JPH0944910A - Optical disc manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a process for producing an optical disk capable of easily producing the optical disk of which warpage is suppressed. SOLUTION: A disk-shaped plate 2 which is higher in bending strength, modulus of elasticity in bending, and rigidity than an optical disk substrate 1 is subjected to an annealing treatment under a load applied thereon at the time of producing the optical disk with which reading out of information is executed from the one surface. The plate 2 subjected to the annealing treatment is thereafter stuck to the surface (information recording surface 1a) on the side opposite to the information reading surface 1b of the optical disk substrate 1. The annealing treatment of the plate 2 is executed at 120 to 150 deg.C if a material mainly composed of polycarbonate is used as the plate 2.

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 disc in which information is read from one side.

[0002]

2. Description of the Related Art In recent years, in the field of information recording, research on optical information recording methods has been actively pursued. This optical information recording system can record / reproduce in a non-contact manner, can achieve a recording density higher than the magnetic recording system by one digit or more, and has a read-only type, a write-once type and a rewritable type. It has a number of advantages such as compatibility, and is considered to be applicable to a wide range of applications from industrial to consumer as a method for realizing inexpensive large-capacity files.

Among them, in particular, digital audio discs, optical video discs, and the like, which are optical discs corresponding to a read-only memory type, have become widespread.

In this optical disc such as a digital audio disc or an optical video disc, a reflective film made of metal such as aluminum is formed on a transparent optical disc substrate on which a concavo-convex pattern such as pits or grooves showing information signals is formed. Formed, and then this reflective film, moisture in the atmosphere,
The structure is such that a protective film for protecting from oxygen is formed. In such an optical disc, reproduction light such as laser light is emitted from the optical disc substrate side to the concavo-convex pattern, and an information signal is detected by the difference in reflectance between the incident light and the return light.

In order to manufacture such an optical disk, first, an optical disk substrate having a concavo-convex pattern is formed by a method such as injection molding, a reflective film is formed on the optical disk substrate by a method such as vapor deposition, and further ultraviolet curing is performed thereon. A protective resin may be formed by applying a mold resin or the like.

[0006]

By the way, in the above-mentioned optical disc, the optical disc substrate may be warped due to the influence of the manufacturing conditions or the temperature change after the manufacturing. However, as described above, since the information signal of this optical disc is detected by the difference in the reflectance between the incident light irradiated on the concave-convex pattern of the optical disc substrate and the return light thereof, the information signal of the warped optical disc is generated. However, if the track position is reproduced, the track position may be erroneously detected and the accurate servo operation may not be performed.

Therefore, the optical disc as described above is provided with a standard for warping, but in order to comply with this standard, it is necessary to strictly regulate the manufacturing conditions of the optical disc substrate. It should be noted that the warpage during manufacturing of the optical disk substrate needs to be set to a value that is about 20% stricter than the warpage standard of the optical disk in consideration of the change over time after manufacturing.

In order to suppress the occurrence of warpage during the manufacture of the optical disk substrate, the mold temperature is stabilized, the mold precision is controlled,
It may be possible to stabilize the timing of releasing the optical disk substrate. However, it is complicated to carry out all of these things, and it also reduces productivity.

Therefore, the present invention has been proposed in view of such conventional circumstances, and an object of the present invention is to provide an optical disk manufacturing method capable of easily manufacturing an optical disk whose warpage is suppressed.

[0010]

A method of manufacturing an optical disk according to the present invention has been proposed to solve the above-mentioned problems. When manufacturing an optical disk from which information is read from one side, For a disc-shaped plate having a bending strength, a bending elastic modulus and a rigidity higher than that of the optical disc substrate, an annealing process is performed while applying a load, and a surface opposite to the information reading surface of the optical disc substrate,
And a step of bonding the plate bodies in this order.

That is, according to the present invention, instead of strictly controlling mold temperature stabilization, mold accuracy control, mold release timing stabilization, and the like during manufacturing of the optical disk substrate, the optical disk substrate is controlled. By bonding the plate bodies together, the warp occurring in the optical disk substrate is corrected and the warp of the optical disk as a whole is suppressed.

