Whiteness and fluorescence of fabrics

A method was devised for measuring the whiteness of fabrics containing optical brighteners. It is simple in operation and gives excellent agreement with the visual appraisal by 27 observers of the whiteness for fabrics with different values for their fluorescence, lightness, yellowness or blueness, and redness or greenness. The fabrics contained different quantities of various blues and optical brighteners. Apart from duplicates it requires only four measurements for each surface, viz., lightness, tristimulus amber and blue reflectance, and the tristimulus blue part of the fluorescent light. Yellowness or blueness, redness or greenness, fluorescence effect on the whiteness, whiteness without fluorescence, and whiteness including fluorescence are calculated from the measurements. The method also indicates which fabrics cannot be called “near white” because they are too gray or too strongly colored. It can be adapted to different compositions of the incident light with regard to the relative intensity of the ultraviolet and visible portions.     

Measurement and assessment of substrates containing fluorescent whitening agents

White, as a color sensation, can be determined by colorimetric methods of measurement. With other than colorimetric methods, no satisfactory correlation between measured value and visual assessment can be expected. The contribution of hue, saturation and luminosity to the degree of whiteness as found by six formulas widely used in industry was analyzed and the results were plotted in the form of a graph. An easy-to-use nomogram for whiteness determination was developed, based on the CIE 1931 2°-color system. Another nomogram is presented which provides an easy means to determine the hue of a sample treated with fluorescent whiteining agents (FWAs). The new whiteness determination is based on the measurement of true tristimulus values for fluorescent samples using the new International Commission on Illumination standard illuminant D 65. The magnitude of the just perceptible difference in whiteness was determined in a panel test using 11 samples and 22 observers. The results were evaluated statistically. Pending standardization of an illuminant, not only for colorimetric measurements, but also for visual assessment of white samples containing FWAs, it would scarcely seem possible to arrive at a more accurate determination of degrees of whiteness. All visual rankings of fluorescent white substrates are widely scattered around a mean value for the different phases of natural daylight. The relative energy emitted by artificial daylight lamps in the near UV region is insufficient in many cases. Xenon lamps are quite satisfactory for instrumental evaluation. In an internationally approved system, with a known hue preference, it would be possible to compare an objective measured value with each subjective result obtained by visual evaluation.     

荧光水性聚氨酯纸张表面施胶剂的制备及应用

以自制5,7-二羟基-4-甲基香豆素（DHMC）为水性聚氨酯荧光增白改性剂,制备了一系列荧光水性聚氨酯（FWPU）乳液,采用FTIR、¹H NMR、DLS和荧光光谱等对荧光水性聚氨酯进行了结构表征和性能测试。将制备得到的荧光水性聚氨酯应用于纸张表面施胶,研究探讨了荧光水性聚氨酯乳液对纸张表面施胶性能的影响。FTIR、¹H NMR分析表明,DHMC已被引入到FWPU分子链中;当w（DHMC）=0.6%时,FWPU乳液粒径为86.17 nm,荧光强度最强为40220.44 a.u.（1 a.u.=27.2114 eV）。FWPU乳液具有良好的纸张表面施胶性能,纸张施胶度51.92 s,白度77.93%。     

荧光染料用于涤纶织物染色的荧光性能研究

在实验条件下，染色织物的荧光反射率随荧光染料的浓度增加而增加，超过一定浓度后，有下降趋势；在pH=5左右，荧光反射率最高；荧光增白剂会提高染色织物的荧光反射率，在荧光黄2GFL中，当荧光增白剂的浓度由0.1％增加到5％时，荧光反射率由8．43增加至18．59，而对非荧光染料只有增艳的作用，不产生荧光。荧光染料染色织物的荧光反射率随着加入非荧光染料量的增加而减弱。     

