KR20210026578A - Display device - Google Patents

Abstract

According to an embodiment of the present invention, a display device includes: a display panel including a plurality of pad electrodes; and a backplate including a first portion at least partially overlapping the plurality of pad electrodes under the display panel and a second portion remaining except for the first portion. The transmittance of the first portion is higher than the transmittance of the second portion. Accordingly, it can be checked whether indentations are formed in the plurality of pad electrodes through the first portion having high transmittance. According to the present invention, bonding defects of a plurality of flexible films can be easily detected.

Description

Display device {DISPLAY DEVICE}

The present invention relates to a display device, and more particularly, to a flexible display device in which indentation is easily detected.

Display devices used in computer monitors, TVs, and mobile phones include organic light emitting displays (OLEDs) that emit light by themselves, and liquid crystal displays (LCDs) that require a separate light source. have.

The range of application of display devices to personal portable devices as well as computer monitors and TVs has been diversified, and research on display devices having a reduced volume and weight while having a large display area is being conducted.

In addition, in recent years, a foldable display device that can be folded and unfolded freely by forming a display element and wiring on a flexible substrate such as plastic, which is a flexible material, and a rollable display device that is manufactured to display images even if rolled up. Is attracting attention as a next-generation display device.

In the case of a display device that is flexible so that at least a portion of the display device can be folded and unfolded or rolled, each component constituting the display device may have a very thin thickness to enable folding or bending. However, according to the inventors of the present invention, as each component of the display device has a very thin thickness, various components of the display device, in particular, the display panel, etc. may be deformed by an external impact. Recognized that it could lead. Accordingly, by disposing a back plate supporting the display panel under the display panel, external shocks are absorbed and deformation of the display device is reduced. At this time, as the backplate, a colored polyimide having a low coefficient of thermal expansion, a high glass transition temperature, low deformation possibility, easy folding, and low price was mainly used.

Meanwhile, a bonding failure between the display panel and a plurality of flexible films was detected by inspecting the indentation of the pad electrode under the back plate. However, the inventors of the present invention have a problem in that when the back plate is made of colored polyimide, the indentation of the pad electrode is not recognized due to the low transmittance of the colored polyimide. I recognized it.

Accordingly, the inventors of the present invention have considered forming the back plate of a transparent material, for example, transparent polyimide, in order to inspect the indentation of the pad electrode. However, in the case of transparent polyimide, it has been recognized that the coefficient of thermal expansion and modulus value are higher than that of colored polyimide, so that the ductility characteristics of the display device are deteriorated, and the price is very high, so that the manufacturing cost is increased.

Accordingly, the inventors of the present invention have invented a back plate having high transmittance and low possibility of deformation during folding so that indentation can be detected in a flexible display device.

An object of the present invention is to provide a display device capable of easily detecting bonding failures of a plurality of flexible films from an indentation of a pad electrode.

Another problem to be solved by the present invention is to provide a display device in which the transmittance of a back plate overlapping a pad electrode is improved without deteriorating the ductility characteristics of a flexible display device.

Another problem to be solved by the present invention is to provide a display device that minimizes damage caused by folding or bending.

The problems of the present invention are not limited to the problems mentioned above, and other problems that are not mentioned will be clearly understood by those skilled in the art from the following description.

In order to solve the above-described problems, a display device according to an exemplary embodiment includes a display panel including a plurality of pad electrodes, a first portion at least partially overlapping the plurality of pad electrodes under the display panel, and It includes a back plate composed of a second portion, which is a portion other than the first portion, and the transmittance of the first portion is higher than that of the second portion. Accordingly, it is possible to check whether indentations are formed on the plurality of pad electrodes through the first portion having high transmittance.

In order to solve the above-described problems, a display device according to another exemplary embodiment of the present invention includes a display panel having at least a part of a flexible display panel, a flexible film bonded to an upper surface of the display panel, and a flexible film disposed on a lower surface of the display panel. In order to optically inspect the connection state of the flexible film and the display panel, the first part may be made of a transparent material including a back plate consisting of a first part overlapping with and a second part other than the first part. have. Therefore, by configuring the first part of a transparent material, it is possible to inspect the bonding failure of the flexible film.

Details of other embodiments are included in the detailed description and drawings.

According to the present invention, bonding defects of a plurality of flexible films can be easily detected through an indentation inspection of a pad electrode without deteriorating the ductility characteristics of the display device.

The present invention can minimize damage to the display device due to folding or bending.

The effects according to the present invention are not limited by the contents exemplified above, and more various effects are included in the present invention.

1 is a plan view of a display device according to an exemplary embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along line II-II' of FIG. 1.
3 is a plan view of a back plate of a display device according to an exemplary embodiment of the present invention.
4 is a graph measuring transmittance of a first portion and a second portion of a back plate of a display device according to an exemplary embodiment of the present invention.
5 is a diagram illustrating a manufacturing process of a back plate of a display device according to an exemplary embodiment of the present invention.
6A and 6B are plan views of a back plate of a display device according to various embodiments of the present disclosure.

Advantages and features of the present invention, and a method of achieving them will become apparent with reference to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different shapes, only these embodiments are intended to complete the disclosure of the present invention, and common knowledge in the technical field to which the present invention pertains. It is provided to completely inform the scope of the invention to those who have, and the invention is only defined by the scope of the claims.

The shapes, areas, ratios, angles, numbers, etc. disclosed in the drawings for explaining the embodiments of the present invention are exemplary, and thus the present invention is not limited to the illustrated matters. The same reference numerals refer to the same elements throughout the specification. In addition, in describing the present invention, when it is determined that a detailed description of a related known technology may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. When'include','have','consists of' and the like mentioned in the present invention are used, other parts may be added unless'only' is used. In the case of expressing the constituent elements in the singular, it includes the case of including the plural unless specifically stated otherwise.

