Patent Description:
A display device is a device for displaying an image, and typically includes a display panel such as an organic light emitting display panel or a liquid crystal display panel.

Recently, a mobile electronic device may include a display device for providing an image to a user. A mobile electronic device having a larger display screen while having a volume or thickness equal to or smaller than a conventional electronic device may have a relatively great weight, and a foldable display device or a bendable display device, having a structure that can be folded and unfolded to provide a larger screen only at the time of use, has been developed.

Relevant prior art is disclosed in the patent applications <CIT> and <CIT>.

The present invention provides a display device as defined in claim <NUM>, in which stepped visibility in a folding area is reduced, and a corresponding method of manufacturing as defined in claim <NUM>. Various embodiments are defined in the dependent claims.

According to the claimed invention, a display device, in which a folding region, a first non-folding region located at a side of the folding region, and a second non-folding region located at another side of the folding region are defined, includes amongst others: a display module; a support member disposed on the display module; and a bonding layer disposed between the display module and the support member. The support member maybe also termed as a support member assembly. The support member includes a first support member disposed in the first non-folding region and a part of the folding region, and a second support member disposed in the second non-folding region and a part of the folding region, the bonding layer is disposed over the folding region, the first non-folding region, and the second non-folding region, the bonding layer includes a first portion disposed in the first non-folding region, a second portion disposed in the second non-folding region, and a third portion disposed in the folding region, and an adhesive force of the third portion to the support member is less than each of an adhesive force of the first portion to the first support member and an adhesive force of the second portion to the second support member.

In an embodiment, the bonding layer may further include a photoinitiator, and a density of the photoinitiator in the third portion may be less than each of a density of the photoinitiator in the first portion and a density of the photoinitiator in the second portion.

In an embodiment, the photoinitiator may react with light in a wavelength band of about <NUM> nanometers (nm) to about <NUM>.

In the claimed invention, the display module includes a display panel and a buffer member disposed between the display panel and the bonding layer, and the buffer member has a thickness in a range of about <NUM> micrometers (µm) to about <NUM>, and the bonding layer has a thickness in a range of <NUM> to <NUM>.

In an embodiment, the display device may further include a support substrate disposed between the bonding layer and the buffer member, where the support substrate may be disposed over the folding region, the first non-folding region, and the second non-folding region, and the support substrate may be in contact with the bonding layer.

In an embodiment, the support substrate may include polyimide or polyurethane.

In an embodiment, the display device may further include an lower bonding layer disposed between the buffer member and the support substrate, where the buffer member and the support substrate may be coupled with each other through the lower bonding layer.

In an embodiment, each of the first support member and the second support member may be coupled with the display module through the bonding layer.

In an embodiment, the first support member and the second support member may be spaced apart from each other by a predetermined distance in the folding region.

In an embodiment, an adhesive force between the third portion and the support member in the folding region may be less than adhesive force between the third portion and the display module in the folding region.

In an embodiment, when the display device in a folded state, the first support member may be attached to the first portion, may be separated from the third portion, may be attached to the second portion, and may be separated from the third portion.

In an embodiment, a modulus of the third portion may be greater than each of a modulus of the first portion and a modulus of the second portion. When used herein, the term modulus refers to the modulus of elasticity (elastic modulus).

According to the claimed invention, a method of manufacturing a display device, includes amongst others a display panel in which a folding region, a first non-folding region located at a side of the folding region, and a second non-folding region located at another side of the folding region are defined, and providing a buffer member on the target panel; providing a bonding layer on the buffer member; masking a portion of the bonding layer overlapping the first non-folding region and the second non-folding region; and irradiating the folding region with an ultraviolet light.

In an embodiment, the providing the bonding layer on the buffer member may include: providing a bonding layer on a substrate; providing a release film on the bonding layer; and removing the substrate and attaching an exposed surface of the bonding layer to the buffer member.

In an embodiment, the method may further include heating the bonding layer after the providing the bonding layer on the substrate and before the providing the release film on the bonding layer.

In an embodiment, the method may further include forming a first support member on the other surface of the bonding layer in the first non-folding region and forming a second support member on the other surface of the bonding layer in the second non-folding region after the attaching of one surface of the exposed bonding layer onto the buffer member.

In an embodiment, the providing the bonding layer on the buffer member may include: providing a bonding layer on a support substrate; providing a release film on the bonding layer; and attaching the support substrate onto the buffer member through an lower bonding layer.

In an embodiment, the bonding layer may include a photoinitiator.

In an embodiment, a density of the photoinitiator in a portion of the bonding layer overlapping the folding region may be less than a density of the photoinitiator in the portion of the bonding layer overlapping the first non-folding region and the second non-folding region.

In an embodiment, a modulus of the photoinitiator in a portion of the bonding layer overlapping the folding region may be greater than a modulus of the photoinitiator in the portion of the bonding layer overlapping the first non-folding region and the second non-folding region.

The above and other features of the invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings, in which:.

The invention now will be described more fully hereinafter with reference to the accompanying drawings, in which various embodiments are shown. This invention may, however, be embodied in many different forms, and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

It will be understood that when an element is referred to as being related to another element such as being "coupled" or "connected" to another element, it can be directly coupled or connected to the other element or intervening elements may be present therebetween. In contrast, it should be understood that when an element is referred to as being related to another element such as being "directly coupled" or "directly connected" to another element, there are no intervening elements present. Other expressions that explain the relationship between elements, such as "between," "directly between," "adjacent to," or "directly adjacent to," should be construed in the same way.

Throughout the specification, the same reference numerals will refer to the same or like parts.

The exemplary term "lower," can therefore, encompasses both an orientation of "lower" and "upper," depending on the particular orientation of the figure. The exemplary terms "below" or "beneath" can, therefore, encompass both an orientation of above and below.

It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the claims.

<FIG> is a perspective view of a display device according to an embodiment, <FIG> is a cross-sectional view taken along the line II-II' of <FIG>, <FIG> is a partially enlarged view of <FIG>, and <FIG> is a cross-sectional view illustrating the display device in a folded state according to an embodiment.

