Invented by Dong-un Jin, Jae-Kyeong Jeong, Hyun-Soo Shin, Yeon-Gon Mo, Samsung Display Co Ltd
The Samsung Display Co Ltd invention works as followsAn organic LED display” is disclosed. The display unit includes an organic light emission layer and a transparent thin film transistor (TFT) to drive the organic light emission layer. The display unit has an organic light emitting layer and a thin film transistor to drive it. It emits light onto two surfaces (upper surface and lower surface). The controlling unit contains an electro-optical film that can be switched between two states by applying voltage. The controlling unit controls the transmission of light from the display unit. The flat panel display can therefore be used to display an image on one or two surfaces. A user can control the selection of display surface manually or automatically. The controlling unit may include a liquid-crystal device, electrophoretic device or electrochromic device.
Background for Flat Panel Display and Driving Method Using the Same
The present invention is a light emitting organic display and, more specifically, relates to a light emitting organic display capable of displaying images on one surface (a upper surface) or two surfaces (anupper and lower surfaces). A user can select the surface for image display, and they can also choose a specific time period. The organic light-emitting display of this invention has a control unit that switches between an opaque and transparent state. This unit also controls the transmission of light so as to display an image either on one surface of the organic display or two surfaces opposite each other.
The advent of a more information-oriented society has led to an increase in the demand for personal computers (PC), navigation systems for cars, personal digital assistants and information communication devices. These products must have high visibility, wide viewing angles, and high response speeds to display moving pictures. Flat panel displays (FPDs) are suitable for these characteristics, so they have been attracted to be the next-generation display.
In general, thin film transistors (TFTs) are widely used as switching devices that operate each pixel of a display device like an organic light-emitting display (OLED), a liquid crystal screen (LCD), and so on. The fabrication of TFTs is of great importance, and an FPD using TFTs that are more efficient and a way to drive the FPD has been proposed.
A thin-film transistor consists of a semiconductor, a gate, a source, and a drainage electrode. The semiconductor layer, gate electrode, source electrode and drain electrode are all made from opaque materials. The semiconductor layer is composed of polysilicon or amorphous silica. These materials are opaque and therefore cannot be used to increase the width of the channel in a TFT used as a switch device for a transparent organic LED display. The narrow width of the channel means that a lot of current can’t flow through the channel and therefore a higher voltage is needed to operate the TFT. The light emitting device in the transparent organic display is deteriorating and the power consumption is increasing. It is also not possible to show an image on the two surfaces of the organic display because the amount of light that passes through the opaque TFT will be blocked by the TFT.
According to an aspect of the invention, in order to achieve the above-mentioned objects, an organic light emitting device (OLED) is provided. The OLED includes a first substrate transparent, an emission film arranged over an upper surface, a thin film transistor transparent arranged to drive the emission layer on the upper surface, a 1st transparent electrode arranged to a lower side of the substrate transparent, a 2nd transparent substrate arranged beneath the lower surface the the 1st transparent electrode, as well
The light shielding layer can be switched into a state when a voltage is applied on the first transparent electrode and to another state when a voltage is applied on the second transparent electrode. The amount of visible light that passes through the light-shielding layer in the first state differs from the amount of visible light that passes through the light-shielding layer in the second state.
The organic light emitting displays can include a transparent second electrode between the light shielding and second transparent substrate. The light shielding can be either a polymer-dispersed liquid crystal or twisted nematic layer of liquid crystal.
The organic light-emitting display can have a side electrode on one side of the light shielding layers, and this light shielding can be an electrophoretic film.
The organic light-emitting display may include a driving device for applying voltage to the transparent electrode layer. This driving device can be controlled manually or automatically by a photosensor.
