DISPLAY DEVICE

A display device is provided. A display device including folding areas, the display device includes a display panel, a first protection member disposed on the display panel, a second protection member disposed on the first protection member, a first adhesive member disposed between the display panel and the first protection member, and a second adhesive member disposed between the first protection member and the second protection member and having an elastic modulus equal to or smaller than an elastic modulus of the first adhesive member.

This application claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2021-0007586 filed on Jan. 19, 2021 in the Korean Intellectual Property Office, the contents of which in its entirety are herein incorporated by reference.

BACKGROUND

1. Field of the Disclosure

The present disclosure relates to a display device.

2. Description of the Related Art

As the information-oriented society evolves, various demands for display devices are ever increasing. For example, display devices are being employed by a variety of electronic devices such as smart phones, digital cameras, laptop computers, navigation devices, and smart televisions.

Recently, a foldable display device is getting a lot of attention. A foldable display device has the advantages of both a smart phone and a tablet PC because it is easy to carry and may have a wide screen. A protective film for such a foldable display device is desirable to have high durability in order to protect the elements in the display device, and to have high flexibility for smooth folding.

SUMMARY

Aspects of the present disclosure provide a display device including a protective film that has impact resistance as well as flexibility.

It should be noted that objects of the present disclosure are not limited to the above-mentioned object; and other objects of the present disclosure will be apparent to those skilled in the art from the following descriptions.

An embodiment of a display device including folding areas, the display device includes a display panel, a first protection member disposed on the display panel, a second protection member disposed on the first protection member, a first adhesive member disposed between the display panel and the first protection member, and a second adhesive member disposed between the first protection member and the second protection member and having an elastic modulus equal to or smaller than an elastic modulus of the first adhesive member.

An embodiment of a display device including a first folding area and a second folding area spaced apart from each other and extended in a first direction, the display device includes a display panel, a first protection member disposed on the display panel, a second protection member disposed on the first protection member and having a storage modulus increasing with a frequency of an external impact applied to the second protection member, a first adhesive member disposed between the display panel and the first protection member, and a second adhesive member disposed between the first protection member and the second protection member, wherein the display device is folded inward along the first folding area and folded outward along the second folding area.

An embodiment of a display device including a first folding area and a second folding area spaced apart from each other and extended in a first direction, the display device includes a display panel, a first protection member disposed on the display panel, a second protection member disposed on the first protection member, a first adhesive member disposed between the display panel and the first protection member, and a second adhesive member disposed between the first protection member and the second protection member, wherein a storage modulus of the first protection member lies in a range of from 1,000 MPa to 2,000 MPa at −20° C., and in a range of from 100 MPa to 2,000 MPa at 85° C.

According to an embodiment of the present disclosure, a protective film of a display device may have impact resistance as well as flexibility.

It should be noted that effects of the present disclosure are not limited to those described above and other effects of the present disclosure will be apparent to those skilled in the art from the following descriptions.

DETAILED DESCRIPTION OF THE EMBODIMENTS

It will also be understood that when a layer is referred to as being “on” another layer or substrate, it may be directly on the other layer or substrate, or intervening layers may also be present. The same reference numbers indicate the same components throughout the specification. In the attached figures, the thickness of layers and regions is exaggerated for clarity.

FIG. 1is a perspective view of a display device according to an embodiment of the present disclosure when it is unfolded.FIG. 2is a perspective view of the display device according to the embodiment of the present disclosure when it is folded. According to the embodiment shown inFIG. 2, the display device1is folded inward along a first folding area FDA1and is folded outward along a second folding area FDA2.

Referring toFIGS. 1 and 2, a display device1according to the embodiment of the present disclosure displays images or videos in a display area DA to be described later, and may include a variety of devices including the display area DA. For example, the display device1according embodiments of the present disclosure may be applied to a mobile phone, a tablet PC, a personal digital assistant (PDA), a portable multimedia player (PMP), a television set, a game machine, a wristwatch-type electronic device, a head-mounted display, a personal computer monitor, a laptop computer, a car navigation system, a car instrument cluster, a digital camera, a camcorder, an outdoor billboard, an electronic billboard, various medical apparatuses, various home appliances such as a refrigerator and a laundry machine, Internet of things (IoT) devices, etc., in addition to a smart phone.

The display device1includes a display area DA and a non-display area NDA. The display area DA may be defined as an area for displaying images. The display area DA may include a plurality of pixels. The plurality of pixels may be arranged in a matrix. No image may be displayed in the non-display area NDA. When the display device1has touch features, the display device1may further include a touch area where a touch input is sensed, and the touch area may overlap with the display area DA. Although not limited thereto, the touch area may be substantially identical to the display area DA.

The shape of the display area DA may conform to the shape of the display device1employing the display area DA. The display area DA may have a rectangular shape having corners at the right angle or rounded corners when viewed from the top. It is to be understood that the shape of the display area DA when viewed from the top is not limited to the rectangle shown in the drawings, but may have other shapes such as a circle and an ellipse.

In the example shown in the drawings, the shorter sides of the rectangle of the display area DA are extended in the first direction DR1, and the longer sides thereof are extended in a second direction DR2perpendicular to the first direction DR1. A third direction DR3is perpendicular to the first direction DR1as well as the second direction DR2, and may refer to the thickness direction of the display device1. It should be understood that the directions referred to in the embodiments are relative directions, and the embodiments are not limited to the directions mentioned.

As used herein, the terms “top”, “upper surface” and “upper side” in the third direction DR3refer to the display side of a display panel10, whereas the terms “bottom”, “lower surface” and “lower” refer to the opposite side of the display panel10, unless stated otherwise.

The non-display area NDA may surround the display area DA. The non-display area NDA may surround all sides of the display area DA, but the present disclosure is not limited thereto. The non-display area NDA may not be disposed near at least some of the four sides of the display area DA. The bezel area of the display device1may be formed as the non-display area NDA.

