In recent years, there have been some major changes in the packaging industry. Affected by regional promotional activities and short-form jobs have become the main jobs of many packaging and printing. Its scope involves food and food packaging, pharmaceutical packaging, beauty and health care product packaging and folding box production field. The more intense competition on the merchandise shelves shows that sellers and printers must find ways to innovate and introduce labels and outer packaging with visual impact. The outer packaging of the product is the last salesman of the product. Only by attracting customers, or through specific commitments made by a certain product manufacturer, can its value be realized. Suppliers have developed new substrates, UV inks and coating materials to respond to market demand in cities, so there are many new methods for label production. It is also common to use several printing processes in a comprehensive manner, so that the printing quality comparable to that of offset printing and gravure printing can be obtained. Supplier response Printing equipment suppliers have responded in a timely manner, striving to innovate in order to stay ahead in a constantly changing industry. The equipment that has been introduced can handle a variety of substrates, and the conversion speed of live parts is fast. One pass can be used for printing with more than one printing process. Currently, several printing processes are commonly used for printing, and the color stability and physical properties of products printed with UV inks and coating materials have been greatly improved. Printing machines with multiple configurations The printing machines currently manufactured can have a variety of process configurations, including flexo or UV flexo printing, gravure printing, silk printing, roto-relief printing, offset printing, and roto-gilding. The new changes that have occurred recently due to the need to gain market share indicate that narrow web printing presses are widening and wide web printing presses are narrowing. This has created interesting new markets that overlap and overlap, such as the use of UV flexo technology to produce folding boxes on linked presses, which is undoubtedly a challenge for traditional sheetfed offset printers. UV curing system-requires (cold) UV Existing printing materials and future printing materials need to be treated with unique heat treatment methods. As the thermal and unsupported film labels and packaging and printing industries are used more and more, the demand for efficient and fast curing UV inks and coatings (which do not damage the substrate and will not cause alignment and positioning errors) has also increased. The measures taken by UV curing equipment manufacturers are to introduce UV curing equipment that can be flexibly used with existing or new printing machines. At present, narrow-width, medium-width and wide-width web printing machines can be equipped with UV curing devices individually, or with hot air and UV drying curing devices. Variable factors affecting substrate and ink UV curing Variable factors that affect the UV curing of substrates and inks include curing depth, surface temperature and different physical properties of the substrate. The requirements for each curing also vary depending on the image accuracy, subtle levels and substrates. The cured ink must give different products different ink film weights, color densities, adhesion and bending elasticity. Printing with UV ink on the board requires the use of unique Western inks. This type of ink is easy to transfer, but also takes into account the different characteristics and performance of the substrate. Interaction of UV ink and UV lamp Many interactions between UV inks and UV lamps will not only affect the characteristics of the final product, but also determine that this will not only affect the characteristics of the final product, but also determine the operating efficiency of the UV curing equipment. We know that light consists of an optical head, and photons are the basic unit of light energy, and they usually propagate in a straight line at the speed of light. Each photon has a certain wavelength, and its energy is related to the same wavelength. When a photon passes through an object, it is reflected, refracted, or absorbed. After the photon is absorbed, the photon is transformed into another form of energy, usually thermal energy. The chemical changes it causes are called photochemical changes. The chemical properties of UV inks-photoinitiators (active ingredients) UV inks are photochemical compounds, usually composed of 4 types: monomers, oligomers, pigments (and other additives) and photoinitiators. The only optically active component is a photoinitiator, which can react with a certain wave of ultraviolet light. When the photons of ultraviolet light collide with the molecules of the photoinitiator, a curing reaction is initiated. [next] Photon absorption efficiency When using UV inks, the following two important contents should be remembered: Refractive photons are wasted without collision with photoinitiator; Photons of certain wavelengths that do not activate the photoinitiator are also useless. All components of UV ink have a light-shielding effect, especially blocking ultraviolet light. The degree of decrease in the intensity of