WO2007086682A1

WO2007086682A1 - Organic electroluminescent compounds and display device using the same as an electrolu¬ minescent material

Info

Publication number: WO2007086682A1
Application number: PCT/KR2007/000423
Authority: WO
Inventors: Sung-Min Chin; So-Young Jung; Sang-Man Si; Keun-Hee Han; Kyung-Hoon Choi; Jung-Su Kwon; Hyo-Jeong Lim; Mi-Young Kwak; Bok-Young Kim; Sung-Min Kim
Original assignee: Gracel Display Inc
Current assignee: Gracel Display Inc
Priority date: 2006-01-24
Filing date: 2007-01-24
Publication date: 2007-08-02
Anticipated expiration: 2008-07-24
Also published as: JP5173836B2; EP2004774A1; KR100684109B1; TWI352110B; JP2009524650A; CN101517033A; CN101517033B; EP2004774A4; TW200728433A

Abstract

The present invention relates to an organic electroluminescent compound represented by Chemical Formula 1 and an electroluminescent device containing the same as an electroluminescent material. The electroluminescent compound according to the present invention is advantageous in that it prominently lowers the driving voltage and considerably enhances the power efficiency when being used as a host material for an OLED device.

Description

ELECTROLUMINESCENT COMPOUNDS AND ORGANIC ELECTROLUMINESCENT DEVICE

USING THE SAME

Technical Field

[1] The present invention relates to an electroluminescent compound comprised of a metal complex, which shows excellent electrical conductivity and electroluminescent property with high efficiency, and an electroluminescent device comprising the same as a host material.

[2]

Background Art [3] The most important factor to determine luminous efficiency in an OLED is the electroluminescent characteristics of electroluminescent material. Though a fluorescent material has been widely used as an electroluminescent material up to the present, a development of phosphorescent material is one of the best solutions to improve luminous efficiency theoretically up to four times in view of electroluminescent mechanism.

[4] Up to now, iridium(iπ) complexes are widely known as phosphorescent dopants, including (acac)Ir(btp) , Ir(ppy) and Firpic, as the red, green and blue one, re- spectively. In particular, a lot of phosphorescent materials have been investigated in Japan and Europe and America, so that development of further improved phosphorescent materials is expected.

[5]

(acac)lr(btp);. !r(PPy)3 Firpic

[6] As a host material for phosphorescent light emitting material, CBP is most widely known up to the present, and OLEDs having high efficiency to which a hole blocking layer such as BCP and BAIq, etc. has been applied have been known. Pioneer (Japan) reported OLEDs having high efficiency using a BAIq derivative as the host.

CBP BCP

[8]

BAIq BAIq DERIVATIVE

[9] Though the materials in prior art are advantageous in view of light emitting property, they have low glass transition temperature and very poor thermal stability, so that the materials tend to be changed during high temperature vacuum- vapor-deposition process. In addition, they are not satisfactory in terms of lifetime of an OLED device, so that development of host materials having better material stability and more excellent EL performance is required.

[10] According to the present invention, developed are metal complex materials exhibiting excellent material stability, excellent electrical conductivity and luminous property of high efficiency as compared to conventional materials. An aromatic ring containing a hetero atom or a side chain substituent hetero atom containing non- bonding electron pair has a property to readily coordinate to metal. Such a coordination shows very stable property in electrochemical aspect, which has been known widely. The present invention developed various ligands, prepared metal complexes having above-mentioned properties and applied them as host materials.

[H] A number of conventional complexes of such type have been researched since the middle of 1990's. However, those materials have been applied merely as an electroluminescent material, but rarely as a host material.

[12]

Disclosure of Invention Technical Problem

[13] The object of the invention is to overcome the disadvantages as described above, and to provide mixed type ligand-metal complexes as electroluminescent materials, which are very excellent in luminous and physical properties as compared to conventional organic host materials or aluminum complexes. Another object of the invention is to provide an electroluminescent device containing the electroluminescent compound thus prepared as a host material. [14]

Technical Solution

[15] The present invention relates to an electroluminescent compound comprised represented by Chemical Formula 1 and an electroluminescent device containing the same as a host material.