The display device1may be a foldable display device. As used herein, a foldable display device refers to a display device that is folded and has both a folded state and an unfolded state. When folded, the device is typically folded at an angle of approximately 180°. It is, however, to be understood that the present disclosure is not limited thereto. For example, when a device is folded at an angle greater than or less than 180°, e.g., at an angle of 90° or more but less than 180° or an angle of 120° or more and less than 180°, the device is also referred to as being folded. In addition, even when not completely folded, the device may be referred to as being folded if the device is not unfolded but is bent somewhat. For example, even if bent at an angle of 90 degrees or less, the device may be referred to as being folded in order to distinguish it from being unfolded as long as the maximum folding angle is 90 degrees or more.

The display device1may include folding areas FDA: FDA1and FDA2(or folding lines). The folding areas FDA may include a first folding area FDA1and a second folding area FDA2separated and spaced apart from each other. The first folding area FDA1may be disposed on one side of the second folding area FDA2in the second direction DR2.

Each of the folding areas FDA may be extended in a direction parallel to one side of the display device1. For example, each of the folding areas FDA may be extended in a direction in which the shorter sides of the display device1are extended (first direction DR1). In the display device1in a rectangular shape having the sides extended in the second direction DR2longer than the sides extended in the first direction DR1, when the folding areas FDA are extended in the first direction DR1as in the example shown in the drawings, the longer sides (the sides extended in the second direction DR2) of the display device1may be reduced to half or less while the shorter sides (the sides extended in the first direction DR1) may remain the same after the display device1has been folded. In an embodiment, the folding areas FDA may be extended in the same direction (the second direction DR2) as the direction of the longer sides (the sides extended in the second direction DR2).

Each of the folding areas FDA may have a predetermined width in the second direction DR2. The width of each of the folding areas FDA in the second direction DR2may be smaller than the width thereof in the first direction DR1.

The display device1may be folded over the folding areas FDA. The design of a foldable display device may be sorted into in-folding design in which the display surface of the display device1is folded inward, and out-folding design in which the display surface thereof is folded outward. The display device1may have either the in-folding design or the out-folding design, or may have in-and-out-folding design. For a display device having the in-and-out-folding design, the device may be folded inward and outward along the same folding area FDA or may be folded inward and outward along different folding areas, respectively. According to the embodiment shown inFIG. 2, the display device1is folded inward along the first folding area FDA1and is folded outward along the second folding area FDA2.

The display device1may include non-folding areas NFA disposed near the folding areas FDA. The non-folding areas NFA may include a first non-folding area NFA1located on one side of the first folding area FDA1in the second direction DR2, a second non-folding area NFA2located on the opposite side of the first folding area FDA1in the second direction DR2, and a third non-folding area NFA3located on the opposite side of the second folding area FDA2in the second direction DR2. The second non-folding area NFA2may be disposed between the first folding area FDA1and the second folding area FDA2. The first non-folding area NFA1may be disposed on one side of the second non-folding area NFA2in the second direction DR2with the first folding area FDA1therebetween. The third non-folding area NFA3may be disposed on the opposite side of the second non-folding area NFA2in the second direction DR2with the second folding area FDA2therebetween.

The first non-folding area NFA1, the second non-folding area NFA2and the third non-folding area NFA3may have the same width in the second direction DR2. Depending on the positions of the folding areas FDA, the width of the first non-folding area NFA1in the second direction DR2, the width of the second non-folding area NFA2in the second direction DR2, and the width of the third non-folding area NFA3in the second direction DR2may be different from one another.

The display area DA and the non-display area NDA of the display device1may overlap the folding areas FDA and the non-folding areas NFA at the same locations. For example, a part of the display area DA may be in the non-folding area NFA, and another part of the display area DA may be in the folding area FA. For example, a part of the non-display area NDA may be in the non-folding area NFA, and another part of the non-display area NDA may be in the folding area FA. For example, a certain location of the display area DA may be in the first non-folding area NFA1. Another location of the non-display area NDA may be in the first non-folding area NFA1. Another location of the display area DA may be in the folding areas FDA.

The display area DA may be disposed across all of the first non-folding area NFA1, the second non-folding area NFA2, and the third non-folding area NFA3. The display area DA may also be located at the first folding area FDA1which is disposed between the first non-folding area NFA1and the second non-folding area NFA2, and at the second folding area FDA2which is disposed between the second non-folding area NFA2and the third non-folding area NFA3. The display area DA of the display device1may be continuously disposed irrespective of the boundaries between the non-folding areas NFA and the folding lines FDA, etc. It is, however, to be understood that the present disclosure is not limited thereto. The display area DA may be located only at one of the first non-folding area NFA1, the second non-folding area NFA2and the third non-folding area NFA3, or the display area DA may be disposed in the first non-folding area NFA1, the second non-folding area NFA2and the third non-folding area NFA3but not in the folding areas FDA.

FIG. 3is a cross-sectional view of a display device according to an embodiment of the present disclosure when the display device is unfolded.FIG. 4is an enlarged view of area A ofFIG. 3.FIG. 5is a cross-sectional view of a display device according to an embodiment when the display device is folded inward at the first folding area.FIG. 6is an enlarged view of area B ofFIG. 5.FIG. 7is a cross-sectional view of the display device according to the embodiment when the display device is folded outward at the second folding area.

Referring toFIGS. 3 to 7, the display device1may include a display panel10, an anti-reflection member20, a first adhesive member PSA1, a first protection member30, a second adhesive member PSA2, and a second protection member40sequentially stacked on one side of the display panel10in the thickness direction (the third direction DR3). The display device1may further include a polymer film layer FL, a cushion layer CU, and a heat dissipation member HP sequentially stacked on the opposite side of the display panel10in the thickness direction (the third direction DR3). It is, however, to be understood that the present disclosure is not limited thereto. Another layer may be further disposed between the layers, and some of the elements stacked on one another may be eliminated. Not only between the anti-reflection member20and the first protection member30and between the first protection member30and the second protection member40, but also between the elements stacked on one another, at least one coupling member such as an adhesive layer and a detachable layer may be disposed to couple the adjacent elements stacked on one another.

