This application claims the benefit of Korean Patent Application No. 10-2009-0109161, filed Nov. 12, 2009 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field
Non-limiting example embodiments of the present invention relate to a display device, and more particularly, to a display device that can display images.
2. Description of the Related Art
Among flat panel display devices, an organic light emitting diode (OLED) display device has attracted attention as a next generation flat panel display device since it provides self emission, a wide viewing angle, a fast response speed, a small thickness, relatively low production costs, and high contrast. In general, such an OLED display device includes a substrate, an anode located on the substrate, an emission layer located on the anode, and a cathode located on the emission layer. In the OLED display device, when a voltage is applied between the anode and the cathode, holes and electrons may be injected into the emission layer, and recombined in the emission layer, thereby generating excitons. The OLED display device emits light using energy generated when the excitons transition from an excited state to a ground state.
To implement a full-color OLED display device, emission layers may be formed corresponding to red (R), green (G) and blue (B) light, respectively. However, in this case, the emission layers corresponding to the R, G and B light have different lifespan characteristics. Thus it is difficult to maintain a white balance when the OLED display device is driven for a long time. To solve this problem, an emission layer is formed to emit a single color of light, and a color filter or color conversion layer is used. The color filter extracts light corresponding to a predetermined color from the light emitted from the emission layer. The color conversion layer changes the light emitted from the emission layer into a predetermined color of light.
Non-limiting example embodiments of the present invention provide a display device which includes a color filter layer and thus has a simple process.
According to non-limiting example embodiments of the present invention, a display device includes: a substrate having a red sub-pixel region, a green sub-pixel region and a blue sub-pixel region; a red color filter layer located on the red, green and blue sub-pixel regions and having a first opening formed in the green sub-pixel region and a second opening formed in the blue sub-pixel region; a green color filter layer located in the first opening; and a blue color filter layer disposed in the second opening.
Additional advantages of the non-limiting example embodiments of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present invention.
These and/or other advantages of the present invention will become apparent and more readily appreciated from the following description of the non-limiting example embodiments, taken in conjunction with the accompanying drawings of which:
Reference will now be made in detail to the present non-limiting example embodiments of the present invention, examples of which may be illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The non-limiting example embodiments may be described below in order to explain the present invention by referring to the figures.
Referring to
Here, each of the red (R) sub-pixel region, the green (G) sub-pixel region and the blue (B) sub-pixel region may include a light extraction region Ra, Ga, Ba, a transistor region Rb, Gb, Bb and a capacitor region Rc, Gc, Bc. The buffer layer 210 serves to prevent diffusion of moisture or impurities generated from the substrate 200.
Subsequently, an amorphous silicon layer (not shown) may be deposited on the buffer layer 210, and may be crystallized by excimer laser annealing (ELA), sequential lateral solidification (SLS), metal induced crystallization (MIC) or metal induced lateral crystallization (MILC). The crystallized silicon layer may be patterned by photolithography and etching, thereby forming a polycrystalline silicon pattern forming a semiconductor layer 220 and electrode 220d in the transistor region Rb, Gb, Bb and the capacitor region Rc, Gc, Bc of each sub-pixel region R, B, G.
A gate insulating layer 230 may be formed on the entire surface of the substrate 200 above the buffer layer 210 and the formed polycrystalline silicon pattern. Here, the gate insulating layer 230 may be formed using a silicon oxide layer, a silicon nitride layer or a stacked layer thereof. The layer 230 can be formed by plasma-enhanced chemical vapor deposition (PECVD) or low-pressure chemical vapor deposition (LPCVD).
Subsequently, a gate electrode material layer (not shown) may be formed on the gate insulating layer 230 and etched by photolithography and/or etching, thereby forming a gate electrode 240a and a second capacitor electrode 240b. The gate electrode 240a may be formed corresponding to a channel region 220b to be described later in the transistor region Rb, Gb, Bb of each sub-pixel region. The second capacitor electrode 240b may be formed in the capacitor region Rc, Gc, Bc of each sub-pixel region R, G, B.
