KR20200079977A - Cover Window and Flexible Display Device Using the Same - Google Patents

Abstract

The present invention relates to a cover window that can prevent reflection and facilitate operations such as folding, etc. by changing a structure of the cover window to protect a display panel, and a display device including the same. The cover window comprises a flexible transparent substrate, a plurality of protruding patterns, and at least one pair of laminated structures of a first insulating layer and a second insulating layer.

Description

Cover window and flexible display device using the same

The present invention relates to a display device, and more particularly, to a flexible display device including a cover window and a cover window capable of omitting a polarizing plate and reducing a radius of curvature by changing an anti-reflection structure to reduce stress during folding.

A video display device that embodies various information as a screen is developing as a thinner, lighter, and higher performance direction as a core technology in the information and communication era. Accordingly, the organic light emitting display device, which can self-emit as a flat panel display device capable of reducing weight and volume, which is a disadvantage of the cathode ray tube (CRT), can omit the light source unit, and the like has been spotlighted.

In the organic light emitting diode display, a plurality of pixels are arranged in a matrix to display an image. Here, each pixel includes a light emitting element and a pixel driving circuit composed of a plurality of transistors that independently drive the light emitting element.

Meanwhile, in recent years, in view of various applications, there is an increasing demand for a flexible display device that can be easily carried in a pocket or a small pouch and display images on a larger screen than when carrying. The flexible display device may be folded or bent when it is carried or stored, and may be implemented in a state in which the display device is unfolded when displaying an image, thereby increasing the image display area and improving the user's visibility and realism. .

The organic light emitting display device is advantageous in application as a flexible display device requiring flexibility because the use of a light source is omitted and the thickness of the device is thin. In the organic light emitting diode display, light is emitted to the outside through reflection and resonance effects between the electrodes facing each other. For this reason, it is necessary to use a reflective electrode on at least a part of the electrode. Accordingly, reflection of external light reflected by the light incident on the reflection electrode side is problematic, and the organic light emitting diode display uses a circular polarizing plate to prevent reflection of external light.

However, the circular polarizing plate has a thick thickness, and thus, when applied to an organic light emitting display device, has a limitation in reducing the radius of curvature as a flexible display device.

Although a method of arranging color filters for a purpose similar to that of a circularly polarizing plate for the purpose of preventing reflection of external light is also proposed, the use of a single color color filter is not possible for color filters, for example, by using three or more color filters. A mask process is added, and thus, there is a problem that the yield is lowered due to a problem in alignment between layers. In addition, when the color filter layer is disposed on the top of the encapsulation structure of the organic light emitting display device, since it is located on the top of the organic light emitting element that is susceptible to high temperature, it is necessary to proceed to a low temperature process, and outgassing management is also required during the process to prevent external light reflection. For this, there is a limitation when using a color filter layer, and there is a risk of causing another problem with the layer located on the top of the encapsulation structure.

The present invention has been devised to solve the above-mentioned problems, and in particular, it is possible to prevent reflection by changing the structure of a cover window protecting a display panel, and to a cover window capable of easily performing operations such as folding and a flexible display device including the same will be.

The cover window of the present invention and the flexible display device to which the same is applied have the anti-reflection property of offset interference by the stacked structure of the protruding pattern and the low-refractive-index layer and the high-refractive-index layer, so that the polarizing plate can be omitted.

A cover window according to an embodiment of the present invention includes a flexible transparent substrate, a plurality of protruding patterns provided on one surface of the transparent substrate, and a refractive index difference of 0.2 or more from each other on the transparent substrate including the plurality of protruding patterns It may include a pair of a stacked structure of the first insulating layer and the second insulating layer having a.

The first insulating layer and the second insulating layer may be transparent organic films.

It is preferable that the wavelength of the reflected light for external light on the surface of the first insulating layer and the wavelength of the reflected light for external light on the surface of the second insulating layer has a phase difference of 180 degrees.

In the stacked structure, the refractive index of the first insulating layer having a low refractive index may be 1.4 to 1.55, and the refractive index of the second insulating layer having a high refractive index may be 1.6 to 2.3.

The plurality of protruding patterns may have a vertical cross section having a trapezoidal shape with a shorter upper surface than the lower surface, and may have a side surface inclined by 15° to 45° with respect to the normal direction of the transparent substrate.

Light passing through the protruding pattern and the layered structure on the transparent substrate may be offset from the front viewing angle to a 30° viewing angle.

The transparent substrate and the protruding pattern may have a refractive index difference of less than 0.1.

A hard coating layer having a different refractive index from the transparent substrate may be further included on the opposite surface of the transparent substrate on which the protruding pattern is not located.

The transparent substrate and the protruding pattern may have a larger refractive index than the first insulating layer, and the hard coating layer may have a smaller refractive index than the transparent substrate and the protruding pattern.

The transparent substrate and the protruding pattern may be less than or equal to the refractive index of the first insulating layer, and the hard coating layer may have a larger refractive index than the transparent substrate and the protruding pattern.