The display panel10displays images or videos. Examples of the display panel10may include a self-luminous display panel such as an organic light-emitting display panel, an inorganic light-emitting display panel, a quantum-dot light-emitting display panel, a micro LED display panel, a nano LED display panel, a plasma display panel, a field emission display panel and a cathode ray display panel, as well as a light-receiving display panel such as a liquid-crystal display panel and an electrophoretic display panel. In the following description, the organic light-emitting display panel will be described as an example of the display panel10, and the organic light-emitting display panel will be referred to as the display panel300unless specifically stated otherwise. It is, however, to be understood that the embodiments of the present disclosure are not limited to the organic light-emitting display panel, and any other display panel listed above or well known in the art may be employed without departing from the scope of the present disclosure. The structure of the display panel10will be described in more detail later.

The anti-reflection member20may be disposed on the display panel10. The anti-reflection member20may reduce reflection of external light. The anti-reflection member20may be implemented as a polarizing film. The anti-reflection member20polarizes the light passing therethrough. It is, however, to be understood that the present disclosure is not limited thereto. The anti-reflection member20may be implemented as a color filter layer in the display panel10.

The first protection member30may be disposed above the anti-reflection member20. The first protection member30serves to cover and protect the display panel10. The first protection member30may have flexibility and thus may be curved, bent, folded, or rolled. The first protection member30may include or may be formed of polyether block amide (PEBA). It is, however, to be understood that the present disclosure is not limited thereto. The first protection member30may include or may be formed of at least one selected from the group consisting of: polyurethane, silicone, pentaerythritol triacrylate (PETA), and copolyester elastomers (COPE).

The first protection member30may be made of a transparent material. The first protection member30may include or may be formed of, for example, glass or plastic. When the first protective member30includes or is formed of glass, the glass may be ultra thin glass (UTG) or thin glass. When the first protection member30includes or is formed of plastic, the plastic may be, but is not limited to, a transparent polyimide.

The storage modulus of the first protection member30may be greater than 0 MPa (megapascal) and equal to or less than 9,000 MPa at −20° C. In some embodiments, the storage modulus of the first protection member30may be in the range of from 25 MPa to 5,000 MPa at −20° C. In some embodiments, the storage modulus of the first protection member30may be in the range of from 25 MPa to 2,000 MPa at −20° C. In some embodiment, the storage modulus of the first protection member30may be in the range of from 1,000 MPa to 2,000 MPa at −20° C. The storage modulus of the first protection member30may be in the range of from 100 MPa to 9,000 MPa at 85° C. In some embodiments, the storage modulus of the first protection member30may be in the range of from 100 MPa to 5,000 MPa at 85° C. In some embodiments, the storage modulus of the first protection member30may be in the range of from 100 MPa to 2,000 MPa at 85° C. In some embodiments, the storage modulus of the first protection member30may be in the range of from 1,000 MPa to 2,000 MPa at 85° C.

When the storage modulus of the first protection member30satisfies the above ranges, the display device1may have sufficient flexibility even when the display device1is folded inward at the first folding area FDA1and is folded outward at the second folding area FDA2, facilitating in-folding of the display device1as well as out-folding thereof.

The storage modulus of the first protection member30may be measured by, but is not limited to, dynamic mechanical analysis (DMA).

The first protection member30may have a second thickness TH2. For example, the second thickness TH2may refer to the thickness in the thickness direction (the third direction DR3) of the first protection member30, and the first protection member30has the second thickness TH2. The second thickness TH2may be, but is not limited to, in the range of from 0.01 μm to 400 μm. In some embodiment, the second thickness TH2may be in the range of from 0.1 μm to 100 μm. In some embodiment, the second thickness TH2may be in the range of from 1 μm to 40 μm.

The first adhesive member PSA1may be disposed between the first protection member30and the anti-reflection member20. The first protection member30and the anti-reflection member20may be attached together by the first adhesive member PSA1. The first adhesive member PSA may include, but is not limited to, a pressure sensitive adhesive or an adhesive. The first adhesive member PSA1may be optically transparent.

The first adhesive member PSA1may have a first thickness TH1. For example, the first thickness TH1may refer to the thickness of the first adhesive member PSA1in the thickness direction (the third direction DR3), and the first adhesive member PSA1may have the first thickness TH1. The first thickness TH1may be, but is not limited to, in the range of from 0.01 μm to 100 μm. In some embodiments, the first thickness TH1may be in the range of from 0.1 μm to 50 μm. In some embodiments, the first thickness TH1may be in the range of from 1 μm to 25 μm.

The second protection member40may be disposed above the first protection member30. The second protection member40may serve to protect the display panel10together with the first protection member30. The second protection member40may have flexibility and thus may be curved, bent, folded, or rolled.

The second protection member40may include or may be formed of a polymer film. The second protection member40may include or may be formed of at least one selected from the group consisting of: polyethylene terephthalate (PET), tri-acetyl cellulous (TAC), transparent polyimide, and aramid.

When the display device1is folded inward at the first folding area FDA1, the display device1may be folded along the first folding axis RX1. When the display device1is folded inward at the first folding area FDA1, a first radius of curvature R1of the second protection member40at the first folding area FDA1may be, for example, in the range of from 0.01 mm to 5.0 mm, or in the range of from 0.1 mm to 1.0 mm. It is, however, to be understood that the present disclosure is not limited thereto. The first radius of curvature R1may refer to a radius of curvature formed by the inner surface of the second protection member40at the first folding area FDA1when the display device1is folded inward at the first folding area FDA1. The first radius of curvature R1may be refer to a radius of curvature formed by the upper surface of the second protection member40disposed on the inner side when the display device1is folded inward as shown inFIGS. 4 and 5.

When the display device1is folded outward at the second folding area FDA2, the display device1may be folded along the second folding axis RX2. When the display device1is folded outward at the second folding area FDA2, a second radius of curvature R2of the second protection member40at the second folding area FDA2may be, for example, in the range of from 0.01 mm to 10.0 mm, or in the range of from 0.1 mm to 4.0 mm. It is, however, to be understood that the present disclosure is not limited thereto. The second radius of curvature R2of the second protection member40may be greater than the first radius of curvature R1. The second radius of curvature R2may refer to a radius of curvature formed by the outer surface of the second protection member40at the second folding area FDA2when the display device1is folded outward at the second folding area FDA2. The second radius of curvature R2may be refer to a radius of curvature formed by the upper surface of the second protection member40disposed on the outer side when the display device1is folded outward as shown inFIG. 6.

