JP2020094122A - Luminescent material and organic electroluminescent element based on the same - Google Patents

Abstract

To provide a novel luminescent material that emits light in a near-infrared region of 800 nm or more.SOLUTION: A luminescent material comprises a compound represented by the formula (1) in the figure. (In the formula, Arand Arare each a benzene ring, thiophene ring, furan ring, or pyrrole ring; Rto Rare each an aromatic hydrocarbon group or aromatic heterocyclic group; X is -S-, -SO-, or a direct coupling; and Ris an aromatic hydrocarbon group, aromatic heterocyclic group, or alkyl group.)SELECTED DRAWING: None

Description

The present invention relates to a light emitting material and an organic electroluminescence device using the same. More specifically, the present invention relates to a light emitting material that can be used as a material for forming a light emitting layer of an organic electroluminescent device, and an organic electroluminescent device using the same.

Near-infrared light is invisible light of 700 to 2500 nm and is widely used in various fields such as optical communication, cameras, and sensors, but light in the wavelength range of 650 to 1000 nm is particularly useful for living organisms. It is used as a light source for devices for acquiring biological information such as vein authentication and pulse oximeters because it easily transmits light. In recent years, although demands for miniaturization of these devices and mounting on wearable devices have been increasing, currently popular devices use inorganic LEDs as a light source and are inferior in flexibility. It was very difficult to meet the demand.

On the other hand, since the organic electroluminescent device is a light emitting device that can be made flexible, it is possible to meet the above-mentioned requirements. However, regarding the material that enables the organic electroluminescent device to emit light in the near infrared region, benzobis There are only a few reported examples of compounds having a skeleton derived from thiadiazole (see Patent Document 1, Non-Patent Documents 1 to 3) and thiadiazole-based compounds (see Patent Documents 2 and 3).

JP, 2013-124231, A JP2012-224567A JP, 2013-177327, A

CHEMISTRY OF MATERIALS, 2012, Vol. 24, p. 2178-2185 APPLIED PHYSICS LETTERS, 2008, Volume 93, 163305 ADVANCED MATERIALS, 2009, Volume 21, p. 111-116

As mentioned above, although there are reports of materials that emit light in the near-infrared region, there are few types of materials that emit light in the wavelength region of 800 nm or more, and most of the organic electroluminescent devices using them have sufficient output. The current situation is not. If we could develop a high-power organic electroluminescent device using a material that emits light in the wavelength region of 800 nm or more, we would like to develop a device that acquires more diverse biometric information, such as downsizing of the device that acquires biometric information and deployment to wearable devices. Not only can it be used as a light source, it is also expected to be applied to various sensors.
Organic electroluminescent devices are constructed by stacking multiple layers made of different materials, and the characteristics required for light-emitting materials may change depending on the materials forming the other layers. In order to promote the development of the organic electroluminescent device that emits light in, it is necessary to increase the variation of materials that emit light in the near infrared region.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a new light emitting material that emits light in the near infrared region of 800 nm or more.

The present inventor examined a novel material that emits light in the near infrared region of 800 nm or more, and found that a compound having a specific structure having a benzothiadiazole skeleton in which a thiazole ring was condensed emits light in the near infrared region. It was When the compound was applied as a light emitting material for an organic electroluminescent device, it was found that an organic electroluminescent device having an emission wavelength in a region of 800 nm or more and high output was obtained, and thus the present invention was achieved. is there.

That is, the present invention provides the following formula (1);

(In the formula, Ar ¹ and Ar ² are the same or different and each represents a group derived from any ring of a benzene ring, a thiophene ring, a furan ring, and a pyrrole ring, which may have a substituent. R ¹ to R ⁴ is the same or different and represents an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent, and R ¹ and R ² and R ³ and R ⁴ may be bonded to each other. good .X is, -S _-, - SO 2 - or .R ⁵ representing a direct bond, an aromatic hydrocarbon group, derived structure benzothiazole represented by the representative) an aromatic heterocyclic group or an alkyl group. A luminescent material comprising a compound having:

Both Ar ¹ and Ar ^{2 in} the above formula (1) are preferably a thiophene ring group.