[16]

[17] [Chemical Formula 1 ]

[18] L¹L²M

1 9

[19] In the formula, L and L are different each other, and selected from those represented by one of the following structural formulas: [20]

[21] wherein M is a divalent metal; X is O, S or Se; A ring is oxazole, thiazole, imidazole, oxadiazole, thiadiazole, benzoxazole, benzothiazole, benzimidazole, pyridine or quinoline, and the pyridine or quinoline may form a fused ring with R via chemical bond, and said A ring may have additional substituent such as C1-C5 alkyl, or phenyl or naphthyl with or without substituent(s); B ring is pyridine or quinoline, and said B ring may have additional substituent such as C1-C5 alkyl, or phenyl or naphthyl with or without substituent(s); and R independently represents hydrogen or C1-C5 alkyl.

[22]

1 9

[23] In the Chemical Formula 1 as described above, the ligands L and L are different each other, and may be selected from those represented by one of the following structural formulas:

[24]

[25] wherein, M is divalent metal; X is O, S or Se; Y is O, S or N-R 4 , Z is CH or N; R 2 and R independently represent hydrogen, phenyl or naphthyl with or without substituent(s); and R 4 is C1-C5 alkyl, or phenyl or naphthyl with or without substituent(s).

[26] In Chemical Formula 1, M is preferably selected from Be, Zn, Mg, Cu and Ni, and

1 9 the ligands L and L are preferably selected from those represented by one of the following structural formulas:

[27]

[28] wherein, X is O, S or Se. [29] The ligands L and L of the electroluminescent compounds according to the present invention are exemplified as follows:

[30]

[31] wherein, X is O or S.

[32] Specifically, the electroluminescent compounds of Chemical Formula 1 according to the present invention may be exemplified as the compounds represented by one of the Chemical Formulas 1-1 through 1-18:

[33] [Chemical Formula 1-1] [34]

[35] [Chemical Formula 1-2] [36]

[37] [Chemical Formula 1-3] [38]

[39] [Chemical Formula 1-4] [40]

[41] [Chemical Formula 1-5] [42]

[43] [Chemical Formula 1-6] [44]

[45] [Chemical Formula 1-7] [46]

[47] [Chemical Formula 1-8] [48]

[49] [Chemical Formula 1-9]

[50]

[51] [Chemical Formula 1-10] [52]

[53] [Chemical Formula 1-11] [54]

[55] [Chemical Formula 1-12] [56]

[57] [Chemical Formula 1-13]

[59] [Chemical Formula 1-14] [60]

[61] [Chemical Formula 1-15] [62]

[63] [Chemical Formula 1-16] [64]

[65] [Chemical Formula 1-17] [66]

[67] [Chemical Formula 1-18]

[68]

[69]

Brief Description of the Drawings

[70]

[71] Fig. 1 EL spectrum of the OLED device prepared according to Comparative

Example 1 [72] Fig. 2 Luminance-applied voltage characteristic of the OLED device prepared according to Comparative Example 1 [73] Fig. 3 Luminous efficiency-luminance characteristic of the OLED device prepared according to Comparative Example 1 [74] Fig. 4 Luminance-applied voltage characteristic of the OLED device prepared according to Example 1 [75] Fig. 5 Luminous efficiency-luminance characteristic of the OLED device prepared according to Example 1 [76] [77] Other and further objects, features and advantages of the invention will appear more fully from the following description. [78] [79]

Mode for the Invention [80] The present invention is further described with respect to the electroluminescent compounds according to the present invention, a process for preparing the same and the electroluminescent properties of the device employing the same, by referring to representative compounds according to the present invention, which are provided for illustration only and are not intended to be limiting in any way. [81] [Preparation Example 1] Compound of Chemical Formula 1-1

[82] In 50 mL of methanol, 2-pyridin-2-yl-phenol (1.0 g, 5.84 mmol) was dissolved, and

10 mL of aqueous IM sodium hydroxide solution was added thereto. To the mixed solution, a solution of beryllium sulfate tetrahydrate (1.05 g, 5.93 mmol) in 10 mL of aqueous methanol (methanol 7 mL: water 3 mL) was added dropwise, and the resultant mixture was stirred at ambient temperature for 2 hours. After completing the stirring, 2-hydroxy-phenyl benzoxazole (1.54 g, 7.30 mmol) dissolved in 50 mL of methanol was slowly added. The reaction solution was then stirred at ambient temperature for 2 hours. The temperature of the solution was raised to 50°C, and the solution was stirred for 10 hours.