Referring to <FIG>, an exemplary embodiment of a display device <NUM> may be a flexible (or foldable) display device. As used herein, foldable may refer to a flexible state, and specifically is a term designated by including bendable and rollable. Furthermore, the folding should be interpreted as including both "partially" folding, "entirely" folding, "in" folding, and "out" folding.

The display device <NUM> may include a folding axis AXIS_F that traverses the upper and lower sides of the display device in a plan view in a thickness direction of the display device <NUM>. The display device may be folded based on the folding axis AXIS_F.

The display device <NUM> may have a substantially planar rectangular shape. The display device <NUM> may have a rectangular shape having vertically planar edges or a rectangular shape having rounded edges. The display device <NUM> may include four edges LS1, LS2, SS1, and SS2. The display device <NUM> may include long-side edges LS1 and LS2 and short-side edges SS1 and SS2. In one embodiment, for example, the long-side edges LS1 and LS2 may extend in a first direction DR1, and the short-side edges SS1 and SS2 may extend in a second direction DR2. A third direction DR3 may be a direction perpendicular to the first and second directions DR1 and DR2 or the thickness direction of the display device <NUM>.

In an embodiment, as shown in <FIG>, the folding axis AXIS_F may extend in a direction traversing the long-side edges LS1 and LS2, for example, in the second direction DR2. In such an embodiment, the long-side edges LS1 and LS2 of the display device <NUM> may be folded. In an alternative embodiment, the folding axis AXIS_F may extend to traverse the short-side edges SS1 and SS2. In such an embodiment, the short-side edges SS1 and SS2 of the display device <NUM> may be folded. Hereinafter, for convenience of description, the embodiments where the folding axis AXIS_F extends to traverse the long-side edges LS1 and LS2 will be described in detail. The folding axis AXIS_F may traverse the center portion of each long-side edges LS1, LS2, but the invention is not limited thereto.

As used herein, the terms "upper portion" and "upper surface" in the thickness direction refer to a display direction or the third direction DR3, and "lower portion" and "lower surface" refer to a direction opposite to the display direction, unless otherwise defined. In addition, the terms "upper", "lower", "left", and "right" in a plan view represent directions when viewed from a top plan view or a plan view in the third direction DR3 based on the display surface at a correct position.

The display device <NUM> may include a display area DA and a non-display area NA disposed around the display area DA. The display area DA is an area where an image is displayed, and the non-display area NA is an area where an image is not displayed. The display area DA may be located at a center portion of the display device <NUM>. In a state where the display device <NUM> is folded, regions in the display area DA divided by the folding axis AXIS_F may overlap each other, and in a state where the display device <NUM> is unfolded again, an image may be displayed in a state where the respective regions in the display area DA are unfolded.

A groove (for example, a notch) recessed downward/upward on a plane is formed in a region adjacent to the first long-side edge LS1 and second long-side edge LS2 of the display device <NUM>, each meeting the folding axis AXIS_F, and a hinge member (not illustrated) or the like for state switching may be coupled to the recessed portion. However, the invention is not limited thereto.

Referring to <FIG>, the display device <NUM> is divided into a folding region FR and non-folding regions NFR1 and NFR2 based on the folding axis AXIS_F.

In such an embodiment, the display device <NUM> may include a folding region FR located at a center portion of the display device and including the folding axis AXIS_F, and non-folding regions NFR1 and NFR2 spaced apart from each other with the folding region therebetween. The first non-folding region NFR1 may be disposed at one side of the folding region FR in the first direction DR1, and the second non-folding region NFR2 may be disposed at the other side of the folding region FR in the first direction DR1.

The folding region FR may be a region where the display device <NUM> is folded or bent with a predetermined curvature in the folding direction, and the non-folding regions NFR1 and NFR2 may be regions where the display device <NUM> is not folded. Each of the non-folding regions NFR1 and NFR2 may be a flat region entirely located on a same plane, or may include a partially bent region without limitations.

The display device <NUM> may include a flexible (display) module <NUM>, as shown in <FIG>. The flexible module <NUM> may include a plurality of laminated members. The flexible module <NUM> may include a display panel <NUM>, a lower functional layer <NUM> disposed under the display panel <NUM>, an upper functional layer <NUM> disposed over the display panel <NUM>, and a window <NUM> disposed over the upper functional layer <NUM>.

The lower functional layer <NUM> may be disposed at a bottom portion of the flexible module <NUM>. The lower functional layer <NUM> may include at least one functional layer. Each of the at least one functional layer may be a layer that performs a buffering function, a heat dissipation function, an electromagnetic wave blocking function, a grounding function, a strength enhancing function, a support function, a pressure sensing function, a digitizing function, or the like. The lower functional layer <NUM> may be defined by a single functional layer. However, the invention is not limited thereto, and lower functional layer <NUM> may have a multi-layer structure including or defined by different functional layers laminated one on another.

In the present invention, the lower functional layer <NUM> includes a buffer member. The buffer member prevents the impact from an outside (for example, the downward direction of the lower functional layer <NUM>) from being transmitted to the display panel <NUM>. The buffer member includes or is formed of a foam material, for example, polyurethane ("PU"), thermoplastic polyurethane ("TPU"), silicon (Si), or polydimethylacrylamide ("PDMA").

The lower functional layer <NUM> may have lower light transmittance than a plurality of members disposed over the display panel <NUM> to be described later. The layers disposed over the display panel <NUM> may have relatively high light transmittance to transmit the light emitted from the display area upward. In contrast, the lower functional layer <NUM> may have relatively low light transmittance to block the light from the display area downward.

A thickness t1 of the lower functional layer <NUM> (also referred to as a first thickness t1) is in a range of about <NUM> micrometers (µm) to about <NUM>. When the first thickness t1 of the lower functional layer <NUM> is equal to or greater than about <NUM>, at the time of folding the display device <NUM>, the folding stress occurring in the folding region FR may be alleviated. When the first thickness t1 of the lower functional layer <NUM> is equal to or less than about <NUM>, the display device <NUM> may be allowed to have a thin thickness.

