As an indispensable consumable in daily office work, commercial packaging, logistics labeling and other scenarios, the core of label paper's efficient color development and precise adhesion lies in the coordinated action of scientific structural design and physical and chemical mechanisms. Different from traditional printing materials that require ink and toner, label paper (especially carbonless and thermal label paper) achieves inkless color development and rapid imaging through its unique working principle, adapting to the needs of various scenarios. This article will detailedly disassemble the working principle of label paper from three dimensions: core structure, color development mechanism and classification differences, and clarify the underlying logic of its operation.

Core Structure of Label Paper: The Basic Guarantee for Color Development

The working principle of label paper first relies on its special layered structure. Different types of label paper (carbonless label paper, thermal label paper) have slightly different structures, but all take "functional coating + substrate" as the core. Each layer has a clear division of labor and works synergistically to support color development and use.

(I) Layered Structure of Carbonless Label Paper

Carbonless label paper (also known as pressure-sensitive color-developing label paper) is a common type of multi-part documents and multi-layer labels. Its core advantage is that it does not require ink and can realize multi-part synchronous color development only through pressure. Structurally, it is divided into single-layer self-sensitive type and multi-layer combined type (the most common is three-layer), and each layer has a dedicated coating:

1.Top Paper (CB Paper): Only a layer of coating (CB layer) containing microcapsules is coated on the back. These microcapsules have a diameter of only 3~7 microns, with a shell made of resin, and the interior is wrapped with carrier oil dissolved with colorless dye (color former). At room temperature, the microcapsules are stable, and the colorless dye cannot overflow, so the surface of the paper appears white.

2.Middle Paper (CFB Paper): As the "bridge" for multi-layer color development, the front side is coated with a coating (CF layer) containing color developer, and the back side is also coated with a microcapsule coating (CB layer). It can not only receive the color development signal from the upper paper, but also transmit it to the lower paper, realizing the effect of multi-part synchronous color development, and it is also the most costly layer in multi-layer carbonless label paper.

3.Bottom Paper (CF Paper): Only a coating (CF layer) containing color developer is coated on the front side, without back-coated microcapsules. Its main function is to receive the color development signal transmitted from the upper layer, present the final content, and serve as the archiving page of multi-layer labels.

4.In addition, self-sensitive carbonless label paper (SC paper) is coated with both color developer and microcapsules on the front side of the same paper, and a microcapsule layer on the back side. It can develop color by pressing itself without multi-layer superposition, which is suitable for simple single-layer labeling scenarios.

(II) Core Structure of Thermal Label Paper

Thermal label paper is a common type in scenarios such as supermarket cash registers and express waybills. Its structure is relatively simple, mainly composed of three parts: substrate, thermal coating and protective layer:

1.Substrate: Mostly paper or film (such as BOPP, PET), which plays the role of carrying the coating and ensuring the toughness of the label, adapting to different use scenarios (such as waterproof and tear-proof requirements).

2.Thermal Coating: The core functional layer, including colorless dye, color developer and sensitizer. At room temperature, the colorless dye does not react with the color developer, and the paper appears white; when stimulated by high temperature, the sensitizer triggers the reaction between the two to achieve color development.

3.Protective Layer: A thin top coating that enhances scratch resistance, water resistance and UV stability, protecting printed content from fading and extending label lifespan.

III. Why Choose Casperg Paper for High-Quality Label Solutions

At Casperg Paper Industrial Co., Ltd.， we specialize in R&D, production and customization of premium carbonless paper, thermal label paper and self-adhesive labels. With strict raw material selection, advanced coating technology and precise quality control, our label paper features:

• High color density: Clear, sharp text with excellent contrast.
• Stable performance: Consistent color development under varying temperature and humidity.
• Durable adhesion: Reliable sticking on diverse surfaces.
• Eco-friendly: Non-toxic, odorless and compliant with international safety standards.

Conclusion