JPH01314126A - Method of molding disc board made of resin - Google Patents

Abstract

PURPOSE:To mold a disc board whose flatness is high by controlling generation of a warp, by a method wherein an ejection operation of a knockout pin is started in conformity with starting of mold break and a moving speed of the knockout pin is established at specific one. CONSTITUTION:Simultaneously with starting of mold break of a bottom force 2 a molded product 9 is released from the bottom force 2 with an ejection operation of a knockout pin 7. Since a moving speed of the knockout pin 7 is established at about a half of a mold break speed, spatial distances L1, L2 among the top A and bottom B of the molded product 9 and cavity plate surfaces (a), (b) of the top and bottom forces 1, 2 are held at the same ones in a raising course of the knockout pin 7. With this construction, temperature conditions of the top A and bottoms B of the molded product 9 become identical with each other, temperature differentials are hardly generated between the top A and bottom B, as a result of which a warp of the molded product 9 taken out of the mold becomes a little value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention targets information recording bodies such as magnetic disks, optical disks, magneto-optical disks, etc., and uses engineering plastic as a material to form a disk 7S by an injection molding machine.
The present invention relates to a method for temporarily molding a resin disk substrate, and in particular to a method for releasing a molded product.

(Prior art) Taking the above-mentioned magnetic disk as an example, a normal magnetic disk is manufactured by machining an aluminum alloy plate into a disk shape, and then applying pressure annealing to flatten the surface. , coat the surface of the substrate with an N1-P plating layer to give it the necessary hardness, and polish it to a mirror finish.Furthermore, a base layer such as Cr, and a magnetic layer such as Co-■ alloy to protect carbon, etc. Conventionally, a laminate structure in which a lubricating layer is continuously sputtered in this order has been widely adopted.However, magnetic disks using aluminum alloy disk substrates do not require the above-mentioned steps to manufacture them. Because of this, the cost is high.

Recently, in order to reduce costs, engineering plastics such as polyetherimide, polyethersulfone, or unsaturated polyester with added inorganic fillers and reinforcing materials have been used instead of the aluminum alloy substrates mentioned above. A technology has been developed to manufacture magnetic disk substrates using injection molding as a material. Substrates injection molded using these resins have advantages over aluminum alloys in terms of productivity and cost, such as high-precision surface smoothness, light weight, and less processing time. many.

Next, in Fig. 3 shows the general configuration of the injection molding machine used for molding the disk substrate described above, 1.2 is an upper mold;
Lower mold, 3 is a fixed plate with upper mold 1 attached, 4 is a movable plate with lower mold attached, 5 is a mold clamping mechanism, 6 is a sprue bush incorporated in upper mold 1, 7 is a knockout incorporated in lower mold 2 Pin 8 is a knockout pin drive mechanism.

As is well known, the molding cycle of such an injection molding machine consists of a series of steps such as mold clamping, molding material injection, holding pressure, mold opening, and mold release, and finally, the molded product is taken out from the mold.

In addition, in the conventional method for the molded product release process in the series of molding cycles described above, the mold is first opened to the extent that it does not interfere with the work of removing the molded product, and the knockout pin is raised in this mold open state. The molded product is released from the mold.

[Problem to be solved by the invention]

By the way, when a thin disk substrate for a magnetic disk (3.5-inch magnetic disk substrate thickness 1.27+*a) is molded using the above conventional molding cycle using an injection molding machine, the molded product of the disk substrate It is observed that large warping occurs.

Here, an unsaturated polyester thermosetting resin was used as the molding material, and the mold temperature was 155°C and the injection pressure was 500°C.
/ C+4 + When the flatness of a disk substrate molded under the injection conditions of 30 to 60 seconds of mold clamping time was measured, the warpage reached as much as 50 um. However, the amount of warpage of the lever is the warpage of the aluminum alloy disk substrate (2
(0 μm or less), and if it continues as it is, it will not be able to meet the standard values required for magnetic disk substrates. For this reason, conventionally, the molded product is heated and pressurized in a separate process after being removed from the mold to correct the warpage that occurs during the molding process, but this method is time-consuming and reduces productivity. This is causing it to decrease.

Therefore, the inventor investigated the cause of the above-mentioned warpage and found that the cause lies in the following points.

In other words, conventionally, thin disk substrates had a small heat capacity (we did not think that a few seconds of demolding time by operating the knockout pins would create a large temperature difference inside the substrate that would cause warping, but we actually measured it). However, it has become clear that in conventional molding cycles, a large temperature difference occurs between the upper and lower surfaces of the molded product during the mold release process. Then, due to the heat generated by the curing reaction, the temperature of the molded product when molded in the mold will be 10 to 15 degrees Celsius higher than the mold temperature (155 degrees Celsius) immediately before the mold is opened. As mentioned above, in conventional molding cycles, especially in the mold release process of the molded product, the knockout pin is operated after the mold is opened.Therefore, when the mold is opened, the bottom surface of the molded product is in a T-shape. While the mold is in close contact with the mold, the top surface releases from the mold before the upper mold and comes into contact with air.
This causes a temperature difference between the upper and lower surfaces of the molded product.