R ^{1 to} R ^{4 in} the above formula (1) are the same or different and each is an aromatic hydrocarbon group or a thiophene ring group which may have a substituent, and R ⁵ is an aromatic hydrocarbon group or an alkyl group. It is preferably a group.

The present invention is also an organic electroluminescent device having a structure in which a plurality of layers including a light emitting layer are laminated between an anode and a cathode, wherein the light emitting layer contains the light emitting material of the present invention. It is also an organic electroluminescent device that operates.

The light emitting material of the present invention is a material having an emission wavelength in the near infrared region of 800 nm or more, and by using this material, an organic electroluminescence having an emission wavelength in the region of 800 nm or more and high output. It becomes possible to obtain an element.

It is the schematic which showed an example of the laminated structure of the organic electroluminescent element which used the light emitting material of this invention for a light emitting layer. FIG. 2 is a diagram showing fluorescence spectra of compound 4 obtained in Example 1 and compound 6 obtained in Example 2. FIG. 5 is a diagram showing a relationship between (a) voltage-current density characteristics and (b) voltage-irradiance of the organic electroluminescent device 1 manufactured in Example 3. FIG. 6 is a diagram showing a relationship between (a) voltage-current density characteristics and (b) voltage-irradiance of the organic electroluminescent element 2 manufactured in Example 4. FIG. 9 is a diagram showing a relationship between (a) voltage-current density characteristics and (b) voltage-irradiance of the organic electroluminescent element 3 manufactured in Example 5.

The present invention is described in detail below.
It should be noted that a combination of two or more of the individual preferred embodiments of the present invention described below is also a preferred embodiment of the present invention.

The light emitting material of the present invention has the following formula (1);

(In the formula, Ar ¹ and Ar ² are the same or different and each represents a group derived from any ring of a benzene ring, a thiophene ring, a furan ring, and a pyrrole ring, which may have a substituent. R ¹ to R ⁴ is the same or different and represents an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent, and R ¹ and R ² and R ³ and R ⁴ may be bonded to each other. good .X is, -S _-, - SO 2 - or .R ⁵ representing a direct bond, an aromatic hydrocarbon group, derived structure benzothiazole represented by the representative) an aromatic heterocyclic group or an alkyl group. It is characterized by including the compound which has.
Since the compound represented by the above formula (1) has a strong electron accepting skeleton and an electron donating skeleton, it emits light in the near infrared region.

Ar ¹ and Ar ² in the above formula (1) are the same or different and each represents a group derived from any ring of a benzene ring, a thiophene ring, a furan ring and a pyrrole ring which may have a substituent.
When Ar ¹ or Ar ² is a group derived from a benzene ring, the bonding position between the group derived from the benzene ring and —NR ¹ R ² or —NR ³ R ⁴ is not particularly limited, but is bonded to the skeleton derived from benzothiazole. It is preferable that the carbon atom is in a para position with respect to the carbon atom.
When Ar ¹ is a group derived from any ring of a thiophene ring, a furan ring, and a pyrrole ring, the bonding position with the benzothiazole-derived skeleton and the bonding position with -NR ¹ R ² are not particularly limited, but the 2-position It is preferable that the carbon atom of is bonded to the skeleton derived from benzothiazole and the carbon atom at the 5-position is bonded to —NR ¹ R ² . The same applies to the bonding position with the benzothiazole-derived skeleton and the bonding position with -NR ³ R ⁴ when Ar ² is a group derived from any ring of a thiophene ring, a furan ring, and a pyrrole ring.
Of these, Ar ¹ and Ar ² are preferably both groups derived from a thiophene ring.
In the present invention, the “ring-derived group” means a group formed by removing a hydrogen atom from the ring, and in the case of a monovalent group, it means a group formed by removing one hydrogen atom. In the case of a group, it means a group formed by removing two hydrogen atoms.

