KR20050115775A - Flat panel display device - Google Patents

Abstract

The present invention provides a flat panel display having improved aperture ratio, light extraction rate and light efficiency, and includes a rear substrate, a plurality of self-luminous elements having at least a light emitting layer provided on the back substrate, and at least one provided for each of the self-luminous elements. A flat panel display device comprising the above transistors, wherein the number of layers interposed between the first electrode and the rear substrate of the self-emitting device connected to the transistors is two or less.

Description

Flat panel display device

The present invention relates to a flat panel display, and more particularly, to a flat panel display having improved aperture ratio, light extraction rate, and light efficiency.

1 illustrates a flat panel using a conventional active matrix type electroluminescent device, which is a type of flat panel display using a self-luminous device having at least one transistor 150 for each pixel and having an electrode 151 connected to the transistor. It is sectional drawing which shows a display apparatus.

Referring to FIG. 1, a buffer layer 182, a gate insulating layer 183, an interlayer insulating layer 184, and a first passivation layer may be disposed between an organic layer 187 including at least a light emitting layer and a rear substrate 181 of a conventional EL device. 185, and a first electrode 161 is interposed. Therefore, when the EL device having the structure described above is a bottom emission type EL device, the light emitted from the organic layer 187 may be extracted to the outside through the rear substrate 181 to be interposed therebetween. Since the light extraction rate is lowered due to reflection between the layers and the like, the distance between the organic layer 187 including the light emitting part and the rear substrate 181 is increased. Accordingly, there is a problem that the light efficiency is lowered, such as the opening ratio becomes smaller.

In addition, when the electroluminescent device having the structure shown in FIG. 1 is a top emission type, the organic layer 187 including the light emitting part is formed on the transistor 150 and the first passivation layer 185 on the upper surface thereof. There is a problem that the thickness t1 of the flat panel display becomes thick.

Disclosure of Invention The present invention is to solve various problems including the above problems, and to provide a flat panel display device having an improved aperture ratio, light extraction rate, and light efficiency by reducing the number of layers interposed between the light emitting unit and the rear substrate. It is done.

In order to achieve the above object and various other objects, the present invention provides a back substrate, a plurality of self-luminous elements having at least a light emitting layer provided on the back substrate, and at least one provided for each self-luminous element. A flat panel display device comprising the above transistors, wherein the number of layers interposed between the first electrode and the rear substrate of the self-emitting device connected to the transistors is two or less.

According to such another feature of the present invention, the first electrode can be provided on the rear substrate.

According to still another feature of the present invention, the first electrode can be provided on the same layer as the semiconductor layer of the transistor.

According to still another feature of the present invention, the first electrode and the semiconductor layer can be separated.

According to still another feature of the present invention, a gate insulating film may be interposed between the first electrode and the rear substrate.

According to still another feature of the present invention, the flat panel display may be a bottom emission type.

According to still another feature of the present invention, the self-luminous element can be an electroluminescent element.

According to still another feature of the present invention, the electroluminescent element may be an organic electroluminescent element.

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

FIG. 2 is a plan view illustrating an organic EL device according to a first exemplary embodiment of the present invention, and FIG. 3 is a pixel portion or a subpixel portion (hereinafter, referred to as a pixel portion) of an active matrix organic EL display device according to the embodiment. Is a cross-sectional view taken along P1 to P7 in FIG.

2 and 3, each pixel unit includes a first thin film transistor 210 driven by a driving circuit, a second thin film transistor 250 driven by the first thin film transistor, and a second thin film transistor. It is provided with a display unit 260 driven by.

The first source electrode 212 of the first thin film transistor 210 is connected to the driving circuit by the first conductive line 220, and the first gate electrode 211 of the first thin film transistor is the second conductive line 230. The first drain electrode 213 of the first thin film transistor is connected to the driving circuit by the first capacitor electrode 241 of the storage capacitor 240 and the second gate electrode 251 of the second thin film transistor 250. Connected with

In the above configuration, it may be assumed that the first data line 220 transmits data and the second data line 230 corresponds to a scan line. The first transistor 210 serves as a switching transistor and the second transistor 250 serves as a driving TR. Of course, two or more transistors may be used in the selection driving circuit. Hereinafter, a case in which two transistors, a switching transistor and a driving transistor, are used will be described.

The second capacitor electrode 242 of the storage capacitor 240 and the second source electrode 252 of the second thin film transistor are connected to the third conductive line 270 and the second drain electrode of the second thin film transistor 250. 253 is connected to the first electrode 261 of the display unit 260. As can be seen from FIG. 3, the second electrode 262 of the display unit is disposed to face the first electrode 261 with a predetermined gap from the first electrode 261, and the first electrode 261 is disposed. An organic film 287 including at least a light emitting layer is disposed between the second electrode 262 and the second electrode 262.

