U.S. patent application number 15/634114 was filed with the patent office on 2017-10-12 for dibenzo[f,h]quinoxaline derivative, method of synthesizing the same, light-emitting element, light-emitting device, electronic appliance, and lighting device.
This patent application is currently assigned to Semiconductor Energy Laboratory Co., Ltd.. The applicant listed for this patent is Semiconductor Energy Laboratory Co., Ltd.. Invention is credited to Hideko INOUE, Yasushi KITANO, Tomohiro KUBOTA, Satoshi SEO, Hayato YAMAWAKI.
Application Number | 20170294594 15/634114 |
Document ID | / |
Family ID | 52668554 |
Filed Date | 2017-10-12 |
United States Patent
Application |
20170294594 |
Kind Code |
A1 |
INOUE; Hideko ; et
al. |
October 12, 2017 |
Dibenzo[f,h]Quinoxaline Derivative, Method of Synthesizing the
Same, Light-Emitting Element, Light-Emitting Device, Electronic
Appliance, and Lighting Device
Abstract
A dibenzo[f,h]quinoxaline derivative in which impurities are
reduced and a novel method of synthesizing the
dibenzo[f,h]quinoxaline derivative in which impurities are reduced
are provided. In addition, a light-emitting element, a
light-emitting device, an electronic appliance, or a lighting
device with high emission efficiency and high reliability in which
the dibenzo[f,h]quinoxaline derivative is used as an EL material is
provided. In the synthesis method, a
2-(chloroaryl)dibenzo[f,h]quinoxaline derivative is used as a
synthetic intermediate in a synthetic pathway so that an impurity
contained in a final product can be removed easily by purification
by sublimation.
Inventors: |
INOUE; Hideko; (Atsugi,
JP) ; KUBOTA; Tomohiro; (Isehara, JP) ; SEO;
Satoshi; (Sagamihara, JP) ; YAMAWAKI; Hayato;
(Atsugi, JP) ; KITANO; Yasushi; (Atsugi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Semiconductor Energy Laboratory Co., Ltd. |
Kanagawa-ken |
|
JP |
|
|
Assignee: |
Semiconductor Energy Laboratory
Co., Ltd.
Kanagawa-ken
JP
|
Family ID: |
52668554 |
Appl. No.: |
15/634114 |
Filed: |
June 27, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14484693 |
Sep 12, 2014 |
9695158 |
|
|
15634114 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 51/5012 20130101;
C09K 2211/1018 20130101; H01L 51/0072 20130101; C07D 409/10
20130101; H01L 51/0074 20130101; C09K 11/06 20130101 |
International
Class: |
H01L 51/00 20060101
H01L051/00; C09K 11/06 20060101 C09K011/06; C07D 409/10 20060101
C07D409/10 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 13, 2013 |
JP |
2013-190214 |
May 9, 2014 |
JP |
2014-097738 |
Claims
1. A light-emitting element comprising: a pair of electrodes; and
an EL layer between the pair of electrodes, wherein the EL layer
contains a dibenzo[f,h]quinoxaline derivative, wherein the
dibenzo[f,h]quinoxaline derivative includes hydrogen at a
3-position and an aryl group at a 2-position of a
dibenzo[f,h]quinoxaline skeleton, wherein the aryl group includes
at least one aryl group or heteroaryl group as a substituent, and
wherein the dibenzo[f,h]quinoxaline derivative contains 10 ppm or
less of chlorine.
2. A light-emitting element comprising: a pair of electrodes; and
an EL layer between the pair of electrodes, wherein the EL layer
contains a light-emitting layer, wherein the light-emitting layer
contains a dibenzo[f,h]quinoxaline derivative, wherein the
dibenzo[f,h]quinoxaline derivative includes hydrogen at a
3-position and an aryl group at a 2-position of a
dibenzo[f,h]quinoxaline skeleton, wherein the aryl group includes
at least one aryl group or heteroaryl group as a substituent, and
wherein the light-emitting layer contains 10 ppm or less of
chlorine.
3. A light-emitting element comprising: a pair of electrodes; and
an EL layer between the pair of electrodes, wherein the EL layer
contains a light-emitting layer, wherein the light-emitting layer
contains a dibenzo[f,h]quinoxaline derivative, wherein the
dibenzo[f,h]quinoxaline derivative includes hydrogen at a
3-position and an aryl group at a 2-position of a
dibenzo[f,h]quinoxaline skeleton, wherein the aryl group includes
at least one aryl group or heteroaryl group as a substituent, and
wherein the dibenzo[f,h]quinoxaline derivative contains 10 ppm or
less of chlorine.
4. The light-emitting element according to claim 1, wherein the
dibenzo[f,h]quinozaline derivative represented by General Formula
(G1), ##STR00036## wherein Ar.sup.1 represents a substituted or
unsubstituted arylene group having 6 to 13 carbon atoms, Ar.sup.2
represents a substituted or unsubstituted aryl group having 6 to 40
carbon atoms or a substituted or unsubstituted heteroaryl group
having 6 to 40 carbon atoms, R.sup.1 to R.sup.8 separately
represent hydrogen, an alkyl group having 1 to 6 carbon atoms, a
phenyl group, or a phenyl group having an alkyl group having 1 to 6
carbon atoms as a substituent, and n is any of 1 to 3.
