JP4424026B2 - 2,7-diaminonaphthalene compound, charge transport material, organic electroluminescent element material, and organic electroluminescent element - Google Patents

Description

  The present invention relates to a novel 2,7-diaminonaphthalene compound, a charge transport material, an organic electroluminescent element material and an organic electroluminescent element using the same. Specifically, a novel 2,7-diaminonaphthalene suitable for use as an organic electroluminescent element as a thin film type device that emits light by applying an electric field to a light emitting layer made of an organic compound, and particularly suitable as a hole transporting layer forming material. The present invention relates to a compound, a charge transport material using the compound, an organic electroluminescent element material, and an organic electroluminescent element provided with a layer containing the 2,7-diaminonaphthalene compound.

Conventionally, as a thin film type electroluminescent (EL) element, there are ZnS, CaS, SrS, etc., which are II-VI group compound semiconductors of inorganic materials, Mn or rare earth elements (Eu, Ce, Tb, Sm, etc.) that are emission centers. ) Is generally used, but an EL element made from the above inorganic material is
1) AC drive is required (50-1000Hz),
2) High drive voltage (~ 200V),
3) Full color is difficult (especially blue),
4) The cost of the peripheral drive circuit is high.
Has the problem.

  However, in recent years, EL devices using organic thin films have been developed to improve the above problems. In particular, in order to improve luminous efficiency, the type of the electrode is optimized for the purpose of improving the efficiency of carrier injection from the electrode, and the hole transport layer made of aromatic diamine and the light emitting layer made of aluminum complex of 8-hydroxyquinoline Development of an organic electroluminescent device provided with (Appl. Phys. Lett., 51, 913, 1987), the emission efficiency is significantly higher than that of conventional EL devices using single crystals such as anthracene. Improvements have been made and are approaching practical properties.

  In addition to the electroluminescent device using the low molecular weight material as described above, as a material of the light emitting layer, poly (p-phenylene vinylene), poly [2-methoxy-5- (2-ethylhexyloxy) -1,4 Development of electroluminescent devices using polymer materials such as -phenylenevinylene] and poly (3-alkylthiophene), and devices that combine low molecular light emitting materials and electron transfer materials with polymers such as polyvinylcarbazole. Has been done.

  In order to apply the organic electroluminescent element to a light source such as a flat panel display or a backlight, it is necessary to sufficiently ensure the reliability of the element. However, conventional organic electroluminescence devices have insufficient heat resistance, and current-voltage characteristics shift to a higher voltage side due to an increase in the environmental temperature and process temperature of the device, or due to local Joule heating during device driving. Deterioration such as a decrease in lifespan and generation and increase of non-light emitting parts (dark spots) was inevitable.

  The main cause of these deteriorations is the deterioration of the thin film shape of the organic layer. This deterioration of the thin film shape is considered to be caused by temperature rise due to heat generation during driving of the element, and due to crystallization (or aggregation) of the organic amorphous thin film. This low heat resistance is considered to be derived from the low glass transition temperature (hereinafter abbreviated as “Tg”) of the material.

  Many compounds having a low molecular weight (for example, a molecular weight of about 400 to 600), particularly hole transport materials, have a low melting point and a high symmetry. The typical aromatic amine compounds that have been widely used as hole transport materials for organic electroluminescent devices are shown below.

  Tg of the aromatic diamine (A-1) is 65 ° C., and N, N′-diphenyl-N, N ′-(3-methylphenyl) -1,1′-biphenyl-4,4′-diamine ( The Tg of TBS of the starburst type aromatic triamine (A-2) is usually 75 ° C (J. Phys. Chem., 97, 6240, 1993) and α-naphthyl. Tg of 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (A-3) having a group introduced therein is 96 ° C. (IEICE Technical Report, OME95-54, 1995) ).

  Organic amorphous thin films formed from these aromatic amine compounds crystallize due to temperature rise, or cause mutual diffusion in a two-layer device structure of a hole transport layer and a light emitting layer. As a result, a deterioration phenomenon in which the light emission characteristics of the element, in particular, the drive voltage becomes high appears, and eventually the drive life is shortened. Further, even when the element is not driven, the temperature of the hole transport material is preferably higher because a temperature increase is expected in steps such as vapor deposition, baking (annealing), wiring, and sealing during element preparation.

  On the other hand, attempts have been made to use a polymer material as a hole transport material for an organic electroluminescence device instead of a low molecular weight compound. For example, polyvinyl carbazole (Technical Report of IEICE, OME90-38, 1990), Polysilane (Appl. Phys. Lett., 59, 2760, 1991), Polyphosphazene (The 42nd Annual Meeting of the Society of Polymer Science, I-8-07 and I-8-08, 1993), etc. It has been reported. However, although polyvinylcarbazole has a high Tg of 200 ° C., it has problems such as hole trapping, and its durability is low. Polysilane has a short driving life of several seconds due to photodegradation and the like, and polyphosphazene has a high ionization potential. However, it does not show the characteristics over conventional aromatic diamine compounds.

  In addition, a hole transport layer in which an aromatic diamine compound is dispersed in polycarbonate or polymethyl methacrylate in an amount of 30 to 80% by weight has been studied (Jpn. J. Appl. Phys., Vol. 31, L960, 1992), the low molecular weight compound acts as a plasticizer to lower Tg, and the device characteristics are also reduced as compared with the case where the aromatic diamine compound is used alone.

  Thus, the present situation is still having a big problem in the heat resistance and drive life of an element toward the practical use of an organic electroluminescent element.

  The heat resistance of organic electroluminescent elements is not improved and the light emission characteristics are unstable, which is a major problem for light sources such as facsimiles, copiers, and backlights for liquid crystal displays. As a display element for flat panel displays, etc. Is also an undesirable characteristic. This is particularly serious when considering application to in-vehicle displays.

  JP-A-8-87122 discloses an organic electroluminescent device containing a 2,7-diaminonaphthalene compound as described below (A-4) and a charge transport layer of an electrophotographic photoreceptor, Japanese Patent Application Laid-Open No. 7-120949 describes a photosensitive layer of an electrophotographic photoreceptor containing a 2,7-diaminonaphthalene compound such as the following (A-5) and (A-6).

  However, the compounds (A-4), (A-5), and (A-6) have a low Tg as the hole transport layer material of the organic electroluminescence device, and organic compounds using the compound for the hole transport layer are used. It is considered that a sufficient driving life cannot be obtained with an electroluminescent element. Further, as will be described later, the diaminonaphthalene compound has greatly different electrochemical characteristics and ionization potential depending on the substitution position of the amino group. Therefore, the characteristics of the organic electroluminescent device using the diaminonaphthalene compound in the hole transport layer are also different. As a result of intensive studies by the present inventors, it has been found that a 2,7-position substitution product is particularly useful as a hole transport material of an organic electroluminescence device. However, JP-A-8-87122 and JP-A-7- No. 120949 does not describe the substitution position of the amino group, electrochemical characteristics, and ionization potential.

  JP-A-2-44363 discloses an electrophotographic photoreceptor containing a diaminonaphthalene compound. The compound described in this publication also has a Tg as a hole transport layer material of an organic electroluminescence device. It is considered low. Furthermore, as described later, as a hole transport material of an organic electroluminescence device, a compound in which a frontier electron orbit is widely spread to an aryl group substituted with a nitrogen atom is useful because of its high hole mobility. However, since the diaminonaphthalene compound described in JP-A-2-44363 has a non-conjugated alkyl group and an aralkyl group substituted on the nitrogen atom, the frontier electron orbital is present on the alkyl group and the aralkyl group substituted on the nitrogen atom. It is considered that the hole mobility does not spread and the hole mobility is small, and it is not preferable as a hole transport layer material of an organic electroluminescence device. In addition, all the exemplified compounds described in this publication are 1,5-position substitution products, and the 2,7-position substitution materials are used as the hole transport layer material of the organic electroluminescence device from the viewpoint of electrochemical characteristics and ionization potential. It is thought that it does not reach.

  Japanese Patent Laid-Open No. 5-234681 describes the following 2,6-diaminonaphthalene compound (A-7) as a specific example of the hole transport layer material of the organic electroluminescence device.

  However, since the compound (A-7) is a 2,6-position substitution product, the ionization potential is low, and it seems that the 2,7-position substitution product is not preferable as the hole transport layer material of the organic electroluminescence device. Further, as described later, the 2,6-position substitution product has a high electron density of the central naphthylene group, and therefore the frontier electron orbit does not spread to the aryl group substituted with the nitrogen atom, and the hole mobility tends to be relatively small. There is. Furthermore, the compound has room for improvement in terms of solubility in organic solvents, and it is considered that there is a problem in terms of productivity.

