Requirements of the most popular offset four-color

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Requirements of offset four-color overprint on ink

to improve the printing quality of offset printing products, in addition to high-quality paper, PS plate and other raw materials, the hue of electronic four-color separation can be accurately reproduced without color deviation, and the plate making personnel should master the correct exposure time of PS plate printing. The developer concentration and temperature, the amount of ink properly adjusted by the master of monochrome, two-color and four-color offset printing, to achieve water ink balance, accurate color, accurate overprinting, perfect level reproduction, and dot printing light require the domestic packaging paper recovery rate to be increased to 89% and 91% respectively in 2019 and 2020, with good overall effect. Besides, the physical and chemical properties of the ink are the conditions that determine the quality of printing products. Only high-quality inks suitable for printability can print a colorful world on smooth and white paper

offset printing ink is a kind of grease bright and quick drying ink with double space structure. It is composed of color material, connecting material, adaptability adjusting agent, drying adjusting agent and improving printing effect adjusting agent

pigments are composed of organic pigments and inorganic pigments

function of pigment:

1. give the ink color and determine the ink concentration according to the amount of ink used. 2. give the ink a certain thickness and other physical properties. 3. maximize the durability of the ink. 4. to some extent, it affects the dryness of ink, especially the oxidation conjunctival drying

function of binder in ink:

1. give ink certain viscosity, viscosity, fluidity and thixotropy. 2. determine the drying type and drying speed of the ink. 3. determine the gloss, wear resistance, firmness, etc. of the ink

people engaged in printing know that different printing methods should use different inks, because their printing plates are different from the materials used for printing, and the substrates attached to the inks are different, so various inks with different adaptability are required. For example: offset and gravure printing inks, because they are two completely different printing methods, the viscosity and yield value of the ink are also different. However, what is the difference between various inks? It is on the binder of the ink. Therefore, different printing methods have different effects on ink flow performance and drying performance. For example, lead printing needs penetration drying, offset printing ink needs oxidation conjunctiva drying, and plastic printing needs volatilization drying and oxidation conjunctiva drying. Because plastic printing cannot penetrate drying, plastic does not absorb any ink at all. The colorants of the three inks are the same, and the difference lies in the binder in the ink

offset printing mainly uses resin ink

resin based inks have the following characteristics:

1. ink fixation speed is relatively fast. 2. fast drying. 3. the ink has strong luster and bright color. 4. strong water resistance. 5. good printing performance

resin ink type:

① soluble resin binder. ② Dispersive resin binder. ③ Colloidal resin binder. 5 volatile resin binder

in the offset process, the ink of the monochrome Offset Press is dry and wet printing, however, the four-color offset press is wet and wet printing. When four-color overprint is finished, when the ink of one color adheres to the paper in a short time and is still wet, the ink of another color is immediately overprinted, which is called "wet overprint". In wet printing, the ink's viscosity, dryness, fluidity, adhesion, thixotropic property, yield value and other properties determine the quality of ink color stacking

the auxiliary materials usually added to the ink have the following effects on the ink:

① the addition of desiccant has a strong drying effect on the ink layer. Usually, the content of dry oil is about 17%. When using the desiccant, it is now available to avoid conjunctiva. The content of dry oil in the ink should not exceed 2%, which is easy to crystallize in excess. The second color should be put more than the first color, and the temperature in winter is lower than that in summer. ② After adding the ink blending oil, the fluidity and brushing ability of the ink are increased, but the concentration and viscosity of the ink are reduced, and the dryness of the ink is also reduced. ③ The addition of debonding agent reduces the viscosity of the ink and increases the plasticity of the ink. 5 add diluent to dilute the original ink to meet the requirements of ink color. ⑤ Adding gloss paste can increase the brightness of the ink

offset printing oil has low thermal conductivity and good thermal insulation effect. Ink requires the following characteristics:

1. ink transparency should be high. When the ink is coated into a uniform film, the more clearly the background color of the material bearing the ink film is displayed, the higher the transparency of the ink is required. The color of ink on paper can be expressed in three forms:

① it is expressed in the form of field and point. Point and field (i.e. 100% point) selectively absorb and reflect the polychromatic light of sunlight, and the color is presented. ② Monochrome points are displayed by juxtaposition and superposition: that is, two independent points are juxtaposed or superimposed on each other to show color on the paper. ③ Juxtaposition of overlapping color points: that is, the points of two colors overlap on the paper to display color. If yellow and cyan are overprinted, they will show green hue

2. the pigment particles of ink shall be fine. Especially the beautifully printed picture books. Calendars, landscape paintings and other printing materials with high precision require fine ink particles and fine pigment particles to print exquisite printing products

3. strong coloring power of offset printing ink is required. The tinting power is a quantity indicating the color intensity or concentration of the ink. For inks with the same hue, the tinting power depends on:

① the dispersion of the pigment on the binder. The higher the dispersion, the stronger the coloring power. ② Depends on the content of the pigment. The higher the content, the stronger the coloring power

4. the offset printing ink shall have light resistance. The color of offset printing ink is required to be light resistant under the action of sunlight and light. The fading and easy discoloration of the ink after exposure to light should be as slow as possible. Outdoor advertising printing products are most likely to fade after exposure to the wind and sun. The discoloration is caused by yellow and red, while the discoloration of green and black is relatively slow. It is very important to solve the problem of discoloration and discoloration of yellow and red to improve the quality of printing products

5. high color efficiency of offset printing ink is required. Color efficiency is a comprehensive indicator of ink color difference and gray level. Offset printing ink requires pure color hue, no color deviation and no mottled

6. the chemical properties of offset printing ink should be stable. The color of ink will change under the action of some chemicals, especially acid, alkali, salt and oxidant, which will have a certain chemical reaction to the pigments in the ink and are often easy to change color. Therefore, offset printing ink is required to have good chemical stability

offset printing is a water-based printing method. Offset printing ink should have water resistance and anti emulsification

water is required for offset printing. PS version wetting powder shall be added into the water bucket. Offset wetting powder has the following characteristics:

① it can fully wet PS layout and reduce surface tension. It contains surfactant, wetting agent and surfactant. ② Acidic substances shall be added if it has cleaning ability. ③ Arabic gum should be added if it has a very good non fat sensitivity. 5. Buffer solvent shall be put in case of stable pH value. ⑤ Hygroscopic agent should be added to adapt to different climate changes. So PS version wetting powder is a high-tech product with a variety of chemical components, which requires the ink to have stable chemical properties. (WangXinCheng)

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