JPH0460013B2 - - Google Patents

Description

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

(Prior Art) 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. Generally, when injection molding a molded product, a fixed mold and a movable mold are maintained at a temperature below the resin solidification temperature, for example, about 90°C, and with these molds closed, molten resin is injected into the cavity, and this resin flows into the mold. After cooling to temperature, it is split open and the molded product is taken out.

In the above method, since the temperature of the molding surface is low, transferability is poor, and precise molded products such as substrates for optical disks cannot be molded. When molding this substrate, etc., during resin injection, the fixed mold and movable mold are heated so that the temperature of the molding surface is higher than the resin solidification temperature, that is, around the glass transition point or higher. After injection filling, the molds are cooled to the resin solidification temperature. Thus, fixed and mobile heating and cooling cycles are required.

(Problems to be Solved by the Invention) In the above method, since the entire fixed mold and movable mold having large heat capacities are heated and cooled, the heating time and cooling time are long, resulting in poor productivity.

(Means for Solving the Problems) The present invention has been made to solve the above-mentioned problems, and its gist is to have a fixed type and a movable type that can be opened and closed with each other. A state in which the fixed and movable inner molds are closed together and the inner and outer molds are separated using a molding mold in which a mold and a movable mold are each composed of an inner mold and an outer mold that can be separated from each other. Then, the inner mold is heated, and with the outer mold in contact with the inner mold, molten resin is injected and filled into the cavity formed between the inner molds, and the inner mold is cooled to solidify the molten resin. The injection molding method is characterized in that the fixed mold and the movable mold are split open to take out the molded product.

(Function) As the fixed and movable inner molds are closed and the outer mold is separated from these inner molds, the inner mold with a small heat capacity is heated, so heating time can be shortened and the heating time can be reduced. Since the heat capacity of the heating section is small, the cooling time can be shortened and productivity can be improved.

(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 carrying out the method of the present invention. This molding die 1 is used for injection molding a substrate of an optical disk. The molding molds 1 are mutually split,
It has a fixed mold 10 and a movable mold 20 that can be closed.

The fixed mold 10 has an inner mold 11 and an outer mold 12 that are separable from each other. These inner mold 11 and outer mold 12
A coil spring 13 is interposed as an elastic body between the inner mold 11 and the outer mold 12 to urge the inner mold 11 away from the outer mold 12. Also, as shown in Figure 2,
A guide pin 14 is fixed to the outer mold 12, and the guide pin 14 guides the movement of the inner mold 11 relative to the outer mold 12. The guide pin 14 penetrates the inner mold 11 and protrudes to the side opposite to the outer mold 12. A flange 14a is provided at this protruding end, and this flange 14a prevents the inner mold 11 urged by the coil spring 13 from falling off.

The inner mold 11 is constructed by connecting a substrate part 15 and a molding part 16. In the inner mold 11,
A passage 17 for heat medium and cooling medium is formed between the substrate part 15 and the molded part 16. A sprue bush 18 is inserted and fixed in the center of the fixed mold 10.

The movable mold 20 has an inner mold 21 and an outer mold 22 that are separable from each other. These inner mold 21 and outer mold 22
A coil spring 23 is interposed as an elastic body between the inner mold 21 and the outer mold 22 to urge the inner mold 21 away from the outer mold 22. Also, as shown in Figure 3,
A bolt-shaped guide pin 24 is fixed to the outer mold 22, and the inner mold 2
1 to guide movement relative to the outer mold 22. The guide pin 24 penetrates the inner mold 21 and protrudes to the side opposite to the outer mold 22. A large-diameter head 24a is provided at this projecting end, and this head 24a prevents the inner mold 21, which is biased by the coil spring 23, from falling off. Note that holes 11a and 21a are formed in the inner molds 11 and 21 to accommodate the protruding ends of the guide pins 14 and 24.

The inner mold 21 is constructed by connecting a substrate section 25 and a molding section 26. In the inner mold 21,
A passage 27 for a heat medium and a cooling medium is formed between the substrate part 25 and the molded part 26.

