U.S. patent application number 10/802770 was filed with the patent office on 2004-10-21 for photochromic compound, photochromic composition and photochromic display element using the same.
This patent application is currently assigned to YAMANASHI TLO CO., LTD.. Invention is credited to Kuwabara, Tetsuo, Mochizuka, Takuo.
Application Number | 20040210058 10/802770 |
Document ID | / |
Family ID | 32906084 |
Filed Date | 2004-10-21 |
United States Patent
Application |
20040210058 |
Kind Code |
A1 |
Kuwabara, Tetsuo ; et
al. |
October 21, 2004 |
Photochromic compound, photochromic composition and photochromic
display element using the same
Abstract
A photochromic display element comprising a photochromic layer
12 containing a 4,4'-bipyridine derivative as a photochromic
compound intervined between a transparent substrate 11 placed at a
front surface side and a substrate 13 placed at a rear surface
side. When a light containing an infrared light having a wavelength
of 830 nm is irradiated, the photochromic display element exhibits
the absorbance spectrum within a visible light region is reversibly
changed whereby the photochromic layer 12 is colored and
bleached.
Inventors: |
Kuwabara, Tetsuo; (Kofu-shi,
JP) ; Mochizuka, Takuo; (Fujieda-shi, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
YAMANASHI TLO CO., LTD.
4-3-11 Takeda
Kofu-shi
JP
400-8511
MURAKAMI CORPORATION
12-25, Miyamoto-cho
Shizuoka-shi
JP
422-8569
|
Family ID: |
32906084 |
Appl. No.: |
10/802770 |
Filed: |
March 18, 2004 |
Current U.S.
Class: |
546/257 |
Current CPC
Class: |
B60R 1/088 20130101;
C09K 9/02 20130101 |
Class at
Publication: |
546/257 |
International
Class: |
C07D 41/04; G02F
001/15 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 18, 2003 |
JP |
2003-114140 |
Claims
1. A photochromic compound which sensitizes a wavelength region of
not less than 700 nm or a specific infrared region to thereby
exhibit absorbency at a visible region.
2. The photochromic compound according to claim 1, which comprises
a 4,4'-bipyridine derivative represented by the following formula
(1): 5
3. The photochromic compound according to claim 1, which comprises
a 4,4'-bipyridine derivative represented by the following formula
(2): 6wherein R.sub.1, R.sub.2, R.sub.3, and R.sub.4 may be the
same or different from each other and each is a condensed aromatic
hydrocarbon or a derivative thereof.
4. The photochromic compound according to claim 1, which comprises
a 4,4'-bipyridine derivative represented by the following formula
(3): 7wherein R.sub.11 and R.sub.12, may be the same or different
from each other and each is an alkyl group having 1 to 10 carbon
atoms or a derivative thereof; and X.sup.- is selected from among
Cl.sup.-, BF.sub.4.sup.-, PF.sub.6.sup.-, AsF.sub.6.sup.-,
ClO.sub.4.sup.-, and NO.sub.3.sup.-.
5. A photochromic composition comprising a solution having the
photochromic compound according to claim 1 dissolved in one solvent
or a mixed solvent selected from among dimethylformamide (DMF),
dimethylacetamide, propylene carbonate, acetonitrile,
gamma-butyllactone, and butanol.
6. A photochromic film comprising a film having the photochromic
compound according to claim 1 dispersed therein.
7. A photochromic composition at least comprising the photochromic
compound according to claim 1 and a ultraviolet absorber, which
absorbs a ultraviolet light.
8. A functional element, comprising a photochromic which sensitizes
a wavelength of not less than 700 nm or a specific wavelength
within an infrared region, and which exhibits absorbance within a
visible region, and a light source which has an energy strength at
a wavelength region of not less than 700 nm or a specific
wavelength within an infrared region enough for being sensitized by
the photochromic compound, wherein a photochromic phenomenon, which
sensitizes a wavelength of not less than 700 nm or a specific
wavelength within an infrared region, and which exhibits absorbance
within a visible region, is utilized.
9. The functional element according to claim 8, which possesses a
ultraviolet shielding member, which shield an incident ultraviolet
light entering in the functional element.
10. The functional element according to claim 8, wherein said
photochromic layer containing the photochromic compound at least
comprises a ultraviolet absorber, which absorber a ultraviolet
light.
11. The functional element according to claim 8, which is a
photochromic display element.
