WO2022048740A1

WO2022048740A1 - Combined thin film encapsulation in flexible display devices and method of fabrication thereof

Info

Publication number: WO2022048740A1
Application number: PCT/EP2020/074452
Authority: WO
Inventors: Hayk Khachatryan; Ilkka Niemela; Vishal GANDHI
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2020-09-02
Filing date: 2020-09-02
Publication date: 2022-03-10
Also published as: CN115943750A; KR20230044287A

Abstract

A flexible display device (1) comprising an organic light emitting layer (2) and a thin film encapsulation (TFE) layer (3) providing a combined functionality of encapsulation, polarization and color filtering by having embedded a black matrix layer (4) and a color filter layer (5) within its organic layer (33) between a first inorganic layer (31) and a second inorganic layer (32). The black matrix layer (4) preferably comprises metal layers to additionally form a dielectric-metal-dielectric (DMD) structure in combination with said first inorganic layer (31) and said second inorganic layer (32) for additional flexibility. The black matrix layer (4) preferably also comprises a wire grid mesh (41) to form a polarizer layer within the TFE layer (3) for improved display performance and for a reduced display stack thickness.

Description

COMBINED THIN FILM ENCAPSULATION IN FLEXIBLE DISPLAY DEVICES AND METHOD OF FABRICATION THEREOF

TECHNICAL FIELD

The disclosure relates to display devices and, more specifically, to flexible display devices. In particular, the disclosure relates to a novel thin film encapsulation layer for flexible OLED display devices and a manufacturing method thereof.

BACKGROUND

With the advancement of an information-oriented society, various requirements for image display on devices have recently developed. Therefore, various display devices, such as liquid crystal display (LCD) devices, plasma display panel (PDP) devices, organic light-emitting display (OLED) devices are being used and manufactured.

OLED is a flat light emitting technology, using a series of organic thin films between two conductors. When electrical current is applied, a bright light is emitted. OLEDs are therefore emissive displays that do not require a backlight and so are thinner and more efficient than LCD displays which do require a white backlight. OLED display devices offer further advantages such as low energy consumption, high luminance, fast response time, wide viewing angle and lightweight, and have been broadly applied in devices such as mobile communication terminals, personal digital assistants (PDAs) and portable computers. OLED display devices are classified into passive matrix type and active matrix type, wherein active matrix type OLED display devices utilize thin film transistors (TFTs) to drive OLEDs. OLED display modules also require additional layers for durability, user interface, and optical functionality. At least one layer each of cover window (CW), touch sensor (TS), and circular polarizer (CP) is generally included, and these must be laminated together with optically clear adhesive (OCA) or liquid optically clear adhesive (LOCA) for best contrast, brightness, and mechanical durability.

Since organic materials in OLED displays are very sensitive to oxygen and moisture, the use of an encapsulation layer is fundamental for the protection of the device and to ensure the required lifetime. In early generations the OLED displays were rigid, sealed in glass barriers. These early OLED displays however cannot provide the promise of flexible form factors, the demand for which is on the rise. In particular, there is an increased demand for display-based consumer electronics coupled with consumer inclination towards energy-efficient, flexible gadgets.

To solve this problem, the structure of the display stack has been fundamentally redesigned, and the concept of flexible displays had been developed. In this concept, the main rigid components, i.e. substrate glass and cover glass, are replaced with flexible components. The substrate is replaced with high temperature resistive polyimide film, while the cover glass is replaced with a thin film encapsulation layer (TFE).

The main goal of the TFE layer is preventing water and oxygen diffusion towards OLED layers. Hence there are very strict requirements for TFE layers with respect to water permeability. Typically, the TFE layer comprises multiple layers including inorganic and organic layers. In most cases, the 3 layered structure has the best performance, wherein the two inorganic layers are usually deposited by a chemical vapor deposition (CVD) method and are therefore referred to as “CVD 1” and “CVD 2” layers. These CVD layers (i.e. inorganic layers) mainly consist of silicon oxide or nitride and these two layers are providing the main barrier properties. The organic layer is mainly an acryl based organic compound and it provides flexibility. The next in important role of the organic layer is covering particles. During deposition of the first CVD layer some particles of 3-5um in size can be deposited on the surface. When these particles move they can mechanically damage the encapsulation layer and result in the OLED display failing. To avoid movement of these particles the first CVD layer is covered by an organic component before the second CVD layer is deposited. The organic component is usually colorless and has very certain reflective index to provide optimal light from OLED device.

A problem that occurs with flexible display panels is when the laminated structure of the flexible display is flexed (bended, folded, rolled, etc.) a displacement is formed due to difference between an inner and outer perimeter. In other words, when the display stack is bended the distance measured on the outer periphery is longer than on the inner periphery. Depending on film properties such as modulus and thickness, two fundamentally different cases can be observed (or mixture of those two).

In a first case, where the modulus of the layers are close to each other, the strain distribution is equal and a neutral plan (NP) is formed. The NP means that in that layer the strain is equal to 0. Above the NP tensile strain may form while below the NP a compressive strain may develop. In case of a single NP, very high strain (stress) may occur at the outermost layers, which leads to deformation of the films and the display panel may crack in regions far from the NP.

