Patent Description:
In recent years, display devices having excellent characteristics such as low profile, flexibility and the like have been developed in the display technical field. On the contrary, currently commercialized main displays are represented by liquid crystal displays (LCDs) and active matrix organic light emitting devices (AMOLEDs).

However, there exist problems such as not-so-fast response time, difficult implementation of flexibility in case of LCDs, and there exist drawbacks such as short life span, not-so-good yield as well as low flexibility in case of AMOLEDs.

On the other hand, light emitting diodes (LEDs) are well known light emitting devices for converting an electrical current to light, and have been used as a light source for displaying an image in an electronic device including information communication devices since red LEDs using GaAsP compound semiconductors were made commercially available in <NUM>, together with a GaP:N-based green LEDs. Accordingly, the semiconductor light emitting devices may be used to implement a flexible display, thereby presenting a scheme for solving the problems. The semiconductor light emitting device has various advantages, such as a long lifespan, low power consumption, excellent initial driving characteristics, and high vibration resistance, compared to a filament-based light emitting device.

The size of such a semiconductor light emitting device has recently been reduced to several tens of micrometers. Therefore, when a display device is implemented using such small-sized semiconductor light emitting devices, a very large number of semiconductor light emitting devices are to be assembled on a wiring board of the display device.

However, in the process of assembling the light emitting devices, it is very difficult to precisely locate a number of semiconductor light emitting devices at desired positions on the wiring board.

On the other hand, although the light emitting devices may be directly attached to the wiring board using an anisotropic conductive film (ACF), a problem may occur in attaching a plurality of light emitting devices for a display.

That is, the electrode of the light emitting device and the electrode (e.g., anode) on a thin film transistor substrate are electrically connected through conductive balls dispersed on an adhesive layer (the adhesive layer in which these conductive balls are dispersed may form an anisotropic conductive film).

In this process, a bonding pressure is applied from the upper side while the conductive balls are positioned between the electrode of the light emitting device and the electrode on the thin film transistor substrate. Due to the bonding pressure, the conductive balls electrically connect the electrode of the light emitting device and the electrode on the thin film transistor substrate.

However, when the bonding pressure is applied, the adhesive layer flows in peripheral directions. That is, the flow of the adhesive layer in the peripheral directions is caused by the action of the bonding pressure.

As the conductive balls flow together with the adhesive layer due to the flow of the adhesive layer, the electrode of the light emitting device and the electrode on the thin film transistor substrate may not be electrically connected (circuit open).

In particular, although several light emitting devices can be electrically connected, there may be limitations in electrical connection of the entire array of many light emitting devices used in a display. That is, in the electrical connection of the entire light emitting device array used as sub-pixels of the display device, a phenomenon in which a plurality of light emitting devices are not electrically connected to the electrodes of the thin film transistor substrate (open) may occur.

In addition, when the number of conductive balls is increased to improve this phenomenon, a short circuit may occur between the two electrodes of the light emitting device.

Therefore, a method for overcoming these problems is required. <CIT>discloses a display device and a method for manufacturing the same.

An object of the present invention is to provide a display device using a light emitting device capable of directly transferring a light emitting device grown on a growth substrate to a thin film transistor substrate, and a method for manufacturing the same.

An object of the present invention is to provide a display device using a light emitting device that does not have problems caused by conductive balls, that is, some light emitting devices are not electrically connected, or the two electrodes of one light emitting device are short-circuited although the light emitting device grown on a growth substrate is directly transferred to a display substrate, and a method for manufacturing the same.

In addition, an object of the present invention is to provide a display device using a light emitting device which is very advantageous for realizing a high resolution display device, and a method for manufacturing the same, since it is possible to directly transfer the light emitting device from a growth substrate to a thin film transistor substrate.

According to a first aspect, the present invention provides a display device according to claim <NUM>.

The conductive balls may be localized on the first adhesive layers.

The conductive balls may be localized between the anode electrode and the first electrode, and between the cathode electrode and the second electrode.

The first adhesive layer may be a conductive adhesive layer. The first adhesive layer may be a non-conductive adhesive layer.

The second adhesive layer may cover the first adhesive layers spaced apart from each other.

The second adhesive layer may cover the entire light emitting device.

The anode electrode and the cathode electrode may be arranged on a polymer insulating layer of a thin film transistor substrate to implement a flexible display.

The polymer insulating layer may have a thickness smaller than a diameter of the conductive ball.

According to a second aspect, the present invention provides a method for manufacturing a display device according to claim <NUM>.

The first substrate may be a growth substrate on which the light emitting device is grown.

The first substrate may be separated by a laser lift-off method.

The second substrate may be a passive matrix substrate or a thin film transistor substrate for implementing an active matrix.

According to an embodiment of the present invention, the following effects are obtained.

First, according to the embodiment of the present invention, it is possible to directly transfer the light emitting device from the growth substrate to the thin film transistor substrate.

In this case, problems caused by the conductive balls, that is, problems in which some light emitting devices are not electrically connected, or the two electrodes of one light emitting device are short-circuited, may not occur.

As described above, it is possible to directly transfer the light emitting device from the growth substrate to the thin film transistor substrate, making it very advantageous to implement a high-resolution display device.

Moreover, according to the present invention, the problems caused by the use of the conventional conductive balls can be solved, thus greatly improving the reliability, precision, and mass productivity of a micro LED display device.

In addition, the light emitting device may be selectively mounted in a desired position on the thin film transistor substrate, so that a display device may be manufactured in a hybrid combination of organic and inorganic light emitting devices. Therefore, it is possible to develop a device having the advantages of LED (inorganic light emitting device) and OLED (organic light emitting device).

In particular, since the LED has no moisture barrier layer unlike OLED, stacking is simple, making it suitable to be applied to a flexible display.

Furthermore, there are additional technical effects not mentioned herein. Those skilled in the art can understand through the whole specification and drawings.

Hereinafter, the embodiments disclosed herein will be described in detail with reference to the accompanying drawings, and the same or similar elements are designated with the same numeral references regardless of the numerals in the drawings and their redundant description will be omitted. The suffixes "module" and "unit or portion" for components used in the following description are merely provided only for facilitation of preparing this specification, and thus they are not granted a specific meaning or function. In addition, when it is determined that detailed descriptions of related known technologies may obscure the gist of the embodiments disclosed in this specification in describing the embodiments disclosed in this specification, the same or similar components are given the same reference numbers regardless of reference numerals, and overlapping descriptions thereof will be omitted in a case where the embodiments disclosed in this specification are described in detail with reference to the accompanying drawings. The suffixes "module" and "unit or portion" for components used in the following description are merely provided only for facilitation of preparing this specification, and thus they are not granted a specific meaning or function. In addition, when it is determined that the detailed description of the related known technology may obscure the gist of embodiments disclosed herein in describing the embodiments, a detailed description thereof will be omitted. Further, it should be noted that the accompanying drawings are only for easy understanding of the embodiments disclosed in the present specification, and should not be construed as limiting the technical details disclosed in the present specification by the accompanying drawings.

Furthermore, although each drawing is described for convenience of description, it is also within the scope of the present invention as defined by the claims, that those skilled in the art implement other embodiments by combining at least two or more drawings.

It is also understood that when an element, such as a layer, region, or substrate, it is referred to as being "on" another element, it may be directly present on the other element or intervening elements in between.

A display device described herein is a concept including all display devices that display information in a unit pixel or a set of unit pixels. Therefore, the display device can be applied not only to a finished product but also to parts. For example, a panel corresponding to a part of a digital TV also independently corresponds to a display device in the present specification. The finished products include a mobile phone, a smartphone, a laptop, a digital broadcasting terminal, a personal digital assistant (PDA), a portable multimedia player (PMP), a navigation system, a slate PC, a tablet, an Ultrabook, a digital TV, a desktop computer, and the like.

