JP2000071301A - Mold for optical disc - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformize the cooling speed difference of a resin causing the generation of the double refraction or warpage important from an aspect of required characteristics of an optical disc. SOLUTION: A mold for an optical disc has cooling means provided at a sprue part 12 and a disc part 13. In this case, the disc part cooling means has a plurality of cooling passages 6, 7, 8 for cooling the disc part at individual set temps. on the circumference of a circle between the inner and outer peripheral parts of the disc part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold apparatus for molding an optical disk substrate such as a CD or DVD.

[0002]

2. Description of the Related Art FIG. 4 is a sectional view showing a conventional structure of a molding die for optical disks such as CDs and DVDs. FIG.
FIG. 3 is a cross-sectional view showing a planar shape of an upper mold of a molding die shown in FIG.
Hereinafter, a conventional optical disk molding die will be described with reference to FIGS. In FIG. 4, 1 is a reference position for opening and closing the mold, 2 is a fixed side of the mold, 3 is a movable side, 4 is a supply port of a molding resin, 5 is a product part, 6 is a sprue part, and 7 is a gate part. is there. A resin in a molten state at 320 to 340 ° C. is injected into the injection molding machine from the supply port 4, and the resin is quenched from this state to about 140 ° C. by a cooling means in a mold, and is taken out as a product. The solidified resin product is sprue part 6,
The sprue part 6 and the gate part 7 are cut in a mold and separated from the product part 5, and are taken out of the mold and discarded. 8
Is a stamper for transferring a recording shape (pit) to an optical disk, and is inserted into a mold by a stamper holder 9 and an outer ring 12.

The sprue section 6 and the gate section 7 are taken out by an ejector pin 10, and the product section 5 is taken out by separating the sleeve pin 11 from a mold. Also, for sprue cooling, a sprue bush 16
A cooling passage 18 surrounding the sprue portion 6 is provided, and a cooling passage 20 is provided in the fixed mirror INS14 for fixed cooling.
21 is provided, and cooling passages 24 and 25 are provided in the movable mirror INS17 for cooling on the movable side.

[0004] Reference numerals 19, 22, 23, and 26 denote O-rings for preventing water leakage in each cooling passage. A cooling medium is supplied to each of the cooling passages. In addition, 13 is a punch and 27 is a die. FIG. 5 shows the cooling passages 18 and 2 on the fixed side 2 in FIG.
FIG. 5 is a cross-sectional view showing 0 and 21 and is usually formed in two circuits of the sprue section cooling passage 18 and the product section cooling passages 20 and 21 in FIG. Since the sprue portion 6 into which the resin in the molten state is injected is hard to be solidified and requires a long time for cooling, the cooling temperature is set to be as low as 50 ° C. or less while the cooling temperature of the product portion is 130 ° C. I have.

[0005]

The optical disk substrate is C
As the recording capacity increases from D to PD and DVD, strict accuracy is also required for optical disk substrates.
In particular, strict specifications are required for birefringence, which is important for optical characteristics, and the CD was 110 nm or less, but the
D requires a standard of 50 nm. By the way, the birefringence is obtained by the following equation.

Birefringence = photoelastic coefficient × principal stress difference (shear stress + thermal stress) In the above equation, the thermal stress is affected by the fluctuation of the cooling rate of the resin filled in the mold. Control is an important factor in meeting birefringence specifications. FIG. 6 shows the temperature distribution of the mold about 1 second after resin injection in the conventional mold configuration. As shown in this temperature distribution, the temperature of the sprue portion is set to 50 ° C., which is lower than the others. In addition, the wall surface temperature of the mold at the inner diameter portion and the outer diameter portion on the disk in the flow pattern of the resin is set to 1 after filling the resin.
A difference of about 14.5 ° C. occurs in seconds. For this reason, thermal stress increases, internal strain increases, birefringence is deteriorated, and this is a factor that adversely affects the disk such as warpage. Therefore, the present invention provides a molding die for an optical disc,
An object is to make the temperature distribution on the mold wall surface, which is a factor affecting such thermal stress, more uniform.

[0007]

In order to achieve this object, the present invention relates to a molding die for an optical disk having cooling means in each of a sprue portion and a disk portion. A molding die for an optical disk, comprising a plurality of cooling passages for cooling, wherein the set temperature of the cooling means of the sprue portion is set to the minimum, and the set temperature of the cooling means adjacent to the outer peripheral side of the disk portion is sequentially set higher. is there.

According to the present invention, the set temperatures of the cooling passages in the mold are individually set, and the sprue portion, the gate portion, the inner peripheral portion, the central portion, and the outer peripheral portion are sequentially cooled at a predetermined temperature. By setting the temperature high, the cooling rate in each part of the disk is made uniform, distortion and warpage occurring on the disk can be minimized, and optical disk products that can maintain the specifications of optical characteristics such as birefringence are provided. can do.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The invention according to claim 1 of the present invention is directed to a molding die for an optical disk having cooling means in each of a sprue portion and a disk portion, wherein the disk portion cooling means is provided at an individual set temperature. It has a plurality of cooling passages for cooling, with the set temperature of the cooling means of the sprue section being the lowest,
According to the present invention, the set temperatures of the cooling passages in the mold are individually set, and the set temperatures of the cooling means adjacent to the disk portion outer peripheral side are sequentially set higher. At the temperature, from the sprue part, the gate part to the inner peripheral part,
By setting the cooling temperature of the central portion and the outer peripheral portion sequentially higher, the cooling rate in each portion of the disk can be made uniform, and the distortion and warpage generated in the disk can be minimized. This has the function of providing an optical disk product that can maintain the standard of characteristics.
Further, according to the present invention, the temperature difference from the inner diameter to the outer diameter of the disk can be significantly reduced, and the temperature difference at which the inner diameter portion and the outer diameter portion reach the glass transition temperature can be reduced, In addition, the time required for uniformizing the resin temperature on the mold wall surface can be shortened and the molding cycle can be shortened.