In a second case the modulus of the layers (films) may be very different, leading to formation of multiple NPs in a laminated stack. Although in the latter case the strain on films is significantly decreased, shear strain in adhesive layers may become a very huge concern. High shear strain leads to delamination, creep and failure of adhesive layers.

Another problem may occur when the flexible display is being flexed (bended, rolled, folded) and the strain in TFE layer exceeds a critical strain value. The reason for this is that the TFE comprises thin inorganic layers (mainly SiNx and SiO2, sometime SiOxNy). The critical strain of these films depends on thickness, but in most cases (0.6-1 urn) the crack onset strain is 0.6%. Therefore, if the strain in TFE layer exceeds 0.6% the display will crack and fail.

A further issue with such display devices is that in order to ensure sufficient contrast ratio and avoid color washing effect the display stack has to include a polarizer (POL) layer. However, this POL layer has a relatively high modulus and thus significantly increases stiffness of a flexible display. The POL layer also increases the total thickness and thus may lead to increase share strain which can be a reason for failure of a display stack. In addition, the POL layer has low yield point and cracks easily, especially at lower temperatures. Although decreasing POL layer thickness may help to solve the stiffness issue, it also results in its poor reliability especially at high temperature and high humidity environment.

These problems and issues restrict wide application of flexible displays, decrease the yield during fabrication, decrease reliability, increase cost and may significantly decrease lifetime of flexible display devices. Thus, addressing these issues became imperative and technical solutions are highly anticipated.

SUMMARY

It is an object to provide an improved display device and method of fabrication therefor which overcomes or at least reduces the problems mentioned above by providing an improved thin film encapsulation solution.

The foregoing and other objects are achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.

According to a first aspect, there is provided a display device comprising a light emitting layer; an encapsulation layer disposed over the light emitting layer; a black matrix layer disposed over the light emitting layer; and a color filter layer disposed over the light emitting layer; wherein at least one of the black matrix layer and the color filter layer is embedded within the encapsulation layer.

Providing a black matrix (BM) layer and a color filter (CF) layer within the display stack allows eliminating the polarizer (POL) layer from the display device, thereby eliminating the above described issues resulting from the POL layer such as increased stiffness and dangerously low yield point. The solution also allows decreasing the total thickness of a display stack while at the same time improving the mechanical performance of the encapsulation layer itself.

Eliminating the POL layer that may potentially absorb 50% of light further improves energy consumption of the display device as it allows achieving the same brightness at 50% of the energy usage with a POL layer. This in turn extends battery operation time and the general lifetime of the display, especially for OLED devices.

In addition, embedding the BM layer and/or the CF layer within the encapsulation layer allows avoiding technical issues related to color washing effect caused by lockage of the light among sub-pixels and poor contrast ratio that may occur when using a combination of BM+CF layers to replace a POL layer, while also further decreasing total thickness of the display stack.

Moving the color filter layer, which is usually embedded in layers on top of the encapsulation layer, within the encapsulation layer further results in improved viewing angle of the display device, thereby providing an improved user experience.

Thus, this encapsulation arrangement combines multiple critical functions of a display device (encapsulation, color filtering, polarization) into one compact solution.

In one embodiment the encapsulation layer is arranged adjacent to the light emitting layer, ensuring a reduced total thickness of the display stack.

In a possible implementation form of the first aspect the encapsulation layer is a thin film encapsulation (TFE) layer comprising a first inorganic layer; a second inorganic layer disposed over the first inorganic layer; and an organic layer disposed between the first inorganic layer and the second inorganic layer; wherein the at least one of the black matrix and the color filter is embedded within the organic layer. Using a TFE layer in the display device ensures optimal resistance against water and oxygen diffusion towards the light emitting layer. In one embodiment the first inorganic layer is an inorganic film comprising any one of SiO2, SiNx, or AI2O3, thereby ensuring optimal water permeability and mechanical properties.

In one embodiment the second inorganic layer is an inorganic film comprising any one of SiNx, SiOx, SiNxOy, or AI2O3, thereby ensuring optimal water permeability and mechanical properties.

In a further possible implementation form of the first aspect the black matrix layer comprises at least one metal layer; wherein both the first inorganic layer and the second inorganic layer are dielectric layers; and wherein the black matrix layer is embedded within the organic layer to form a dielectric-metal-dielectric structure in combination with the first inorganic layer and the second inorganic layer. Embedding at least one metal layer inside the TFE structure as a dielectric-metal- dielectric (DMD) structure improves crack resistance and mechanical durability of the display device by improving the barrier properties, mechanical flexibility, and heat dissipation, which are essential requirements for display device encapsulation, especially for OLED displays.

In one embodiment the plurality of metal layers comprise any one or a combination of aluminum, silver, titanium, chromium, molybdenum, Tungsten and copper, thereby ensuring optimal mechanical and thermal resistance properties.