JP-A-6-120541 discloses an organic solar cell containing a diaminoacenaphthene compound as a charge transporting dye, and JP-A-4-181260 and JP-A-2-44364 contain diaminophenanthrene. There is a description of an electrophotographic photosensitive member, and JP-A-2-44365 discloses a description of an electrophotographic photosensitive member containing diaminoanthracene. However, these compounds in which two or more amino groups are substituted on a condensed ring group formed by condensation of three or more rings are substituted with nitrogen atoms because the electron cloud of the central condensed ring group is greatly spread. It is considered that the frontier electron orbit does not spread to the aryl group, the hole mobility is relatively small, and it is not preferable as the hole transport layer material. Further, compounds in which two or more amino groups are substituted on these three or more condensed ring groups have low LUMO (lowest unoccupied molecular orbital) energy levels, and have absorption and emission wavelengths in a relatively long wavelength region. Therefore, there is a problem particularly as a hole transport layer material of a blue organic electroluminescent element.
JP-A-8-87122 Japanese Patent Laid-Open No. 7-120949 JP-A-2-44363 Japanese Patent Laid-Open No. 5-234681 JP-A-6-120541 JP-A-4-181260 Japanese Patent Laid-Open No. 2-44364 JP-A-2-44365 Appl.Phys.Lett., 51, 913, 1987 J. Phys. Chem., 97, 6240, 1993 IEICE technical report, OME95-54, 1995 IEICE technical report, OME90-38, 1990 Appl.Phys.Lett., 59, 2760, 1991 42nd Annual Meeting of the Society of Polymer Science, I-8-07 and I-8-08, 1993 Jpn.J.Appl. Phys., 31, L960, 1992

  The present invention solves the above-mentioned conventional problems, is capable of low-voltage and high-efficiency driving, has excellent heat resistance and driving stability, and can maintain stable light emission characteristics at high temperatures for a long time. It is an object of the present invention to provide a novel 2,7-diaminonaphthalene compound capable of realizing the above, a charge transport material, an organic electroluminescent element material and an organic electroluminescent element using the compound.

（一般式（Ｉ）中、Ｒ^１〜Ｒ^４は、各々独立に、下記置換基群Ｉから選ばれる置換基を有していても良い芳香族基を表すか、あるいはＲ^１とＲ^２、Ｒ^３とＲ^４が結合して、各々独立に、下記置換基群Ｉから選ばれる置換基を有していても良い環を形成する。
但し、Ｒ^１〜Ｒ^４、Ｒ^１とＲ^２が結合して形成する環、およびＲ^３とＲ^４が結合して形成する環のうちの少なくとも１つは、３環以上が縮合してなる、下記置換基群Ｉから選ばれる置換基を有していても良い芳香族縮合環基を表す。）
置換基群Ｉ：炭素数１〜１０のアルキル基、炭素数２〜１１のアルケニル基、炭素数２〜１１のアルキニル基、アラルキル基、炭素数２〜１１のアルコキシ基、アリールオキシ基、ジアルキルアミノ基、アルキルアリールアミノ基、ジアリールアミノ基、炭素数２〜１１のアシル基、炭素数２〜１１のアルコキシカルボニル基、芳香族炭化水素基、芳香族複素環基
尚、上記の置換基は、更に置換基として、炭素数１〜１０のアルキル基又は芳香族炭化水素基を有していてもよい。 The 2,7-diaminonaphthalene compound of the present invention is represented by the following general formula (I).

(In the general formula (I), R ^{1 to} R ⁴ each independently represents an aromatic group which may have a substituent selected from the following substituent group I , or R ¹ and R ² , R ³ and R ⁴ are bonded to each other to form a ring which may have a substituent selected from the following substituent group I.
However, at least ^one of R ^{1 to} R ⁴ , the ring formed by combining R ¹ and R ² , and the ring formed by combining R ³ and R ⁴ is formed by condensation of three or more rings. Represents an aromatic condensed ring group which may have a substituent selected from the following substituent group I. )
Substituent group I: C1-C10 alkyl group, C2-C11 alkenyl group, C2-C11 alkynyl group, aralkyl group, C2-C11 alkoxy group, aryloxy group, dialkylamino Group, alkylarylamino group, diarylamino group, acyl group having 2 to 11 carbon atoms, alkoxycarbonyl group having 2 to 11 carbon atoms, aromatic hydrocarbon group, aromatic heterocyclic group
In addition, said substituent may have a C1-C10 alkyl group or aromatic hydrocarbon group as a substituent further.

  That is, the present inventor studied to further improve the current efficiency, light emission efficiency, drive life characteristics, and the like of the organic electroluminescent device, and as a result, the novel 2,7-diamino represented by the above general formula (I) was obtained. Because of the presence of three or more aromatic condensed ring groups in the molecule of the naphthalene compound, Tg is high, it has an appropriate ionization potential, has a high hole transport ability, and improves current efficiency and light emission efficiency. Further, the present invention has been found out that it is effective in improving driving stability and driving life.

  The 2,7-diaminonaphthalene compound of the present invention represented by the above general formula (I) has a high Tg due to its molecular structure, and it is possible to obtain an organic thin film that does not easily crystallize. The 2,7-diaminonaphthalene compound of the present invention has an ionization potential and an oxidation-reduction potential of about 4.9 to 5.3 eV and about 0.6 to 1.0 V vs. SCE, respectively. It has an appropriate value as a hole transport layer material. Therefore, the organic electroluminescent element using the 2,7-diaminonaphthalene compound of the present invention as the hole transport layer material exhibits high current efficiency and luminous efficiency.

  On the other hand, the ionization potential and oxidation-reduction potential of diaminonaphthalene compounds having different amino group substitution positions (that is, 2,6-diaminonaphthalene compound, 1,4-diaminonaphthalene compound, 1,5-diaminonaphthalene compound) correspond to each other. Compared to the 2,7-diaminonaphthalene compound, it is lower by about 0.2 to 0.5 eV and 0.2 to 0.5 V, respectively. For this reason, when the diaminonaphthalene compound having a different substituent is used as a hole transport layer material, an exciplex with a molecule used in the light emitting layer is easily formed. The efficiency is low.

  Usually, the positive charge of a radical cation obtained by one-electron oxidation of an aromatic diamine is localized at the center and hinders hole movement. However, since the 2,7-diaminonaphthalene compound of the present invention has an aromatic condensed ring group having a larger electron cloud as a substituent compared to the central naphthalene ring, the positive charge is delocalized. And exhibits a high hole transport ability. Furthermore, since the 2,7-diaminonaphthalene compound of the present invention has a weaker interaction between two nitrogen atoms than the above-mentioned diaminonaphthalene compound having a different substitution position of the amino group, a positive charge at the central naphthylene group is present. It is considered that the locality of the metal is less likely to occur and has a higher hole transport ability. For this reason, the organic electroluminescent element using the 2,7-diaminonaphthalene compound of the present invention as a hole transport layer material is excellent in driving stability.

  The charge transport material of the present invention contains such a 2,7-diaminonaphthalene compound of the present invention, and the organic electroluminescent element material of the present invention has such a 2,7-diaminonaphthalene compound of the present invention. Is included.

  That is, since the 2,7-diaminonaphthalene compound represented by the general formula (I) has a high Tg and a high charge transport property, an electrophotographic photosensitive member, an organic electroluminescence device as a charge transport material. , Photoelectric conversion elements, organic solar cells, organic rectification elements and the like. In addition, by using the 2,7-diaminonaphthalene compound represented by the general formula (I), an organic electroluminescent element that has excellent heat resistance and can be stably driven (emitted) for a long period of time can be obtained. Suitable as a material.

  The organic electroluminescent device of the present invention is an organic electroluminescent device having a light emitting layer between an anode and a cathode, and has such a layer containing the 2,7-diaminonaphthalene compound of the present invention, and is heat resistant. It is a stable organic electroluminescence device having excellent luminous efficiency and a long driving life.

  According to the present invention, a novel 2,7-diaminonaphthalene compound having a high hole transport capability, an appropriate ionization potential, and excellent heat resistance, and preferably the 2,7-diaminonaphthalene compound are transported by holes. By using it for the layer, an organic electroluminescence device having high current efficiency and light emission efficiency, low voltage driving, excellent driving stability and heat resistance, and stable light emission characteristics can be obtained.

