Imprinting technology is a technology in which a mold for molding a pattern is pressed into a liquid resin or the like upon a substrate, and transfers the pattern of the mold to the resin. Depressions and protrusions patterns exist at sizes ranging from nano-scale (10 nm level) to about 100 μm, and these patterns are used in various types of fields such as semiconductor materials, optical materials, recording media, micro machines, biotechnology, environment, or the like.
Types of imprinting are exemplified by thermal imprinting, photo imprinting, or the like. Thermal imprinting presses a mold having a certain geometry formed in the surface thereof against a thermoplastic resin melted at a temperature greater than or equal to the glass transition temperature, thermally imprints the surface geometry of the mold into the thermoplastic resin, and peels off the imprinted thermoplastic resin from the mold after cooling. Photo imprinting presses the same type of mold against a photo-curable resin, causes curing of the photo-curable resin by ultraviolet radiation, and then peels the cured photo-curable resin from the mold.
On the other hand, in consideration of the need for the mold to have strength, toughness, processability, and dimensional stability, materials such as quartz, silicon, or the like have been conventionally used for the mold. However, such materials have problems such as easy breakage, high cost, time required for production, or the like. In order to solve such problems, mass production is being attempted by using such a quartz or the like mold as a master mold, obtaining a resin mother pattern, and further producing a replica mold based on the mother pattern. Due to general utility and cost, resin replica molds are used as replica molds.
A photo-curable acrylic resin copolymer of methyl methacrylate, at least one type of (meth)acrylate ester where the alcohol residue is a 2 to 10 carbon number alkyl, and a glycidyl group-containing (meth)acrylate is known as a resin for undergoing imprinting (for example, see Patent Document 1).
Moreover, active energy beam curable resin formed of (meth)acrylic acid and an glycidyl group-containing epoxy compound is known to have excellent strength, adhesion, and cracking resistance (for example, see Patent Document 2).
These resins are cured compositions that include a compound including a glycidyl group as a monomer by using active energy beam (e.g. ultraviolet radiation or the like). During the reaction, a carboxylic acid group, hydroxyl group, or the like reacts with the glycidyl group, and the ring opening of the epoxy group causes the epoxy resin to cure.
On the other hand, when a resin replica mold is obtained from the master mold, and when glycidyl groups exist in the resin forming the replica mold (resin mold), compatibility between the surface of the master mold and the surface of the replica mold becomes high, the replica mold becomes difficult to peel from the master pattern, and sometimes the form of the formed replica mold is disrupted during demolding.
Moreover, various types of optical devices are formed by placing and pressing a resin film against the surface of this replica mold, so as to transfer the depressions and protrusions geometries formed in the surface of the replica mold to the resin surface. However, during such molding, attachment of the resin film to the replica mold often occurs and makes it difficult to peel the resin film from the replica mold.
To avoid the above problem, a mold release agent layer is formed on the surface of the replica mold. However, simultaneous with the mold release agent layer becoming a mold release agent layer for the resin film, the mold release agent layer also becomes a mold release agent layer for the replica mold formed from resin. Thus, when the depressions and protrusions formed in the replica mold are transferred to the resin film, the mold release agent layer peels from the surface of the replica mold and sometimes transfers and attaches to the surface of the resin film onto which the depressions and protrusions were formed.
In order to prevent such transfer and attachment of the mold release agent layer, an oxide layer formed of an inorganic oxide is formed on the surface of the replica mold, and the shedding of the mold release agent layer from the surface of the replica mold is prevented. Although it is possible to prevent shedding of the mold release agent layer from the oxide layer by formation of a mold release agent layer with this oxide layer interposed between the mold release oxide layer and the mold, adhesion of this oxide film to the resin film is not necessarily good.
Therefore, there is a problem in that, even when the mold release agent layer and the oxide film are integrated, there still may be transfer of the integrated mold release agent layer and oxide film to the surface of the imprinted resin film.