Method for manufacturing flexible flat device

This application claims the benefit of the Korean Patent Application No. 10-2010-0111906 filed on Nov. 11, 2010, which is hereby incorporated by reference.

The present invention relates to a method for manufacturing a flexible flat device, and more particularly, to a method for manufacturing a flexible flat device, in which various processes are carried out under the circumstance that a flexible substrate is adhered onto a glass substrate, and the glass substrate is separated from the flexible substrate after completion of the various processes.

A paper-like flexible device such as a flexible display device is capable of being bent or rolled so that it allows good portability and easy keeping. In this respect, the flexible device has been actively studied and developed as a next-generation device.

The flexible device is manufactured by forming several elements on a flexible substrate. For this, the flexible device, including the flexible substrate, is repetitively loaded into and unloaded from various apparatuses. The flexible properties of the flexible substrate, however, make it difficult to transfer the device during the manufacturing process.

The flexible properties of the flexible substrate, however, make it difficult to transfer the flexible substrate by the use of general transfer. Thus, for convenience of conveyance, the flexible substrate is transferred while being adhered onto a rigid glass substrate, and the various processes are applied to the flexible substrate adhered onto the rigid glass substrate. After completion of the various processes, the glass substrate is separated from the flexible substrate, thereby completing a flexible flat device.

Specifically, some efforts have been made to transfer and form elements, such as organic light-emitting device (OLED), on the flexible substrate while the flexible substrate is adhered to a rigid glass substrate via an adhesive layer made of hydrogenated amorphous silicon (a-Si:H).

To this date, however, this procedure for transferring and forming elements on the flexible substrate requires an additional plasma-enhanced chemical vapor deposition (PECVD) for formation of the adhesive layer made of the hydrogenated amorphous silicon (a-Si:H), and further requires an additional laser irradiation process for removing the adhesive strength of the adhesive layer.

Accordingly, more efficient procedure for transferring and forming elements on the flexible substrate would be beneficial in manufacturing process of a flexible device.

Accordingly, the present invention is directed to a method for manufacturing a flexible flat device that substantially obviates one or more problems due to limitations and disadvantages of the related art.

One aspect of the present invention is to provide a method for manufacturing a flexible device, which facilitates to enhance the efficiency of the manufacturing process.

Additional advantages and features of the invention is set forth in part in the description which follows and in part is apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out below and by claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, there is provided a method for manufacturing a flexible device comprising: forming an adhesive layer on a support substrate; adhering a flexible substrate onto the adhesive layer; forming a device layer on the flexible substrate; and separating the support substrate from the flexible substrate, wherein the adhesive layer comprises a self-assembled monolayer (SAM).

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

FIGS. 1A to 1D illustrate a method for manufacturing a flexible device according to one embodiment of the present invention.

FIGS. 2A to 2E illustrate a method for manufacturing a flexible device according to another embodiment of the present invention.

Reference will now be made in detail to some embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

Hereinafter, a flexible flat device according to the present invention will be described with reference to the accompanying drawings.

The following embodiments and Examples have been included to provide guidance to one of ordinary skill in the art for practicing representative embodiments of the presently disclosed subject matter. In light of the present disclosure and the general level of skill in the art, those of skill can appreciate that the following Examples are intended to be exemplary only and that numerous changes, modifications, and/or alterations can be employed without departing from the scope of the presently disclosed subject matter.

FIGS. 1A to 1D illustrate a method for manufacturing a flexible device according to one embodiment of the present invention.

First, as shown in FIG. 1A , an adhesive layer 200 is formed on a support substrate 100 .

According to some embodiments of the present invention, the support substrate includes any substrate that is rigid enough to provide mechanical support to another layer placed on it. In further embodiments, the support substrate may be a transparent substrate, including, but not limited to, a glass substrate.

The adhesive layer 200 functions as an adhesive between the support substrate 100 and a flexible substrate described herein. In some embodiments, the adhesive layer 200 is formed of a material which has a good heat resistance to endure a high-temperature manufacturing process. In additional embodiments, the adhesive layer also has such adhesive strength to allow a good adhesion between the support substrate 100 and the flexible substrate during the manufacturing process, and/or to allow an easy separation of the support substrate 100 from the flexible substrate without carrying out an additional process after the manufacturing process.

The present invention relates to an adhesive layer with the above properties comprising a self-assembled monolayer (SAM).

As used herein, a SAM refers to a thin monolayer that is spontaneously coated onto a surface of a given substrate and is regularly aligned thereon. In detail, self-assembly refers to a phenomenon in which sub-unit molecules are spontaneously assembled due to interactions between the molecules to form a predetermined structure through a spontaneous reaction. A molecule used in forming a sub-unit of a SAM is formed of three portions. That is, the molecule includes a reaction group as a head portion that is coupled to a substrate, an alkane chain as a body portion that allows regular formation of a monolayer, and a functional group as a tail portion that determines a particular function of the monolayer.

Accordingly, the SAM in some embodiments of the present invention is an organized monolayer of molecules showing an affinity for a specific substrate material. In additional embodiments, the SAM is made of a material that allows both the heat resistance and adhesive strength.

For example, the SAM may comprise a silane-based compound, including, but not limited to a thiol containing silane-based compound, amine containing silane-based compound, and a mixture thereof.

The thiol containing silane-based compound includes, but is not limited to, the following chemical formulas 1 to 6 or the sale thereof

‘R 1 ’ to ‘R 3 ’ are independently alkyl, functionalized alkyl, aryl, or alkoxy, including, but not limited to, CH 3 or (CH 2 ) n CH 3 ; and ‘m’ and ‘n’ are independently an integer of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more. The benzene groups shown in the chemical formula herein may substituted and also may be replaced with other substituted or non-substituted aromatic group.

