製品知識

サファイアガラスの欠点について考えたことはありますか?

その制限を理解することは、その使用について情報に基づいた意思決定を行うために非常に重要です。

サファイアガラスの欠点を掘り下げ、考えられる解決策を探ってみましょう。

サファイア ガラスには多くの利点がありますが、特定の用途での使用が制限される可能性があるいくつかの欠点もあります。

Some of the main drawbacks of sapphire glass include:

Cost:

The production cost of sapphire glass is higher compared to other types of glass or transparent materials. The process of growing synthetic sapphire crystals is complex and time-consuming, involving high temperatures, specialized equipment, and precise control of growth conditions, which increases production costs. Therefore, sapphire glass is often more expensive than traditional glass or other transparent materials, making its cost-effectiveness lower in some applications.

Brittle Nature:

Despite its high hardness, sapphire glass is relatively brittle compared to materials like tempered glass. Under certain conditions, sapphire glass is prone to fracture or breakage, especially when subjected to significant impact or pressure. This brittleness makes sapphire glass more susceptible to damage in applications involving high impact forces or mechanical stress.

Difficulty in Processing:

Sapphire glass is more challenging to process compared to other materials. It is a crystalline material that requires specialized cutting, grinding, and polishing techniques, which can be more time-consuming and expensive. Additionally, sapphire glass is difficult to bond or join, which may limit its use in applications requiring bonding or sealing.

Limited Size and Thickness:

Due to the challenges in growing large and thick sapphire crystals, the size and thickness of sapphire glass are relatively limited. Compared to traditional glass, sapphire glass typically has smaller dimensions and thinner thicknesses, which may not be suitable for some applications requiring larger or thicker glass components.

Weight:

Sapphire glass has a higher density than traditional glass, meaning it can be heavier for a given size and thickness. This may be a disadvantage in weight-sensitive applications or when designing lightweight devices, where the weight of sapphire glass needs to be considered.

More Energy-Intensive Production:

The production of synthetic sapphire crystals used for sapphire glass requires high temperatures and energy-intensive processes, which may result in higher energy consumption and environmental impact compared to other materials. This may be a concern for applications or industries with environmental considerations.

Reflectance Without Anti-Reflective (AR) Coating:

Sapphire glass has a relatively high refractive index, which can lead to significant reflection on its surface without proper anti-reflective (AR) coating. This may result in unnecessary reflection or glare in certain applications, such as displays or optical lenses, requiring additional AR coatings to mitigate this issue.

While sapphire glass offers many advantages, it also has several drawbacks, including higher cost, brittleness, processing difficulties, limited size and thickness, weight, more energy-intensive production, and reflectance without AR coating. When evaluating the suitability of sapphire glass for specific applications, these limitations need to be considered, and alternative materials may be preferred based on the requirements and constraints of the application.

時計を着用したことのある友人は、この現象を経験したことがあるかもしれません。太陽光の下では、時計のガラス表面が光を激しく反射し、時刻の読み取りに影響を与えます。

ガラス表面の反射率が高いため、強い光の下では時間を明確に読み取ることが困難になり、時計の実用性が低下し、ユーザーエクスペリエンスに影響を与えます。

To address this issue, it is possible to apply a coating to the watch glass using anti-reflective coating technology to reduce the reflection of the glass surface and improve the readability of the watch under different lighting conditions. By using AR coating technology, the watch glass surface can effectively reduce glare and reflection, allowing for clear time reading under various lighting conditions.

Let’s take a look at the classification of watch glass coatings;

Types of Watch Glass Coatings

Watch glass coating refers to the application of a protective layer on the surface of a watch glass to enhance its durability, scratch resistance, and overall performance. This coating is typically applied using advanced techniques such as physical vapor deposition (PVD) or chemical vapor deposition (CVD). The purpose of watch glass coating is to improve the surface properties of the glass, making it more resistant to scratches, smudges, and other forms of damage that can occur during daily wear.

