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.

NOVEL ACID-TYPE HAIR COLOR TECHNOLOGY Inside of hair� I z II z � Hair pro Carboxyl group of hair protein 45 Fi gu re 12. Proposed mechanism of the formation of dye complex with aluminum ion. The state of the aluminum ion in the hair was speculated by X-ray fluorescent spectrum. This model shows that one or two ligands of aluminum ion combine with hair protein and dye. COLOR BRIGHTNESS EFFECT AND COLOR LONGEVITY EFFECT The color brightness and the color longevity effects of the "permanent" acid hair color described in the result of the tress rest were superior to chose of the conventional oxidative hair color, especially in the fashion shade. And the panel test verified char the "permanent" acid-type hair color was comparable to the conventional oxidative hair color in terms of the color brightness effect and the color longevity effect. In Figure 7B, the "permanent" acid-type hair color seems to have more brightness than that of the con­ ventional hair color. Since a conventional oxidative hair color bleaches and dyes hair simultaneously, the color brightness effect may be reduced by the bleaching process (4). However, this "permanent" acid-type hair color can show rhe color brightness effect more effectively than char of a conventional oxidative hair color, because the "perma­ nent" acid-type hair color requires no bleaching process. The result of the sensory evaluation described above also suggests chat the "permanent" acid-type hair color was also preferable in terms of smoothness and shine. Acid-type hair color that was considered "semi-permanent hair color" was improved to perform at least at the same level as "permanent hair color" by the dye-metal ion complex technology. Furthermore, rhe "permanent" acid-type hair color (1) does not damage the hair as occurs after using the conventional oxidative hair color, (2) needs no patch rest for evaluating safety, and (3) causes no irritating smell such as that a\ways generated upon the use of a conventional hair color (9,13). These factors also give a considerable advantage to the "permanent" acid-type hair color.