Method of fabricating organic light emitting display

A method of fabricating a donor substrate for a laser induced thermal imaging (LITI) process. A base substrate is prepared. A light-to-heat conversion layer is formed on the base substrate. A buffer layer is formed on the light-to-heat conversion layer. The surface roughness of the buffer layer is increased by treating the surface of the buffer layer. A transfer layer is formed on the surface-treated buffer layer. By using the donor substrate, a patterning process can be performed better during the fabrication of the OLED.

CLAIM OF PRIORITY

This application claims priority to and the benefit of Korean Patent Application No. 2004-68757, filed Aug. 30, 2004, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of fabricating an organic light emitting display (OLED) and, more particularly, to a method of fabricating an OLED using a donor substrate having a surface-treated buffer layer.

2. Description of the Related Art

Among flat panel displays (FPDs), an organic light emitting display (OLED) is quite appropriate for a medium that displays moving images irrespective of its sizes because the OLED has a fast response speed of 1 millisecond or less and a wide viewing angle, consumes low power, and is an emissive display. Also, the OLED can be fabricated at low temperature and in a simple process based on a conventional semiconductor manufacturing technology. For these reasons, the OLED has attracted much attention as the next-generation flat panel display (FPD).

The OLED can largely be classified into a polymer type using a wet process and a small-molecule type using a deposition process, according to the types of material and process used for an organic light emitting device. If an emission layer (EML) is formed of a small-molecule material, it is deposited in vacuum using a shadow mask. If the EML is formed of a polymer material, it is formed by an inkjet printing method. However, it is difficult to perform the vacuum deposition process using the shadow mask on a large-sized substrate. Also, since the inkjet printing method is a wet process, an underlying layer should be formed of only limited kinds of materials, and a bank structure should definitely be formed on a substrate.

As a substitute for the above-described methods of patterning the EML, a laser-induced thermal imaging (LITI) process has recently been developed.

During the LITI process, a pattern is formed by transferring a pattern forming material to a target substrate using laser beams irradiated from a light source. Such an LITI process requires a donor substrate on which a transfer layer is formed, a light source, and an acceptor substrate.

The donor substrate includes a base substrate, a light-to-heat conversion layer, and a transfer layer. During a transfer process using the donor substrate, laser beams are irradiated on a predetermined region of the base substrate and then converted into heat by the light-to-heat conversion layer. The heat transforms adhesion properties between the transfer layer and the light-to-heat conversion layer so that the transfer layer is transferred to the acceptor substrate.

Accordingly, the performance of the donor substrate depends on adhesion properties between the donor substrate and the transfer layer, and a poor adhesion between the transfer layer and the light-to-heat conversion layer may cause failures during the process of transferring the transfer layer to the acceptor substrate.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to solve aforementioned problems associated with conventional displays.

It is also an object of the present invention to provide a method of fabricating an organic light emitting display (OLED) using a donor substrate, in which adhesion properties between the donor substrate and the transfer layer are enhanced and a patterning process can be performed better during the fabrication of the OLED by interposing a buffer layer between a transfer layer and a light-to-heat conversion layer and then surface-treating the buffer layer.

It is still an object of the present invention to provide an improved method of transferring a pattern forming material to a target substrate.

According to an aspect of the present invention, a method of fabricating a donor substrate for a laser induced thermal imaging (LITI) process includes: preparing a base substrate of a donor substrate; forming a light-to-heat conversion layer on the base substrate; forming a buffer layer on the light-to-heat conversion layer; increasing the surface roughness of the buffer layer by treating the surface of the buffer layer; and forming a transfer layer on the surface-treated buffer layer.

According to an aspect of the present invention, a method of transferring a pattern forming material to a target substrate includes: preparing a donor substrate by a process comprising preparing a base substrate, forming a light-to-heat conversion layer on the base substrate, forming a buffer layer on the light-to-heat conversion layer, increasing surface roughness of the buffer layer, and forming a transfer layer on the surface-treated buffer layer; irradiating laser beams on a predetermined region of the donor substrate, the laser beams converted into heat by the light-to-heat conversion layer to transform adhesion properties between the transfer layer and the light-to-heat conversion layer; and transferring the transfer layer to the target substrate.

