Flexible display device

A flexible display device according to an example embodiment includes: a substrate; a driver integrated circuit (IC) in a non-display portion of the substrate and configured to supply a driving voltage to a display portion of the substrate; a flexible printed circuit board attached to the non-display portion at an outer side of the driver IC; and a printed circuit board attached to the flexible printed circuit board and configured to transfer the driving voltage to the driver IC, wherein the driver IC comprises a base layer, a plurality of bumps at a bottom surface of the base layer, a first layer at an upper surface of the base layer, and second layers at the first layer to correspond to locations of the plurality of bumps.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2015-0054043 filed in the Korean Intellectual Property Office on Apr. 16, 2015, the entire content of which is incorporated herein by reference.

BACKGROUND

Aspects of embodiments of the present invention relate to a flexible display device.

2. Description of the Related Art

Related art flexible display devices may be manufactured using a flexible plastic substrate such as a low temperature poly-silicon (LIPS), polyimide, and the like. A pixel array is formed on the flexible substrate, and the pixel array includes data lines and gate lines formed to cross each other, a thin film transistor (TFT), and a pixel electrode.

A driver IC is formed at an outer side of the flexible substrate to supply a driving signal and a voltage to the pixel array. In this case, the driver IC is formed of a gate driver IC and a data driver IC, and is formed using a chip on glass (COG) method, a chip on plastic (COP) method, or a chip on film (COF) method.

In addition, a printed circuit board (PCB) including a driver circuit other than the driver IC is connected to the flexible substrate using a flexible printed circuit board (FPCB). The driver IC is connected to a pad formed in the flexible substrate through a plurality of bumps, and supplies a driving voltage VCC, a ground voltage GND, a data output signal, and an enable signal to the pixel array of the flexible substrate.

The driver IC is attached to an outer portion of the substrate by thermal compression, and a compression tool applies a predetermined temperature and pressure to the driver IC such that the driver IC is compressed.

The thermal compression is applicable to a rigid driver IC, but a problem may occur when the thermal compression is applied to a flexible driver IC of a flexible display device. Thus, a shock absorbing member may be provided between the compression toll and the driver IC, and when the compression tool presses the driver IC, the shock absorbing member may press a center portion of the driver IC, and thus the driver IC may subside in a portion where no bumps are provided such that subsidence damage and cracks may occur in the driver IC around the bumps.

The above information disclosed in this Background section is only to enhance the understanding of the background of the invention, and therefore it may contain information that does not constitute prior art.

SUMMARY

Aspects of embodiments of the present invention relate to a flexible display device, and a flexible display device including a driver integrated circuit (IC) formed at an outer side of a flexible substrate.

According to aspects of embodiments of the present invention, a flexible display device includes a plastic layer of a driver IC that is formed as a double layer and protruding layers are formed corresponding to locations where bumps are formed, thereby preventing or reducing defects such as subsidence damage, cracks, and the like of the driver IC due to the presence of a shock absorbing member during thermal compression.

A flexible display device according to some example embodiments includes: a substrate; a driver integrated circuit (IC) in a non-display portion of the substrate and configured to supply a driving voltage to a display portion of the substrate; a flexible printed circuit board attached to the non-display portion at an outer side of the driver IC; and a printed circuit board attached to the flexible printed circuit board and configured to transfer the driving voltage to the driver IC, wherein the driver IC comprises a base layer, a plurality of bumps at a bottom surface of the base layer, a first layer at an upper surface of the base layer, and second layers at the first layer to correspond to locations of the plurality of bumps.

The plurality of bumps at the bottom surface of the base layer may be electrically connected to a substrate pad portion on the substrate.

The base layer may be attached to the substrate by an anisotropic conductive film.

The plurality of bumps may be distributed across the bottom surface of the base layer, and the second layers may be in a shape of a closed loop on the first layer to correspond to locations of the bumps.

The plurality of bumps may be distributed across the bottom surface of the base layer, and the second layers may be in a shape of an island on the first layer to correspond to locations of the bumps.

The base layer may include silicon.

The first layer and the second layers may include polyimide (PI) or polyethylene terephthalate (PET).

The plurality of bumps may include at least one of one of gold (Au), silver (Ag), or copper (Cu).

