Imprinting device

An imprinting device capable of realizing uniform transfer regardless of the thickness of a substrate includes a stage having a placement area for placing a substrate to which a transferred object is applied, a thin-plate mold with flexibility having a fine pattern on a first surface facing the placement area of the stage, which is held with a predetermined tension and a pressing roll which can press a second surface opposite to the first surface of the mold, in which the stage has plural adsorption holes around the placement area, and the adsorption holes start adsorption in synchronization with movement of the pressing roll.

TECHNICAL FIELD

The technical field relates to an imprinting device forming a fine pattern.

BACKGROUND

In recent years, in optical components used for products such as a display and a lighting device, it is desirable to realize a device having the expression of an unprecedented new function which controls reflection and diffraction of light by forming a fine pattern (from nanometer (nm) order to micron (μm) order) exerting particular optical characteristics. As methods for forming the fine pattern, an imprinting technique is attracting attention recently in addition to a photolithography technique and an electron beam lithography technique. The imprinting technique is a technique of transferring the fine pattern of a mold by pressing the mold in which the fine pattern is formed on the surface onto a transferred object.

As specific methods, there are a thermal imprinting method and a UV imprinting method. The thermal imprinting method includes a process of applying a thermoplastic resin as a transferred object on a substrate and heating the thermoplastic resin to be higher than a glass transition temperature to soften the thermoplastic resin, a process of pressing a mold onto the softened thermoplastic resin to transfer the fine pattern of the mold and a process of cooling the thermoplastic resin to be cured.

The UV imprinting method includes a process of applying a UV curing resin as a transferred object on a substrate and pressing a mold onto the uncured UV curing resin to transfer the fine pattern of the mold and a process of curing the UV curing resin by irradiating the UV curing resin with a UV light while pressing the mold.

Although the thermal imprinting method has an advantage that the selectivity in the material of the transferred object is wide, there is a disadvantage that the throughput is low as the heating process and the cooling process of the thermoplastic resin are necessary. On the other hand, in the UV imprinting method, the selectivity in the material is narrower than that of the thermal imprinting method as the material of the transferred object is limited to the UV curing resin. However, the heating process and the cooling process are not necessary and the transfer can be completed for several seconds to several tens of seconds, therefore, the throughput is extremely high. Which of the thermal imprinting method and the UV imprinting method is adopted depends on devices to which the method is applied. The UV imprinting method is considered to be suitable for the mass production method when there is no problem caused by the material.

As a method of forming the fine pattern, a flat-plate imprint is in common use, in which a flat-plate mold30in which a fine pattern33is formed is vertically pressurized with respect to a resin70applied on a surface of a substrate71to thereby transfer the fine pattern33of the mold30to the resin70as shown inFIG. 9.

However, as a surface of the mold30contacts a surface of the resin70in this method, it is highly likely that microbubbles remain inside the fine pattern33of the mold30and that a transfer defect occurs. In order to inhibit the transfer defect due to the bubbles, it is necessary to perform the imprinting under a vacuum environment. In that case, there are problems that costs for a vacuum apparatus are required and that the throughput is reduced as a fixed period of time is necessary for allowing the apparatus to reach a given degree of vacuum.

In JP-A-2014-54735 (Patent Document 1), a roll-type UV imprinting method as shown inFIG. 10is adopted for solving the above problems. In this method, the thin-plate mold30in which the fine pattern33is formed is fed in a feeding direction X while pressurizing the mold30with respect to the UV curing resin70applied to the substrate71by a pressing roll10, thereby sequentially transfer the fine pattern33of the mold30to the UV curing resin70. The UV curing resin70is cured by being irradiated with a UV light61by a UV irradiator60installed behind the pressing roll10.

In this method, the mold30is sequentially pressed onto the substrate71by moving the pressing roll10, therefore, the air is easily released to the feeding direction X of the pressing roll10and the fine pattern33of the mold30can be formed without trapping the air inside the fine patterns33. Furthermore, as a pressed area between the mold30and the substrate71has a line shape, the pressure for the transfer can be reduced. Additionally, as the processing can be performed under atmospheric pressure, a large-scale vacuum apparatus is not required.

