JPH0433261B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature control device for a mold for injection molding disc-shaped molded products, particularly optical information recording discs.

Conventionally, there have been devices of this type as shown in FIGS. 1 and 2 (cross-sectional view taken along the line A--A in FIG. 1).

In FIGS. 1 and 2, 20 is the first mold, 30
is the second mold, and the first mold 20 and the second mold 30
A cavity space 40 is formed between the two.

Further, 50b, 60b, and 70b are annular flow paths for cooling water, respectively, and a first cooling area is formed by the cooling water inlet 50a, the annular flow path 50b, and the cooling water outlet 50c, and similarly, the cooling water inlet 60a,
70a, annular channels 60b, 70b and cooling water outlets 60c, 70c form a second (third) cooling zone.

With such multiple spiral cooling channels,
An attempt was made to maintain a uniform temperature throughout the cavity space 40 to reduce residual stress due to heat in the molded product.

However, although such conventional temperature control devices can reduce residual stress over almost the entire molded product, the outermost edge has a large contact area with the mold, so it is difficult to cool the molten resin. There were drawbacks such as residual stress and sink marks on the inner periphery due to the difference in speed.

In particular, in thin-walled molding such as optical information recording disks, when the injection pressure is high, a density gradient is created in the resin near the outer peripheral edge, and residual stress generated during cooling is added to the resin density difference, resulting in birefringence and sink marks. This had a negative effect on signal reading on the outer periphery. (In the case of optical disks, the molded disk becomes part of the optical path of the reading beam.) In addition, sink marks can interfere with the protective film coating on the signal surface, and residual stress can cause cracks on the outermost periphery due to aging. It became the cause.

In addition to controlling the temperature of the mold, possible ways to reduce residual stress and sink marks include creating a gap around the outside of the mold to allow the resin to escape, and increasing the wall thickness around the outside of the molded product. . However, these methods are not preferable because they require changing the shape of the molded product and post-processing.

For reference, the cavity space 4 of the mold when the temperature is set at 100℃ using a conventional temperature control device.
The measurement results of the zero surface temperature are shown below.

Inner circumference of the disk 83℃ Middle circumference of the disk 84℃ Outer circumference of the disk 85℃ Annular member forming the outermost edge of the disk 81℃ In the annular member forming the outermost edge, the contact area between the molten resin and the mold It can be seen that the cavity surface temperature is several degrees lower than that of other parts because of the large value.

An object of the present invention is to overcome the drawbacks of the above-mentioned conventional techniques, and to reduce residual stress, sink marks, etc. near the outermost peripheral edge of a molded product.
Another object of the present invention is to provide a temperature control device that can reduce birefringence.

Hereinafter, the present invention will be specifically explained with reference to the drawings.

FIG. 3 is a sectional view of a temperature control device according to one embodiment of the present invention, and FIG. 4 is a sectional view of the same device according to another embodiment.

In FIG. 3, 1 is the first mold, 2 is the second mold, 3 is the cavity space formed by the first mold 1 and the second mold 2, and 4 is the temperature of the first mold 1. Reference numeral 5 designates a temperature control refrigerant flow path of the second mold 2, 6 a stamper, 7 an annular mold member that contacts the outermost peripheral end surface of the disk, and 8 a mold surface 9 at the outer peripheral end of the cavity. 1 is an air gap, and 10 is a coolant flow path for controlling the temperature of the annular mold member 7. 11
is a bush, and a spill 12 for flowing molten resin into the cavity space 3 is formed.
Although it is possible to bring the outer peripheral end of the annular mold member 7 into close contact with the first mold 1, if necessary, an air gap 13 may be provided to heat the annular mold member 7 in the same manner as the air gap 9. It may be blocked.

If a mold temperature control device having such a configuration is used, first, the surface temperature of the cavity space 3 is maintained at a uniform temperature across the front surface by the refrigerant flowing through the temperature control refrigerant channels 4 and 5. be able to. This is based on the fact that the present invention also includes the structure for cooling the flat surface of the disk shown in FIGS. 1 and 2 as is. However, in the present invention, the temperature of the annular mold member 7 in contact with the outermost peripheral end surface of the disk is also controlled by the independent refrigerant flowing through the annular refrigerant flow path 10. Therefore, it goes without saying that the mold surface 8 at the outer peripheral end of the cavity can be kept at substantially the same temperature as the other cavity surfaces, but can also be kept at a different temperature depending on the case.

In the above embodiment, the temperature of the annular mold member 7 is adjusted by flowing a coolant through the annular channel 10, but as shown in FIG. It is also possible to heat only the Furthermore, a gap 15 of several microns may be provided at the contact portion between the annular mold member 7 and the second mold 2 to the extent that the molten resin does not flow out, thereby increasing the thermal insulation effect (this is shown in FIG. 3). The same applies to the examples.) Furthermore, instead of the air gaps 9, 13, packings made of a heat insulating material may be used.

As explained above, since the temperature control device of the present invention has the above configuration, it is possible to independently adjust the temperature of the annular mold member that comes into contact with the outermost peripheral end surface of the disk, and therefore It is possible to reduce the residual stress, the accompanying birefringence, and the sink mark that occurs on the inner periphery.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional temperature control device, FIG. 2 is a sectional view taken along the line A-A in FIG. The figure is a sectional view of the same device according to another embodiment. DESCRIPTION OF SYMBOLS 1...First mold, 2...Second mold, 3...Cavity space, 4, 5...Refrigerant channel for temperature adjustment, 7
... Annular mold member, 10 ... Refrigerant channel for temperature adjustment, 14 ... Band heater.

Claims (1)

[Claims] 1. A temperature control device for a mold for injection molding a disk-shaped molded product, in which a temperature control means independent of the cooling means for the flat surface of the disk is provided in the annular mold member that comes into contact with the outermost peripheral end surface of the disk. A temperature control device for an injection mold, characterized by: