JP2002337201A - Method for manufacturing optical disk substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an optical disk substrate capable of suppressing the deformation of the substrate when the unevenness formed on a stamper is transferred to the substrate by an injection molding method. SOLUTION: The stamper 3 is mounted on at least one of a pair of fitted molds and a molten resin charged in the molds and, after the resin is cooled and solidified, the molds are opened to take out a molded product. When the angle of a wall surface in the diameter direction of the unevenness formed on the stamper is set to θ, the molds are opened at a speed of 14cotθ [mm/s] or less while blowing off air from the mold 1 on the stamper mounted side to peel the stamper and the molded product.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical disk substrate for transferring irregularities formed on a stamper.

[0002]

2. Description of the Related Art A substrate of an optical disk is manufactured by injection molding a thermoplastic resin. The mold for that, roughly divided, consists of a pair of mating members, fills the cavity formed between the mated members with molten resin, cools and solidifies,
Remove from mold. With reference to the cross-sectional view of the injection molding machine shown in FIG. 11, a method of molding an optical disk substrate will be described.

In FIG. 11, reference numeral 101 denotes a base of an injection molding machine, on which an injection system 102 and a mold clamping system 103 are installed. The injection system 102 has a mini hopper 104 for temporarily storing the dried resin, from which pellet-shaped resin is supplied to the screw 105. A heater 106 is disposed around the screw 105, and the resin is melted by the heat, and the screw 105 is rotated to knead the resin while the screw 105 is retracted to perform measurement. Screw 1
At the base of 05, an injection piston 107 is provided to inject the measured molten resin. A screw 105 used for injection molding of a conventional optical disk substrate is an in-line screw, and weighing and injection are performed by the same screw. this is,
This is to prevent the resin from burning and the like.

In the mold clamping system 103, two large plates 10
A pair of fitting dies is attached to 8a and 108b with bolts. One is a fixed mold 109 and the other is a movable mold 110. The fixed mold 109 and the movable mold 11
Cavity 1 formed between 0 and 0 in a closed state
11 is filled with a molten resin. The mold clamping system 103 has a tie bar 112, and is configured such that the movable side moves while the large plates 108a and 108b face each other in parallel. In the direct pressure system, the large plate 108 b on the movable side is pressed by the mold clamping piston 113. The molten resin is cooled and solidified while applying a mold clamping pressure in the mold, and is then taken out of the mold by a take-out machine (not shown).

FIG. 1 is a sectional view of a mold. The mold is composed of a pair of the fixed mold 1 and the movable mold 2 as described above.
Here, a case is shown in which the stamper 3 having the information unevenness is mounted on the fixed mold 1. A sprue bush 4 having a sprue portion into which the molten resin flows is disposed in the fixed mold 1. A stamper holder 5 is installed around the sprue bush 4 and engages with the inner peripheral portion of the stamper 3 to hold the stamper holder 3 on the fixed mirror plate 6. The fixed mirror panel 6 is attached to a fixed base 7. A fixed-side butting ring 8 is arranged at the outermost periphery of the fixed mold 1, and is positioned by fitting and abutting with the movable-side butting ring 9.

[0006] The movable mold 2 is arranged in order from the inside,
Ejector pin 10, Cut punch 11, Ejector sleeve 12, Movable fixed bush 13, Movable mirror surface board 1
4 An outer peripheral ring 15 that defines the outer periphery of the disk is arranged on the outer peripheral side of the movable mirror panel 14. The outer peripheral ring 15 is mounted on the movable mold 2 side, and is configured to be pressed against the fixed mold 1 by a spring force when the movable mold 2 and the fixed mold 1 are closed. The movable-side mirror surface plate 14 and the movable-side butting ring 9 are attached to a movable-side base 16.

The cut punch 11 is protruded before the resin solidifies to form an inner hole in the molded substrate. After the ejector pins 10 and the ejector sleeves 12 are solidified, the molded substrate 1
When the mold 7 is taken out of the mold, it is used to project the cold slug portion and the molded substrate portion, respectively. When the molded substrate is taken out, the air passage A communicates between the sprue bush 4 and the stamper holder 5 in the fixed mold 1, and the air passage B communicates with the movable fixed bush 13 and the movable mirror plate 14 in the movable mold 2. And blow out air, respectively.

In the above-described injection molding machine, conventionally, the opening speed of the mold has been set to the maximum speed at which the mold can be taken out stably. This is to shorten the molding cycle by shortening the time required for removing the substrate.

Japanese Patent Application Laid-Open No. 10-154359 discloses a technique for opening a mold at a low speed while blowing air from a fixed mold in order to suppress bending of a molded substrate. This is to prevent the mold from being forcibly opened before the molded substrate is separated from the fixed mold, regardless of whether the stamper is installed on the fixed mold side or the movable mold side. Done without.

