Analysis of Factors Affecting Thermal Transfer Quality Text / Song Qi The thermal transfer process refers to a printing method in which a transfer pattern of a pigment or a dye is used as a medium to transfer a pattern of an ink layer on a medium to a substrate by heating or pressing. The basic principle of thermal transfer is to directly contact the ink-coated medium with the substrate. Through the heating and pressing of the thermal print head and the impression cylinder, the ink on the medium is melted and transferred to the substrate to obtain the desired The process of print. In recent years, the printing technology has been increasingly applied to steel drum packaging. The main advantage of thermal sublimation transfer technology is that the transfer image is colorful and rich in layers, and the effect can be compared with direct printing. First, the classification of thermal transfer Thermal transfer is generally divided into two categories: hot press transfer and sublimation transfer. The hot press printing technology first uses a printing method such as screen printing or gravure printing to print the graphic on a thermal transfer paper or a plastic film, and then transfers the image to a fabric, leather or the like by heat and pressure. At present, the commonly used hot press transfer technology includes high temperature heat transfer, low temperature heat transfer, flocking heat transfer and osmotic foam heat transfer. Second, the characteristics of thermal transfer Thermal transfer due to the relationship between the heat of the image, the color of the finished image will be stronger than that of the water transfer, and it will not easily fall out. It has corrosion resistance, impact resistance, aging resistance, wear resistance, high temperature resistance and fire resistance. It can maintain the characteristics of no discoloration for ten to several decades, so the thermal transfer technology is especially suitable for steel drums with special requirements for image retention. The image of thermal transfer is colorful and rich in layers, which can be applied to the production of small-volume steel drums, and the selection of substrates for thermal transfer is extensive, which makes thermal transfer always in an irreplaceable position. Third, the factors affecting the thermal transfer process Thermal transfer is a process that is an important part of the entire steel drum production process. It is closely related to other links. How to control the stability of this process is an important guarantee for the quality of printed matter. Let’s take a look at the impact of thermal transfer. An important factor in the process. Hot print head The thermal print head is mainly composed of a surface protective film, a bottom protective layer and a heating element. The heating element is a conductive mesh screen, and the heat generated by the voltage pulse is thermally diffused, so that the ink particles of the image portion are embossed and melted to complete the ink transfer. The printing speed of thermal transfer depends on the time required for each line of text. Therefore, the thermal transfer head and the transfer paper should have good heat transfer properties, so that the heat generated by the heating element can be quickly transmitted to the surface of the substrate through the protective layer, the transfer paper substrate and the void to ensure that the ink has Enough transfer time. 2. Ink The composition of the thermal transfer ink is generally three parts of a pigment (pigment or dye), a wax and an oil, wherein the wax is a main component of the thermal transfer ink. The basic constitution of a general thermal transfer ink can be referred to Table 1. Table 1 Basic composition of thermal transfer ink ingredient proportion Carbon black 10% Hydrocarbon wax 50% Ester wax 30% additive 10% Table 2 is an example of a screen printing thermal transfer ink formulation in which N-methoxymethyl polyamide is dissolved in a solvent such as benzyl alcohol, toluene or ethanol, added with a heat resistant pigment and bentonite, and then ground. Screen printing ink. The ink is printed onto a carrier (e.g., thermal transfer paper) by a screen printing method, and then the fabric is subjected to hot press transfer. Table 2 Thermal transfer ink formula ingredient proportion N-methoxymethyl polyamide 19% Benzyl alcohol 40% Toluene 17% Ethanol 6% Bentonite 9% pigment 9% When printing, the viscosity of different inks has a direct relationship with the heating temperature, and the heating temperature and the viscosity of the ink should be strictly controlled. It has been proved that when the heating temperature is 60 to 100 ° C and the ink is melted, the viscosity of the ink is stable at about 0.6 Pa·s. In general, the closer the ink is to this state, the better the transfer performance. In recent years, with the improvement of technology, the storage temperature of printed products has been increased from 45 ° C to 60 ° C, which greatly expands the use range of thermal transfer. In addition, the use of transparent pigments or clear dyes provides a good color tone for color prints. 