Semiconductor Energy Laboratory Co., Ltd.

Tomoyuki Iwabuchi

Yu Yamazaki

Mitsuaki Osame

Aya Anzai

Hiroyuki Miyake

Shunpei Yamazaki

Ryota Fukumoto

Ryo Arasawa

Kazutaka Inukai

Keisuke Miyagawa

Akihiro Kimura

Hajime Kimura

Yasuyuki Arai

Shuhei Nagatsuka

Kazuo Nishi

Shou Nagao

Mizuki Sato

Yuki Hata

Hideyuki Ebine

Tatsuro Ueno

Hitomi Ushitani

Jun Koyama

Satoshi Seo

Yoshiharu Hirakata

Kei Takahashi

Masahiko Hayakawa

Yoshifumi Tanada

Yasunori Yoshida

Kaoru Tsuchiya

Teruyuki Fujii

Yukari Ando

Ryo Nozawa

A photodetector of the invention is characterized by having a plurality of detector elements that are arranged over a light-transparent substrate and are connected in parallel. A foldable portable communication tool having two display portions of the invention is characterized by including one photodetector which includes a plurality of detector elements connected in parallel.

Multidirectional photodetector, a portable communication tool having thereof and a method of displaying

A problem in that a light emitting element slightly emits light is solved by an off current of a thin film transistor connected in series to the light emitting element, thereby a display device which can perform a clear display by increasing contrast, and a driving method thereof are provided. When the thin film transistor connected in series to the light emitting element is turned off, a charge held in the capacitance of the light emitting element itself is discharged. Even when an off current is generated at the thin film transistor connected in series to the light emitting element, this off current charges this capacitance until the capacitance of the light emitting element itself holds a predetermined voltage again. Accordingly, the off current of the thin film transistor does not contribute to light emission. In this manner, a slight light emission of the light emitting element can be reduced.

Display device and driving method of the same

There is provided a method for deciding a duty factor in driving a light-emitting device and a driving method using the duty factor that enable restraint of deterioration of light-emitting elements and improvement in reliability. In a method for deciding a duty factor of a light-emitting device that performs display based on an analog video signal, with respect to a characteristic obtained by multiplying the characteristic of luminance after X hours in relation to the current density and the characteristic of luminance after X hours in relation to the duty factor when the total quantity of electricity flowing through light-emitting elements in one frame period is defined at a specific value, a range of duty factor that enables realization of luminance approximately exceeding a value that is 0.8 times a maximum value is regarded as an optimum range of duty factor.

Method for deciding duty factor in driving light-emitting device and driving method using the duty factor

In order to achieve lower power consumption, a technique of performing display (partial display) by utilizing only a part of a display area is used. For example, a display area is divided, a plurality of driver circuits for driving the divided display areas independently are provided, and only a region where a fixed pattern is displayed is driven in a power saving mode, thereby partial display is performed; however, display cannot be performed at an arbitrary position. Alternatively, partial display can be performed by inputting a video signal to a pixel in an arbitrary display area; however, a structure of a driver circuit is complicated. The object of the invention is to provide a display device which can perform partial display at an arbitrary position and reduce power consumption. In partial display, operation of a signal line driver circuit is set so as to be stopped and a non-display signal is set so as to be outputted from the signal line driver circuit when a pixel in a non-display area is selected.

Display device where supply of clock signal to driver circuit is controlled

According to a driving method of applying a reverse bias voltage, capacitance occurs due to a stacked structure of a conductor, an insulator and a conductor, or due to a structure of a TFT. This capacitance prevents normal operation. The invention provides a pixel configuration including at least a driving transistor for driving a light emitting element and a switching transistor for controlling the driving transistor, wherein the switching transistor is turned on in the case of applying a forward bias voltage after applying a reverse bias voltage. As a result, it is prevented that the potential changes due to unwanted capacitive coupling.

Light emitting device and driving method thereof

Power consumption required for charging and discharging a source signal line is reduced in an active matrix EL display device. A bipolar transistor (Bi) has a base terminal B connected to an output terminal cof an operational amplifier (OP), a collector terminal C connected to a low power potential (GND), and an emitter terminal E connected to a resistor R. A high power potential (VBH) is a potential in synchronization with a high power potential of a light emitting element. A potential of the output terminal cof the operational amplifier (OP) is outputted as a buffer low power potential (VBL). The low power potential (VBL) corresponds to a potential difference between the high power potential (VBH) and a high power potential (V). Accordingly, the low power potential (VBL) can follow the high power potential (VBH), that is a high power potential of the light emitting element.