In a further possible implementation form of the first aspect the black matrix layer comprises a wire grid mesh, the wire grid mesh arranged to convert unpolarized light beams into polarized light beams by only transmitting vertical components of the unpolarized light beams and absorbing or reflecting horizontal components of the unpolarized light beams. Using a wire grid mesh enables improving display performance and reducing any issues resulting from emitting a standard polarizer layer as described above, by reducing light lockage as well as ambient light reflection through the use of the black matrix layer as a metal grid polarizer layer that can convert any unpolarized beam into one with a single linear polarization. In one embodiment the wire grid mesh is arranged with a mesh size of up to 500nm in height, and up to 500nm in width, which ensures optimal performance and ambient light reflection reduction.

In a further possible implementation form of the first aspect the display device further comprises a polarizer layer embedded within the encapsulation layer and arranged to cover the at least one of the black matrix layer and the color filter layer. The addition of a polarizer layer helps further reducing issues resulting from emitting a standard polarizer layer as described above, by reducing light lockage.

In a further possible implementation form of the first aspect the polarizer layer is an inorganic layer of a high reflective index material, thereby providing a quarter polarizer function.

In one embodiment the polarizer layer is arranged with a thickness between 1- 10nm, and made of at least one of TiO2, or AI2O2 and the like, which ensures optimal layer thickness and mechanical properties of the display stack.

In a further possible implementation form of the first aspect the polarizer layer comprises a colorless polymer with a refractive index between 1.2 to 1.6, which ensures optimal reduction light lockage and improves display performance.

In a further possible implementation form of the first aspect the encapsulation layer further comprises a planarization layer covering at least one of the black matrix layer and the color filter layer and forming a planar top surface, thereby ensuring optimal support surface for a second inorganic (CVD) layer of the encapsulation layer.

In one embodiment the planarization layer comprises a colorless acrylic monomer, ensuring optimal optical performance.

In a further possible implementation form of the first aspect the display device further comprises a base substrate; and an electric circuit arranged between the base substrate and the light emitting layer, the electric circuit comprising a plurality of thin film transistors, thereby resulting in an optimal display arrangement for the display device.

In a further possible implementation form of the first aspect the base substrate is a flexible substrate and the display device is a flexible display device, thereby ensuring improved flexibility.

In one embodiment the base substrate is made from polyimide, which further ensures optimal mechanical flexibility and strain resistance.

In a further possible implementation form of the first aspect the light emitting layer comprises a first electrode; a second electrode; and an electroluminescent layer arranged between the first electrode and the second electrode, wherein the first electrode is connected to at least one of the plurality of thin film transistors, which ensures optimal display performance of the device.

In a further possible implementation form of the first aspect the color filter layer comprises color filters of different colors, wherein adjacent color filters with different colors are in contact with each other, which ensures optimal display performance.

In a further possible implementation form of the first aspect the display device further comprises a touch screen panel disposed over the encapsulation layer, thereby enabling additional touch functionality for the display device.

In a further possible implementation form of the first aspect the display device further comprises a cover window arranged as an outer layer of the display device, the cover window being connected by pressure sensitive adhesive to any one of the encapsulation layer, or a touch screen panel disposed over the encapsulation layer. This ensures an optimal arrangement and mechanical protection of the display stack layers.

In one embodiment the light emitting layer is an organic light emitting layer, and the display device is an organic light emitting device, which ensures optimal display performance. According to a second aspect, there is provided a method of manufacturing a display device, the method comprising forming a light emitting layer; and forming an encapsulation layer on the light emitting layer; wherein forming the encapsulation layer comprises forming a pattern of at least one of a black matrix layer and a color filter layer embedded within the encapsulation layer.

Forming a black matrix (BM) layer and a color filter (CF) layer within a display stack allows eliminating the polarizer (POL) layer from the display device, thereby eliminating the above described issues resulting from the POL layer such as increased stiffness and dangerously low yield point. The solution also allows decreasing the total thickness of a display stack while at the same time improving the mechanical performance of the encapsulation layer itself.

In addition, forming the BM layer and/or the CF layer within the encapsulation layer allows avoiding technical issues related to color washing effect caused by lockage of the light among sub-pixels and poor contrast ratio that may occur when using a combination of BM+CF layers to replace a POL layer, while also further decreasing total thickness of the display stack.

In a possible implementation form of the second aspect forming the encapsulation layer comprises forming a first inorganic layer; forming a pattern of a black matrix layer on the first inorganic layer, the pattern comprising gaps; forming a color filter layer by disposing color filters in the gaps; forming an organic layer with a planar top surface on top of the preceding layers; and forming a second inorganic layer on the planar top surface of the organic layer. Forming the encapsulation layer by forming a black matrix pattern with gaps and disposing color filters in the gaps ensures optimal manufacturing accuracy and a reduction of possible failures. In addition, creating a planar top surface of the organic layer provides an optimal support surface for the second inorganic layer.

In a further possible implementation form of the second aspect forming any one of the first inorganic layer and second inorganic layer comprises chemical vapor deposition up to a thickness between 0,1 -6pm, more preferably between 1-2pm, which ensures optimal display stack thickness and mechanical performance.

