Patent ID: 12218293

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The following exemplary embodiments are provided by way of example so as to fully convey the spirit of the present disclosure to those skilled in the art to which the present disclosure pertains. Accordingly, the present disclosure is not limited to the embodiments disclosed herein and can also be implemented in different forms. In the drawings, widths, lengths, thicknesses, and the like of elements can be exaggerated for clarity and descriptive purposes. When an element or layer is referred to as being “disposed above” or “disposed on” another element or layer, it can be directly “disposed above” or “disposed on” the other element or layer or intervening elements or layers can be present. Throughout the specification, like reference numerals denote like elements having the same or similar functions.

A pixel module according to one or more exemplary embodiments of the present disclosure includes a circuit board, unit pixels arranged on the circuit board, and a molding member covering the unit pixels. The molding member includes a light diffusion layer and a black molding layer covering the light diffusion layer.

In at least one variant, the light diffusion layer may include silica or TiO2particles in a transparent matrix. The black molding layer may include a light absorbing material in a matrix. Furthermore, the light absorbing material may include carbon black. The carbon black may be coated on surfaces of organic or inorganic particles. The inorganic particles may include silica or TiO2.

In an exemplary embodiment, the black molding layer may include a plurality of layers having different concentrations of the light absorbing material.

A layer with a higher concentration of light absorbing material may be disposed further apart from the light diffusion layer.

In another exemplary embodiment, a concentration of the light absorbing material in the black molding layer may be gradually decreased from the light diffusion layer in a thickness direction of the black molding layer.

The molding member may further include a transparent molding layer disposed between the unit pixel and the light diffusion layer.

The unit pixel may include at least three light emitting devices disposed adjacent to one another.

Furthermore, the unit pixel may further include a step adjustment layer disposed between the light emitting devices.

A thickness of at least one of the light diffusion layer and the black molding layer may vary along a lateral direction of the circuit board.

The black molding layer may have a smaller thickness in an upper region of the unit pixel than in a region between the unit pixels.

An upper surface of the protection layer and upper surfaces of the connection electrodes may be flush with one another. The molding member may have a thickness within a range of 50 μm to 400 μm.

Furthermore, the molding member may be formed through a vacuum lamination technique using a film including the light diffusion layer and the black molding layer.

The pixel module may have a viewing angle of 120 degrees or less, and a maximum Δu′v′ may not exceed 0.01 in a range of +−45 degrees.

A displaying apparatus according to one or more exemplary embodiments of the present disclosure includes a panel substrate and a plurality of pixel modules disposed on the panel substrate. Each of the pixel modules includes a circuit board, unit pixels arranged on the circuit board, and a molding member covering the unit pixels. The molding member includes a light diffusion layer and a black molding layer covering the light diffusion layer.

The molding member may further include a transparent molding layer disposed between the unit pixel and the light diffusion layer.

Hereinafter, exemplary embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings.

FIG.1is a schematic plan view illustrating a displaying apparatus10000according to an exemplary embodiment, andFIG.2is a schematic plan view illustrating a pixel module1000according to an exemplary embodiment.

Referring toFIGS.1and2, the displaying apparatus10000may include a panel substrate2100and a plurality of pixel modules1000.

The displaying apparatus10000is not particularly limited, but it may include a virtual reality (VR) displaying apparatus such as a micro LED TV, a smart watch, a VR headset, or an argument reality (AR) displaying apparatus such as augmented reality glasses.

The panel substrate2100may include a circuit for a passive matrix driving or active matrix driving manner. In an exemplary embodiment, the panel substrate2100may include interconnections and resistors therein, and in another exemplary embodiment, the panel substrate2100may include interconnections, transistors, and capacitors. The panel substrate2100may also have pads on an upper surface thereof that may be electrically connected to the disposed circuits.

In an exemplary embodiment, the plurality of pixel modules1000is arranged on the panel substrate2100. Each of the pixel modules1000may include a circuit board1001, a plurality of unit pixels100disposed on the circuit board1001, and a molding member200covering the unit pixels100. In another exemplary embodiment, the plurality of unit pixels100may be arranged directly on the panel substrate2100, and the molding member200may cover the unit pixels100.

Each of the unit pixels100includes a plurality of light emitting devices10a,10b, and10c. The light emitting devices10a,10b, and10cmay emit light of different colors from one another. The light emitting devices10a,10b, and10cin each of the unit pixels100may be arranged in a line, as illustrated inFIG.2. In an exemplary embodiment, the light emitting devices10a,10b, and10cmay be arranged in a vertical direction with respect to a display screen on which an image is implemented. However, the inventive concepts are not limited thereto, and the light emitting devices10a,10b, and10cmay be arranged in a lateral direction with respect to the display screen on which the image is implemented.

When the light emitting devices10a,10b, and10care mounted directly on the panel substrate2100, a mounting failure of the light emitting devices difficult to handle is likely to occur. In this case, since all of the light emitting devices and the panel substrate2100need to be discarded, a significant cost loss may occur. On the contrary, by first manufacturing the unit pixel100on which the light emitting devices10a,10b, and10care mounted, and then selecting favorable unit pixels100and mounting them on the panel substrate2100, cost loss may be reduced.

Hereinafter, each element of the displaying apparatus10000will be described in detail in an order of the light emitting devices10a,10b, and10c, the unit pixel100, and the pixel module1000disposed in the displaying apparatus10000.

First,FIG.3Ais a schematic plan view illustrating the light emitting device10aaccording to an exemplary embodiment, andFIG.3Bis a schematic cross-sectional view taken along line A-A′ ofFIG.3A. Herein, the light emitting device10ais exemplarily described, but since the light emitting devices10band10chave a substantially similar structure to that of the light emitting device10a, repeated descriptions thereof will be omitted.

Referring toFIGS.3A and3B, the light emitting device10amay include a light emitting structure including a first conductivity type semiconductor layer21, an active layer23, and a second conductivity type semiconductor layer25, an ohmic contact layer27, a first contact pad53, a second contact pad55, an insulation layer59, a first electrode pad61, and a second electrode pad63.

The light emitting device10amay have a rectangular shape having a major axis and a minor axis in plan view. For example, a length of the major axis may have a size of about 100 μm or less, and a length of the minor axis may have a size of about 70 μm or less. The light emitting devices10a,10b, and10cmay have substantially similar shapes and sizes. The shape of the light emitting device10ais not limited to the rectangular shape having the major axis length and the minor axis length, but may be another external shape such as a square shape.

The light emitting structure, that is, the first conductivity type semiconductor layer21, the active layer23, and the second conductivity type semiconductor layer25may be grown on a substrate. The substrate may be one of various substrates that are used to grow semiconductors, such as a gallium nitride substrate, a GaAs substrate, a Si substrate, a sapphire substrate, especially a patterned sapphire substrate. The growth substrate may be separated from the semiconductor layers using a process such as a mechanical grinding, a laser lift off, a chemical lift off process, or the like. However, the inventive concepts are not limited thereto, and, in some exemplary embodiments, a portion of the substrate may remain to constitute at least a portion of the first conductivity type semiconductor layer21.

In an exemplary embodiment, in a case of the light emitting device10aemitting red light, the semiconductor layers may include aluminum gallium arsenide (AlGaAs), gallium arsenide phosphide (GaAsP), aluminum gallium indium phosphide (AlGaInP), or gallium phosphide (GaP).

In a case of the light emitting device10bemitting green light, the semiconductor layers may include indium gallium nitride (InGaN), gallium nitride (GaN), gallium phosphide (GaP), aluminum gallium indium phosphide (AlGaInP), or aluminum gallium phosphide (AlGaP).

In an exemplary embodiment, in a case of the light emitting device10cemitting blue light, the semiconductor layers may include gallium nitride (GaN), indium gallium nitride (InGaN), or zinc selenide (ZnSe).