For reference, FIG. 2 illustrates a first conductive wire 220, a first source electrode 212, a first gate electrode 211, a first drain electrode 213, and a second conductive wire 230 not shown in FIG. 3. 3, components not shown in FIG. 2, namely, the substrate 281, the buffer layer 282, the gate insulating film 283, the interlayer insulating film 284, the second electrode 262, and the second electrode 262 are formed. 2 protective film 289 is shown.

When a voltage is applied to the first gate electrode 211 by the driving circuit, a conductive channel is formed in the semiconductor layer 280 connecting the first source electrode 212 and the first drain electrode 213. When charge is supplied to the first source electrode 212 by the conductive wire 220, the charge is transferred to the first drain electrode 213. The amount of charge that determines the amount of light generated in the organic layer 287 including at least the light emitting layer by the driving circuit is supplied to the third conductive line 270, and the second gate electrode 251 is provided by the first drain electrode 213. ), The charge of the second source electrode 252 is transferred to the first electrode 261 of the self-luminous element via the second drain electrode 253.

A detailed configuration of the pixel portion will be described with reference to FIG. 3. P1 through P2 show the display portion 260 of the pixel portion, P2 through P3 show the second thin film transistor 250, and P3 through P7 show the storage capacitor 240.

A buffer layer 282 may be formed on the entire surface of the substrate 281 as illustrated in FIG. 3, and a second thin film transistor 250 is provided on the buffer layer 282. The first passivation layer 285 is formed to cover the entire surface 250.

The second drain electrode 253 and the second drain electrode 253 and the interlayer insulating film 284, the gate insulating film 283, and the buffer layer 282 of the second thin film transistor 250 respectively correspond to the second drain electrode 253. In addition to the first contact hole formed to contact the semiconductor layer 280, a second contact hole is provided, and the second drain hole 253 and the rear substrate 281 are provided on the second contact hole. The first electrode 261 is in contact. Of course, the second contact hole may be simultaneously formed when forming the contact holes of the first contact hole and the second source electrode 252.

An organic layer 287 including at least a light emitting layer is formed on the first electrode 261. The second electrode 262 may be entirely formed on the organic layer 287, and a second passivation layer 289 may be formed on the second electrode 262 as necessary. When the low molecular weight organic material is used, the organic film 287 may be provided as a multilayer film including a hole transport layer, a light emitting layer, an electron transport layer, and the like. In this case, the hole transport layer and the electron transport layer may be formed entirely. When the organic layer 287 is made of a polymer organic material, the organic layer 287 may be provided as a hole transport layer and a light emitting layer.

Examples of the material for forming the light emitting layer include phthalocyanine (CuPc: copper phthalocyanine), N, N-di (naphthalen-1-yl) -N, N'-diphenyl-benzidine (N, N'-Di (naphthalene-1- Low molecular organic materials such as yl) -N, N'-diphenyl-benzidine (NPB), tris-8-hydroxyquinoline aluminum (Alq3), or poly-phenylenevinylene (PPV) -based and polyfluorene A polymer organic material such as a (polyfluorene) -based or the like is used, and when an electric charge is supplied to the first electrode and the second electrode, an exciton is generated by combining holes and electrons, and this exciton is in a ground state in an excited state. The light emitting layer emits light as it changes to. The light emitting layer includes a poly (1,4-phenylenevinylene) derivative, nile red, and 4- (dicyanomethylene) -2-methyl-6- (Juloli), which causes the light emitting layer to emit red light. Din-4-yl-vinyl) -4H-pyran (DCM2), 2,3,7,8,12,13,17,18-octaethyl, 21H, 23H-phosphine platinum (II) (PEOEP), 4 10, which allows the light emitting layer to emit green light, such as (dicymethylene) -2-tertbutyl-6- (1,1,7,7-tetramethylzololidyl-9-enyl) -4H-pyran -(2-benzothiazolyl) -2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H, 5H, 11H- [1] benzopyrano [6,7,8- ij] quinolizine (C545T), tri (8-hydroxyquinolato) aluminum (Alq3), tris (2- (2-pyridylphenyl-C, N)) iridium (II) (Ir) ppy, and the like, Or fluorene-based polymers, spirofluorene-based polymers, or dicarbazole stilbenes (DCS) (also called "bis [carbazole- (9)]-stilbenes), which cause the light emitting layer to emit blue light. Carbazole low molecular weight, 4,4'-bis (2,2'-diphenylethen-1-yl ) Biphenyl {4,4'-Bis (2,2'-diphenylethen-1-yl) biphenyl} (DPBVi) N, N'-bis (naphthalen-1-yl) -N, N-bis (phenyl) benzidine {N, N'-Bis (naphthalene-1-yl) -N, N'-bis (phenyl) benzidine} (α-NPD) and the like.

