Electro-luminescent display device

The present invention provides an electro-luminescent (EL) display device and a method of fabricating the same. The EL display device includes a substrate including a display region. The display origin may include a first electrode layer, a second electrode layer, and an emission portion interposed therebetween. A seal member may seal at least the display region. A blocking layer interposed between the seal member and the second electrode layer may overlap the display region.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Korean Patent Application No. 10-2004-0045047, filed on Jun. 17, 2004, in the Korean Intellectual Property Office, the disclosure of which is herein incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to flat panel displays generally, and more particularly, to an electroluminescent (EL) display device having a structure that prevents an emission portion from being damaged during fabrication.

2. Description of the Related Art

Flat panel displays, such as liquid crystal displays (LCDs) or organic or inorganic electro-luminescent (EL) displays, may be either a passive matrix (PM) type or active matrix (AM) type depending on the driving method employed. In a PM type flat panel display, a plurality of anodes are arranged in columns and a plurality of cathodes are arranged in rows. In operation, a row driving circuit transmits a scan signal to a single cathode selected from a row. Similarly, a column driving circuit transmits a data signal to a pixel selected from a row.

AM type flat panel display is widely used as a device for displaying moving pictures since it efficiently processes high bandwidth signals by using a thin film transistor (TFT) to control the signal input to each pixel.

An organic EL display sandwiches an organic emission layer between an anode and a cathode. When an anode voltage and a cathode voltage are applied to the anode and the cathode, respectively, holes introduced from the anode are transported to the emission layer via a hole transport layer, and electrons introduced from the cathode are transported to the emission layer via an electron transport layer. In the emission layer, the electrons and the holes recombine to produce excitons. As the excited state of the excitons changes to a ground state, fluorescent molecules on the emission layer emit light to form an image. Full-color organic EL displays include pixels emitting three colors, red (R), green (G), and blue (B).

For EL displays generally, and organic EL displays particularly, longevity of the display depends on keeping an organic emission portion of a display region as free from moisture as possible.

Various conventional methods and apparatuses have attempted to provide a moisture-proof solution. One such method disclosed in Korean Patent Laid-open Publication No. 2002-0065125 applies an ultraviolet (UV)-curing sealant to the edge of an emission substrate, assembles the emission substrate to a seal substrate, and cures the sealant with UV rays. The energy of the UV rays may however permeate an organic emission portion. During the sealing of the organic emission portion, however, such energy may transmit through an upper layer formed on the organic emission portion and damage the organic emission portion.

Another technique disclosed in Korean Patent Laid-open Publication No. 2000-0065694 interposes a LiF layer between a cathode and an emission layer to improve color efficiency. A similar approach was adopted in Japanese Patent Laid-open Publication No. 2000-200683, which interposes a LiF layer as an electron injection layer (EIL) between a cathode and an organic layer.

In both cases, the LiF layer is limited in thickness. Accordingly, the LiF layer cannot effectively protect the organic emission portion from external energy, such as UV rays. Accordingly, a solution is needed that provides a moisture-proof emission layer and a method of manufacturing the same that minimizes or prevents damage to the emission layer during manufacture.

SUMMARY OF THE INVENTION

The present invention provides an electro-luminescent (EL) display device, in which an emission portion is effectively sealed against moisture and external energy so as to increase the life span of the EL display.

In one embodiment, an EL display device comprises a substrate including a display region. The display region may have a first electrode layer, a second electrode layer, and an emission portion interposed therebetween. A seal member may seal at least the display region. A blocking layer interposed between at least a portion of the seal member and the second electrode layer may overlap at least the display region.

Another embodiment of the invention provides a method of fabricating an EL display device. The method includes forming at least one display region on one surface of an integral substrate, each display region comprised of one or more pixels; forming a blocking layer on at least a portion of the display region; forming one or more seal layers on the blocking layer; curing the seal layers; and scribing the integral substrate.