In a further possible implementation form of the second aspect forming any one of the first inorganic layer and second inorganic layer comprises atomic layer deposition up to a thickness between 20-200nm, more preferably between 50- 80nm, which ensures optimal display stack thickness and mechanical performance.

In a further possible implementation form of the second aspect forming the pattern of a black matrix layer comprises forming a plurality of metal layers; wherein the color filter layer is a dielectric layer; and wherein forming the encapsulation layer comprises embedding both the black matrix layer and the color filter layer within the encapsulation layer, arranged in a dielectric-metal-dielectric arrangement. Embedding a plurality of metal layers inside the TFE structure as a dielectric-metal- dielectric (DMD) structure improves crack resistance and mechanical durability of the display device by improving the barrier properties, mechanical flexibility, and heat dissipation, which are essential requirements for display device encapsulation, especially for OLED displays.

In a further possible implementation form of the second aspect forming the pattern of a black matrix layer comprises fabricating a wire grid mesh arranged to convert unpolarized light beams into polarized light beams by only transmitting vertical components of the unpolarized light beams and absorbing or reflecting horizontal components of the unpolarized light beams. Using a wire grid mesh enables improving display performance and reducing any issues resulting from emitting a standard polarizer layer as described above, by reducing light lockage as well as ambient light reflection through the use of the black matrix layer as a metal grid polarizer layer that can convert any unpolarized beam into one with a single linear polarization.

In one embodiment fabricating the wire grid mesh comprises at least one of direct deposition by a selective ALD process, FMM mask deposition, or sputtering then etching, which ensures optimal manufacturing accuracy and a reduced display stack thickness.

In a further possible implementation form of the second aspect forming the color filter layer comprises material deposition up to up to a thickness of 3-4um, using any one of the methods of dying, pigment deposition, printing, or electrodeposition.

In one embodiment forming the color filter layer comprises dying, wherein materials used for forming the color filters comprise at least one of gelatin, casein, and synthetic products such as polyvinyl alcohol, and polyvinyl pyrrolidone.

In another possible embodiment the color filter layer comprises pigment deposition, and materials used as matrix comprise any one of acrylic, or epoxy acrylate photopolymerizable materials.

In another possible embodiment forming the color filter layer comprises printing using any one of the methods of screen printing, flexographic printing, offset printing, or intaglio printing.

In a further possible implementation form of the second aspect forming the encapsulation layer comprises forming a polarizer layer arranged to cover the pattern of at least one of a black matrix layer and a color filter layer embedded within the encapsulation layer. The addition of a polarizer layer helps further reducing issues resulting from emitting a standard polarizer layer as described above, by reducing light lockage. In a further possible implementation form of the second aspect the method of manufacturing a display device further comprises providing a base substrate; and forming an electric circuit between the base substrate and the light emitting layer, the electric circuit comprising a plurality of thin film transistors, thereby resulting in an optimal display arrangement for the display device.

In a further possible implementation form of the second aspect the method of manufacturing a display device further comprises disposing a touch screen panel over the encapsulation layer, thereby enabling additional touch functionality for the display device.

In a further possible implementation form of the second aspect the method of manufacturing a display device further comprises arranging a cover window as an outer layer of the display device, the cover window being connected by pressure sensitive adhesive to any one of the encapsulation layer, or a touch screen panel disposed over the encapsulation layer. This ensures an optimal arrangement and mechanical protection of the display stack layers.

These and other aspects will be apparent from and the embodiment(s) described below.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed portion of the present disclosure, the aspects, embodiments and implementations will be explained in more detail with reference to the example embodiments shown in the drawings, in which:

Fig. 1 shows a schematic cross-section of a display device in accordance with one embodiment of the first aspect;

Fig. 2 shows a schematic cross-section of a display device in accordance with another embodiment of the first aspect; Fig. 3 shows a schematic cross-section of an encapsulation layer of a display device in accordance with another embodiment of the first aspect;

Fig. 4 shows a schematic cross-section of an encapsulation layer of a display device in accordance with another embodiment of the first aspect;

Fig. 5 shows a schematic cross-section and top view of an encapsulation layer of a display device in accordance with another embodiment of the first aspect;

Fig. 6 shows a schematic illustration of a functioning of a wire grid mesh of a display device in accordance with another embodiment of the first aspect; and

Figs. 7A through 7D show steps of a method in accordance with an embodiment of the second aspect.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are set forth by way of examples in order to provide a thorough understanding of the relevant disclosure. However, it should be apparent to those skilled in the art that the present disclosure may be practiced without such details. In other instances, well known methods, procedures, systems, components, and/or circuitry have been described at a relatively high-level, without detail, in order to avoid unnecessarily obscuring aspects of the present disclosure.

Furthermore, when a first part such as a layer, a film, a region, or a plate is disposed on a second part, the first part may be not only directly on the second part but one or more third parts may intervene between them. In addition, when it is expressed that a first part such as a layer, a film, a region, or a plate is formed on a second part, the surface of the second part on which the first part is formed is not limited to an upper surface of the second part but may include other surfaces such as a side surface or a lower surface of the second part. Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

Fig. 1 illustrates a display device 1 according to an exemplary embodiment of the present disclosure comprising a light emitting layer 2, and an encapsulation layer 3 disposed over the light emitting layer 2.