By way of example, the gate electrode material layer may be formed using molybdenum (Mo), tungsten (W), tungsten-molybdenum (MoW), tungsten silicide (WSi2), molybdenum silicide (MoSi2), aluminum (Al), etc. These materials may be independently used or mixed with one another. The gate electrode material layer may be formed by sputtering or vacuum deposition.
Subsequently, impurities may be injected into the semiconductor layer 220 using the gate electrode 240a and the second capacitor electrode 240b as a mask, thereby forming in the semiconductor layer 220 source and drain regions 220a and 220c and a channel region 220b in the transistor region Rb, Gb, Bb of each sub-pixel region, and a first capacitor electrode 220d in the capacitor region Rc, Gc, Bc of each sub-pixel region R, G, B. As shown, the first capacitor electrode 220d, the gate insulating layer 230 and the second capacitor electrode 240b may constitute a lower capacitor.
The impurities may be one selected from n-type and p-type impurities. The n-type impurities may be phosphorous (P), arsenic (As), bismuth (Bi), antimony (Sb), or a combination thereof. The p-type impurities may be boron (B), boron fluoride (BF), aluminum (Al), gallium (Ga), titanium (Ti), indium (In) or a combination thereof. However, the present invention may not be limited thereto.
Referring to
Referring again to
Referring to
Here, each of the color filter layers 250R, 250G and 250B may include an acrylic resin as a support, a pigment, and a polymer binder. The color filter layers 250R, 250G and 250B may also include a functional monomer. Here, according to the kind of the pigment exhibiting a color, the color filter layers 250R, 250G and 250B may be classified into the red color filter layer 250R, the green color filter layer 250G, and the blue color filter layer 250B.
The red color filter layer 250R, the green color filter layer 250G and the blue color filter layer 250B transmit light emitted from an emission layer formed in a subsequent process to have wavelengths in red, green and blue regions, respectively.
The polymer binder may protect a liquid monomer from a developing solution at room temperature, and may influence the stability of pigment dispersion. The polymer binder may further influence the reliability of RGB patterns such as heat resistance and light resistance. The pigment may be an organic particle having excellent resistances to light and heat, which scatters light. As the particle may become relatively smaller, the pigment has relatively higher transparency and may have a more excellent dispersion characteristic.
Meanwhile, in the shown example, each of the color filter layers 250R, 250G and 250B may be formed to a thickness of about 1.0 to 2.5 μm. When the thickness of the color filter layer may be less than about 1.0 μm, color purity may decrease, and when the thickness of the color filter layer may be more than about 2.5 μm, the transparency may decrease, and a crystal of the pigment may be extracted or the color filter layer or a color filter may have a crack.
Each of the color filter layers 250R, 250G and 250B may be formed by pigment dispersion or dying, but the present invention may not be limited thereto. Each of the color filter layers 250R, 250G and 250B may be formed during a process of fabricating a transistor, and may serve as an interlayer insulating layer. For this reason, a separate process of forming a color filter layer may not be needed, and a process for an interlayer insulating layer can be omitted, thereby simplifying the process.
As described above, the red color filter layer 250R may be used as an interlayer insulating layer. The opening 260G for defining the light extraction region Ga of the green (G) sub-pixel region and the opening 260B for defining the light extraction region Ba of the blue (B) sub-pixel region may be formed in the red color filter layer 250R, and the green color filter layer 250G and the blue color filter layer 250B may be formed in the openings 260G and 260B, respectively. The reason why the red color filter layer 250R may be used as an interlayer insulating layer may be that the red color filter layer 250R may be the least damaged by plasma used in an etching process of the gate insulating layer 230 as compared to the materials used in the other color filter layers 250B, 250G. Specifically, to form the contact holes 261 exposing the source and drain regions 220a and 220c in the gate insulating layer 230, a dry etching process may be performed using the color filter layer 250R as a mask. Accordingly, a surface of the color filter layer 250R may be damaged by plasma used in the dry etching process. Here, since the red color filter layer 250R as compared to the green and blue color filter layers 250B, 250G may be the least damaged by the plasma, the red color filter layer 250R may be used as an interlayer insulating layer and the green and blue color filter layers 250B, 250G may be formed after the dry etching process may be performed.