The first layer and the second layers may be integrally formed on the base layer in a shape of protrusions in locations that correspond to locations of the plurality of bumps.

The first layer and the second layers may be integrally formed on the base layer corresponding only to locations of the plurality of bumps.

A display element layer including an organic light emitting element and a thin film encapsulation layer covering the substrate and the display element layer may be formed at the display portion.

According to some example embodiments, in the flexible display device, the driver IC may be formed as a double layer at an outer side of the substrate of the flexible display device and layers may be formed in the shape of protrusions corresponding to locations where bumps are formed so that instances of subsidence damage and cracks of the driver IC due to the shock absorbing member during a thermal compression process can be prevented or reduced.

DETAILED DESCRIPTION

Further, in example embodiments, because like reference numerals designate like elements having the same configuration, a first example embodiment is representatively described, and in other example embodiments, aspects of configurations that differ from the first example embodiment will be described. That is, some repetitive description of the same or similar features may be omitted for brevity.

It is noted that the drawings are schematic, and not illustrated in accordance with a scale. Relative dimensions and ratios of portions in the drawings are illustrated to be exaggerated or reduced in size for clarity and convenience in the drawings, and any dimensions are just examples and are not limiting. In addition, like structures, elements, or components illustrated in two or more drawings use like reference numerals to show similar features. It will be understood that when an element such as a layer, film, region, or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present.

The example embodiments show example embodiments in some detail. As a result, various modifications to the described embodiments are still within the spirit and scope of the present invention. Therefore, the example embodiments are not limited to a specific aspect of an illustrated region, and for example, include modifications made for manufacturing.

Hereinafter, a flexible display device according to an example embodiment will be described with reference toFIG. 1andFIG. 2.

FIG. 1is a top plan view of a flexible display device according to an example embodiment,FIG. 2Ais a schematic cross-sectional view of a driver IC of the flexible display device according to the example embodiment, andFIG. 2Bis a schematic cross-sectional view of a connection relationship of the driver IC of the flexible display device according to the example embodiment.

Referring toFIG. 1,FIG. 2A, andFIG. 2B, a flexible display device100according to an example embodiment includes a substrate10, a driver IC15provided in a non-display portion NA of the substrate10and supplying a driving voltage to a display portion DA, an FPCB20attached to the non-display portion NA at the outer side of the driver IC15, and a PCB30attached to the PFCB20and transmitting the driving voltage to the driver IC15of the substrate10.

The substrate10may be formed by coating a plastic material such as a low temperature poly silicon (LTPS), polyimide, and the like such that the substrate10has flexibility.

The substrate10may be divided into a display portion (or display area) DA and a non-display portion (or non-display area) NA, and a display element layer including an organic light emitting element and a thin film encapsulation layer covering and protecting the substrate10, and the display element layer may be formed in the display portion DA. The display element layer includes an element region where an active element such as a thin film transistor (TFT) is formed and a light emission region where an emission layer is formed. The element region and the light emission region may be separated from each other or may overlap each other. A pixel array is formed on the display portion DA. The pixel array includes a plurality of data lines and a plurality of gate lines that alternately cross each other, a thin film transistor, and a pixel electrode.

The thin film encapsulation layer is formed on the display element layer, and faces opposite to the substrate10. The thin film encapsulation layer may prevent or reduce instances of oxygen and moisture entering from the outside to protect the display element layer.

The driver IC15is arranged or located in the non-display portion NA. The driving IC15is a part where a circuit chip and the like are installed, and it converts a driving signal input from the PCB30through the FPCB20attached to the non-display portion NA and supplies the converted driving signal to the display portion DA. In the example embodiments, the driver IC15is arranged or located, for example, in the non-display portion NA, but the driver IC15may be installed in the FPCB20.

As shown inFIG. 2A, the driving IC15includes a base layer2, a plurality of bumps8formed in the bottom surface of the base layer2, a first layer4formed on the upper surface of the base layer2, and second layers6formed on the first layer4to correspond to locations where the plurality of bumps8are formed.

The base layer2may be made of silicon, and the first layer4and the second layer6may be made of a flexible and heat-resistive material such as polyimide (PI) or polyethylene terephthalate (PET). In addition, the plurality of bumps8may be made of one of gold (Au), silver (Ag), copper (Cu), and the like.