Each layer of the laminated structure may have the same thickness in the corresponding portion of the transparent substrate and the corresponding portion of the protruding pattern.

The flexible display device of the present invention for achieving the same object includes a substrate having a plurality of sub-pixels, a thin film transistor provided in each sub-pixel of the substrate, and a light emitting layer that is connected to the thin film transistor and emits a predetermined color in the light emitting unit A light emitting device including a, an encapsulation layer protecting the light emitting device and an upper portion of the encapsulation layer may include the above-described cover window.

The protruding patterns of the cover window may correspond to the light emitting portion or to areas other than the light emitting portion.

In addition, the first to third sub-pixels, the light-emitting layer of the first sub-pixel is a first color light-emitting layer that emits light of a first wavelength, the light-emitting layer of the second sub-pixel has a longer wavelength than the first wavelength A second color emission layer emitting light of a second wavelength, and the emission layer of the third sub-pixel may be a third color emission layer emitting light of a third wavelength having a longer wavelength than the second wavelength.

Among the plurality of protrusion patterns, a protrusion pattern corresponding to the first sub-pixel may be relatively large.

The protruding pattern may be elongated in correspondence with the column of the sub-pixels.

The plurality of protruding patterns may be divided for each light emitting part of the sub-pixel.

The plurality of protruding patterns may be a polyhedral frustum or a truncated cone.

The protrusion pattern may correspond to the first sub-pixel, the second sub-pixel, and the third sub-pixel in order, so that the height may gradually decrease.

The surface of the protruding pattern may be hemispherical.

Each layer of the laminated structure may be provided with the same thickness without a step difference in each region along the surface of the protruding pattern.

The cover window of the present invention and the flexible display device including the same have the following effects.

First, a cover window is formed in a stacked structure of a plurality of spaced apart protruding patterns on a transparent substrate and a low refractive index layer and a high refractive index layer on a transparent substrate including the protruding pattern, thereby canceling out at multiple interfaces having different refractive indices for external light. By having the anti-reflection property of interference, external light reflection is prevented, whereby the polarizing plate can be omitted.

Second, by omitting the polarizing plate in the flexible display device, the thickness of the flexible display device can be improved by removing the polarizing plate having a thick and brittle characteristic, and the limitation of the radius of curvature can be eliminated.

Third, each layer having a difference in refractive index of the cover window is formed by coating the organic film, and as a configuration located on the top of the organic light emitting element array, the cover window is separately formed with an insulating pattern having a protruding pattern on the surface and a difference in the refractive index to cover the window The formation process of the and the process of forming the organic light emitting device array are independently managed, thereby preventing damage to the organic light emitting device array due to the high temperature during the manufacturing process of the cover window.

Fourth, by forming an insulating layer having a refractive index difference in the cover window with an organic film, folding, bending, rolling, and the like can be performed according to various types of use in the flexible display device.

1 is a cross-sectional view showing a cover window of the present invention
2 is a cross-sectional view showing a flexible display device to which the cover window of FIG. 1 is applied.
3A is a diagram showing offset interference
Figure 3b is a diagram showing a form of reinforcement interference
Figure 3c is a diagram showing another form of constructive interference
Figure 4a is a perspective view showing the description of the cover window according to the first embodiment of the present invention
Figure 4b is a view showing a cover window according to a first embodiment of the present invention and its external light reflection prevention effect
Figure 4c is a plan view showing the arrangement of the light emitting array unit corresponding to the cover window according to the first embodiment of the present invention
Figure 5a is a cross-sectional view showing a cover window according to a second embodiment of the present invention
Figure 5b is a plan view showing the arrangement of the light emitting array unit corresponding to Figure 5a
6 is a cross-sectional view showing a cover window according to a third embodiment of the present invention
Figure 7a is a cross-sectional view showing a cover window according to a fourth embodiment of the present invention
7B is a plan view showing the arrangement of the light emitting array unit corresponding to FIG. 7A.
8 is a cross-sectional view showing a cover window according to a fifth embodiment of the present invention
9 is a cross-sectional view showing a cover window according to a sixth embodiment of the present invention
10 is a sectional view showing a cover window according to a seventh embodiment of the present invention

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. Throughout the specification, the same reference numerals refer to substantially the same components. In the following description, when it is determined that a detailed description of the technology or configuration related to the present invention may unnecessarily obscure the subject matter of the present invention, the detailed description is omitted. In addition, the component names used in the following description are selected in consideration of the ease of preparing the specification, and may be different from the names of parts of actual products.

The shapes, sizes, ratios, angles, numbers, etc. disclosed in the drawings for describing various embodiments of the present invention are exemplary and the present invention is not limited to the details shown in the drawings. Throughout this specification, the same reference numerals refer to the same components. In addition, in the description of the present invention, when it is determined that detailed descriptions of related known technologies may unnecessarily obscure the subject matter of the present invention, detailed descriptions thereof will be omitted. When'include','have','consist of', etc. mentioned in this specification are used, other parts may be added unless'~man' is used. When a component is expressed as a singular number, the plural number is included unless otherwise specified.

