Replica master mold, method of manufacturing replica master mold, article, and method of manufacturing formation object

A replica master mold 10 comprises: a base material layer 11; and a surface shape body 12 formed on the base material layer 11 and having a fine irregular pattern, wherein a softening temperature of the surface shape body 12 is higher than a softening temperature of the base material layer 11.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Japanese Patent Application No. 2016-094103 filed on May 9, 2016 and Japanese Patent Application No. 2016-162922 filed on Aug. 23, 2016, the entire disclosures of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a replica master mold, a method of manufacturing a replica master mold, an article, and a method of manufacturing a formation object.

BACKGROUND

One of the fine processing technologies is imprint technology by which a master mold having a fine irregular (concave-convex) pattern formed on its surface is prepared and the fine irregular pattern of the master mold is pressed against a resin sheet or the like to transfer the fine irregular pattern of the master mold to the resin sheet. For example, imprint technology is used in the formation of a fine irregular structure for antireflection on a display panel of a smartphone, a tablet terminal, or the like.

Formation objects on which fine structures are formed by imprint have conventionally been approximately planar display panels and the like. In recent years, however, there has been growing demand to form fine structures on three-dimensional formation objects such as three-dimensionally shaped display panels, lens surfaces of camera and the like, and panel surfaces of automotive instruments.

In imprinting, typically, a master mold having a fine irregular pattern corresponding to a fine structure to be formed on a formation object is prepared. A master mold (replica master mold) to which the fine irregular pattern of the master mold has been transferred is then produced, and the fine irregular pattern is transferred to the formation object using the replica master mold.

JP 5276436 B2 (PTL 1) discloses a technique of transferring a fine irregular pattern of a master mold to flexible polymer foil (film) of a cycloolefin copolymer (COC) or the like to produce a polymer stamp (replica master mold) and transferring the fine irregular pattern to a formation object using the polymer stamp. The polymer stamp is formed from flexible polymer foil, and has flexibility. Hence, by softening the film through heating and applying liquid pressure to the polymer stamp, the polymer stamp can be deformed in conformity with the shape of the three-dimensional formation object. The polymer stamp deformed in conformity with the shape of the formation object is then brought into close contact with a photo-curable resin applied onto the formation object, and the photo-curable resin is irradiated with light to be cured. A fine structure can thus be formed on the formation object.

CITATION LIST

Patent Literature

SUMMARY

Technical Problem

According to PTL 1, the polymer stamp is produced by transferring the fine irregular pattern of the master mold to the flexible polymer foil. That is, the polymer stamp (replica master mold) disclosed in PTL 1 is a single-layer film made of a flexible polymer such as a COC. Therefore, when the polymer stamp is heated to deform in conformity with the shape of the formation object, the irregular portions of the polymer stamp may soften, causing the shape of the fine irregular pattern to be distorted. If the shape of the fine irregular pattern of the replica master mold is distorted, transfer of an accurate fine irregular pattern corresponding to the fine irregular pattern of the master mold is hampered.

It could be helpful to provide a replica master mold, a method of manufacturing a replica master mold, an article, and a method of manufacturing a formation object that can prevent a distortion of a fine irregular pattern in a replica master mold and suppress a decrease in transfer accuracy.

Solution to Problem

A replica master mold according to the present disclosure comprises: a base material layer; and a surface shape body formed on the base material layer and having a fine irregular pattern, wherein a softening temperature of the surface shape body is higher than a softening temperature of the base material layer.

Preferably, in the replica master mold according to the present disclosure, the base material layer has flexibility.

Preferably, in the replica master mold according to the present disclosure, the base material layer and the surface shape body are fixed by an intermediate layer composed of one or more layers.

Preferably, in the replica master mold according to the present disclosure, a release layer is formed on a surface of the fine irregular pattern of the surface shape body.

Preferably, in the replica master mold according to the present disclosure, the surface shape body is made of an inorganic compound.

Preferably, in the replica master mold according to the present disclosure, the base material layer has an elongation percentage of 10% or more.

Preferably, the replica master mold according to the present disclosure has a curved surface whose curvature radius is greater than a height of the fine irregular pattern.

A method of manufacturing a replica master mold having a curved surface comprises: heating the replica master mold to higher than or equal to the softening temperature of the base material layer; and deforming the heated replica master mold to have the curved surface whose curvature radius is greater than the fine irregular pattern.

An article according to the present disclosure comprises a fine structure formed by transfer using the replica master mold or by attachment of the replica master mold.

A method of manufacturing a formation object according to the present disclosure is a method of manufacturing a formation object having a fine structure formed thereon, and comprises: preparing a replica master mold that includes a base material layer and a surface shape body formed on the base material layer and having a fine irregular pattern corresponding to the fine structure, a softening temperature of the surface shape body being higher than a softening temperature of the base material layer; heating the replica master mold to a temperature higher than or equal to the softening temperature of the base material layer and lower than the softening temperature of the surface shape body, to deform the replica master mold in conformity with a shape of the formation object; and forming the fine structure on the formation object, by transfer using the replica master mold or by attachment of the replica master mold.

Advantageous Effect

A replica master mold, a method of manufacturing a replica master mold, an article, and a method of manufacturing a formation object according to the present disclosure can prevent a distortion of a fine irregular pattern in a replica master mold and suppress a decrease in transfer accuracy.

DETAILED DESCRIPTION

One of the disclosed embodiments is described below, with reference to drawings. Note that the present disclosure is not limited to the following embodiment, and various modifications are possible within the scope of the present disclosure. In the drawings, the same reference signs represent the same or similar components.

(Structure of Replica Master Mold)

FIG.1is a diagram illustrating an example of the structure of a replica master mold10according to one of the disclosed embodiments.

