KR20060121486A - Two-side flat panel display apparatus - Google Patents

Abstract

A two-side flat panel display apparatus is provided to obtain thin and light characteristics by forming an AMOLED(Active Matrix Organic Light Emitting Diode) element at one side of a substrate and an EPD(ElectroPhoretic Display) element at the other side of the same substrate. In a two-side flat panel display apparatus, a first display element(200) is formed at one side of a substrate(100). A second display element(300) is formed at the other side of the substrate(100). The second display element(300) is a different kind of a display element with the first display element(200).

Description

Two-side flat panel display apparatus

1 is a schematic cross-sectional view of a double-sided flat panel display according to the present invention.

FIG. 2 is a cross-sectional view illustrating in detail a double-sided flat panel display device employing a top emission type AMOLED device on one surface (top) of FIG. 2 and an EPD device on the other surface (lower surface).

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-sided flat panel display device, wherein a first display element is formed on one side of a substrate, and a second display element of a different type from the first display element is formed on another side to implement a different screen on each display. And a double-sided flat panel display.

Various display devices such as liquid crystal displays (LCDs), plasma displays (PDPs), inorganic or organic light emitting displays (LEDs, OLEDs), etc. are being researched, developed, and put into practical use as flat panel displays. In particular, OLED is attracting attention as a next-generation display because of various advantages such as low power consumption and applicable to a flexible display due to the use of organic devices.

The flat panel display is classified into a passive matrix (PM) type and an active matrix (AM) type of an active driving method according to a driving method.

In the passive matrix type, the anode and the cathode are simply arranged in columns and rows, respectively, so that the cathode is supplied with a scanning signal from a row driving circuit, and only one of the plurality of rows is selected. In addition, a data signal is input to each pixel in the column driving circuit.

The active matrix type is a thin film transistor (hereinafter referred to as "TFT") that controls the input signal for each pixel, and is suitable for a large amount of signal processing, a lot of research as a display device for implementing a video Is being developed.

In general, flat panel displays including OLEDs generally have a unidirectional display that implements a screen in only one direction on a substrate. However, efforts to implement a screen in both directions are being researched and developed. Although it is feasible, it is attracting attention as a bidirectional display device due to the development of nano-technical thin film processing technology.

The OLED is divided into a bottom emission type, a top emission type, and a double emission type according to its emission direction. Among them, a simple example of the bidirectional display implementation of the OLED is formed on a transparent substrate. It is sealed with a transparent substrate so that the same screen is displayed in both directions.

However, in this case, there is a problem in that a screen is different in both directions in that one direction is necessarily reversed. In order to solve this problem, OLED devices are formed on each of the other substrates to be bonded to each other, or OLED devices are formed on both sides of the same substrate to implement each screen. There are cost problems and thickness problems due to the use of two substrates. If OLED elements are formed on both sides of the same substrate, either display element may be damaged during the process, and the lifetime and reliability of the OLEDs during the formation process There remains a problem that it is difficult to effectively block oxygen / moisture etc. which are fatal to the back from both OLEDs.

The present invention was devised to solve the problems of the prior art, and an object of the present invention is to form a first display device having a relatively difficult process, such as a moving image, on one surface of the same substrate, while on the other surface By forming a second display device having a relatively easy process that does not affect the first display device, a thin and light double-sided flat panel display device using a same substrate while implementing different screens in both directions is provided.

In order to achieve the above object, the present invention includes a substrate, a first display element formed on one surface of the substrate and a second display element formed on the other surface of the substrate, the second display element is the first display Provided is a double-sided flat panel display device characterized by being a display element of a different kind from the element.

While the first display device is relatively difficult to process, an active matrix type top-emitting OLED or reflective LCD device, etc., which can be a main screen in a double-sided flat panel display device, can be implemented. 2 The display element is a digital paper display such as an electrophoretic display (EPD) or an electrochromic display (ECD) using a relatively easy-to-process electronic ink suitable as an auxiliary screen. It is preferable to use a DPD) element. In a preferred embodiment of the present invention, a double-sided flat panel display having an AMOLED device on one side and an EPD device on the other side will be described.

Hereinafter, with reference to the accompanying drawings will be described a preferred embodiment of the present invention.

1 is a cross-sectional view schematically illustrating a cross-section of a double-sided flat panel display device according to an embodiment of the present invention, wherein the front emission type AMOLED device 200 is formed on one surface (upper surface) of the substrate 100 so that the screen is formed on the upper surface of the substrate ( And the EPD element 300 is formed on the other side (bottom side) of the substrate 100.