5. The light-emitting element according to claim 2, wherein the
dibenzo[f,h]quinozaline derivative represented by General Formula
(G1), ##STR00037## wherein Ar.sup.1 represents a substituted or
unsubstituted arylene group having 6 to 13 carbon atoms, Ar.sup.2
represents a substituted or unsubstituted aryl group having 6 to 40
carbon atoms or a substituted or unsubstituted heteroaryl group
having 6 to 40 carbon atoms, R.sup.1 to R.sup.8 separately
represent hydrogen, an alkyl group having 1 to 6 carbon atoms, a
phenyl group, or a phenyl group having an alkyl group having 1 to 6
carbon atoms as a substituent, and n is any of 1 to 3.
6. The light-emitting element according to claim 3, wherein the
dibenzo[f,h]quinozaline derivative represented by General Formula
(G1), ##STR00038## wherein Ar.sup.1 represents a substituted or
unsubstituted arylene group having 6 to 13 carbon atoms, Ar.sup.2
represents a substituted or unsubstituted aryl group having 6 to 40
carbon atoms or a substituted or unsubstituted heteroaryl group
having 6 to 40 carbon atoms, R.sup.1 to R.sup.8 separately
represent hydrogen, an alkyl group having 1 to 6 carbon atoms, a
phenyl group, or a phenyl group having an alkyl group having 1 to 6
carbon atoms as a substituent, and n is any of 1 to 3.
7. The light-emitting element according to claim 4, wherein the
heteroaryl group contains one of a carbazole skeleton, a
dibenzothiophene skeleton and a dibenzofuran skeleton.
8. The light-emitting element according to claim 5, wherein the
heteroaryl group contains one of a carbazole skeleton, a
dibenzothiophene skeleton and a dibenzofuran skeleton.
9. The light-emitting element according to claim 6, wherein the
heteroaryl group contains one of a carbazole skeleton, a
dibenzothiophene skeleton and a dibenzofuran skeleton.
10. The light-emitting element according to claim 1, wherein the
dibenzo[f,h]quinozaline derivative represented by Formula (200).
##STR00039##
11. The light-emitting element according to claim 2, wherein the
dibenzo[f,h]quinozaline derivative represented by Formula (200).
##STR00040##
12. The light-emitting element according to claim 3, wherein the
dibenzo[f,h]quinozaline derivative represented by Formula (200).
##STR00041##
13. The light-emitting element according to claim 1, wherein the
light-emitting element keeps 90% or more of an initial luminance
after 200 hours under a current with a density of 10
mA/cm.sup.2.
14. The light-emitting element according to claim 2, wherein the
light-emitting element keeps 90% or more of an initial luminance
after 200 hours under a current with a density of 10
mA/cm.sup.2.
15. The light-emitting element according to claim 3, wherein the
light-emitting element keeps 90% or more of an initial luminance
after 200 hours under a current with a density of 10 mA/cm.sup.2.
Description
[0001] This application is a continuation of copending U.S.
application Ser. No. 14/484,693, filed on Sep. 12, 2014 which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0002] The present invention relates to an object, a method, or a
fabrication method. In addition, the present invention relates to a
process, a machine, manufacture, or a composition of matter. In
particular, one embodiment of the present invention relates to a
semiconductor device, a display device, a light-emitting device, a
driving method thereof, or a fabrication method thereof. In
particular, one embodiment of the present invention relates to a
dibenzo[f,h]quinoxaline derivative and a novel method of
synthesizing the same. In addition, one embodiment of the present
invention relates to a light-emitting element, a light-emitting
device, an electronic appliance, and a lighting device that include
the dibenzo[f,h]quinoxaline derivative.
2. Description of the Related Art
[0003] A light-emitting element with a structure in which an EL
layer is provided between a pair of electrodes is a self-luminous
light-emitting element in which carriers (holes and electrons) are
injected from the pair of electrodes by application of an electric
field and recombined in the EL layer to generate energy, so that
light is emitted.
[0004] An organic compound is mainly used as an EL material for an
EL layer in a light-emitting element and greatly contributes to an
improvement in the characteristics of the light-emitting element.
For this reason, a variety of novel organic compounds have been
developed (e.g., Patent Document 1).
REFERENCE
[0005] Patent Document 1: Japanese Published Patent Application No.
2011-201869
SUMMARY OF THE INVENTION
[0006] In a synthesis of an organic compound, a simple and
inexpensive method is preferably employed, but the important thing
is that contained substances (impurities) that cannot be removed
technically be as few as possible. As a method of synthesizing, for
example, a dibenzo[f,h]quinoxaline derivative, a synthesis method
in which a monochlorinated dibenzo[f,h]quinoxaline derivative is
used as a source material is known (e.g., Patent Document 1).
However, in this synthesis method, a dibenzo[f,h]quinoxaline
derivative having a plurality of chlorine atoms is likely to be
contained as an impurity. Such an impurity is difficult to remove
and might be mixed in a final product.
[0007] Note that in fabrication of a light-emitting element,
formation of an EL layer affects characteristics of the
light-emitting element and is thus very important. When an impurity
such as a chloride is contained in an EL material used for the EL
layer, the characteristics of the light-emitting element are
degraded.
[0008] In view of the above, one embodiment of the present
invention provides a dibenzo[f,h]quinoxaline derivative in which
impurities are reduced and a novel method of synthesizing the
dibenzo[f,h]quinoxaline derivative in which impurities are reduced.
