Offset four-color printing ink requirements

Improve the printing quality of offset printing products, in addition to high-quality paper, PS plate and other raw materials, electronic four-color color hue accurately reproduce, not color cast, plate-making personnel to master the correct version of the PS plate exposure time. Developer concentration and temperature, monochromatic, two-color, four-color offset master just right to adjust the amount of ink to achieve ink balance, color accuracy, accurate overprinting, tone reproduction level perfect, clear and clean dot printing, the overall effect is good, the ink Physical and chemical properties are the conditions that determine the quality of printed products. Only high-quality inks suitable for printability can print colorful and colorful worlds on glossy, white paper.

The offset printing ink is a resin bright fast drying type ink, which is composed of a color material, a binder, an adjustability adjuster, a desiccant adjuster, and a print effect modifier.

The colorant consists of organic pigments and inorganic pigments.

The role of pigments:

1. The ink is colored and the ink concentration is determined according to the amount. 2. Give the ink a certain thickness and other physical properties. 3. Maximize the ink's durability. 4. To a certain extent, the ink dryness is affected, and the oxidative conjunctiva type drying is the most significant.

The role of the binder in the ink:

1. Give the ink a certain viscosity, viscosity, flowability and thixotropy. 2. Determine the type of ink drying and drying speed. 3. Determine the ink gloss, wear resistance, firmness and so on.

Those who work in printing know that different printing methods should use different inks because their printing plates and printing materials are not the same, and the substrates to which the inks are attached are different, so they require various types of inks with different aptitudes. For example, the inks used for offset and gravure are different because they are two completely different printing methods. The required viscosity and yield value of the ink are also different. However, where is the difference between various inks? It is on the ink binder. Therefore, different printing methods have different ink flow and drying performance forms. For example, lead printing needs infiltration and drying, offset inks need to be oxidized and conjunctiva dry, and plastic printing requires volatile drying and oxidative conjunctiva drying. Because plastic printing cannot penetrate and dry, plastic simply does not absorb a bit of ink. The color of the three inks is the same. The difference is in the link material in the ink.

Offset is mainly resin ink.

Resin ink has the following characteristics:

1. Ink fixation is faster. 2. Fast drying. 3. Ink luster, bright color. 4. Strong water resistance. 5. Printing performance is better.

Resin ink type:

1 Dissolving resin binder. 2 dispersion resin binder. 3 colloidal resin binder. 5 volatile resin binder.

In the offset printing process, the ink of the single-color offset printing press is dry-wet printing. However, the four-color offset printing press is wet-on-wet printing. In the four-color overprinting, when a color is printed, the ink is still wet on the paper in a short time, and the ink immediately overprinted with another color is called “wet wet”. The properties of the ink, such as viscosity, dryness, fluidity, adhesion, thixotropy, and yield value, determine the color of the ink when wet and wet.

Ink additives usually added to the ink have the following effects on the ink:

1 The addition of desiccant has a strong squeezing effect on the ink layer, usually adding about 17% of the dry oil content, and when using a desiccant, it is used now to avoid conjunctiva. Dry oil content in the ink can not exceed 2%, excessive easy to crystallize, the second color than the first color to put more, the winter temperature is lower than summer to put a little more. 2 The addition of varnish increases the fluidity of the ink and improves the brushing properties. However, it reduces the concentration and viscosity of the ink and reduces the drying of the ink. 3 Adding a detackifier reduces the viscosity of the ink and also increases the plasticity of the ink. 5 Add dilute agent to dilute the original ink to meet the requirements of the ink. 5 Add bright paste to increase the brightness of the ink.

Offset inks require the following features:

1. The transparency of the ink is high. When the ink is applied as a uniform film, it is required that the clearer the underlying color of the substance that bears the ink film, the higher the transparency of the ink is required. The color of ink on paper has three manifestations:

1 In the form of field and dot, the color of the sun's polychromatic light is selectively absorbed and reflected by the dot and field (ie, 100% dots). 2 The appearance of the juxtaposition and superimposition of the monochrome dots: that is, two independent dots juxtaposed with each other or superimposed on the paper to present color. 3 juxtaposition of overlapping dots: the dots of two colors overlap on the paper to show colors. The yellow hue and the cyan color show green hue when overprinted.

2. The pigment particles of the ink are delicate. Especially beautifully printed pictures. Prints such as wall calendars, landscapes, etc., which require high precision, require delicate ink particles. Fine color particles can be used to print fine print products.

3. Requires strong coloring of offset inks. Coloring power is a quantity that represents the color intensity or concentration of an ink. For inks of the same color, the tinting strength depends on:

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

4. Offset inks require lightfastness. The color of the offset ink is required to be light-resistant under the influence of sunlight and light. The degree of discoloration and easy discoloration of the ink after being irradiated with light is as slow as possible, and the printed products of outdoor advertising are most likely to fade after being exposed to the sun and the sun. The color change is yellow and red. The two colors, cyan and black, are discolored and fading is relatively sluggish. To solve the problems of fading and discoloration of yellow and red colors, it is crucial to improve the quality of printed products.

5. Requires high color efficiency of offset inks. Color efficiency is a comprehensive index of ink color difference and gray scale. Offset printing ink requires the hue of the color to be pure, non-colored, and non-colored.

6. The chemical properties of offset inks can be stabilized. The color of the ink will change under the effect of some chemicals, especially the acid, alkali, salt, oxidant will have a certain chemical reaction to the color material in the ink, and it is often easy to change color. Therefore, the offset ink is required to have good chemical stability.

Offset printing is a method of printing with water. Offset printing inks must have water resistance and anti-emulsification properties.

Offset to use water. The PS version of wetting powder should be added to the bucket. Offset wetting powder has the following characteristics:
1 It can fully wet the PS plate and reduce the surface tension. With surfactants, wetting agents, surfactants. 2 has the cleaning ability to add acidic substances. 3 has a very good fat-free ability to add gum arabic. 5 To stabilize the pH, put a buffering solvent. 5 can adapt to different climate changes to add moisture absorbent. Therefore, the PS version of the wetting powder is a high-tech product with various chemical components and requires the ink to have stable chemical properties.

(Wang Xincheng)