However, it will be readily apparent to those skilled in the art that the configuration according to the embodiments described in the present specification may be applied to another type of display device.

In addition, a semiconductor light emitting device mentioned in this specification is a concept including an LED, a micro LED, and the like, and may be used interchangeably therewith.

<FIG> is a conceptual view illustrating an embodiment of a display device using a semiconductor light emitting device according to the present disclosure.

As shown in <FIG>, information processed by a controller (not shown) of a display device <NUM> may be displayed using a flexible display.

The flexible display may include, for example, a display that can be warped, bent, twisted, folded, or rolled by external force.

Furthermore, the flexible display may be, for example, a display manufactured on a thin and flexible substrate that can be warped, bent, folded, or rolled like paper while maintaining the display characteristics of a conventional flat panel display.

When the flexible display remains in an unbent state (e.g., a state having an infinite radius of curvature) (hereinafter referred to as a first state), the display area of the flexible display forms a flat surface. When the display in the first sate is changed to a bent state (e.g., a state having a finite radius of curvature) (hereinafter referred to as a second state) by external force, the display area may be a curved surface. As shown in <FIG>, the information displayed in the second state may be visual information output on a curved surface. Such visual information may be implemented by independently controlling the light emission of sub-pixels arranged in a matrix form. The unit pixel may mean, for example, a minimum unit for implementing one color.

The unit pixel of the flexible display may be implemented by a semiconductor light emitting device. In the present disclosure, a light emitting device (LED) is exemplified as a type of the semiconductor light emitting device configured to convert electric current into light. An example of the light emitting device may be a light emitting diode (LED). Such a light emitting diode is formed to have a small size, so that it can serve as a unit pixel even in the second state.

Hereinafter, a flexible display implemented using the light emitting diode will be described in more detail with reference to the drawings.

<FIG> is a partially enlarged view of portion A of <FIG>.

<FIG> are cross-sectional views taken along lines B-B and C-C in <FIG>.

As shown in <FIG>, <FIG>, the display device <NUM> using a passive matrix (PM) type semiconductor light emitting device is exemplified as the display device <NUM> using a semiconductor light emitting device. However, the examples described below are also applicable to an active matrix (AM) type semiconductor light emitting device.

The display device <NUM> shown in <FIG> may include a substrate <NUM>, a first electrode <NUM>, a conductive adhesive layer <NUM>, a second electrode <NUM>, and at least one semiconductor light emitting device <NUM>, as shown in <FIG>.

The substrate <NUM> may be a flexible substrate. For example, to implement a flexible display device, the substrate <NUM> may include glass or polyimide (PI). Any insulative and flexible material such as polyethylene naphthalate (PEN) or polyethylene terephthalate (PET) may be employed. In addition, the substrate <NUM> may be formed of either a transparent material or an opaque material.

The substrate <NUM> may be a wiring substrate on which the first electrode <NUM> is disposed. Thus, the first electrode <NUM> may be positioned on the substrate <NUM>.

As shown in <FIG>, an insulating layer <NUM> may be disposed on the substrate <NUM> on which the first electrode <NUM> is positioned, and an auxiliary electrode <NUM> may be positioned on the insulating layer <NUM>. In this case, a stack in which the insulating layer <NUM> is laminated on the substrate <NUM> may be a single wiring substrate. More specifically, the insulating layer <NUM> may be formed of an insulative and flexible material such as PI, PET, or PEN, and may be integrated with the substrate <NUM> to form a single substrate.

The auxiliary electrode <NUM>, which is an electrode that electrically connects the first electrode <NUM> and the semiconductor light emitting device <NUM>, is positioned on the insulating layer <NUM>, and is disposed to correspond to the position of the first electrode <NUM>. For example, the auxiliary electrode <NUM> may have a dot shape and may be electrically connected to the first electrode <NUM> by an electrode hole <NUM> formed through the insulating layer <NUM>. The electrode hole <NUM> may be formed by filling a via hole with a conductive material.

As shown in <FIG> or <FIG>, a conductive adhesive layer <NUM> may be formed on one surface of the insulating layer <NUM>, but embodiments of the present disclosure are not limited thereto. For example, a layer performing a specific function may be formed between the insulating layer <NUM> and the conductive adhesive layer <NUM>, or the conductive adhesive layer <NUM> may be disposed on the substrate <NUM> without the insulating layer <NUM>. In a structure in which the conductive adhesive layer <NUM> is disposed on the substrate <NUM>, the conductive adhesive layer <NUM> may serve as an insulating layer.

The conductive adhesive layer <NUM> may be a layer having adhesiveness and conductivity. For this purpose, a material having conductivity and a material having adhesiveness may be mixed in the conductive adhesive layer <NUM>. In addition, the conductive adhesive layer <NUM> may have ductility, thereby providing making the display device flexible.

As an example, the conductive adhesive layer <NUM> may be an anisotropic conductive film (ACF), an anisotropic conductive paste, a solution containing conductive particles, or the like. The conductive adhesive layer <NUM> may be configured as a layer that allows electrical interconnection in the direction of the Z-axis extending through the thickness, but is electrically insulative in the horizontal X-Y direction. Accordingly, the conductive adhesive layer <NUM> may be referred to as a Z-axis conductive layer (hereinafter, referred to simply as a "conductive adhesive layer").

The ACF is a film in which an anisotropic conductive medium is mixed with an insulating base member. When the ACF is subjected to heat and pressure, only a specific portion thereof becomes conductive by the anisotropic conductive medium. Hereinafter, it will be described that heat and pressure are applied to the ACF. However, another method may be used to make the ACF partially conductive. The other method may be, for example, application of only one of the heat and pressure or UV curing.

In addition, the anisotropic conductive medium may be, for example, conductive balls or conductive particles. For example, the ACF may be a film in which conductive balls are mixed with an insulating base member. Thus, when heat and pressure are applied to the ACF, only a specific portion of the ACF is allowed to be conductive by the conductive balls. The ACF may contain a plurality of particles formed by coating the core of a conductive material with an insulating film made of a polymer material. In this case, as the insulating film is destroyed in a portion to which heat and pressure are applied, the portion is made to be conductive by the core. At this time, the cores may be deformed to form layers that contact each other in the thickness direction of the film. As a more specific example, heat and pressure are applied to the whole ACF, and an electrical connection in the Z-axis direction is partially formed by the height difference of a counterpart adhered by the ACF.

As another example, the ACF may contain a plurality of particles formed by coating an insulating core with a conductive material. In this case, as the conductive material is deformed (pressed) in a portion to which heat and pressure are applied, the portion is made to be conductive in the thickness direction of the film. As another example, the conductive material may be disposed through the insulating base member in the Z-axis direction to provide conductivity in the thickness direction of the film. In this case, the conductive material may have a pointed end.

The ACF may be a fixed array ACF in which conductive balls are inserted into one surface of the insulating base member. More specifically, the insulating base member may be formed of an adhesive material, and the conductive balls may be intensively disposed on the bottom portion of the insulating base member. Thus, when the base member is subjected to heat and pressure, it may be deformed together with the conductive balls, exhibiting conductivity in the vertical direction.

However, the present disclosure is not necessarily limited thereto, and the ACF may be formed by randomly mixing conductive balls in the insulating base member, or may be composed of a plurality of layers with conductive balls arranged on one of the layers (as a double-ACF).

The anisotropic conductive paste may be a combination of a paste and conductive balls, and may be a paste in which conductive balls are mixed with an insulating and adhesive base material. Also, the solution containing conductive particles may be a solution containing any conductive particles or nanoparticles.

Referring back to <FIG>, the second electrode <NUM> is positioned on the insulating layer <NUM> and spaced apart from the auxiliary electrode <NUM>. That is, the conductive adhesive layer <NUM> is disposed on the insulating layer <NUM> having the auxiliary electrode <NUM> and the second electrode <NUM> positioned thereon.