Another embodiment of the present invention provides a
light-emitting element, a light-emitting device, an electronic
appliance, or a lighting device with high emission efficiency and
high reliability in which the dibenzo[f,h]quinoxaline derivative is
used as an EL material. Another embodiment of the present invention
provides a novel material. Another embodiment of the present
invention provides a novel light-emitting element and a novel
light-emitting device. Note that the descriptions of these objects
do not disturb the existence of other objects. In one embodiment of
the present invention, there is no need to achieve all the objects.
Other objects will be apparent from and can be derived from the
description of the specification, the drawings, the claims, and the
like.
[0009] One embodiment of the present invention is a method of
synthesizing a dibenzo[f,h]quinoxaline derivative that can reduce
impurities and a dibenzo[f,h]quinoxaline derivative in which
impurities are reduced. In the synthesis method, a
2-(chloroaryl)dibenzo[f,h]quinoxaline derivative is used as a
synthetic intermediate in a synthetic pathway so that an impurity
contained in a final product can be removed easily by purification
by sublimation.
[0010] Note that in the synthesis method, a
2-chlorodibenzo[f,h]quinoxaline derivative and a chloroaryl boronic
acid are coupled to obtain the
2-(chloroaryl)dibenzo[f,h]quinoxaline derivative as a synthetic
intermediate. At this time, an impurity in which a
dibenzo[f,h]quinoxaline skeleton of the
2-chlorodibenzo[f,h]quinoxaline derivative is substituted by a
plurality of chlorine atoms is contained. However, by a chemical
reaction, the plurality of chlorine atoms of the
dibenzo[f,h]quinoxaline skeleton are substituted by a chloroaryl
group or a hydrogen atom. Then, the
2-(chloroaryl)dibenzo[f,h]quinoxaline derivative obtained through
this reaction and an aryl boronic acid or a heteroaryl boronic acid
are coupled. In this manner, a dibenzo[f,h]quinoxaline derivative
in which impurities are reduced can be produced as a final product.
One embodiment of the present invention includes such a synthesis
method. In addition, one embodiment of the present invention
includes the 2-(chloroaryl)dibenzo[f,h]quinoxaline derivative
serving as a synthetic intermediate.
[0011] Thus, one embodiment of the present invention is a
dibenzo[f,h]quinoxaline derivative in which the 2-position of a
dibenzo[f,h]quinoxaline skeleton is bonded to an aryl group. The
aryl group has at least one aryl group or heteroaryl group as a
substituent. The chlorine content of the dibenzo[f,h]quinoxaline
derivative is 10 ppm or less.
[0012] Another embodiment of the present invention is a
dibenzo[f,h]quinoxaline derivative represented by General Formula
(G1) that has a chlorine content of 10 ppm or less.
##STR00001##
[0013] In General Formula (G1), Ar.sup.1 represents a substituted
or unsubstituted arylene group having 6 to 13 carbon atoms;
Ar.sup.2 represents a substituted or unsubstituted aryl group
having 6 to 40 carbon atoms or a substituted or unsubstituted
heteroaryl group having 6 to 40 carbon atoms; R.sup.1 to R.sup.8
separately represent hydrogen, an alkyl group having 1 to 6 carbon
atoms, a phenyl group, or a phenyl group having an alkyl group
having 1 to 6 carbon atoms as a substituent; and n is any of 1 to
3.
[0014] Another embodiment of the present invention is a
dibenzo[f,h]quinoxaline derivative that has a chlorine content of
10 ppm or less and obtained by coupling a
2-(chloroaryl)dibenzo[f,h]quinoxaline derivative and an aryl
boronic acid or a heteroaryl boronic acid. The
2-(chloroaryl)dibenzo[f,h]quinoxaline derivative is obtained by
coupling a 2-chlorodibenzo[f,h]quinoxaline derivative and a
chloroaryl boronic acid.
[0015] Another embodiment of the present invention is a method of
synthesizing a dibenzo[f,h]quinoxaline derivative that includes a
step of coupling a 2-(chloroaryl)dibenzo[f,h]quinoxaline derivative
and an aryl boronic acid or a heteroaryl boronic acid. The
2-(chloroaryl)dibenzo[f,h]quinoxaline derivative is obtained by
coupling a 2-chlorodibenzo[f,h]quinoxaline derivative and a
chloroaryl boronic acid.
[0016] Another embodiment of the present invention is a
light-emitting element that includes any of the above
dibenzo[f,h]quinoxaline derivatives.
[0017] Another embodiment of the present invention is a
light-emitting element that includes a dibenzo[f,h]quinoxaline
derivative obtained by the any of the above synthesis method.
[0018] Another embodiment of the present invention is a
light-emitting element in which an EL layer is provided between a
pair of electrodes. In the light-emitting element, the chlorine
content of a substance contained as a main component in a
light-emitting layer at least included in the EL layer is set to 10
ppm or less, so that the light-emitting element keeps 90% or more
of the initial luminance after 200 hours under current with a
density of 10 mA/cm.sup.2.
[0019] Another embodiment of the present invention is a
light-emitting element in which an EL layer is provided between a
pair of electrodes. In the light-emitting element, the chlorine
content of a dibenzo[f,h]quinoxaline derivative used as a main
component in a light-emitting layer at least included in the EL
layer is set to 10 ppm or less, so that the light-emitting element
keeps 90% or more of the initial luminance after 200 hours under
current with a density of 10 mA/cm.sup.2.