The first conductivity type and the second conductivity type have opposite polarities, when the first conductivity type is an n-type, the second conductivity type becomes a p-type, or, when the first conductivity type is a p-type, the second conductivity type becomes an n-type.

The first conductivity type semiconductor layer21, the active layer23, and the second conductivity type semiconductor layer25may be grown on the substrate in a chamber using a known process such as metal organic chemical vapor deposition (MOCVD) process. In addition, the first conductivity type semiconductor layer21includes n-type impurities (e.g., Si, Ge, and Sn), and the second conductivity type semiconductor layer25includes p-type impurities (e.g., Mg, Sr, and Ba). In a case of the light emitting device10bor10cemitting green light or blue light, the first conductivity type semiconductor layer21may include GaN or AlGaN containing Si as a dopant, and the second conductivity type semiconductor layer25may include GaN or AlGaN containing Mg as a dopant.

Although the first conductivity type semiconductor layer21and the second conductivity type semiconductor layer25are shown as single layers in the drawings, these layers may be multiple layers. Additionally, or alternatively, the first conductivity type semiconductor layer21and the second conductivity type semiconductor layer25may also include a superlattice layer. The active layer23may include a single quantum well structure or a multiple quantum well structure, and a composition ratio of a compound semiconductor may be adjusted to emit a desired wavelength. For example, the active layer23may emit blue light, green light, red light, or ultraviolet light.

The second conductivity type semiconductor layer25and the active layer23may have a mesa M structure and may be disposed on the first conductivity type semiconductor layer21. The mesa M may include the second conductivity type semiconductor layer25and the active layer23, and may include a portion of the first conductivity type semiconductor layer21as shown inFIG.3B. The mesa M is located on a partial region of the first conductivity type semiconductor layer21, and an upper surface of the first conductivity type semiconductor layer21may be exposed around the mesa M.

In the illustrated exemplary embodiment, the mesa M is formed so as to expose the first conductivity type semiconductor layer21. The first conductivity type semiconductor layer21is disposed around the mesa M. In another exemplary embodiment, a through hole may be formed through the mesa M to expose the first conductivity type semiconductor layer21.

In some forms, the first conductivity type semiconductor layer21may have a flat light exiting surface. In other forms, the first conductivity type semiconductor layer21may have a concave-convex pattern formed by surface texturing on a side of the light exiting surface. Surface texturing may be carried out by patterning, for example, using a dry or wet etching process. For example, cone-shaped protrusions may be formed on the light exiting surface of the first conductivity type semiconductor layer21, a height of the cone may be about 2 μm to about 3 μm, a distance between the cones may be about 1.5 μm to about 2 μm, and a diameter of a bottom of the cone may be about 3 μm to about 5 μm. The cone may also be truncated, in which an upper diameter of the cone may be about 2 μm to about 3 μm.

In another exemplary embodiment, the concave-convex pattern may include a first concave-convex pattern and a second concave-convex pattern additionally formed on the first concave-convex pattern.

By forming the concave-convex pattern on the surface of the first conductivity type semiconductor layer21, total internal reflection may be reduced, thereby increasing light extraction efficiency. Surface texturing may be carried out on the first conductivity type semiconductor layers of all of the first, second, and third light emitting devices10a,10b, and10c, and thus, viewing angles of light emitted from the first, second, and third light emitting devices10a,10b, and10cmay become uniform. However, the inventive concepts are not limited thereto, and at least one of the light emitting devices10a,10b, and10cmay have a flat surface without including the concave-convex pattern.

The ohmic contact layer27is disposed on the second conductivity type semiconductor layer25to be in ohmic contact with the second conductivity type semiconductor layer25. The ohmic contact layer27may be formed of a single layer or multiple layers, and may be formed of a transparent conductive oxide film or a metal film. For example, the transparent conductive oxide film may include ITO, ZnO, or the like, and the metal film may include a metal such as Al, Ti, Cr, Ni, Au, Ge, Pt, or the like and alloys thereof.

The first contact pad53is disposed on the exposed first conductivity type semiconductor layer21. The first contact pad53may be in ohmic contact with the first conductivity type semiconductor layer21. For example, the first contact pad53may be formed of an ohmic metal layer in ohmic contact with the first conductivity type semiconductor layer21. The ohmic metal layer of the first contact pad53may be appropriately selected depending on a semiconductor material of the first conductivity type semiconductor layer21.

The first contact pad53may be omitted. The second contact pad55may be disposed on the ohmic contact layer27. The second contact pad55is electrically connected to the ohmic contact layer27. In another form, the second contact pad55may be omitted. The insulation layer59covers the mesa M, the ohmic contact layer27, the first contact pad53, and the second contact pad55. The insulation layer59has openings59aand59bexposing the first contact pad53and the second contact pad55. The insulation layer59may be formed as a single layer or multiple layers. The insulation layer59may include an insulating material such as SiO2, SiNx, Al2O3, and further, the insulation layer59may include a distributed Bragg reflector in which insulation layers having different refractive indices from one another are stacked. For example, the distributed Bragg reflector may include at least two insulation layers selected from SiO2, Si3N4, SiON, TiO2, Ta2O5, Nb2O5, and MgF2.

The distributed Bragg reflector reflects light emitted from the active layer23. The distributed Bragg reflector may exhibit high reflectance over a relatively wide wavelength range including a peak wavelength of light emitted from the active layer23, and may be designed in consideration of an incident angle of light. In an exemplary embodiment, the distributed Bragg reflector may have a higher reflectance for light incident at an incident angle of 0 degree than that for light incident at a different incident angle. In another exemplary embodiment, the distributed Bragg reflector may have a higher reflectance for light incident at a particular incident angle than that for light incident at the incident angle of 0 degree. For example, the distributed Bragg reflector may have a higher reflectance for light incident at an incident angle of 10 degree than that for light incident at the incident angle of 0 degree.

Meanwhile, the light emitting structure of the blue light emitting device10chas higher internal quantum efficiency compared to those of the light emitting structures of the red light emitting device10aand the green light emitting device10b. Accordingly, the blue light emitting device10cmay exhibit higher light extraction efficiency than those of the red and green light emitting devices10aand10b. As such, it may be difficult to properly maintain a color mixing ratio of red light, green light, and blue light.

To adjust the color mixing ratio of red light, green light, and blue light, the distributed Bragg reflectors applied to the light emitting devices10a,10b, and10cmay be formed to have different reflectance from one another. For example, the blue light emitting device10cmay have the distributed Bragg reflector having a relatively low reflectance compared to those of the red and green light emitting devices10aand10b. By way of example only, the distributed Bragg reflector formed in the blue light emitting device10cmay have a reflectance of 95% or less at the incident angle of 0 degree for blue light generated in the active layer23, and further 90% or less, the distributed Bragg reflector formed in the green light emitting device10bmay have a reflectance of about 95% or more and 99% or less at the incident angle of 0 degree for green light, and the distributed Bragg reflector formed in the red light emitting device10amay have a reflectance of 99% or more at the incident angle of 0 degree for red light.

In an exemplary embodiment, the distributed Bragg reflectors applied to the red, green, and blue light emitting devices10a,10b, and10cmay have a substantially similar thickness. For example, a difference in thickness between the distributed Bragg reflectors applied to these light emitting devices10a,10b, and10cmay be 10% or less of a thickness of a thickest distributed Bragg reflector. By reducing the thickness difference between the distributed Bragg reflectors, process conditions applied to the red, green, and blue light emitting devices10a,10b, and10c, for example, a process of patterning the insulation layer59, may be similarly set, and furthermore, it is possible to prevent the unit pixel manufacturing process from becoming complex. Moreover, the distributed Bragg reflectors applied to the red, green, and blue light emitting devices10a,10b, and10cmay have a substantially similar stacking number. However, the inventive concepts are not limited thereto.

In another exemplary embodiment, the different light emitting devices10a,10b, and10cmay include different insulation layers59. For example, the red light emitting device10amay have the distributed Bragg reflector described above, and the green and blue light emitting devices10band10cmay have a single-layered insulation layer59.

