JPS62135334A - Method and apparatus for preparing disk substrate for recording optical information - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applicable to optical information recording devices such as compact discs, video discs, and optical disc memories for computers, in which information is written and read by irradiating a light beam. The present invention relates to a method for manufacturing a disk substrate applied to a disk and a manufacturing apparatus for carrying out the method.

[Prior Art] In recent years, injection molded polymeric materials have become the main type of optical information recording disk substrates because they are inexpensive to manufacture and are lightweight and easy to handle.

FIG. 3 is a cross-sectional view showing an example of a conventionally known manufacturing apparatus for a disk substrate for optical information recording.
．． It has 3. One side of the cavity l is formed by a stamper 4 on which a predetermined uneven pattern is formed in advance.

The stamper 4 is fixed to the mold 3 by a mounting member 5. Further, the mold 2 is provided with a spool 6 and a gate 7 that communicate with the cavity 1.

The conventional disk substrate manufacturing apparatus described above connects an injection machine (not shown) to the injection port 6a formed in the mold 2,
A molten polymer substance is injected into the cavity 1 under high pressure through the spool 6 and the gate 7, and after filling, the mounting member 5 is raised to push out the polymer substance remaining in the gate part 7 to a predetermined amount. It is possible to mold a shaped optical information recording disk substrate.

However, the following defects are likely to occur in the injection molded product of the polymeric material produced as described above. Namely, in the vicinity of the gate section 7, the diameter of the flow path for the molten polymeric material is small. Because of the large change, not only are external defects such as weld lines and sink marks likely to be formed, but also residual stress is likely to occur when the mounting member 5 is lifted and pushed out. Since the molten polymer substance is filled into the molds 2 and 3 while being cooled, the temperature of the polymer substance decreases, resulting in poor fluidity, and the molecules of the polymer substance are oriented in the direction of flow. , there is a problem that optical distortion is likely to occur.

Furthermore, a part of the cavity surface has a width of 0.46 μm, a depth of about 1100 nm, and a pitch of 1.6 μm for transferring pre-groups, and a width of about 0.50 μm and a depth of about 200 nm for transferring prepits. Since the stamper 4 is formed with a fine uneven pattern, the wraparound of the polymer material is insufficient, making it impossible to accurately transfer pre-groups and pre-pits, which tends to cause tracking errors or S There is a problem that the /N ratio is low.

In recent years, in this type of optical information recording disc.

Increasing the recording capacity has become one of the most important technical issues, but as mentioned above, large optical distortions occurring at the inner and outer peripheries of the disk substrate make it difficult to record information signals normally. Playback is not possible and the recording area cannot be expanded. In addition, in order to realize magneto-optical disks, which are attracting attention as erasable and rewritable optical information recording disks, a disk substrate with even lower optical distortion than optical disks is required. There is a demand for a disk substrate with small optical distortion in the outer circumferential portion and the outer circumferential portion.

Traditionally, injection molding methods have been used to prevent external defects such as weld lines and sink marks, as well as residual stress during molding, by applying ultrasonic vibrations to the gates, cut-outs, and uneven thickness areas of the mold. There is a known method for applying a A method is known in which molding is performed while applying ultrasonic vibrations to a polymer material introduced into the material (Japanese Patent Laid-Open No. 58-140222). Furthermore, as a method for increasing the fluidity of molten polymeric material, a method is known in which the polymeric material is filled into a mold and then instantaneously melted using high frequency waves (Japanese Patent Application Laid-open No. 5O-450
39).

[Problem that the invention seeks to solve]

However, among the above-mentioned conventional examples, the first conventional example is effective in preventing weld lines, sink marks, and residual stress that occur at the gate part and push-cut part of the mold, but it is effective in preventing optical distortion and residual stress in the outer peripheral part. The second conventional example is an injection molding method that is not effective at all in improving the transferability of a concave-convex pattern and is applied to the production of a plastic lens.

No consideration has been given to improving the transferability of fine concavo-convex patterns. Furthermore, the third conventional example is as follows.