The display panel <NUM> is disposed over the lower functional layer <NUM>.

The display panel <NUM> may display an image by an input data signal. In an exemplary embodiment the display panel <NUM> may be an organic light emitting display panel, a liquid crystal display panel, a plasma display panel, an electrophoretic display panel, an electrowetting display panel, a quantum dot light emitting display panel, or a micro light emitting diode ("LED") display panel, for example. Hereinafter, for convenience of description, embodiments where the display panel <NUM> is an organic light emitting display panel will be described in detail.

In an embodiment, the display panel <NUM> may include a flexible substrate including a flexible polymer material such as polyimide ("PI"). In such an embodiment, the display panel <NUM> may be bent, warped, folded, or rolled. The display panel <NUM> may have a shape similar to the planar shape of the display device <NUM>.

A plurality of pixels PX may be arranged in the display area DA of the display panel <NUM>, and signal lines and drive circuits for applying signals to the respective pixels PX may be arranged in the non-display area NA of the display panel <NUM>. In an embodiment, a black matrix having a shape of a rectangular frame in a plan view may be provided in the non-display area NA.

The pixel PX may include a light emitting layer and a circuit layer for controlling the amount of light emitted from the light emitting layer. The circuit layer may include a plurality lines, a plurality of electrodes, and a transistor. In an embodiment, the light emitting layer may include an organic light emitting material. The light emitting layer may be encapsulated by an encapsulation film. The encapsulation film may encapsulate the light emitting layer to prevent moisture and the like from inflowing from the outside. The encapsulation film may be an inorganic single-layer film or an inorganic multi-layer film, or may be a laminated film in which inorganic films and organic films are alternately laminated.

The upper functional layer <NUM> may be disposed over the display panel <NUM>.

The upper functional layer <NUM> may include at least one functional layer. Each of the at least one functional layer may be a layer that performs a touch sensing function, a color filtering function, a color conversion function, a polarization function, an anti-reflection function or a biometric information recognition function (for example, a fingerprint recognition function). The upper functional layer <NUM> may include, for example, an anti-reflection member. The functional layer may be a sheet layer, a film layer, a thin film layer, a coating layer, a panel, or a plate. The upper functional layer <NUM> may be defined by a single functional layer. However, the invention is not limited thereto, and the upper functional layer <NUM> may have a multi-layer structure including or defined by different functional layers laminated one on another.

The window <NUM> may be disposed over the upper functional layer <NUM>.

The window <NUM> covers and protects the underlying members <NUM>, <NUM>, and <NUM>. The window <NUM> may include or be made of a glass, quartz, or the like. The thickness of the window <NUM> may be less than about <NUM>. When the thickness of the window <NUM> is less than <NUM>, stress is reduced at the time of folding, and degree of deformation of a structure may be mitigated even if a folded state and an unfolded state are repeated. In an alternative embodiment, the window may include a chemically reinforced ultrathin glass ("UTG").

The flexible module <NUM> may include a plurality of adhesive films, e.g., first to third adhesive films <NUM>, <NUM>, and <NUM>, for coupling the display panel <NUM>, the lower functional layer <NUM>, the upper functional layer <NUM> and the window <NUM> to one another. The first adhesive film <NUM> may be disposed between the lower functional layer <NUM> and the display panel <NUM> to attach the lower functional layer <NUM> and the display panel <NUM> to each other, the second adhesive film <NUM> may disposed between the display panel <NUM> and the upper functional layer <NUM> to attach the display panel <NUM> and the upper functional layer <NUM> to each other, and the third adhesive film <NUM> may be disposed between the upper functional layer <NUM> and the window <NUM> to attach the upper functional layer <NUM> and the window <NUM> to each other.

Each of the plurality of adhesive films <NUM>, <NUM>, <NUM> is a film having adhesive properties on both upper and lower surfaces thereof, and may be, for example, a pressure sensitive adhesive ("PSA") film, an optical clear adhesive ("OCA") film, or an optical clear resin ("OCR") film. Each of the plurality of adhesive films <NUM>, <NUM>, <NUM> may include an acrylic resin or a silicon-based resin. In an embodiment, each of the plurality of adhesive films <NUM>, <NUM>, <NUM> may have an elongation rate in a range of about <NUM>% to about <NUM>,<NUM>%.

The display device <NUM> includes support members <NUM> and <NUM> and a bonding layer <NUM>.

In an embodiment, the support members <NUM> and <NUM> may prevent the display panel <NUM> from being bent by an external force or may alleviate the degree of bending (for example, bending angle or bending curvature radius). In such an embodiment, the support members <NUM> and <NUM> may maintain the display panel <NUM> in a relatively flat state even if an external force is applied.

The support members <NUM> and <NUM> may include a rigid or semi-rigid material. In an embodiment, the support members <NUM> and <NUM> may include a metal material such as stainless steel ("SUS") or aluminum, or a polymer material such as polymethyl metacrylate ("PMMA"), polycarbonate ("PC"), polyvinylalcohol ("PVA"), acrylonitirle-butadiene-styrene ("ABS"), or polyethylene terephthalate ("PET"). In one embodiment, for example, each of the support members <NUM> and <NUM> may be a stainless steel film having a thickness in a range of about <NUM> to about <NUM>. In one alternative embodiment, for example, each of the support members <NUM> and <NUM> may be an aluminum film having a thickness in a range of about <NUM> to about <NUM>.

In an embodiment, the support members <NUM> and <NUM> may be defined by a first support member <NUM> and a second support member <NUM>, which are spaced apart from each other. The first support member <NUM> may be disposed over the first non-folding region NFR1 and a part of the folding region FR. The second support member <NUM> may be disposed over the second non-folding region NFR2 and a part of the folding region FR. The first support member <NUM> may be spaced apart from the second support member <NUM> by a predetermined distance D, based on the folding axis AXIS_F. In one embodiment, for example, the distance D between the first support member <NUM> and the second support member <NUM> may be about <NUM> or less. The support members <NUM> and <NUM> may also be referred to as support plates, jig plates, or the like.

