IR-Absorbing Dyes

The choice of the absorber dye is obviously defined principally by the wavelength of the laser used in the process. However, since some of the near-IR absorbing dye is likely to be transferred in the process, it should not interfere with the colours in the final print and preferably be colourless. Colourless near-IR absorbers are difficult to find and workers at the Imation Company overcame this problem by using an IR absorber (4.21), exhibiting broad absorption at 790- 900 nm and addressable at 830 nm, which bleached out during the process. ... 

Table 6.1 Classes of IR-absorbing dyes for optical recording layers...

Fig. 13.37 Structures of indoleninecyanine (A), azulenium (B), quinonoid (C), anthraquinone (D), and imminium (E) and diiminium (F) IR-absorbing dyes, where R = alkyl or alkoxy.

IR-absorbing dyes with high quantum yields of fluorescence are hard to come by. Explain. [Low rate constants of fluorescence (Equation 2.11), fast competing IC (Equation 2.22)]. 

Lee J, Leventis HC, Haque SA, Torres T, Gratzel M, Nazeeruddin MdK (2011) Panchromatic response composed of hybrid visible-light absorbing polymers and near-IR absorbing dyes for nanocrystalline Ti02-based solid-state solar cells. J Power Source 196 596-599... 

The GaAs laser used as light source emits at about 820 nm. Thus dyes in the actual sense are not needed rather, ir-absorbers for the spectmm between 750—850 nm Httie experience is available on this class of dyes, especially as far as their stabiHty is concerned, although much work has been done in this area. Also, infrared sensitive dyes and pigments, used in electrophotography, may be very suitable for WORM disks (8). 

The squarylium (4.6) and croconium (4.7) dyes are closely related structurally to cyanines but are in fact donor-acceptor molecules and consequently the design principles of near-IR absorbers based on these chromophores are different. The synthesis of these chromophores is achieved easily by reacting either squaric acid, or preferably an alkylated derivative, e.g. di-n-butyl squarate, or croconic acid with electron-donor molecnles. The croconium dyes absorb at significantly longer wavelengths than the sqnarylinms as shown in Figure 4.2. 

Laser thermal transfer uses similar dyes, but a semiconductor infrared laser supplies the energy, which is converted to heat by an IR absorber in the transfer ribbon [7,10],... 

Arslanoglu Y, Mert-Sevim A, Hamuryudan E, Guel A (2005) Near-IR absorbing phthalocyanines. Dyes Pigm 68(2-3) 129-132... 

Dithiolene complexes, and more specifically the nickel derivatives, are involved in materials used for optical data storage, such as compact disc or laser disc read-only memory (CD- or LD-ROM), and also in copiers or photography related devices. In the latter case, it is the IR-absorbing property that is exploited. Some of these compounds can be found in reviews by Mueller-Westerhoff et al. (353, 354). Recent patents are given as examples in references (458—481). In the field of optical storage, short reviews were published in 1988 (482) and 1990 (362, 483). Here, the dithiolene complexes act as inhibitors of the laser-induced fading of the colored thin layers of the optical discs. They also act as an antioxidant and increase the photostability of the cyanine dyes that constitute the recording layer. Contrary to what was observed for the two... 

IR absorbers and reflectors are used to limit the heat development in rooms (e.g., in greenhouses) and are incorporated in agricultural films or in glazing. Typical materials range from kaolin (aluminum silicate) or other silicates and hydrotalcites [68] in agricultural films to dyes (e.g., phthalocyanines or anthraquinones). Furthermore, dyes with near-IR absorption are added to enhance laser welding of polymers. 

Matsuoka, M. (ed.), 1990, Ir rartd Absorbing Dyes, Plenum Press, New York, 224 pp. 

An IR-sensitive dye which had the peak of absorbance at 806 nm (IR-806) was used in work. Multiple types of capsules were fabricated using different core and shell materials. Capsules of the first type with (PAH/IR-806)4/PAH shell structure were fabricated on calcium carbonate cores. Capsules of the second type with IR-806 last layer adsorbed from the solution were fabricated on the surface of 4 fim manganese carbonate particles. 

It was shown that capsules without IR-sensitive dye did not absorb laser radiation. On the other hand, 60 mW laser beam power was enough to deform capsules shells containing an IR-806 dye. 

To prepare capsules sensitive to the electromagnetic radiation of optical band, silver nanoparticles with an average size about 8 nm were used. Nanoparticles were synthesized during the capsule fabrication process using the method described in work. The capsules obtained by this technique had (PSS/PAH)2-Ag-(PAH/PSS)2 structure. Nanoparticles absorbance peak was found to be located at 400 nm. Only 25 mW laser beam power was needed to deform capsule shells in this case, and the shells destruction occured at 70 mW laser beam power. This means that nanoparticles absorbed laser light energy more effectively than the IR-sensitive dye. 

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