The second protection member40may have a fourth thickness TH4. For example, the fourth thickness TH4may refer to the thickness in the thickness direction (the third direction DR3) of the second protection member40, and the second protection member40has the fourth thickness TH4. The fourth thickness TH4of the second protection member40may be greater than the second thickness TH2of the first protection member30, but is not limited to such. The fourth thickness TH4may be, but is not limited to, in the range of from 0.01 μm to 500 μm, in the range of from 0.1 μm to 100 μm, or in the range of from 1 μm to 50 μm.

The second protection member40includes or is formed of a material having a storage modulus that varies according to an external impact, and thus the modulus of the second protection member40may vary according to an external impact. When the display device1is folded inward as well as outward, the modulus of the second protection member40may vary according to an external impact, and thus, both flexibility and impact resistance may be obtained.

FIG. 8is a graph showing a relationship between the storage modulus of the second protection member40and external impact according to an embodiment. The horizontal axis (x-axis) of the graph shown inFIG. 8represents the frequency (Hz) of a sinusoidal load applied as the external impact to the second protection member40, and the vertical axis (y-axis) represents the storage modulus.

Referring toFIG. 8, the storage modulus of the second protection member40may vary according to the frequency. The storage modulus of the second protection member40may increase as the frequency increases.

In the graph of the storage modulus of the second protection member40according to the frequency of the second protection member40, the slope may be changed with respect to the frequency of 1 Hz. For example, the slope in the graph of the storage modulus of the second protection member40according to the frequency of the second protection member40is greater when the frequency is greater than 1 Hz than when the frequency is less than 1 Hz. The storage modulus of the second protection member40increases as the frequency of the external impact applied to the second protection member40increases, and the storage modulus may increase more according to the increase in frequency when the frequency is greater than 1 Hz than when the frequency is less than 1 Hz.

At a frequency which is equal to or greater than 1 Hz, it may be regarded that an external impact is applied to the second protection member40. When an external impact with a frequency of 1 Hz or more is applied to the second protection member40, the storage modulus may increase, and the larger the external impact is, the more the storage modulus of the second protection member40may increase.

For example, when the frequency of the external impact applied to the second protection member40is 1 Hz, the storage modulus of the second protection member40may be greater than 6 gigapascal (GPa). When the frequency of the external impact applied to the second protection member40is 30,000 Hz, the storage modulus of the second protection member40may be greater than 8 GPa. Specifically, when the frequency of the external impact applied to the second protection member40is 1 Hz, the storage modulus of the second protection member40may be in the range of from 6 GPa to 1,000 GPa, or may be in the range of from 6 GPa to 100 GPa. When the frequency of the external impact applied to the second protection member40is 30,000 Hz, the storage modulus of the second protection member40may be in the range of from 8 GPa to 1,000 GPa, or may be in the range of from 8 GPa to 100 GPa. It is, however, to be understood that the storage modulus of the second protection member40is not limited thereto.

Even if an external impact is applied to the second protection member40and the storage modulus has increased, after the impact is gone, the storage modulus of the second protection member40may be restored to the original value before the external impact was applied. It is, however, to be understood that the present disclosure is not limited thereto.

The storage modulus according to the frequency of the second protection member40may be measured by dynamic mechanical analysis (DMA), but the present disclosure is not limited thereto.

As the storage modulus of the second protection member40increases due to an external impact, the second protection member40may have both flexibility and impact resistance against external impact. For example, when the display device1is folded inward at the first folding area FDA1, the second protection member40may have flexibility at the first folding area FDA with a relatively low modulus. At the same time, when the display device1is folded outward at the second folding area FDA2and an external impact is applied to that area, the storage modulus may increase and impact resistance may be obtained in that area. Accordingly, even though the display device1is folded inward and outward, the second protection member40may have both flexibility and impact resistance.

Referring again toFIGS. 3 to 7, the second adhesive member PAS2may be disposed between the second protection member40and the first protection member30. The second protection member40and the first protection member30may be attached together by the second adhesive member PSA2. The second adhesive member PSA2may include or may be formed of, but is not limited to, a pressure sensitive adhesive or an adhesive. The second adhesive member PSA2may include or may be formed of, but is not limited to, the same material as the first adhesive member PSA1. The second adhesive member PSA2may be optically transparent.

The second adhesive member PSA2may have a third thickness TH3. For example, the third thickness TH3may refer to the thickness of the first adhesive member PSA1in the thickness direction (the third direction DR3), and the second adhesive member PSA2may have the third thickness TH3. The third thickness TH3may be substantially equal to the first thickness TH1of the first adhesive member PSA1, but the present disclosure is not limited thereto.

The elastic modulus of the second adhesive member PSA2may be equal to or smaller than the elastic modulus of the first adhesive member PSA1. Although not limited thereto, for example, the elastic modulus of the first adhesive member PSA1may be greater than 0 kPa (kilopascal) and less than 1,500 kPa at −20° C. In some embodiment, the elastic modulus of the first adhesive member PSA1may be greater than 0 kPa and less than 750 kPa at −20° C. In some embodiment, the elastic modulus of the first adhesive member PSA1may be greater than 0 kPa and less than 150 kPa at −20° C. The elastic modulus of the second adhesive member PSA2may be greater than 0 kPa (kilopascal) and less than 1,000 kPa −20° C. In some embodiment, the elastic modulus of the second adhesive member PSA2may be greater than 0 kPa and less than 500 kPa −20° C. In some embodiment, the elastic modulus of the second adhesive member PSA2may be greater than 0 kPa and less than 100 kPa at −20° C.

When the elastic modulus of the first adhesive member PSA1and the elastic modulus of the second adhesive member PSA2are within the above ranges, and the elastic modulus of the second adhesive member PSA2is equal to or less than that of the first adhesive member PSA1, it is possible to have the impact resistance in the out-folding area while having flexibility in the in-folding area even when the display device1is folded inward and outward at the different areas. In other words, as the second adhesive member PSA2having a relatively small elastic modulus is disposed between the first protection member30and the second protection member40, the impact resistance against external impact may be improved. As the first adhesive member PSA1having a relatively large elastic modulus is disposed between the anti-reflection member20and the first protection member30, the flexibility may be improved.

