Transparent display technology is an emerging display technology. When a transparent display device display an image, objects disposed behind the transparent display device also can be seen through the device. That needs to enhance a transmittance of the transparent display device without losing its color gamut and contrast.
Meanwhile, the transparent display technology is a typical representative of the green display technology. For example, a conventional liquid crystal display needs a backlight module as a light source to display an image. The transparent display may use an ambient light to meet the need of the backlight. Especially in the daytime, the transparent display almost needs no backlight. The power consumption of the transparent display is about one-tenth of the ordinary liquid crystal display.
In order to improve the transmittance of the transparent display device, the original three primary colors of RGB color filter is usually reduced to 1/3 colors. However, by doing so, the color saturation of the image is also decreased.
Therefore, it needs to develop a transparent display device with high color saturation and high transmittance.
In order to increase the brightness of an image displayed by a transparent display device, an optical sheet can be placed under a light guide plate thereof, to reflect the light emitted from the light guide plate to the bottom and reflect it back to the light guide plate. The light guide plate includes a first refractive layer and a second refractive layer to allow a natural light transmits through the light guide plate. The first refractive layer is located adjacent to the liquid crystal panel. The second refractive layer has a higher refractive index than the first refractive layer. A first polarized light in the light guide plate is total reflected by a interface between the first refractive layer and the second refractive layer, and incident on the liquid crystal panel above the light guide plate, and a natural light transmits through the first and the second refraction layers incident on the liquid crystal panel, so that the user in front of the display device can see an object behind the light guide plate. However, the addition optical sheet and the special design of the light guide plate will increase the manufacturing cost of the display device.