Examples of the substituent in the benzene ring, thiophene ring, furan ring or pyrrole ring-derived group which may have a substituent include an aromatic hydrocarbon group; an aromatic heterocyclic group; a halogen atom; a cyano group; Examples include an alkyl group having 1 to 18 carbon atoms; an alkoxy group having 1 to 12 carbon atoms; an aryloxy group having 6 to 12 carbon atoms; an alkylamino group having 2 to 12 carbon atoms; and an arylamino group having 7 to 18 carbon atoms. Be done.

Preferable examples of the aromatic hydrocarbon ring forming the aromatic hydrocarbon group include those having 6 to 18 carbon atoms, specifically, aromatic hydrocarbon rings such as benzene, naphthalene, anthracene, and phenanthrene. Are more preferred.
The upper limit of the carbon number of the aromatic hydrocarbon group is preferably 14, more preferably 10, and specifically, a group derived from benzene is particularly preferable.

The aromatic heterocycle forming the aromatic heterocyclic group is an aromatic ring containing a hetero atom which is an atom other than carbon and hydrogen as a ring-constituting atom, and ones having 2 to 12 carbon atoms are preferred. Specifically, a five-membered heterocyclic ring such as triazole, imidazole, oxazole, isoxazole, thiazole, isothiazole, pyrazole, pyrrole, indole, carbazole, furan, benzofuran, dibenzofuran, thiophene, benzothiophene, dibenzothiophene; Six-membered heterocycles such as pyridine, pyrazine, pyrimidine and triazine are preferred.
Among these, the aromatic heterocyclic group preferably has an upper limit of 8 carbon atoms, more preferably 6 carbon atoms, and even more preferably 5. Further, the lower limit of the carbon number is preferably 2, and more preferably 3. As the aromatic heterocycle forming the aromatic heterocyclic group, those having a nitrogen atom such as pyridine, pyrazine, furan, pyrrole, thiophene and pyrrolidone are particularly preferable.

The halogen atom is preferably a fluorine atom or a chlorine atom, and more preferably a fluorine atom.

Preferred examples of the alkyl group having 1 to 18 carbon atoms include a linear alkyl group having 1 to 18 carbon atoms, a branched alkyl group having 3 to 18 carbon atoms, and a cycloalkyl group having 3 to 18 carbon atoms. As.
Specific examples of the linear alkyl group having 1 to 18 carbon atoms include methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, Examples thereof include n-octyl group and n-decyl group.
Specific examples of the branched chain alkyl group having 3 to 18 carbon atoms include an isopropyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an isopentyl group, an isohexyl group and a 2-ethylhexyl group.
Specific examples of the cycloalkyl group having 3 to 18 carbon atoms include cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group and the like.

The alkoxy group having 1 to 12 carbon atoms is a methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, isobutoxy group, tert-butoxy group, n-pentyloxy group, n-hexyloxy group. Preferred are straight-chain or branched-chain ones such as n-heptyloxy group and n-octyloxy group.

Examples of the aryloxy group having 6 to 12 carbon atoms include a phenyloxy group and a benzyloxy group.
Preferred examples of the alkylamino group having 2 to 12 carbon atoms include an acyclic or cyclic dialkylamino group having 2 to 12 carbon atoms such as a dimethylamino group, a diethylamino group, a pyridinyl group, a piperidinyl group and a morpholinyl group. ..
Examples of the arylamino group having 7 to 18 carbon atoms include N-alkyl-N-arylamino groups such as N-methyl-N-phenylamino group; carbons such as diphenylamino group, carbazolyl group, phenoxazinyl group and phenothiazinyl group. Preferable examples are diarylamino groups of the formulas 12-18.

The substituent may be further substituted with a halogen atom, a hetero atom, an alkyl group, an alkoxy group, an alkenyl group, an alkynyl group, a group derived from an aromatic ring, or the like as long as the effects of the present invention can be exhibited. The position and number of the substituent bonded are not particularly limited.