SUMMARY

However, the imprinting method described in Patent Document 1 has a problem that, when there is a level difference at an end portion of the substrate71, the mold30floats from the substrate71after the pressing roll10passes the end portion of the substrate71and the transfer of the fine pattern in the end portion of the substrate71is significantly deteriorated. For example, in the case where the substrate71is thicker than a plate40provided around the substrate71as shown inFIG. 11, there is a danger that the mold30is bent and floated from the substrate71as the stress by the pressing roll10is concentrated on a corner of the substrate71. On the other hand, in the case where the substrate71is thinner than the plate40, the mold30floats when the pressing roll10runs on a corner of the plate40.

In view of the above, an imprinting device capable of realizing uniform transfer regardless of the thickness of the substrate is provided.

According to an embodiment, an imprinting device includes a stage having a placement area for placing a substrate to which a transferred object is applied, a thin-plate mold with flexibility having a fine pattern on a first surface facing the placement area of the stage, which is held with a predetermined tension and a pressing roll which can press a second surface opposite to the first surface of the mold. The stage has plural adsorption holes around the placement area, and the adsorption holes start adsorption in synchronization with movement of the pressing roll.

In the imprinting device, the adsorption holes start adsorption at the time when or just after the pressing roll passes the adsorption holes to thereby adsorb and hold the mold, therefore, it is possible to prevent the mold from floating in a step portion after the pressing roll passes an end portion of the substrate, which can realize uniform transfer regardless of the thickness of the substrate.

The imprinting device can further include a controller configured by instructions stored in a memory to turn on and off the adsorption holes to adjust the adsorbability.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a structure of an imprinting device according to an embodiment will be explained with reference to the drawings. As shown inFIG. 1, an imprinting device1according to the embodiment includes a pressing roll10, a holding roll20, a mold30, a stage40, a plate50, a UV irradiator60and a controller80. The imprinting device1according to the embodiment adopts a roll-type UV imprinting method.

The pressing roll10has a cylindrical shape, having a shaft11in the center thereof and rotating freely around the shaft11. The pressing roll10can also move on a flat surface perpendicular to a direction of the shaft11(axial direction Z). In other words, the pressing roll10can move in a direction approaching the stage (pressing direction Y) and a direction perpendicular to the axial direction Z and the pressing direction Y (feeding direction X). The holding roll20also has a cylindrical shape, having a shaft21in the center thereof and rotating freely around the shaft21. A direction of the shaft21is parallel to the axial direction Z of the pressing roll10. The holding roll20can also move on the flat surface perpendicular to the axial direction Z in the same manner as the pressing roll10. The holding roll20is held by, for example, a unit common to the pressing roll10and moves in synchronization with the movement of the pressing roll10while keeping a fixed interval L1between the center of the shaft21of the holding roll and the center of the shaft11of the pressing roll10. However, it is not necessary that the pressing roll10and the holding roll are held by the common unit, and may be held by different units as long as they move in synchronization with each other.

The mold30has a thin-plate shape and is arranged between the pressing roll10/the holding roll20and the stage40as shown inFIG. 1andFIG. 2. The mold30has a first surface31facing the stage and a second surface32opposite to the first surface31, and a fine pattern33is formed on at least part of the first surface31. Although the case where the fine pattern33is formed on the entire surface of the mold30is shown inFIG. 1, the fine pattern33may be formed in a part of the mold30as shown inFIG. 2. One end of the mold30is held by a movable holding portion34and the other end thereof is held by a fixed holding portion35. A tension applied to the mold30and an angle of the mold30with respect to the stage can be arbitrarily adjusted by moving the movable holding portion34. The mold30is a material having UV transmittance and flexibility, which is, for example, a PET film, however, the material is not limited to that.

The stage40has a placement area41for placing a substrate71to which a UV curing resin70as a transferred object is applied, and the placement area41faces the first surface31of the mold30as shown inFIG. 1andFIG. 3. The interval L1between the center of the shaft11of the pressing roll10and the center of the shaft21of the holding roll20is preferably set to be longer than a length L2of the placement area41of the stage40. Substrate adsorption holes42are formed in the placement area41. Plural mold adsorption holes43are formed around the placement area41. It is desirable that the mold adsorption holes43are independent of one another to allow a gas to be injected therefrom, the reason of which will be described later. It is also desirable that adsorbability and a flow rate of the gas can be adjusted.