Specifically, it can be seen that, when the color filter layer may be used as the interlayer insulating layer, the optical efficiency may be lower in a short wavelength range (e.g., at about 450 nm or lower), than when the general organic layer may be used as the interlayer insulating layer. In addition, as the wavelength may become longer, it can be seen that, when the color filter layer may be used as the interlayer insulating layer, the optical efficiency may be substantially equal to or relatively higher than when the general organic layer may be used as the interlayer insulating layer.
In other words, when the color filter layer may be used as the interlayer insulating layer, even though it may be damaged by plasma, it can be seen that the optical efficiency may be relatively low at short wavelengths, whereas, the optical efficiency may be substantially equal or relatively higher than the general organic layer at long wavelengths. Thus, among the red, green and blue color filter layers 250R, 250B, 250G, the non-limiting example embodiments of the present invention use the red color filter layer 250R that may be the least damaged by plasma due to it having the longest wavelength range. However, while shown as using the red color filter layer 250R as being least damaged by the plasma, it may be understood that others of the color layers 250B, 250G can be used as the interlayer insulating layer instead of or in addition to the red color filter layer 250R and still be acceptable relative to the general organic layer.
Subsequently, referring to
The first electrode 280 may be formed by sputtering, ion plating or evaporation, and then patterned by wet etching to be selectively removed using a pattern such as a photo resist (PR) formed by photolithography after deposition. The wet etching process patterning the first electrode 280 may prevent damage to a color filter layer 250R, 250G, 250B using an etchant having a relatively high etch rate between the first electrode 280 and the color filter layers 250R, 250G, 250B.
The first electrode 280 may be formed on the red color filter layer 280R used as an interlayer insulating layer in the red (R) sub-pixel region. The first electrode 280 may be formed on the green color filter layer 250G formed in an opening 260G of the red color filter layer 250R in the green (G) sub-pixel region. The first electrode 280 may be formed on the blue color filter layer 250B formed in the opening 260B of the red color filter layer 250R in the blue (B) sub-pixel region.
Referring to
While the source and drain electrodes 270a and 270b may be formed, a third capacitor electrode 270c may be formed in the capacitor region Rc, Gc, Bc of each sub-pixel region R, G, B. Here, the second capacitor electrode 240b, the red color filter layer 250R and the third capacitor electrode 270c constitute an upper capacitor. However, it may be understood that the third capacitor 270c can be otherwise formed.
Here, the metal layer used to form the electrodes 270a, 270b, 270c can be a single layer of molybdenum (Mo), a molybdenum-tungsten (MoW) alloy, aluminum or an aluminum-neodymium (Nd) alloy, or a stacked layer thereof.
As described above, the semiconductor layer 220, the gate electrode 240a and the source and drain electrodes 270a and 270b constitute a transistor, which may be formed in the transistor region Rb, Gb, Bb as described above. Here, the transistor may employ the red color filter layer 250R as the interlayer insulating layer to electrically insulate the gate electrode 240a from the source and drain electrodes 270a and 270b.
Subsequently, referring to
Subsequently, referring
A white light emitting material for the emission layer 290 may be obtained by mixing two different color emitting materials with each other and adding other light emitting materials thereto. For example, after a red light emitting material may be mixed with a green light emitting material, a blue light emitting material may be added thereto, and thus a white light emitting material may be obtained. The red light emitting material may be formed using BSA-2 (i.e., a relatively low molecular weight material), polythiophene (PT) (i.e., a high molecular weight material), or a derivative thereof. These materials may be independently used or mixed with each other. The green light emitting material may be formed using relatively low molecular weight materials such as Alq3, bis(benzoquinoline)beryllium (BeBq2) and tris(4-methyl-8-quinolinolate)aluminum (Almq), high molecular weight materials such as poly(p-phenylenevinylene) (PPV) and derivatives thereof. The blue light emitting material may be formed using a relatively low molecular weight material such as ZnPBO, Bis(2-methyl-8-quinolinolato-N1,O8)-(1,1-biphenyl-4-olato)aluminum (Balq), 4,4′-bis(2,2′-diphenylvnyl)-1,1′-biphenyl) (DPVBi), or OXA-D, a high molecular weight material such as polyphenylene (PPP), or a derivative thereof. These materials may be independently used or mixed with one another.
