Direct bonding refers to a protective glass or cover that is glued in front of a display to enhance its readability, ruggedness and durability. When a regular display or waterproof TV is used in an outdoor environment or bathroom or wet environment, there are some factors that affect its readability. The most common one is “fog”, or condensation, which forms on the inner surface of display’s vandal shield. Another factor is the reflection of sunlight, which causes a mirror-image on the display, especially on the mirror TV. Both phenomena can be solved by using direct bonding (also called optical bonding).
Direct bonding technology is also used for laminating the ITO sensor and glass to make touch panel, as well as naked eye 3D film and glass.
Optical bonding(direct bonding)uses optical-grade adhesive to glue a glass or plastic cover to the top surface of a display. The main goal of optical bonding is to improve the display performance. This method eliminates the air gap between the cover glass and the display. Moreover, anti-reflective coating is often used in optical bonding glass. The real problem for display readability in outdoor environments or the bathroom is not the display’s brightness but its contrast. Contrast means the ratio of the white level to the black level; in other words, the contrast ratio of display means the difference of light intensity between the brightest white pixel and the darkest black pixel. Optical bonding can increase the display’s contrast ratio by reducing the amount of reflected ambient light.
In SWI, direct bonding technology is used for CTP production(ITO sensor + glass), naked eye 3D glass lamination(3D film + glass), and LCD display bonding(LCD + glass/plastic cover). The bonding materials SWI uses are OCA(Optically Clear Adhesive), LOCA(Liquid Optically Clear Adhesive) and SOCA(Solid Optically Clear Adhesive). The size capabilities of direct bonding arefrom 0.4” through 110”.
- Increased ruggedness: Bonding a sheet of glass on top of the display increases the ruggedness of the display.
- Improved durability: A bonded display is better able to resist scratches, fluids, stains and dirt.
- Condensation: The elimination of an air gap between the cover glass and the display means that moisture cannot penetrate and cause fogging on display’s surface.
- Extended temperature range and EMI filtering: The temperature range of the display can be extended by incorporating ITO heaters on the cover glass; EMI filters can be added via the same mechanism.