KR102501045B1 - Foldable display device - Google Patents

Abstract

The present invention relates to a foldable display device, and more particularly, to a foldable display device including a back plate with improved durability.
The feature of the present invention is that the back plate located on the back side of the OLED panel is divided into a folding area and a non-folding area, and is made of liquid metal in response to the folding area, and has strong rigidity in response to the non-folding area. It is characterized in that it is made of a metal such as stainless steel (SUS) having a.
Through this, the foldable display device of the present invention does not have any restrictions in folding and unfolding the foldable display device. In addition, it is possible to prevent a physical step difference or other pressing characteristics of the folded and non-folded areas from occurring due to different materials of the back plate, thereby increasing the physical It is possible to prevent the phosphorus boundary from being visually recognized.
Through this, finally, it is possible to prevent the display quality of the OLED panel from deteriorating.

Description

Foldable display device {Foldable display device}

The present invention relates to a foldable display device, and more particularly, to a foldable display device including a back plate with improved durability.

In recent years, as society has entered the information age in earnest, the display field that processes and displays a large amount of information has developed rapidly, and in response to this, various flat display devices have been developed. Be in the spotlight.

Specific examples of such a flat panel display device include a liquid crystal display device (LCD), a plasma display panel device (PDP), a field emission display device (FED), and an electroluminescence display. Electroluminescence Display device (ELD), Organic Light Emitting Diodes (OLED), and the like. These flat-panel display devices show excellent performance in thinning, lightening, and low power consumption, compared to existing cathode ray tube (Cathode Ray Tube) : It is rapidly replacing the CRT).

On the other hand, since such a flat panel display device uses a glass substrate to withstand high heat generated during a manufacturing process, there are limitations in imparting lightness, thinness, and flexibility.

Therefore, a flexible display device manufactured using a flexible material such as plastic instead of a conventional inflexible glass substrate to maintain display performance even when bent like paper is rapidly emerging as a next-generation flat panel display device.

Flexible display devices use plastic thin film transistor substrates instead of glass, so they can be unbreakable with high durability, bendable that can be bent without breaking, rollable that can be rolled up, and foldable folder. It can be divided into foldable, etc., and such a flexible display has advantages of space utilization, interior and design, and can have various application fields.

In particular, in recent years, research into a foldable display device that can be carried in a folded state and displays an image in an unfolded state has been actively conducted in order to realize a large area along with ultra-thin, light weight, and miniaturization.

Foldable display devices can be applied to various fields, such as TVs and monitors, as well as mobile devices such as mobile phones, ultra mobile PCs, electronic books, and electronic newspapers.

This foldable display device largely consists of a display panel for realizing an image, a back plate positioned below the display panel to support the display panel, and a cover window positioned in front of the display panel to protect the display panel. (cover window) included.

On the other hand, since the foldable display device must be foldable and unfoldable, all of the display panel, back plate, and cover window are made in the form of a very thin film, but such a foldable display device has a problem of very weak impact resistance.

Therefore, recently, in order to improve the impact resistance of foldable display devices, the back plate is divided into a folding area and a non-folding area, and is made of a soft material corresponding to the folding area and strong rigidity corresponding to the non-folding area. A configuration to be made of a hard material has been proposed.

However, this configuration also has a problem in that impact resistance is not supplemented for the folding area.

The present invention is to solve the above problems, and a first object is to improve the impact resistance of a foldable display device.

In addition, while improving the durability of the back plate, the physical step of the back plate or other pressing characteristics of the folded and non-folded areas are prevented from being transferred to the display panel.

Through this, the third object is to prevent the display quality of the display panel from deteriorating.

In order to achieve the object as described above, the present invention is a display panel on which an image is implemented; a cover window positioned in front of the display panel; A foldable display device including a backplate positioned behind the display panel and divided into a folding area and a non-folding area made of liquid metal is provided.

At this time, the liquid metal is made of an alloy of gallium (Ga)-in (In)-tin (Sn) whose modulus is changed by an external voltage, a printed circuit board is connected to one edge of the display panel, and the liquid metal The metal is connected to the printed circuit board through a connection wire.

In addition, a resistor is connected to the liquid metal, and the liquid metal is made of an alloy of sodium (Na)-potassium (K) whose modulus changes by temperature change, and the non-folding area includes stainless steel (SUS) made of metal that

In addition, the liquid metal covers one side or the whole of the metal.