Calcium sulphate as pigment for improved functional properties of coated paper

In the last few years, interest and demand of high bright paper have forced paper manufacturers to think new ways to improve brightness and whiteness of coated paper. Pigment coating is widely used to enhance the optical properties such as brightness, whiteness, and gloss of paper and paperboard. These optical properties are the most important for end user and also determine the final cost of coated paper. Calcium sulphate has inherent better optical properties compared to other conventional pigments for example ground calcium carbonate, precipitated calcium carbonate and kaolin clay. The present study was carried out with an aim to synthesize calcium sulphate using waste procured from phosphoric acid industry and to study its impact on the rheology of coating color as well as optical properties of coated paper. Addition of calcium sulphate improved the water retention property of coating color which can be helpful for improving the machine runnability. The results also revealed that calcium sulphate can be used as a pigment to produce coated paper of high brightness and whiteness. The brightness and whiteness of the coated paper were improved 4 and 15 points, respectively by using 50 parts of calcium sulphate as a pigment replacing clay from the coating formulation. The surface strength in terms of IGT pick value of coated sheets was found significantly comparable using calcium sulphate as pigment. The print gloss results were observed analogous with matt grade coated paper.     

Synthesis of ultrabright nanoporous fluorescent silica discoids using an inorganic silica precursor

The templated sol-gel synthesis of ultrabright fluorescent nanoporous silica particles based on the use of organic silica sources has previously been reported. The use of organosilanes as the main silica precursors has a number of issues, in particular, the low robustness of the synthesis due to instability of the organic silica source. Here we report on a novel synthesis of ultrabright fluorescent nanoporous silica discoids (a specific shape in-between the sphere and disk) of 3.1 ± 0.7 microns in size, which were prepared using a stable inorganic sodium silicate silica source. Organic fluorescent dye Rhodamine 6G (R6G) was physically (non-covalently) entrapped inside cylindrical nanochannels of ～4-5 nm in diameter. In contrast to the synthesis with organic silica precursors, the obtained particles showed an excessive leakage of dye. To prevent this leakage, we modified the synthesis by adding a small amount of a secondary silica source. The synthesized particles show virtually no leakage, high photostability, and a brightness equivalent to the fluorescence of up to 7 × 10(7) free R6G molecules. This is about 7 times higher than the fluorescent brightness of particles of the same size made of CdSe/ZnS quantum dots, and 420 times higher than the brightness of the same volume of aqueous solution of free R6G dye.     

Assessment of whiteness and tint of fluorescent substrates with good interinstrument correlation

White is primarily a sensation like blue, green, or red and, as such, is not measurable directly. Only a physical property, the spectral reflectance of a sample, can be measured directly. But this is not a standard, fixed quantity; it depends on a number of individual properties of the measuring instrument used. the entire geometry of the illuminating chamber—generally speaking a sphere is used for samples with a structured surface—is incorporated in the measuring results. the size of the aperture and the exclusion or inclusion of gloss also influence reflectance. High whiteness is obtainable only with the aid of fluorescent whitening agents [FWAs], and is hence a fluorescent color, which demands specific qualities of the illumination. the sample illumination must be identical with that for which the colorimetric values have been calculated. Nowadays, however, this is usually standard illuminant D65, which can be simulated only approximately in measuring instruments. In addition, all lamps used are subject to changes in spectral energy distribution. the problem is how to obtain constant, comparable results, namely whiteness, tint, and lightness for fluorescent materials using measuring instruments of different designs incorporating different means of simulating standard illuminant D65 or other D illuminants. This article presents a method that has been in use in industry for about 20 years. the method in question comprises two parts: first, on the hardware side, sample illumination that has to meet specific requirements, match the UV excitation required, and remain stable; second, on the software side, the two critical dimensions of whiteness and tint are calculated indirectly from the measuring results. Only in this way is it possible to achieve a large measure of comparability between different instruments. In principle, the method is also suitable for different illuminants and for any white preference. In all other methods of assessment the parameters are not matched to the instrument characteristics. If the results obtained with different measuring instruments are to be compared, difference values have to be used, entailing the need for standards and involving all the drawbacks associated with them.     

