JP2000094480A - Molding die and injection molding machine for disk-shaped recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding die for disk-shaped recording medium for forming a disk base having very small recesses and projections on its surface and a little surface vibration. SOLUTION: A molding die is constituted of a fixed side mold 10 and a movable side mold 11. A fixed side plate temperature control circuit 37 is provided on a fixed side plate 6 of the fixed side mold 10, while a movable side mirror temperature control circuit 40 is provided on a movable side mirror 7 of the movable side mold 11. The fixed side mold 10 is provided with a thick plate stamper 1 constituted a stamper 2 formed of a thin sheet metal having recessed and projected signals and a thick metal plate 4 bonded together by plating 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding die for a disc-shaped recording medium for recording audio, video and other various recording information, and an injection molding machine using the same.
More specifically, a metal stamper obtained by joining a thin stamper having minute uneven signals and grooves obtained by a mastering process to a thick metal plate of the same or different material with a low melting point alloy (such as a solder alloy) is used. The present invention relates to a molding die for a disk-shaped recording medium and an injection molding machine capable of producing a disk by producing a die and performing injection molding using the molding die to produce a disk without an ultra-flat substrate noise. It is.

[0002]

2. Description of the Related Art Optical recording media and magnetic recording media are known as recording media for audio, video and other various information. These recording media are phase-change optical disks that use the reflectance change due to the change in the crystal structure of the recording film by laser light on a plastic substrate on which information signals are written by embossed pits or groups, and magneto-optical that uses the magneto-optical effect of the recording film. There are a disk and a magnetic disk for writing signals magnetically.

[0003] As a method of forming an information recording layer having fine irregularities such as phase pits and pre-groups in which data information, tracking servo signals and the like are recorded on the information recording layer, a plastic substrate formed by injection molding using a stamper is used. It is commonly used today.

FIG. 7 shows an injection molding die structure generally used for an optical disk using a conventional thin plate stamper. FIG. 8 is a schematic view of an injection molding machine, in which a mold having the stamper attaching structure of FIG. 7 is attached to the mold portion 49 of FIG. 8 to obtain a duplicated plastic substrate from the stamper on which signals are formed.

The thin plate stamper of about 0.3 mm used in FIG. 7 is produced through a series of mastering steps and an electroforming process shown in FIG. As is evident from FIG. 10, a plating step of electroforming after applying a very thin metal film to the glass master disc coated with a resist by a laser exposure apparatus and dried by exposure and development conductive treatment (electroless plating or spattering). After passing through (generally, plating to a film thickness of about 0.3 mm), the inner and outer diameters are formed by punching, lathing, or the like.

[0006]

The disadvantage of the substrate obtained by disk molding is that the stamper expands in the radial direction and rotates by the stress and heat when the resin is filled at the stage when the molten resin is injected into the mold cavity. Strength is given and it is easy to make abrasion with the mold. The rotational force of the stamper is generated by the rotational force caused by the rotation of the screw when the resin is melted in the cylinder of the molding machine, and the moment in the rotational direction when the resin passes through the gate in the mold.

In the stage from cooling to solidification, the stamper causes the resin to undergo volume relaxation due to stress relaxation within a certain period of time and progress of cooling, and only uniform linear movement due to unevenness in stress at the time of molding and minute unevenness of the contacting mold surface. In addition, because the stamper is thin, the stamper is thin, and the polishing marks during backside polishing, which is performed for adjusting the plating bumps on the backside and the thickness of the stamper, are added. It is transferred and remains on the disk together with the scratches as inverted irregularities.

[0008] These problems are caused by the compact disk (C
D), video disk (VD), etc., low numerical aperture (low NA)
At the time of the recording, the depth of focus was not considered a problem, but in the case of a high numerical aperture (high NA) disk, the laser beam was sharply stopped down as shown in FIG. And surface runout are likely to cause focus errors and tracking errors. In addition to the deformation accompanying the expansion and contraction rotation of the stamper, expansion and contraction stresses are generated in the stamper due to the pressure and temperature at the time of injection inside the disk. Distortion remains.

The internal stress of the disk decreases with cooling and solidification, but most of the internal stress is not relieved until solidification and remains in the substrate as residual stress. The stress resulting from the volume contraction of the disk and the expansion / contraction movement of the stamper is a birefringence. And radial,
It also causes circumferential warpage (SKEW).

[0010] As described above, the thermal expansion and contraction of the stamper are performed under the condition where the mold in which the resin is cooled and solidified is pressurized, so that the scratches between the mirror surface of the mold and the back surface of the stamper and the surface of the mold are caused. Occurs between. The scratches are easily scratched because the stamper has a nickel hardness similar to that of a SUS-402 material generally used as a mold material. As an example, the Vickers hardness obtained by quenching and tempering a SUS material is around 650, while the hardness of nickel is 75.
It is around 0. For this reason, in a disk mold, a hard coat such as titanium nitride (Ti-N) or silicon nitride (Si-N) is applied to the surface of the mold by several microns to increase the surface hardness and to prevent damage to the mold surface. General. However,
These methods are not perfect. For example, titanium nitride (Ti-N) has a Vickers hardness of 2,000 to 3,000, which is hard but as thin as several microns, so that the influence of the base SUS appears, and the life is longer than that without a coating, but there is no damage. And the maintenance of rewrapping / recoating had to be performed periodically.

On the other hand, in a discrete hard disk, there is a medium on which a fine uneven signal similar to that of an optical disk is transferred to a plastic substrate. However, unlike an optical disk, signal reading is extremely narrow, with a flight head having a distance between the disk and head of 50 nm or less. Stricter standard values, such as warpage, deformation, and roundness of the disk, than required for the optical disk are required.