Hereinafter, a mold structure of an optical disc mold according to an embodiment of the present invention will be described with reference to FIG. 1 and FIG. In FIG. 1, reference numeral 1 denotes an open / close position on a fixed side and a movable side of a mold. Reference numeral 2 denotes a fixed side of the molding die.
A sprue cooling passage 5, a disk inner peripheral cooling passage 6, a central cooling passage 7, and an outer peripheral cooling passage 8 are provided. Reference numeral 3 denotes a movable side of the molding die, which is a gate cooling passage 9, a disk inner peripheral cooling passage 10, a central cooling passage 15, and an outer peripheral cooling passage 1.
0 is provided. Reference numeral 12 denotes a sprue, 13 denotes a disk, and 14 denotes a gate. A cooling medium of a predetermined temperature is supplied to each of the cooling passages. A high-temperature molten resin of 320 ° C. to 340 ° C. is supplied to the injection molding machine from the supply port 4,
It is quenched to about 140 ° C by a mold, solidified and taken out. A disc (1.2 mm thick for CD, DV
(D: 0.6 mm thickness) in the circumference and in the thickness direction, particularly in the circumferential direction, the cooling rate is greatly different, so that the thermal stress difference becomes large, which is a factor of deteriorating the birefringent optical characteristics. According to the present invention, in order to make the cooling rate uniform, the solidification pattern of the resin when the resin is supplied to the injection molding machine from the supply port 4 is changed depending on the resin to be filled, and further, the setting of each cooling passage in the mold is performed. The temperature is variable.
In particular, the sprue section 12 and the gate section 14 having a high cooling rate
Is cooled from both sides of the fixed side 2 and the movable side 3 by the sprue part cooling passage 5 and the gate part cooling passage 9 and the cooling temperature is closest to the supply port 4 for injecting the high-temperature molten resin. The temperature is set to 30C to 30C. The size of the disc 13 is 15 mm for CD and DVD,
The outer diameter is standardized to 120 mm, but in the process of filling the resin with 15 mm in the circumferential direction from the gate portion 14 and further 120 mm from the inner diameter portion to the outermost diameter, the inner peripheral portion, the central portion, and the outer peripheral portion of the disk 13 are filled. In order to make the cooling rate uniform, the fixed side mirror 16
In both the movable mirror 17 and the movable mirror 17, the inner peripheral cooling passages 6, 10, the central cooling passages 7, 15 and the outer peripheral cooling passages 8, 11 are provided between the inner diameter portion and the outer diameter portion of the disk.

In this embodiment, the temperature of the cooling passages 5 and 9 of the sprue and the gate is set to 20 ° C. to 30 ° C. based on the solidification pattern of the resin analyzed in advance, and the inner peripheral cooling passages 6 and 9 are set. 10 is set to 70-100 ° C., the temperature of the central cooling passages 7 and 15 is set to 90 ° -110 ° C., and the temperature of the outer peripheral cooling passages 8 and 11 is set to 120 °.
By setting to ~ 140 ° C, as shown in FIG.
Although the temperature difference of the product surface mold was 14.5 ° C. in the conventional apparatus, it can be greatly improved to 8.1 ° C. in the present invention, and the inner and outer diameters are glass dislocation. The temperature difference to reach the temperature can be reduced from 1.1 ° C. to 0.3 ° C., and the time for equalizing the resin temperature on the metal wall surface can also be reduced from 3 seconds to 2 seconds. The temperature of the surface of the subsequent disk can be made uniform.

In the present embodiment, three passages of a circumferential portion, a central portion and an outer peripheral portion are provided as cooling passages for the disk portion. However, the present invention is not limited to this embodiment.
Further, the set temperature of each passage is merely an example, and is appropriately changed according to the characteristics of the resin to be molded.

[0013]

As described above in detail, according to the present invention,
The set temperature of the cooling passages in the mold is individually set at a predetermined temperature, and the inner, central, and outer peripheral portions are sequentially set to have higher temperatures from the cooling temperature of the sprue portion. It is possible to provide an optical disk product, in particular, a DVD-ROM and a RAM, which can make the cooling rate in each part uniform, minimize distortion and warpage generated in the disk, and maintain the standard of optical characteristics such as birefringence. .

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a mold apparatus according to an embodiment of the present invention.

FIG. 2 is a plan view of a fixing unit side of FIG. 1;

FIG. 3 is a diagram comparing various temperature conditions of a mold apparatus according to an embodiment of the present invention and a conventional apparatus.

FIG. 4 is a cross-sectional view of a conventional mold apparatus for forming a disk substrate such as a CD or DVD.

FIG. 5 is a plan view of the fixed side of FIG.

FIG. 6 is a diagram in which the temperature distribution of a conventional mold apparatus is analyzed.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 open / close reference position 2 fixed mold 3 movable mold 4 supply port 5 sprue cooling passage 6 inner peripheral cooling passage 7 central cooling passage 8 outer peripheral cooling passage 9 gate cooling passage 10 inner cooling passage 11 Outer peripheral cooling passage 12 Sprue 13 Disk 14 Gate 15 Central cooling passage 16 Fixed mirror 17 Movable mirror

Claims (1)

[Claims] In a molding die for an optical disk having cooling means in each of a sprue part and a disk part, the disk part cooling means has a plurality of cooling passages for cooling at individual set temperatures, respectively. A molding die for an optical disk, wherein the set temperature of the cooling means is set to be the lowest and the set temperature of the cooling means adjacent to the outer periphery of the disk portion is set to be sequentially higher.