As shown inFIG. 2B, the plurality of bumps8formed in the bottom surface of the base layer2are electrically connected to a plurality of substrate pad portion9formed on the substrate10.

In order to attach the driving IC15to the substrate10, the driver IC15is pressed using a compression tool50, interposing a shock-absorbing member40therebetween. Pressure of about 30 Mpa to about 150 Mpa is applied to the compression tool50with a temperature of about 200° C. to about 500° C. for thermal compression of the driver IC15to the substrate10. The shock absorbing member40provided between the compression tool50and the driving IC15is made of a material such as sponge, and since the shock absorbing member40is replaceable and can compensate for flatness of the driver IC, the shock absorbing member40may prevent or reduce instances of foreign materials remaining in the driver IC15. The shock absorbing member40is made of any suitable shock absorbing material, such as silicon, Teflon® (e.g., polytetrafluoroethylene), and the like.

The second layers6are formed on the first layer4corresponding to the locations where the plurality of bumps8are formed. That is, the second layers6are formed to protrude on the first layer4, and the shock absorbing member40arranged or positioned on the second layers6is pressed and thus a center portion of the shock absorbing member40is inserted into a space between the first layer4and the second layers6. Accordingly, subsidence of the driver IC due to the pressed shock absorbing member40and instances of subsidence damage and cracks around the bumps8due to the subsidence of the driver IC can be prevented or reduced.

Meanwhile, the second layer2is attached to the substrate10by an anisotropic conductive film (ACF). The anisotropic conductive film fills between the substrate10and the driving IC15and is cured such that the driving IC15can be fixed to the substrate10. The anisotropic conductive layer may include a polymer and conductive particles included in the polymer, and the conductive particles are arranged or positioned between the bumps8and the substrate pad portion9such that the substrate10and the driver IC can be electrically connected with each other.

FIG. 3is a cross-sectional view of a driver IC of a flexible display device according to another example embodiment. As shown inFIG. 3, a driving IC17may be single layers7formed by integrally forming a first layer and second layers on a base layer2, and the integrally formed single layers7may be formed on the base layer2corresponding to locations where a plurality of bumps8are formed.FIG. 4is a schematic cross-sectional view of a driver IC of a flexible display device according to another example embodiment. As shown inFIG. 4, an integrally formed single layer7of a driving IC19may be formed to protrude from the base layer2corresponding to locations where a plurality of bumps8are formed.

FIG. 5Aschematically shows a bottom surface of a driver IC according to an example embodiment, andFIG. 5Bschematically shows a top surface of the driver IC according to the example embodiment.

Referring toFIG. 5AandFIG. 5B, a plurality of bumps8of a driver IC15are linearly arranged in the bottom surface of a base layer2, a first layer4is arranged or formed on the top surface of the base layer2, and second layers6are linearly arranged on the first layer4so as to correspond to locations where the plurality of bumps8are formed. Because the second layers6are formed to protrude from the first layer4, a space where a shock absorbing member40subsides when thermal compression is performed is formed, such that instances of subsidence damage of the driver IC15due to the pressed shock absorbing member40can be prevented or reduced.

FIG. 6Ais a schematic bottom view of a driver IC according to another example embodiment,FIG. 6Bis a schematic top view of a driver IC according to another example embodiment, andFIG. 6Cis a schematic top view of a driver IC according to another example embodiment.

As shown inFIG. 6A, a plurality of bumps8of a driving IC15may be formed everywhere in (e.g., distributed across, for example, in regular or even intervals) the bottom surface of a base layer2. In this case, as shown inFIG. 6B, second layers6may be formed in the shape of a closed loop on a first layer4so as to correspond to locations where the plurality of bumps8are formed. Further, as shown inFIG. 6C, the second layers6may be formed in the shape of an island rather than being formed in the shape of a closed loop on the first layer4.

As described, in the flexible display devices according to the example embodiments, the driver IC is formed as a double layer at an outer side of the substrate of the flexible display device, and layers are formed in the shape of protrusions corresponding to locations where bumps are formed so that instances of subsidence damage and cracks of the driver IC due to the shock absorbing member during a thermal compression process can be prevented or reduced.