[83] After completion of the stirring, the precipitate produced was filtered, washed with water (50 mL) and acetone (50 mL), and dried to obtain the title compound, Compound (1-1) (0.80 g, 2.04 mmol, yield: 34%). [84] MS/FAB : 391 (found), 391.43 (calculated)

[85] EA: C 73.55%, H 4.59%, N 7.05%, O 12.41%

[86] [Preparation Example 2] Compound of Chemical Formula 1-2

[87] In 50 mL of methanol, 2-pyridin-2-yl-phenol (1.0 g, 5.84 mmol) was dissolved, and

10 mL of aqueous IM sodium hydroxide solution was added thereto. To the mixed solution, zinc acetate (0.95 g, 5.18 mmol) dissolved in methanol (10 mL) was added dropwise, and the resultant mixture was stirred at ambient temperature for 2 hours. After completing the stirring, 2-hydroxy-phenyl benzoxazole (1.50 g, 7.10 mmol) dissolved in 50 mL of methanol was slowly added. The reaction mixture was then stirred at ambient temperature for 10 hours.

[88] After completion of the stirring, the precipitate produced was filtered, washed with water (50 mL) and acetone (50 mL), and dried to obtain the title compound, Compound (1-2) (0.72 g, 1.61 mmol, yield: 27%). [89] MS/FAB: 447(found), 447.79(calculated)

[90] EA: C 64.22%, H 4.01%, N 6.05%, O 10.95%

[91] [Preparation Example 3] Compound of Chemical Formula 1-3

[92] The same procedure as Preparation Example 1 was carried out by using

2-hydroxy-phenyl benzoxazole (1.23 g, 5.82 mmol), 10-hydroxybenzo[/ϊ]quinoline (1.48 g, 7.58 mmol) and beryllium sulfate tetrahydrate (1.05 g, 5.93 mmol), to obtain the title compound, Compound (1-3) (0.35 g, 0.84 mmol, yield: 14%). [93] MS/FAB: 415(found), 415.46(calculated)

[94] EA: C 75.02%, H 4.27%, N 6.64%, O 11.65% [95] [Preparation Example 4] Compound of Chemical Formula 1-4

[96] The same procedure as Preparation Example 2 was carried out by using

2-hydroxy-phenyl benzoxazole (1.23 g, 5.82 mmol), 10-hydroxybenzo[/ϊ]quinoline (1.48 g, 7.58 mmol) and zinc acetate (0.95 g, 5.18 mmol), to obtain the title compound, Compound (1-4) (0.52 g, 1.10 mmol, yield: 19%). [97] MS/FAB : 471 (found), 471.81 (calculated)

[98] EA: C 66.08%, H 3.79%, N 5.84%, O 10.30%

[99] [Preparation Example 5] Compound of Chemical Formula 1-5

[100] The same procedure as Preparation Example 1 was carried out by using

2-hydroxy-phenyl benzoxazole (1.23 g, 5.82 mmol), 2-hydroxy-phenyl benzothiazole (1.72 g, 7.57 mmol) and beryllium sulfate tetrahydrate (1.05 g, 5.93 mmol), to obtain the title compound, Compound (1-5) (0.96 g, 2.15 mmol, yield: 37%). [101] MS/FAB: 447(found), 447.52(calculated)

[102] EA: C 69.68%, H 4.01%, N 6.16%, O 10.85% S 7.05%

[103] [Preparation Example 6] Compound of Chemical Formula 1-6

[104] The same procedure as Preparation Example 2 was carried out by using

2-hydroxy-phenyl benzoxazole (1.23 g, 5.82 mmol), 2-hydroxy-phenyl benzothiazole (1.72 g, 7.57 mmol) and zinc acetate (0.95 g, 5.18 mmol), to obtain the title compound, Compound (1-6) (1.36 g, 2.70 mmol, yield: 46%). [105] MS/FAB: 503(found), 503.88(calculated)

