A Detailed Introduction To Hot Stamping (Heat Transfer) For Bag LogosⅠ
Hot stamping, also known as foil stamping or heat transfer printing, is a prevalent and crucial finishing process in bag manufacturing. It involves using heat and pressure to transfer a design onto a material's surface and is widely used on various substrates such as leather, PU, and canvas.
I. Working Principle
The core principle of hot stamping is thermal transfer. The process hinges on three critical elements: heat, pressure, and dwell time (time).
A custom-made metal stamping die (often made from brass, zinc, or magnesium) is heated by the machine's heating element. A specialized foil film (e.g., metallized foil or pigment foil) is then placed between the heated die and the substrate (the bag material). Upon application of significant pressure for a set duration, the coating layers of the foil (e.g., the release layer, colour layer, and adhesive layer) separate from the polyester carrier film and permanently bond to the substrate's surface.
This process results in a crisp, glossy logo. It is a complex interplay of physical and chemical changes, primarily involving the melting and subsequent curing of the adhesive layer.
II. Process Methods and Classifications
The hot stamping process can be categorized based on the materials used:
1.Metallized Foil Stamping: This is the most common type. Metallized foil typically consists of multiple layers (carrier, release layer, lacquer (colour) layer, metallized layer, and adhesive layer). The application of heat and pressure transfers the coloured lacquer and metallized layer together, creating a signature metallic sheen. Available in gold, silver, colours, and holographic effects, this is commonly referred to as "gold stamping" or "silver stamping."
2.Pigment Foil Stamping: This foil lacks a metallic layer. Instead, it transfers a solid, opaque pigment layer, resulting in a matte or glossy solid colour finish (e.g., black, white, red). It offers excellent opacity, making it ideal for applying light-coloured logos onto dark materials.
3.TPU (Thermoplastic Polyurethane) Foil Stamping: This process uses a TPU film. The resulting logo has a slightly raised, soft-touch, and elastic quality. Highly durable and abrasion-resistant, this effect is frequently used for logos on sportswear and outdoor gear bags.
4.Die-Sunk Stamping: A combination technique. A depression is first embossed into the material (like leather) using hydraulic or heat pressure. The hot stamping is then precisely applied within this recessed area. This creates a logo with rich colour and pronounced three-dimensional depth, yielding a high-end, sophisticated appearance.
5.Foil Stamping with Embossing/Debossing: This combines stamping with embossing (raising the design) or debossing (pressing the design in) into a single operation. The logo possesses both a textured, raised or recessed profile and the metallic or coloured finish of the foil, creating strong visual hierarchy and tactility.
The standard production workflow is: Die creation -> Mounting the die and calibrating temperature, pressure, and time -> Positioning the substrate and foil -> Activating the press for stamping -> Cooling and releasing (peeling away the carrier film).