The replica master mold10illustrated inFIG.1includes a base material layer11and a surface shape body12.

The base material layer11is a sheet-shaped base material, and has flexibility and also desirably has a sufficient elongation percentage (e.g. 10% or more) to deform in conformity with the shape of a three-dimensional formation object. The thickness of the base material layer11is preferably thin, so as to deform in conformity with the shape of the three-dimensional formation object. The thickness of the base material layer11is preferably 500 μm or less, and more preferably 100 μm or less. Herein, “having flexibility” means being able to be bent and flexed by human hand. Herein, the “elongation percentage” can be determined, for example, by the following method.

A base material to be measured is made into a strip of 10.5 cm in length and 2.5 cm in width, as a measurement sample. The tensile elongation percentage of the obtained measurement sample is measured using a tensile tester (Autograph AG-5kNXplus produced by Shimadzu Corporation) (measurement conditions: tension rate=100 mm/min; inter-chuck distance=8 cm). In the measurement of the elongation percentage, the measurement temperature differs depending on the type of the base material. The elongation percentage is measured at a temperature close to or not lower than the softening point of the base material. In detail, the temperature is 10° C. to 250° C. For example, in the case where the base material is polycarbonate or a PC/PMMA laminate, the elongation percentage is preferably measured at 190° C.

The base material layer11is made of, for example, polymethyl methacrylate (PMMA), polycarbonate (PC), polyvinyl chloride (PVC), polyvinyl alcohol (PVA), polyethylene (PE), amorphous polyethylene terephthalate (APET), polystyrene (PS), triacetyl cellulose (TAC), cyclic olefin polymer (COP), polyethylene terephthalate (PET), or the like. In terms of the process steps after the manufacture of the replica master mold10, the base material layer11is preferably made of PMMA, PC, PVC, TAC, or the like.

The surface shape body12is formed on the base material layer11and has a predetermined thickness. A fine irregular pattern is formed on the surface of the surface shape body12. The surface shape body12is made of a resin curable by active energy rays, such as a polymer of an acrylate monomer, a methacrylate monomer, or the like. The surface shape body12may be made of an inorganic compound. The surface shape body12is made of such a material whose softening temperature is higher than the softening temperature of the base material layer11. The softening temperature is a temperature at which a film softens and deforms by pressure application or the like, and corresponds to a storage elastic modulus (E′) of 0.3 GPa or less in dynamic viscoelasticity measurement (DMA measurement).

In the replica master mold10according to this embodiment, the softening temperature of the surface shape body12is higher than the softening temperature of the base material layer11. Therefore, even in the case where the base material layer11is heated to its softening temperature in order to deform the replica master mold10in conformity with the shape of the three-dimensional formation object, the surface shape body12does not soften. It is thus possible to prevent a distortion of the fine irregular pattern of the surface shape body12and suppress a decrease in transfer accuracy.

The structure of the replica master mold10is not limited to that illustrated inFIG.1. As an example, the replica master mold10may have a structure in which an intermediate layer13as a binder layer is formed approximately flat between the base material layer11and the surface shape body12to fix the base material layer11and the surface shape body12having the fine irregular pattern, as illustrated inFIG.2.

As another example, the replica master mold10may have a structure in which the intermediate layer13having a predetermined thickness and the fine irregular pattern is formed on the base material layer11and the surface shape body12is formed so as to cover the surface of the intermediate layer13, as illustrated inFIG.3A. The intermediate layer13may be composed of a plurality of layers, as illustrated inFIG.3B. InFIG.3B, an approximately flat intermediate layer13-2is formed on the base material layer11, and an intermediate layer13-1having a predetermined thickness and the fine irregular pattern is formed on the intermediate layer13-2. The surface shape body12is formed so as to cover the surface of the intermediate layer13-1.

As illustrated inFIGS.2,3A, and3B, the provision of the intermediate layer13can improve the adhesiveness between the base material layer11and the surface shape body12and improve the optical characteristics. The intermediate layer13is made of, for example, PC, an acrylate monomer having resin penetrability, or a multifunctional oligomer of urethane series or the like.

To enhance releasability, a layer made of an acrylic monomer containing fluorine or silicone or a layer made of an oxide may be formed on the surface of the surface shape body12, as a release layer. By depositing an oxide on the surface of the surface shape body12, a distortion of the fine irregular pattern of the surface shape body12can be prevented more reliably.

(Overview of Formation of Fine Structure on Formation Object Using Replica Master Mold)

An overview of the formation of a fine structure using the replica master mold10is given below, with reference toFIGS.4A to4D. In the following description, it is assumed that a formation object on which a fine structure is to be formed has, for example, a convex surface like a convex lens, and the fine structure is formed on the convex surface.

First, as illustrated inFIG.4A, a master mold14having a fine irregular pattern corresponding to the fine structure to be formed on the formation object is manufactured. The master mold14is manufactured by a known manufacturing method for a master mold for imprint. For example, a resist layer is formed on a quartz plate, and irradiated with light (exposed to light) according to the fine irregular pattern to be formed. Following this, a developer is applied onto the resist layer, and the resist layer is developed to form a resist pattern corresponding to the fine irregular pattern on the resist layer. Etching is then performed using, as a mask, the resist layer on which the resist pattern is formed, to form the fine irregular pattern on the quartz plate. The master mold14is not limited to a plate shape, and may have a roll shape.

Next, the replica master mold10illustrated inFIG.4Bis manufactured using the master mold14. In the manufacture of the replica master mold10using the master mold14, for example, an uncured photo-curable resin is sandwiched between the master mold14and the base material layer11, and then irradiated with light (ultraviolet light) to be cured. By sandwiching the uncured photo-curable resin between the master mold14and the base material layer11, the fine irregular pattern of the master mold14is transferred to the uncured photo-curable resin. The uncured photo-curable resin is then irradiated with ultraviolet light, and thus cured in a state in which the fine irregular pattern has been transferred. After this, the master mold14is released from the cured photo-curable resin. The cured photo-curable resin serves as the surface shape body12. The replica master mold10in which the surface shape body12having the fine irregular pattern is formed on the base material layer11can thus be manufactured.