The display device 1 may be a liquid crystal display (LCD) device, an electrophoretic display (EPD) device, an electrowetting display (EWD) device, or a light-emitting diode (LED) display device. In an embodiment the light emitting layer 2 is an organic light emitting layer, and the display device 1 is an organic light emitting diode (OLED) display device.

In an embodiment, the display device 1 is a flexible organic light emitting diode (FOLED) display device comprising a flexible plastic substrate on which an electroluminescent organic semiconductor is deposited allowing the device to be bent or rolled while still operating.

The encapsulation layer 3 is configured to prevent water and oxygen diffusion toward the light emitting layer 2. In an embodiment, the water permeability of the encapsulation layer 3 is less than 5*10^A-6 g water per square meter per day. In an embodiment, the encapsulation layer 3 is arranged adjacent to the light emitting layer 2, while in other possible embodiments intermittent layers may be present. The encapsulation layer 3 itself may comprise multiple layers including inorganic and organic layers, as will be explained below.

The display device 1 further comprises a black matrix layer 4 and a color filter layer 5. The color filter layer 5 may comprise color filters 51 of different colors as illustrated in Fig. 5, wherein adjacent color filters 51 with different colors may or may not be in contact with each other. The color filters 51 may be configured to generate red (R), green (G), and blue (B) pixels. The black matrix layer 4 may be arranged in a pattern between individual color filters of the color filter layer 5 and may comprise any material such as chromium or molybdenum suitable to reduce light leakage.

Both the black matrix layer 4 and the color filter layer 5 are disposed over the light emitting layer 2, with at least one of the black matrix layer 4 and the color filter layer 5 being embedded within the encapsulation layer 3. In an embodiment, both the black matrix layer 4 and the color filter layer 5 is embedded within the encapsulation layer s, as illustrated in Fig. 1. This allows eliminating the polarizer (POL) layer from the display device, thereby eliminating possible issues resulting from the POL layer such as increased stiffness and dangerously low yield point of the display device 1 , as well as decreasing the total thickness of a display stack and improving the mechanical performance of the encapsulation layer 3 itself. In addition, embedding the black matrix layer 4 and the color filter layer 5 within the encapsulation layer 3 allows avoiding technical issues related to color washing effect caused by lockage of the light among sub-pixels and poor contrast ratio that may occur when using a combination of a black matrix layer 4 and a color filter layer 5 to replace a POL layer. Moving the color filter layer 5 within the encapsulation layer 3 further results in improved viewing angle of the display device 1 , as illustrated in Fig. 3 (by dashed arrows).

As illustrated in Fig. 1 , the black matrix layer 4 may be arranged in a same plane as the color filter layer 5. The black matrix layer 4 may also be arranged in a different plane from the color filter layer 5, as shown in Fig. 2 through Fig. 5.

Fig. 2 illustrates a further exemplary embodiment of the present disclosure, wherein the encapsulation layer 3 is arranged as a thin film encapsulation (TFE) layer comprising a first inorganic layer 31 , a second inorganic layer 32 disposed over the first inorganic layer 31 , and an organic layer 33 disposed between the first inorganic layer 31 and the second inorganic layer 32. In this embodiment, the black matrix layer 4 and/or the color filter layer 5 is embedded within the organic layer 33. The first inorganic layer 31 may be arranged as an inorganic film comprising any one of SiO2, SiNx, or AI2O3. The second inorganic layer 32 may be arranged as an inorganic film comprising any one of SiNx, SiOx, SiNxOy, or AI2O3.

In an embodiment the encapsulation layer 3 may further comprise a polarizer layer

6 arranged to cover at least one of the black matrix layer 4 and/or the color filter layer 5. The polarizer layer 6 may be an inorganic layer of a high reflective index material, such as TiO2, or AI2O2 and the like, providing a quarter polarizer function. The polarizer layer 6 may be arranged with a thickness between 1-1 Onm within encapsulation layer s. In an embodiment, the polarizer layer 6 comprises a colorless polymer with a refractive index between 1.2 to 1.6.

In an embodiment the encapsulation layer 3 may further comprise a planarization layer 7 covering at least one of the black matrix layer 4 and the color filter layer 5 and forming a planar top surface, as illustrated in Fig. 7D. The planarization layer

7 may comprise a colorless acrylic monomer for optimal optical performance.

As shown in Fig. 2 and 3, the display device 1 may further comprise a base substrate 8 and an electric circuit 9 arranged between the base substrate 8 and the light emitting layer 2.

The base substrate 8 is not specifically limited to a specific material as long as the material can serve the function that the base substrate 8 is used for. For example, the base substrate 8 may be formed of an insulating material such as glass, plastic, or crystal. An organic polymer for forming the base substrate 8 may include polyimide (PI), polycarbonate (PC), polyethyeleneterepthalate (PET), polyethylene (PE), polypropylene (PP), polysulphone (PSF), methylmethacrylate (PMMA), triacetyl cellulose (TAC), cyclo-olefin polymer (COP), and cyclo-olefin copolymer (COC). The base substrate 8 may be adequately selected in consideration of mechanical strength, thermal stability, transparency, surface roughness, tractability, waterproofing property, and the like.