3. Transfer medium The substrate of the transfer paper is generally divided into a paper substrate, a polyester substrate and a celluloid substrate, and different substrates have different properties, so the following reference factors of the substrate should be noted when selecting the transfer paper. 1) Physical properties The physical properties of the transfer paper are shown in Table 3. Table 3 Physical properties of transfer paper material Gram weight (g/cm) Thickness (mm) Density (g/cm) Smoothness (s, front / back) Thermal conductivity (mw/cm ° C) paper A 7.44 0.0084 0.87 545/375 1.67 B 8.30 0.0089 0.93 400/353 - C 9.52 0.0127 0.75 162/133 - D 12.21 0.0147 0.83 182/214 - Polyester A 7.90 0.0056 1.41 0～2000 1.48 B 10.21 0.0063 1.63 2000/666 - celluloid A 27.2 0.0183 1.45 2400/2400 2.67 The above are the physical properties of the three thermal transfer paper substrates. The following three aspects can be considered when selecting: ◠The thickness of the substrate should generally not exceed 20μm; ◠The substrate should have a high degree of smoothness to ensure the transfer rate of the ink; ◠The substrate should have sufficient strength to ensure that it is not torn during transfer paper processing and printing. 2) Chemical properties Making the ink adhere well is two important manifestations of the chemical properties of the transfer paper substrate. The chemical properties of the transfer paper in production directly affect the quality of the print. If the transfer paper does not allow the ink to adhere well, or if the amount of ink is not well mastered in production, printing waste is caused. A good printing process and good prints must be based on a good grasp of the chemical properties of the transfer paper. 3) Good thermal performance Since the transfer process is carried out by means of high temperature means, the material of the transfer paper must be able to withstand the influence of the transfer temperature and maintain the properties. In general, the thermal properties of the substrate of the thermal transfer paper are good and can be expressed by the following factors: ◠The lower the heat resistance of the heat-resistant substrate, the thinner the thickness, the better the heat transfer, and the better the thermal properties; ◠Smoothness The smoother the surface of the substrate, the lower the heat resistance and the better the thermal performance; ◠The heat-resistant thermal head temperature is generally around 300 °C. The substrate must be able to ensure that the main properties do not change at this temperature. 4. Substrate steel drum Experience has shown that the quality of the printed steel with a rough surface is better, which is a remarkable feature of thermal transfer. Because the rough surface of the steel drum indicates that the substrate has a large surface energy, the ink on the transfer paper can be transferred to the steel drum well, and the desired level and tone are obtained; but too rough will affect the ink. Normal transfer is not conducive to the realization of the printing process. Fourth, the current status of thermal transfer analysis Thermal transfer is a type of thermal printing. The introduction time from abroad is not too long, but it has developed rapidly in China in recent years. At the beginning, some foreign investors who invested in mainland China brought it to China, and the raw materials used were mainly imported, mainly used in certain specific fields. After foreign companies introduced soft packaging technology into China, there was a large demand for this technology in the country, and the market gradually expanded, and today it has attracted the attention of the printing industry. The range of applications of thermal transfer technology has been expanding and has been applied to many industries, such as thermal transfer technology in the steel drum manufacturing industry. The steel drum thermal transfer process has the advantages of simple, fast and non-polluting process, and the obtained printed products are rich in layers, bright in color, high in precision, good in picture quality, strong in transfer image, and the transfer layer is firmly combined with the steel drum. A series of advantages such as smooth surface, good wear resistance and so on. The rise of steel drum thermal transfer process is due to the fact that ordinary silk screen printing on the surface of steel drums does not meet the requirements of high user color. With the maturity of steel drum thermal transfer technology, this process has been widely used. The production of various barrel enterprises, and enterprises are currently trying to carry out large-area thermal transfer of the steel drum as a whole, and achieve the purpose of producing various patterns of colored steel drums. It can be said that with the further maturity of the process and the continuous integration of new technologies, thermal transfer, as a kind of special printing, will have a very broad prospect in the field of steel drum printing, and will receive more and more attention. Printed Swim Ring,Swim Ring For Kids,Inflatable Pvc Swim Ring,Summer Swim Ring J&TZ CO.,LTD , https://www.inflatable-toy.com