Yet another embodiment of the invention provides a method of fabricating an EL display device. The method includes forming at least one display region on one surface of an integral substrate, the display region comprised of one or more pixels; forming a plurality of seal layers for sealing the display region on at least a portion of the display region; curing at least portions of the seal layers; and scribing the integral substrate. The step to forming the seal layers may comprise forming a blocking layer between at least one adjacent pair of seal layers.

Another embodiment of the invention provides a method of fabricating an EL display device. The method includes forming at least one display region on one surface of an integral substrate, the display region comprised of one or more pixels; forming a blocking layer on the display region; sealing the display region and a seal substrate using a sealant; curing at least the sealant; and scribing the integral substrate.

Another embodiment of the invention provides a method of fabricating an EL display device. The method includes forming at least one display region on one surface of an integral substrate, the display region comprised of one or more pixels; forming a blocking layer on one surface of a seal substrate that corresponds to the display region; sealing the display region along with the seal substrate using a sealant; curing at least the sealant; and scribing the integral substrate.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1Ais a perspective view of an electro-luminescent (EL) display device manufactured according to the principles of the present invention.

Referring toFIG. 1A, a display region200comprised of one or more pixels is located on one surface of a substrate110. A pad portion700is located on at least one side of the display region200. The pad portion700includes a terminal portion600, which includes one or more terminals.

The pad portion700may further include electronic elements, each having a driving circuit portion such as a driver. Specifically, electronic elements that transmit electric signals to the display region200, for example, vertical/horizontal driving circuit portions, such as scan and data drivers that transmit a scan signal and/or a data signal to the pixels of the display region200, may be located outside the display region200. Like a vertical driving circuit500shown inFIG. 1A, the vertical/horizontal driving circuit portions may be interposed between the display region200and the terminal portion600. A vertical/horizontal driving circuit portion may be a chip on glass (COG) integrated circuit (IC), or may not be included in the pad portion700but be an external electrical element such as a flexible printed circuit (FPC).

FIG. 1Bis an exploded view of a portion “A” shown inFIG. 1A. Here, the portion “A” corresponds to one pixel. AlthoughFIG. 1Billustrates by way of example that one pixel comprises two top gate type thin film transistors and a single capacitor, the present invention is not limited thereto.

A gate electrode55of a first thin film transistor TFT1, which determines the selection of a pixel, extends from a scan line via which a scan signal is applied. When an electrical signal, such as the scan signal, is applied to the scan line, a data signal input via a data line is transmitted from a source electrode57aof the first thin film transistor TFT1through a semiconductor active layer53of the first thin film transistor TFT1to a drain electrode57bof the first thin film transistor TFT1.

An extension portion57cof the drain electrode57bof the first thin film transistor TFT1is connected to one end of a first electrode58aof the capacitor. The other end of the first electrode58aof the capacitor forms a gate electrode150of a second thin film transistor TFT2which is a driving thin film transistor. A second electrode58bof the capacitor is electrically connected to a drive line31, which connects to a driving power supply line (not shown).

Referring toFIG. 1C, the portion between reference characters (a) and (d) is a section of the second thin film transistor TFT2as the driving thin film transistor, the portion between (e) and (f) is a section of a pixel opening194, and a portion between (g) and (h) is a section of the drive line. In the second thin film transistor TFT2, a semiconductor active layer130is formed on a buffer layer120formed on one surface of the substrate110. The semiconductor active layer130may be formed of amorphous silicon (a-Si) or polycrystalline silicone (poly-Si). Although not shown in the drawings, the semiconductor active layer130includes a source region and a drain region, each of which is doped with n+or p+-type dopants, and a channel region. Such a semiconductor active layer130may be formed of an organic semiconductor and may have various structures.

The gate electrode150of the second thin film transistor TFT2is located on the semiconductor active layer130. The gate electrode150may be formed of a material such as MoW or Al/Cu, in consideration of close adhesion to adjacent layers, flatness of stacked layers, and easy processing, but the present invention is not limited thereto.

In order to electrically insulate the gate electrode150from the semiconductor active layer130, a gate insulating layer140is located therebetween. An interlayer160, which may be either a single or multilayer insulating layer, may be formed on the gate electrode150and the gate insulating layer140, and source and drain electrodes170aand170bof the second thin film transistor TFT2are formed thereon. The source and drain electrodes170aand170b may be formed of a metal such as MoW, and annealed later to be in ohmic contact with the semiconductor active layer130.