12. The functional element according to claim 8, which is an
anti-glare mirror.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a photochromic compound, a
photochromic composition, and a photochromic functional element
using the same. More particularly, the present invention relates to
a photochromic functional element which can be used in an
anti-glare mirror for automobile or such.
[0003] 2. Description of the Related Arts
[0004] In the conventional automobile mirror, a technique has been
developed which imparts mirror to an anti-glare property in order
to improve visibility. The term "anti-glare property" used herein
is a property that sunshine in the daytime, a headlight of next car
in the nighttime and the like are reflected by an automobile mirror
to decrease dazzling felt by a driver or a fellow passenger. As a
mirror possessing such an anti-glare property, there is a mirror
which utilizes a color mirror (so-called blue mirror) having a
reflectance peak at a blue side (short wavelength side) and having
a blue color on the surface thereof.
[0005] The human visibility has a peak at a wavelength of
approximately 555 nm under a light condition, and yellowish green
color becomes clearly visible. As the surroundings become dark, the
peak of the visibility is gradually shifted toward a blue side, and
the peak wavelength is to be at approximately 505 nm. In the blue
mirror, the peak of reflectance characteristic exists in a range of
from 400 to 510 nm. Consequently, the image reflected by the blue
mirror has a peak deviating from the peak of the human visibility
in the daytime and, thus it looks slightly dark, preventing
dazzling of the sunshine. In the nighttime, the blue mirror has a
peak accorded with the peak of the human visibility and, thus, the
reflected image looks bright, excelling in visibility.
[0006] Typical examples of the conventional techniques which impart
anti-glare property to an automobile mirror include those which
apply a liquid crystal material, electrochromic material or such.
Amongst them, a reflectance-variable, automobile mirror utilizing
an electrochromic material will be described (See Japanese Patent
Laid-Open No. 09-120,088).
[0007] As shown in FIG. 8, in an automobile mirror 300 having a
reversibly variable transmittance, a prism-shaped mirror 180 is
laminated on a surface 131 of a device having a reversibly variable
transmittance by means of a transparent laminating material (layer
19). The prism-shaped mirror 180 comprises a prism-shaped piece 18
composed of an essentially transparent solid material (such as
glass or transparent plastic), and a layer 18A of a highly
reflective material (such as silver) adhered onto the surface of
the solid material by a technique common to the mirror processing
field, so that a light passing through the solid material and
arriving at the reflective material layer is reflected toward the
original direction via the solid material layer in a high ratio
(preferably at least approximately 80%). The highly reflective
layer 18A makes up reflective means for mirror.
[0008] The mirror comprises devices (electrochromic devices) having
a reversibly variable transmittance through which a light before
and after reflected from the reflecting means is passed. A wall
100, electrochromic elements 10 and 10A; a wall 130, electrochromic
elements 13 and 13A; a spacer 11; a solution space 12; and a line
or a strip 16 shown in FIG. 8 correspond to elements for the device
(not shown), and the line or strip shown in FIG. 8 extends to lead
lines of the device (not shown). The lead lines of the device (not
shown) are connected to an element for controlling power supply
(for example, switching means, means for controlling electric
potential between electrodes).
[0009] The automobile mirror having a reversibly variable
transmittance configured as described above is usually in a
bleached state, where a light entering from the wall 100 (which is
a solid material comprising glass or transparent plastic) is passed
through the interiors of the electrochromic elements 13 and 13A,
and is reflected at the reflective means 18A to be in a highly
reflective state, exhibiting a function as a mirror. At the time of
coloration, the light transmittance thereof is decreased so that
the device is to be in a low reflective state where the reflected
light is decreased, exhibiting an anti-glare function. In the case
where such electrochromic elements are utilized in antiglare
mirror, responding to the application of voltage and to making a
short circuit, mutual switching between the coloration at the time
of exhibiting anti-glare function and the bleaching at a usual mode
is carried out.
[0010] However, in the automobile mirror having a reversibly
variable transmittance utilizing such electrochromic elements, a
sensor, which can sensitize a relatively strong light such as
sunshine and a light from a head light of next car, a control
circuit which controls the actuation of the electrochromic elements
based on a signal produced from the sensor and other device should
be separately required, leading to a problem associated with
complicated configuration.
