Analysis: What factors will affect the color difference of Cigarette Packaging Design

Analysis: What factors will affect the color difference of Cigarette Packaging Design

How to make a batch of printing or several batches of printing ink color is a basic requirement, but also an important problem. For the manufacturer, the color of the packaging has become an important means and symbol to distinguish the product (even become the logo color of the enterprise). Everywhere, consumers recognize the red of Coca-Cola, the orange-yellow of Tide laundry detergent and the colors of many products. If the packaging looks different, consumers may think the quality of the product is unstable and even doubt the authenticity of the product. Therefore, these well-known enterprises attach great importance to the color of product packaging, requiring that the ink color must be stable and consistent.

The consistency of color is only relative. It is difficult to control the color difference in the same batch, and it is even more difficult to control the color difference in large batches or between different batches. Intaglio printing of plastic flexible packaging is mostly multi-batch printing and mass printing. It is a very important subject for plastic flexible packaging printing enterprises to control color difference.

One, ink

Ink is one of the main factors that determine the consistency of printing color. The ink itself also has the same batch color difference and the color difference between different batches, which is an important indicator to reflect the quality of ink.

To solve the color problem of plastic gravure printing, the first thing is to choose stable quality, color without deviation of ink. A batch of printing is best to use the same batch of ink (preparation of spot color ink is best a sufficient amount of modulation) printing, because different batches of ink is difficult to ensure that there is no difference in color. If the ink color deviation is too large, it is difficult to control the consistency of printing ink through other methods, especially when printing layers.

Secondly, the amount of ink added to the ink tank each time in the printing process is required to be less, in order to maintain the frequent addition of new ink. Especially for the small amount of ink patterns, if the amount of ink is too much, the ink will be oxidized and become old when exposed to the air for a long time, such as black ink with gray, not so black as new ink; Old red ink will turn dark red, not as bright as new ink. In the printing process, it is necessary to strictly control the volatile speed of the mixed solvent used in the ink. When the volatile speed is too fast, the transfer rate of the ink may be reduced, and then affect the color of the printing.

In addition, in the use of two component ink to fully stir, less frequently matched. Otherwise, it is difficult to maintain the stability of ink viscosity, and may also cause other printing failures.

Two, scraper

The contact position, Angle and pressure between the scraper and the plate drum have a great influence on the ink color of the printing, especially the ink color of the shallow layer, so the ideal state is that the scraper is in the same position from beginning to end. However, due to various reasons, the position, Angle and pressure of the scraper have to be adjusted in the printing process, so we must understand the influence of its change on the printing color and take corresponding measures.

The contact position between the scraper and the plate drum determines the distance between the knife and the plate contact point and the imprint point. The length of the distance should be adjusted according to the printing speed, ink viscosity, mesh depth, layout quality, etc. Generally speaking, the longer the distance, the greater the drying degree of ink in the net hole, the lower the transfer rate of ink. In terms of its impact on the printing effect, it is equivalent to the partial withdrawal of the ink color. At the same time, the long distance is also a test of ink adaptability. On the contrary, the distance is short, the transfer rate of ink is relatively high, but also make the page on some small grain transfer to the printing material.

The Angle of the scraper is the Angle between the tangent line of the contact point between the scraper blade and the plate drum and the scraper. Improve the scraper Angle, easy to clean the ink of the layout, make the picture and text clear, but also may produce the ink layer is too thin, the ink film luster is poor, but also easy to damage the plate drum. On the contrary, reduce the Angle of the scraper, the printing ink layer becomes thicker, the printing luster is good, but the picture and text corners are easy to blur.

The pressure of scraper also has a certain influence on the ink color, the ink color becomes lighter when the pressure increases. Printing ink tends to get darker when the pressure gets lighter.

Three, printing plate drum

The influence of plate drum on ink consistency is mainly manifested in the following aspects:

1, blocked version: blocked version because of some reason caused by the network point blockage (ink curing, high viscosity or foreign body insoluble matter caused by) and caused by the phenomenon of reduced transfer rate. At this time, the transfer of ink is reduced, thus affecting the hue. Block plate when the occurrence of solvent or special cleaning agent (the use of general cleaning powder is easy to cause other failures) clean the plate drum, at the same time for blocking the cause of the corresponding measures to be taken, so that it can return to normal.

Blocking the plate of many factors, in addition to the use of two-component ink and other easy to cause chemical reactions when the ink chemical changes caused by insoluble factors, other reasons can be summarized as ink dry solid in the layout, mixed with impurities, plate quality is low and other factors. In addition, in the printing process such as ink mixed with water or other types of ink, it will affect the fluidity of the ink, resulting in pigment recondensation, will also produce blocking plate fault.

In addition, before printing to the plate drum for detailed inspection. If the printing plate drum adheres to oil, etc., it will produce printing faults similar to blocking plate during printing.

2, printing plate drum wear

When the printing volume is larger, the printing plate drum wear degree is larger, the printing ink color will change, generally speaking, it tends to become lighter (because the net hole becomes lighter, the amount of ink is reduced). Therefore, after a certain number of printing after the need to re - plated plate. Printing plate drum net shallow although can be adjusted through other processes to maintain the stability of the color, but after excessive use will lose the value of re plating plate, only re plate.

Printing plate drum in the use of the process may also occur a variety of failures and damage. Due to many influencing factors in plate making, it is almost impossible to completely repeat the original plate making process conditions, so after plate making, even under the same printing conditions, it is often difficult to obtain the exact same printing effect with the original. In order to solve this problem, if the printing batch is large and frequently printed live parts, you can consider making two sets of plates or even multiple sets of plates to solve the problem.

