JPS61197213A - Injection molding method for precision molded article - Google Patents

Abstract

PURPOSE:To contrive an improvement in productivity by shortening a heating or cooling period of time, by a method wherein a stamper is heated by a noncontacting heating device under a state wherein a stationary mold and movable mold are broken and molten resin is injected and the stamper is filled with the molten resin. CONSTITUTION:A stamper 30 is heated by a noncontacting heating device 40 under a state wherein a movable mold 20 is separated from a stationary mold 10. As for the heating device 40, a device such as hot air supply or heat radiation is used. Then the heating device 40 is removed from a space between the stationary mold 10 and movable mold 20, directly after which the movable mold 20 and the stationary mold 10 are clamped by moving the movable mold 20 in the direction of the stationary mold 10, molten resin is injected into a cavity 35 formed between these molds 10, 20 through a sprue 11 and the cavity 35 is filled with the molten resin. With this construction, as a fine spiral groove of the stamper 30 is filled with the resin a base for a high precision optical disc can be obtained easily.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for injection molding precision molded products such as substrates for optical disks.

(Conventional technology) When injection molding resin, a mold is used.

The molding die has a fixed die and a movable die that can be closed and opened with each other. When injection molding general molded products,
Fixed type and movable type at a temperature below the resin solidification temperature, e.g. approximately 90°.
C, and with the molds closed, molten resin is injected into the cavity, and after the resin has cooled to the mold temperature, it is opened and the molded product is taken out.

In the above method, the temperature of the molding surface is low, resulting in poor transferability.
It is not possible to mold substrates for optical disks. When molding this substrate/board, the temperature of the stamper (molding surface) provided on the movable mold is fixed at or above the resin solidification temperature during resin injection. After heating the mold and moving mold and injection filling with resin, the molds are cooled to the resin solidification temperature. Thus, fixed and mobile heating and cooling cycles are required.

(Problem to be solved by the invention) In the above method,
Since the entire fixed type and mobile type, which have a large heat capacity, are heated and cooled, the heating time and cooling time are long, resulting in poor productivity.

(Means for solving the problem α) The present invention has been made to solve the above problems.
, the main body has a fixed mold and a movable mold that can be opened and closed with each other, and the fixed mold and the movable mold are split open using a molding die in which at least one of the powerful molds is equipped with a stamper. In this state, the tamper is heated by a non-contact heating device, and with the fixed mold and movable mold closed, molten resin is injected into the cavity, and after the molten resin is solidified, the fixed mold and movable mold are closed. This is an injection molding method for precision molded products, the main feature of which is to take out the molded product by splitting it open.

(Function) Since the stamper is heated by a non-contact heating device and the molten resin is injected and filled, it is possible to mold a precision molded product with good transferability and high precision. In addition, fixed molds and movable molds only need to be maintained at or below the resin solidification temperature, which eliminates the need for heating and cooling cycles for molds with large heat capacity, which reduces heating and cooling time and improves productivity. can be done.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. @
1 to 3 show a molding die 1 used when injection molding an optical disk substrate. The molding die 1 includes a fixed die 10 and a movable die 20 that can be opened and closed with each other.

The fixed mold 10 has a sprue 11 in the center and a passage 12 through which a heat medium circulates.

The movable mold 20 is equipped with a disk-shaped stamper 30 having three thicknesses and a fine spiral groove on its surface.

As shown in FIG. 3, a center core 21 is inserted and fixed in the center of the movable mold, and the periphery of the center hole 30a of the stamper 30 is fixed by this center core 21. Further, a ring core 22 is fixed to the movable die 20, and the outer peripheral edge of the stamper 30 is lightly pressed by the ring core 22. Since the stamper 30 is not strongly pressed against the movable mold 20 except for the central portion, a small gap (not shown) is naturally formed between the stamper 30 and the surface 20a of the movable mold 20. The movable mold 2o is provided with a passage 23 through which a heat medium circulates, and an ejecting pin 24 that penetrates the center core 21.

