Flexible flat panel display

A flexible flat panel display prevents electronic units, such as a flexible printed circuit board and a driving IC, from being separated from the flexible flat panel display even when the display unit is bent. The flexible flat panel display includes: a flexible display unit including a display area adapted to display an image, a first side and a second side parallel to edges of the display area, and a third side and a fourth side perpendicular to the first and second sides, the third side and the fourth being adapted to being bent; and electronic units arranged solely on at least one of the first and second sides and absent the third and fourth sides.

CLAIM OF PRIORITY

This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application for FLEXIBLE FLAT PANEL DISPLAY DEVICE earlier filed in the Korean Intellectual Property Office on the 14 of Oct. 2005 and there duly assigned Serial No. 10-2005-0096939.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a flexible flat panel display, and more particularly, to a flexible flat panel display which prevents electronic units such as a driving Integrated Circuit (IC) and a flexible printed circuit board from being separated from the flexible flat panel display even when the flexible flat panel display is bent.

2. Description of the Related Art

A flat panel display such as a liquid crystal display, an organic light emitting device, or an inorganic light emitting device has a flat shape and can be used as a flexible display.

In order to be connected to an external circuit device, the flat panel display is bonded to a flexible printed circuit board. A driving Integrated Circuit (IC) is directly mounted on the flexible display. The flexible printed circuit board or the driving IC is bonded to a pad unit formed on an edge of the flat panel display via an anisotropy conductive adhesive. Alternatively, the flexible printed circuit board or the driving IC is attached to a lateral or longitudinal side of a flat panel display.

The flexible flat panel display can be bent in at least one direction, and can be used in a bent state. For example, the flexible flat panel display can be bent in a specific direction and attached to a cylinder or the like.

However, when the flexible flat panel display is bent, the flexible printed circuit board or the driving IC placed on a bent side will likely separate from the flexible flat panel display due to the bending stress. In this case, the flat panel display is electrically open and an image cannot be displayed.

SUMMARY OF THE INVENTION

The present invention provides a flexible flat panel display in which a flexible printed circuit board and a driving Integrated Circuit (IC) are not separated from the flexible flat panel display even when the flexible flat panel display is bent.

According to one aspect of the present invention, a flexible flat panel display is provided, the flexible flat panel display including: a flexible display unit including a display area adapted to display an image, a first side and a second side parallel to edges of the display area, and a third side and a fourth side perpendicular to the first and second sides, the third side and the fourth being adapted to being bent; and electronic units arranged solely on at least one of the first and second sides and absent the third and fourth sides. The electronic unit is arranged on the first side and includes a scan driving circuit. The electronic unit arranged on the first side includes a scan driving IC including the scan driving circuit. The electronic unit arranged on the first side includes a scan driving unit including the scan driving circuit and is patterned on the first side.

The electronic unit is preferably arranged on the second side and includes a data driving circuit. The electronic unit arranged on the second side preferably includes a data driving IC including the data driving circuit. The electronic unit arranged on the second side preferably includes a data driving unit which includes the data driving circuit and is patterned on the second side.

The electronic unit is alternatively preferably arranged on the first side and includes a flexible circuit board bonded to the first side.

The electronic unit is alternatively preferably arranged on the second side and includes a flexible circuit board bonded to the second side.

The electronic unit is preferably arranged on the first side and includes a first scan driving circuit and a first data driving circuit. The electronic unit arranged on the first side preferably includes a first scan driving IC including the first scan driving circuit. The electronic unit arranged on the first side alternatively preferably includes a first scan driving unit including the first scan driving circuit and is patterned on the first side. The electronic unit arranged on the first side alternatively preferably includes a first data driving IC including the first data driving circuit. The electronic unit arranged on the first side alternatively preferably includes a first data driving unit including the first data driving circuit and is patterned on the first side.

The electronic unit is alternatively preferably arranged on the second side and includes a second scan driving circuit and a second data driving circuit. The electronic unit arranged on the second side preferably includes a second scan drive IC including the second scan driving circuit. The electronic unit arranged on the second side alternatively preferably includes a second scan driving unit including the second scan driving circuit and is patterned on the second side. The electronic unit arranged on the second side alternatively preferably includes a second data driving IC including the second data driving circuit. The electronic unit arranged on the second side alternatively preferably includes a second data driving unit including the second data driving circuit and is patterned on the second side.