The transparent thin film transistor may include a semiconductor layer made of transparent material, a gate electrode that is transparent, a source electrode that is transparent, and a drain electrode which can be transparent. The transparent gate electrodes, transparent source electrodes, and transparent drain electrodes are made from a material like indium tin dioxide (ITO), zinc oxide indium (IZO), or itzo indium tin tin. The transparent semiconductor layer is made of a wide-band semiconductor substance with a band gap at least 3.0eV. The wide band semiconductor substances are formed of a material such as zinc oxide (ZnO), zinc tin oxide (ZnSnO), cadmium tin oxide (CdSnO), gallium tin oxide (GaSnO), thallium tin oxide (TlSnO), indium gallium zinc oxide (InGaZnO), copper aluminum oxide (CuAlO), strontium copper oxide (SrCuO), layered oxychalcogenide (LaCuOS), gallium nitride (GaN), indium gallium nitride (InGaN), aluminum gallium nitride (AlGaN), indium gallium aluminum nitride (InGaAlN), silicon carbide (SiC), or diamond.
The following will describe a flat-panel display (FPD), and how to drive it, according to preferred embodiments.
To simplify the description of the invention, the word “transparent” is used to describe it. The word ‘transparent’ can be used to mean ‘transparent or transmissive. According to the present invention, to make it easier to understand, the term controlling unit is used for a device capable of controlling light transmission. This is connected to an emitter panel which includes an organic LED display. “The controlling unit may be a liquid-crystal display (LCD), field emission display, plasma display panel (PDP), electro luminescent or vacuum fluorescent display.
FIG. The figure 1 shows a sectional schematic view of a thin-film transistor 113 in an organic light-emitting display. Referring to FIG. 1. Organic light emitting displays 120 include substrate 100, a buffer layer formed on substrate, a semiconductor layer configured with active layer(s) 102a and ohmic contacts layers (semiconductor layer102b), and a gate insulating material 103 formed over the semiconductor layer and buffer layer. Gate electrode 104 forms on gate insulating layers 103, above semiconductor layer 102. On the gate electrode, an interlayer insulating film 105 is formed. Electrode 106 is composed of source electrodes 106a and 106b and is formed over a region in interlayer insulation layer 105. They are connected to the ohmic contacts layers 102b via cavities created between gate insulating material 103 and interlayer insulation layer 105. On source and drain electrodes, 106a and 106b are formed planarization layer. The first electrode layer 108, which is formed over a region on planarization 107 and connected to the drain electrode 106b via a groove in planarization 107 is then attached. On first electrode layer and planarization layers 107, pixel defining layer (109) is formed. The pixel defining layer has an aperture (140) to expose at the very least a portion of first electrode layer. “Emission layer 110 forms inside aperture 140 and second electrode layer is formed over emission layer 110, pixel defining layers 109 and pixel-defining layer 109.
FIG. The schematic sectional diagram of FIG. 2 shows an organic light-emitting display that is constructed in accordance with a first embodiment. Referring to FIG. Referring to FIG.
The following will describe the controlling unit 320 in detail. The first substrates 313 of the controlling unit 320 and the second substrates 317 are arranged so that their inner surfaces face each other. In the inner surfaces, first substrates 313 and 317 are respectively formed with a transparent electrode 314. Between first transparent electrode 314 a liquid crystal layer 315 is interposed. This is a light-shielding layer. The first polarizing sheet 312 and the second polarizing layer 318 are located on the outer surfaces of both substrates 313 and 317.
The “Controlling Unit 320” also includes a driving unit, (not shown), to apply voltage to the first transparent electrode 314, and the second transparent electrode 316. The driving unit can be controlled manually or automatically by being connected to a photo-sensing device.
When voltage (or a second voltage) is applied, only a linear first polarization light, whose direction of polarization is parallel to the polarization axis on first polarizing sheet 312, can pass through first polarizing sheet 312. Due to the vertical alignment of the liquid crystal molecules in liquid crystal sheet 315 due to the voltage applied, the first polarization does not change into a second polarization as it passes through liquid cristal layer 315. Second polarizing plates 318 block the first linear wave, which passes through liquid crystal layer 315. Only a second linear wave can pass by second polarizing plates 318. The screen of the controlling unit 320 turns black (or dark) or into a second condition.Click here to view the patent on Google Patents.