Embodiments of the present invention will be described in detail below. However, the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention is not specified by these contents.
In the present invention, the “aromatic group” means “aromatic hydrocarbon group and aromatic heterocyclic group”. Therefore, the “aromatic condensed ring group” introduced into the general formula (I) means , It may be an aromatic condensed ring group in which only three aromatic hydrocarbon rings are condensed, or an aromatic condensed ring group in which only three aromatic heterocycles are condensed, Further, it may be an aromatic condensed ring group obtained by condensing three or more aromatic hydrocarbon rings and aromatic heterocyclic rings in total.

  First, the 2,7-diaminonaphthalene compound of the present invention represented by the general formula (I) will be described.

In the general formula (I) showing the 2,7-diaminonaphthalene compound of the present invention, R ^{1 to} R ⁴ each independently represents an aromatic group which may have a substituent, or R ^1. And R ² , R ³ and R ⁴ are bonded to each other to form an optionally substituted ring, but R ^{1 to} R ⁴ , R ¹ and R ² are bonded to each other. At least one of the ring and the ring formed by combining R ³ and R ⁴ represents an aromatic condensed ring group which may have a substituent formed by condensation of three or more rings.

Specific examples of R ^{1 to} R ⁴ include phenyl group, naphthyl group, phenanthryl group, anthryl group, pyrenyl group, fluorenyl group, benzofluorenyl group, fluoranthenyl group, perylenyl group, thienyl group, benzothienyl group, A group consisting of a 5- or 6-membered monocyclic ring such as a furyl group, a benzofuryl group, an indolyl group, a carbazolyl group, a benzocarbazolyl group, a pyridyl group, a quinolyl group, a quinoxalyl group, or a 2-5 condensed ring of these rings Preferably, a phenyl group, a naphthyl group, a phenanthryl group, an anthryl group, and a fluorenyl group can be mentioned. Any of these may have a substituent.

（式中、Ｒ^５，Ｒ^６，Ｒ^７はアルキル基、芳香族炭化水素基、または水素原子を示す。）
なお、これらはいずれも置換基を有していても良い。 When R ¹ and R ² , or R ³ and R ⁴ are bonded to each other to form a ring, preferred specific examples of this ring are shown below, but are not limited thereto.

(In the formula, R ⁵ , R ⁶ and R ⁷ represent an alkyl group, an aromatic hydrocarbon group, or a hydrogen atom.)
Any of these may have a substituent.

In the 2,7-diaminonaphthalene compound of the present invention represented by the general formula (I), R ^{1 to} R ⁴ , a ring formed by combining R ¹ and R ² , and R ³ and R ⁴ are combined. At least one of the rings formed in this way is an aromatic condensed ring group that may have a substituent formed by condensation of three or more rings. Since the Tg of the compound is increased by having the aromatic condensed ring group, the heat resistance of the device is improved, for example, when used in a layer of an organic electroluminescence device described later.

In addition, from the point of delocalization of the positive charge in the compound, at least one selected from R ^{1 to} R ⁴ may have a substituent formed by condensation of three or more rings. The case where it is a cyclic group is more preferable.

  The aromatic condensed ring group is an anthryl group, a phenanthryl group, a pyrenyl group, a fluorenyl group, a pyrenyl group, or the like, such as a 5-membered to 6-membered ring, preferably 4 or more, and usually 5 or less. An aromatic hydrocarbon group consisting of a condensed ring, an acridinyl group, a phenanthridinyl group, a benzocarbazolyl group, etc., a 5-membered to 6-membered ring, preferably 4 or more rings, An aromatic heterocyclic group composed of 5 or less condensed rings is exemplified.

  Among the condensed rings, more preferable are condensed aromatic hydrocarbon rings, and particularly preferable is a phenanthryl group. By having a phenanthryl group, the continuous drive characteristics of the organic electroluminescent device having a layer containing the compound are dramatically improved.

The position to which the aromatic fused ring group is bonded may be any of R ^{1 to} R ⁴ , but each R ¹ or R ² and R ³ or R ⁴ has one each. The case is particularly preferred.

In addition, for synthesis, a highly symmetrical compound in which —NR ¹ R ² and —NR ³ R ⁴ are equal to each other is preferable. However, by using —NR ¹ R ² and —NR ³ R ⁴ as different groups, There is an advantage that the amorphous property of the thin film to be included increases, and such a non-target compound is also preferable.

Aromatic groups R ¹ to R ^4, examples of R ¹ and R ² or R ³ and ring R ⁴ is formed by bonding, and the aromatic condensed substituents wherein the ring group may have, is not particularly limited For example, an alkyl group having 1 to 10 carbon atoms such as a methyl group, an ethyl group, a t-butyl group, or a cyclohexyl group, an alkenyl group having 2 to 11 carbon atoms such as a vinyl group, or an ethynyl group having 2 to 11 carbon atoms. Aralkyl groups such as alkynyl group, benzyl group and phenethyl group, alkoxy groups having 2 to 11 carbon atoms such as methoxy group and ethoxy group, aryloxy groups such as phenoxy group, dimethylamino group, diisopropylamino group and ethylmethylamino group Dialkylamino groups such as methylphenylamino group; diphenylamino group, ditolylamino group, phenylnaphthylamino group, N-carba Diarylamino group such as zolyl group; acyl group having 2 to 11 carbon atoms such as acetyl group, alkoxycarbonyl group having 2 to 11 carbon atoms such as methoxycarbonyl group and ethoxycarbonyl group; phenyl group, naphthyl group, phenanthryl group, anthryl Group, pyrenyl group, fluorenyl group, benzofluorenyl group and other aromatic hydrocarbon groups; thienyl group, benzothienyl group, furyl group, benzofuryl group, indolyl group, carbazolyl group, benzocarbazolyl group, pyridyl group, quinolyl group One or more substituents selected from a group, an aromatic heterocyclic group such as a quinoxalyl group, and the like, and these may be further substituted. The further substituent is not particularly limited, and examples thereof include the above-described alkyl group and aromatic hydrocarbon group. Two or more of these substituents may be introduced on the ring such as R ^{1 to} R ^{4. In} this case, the position of the substituent is arbitrary, and the plurality of substituents may be the same as each other. It may be different.

Aromatic group in R ¹ to R ^4, ring R ¹ and R ² or R ³ and R ⁴ is formed by bonding, and the aromatic condensed ring group, the substituent may have, preferred among the above-mentioned Are a methyl group, a phenyl group, a tolyl group, a t-butyl group, a biphenyl group, and an ethyl group.

  Among such 2,7-diaminonaphthalene compounds of the present invention, the target compound is easily synthesized as follows using, for example, 2,7-dihydroxynaphthalene (B) as a starting material.

That is, first, 2,7-dihydroxynaphthalene (B) and the aromatic amine represented by the general formula (II) are subjected to a dehydration reaction at a molar ratio of 1: 2. By reacting the obtained intermediate represented by the general formula (C) with the aromatic halide represented by the general formula (III), 2,7 of the present invention represented by the general formula (D) is obtained. -A diaminonaphthalene compound is obtained. In the general formulas (II), (C), (III), and (D), Ar ¹ and Ar ² each independently represent an aromatic group that may have a substituent. However, at least one of Ar ¹ and Ar ² represents an aromatic condensed ring group which may have a substituent formed by condensation of three or more rings. X is a halogen atom such as iodine, bromine or chlorine.

  In the case of an asymmetric type 2,7-diaminonaphthalene compound, two types of aromatic amines are used and reacted with 2,7-dihydroxynaphthalene (B) stepwise as shown below. Can be synthesized.

That is, first, 2,7-dihydroxynaphthalene (B) and the aromatic amine represented by the general formula (IV) are dehydrated at a molar ratio of 1: 1. Subsequently, the obtained intermediate represented by the general formula (E) and the aromatic amine represented by the general formula (V) are subjected to a dehydration reaction at a molar ratio of 1: 1. By reacting the obtained intermediate represented by the general formula (F) with the aromatic halide represented by the general formula (VI), 2,7 of the present invention represented by the general formula (G) is obtained. -A diaminonaphthalene compound is obtained. In general formulas (IV) to (VI), (E), (F), and (G), Ar ^{3 to} Ar ⁵ each independently represents an aromatic group that may have a substituent. . However, at least one of Ar ^{3 to} Ar ⁵ represents an aromatic condensed ring group which may have a substituent formed by condensation of three or more rings. X is a halogen atom such as iodine, bromine or chlorine.

  The untargeted 2,7-diaminonaphthalene compound can also be synthesized by using two types of aromatic halides and reacting them stepwise as follows.