In interpreting the components included in various embodiments of the present invention, it is interpreted as including an error range even if there is no explicit description.

In explaining various embodiments of the present invention, when describing the positional relationship, for example,'~top','~top','~bottom','~side', etc. When the positional relationship of parts is described, one or more other parts may be located between the two parts unless'right' or'direct' is used.

In describing various embodiments of the present invention, in the case of explaining the time relationship, temporal sequential relationships such as'after','following','after','before', etc. When is described, it may also include a case where it is not continuous unless'right' or'direct' is used.

In describing various embodiments of the present invention,'first','second', etc. may be used to describe various components, but these terms are only used to distinguish between the same and similar components. to be. Therefore, in the present specification, the components modified with'first' may be the same as the components modified with'second' within the technical spirit of the present invention, unless otherwise specified.

Each of the features of the various embodiments of the present invention may be partially or totally combined or combined with each other, technically various interlocking and driving may be possible, and each of the various embodiments may be independently implemented with respect to each other or may be implemented together in an associative relationship. It might be.

1 is a cross-sectional view showing a cover window of the present invention.

As shown in FIG. 1, the cover window of the present invention includes a flexible transparent substrate 201, a plurality of protruding patterns 202 provided on one surface of the transparent substrate 201, and the plurality of protruding patterns 202. On the transparent substrate 201 included, a stack structure 210 of the first insulating layer 211 and the second insulating layer 212 having a refractive index difference of 0.2 or more with each other may be included.

The protruding pattern 202 may be the same material as the transparent substrate 201, and the difference in refractive index between other materials or the optical material is less than 0.1, so that the phase difference between the two interfaces is not generated. The protruding pattern 202 further forms the transparent substrate 201 by the thickness of the protruding pattern 202, and removes the protruding pattern 202 from the portion excluding the protruding pattern 202 on the removed transparent substrate 201 The remaining or protruding pattern 202 may be formed by coating a material having a similar refractive index to the transparent substrate 201.

The cover window of the present invention may be formed by integrally forming the transparent substrate 201 and the protruding pattern 202 with the same material and 200.

The plurality of protruding patterns 202 may have a vertical cross section having a trapezoidal shape with a shorter upper surface than the lower surface, and may have a side surface inclined by 15° to 45° with respect to the normal direction of the transparent substrate. This is because, when incident into the cover window, it enters in the normal direction of the side surface of the protruding pattern 202, because the phase of each other's light propagation wavelength is reversed by 180° from approximately the front viewing angle to the 30° viewing angle, and has an effect of canceling interference.

1, a first insulating layer 211 of a low refractive index, a second insulating film 212 of a high refractive index, a third insulating film 213 of a low refractive index, and a fourth insulating film 214 of a high refractive index of the laminated structure 210 are shown in FIG. It is shown as including, in addition to the illustrated low/high/low/high refractive index two-layer stacked structure 210, it is also possible to stack a pair of low-refractive-index layers and a high-refractive-index layer as a minimum unit.

By arranging layers having different refractive indices, when light is reflected from the outside, when light is reflected at the interfaces of the first to fourth insulating layers 211, 212, 213, and 214, a low refractive index insulating layer ( The phases of the light reflected from the surfaces of 211 and 213 and the phases of the light reflected from the surfaces of the high-refractive-index insulating layers 212 and 214 are 180° to each other, thereby canceling interference and reducing the amount of light going out.

In the cover window of the present invention, the transparent substrate 201 may be in the form of a film containing one selected from the group consisting of polyimide polymers, polyester polymers, silicone polymers, acrylic polymers, polyolefin polymers, and copolymers thereof. . Among them, in the case of a polyimide-based polymer, it can be applied in a high-temperature process, and it is easy to handle in the present invention in which a specific pattern is formed and a predetermined layer is formed as a material that can be coated.

The cover window is located at the top of the flexible display panel to protect the surface of the display panel and prevent external light, and not only the transparent substrate 201, but also the protruding pattern 202 formed thereon. The laminated structure 210 of the insulating film has a total thickness of 20 µm or less for use in a flexible display device, and it is preferable that each or the whole is a flexible material.

In this regard, the first to fourth insulating layers 211, 212, 213, and 214 are preferably transparent organic films. It is possible to form a low-refractive-index film and a high-refractive-index film for both the inorganic film and the organic film. When the inorganic film is uniformly formed to a certain thickness, it is preferable to form an organic film having good elasticity, because it has a fragile property in a stressful state during folding. In addition, the formation of a transparent organic film is for transmitting light emitted from the display panel through the cover window without loss when the cover window is applied on the display panel. Each of the first to fourth insulating layers 211, 212, 213, and 214 is formed to a thickness of 3 µm or less to prevent the flexibility of the insulating layers from being deteriorated.

