JP2001170981A - Method for molding disk substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that when two molded disk substrates are laminated into a disk in a mold and when the required thicknesses of the substrates are different, conventionally shims are inserted into the back of the mirror surface plate of the mold with the mold disassembled, care is required not to foul and break the plate, and the shims must be replaced repeatedly while shims of different plate thicknesses are molded to require labor and time. SOLUTION: Corresponding to the required plate thicknesses of the disk substrates to be molded in respective cavities, the temperature of a nozzle installed in every cavity in the mold is set up, and the temperature of the nozzle corresponding to the cavity of one substrate of a thinner required plate thickness is made lower than the temperature of the nozzle corresponding to the other substrate of a thicker required plate thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a disk substrate such as a DVD, which is formed by forming two disk substrates with the same mold and then bonding them together to form a disk.
9 relates to forming that requires a very delicate required thickness difference.

[0002]

2. Description of the Related Art A technique for forming two disks, such as a DVD, on a single disk by forming and bonding two disk substrates with the same mold is disclosed in detail in Japanese Patent Application Laid-Open No. Hei 9-155986. As is clear from the description of the publication, resin passages, nozzles, cavities and the like in the same mold are manufactured as a pair with the same dimensions, and the molten resin is equally branched and filled in the pair of cavities. The disk substrates are formed with the same dimensions. However, for example, in DVD-9, which is a disc of the type in which pit information is read by laser light from only one side of the bonded disc, the required thickness of the disc substrate layer 0 on the reading side is 0.570 mm, The required plate thickness of the disk substrate layer 1 is 0.600 mm. Conventionally, in order to form a disk substrate having such a thickness difference, a thickness of 3 mm is provided on the back of a mirror plate forming a cavity corresponding to layer 0.
The thickness of the cavity was reduced by inserting a shim of about 0 μm.

[0003]

The insertion of the shim must be performed by disassembling the mold, and is a very laborious operation that requires careful attention so as not to contaminate or damage the mirror plate. In addition, it is necessary to replace shims of different thicknesses many times while forming them in accordance with the thickness of the layer 1, which consumes a great deal of labor and time.

[0004]

Therefore, the temperature of the nozzles provided for each cavity in the mold is set in accordance with the required thickness of the disk substrate to be molded in each cavity. Of the two disk substrates to be combined, the nozzle temperature corresponding to the cavity of the disk substrate whose required plate thickness is smaller than the other is set so that the nozzle temperature corresponding to the cavity of the disk substrate whose other required plate thickness is thicker is lower. It is molded.

[0005]

Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing a mold for implementing the present invention and a control device therefor. Reference numeral 1 denotes an injection nozzle of an injection molding machine, which presses against a guide bush of the mold in order to fill the mold with molten resin plasticized and melted by an injection device (not shown). Reference numeral 2 denotes a fixed die, which is mounted on a fixed plate of an injection molding machine. Reference numeral 3 denotes a movable mold, which is attached to a movable plate of an injection molding machine and is separated from and close to the fixed mold 2.
When the movable mold 3 is close to the fixed mold 2 and the molds are matched, a first cavity 9 and a second cavity 12 are formed. A first sprue portion 8 and a second sprue portion 11 communicate with the first cavity 9 and the second cavity 12, respectively, and each sprue portion is connected to the resin passage 4. Resin passage 4
Are the guide bush 5, the manifold 6, the first nozzle 7
And the molten resin that is formed by being pierced in the second nozzle 10 and is injected from the injection nozzle 1 passes through the guide bush 5 and branches in the manifold 6, one of which is directed to the first nozzle 7.
The other is guided to the second nozzle 10 with an equal distance and an equal cross-sectional area. The guide bush 5, the manifold 6, the first nozzle 7, and the second nozzle 10 are heated and controlled to predetermined temperatures by heaters 18, 17, 15, and 13, respectively, so that the molten resin is not cooled and solidified in the resin passage 4 and One nozzle 7 and second nozzle 1
It has an equal flow resistance up to zero. The heaters 18, 15, and 13 are circular band heaters, and the heater 17 is a rod-shaped cartridge heater. A temperature detector such as a thermocouple is provided for each heater to be heated, and a closed loop control by a PID or the like is performed so that a temperature signal of the temperature detector becomes equal to a set value in a temperature setter provided in the control device 19. .

