Third, light box advertising pattern production process
The color of the light box pattern printing is superior to the graphics and the presentation in visual communication. Whether each element can truly reproduce the intention of the advertising designer and play the best effect of visual communication, it is necessary to buy through various printing methods. The color pattern reproduction principle of the light box is based on gradation reproduction. In order to meet the requirements of the printing process, the screen images, photographic screens, or electronic color screens are used to decompose images of successively tuned originals into dots similar to a mosaic shape. The human eye cannot distinguish between different density levels at the observation distance. The image pixel network points achieve a continuous tone visual effect on the viewing distance.
Regardless of which printing process is used, the level and clarity of the manuscript should be reproduced as efficiently as possible on the printed matter. Select the original to consider: five factors: color, tone value, structure, color saturation, and morphology.
The key to color tone reproduction is color separation screening, which is based on the surface properties of the substrate (smoothness, roughness, texture, and absorbency); the size and viewing distance of the printed material; The scope of contrast and the role of subtle layers; printing ink (particle size, viscosity, drying characteristics of pigment); color intensity and light resistance; printing speed
1. Determine the number of color separation screens:
People are not distorted when viewed from distances away from prints, but can also be reproduced in subtle levels with hue and saturation in the normal range. This should fully consider the relationship between the screen and the viewing distance (see Table 3).
table 3
Printed web inspection distance screening number/cm
A5 below 0.5m 36 to 48
A4 0.5 or less 24-36
A3 0.5 to 1m 18 to 24
A2 1～3m 15～20
A1 2～5m 12～18
A0 3～10m 12～15
More large-scale 3 ~ 20m 6 ~ 12
2. The choice of screening angle:
Choosing a good screening angle is an important part of reducing the appearance of moire. In color reproduction, different color separations must use different screening angles in order to suppress moiré as much as possible. For this reason, the difference between screen angles is 30° for eye-catching colors (cyan, magenta, black). The yellow version is an unobtrusive color and can be written with a 15° difference between other colors, such as the specific screening angle of a four-tone tone screen (see Table 4).
Table 4
Image main colors
Screen angle
Huang Pinhong Qing Hei
The main color is black 0° 15° 75° 45°
The main colors are yellow and magenta (skin color can be orange) 0° 45° 75° 15°
The main colors are yellow and green (green tone) 0° 15° 45° 75°
3. Color inkjet printing technology applications:
Inkjet printing is a non-pressure printing method that uses computer control to take fine ink flow from a nozzle onto a substrate to obtain text and images. It integrates electronics, machinery, fluids, ultrasound, microcomputer and other multi-disciplinary technologies and has become one of the high-tech fields in the field of color printing. Due to the use of ink jet printing technology in outdoor large-scale advertisements in recent years, the color tone levels, sharpness, and color saturation of advertisement patterns have reached a near-perfect level.
(1) Inkjet printing composition system:
Inkjet printing system consists of system controller, inkjet controller, nozzle, substrate drive mechanism, substrate and other components.
The output ink dot of the inkjet printing system is a key factor in determining the print quality. The size of ink dots is expressed in dots per inch. Color screen printing is generally 300dpi, 600dpi, 720dpi, 1024dpi, etc. Some large-format advertising poster printing can meet the requirements with 9-72dpi.
(2) Types of ink jet printers:
Inkjet printers can be classified into two categories, continuous inkjet printers and intermittent inkjet printers (see Figure 1).
(3) Color inkjet printing:
The main body of the color ink jet printing system receives color information through a variety of different information sources, such as color graphic terminals, color scanners, digital cameras, color word processors, and various analog or digital document collection systems. The information source sends the three primary color red, green, and blue information of spring light to the printer interface, and stores the information to be copied into the main memory. Then the color converter converts the red, green, and blue color information to blue and magenta. The color separation and screening signals of the four-color inks of yellow, black and black are controlled by a gray controller and the ink signals of the above four colors are respectively sent to the electrodes of the corresponding color nozzles to control the ink jets of the nozzles.
