The "tech outer layer" of the tiny dial: A deep analysis of the advanced technology of PVD in watches

When you touch the smooth matte black case of the watch, admire the warm and lustrous appearance of the rose gold strap under the light, or marvel at the intact appearance of the diving watch in the deep sea environment, you might not think that these stunning textures and durability are all attributed to a key technology - physical vacuum deposition (PVD). As the most widely used surface treatment process in modern watchmaking, physical vacuum deposition, with its environmentally friendly, efficient, and excellent membrane layer performance characteristics, has become the core support for the aesthetic upgrade and functional enhancement of watches, and has dressed each precise timepiece with a "tech outer layer". Today, let's deeply uncover the mystery of the physical vacuum deposition of watches.

To understand physical vacuum deposition of watches, one must first clarify its core definition: In a high vacuum environment, through physical methods (such as sputtering, evaporation), the solid coating materials of metals, ceramics, etc. are transformed into atomic, ion, or molecular states, and deposited on the surface of watch components to form a film. This technology is called PVD (Physical Vapor Deposition) in English. Compared with traditional electroplating processes, its greatest advantage lies in the uniform and dense film layer, strong adhesion, environmental friendliness without pollution (no chemical electrolyte and heavy metal emissions), and the ability to precisely control the thickness and composition of the film layer, perfectly meeting the strict requirements of watches for precision, durability, and aesthetics. Therefore, it has become the mainstream choice in the high-end watchmaking industry.

The core principle of the physical vacuum coating for watches is essentially "the migration and deposition of matter in the gaseous state". The entire process is completed in a high vacuum environment, avoiding interference from air molecules on the quality of the film layer. In simple terms, this process is like cultivating a special "film plant" in a vacuum "greenhouse". It mainly consists of three key steps:

1. The first step is vacuum preparation. Clean watch components (case, strap, dial, etc.) are placed in a sealed vacuum chamber. Through a three-stage vacuum pumping system consisting of "mechanical pump + rotary pump + molecular pump", the pressure inside the chamber is reduced to a high vacuum state of 10⁻³ to 10⁻⁵ Pa - this pressure is equivalent to the atmospheric pressure of outer space on Earth, minimizing the influence of air impurities on the coating quality.
2. The second step is material ionization and vaporization. Through physical methods such as magnetron sputtering or arc discharge, the coating materials (referred to as "target materials" in the industry) undergo ionization or vaporization to form tiny high-energy particles.
3. The third step is film deposition. Under the guidance of an electric field, these high-energy particles will move uniformly towards the surface of the watch components and eventually tightly adhere to form a thin film. Throughout the process, parameters such as temperature, vacuum degree, gas ratio, and target material current need to be precisely controlled, with errors needing to be at the micrometer level, to ensure the uniformity and adhesion of the film layer.

In the watch industry, physical vacuum coating (PVD) is mainly divided into two core processes - magnetron sputtering and arc ion plating. Due to their different principles, these two processes have distinct application scenarios and membrane layer properties. Together, they cover all dimensions of watch requirements, from decoration to functionality.

• Among them, the magnetron sputtering process is the "main force" of decorative coatings for watches. Its core principle is to control the trajectory of electrons through a magnetic field, allowing electrons to continuously bombard the surface of the target material, causing the atoms of the target material to detach and deposit on the surface of the workpiece. The advantages of this process are excellent uniformity of the membrane layer and high surface finish, enabling precise reproduction of the fine texture of metals. Therefore, it is widely used to prepare decorative membrane layers such as rose gold, champagne gold, and matte black. For example, the popular rose gold watch case is formed by adjusting the composition ratio of titanium target and chromium target, combined with reactive gases such as nitrogen, to create a nitrogenized titanium membrane layer that is consistent with the texture of 18K gold.
• The arc ion plating process is the "outstanding performer" of functional coatings. It generates high temperature through arc discharge, directly ionizing the target material into high-energy ions, and then depositing them onto the surface of the workpiece to form a membrane layer. The membrane layer formed by this process has extremely high hardness and stronger adhesion, and is particularly suitable for preparing wear-resistant and corrosion-resistant functional membrane layers. For example, the diamond-like carbon (DLC) membrane commonly used in the watch industry is prepared through the arc ion plating process and is widely used in the watch cases and movement components of sports watches and tools.

The value of physical vacuum coating for modern watches is primarily reflected in the breakthrough in aesthetic expression. It completely breaks the color limitations of traditional watch materials, enabling ordinary substrates to present high-end textures. In the past, the colors of watches were largely dependent on the materials themselves - the golden yellow of gold, the silver white of stainless steel, and the light gray of titanium metal. The choices were very limited; while the physical vacuum coating technology has enabled a "qualitative leap" in the colors and textures of watches. By changing different target materials and reaction gases, ordinary stainless steel watch cases can easily achieve various styles: using a titanium target combined with nitrogen gas can produce different layers of rose gold from light pink to deep rose, with a warm and delicate texture that is almost indistinguishable from high-purity K gold; using a chromium target combined with acetylene gas can create a low-key and luxurious matte black layer, which is wear-resistant and not prone to fingerprints; and there is also an advanced multi-layer magnetic sputtering process, by stacking different refractive index layers, it can achieve a gradient colorful effect from light blue to light purple, making the simple design of the watch more visually memorable. A classic series of a Swiss watch brand has adopted the multi-layer physical vacuum coating technology, using only 316L stainless steel substrate to achieve an appearance consistent with 18K rose gold, not only reducing the production cost by 30%, but also avoiding the environmental pressure caused by the mining of precious metals, becoming a model that balances aesthetics and environmental protection in the industry.

