What is the theory of dye color development?

A substance's selective absorption of different light will show various colors, and the color of the substance is the complementary color of the light wave it absorbs. The same is true for dyes. The color of dyes is also the complement of the color of the light waves they absorb, and it is a reflection of people's vision on the light absorption characteristics of dyes.

In the molecular structure of the dye, there are chromophore groups in the range of 380 ~ 780nm wavelength. In addition, there are also chromophore groups that promote the chromophore group, such as -NH2, -NR2 and so on.

The chromophore and the chromophore assist in a synergistic manner, which enables the dye to selectively absorb light waves. When certain groups in the structure generate color that is conducive to the development of the dye, the absorption of the light wave by the dye proceeds in the direction of increasing the wavelength. The color development theory calls this effect, which increases the absorption wavelength, a dark effect.

This theory is of great help in the research and development of dark dyes. For example, the dark effect on nylon and vinegar fabrics is not ideal, and generally only light and medium colors can be dyed.

In the traditional process, acid and disperse dyes are used for dyeing. In order to obtain a deep color, only the amount of dye is increased, the effect is not obvious, and the amount of dye waste is large. It has been reported abroad that the use of triazole disperse dyes to dye nylon fibers has a deepening effect, and the dyed fabric has a higher washfastness and sun fastness. The main method is to replace the hydrogen atom on the triazole ring with a thiomethyl group (CH3S-) in the dye structure, so that the absorption of the light wave by this dye moves to the long wave direction, thereby generating a dark effect. Under the premise of this, a deeper dyeing effect can be achieved than the original dye.

1. Surface coloration and reflection theory

This is a method currently widely used to evaluate the color depth of dyed fabrics. Generally, the K / S value (KabelKamunk function value) is calculated at the maximum absorption wavelength (λmax) of the reflection or projection spectrum of a colored object, and the relative depth of color is represented by this value. Under the guidance of theory, through the finishing technology of the fabric after dyeing, the microscopic result of the surface of the dyed fabric is changed, so that it has a certain diffuse reflection of light waves, so as to obtain a dark effect.

2. Dye diffusion theory

Dyeing theory believes that the key to making a dyed object darker is to increase the dye uptake of the fabric. Dyeing rate refers to the ratio of the amount of dye applied to the fabric to the amount of dye put into the dye bath. Because this kind of evaluation method to obtain the dark effect is very clear and the reflection result is obvious, it is always one of the first considerations in the dyeing process in the dyeing process. Some dark research and dark-dark dyeing mostly start from improving the dyeing rate of the fabric, which has guiding significance for actual production.

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