In the history and growth of the screen printing industry, many technological innovations have emerged that have made a significant contribution to the industry. These include the use of knife stencils, the use of ready-to-use screen inks, the standardization of photographic printing plates, the creation of screen printing international associations, the generation of mechanical printing, the spread of information technology required by screen printers, and fluorescence Ink development and so on.
Daylight-type fluorescent screen printing inks were put into use in 1948, and they were impressed with their neon-like brilliance, dramatic colors, attractive attraction and artistic expression. Because its effect can be best used in the field of screen printing, it is often used in screen printing workshops. Silk screen printing is an ideal printing method for fluorescent inks because it has a uniform ink film layer that is required for the luster, stability, and weather resistance of fluorescent inks. Fluorescent ink pigments have a coarser grain size than conventional pigments and were first used for rough screen printing. However, in recent years, more and more fluorescent inks that can be used for fine screen printing continue to emerge. Fluorescent inks are mainly used for printing window displays, decals, bumper guards, industrial insurance equipment, body advertising, letters, posters (posters), 24 inch posters, notepads, signal flags, magazine covers, invitations, outdoor advertising, Cloth labels and so on. Due to the great difference between fluorescent inks and common ink colors, fluorescent inks play an important role in screen-printed outdoor and indoor advertising.
Fluorescent inks are luminescent materials and are substances that emit light. The substance absorbs the energy of solar radiation when it is exposed to sunlight and then stores it in the form of heat, or a photochemical reaction takes place, or the energy is emitted in the form of visible light. The absorbed radiant energy is shorter than the emitted energy wavelength. People absorb light of different colors and then emit it as fluorescence. The phenomenon of emitting light in the dark after absorbing light is called phosphorescence. The difference between the two is that the phosphor absorbs natural light or artificial light and emits light in a dark environment after the light is removed, and the fluorescent light must absorb light in the presence of light to emit light. Fluorescent inks can also emit light in the presence of "night light" or violet light. However, it does not glow in the dark and no light. The fluorescent ink not only shows its own color, but also has the ability to absorb light and change the light intensity so that the color it exhibits has a stronger light intensity, but the hue (or color) does not change.
Ordinary inks or dyes display colors by reflected light, and each ink color has a different wavelength and output energy. For example, the red light reflects red and absorbs other colors. The fluorescent red not only has partially reflected red, but also converts other colors (green, blue, and purple) into red wavelengths that emit as red light, so the color appears to radiate from the interior of the object. It is this luminescent property that makes the ink known as fluorescent ink. Printers use fluorescent inks for printing to obtain four times the brightness and visibility of ordinary inks. Fluorescent inks appear bright in dim light, such as at dusk and dawn.
The reflection characteristics of ordinary ink color and fluorescent ink color are different, and the unit of measurement is angstrom. Fluorescent ink converts short-wavelength light into long-wavelength light and superimposes to generate fluorescence. Through conversion and superposition, a fluorescent color with special brightness and visibility is formed.
Normally, daylight-type fluorescent colors indicate a direct lifetime in sunlight of 30 days. But now the life of the color in the room has been greatly improved. This color can be extended indefinitely indoors. It can be used to express vivid and jumping colors. At present, fluorescent inks have the advantages of fine background, fast drying, and ease of use for thinner ink layers. Attention should be paid to the use instructions when using them.
Fluorescent ink pigments are based on fluorescent pigments, carefully chemically compounded, stirred and mixed with plastic resins under experimental control. The daylight fluorescent color is the color formed by the dye suspended in a colorless, transparent, insoluble resin. The resin esters are based on powdered substances and are added to specific binders with careful mixing and stirring. As shown in Figures 23 and 24. Compared with resin esters, the amount of dyes only accounts for a very small proportion. However, to obtain maximum ink brightness, it is necessary to add a certain amount of dye or resin to the fluorescent color.
The use of fluorescent inks <br> There are generally two types of fluorescent inks: oil-based and fast-drying. The ink is printed using an industrial standard screen plate, but the screen plate must have solvent resistance. For example, a fast-drying fluorescent ink cannot be used for a lacquer-coated knife-printed screen. This should be clearly stated in the user instructions. There are many kinds of fluorescent inks with different colors in the market, and it must be clearly used before use. Each color of thinner should be used according to the manufacturer's instructions. Daylight fluorescent colors cannot be mixed with other fluorescent colors or other types of inks because mixing may result in no longer having luminescent properties. Excessive use of diluent will reduce brightness and stability, so it must be appropriate. In indoor conditions without direct sunlight, the printing ink layer can maintain its effect for months. The ink can be printed using screens No. 12 or No. 14 and screens of the same nature. However, in order to carry out outdoor printing requiring relatively high durability and durability, it is necessary to use No. 8 or No. 10 mesh and a screen of the same nature for printing. Fluorescent ink printing usually uses a single-edged squeegee, either manually or mechanically. Of course, a double-edged squeegee or a smaller pressure can be used to obtain a thicker ink film layer. The thicker the film, the stronger the anti-exposure performance. The ink can be dried by natural drying or forced drying in a dryer.
