JPH0367615B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an annealing apparatus that heat-treats a resin substrate molded as an optical disk substrate to remove residual stress and the like.

[Background Art and Problems Therein] In recent years, the practical use of polycarbonate resin substrates as substrates for optical memory disks has been studied. The transparent substrate of an optical disk is irradiated with a beam of light, which causes the grooves to reproduce and record stored signals, so birefringence greatly affects the quality of the optical disk. Since this is caused by residual stress within the birefringent substrate, it is necessary to remove the residual stress from the molded resin substrate.

In addition, in order to increase the recording density of optical disks, it is necessary to control the focus of the beam light very strictly and to improve the flatness accuracy of the resin substrate, thereby reducing surface wobbling of the resin substrate. A high level of planar accuracy must be ensured.

Annealing is performed to remove residual stress and correct flatness of a molded resin substrate, and conventional annealing methods include a hot press method and a rotation method. The former is a method in which a resin substrate is sandwiched between two molds and heat and pressure are applied to the resin substrate. According to this, there is a risk that the guide groove for the memory signal formed in the resin substrate may be destroyed by the pressure, and there is also a problem that dents are likely to occur in the resin substrate due to uneven contact with the mold. The latter is a method in which the resin substrate is rotated at high speed at a constant temperature. According to this method, since the centrifugal force changes according to the distance from the center of rotation of the resin substrate, the stress acting on the resin substrate is not uniform, and there is a problem in correcting the flatness accuracy.

[Object of the Invention] An object of the present invention is to reduce the residual stress of a resin substrate, and to do so while correcting and improving the flatness accuracy of the resin substrate, and to improve the quality of optical disks.
An object of the present invention is to provide an annealing device for a resin substrate that contributes to high recording density.

[Means and effects for solving the problems] Therefore, the configuration of the present invention includes a heating body having an upper surface having a shape corresponding to the back surface of a resin base having a guide groove for optical recording on the surface, and a base that supports the heating body and has a space communicating with the periphery of the upper surface of the heating body, the space is vacuum-suctioned, and the resin base placed with the surface facing up is placed on the heating body. It is characterized by being adsorbed to.

In short, in the present invention, the residual stress is removed by heating the resin substrate with a heating body, and this removal is performed while the resin substrate is adsorbed to the heating body,
Therefore, the flatness accuracy of the resin substrate can be improved by the flatness accuracy of the heating body, and by heating and straightening from the back side of the resin base, it is possible to prevent the influence on the recording guide groove on the front side. The suction can also prevent thermal shrinkage of the resin substrate, and by applying suction around the heating body, it is possible to avoid the influence on the recording area where the guide groove is located.

[Example] FIGS. 1 and 2 show an apparatus according to this example. FIG. 1 is a half-cut plan view, and FIG. 2 is a longitudinal sectional view. The resin substrate 1 to be annealed by this device is molded from thermoplastic polycarbonate resin or the like by injection compression molding using a pair of molds. Guide grooves for storage signals are transferred. A guide groove formed by this transfer is formed on one surface 1A of the resin substrate 1.

The heating body 2 on which the resin substrate 1 is placed is the resin substrate 1
It is formed into a disk shape corresponding to the shape of. A through hole 3 for heat medium circulation is bored inside the heating body 2, and a heat medium such as silicon, biphenyl, phenyl ether, etc. flows through the through hole 3, and the heating body 2
is heated to a predetermined temperature. The upper surface 2A of the heating body 2, which is the surface on which the resin substrate 1 is placed, is highly polished to a high degree of flatness, and therefore the flatness accuracy of the upper surface 2A is highly improved.

The base 4 on which the heating element 2 is placed is disk-shaped, and a vertical peripheral wall 4B is formed at the end of the bottom 4A, so that the base 4 has a recess 5 with an open top surface.
is provided. An air intake hole 6 is formed through the ring-shaped circumferential wall 4B, and an air passage 7 connected to an air intake means such as a vacuum pump is connected to the air intake hole 6. A first heating element support member 8 is arranged in the center of the recess 5 of the base 4 and has three concentric steps 8A, 8B, and 8C. Two heating body support members 9 are arranged. As shown in FIG. 1, a plurality of second heating element supporting members 9 are provided in the circumferential direction along the peripheral side wall 4B of the base 4.

A first hole 2B is formed in the center of the heating body 2.
By inserting the middle part 8B of the heating element support member 8, the center part of the heating element 2 is placed on the upper surface 8D of the lower part 8C. At the same time, the vicinity of the outer end of the heating element 2 is placed on the upper surface of the second heating element support member 9. As a result, the heating element 2 is placed on the base 4 inside the recess 5 while being supported by the two types of heating element support members 8 and 9, and this arrangement is such that the heating element 2 and the bottom 4A of the base 4 space between 10
This will be carried out with the following. As a result of the above, the upper opening of the recess 5 is closed by the heating body 2;
Between the outer peripheral surface of the middle part 8B of the first heating element support member 8 and the center hole 2B of the heating element 2, and between the inner peripheral surface of the peripheral side wall 4B of the base 4 and the outer peripheral surface of the heating element 2. Gaps 11 and 12 are ensured. Further, a gap 13 is also provided between the upper surface 8D of the lower stage portion 8C of the first heating element support member 8 and the lower surface of the heating element 2. Said gap 1
1 and 12 are provided by appropriately setting the respective diameter dimensions of the heating body 2, the peripheral side wall 4B of the base 4, and the middle part 8B of the first heating body support member 2,
The gap 13 is the lower part 8C of the first heating element support member 8.
This is provided by forming minute irregularities, minute grooves, etc. on the upper surface 8D.