In addition, resin materials have a large coefficient of thermal expansion (and a low modulus of elasticity), so the warpage that occurs in molded products is also large. Based on the results, we provide a method for molding a resin disk substrate that suppresses the occurrence of warpage and makes it possible to mold a disk substrate with high flatness by improving the mold opening 0M mold process in the molding cycle of an injection molding machine. The purpose is to

[Means to solve the problem]

In order to solve the above problems, in the molding method of the present invention, in the mold release step in which the molded product is ejected from the mold cavity by operating the knockout pin, the ejection operation of the knockout pin is started at the same time as the opening of the mold starts. At the same time, the moving speed of the knockout pin shall be set to approximately 2 times the mold opening speed of the mold.

[Effect]

As in the above method, when the knockout pin is operated to protrude at the same time as the opening of the mold starts, and the moving speed of the knockout pin is set to 2 of the mold opening speed, the molded product will have both the upper and lower sides of the upper die of the mold. The mold is released from the lower mold at the same time, and within the stroke range of the knockout pin, the distance between the upper and lower surfaces of the molded product and the upper and lower molds that face them also becomes -. As a result, the surface temperature conditions of the molded product become the same, and no temperature difference occurs between the upper and lower surfaces, and as a result, the occurrence of warpage is suppressed and the flatness of the disk substrate is improved.

〔Example〕

FIG. 1 is an explanatory diagram of the mold release operation of a molded product according to the method of the present invention, and FIG. 2 is a plan view of a disk substrate showing the flatness measurement points of a magnetic disk substrate. In the figures, the same members corresponding to those in FIG. 3 are given the same reference numerals.

Here, the series of injection molding cycles is basically the same as described in Figure 3, including mold clamping, material injection, and holding pressure.

The disc-shaped molded product 9 formed in this step is removed from the mold and then machined to form a donut disc-shaped disc substrate 10 as shown in FIG. 2. Finished in. In FIG. 2, reference numeral 11 indicates a center hole punched in the center of the disk substrate 10.

By the way, according to the present invention, among the above molding cycles,
In particular, the process of opening the mold and releasing the molded product is performed at the same time, and the knockout pin 7 is projected and operated at the same time as the lower mold 2 of the mold starts moving downward. Further, in this process, the moving speed vl of the knockout pin 7 is set to approximately % of the mold opening speed v2 of the lower mold 2. Note that the operation control in this case is performed by linking the mold clamping mechanism 5 and the knockout pin drive mechanism 8 shown in FIG. Then, the knockout pin 7 moves for a predetermined stroke (30m
m) and then continue to open the lower mold 2 to a distance If (100 m5) that does not pose a problem in taking out the molded product 9.
Here, the molded product 9 is taken out of the mold.

With this molding cycle method, as shown in FIG. 1, the molded product 9 is released from the lower mold 2 by the knockout pink ejection operation at the same time that the lower mold 2 starts to open. Moreover, as mentioned above, since the moving speed of the knockout pin 7 is set to the mold opening speed A, the upper and lower surfaces A and B of the molded product 9 are
and upper mold 1. Distance #L1 between the cavity plate surfaces a and b of the lower mold 2. L2 will be held at the same distance during the knockout and 77 climbs. As a result, the temperature conditions on the upper and lower surfaces A and B of the molded product 9 are the same, and the upper surface A
Almost no temperature difference occurs between the lower surface B and the lower surface B, and as a result, the warpage of the molded product 9 taken out from the mold is also small.

Regarding this point, in order to evaluate the magnetic disk substrate of the molded product 9 molded by the method described above, the inventor wrote the code 11 on the surface of the magnetic disk substrate 10 as shown in FIG.
As a result of actually measuring the flatness of the board along each of the trajectories B and H with a stylus-type flatness measuring device, the maximum value of warpage was 10 μm.
The average value was 5 μm, and it was confirmed that the flatness could be significantly improved compared to resin disk substrates molded by conventional methods.

Although the above example uses thermosetting resin of unsaturated polyester as the molding material, it has been confirmed that similar effects can be obtained with other resin materials. Further, the molding method of the present invention is not limited to application to magnetic disk tables, and similar effects can be achieved even when applied to disk substrates of information recording media such as optical disks and magneto-optical disks.

〔Effect of the invention〕

According to the above-described molding method of the present invention, it is possible to satisfactorily suppress the occurrence of warping of the molded product and obtain a disk substrate with high flatness.
As resin disk substrates used in information recording media such as magnetic disks, optical disks, and magneto-optical disks, it is possible to manufacture high-quality disk substrates with high productivity that are comparable to conventional aluminum alloy disk substrates. can.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the release operation of a molded product by the method of the present invention;
Figure 2 is a plan view of the magnetic disk substrate showing the flatness measurement points, and Figure 3 is a schematic diagram of the configuration of the injection molding machine. Mechanism, 7: Knockout pin, 8: Knockout pin drive mechanism, Fig. 2 Fig. 3

Claims (1)

[Claims] 1) In a method of molding a thin resin disk substrate through a series of molding cycles using an injection molding machine, the mold is opened during the mold release process in which the molded product is ejected from the mold cavity by operating a knockout pin. A method for molding a resin disk substrate, characterized in that a knockout pin ejecting operation is started at the same time as the start, and the moving speed of the knockout pin is set to about 1/2 of the mold opening speed of a mold.