After the conductive adhesive layer <NUM> is formed with the auxiliary electrode <NUM> and the second electrode <NUM> positioned on the insulating layer <NUM>, the semiconductor light emitting device <NUM> is connected thereto in a flip-chip form by applying heat and pressure. Thereby, the semiconductor light emitting device <NUM> is electrically connected to the first electrode <NUM> and the second electrode <NUM>.

<FIG> is a conceptual view illustrating the flip-chip type semiconductor light emitting device of <FIG>.

Referring to <FIG>, the semiconductor light emitting device may be a flip chip-type light emitting device.

For example, the semiconductor light emitting device may include a p-type electrode <NUM>, a p-type semiconductor layer <NUM> on which the p-type electrode <NUM> is formed, an active layer <NUM> formed on the p-type semiconductor layer <NUM>, an n-type semiconductor layer <NUM> formed on the active layer <NUM>, and an n-type electrode <NUM> disposed on the n-type semiconductor layer <NUM> and horizontally spaced apart from the p-type electrode <NUM>. In this case, the p-type electrode <NUM> may be electrically connected to the auxiliary electrode <NUM>, which is shown in <FIG>, by the conductive adhesive layer <NUM>, and the n-type electrode <NUM> may be electrically connected to the second electrode <NUM>.

Referring back to <FIG>, <FIG>, the auxiliary electrode <NUM> may be elongated in one direction. Thus, one auxiliary electrode may be electrically connected to the plurality of semiconductor light emitting devices <NUM>. For example, p-type electrodes of semiconductor light emitting devices on left and right sides of an auxiliary electrode may be electrically connected to one auxiliary electrode.

More specifically, the semiconductor light emitting device <NUM> may be press-fitted into the conductive adhesive layer <NUM> by heat and pressure. Thereby, only the portions of the semiconductor light emitting device <NUM> between the p-type electrode <NUM> and the auxiliary electrode <NUM> and between the n-type electrode <NUM> and the second electrode <NUM> may exhibit conductivity, and the other portions of the semiconductor light emitting device <NUM> do not exhibit conductivity as they are not press-fitted. In this way, the conductive adhesive layer <NUM> interconnects and electrically connects the semiconductor light emitting device <NUM> and the auxiliary electrode <NUM> and interconnects and electrically connects the semiconductor light emitting device <NUM> and the second electrode <NUM>.

The plurality of semiconductor light emitting devices <NUM> may constitute a light emitting device array, and a phosphor layer <NUM> may be formed on the light emitting device array.

The light emitting device array may include a plurality of semiconductor light emitting devices having different luminance values. Each semiconductor light emitting device <NUM> may constitute a unit pixel and may be electrically connected to the first electrode <NUM>. For example, a plurality of first electrodes <NUM> may be provided, and the semiconductor light emitting devices may be arranged in, for example, several columns. The semiconductor light emitting devices in each column may be electrically connected to any one of the plurality of first electrodes.

In addition, since the semiconductor light emitting devices are connected in a flip-chip form, semiconductor light emitting devices grown on a transparent dielectric substrate may be used. The semiconductor light emitting devices may be, for example, nitride semiconductor light emitting devices. Since the semiconductor light emitting device <NUM> has excellent luminance, it may constitute an individual unit pixel even when it has a small size.

As shown in <FIG>, a partition wall <NUM> may be formed between the semiconductor light emitting devices <NUM>. In this case, the partition wall <NUM> may serve to separate individual unit pixels from each other, and may be integrated with the conductive adhesive layer <NUM>. For example, by inserting the semiconductor light emitting device <NUM> into the ACF, the base member of the ACF may form the partition wall.

In addition, when the base member of the ACF is black, the partition wall <NUM> may have reflectance and increase contrast even without a separate black insulator.

As another example, a reflective partition wall may be separately provided as the partition wall <NUM>. In this case, the partition wall <NUM> may include a black or white insulator depending on the purpose of the display device. When a partition wall including a white insulator is used, reflectivity may be increased. When a partition wall including a black insulator is used, it may have reflectance and increase contrast.

The phosphor layer <NUM> may be positioned on the outer surface of the semiconductor light emitting device <NUM>. For example, the semiconductor light emitting device <NUM> may be a blue semiconductor light emitting device that emits blue (B) light, and the phosphor layer <NUM> may function to convert the blue (B) light into a color of a unit pixel. The phosphor layer <NUM> may be a red phosphor <NUM> or a green phosphor <NUM> constituting an individual pixel.

That is, the red phosphor <NUM> capable of converting blue light into red (R) light may be laminated on a blue semiconductor light emitting device at a position of a unit pixel of red color, and the green phosphor <NUM> capable of converting blue light into green (G) light may be laminated on the blue semiconductor light emitting device at a position of a unit pixel of green color. Only the blue semiconductor light emitting device may be used alone in the portion constituting the unit pixel of blue color. In this case, unit pixels of red (R), green (G), and blue (B) may constitute one pixel. More specifically, a phosphor of one color may be laminated along each line of the first electrode <NUM>. Accordingly, one line on the first electrode <NUM> may be an electrode for controlling one color. That is, red (R), green (G), and blue (B) may be sequentially disposed along the second electrode <NUM>, thereby implementing a unit pixel.

However, embodiments of the present disclosure are not limited thereto. Unit pixels of red (R), green (G), and blue (B) may be implemented by combining the semiconductor light emitting device <NUM> and the quantum dot (QD) rather than using the phosphor.

Also, a black matrix <NUM> may be disposed between the phosphor conversion layers to improve contrast. That is, the black matrix <NUM> may improve contrast of light and darkness.

However, embodiments of the present disclosure are not limited thereto, and anther structure may be applied to implement blue, red, and green colors.

<FIG> are conceptual views illustrating various examples of implementation of colors in relation to a flip-chip type semiconductor light emitting device.

Referring to <FIG>, each semiconductor light emitting device may be implemented as a high-power light emitting device emitting light of various colors including blue by using gallium nitride (GaN) as a main material and adding indium (In) and/or aluminum (Al).

In this case, each semiconductor light emitting device may be a red, green, or blue semiconductor light emitting device to form a unit pixel (sub-pixel). For example, red, green, and blue semiconductor light emitting devices R, G, and B may be alternately disposed, and unit pixels of red, green, and blue may constitute one pixel by the red, green and blue semiconductor light emitting devices. Thereby, a full-color display may be implemented.

Referring to <FIG>, the semiconductor light emitting device <NUM> a may include a white light emitting device W having a yellow phosphor conversion layer, which is provided for each device. In this case, in order to form a unit pixel, a red phosphor conversion layer <NUM>, a green phosphor conversion layer <NUM>, and a blue phosphor conversion layer <NUM> may be disposed on the white light emitting device W. In addition, a unit pixel may be formed using a color filter repeating red, green, and blue on the white light emitting device W.

Referring to <FIG>, a red phosphor conversion layer <NUM>, a green phosphor conversion layer <NUM>, and a blue phosphor conversion layer <NUM> may be provided on an ultraviolet light emitting device. Not only visible light but also ultraviolet (UV) light may be used in the entire region of the semiconductor light emitting device. In an embodiment, UV may be used as an excitation source of the upper phosphor in the semiconductor light emitting device.

Referring back to this example, the semiconductor light emitting device is positioned on the conductive adhesive layer to constitute a unit pixel in the display device. Since the semiconductor light emitting device has excellent luminance, individual unit pixels may be configured despite even when the semiconductor light emitting device has a small size.

Regarding the size of such an individual semiconductor light emitting device, the length of each side of the device may be, for example, <NUM> or less, and the device may have a rectangular or square shape. When the semiconductor light emitting device has a rectangular shape, the size thereof may be less than or equal to <NUM>×<NUM>.

