Color Difference Control of Large-format Offset Packaging Products

Measures for Controlling Color Differences in Printing

Prepress measures

1. The original must be unified

The manuscript is the beginning of the entire printing process, so analyzing and producing the manuscript is critical to the quality of the print. Therefore, the same product is used to produce the same manuscript in different companies, and avoiding deviation due to manuscripts is the most basic requirement.

2. Platemaking company should have basic qualification requirements

The materials used by the platemaking company must be regulated, especially the quality of the film.

Film output is the first substantial control factor in the printing process. Various parameters on the film will directly affect the printing process control. If the various deviations of the film can be controlled within the allowable range, the various printing processes The deviation control is relatively easy, and the quality of the printed product obtained is relatively uniform. For the current output center, the main control methods are film density and film linearity.

Film density: As long as the film density can be controlled within a relatively safe density range, the usability and uniformity of the film can be guaranteed. To ensure that the film density is within the safe density range, the requirements for the control row machines are relatively high, requiring high machine stability, wide range of adjustable factors, and large margins.

Using high-temperature deep-groove development, double sinks, and rapid drying, the film has the best permeability and density, and the linearity of the dots is the most stable.

3. The related equipment must have both digital proofing and traditional proofing capabilities

Digital proofing through ICC color management operations, so that customer electronic files can be efficiently and accurately restored to the real effect, saving the time of the traditional proofing; traditional proofing through the review of the proofs, the wrong version of the film, school color and size of the wrong To the decisive role, the defects of the film can be found in time, and the printing loss caused by the wrong version can be avoided.

The measures to be taken during the printing stage

Determine the appearance of the paper indicators: paper is a print carrier, its surface characteristics such as whiteness and printability determines the degree of color contrast of the final print, to some extent directly determine the hue of the print.

The suitability of paper printing includes silk fibroin, tensile strength, surface strength, moisture content, smoothness, degree of sizing and whiteness of the paper.

Tensile strength of the paper: The maximum tension that the paper can withstand. The change in printing speed has an effect on its tensile strength.

Surface strength: In the printing process, it is affected by the peeling force of the ink and has the properties of resistance to powder dropping, hair loss, blistering and tearing.

Moisture content: The moisture content of the paper should be controlled between 6% and 8%. When the moisture content changes with changes in the temperature and humidity of the environment, it will cause deformation, resulting in poor printing, resulting in color differences.

Smoothness: The extent to which the paper surface is uneven. According to the principle of light reflection and refraction, rough and uneven paper is printed with dark colors. The flat paper is bright.

Whiteness index: The whiteness of the paper refers to the ability of the paper to fully reflect light after being illuminated by light, that is, the ratio of the reflected light to the incident light under test conditions, which is also referred to as brightness. High whiteness paper can increase the contrast between ink and paper, and the printing color can be brighter.

Color index: The color of the paper will largely change the appearance of the print.

The hue of the paper will affect the reduction of the color. By controlling the hue of the paper, the hue of the printed ink will be adjusted so that it will reach the gray balance again. Among them, the reddish, partial blue, and yellowish color of the paper have the greatest impact on the printed products.

Determine the ink index: ink is a material that directly reflects the level and color of the printed product and expresses the content of the printed product. Therefore, the accuracy of the hue directly affects the quality of the printed product. Factors considered in the selection of the ink brand include: whether the ink hue control indicator meets the requirements, whether the printability meets the requirements of the printing press, whether the production cost is coordinated with the packaging product, and whether the quality of the ink product is stable over a long period of time.

Ink suitability requirements: ink viscosity, fluidity, drying speed must meet the printing requirements, otherwise it will be in the printing process, because the ink can not be transferred, resulting in the color can not be restored, so that the formation of finished products in the hue difference.

Color difference control during production

Ink balance. Less ink thick water is the best process condition for ink balance. It has the characteristics of reducing dot distortion, maintaining a clear dot layer, low emulsification value, and bright and glossy ink.

The effects of ink emulsification on the product are mainly reflected in the following aspects: the ink and ink balance is damaged, the dots are juxtaposed, and the hue shift occurs after overlapping; dot area is deformed, with burrs, is not smooth, the level of performance is unclear; the product is not stable in ink, and the batch size The product is not uniform in ink; the ink is dark and dull; the imprinting is slow and dry, and it is easy to get dirty.

Formulation and use of fountain solution. The rational allocation of fountain solution is an important basis for achieving the best ink-water balance and ensuring consistent color. The deployment is based on the proportion of 20% of alcohol and 2% of fountain solution. The water temperature should be kept at 10°C and the pH value should be between 4.5-5.2.

Addition of ink accessories. The purpose of adding the ink accessories is to ensure the printability of the ink, reduce the gray components in the ink, and facilitate the correct synthesis of colors. The commonly used auxiliary materials include several kinds of adhesive remover, diluent and desiccant. According to different requirements, different auxiliary materials are used. Under normal circumstances, no auxiliary materials are used, and the use must be strictly controlled within the range of usage.

Printing pressure adjustment. To ensure a good transfer of outlets, clear printed outlets, smooth spots, low expansion values, constant lining materials, and maintaining proper and balanced printing pressure are the key conditions for achieving consistent ink printing.