Although it is effective in increasing the fluidity of polymeric substances.

Difficult to strictly control heating conditions.

There is a problem in that the polymeric substance decomposes and deteriorates when it is overheated.

[Means for solving problems]

In order to achieve precise transfer of uneven patterns.

It is necessary to melt the surface layer of the molten polymer material to improve the fluidity of the armpit region and to disturb the orientation of the molten polymer material in the flow direction. The present invention was made based on the above-mentioned knowledge, and the present invention has been made based on the above-mentioned knowledge. The present invention is characterized by realizing a method for manufacturing an optical information recording disk substrate that has excellent transferability and is free from optical distortion by applying ultrasonic vibration to the substrate.

〔Example〕

FIG. 1 is a cross-sectional view showing an embodiment of a manufacturing apparatus applied to the method of manufacturing an optical information recording disk substrate according to the present invention, and reference numeral 8.9 in the figure is a movable insertion piece; 10
．． 11 is an ultrasonic generator, 12 is an ultrasonic generator circuit,
Other members similar to those shown in FIG. 3 are designated by the same reference numerals.

The mold 2 is formed to be divisible from the mold 3, and after injection molding, the molds 2 and 3 can be divided to take out the solidified product. In addition, an injection machine (not shown) is arranged on the side of the injection port 6a of the spool 6 provided in the mold 2, and the injection machine is installed at the same time as the molds 2 and 3 are integrated. 6a, so that the molten polymer material is injected into the cavity 1.

The movable insertion pieces 8 and 9 are each formed into a ring shape with a diameter capable of applying ultrasonic vibration to the required areas of the inner and outer peripheries of the cavity 1, and one side thereof covers a part of the cavity 1. It is arranged in the mold 2 in such a manner as to be configured.

The ultrasonic oscillator 10.11 is made of silicon-lead titanate, and is configured to be able to oscillate ultrasonic vibrations of 15 KHz to 2 MHz by adjusting the ultrasonic oscillation circuit 10. This ultrasonic oscillator 10
．． 11 is set within the mold 2°3 so as to suppress the movable insert piece 8.9.

Hereinafter, a method for manufacturing an optical information recording disk substrate using the above-mentioned manufacturing apparatus will be described.

First, the molds 2.3 are assembled together, and the injection port 6a of the mold 2 is
Connect the injection machine to. In this state, the molten polymer substance is injected from the injection machine, and the cavity 1 is filled with the molten polymer substance through the spool 6 and the gate 7. After the cavity 1 is sufficiently filled with the polymeric substance, the molds 2 and 3 are cooled to solidify the polymeric substance, and the injection machine is moved to the mold 2.
At the same time, the molds 2 and 3 are separated and the product is taken out.

As described above, when a polymeric material is injected while applying ultrasonic vibration to the movable inserting pieces 8 and 9, the energy of the ultrasonic vibration causes the flow direction of the polymeric material to change in the portion in contact with the movable inserting pieces 8 and 9. As the orientation is disturbed, the temperature increases, fluidity increases, transferability improves, and optical distortion decreases. In particular, as shown in Figure 1,
When a molten polymeric material is injected from the center of the cavity 1 and filled to the outer periphery by the injection pressure, the temperature of the polymeric material decreases as it reaches the outer periphery, and its fluidity decreases, resulting in poor transferability. Since there is a tendency for the transferability to be poor, this is particularly effective in improving the transferability in the outer peripheral area. Furthermore, after pushing out the residual polymeric substance in the gate part 7, when the ultrasonic oscillator 10 disposed in the inner peripheral part of the cavity l is activated to apply ultrasonic vibration to the armpit, the residual polymeric substance is pushed out. Residual stress remaining on the inner peripheral portion of the disk substrate can be removed.

Figure 2 shows a comparison of the birefringence generated in a disk substrate manufactured by the method of the present invention and the birefringence generated in a disk substrate manufactured by a conventional manufacturing method.The sample was a polycarbonate disk substrate with a diameter of 130 nos. It was manufactured by continuously applying 20 KHz ultrasonic vibration from the start of injection to the completion of cooling of the filled polymer material. Further, birefringence was measured by a transmission method using an ellipsometer (laser wavelength: 633 nm).