There are several types of coatings used in watchmaking:

• Anti-Reflective Coating（AR Coating）: This type of coating is applied to reduce glare and reflections on the watch glass, improving visibility and readability, especially in bright light conditions.
• Scratch-Resistant Coating: This coating is designed to make the watch glass more resistant to scratches, ensuring that it maintains its clarity and appearance over time.
• Anti-Fingerprint Coating: This coating helps repel fingerprints and smudges, keeping the watch glass clean and free from unwanted marks.
• Water-Repellent Coating: Some watch glasses are coated with a water-repellent layer to improve water resistance and prevent water droplets from adhering to the surface.
• UV-Protection Coating: This type of coating helps protect the watch glass from the harmful effects of ultraviolet (UV) radiation, which can cause discoloration and degradation over time.

Overall, watch glass coating plays a crucial role in enhancing the performance and longevity of a watch, ensuring that it remains in optimal condition for years to come

The most commonly used coating for watch glass is the AR coating.

What is the AR Coating on Watch Glass?

Let’s take a look at the classification of watch glass coatings.

Everyone knows that any glass will produce glare, including flat and curved glass. Therefore, like many optical instruments’ lenses (including eyeglass lenses), coating treatment is needed on the glass to reduce glare and increase transmittance. Especially for watches with relatively large diameters and curved glass, additional coating treatment is required.

Among the available optical film materials, the higher the refractive index, the stronger the glare. Magnesium fluoride (MgF2) has the smallest refractive index, only about 1.38, which is much lower than the refractive index of ordinary glass and even lower than that of sapphire glass. Therefore, using magnesium fluoride as the material to coat the glass of watches can reduce the reflectance of light from 4% to 1.8%.

Anti-reflective coating, also known as AR coating, is a thin layer of material coated on the glass surface, using the most advanced magnetron sputtering coating technology internationally to coat a layer of anti-reflective film on the surface of ordinary tempered glass.

AR (anti-reflective) coatings can be applied not only to sapphire glass but also to other types of glass surfaces, such as mineral glass or organic glass. The main function of AR coating is to reduce light reflection and improve light transmittance, thereby enhancing visual clarity.

This coating is particularly useful for those who need to read watches clearly under any lighting conditions. AR coating makes the colors transmitted through the glass more vivid and realistic.

Therefore, the effect of coating sapphire watch glass will be better. Especially for watches with relatively large diameters and curved glass, additional coating treatment is required.

Note: Coating cannot completely eliminate glare but can only reduce it.

Glass treated with coating will show a faint bluish-purple color.

There are various compounds available for application on watch glass, and these compounds differ in AR performance, durability, and readability. For example, some anti-glare films can give the glass a slight blue hue.

Some watches will mark to indicate that the watch glass has been coated, such as Omega watches. On the watch card or tag, a circle with the letter “あ” inside indicates that the watch glass has been coated, while “AA” indicates that both sides of the watch glass have been coated. Watches usually have many reflective spots, including the case, dial, hands, and are either shiny gold or shiny silver. Therefore, coating is also one of the measures to make it more convenient to wear watches. The coating on the watch glass is not as obvious as that on camera lenses, and it is often difficult to detect.

Anti-reflective coating is an important function of watches, and there is a significant difference between watches with and without anti-reflective coatings. Additionally, it can enhance the aesthetic appearance of the lens, making it look clearer and more transparent.

The history of AR coating on watch glass

The history of AR coating on watch glass dates back to the late 19th century when the concept was first discovered by Lord Rayleigh in 1886. He observed that slightly tarnished glass allowed more light to pass through compared to brand new glass, which reflected more light.

However, it wasn’t until the mid-20th century that significant advancements were made in the development and application of anti-reflective coatings on watch glass. In 1935, Soviet scientist Olexander Smakula perfected the technology for creating and applying anti-reflective coatings on optical lenses, which laid the foundation for further developments in the field.