The first electrode pad61and the second electrode pad63are disposed on the insulation layer59. The first electrode pad61may extend from an upper region of the first contact pad53to an upper region of the mesa M, and the second electrode pad63may be disposed in the upper region of the mesa M. The first electrode pad61may be connected to the first contact pad53through the opening59a, and the second electrode pad63may be electrically connected to the second contact pad55. The first electrode pad61may be directly in ohmic contact with the first conductivity type semiconductor layer21, and in this case, the first contact pad53may be omitted. In addition, when the second contact pad55is omitted, the second electrode pad63may be directly connected to the ohmic contact layer27.

The first and/or second electrode pads61and63may be formed of a single layer or a multilayer metal. As a material of the first and/or second electrode pads61and63, metals such as Al, Ti, Cr, Ni, Au, or the like and alloys thereof may be used. For example, the first and second electrode pads61and63may include a Ti layer or a Cr layer as an upper most layer, and an Au layer thereunder.

Although the light emitting device10aaccording to the exemplary embodiment has been briefly described with reference to the drawings, the light emitting device10amay further include a layer having additional functions in addition to the above-described layers. For example, various layers such as a reflection layer for reflecting light, an additional insulation layer for insulating a specific element, and a solder preventing layer for preventing diffusion of solder may be further included.

In addition, when a flip chip type light emitting device is formed, the mesa may be formed to have various shapes, and locations and shapes of the first and second electrode pads61and63may also be variously modified. Further, the ohmic contact layer27may be omitted, and the second contact pad55or the second electrode pad63may directly contact the second conductivity type semiconductor layer25.

FIG.4Ais a schematic plan view illustrating a unit pixel100according to an exemplary embodiment,FIG.4Bis a schematic cross-sectional view taken along line B-B′ ofFIG.4A, andFIG.4Cis a schematic cross-sectional view taken along line C-C′ ofFIG.4A.

Referring toFIGS.4A,4B, and4C, the unit pixel100may include a transparent substrate121, first, second, and third light emitting devices10a,10b, and10c, a surface layer122, a light blocking layer123, an adhesive layer125, a step adjustment layer127, connection layers129a,129b,129c, and129d, and an insulation material layer131.

The unit pixel100provides a single pixel including the first, second, and third light emitting devices10a,10b, and10c. The first, second, and third light emitting devices10a,10b, and10cemit light of different colors, and the first, second, and third light emitting devices10a,10b, and10ccorrespond to subpixels, respectively.

The transparent substrate121is a light transmissive substrate such as PET, glass substrate, quartz, sapphire substrate, or the like. The transparent substrate121is disposed on a light exiting surface of the displaying apparatus (10000inFIG.1), and light emitted from the light emitting devices10a,10b, and10cis emitted externally through the transparent substrate121. The transparent substrate121may have an upper surface and a lower surface. The transparent substrate121may include a concave-convex pattern121pon a surface facing the light emitting devices10a,10b, and10c, that is, the upper surface. The concave-convex pattern121pscatters light emitted from the light emitting devices10a,10b, and10cto increase a viewing angle. In addition, light emitted from the light emitting devices10a,10b, and10chaving different viewing angle characteristics from one another may be emitted at a uniform viewing angle by the concave-convex pattern121p. As such, it is possible to prevent an occurrence of color difference depending on the viewing angle.

The concavo-convex pattern121pmay be regular or irregular. The concavo-convex pattern121pmay have a pitch of about 3 μm, a diameter of about 2.8 μm, and a height of about 1.8 μm, for example. The concavo-convex pattern121pmay be a pattern generally applied to a patterned sapphire substrate, but the inventive concepts are not limited thereto.

The transparent substrate121may also include an anti-reflection coating, may include an anti-glare layer, or may be treated with an anti-glare treatment. The transparent substrate121may have a thickness of about 50 μm to about 300 μm for example.

The transparent substrate121is disposed on the light exiting surface, and the transparent substrate121does not include a circuit. However, the inventive concepts are not limited thereto, and, in some exemplary embodiments, the transparent substrate121may include the circuit. Although a single unit pixel100is illustrated to be formed on a single transparent substrate121, a plurality of unit pixels100may be formed on the single transparent substrate121.

The surface layer122covers the concave-convex pattern121pof the transparent substrate121. The surface layer122may be formed along a shape of the concave-convex pattern121p. The surface layer122may improve adhesion of the light blocking layer123formed thereon. For example, the surface layer122may be formed of a silicon oxide layer. The surface layer122may be omitted depending on a type of the transparent substrate121.

The light blocking layer123is formed on the upper surface of the transparent substrate121. The light blocking layer123may contact the surface layer122. The light blocking layer123may include an absorbing material which absorbs light such as carbon black. The light absorbing material may prevent light generated in the light emitting devices10a,10b, and10cfrom leaking from a region between the transparent substrate121and the light emitting devices10a,10b, and10ctoward a side surface thereof, and may improve contrast of the displaying apparatus.

The light blocking layer123may have windows123a,123b, and123cfor a light path, so that light generated in the light emitting devices10a,10b, and10cis incident on the transparent substrate121, and for this purpose, the light blocking layer123may be patterned so as to expose the transparent substrate121. Widths of the windows123a,123b, and123cmay be narrower than those of the light emitting devices, but the inventive concepts are not limited thereto. For example, the widths of the windows123a,123b, and123cmay be greater than those of the light emitting devices10a,10b, and10c, and thus, a gap may be formed between the light emitting device10aand the light blocking layer123.

The adhesive layer125is attached onto the transparent substrate121. The adhesive layer125may cover the light blocking layer123. The adhesive layer125may be attached onto an entire surface of the transparent substrate121, but the inventive concepts are not limited thereto, and, in some exemplary embodiments, the adhesive layer125may be attached to a portion of the transparent substrate121so as to expose a region near an edge of the transparent substrate121. The adhesive layer125is used to attach the light emitting devices10a,10b, and10cto the transparent substrate121. The adhesive layer125may fill the window123a,123b, and123cformed in the light blocking layer123, as shown inFIG.4B.

The adhesive layer125may be formed as a light transmissive layer, and transmits light emitted from the light emitting devices10a,10b, and10c. The adhesive layer125may be formed using an organic adhesive. For example, the adhesive layer125may be formed using a transparent epoxy. In addition, the adhesive layer125may include a diffuser such as SiO2, TiO2, ZnO, or the like to diffuse light. A light diffuser prevents the light emitting devices10a,10band10cfrom being observed from the light exiting surface.

Meanwhile, the first, second, and third light emitting devices10a,10b, and10care disposed on the transparent substrate121. The first, second, and third light emitting devices10a,10b, and10cmay be attached to the transparent substrate121by the adhesive layer125. The first, second, and third light emitting devices10a,10b, and10cmay be disposed corresponding to the windows123a,123b, and123cof the light blocking layer123.

The first, second, and third light emitting devices10a,10b, and10cmay be disposed on a flat surface of the adhesive layer125as shown inFIGS.4B and4C. The adhesive layer125may be disposed under lower surfaces of the light emitting devices10a,10b, and10c. In another exemplary embodiment, the adhesive layer125may partially cover side surfaces of the first, second, and third light emitting devices10a,10b, and10c.

The first, second, and third light emitting devices10a,10b, and10cmay be, for example, a red light emitting device, a green light emitting device, and a blue light emitting device. Since a detailed configuration of each of the first, second, and third light emitting devices10a,10b, and10cis the same as described above with reference toFIGS.3A and3B, a detailed description thereof will be omitted.

