Overview of sun fastness</p
日晒牢度指有颜色的织物受日光作用变色的程度，也称耐光色牢度。
The test method can be either exposed to the sun or exposed to a sun machine, that is, the sample is placed with a set of blue wool standards (divided into 3 levels according to the degree of fading under light exposure), and placed at the same time as the Expose the sample under artificial light sources under specified conditions according to specified conditions, and then compare the discoloration of the sample with that of the blue wool standard to evaluate the sunlight fastness grade of the sample. �</p
将照晒后的试样褪色程度与标准色样进行对比，欧洲标准分为8级，8级好，1级差。美国标准分为5级。
日晒牢度差的织物切忌阳光下长时间曝晒，宜于放在通风处阴干。
1. Factors affecting light fastness</p
It is related to the dye structure: Generally speaking, the light fastness of anthraquinone dyes, phthalocyanine dyes, sulfurized blue sulfide and metal complex dyes is relatively good; the light fastness of most insoluble azo dyes is also relatively high; Even aniline azo dyes have low light fastness; triarylmethane dyes are not light fast. �</p
与纤维种类有关：①靛蓝在羊毛上耐晒而在纤维素上的日晒牢度却很低；②凡拉明蓝盐B在粘胶上的日晒牢度要比在棉上高的多。
与染料浓度有关：一般浓度低的比浓度高的牢度差，这种情况在偶氮染料上表现尤为明显。
与外界条件的影响有关：空气含湿量的高低、气温的高低对日晒牢度影响也很大。一般在含湿高的情况下，日晒牢度较低。如：凡拉明蓝在南方比在北方地区容易泛红褪色。
与助剂有关：现在有很多的助剂可以有效改善日晒牢度。
2. Measures to improve light fastness</p
Dye selection (main influencing factors)</p
①High light fastness of yellow spectrum: Reactive dyes use pyrazolin tungsten and naphthalene trisulfonic acid as the parent structure;</p
②High light fastness in the blue spectrum: Reactive dyes use anthraquinone, phthalocyanine, and methyl ester as the parent structure;</p
③The light fastness of red spectrum reactive dyes is generally low, especially light colors. Only two adjacent positions of some azo groups contain hydroxyl groups with coordination ability, forming a stable chelate ring with copper, which can improve the light fastness. degree;</p
④When selecting dyes for color matching, the light fastness level of each component of the dye must be equivalent. As long as the light fastness of any one of the components, especially the component with a small amount, cannot reach the light fastness level of the light color. The requirements for dyeing materials will make the light fastness of the final dyeing materials unable to meet the standards. �</p
3. Other measures</p
①染料浮色的影响，染后皂洗不彻底，未固着染料和水解染料残留于布面上也会影响染色物的耐光牢度，它们的耐光牢度明显低于已固着的活性染料� The more complete the soaping is, the better the light fastness will be;
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