In the stacked structure, the refractive index of the first insulating layer having a low refractive index may be 1.4 to 1.55, and the refractive index of the second insulating layer having a high refractive index may be 1.6 to 2.3. The first and second insulating layers 211 and 212, the second and third insulating layers 212 and 213, and the third insulating layers 213 and 214 that are in contact with each other have a refractive index difference between each other that exceeds 0.2.

Meanwhile, each layer 211 to 214 of the layered structure 210 has the same thickness in the corresponding portion of the transparent substrate 201 and the corresponding portion of the protruding pattern 202. This does not have a step-by-region level difference because the first to fourth insulating layers 211, 212, 213, and 214 are sequentially stacked on the transparent substrate 201 including the protruding pattern 202 without a mask.

Hereinafter, a flexible display device to which the cover window of the present invention is applied will be described.

2 is a cross-sectional view illustrating a flexible display device to which the cover window of FIG. 1 is applied.

2, the flexible display device of the present invention includes a substrate 111 having a plurality of sub-pixels, thin film transistors 130 and T provided in each sub-pixel of the substrate, and the thin film transistors 130 and T. A light emitting element 120 including a light emitting layer 124 that is connected to and emits a predetermined color in the light emitting unit, and an encapsulation layer 140 and an encapsulation layer 140 on the encapsulation layer 140 that protect the light emitting element. A cover window having the structure 210 on the transparent substrate 201 and the protruding pattern 202 may be included.

The transparent surface 201 observed from the outside by forming the protruding pattern 202 and the stacked structure 210 of the cover window to correspond to the surface on which the arrays of the thin film transistors 130 and T and the light emitting device 120 are formed. ) Has a flattened surface. Therefore, even when the back surface of the transparent substrate 201 is touched from the outside, damage to the internal structure is prevented.

On the other hand, in the flexible display device of the present invention, the substrate 111 is in the form of a film containing one selected from the group consisting of polyimide polymers, polyester polymers, silicone polymers, acrylic polymers, polyolefin polymers, and copolymers thereof. Can be Among these materials, polyimide is widely used as a plastic substrate because it can be applied to high temperature processes and is a material that can be coated. In some cases, a substrate (array substrate) is also referred to as a concept including a device and a functional layer formed on a plastic film, for example, a switching TFT, a driving TFT connected to a switching TFT, an organic light emitting element connected to a driving TFT, a protective film, and the like. .

In some cases, a buffer layer may be further provided on the substrate 111. The buffer layer is a functional layer for protecting a thin film transistor (TFT) from impurities such as alkali ions flowing out of the substrate 111 or lower layers. The buffer layer may be made of silicon oxide (SiOx), silicon nitride (SiNx), or multiple layers thereof.

The thin film transistors 130 and T are placed on the substrate 111. The thin film transistor may have a form in which the gate electrode 132, the gate insulating film 112, the semiconductor layer 134, the interlayer insulating film 114, and the source and drain electrodes 136 and 138 are sequentially arranged. The semiconductor layer 134 is positioned on the substrate 111 or the buffer layer. The semiconductor layer 134 may be made of polysilicon (p-Si), in which case a predetermined region may be doped with impurities. Further, the semiconductor layer 134 may be made of amorphous silicon (a-Si), or may be made of various organic semiconductor materials such as pentacene. Furthermore, the semiconductor layer 134 may be made of oxide. The gate insulating layer 112 may be formed of an insulating inorganic material such as silicon oxide (SiOx) or silicon nitride (SiNx), or may be formed of an insulating organic material. The gate electrode 132 may be formed of various conductive materials, such as magnesium (Mg), aluminum (Al), nickel (Ni), chromium (Cr), molybdenum (Mo), tungsten (W), gold (Au), or alloys thereof. And the like.

The interlayer insulating layer 114 may be formed of an insulating material such as silicon oxide (SiOx) or silicon nitride (SiNx), or may be formed of an insulating organic material. Selective removal of the interlayer insulating layer 114 and the gate insulating layer 112 may form a contact hole in which the source and drain regions are exposed.

The source and drain electrodes 136 and 138 are formed of a single layer or a multi-layer shape as an electrode material on the interlayer insulating layer 114.

The passivation layer 118 and the planarization layer 128 may be positioned on the thin film transistor. The protective layer 118 and the planarization layer 128 protect the thin film transistor and planarize the upper portion. The planarization layer 128 may be formed in various forms, and may be formed of an organic insulating film such as Benzocyclobutene (BCB) or acrylic (Acryl), and the protective film 118 includes a silicon nitride film (SiNx), a silicon oxide film (SiOx), and the like. It may be formed of the same inorganic insulating film. Each of the protective layer 118 and the planarization layer 128 may be formed of a single layer, or may be composed of a double layer or multiple layers.