As is clear from this graph, during injection molding.

This is a disk substrate made by applying ultrasonic vibration.

Compared to a disk substrate manufactured without applying ultrasonic vibration, the birefringence at the inner and outer circumferences is approximately 8% to 11%.
%, and the birefringence is improved to approximately the same degree as the birefringence in the intermediate region of the disk substrate.

Note that the following are examples of polymeric substances that can be applied to the present invention.

Any material may be used as long as it is transparent and has plasticity, and there are no particular limitations, but the material has a refractive index of 1.4 to 1.6.

For example, polycarbonate, polymethyl methacrylate, or modified products thereof are preferred.

Furthermore, the frequency of the ultrasonic vibration can be arbitrarily adjusted depending on the type of polymeric substance, temperature conditions, and the like.

Furthermore, in the above embodiment, a case has been described in which the movable insertion piece 8°9 is set only on the opposite side of the stamper 4. However, the gist of the present invention is not limited to this, and the movable insertion piece 8°9 is set on the side opposite to the stamper 4. It is also possible. Movable insert piece 8.
9 is set on the stamper 4 side, it is expected that the transferability of the uneven pattern will be further improved.

Further, in the above embodiment, a case was explained in which ultrasonic vibration was applied continuously from the start of injection to the completion of cooling of the filled polymer material, but the gist of the present invention is not limited to this. Instead, ultrasonic vibrations can be applied during any process, such as applying ultrasonic vibrations when cooling is complete.

〔Effect of the invention〕

As explained above, according to the present invention, ultrasonic vibrations are applied to the inner and outer peripheries of the cavity during any process from the time when a molten polymer substance is injected into the cavity until the product is taken out. As a result, the orientation of the molten polymer material in the flow direction is disturbed, the fluidity is improved, and the optical distortion and transferability in the core portion can be significantly improved.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing an embodiment of the disk substrate manufacturing apparatus according to the present invention, and Fig. 2 shows the birefringence caused in the optical information recording disk substrate manufactured by the method of the present invention and the birefringence produced by the conventional manufacturing method. FIG. 3 is a cross-sectional view showing an example of a conventionally known disk substrate manufacturing apparatus. l: cavity, 2.3: mold, 4 nistamper. 5: Mounting member, 6: Spool, 7: Gate. 8.9: Movable piece, to, tz ultrasonic oscillator. 12: Ultrasonic oscillator circuit Figure 1 1: Cavity 7: 7'-to 2.3:
Food type 8, 9: Possible pruning type 4 nistamper
+o, ++ [Suganaron Shichinin Alley 5: Attachment fan sweet
12; Qi [affirmative reaction micro-circuit well 6: Swab - 2 and Fig. 2 + (・Power・Ranojii! IIL (mm) Fig. 3

Claims (3)

[Claims] (1) Inject a molten polymer substance into a cavity in which a predetermined uneven pattern is formed, and after the molten polymer substance fills the cavity, the mold is cooled and the solidified product is taken out. In the method for manufacturing a disk substrate for optical information recording, in any process from the time when the polymer substance is injected into the cavity until the product is taken out,
A method for manufacturing an optical information recording disk substrate, comprising applying ultrasonic vibration to the center and outer periphery of the cavity. (2) An optical information recording disc comprising a mold in which a part of the cavity surface is formed with a stamper on which a predetermined uneven pattern is formed, and a spool and a gate are formed to communicate with the center of the cavity. In the substrate manufacturing equipment,
An apparatus for manufacturing an optical information recording disk substrate, characterized in that an ultrasonic oscillator is disposed so that ultrasonic vibrations are applied to at least the center and outer periphery of the cavity. (3) A movable piece connected to an ultrasonic oscillator is disposed in the mold corresponding to the center and outer periphery of the cavity so as to constitute a part of the cavity surface. A manufacturing apparatus for an optical information recording disk substrate according to scope 2.