As described above, according to the present invention, the back plate located on the rear surface of the OLED panel is divided into a folding area and a non-folding area, and is made of liquid metal corresponding to the folding area, and the non-folding area is made of liquid metal. Correspondingly, by making it made of metal such as stainless steel (SUS) having strong rigidity, there is an effect that there is no restriction in folding and unfolding of the foldable display.

In addition, since the durability of the back plate itself is improved, there is an effect of preventing breakage of the OLED panel from occurring due to bending stress of the back plate.

In addition, it is possible to prevent a physical step difference or other pressing characteristics of the folded and non-folded areas from occurring due to different materials of the back plate, thereby increasing the physical There is an effect of preventing the phosphorus boundary from being visually recognized.

Through this, there is an effect of preventing the display quality of the OLED panel from deteriorating.

1 is a schematic diagram schematically illustrating a foldable display device according to an embodiment of the present invention;
2 is a schematic cross-sectional view of the display panel of FIG. 1;
3A to 3B are schematic diagrams schematically showing how the liquid metal of the back plate of the foldable display device according to the embodiment of the present invention and the printed circuit board of the OLED panel are connected to each other.
4A to 4C are schematic views schematically illustrating various aspects of a backplate of a foldable display device according to an embodiment of the present invention;

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

1 is a schematic diagram schematically illustrating a foldable display device according to an exemplary embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view of the display panel of FIG. 1 .

As shown, the foldable display 100 includes a display panel 110 for realizing an image, a back plate 120 supporting the display panel 110, and protecting the display panel 110. It includes a cover window (cover window: 130) for

At this time, if the direction in the drawing is defined for convenience of explanation, the back plate 120 is positioned on the rear surface of the display panel 110 under the premise that the display surface of the display panel 110 faces forward, and the display panel 110 In front of ), the cover window 130 is located.

Here, the display panel 110 includes a liquid crystal display device (LCD), a plasma display panel device (PDP), a field emission display device (FED), an electroluminescent display device ( It can be made of either Electroluminescence Display device (ELD) or Organic Light Emitting Diodes (OLED). It is better to use OLED, a representative flexible display device that can maintain display performance even when bent like paper. desirable.

OLED is a self-luminous device, and since it does not require a backlight used in a liquid crystal display device, which is a non-emissive device, it is possible to be lightweight and thin.

In addition, it has excellent viewing angle and contrast ratio compared to liquid crystal displays, is advantageous in terms of power consumption, can be driven at low DC voltage, has a fast response speed, is resistant to external shocks because the internal components are solid, and has a wide operating temperature range. It has advantages.

In particular, since the manufacturing process is simple, there is an advantage in that production costs can be significantly reduced compared to conventional liquid crystal display devices.

In the display panel 110 made of such an OLED, the substrate 101 on which the driving thin film transistor DTr and the light emitting diode E are formed is encapsulated by a protective film 102 .

Here, with reference to FIG. 2 , the display panel 110 made of OLED (hereinafter, referred to as an OLED panel) will be examined in detail.

A semiconductor layer 104 is formed in the pixel region P on the substrate 101. The semiconductor layer 104 is made of silicon, and the central portion thereof has a high concentration to the active region 104a constituting a channel and both sides of the active region 104a. It is composed of source and drain regions 104b and 104c doped with impurities of .

A gate insulating film 105 is formed above the semiconductor layer 104 .

A gate electrode 107 and a gate wiring extending in one direction (not shown) are formed above the gate insulating film 105 to correspond to the active region 104a of the semiconductor layer 104 .

In addition, a first interlayer insulating film 106a is formed on the entire upper surface of the gate electrode 107 and the gate wiring (not shown), and at this time, the first interlayer insulating film 106a and the gate insulating film 105 below the active region 104a) first and second semiconductor layer contact holes 109 exposing source and drain regions 104b and 104c located on both sides, respectively.

Next, the upper portion of the first interlayer insulating film 106a including the first and second semiconductor layer contact holes 109 is spaced apart from each other and exposed through the first and second semiconductor layer contact holes 109 ( Source and drain electrodes 108a and 108b contacting 104b and 104c, respectively, are formed.

