PRINTING BASIS

Chinese printing has a long history because that a formal wood block printing was invented in China as early as about 740 AD. In the Northern Song Dynasty, the movable-type printing invented by Bi Sheng was one of the four great inventions along with gunpowder, compass and papermaking. Printing provided the basis and possibility for the widespread spread of writing and civilization.

Printing according to the form of plate can be divided into letterpress, gravure, lithography, hole plate four categories. The printing press is a six-color offset press (Komori S-26) of our company. Offset printing is the main printing way of lithography. Offset printing refers to the printing ink from the plate to the blanket, and then transferred to the substrate. The ink holdout is better than direct printing.

Printing has seven elements, such as printing environment, water, ink, printing plate, paper, rubber, lubricating oil. Ink is one of the indispensable part and the main part of color. According to different drying methods, offset printing ink is divided into conventional offset ink and UV offset ink.

Komori printing machine consists of six parts including paper feeding, registration, printing, water supply, ink and paper receiving. Each department performs its own duties and completes printing together.

Color basis

It is well known that visible light ranges is from 380 nm to 780nm. The light of single wavelength is called monochromatic light. However, the everbright that our general daily place contacts is compound light, such as fluorescent lamp, sunshine and so on. Visible light produces color vision by stimulating the human's eyes, which play the role of imaging and sensing. From the perspective of visual function, the whole eyeball is mainly divided into two major refractive and photosensitive system. The refractive system consists of the cornea, pupil, aqueous humor, lens and vitreous body. It can form clean the image of objects at different distances on the retina. Photosensitive system composed of the retina including visual cell layer: the cones (low sensitivity, under the condition of bright, has the fine resolution, good color and detail), stem cells (high photosensitivity, a resolution ability is low and cannot distinguish between colors under the condition of dark,); Bipolar cell layer and innermost layer.

Human's eyes visual phenomena: 1 dark adaptation: need 45 mins, rod cells play a major role. 2 bright adaptation: 1 mins, cone cells play a major role. 3. Color adaptation: They will have complementary color components of the original color adaptation light when people observe another color after a certain color stimulation. Printing is generally recommended to see color under a standard light source. 4. Contrast with same color: human vision will feel that one color changes to the opposite color when two colors are placed in the instrument for observation. 5 sequential color contrast: sequential color contrast refers to the feeling of two colors will be superimposed when you first look at one color and then look at the second color. This will cause the phenomenon of color instability.

Visual theory of color: 1. Color mixing law: color light plus color method, red, green and blue are the three primary colors. They mainly are used for self-luminous body (used for natural light mixing, screen, etc.); Color subtractive method, cyan, magenta and yellow are the three primary colors. They mainly are used for material absorption of light after the color. 2 The three primary colors can be any color. However, red, blue and green can form the most mixed colors. Thus, red, blue and green are usually chosen as the primary colors. In the color matching experiment, the values of three primary colors required for matching with the color to be measured are called tristimulus values, which are denoted as RGB. RGB represents the number of red, green and blue colors respectively. 3 Modern colorimetry uses a set of color measurement principles, conditions, datas and calculation methods specified by the CIE, known as the CIE standard colorimetry system. CIE has tried a lot, such as from CIE1931RGB to CIE1931XYZ, to CIE1976Lab, to CIE94, and CIEDE2000. They are based on visual evaluation. However, they are still not perfect so far. In textile, CMC color difference formula is used to compensate for the visual consistency defect. 4Metachromatism: visually identical but spectral colours are used for printing and reproduction.