[0011] So, glazing has been suggested in Japanese Patent Laid-Open
No. 10-114007 in which a photochromic material, whose absorbance at
a visible light region is reversibly varied upon irradiation of a
light with a specific wavelength is applied to glazing so that the
glazing can become dark upon receiving a strong light such as
sunshine whereby the light reflectance thereof is decreased to
prevent a driver and others who get into a car from being dazzled
(Japanese Patent Laid-Open Publication No. 10-114007).
[0012] Examples of the photochromic materials applied to this
glazing include a material comprising a silver salt, particularly a
silver halide, as an active component dispersed in a glassy matrix
so that the active component such as the silver halide just
mentioned is reversibly transformed into a state of a metal bonded
body, and a material comprising an organic dyestuff (pigment) as an
active component dispersed in a polymeric matrix.
[0013] In the glazing utilizing the later material, the
photochromic material absorbs a light at a ultraviolet region to
thereby be reversibly isomerized, causing coloration or bleaching
in a reversible manner. Typical examples of the organic pigments
include compounds derived from spirooxazine and spiropyran.
[0014] However, in the glazing utilizing the photochromic material
described above, irradiation of ultraviolet contained in sunshine
is required for causing coloration and bleaching of the
photochromic material in a reversible manner. For this reason, even
if a light from a head light of an oncoming car enters into the
glazing, it has been difficult to colors the mirror enough for
preventing a driver or such from dazing due to its weak strength of
ultraviolet possessed by the automobile head light. Consequently,
in such a case, a light source, which can irradiate with the
photochromic materials a ultraviolet light at a strength sufficient
for reversibly changing coloration and bleaching, is required to be
separately placed. This poses a problem in terms of insufficient
practical use.
[0015] The present invention has been made in light of the above
problems, and a first object of the present invention is to provide
a photochromic material, which does not exhibit any photochromic
property against a light having a wavelength within a visible
region and which absorbs a given wavelength within a wavelength
region of not less than 700 nm (particularly infrared region) into
a visible region, and to provide a functional element using such a
phenomenon. Specifically, in the photochromic material and the
photochromic phenomenon according to the present invention, since
it sensitizes a specific wavelength within a wavelength region of
not less than 700 nm (particularly infrared region) to exhibit a
photochromic property, a light having a ultraviolet wavelength
region is not required for the exhibition of a photochromic
property.
[0016] A second object of the present invention is to provide a
functional element such as a photochromic display element
applicable to an automobile mirror having an anti-glare property
utilizing such a photochromic material and such a photochromic
phenomenon as described above.
SUMMARY OF THE INVENTION
[0017] We have examined various compounds each having an electron
donor and an electron acceptor within the molecule thereof, and
exhibiting a photochromic phenomenon upon being excited with a
specific light for the characteristics of their excitation
wavelength.
[0018] As a result, it has been clarified that when a light (such
as a xenon light source) having a prescribed energy at a specific
wavelength (for example, 830 nm) within an infrared region of not
less than 750 nm is irradiated to 4,4'-bipyridine derivative
represented by the following formula (1): 1
[0019] the absorbance of the 4,4'-bipyridine derivative at
approximately 610 nm as a center is increased and the
4,4'-bipyridine derivative is blue-colored, while it becomes
gradually a transparent color, when the irradiation of the
above-mentioned light is stopped or (the derivative is placed in a
dark portion to decrease the light absorbency thereof.
[0020] It is noted that the conventional photochromic compound is
required to be irradiated with a light having a ultraviolet light
region of from 380 nm to 400 nm to exhibit its photochromic
phenomenon as a rule.
[0021] With regard to compound analogue to the 4,4'-bipyridine
derivative represented by the formula (1) described above
(derivatives in which a benzene ring at the terminal of the
dendrimer construction adducted to the 4,4'-bipyridine is
substituted with other substituent (e.g., naphthalene)), Ghaddar et
al., of North Carolinian University have been reported the change
in the absorbance of various 4,4'-bipyridine derivatives at a
wavelength of 600 nm, which is within a visible light region,
excited by a ultraviolet light having a wavelength of 266 nm
(Journal of American Chemical Society, 2002, 124, P8285-8289).
However, this report shows the photochromic property within a
ultraviolet light region, and does not show any photochromic
property against irradiation of a light having a wavelength region
of not less than 700 nm (especially infrared region). Also, this
report does not disclose the 4,4'-bipyridine derivative represented
by the formula (1) described above, (derivatives whose the terminal
of the dendrimer construction adducted to the 4,4'-bipyridine is a
benzene ring).