In interpreting the constituent elements, it is interpreted as including an error range even if there is no explicit description.

In the case of a description of the positional relationship, for example, if the positional relationship of two parts is described as'upper','upper of','lower of','next to','right' Or, unless'direct' is used, one or more other parts may be located between the two parts.

When an element or layer is referred to as “on” another element or layer, it includes all cases in which another layer or another element is interposed directly on or in the middle of another element.

Also, the first, second, etc. are used to describe various components, but these components are not limited by these terms. These terms are only used to distinguish one component from another component. Accordingly, the first constituent element mentioned below may be a second constituent element within the technical idea of the present invention.

The same reference numerals refer to the same elements throughout the specification.

The area and thickness of each component shown in the drawings are illustrated for convenience of description, and the present invention is not necessarily limited to the area and thickness of the illustrated component.

Each of the features of the various embodiments of the present invention can be partially or entirely combined or combined with each other, technically various interlocking and driving are possible, and each of the embodiments may be independently implemented with respect to each other or can be implemented together in an association relationship. May be.

Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a plan view of a display device according to an exemplary embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line II-II' of FIG. 1. 1 and 2, a display device 100 according to an exemplary embodiment of the present invention includes a cover window 110, a polarizing plate 120, a display panel 130, a back plate 140, and an adhesive layer 150. , A plurality of flexible films 160 and a conductive adhesive layer 170. In FIG. 1, for convenience of description, only the display panel 130 and a plurality of flexible films 160 are illustrated among various constituent elements of the display device 100.

The display panel 130 is a panel on which an image is implemented, and a display device for implementing an image and a circuit, wiring, and components for driving the display device may be disposed. The display panel 130 may be a flexible display panel. For example, the display panel 130 may be a foldable display panel that can be folded or a rollable display panel that can be wound around a roller. Hereinafter, for convenience of description, it is assumed that the display panel 130 is a foldable display panel, but the description is not limited thereto.

Referring to FIG. 1, the display panel 130 includes a display area AA and a non-display area NA. The display panel 130 includes a flexible area FA and a rigid area NFA. That is, the display panel 130 may classify an area according to whether or not an image is displayed, and may classify an area according to whether or not it is folded. That is, a specific area of the display panel 130 may be defined according to whether an image is displayed or folded. For example, the specific area of the display panel 130 may be the display area AA and the flexible area FA.

The display area AA is an area for displaying an image, and a display element for displaying an image and a circuit unit for driving the display element may be disposed. For example, when the display device 100 is an organic light-emitting display device, the display device may include an organic light-emitting device, and when the display device 100 is a liquid crystal display device, the display device may include a liquid crystal device. have. Hereinafter, for convenience of description, it is assumed that the display device 100 according to various embodiments of the present disclosure is the display device 100 including an organic light emitting device, but is not limited thereto.

The circuit unit may include various thin film transistors, capacitors, and wirings for driving the organic light emitting device. For example, the circuit unit may include various components such as a driving thin film transistor, a switching thin film transistor, a storage capacitor, a gate wiring, and a data wiring, but is not limited thereto.

The non-display area NA is an area in which an image is not displayed, and is an area in which circuits, wirings, components, etc. for driving the display elements in the display area AA are arranged. A driving circuit such as a gate driver and a data driver may be disposed in the non-display area NA.

The non-display area NA may be defined as an area surrounding the display area AA as illustrated in FIG. 1. However, the non-display area NA may be defined as an area extending from the display area AA, or may be defined as an area in which no display element is disposed, but is not limited thereto.

Meanwhile, the display panel 130 may be defined as a display area AA and a non-display area NA, but may be defined as a soft area FA and a rigid area NFA.

The flexible area FA is an area in which the display panel 130 is folded, that is, a bendable area. The flexible area FA is an area that is folded based on the folding axis FX, and the flexible area FA may be folded with a specific radius of curvature. Since the flexible area FA is an area in which the display panel 130 is folded, it may also be defined as a folding area. The flexible area FA includes a part of the display area AA adjacent to the folding axis FX and a part of the non-display area NA.

1 illustrates that the folding axis FX is disposed in the center of the display panel 130, the position and number of the folding axis FX may be variously changed, and the position and number of the folding axis FX may be changed. Accordingly, the soft area FA may also be variously changed, but is not limited thereto.

The rigid area NFA is an area in which the display panel 130 maintains a flat state. The rigid area NFA includes a part of the display area AA and a part of the non-display area NA. Since the rigid area NFA is an area in which the display panel 130 is not folded, it may also be defined as a non-folding area. The rigid area NFA is an area extending to both sides of the soft area FA. That is, the rigid region NFA may be defined with the soft region FA interposed therebetween.

Also, when the display device 100 is in a folded state, the rigid regions NFA on both sides of the flexible region FA may be disposed to face each other while maintaining a flat state. For example, when the display device 100 is flatly unfolded, the flexible area FA and the rigid area NFA on both sides of the flexible area FA may form one plane. On the other hand, when in the folded state, the display device 100 may be disposed so that the rigid regions NFA face each other on the upper or lower surface of the display device 100 according to the folding direction of the display device 100.

Specifically, when the display device 100 is in-folded, the display device 100 may be folded so that the top surfaces of the display device 100 respectively overlapping the rigid region NFA face each other. In addition, when the display device 100 is out-folded, the display device 100 may be folded so that the lower surfaces of the display device 100 respectively overlapping the rigid area NFA face each other. Hereinafter, for convenience of description, description will be made on the assumption that the display device 100 according to the exemplary embodiment is out-folded, but the display device 100 may be in-folded, but is not limited thereto.

Referring to FIG. 2, the cover window 110 may protect the polarizing plate 120 and the display panel 130 under the cover window 110 from external shock, moisture, heat, and the like. The cover window 110 may be made of a material having impact resistance and light transmittance. For example, the cover window 110 is a substrate made of glass, or made of a plastic material such as polymethylmethacrylate (PMMA), polyimide (PI), and polyethylene terephthalate (PET). It may be a thin film, but is not limited thereto.