FIG. 1 shows a first nozzle 7 and a second nozzle 10.
Only the temperature control loop of FIG. The temperature signals of the thermocouples 14 and 16 are input to the control device 19, and the temperature signals are compared with the signals of the first setting device 20 and the second setting device 21 provided in the control device 19, and PID calculation is performed. 19 adjusts the amount of electric power output to the heaters 13 and 15 so that the signals of the thermocouples 14 and 16 become equal to the signals of the first setting device 20 and the second setting device 21, respectively.

Next, a method for forming a disk substrate will be described. After the movable mold 3 is mated with the fixed mold 2, the molten resin injected and filled from the injection nozzle 1 pressed against the fixed mold 2 passes through the resin passage 4 through the first nozzle 7 and the first sprue portion. 8 to the first cavity 9 and the second nozzle 1
0, and flows into the second cavity 12 from the second sprue portion 11 respectively. When the injection process is completed by applying a slight holding pressure after filling the cavity with the molten resin, the molten resin in the cavity is rapidly cooled and solidified. In the process, a central opening is formed in the center of the disk substrate by a gate cutter (not shown) provided in the movable mold 3,
The sprue is separated from the disk substrate. Thereafter, the movable mold 3 is separated from the fixed mold 2 and opened. After the sprue is projected by an ejector (not shown) provided in the movable mold 3, the disk substrate is further released and projected,
It is sent to processes such as vacuum deposition and thin film coating. The above steps are performed simultaneously in the first cavity 9 and the second cavity 12.

FIG. 2 shows an example of the relationship between the temperature of the first nozzle 7 and the second nozzle 10 and the product thickness of the disk substrate formed in the first cavity 9 and the second cavity 12 corresponding thereto. Show. As is apparent from FIG. 2, the thickness of the disk substrate made of the molten resin that has passed through the nozzle decreases as the nozzle temperature decreases. In this example, if the nozzle temperature decreases by 5 ° C., the average thickness decreases by 15 μm. Therefore, in order to achieve the required plate thickness of DVD-9 of 0.570 mm for layer 0 and 0.600 mm for layer 1, the nozzle temperature of layer 1 360 is required. The nozzle temperature of layer 0 is 3
The temperature may be set to 50 ° C. The reason why the plate thickness of the disk substrate is reduced due to the decrease in the temperature of the nozzle is that the flow resistance of the molten resin at the nozzle portion increases. Therefore, by collecting in advance the relationship data between the nozzle temperature in actual molding and the disk substrate thickness in the molding raw materials, molds, temperature conditions, and the like to be used, the thickness of the disk substrate can be controlled by setting the nozzle temperature. Can be adjusted.

[0009]

According to the present invention, since the molding of the disk substrate is performed as described above, the temperature setting value of the nozzle can be corrected and corrected without performing a troublesome operation of inserting a shim into the mirror surface plate of the mold. The thickness of the disk substrate can be adjusted only by changing, and the productivity of the disk substrate can be extremely increased.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a mold embodying the present invention and a control device thereof.

FIG. 2 is a table showing an example of a relationship between a nozzle temperature and a product plate thickness of a disk substrate formed in a cavity corresponding to the nozzle temperature.

[Explanation of symbols]

 1 ... Injection nozzle 2 ... Fixed mold 3 ... Movable mold 4 ... Resin passage 5 ... Guide bush 6 ... Manifold 7 ... First nozzle 8 ... First Sprue portion 9 First cavity 10 Second nozzle 11 Second sprue portion 12 Second cavity 13, 15, 17, 18 Heater 14, 16 Thermocouple 19 Control device 20: First setting device 21: Second setting device

Claims (2)

[Claims] In a method of manufacturing a disk by bonding disk substrates formed by cavities formed in pairs in the same mold, a method of manufacturing a disk according to a required plate thickness of a disk substrate formed in each cavity. A method for forming a disk substrate, comprising setting a temperature of a nozzle provided for each cavity in a mold. 2. A nozzle temperature corresponding to a cavity of a disk substrate having a required thickness smaller than the other of two disk substrates to be bonded corresponds to a cavity of a disk substrate having a larger required thickness. 2. The method for forming a disk substrate according to claim 1, wherein the temperature is set so as to be lower than the temperature of the nozzle.