Display device and manufacturing method for the same

An embodiment relates to a display device and a manufacturing method of the display device. The display device includes a flexible substrate including a display region and a non-display region outside the display region, and a flexible substrate disposed on the flexible substrate of the display region, wherein a groove is provided on a back surface of the flexible substrate.

CROSS-REFERENCE TO RELATED APPLICATION

Korean patent application 10-2018-0028140 filed on Mar. 9, 2018 in the Korean Intellectual Property Office, and entitled: “Display Device and Manufacturing Method for the Same,” is incorporated by reference herein in its entirety.

BACKGROUND

Embodiments relate to a display device and a manufacturing method of the display device, and more particularly, to a display device having flexibility and a manufacturing method of the display device.

2. Description of the Related Art

In recent years, flat panel display devices have been actively researched and developed. Since the flat panel display devices are thinner and lighter, their use range is expanding. In addition, since the flat panel display devices have recently become flexible, the flat panel display devices are easier to carry and the application targets are also increasing.

SUMMARY

Embodiments are directed to a display device including a flexible substrate including a display region and a non-display region, the non-display region being outside the display region, and a display unit on the flexible substrate of the display region. A groove is provided on a back surface of the flexible substrate.

The flexible substrate may be made of an organic material.

The flexible substrate may include at least one organic layer and at least one inorganic layer.

The display unit may includes a plurality of scan lines arranged in a first direction, a plurality of data lines arranged in a second direction intersecting the first direction, and a plurality of pixels connected to the plurality of scan lines and the plurality of data lines. Each of the plurality of pixels may include a light emitting element and a thin film transistor connected to the light emitting element.

An inner surface of the groove may be in a carbonized state produced by irradiating a laser beam onto the inner surface.

A depth of the groove may be 3% to 10% of a thickness of the flexible substrate.

The display device may further include a protecting film attached to the back surface of the flexible substrate. The protecting film may include an opening that exposes the groove.

Embodiments are also directed to a manufacturing method of a display device, the method including providing a first substrate, forming a second substrate including a display region and a non-display region on the first substrate, the non-display region being formed to be outside the display region, forming a display unit on the second substrate in the display region, forming a carbonized mark by irradiating a laser beam to a predetermined region of a back surface of the second substrate, separating the first substrate from the second substrate, attaching a protecting film to the back surface of the second substrate, and cutting the protecting film corresponding to both side portions of the carbonized mark. In cutting the protecting film, a cut portion of the protecting film is detached with the carbonized mark to form a groove on the back surface of the second substrate, and an opening is formed in the protecting film to expose the groove.

The first substrate may be a glass substrate.

The second substrate may be formed of an organic material.

The second substrate may be formed by laminating at least one organic layer and at least one inorganic layer.

Separating the first substrate may include irradiating the laser beam onto the back surface of the second substrate through the first substrate.

Forming the carbonized mark on the back surface of the second substrate may be performed after separating the first substrate.

The protecting film may include an adhesive layer adhered to the second substrate. The method further may include detaching and removing a portion of the adhesive layer corresponding to the groove with the carbonized mark.

The laser beam may have a wavelength of 300 nm to 400 nm

DETAILED DESCRIPTION

FIG. 1illustrates a schematic plan view of a display device according to an embodiment, andFIG. 2illustrates a cross-sectional view of the display device according to the embodiment, taken along the line X1-X2ofFIG. 1.

Referring toFIGS. 1 and 2, the display device may include a flexible substrate200, a display unit300disposed on the flexible substrate200and displaying images, and a protecting film500disposed on a back surface of the flexible substrate200, stacked in a first direction D1.

The flexible substrate200may include a display region240and a non-display region260outside the display region240. The non-display region260may surround the display region240along a second direction D2and a third direction D3.

The flexible substrate200may be made of an organic material, or may be composed of multiple layers including at least one organic layer and at least one inorganic layer. As an example, the flexible substrate200may have a structure in which a first organic layer210, an inorganic layer220, and a second organic layer230are sequentially stacked.

The display unit300may be disposed on the flexible substrate200in the display region240. The display unit300may include a plurality of scan lines310arranged in a first direction, a plurality of data lines320arranged in a second direction intersecting the first direction, and a plurality of pixels330connected to the plurality of scan lines310and the plurality of data lines320.

A scan driver340for supplying scan signals to the plurality of scan lines310and a data driver350for supplying data signals to the plurality of data lines320may be disposed on the flexible substrate200in the non-display region260.

