Thermochromism thermochromic pigments, applications

Composite thermochromic pigments consist of three components a pH sensitive dye, a proton donor, which acts as the colour developer, and a hydrophobic, nonvolatile co-solvent. To achieve the desired effect the components are mixed in specific ratios and usually encapsulated to protect the system in subsequent applications. A review of the patent literature on these compositions has been published. ... 

The main application area for these indirectly thermochromic, reversible systems is the manufacture of organic thermochromic pigments. 

Composite thermochromic pigments consist of three main components pH-sensitive dye, proton donor that acts as a colour developer, and hydrophobic, non-volatile cosolvent. To achieve the desired effect, these three components are mixed in a specific ratio and most often encapsulated, which preserves the system from external influences and significantly increases applicability. 

The application area for thermochromic pigments is vast indeed. In the context of indicators they may be used for visual density identification of atomic species caused... 

Typically the chromophores used are pH sensitive, i.e. acidochromic or ionochromic (see section 1.4), and the medium is one whose pH varies with temperature. A variety of pH sensitive chromophores are known that are readily synthesised and can be modified to provide a wide range of shades. Application of these pH sensitive dyes in pressure and thermally sensitive papers for digital printing, e.g. fax papers, where the whole object is for the process to be irreversible, will be covered under ionochromism. The main area of application for reversible indirect thermochromic materials is as thermochromic organic pigments, as will be described below (section 1.3.4.1). 

Cholesteric LCs can act as hosts for dyes to produce coloured displays (see section 5.2.2.1 below) " their temperature dependent colour change has found applications in thermochromic inks, °" and as pigments and copy safe colours their selective reflecting capabilities have been applied in colours and filters for reflective displays and projection systems, " reflective polarisers and their electrical field induced switching in displays and smart reflectors, in colour patterning for full-colour recording. ... 

One of the main arms of high added value products is the development of properties that directly affect the safety and comfort of users. One of the ways to accomplish this is by using microencapsulation processes to impart new functionalities and properties to textiles (Anon, 2008). Thermochromic microencapsulated pigments bear the potential for medical application in terms of registering elevated body temperature of patients, thus allowing easier monitoring and point of care diagnosis. 

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