The Anomalous Fading of Some Fluorescent Dyes and Brighteners on Hydrophilic Fibres

The fastness to light of a number of fluorescent yellow dyes and fluorescent brightening agents (FBA) on several fibres at different concentrations has been assessed both visually and by colour-difference measurements. One acid dye on wool, six FBA on wool and two FBA on cotton showed anomalous fading (i.e. the light fastness decreased with increasing concentration). Results of extraction experiments showed that this could be accounted for by the formation of coloured decomposition products from the dye or FBA and, with wool, from the fibre also. With FBA on wool and cotton there appears to be an optimum concentration above which both the fastness to light and the whiteness fall.     

Comparison of Formulae for the Determination of Fluorescent and Non–fluorescent Whiteness

The prediction capabilities of simple whiteness formulae based on photometer reflectance readings (A, G, B) as compared to linear formulae with adjustable parameters based on chromaticity values (x, y, Y) have been investigated. For each formula, the instrumentally determined whiteness was compared with visually estimated whiteness using the plates of the Ciba–Geigy Plastic White (CGPW) Scale as a standard. This was carried out for a set of 48 fluorescent cotton cloth samples previously studied, as well as for a new set of 86 non–fluorescent cotton cloth samples. As expected, the AGB formulae were inferior to those based on chromaticity values; however, the Taube formula performed quite well for fluorescent samples. On the set of non–fluorescent samples, a formula having green hue preference was required; the Berger formula was found to be the most successful among the simple AGB formulae.     

Controlling the Fluorescence of Benzofuran‐Modified Uracil Residues in Oligonucleotides by Triple‐Helix Formation

We developed fluorescent turn‐on probes containing a fluorescent nucleoside, 5‐(benzofuran‐2‐yl)deoxyuridine (dU^BF) or 5‐(3‐methylbenzofuran‐2‐yl)deoxyuridine (dU^MBF), for the detection of single‐stranded DNA or RNA by utilizing DNA triplex formation. Fluorescence measurements revealed that the probe containing dU^MBF achieved superior fluorescence enhancement than that containing dU^BF. NMR and fluorescence analyses indicated that the fluorescence intensity increased upon triplex formation partly as a consequence of a conformational change at the bond between the 3‐methylbenzofuran and uracil rings. In addition, it is suggested that the microenvironment around the 3‐methylbenzofuran ring contributed to the fluorescence enhancement. Further, we developed a method for detecting RNA by rolling circular amplification in combination with triplex‐induced fluorescence enhancement of the oligonucleotide probe containing dU^MBF.     

Quantitative evaluation of perceived whiteness based on a color vision model

This article describes a new perceived whiteness index, C/V index, which focuses on the brightness‐enhancement effect of color components included in the spectral reflectance factor distribution of approximate white objects or in the spectral power distribution of illuminations. The index is developed on the basis of a color vision model. The perceived whiteness of 18 approximate white samples was evaluated, and then a predictability of the index was compared with 17 types of existing whiteness indices. As a result, the C/V index was one of the indices indicating the best predicting performance. The aforementioned findings show that the C/V index is effective in evaluating the perceived whiteness of approximate white objects and the brightness‐enhancement effect of color components is an important factor in determining the perceived whiteness. © 2009 Wiley Periodicals, Inc. Col Res Appl, 2010     

Whitening regenerated cellulose fibers using fluorescent agent,surfactants, and salt—color indices measurements