By the end of World War II, the aviation industry had already adopted anti-reflective coatings for pilot watches. Pilots flying above cloud layers often faced intense glare from the sun, making it difficult to read their watches. Anti-reflective coatings became essential for improving readability in such conditions, leading to their widespread use in aviation timepieces.

Since then, advancements in materials and manufacturing techniques have allowed for the widespread adoption of AR coatings in the watchmaking industry. Today, AR coatings are a standard feature in many high-quality watches, offering improved readability and aesthetic appeal by reducing glare and reflections on the watch glass.

How many types of AR coating are there for watch glass?

The AR coating on watch glass mainly consists of two types:

• Double-sided coating: Coating is applied on both sides of the watch glass, enhancing anti-reflective effects but being less durable due to the outer coating’s susceptibility to scratches.
• Single-sided coating: Coating is applied only on one side of the glass, partially resolving reflection issues but reducing anti-reflective capability.

Apart from these two methods, there’s also spot coating, as seen in Rolex Oyster watches where the date magnifier is coated. This approach ensures anti-reflective effects and is located on the inner side, minimizing damage risks.

Some high-end brands may also apply anti-glare coating on the transparent case back or movement area to reduce light interference. Overall, there are various AR coating methods for watch glass, each with its pros and cons. The choice of coating method depends on practical needs and usage environments.

In the watchmaking industry, coating methods for watch glass are generally divided into two types: double-sided coating and single-sided coating. To further improve light transmission, multiple layers of coating can be applied on both sides of the glass.

Both coating methods have their advantages and disadvantages.

Double-sided coating involves applying coating on both sides of the glass, which increases AR efficiency but is less durable because the outer coating is prone to scratching.

Single-sided coating covers only one side of the glass, which avoids reflection issues but reduces anti-reflective capability.

In addition to these two methods, there’s also spot coating. For example, Rolex Oyster watches usually have no coating on the inner and outer sides of the mirror but the date magnifier is coated.

The reason for this operation is likely due to Rolex’s consideration of coating durability. Rolex watches are known for their precision and durability. Although the mirror may reflect light, it’s practical as long as you avoid direct light. Only coating the date display window makes sense because it’s small and curved, and without anti-glare, it’s hard to see clearly, causing significant interference. Moreover, Rolex’s coating is done on the inner side where the magnifier and mirror are bonded, an area that’s not prone to scratches or damage.

Of course, some high-end brands may also apply anti-glare coating on the transparent case back or movement area to reduce light interference. This helps prevent lubricating oil degradation due to light affecting the movement’s operation.

Advantages of Watch Glass AR Coating:

This technology has been widely applied in the watch manufacturing industry, but it also has its pros and cons.

Advantages:

• Enhanced Durability: Coated glass enhances the hardness of the watch surface, thereby improving its durability.
• Scratch Resistance: Coated glass effectively prevents scratches on the watch surface, preserving the aesthetic appeal of the watch.
• Anti-Glare: Coated glass reduces reflections on the watch surface, making the watch clearer and more visible in sunlight.
• Stain Resistance: Coated glass prevents contamination of the watch surface, making it easier to clean.

Disadvantages of Watch Glass AR Coating:

• Prone to Scratching: Although coated glass enhances the hardness of the watch surface, it is still susceptible to scratches, especially after prolonged use. While the sapphire glass surface may remain intact if scratched, the coating may be prone to visible scratches.
• Susceptible to Peeling: Coated glass is prone to peeling, particularly under prolonged exposure to vibrations or substances like seawater, sweat, hot water, or chemicals. Therefore, durability is a concern.
• Not Suitable for Diving: Coated glass is not suitable for diving as it cannot withstand the pressure of high-pressure water.
• Color Fading: Coated glass may change color over time due to prolonged exposure to sunlight, affecting the aesthetic appeal of the watch.
• Easy Wear and Tear: The external anti-reflective coating on watch glass is prone to wear and tear, becoming visibly apparent when scratched due to the reflection difference between the coated and scratched areas.
• Moisture Sensitivity: Watches stored for a prolonged period should be protected from moisture. Exposure to a humid environment can lead to mold formation on the glass surface and damage to the coating layer. Therefore, it’s essential to use desiccants in watch boxes and avoid humid environments.

