Thermal sublimation printers are sensitive to dust. If dust enters the print head or ribbon, the print quality is likely to have a serious effect, such as the formation of a long thin white line, causing the entire photo to be scrapped. In addition, the thermal sublimation printer also has a high temperature requirement for the work. If it is continuously operated for a long time, the color accuracy may be affected due to poor heat dissipation.
Transfer of thermal imaging imaging materials
1) Thermal transfer imaging material
In general, thermal transfer imaging materials consist of a support heat-resistant smooth layer, a dye transfer layer.
The support of the ribbon must have good heat resistance, high strength, and low price. From these considerations, the PET film is the best material, and the thickness thereof is usually between 3.0 and 9.0 μm. However, in terms of improving the thermal conductivity, the resolution and reducing the weight and weight of the body, it is necessary to use a relatively thin film. material. As a support for a recording medium, a paper base is generally used.
The main function of the heat-resistant smooth layer is to reduce the friction and allow the thermal head to move back and forth without any hindrance on its surface, without being damaged. Therefore, it must have heat resistance, smoothness, no wear on the thermal head, no charge, and no adverse effects on the dye transfer layer. Its main components are highly heat resistant synthetic resins and various lubricious substances. A thermosetting cross-linked polymer may be used as needed to improve physical strength and heat resistance.
Melt-type dye transfer layers are mainly produced by mixing inorganic or organic pigments and binder resins due to the different transfer mechanisms. During heat transfer, all heated parts are transferred. The binder is mainly a wax-like substance and a small amount of synthetic resin having a low softening point. Depending on the use, the amount of wax can be reduced to increase the heat resistance, rubbing resistance, and chemical resistance of the image, and various types of synthetic resins are used.
The thermal transfer image forming material has a single-layered structure and a double-layered structure. The single-layered structure is shown in FIG. 4 and consists of a pigment, a filler, a wax or a resin, and a support. Among them, the role of fillers, such as Al2O3 particulate germanium, is to increase the heat transfer rate of the heat-sensitive coating, to melt the surrounding binder and wax as quickly as possible, and to accelerate the transfer of the binder and the color former.
The double-layer structure is shown in Fig. 5, which consists of a wax layer, a dye layer and a support. The dye diffuses into the molten wax coating under the action of a heat source, and the wax coating is transferred onto the receiving medium to form a print. The amount of dye molecules that enter the wax coating can be controlled by changing the thermal energy of the heat source, that is, the density of the resulting image is controlled, and there is a good linear relationship between the image density and the pulse width of the print signal.
2) Thermal Sublimation Imaging Materials
The final image formation effect of sublimation transfer is not only related to the printer but, more importantly, it is directly related to the imaging material. That is, the dye donor and the dye receiver that complete the image formation are the key to sublimation imaging.
1 dye donor
The basic structure of the dye-donor is shown in Figure 6, and usually consists of a very thin substrate, positive on the substrate. Both sides have a coating, the front of the substrate is coated with a dye layer, which includes a printing dye and a polymeric binder. There is also an auxiliary layer or layer between the dye layer and the substrate. The backside of the substrate is coated with a sliding layer. The purpose is to provide a lubricated surface to prevent the thermal print head from scratching.
The support substrate as a dye donor requires not only a flatness but also an abrupt change in temperature because the dye is to be transferred in sublimation during printing. According to the recording data requirements, the sudden temperature change is very frequent. The support that satisfies such conditions includes polyesters, and generally have a thickness of 2 μm to 30 μm.
The sliding layer is applied on the back of the substrate to protect it and prevent it from adhering to the print head. The sliding layer is usually required to be as thin and uniform as possible so as not to affect the degree of heat transfer; there is no effect on the thermal head, and no thermal head is contaminated; The layer has a bad influence and usually consists of a crosslinked resin and a lubricating material.
The dye layer may contain a single color dye or a continuous repeating region containing different color dyes, such as cyan, magenta, yellow, and black, and when the dye donor uses two or more main color dyes, it can be colored. image.
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