The first, second, and third light emitting devices10a,10b, and10cmay be arranged in a line, as illustrated inFIG.4A. For instance, the first, second, and third light emitting devices10a,10b, and10care arranged side by side and surrounded by connection layers. In particular, in a case that the transparent substrate121is a sapphire substrate, the sapphire substrate may include clean-cut surfaces (e.g., m-plane) and non-clean-cut surfaces (e.g., a-plane) due to a location of a crystal plane along a cutting direction. For example, when the sapphire substrate is cut into a quadrangular shape, two cutting planes on both sides thereof (e.g., m-plane) may be cut cleanly along the crystal plane, and two remaining cutting planes (e.g., a-plane) disposed in a direction perpendicular to the cutting planes may not be cut cleanly. In this case, the clean-cut surfaces of the sapphire substrate121may be flush with an arrangement direction of the light emitting devices10a,10b, and10c. For example, inFIG.4A, the clean-cut surfaces (e.g., m-plane) may be disposed up and down, and the two remaining cut surfaces (e.g., a-plane) may be disposed left and right.

In addition, each of the first, second, and third light emitting devices10a,10b, and10cmay be arranged in parallel to one another in a major axis direction. Minor axis directions of the first, second, and third light emitting devices10a,10b, and10cmay coincide with an arrangement direction of the light emitting devices.

The first, second, and third light emitting devices10a,10b, and10cmay have been those described above with reference toFIGS.3A and3B, but the inventive concepts are not limited thereto, and various light emitting devices of a lateral type or a flip-chip structure may be used.

The step adjustment layer127covers the first, second, and third light emitting devices10a,10b, and10cand the adhesive layer125. The step adjustment layer127has openings127aexposing the first and second electrode pads61and63of the light emitting devices10a,10b, and10c. The step adjustment layer127assists to securely form the connection layers by uniformly adjusting elevations of surfaces on which the connection layers129a,129b,129c, and129dare formed. The step adjustment layer127may be formed of, for example, photosensitive polyimide.

The step adjustment layer127may be disposed in a region surrounded by an edge of the adhesive layer125, but the inventive concepts are not limited thereto. For example, the step adjustment layer127may be formed to partially expose the edge of the adhesive layer125, as shown inFIG.4B.

A side surface of the step adjustment layer127may be inclined at an angle less than 90 degrees with respect to an upper surface of the adhesive layer125. For example, the side surface of the step adjustment layer127may have an inclination angle of about 60 degrees with respect to the upper surface of the adhesive layer125.

The first, second, third, and fourth connection layers129a,129b,129c, and129dare formed on the step adjustment layer127. The connection layers129a,129b,129c, and129dmay be connected to the first and second electrode pads61and63of the first, second, and third light emitting devices10a,10b, and10cthrough the openings127aof the step adjustment layer127, as shown inFIGS.3A and3B.

In an exemplary embodiment, as illustrated inFIGS.4A and4B, the first connection layer129amay be electrically connected to a second conductivity type semiconductor layer of the first light emitting device10a, the second connection layer129bmay be electrically connected to a second conductivity of the second light emitting device10b, the third connection layer129cmay be electrically connected to a second conductivity type semiconductor layer of the third light emitting device10c, and the fourth connection layer129dmay be commonly electrically connected to first conductivity type semiconductor layers of the first, second, and third light emitting devices10a,10b, and10c. The first, second, third, and fourth connection layers129a,129b,129c, and129dmay be formed together on the step adjustment layer127, and may include, for example, Au.

In another exemplary embodiment, the first connection layer129amay be electrically connected to the first conductivity type semiconductor layer of the first light emitting device10a, the second connection layer129bmay be electrically connected to the first conductivity type semiconductor layer of the second light emitting device10b, the third connection layer129cmay be electrically connected to the first conductivity type semiconductor layer of the third light emitting device10c, and the fourth connection layer129dmay be commonly electrically connected to the second conductivity type semiconductor layers of the first, second, and third light emitting devices10a,10b, and10c. The first, second, third, and fourth connection layers129a,129b,129c, and129dmay be formed together on the step adjustment layer127.

The insulation material layer131may be formed to have a thickness smaller than that of the step adjustment layer127. A sum of the thicknesses of the insulation material layer131and the step adjustment layer127may be about 1 μm or more and about 50 μm or less, but the inventive concepts are not limited thereto. Meanwhile, a side surface of the insulation material layer131may have an inclination angle less than 90 degree with respect to the upper surface of the adhesive layer125, for example, an inclination angle of about 60 degree.

The insulation material layer131covers side surfaces of the step adjustment layer127and the connection layers129a,129b,129c, and129d. In addition, the insulation material layer131may cover a portion of the adhesive layer125. The insulation material layer131may have openings131a,131b,131c, and131dexposing the connection layers129a,129b,129c, and129d, and thus, pad regions of the unit pixel100may be defined.

In an exemplary embodiment, the insulation material layer131may be a translucent material, and may be formed of an organic or inorganic material. The insulation material layer131may be formed of, for example, polyimide. When the insulation material layer131along with the step adjustment layer127is formed of polyimide, all of lower, side, and upper surfaces of the connection layers129a,129b,129c, and129dmay be surrounded by the polyimide, except for the pad regions.

Meanwhile, the unit pixel100may be mounted on a circuit board using a bonding material such as solder, and the bonding material may bond the connection layers129a,129b,129c, and129dexposed to the openings131a,131b,131c, and131dof the insulation material layer131to pads on the circuit board.

According to the illustrated exemplary embodiment, the unit pixel100does not include separate bumps, and the connection layers129a,129b,129c, and129dare used as bonding pads. However, the inventive concepts are not limited thereto, and bonding pads covering the openings131a,131b,131c, and131dof the insulation material layer131may be formed. In an exemplary embodiment, the bonding pads may be formed to partially cover the light emitting devices10a,10b, and10coutside of upper regions of the first, second, third, and fourth connection layers129a,129b,129c, and129d.

In the illustrated exemplary embodiment, the light emitting devices10a,10b, and10care described as being attached to the transparent substrate121by the adhesive layer125, but the light emitting devices10a,10b, and10cmay be coupled to the transparent substrate121using another coupler instead of the adhesive layer125. For example, the light emitting devices10a,10b, and10cmay be coupled to the transparent substrate121using spacers, and thus, gas or liquid may be filled in a region between the light emitting devices10a,10b, and10cand the transparent substrate121. An optical layer that transmits light emitted from the light emitting devices10a,10b, and10cmay be formed by the gas or liquid. The adhesive layer125described above is also an example of the optical layer. Herein, the optical layer is formed of a material such as gas, liquid, or solid, different from those of the light emitting devices10a,10b, and10c, and thus, is distinguished from the materials of the semiconductor layers in the light emitting devices10a,10b, and10c.

FIG.5Ais a schematic partial cross-sectional view taken along line D-D′ ofFIG.2to illustrate the pixel module1000according to an exemplary embodiment, andFIG.5Bis a schematic partial cross-sectional view taken along line E-E′ ofFIG.2.

Referring toFIGS.5A and5B, the pixel module1000includes the circuit board1001and the unit pixels100arranged on the circuit board1001. Furthermore, the pixel module1000may further include the molding member200covering the unit pixels100.

The circuit board1001may include a circuit for electrically connecting the panel substrate2100and the light emitting devices10a,10b, and10c. The circuits in the circuit board1001may be formed in a multi-layer structure. The circuit board1001may also include a passive circuit for driving the light emitting devices10a,10b, and10cin a passive matrix driving manner or an active circuit for driving the light emitting devices10a,10b, and10cin an active matrix driving manner. The circuit board1001may include pads1003exposed on a surface thereof.

Since a detailed configuration of the unit pixels100is the same as described above with reference toFIGS.4A,4B, and4C, a detailed description thereof will be omitted to avoid redundancy. The unit pixels100may be arranged on the circuit board1001. The unit pixels100may be arranged in various matrices, such as 2×2, 2×3, 3×3, 4×4, 5×5, and the like.