In addition to the aesthetic upgrade, the core value of physical vacuum coating is to provide a "invisible armor" for the watch, significantly enhancing its durability and service life. As a precision instrument worn daily, the case and strap of the watch need to endure friction and corrosion from sweat over a long period, while the components of the movement rely on extremely low friction loss to ensure accurate timekeeping. The physical vacuum coating film layer precisely addresses these issues. Although this film layer is thin (typically only a few micrometers to several tens of micrometers, equivalent to one-tenth of the diameter of a hair strand), its performance is extremely excellent: for example, the DLC-like diamond-like carbon film prepared by arc ion plating has a hardness of over HV2000, far exceeding stainless steel (HV200-300), which can increase the hardness of the watch case surface by 2-3 grades, making it less prone to scratches from daily impacts and friction; to address the problem of fingerprints on titanium alloy straps, the anti-fingerprint PVD film layer prepared by magnetron sputtering can make fingerprints difficult to adhere, while also preventing corrosion from salt and grease in sweat, maintaining cleanliness and freshness over a long period of wearing. For the precise components inside the movement, such as gears and escapement wheels, by using physical vacuum coating of molybdenum disulfide solid lubricating film or tungsten carbide hard film, the friction coefficient can be reduced to below 0.05, reducing power loss by 15% and making the watch's timekeeping more accurate. Test data from a self-developed movement brand shows that after PVD coating treatment, the swing amplitude attenuation rate of the movement after five years drops from 12% to 4%, truly achieving the quality commitment of "lasting precision".

From the perspective of the specific components of the watch, the application of physical vacuum deposition coating (PVD) covers almost all key parts, achieving "precise adaptation and all-round protection".

• The case and strap, which are the visual focus and frequently contacted parts, are the main application scenarios of PVD coating: the common all-black style of sports watches often uses arc ion deposition DLC film, which combines wear resistance and corrosion resistance; the rose gold and champagne gold styles of luxury watches mainly use magnetic control sputtering PVD film to ensure uniform and fine texture; the case and strap of diving watches will adopt multi-layer PVD coating technology, first depositing a layer of corrosion-resistant chromium film, then depositing a decorative film to ensure long-term stability in deep-sea high-pressure and high-salt environments.
• The scales and numbers on the dial are coated with zinc sulfide night light film through vacuum evaporation coating (a branch process of PVD) to ensure clear reading of time in darkness; the background of the dial of high-end watches can also be plated with pearl mother-of-pearl film or metallic texture film through magnetic control sputtering to enhance visual depth.
• The sapphire watch crystal is coated with multi-layer magnetic control sputtering PVD anti-reflective film, reducing the reflectivity from over 8% to below 1%, significantly improving the clarity of reading time.
• Even the tiny gears, springs, etc. inside the movement will be coated with precise PVD coating to reduce friction loss and ensure the stability of timekeeping.

It is worth noting that physical vacuum coating (PVD) is also a significant breakthrough for the watch industry in achieving green manufacturing. This is also one of the key reasons why it can replace traditional electroplating and become the standard for high-end watchmaking. The traditional electroplating process requires the use of a large amount of chemical reagents, generating wastewater and waste gas containing heavy metals, which cause severe pollution to the environment. In contrast, physical vacuum coating is carried out throughout in a high-vacuum environment, without the need for chemical electrolytes. It achieves material migration and deposition through physical means, with zero emission of heavy metals and zero pollution throughout the process. This solves the environmental protection problem of surface treatment at its source. With the enhancement of global environmental awareness, more and more watch brands are adopting the PVD process as their core surface treatment technology. It is not only widely used in mass production series but also through customized PVD coating solutions in high-end custom series, achieving a balance between environmental protection and high-end texture. Nowadays, the environmental attributes of PVD technology have become an important support for the brand's sustainable development, and also aligns with the demands of modern consumers for green consumption.

From the perspective of technological development, the physical vacuum deposition coating (PVD) for watches is advancing towards greater precision, greater diversity, and more customization. In terms of precision, the current PVD coating process can control the thickness error of the coating layer within 0.1 microns and the color error within the level of ΔE < 0.5, reaching a level where it is indistinguishable to the naked eye, ensuring that the appearance texture of each watch is highly consistent. In terms of diversity, customized PVD coating solutions for different usage scenarios are constantly emerging: such as an extremely corrosion-resistant PVD film suitable for deep-sea diving, a high-temperature-resistant PVD film suitable for extreme temperature environments, and a biocompatible PVD film suitable for medical scenarios, etc., further expanding the application boundaries of watches. In terms of customization, with the upgrading of consumption, consumers' personalized demands for watches are increasing day by day. PVD technology, with its customizable colors and textures, has become an important breakthrough point for brand differentiation competition - some brands have launched PVD customization services, which can customize the exclusive color and gradient effect of the watch case coating according to user needs, making the watch truly become a unique wearable art piece.

Between the small dials, the physical vacuum deposition coating (PVD) technology uses the power of technology to balance aesthetics and functionality. It gives ordinary substrates a high-end texture, enhances the durability of precision timepieces, and aligns with the development trend of the times with its environmental attributes. When we next admire the exquisite appearance of a watch and trust its accurate timekeeping, we might as well take a look at this micron-level "technology coat" - it is precisely this seemingly insignificant film that carries the ultimate pursuit of detail in modern watchmaking, allowing "time aesthetics" to last for a long time, and upgrading the watch from a simple timekeeping tool to a wearable art piece with texture, durability, and environmental value.