Sharp Kabushiki Kaisha Corporation

Hirohide Terasaki

Youko Ohta

Nobuyuki Takahashi

Takayoshi Tanabe

Kenichi Ukai

Hisashi Oyama

A liquid crystal display with a back-light control function is provided with a PWM dimmer driving circuit section for applying a PWM dimming to a fluorescent tube provided on the back surface of a liquid crystal panel by controlling an inverter section. The PWM dimming frequency by the PWM dimmer driving circuit section is set such that m flashes occur (m is an integer of not less than n, and is not a multiple of n) in n screen display periods of the liquid crystal panel (n is an integer of not less than 2), for example, 5 frequency occurs in 2 display periods. Based on a display panel vertical synchronizing signal corresponding to the vertical driving frequency of the liquid crystal panel, the PWM dimmer driving circuit section controls the inverter section while synchronizing a lighting timing of the fluorescent tube with a driving timing of the liquid crystal panel. As a result, an occurrence of flicker and flutter can be prevented effectively. Moreover, a sound noise generated in the inverter section can be reduced. Furthermore, variations in dimming can be reduced.

Liquid crystal display with back-light control function

A lighting apparatus for irradiating a liquid crystal display panel from the back includes a light guiding plate having at least an end which is bent in a direction opposite to the liquid crystal display panel, and a light source disposed on the back surface of the light guiding plate with respect to the liquid crystal display panel. Light from the light source is incident on the bent section of the light guiding plate, reflected by a reflector covering the outside surface of the bent section, and then falls on a section corresponding to a data display space of the liquid crystal display panel. This structure enables an increase in the ratio of the area of a light emitting section to the area of the entire lighting apparatus.

Lighting apparatus

A back light device of a liquid crystal display device includes fluorescent tubes on both ends of a light guiding plate. When viewed from a section which is perpendicular to the fluorescent tubes, shapes or internal constitution of the light guiding plate are asymmetrical in order to prevent irregularity of the luminance of a display area of a liquid crystal display panel caused by, e.g., a different in optical characteristics between the fluorescent tubes, a difference between positioning of each fluorescent tubes and the light guiding plate. In other words, a border of the shapes or of the internal constitution of the light guiding plate is set in a position that is nearer to the section where a quantity of incident light is relatively small according to a ratio of the quantities of incident lights on each section obtained by cutting a face that intersect a circumferential end of the display area on the light guiding plate at right angels. As a result, the display area on the liquid crystal display panel is prevented from becoming dark on the section side where a quantity of incident light is smaller.

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Tenri, Japan

Hirohide Terasaki