KR102416889B1 - Organic light emitting display device - Google Patents

Abstract

The present invention relates to an organic light emitting diode display capable of improving reliability, wherein the organic light emitting display device includes a capping layer disposed between a cathode electrode of a light emitting device disposed on an active region of a substrate and an encapsulation protective layer. Since the capping layer is disposed to cover the upper surface and the side surface of the cathode electrode of the light emitting device, it is possible to prevent interfacial contact between the cathode electrode having poor adhesion and the encapsulation protective layer.

Description

Organic light emitting display device {ORGANIC LIGHT EMITTING DISPLAY DEVICE}

The present invention relates to an organic light emitting display device, and more particularly, to an organic light emitting display device capable of improving reliability.

A video display device that implements various information on a screen is a key technology in the information and communication era, and is developing in the direction of thinner, lighter, portable and high-performance. Accordingly, as a flat panel display capable of reducing the weight and volume, which are disadvantages of a cathode ray tube (CRT), an organic light emitting display device that displays an image by controlling the amount of light emitted by the emission layer is in the spotlight. The organic light emitting diode display is a self-luminous device, and has low power consumption, high response speed, high luminous efficiency, high luminance, and a wide viewing angle.

Organic materials and metal materials included in the organic light emitting diode display are easily oxidized by external factors such as moisture (H2O) or oxygen (O2). In particular, when adhesion between a plurality of thin film layers included in the organic light emitting diode display is not good, moisture or oxygen permeates into the organic layer disposed between the anode and the cathode electrode. As the organic layer is deteriorated by the moisture or oxygen, a pixel shrinkage defect that turns black from the edge of each sub-pixel occurs. In addition, if the pixel shrinkage defect persists for a long time, a dark spot defect in which the entire area of the sub-pixel is discolored black, and thus reliability is deteriorated.

SUMMARY OF THE INVENTION The present invention is to solve the above problems, and the present invention is to provide an organic light emitting diode display capable of improving reliability.

In order to achieve the above object, an organic light emitting display device according to the present invention includes a capping layer disposed between a cathode electrode of a light emitting device disposed on an active region of a substrate and an encapsulation protection layer, and the capping layer is formed of the light emitting device. Since it is disposed to cover the upper surface and the side surface of the cathode electrode, interfacial contact between the cathode electrode having poor adhesion and the encapsulation protective layer can be prevented.

The present invention includes a capping layer disposed between the encapsulation protective layer and the cathode electrode to cover the upper surface and the side surface of the cathode electrode. With such a capping layer, the present invention can prevent direct interfacial contact between the encapsulation protective layer and the cathode electrode, thereby preventing the film lifting phenomenon of the encapsulation protective layer. Accordingly, according to the present invention, it is possible to effectively block the inflow of moisture or oxygen from the outside to the interface between the encapsulation protective layer, each of the cathode electrode, and the capping layer, thereby improving reliability. In addition, since the capping layer of the present invention extends to the inactive region, it is possible to protect the circuit driver (eg, the scan driver, the shorting bar, etc.) disposed in the inactive region from external impact.

1 is a block diagram illustrating an organic light emitting diode display according to the present invention.
FIG. 2 is a cross-sectional view of the organic light emitting diode display taken along line "I-I'" in FIG. 1 .
FIG. 3 is a circuit diagram illustrating a sub-pixel disposed in the active region shown in FIG. 1 .
FIG. 4 is a cross-sectional view of the organic light emitting diode display taken along line "II-II'" in FIG. 2 .
FIG. 5 is a cross-sectional view of the organic light emitting diode display taken along line “III-III′” in FIG. 3 .
6A is a cross-sectional view illustrating an organic light emitting diode display according to a comparative example, and FIG. 6B is a cross-sectional view illustrating an organic light emitting display apparatus according to an exemplary embodiment of the present invention.

Hereinafter, an embodiment according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a plan view and a cross-sectional view of an organic light emitting display device according to the present invention.

The organic light emitting diode display illustrated in FIGS. 1 and 2 includes first and second substrates 101 and 111 facing each other with the organic light emitting diode 130 interposed therebetween.

The first substrate 101 is formed of a glass or plastic substrate. In the case of a plastic substrate, a polyimide-based or polycarbonate-based material may be used to have flexibility.