And, a second interlayer having a drain contact hole 112 exposing the drain electrode 108b above the first interlayer insulating film 106a exposed between the source and drain electrodes 108a and 108b and the two electrodes 108a and 108b. An insulating film 106b is formed.

At this time, the semiconductor layer 104 including the source and drain electrodes 108a and 108b and the source and drain regions 104b and 104c in contact with the electrodes 108a and 108b and a gate insulating film formed on the semiconductor layer 104 105 and the gate electrode 107 form a driving thin film transistor (DTr).

Meanwhile, although not shown in the drawings, a data line (not shown) intersecting with a gate line (not shown) to define the pixel region P is formed. Also, the switching thin film transistor (not shown) has the same structure as the driving thin film transistor DTr and is connected to the driving thin film transistor DTr.

In addition, the switching thin film transistor (not shown) and the driving thin film transistor (DTr) are shown as an example of a co-planar type in which the semiconductor layer 104 is made of a polysilicon semiconductor layer in the drawing, and as a modification thereof, pure And it may be formed as a bottom gate type made of impurity amorphous silicon.

In addition, in the region substantially displaying an image on the upper part of the second interlayer insulating film 106b, for example, a material having a relatively high work function value is used as a component constituting the light emitting diode E, forming an anode. One electrode 111 is formed.

The first electrode 111 is connected to the drain electrode 108b of the driving thin film transistor DTr.

The first electrodes 111 are formed for each pixel region P, and a bank 119 is positioned between the first electrodes 111 formed for each pixel region P.

That is, the first electrode 111 is formed in a structure separated for each pixel region P by using the bank 119 as a boundary for each pixel region P.

An organic emission layer 113 is formed on the first electrode 111 .

Here, the organic light emitting layer 113 may be composed of a single layer made of a light emitting material, and to increase light emitting efficiency, a hole injection layer, a hole transport layer, an emitting material layer, and an electron It may be composed of multiple layers of an electron transport layer and an electron injection layer.

The organic light emitting layer 113 expresses red (R), green (G), and blue (B) colors. In a general method, red (R), green (G), and blue colors are displayed for each pixel area (P). (B) Separate organic materials (113a, 113b, 113c) emitting color are patterned and used.

In addition, a second electrode 115 forming a cathode is formed on the upper side of the organic light emitting layer 113 .

At this time, the second electrode 115 has a double layer structure and includes a translucent metal film in which a metal material having a low work function is thinly deposited. In this case, the second electrode 115 may have a two-layer structure in which a transparent conductive material is thickly deposited on a translucent metal film.

Accordingly, light emitted from the organic light emitting layer 113 is driven in a top emission type that is emitted toward the second electrode 115 .

Alternatively, the second electrode 115 may be formed of an opaque metal film, and light emitted from the organic light emitting layer 113 may be driven in a bottom emission type that is emitted toward the first electrode 111 .

When a predetermined voltage is applied to the first electrode 111 and the second electrode 115 according to the selected color signal, the OLED panel 110 generates holes injected from the first electrode 111 and the second electrode 115. Electrons provided from are transported to the organic light emitting layer 113 to form excitons, and when these excitons transition from an excited state to a ground state, light is generated and emitted in the form of visible light.

At this time, since the emitted light passes through the transparent second electrode 115 or the first electrode 111 and goes out, the OLED panel 110 implements an arbitrary image.

A protective film 102 in the form of a thin film is formed on the driving thin film transistor (DTr) and the light emitting diode (E), and the OLED panel 101 is encapsulated through the protective film 102, In order to prevent external oxygen and moisture from penetrating into the OLED panel 110, the protective film 102 is used by laminating at least two inorganic protective films 102a. At this time, two inorganic protective films 102a It is preferable that an organic protective film 102b is interposed therebetween to supplement the impact resistance of the inorganic protective film 102a.

On the other hand, the substrate 101 may be made of thin polyimide to have a flexible property, but the substrate 101 made of such thin polyimide is not suitable for the formation process of components such as thin film transistors (DTr). Therefore, a process of forming a component such as a thin film transistor (DTr) is performed in a state in which a substrate made of polyimide is attached to a carrier substrate such as a glass substrate. Thereafter, the OLED panel 110 can be obtained by separating the carrier substrate and the substrate made of polyimide.