[0020] Another embodiment of the present invention is a
light-emitting element in which an EL layer is provided between a
pair of electrodes. In the light-emitting element, the chlorine
content of a dibenzo[f,h]quinoxaline derivative represented by
General Formula (G1) used as a main component in a light-emitting
layer at least included in the EL layer is set to 10 ppm or less,
so that the light-emitting element keeps 90% or more of the initial
luminance after 200 hours under current with a density of 10
mA/cm.sup.2.
##STR00002##
[0021] In General Formula (G1), Ar.sup.1 represents a substituted
or unsubstituted arylene group having 6 to 13 carbon atoms;
Ar.sup.2 represents a substituted or unsubstituted aryl group
having 6 to 40 carbon atoms or a substituted or unsubstituted
heteroaryl group having 6 to 40 carbon atoms; R.sup.1 to R.sup.8
separately represent hydrogen, an alkyl group having 1 to 6 carbon
atoms, a phenyl group, or a phenyl group having an alkyl group
having 1 to 6 carbon atoms as a substituent; and n is any of 1 to
3.
[0022] Another embodiment of the present invention is a
light-emitting device that includes any of the above-described
light-emitting elements.
[0023] Note that one embodiment of the present invention includes
not only a light-emitting device including the light-emitting
element but also an electronic appliance and a lighting device each
including the light-emitting device. The light-emitting device in
this specification refers to an image display device and a light
source (e.g., a lighting device). In addition, the light-emitting
device includes, in its category, all of a module in which a
light-emitting device is connected to a connector such as a
flexible printed circuit (FPC), a tape carrier package (TCP), a
module in which a printed wiring board is provided on the tip of a
TCP, and a module in which an integrated circuit (IC) is directly
mounted on a light-emitting element by a chip on glass (COG)
method.
[0024] In one embodiment of the present invention, a
dibenzo[f,h]quinoxaline derivative in which impurities are reduced
and a method of synthesizing the dibenzo[f,h]quinoxaline derivative
can be provided. In one embodiment of the present invention, a
light-emitting element, a light-emitting device, an electronic
appliance, or a lighting device with high emission efficiency and
high reliability in which the dibenzo[Pi]quinoxaline derivative is
used as an EL material can be provided. In one embodiment of the
present invention, a novel material can be provided. In one
embodiment of the present invention, a novel light-emitting element
or a novel light-emitting device can be provided. Note that the
description of these effects does not disturb the existence of
other effects. One embodiment of the present invention does not
necessarily achieve all the objects listed above. Other effects
will be apparent from and can be derived from the description of
the specification, the drawings, the claims, and the like.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 illustrates a structure of a light-emitting
element.
[0026] FIGS. 2A and 2B each illustrate a structure of a
light-emitting element.
[0027] FIGS. 3A and 3B illustrate a light-emitting device.
[0028] FIGS. 4A to 4D illustrate electronic appliances.
[0029] FIG. 5 illustrates lighting devices.
[0030] FIGS. 6A and 6B are .sup.1H-NMR charts of an intermediate
represented by Structural Formula (100).
[0031] FIGS. 7A and 7B are .sup.1H-NMR charts of an EL material
represented by Structural Formula (200).
[0032] FIG. 8 illustrates a structure of each of a light-emitting
element 1, a comparative light-emitting element 2, and a
comparative light-emitting element 3.
[0033] FIG. 9 shows current density-luminance characteristics of
the light-emitting element 1, the comparative light-emitting
element 2, and the comparative light-emitting element 3.
[0034] FIG. 10 shows voltage-luminance characteristics of the
light-emitting element 1, the comparative light-emitting element 2,
and the comparative light-emitting element 3.
[0035] FIG. 11 shows reliability of each of the light-emitting
element 1, the comparative light-emitting element 2, and the
comparative light-emitting element 3.
[0036] FIGS. 12A and 12B are .sup.1H-NMR charts of an intermediate
represented by Structural Formula (101).
[0037] FIG. 13 shows correlations between the chlorine contents of
EL materials and the reliability of light-emitting elements.
DETAILED DESCRIPTION OF THE INVENTION
[0038] Hereinafter, embodiments of the present invention will be
described with reference to the accompanying drawings. Note that
the present invention is not limited to the following description,
and various changes and modifications can be made without departing
from the spirit and scope of the present invention. Therefore, the
present invention should not be construed as being limited to the
description in the following embodiments.
Embodiment 1
[0039] In this embodiment, a method of synthesizing a
dibenzo[f,h]quinoxaline derivative of one embodiment of the present
invention is described. Note that the dibenzo[f,h]quinoxaline
derivative includes a 2-aryl dibenzo[f,h]quinoxaline derivative or
a 2-heteroaryl dibenzo[f,h]quinoxaline derivative.
[0040] One embodiment of the present invention is a method of
synthesizing a dibenzo[f,h]quinoxaline derivative in which
impurities are reduced. In this method,
2-(chloroaryl)dibenzo[f,h]quinoxaline derivative is used as a
synthetic intermediate in a synthetic pathway so that an impurity
contained in a final product can be removed easily by purification
by sublimation.
