Gold and silver ink composition and application

Prints printed with gold and silver inks are very popular with consumers, but there are a series of difficulties in the production, storage and use of these inks. This is a big challenge for screen printers. Before using metal powder inks, you need to understand the difference between gold and silver inks and traditional inks. First look at the composition of the printing ink of gold and silver fan nets, which special requirements for the printing process, and understand which applications of this ink apply, and which do not apply.

What is gold and silver ink?

The main components of gold and silver fan net printing inks are: metal powder raw materials and liquid resin (ie, ink binder). The ink binder serves as a pigment binder and protects the ink film after drying.

The metal powder used in gold ink and silver ink is easily oxidized copper powder and **, which loses its metallic luster under the influence of moisture, atmosphere, heat and certain chemicals. Such as copper powder in the link material is acidic or in the presence of a trace * is prone to black, after printing and the role of the atmosphere will slowly lose its luster, hair Ukraine.

Its storage performance and printing performance are not good. The remaining ink is generally not to be used again. Gold ink used in a certain percentage of the **, according to the proportion of different gold red or fluorescent, can also be made of ** and transparent yellow ink, its gloss is not as good as copper ink made of copper powder, but the gloss It stays for a long time and has good chemical resistance and toxicity.

In golden gold, which looks gold, the pigment is made of a mixture of copper and zinc in different proportions. If the proportion of zinc is large (about 70% copper, 30% zinc), the golden color of the ink will appear light green, known as rich gold; if the proportion of copper is greater (90% copper, 10% zinc) The ink will appear light red, usually called palegold. The above ratio is the two limits between which the color between the above two shades can be obtained. These shades are microstained with a clear orange colorant to give a color matching those specified in the normal color (eg, Pantone color scale) system.

The silver ink is made by dispersing ** in petroleum solvents and then blending the binder. There are two kinds of silver ink: one is that ** floats on the surface of the ink film, and its irregular reflection on the light can produce a sparkling silver effect; and the second one is dispersed in the link material, and the appearance is silver-white metal.

The inks of gold ink and silver ink generally use resins with extremely low acid value and amine value so as not to affect the gloss of the ink, such as ethyl cellulose, cellulose, polyvinyl acetate, and polyamide resins, and some wax materials are added. To improve the pigment's suspension. Gold ink and silver ink can also be formulated as solvents. However, due to their small viscosity, they are often used immediately. The polarity of the solvent does not need to be too large, or the pigment is too wetted to precipitate. Xylene, ***, etc. can be used as a solvent for gold ink and silver ink. Among them, bright lacquer is used for improving the gloss of ink. Dibutyl ester is used to increase the fluidity of the ink. Due to addition of dibutyl ester and No. 0 dynamizing oil, the drying performance of the ink is affected, and some dry oil is added. , can make the ink quickly dry. The pearlescent color is made by dispersing a pearlescent pigment (or **) in a binder or transparent light ink. The original color of the ink film and the multiple reflection caused by the color of the metal powder form a pearl-like luster effect, hence the name Pearly.

The size of the metallic pigment particle depends on its final use. For screen printing, the pigment particle size is usually between 3 and 15 μm. The specific requirements of the screen printing for the pigment particle size depend on the end use of the print.

The larger the size of the particles, the better the reflective properties of the ink film after printing and the higher the gloss. Because when the pigment particles are relatively large, the surface of the pigment particles is relatively large, and more light is reflected by it, so the gloss is higher. However, oversized pigments can make it difficult to efficiently transfer the ink during printing because it requires a larger mesh. The finer metal pigment particles are easier to transfer, unlike those that are too large to pass through the mesh screen, but the fine pigment particles sacrifice gloss.

Therefore, the low-grade prints, such as T-shirts, can be applied with coarse pigment particles; while the high-grade prints, such as CD, have the smallest pigment particles.

But in reality, gold and silver inks containing pigments that just reach the ideal size are not present—inks usually contain a mixture of pigment particles, the size of which is mostly in the target range. Although the level of pigment crushing technology has improved and the ability to separate particles by size has also increased, ink produced using coarse and fine pigment particles has almost no difference in printing. This shows that during the printing process, some pigment particles cannot pass through the mesh and remain on the surface of the screen.