[0022] In contrast, we have clarified for the first time that the
4,4'-bipyridine derivative represented by the formula (1)
sensitizes a specific wavelength of an infrared region to exhibit a
photochromic phenomenon. Also, by the use of the 4,4'-bipyridine
derivative having such a characteristic, a photochromic display
element has newly realized, which sensitizes a specific wavelength
of an infrared region contained in a head light utilizing a white
and bright xenon light source, which has recently appeared and
which has been used in a part of an automobile, to exhibit a blue
color. It has been found that a functional element utilizing a
photochromic phenomenon that sensitizes a wavelength of not less
than 700 nm or specific wavelength within a infrared region and
exhibits absorption in a visible wavelength region can be realized,
resulting in the present invention.
[0023] Such a phenomenon that a colored state and bleached state
are reversibly exhibited by irradiation of a specific wavelength
within an infrared region and non-irradiation is considered to
bring about a photochemical reaction of the 4,4'-bipyridine
derivative represented by the formula (1) where at the time of
coloration, it is reduced to be colored and at the time of
bleaching, it is in a stable construction due to the reversible
reaction.
[0024] It has been clarified that the photochromic material, which
attain these and other objects of the present invention may be made
up of any of substances having a construction or properties
analogies to that of the 4,4'-bipyridine derivative (biologen
derivative) represented by the formula (1). It has also been
clarified that depending upon the construction or such, these
substances each sensitizes a light having a prescribed energy at a
specific wavelength of not less than 700 nm, being not restricted
to an infrared region of not less than 750 nm, to exhibit a
photochromic phenomenon.
[0025] For example, a 4,4'-bipyridine derivative represented by the
following formula (2) in which the terminal benzene ring of the
dendrimer construction adducted to 4,4'-bipyridine is substituted
with other condensed ring (such as naphthalene) falls under the
photochromic material according to the present invention. 2
[0026] wherein R.sub.1, R.sub.2, R.sub.3, and R.sub.4 may be the
same or different from each other and each is a condensed aromatic
hydrocarbon or a derivative thereof.
[0027] Also, a 4,4'-bipyridine derivative represented by the
following formula (3) falls under the photochromic material
according to the present invention. 3
[0028] wherein R.sub.11 and R.sub.12, may be the same or different
from each other and each is an alkyl group having 1 to 10 carbon
atoms or a derivative thereof; and X.sup.- is selected from among
Cl.sup.-, BF.sub.4.sup.-, PF.sub.6.sup.-, AsF.sub.6.sup.-,
ClO.sub.4.sup.-, and NO.sub.3.sup.-.
[0029] The photochromic composition according to the present
invention comprises a solution having the photochromic compound
according to the present invention dissolved in one solvent or a
mixed solvent selected from among dimethylformamide (DMF),
dimethylacetamide, propylene carbonate, acetonitrile,
gamma-butyllactone, and butanol.
[0030] A photochromic film according to the present invention may
comprise a film having the photochromic compound according to the
present invention contained in a dissolved form.
[0031] By such a configuration, a photochromic composition having
the photochromic compound according to the present invention
dispersed in a prescribed solvent or a polymer film having the
photochromic compound according to the present invention dispersed
therein may be composed, which makes it easy to realize various
functional elements applied to the photochromic compound according
to the present invention such as display elements. What is more,
the use of the photochromic compound according to the present
invention meets a production of functional elements satisfying
various needs including its function, its performance, and a
cost.
[0032] It is noted that the photochromic film according to the
present invention may be formed, for example, by a process
comprising adding PVP (polyvinyl pyrolidone), polymethyl
metacrylate (PMMA) or such to be thicken, followed by film
formation. Also, it can be formed by a process comprising adding
the photochromic compound according to the present invention to a
composition whose monomer component is polymerizable by
vinyl-addition polymerization, ring-opening addition polymerization
or a combination thereof (such as epoxy, acrylic and urethane
monomers), followed by polymerization. Furthermore, it can be
formed by the addition of the photochromic compound according to
the present invention, utilizing any of the known resin formation
techniques such as ultraviolet curing and thermal curing. It should
be noted that kinds of the polymers making up a matrix for
compounding the photochromic compound according to the present
invention are not specifically restricted, and various polymers are
applicable as long as they can highly disperse the photochromic
compound according to the present invention and they are chemically
stable.