[0010]

As the density of optical discs increases, it becomes necessary to reduce the intervals such as the width and length of pits and grooves. In this state, if the plane portion is widened, the contrast as a signal increases, so that the inclination angle of the end face needs to be made more vertical.

However, as the inclination angle of the end face of the pit or groove becomes closer to the vertical, as shown in FIG. The end surfaces of the pits and grooves on the formed substrate side are rubbed. Therefore, as shown in FIG. 10B, the inclination of one side of the pit or the groove becomes gentle, and a bulging deformation shown as “pit deformation amount” occurs around the pit.

Therefore, in order to obtain a high-density molded substrate, even if the molded substrate is peeled off from the stamper by air, the fine pits and grooves may be slanted on one side or may be raised around the pits and grooves. There is a problem that deformation occurs and a molded substrate with good signal quality cannot be obtained.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method of manufacturing an optical disk substrate, in which a deformation caused when a pit or a groove formed in a stamper is transferred to a molded substrate and peeled off is suppressed. And

[0014]

According to a method of manufacturing an optical disc substrate of the present invention, a stamper is mounted on at least one of a pair of fitting dies, a mold is filled with a molten resin, and after cooling and solidifying, the mold is cooled. Is a manufacturing method for taking out a molded substrate by opening the stamper. When the wall surface angle in the radial direction of the unevenness formed on the stamper is defined as θ, 14 cot θ [mm / s] The mold is opened at the following speed to separate the stamper and the molded substrate.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described.
The details will be described below with reference to the drawings.

The configuration of the optical disk mold used in the embodiment of the present invention is the same as the conventional mold shown in FIG.
FIG. 2 is a schematic diagram showing a state immediately after the mold is started to be opened.
The cut punch 11 is protruded while the resin is molten to form an inner hole. Even if the mold is opened, if the opening width limit of the outer peripheral ring 15 is 0.5 mm, the outer peripheral ring 15 does not move to that point because the outer peripheral ring 15 is pressed against the fixed mold 1 by a spring. In this state, when the movable mirror surface 14 is compared with the surface of the stamper 3, since there are more irregularities on the surface of the stamper 3 and the resin enters, the stamper 3
The substrate 17 is peeled from the substrate 17 and requires a force, and is not easily peeled. Therefore, if air is not supplied to the air passage A, the substrate 17 is stuck to the stamper 3. However, since the inner hole of the substrate 17 is fitted to the cut punch 11, the substrate 17 is pulled toward the movable mold 2 by friction.

Here, when air is supplied from the air passage A, the air that has flowed into the mold is guided between the stamper 3 and the substrate 17 and acts to separate the stamper 3 from the substrate 17. FIG. 2 shows the state of deformation of the substrate 17 in an exaggerated manner.

When air is blown out from the inner periphery of the stamper 3 before or immediately after the mold is opened, and when the mold is opened at a low speed, the peel angle between the stamper 3 and the substrate 17 is suppressed. The position of the separating boundary gradually moves from the inner circumference to the outer circumference. Therefore, the deformation of the irregularities on the substrate 17 to which the irregularities of the stamper 3 are transferred is suppressed to a minimum. The position where the air can be blown out on the side where the stamper 3 is mounted is a portion inside the stamper 3 where the mold surface is not covered by the stamper 3.

The following experiment was conducted to confirm the effects of the present embodiment and to obtain detailed conditions for implementation. First, using a stamper with a wall angle of 78 degrees, a single pit having a track pitch of 283 nm, a pit width of 140 nm, a pit length of 231 nm, a pit interval of 546 nm, and a pit depth of 63 nm was formed. Molding was performed. The substrate has an inner diameter of 15 mm and an outer diameter of 120 m
m and thickness were 0.6 mm. As a substrate material, AD5503 manufactured by Teijin Chemicals Ltd., which is a polycarbonate resin, was used. The mold temperature is 120 ° C, the maximum clamping force is 20 tons,
The filling time was 0.1 second. Air blowing from the fixed mold 1 on which the stamper 3 is mounted is before the mold is opened, and air blowing from the movable mold 2 on which the stamper 3 is not mounted finishes peeling of the stamper 3 from the substrate 17. And then set. If air blowing from the movable mold 2 is performed before the stamper 3 and the substrate are separated, the portion of the substrate 17 once separated from the stamper 3 is pressed again to the stamper side to hit a pit formed on the substrate 17. This is because there is a risk of deformation due to contact.

