JP2005531098A - Method and apparatus for forming a microstructure on a polymer substrate - Google Patents

Abstract

Method and apparatus for forming a microstructure on a surface of a polymer web for use in an optical memory substrate. The microstructure is formed by superimposing a hot stamper on the web of material with a selected time / temperature profile. The stamper is heated to melt and flow the surface of the web and stabilize before leaving. The stamper is carried by a support that is independent of the pressurizer. The web of polymeric material may be provided with a glidant to improve imaging. Further described herein is a method and apparatus for fabricating optical memory modules such as disks with a novel stamper, film coater, and finisher.

Description

  The present invention relates to U.S. Patent Application No. 600/300997, filed June 26, 2001, and is entitled to benefit from its prior filing date and priority, the disclosure of which is incorporated herein by reference. .

  The present invention relates generally to a method and apparatus for fabricating an optical memory. More precisely, the present invention relates to the formation of a working substrate for an optical memory or an optical disk using a continuous supply device or an inter-roll supply device.

  CD (Compact Disc) CD-R, CD-RW; DVD (Digital Multipurpose Disc) DVD-R, DVD-ROM, DVD-RAM, DVD-RW, DVD-RW; PD (Phase Change Disc); Optical storage disks (such as magneto-optical) are generally manufactured by first forming a substrate and then depositing one or more thin film layers on the substrate. Optical memory substrates are usually formed with a series of grooves and / or holes arranged as concentric grooves or as a continuous spiral. Grooves and holes may be used for laser beam tracking, address information, time adjustment, error correction, data, and the like. A substrate used for an optical disk is typically an injection molding method in which a molten polymer material is injected into a disk-shaped mold having a single surface having a microstructure formed in a mold to be replicated. Molded. The microstructure formed in the mold is typically provided by a replaceable insert, commonly referred to as a stamper. The injection molding process consists of a series of precisely timed processes, closing the mold, injecting the molten polymer, controlling and reducing the maximum injection pressure, cooling, center hole Forming the mold, opening the mold, and taking out the duplicated disk and accompanying sprue. Following the molding process, typically the disk substrate is coated with one or more thin film layers. The substrate will then be coated with various insulating and / or protective layers, bonding adhesives, decorative plates, labels, and the like.

  Injection molding processes such as those described above provide high quality optical storage disks with acceptable levels of birefringence and flatness, but the disk production rate is only a few seconds. About 60% of this time is attributed to the molding process, and the rest is needed by opening the mold, removing the disk and sprue, and then closing the mold before the next cycle begins. is there. Furthermore, current attempts to improve production rates using various new die cutting techniques and multi-cavity molds have had limited success.

  Not only is the production rate lower than desired, but injection molding requires complex closed loop control over many factors. For example, mold and polymer temperatures, pressure clamping force, injection profile, and retention time are all competing or often opposite to the birefringence, flatness, and accuracy of the replicated appearance. Has an impact. It should also be noted that the thinner the disc being replicated, the greater the difficulty of molding. Therefore, a standard CD substrate of about 1.2 mm thickness uses special techniques such as increasing the mold cavity cross-section during the main injection phase, injection pressure molding, coining, “bump molding”, etc. However, in the case of a standard DVD substrate having a thickness of about 0.6 mm, they are required in order to satisfy the standards of birefringence and flatness at the same time.

  Future trends in optical memory products are towards thinner substrates and / or smaller disks. It would not be practical to make these products directly using injection molding. In the case of a small-diameter disk (ie, 5-8 cm) such as those used in personal digital assistants (PDAs) and digital electronic cameras, disturbances due to the center gate method can affect the quality of the innermost groove of the disk. possible. These turbulences are associated with local turbulence near the mold center gate, shifts, and changes in clogging, and can result in poor local flatness and large birefringence. These problems will emerge as the minimum groove diameter decreases.

  In order to increase the manufacturing speed, many optical memory manufacturing methods using a continuous web processing method have been proposed. These methods are built on the concept of passing a web between a roll and a stamper to form a microstructured pattern on a continuous web of material.

  To date, two types of continuous web processing methods have been proposed. These methods consist of “in-line” and “off-line” methods. The in-line continuous web method integrates web extrusion and microstructural patterning in the same process, while the off-line continuous web method webs on a standard web material produced on a separate production line. Is formed. The purpose of in-line molding is to bring the web into contact with the stamper while the web is still hot immediately after extrusion. Examples of in-line methods are US Pat. Nos. 5,137,661, 4,790,893, 5,433,897, 5,368,789, and 5,281,371. Nos. 5,460,766, 5,147,592, and 5,075,060, the disclosures of which are incorporated herein by reference. The integration of web extrusion and web molding requires disk manufacturers to engage in web extrusion as well as optical disk production operations. This makes the entire system a very complex process, in the way this method does not want it. Furthermore, disk manufacturers do not want to experience the same scale economy that plastic web manufacturers are experiencing, so the cost per unit for disks molded in-line is off. • Will be higher than for the line method. Thus, the inventors provide an opportunity for off-line processes not only to improve raw material throughput, cost and complexity reduction, and short start-up time, but also increase process flexibility. Propose that.

  In the case of optical memory manufacturing, one method of web molding that may be used in the in-line method is entitled “Directed Energy Assisted In Vacuo Micro Embossing” issued December 28, 1999, and is US Pat. No. 6,007,888. Proposed by Mr. Kaim in the issue, the disclosure of which is incorporated herein by reference. Kaim discloses a continuous manufacturing method using a directional energy assisted microembossing process. The patent describes a directional energy source used to heat the web material and stamper before being pressed together by a set of nip rollers.

  Although Mr. Kyim is well evaluated for the teaching content, many factors appear that are not usually a problem when increasingly high data density devices are formed. For example, the present inventors have found that there are unavoidable fluctuations in the surface texture and web thickness of the web, which may hinder the reproduction of fine microstructures. These variations result in local non-uniform contact pressure between the web and the stamper. In a method where the web softens to form a microstructure, simply increasing the average contact pressure does not adequately solve this problem, but excessive high contact pressure causes elastic rebound in the web material after pressure relief. This is because it may cause distortion of the image on the surface. The relative movement of the stamper and the web can cause “smear”. Smear distorts the shape of data grooves and / or holes on a microscopic scale. These distortions can interfere with tracking and increase the read back error rate. Accordingly, there is a need for a method and / or apparatus that can accommodate the negative effects caused by web surface texture and web thickness variations.

  In order to accurately replicate the stamper microstructure, many have attempted to keep the stamper in contact with the web long enough to relax the displaced polymer and cool the substrate. However, the inventors have found that simply increasing the contact time is not an acceptable answer due to the resulting warpage. As will be appreciated, warped discs cause significant read problems. Warp-related problems become a more serious problem for writable discs that can degrade the quality of the recording and can further exacerbate the detrimental effects of warping during read back. Accordingly, there is a need for a method and / or apparatus for continuous production of optical memory that limits warpage during substrate fabrication.

  In accordance with the foregoing discussion, the present invention provides a method and / or apparatus that includes feeding a web of material to a substrate forming apparatus for manufacturing an optical memory or optical memory substrate, and / or an optical disc.

  In one aspect of the invention, a method is provided for forming a polymeric material with a limited thermal load on the web.

  In another aspect of the invention, a method is provided for molding a polymeric material by melt molding a microstructure on the surface of a web of material.

  In another aspect of the present invention, a method is provided for forming a microstructure on a surface of a polymeric material using an induction heated stamper.

  In another aspect of the invention, the polymeric material web is provided by providing a surface comprising the glidant to the polymeric material web and forming a microstructure on the surface of the polymeric material with a heated stamper. There is provided a method of forming a microstructure on the surface of the substrate.

  In another aspect of the present invention, for use in a continuous web forming process comprising providing a transferable image to a stamper, bending the stamper, and increasing the thickness of the stamper after being bent. A method of making a stamper is provided.

  In another aspect of the invention, a method is provided for forming a polymeric material by providing limited thermal expansion / contraction during web forming. In one preferred aspect thereof, the stamper has a smaller coefficient of thermal expansion than nickel. In another preferred aspect, the stamper is limited in temperature changes upon contact with the web.

  In another aspect of the present invention, a web supply device, a web forming device, and a web forming device each include a stamper and a set of nip rollers that form a nip region in conjunction with the web supply device. There is provided an apparatus for forming a microstructure on the surface of a polymeric material comprised of, which is carried by a support removable from a nip roller.