A substrate for an optical disk is injection molded using the molding die 1 having the above configuration. In advance, a heat medium is flowed through each passage 12.23 of the stationary mold 10 and the movable mold 20, and these molds 10.20 are maintained at or below the resin solidification temperature, for example, about 90° C.1. Note that the temperature of this mold 10.20 is such that the molten resin maintains fluidity during injection, which will be described later, and reaches the cavity 35.
The temperature must be above a certain level so that the inside of the container is completely filled.

As shown in FIG. 1, the stamper 30 is heated by a non-contact type heating device 40 while the movable die 20 is separated from the fixed die 10. As the heating device 40, means such as hot air supply, heat radiation, high frequency induction, laser irradiation, etc. can be used. Note that when using a high frequency induction heating device, it is preferable to embed a material insensitive to high frequencies, such as copper or cadmium, on the back side of the stamper 30 to efficiently perform high frequency heating. The above-mentioned heating is performed so that the stamper 3o is heated to a temperature around or above the glass transition point of the resin, for example, about 15"C.
Do this until At this time, the stamper 3, which has a small heat capacity,
0 is heated, and furthermore, a minute gap is formed between the stamper 30 and the surface 20a of the movable mold 2o, and the movable mold 2
Since there is little loss of heat to the stamper 30, the temperature of the stamper 30 can be instantly raised to a predetermined temperature, and the heating time can be shortened.

Next, as shown in FIG.
and the movable mold 20, and immediately after this, the movable mold 20 is moved toward the fixed mold 10 and closed, and these molds 10.2
Molten resin is injected and filled from the sprue 11 into the cavity 35 formed between the holes. As a result, the fine spiral grooves of the stamper 30 are transferred to the resin. As described above, since the stamper 30 is heated to about or above the glass transition point of the resin, good transfer is performed and a highly accurate optical disk substrate can be obtained.

Next, the molten resin is cooled to the temperature of the stationary mold 10 and the movable mold 2 and solidified. The stamper 30, which has a small heat capacity, is the only part that is heated to a high temperature.
Heating at 0 does not particularly extend the cooling time.

Next, the movable mold 20 is moved backward, separated from the fixed IO car, and the ejection pin 24 is activated to take out the molded product.

The present invention is not limited to the above-mentioned embodiments, and various embodiments are possible. For example, the method of the present invention can be applied to molding precision products other than substrates for optical disks. Furthermore, a material with low thermal conductivity may be provided on the back side of the stamper to heat the stamper more efficiently.

(Effects of the Invention) As explained above, in the method of the present invention, since the stamper is heated by a non-contact heating device and molten resin is injected and filled, it is possible to mold a precision molded product with good transferability and high precision. I can do it. In addition, only the stamper needs to be heated, and the stationary type and movable type can be maintained at, for example, the resin solidification temperature or lower, which eliminates the need for heating and cooling cycles for these molds with large heat capacity, reducing heating and cooling times. It is possible to improve productivity.

[Brief explanation of the drawing]

FIGS. 1 and 2 are sectional views illustrating one embodiment of the method of the present invention, and FIG. 3 is an enlarged sectional view showing the support structure of the tamper. DESCRIPTION OF SYMBOLS 1... Molding die, 10... Fixed mold, 20... Movable mold, 30... Stamper, 35... Cavity, 40
...Non-contact heating device

Claims (1)

[Claims] (1) Using a molding die that has a fixed mold and a movable mold that can be opened and closed with each other, and a stamper is provided on at least one of the molds, the stamper can be stamped with the fixed mold and the movable mold separated. is heated by a non-contact heating device, and with the fixed mold and movable mold closed, molten resin is injected and filled into the cavity, and after the molten resin has solidified, the fixed mold and movable mold are split open. An injection molding method for precision molded products, which is characterized by taking out the molded product.