JPH0582522U - Mold for optical disk substrate molding - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain a stamper presser capable of preventing the occurrence of bumps on a molded substrate and thereby increasing the number of substrates that can be molded by one stamper. [Structure] Stamper 5 for molding optical disk substrate
Is pressed and fixed to the movable mold 2 by the outer stamper holder 7 and the inner stamper holder 8. At that time, immediately below the portion where the outer peripheral side stamper retainer 7 and the inner peripheral side stamper retainer 8 press the stamper 5, as a member that blocks the circulation of the atmosphere, a fluorine resin O-ring 9 and a fluorine resin circle. An annular sheet 10 is provided.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a mold to which a stamper is pressed and fixed when molding an optical disk substrate.

[0002]

[Prior Art]

 In recent years, compact discs and video discs dedicated to reproduction, recordable optical discs, magneto-optical recording discs capable of recording / reproducing and erasing, phase-change discs, etc. have been used as information recording media.

From the viewpoint of productivity, the substrates of these disks are often manufactured by injection molding or injection compression molding of a plastic material such as polycarbonate resin. In these methods, a void is formed by two molds, and a molten resin is poured into the void to mold the substrate. At this time, a mold of a molded substrate called a stamper is attached to one of the molds. On one surface of the stamper, a recording portion for transferring and forming necessary information on the molded substrate is formed in an annular shape at a portion except the outer peripheral edge portion and the inner peripheral edge portion of the substrate. The outer peripheral edge and the inner peripheral edge other than the recording area are non-recording areas.

Then, a stamper holder is used so that the stamper does not move even if continuous molding is performed for a long time. The stamper holder is fixed by pressing the stamper onto the mold within the annular area of the non-recording area on the inner and outer sides of the stamper. In addition, in the mold for fixing the stamper, exhaust is performed from the hole provided on the contact surface with the stamper to create a depressurized state between the mold and the stamper, which further secures the holding.

[0005]

[Problems to be Solved by the Invention]

 By using the above method, the stamper does not move or rotate even during continuous molding for several weeks, but as the number of molded sheets increases, the non-recording area on the outer and inner peripheral parts of the surface of the formed substrate is first. In addition, minute irregularities called bumps are generated. Then, as the number of molded sheets increases, the bumps gradually become larger and deeper and also appear in the recording area sandwiched between the non-recording areas.

In an optical recording medium formed using a substrate having such bumps, the error rate becomes large and the mechanical characteristics deteriorate. For this reason, if bumps are generated, the substrate cannot be molded any more, and there is a problem that the number of substrates that can be molded by one stamper is limited.

[0007]

[Means for Solving the Problems]

 A mold for molding an optical disk substrate according to the present invention is a mold used for fixing a stamper when molding a substrate for an optical disk, and at least an outer peripheral side stamper presser is provided on a surface of the mold in contact with the stamper. The feature is that a member that blocks the circulation of the atmosphere is provided directly below the part that holds down the stamper.

As a result of diligent study on the cause of the above-mentioned problems, the present inventor has found that the bump deforms the stamper due to the polymer used for the substrate molding material adhering to the back surface of the stamper. We found that the shape was reflected on the substrate surface. In addition, because the adhesion of the polymer does not sufficiently block the atmosphere between the die / stamper / stamper holder, the polymer vapor present in the atmosphere of the cavity for molding the substrate is It was found that this was due to the fact that it entered the space between the mold and the stamper along with the atmosphere, and that it first began to condense in the non-recorded areas on the inner and outer circumferences, and gradually reached the inner recorded areas.

Based on this finding, by sufficiently blocking the atmosphere flow between the stamper and the mold, it is possible to prevent the polymer vapor from entering between the stamper and the mold, and prevent the polymer from adhering to the back surface of the stamper. Therefore, we came to think that the number of sheets that can be molded with one stamper could be dramatically increased.

There are various possible circulation paths of the atmosphere between the mold and the stamper, such as when passing through a gap between the stamper and the stamper holder. It is effective and preferable to provide an atmosphere blocking member at the edge of the contact portion between the mold and the stamper. At this time, the atmosphere blocking member must prevent the stamper from being deformed. Therefore, it is preferable that the atmosphere blocking member provided between the die and the stamper is provided immediately below the portion where the stamper holder holds the stamper against the die.

Bumps are generated from the inner and outer ends of the substrate. By the way, in a normal substrate, a non-recording portion is provided on the outer peripheral side and the inner peripheral side so as to sandwich the recording portion. The non-recording portions have a width of only a few mm on the outer peripheral side, but are wider on the inner peripheral side than on the outer peripheral side. Therefore, in order to mold a large number of substrates, it is effective to prevent the bumps from being generated especially from the outer peripheral side. The stamper is usually fixed to the inner circumference side and the outer circumference side separately by a stamper retainer. For this reason, it is preferable that the atmosphere blocking member provided in the mold in the present invention is used at least on the outer circumference side. Needless to say, it is even more preferable to use it on the inner peripheral side.

