TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation: No general method for the preparation of the azo compound (I) is given in the specification. Preferred Compound: The azo compound (I) is a compound of formula (II).V1a to V3a=a substituent;orV2a+V3a=saturated or unsaturated 5- or 6-membered ring (where the total number of carbon atoms and hetero atoms in the ring is 3 to 6).Provided that R, V1a, V2a and V3a do not include any of a carboxyl, sulfo or quaternary ammonium group; and when V2a and V3a are bonded with each other to form a ring, the ring is optionally a heterocyclic or aromatic, saturated or unsaturated ring. SPECIFIC COMPOUNDS - 36 Compounds are disclosed as the compound (I), e.g. 4-(3-cyano-benzo(e)pyrazolo(5,1-c)(1,2,4)triazin-8-ylazo)-1-hydroxy-5-methanesulfonylamino-naphthalene-2-sulfonic acid diethylamide (IA), 8-(4-hydroxy-phenylazo)-isothiazolo(4,3-c)cinnoline-3-carbonitrile, 1-hydroxy-4-(3-methyl-benzo(e)pyrazolo(5,1-c)(1,2,4)triazin-8-ylazo)-naphthalene-2-carboxylic acid diethylamide, N-(6-(3-cyano-benzo(e)pyrazolo(5,1-c)(1,2,4)triazin-8-ylazo)-3-hydroxy-pyridin-2-yl)-propionamide and 8-(3-chloro-4-hydroxy-phenylazo)-benzo(e)pyrazolo(5,1-c)(1,2,4)triazine-3-carbonitrile.    EXAMPLE - 8-Amino-benzo(e)pyrazolo(5,1-c)(1,2,4)triazine-3-carbonitrile (1 g) was dissolved in phosphoric acid (85 wt.%, 20 ml). Then, sodium nitrite (0.36 g) was divided and gradually added to the solution over 30 minutes while stirred at less than or equal to 0 degrees C. The solution was further stirred for 2 hours at 0-5 degrees C to obtain 3-cyano-benzo(e)pyrazolo(5,1-c)(1,2,4)triazine-8-diazonium. Subsequently, 1-hydroxy-5-methanesulfonylamino-naphthalene-2-sulfonic acid diethylamide (b1) (1.4 g) was dissolved in methanol (150 ml). Then, the diazonium salt was divided and gradually added to the solution of the compound (b1) while stirred at less than or equal to 0 degrees C. The mixture was stirred at 0-5 degrees C for 1 hour and then stirred at 20-25 degrees C (room temperature) for 1 hour. Subsequently, water (200 ml) was added to the reaction mixture. Deposited crystals thus obtained were filtrated and dried, and then purified by column chromatography. Consequently, 4-(3-cyano-benzo(e)pyrazolo(5,1-c)(1,2,4)triazin-8-ylazo)-1-hydroxy-5-methanesulfonylamino-naphthalene-2-sulfonic acid diethylamide (d1) was obtained (20% in yield). The obtained compound (d1) had a melting point of 258-260 degrees C. The absorption spectrum of the compound (d1) was determined in N,N'-dimethyl formaldehyde. As a result, the compound (d1) showed the absorption maximum lambda max at 677 nm, confirming that the dye had good hue.