[106] EA: C 61.88%, H 3.54%, N 5.46%, O 9.73%, S 6.26%

[107] [Preparation Example 7] Compound of Chemical Formula 1-7

[108] The same procedure as Preparation Example 1 was carried out by using

2-hydroxy-phenyl benzothiazole (1.32 g, 5.80 mmol), 2-pyridine-2-yl-phenol (1.30 g, 7.59 mmol) and beryllium sulfate tetrahydrate (1.05 g, 5.93 mmol), to obtain the title compound, Compound (1-7) (0.59 g, 1.45 mmol, yield: 25%). [109] MS/FAB: 407(found), 407.50(calculated)

[110] EA: C 70.64%, H 4.35%, N 6.76%, O 7.96%, S 7.75%

[111] [Preparation Example 8] Compound of Chemical Formula 1-8

[112] The same procedure as Preparation Example 2 was carried out by using

2-hydroxy-phenyl benzothiazole (1.32 g, 5.80 mmol), 2-pyridine-2-yl-phenol (1.30 g, 7.59 mmol) and zinc acetate (0.95 g, 5.18 mmol), to obtain the title compound, Compound (1-8) (0.83 g, 1.79 mmol, yield: 31%). [113] MS/FAB: 463(found), 463.86(calculated)

[114] EA: C 62.04%, H 3.82%, N 5.98%, O 7.02%, S 6.83%

[115] [Preparation Example 9] Compound of Chemical Formula 1-9

[116] The same procedure as Preparation Example 1 was carried out by using

2-hydroxy-phenyl benzothiazole (1.32 g, 5.80 mmol), 10-hydroxybenzo[/ϊ]quinoline (1.48 g, 7.58 mmol) instead of 2-hydroxy-phenyl benzoxazole, and beryllium sulfate tetrahydrate (1.05 g, 5.93 mmol), to obtain the title compound, Compound (1-9) (0.98 g, 2.27 mmol, yield: 39%).

[117] MS/FAB: 431(found), 431.52(calculated)

[118] EA: C 72.22%, H 4.10%, N 6.40%, O 7.62%, S 7.33%

[119] [Preparation Example 10] Compound of Chemical Formula 1-10

[120] The same procedure as Preparation Example 4 was carried out by using

2-hydroxy-phenyl benzothiazole (1.32 g, 5.80 mmol), 10-hydroxybenzo[/ϊ]quinoline (1.48 g, 7.58 mmol) and zinc acetate (0.95 g, 5.18 mmol), to obtain the title compound, Compound (1-10) (1.22 g, 2.50 mmol, yield: 43%). [121] MS/FAB: 487(found), 487.88(calculated)

[122] EA: C 63.93%, H 3.65%, N 5.64%, O 6.70%, S 6.44%

[123] [Preparation Example 11] Compound of Chemical Formula 1-11

[124] The same procedure as Preparation Example 1 was carried out by using

2-hydroxy-phenyl benzoxazole (1.23 g, 5.82 mmol),

2-(l-phenyl-lH-benzoimidazol-2-yl)-phenol (2.17 g, 7.58 mmol) and beryllium sulfate tetrahydrate (1.05 g, 5.93 mmol), to obtain the title compound, Compound (1-11) (0.56 g, 1.11 mmol, yield: 19%).

[125] MS/FAB: 506(found), 506.57(calculated)

[126] EA: C 75.67%, H 4.50%, N 8.20%, O 9.68%

[127] [Preparation Example 12] Compound of Chemical Formula 1-12

[128] The same procedure as Preparation Example 2 was carried out by using

2-hydroxy-phenyl benzoxazole (1.23 g, 5.82 mmol),

2-(l-phenyl-lH-benzoimidazol-2-yl)-phenol (2.17 g, 7.58 mmol) and zinc acetate (0.95 g, 5.18 mmol), to obtain the title compound, Compound (1-12) (0.72 g, 1.28 mmol, yield: 22%).