Tables 1 and 2 show the folding strains of the first protection member30and the second protection member40measured at the time of in-folding according to the elastic modulus of the first adhesive member PSA1and the elastic modulus of the second adhesive member PSA2at −20° C. and 85° C., respectively. The thickness of the second protection member40is 50 μm, and the second protection member40includes or is formed of optically transparent polyimide. Further, the thickness of the first protection member30is 75 μm, and the first protection member30includes or is formed of pentaerythritol triacrylate (PETA).

In Table 1, each of the elastic modulus of the first adhesive member PSA1and the elastic modulus of the second adhesive member PSA2is measured by a universal testing machine (UTM) at −20° C. In Table 2, each of the elastic modulus of the first adhesive member PSA1and the elastic modulus of the second adhesive member PSA2is measured by a universal testing machine (UTM) at −85° C.

When the folding strain (%) of the second protection member40is less than or equal to 2.3%, and the folding strain (%) of the first protection member30is equal to or less than 7.0%, the folding characteristics may be maintained, and the mechanical stability of the display device1may be maintained no matter how many times the second protection member40is repeatedly folded. In other words, when the folding strain of the second protection member40and the folding strain of the first protection member30are within the above ranges, it is possible to suppress or prevent the deterioration of the folding performance of the first protection member30and the second protection member40no matter how many times the display device1is repeatedly folded.

When the folding strain of the second protection member40and the folding strain of the first protection member30are within the above ranges, it is possible to suppress or prevent defects such as buckling between adjacent layers stacked on one another.

In Examples 1 to 10, the elastic modulus of the second adhesive member PSA2is less than 150 kPa, the elastic modulus of the first adhesive member PSA1is less than 100 kPa, and the elastic modulus of the second adhesive member PSA2is equal to or smaller than the elastic modulus of the adhesive member PSA1. In Comparative Examples 1 to 8, the elastic modulus of the second adhesive member PSA2is less than 150 kPa, the elastic modulus of the first adhesive member PSA1is less than 100 kPa, and the elastic modulus of the second adhesive member PSA2is greater than the elastic modulus of the adhesive member PSA1.

Comparing Examples to Comparative Examples, when the elastic modulus of the second adhesive member PSA2is less than 150 kPa, the elastic modulus of the first adhesive member PSA1is less than 100 kPa, and the elastic modulus of the second adhesive member PSA2is equal to or smaller than the elastic modulus of the adhesive member PSA1, the folding strain of the second protection member40and the folding strain of the first protection member30are reduced more than when the elastic modulus of the second adhesive member PSA2is greater than that of the first adhesive member PSA1. Accordingly, the folding performance of the first protection member30and the second protection member40may be maintained more reliably. In addition, when the folding strain of the second protection member40and the folding strain of the first protection member30are reduced, it is possible to suppress or prevent defects such as buckling between adjacent layers stacked on one another more effectively.

In the Examples, when the elastic modulus of the second adhesive member PSA2is smaller than that of the first adhesive member PSA1, the folding strain of the second protection member40and the folding strain of the first protection member30are reduced more when the elastic modulus of the second adhesive member PSA2is equal to that of the first adhesive member PSA1.

Although not shown in the drawings, a hard coating layer may be further disposed on the second protection member40. The hard coating layer may protect the surface of the second protection member40. For example, the hard coating layer may perform at least one of functions of anti-scattering when the second protection member40is broken, shock absorption, anti-scratch, anti-fingerprint, and anti-glare.

The polymer film layer FL may be disposed under the display panel10. The polymer film layer FL may include or may be formed of, for example, polyimide (PI), polyethylene terephthalate (PET), polycarbonate (PC), polyethylene (PE), polypropylene (PP), polysulfone (PSF), polymethyl methacrylate (PMMA), triacetyl cellulose (TAC), or cycloolefin polymer (COP). The polymer film layer FL may include a functional layer on at least one surface. The functional layer may include or may be formed of, e.g., a light-absorbing layer. The light-absorbing layer may include or may be formed of a light-absorbing material such as a black pigment and dye. The light-absorbing layer may be formed on a polymer film by coating or printing a black ink.

The cushion layer CU may be disposed under the polymer film layer FL. The cushion layer CU may increase durability against impacts that may be exerted in the thickness direction (third direction DR3) of the display device1, and may mitigate impact on the display device1when it is dropped. The cushion layer CU may include or may be formed of polyurethane or the like.

The heat dissipation member HP may be disposed under the polymer film layer FL. The heat dissipation member HP serves to diffuse heat generated from the display panel10or other elements of the display device1. The heat dissipation member HP may include a metal plate. The metal plate may include or may be formed of, for example, metal having excellent thermal conductivity such as copper and silver. The heat dissipation member HP may include a heat dissipation sheet including graphite, carbon nanotubes, etc.

In order to facilitate folding of the display device1, some layers of the display device1may be separated into individual ones at the folding area FDA. For example, the heat dissipation member HP forming the bottom layer of the display device1and having a small flexibility may be separated into two individual heat dissipation members disposed at the first folding area FDA1and the second folding area FDA2, respectively.

For example, each of the cushion layer CU and the polymer film layer FL may also be separated into two individual ones at the first folding area FDA1and the second folding area FDA2, respectively. However, if they have enough flexibility, they may be continuously extended on the folding areas FDA and the non-folding areas NFA.

When the display device1is folded inward along the first folding area FDA1as shown inFIG. 5, the second non-folding area NFA2may overlap the first non-folding area NFA1in the thickness direction. When the display device1is folded outward along the second folding area FDA2as shown inFIG. 7, the second non-folding area NFA2may overlap the third non-folding area NFA3in the thickness direction.

Unlike the separated heat dissipation member HP, the display panel10, the polymer film layer FL, cushion layer CU, the anti-reflection member20, the first protection member30and the second protection member40, which are continuous example regardless of the folding areas FDA, may be curved along the width direction of the first folding area FDA1and the second folding area FDA2to form a curve in the cross section.