That is, 2,7-dihydroxynaphthalene (B) and the aromatic amine represented by the general formula (VII) are subjected to a dehydration reaction at a molar ratio of 1: 2. The obtained intermediate represented by the general formula (H) is reacted with the aromatic halide represented by the general formula (VIII) at a molar ratio of 1: 1. The intermediate represented by the general formula (J) thus obtained is reacted with the aromatic halide represented by the general formula (IX) at a molar ratio of 1: 1, thereby being represented by the general formula (K). The 2,7-diaminonaphthalene compound of the present invention is obtained. In general formulas (VII) to (IX), (H), (J), and (K), Ar ^{6 to} Ar ⁸ each independently represents an aromatic group that may have a substituent. . However, at least one of Ar ^{6 to} Ar ⁸ represents an aromatic condensed ring group which may have a substituent formed by condensation of three or more rings. X is a halogen atom such as iodine, bromine or chlorine.

In the general formula (I), a 2,7-diaminonaphthalene compound in which R ¹ and R ² , or R ³ and R ⁴ are combined to form a ring is produced as described above. The substituent on the amine group of the 2,7-diaminonaphthalene compound is obtained by performing a condensation reaction or reacting 2,7-dihydroxynaphthalene (B) with a cyclic secondary amine.

  As for the molecular weight of the 2,7-diaminonaphthalene compound of the present invention represented by the general formula (I), the lower limit is usually about 450, preferably about 500, and the upper limit is usually about 1500, preferably about 1000. . If the lower limit is not reached, Tg may decrease, and if it exceeds the upper limit, film formation by vapor deposition may be difficult.

  Preferred specific examples of the 2,7-diaminonaphthalene compound of the present invention represented by the general formula (I) are shown in the following Table-1 (No. 1 to No. 94), but are not limited thereto. .

  Since the 2,7-diaminonaphthalene compound of the present invention represented by the general formula (I) has a high charge transporting property, an electrophotographic photosensitive member, an organic electroluminescence device, a photoelectric conversion device, an organic material can be used as a charge transporting material. It can be suitably used for solar cells, organic rectifying elements, and the like. In particular, the compound is suitable as an electron transporting compound because of its excellent hole transporting property.

  In addition, by using the 2,7-diaminonaphthalene compound of the present invention represented by the general formula (I), an organic electroluminescent device that is excellent in heat resistance and stably driven (emits light) for a long period of time can be obtained. It is also suitable as an organic electroluminescent element material.

Next, the organic electroluminescent element of the present invention constituted by using the 2,7-diaminonaphthalene compound of the present invention will be described.
The organic electroluminescent element of the present invention has a light emitting layer between an anode and a cathode, and has a layer containing the 2,7-diaminonaphthalene compound of the present invention represented by the general formula (I). Features.
In the organic electroluminescent device of the present invention, the 2,7-diaminonaphthalene compound may be contained in any layer of the organic electroluminescent device, but preferably has a hole transport property between the anode and the luminescent layer. Contained in the layer.

  In the organic electroluminescent element of the present invention, two or more kinds of the 2,7-diaminonaphthalene compound may be contained in the same layer, and the 2,7-diaminonaphthalene compound is contained in two or more layers. It may be contained. In such a case, the 2,7-diaminonaphthalene compound contained in these layers may be the same or different.

  In the organic electroluminescent device of the present invention, when there is one layer between the anode and the light emitting layer, this is referred to as a “hole transport layer”, and when there are two or more layers, the layer in contact with the anode is referred to as “anode The “buffer layer” and the other layers are collectively referred to as a “hole transport layer”.

  Hereinafter, with reference to the drawings, the organic electroluminescent device of the present invention will be described with reference to the case where the 2,7-diaminonaphthalene compound of the present invention represented by the general formula (I) is contained in the hole transport layer. The embodiment will be described in detail.

  1 to 3 are cross-sectional views schematically showing structural examples of the organic electroluminescent element of the present invention, but the organic electroluminescent element of the present invention is not limited to the illustrated one. 1 to 3, 1 represents a substrate, 2 represents an anode, 3 represents an anode buffer layer, 4 represents a hole transport layer, 5 represents a light emitting layer, 6 represents an electron transport layer, and 7 represents a cathode.

  The substrate 1 serves as a support for the organic electroluminescent element, and a quartz or glass plate, a metal plate or a metal foil, a plastic film, a sheet, or the like is used. In particular, a glass plate or a transparent synthetic resin plate such as polyester, polymethacrylate, polycarbonate, or polysulfone is preferable. When using a synthetic resin substrate, it is necessary to pay attention to gas barrier properties. If the gas barrier property of the substrate is too small, the organic electroluminescent element may be deteriorated by the outside air that has passed through the substrate, which is not preferable. For this reason, when a synthetic resin substrate is used, a method of ensuring a gas barrier property by providing a dense silicon oxide film or the like on at least one side is also a preferable method.

  An anode 2 is provided on the substrate 1. The anode 2 plays a role of hole injection into the hole transport layer 4. This anode 2 is usually made of metal such as aluminum, gold, silver, nickel, palladium, platinum, metal oxide such as oxide of indium and / or tin, metal halide such as copper iodide, carbon black, or It is composed of a conductive polymer such as poly (3-methylthiophene), polypyrrole, or polyaniline. In general, the anode 2 is often formed by a sputtering method, a vacuum deposition method, or the like. When the anode 2 is formed using fine metal particles such as silver, fine particles such as copper iodide, carbon black, conductive metal oxide fine particles, and conductive polymer fine powder, an appropriate binder resin solution is used. The anode 2 can also be formed by being dispersed on the substrate 1 and coated on the substrate 1. Further, when the anode 2 is formed using a conductive polymer, a thin film is directly formed on the substrate 1 by electrolytic polymerization, or the anode 2 is formed by applying a conductive polymer solution on the substrate 1. (Appl. Phys. Lett., 60, 2711, 1992). The anode 2 may have a laminated structure formed by laminating layers made of different materials.

  The thickness of the anode 2 varies depending on the required transparency. When transparency is required, it is desirable that the visible light transmittance is 60% or more, preferably 80% or more. In this case, the lower limit of the thickness of the anode 2 is usually 5 nm, preferably 10 nm. The upper limit is usually 1000 nm, preferably 500 nm. In the case of being opaque, the thickness of the anode 2 is arbitrary. For example, the anode 2 may be formed of metal or the like to serve as the substrate 1.

In the organic electroluminescent element of FIG. 1, a hole transport layer 4 is provided on the anode 2.
The conditions required for the material of the hole transport layer 4 include high hole injection efficiency from the anode 2, which can efficiently transport the injected holes, and the holes in the light emitting layer 5. The material must be able to be delivered efficiently. For this purpose, it is possible to form a stable amorphous film having a high hole mobility, an appropriate ionization potential, high transparency to visible light, and not easily crystallizing. Therefore, it is required that impurities that become traps are less likely to be generated during manufacture or use. Therefore, a material having an ionization potential of about 4.9 to 5.3 eV, a small absorption in the visible light region, a wide delocalization of the frontier electron orbit, and a high glass transition temperature Tg is preferable.

  Since the 2,7-diaminonaphthalene compound of the present invention represented by the general formula (I) sufficiently satisfies these conditions, the 2,7-diaminonaphthalene compound of the present invention is used in the organic electroluminescence device of the present invention. Is preferably used as a hole injecting / transporting layer forming material provided between the anode 2 and the light emitting layer 5 described later.

The ionization potential is defined as the energy required to emit electrons at the HOMO (highest occupied molecular orbital) level of a substance to the vacuum level, and can be directly measured by photoelectron spectroscopy or electrochemically. It can also be obtained by correcting the measured oxidation potential with respect to the reference electrode. In the case of the latter method, for example, when a saturated sweet potato electrode (SCE) is used as a reference electrode,
Ionization potential = oxidation potential (vs.SCE) + 4.3 eV
("Molecular Semiconductors", Springer-Verlag, 1985, page 98).

  The hole transport layer 4 containing the 2,7-diaminonaphthalene compound of the present invention represented by the general formula (I) is formed on the anode 2 by a coating method or a vacuum deposition method. In the case of the coating method, the 2,7-diaminonaphthalene compound of the present invention is dissolved in a solvent, and if necessary, an additive such as a binder resin or coating property improving agent that does not trap holes is added thereto. A layer may be formed on the anode 2 by a known wet film forming method using the prepared coating solution. Here, examples of the wet film forming method include normal coating methods such as a spray method, a printing method, a spin coating method, a dip coating method, and a die coating method, and various printing methods such as an ink jet method and a screen printing method.

  As the binder resin, polycarbonate, polyarylate, polyester or the like is used. When the amount of the binder resin in the hole transport layer 4 is large, the hole mobility is lowered. Therefore, the binder resin is preferably used so that the content in the hole transport layer 4 is 50% by weight or less.

