disk, a mold having a space (cavity) corresponding to a desired disk shape is used inside a mold, and the mold is melted in the cavity. There is a method of molding a disc by injecting, cooling, and solidifying a plastic resin or the like, which is called a so-called injection molding method.

Usually, a mold used in such an injection molding method has a structure in which one plane passing through a cavity is a cut surface and can be horizontally divided into two parts. At the time of recording disk molding, plastic molten resin injected into the cavity is
By bringing the movable mold half (hereinafter referred to as the movable mold body) into pressure contact with the fixed mold half (hereinafter referred to as the fixed mold body) of the mold, The information pits and grooves are transferred to the recording surface of the stamper disk with a molten plastic resin.

[0004] Thereafter, the disk substrate is cooled, and after the cooling is completed, the movable body is separated from the fixed mold body, and the molded product (disk substrate) is taken out of the mold and post-processed to be used as a product. .

FIG. 1 shows an example of a conventional mold used for injection molding of such a disk. FIG. 2 shows the appearance of an injection molding machine in which the mold is installed.

[0006] Recently, due to the improvement of the performance of the molding machine, the molding machine body has been miniaturized, and the distance between the tie bars 18 for operating the movable side platen 2 has also been reduced. Therefore, the disk mold has also been miniaturized. ing.

In this mold, the center of the mold is provided with components for differentially moving the movable cut punch 8 and the floating punch 12 and the like. Therefore, the structure is complicated and the inside of the movable body 4 is greatly hollowed out. ing. For this reason, the central portion X of the movable-side mold mirror surface 6 has a structure having a slight distortion. Since the strength of the mold plate thickness is proportional to the square of the plate thickness ratio,
Reducing the thickness of the mold body greatly reduces the strength.

In addition, the fixed mold body 3 is thinned as well as the mounting portion of the sprue bush 7 of the fixed mold.
The fixed-side mirror surface 5 also has a structure having a distortion similarly to the movable-side mirror surface 6.

This mold comprises a fixed platen 1 and a movable platen 2, a fixed mold body 3 and a movable mold body 4, and a nozzle 1
The molten plastic resin injected from 7 is inserted into the space between the fixed and movable mirror surfaces, that is, the disk substrate 15, pressurized by the movable platen 2, and the movable mirror surface 6 is moved through the movable mold body 4. Then, the molten plastic resin is pressed into contact with the substrate, and the molten plastic resin is transferred to the recording surface of the disk substrate by the stamper 9 to form a substrate such as a disk. At this time, the sprue 16 is cut by the cut punch 8, cooled as it is at the same time as the disk substrate 15, and the movable die opening is performed.
The disk substrate 15 is lifted from the movable mold by the 1 and the floating punch 12, the sprue 16 is taken out simultaneously with the disk substrate 15 by a robot or the like, only the sprue 16 is removed, and the disk substrate 15 is sent as a product to the next step.

In this state, fixing by pressing the disk substrate, fixing holding the inner peripheral portion of the movable mirror surface, and movable mold bodies 3 and 4 are used to install cut punches, sprue bushes, and other components inside the mold body. It is greatly hollowed out.
For this reason, when the molten plastic resin in the cavity is pressurized, the central portions of the two mirror surfaces 5 and 6 of the mold are slightly distorted, and when cooled as it is, a difference in thickness occurs between the inner and outer circumferences of the disk substrate as shown in FIG.

In the conventional disk substrate manufacturing, the cycle time is long and the substrate is cooled slowly,
The thicknesses of the movable side mirror surfaces 5 and 6 were large, and the mirror surface contributed to the thickness unevenness of the disk base in terms of strength. In addition, the conventional disk substrate is not a numerical value in which the thickness difference between the inner and outer peripheries is a problem due to its characteristics.

However, in order to reduce the cycle time of the product and to make the thickness of the disk substrate thinner, and to increase the cooling speed, the distance between the disk surface and the cooling water channel is shortened. The thickness of the mirror surfaces 5, 6 has become thinner, and it has become common to increase the amount of mold cooling water in order to increase the mold cooling speed. For this reason, the temperature in the mold is made uniform, the disc can be sufficiently molded even if the mold body is downsized, and the mold body has been reduced in weight in consideration of handling, workability, and the like. .

For this reason, it has been found that in a recent high-density molded product having a thinner disk substrate, a difference in the inner and outer peripheral thicknesses of the conventional disk substrate causes a problem in substrate characteristics. It is necessary to improve the thickness difference with respect to.

[0014]

The plastic substrate used for such a disk substrate has a thickness of about 0.2 to 1.5.
mm and a diameter of about 30 to 300 mm, and an acrylic resin or a polycarbonate resin is generally used as a material. In the disk substrate molding, the following problems have occurred in the conventional mold.