Hereinafter, a stack structure of the display panel10according to an embodiment will be described in detail with reference toFIG. 9.

FIG. 9is a cross-sectional view of a display panel according to an embodiment of the present disclosure.

Referring toFIG. 9, the display panel10according to an embodiment of the present disclosure may include a plurality of pixels. Each of the pixels may include at least one thin-film transistor TR. The display panel10may include a substrate SUB, a barrier layer110, a buffer layer120, a semiconductor layer130, a first insulating layer ILL a first gate conductive layer140, a second insulating layer IL2, a second gate conductive layer150, a third insulating layer IL3, a data conductive layer160, a via layer VIA, an anode electrode ANO, a pixel-defining layer PDL defining an opening OP exposing the anode electrode ANO, a spacer SC disposed on the pixel-defining layer PDL, an emissive layer EML at least partially disposed in the opening OP of the pixel-defining layer PDL, a cathode electrode CAT disposed on the emissive layer EML and the pixel-defining layer PDL, and an encapsulation layer ENL disposed on the cathode electrode CAT. Each of the layers described above may be made up of a single film, or a stack of multiple films. Other layers may be further disposed between the layers.

The substrate SUB supports the layers disposed thereon. The substrate SUB may be made of an insulating material such as a polymer resin. Examples of the polymer material may include polyethersulphone (PES), polyacrylate (PA), polyacrylate (PAR), polyetherimide (PEI), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), polyallylate, polyimide (PI), polycarbonate (PC), cellulose triacetate (CAT), cellulose acetate propionate (CAP) or a combination thereof. It is, however, to be understood that the present disclosure is not limited thereto. The substrate SUB may be a transparent plate or a transparent film.

The substrate SUB may be a flexible substrate that may be bent, folded, or rolled. An example of the material of the flexible substrate may be, but is not limited to, polyimide (PI).

The barrier layer110is disposed on the substrate SUB. The barrier layer110may prevent impurity ions from diffusing, may prevent permeation of moisture or outside air, and may provide a flat surface. The barrier layer110may include or may be formed of at least one of silicon oxide (SiOx), silicon nitride (SiNx), and silicon oxynitride (SiOxNy). It is, however, to be understood that the present disclosure is not limited thereto. The barrier layer110may be eliminated depending on the type of the substrate SUB or process conditions.

The buffer layer120is disposed on the barrier layer110. The buffer layer120may prevent impurity ions from diffusing, may prevent permeation of moisture or outside air, and may provide a flat surface. The buffer layer120may include or may be formed of silicon nitride (SiNx), silicon oxide (SiOx), or silicon oxynitride (SiOxNy). The buffer layer120may be eliminated depending on the type of the substrate SUB, process conditions, etc.

The semiconductor layer130is disposed on the buffer layer120. The semiconductor layer130forms the channel of the thin-film transistor TR of the pixel. The semiconductor layer130may include or may be formed of polycrystalline silicon. It is, however, to be understood that the present disclosure is not limited thereto. The semiconductor layer130may include or may be formed of at least one of monocrystalline silicon, low-temperature polycrystalline silicon, amorphous silicon, and an oxide semiconductor. Alternatively, the semiconductor layer130may include or may be formed of an oxide semiconductor. For example, the oxide semiconductor may include or may be formed of at least one of indium-gallium-zinc oxide (IGZO), zinc-tin oxide (ZTO), indium-tin oxide (IZO), etc.

The first insulating layer IL1is disposed on the semiconductor layer130. The first insulating layer IL1may be a first gate insulating film that has a gate insulating features. The first insulating layer IL1may include or may be formed of at least one of a silicon compound and a metal oxide.

The first gate conductive layer140is disposed on the first insulating layer ILL The first gate conductive layer140may include a gate electrode GAT of the thin-film transistor TR of the pixel, a scan line connected thereto, and a first electrode CE1of a storage capacitor.

The first gate conductive layer140may include or may be formed of at least one metal selected from the group consisting of: molybdenum (Mo), aluminum (Al), platinum (Pt), palladium (Pd), silver (Ag), magnesium (Mg), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), calcium (Ca), titanium (Ti), tantalum (Ta), tungsten (W), and copper (Cu).

A second insulating layer IL2may be disposed on the first gate conductive layer140. The second insulating layer IL2may be an interlayer dielectric layer or a second gate insulating layer. The second insulating layer IL2may include or may be formed of an inorganic insulating material such as silicon oxide, silicon nitride, silicon oxynitride, hafnium oxide, aluminum oxide, titanium oxide, tantalum oxide, and zinc oxide.

The second gate conductive layer150is disposed on the second insulating layer IL2. The second gate conductive layer150may include a second electrode CE2of the storage capacitor. The second gate conductive layer150may include or may be formed of at least one metal selected from the group consisting of: molybdenum (Mo), aluminum (Al), platinum (Pt), palladium (Pd), silver (Ag), magnesium (Mg), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), calcium (Ca), titanium (Ti), tantalum (Ta), tungsten (W) and copper (Cu). The second gate conductive layer150may be made of, but is not limited to, the same material as the first gate conductive layer140.

The third insulating layer IL3is disposed on the second gate conductive layer150. The third insulating layer IL3may be an interlayer dielectric film. The third insulating layer IL3may include or may be formed of an inorganic insulating material such as silicon oxide, silicon nitride, silicon oxynitride, hafnium oxide, aluminum oxide, titanium oxide, tantalum oxide, and zinc oxide.

The data conductive layer160is disposed on the third insulating layer IL3. The data conductive layer160may include a first electrode SD1and a second electrode SD2of a thin-film transistor TR of a pixel, and a first voltage line ELVDDE of the display panel. The first electrode SD1and the second electrode SD2of the thin-film transistor TR may be electrically connected to the source region and the drain region of the semiconductor layer130, respectively, through contact holes passing through the third insulating layer IL3, the second insulating layer IL2and the first insulating layer ILL The first supply voltage line ELVDDE may be electrically connected to the second electrode CE2of the storage capacitor through a contact hole penetrating through the third insulating layer IL3.