[0041] A 2-(chloroaryl)dibenzo[f,h]quinoxaline derivative
represented by General Formula (G0) can be synthesized by, for
example, Synthesis Scheme (A-1). In other words, as shown in
Synthesis Scheme (A-1), a 2-chlorodibenzo[f,h]quinoxaline
derivative (General Formula (A1)) is made to react with a
chloroaryl boronic acid (General Formula (A2)), whereby the
2-(chloroaryl)dibenzo[f,h]quinoxaline derivative is obtained.
##STR00003##
[0042] In Synthesis Scheme (A-1), Ar.sup.1 represents a substituted
or unsubstituted arylene group having 6 to 13 carbon atoms; R.sup.1
to R.sup.8 separately represent hydrogen, an alkyl group having 1
to 6 carbon atoms, a phenyl group, or a phenyl group having an
alkyl group having 1 to 6 carbon atoms as a substituent; n is any
of 1 to 3; and R.sup.9 represents hydrogen or an alkyl group. Note
that R.sup.9 may be bonded to form a ring structure. For example, a
dialkoxyboryl group such as a pinacolboryl group may be used.
[0043] In Synthesis Scheme (A-1), the
2-chlorodibenzo[f,h]quinoxaline derivative (General Formula (A1))
that is a source material is generally likely to contain a
chlorinated (monochlorinated or dichlorinated)
2-chlorodibenzo[f,h]quinoxaline derivative (e.g., General Formula
(A1')) as an impurity. Thus, a chlorinated (monochlorinated or
dichlorinated) 2-(chloroaryl)dibenzo[f,h]quinoxaline derivative
(i.e., an impurity represented by, for example, General Formula
(G0') in which the 2-(chloroaryl)dibenzo[f,h]quinoxaline derivative
represented by General Formula (G0) is partly substituted by a
plurality of chlorine atoms) can be obtained. However, in the
method of synthesizing a dibenzo[f,h]quinoxaline derivative
described in this embodiment, a dechlorination reaction in which a
chlorine atom is replaced by a hydrogen atom is likely to occur in
a chlorinated (monochlorinated or dichlorinated)
2-chlorodibenzo[f,h]quinoxaline derivative (i.e., an impurity
represented by, for example, General Formula (A1') in which the
2-chlorodibenzo[f,h]quinoxaline derivative represented by General
Formula (A1) is partly substituted by a plurality of chlorine
atoms) or a chlorinated (monochlorinated or dichlorinated)
2-(chloroaryl)dibenzo[f,h]quinoxaline derivative (i.e., an impurity
represented by, for example, General Formula (G0') in which the
2-(chloroaryl)dibenzo[f,h]quinoxaline derivative represented by
General Formula (G0) is partly substituted by a plurality of
chlorine atoms), which can exist in the reaction system, while
yield of an objective substance by the reaction is kept. Thus,
generation of an impurity such as the impurity represented by
General Formula (G0') can be suppressed. Note that the
dechlorination reaction can be accelerated by increasing the
solubility of the 2-(chloroaryl)dibenzo[f,h]quinoxaline derivative
represented by General Formula (G0) and decreasing the steric
hindrance of Ar.sup.1. Thus, Ar.sup.1 in Synthesis Scheme (A-1) is
preferably a substituted or unsubstituted phenyl group.
##STR00004##
[0044] Next, as shown in Synthesis Scheme (A-2), the
2-(chloroaryl)dibenzo[f,h]quinoxaline derivative (General Formula
(G0)) and an aryl boronic acid or a heteroaryl boronic acid
(General Formula (A3)) are coupled, whereby a
dibenzo[f,h]quinoxaline derivative (General Formula (G1)) that has
an aryl group or a heteroaryl group as a substituent is
synthesized.
##STR00005##
[0045] In Synthesis Scheme (A-2), Ar.sup.1 represents a substituted
or unsubstituted arylene group having 6 to 13 carbon atoms;
Ar.sup.2 represents a substituted or unsubstituted aryl group
having 6 to 40 carbon atoms or a substituted or unsubstituted
heteroaryl group having 6 to 40 carbon atoms; R.sup.1 to R.sup.8
separately represent hydrogen, an alkyl group having 1 to 6 carbon
atoms, a phenyl group, or a phenyl group having an alkyl group
having 1 to 6 carbon atoms as a substituent; n is any of 1 to 3;
and R.sup.9 represents hydrogen or an alkyl group. Note that
R.sup.9 may be bonded to form a ring structure. For example, a
dialkoxyboryl group such as a pinacolboryl group may be used.
[0046] As described above, the
2-(chloroaryl)dibenzo[f,h]quinoxaline derivative (General Formula
(G0)) synthesized by Synthesis Scheme (A-1) has a very small
content of impurities represented by, for example, General Formula
(G0') in which the 2-(chloroaryl)dibenzo[f,h]quinoxaline derivative
represented by General Formula (G0) is partly substituted by a
plurality of chlorine atoms. Consequently, in the
dibenzo[f,h]quinoxaline derivative (General Formula (G1))
synthesized by Synthesis Scheme (A-2), a chlorinated
dibenzo[f,h]quinoxaline derivative (General Formula (G1')) is
unlikely to be generated. This leads to a long lifetime of a
light-emitting element.
##STR00006##
[0047] In fact, as described in detail in Example, the
dibenzo[f,h]quinoxaline derivative (General Formula (G1))
synthesized by Synthesis Scheme (A-2) has a longer lifetime than a
dibenzo[f,h]quinoxaline derivative (General Formula (G1))
synthesized by Synthesis Scheme (B-1).