Summary:

The advantages of watch-coated glass technology are significant, as it enhances the watch’s durability, scratch resistance, anti-reflective properties, and stain resistance. However, it also has some disadvantages, such as susceptibility to scratching, easy peeling, unsuitability for diving, and susceptibility to discoloration. Therefore, when purchasing a watch, careful consideration is required.

The production process of AR coating involves several steps:

1. Clean the sapphire surface to remove any dirt, dust, or oil that may affect the coating’s quality.
2. Apply the coating using the physical vapor deposition (PVD) process, where the glass is placed in a vacuum chamber and a thin layer of material is deposited onto the surface using sputtering.
3. Ensure the coating process is carried out in a controlled environment to achieve uniform coating and consistent thickness across the entire lens.
4. After coating, remove the glass from the vacuum chamber and inspect it to ensure there are no defects in the coating.
5. Harden the coating by exposing the glass to ultraviolet (UV) light, which activates chemical reactions in the coating, making it harder and more durable.

It’s important to note that, like any surface treatment, it may be susceptible to scratching and may require periodic maintenance. To address this, a layer of sapphire coating can be applied on top of the AR coating.

What color is the AR coating on watch glass?

The AR coating on watch glass is typically transparent, but in some cases, it may have a colored tint such as blue, green, or purple. However, whether transparent or colored, it’s not easily noticeable, and colored coatings are usually only discernible at specific angles of light.

最終的な考え:

In conclusion, the application of AR coating on watch glass is a significant advancement in watchmaking technology, offering both advantages and disadvantages. While it enhances durability, scratch resistance, and visibility under various lighting conditions, it is also prone to scratching, peeling, and discoloration over time. Therefore, when choosing a watch, it’s essential to weigh these factors and consider the intended usage environment. Overall, AR coating plays a crucial role in enhancing the performance and longevity of watches, contributing to a better user experience.

In the watch industry, why do most luxury watches choose to use sapphire crystal glass? Is sapphire crystal glass truly a symbol of high-end watch quality?

Why do people generally believe that watches with sapphire crystal glass are of higher quality?

We aim to unravel the performance and various differences between sapphire crystal glass and mineral glass through comparative analysis, providing wise selection advice for watch enthusiasts.

We first take a look at the three most common types of watch crystal materials:

1. Sapphire Glass
2. Mineral Glass (Inorganic Glass)
3. Acrylic Glass (Organic Glass)

We’ve covered watch glass in full before:

Everything I Learned About Watches Glasses From the Watch Factory

The Differences between Sapphire Watch Glass, Mineral Glass and Acrylic Glass?

The differences between these glass materials are as follows:

Acrylic Glass

Acrylic glass, commonly known as acrylic or organic glass, is a type of material used for watch crystals. It has a softer texture and higher malleability. In the past, many watches used this material, including antique watches found in the market today.

Pros:

• Excellent elasticity and resistant to shattering, often referred to as safety glass.

Cons:

• Susceptible to scratching and slightly lower transparency.

Reasons for Choosing:

• Low cost, scratches can be polished by a watchmaker without the need for replacement. If scratches are too deep, the crystal can be replaced inexpensively.

Mineral Crystal Glass

Mineral crystal glass, also known as Hardlex or Acrylic Crystal, is a type of glass reinforced with minerals. It was developed due to the scarcity of natural crystals.

Pros:

• High hardness, excellent transparency, clear and bright appearance.

Cons:

• Higher unit price compared to Acrylic Glass.

Reasons for Choosing:

• Moderate cost, high hardness, scratch-resistant, clear and transparent with no bubbles or watermarks, and it possesses piezoelectric properties, offering special health benefits.