3. Printing plate design and color management

The influence of printing and post-press processing technology should be fully considered in plate design. For example, the color of some dot areas is easy to occur and level, in the plate to deal with. Many plate-making enterprises have begun to use color management software, which has played a positive role in improving the quality of color restoration.

Four, printing conditions and environment

In the printing process, the color of the ink film mainly depends on the ink concentration and transfer rate. For a specific substrate and a specific ink, the concentration of ink is relatively fixed, and the transfer rate depends on the ink viscosity, dryness and layout network conditions and other factors, but also by the printing speed, printing pressure, scraper pressure, scraper position, scraper Angle and environmental conditions (temperature and humidity) and other factors. It needs to be pointed out here that these conditions change on the printing of the highlight, dark, intermediate degree of influence is different.

1, ink viscosity and drying speed change:

Ink viscosity changes can directly affect the color of printing. When the viscosity is high, the color concentration is relatively high, conversely, when the viscosity is low, the color concentration is also relatively low. This effect can sometimes be quite obvious and must be taken seriously. According to the requirements of the printing process, the viscosity of the ink should be moderate, too large viscosity is not conducive to the transfer of ink, easy to produce paste plate phenomenon; Too small viscosity is prone to electrostatic phenomenon, which is not conducive to the control of ink color.

The change in ink viscosity has a subtle effect on the area of ink drift or dot flow, especially in multi-color printing. Therefore, when the printing speed is certain, the viscosity of the ink is required to remain consistent from beginning to end. It is best to use the automatic viscosity control instrument.

When the proportion of solvent in ink changes, the drying speed of ink will change, and then affect the transfer rate of ink and printing color. For some less ink, placed in the ink tank and used for a period of time, due to the automatic volatilization of the solvent, not only will affect the viscosity of the ink, but also will affect the proportion of solvent and volatilization speed, so to timely add the solvent.

2. Changes in ambient temperature and humidity

Room temperature and ink liquid temperature if there is a large change, ink flow state will change, the tone will also change.

This is because the temperature changes affect the ink viscosity. At the same time, high temperature, low temperature weather to highlight the ink transfer rate will have a significant impact. Therefore, when printing high-grade products, in any case, the temperature and humidity of the printing workshop should be controlled. In addition, when using ink in winter to preheat in advance, in order to reduce the temperature of the ink itself.

3. Separation of synthetic colors:

This phenomenon is likely to occur in light colors and mixtures of different specific weights such as organic and inorganic pigments. Especially when the ink in the ink tank does not flow, precipitation will promote the separation of synthetic color, so pay attention to the smooth ink cycle. In addition, when mixing, such as insufficient mixing, with the printing process, the concentration of a certain color has a tendency to increase, so before the formal printing machine should be used such as mechanical or other methods to fully stir the ink.

4, ink deterioration makes color worse

Due to a long time printing, ink solvent composition changes, or moisture in the air mixed with ink to cause ink deterioration, so that the color deteriorates.

In order to prevent the ink temperature drop due to the heat of vaporization, you can use a slow drying solvent. In high temperature, high humidity weather, there may be a certain amount of water mixed with ink, abnormal in the occurrence of new ink should be added, or all replaced, used many times the remaining ink due to mixed into a lot of dust, should be regularly filtered or abandoned.

5. Other printing conditions

Printing discoloration will occur due to overlapping dots and irregular wind exposure to the layout, or changes in printing speed and drying speed.

Five, the impact of post-press processing

1. Changes in post-press processing technology:

The use of different post-press processing (such as extrusion compound and dry compound) on the printing color also has a certain impact. At the same time, extrusion compound sometimes causes pigment changes at high temperature. In addition, when heat sealing is carried out at a temperature above 200℃, the hue of the heating part may become darker, which is due to the melting of the heating colorant and the formation of micro-crystallization when recrystallization occurs during cooling, causing the coloring power to rise.

2, the change of post-press processing substrate:

The change of substrate in post-press processing, such as the change of aluminum layer of aluminized film, will directly affect the overall hue. Of course, printing substrate color bias will also have a slight impact on the overall hue.

3. Photochemical reaction:

When the ink colorant light resistance, weather resistance is poor, may cause the printing color changes due to photochemical reactions.

4. Influence of packaging contents:

When the contents contain volatile and migratory active substances, the color of the package printing may also change due to corrosion. Therefore, we should choose the appropriate ink according to the end use of packaging printing products (or negotiate with ink manufacturers).

Six, naked eye viewing and use of color control instrument detection

Customers expect a high degree of consistency in the ink color of packaging prints, but the results of everyone observing the color are not exactly the same. What customers need is persuasive data, namely quantitative data of color. Although the naked eye is good at seeing colors, it is not good at remembering colors (it cannot accurately measure colors unless products are placed side by side). Therefore, the naked eye is no longer considered a reliable guarantee of determining ink colors. From the naked eye to the light density meter, colorimeter and then to the spectrophotometer, the development of the desktop spectrophotometer now, the color measurement results are more accurate, enough to make up for the human eye fatigue effect, visual retention, visual memory and other adverse effects on the color observation. Of course, it still needs time to use color control instrument extensively in our country.

As part of the color management process, color detection is an indispensable step and the first step of color management. At the same time, the color stability will be affected at any time in the process of printing press, so the use of online color control device to measure and monitor the color stability will be an important development trend.