In possible embodiments the base substrate 8 may be a flexible substrate enabling the display device 1 to be used as a flexible display device 1. In an embodiment the base substrate 8 may be made from polyimide. As illustrated further in Fig. 3, the electric circuit 9 may comprise a plurality of thin film transistors 10, and the light emitting layer 2 may comprise a first electrode 21 , a second electrode 22, and an electroluminescent layer 23 arranged between the first electrode 21 and the second electrode 22. As also shown in Fig. 3, the first electrode 21 may be connected to at least one of the thin film transistors 10.

As also illustrated in Fig. 3, the display device 1 may further comprise a touch screen panel 11 disposed over the encapsulation layer s, and a cover window 12 arranged as an outer layer of the display device 1. The touch screen panel 11 may recognize touch of a user, proximity touch of the user, touch of an object (for example, a stylus pen), or proximity touch of the object. The proximity touch may represent a phenomenon in which the touch screen panel 11 recognizes an approach by a user or object to a position in proximity to the touch screen panel 11 as a touch even though the user or object does not directly touch the touch screen panel 11. The touch screen panel 11 may be disposed on the thin film encapsulation layer (TFE) 3 at least partly by a transfer process. In embodiments, detecting electrodes of the touch screen panel 11 can be formed by a transfer process.

The cover window 12 may be connected by pressure sensitive adhesive (PSA) 13 to any or both of the encapsulation layer 3 and the touch screen panel 11 .

Fig. 4 illustrates another exemplary embodiment of the present disclosure, wherein the black matrix layer 4 comprises at least one metal layer. In possible embodiments, the black matrix layer 4 may comprise any one or a combination of aluminum, silver, titanium, chromium, molybdenum, Tungsten and copper layers.

In this embodiment both the first inorganic layer 31 and the second inorganic layer 32 are arranged as dielectric layers, and the black matrix layer 4 is embedded within the organic layer 33 to form a dielectric-metal-dielectric (DMD) structure in combination with the first inorganic layer 31 and the second inorganic layer 32, which DMD arrangement improves crack resistance and mechanical durability of the display device 1 by improving the barrier properties, mechanical flexibility, and heat dissipation, which are essential requirements for display device 1 encapsulation, especially for OLED displays.

Fig. 5 illustrates another exemplary embodiment of the present disclosure, wherein the black matrix layer 4 comprises a wire grid mesh 41 arranged to convert unpolarized light beams 14 into polarized light beams 15 by only transmitting vertical components of the unpolarized light beams 14 and absorbing or reflecting horizontal components of the unpolarized light beams 14. This functioning of the wire grid mesh 41 arrangement of the black matrix layer 4 is further illustrated in Fig. 6, showing unpolarized light beams 14, the horizontal components of which are absorbed and/or reflected by the wire grid mesh 41 to create polarized light beams 15.

In an embodiment, the wire grid mesh 41 is arranged with a mesh size of up to 500nm in height, and up to 500nm in width for optimal polarizing effect.

In a possible embodiment, the features illustrated and explained throughout Figs. 1 to 5 are combined, i.e. both the black matrix layer 4 and the color filter layer 5 are embedded within the organic layer 33 of the TFE encapsulation layer 3 so that the black matrix layer 4 forms a DMD structure in combination with the first inorganic layer 31 and the second inorganic layer 32, while the black matrix layer 4 is further arranged in a wire grid mesh 41 to convert unpolarized light beams 14 into polarized light beams 15 and thereby providing polarization function for the TFE encapsulation layer 3, in addition to reduced thickness and improved mechanical and optical properties.

Figs. 7A through 7D illustrate steps of a method of manufacturing a display device 1 according to another exemplary embodiment of the present disclosure. Steps and features that are the same or similar to corresponding steps and features previously described or shown herein are denoted by the same reference numeral as previously used for simplicity. Fig. 7A illustrates a first manufacturing step, wherein a light emitting layer 2 is first formed, followed by forming an encapsulation layer 3 on the light emitting layer 2. In particular, as a first step of forming the encapsulation layer 3, a first inorganic layer 31 is formed on the light emitting layer 2.

In an embodiment, forming the first inorganic layer 31 comprises chemical vapor deposition CVD up to a thickness between 0,1 -6pm, more preferably between 1- 2pm. In another embodiment, forming the first inorganic layer 31 comprises atomic layer deposition ALD up to a thickness between 20-200nm, more preferably between 50-80nm.

In a following step of forming the encapsulation layer 3 illustrated in Fig. 7B, a pattern of a black matrix layer 4 is formed on the first inorganic layer 31 , the pattern comprising gaps 42 as shown also in Fig. 5. The step of forming the pattern of a black matrix layer 4 may comprise direct deposition by a selective ALD process, FMM mask deposition, or sputtering followed by etching.