Sapphire Crystal Glass

Sapphire crystal glass is a crystalline surface made from artificially compressed sapphire crystals, which are aluminum oxide crystals with impurities like iron oxide and titanium oxide removed. Chemically, Acrylic Sapphire is identical to natural sapphire and does not possess a “blue” color.

Pros:

• High density and scratch resistance, with hardness second only to diamond.
• Excellent light transmission, low friction, high temperature resistance, and superior durability compared to mineral crystal and Acrylic Glass .

Cons:

• Not shock-resistant, vulnerable to impact, pressure, or drops, which may lead to cracks upon impact.

Which Material is Superior?

In terms of hardness and abrasion resistance: Acrylic Glass < Mineral crystal glass < Sapphire crystal glass.

Each has its advantages: Acrylic Glass is less likely to break and can be polished; mineral crystal glass has moderate scratch resistance and stronger resistance to vertical impacts than sapphire crystal glass; sapphire crystal glass, despite its high hardness, is prone to breakage and incurs higher repair costs.

For high-end customers, sapphire crystal glass is recommended due to its special physical and chemical properties, high hardness (Mohs scale 9), superior wear resistance, and resistance to corrosion.

Lower-end watches often use organic glass, also known as acrylic, which despite being prone to scratches, is resilient and widely used in low-end watches.

Each material has its advantages and is chosen based on factors such as cost, scratch resistance, transparency, and durability.

Watch Glass: Sapphire Glass VS Mineral Glass

Sapphire crystal glass and mineral glass are two common materials used in watchmaking and the production of certain optical components. Here are some key differences between them:

1. Material Composition:
   • Sapphire Crystal Glass: Made from Acrylic Sapphire, a crystalline form of aluminum oxide. It is highly transparent and scratch-resistant.
   • Mineral Glass: Composed of various minerals, typically a hardened form of glass. It is less scratch-resistant compared to sapphire crystal.
2. Hardness:
   • Sapphire Crystal Glass: One of the hardest materials（Mohs: 9), second only to diamonds ( Mohs: 10). It is highly resistant to scratches.
   • Mineral Glass: While hardened, it is not as scratch-resistant as sapphire crystal and may show signs of wear over time.

Generally speaking, sapphire crystal is three times stronger than mineral glass and 20 times stronger than plastic glass.

1. 1. Scratch Resistance:
      • Sapphire Crystal Glass: Extremely resistant to scratches, making it ideal for applications where durability is crucial.
      • Mineral Glass: Can still resist scratches to some extent, but it is more prone to visible scratches compared to sapphire crystal.
   2. Clarity:
      • Sapphire Crystal Glass: Offers excellent transparency and clarity, allowing for a clear view of the dial and components underneath.
      • Mineral Glass: Generally provides good clarity but may have some distortion compared to sapphire crystal.
   3. Cost:
      • Sapphire Crystal Glass: Typically more expensive to produce, which can contribute to higher overall product costs.
      • Mineral Glass: Generally more cost-effective, making it a popular choice for more budget-friendly options.
   4. Weight:
      • Sapphire Crystal Glass: Heavier than mineral glass due to its density.
      • Mineral Glass: Lighter in comparison.
   5. Applications:
      • Sapphire Crystal Glass: Commonly used in high-end watches, camera lenses, and other applications where scratch resistance is crucial.
      • Mineral Glass: Found in a wide range of watches, eyeglasses, and other optical instruments.
   6. Shape:
      • Sapphire Crystal Glass: Sapphire crystal glass is limited to flat only.
      • Mineral Glass: Mineral crystal glass can be manufactured in a variety of forms.

Watch Glass: Sapphire Glass VS Acrylic Glass

In modern watches, the most commonly used material for the watch crystal is sapphire crystal glass. However, historically, watches have not always been made exclusively with this material as the watch crystal.