With the method described above, the fine irregular pattern formed on the surface shape body12is inversion of the fine irregular pattern formed on the master mold14. This is, however, not a limitation. For example, the replica master mold10including the surface shape body12having the same fine irregular pattern as the fine irregular pattern of the master mold14can be manufactured by transferring the fine irregular pattern of the master mold14to another transfer object, transferring the fine irregular pattern that has been transferred to the other transfer object to the uncured photo-curable resin, and then curing the photo-curable resin to form the surface shape body12.

Instead of the above-mentioned method (light transfer method) of pressing the master mold14against the uncured photo-curable resin and then curing the photo-curable resin, a thermal transfer method using a thermosetting resin may be used to manufacture the replica master mold10. The process of manufacturing the replica master mold10will be described in detail later.

After separating the replica master mold10from the master mold14, the replica master mold10is heated, and pressed against a die15that conforms to the shape of the formation object, as illustrated inFIG.4C. As a result, the replica master mold10deforms (preforms) in conformity with the shape of the die15, i.e. the shape of the formation object. Here, the replica master mold10is pressed against the die15, with the surface shape body12facing the die15. The process illustrated inFIG.4C(process of deforming the replica master mold10) will be described in detail later.

Next, as illustrated inFIG.4D, an uncured photo-curable resin17is applied to the surface of a formation object16, and the replica master mold10deformed in conformity with the shape of the die15(formation object16) is pressed against the photo-curable resin17with the surface shape body12facing the photo-curable resin17. As a result of the surface shape body12being pressed against the uncured photo-curable resin17, the fine irregular pattern of the surface shape body12is transferred to the photo-curable resin17. The uncured photo-curable resin17is then irradiated with light (ultraviolet light) to be cured, thus forming the fine structure on the formation object16.

(Process of Manufacturing Replica Master Mold)

The process of manufacturing the replica master mold10illustrated inFIG.4Bis described in detail below, with reference toFIGS.5A and5B.

The following describes not the above-mentioned light transfer method, but a method by which the resin is softened by heating and the master mold14is pressed against the softened resin to transfer the fine irregular pattern formed on the master mold14to the softened resin.

The process of manufacturing the replica master mold10mainly includes a heating step, a transfer step, and a release step.

First, as illustrated inFIG.5A, a laminate10ain which an approximately flat resin layer12ais formed on the base material layer11is prepared. The resin layer12ais made of the same material as the surface shape body12. The softening temperature of the resin layer12ais therefore higher than the softening temperature of the base material layer11.

In the heating step, the laminate10ais heated until the resin layer12asoftens. Examples of the heating method include conduction heating by contact with a high-temperature body, convection heating by convection of a high-temperature fluid, and radiation heating using infrared light (IR) or the like.

In the transfer step, the heated resin layer12ais pressed against the master mold14, as illustrated inFIG.5B. By pressing the heated resin layer12aagainst the master mold14, the fine irregular pattern formed on the master mold14is transferred to the resin layer12a. Examples of the method of pressing the resin layer12aagainst the master mold14include fluid pressurization using gas or liquid, and clamping the ends of the laminate10aand pressing it against the master mold14. In the heating step, the laminate10ais heated until the resin layer12asoftens. This means the base material layer11whose softening temperature is not higher than the softening temperature of the resin layer12ahas softened, too. Accordingly, with the use of vacuum forming, pressure forming, TOM (Three dimension Overlay Method) forming, or the like, the base material layer11follows the shape of the master mold14. This enables the transfer of the fine irregular pattern to the resin layer12ain a more reproducible manner.

In the release step, the laminate10aafter the transfer step is cooled, to cure the base material layer11and the resin layer12a. Following this, the master mold14is separated from the resin layer12a. As a result, the replica master mold10in which, on the base material layer11, the resin layer12ato which the fine irregular pattern of the master mold14has been transferred is formed as the surface shape body12is obtained.

(Deformation of Replica Master Mold)

The process of deforming the replica master mold10illustrated inFIG.4Cis described in detail below, with reference toFIGS.6A to6E. The following describes a process of deforming the replica master mold10by push-up forming.

First, as illustrated inFIG.6A, the die15that conforms to the shape of the formation object16is placed on a stage21. The stage21has sidewalls22on its periphery, and is movable along the sidewalls22(movable vertically inFIG.6A). Each sidewall22is provided with a support23for supporting the replica master mold10. The supports23support the replica master mold10so as to face the die15. The replica master mold10is supported with the surface shape body12facing the die15. On the side of the replica master mold10supported by the supports23opposite to the die15, a quartz plate24supported by the sidewalls22and facing the stage21is provided. The quartz plate24allows light to pass through. The stage21, the sidewalls22, the supports23, and the quartz plate24are arranged so as to seal a region25surrounded by the stage21, the sidewalls22, and the replica master mold10supported by the supports23and seal a region26surrounded by the quartz plate24, the sidewalls22, and the replica master mold10supported by the supports23.

The replica master mold10supported by the supports23is heated to a temperature higher than or equal to the softening temperature of the base material layer11and lower than the softening temperature of the surface shape body12. As mentioned above, the softening temperature of the surface shape body12is higher than the softening temperature of the base material layer11. Accordingly, the base material layer11softens, but the surface shape body12does not soften. Hence, no distortion of the shape of the fine irregular pattern formed on the surface of the surface shape body12occurs.