Therefore, in the disk forming by the stamper method, as described above, the problems such as roundness, surface accuracy, and warpage cannot be cleared by the influence of the thermal expansion and shrinkage of the stamper during the forming process. After the resist coating, laser exposure, and development, which are the mastering processes of the optical disk, the substrate forming method using a direct mold is performed in which the necessary unevenness signal is created on the mold surface by performing etching instead of the electroforming process, and the disk substrate is formed. is there.

However, this method of directly forming a signal pattern on the surface of a mold requires a complicated process, equipment, time and cost as shown in FIG. The steps will be described below. First, the roughened mold material is processed into a mold shape. Next, the mirror surface is set to the JIS maximum height (Ry) = 0.2.
Perform surface grinding finish to a surface roughness of about mm. Next, the diamond abrasive grains are gradually refined, and finally a mirror lap of about 2 microns is performed. In the case of a mirror surface mold that has been used for the reading surface of a compact disk (CD) or a digital versatile disk (DVD), lapping at this level was sufficient, but fine polishing flaws remained, and this surface There was no problem because the laser spot diameter was large when using as a disk reading surface, but it caused noise and errors when used as a signal surface, and these polished minute scratches could not be used on the signal surface . Next, depending on the situation, 1 abrasive grain
Further fine polishing of not more than μm is repeatedly performed, and metal sputter lapping is repeated several times on the lapping surface to remove scratches and fine irregularities, thereby obtaining a surface similar to the optical glass surface. Finally, a mastering process is performed on the mirror-finished plate thus completed, and after development, patterning is performed by etching to obtain a mold with a signal.

In a high-density disk corresponding to a high numerical aperture (high NA), a disk obtained from a conventional thin stamper of about 0.3 mm has the above-mentioned stress, heat, heat,
Small irregularities and deformation of the stamper due to expansion, contraction, etc., scratches on the surface of the stamper and the mold surface, and traces of polishing on the back surface of the stamper affect the disc.
There is negligible noise for low numerical aperture (low NA) disks up to D (FIG. 12).

Since this noise hardly exists on the reading surface side of the disk and does not exist on the stamper itself as shown in FIG. 13, the stamper deformation in the molding process is caused as described above. It is clear that. The vertical runout of the stamper alone was measured by attaching the stamper to a glass plate.

FIG. 12 shows a measurement example in which the same disk has a large noise on the thin stamper side surface and a small noise on the side corresponding to the opposite thick plate stamper, that is, the reading surface side surface. FIG. 13 shows the stamper itself. By comparing the two with the noise measurement results, it can be seen that the noise is large in the molded disk, and it can be determined that the thin stamper is the result of minute deformation during molding.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is intended to provide a molding die and an injection molding machine for a disk-shaped recording medium capable of obtaining a disk substrate having a small surface unevenness and a small surface runout. The purpose is to provide. Further, another object of the present invention is to provide a molding die and an injection molding machine for a disc-shaped recording medium, which can prevent the occurrence of the warpage of the disc due to the non-uniform temperature distribution on the front and back surfaces of the disc. I do. Still another object of the present invention is to provide a molding die and an injection molding machine for a disc-shaped recording medium, which can prevent a thick plate stamper from rotating in the die during molding. Still another object of the present invention is to provide a molding die and an injection molding machine for a disk-shaped recording medium which can absorb a dimensional change of a thick plate stamper due to thermal expansion and contraction. Still another object of the present invention is to provide a molding die and an injection molding machine for a disk-shaped recording medium which can make a thick plate stamper adhere to a fixed side plate. Still another object of the present invention is to provide a molding die for a disk-shaped recording medium and an injection molding machine which can lower the melting temperature of solder at the time of joining. Furthermore, the present invention relates to thermal expansion in injection molding and the like,
An object of the present invention is to provide a molding die for a disk-shaped recording medium and an injection molding machine that can prevent the surface of the die from being damaged by repeated expansion and contraction of cooling. Still another object of the present invention is to provide a molding die and an injection molding machine for a disk-shaped recording medium which can enhance the cooling efficiency of the resin.

[0018]

A thin plate stamper obtained by using a conventional mastering process is used for rough grinding with a thin plate stamper obtained by using a conventional mastering process. By using a thick plate stamper finished with a thick plate stamper joined with a low melting point alloy such as solder and a mold structure with a dedicated guide structure, the stamper is exposed to the thermal expansion and contraction of the stamper under pressure during molding. Absorbs or prevents irregularities due to scratches with the mold by microdeformation or rotation, realizes a flat surface at the micro level on the resulting substrate surface, and if the optical disk is a disk-shaped recording medium with almost no molded substrate noise Instead, it aims to produce and provide an ultra-flat disk-shaped substrate including a hard disk substrate at low cost in a short time.

In order to achieve the above object, a thin stamper obtained by directly passing through a mastering process generally used in a conventional optical disc is joined to a metal disc or a disc plated with ceramic or the like by soldering. The adoption of an easy-to-detach mold structure using a plate stamper allows the solder layer to act as a buffer layer as well as to join, and to prevent minute irregularities due to scratches on the mold member, which was a problem with the conventional stamper method. 2m thick plate part
m, which does not affect the surface of the thin plate because it is thicker than m, and the material of the thick plate is made softer than the hardness of the mold components. It becomes a mold structure.

The molding die for a disc-shaped recording medium according to the present invention comprises:
In a pair of disk-shaped recording medium molding dies separated into a fixed mold and a movable mold each provided with a temperature control circuit section, the fixed mold includes a thin metal stamper having an uneven signal. It is formed by joining a thick metal plate.