In addition, even when a square semiconductor light emitting device having a side length of <NUM> is used as a unit pixel, sufficient brightness to form a display device may be obtained.

Therefore, for example, in case of a rectangular pixel having a unit pixel size of <NUM>×<NUM> (i.e., one side by the other side), a distance of a semiconductor light emitting device <NUM>, 150a, or 150b becomes sufficiently long relatively.

Thus, in this case, it is able to implement a flexible display device having high image quality over HD image quality.

The above-described display device using the semiconductor light emitting device may be prepared by a new fabricating method. Such a fabricating method will be described with reference to <FIG> as follows.

<FIG> shows cross-sectional views of a method of fabricating a display device using a semiconductor light emitting device according to the present disclosure.

Referring to <FIG>, first of all, a conductive adhesive layer <NUM> is formed on an insulating layer <NUM> located between an auxiliary electrode <NUM> and a second electrode <NUM>. The insulating layer <NUM> is tacked on a wiring substrate <NUM>. On the wiring substrate <NUM>, a first electrode <NUM>, the auxiliary electrode <NUM> and the second electrode <NUM> are disposed. In this case, the first electrode <NUM> and the second electrode <NUM> may be disposed in mutually orthogonal directions, respectively. In order to implement a flexible display device, the wiring substrate <NUM> and the insulating layer <NUM> may include glass or polyimide (PI) each.

For example, the conductive adhesive layer <NUM> may be implemented by an anisotropic conductive film. To this end, an anisotropic conductive film may be coated on the substrate on which the insulating layer <NUM> is located.

Subsequently, a temporary substrate <NUM>, on which a plurality of semiconductor light emitting devices <NUM> configuring individual pixels are located to correspond to locations of the auxiliary electrode <NUM> and the second electrodes <NUM>, is disposed in a manner that the semiconductor light emitting device <NUM> confronts the auxiliary electrode <NUM> and the second electrode <NUM>.

In this regard, the temporary substrate <NUM> is a growing substrate for growing the semiconductor light emitting device <NUM> and may include a sapphire or silicon substrate.

The semiconductor light emitting device is configured to have a space and size for configuring a display device when formed in unit of wafer, thereby being effectively used for the display device.

Subsequently, the wiring substrate <NUM> and the temporary substrate <NUM> are thermally compressed together. For example, the wiring substrate and the second substrate <NUM> may be subjected to thermocompression by applying an ACF press head. By the thermocompression, the wiring substrate <NUM> and the temporary substrate <NUM> are bonded together. Owing to the property of an anisotropic conductive film having conductivity by thermocompression, only a portion among the semiconductor light emitting device <NUM>, the auxiliary electrode <NUM> and the second electrode <NUM> has conductivity, via which the electrodes and the semiconductor light emitting device <NUM> may be connected electrically. In this case, the semiconductor light emitting device <NUM> is inserted into the anisotropic conductive film, by which a partition may be formed between the semiconductor light emitting devices <NUM>.

Then the temporary substrate <NUM> is removed. For example, the temporary substrate <NUM> may be removed using Laser Lift-Off (LLO) or Chemical Lift-Off (CLO).

Finally, by removing the temporary substrate <NUM>, the semiconductor light emitting devices <NUM> exposed externally. If necessary, the wiring substrate <NUM> to which the semiconductor light emitting devices <NUM> are coupled may be coated with silicon oxide (SiOx) or the like to form a transparent insulating layer (not shown).

In addition, a step of forming a phosphor layer on one side of the semiconductor light emitting device <NUM> may be further included. For example, the semiconductor light emitting device <NUM> may include a blue semiconductor light emitting device emitting Blue (B) light, and a red or green phosphor for converting the blue (B) light into a color of a unit pixel may form a layer on one side of the blue semiconductor light emitting device.

The above-described fabricating method or structure of the display device using the semiconductor light emitting device may be modified into various forms. For example, the above-described display device may employ a vertical semiconductor light emitting device.

Furthermore, a modification or embodiment described in the following may use the same or similar reference numbers for the same or similar configurations of the former example and the former description may apply thereto.

<FIG> is a perspective diagram of a display device using a semiconductor light emitting device according to another embodiment of the present disclosure, <FIG> is a cross-sectional diagram taken along a cutting line D-D shown in <FIG>, and <FIG> is a conceptual diagram showing a vertical type semiconductor light emitting device shown in <FIG>.

Referring to the present drawings, a display device may employ a vertical semiconductor light emitting device of a Passive Matrix (PM) type.

The display device includes a substrate <NUM>, a first electrode <NUM>, a conductive adhesive layer <NUM>, a second electrode <NUM> and at least one semiconductor light emitting device <NUM>.

The substrate <NUM> is a wiring substrate on which the first electrode <NUM> is disposed and may contain polyimide (PI) to implement a flexible display device. Besides, the substrate <NUM> may use any substance that is insulating and flexible.

The first electrode <NUM> is located on the substrate <NUM> and may be formed as a bar type electrode that is long in one direction. The first electrode <NUM> may be configured to play a role as a data electrode.

The conductive adhesive layer <NUM> is formed on the substrate <NUM> where the first electrode <NUM> is located. Like a display device to which a light emitting device of a flip chip type is applied, the conductive adhesive layer <NUM> may include one of an Anisotropic Conductive Film (ACF), an anisotropic conductive paste, a conductive particle contained solution and the like. Yet, in the present embodiment, a case of implementing the conductive adhesive layer <NUM> with the anisotropic conductive film is exemplified.

After the conductive adhesive layer has been placed in the state that the first electrode <NUM> is located on the substrate <NUM>, if the semiconductor light emitting device <NUM> is connected by applying heat and pressure thereto, the semiconductor light emitting device <NUM> is electrically connected to the first electrode <NUM>. In doing so, the semiconductor light emitting device <NUM> is preferably disposed to be located on the first electrode <NUM>.

If heat and pressure is applied to an anisotropic conductive film, as described above, since the anisotropic conductive film has conductivity partially in a thickness direction, the electrical connection is established. Therefore, the anisotropic conductive film is partitioned into a conductive portion and a non-conductive portion.

Furthermore, since the anisotropic conductive film contains an adhesive component, the conductive adhesive layer <NUM> implements mechanical coupling between the semiconductor light emitting device <NUM> and the first electrode <NUM> as well as mechanical connection.

Thus, the semiconductor light emitting device <NUM> is located on the conductive adhesive layer <NUM>, via which an individual pixel is configured in the display device. As the semiconductor light emitting device <NUM> has excellent luminance, an individual unit pixel may be configured in small size as well. Regarding a size of the individual semiconductor light emitting device <NUM>, a length of one side may be equal to or smaller than <NUM> for example and the individual semiconductor light emitting device <NUM> may include a rectangular or square element. For example, the rectangular element may have a size equal to or smaller than <NUM>×<NUM>.

The semiconductor light emitting device <NUM> may have a vertical structure.

Among the vertical type semiconductor light emitting devices, a plurality of second electrodes <NUM> respectively and electrically connected to the vertical type semiconductor light emitting devices <NUM> are located in a manner of being disposed in a direction crossing with a length direction of the first electrode <NUM>.

Referring to <FIG>, the vertical type semiconductor light emitting device <NUM> includes a p-type electrode <NUM>, a p-type semiconductor layer <NUM> formed on the p-type electrode <NUM>, an active layer <NUM> formed on the p-type semiconductor layer <NUM>, an n-type semiconductor layer <NUM> formed on the active layer <NUM>, and an n-type electrode <NUM> formed on then-type semiconductor layer <NUM>. In this case, the p-type electrode <NUM> located on a bottom side may be electrically connected to the first electrode <NUM> by the conductive adhesive layer <NUM>, and the n-type electrode <NUM> located on a top side may be electrically connected to a second electrode <NUM> described later. Since such a vertical type semiconductor light emitting device <NUM> can dispose the electrodes at top and bottom, it is considerably advantageous in reducing a chip size.