The light emitting device may have a shape in which the first electrode 122, the organic light emitting layer 124, and the second electrode 126 are sequentially arranged. That is, for example, in the case of an organic light emitting device, the organic light emitting device includes a first electrode 122 formed on the planarization layer 128, an organic light emitting layer 124 and an organic light emitting layer located on the first electrode 122 It may be composed of a second electrode 126 located on (124).

The first electrode 122 is electrically connected to the drain electrode 138 of the driving thin film transistor through the contact hole. When the display panel 100 is a top emission method, the first electrode 122 may be made of an opaque conductive material having high reflectance. For example, the first electrode 122 may be formed of silver (Ag), aluminum (Al), gold (Au), molybdenum (Mo), tungsten (W), chromium (Cr), or alloys thereof. .

The bank 125 is formed in a region other than the light emitting region. Accordingly, the bank 125 has a bank hole exposing the first electrode 122 corresponding to the emission region. The bank 125 may be made of an inorganic insulating material such as a silicon nitride film (SiNx) or a silicon oxide film (SiOx) or an organic insulating material such as BCB, acrylic resin or imide resin.

The organic light emitting layer 124 is positioned on the first electrode 122 exposed by the bank 125. The organic light emitting layer 124 may include a light emitting layer, an electron injection layer, an electron transport layer, a hole transport layer, a hole injection layer, and the like. The organic light emitting layer may be configured as a single light emitting layer structure that emits one light, or may be composed of a plurality of light emitting layers to emit white light.

The second electrode 126 is positioned on the organic emission layer 124. When the display panel is a top emission method, the second electrode 116 is formed of a transparent conductive material such as Indium Tin Oxide (ITO) or Indium Zinc Oxide (IZO). The light generated in the emission layer 124 is emitted to the second electrode 126.

The encapsulation layer 140 is positioned on the second electrode 126. The encapsulation layer 140 prevents oxygen and moisture penetration from outside in order to prevent oxidation of the light emitting material and the electrode material. When the organic light emitting device is exposed to moisture or oxygen, a pixel shrinkage phenomenon in which the emission region is reduced may occur, or a dark spot in the emission region may occur. The encapsulation layer may be made of an inorganic film made of a glass, metal, aluminum oxide (AlOx) or silicon (Si)-based material, or may have a structure in which an organic film and an inorganic film are alternately stacked. The inorganic film serves to block the penetration of moisture or oxygen, and the organic film serves to flatten the surface of the inorganic film. The reason for forming the encapsulation layer as a multi-layered thin film layer is to make the movement path of moisture or oxygen longer and more complicated than a single layer, making it difficult to penetrate moisture/oxygen to the organic light emitting device.

The illustrated encapsulation layer 140 may be formed, for example, in a structure in which inorganic films 142 and 146 and organic films 144 are alternately stacked. Including at least one pair of inorganic films 142 and 146 and an organic film 144 is suitable for improving barrier properties.

In order to increase the strength and/or rigidity of the display panel, one or more support layers (not shown) may be provided below the substrate 11. The support layer is attached to the opposite side (the second side) of the side (first side) where the organic light emitting element is located on both sides of the substrate 111. The support layer is polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polyethylene ether phthalate (polyethylene ether phthalate), polycarbonate (polycarbonate), polyarylate (polyarylate), polyether imide (polyether imide), polyether sulfonate (polyether sulfonate), polyimide (polyimide), polyacrylate (polyacrylate) or may be made of a thin film composed of a combination of other suitable polymers. Other suitable materials that can be used to form the support layer may be thin glass, a metal foil shielded with a dielectric, a multi-layer polymer, a polymer film containing a polymer material combined with nanoparticles or microparticles, and the like.

Meanwhile, in the example illustrated in FIG. 2, the touch sensor including the first touch electrode 152e and the second touch electrodes 154: 154e and 154b crossing each other on the encapsulation layer 140 is a touch substrate layer 196 ) It is formed on the top.

The main patterns 154e of the first touch electrode 152e and the second touch electrode are located on the same layer and are connected to the main pattern 154e of the second touch electrode of the bridge pattern 154b located on the other layer. For insulation between the bridge pattern 154b and the first touch electrode 152e, a touch insulating layer 158 is positioned therebetween.

The touch sensor may be directly formed on the encapsulation layer 140 and is added for the user's touch recognition. In some cases, even in a structure in which the touch sensor is omitted, an external light reflection prevention function may be provided in the display device of the present invention.

The cover window 200+210 described in FIG. 1 may be attached to the encapsulation layer 140 including the touch sensor through the adhesive layer 250. The adhesive layer 250 is a transparent adhesive such as OCA (Optical Clear Adhesive) and does not impair the anti-reflection function of the cover window.

On the other hand, in the flexible display device of the present invention, R, G, and B sub-pixels are shown, respectively, which can be determined by the emission color of the organic light-emitting layer 124 of the light-emitting element 120 in each sub-pixel. The region where the organic light emitting layer 124 emits light is through the open region of the bank 125 that defines the light emitting unit.