When the mold is filled with the resin and the resin is cooled and solidified into the shape of the substrate and then taken out of the mold, the molding is performed by changing the opening speed of the mold, and the pits on the outer peripheral side and the inner peripheral side of the substrate are formed. The angle of the side wall and the height due to the bulging deformation around the pit shown in FIG. 10B were measured with an atomic force microscope.
The results are shown in FIGS. 3, 4, and 5, respectively. For the angle of the side wall, the maximum value at the half-value depth of one pit is defined as the angle in the pit, the angle is determined for a plurality of pits, the average value between the pits, the maximum value,
The minimum value was determined. The distance at which the mold was opened at a low speed was kept constant at 2 mm, and thereafter, was set to 40 mm / s.

From FIG. 3, the angle of the inner peripheral side wall surface of the pit is:
Regardless of the opening speed of the mold, it was about 78 degrees, which is equivalent to that of the stamper. From FIG. 4, the angle of the outer peripheral side wall surface of the pit becomes larger as the opening speed of the mold is lower,
It can be seen that the degree was about 71 degrees at 20 mm / s, but was improved to about 76 degrees at 1 mm / s. From FIG. 5, the bulging deformation height around the pit did not change at about 6 nm when the mold was opened at high speed, but the mold was 3 mm / s.
It can be seen that it decreased when opened at the following speed.

As a result, it was found that if the opening speed of the mold was 3 mm / s or less, the angle of the outer peripheral side wall surface of the pit and the bulging deformation around the pit were suppressed, and a substrate with good signal quality was obtained.

Next, the mold opening speed is made as low as 1 mm / s,
By changing the distance between the substrate 17 and the stamper 3 that open at the low speed, the swelling height around the pit was examined. The result is shown in FIG. FIG. 6 shows that if the initial low-speed mold opening distance is 0.5 mm or more, the bulging deformation height around the pit is suppressed. In consideration of the variation of the substrate 17, the distance of the low speed mold opening is desirably 1 mm or more. In addition, if the distance of the low-speed mold opening is long, the cycle for forming the substrate is lengthened, and the productivity is reduced. Therefore, it is desirable that the distance of the mold opening at this low speed is 3 mm or less.

As described above, the mold opening speed when the distance between the substrate 17 and the stamper 3 is about 1 mm is related to the bulging deformation around the pits. It is thought to peel off. Therefore, it is considered that the effect of suppressing the deformation of the unevenness on the substrate 17 does not depend on the thickness of the substrate 17.

Using the same stamper as in the case where the thickness of the substrate is 0.6 mm, molding was performed with the thickness of the substrate being 1.1 mm. FIG. 7 and FIG. 8 show the results of examining the relationship between the pit wall angle on the outer peripheral side of the substrate and the height of the bulge around the substrate while changing the mold opening speed. Mold opening speed is 1 ~
If it is 2 mm / s, the pit wall angle approaches the value of the stamper, the height of the surrounding swell is suppressed, and the thickness is reduced to 0.
A result equivalent to that of the 6 mm substrate was obtained. That is, the influence of the thickness of the substrate was not observed. Although the rigidity of the substrate is proportional to the cube of the thickness, it was found from the above results that the deformation of the pits was not related to the rigidity. Therefore, it can be seen that it does not depend on the resin material of the substrate.

Next, the thickness of the substrate was 0.6 mm, the mold opening speed was 1 mm / s and 40 mm / s, and the mold opening was temporarily stopped for 1 second when the mold opening amount reached 1 mm.
As a result, when the polarizing plate was passed through the outer periphery of the substrate, the substrate formed under any of the conditions showed unevenness, and it was determined that the substrate was stuck to the stamper and the peeling was temporarily stopped. Therefore, it is desirable to keep the mold open continuously until the stamper and the substrate are completely separated.

The effect of the pit wall angle on the mold opening speed for suppressing the deformation of the pit wall angle will be discussed below.

FIG. 9 shows a model at the moment when one pit is separated from the substrate and the stamper. Here, the peel angle is φ,
Assuming that the pit wall angle is θ, when the condition of (Equation 1) is satisfied, the substrate is peeled off without forming a reverse taper with respect to the pit of the stamper.

[0029]

0 ≦ φ ≦ π / 2−θ When the mold opening speed is v, there is a relationship of (Expression 2).

[0030]

## EQU2 ## where C is a proportional coefficient. Therefore, the maximum mold opening speed v ^* at which the deformation of the pit wall angle is suppressed is represented by (Equation 3).

[0031]

[Mathematical formula-see original document] v ^* = C ^* tan ([pi] / 2- [theta]) = C * cot [theta] As a result of the experiment, when θ = 78 [deg.], V ^* = 3 mm / s. Therefore, the condition of (Equation 4) is obtained.