Referring to <FIG> again, a phosphor layer <NUM> may formed on one side of the semiconductor light emitting device <NUM>. For example, the semiconductor light emitting device <NUM> may include a blue semiconductor light emitting device <NUM> emitting blue (B) light, and a phosphor layer <NUM> for converting the blue (B) light into a color of a unit pixel may be provided. In this regard, the phosphor layer <NUM> may include a red phosphor <NUM> and a green phosphor <NUM> configuring an individual pixel.

Namely, at a location of configuring a red unit pixel, the red phosphor <NUM> capable of converting blue light into red (R) light may be stacked on a blue semiconductor light emitting device. At a location of configuring a green unit pixel, the green phosphor <NUM> capable of converting blue light into green (G) light may be stacked on the blue semiconductor light emitting device. Moreover, the blue semiconductor light emitting device may be singly usable for a portion that configures a blue unit pixel. In this case, the unit pixels of red (R), green (G) and blue (B) may configure a single pixel.

Yet, the present disclosure is non-limited by the above description. In a display device to which a light emitting device of a flip chip type is applied, as described above, a different structure for implementing blue, red and green may be applicable.

Regarding the present embodiment again, the second electrode <NUM> is located between the semiconductor light emitting devices <NUM> and connected to the semiconductor light emitting devices electrically. For example, the semiconductor light emitting devices <NUM> are disposed in a plurality of columns, and the second electrode <NUM> may be located between the columns of the semiconductor light emitting devices <NUM>.

Since a distance between the semiconductor light emitting devices <NUM> configuring the individual pixel is sufficiently long, the second electrode <NUM> may be located between the semiconductor light emitting devices <NUM>.

The second electrode <NUM> may be formed as an electrode of a bar type that is long in one direction and disposed in a direction vertical to the first electrode.

In addition, the second electrode <NUM> and the semiconductor light emitting device <NUM> may be electrically connected to each other by a connecting electrode protruding from the second electrode <NUM>. Particularly, the connecting electrode may include an n-type electrode of the semiconductor light emitting device <NUM>. For example, the n-type electrode is formed as an ohmic electrode for ohmic contact, and the second electrode covers at least one portion of the ohmic electrode by printing or deposition. Thus, the second electrode <NUM> and the n-type electrode of the semiconductor light emitting device <NUM> may be electrically connected to each other.

Referring to <FIG> again, the second electrode <NUM> may be located on the conductive adhesive layer <NUM>. In some cases, a transparent insulating layer (not shown) containing silicon oxide (SiOx) and the like may be formed on the substrate <NUM> having the semiconductor light emitting device <NUM> formed thereon. If the second electrode <NUM> is placed after the transparent insulating layer has been formed, the second electrode <NUM> is located on the transparent insulating layer. Alternatively, the second electrode <NUM> may be formed in a manner of being spaced apart from the conductive adhesive layer <NUM> or the transparent insulating layer.

If a transparent electrode of Indium Tin Oxide (ITO) or the like is sued to place the second electrode <NUM> on the semiconductor light emitting device <NUM>, there is a problem that ITO substance has poor adhesiveness to an n-type semiconductor layer. Therefore, according to the present disclosure, as the second electrode <NUM> is placed between the semiconductor light emitting devices <NUM>, it is advantageous in that a transparent electrode of ITO is not used. Thus, light extraction efficiency can be improved using a conductive substance having good adhesiveness to an n-type semiconductor layer as a horizontal electrode without restriction on transparent substance selection.

Referring to <FIG> again, a partition <NUM> may be located between the semiconductor light emitting devices <NUM>. Namely, in order to isolate the semiconductor light emitting device <NUM> configuring the individual pixel, the partition <NUM> may be disposed between the vertical type semiconductor light emitting devices <NUM>. In this case, the partition <NUM> may play a role in separating the individual unit pixels from each other and be formed with the conductive adhesive layer <NUM> as an integral part. For example, by inserting the semiconductor light emitting device <NUM> in an anisotropic conductive film, a base member of the anisotropic conductive film may form the partition.

In addition, if the base member of the anisotropic conductive film is black, the partition <NUM> may have reflective property as well as a contrast ratio may be increased, without a separate block insulator.

For another example, a reflective partition may be separately provided as the partition <NUM>. The partition <NUM> may include a black or white insulator depending on the purpose of the display device.

In case that the second electrode <NUM> is located right onto the conductive adhesive layer <NUM> between the semiconductor light emitting devices <NUM>, the partition <NUM> may be located between the vertical type semiconductor light emitting device <NUM> and the second electrode <NUM> each. Therefore, an individual unit pixel may be configured using the semiconductor light emitting device <NUM>. Since a distance between the semiconductor light emitting devices <NUM> is sufficiently long, the second electrode <NUM> can be placed between the semiconductor light emitting devices <NUM>. And, it may bring an effect of implementing a flexible display device having HD image quality.

In addition, as shown in <FIG>, a black matrix <NUM> may be disposed between the respective phosphors for the contrast ratio improvement. Namely, the black matrix <NUM> may improve the contrast between light and shade.

In the display device using the semiconductor light emitting device of the present disclosure described above, the semiconductor light emitting device is disposed on a wiring board in a flip chip type and used as an individual pixel.

<FIG> is a schematic diagram illustrating an example of a process for mounting a light emitting device using a conductive adhesive layer.

As described above, a conductive adhesive layer <NUM> may form a state in which a plurality of conductive balls <NUM> are dispersed in a non-conductive adhesive layer (paste) <NUM>. In this case, the conductive balls <NUM> may be distributed throughout the adhesive layer <NUM>.

Here, the conductive adhesive layer <NUM> may be an anisotropic conductive film (ACF).

As shown in (a) of <FIG>, when the conductive adhesive layer <NUM> is placed on a horizontal light emitting device <NUM> in which the first electrode <NUM> and the second electrode <NUM> are located on the same plane, the same state as in (b) of <FIG> may be achieved.

As described above, the anisotropic conductive medium may be, for example, conductive balls or conductive particles. For example, the anisotropic conductive film (ACF) is a film in which the conductive balls <NUM> are mixed with an insulating base member (adhesive layer; <NUM>), and when heat and/or pressure is applied thereto, only a specific portion is caused to have conductivity due to the conductive balls <NUM>.

<FIG> is a photograph showing an actual example of a light emitting device attached by a conductive adhesive layer.

As shown, conductive balls that have conductivity are attached between a light emitting device <NUM> and electrodes (not visible because they are covered by the light emitting device), but conductive balls <NUM> that do not have conductivity are distributed in other portions.

<FIG> is a cross-sectional schematic view illustrating an example of a process of mounting a light emitting device using a conductive adhesive layer.

Referring to <FIG>, a state in which the light emitting device <NUM> is bonded to a substrate <NUM> by the conductive balls <NUM> is illustrated.

That is, the electrode <NUM> of the light emitting device <NUM> and the electrode (e.g., an anode; <NUM>) on the substrate <NUM> may be electrically connected by the conductive balls <NUM> dispersed on the adhesive layer <NUM>.

In this case, the conductive balls <NUM> applies a bonding pressure (P) from the upper side while being positioned between the electrode <NUM> of the light emitting device <NUM> and the electrode <NUM> on the substrate <NUM>. Due to the bonding pressure (P), the conductive balls <NUM> electrically connect the electrode <NUM> of the light emitting device <NUM> and the electrode <NUM> on the substrate <NUM>.

On the other hand, when the bonding pressure (P) is applied thereto, the adhesive layer <NUM> flows in the peripheral direction (F). That is, the flow (F) of the adhesive layer <NUM> in the peripheral direction is caused by the action of the bonding pressure (P).