According to still an aspect of the present invention, a method of transferring a pattern forming material to a target substrate includes: preparing a donor substrate, the donor substrate constructed with a transfer layer, a light-to-heat conversion layer, and a surface-treated buffer layer interposed between the transfer layer and the light-to-heat conversion layer; irradiating laser beams on a predetermined region of the donor substrate, the laser beams converted into heat by the light-to-heat conversion layer to transform adhesion properties between the transfer layer and the light-to-heat conversion layer; and transferring the transfer layer to the target substrate.

The surface treatment of the buffer layer may be performed using oxygen ions or radical-based gases.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1A and 1Bare cross-sectional views illustrating a method of a donor substrate for a laser induced thermal imaging (LITI) process according to an exemplary embodiment of the present invention.

Referring toFIG. 1A, a base substrate100is prepared. The base substrate100may be a flexible substrate such as a plastic film, or a hard substrate such as a glass substrate.

A light-to-heat conversion layer120is formed on the base substrate100.

Before the light-to-heat conversion layer120is formed, a primer layer110may be formed on the base substrate100.

The primer layer110may be used to reinforce an adhesion between the base substrate100and the light-to-heat conversion layer120. Also, the primer layer110may be used to treat the surface of the base substrate100and thus, assist in forming the light-to-heat conversion layer120with improved uniformity.

The light-to-heat conversion layer120is formed of a light absorption material that absorbs light in the infrared and visible regions. Also, the light-to-heat conversion layer120may be formed of an organic layer containing a material that absorbs laser beams, a metal layer, or a combination thereof.

The light-to-heat conversion layer120converts laser beams irradiated from a laser irradiating system into thermal energy. Then, the thermal energy transforms adhesion properties between the transfer layer140and the light-to-heat conversion layer120. Thus, a region of the transfer layer140on which the laser beams are irradiated is transferred to a substrate as a subject, so that a patterning process is performed.

A buffer layer130is formed on the light-to-heat conversion layer120. The buffer layer130prevents a transfer material from being damaged and effectively controls an adhesion between the transfer layer140and the donor substrate.

The buffer layer130may be formed of an organic or inorganic material, which is a polymer, a metal, or metal oxide.

The surface of the buffer layer130is treated to increase its surface roughness. In this case, the surface treatment of the buffer layer130may be performed, preferably using oxygen ions or radical-based gases200.

FIG. 2Ais a photograph of the surface after forming a buffer layer, andFIG. 2Bis a photograph of the surface after surface-treating the buffer layer.

In comparison withFIG. 2A,FIG. 2Billustrates that after the buffer layer is surface-treated, the surface roughness of the buffer layer increases.

Accordingly, by treating the surface of the buffer layer130interposed between the transfer layer140and the light-to-heat conversion layer120, adhesion properties between the donor substrate and the transfer layer140are enhanced.

Referring toFIG. 1B, the transfer layer140is formed on the surface-treated buffer layer130.

The transfer layer140of the donor substrate may be an emission layer (EML) of the organic light emitting device.

In addition, the transfer layer140of the donor substrate may further include at least one selected from the group consisting of a hole injection layer, a hole transport layer, a hole blocking layer, and an electron injection layer.

FIG. 3is a cross-sectional view illustrating a process of performing an LITI method on a unit pixel of an organic light emitting display (OLED) using the above-described donor substrate.

Referring toFIG. 3, a donor substrate150, which is fabricated by the above-described method according to the present invention, is disposed over a substrate210on which a thin-film transistor (TFT) and a pixel electrode290are formed.

Specifically, the TFT including a semiconductor layer230, a gate electrode250, a source electrode270a, and a drain electrode270bis disposed on the substrate210, and the pixel electrode290is connected to one of the source and drain electrodes270aand270bof the TFT and exposed by a pixel defining layer295.

Once an LITI process600is performed on the donor substrate150, a transfer layer140ais transferred to the exposed portion of the pixel electrode290so that an EML is patterned.

After the patterning process is finished, an opposite electrode is formed, thereby completing the OLED.

In the exemplary embodiments of the present invention as described above, a donor substrate is fabricated by interposing a surface-treated buffer layer between a transfer layer and a light-to-heat conversion layer, so that adhesion properties between the transfer layer and the light-to-heat conversion layer can be enhanced.

Further, by using the above-described donor substrate, a patterning process can be performed better during the fabrication of the OLED.

Although the present invention has been described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that a variety of modifications and variations may be made to the present invention without departing from the spirit or scope of the present invention defined in the appended claims, and their equivalents.