As described above, an electric charge injection layer formed of a component for smoothly injecting charges into upper and lower portions of the light emitting layer in the organic layer 287 and / or an electric charge transfer layer for smoothly transferring charges. ) May be provided. The charge injection layer may be classified into an electron injection layer (EIL) and a hole injection layer (HIL), and the charge transport layer may be an electron transport layer (ETL) and a hole transport layer (HTL). hole transfer layer). The electron injection layer may be formed of lithium fluoride, calcium, barium, or the like.

The hole injection layer may be formed of CuPc or Starburst type amines such as TCTA, m-MTDATA, m-MTDAPB, and the hole transport layer is N, N'-bis (3-methylphenyl) -N, N ' -Diphenyl- [1,1-biphenyl] -4,4'-diamine (TPD), N, N'-di (naphthalen-1-yl) -N, N'-diphenylbenzidine, N, N ' -Di (naphthalene-1-yl) -N, N'-diphenyl-benxidine (α-NPD) and the like, the electron injection layer is LiF, NaCl, CsF, Li ₂ O, BaO, etc. The transport layer is an A oxazole compound, an isoxazole compound, a triazole compound, an isothiazole compound, an oxadiazole compound, a thiadiazole compound, a perylene compound, an aluminum complex ( Examples: Alq3 (tris (8-quinolinolato) -aluminum) BAlq, SAlq, Almq3, gallium complexes (e.g. Gaq'2OPiv, Gaq'2OAc, 2 (Gaq'2) ) And the like.

On the other hand, when the EL device having the structure described above is a bottom emission type, the substrate 281, the buffer layer 282, the gate insulating film 283, the interlayer insulating film 284, the first passivation film 285, and the first electrode 261 is formed of a transparent material, and the second electrode 262 is formed of lithium (Li), magnesium (Mg), aluminum (Al), aluminum-lidium (Al-Li), calcium (Ca), magnesium-indium ( Mg-In) and magnesium-silver (Mg-Ag). When the EL device is a top emission type, the first electrode 261 may be formed of a metal material having good light reflectivity, and the second electrode 262 and the second passivation layer 289 may be formed of a transparent material. The EL device according to the present invention may be a bottom emission type or a top emission type, and the light generated from the EL device may be emitted through at least one of the first electrode and the second electrode. When the first electrode or the second electrode is transparent, the electrode may be formed of ITO or the like.

Finally, the storage capacitor 240 includes a lower electrode 241 and an upper electrode 242. The lower electrode 241 may be integrally formed with the second gate electrode 251, and the upper electrode 242 may be It may be integrally formed with the second source electrode 252. The storage capacitor 240 functions to maintain current to the first electrode 261 or to improve driving speed.

In the structure as described above, the organic film 287 including the first electrode 261 and the light emitting portion is provided on the back substrate 281, so that in the case of the bottom emission type, the organic film 287 including the light emitting portion. ) And an interface between the back substrate 281 and the organic layer 287, the first electrode 261, the first electrode 261, and the back substrate 281 reduces the number of reflections, and the like. By reducing the light extraction rate can be increased, it is also possible to increase the aperture ratio, such as to form a wider light emitting portion than the conventional structure shown in FIG. In addition, a thinner flat panel display device can be realized by reducing the thickness t2 of the device according to the present embodiment, regardless of the thickness t1 of the conventional device as shown in FIG. Will be.

In the first embodiment as described above, the organic electroluminescent device has been described as an embodiment thereof, but the present invention is not limited to the organic electroluminescent device as described above, and the inorganic electroluminescent device and at least one or more transistors are provided. Obviously, the present invention can be applied to any flat panel display device using a self-light emitting device having an electrode connected to the transistor. For convenience, a description will be given of the organic electroluminescent display device as the first embodiment described above.

4 is a cross-sectional view of a flat panel display when the display device according to the second exemplary embodiment of the present invention is an organic electroluminescent device.

Referring to FIG. 4, the first electrode 361 constituting the display unit 360 is positioned on the same layer as the semiconductor layer 380 of the second thin film transistor 350. In particular, in the case of FIG. This is the case provided on the buffer layer 382 provided on the 381. The components other than the positions of the organic layer 387 including the first electrode 361 are the same as those described in the configuration of the organic EL device according to the first embodiment.

In the present exemplary embodiment, the organic layer 387 including the first electrode 361 and the light emitting unit is provided on the same layer as the semiconductor layer 380 of the second thin film transistor 350. An interface between the organic layer 387 including the light emitting unit and the rear substrate 381 is interposed between the organic layer 387, the first electrode 361, the first electrode 361, and the buffer layer 382. In addition, the light extraction rate may be increased by reducing the number of the buffer layer 382 and the back substrate 381 to reduce reflection, etc., and may also form a light emitting part more widely than the conventional structure shown in FIG. 1. The opening ratio can be raised. In addition, a thinner flat panel display device can be realized by reducing the thickness t3 of the device according to the present embodiment, regardless of the thickness t1 of the conventional device as shown in FIG. Will be.