Take Rolex for example, modern Rolex watches have all switched to sapphire crystal glass, but in earlier times, before the end of the last century, Rolex also used plastic material acrylic for making the watch crystal. Acrylic material had two main advantages:

• Impact Resistance: Acrylic crystal, also known as plastic glass, is a reliable and durable material, especially resistant to impact. When tapped with a fingertip, it produces a clear and loud sound.
• Less Likely to Shatter: If an acrylic crystal breaks, it typically does not shatter into small fragments. As a result, there is almost no risk of damaging the watch dial, hands, or internal movement.

Of course, acrylic crystal is not without its drawbacks. Its biggest disadvantage is that it is not scratch-resistant and does not provide sufficient water resistance.

Acrylic material is a polymer composed of polymethyl methacrylate. In the era before sapphire crystal material became widespread, acrylic was the mainstream material used by various watch manufacturers.

The reason watchmakers favored it was because it offered a certain degree of impact resistance and protection. Even if an acrylic crystal were to break from a strong impact, it was less likely to shatter into fine particles, minimizing the impact on the watch dial.

However, acrylic crystals gradually began to be replaced because they had some noticeable drawbacks. For example, they had lower hardness and were prone to scratching, resulting in visible scratches on the crystal.

Additionally, acrylic crystals had poorer transparency, giving watches a slightly hazy appearance. Moreover, from a manufacturing perspective, plastic glass tended to be thicker, adding weight to the watch and making it less suitable for producing ultra-thin watches.

Today, well-known trendy sports watches like Casio’s G-SHOCK still use acrylic crystal glass. However, acrylic crystals have seen a resurgence in some popular sports watches today due to their impact resistance and less likelihood of shattering, and the lack of transparency does not significantly affect watches with LED screens.

Rolex gradually transitioned to technologically advanced sapphire crystal glass in the 1980s. This material is primarily composed of aluminum oxide (Al2O3), which is not a natural gemstone but rather synthetically produced. This allowed watch manufacturers to enjoy the benefits similar to natural sapphire without a significant increase in production costs.

The benefits of sapphire crystal glass lie in its high hardness, reaching a Mohs hardness of 9, which is just slightly lower than that of diamond. This means that it is not easy to scratch sapphire crystal, making it resistant to scratches.

Additionally, sapphire crystal glass has better transparency, providing a bright and clear appearance to the watch. Furthermore, it can be processed to a thinner degree, allowing for a reduction in the overall thickness of the watch.

However, these advantages do not necessarily mean that sapphire crystal glass is superior to acrylic glass. Along with its high hardness comes the risk that sapphire crystal may shatter more easily upon strong impact. In such cases, it can pose a threat to the watch dial and movement structure, especially for watches with hollowed-out or open-face designs. Therefore, while sapphire crystal glass may be highly durable, if it does shatter, the damage to the watch can be more severe.

But, Why do various brands still choose sapphire crystal material and abandon acrylic glass material?

The answer is not hard to guess. Because in daily wear, the chance of the watch being lightly scratched by external factors is greater than the chance of the watch being strongly impacted. Additionally, the technology of producing sapphire crystal glass has become very popular and does not significantly increase costs. Therefore, switching to sapphire crystal glass has become a better choice for watch factories.

Apart from these two materials, watch factories also use mineral glass to make watches, which is somewhat between acrylic glass and sapphire crystal glass. Although watches using mineral glass are not very common nowadays, they still occasionally appear in the works of some brands. However, in terms of prevalence, sapphire crystal is still the mainstream material in the watch industry.

Mineral glass is mostly used in some classic retro watches that require special crystal shapes to complement the overall style of the watch, such as single-domed and double-domed crystals. Single-domed crystals enhance the magnification effect on the dial, while double-domed crystals create a more ideal and prominent depth effect on the dial.

Whether it’s a single-domed or double-domed crystal, it adds a retro feel to the overall design of the watch, making the dial visually compelling and easy to read. This type of crystal not only achieves a three-dimensional visual effect with its convex shape but also enhances the magnification effect of the dial elements, allowing for thinner and more delicate watch designs.