Therefore, the plate body is required to have a bending strength, a bending elastic modulus, and a rigidity larger than those of the optical disk substrate, and to be less warped than the optical disk substrate. In order to make the plate body have a bending strength, a bending elastic modulus, and a rigidity larger than those of the optical disk substrate, the plate body is preferably made of glass fiber-reinforced plastic.

However, in such a reinforced plastic containing glass fibers, the glass fibers are easily oriented during injection molding, and if the glass fibers are cooled while being oriented, an anisotropy occurs in the shrinkage ratio, so that the plate body is warped. Easy to cause.

Therefore, in the present invention, before the plate body is bonded to the optical disk substrate in this way, the plate body itself is annealed so as to remove the warp occurring in the plate body itself.

When annealing this plate,
It is efficient to stack a plurality of the plate bodies and interpose a spacer therebetween. In this case, the spacer is preferably made of a material having a higher thermal conductivity than the plate body.

When the plate is made of glass fiber-containing polycarbonate, for example, the plate is preferably annealed at 100 ° C. to 150 ° C. This is because if the annealing temperature is lower than 100 ° C, the warp generated in the plate cannot be sufficiently removed, and if the annealing temperature is higher than 150 ° C, the plate is softened and a predetermined shape cannot be maintained.

By the way, in the present invention, it has been described above that the plate body to be bonded to the optical disk substrate is preferably made of glass fiber-reinforced plastic, but the glass fiber content is 10% to 30% by volume. % Is preferable. If the glass fiber content is too low, the plate cannot have sufficient rigidity. Conversely, if the glass fiber content is too high, the bending strength and bending elastic modulus of the plate increase. It becomes too difficult to use as a plate.

The above-mentioned glass fibers have a diameter of 3 to 2 in pellets of reinforced plastic containing glass fibers.
Those having a length of 0 μm and a length of about 300 μm can be used, but by kneading with a screw of an injection molding machine, they are finally crushed to a length of about 30 μm. Also,
Glass beads may be used as the glass fibers, and in this case, those having a diameter of about 5 μm to 10 μm may be used.

Further, in order to correct the warp of the optical disk substrate and improve the strength of the optical disk by applying the present invention and bonding the plate, the thickness of the plate is 1 mm or more, It is desirable to design the diameter of the plate body to be larger than that of the optical disk substrate. In addition, the diameter of the plate is D
Assuming that the diameter is ₁ and the diameter of the optical disk substrate is D ₂ , the relationship between them is D ₂ ≦ D ₁ ≦ 1.02D ₂ , which is preferable.

When the optical disc is manufactured as described above, it is possible to obtain an optical disc in which the warp is suppressed and the strength is high.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a specific embodiment to which the present invention is applied will be described with reference to the drawings.

Here, an optical disc as shown in FIG. 1 was manufactured. This optical disk has a disk-shaped optical disk substrate 1 having one surface as an information recording surface 1a and the other surface as an information reading surface 1b, and has a bending strength, a bending elastic modulus and a rigidity higher than those of the optical disk substrate 1. A large disc-shaped plate body 2 is attached and bonded.

The optical disk substrate 1 is a transparent substrate made of polycarbonate and having a diameter of 200 mm, and an information recording surface 1a is formed by forming a concavo-convex pattern such as pits and grooves indicating information signals. Also,
Although not shown, a reflective film made of a metal such as aluminum and a protective film for protecting the reflective film from moisture and oxygen in the atmosphere are sequentially formed on the information recording surface 1a.

On the other hand, the plate 2 is made of polycarbonate containing 20% by volume of glass fiber, and has a diameter of 200 m.
m, and a thickness of 1.5 mm. And
The plate body 2 is attached to the information recording surface 1a side of the optical disc substrate 1 via the above-described reflective film and protective film.

In order to reproduce such an optical disk, reproduction light such as laser light is applied to the concave-convex pattern from the side of the information reading surface 1b of the optical disk substrate 1, and the reflectance of the incident light and the return light is changed. The information signal may be detected by the difference.