Further, the injection molding machine for a disk-shaped recording medium according to the present invention is a disk-shaped injection molding machine having a pair of dies separated into a fixed die and a movable die each having a temperature control circuit. In an injection molding machine for a recording medium, the fixed mold includes a thick stamper formed by joining a thin metal stamper having a concavo-convex signal and a thick metal plate.

According to the molding die for a disk-shaped recording medium and the injection molding machine of the present invention, the molten resin is formed by forming the thick metal stamper by joining the thin metal stamper and the thick metal plate. The stamper expands in the radial direction due to the stress and heat when the resin is filled into the cavity at the stage of being injected into the cavity, and the occurrence of abrasion with the mold due to the application of a rotational force can be prevented.

In the molding die for a disc-shaped recording medium according to the present invention, a groove of a cooling temperature control circuit is provided on the back surface of the thick metal plate used for the thick stamper, and the temperature control on the side of the thick stamper is performed. The temperature and the temperature of the fixed plate are controlled independently.

Further, in the injection molding machine for a disk-shaped recording medium of the present invention, a groove of a temperature control circuit for cooling is provided on the back surface of the thick metal plate used for the thick stamper, and the temperature control on the side of the thick stamper is performed. The temperature and the temperature of the fixed plate are controlled independently.

According to the molding die and the injection molding machine for a disk-shaped recording medium of the present invention, by controlling the temperature control temperature of the thick plate stamper side and the temperature control temperature of the fixed side plate independently, the resin The temperature can be controlled where the distance is closer.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention, that is, embodiments of the invention relating to a molding die for a disk-shaped recording medium and an injection molding machine will be described with reference to FIGS. It will be described with reference to FIG.

First, an embodiment of the first invention will be described. FIG. 1A schematically shows a molding die for a disk-shaped recording medium of the present invention. As can be seen from the figure, the molding die is a pair of dies which are largely separated into a movable die 11 and a fixed die 10.

The movable mold 11 includes the movable mirror 7 and the movable mirror temperature control circuit 40 as constituent elements. The fixed-side mold 10 includes an easily attachable / detachable thick-plate stamper 1 formed by joining a stamper 2 made of a thin metal plate having a concavo-convex signal through a mastering process and a thick metal plate with a low-melting-point alloy. 6 and the fixed-side plate temperature control circuit 37 are its constituent elements. It should be noted that the thick plate stamper 1 shown in FIG. 1B, that is, a stamper 2 made of a thin metal plate having a concavo-convex signal through a mastering process and a thick plate metal plate 4 are joined by a low melting point alloy (solder 3) for easy attachment and detachment. The method of manufacturing the thick plate stamper 1 will be described later in detail.

The total thickness of the top plate 14 of the fixed-side plate temperature control circuit 37 and the thickness of the thick plate stamper 1 is equal to the top plate thickness 15 of the movable-side mirror temperature control circuit 40, or The thickness of the thick stamper 1 was adjusted so that the surface temperatures of the fixed side and the movable side became equal. That is, in the fixed mold, the total thickness of the thick plate stamper 1 and the top plate thickness 14 of the fixed side plate temperature control circuit 37 is equal to or the same as the top plate thickness 15 of the movable mirror temperature control circuit 40. The thickness of the thick plate stamper 1 was changed to be the same as the movable-side surface temperature when the heating medium was branched from the mold temperature controller and the fixed-side and movable-side molds were temperature-controlled and heated. . With this configuration, it is possible to prevent the temperature distribution between the front and back surfaces of the formed disk from becoming non-uniform, and to prevent the disk from warping.

The fixed side plate 6 of the fixed side mold 10
Concentric grooves for vacuum suction of the thick stamper 1 are provided on the inner and outer circumferences of the surface of the thick stamper 1, and the bottom of the thick stamper 1 has a flat and easily removable structure. That is, concentric grooves are machined on the inner and outer circumferences of the surface of the fixed plate 6 which are in contact with the surface of the thick plate stamper 1 opposite to the stamper side, and these grooves are connected to communication holes (shown in the figure) in the fixed plate. No) through an external vacuum suction mechanism.

By this vacuum suction, the thick plate stamper 1 is closely attached to the fixed side plate 6 without being separated, and there is no gap with the fixed side plate 6 so that heat of the resin can be smoothly transmitted to the fixed side plate temperature control circuit 37. Note that the center chuck 42 in FIG. 1A does not hold the thick plate stamper 1 as thin as about 0.2 mm at the portion that holds the thick plate stamper 1 and prevents the stamper 2 from being turned up by the resin during injection. It is used for.

Next, a method of fixing a thick stamper by a mechanical chuck will be described. In the conventional mold, a number of structures for absorbing the expansion and contraction of the stamper to achieve the gas escape effect in the cavity have been found. However, as shown in FIGS.
Since the movable-side mirror mold is of a dive type (the movable-side mirror has a convex shape), a clearance 43 from the fixed side is inevitably required, and the gas escapes from here.

As shown in FIG. 1, the molding die according to the present invention has a similar structure having an outer peripheral ring 12 as in the conventional die structure (FIG. 7). The structure of the stamper 1 does not need to absorb the expansion and contraction of the stamper during the molding process and has a clearance within a range in which resin burrs do not appear as in the prior art, and the stamper 1 is lightly contacted.

Next, nickel (N
i) A method of manufacturing a thick stamper bonded to a stamper will be described with reference to FIG. First, 0.3 obtained through the mastering step and the electroforming step described with reference to FIG.
mm stamp Ni stamper inside diameter φ22mm, outside diameter φ138
Homming with a pressing machine or lathe.