The whitening efficiency of regenerated cellulose fibers using sodium 4,4′‐distyrylbiphenyl sulfonate in the presence of an anionic surfactant (sodium dodecylsulfate) and a cationic surfactant (dodecyl trimethyl ammonium chloride) and salt (NaCl) was determined by fluorescence spectroscopy and color index values (brightness, whiteness, and yellowness). Epifluorescence images gave an intense blue color with an apparent uniform emission distribution. In absence of salt, the whitening efficiency was higher for aqueous solutions containing cationic surfactant below critical micellar concentration (cmc). In presence of salt, whitening efficiency was higher for anionic surfactant and more important. The concentration of surfactant required for greater brightness, whiteness, and yellowness was lower than that required in absence of salt. These data were discussed by the decrease of the cmc and by the screening of the modified cellulose fibers by counter ions coming from the salt. The role of surfactants was explained by the admicelization during the sorption process. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Fluorescence monitoring of twin screw extrusion

An optical fiber probe has been constructed in order to obtain real-time measurements of fluorescence radiation during twin screw mixing and extrusion of plasticized polybutadiene and calcium carbonate particulate. The probe consists of an optical fiber bundle which was inserted along the axis of a half-inch sensor bolt, and it was used to transmit optical excitation energy to the processed material and to detect the subsequent fluorescence. The source of fluorescence radiation was a fluorescent dye which was doped into the processed ingredients at very low concentrations. Although most of our measurements were taken with the probe positioned close to the exit die, the sensor bolt can be placed in any instrumentation port along the extruder line. Experiments were carried out to measure residence time distribution, quality-of-mix, and mix concentrations as a function of processing conditions. Product mix changes in response to variations in material feed rates and screw RPM were also observed. Values of residence time were obtained by measuring the transit times for the dye to travel from an upstream injection port to the measurement probe, a distance of 63 cm. Flow instabilities, such as mat formation of the solids, were observed by noting the abrupt changes and discontinuities in the fluorescence signal.     

Effect of chromatic components on facial skin whiteness

Although the color measurement of facial skin becomes more common in dermatology and cosmetics, little is known about the relationship between subjective color perception and colorimetric values in facial skin. In this study, the possible relationships among perceived whiteness and the metric lightness, chroma and hue angle of Japanese females' facial skin color were investigated. First, the perceived brightness of the facial skin of Japanese females was evaluated visually and compared with metric lightness, chroma and hue angle, and the effect of hue and chroma on the perceived brightness was discussed. Second, a psychophysical experiment on the whiteness of the facial images and synthesized skin color plate images was conducted for examining the effect of hue and chroma on the perceived whiteness more precisely and independently. The results of two experiments showed that in regard to the facial skin color of the Japanese female, metric lightness disagrees with perceived whiteness or brightness in a narrow lightness range. The reddish facial skin color appeared brighter or whiter than that of a yellowish one in high lightness regions, and the low‐chroma facial skin color appeared brighter or whiter than a high‐chroma one. However, in the color plate images, a change in perceived whiteness by hue could not be confirmed, and the change in perceived whiteness by chroma was weaker than that from facial images. These results indicated that a higher‐level process of face recognition affected whiteness perception, and the criterion of facial skin whiteness was determined by facial skin color distribution. © 2011 Wiley Periodicals, Inc. Col Res Appl, 2011;     

On attributes of achromatic and chromatic object‐color perceptions

Adapting luminance dependencies of various color attributes of object colors (lightness, brightness, whiteness‐blackness, whiteness‐blackness strength, chroma, and colorfulness) were clarified under white illumination with various adapting illuminances. The correlation between the perceptions of lightness and brightness and those of whiteness‐blackness and whiteness‐blackness strength is also clarified for achromatic object colors. The difference between the increase of brightness and that of whiteness‐blackness contrast (the effect studied by Stevens and Jameson—Hurvich) by raising their adapting illuminance is resolved without any contradiction. It is also shown that the nonlinear color‐appearance model developed by the author and his colleagues is able to explain the complex characteristics of all the above color attributes of object colors by making minor modifications to it. In addition, two kinds of classifications of various color attributes are given; one is based on the similarity of perception level, and the other on the degree of adapting illuminance dependency. © 2000 John Wiley & Sons, Inc. Col Res Appl, 25, 318–332, 2000     

荧光增白剂BL和BW的应用研究

研究了荧光增白剂BL、BW、CF-351、CBS-X对洗衣粉的粉体白度、棉织物白度、棉织物色光等的应用效果.结果表明,荧光增白剂BL和BW在洗衣粉粉体白度、棉织物白度、棉织物色光等方面都较传统CF-351、CBS-X应用效果有较大提高,其中BL应用效果优于BW.     

