We all know that thermal paper will change color when used for a long time, and the cause of discoloration is the color changing layer inside the thermal paper. Below we will reveal the mystery inside the color-changing layer of thermal paper. The thermal paper color changing layer is composed of the following raw materials. First, leuco dye 1. Benzoquinones These types of thermal paper color-changing leuco dyes, the earliest used is the dye CVL (PH-1). It has a bright cobalt blue color when it is colored. The advantage is that the color reaction is fast, the color is deep, and it is not sublimated. Although it has the disadvantages of poor light resistance after color development, it is widely used because of its low price. In order to improve the performance of thermal paper materials, it has become a research hotspot to use CVL with other substances. 2. Both phenothiazine and phenoxazines belong to heterocyclic molecules. Among them, the most used one is the phenothiazine dye benzoyl methylene blue BLMB. It is characterized by slow coloration, but it is not easy to fade once it is colored. If BLMB is used in combination with CVL, BLMB is not easy to fade, so as to compensate for the shortcomings of CVL fading, thermal paper with better performance can be obtained. The dye molecule is a phenoxazine compound. When these two types of compounds act on a color developer, the amide bond is broken to form a colored dye. 3. Fluorane-based fluorans are the mainstream of the development of thermal paper dyes in the world today, and have the most promising future. It can display yellow, orange, red, green, black and other colors, and it is most common to display black fluoran dyes. If a fluoran compound is used in combination, different colors can be prepared. For example, a greenish F-4 can be mixed with a reddish F-3 to obtain a stable black color. Second, the color developer In addition, it is often necessary to add some additives to the color paper of the thermal paper to improve the performance of the thermal paper. For example, fillers are added to increase the opacity of the paper, and the contrast between the image and the background color is increased; the binder is added to give the coating a good surface strength and printing performance, and a colloidal protective film is formed between the dye and the developer to make two Isolation prevents premature reaction; adding a sensitizer to lower the melting point of the developer, and thus achieving the effect of controlling the reaction speed of the thermal paper coating. Plastic Toothbrush,Plastic Toothbrushes,Travel Plastic Toothbrush,Recycled Plastic Toothbrush Guangzhou China Han Oral Products Co., Ltd. , https://www.gzchinahan.com
The leuco dye is usually composed of an organic molecule having a lactone ring or a heterocyclic structure. Ideal thermal paper color change layer The leuco dye itself should be colorless or nearly white. It is stable at normal temperature, will not be oxidized by air, does not change color when it is light, is insoluble in water, and can react quickly with the developer to produce high concentration. Colored dyes. Here are three types of commonly used thermal paper color changing layers leuco dyes.
The chromogenic agent usually functions as a proton donor, generally an organic solid acidic substance, and a phenolic compound is often used. Preferably, the developer is itself colorless or nearly white, has a low melting point, is insoluble in water, and reacts rapidly with a leuco dye. Bisphenol A (BPA) is a commonly used color developer. It has the disadvantage of high melting point (156~158°C) and low colorimetric sensitivity. It needs to be combined with sensitizer. Developers having a low melting point and high sensitivity have been developed, such as benzyl p-hydroxybenzoate.
The mystery inside the color paper of the thermal paper