The unit pixels100may be bonded to the circuit board1001through a bonding material1005. For example, the bonding material1005bonds connection layers129a,129b,129c, and129dexposed through the openings131a,131b,131c, and131dof the insulation material layer131described with reference toFIGS.4A,4B, and4Cto pads1003. The bonding material1005may be, for example, a solder such as AuSn, In, InSn, Au, Sn, ACF, ACP, or the like, and when using the bonding material1005as the solder, the unit pixel100and the circuit board1001may be bonded through a reflow process after a solder paste is disposed on the pads1003on the circuit board1001using appropriate technology such as screen printing. The pads1003on the circuit board1001may protrude above an upper surface of the circuit board1001, or may be disposed under the upper surface of the circuit board1001.

According to the illustrated exemplary embodiment, the bonding material1005having a single structure may be disposed between the connection layers129a,129b,129c, and129dand the pads1003, and the bonding material1005may directly connect the connection layers129a,129b,129c, and129dand the pads1003.

The molding member200covers the plurality of unit pixels100. A total thickness of the molding member200may be in a range of about 50 μm to 400 μm. The molding member200may include a light diffusion layer230and a black molding layer250. The light diffusion layer230may include a transparent matrix such as an epoxy molding compound and light diffusion particles dispersed in the transparent matrix. The light diffusion particles may be, for example, silica or TiO2, without being limited thereto. The light diffusion layer230may have, for example, a thickness within a range of about 25 μm to about 200 μm, and the light diffusion particles may be included in the light diffusion layer230, for example, within a range of about 0.2 wt % to 10 wt % based on a total weight of the light diffusion layer230. The light diffusion layer230scatters light emitted from the light emitting devices10a,10b, and10c. The light diffusion layer230assists to uniformly mix light of different colors emitted from the unit pixel100, and also prevents light emitted to a side surface of the unit pixel100from being emitted to the outside.

The black molding layer250includes a material that absorbs light in a matrix. The matrix may be, for example, a dry-film type solder resist (DFSR), photoimageable solder resist (PSR), an epoxy molding compound (EMC), or the like, without being limited thereto. The light absorbing material may include a light absorbing dye such as carbon black. The light absorbing dye may be directly dispersed in the matrix, or may be coated on surfaces of organic or inorganic particles to be dispersed in the matrix. Various types of organic or inorganic particles may be used so as to coat the light absorbing material. For example, particles coated with TiO2or silica particles with carbon black may be used. The black molding layer250may be formed to have a thickness within a range of about 25 μm to about 200 μm. A light transmittance may be adjusted by adjusting a concentration of the light absorbing material contained in the molding member200. The light absorbing material may within a range of about 0.05 wt % to about 10 wt % relative to a total matrix weight.

In other forms, the black molding layer250may be formed as a single layer in which the light absorbing material is uniformly dispersed, but the inventive concepts are not limited thereto. The black molding layer250may be formed of a plurality of layers having different concentrations of the light absorbing material. For example, the black molding layer250may include two layers having different concentrations of the light absorbing material. In this case, a first layer disposed closer to the light diffusion layer230may contain more light absorbing material than a second layer. A total absorption of light emitted upward from the unit pixel100may be reduced by making a light absorptivity of the first layer higher than that of the second layer, and thus, luminance of the pixel module1000may be increased.

In an exemplary embodiment, when the black molding layer250is formed of the plurality of layers, the layers may be clearly distinguished from one another. For example, after the layers having different concentrations of the light absorbing material are individually manufactured as films, the black molding layer250may be manufactured by sandwiching the films. Alternatively, the black molding layer250may be formed by continuously printing the layers having different concentrations of the light absorbing material. In another exemplary embodiment, the black molding layer250may be formed such that the concentration of the light absorbing material gradually decreases in a thickness direction thereof.

Light incident vertically from the unit pixels100has a short path passing through the black molding layer250and thus, easily passes through the black molding layer250, but light incident with an inclination angle has a long path through the black molding layer250, and thus, most of light is absorbed in the black molding layer250. As such, light interference between the unit pixels100may be prevented by the black molding layer250, and thus, a contrast of the displaying apparatus may be improved and moreover, a color deviation may be reduced.

The black molding layer250may be formed to have a thickness equal to or smaller than that of the light diffusion layer230. For example, in a region between the unit pixels100, the black molding layer250may have a thickness equal to or smaller than that of the light diffusion layer230. Meanwhile, the light diffusion layer230and the black molding layer250in an upper region of the unit pixel100may be thinner than the light diffusion layer230and the black molding layer250in the region between the unit pixels100, respectively. Furthermore, as shown inFIGS.5A and5B, the thickness of the black molding layer250in the upper region of the unit pixels100may be greater than that of the light diffusion layer230, without being limited thereto. For example, in the upper region of the unit pixels100, the thickness of the black molding layer250may be smaller than that of the light diffusion layer230.

In addition, in the upper region of the unit pixels100, the light diffusion layer230may have a convex upper surface, and the black molding layer250may have a flat upper surface compared to that of the light diffusion layer230. As the thickness of the light diffusion layer230increases, the thickness of the convex portion of the light diffusion layer230increases in the upper region of the unit pixels100. The thickness of the light diffusion layer230may vary along a lateral direction of the circuit board1001. In particular, the light diffusion layer230may have a relatively smaller thickness in the upper region of the unit pixels100than in the region between the unit pixels100. The thickness of the black molding layer250may also vary along the lateral direction of the circuit board1001. In particular, the black molding layer250may have a relatively smaller thickness in the upper region of the unit pixels100than in the region between the unit pixels100.

A ratio of a minimum thickness of the black molding layer250to a maximum thickness of the light diffusion layer230in the upper region of the unit pixels100may be greater than a ratio of a maximum thickness of the black molding layer250to a minimum thickness of the light diffusion layer230in the region between the unit pixels100. For example, although the light diffusion layer230and the black molding layer250have the same thickness in the region between the unit pixels100, the black molding layer250may be thicker than the light diffusion layer230in the upper region of the unit pixels100.

In another exemplary embodiment, the ratio of the minimum thickness of the black molding layer250to the maximum thickness of the light diffusion layer230in the upper region of the unit pixels100may be smaller than the ratio of the maximum thickness of the black molding layer250to the minimum thickness of the light diffusion layer230in the region between the unit pixels100. For example, although the light diffusion layer230and the black molding layer250have the same thickness in the region between the unit pixels100, the black molding layer250may be thinner than the light diffusion layer230in the upper region of the unit pixels100. By forming the black molding layer250relatively thick in the region between the unit pixels100and forming the black molding layer250relatively thin in the upper region of the unit pixels100, it is possible to increase an efficiency of light emitted upward from the unit pixels100and to further improve a contrast by blocking light incident with an inclination angle.

The molding member may be formed using, for example, appropriate techniques such as lamination, spin coating, slit coating, printing, or the like. As an example, the molding member200may be formed on the unit pixels100by a vacuum lamination technique after constricting the light diffusion layer230and the black molding layer250. The vacuum lamination technique will be described again later.

For example, after the light diffusion layer230is applied, the black molding layer250in a form of a film may be formed on the unit pixels100by a vacuum lamination technique.

A displaying apparatus10000may be provided by mounting the plurality of pixel modules1000shown inFIGS.5A and5Bon the panel substrate2100ofFIG.1. The circuit board1001has bottom pads connected to the pads1003. The bottom pads may be disposed to correspond one-to-one to the pads1003, but the number of the bottom pads may be reduced through a common connection.

In the illustrated exemplary embodiment, since the unit pixels100are formed into the pixel module1000, and the pixel modules1000are mounted on the panel substrate2100, the displaying apparatus10000may be provided, and thus, a process yield of the displaying apparatus may be improved. However, the inventive concepts are not limited thereto, and the unit pixels100may be directly mounted on the panel substrate2100.

FIG.6AandFIG.6Bare schematic partial cross-sectional views taken along line D-D′ and E-E′ ofFIG.2to illustrate a pixel module1000aaccording to an exemplary embodiment.

