Application of special printing technology for screen printing

3. Fluorescent printing.

Fluorescent printing is different from light printing. Fluorescence was first discovered in natural fluorite (also known as fluorite), and it emits a non-primary-colored flash of light under the irradiation of ultraviolet light (such as sunlight). Fluorescence flash is not caused by the reflection of light caused by high temperatures. When the light source is removed, there is no reflected light and flash phenomenon, which is different from phosphorescence. Fluorescence is a type of flash that reflects ultraviolet light into visible light, increasing the amount of reflected light and increasing brightness. Such as the common fluorescent whitening agent, it can absorb the ultraviolet light that can not be seen by the naked eye and reflect blue light or blue-green light, offsetting the complementary yellow light on the cotton cloth, making the cotton cloth more white. The fluorescent coating itself is not a luminescent dye. In short, it is an optical brightener with a primary color. The more ultraviolet content it emits, the stronger the fluorescence, and the main color will not be thickened. There is no UV Under the monochromatic visible light, only the main color is displayed without significant fluorescence, which is where the fluorescent paint (or dye) is different from the normal dye. For example, a fabric dyed with a common dye (such as salt lake blue) is exposed to ultraviolet rays and becomes black instead of lake blue, because ultraviolet rays do not contain blue-green and any visible light, but will have strong fluorescence The salt-based rose-red dyed fabric, illuminated with the same UV light, produces bright red-yellow fluorescence, which means it can turn the short-wave UV light into a long wave visible to the inner eye.

After the dye absorbs the light quantum in the light, the dye molecule is intensified to an intensified state, and the absorbed energy can be released in various forms through molecular collision or other actions. The form of energy released may be thermal energy, light energy (ie, fluorescence), chemical energy (based on photochemistry), or decomposition energy (decomposition of dye).

The general dye is mainly to convert the absorbed energy into heat energy, and only a small part is converted into decomposition energy. Fluorescent dyes are mainly converted to light energy, and only a small portion is converted into heat and chemical energy. Since the wavelength of the light reflected by the fluorescent paint (or dye) is longer than the wavelength of the absorbed light, the emitted fluorescent band is always on the long wavelength side of the absorption band. As a result, the yellow dye absorbs blue light, and the fluorescence is blue-green light (or green light). Therefore, the yellow fluorescent coating must be bluer or greener than the non-fluorescent general yellow dye. At the same time, the amount of light reflected by fluorescent coatings (or dyes) must increase, often more than the original number. The greater the amount of reflected light, the better the fluorescence, and the degree of fluorescence is measured by this amount. In fact, many dyes have fluorescent properties, but their fluorescence does not all fall within the visible spectrum and we cannot see it with the naked eye. The above-mentioned fluorescent paint (or dye) refers to those paints or dyes that can increase the amount of reflected light under sunlight, so it should be called "daylight fluorescent dye".

The fluorescent printing process is the same as the general screen printing process except that the printing paste is prepared using a fluorescent dye.

4. Gold and silver printing.

Gold and silver powder printing gold and silver powder are actually copper-zinc alloy and pure aluminum powder. Gold powder is divided into light golden, medium golden and dark golden by color. Silver powder contains 99.5% pure aluminum. Due to the active nature of aluminum powder, the surface is easy to generate oxidized strands, and the lower explosive density of powder in air is 27 to 50 g/cm3, and water will release hydrogen, affecting the stability of color paste, so it is less practical than gold powder. Printing is common. The following focuses on the process of gold powder printing points.

1 gold powder printing process points.

a. The commonly used fineness of gold powder is 100 to 1200 mesh. The finer the particles, the more reddish the light and the poorer luster. On the contrary, the coarser the particles, the stronger the luster, the stronger the luster, and the better the scrubbing fastness. Therefore, the number of meshes should be selected properly, and the finer the finer the general coating selection, the better. Often controlled between 200-400 mesh.

b. The penetrant contributes to the increase of brightness, and the diffusion agent NNO and penetrant JFC are more commonly used.

c. Antioxidants can retard the oxidation rate of gold powder in the air, prevent the formation of oxide film and dark, commonly used are metol (sulfuric acid methylaminophenol) and benzotriazethasone, this agent is not directly added Adjusted in emulsified paste.

d. Emulsification paste, such as using ordinary pulp, is easy to separate and oxidize, so it should be specially formulated. Its formula is:

Special white oil 700ml
Water Xml
Ping Ping plus O 50ml
Diffusion agent NNO 40ml
Thickener M 20ml
Benzotriazole (alcohol equal amount) 10ml
1 litre (2000 rpm)

2 gold powder printing process recipes and processes.

a. Formula:

Gold powder (400 mesh) 350g
Adhesive MR-96 400g
Dedicated emulsifying paste 250g

b. Process flow: printing gold powder→baking (160°C, 1.5 minutes)→rolling resin→→baking (temperature, time same as before)→→tentiveness→→calendering→→shrinkage proofing→ inspection.

The purpose of the above calendering is to increase gloss, reduce friction and prevent powder fall. In the case of low demand for golden light but high requirements for fastness, golden powder can be used to replace some of the amount of powdered gold, especially when used in black or dark sauce. It is often called “flying gold”.

3 gold flower tube carving and arrangement.

The most prominent part of the engraving is the depth of 0.02mm, which is usually about 0.12mm, and the flying face is larger, which is conducive to the smooth flow of printing ink.

The use of engraved flower tube for the printing of gold powder is most straightforward and it is usually divided into two times. Usually it is usually placed in the final process. When screen printing is used, the screen printing plate is preferably a hot platen, which is generally printed in single or double numbers. When co-printed with other dyes, specific arrangements should be made depending on the pattern and dye properties. Such as overprinting with vat dyes, first printed with gold powder is appropriate, oxidation is best to use cold water, not using acid and strong oxidants.
(to be continued)