Interpretation of Thermal Imaging Digital Printing Technology (2)

Generally speaking, dye layers contain sublimation dyes, binders, etc. Among them, the general requirements for sublimation dyes are high sublimability, good storage stability at room temperature, good heat resistance, and no heat generation under heating conditions of the heating head. Decomposition; good color reproducibility; high molecular light absorption coefficient; good resistance to light, moisture, and chemicals; high solubility to water-binding resins or high particle dispersibility.
2 dye receptors

The basic structure of the dye-receiver is shown in Figure 6. The support is first coated on the support and the dye-receiving layer is coated on the top. In general, the support is required to have heat resistance, homogeneity, smooth surface, and a certain degree of flexibility. The thickness is generally 100 to 200 μm, and the base may be a transparent film or various plastic films such as polyolefins.

The dye-receiving layer is intended to receive dyes that have been heat-transmitted from the dye-donor. The dye-receiving layer generally contains an absorbable resin, such as polyester, in order to improve the clarity of the transferred image, improve the whiteness of the receiving layer, improve the retransfer of the protective transfer image, and impart rewrite stability to the receiving surface. A white pigment can also be added to the layer. This pigment is generally titanium oxide. In order to better improve the light resistance of the transferred image, UV absorbers, light stabilizers, antioxidants, and the like may also be added. In order to improve the release performance, a release agent may be added to the dye receiving layer, and a solid wax or the like may be generally used as a release agent.

There may also be one or more intermediate layers between the film base and the receiving layer. The intermediate layer plays a different role depending on the material and can play a role in buffering, loosening the dye diffusion resistance, and can also satisfy two or more functions. Can also be used as adhesion layer, such as dye diffusion layer is to prevent dye diffusion to the substrate, the adhesive used for these layers, can be water soluble, but also oil soluble, but is commonly used water soluble, especially gelatin.

3) thermal transfer imaging and thermal sublimation imaging material structure characteristics

The sublimation imaging material is a sublimation dye in a heated part that transfers in a single molecular form. The film-forming resin and other components as the dispersed phase do not transfer with the dye molecules, while the heat transfer imaging material transfers all the components in the heated part. Therefore, the coating structure and production process of the sublimation type image forming material are much more complicated than the thermal transfer image forming material. The sublimation type heat transfer image forming material is usually designed as a multi-coating structure. Among them, at least two coatings contain a sublimation dye, that is, at least one dye supply layer, hereinafter referred to as a lower layer and a dye diffusion layer, hereinafter referred to as an upper layer, and the lower layer is capable of releasing a dye more than the upper layer. That is, if the lower layer and the upper layer are separately coated on the same support, respectively, and they are respectively combined with the same image-receiving paper, and heat transfer is performed by heating with the same thermal head or laser, the transfer to the image-receiving paper is performed. The optical density of the dye on the upper layer should be greater than the upper layer, so that in multiple thermal transfer printing, the dye density obtained by each printing does not decrease evenly.

4 Sublimation Printing Features

1) High quality image and photo output function

Since the shade of each color of the dye sublimation printer is controlled by the temperature of the print head, and each color point of the print can show a 256-level change in concentration, the pigment is applied to the paper by the vapor phase during the sublimation process. The primary colors merge to form a continuous color gradation. Furthermore, since the color thermal sublimation printer does not have the problem of ink droplet diffusion, its actual resolution has reached a very ideal level. 300 dpi thermal sublimation printing is equivalent to 4800×4800 dpi color The effect of inkjet printing. Therefore, in terms of printing effects, images printed using sublimation can be as fine as a spray, lubricated, and the color fidelity and reproducibility of printed images are superior to those of inkjet printers and color laser printers.

2) Long-term preservation does not fade

When using a sublimation printer to output images, the printer will apply a protective film to the image. This function is unique to dye-sublimation printers. After the image is applied to the film, the photos are not only waterproof but also anti-oxidant. Compared with traditional inkjet printers, the photos are much longer, have long-lasting preservation and do not fade, and their overall color feel will be brighter and brighter.