[129] MS/FAB: 562(found), 562.93(calculated)

[130] EA: C 68.16%, H 4.05%, N 7.36%, O 8.68%

[131] [Preparation Example 13] Compound of Chemical Formula 1-13

[132] The same procedure as Preparation Example 1 was carried out by using

2-(l-phenyl-lH-benzoimidazol-2-yl)phenol (1.67 g, 5.83 mmol), 2-pyridin-2-yl-phenol (1.30 g, 7.59 mmol) and beryllium sulfate tetrahydrate (1.05 g, 5.93 mmol), to obtain the title compound, Compound (1-13) (0.84 g, 1.80 mmol, yield: 31%). [133] MS/FAB : 466(found), 466.55(calculated)

[134] EA: C 77.08%, H 4.87%, N 8.90%, O 6.98%

[135] [Preparation Example 14] Compound of Chemical Formula 1-14

[136] The same procedure as Preparation Example 2 was carried out by using

2-(l-phenyl-lH-benzimidazol-2-yl)-phenol (1.67 g, 5.83 mmol), 2-pyridine-2-yl-phenol (1.30 g, 7.59 mmol) and zinc acetate (0.95 g, 5.18 mmol), to obtain the title compound, Compound (1-14) (0.88 g, 1.68 mmol, yield: 29%). [137] MS/FAB : 522(found), 522.91 (calculated)

[138] EA: C 68.81%, H 4.33%, N 7.92%, O 6.32%

[139] [Preparation Example 15] Compound of Chemical Formula 1-15

[140] The same procedure as Preparation Example 1 was carried out by using

2-(l-phenyl-lH-benzoimidazol-2-yl)-phenol (1.67 g, 5.83 mmol), 10-hydroxybenzo[/ϊ] quinoline (1.50 g, 7.68 mmol) and beryllium sulfate tetrahydrate (1.05 g, 5.93 mmol), to obtain the title compound, Compound (1-15) (0.26 g, 0.53 mmol, yield: 9%). [141] MS/FAB: 490(found), 490.57(calculated)

[142] EA: C 78.20%, H 4.68%, N 8.42%, O 6.70%

[143] [Preparation Example 16] Compound of Chemical Formula 1-16

[144] The same procedure as Preparation Example 2 was carried out by using

2-(l-phenyl-lH-benzimidazol-2-yl)-phenol (1.67 g, 5.83 mmol), 10-hydroxybenzo[/ϊ] quinoline (1.50 g, 7.68 mmol) and zinc acetate (0.95 g, 5.18 mmol), to obtain the title compound, Compound (1-16) (0.42 g, 0.77 mmol, yield: 13%). [145] MS/FAB: 546(found), 546.93(calculated)

[146] EA: C 70.13%, H 4.16%, N 7.58%, O 5.98%

[147] [Preparation Example 17] Compound of Chemical Formula 1-17

[148] The same procedure as Preparation Example 1 was carried out by using

2-hydroxy-phenyl benzothiazole (1.32 g, 5.80 mmol),

2-(l-phenyl-lH-benzoimidazol-2-yl)-phenol (2.17 g, 7.58 mmol) and beryllium sulfate tetrahydrate (1.05 g, 5.93 mmol), to obtain the title compound, Compound (1-17) (0.64 g, 1.22 mmol, yield: 21%).

[149] MS/FAB: 522(found), 522.64(calculated)

[150] EA: C 73.42%, H 4.34%, N 7.97%, O 6.25%, S 6.04%

[151] [Preparation Example 18] Compound of Chemical Formula 1-18

[152] The same procedure as Preparation Example 2 was carried out by using

2-hydroxy-phenyl benzothiazole (1.32 g, 5.80 mmol),

2-(l-phenyl-lH-benzimidazol-2-yl)-phenol (2.17 g, 7.58 mmol) and zinc acetate (0.95 g, 5.18 mmol), to obtain the title compound, Compound (1-18) (0.94 g, 1.62 mmol, yield: 28%).

[153] MS/FAB: 578(found), 578.99(calculated)

[154] EA: C 66.22%, H 3.94%, N 7.16%, O 5.70%, S 5.49%

[155] [Example 1 - 18] Manufacture of OLED device by using the compounds according to the present invention

[156] OLED devices having the structure employing the host materials according to the present invention were manufactured. [157] First, a transparent electrode ITO thin film (15 Ω/D) obtained from a glass for OLED was subjected to ultrasonic washing with trichloroethylene, acetone, ethanol and distilled water, subsequently, and stored in isopronanol before use.

