The Characteristics and Process Arrangement of Paper Packaging Screen Printing Method

Paper packaging mainly refers to cartons, cartons, paper bags, etc. used in the packaging of goods, and corrugated boxes used for transportation and packaging. Screen printing has the characteristics of thick ink layer, rich graphic layers, strong three-dimensional sense, and wide printing materials, and has gradually increased in the application of high-end tobacco and alcohol, food packaging cartons. The use of UV screen inks to print scrubs, refractions, ice and wrinkles on cigarette packs has greatly stimulated consumers’ desire to purchase.

Screen printing features and process arrangements

1. Screen printing process arrangement

Screen printing is a direct printing method, there are three kinds of process arrangements:

1 Cardboard → Screen Printing → Post-press processing, that is, first screen printing on corrugated cardboard or other cardboard, and then making cartons and cartons as required;
2 cartons → screen printing, that is, directly on the prepared corrugated boxes or other cartons, cartons for screen printing;
3 Secondary processing, that is, first screen printing on the surface board, and then made into corrugated cardboard according to need, and then made into cartons, cartons products.

2. Screen printing features

1 Wide adaptability: Screen printing format can be large or small;
2 Ink thick: In all printing processes, the screen printing ink layer is the thickest, the saturation is high, the spot color printing effect is better;
3 Low cost: Easy screen printing and simple printing process;
4 print quality and stability;
5 low production efficiency: screen printing speed is slow, not suitable for online production;
6 The image has low precision: the resolution of screen printing is not high, and the number of conventional screen lines is 24 lines/cm to 32 lines/cm.

3 screen printing application

Screen printing is suitable for small batch production, high printing appearance requirements, unlimited cardboard thickness, and no damage to the packaging products.

Screen printing process

1. Screen printing

(1) Screen selection

1 Nylon wire mesh: Nylon wire mesh has high strength, high abrasion resistance, high alkali resistance, slightly poor acid resistance, good ink permeability, small wire diameter, good elasticity, and vivid marking;
2 Polyester Mesh: Polyester Mesh has good stability, high strength, corrosion resistance, better performance than nylon mesh, high stretch tension, suitable for high-precision printing;
3 stainless steel wire mesh: Stainless steel wire mesh has high strength, good stability, small wire diameter, high mesh, good resistance, long life, poor elasticity, easy to break by impact, suitable for precision printing, not suitable for curved surface printing;
4 Nickel-plated polyester mesh: Nickel-plated polyester mesh combines the strengths of polyester mesh and stainless steel mesh. It has wide applicability, moderate price, and poor corrosion resistance.

The screen has a plain weave, a twill weave, a half weave, and a full weave. White screens can cause diffuse reflection when exposed, and golden, red, and amber absorb ultraviolet light and prevent halation. The number of screen meshes is 30 mesh/cm, 40 mesh/cm, 60 mesh/cm, 80 mesh/cm, 120 mesh/cm, 140 mesh/cm, and 160 mesh/cm. In general, mesh The number is large and the mesh is small. Filament dense mesh with high resolution; thick coarse mesh with low resolution. When printing curved surfaces, use a large flexible screen, such as nylon mesh; when printing large absorbent substrates, use a screen with a large mesh area; when printing smooth surfaces, use a high elasticity, high tension screen; printing rough surface When using low-mesh screens, low-elongation, high-tension screens are used for high-precision prints, and 28 mesh/cm~78 mesh/cm screens are used for printing signs, textiles, and knitwear; For paper, metal, glass, leather, and plastic, use a mesh of 40 mesh/cm to 140 mesh/cm.

(2) stretch net

Screen frame net frame has wooden frame, metal frame, plastic frame, combo box and so on. When the net is stretched, the net frame is first cleaned, and the net can be manually, mechanically or pneumatically applied, and the nets can be bonded and trimmed after stretching. Stretch net requires proper screen tension, uniform and stable, uniform wire, avoid oblique pull, and the warp and weft yarns are parallel to each other.

(3) Plate Making

1 Direct method: Screen cleaning → Photosensitive adhesive → Printing → Developing → Retouching. This method is time-consuming coating, adjustable film thickness, combined with a solid, resistant to India, the image is easy to saw out.
2 indirect method: photosensitive film → printing → development → film → film base → repair. This method is complicated to operate, the lines are smooth, the film is not strong, the resistance to printing is low, and the thickness of the film is constant.
3 mixing method: screen cleaning → foil → printing → development → revision. This method is easy to operate, has a fixed thickness, a smoother line, and is more rigid.