In an embodiment, forming the pattern of a black matrix layer 4 comprises forming a plurality of metal layers. In this embodiment, also illustrated in Fig. 4, both the first inorganic layer 31 and the second inorganic layer 32 are dielectric layers, and forming the encapsulation layer 3 comprises embedding the black matrix layer 4 within the encapsulation layer 3, arranged in a dielectric-metal-dielectric DMD arrangement in combination with the first inorganic layer 31 and the second inorganic layer 32 to improve crack resistance and mechanical durability of the display device 1 .

In a further possible embodiment, optionally combined with the embodiment above dielectric-metal-dielectric DMD arrangement, forming the pattern of a black matrix layer 4 comprises fabricating a wire grid mesh 41 arranged to convert unpolarized light beams 14 into polarized light beams 15 by only transmitting vertical components of the unpolarized light beams 14 and absorbing or reflecting horizontal components of the unpolarized light beams 14, as illustrated in Fig. 6. In a possible embodiment the wire grid mesh 41 is formed with a mesh size of up to 500nm in height, and up to 500nm in width for optimal polarizing performance.

In a following step of forming the encapsulation layer s illustrated in Fig. 7C, a color filter layer 5 is formed by disposing color filters 51 in the previously formed gaps 42 of the black matrix layer 4. The gaps 42 may be formed as part of the wire grid mesh 41. Forming the color filter layer 5 may comprise material deposition up to up to a thickness of 3-4um, using any one of the methods of dying, pigment deposition, printing, or electrodeposition.

In an embodiment wherein forming the color filter layer 5 comprises dying, the materials used for forming the color filters 51 may comprise at least one of gelatin, casein, and synthetic products such as polyvinyl alcohol PVA, and polyvinyl pyrrolidone.

In an embodiment wherein forming the color filter layer 5 comprises pigment deposition, the materials used as matrix may comprise any one of acrylic, or epoxy acrylate photopolymerizable materials.

In an embodiment wherein forming the color filter layer 5 comprises printing, any one of the methods of screen printing, flexographic printing, offset printing, or intaglio printing may be used.

In a following step of forming the encapsulation layer 3 illustrated in Fig. 7D, an organic layer 33 with a planar top surface is formed on top of the preceding layers (black matrix layer 4 and color filter layer 5). In an embodiment the planar top surface is arranged as a planarization layer 7 and comprises a colorless acrylic monomer flattened on its top surface.

In an embodiment forming the encapsulation layer 3 may further comprise a step of forming a polarizer layer 6 as described above in detail, arranged to cover the pattern of the black matrix layer 4 and the color filter layer 5 embedded within the encapsulation layer 3. Finally, a second inorganic layer 32 is formed on the planar top surface of the organic layer 33. In an embodiment, forming the second inorganic layer 32 comprises chemical vapor deposition CVD up to a thickness between 0,1 -6pm, more preferably between 1-2pm. In another embodiment, forming the second inorganic layer 32 comprises atomic layer deposition ALD up to a thickness between 20-200nm, more preferably between 50-80nm.

As illustrated in Fig. 3, the method of manufacturing a display device 1 according to another exemplary embodiment of the present disclosure may further comprise providing a base substrate 8 and forming an electric circuit 9 between the base substrate 8 and the light emitting layer 2, the electric circuit 9 comprising a plurality of thin film transistors 10.

In a further embodiment, as also illustrated in Fig. 3, a touch screen panel 11 may be disposed over the encapsulation layer 3.

In a further embodiment, as also illustrated in Fig. 3, a cover window 12 may be arranged as an outer layer of the display device 1 . The cover window 12 may be connected by pressure sensitive adhesive 13 PSA to the encapsulation layer 3, and/or a touch screen panel 11 disposed over the encapsulation layer 3.

The various aspects and implementations have been described in conjunction with various embodiments herein. However, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed subject-matter, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

The reference signs used in the claims shall not be construed as limiting the scope.

Claims

1. A display device (1) comprising: a light emitting layer (2); an encapsulation layer (3) disposed over said light emitting layer (2); a black matrix layer (4) disposed over said light emitting layer (2); and a color filter layer (5) disposed over said light emitting layer (2); wherein at least one of said black matrix layer (4) and said color filter layer (5) is embedded within said encapsulation layer (3).

2. The display device (1 ) according to claim 1 , wherein said encapsulation layer (3) is a thin film encapsulation (TFE) layer comprising: a first inorganic layer (31); a second inorganic layer (32) disposed over said first inorganic layer (31); and an organic layer (33) disposed between said first inorganic layer (31) and said second inorganic layer (32); wherein said at least one of said black matrix layer (4) and said color filter layer (5) is embedded within said organic layer (33).

3. The display device (1 ) according to claim 2, wherein said black matrix layer (4) comprises at least one metal layer; wherein both said first inorganic layer (31 ) and said second inorganic layer (32) are dielectric layers; and wherein said black matrix layer (4) is embedded within said organic layer (33) to form a dielectric-metal-dielectric (DMD) structure in combination with said first inorganic layer (31) and said second inorganic layer (32).