[158] Then, an ITO substrate was equipped in a substrate folder of vacuum vapor-deposit device, and 4,4',4"-tris(N,N-(2-naphthyl)-phenylamino)triphenylamine (2-TNATA) represented by following structural formula was placed in a cell of the vacuum vapor- deposit device, which was then ventilated up to 10^" torr of vacuum in the chamber. Electric current was applied to the cell to evaporate 2-TNATA to vapor-deposit a hole injection layer having 40 nm of thickness on the ITO substrate.

[159]

2-TNATA

[160] Then, to another cell of the vacuum vapor-deposit device, charged was N,N'-bis(α-naphthyl)-N,N'-diphenyl-4,4'-diamine (NPB), and electric current was applied to the cell to evaporate NPB to vapor-deposit a hole transport layer of 20 nm of thickness on the hole injection layer.

[161]

NPB

[162] [163] After forming the hole injection layer and hole transport layer, an electroluminescent layer was vapor-deposited thereon as follows. In one cell of the vacuum vapor-deposit device, charged was a compound selected from Compounds 1-1 through 1-18 which was purified via sublimation in vacuo under 10^" torr, as a host material, and in another cell, charged was (NPy) Ir(acac). The two materials were evaporated at different rates to give doping of 4-10 mol%, to vapor-deposit light emitting layer having 30 nm of thickness on the hole transport layer.

[164]

(Npy)₂Ir(acac)

[165] Then, tris(8-hydroxyquinoline)aluminum(III) (AIq) represented by following structural formula was vapor-deposited as an electron transport layer in a thickness of 20 nm, and lithium quinolate (Liq) represented by following structural formula was vapor-deposited as an electron injection layer in a thickness of 1 to 2 nm. Thereafter, an Al cathode was vapor-deposited in a thickness of 150 nm by using another vapor- deposit device to manufacture an OLED.

[166]

AIq Liq

[167] [Comparative Example 1] [168] An OLED device was made according to the same procedure as described in Example 1, but bis(2-methyl-8-quinolinato)(p-phenylphenolato)aluminum(III) (BAIq) was charged to another cell in the vacuum vapor-deposit device as a light emitting host material, while (NPy) Ir(acac) was charged as a light emitting material in still another cell, and the two materials were evaporated at different rates to give doping of 4-10 mol%, to vapor-deposit a light emitting layer having 30 nm of thickness on said hole transport layer.

[169]

BAIq (Npy)₂lr(acac)

[170] [Example 19] [171] Confirmation of OLED properties [172] The luminous efficiency and power efficiency of each OLED device containing the electroluminescent compound according to the present invention prepared from one of Examples 1-18 and the conventional electroluminescent compound prepared from Comparative Example 1 were measured at 1,000 cd/m , of which the results are shown in Table 1.

[173] From the Table showing the light emitting properties of the complexes developed by the present invention, it is found that the complexes developed by the present invention exhibit excellent properties in terms of performances as compared to conventional material.

[174] Table 1

[175] As can be seen from the Table, when the electroluminescent material according to the present invention is applied as a host, the EL performance is noticeably improved as a rule.

[176] Fig. 1, an EL spectrum of Comparative Example 1 wherein (NPy) Ir(acac) compound (emitting orange-red light) was used as an electroluminescent material and BAIq as a host material, shows maximum EL peak at about 624 nm. From Fig. 2 showing luminance-applied voltage characteristic of Comparative Example 1, it is confirmed that driving voltage of the device of Comparative Example 1 is about 5 V, and the driving voltage at 1,000 cd/m (standard of Table 1) was 7.49 V. From Fig. 3 which shows luminous efficiency-luminance characteristic of Comparative Example 1 and Table 1, it is confirmed that the device of Comparative Example 1 showed luminous efficiency of about 6.16 cd/A at the luminance of about 1,000 cd/m , and color coordinates of (0.677,0.321).

