Sticker printing materials
Self-adhesive materials, also known as self-adhesive materials, pressure-sensitive materials or sticky notes, are the basic materials for label printing, mainly used for packaging and decoration printing.
Adhesive materials can be divided into self-adhesive printing materials, decorative materials, sealing materials and special materials according to their different uses. Here mainly introduces self-adhesive printing materials.
The basic composition of stickers printing materials. It is mainly composed of surface printing layer, adhesive layer and peeling layer.
Surface printing layer
The materials used for the surface printing layer are generally the following two, namely the paper-based printing layer and the film printing layer.
(1) Paper-based printing layer. The paper-based printing layer currently uses a lot of offset paper, coated paper, various kinds of glossy paper and fluorescent paper, aluminum foil and other special paper. The requirements for the paper-based printed layer should meet the relevant national standards.
(2) Film printing layer. The film printing layer includes the following types.
â‘ Transparent film. Transparent films are divided into composite films and printing films.
Composite film. There are mainly polypropylene film (PP), polyethylene film (PE) and polyvinyl chloride film (PVC). Film for printing. Mainly include polyester film (PET), polyethylene film (PE) and polyvinyl chloride film (PVC).
â‘¡Translucent film. Including polyester film (PET) and polyethylene film (PE).
â‘¢ Opaque film. There are mainly golden polyester film and silver polyester film.
â‘£Color film. Polyvinyl chloride film is generally used.
⑤ Special film.
2. Adhesive layer
The adhesive layer is closely related to the performance and application range of the sticker printing materials, and is one of the important performance indexes of the sticker printing materials.
There are three types of adhesives: rubber type, resin type and mixed type.
The main performance indicators of the adhesive are as follows:
Coating thickness: 0.02 ± 0.005mm;
Viscosity (25 ℃): 6 ± 0.5 Pa? S;
Solid content: (30 ～ 33)%;
180 ° peel strength: ≥1000g / 2.5 cm (10cm / min).
Reasonable selection should be based on the use and performance parameters during use.
3. Peel off layer
It is made by coating silicone oil on the surface of the paper base or film substrate to prevent the adhesive from sticking to the peeling layer substrate, and at the same time, it can also ensure that the surface printing layer and the peeling substrate layer have a certain viscosity to facilitate printing and Die cutting, etc.
There are two types of substrates for the release layer: paper substrates and film substrates.
â‘ Paper substrate. There are two types of paper substrates: translucent paper type and multi-layer kraft paper type. Most of them adopt translucent paper type. The multi-layer kraft paper type is only used as base paper such as sealing strip.
â‘¡Film base material. This kind of substrate is a high-grade substrate with good dimensional stability and light resistance, mainly polyester film type and polypropylene film type. Because of its high price, this substrate is limited to labels for high-end products.
The above-mentioned various surface printing layers, peeling layers and adhesive layers can be combined in various ways to produce self-adhesive printing materials with different performances and different specifications, and users can make reasonable selections according to product requirements.
Printability
Printability refers to the overall performance of the substrate, printing ink, and other materials that match the printing conditions and are suitable for printing operations.
In the printing of adhesive labels, due to the different printing methods and imprinting methods, the printing conditions are different, so there are different requirements on the substrate and ink. But for now, most of them use letterpress printing, and letterpress printing accounts for more than 70% of the total amount of self-adhesive label printing, and most of them use flat-pressed or round flattened imprinting methods. Therefore, it is mainly aimed at some properties of paper and film substrates suitable for letterpress printing.
1. Printability of paper printing
In addition to the printability requirements of general letterpress printing, the printability of paper printing should also pay attention to the printability problems related to label printing.
The technical solutions for label relief printing are different, and the requirements for printability are also different.The process solutions are as follows, that is, the printing process scheme is multi-color overprint bronzing printing before or after printing + laminating printing + bronzing + laminating
â‘ Color block and line printing. For color block and line printing, due to the large amount of ink required, the printing unit should provide a large amount of ink transfer, but the sticker printing surface is smooth, the density of the substrate is large, and the ink layer after printing Not easy to conjunctiva, prone to rubbing faults. In order to improve the printability, in addition to the reasonable selection of bright and quick-drying ink, we must pay attention to control the printing environment temperature and printing speed.
â‘¡Bronzing. The bronzing process has been widely used in the printing of self-adhesive labels, but to obtain good printing results, attention should also be paid to the printability issues related to bronzing. If the printing machine is not equipped with a drying device, no matter whether the printing process is followed by the bronzing process, or if the printing process is followed by bronzing and printing process, the printing quality will be affected due to the reduction of the bronzing effect of the ink layer and the anodized aluminum. Therefore, in general, the printing machine should be equipped with a drying device, and control the ambient temperature and printing speed. If you use quick-drying ink, you can directly stamp on the printed surface after printing. If you use photosensitive ink, because the printing ink layer is fully cured before bronzing, it will not affect the quality of bronzing.
â‘¢Laminating. When printing high-end label products, the laminating process is often carried out after printing, that is, the transparent plastic film is pasted on the surface of the printed matter by hot pressing to protect and increase the gloss. The foil stamping process is generally not applied to the products after the film coating, because the surface of the film coating is not polarized. If the gold foil is stamped, the anodized aluminum is not easy to stick to the film surface.
2. Film printing
The printing method of self-adhesive film is basically the same as that of ordinary plastic film printing, but there are not many types of film suitable for letterpress printing, mainly including polyester gold and silver strands, transparent film and polyethylene film.
There are three main technical schemes for thin-film relief printing, namely simple color printing, printing + bronzing and printing + laminating. Due to the smooth surface of the film, it is a non-absorbent material, so its drying speed is slow, the amount of ink should be controlled during printing, the printing speed should be appropriately reduced, and the printing environment should be reasonably controlled.
The prepress corona treatment of film printing is also an important link. For non-polar film substrates, corona treatment should be performed before printing to increase the surface polarity to meet the basic requirements for ink adhesion.
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