R ^{1 to} R ⁴ in the above formula (1) are the same or different and each represents an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent, and R ¹ and R ² , R ³ and Each R ⁴ may be bonded.
When the ring represented by R ^{1 to} R ⁴ is an aromatic heterocyclic group, the aromatic heterocyclic group and the N atom are preferably bonded to each other at the carbon atom at the 2-position of the aromatic heterocycle. Further, when R ¹ is an aromatic heterocyclic group and R ¹ and R ² are bonded to each other, it is preferable that R ³ is bonded to the carbon atom at the 3-position of the aromatic heterocycle. When R ² is an aromatic heterocyclic group and R ¹ and R ² are bonded to each other, or when R ³ or R ⁴ is an aromatic heterocyclic group and R ³ and R ⁴ are bonded to each other Similarly, it is preferable to bond at the carbon atom at the 3-position of the aromatic heterocycle.
And R ¹ is an aromatic hydrocarbon group, if R ¹ and R ² are attached, the aromatic hydrocarbon ring, bond and R ² in the ortho-position carbon atom of the carbon atom bonded to the N atom Preferably. When R ² is an aromatic hydrocarbon group and R ¹ and R ² are bonded to each other, or when R ³ or R ⁴ is an aromatic hydrocarbon group and R ³ and R ⁴ are bonded to each other Similarly, it is preferable to bond at the carbon atom in the ortho position of the carbon atom bonded to the N atom of the aromatic hydrocarbon ring.

Specific examples of the aromatic hydrocarbon ring forming the aromatic hydrocarbon group and the aromatic heterocyclic group in R ^{1 to} R ⁴ and the aromatic heterocycle include specific examples of the substituents of Ar ¹ and Ar ² described above. Specific examples of the aromatic hydrocarbon ring and aromatic heterocycle in the aromatic hydrocarbon group and aromatic heterocyclic group included in the examples are the same.
Among these, it is preferable that R ^{1 to} R ⁴ are the same or different and are an aromatic hydrocarbon group or a thiophene ring group which may have a substituent.

Specific examples of the substituent in the case where R ^{1 to} R ⁴ are an aromatic hydrocarbon group having a substituent or an aromatic heterocyclic group are the same as the specific examples of the substituent in Ar ¹ and Ar ² described above. There are things.

R ⁵ in the above formula (1) represents an aromatic hydrocarbon group, an aromatic heterocyclic group or an alkyl group.
Specific examples of the aromatic hydrocarbon ring forming the aromatic hydrocarbon group and the aromatic heterocyclic group, and specific examples of the aromatic heterocycle include aromatic hydrocarbons contained in the specific examples of the substituents of Ar ¹ and Ar ² described above. Specific examples of the aromatic hydrocarbon ring and aromatic heterocycle in the hydrogen ring group and aromatic heterocycle group are the same.
Examples of the alkyl group include the same groups as the alkyl groups having 1 to 18 carbon atoms in the specific examples of the substituents of Ar ¹ and Ar ² described above. Of these, a methyl group, an ethyl group, an isopropyl group, a tert-butyl group, or a 2-ethylhexyl group is preferable. More preferably, it is either a methyl group or an ethyl group.

The method of synthesizing the compound having a benzothiazole-derived skeleton represented by the above formula (1) is not particularly limited, but for example, referring to JP-A-2015-172131 or JP-A-2017-59668, one of the following It can be synthesized by a reaction. In the reaction scheme below, DMAP represents N,N-dimethyl-4-aminopyridine, MW represents microwave, and ODCB represents orthodichlorobenzene. Further, DMF represents N,N-dimethylformamide, mCPBA represents meta-chloroperbenzoic acid, X ¹ represents an iodine atom, a bromine atom or a chlorine atom, and M represents a metal substituent (boron) used in the cross coupling reaction. , Tin, zinc, magnesium, etc.).

