In recent years, there have been some major changes in the packaging industry. Short-lived jobs that are affected by regional promotions have become the main livelihood for many packaging and printing industries. The scope of these activities involves the fields of food packaging, pharmaceutical packaging, beauty and health product packaging, and folding box production. . The more fierce competition on the Shelves of goods shows that sellers and printers must try to innovate and launch visually impactful labels and product packaging.
Product packaging is the last salesperson of a product. Only through the attraction of customers or the specific commitments made by a certain product manufacturer can one realize their value. Suppliers responded to market demand with the development of new substrates, UV inks, and coating materials, so there are many new ways to produce labels today. It is also common to use several printing processes in combination, so that printing quality comparable to plain printing and gravure printing can be obtained.
The supplier's responsive printing supplier responded in a timely manner and worked hard to innovate to stay ahead of the ever-changing industry. The devices that have been introduced are able to handle a wide variety of substrates, with fast job conversions and one pass, which can be printed using more than one printing process. At present, several printing processes are commonly used for printing. The color stability and physical properties of products printed with UV inks and coating materials are greatly improved.
Printers with multiple configurations The current manufacturing press can have a variety of process configurations, including flexo or UV flexo, gravure, screen printing, rotary embossing, offset printing, and rotary bronzing. Recent changes due to the need to gain market share show that narrow web presses are becoming wider and web presses are narrowing. This creates an interesting new market that overlaps, for example using UV flexo technology to produce folding boxes on linkage printers, which is a challenge for traditional single-sheet offset printers.
UV system - need (cold) UV
Nowadays some printed materials and future printed materials need to be treated with unique heat treatment methods. As heat-sensitive unsupported films are used more and more in the label and packaging printing industry, the need for efficient, fast-curing UV inks and coatings (without damaging the substrate and not causing alignment errors) has increased. UV curing equipment manufacturers have taken steps to introduce UV curing equipment that can be used flexibly with existing or new presses. Currently, narrow, medium, and wide web presses can be individually equipped with UV curing devices, and can also be equipped with hot air and UV drying curing devices.
Variable factors that affect the UV-curing of substrates and inks Variable factors that affect the printing and UV-curing of inks include the depth of cure, surface temperature, and the characteristics of the substrate. Each time the solids requirement is also due to image accuracy, subtle levels and substrate ink film weight, color density, adhesion force and bending elasticity. Printing with a UV ink on the oil box requires the use of a unique ink formulation. This ink is easy to transfer, but also take into account the different characteristics and properties of the substrate.
Interaction of UV inks and UV lamps Many interactions between UV inks and UV lamps can affect not only the characteristics of the final product, but also the efficiency of UV curing equipment. We know that light is made up of photons, which are the basic units of light energy and usually travel straight at the speed of light. Each photon has a certain wavelength, and its energy size is related to the wavelength. When photons pass through an object, they are reflected, refracted, or absorbed. After photons are absorbed, photons can be converted into a form of energy, usually cooked energy. The chemical changes it causes are called photochemical changes.
Chemical Properties of UV Inks - Photoinitiated (Active Ingredients) UV inks are photochemical compounds that typically consist of four components: monomers, oligomers, pigments (and other additives), and photoinitiators. The only optically active ingredient is a photoinitiator that reacts with certain wavelengths of ultraviolet light. When the UV photons collide with the molecules of the photoinitiator, a curing reaction is initiated.
