The present invention relates to optical data storage disks and, more particularly, to replicating such data storage disks.
Data storage disks are typically produced using a disk replication process. A master disk is made having a desired surface relief pattern formed therein. The surface relief pattern is typically created using an exposure step (e.g., by laser recording) and a subsequent development step. The master disk is used to make a stamper, which in turn is used to stamp out replicas in the form of replica disk substrates as part of a disk molding or stamping process. As such, the surface relief pattern, information and precision of a single master can be transferred into many inexpensive replica disk substrates.
Conventional mold assemblies, although usually referred to as xe2x80x9cstampersxe2x80x9d for historical reasons, typically include a fixed side and a moving side. The stamper portion is typically attached to the moving side for replicating a desired surface relief pattern (i.e., lands, grooves and/or pits) into the replica disk substrate. A movable gate cut may be provided for cutting a central opening in the replica disk substrates. The stamper is usually secured to the moving side using an inner holder, wherein the inner holder fits over the stamper. Several more tooling parts may be located at the center of the mold assembly.
In one conventional process, during the disk molding process, a resin, typically optical grade polycarbonate, is forced in through a channel into a substrate cavity within the mold assembly to form the replica disk substrate. The surface relief pattern or formatted surface is replicated in the replica disk substrate by the stamper as the cavity is filled. After filling, the gate cut is brought forward to cut a center hole in the replica disk substrate. After the replica disk has sufficiently cooled, the mold assembly is opened and the gate cut and a product eject may be brought forward for ejecting the formatted replica disk substrate off of the stamper. The inner holder may be removable to allow changeout of the stamper.
In another conventional process, a disk is coated with a relatively thin polymer layer into which the fine details are stamped. The starting composition is not molten plastic, but can be an element comprising a very thin embossable radiation-reflective layer overlying an embossable, heat-softenable layer which can be simply thermoplastic or can also be radiation-curable. Optionally, the heat-softenable composition can be coated on a substrate. Impressing the stamper information into the heat-softenable layer can be done with a platen or roll embosser. Radiation curing helps retain the desired relief shape by crosslinking. Disks are provided with a reflective layer either before or after they are impressed with the information-carrying relief pattern.
A significant disadvantage with both of the high pressure, high temperature relief-forming methods described above is the potential for image distortion and internal stresses in the disks produced. Regardless of the particular conventional process used, one shortcoming of the techniques employed in this field is the lack of parallelism between the two platens of the stamper. The parallelism, or lack thereof, affects the pressure gradient across various regions of the blank disk as well as the precision and accuracy with which the fine details are transferred to the blank disk. Methods for replicating disks have relied on precision manufacturing and assembly of the stamping equipment to provide the tolerances needed for accurate disk replication. These methods increase the complexity and costs of the stamping equipment as well as their maintenance, calibration and operation. Therefore, a need, unmet by the prior art, exists for a less expensive and less complex stamping machine which provides the precision needed to accurately replicate optical data storage disks.
These and other shortcomings of the prior art are addressed by a stamper assembly which incorporates a self-leveling mechanism into at least one of the stamper platens which acts to dynamically bring the two platens into a parallel relationship during the stamping operation. As a result, the yield of the replication process is increased due to increased accuracy, the manufacturing cost and complexity of stamping equipment are reduced, and the repair, maintenance and operating costs of the stamping equipment is reduced.
One aspect of embodiments of the present invention for addressing the needs unmet by the prior art relates to a stamper module for optical disk replicating equipment which includes a platen which can connect with a stamper and a platen which can connect with a disk. The stamper module also includes means that dynamically orient the first and second platen into a parallel orientation during the stamping operation.
Another aspect of embodiments of the present invention relates to a stamper module for optical disk replicating equipment which includes a first and second platen in which a ball joint is connected with the first platen. The ball joint operates such that when the first and second platen are performing a stamping operation, the ball joint swivels to orient the first platen and the second platen in parallel.
Yet a further aspect of embodiments of the present invention relates to a stamper module for optical disk replicating equipment which includes a first and second platen each having a surface opposing the other. In accordance with this aspect, the module also includes a ball joint attached to the first platen and a pressure train configured to bring the opposing surfaces towards one another during a stamping operation. The position of the ball joint allows the ball joint to swivel during the stamping operation so as to orient the opposing surface parallel to one another during stamping.
The foregoing and other features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.