The scan driver340and the data driver350may be manufactured together on the flexible substrate200in the process of forming the display unit300or may be manufactured in the form of an integrated circuit (IC) chip and then mounted on the flexible substrate200.

A pad unit360may be disposed on one side of the non-display region260to receive signals from outside. The pad unit360may be electrically connected to the scan driver340and the data driver350through wirings362.

The display device according to the embodiment may include a control unit. The control unit may receive image signals from the outside, generate data signals, and provide the generated data signals to the data driver350. The control unit may receive synchronous signals and clock signals from the outside, generate control signals, and provide the control signals to the scan driver340and the data driver350.

FIG. 3illustrates a cross-sectional view for explaining one of the pixels330shown inFIG. 1.

Referring toFIG. 3, each of the plurality of pixels330may include a light emitting element280and a pixel circuit for driving the light emitting element280. The pixel circuit may include a thin film transistor270for transmitting signals to the light emitting element280and a capacitor for maintaining the signals.

A current flowing through the light emitting element280may be controlled according to a data signal provided through the data line320, such that each pixel330may emit light of a predetermined luminance corresponding to the data signal.

The light emitting element280may include, for example, an organic light emitting diode (OLED).

The light emitting element280may include a first electrode281, a second electrode284, and an organic thin film layer283interposed between the first electrode281and the second electrode284.

The thin film transistor270may be disposed on the flexible substrate200in the display region240. The thin film transistor270may include a semiconductor layer272providing source and drain regions and a channel region, a gate electrode274disposed on the semiconductor layer272in the channel region, and source and drain electrodes276electrically connected to the semiconductor layer272in the source and drain regions.

The display unit300configured as described above may be sealed with a sealing film370.

The display device according to the embodiment may include a groove200bthat extends along the back surface of the flexible substrate200in the third direction D3. For example, the grooves200bmay be between the display region240and the data driver350. The protecting film500may be attached to the back surface of the flexible substrate200including the groove200b.

The protecting film500may include a base film510and an adhesive layer520. The base film510may be attached to the flexible substrate200by the adhesive layer520. An opening500amay be formed in the protecting film500such that the groove200bis exposed.

A predetermined carbonized mark200amay remain on an inner surface of the groove200bwith an irregular surface due to carbonization. A depth of the groove200bmay be, for example, about 3% to 10% of a total thickness of the flexible substrate200in the first direction D1.

Embodiments will now be described in detail with reference to a manufacturing method of the display device according to the embodiments.

FIGS. 4A to 4Fillustrate cross-sectional views of stages of a manufacturing method of the display device according to the embodiment.FIGS. 4A to 4Fillustrate cross-sections taken along the line X1-X2inFIG. 1.

Referring toFIG. 4A, a first substrate100may be provided as a supporting substrate. The first substrate100may be a transparent substrate having thermal resistance, and may be, for example, a glass substrate.

The second substrate200may be formed on the first substrate100.

The second substrate200may be a substrate of the display device. The second substrate200may include the display region240and the non-display region260outside the display region240.

The second substrate200may be formed by depositing or coating the organic material on the first substrate100, or may be formed into a multilayer structure by alternately depositing or coating at least one organic layer and at least one inorganic layer. As an example, the second substrate200may be formed by sequentially forming the first organic layer210, the inorganic layer220, and the second organic layer230on the first substrate100.

The inorganic layer220may be a barrier layer that blocks the penetration of foreign substances, moisture or outside air from the bottom. The inorganic layer220may include one or more materials selected from silicon nitride, aluminum nitride, zirconium nitride, titanium nitride, hafnium nitride, tantalum nitride, silicon oxide, aluminum oxide, titanium oxide, tin oxide, cerium oxide and silicon oxynitride (SiON).

The second organic layer230may be formed of the same material as the first organic layer210or one of the organic materials described above.

Referring toFIG. 4B, the display unit300may be formed on the second substrate200in the display region240. The sealing film370may be formed on the second substrate200including the display unit300.

The display unit300may include the plurality of scan lines310arranged in the first direction, the plurality of data lines320arranged in the second direction intersecting the first direction, and the plurality of pixels330connected to the plurality of scan lines310and the plurality of data lines320.

Each of the plurality of pixels330may include the light emitting element280and the pixel circuit for driving the light emitting element280. The pixel circuit may include the thin film transistor270to transmit signals to the light emitting element280and the capacitor for maintaining the signals.

As an example, the pixels330may be manufactured as follows.

