What Is a Light Guide?
A light guide plate is an optical component that allows light sources, such as LEDs, to enter from the edge of the plate and emit light on the surface.
When the surface of the plate is smooth, the incident light repeatedly undergoes total reflection, and the light is emitted on the opposite side of the plate. By processing this smooth surface to change the direction of light, it is possible to make the surface light-emitting.
Light guides are mainly installed on the back of “transmissive LCDs” and are often used in the “backlight method” to illuminate the LCDs, requiring light guides with a high degree of uniformity to illuminate the LCDs evenly.
In recent years, demand for products using “reflective LCDs,” which consume less power and are lighter, has been increasing. Light guides used for reflective LCDs are installed in front of the LCDs in a “front light system,” so light guides with a high degree of transparency are required. However, light guides with high transparency are extremely difficult to process, so the number of manufacturers who can produce them is limited.
The development cycle of electronic devices is expected to shorten further in the future, and Light guides must also be developed in a short period to ensure the superiority of new products.
Uses of Light Guides
Backlight Method
Mainly used as lighting for “transmissive LCD products.” They are used as lighting for products such as LCD TVs and smartphones, as well as for store signboards and poster panels. Demand for general lighting such as ceiling lights is also increasing.
Front Light Method
This type of lighting is mainly used for “reflective LCD products.” It is used for electronic paper, wearable devices, and digital signage (electronic signage). As a new application of the front light method, its use as lighting for “image processing inspection equipment” is attracting attention. By using highly transparent light guides, it is possible to provide a wide field of view to the workpiece while ensuring uniform illumination of the entire area.
Light Guides Manufacturing Method
Light guides can be manufactured by a variety of manufacturers, depending on the purpose of use and quantity.
Injection Molding Method
This is a common method that has been used for a long time. For mass production, it is possible to manufacture at a low cost. However, the mold must be repeatedly modified until the optimum optical pattern is produced.
Main applications: LCD meters, amusement products, smartphones
Laser Processing Method
This is a surface emitting system that uses a laser processing machine to engrave “dots” or “grooves” on the surface of a plate. Many manufacturers are capable of processing, and since molds and plates are not required, manufacturing can be done at a low cost. It is often used for inexpensive products that do not require a high degree of uniformity.
Main applications: Backlight for store signboards, poster panels, shelves, ceiling lights
Screen Printing Method
This system uses a printing plate to print “reflective dots” on the surface of a board for reflection. Although a plate is required, it is less expensive than a molding die. Because of the limited mesh size of the plate, it is often used for inexpensive products that do not require a high degree of uniformity.
Main applications: Backlighting for store signboards, poster panels, shelves, ceiling lights
Inkjet Lens Printing Method
This is the newest method of light guide manufacturing. An inkjet printer is used to produce an “optical lens” on the surface of the plate. The diameter of the lens is extremely small, approximately 32 µm, enabling light distribution design with a high degree of uniformity. The greatest feature of this process is that the lenses themselves are transparent, making it possible to produce light guides with a high degree of transparency, which is difficult to achieve with other manufacturing methods. In addition, since inkjet printers are used and no molds or plates are needed, it is possible to respond to short delivery times and in small quantities. However, the number of manufacturers that can produce this product is limited, and it is not suitable for inexpensive product applications, such as backlighting for store signboards.
Since high-definition printing like that shown in the photo is possible, demand for stand-alone Light guides for use in in-store displays is also increasing.
Main applications: For electronic readers, amusement products, image inspection and processing equipment, pre-production prototypes, store displays
While there are a variety of manufacturing methods for light guides, in many cases, the manufacturing method that best suits the purpose has not been selected. If you are having trouble selecting a light guide, a good way to start is to request a sample prototype from the manufacturer and make a comparative evaluation.