The organic emission layer 290 may include a hole transporting compound, an electron transporting compound or a mixture thereof as a host material, and serves to inject holes and electrons, transport holes and electrons, or generate excitons by recombination of holes and electrons. The organic emission layer 290 may also include a compound which may be relatively electrically neutral. The hole transporting compound used as the host material of the organic emission layer may be formed using a triazole derivative, an imidazole derivative, a phenyldiamine derivative, arylamine derivative or an aromatic tertiary amine, and preferably, a tetraarylbenzidine compound (triaryldiamine or triphenyldiamine (TPD)) of a triphenyldiamine derivative. The electron transporting compound used as the host material of the organic emission layer may be formed using tris(8-quinolinato) aluminum (Alq3).
The organic emission layer 290 has a structure in which the host material such as the hole transporting compound, the electron transporting compound or a combination thereof may be doped with a dopant such as a fluorescent material. In the non-limiting example embodiments of the present invention, a rubrene-based compound, a coumarine-based compound, a quinacridone-based compound or a dicyanomethylpyran-based compound may be used. These materials may be independently used or mixed with each other as the fluorescent material contained as a dopant. By adding a small amount of the dopant, emission efficiency and endurance may be improved. The emission layer 290 may be stacked by vacuum deposition or spin coating.
Meanwhile, when the emission layer 290 emits blue light, a color conversion layer may be formed instead of the color filter layer 250R, 250G, 250B. In other words, when the emission layer 290 emits blue light, the red color filter layer 250R may be replaced with a red color conversion layer, the green color filer layer 250G with a green conversion layer, and the blue color filter layer 250B with a blue color conversion layer.
The color conversion layer may include a fluorescent material and a polymer binder. The fluorescent material emits light with a longer wavelength than incident light when the fluorescent material may be excited due to the light entering from the emission layer and then transitions to a ground state. The color conversion layers may be classified as a red color conversion layer converting the incident light into red light, a green color conversion layer converting the incident light into green light, and a blue color conversion layer converting the incident light into blue light according to the kind of the fluorescent material. The color conversion layers may be formed by pigment dispersion or dying, but may not be limited thereto. The color conversion layer may be formed by pigment dispersion in which exposure and development may be repeatedly performed.
Subsequently, referring to
Subsequently, the substrate 200 having the second electrode 291 may be attached to an upper substrate (not shown) to be encapsulated by a common method, and thus a bottom-emission active matrix OLED display device may be completed.
To drive such an OLED display device, the emission layer 290 may emit white light toward the substrate 200. The white light emitted from the emission layer 390 may be extracted to the outside through the first electrode 280, which may be a transparent electrode, and the transparent substrate 200. Here, the color filter layers 250R, 250G and 250B may be located in the light extraction region Ra, Ga, Ba of each sub-pixel region R, G, B, which may be a path through which the light extracted from the white emission layer 290 to the outside passes. The white light may be extracted to the outside through the corresponding red, green and blue color filter layers 250R, 250G and 250B, thereby implementing a full-color OLED display device, which may be capable of emitting red (R), green (G) and blue (B) light.
Referring to
To be specific, the OLED display device formed in a general structure may have a separately-formed black matrix, which may be formed using a chromium oxide (CrOx) layer and a chromium (Cr) layer, in a region excluding a portion corresponding to a pixel electrode of a substrate in order to block reflective light having a bad influence on displaying images. However, in the present non-limiting example embodiments, the second capacitor electrode 240b′ may be used as a black matrix by being extended to a predetermined region of the light extracting region. Thus, the second capacitor electrode 240b′ can block reflective light in a region excluding the light extraction region and inhibit a light leak current of a transistor.
Consequently, since a red color filter layer may be used as an interlayer insulating layer to electrically insulate a gate electrode from source and drain electrodes, the present invention does not need a separate process to form a color filter layer and a process for an interlayer insulating layer, and thus can have a simple process.
Although the present invention has been described with reference to predetermined non-limiting example embodiments thereof, it will be understood by those skilled in the art that a variety of modifications and variations may be made to the present invention without departing from the spirit or scope of the present invention defined in the appended claims and their equivalents.
Number | Date | Country | Kind |
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10-2009-0109161 | Nov 2009 | KR | national |