Next, a circular thick metal plate SUS- having a thickness of 5 mm and having the same or a slightly larger outer diameter than the above-described stamper is used.
420J (trade name: STAVAX disc, manufactured by Wooddeholm Co., Ltd.) is polished easily, and then plated with copper to facilitate solder bonding. Note that the thickness of the thick metal plate of the thick stamper is not limited to the above-described 5 mm, and other thicknesses can be adopted. That is, the thickness of the thick metal plate is preferably in the range of 2 to 10 mm. The thickness of the thick metal plate is required to be 2 mm or more in consideration of deformation due to mechanical processing, polishing, heat at the time of stamper joining, etc. Conversely, if the thickness is more than 10 mm, the thermal efficiency of the mold becomes poor, and a molding cycle cannot be taken.

Next, as shown in the process shown in FIG. 2, a zinc chloride-based flux is applied to both the stamper 2 and the thick metal plate 4 and dried. The flux is indispensable for soldering, and the effect of the flux at the time of bonding between metals is to clean the metal surface, remove the oxide film and prevent reoxidation, reduce the interfacial tension, reduce the surface tension of the metal, And the effect of increasing wettability and fluidity.

Next, the SUS-420J thick metal plate is heated to a temperature equal to or higher than the liquidus line of the solder on a heated soldering die as shown in FIG. 3, and the solder is set. Let melt. As the solder, for example, Sn-P
A high-temperature solder of b = 5: 95 (liquidus = 314 ° C., solidus = 300 ° C.) can be used. The liquidus refers to the temperature at which primary crystals (metal crystals) start to precipitate from the molten state of the solder, and the solidus refers to the temperature at which the melted solder is completely solidified. Further, the composition of the solder is not limited to the above composition. For example, in addition to the above, the composition of the solder is Pb-Sn-Ag = 92.5-5-2.5
(Solidus 300 ° C.) and Pb-Ag-In = 90-5
-5 (solidus 292 ° C.) or the like can be used.

Next, the mold is set on the basis of the thin plate stamper and the center positioning guide, and the mold is heated to a temperature lower than the solidus temperature, preferably 100 ° C. or lower while heating and suctioning gas and excess solder from the communication hole by vacuum. Cool to temperature. In addition, in this solder joining, the whole is pressurized by a hydraulic press other than the vacuum suction (for example, a gauge pressure of 10 to 30 kg / c).
m ² ).

Next, after cooling to room temperature, the flux and solder protruding from the end face are washed and removed as necessary. Finally, the thick plate stamper thus obtained is attached to the mold for the thick plate stamper described with reference to FIG.

Next, a case where a resin is injection-molded using a mold manufactured by the above-described method will be described. Here, a disk substrate was obtained by injection molding using the same polycarbonate resin as a conventional optical disk. The injection molding conditions in this case are as follows. Polycarbonate (Product name Grade: AD-9000TG, Teijin Chemicals K
K) Glass transition point = 145 ° C. Flexural modulus = 2,200 MPa Water absorption = 0.3% Molding conditions Mold temperature: 130 ° C. Resin temperature: 330 ° C. Injection speed: Average 160 mm / sec Cooling time: 12 seconds

The remaining amount of the focus error of the disk thus obtained was measured. FIG. 4 shows the results. As shown in the figure, a frequency component of 1 kHz or more (high-pass filter (HPF): 1 kHz) and a frequency component of 4 kHz or more (high-pass filter (HPF): 4 kHz)
About a radius of 25 mm (linear velocity 6.28 m /
s) and vertical plane runout at a radius of 40 mm (linear velocity of 10.05 m / s).

As can be seen from the drawing, the remaining amount of the focus error of the disk obtained in this manner was much smaller than that of the conventional stamper.
That is, the vertical runout on the signal side of the disk formed by the thick stamper is smaller than that of the conventional stamper side surface shown in FIG.

As described above, according to the embodiment of the present invention, a high numerical aperture (high NA) high-density disk does not cause a problem in the conventional low numerical aperture (low NA) optical system, and the heat generated during the disk forming process does not matter. Focus error due to micro-deformation of the plastic substrate formed by expansion and shrinkage has been reduced to almost negligible level by a thick stamper.

Also, in the conventional disk forming using a thin stamper of about 0.3 mm, the trace of pressure back polishing by a polishing cloth which occurs in the back polishing step after electroforming plating is macroscopically applied to the signal surface due to the pressure at the time of forming. It appeared uneven. No trace of polishing on the back side was observed at all from the thick plate stamper subjected to the solder bonding process, and it was confirmed that the leveling action by the solder flattened the unevenness with the thick plate stamper.

Further, in the conventional disk molding using a thin stamper having a thickness of about 0.3 mm, foreign matters are easily caught between the stamper and the mold when the stamper is attached, and the stamper is likely to be damaged. Even if great care was taken at the time of attaching the stamper, this foreign matter was not understood unless dust and lint were easily formed and formed. For this reason, it was necessary to pay attention to the cleaning of the surface of the stamper and the mold and the working environment so as not to catch foreign matter. These problems at the time of attaching the stamper can be neglected because of the thick plate stamper, and as a result, the working time is reduced and the simplicity is achieved.

Further, the complicated and multi-step process of the mirror surface of the mold, which is required for the disk formed by the direct etching mold having the same concept as the thick plate stamper, is not required. Only with this, the process can be simplified and the production time can be shortened. That is, since the direct mold method by etching requires a complicated process and time, the conventional thick plate stamper used by joining the stamper of the disc has advantages in terms of time, process, and cost.

Next, an embodiment of the second invention will be described. Here, a molding die using a metal having high thermal conductivity was examined for members of the thick plate stamper and the fixed side plate constituting the temperature control circuit in contact with the thick plate stamper.