In the case of the vacuum deposition method, a crucible containing the 2,7-diaminonaphthalene compound of the present invention is placed in a vacuum vessel, and the anode 2 is placed facing the crucible. After evacuating the inside of this vacuum vessel to about 10 ⁻⁴ Pa with a vacuum pump, the crucible is heated to evaporate the 2,7-diaminonaphthalene compound, and the generated vapor is deposited on the anode 2.

The hole transport layer 4 may be formed by using one of the 2,7-diaminonaphthalene compounds of the present invention alone, or may be formed by mixing two or more kinds as necessary. . Moreover, you may contain aromatic amines other than the 2,7- diamino naphthalene compound of this invention in the range which does not impair the performance of the element of this invention. The hole transport layer 4 further includes, as an acceptor, an aromatic carboxylic acid metal complex and / or metal salt (Japanese Patent Laid-Open No. 4-320484), a benzophenone derivative and a thiobenzophenone derivative (Japanese Patent Laid-Open No. 5-295361). Further, fullerenes (JP-A-5-331458) or the like may be doped at a concentration of 10 ⁻³ to 10% by weight to generate holes as free carriers. In this way, the drive voltage can generally be lowered. Furthermore, a known hole transport material may be used in combination with the hole transport layer 4 as long as the excellent properties of the 2,7-diaminonaphthalene compound of the present invention are not impaired.

  Examples of the known hole transporting material include 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane, 4,4′-bis [N- (1-naphthyl) -N-phenylamino. Aromatic amines containing two or more tertiary amines typified by biphenyl and having two or more condensed aromatic rings substituted with nitrogen atoms (Japanese Patent Laid-Open No. 5-234681), a starburst with a derivative of triphenylbenzene Aromatic triamines having a structure (US Pat. No. 4,923,774), N, N′-diphenyl-N, N′-bis (3-methylphenyl) biphenyl-4,4′-diamine, etc., and aromatic diamino groups in the pyrenyl group A compound in which a plurality of are substituted, an aromatic diamine having a styryl structure (Japanese Patent Laid-Open No. 4-290851), a thiophene group linked with an aromatic tertiary amine unit (Japanese Patent Laid-Open No. 4-304466), a starburst type Aromatic triamine (Japanese Patent Laid-Open No. 4-308688) Publication), a tertiary amine linked by a fluorene group (JP-A-5-25473), a triamine compound (JP-A-5-239455), bisdipyridylaminobiphenyl, N, N, N-triphenylamine derivatives (JP-A-6-1972), aromatic diamines having a phenoxazine structure (JP-A-7-138562), diaminophenylphenanthridine derivatives (JP-A-7-252474), silazane compounds (US Pat. 4,950,950), silanamine derivatives (JP-A-6-49079), phosphamine derivatives (JP-A-6-25659), and the like. These compounds may be used alone or as a mixture of two or more as necessary.

  The content of the 2,7-diaminonaphthalene compound of the present invention in the hole transport layer 4 is preferably 50% by weight or more, and more preferably 80% by weight or more in the layer.

  The thickness of the hole transport layer 4 is usually 5 nm or more, preferably 10 nm or more, and is usually 300 nm or less, preferably 100 nm or less. In order to uniformly form such a thin film, a vacuum deposition method is generally used.

  In the element shown in FIG. 1, a light emitting layer 5 is provided on the hole transport layer 4. The light emitting layer 5 is a recombination of holes injected from the anode 2 and moving through the hole transport layer 4 and electrons injected from the cathode 7 and moved through the electron transport layer 6 between the electrodes to which an electric field is applied. The main component is a light-emitting compound that is excited by the light and exhibits strong light emission (fluorescence or phosphorescence). This luminescent compound needs to have a stable thin film shape, exhibit a high (luminescence) quantum yield in the solid state, and can efficiently transport holes and / or electrons. . Further, it is required to be a compound that is electrochemically and chemically stable and does not easily generate impurities as traps during production or use.

  As a compound that satisfies such conditions and forms a light-emitting layer exhibiting fluorescence, a complex compound such as an aluminum complex of 8-hydroxyquinoline (Japanese Patent Laid-Open No. 59-194393), 10-hydroxybenzo [h] quinoline Complex compounds (JP-A-6-322362), bisstyrylbenzene derivatives (JP-A1-245087, JP-A-2-222484), bisstyrylarylene derivatives (JP-A-2-247278), (2- Hydroxyphenyl) benzothiazole metal complexes (JP-A-8-315983), silole derivatives and the like. Of the hole transporting materials described above, an aromatic amine compound having a light emitting property can also be used as the light emitting layer material. These light emitting layer materials are usually laminated on the hole transport layer 4 by a vacuum deposition method.

  For the purpose of improving the luminous efficiency of the device and changing the emission color, for example, doping a fluorescent dye for lasers such as coumarin with an aluminum complex of 8-hydroxyquinoline as a host material (J. Appl. Phys., Volume 65 3610 (1989)). This doping technique can also be applied to the light emitting layer 5, and various fluorescent dyes can be used as a doping material in addition to coumarin. Examples of fluorescent dyes that emit blue light include perylene, pyrene, anthracene, coumarin, and derivatives thereof. Examples of the green fluorescent dye include quinacridone derivatives and coumarin derivatives. Examples of yellow fluorescent dyes include rubrene and perimidone derivatives. Examples of red fluorescent dyes include DCM compounds, benzopyran derivatives, rhodamine derivatives, benzothioxanthene derivatives, azabenzothioxanthene and the like.

  In addition to the above fluorescent dyes for doping, depending on the host material, listed in Laser Research, 8, 694, 803, 958 (1980); 9, 9, 85 (1981) Fluorescent dyes and the like can be used as the doping material for the light emitting layer.

The amount by which the fluorescent dye is doped with respect to the host material is preferably 10 ⁻³ wt% or more, and more preferably 10 wt% or less. If the doping amount is less than 10 ⁻³ wt%, it may not be possible to contribute to the improvement of the light emission efficiency of the device. If it exceeds 10 wt%, concentration quenching may occur, leading to a decrease in light emission efficiency.

  On the other hand, a light-emitting layer that emits phosphorescence is usually formed including a phosphorescent dopant and a host material. Examples of the phosphorescent dopant include organometallic complexes containing a metal selected from Groups 7 to 11 of the periodic table, and charge transporting organic compounds having a T1 higher than the T1 (lowest excited triplet level) of the metal complex. It is preferable to use it as a host material.

  Preferred examples of the metal in the phosphorescent organometallic complex containing a metal selected from Groups 7 to 11 of the periodic table include ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, and gold.

  As the host material used for the light emitting layer exhibiting phosphorescence, in addition to the materials described above as the host material used for the light emitting layer exhibiting fluorescence, 4,4′-N, N′-dicarbazole biphenyl and the like can be used. Carbazole derivatives (WO 00/70655), tris (8-hydroxyquinoline) aluminum (USP 6,303,238), 2,2 ′, 2 ″-(1,3,5-benzenetolyl) tris [1-Phenyl-1H-benzimidazole] (Appl. Phys. Lett., Vol. 78, Item 1622, 2001), polyvinylcarbazole (Japanese Patent Laid-Open No. 2001-257076), and the like.

  Furthermore, the light emitting layer 5 in the organic electroluminescent element of the present invention may contain the aforementioned fluorescent dye together with the host material and the phosphorescent dopant.

  The amount of the organometallic complex contained as a dopant in the light emitting layer 5 is preferably 0.1% by weight or more, and more preferably 30% by weight or less. If this amount is less than 0.1% by weight, it may not contribute to the improvement of the light emission efficiency of the device. If it exceeds 30% by weight, concentration quenching occurs due to the formation of a dimer between organometallic complexes, and the light emission efficiency. May lead to a decline.

  The amount of the phosphorescent dopant in the light emitting layer exhibiting phosphorescence tends to be preferably slightly larger than the amount of the fluorescent dye (dopant) contained in the light emitting layer in a conventional device using fluorescence (singlet). There is. When the fluorescent dye is contained in the light emitting layer together with the phosphorescent dopant, the amount of the fluorescent dye is preferably 0.05% by weight or more, more preferably 0.05% by weight or more, and preferably 10% by weight or less. 2% by weight or less is more preferable.

  The thickness of the light emitting layer 5 is usually 3 nm or more, preferably 5 nm or more, and is usually 200 nm or less, preferably 100 nm or less.

The light emitting layer 5 can also be formed by the same method as the hole transport layer 4, but usually a vacuum deposition method is used.
Hereinafter, a method of doping the above-described fluorescent dye and / or phosphorescent dye (phosphorescent dopant) into the host material of the light emitting layer will be described.