A protective layer180, which may include a passivation layer and/or a planarization layer, is formed on the source and drain electrodes170aand170b, and a first electrode layer190is formed thereon. The first electrode layer190is electrically connected to one of the source and drain electrodes170aand170bthrough a via hole181formed in the protective layer180. For rear surface emission displays, the first electrode layer190may include a transparent electrode formed of indium tin oxide (ITO). For front surface emission displays, the first electrode layer190may include a reflective electrode formed of Al/Ca and a transparent electrode formed of ITO. The first electrode layer190may be varied as necessary. Here, although it is described to clarify explanation that the first electrode layer190serves as an anode, the present invention is not limited thereto. That is, the first electrode layer190may act as a cathode. Alternatively, other various structures can be used.

The protective layer180may have various forms. For example, the protective layer180may be formed of an organic or inorganic material and may include a single layer or a double layer of, for example, a SiNx, layer and an organic layer of a benzocyclobutene (BCB) or acryl layer.

On the protective layer180outside the pixel opening194corresponding to the first electrode layer190, a pixel defining layer191may be formed. An emission portion192including an emission layer may be located on one surface of the first electrode layer190, in the pixel opening194.

The emission portion192may comprise either a monomer or polymer organic layer. A monomer organic layer can be formed by stacking a hole injection layer (HIL), a hole transport layer (HTL), an organic emission layer (EML), an electron transport layer (ETL), and an electron injection layer (EIL) in a simple or complex structure. Various organic materials can be used, including copper phthalocyanine (CuPc), N,N′-Di(naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPB), and tris-8-hydroxyquinoline aluminum (Alq3). These monomer organic layers are formed by vacuum deposition.

A polymer organic layer can comprise a hole transport layer (HTL) and an emission layer (EML). Here, the hole transport layer can be formed of PEDOT, and the emission layer can be formed of a polymer organic material, such as poly-phenylenevinylene (PPV)-containing material and polyfluorene-containing material, by screen printing or inkjet printing.

A second electrode layer210, as a cathode, is formed on the entire or part of the surface of the emission portion192. Also, the second electrode layer210may be formed of Al/Ca, ITO, or Mg—Ag according to the emission type. The second electrode layer210may be a single or double layer and further include an alkaline layer or an alkaline earth metal fluoride layer such as a LiF layer.

On one surface of the second electrode layer210, a seal layer220is formed to protect at least the display region200. The seal layer220may be formed of an inorganic material such as SiO2or SiNxor an organic material such as siloxane, siloxane derivatives, or acrylate. AlthoughFIG. 1Cshows that the seal layer220includes two seal layers220aand220b, the seal layer220of the present invention may be a single layer or a multiple layer instead.

In the EL display device of the present invention, a blocking layer230formed of one or more layers is interposed between the second electrode layer210and the seal layer220. However, the present invention is not limited thereto. If the seal layer220includes multiple seal layers, the blocking layer230may be interposed therebetween.

The seal layer220, especially the seal layer220formed of an organic material, must be cured for activation. The curing of the seal layer220may be performed using various methods, such as ultraviolet (UV) irradiation or heat curing. Heat and/or UV rays are applied from the outside of the seal layer220toward the second electrode layer210. Particularly, the front surface emission display device includes the thin second electrode layer210. Thus, the applied heat and/or UV rays may permeate the second electrode layer210and damage the emission portion192. However, the blocking layer230interposed between the second electrode layer210and the seal layer220prevents damage to the emission portion192.

The blocking layer230may be formed of various materials, such as Li, Ca, LiF, CaF2, or MgF2.

In addition to the type of material used to form the blocking layer230, the thickness of the blocking layer230should be considered. As the blocking layer230becomes thicker, the emission portion192located under the second electrode layer210is protected more effectively, but process time lengthens. If the blocking layer230is excessively thick, the color coordinate of light emitted from the emission portion192may be shifted. On the other hand, if the blocking layer230is excessively thin it will transmit heat and UV rays and thus may not properly function as a blocking layer. Accordingly, the thickness of the blocking layer230should be appropriately adjusted and is preferably about 10 Å to about 50 Å of the above-description.

