Storage ink characteristics and application

Luminous ink will be a kind of ink in a wide range of applications in the field of modern printing. It can be used for printing official documents, securities, documents, and advanced cigarettes, wine, medicines, cosmetics, and even applying a light-storing ink in some currencies. To anti-counterfeiting effect.

The main component of the fluorescent ink is a fluorescent pigment, and the main component of the light-storing ink is a light-storing pigment. The difference between the two types of pigments is:

Fluorescent pigments: When external light (including ultraviolet light) is irradiated, certain forms of energy absorbed do not convert into heat energy but excite photons to release the absorbed energy in a form of low visible light, thereby generating fluorescent phenomena of different hue, different shades of light In combination with the formation of an unusually bright color, the luminescent phenomenon disappears when the illumination ceases, and this is called a fluorescent pigment. Fluorescent inks have poor lightfastness and are not suitable for long-term outdoor use.

Light-storing pigments: The light-storing pigment is a long-lasting phosphorescent material referred to as a long afterglow material, also known as a luminous material. This type of material has structural defects and impurity defects in the crystal lattice of the crystals formed during the synthesis process. The light emission caused by the material lattice defects is called self-excitation light, and the light emission caused by impurity defects is called activating light emission. The practical application of various types of light-emitting materials is mostly activated light-emitting materials. Luminous materials are based on the principle of light emission. Its excitation light sources are generally daylight and artificial light sources (lights). The light-emitting time varies and does not include radioactivity. It is safe for people and the environment. This luminescent material emits light in a dark environment without external light sources, and its luminous time is called afterglow. Long afterglow luminescent material is a type of energy absorbed by the excitation light and stored, after the light excitation stopped, and then slowly release the stored energy in the form of light. And it can last for a few or even a dozen hours of glowing material. This process of absorbing light → emitting light → storing → re-emitting light and repeating it indefinitely many times can be similar to the battery of a mobile phone in people's hands, and the principles of charging → discharging → recharging → re-discharging repeated use are similar. Therefore, it has been suggested that a long-lasting phosphor is called a light-storing type light-emitting material, and an ink prepared using this material is naturally called a light-storing ink. Long afterglow materials are used in a wide range of applications, including many types of products. Long afterglow materials are used to make luminescent paints, luminescent inks, luminescent plastics, luminescent fibers, luminescent paper, luminescent glass, luminescent ceramics, luminescent marble, and glowing concrete. In safety emergency, transportation, construction and decoration, instrumentation, electrical switch display and daily consumer goods decoration and many other aspects. The preparation methods and precautions for use of the printing inks and light-storage printing pastes related to the printing industry are described below:

First, light storage ink (light-emitting ink)

The names of light-emitting inks have been introduced in many books and magazines in the past. However, today's paper is very different from them. Its essence should be called light-storing inks.

The light-storing ink is a light-storing ink produced by adding a certain proportion of a light-storing material to the raw material of the clear ink and then processing it. The light-storing material in the ink, the long-lasting light-emitting material used, which is a type of visible light that absorbs sunlight or artificial light sources. In addition, substances that continue to emit light after the excitation is stopped. With the use of sunlight or light for light storage, and then emit light at night or in the dark, is a kind of energy storage, energy saving light-emitting materials. The long afterglow material does not consume electrical energy, but it can store the absorbed light energy of natural light and present bright and identifiable visible light in a dark environment. It has lighting function and can also play a role of indication and decoration. A "green" light source material. It has also been mentioned in front that it can also contain radioactive materials without relying on external light sources and rely on radioactive energy to make it glow. This kind of ink is also called self-luminous ink. The radiant energy of luminescent inks, starting with natural uranium, later uses artificial radioisotopes, but such inks have an impact on the environment or the safety of people. The afterglow time of the aluminate system, silicate system, and sulphide system light-storage type light-emitting materials, especially the alkaline earth aluminate long afterglow materials activated by rare earths, can reach over 12 hours, and has a long-term cycle of daylight storage and nighttime light emission. The characteristics of light storage and light emission have very broad application prospects.

1, the composition of the storage ink

Luminescent inks are made from luminescent pigments (light-storing materials), organic resins, organic solvents, and auxiliaries in certain proportions through special processing techniques. The selected resin should have good light transmittance, and the color of the resin has an effect on its light-emitting brightness. Therefore, the principle of choosing the resin and varnish is colorless or light-colored and has good transparency. Since the light-storing material is a weakly alkaline substance, it is preferable to select the resin as neutral or weakly acidic. The types of resins or varnishes selected are as follows: Epoxy resin (E440), polyurethane resin, amino varnish, polyester resin, acrylic resin, hydroxy acrylic resin, acrylic polyurethane varnish (two-component), light color alkyd varnish, fluorine Resin and so on. If a neutral transparent organic resin is selected, the particle size of the light-storing material should be controlled within the range of 45 to 65 microns so that a practical light-storing ink can be produced. Usually based on different substrates to choose different types of transparent varnish, such as printing materials for metal materials, metal varnish should be used, the substrate is PVC material, optional PVC varnish.