  In the case of coating, the above light emitting layer host material, dope dye, and if necessary, additives such as a binder resin that does not become an electron trap or a light quenching quencher, and a coating property improving agent such as a leveling agent are added and dissolved. The applied coating solution is prepared, applied onto the hole transport layer 4 by a method such as spin coating, and dried to form the light emitting layer 5. Examples of the binder resin include polycarbonate, polyarylate, and polyester. If the binder resin is added in a large amount, the hole / electron mobility is lowered. Therefore, it is desirable that the binder resin is small.

In the case of the vacuum deposition method, the host material is put in a crucible installed in a vacuum vessel, the dye to be doped is put in another crucible, and the inside of the vacuum vessel is exhausted to about 10 ⁻⁴ Pa by an appropriate vacuum pump. Thereafter, each crucible is heated at the same time to evaporate the host material and the dye and form a layer on the substrate placed opposite the crucible. As another method, a mixture of the above materials in a predetermined ratio may be evaporated using the same crucible.

  When each said dopant is doped in the light emitting layer 5, it may be uniformly doped in the film thickness direction of the light emitting layer 5, and there may be concentration distribution in the film thickness direction. For example, doping may be performed only in the vicinity of the interface on the hole transport layer 4 side, or conversely, doping may be performed only in the vicinity of the interface on the cathode 7 side.

  In addition, the light emitting layer 5 may contain components other than the above in the range which does not impair the performance of this invention.

  In the element shown in FIG. 1, the cathode 7 provided on the light emitting layer 5 plays a role of injecting electrons into the light emitting layer 5 directly or via an arbitrary layer. The material used for the cathode 7 can be the material used for the anode 2, but a metal having a low work function is preferable for efficient electron injection, such as tin, magnesium, indium, calcium, A suitable metal such as aluminum or silver or an alloy thereof is used. Specific examples include low work function alloy electrodes such as magnesium-silver alloys, magnesium-indium alloys, and aluminum-lithium alloys.

  The film thickness of the cathode 7 is usually the same as that of the anode 2. For the purpose of protecting the cathode 7 made of a low work function metal, it is preferable to further stack a metal layer having a high work function and stable to the atmosphere on the element because the stability of the device is increased. For this purpose, metals such as aluminum, silver, copper, nickel, chromium, gold, platinum are used.

  For the purpose of further improving the efficiency of hole injection and improving the adhesion of the whole organic layer to the anode 2, an anode buffer is provided between the hole transport layer 4 and the anode 2 as shown in FIGS. Inserting layer 3 has also been done. By inserting the anode buffer layer 3, the driving voltage of the initial element is lowered, and at the same time, an increase in voltage when the element is continuously driven with a constant current is suppressed. The conditions required for the material used for the anode buffer layer 3 are that the contact with the anode 2 is good and a uniform thin film can be formed, and it is thermally stable, that is, the melting point and Tg are high, and the melting point is 300. More than 100 ° C. and Tg of 100 ° C. or more are required. Furthermore, the ionization potential is low, hole injection from the anode 2 is easy, and the hole mobility is high.

  For this purpose, phthalocyanine compounds such as copper phthalocyanine (JP-A 63-295695), polyaniline (Appl. Phys. Lett., 64, 1245, 1994), polythiophene (Optical Materials) , 9, 125, 1998), etc., sputtered carbon films (Synth. Met., 91, 73, 1997), vanadium oxide, ruthenium oxide, molybdenum oxide, etc. Metal oxides (J. Phys. D, 29, 2750, 1996) have been reported.

  In addition, a layer containing a hole injection / transporting low molecular organic compound and an electron accepting compound (described in JP-A-11-251067, JP-A-2000-159221, etc.), an aromatic amino group, etc. A layer obtained by doping the contained non-conjugated polymer compound with an electron-accepting compound as necessary (Japanese Patent Laid-Open Nos. 11-135262, 11-283750, 2000-36390, Examples include JP 2000-150168, JP-A 2001-223084, and WO 97/33193), or layers containing a conductive polymer such as polythiophene (JP-A 10-92584). It is not limited to.

As the anode buffer layer 3 material, it is possible to use either a low molecular compound or a high molecular compound.

  In the case of the anode buffer layer 3, a thin film can be formed in the same manner as the hole transport layer 4, but in the case of an inorganic substance, a sputtering method, an electron beam evaporation method, or a plasma CVD method is further used.

  When the anode buffer layer 3 formed as described above is formed using a low molecular weight compound, the lower limit is usually 3 nm, preferably about 10 nm, and the upper limit is usually 100 nm, preferably about 50 nm. is there. The lower limit of the thickness of the anode buffer layer 3 formed using the polymer compound is usually 5 nm, preferably about 10 nm, and the upper limit is usually about 1000 nm, preferably about 500 nm.

  For the purpose of further improving the light emission efficiency of the device, an electron transport layer 6 may be provided between the light emitting layer 5 and the cathode 7 as shown in FIG. The electron transport layer 6 is formed of a compound that can efficiently transport electrons injected from the cathode 7 between the electrodes to which an electric field is applied in the direction of the light emitting layer 5.

  The electron transporting compound used for the electron transporting layer 6 is a compound that has high electron injection efficiency from the cathode 7 and has high electron mobility and can efficiently transport injected electrons. is necessary.

  Materials satisfying such conditions include complex compounds such as aluminum complexes of 8-hydroxyquinoline (Japanese Patent Laid-Open No. 59-194393), complex compounds of 10-hydroxybenzo [h] quinoline, oxadiazole derivatives, Styryl biphenyl derivative, silole derivative, 3- or 5-hydroxyflavone complex compound, benzoxazole complex compound, benzothiazole complex compound, trisbenzimidazolylbenzene (US Pat. No. 5,645,948), quinoxaline compound (JP-A-6-207169) Phenanthroline derivatives (JP-A-5-331459), 2-t-butyl-9,10-N, N'-dicyanoanthraquinonediimine, n-type hydrogenated amorphous silicon carbide, n-type zinc sulfide, n-type Examples include zinc selenide.

  The thickness of the electron transport layer 6 is usually 5 nm or more, preferably 10 nm or more, and is usually 200 nm or less, preferably 100 nm or less.

  The electron transport layer 6 is formed by laminating on the light emitting layer 5 by a coating method or a vacuum deposition method in the same manner as the hole transport layer 4. Usually, a vacuum deposition method is used.

Further, an ultrathin insulating film (film thickness) such as LiF, MgF ₂ , or Li ₂ O is formed at the interface between the cathode 7 and the light emitting layer 5 in FIGS. 1 or 2 or the interface between the cathode 7 and the electron transport layer 6 in FIG. Inserting 0.1 to 5 nm is also an effective method for improving the efficiency of the device (Appl. Phys. Lett., 70, 152, 1997; JP 10-74586; IEEE Trans. Electron). Devices, 44, 1245, 1997).

  The organic electroluminescent element of the present invention may have an arbitrary layer between the anode and the cathode in addition to the above-described layers. For example, in order to prevent holes that have not recombined in the light emitting layer from passing through to the cathode side, a hole blocking layer is provided so as to contact the cathode side interface of the light emitting layer, or an electron transport layer or a hole transport layer is provided. Each may be configured by laminating a plurality of layers. Also, the layer structure can be reversed from that shown in FIG. 1, that is, the cathode 7, the light emitting layer 5, the hole transport layer 4, and the anode 2 can be laminated on the substrate 1 in this order. It is also possible to provide the organic electroluminescent element of the present invention between two substrates, at least one of which is highly transparent. Similarly, it is also possible to laminate in a structure opposite to the above-described layer structure shown in FIGS.

  The organic electroluminescent device of the present invention can be applied to any of the organic electroluminescent devices in a single device, an element having a structure arranged in an array, and a structure in which an anode and a cathode are arranged in an XY matrix. can do.

  According to such an organic electroluminescent device, the hole transport layer 4 has a high hole injecting and transporting capability, has few barriers with the interface of the light emitting layer, has a high Tg, and is easily crystallized. By including the 2,7-diaminonaphthalene compound of the present invention, an organic electroluminescence device having high current efficiency and light emission efficiency, capable of being driven at a low voltage, and excellent in driving stability and heat resistance is provided. .

  In addition, since the 2,7-diaminonaphthalene compound represented by the general formula (I) according to the present invention can basically be used for a hole injection / transport layer, in FIGS. Not only the hole transport layer but also any layer provided between the anode and the light emitting layer can be employed.

  EXAMPLES Next, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited to description of a following example, unless the summary is exceeded.