Next, as illustrated inFIG.6B, the regions25and26are vacuumed. The stage21is movable vertically along the sidewalls22, as mentioned above. As a result of vacuuming the region25, the stage21moves upward (i.e. toward the replica master mold10supported by the supports23).

The stage21moves upward, and the die15pushes up the replica master mold10supported by the supports23, as illustrated inFIG.6C. As a result of being pushed up by the die15, the replica master mold10deforms along the shape of the die15. Merely pushing up by the die15, however, cannot bring the die15and the replica master mold10into close contact with each other without any gap, and there are gaps27between the die15and the replica master mold10in the vicinity of the ends of the die15.

Next, as illustrated inFIG.6D, in a state in which the die15pushes up the replica master mold10, compressed air is introduced into the region26, to apply pressure to the replica master mold10. This brings the die15and the replica master mold10into close contact with each other even in the vicinity of the ends of the die15. In this state, the replica master mold10is cooled, and removed from the supports23and the die15. The replica master mold10deformed along the shape of the die15is thus produced, as illustrated inFIG.6E.

(Formation of Fine Structure on Formation Object)

The process of forming the fine structure on the formation object16illustrated inFIG.4Dis described in detail below, with reference toFIGS.7A to7D. The following describes an example of forming the fine structure on the formation object16of a three-dimensional shape. The term “formation object of a three-dimensional shape” refers to a formation object having a curved surface whose curvature radius is greater than the height of the fine structure (fine irregular pattern) formed on the replica master mold10. As mentioned above, the replica master mold10is deformed in conformity with the shape of the formation object16. Therefore, the replica master mold10deformed in conformity with the shape of the formation object16has a curved surface whose curvature radius is greater than the height of the fine structure (fine irregular pattern) formed on the replica master mold10.

The process of forming the fine structure on the formation object16mainly includes an application step, a transfer step, a photo-curing step, and a release step.

In the application step, as illustrated inFIG.7A, the uncured photo-curable resin17is applied to the surface of the formation object16. As the method of applying the photo-curable resin17to the formation object16, various methods such as spray coating, inkjet coating, dispenser coating, dip coating, dropper dropping, and spin coating can be used depending on the viscosity of the photo-curable resin17and the shape of the formation object16. An intermediate layer may be provided between the formation object16and the photo-curable resin17, to improve the adhesiveness between the formation object16and the photo-curable resin17, the optical characteristics, and the like.

In the transfer step, as illustrated inFIG.7B, the replica master mold10is pressed against the photo-curable resin17applied to the formation object16. As mentioned above, the replica master mold10is deformed in conformity with the shape of the die15(formation object16) in a state in which the surface shape body12faces the formation object16. Accordingly, by pressing the replica master mold10against the formation object16, the surface shape body12is pressed against the photo-curable resin17. As a result of the surface shape body12being pressed against the photo-curable resin17, the fine irregular pattern formed on the surface shape body12is transferred to the photo-curable resin17.

Examples of the method of pressing the replica master mold10against the formation object16(photo-curable resin17) include fluid pressurization using gas, liquid, or the like from the base material layer11side, pressing using an elastic solid, and pressing using a roller.

In the photo-curing step, as illustrated inFIG.7C, in a state in which the replica master mold10is pressed against the photo-curable resin17, active energy rays are applied to the photo-curable resin17to cure the photo-curable resin17. The active energy rays are, for example, rays of light emitted from a light source such as a mercury lamp, a metal halide lamp, or an ultraviolet light emitting diode (LED).

In the case where the replica master mold10allows the active energy rays to pass through, the active energy rays may be applied to the photo-curable resin17from the replica master mold10side. In the case where the formation object16allows the active energy rays to pass through, the active energy rays may be applied to the photo-curable resin17from the formation object16side.

In the release step, as illustrated inFIG.7D, the formation object16and the replica master mold10are separated from each other. On the surface of the formation object16, the photo-curable resin17to which the fine irregular pattern of the surface shape body12of the replica master mold10has been transferred is cured to form a fine structure17a. The formation object16(article) having the fine structure17aformed thereon is thus manufactured.

The separation of the formation object16and the replica master mold10needs to be performed without the surface shape body12of the replica master mold10dropping off or the replica master mold10being damaged. In this embodiment, the replica master mold10is film-shaped, and therefore deforms more flexibly than conventional master molds made of quartz, metal, or the like. Hence, the replica master mold10is less likely to be damaged upon the release. The release of the film-shaped replica master mold10is typically performed by deforming and separating the replica master mold10from its end. The separation may be facilitated by optionally deforming the formation object16or spraying a fluid such as air between the replica master mold10and the formation object16.

The replica master mold10and the formation object16may be bonded together to form the fine structure on the formation object16. In this case, by attaching the replica master mold10to the formation object16with, for example, an adhesive applied to the base material layer11side of the replica master mold10, the fine structure17acan be formed on the formation object16(i.e. the replica master mold10attached to the formation object16serves as the fine structure17a).

Although the foregoing embodiment describes the case where the process of deforming the replica master mold10in conformity with the shape of the formation object16and the process of forming the fine structure17aon the formation object16using the deformed replica master mold10are separate steps, a modification may be made to combine these steps.

The deformation of the replica master mold10and the formation of the fine structure17aon the formation object16according to a modification are described below. The deformation of the replica master mold10and the formation of the fine structure17aon the formation object16according to this modification are performed using the device including the stage21, the sidewalls22, the supports23, and the quartz plate24and used in the deformation of the replica master mold described with reference toFIGS.6A to6E.

First, the formation object16to which the photo-curable resin17has been applied is placed on the stage21. Moreover, the replica master mold10is supported by the supports23, with the surface shape body12facing the formation object16.