Referring toFIGS.6A and6B, the pixel module1000aaccording to the present exemplary embodiment is substantially similar to the pixel module1000described with reference toFIGS.5A and5B, except that a molding member200aincludes a transparent molding layer210, a light diffusion layer230a, and a black molding layer250a.

The transparent molding layer210is formed of a transparent material such as an epoxy molding compound. The light diffusion layer230ais disposed on the transparent molding layer210, and the black molding layer250ais disposed on the light diffusion layer230a. Since the light diffusion layer230aand the black molding layer250aare similar to the light diffusion layer230and the black molding layer250described above, a detailed description of the same elements will be omitted to avoid redundancy. A total thickness of the molding member200amay range from about 50 μm to about 400 μm, the transparent molding layer210in the range from about 20 μm to about 150 μm, the light diffusion layer230afrom about 15 μm to about 150 μm, and the black molding layer250afrom about 15 μm to about 150 μm.

As shown inFIGS.6A and6B, the transparent molding layer210may have a thickness larger than a thickness of the light diffusion layer230aor the black molding layer250a. Furthermore, the transparent molding layer210may have a thickness equal to or larger than total thicknesses of the light diffusion layer230aand the black molding layer250a. For example, in the region between the unit pixels100, the transparent molding layer210may have the thickness greater than or equal to the total thicknesses of the light diffusion layer230aand the black molding layer250a. In the region between the unit pixels100, the black molding layer250amay have the thickness equal to or smaller than the light diffusion layer230a.

Meanwhile, the transparent molding layer210and the light diffusion layer230ain the upper region of the unit pixel100may be thinner than the transparent molding layer210and the light diffusion layer230ain the region between the unit pixels100, respectively. In contrast, the black molding layer250amay have a substantially uniform thickness without a change in thickness, as shown inFIGS.6A and6B.

The thickness of the black molding layer250ain the upper region of the unit pixels100may be greater than the thickness of the transparent molding layer210and/or the thickness of the light diffusion layer230a, without being limited thereto. For example, in the upper region of the unit pixels100, the thickness of the black molding layer250amay be smaller than the thickness of the transparent molding layer210or the thickness of the light diffusion layer230a. Meanwhile, in the upper region of the unit pixels100, the thickness of the transparent molding layer210may be greater than the thickness of the light diffusion layer230a.

In the upper region of the unit pixels100, the transparent molding layer210may have a convex upper surface, and the light diffusion layer230aand the black molding layer250amay have a flat upper surface compared to the transparent molding layer210. Although the upper surface of the light diffusion layer230ais illustrated as being flat, the upper surface of the light diffusion layer230amay also have a convex shape, and the upper surface of the black molding layer250amay be relatively flatter than the upper surface of the light diffusion layer230a.

As the thickness of the transparent molding layer210increases, the thickness of the convex portion of the transparent molding layer210in the upper region of the unit pixels100increases. The thicknesses of the transparent molding layer210and the light diffusion layer230amay vary along the lateral direction of the circuit board1001. In particular, the transparent molding layer210and the light diffusion layer230amay have a relatively smaller thickness in the upper region of the unit pixels100than in the region between the unit pixels100. The thickness of the black molding layer250amay not substantially change along the lateral direction of the circuit board1001. However, the present disclosure is not limited thereto, and the black molding layer250amay also have a relatively smaller thickness in the upper region of the unit pixels100than in the region between the unit pixels100.

A ratio of a minimum thickness of the black molding layer250ato a minimum thickness of the light diffusion layer230ain the upper region of the unit pixels100may be greater than a ratio of a maximum thickness of the light diffusion layer230ato a maximum thickness of the black molding layer250in the region between the unit pixels100. For example, although the light diffusion layer230aand the black molding layer250ahave the same thickness in the region between the unit pixels100, the black molding layer250amay be thicker than the light diffusion layer230ain the upper region of the unit pixels100.

FIG.7Ais a schematic cross-sectional view illustrating a unit pixel100aaccording to another exemplary embodiment, andFIG.7Bis a schematic plan view illustrating the unit pixel100aaccording to another exemplary embodiment.

Referring toFIGS.7A and7B, the unit pixel100ahas a structure in which first, second, and third light emitting stacks320,330, and340are stacked, which is different from the unit pixel100described with reference toFIGS.4A,4B, and4C.

The unit pixel100aincludes a light emitting stacked structure, a first connection electrode350a, a second connection electrode350b, a third connection electrode350c, and a fourth connection electrode350dformed on the light emitting stacked structure, and a passivation layer390surrounding the connection electrodes350a,350b,350c, and350d. The unit pixel100amay also include a substrate311. Meanwhile, the light emitting stacked structure may include the first light emitting stack320, the second light emitting stack330, and the third light emitting stack340. Although the light emitting stacked structure has been illustrated as being configured to include the three light emitting stacks320,330, and340, the inventive concepts are not limited to a specific number of light emitting stacks. For example, in some exemplary embodiments, the light emitting stacked structure may include two or more light emitting stacks. Herein, as shown inFIG.7A, the unit pixel100aincludes the three light emitting stacks320,330, and340according to an exemplary embodiment.

The substrate311may be a light transmissive insulating substrate. However, in some exemplary embodiments, the substrate311may be formed to be translucent or partially transparent so as to transmit only light of a specific wavelength or transmit only a portion of light of a specific wavelength. The substrate311may be a growth substrate on which the first light emitting stack320may be epitaxially grown, for example, a sapphire substrate. However, the substrate311is not limited to the sapphire substrate, and may include various other transparent insulating materials. For example, the substrate311may include a glass, a quartz, a silicon, an organic polymer, or an organic-inorganic composite material, and may be, for example, such as silicon carbide (SiC), gallium nitride (GaN), indium gallium nitride (InGaN), aluminum gallium nitride (AlGaN), aluminum nitride (AlN), gallium oxide (Ga2O3), or a silicon substrate. In addition, the substrate311may include irregularities on an upper surface thereof, and may be, for example, a patterned sapphire substrate. By including the irregularities on the upper surface, extraction efficiency of light generated in the first light emitting stack320in contact with the substrate311may be increased. The irregularities of the substrate311may be employed so as to selectively increase a luminous intensity of the first LED stack320compared to the second LED stack330and the third LED stack340.

The first, second, and third light emitting stacks320,330, and340are configured to emit light towards the substrate311. Accordingly, light emitted from the third light emitting stack340may pass through the first and second light emitting stacks320and330. According to an exemplary embodiment, the first, second, and third light emitting stacks320,330, and340may emit light of different peak wavelengths from one another. In general, as the light emitting stack disposed farther from the substrate311emits light of a longer wavelength than that of the light emitting stack disposed near the substrate311, a light loss may be reduced. In some forms, so as to adjust a color mixing ratio of the first, second, and third light emitting stacks320,330, and340, the second LED stack330may emit light of a shorter wavelength than that of the first LED stack320. Accordingly, the luminous intensity of the second LED stack330may be reduced and the luminous intensity of the first LED stack320may be increased. It is possible to dramatically change a luminous intensity ratio of light emitted from the first, second, and third light emitting stacks. For example, the first light emitting stack320may be configured to emit green light, the second light emitting stack330to emit blue light, and the third light emitting stack340to emit red light. Accordingly, it is possible to relatively decrease the luminous intensity of blue light and relatively increase the luminous intensity of green light, and as a result, the luminous intensity ratio of red, green, and blue to be close to 3:6:1 may be easily adjusted. Furthermore, an emission area of the first, second, and third LED stacks320,330, and340may be less than or equal to about 10000 um2, further, may be less than or equal to 4000 um2, furthermore, less than or equal to 2500 um2. In addition, the emission area may be increased as a distance to the substrate311decreases, and the luminous intensity of green light may be further increased by disposing the first LED stack320emitting green light closest to the substrate311.

