CONTINUOUS MAGNETIC NANOIMPRINTING

PRIORITY CUAIM

[0001] This application claims priority from Singapore Patent Application No. 10201810570T filed on 26 November 2018.

TECHNICAU FIEUD

[0002] The present invention relates to nanoimprinting, and more particularly relates to systems and devices for continuous magnetic nanoimprinting.

BACKGROUND OF THE DISCUOSURE

[0003] With running speeds of up to thirty meters per minute or greater, thermal and ultraviolet roll-to-roll nanoimprint tools can be used for high throughput nanoimprinting and up-scaling of processes related to imprinting. The typical size of an embossing drum/roller is up to one meter in diameter. While fast imprinting speeds can be achieved, an optimized imprint area may not be fully realized and may not necessarily be continuous due to the design challenges involved in mounting a mold onto the embossing drum/roller.

[§004] Clamp devices such as screws and adhesive and slots are conventionally used for mounting of the mold onto the embossing drum/roller. The clamps and slots occupy space on the embossing drum/roller thereby limiting the effective imprint area and inducing scratches and other damage to the imprinted material and film.

[0005] In addition, the mounting of an imprint mold is typically very time consuming. The lengthy mounting time for mounting molds for thermal roll to roll imprinting is required to fix the position of the imprint mold mounting clamps and screws. In addition, for ultraviolet embossing, an epoxy is required in addition to clamps and screws to affix the mold to the dmm/roller. Such epoxy minimally takes six hours to cure for the mold to gain the full adhesive strength for nanoimprinting.

[0006] Finally, tensioning is required to assure that the imprint mold has proper contact with the embossing dmm/roller. To prevent the imprint mold from deforming or breaking during the tensioning, a minimum thickness of the imprint mold is required. In addition, the imprint mold dimensions must necessarily be determined by embossing drum/roller as such dimensions are fixed due to the pre-fabricated undercut slot insert of the embossing drum/roller, further limiting the types, shapes and sizes of molds that can be used, as well as the embossing process.

[0007] Thus, there is a need for systems and devices for nanoimprinting that reduce the time and complexity of the mold attachment process, that permit use of molds that are not defined by the dmm/roller specifications and optimally use the drum/roller surface and that are able to overcome that above mentioned shortcomings and further provide other related advantages. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background of the disclosure.

SUMMARY

[0008] According to at least one embodiment of the present invention, a system for continuous roll-to-roll imprinting is provided. The system includes an embossing drum and an imprinting mold. The embossing drum includes an inner magnetic core for mechanically inducing a magnetic force at an outer surface of the embossing drum. The imprinting mold magnetically adheres to the embossing drum in response to the magnetic force.

[0009] According to another embodiment of the present invention, an embossing drum for continuous roll-to-roll nanoimprinting is provided. The drum includes an inner magnetic core and a drum outer surface. The inner magnetic core mechanically induces a magnetic force at the drum outer surface, and a gap is defined between the inner magnetic core and the drum outer surface having a gap distance 0.1mm to

0.5mm.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views and which together with the detailed description below are incorporated in and form part of the specification, serve to illustrate various embodiments and to explain various principles and advantages in accordance with a present embodiment.

[0011] FIG. 1 is a top perspective view of a conventional roll-to-roll embossing system.

[0012] FIG. 2, comprising FIGS. 2A, 2B and 2C depicts conventional mold mounting devices, wherein FIG. 2A depicts a top perspective view of a thermal embossing drum with a conventional slot mold mounting with screws, FIG. 2B depicts a side perspective view of a conventional roll-to-roll embossing drum/roller with slots and clamps for mold mounting, and FIG. 2C depicts a top planar view illustrating application of epoxy to a mold for conventional mounting to, for example, the drum of FIG. 2B. [0013] FIG. 3 depicts a side perspective view of a magnetized mold on a roll-to-roll embossing drum/roller in accordance with present embodiments.

[0014] And FIG. 4, comprising FIGs. 4A, 4B and 4C, depicts views of an internal magnetic core of a roll-to-roll embossing drum/roller in accordance with the present embodiments wherein FIG. 4A depicts a first side perspective view of an illustration of the magnetic core where the magnetic core is standing on its end, FIG. 4B depicts a second side perspective view of an illustration of the magnetic core where the magnetic core is laying on its side, and FIG. 4C is a side perspective view of an actual magnetic core.

