Organic electroluminescent device and display unit

1. An organic electroluminescent device comprising:

an anode;

a cathode; and

an organic layer held between them which includes

a light-emitting layer,

a naphthacene compound layer containing a naphthacene compound, and

an electron transport layer;

said light-emitting layer being composed of a light-emitting guest material and an aromatic hydrocarbon compound having the skeleton of anthracene, and

said naphthacene compound layer containing no less than 80 wt % of naphthacene compound represented by the formula (1) below and having a thickness of 0.5 to 10 nm and being in contact with that side of said electron transport layer which faces said light-emitting layer

where, R 1 to R 8 independently denote a hydrogen atom, halogen atom, hydroxyl group, cyano group, nitro group, any of carbonyl group, carbonyl ester group, alkyl group, alkenyl group, and alkoxyl group, which may be substituted with a group having no more than 20 carbon atoms, and any of silyl group, aryl group, and heterocyclic group, which may be substituted with a group having no more than 30 carbon atoms.

2. The organic electroluminescent device as defined in claim 1 , wherein the naphthacene compound layer contains no less than 80 wt % of naphthacene compound represented by the formula (2) below

where, R 1 to R 4 independently denote any of hydrogen atom, substituted or unsubstituted phenyl group, substituted or unsubstituted biphenyl group, substituted or unsubstituted naphthyl group, heterocyclic group, phenyl-substituted heterocyclic group, and condensed polycyclic aromatic heterocyclic group having no more than 13 carbon atoms.

3. The organic electroluminescent device as defined in claim 2 , wherein R 1 to R 4 in the formula (2) for the naphthacene compound layer independently denote any of hydrogen atom, substituted or unsubstituted phenyl group, substituted or unsubstituted biphenyl group, and substituted or unsubstituted naphthyl group.

4. The organic electroluminescent device as defined in claim 1 , wherein the naphthacene compound layer has a thickness of 1 to 5 nm.

5. The organic electroluminescent device as defined in claim 1 , which has an auxiliary light-emitting layer formed between the light-emitting layer and the naphthacene compound layer.

6. The organic electroluminescent device as defined in claim 1 , the light-emitting guest material is an organic material that emits blue or green light.

7. The organic electroluminescent device as defined in claim 1 , wherein the light generated by the light-emitting layer experiences multiple interference between any layers held between the anode and cathode and then emanates from either the anode or the cathode.

8. The organic electroluminescent device as defined in claim 1 , wherein the light generated by the light-emitting layer experiences multiple interference between any layers held between the anode and cathode and then emanates from the cathode.

9. A display unit comprising:

a substrate; and

an array of organic electroluminescent devices arranged thereon, with at least a portion of said organic electroluminescent devices being the one which includes

an anode,

a cathode, and

an organic layer held between them which includes

a light-emitting layer,

a naphthacene compound layer containing a naphthacene compound, and

an electron transport layer;

said light-emitting layer being composed of a light-emitting guest material and an aromatic hydrocarbon compound having the skeleton of anthracene, and

said naphthacene compound layer containing no less than 80 wt % of naphthacene compound represented by the formula (1) below and having a thickness of 0.5 to 10 nm and being in contact with that side of said electron transport layer which faces said light-emitting layer

where, R 1 to R 8 independently denote a hydrogen atom, halogen atom, hydroxyl group, cyano group, nitro group, any of carbonyl group, carbonyl ester group, alkyl group, alkenyl group, and alkoxyl group, which may be substituted with a group having no more than 20 carbon atoms, and any of silyl group, aryl group, and heterocyclic group, which may be substituted with a group having no more than 30 carbon atoms.

10. The display unit as defined in claim 9 , wherein at least a portion of the organic electroluminescent devices are blue light-emitting ones.

11. The display unit as defined in claim 9 , wherein at least a portion of the organic electroluminescent devices are green light-emitting ones.

12. The display unit as defined in claim 9 , wherein the substrate has organic electroluminescent devices emitting blue, green, and red light arranged thereon, and said organic electroluminescent devices emitting blue light and/or said organic electroluminescent devices emitting green light constitute at least a portion of said organic electroluminescent devices.