Printing Basics Lecture: Ink and Color (1)

The ink is mainly composed of colored bodies (pigments and dyes) and binders. Therefore, it can be considered that ink is a comprehensive enterprise of two industries, pigment and binder. Although most ink factories do not produce pigments, it is also an industrial unit that uses a large number of pigments. Therefore, in addition to the need for a broad understanding of the properties and application properties of pigments and binders, the ink industry should further understand their manufacturing and basic properties, as well as the characteristics of the disperse system formed by the combination of the two. Only in this way can the ink be designed and manufactured better. It is true that an excellent ink worker should further master and be familiar with the use of ink, such as printing and substrates (such as paper and plastic film). Otherwise, he is still not an ideal ink worker.

Therefore, we will extensively discuss some of the issues related to the above, such as color, rheology, dispersion theory, the relationship between substrates and inks, the manufacture of various inks, printing and printing problems, and so on.

In addition to printing performance, the final expression of ink is still dependent on color. In other words, the quality of a print, its visibility, and its authenticity depend on the effect of color. Therefore, the color of ink is one of the topics we will focus on.

The theory of color is generally quite esoteric, and there are even many basic concepts that are still at a relatively unclear stage. Therefore, we only discuss the colors as much as possible from the perspective of ink manufacturing.

First, radiation energy

The electromagnetic waves emitted by the sun are one of the world’s basic energy sources.

Electromagnetic radiation is the foundation of many things in our world of life. For example, radio, television broadcasting, X-ray medical research, photography, microwave heating, color matching, etc., all of which are the result of electromagnetic energy. If you leave electromagnetic radiation, these phenomena will not exist.

The concept of electromagnetic radiation has now been widely accepted by people. Due to the accelerating effect of the charge, energy is constantly generated and propagated through the space at a constant speed of 3.0 x 108 m/s (186,000 f/s).

All kinds of radiation energy include the concept of radiation wavelength and frequency can be summarized in a wide range of electromagnetic spectrum, the relationship is;

C=vλ

Where: C = speed of light (radiation energy) - 3.0 x 108 m / sec;

v=frequency (Hertz);

λ = wavelength (m).

The visible spectrum of the electromagnetic spectrum includes a short-wavelength xenon beam and a long-wavelength radio wave.

It must be pointed out that in the entire spectrum, the visible part is very narrow (from about 400-700 nm), which gives us the spectral color. The two ends of the color spectrum show that the human eye has no induction of electromagnetic radiation, and in the middle at about 555 nm, it means that the human eye has suitable induction energy.

Electromagnetic radiation occurs due to the accelerated movement of the charge, and some radiation sources are as follows:

1. Blackbody Radiation

The color of the metal changes after it is heated, such as the first light red, the temperature is generally about 500°C (878°F), about 850°C (1562°F) when the red color is dark, and 1000°C when it is yellow (1832 °F), to 1150 °C (2162 °F) is white, and so on.

From this it can be known that the composition of the light of a hot object varies with its temperature. Different materials have different amounts of light emitted at the same temperature. For example, at the same temperature, incandescent carbon emits more wavelength-like light than incandescent platinum. In order to have standard conditions for thermal radiation, Kjeldahl (note: the absolute temperature of the blackbody is expressed in terms of the Kelvin range (K).) A "blackbody" hypothesis is proposed and its maximum emittance is given. Set to 1, and all other objects emit only part of this black body. And define: The black body can absorb all the light (no reflection or transmission of light), which can further define: The light from the black body is caused entirely by its own radiation.

If it is assumed that the sun is an ideal emitter of electromagnetic radiation (blackbody) and it is assumed that the major part of the radiation is light (such as its visible thin surface), the effective black body temperature of the sun's surface is about 5800°K (5527°C). . The solar radiation at this temperature contains a certain proportion of the ultraviolet region wave, like the visible region.

The temperature of the sun is measured from the reception of radio energy, ranging from about 6400°K at short wavelengths to 1,200,000°K at long wavelengths. According to theoretical calculations, the center temperature of the sun should be 20,000,000°K.

The sun's radiation is not only an obvious hybrid (light) beam (for example, it first touches the earth's atmosphere), but these radiations mix with the atmosphere and cause significant changes. For example, high-energy ultraviolet and X-ray radiation that radiates from the sun is generally blocked at high altitudes in the Earth's atmosphere. Only rockets and satellites can detect it. A strong emission line with a wavelength shorter than 180 nm can be observed here. These collisions of short-wave radiation (action) produce the Earth's ionosphere (ionization of the earth's atmosphere envelope). As the oxygen molecules absorb ultraviolet rays, ozone (triatomic oxygen) layers are formed at 12-30 degrees above the earth's surface.

Electromagnetic radiation that reaches the Earth's surface is a heterogeneous mixture of shielding wavelengths (approximately 1/3 of the thermal or infrared type and 2/3 of visible light type), which may sometimes be classified as "clean sky light," due to their different composition. Sunny light, "direct sunlight" and "north (half-day) light" and so on. Although there is no better way to evaluate the durability of outdoor colors, there is still a need in the art for some light sources for the laboratory to act as average sunlight conditions.

In order to meet this requirement, the International Commission on International Illumination (Commission Internationale de I'Eclairage, C.I.E.) recommended several standard light sources for color measurement in 1931. The color measurement work is very useful, that is usually said A light source, B light source and C light source. C light source is often referred to as "the northern half of the sky" (also known as North light).

2. Photochemistry

Photochemistry is the study of chemical processes caused by electromagnetic radiation. For example, the reaction between ultraviolet, visible, and infrared radiation energy and (absorbing) substances.

Clothes drying in the sun will turn white, imaging of photographic materials and so on are all photochemical processes. Chemical processes caused by radiant energy come in many forms, such as:

(1) Accelerate the reaction, otherwise it is in an inert state.

(2) The reaction is triggered. When the reaction starts, it will continue spontaneously. (For example, in the dark and without light, hydrogen and chlorine are rarely reacted, but under the ultraviolet light, it can cause violent reaction and explosion. ).

(3) Make the molecules in the reaction into a high energy state.