[0015] Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been depicted to scale.

DETAILED DESCRIPTION

[0016] The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description. It is the intent of the present embodiment to present a design for a clamp-free and slot-free embossing drum/roller for continuous roll-to-roll imprinting which fully utilizes imprint area of the embossing drum/roller. Mechanical induced magnets are integrated into the embossing drum/roller for adhering the mold to the embossing drum/roller for a seamless and continuous imprint area, thereby maximizing the imprint area and improving the speed of mold mounting.

[0017] Referring to FIG. 1, a top perspective view 100 of a conventional embossing system includes a roll-to-roll drum/roller 102 which measures approximately one meter in diameter. Note that the term“roller” refers to solid device and the term

“drum” refers to a hollow device. Those skilled in the art will realize that reference hereafter to“drum” to describe present embodiments does not limit the present embodiments only to drums as the present embodiments also include rollers.

[0018] Such conventional embossing systems can emboss at speeds of up to thirty meters per minute or greater. Thus, thermal and ultraviolet (UV) roll-to-roll nanoimprint drums can be used for high throughput nanoimprinting and up-scaling of processes related to imprinting. The system depicted in FIG. 1 is a UV roll-to-roll system with UV light devices 104, 106.

[0019] While fast imprinting speeds can be achieved, an optimized imprint area is typically not fully realized and the imprinting process may not necessarily be continuous due to design challenges involved in mounting a mold onto the embossing drum. FIGS. 2 A, 2B and 2C highlight these design challenges. FIG. 2 A depicts a top perspective view 200 of a thermal embossing drum 202 with a conventional slot mold mounting with screws 204. The screws 204 are used to mount a mold to the drum 202. The screws 204 mount the mold into slots 206 and, after mounting the mold, are removed for operation.

[0020] FIG. 2B depicts a side perspective view 220 of a conventional roll-to-roll embossing drum 222 with slots 224 for mold mounting. FIG. 2C depicts a top planar view 240 illustrating application of epoxy 242 to a mold 244 for conventional mounting (i.e., clamping) of the mold 244 to, for example, the drum 222.

[0021] The slots 206, 224 and screws 204 take up space on the conventional embossing drum 222 which limits the effective imprint area. In addition, the slots 206, 224 and screws 204 may induce scratches or other damage to the imprinted material or film. [0022] In addition, using the slots 206, 224 and screws 204 to mount an imprint mold is time consuming as time must be spent to fix position of the screws 204 and clamping means to mount the imprint mold to the drum. For UV embossing, in addition to screws and clamps, the epoxy 242 is required and the epoxy 242 takes a minimum of six hours to cure in order for the mold to gain full adhesive strength for nanoimprinting.

[0023] Referring to FIG. 3, a side perspective view 300 of a system for roll-to-roll nanoimprinting in accordance with present embodiments is depicted. The system includes a magnetized mold 302 on a roll-to-roll embossing drum 304. Due to the magnetic adherence of the mold 302 to the embossing drum 304, the embossing drum 304 is slot-free and clamp-free allowing full utilization of an imprint area on the drum 304 thereby advantageously enabling continuous roll-to-roll imprinting. Conventional roll-to-roll systems use nickel films or plates as imprint mold material and steel as drum surface material. The present embodiments can also use embossing drums formed of steel and imprint molds made of nickel films or plates as mechanical induced magnets integrated into the embossing drum 304 create a magnetic flux for adhering the nickel imprint mold 302 to the embossing drum 304 for imprinting. Since the embossing drum 304 does not include conventional slots and clamps such as screws for mounting of the imprint mold 302, the imprint area of the mold 302 on the embossing drum 304 is seamless and continuous, advantageously maximizing the imprint area while improving the speed of mold mounting. Dismantling of the mold 302 from the drum 304 is also simplified in accordance with the present embodiments since only disruption or redirection of the magnetic flux adhering the mold 302 to the surface of the drum 304. This can be done by lifting a corner of the mold 302 from the surface of the drum 304 or inserting a magnetic insulating material (e.g., plastic) between a portion of the mold and the surface of the drum to redirect/dismpt the magnetic flux, thereby facilitating removal of the mold 302 form the drum 304.