First, the space between the tie bars 18 is reduced due to the miniaturization of the equipment main body due to the improvement of the molding machine performance, and the disk mold inserted between them is also designed to be miniaturized. In this mold, the plate thickness of the movable-side mold body 4 is also reduced, and particularly, in the portion where the movable-side cut punch 8 and the floating punch 12 are operated, the hollow portion of the movable-side mold body 4 is structurally large. Mold body 4 center X
2 is as thin as 25 to 40 mm.

For this reason, for example, the plate thickness of X2 is 35 mm
When the thickness of the recording portion of the disk substrate is measured, the inner peripheral portion is suddenly thicker than the outer peripheral portion as shown in FIG. 3 and a thickness difference of 5 to 12 μm is generated. When the thickness difference of the circumferential portion is included in this, a large thickness difference occurs.

Similarly, both the fixed-side mold body 3 and the fixed-side sprue bush 7 have the same structure as the movable-side cut punch 8, and a difference of 5-12 μm is generated between the outer circumference and the outer circumference.

[0018]

As a result of intensive studies on such a problem, this thickness difference is proportional to the resin pressure in the cavity as shown in FIG. It is presumed that it is not due to the condition but due to the mechanical elastic action of the mold body, that is, due to the distortion of both the fixed and movable mirror surfaces 5, 6. It has been found that a thin disk with less unevenness in thickness can be manufactured.

That is, the present invention relates to a mold for molding a thin-walled disc having a cavity between both mirror surfaces of the fixed and movable molds, injecting a molten plastic resin therebetween, and applying pressure from the movable platen. The minimum plate thickness (X1, X2) at the center of both the movable side mold main bodies is fixed to 50 m, fixed to receive the internal pressure to pressurize the resin, fixed to hold both mirror surfaces on the movable side.
It is intended to provide a mold for forming a thin-walled disc characterized by having at least m.

Further, the present invention is characterized in that the center portion of the movable mold body is provided with a hollow for operating a cut punch or a floating punch, and in particular, the diameter of the cavity is 30 to 300 mm and the depth is 30 mm. 0.2-1.5mm
It is intended to provide a mold for molding a thin-walled disc characterized by the following.

The present invention also provides a method of manufacturing a thin-walled disc having a cavity between both mirror surfaces of a fixed and movable mold and injecting a molten plastic resin therebetween and pressing the resin from the movable platen. It is characterized in that a mold having a minimum thickness (X1, X2) of 50 mm or more at the center of both the movable-side mold main bodies is used. It is intended to provide a method of manufacturing a thin disk.

In particular, the present invention relates to such a thin disk having a diameter of 3
0 to 300 mm, a thickness of 0.2 to 1.5 mm, and a center portion thereof is hollowed out, in particular, the resin is an acrylic resin, a polycarbonate resin, an epoxy resin, an amorphous olefin resin, or An object of the present invention is to provide a method for producing a thin-walled disc characterized by using these copolymers.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION In a molding die composed of a fixed die body and a movable die body, a plastic resin that is melted is injected into a cavity for forming a thin disk, and the movable die body is moved from the movable platen. In turn, the mold mirror surface is pressurized with hydraulic pressure, etc. to form a thin disk, but a cut punch, a sprue bush, etc. are installed and operated in the center of the mold, so the center of the mold body is greatly hollowed out ing. In this case, by making the thickness of the die body of the die body hollowed portion such that the mirror surface of the die is not distorted, the difference in substrate thickness between the inner and outer peripheries of the recording surface of the substrate when the thin disk is pressed is reduced. It is characterized by doing.

The above problem is achieved by the following. That is, the configuration of the first invention according to the disk substrate molding die of the present invention includes the stamper 9 formed by forming information pits and grooves on the information transfer surface. The molten plastic resin is injected into a cavity formed by clamping the molds 3 and 4, and the information pits and grooves of the stamper 9 are transferred to the molten plastic resin to form a disk substrate. In the disk substrate molding die, the distortion of the mirror surfaces 5 and 6 of the fixed and movable molds is changed by the resin pressure in the cavity.
A structure that does not distort, that is, the minimum thickness X2 of the movable-side mold body 4 is set to 50 mm or more even in the hollow part of the movable-side mold body 4 of the movable-side cut punch 8, and The movable-side mold main body 4 having the same mold strength as that of the part where the strength is maintained is required.

The fixed side sprue 7 is also hollow at the center of the fixed side mold body 3 in the same manner as described above, is weak in strength, is pressed by the movable side platen, and has a mirror surface due to the pressure of the molten plastic resin. The distortion at the inner periphery is greater than at the outer periphery. For this reason, the minimum thickness X1 of the fixed-side mold body 3 at the inner peripheral portion needs to be 50 mm or more.

