Planar light source device, display device, terminal device, and method for driving planar light source device

Abstract

A display device having an optical waveguide and a light source are provided, and also having a louver, a transparent / scattering state switching element, and a transmissive liquid crystal display panel provided in the order indicated on the side of the light-emitting surface of the optical waveguide. The transparent / scattering state switching element switches between a state for scattering the incident light and a state for transmitting the light without scattering. The light source drive circuit causes the transparent / scattering state switching element to transfer from the transparent state to the scattering state, and when the viewing angle range of the display is switched from narrow to wide, the intensity of the light source is gradually increased in conjunction with the transition state of the transparent / scattering state switching element. By this configuration, abnormal flashing during switching of the radiation angle can be prevented in a planar light source device that is capable of switching the radiation angle range.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a planar light source device capable of switching the radiation angle of illuminating light, to a display device provided with this planar light source device and capable of switching the angle range of visibility, to a terminal device equipped with this display device, and to a method for driving the planar light source device. [0003] 2. Description of the Related Art [0004] Because of their thin profile, light weight, small size, low energy consumption, and other advantages, display devices that use liquid crystals have been widely deployed and used in a range of devices that includes monitors, televisions (TV: Television), and other large terminal devices; notebook-type personal computers, cash dispensers, vending machines, and other mid-sized terminal devices; and personal TVs, PDAs (Personal Digital Assistance: personal information terminal), mobile telephones, mobile gaming dev...

AI Technical Summary

Benefits of technology

[0016] An object of the present invention is to provide a planar light source device capable of switching the range of radiation angles, wherein the planar light source device can prevent abnormal flashing when the radiation angle is switched; to provide a display device that is equipped with this planar light source device and is capable of switching the range of viewing angles; to provide a terminal device in which this display device is installed; and to provide a method for driving the planar light source device.

Problems solved by technology

Energy consumption can be reduced in the reflective type, since it can utilize external light in the display device, but contrast and other aspects of display performance are inferior compared to the transmissive type.

This problem of grayscale inversion was relatively insignificant in mobile telephones and other terminal devices when the display content consisted mainly of telephone numbers and other characters.

The visual characteristics do not improve at this time, but when the display need only be correctly recognized by a single user, the viewing angle characteristics resemble those of a conventional TN liquid crystal, and a user can use the display without the display being correctly recognized by another person.

As a result, light is not transmitted to positions where the display unit is viewed at an angle to the left or right in the horizontal direction, the screen is darkened when viewed from such a position, and it becomes impossible to recognize the displayed content.

However, in the aforementioned first and second conventional viewing-angle-controlled liquid crystal display devices, there is abnormal flashing that causes discomfort for the user when the switch is made from narrow-angle display having a narrow range of viewing angles to wide-angle display having a wide range of viewing angles.

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