The OLED panel 110 is integrally modularized through the cover window 130 and the back plate 120, and a cover window capable of protecting the OLED panel 110 from the front side of the OLED panel 110 on which an image is implemented. 130 is attached through the first optical adhesive layer 140, and the back plate 120 for supporting the OLED panel 110 is attached to the rear surface of the OLED panel 110 through the second optical adhesive layer 150. do.

Here, the first and second optical adhesive layers 140 and 150 are formed of OCA (Optical Cleared Adhesive).

The cover window 130 protects the OLED panel 110 from external impact, and transmits light emitted from the OLED panel 110 so that an image displayed on the OLED panel 110 can be viewed from the outside.

The cover window 130 is made of polymethylmethacrylate (PMMA), polycarbonate (PC), cycloolefin polymer (COP), polyethylene terephthalate (polyethylene terephthalate) having impact resistance and light transmission. terephthalate, PET).

Since the substrate 101 of the OLED panel 110 is too thin, the back plate 120 is attached to the rear surface of the OLED panel 110 to support the OLED panel 110 .

Here, the characteristic configuration of the present invention is defined by dividing the back plate 120 located on the rear surface of the OLED panel 110 into a folding area and a non-folding area, and corresponding to the folding area by liquid metal (210) It is characterized in that it is made of metal 220 corresponding to the non-folding area.

That is, the back plate 120 includes a folding area, which is a folded area such that a curvature is formed when the foldable display device 100 is folded, and both sides of the folding area maintain a flat state even when the foldable display device 100 is folded. It can be defined by being divided into non-folding areas. At this time, it is made of liquid metal 210 corresponding to the folding area and made of metal 220 such as stainless steel (SUS) having strong rigidity corresponding to the non-folding area. it is to bear

Here, the modulus of the liquid metal 210 changes depending on the external voltage. The liquid metal 210 according to the embodiment of the present invention is formed in the form of a plurality of beads when no voltage is applied, and has a strong modulus. When a voltage is applied, it changes the form of charge distribution on the surface, so it has flowability through a change in surface tension and has a flexible property.

The liquid metal 210 having a flexible property has a low modulus value and thus has low stiffness.

The liquid metal 210 is a transition metal including mercury (Hg), sodium (Na), lithium (Ni), lead (Pb), bismuth (Ni), tin (Sn), gallium (Ga), and the like. ) or a heavy metal alloy. The liquid metal 210 according to an embodiment of the present invention has a modulus that is changed by a voltage applied from the outside, gallium (Ga) -in (In) -tin It may be made of an alloy of (Sn).

Gallium (Ga) may be included in an amount of 50 to 95 wt% based on the total amount of the alloy of gallium (Ga), phosphorus (In), and tin (Sn), and phosphorus (In) is gallium (Ga), phosphorus (In), tin (Sn) (Sn) may be included in an amount of 5 to 30 wt% based on the total amount of the alloy, and tin (Sn) may be included in an amount of 0 to 20 wt% based on the total amount of the alloy of gallium (Ga), phosphorus (In), and tin (Sn).

When gallium (Ga), phosphorus (In), and tin (Sn) are included within the above content ranges, the modulus of the liquid metal 210 changes according to the voltage applied from the outside.

Therefore, in the foldable display device 100 of the present invention, when the foldable display device 100 is to be folded, the foldable area of the back plate 120 has a flexible property, so that the foldable display device 100 can be folded. Can be easily folded. Through this, the folding and unfolding of the foldable display device 100 of the present invention is not restricted.

That is, in the general foldable display device 100, plastic deformation of the back plate 120 occurs while folding and unfolding operations are repeated, thereby limiting folding and unfolding of the foldable display device 100.

However, as in the embodiment of the present invention, the back plate 120 is divided into a folding area and a non-folding area, and corresponding to the folding area, it has a flexible property when folded and has a strong modulus when unfolded. Even if folding and unfolding operations of the display device 100 are repeated, occurrence of plastic deformation of the back plate 120 may be minimized.

Accordingly, restrictions in folding and unfolding of the foldable display device 100 may be prevented.

In addition, as the back plate 120 is entirely made of metal (=liquid metal 210, metal 220), durability is improved, and plastic deformation of the back plate 120 can be minimized through this. there is.

