Semiconductor Energy Laboratory Co., Ltd.

Keisuke Miyagawa

Shunpei Yamazaki

Mitsuaki Osame

Satoshi Seo

Aya Anzai

Jun Koyama

Yoshifumi Tanada

Hajime Kimura

Masahiko Hayakawa

Yu Yamazaki

Yukari Ando

Hiroko Abe

Tomoyuki Iwabuchi

Kazuo Nishi

Ryota Fukumoto

Yu Kojima

Hisashi Ohtani

Shou Nagao

Aya Miyazaki

Mitusaki Osame

A light emitting device that achieves long life, and which is capable of performing high duty drive, by suppressing initial light emitting element deterioration is provided. Reverse bias application to an EL element () is performed one row at a time by forming a reverse bias electric power source line () and a reverse bias TFT (). Reverse bias application can therefore be performed in synchronous with operations for write-in of an image signal, light emission, erasure, and the like. Reverse bias application therefore becomes possible while maintaining a duty equivalent to that of a conventional driving method.

Light emitting device and method of driving the light emitting device

The inventors found out that in the case of performing a low gray scale display in which a very small amount of current is supplied to a light emitting element, variations in threshold voltages of driving transistors become notable since the gate-source voltage is low. In view of this, the invention provides a display device in which variations in the threshold voltages of the driving transistors are reduced even in the low gray scale display, and a driving method thereof. According to the invention, a gate-source voltage of the driving transistor is set higher in the low gray scale display than that in the high gray scale display. As one mode to achieve this, different power source lines are provided for the low gray scale display and the high gray scale display and their potentials are set to be different.

Display device

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 compact and lightweight display device having an image pickup function and a two-way communication system which can shoot an image of a user as an object and display an image at the same time without degrading image quality by disposing a semi-transmitting mirror or the like which blocks an image on the display screen (display plane). The display device having the image pickup function includes a display panel capable of transmitting visible light at least and arranging display elements which can be controlled by voltage or current, and an image pickup device disposed around the display panel. The image pickup device is input with data of an image of a user or the like by a reflector, or equipped with a fiberscope bundling optical fibers.

Display device having image pickup function and two-way communication system

A conventional setting voltage was a value with an estimated margin of a characteristic change of a light emitting element. Therefore, a voltage between the source and drain of a driver transistor Vhad to be set high (V&#x2267;V&#x2212;V+a). This caused high heat generation and power consumption because a voltage applied to the light emitting element. The invention is characterized by feedbacking a change in a current value in accordance with the deterioration of a light emitting element and a power source voltage controller which modifies a setting voltage. Namely, according to the invention, the setting voltage is to be set in the vicinity of the boundary (critical part) between a saturation region and a linear region, and a voltage margin for the deterioration is not required particularly for an initial setting voltage.

Display device and controlling method thereof

A driving method of a light emitting device, in which when an N-type driving TFT is connected to an anode of a light emitting element or a P-type driving TFT is connected to a cathode thereof, the driving TFT operates in a saturation region and an image can be displayed with a desired gray scale level depending on a video signal. In addition, a light emitting device adopting the driving method is provided. According to the invention, when a potential having image data is supplied to a gate of a driving TFT depending on a video signal, a reverse bias voltage is applied to the driving TFT and a light emitting element which are connected in series with each other. Meanwhile, when a pixel displays an image depending on the video signal, a forward bias voltage is applied to the driving TFT and the light emitting element.

Driving method of light emitting device and light emitting device

The invention provides a display device with which a user's view is not completely interrupted by an image that is displayed artificially and of which optical system is easy in design. In addition, the invention provides a telecommunication system capable of providing additional visual information by the use of the display device. According to the invention, an image can be displayed while securing a user's view by using a light emitting device that can display an image and transmit light as a display device. Specifically, a pair of electrodes included in a light emitting element is formed to transmit light so as to transmit the outside light. By crossing a visual axis of a user and a pixel portion of the light emitting device, both of the outside light and the light emitted from the pixel portion can enter into the eyeballs of a user.

Display device and telecommunication system

If a potential of a gate electrode of a driving transistor varies after a gray scale signal is inputted into each pixel, a current value of a current supplied to a light emitting element varies so that accurate gray scale display cannot be obtained. In particular, in the case of performing black display, current may flow, which makes clear black display difficult. Accordingly, the invention provides a light emitting device capable of performing accurate gray scale display, and a driving method thereof. According to the invention, a signal for display is inputted plural times within a predetermined timing period, or a writing operation period is lengthened. Consequently, the gate voltage of the transistor is determined after the anode potential of the light emitting element is stabilized, and therefore accurate gray scale display can be performed.

Growing community of inventors

Kanagawa, Japan

Keisuke Miyagawa