(4) Direct Screen Plate Making

The screen-to-plate version is referred to as CTS (Computer To Screen).

1 Laser Ablation Direct Platemaking: First apply a stencil sensitized film on a metal wire mesh, burn through the sensitized layer with a laser, the mesh of the graphic part is transparent, and the pre-press system controls the ablation place. This method can only be used for metal. network.
2 laser exposure direct plate-making: first coated with photosensitive emulsion on the screen, pre-press system computer-controlled laser imaging on the screen, made of screen version. This plate-making method uses special photo-resist, the ultraviolet light wave range is narrow, and the laser exposure system is expensive.
3 inkjet imaging system: First coated with photosensitive adhesive on the screen, pre-press system computer-controlled inkjet system to block the light-emitting ink to the photo-sensitive layer, and then full UV exposure. The part of the image is not sensitive, and the photosensitive resist is washed away; This method can use ordinary photosensitive adhesive, without losing details of the image.

Screen printing machine

Screen printers have manual screen printers, semi-automatic screen printers, and automatic screen printers. There are also open-book type, table lift, slide table, roller table, curved work table, curved type, roller screen type, double drum screen printing machine, according to the need to choose.

3. Special screen printing methods

1UV imitation metal etching printing UV (ultraviolet) imitation metal etching printing is printed on the substrate with a metallic mirror gloss after a layer of rugged translucent ink, after UV curing, similar to the shiny metal surface is etched or frosted effect. The prints are elegant and luxurious and are used for high-end packaging. This printing method uses a UV-curable imitation metal etching ink. The substrate is gold cardboard, silver cardboard, or a composite material, and the mesh is from 70 mesh/cm to 100 mesh/cm.
2UV wrinkle pattern ink printing UV wrinkle pattern ink printing is UV wrinkle ink printed on the surface of the substrate after UV curing to form a special wrinkle pattern decorative effect. This printing method uses 40 mesh/cm~60 mesh/cm mesh, and the ink film thickness is 20~30μ.
3 Ice effect printing The ice effect printing is on the surface of the substrate with metallic luster. Ice silk ink is printed on it with silk screen, and after being cured by ultraviolet rays, it shows an ice pattern. The printing material of this printing method is a gold and silver cardboard, and a mesh of 60 mesh/cm~100 mesh/cm is used.
4 Foaming Printing Foaming printing is the use of micro-ballooning inks, which are printed on paper or other substrates with silk screens. The images are raised and widely used in the printing of bookbinding, braille, maps, and packaging. This printing method uses 30 mesh/cm to 50 mesh/cm mesh.

Screens can also be used for scented ink screen printing, pearl ink screen printing, liquid crystal ink screen printing, phosphor ink screen printing, fluorescent ink screen printing, crystal glossy screen printing and so on.

High-speed rotary screen printing production line

Due to the flat press screen printing method, the printing speed is low, the ink curing speed is slow, the printing quality is difficult to control, and the printing material consumes a large amount, which can not meet the needs of cigarette cartons for scale and mass production. High-speed rotary screen printing production line, fast printing speed, high productivity, stable quality of printing products, low consumption, change the traditional flat pressure flat screen printing, manual feeding, ink supply, suitable for high-speed automatic, large-scale mass production of exquisite Fold the tray.

Web Rotation Screen printing uses a nickel metal round screen plate, a built-in doctor blade, and an automatic ink supply system. The doctor blade transfers the printing ink from the circular screen plate to the surface of the substrate supported by the impression cylinder. The entire printing process from paper feeding, ink supply, color registration, UV drying, etc. are fully controlled by the computer.

The round screen printing plate is suitable for large-format rotary printing, the maximum speed can reach 125m/min, and the screen can be used repeatedly. Therefore, roll web screen printing can not only meet the requirements of special effects such as printing frosting and ice flower, but also can be used to hot-stamp holographic anti-counterfeit labels, embossed dentifrices and die-cutting indents, making it easy to realize high-speed automatic printing of paper boxes.

Source: China Packaging News