Meanwhile, the cover window 110 may be made of a material having a high tensile Young's modulus and a high modulus value, that is, a material having a high hardness in order to reduce cracks due to external impact. However, in the case of a material having a large modulus value, the display device 100 may be broken without being bent when the display device 100 is folded. However, even if a material having a high modulus value is less than a certain thickness, folding may be possible. Accordingly, the cover window 110 may have a very thin thickness. For example, the cover window 110 may be a thin plastic film, but is not limited thereto.

In addition, although not shown in the drawings, in order to improve the surface hardness of the cover window 110, a hard coating layer may be further disposed on one or both sides of the cover window 110, but is not limited thereto.

The polarizing plate 120 is disposed under the cover window 110. The polarizing plate 120 may selectively transmit light to reduce reflection of external light incident on the display panel 130. Specifically, the display panel 130 includes various metal materials applied to thin film transistors, wirings, and electroluminescent devices. Accordingly, external light incident on the display panel 130 may be reflected from the metallic material, and visibility of the display device 100 may be reduced due to the reflection of the external light. Accordingly, by disposing the polarizing plate 120 on one surface of the display panel 130, reflection of external light may be prevented, and outdoor visibility of the display device 100 may be improved. However, components of the display device 100 of FIGS. 1 and 2 are exemplary, and the polarizing plate 120 may be omitted according to an embodiment of the display device 100.

Meanwhile, although not shown in FIG. 2, a touch panel may be further disposed. The touch panel is a component that senses a user's touch input, such as a screen touch or a gesture on the display device 100, and may be implemented in a resistive film method, a capacitive method, an optical method, or an electromagnetic method. The touch panel may be formed of an add-on type, an on-cell type, or an in-cell type according to the arrangement of the touch panel, but is not limited thereto. Does not.

Referring to FIG. 2, a plurality of pad electrodes PE are disposed in the rigid area NFA of the non-display area NA of the display panel 130. The plurality of pad electrodes PE are electrodes for electrically connecting the plurality of flexible films 160 and the display panel 130. Signals from the printed circuit board and the plurality of flexible films 160 may be transmitted to the display device and the circuit unit of the display area AA through the plurality of pad electrodes PE. In this case, a part of the non-display area NA in which the plurality of pad electrodes PE are disposed may also be defined as a pad area.

1 and 2, a plurality of flexible films 160 are bonded to the upper surface of the display panel 130. The plurality of flexible films 160 are films for supplying signals to display elements and circuits of the display area AA by arranging various components on a flexible base film, and may be electrically connected to the display panel 130. One end of the plurality of flexible films 160 is disposed in the non-display area NA in which the plurality of pad electrodes PE are disposed among the non-display area NA of the display panel 130 to display a power supply voltage and a data voltage. It can be supplied to a plurality of display elements and circuit units in the area AA. Meanwhile, although FIG. 1 shows that there are four flexible films 160 and bonded to the short side of the display panel 130, the number and arrangement of the plurality of flexible films 160 may be variously changed according to design. And is not limited thereto.

A driving IC such as a gate driver IC and a data driver IC may be disposed on the plurality of flexible films 160. The driving IC is a component that processes data for displaying an image and a driving signal for processing it. The driving IC may be disposed in a manner such as a chip on glass (COG), a chip on film (COF), a tape carrier package (TCP), or the like, depending on the mounting method. However, for convenience of description, it has been described that the driving IC is a chip-on film type mounted on a plurality of flexible films 160, but is not limited thereto.

Referring to FIG. 2, a plurality of flexible films 160 may be electrically connected to the display panel 130 through a conductive adhesive layer 170. Specifically, a conductive adhesive layer 170 is disposed between the plurality of flexible films 160 and the plurality of pad electrodes PE, so that the plurality of flexible films 160 can be electrically connected to the plurality of pad electrodes PE. have. In this case, the conductive adhesive layer 170 may be an anisotropic conductive film (ACF) in which a plurality of conductive balls are dispersed, but is not limited thereto.

Referring to FIG. 2, a back plate 140 is disposed under the display panel 130. When the substrate constituting the display panel 130 is made of a plastic material such as polyimide, the manufacturing process of the display device 100 proceeds while a support substrate made of glass is disposed under the substrate, After forming a component such as the polarizing plate 120 on the support substrate may be released. However, since a component for supporting the substrate is required even after the support substrate is released, the back plate 140 for supporting the substrate may be disposed under the substrate of the display panel 130. In addition, the back plate 140 not only supports the display panel 130, but also protects the display panel 130 from external moisture, heat, shock, and the like.

The back plate 140 includes a first portion 141 that at least partially overlaps the plurality of pad electrodes PE and a second portion 142 that is the remaining portion except for the first portion 141. The first portion 141 has a higher transmittance than the second portion 142, so that the indentation formed by pressing or crushing a plurality of conductive balls under the back plate 140 can be inspected. The first portion 141 and the second portion 142 of the back plate 140 will be described in detail later with reference to FIGS. 3 and 4.

The plurality of adhesive layers 150 are disposed between other components of the display device 100 to adhere each component to the other components. Specifically, the plurality of adhesive layers 150 are disposed between the cover window 110 and the polarizing plate 120, between the polarizing plate 120 and the display panel 130, and between the display panel 130 and the back plate 140, respectively. . The plurality of adhesive layers 150 may be made of an adhesive material, for example, OCA (Optical Clear Adhesive), PSA (Pressure Sensitive Adhesive), or the like, but is not limited thereto.

Meanwhile, although not shown in the drawing, a mid frame may be further disposed under the back plate 140. The mid frame is made of a rigid material such as metal to protect and support the back plate 140 and the display panel 130 on the mid frame.