The bonding layer <NUM> is disposed over the folding region FR, the first non-folding region NFR1, and the second non-folding region NFR2. In the claimed invention, the bonding layer <NUM> is integrally formed as a single unitary unit under the flexible module <NUM>.

The bonding layer <NUM> may include or be made of, for example, a PSA, an OCA, or an OCR.

A thickness t2 of the bonding layer <NUM> (also referred to as a second thickness t2) may be in range of about <NUM> to about <NUM>.

The bonding layer <NUM> may include a plurality of distinct portions or portions having different properties from one another. In the present invention, as shown in <FIG>, the bonding layer <NUM> includes a first portion <NUM> located in the first non-folding region NFR1, a second portion <NUM> located in the second non-folding region NFR2, and a third portion <NUM> located in the folding region FR. In such an embodiment, the boundary between the first portion <NUM> and the third portion <NUM> may be aligned with the boundary between the first non-folding region NFR1 and the folding region FR, and the boundary between the second portion <NUM> and the third portion <NUM> may be aligned with the boundary between the second non-folding region NFR2 and the folding region FR. The first portion <NUM> may overlap the first support member <NUM> in the thickness direction (or the third direction DR3), the second portion <NUM> may overlap the second support member <NUM> in the thickness direction, and the third portion <NUM> may partially overlap a portion of the first support member <NUM> and the second support member <NUM> extending to the folding region FR and also overlap a space between the first support member <NUM> and the second support member <NUM>.

Referring to <FIG>, in an embodiment, the bonding layer <NUM> may further include a photoinitiator LI. The photoinitiator LI may be an initiator that reacts with light in a wavelength band of about <NUM> nanometers (nm) to about <NUM>. In such an embodiment, the bonding layer <NUM> includes the photoinitiator LI, as will be described later, such that a portion of the bonding layer <NUM>, i.e., the portion overlapping folding region FR, may be irradiated with ultraviolet light in the wavelength band of about <NUM> to about <NUM> to form the third portion <NUM> having a greater modulus than each of the first portion <NUM> and the second portion <NUM>.

In an embodiment, each of the modulus of the first portion <NUM> of the bonding layer <NUM> and the modulus of the second portion <NUM> thereof may be less than the modulus of the third portion <NUM> of the bonding layer <NUM>. In such an embodiment, the modulus of the third portion <NUM> of the bonding layer <NUM> may be greater than each of the modulus of the first portion <NUM> and the modulus of the second portion <NUM>. In such an embodiment, the rigidity or hardness of the third portion <NUM> may be greater than the rigidity or hardness of each of the first portion <NUM> and the second portion <NUM>.

The modulus difference of the plurality of portions <NUM> to <NUM> of the bonding layer <NUM> may be related to a bonding force with the above-described support members <NUM> and <NUM>. The bonding force may include adhesive force. The bonding layer <NUM> may include a surface contacting the lower functional layer <NUM> and an opposite surface opposite to the surface. A surface and an opposite surface of the first portion <NUM> may be in contact with the lower functional layer <NUM> and the first support member <NUM>, respectively, a surface and an opposite surface of the second portion <NUM> may be in contact with the lower functional layer <NUM> and the second support member <NUM>, respectively, and a surface and an opposite surface of the third portion <NUM> may be in contact with the lower functional layer <NUM> and the support members <NUM> and <NUM>, respectively.

In an embodiment, in a state where the surface of the bonding layer <NUM> is coupled to the lower functional layer <NUM>, the above-described ultraviolet light irradiation process may be performed. The opposite surface of the portion irradiated with ultraviolet light, that is, the third portion <NUM>, may have a smaller bonding force than the opposite surface of each of the first portion <NUM> and the second portion <NUM>.

In an embodiment, a first bonding force F1 (or first adhesive force) may be applied between a surface of the first portion <NUM> of the bonding layer <NUM> and the lower function member <NUM>, a second bonding force F2 (or second adhesive force) may be applied between a surface of the second portion <NUM> of the bonding layer <NUM> and the lower function member <NUM>, a third bonding force F3 (or third adhesive force) may be applied between a surface of the third portion <NUM> of the bonding layer <NUM> and the lower function member <NUM>, a fourth bonding force F4 (or fourth adhesive force) may be applied between an opposite surface of the first portion <NUM> of the bonding layer <NUM> and the first support member <NUM>, a fifth bonding force F5 (or fifth adhesive force) may be applied between an opposite surface of the second portion <NUM> of the bonding layer <NUM> and the second support member <NUM>, and a sixth bonding force F6 (or sixth adhesive force) may be applied between an opposite surface of the third portion <NUM> of the bonding layer <NUM> and first support member <NUM> or between the opposite surface of the third portion <NUM> of the bonding layer <NUM> and the second support member <NUM>.

The first bonding force F1 may be substantially the same as the second bonding force F2.

Each of the fourth bonding force F4 and the fifth bonding force F5 are greater than the sixth bonding force F6. In the claimed invention, as described above, the third portion <NUM> is irradiated with ultraviolet light or cured with ultraviolet light and thus the adhesive force of the opposite surface of the third portion <NUM> is decreased.

The sixth bonding force F6 may be less than the third bonding force F3. In an embodiment, as described above, since a surface of the third portion <NUM> is irradiated with ultraviolet light or cured with ultraviolet light in a state where the third portion <NUM> of the bonding layer <NUM> is coupled to the lower functional layer <NUM>, the adhesive force of the opposite surface of the third portion <NUM> of the exposed bonding layer <NUM> is decreased, whereas the bonding force between the surface of the third portion <NUM> and the lower functional layer <NUM> may be maintained.