As the conductive balls <NUM> flow together with the adhesive layer <NUM> by the flow of the adhesive layer <NUM>, the electrode <NUM> of the light emitting device <NUM> and the electrode <NUM> on the substrate <NUM> may not be electrically connected (circuit open).

In particular, although several light emitting devices <NUM> can be electrically connected, there may be a limit to the electrical connection of the entire array of many light emitting devices <NUM> used in a display. That is, in the electrical connection of the entire array of light emitting devices <NUM> used as sub-pixels of the display device, there may occur a phenomenon in which the plurality of light emitting devices <NUM> are not electrically connected to the electrodes <NUM> of the substrate <NUM> (open).

In addition, when the number of conductive balls <NUM> is increased to resolve this phenomenon, a short circuit may occur between the two electrodes <NUM> and <NUM> of the light emitting device <NUM> (see <FIG>).

Therefore, an object of one embodiment of the present disclosure is to provide a light emitting device assembly <NUM> structure (see <FIG>) that can solve the problem when using the conductive adhesive layer <NUM> as described above and a display device in which each pixel is configured by using the light emitting device assembly <NUM> structure.

According to an embodiment of the present disclosure, the conductive ball may be localized only on the electrode of the light emitting device, thereby solving the problem of using the conventional conductive adhesive layer <NUM> described above.

<FIG> is a schematic diagram illustrating a process of mounting a light emitting device using a conductive adhesive layer according to an embodiment of the present disclosure.

Referring to <FIG>, conductive balls <NUM> may be localized only on the first electrode <NUM> and the second electrode <NUM> of the light emitting device <NUM>. In addition, the conductive balls <NUM> localized only on the first electrode <NUM> and the second electrode <NUM> may be covered by an adhesive layer <NUM>.

As shown in (a) of <FIG>, in a horizontal light emitting device <NUM> in which the first electrode <NUM> and the second electrode <NUM> are positioned on the same plane, the conductive balls <NUM> are localized only on the first electrode <NUM> and the second electrode <NUM> and an adhesive layer <NUM> is then coated, which results in the state as shown in (b) of <FIG>.

The conductive balls <NUM> are localized only on the first electrode <NUM> and the second electrode <NUM> on the light emitting device <NUM> to form an anisotropic conductive medium. In this way, a film in which the conductive balls <NUM> are mixed with an insulating base member (adhesive layer; <NUM>) is positioned on the light emitting device <NUM> to form a light emitting device assembly <NUM>.

In this case, when heat and/or pressure is applied to the light emitting device assembly <NUM>, only the first electrode <NUM> and the second electrode <NUM> of the light emitting device <NUM> are caused to have conductivity due to the conductive balls <NUM>.

In addition, a separate adhesive layer <NUM> (see <FIG>) may be provided to localize the conductive balls <NUM> only on the first electrode <NUM> and the second electrode <NUM>. The adhesive layer <NUM> may be positioned on the first electrode <NUM> and the second electrode <NUM> to be spaced apart from each other. That is, the adhesive layer <NUM> may be provided to separately cover the first electrode <NUM> and the second electrode <NUM>.

Meanwhile, a vertical light emitting device may be used instead of a horizontal light emitting device.

<FIG> is a photograph showing an actual example of a light emitting device attached by a conductive adhesive layer according to an embodiment of the present disclosure.

As shown, it can be seen that the conductive balls <NUM> are localized only on the first electrode <NUM> and the second electrode <NUM> of the light emitting device <NUM>.

Since the conductive balls <NUM> may be localized only on the first electrode <NUM> and the second electrode <NUM> of the light emitting device <NUM>, it is possible to prevent some light emitting devices from being not electrically connected normally or the two electrodes from being short-circuited when manufacturing the display device as described above.

<FIG> is a cross-sectional view illustrating a display device using a semiconductor light emitting device according to an embodiment of the present disclosure.

Referring to <FIG>, a display device may include a plurality of anode electrodes <NUM>, a plurality of cathode electrodes <NUM> respectively positioned on one side of the anode electrodes <NUM>, and a plurality of light emitting device <NUM> assemblies each electrically connected to the anode electrode <NUM> and the cathode electrode <NUM> to respectively constituting sub-pixels.

The anode electrode <NUM> and the cathode electrode <NUM> may be arranged in pairs on the substrate <NUM>. Here, the substrate <NUM> may be a thin film transistor (TFT) substrate. That is, the light emitting device assemblies arranged on the thin film transistor substrate <NUM> may implement a display device using semiconductor light emitting devices.

That is, referring to <FIG>, the display device <NUM> having an active matrix (AM) structure is shown. However, the present disclosure is not limited to the AM structure and may be implemented as a display device having a PM (passive matrix) structure.

Here, the anode electrode <NUM> may be connected through a drain electrode (Drain) and a via electrode <NUM> of the thin film transistor <NUM> serving as a switching transistor.

The thin film transistor substrate <NUM> may include a plurality of individual thin film transistors <NUM>. The thin film transistor <NUM> may include a gate electrode (Gate), a gate insulator (GI) positioned on the gate electrode (Gate), a drain electrode (Drain) and a source electrode (Source) positioned on the gate insulator (GI). Hereinafter, a detailed description of the thin film transistor substrate <NUM> will be omitted.

A color correction layer <NUM> may be positioned in the insulating layer <NUM> corresponding to each sub-pixel <NUM>. The color correction layer <NUM> may correct the color of each pixel.

A planarization layer <NUM> may be positioned on the thin film transistor substrate <NUM>, and the insulating layer <NUM> may be positioned on the planarization layer. When implementing a flexible display, the insulating layer <NUM> may be formed of a polymer. In this case, the insulating layer <NUM> may be referred to as a polymer insulating layer <NUM>. In addition, the thickness of the polymer insulating layer <NUM> may be adjusted for assembly of the light emitting device assembly <NUM>. For example, the thickness of the polymer insulating layer <NUM> may be smaller than the diameter of the conductive ball <NUM>. Details will be described later.

The anode electrode (positive electrode) <NUM> connected to the individual thin film transistor <NUM> may be disposed on the insulating layer <NUM>. As described above, the individual thin film transistor <NUM> and the anode electrode <NUM> may be connected through the via electrode <NUM> passing through the planarization layer <NUM> and the insulating layer <NUM>.

As described above, the light emitting device assembly <NUM> may include a light emitting device <NUM>, a first electrode <NUM> positioned on the light emitting device <NUM> and electrically connected to the anode electrode <NUM> through the conductive balls <NUM>, and a second electrode <NUM> positioned on the light emitting device <NUM> and electrically connected to the cathode <NUM> through the conductive balls <NUM>.

In addition, the light emitting device assembly <NUM> may include first adhesive layers <NUM> positioned spaced apart from each other on the first electrode <NUM> and a second adhesive layer with non-conductivity (Nonconducting film (NCF)) <NUM> positioned on the first adhesive layer <NUM>.

In this case, the second adhesive layer <NUM> may cover the first adhesive layers <NUM> at two positions spaced apart from each other. Also, the second adhesive layer <NUM> may cover the entire light emitting device <NUM>.

Referring to <FIG>, the conductive balls <NUM> may be localized on the first adhesive layer <NUM>. That is, the conductive balls <NUM> may be localized between the anode electrode <NUM> and the first electrode <NUM> and between the cathode electrode <NUM> and the second electrode <NUM>. These localized conductive balls <NUM> have been identified above.

The first adhesive layer <NUM> may be a conductive or non-conductive adhesive layer. <FIG> illustrates a state in which the conductive balls <NUM> are positioned between the first adhesive layer <NUM> and the anode electrode <NUM> and between the first adhesive layer <NUM> and the cathode electrode <NUM> for convenience. However, in practice, the conductive balls <NUM> may penetrate the first adhesive layer <NUM> to contact the first electrode <NUM> and the second electrode <NUM>, separately.