The size of the pigment particles is too fine and will sacrifice some of the gloss. However, the greater benefit is that a very good surface coverage can be achieved (the same weight of pigment, the finer particles than the coarse distribution area). The challenge for screen-printing manufacturers is to produce inks with the most delicate pigments that can achieve high coverage, good gloss, and tight distribution.

Gold and silver ink ratio

Metal pigment particles are usually coated with a layer of fatty acid during processing. During the printing process, the acid can help the pigment particles to float on the surface of the ink film, while the pigment particles are distributed in a thin sheet to obtain a smooth, light-reflecting ability. On the surface, such an ink ink film is referred to as a "layered ink film."

Because the pigment is on the surface of the ink film, it is easily peeled off and worn. This problem is more pronounced on coarser pigment particles. If the size is smaller, the exposed surface area will be smaller and will be stronger. To solve this problem, only non-layered gold and silver inks are used. At this time, the pigment particles will settle to the bottom of the ink film, greatly improving their adhesion, but because the particles are not regularly aligned at the bottom, the light must pass through the binder material and enter the bottom so that it can be reflected by the particle surface and sacrifice the gloss. Non-layered gold and silver inks are particularly widely used in silver inks, and are less commonly used in gold inks.

The printer will ask whether the ink can be used outdoors, and in some cases it is possible. If the gold and silver pigments are specially treated, they can resist the tarnish and oxidation defects of outdoor exposure. When these pigments, similar to automotive coatings, are used for screen printing, the prints are not only resistant to ultraviolet light, they can even be subjected to salt spray and other extreme weather conditions. However, inks using the above-mentioned particles as pigments are much more expensive than those using ordinary metallic pigments. It is also important to note that the treated gold pigment is not as resistant to extreme conditions as the treated silver pigment.

The chemical characteristics of gold and silver pigments determine that they cannot be directly added to the ink as a finished product. In most cases, metal powders are sold as part of screen printing inks, and the binders are added during use. This is because the metal pigments are mixed with the transparent binder for a long period of time, and are easily chemically reacted and emulsified. Under different conditions, after the metal pigment particles are mixed with the binder, the shelf life of the ink is also different, usually within a few hours to several months. Manufacturers of pigments and inks have been working to solve the problem of limited shelf life of inks. Now, some finished gold and silver vermicelli screen printing inks containing metal particles have been introduced, and their shortest shelf life is 6 months. It is expected that this ink will become the market leader in the next five years.

The use of gold and silver ink

When gold and silver inks are printed, the choice of printing materials is very critical, because there are many pores in the surface, and the substrate with permeability will absorb the transparent resin liquid, especially when the ink viscosity is low, the resin is absorbed and the pigment particles will be Leaving on the surface of printing materials, the resin composition is small, will cause the silver powder to appear gray, and the gold powder will appear brown. If there is no other choice but to use absorbable printing materials, it is best to print a layer of ink (like traditional transparent varnish) to seal the pores on the surface of the substrate and then print the gold on it. Silver ink. A layer of varnish is applied over the metallic ink film to resist peeling and abrasion of the particles in the ink. However, the more transparent polish on the metallic pigment particles, the weaker the reflective performance and gloss of the ink film.

Metal pigments are easily oxidized. Take gold powder pigments as an example. Oxidation takes place on copper and zinc particles, resulting in a reduction in gloss of the ink layer. In some cases, the ink may even appear light green. The aluminum pigment in the silver pigment easily becomes gray and white after oxidation. Oxidation is one of the reasons why the color consistency of gold and silver inks is difficult to achieve.

Another reason for the inconsistency of color consistency is the arrangement of pigments, especially layered gold-silver ink, which floats on the surface of the ink film and forms many voids (the larger the size of the color particles, the larger the gap). After printing, the appearance of these small voids allows the color of the substrate or the underlying ink color to be visually morphed through the surface color of the metal layer. For example, a silver ink in a blue background will appear light blue; if gold ink is preprinted with a yellow or green ink film, the ink's gold color will be changed. Using non-color such as white or light gray as the base color can alleviate this problem. Silver pigments usually exhibit a dark hue, and gold powder can not only show dark hue, light hue and various hue between the two, but also can be used to obtain a series of "oxidized hue", meaning that the pigment allows and controls the conditions The resulting oxide reacts and the reaction results include gold tones with lemon yellow or light orange.