According to another aspect of the present invention, a flexible flat panel display is provided including: a display area adapted to be bent in at least one direction and to display an image; a plurality of first wires intersecting the display area and extending along sides of the display area, the sides of the display area being bent; and a plurality of second wires intersecting the display area and extending along other sides of the display area, the other sides of the display area not being bent; the first wires and the second wires extending along the sides of the display area to locations external to the display area.

The first wires and the second wires preferably extend in opposite directions external to the display area. The first wires and the second wires alternatively preferably extend in the same direction external to the display area.

External to the display area, some of the first wires and second wires alternatively preferably extend in one bending direction of the bent sides of the display area, and the other of the first wires and second wires preferably extend in another bending direction different from the one bending direction.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is a plan view of a flexible flat panel display according to an embodiment of the present invention.

Referring toFIG. 1, the flexible flat panel display includes a flexible display unit1, and a first electronic unit2and a second electronic unit3bonded to the display unit1. The flexible display unit1, as shown inFIG. 1, can have a rectangular shape, and includes a first side12aand a second side12b, which are short sides parallel to each other, and a third side12cand a fourth side12dwhich are long sides parallel to each other.

The flexible display unit1can be bent in at least one direction. In the present embodiment, the flexible display unit1can be bent in the arrow directions indicated inFIG. 1. That is, the first side12athrough the fourth side12dof the flexible display unit1can be bent, and the flexible display unit1can be used in a state in which the long sides, i.e., the third and fourth sides12cand12d, are bent.

A display area10is formed in the center of the flexible display unit1. The display area10can be formed using an Active-Matrix (AM) organic light emitting device, as shown inFIG. 2.

Referring toFIG. 2, each pixel of the AM organic light emitting device according to an embodiment of the present invention includes at least two Thin Film Transistors (TFTs), that is, a driving TFT M1and a switching TFT M2, a storage capacitor Cstand an Organic Light Emitting Diode (OLED).

The switching TFT M2is turned on or off in response to a scan signal supplied to a scan line Scan, and transmits a data signal supplied to a data line Data to the storage capacitor Cstand the driving TFT M1. The driving TFT M1determines a current flowing into the OLED from a Vdd line in response to the data signal supplied through the switching TFT M2. The storage capacitor Cststores the data signal transmitted through the switching TFT M2for one frame.

InFIG. 2, the driving TFT M1and the switching TFT M2are P type Metal Oxide Semiconductor (PMOS) TFTs, but the present invention is not limited thereto. At least one of the driving TFT M1and the switching TFT M2can be an N type Metal Oxide Semiconductor (NMOS) TFT. Moreover, the number of thin film transistors and capacitors is not limited to the above description, and more thin film transistors and capacitors can be included in each pixel.

FIG. 3is a cross-sectional view of an example of a portion of the AM organic light emitting display ofFIG. 2. Referring toFIG. 3, the driving TFT M1and the OELD are formed on a substrate101. Although the switching TFT M2and the storage capacitor Cstare not illustrated inFIG. 3, they can be formed by the same processes used to form the driving TFT M1.

The substrate101can be made of acryl, polyimide, polycarbonate, polyester, mylar, or an other plastic material, but the present invention is not limited thereto. For example, the substrate101can be made of a metal foil, such as Stainless Steel (SUS) or tungsten, or a thin glass. The substrate101is flexible.

An insulating layer102, such as a barrier layer and/or a buffer layer, can be formed on the substrate101to prevent diffusion of impurity ions and penetration of moisture or air and to planarize a surface of the substrate101.

An active layer107of the driving TFT M1is formed of a semiconductor material on the insulating layer102, and a gate insulating layer103is formed to cover the active layer107. The active layer107can be formed of an inorganic semiconductor, such as amorphous silicon or poly silicon, or an organic semiconductor.

A gate electrode108is disposed on the gate insulating layer103, and an interlayer insulating layer104is formed to cover the gate electrode108. Then, source/drain electrodes109are formed on the interlayer layer104, and a passivation layer105and a pixel defining layer106are sequentially formed to cover the source/drain electrodes109.

The gate electrode108and the source/drain electrodes109can be formed of a metal, such as Al, Mo, Au, Ag, Pt/Pd, or Cu, but the present invention is not limited thereto. The gate electrode108and the source/drain electrodes109can be coated with a resin paste including a metal powder, or can be formed of a conductive polymer.

