The Fundamental Technology of Optical Elastic Resin (SVR)

Main benefit of SVR

Optical elastic resin (SVR) is used to bond the top plate and LCD module in displays by filling the air gap between the substrates. Some applications include but are not limited to smartphones and tablets.

A main benefit of SVR is that it can significantly improve visibility. Filling the air gap minimizes both the reflection of outside light and the diffusion of light inside the display panel (internal reflection). In addition, the high elasticity of the resin enhances impact resistance, making it suitable for use in slimmer smartphones and tablets.

The core principle of SVR

Let us look at the core principle of the SVR technology. When a straw is placed in a glass of water, it appears slightly bent at the surface. This is due to the difference in the refractive indices of air and water.

In older mobile phones, the difference in refractive indices of the top plate and the air gap caused poor display visibility, especially outdoors. In contrast, reflection is minimized by filling the air gap with SVR with the same refractive index as the top plate (glass or plastic). There are no refraction points on a way of external light to the LCD. As a result, the reflection, brightness, and contrast, which is approximately 12% in structures with the air gap, can theoretically be reduced to approximately 4% in structures filled with an SVR, thereby improving visibility, brightness and contrast

Adopted for a wide variety of displays for different applications

The technical requirements for SVR vary according to the specifications of the devices in which they are used. Since the commercialization of SVRs in 2007, they are now used in many smartphones, tablets, and LCD TVs. Dexerials’ has the capability to customize SVRs in order to meet the different needs of customers.

Recently, there has been an increase in use of SVRs for automotive applications. In particular, the use of 2.5D or 3D top plates with curved surfaces is expanding due to the diversification of in-vehicle display designs. There are instances where it is difficult to apply flat optically clear adhesive films (OCA/LOCA) to such curved surfaces. Liquid SVRs, however, can fill the air gap between the semi-cylindrical top plate and the display, and are being used by automotive OEMs and Tier 1 component manufacturers.

The development of the SVR and the benefits it brought to smartphones

The development of the SVR began with the growing need for slimmer and lighter cell phones (flip phones). As shown in the illustration below, the width of Japanese flip phones in 2004 was over 20 mm. By 2007, the width of the slimmest phones was reduced to around 12 mm. As new flip phones were being released several times a year, there was an endless need for slimmer, lighter phones with larger screens.

However, a slimmer cell phone makes it more vulnerable to impact and bending. By filling the air gap in the display with an SVR, Dexerials was able to satisfy the contradictory needs of both slimmer and more rigid displays. SVRs also reduce glare, which improves the brightness and contrast of the LCD, resulting in better screen visibility. Also, the ability to display the same brightness level with less power led to longer battery life.

Today’s smartphones have revolutionized the lives of people around the world. The SVR functionality originated in the flip phone era has been carried over to the present, and Dexerials is proud of the role it has played in making smartphones slimmer, lighter and with larger screens. Dexerials will continue developing products that lead to the further evolution of smartphones.