  In another aspect of the present invention, the web feeding device, the polymer material molding stamper, and the stamper are carried on an annular path and interlocked with the web feeding device, and a cutting machine for cutting the web material after molding, There is provided an apparatus for use in fabricating an optical memory comprising a collector for collecting the pieces of web material after cutting.

  In another aspect of the invention, preparing a roll of polymeric web material having a layer of a softer material that can be removed, forming the web with a heated stamper, and forming the molded polymeric material There is provided a method of forming a microstructure on the surface of a polymeric material for use in an optical memory comprising the step of re-rolling.

  In another aspect of the present invention, the web feeding device, the polymer material molding stamper, the stamper is transported on the annular path and interlocked with the web feeding device, a cutting machine for cutting the web material after molding, cutting An accumulator for storing the divided pieces of web material later, an indexer for providing positioning holes in the divided pieces of web material, a masking device for covering the divided pieces of web material after molding, and after masking An apparatus is provided for use in fabricating an optical memory, comprising at least one coating applicator, for applying a thin film to a piece of web material.

  In another aspect of the present invention, a platform for supporting a molded web material segment, a plurality of optical positioning sensors for centering an image of the molded web material on a die track, and on the platform A web cutting device is provided for use in making an optical memory from continuous web processing, comprising a die for cutting a supported web.

  In another aspect of the present invention, a polymeric material for use in fabricating an optical memory is molded by providing a nip region with sufficient follow-up to account for web surface and thickness variations. A way to do it is provided.

  In another aspect of the invention, providing a web of polymeric material, providing a heated stamper, and pressurizing the heated stamper and substrate between a set of nip rollers. A method of forming a microstructure on the surface of a polymer material for use in an optical memory comprising the steps of: at least one of the nip rollers has a compliant outer surface with a Shore D hardness of 80 or less Has been.

  In another aspect of the present invention, the coating (s) coating device (s), web cutting device (s), cassette stacking device, web indexing machine, take-up roll, and finished product optical memory disk An apparatus for making an optical memory disk is provided that includes one or more of other components capable of producing a semi-finished product disk.

  In another aspect of the invention, a method is provided for coating an embossed optical memory substrate by masking a piece of web material prior to coating.

  To facilitate an understanding of the various aspects and embodiments of the present invention, reference should be made to the accompanying drawings, wherein like numerals designate like elements. The drawings are only exemplary and should not be construed as limiting the invention.

  Reference will now be made in detail to various aspects and embodiments of the present invention.

  Referring to FIG. 1, an apparatus for molding an optical memory according to the present invention is depicted. The apparatus comprises a web dispenser or simply a web dispenser (not shown), a web track on which the web material 12 moves, and a web forming device disposed in the web track. The web forming apparatus 10 includes a stamper 14. The stamper is accompanied by a microstructure image for forming the web. The stamper can be carried by the support 28 and heated by a suitable heating device 18 and / or heated by a drum or roller 22 in thermal contact with the stamper.

  The pressure roller 20 and the support roller 22 are disposed in the web track and press the stamper against the surface of the web material and push it. The pressure roller and the support roller form the nip region 16. As shown, the nip region 16 includes the narrowest portion between the pressure roller 20 and the support roller 22. In practice, the nip region 16 may be provided by any means suitable for pressurizing the stamper and web simultaneously.

  The stamper can be any tool suitable for leaving a trace on the web material or optical memory substrate. In an alternative embodiment, the stamper can take any shape, such as an oval, oval, rectangular, triangular, or irregular shape, but is preferably a disc-shaped embossing tool. The stamper preferably has fine features such as grooves and / or holes that create a microstructure in the optical memory substrate. Fine features will range in width, length and depth from greater than a few microns to as small as 0.01 microns or less. FIG. 13 is an AFM enlarged perspective view of a stamper surface having fine features and a web surface embossed with a high temperature stamper and incorporating the fine features into the surface of the optical quality web material. Indicates.

  The stamper can be heated to the highest processing temperature while maintaining both the ability to form a microstructure on the surface of the web and the ability to easily transfer energy to the interface between the stamper and the polymeric material upon contact. Preferably, it is formed from a rigid material. Exemplary stamper materials include nickel, chromium, cobalt, copper, iron, zinc, etc. and various alloys of these metals. The stamper may be composed of a single monolithic material or multiple layers of the same material or different materials. The stamper is preferably made of a plate made of a material having a thickness of 0.1 to 1.0 mm, and more preferably made of a plate made of a material having a thickness of about 0.3 mm, plus or minus 0.1 mm. As shown in FIG. 1, the stamper is flat. It will also be appreciated that in alternative embodiments, the stamper may be curved. A curved stamper allows the stamper to easily move along a curved track, such as a repetitive annular path on a drum that is particularly useful for continuous processing.

  In a preferred embodiment of the invention, the curved stamper is preferentially created to reduce ellipsoidal distortion. It has been found that simply bending a flat stamper into the shape of a transporter or drum can introduce elliptical strain along the direction of curvature. The magnitude of the axial ratio is related to the radius of curvature (for example, the radius of the drum or moving track) and the thickness of the stamper at the time of bending. It has been found that stretching, compressing, and / or elastically displacing the web material introduces image distortion that must be offset. A useful stamper preferably has a microstructured image with distortion corrected to an optimal state so that the stamper is suitable for use in the fabrication of optical memory disks. The optimally distorted curved stamper may be fabricated by any suitable method, such as changing the initial shape of the image and then forming the modified image on the curved stamper. However, in order to utilize the current production equipment for producing a flat stamper, a curved stamper is produced by imaging the optimum corrected microstructure pattern into a thin and flat stamper and then bending the stamper. Is preferred. After the stamper is curved, the thickness of the stamper is increased to obtain the desired thickness for the curved stamper. By increasing the thickness of the curved stamper after bending, the stamper, when used with a curved transporter, optimizes image pre-distortion while meeting the required thermal mechanical requirements. It will be preferentially formed. For example, the optimal corrected microstructure pattern is formed on a relatively thin workpiece (such as a thickness of 0.1 mm or less). The relatively thin workpiece is curved to the desired radius of curvature (1-10 inches, more preferably 1-5 inches, etc.) and then stacked to the desired stamper thickness. The thickness of the curved stamper may be stacked by any suitable method such as plating, bonding, soldering, coating, or the like. The final stamper thickness is preferably 0.2 mm or more, and most preferably about 0.3 mm. The thickness of the stamper is preferably stacked on the back surface of the stamper, for example, the side facing the microstructure side. Forming the workpiece into a curved transporter shape while being relatively thin directly reduces undesirable bending distortions on the image side of the stamper surface. Subsequent addition of material to the back of the pre-curved stamper allows the mechanical and thermal properties to be changed without worrying about excessive bending strain. In addition, in embodiments where the stamper is configured for use with a curved conveyor, the layered structure reduces stamper distortion during heating and cooling, such as a stamper / drum interface as discussed in detail below. Another benefit is brought about by changing the back side that affects lubricity.

  It has been found that the movement of the stamper and the web during embossing can cause “smear” of the image. The present invention addresses problems such as smear by providing a continuous web method for optical memory fabrication with a web forming device adapted to reduce dimensional variations at the stamper / web interface. Squeezing. While a pure monolithic nickel stamper may be useful in one or more embodiments of the present invention, it has been found that a pure monolithic nickel stamper does not necessarily have optimal thermal expansion / contraction properties. It was. Furthermore, heat transfer from the stamper to other components of the web forming apparatus can have a strong effect on the shrinkage of the stamper. Therefore, the preferred web forming apparatus provides limited heat shrinkage of the stamper upon contact with the web. In this preferred embodiment, the web forming device provides a stamper shrinkage on contact with the web of less than 0.5%, more preferably less than 0.1%, more preferably less than 0.01%. Has been modified.

  In this preferred embodiment, stamper dimensional variation is limited by providing the stamper with a coefficient of thermal expansion (and contraction) that is substantially consistent with the thermal response of the stamper / web interface. Under certain circumstances, particularly when a very hot stamper contacts a cold web or cold press, this contact causes the hot stamper to cool and shrink quickly. The shrinkage is so great that image distortion occurs. By adjusting the thermal expansion / contraction characteristics of the stamper, the offset movement of the stamper / web upon stamper contact is reduced and image forming is improved. According to this preferred embodiment, the stamper has a smaller amount of thermal shrinkage than that of pure nickel or that of a conventional nickel stamper. Thermal expansion / shrinkage is preferably less than 1% throughout the web contact, more preferably less than 0.1%, more preferably less than 0.01%. Reduced thermal expansion and / or contraction may be provided by any suitable means, such as forming the stamper from a low coefficient of thermal expansion material, or forming the stamper as a multilayer structure. Reduced thermal expansion may be provided by making the stamper from an alloy or ceramic, or coating the stamper with another material having a low coefficient of thermal expansion. For example, the stamper may be fabricated by coating a conventional nickel stamper with another metal, metal alloy, or ceramic that has a low coefficient of thermal expansion. By choosing a material with a low coefficient of thermal expansion, a stamper can be provided that is substantially free of relative shrinkage that can be measured upon web contact.