A thick stamper made of a Ni thick plate having a linear expansion coefficient relatively close to that of the Ni stamper was manufactured. That is, considering the heat of the resin at the time of molding the disk and cooling in the mold, a combination of a nickel thick plate (manufactured by Daido Incoalloy, trade name: Nickel 200) and Ni
A die using a thick plate stamper bonded to a stamper was manufactured.
This nickel 200 is made of SUS-420J (STAVA
X) has a higher thermal conductivity and is almost the same as Ni plating, which is the composition of the stamper, and therefore has the same linear expansion coefficient and thermal conductivity. Make the same movement with.

[0049]

[Table 1]

The configuration of the molding die of the present invention was the same as that of the first embodiment except for the configuration described above.

The thick plate stamper prepared according to the thick plate stamper forming step of the first embodiment of the present invention is inserted into the mold of FIG. 1, and the disk is formed under the same conditions as in the first embodiment of the present invention. As a result, as in the first embodiment, a disk having a small vertical plane deflection as in FIG. 4 was obtained. Further, nickel 200 has a high thermal conductivity and a high cooling efficiency, so that the melting temperature of solder at the time of joining can be lowered. That is, since the thermal conductivity is high, the temperature of the solder portion can be reduced.

Next, an embodiment of the third invention will be described. Here, when the thick metal plate used for the thick stamper is made of a simple metal having a composition softer than the fixed side plate member, or the thick metal plate used for the thick stamper has a softer surface. The case of being coated with metal was examined. That is, the case where the surface of the thick metal plate was covered with a soft metal even when the thick metal plate of the thick stamper was a copper alloy or the same mold member was examined.

A copper alloy having a linear expansion coefficient relatively close to that of a Ni stamper, that is, Cu-Ni-Si 3 which is used as a mold material as a combination of materials having a similar linear expansion coefficient.
A thick plate stamper was used, which was a joint between a base alloy HR750 (Kobe Steel) and a Ni stamper. The molding die of the present invention had the same configuration as that described in the first embodiment of the present invention, except for the configuration described above.

The thick plate stamper prepared according to the thick plate stamper forming step of the first embodiment of the present invention is inserted into the mold shown in FIG. 1, and disk molding is performed under the same conditions as in the first embodiment of the present invention. As a result, as in the first embodiment, a disk having a small vertical plane deflection as in FIG. 4 was obtained.

Further, since the copper alloy is used, the hardness is softer than that of the metal of the SUS-based mold member, and the damage to the mold member is reduced. That is, it is possible to prevent the mold surface from being damaged by repeated expansion and contraction of thermal expansion and cooling in injection molding and the like.

Also, the T used in the conventional stamper mold is used.
Hard coating treatment such as iN was not required, so that the production time of the mold and the maintenance cost could be reduced. Further, the ternary alloy (HR750) has a high thermal conductivity and a high cooling efficiency, so that the melting temperature of solder at the time of joining can be lowered. That is, since the thermal conductivity is high, the temperature of the solder portion can be reduced.

Next, an embodiment of the fourth invention will be described. Here, the mounting structure of the thick plate stamper and the detent mechanism were studied.

Conventionally, in injection molding, a resin is melted by external heating of a cylinder, and when the resin is injected into a mold by rotation of a screw at the time of injection, a rotational force is also generated in the resin, and the resin is filled while rotating spirally.

As shown in FIG. 7, the conventional stamper employs either a mechanical clamp or a vacuum clamp which lightly presses a nail at a part of the center as a mounting method. The outer periphery is in a free state in order to cope with thermal expansion and contraction. For this reason, the structure is such that the rotation of the stamper easily occurs due to the rotational moment of the resin at the time of injection filling.

The mechanical clamp has a structure in which a stamper is mechanically attached at a portion described as a center chuck in FIG. 7, and a compact disk (C
D) and digital versatile disc (DVD)
It is generally performed in molding. The vacuum clamp is a method of fixing a stamper by, for example, digging a groove on the back surface of the stamper in FIG. 1 and connecting the groove to external vacuum suction.

As a method of preventing the rotation of the stamper, a method of processing the outer periphery of the stamper into a U-shape and setting a guide pin on a mold to prevent the rotation of the stamper is used to prevent the rotation of the stamper (JP-A-1-159226). ).

However, in this method, abrasion due to expansion and contraction in the radial direction of the stamper cannot be prevented. In addition, if the inner and outer peripheries of the stamper are integrally formed (pressed) in a U-shape, the mold becomes complicated and expensive. In addition, in the case of a U-shaped alteration after machining into a disk shape, a plurality of alterations and guides are required with high accuracy, the cost is increased, and the mold surface is hard-coated with Ti-N or the like to prevent scratches. It was necessary to make it hard to stick.

Here, a guide hole and a guide pin to be fitted respectively to the back surface of the thick plate stamper and the fixed mold are provided outside the effective diameter of the disk. That is, as shown in FIG. 1, when the thick stamper has a disk shape, a female guide hole 9 is provided on the back surface of the thick metal plate of the thick stamper, and a convex guide pin 8 is provided on the mold body. Thereby, the thick plate stamper was set and fitted to the mold. The molding die of the present invention had the same configuration as that described in the first embodiment of the present invention, except for the configuration described above.

A thick plate stamper prepared according to the thick plate stamper forming step of the first embodiment of the present invention is inserted into the mold shown in FIG. 1, and disk molding is performed under the same conditions as in the first embodiment of the present invention. As a result, as in the first embodiment, a disk having a small vertical plane deflection as in FIG. 4 was obtained.

The stamper is joined to the thick metal plate and does not rotate unless the temperature is higher than the liquidus line of the solder. The rotation of the thick stamper is stopped by the guide pins. That is, it was possible to prevent the thick plate stamper from rotating in the mold due to the rotational stress of the resin during molding.