Photo-absorption efficiency using UV inks, should remember the following two important elements:
Photons that have not collided with photoinitiators are wasted. Some photofilters that do not activate photoinitiators are also ineffective. All constituents of the UV ink have a light-shielding effect, in particular blocking UV light. The degree of reduction in the intensity of light passing through an absorbent material obeys the Beer-Lamber wave law. The law describes how the intensity of light is reduced due to the thickness of the ink film and the absorption characteristics. From this we can draw two additional basic conclusions:
The molecules of the photoinitiator are uniformly dispersed in the UV ink. The intensity of the light emitted on the surface of the UV ink print is distributed uniformly over the ink layer (UV illuminance)
Irradiance Luminance, sometimes called the energy intensity of a UV lamp, refers to the irradiation power per unit area of ​​the printing surface at any point in the curing process. Irradiance is measured in watts or milliwatts/cm2. The irradiance value is the maximum value of the UV lamp and can usually be found at the focus of the UV light on the surface of the substrate. The illuminance is determined by several factors such as the power of the UV lamp, its diameter, and the properties of the reflector used to reflect and focus the UV energy on the curing device. The greater the illuminance, the greater the power of the illumination at any level in the ink film.
Ultraviolet radiation dosing dose This term refers to the amount of time of exposure, or the amount of energy released on the surface within a specified time, measured in Joules or millijoules/cm2 (1 watt/cm2 X1 is 1 Joule/cm2). Does the 1 second dose of 1W/cm2 produce the same cure as a 2 second 1/2W/cm2 dose? The answer is no, because the dose does not explain the depth of the radiation and does not fully describe the release of the UV lamp's energy. We used UV inks to print on polycarbonate substrates with a screen resolution of 154/cm, and cured under different UV lamp conditions. After comparing the curing effects, it was found that the UV illuminance was the most important factor in the curing effect, not the irradiation dose.
Under the condition that the UV lamp's illumination conditions are not changed, let the printed text pass one or two times under the UV lamp with different peak power of the illumination, and then compare the depth of illumination of the UV ink with the illumination intensity of the next and the illumination dose. The impact. Passing printed text under UV light with lower power actually increased the depth of cure, but it did not double as expected. In fact, if the printing image is passed under the UV lamp for the third time, the increase in cure will be further reduced. Increasing the exposure time does not make up for the lack of UV lamp irradiation intensity.
Spectral selection Ultraviolet wavelength is 200-450 nm. The limit of the short wavelength is 200 nanometers, because the short wavelength can not be transmitted in the air. At 450 nm, the beginning of the spectrum of visible light is at the large paper. In the case of screen printing UV inks, both bands function simultaneously. Short waves act on the surface of the ink, while long waves act more deeply on the interior of the ink. Loss of shortwave ink surface becomes sticky. Loss of adhesion of long wave ink will decrease.
UV solid lamp UC curing lamp with mercury as the main source of light. Some metal halides are also often added inside the lamp in order to obtain UV curing lamps with different UV spectra. Since all UV lamps have mercury in them and produce a variety of wavelengths, including short wavelengths, the surface of the ink can be cured to a certain degree by shortwave energy. The addition of a metal halide can increase the output of a specific longer wavelength ultraviolet light, so that the degree of dry curing and the adhesion of the appropriately matched UC ink are enhanced.
Some of the frequently used UV lamps include:
H-type lamp, facing the transparent light ink and ink D-type lamp, facing some of the color screen printing ink V-lamp, difficult to penetrate the previous defects of the ink / white ink. The use of metal halide UV lamps in the past, the drawback is that often need Adjust the power regulator. Now that you have a solid-state stepless power supply, you can start the UV lamp without adjustment.
Reduce heat and surface temperature, control infrared When the substrate can not be exposed to excessive heat, or UV coating may be damaged due to excessive heat, the temperature becomes a problem that should be solved. For example, in color silk screen printing, in order to minimize the dot gain when UV ink is used, the test should be controlled to be lower. During the use of the UV lamp, infrared (IR) energy (not generated by mercury or metal halide) is generated due to temperature increase and emitted by the quartz lamp.
The air-cooling device in the dry curing system can be used to lower the surface temperature, and the print can also pass through the curing chamber at a faster speed to obtain the surface temperature.
Consumer and Market Demand Consumer goods distributors will continue to demand greater room for printing images in order to maintain their existing market share. The above-mentioned needs of dealers can be met by a wide variety of printer configurations, an ever-increasing variety of printing consumables, and continuous advancements in UV curing technology.