The daylight fluorescent color is best used in dark environments and contrasting colors, especially on the white surface. For best impact, fluorescent colors should not be used alone. It can be used to highlight a particularly important point. It can also be set off with 50% gray or the opposite color. Half-tone printing with fluorescent ink is not practical unless the halftone black ink is printed on a surface that has been coated with a solid fluorescent ink. When using fluorescent ink to print text, the space between the words must be wide enough for reading. The fluorescent ink should be leveled after printing. The flat ink film absorbs light, and the smooth ink film reflects light, preventing light from interacting with the fluorescent ink.
Fluorescent inks and phosphorescent inks are not radioactive and are harmless. However, it should be emphasized that self-emitting radioactive inks are also commonly used in screen printing, such as dial numbers. They are harmful to those who have no experience.
Fast-Drying Fluorescent Inks <br> Fast-drying Fluorescent Inks are inks made from fluorescent pigments added to fast-drying binders. The ink has good brightness and flexibility and is suitable for outdoor poster printing. Most of them are dried by evaporation. They must use lacquer screens such as photographic type, water-based film type, ink type, and knife-cut stencil printing.
When the fluorescent ink is to be printed on a non-white surface, the surface should first be coated with a white base. The fast-drying fluorescent ink can be printed on the uncoated cloth label and can be printed on the surface of the pigment or nylon. A test should be done when it is not known whether the ink is bonded to the printed surface.
The life of fluorescent ink printing products is determined by the ink, not by the product itself. If the quick-drying ink can prevent direct sunlight, the life of the printed product can be greatly improved. In the absence of light, fluorescent ink printing products can be preserved and maintain their original appearance.
The quick-drying ink takes about 30 minutes to dry naturally, and mechanical drying can shorten the time to 30 seconds to 2 minutes.
The preferred ventilation area is the conditions required for printing and drying. The drying process must be completed as quickly as possible to prevent blemishes from appearing during printing. A single-edged squeegee can produce an ink layer thickness of about 0.0025 to 0.0038 cm. After printing, the screen can be cleaned with paint thinner, toluene, xylene, naphtha, or the manufacturer's recommended solvent. Indoor products can be screen printed with Number8XX~14XX; outdoor products can be screen printed with Number8XX~10XX.
After large-scale outdoor advertisements are made, it is recommended to use clean water, because the sticker absorbs ultraviolet rays and weakens the luster of the fluorescent ink.
Oil Based Fluorescent Inks <br> Oil Based Fluorescent Ink If the ink can be printed better, the brightness can be kept the same time as the fast drying ink, and the outdoor print can be kept for about 3 to 6 months. It takes 1 to 4 hours for the ink to dry by oxidative polymerization, which is mainly related to the printing substrate, ink layer thickness, and workshop conditions. The drying of the ink can also be accelerated by gas heating, infrared rays, and spray drying agents. It is also possible to dry using a common ink drying method. Oil-based fluorescent inks can be printed with most screen printing and can be printed on paper, wood, glass, metal, decals, and other surfaces with a white base coating. The ink can be printed with screens 8~16.
Oil-based fluorescent inks can be diluted with mineral spirits or the manufacturer's recommended solvent. The printing of letters should be in bold type with some contrast. Do not overprint the varnish on the ink, it will reduce the fluorescence effect.
Oil-based inks should not be mixed with fast-drying fluorescent inks. The use of oil-based fluorescent inks for wide-format advertising printing also requires the use of clean water to wash away stickers.
Luminescent fluorescent ink <br> The fluorescent inks described above are all daylight fluorescent inks. The following describes the fluorescent luminous inks. Luminous fluorescent inks are best used in screen printing. The ink is responsive to "night light". Sometimes people call the color of luminous fluorescent inks "invisible light" because it appears neutral or nearly white under sunlight or incandescent light. Most luminous fluorescent inks do not differ from ordinary inks during the day, but they can emit brilliant brilliance under a night light or near-ultraviolet light. The light source can be a mercury lamp or a fluorescent night light. The biggest difference between the luminous fluorescent ink and the daylight fluorescent ink is that the latter can emit light in both day and night light, while the former only emits light under the night light.
The printing of luminous fluorescent inks is similar to the printing of daylight fluorescent inks. It cannot be mixed with ordinary inks, because in the nighttime, ordinary inks will affect the fluorescent effect of fluorescent inks. In addition, the printer should follow the manufacturer's instructions when using it.
In summary, fluorescent inks play a key role in screen printing. Its use brings brilliant colors to screen printing.
Source: Membrane Switch Technology Forum