Gold powder pigments can also produce light shades such as green or purple, which are obtained by adding various color pigments to gold powder inks. However, these colors are more unstable and appear to be inconsistent with pure metallic colors, and are also prone to discoloration.

Light-colored silver powders often use transparent colorants so that they look like powdered gold pigments. This method also solves the oxidation problem of gold powder. Such silver powder can be used for non-layered glossy ink, but the color is not as clear as the standard layered silver ink.

In addition to traditional colors, most color systems point to a series of metallic inks. A silver metallic pigment is used as the base color and then colored with a red, yellow or orange ink. The challenge for making this type of ink is that some of the red, orange, and yellow pigments used for color matching may react with metallic pigments, thus destroying the printed graphics. Producers need to be extremely careful when deploying metal colors to avoid the above problems.

The use of tinted gold and silver inks increases the area of ​​coverage and allows the specific color to be formulated more accurately. However, some of the ingredients added to the tint will reduce the gloss of the gold and silver pigments. When the customer proposes the maximum reflection capability as a condition, it is recommended to use dark colors, pale gold colors, and silver powders in their purest forms. Another factor that affects post-print gloss is the color purity or clarity of the resin used to make the ink. The higher the clarity of the resin, the more reflected light and the better the gloss of the ink.

When discussing the appearance of gold-silver ink, we should note a phenomenon: Since metal pigments are used in gold and silver inks, the appearance of the ink film after printing will change with the viewing angle. This is why it is generally not recommended to use traditional printing spectrophotometers to measure gold and silver prints. The accurate measurement tool is a spectrophotometer for the automation industry. The device recognizes colors from multiple angles and finally obtains an average value, which can accurately determine the color, but the price of such a device is usually unacceptable for a screen printing company.

The metal pigment particles are purchased separately from the binder and are very slow and careful when mixed; because the rapid mixing generates heat, it promotes oxidation, causes the metal flakes to decompose, turns silver into gray, turns gold into brown, and Reduce reflection and gloss.

The proportion of the pigment mixture varies depending on the size of the pigment flakes, and is also related to the desired ink film after printing. Generally speaking, it is safe to start mixing with 8% silver pigment or 15% gold pigment by weight. According to the ink manufacturer's recommendations to ensure the ink adhesion and appearance.

If possible, using the least pigment should be the best. Because the result will be better ink transfer properties and higher durability. Many printers think that adding more pigment powder to the mixture does not increase the gloss of the ink. The fact is that the smaller the number of pigments, the better the adhesion, and the more uniform the ink film, the more uniform it means that the smoother the surface, the better the reflective performance, and the better the gloss, of course. Therefore, the minimum amount of pigment should be used to meet the target color and coverage area.

When mixing silver inks, extreme care must be taken if the aluminum pigments are in powder form. Because ** can react with water or moisture to release hydrogen, it can cause an explosion. Therefore, if you insist on using ** to make silver ink, be sure to store the ** in a dry, suitable temperature place. In contrast, the presence of aluminum in a paste form is relatively safe, and all manufacturers also supply paste-like pigments that are solvent-based, water-based, and UV-dry ink compatible.

The Future of Screen Printing Gold and Silver Ink

Screen-printing ink makers are still working hard to refine gold and silver inks, making them easier to use and producing shocking results. In recent developments, metallic effect ink types have included new effects that provide the same appearance as chrome plating. But in order to get a real example of the chromium effect, the printer must carefully test to determine how much pigment is needed. The less commonly used pigment, the better the effect.

Gold and silver inks, especially silver inks, are completely impervious to radiation and this feature makes them ideal inks for screen printing applications, such as selective blocking of light in certain instruments. However, when metallic silver, which is highly reflective, is used as a protective coating, the color of the graphic printed thereon will change.

The good effects of screen printing of gold and silver inks can increase the value of many products related to prints, including binding, labeling, packaging decoration, and eye-catching graphics.

As with any other product, screen printers understand the composition, production process, and performance limitations of gold and silver inks. They can introduce the advantages of such inks to customers as much as possible. Therefore, gold and silver inks are printed. Another golden opportunity!