In addition, as described above, in the bonding process of the light emitting device assembly <NUM>, the light emitting device assembly <NUM> is subjected to pressure while being placed on the anode electrode <NUM> and the cathode electrode <NUM>, and in this case, the conductive balls <NUM> penetrate the first adhesive layer <NUM> and the second adhesive layer <NUM> to electrically connect the anode electrode <NUM> and the cathode electrode <NUM> to the first electrode <NUM> and the second electrode <NUM>, respectively. Also, the shape of the conductive balls <NUM> may practically be changed from a spherical shape to an elliptical shape, for example.

On the other hand, the conductive balls <NUM> localized between the anode electrode <NUM> and the first electrode <NUM> and between the cathode electrode <NUM> and the second electrode <NUM> may be formed by patterning an anisotropic conductive film (ACF).

In addition, at least one of the first adhesive layer <NUM> and the second adhesive layer <NUM> may be colored in white, black, or other colors by using a coloring material capable of producing a color such as TiO2.

<FIG> are cross-sectional views illustrating a process of manufacturing a display device using semiconductor light emitting devices according to an embodiment of the present disclosure.

Hereinafter, the process of manufacturing a display device according to an embodiment of the present disclosure will be described in detail with reference to <FIG>.

First, referring to <FIG>, a light emitting device <NUM> arranged on a first substrate <NUM> may be prepared. A plurality of light emitting devices <NUM> respectively forming sub-pixels of the display device may be provided on the first substrate <NUM>. Although two light emitting devices <NUM> are illustrated in <FIG>, this is only an example, and a plurality of light emitting devices <NUM> partitioned according to the pixel spacing (pixel pitch) of the display device may be provided on the first substrate <NUM>.

In this case, the first substrate <NUM> may be a growth substrate on which the light emitting devices <NUM> are grown. For example, the light emitting device <NUM> may be a gallium nitride based semiconductor light emitting device. Also, for example, the first substrate <NUM> may be a sapphire substrate.

After a semiconductor layer for forming the light emitting device <NUM> is formed on the first substrate <NUM>, the semiconductor layer is partitioned and shaped through exposure and etching processes, and the first electrode <NUM> and the second electrode <NUM> are formed, thus manufacturing the light emitting devices <NUM> respectively forming sub-pixels. Such exposure and etching processes (hereinafter referred to as a photo process) are very high-precision processes, and when the light emitting device <NUM> manufactured by the photo process is transferred to the thin film transistor substrate <NUM> as it is, it can be very advantageous to realize a high-resolution display device.

Accordingly, an embodiment of the present disclosure may provide a method for directly transferring the light emitting device <NUM> to the thin film transistor substrate <NUM>, light emitting device <NUM> being manufactured by being grown on the growth substrate and partitioned to form an individual unit sub-pixel.

Referring to <FIG>, a first electrode <NUM> and a second electrode <NUM> may be provided on the same surface on each light emitting device <NUM> to be spaced apart from each other. That is, the light emitting device <NUM> may be a horizontal light emitting device.

In this case, as described above, the individual light emitting devices <NUM> may be arranged on the first substrate <NUM> at very precise distance intervals.

Thereafter, referring to <FIG>, a first adhesive layer <NUM> may be formed on the first electrode <NUM> and the second electrode <NUM>. As illustrated, the first adhesive layer <NUM> may be formed to cover the first electrode <NUM> and the second electrode <NUM> separately. Accordingly, the first adhesive layers <NUM> may be spaced apart from each other on the first electrode <NUM> and the second electrode <NUM>. However, in some cases, the first adhesive layer <NUM> may also be formed between the individual light emitting devices <NUM>.

Meanwhile, the first adhesive layer <NUM> may be conductive or non-conductive.

As described above, the first adhesive layer <NUM> may be locally formed on the first electrode <NUM> and the second electrode <NUM>. Accordingly, the first adhesive layer <NUM> may have substantially the same shape as the first electrode <NUM> and/or the second electrode <NUM>. In this case, the size of the first adhesive layer <NUM> may be larger than the size of the first electrode <NUM> and/or the second electrode <NUM>.

Next, referring to <FIG>, conductive balls <NUM> may be positioned on the first adhesive layer <NUM>. In this case, the conductive balls <NUM> are positioned only on the upper surfaces of the first adhesive layers <NUM> that are locally positioned on the first electrode <NUM> and the second electrode <NUM>, so that the conductive balls <NUM> may be localized on the first electrode. <NUM> and the second electrode <NUM>.

In a method of attaching the conductive balls <NUM> to the upper surfaces of the first adhesive layers <NUM>, as shown in <FIG>, a sheet <NUM> in which the conductive balls <NUM> are dispersed may be used.

That is, the conductive balls <NUM> may be attached to the upper surface of the first adhesive layer <NUM> by allowing the first adhesive layer <NUM> localized on the first electrode <NUM> and the second electrode <NUM> to contact a sheet <NUM> in which the conductive balls <NUM> are dispersed.

Meanwhile, as shown in <FIG>, the conductive balls <NUM> may be attached to the upper surface of the first adhesive layer <NUM> in the same manner by spraying the conductive balls <NUM> onto the first adhesive layer <NUM> localized on the first electrode <NUM> and the second electrode <NUM>, through a nozzle <NUM>.

<FIG> illustrates a state in which the conductive balls <NUM> are attached only to the upper surface of the first adhesive layer <NUM> localized on the first electrode <NUM> and the second electrode <NUM> by the above-described process.

Meanwhile, as described above, the conductive balls <NUM> localized between the cathode electrode <NUM> and the second electrode <NUM> may be formed by patterning the anisotropic conductive film (ACF).

Next, referring to <FIG>, the conductive balls <NUM> attached only to the upper surface of the first adhesive layer <NUM> localized on the first electrode <NUM> and the second electrode <NUM> may be covered by using the second adhesive layer <NUM>.

The second adhesive layer <NUM> may cover the entire light emitting device <NUM>. In this way, the light emitting device <NUM> covered by the second adhesive layer <NUM> may constitute the light emitting device assembly <NUM>.

In this case, the shape of the second adhesive layer <NUM> may be substantially the same as the shape of the light emitting device <NUM>.

Thereafter, referring to <FIG>, the light emitting device assembly <NUM> may be attached on the second substrate <NUM>.

That is, the first electrode <NUM> and the second electrode <NUM> of the each light emitting device <NUM> may be boned to the anode electrode <NUM> and the cathode electrode <NUM> disposed on the second substrate <NUM> using the conductive balls <NUM>.

Specifically, the second adhesive layer <NUM> of the light emitting device assembly <NUM> is directed toward the anode electrode <NUM> and the cathode electrode <NUM> of the second substrate <NUM> to bond the second adhesive layer <NUM> to the second substrate <NUM>.

In this case, the first electrode <NUM> and the second electrode <NUM> are aligned with the positions of the anode electrode <NUM> and the cathode electrode <NUM> disposed on the second substrate <NUM> to bond the light emitting device assembly <NUM> to the anode electrode <NUM> and the cathode electrode <NUM> disposed on the second substrate <NUM>.

Thereafter, by applying pressure, the conductive balls <NUM> may contact between the first electrode <NUM> and the anode electrode <NUM> to electrically connect the first electrode <NUM> and the anode electrode <NUM>. In some cases, heat may be applied together with the pressure.

In addition, the conductive balls <NUM> may contact between the second substrate <NUM> and the cathode electrode <NUM> to electrically connect the second substrate <NUM> and the cathode electrode <NUM>.

In this case, as described above, the second substrate <NUM> may be a thin film transistor substrate capable of implementing an active matrix type display.