  In another embodiment, stamper dimensional variations are reduced by limiting heat loss from the stamper to the web forming device components, the web, or both. Heat loss is limited in a number of ways, including providing biasing heat to the stamper support rollers, insulating the stamper from the pressed parts, and reducing the stamper contact time with the web. In particular, when the stamper is heated independently from the press or the support roller, the heat is drawn from the stamper to the support roller, causing the stamper to contract. By providing biasing heat to the stamper support rollers, heat transfer from the stamper is limited and thermal contraction of the stamper is reduced. Alternatively or in addition, the stamper may be thermally isolated from the support roller. The stamper may be thermally isolated from the support roller by any suitable means, such as coating the stamper with an insulator or coating the support roller with an insulator. Preferably, the heat loss from the stamper to the stamper support roller is less than 50%, more preferably less than 10%, more preferably less than 1%.

  By reducing the contact time between the heated stamper and the web, a reduction in dimensional variation is achieved by limiting heat loss from the entire stamper. The decrease in the stamper temperature or the temperature of the entire stamper is preferably 50 ° C. or lower, more preferably 25 ° C. or lower, and further preferably 10 ° C. or lower. Reduction in contact time may be achieved by increasing the speed of the web and / or increasing the speed of the annular path over which the stamper is carried. However, increasing the amount of heat carried by the stamper may also be effective if the rate is increased as desired to carry sufficient energy to melt flow the web surface. The longitudinal contact (web movement direction) with the web stamper in the nip region is preferably short in both length and time. The web preferably moves at a speed of 3 to 30 inches per second. The contact time between the stamper and the web is preferably 300 milliseconds or less, and more preferably 20 milliseconds or less. The contact time is most preferably 10 milliseconds or less, but is preferably greater than 0.5 milliseconds. In particular, when the stamper and the web are pressed together in the nip or nip region, the length of contact in the longitudinal direction is preferably 20 mm or less, and more preferably 5 mm or less. By limiting the contact (such as length and / or time) between the web and the stamper, substrate warpage can be reduced.

  The stamper may be conveyed through the nip area by any suitable means. Referring again to FIG. 1, the stamper 14 is carried through the nip region 16 by the support 28. The support may be a web, sheet, chain, belt, carriage, “ferris wheel structure”, carriage, ring, rail, drum, roller, and the like. The support 28 is preferably a closed annular path so that the stamper 14 is repeatedly passed through the nip region 16. As shown in FIG. 1, the support 28 is a flat thin plate. In an alternative embodiment such as that shown in FIGS. 2 and 4, the support will be a carriage.

  The stamper may be pressed against the web by any suitable pressing or pressing device. The device for pressing is preferably a set of rolls forming a clamping point or nip. The press preferably transmits a pressure of 500 PLI (pounds per linear inch) or less to the stamper / web contact area. The nip pressure is preferably in the range between 50 PLI and 300 PLI.

  As shown in FIGS. 1, 2 and 4, pressure roller 20 and support roller 22 provide a nip region 16 for pressing the stamper and web together. In particular, when the stamper and the web are pressed together with a round press such as a drum, the contact length in the longitudinal direction is preferably 20 mm or less, more preferably 5 mm or less, and 1 to 2 mm. Is more preferable. The pressure roller 20 and the support roller 22 are preferably drums or rolls assembled from rigid materials such as metals, alloys, ceramics and the like. The pressure roller 20 and the support roller 22 preferably have a smooth finished surface. In a preferred embodiment, to affect the time / temperature curve of the stamper / web interface (as described above) and / or to affect the lubricity of the stamper / drum interface, and / or The support roller 22 is coated with a material selected to provide a compliant surface (as described below). The properties of the support roller must prevent debris from forming when in contact with the stamper. Typical coating materials are chromium, cobalt, nickel, iron, steel, stainless steel, molybdenum, titanium, zirconium, zirconium oxide, silicon nitride, titanium nitride, synthetic diamond (DLC), Teflon or Teflon filling of the above or similar materials Including substrate. The pressure roller 20 and the support roller 22 are preferably rotatable. The roll may be free rotating or rotated by one or more drive devices 24 and 26. The driving devices 24 and 26 are preferably independent of each other. If the support roller 22 is heated at a bias temperature, it is operated at a temperature that is cooler than the maximum processing temperature achieved on the web / stamper interface side of the stamper 14. By actively controlling the temperature of the support roller, improved heat transfer from the stamper to the support roller is achieved, and improved microstructural replication is achieved.

  A preferred method of forming a web with a stamper and a pair of nip rollers is to increase the nip pressure to reduce stamper bending strain along the web, as well as to reduce cross web deformation or web displacement strain. It includes balancing stamper bending strain against web stretch strain by reducing nip pressure. For example, a 55 Shore D hardness nip roller is used with an 8 inch nip drum having a curved stamper. By varying the clamping force between 600 and 900 pounds, the image quality can be improved by balancing the axial ratio between crossing the web and along the web.

  Although the apparatus disclosed herein can be applied to form any type of web material, the web material is a heavyweight having appropriate optical, mechanical, and thermal properties for making optical memory disks. A coalescent material is preferred. Preferably, the web material is a thermoplastic polymer such as polycarbonate, polymethyl methacrylate, polyolefin, polyester, poly vinyl chloride, poly sulfone, cellulose derivative material, and the like. The web material preferably has a refractive index suitable for use in an optical memory disk (eg, 1.45 to 1.65). The web thickness is preferably from about 0.05 mm to about 1.2 mm, depending on the intended application. The web 12 preferably has a width sufficient to replicate one, two, three, four or more images across the web. The web material may include one or more additions of antioxidants, UV absorbers, UV stabilizers, fluorescent or absorbing dyes, antistatic agents, mold release materials, fillers, plasticizers, softeners, surface glidants, etc. Will contain the agent. The web material is preferably a pre-made roll that is formed “off-line” as it is supplied to the substrate forming apparatus at ambient temperature or to the apparatus at ambient temperature. Feeding the web material in the form of a roll to the device at ambient temperature allows for greater process flexibility and efficiency.

  To form the stamp, the stamper is heated with a heater prior to contacting the web. The heater may be any suitable heating device, such as a directional energy source, an induction heating source, a conduction heating source, a radiant heating source, etc., or any combination or equivalent. The stamper is preferably heated independently of other equipment components including nips, webs, rolls, and the like. The stamper is preferably heated immediately before being transported to the nip region. Preferably, the support drum is also heated.

  Heating is preferably provided by an induction heating coil that produces direct resistance heating of the stamper. The induction heating coil is preferably made of a conductive material such as copper, aluminum, silver or the like. The induction heating coil will consist of a series of contoured conductors coupled with a suitable energy source. The induction heating coil is preferably water cooled. The induction heating coil is preferably placed adjacent to the stamper so that resistive heating occurs in the stamper when the induction heating coil receives power. The induction heating coil is preferably placed within a range of 1 mm to 50 mm from the stamper. When the stamper is heated by the induction heating coil, it is raised to a temperature sufficient to melt and flow the surface of the web. Choose the amount and uniformity of coupling with the stamper by adjusting the dimensions and geometric dimensions of the induction coil, selecting the appropriate stamper material, and changing the distance between the stamper and the induction heating coil I can do it. As shown in FIGS. 1, 2 and 4, the induction heating coil 18 is located upstream of the replication region and adjacent to the stamper trajectory.

  During embossing, web warping can be caused by excessive shrinkage of the web material and / or annealing of the secondary surface. Even a slight amount of warping of the substrate can be a problem for an optical memory device. The present invention contemplates various methods for reducing the likelihood of warpage. This method includes one or more of the following: controlling the time relationship to the stamper / web interface temperature as the web passes through the nip region, reducing the total processing time at temperatures above the glass transition temperature Tg. And / or limiting the depth to be heated above the Tg of the web. Web warping may also be reduced by changing the wrap angle of the web and / or adding and heating the web from both sides. Each of these methods may be used separately or in combination to improve the duplicate image and reduce warpage.