The feature of the present invention resides in that the contact portion between the die and the stamper is provided with a member that blocks the circulation of the atmosphere. However, even in the conventional die, the stamper is pressed by the stamper retainer. By pressing against the mold, the mold and the stamper were in macro contact. However, because of the contact between nickel, which is a stamper material, and a material that is relatively hard, it was easy to pass through the atmosphere due to insufficient surface smoothness. Therefore, it is preferable to use a plastic exhibiting rubber elasticity or a relatively soft metal material such as copper, brass, silver, gold or aluminum as the member for blocking the atmosphere flow of the present invention. Among them, a material having a high rubber elasticity is preferable because it has an excellent atmosphere shielding property. From that point, a plastic rubber elastic material is preferable.

Since the mold and the like may be used at a temperature of 100 ° C. or higher depending on the purpose of use, it is preferable that the atmosphere blocking member is made of a material having high heat resistance. From this point of view, among the rubber elastic materials of plastic type, silicone rubber and fluorine resin type rubber are preferable. Among these, fluororesin rubber having a lower gas permeability is preferable.

As the atmosphere blocking member, a ring-shaped member having a circular cross section such as a circle or an ellipse has a large pressing force because the width of the contact portion with the stamper is narrow. It is more preferable because it has a large effect of shielding the atmosphere. Further, it is preferable to provide a U-shaped groove, a V-shaped groove, a concave groove, or the like on the surface of the mold to prevent the position of the atmosphere flow blocking member from being displaced.

If the size of the atmosphere flow blocking member is too large compared to the depth of the groove, the space between the die surface and the stamper becomes large, and when fixed by pressing the stamper or depressurizing it. The stamper may be deformed. Therefore, for example, when silicon rubber or fluorine resin rubber having a circular cross section is used, its diameter is preferably larger than the depth of the groove by about 0.1 to 2 mm.

The optical disk substrate in the present invention means a compact disk for reproduction only, a video disk, a write-once optical disk, a magneto-optical recording capable of repeating recording, reproducing and erasing, a phase change type disk, a laser, etc. A substrate for a recording medium using light is considered, but it is particularly preferably used for a magneto-optical recording medium.

[0017]

【Example】

 FIG. 1 is a schematic sectional view of a molding portion in an optical disk substrate molding apparatus to which a stamper holder according to an embodiment of the present invention is attached. In the figure, 1 is a fixed-side mold, 2 is a movable-side mold, 3 is a space formed between the fixed-side mold 1 and the movable-side mold 2, and 4 is for injecting a substrate material into the space 3. Introducing path, 5 is a stamper attached to the movable-side mold 2, 6 is a recording portion provided on the stamper 5 for transferring a predetermined pattern to a molding substrate, 7 is a stamper presser for the outer peripheral side of the stamper 5, and 8 Is a stamper for the inner peripheral side of the stamper 5, 9 is an O-ring made of fluororesin, and 10 is an annular sheet made of fluororesin. In addition, in order to facilitate understanding of the device configuration, the dimensional ratio is partially exaggerated in FIG.

In order to confirm the effect of pressing the stamper according to the present invention, continuous substrate molding was performed as follows, and the occurrence of bumps on the molded substrate was observed.

An injection compression molding apparatus was used as an apparatus for molding the substrate. The injection compression molding apparatus is provided with a fixed mold 1 and a movable mold 2, and a gap 3 is formed between the two molds. The heated and melted substrate material is injected into the void 3 through the introduction path 4. Then, the injection pressure causes the movable mold 2 to move, and the space between the two molds opens by a predetermined dimension. After that, the open molds are compressed, and the pressure spreads the substrate material between the molds to form the substrate.

At this time, the stamper 5 is fixed to the movable mold 2 by the outer peripheral side stamper presser 7 and the inner peripheral side stamper presser 8. The stamper 5 is provided with a predetermined pattern as the recording portion 6, and the pattern is transferred to the recording portion of the base plate when the substrate is molded.

The substrate to be molded has an annular shape with an outer diameter of 130 mm and an inner diameter of 15 mm, and its thickness is 1.2 mm. Polycarbonate resin was used as the substrate material.

On the other hand, the stamper 5 has an annular shape with an outer diameter of 145 mm and an inner diameter of 35 mm, and its thickness is 300 μm. A recording portion 6 for transferring a pattern required for the substrate to be molded is formed in an annular shape in a range from 120 mm in diameter to 60 mm or more in diameter on the surface on which the substrate is molded. The material for this damper 5 was nickel.