The amine containing silane-based compound includes, but not limited to, the following chemical formulas 7 to 12 or the salt thereof

‘R 1 ’ to ‘R 3 ’ are independently alkyl, functionalized alkyl, aryl, or alkoxy, including, but not limited to, CH 3 or (CH 2 ) n CH 3 ; and ‘m’ and ‘n’ are independently an integer of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more. The benzene groups shown in the chemical formula herein may substituted and also may be replaced with other substituted or non-substituted aromatic group.

The SAM may be formed by a simple process, including, but not limited to, spin coating, dip coating, or spray coating method.

As shown in FIG. 1B , the flexible substrate 300 is adhered onto the adhesive layer 200 .

The flexible substrate 300 may be made of common substrate materials, including, but not limited to polyethylene terphthalate, polyacrylate, polyesthersulphone, polyethylene naphthalate, polyimide, and the mixture thereof, where the polyimide is preferred in combination with the compounds disclosed herein. For example, the flexible substrate 300 may be made of various materials for polymer film which are generally known to those skilled in the art.

The above adhering process of the flexible substrate 300 onto the adhesive layer 200 may comprise positioning the polymer film, e.g. polyimide film, onto the adhesive layer 200 , and optionally heating the polymer film positioned onto the adhesive layer 200 inside a high-temperature furnace.

As shown in FIG. 1C , a device layer 400 is formed on the flexible substrate 300 .

The device layer 400 may correspond to various types of display device to which the flexible device according to the present invention is capable of being applied.

In some embodiments, the device layer comprises various display devices, including, but not limited to, flat display devices, such as organic light-emitting device (OLED), and liquid crystal display (LCD).

When the device layer comprises the OLED, in additional embodiments of the present invention, the OLED may comprise a thin film transistor, an anode, a light-emitting layer, a cathode, and a sealing layer. In further embodiments, the light-emitting layer may comprise a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer.

When the device layer comprises the LCD, in yet additional embodiments of the present invention, the LCD may comprise a thin film transistor, a pixel electrode, and a common electrode; and/or the LCD may comprise a light-shielding layer and a color filter layer.

The OLED or LCD described herein may be formed in various structures by various methods generally known to those skilled in the art.

As shown in FIG. 1D , the support substrate 100 is separated from the flexible substrate 300 , to thereby form a flexible device 1 with the device layer 400 on the flexible substrate 300 . The adhesive layer may remain on the flexible substrate and/or on the support layer. In some embodiments, the support substrate can be cleaned and reused. The use of the adhesive layer according to further embodiments of the present invention permits the support substrate to be reclaimed or recycled for repeated use without the use of solvent.

The above process for separating the support substrate 100 from the flexible substrate 300 may be carried out in a mechanical method using a jig without an additional preliminary chemical reaction through laser irradiation.

In case of the method according to one embodiment of the present invention, the laser irradiation process for separation of the support substrate 100 is not carried out, and thus there is no potential adverse effect on the device layer 400 due to the irradiation.

FIGS. 2A to 2E illustrate a method for manufacturing a flexible device according to another embodiment of the present invention. In this embodiment, an additional process of UV irradiation is carried out for separation of a support substrate 100 from a flexible substrate 300 . Hereinafter, the method for manufacturing the flexible device according to another embodiment of the present invention will be described with reference to FIGS. 2A to 2E .

First, as shown in FIG. 2A , an adhesive layer 200 is formed on a support substrate 100 .

The support substrate 100 may be formed of a glass substrate, and the adhesive layer 200 may be formed of a self-assembled monolayer (SAM).

In some embodiments, the adhesive layer 200 comprises a silane-based compound as described herein.

As shown in FIG. 2B , a flexible substrate 300 is adhered onto the adhesive layer 200 .

In some embodiments, the flexible substrate 300 comprises polyimide. The above adhering process of the flexible substrate 300 onto the adhesive layer 200 may comprise positioning the polymer film such as polyimide onto the adhesive layer 200 , and optionally heating the polymer film positioned onto the adhesive layer 200 .

As shown in FIG. 2C , a device layer 400 is formed on the flexible substrate 300 .

The device layer 400 may be formed of various display devices as described herein.

As shown in FIG. 2D , the lower surface of the support substrate 100 is irradiated with UV rays. This UV-ray irradiation enables a relatively-easy separation process between the flexible substrate 300 and the support substrate 100 .

In some embodiments, instead of the UV-ray irradiation, it is possible to irradiate laser. In this case, it is preferable to use laser with a wavelength of about 500 nm or less. In further embodiments, 248 or 308 excimer laser may be used. As used herein, the term “about” refers to a range of values ±10% of a specified value. For example, the phrase “about 500 nm” includes ±10% of 500 nm, or from 450 nm to 550 nm.

As shown in FIG. 2E , the support substrate 100 is separated from the flexible substrate 300 , to thereby complete a flexible device 1 with the device layer 400 on the flexible substrate 300 . As described previously, the adhesive layer may remain on the flexible substrate and/or on the support layer.

The above process for separating the support substrate 100 from the flexible substrate 300 may be carried out in a mechanical method using a jig.

As described herein, in comparison to the existing method for manufacturing the flexible device requiring the plasma-enhanced chemical vapor deposition (PECVD) method for creating an adhesive layer, the method for manufacturing the flexible device according to the present invention is simplified by the use of SAM.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.