Following this, the region25is vacuumed, and compressed air is introduced into the region26. As a result of vacuuming the region25, the stage21moves upward (i.e. toward the replica master mold10supported by the supports23). With the movement of the stage21, the formation object16to which the photo-curable resin17has been applied pushes up the replica master mold10supported by the supports23. As mentioned above, merely pushing up the replica master mold10cannot eliminate a gap between the formation object16and the replica master mold10. In this modification, the region25is vacuumed, and compressed air is introduced into the region26. The introduction of the compressed air applies pressure to the replica master mold10. This can bring the replica master mold10and the formation object16into close contact with each other without any gap.

Next, in a state in which the region25is vacuumed and compressed air is introduced into the region26, light is applied from above the quartz plate24. As mentioned above, the quartz plate24allows light to pass through. Accordingly, by forming the replica master mold10to allow light to pass through, too, the photo-curable resin17applied to the formation object16is irradiated with light and as a result cured.

Next, the formation object16and the replica master mold10are separated from each other. On the surface of the formation object16, the photo-curable resin17to which the fine irregular pattern of the surface shape body12of the replica master mold10has been transferred is cured to form the fine structure17a.

Although the above describes an example in which the formation object16has a convex surface and the fine irregular pattern is formed on the convex surface of the formation object16, this is not a limitation. The presently disclosed technique is also applicable to the case where the formation object has a concave surface and the fine irregular pattern is formed on the concave surface. An example of forming the fine structure17a(fine irregular pattern) on a concave surface of a concave-surfaced formation object16A as illustrated inFIG.8is described below.

The formation object16A having the fine structure17a(fine irregular pattern) formed on its concave surface is, for example, used as a top plate (cover) attached to the front of a display body18of a liquid crystal display (LCD) or the like with an air gap therebetween, as illustrated inFIG.8. The formation object16A is also used as an antireflection member provided on the inner side (display body side) of a touch panel.FIG.8illustrates an example in which a fine structure19for antireflection is formed on the front of the display body18, too. The fine structure19includes, for example, an approximately flat base film such as a triacetylcellulose (TAC) film provided on the front of the display body18, and a photo-curable resin (e.g. acrylic ultraviolet curable resin) provided on the base film and having a fine irregular pattern. The structure, formation method, etc. of the fine structure19are known to those skilled in the art and do not directly relate to the present disclosure, and so their description is omitted.

The process of deforming the replica master mold10in conformity with the shape of the formation object16A is described in detail below, with reference toFIGS.9A to9E. The following describes a process of deforming the replica master mold10by push-up forming. Here, the description of the same structures inFIGS.9A to9Eas those inFIGS.6A to6Eis omitted.

First, as illustrated inFIG.9A, a die15A having a concave surface that conforms to the shape of the concave surface of the formation object16is placed on the stage21. The die15A is supported with its concave surface facing the replica master mold10supported by the supports23. The replica master mold10is supported with the surface shape body12facing the die15A.

Next, the replica master mold10supported by the supports23is heated to a temperature higher than or equal to the softening temperature of the base material layer11and lower than the softening temperature of the surface shape body12. As mentioned above, the softening temperature of the surface shape body12is higher than the softening temperature of the base material layer11. Accordingly, the base material layer11softens, but the surface shape body12does not soften. Hence, no distortion of the shape of the fine irregular pattern formed on the surface of the surface shape body12occurs.

Next, as illustrated inFIG.9B, the regions25and26are vacuumed. The stage21is movable vertically along the sidewalls22, as mentioned above. As a result of vacuuming the region25, the stage21moves upward (i.e. toward the replica master mold10supported by the supports23).

The stage21moves upward, and the die15A pushes up the replica master mold10supported by the supports23, as illustrated inFIG.9C. As a result of being pushed up by the die15A, the replica master mold10deforms along the shape of the die15A (i.e. the concave surface of the die15A). Merely pushing up by the die15A, however, cannot bring the die15A and the replica master mold10into close contact with each other without any gap, and there are gaps27between the die15A and the replica master mold10in the vicinity of the ends of the die15A.

Next, as illustrated inFIG.9D, in a state in which the die15A pushes up the replica master mold10, compressed air is introduced into the region26, to apply pressure to the replica master mold10. This brings the die15A and the replica master mold10into close contact with each other even in the vicinity of the ends of the die15A. In this state, the replica master mold10is cooled, and removed from the supports23and the die15A. The replica master mold10deformed along the shape of the die15A is thus produced, as illustrated inFIG.9E.

The process of forming the fine structure on the concave surface of the formation object16A is described in detail below, with reference toFIGS.10A to10D. InFIGS.10A to10D, the same structures as those inFIGS.7A to7Dare given the same reference signs, and their description is omitted.

The process of forming the fine structure on the formation object16A mainly includes an application step, a transfer step, a photo-curing step, and a release step.

In the application step, as illustrated inFIG.10A, the uncured photo-curable resin17is applied to the concave surface of the formation object16A. As the method of applying the photo-curable resin17to the formation object16A, various methods such as spray coating, inkjet coating, dispenser coating, dip coating, dropper dropping, and spin coating can be used depending on the viscosity of the photo-curable resin17and the shape of the formation object16A. An intermediate layer may be provided between the formation object16A and the photo-curable resin17, to improve the adhesiveness between the formation object16A and the photo-curable resin17, the optical characteristics, and the like.

In the transfer step, as illustrated inFIG.10B, the replica master mold10is pressed against the photo-curable resin17applied to the formation object16A. As mentioned above, the replica master mold10is deformed in conformity with the shape of the die15A (formation object16A) in a state in which the surface shape body12faces the formation object16A. Accordingly, by pressing the replica master mold10against the formation object16A, the surface shape body12is pressed against the photo-curable resin17. As a result of the surface shape body12being pressed against the photo-curable resin17, the fine irregular pattern formed on the surface shape body12is transferred to the photo-curable resin17.

