The packaging and printing process includes offset printing, gravure printing, flexo printing, special printing, etc. The types of substrates are much more complicated and complicated than commercial printing. The printing characteristics are also different from those of commercial printing. Therefore, digital printing of packaging and printing needs to be achieved. The considerations are far more complex than four-color printing and require different proofing schemes for different characteristics of the printing process. At present, digital proofing methods that are mainly applied in the field of packaging and printing include inkjet printing, ribbon printing, and thermal sublimation. Various proofing methods meet different requirements to a certain extent, but at present there is almost no proofing technology that can be comprehensive. To meet the needs of packaging and proofing, digital proofing in the field of packaging and printing still has a lot of room for development.
First, digital proofing how to achieve spot color proofing
In the traditional proofing and printing, the spot color is achieved by spot color ink to achieve spot color proofing and printing. In the digital proofing system of the ink-jet type, the ink in the printing apparatus is generally used to simulate a spot color according to a certain proportion of printing, and in the printing of the ribbon, a corresponding spot color band can be used to achieve the proofing requirement.
1. Spot color characteristics
In the typesetting software, spot color is defined in the field, and no matter how light it is printed, it is printed in the field. Of course, spot colors can be added to display any shades of light, called shallow meshes. Defining spot colors with separate channels in image processing software such as Photoshop.
Since each spot color has a fixed hue, the accuracy of printing colors can be guaranteed, and the accuracy of color transfer is greatly solved, especially when certain standard colors require very accurate color, or the substrate is printed in four colors. In the case of difficult control, spot colors are generally used. On the other hand, the color range of spot colors is larger than the range of four colors, and some colors cannot be represented by CMYK four colors at all.
Printing using spot colors increases the cost of printing. Therefore, high-fidelity five-color, six-color, and seven-color color separation models are used for printing in addition to four-color printing, thereby improving the color gamut of four-color printing and reducing the printing cost.
2. Digital proofing how to spot color proofing
The principle of printing spot colors through ribbons is relatively simple: Use ribbons corresponding to spot colors for printing to print. This method can be used for gold and silver proofing, but sometimes the sample will appear obvious bars, four-color proofing is worse than inkjet printing, it is difficult to meet the same format with four colors and spot colors.
The ink jet method cannot realize the simulation of some special colors such as gold and silver, but most of the spot color simulation can be realized when the corresponding equipment and software are selected. Here I use the BlackMagic digital proofing system as an example to introduce the process of spot color proofing.
(1) Define the spot color in the typesetting software, define the spot color with the Pantone color base in Illustrator, and store the file as SOPT1.ai.
(2) Print this file PS and name it spot.ps. Be careful not to choose to convert spot colors to four colors.
(3) Explain the file with HQ-RIP. The spot color of this file is separated into independent color version.
(4) In the BlackMagic digital proofing system, the spot color library of the typesetting software can be transferred into the system, and a special color can also be newly created in the system, thereby realizing the spot color defined in the typesetting file when digital proofing is performed. correspond. The spot colors defined in the SPOT1.ai file in the BlackMagic software are directly called into the digital proofing spot color library.
(5) After the RIP-interpreted file is detected by BlackMagic's data monitor, the operator can submit the color-separated spot color file to the spot color version defined by the imported spot color library to complete spot color proofing.
Second, digital proofing how to meet the needs of different types of substrate proofing
There are various kinds of substrates in packaging and printing, and the surface of digitally-printed substrates must contain a print coating. Therefore, digital proofing generally uses limited types of substrates for effect simulation to represent different types of actual printing results. For example, iron printing is used for packaging in the printing process, but iron proofing is not generally used for direct proofing in the printing process. Instead, a printed sheet with the same effect as the iron sheet is selected to simulate the proofing effect.
Due to the differences in the process, ink and substrate of the packaging and printing, the final ink phase and the overprint ratio of the printing are greatly different from the four-color offset printing. In the digital proofing, the linear and color space adjustment of each channel is used to achieve Simulate the characteristics of different processes.
Different types of packaging and printing substrates, their spectral characteristics and light reflection conditions are also inconsistent, so in the color measurement also need to choose different measurement tools and measurement methods. For example, in the color measurement of plastic products and metal products, it is necessary to consider the reflection characteristics of light from the two media.
At present, most of the digital proofing in the packaging industry can only perform color simulations, but seldom involve digital control of the characteristics of gloss, reflection characteristics, etc., but the proofing of packaging and printing will increase with the increasing demand for proofing and continuous technology. Development and continuous improvement and improvement.
Source: Digital Printing