The light emitting material of the present invention is a material having an emission wavelength in a region of 800 nm or more, and when used as a material of a light emitting layer of an organic electroluminescent device, it has an emission wavelength in a region of 800 nm or more and has a high output. An organic electroluminescent device can be obtained. Such an organic electroluminescent device, that is, an organic electroluminescent device having a structure in which a plurality of layers including a light emitting layer are laminated between an anode and a cathode, and the light emitting layer comprises the light emitting material of the present invention. An organic electroluminescent device containing the same is also included in the present invention.

The organic electroluminescent element of the present invention is not particularly limited in the laminated structure as long as it has a structure in which a plurality of layers including a light emitting layer are laminated between an anode and a cathode, and an electron, an anode, a cathode and a light emitting layer are also included. It may have one or more of an injection layer, an electron transport layer, a hole transport layer, a hole injection layer, a hole blocking layer, and the like.
Known materials can be used as materials for the anode, the cathode, and each layer constituting the organic electroluminescent element other than the light emitting layer.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In addition, "%" means "mol mass%" unless otherwise specified.

(Synthesis Example 1) Synthesis of 2-(methylthio)-1,3-benzothiazole-5,6-diamine (Compound 1)

2-Chloro-5-nitrobenzene-1,4-diamine (10.0 g, 53.3 mmol), sodium ethyl xanthate (16.9 g, 117 mmol), and dimethylformamide (350 mL) were placed in a 1 L two-necked flask, and the temperature was 100°C. Stirred for 2.5 hours. The reaction solution was cooled in a water bath, methyl iodide (8.29 mL, 133 mol) was added dropwise, and the mixture was stirred for 17.5 hours. The reaction solution was poured into water, the precipitated solid was collected by filtration, and dried under reduced pressure at 50°C. The obtained solid was put in a 1 L two-necked eggplant flask, and then tin chloride dihydrate (55.0 g, 244 mmol), water (68 mL) and hydrochloric acid (12M, 1.8 mL, 22 mmol) were added, and the mixture was heated at 70° C. for 22 minutes. The mixture was heated and stirred for hours. The reaction solution was concentrated, neutralized with saturated aqueous sodium hydrogen carbonate solution (500 mL), and the precipitated solid was collected by filtration. The solid was dried under reduced pressure at 50° C. and purified by silica gel column chromatography to obtain 11.3 g of Compound 1 (yield 65%).
The physical properties were as follows.
¹ H-NMR (DMSO-d6); δ 6.98 (s, 1H), 6.92 (s, 1H), 4.76 (s, 2H), 4.71 (s, 2H), 2.67 ( s, 3H). ¹³ C-NMR (DMSO-d6): 159.39, 146.14, 135.58, 134.84, 123.38, 105.32, 103.97, 15.65.

Synthesis Example 2 Synthesis of 6-(methylthio)thiadiazolo[5,4-f]-2,1,3-benzothiadiazole (Compound 2)

The compound 1 (3.0 g, 14.2 mmol), triethylamine (15.8 mL, 114 mmol), and dichloromethane (200 mL) were put into a 500 mL two-necked flask, and sales were expanded in an ice bath. Thionyl chloride (4.2 mL, 57.9 mmol) was added dropwise thereto, and the mixture was stirred at room temperature for 17 hours. The reaction solution was neutralized with saturated aqueous sodium hydrogen carbonate solution, and the aqueous layer was extracted with dichloromethane. The combined organic layers were dried over sodium sulfate, filtered and concentrated, and the obtained residue was purified by silica gel column chromatography to obtain 3.21 g of compound 2. (Yield 94%)
The physical properties were as follows.
¹ H-NMR (CDCl ₃ ): δ 8.37 (s, 1H), 8.32 (s, 1H), 2.87 (s, 3H); ¹³ C-NMR (CDCl ₃ ): 172.94, 155. .69, 153.93, 152.00, 140.61, 111.68, 110.53, 15.76.

