Development of attenuated total reflection prism for IR microscopy and some applications to local analysis

Attenuated total reflection (ATR) IR microscopy has been investigated for the local analysis of the surface of materials, such as polymer and polymer composite. The unique ATR prism, made from zinc selenide, was designed to achieve ATR measurement in the transmission path of the conventional infrared microscope. The prism is pillar shaped-having hexagonal cross section with one corner recessed inward. The prism comprises four totally reflecting surfaces including a sample-contacted surface on which the infrared beam is focused. The reflecting surfaces are so oriented that the optical axis of the incident beam agrees well with that of the outgoing beam even if the measured point of interest is changed on the sample surface. Consequently, this ATR system actualized not only the point analysis but line and area analyses indispensable for the local analysis of the sample surface. The minimum measurement size in the point analysis was about 10 μm square. The precision of absorption intensity and the spatial resolution in the line analysis were 1.0% in the RSD and 20 μm in length, respectively. The effective dimensions for the area analysis were 1.3 mm by 6.6 mm.