Research Divisions

Functional Thin Film Division

Our division focuses on advancing the science and technology required to create next-generation thin-film devices with innovative optoelectronic functions.

We develop materials and processes such as functional polymer microparticles, liquid-crystalline materials, and carbon nanotubes, while pursuing precise control of their nanostructures. Our research also includes the design of novel organic thin-film devices, improvement of optical and electronic performance, enhancement of device stability and lifetime, and the clarification of coating and film-formation processes based on particle-dispersion evaluation.

Through these efforts, we aim to contribute to the advancement of high-performance thin-film manufacturing technologies.

Members

  • Masahiro FUNAHASHI (Professor)（Division Head）
  • Hideto MINAMI (Professor)
  • Yoshiyuki KOMODA（Associate Professor）
  • Shohei HORIKE（Associate Professor）
  • Azumi AKIYAMA（Assistant Professor）
  • Toyoko SUZUKI（Assistant Professor）
  • Yasuko KOSHIBA（Research Associate）

Research Topics

Nanostructure control and device applications to liquid crystalline mixed conductor films

Nanosegregated liquid crystalline semiconductors, in which a cyclotetrasiloxane ring is introduced into an extended π-electron conjugated system, can undergo polymerization and insolubilization upon exposure of thin films to acid vapors. By introducing functional sites such as crown ethers into the side chains, it is possible to fabricate electrochemically functionalized thin films where ion-conducting sites and electrochemically active sites are segregated. Applications to electrochromism and sensing devices are being explored.


(a) Functional liquid crystal 1 bearing a crown ether moiety
(b) AFM images of a thin film of complex of compound 1 with NaOTf
(c) Polarizing optical micrograph of compound 1
(d) Electrochromism of insolubilized thin film of compound 1.


Structural and functional control of carbon nanotubes and their device applications

Carbon nanotubes (CNTs) are one-dimensional nanostructures composed of sp2 carbon and exhibit excellent electrical conductivity. In our group, we are studying on the development of dopants and doping methods to modulate the functional device of CNTs stably, as well as on orientation control aimed at realizing functionalities unique to their one-dimensional nature. We are conducting researches applied to thermoelectric generators, infrared sensors, and other devices.

Schematic for (a) n-doping of CNTs by bicyclic guanidine base, (b) quantum chemical calculation of doped state of CNTs, (c) stabilization of p-doped state of CNTs by anion exchange and (d) electrochemical method to produced p- and n-doped CNT films.


Control of shell permeability of capsule particles

Figure Confocal laser scanning microscope images of poly([MTMA][TFSA]-EGDMA)/PBMA (a,c) and poly([MTMA]Br-EGDMA)/PBMA (b,d) hollow composite particles dispersed in Rh.B aq. (a,b) and Nile red (c,d)

Poly(ionic liquid) (PIL) particles with a single-hollow structure are prepared by suspension polymerization. The obtained PIL hollow particles’ shells can be changed from hydrophobic to hydrophilic by anion exchange. In the case of hydrophilic PIL hollow particles, the water-soluble fluorescent materials can penetrate the hollow structure, whereas, in the case of hydrophobic PIL hollow particles, penetration of the fluorescent materials is restricted.


Two-dimensional colloidal structures utilizing hydrogen bonding interactions

Figure　Scheme for the preparation of two-dimensional colloidal structures utilizing hydrogen bonding interactions between colloidal stabilizers

Mixing of two kinds of disc-like polystyrene (PS) particles stabilized by polyvinylpyrrolidone (PVP) or polyacrylic acid (PAA), which existed only on the lateral side of the discs, resulted in the formation of a two-dimensional colloidal structure by hydrogen bonding interaction in the absence of a template.


Rheological Analysis of Particle Dispersion

Fig. 1 Internal structure and related viscoelastic behavior of LiB cathode slurry

To obtain desirable particulate film from particle dispersion, understanding the internal structure of dispersed particles is indispensable. However, due to the opaque nature of particle dispersion, the evaluation or observation of the structure using transmitted lights is not applicable. Therefore, the stress response against strain applied to particle dispersion, known as rheological analysis, must be a powerful tool. Our objective is to understand the internal structures and their dynamics by combining rheological evaluation with AC impedance, pulsed NMR techniques, and others.


Analysis of the Coating and Drying Processes of Particle Dispersion (Komoda)

Fig.2 Simultaneous measurement device for drying rate and stress in the coating film drying process

We examine the effects of the shear application in coating and the solvent evaporation in drying on the internal structure of particle dispersions. Considering the difference in shear histories depending on the coating apparatus, we investigate the operating conditions to control the shape and structure of coating layers. We also study the drying conditions and underlying mechanism to control the internal structure of coating layers through the simultaneous measurements of drying rate, particle packing state, stress development, and others.


 

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