  The present invention provides a method of forming a polymer web substrate by melt-flowing the surface of the web. Melt flow molding is a processing method in which the surface of the web material is heated into a melt, displaced, and then stabilized. As will be noted, forming a polymer substrate by interfacial melt flow is different from traditional compression relaxation methods. In melt flow, when the stamper strikes the web, the surface of the web is heated to such an extent that the material melts and flows locally. Material displacement and local flow cause the web surface to quickly and accurately conform to the shape of the microstructure pattern on the stamper. The web surface can be stabilized before stamper separation occurs. In comparison, the compression relaxation method uses force to distort and displace the material for a period of time at a temperature below the melting point or flow temperature to reduce the strain generated in the web by the compression force. to enable. By using melt flow molding instead of compression relaxation, the time required for image formation is significantly reduced and the overall heating of the web is also limited.

  In a preferred embodiment of the melt flow molding process, the surface of the stamper is fed at or above the melt flow temperature (Tf). Increasing the stamper / web interface temperature instantaneously above or above Tf allows the web surface to be molded into the stamper microstructure in a fast and unstrained manner. The stamper / web interface must be high enough to melt and flow the web surface, but need not be so high that the entire cross section of the web is melted. The web is preferably from the interface down to a depth of 0.2 mm or less, more preferably down to a depth of 0.1 mm or less, more preferably further down to a depth of 0.05 mm or less, most preferably 1 down. Melt flow to a depth of less than a micron. Limiting the thermal penetration depth of the process to a minimum value, such as to the depth of the structure being molded, minimizes material subsurface displacement and subsurface annealing, reducing strain and warpage. can do.

  The melt flow time / temperature curve balances the stamper maximum temperature with the thermal properties of the stamper, matches the initial temperature and thermal response of the web, matches the initial temperature and thermal response of the stamper / web interface, And / or may be provided in a number of ways including changing the thermal properties of the roll forming the nip region. FIG. 3 shows a typical example of a time / temperature curve for a melt molding process according to a preferred embodiment of the present invention. As shown, the temperature of the web during embossing (y-axis) is taken against time (x-axis). Within the contact time, the web surface temperature has a steep slope from ambient temperature or T cold (graph point A) to Tf (graph point B) or above and then [rapidly] cooled to produce a stamper. Stabilizes the image before it leaves the web. Alternatively, the web may be preheated above ambient temperature or above Tg before contacting the stamper with the web. Preferably, the web surface temperature is lowered to Tf or below (indicated by point C in the graph) before the stamper leaves the web.

  The stamper preferably leaves the web at an interface temperature below the melt flow temperature of the web (eg, below Tf). Interfacial cooling rate depends on a number of conditions, including heat conduction into the web, thermal properties of the web / stamper interface, thermal conductivity of the stamper, supplying one or more insulating layers, and aggressive interface temperature. It should generally be noted that it can be affected by control. The stamper is preferably separated at a temperature higher than the glass transition temperature Tg. Thanks to the low forming stress associated with melt forming, the treated surface of the web can maintain its microstructure after leaving the stamper while cooling.

  While not wishing to be bound by theory, the polymer response to displacement forces includes a viscous component and an elastic component. In Tf, the viscous component is dominant, and in T cold (temperature below Tg), the elastic component is dominant. Above the Tg (glass transition temperature), a transition occurs where an increase in free volume causes the molecule to rotate or translate. This degree of freedom causes the molecules to pass each other and the viscous behavior becomes more dominant. Embossing of the polymer material at Ts or T soft (temperature below Tf but above Tg) requires substantial relaxation of the strain prior to stamper separation. In comparison, various embodiments of the present invention emboss a disk substrate at or above Tf, and the stamper / web laminate need not be below Tf and not necessarily below Tg prior to separation. Is intended to cool down. The optimal temperature point reached in the various embodiments of the present invention is sufficient to avoid the microscopic and macroscopic distortions associated with stamper shrinkage while at the same time maintaining the shape of the microstructure within the web after separation. To stabilize. The melt molding process of the present invention tends to eliminate the polymer relaxation time constraints associated with the traditional “high temperature embossing” performed by providing the stamper with a low viscosity interface. Melt molding improves the process tolerances to web thickness and texture variations by reshaping the surface. Melt molding can take advantage of soot, enhanced surface mobility prior to stamper / web separation, as well as rapid surface re-stabilization. By controlling the time / temperature curve at the stamper / web interface, the microstructure on the stamper is transferred to the web with reduced defects such as micro-bleeding (smear), groove shape distortion, and warpage. Will. A further advantage derived from the short time / high temperature profile is the limited thermal penetration depth into the web material. Limited thermal penetration can help reduce polymer subsurface annealing, which has been found to contribute to overall warpage. Fast melt molding can reduce the thermal load transferred to the web. A reduced thermal load can reduce the thermal penetration depth. By modifying the shape of the time / temperature curve, the average thermal exposure can be reduced and extremely high surface maximum temperatures with rapid cooling can be achieved. There will be practical limits imposed by being unstable to temperature.

  Although a wide range of temperature-versus-time curves can be achieved by proper selection of materials, excessively high maximum temperatures are not desirable. It has been found that melt flow molding could be provided more easily if the difference between Tf and Tg could be temporarily reduced without compromising the physical properties of the entire web polymer. Applicants believe that selectively applying a glidant to the surface of the web prior to melt molding will lower the required melt molding maximum temperature without compromising the overall physical properties of the web polymer. I discovered that. In order to incorporate better rheological properties without the undesirable consequences of overheating, it is advisable to use additives on the web surface or surface site to temporarily improve the flow properties It has been found.

  The web material is preferably provided with a glidant. A glidant is any material or composition that imparts high flow properties to the basic web material in the melt flow state. The glidant is preferably a substance that effectively lowers the melt flow temperature of the surface and / or a substance that increases the cooling rate of the surface. The glidant is preferably supplied in an amount sufficient to reduce the dynamic viscosity of the web at a given temperature. The glidant is preferably supplied at 0.1% to 1.0% by weight at the web surface. Therefore, it is preferred that the web material has a glidant lower than the value reported for raw or glidant-free material and has at least sufficient glidant to lower Tf, with a typical maximum processing temperature of 5% Is preferably supplied in an amount sufficient to reduce by 50%. By providing an amount of glidant sufficient to modify the melt flow properties of the web, an improved optical memory quality microstructure can be produced by melt molding.

  The glidant is preferably supplied to a certain depth on or in the web surface. It is preferred that the glidant is supplied to the depth of the produced feature or just below the produced feature. The glidant is preferably supplied to a depth of at least 0.003 microns. The glidant may be supplied over the entire cross section of the web, but is preferably supplied up to 50% of the top, more preferably up to 10% of the top. The glidant is preferably supplied to a depth of 10 microns from the surface, more preferably to a depth of 3 microns from the surface. In the preferred application, only the first 1.5 microns of the surface site contains the glidant.

  Water has been found to be a particularly useful glidant. Not only has water been found to be an effective glidant, but it can also be used by the web / stamper by actively cooling the web surface and creating an obstacle to the continuous transfer of heat from the stamper. The time / temperature curve at the interface can be advantageously changed. In addition, the large heat of water evaporation promotes rapid cooling at the stamper / web interface and reduces image stabilization time. Traditionally, the water present in the web during high temperature embossing has been a major problem because the water trapped in the web evaporates to produce gaseous bubbles. These bubbles are typically formed at the web-stamper interface, forming a concave depression on the web surface. These bubbles will degrade the optical quality of the final product. Typical solutions to the water problem have been either drying the web or treating the web at a relatively low temperature (below Tg) to remove the water. Applicants have noted that the presence of water on the web surface during melt molding not only improves the quality of the microstructure in which the proper amount of water is transferred to the web, but can also improve it without forming water vapor bubbles. So I found that it is actually beneficial. Preventing harmful water evaporation would be achieved by reducing the thermal penetration depth and providing a short processing time. Since the effectiveness of the melt molding process is enhanced by the presence of water, the maximum processing temperature can be reduced. Lowering the requirement for maximum temperature further reduces thermal penetration and thereby results in less warpage. Water is preferably supplied in an amount of about 0.1 to 0.4 percent by weight of the web material. Moisture may be added, removed, or both to provide the preferred amount of water to the web surface. In some cases, the web is dried prior to embossing. In another example, the web is subjected to a water surface treatment prior to embossing. In other cases, it may be necessary to surface condition the web by first drying the web and then treating the pre-dried web with water just prior to embossing.