Hereinafter, the first portion 141 and the second portion 142 of the back plate 140 of the display device 100 according to an exemplary embodiment will be described with reference to FIGS. 3 and 4 and Table 1. It will be described in detail.

3 is a plan view of a back plate of a display device according to an exemplary embodiment of the present invention. 4 is a graph measuring transmittance of a first portion and a second portion of a back plate of a display device according to an exemplary embodiment of the present invention.

Referring to FIG. 3, the back plate 140 includes a first portion 141 and a second portion 142. The first portion 141 may overlap the rigid region NFA. At least a portion of the first portion 141 may overlap the non-display area NA of the rigid area NFA. For example, the first portion 141 may overlap the non-display area NA in which the plurality of pad electrodes PE are disposed. Accordingly, since the first portion 141 overlaps the rigid region NFA, it can always maintain a flat state.

At least a portion of the second portion 142 may overlap the entire soft area FA. For example, the second part 142 may overlap the entire display area AA and a part of the non-display area NA. Accordingly, since at least a portion of the second portion 142 overlaps the flexible area FA, at least a portion of the second portion 142 may be bent together as the display panel 130 is bent.

Meanwhile, in FIG. 3, the first portion 141 is shown to overlap only the non-display area NA, but the first portion 141 may be disposed up to a portion of the display area AA corresponding to the rigid area NFA. And is not limited thereto.

The transmittance of the first portion 141 overlapping the plurality of pad electrodes PE is higher than that of the second portion 142. The first portion 141 is made of a material having a higher transmittance than the second portion 142, and a portion of the display panel 130 on the first portion 141 may be visually recognized from the lower portion of the back plate 140.

Specifically, the first part 141 may be made of a transparent material. For example, the first part 141 is transparent polyimide (CPI), polycarbonate (PC), polyethylene terephthalate (PET), cyclo olefin polymer (COP), and It may be made of a transparent material such as acrylic.

The second part 142 may be made of an opaque material. For example, the second portion 142 may be made of colored polyimide such as yellow polyimide (YPI).

Hereinafter, the transmittance of the first portion 141 and the second portion 142 will be described in more detail with reference to FIG. 4.

In FIG. 4, the horizontal axis represents wavelength (nm), and the vertical axis represents transmittance (%).

Referring to FIG. 4, the first portion 141 has a transmittance of about 90% for light of about 380 nm to 800 nm, which is a visible light wavelength band. Accordingly, the first portion 141 may transmit about 90% of the light in the visible wavelength band, and may be a substantially transparent portion.

The second portion 142 has a transmittance of about 70% for light from about 550 nm to 800 nm. The second part 142 may transmit about 70% of green light and red light without transmitting blue light among the light in the visible light wavelength band, and may be a translucent or opaque part.

Accordingly, since the first portion 141 has a high transmittance, the plurality of pad electrodes PE of the display panel 130 disposed on the first portion 141 under the first portion 141 may be visually recognized. I can. On the other hand, the second part 142 transmits only a part of the light in the visible wavelength band with a lower transmittance compared to the first part 141, so that the second part 142 is disposed on the second part 142 under the second part 142. Components of the display panel 130 may be difficult to clearly recognize.

Meanwhile, the second part 142 may have a modulus value of about 3 to 4.5 GPa, and the first part 141 may have a modulus value of 3 GPa or less or 4.5 GPa or more. For example, the first part 141 may have a modulus value of 3 GPa or less or 5 to 7 GPa, and the second part 141 may have a modulus value of 3 GPa. If the first part 141 having a modulus value of 3 GPa or less or 4.5 GPa or more is disposed in the flexible area FA, the display device 100 may be damaged by the first part 141.

Hereinafter, referring to [Table 1] together in order to describe the arrangement of the first portion 141 and the second portion 142 according to the modulus value of the first portion 141 and the second portion 142 in more detail. .

Out-folding (4R) Experimental Example 1
(Colored polyimide) Experimental Example 2
(Transparent polyimide) Experimental Example 3
(Polycarbonate) Modulus of backplate (GPa) 3 6.2 1.4 Backplate thickness (um) 50 50 50 High temperature and high humidity
Static folding
(static folding) 500 hr
60℃
90% No specific matters Hard coating crack Organic emission layer peeling and adhesive layer buckling Room temperature dynamic folding
(dynamic folding) 200K
Room temperature No specific matters Hard coating crack and cover window break No specific matters

[Table 1] is a table showing evaluation results of the display devices according to the case where the display devices according to Experimental Examples 1 to 3 are statically folded under high temperature and high humidity conditions and when they are dynamically folded under room temperature conditions.

The display devices of Experimental Examples 1 to 3 are display devices in which the entire backplate is made of the same material in the structure of the display device 100 illustrated in FIGS. 1 to 3. Specifically, the display device of Experimental Example 1 is a display device in which the back plate is made of colored polyimide in the structure of the display device 100 of FIGS. 1 to 3. The display device of Experimental Example 2 is a display device in which the back plate is made of transparent polyimide in the structure of the display device 100 of FIGS. 1 to 3. The display device of Experimental Example 3 is a display device in which a back plate is made of polycarbonate in the structure of the display device 100 of FIGS. 1 to 3. In Experimental Examples 1 to 3, the material and modulus values of each of the backplates were different, and the thickness was the same as 50 μm.

In the case of the static folding item under high temperature and high humidity conditions, the display device was evaluated after fixing the display device in an out-folded state with a radius of curvature of 4R for 500 hours in an environment with a temperature of 60°C and a humidity of 90%.

In the case of the dynamic folding item under room temperature conditions, the display device was evaluated after repeatedly out-folding the display device 200K times with a radius of curvature of 4R in an environment where the temperature is at room temperature.

