Page 553 - Book Hosokawa Nanoparticle Technology Handbook

25 DEVELOPMENT OF NEW COSMETICS BASED ON NANOPARTICLES APPLICATIONS
asperity such as skin wrinkles or skin pores.
Recently, by coating spherical-shaped particles on
plate particles, the powdery appearance is reduced
while increasing the adherence to skin and increasing
the defocusing effect. Even the PMMA nanoparticle
coated red interference color pearl material men-
tioned above is an example of this application, and in
this case the two technologies of color correction by
interference colors and shape correction by scattering
have been combined.
A functional optical particle with a fine feather-like
coating has also been developed by growing fiber
shaped crystals of zinc oxide in the nanolevel on the
surface of titanium dioxide coated mica (Fig. 25.6).
The diffused reflection characteristic is excellent due
to the fibers of zinc oxide, and a finish with a very
good natural translucent color is obtained. In addition,
zinc oxide has the effect of solidifying sebum cuta-
Figure 25.5
Electron microscope photograph of PMMA coated particle. neum, and has the feature that the makeup does not
come off with elapsing of time.
Even functional optical particles have been devel-
(2) Adapting to the environmental light oped that have the effect of hiding sagging skin. For
this, spherical moss shaped barium sulfate crystals of
While a skin with makeup applied to it looks whitish 1.0–1.5 m size are grown on the surface of red inter-
and has a floating appearance in sunlight outdoors, ference color titanium dioxide coated mica (Fig. 25.7).
but appears as a blurred yellow surface indoors in flu- Since light is incident from above on the forehead and
orescent light. In order to solve this problem, a pho- cheeks of the face, while the moss shaped crystals
tochromic powder was developed using 25 nm reflect light in a diffused manner, the titanium dioxide
titanium dioxide doped with iron [14]. These skin col- coated mica reflects light directly and generates a red
ored nanoparticles change to golden brown color color close to the skin color thereby rendering a natural
when exposed to ultraviolet light, and have not only skin color.
the effect of preventing whitishness outdoors, but also On the other hand, since the light is incident at an
have the effect of protecting against ultraviolet light. inclined angle on the shadow areas such as sagging
By further developing this type of photochromic
nature, color-rendering type pearl material has been parts, etc. of the skin, the moss shaped crystals reflect
in a diffused manner almost the entire incident light
developed [15] that is not only bright but also has thereby making the sagging parts of the skin not
changing color phase due to the effect of interference prominent. In a sensory test conducted with women in
with titanium dioxide coated mica. For example, by the age group of 40–50 years, the sags were decreased
coating iron doped titanium dioxide having pho- resulting in a lifted-up appearance of the face, and
tochromic action on the surface of titanium dioxide even in computer simulations, a result of the apparent
coated mica having red interference color, the mate- age being 10 years younger than the actual age was
rial will appear white when no ultraviolet light is inci- obtained.
dent on it, and when ultraviolet light is incident on it,
the outer layer changes to black and the interference (4) Skin care particles [16]
color becomes clear. Therefore, the particle changes While the major purpose of cosmetics is skin care, the
from white to red due to ultraviolet light. This color so-called “skin care particles” have been developed
rendering type red pearl material prevents the blurred that improve skin problems using the dermatology for
yellowish appearance under a fluorescent light with this purpose. This particle, which cares for the skin by
slight yellowishness by generating a red interference efficiently adsorbing and deactivating an enzyme
color. called “urokinase” that induces dry skin, has, as is
On the other hand, under a strong light source such
as sunlight, the overall reflectivity decreases and shown in Fig. 25.8, a coating of very thin silica of
2–3 nm on zinc oxide of about 30 nm size. This skin
exhibits superior color rendering that prevents care particle has a much higher skin care effect com-
whitishness. Because of this, it is possible to realize a pared to only zinc oxide or only silica independently.
beautiful makeup skin in any light environment.
The reason for this is considered to be that the amount
of urokinase that is pulled and adsorbed by electrical
(3) Shape correction charge has been increased by the silica coating on the
It is possible to use the defocusing effect by light zinc oxide, which itself has deactivating effect on
scattering of spherical particles in order to correct urokinase.

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