Referring toFIG. 3, a buffer layer271may be formed on the flexible substrate200.

The buffer layer271may prevent penetration of foreign substances, moisture, or outside air from the bottom, and may planarize the surface of the second substrate200. The buffer layer271may be formed of silicon oxide, silicon nitride, silicon oxynitride, or the like.

The semiconductor layer272may be formed on the buffer layer271to provide the source and drain regions and the channel region.

The semiconductor layer272may be formed of amorphous silicon, polysilicon, oxide semiconductor, or the like.

The gate electrode274is formed on the semiconductor layer272in the channel region to be insulated from the semiconductor layer272by a gate insulating layer273.

The plurality of scan lines310, the wirings362, and the pad unit360may be formed in the process of forming the gate electrode274.

An interlayer insulating layer275may be formed on the gate insulating layer273including the gate electrode274. A contact hole may be formed in the interlayer insulating layer275and the gate insulating layer273such that the semiconductor layer272in the source and drain regions is exposed. The source and drain electrodes276may be formed on the interlayer insulating layer275to be connected to the semiconductor layer272in the source and drain regions through the contact hole.

The plurality of data lines320, the wirings362, and the pad unit360may be formed in the process of forming the source and drain electrodes276.

A planarization layer277may be formed on an upper portion including the thin film transistor270configured as described above.

A via hole may be formed in the planarization layer277so as to expose the source or drain electrode276. The first electrode281may be formed on the planarization layer277, for example, as an anode electrode to be connected to the source or drain electrode276through the via hole.

The first electrode281may include a reflective film formed of Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr or a compound thereof and a transparent or translucent conductive film formed on the reflective film. The transparent or semitransparent conductive film may be selected from indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium oxide (In2O3), indium gallium oxide (IGO), and aluminum zinc oxide (AZO).

A pixel defining film282may be formed on the planarization layer277including the first electrode281. The pixel defining film282may be patterned to expose the first electrode281of a light emitting region to form an opening. The organic thin film layer283may be formed on the first electrode281in the opening.

The organic thin film layer283may include a hole injection layer, a hole transport layer, an organic light emitting layer, an electron transport layer, and an electron injection layer. The organic thin film layer may further include an auxiliary layer or an intermediate layer.

The second electrode284may be formed on the pixel defining film282including the organic thin film layer283, for example, as a cathode electrode.

The second electrode284may be a transparent or semitransparent electrode and may be formed of a metal having a low work function including Li, Ca, LiF/Ca, LiF/Al, Al, Ag, Mg, and a compound thereof.

The sealing film370may be formed on a protecting film after forming the protecting film such that the light emitting element280constructed as described above may be protected from the outside air.

The sealing film370may have a laminated structure of organic layers and inorganic layers. The organic layers and the inorganic layers may be alternately laminated. An uppermost layer may be formed of an inorganic layer to prevent penetration of moisture or outside air. The inorganic layer may be formed so as to cover an outer surface of the organic layer.

Referring toFIG. 4C, a laser beam L may be irradiated to a predetermined region on the back surface of the second substrate200. A carbonized mark200amay be formed by carbonizing a predetermined thickness of the second substrate200using the laser beam L.

The region irradiated with the laser beam L may be a region where the display device is bent. A size and a shape of the region may be variously changed as desired.

In some implementations, the region irradiated with the laser beam L may correspond to the non-display region260as shown inFIG. 4C. In some implementations, the region irradiated with the laser beam L may correspond to the display region240.

The laser beam L may be an excimer laser, a solid state laser, or the like.

The laser beam L may be selected according to the material of the second substrate200. For example, when the second substrate200includes polyimide (PI), the laser beam L having a wavelength of about 300 nm to 400 nm may be used such that energy of the laser beam L may be absorbed.

When the laser beam L having an energy of 190 mJ (megajoule) to 200 mJ is irradiated once, the carbonized mark200ahaving a thickness of 0.3 μm to 0.4 μm may be formed. For example, the laser beam L may be irradiated 10 to 15 times to form the carbonized mark200ato have a thickness of 3 μm to 5 μm.

The energy of the laser beam L and the number of times of irradiation may be varied as desired.

As an example, the carbonized mark200amay be formed by the above-described manner to correspond to about 3% to 10% of the entire thickness of the second substrate200.

Referring toFIG. 4D, the first substrate100may be separated from the second substrate200.

The first substrate100may be separated from the second substrate200by irradiating a laser beam onto the back surface of the second substrate200through the first substrate100.

