1. Selection of connecting material (resin):

1-1. Effect of binder (resin) viscosity and solid content on color concentration and surface gloss:

Resin in the ink mixing oil. Since the choice of color-changing ink has a very important impact on the color concentration and surface gloss of thermal color-changing ink, this effect is more significant for black ink. The pigment content is much higher than that of ordinary ink. If the color-changing ink is prepared with the resin of ordinary ink This will cause the ink to become too viscous and unusable. Therefore, when adjusting ink, you can only reduce the amount of resin and increase the amount of solvent to reduce the viscosity of the ink. The consequence of this is that when the ink layer of the printed product dries, the resin content is very small and is not enough to fill the gaps between the pigments, making the surface of the ink layer uneven and dull, causing diffuse reflection of light. Therefore, the apparent color density of the ink layer is low and the grayscale is high. For black ink, it looks gray but not black. (If a layer of transparent varnish is printed on the surface of this print, the blackness can be obviously increased.) Therefore, the preparation of thermochromic ink must use resin with high solid content and low viscosity (low polymerization degree or low molecular weight). This is how you get good results.Pearlescent Pigments, color-changing pigments,Fluorescent Pigments

1-2. The relationship between the type of binder (resin) and its refractive index and the color concentration and transparency of the color-changing ink (paint) after decolorization:

Thermal decolorizing series (R series) color-changing pigments are often used to print "cover-display" patterns, which require the color-changing ink layer on the surface of the printed product to completely cover the underlying pattern when it develops color, and to be as transparent as possible after reaching the decolorizing temperature so that the underlying pattern can be clearly displayed. In this type of application, if the resin is not selected properly, "white fog" will be generated after the covering ink layer is decolorized, making the underlying pattern unclear. The basic reason is that the optical refractive index of the selected resin is inconsistent with that of the wall material of the color-changing pigment microcapsule. Countless microcapsules are dispersed in the ink layer to form a large number of optical refractive interfaces, just like the white opaque phenomenon formed after a piece of transparent glass is crushed. Proper selection of resin can greatly reduce the amount of light in the color-changing ink layer.

This refraction phenomenon makes the ink layer more transparent after decolorization. Generally speaking, the transparency of alkyd resin and acrylic resin is better, while the transparency of polyamide resin and nitrocellulose is extremely poor.

2. The choice of solvent and its influence on color change performance:

2-1. The influence of the refractive index of the solvent on the color concentration of the color-changing ink (coating):

The optical refractive index of the color-changing pigment microcapsule material is about 1.50-1.54. When the optical refractive index of the solvent is the same or close to it, the color concentration of the ink is higher, such as toluene, xylene and benzyl alcohol (the optical refractive index is 1.496, 1.493 and 1.540 respectively). On the contrary, when the optical refractive index of the two is greatly different, the apparent color concentration of the ink is lower. For example, n-propanol (1.386), isopropanol (1.377), acetone (1.359), ethyl acetate (1.372), butyl acetate (1.394), ethylene glycol ethyl ether (1.392).

However, the effect of solvent on the color concentration of color-changing ink is temporary. After printing, as the solvent in the ink layer evaporates, this effect will gradually disappear.

2-2. Effect of solvent on pigment discoloration performance:

Thermochromic pigments have different tolerances to different solvents. Soaking in some solvents for 6 months will not affect their color-changing properties, but other solvents can corrode the surface of the microcapsules and penetrate into the interior within a few hours to a few weeks, causing the color-changing properties of the pigment to fade or even disappear completely. After the solvent evaporates, some of this color-changing performance fading can be partially restored, while some are completely irreversible. Generally speaking, solvents containing less than 3 carbon atoms are more destructive to color-changing pigments, and solvents containing more than 6 carbon atoms have little effect on the pigment. In addition, the corrosive effect of solvents will be more obvious at higher temperatures. The following is the approximate time required for the color-changing properties of thermochromic pigments to fade when immersed in different solvents at a temperature of 20°C. Pearlescent pigments, color-changing pigments, fluorescent pigments

Since the solvent resistance of products of different colors and batches is not the same, the specific data is subject to actual measurement. The following data is for reference only.

Based on the above reasons, the following measures should be taken when mixing inks and coatings:

---Try to use less or no alcohol solvents below C4 and replace them with other solvents.For example, cyclohexanone may be used instead of propanol.

---When solvents such as propanol must be used, the ink (paint) should be prepared as it is used and avoid storage.

Because the color-changing pigments produced by our company are easily dispersed in the resin liquid, all ink (paint) components except the color-changing pigments can be prepared, and the specified amount of color-changing pigments can be added before printing. After stirring evenly, it can be added to the ink fountain to start printing. You can also prepare the ink components except propanol, isopropanol, etc. (including color-changing pigments), add the specified amount of the above solvents before use, stir evenly and start printing. Be careful not to prepare too much ink at a time, prepare it as needed, and do not store it.

Special note: Finished diluents/mixed solvents and some resin solutions commonly used in the ink industry may contain ingredients such as ethanol, acetone, propanol, etc. that damage the performance of color-changing pigments. Even if the content of harmful ingredients is very small, it will cause serious effects.