The data conductive layer160may include or may be formed of at least one metal selected from the group consisting of: aluminum (Al), molybdenum (Mo), platinum (Pt), palladium (Pd), silver (Ag), magnesium (Mg), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), calcium (Ca), titanium (Ti), tantalum (Ta), tungsten (W), and copper (Cu). The data conductive layer160may be made up of a single layer or multiple layers. For example, the data conductive layer160may have a stack structure of Ti/Al/Ti, Mo/Al/Mo, Mo/AlGe/Mo, or Ti/Cu.

The via layer VIA (or a planarization layer) is disposed on the data conductive layer160. The via layer VIA covers the data conductive layer160. The via layer VIA may include or may be formed of an organic insulating material. When the via layer VIA includes an organic material, it may have a flat upper surface despite the level differences thereunder.

The anode electrode ANO is disposed on the via layer VIA. The anode electrode ANO may be disposed on a surface VIAa of the via layer VIA. The anode electrode ANO may be a pixel electrode disposed in each of the pixels. The anode electrode ANO may be connected to the second electrode SD2of the thin-film transistor TR through a contact hole CNT penetrating the via layer VIA. The anode electrode ANO may at least partially overlap the emission area EMA of the pixel.

The anode electrode ANO may have, but is not limited to, a stack structure of a material layer having a high work function such as indium-tin-oxide (ITO), indium-zinc-oxide (IZO), zinc oxide (ZnO) and indium oxide (In2O3), and a reflective material layer such as silver (Ag), magnesium (Mg), aluminum (Al), platinum (Pt), lead (Pb), palladium (Pd), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), lithium (Li), calcium (Ca) or a mixture thereof. A layer having a higher work function may be disposed on a higher layer than a reflective material layer so that it may be closer to the emissive layer EML. The anode electrode ANO may have, but is not limited to, a multilayer structure of ITO/Mg, ITO/MgF, ITO/Ag, or ITO/Ag/ITO.

The pixel-defining layer PDL may be disposed on the anode electrode ANO. The pixel-defining layer PDL may be disposed over the anode electrode ANO and may include an opening OP exposing the anode electrode ANO. The opening OP may be defined by the pixel-defining layer PDL, and may penetrate the pixel-defining layer PDL in the thickness direction. The emission area EMA and the non-emission area NEM may be distinguished by the pixel-defining layer PDL and the opening OP thereof. The pixel-defining layer PDL may include or may be formed of an organic insulating material. It is, however, to be understood that the present disclosure is not limited thereto. The pixel-defining layer PDL may include or may be formed of an inorganic material.

The spacer SC may be disposed on the pixel-defining layer PDL. The spacer SC may protrude from at least a part of the pixel-defining layer PDL on one side (upper side) in the thickness direction. The spacer SC may serve to maintain a gap with elements disposed thereabove. Although not limited thereto, for example, the spacer SC may prevent defects such as dent on the display panel10by a fine metal mask (FMM). The spacer SC may include or may be formed of an organic insulating material like the pixel-defining layer PDL. Although not limited thereto, the spacer SC may be formed via the same process with the pixel-defining layer PDL.

The emissive layer EML may be disposed on the anode electrode ANO exposed by the pixel-defining layer PDL. The emissive layer EML may include or may be formed of an organic material layer. The organic material layer of the emission layer may include an organic emission layer. In some embodiment, the organic material layer of the emission layer may further include a hole injecting/transporting layer and/or an electron injecting/transporting layer.

The cathode electrode CAT may be disposed on the emissive layer EML. The cathode electrode CAT may be a common electrode disposed across the pixels. The anode electrode ANO, the emissive layer EML and the cathode electrode CAT may form an organic light-emitting element.

The cathode electrode CAT may include or may be formed of a material layer having a small work function such as Li, Ca, LiF/Ca, LiF/Al, Al, Mg, Ag, Pt, Pd, Ni, Au, Nd, Ir, Cr, BaF and Ba, or a compound or mixture thereof (e.g., a mixture of Ag and Mg). The cathode electrode CAT may further include a transparent metal oxide layer disposed on the material layer having a small work function.

The encapsulation layer ENL including a first encapsulation film EN1, a second encapsulation film EN2and a third encapsulation film EN3is disposed on the cathode electrode CAT. The first encapsulation film EN1and the third encapsulation film EN3may be in contact with each other at the end of the encapsulation layer ENL. The second encapsulation film EN2may be encapsulated by the first encapsulation film EN1and the third encapsulation film EN3.

Each of the first encapsulation film EN1and the third encapsulation film EN3may include or may be formed of an inorganic material. Although not limited thereto, the inorganic material may include or may be formed of, for example, silicon nitride, silicon oxide, or silicon oxynitride. The second encapsulation film EN2may include or may be formed of an organic material. Although not limited thereto, the organic material may include or may be formed of, for example, an organic insulating material.

Hereinafter, other embodiments of the present disclosure will be described. In the following description, the same or similar elements will be denoted by the same or similar reference numerals, and redundant descriptions thereof will be omitted or briefly described. Descriptions will be made focusing on differences from the above embodiment.

FIG. 10is a cross-sectional view showing a part of a display device according to another embodiment of the present disclosure.

The embodiment ofFIG. 10is different from the embodiment ofFIG. 4in that a second thickness TH2_1of a first protection member30_1of a display device1_1is greater than a fourth thickness TH4of a second protection member40. Although not limited thereto, the second thickness TH2_1of the first protection member30_1may be, for example, in the range of from 0.01 μm to 750 μm, in the range of from 0.1 μm to 200 μm, or in the range of from 1 μm to 75 μm. Alternatively, the second thickness TH2_1of the first protection member30_1may be, for example, in the range of from 0.01 μm to 1,000 μm, in the range of from 0.1 μm to 300 μm, or in the range of from 1 μm to 100 μm.

Table 3 shows the results of measuring the height at which bright spots occur according to the thickness of the first adhesive member PSA1, the first protection member30_1, the second adhesive member PSA2, and the second protection member40. Herein, the height at which a bright spot occurs may refer to a height at which bright spot defects occur in the display device when an object is dropped from above the display device onto the display device. Therefore, it may be understood that the higher the height at which a bright spot occurs is, the greater the impact resistance is.