##STR00007##
[0048] In Synthesis Scheme (B-1), a 2-chlorodibenzo[f,h]quinoxaline
derivative (General Formula (A1)) and a boronic acid (General
Formula (B2)) having Ar.sup.1 and Ar.sup.2 which are an aryl group
or a heteroaryl group as substituents are coupled, whereby a
dibenzo[f,h]quinoxaline derivative (General Formula (G1)) is
synthesized. The symbols in Synthesis Scheme (B-1) are the same as
those in Synthesis Scheme (A-2).
[0049] In that case, the 2-chlorodibenzo[f,h]quinoxaline derivative
(General Formula (A1)) that is a source material is generally
likely to contain a chlorinated (monochlorinated or dichlorinated)
2-chlorodibenzo[f,h]quinoxaline derivative (General Formula (A1'))
as an impurity, which makes separation and purification
difficult.
##STR00008##
[0050] When a reaction shown in Synthesis Scheme (B-1) is performed
using the 2-chlorodibenzo[f,h]quinoxaline derivative (General
Formula (A1)) containing a chlorinated (monochlorinated or
dichlorinated) 2-chlorodibenzo[f,h]quinoxaline derivative (General
Formula (A1')), chlorine that is not terminated with a boronic acid
(General Formula (B2)) remains as shown in Synthesis Scheme (B-1').
Consequently, a chlorinated dibenzo[f,h]quinoxaline derivative,
which is represented by General Formula (G1'), is generated. This
has a significant adverse effect on the reliability of a
light-emitting element.
##STR00009##
[0051] Generation of the chlorinated dibenzo[f,h]quinoxaline
derivative (General Formula (G1')) can be suppressed and an adverse
effect attributed to the chlorinated dibenzo[f,h]quinoxaline
derivative (General Formula (G1')) can be avoided as long as it is
possible to terminate all chlorine atoms of the chlorinated
2-chlorodibenzo[f,h]quinoxaline derivative, which is represented by
General Formula (A1'), with a boronic acid (General Formula (B2))
in the reaction in Synthesis Scheme (B-1').
[0052] However, in the case where chlorine atoms are bonded to the
respective adjacent carbon atoms (specifically, the 2-position and
the 3-position of pyrazine) in the chlorinated (monochlorinated or
dichlorinated) 2-chlorodibenzo[f,h]quinoxaline derivative, which is
represented by General Formula (A1'), steric hindrance is large;
thus, it is difficult to terminate all of the chlorine atoms with
the aryl boronic acid (General Formula (B2)). In other words, in
the case where the chlorinated (monochlorinated or dichlorinated)
2-chlorodibenzo[f,h]quinoxaline derivative represented by General
Formula (A1') exists, it is difficult to suppress generation of the
chlorinated dibenzo[f,h]quinoxaline derivative, which is
represented by General Formula (G1').
[0053] In addition, the property of the chlorinated
dibenzo[f,h]quinoxaline derivative (General Formula (G1')) is
similar to that of the dibenzo[f,h]quinoxaline derivative (General
Formula (G1)); thus, the chlorinated dibenzo[f,h]quinoxaline
derivative is difficult to separate once generated. Particularly in
the case where R.sup.1 and R.sup.2 each represent a phenyl group
and the phenyl groups are bonded to each other at the ortho
position to form a dibenzo[f,h]quinoxaline ring, the solubility is
low and the separation is difficult.
[0054] Thus, the synthesis method of one embodiment of the present
invention that can suppress generation of the chlorinated
dibenzo[f,h]quinoxaline derivative (General Formula (G1')), which
is shown in Synthesis Scheme (A-1) and Synthesis Scheme (A-2),
enables synthesis of a dibenzo[f,h]quinoxaline derivative in which
impurities are reduced.
[0055] Note that the 2-(chloroaryl)dibenzo[f,h]quinoxaline
derivative (General Formula (G0)) is a useful novel compound and
one embodiment of the present invention. Since many kinds of the
compounds (General Formula (A1) and General Formula (A2)) used in
Synthesis Scheme (A-1) are commercially available or can be
synthesized, many kinds of the
2-(chloroaryl)dibenzo[f,h]quinoxaline derivative (General Formula
(G0)) can be synthesized by the above synthesis method. Shown below
are specific structural formulae of the
2-(chloroaryl)dibenzo[f,h]quinoxaline derivative represented by
General Formula (G0) (Structural Formulae (100) to (116)). Note
that one embodiment of the present invention is not limited
thereto.
##STR00010## ##STR00011## ##STR00012## ##STR00013##
##STR00014##
[0056] Shown below are specific structural formulae (Structural
Formulae (200) to (213)) of the dibenzo[f,h]quinoxaline derivative
(General Formula (G1)) that is obtained by using the
2-(chloroaryl)dibenzo[f,h]quinoxaline derivative (General Formula
(G0)) as an intermediate in the synthesis method of one embodiment
of the present invention. Note that one embodiment of the present
invention is not limited thereto.