Example 1: Synthesis of Exemplified Compound (1) The 2,7-diaminonaphthalene compound of the present invention represented by the following structural formula (Exemplary Compound (1): No. 1 Compound in Table 1) was synthesized.

1) Synthesis of N, N′-bis (4-methylphenyl) -2,7-diaminonaphthalene

  Add 4mL of tetraethylene glycol dimethyl ether to 16.3g (0.102mol) of 2,7-dihydroxynaphthalene, 27.3g (0.245mol) of p-toluidine and 1.3g (0.005mol) of iodine, and react at 165 ° C for 5.5 hours under nitrogen atmosphere I let you. After completion of the reaction, 150 mL of ethanol was added to the reaction solution and refluxed for 10 minutes. After allowing to cool, the obtained crystals were collected by filtration to obtain 27.5 g (0.081 mol, yield 80%) of white needle crystals.

2) Synthesis of N, N′-bis (4-methylphenyl) -N, N′-di (9-phenanthryl) -2,7-diaminonaphthalene

  N, N′-bis (4-methylphenyl) -2,7-diaminonaphthalene 6.40 g (0.019 mol), 9-iodophenanthrene 16.0 g (0.042 mol), copper 2.4 g (0.038 mol) and potassium carbonate 7.8 g ( 0.057 mol) was added with 30 mL of tetraethylene glycol dimethyl ether, and the mixture was reacted at 200 ° C. for 8 hours under nitrogen. After completion of the reaction, 150 mL of tetrahydrofuran (THF) was added to the reaction solution, and insoluble matters were filtered off. The THF contained in the filtrate was distilled off under reduced pressure, poured into methanol, and the resulting precipitate was collected by filtration. The resulting precipitate was purified by silica gel column chromatography (developing solvent: hexane / toluene = 3/1) and washed with methanol to obtain 7.54 g (0.011 mol, yield 58%) of milky white powder.

  When 0.72 g of this milky white powder was purified by sublimation, 0.51 g (yield 72%) of a pale yellow candy-like solid was recovered. When the collected product was subjected to mass spectrometry, the molecular weight was 690. Thus, it was confirmed that the pale yellow candy-like solid was the exemplified compound (1). Further, when differential thermal analysis measurement was performed by DSC-20 manufactured by Seiko Electronics Co., Ltd., Tg was as high as 152 ° C. The melting point could not be detected due to the high amorphous nature.

The ¹ H-NMR (CDCl ₃ , 270 MHz) data of the light yellow candy-like solid is shown below.
8.69 (d, 2H, J = 9.3)
8.66 (d, 2H, J = 9.3)
8.06 (dd, 2H, J = 8.2, 0.9)
7.70 (dd, 2H, J = 7.7, 1.6)
7.62 (dd, 2H, J = 6.9, 1.6)
7.60-7.49 (m, 6H)
7.55 (s, 2H)
7.43 (ddd, 2H, 7.2, 6.9, 0.9)
7.13 (dd, 2H, J = 8.9, 2.0)
7.02-6.99 (m, 8H)
6.89 (d, 2H, J = 2.0)
2.26 (s, 6H)

Example 2: Synthesis of Exemplified Compound (91) A 2,7-diaminonaphthalene compound of the present invention represented by the following structural formula (Exemplary Compound (91): Compound No. 91 in Table 1) was synthesized.

1) Synthesis of 2,7-bis (trifluoromethylsulfonyloxy) naphthalene

To 11.8 g (0.074 mol) of 2,7-dihydroxynaphthalene was added 300 mL of methylene chloride and 50 mL of triethylamine, and the mixture was cooled to 0 ° C. under nitrogen. After adding 50.0 g (0.177 mol) of trifluorosulfonic anhydride from the dropping funnel over 2 hours, the temperature was raised to room temperature over 2 hours and stirred at room temperature for 30 minutes. The reaction mixture was discharged into 300 mL of water and stirred, and then the organic layer was separated. After drying over anhydrous magnesium sulfate, filtration, concentration, and recrystallization with methanol, 23.6 g of white crystals
(0.056 mol, yield 75%) was obtained.

2) Synthesis of 2,7-bis (N-carbazolyl) naphthalene

Add 30 mL of xylene to 3.50 g (0.0083 mol) of 2,7-bis (trifluoromethylsulfonyloxy) naphthalene, 3.31 g (0.0198 mol) of carbazole and 6.48 g (0.0469 mol) of potassium carbonate, and heat to 80 ° C under nitrogen Then, 10 mL of a xylene solution of a catalyst prepared from 0.17 g (0.00016 mol) of tris (dibenzylideneacetone) dipalladium (0) and 0.36 g (0.00065 mol) of 1,1′-bis (diphenylphosphino) ferrocene was added for 5 minutes. Added over. The mixture was reacted at 120 ° C. for 8 hours, cooled to room temperature, and concentrated. Chloroform and water were added to dissolve the precipitate, and the organic layer was separated. After drying over anhydrous magnesium sulfate, filtration, concentration, purification by silica gel column chromatography (developing solvent: hexane / toluene = 4/1) and washing with methanol, 0.85 g of white powder
(0.0019 mol, yield 22%) was obtained.

  When the white powder was subjected to mass spectrometry, the molecular weight was 458. Thus, it was confirmed that the white powder was the exemplified compound (91). Moreover, when differential thermal analysis measurement was carried out by DSC-20 by Seiko Electronics Co., Ltd., Tg was 93 degreeC and melting | fusing point was 250 degreeC.

The ¹ H-NMR (CDCl ₃ , 270 MHz) data of the white powder is shown below.
8.20 (d, 2H, J = 8.5)
8.19 (dd, 4H, J = 8.0, 1.5)
8.12 (d, 2H, J = 1.9)
7.79 (dd, 2H, J = 8.5, 1.9)
7.53 (dd, 4H, J = 8.0, 1.5)
7.45 (ddd, 4H, 8.0, 7.6, 1.5)
7.33 (ddd, 4H, 8.0, 7.6, 1.5)

Example 3 Electrochemical / Spectroscopic Measurement of Exemplary Compound (1) Using BAS Electrochemical Analyzer 650A, BCE GCE as a working electrode in a 0.1 M tetrabutylammonium perchlorate solution in methylene chloride When the cyclic voltammetry of Exemplified Compound (1) was measured using Pt line as the electrode and Ag line as the reference electrode, the oxidation-reduction potential was 0.83 V vs. SCE, and it was used as the hole transport layer material of the organic electroluminescence device. A moderate value was shown. The oxidation-reduction potential was converted using ferrocene / ferrocenium as the internal standard substance.

  Moreover, it was 5.07 eV when the ionization potential of the thin film sample of the exemplary compound (1) formed by vacuum deposition was measured using an ultraviolet electron analyzer (AC-1) manufactured by Riken Keiki Co., Ltd. An appropriate value was shown as the hole transport layer material of the organic electroluminescence device.

  Moreover, the result of having measured the absorption spectrum of the visible part of this thin film sample is shown in FIG. As shown in FIG. 4, it showed high transparency in the visible light region.

Comparative Example 1: Synthesis of Comparative Compound (L) Comparative compound represented by the following structural formula in the same manner as in Example 1 except that 2,6-dihydroxynaphthalene was used instead of 2,7-dihydroxynaphthalene. (L) was synthesized.

Comparative Example 2: Electrochemical / spectroscopic measurement of the comparative compound (L) When the cyclic voltammetry of this comparative compound (L) was measured in the same manner as in Example 3, the redox potential was 0.51 V vs. SCE. Met. The oxidation-reduction potential was converted using ferrocene / ferrocenium as the internal standard substance. Further, the ionization potential of the thin film sample was measured in the same manner as in Example 3. As a result, it was 4.75 eV, and both were lower than the exemplified compound (1). Moreover, the result of having measured the absorption spectrum of the visible part of a thin film sample is as showing in FIG. 4, and transparency was also inferior to exemplary compound (1).

Example 4 Production of Organic Electroluminescent Device Using Exemplary Compound (1) An organic electroluminescent device having the structure shown in FIG. 3 was produced by the following method.

  An indium tin oxide (ITO) transparent conductive film deposited on a glass substrate with a thickness of 120 nm (manufactured by Geomat Corp .; electron beam film-formed product; sheet resistance 15 Ω / sq) is 2 mm using ordinary photolithography and hydrochloric acid etching. The anode 2 was formed by patterning into a stripe having a width. The patterned ITO substrate was cleaned in the order of ultrasonic cleaning with acetone, water with pure water, and ultrasonic cleaning with isopropyl alcohol, dried with nitrogen blow, and finally subjected to ultraviolet ozone cleaning.