Although the carbonized mark may be formed on the back surface of the second substrate200by the irradiation of the laser beam, the carbonized mark being formed at this time may be insignificant. In some implementations, the energy of the laser beam or the number of times of irradiation may be controlled such that the carbonized mark is not formed on the back surface of the second substrate200or a state of the back surface of the second substrate200may not be affected.

In the above embodiment, after the carbonized mark200ais formed on the back surface of the second substrate200as shown inFIG. 4C, the first substrate100is separated from the second substrate200as shown inFIG. 4D.

As another embodiment, the carbonized mark200amay be formed on the back surface of the second substrate200after the first substrate100is separated from the second substrate200.

Referring toFIG. 4E, the protecting film500may be attached to the exposed back surface of the second substrate200. The protecting film500may include the base film510and the adhesive layer520. The base film510may be attached to the second substrate200by the adhesive layer520. The protecting film500may protect the exposed back surface of the second substrate200and may support the second substrate200during bending.

Referring toFIG. 4F, the protecting film500may be cut at locations corresponding to both sides of the carbonized mark200a.

The laser beam L may be irradiated to locations of the protecting film500corresponding to both sides of the carbonized mark200a. When the protecting film500is cut as described above, a cut portion of the protecting film500may be detached along with the carbonized mark200asuch that the groove200bmay be formed on the back surface of the second substrate200. The opening500amay be formed in the protecting film500such that the groove200bis exposed.

The carbonized mark200amay be formed by burning the second substrate200by the laser beam L. The carbonized mark200amay include powder generated by carbonization. When the protecting film500is cut, most of the carbonized mark200amay be separated from the second substrate200such that the base film510may be easily removed with the adhesive layer520.

A predetermined portion of the carbonized mark200amay remain on the inner surface of the groove200bwith the irregular surface due to carbonization.

In order to easily bend or fold the display device, the portion of the protecting film500corresponding to a bending region may be cut to form the opening500a. In order to form the opening500a, a process of cutting the protecting film500and a process of removing the adhesive layer520exposed through the opening500amay be performed.

According to an embodiment, the process of forming the opening500amay be simplified by forming the carbonized mark200aon the back surface of the second substrate200. The thickness of the second substrate200in the bending region may be reduced by forming the groove200bon the back surface of the second substrate200corresponding to the opening500a.

The depth of the groove200bmay be, for example, about 3% to about 10% of the total thickness of the flexible substrate200. When the depth of the groove200bis more than 3% of the total thickness of the flexible substrate200, it may be less difficult to effectively reduce a radius of curvature. When the depth of the groove200bis 10% or less of the total thickness of the flexible substrate200, defects due to cracks or delamination in the elements formed on the flexible substrate200or the wires during bending, or breaking of the flexible substrate200may be avoided.

FIG. 5illustrates a cross-sectional view showing a bending state of the display device according to an embodiment.

The display device according to the embodiment may be easily bent due to the presence of the groove200band the opening500a.

The size (width) of the groove200bmay be controlled by the width of the laser beam L. The non-display region260may not be increased in order to secure the bending region.

The radius of curvature may be reduced by reducing the thickness of the second substrate200in the bending region by the formation of the groove200b. The stress in portions A, B, and C where the stress is concentrated in the bending region may be reduced.

In addition, when bending is facilitated, the second substrate200may be easily bent and accommodated in a narrow space of a case, thereby effectively reducing the size of the display device.

By way of summation and review, flat panel display devices having flexibility are bendable or foldable, which is advantageous in reducing a size of the display devices and improving visibility at various angles. However, since the thickness of the display devices is small, defects may easily occur in a manufacturing process, a high manufacturing cost is required, and a lifetime of the display devices may be reduced due to stress caused by bending.

According to embodiments, a carbonized mark may be formed in the bending region of the substrate. When a opening is formed in the protecting film, the protecting film in the opening may be easily removed to form a groove due to the presence of the carbonized mark. The thickness of the substrate in the bending region may be reduced by forming the groove in the back surface of the substrate.

The process of forming the opening in the protecting film may be simpler than a general process. The production time and cost may be reduced, and the thickness of the substrate in the bending region may be reduced, such that the radius of curvature may be reduced and the stress due to bending may be reduced.

Further, the widths of the groove and the opening may be controlled by controlling the width of the laser beam. The increase of the non-display region caused by securing the bending region may be prevented. The substrate may be easily bent, and the size of the display device may be effectively reduced.