##STR00015## ##STR00016## ##STR00017## ##STR00018##
##STR00019##
[0057] Note that the molecular weight of the
dibenzo[f,h]quinoxaline derivative (General Formula (G1)), which is
synthesized by the synthesis method of one embodiment of the
present invention, is preferably greater than or equal to 400 and
less than or equal to 2000. In the case where the molecular weight
is less than 400, film quality is poor because of crystallization
or the like in fabrication of a light-emitting element, which
adversely affects the reliability of the light-emitting element. In
the case where the molecular weight is greater than 2000, it is
difficult to perform purification by sublimation or vacuum
evaporation.
[0058] In the method of synthesizing the dibenzo[f,h]quinoxaline
derivative of one embodiment of the present invention, which is
described above, the 2-(chloroaryl)dibenzo[f,h]quinoxaline
derivative is generated as a synthetic intermediate so that an
impurity contained in a final product can be removed easily by
purification by sublimation.
[0059] In other words, a dibenzo[f,h]quinoxaline derivative
obtained by the synthesis method of one embodiment of the present
invention described above (i.e., a dibenzo[f,h]quinoxaline
derivative in which an aryl group is bonded at the 2-position of a
dibenzo[f,h]quinoxaline skeleton and the aryl group has at least
one aryl group or heteroaryl group as a substituent) can have a
chlorine content of 10 ppm or less.
[0060] Note that the synthesis method of one embodiment of the
present invention enables synthesis of a dibenzo[f,h]quinoxaline
derivative in which impurities are reduced; thus, by using the
synthesized dibenzo[f,h]quinoxaline derivative as an EL material, a
light-emitting element, a light-emitting device, an electronic
appliance, or a lighting device with high emission efficiency and
high reliability can be obtained. A light-emitting element, a
light-emitting device, an electronic appliance, or a lighting
device with low power consumption can also be obtained.
[0061] Note that the structure described in this embodiment can be
combined as appropriate with any of the structures described in the
other embodiments.
Embodiment 2
[0062] In this embodiment, a light-emitting element in which the
dibenzo[f,h]quinoxaline derivative obtained by the synthesis method
of one embodiment of the present invention can be used as an EL
material is described with reference to FIG. 1. In the
dibenzo[f,h]quinoxaline derivative, an aryl group is bonded at the
2-position of a dibenzo[f,h]quinoxaline skeleton and the aryl group
has at least one aryl group or heteroaryl group as a
substituent.
[0063] In a light-emitting element described in this embodiment, as
illustrated in FIG. 1, an EL layer 102 including a light-emitting
layer 113 is interposed between a pair of electrodes (a first
electrode (anode) 101 and a second electrode (cathode) 103), and
the EL layer 102 includes a hole-injection layer 111, a
hole-transport layer 112, an electron-transport layer 114, an
electron-injection layer 115, and the like in addition to the
light-emitting layer 113.
[0064] When voltage is applied to such a light-emitting element,
holes injected from the first electrode 101 side and electrons
injected from the second electrode 103 side recombine in the
light-emitting layer 113 to raise a light-emitting substance
contained in the light-emitting layer 113 to an excited state. The
light-emitting substance in the excited state emits light when it
returns to the ground state.
[0065] Although the dibenzo[f,h]quinoxaline derivative synthesized
by the synthesis method of one embodiment of the present invention
can be used for any one or more layers in the EL layer 102
described in this embodiment, the dibenzo[f,h]quinoxaline
derivative is preferably used for the light-emitting layer 113, the
hole-transport layer 112, or the electron-transport layer 114. In
other words, the dibenzo[f,h]quinoxaline derivative is used in part
of a light-emitting element having a structure described below.
[0066] In particular, by using the dibenzo[f,h]quinoxaline
derivative obtained by the synthesis method of one embodiment of
the present invention for a light-emitting layer, the chlorine
content of a substance contained as a main component in the
light-emitting layer can be 10 ppm or less. Consequently, it is
possible to fabricate a light-emitting element that keeps 90% or
more of the initial luminance after 200 hours under current with a
density of 10 mA/cm.sup.2.
[0067] In other words, the light-emitting element of one embodiment
of the present invention is a light-emitting element in which an EL
layer is provided between a pair of electrodes and the chlorine
content of a dibenzo[f,h]quinoxaline derivative used as a main
component in a light-emitting layer at least included in the EL
layer is set to 10 ppm or less, so that the light-emitting element
keeps 90% or more of the initial luminance after 200 hours under
current with a density of 10 mA/cm.sup.2.
[0068] In addition, the light-emitting element of one embodiment of
the present invention is a light-emitting element in which an EL
layer is provided between a pair of electrodes and the chlorine
content of a dibenzo[f,h]quinoxaline derivative represented by
General Formula G1 used as a main component in a light-emitting
layer at least included in the EL layer is set to 10 ppm or less,
so that the light-emitting element keeps 90% or more of the initial
luminance after 200 hours under current with a density of 10
mA/cm.sup.2.
[0069] A specific example in which the light-emitting element
described in this embodiment is fabricated is described below.
[0070] As the first electrode (anode) 101 and the second electrode
(cathode) 103, a metal, an alloy, an electrically conductive
compound, a mixture thereof, and the like can be used. Specific
examples are indium oxide-tin oxide (indium tin oxide (ITO)),
indium oxide-tin oxide containing silicon or silicon oxide, indium
oxide-zinc oxide (indium zinc oxide), indium oxide containing
tungsten oxide and zinc oxide, gold (Au), platinum (Pt), nickel
(Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe),
cobalt (Co), copper (Cu), palladium (Pd), and titanium (Ti). In
addition, an element belonging to Group 1 or Group 2 of the
periodic table, for example, an alkali metal such as lithium (Li)
or cesium (Cs), an alkaline earth metal such as calcium (Ca) or
strontium (Sr), magnesium (Mg), an alloy containing such an element
(MgAg, AlLi), a rare earth metal such as europium (Eu) or ytterbium
(Yb), an alloy containing such an element, graphene, and the like
can be used. The first electrode (anode) 101 and the second
electrode (cathode) 103 can be formed by, for example, a sputtering
method or an evaporation method (including a vacuum evaporation
method).
