270
S. Kobatake
in the USA. Although there were inorganic glass light-controllable lenses that used
silver halide until then, it is the first in the world as plastic lenses. Spiropyran differs
in that photoisomers form zwitterions, whereas spirooxazine colors on neutral openring molecules. Various spirooxazines were studied by 1990, but they were not as
good as inorganic glass light-controllable lenses. After that, researches on dimming
materials using naphthopyran were conducted, and in 1999, light-controllable lenses
that developed naphthopyran to gray or brown developed on the market from each
company, which is now mainstream.
7.5 Fulgide
The history of fulgide is old, and it was first synthesized by Stobbe in 1905 (Stobbe
1911). The photochromic reaction belongs to a pericyclic reaction which isomerizes between hexatriene-cyclohexadiene, which is known as the 6π-electron cyclic
reaction. Fulgide developed by Stobbe is a thermally unstable T-type photochromic
compound, and side reactions from the colored state proceed (Fig. 7.8a). On the other
hand, P-type fulgide was synthesized by Heller in 1981 (Heller and Oliver 1981;
Darcy et al. 1981). In particular, the P-type fulgide is called furylfulgide because
of the presence of the furyl group as the aromatic ring (Fig. 7.8b). As a P-type
photochromic compound, it is historically a very important compound, which was
noticed in the 1980s. Many researches and developments have been made because
it can be applied to optical memories (Yokoyama 2000), but research on P-type
photochromic compounds gradually shifted to diarylethene, which was discovered
in the late 1980s, because fulgide has drawback of showing cis-trans isomerization
and low repeated durability.
colorless
colored
(a)
O
O
O
H 3 C
H 3 C
CH 3
O
O
O
CH 3
H 3 C
CH 3
O
O
O
CH 3
H 3 C
CH 3
H
(cis-trans isomerization)
(photochromic reaction)
(b)
O
O
O
H 3 C
H 3 C
CH 3
O
O
O
CH 3
H 3 C
CH 3
O
O
O
CH 3
H 3 C
CH 3
H 3 C
O
CH 3
H 3 C
O
CH 3
H 3 C
O
H 3 C
O
O
O
CH 3
CH 3
colorless
[O]
UV
UV
UV
Vis. or
colorless
colored
colorless
UV
UV
UV
Vis.
(cis-trans isomerization)
(photochromic reaction)
Δ
Fig. 7.8 Photochemical reactions of a T-type fulgide and b P-type furylfulgide
S. Kobatake
in the USA. Although there were inorganic glass light-controllable lenses that used
silver halide until then, it is the first in the world as plastic lenses. Spiropyran differs
in that photoisomers form zwitterions, whereas spirooxazine colors on neutral openring molecules. Various spirooxazines were studied by 1990, but they were not as
good as inorganic glass light-controllable lenses. After that, researches on dimming
materials using naphthopyran were conducted, and in 1999, light-controllable lenses
that developed naphthopyran to gray or brown developed on the market from each
company, which is now mainstream.
7.5 Fulgide
The history of fulgide is old, and it was first synthesized by Stobbe in 1905 (Stobbe
1911). The photochromic reaction belongs to a pericyclic reaction which isomerizes between hexatriene-cyclohexadiene, which is known as the 6π-electron cyclic
reaction. Fulgide developed by Stobbe is a thermally unstable T-type photochromic
compound, and side reactions from the colored state proceed (Fig. 7.8a). On the other
hand, P-type fulgide was synthesized by Heller in 1981 (Heller and Oliver 1981;
Darcy et al. 1981). In particular, the P-type fulgide is called furylfulgide because
of the presence of the furyl group as the aromatic ring (Fig. 7.8b). As a P-type
photochromic compound, it is historically a very important compound, which was
noticed in the 1980s. Many researches and developments have been made because
it can be applied to optical memories (Yokoyama 2000), but research on P-type
photochromic compounds gradually shifted to diarylethene, which was discovered
in the late 1980s, because fulgide has drawback of showing cis-trans isomerization
and low repeated durability.
colorless
colored
(a)
O
O
O
H 3 C
H 3 C
CH 3
O
O
O
CH 3
H 3 C
CH 3
O
O
O
CH 3
H 3 C
CH 3
H
(cis-trans isomerization)
(photochromic reaction)
(b)
O
O
O
H 3 C
H 3 C
CH 3
O
O
O
CH 3
H 3 C
CH 3
O
O
O
CH 3
H 3 C
CH 3
H 3 C
O
CH 3
H 3 C
O
CH 3
H 3 C
O
H 3 C
O
O
O
CH 3
CH 3
colorless
[O]
UV
UV
UV
Vis. or
colorless
colored
colorless
UV
UV
UV
Vis.
(cis-trans isomerization)
(photochromic reaction)
Δ
Fig. 7.8 Photochemical reactions of a T-type fulgide and b P-type furylfulgide