Next, referring to <FIG>, the first substrate <NUM> may be removed.

As described above, the first substrate <NUM> is a growth substrate for the light emitting device <NUM>, and may be, for example, a sapphire substrate. The first substrate <NUM> may be removed by a laser lift-off method, a chemical lift-off method, or the like.

That is, the interface between the growth surface of the light emitting device <NUM> and the first substrate <NUM> may be separated by irradiating a laser from the first substrate <NUM> toward the light emitting device assembly <NUM>.

<FIG> show a state in which all the light emitting device assemblies <NUM> are attached at the same time or as a group.

However, as shown in <FIG>, it is also possible to selectively assemble some light emitting device assemblies <NUM>. For example, the light emitting device assembly <NUM> may be assembled by color, or the light emitting device assembly <NUM> may be assembled for each group by classifying the light emitting device assemblies <NUM> into groups for a specific purpose.

For example, a method of selectively attaching the blue light emitting device assembly <NUM> first and then attaching the green light emitting device assembly <NUM> is possible.

<FIG> shows a state in which the light emitting device assemblies <NUM> on one side only are attached to the second substrate <NUM>. Then, referring to <FIG>, only the attached light emitting device assemblies <NUM> may be selectively separated from the first substrate <NUM>.

In <FIG> and <FIG>, for convenience, it is shown that the conductive balls <NUM> are positioned between the first adhesive layer <NUM> and the anode electrode <NUM> and between the first adhesive layer <NUM> and the cathode electrode <NUM>. However, in practice, the conductive balls <NUM> may penetrate the first adhesive layer <NUM> to contact the first electrode <NUM> and the second electrode <NUM>, separately.

<FIG> is a photograph illustrating a state in which a light emitting device of a display device using a semiconductor light emitting device is bonded according to an embodiment of the present disclosure. In addition, <FIG> is a photograph showing a state in which the light emitting device is turned on in the state of <FIG>.

Referring to <FIG>, it is shown that the second adhesive layer <NUM> is positioned outside the light emitting device <NUM>.

Since the conductive balls <NUM> are all located under the electrode of the light emitting device <NUM>, the conductive balls <NUM> are not shown in the photograph. That is, the light emitting device <NUM> is bonded while the conductive balls <NUM> are localized on the electrodes of the light emitting device <NUM>, so that the conductive balls <NUM> are not visible in other portions.

<FIG> shows a state in which the light emitting device <NUM> bonded as described above are turned on.

<FIG> is a cross-sectional photograph showing an example of a state in which a light emitting device is boned to an electrode by conductive balls.

<FIG> is a cross-sectional view illustrating a second substrate of a display device using a semiconductor light emitting device according to an embodiment of the present disclosure.

As described above, the planarization layer <NUM> may be located on the thin film transistor substrate <NUM>, and the insulating layer <NUM> may be located on the planarization layer. When implementing a flexible display, the insulating layer <NUM> may be formed of a polymer. In this case, the insulating layer <NUM> may be referred to as a polymer insulating layer <NUM> (PAC).

In this case, the thickness of the polymer insulating layer <NUM> may be adjusted for assembly of the light emitting device assembly <NUM>. For example, the thickness of the polymer insulating layer <NUM> may be smaller than the diameter of the conductive ball <NUM>.

As described above, the light emitting device <NUM> (LED) is bonded to the electrodes <NUM> and <NUM> by applying pressure. However, when the thickness of the polymer insulating layer <NUM> is thick, as shown in portion A of <FIG>, the electrodes <NUM> and <NUM> may collapse due to pressure.

The collapse of the electrodes <NUM> and <NUM> caused by the pressure may be improved according to the thickness "T" of the polymer insulating layer <NUM>. For example, depending on the thickness "T" of the polymer insulating layer <NUM>, the pressure required for bonding of the light emitting device <NUM> may be distributed to the planarization layer <NUM> on the lower side.

For example, when the thickness T of the polymer insulating layer <NUM> is smaller than the diameter of the conductive ball <NUM>, the propagation of the pressure may effectively spread to the planarization layer <NUM> on the lower side, which is made of hard glass.

More preferably, the thickness T of the polymer insulating layer <NUM> may be <NUM>% or less of the diameter of the conductive ball <NUM>. However, for the intrinsic insulating properties or for the provision of the color correction layer <NUM>, the thickness T of the polymer insulating layer <NUM> may be equal to or greater than the half (<NUM>%) of the diameter of the conductive ball <NUM>. That is, the thickness T of the polymer insulating layer <NUM> may be <NUM>% to <NUM>% of the diameter of the conductive ball <NUM>. Also, as described above, the thickness T of the polymer insulating layer <NUM> may be <NUM>% to <NUM>% of the diameter of the conductive ball <NUM>.

As described above, according to the embodiment of the present disclosure, it is possible to directly transfer the light emitting device <NUM> from the growth substrate <NUM> to the thin film transistor substrate <NUM>.

In this case, as described above, problems caused by the conductive balls, that is, problems in which some light emitting devices are not electrically connected, or the two electrodes of one light emitting device are short-circuited, may not occur.

As described above, it is possible to directly transfer the light emitting device <NUM> from the growth substrate <NUM> to the thin film transistor substrate <NUM>, making it very advantageous to implement a high-resolution display device.

The reason for this is that the arrangement of the light emitting devices <NUM> manufactured by a precise photo process may be disturbed if an intermediate transfer substrate such as a donor substrate is used. In this process, the precision of the position of the array may be deteriorated.

Therefore, when the light emitting device <NUM> manufactured by a precise photo process is transferred to the thin film transistor substrate <NUM> as it is, it may be very advantageous to implement a high-resolution display device.

Moreover, according to the present disclosure, the problems caused by the use of the conventional conductive balls can be solved, thus greatly improving the reliability, precision, and mass productivity of a micro LED display device.

In particular, since the LED has no moisture barrier layer unlike OLED, stacking is simple, making it suitable to be applied to a flexible display. For example, referring to <FIG>, the size of the light emitting device assembly <NUM> is enlarged, but the area occupied by the light emitting device assembly <NUM> in the entire display device <NUM> is very small, and the remaining portion may have properties/structures that can be mostly bent.

Accordingly, the display device <NUM> according to the embodiment of the present disclosure is suitable for a flexible display.

The above description is merely illustrative of the technical idea of the present invention, and various modifications and variations may be made without departing from the scope of the present invention as defined by the claims by those skilled in the art.

Accordingly, the embodiments disclosed in the description not intended to limit the technical idea of the present invention, and the scope of the present invention is not limited by these embodiments.

Claim 1:
A display device comprising
a plurality of anode electrodes (<NUM>) separated from each other;
a plurality of cathode electrodes (<NUM>) positioned on one side of the plurality of anode electrodes (<NUM>), respectively; and
a plurality of light emitting device assemblies (<NUM>), wherein a light emitting device assembly (<NUM>) among the plurality light emitting device assemblies is electrically connected to an anode electrode (<NUM>) and a cathode electrode (<NUM>) among the plurality of anode electrodes and the plurality of cathode electrodes to configure an individual sub-pixel,
wherein the light emitting device assembly (<NUM>) includes:
a light emitting device (<NUM>);
a first electrode (<NUM>) disposed on the light emitting device (<NUM>) and electrically connected to the anode electrode (<NUM>) by conductive balls (<NUM>);
a second electrode (<NUM>) disposed on the light emitting device (<NUM>) and electrically connected to the cathode electrode (<NUM>) by conductive balls (<NUM>);
first adhesive layers (<NUM>) disposed on the first electrode (<NUM>) and the second electrode (<NUM>) respectively to be spaced apart from each other; and
a second adhesive layer (<NUM>) positioned on the first adhesive layers (<NUM>), the second adhesive layer (<NUM>) being non-conductive.