  It will be appreciated that although water is a preferred material, other glidants may be used. Other glidants include plasticizers, resin emulsions, and mold release agents that can be applied to the surface or integrated in the proper amount on the surface of the web. Preferred glidants will comprise one or more compounds selected from the fatty acid esters and the chemical family of fatty acids. Preferred glidants include the fatty acid ester pentaerythritol tetrastearate. The glidant is supplied to the web by any suitable means such as dipping, coating, spray coating, fine spraying, absorption, dampening in a humidified bath, evaporation chamber, addition to the initial plastic resin, addition to the initial extrusion raw material, etc. May be. The glidant is preferably added in a manner that provides a uniform coating of material on the surface of the web material. Preferably, the glidant provides properties suitable for temporarily lowering the effective web Tf during melt molding and / or provides a permanent increase in web surface Tg as a result of process conditions.

  In order to achieve a favorable temperature profile during web forming, the roll or drum that forms the nip area is used to maintain proper heating / cooling of the web / stamper interface, such as positive or passive heating or cooling. Adapted with sufficient heat transfer characteristics. Referring to FIG. 4, rolls 20 and 22 are thermally conductive and are provided with an outer layer 21 and an insulating layer 23 (respectively) that are in the time it takes for the stamper 14 to leave the web 12. Is not necessarily lower than its glass transition temperature (Tg) but is selected to have sufficient thermal insulation to cool below the melt flow temperature (Tf). If either the outer layer 21 or the insulating layer 23 is excessively insulative, the web surface may not cool enough to fully stabilize during the time it takes the stamper 14 to leave the web. The shape of the structure will change. If the insulation of the outer layer 21 or the insulating layer 23 is insufficient, the stamper 14 will be too cold to shrink before leaving the web, resulting in fine structure smearing and groove shape distortion.

  In a preferred embodiment of the method of molding the polymeric web material, the web is also heated on the side opposite to the side on which the microstructure is molded, for example the “back side”. Heating the “back side” of the web reduces the residual warping force due to cooling after annealing. Heat may be supplied to the backside by any suitable heating device. The heat is preferably supplied to the web by a heated roll that is configured to reduce the thermal penetration depth caused by radiant heat or in contact with the stamper. The backside of the web may be heated, such as by radiant heat or conduction heat, before entering the process nip region, or it may be heated in the process nip region at the same time as the microstructure formation. The back surface is preferably heated in an amount sufficient to balance the subsurface annealing that occurs on the stamper side. The back surface may be heated in the same way that the stamper is heated, such as induction heating. This approach will be extended to achieve simultaneous melt molding of both sides of the web.

  In practice, the web material may be conveyed to the nip area in advance of any suitable web feeding means. The feeding means is preferably a device suitable for continuously transporting the web material to the stamper along the web track, such as a thin plate feeding device, a folded material feeding device, a roll feeding device, a web extruder, etc. . The web feeder is preferably a roll feeder for feeding a pre-made roll of polymeric web material to the nip area, such as that shown at 300 in FIGS. The roll of polymeric web material preferably includes a removable film or protective layer of material, such as a layer of softer plastic film on the web. By using a web with a softer protective layer, the web can be rolled, unwound and unwound with minimal or no surface scratches that would otherwise affect the web's use in optical memory devices. It will be done.

  The web supply device is supplemented by a winding device such as a winding roll for collecting the processed or molded web. Instead of using a take-up roll, the web may be cut into pieces after molding (as described below) or further processed into a finished or semi-finished optical memory disk.

  The web forming device is preferably adapted to accommodate variations in web tension so that the web does not become too tight or too loose. A web that is too tight can result in the web breaking, and a web that is too loose can get stuck and cause other problems. Furthermore, tension control across the nip area must be managed to reduce the material displacement of the secondary surface and the axial ratio of the replicated image. To accommodate web tension variations, the device will include one or more tension rollers. Tension rollers are commonly known in material handling operations and are used to control web speed and tension.

  The tension is controlled across the nip area, at the nip feed point, at the nip feed point and across the other devices. The tension at the nip feed point is close to zero or neutral.

  The apparatus will have one or more guide rollers to guide the web in the web trajectory, to change the angle of the web entering and exiting the nip area, as well as to change the direction of the web. Preferably there is at least one guide and / or tension roller for guiding the web to the process nip region and at least one guide and / or tension roller for guiding the web out of the nip region. These guide and / or tension rollers may serve the added purpose of establishing process nip area feed and feed contact and separation angles between the web and stamper. The guide roller on the side exiting the nip area allows an initial web / stamper separation angle of about 90 degrees plus / minus 1 degree. The guide roller preferably guides the web away from the stamper immediately after leaving the nip.

  With reference to FIGS. 1, 2 and 4, the heated stamper 14 is carried by the support 28 to the nip region 16. The stamper 14 is preferably temporarily superimposed on the web 12 as a result of free floating through the nip region. The support 28 is preferably independent of or attached to the nip rollers 20 and 22 and parts thereof. The independence of the support 28 will cause the stamper 14 to float substantially freely on the web 12 as the stamper is temporarily superimposed on the web in the process nip region 16. By superimposing the stamper on the web using an independent support, a stamper with more than one, preferably more than two degrees of freedom of movement will be realized. By having more than one degree of freedom, the stamper 14 can better cope with or adapt to the strain introduced by the roll pressure into the web 12 during the melt forming process, and more perfectly the web texture and thickness variation. It is possible to correspond to.

  Referring now to FIG. 2, a web forming apparatus according to a preferred embodiment of the present invention is depicted, comprising a web forming apparatus 10 having a special support that reduces the angle at which the stamper enters the nip region 16. Yes. The apparatus includes a web supply device 42, a web track 44 in communication with the web supply device 42, a nip or nip region 16 disposed within the web track 44, and a stamper. The stamper 14 is carried by a set of “annular bands” 118, 128 that follow the web track 44 through the nip region 16 and form a support that carries the stamper 14 between the pressure and support rollers 20 and 22. . The support is preferably removed from the pressure and support rollers 20 and 22 and preferably results in the stamper 14 temporarily overlapping the surface of the web 12 in the nip region 16. As shown, the annulus forms a carriage 114 on which the stamper rests. The carriage 114 provides a means for carrying the stamper independently through the nip region 16. By carrying the stamper 14 independently into and through the nip region, better thermal management of the process is provided. In addition, by independently carrying the stamper 14 through the nip region, the stamper is kept more flat, thereby reducing the axial ratio resulting from forming a curved stamper in the form of a small diameter transport drum. To reduce.

  As shown, the carriage 114 is supported around the support roller 22 on a plurality of rollers 30, 32, 34. The rollers 30, 32, and 34 freely rotate the rails 118 and 128. The stamper 14 will be joined between and supported by the rails 118, 128 by suitable means. The rails are preferably separated by a distance equal to the width of the support roller 20 (across the web) so that only the stamper (as opposed to the rail) contacts the support roller during operation. The rails 118, 128 preferably have a perimeter that is substantially greater than that of the support rollers. The ratio of the circumference of the rail to the support roller is preferably at least 5: 4, more preferably about 13: 8 or more. A rail having a large perimeter will help keep the stamper passing through the nip region 16 flat.

  In operation, the support roller 22 engages the back surface of the stamper 14 to guide the stamper into contact with the web 12, while the pressure roller 20 presses the web against the front surface of the stamper. The roll surface is preferably chosen to provide the required contact uniformity, optimize the dynamic shape of the nip area, and balance the pressure distribution to minimize overall image distortion. The pressure roller and / or the support roller preferably have a followable surface. A pressure roller having a compliant surface and / or a support roller can provide the stamper with sufficient flexibility to improve image formation in response to variations in web thickness. The compliant material is preferably between 0.05 and 0.5 inches thick, more preferably about 0.125 plus or minus 0.1 inches thick. The trackable material 21 is preferably selected to have a hardness grade of less than 80 Shore D hardness, preferably between Shore A hardness 90 and Shore D hardness 60. The support roller 22 may also include a layer 23 of compliant material, which may be the same as the compliant material of the pressure roller, and may be different (thickness, compliant, elastic, lubricious, and / or heat transfer characteristics). Sometimes). If both rolls have a compliant surface, the combined properties provide pressure and heat transfer uniformity without introducing pressure, shear and / or velocity instabilities into the stamper / web laminate. The surfaces are preferably adapted to optimize. Preferred conformable materials include, but are not limited to, nitrile, EPDM, kapton, epoxide, filled epoxide, Teflon, and Teflon-injected polymers, metal or ceramic bodies. Any material with followability and heat transfer characteristics suitable for melt molding optical memory microstructures with radial deviation plus or minus less than 0.8 degrees and tangential deviation plus or minus 0.3 degrees may be used. Is to be understood.