First, Experimental Example 1 is a case where the back plate is made of colored polyimide, and the modulus value of the back plate is about 3 GPa. In this case, when the display device of Experimental Example 1 is statically folded under a high temperature and high humidity condition or is dynamically folded under a room temperature condition, it can be confirmed that no damage or the like occurs in the display device of Experimental Example 1. In addition, in the case of colored polyimide, compared to the transparent polyimide used as the backplate of Experimental Example 2, the coefficient of thermal expansion is low, and the glass transition temperature is very high at about 380°C, so that deformation can be minimized even in a high temperature environment. Accordingly, when the colored polyimide is used as a back plate of a flexible display device such as a foldable display device or a rollable display device, damage due to the back plate may not occur.

Experimental Example 2 is a case where the back plate is made of transparent polyimide, and the modulus value of the back plate is about 6.2 GPa. That is, the backplate of Experimental Example 2 has a higher modulus value compared to the backplate of Experimental Example 1. In this case, when the display device of Experimental Example 2 is statically folded under a high-temperature, high-humidity condition, it can be seen that cracks occur in the hard coating layer disposed on one or both sides of the cover window. In particular, in the case of the transparent polyimide, the coefficient of thermal expansion is high, and the glass transition temperature is about 350°C, which may be deformed in a high temperature environment.

In addition, when the display device of Experimental Example 2 is dynamically folded under room temperature conditions, it can be confirmed that the cover window is broken. Specifically, when the display device is out-folded, tensile stress is applied to the components of the display device arranged above the neutral surface based on the neutral surface, for example, on the cover window side, and placed on the lower side of the neutral surface. Compressive stress may be applied to components of the displayed display device, for example, a back plate. In this case, as the modulus value of the back plate increases, the neutral surface may descend toward the back plate side, and tensile stress applied to the cover window side may increase. Accordingly, when a transparent polyimide having a relatively high modulus value is used as a back plate of a flexible display device, tensile stress may increase, and thus the display device may be damaged.

Experimental Example 3 is a case where the back plate is made of transparent polycarbonate, and the modulus value of the back plate is about 1.4 GPa. The backplate of Experimental Example 3 has a lower modulus value compared to the backplate of Experimental Example 1. When the display device of Experimental Example 3 is statically folded under a high temperature and high humidity condition, it can be seen that the organic emission layer of the display panel 130 is peeled off or buckling occurs in the adhesive layer 150. As described above, as the modulus value of the back plate increases, the neutral surface may descend toward the back plate side. Conversely, as the modulus value of the back plate decreases, the neutral plane may rise toward the cover window 110 side. Therefore, in the display device of Experimental Example 3 including the backplate having the lowest modulus value, the neutral plane rises and is applied to components adjacent to the backplate, for example, the display panel 130 or the adhesive layer 150. Losing compressive stress can increase. Therefore, the organic emission layer having relatively weak adhesive strength among the constituent elements of the display panel 130 may be peeled off, or buckling may occur in the adhesive layer 150 that adheres each constituent element of the display device. Accordingly, when a polycarbonate having a relatively low modulus value is used as a back plate of a flexible display device, compressive stress may increase and the display device may be damaged.

In summary, when a material having a relatively low modulus value or a high modulus value is disposed in the flexible region FA, compressive stress or tensile stress increases, and the display device 100 may be damaged. Accordingly, in the flexible region FA, a material having a modulus value in the range of 3 to 4.5 GPa, for example, a second part 142 made of colored polyimide, is disposed to minimize damage to the display device 100. At the same time, the display panel 130 can be protected from external impact, moisture, and the like.

On the other hand, although not used in Experimental Examples 1 to 3, among the transparent materials that can be used as the first part 141, the modulus value of the cycloolefin polymer is 2.2 GPa, and the modulus value of the acrylic is 1.7 GPa. When the formed first portion 141 overlaps the flexible region FA, the compressive stress may increase and the display device 100 may be damaged, similar to the display device of Experimental Example 3.

And, among the transparent materials that can be used as the first part 141, polyethylene terephthalate has a modulus value of about 3 GPa. However, since polyethylene terephthalate recovers strain, that is, plastic deformation occurs relatively easily compared to colored polyimide, when the first portion 141 made of polyethylene terephthalate is disposed in the ductile region FA, it is folded. Marks may remain, and the flatness of the display device 100 may deteriorate.

Accordingly, the first part 141 made of transparent materials having a modulus value of 3 GPa or less and 4.5 GPa or more and a low strain recovery may be disposed only in the rigid region NFA to minimize damage to the display device 100. have.

In addition, a second portion 142 made of colored polyimide having a modulus value of 3 GPa to 4.5 GPa and a low plastic deformation possibility is disposed in the flexible region FA, thereby minimizing damage to the display device 100 due to folding. have.

Meanwhile, as described above, a plurality of pad electrodes PE are disposed in the non-display area NA overlapping the rigid area NFA, and a plurality of pad electrodes PE are disposed on the plurality of pad electrodes PE through the conductive adhesive layer 170. The flexible film 160 of may be bonded to be electrically connected. In this case, the plurality of pad electrodes PE and the plurality of flexible films 160 may be electrically connected by compressing the conductive balls. Therefore, by inspecting whether a plurality of conductive balls between the plurality of pad electrodes PE and the plurality of flexible films 160 are compressed, it is possible to detect a bonding failure between the plurality of pad electrodes PE and the plurality of flexible films 160. I can.

Specifically, as the plurality of flexible films 160 and the plurality of pad electrodes PE are pressed together, the plurality of conductive balls are crushed, and indentations may be formed on the plurality of pad electrodes PE. The indentation refers to a mark pressed by a plurality of conductive balls, and not only the plurality of pad electrodes PE, but also various insulating layers under the plurality of pad electrodes PE and the substrate of the display panel 130 are formed. I can. Further, by performing an optical, that is, vision method inspection whether such an indentation exists under the display panel 130, a bonding failure between the plurality of flexible films 160 and the plurality of pad electrodes PE may be detected.