(Synthesis example 3) Synthesis of 4,8-dibromo-6-(methylthio)thiadiazolo[5,4-f]-2,1,3-benzothiadiazole (Compound 3)

Compound 2 (3.16 g, 13.2 mmol) and iron(III) chloride hexahydrate (2.16 g, 7.99 mmol) were placed in a 100 mL two-necked flask, and bromine (22.0 mL, 427 mmol) was added thereto. It was The mixture was heated with stirring at 50° C. for 5 hours, and then saturated aqueous sodium hydrogen carbonate solution was slowly added. The precipitated solid was collected by filtration, washed with water, and dried under reduced pressure at 50°C. This was purified by silica gel column chromatography to obtain 4.85 g of compound 3. (Yield 92%)
The physical properties were as follows.
_{^{1 H-NMR (CDCl 3)}} : δ2.92 (s, 3H); 13 C-NMR (CDCl 3): 173.60,152.53,152.15,149.82,142.84,102.96 , 102.37, 16.15.

Example 1 4,8-Bis[5-(N,N-diphenylamino)thiophen-2-yl]-6-(methylthio)thiadiazolo[5,4-f]-2,1,3-benzothiadiazole Synthesis of (Compound 4)

Compound 3 (2.00 g, 5.04 mmol), Pd(P ^t Bu ₃ ) ₂ (257 mg, 0.50 mmol), 5-(N,N-diphenylamino)-2-tributylstannylthiophene in a 200 mL two-necked flask. (6.80 g, 12.59 mmol) and THF (100 mL) were added, and the mixture was stirred at 70° C. for 15 hours. After allowing to cool to room temperature, the mixture was concentrated, and the residue was subjected to silica gel chromatography to obtain a crude purified product of compound 4. This was dispersed and washed with dichloromethane and with acetone to obtain 1.50 g of compound 4. (Yield 40%)
The physical properties were as follows.
¹ H-NMR (acetone-d6): δ8.86 (d, 1H, J=4.0 Hz), 7.89 (d, 1H, J=4.0 Hz), 7.37-7.42 (m, 8H), 7.31 (d, 4H, J=8.0 Hz), 7.26 (d, 4H, J=8.0 Hz), 7.13-7.19 (m, 4H), 6.82( d, 1H, J=4.0 Hz), 6.73 (d, 1H, J=4.0 Hz), 2.77 (s, 3H).
In addition, the result of measurement of the fluorescence spectrum of Compound 4 (fluorescence spectrophotometer F-7000 manufactured by Hitachi High-Tech Science Co., Ltd., solvent: chloroform) is shown in FIG.

(Synthesis Example 4) Synthesis of 4,8-dibromo-6-(methylsulfonyl)thiadiazolo[5,4-f]-2,1,3-benzothiadiazole (Compound 5)

Compound 3 (199 mg, 0.50 mmol) and chloroform (40 mL) were placed in a 100 mL two-necked flask, and mCPBA (493 mg, 2.00 mmol) was added with stirring. After stirring at room temperature for 30 hours, saturated aqueous sodium hydrogen carbonate solution was added, and the mixture was extracted with chloroform. The organic layer was dried over sodium sulfate, filtered and concentrated, and the residue was purified by column chromatography to obtain 157 mg of compound 5. (Yield 73%)
The physical properties were as follows.
_{^{1 H-NMR (CDCl 3)}} : δ3.54 (s, 3H); 13 C-NMR (CDCl 3): δ171.12,152.29,151.09,150.88,141.59,110.45 , 104.85, 41.70.

Example 2 4,8-Bis[5-(N,N-diphenylamino)thiophen-2-yl]-6-(methylsulfonyl)thiadiazolo[5,4-f]-2,1,3-benzo Synthesis of thiadiazole (compound 6)