Further, since the stamper is joined to the thick metal plate, it is not necessary to provide a stopper for the stamper by additional processing such as a U-shaped groove to prevent the rotation of the stamper, and the positioning and the stopper of the stamper are prevented by the guide pin. Prevention of abrasion with the mold was achieved by the combined use.

Next, an embodiment of the fifth invention will be described. Here, a rotation prevention mechanism using a polygonal thick plate stamper was examined. That is, the thick metal plate used for the thick stamper is a polygonal metal plate that inscribes or includes the outer diameter of the disk-shaped thin metal stamper. Further, the fixed mold has a concave portion in which the polygonal thick plate stamper is fitted, and a clearance is provided between the thick plate stamper and the concave portion.

In the embodiment of the present invention, as shown in FIG. 5, the thick metal plate 4 for joining the stamper 2 has a polygonal structure, and the polygon inscribes the stamper 2 or the polygon has a larger diameter. The stamper 2 was soldered to a thick metal plate 4 having Here, the thickness of the thick metal plate is 2 mm or more.

Further, the mold to which the thick plate stamper is attached is provided with a clearance within a range for absorbing the expansion width due to the thermal expansion and contraction of the thick plate stamper. Here, the clearance is, for example, about 5 μm. Also, the center of the thick plate stamper and the mold is fitted to the mold with the inner diameter of the stamper. The molding die of the present invention had the same configuration as that described in the first embodiment of the present invention, except for the configuration described above.

The thick plate stamper prepared according to the thick plate stamper forming step of the first embodiment of the present invention is inserted into the mold shown in FIG. 1, and disk molding is performed under the same conditions as in the first embodiment of the present invention. As a result, as in the first embodiment, a disk having a small vertical plane deflection as in FIG. 4 was obtained.

Also, by combining a polygonal thick plate stamper and a concave mold into which the thick plate stamper fits, each corner and ridge of the polygon plays a role of a guide, and the direction of resin rotation at the time of molding the disk is increased. This prevents the thick plate stamper from rotating in the mold due to the above-mentioned stress, and can also absorb the dimensional change of the thick plate stamper due to thermal expansion and contraction.

Further, the positioning and the rotation of the stamper can be used together by the polygonal guide, thereby preventing abrasion with the mold.

Next, an embodiment of the sixth invention will be described. Here, a groove for a cooling temperature control circuit was provided on the back surface of the thick metal plate used for the thick plate stamper, and a temperature control circuit was also provided on the fixed side plate. In addition, the temperature control temperature of the thick plate stamper and the temperature control temperature of the fixed side plate were controlled independently.

Injection molding In general, after a molten resin is filled in a mold, the resin is heated to a glass transition temperature (for example,
The glass transition point of the resin is 145 ° C.). Therefore, the faster the resin is solidified in the mold, the shorter the cycle time of the molding process. But,
When the resin is rapidly cooled, the birefringence of the disk increases due to stress during molding and the like, and when the mold temperature is low, signal transfer failure occurs. Therefore, it is necessary to solve these problems.

Therefore, a cooling method using a double temperature control circuit was examined here. That is, grooves for cooling temperature control circuits are formed on the back surface of the thick plate stamper, and double temperature control with the temperature control circuit of the fixed plate is performed, thereby improving the cooling efficiency and mechanical characteristics such as birefringence.

More specifically, in the mold structure shown in FIG. 6, a groove of a temperature control circuit different from the temperature control circuit of the fixed plate is formed on the back surface of the thick plate stamper, and a two-stage structure is formed via a sealing mechanism such as an O-ring. A mold having a mold temperature control structure was prepared.

Here, the temperature control circuit of the fixed mold has a temperature control circuit composed of a thick plate stamper and a fixed plate, and each of them has its own temperature control circuit. Further, the movable side mold may be divided into a movable side mirror and a movable side plate as in the case of the fixed side mold, and may be a conventional single temperature control circuit.

Here, a description will be given of a case where the temperature control circuit of the fixed mold has a temperature control circuit provided independently for each of the thick plate stamper and the fixed plate. In addition, the signal of the start of the double temperature control of the thick plate stamper was linked with the injection start timer (including the start delay time) of the molding machine, and a refrigerant having a temperature different from the mold temperature control temperature was allowed to flow for an arbitrary time until the end of cooling.

That is, the temperature control circuit of the fixed-side thick plate stamper and the temperature control circuit of the fixed-side plate include a 100 ° C. temperature controller and a 130 ° C.
Each of them is connected from a temperature controller at ℃ and pressurized and heated water is connected via a solenoid valve with a three-way switching valve. A mechanism that enables switching is provided.

Table 1 shows an example of the molding process and the switching temperature of each stage in this case. Example 1 described in the table shows the case where the temperature control temperature of the fixed plate is synchronized with the molding process signal. is there. In addition, the temperature of the fixed side plate was adjusted to 130 ° C.
Example 2 is a case where the temperature is controlled by always connecting the heating medium with the temperature controller and flowing the heating medium.

[0081]

[Table 2]

The molding die of the present invention has the same configuration as that of the first embodiment except for the above-mentioned configuration.

In Example 1 and Example 2, the thick plate stamper prepared according to the thick plate stamper forming process of the first embodiment of the present invention is inserted into the mold of FIG. When the disk was formed under the same conditions as in the first embodiment, a disk having a small vertical plane runout was obtained as in FIG. 4 as in the first embodiment of the present invention.

Further, the thus obtained 1.2 mm
The birefringence of the thick disk is good on both the inner and outer circumferences, and the cycle time of Examples 1 and 2 is reduced to 7 seconds, compared to the conventional cycle time of single temperature control at 130 ° C of 10 seconds. Was done.

