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A light guide plate is a panel or component that diffuses incoming light and emits uniform light on the surface. It is mainly used as a component of the backlight of LCD monitors. By using the light guide plate for the panel, it is not necessary to put a fluorescent lamp or LED on the back, and it is possible to manufacture a thin, even and efficient panel. There are several manufacturing methods for the light guide plate, and the characteristics differ depending on this manufacturing method.

Usage of light guide plate

It is mainly used for the purpose of “lighting thinly, evenly and evenly” such as backlight parts for LCD monitors, poster advertising panels in the city, and LED lighting. Most of them are basically panel-shaped, but they are not limited to a single flat plate shape, and there are various shapes that diffuse the light from a small light source such as a glowing button of an electric appliance. It is also used for parts that require space-saving and uniform light emission.

Light guide plate principle

The light guide plate is made by processing the surface of the acrylic plate by methods such as “laser processing”, “silk printing”, “V-groove cutting”, and “injection molding” to allow light that would normally escape to the surface. By changing the reflection angle above, uniform light is emitted from the issuing surface. In addition to this, by combining members such as “reflective sheet” and “diffusing material”, light can be diffused brighter and more effectively.

It has different characteristics depending on the surface processing method, so it will be explained below.

  1. Laser processing
    This is a method of forming dots on the surface with a laser. This processing method can process panels of various sizes, and is characterized by high brightness and long-distance light emission. It is cheap, but not suitable for mass production.
  2. Silk printing
    This is a method of printing a dot pattern on the surface. It can achieve uniform high-brightness issuance and is also suitable for mass production.
  3. It is a method of digging a groove on the surface with a V-groove cut plotter. It is not suitable for thin panels due to its easy quality variation and the characteristic of digging the surface. It is also not suitable for large panels.
  4. Injection molding
    This is a method to reproduce the processed shape of the surface with a mold. It requires mold costs, but is most suitable for mass production. On the other hand, when making a large panel, the mold becomes large and the cost increases, so it is basically used for small panels.

Light guide plate for image processing lighting

There are various ways to use the light guide plate, and one of them is lighting for image processing.

For example, if the object to be imaged is a mirror-finished medium with a large amount of specularly reflected light components, the light source may be reflected in the object to be imaged as it is when the light is irradiated using illumination without a light guide plate. In that case, even lighting can be achieved by illuminating with a light guide plate. Ring lighting, which is often used for photography, is an example of using the diffusion of light by a light guide plate to suppress unevenness from the imaged object.

In addition, a technology called flat dome lighting, which has contributed to slimming and space saving by devising a light guide plate, has also appeared, which was previously only possible with coaxial epi-illumination.

This is a lighting that realizes the same function as coaxial epi-illumination evenly by illuminating the LED from the side of the dot pattern printed on acrylic and arranging the imaging target under the illumination.

Development of film light guide plate

According to DZOptics, the film light guide plate is a technology in which the surface of a transparent film is finely processed such as a prism, and light such as an LED is incident from the end face to emit light from the surface.

It is formed by transferring a pattern to a transparent thin film, and is also used for lighting and illumination of mobile devices.

In addition, it is thin and can be bent and used, so it is expected to have new applications.

In order to meet the needs for thinner LCD backlights in recent years, the backlight must be made smaller. The thickest part in the backlight is the light
guide plate, but if a film-type light guide plate can be used, we can expect great expectations for the miniaturization of the backlight.

The film light guide plate not only makes it possible to emit the required amount of light in the required direction by microfabrication, but it is also possible to display multiple colors and patterns and to express movement by dimming.

It has a high degree of freedom in shape and can be attached to a quadric surface to make it shine, and the range of application is wider than that of conventional light guide plates.

Some of them are as thin as 50 to 200 μm, and there are high expectations for future development.


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