In the photo-curing step, as illustrated inFIG.10C, in a state in which the replica master mold10is pressed against the photo-curable resin17, active energy rays (e.g. ultraviolet light) are applied to the photo-curable resin17to cure the photo-curable resin17.

In the release step, as illustrated inFIG.10D, the formation object16A and the replica master mold10are separated from each other. On the surface of the formation object16A, the photo-curable resin17to which the fine irregular pattern of the surface shape body12of the replica master mold10has been transferred is cured to form the fine structure17a. The formation object16A (article) having the fine structure17aformed thereon is thus manufactured.

The process of deforming the replica master mold10in conformity with the shape of the formation object16A and the process of forming the fine structure17aon the formation object16A using the deformed replica master mold10may be combined.

First, the photo-curable resin17is applied to the concave surface of the formation object16A by spin coating or the like. The formation object16A having the photo-curable resin17applied to its concave surface is then placed on the stage21of the device illustrated inFIGS.6A to6DorFIGS.9A to9D. The replica master mold10is supported by the supports23, with the surface shape body12facing the formation object16A.

Following this, the region25is vacuumed, and compressed air is introduced into the region26(vacuum differential pressure). As a result of vacuuming the region25, the stage21moves upward (i.e. toward the replica master mold10supported by the supports23). With the movement of the stage21, the formation object16A to which the photo-curable resin17has been applied pushes up the replica master mold10supported by the supports23. As mentioned above, merely pushing up the replica master mold10cannot eliminate a gap between the formation object16A and the replica master mold10. In view of this, the region25is vacuumed, and compressed air is introduced into the region26. The introduction of the compressed air applies pressure to the replica master mold10. This can bring the replica master mold10and the formation object16A into close contact with each other without any gap.

Next, in a state in which the region25is vacuumed and compressed air is introduced into the region26, light is applied from above the quartz plate24. As mentioned above, the quartz plate24allows light to pass through. Accordingly, by forming the replica master mold10to allow light to pass through, too, the photo-curable resin17applied to the formation object16A is irradiated with light and as a result cured.

Next, the formation object16A and the replica master mold10are separated from each other. On the surface (concave surface) of the formation object16A, the photo-curable resin17to which the fine irregular pattern of the surface shape body12of the replica master mold10has been transferred is cured to form the fine structure17a.

As described above, in this embodiment, the replica master mold10includes the base material layer11and the surface shape body12formed on the base material layer11and having the fine irregular pattern, and the softening temperature of the surface shape body12is higher than the softening temperature of the base material layer11.

Hence, in the case of heating the replica master mold10in order to deform the replica master mold10, by heating the replica master mold10at a temperature higher than or equal to the softening temperature of the base material layer11and lower than the softening temperature of the surface shape body12, the replica master mold10can be deformed with only the base material layer11being softened. Since the surface shape body12does not soften, the shape of the fine irregular pattern is not distorted, and a decrease in transfer accuracy caused by a distortion of the fine irregular pattern can be suppressed.

EXAMPLES

More detailed description is given below by way of examples and comparative examples, although the present disclosure is not limited to these examples.

(Production of Master Mold)

The production of the master mold14is described below.

A glass base material (glass roll master mold) of 126 mm in outer diameter was prepared. A diluted resist obtained by diluting a photoresist to 1/10 in mass ratio by a thinner was applied to the surface of the glass roll master mold by dipping so as to have an average thickness of about 70 nm on the cylindrical surface of the glass roll master mold, to form a resist layer. The glass roll master mold having the resist layer formed thereon was then conveyed to an exposure device, and the resist layer was exposed to pattern, on the resist layer, a spiral latent image having a hexagonal lattice pattern between adjacent three tracks. In detail, the region subjected to the formation of the hexagonal lattice exposure pattern was irradiated with laser light of 0.50 mW/m, to form the hexagonal lattice exposure pattern.

Next, a development treatment was performed on the resist layer on the glass roll master mold, to dissolve the resist layer in the exposed portion and develop the resist layer. In detail, the undeveloped glass roll master mold was placed on a turntable of a development device and, while rotating the turntable, a developer was dropped on the surface of the glass roll master mold to develop the resist layer. In this way, the glass roll master mold with the resist layer being open in the hexagonal lattice pattern was obtained.

Next, plasma etching was performed in a CHF3gas atmosphere using a roll etching device. As a result, on the surface of the glass roll master mold, etching progressed only in the hexagonal lattice pattern portion exposed from the resist layer, whereas the other regions were not etched as the resist layer served as a mask. An elliptical cone-shaped concave portion was thus formed in the glass roll master mold. In the etching, the etching amount (depth) was adjusted based on the etching time. Lastly, the resist layer was removed by oxygen ashing, thus obtaining the glass roll master mold (master mold) having the concave hexagonal lattice pattern.

(Production and Deformation of Replica Master Mold)

A replica master mold was produced using the glass roll master mold (master mold) obtained as described above, and deformed in conformity with the shape of a formation object. The production of a replica master mold and the deformation (preforming) of the replica master mold according to each of the examples and comparative examples are described below. The softening temperature was measured as follows: A film-shaped sample produced with a thickness of 50 μm to 200 μm was stamped into 40 mm×0.5 mm. The dynamic viscoelasticity E′ was measured using a dynamic viscoelasticity measurement device (product name “Rheometrics System Analyzer-3 (RSA-3)” produced by Texas Instruments Inc.), and the temperature corresponding to dynamic viscoelasticity E′=0.3 GPa was taken to be the softening temperature.

