Chemical Engineering: Basic Concepts of Light and Dye Color Development

(1) The nature of light The color of dyes and The structure of the dye molecule itself is also related to the properties of the light that illuminates the dye material. The various colors in nature perceived by the naked eye are the result of external light sources shining on various objects, and the absorption and reflection of light by various objects. Therefore, to correctly understand the relationship between light and dye structure, we must first understand the physical properties of light.

Visible light, y-rays, ultraviolet rays, infrared rays, X-rays, and radio waves are all electromagnetic waves with different wavelengths. Generally, the wavelength of visible light is ~760nm. Electromagnetic waves; infrared electromagnetic waves with wavelengths of 7&0~6000nm; radio wavelengths are longer. Usually expressed in cm or km, the ultraviolet wavelength is shorter than visible light. The wavelength is below 40nm, and the shorter wave positions are X-rays and y-rays.

Light has dual properties of wave nature and granularity. Light of various wavelengths is actually a stream of photons of various energies.

The energy ou of a photon is inversely proportional to its wavelength. The energy quality of all ultraviolet rays is higher than that of visible light, while the energy of infrared rays is lower than that of visible light. In the same way, in visible light, light with short wavelength has high energy, and light with long wavelength has low energy.

(2) Absorption of light by matter If all visible light passes through a transparent object, the object is white; if all the light shining on the object is absorbed, the object is black; if the object can combine various different components that make up white light If colored light is absorbed to the same extent, the object is gray. An object is colored only if it chooses to absorb light in certain bands of the visible light system and reflect light in other bands. Reactive dyes are the so-called dyeing of objects. They are the result of selective absorption of visible light. However, the color felt is not the spectral color of the absorbed light wavelength, but the spectral color of the reflected light, which is the complementary color of the absorbed light. If an object chooses to absorb light with a wavelength of 500~550nm (spectral color is green), it will feel The color is purple-red. Purple-red is the complementary color of green spectrum color, while yellow is the complementary color of blue spectrum color, and yellow-green is the complementary color of purple spectrum color.

Disperse dyesThe purity of the color and the absorption of visible light by the dye It is related to the range. If the absorption is close to one wavelength, the purity of the color is higher. After the dye absorbs visible light, the amount of reflected light that is not absorbed but is reflected is a measure of the dye. The more reflected light, the greater the brightness.

(3) The three primary colors can be found through experiments. By mixing the three colors of red, yellow, and blue in a certain proportion, you can get For other colors of light, this color mixing method is called additive mixing of colors. These three colors of light are independent of each other, that is, any of these three colors of light cannot be produced by mixing the other two kinds of light. Therefore, the three colors red, yellow, and blue are called the three primary colors. Red light of 700nm, yellow light of 546.1nm and blue light of 435.8nm are selected as the three primary colors by the International Commission on Illumination. With the three primary colors, various color spectrums can be spelled out.