Jun Taniguchi

Fabrication of antireflection structure film by roll-to-roll ultraviolet nanoimprint lithography

Antireflection (AR) films are useful in preventing the reflection of light from the displays of mobile phones and tablet computers. In particular, films with an AR structure known as the moth-eye structure show excellent performance in preventing light reflection. In a previous study, the authors reported the fabrication of an AR structure by oxygen ion-beam irradiation of glassy carbon (GC). The fabricated pattern consisted of a series of self-assembled conical structures and it had a low-reflection surface. In this study, the authors transferred this AR structure onto a polymer film by roll-to-roll ultraviolet nanoimprint lithography using a replica mold produced from a GC master mold with the AR structure. As a result, the authors were able to produce high-performance AR film at a feed rate of 1.8 m/min. The reflectivity of the film was about 0.1% and its transmittance was about 95% at visible wavelengths.

Thermal roll-to-roll imprinted nanogratings on plastic film

Nanogratings can be used in various fields, such as optics, electronics, or energy conversion. In the next generation, the desired area of nanogratings will be in excess of 1 m2 and there is therefore a demand for an effective nanopatterning technique capable of fabricating future devices on this scale at low cost and in high volume. The roll-to-roll nanoimprint (R2RNIL) technique has received much attention because of its simplicity and high throughput. Thermal R2RNIL (T-R2RNIL), in particular, is expected to provide a major breakthrough because, for example, the costs of materials for the technique are much lower than those for ultraviolet R2RNIL, which requires a photocurable resin. Furthermore, T-R2RNIL is a dry process and is therefore more suited to industrial application. In T-R2RNIL with a nanograting mold, understanding the replication behavior, which varies with the process temperature, is a key to obtaining the required features. The authors examined T-R2RNIL high-speed patterning of nanogratin...

Fabrication of double-sided self-supporting antireflection-structured film by ultraviolet nanoimprint lithography

Ultraviolet nanoimprint lithography (UV-NIL) is the most effective method for the fabrication of antireflection (AR) films. Interface reflection is one of the challenges in AR film fabrication. To apply the fabricated AR film to any surfaces, an adhesive material is needed. However, owing to the difference in refractive index between the AR film and the adhesive material, interface reflection still occurs. Therefore, an AR film that can prevent the reflection at its front and back surfaces was studied. Thus, we proposed the fabrication of a double-sided self-supporting antireflection-structured (DSARS) film. As a result, the reflectivity of the fabricated DSARS film is 0.1% at visible light wavelengths. The DSARS film also suppresses the adhesive interface reflection.

Lifetime prolongation of release agent on antireflection structure molds by means of partial-filling ultraviolet nanoimprint lithography

Release agent becomes an imperative element in ultraviolet nanoimprint lithography (UV-NIL) for preventing the adhesive resin from adhering to the surface of antireflection structures (ARS) mold. However, complete filling the resin of a high-aspect-ratio ARS mold during UV-NIL generates a strong release force (RF) that deteriorates the release agent and shortens the lifetime of the ARS mold. In this paper, we proposed a technique of partial-filling UV-NIL in order to reduce the RF and consequently, prolong the lifetime of the release agent on ARS mold. The release and optical properties of the ARS were measured to determine the lifetime of the release agent on the mold, and complete-filling UV-NIL was also executed for comparison. By means of partial-filling UV-NIL, we successfully fabricated ARS films with excellent performance up to 75th imprint compared to complete-filling UV-NIL up to the 40th imprint.