The second substrate 111 is disposed to face the first substrate 101 . The second substrate 111 is formed of a material such as glass, polymer, or metal according to the emission direction of the organic light emitting diode display. For example, when the organic light emitting display device is a bottom emission type, the second substrate 111 is formed of a material such as an opaque metal, and when the organic light emitting display device is a top emission type, the second substrate 111 is transparent glass. It is made of a material such as The second substrate 111 is formed to have a smaller area than the first substrate 101 to expose the pad area PA formed on the first substrate 101 .

The first and second substrates 101 and 111 are bonded using at least one of the pillar 126 and the dam 128 .

The pillar 126 is disposed on the organic light emitting device 130 to overlap the organic light emitting device 130 . Accordingly, the filler 126 is formed using a transparent material so that the luminance does not decrease while the light emitted from the organic light emitting diode 130 is transmitted to the second substrate 111 . For example, the filler 126 may use epoxy or olefin, talc, calcium oxide (CaO), barium oxide (BaO), zeolite (zeolite) and silicon oxide (SiO) and the like.

Since the dam 128 is disposed to surround the active area AA in which the organic light emitting diode 130 is formed on a plane, it is formed using an opaque material or a transparent material. The dam 128 adhesively seals the first substrate 101 and the second substrate 111 together with the filler 126 . The dam 128 may be formed using an organic material including a photocurable material or a thermally curable material, including epoxy, acrylic, and silicone.

The organic light emitting diode display having the first and second substrates 101 and 111 is divided into an active area AA and an inactive area NA.

The active area AA is an area in which a plurality of sub-pixels SP are arranged in a matrix form to implement an image. Each sub-pixel SP includes a pixel driving circuit and an organic light emitting device 130 as shown in FIG. 3 .

The pixel driving circuit includes first and second switching transistors ST1 and ST2 , a driving transistor DT, and a capacitor Cst. Here, the configuration of the pixel driving circuit is not limited to the structure of FIG. 3 , and various configurations of the pixel driving circuit may be used.

The first switching transistor ST1 is turned on under the control of the first scan line SL1 to transfer the data voltage from the data line DL to the gate electrode of the driving transistor DT.

The second switching transistor ST2 is turned on under the control of the second scan line SL2 to transfer the reference voltage from the reference line RL to the source electrode of the driving transistor DT, and in the sensing mode, the driving transistor A current of (DT) may be transferred to the reference line (RL). The first and second switching transistors ST1 and ST2 may be controlled by different scan lines SL1 and SL2 or may be controlled by the same scan line.

The driving transistor DT is switched according to the data signal supplied from the first switching transistor ST1 to control a current flowing from the high potential voltage EVDD supply line PL to the organic light emitting diode 130 .

The storage capacitor Cst is connected between the scan terminal of the driving transistor DT and the low potential voltage EVSS supply line, charges a difference voltage therebetween, and supplies it as the driving voltage of the driving transistor DT.

The organic light emitting diode 130 is electrically connected between the source terminal of the driving transistor DT and the low potential voltage EVSS supply line, and emits light by a current corresponding to the data signal supplied from the driving transistor DT. To this end, the organic light emitting diode 130 includes an anode electrode 132 connected to the source terminal of the driving transistor DT, an organic layer 134 formed on the anode electrode 132 , and a cathode electrode formed on the organic layer 134 . (136) is included. Here, the organic layer 134 may include a hole injection layer/a hole transport layer/a light emitting layer/an electron transport layer/an electron injection layer and the like.

Accordingly, each of the sub-pixels SP controls the amount of current flowing from the high potential power VDD to the organic light emitting diode 130 by using the switching of the driving transistor DT according to the data signal to control the organic light emitting diode 130 . ) to express a predetermined color by emitting light.

The inactive area NA is disposed to surround the active area AA. A scan driver 150 , a signal pad, a low potential voltage shorting bar 154 , and a high potential voltage shorting bar VSS are disposed in the inactive area NA.

The scan driver 150 is disposed on both left and right sides of the display area AA, or is disposed on any one of the left and right sides of the display area AA. The scan driver 150 sequentially drives the scan lines SL disposed in the active area AA in response to a scan control signal from a timing controller (not shown). The scan driver 150 supplies a high-state scan pulse for each corresponding scan period of each scan line SL, and supplies a low-state scan pulse for the remaining period in which the scan line SL is driven.

As shown in FIGS. 1 and 2 , the scan driver 150 is implemented as a GIP (Gate In Panel) type and is directly formed in the inactive area NA. A scan control signal and the like from the timing controller are supplied to the scan driver 150 through the GIP line 148 . A planarization layer 124 , a capping layer 138 , and an encapsulation protection layer 118 are disposed on the scan driver 150 . Here, the planarization layer 124 is formed to cover the pixel driving circuit including the first and second switching transistors ST1 and ST2 and the driving transistor DT.

