JPH07227893A - Molding method of disk molded piece - Google Patents

Abstract

PURPOSE:To obtain a disk molded piece having excellent optical characteristics that double refraction index at each part is equal, by cooling a periphery of a sprue and a tip of a male cutter during a period from about a time when an injection of a melted resin to a cavity is completed until a time when a forward movement of an ejector is completed. CONSTITUTION:At the time of molding, a fixed mold 10 and a movable mold 20 are closed together and a melted resin is injected into a cavity C of them from a nozzle N. A cooling medium is made to flow to cooling grooves 13 and 23 of mirror plates 12 and 22 of the fixed mold and the movable mold so as to cool the mirror faces to specific temperatures respectively. After a molded piece P in the cavity C is cooled, a male cutter 24 is made to proceed so as to cut a gate G. Thereafter, an ejector 25 is made to proceed so as to protrude the molded piece P from the cavity C. At that time, during a period from about a time when the injection of the melted resin into the cavity C is completed until a time when the forward movement of the ejector 25 is completed, the cooling medium is made to flow to a periphery of a sprue S and passages 17 and 27 at the tip of the male cutter 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding a disk molded product.

[0002]

2. Description of the Related Art For injection molding of disk molded products such as compact disks and laser disks, for example, a mold apparatus as shown in FIG. 2 is used. In the figure, reference numeral 10 is a fixed type, 11 is a fixed side mounting plate, and 12 is a fixed type mirror plate. A cooling groove 13 is provided in the fixed mirror plate 12. On the other hand, reference numeral 2
0 is a movable type, 21 is a movable side mounting plate, 22 is a movable mirror plate, and the movable mirror plate 22 is also provided with a cooling groove 23. This fixed mirror plate 12
With the movable mirror plate 22, the molded product cavity C is formed.

The fixed die 10 has a mescatter 1 on its outer periphery.
The sprue bush 15 having the number 4 is fitted. Reference numeral 17 is a coolant channel formed around the sprue S. Then, the movable die 20 is provided with an male cutter 24 corresponding to the mescatter 14 so as to be movable back and forth with respect to the molded product cavity C. The oscatter 24 is for opening and closing the gate G for introducing the molten resin into the molded product cavity C and for defining the inner hole portion H of the disk molded product P as shown in FIG. Also called. When the male cutter 24 moves back and forth and the tip of the male cutter 24 moves in and out of the mescatter 14, the gate G is opened and closed. An ejector 25 is provided on the outer circumference of the male cutter 24. The ejector 25 is for ejecting a molded disc molded product from the surface of the cavity C, and is provided in sliding contact with the male cutter 24 so as to be movable back and forth. Reference numeral 26 is a center pin, and 27 is a coolant passage formed around the tip of the male cutter 24.

Molding of a disk molded product using the above apparatus is performed as follows. First, cooling water is flowed through the coolant passages 17 and 27 around the sprue S and the tip of the male cutter 24 to cool them to 10 to 20 ° C. In this state, the molten resin is injected into the molded product cavity C. At that time, an appropriate cooling medium is passed through the cooling grooves 13 and 23 of the fixed mirror plate 12 and the movable mirror plate 22, respectively, so that the mirror surface (also referred to as cavity surface) temperature of both mirror plates 12 and 22 is compacted into a compact disk. About 70 to 90
C., and cooled to about 50-60.degree. C. during laser disk molding. After that, move the OSCATA 24 forward to the gate G
To cut. After the gate is cut, the mold is opened, the ejector 25 and the center pin 26 are advanced, and the disk molded product is ejected and released from the mold.

In addition, the periphery of the sprue S and the male cutter 2
The reason why the cooling of the four tips is performed separately from the mirror surface temperature control of both mirror plates 12 and 22 and is set to a low temperature is as follows. That is, since the diameter of the sprue S portion is approximately three times as large as the thickness of the disk molded product formed by the mirror surface portions of both mirror plates 12 and 22, or more than that in some places, it is cooled in a short time. This is because the temperature around the sprue S and the tip of the male cutter 24 must be lower than the mirror surfaces of the mirror plates 12 and 22.