4. The display device (1) according to any one of claims 1 to 3, wherein said black matrix layer (4) comprises a wire grid mesh (41), said wire grid mesh (41) arranged to convert unpolarized light beams (14) into polarized light beams (15) by only

23 transmitting vertical components of said unpolarized light beams (14) and absorbing or reflecting horizontal components of said unpolarized light beams (14).

5. The display device (1) according to any one of claims 1 to 4, further comprising: a polarizer layer (6) embedded within said encapsulation layer (3) and arranged to cover said at least one of said black matrix layer (4) and said color filter layer (5).

6. The display device (1 ) according to claim 5, wherein said polarizer layer (6) is an inorganic layer of a high reflective index material.

7. The display device (1) according to any one of claims 5 or 6, wherein said polarizer layer (6) comprises a colorless polymer with a refractive index between 1.2 to 1.6.

8. The display device (1) according to any one of claims 1 to 7, wherein said encapsulation layer (3) further comprises: a planarization layer (7) covering at least one of said black matrix layer (4) and said color filter layer (5) and forming a planar top surface.

9. The display device (1) according to any one of claims 1 to 8, further comprising: a base substrate (8); and an electric circuit (9) arranged between said base substrate (8) and said light emitting layer (2), said electric circuit (9) comprising a plurality of thin film transistors (10).

10. The display device (1) according to any one of claims 1 to 9, wherein said base substrate (8) is a flexible substrate and said display device (1) is a flexible display device (1).

11. The display device (1 ) according to any one of claims 1 to 10, further comprising: a touch screen panel (11) disposed over said encapsulation layer (3).

12. The display device (1 ) according to any one of claims 1 to 11 , further comprising: a cover window (12) arranged as an outer layer of said display device (1), said cover window (12) being connected by pressure sensitive adhesive (13) (PSA) to any one of said encapsulation layer (3), or a touch screen panel (11 ) disposed over said encapsulation layer (3).

13. A method of manufacturing a display device (1), the method comprising: forming a light emitting layer (2); and forming an encapsulation layer (3) on said light emitting layer (2); wherein forming said encapsulation layer (3) comprises forming a pattern of at least one of a black matrix layer (4) and a color filter layer (5) embedded within said encapsulation layer (3).

14. The method according to claim 13, wherein forming said encapsulation layer (3) comprises: forming a first inorganic layer (31); forming a pattern of a black matrix layer (4) on said first inorganic layer (31 ), said pattern comprising gaps (42); forming a color filter layer (5) by disposing color filters (51) in said gaps (42); forming an organic layer (33) with a planar top surface on top of the preceding layers; and forming a second inorganic layer (32) on said planar top surface of said organic layer (33).

15. The method according to claim 14, wherein forming any one of said first inorganic layer (31) and second inorganic layer (32) comprises chemical vapor deposition (CVD) up to a thickness between 0,1 -6pm, more preferably between 1- 2pm.

16. The method according to any one of claims 14 or 15, wherein forming any one of said first inorganic layer (31) and second inorganic layer (32) comprises atomic layer deposition (ALD) up to a thickness between 20-200nm, more preferably between 50-80nm.

17. The method according to any one of claims 14 to 16, wherein forming said pattern of a black matrix layer (4) comprises forming a plurality of metal layers; wherein both said first inorganic layer (31 ) and said second inorganic layer (32) are dielectric layers; and wherein forming said encapsulation layer (3) comprises embedding said black matrix layer (4) within said encapsulation layer (3), arranged in a dielectric-metal- dielectric (DMD) arrangement in combination with said first inorganic layer (31 ) and said second inorganic layer (32).

18. The method according to any one of claims 13 to 17, wherein forming said pattern of a black matrix layer (4) comprises fabricating a wire grid mesh (41) arranged to convert unpolarized light beams (14) into polarized light beams (15) by only transmitting vertical components of said unpolarized light beams (14) and absorbing or reflecting horizontal components of said unpolarized light beams (14).

19. The method according to any one of claims 13 to 18, wherein forming said color filter layer (5) comprises material deposition up to up to a thickness of 3-4um, using any one of the methods of dying, pigment deposition, printing, or electrodeposition.

20. The method according to any one of claims 13 to 19, wherein forming said encapsulation layer (3) comprises:

26 forming a polarizer layer (6) arranged to cover said pattern of at least one of a black matrix layer (4) and a color filter layer (5) embedded within said encapsulation layer (3).

21 . The method according to any one of claims 13 to 20, further comprising: providing a base substrate (8); and forming an electric circuit (9) between said base substrate (8) and said light emitting layer (2), said electric circuit (9) comprising a plurality of thin film transistors (10).

22. The method according to any one of claims 13 to 21 , further comprising: disposing a touch screen panel (11 ) over said encapsulation layer (3).

23. The method according to any one of claims 13 to 22, further comprising: arranging a cover window (12) as an outer layer of said display device (1 ), said cover window (12) being connected by pressure sensitive adhesive (13) (PSA) to any one of said encapsulation layer (3), or a touch screen panel (11 ) disposed over said encapsulation layer (3).

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