The outer-peripheral-side stamper holder 7 has a structure in which the stamper 5 is pressed and fixed to the movable-side mold 2 within an annular shape with a diameter of 130 mm from the outer peripheral side of the stamper 5. On the other hand, the inner-peripheral-side stamper presser 8 has a structure in which the stamper 5 is pressed against the movable-side mold 2 within an annular range having a diameter of 40 mm from the inner peripheral side of the stamper 5.

An O-ring 9 made of a fluororesin was used immediately below the outer circumferential stamper retainer 7 as an atmosphere blocking member provided in the movable mold 2 for fixing the stamper 5. Further, an annular sheet 10 made of fluororesin is used just below the stamper holder 8 for the inner peripheral side.

Here, when an O-ring is provided as a member for shutting off the atmosphere, an O-ring mounting groove is provided directly below the outer peripheral stamper holder 7 in the movable die 2.

In Example 1, the atmosphere blocking member is provided on both the inner and outer stamper holders. Further, in Example 2, an atmosphere blocking member was provided only on the outer side of the stamper holder.

On the other hand, in Comparative Example 1, the atmosphere blocking member was provided only on the stamper holder on the inner peripheral side. Further, as Comparative Example 2, no atmosphere blocking member was provided on both the inner and outer stamper holders.

The substrate was continuously molded under the above conditions. The continuous molding was performed until the generation of bumps was confirmed in the recording portion of the substrate with the upper limit of 30,000 sheets. At that time, a sample was taken out every 1,000 sheets, and the state of bump generation on the substrate was confirmed by visual observation with the transmitted light of the mercury lamp. At that time, the substrate was divided into an inner peripheral side and an outer peripheral side, and they were further divided into a non-recording area and a recording area to record the bump occurrence state. The results are shown in Table 1.

As shown in Table 1, in the case of Example 1 in which the atmosphere blocking members were provided on both the inner and outer stamper presses, no bumps were observed even with 30,000 sheets. .

Further, in the case of the embodiment 2 in which the atmosphere blocking member is provided only on the outer stamper holder, the bumps are generated in the non-recording portion on the inner circumference side in 8,000 sheets, but the recording portion on the inner circumference side is formed. The bumps were generated at 16,000 sheets. In this case, no bump was observed on the outer peripheral side.

On the other hand, in the case of Comparative Example 1 in which the atmosphere blocking member is provided only on the inner peripheral side stamper holder, bumps are generated in the non-recording area on the outer peripheral side at 7,000 sheets and the outer peripheral side at 10,000 sheets. Occurrence of bumps was observed in the recording part on the side. However, in this case, no bump was observed on the inner circumference side.

Further, in the case of Comparative Example 2 in which the atmosphere blocking member was not provided on both the inner and outer stamper holders, the inner peripheral non-recording portion and the outer peripheral non-recording portion were 6,000 sheets. , 9,000 bumps were generated on the outer peripheral side recording area, and 13,000 sheets, inner peripheral side recording area.

As the substrate, it is necessary that at least bumps are not generated in the recording portion, and for that reason, it is effective from the above results to provide an atmosphere shielding member at least on the outer side stamper holder. I understand.

[0034]

[Table 1]

[0035]

[Effect of the device]

 As described above, by using the stamper holder of the present invention, it is possible to prevent the polymer vapor existing in the atmosphere around the mold from flowing around to the back surface of the stamper. As a result, the stamper is less likely to be deformed during the molding of the substrate, and the number of substrates that can be molded by one stamper can be increased.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a molding portion in an optical disk substrate molding apparatus.

[Explanation of symbols]

 1 Fixed-side mold 2 Movable-side mold 3 Void formed by two molds 4 Board material introduction path 5 Stamper 6 Stamper recording part 7 Outer peripheral side stamper presser 8 Inner peripheral side stamper presser 9 O-ring 10 Annular sheet

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Claims (4)

[Scope of utility model registration request] 1. A mold used for fixing a stamper when molding a substrate for an optical disk, in a surface of the mold contacting the stamper, at least directly below a portion where the outer stamper holder presses the stamper,
A mold for molding an optical disk substrate, which is provided with a member for blocking the circulation of the atmosphere. 2. A member for cutting off the flow of the atmosphere is provided immediately below a portion of the surface of the die that contacts the stamper, where the inner-peripheral-side stamper retainer presses the stamper. Mold for optical disc substrate molding. 3. The stamper holder for molding an optical disk substrate according to claim 1, wherein the member for blocking the circulation of the atmosphere is made of a plastic rubber elastic material. 4. The stamper holder for molding an optical disk substrate according to claim 3, wherein the member for blocking the circulation of the atmosphere is made of a silicone rubber material or a fluororesin rubber material.