Why use Mineral glass instead of Sapphire crystal glass?

This is because some watch crystals, not flat, have protruding edges that are prone to being knocked. Sapphire is also very fragile, so using regular glass is more reliable in comparison. Of course, to address the issue of scratch resistance on the crystal surface, some watch manufacturers also apply a sapphire coating to acrylic glass to achieve its scratch-resistant properties. Additionally, mineral acrylic glass is much cheaper than sapphire.

Price Comparison on Sapphire vs Mineral and Acrylic Watch Glass

Is sapphire expensive? In reality, with the widespread application of sapphire crystal glass, its market price has become very affordable. Nowadays, many popular watch brands on the market use sapphire crystal glass. However, compared to mineral glass and acrylic, sapphire crystal glass is relatively expensive.

FAQ

What is Mineral Watch Glass?

Mineral glass, also known as acrylic crystal, is a commonly used material in watchmaking. It is an ordinary crystal glass that undergoes polishing and hardening processes. Unlike sapphire crystal glass, mineral glass has a lower hardness. It was developed due to the scarcity of natural crystals, which couldn’t meet the demands of the industry. Its high transparency makes it suitable for various crafts, contributing to its popularity. The process of making mineral glass involves melting silica and lead oxide, resulting in a shiny surface with clarity achieved through advanced polishing technology.

Mineral-strengthened glass has a hardness of 7, making it resistant to scratches from most daily objects like knives and steel saw blades, which typically have lower hardness levels. However, it’s important to be cautious as sand grains, which also have a hardness of 7, can scratch the surface. Choosing a sapphire surface is preferable if possible. Sapphire surfaces, created by coating the glass with a layer of synthetic sapphire, offer a surface hardness of 9, making them highly resistant to scratches from anything except diamond and sapphire. Additionally, they are resistant to damage from sand grains.

Are Watches with Mineral Glass Good?

Answer 1:

Mineral crystal glass, also known as Acrylic Crystal, is a type of material used in watches. It is typically ordinary crystal glass that is polished and hardened, although its hardness is lower than that of sapphire crystal. This glass was developed due to the scarcity and difficulty in mining natural crystals, which couldn’t meet the demand. Because of its high transparency, it is popular for various crafts. Mineral crystal glass is crystalline with a high hardness (Mohs hardness of 7), good thermal conductivity, and a cool sensation when touched. It appears clear and bright against light, without small bubbles or watermarks, making it relatively expensive.

Answer 2:

The scratch resistance of mineral-strengthened glass is slightly inferior to sapphire glass, as its hardness is about 7, while sapphire glass has a hardness of 9. However, mineral-strengthened glass has higher overall compressive strength than sapphire glass. Therefore, all deep diving watches (deeper than 200 meters) use mineral-strengthened glass for their watch glass. Although sapphire glass has excellent scratch resistance, its thickness is only 5 micrometers, and its overall compressive strength is lower than that of mineral-strengthened glass, rendering it unsuitable for deep diving watches.

What is the Anti-glare Watch Glass?

In simple terms, anti-glare coating is a multi-layer film electroplated onto the lens to prevent light reflection. It’s commonly used in professional aviation, diving watches, or watches with large mirror curvature. It can be divided into double-layer anti-glare glass and single-layer anti-glare glass. The difference lies in the former being electroplated on both sides of the lens, while the latter is only coated on the inner side of the glass. The effectiveness of both types is similar.

The main function of anti-glare coating is to prevent glare and reflection, enabling better readability. When viewed from the front, it may appear as if it’s not mounted on the mirror, but from a specific angle, it reflects a layer of bluish color, similar to the eyes on the coating.

最終的な考え:

Ultimately, the choice between sapphire crystal glass, mineral glass and Acrylic glass depends on the specific requirements of the application, budget considerations, and the desired level of durability and scratch resistance. And it’s not the sapphire crystal that makes the watch better.