36 pH 2.30 3.00 3.50 3.80 4.10 JOURNAL OF COSMETIC SCIENCE Table V Rerationship Between pH and Color Brightness Effect LlEc.lyec.l hair 51.54 47.86 46.55 44.09 42.97 Error range (mean +/- S.D.) 50.94-52.16 47.80--47.91 46.08--47.02 43.44--44.74 42.25--43.69 Tresses were dyed by acid-type hair colors, which contained 1.6% glycolic acid, for 10 min. The pH levels were adjusted by sodium lactate. LlEd yed hair is the degree of color change before and after dyeing. The error range was caliculated by using the mean value and the standard deviation (S.D.). Dye-metal ion complex Figure 1. Microscopic photographs by polarizing microscope. The benzyl alcohol phase contains acid orange 7, and the water phase contains A1Cl3 ·6H20. When the benzyl alcohol phase and the water phase contact, there is a concentration gradient of benzyl alcohol and water in the boundary phase. The dissolved A1Cl5 ·6H 2 0 diffuses to the benzyl alcohol phase and forms a complex with acid orange 7 at a certain concentration of benzyl alcohol. In the area close to the boundary face between the water phase and the benzyl alcohol phase in the benzyl alcohol phase, formation of the deposit considered to be the dye-metal ion complex was observed. is shown in Table VI. The longevity is represented by the LiE value ratio immediately after dyeing and washing. Table VI indicates that A1Cl 3 ·6H 2 O is substantially superior to the other metal ions in producing color longevity. ZrC14 formed precipitation, and no experiment was done. The results indicate that a specific metal ion provides color longevity under the specific pH. It is suggested that the color longevity effect depends on the strength of the bond between acid dyes and metal ions under the specific pH. To determine the optimal concentration of AlC13 ·6H2O, various concentrations of the ion were investigated. Figure 4 shows that 0.5% of A1Cl 3 ·6H2O was the optimal concentration to obtain color brightness. Using AlC1 3 ·6H2O in this hair color formula is one of the key technologies of this study. PERFORMANCE OF "PERMANENT" ACID-TYPE HAIR COLOR (FIGURE 5) Based on the results described above, the formula of Sample C in Table I was selected

8 NOVEL ACID-TYPE HAIR COLOR TECHNOLOGY 5 3 2 1 Concentration of benzyl alcohol (%) 0 Precipitation of Al-Dye complex 37 Figure 2. Formation of dye-metal ion complex. The concentration of benzyl alcohol was adjusted to 8%, 5%, 3%, 2%, 1 % and 0% (from left to right) in the solution of A1Cl 3 ·6H20 (0.5%) and acid orange 7 (0.5%). A1Cl 3 ·6H20 and acid orange 7 form a light precipitate (Al-Dye complex) with benzyl alcohol at 2% or less. With more than 3% of benzyl alcohol, no complex was observed. 20 15 10 5 0 Concentration of ethyl alcohol (%) Benzyl alcohol phase Figure 3. Separation of the benzyl alcohol phase. The concentration of ethanol was adjusted to 20%, 15%, 10%, 5%, and 0% (from left to right) in the solution of A1Cl3 ·6H20 (0.5%), acid orange 7 (0.05%), and benzyl alcohol (8%). The benzyl alcohol phase was dissolved evenly in the system under the presence of ethyl alcohol greater than 20%. as the final formula of the "permanent" acid-type hair color. A1Cl 3 ·6H 2 0 (0.5%) and glycolic acid (1.6%) were formulated in an acid-type hair colorant that can give the best performance of color brightness and color longevity. The pH of "permanent" acid-type hair color was adjusted to 3.5 with sodium lactate. The tresses (2 g) were created with the hair colorant (10 g) obtained as described in the Methods section at 30°C for 30 min. The color brightness and color longevity effects were investigated as described in the method.