A plate50is provided on an area except the placement area41on the stage40and a height thereof is approximately the same as a thickness of the substrate71to be used. In other words, a concave portion having approximately the same width and depth as the substrate71is formed by the stage40and the plate50, and the substrate71is fitted to the concave portion. The plate50has plural through holes51. The through holes51of the plate50are respectively connected to mold adsorption holes43on the stage40.

The UV irradiator60is arranged on the second surface32side of the mold30at a position where the UV irradiator60can emit a UV light61which is collimated toward the stage40and where the emitted UV light61is not blocked by the holding roll20and the pressing roll10. For example, the UV irradiator60applies the UV light61in the pressing direction Y of the pressing roll10. In this case, the UV irradiator60is installed at a position where the UV irradiator60does not overlap with the pressing roll10and the holding roll20when seen from the pressing direction Y. The UV irradiator60is, for example, an LED, and is not limited to this.

Next, the imprinting method using the imprinting device1according to the embodiment will be explained. The pressing roll10and the mold adsorption holes43are respectively connected to the controller80, and the controller80controls operation of the pressing roll10and the mold adsorption holes43. It is also preferable that the controller80is also connected to the holding roll20and the UV irradiator60to also control the holding roll and the UV irradiator60as shown inFIG. 1.

First, the substrate71to which the uncured UV curing resin70is applied is placed on the placement area41of the stage40so that the UV curing resin70faces the mold30. Accordingly, the substrate71is fitted to the concave portion formed by the stage and the plate50. At this time, the substrate71is aligned in a predetermined position, being adsorbed and held on the placement area41of the stage40by the substrate adsorption holes42. Then, the pressing roll10is moved in the pressing direction Y while holding the mold30with a predetermined tension and an angle. Accordingly, the pressing roll10contacts and presses the second surface32of the mold30, and the mold30having flexibility is deformed along the movement of the pressing roll10. When the pressing roll10moves in the pressing direction Y, the pressure is vertically applied to the substrate71placed on the stage40. At this time, the magnitude of the pressure is measured by a load cell (not shown). When the measured pressure reaches a given pressure, the pressing roll10is moved in the feeding direction X. When the pressing roll10moves in the feeding direction X, the pressing roll10rotates by being affected by the friction force with respect to the second surface32of the mold30. Then, the first surface31of the mold30sequentially contacts the UV curing resin70on the substrate71, and the fine pattern33formed on the first surface31is sequentially transferred to the UV curing resin70. The holding roll20shown inFIG. 1moves in synchronization with the movement of the pressing roll10while keeping the fixed interval L1with respect to the pressing roll10.

In this case, the mold adsorption holes43are configured to start adsorption in synchronization with the movement of the pressing roll10as shown inFIG. 4andFIG. 5. As the mold adsorption holes43are respectively connected to the through holes51of the plate50, when the mold adsorption holes43start adsorption, the mold30is adsorbed and held on the plate50through the through holes51. Specifically, when the shaft11of the pressing roll10passes the mold adsorption holes43, or just after passing the mold adsorption holes43, the mold adsorption holes43are preferably turned on in order. In the plural mold adsorption holes43ofFIG. 4, ones filled in white indicate an off-state of adsorption, and ones filled in black indicate an on-state of adsorption.

Suppose that the mold adsorption holes43are turned on before the shaft11of the pressing roll10passes the mold adsorption holes43, the mold30contacts the UV cursing resin70before being pressurized by the pressing roll10, which may mix bubbles and cause a transfer defect. When the mold adsorption holes43are turned on after the shaft11of the pressing roll10completely passes the mold adsorption holes43, there is a danger that the mold30is deformed at a step portion between the substrate71and the plate50and that the fine pattern33is not transferred in an end portion of the substrate71. The structure of the holding roll20shown inFIG. 1is omitted inFIG. 4toFIG. 8.