In the flexible display device of the present invention, the protruding pattern 202 of the cover window corresponds to a light emitting unit in a sub-pixel or a region other than the light emitting unit, thereby uniformizing anti-reflection characteristics through the cover window between the light emitting units.

Specifically, the principle of the cover window of the present invention will be described.

3A is a diagram showing offset interference.

As shown in FIG. 3A, when the first layer 10 and the second layer 20 having different refractive indices have mutually canceling characteristics upon incidence, they appear as 180-degree phase reversal characteristics and substantially two. When the light of wavelength is added, the final light is canceled.

(d는 반사광이 일어나는 두 계면 사이의 두께, n은 두 계면 사이의 층의 굴절률, m은 차수)의 조건을 따른다. 반사광의 파장에 대해 위 조건을 만족할 경우, 상쇄 간섭 효과가 있다.In this case, the offset interference

(d is the thickness between two interfaces where reflected light occurs, n is the refractive index of the layer between the two interfaces, m is the order). When the above conditions are satisfied for the wavelength of reflected light, there is a canceling interference effect.

3B is a diagram showing one type of constructive interference, and FIG. 3C is a diagram showing another form of constructive interference.

As shown in FIG. 3B, when the angle of the incident light decreases, when the phase difference of the amplitude is 180 degrees or less, the interference light is reinforced and the reflected light increases according to the wavelength.

In addition, as illustrated in FIG. 3C, in the reflected light at the interface of the incident light, when the amplitudes due to the refractive index and the thickness are similar and have a 180 degree phase delay, constructive interference occurs.

When there is such a constructive interference effect, the visibility of reflection of light of a specific wavelength may be prominent, and thus the cover window of the present invention is provided with a protruding pattern, thereby causing a level of offset interference as shown in FIG. 3A for the wavelength of reflected light.

4A is a perspective view showing a description of a cover window according to a first embodiment of the present invention, and FIG. 4B is a view showing a cover window according to the first embodiment of the present invention and its external light reflection preventing effect. 4C is a plan view showing the arrangement of the light emitting array unit corresponding to the cover window according to the first embodiment of the present invention.

4A, the cover window of the present invention includes a transparent substrate 201 and a protruding pattern 202 as a base layer 200. And, as shown in Figure 4b, the cover window of the present invention, the first to fourth insulating layers 211 and 212 of different refractive index differences (refractive index difference of 0.2 or more between adjacent insulating layers) on the base layer 200, 213 and 214 are stacked stacked structures 210.

In this case, it is preferable that the plurality of protruding patterns 202 have a vertical cross section of a trapezoidal shape with a shorter upper surface than the lower surface, and a side surface inclined by 15° to 45° with respect to the normal direction of the transparent substrate. This is because when light enters the cover window, it enters the normal direction of the side surface of the protruding pattern 202, because the phase of each other's light propagation wavelength is reversed by 180° from approximately the front viewing angle to the 30° viewing angle, and has the effect of canceling interference. to be. That is, the range indicated by the arrow in FIG. 4B is an area where full cancellation interference occurs.

The protruding pattern is not limited to a trapezoid on a vertical cross section. The plurality of protruding patterns may be a polyhedral frustum or a truncated cone.

As shown in FIG. 4C, the protruding pattern 202 of the present invention may be arranged according to a column in which the first to third light emitting units 310a, 310b, and 310c of sub-pixels are arranged. In this case, the second light emitting part 310b having the largest area among the light emitting parts is a blue light emitting part and has a relatively large light emitting area to compensate for the insufficient light emission efficiency of blue. Meanwhile, the first to third light emitting units 310a, 310b, and 310c refer to red, blue, and green light emitting units, respectively.

The third light emitting unit 310c that emits green light has a relatively larger arrangement, because the green light emission efficiency is relatively higher than the red and blue efficiency, thereby contributing to the efficiency of luminance in the entire display device as a large proportion. This is to increase the overall luminance efficiency.

In some cases, the first and second light emitting units 310a and 310b in the same sub-pixel column and the different pixel columns according to the characteristics of the first to third light emitting units 310a, 310b and 310c having different areas The height and refractive index of the protruding pattern 202 may be different for the third light emitting part 310c.

Reference numeral 125, which is not described, denotes a bank, and is indicated to indicate a point that is a light emitting unit that is a portion exposed by the bank.

5A is a cross-sectional view showing a cover window according to a second embodiment of the present invention, and FIG. 5B is a plan view showing the arrangement of the light emitting array unit corresponding to FIG. 5A.

5A, the cover window according to the second embodiment of the present invention has projecting patterns 402 (402a, 402b, 402c) having different heights on the transparent substrate 401.

In addition, the insulating layer stacked structure 410 is composed of a stack of a first insulating layer 411 having a low refractive index and a second insulating layer 412 having a high refractive index.

Here, the protruding patterns 402: 402a, 402b, and 420c of different heights correspond to the red light-emitting portion 310a, the green light-emitting portion 310c, and the blue light-emitting portion 310b in order from a low height.