The first to third light emitting stacks320,330, and340include, as those described with reference toFIGS.3A and3B, a first conductivity type semiconductor layer21, an active layer23, and a second conductivity type semiconductor layer25, respectively. According to an exemplary embodiment, the first light emitting stack320may include a semiconductor material emitting green light, such as GaN, InGaN, GaP, AlGaInP, AlGaP, or the like. The second light emitting stack330may include a semiconductor material emitting blue light, such as GaN, InGaN, ZnSe, or the like, without being limited thereto. According to an exemplary embodiment, the third light emitting stack340may include, for example, a semiconductor material emitting red light such as AlGaAs, GaAsP, AlGaInP, GaP, or the like, without being limited thereto.

According to an exemplary embodiment, each of the first conductivity type semiconductor layers21and the second conductivity type semiconductor layers25of the first, second, and third light emitting stacks320,330, and340may have a single-layered structure or a multi-layered structure and, in some exemplary embodiments, may include a superlattice layer. Furthermore, the active layers23of the first, second, and third light emitting stacks320,330, and340may have a single quantum well structure or a multiple quantum well structure.

A first adhesive layer325is disposed between the first light emitting stack320and the second light emitting stack330, and a second adhesive layer335is disposed between the second light emitting stack330and the third light emitting stack340. The first and second adhesive layers325and335may include a non-conductive material that transmits light. For example, the first and second adhesive layers325and335may include an optically clear adhesive (OCA), which may include epoxy, polyimide, SUB, spin-on-glass (SOG), benzocyclobutene (BCB), without being limited thereto.

According to an exemplary embodiment, each of the first, second, and third light emitting stacks320,330and340may be driven independently. More specifically, a common voltage may be applied to one of the first and second conductivity type semiconductor layers of each of the light emitting stacks, and an individual light emitting signal may be applied to another one of the first and second conductivity type semiconductor layers of each of the light emitting stacks. Referring back toFIGS.3A and3B, the first conductivity type semiconductor layer21of each of the light emitting stacks may be n-type, and the second conductivity type semiconductor layer25may be p-type. In the first light emitting stack320, the second light emitting stack330, and the third light emitting stack340, the n-type semiconductor layer and the p-type semiconductor layer may be arranged in the same sequence, but the inventive concepts are not limited thereto. For example, the first light emitting stack320may have a reversely stacked sequence compared to those of the second light emitting stack330and the third light emitting stack340. The first, second, and third light emitting stacks320,330, and340may have a common p-type light emitting stacked structure in which the p-type semiconductor layers are commonly electrically connected, or may have a common n-type light emitting stacked structure in which the n-type semiconductor layers are commonly electrically connected.

According to the illustrated exemplary embodiment, each of the connection electrodes350a,350b,350c, and350dmay have a substantially elongated shape protruding from the substrate311. The connection electrodes350a,350b,350c, and350dmay include a metal such as Cu, Ni, Ti, Sb, Zn, Mo, Co, Sn, Ag, or an alloy thereof, without being limited thereto. For example, each of the connection electrodes350a,350b,350c, and350dmay include two or more metals or a plurality of different metallic layers so as to reduce stress from the elongated shape of the connection electrodes350a,350b,350c, and350d. In another exemplary embodiment, when the connection electrodes350a,350b,350c, and350dinclude Cu, an additional metal may be deposited or plated to suppress oxidation of Cu. In some exemplary embodiments, when the connection electrodes350a,350b,350c, and350dinclude Cu/Ni/Sn, Cu may prevent Sn from infiltrating into the light emitting stacked structure. In some exemplary embodiments, the connection electrodes350a,350b,350c, and350dmay include a seed layer for forming a metallic layer during a plating process, which will be described later.

As shown inFIGS.7A and7B, each of the connection electrodes350a,350b,350c, and350dmay have a substantially flat upper surface, and thus, an electrical connection between an external line or an electrode and the light emitting stacked structure may be facilitated, which will be described later. According to an exemplary embodiment of the present disclosure, when the unit pixel100ais a micro-LED, which has a surface area less than about 10,000 μm2as known in the art, or less than about 4,000 μm2or 2,500 μm2in other exemplary embodiments, the connection electrodes350a,350b,350c, and350dmay overlap a portion of at least one of the first, second, and third light emitting stacks320,330, and340as shown inFIGS.7A and7B. In the illustrated exemplary embodiment, the connection electrodes350a,350b,350c, and350dare illustrated as having a quadrangular pillar shape, but the present disclosure is not limited thereto. As one example, the connection electrodes350a,350b,350c, and350dmay have a cylindrical shape. Furthermore, areas of lower surfaces of the connection electrodes350a,350b,350c, and350dmay be larger than those of the upper surfaces thereof. For example, when the first to third light emitting stacks320,330, and340are patterned so as to form electrodes, the connection electrodes350a,350b,350cand350dmay cover side surfaces of the first to third light emitting stacks320,330, and340.

In general, during manufacturing, an array of a plurality of unit pixels100ais formed on the substrate311. The substrate311may be cut along scribing lines to be singularized (isolated) into each unit pixel100a, and the unit pixel100amay be transferred to another substrate or tape using various transferring techniques. In this case, when the unit pixel100aincludes the connection electrodes350a,350b,350c, and350dand one or more connection electrodes350a,350b,350c, and350dmay have metallic bumps or pillars protruding outward, the structure in which the connection electrodes350a,350b,350c, and350dmay be exposed to the outside in a transferring step. Moreover, when the unit pixel100aincludes a micro-LED, which has a surface area less than about 10,000 μm2, or less than about 4,000 μm2, or less than about 2,500 μm2, depending upon applications, handling of the unit pixel100amay become more difficult due to its small form factor.

For example, when the connection electrodes350a,350b,350c, and350dhave a substantially elongated shape such as a rod, transferring the unit pixel100ausing a conventional vacuum method is difficult due to a protruding structure of the connection electrode due to an insufficient suction area. In addition, the exposed connection electrode may be directly affected by various stresses during subsequent processes, such as when the connection electrode is in contact with a manufacturing device, which may damage the structure of the unit pixel100a. As another example, by attaching an adhesive tape on an upper surface (e.g., a surface opposite to the substrate311) of the unit pixel100a, a contact area between the unit pixel100aand the adhesive tape may be limited to the upper surfaces of the connection electrodes350a,350b,350c, and350dwhen the unit pixel100ais transferred. In this case, unlike when the adhesive tape is attached to a lower surface of the substrate, an adhesive force of the unit pixel100ato the adhesive tape may be weakened, and the unit pixel100amay be undesirably separated from the adhesive tape during transferring. As yet another example, when the unit pixel100ais transferred using a conventional pick-and-place method, an ejection pin may directly contact a portion of the unit pixel100aand damage a top structure of the light emitting structure. In particular, the ejection pin may strike a center of the unit pixel100a, and cause physical damage to the top light emitting stack of the unit pixel100a.

According to an exemplary embodiment of the present disclosure, the passivation layer390may be formed on the light emitting stacked structure. More specifically, as shown inFIG.7A, the passivation layer390is formed between the connection electrodes350a,350b,350c, and350dto cover side surfaces of the connection electrodes350a,350b,350c, and350d. Furthermore, although the passivation layer390has described as being disposed on the light emitting stacked structure inFIGS.7A-7B, in other forms, the passivation layer390may at least partially cover the side surfaces of the first to third light emitting stacks320,330, and340. In that case, the side surfaces of the first to third light emitting stacks320,330, and340may not be exposed to the outside of the unit pixel100aby being covered with the passivation layer390and/or another insulation layer.

The passivation layer390may be formed substantially flush with the upper surfaces of the connection electrodes350a,350b,350c, and350d. The passivation layer390may include an epoxy molding compound (EMC), which may be formed in various colors such as black, white, or transparent. However, the inventive concepts are not limited thereto. For example, in some exemplary embodiments, the passivation layer390may include polyimide (PID), and in this case, the PID may be provided as a dry film rather than a liquid type so as to increase a level of flatness when applied to the light emitting stacked structure. In some exemplary embodiments, the passivation layer390may include a photosensitive material. In this manner, the passivation layer390may protect the light emitting stacked structure from an external impact that may be applied during subsequent processes, as well as providing a sufficient contact area to the unit pixel100aso as to facilitate its handling during subsequent transferring steps. In addition, the passivation layer390may prevent light leakage toward the side surface of the unit pixel100aso as to prevent or at least suppress interference of light emitted from adjacent unit pixels100a.

