JPS6327219A - Injection molding method for disklike recording medium - Google Patents

Abstract

PURPOSE:To contrive an improvement in transfer properties and a reduction in orientation of resin, by a method wherein when a filling quantity of molten resin arrives at a necessary quantity which does not come to fill out a cavity, a movable mold is moved at a necessary speed while injection filling is kept continuing, the injection filling is suspended directly before the complete injection filling and pressurization is performed. CONSTITUTION:A movable mold 1 and stationary mold 2 which are in a state of mold break are clamped together by a movement of a movable platen 7 at a high speed. It is preferable that a depth of a cavity 3 to be formed through the mold clamping is less than 3 times as thick as a thickness of a molded product. When a cavity 3 of predetermined capacity is formed, the cavity 3 is filled with molten resin 5 through injection by suspending the movable platen 7. Then when the molten resin 5 arrives at a predetermined filling quantity (40-80%) which is prior to filling of the cavity 3, the movable mold 1 is moved in the direction of the stationary mold 2 by moving forward the movable platen 7 again without suspending injection filling and the filling of the molten resin 5 is suspended directly before the complete filling of the same. Then pressure is applied to the movable mold 1, the molten resin 5 is pressurized and compressed, transfer properties are improve and a disklike recording medium 6 wherein orientation properties have been reduced is molded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for forming a disk shape for a disc-shaped recording medium such as a video disc, a draw disc, or a disc.
Ru.

[Prior Art] Generally, for disc-shaped recording media such as video discs and combination mill discs, a disc (stand bar) having protrusions corresponding to minute signal bits is inserted into a mold cavity, and the disc is inserted into the cavity. It was molded by so-called injection molding, which involves injection filling with molten resin.

However, compared to the Conva Mill Disc, which has a small diameter of 12 cm and has good moldability, and the acrylic disc, which has a diameter of 20 to 30 cm and has good fluidity, even though it has a large diameter, compared to the Niko 1 to 30 cm disc. Video discs made of resin can be molded by ordinary index molding without much problem, but W" diameter 20
- The 30cm disc is made of polycarbonate resin (compared to acrylic resin, it has poor fluidity, but it has low moisture absorption, so it has good adhesion to the Flumilum anti-film that is vaporized after molding, has high heat resistance, and is impact resistant. Also, polycarbonate resin has traditionally been used for Konbaku 1 to Disk.
fter (abbreviation for W4te), which performs both signal acquisition and reading, so those that require low birefringence due to internal distortion are internal, and in that case, low distortion is required. , turn′! This is done by injection compression molding which has excellent y properties.

There are two types of injection compression molding methods used for disk molding. One is to increase the volume of the mold before the start of the injection process, and perform injection filling in that state. , after filling is completed 19
One method is to apply n-contracting force (tt -"j- to the resin by clamping the mold). The other method is to inject molten resin into a mold that has been completely RVR N-vinced at low pressure, and then The mold is opened by injection pressure, and strong 41! tightening is performed after injection and filling to apply IT' clamping force to the resin. δ1, the resin filled there was contracted by 11 times by mold clamping l).

[Problem 5 to be solved by the invention] However, even with the above-mentioned injection compression molding, the molded disk is just beyond the practical range, and it is difficult to set stable molding conditions. In this case, a large amount of time was spent on molding technology, and even higher density was required. , which was made in view of the above circumstances,
The purpose of the present invention is to provide a new injection compression molding method that can increase the filling speed and improve transferability compared to conventional methods, and reduce the orientation of the resin.

[Means for Solving Problem 1] This invention for the above-mentioned purpose is to change the shape of a disc-shaped recording medium such as a video disc, a compact disc, etc. from a fixed mold and a movable mold that fit together. Injection filling of the molten resin is started in a state where the volume of the mold is large, and the injection filling is started when the required interval between fillings is reached, which does not completely fill the mold. While continuing, the movable mold is moved at a predetermined speed to start reducing the P filler volume, and injection filling is stopped just before the molten resin is completely filled, and then a predetermined pressure is applied to the movable mold to completely fill the molten resin. The main idea is to perform cooling and maintenance under the respective pressures.

[Function] In this invention, injection filling is started in a state where the cavity volume is larger than the cavity volume taking into account the compression allowance, so injection can be started at low pressure and high speed. When a predetermined amount of resin is filled, the movable mold is moved forward again to cover the cavity, which spreads out the resin in the cavity. This alleviates the decrease in the spreading speed of the resin as injection filling progresses, and also reduces the flow of the resin. Since the force is applied perpendicular to the direction, orientation in the flow direction is reduced. 1 Complete the 04 discharge just before the cavity fills,
Since the cavity is filled by moving the movable mold forward, there is no need to leave unnecessary filling in the goo parts 1 to 1.

Furthermore, after that, pressure is applied to the movable mold to uniformly apply compressive force to the entire surface of the molten resin! :j and control of compression force = 1
− Jz low strain and cooling shrinkage relaxation orientation is performed.

[Example] In the figure, 1 is a movable mold, and 2 is a fixed mold, and by fitting these two molds together, a cavity 3 is formed in which a disc-shaped recording medium (for example, a video disc, a compact ice cream, etc.) is molded. There is.