As shown in FIG. 1, the EPD device 300 may be formed of a reflective EPD device such that the screen faces the substrate 100 downward direction (the substrate lower arrow direction). Various materials may be used as the substrate 100. However, in order to prevent the overlapping between the screens and the like due to the characteristics of the present invention, stainless steel (SUS), aluminum (alumina), titanium-based metals such as carbon or carbon are contained. It is preferable to use an opaque substrate such as plastic.

On the other hand, in order to improve the luminous efficiency of the AMOLED device 200 and the EPD device 300, it is more preferable to use a metal substrate having a high light reflectance.

2 illustrates a top emission type AMOLED device as a first display device on one surface (top) of a substrate according to an exemplary embodiment of the present invention, and an EPD device as a second display device on the other side (bottom) of a substrate. It is sectional drawing showing in detail about a part of double-sided flat panel display apparatus.

First, as the first display device on the upper surface of the substrate, the AMOLED 200 device is formed with the thin film transistor 210 formed on the substrate 100 and the organic light emitting device 220 thereon.

The thin film transistor 210 includes a semiconductor active layer 211, a gate electrode 213 insulated from the semiconductor active layer, and source and drain electrodes 216a and 216b in contact with the semiconductor active layer.

The semiconductor active layer 211 is formed on the buffer layer 202 made of silicon oxide (SiO _{2 )} and / or silicon nitride (SiN _x ) formed on the substrate 211, and is a source and a drain which are portions in which impurity ions are implanted. It is divided into a region and a channel region into which impurity ions are not implanted.

A gate insulating film 212 is formed on the semiconductor active layer 211 so as to cover the gate insulating film 211, and a gate electrode 213 is formed on a portion of the gate insulating film 212 corresponding to the channel region of the semiconductor active layer, and the gate insulating film is formed thereon. An interlayer insulating film 214 is formed to cover the gap. A contact hole 212a is formed in the gate insulating film 212 and the interlayer insulating film 214, and source and drain electrodes 216a and 216b are formed on the interlayer insulating film. As shown in FIG. 2, a semiconductor active layer is formed through the contact hole. It is in contact with the source and drain regions of.

The planarization layer 218 is formed on the source and drain electrodes 216a and 216b, and the planarization layer 218 is selectively removed to expose the drain electrode 216b, thereby forming the via hole 219. A metal film having a high reflectance and a work function is formed on the via hole 219. The metal film is selectively removed to form the pixel electrode 221 of the organic light emitting diode 220, and to form a lower via hole 219. Electrical connection to the drain region.

The organic light emitting diode 220 includes a pixel electrode 221 of the organic light emitting diode, a pixel defining layer 222 covering a portion of the pixel electrode 221, an organic film 223 including a light emitting layer, and an opposite electrode of the organic light emitting diode. 224.

 The pixel electrode 221 and the counter electrode 224 are insulated from each other by the organic layer 223, and apply voltages having different polarities to the organic layer 223 to emit light in the organic layer.

On the other hand, the pixel electrode 221 functions as an anode electrode, and the counter electrode 224 functions as a cathode electrode. Of course, the polarities thereof may be reversed.

The pixel electrode 221 may be provided as a transparent electrode or a reflective electrode. Preferably, the pixel electrode 221 is provided as a reflective electrode, and when used as a reflective electrode, Ag, Mg, Al, Pt, Pd, Au After forming a reflecting film with Ni, Nd, Ir, Cr, a compound thereof, and the like, ITO, IZO, ZnO or In ₂ O ₃ is formed thereon.

On the other hand, the counter electrode 224 may also be provided as a transparent electrode or a reflective electrode, the transparent electrode is preferable for the top emission in the nature of the present invention, since the counter electrode serves as a cathode, a metal having a low work function, that is Li , Ca, LiF / Ca, LiF / Al, Al, Mg and their compounds are deposited to face the organic film 223, and then formed transparent electrodes such as ITO, IZO, ZnO or In ₂ O ₃ thereon. The auxiliary electrode layer 225 or the bus electrode line is formed of a solvent material.

The organic layer 223 may be a low molecular or high molecular organic layer. When the low molecular organic layer is used, a hole injection layer (HIL), a hole transport layer (HTL), and an organic emission layer (EML) are used. The electron transport layer (ETL), the electron injection layer (EIL), and the like may be formed by stacking a single or a complex structure.