The upper step 8A of the first heating element support member 8 is inserted into the center hole 1B of the resin substrate 1, and the outer end of the resin substrate 1 is inserted into the flat step 4C formed on the upper surface of the peripheral side wall 4B of the holder 4. It will be posted. As a result, the resin substrate 1
is placed on the heating body 2 and ready for annealing treatment. The resin substrate 1 is placed on the heating body 2 with the surface 1A on which the storage signal guide groove is formed facing upward.

The air intake means is driven to exhaust air from the space 10 from the air intake hole 6. As a result, the space 10 is vacuum-suctioned, and the air present on the upper surface 2A side of the heating body 2 is also suctioned through the gap 13 and the gaps 11 and 12, so that the resin substrate 1 is moved to the top surface of the heating body 2. It is adsorbed by 2A. After this, heating element 2
A heating medium is caused to flow through the through holes 3 to raise the temperature of the heating body 2. Thereby, the resin substrate 1 is heated by the heating body 2. When the material of the resin substrate 1 is polycarbonate resin, the heating temperature is 140 to 180°C,
The heating time is 30 to 60 minutes. Residual stress in the resin substrate 1 is reduced by this heat treatment.

Further, this heat treatment is performed while the resin substrate 1 is adsorbed to the upper surface 2A of the heating body 2, and since this upper surface 2A of the heating body is a surface with a high degree of flatness accuracy as described above, the resin substrate 1 is corrected to approximately the same high degree of flatness accuracy as the upper surface 2A, and the occurrence of surface runout and warpage of the resin substrate 1 is prevented. Furthermore, since the resin substrate 1 is heated while the resin substrate 1 is fixed to the heating body 2 by the adsorption, thermal shrinkage of the resin substrate 1 due to heating can be suppressed to an extremely small level.

In addition to the above, the resin substrate 1 is attracted to the heating body 2 with the surface 1A on which the storage signal guide groove is formed facing upward, and since this surface 1A does not come into contact with the heating body 2, the guide groove is destroyed. Never.

In addition, since the adsorption of the resin substrate 1 is carried out through the gaps 11 and 12 formed around the heating element 2, the upper surface 2A of the heating element 2 does not have any openings for suction, so that the resin substrate 1 is tightly attached. The rear surface of the recording area of the resin substrate 1 will not be deformed due to the opening or the like, and the recording area of the resin substrate 1 will have good optical characteristics.

After the above heat treatment, the flow of the heat medium through the through holes 3 of the heating body 2 is stopped, and the resin substrate 1 is cooled. This cooling may be done by natural cooling, or by circulating a cooling medium through the through holes 3 of the heating element 2, or by
Forced cooling may be performed, such as by pressing the resin substrate 1 removed from the mold against a cooling mold.

When the resin substrate that has been arned as described above is used as a substrate for an optical disk, the birefringence will be reduced to 1/6 to 1/3 due to the reduction of residual stress, for example, birefringence of 60 nm will be reduced to 10 to 20 nm. In addition, the thermal shrinkage rate of the resin substrate is kept to an extremely small value of 1.5% or less.

Although the heating body of this embodiment was of a thermal fluid type in which a heat medium was circulated through an internal through hole, it may be of an electric heating type by providing a heating wire inside. If necessary, any material that can heat-process the resin substrate placed thereon may be used. Further, the structure in which the heating body is arranged on the base is not limited to that of this embodiment, and can be any structure. Furthermore, the shape of the heating body and the base may be arbitrary, and if necessary, Any configuration may be used as long as the heating body is placed on the base and a space is created between the heating body and the base to be vacuumed.

[Effects of the Invention] According to the present invention, the residual stress of the resin substrate is reduced, so the birefringence of the optical disk can be reduced, and the quality of the optical disk can therefore be improved. Because the plane accuracy is improved,
It becomes possible to realize high recording density of optical discs.

[Brief explanation of drawings]

The drawings show one embodiment, and FIG. 1 is a half-sectional plan view of the device, and FIG. 2 is a longitudinal sectional view of the device. 1...Resin substrate, 1A...Surface on which guide grooves are formed,
2... Heating body, 3... Heat medium through hole, 4... Base, 6...
Intake hole, 10...space.

Claims (1)

[Claims] 1. A heating body having an upper surface having a shape corresponding to the back surface of a resin base having a guide groove for optical recording on the surface;
A resin base supporting the heating element and having a space between the heating element and the heating element that communicates with the periphery of the upper surface of the heating element, the space being vacuum-suctioned and placed with the surface facing up. A resin-based annealing device, characterized in that the heating element adsorbs .