A center core 28 is inserted and fixed in the center of the inner mold 21. The center core 28 is thin and fixes the center portion of the stamper 30 having a fine spiral groove on its surface. This stamper 30 has an inner mold 21
It is arranged along the surface 26a of the molded part 26. Further, a ring core 31 is fixed to the molding part 26, and this apple core 31 lightly presses the peripheral edge of the stamper 30.

The movable mold 20 is provided with an ejection pin 32 that penetrates the outer mold 22 and the center core 28.

A substrate of an optical disk is injection molded using the molding die 1 having the above configuration. To explain in detail, first, as shown in FIG. 4, the movable mold 20 is moved toward the fixed mold 10 and the inner molds 11 and 21 are closed. As a result, a molding cavity 33 is formed by the surface 16a of the molding part 16, the stamper 30, the center core 28, and the apple core 31. However, the outer molds 12, 22
are kept away from the inner molds 11 and 21. In this state, a heat medium is passed through the passages 17 and 27 of each inner mold 12 and 21 to heat the inner molds 12 and 21. This heating is performed until the stamper 30 reaches the glass transition point of the resin or higher, for example about 150°C. At this time, the outer molds 12, 22 are separated from the inner molds 11, 21 and are not heated, and only the inner molds 11, 21, which have a small heat capacity, are heated, and the inner molds 11, 21 are closed, so heat dissipates. Since the amount is small, heating time can be shortened.

Next, move the movable mold 20 to the coil springs 13 and 2.
3, the inner molds 11 and 21 and the outer mold 1 of the fixed mold 10 and the movable mold 20 are moved as shown in FIGS. 1 and 5.
2 and 22 are all joined. Immediately after this, molten resin is injected and filled into the cavity 33 from the runner 18a of the sprue bush 18. This results in
The fine spiral grooves of the stamper 30 are transferred to the resin. Since the stamper 30 is heated above the glass transition point of the resin as described above, good transfer is performed and a highly accurate optical disk substrate is obtained.

Next, a cooling medium is flowed through the passages 16, 26 of the inner molds 11, 21 to cool the inner molds 11, 21 to a temperature below the resin solidification temperature, for example, about 90° C., thereby solidifying the filled resin. During this cooling, since the outer molds 12 and 22 are not heated, it is only necessary to cool the inner molds 11 and 21, which have small heat capacities, and heat is also dissipated from the inner molds 11 and 21 to the outer molds 12 and 22. cooling time can be shortened.

Next, as shown in FIG. 6, the movable mold 20 is moved backward and completely separated from the fixed mold 10, and the ejection pin 32 is activated to take out the molded product.

The present invention is not limited to the above 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.

(Effects of the Invention) As explained above, in the method of the present invention, the fixed and movable inner molds are closed and the outer mold is separated from these inner molds, and the inner mold with a small heat capacity is heated. Because of this, it can be heated in a short time,
Moreover, this inner mold can be cooled in a short time, and productivity can be improved. Therefore, it is suitable for injection molding that requires heating and cooling cycles such as precision product molding.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a molding die used to carry out the method of the present invention, Fig. 2 is a sectional view showing the inner mold guide means in a fixed mold, taken from a different direction from Fig. 1; The figure is a sectional view showing the inner mold guiding means in the movable mold, and FIGS. 4 to 6 are schematic sectional views illustrating step by step the molding of an optical disk substrate by the method of the present invention. 1... Molding die, 10... Fixed mold, 11... Inner mold, 1
2...Outer mold, 20...Movable mold, 21...Inner mold, 22...Outer mold, 33...Cavity.

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 the fixed mold and the movable mold each consist of an inner mold and an outer mold that can be separated from each other, the fixed mold With the inner molds of the movable molds closed together and the inner mold and outer mold separated, the inner mold is heated, and with the outer mold in contact with the inner mold, a mold is formed between the inner molds. An injection molding method characterized by injecting and filling a molten resin into a cavity, cooling an inner mold to solidify the molten resin, and then separating a fixed mold and a movable mold to take out a molded product.