FIG. 2A,FIG. 2B,FIG. 2C, andFIG. 2Dare perspective and cross-sectional views illustrating a process of fabricating an organic EL display according to embodiments of the present invention.

On one surface of a large integral substrate110′, which will later be scribed into individual organic EL displays, a display region comprised of one or more pixels is formed, and a pad portion, which includes a terminal portion600comprised of one or more terminals located on at least one side of the display region200. In order to seal at least the display region200along with the integral substrate100′ using a sealant210, a seal portion300is located between the display region200and the terminal portion600.

The pad portion may further include electronic elements, each having a driving circuit portion500such as a driver. Specifically, electronic elements that transmit electric signals to the display region200, for example, vertical/horizontal driving circuit portions, such as scan data drivers that transmit a scan signal and/or a data signal to the pixels of the display region200, may be located between the display region200and the seal portion300or outside the seal portion300. A vertical/horizontal driving circuit portion may be a COG IC or be an external electronic element such as an FPC. The vertical/horizontal driving circuit portion may have various forms. The structure of each pixel constituting the display region200is described above and thus will not be repeated here.

A sealant310is coated on each seal portion300of each organic EL display formed on the integral substrate110′, and a seal substrate400as a seal member is located thereon. The seal substrate400and the integral substrate110′ are sealed so that the display region200is sealed. As shown inFIG. 2B, a predetermined plenum (space or enclosure in which a moisture-proof gas is at a pressure greater than that of the outside atmosphere) may be formed between the seal substrate400and a stack portion stacked on the integral substrate110′. Optionally, as shown inFIG. 2C, the seal substrate400may contact the stack portion through an adhesive410to prevent depression of the seal substrate400due to the plenum. The seal substrate400is not limited to the above-described structure, and various other structures may be used instead.

During the sealing process, as shown inFIG. 2B, UV rays and/or heat is applied to the top surface of the seal substrate400to effectively cure the sealant310and /or the adhesive. To prevent damage to the emission portion192due to the applied UV rays and/or heat, a blocking layer230is interposed between the second electrode layer210and the seal substrate400. As described in the previous embodiment, the blocking layer230may be formed of Li, Ca, LiF, CaF2, or MgF2to a thickness of about 10 Å to about 50 Å.

After curing the sealant310and/or the adhesive, as shown inFIG. 2D, the integral substrate110′ is scribed, thus obtaining individual organic EL display devices.

A blocking layer of an organic EL display having a seal substrate is not limited to the above-described embodiments but can have other structures. For example, as shown inFIG. 3, a blocking layer230may be formed on one surface of a seal substrate400as a seal member, which faces a display region200. That is, the blocking layer230is located to correspond to the display region200. Optionally, the blocking230may be formed on an entire surface of the seal substrate400, except on a seal portion300, which should contact the sealant310to form a reliable moisture-proof structure. As described above, after a blocking layer is formed on one surface of a seal substrate, an integral substrate and a seal substrate are sealed using a sealant, the sealant is cured, and then the integral substrate is scribed into respective EL displays.

The foregoing embodiments are merely exemplary, and do not limit the present invention. Although an AM type organic EL display is described in the embodiments, the present invention can be applied to inorganic EL displays or PM type display devices.

In an EL display device manufactured according to the principles of the present invention, the following effects may be obtained: A blocking layer located between a seal member and a second electrode layer prevents damage to an emission portion due to externally applied UV rays and/or heat. Second, since the EL display of the present invention includes a blocking layer of an appropriate thickness, not only is damage to an emission portion due to externally applied energy prevented, but also the color coordinate of light emitted from the emission portion is not shifted. Third, in the EL display of the present invention, a blocking layer may be located on one surface of a second electrode layer stacked on an integral substrate, or one surface of a seal substrate, which faces a display region. That is, the blocking layer may be formed in appropriate positions according to the design specification.