Compound 5 (2.25 g, 5.24 mmol), Pd(P ^t Bu ₃ ) ₂ (268 mg, 0.52 mmol), 5-(N,N-diphenylamino)-2-tributylstannylthiophene in a 200 mL two-necked flask. (7.08 g, 13.11 mmol) and THF (105 mL) were added, and the mixture was stirred at 70° C. for 15 hours. After cooling to room temperature, the mixture was concentrated, and the residue was subjected to silica gel chromatography to obtain a crude purified product of compound 6, which was dispersed and washed with dichloromethane and then with acetone to obtain 1.44 g of compound 6. (36% yield)
The physical properties were as follows.
¹ H-NMR (CD ₂ Cl ₂ ): δ 8.76 (d, 1 H, J=4.5 Hz), 7.85 (d, 1 H, J=4.5 Hz), 7.30-7.37 (m , 12H), 7.25 (d, 4H, J=7.5Hz), 7.11-7.18 (m, 4H), 6.75 (d, 1H, J=4.5Hz), 6.69. (D, 1H, J=4.5 Hz), 3.34 (s, 3H).
Moreover, the result of the measurement of the fluorescence spectrum of Compound 6 (Fluorescence spectrophotometer F-7000 manufactured by Hitachi High-Tech Science Co., Ltd., solvent: chloroform) is shown in FIG.

(Fabrication of organic electroluminescent device)
(Example 3)
Process [1]
A commercially available transparent glass substrate with an ITO electrode layer having an average thickness of 0.7 mm was prepared. At this time, the ITO electrode (anode) of the substrate used was patterned to have a width of 2 mm. This substrate was ultrasonically cleaned in acetone and isopropanol for 10 minutes each, and then steam cleaned in isopropanol for 5 minutes. This substrate was dried by nitrogen blow, and UV ozone cleaning was performed for 20 minutes.
Process [2]
Next, the substrate 1 on which the anode was formed was fixed to the substrate holder of the vacuum vapor deposition device. In addition, molybdenum oxide (MoO ₃ ) and N,N′-di(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine represented by the following formula (2) are shown. (Α-NPD) and 4,8-bis[5-(N,N-diphenylamino)thiophen-2-yl]-6-(methylthio)thiadiazolo[5,4-f]− synthesized in Example 1. 2,1,3-benzothiadiazole (Compound 4), rubrene, tris(8-quinolinolato)aluminum (Alq3), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) Lithium fluoride (LiF) and Al were placed in an alumina crucible and set in a vapor deposition source.
Then, as in the following steps [3] and [4], the inside of the chamber of the vacuum vapor deposition apparatus is decompressed to a pressure of 1×10 ⁻⁵ Pa, and the hole injection layer is formed by a vacuum vapor deposition method by resistance heating. 3, the hole transport layer 4, the light emitting layer 5, the electron transport layer 6, the electron injection layer 7, and the cathode 8 were successively formed.
Process [3]
First, the hole injection layer 3 made of MoO 3 and having a thickness of 0.75 nm was formed. Next, α-NPD having a thickness of 40 nm was formed as the hole transport layer 4.
Process [4]
Then, the compound 4 was formed in 10 nm as the light emitting layer 5. Further, as the electron transport layer 6 and the electron injection layer 7, Alq3 of 20 nm and LiF of 1 nm were formed. Finally, a film of Al having a thickness of 100 nm was formed to form the cathode 8. The cathode 8 was formed using a stainless steel vapor deposition mask so that the vapor deposition surface had a strip shape with a width of 2 mm, and the organic EL device produced had an emission area of 4 mm ² .
The average thickness of each layer was measured at the time of film formation by a crystal oscillator film thickness meter. This produced the organic electroluminescent element 1.

(Example 4)
Instead of the step [4] of Example 3, the following step [4-2] was carried out to fabricate the organic electroluminescent element 2.
Process [4-2]
Subsequently, as the light emitting layer 5, a film having a thickness of 25 nm was formed by co-evaporation of the compound 4 and rubrene. The ratio was controlled using a quartz oscillator film thickness meter so that the compound 4 had a mass ratio of 4%. Further, as the electron transport layer 6 and the electron injection layer 7, BCP of 80 nm and LiF of 1 nm were formed. Finally, a film of Al having a thickness of 100 nm was formed to form the cathode 8. The cathode 8 was formed using a stainless steel vapor deposition mask so that the vapor deposition surface had a strip shape with a width of 2 mm, and the light emitting area of the produced organic EL element was 4 mm ² . The average thickness of each layer was measured at the time of film formation by a crystal oscillator film thickness meter. This produced the organic electroluminescent element 2.