In this example, a PVC film (softening temperature: 84° C.) of 200 μm in average thickness was used as the base material layer11. An ultraviolet curable resin composition (softening temperature: 116° C.) was dropped on the PVC film using a dropper. The ultraviolet curable resin composition contains 90 parts by mass ester acrylate (product name “SP-10” produced by DIC Corporation) and 10 parts by mass fluorineacrylate monomer (product name “FAAC-6” produced by Unimatec Corporation).

After this, the PVC film on which the ultraviolet curable resin composition had been dropped and the above-described glass roll master mold having the concave hexagonal lattice pattern were brought into close contact with each other. Ultraviolet rays were applied from the PVC film (base material layer) side at an irradiance level of 1500 mJ/cm2using a metal halide lamp, to cure the ultraviolet curable resin composition. Subsequently, the glass roll master mold was separated from the cured ultraviolet curable resin composition. As a result of this process, a replica master mold in which the cured ultraviolet curable resin composition as the surface shape body12was formed on the PVC film as the base material layer11was obtained.

The obtained replica master mold was then deformed in conformity with the shape of the formation object16. In this example, a convex lens with an outer diameter of 12.7 mm and an F value of 15 was used as the formation object16, and the replica master mold was deformed by push-up forming at a deformation process temperature of 120° C.

In this example, the intermediate layer13having the fine irregular pattern was formed as illustrated inFIGS.3A and3B, and the surface shape body12was formed on the intermediate layer13, to produce a replica master mold. In detail, a PMMA film (softening temperature: 102° C.) was used as the base material layer11. A layer made of PC (softening temperature: 148° C.) and a layer made of an ultraviolet curable resin (product name “SK1900” produced by Dexerials Corporation) (softening temperature: 157° C.) were formed on the PMMA film, as the intermediate layer. The PMMA film having the intermediate layer formed thereon and the glass roll master mold were then brought into close contact with each other. Ultraviolet rays were applied from the PMMA film (base material layer) side at an irradiance level of 1500 mJ/cm2using a metal halide lamp, to cure the ultraviolet curable resin. As a result of this process, the intermediate layer having the fine irregular pattern was formed. A tungsten oxide layer (softening temperature: 1473° C.) which is an inorganic compound was then formed as the surface shape body12on the intermediate layer having the fine irregular pattern, to obtain a replica master mold.

The obtained replica master mold was then deformed in conformity with the shape of the same convex lens as in Example 1. In this example, the replica master mold was deformed by push-up forming at a deformation process temperature of 190° C.

In this example, the approximately flat intermediate layer13was formed as illustrated inFIG.2, and the surface shape body12was formed on the intermediate layer13, to produce a replica master mold. In detail, a PET film (softening temperature: 125° C.) of 188 μm in average thickness was used as the base material layer11. An intermediate layer (easily adhesive layer) for improving adhesiveness was formed on the PET film, and an ultraviolet curable resin (product name “SK1900” produced by Dexerials Corporation) (softening temperature: 157° C.) was applied onto the intermediate layer.

The PET film having the ultraviolet curable resin applied thereon and the glass roll master mold were then brought into close contact with each other. Ultraviolet rays were applied from the PET film (base material layer) side at an irradiance level of 1500 mJ/cm2using a metal halide lamp, to cure the ultraviolet curable resin. As a result of this process, a replica master mold in which the cured ultraviolet curable resin as the surface shape body12was formed on the PET film as the base material layer11was obtained.

The obtained replica master mold was then deformed in conformity with the shape of the same convex lens as in Example 1. In this example, the replica master mold was deformed by push-up forming at a deformation process temperature of 160° C.

Comparative Example 1

In this comparative example, a COC film (softening temperature: 128° C.) of 100 μm in average thickness was used as the base material layer11. A single-layer base material (softening temperature: 128° C.) having a fine irregular pattern was formed on the COC film as the surface shape body12, to obtain a replica master mold. In this comparative example, the softening temperature of the COC film as the base material layer11and the softening temperature of the single-layer base material as the surface shape body12are the same.

The obtained replica master mold was then deformed in conformity with the shape of the same convex lens as in Example 1. In this example, the replica master mold was deformed with a vacuum differential pressure of 0.1 MPa at a deformation process temperature of 150° C.

Comparative Example 2

In this comparative example, a PET film (product name “COSMOSHINE A4300” produced by Toyobo Co., Ltd.) (softening temperature: 184° C.) was used as the base material layer11. An intermediate layer (easily adhesive layer) for improving adhesiveness was formed on the PET film, and an ultraviolet curable resin (product name “SK1900” produced by Dexerials Corporation) (softening temperature: 157° C.) was applied onto the intermediate layer, as in Example 3.

The PET film having the ultraviolet curable resin applied thereon and the glass roll master mold were then brought into close contact with each other. Ultraviolet rays were applied from the PET film (base material layer) side at an irradiance level of 1500 mJ/cm2using a metal halide lamp, to cure the ultraviolet curable resin. As a result of this process, a replica master mold in which the cured ultraviolet curable resin as the surface shape body12was formed on the PET film as the base material layer11was obtained.

The obtained replica master mold was then deformed in conformity with the shape of the same convex lens as in Example 1. In this comparative example, the replica master mold was deformed by push-up forming with a vacuum differential pressure of 0.1 MPa at a deformation process temperature of 220° C.

The evaluation results of the replica master molds produced and deformed according to Examples 1 to 3 and Comparative Examples 1 and 2 described above are explained below.

FIG.11Ais a cross-section photograph of the fine irregular pattern before and after preforming of the replica master mold according to Example 1, taken by a scanning electron microscope (SEM).FIG.11Bis a cross-section photograph of the fine irregular pattern before and after preforming of the replica master mold according to Example 2.FIG.11Cis a cross-section photograph of the fine irregular pattern before and after preforming of the replica master mold according to Example 3.FIG.11Dis a cross-section photograph of the fine irregular pattern before and after preforming of the replica master mold according to Comparative Example 1.FIG.11Eis a cross-section photograph of the fine irregular pattern before and after preforming of the replica master mold according to Comparative Example 2. InFIGS.11A to11E, the photographed image after preforming of the replica master mold is a photographed image of a vertex portion of the convex lens.