[177] As can be seen from Fig. 4 which shows luminance-applied voltage characteristic of the OLED device prepared according to Example 14, the device of Example 14 employing the electroluminescent compound according to the present invention showed driving voltage of about 3 V, and luminance of about 1,000 cd/m at about 4.86 V; the result shows decrease of driving voltage by at least 2.6 V as compared to the device of Comparative Example 1.

[178] Further, as can be seen from Fig. 5 which shows luminous efficiency-luminance characteristic of the device according to Example 14, it showed luminous efficiency of about 6.67 cd/A at 1,000 cd/m of luminance; which shows higher luminous efficiency by about 0.5 cd/A as compared to the device of Comparative Example 1 at the same luminance.

[179] With respect to power efficiency which is considered important in a practical panel, since the term voltage is included in the denominator in Formula 1 below, the device having lowered driving voltage becomes far advantageous in terms of power consumption:

[180] Power efficiency(lm/W)=(π x luminance)/(current density x voltage) (1)

[181] As can be seen from Table 1 above, the device employing an electroluminescent compound according to the present invention as the host material lowers the driving voltage to induce increase of power efficiency by 0.5 ~ 2.0 lm/W, thereby improving the power consumption.

[182]

Industrial Applicability

[183] When the electroluminescent compounds according to the present invention are employed in OLED devices as a host material, driving voltage is noticeably lowered and power efficiency is considerably increased. Thus, the compounds in the present invention are suitable for an OLED material in next generation, and expected to greatly contribute for the development of large size display adopted OLED.

[184]

[185]

[186]

Claims

Claims [1] An electroluminescent compound represented by Chemical Formula 1 :

[Chemical Formula 1]

L¹L²M wherein, L and L are different each other, and selected from those represented by one of the following structural formulas:

wherein, M is a divalent metal; X is O, S or Se; A ring is oxazole, thiazole, imidazole, oxadiazole, thiadiazole, benzoxazole, benzothiazole, benzimidazole, pyridine or quinoline, and the pyridine or quinoline may form a fused ring with R via chemical bond, and said A ring may have additional substituent such as C1-C5 alkyl, or phenyl or naphthyl with or without substituent(s); B ring is pyridine or quinoline, and said B ring may have additional substituent such as C1-C5 alkyl, or phenyl or naphthyl with or without substituent(s); and R independently represents hydrogen or C1-C5 alkyl.

[2] An electroluminescent compound according to claim 1, wherein the ligands L and L are different each other, and selected from those represented by one of the following structural formulas:

wherein, M is divalent metal; X is O, S or Se; Y is O, S or N-R 4 , Z is CH or N; R and R independently represent hydrogen, phenyl or naphthyl with or without substituent(s); and R 4 is C1-C5 alkyl, or phenyl or naphthyl with or without substituent(s).

[3] An electroluminescent compound according to claim 1, wherein M is selected from Be, Zn, Mg, Cu and Ni.

[4] An electroluminescent compound according to claim 1, wherein the ligands L and L² are different each other and selected from those represented by one of the following structural formulas:

wherein, X is O, S or Se.

[5] An electroluminescent compound according to claim 4, wherein the ligands L and L² are different each other, and selected from those represented by one of the following structural formulas:

wherein, X is O or S.

[6] An electroluminescent compound according to claim 5, which is selected from the compounds represented by one of Chemical Formulas 1-1 through 1-18: [Chemical Formula 1-1]

[Chemical Formula 1-2]

[Chemical Formula 1-3]

[Chemical Formula 1-4]

[Chemical Formula 1-5]

[Chemical Formula 1-6]

[Chemical Formula 1-7]

[Chemical Formula 1-8]

[Chemical Formula 1-9]

[Chemical Formula 1-10]

[Chemical Formula 1-11]

[Chemical Formula 1-12]

[Chemical Formula 1-13]

[Chemical Formula 1-14]

[Chemical Formula 1-15]

[Chemical Formula 1-16]

[Chemical Formula 1-17]

[Chemical Formula 1-18]

[7] An electroluminescent device comprising an electroluminescent compound according to any one of claims 1 to 6. [8] An electroluminescent device according to claim 7, in which the electroluminescent compound is used as a host material in an emitting layer.