From the results of Examples 1 and 2, it is understood that the temperature control of the thick plate stamper is more important than the temperature control of the fixed plate. Although the temperature of the fixed plate was set to 130 ° C. in Example 2 described above, the temperature of the fixed plate was set to 100 ° C. in order to increase cycle time.
C. or lower.

As described above, by employing a double temperature control circuit, the cooling efficiency of the resin can be increased, and there are great advantages such as birefringence, warpage and cycle time. In other words, as a result of adopting a double temperature control mechanism in which the same mold has a two-layer structure and adjusts each structure at different temperatures, mold temperature control which has been performed only at a uniform temperature has been adapted to each molding stage. The effects of securing the transfer and increasing the cooling efficiency by different temperature control mechanisms were confirmed.

In the above-described embodiments of the present invention, molding dies have been described. However, it is needless to say that these molding dies can be applied to ordinary injection molding machines for disk-shaped recording media.

The present invention is not limited to the above-described embodiment, but can adopt various other configurations without departing from the gist of the present invention.

[0089]

The present invention has the following effects. By joining a thin metal stamper and a thick metal plate to form a thick stamper, a disk substrate with less surface irregularities and surface runout can be obtained.

Further, the total thickness of the top plate of the fixed-side temperature control circuit section and the thickness of the thick plate stamper is made equal to the top plate thickness of the movable-side temperature control circuit section, or the thickness of the thick plate stamper is reduced. By adjusting the surface temperature of the fixed side and the surface temperature of the movable side substantially equal to each other, it is possible to prevent the warpage of the disk due to the non-uniform temperature distribution between the front and back surfaces of the disk.

Further, by providing guide holes and guide pins to be fitted respectively on the back surface of the thick plate stamper and the fixed mold, it is possible to prevent the thick stamper from rotating in the mold during molding. .

Further, the thick metal plate is formed into a polygonal shape in which the outer diameter of the disk-shaped thin metal stamper is inscribed or includes, so that the thick metal stamper is prevented from rotating in the mold during molding. be able to.

[0093] Further, by providing a concave portion in which the polygonal thick plate stamper is fitted in the fixed mold and providing a clearance between the thick plate stamper and the concave portion, the size of the thick plate stamper due to thermal expansion and contraction is provided. Can absorb changes.

By providing concentric grooves for vacuum suction of the thick plate stamper on the inner and outer circumferences of the fixed plate surface of the fixed mold, the thick stamper can be brought into close contact with the fixed plate.

Further, by using a metal having high thermal conductivity for the members constituting the temperature control circuit that comes into contact with the thick plate stamper, the melting temperature of the solder at the time of joining can be reduced.

The thick metal plate used for the thick stamper is made of a simple metal having a composition softer than that of the fixed plate member, or its surface is coated with a metal having a softer composition, so that injection molding or the like can be performed. The mold surface can be prevented from being damaged by repeated expansion and contraction of thermal expansion and cooling.

Further, a groove of a temperature control circuit for cooling is provided on the back surface of the thick metal plate used for the thick plate stamper, and the temperature control temperature of the thick plate stamper side and the temperature control temperature of the fixed side plate are independently controlled. By doing so, the cooling efficiency of the resin can be increased.

[Brief description of the drawings]

FIG. 1 is a sectional view of a molding die for a disk-shaped recording medium according to the present invention and a sectional view of a thick plate stamper used therein.

FIG. 2 is a view showing a manufacturing process of a thick stamper used for a molding die according to the present invention.

FIG. 3 is a sectional view showing a mold for joining a thick plate stamper used in a molding die according to the present invention.

FIG. 4 is a view showing a result of measuring a vertical plane run-out of a disk molded by using a molding die according to the present invention.

FIG. 5 is a plan view and a cross-sectional view of a polygonal thick plate stamper used for a molding die according to the present invention.

FIG. 6 is a cross-sectional view showing a temperature control circuit used in a molding die according to the present invention.

FIG. 7 is a cross-sectional view showing a conventional molding die, and a cross-sectional view showing details of a part thereof.

FIG. 8 is a sectional view showing a molding die according to the present invention and an injection molding machine using a conventional molding die.

FIG. 9 is a sectional view showing a positional relationship between an optical disk and a lens.

FIG. 10 is a diagram showing a manufacturing process of an optical disc, which includes a mastering process and an electroforming process.

FIG. 11 is a diagram showing a manufacturing process of a direct etching mold.

FIG. 12 is a view showing a result of measuring surface runout of a stamper side surface and a reading surface side surface of a disk manufactured by using a conventional molding die.

FIG. 13 is a view showing a result of measuring a surface runout of a conventional thin plate stamper alone.

[Explanation of symbols]

1) thick plate stamper, 2) stamper, 3) solder,
4 mm thick metal plate, 5 mm disc, 6 mm fixed side plate, 7 mm movable mirror, 8 mm guide pin, 9 mm
Guide hole, 10 ‥‥ fixed mold, 11 ‥‥ movable mold,
12 ‥‥ outer ring, 13 ‥‥ clearance (gas escape), 14, 15 ‥‥ top plate thickness, 16 ‥‥ fixed side mounting plate, 17 ‥‥ movable side mounting plate, 18 ‥‥ sprue, 19 ‥
{Gate cut punch, 20} Lens, 21} Optical disk, 22} Substrate, 23} Light reflection layer, 24 # Recording layer, 25 # Light transmission layer, 26 # Information signal, 27 #
Laser beam, 28 ° flux, 29, 30 ° communicating hole, 31 ° heater, 32 ° cooling water hole, 33 ° center positioning guide, 34 ° outer ring, 35 ° upper die, 36 ° {Lower die, 37} Fixed side plate temperature control circuit, 38} Thick plate stamper temperature control circuit, 39} Movable side plate temperature control circuit, 40} Movable side mirror temperature control circuit, 41
{Fixed mirror, 42} Center chuck, 43}
‥ Clearance, 44 ‥‥ Fixed side mold plate, 45 ‥‥ Movable side mold plate, 46 ‥‥ Clearance, 47 ‥‥ Fixed side frame plate, 4
8 Injection molding machine, 49 Mold, 50 Heating cylinder, 51 Hopper, 52 Hydraulic motor, 53
{Hydraulic cylinder, 54} Screw, 55} Cooling water groove, 56} Resist, 57} Die, 58} Glass master, 59} Photo resist, 60} Latent image of groove or pit row, 61 ‥‥ groove, 62 ‥‥ pit, 63 ‥‥ land, 64 ‥‥ Ni plating layer