In an embodiment of the display device <NUM>, a density of the photoinitiator LI of the third portion <NUM> may be less than a density of the photoinitiator LI of each of the first portion <NUM> and the second portion <NUM>. Herein, the density of the photoinitiator LI may refer to as the number of the particles of the photoinitiator LI in a unit area of the bonding layer <NUM>. In such an embodiment, the third portion is irradiated with ultraviolet light capable of reacting with the photoinitiator LI, and the first portion <NUM> and the second portion <NUM> are not irradiated with ultraviolet light through a masking process to be described later such that the density of the photoinitiator LI of the third portion <NUM> may become less than the density of the photoinitiator LI of each of the first portion <NUM> and the second portion <NUM>.

Referring to <FIG>, the folding region FR of the flexible module <NUM> and the bonding layer <NUM> may be folded with a predetermined curvature by an external force, but the non-folding regions NFR1 and NFR2 of the flexible module <NUM> and the bonding layer <NUM> may not be folded by an external force. In such an embodiment, the flexible module <NUM> and the bonding layer <NUM> may be located on the flat surfaces constituting a same plane in the non-folding regions NFR1 and NFR2, respectively.

When an external force is applied to one side of the display device <NUM>, for example, the right side thereof along the folding direction (upward direction in <FIG>), the folding region FR may be bent or folded, and the second non-folding region NFR2 may overlap or face the first non-folding region NFR1 after moving or rotating along the folding direction.

In an embodiment, where the support members <NUM> and <NUM> include or are made of a rigid material and are folded, bending stress may occur if the support members <NUM> and <NUM> attached to and the flexible module <NUM> are bent. The bending stress may be transmitted to the overlying flexible module <NUM> to cause defects.

Thus, it is desired that the support members <NUM> and <NUM> and the flexible module <NUM> are not bonded to each other in the folding region FR. In the claimed invention, the bonding force (the sixth bonding force F6) between the third portion <NUM> of the bonding layer <NUM> disposed in the folding region FR of the supporting members <NUM> and <NUM> and each of the supporting members <NUM> and <NUM> is weakened, so that, when folding the display device <NUM>, a surface of the third portion <NUM> of the bonding layer <NUM> may be attached to the lower functional layer <NUM>, and the opposite surface of the third portion <NUM> thereof may be separated from the support members <NUM> and <NUM>.

Thus, in such an embodiment, bending stress due to the support members <NUM> and <NUM> may be effectively prevented from occurring in the folding region FR.

In the claimed display device <NUM>, the bonding layer <NUM> is integrally formed as a single unitary unit and disposed over the folding region FR, the first non-folding region NFR1, and the second non-folding region NFR2. Thus, a step difference between the folding region FR and the adjacent non-folding regions NFR1 and NFR2, which may be viewed from an outside, may be prevented from occurring. In an embodiment, as described above with reference to <FIG> and <FIG>, the support members <NUM> and <NUM> are partially spaced apart from each other at the central portion of the folding region FR, so that the space therebetween may be viewed in an upward direction. In an embodiment of the display device <NUM>, the bonding layer <NUM> may be disposed to overlap the space in the thickness direction, thereby preventing the space the support members <NUM> and <NUM> from being viewed or recognized from an outside.

Hereinafter, an embodiment of a method of manufacturing a display device will be described. In such an embodiment, the same or like components as those of the embodiments described above are referred to by the same reference numerals, and any repetitive detailed description thereof will be omitted or simplified.

<FIG> is a flowchart illustrating a method of manufacturing a display device according to an embodiment, and <FIG> are cross-sectional views illustrating the process steps of a method of manufacturing a display device according to an embodiment.

Referring to <FIG>, first, a target panel in which a folding region FR, a first non-folding region NFR1 located at one side of the folding region FR, and a second non-folding region NFR2 located at another side of the folding region FR are defined, and a buffer member disposed on the target panel are provided (S10).

The target panel may refer to a component substantially the same as that of the display panel <NUM> of <FIG>, and the buffer member may refer to a component substantially the same as that of the lower functional layer <NUM> of <FIG>.

Subsequently, a bonding layer is provided or formed on the buffer member <NUM> (S20).

One surface of the bonding layer (refer to '940b' of <FIG>) may be attached to the lower surface of the buffer member <NUM>.

The providing or forming the bonding layer 940b on the buffer member <NUM> (S20) may include a plurality of processes.

Referring to <FIG>, the providing or forming the bonding layer 940b on the buffer member <NUM> (S20) may include applying a bonding material 940a onto a substrate SUB.

The bonding material 940a may be a PSA, an OCA, or an OCR having adhesive properties at a surface and on an opposite surface thereof after heat is applied thereto, which will be described later. The bonding material 940a may further include the photoinitiator LI described above with reference to <FIG>.

Referring to <FIG>, after the applying the bonding material 940a onto the support substrate SUB, the bonding material 940a is heated to form a first bonding material 940b. The bonding material 940a may be a solution material in which an adhesive material is dispersed in a solvent. The bonding material 940a is heated to remove the solvent to form the first bonding material 940b.

Subsequently, referring to <FIG>, after the first bonding material 940b is formed, a release film RF is provided or formed on the first bonding material 940b. The release film RF may include or be made of at least one selected from PET, PC, and paper.

The support substrate SUB may be disposed on a surface of the first bonding material 940b, and the release film RF may be disposed on an opposite surface of the first bonding material 940b. A surface of the release film RF may contact the first bonding material 940b, and an opposite surface of the release film RF, which is opposite to the surface of the release film RF, may be exposed.

Subsequently, referring to <FIG>, after the release film RF is provided or formed on the first bonding material 940b, the support substrate SUB is removed on from the opposite surface of the first bonding material 940b. Thus, the opposite surface of the first bonding material 940b may be exposed.

Subsequently, referring to <FIG> and <FIG>, the exposed opposite surface of the first bonding material 940b is attached to a surface of the buffer member <NUM> (S20).

In an embodiment, as shown in <FIG>, the release film RF may be attached to the surface of the first bonding material 940b.