The low potential voltage shorting bar 154 and the high potential voltage shorting bar 152 are disposed between the active area AA and the pad area PA as shown in FIG. 4 . Meanwhile, the high voltage shorting bar 152 may be additionally disposed in the inactive area NA to be adjacent to the lower side of the active area AA as shown in FIG. 5 .

The low potential voltage shorting bar 154 is directly connected to the cathode electrode 136 as shown in FIG. 4 to supply the low potential voltage EVSS to the cathode electrode 136 .

As shown in FIG. 4 , the high potential voltage shorting bar 152 is disposed between the low voltage shorting bar 154 and the active area AA to supply the high potential voltage EVDD to the driving transistor DT. At this time, in order to prevent an electrical short between the high potential voltage shorting bar 152 and the cathode electrode 136 , a planarization layer 124 and an organic light emitting diode are disposed between the high potential voltage shorting bar 152 and the cathode electrode 136 . At least one of the organic layers 134 of the device 130 is disposed.

In this way, not only the encapsulation protective layer 118 but also the capping layer 138 is disposed on at least one of the scan driver 150 , the low potential voltage shorting bar 154 , and the high potential voltage shorting bar 152 . In this case, since the capping layer 138 is made of an organic insulating material, an external impact may be alleviated. Accordingly, the capping layer 138 may prevent the scan driver 150 , the low potential voltage shorting bar 154 , and the high potential voltage shorting bar 152 from being damaged from external impact.

The signal pad 156 is disposed in the pad area AA in the inactive area NA. The signal pad 156 receives driving signals for controlling the switching transistors ST1 and ST2 and the driving transistors DT included in the pixel driving circuit from a data driver (not shown) or the like.

An encapsulation protection layer 118 is disposed on the first substrate 101 to expose the signal pad 156 . That is, the encapsulation protective layer 118 is formed on the first substrate 101 to cover the pixel driving circuit, the organic light emitting diode 130 , the shorting bars 152 and 154 , and the scan driver 150 . The encapsulation protective layer 118 protects the pixel driving circuit, the organic light emitting diode 130 , the shorting bars 152 and 154 , and the scan driver 150 from external moisture or oxygen.

The encapsulation protective layer 118 is formed of an inorganic film or a structure in which inorganic or organic films are alternately stacked. The inorganic film of the encapsulation protective layer 118 is formed of a material that does not contain hydrogen gas during a manufacturing process. For example, when the encapsulation protective layer 118 is formed of SiNx using NH3 gas, hydrogen groups contained in NH3 are diffused into the active layers of the thin film transistors ST1, ST2, and DT during the manufacturing process. The diffused hydrogen reacts with oxygen included in the active layer made of the oxide semiconductor to change the characteristics (for example, threshold voltage, etc.) of the thin film transistors ST1, ST2, and DT. Reliability is reduced. Accordingly, the inorganic layer of the encapsulation protective layer 118 of the present invention is formed of an inorganic insulating material such as silicon oxide (SiOx) or aluminum oxide (Al2O3). The organic layer of the encapsulation protective layer 118 is formed of an organic insulating material such as acrylic resin, epoxy resin, polyimide, polyethylene, or silicon oxycarbon (SiOC).

A capping layer 138 is disposed between the encapsulation protective layer 118 and the cathode electrode 136 . The capping layer 138 has a specific refractive index in the case of top emission, and may serve to collect light to improve emission of light, and in case of bottom emission, the organic light emitting device 130 ) serves as a buffer for the cathode electrode 136 of the.

The capping layer 138 is disposed to cover an upper surface and a side surface of the cathode electrode 136 to prevent the encapsulation protective layer 118 from contacting the cathode electrode 136 . Accordingly, adhesion between each of the cathode electrode 136 and the encapsulation protective layer 118 and the capping layer 138 is improved. This will be described in detail with reference to FIGS. 6A and 6B .