[0033] As described above, the functional element according to the
present invention comprises a photochromic which sensitizes a
wavelength of not less than 700 nm or a specific wavelength within
an infrared region, and which exhibits absorbance within a visible
region, and a light source which has an energy strength at a
wavelength region of not less than 700 nm or a specific wavelength
within an infrared region enough for being sensitized by the
photochromic compound, wherein a photochromic phenomenon, which
sensitizes a wavelength of not less than 700 nm or a specific
wavelength within an infrared region, and which exhibits absorbance
within a visible region, is utilized.
[0034] The functional element constructed as described above
basically possesses an effect that it sensitizes a light (for
example, a xenon light source) having a prescribed energy at a
wavelength region of not less than 700 nm, particularly at a
specific wavelength within an infrared region of not less than 750,
nm to exhibit a photochromic phenomenon. Specifically, a
photochromic display element can be realized, which reversibly
brings out coloration within a visible light region and bleaching
by irradiation of a light (for example, a xenon light source)
having a prescribed energy at a wavelength region of not less than
700 nm, particularly at a specific wavelength within an infrared
region of not less than 750 nm.
[0035] The functional element according to the present invention
may be constructed to possess a ultraviolet shielding member, which
shield an incident ultraviolet light entering in the functional
element.
[0036] In the functional element constructed as described above,
since a member for shielding an ultraviolet light is provided at a
side where a light enters in the photochromic layer, the
deterioration of the photochromic layer due to a ultraviolet light
can be prevented.
[0037] Also, since a member for shielding an ultraviolet light is
provided at a side where a light enters in the photochromic layer,
even if the photochromic layer is to sensitize a light within a
ultraviolet region to exhibit a photochromic phenomenon (for
example, in the case where the layer is composed of the
photochromic compound represented by the formula (1)), the
photochromic phenomenon exhibited by being sensitized to a light
within a ultraviolet region can be avoided.
[0038] The functional element according to the present invention
may be constructed such that the photochromic layer containing the
photochromic compound at least contains a ultraviolet absorber,
which absorbs a ultraviolet light.
[0039] Similarly, the photochromic composition and the photochromic
film according to the present invention may have a construction at
least comprising the photochromic compound and a ultraviolet
absorber, which absorbs a ultraviolet light.
[0040] In the functional element, the photochromic composition, and
the photochromic film according to the present invention, the
deterioration of the photochromic layer due to a ultraviolet light
can be prevented.
[0041] Also, even if the photochromic layer is to sensitize a light
within a ultraviolet region to exhibit a photochromic phenomenon
(for example, in the case where the layer is composed of the
photochromic compound represented by the formula (1)), the
photochromic phenomenon exhibited by being sensitized to a light
within a ultraviolet region can be avoided by the ultraviolet
absorber.
[0042] An example of the functional element includes a photochromic
display element.
[0043] As the display elements utilizing an emitter, various
industrial products such as automobile meters, and display portions
of cellular phones have been put into practical use. In these
display element, when a light source (such as a xenon light source)
having a prescribed energy at a specific wavelength region within a
wavelength region of not less than 700 nm is used as a light
source, and when the photochromic materials according to the
present invention, which can be sensitive to the light source, is
used, a display element can be made with no complicated control
circuit. Also, the display element according to the present
invention can be jointly used as a dimming element together with
any of the conventional techniques.
[0044] Especially, as in the display element, another example of
the functional element includes an anti-glare mirror.
[0045] Being applied to an automobile mirror, the present invention
can solve the problem in terms of complicated configuration due to
control circuits for controlling the actuation of an electrochromic
element, and the like as in an anti-glare mirror utilizing the
conventional electrochromic element. Also, in the present
invention, there is no need for separately providing a light source
for irradiating a ultraviolet light in order to exhibit a
photochromic phenomenon as in the conventional anti-glare mirror
utilizing a photochromic material. Consequently, an anti-glare
mirror, which can solely realize an anti-glare function without any
sensor and control circuit can be provided, having extremely high
practical application.
BRIEF DESCRIPTION OF THE DRAWINGS
[0046] FIG. 1 is a cross-sectional view schematically showing a
configuration of a photochromic display element according to a
first embodiment of the present invention.
[0047] FIG. 2 is a cross-sectional view schematically showing a
configuration of a photochromic display element according to a
second embodiment of the present invention.