2. Preparation of storage ink

Storage ink production process: The production technology of the storage ink directly affects its luminescent properties and application characteristics. Therefore, the process conditions must be strictly controlled and the following issues should be noted.

(1) The preparation of light-storing inks should be done in glass or enamel containers.

(2) The particle size of the light-storing material is selected to be as small as possible so that the light-storage material can be evenly distributed in the ink material.

(3) When the ink is formulated, no grinding means may be used. In order to make the light-storage material evenly distributed, a high-speed stirring method may be used.

(4) The relative density of the light-storage material is 3.6 to 4.1. The light-storage material can easily sink during preparation. By using an anti-settling agent (fumed silica), the shelf life of the light-storage ink can be increased.

(5) Do not use heavy metal compounds as additives.
Although the storage of light-storage printing paste is made of a light-storing type light-emitting material and a transparent printing paste, the requirements for the printing paste composition should be that the use of an adhesive, a paste, and an auxiliary additive all have no effect on the light-storage material; Aluminate, silicate, and sulfide system light storage materials are safe to humans and the environment. Such as the use of rare earth alumina light storage luminous material is easy to be hydrolyzed, so when preparing printing paste, it is best to use a special white emulsified paste made from white flame oil (similar to A paste), printing soft hand feeling is good, the film has good transparency Adhesive ingredients, generally do not add cross-linking agent to meet the various standards of fastness. If the rheological properties of the printing paste are changed due to the addition of a light-storing pigment, an oil-based rheological property modifier and a hand-feeling fastness adjusting agent may be added in order to obtain the best printing effect. The light-storing printing paste is an oil-based printing paste. Therefore, in principle, the paste cannot be used to modulate the printing paste using a thickener paste compound that is synthesized by the all-aqueous phase system. Since the light-storing material is more expensive, it will be affected by the loss of partial hydrolysis. effect.

The biggest disadvantage of aluminate materials is poor water resistance, which leads to decomposition of water, resulting in reduced luminescence and even complete loss of luminescence. When it is necessary to use an aqueous slurry, the surface of the light-storing material may be first subjected to surface coating treatment (ie, light-emitting material is micro-gelled), so that the water-repellent performance can be improved. Furthermore, from the viewpoint of the properties of the ingredients, a neutral or alkaline transparent printing paste is used together with the light-storing material. The preparation method is: in a clean stainless steel container, the paste→adhesive→variable-speed emulsification is performed in the following order: Stir at high speed into a homogenous slurry → Add oily rheology modifier and feel fastness modifier → Medium speed into a light storage printing paste Ready-to-use stock slurry.

Prior to printing, 20% to 25% (mass) of the light-storing material is added to the above slurry, and then blended at medium or slow speed for printing on the machine. Do not use high-speed beating when mixing, so as not to affect the luminous effect.

3, the use of gloss ink should pay attention to the following matters:

(1) The viscosity of the prepared storage ink is between 300~500Pa. Around s, during printing, the viscosity of the ink should be adjusted with thinner to suit the printing process.

(2) When using screen printing inks for screen printing patterns or logos, polyester screens below 200 mesh should generally be selected. 80-120 mesh screen cloths can be used to obtain the best luminous effect.

(3) When using a light-storing ink, consider printing on a white substrate as much as possible. This can better improve the brightness and afterglow time of the printed pattern or logo.

(4) When the coating thickness of the printing and accumulating ink is controlled at 130 to 150 μm, the light emitting effect is the best. Therefore, this thickness can be achieved by using 80 mesh screen printing twice.

(5) When the substrate is a transparent object, the white ink should be printed before printing the light-storing ink, which can improve the light-emitting effect.

4, storage ink practical examples

Examples of application of light-storage light-emitting ink screen printing are as follows: The formula of light-storing light-emitting ink is (mass ratio): PVC ink (ss-777) 50 than light-storage material (PLO-7D) 50; printing method: use 100 mesh screen plate , printing on copperplate sticker paper twice, the afterglow luminance value after printing is as follows:

Afterglow time 1min 5min 10min

Afterglow brightness mcd/m2 815 207 103

Second, light storage printing paste

1. Composition and preparation of luminous luminous printing paste

There are two problems that must be solved when storing light-emitting luminescent materials on textile printing:

(1) The protection of the light-storing luminescent material and its own stability.

(2) The combination of the light-storing light-emitting material and the fabric forms a uniform one-piece pattern.

Source: 21st Century Fine Chemicals Network