While anti-reflective and anti-glare are terms used interchangeably, they are technically not the same.
Are you in a situation where you’re considering anti-reflective or anti-glare surface treatments? Or are you just curious about what the difference is?
Then you’ve clicked on the right article! In the following, we will go through what anti-reflection and anti-glare means and compare them to understand the pros and cons of each surface treatment.
The aim of adding anti-glare or anti-reflective properties to a cover glass is ultimately the same – to enhance and optimize the readability of the display. The difference between anti-glare and anti-reflective coatings is that they achieve this readability in two completely different ways.
While it is seemingly a simple question to answer, it’s important to visualize how a reflection would behave without any anti-glare or anti-reflective coatings. The image below shows how light bounces off a surface when it passes from one material to another.
Figure 1: Simplified illustration of specular reflections on a surface with no surface treatment.
For cover glass made of PMMA, the reflected fraction of the incoming light is approx. 4% when passing from air to PMMA and from PMMA to air. This means that 8% of the total light is reflected, and the remaining 92% of the incoming light is transmitted.
On a smooth, glossy surface, light bounces off, as shown in the image above, which results in a mirror-like reflection. Take a lot of light that behaves this way – let’s say sunlight – and you get a reflective surface, which makes it difficult to read the display.
To remedy this, we can apply anti-glare or anti-reflective coatings to our cover glass solutions. In the following, we will look at these surface treatment options to understand how they work.
Anti-glare coatings aim to scatter the light reflected off the surface in all directions. Here’s an illustration of how that might look:
Figure 2: Simplified illustration of diffused reflections on a surface with anti-glare surface treatment.
It’s important to remember that an anti-glare surface doesn’t reduce overall reflectance but scatters the same amount of light over a wider angle. Because the human eye only sees a fraction of the scattered light, the perceived brightness of the reflection is significantly reduced, making it easier to read the display. This technology is often used in displays such as the computer or tablet screen on which you might be reading this article right now.
The main advantage when applying an anti-glare surface treatment is a dramatic improvement in readability in environments where glare from ambient light sources could be an issue. Anti-glare coatings are a cost-effective way to reduce reflections from sunlight, overhead lighting, and other sources of light that could reflect onto the display.
However, there are also drawbacks to anti-glare surface treatments. Because of the way anti-glare coatings work, all light coming from the display underneath is also diffused because of the tiny particles that are essentially the anti-glare coating. This results in a loss of image quality from the display, so the information on the screen will appear with lower image quality compared to a display with a cover glass with no surface treatments.
Furthermore, due to the relatively rough surface of anti-glare coatings, they also tend to contaminate quite easily when touched, making cleaning with anti-viral and anti-bacterial disinfectants more difficult.
While an anti-glare surface scatters the reflected light, an anti-reflective coating reduces the amount of light reflected. This happens without spreading the passing light, as illustrated by the following image:
Figure 3: Simplified illustration of the effect of anti-reflective surface treatment on a display cover glass.
The main advantage of anti-reflective coatings is that they reduce reflections much more than anti-glare coatings, without diffusing light and reducing the image quality of the display underneath the cover glass.
Ultimately, this means excellent image quality and minimal reflections from the display. Compared to anti-glare coatings with an 8% reflection output, anti-reflective surface treatments can easily have less than 0,5% reflectance and over 99% transmittance. This means that less than 0,5% of the light that hits the surface is reflected, and more than 99% of the light from the display is transmitted through the cover glass, compared to around 92% with anti-glare coatings. The result is maximum display brightness and image quality.
The downside to this method is, of course, cost. It is usually considerably more expensive than anti-glare solutions.
As with many things in life, whether you can tell the difference between anti-glare and anti-reflective surface coatings depends on many factors. The user experience between two displays with either coating will be broadly similar since most visual artifacts in a real-life scenario come from external sources.
Whether the additional cost of an anti-reflective coating is worth it depends on your specific application. If you want to know more about your project, we would love to talk with you. If that sounds interesting, don’t hesitate to get in touch with us.
In high-resolution displays, anti-glare surface treatments reach a certain limit because the anti-glare structure must be finer and finer to avoid image distortion. Eventually, you’ll end up with a glossy surface which results in no reflection control.
In these scenarios, it’s usually worth choosing an anti-reflective surface treatment since these are invisible to the human eye and therefore don’t compromise the image quality of the display underneath.
In the end, optimal readability is what you want.
If cost was no issue, anti-reflective surface coating is the superior alternative of the two since it is more effective at reducing reflections without the risk of compromising the readability and resolution of the display underneath the cover glass.
Since cost is usually an essential consideration in the R&D process, anti-glare surface treatments are often the optimal choice from a value perspective since an anti-reflective coating doesn’t significantly increase the display’s image quality.
As mentioned earlier, anti-glare surface treatments work well for vertically mounted displays such as desktop or laptop monitors. Anti-glare also works well for other displays that aren’t regularly exposed to very bright illumination, such as direct sunlight.
Anti-reflection treatments are, therefore, best suited for high-demand applications, where maximum readability under all lighting conditions is critical. This is the case in a lot of light sensing and scanning applications, where the performance of the sensor behind the optical filter is highly dependent on the features of the optical filter in front of the sensor.
It is worth noting that if your design calls for cover glass material with specific properties such as impact resistance or flame retardancy, you could be limited in your choice of anti-glare or anti-reflective surface treatments. This is because not all surface treatments can be applied to all materials.
We hope this article has given you some insights about anti-glare and anti-reflective surface treatments.
Do you have a project coming up where you need a display cover glass? Then we would love to help you in finding the right solution.
You can always get in touch with us if you want to draw on our expertise. We’re ready to help you find a customized solution for your project.