FIG.8is a schematic cross-sectional view illustrating a pixel module1000baccording to another exemplary embodiment.

Referring toFIG.8, the pixel module1000baccording to the present exemplary embodiment is substantially similar to the pixel module1000described with reference toFIGS.5A and5B, except that a unit pixel100ais used instead of the unit pixel100.

Connection electrodes350a,350b,350c, and350dof the unit pixel100aare bonded to the pads1003on the circuit board1001. As shown inFIGS.5A and5B, the bonding material1005may be disposed between the connection electrodes and the pads1003. As shown inFIG.8, the pads1003may be disposed below the upper surface of the circuit board1001. However, the present disclosure is not limited thereto, and as shown inFIGS.5A and5B, the pads1003may protrude from the upper surface of the circuit board1001.

FIG.9is a schematic cross-sectional view illustrating a pixel module1000caccording to another exemplary embodiment.

Referring toFIG.9, the pixel module1000caccording to the present exemplary embodiment is substantially similar to the pixel module1000bdescribed with reference toFIG.8, except that a molding member200ais used instead of the molding member200. The molding member200ais described above with reference toFIGS.6A and6B.

Connection electrodes of the unit pixel100aare bonded to the pads1003on the circuit board1001. As shown inFIGS.5A and5B, the bonding material1005may be disposed between the connection electrodes and the pads1003.

FIGS.10A,10B, and10Care schematic cross-sectional views illustrating a method of manufacturing a pixel module1000according to an exemplary embodiment.

First, referring toFIG.10A, the light diffusion layer230and the black molding layer250are constricted. Each of the light diffusion layer230and the black molding layer250may be formed in a form of a film, and these films may be bonded in close contact with each other. Each of the light diffusion layer230and the black molding layer250may be manufactured in the form of the film using applying and drying techniques on a temporary substrate.

Referring toFIG.10B, unit pixels100are disposed on the circuit board1001. The unit pixels100may be transferred to the circuit board1001in a group. The unit pixels100may be bonded to pads1003on the circuit board1001using a bonding material1005. Although the pads1003are illustrated as protruding from an upper surface of the circuit board1001inFIGS.10B-10C, the pads1003may be exposed through, for example, an opening of a solder resist. Accordingly, the pads1003may be placed below the upper surface of the circuit board1001, for example, an upper surface of the solder resist. The bonding material1005may be disposed on each of the pads1003, and the unit pixels100may be bonded to the pads1003by the bonding material1005.

Referring toFIG.10C, the light diffusion layer230and the black molding layer250described with reference toFIG.10Acover the unit pixels100through a vacuum lamination process. Accordingly, the molding member200covering the unit pixels100is formed, as shown inFIG.10C.

By using the vacuum lamination process, it is possible to easily form a uniform molding member200over a large area. In addition, different optical layers may be easily formed through a simple process using the vacuum lamination process. In the illustrated exemplary embodiment, although a process of forming the molding member200including the light diffusion layer230and the black molding layer250has been described, a molding member (200ainFIG.6A) may be formed using the vacuum lamination process after the transparent molding layer210, the light diffusion layer230a, and the black molding layer250aare constricted.

In particular, when the molding member200is formed using the vacuum lamination process, the light diffusion layer230located in an upper portion of the unit pixel100may have a convex shape, as shown inFIG.10C. An upper surface of the black molding layer250may have a flat surface, and thus, a thickness of the black molding layer250located in the upper portion of the unit pixel100may be smaller than a thickness of the black molding layer250located between the unit pixels100. In addition, as shown inFIG.6A, when the molding member200ais formed using the vacuum lamination process, the transparent molding layer210located in the upper portion of the unit pixel100may have a convex shape, and the light diffusion layer230aand the black molding layer250amay have a flat upper surface.

The present disclosure is not limited to the method of manufacturing the molding members200and200ausing the vacuum lamination process. For example, various techniques such as a printing technique may be used. In addition to the vacuum lamination process, when the molding members200and200aare formed using a liquid material such as the printing technique, the light diffusion layer230or the transparent molding layer210located in the upper portion of the unit pixel100may also have a flat upper surface.

Experimental Embodiment

FIGS.11A,11B,11C,11D, and11Eare graphs illustrating a normalized light distribution of a pixel module according to structures of various molding members. Herein, the pixel modules were manufactured using unit pixels of the same stacked structure, except that molding structures were different from one another. Molding members of Comparative Example 2, Comparative Example 3, Inventive Example 1, and Inventive Example 2 below were all formed using a vacuum lamination process. For each sample, it can be determined as favorable that a viewing angle is less than 120 degrees, and a maximum value of Δu′v′ in a range of left and right +−45 degree is less than 0.01.

A molding member was not formed in Comparative Example 1 (FIG.11A), and a single layer of a black molding layer containing 0.2 wt % based on a total weight of a molding member was formed to have a thickness of about 220 μm in Comparative Example 2 (FIG.11B). In Comparative Example 3 (FIG.11C), a molding member was formed using 150 μm of a transparent molding layer and 50 μm of a black molding layer containing 0.2 wt % carbon black.

Meanwhile, in Inventive Example 1 (FIG.11D), 150 μm of a light diffusion layer containing about 0.7 wt % of TiO2particles and 50 μm of a black molding layer containing 0.2 wt % of carbon black were used, and in Inventive Example 2 (FIG.11E), 150 μm of a light diffusion layer containing about 1.0 wt % of TiO2particles and 50 μm of a black molding layer containing 0.2 wt % of carbon black were used.

In Comparative Example 1 (FIG.11A), a viewing angle was relatively wide at about 154.4 degrees, and a maximum Δu′v′ at +−45 degrees was significantly high as 0.043, indicating a large color deviation.

Meanwhile, in Comparative Example 2 (FIG.11B), a viewing angle was about 132.0 degrees which is smaller compared to that of Comparative Example 1 in which the molding member was not formed, and a maximum Δu′v′ at +−45 degrees was 0.023 which was smaller than that of Comparative Example 1, but a color deviation thereof was still quite high.

Comparative Example 3 (FIG.11C) had a viewing angle of about 131.4 degrees, and a maximum Δu′v′ at +−45 degrees was 0.018, which was improved compared to Comparative Example 2, but the viewing angle was still relatively wide and a color deviation thereof was quite high.

Meanwhile, Inventive Example 1 (FIG.11D) had a viewing angle of about 111.4 degrees, and a maximum Δu′v′ at +−45 degrees was 0.007, which had significantly improved viewing angle and color deviation compared to those of Comparative Examples 1 to 3. In particular, the maximum Δu′v′ at +−45 degrees indicating color deviation is less than 0.01, and thus, it can be seen that the color deviation is significantly reduced.

Inventive Example 2 (FIG.11E) had a viewing angle of about 110.9 degrees, and a maximum Δu′v′ at +−45 degrees was 0.006, which had significantly improved viewing angle and color deviation compared to those of Comparative Examples 1 to 3. In particular, the maximum Δu′v′ at +−45 degrees indicating color deviation is less than 0.01, and thus, it can be seen that the color deviation is significantly reduced.

As it can be seen from the above experiment, the viewing angle and the color deviation may be reduced by using the molding member including the light diffusion layer and the black molding layer.

Although some embodiments have been described herein, it should be understood that these embodiments are provided for illustration only and are not to be construed in any way as limiting the present disclosure. It should be understood that features or components of an exemplary embodiment can also be applied to other embodiments without departing from the spirit and scope of the present disclosure.