A method of manufacturing the optical disc having the above-mentioned structure will be described below.

First, a pellet of polycarbonate is used to mold an optical disk substrate 1 having a concavo-convex pattern by injection molding, and then a reflection film is formed thereon by a technique such as vapor deposition, and an ultraviolet curable resin or the like is further formed thereon. Was applied to form a protective film.

On the other hand, using a polycarbonate pellet containing 20% of glass fiber, a plate 2 having the same diameter as that of the optical disk substrate 1 was formed by injection molding.

At this time, the warp of the plate body 2 is about +2 mrad at a position of 50 mm from the center, whereas it is about -4 mrad at a position of 100 mm from the center (outer edge portion). Was becoming. The warpage was evaluated by the angle between the surface of the plate 2 and the horizontal surface when the plate 2 was placed on the horizontal surface.

Next, the plate body 2 obtained as described above
Then, an annealing process was performed while applying a weight as shown in FIG.

Specifically, a plurality of plate bodies 2 are placed on the fixed base 5 by inserting the holes 2a into the poles 6, respectively, and then the weight 7 and the holes 7a are inserted into the poles 6.
It was put on the plate body 2 by being inserted into. At this time, a plurality of the plate bodies 2 may be stacked, but here, as shown in FIG. 2, the spacer 8 is interposed between the plate bodies 2. The spacer 8 is a disk made of aluminum and has a diameter substantially equal to that of the plate body 2 and a thickness of 1.5 mm. And, in this way, the plate body 2 is 10 g /
5 hours at 110 ° C with a weight of cm ² .
An annealing process was performed.

As a result, the warp of the plate member 2 is -1 mr at the position (outer edge) at a distance of 100 mm from the center.
It decreased to about ad.

After that, when the plate 2 was bonded to the optical disk substrate 1 to complete an optical disk, the warp of the entire optical disk was + at a position where the distance from the center was 50 mm.
It was about 2 mrad, and it was about -1 mrad at a position (outer edge) at a distance of 100 mm from the center, which was very small.

This is a plate body 2 as compared with the optical disc substrate 1.
This is because the rigidity is higher, and even if the optical disc substrate 1 is warped, the optical disc substrate 1 follows the shape of the plate body 2 and the warp is corrected.

Therefore, when the optical disc is manufactured as described above, the molding conditions of the optical disc substrate 1 can be relaxed more than before. That is, the optical disc substrate can be easily manufactured and the productivity can be improved.

Further, in the optical disc obtained as described above, even if there is a temperature change after the plate body 2 is bonded to the optical disc substrate 1, the warp of the optical disc substrate 1 due to the temperature change is suppressed by the plate body 2. .

By the way, in the present embodiment, in order to obtain an optical disk in which the warp is suppressed, the plate body 2 is annealed to remove the warp generated in the plate body 2. The condition of is determined by the following experiment.

First, the annealing temperature was optimized. Specifically, the annealing temperature is 90 ° C., 100 ° C., 110
C., 120.degree. C., 130.degree. C., or 140.degree. C. was set, the plate 2 was annealed, and then the warp of the plate 2 was measured. The weight applied to the plate during annealing was 10 g / cm ² , and the annealing time was
It was set to 5 hours. The results are shown in FIG. 3 together with the warped state of the plate body 2 before the annealing treatment.

From FIG. 3, it is understood that when the annealing temperature is 100 ° C. or higher, the warp of the outer edge portion of the plate body 2 can be suppressed to −2 mrad or less.

Next, the change in the warp of the plate 2 with the annealing time was examined. Specifically, the annealing temperature is 110 ° C.,
After applying a load of 10 g / cm ² to the plate body 2, the annealing time was set to any of 2 hours, 5 hours, and 10 hours, and the plate body 2 was annealed. FIG.
The warped state of the plate body 2 that has been annealed for each annealing time is shown together with the warped state of the plate body 2 before the annealing process.

From FIG. 4, it is understood that when the annealing time is set to 5 hours or more, the warp of the outer edge portion of the plate body 2 is suppressed to -2 mrad or less.