Light emitting device

Degradations in light emitting elements occur with the passage of time. The invention provides a method of driving a light-emitting device provided with a plurality of pixels, which includes a light-emitting means with a first and a second electrodes, a drive means for supplying the light-emitting means with a current in response to an analog video signal, and a setting means for setting a sustaining period and an off time period within a frame period. The method of driving a light-emitting device is characterized by including the steps of: supplying the light-emitting means with the current in response to the analog video signal during the sustaining period; and turning the drive means off thereby to make the light-emitting means nonluminous or making the first and the second electrodes identical in potential thereby to make the light-emitting means nonluminous during the off time period.

Method of driving light-emitting device

A light emitting element has a property that a resistance value (internal resistance value) thereof changes according to the ambient temperature. Specifically, assuming that the room temperature is a normal temperature, when the ambient temperature becomes higher than the normal temperature, a resistance value is decreased, and when the ambient temperature becomes lower than the normal temperature, a resistance value is increased. Therefore, when the ambient temperature changes or degradation is caused with time due to the aforementioned property of the light emitting element, luminance varies. The invention provides a display device where an effect of current fluctuation of a light emitting element, which is caused by the change in ambient temperature and degradation with time, is suppressed. The display device comprises a monitoring element, to which a current is supplied from a current source. A voltage applied to the monitoring element is applied to a light emitting element.

Display device, driving method thereof and electronic appliance

The invention provides a light emitting device which is capable of displaying on both sides, has a small volume, and is capable of being used as a module. A light emitting element represented by an EL element and the like is used in a pixel portion, and two pixel portions are provided in one light emitting device. A first pixel portion has a structure to emit light only from a counter electrode side of the light emitting element. A second pixel portion has a structure to emit light only from a pixel electrode side of the light emitting element. That is, in the first pixel portion and the second pixel portion, directions of light emission are reverse in front and back.

To provide a display device having a test circuit with high accuracy for testing in the step after a counter substrate is attached and before shipping, and to provide a display device having a correction circuit inside the display device, for the case where a defect occurs. A pixel circuit operated by a gate line and a source line, a first wiring formed at the same time as the gate line, a second wiring formed at the same time as the source line, and a test circuit of detecting a defect of the pixel circuit by using potentials of the first wiring and the second wiring are provided over a substrate.

Display device including test circuit, and electronic apparatus having the display device

Degradations in light emitting elements occur with the passage of time. A method of driving a light-emitting device is characterized by including the steps of: supplying a light-emitting element with the current in response to an analog video signal during a sustaining period; and turning switch off thereby to make the light-emitting element nonluminous or making first and the second electrodes identical in potential thereby to make the light-emitting element nonluminous during an off time period.

It is provided a display device that prevents, when applying a reverse bias, an anode line and a power supply line included in a signal line driver circuit from being short-circuited, and a driving method thereof. According to the invention, a reverse bias applying circuit is provided in a scan line driver circuit or a signal line driver circuit, a signal from the reverse bias applying circuit is supplied to a transistor disposed between a signal line and an anode line, and thereby the transistor is turned off. The reverse bias applying circuit comprises an analog switch or a clocked inverter and a biasing transistor, and drives so as to invert potentials of the anode line and a cathode line and apply a reverse bias to a light emitting element, while turn off the analog switch and turn on the biasing transistor. Then, a potential of the anode line becomes equal to that of a scan line, and thereby turning off the transistor between the anode line and the signal line assuredly.

Display device and driving method thereof

A light emitting device capable of suppressing generation of pseudo-contours by increasing the frame frequency while suppressing the drive frequency of a driver circuit is provided. According to the present invention, gray scales are displayed not only by controlling the emission period of a light emitting element, but also by controlling the luminance of the light emitting element. Specifically, one frame period is divided into a plurality of sub-frame periods each having an equal length, and the luminance of the light emitting element in each sub-frame period is controlled to have different levels. By controlling the total sum of the luminance level of the sub-frame periods that are selected with a video signal, a desired gray scale can be displayed.

A semiconductor device with less power consumption and an electronic appliance using the same. The semiconductor device of the invention is supplied with a first potential from a high potential power source and a second potential from a low potential power source. Upon input of a first signal to an input node, an output node outputs a second signal. With the semiconductor device of the invention, a potential difference of the second signal can be controlled to be smaller than a potential difference between the first potential and the second potential, thereby power consumption required for charging/discharging wires can be reduced.

Growing community of inventors

Kanagawa, Japan

Tomoyuki Iwabuchi