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yuji Akiyama 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Norimura Minami 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation F term (reference) 4F202 AA28 AG19 AH38 AH79 AJ02 AJ09 CA11 CD21 CD27 CN05 CN21 CP06 4F206 AA28 AG19 AH38 AH79 AJ02 AJ09 JA07 JN43 JQ81

Claims (20)

[Claims] 1. A pair of disk-shaped recording medium molding dies separated into a fixed mold and a movable mold each provided with a temperature control circuit section, wherein the fixed mold has an uneven signal. A molding die for a disk-shaped recording medium, comprising a thick plate stamper formed by joining a thin metal stamper having a thickness and a thick metal plate. 2. The sum of the top plate thickness of the fixed-side temperature control circuit section and the thickness of the thick plate stamper is equal to the top plate thickness of the movable-side temperature control circuit section, or the thickness of the thick plate stamper is reduced. 2. The molding die for a disk-shaped recording medium according to claim 1, wherein the surface temperature on the fixed side and the surface temperature on the movable side are made substantially equal by adjusting. 3. The molding die for a disc-shaped recording medium according to claim 1, wherein the back surface of the thick plate stamper and the fixed die have a guide hole and a guide pin to be fitted respectively. 4. A thick metal plate used for a thick stamper,
2. The molding die for a disk-shaped recording medium according to claim 1, wherein the metal die is a polygonal metal plate that inscribes or includes the outer diameter of the disk-shaped sheet metal stamper. 5. The disk-shaped die according to claim 4, wherein the fixed mold has a concave portion into which the polygonal thick plate stamper is fitted, and a clearance is provided between the thick plate stamper and the concave portion. Mold for recording media. 6. The disk-shaped recording medium according to claim 1, wherein the fixed-side mold has concentric grooves for vacuum suction of a thick plate stamper on the inner periphery and the outer periphery of the fixed-side plate surface. Molding mold. 7. The disk-shaped recording medium according to claim 1, wherein the thick plate stamper and a member constituting a temperature control circuit in contact with the thick plate stamper are made of metal having high thermal conductivity. Molding mold. 8. A thick metal plate used for a thick plate stamper,
2. A molding die for a disk-shaped recording medium according to claim 1, wherein the metal mold has a softer composition than the fixed side plate member, or has a surface coated with a metal having a softer composition. 9. A molding die for a disc-shaped recording medium, wherein a groove of a temperature control circuit for cooling is provided on a back surface of a thick metal plate used for a thick stamper. 10. The molding die for a disk-shaped recording medium according to claim 9, wherein the temperature control temperature of the thick plate stamper and the temperature control temperature of the fixed plate are controlled independently. 11. An injection molding machine for a disk-shaped recording medium having a pair of molds separated into a fixed mold and a movable mold each provided with a temperature control circuit unit, wherein the fixed mold is provided. (1) An injection molding machine for a disk-shaped recording medium, comprising a thick plate stamper formed by joining a thin metal stamper having a concavo-convex signal and a thick metal plate. 12. The sum of the thickness of the top plate of the fixed-side temperature control circuit and the thickness of the thick plate stamper may be equal to the top plate of the movable-side temperature control circuit, or the thickness of the thick plate stamper may be reduced. The injection molding machine for a disc-shaped recording medium according to claim 11, wherein the surface temperature on the fixed side and the surface temperature on the movable side are made substantially equal by adjusting. 13. The back side of the thick plate stamper and the fixed side mold,
The injection molding machine for a disk-shaped recording medium according to claim 11, wherein the injection molding machine has a guide hole and a guide pin to be fitted respectively. 14. The metal plate used for the metal plate stamper is a polygonal metal plate that inscribes or includes the outer diameter of the disk-shaped metal thin plate stamper. Injection molding machine for disc-shaped recording media. 15. The disk-shaped mold according to claim 14, wherein the fixed mold has a concave portion into which a polygonal thick plate stamper is fitted, and a clearance is provided between the thick plate stamper and the concave portion. Injection molding machine for recording media. 16. The disk-shaped recording medium according to claim 11, wherein the fixed-side mold has concentric grooves for vacuum suction of a thick-plate stamper on the inner periphery and the outer periphery of the fixed-side plate surface. Injection molding machine. 17. The disk-shaped recording medium according to claim 11, wherein the thick plate stamper and a member forming a temperature control circuit in contact with the thick plate stamper are made of a metal having high thermal conductivity. Injection molding machine. 18. A thick metal plate used for a thick stamper is characterized by being composed of a simple metal having a composition softer than that of the fixed side plate member, or having a surface coated with a metal having a soft composition. An injection molding machine for a disk-shaped recording medium according to claim 11. 19. An injection molding machine for a disk-shaped recording medium, characterized in that a groove of a temperature control circuit for cooling is provided on the back surface of a thick metal plate used for a thick stamper. 20. The injection molding machine for a disk-shaped recording medium according to claim 19, wherein the controlled temperature of the thick-plate stamper and the controlled temperature of the fixed-side plate are independently controlled.