Self-adhesive printing materials and their printability

Self-adhesive materials, also known as self-adhesive materials, pressure-sensitive materials or sticky notes, are the basic materials for label printing and are mainly used for packaging, decoration and printing.

Self-adhesive materials can be divided into self-adhesive printing materials, decoration materials, sealing materials, and special materials according to their different uses. Here, the adhesive printing materials are mainly introduced.

The basic composition of sticker printing material. It consists of a surface print layer, an adhesive layer, and a release layer.

Surface printing layer

The surface printing layer generally uses the following two materials, namely, a paper-based printing layer and a thin film printing layer.

(1) Paper-based printing layer. Paper-based printing layers currently use more offset paper, coated paper, bright and colored light and fluorescent paper, aluminum foil and other special paper. The requirements for the paper-based printing layer should comply with relevant national standards.

(2) Thin film print layer. Thin film print layers include the following types.

1 transparent film. The transparent film is divided into a composite film and a printing film.

Composite film. Mainly polypropylene film (PP), polyethylene film (PE) and polyvinyl chloride film (PVC) and so on. Printing film. Mainly include polyester film (PET), polyethylene film (PE) and polyvinyl chloride film (PVC).

2 translucent film. Including polyester film (PET) and polyethylene film (PE).

3 opaque film. There are mainly gold polyester film and silver polyester film.

4 color film. General use polyvinyl chloride film.

5 special film.

2. Adhesive layer

The adhesive layer is closely related to the performance and application range of the adhesive printing material and is one of the important performance indicators of the adhesive printing material.

There are three types of adhesives: rubber, resin, and hybrid.

The main performance indicators for adhesives are as follows:

Coating thickness: 0.02±0.005mm;

Viscosity (25°C): 6±0.5Pa·s;

Solid content: (30 ~ 33)%;

180° peel strength: ≥1000 g/2.5 cm (10 cm/min).

Use should be based on purpose and performance parameters for a reasonable choice.

3. Peeling layer

Applying silicone oil on the surface of paper or film substrate to prevent the adhesive from sticking to the peeling layer substrate, and at the same time guaranteeing a certain adhesiveness between the surface printing layer and the peeling substrate layer for printing and Die cutting and so on.

The base material of the release layer includes two types, a paper base material and a film base material.

1 paper substrate. There are two types of paper substrates, translucent paper and polykraft paper. Most of them are translucent paper type, and the polykraft paper is used only as a base paper such as a sealing tape.

2 film substrate. This substrate is a high-grade substrate with good dimensional stability and light resistance, mainly polyester film type and polypropylene film type. This type of substrate is limited to high-end products because of its high price.

The above-mentioned various surface printing layers, peeling layers and adhesive layers can be combined in various ways to produce adhesive printing materials with different properties and different specifications. Users can make reasonable selections according to product requirements.

Printability

Printability refers to the total performance of substrates, printing inks, and other materials that are compatible with printing conditions and suitable for printing operations.

In the label printing, different printing methods and imprinting methods have different printing conditions, so there are different requirements for substrates and inks. However, at present, most of them use letterpress printing. Letterpress printing accounts for more than 70% of the total amount of sticker printing, and most of them use flat-press or flat-press imprint methods. Therefore, it is mainly aimed at some properties of paper and film substrates that are suitable for relief printing.

1. Printability of paper printing

In addition to meeting the printability requirements of general letterpress printing, the printability of paper printing should also pay attention to the printability problems associated with label printing.

Different from the technical scheme of label relief printing, the requirements for printability are also different. The process scheme includes the following: the printing process scheme multi-color overprinting or postpress bronzing + laminating + bronzing + lamination

1 color block and line printing. For color and line printing, because of the large amount of ink required, the printing unit should be able to provide a larger amount of ink, but the adhesive printing surface is smooth, the density of the substrate is larger, and the ink layer is printed. It is not easy to conjunctiva. In order to improve the printability, in addition to the rational choice of fast-drying ink, but also pay attention to control the printing environment temperature and printing speed.

2 hot stamping. The bronzing process has been widely used in label printing, but in order to obtain a good printing effect, it is also necessary to pay attention to printability problems related to bronzing. If the printing machine is not equipped with a drying device, whether it is used after the first printing bronzing process, or after the first gold gilding printing process, the bronzing effect of the contact between the ink layer and the anodized aluminum will affect the quality of the printing product. Therefore, under normal circumstances the printing press should be equipped with a drying device to control the ambient temperature and printing speed. If fast drying inks are used, they can be stamped directly on the printed surface. If a photosensitive ink is used, since the ink layer is sufficiently cured prior to hot stamping, it will not affect the quality of the gold foil.

3 covered. Printing high-end label products, often in the printing process after the film, that is, transparent plastic film by hot pressing and affixed to the surface of the print, to protect and increase the role of gloss. The gilding process is generally not performed for the film-covered products because the surface of the film is not treated with polarity. If the bronzing is performed, the galvanized aluminum is not easily affixed to the surface of the film.

2. Film printing

Self-adhesive film printing method is basically the same as ordinary plastic film printing, but there are not many types of film suitable for letterpress printing. There are mainly polyester gold and silver stocks, transparent film and polyethylene film, which should be noted during use.

Thin-film relief printing process mainly includes the following three types: simple color printing, printing + hot stamping, and printing + laminating. Because the surface of the film is smooth, it is a non-absorbent material, so its drying speed is slow, the amount of ink should be controlled during printing, and the printing speed should be appropriately reduced to reasonably control the printing environment.

Preprint corona treatment for film printing is also an important step. For non-polar film substrates, corona treatment should be performed prior to printing to increase the surface polarity to meet the basic requirements for ink adhesion.

Reproduced from: China and Hong Kong silk screen network