Table 1 shows the height of the fine irregular pattern before preforming, the height of the fine irregular pattern after preforming, the residual factor which is the ratio of the height of the fine irregular pattern before preforming and the height of the fine irregular pattern after preforming, and the visual evaluation result of the deformed replica master mold, for each of the replica master molds according to Examples 1 to 3 and Comparative Examples 1 and 2.

As illustrated inFIGS.11A to11Cand Table 1, in Examples 1 to 3, the fine irregular pattern was transferred to the replica master mold with no distortion of the fine irregular pattern between before and after preforming (high residual factor). Thus, the fine irregular pattern was formed while the replica master mold maintained the three-dimensional shape.

As illustrated inFIGS.11D and11Eand Table 1, in Comparative Examples 1 and 2, the fine irregular pattern was distorted between before and after preforming (low residual factor).

Moreover, in Examples 1 to 3, the replica master mold was deformed in conformity with the shape of the formation object (evaluation result: “good”). In Comparative Examples 1 and 2, on the other hand, the replica master mold was not deformed in conformity with the shape of the formation object (evaluation result: “poor”). The evaluation result “good” indicates that the replica master mold had no wrinkles or cracks and was in contact with the die throughout the curved surface.

Next, using the replica master mold according to Example 2 and the replica master mold according to Comparative Example 1, a fine structure was formed on the above-described convex lens as a formation object, and the optical characteristics (reflectance characteristics) of the formed fine structure were evaluated.

In the formation of the fine structure on the convex lens, an ultraviolet curable resin (product name “SK1120” produced by Dexerials Corporation) was applied onto the convex lens, and each of the replica master mold according to Example 2 and the replica master mold according to Comparative Example 1 was pressed against the ultraviolet curable resin. Ultraviolet rays were then applied from the base material layer side at an irradiance level of 1500 mJ/cm2, to cure the ultraviolet curable resin. Subsequently, the replica master mold was separated to obtain the convex lens on which the fine structure made of the cured ultraviolet curable resin was formed.

FIG.12Ais a diagram illustrating the reflection characteristics of the fine structure formed using the replica master mold according to Example 2.FIG.12Bis a diagram illustrating the reflection characteristics of the fine structure formed using the replica master mold according to Comparative Example 1.

As illustrated inFIG.12B, the fine structure formed using the replica master mold according to Comparative Example 1 had a reflectance of about 4.2%. On the other hand, the fine structure formed using the replica master mold according to Example 2 had a reflectance of about 0.5%, exhibiting good antireflection optical characteristics. As mentioned above, in the replica master mold according to Comparative Example 1, the fine irregular pattern was distorted. This caused a distortion of the irregular shape of the fine structure formed using the replica master mold according to Comparative Example 1, and made it impossible to achieve good reflectance characteristics. In the replica master mold according to Example 2, on the other hand, the fine irregular pattern was hardly distorted. Consequently, the irregular shape of the fine structure formed using the replica master mold according to Example 2 was not distorted, so that good reflectance characteristics were achieved.

The presently disclosed technique is applicable not only to the formation of a fine structure on the convex surface of the convex-surfaced formation object16but also to the formation of a fine structure on the concave surface of the concave-surfaced formation object16A, as mentioned earlier. In this example, a fine structure is formed on a concave surface. The process of deforming the replica master mold10in conformity with the shape of the formation object16A and the process of forming the fine structure17aon the formation object16A using the deformed replica master mold10were combined in this example.

In this example, a plate made of polycarbonate and having a cylindrical shape was used as the formation object16A. This plate is, for example, used as a top plate (cover) attached to the front of a display body of a LCD or the like with an air gap therebetween. The formation object16A used had a curvature radius R of 500 mm, a length in the curvature radius R direction of 200 mm, and a width (depth) of 140 mm.

First, an uncured acrylic ultraviolet curable resin was applied onto the concave surface of the formation object16A by spin coating. The spin coating was performed by rotating the formation object16A at 1000 rpm for 30 sec.

Following this, the formation object16A having the acrylic ultraviolet curable resin applied on its concave surface was placed on the stage21, and the regions25and26were vacuumed to −0.1 MPa by a rotary pump. By vacuuming the regions25and26, the formation object16A placed on the stage21was pressed against the replica master mold supported by the supports23. In this example, a PET film (product name “A4300” produced by Toyobo Co., Ltd.) of 100 μm in average thickness was used as the replica master mold (film mold).

Atmospheric pressurization was then performed on the film mold side, i.e., the region26side. This enables the film mold and the formation object16A to be in close contact with each other without any gap.

After this, in a state in which the film mold and the formation object16A were in close contact with each other, ultraviolet light was applied from the film mold side. A metal halide lamp was used as an ultraviolet light source, and ultraviolet rays were applied at an irradiance level of 1000 mJ/cm2. As a result of being irradiated with the ultraviolet light, the uncured acrylic ultraviolet curable resin applied on the concave surface of the formation object16A cured. The film mold was then separated from the formation object16A. As a result of this process, a fine structure with a pitch of 150 nm to 230 nm and a height of 200 nm to 250 nm was formed on the concave surface of the formation object16A.

While the disclosed techniques have been described above by way of drawings and embodiments, various changes or modifications may be easily made by those of ordinary skill in the art based on the present disclosure. Such various changes or modifications are therefore included in the scope of the present disclosure.

REFERENCE SIGNS LIST