Michal Vik

Colour Shift Photochromic Pigments in Colour Space CIE L*a*b*

ABSTRACT One of possibilities for protection of human body against acute and cumulative exposure to ultraviolet is the wearing of special protective clothes. Nevertheless on the other side the protective clothes have not the same barrier features against the UV light. The aim of present research work in LCAM on the Technical University of Liberec is research and development of original method of measurement by flexible textile based sensors reacting on the UVA part of electromagnetic radiation. In this article is publicized information about testing above mentioned sensors with weave structure and non-woven textiles. Results show that produced sensors shows sensitivity as to time of exposition so also to intensity of irradiation and their response characteristics is same as for classical luxmeters.

Effect of drawing ratio on difference in optical density and mechanical properties of mass colored photochromic polypropylene filaments

Abstract Photochromic textiles have been used in the sensible materials (sensor) in the smart textiles and esthetic materials in the fashion industry due to the color changing properties, which gives immense inspiration to prepare photochromic textile materials, in this regards we take more attention to prepare the mass dyed polypropylene filaments with photochromic pigments. Metallocene polypropylene filaments were doped by different concentration of photochromic pigment. In our experimental work, the optical and mechanical properties of these multifilaments depending on their drawing ratio were investigated. The photochromic pigment used was 5-Chloro-13-dihydro-133-trimethylspiro[2H-indole-23′-(3H)naphtha [2,1b](14)oxazine]. Regarding the optical properties, our investigation confirms the known effect of the primary reflectance on the depth of shade of colored multifilaments as shown by linear increase in difference in optical density with increasing ratio of fineness.

A review of photochromism in textiles and its measurement

ABSTRACT Photochromism is a light-induced reversible change in colour defined as: ‘A reversible transformation in a chemical species between two forms having different absorption spectra brought about by photo-irradiation.’ This issue of Textile Progress provides a review of photochromism, the different methods for producing photochromic textiles, their properties, the measurement of kinetic colour changes, and their application in photochromic textiles. Photochromism can be utilised in a variety of textile products from everyday clothing to high-technology applications such as protective textiles, medical textiles, geo-textiles and sports textiles. Although photochromic materials have been used since 1960 to cut down the transmission of light through the lenses in sunglasses, there has been limited further development since that time due to technical difficulties not only in the application of photochromic colourants, but also with the measurement of kinetic colour-changing properties. Renewed interest in photochromic textiles has arisen due to improved commercial potential in particular for applications as photochromic nanofibres, in ‘smart’ textiles and in ‘smart’ clothing.

Photochromic Textiles and Measurement of Their Temperature Sensitivity

Our previous papers (Vikova & Vik, 2005) described a unique device, now patented in the Czech Republic in the authors name, for photochromic measurement in a reflectance mode together with a methodology. This device allows photochromic sensors to test the colorimetric and spectral characteristics of photochromic textiles, and also fatigue tests for control of colour change stability. This concept of colorimetric and spectral parameters also finds the dependence of colour change on the intensity of UV irradiation and temperature. In this paper, we would like to describe the dependence of colour change on temperature for the photochromic Photopia AQ Ink system (Blue, Purple and Yellow) produced by Matsui Shikiso Chemical Co.Ltd. It is known that the reversion of photochromic compounds from coloured to colourless is promoted thermally. The photochromic structure can achieve a lower level of saturated absorbance at higher temperatures when thermo reversible photochromic systems, such as spirooxazines and chr...

Colorimetric Properties of Photochromic Textiles

Photochromism is a chemical process in which a compound undergoes a reversible change between two states having separate absorption spectra, i.e. different colors. The change of color in one direction occurs under influence of electromagnetic radiation, usually UV light, and in the other direction by altering or removing the light source or alternatively by using thermal means. Based on photochromic pigment we developed simple textile sensor sensitive to UV light, which is usable for visual indication of intensity UV-A radiation. Main attention was given to colorimetric properties of photochromic textiles during decay phase of photochromic color change, such as saturation change and fatigue resistance.

Description of photochromic textile properties in selected color spaces

Research in color science includes studies on the spectral properties of light and the perception of color by the human eye and the brain. Color spaces allow the description of the position of a color by using three basic attributes, namely lightness, chroma and hue. Photochromic pigments used as a component of ultraviolet sensors can help to define color changes in time through the measurement of color differences in exposition and decay phases. The change of color can be evaluated in terms of the light source employed, reversion and the kinetics of photochromic effects. Commercial spectrometers are not suitable for this type of measurement. These instruments cannot measure the kinetics of exposure and the decay phase of photochromic materials. A unique spectrophotometer and a methodology for measuring colorimetric and spectral data of photochromic pigments in selected color spaces are presented. This work is the first step towards standardization of the measurement of color-changing materials containing functional dyestuffs, such as photochromic pigments.

The determination of absorbance and scattering coefficients for photochromic composition with the application of the black and white background method

Fresnels postulates and equations of energy transfer, including approximate Kubelka – Munk theory, also allow the determination of other optical parameters for measured materials as for example absorbance coefficient k and scattering coefficients. In the case of colorants it is possible to determine molar coefficient ε0 by absorption spectrophotometry and Lambert – Beer Law from a calibration set with a different concentration of specific substance. If we use recommended solvents for the photochromic pigments, from the capsules the pigments not only flood out, but also use additives (HALS). This situation results in turbid solution, where use of Lambert – Beer Law is problematic from point of their turbidity. An advantage for the case of finalized photochromic pigments applied on the textile or other substrates in determination of absorption k and scattering s coefficients is the black and white background method.

Characterization and optimization of an inkjet-printed smart textile UV-sensor cured with UV-LED light

For the development of niche products like smart textiles and other functional high-end products, resource-saving production processes are needed. Niche products only require small batches, which m ...

Polarimetric Sensing Technique for Textile Material

The identification and measuring of geometrical dimensions of very small objects including textile is the biggest achievement of the image processing techniques. Not only the analysis of the basic structure of yarn like hairiness, thickness and number of twist but also the external structural analysis like twist parameters and linear density co-efficient is possible with outstanding approach of image analysis new techniques. Dyed polyester samples by using different dyestuffs were examined with the polarized light with the help of optical light microscopy. It was observed that the dyestuffs possess strong dichroism and the relationship between dichroism and the concentration of dyestuff was examined. Dark field and Bright field illuminations together with imaging polarimetry are compared in terms of depth of field tolerance and image quality. Experiments show that passive imaging polarimetry illumination is superior in terms of depth of field tolerance and contrast allowing significant improvement of textile structure investigation.

Inkjet printing and UV-LED curing of photochromic dyes for functional and smart textile applications

Health concerns as a result of harmful UV-rays drive the development of UV-sensors of different kinds. In this research, a UV-responsive smart textile is produced by inkjet printing and UV-LED curing of a specifically designed photochromic ink on PET fabric. This paper focuses on tuning and characterizing the colour performance of a photochromic dye embedded in a UV-curable ink resin. The influence of industrial fabrication parameters on the crosslinking density of the UV-resin and hence on the colour kinetics is investigated. A lower crosslinking density of the UV-resin increases the kinetic switching speed of the photochromic dye molecules upon isomerization. By introducing an extended kinetic model, which defines rate constants kcolouration, kdecay and kdecolouration, the colour performance of photochromic textiles can be predicted. Fabrication parameters present a flexible and fast alternative to polymer conjugation to control kinetics of photochromic dyes in a resin. In particular, industrial fabrication parameters during printing and curing of the photochromic ink are used to set the colour yield, colouration/decolouration rates and the durability, which are important characteristics towards the development of a UV-sensor for smart textile applications.