Next, the change in warpage due to the magnitude of the load applied to the plate 2 during annealing was examined. Specifically, after setting the annealing temperature to 110 ° C. and the annealing time to 5 hours, the load applied to the plate body 2 is 5 g / cm ² , 10 g / c.
The plate body 2 was annealed by setting it to be m ² , 20 g / cm ² , or 30 g / cm ² . FIG.
The plate body 2 after the annealing treatment performed while applying each weight to
The warped state of the plate body 2 is shown together with the warped state of the plate body 2 before the annealing treatment.

From FIG. 5, the weight applied during annealing is 1
When it is 0 g / cm ² or more, the warp of the outer edge portion of the plate body 2 is −
It can be seen that it can be suppressed to 2 mrad or less.

From these results, when the plate body 2 is formed of polycarbonate containing 20% by volume of glass fiber in a volume of 200 mm and a thickness of 1.5 mm, the plate body 2 is an optical disk. Before bonding to the substrate 1, while applying a load of 10 g / cm ² or more,
It was found that it is preferable to anneal at 00 ° C. or higher for 5 hours or longer.

Although the optical disk manufacturing method according to the present invention has been described above, the present invention is not limited to the above-described embodiments, and various modifications and changes can be made. For example, when the plate body 2 is annealed, only a plurality of the plate bodies 2 may be stacked and a weight may be applied from above. Also, the configuration of the optical disc manufactured by applying the present invention can be modified and changed without departing from the spirit of the present invention. For example, the constituent materials are not limited to the above-mentioned materials as long as the plate body 2 has higher rigidity than the optical disk substrate 1. However,
It is necessary to appropriately optimize the annealing conditions depending on the material and size of the plate body 2.

[0046]

As is apparent from the above description, if the plate body is annealed while being weighted and then bonded to an optical disk substrate, an optical disk with suppressed warpage can be easily manufactured. Further, the strength is higher than that of the conventional optical disc having no plate.

Since the optical disc obtained in this manner has a suppressed warp, the concavo-convex pattern of the optical disc substrate can be accurately detected, and an accurate servo operation can be performed.

Further, according to the present invention, even if the optical disk substrate is warped, it is corrected by adhering the plates, so that it is necessary to strictly control the manufacturing conditions when the optical disk substrate is molded. Since it is eliminated, the optical disk substrate can be easily molded and the yield is improved.

Therefore, by applying the present invention, it becomes possible to manufacture a highly reliable optical disk with high productivity.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a configuration example of an optical disc manufactured by applying the present invention.

FIG. 2 is a schematic perspective view showing a state in which a plate body is weighted.

FIG. 3 is a characteristic diagram showing a warp of a plate body annealed at various temperatures as a relationship with a distance from the center of the plate body.

FIG. 4 is a characteristic diagram showing the warp of a plate body that has been annealed for various times as a relationship with the distance from the center of the plate body.

FIG. 5 is a characteristic diagram showing a warp of a plate that has been annealed while applying various weights as a relationship with a distance from the center of the plate.

[Explanation of symbols]

 1 optical disk substrate 2 plate 5 fixing base 6 pole 7 weight 8 spacer

Claims (4)

[Claims] 1. When manufacturing an optical disc in which information is read from one side, annealing is performed while applying a load to a disc-shaped plate body having a bending strength, a bending elastic modulus and a rigidity higher than those of an optical disk substrate. A method of manufacturing an optical disc, comprising: a treatment step; and a step of adhering the plate body to a surface of the optical disc substrate opposite to an information reading surface in this order. 2. The method of manufacturing an optical disk according to claim 1, wherein the annealing treatment is performed on the plate body while a plurality of the plate bodies are stacked and a spacer is interposed therebetween. 3. The method of manufacturing an optical disc according to claim 2, wherein the spacer is made of a material having a higher thermal conductivity than that of the plate body. 4. The method for manufacturing an optical disk according to claim 1, wherein the plate body is made of glass fiber-reinforced plastic.