Therefore, by disposing the first portion 141 made of a transparent material in the rigid region NFA that always maintains a flat state, the indentation formed on the display panel 130 under the back plate 140 may be inspected. At this time, the transparent material forming the first part 141 may cause damage to the flexible display device 100 as described in Table 1, but the rigid region maintaining a flat state, not the flexible region FA Since it is disposed only in the (NFA), damage to the display device 100 can be minimized.

In addition, when the first part 141 is made of transparent polyimide, the price of the transparent polyimide is higher than that of the colored polyimide constituting the second part 142, so that the first part 141 made of transparent polyimide is at least By arranging so as to overlap only the plurality of pad electrodes PE, it is possible to reduce the manufacturing cost of the back plate 140.

Hereinafter, an exemplary manufacturing process of the back plate 140 of the display device 100 according to an exemplary embodiment will be described with reference to FIG. 5.

5 is a diagram illustrating a manufacturing process of a back plate of a display device according to an exemplary embodiment of the present invention.

Referring to FIG. 5, the back plate 140 may be formed by a solution casting method. In the solution casting method, a material constituting the back plate 140 is dissolved in a solvent, and then applied to the base substrate RF, dried, and cured to form the back plate 140.

First, a material constituting the back plate 140, for example, a transparent polyimide constituting the first portion 141 and a colored polyimide constituting the second portion 142, is dissolved in a solvent, and the transparent polyimide solution 41 ) And a colored polyimide solution 42 may be formed.

Subsequently, referring to FIG. 5, the polyimide solutions 41 and 42 may be applied on the substrate RF. At this time, the transparent polyimide solution 41 is applied from the first nozzle N1 disposed on the first part 141 and colored polyimide from the second nozzle N2 disposed on the second part 142 Solution 42 may be applied. That is, the first portion 141 and the second portion 142 of the back plate 140 may be formed at the same time.

Next, the solvent is removed through a drying and curing process, and only the polyimide is left on the substrate (RF), so that the first part 141 made of transparent polyimide and the second part 142 made of colored polyimide are integrated. The configured back plate 140 can be manufactured.

At this time, since the first part 141 and the second part 142 are formed at the same time, the transparent polyimide and the colored polyimide may be somewhat mixed at the interface between the first part 141 and the second part 142. . That is, the interface between the first portion 141 and the second portion 142 may be unclearly formed. However, in order to control the interface between the first portion 141 and the second portion 142, physical properties such as viscosity of the transparent polyimide solution 41 and the colored polyimide solution 42 may be adjusted. In addition, even if the interface between the first portion 141 and the second portion 142 is unclearly formed, since the interface is disposed only in the rigid region NFA, the ductility characteristics of the display device 100 may not be affected. have.

Meanwhile, in FIG. 5, it has been described that the back plate 140 is formed by a solution casting method in which a polyimide solution is applied on the substrate RF, but the material forming the back plate 140 is a spin coating method, a spray method, and a roll coating method. It may be applied in various ways such as a method, and the back plate 140 may be formed by an extrusion method, but is not limited thereto.

In the display device 100 according to the exemplary embodiment, a portion of the back plate 140 overlapping the plurality of pad electrodes PE is formed of a transparent material, thereby preventing bonding failure of the plurality of flexible films 160. It can be easily detected. The back plate 140 includes a first portion 141 and a second portion 142. The first portion 141 is a portion having a transmittance of about 90% for light in the visible wavelength band, and is a substantially transparent portion. The first portion 141 is disposed to overlap the non-display area NA in which the plurality of pad electrodes PE is formed among the rigid area NFA. In addition, a second portion 142 having a low transmittance is disposed in the remaining portions except for the first portion 141, for example, the entire flexible region FA and the remaining portion of the rigid region NFA. The plurality of pad electrodes PE are electrically connected to the plurality of flexible films 160 to transmit various signals to the display elements and circuit units of the display area AA. In this case, the plurality of pad electrodes PE and the plurality of flexible films 160 may be electrically connected by compressing a plurality of conductive balls dispersed in the conductive adhesive layer 170. In addition, a plurality of conductive balls may be pressed on the plurality of pad electrodes PE to form an indentation. Bonding defects of the plurality of flexible films 160 may be detected by optically inspecting the plurality of pad electrodes PE, the insulating layers under the plurality of pad electrodes PE, and the indentations formed even on the substrate. The first portion 141 of the back plate 140 overlapping the plurality of pad electrodes PE is formed of a transparent material, so that the indentation can be easily inspected. If the first portion 141 overlapping the plurality of pad electrodes PE is made of a material having a low transmittance, it is difficult to optically detect the indentation formed on the plurality of pad electrodes PE, and the plurality of flexible films 160 ) Bonding defects are also difficult to detect. Accordingly, in the display device 100 according to the exemplary embodiment, the first portion 141 having high transmittance is disposed on a portion of the back plate 140 overlapping the plurality of pad electrodes PE to provide a plurality of flexible films. The bonding failure of 160 can be easily detected.

In addition, in the display device 100 according to the exemplary embodiment, the first portion 141 is disposed so as to overlap only at least a plurality of pad electrodes PE, so that the manufacturing cost of the back plate 140 may be reduced. . For example, the first part 141 of the back plate 140 may be made of transparent polyimide, and the second part 142 may be made of colored polyimide. At this time, since the price of the transparent polyimide is more expensive than the price of the colored polyimide, when the back plate 140 is formed of only transparent polyimide, the manufacturing cost of the back plate 140 may increase. However, in the display device 100 according to the exemplary embodiment of the present invention, the manufacturing cost of the back plate 140 is reduced by disposing the first portion 141 with a minimum area only on at least a plurality of pad electrodes PE. can do. For example, the first portion 141 may have an area of about 5% of the total area of the back plate 140. Accordingly, in the display device 100 according to the exemplary embodiment, the first portion 141 is disposed with a minimum area to inspect the indentations of the plurality of pad electrodes PE, and the remaining portions are inexpensive. By arranging the second part 142, it is possible to reduce the manufacturing cost of the back plate 140.