However, in the disk molded product molded as described above, the birefringence in the inner peripheral region largely changes to the negative side as compared with the outer peripheral region and the middle peripheral region, which is a problem in optical characteristics. was there. As a result of various studies on the cause, it was found that the cooling temperature around the sprue S and the tip of the male cutter 24 is extremely lower than the cooling temperatures of the mirror plates 12 and 22. That is, the inner peripheral region of the disk molded product is formed at a position closer to the sprue S and the tip of the male cutter than the middle peripheral region or the outer peripheral region. This is because they are also molded in a low temperature state.

However, in order to solve the birefringence problem, the cooling temperature around the sprue S and the tip of the male cutter 24 is set to the cooling temperature of each mirror plate 12, 22 (70 to 70).
When the temperature is close to 90 ° C. or 50 to 60 ° C., the sprue S may be insufficiently cooled and the sprue S portion may be deformed. Moreover, since the resin in the sprue S portion is taken out by an appropriate chuck mechanism or the like, the deformed sprue S may cause frequent chuck errors.

[0008]

The present invention has been proposed in order to solve the above-mentioned problems, and a disk molded product having good optical characteristics can be obtained without causing problems such as sprue deformation. The present invention provides a molding method that can be performed.

[0009]

That is, the present invention is
The movable mold is provided with a male cutter that opens and closes the gate of the molten resin into the cavity of the disk molded product formed by the fixed mirror plate and the movable mirror plate and that defines the inner hole of the disk molded product so that it can move back and forth. An ejector for ejecting a disk molded product from the cavity surface is provided on the outer periphery of the male cutter so as to be slidably movable back and forth, so that the periphery of the fixed sprue and the tip of the movable male cutter can be cooled. In a method for injection-molding a disk molded product by an apparatus, cooling of the sprue periphery and the tip of the male cutter is performed only before and after completion of injection of the molten resin into the molded product cavity and completion of ejector advance. The present invention relates to a method for molding a disk molded product.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a time chart at the time of molding a disk molded product by the molding method of the present invention.

The molding method of the present invention is preferably carried out by a known injection molding die apparatus as shown in FIG. 2, and when molding a disk molded product, after the molten resin is injected into the molded product cavity C, The periphery of the sprue S and the tip of the male cutter 24 are cooled only before and after the completion of injection to the time when the advance of the ejector 25 is completed. The cooling start timing around the sprue S and the cooling start timing at the tip of the male cutter 24 may be different from the simultaneous case.

As can be understood from the time chart of FIG. 1 and FIG. 2, first, the fixed mold 10 and the movable mold 20 are closed, the pressure is increased for mold clamping, and then the nozzle of the injection device is inserted into the molded product cavity C. Molten resin is injected from N. This injection is similar to the conventional one. Meanwhile, the male cutter 24 is retracted. Further, a coolant such as water is made to flow into the cooling grooves 13 and 23 of the fixed mirror plate 12 and the movable mirror plate 22, so that the mirror surfaces of both mirror plates 12 and 22 have a predetermined temperature, that is, about 70 when the compact disc is molded. ~ 9
It is cooled to 0 ° C., and to about 50 to 60 ° C. when forming a laser disk. On the other hand, the refrigerant is not passed through the refrigerant passage 17 around the sprue S and the refrigerant passage 27 at the tip of the male cutter 24.

After the molten resin is injected into the molded product cavity C and the molded product P in the cavity C is cooled, the male cutter 24 is advanced and the gate G is cut.

Before and after the injection of the molten resin into the molded product cavity C is completed, the refrigerant is flowed around the sprue S and the refrigerant passages 17 and 27 at the tip of the male cutter 24,
The part is cooled to a temperature of 10 to 20 ° C. or lower. In this example, the refrigerant flows into the refrigerant channels 17 and 27 after the injection of the molten resin into the cavity C is completed, but the type, shape and thickness of the disk molded product to be molded, or the refrigerant. Depending on the type and the like, the inflow may be started after the start of injection and before the completion of injection.