In addition, by minimizing the plastic deformation of the back plate 120 , damage to the OLED panel 110 due to bending stress of the back plate 120 can be prevented.

In addition, in the foldable display device 100 according to an embodiment of the present invention, even if the back plate 120 is divided into a folded area and a non-folded area in order to minimize plastic deformation of the back plate 120, the back plate 120 As it is entirely made of metal (=liquid metal 210, metal 220) material, physical steps are generated in the back plate 120 due to different materials or different pressing characteristics of the folded and non-folded areas cause OLED It is possible to prevent a physical boundary between a folded area and a non-folded area from being visually recognized on the upper side of the panel 110 .

Therefore, it is possible to prevent the display quality of the OLED panel 110 from deteriorating.

As described above, in the present invention, the back plate 120 positioned on the rear surface of the OLED panel 110 in the foldable display device 100 is divided into a folding area and a non-folding area, and liquid corresponding to the folding area is defined. It is characterized in that it is made of metal (liquid metal: 210) and made of metal (220) such as stainless steel (SUS) having strong rigidity corresponding to the non-folding area.

Through this, the folding and unfolding of the foldable display device 100 of the present invention is not restricted.

In addition, since the durability of the back plate 120 itself is improved, damage to the OLED panel 110 due to bending stress of the back plate 120 can be prevented.

In addition, it is possible to prevent a physical step from occurring due to different materials of the back plate 120 or other pressing characteristics between the folded and non-folded areas, and thus the folded area and the upper part of the OLED panel 110 A physical boundary between non-folded areas may be prevented from being visually recognized.

Finally, through this, it is possible to prevent the display quality of the OLED panel 110 from deteriorating.

On the other hand, the liquid metal 210 located in the folding area of the back plate 120 is connected to the printed circuit board (115, see FIG. 3A) provided in the OLED panel 110 and receives a voltage to change the modulus. Referring to the drawings below, a connection between the liquid metal 210 and the printed circuit board 115 (see FIG. 3A) will be examined in more detail.

3A to 3B are schematic diagrams schematically showing how liquid metal of a back plate of a foldable display device according to an embodiment of the present invention and a printed circuit board of an OLED panel are connected to each other.

For convenience of description, a description and illustration of the cover window (130 in FIG. 1) and the first and second optical adhesive layers (140 and 150 in FIG. 1) in the foldable display device 100 according to an embodiment of the present invention. will be omitted and only the characteristic parts will be examined in detail.

As shown, the back surface of the OLED panel 110 is divided into a folding area made of liquid metal 210 and a non-folding area made of metal 220 such as stainless steel (SUS) having strong rigidity. (120) is located.

In addition, along one edge of the OLED panel 110, a printed circuit board 115 is connected via a connecting member 113 such as a flexible circuit board or a tape carrier package (TCP), so that the OLED panel 110 ) is supplied with a driving signal from the driving circuit elements 117 mounted on the printed circuit board 115.

At this time, the liquid metal 210 located in the folding area of the back plate 120 receives voltage from the driving circuit element 117 provided on the printed circuit board 115. As shown in FIG. 3A, the printed circuit A connection wire 119 extends from the substrate 115 to the rear surface of the OLED panel 110 and can be electrically connected to the liquid metal 210 positioned in the folded region of the back plate 120 .

Alternatively, as shown in FIG. 3B, the connection wiring 119 connected to the printed circuit board 115 extends to the rear surface of the back plate 120, and the liquid metal 210 positioned in the folded area of the back plate 120. ) and electrically connected.

Therefore, when voltage is applied to the liquid metal 210 through the connection wiring 119 connected to the printed circuit board 115, the liquid metal 210 has flowability through a change in surface tension and thus has a flexible property. .

And, when voltage is not applied, the liquid metal 210 has a strong modulus made up of a plurality of bead shapes.

Meanwhile, a resistor (not shown) may be connected to the liquid metal 210 of the back plate 120 to increase the temperature of the resistor (not shown) by the voltage applied from the printed circuit board 115. At this time, the liquid metal 210 may be made of a sodium (Na)-potassium (K) alloy whose modulus changes in response to a temperature change of resistance (not shown).