6 is a cross-sectional view showing a cover window according to a third embodiment of the present invention.

As shown in FIG. 6, the cover window according to the third embodiment of the present invention allows the upper surface of the protruding pattern 502 to be hemispherical, and each insulating layer 511, 512 of the stacked structure 510 is also protruded. It follows the top surface of the pattern 502.

The protrusion pattern may correspond to the first sub-pixel, the second sub-pixel, and the third sub-pixel in order, so that the height may gradually decrease.

The surface of the protruding pattern may be hemispherical.

The stacked structure 510 includes a low refractive index first insulating layer 511 and a high refractive index second insulating layer 512.

7A is a cross-sectional view showing a cover window according to a fourth embodiment of the present invention, and FIG. 7B is a plan view showing the arrangement of the light emitting array unit corresponding to FIG. 7A.

7A, the cover window 600 according to the fourth embodiment of the present invention may independently form each of the protruding patterns 602: 602a, 602b, and 602c on the transparent substrate 601 in an island shape. In addition, the island shape may be a structure corresponding to each of the light emitting layers R, G, and B, as shown in FIG. 7B. In this case, the island-like protruding pattern 602 corresponds to each of the light emitting layers R, G, and B, so that the offset interference of the reflected light appears in a limited area, and the anti-reflection effect can be further improved.

Although the insulating layer stacked structure is not disclosed in FIG. 7A, as described above, the low refractive index first insulating layer and the high refractive index second insulating layer may be stacked.

Hereinafter, an embodiment for changing the structure of the transparent substrate back side will be described.

8 is a cross-sectional view showing a cover window according to a fifth embodiment of the present invention.

8, the cover window according to the fifth embodiment of the present invention, when the transparent substrate 201 is made of a high refractive index film of 1.55 to 1.65, the low-refractive-hard coating layer 700 is further attached to the back side to externally It improves the surface protection effect and further improves the anti-reflection effect by the offset interference effect.

Here, the stacked structure is the first to fourth insulating layers 211 to 214 as in the first embodiment described above, and the insulating layers adjacent to each other have a refractive index difference of 0.2 or more.

9 is a cross-sectional view showing a cover window according to a sixth embodiment of the present invention.

As shown in FIG. 9, the cover window according to the sixth embodiment of the present invention has a high refractive index hard coating layer 720 having a higher refractive index than that of the transparent substrate 711 when the transparent substrate 711 having a low refractive index is used. will be. Also in this case, the external surface protection effect is improved and the anti-reflection effect by the offset interference effect is further improved.

Similarly, in the sixth embodiment, the stacked structure is made of the first to fourth insulating layers 211 to 214 as in the first embodiment described above, and the insulating layers adjacent to each other have a refractive index difference of 0.2 or more.

10 is a cross-sectional view showing a cover window according to a seventh embodiment of the present invention.

10, the cover window according to the seventh embodiment of the present invention is the same in that the above-described fifth embodiment and the low-refractive-index hard coating layer 700 are applied, but the first insulating layer 731 and the second insulating layer It has a difference in that a pair of 732 stacked structures 730 is provided.

For example, the sub-pixels include first to third sub-pixels, and the light-emitting layer of the first sub-pixel is a first color light-emitting layer (B) emitting light of a first wavelength, and the second sub-pixels The light emitting layer is a second color light emitting layer (G) that emits light of a second wavelength with a longer wavelength than the first wavelength, and the light emitting layer of the third sub pixel emits light of a third wavelength with a longer wavelength than the second wavelength. It may be a light emitting layer (B).

Among the plurality of protrusion patterns 202 of the cover window, a protrusion pattern corresponding to the first sub-pixel may be relatively large.

The protruding pattern may be elongated in correspondence with the column of the sub-pixels.

The plurality of protruding patterns may be divided for each light emitting part of the sub-pixel.

Each layer of the laminated structure may be provided with the same thickness without a step difference in each region along the surface of the protruding pattern.

The cover window of the present invention changes the thickness and the refractive index of the insulating layers in accordance with the conditional expression according to the offset interference by the laminated structure having the difference between the refractive index thereon and the provided protruding pattern so that the reflected light interferes with the interference at multiple interfaces. This is to avoid being admitted. Therefore, the use of the polarizing plate can be omitted, and the arrangement of the color filter layer functioning as the polarizing plate can be omitted, so that the thickness can be reduced and the flexible display device can be easily used.

Then, the cover window is formed in a stacked structure of a plurality of spaced apart protruding patterns on a transparent substrate and a transparent substrate including the protruding patterns in a low-refractive-index layer and a high-refractive-index layer, thereby canceling out at multiple interfaces having different refractive indices for external light. By having the anti-reflection property of interference, external light reflection is prevented, whereby the polarizing plate can be omitted.

In addition, by omitting the polarizing plate in the flexible display device, the flexibility of the flexible display device is improved by removing the polarizer having a thick and brittle characteristic, and the limitation of the radius of curvature can be eliminated.