Subsequently, referring to <FIG> and <FIG>, a portion of the first bonding material 940b overlapping the first non-folding region NFR1 and second non-folding region NFR2 is masked (S30) or covered by a mask.

The masking the portion of the first bonding material 940b overlapping the first non-folding region NFR1 and second non-folding region NFR2 (S30) may include providing or forming a first masking member MK1 in the first non-folding region NFR1 of the exposed opposite surface of the release film RF, and providing or forming a second masking member MK2 in the second non-folding region NFR2 of the exposed opposite surface of the release film RF. Thus, a portion of the release film RF, i.e., the portion overlapping the folding region FR, may be exposed.

Subsequently, referring to <FIG> and <FIG>, the folding region FR is irradiated with ultraviolet light UV (S40).

The irradiating the folding region FR with ultraviolet light UV (S40) may include irradiating not only the folding region FR but also non-folding regions NFR1 and NFR2 with ultraviolet light UV. However, the ultraviolet light UV applied to the non-folding regions NFR1 and NFR2 is blocked by the first and second masking members MK1 and MK2, and thus the ultraviolet light UV may not reach a portion of the first bonding material 940b overlapping the first and second masking members MK1 and MK2.

The folding region FR is irradiated with ultraviolet light UV, thereby forming the bonding layer <NUM> described with reference to <FIG>.

Subsequently, the masking members MK1 and MK2 and the release film RF are removed from the bonding layer <NUM>.

Subsequently, a first support member <NUM> is provided or formed in the first non-folding region NFR1 on the opposite surface of the bonding layer <NUM> and a part of the folding region FR, and a second support member <NUM> is provided or formed in the second non-folding region NFR1 on the opposite surface of the bonding layer <NUM> and a part of the folding region FR.

In the claimed invention, as described above, the bonding force (the sixth bond force F6) between each of the support members <NUM> and <NUM> and the third portion <NUM> of the bonding layer <NUM> disposed in the folding region FR of and each of the support members <NUM> and <NUM> is weakened, so that, at the time of folding, the surface of the third portion <NUM> of the bonding layer <NUM> is attached to the lower functional layer <NUM>, and the opposite surface of the third portion <NUM> may be separated from the support members <NUM> and <NUM>.

Thus, in the folding region FR, bending stress due to the support members <NUM> and <NUM> may be effectively prevented from occurring.

In the claimed method of manufacturing a display device, the bonding layer <NUM> is integrally formed as a single unitary unit over the folding region FR, the first non-folding region NFR1, and the second non-folding region NFR2. Thus, a step difference between the folding region FR and the adjacent non-folding regions NFR1 and NFR2, which may be viewed from an outside, may be prevented from occurring.

<FIG> are cross-sectional views illustrating the process steps of a method of manufacturing a display device according to an alternative embodiment.

The embodiment of a method of manufacturing a display device shown in <FIG> is substantially the same as the above-described method of manufacturing a display device except for forming a bonding layer on the buffer member.

In such an embodiment of the method of manufacturing a display device, a bonding material 940a_1 may be directly applied onto the buffer member <NUM>.

The bonding material 940a_1 may be a PSA, an OCA, or an OCR having adhesive properties at a surface and an opposite surface thereof after a process of applying heat to be described later. The bonding material 940a_1 may further include the photoinitiator LI described above with reference to <FIG>.

Referring to <FIG>, after the directly applying the bonding material 940a_1 onto the support substrate SUB, the bonding material 940a_1 is heated to form a first bonding material 940b_1. The bonding material 940a_1 may be a solution material in which an adhesive material is dispersed in a solvent. The bonding material 940a_1 is heated to remove the solvent to form the first bonding material 940b_1.

Subsequently, referring to <FIG>, after the first bonding material 940b_1 is formed, a release film RF is provided or formed on the first bonding material 940b_1. The release film RF may include or be made of at least one selected from PET, PC, and paper.

The buffer member <NUM> may be disposed on a surface of the first bonding material 940b_1, and the release film RF may be disposed on an opposite surface of the first bonding material 940b_1. A surface of the release film RF may contact the first bonding material 940b_1, and an opposite surface of the release film RF, which is opposite to the surface of the release film RF, may be exposed.

Subsequently, referring to <FIG>, a portion of the first bonding material 940b_1 overlapping the first non-folding region NFR1 and second non-folding region NFR2 is masked.

The masking the portion of the first bonding material 940b_1 overlapping the first non-folding region NFR1 and second non-folding region NFR2 may include providing or forming a first masking member MK1 in the first non-folding region NFR1 of the exposed opposite surface of the release film RF, and providing or forming a second masking member MK2 in the second non-folding region NFR2 of the exposed opposite surface of the release film RF. Thus, the portion of the release film RF overlapping the folding region FR may be exposed.

Subsequently, referring to <FIG>, the folding region FR is irradiated with ultraviolet light UV.

The irradiating the folding region FR with ultraviolet light UV may include irradiating not only the folding region FR but also non-folding regions NFR1 and NFR2 with ultraviolet light UV. However, the ultraviolet light UV applied to the non-folding regions NFR1 and NFR2 is blocked by the first and second masking members MK1 and MK2, and thus the ultraviolet light UV may not reach a portion of the first bonding material 940b_1 overlapping the first and second masking members MK1 and MK2.

In the present invention, as described above, the bonding force (the sixth bond force F6) between each of the support members <NUM> and <NUM> and the third portion <NUM> of the bonding layer <NUM> disposed in the folding region FR of and each of the support members <NUM> and <NUM> is weakened, so that, at the time of folding, a surface of the third portion <NUM> of the bonding layer <NUM> is attached to the lower functional layer <NUM>, and an opposite surface of the third portion <NUM> may be separated from the support members <NUM> and <NUM>.

In the claimed method of manufacturing a display device, the bonding layer <NUM> is integrally formed as a single unitary unit over the folding region FR, the first non-folding region NFR1, and the second non-folding region NFR2. Thus, a step difference between the folding region FR and the adjacent non-folding regions NFR1 and NFR2, which may be viewed or recognized from an outside, may be effectively prevented from occurring.