[0048] FIG. 3 is a cross-sectional view schematically showing a
configuration of a photochromic display element according to a
third embodiment of the present invention.
[0049] FIG. 4 is a cross-sectional view schematically showing a
configuration of a photochromic display element according to a
fourth embodiment of the present invention.
[0050] FIG. 5 is a drawing for explaining a process for
synthesizing a photochromic compound according to the present
invention.
[0051] FIG. 6 is a graph showing spectral characteristics of a
light with which the photochromic compound according to the present
invention is irradiated.
[0052] FIG. 7 is a graph showing a change in absorbance when a
light having spectral characteristics shown in FIG. 6 with which
the photochromic compound according to the present invention is
irradiated.
[0053] FIG. 8 is a plane view schematically showing a configuration
of a reflectance-variable, automobile mirror, which is an
automobile mirror utilizing the conventional electrochromic
material.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0054] Embodiments of the present invention will now be described
by referring to the drawings.
[0055] (Photochromic Element According to First Embodiment)
[0056] FIG. 1 is a cross-sectional view schematically showing a
configuration of a photochromic display element 1 according to a
first embodiment of the present invention. As shown in FIG. 1, a
photochromic element 1 is composed of a transparent substrate 12
placed on a front surface side, and a substrate 14 placed on a rear
surface side between which a photochromic layer 13, which contains
a photochromic compound and which exhibits a photochromic
phenomenon, is intervened.
[0057] The transparent substrate 12 at the front surface side and
the substrate 14 at the rear surface side are both made of glass.
The photochromic layer 13 is composed, for example, of a
photochromic compound represented by the formula (1). At a front
surface side of the transparent substrate 12 at the front surface
side, a ultraviolet light shielding member 15 for shielding a
ultraviolet light is provided.
[0058] The present invention is not specifically restricted to the
substrates making up the substrate 12 and the substrate 14,
respectively, any of the conventional transparent substrates and
substrates can be applied as long as they have a transparency
and/or strength required in the present invention. For example,
glass such as a soda lime glass and a transparent resin such as an
acrylic plate may be used. Also, in the present invention, the
ultraviolet light shielding member 15 is not specifically
restricted, and any of the conventional ultraviolet light shielding
members is applicable as long as they can prevent the photochromic
compound according to the present invention from being deteriorated
through a ultraviolet light. For example, a ultraviolet cutting
film may be applied to the transparent substrate 12 via an
adhesive. Also, a thin film for shielding a ultraviolet light may
be formed onto the transparent substrate 12 by any of various
methods. Alternatively, the transparent substrate 12 itself may be
made of ultraviolet absorbing glass or colored glass.
[0059] The photochromic element 1 according to the first embodiment
of the present invention constructed as described above basically
possesses an effect that it sensitizes a light (for example, a
xenon light source) having a prescribed energy at a wavelength
region of not less than 700 nm or a specific wavelength within an
infrared region to exhibit a photochromic phenomenon. Specifically,
a photochromic display element can be realized, which reversibly
brings out coloration within a visible light region and bleaching
by irradiation of a light (for example, a xenon light source)
having a prescribed energy at a wavelength region of not less than
700 nm or a specific wavelength within an infrared region.
[0060] In the functional element constructed as described above,
since a member for shielding an ultraviolet light is provided at a
side where a light enters in the photochromic layer, the
deterioration of the photochromic layer due to a ultraviolet light
can be prevented.
[0061] Also, since a member for shielding an ultraviolet light is
provided at a side where a light enters in the photochromic layer,
even if the photochromic layer is to sensitize a light within a
ultraviolet region to exhibit a photochromic phenomenon (for
example, in the case where the layer is composed of the
photochromic compound represented by the formula (1)), the
photochromic phenomenon exhibited by being sensitized to a light
within a ultraviolet region can be avoided.
[0062] In the first embodiment described above, the photochromic
element 1 may be constructed so as to possess a light reflective
layer at a front surface of the substrate 14 placed at the rear
surface side (a surface at the side of the photochromic layer or a
surface at the opposite side). Also, the substrate 14 itself may be
composed of a light-reflective substrate comprising a
light-reflective material.
[0063] In such a configuration, a mirror serving as the function of
the photochromic element can be realized. This configuration is
suitably for an automobile anti-glare mirror.