In the production of the thin disk of the present invention, an acrylic resin, a polycarbonate resin, an epoxy resin, an amorphous olefin resin, or a copolymer thereof can be used as the resin, and inorganic glass or the like can be used. I can do it. Among them, acrylic resin and polycarbonate resin are particularly preferable for producing a recording disk substrate.

[0027]

Embodiments of the present invention will be described below with reference to FIG. First, the disk substrate formed using the molding die according to the present invention will be described in detail.

[First Embodiment] In FIG. 1, the plate thickness of the fixed mold body 3 is reduced by the sprue bush 7 installed on the fixed mold body 3 fixed to the fixed platen 1. The plate thickness X1 is set to 50 mm, and the cut punch 8 and the floating punch 12 installed on the movable mold body 4 fixed to the movable platen 2
Molding test using a mold with a minimum plate thickness X2 of 50 mm, the thickness of the movable side mold body 4 being reduced by 50 mm, a disk substrate thickness of 1.2 mm, an outer diameter of 120 mm, and a pressure in the cavity of about 30 MPa. Was carried out.

As a result, when a conventional mold having X1 and X2 of 35 mm was used, the difference between the inner and outer circumferences was 12 μm.
In the mold test of the present invention, the thickness could be reduced to 5 μm or less. Further, the test was carried out by increasing the pressure in the cavity with this mold, and a uniform disk substrate could be obtained without increasing the thickness unevenness of the substrate in the inner and outer peripheral directions as compared to the preceding paragraph.

[Second Embodiment] In the first embodiment, the fixed side
The thickness of the central part of the movable mold body (X1, X2) is 75m each
A molding test was carried out under the same conditions using a mold set to m. As a result, in the mold test of the present invention, the difference between the inner and outer circumferences could be reduced to 3.5 μm or less.

[0031]

According to the present invention, in a thin-walled disk forming die having a space corresponding to a desired thin-walled disk shape when injection molding a thin-walled disk, a plastic resin melted in a portion forming the space. And the thickness of the disk substrate can be reduced to 5 μm or less in the circumferential direction of the disk substrate with respect to the mold structure without distorting the inner and outer peripheries of the die mirror surface when the disk substrate is molded and pressed. A thin-walled disk forming die that can form disks has been realized. As a result, warpage and surface runout were reduced to 以下 or less, and the mechanical properties of the disk substrate were improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a disk injection molding die.

FIG. 2 is an external view of an injection molding machine in which a mold is installed.

FIG. 3 is a thickness difference diagram with respect to the inner and outer peripheries of a substrate.

FIG. 4 is a diagram showing the difference between the internal cavity pressure and the thickness of the substrate.

[Explanation of symbols]

 1. Fixed side platen 2. 2. Moving platen Fixed mold body 4. Movable mold body5. Fixed side mirror surface 6. Movable mirror surface 7. Sprue bush 8. Cut punch 9. Stamper 10. Cavitation 11. Sprue retainer 12. Floating punch 13. Sprue cooling pipe 14. 14. Cut punch cooling pipe Disk substrate 16. Sprue 17. Nozzle 18. Tie bar 19. Molding machine body X1. Fixed side die body center plate thickness X2. Movable mold body center plate thickness

Claims (6)

[Claims] 1. A mold which has a cavity between both mirror surfaces of a fixed and movable mold and injects a molten plastic resin therebetween and pressurizes from a movable platen to form a thin disk. A mold for forming a thin disk, wherein the minimum thickness of the central portion of both the fixed and movable mirror main bodies which receives the internal pressure to pressurize and the movable and movable mirror surfaces is 50 mm or more. 2. The thin disk molding die according to claim 1, wherein a center portion of the movable die main body is formed with a hollow for operating a cut punch and a floating punch. 3. The cavity has a diameter of 30 to 300 m.
3. A mold for forming a thin disk according to claim 1, wherein the mold is a cylindrical space having a depth of 0.2 to 1.5 mm. 4. A method for manufacturing a thin-walled disc having a cavity between two mirror surfaces of a fixed and movable mold and injecting a molten plastic resin therebetween and pressurizing the resin from a movable platen. A method of manufacturing a thin disk, comprising using a mold having a minimum plate thickness of 50 mm or more at the center of both the fixed and movable side mold main bodies, wherein the fixed and movable side mirror surfaces which hold both internal surfaces of the fixed and movable sides are received. 5. The thin disk having a diameter of 30 to 300 mm,
5. The method for producing a thin disk according to claim 4, wherein the thickness is 0.2 to 1.5 mm, and a center portion thereof is hollowed out. 6. The resin according to claim 1, wherein the resin is an acrylic resin, a polycarbonate resin, an epoxy resin, an amorphous olefin resin,
6. The method for producing a thin-walled disk according to claim 5, which is a copolymer thereof.