<FIG> is a cross-sectional view of a display device according to another alternative embodiment.

Referring to <FIG>, a display device <NUM> is substantially the same as the display device <NUM> of <FIG> except that the display device <NUM> further includes a lower support substrate <NUM> between the lower functional layer <NUM> and the bonding layer <NUM> and a lower bonding layer <NUM> between the lower support substrate <NUM> and the lower functional layer <NUM>.

In such an embodiment, as shown in <FIG>, the display device <NUM> may include a lower support substrate <NUM> between the lower functional layer <NUM> and the bonding layer <NUM> and a lower bonding layer <NUM> between the lower support substrate <NUM> and the lower functional layer <NUM>.

The lower support substrate <NUM> may include an organic insulating material. In one embodiment, for example, the organic insulating material may include at least one material selected from polyethersulphone ("PES"), polyacrylate ("PA"), polyarylate ("PAR"), polyetherimide ("PEI"), polyethylene napthalate ("PEN"), PET, polyphenylene sulfide ("PPS"), polyallylate, PI, PC, cellulose triacetate ("CAT"), cellulose acetate propionate ("CAP"), polyurethane ("PU"), and combinations thereof.

In an embodiment, the lower support substrate <NUM> may include PU or PI.

In such an embodiment, the lower support substrate <NUM> and the bonding layer <NUM> may collectively define a single-sided tape. A surface of the bonding layer <NUM> may be attached to the lower support substrate <NUM>, and an opposite surface of the bonding layer <NUM> may be attached to the underlying support members <NUM> and <NUM>.

The single-sided tape including the lower support substrate <NUM> and the bonding layer <NUM> may be coupled with the lower functional layer <NUM> through the lower bonding layer <NUM>. That is, the lower bonding layer <NUM> may serve to couple the lower functional layer <NUM> and the single-sided tape to each other.

The lower bonding layer <NUM>, as a layer having adhesive properties on both upper and lower surfaces thereof, may include or be formed of a PSA, an OCA, or an OCR. The lower bonding layer <NUM> may include acrylic resin or silicone resin. The lower bonding layer <NUM> may have an elongation rate in a range of about <NUM> % to about <NUM> %.

<FIG> are cross-sectional views illustrating the process steps of a method of manufacturing a display device according to another alternative embodiment.

The method of manufacturing a display device shown in <FIG> is substantially the same as the above-described method of manufacturing a display device except for forming a bonding layer on the buffer member.

In an embodiment, referring to <FIG>, the forming a bonding layer on the buffer member may include applying a bonding material 940a onto the lower support substrate <NUM>.

The bonding material 940a may be a PSA, an OCA, or an OCR having adhesive properties at a surface and an opposite surface thereof after applying heat to be described later. The bonding material 940a may further include the photoinitiator LI described above with reference to <FIG>.

Referring to <FIG>, after the applying the bonding material 940a onto the lower support substrate <NUM>, the bonding material 940a is heated to form a first bonding material 940b. The bonding material 940a may be a solution material in which an adhesive material is dispersed in a solvent. The bonding material 940a is heated to remove the solvent to form the first bonding material 940b.

Subsequently, referring to <FIG>, after the first bonding material 940b is formed, a release film RF is provided or formed on the first bonding material 940b. The release film RF may include or be made of at least one material selected from PET, PC, and paper.

The lower support substrate <NUM> may be disposed on one surface of the first bonding material 940b, and the release film RF may be disposed on the other surface of the first bonding material 940b. A surface of the release film RF may contact the first bonding material 940b, and an opposite surface of the release film RF, which is opposite to the surface of the release film RF, may be exposed.

Subsequently, referring to <FIG>, after the release film RF is provided or formed on the first bonding material 940b, the upper surface of the lower support substrate <NUM> under which the first bonding material 940b is formed is attached to a surface of the buffer member <NUM> through the lower bonding layer <NUM>.

In an embodiment, as shown in <FIG>, the release film RF may be attached to an opposite surface of the first bonding material 940b.

Subsequently, referring to <FIG>, a portion of the first bonding material 940b overlapping the first non-folding region NFR1 and second non-folding region NFR2 is masked.

The masking the portion of the first bonding material 940b overlapping the first non-folding region NFR1 and second non-folding region NFR2 may include providing or forming a first masking member MK1 in the first non-folding region NFR1 of the exposed opposite surface of the release film RF, and providing or forming a second masking member MK2 in the second non-folding region NFR2 of the exposed opposite surface of the release film RF. Thus, the portion of the release film RF overlapping the folding region FR may be exposed.

Subsequently, the folding region FR is irradiated with ultraviolet light UV.

The irradiating the folding region FR with ultraviolet light UV may include irradiating not only the folding region FR but also non-folding regions NFR1 and NFR2 with ultraviolet light UV. However, the ultraviolet light UV applied to the non-folding regions NFR1 and NFR2 is blocked by the first and second masking members MK1 and MK2, and thus the ultraviolet light UV may not reach a portion of the first bonding material 940b overlapping the first and second masking members MK1 and MK2.

Subsequently, a first support member <NUM> is provide or formed in the first non-folding region NFR1 on the opposite surface of the bonding layer <NUM> and a part of the folding region FR, and a second support member <NUM> is formed in the second non-folding region NFR1 on the opposite surface of the bonding layer <NUM> and a part of the folding region FR.

As described above, the bonding force (the sixth bond force F6) between each of the support members <NUM> and <NUM> and the third portion <NUM> of the bonding layer <NUM> disposed in the folding region FR of and each of the support members <NUM> and <NUM> is weakened, so that, at the time of folding, a surface of the third portion <NUM> of the bonding layer <NUM> is attached to the lower functional layer <NUM>, and an opposite surface of the third portion <NUM> may be separated from the support members <NUM> and <NUM>.