In the display device 100 according to an exemplary embodiment, a portion of the back plate 140 overlapping the flexible area FA is configured as a second portion 142 made of colored polyimide, and the display device according to the folding It is possible to minimize the breakage of (100). First, in order to inspect the indentations of the plurality of pad electrodes PE, at least a portion of the back plate 140 may be formed of a first portion 141 having a high transmittance. However, in the case of a transparent material forming the first part 141, for example, transparent polyimide, polycarbonate, polyethylene terephthalate, cycloolefin polymer, or acrylic, the modulus value is too low or high. During folding, compressive stress or tensile stress applied to the display device 100 is increased. Accordingly, when the first portion 141 made of a transparent material overlaps the flexible area FA, the display device 100 may be damaged. Therefore, when the display device 100 is folded, a colored polyimide with minimal plastic deformation is disposed under the flexible area FA, without increasing compressive stress and tensile stress, thereby damaging the display device 100. Can be minimized. That is, in the display device 100 according to an embodiment of the present invention, at least a portion of the back plate 140 overlapping the flexible area FA is formed of the second portion 142 made of colored polyimide, so that it can be folded. Accordingly, damage to the display device 100 may be minimized. Accordingly, the display device 100 according to the exemplary embodiment of the present invention comprises a first material made of a transparent material in a portion of the non-display area NA overlapping the rigid area NFA to inspect the indentations of the plurality of pad electrodes PE. The display area AA overlapping the flexible area FA so as to be able to detect bonding failure of the plurality of flexible films 160 by arranging the portion 141 and not cause damage to the display device 100 due to folding. ) And the non-display area NA, the second portion 142 made of colored polyimide having excellent ductility is disposed to minimize damage to the display device 100.

6A and 6B are plan views of a back plate of a display device according to various embodiments of the present disclosure. 6A is a plan view of a back plate of a display device according to another exemplary embodiment of the present invention. 6B is a plan view of a back plate of a display device according to another exemplary embodiment of the present invention. The display device of FIGS. 6A and 6B is different from the display device 100 of FIGS. 1 to 5 in that only the first portions 641a and 641b and the second portions 642a and 642b of the backplates 640a and 640b are different. However, since the other components are substantially the same, redundant descriptions will be omitted.

Referring to FIG. 6A, a back plate 640a of a display device according to another exemplary embodiment includes a plurality of first portions 641a and second portions 642a. The first portion 641a is disposed in each of the rigid regions NFA on both sides of the flexible region FA. The first portion 641a is disposed in the non-display area NA adjacent to the short side of the display device.

A second portion 642a is disposed between the pair of first portions 641a. The second portion 642a is disposed in the entire flexible region FA and a part of the rigid region NFA. The second portion 642a is disposed in the entire display area AA and in the non-display area NA adjacent to the long side.

Referring to FIG. 6B, a back plate 640b of a display device according to another exemplary embodiment includes a plurality of first portions 641b and second portions 642b. The first portion 641b is disposed in each of the rigid regions NFA on both sides of the flexible region FA. In the rigid region NFA, the first portion 641b is disposed to surround the second portion 642b. The first portion 641b is disposed in the non-display area NA adjacent to the short side of the display panel 130 and a portion of the non-display area NA adjacent to the long side of the display panel 130.

The second portion 642b is disposed in the entire flexible region FA and a part of the rigid region NFA. The second part 642b is adjacent to the long side of the entire display area AA and the non-display area NA, and a portion of the non-display area NA overlapping the soft area FA and adjacent to the soft area FA. It is disposed in a part of the non-display area NA overlapping the rigid area NFA.

In the display device according to various embodiments of the present disclosure, the first portions 641a and 641b and the second portions 642a and 642b of the backplates 640a and 640b may be designed in various shapes. Specifically, the first portions 641a and 641b may be disposed in various shapes according to the arrangement of the plurality of flexible films 160. First, when a plurality of flexible films 160 are bonded to both short sides of the display panel 130, as shown in FIG. 6A, so as to overlap the non-display area NA disposed on both short sides of the display panel 130. The first portion 641a may be disposed. When the plurality of flexible films 160 are bonded to the short sides and part of the long sides of the display panel 130, the ratio of the non-display area NA of the short sides of the display panel 130 and the short sides as shown in FIG. 6B The first portion 641b may be disposed in a part of the non-display area NA on the long side adjacent to the display area NA. That is, only the second portions 642a and 642b are disposed in the flexible area FA, and the first portions 641a and 641b may be disposed in various shapes in the rigid area NFA excluding the flexible area FA. . Accordingly, in the display device according to various embodiments of the present disclosure, the second portions 642a and 642b are disposed in the flexible area FA, and the position of the plurality of flexible films 160 is considered to be within the rigid area NFA. The first portions 641a and 641b can be designed freely, and thus the degree of freedom in designing the display device can be increased.

A display device according to example embodiments may be described as follows.

In the display device according to an exemplary embodiment of the present invention, a display panel including a plurality of pad electrodes, and a first portion of a lower portion of the display panel overlapping the plurality of pad electrodes and the remaining portions excluding the first portion It includes a two-part backplate, and the transmittance of the first part is higher than that of the second part.

According to another feature of the present invention, the modulus value of the first portion may be higher than the modulus value of the second portion.

According to another feature of the present invention, the first part may be made of transparent polyimide, and the second part may be made of colored polyimide.

According to another feature of the present invention, the first part may have a modulus value of 5 to 7 GPa, and the second part may have a modulus value of 3 to 4.5 GPa.