  Referring to FIG. 5, a preferred embodiment of an optical memory medium manufacturing apparatus 200 is shown. The apparatus 200 includes a web dispensing apparatus 300, a web material forming apparatus 10, a film coating apparatus 400, a web cutting apparatus 500, and a cassette loading or accumulating apparatus 600. The apparatus 200 will be used to process a continuous web 12 of material to produce a finished optical memory storage medium such as an optical disc.

  As shown in FIG. 5, a roll 310 of web material 12 is supplied by a web dispensing device 300. The web material 12 can be of any width and thickness useful for making optical memory substrates. The scroll 310 is mounted in a replaceable state on the reel 320 stored in the payout device 300. The web material 12 supplied from the roll 310 passes through one or more guide / tension rollers 330 to the forming apparatus 10.

  Since various embodiments of the substrate forming apparatus have been examined previously, it should be understood that any embodiment of the web forming apparatus previously examined can be used with the apparatus 200 described herein. The molding apparatus 10 receives web material from the web dispensing apparatus 300. The disk substrate forming apparatus 10 is used for forming a fine pattern into a web. After the microstructure is formed into the web material, the material may be further processed to complete the fabrication of the optical memory device more fully. The material will be sent to the coating applicator 400 for further processing of the web material.

  The various coatings are applied to the web material either in a continuous manner as the web prior to cutting into strips of web material or by batch processing after cutting. The coating applicator 400 includes one or more coating devices 410, 412, etc. that are used to apply the coating to the web 12. The coating apparatus is capable of maintaining a vacuum around the web and uses one or more coating methods such as CVD, PVD, PCVD, PECVD, PML, LML, sputtering, or other deposition methods to coat the coating. Is added.

Table 1 below identifies example processing methods, coatings, and film thicknesses that may be used to form the desired coatings on the phase change optical memory substrate.

  The coating device 410 will be used to apply a dielectric antireflective coating in the thickness range of about 500 to 2000 angstroms, more preferably in the range of 60 to 150 nanometers. The dielectric coating may be composed of any suitable material such as silicon dioxide, silicon nitride, titanium oxide, zinc sulfide, silicon oxide, germanium nitride, germanium oxide, silica, alumina, combinations of the above, or the like. . Preferably, the dielectric antireflective coating has a refractive index of about 2.2. For this reason, silicon nitride that can be deposited with a refractive index of about 1.9 and titanium oxide that can be deposited with a refractive index of about 2.3 would be preferred.

  Although any type of deposition method may be used to add the dielectric antireflective layer, in one preferred embodiment, a microwave PECVD method is used. Examples of microwave PECVD methods and apparatus that can be used for coating are described in U.S. Pat. Nos. 5,411,591, 5,562,776, 5,567,241, 5,670,224, No. 6,186,090 and 6,209,482, the disclosures of each of which are incorporated herein by reference. Microwave PECVD methods such as those disclosed in the above cited patents may be preferred over other deposition techniques because of the rate at which deposition can be performed. Increasing the deposition rate also makes it possible to shorten the overall length of the deposition chamber required for coating. Reducing the deposition chamber length can significantly reduce the costs associated with the deposition process.

  A storage layer coating device 412 may be used to add the phase change storage material. The memory material coating preferably contains a chalcogenide alloy in the range of about 4 to 30 nanometers thick, more preferably about 20 to 25 nanometers thick. Although any type of deposition method may be used to apply the chalcogenide alloy coating, in a preferred embodiment it is sputtered onto the web.

  The second dielectric coating device 414 will be used to apply a dielectric antireflective coating in the range of about 150 to 2000 angstroms thickness, more preferably in the range of 20 to 25 nanometers thickness. Suitable dielectric materials include those described above. Although any type of deposition method may be used to add the second dielectric layer, in one preferred embodiment, a microwave PECVD method is used.

  A coating device 416 for reflective or heat loss material deposition is used to add a thin layer of metal, such as aluminum or the like, in the range of about 1 to 1000 nanometers thick, more preferably in the range of 60 to 150 nanometers. Will be used. In any preferred embodiment, the reflective or heat loss layer is sputtered or vapor deposited onto the web 12, although any type of deposition method may be used to apply a coating of a suitable material.

  The coating device 418 will be used to apply a protective coating. The protective coating is preferably 1000 to 7000 nanometers thick. The protective coating may be formed from any suitable optically transparent material such as thermosetting resin, UV resin, acrylate, and the like. In one preferred embodiment, a polymer multilayer or liquid multilayer (PML / LML) method is used to provide the acrylate coating. The PML method involves vacuum flash deposition of liquid monomer, producing a liquid condensed film, which is then radiation cross-linked to form a solid film. The LML method involves vacuum coating the liquid monomer directly onto the substrate by means of extrusion, gravure roll, spraying, etc., followed by radiation crosslinking of the thin liquid film monomer. The LML method may require coatings in excess of 10 micrometers, so PML may be preferred for the formation of acrylate coatings.

  Isolating the respective vacuum deposition chambers, such as coating devices 410, 418, from each other, from web forming, and from the dispensing device may be accomplished by any suitable isolating device, such as a gas regulating valve.

  The material and thickness of the two dielectric coatings must be carefully selected to satisfy several functions in the finished optical disc. These dielectric coatings will prevent exposure of the phase change coating to oxygen or water, which may oxidize the phase change material and change its properties. The dielectric coating will also be used to provide good contrast and to help the laser used to “write” to the disk be absorbed primarily by the phase change coating. The dielectric layer can also affect the thermal properties of the optical disc. The second dielectric coating between the phase change coating and the aluminum coating has sufficient thermal conductivity to prevent the laser targeted area of the phase change coating from overheating, but the aluminum coating It is chosen so that it is not thermally conductive enough to give excessive heat loss. Finally, the dielectric coating provides a rigid support when the phase change material sandwiched between them is heated with a laser.

  It is clearly understood that the microwave PECVD method referred to above for applying a dielectric coating can cause the deposition of dielectric material on a lens that insulates the microwave source from the PECVD chamber. . In order to facilitate continuous web processing, a new method has been developed that effectively replaces lenses according to continuity criteria.

  Referring to FIG. 6, a web 12 of a material used for manufacturing an optical disc is coated with the material in a vapor deposition chamber 440 of a coating apparatus 410. The vapor deposition chamber 440 includes an opening 442. A web 420 between polyester reels or other flexible, microwave transparent material may be used to shield the lens between the microwave source 430 and the deposition chamber 440. The microwave transparent web will be drawn continuously or intermittently from the first reel 422 through the opening 442 onto the second reel 424. Opposing rollers 426 or other means may be provided to form a seal at the intersection of the opening 442 and the polyester web 420. Polyester web 420 will repeatedly wind back and forth through openings 442 during PECVD operations until replacement is forced by deposition of material (dielectric coating material) on surface 421. Using the polyester web 420 to provide a microwave “window” in the deposition chamber 440 significantly increases the lifetime of the window.

  The previous examination of coatings used in the production of phase change optical memory storage devices is only intended to be exemplary. In order to produce a wide variety of optical memory storage devices, such as those examined in the background section of this application, this device can be applied to any number of different coatings in different orders, different thicknesses. What can be used is understandable. Accordingly, a detailed examination of the phase change memory device should not limit the scope of the present application.

  Referring again to FIG. 5, after coating, the web 12 exits the coating applicator 400 and enters an apparatus 500 for cutting or cutting the web. The web cutting device 500 may be any device suitable for separating a web into divided pieces or strips 510 that are one or more in length or width and can take several discs. The web cutting device will include a rotary cutting machine for cutting the web. The web cutting device may include a device for removing dust or debris generated by a cutting machine such as ionized air and vacuum.

  After the strip 510 is formed, it will be collected or collected into a container or removable cassette 610 using the accumulator 600. By collecting the discs in an accumulator, the production speed can be increased, and by collecting the web pieces in a removable cassette, the web pieces can be finished either off-line or on multiple lines. Can be processed. The finishing of the disc may be done directly from the web or from an embossed or coated material.

  In the disc finishing process, it is necessary to accurately form the outer peripheral portion (outer diameter, od.) And the central portion (inner diameter, id) of the replicated substrate and disc microstructure. The finishing of the disk may include any of a variety of operations such as drilling, cutting, milling, or other means of forming the disk's id and od.