Referring to <FIG>, a display device <NUM> is substantially the same as the above-described display device <NUM> except that a bonding layer 940_1 further includes a fourth portion between the first portion <NUM> and the third portion <NUM> and a fifth portion <NUM> between the second portion <NUM> and the third portion <NUM>.

In an embodiment of the display device <NUM>, as shown in <FIG>, an inner side surface of the first portion <NUM> may be indented in a direction from the folding region FR toward the first non-folding region NFR1 via the boundary between the first non-folding region NFR1 and the folding region FR, and an inner side surface of the second portion <NUM> may be indented in a direction from the folding region FR toward the second non-folding region NFR2 via the boundary between the second non-folding region NFR2 and the folding region FR.

The fourth portion <NUM> may overlap the first non-folding region NFR1, and the fifth portion <NUM> may overlap the second non-folding region NFR2. Each of the fourth portion <NUM> and the fifth portion <NUM> may be disposed in a same layer as the adjacent first portion <NUM>, second portion <NUM> and third portion <NUM>.

The modulus of each of the fourth portion <NUM> and the fifth portion <NUM> may be less than the modulus of the third portion <NUM>, and may be greater than the modulus of each of the first portion <NUM> and the second portion <NUM>.

The density of the photoinitiator LI in each of the fourth portion <NUM> and the fifth portion <NUM> may be greater than the density of the photoinitiator LI in the third portion <NUM>, and may be less than the density of the photoinitiator LI in each of the first portion <NUM> and the second portion <NUM>.

The bonding force between the other surface of the fourth portion <NUM> and the first support member <NUM> may have a value between the fourth bonding force F4 between the first portion <NUM> and the first support member <NUM> and the sixth bonding force F6 between the third portion <NUM> and the first support member <NUM>. The bonding force between the other surface of the fifth portion <NUM> and the second support member <NUM> may have a value between the fifth bonding force F5 between the second portion <NUM> and the second support member <NUM> and the sixth bonding force F6 between the third portion <NUM> and the second support member <NUM>.

It is preferred that, at the time of folding the display device <NUM>, the fourth portion <NUM> and the fifth portion <NUM>, unlike the third portion <NUM>, may have double-sided adhesive force to such a degree that the display device <NUM> is folded in a state in which the fourth portion <NUM> and the fifth portion <NUM> are attached to all the support members <NUM> and <NUM> and the lower functional layer <NUM>.

In such an embodiment of the display device <NUM>, since the bonding layer 940_1 further includes the fourth portion <NUM> and the fifth portion <NUM> having a value between the adjacent portions, thus coupling failure such as peeling, which may occur when the modulus of the bonding layer 940_1 is greatly changed between the folding region FR and the non-folding regions NFR1 and NFR2, may be effectively prevented.

As described above, the bonding force (the sixth bond force F6) between each of the support members <NUM> and <NUM> and the third portion <NUM> of the bonding layer 940_1 disposed in the folding region FR of and each of the support members <NUM> and <NUM> is weakened, so that, at the time of folding, the surface of the third portion <NUM> of the bonding layer 940_1 is attached to the lower functional layer <NUM>, and the opposite surface of the third portion <NUM> may be separated from the support members <NUM> and <NUM>.

In an embodiment of the display device <NUM>, the bonding layer 940_1 is integrally formed as a single unitary unit over the folding region FR, the first non-folding region NFR1, and the second non-folding region NFR2. Thus, a step difference between the folding region FR and the adjacent non-folding regions NFR1 and NFR2, which may be viewed from an outside, may be prevented from occurring.

As described above, in embodiments of a display device according to the invention, stepped visibility in the folding area is reduced.

The invention should not be construed as being limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concept of the invention to those skilled in the art.

Claim 1:
A display device (<NUM>), in which a folding region (FR), a first non-folding region (NFR1) located at a side of the folding region (FR), and a second non-folding region (NFR2) located at another side of the folding region (FR) are defined,
the display device (<NUM>) comprising:
a display module (<NUM>);
a support member (<NUM>, <NUM>) disposed under the display module (<NUM>); and
a first bonding layer (<NUM>) disposed between the display module (<NUM>) and the support member (<NUM>, <NUM>),
wherein the support member (<NUM>, <NUM>) includes a first support member (<NUM>) disposed in the first non-folding region (NFR1) and a part of the folding region (FR), and a second support member (<NUM>) disposed in the second non-folding region (NFR2) and a part of the folding region (FR),
the first bonding layer (<NUM>) is disposed in the folding region (FR), the first non-folding region (NFR1), and the second non-folding region (NFR2),
the first bonding layer (<NUM>) includes a first portion (<NUM>) disposed in the first non-folding region (NFR1), a second portion (<NUM>) disposed in the second non-folding region (NFR2), and a third portion (<NUM>) disposed in the folding region (FR), and
adhesive forces (F6) of the third portion (<NUM>) of the first bonding layer (<NUM>) to the first and second support members (<NUM>, <NUM>) are less than each of an adhesive force (F4) of the first portion (<NUM>) of the first bonding layer (<NUM>) to the first support member (<NUM>) and an adhesive force (F5) of the second portion (<NUM>) of the first bonding layer (<NUM>) to the second support member (<NUM>),
the first bonding layer (<NUM>) is integrally formed as a single unitary unit over the folding region (FR), the first non-folding region (NFR1), and the second non-folding region (NFR2) wherein
the display module (<NUM>) includes a display panel (<NUM>) and a buffer member (<NUM>)
disposed between the display panel (<NUM>) and the first bonding layer (<NUM>), characterised in that the
buffer member (<NUM>) is configured to prevent an impact from an outside from being transmitted to the display panel (<NUM>),
wherein the buffer member (<NUM>) includes or is formed of a foam material so as to prevent the impact from an outside,
wherein the buffer member (<NUM>) has a thickness in a range of about <NUM> to about <NUM>, and
wherein the first bonding layer (<NUM>) has a thickness in a range of about <NUM> to about <NUM>.