Since the capping layer 38 of the comparative example shown in FIG. 6A is formed to have the same line width as the organic layer 134, it is disposed in the active region. Accordingly, since the capping layer 38 of the comparative example exposes a portion and a side surface of the upper surface of the cathode electrode 136 , the cathode electrode 136 comes into contact with the encapsulation protective layer 18 . However, due to poor adhesion between the cathode electrode 136 and the encapsulation protective layer 18, an interfacial separation between the encapsulation protective layer 18 and the cathode electrode 136 occurs, causing the encapsulation protective layer 18 to float. . Moisture penetrates into the interface between the encapsulation protective layer 18 and the cathode electrode 136 , thereby damaging the organic layer 134 . Accordingly, in order to improve adhesion between the encapsulation protective layer 18 made of an inorganic insulating material and the cathode electrode 136 , the surface of the cathode electrode 136 is roughened through a surface etching process of the cathode electrode 136 . However, it is difficult to secure the surface roughness of the cathode electrode 136 to a desired level, and the residue generated during the etching process is not removed but remains on the surface of the cathode electrode 136 and appears as a stain.

On the other hand, the capping layer 138 according to the embodiment of the present invention shown in FIG. 6B is formed to have a larger area than the organic layer 134 and extends to an inactive region to partially overlap the dam 128 . Accordingly, since the capping layer 138 is disposed to cover the upper surface and the side surface of the cathode electrode 136 , the cathode electrode 136 comes into contact with the capping layer 138 and directly contacts the encapsulation protective layer 118 . won't do it In this case, the capping layer 138 is formed of an organic material having a -CHO group. Since the -OH group of the capping layer 138 improves the bonding strength between the cathode electrode 136 and the encapsulation protective layer 118 , the capping layer 138 and the cathode electrode 136 even if the surface roughness of the cathode electrode 136 is low. ), there is no interfacial separation between them.

As described above, in the present invention, the capping layer 138 is disposed between the encapsulation protective layer 118 and the cathode electrode 136 to cover the upper surface and the side surface of the cathode electrode 136 . Due to the capping layer 138 , in the present invention, direct interfacial contact between the encapsulation protective layer 118 and the cathode electrode 136 can be prevented, thereby preventing the film lifting phenomenon of the encapsulation protective layer 118 . Accordingly, according to the present invention, it is possible to effectively block the inflow of moisture or oxygen from the outside to the interface between the encapsulation protective layer 118 and the cathode electrode 136 and the capping layer 138 , thereby improving reliability.

In addition, since the capping layer 138 of the present invention extends to the inactive area NA, a circuit driver (eg, the scan driver 150 , the shorting bars 152 and 154, etc.) disposed in the inactive area NA is used. It can be protected from external impact.

The above description is merely illustrative of the present invention, and various modifications may be made by those of ordinary skill in the art to which the present invention pertains without departing from the technical spirit of the present invention. Therefore, the embodiments disclosed in the specification of the present invention do not limit the present invention. The scope of the present invention should be construed by the following claims, and all technologies within the scope equivalent thereto should be construed as being included in the scope of the present invention.

101,111: substrate 118: encapsulation protective layer
126: pillar 128: dam
130: organic light emitting device 132: anode electrode
134: organic layer 136: cathode electrode
138: capping layer 150: scan driver
152: low potential voltage shorting bar 154: high potential voltage shorting bar

Claims (6)

a first substrate including an active region and an inactive region surrounding the active region;
a light emitting device disposed on the active region of the first substrate;
an encapsulation protective layer disposed on the light emitting device;
a second substrate disposed on the encapsulation protective layer;
a capping layer disposed between the encapsulation protective layer and the cathode electrode to cover an upper surface and a side surface of the cathode electrode of the light emitting device;
a dam disposed between the first substrate and the second substrate and overlapping the inactive region;
a filler positioned between the encapsulation protective layer and the second substrate and surrounded by the dam;
The first substrate and the second substrate are bonded by the dam,
An end portion of the capping layer and an end portion of the encapsulation protection layer overlap the dam. The method of claim 1,
The capping layer has a larger area than the organic layer of the light emitting device. The method of claim 1,
The cathode electrode of the light emitting device is in contact with the capping layer and not in contact with the encapsulation protective layer. The method of claim 1,
The filler is in contact with the encapsulation protective layer and the second substrate. The method of claim 1,
The capping layer is made of a material having a -OH group. The method of claim 1,
a low potential voltage shorting bar for supplying a low potential voltage to the cathode electrode of the light emitting device;
a high potential voltage shorting bar supplying a high potential voltage to a driving transistor connected to the light emitting device;
Further comprising a scan driver for driving a scan line connected to at least one switching transistor connected to the driving transistor,
The low potential voltage shorting bar, the high potential voltage shorting bar and the scan driver are disposed in an inactive area of the substrate,
The capping layer is disposed on at least one of the low potential voltage shorting bar, the high potential voltage shorting bar, and the scan driver.

Images