JPH01278322A - Disc injection molding die - Google Patents

Abstract

PURPOSE:To manufacture a disc injection molding die of simple structure with which optical distortion can hardly remain by providing a plurality of cooling openings for adjusting and controlling the temperature in a cavity along the cavity in a manner that the temperature difference can be made between inner and outer peripheries. CONSTITUTION:An injection molding die is provided with a fixed side mold 1 and a movable side mold 2, and the movable side mold 2 is opened and closed by means of a hydraulic cylinder or the like. A guide channel or a stamper 6 which will turn into a matrix with information written on is fixed to the movable side mold 2 by means of an outer ring 3, and a spool 4 forms a flow inlet in which molten high molecular substance flows to the inside of a cavity 5. The diameter of a cooling opening 7 gets larger from the inner peripheral side toward the outer peripheral side to control the temperature of the innermost side and outermost side of the cavity 5 between 1-10 deg.C. When the molten high molecular substance is injected into the cavity 5, the cooling and solidifying speed on the peripheral side is controlled by setting the temperature of the outer peripheral side (end section) in the cavity 5 higher than that of the inner peripheral side, and the temperature distribution of the molten high molecular substance becomes constant in the cavity at the time of completion of filling to manufacture a disc base with small residual stress.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a disk injection mold for molding the substrate of an optical information recording disk that writes and reads information by irradiating it with a light beam. It is something.

[Conventional technology]

In recent years, as such optical information recording disk substrates, substrates made by injection molding of transparent thermoplastic polymer materials, which are inexpensive to manufacture, lightweight, and easy to handle, have been considered.

However, in injection molded products made of polymeric materials, not only are external defects such as weld lines and cracks easily formed in the gate area and surrounding areas, but also uneven injection pressure and temperature distribution during molding. Additionally, there is a problem in that distortions are likely to occur due to the orientation of the molten polymer material as it flows through the cavity surface of the mold.

Optical information recording discs read and write information by irradiating a light beam onto the disc substrate and reflecting the light from recording grooves on a reflective film formed on the inner surface of the disc. Birefringence greatly affects the quality of the material.

In view of the above requirements, a method for manufacturing a disk substrate with low birefringence has been desired, and a mold thereof has also been developed.

Conventionally, injection compression molds have been used to prevent appearance defects such as weld lines and sink marks, as well as residual stress during molding, as shown in Figure 4. , a resin reservoir 10 is provided on the outer periphery, and a resin filling detection sensor 11 is further provided (Japanese Patent Application Laid-Open No. 61-8
0634), and as a method to prevent optical distortion caused by the orientation of the molten polymer material during injection molding, there is a method in which the polymer material flowed into the mold is molded while applying ultrasonic vibrations. is known (Japanese Unexamined Patent Publication No. 58-14022)
2).

In FIG. 4, reference numeral 1 indicates a fixed side mold, and 2 indicates a movable side mold, and the movable side mold is closed and opened by a hydraulic cylinder or the like. 4 is a sprue that serves as an inlet for the molten polymer material to flow into the cavity 5, 6 is a guide groove or a stamper that is a master disk on which information is written, 9 is a throttle member, 10 is a resin reservoir, and 11 is a resin filling detection sensor. It shows.

[Problem to be solved by the invention]

However, in the former injection compression molding mold equipped with the resin filling detection sensor 11, the temperature of the mold cavity surface is constant, so when the molten polymer material flows in, it is inevitable that the gate part and the outer peripheral end part Temperature differences occur, resulting in differences in residual stress during cooling, and this is not a complete removal method.

In addition, the latter method of removing residual strain using ultrasonic vibration aims to make the optical properties uniform by remelting the solidified molded product, so the polymer material is likely to be heated to an unduly high temperature, resulting in deterioration. There is a risk that new problems will arise.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain a disk injection mold that has a simple structure and is less likely to leave optical distortion.

[Means to solve the problem]

In the disk injection mold according to the present invention, cooling holes for adjusting and controlling the temperature inside the cavity are arranged so as to create a temperature difference from the inner circumferential side to the outer circumferential side.

[Effect]

In this invention, when the molten polymer material is injected into the cavity, the temperature of the outer circumferential side (end part) in the cavity is set higher than that of the inner circumferential side, thereby suppressing the cooling and solidification speed of the outer circumferential side. However, when the molten polymer substance is completely filled into the cavity, the temperature distribution becomes constant, and a disk substrate with less residual stress can be obtained.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a simplified sectional view of a disk injection mold according to an embodiment of the present invention. In FIG. 1, 1 is a stationary side mold;
2 is a movable mold, and the mold is closed and opened by a hydraulic cylinder or the like. 3 is a guide groove or an outer circumferential ring for fixing the stamper 6, which serves as a master disk on which information is written, to the movable mold 2;
A sprue 4 serves as an inlet through which the molten polymer material flows into the cavity 5. Reference numeral 7 denotes a temperature control cooling hole for adjusting the temperature of the cavity 5. The diameter of this cooling hole increases from the inner circumferential side to the outer circumferential side, and the temperature difference between the innermost circumferential side and the outermost circumferential side is 1. It is possible to control the temperature between ~10°C.

FIG. 2 shows another embodiment of the present invention, in which the temperature control cooling holes 7 are all made the same diameter, and instead, new temperature control cooling holes 8 with a smaller diameter are placed closer to the surface of the cavity 5. It is arranged so that a temperature difference can be created between the inner and outer circumferences.

FIG. 3 shows a comparison of the birefringence values of a substrate molded using the mold of the present invention with conventional values. As is clear from this graph, it can be seen that a good substrate is produced with little variation in birefringence between the inner and outer peripheries.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to obtain a disk substrate made of a polymer material with less thermal distortion due to residual stress, and it is possible to produce a disk substrate with high precision and high quality.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a disk injection mold according to an embodiment of the present invention, FIG. 2 is a vertical cross-sectional view showing another embodiment of the present invention, and FIG. 3 is a conventional product and a mold according to the present invention. FIG. 4 is a graph showing the comparison of birefringence of substrates molded with a disk injection mold. FIG. 4 is a vertical cross-sectional view of a conventional disk injection mold. In the figure, 1 is a fixed side mold, 2 is a movable side mold, 3 is a stamper outer periphery press ring, 4 is a sprue, 5 is a cavity, 6 is a stamper, 7 is a cooling hole for temperature control, and 8 is a cooling hole for auxiliary flat stamping. . Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] In a mold for injection molding a disc substrate of a predetermined shape at high speed and high pressure, multiple cooling holes are arranged along the cavity to adjust and control the temperature inside the cavity to create a temperature difference between the inner and outer circumferences. A mold for disc injection molding.