[0032]

Equation 4] v ^* = 14cotθ Thus [mm / s], in order to suppress the deformation of the pit wall angles when the pit wall angles of θ is the mold opening speed it can be seen that as long than 14Cotshita.

In the above embodiment, the case where the stamper 3 is mounted on the fixed mold 1 has been described. However, the separation between the stamper 3 and the substrate 17 is the same even when the stamper 3 is mounted on the movable mold 2. State. Therefore, a similar result is obtained when the stamper 3 is mounted on the movable mold 2. Further, in the above embodiment, the case where the pit is formed on the stamper 3 has been described. However, the present invention can be similarly applied to the case where the groove is formed on the stamper 3.

Further, in the above embodiment, the case where the outer peripheral ring 15 is mounted on the movable mold 2 side has been described, but the same effect can be obtained even when the outer peripheral ring 15 is mounted on the fixed mold 1 side. Is obtained.

[0035]

According to the present invention, the deformation that occurs when the pits and grooves formed on the stamper are transferred to the molded substrate by the injection molding method is suppressed. As a result, an optical disc substrate with improved signal quality can be manufactured.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a mold used in an embodiment of the present invention and a conventional example.

FIG. 2 is a cross-sectional view showing a state where a stamper and a substrate are separated in the embodiment of the present invention.

FIG. 3 is a graph showing the relationship between the pit wall angle on the inner peripheral side of the substrate and the mold opening speed in the embodiment of the present invention.

FIG. 4 is a graph showing the relationship between the pit wall angle on the outer peripheral side of the substrate and the mold opening speed in the embodiment of the present invention.

FIG. 5 is a graph showing a relationship between a bulging deformation amount around a pit of a substrate and a mold opening speed in the embodiment of the present invention.

FIG. 6 is a graph showing a relationship between a low-speed mold opening amount and a bulging deformation amount around a pit according to the embodiment of the present invention.

FIG. 7 is a graph showing the relationship between the pit wall angle on the outer peripheral side of the substrate and the mold opening speed in the embodiment of the present invention.

FIG. 8 is a graph showing a relationship between a bulging deformation amount around a pit of a substrate and a mold opening speed in the embodiment of the present invention.

FIG. 9 is a schematic cross-sectional view showing the state at the moment when the stamper and the substrate are separated.

FIG. 10 is a schematic cross-sectional view showing a state of deformation of the substrate surface when the stamper and the substrate are separated.

FIG. 11 is a sectional view showing the structure of a conventional injection molding machine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1,109 Fixed mold 2,110 Movable mold 3 Stamper 4 Sprue bush 5 Stamper holder 6 Fixed mirror surface board 7 Fixed side base 8 Fixed side butting ring 9 Movable side butting ring 10 Ejector pin 11 Cut punch 12 Ejector sleeve 13 Movable fixed bush 14 Movable mirror surface plate 15 Outer ring 16 Movable base 17 Substrate 101 Pedestal 102 Injection system 103 Mold clamping system 104 Mini hopper 105 Screw 106 Heater 107 Injection piston 108a, 108b Large plate 111 cavity 112 Tie bar 113 Mold clamping piston

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F202 AH79 AM32 AM35 AR07 AR08 AR12 CA11 CB01 CK43 CM02 CM08 4F206 AH79 AM32 AM35 AR07 AR08 AR12 JA07 JN41 5D121 AA02 DD05 DD20

Claims (6)

[Claims] 1. Production of an optical disk substrate in which a stamper is mounted on at least one of a pair of fitting dies, a molten resin is filled in the dies, and after cooling and solidification, the dies are opened to take out a molded substrate. In the method, when the angle of the wall surface in the radial direction of the concavities and convexities formed on the stamper is θ, while blowing air from the mold on the side where the stamper is mounted, the mold is removed at a speed of 14 cot θ [mm / s] or less. A method for manufacturing an optical disk substrate, comprising opening the stamper and separating the molded substrate from the stamper. 2. The method according to claim 1, wherein air is blown from inside the stamper. 3. A method in which air is blown from the mold surface on the side of the stamper mounting side before or immediately after the mold is opened, and air is blown from the other mold surface after the stamper and the molded product are separated. Item 3. The method for manufacturing an optical disk substrate according to Item 1. 4. The method for manufacturing an optical disk substrate according to claim 1, wherein when the mold is opened, a range of a distance between the substrate and the stamper which is opened at a first step speed is 0.5 mm or more. 5. The method of manufacturing an optical disk substrate according to claim 4, wherein when opening the mold, the range of the distance between the substrate and the stamper opened at the first speed is 3 mm or less. 6. The method for manufacturing an optical disk substrate according to claim 1, wherein the operation of opening the mold is continuously performed until the stamper and the molded product are completely separated.