(4) Inkjet printing materials:
a. Coloring material:
High-grade special inks for yellow (Y), magenta (M), cyan (C), and black (K) inks for color inkjets. The printing performance must be stable, non-toxic, non-blocking, and has good jetting properties. , such as a liquid ink performance indicators (see Table 5).
table 5
Relative density (g/ml) Surface tension (n/m) Viscosity (pa·s) Resistivity (Ω/an) Particle size (μm) pH Drying time (S)
0.8-1.0 0.02-0.03 0.0015-0.003 100-500 <0.1 6.5-8.5 0.1
At present, a wax-based solid ink is widely used. Its coloring material is a pigment, which has excellent light resistance and is not easy to fade. The printing process is fixed on the surface of the substrate and does not penetrate into the interior of the substrate. The print has a good definition.
b. Printing materials:
The types of printing materials that can be used are special paper, inkjet film and light box cloth. In terms of paper, in order to prevent ink dots from spreading on the paper, the surface of the paper is required to be smooth. High-gloss photographic paper is generally used, and its surface is coated with a very thin transparent coating.
4. Color screen printing technology application:
Screen printing is an ancient and unique printing technology. The author once described the application of screen printing technology in the title of “Application of Any Light Box Advertising in Color Silk Screen Technology†in the issue of “China Printing†magazine, Issue 10 of 2001. Screen printing has advantages that are not available in other printing methods. The application of various types of outdoor advertising occupies a considerable proportion, and it has the advantage of being capable of mass copying and low cost.
(1) The key to color screen printing lies in the process of making color continuous tone images. The following issues should be considered in the process of plate making:
a. The magnification of the image must take into account the proportion of the screen.
b. The original version of the normal situation is a positive image, but if it is printed on the transparent material surface, the original version should be positive.
c. Yellow, magenta, cyan and black four-color film screen angle should not only avoid mutual interference and appearance of moire, but also consider the influence of the screen's latitude and longitude on the color reproduction.
(2) Matters needing attention in material selection and process:
a. All four frames must use metal frames, and the specifications must be exactly the same.
b. Wire mesh should be used with high-precision, halo-resistant dyeing screens, the number of which is determined by the magnification of the printed pattern.
C. When stretching the net, the four plates should be on the same device or under the same conditions. It is advisable to use the “one net stretch four†method to ensure that the tension and accuracy of the four mesh frames are consistent. The stretched mesh should be placed for 1 to 2 days before use to ensure that it is fully "relaxed."
d. The direct method is used to make the template, and the coating thickness of the photosensitive adhesive should be uniform. Keep the pumping, light source, exposure time and development on the same rung (with the step scale). The template should be kept and used under the specified conditions.
e. Large or precision screen printers are used for printing. The operating room temperature is controlled between 18°C ​​and 25°C, and the humidity is controlled within the range of 50% to 70%.
f. The net distance of printing should be as small as possible to improve overprint accuracy and reduce moire phenomenon.
g. The length of the squeegee should be the same and the pressure is small. The squeegee angle is about 75° to 80°, and the hardness is slightly larger, ie, the Shore hardness is about 70, and the cutting edge should be sharp.
h. The uniform ink should be thin (approximately 20 μm) and uniform to prevent the ink from filling the mesh.
i. The choice of ink must match that of the receiving material, and the spectral characteristics of the three primary inks should be better, the transparency should be higher, the viscosity can be slightly larger, making the outlet stand up and avoid expanding. Slow-drying, imprinting, and quick-drying inks on plates should be used.
j. Various printing materials must be processed properly before printing.
k. Printing color sequence is generally used to print darker non-principal color, after the main color printing, in order to overprint: If the color sequence on the transparent plastic material should be reversed mining, and need to first print the background color, and then press Color sequence overprinting.