  Referring to FIG. 7, there is shown a disk finishing apparatus 800 according to a preferred embodiment of the present invention. The disc finishing device is adapted to accept strips 510 from the stacking device 610. In starting the disc finishing device, the web strip 510 is lowered from the cassette onto the conveyor. The strip will be sent to a rough cut or square cut 820. In the square cut portion, the elongated piece 510 is cut into small shapes such as a square piece 822 containing only one disc. After the strip 510 is cut into square pieces 822, the square pieces are then conveyed to the separator ring embossing 830 to form the raised portion of the substrate material (ie, the disk separator ring). Separation rings prevent the stacked disks from being easily separated and scratched into the microstructure when stacked together. After the separation rings are formed on the disk substrate, each is sent to a center hole punch or punch 840 and then to a debris (material outside the disk) removal section 850. After the central hole and the debris around the disc have been removed, each semi-finished disc is laminated with a laminating portion 852.

  Referring to FIG. 8, a preferred web cutting section is depicted with a device 842 for centering the microstructure of the disk substrate. The apparatus 842 includes a table or table 844 disposed above the web 12 on which the disk substrate microstructure pattern 13 is formed. The table 844 could be selectively translated in the X and Y directions by motor drive components (not shown). The optical sensor 846 is supported on the table and faces the web 12 at a right angle. The optical sensor 846 supplies a detection signal to the control device 848. The detection signal received by the controller 848 will be used to control the centering and translation of the table 844. The table 844 is translated so that each of the optical sensors 846 is positioned directly above the edge of the microstructured pattern edge on the disk substrate. When the table 844 is centered on the fine structure pattern, the punching device 860 mounted at the center of the table 844 forms the central hole (id) and / or (od) of the memory device. Will be used to do.

  A preferred embodiment of the drilling device is shown at 860 in FIG. The perforating device 860 will include a stepped core die 862, a silicone bed 864, a barb 866, and a die button 868. The die may be composed of any suitable material. The dice may comprise one or more stages. Preferably, each step has a depth suitable for clean drilling in the polymer substrate. The ridges 866 are arranged to apply a downward biasing force to the bed to secure the web 12 between the bed 864 and the die button 868. A stepped core die 862 will be pushed down through the web 12 to form a central hole therein. The step formed in the core die 862 can reduce the possibility of forming a central hole with jagged or irregular edges.

  Referring now to FIG. 10, an alternative embodiment of an apparatus for forming an optical memory 200, where like numerals represent like components shown in other figures. As shown in FIG. 10, the web dispensing device includes a laminating device 340 for continuous web dispensing from a plurality of webs 310 of web material.

  The apparatus shown as a typical example in FIG. 10 will be particularly useful in the production of DVD optical substrates. As mentioned earlier, DVDs are produced by joining two discs. The surface of the information-carrying disc joined to the opposing disc is the same as the surface to which one or more coatings will be added. However, this coating does not help to form a mechanically strong and hermetically sealed bond between the information-carrying disc and the opposing disc. Accordingly, it is necessary to place a part of the information mounting disk, that is, the outer edge and the inner periphery of the peripheral part without covering them. As such, an apparatus that masks a portion of the substrate prior to coating may be used to mold a disk substrate with uncoated internal and external positions that are useful in the memory device to be bonded. is there.

  According to a preferred embodiment of the device for masking a part of the substrate before coating, an indexing device may be provided so that the edge of the memory device is shaped accurately. The indexing of the substrate will be provided by one or more front and back perforations, items 900 and 950 in FIG. 10, respectively. Indexing allows for accurate disc removal, integration, and coating of web material.

  For example, FIG. 11 shows the disk substrate 13 at various stages of molding, A, B, C, and D, showing the progress of the disk substrate as it passes through various processing sections. In stage A, the front perforation 900 (FIG. 10) drills a central hole 15 and one or more positioning holes 17 in the web. The center hole 15 may be formed by any means such as a drilling device, melting, drilling, cutting, or the like as shown in FIG. The center hole 15 will have a diameter that is the same as or smaller than the final hole of the finished optical disc. If the diameter of the center hole is smaller than that required for the finished optical disc, it will be increased in subsequent processing steps. Similar to the center hole 15, the positioning hole 17 may be formed by any means such as a sprocket drill. The locating hole may or may not completely penetrate the web 12. Preferably, the center hole 15 is precisely equidistant from each of the positioning holes 17 so that the relationship of the positioning hole to the center hole is known.

  Continuing to refer to stage A, after the central hole 15 and the positioning hole 17 are formed in the web 12, the web moves to the web forming apparatus 10. The forming apparatus 10 will include means for engaging the positioning hole 17 such as a nail or key. By engaging the positioning holes, the stamper can be positioned on the web 12 so that the fine structure pattern is precisely arranged around the central hole 15.

  Referring to stage B of FIG. 11, after the microstructure pattern is formed on the web 12, the disk substrate 13 is sent to the rear perforation 950 (FIG. 10). A central plug 952 is inserted into the central hole 15 at the rear perforation 950. Center plug 952 may be constructed of any suitable material. The central plug 952 may be fixed to the disk substrate 13 by any appropriate means. The central plug 952 is larger than the central hole 15 so as to mask the inner peripheral portion 954 of the disk substrate 13. The masked inner peripheral portion 954 is preferably fixed so as to have a width close to that of the conventional medium.

  Referring to Step C of FIG. 11, the outer mask 956 is applied over the disc substrate when it is in the rear perforation 950. The outer mask 956 is positioned on the web 12 by meshing with the web positioning holes 17. The outer mask 956 may be composed of any suitable material. The outer mask 956 may be fixed to the disk substrate 13 by any suitable method. Since the diameter of the inner opening 957 of the outer mask 956 is smaller than the final diameter of the disk substrate 13, the outer peripheral portion 958 of the disk substrate is masked. The masked outer peripheral portion 958 preferably has a width of about 1/2 to 3 mm, more preferably about 1 mm.

  After the plug 952 and outer mask 956 are in place, the disk substrate 13 is transported from the rear perforation 950 to the web cutting device 500 and the web 12 is cut into strips 510 of appropriate length and / or width. Is done. The strips 510 may be collected for further processing in a batch process or immediately transferred to the coating device 400. In the coating device 400, the elongated piece is placed in a groove disposed along the cylindrical inner surface of the rotating drum unit 450. The strips 510 are loaded into the drum 450 such that the masked surface of the disk substrate 13 is exposed to the interior of the drum or the flow of coating. The drum may be sealed by any suitable device throughout the coating process.

  The drum 450 of the coating device 400 will be prepared to rotate at right angles to the web 12 dispensing direction. Adjusting the drum perpendicular to the web payout direction causes the web strip 510 to advance linearly directly into the drum 450. The side of the drum 450 facing the web cutting device 500 is open so that one or more coating devices 410 can be inserted. The coating device 410 is mounted on an inner wall that can be sealed in the drum. When the wall on which the coating device 410 is mounted is closed, the web strip 510 disposed along the inner wall of the drum is transported through various coating areas defined by the coating device 410. Can rotate around its axis. A side view of the drum 450 and the deposition chamber 440 defined thereby is shown in FIG. In order to perform the coating process using the drum-type coating apparatus 400, it may be necessary to cool the drum 450 or the substrate in the drum. One way to cool the drum 450 is to provide a water cooling jacket around the outside of the drum. The use of a water cooling jacket allows control over the temperature of the drum and for the web strip located inside the drum.

  With continued reference to FIG. 11, after the disk substrate 13 is coated, the plug 952 and the outer mask 956 will be removed. At that time, the disk substrate 13 is coated on the surface except for the outer peripheral portion 958 and the inner peripheral portion 954, and looks as shown in stage D. The strip web that has reached stage D will be sent to a finishing line such as those examined above in connection with FIG. However, the finishing part for the disk substrate that has reached stage D will require an additional finishing part to join the information mounting substrate to the counter substrate (not written or embossed material). Let's go.

  An alternative embodiment of the drum-type coating device 400 is to rotate the coating device 400 on the same straight line as the web discharge direction. As a result, the disk substrate in strip or web form will be loaded directly onto the rotating drum 450.

