Technical points of color decoration in the most p

Technical points of color decoration in special ink printing

this paper mainly introduces the technical points of color decoration and some troubleshooting methods

first, the technical points of color decoration

mainly include the following aspects

1, gold and silver

in order to ensure the purity of ink color, when printing gold and silver ink in the last pass, first wet the holes with plate washer 783, clean the layout, and wait for the solvent to evaporate completely before inking, because the gold and silver ink will react with the solvent, causing the ink to change color. Due to the poor fluidity of gold and silver inks, ink blending oil or slow drying agent is often added to increase the fluidity of the ink, which can also prevent the formation of oxide film and darken the ink film without adding a small amount of yellow ink. If you want to bring out the luster of gold/silver foil, you can add more slow drying agent appropriately

2. Pearlescent ink

pearlescent pigments can be used together with transparent pigments or dyes to obtain a unique pearlescent effect, but it should be avoided to mix with opaque pigments and complementary pearlescent pigments. When using silver white pearlescent pigments, a small amount of carbon black paste or blue paste should be added to enhance its pearlescent effect. Pearlescent pigments have good dispersibility, and the long-term effect of strong shear force should be avoided. This kind of ink will precipitate in the low viscosity inking oil, so it should be gently stirred before use, which will not affect the use effect

3. Luminous ink

luminous ink can be prepared by adding a certain proportion of light storage material to transparent light oil. The particle size of light storage material should be controlled within 45 ~ 65 μ M range, so as to prepare a good luminous ink. Precautions for the use of luminous ink: the viscosity of the processed luminous ink is about 300 ~ 500 PA · s, which is slightly thicker. When printing, adjust the ink viscosity with diluent according to the printing speed to meet the needs of printing. When printing patterns and logos with luminous ink, polyester yarn below 150 mesh is generally selected. In order to obtain the best luminous effect, 80 ~ 120 mesh yarn can be selected. The luminous ink printed on the white substrate can improve the luminous brightness and afterglow time of the printed pattern or logo. The coating thickness of printing luminous ink shall be controlled within 130 ~ 150 μ M, the luminous effect is the best. If it is printed twice with 80 mesh silk, this thickness can be achieved

4. Fluorescent ink

fluorescent ink is suitable for silk and high tension plates with less than 300 meshes. When the transfer amount of printing ink on the substrate is 50 ~ 60 g/m2, its color development and light resistance are ideal. Gloss processing will slightly weaken the fluorescent effect, so use a bright oil with good transparency. When the substrate is a transparent object, white ink must be printed before printing fluorescent ink, which can improve the fluorescent effect. It can also be printed on paper with high whiteness. The higher the whiteness of the paper, the better the printing effect. When printing the base color with fluorescent ink, if it is printed in the same color system, the color will be better and the lightfastness will be improved. When used in four-color color printing, if magenta and yellow are printed, bright colored prints can be obtained. Pay attention to the printing sequence to improve the printing effect

uv inks have a wide range of colors to choose from. If you choose inks with strong coloring power, you will use less; The greater the dispersion of pigment, the stronger the coloring power; The smaller the pigment particle, the greater the hiding power. The primary color is generally used for color matching and ink matching. For example, on electronic components, silver and black background colors are generally used, and the contrast cannot be too large. Do not mix colors with high content of white, black and blue. Specific colors interfere with the absorption of light energy, resulting in difficult curing. The proportion of pigments should not be too large, and it should be accurately controlled, otherwise it will affect the UV curing of UV ink, because the larger the proportion of pigments contained in the UV ink layer, the greater the blocking effect of the ink layer on UV. It takes more time to completely cure the ink layer. If the ink layer cannot be completely cured, the wear resistance, solvent resistance and other properties of the printed matter are poor. Printed with crystal glue or UV crystal glue, you can't see a significant effect. After sprinkled with colorful flash film, it looks as gorgeous as a greeting card

II. Defects and Countermeasures

some faults and defects are easy to appear in color decoration, and the following countermeasures are mainly taken

1. Discoloration

the color of the ink film changes during use, and its hue, lightness and chromaticity obviously deviate from the standard color code

causes:

(1) caused by eye irradiation (mainly in the short wave section), humidity, high temperature, corrosive gases in the air (such as sulfur dioxide)

(2) the weather resistance of the ink used is poor

(3) organic pigments migrate through the ink film during the aging of the ink film and the precipitation of plasticizers

prevention and treatment:

(1) select the appropriate ink according to the service conditions of the substrate

(2) use ink with excellent weather resistance

2. Fade

during use, the color of the ink film becomes lighter

reasons:

(1) sunlight, chemicals, air pollution and other effects, make the color decline

(2) the effect of heat and ultraviolet makes the resin deteriorate

(3) the selected ink (or the pigment contained in the ink) has poor weather resistance or is not suitable for outdoor use

prevention and treatment:

(1) select the ink with excellent weather resistance according to the use environment

(2) use non fading ink

3. Fading

when wiping the surface of the ink layer with a cloth, the cloth is stuck with the color of the ink

reason:

it is mainly caused by the penetration of pigments (especially organic pigments) contained in the ink into the surface of the ink film

prevention and treatment:

(1) improve the ink formula

(2) add resin to the selected ink or cover it

4. color difference

the hue, lightness and saturation of the printed ink film are different from the standard color standard

reasons:

(1) there are great differences between batches of ink used

(2) some parts were not cleaned when changing color

(3) inconsistent drying conditions, especially drying

(4) ink replenishment causes printing stains

prevention and control: for many companies in the composite industry,

(1) strengthen the incoming inspection of ink

(2) some parts must be cleaned when changing color

(3) the drying conditions (drying time, temperature) should be strictly controlled

(4) add ink as little as possible or only on the surface with distinct boundaries

5. floating color, color layering

due to the difference in particle size, shape, density, dispersion, cohesion and so on, the pigment on the surface and lower layer of the ink film is unevenly distributed, resulting in the difference in hue at all levels

reasons:

floating color is related to the inconsistent distribution of pigments in the solvent during the formation of ink film, and the unreasonable ink formula and inking process are the main reasons

(1) when mixing inks with more than two pigments, due to the inconsistent volatilization of solvent inside the uneven pore layer of ink particles and the surface, it is easy to convection and produce floating color phenomenon

(2) the density of pigments in ink varies greatly

(3) improper selection of operation methods and equipment

prevention and treatment:

(1) improve the ink formula and manufacturing process (such as selecting pigments that are not easy to float and are easy to disperse, and improving the dispersion process of pigments)

(2) adding anti floating color agents, such as silicone oil, has a significant effect on preventing floating color

(3) select appropriate modulation methods and equipment

6. uneven color (color blooming)

the color of the ink film is locally uneven, with spots, stripes and disordered hues. It is generally caused by improper printing operation of ink and the interaction between ink components and some substances

reason:

(1) the pigments in the ink are poorly dispersed or the mixing of more than two kinds of paints is insufficient

(2) the solvent force of the solvent used is insufficient or the viscosity of the operation is inappropriate

(3) printing too thick makes the pigments in the ink film produce "convection" inside and outside

(4) all gases (such as ammonia, sulfur dioxide, etc.) and acids and bases that interact with the ink film in the operation site

prevention and treatment:

(1) choose pigments with good dispersibility and miscibility

(2) select the appropriate solvent, and adopt the printing viscosity and film thickness that meet the process requirements

(3) the same type of ink and the same type of ink produced by the same manufacturer should be used when preparing multicolor paint

7. Poor gloss

the ink layer did not reach its due gloss after drying, and the gloss of the ink layer decreased shortly after printing

reasons:

(1) improper selection of pigments, poor miscibility of resins, and improper selection of solvents

(2) the ink absorption of the printing surface is large and uneven

(3) the printing surface is rough and uneven

(4) insufficient air exchange when drying the ink layer

(5) printing under high temperature, high humidity or extremely low temperature

prevention and treatment:

(1) select appropriate inks and solvents through experiments

(2) printing backing ink to improve the non-uniformity of the printing surface, i.e. roughness

(3) strictly control the drying conditions of the ink layer, and the ventilation in the drying room should be appropriate

(4) pay attention to the printing process control to ensure the uniform thickness of the ink layer

(5) Polish after the ink layer is dry and cured

(6) control the environmental conditions of printing operation

8. Uneven metal gloss

when printing metal decorative ink, due to the uneven thickness of printing, the solvent used does not match the ink, resulting in uneven distribution and orientation of metal powder, resulting in uneven appearance color of the film

reasons:

(1) improper ink formula (such as low content of metal powder, high concentration of solvent, low molecular weight of resin, slow drying of resin, etc.)

(2) improper selection of printing viscosity (too low or too high)

(3) the ink layer is too thick or the film thickness is uneven, and the operation is unskilled

(4) the interval between ink priming and varnishing is too short

(5) low ambient temperature

prevention and treatment:

(1) improve the ink formula and use slow volatile solvents

(2) the viscosity of the ink should be appropriate

(3) the ink base color and varnish should be properly dried with hot air at 60 ~ 80 ℃

(4) adjust the ambient temperature of printing to an appropriate range

9. copper light

the surface of the ink film is copper, and it turns green and purple under the sunlight

reason:

(1) exposed to sunlight, ultraviolet light or high temperature

(2) caused by the migration of red, blue and other pigments, especially when the pigment particles are less than 0.1 μ M hour

prevention and treatment:

choose the ink with good weather resistance, and choose the appropriate pigment in color matching

10. exposure and poor covering

the phenomenon that the printing surface is not printed with ink is called exposure (commonly known as lack of ink). The phenomenon that the printing ink layer is thin or the ink covering force is poor, and the bottom surface is not covered (bottom color) is called poor covering

reason:

(1) the pigment content of the ink itself is low or the ink is not stirred evenly before use

(2) the viscosity of printing ink is low and the ink layer is too thin

(3) the shape of the substrate is complex, and printing leakage occurs

(4) the color difference between the ground color and the surface ink color is too large, such as printing light ink with high brightness on a deep ground color

prevention and treatment:

(1) use ink with strong hiding power, and the ink should be fully stirred before use and during printing

(2) properly increase the working viscosity of the ink, and each printing operation should reach the specified ink layer thickness

(3) improve the proficiency of operation

(4) the background color should be as close as possible to the color of the surface ink layer

11. the ink layer turns white

the surface of the ink layer during and after printing is milky white, resulting in cloud like whitening and light loss. It usually occurs when printing volatile ink. In serious cases, it will completely lose luster, and micropores appear on the ink layer, causing adhesion