Thereafter, the mold is depressurized and the mold is opened. Then, the ejector 25 advances, and when the advancement is completed and the molded product P is projected from the surface of the cavity C, the periphery of the sprue S and the male cutter 2 are removed.
The flow of the refrigerant into the refrigerant passages 17 and 27 at the four ends is stopped, and the cooling around the sprue S and the tip of the male cutter 24 is completed. At the same time, the ejector 25 and the male cutter 24 are retracted to prepare for the next molding.

The obtained disk molded article had a birefringence index in the inner peripheral region close to that in the middle and outer peripheral regions.
This is because the periphery of the sprue S and the tip of the male cutter 24 are not cooled at the time of injection of the molten resin, so that the molten resin is not affected by the low temperature of the periphery of the sprue and the tip of the male cutter at the time of injection and is formed around the sprue and the tip of the male cutter. This is because it does not adversely affect the inner area of the disc.

As the cooling medium around the sprue S and the tip of the male cutter 24, a known cooling medium such as water or air cooled to an appropriate temperature can be used, but it is more preferable to use ultra low temperature air. This ultra-low temperature air causes a large pressure difference between the center and the outer periphery of the vortex when the compressed air expelled into the tube at the sonic velocity expands rapidly and becomes a vortex while rotating at high speed and moves to the end. It is generated and is made to have a low temperature by moving air toward the central portion. For example, TM of TOOL & MACHINE
It can be preferably generated by an S-630 series tube. If this ultra-low temperature air is used, the surroundings of the sprue S and the tip of the male cutter 24 can be effectively cooled in a short time. Therefore, the cooling start time is delayed, and the temperature of the resin around the sprue S and the tip of the male cutter 24 and the cavity of the molded product are delayed. The temperature of the resin in C can be equalized for a longer period of time and the birefringence problem can be eliminated more completely.

[0018]

As shown and described above, according to the method for molding a disk molded article of the present invention, the sprue is only provided before and after the completion of the injection of the molten resin into the cavity of the molded article until the completion of the advance of the ejector. Since the periphery and the tip of the male cutter are cooled, the resin around the sprue and the tip of the male cutter are not extremely cooled by the periphery of the sprue and the tip of the male cutter during injection. As a result, the resin around the sprue and near the tip of the male cutter, that is, the resin that is the inner peripheral area of the disk molded product, and the resin in the center and outer peripheral portion of the molded product cavity, that is, the resin that is the middle and outer peripheral areas of the disk molded product. The difference in temperature between the two is small, and a disk molded product having good optical characteristics in which the birefringences of the inner peripheral region, the middle peripheral region and the outer peripheral region are almost equal can be obtained.

[Brief description of drawings]

FIG. 1 is a time chart showing molding of a disk molded product by the molding method of the present invention.

FIG. 2 is a cross-sectional view showing a main part of a general disc molding die.

FIG. 3 is a plan view of a general disc molded product.

[Explanation of symbols]

 10 Fixed Type 11 Fixed Side Mounting Plate 12 Fixed Type Mirror Plate 13 Cooling Groove 14 Mescatta 15 Sprue Bushing 17 Refrigerant Flow Path around the Sprue 20 Movable Type 21 Movable Side Mounting Plate 22 Movable Mirror Plate 23 Cooling Groove 24 Oscatter 25 Ejector 27 Refrigerant channel at Oscata tip C Molded product cavity G Gate S Sprue P Disc molded product H Inner hole

Claims (1)

[Claims] 1. A male cutter for opening and closing a gate of molten resin into a cavity of a disk molded product formed by a fixed mirror plate and a movable mirror plate and defining an inner hole of the disk molded product is movable back and forth. An ejector that projects a disk molded product from the cavity surface is provided in a slidable contact with the outer periphery of the male cutter so as to move back and forth to cool the periphery of the fixed mold sprue and the tip of the movable male cutter. In a method for injection-molding a disk molded product by the device thus obtained, cooling of the sprue periphery and the tip of the male cutter is performed only before and after the completion of injection of the molten resin into the molded product cavity and the completion of advance of the ejector. A method for molding a disk molded article, which is characterized by the above.