[0024] In order to assure direct contact of the mold 302 to the outer surface of the embossing drum 304 and avoid uneven contact across the imprint area, a surface smoothness of a bottom side of the imprint mold 302 should be substantially the same as a surface smoothness of the outer surface of the embossing drum 304, In accordance with the present embodiments, the surface smoothness is approximately 0.2 to 0.8 microns to ensure conformal contact between the imprint mold 302 and the embossing drum 304.

[0025] Systems and devices in accordance with the present embodiments use mechanically induced magnetism for adherence of the mold 302 to the embossing drum 304. This magnetism is generated by an inner magnetic core inside the drum 304. Referring to FIGs. 4A, 4B and 4C, views 400, 420, 440 depict internal magnetic cores 402, 442 of a roll-to-roll embossing drum 304 in accordance with the present embodiments. FIG. 4A depicts a first side perspective view 400 of an illustration of the magnetic core 402 where the magnetic core 402 is standing on its end and FIG. 4B depicts a second side perspective view 420 of an illustration of the magnetic core 402 where the magnetic core 402 is laying on its side.

[0026] Mechanically-induced magnetism is used for design of the magnetic core 402 instead of electrically-induced magnetism (i.e., electro-magnetism) as the embossing drum can be heated up to 200 °C during imprinting and electrical components will not survive temperature used during thermal roll-to-roll processes. In accordance with the present embodiments, uniform and strong mechanically-induced magnetic force of up to 1800 Gauss ±10% can be generated by a series of permanent magnets forming the magnetic core 402. The magnets are arranged in Halbach arrays and affixed to a moving inner portion of the drum. In accordance with the present embodiments, a small gap is defined between the inner magnetic core 402 and the surface of the drum 304 to break the heat transfer from the surface of the drum 304 to the magnetic core 402. The gap is less than 0.5mm but more than 0.1mm to 0.2mm, and preferably between 0.25mm and 0.35mm, so that the gap is large enough to interrupt the heat transfer but small enough so as not to unduly reduce magnetic flux (i.e., the magnetic flux generated at the surface of the drum 304 by the inner magnetic core 402 reduces exponentially with distance therebetween).

[0027] Referring to FIG. 4C, a side perspective view 440 of a magnetic core 442 in accordance with the present embodiments includes a plurality of permanent magnets arranged in the Halbach arrays such that the north poles (or south poles) are pointing towards the surface of the embossing/imprint roller 304. No specific arrangement of the permanent magnets is required (the arrangement can be N-S-N-S or N-N-S-S or both) so long as all north poles or all south poles of the magnets 444 of the magnetic core 442 are pointing towards the surface of the roller 304. The magnets 444 are specially shaped and sized, strong magnets capable of operating at high temperature made of materials such as Neodymium iron boron (NdFeB) or Samarium Cobalt (SmCo) and polarized as required. In accordance with the present embodiments, the magnets preferably have the properties as shown in Table 1:

TABLE 1

[0028] Using the magnets 444 for mechanically-inducing magnetism for mounting the mold 302 to the drum 304, no tension force is required. The mold 302 is merely placed onto the drum 304, adhering by magnetism. Thus, no minimum thickness of the imprint mold is required to prevent breaking or deformation of the mold during tensioning. And with no need for slots or screws or other clamping means, dimensions of the imprint mold 302 can fully optimize the surface of the roller 304.

[0029] Thus, it can be seen that the present embodiments provide systems and devices for nanoimprinting that reduce the time and complexity of the mold attachment process, that permit use of molds that are not defined by the dmm/roller specifications and optimally use the dmm/roller surface. The mold 302 advantageously adheres to the drum 304 by mechanically induced magnetism created by the inner magnetic core 402, 442.

[0030] While exemplary embodiments have been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should further be appreciated that the exemplary embodiments are only examples, and are not intended to limit the scope, applicability, operation, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention, it being understood that various changes may be made in the function and arrangement of steps and method of operation described in the exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.