The gate insulating layer103, the interlayer layer104, the passivation layer105, and the pixel defining layer106can be formed as insulators having a single layer or multiple layers formed of an organic material, an inorganic material, or a compound of organic and inorganic materials.

The layer structure of the driving TFT M1is not limited to that described above, and the driving TFT M1can have a variety of layer structures.

A pixel electrode110, that is, one electrode of the OLED, is formed on the passivation layer105, and the pixel defining layer106is formed on the pixel electrode110. Then, a predetermined opening portion is formed on the pixel defining layer106to exposed the pixel electrode110, and an organic light emitting layer111of the OLED is formed in the open portion.

The OLED displays a predetermined image by emitting red, green, and blue light according to a current flow, and includes the pixel electrode110connected one of the source/drain electrodes109of the driving TFT M1, a counter electrode112covering all of the pixels, and the organic light emitting layer111that is interposed between the pixel electrode110and the counter electrode112and emits light.

The pixel electrode110and the counter electrode112are insulated from each other by the organic light emitting layer111, and the organic light emitting layer111emits light by applying voltages of different polarities.

The organic light emitting layer111can be a small molecule organic layer or a polymeric organic layer. When a small molecule organic layer is used, the organic layer can be formed by a structure of a Hole Injection Layer (HIL), a Hole Transport Layer (HTL), an EMission Layer (EML), a Electron Transport Layer (ETL), an Electron Injection Layer (EIL), or the like, and an available organic material can be copper phthalocyanine (CuPc), N,N′-Di(naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPB), tris-8hydroxyquinoline aluminium (Alq3), or the like. The small molecule organic layer is formed by a vapor deposition method.

In the case of a polymeric organic layer, the organic layer is formed by an HTL and an EML, and the HTL is made of polyethylenedioxythiophene (PEDOT), and the EML is made of a polymeric organic material, such as poly-phenylenevinylene (PPV) group or a polyfluorene group, and is formed by a screen printing or an inkjet printing method.

The organic layer is not limited to the above description, and can be formed in various ways.

The pixel electrode110acts as an anode electrode, and the counter electrode112acts as a cathode electrode. However, the functions of the pixel electrode110and the counter electrode112can be reversed.

In the case of a bottom emission type, the pixel electrode110can be a transparent electrode, and the counter electrode112can be a reflective layer. The transparent electrode can be made of ITO, IZO, In2O3, or ZnO, which is transparent and has a high work function, and the reflective layer can be made of a metal, such as Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, or a compound of these metals, which has a low work function.

In the case of a top emission type, the pixel electrode110can be a reflective electrode, and the counter electrode112can be a transparent electrode. In this case, the reflective electrode, that is, the pixel electrode110, is fabricated by forming a reflective layer made of Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, or a compound of these metals and then forming a layer made of ITO, IZO, ZnO, or In2O3, which has a high work function, on the reflective layer. The transparent electrode, that is, the counter electrode112is formed in a thin film, by depositing metal with a low work function, that is, Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, or a compound of these metals, and then forming an auxiliary electrode layer or a bus electrode line with a transparent conductive material, such as ITO, IZO, ZnO, or In2O3.

In the case of a dual emission type, both the pixel electrode110and the counter electrode112can be transparent electrodes.

The material of the pixel electrode110and the counter electrode112is not limited to that described above. The pixel electrode110and the counter electrode112can be made of a conductive material or conductive paste containing conductive particles, such as Ag, Mg, or Cu. When the conductive paste is used, the conductive paste can be printed using a inkjet printing method, and after printing, an electrode can be formed by plasticizing the paste.

After fabricating the OLED, the top of the OLED is sealed to protect it from air.

Referring again toFIG. 1, the scan lines Scan shown inFIG. 2extend toward the outside of the display area10and are connected to scan wires14, and the data line Data extends toward the outside of the display area10and are connected to data wires16.

The scan wires14and the data wires16extend in a bending direction of the flexible display unit1, that is, along bent sides of the flexible display unit1. Specifically, the scan wires14are stretched from the display area10to the third side12cand the fourth side12d, extend along the third side12cand the fourth side12d, and form a scan pad on the second side12b. The data wires16extend along the first side12aand form a data pad on the first side12a.

