NOVEL ACID-TYPE HAIR COLOR TECHNOLOGY (8) AI-Dye/CD 3 OD (C) Al-Dye-EDT A/CD 3 OD 9.0 8.5 8.0 7.5 7.0 1 H-NMR spectrum 6.5 43 PPM 6.0 Figure 10. The NMR spectra of the Al-Dye complex. Acid orange 7 in CD3OD medium (Dye/CD3OD), the complex of aluminum ion and acid orange 7 in CD3OD medium (Al-Dye/CD3OD), and the complex dissolved by EDTA in CD3OD medium (Al-Dye-EDTA/CD3OD) were respectively analyzed by NMR spectra. Small peaks, which were considered to be the chelate, are indicated by the allowheads. the aluminum ion and acid orange 7. In other major peaks, the aluminum ion was considered to combine with acid orange 7 by an ionic bond. SENSORY EVALUATION The results of sensory evaluation are shown in Figure 11. The result of Test 1 confirmed that the "permanent" acid-type hair color was slightly superior to a conventional acid­ type hair color in terms of its color brightness effect and clearly superior in terms of its one-month longevity effect. The result of Test 2 confirmed that the "permanent" acid­ type hair color for gray coverage was comparable to a conventional oxidative hair color in terms of its color brightness effect and its one-month color longevity effect. The result of Test 3 confirmed that the "permanent" acid-type hair color for fashion shade was slightly superior to a conventional oxidative hair color in terms of its color brightness effect, but its one-month color longevity effect was comparable. The degree of smooth­ ness and shine after one month was superior to that of conventional oxidative hair color. DISCUSSION FORMATION OF DYE-METAL COMPLEX WITHIN HAIR The result of this study indicates that Al-Hair, Al-Dye, and Al-Hair-Dye have different fluorescent X-ray spectra, suggesting that the state of ligand of the aluminum ions is

44 Q) ..c ctS "- Q) Q) "- a. .._. Q) 2 1 0 0 -1 (.) CJ) -2 JOURNAL OF COSMETIC SCIENCE Figure 11. Sensory evaluation of "permanent" acid-type hair color. The evaluation was done by the panelists (34 females) who compared the "permanent" acid-type hair color with their daily-use conventional hair color. The y-axis represents the scores of a preferable number of panelists. The closed triangle("-), diamond ( ♦ ), and square (■) represent the users of an acid-type hair color for gray coverage, the users of oxidative hair color for gray coverage, and the users of a oxidative hair color for fashion shade, respectively. different among these samples. It is speculated that an aluminum ion can theoretically combine with three molecules of dye in Al-Dye or with the free carboxyl group of hair protein in Al-Hair. It is also speculated that one or two ligands of aluminum ion combine with hair protein and with dye in Al-Hair-Dye. At the beginning of this study, the authors thought that the dye-metal ion complex consists of dye and metal ion. But, by this study, it is speculated that the complex consists of dye, metal ion, and hair protein. The result described above indicates that the state of the bond between the aluminum ion and acid orange 7 was speculated to be a mainly ionic bond, though chelate interaction may contribute to the formation of the complex. The proposed model of the state of aluminum ion, dye, and hair protein is shown in Figure 12. We speculate that the aluminum ion may play the role of "glue" between hair protein and dye. Further work will be necessary to investigate (a) how many Al 3 + -related ligands create the bond and (b) how much of the conventional dyeing mechanism contributes to the dyeing system of the "permanent" acid-type hair color.