[0064] In the present invention, materials for the light-reflective
layer and the light-reflective substrate are not specifically
restricted, and various materials having a light-reflective
function conventionally known are applicable, as long as they
exhibits the effects of the present invention. Amongst them, from
the viewpoints of a light-reflective function, chemical stability,
productivity, and a cost, the light-reflective layer and the
light-reflective substrate may be composed of a thin metal film
comprising Cr as a main component. Also, the production of the
light-reflective layer is not specifically restricted in the
present invention, and the light-reflective layer may be produced
by any of various known methods in which various kinds of known
light-reflective substances (such as Al, Cr, Ni, Ag, and Rh) may be
formed into a layer having a prescribed thickness including, but
being not restricted to, wet processes such as application methods,
plating methods, and electrophoresis methods as well as dry
processes such as deposition methods and sputtering methods. Also,
it is possible to obtain a given color and a given reflecting ratio
by a combination of an optical thin film with a reflective
metal.
[0065] (Photochromic Element According to Second Embodiment)
[0066] FIG. 2 is a cross-sectional view schematically showing a
configuration of a photochromic element 2 according to a second
embodiment of the present invention. As shown in FIG. 2, a
photochromic element 2 is composed of a transparent substrate 22
placed on a front surface side, and a substrate 24 placed on a rear
surface side between which a photochromic layer 23, which contains
a photochromic compound and which exhibits a photochromic
phenomenon, is intervened.
[0067] The transparent substrate 22 at the front surface side and
the substrate 24 at the rear surface side are both made of glass.
The photochromic layer 23 is composed, for example, of a
photochromic compound represented by the formula (1). An
ultraviolet absorber, which absorbs a ultraviolet light, is
compounded in the photochromic layer 23.
[0068] The ultraviolet absorber to be used in the present invention
are not specifically restricted, and various ultraviolet absorbers
known in the art may be applied as long as they can prevent the
photochromic compound according to the present invention from being
deteriorated. In the present invention, for example, a benzophenone
type ultraviolet absorber (2,4-dihydroxybenzophenone) or such
commercially available from Sumitomo Chemicals Co., Ltd., Dainippon
Ink and Chemicals Inc., or Dow Chemicals Inc. may be compounded in
a photochromic solution making up the photochromic layer or a
polymer film containing the photochromic compound, after confirming
that the ultraviolet absorber to be used can be well dissolved in a
solvent composition.
[0069] The photochromic element 2 according to the first embodiment
of the present invention constructed as described above basically
possesses an effect that it sensitizes a light (for example, a
xenon light source) having a prescribed energy at a wavelength
region of not less than 700 nm or a specific wavelength within an
infrared region to exhibit a photochromic phenomenon. Specifically,
a photochromic display element can be realized, which reversibly
brings out coloration within a visible light region and bleaching
by irradiation of a light (for example, a xenon light source)
having a prescribed energy at a wavelength region of not less than
700 nm or a specific wavelength within an infrared region.
[0070] The ultraviolet absorber in the photochromic element 2 can
prevent the photochromic layer or the composition from being
deteriorated through an ultraviolet light.
[0071] Also, even if the photochromic layer is to sensitize a light
within a ultraviolet region to exhibit a photochromic phenomenon
(for example, in the case where the layer is composed of the
photochromic compound represented by the formula (1)), the
photochromic phenomenon exhibited by being sensitized to a light
within a ultraviolet region can be avoided by means of the
ultraviolet absorber.
[0072] In the second embodiment described above, the photochromic
element 2 may be constructed so as to possess a light reflective
layer at a front surface of the substrate 24 placed at the rear
surface side (a surface at the side of the photochromic layer or a
surface at the opposite side).
[0073] In such a configuration, a mirror serving as the function of
the photochromic element can be realized. This configuration is
suitably for an automobile anti-glare mirror.
[0074] For example, as shown in FIG. 3 (third embodiment), a
photochromic display element 3 may be composed of a transparent
substrate 32 placed on a front surface side, and a light reflective
film 35 placed on a front surface side of a substrate 34 between
which a photochromic layer 33, which contains a photochromic
compound and which exhibits a photochromic phenomenon, is
intervened. The photochromic layer 33 has a ultraviolet absorber
which absorbs a ultraviolet light compounded therein. This
configuration is suitable as an automobile anti-glare mirror.
[0075] In the second embodiment described above, the substrate 24
placed at the rear surface side may be composed of a
light-reflective substrate.