When adopting the imprinting device1according to the embodiment, uniform transfer can be realized regardless of the thickness of the substrate71. For example, in the case where the substrate71is thicker than the plate50as shown inFIG. 6, the mold30is sequentially adsorbed and held by the mold adsorption holes43at the time when, or just after the pressing roll10passes the step portion, therefore, the bending of the thin-plate mold30in the step portion can be suppressed after the pressing roll10passes, and the floating of the mold30from the UV curing resin70can be prevented. Moreover, in the case where the substrate71is thinner than the plate50as shown inFIG. 7, the mold30is sequentially adsorbed and held by the mold adsorption holes43at the time when, or just after the pressing roll10passes the step portion, therefore, the mold30follows the step portion and it is possible to prevent the end portion of the mold30from being floated from the UV curing resin70after the pressing roll10passes. Therefore, it is possible to transfer the fine pattern to the end portion of the substrate71, which can realize uniform transfer regardless of the thickness of the substrate71. As the surface of the pressing roll10has certain elasticity, the surface of the pressing roll10can move along the surface of the substrate71even when the substrate71is thinner than the plate40as shown inFIG. 7.

Next, the UV curing resin70is cured by irradiating the UV curing resin70with the UV light61by using the UV irradiator60shown inFIG. 1. As the mold30is the material having UV transmittance, the UV light61can be applied to the UV curing resin70through the mold30by applying the UV light61toward the stage40from the second surface32side of the mold30.

Lastly, the mold30is released from the TV curing resin70. Specifically, the pressing roll10is moved in an opposite direction to the feeding direction X as shown inFIG. 8, and the mold30can be peeled off from the UV curing resin70by using a tension relating to the mold30. At this time, it is necessary to stop the adsorption of the mold adsorption holes43. Furthermore, when the gas can be injected from the mold adsorption holes43, it is possible to assist the peeling of the mold30by injecting the gas sequentially in synchronization with the movement of the pressing roll10. Specifically, it is desirable that the gas is sequentially injected from the mold adsorption holes43at the time when or just after the pressing roll10passes. In the case where the flow rate of the gas can be adjusted, the assist force for releasing the mold can be controlled so as to correspond to respective places.

In the imprinting device1according to the embodiment, the interval L1between the center of the shaft11of the pressing roll and the center of the shaft21of the holding roll20is preferably set to be larger than the length L2of the placement area41of the stage40as shown inFIG. 1. The holding roll20is provided for holding a portion of the mold30so as not to be separated from the UV curing resin70after the pressing roll10passes. When the interval L1between the center of the shaft11of the pressing roll and the center of the shaft21of the holding roll20is larger than the length L2of the placement area41of the stage40, the UV light61is applied in a state where the substrate71exists between the pressing roll10and the holding roll20when seen from the pressing direction Y, thereby performing irradiation of the UV light61at a time.

The imprinting device1according to the embodiment is not limited to the cylindrical holding roll20in the above description. For example, a holding member not having a cylindrical shape may be used instead of the holding roll20as long as the portion of the mold30can be held so as not to be separated from the UV curing resin70after the pressing roll10passes.

Moreover, the imprinting device1is not limited to the concave portion by the plate50and the stage40as in the above description. For example, in the case where the stage40has the concave portion, the substrate can be fitted into the concave portion of the stage even when the plate does not exist. In the case where the plate50is used, the suitable concave portion can be formed with respect to the substrate71having an arbitrary shape and thickness by appropriately selecting a plate having approximately the same as the shape and thickness of the substrate71.

the imprinting device1is not limited to the UV imprinting method explained above. A thermal imprinting method can be also adopted. In the case of the thermal imprinting method, the mold30is not limited to the material having UV transmittance. As a material of the transferred object, a thermosetting resin which is softened by being heated to be higher than a glass transition temperature is used instead of the UV curing resin. It is further necessary to have a mechanism for heating and cooling the thermosetting resin instead of the UV irradiator60. For example, a heater is provided in the stage40to thereby heat the thermosetting resin by the heater through the substrate71, and a cooling flow path is provided in the pressing roll10and a cooling water or a cooling gas flows in the cooling flow path to thereby cool the thermosetting resin through the surface of the pressing roll10and the mold30.

The imprinting device1is not limited to the substrate adsorption holes42described above. For example, the substrate71can be held by adhesive bonding. It is preferable to hold the substrate71by the substrate adsorption holes42as it is easy to release the holding.

In the drawings, the case where the circular substrate71seen from the pressing direction Y of the pressing roll10is used and the placement area41of the stage40is also circular is shown, however, the imprinting device1is not limited to this. For example, polygonal shapes can be adopted.

The present invention is useful for an imprinting device capable of realizing uniform transfer regardless of the thickness of a substrate.