Comparative Example 9 may be substantially identical to the display device1(seeFIG. 1) according to the embodiment ofFIG. 4, and the thickness (the second thickness TH2) of the first protection member30(seeFIG. 4) may be smaller than the thickness (the fourth thickness TH4) of the second protection member40. In Examples 11 and 12, the thickness of the first protection member30_1(the second thickness TH2_1) is greater than the thickness of the second protection member40(the fourth thickness TH4).

Comparing Comparative Example 9 to Example 11 and Example 12, when the thickness of the first protection member30_1(the second thickness TH2_1) is greater than the thickness of the second protection member40(the fourth thickness TH4), the height at which a bright spot occurs is higher than when the thickness of the first protection member30(seeFIG. 4) (the second thickness TH2(seeFIG. 4)) is smaller than the thickness of the second protection member40(the fourth thickness TH4). For example, when the thickness of the first protection member30_1(the second thickness TH2_1) is greater than the thickness of the second protection member40(the fourth thickness TH4), the impact resistance may be more improved than when the thickness of the first protection member30(seeFIG. 4) (the second thickness TH2(seeFIG. 4)) is smaller than the thickness of the second protection member40(the fourth thickness TH4).

Comparing Example 11 to Example 12, when the thickness of the first protection member30_1(the second thickness TH2_1) is greater than the thickness of the second protection member40(the fourth thickness TH4), the height at which a bright spot occurs becomes higher as the thickness of the first protection member30(seeFIG. 4) (the second thickness TH2(seeFIG. 4)) becomes larger. For example, when the thickness of the first protection member30_1(the second thickness TH2_1) is greater than the thickness of the second protection member40(the fourth thickness TH4), the impact resistance may be improved as the thickness of the first protection member30(seeFIG. 4) (the second thickness TH2(seeFIG. 4)) becomes larger.

Even in this instance, the storage modulus of the second protection member40may increase according to an external impact, and thus the display device1_1may have both flexibility and impact resistance. Since the elastic modulus of the second adhesive member PSA2is equal to or smaller than the elastic modulus of the first adhesive member PSA1, it is possible to suppress or prevent deterioration of the folding performance. As the thickness of the first protection member30_1(the second thickness TH2_1) is greater than the thickness of the second protection member40(the fourth thickness TH4), the impact resistance may be improved.

FIG. 11is a cross-sectional view showing a part of a display device according to yet another embodiment of the present disclosure.

The embodiment ofFIG. 11is different from the embodiment ofFIG. 10in that a first thickness TH1_2of a first adhesive member PAS1_2of a display device1_2is greater than a third thickness TH3of a second adhesive member PAS2. Although not limited thereto, the first thickness TH1_2of the first adhesive member PSA_2may be, for example, in the range of from 0.01 μm to 500 μm, in the range of from 0.1 μm to 150 μm, or in the range of from 1 μm to 50 μm.

Table 4 shows the results of measuring the height at which bright spots occur according to the thickness of the first adhesive member PSA1_2, the first protection member30, the second adhesive member PSA2, and the second protection member40.

Comparative Example 10 may be substantially identical to the display device10_1(seeFIG. 10) according to the embodiment ofFIG. 10, and the thickness (the first thickness TH1) of the first adhesive member PSA1(seeFIG. 10) may be smaller than the thickness (the third thickness TH3) of the second adhesive member PAS2(seeFIG. 10). In Example 13, the thickness of the first adhesive member PAS_2(the first thickness TH1_2) is greater than the thickness of the second adhesive member PAS2(the third thickness TH3).

Comparing Comparative Example 10 to Example 13, when the thickness of the first adhesive member PAS1_2(the first thickness TH1_2) is greater than the thickness of the second adhesive member PSA2(the third thickness TH3), the height at which a bright spot occurs is higher than when the thickness of the first adhesive member PSA1_2(seeFIG. 10) (the second thickness TH2(seeFIG. 10)) is equal to the thickness of the second adhesive member PSA2(the third thickness TH3). For example, when the thickness of the first adhesive member PSA1_2(the first thickness TH1_2) is greater than the thickness of the second adhesive member PAS2(the third thickness TH3), the impact resistance may be more improved than when the thickness of the first adhesive member PSA1_2(seeFIG. 10) (the first thickness TH1(seeFIG. 10)) is smaller than the thickness of the second adhesive member PAS2(the third thickness TH3).

Even in this instance, the storage modulus of the second protection member40may increase according to an external impact, and thus the display device1_2may have both flexibility and impact resistance. Since the elastic modulus of the second adhesive member PSA2is equal to or smaller than the elastic modulus of the first adhesive member PSA1, it is possible to suppress or prevent deterioration of the folding performance. As the thickness of the first adhesive member PAS1_2(the first thickness TH1_2) is greater than the thickness of the second adhesive member PAS2(the third thickness TH3), the impact resistance may be improved.

FIG. 12is a perspective view of a display device according to yet another embodiment of the present disclosure when it is unfolded.FIG. 13is a perspective view showing the display device according to the embodiment ofFIG. 12when it is folded inward.FIG. 14is a perspective view showing the display device according to the embodiment ofFIG. 12when it is folded outward.

The embodiment ofFIGS. 12 to 14is different from the embodiment ofFIG. 1in that a display device1_3is folded inward and outward at the same folding area FDA. For example, the display device1_3may include a folding area FDA and non-folding areas NFA, and the display device1_3may include a first folding area FDA1, and a first non-folding area NFA1and a second non-folding area NFA2respectively disposed on one side and the opposite side of the first folding area FDA1in the second direction DR2. For example, the first folding area FDA1may be folded inward as shown inFIG. 13and may be folded outward as shown inFIG. 14.

Even in this instance, the storage modulus of the second protection member40may increase according to an external impact, and thus the display device1_3may have both flexibility and impact resistance. Since the elastic modulus of the second adhesive member PSA2is equal to or smaller than the elastic modulus of the first adhesive member PSA1, it is possible to suppress or prevent deterioration of the folding performance. A display device employing a variety of folding designs may be implemented as required by users.