Whiteness-blackness and brightness response in a nonlinear color-appearance model

The achromatic response of the nonlinear color-appearance model is developed to predict the perceptions of whiteness-blackness, brightness, and lightness of object colors. The distinction between whiteness-blackness and brightness perceptions of achromatic colors is especially important in an adapting condition with nonuniform illumination or in a haploscopic match between different adapting fields. In the whiteness–blackness response, the reference gray is introduced from the viewpoint of opponency of achromatic response, and the whiteness–blackness response is divided into whiteness–grayness and grayness–blackness responses. By giving different weights for the whiteness–grayness and grayness–blackness responses, the metric lightness in the nonlinear color-appearance model agrees very closely with the CIE 1976 L* function without any alteration to the model formulation.     

Impact of spectral power distribution of daylight simulators on whiteness specification for surface colors

The impact of spectral power distribution of daylight simulators (ie, D65 simulators) on surface whiteness specification was investigated by focusing on how CIE whiteness and tint values of 8 whiteness samples with fluorescent whitening agents (FWAs) vary under different D65 simulators. Large variations in both whiteness (～16 points) and tint (～1.6 points) are observed under the D65 simulators above BB grade, as characterized using the CIE metamerism index. However, it is found the variations of the whiteness and tint values are smaller under the D65 simulators whose radiant power in the UVA band (ie, 300‐340 nm) was within ±30% in comparison to CIE standard D65 illuminant, as defined in BS 950, which may be a better alternative for evaluating the quality of a D65 simulator for surface white specification using CIE whiteness and tint formulas. The findings also suggest the necessity to fine‐tune or revise the CIE whiteness and tint formulas to characterize the surface whiteness under nonperfect D65 simulators or arbitrary light sources.     

New method for measuring an optical property of a sample treated by FWA

In this article, a new method for measuring a total spectral radiance factor of a FWA‐treated sample illuminated by a specific standard illuminant is introduced. The method replaces an unstable real fluorescent standard by a bi‐spectral luminescent radiance factor data, which works as a virtual fluorescent standard (VFS) by knowing spectral intensity distributions of illuminations applied to the sample. The method utilizes two illuminations I₁ and I₂ whose relative spectral intensity distributions are different from each other and synthesizes a virtual illumination presenting the identical fluorescent spectral radiance factor to that presented by the standard illuminant with the VFS of the specific bi‐spectral luminescent radiance factor by linearly combining I₁ and I₂ with the suitable weighting factors. The applicability of the method is examined in principle by comparing ISO brightness and CIE whiteness index of fluorescent standard paper as a test sample obtained by this new method to the assigned values. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 195–200, 2007     

Determination of Fluorescent Whiteness: Experience in Using Linear Whiteness Formulae

Experience has been obtained in the use of two linear whiteness formulae on a varied set of near-white cloth samples. Visual assessments of whiteness were made with the aid of the Ciba-Geigy Plastic White Scale plates. These were compared with predicted whiteness values based on the tristimuhis total radiance factors (reflectance plus fluorescent emission) measured with a photometer fitted with illuminant D60. Good agreement was obtained when the parameters of the prediction formulae were determined by regression analysis, using measurements made on the plates of the White Scale with the same photometer. The closeness of agreement for the cloth samples was examined as a function of hue preference angle. It was found that the formula based on chromaticity coordinates gave superior results to the formula using the radiance factors directly. The practical application of the formula based on chromaticity coordinates is described.