1. A light-emitting element comprising:
a cathode;
an anode;
a light-emitting portion interposed between the cathode and the anode and having a light-emitting layer that emits light on energization between the cathode and the anode; and
a hole-injection layer interposed between and in direct contact with the anode and the light-emitting layer and having a capability of receiving holes, wherein:
the hole-injection layer is mainly composed of a benzidine derivative.
2. The light-emitting element according to claim 1, wherein the hole-injection layer has an average thickness in the range of 80 to 200 nm.
3. The light-emitting element according to claim 1, wherein the distance between the anode and the cathode is in the range of 150 to 300 nm.
4. The light-emitting element according to claim 1, wherein the anode has the surface thereof on the hole-injection layer side treated with plasma.
5. The light-emitting element according to claim 1, wherein the anode is composed of indium tin oxide.
6. The light-emitting element according to claim 1, wherein:
the light-emitting portion has several light-emitting layers; and
the hole-injection layer is interposed between and in direct contact with the anode and the closest light-emitting layer to the anode.
7. The light-emitting element according to claim 6, wherein:
the light-emitting portion contains first, second, and third light-emitting layers for emission of light in different colors, layered in this order from the side of the anode to the side of the cathode; and
the hole-injection layer is interposed between and in direct contact with the anode and the first light-emitting layer.
8. The light-emitting element according to claim 7, wherein the first light-emitting layer contains an acene compound.
9. The light-emitting element according to claim 8, wherein the acene compound is a naphthacene derivative
10. The light-emitting element according to claim 8, wherein the content ratio of the acene compound in the first light-emitting layer is in the range of 90 to 99.99 wt %.
11. The light-emitting element according to claim 7, wherein the light-emitting portion has an intermediate layer interposed between the first and second light-emitting layers.
12. The light-emitting element according to claim 7, wherein the first light-emitting layer emits red light on energization between the cathode and the anode, and the second and third light-emitting layers emit blue and green light or vice versa on energization between the cathode and the anode
13. The light-emitting element according to claim 1, wherein the benzidine derivative has a content ratio in the range of 50 to 100 wt % with respect to the hole-injection layer.
14. A light-emitting apparatus comprising the light-emitting element according to claim 1.
15. A display comprising the light-emitting apparatus according to claim 14.
16. An electronic device comprising the display according to claim 15.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A ninhydrin reagent for use in a method for analysing nitrogen-containing compounds, the ninhydrin reagent comprising:
ninhydrin;
an aqueous buffer, wherein the ninhydrin reagent has a pH, and wherein the buffer maintains the pH at a value between 4.5 to 5.5; and
a temperature-dependent reducing agent, which agent is inactive in the reduction of ninhydrin at a first temperature, wherein the first temperature is no greater than 30\xb0 C., and active in reducing ninhydrin to hydrindantin at a second temperature, wherein the second temperature is higher than the first temperature, further wherein the second temperature is at least 100\xb0 C.; and
wherein the ninhydrin reagent is essentially free from hydrindantin.
2. The ninhydrin reagent according to claim 1, wherein the first temperature is from 10\xb0 C. to 20\xb0 C.
3. The ninhydrin reagent according to claim 1, wherein the temperature-dependent reducing agent is a compound having an activity of at least 50% of its initial activity after 24 months.
4. The ninhydrin reagent according to claim 1, wherein the temperature-dependent reducing agent comprises one or more saccharides.
5. The ninhydrin reagent according to claim 4, wherein the temperature-dependent reducing agent is selected from the group consisting of: Glucose, Fructose, Glyceraldehyde, Galactose, Ribose, Xylose, Erythrose, Threose, Lyxose, Arabinose, Allose, Altrose, Mannose, Gulose, Idose, Talose and L-Glycero-D-manno-heptose, Dihydroxyacetone, Erythrulose, Ribulose, Xylulose, Psicose, Sorbose, Tagatose, Sedoheptalose, or a mixture thereof; Lactose, Maltose, Trihalose, Cellobiose, Kojibiose, Nigerose, Isomaltose, Sophorose, Laminaribiose, Gentiobiose, Turanose, Maltulose, Palatinose, Gentiobiulose, Mannobiose, Melibiose, Melibiulose, Rutinose, Xylobiose or a mixture thereof; and Stachyose, Dextrin, Maltodextrin, or a mixture thereof.
6. The ninhydrin reagent according to claim 1, wherein the temperature-dependent reducing agent comprises one or more carboxylic acids andor a salt thereof.
7. The ninhydrin reagent according to claim 6, wherein the temperature-dependent reducing agent comprises a Group I or Group II metal salt of a carboxylic acid.
8. The ninhydrin reagent according to claim 6, wherein the carboxylic acid is formic acid or a salt thereof.
9. The ninhydrin reagent according to claim 1, wherein the temperature-dependent reducing agent comprises one or more compounds having one or more aldehyde andor ketone groups.
10. The method according to claim 9, wherein the temperature-dependent reducing agent comprises acetone.
11. The ninhydrin reagent according to claim 1, wherein the temperature-dependent reducing agent comprises a sulfite, thiosulfate, a phosphite andor a hypophosphite.
12. The ninhydrin reagent according to claim 1, wherein the concentration of the temperature-dependent reducing agent is from 0.01% to 20% wv or vv.
13. The ninhydrin reagent according to claim 1, wherein the concentration of ninhydrin in the ninhydrin reagent is from 1 to 2.5% wv or vv.
14. The ninhydrin reagent according to claim 1, wherein the buffer comprises acetic acid, ethanoic acid or propanoic acid.
15. The ninhydrin reagent according to claim 1, further comprising one or more organic solvents.
16. The ninhydrin reagent according to claim 15, wherein the organic solvent is selected from the group consisting of dimethylsulfoxide, ethylene glycol, propylene glycol, sulfolane, carbitol, propylene glycol monomethyl ether, methylcellosolve and methanol.
17. The ninhydrin reagent according to claim 15, wherein the concentration of organic solvent is from 35% to 55% vv.
18. A method of analysing a nitrogen-containing compound, the method comprising:
i) providing a ninhydrin reagent according to claim 1;
ii) heating the ninhydrin reagent to at least the second temperature to form a hydrindantin-containing mixture; and
iii) contacting the hydrindantin-containing mixture with the nitrogen-containing compound to produce a product.
19. The method according to claim 18, wherein the product of step (iii) has a colour, the method further comprising analysing the colour of the product of step (iii).