The first electronic unit2is connected to the data pad formed on the first side12a, and the second electronic unit3is connected to the scan pad formed on the second side12b. The first electronic unit2can include a data driving IC21, a flexible printed circuit board22on which the data driving IC21is mounted, and a printed circuit board23connected to the flexible printed circuit board22. The flexible printed circuit board22can be bonded to the data pad. The second electronic unit3includes a scan driving IC31, a flexible printed circuit board32on which the scan driving IC31is mounted, and a printed circuit board33connected to the flexible printed circuit board32. The flexible printed circuit board32is bonded to the scan pad.

Although other signal wires including Vdd wires are not illustrated inFIG. 1, the signal wires extend in a bending direction, that is, along the bent sides, and form pads on the first side12aand the second side12b. Moreover, the signal wires are connected to the first electronic unit2and the second electrode unit3, or an additional electronic unit and provides them with a signal and current.

According to the present embodiment, as shown inFIG. 1, the third side12cand the fourth side12dare not connected to any electronic units. Therefore, even when the flexible display unit1is bent, the first electronic unit2and the second electronic unit3are not affected by a bending stress, and the first and second electronic units2and3are prevented from being separated from the flexible display unit1.

FIG. 4is a plan view of a flexible flat panel display according to another embodiment of the present invention. The flexible flat panel display ofFIG. 4solves a problem where the pixel response speeds can be different due to the long scan wires14. To this end, a scan section of the display area10is divided into two sections, and a first scan section extends to the first side12avia first scan wires14aand is connected to a first scan driving IC51of a fourth electronic unit5, and a second scan section extends to the second side12bvia second wires14band is connected to a second scan driving IC71of a sixth electronic unit7. Hence, a distance difference between the farthest pixel and the closest pixel from each of the scan driving IC can be somewhat reduced, and therefore, voltage drop in the scan lines and differences between response speeds can be reduced. Moreover, in this case, a part of the data line extends to the first side12aand is connected to a first data driving IC41of a third electronic unit4, and the other part extends to the second side12band is connected to a second driving IC61of a fifth electronic unit6. The third, fourth, fifth, and sixth electronic units4,5,6, and7includes flexible printed circuit boards42,52,62, and72and printed circuit board43,53,63, and73, respectively.

The present embodiment is not limited to the above-described electronic units including the flexible printed circuit board on which a scan driving IC or a data driving IC are mounted, and/or the printed circuit board. The electronic units can include a scan driving unit having a scan diving circuit or a data driving unit having a data driving circuit, wherein the scan driving circuit and the data driving circuit are formed by a deposition and patterning method.

Referring toFIG. 5, the first electronic unit2is formed by a data driving unit24including a data driving circuit. Referring toFIG. 6, the second electronic unit3is formed by a scan driving unit34including a scan driving circuit. The data driving unit24and the scan driving unit34can be a data driving IC and a scan driving IC. The data driving unit24and the scan driving unit34can include a plurality of PMOS TFTs, NMOS TFTs, or CMOS TFTs. Although not illustrated, each of the first electronic unit and the second electronic unit can formed by a data driving unit including a data driving circuit and a scan driving unit including a scan driving circuit.

FIG. 7is a plan view of a flexible flat panel display according to another embodiment of the present invention. InFIG. 7, the third electronic unit4and the fifth electronic unit6are formed by a first data driving unit44and a second data driving unit64, each of which includes a data driving circuit, and the fourth electronic unit5and the sixth electronic unit7are formed by a first scan driving unit54and a second scan driving unit74, each of which includes a scan driving circuit. Although not illustrated, each of the third through sixth electronic units4,5,6, and7can be formed by a data driving unit including a data driving circuit and a scan driving unit including a scan driving unit.

The present invention is applied not only to a structure in which a scan driving IC and a data driving IC are mounted on a flexible printed circuit board and the flexible printed circuit board is connected to the flexible display unit, but also to a structure in which the scan driving IC and the data driving IC are directly mounted on the first side and/or the second side of the flexible display unit.

A flexible printed circuit board according to the present invention is applied not only to the organic light emitting display described above, but also to any flexible flat panel display.

According to the present invention, electronic units such as a flexible printed circuit board and a driving IC are not mounted on sides of a flexible display unit to be bent, but are mounted on sides perpendicular to the bent sides, and thus the electronic units are not affected by a bending stress even when a flexible display unit is bent and the electronic units are prevented from being separated from the flexible display unit.