The volume of this cavity 3 can be changed by moving the movable mold 1, and the volume can be changed by pressing the molten resin 5 injected into the cavity 3 from the passage 4 provided in the fixed mold 2 with the movable mold 1. The cavity 3 has a depth sufficient to form the recording medium 6 in a disk shape by reducing the amount of the recording medium 6.

As shown in FIG. 5, the movable mold 1 is attached to the movable platen 7 (
The fixed mold 2 is attached to the fixed platen 8.

The movable platen 7 is provided so as to be able to slide back and forth on a tie bar 10 that is horizontally suspended between the fixed platen 8 and the mold clamping cylinder 9, and its back surface is connected to a mold clamping ram 11 inserted into the mold clamping cylinder. connected.

The mold clamping ram 11 has a small diameter cylinder part inside, and a rear booster ram 12 is inserted into the cylinder part, and the large diameter part at the tip of the booster ram 12 connects the cylinder part to the oil chamber. It is divided into sections 13 and 14.

In addition, the mold clamping ram 11 has an oil chamber 1581 inside the mold clamping cylinder 9.
It is divided into 6 sections.

Next, the molding method will be explained.

As shown in Figure 1, the movable tensioner 1 and the fixed mold 2 are in the state where the first mold is open.
The mold is closed in the state shown in FIG. 2 by moving the movable platen 7 at high speed.

The depth of the cavity 3 formed by closing the mold is preferably within 318 mm of the wall thickness of the molded product, and C1! When a predetermined volume of 1 Yaviday 3 is formed by closing, the movable platen 7 is stopped and the -VV biddy 3 is filled with molten resin 5 from the indexing device 17 whose nozzle touches the resin path 4 of the -C1 fixed mold 2. do. Therefore, the molten resin 5 satisfies 1 Yaviti 3 J
Once the previous predetermined filling interval (40-80%) is reached,
Move again without stopping injection filling 51! ! 7 is moved forward at a predetermined speed to move the movable mold 1 in the direction of the fixed platen 2. .

In this state, the volume of the cavity 1 is reduced as the 5-fold closure progresses, and the molten resin 15 in the cavity 3 is spread out, so the reduction in the spreading speed of the tip of the molten resin 1 is alleviated as injection filling progresses. At the same time, the molten resin is subjected to a force perpendicular to the flow direction, thereby reducing its orientation in the flow direction.

The spreading speed of the molten resin 5 in this state is controlled by controlling the forward speed of the movable platen 7.

Then, the Q1 discharge is completed just before the cavity 3 is completely filled, and then the movable plate moves forward, so that the 1-l nozzle 3 is able to estimate the compression amount /V as shown in Fig. 3.
The cavity buoy 3 is filled with molten resin.

Filling with molten resin 5 is stopped immediately before complete filling. Then, a tensile force is applied to the movable mold 1 together with the movable platen 7, and the molten resin 5 is pressurized and compressed, and a disk-shaped recording medium 6 is molded there. Similar to the compressed T culm that goes into compression molding, the P-■-T curve (the properties of Plus Deck material 1 shows the relationship between 1 royal power, specific volume, and temperature, so the horizontal axis shows depletion and combination. Take the specific volume on the axis, and put the specific volume at each temperature under the specified pressure on it.
I'm getting tired. , (Reni J: If you reduce the humidity under a certain pressure, you can see how the specific volume decreases accordingly.)
The compression force is controlled in multiple stages along the Due to the bending, the strain caused by residual stress is further reduced, cooling shrinkage and orientation are alleviated, and transferability is improved.

[Effect 1] According to the present invention, in addition to inheriting the effects of conventional Tsurugiyama compression molding, it also improves the ease of starting application and the fluidity during the injection process, and enables high-speed, low-pressure filling. The generation of distortion due to internal stress is suppressed, the transferability is further improved, and the orientation is reduced. Furthermore, since these are synergistically improved in the next compression process, the molding quality can be greatly improved, and the range of molding conditions can be expanded, so even materials with large diameters and poor fluidity can be molded easily. Play the role of a master who can do it.

[Brief explanation of the drawing]

The drawings illustrate the method for injection molding a disk-shaped recording medium according to the present invention, and FIGS. 1 to 4 are cross-sectional views of a mold showing the culm in order, and FIG. 5 is a schematic illustration of an injection molding machine. FIG. 1...Movable type 2...Fixed type 3...4
Yabitei 5... Molten resin 5... Disk-shaped recording medium patent applicant Nissei Jushi Kogyo Co., Ltd. Figure 1 Figure 3 Figure 4

Claims (1)

[Claims] A cavity for molding disc-shaped recording media such as video discs and compact discs is variably formed from a fixed mold and a movable mold that fit together, and injection filling of molten resin is started when the volume of the cavity is large. Then, when the filling interval reaches the required time that does not completely fill the cavity, the movable mold is moved at a predetermined speed while injection filling is continued to start reducing the cavity volume, and just before the molten resin is completely filled. Injection molding of a disc-shaped recording medium, characterized in that after injection filling is stopped, a predetermined pressure is applied to the movable mold to completely fill the molten resin and control the pressure, and cooling and holding is performed under that pressure. Method.