4A to 4C are schematic diagrams schematically illustrating various aspects of a backplate of a foldable display device according to an exemplary embodiment of the present invention.

As shown in FIG. 4A, the back plate 120 is divided into a folding area and a non-folding area, the folding area is made of liquid metal 210, and the non-folding area is made of stainless steel (SUS) having strong rigidity. It may be formed of the same metal 220, and as shown in FIG. 4B, the liquid metal 210 may be formed to cover one surface of the metal 220 in the non-folding area.

In addition, as shown in FIG. 4C, the liquid metal 210 may be formed to completely cover the metal 220 in the non-folding area.

Here, the durability of the back plate 120 can be further improved when the foldable display device (100 in FIG. 3B) is unfolded by positioning the liquid metal 210 even in the non-folding area as shown in FIGS. 4B and 4C. In addition, it is possible to further minimize the occurrence of physical steps due to different materials of the back plate 120 or the occurrence of other pressing characteristics between the folded and non-folded regions, and to the top of the OLED panel (110 in FIG. 3B). A physical boundary between the folded area and the non-folded area may be prevented from being visually recognized.

Here, in the back plate 120 of the foldable display device ( 100 in FIG. 3B ) according to an embodiment of the present invention, the metal 220 is first placed in the non-folding area and then the liquid metal 210 is injected into the folding area. In addition, the liquid metal 210 is injected into the folded area and at the same time the liquid metal 210 is injected into the non-folded area so that the liquid metal 210 covers one surface of the metal 220 or the entire metal 210. It can be formed to completely enclose it.

As described above, the present invention defines the back plate 120 positioned on the rear side of the OLED panel (110 in FIG. 3B) in the foldable display device (100 in FIG. 3B) by dividing it into a folding area and a non-folding area, It is characterized in that it is made of liquid metal (210) corresponding to the folding area and is made of metal 220 such as stainless steel (SUS) having strong rigidity corresponding to the non-folding area.

Through this, the folding and unfolding of the foldable display device (100 in FIG. 3B) of the present invention is not restricted.

In addition, since the durability of the back plate 120 itself is improved, damage to the OLED panel ( 110 in FIG. 3B ) due to bending stress of the back plate 120 can be prevented.

In addition, it is possible to prevent a physical step from occurring due to the different materials of the back plate 120 or other pressing characteristics between the folded and non-folded areas, and to the top of the OLED panel (110 in FIG. 3B). A physical boundary between the folded area and the non-folded area may be prevented from being visually recognized.

Through this, finally, it is possible to prevent the display quality of the OLED panel (110 in FIG. 3B) from deteriorating.

The present invention is not limited to the above embodiments, and can be practiced with various changes without departing from the spirit of the present invention.

100: foldable display device
110: display panel (OLED panel)
120: back plate (210: liquid metal, 220: metal)
130: cover window
140, 150: first and second optical adhesive layers

Claims (8)

a display panel on which images are implemented;
A back plate located at the rear of the display panel and defined by being divided into a folding area made of liquid metal and a non-folding area made of metal
including,
The liquid metal extends from the folding area to the non-folding area and surrounds the rear surface of the metal.
According to claim 1,
The liquid metal is a foldable display device made of an alloy of gallium (Ga)-phosphorus (In)-tin (Sn) whose modulus is changed by an external voltage.
According to claim 1,
A printed circuit board is connected to one edge of the display panel, the liquid metal is connected to the printed circuit board through a connection wire, and the connection wire extends to a rear surface of the display panel between the display panel and the back plate. foldable display device.
a display panel on which images are implemented;
A back plate located behind the display panel and defined by being divided into a folding area and a non-folding area made of liquid metal
including,
A resistor is connected to the liquid metal, and the liquid metal is made of a sodium (Na)-potassium (K) alloy whose modulus changes with a temperature change.
According to claim 1,
The foldable display device of claim 1 , wherein the non-folding area is made of metal including stainless steel (SUS).
According to claim 1,
The liquid metal further surrounds the front and side surfaces of the metal foldable display.
According to claim 1,
A foldable display device in which a cover window is positioned in front of the display panel. According to claim 1,
A printed circuit board is connected to one edge of the display panel, the liquid metal is connected to the printed circuit board through a connection wire, and the connection wire extends to a rear surface of the back plate.

Images