  The previously disclosed embodiments of the present invention may be used with or separately from melt molding. Melt forming is intended to form a microstructure into the surface of a web in a very short time (on the order of tens of milliseconds, preferably even shorter). Such an embodiment would also be useful for other replication processes. While the invention has been described in detail in the drawings and foregoing description, it should be understood that the invention and the concepts herein are applicable to any shaped material, so they are illustrative and not of a limiting nature. Should be considered. It will be apparent to those skilled in the art that changes and modifications of the present invention can be made without departing from the scope and spirit of the invention. For example, the dimensions of the optical substrate and the microstructure formed there can be varied without departing from the scope and spirit of the invention. Materials used to assemble various components used in embodiments of the present invention, such as pressure and support rollers, stampers, stamper supports, and heating devices, without departing from the intended scope of the present invention. Can be changed. Further, it can be appreciated that the stamper support and the support roller can be integrated to provide a single structure. The stamper will then be pulled away from the support roller with the insulator. Furthermore, it will be appreciated that the present invention can be extended to embodiments using web, paper, or any other form of optical memory substrate. Furthermore, using one or more of the embodiments described above in combination or alone, from a web material of 1.2 mm or less, a radial deviation plus or minus 0.8 degrees, a tangential deviation plus or minus 0.3 degrees, An optical memory disk can be fabricated having a birefringence of less than 100 nm for double pass, preferably less than 90 nm for double pass, and more preferably less than 60 nm for double pass. Accordingly, the present invention is intended to embrace all such modifications and variations that fall within the scope of the appended claims and their equivalents.

1 is a perspective view of an apparatus for forming web material for use in an optical memory according to the present invention. FIG. FIG. 4 is a perspective view of another apparatus according to the present invention for forming web material. 2 is a graph of temperature versus time curves for web surface melt molding according to the present invention. 1 is a side plan view of an apparatus according to the present invention for forming web material. FIG. 1 is a side view of a continuous web optical memory production line according to the present invention. FIG. 1 is a side view of an apparatus for applying a coating to an optical memory substrate according to the present invention. FIG. 1 is a side view of an apparatus for finishing an optical memory according to the present invention. FIG. 1 is a perspective view of an apparatus for finishing an optical memory product according to the present invention. FIG. 1 is a side view of an apparatus for drilling holes in web material according to the present invention. FIG. 1 is a side view of an optical memory production facility according to the present invention. FIG. FIG. 3 is a top plan view of an apparatus for finishing an optical memory by a masking process according to the present invention. 1 is a side view of an apparatus for applying a coating to a web according to the present invention. FIG. 2 is a perspective view of a stamper surface and a web surface after embossing according to the present invention. FIG.

Claims (43)

  A method of forming a microstructure on the surface of a polymer material, comprising the steps of preparing a web of polymer material and melt-molding the surface of the web with a heated stamper.   The method of claim 1, wherein the stamper is heated by induction heating.   The method of claim 1, wherein the polymeric material web comprises a glidant.   The method of claim 1, wherein the polymeric material web comprises an amount of water sufficient to promote surface flow during melt molding.   The method according to claim 1, wherein the temperature change of the heated stamper is 50 ° C. or less.   The method of claim 1, wherein the stamper contact time with the material being molded is 300 milliseconds or less. The method of claim 1, wherein the stamper has a smaller coefficient of thermal expansion than nickel.   The method of claim 1, wherein melt forming comprises contacting the web with a stamper between a set of drums, the stamper being carried by a support removed from the drum.   The method of claim 1, wherein the temperature of the heated stamper is higher than the melt flow temperature (Tf) of the polymeric material when in contact with the web.   The method of claim 9, further comprising the step of pulling the stamper away from the web when the surface of the web is at a temperature below the melt flow temperature (Tf) of the polymeric material.   The method of claim 9, further comprising the step of pulling the stamper away from the web when the surface of the web is below the melt flow temperature (Tf) of the polymeric material and above the glass transition temperature (Tg). Method.   The method of claim 1, further comprising the step of heating the web on the opposite side of the stamper during molding.   The molding includes the step of contacting the web with a stamper between a set of drums, wherein the web side drum is provided at a temperature sufficient to prevent annealing from the stamper. the method of.   14. The method of claim 13, wherein the web side drum is provided at a temperature below the maximum processing temperature.   The method of claim 1, wherein forming comprises contacting the web with a stamper between a set of drums, wherein at least one drum has a compliant outer surface with a Shore D hardness of 80 or less. .   A method of forming a microstructure on a surface of a polymer material, comprising the steps of preparing a web of a polymer substrate and forming a microstructure with a stamper heated on the surface of the polymer material.   A method for forming a microstructure on a web surface of a polymer material, comprising the steps of: providing a surface comprising a glidant to the polymer material web; and forming a microstructure on the surface with a heated stamper.   The method of claim 17, wherein the surface glidant comprises a fatty acid ester or a fatty acid.   Forming a microstructure on the surface of the polymeric material web, comprising the steps of providing a web of polymer material having a surface region containing water and forming a microstructure in the surface region with a heated stamper; Method.   20. The method of claim 19, wherein water is provided in an amount sufficient to lower Tf below that of the dried material.   20. The method of claim 19, wherein water is provided in an amount sufficient to promote surface flow during molding and less than an amount that causes substantial bubble formation.   20. The method of claim 19, wherein water is 0.1% to 0.4% by weight of the polymeric material.   20. A method according to claim 19, characterized in that the water is supplied from the surface to a depth of 10 [mu] m.   20. The method of claim 19, wherein the water is supplied from the surface to a depth of 3 [mu] m.   20. The method of claim 19, wherein the water is supplied to a depth of at least 0.003 [mu] m.   A method for manufacturing a stamper for use in a continuous web forming process, comprising: providing a transferable image on the stamper; bending the stamper; and increasing the thickness of the stamper.   A step of preparing a web of polymer material, a step of forming a microstructure on the surface of the polymer material by a high temperature stamper and a short contact time such that the temperature change of the high temperature stamper during molding is 50 ° C. or less And forming a microstructure on the surface of the polymeric material.   28. The method of claim 27, wherein the temperature change is 25 ° C. or less.   28. The method of claim 27, wherein the temperature change is 10 ° C. or less.   28. The method of claim 27, wherein the contact time between the stamper / material is 300 milliseconds or less.   Preparing a web of polymer material and forming a microstructure on the surface of the polymer material using a stamper having a thermal expansion coefficient smaller than that of nickel. A method of forming a microstructure with a high temperature stamper.   An optical memory comprising a web forming device comprising a web feeding device, a stamper and a pair of rollers forming a nip region in conjunction with the web feeding device, wherein the stamper is carried by a support separated from the rollers A device for forming a fine structure on the surface of a polymer material used in the process.   33. The apparatus of claim 32, wherein the support comprises a carriage that independently carries the stamper through the nip region.   One of the rollers is a support roller for pressing the stamper against the web, and the carriage has a set of rigid annulus for supporting the stamper, and the annulus has a diameter larger than the diameter of the support roller. 34. The apparatus of claim 33, wherein:   35. The apparatus of claim 34, wherein the ratio of the diameter of each annulus to the diameter of the support roller is at least 5: 4.   35. The apparatus of claim 34, wherein the ratio of the diameter of each annulus to the diameter of the support roller is at least 13: 8. An apparatus used for manufacturing an optical memory, comprising:
Web feeding device;
A stamper for molding the polymer material carried on the ring and interlocking with the web feeding device;
A web cutting machine for dividing the web material after forming; and
Collector for collecting pieces of web material after cutting.   38. The apparatus of claim 37, wherein the collector comprises a removable cassette for storing a piece of web material after cutting. A method of forming a microstructure on the surface of a polymer material used in an optical memory, comprising the following steps.
Providing a roll of polymeric web material with a layer of removable softer material;
Forming a web with a heated stamper; and re-rolling the formed polymeric material. An apparatus used for manufacturing an optical memory, comprising:
Web feeding device;
A stamper for molding the polymer material carried on the ring and interlocking with the web feeding device;
Web cutting machine for dividing the web material after molding;
An accumulator for receiving pieces of web material after cutting;
An indexer for providing a recording hole in the segment of web material;
A masking device that covers the molded piece of web material to form a coating; and
At least one coat applicator for applying a thin film to a piece of web material after masking. A web splitting device used to manufacture optical memory from a continuous web process, comprising:
A pedestal that supports the molded piece of web material;
A plurality of optical positioning sensors for centering an image of the molded web material on the die track; and a die for cutting the web supported on the platform.   Providing a web of polymeric material; providing a heated stamper; and pressing the heated stamper and substrate between a set of nip rollers, wherein at least one of the nip rollers One is a method of forming a fine structure on the surface of a polymer material used for an optical memory, which has a followable outer surface with a Shore D hardness of 80 or less.   43. The method of claim 42, wherein the compliant outer surface has a hardness from Shore A hardness 90 to Shore D hardness 60 and a thickness from 0.05 to 0.5 inches.

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