light when passing through an absorbing substance complies with the Bill-Lamb wave law. This law describes how the intensity of light becomes smaller due to the influence of ink film thickness and absorption characteristics. From this, two other basic conclusions can be drawn: The molecules of the photoinitiator are evenly dispersed in the UV ink; Energy intensity (UV irradiance) Irradiance is sometimes referred to as the energy intensity of a UV lamp, and refers to the irradiated power per unit area of ​​the printed surface at any time during the curing process. The unit of measurement for irradiance is watts or milliwatts / cm2. The irradiance value is the maximum irradiance value of the UV lamp, which can usually be obtained at the focal point of the UV light on the surface of the substrate. The irradiance is determined by factors such as the performance of the UV energy reflector for several decades, such as a day. The greater the irradiance, the greater the irradiation power of any layer in the ink film. UV radiation dose The term ratio of dose refers to the amount of irradiation time, or the energy released on the surface within a specified time, and its measurement unit is Joule or millijoules / cm2 (1 watt / cm2X1 is called 1 Joule / cm2). Is the curing effect produced by the dosage of 1W / cm2 per second the same? The answer is no, because the dose does not indicate the depth of irradiation, and it does not fully describe the liberation of UV quantity. We used UV ink to print on polycarbonate substrates with 154 lines / cm screen line number, and then performed curing treatment under different UV lamp irradiation conditions to compare the curing effect and found that it is the key to curing effect. The effect is UV irradiance, not radiation dose. Under the condition that the irradiation condition of the UV lamp is unchanged, let the printed image pass through the UV lamp with different irradiation power peak once or twice, and then compare the curing depth of the UV ink with the irradiance and irradiation dose The impact. Allowing printed graphics to pass twice under a lower-power UV lamp did increase the curing depth, but it did not double as expected. In fact, if the printed image is passed under the UV lamp for the third time, its curing increase will be further reduced. Increasing the irradiation time does not make up for the lack of irradiation intensity of UV lamps. [next] Spectral selection The wavelength of ultraviolet light is 200-450 nm. The short-wavelength limit is 200 nanometers, because no longer can the wavelength be propagated in the air. At about 450 nm is the starting point of the visible light spectrum. When using silk screen UV inks, the two bands work simultaneously. Short waves have an effect on the ink surface, while long waves have a deeper effect on the interior of the ink. Loss of short-wave ink surface will become sticky. Loss of long-wave ink adhesion will decrease. UV curing lamp The UV curing lamp uses mercury as the main light source. Some metal halides are often added to the lamp in order to obtain UV curing lamps with different ultraviolet spectrums. Since all UV lamps contain mercury, which produces a variety of wavelengths, including shortwaves, the ink surface can be cured to a certain degree through short-wave energy. The added metal halide can increase the output of ultraviolet rays with a specific longer wavelength, so that the drying and curing degree and adhesion of the UV ink appropriately matched can be enhanced. Some of the frequently used UV lamps include: H-shaped lamp, facing transparent bright ink and ink; Past flaws In the past, when using a metal halide-added UV lamp, the disadvantage is that the power regulator needs to be adjusted frequently. Now that there is a solid energy stepless transformer power supply, the UV lamp can be started without adjustment. Reduce heat and surface temperature, control infrared When the substrate cannot withstand excessive heat, or the UV coating may be damaged due to excessive heat, temperature becomes a problem. For example, in color screen printing, in order to minimize the increase of the outline point when using UV ink, the temperature should be controlled lower. During use, the UV lamp will generate infrared (IR) energy (not generated by mercury or metal halide) due to the temperature increase, and it will be emitted by the quartz lamp. The air cooling device in the drying and curing system can be used to reduce the surface temperature, and the surface temperature can also be printed through the curing chamber at a faster speed. Customer and market needs Consumer goods distributors will continue to demand greater choice of printed images in order to maintain their existing market share. Various configurations of printing machines, increasing types of printing consumables and the continuous advancement of UV curing technology can meet the above needs of dealers. Rack Trolley,Rack Trolley For Kitchen,Rack Baking Trolley,Kitchen Rack And Trolley Jiangmen Junerte Stainless Steel Kitchenware Co.,Ltd , https://www.jetkitchenwarejm.com
The photons striking the surface of the UV ink print are unevenly distributed on the ink layer.
D type lamp, facing some color screen printing ink;
V-shaped lamp, it is difficult to transmit ink / white ink.
UV ink curing treatment and process configuration