Organic materials that can be used include copper phthalocyanine (CuPc), N, N'-di (naphthalen-1-yl) -N-N'-diphenyl-benzidine (N, N'-Di (naphthalene-1-) yl) -N-N'-diphenyl-benzidine (NPB), tris-8 hydroxyquinoline aluminum (Alq3) and the like can be variously applied. These low molecular weight organic layers are formed by the vacuum deposition method.

In the case of the polymer organic layer, the structure may include a hole transporting layer (HTL) and a light emitting layer (EML). In this case, PEDOT is used as the hole transporting layer, and PPV (Poly-Phenylenevinylene) and polyfluorene are used as the light emitting layer. By using a polymer organic material such as), it can be formed by screen printing or ink jet printing.

A protective layer 230 is formed on the auxiliary electrode layer 225 to protect the organic layer 223, in particular, the electron transport layer ETL and the electron injection layer EIL, from oxygen or moisture. A protective cap is mounted using a sealant and a transparent substrate to form a top emission type active OLED device as the first display device.

Next, the EPD 300 element as the second display element on the bottom surface of the substrate is provided with two transparent substrates 310 and 330 made of the substrate 100 and polyethylene and an electric ink having an electronic ink therebetween. It is formed to include the movable film 320.

A transparent image electrode 312 is formed on one of the transparent substrates, a transparent counter electrode 332 is formed on the other transparent substrate 330, and the electronic ink of the electrophoretic film 320 is about 10 to 50 μm. A plurality of microcapsules 325 of size are included. Each microcapsule 325 includes positively charged white particles 321 and negatively charged black particles 322 floating in the electrophoretic membrane 320 made of a fluid.

In brief, the action of the EPD, when a negative electric field is applied to the counter electrode 332, the white particles 321 move to the surface of the microcapsules 325 in the direction of the counter electrode 332 (black particles 322 Of course, the display element can be seen to be bright, and conversely, when a positive electric field is applied to the counter electrode 332, the black particles 322 are microcapsules 325 in the direction of the counter electrode 332. It moves to the side of, and the display element becomes dark.

When the electric field is removed, the microscopic particles remain intact, the display is bistable and substantially power-free. Therefore, power consumption can be reduced when there is no new screen configuration, which is excellent in terms of power consumption.

Although the EPD using the microcapsules has been described as the second display element, the use of a twist ball display using a twist ball or a display capable of realizing a color screen by electrochromic dye Of course it is possible. On the other hand, electrochromic displays (ECDs), which use color changing properties when applied with current, are also being researched and considered as ideal DPD devices in terms of high resolution color implementation and low power consumption.

Thus, by forming the AMOLED element on one side of the substrate and the EPD element on the other side of the substrate, the first display element by the AMOLED element is used as the main screen of a mobile phone or PDA for moving image, etc. On the other hand, the second display element by the EPD element can implement a double-sided flat panel display device that can be used for an auxiliary window or a digital paper display (DPD), such as a mobile phone, by using a single substrate as described above, light and thin double-sided A flat panel display can be implemented.

On the other hand, since the EPD device has a small and simple process, it does not affect the OLED device during the process, thereby solving the problem of OLED damage and blocking the penetration of oxygen and moisture. Forming and then forming an OLED device can also be considered.

As described above, the present invention is not necessarily limited to the above-described AMOLED device and EPD device, and various display devices such as a reflective LCD capable of moving images as described above can be used as the first display device instead of the AMOLED device. As a matter of course, the second display element may also use various types of display elements that may be employed in an external window or a DPD. In addition, the present invention has been described with reference to the embodiments shown in the drawings, which are merely exemplary and will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. . Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

As described in detail above, the present invention forms a display device capable of moving images such as an AMOLED device on one surface of the same substrate and a display device of a relatively simple process such as an EPD device on the other surface of the substrate, thereby allowing different screens on each side of the substrate. It is possible to implement, but there is an advantage that can provide a thinner and lighter double-sided flat panel display by using a single substrate.

On the other hand, by using an excellent EPD and the like on the other side of the substrate in terms of power consumption, it is expected that the double-sided flat panel display according to the present invention will be considerably superior in terms of power consumption and cost than the conventional double-sided display.

Claims (4)

Board; A first display element formed on one surface of the substrate; And A second display element formed on the other side of the substrate, The second display element is a display element of a different type from the first display element. According to claim 1, And the first display element is an active matrix organic light emitting display (AMOLED) element. According to claim 1, And the second display element is an electrophoretic display (EPD) or an electrochromic display (ECD) element. The method according to any one of claims 1 to 3, The substrate is a double-sided flat panel display, characterized in that the metal-based or plastic-based opaque substrate, such as stainless steel (SUS), aluminum (alumina) or titanium.

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