In this case, since the first electrode 361 and the semiconductor layer 380 are connected by the second drain electrode 353, a method of directly contacting the first electrode 361 and the semiconductor layer 380. You can also think. However, in the case of the bottom emission type, since the first electrode 361 is made of ITO or the like, the contact between ITO and Si is very high and thus difficult to be applied to the thin film transistor. That is, a very high Schottky barrier between ITO and Si and the formation of SiO ₂ due to oxidation of the Si surface during or after ITO deposition causes high contact resistance. Therefore, as shown in FIG. 4, the first electrode 361 and the semiconductor layer 380 must be contacted using the second drain electrode 353 through the contact holes, and the first electrode 361 and the semiconductor are in contact with each other. Layer 380 should be separated and not in direct contact. In this case, a second drain electrode 353 having a shape as shown in FIG. 4 may be provided for convenience of the process. In addition, the first electrode 361 and the semiconductor may be provided through various types of second drain electrodes 353. It is apparent that the layers 380 can be connected.

5 is a cross-sectional view showing an organic EL device according to a third preferred embodiment of the present invention.

In the present exemplary embodiment, the first electrode 461 of the display unit 460 has the same structure as described in the above embodiments except that the first electrode 461 is provided on the gate insulating film 483. Also in this embodiment, the structure as shown in FIG. 5 can increase aperture ratio, light extraction rate, light efficiency, etc., and can also reduce the thickness t4 of the display element.

As described above, in the above embodiments, the organic electroluminescent device has been described as the embodiment, but the present invention is not limited to the above organic electroluminescent device. For example, it is apparent that the present invention can be applied to all flat panel display devices using an inorganic electroluminescent device and other self-light emitting devices having at least one transistor and connected to the transistor.

According to the flat panel display of the present invention made as described above, the following effects can be obtained.

First, the thickness of the flat panel display device can be reduced by making the position of the display unit closer to the rear substrate.

Second, in the case of the bottom emission type, by reducing the number of layers interposed between the light emitting portion and the back substrate, the light extraction rate can be increased by reducing the reflection at each interface.

Third, the light emitting part may be located closer to the rear substrate, thereby increasing the aperture ratio than the conventional display device.

Although the present invention has been described with reference to the embodiments shown in the drawings, these are merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

1 is a cross-sectional view showing a conventional active matrix type electroluminescent device.

2 is a plan view showing an electroluminescent device according to a preferred embodiment of the present invention.

3 is a cross-sectional view of a subpixel unit of the active matrix type electroluminescent display according to the embodiment taken along P1 to P7 of FIG.

4 is a cross-sectional view showing an electroluminescent device according to another preferred embodiment of the present invention.

5 is a cross-sectional view showing an electroluminescent device according to another preferred embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

210: first thin film transistor 211: first gate electrode

212: first source electrode 213: first drain electrode

220: first conductor 230: second conductor

240: storage capacitor

150, 250, 350, 450: second thin film transistor

151, 251, 351, 451: second gate electrode

152, 252, 352, 452: second source electrode

153, 253, 353, and 453: second drain electrodes 160, 260, 360, and 460: display unit

161, 261, 361, 461: first electrode 162, 262, 362, 462: second electrode

270: third conductive wire 180, 280, 380, 480: semiconductor layer

181, 281, 381, 481: substrate 182, 282, 382, 482: buffer layer

183, 283, 383, 483: gate insulating film 184, 284, 384, 484: interlayer insulating film

185, 285, 385, 485: first passivation layer 186, 286, 386, 486: planarization layer

187, 287, 387, 487: light emitting portions 189, 289, 389, 489: second protective film

Claims (8)

Back substrate; A plurality of self-luminous elements having at least a light emitting layer provided on the rear substrate; And At least one transistor provided for each of the self-luminous elements; And at least two layers interposed between the first electrode and the rear substrate of the self-luminous device connected to the transistor. The method of claim 1, And the first electrode is provided on the rear substrate. The method of claim 1, And the first electrode is on the same layer as the semiconductor layer of the transistor. The method of claim 3, wherein And the first electrode and the semiconductor layer are separated. The method of claim 1, And a gate insulating film interposed between the first electrode and the rear substrate. The method according to any one of claims 1 to 5, And the flat panel display is a bottom emission type. The method according to any one of claims 1 to 5, And the self-luminescent element is an electroluminescent element. The method of claim 7, wherein And the electroluminescent element is an organic electroluminescent element.