(Example 5)
Instead of the step [4] of Example 3, the organic electroluminescent element 3 was produced by the following step [4-3].
Process [4-3]
Subsequently, as the light emitting layer 5, a film having a thickness of 25 nm was formed by co-evaporation of the compound 4 and rubrene. The ratio was controlled using a quartz oscillator film thickness meter so that the compound 4 had a mass ratio of 4%. Further, as the electron transport layer 6 and the electron injection layer 7, BCP of 40 nm and LiF of 1 nm were formed. Finally, a film of Al having a thickness of 100 nm was formed to form the cathode 8. The cathode 8 was formed using a stainless steel vapor deposition mask so that the vapor deposition surface had a strip shape with a width of 2 mm, and the light emitting area of the produced organic EL element was 4 mm ² . The average thickness of each layer was measured at the time of film formation by a crystal oscillator film thickness meter. This produced the organic electroluminescent element 3.

(Measurement of emission characteristics of organic electroluminescent device)
With respect to the organic electroluminescent elements 1 to 3 produced in Examples 3 to 5, voltage application and current measurement were performed on the elements with a "2400 type source meter" manufactured by Keithley. Also, the irradiance was measured by using a photodetector capable of measuring up to 1000 nm. The measurement was performed under an argon atmosphere.
The results of Examples 3 to 5 are shown in FIGS.

As shown in FIG. 3, even in the organic electroluminescent device 1 of Example 3 in which the light emitting layer was formed only by the compound 4, some illuminance was exhibited (FIG. 3: 0.1 mW/cm ² @). 10V). In addition, it was confirmed from a separately measured fluorescence spectrum (FIG. 2) that the peak top was about 820 nm. Further, in FIG. 4, which is a result of the organic electroluminescent device 2 of Example 4, the irradiance reaches 0.8 mW/cm ² @13 V by using the light emitting layer of the host guest. Regarding the organic electroluminescent device 2, in addition to that, it is observed that the driving stability is increased.
In FIG. 5, which is the result of the organic electroluminescent device 3 of Example 5 in which the electron transport layer was further thinned, the irradiance reached 1 mW/cm ² @8.5V. In addition, it was confirmed from a separately measured fluorescence spectrum (FIG. 2) that the peak top was about 850 nm.
From these, it was shown that the compound having a benzothiazole-derived skeleton of the present invention is useful as a near-infrared light emitting material.

1: Substrate 2: Anode 3: Hole injection layer 4: Hole transport layer 5: Light emitting layer 6: Electron transport layer 7: Electron injection layer 8: Cathode

Claims (4)

Formula (1) below;

(In the formula, Ar ¹ and Ar ² are the same or different and each represents a group derived from any ring of a benzene ring, a thiophene ring, a furan ring, and a pyrrole ring, which may have a substituent. R ¹ to R ⁴ is the same or different and represents an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent, and R ¹ and R ² and R ³ and R ⁴ may be bonded to each other. good .X is, -S _-, - SO 2 - or .R ⁵ representing a direct bond, an aromatic hydrocarbon group, derived structure benzothiazole represented by the representative) an aromatic heterocyclic group or an alkyl group. A light emitting material comprising a compound having: The light emitting material according to claim ¹ , wherein Ar ¹ and Ar ^{2 in} the formula (1) are both thiophene ring groups. R ^{1 to} R ^{4 in} the above formula (1) are the same or different and are an aromatic hydrocarbon group or a thiophene ring group which may have a substituent, and R ⁵ is an aromatic hydrocarbon group or an alkyl group. It is a group, The light emitting material of Claim 1 or 2 characterized by the above-mentioned. An organic electroluminescence device having a structure in which a plurality of layers including a light emitting layer are laminated between an anode and a cathode,
An organic electroluminescent device comprising the light emitting layer containing the light emitting material according to claim 1.

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