According to another feature of the present invention, the modulus value of the first portion may be lower than the modulus value of the second portion.

According to another feature of the present invention, the first part is made of any one of polycarbonate (PC), polyethylene terephthalate (PET), cyclo olefin polymer (COP), or acryl. And the second part may be made of colored polyimide.

According to another feature of the present invention, the first part may have a modulus value of 3 GPa or less, and the second part may have a modulus value of 3 to 4.5 GPa.

According to another feature of the present invention, the display panel is a region other than the flexible region and the flexible region, further includes a rigid region in which a plurality of pad electrodes are disposed, at least a part of the second portion overlaps the entire flexible region, and , The first part may overlap the rigid region.

According to another feature of the present invention, the display panel further includes a display area at least partially overlapping the soft area and a non-display area at least partially overlapping the rigid area, and at least a portion of the first portion is in the non-display area. Can be nested.

According to another feature of the present invention, a conductive adhesive layer disposed on a plurality of pad electrodes and in which a plurality of conductive balls are dispersed, and a flexible film bonded to the plurality of pad electrodes through the conductive adhesive layer are further included, and the plurality of pads A mark pressed by a plurality of conductive balls may be disposed on the electrode.

In the display device according to another exemplary embodiment of the present invention, a display panel having at least a portion of which is flexible, a flexible film bonded to an upper surface of the display panel, and a first portion and a first portion disposed on a lower surface of the display panel and overlapping the flexible film are The first part may be made of a transparent material to optically inspect a connection state between the flexible film and the display panel including a back plate including a second part, which is a part other than the part.

According to another feature of the present invention, it is disposed between the display panel and the flexible film, further comprising a conductive adhesive layer including a plurality of conductive balls, and an indentation formed by crushing some of the plurality of conductive balls is disposed at one end of the display panel. Can be.

According to another feature of the present invention, the first part may be made of transparent polyimide, and the second part may be made of yellow polyimide.

According to another feature of the present invention, the coefficient of thermal expansion of the second portion may be lower than that of the first portion.

According to another feature of the present invention, the first portion may be configured to maintain a flat state, and at least a portion of the second portion may be configured to be bent together as the display panel is bent.

Although the embodiments of the present invention have been described in more detail with reference to the accompanying drawings, the present invention is not necessarily limited to these embodiments, and various modifications may be made without departing from the spirit of the present invention. . Accordingly, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention, but to explain the technical idea, and the scope of the technical idea of the present invention is not limited by these embodiments. Therefore, it should be understood that the embodiments described above are illustrative in all respects and are not restrictive. The scope of protection of the present invention should be construed by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

100: display device
110: cover window
120: polarizer
130: display panel
140, 640a, 640b: back plate
141, 641a, 641b: first part
142, 642a, 642b: second part
150: adhesive layer
160: flexible film
170: conductive adhesive layer
41: transparent polyimide solution
42: colored polyimide solution
AA: display area
NA: Non-display area
FA: soft area
NFA: rigid area
FX: folding axis
PE: pad electrode
N1: first nozzle
N2: second nozzle
RF: description

Claims (15)

A display panel including a plurality of pad electrodes; And
A back plate including a first portion under the display panel, at least partially overlapping the plurality of pad electrodes, and a second portion remaining except for the first portion,
The display device, wherein the transmittance of the first portion is higher than that of the second portion. The method of claim 1,
The display device, wherein a modulus value of the first portion is higher than a modulus value of the second portion. The method of claim 2,
The first part is made of transparent polyimide,
The second portion is a display device made of colored polyimide. The method of claim 3,
The first portion has a modulus value of 5 to 7 GPa, and the second portion has a modulus value of 3 to 4.5 GPa. The method of claim 1,
The display device, wherein a modulus value of the first portion is lower than a modulus value of the second portion. The method of claim 5,
The first part is made of any one of polycarbonate (PC), polyethylene terephthalate (PET), cyclo olefin polymer (COP), or acrylic,
The second portion is a display device made of colored polyimide. The method of claim 6,
The first portion has a modulus value of 3 GPa or less, and the second portion has a modulus value of 3 to 4.5 GPa. The method of claim 1,
The display panel is an area other than the flexible area and the flexible area, and further includes a rigid area in which the plurality of pad electrodes are disposed,
At least a portion of the second portion overlaps the entire soft region,
The first portion overlaps the rigid region. The method of claim 3,
The display panel further includes a display area at least partially overlapping the flexible area and a non-display area at least partially overlapping the rigid area,
At least a portion of the first portion overlaps the non-display area. The method of claim 1,
A conductive adhesive layer disposed on the plurality of pad electrodes and having a plurality of conductive balls dispersed therein; And
Further comprising a flexible film bonded to the plurality of pad electrodes through the conductive adhesive layer,
The display device, wherein a mark pressed by the plurality of conductive balls is disposed on the plurality of pad electrodes. A display panel that is at least partially flexible;
A flexible film bonded to an upper surface of the display panel; And
A back plate disposed on a lower surface of the display panel and comprising a first portion overlapping the flexible film and a second portion remaining excluding the first portion,
The display device, wherein the first portion is made of a transparent material to optically inspect a connection state between the flexible film and the display panel. The method of claim 11,
Further comprising a conductive adhesive layer disposed between the display panel and the flexible film and including a plurality of conductive balls,
A display device, wherein an indentation formed by partially crushing the plurality of conductive balls is disposed at one end of the display panel. The method of claim 11,
The first portion is made of transparent polyimide, and the second portion is made of yellow polyimide. The method of claim 11,
The display device, wherein the coefficient of thermal expansion of the second portion is lower than that of the first portion. The method of claim 11,
The first portion is configured to maintain a flat state, and at least a portion of the second portion is configured to be bent together as the display panel is bent.

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