  Next, as the anode buffer layer 3, an aromatic diamine-containing polyether (P-1) (weight average molecular weight 25,300; glass transition temperature 171 ° C.) having the following structure and 10% by weight of the following compound (P-1) ( P-2) was spin-coated on the glass substrate under the following conditions.

Solvent: Ethyl benzoate (P-1) Concentration: 20 [mg / ml]
(P-2) Concentration: 2 [mg / ml]
Spinner speed: 1500 [rpm]
Spinner rotation time: 30 [seconds]
Drying conditions: 1.5 hours at 100 ° C

  The anode buffer layer 3 having a uniform thin film shape with a film thickness of 30 nm was formed by the above spin coating.

Next, the substrate 1 on which the anode buffer layer 3 was applied and formed was placed in a vacuum evaporation apparatus. After roughly exhausting the equipment with an oil rotary pump, use an oil diffusion pump equipped with a liquid nitrogen trap until the vacuum inside the equipment is 2 × 10 ^-6 Torr (about 2.7 × 10 ^-4 Pa) or less. Exhausted.

The exemplified compound (1) was placed in a ceramic crucible placed in this apparatus, and vapor deposition was performed by heating with a tantalum wire heater around the crucible. The degree of vacuum during deposition is 1.3 × 10 ⁻⁶ Torr (about 1.7 × 10 ⁻⁴ Pa), and a hole transport layer 4 having a film thickness of 40 nm is formed at a deposition rate of 0.1 to 0.17 nm / second (average 0.13 nm / second). Filmed.

Subsequently, aluminum 8-hydroxyquinoline complex (Al (C ₉ H ₆ NO) ₃ ) and C545T represented by the following structural formulas (Q-1) and (Q-2) were simultaneously deposited as materials for the light-emitting layer 5. . The ratio of C545T to the 8-hydroxyquinoline complex of aluminum was adjusted to 0.8% by weight.

The degree of vacuum during the deposition is 0.7 × 10 ⁻⁶ Torr (about 0.9 × 10 ⁻⁴ Pa), the deposition rate of aluminum 8-hydroxyquinoline complex is 0.15 nm / second, and the deposition rate of C545T is 0.0012 nm / second. A light emitting layer 5 having a thickness of 30 nm was formed.

Subsequently, the aluminum 8-hydroxyquinoline complex (Q-1) is deposited as the electron transport layer 6 in the same manner as the hole transport layer 4, and the vacuum at the time of aluminum 8-hydroxyquinoline complex deposition is obtained. The degree was 0.6 × 10 ⁻⁶ Torr (about 0.8 × 10 ⁻⁴ Pa), the deposition rate was 0.2 nm / second, and the thickness of the deposited electron transport layer 6 was 30 nm.

  In addition, the substrate temperature at the time of vacuum-depositing said positive hole transport layer 4, the light emitting layer 5, and the electron carrying layer 6 was kept at room temperature.

Here, the element on which the electron transport layer 6 has been deposited is once taken out from the vacuum deposition apparatus to the atmosphere, and a 2 mm wide stripe-shaped shadow mask is orthogonal to the ITO stripe of the anode 2 as a mask for cathode deposition. In close contact with the element. This element was placed in another vacuum deposition apparatus, and evacuated until the degree of vacuum in the apparatus was 2.5 × 10 ⁻⁶ Torr (about 3.2 × 10 ⁻⁴ Pa) or less in the same manner as in the formation of the organic layer.

Subsequently, lithium fluoride (LiF) was vapor-deposited as a cathode 7 at a deposition rate of 0.01 nm / second and a degree of vacuum of 5.8 × 10 ⁻⁶ Torr (about 7.5 × 10 ⁻⁴ Pa) using a molybdenum boat. A film having a thickness of nm was formed on the electron transport layer 6. Next, aluminum is similarly heated by a molybdenum boat to form an aluminum layer with a film thickness of 80 nm at a deposition rate of 0.5 nm / second and a degree of vacuum of 1 × 10 ⁻⁵ Torr (about 1.3 × 10 ⁻³ Pa) to form a cathode. 7 was completed. The substrate temperature at the time of vapor deposition of the above two-layered cathode 7 was kept at room temperature.

As described above, an organic electroluminescent element having a light emitting area portion having a size of 2 mm × 2 mm was obtained. The light emission characteristics of this element are shown in Table-2, and the drive life is shown in Table-3. In Table 2, the light emission luminance is a value at a current density of 250 mA / cm ² , the light emission efficiency is a value at 100 cd / m ² , the luminance / current is the gradient of the luminance-current density characteristic, and the voltage is 100 cd / m ² . The values of are shown respectively. In Table 3, the drive life is the initial luminance of 5000 cd / m ² , and the luminance half time at room temperature driving.

  As shown in Table 2, it is clear that the use of the hole transport layer containing the exemplary compound (1) achieved a reduction in driving voltage, and a high-luminance and high-efficiency device was obtained. Further, from Table 3, it is clear that an element having a long driving life and excellent heat resistance was obtained.

Comparative Example 3: Preparation of Organic Electroluminescent Device Using Comparative Compound (L) As a material for the hole transport layer 4, instead of the exemplified compound (1), a comparative compound (L) which is a 2,6-diaminonaphthalene compound is used. An organic electroluminescent element was produced in the same manner as in Example 4 except that it was used. The light emission characteristics of this element are shown in Table-2.

Comparative Example 4: Production of Organic Electroluminescent Device Using Comparative Compound (A-3) As a material for the hole transport layer 4, instead of the exemplified compound (1), the 4,4′-bis [N- (1- An organic electroluminescent device was produced in the same manner as in Example 4 except that naphthyl) -N-phenylamino] biphenyl (A-3) was used. The light emission characteristics of this element are shown in Table-2, and the drive life is shown in Table-3.

  As shown in Table-2 and Table-3, the luminous efficiency of the devices produced in Comparative Examples 3 and 4 was lower than that of the device produced in Example 4, and the driving life was short.

  The organic electroluminescence device according to the present invention is a light source (for example, a light source of a copying machine, a backlight of a liquid crystal display or an instrument) taking advantage of the characteristics of a flat panel display (for example, a wall-mounted television for an OA computer) or a surface light emitter. Application to light sources), display boards, and marker lamps is conceivable, and the technical value is particularly great as an in-vehicle display element that requires high heat resistance and long life.

It is typical sectional drawing which showed an example of embodiment of the organic electroluminescent element of this invention. It is typical sectional drawing which showed another example of embodiment of the organic electroluminescent element of this invention. It is typical sectional drawing which showed another example of embodiment of the organic electroluminescent element of this invention. 4 is an absorption spectrum chart of a thin film sample measured in Example 3 and Comparative Example 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Anode 3 Anode buffer layer 4 Hole transport layer 5 Light emitting layer 6 Electron transport layer 7 Cathode

Claims (6)

2,7-diaminonaphthalene compound represented by the following general formula (I).

(In the general formula (I), R ^{1 to} R ⁴ each independently represents an aromatic group which may have a substituent selected from the following substituent group I , or R ¹ and R ² , R ³ and R ⁴ are bonded to each other to form a ring which may have a substituent selected from the following substituent group I.
However, at least ^one of R ^{1 to} R ⁴ , the ring formed by combining R ¹ and R ² , and the ring formed by combining R ³ and R ⁴ is formed by condensation of three or more rings. Represents an aromatic condensed ring group which may have a substituent selected from the following substituent group I. )
Substituent group I: C1-C10 alkyl group, C2-C11 alkenyl group, C2-C11 alkynyl group, aralkyl group, C2-C11 alkoxy group, aryloxy group, dialkylamino Group, alkylarylamino group, diarylamino group, acyl group having 2 to 11 carbon atoms, alkoxycarbonyl group having 2 to 11 carbon atoms, aromatic hydrocarbon group, aromatic heterocyclic group
In addition, said substituent may have a C1-C10 alkyl group or aromatic hydrocarbon group as a substituent further. The aromatic condensed ring group which may have a substituent formed by condensation of three or more rings is a phenanthryl group which may have a substituent selected from the substituent group I. The 2,7-diaminonaphthalene compound described.   A charge transport material comprising the 2,7-diaminonaphthalene compound according to claim 1 or 2.   Organic electroluminescent element material containing the 2,7- diamino naphthalene compound of Claim 1 or 2.   An organic electroluminescent device having a light emitting layer between an anode and a cathode, wherein the organic electroluminescent device has a layer containing the 2,7-diaminonaphthalene compound according to claim 1.   The organic electroluminescent element of Claim 5 which has a layer containing the said 2,7- diamino naphthalene compound between an anode and a light emitting layer.

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