[0076] In such a configuration, a mirror having the function of the
photochromic display element can also be realized.
[0077] For example, as shown in FIG. 4 (fourth embodiment), a
photochromic display element 4 may be composed of a transparent
substrate 42 placed on a front surface side, and a light-reflective
substrate 45 placed on a rear surface side between which a
photochromic layer 43, which contains a photochromic compound and
which exhibits a photochromic phenomenon, is intervened. The
photochromic layer 43 has a ultraviolet absorber which absorbs a
ultraviolet light compounded therein. This configuration is
suitable as an automobile anti-glare mirror.
[0078] In the present invention, materials for the light-reflective
substrate placed on the rear side are not specifically restricted,
and various materials having light-reflective characteristics,
which can exhibit the effects of the present invention are
applicable. Examples which can be used in the present invention
include substrates having a layer of any of various
light-reflective substances (such as Al, Cr, Ni, Ag, and Rh) formed
on the surface, substrates made of the light-reflective substances
just mentioned or aluminum alloy plates or stainless steel plates
having a prescribed glossiness.
EXAMPLES
[0079] Photochromic compounds and photochromic elements utilizing
the photochromic compounds according to the present invention will
now be specifically described.
[0080] 4,4'-Bipyridine derivative represented by the following
formula (1) was synthesized by a method shown below. 4
[0081] To a solution of a compound shown in FIG. 5 (1)
[3,5-dibenzyloxybenzyl bromide, alias: 3,5-bis(benzyloxy)benzyl
bromide] in dry acetonitrile, a solution of a compound shown in
FIG. 5 (2) [4,4'-bipyridine, alias: 4,4'-bipyridyl]] in dry
acetonitrile was added dropwise under a reflux condition over a
period of several ten minutes, and the mixture was refluxed over a
period of several days. After the reaction was completed, the
solution was allowed to cool down to a room temperature. This gave
a yellow crystal. This was washed with acetonitorile and with ether
and recrystallized from methanol to obtain 4,4'-bipyridine
derivative represented by the formula (1).
[0082] The resulting 4,4'-bipyridine derivative (12 mg) and 50 mg
of polyvinylpyrolidone ultraviolet absorber were weighted and they
were dissolved in 0.5 ml of DMF dimethylformamide) to prepare a
solution of 4,4'-bipyridine derivative in DMF.
[0083] Subsequently, the solution od 4,4'-bipyridine derivative in
DMF was applied to a soda lime glass, dried in vacuo at 60.degree.
C. to obtain an approximately 0.1 mm thick film. This film was then
sandwiched bween ultraviolet light shielding films (UV cutting
films available from Achilles Co., Ltd. under a trade name of
Achilles Vinylus), irradiated with a light from a xenon lamp having
spectral characteristics shown in FIG. 6, and was measured for
distribution of absorbance before and after the irradiation. As a
result, the absorbance of the film containing the 4,4'-bipyridine
derivative was changed as shown in FIG. 7.
[0084] As shown in FIG. 6, this xenon lamp has peak of emission
spectrum (bright line spectrum of xenon) at approximately 830 nm,
which is within a wavelength region of not less than 700 nm and
within an infrared region.
[0085] As shown in FIG. 7, it can be understood that in the film
containing the 4,4'-bipyridine derivative, the absorbance is
instantly increased at approximately 610 nm as a center upon the
irradiation with a light of the xenon lamp. Also, it can be
understood that as the time elapse after stopping the irradiation
with a light of the xenon lamp is increased from 5 minutes, to 20
minutes, to 30 minutes, and to 90 minutes, the absorbency at
approximately 610 nm as a center is gradually decreased, and is
returned to be its original state.
[0086] As described above, the 4,4'-bipyridine derivative
sensitizes a light containing an infrared of 830 nm whereby the
absorbance at approximately 610 nm as a center, which is within a
visible light region, is increased to have a blue color. In
addition, when the irradiation with a light containing the infrared
light is stopped (or is placed in a dark portion), the derivative
becomes colorless. Accordingly, the derivative has been found to
exhibit a photochromic phenomenon in which a colored state of a
blue color and colorless bleached state are reversibly brought
about.
[0087] While the present invention has been described by referring
to the embodiments, the present invention is not restricted
thereto, and various modification and alternation can be made
without departing from the scope and the sprits of the present
invention.
* * * * *