On the other hand, each layer having a difference in refractive index of the cover window is formed by coating the organic film, and the cover window is separately disposed on the organic light emitting element array, and the cover window is separately formed with an insulating pattern having a protruding pattern on the surface and a difference in refractive index. The formation process of the and the process of forming the organic light emitting device array are independently managed, thereby preventing damage to the organic light emitting device array due to the high temperature during the manufacturing process of the cover window.

By forming an insulating layer having a refractive index difference in the cover window with an organic layer, folding, bending, rolling, and the like can be performed according to various types of use in the flexible display device.

On the other hand, the present invention described above is not limited to the above-described embodiments and the accompanying drawings, it is possible that various substitutions, modifications and changes are possible within the scope without departing from the technical spirit of the present invention. It will be clear to those with ordinary knowledge.

111: substrate 120: light-emitting element
130: thin film transistor 140: encapsulation layer
201: transparent substrate 202: protruding pattern
210: laminated structure 211~214: insulating layer
310a: Red light emitting part (first light emitting part) 310b: Blue light emitting part (second light emitting part)
310c: Green light emitting part (third light emitting part)

Claims (21)

A flexible transparent substrate;
A plurality of protruding patterns provided on one surface of the transparent substrate;
On the transparent substrate including the plurality of protruding patterns, a cover window including a pair of stacked structures of a first insulating layer and a second insulating layer having a refractive index difference of 0.2 or more from each other. According to claim 1,
The first insulating layer and the second insulating layer are transparent organic film cover windows. According to claim 1,
The wavelength of the reflected light for external light at the surface of the first insulating layer
The wavelength of the reflected light with respect to external light on the surface of the second insulating layer has a phase difference of 180 degrees. According to claim 1,
In the stacked structure, the refractive index of the first insulating layer having a low refractive index is 1.4 to 1.55,
The refractive index of the second insulating layer having a high refractive index is 1.6 to 2.3. According to claim 1,
The plurality of protruding patterns have a vertical cross section of a trapezoidal shape with a shorter upper surface than the lower surface, and a cover window having a side surface inclined by 15° to 45° with respect to the normal direction of the transparent substrate. The method of claim 5,
In the transparent substrate, the light passing through the protruding pattern and the layered structure is offset from the front viewing angle to a viewing angle of 30°. According to claim 1,
The transparent substrate and the protruding pattern cover window having a refractive index difference of less than 0.1. According to claim 1,
A cover window further comprising a hard coating layer having a different refractive index from the transparent substrate on the opposite surface of the transparent substrate where the protruding pattern is not located. The method of claim 8,
The transparent substrate and the protruding pattern have a larger refractive index than the first insulating layer,
The hard coating layer has a lower refractive index than the transparent substrate and the protruding pattern. The method of claim 8,
The transparent substrate and the protruding pattern is less than or equal to the refractive index of the first insulating layer,
The hard coating layer is a cover window having a larger refractive index than the transparent substrate and the protruding pattern. According to claim 1,
Each layer of the laminated structure has a cover window having the same thickness in a corresponding portion of the transparent substrate and a corresponding portion of the protruding pattern. A substrate having a plurality of sub-pixels;
A thin film transistor provided in each sub-pixel of the substrate;
A light emitting element connected to the thin film transistor and including a light emitting layer emitting a predetermined color in the light emitting unit;
An encapsulation layer protecting the light emitting element; And
A flexible display device including the cover window of any one of claims 1 to 11 on the encapsulation layer. The method of claim 12,
The protruding patterns of the cover window correspond to the light emitting portion or a flexible display device corresponding to an area excluding the light emitting portion. The method of claim 12,
The sub-pixels include first to third sub-pixels,
The light emitting layer of the first sub-pixel is a first color light emitting layer that emits light of a first wavelength,
The light emitting layer of the second sub-pixel is a second color light emitting layer that emits light of a second wavelength having a longer wavelength than the first wavelength,
The light emitting layer of the third sub-pixel is a third color light emitting layer that emits light of a third wavelength having a longer wavelength than the second wavelength. The method of claim 14,
A flexible display device in which a protrusion pattern corresponding to the first sub-pixel among the plurality of protrusion patterns is relatively large. The method of claim 12,
The protruding pattern is a flexible display device that is elongated in correspondence with the column of the sub-pixels. The method of claim 12,
The plurality of protruding patterns is a flexible display device divided for each light emitting part of the sub-pixel. The method of claim 12,
The plurality of protruding patterns is a polyhedral frustum or a flexible display device having a truncated cone. The method of claim 14,
The protrusion pattern corresponds to the first sub-pixel, the second sub-pixel, and the third sub-pixel in order, so that the height is gradually reduced. The method of claim 12,
The surface of the protruding pattern is a semi-spherical flexible display device. The method of claim 12,
Each layer of the stacked structure is a flexible display device provided with the same thickness without a step difference in each region along the surface of the protruding pattern.

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