[0071] The hole-injection layer 111 injects holes into the
light-emitting layer 113 through the hole-transport layer 112 with
a high hole-transport property. The hole-injection layer 111
contains a substance with a high hole-transport property and an
acceptor substance, so that electrons are extracted from the
substance with a high hole-transport property by the acceptor
substance to generate holes and the holes are injected into the
light-emitting layer 113 through the hole-transport layer 112. The
hole-transport layer 112 is formed using a substance with a high
hole-transport property.
[0072] Specific examples of the substance with a hole-transport
property, which is used for the hole-injection layer 111 and the
hole-transport layer 112, include aromatic amine compounds such as
4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB
or a-NPD),
N,N-bis(3-methylphenyl)-N,N-diphenyl-[1,1'biphenyl]-4,4'-diamine
(abbreviation: TPD), 4,4',4''-tris(carbazol-9-yl)triphenylamine
(abbreviation: TCTA),
4,4',4''-tris(N,N-diphenylamino)triphenylamine (abbreviation:
TDATA),
4,4',4''-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine
(abbreviation: MTDATA), and
4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl
(abbreviation: BSPB);
3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole
(abbreviation: PCzPCA1); 3,
6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole
(abbreviation: PCzPCA2); and
3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole
(abbreviation: PCzPCN1). Other examples include carbazole
derivatives such as 4,4'-di(N-carbazolyl)biphenyl (abbreviation:
CBP), 1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation:
TCPB), and 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole
(abbreviation: CzPA). The substances listed here are mainly ones
that have a hole mobility of 10.sup.-6 cm.sup.2/Vs or higher. Note
that any substance other than the substances listed here may be
used as long as the hole-transport property is higher than the
electron-transport property.
[0073] A high molecular compound such as poly(N-vinylcarbazole)
(abbreviation: PVK), poly(4-vinyltriphenylamine) (abbreviation:
PVTPA),
poly[N-(4-{N-[4-(4-diphenylamino)phenyl]phenyl-N'-phenylamino}phenyl)meth-
acrylami de] (abbreviation: PTPDMA), or
poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine]
(abbreviation: Poly-TPD) can also be used.
[0074] Examples of the acceptor substance that is used for the
hole-injection layer 111 include transition metal oxides and oxides
of metals belonging to Groups 4 to 8 of the periodic table.
Specifically, molybdenum oxide is particularly preferable.
[0075] The light-emitting layer 113 is a layer containing a
light-emitting substance. The light-emitting layer 113 may contain
only a light-emitting substance; alternatively, an emission center
substance (guest material) may be dispersed in a host material in
the light-emitting layer 113. Note that a substance that has high
triplet excitation energy is preferably used as the host
material.
[0076] There is no particular limitation on the material that can
be used as the light-emitting substance and the emission center
substance in the light-emitting layer 113. A light-emitting
substance converting singlet excitation energy into luminescence
(hereinafter, referred to as fluorescent substance) or a
light-emitting substance converting triplet excitation energy into
luminescence (hereinafter, referred to as phosphorescent substance)
can be used. Examples of the light-emitting substance and the
emission center substance are given below.
[0077] As an example of the light-emitting substance converting
singlet excitation energy into luminescence, a substance emitting
fluorescence can be given.
[0078] Examples of the substance emitting fluorescence include
N,N'-bis[4-(9H-carbazol-9-yl)phenyl]-N,N'-diphenylstilbene-4,4'-diamine
(abbreviation: YGA2S),
4-(9H-carbazol-9-yl)-4'-(10-phenyl-9-anthryl)triphenylamine
(abbreviation: YGAPA),
4-(9H-carbazol-9-yl)-4'-(9,10-diphenyl-2-anthryl)triphenylamine
(abbreviation: 2YGAPPA),
N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine
(abbreviation: PCAPA), perylene, 2,5,8,11-tetra(tert-butyl)perylene
(abbreviation: TBP),
4-(10-phenyl-9-anthryl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine
(abbreviation: PCBAPA),
N,N''-(2-tert-butylanthracene-9,10-diyldi-4,1-phenylene)bis[N,N',N'-triph-
enyl-1,4-phenylenediamine] (abbreviation: DPABPA),
N,9-diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazol-3-amine
(abbreviation: 2PCAPPA),
N-[4-(9,10-diphenyl-2-anthryl)phenyl]-N,N,N-triphenyl-1,4-phenylenediamin-
e (abbreviation: 2DPAPPA),
N,N,N',N',N'',N'',N''',N'''-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetr-
aamine (abbreviation: DBC1), coumarin 30,
N-(9,10-diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazol-3-amine
(abbreviation: 2PCAPA),
N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazol-3-ami-
ne (abbreviation: 2PCABPhA),
N-(9,10-diphenyl-2-anthryl)-N,N',N'-triphenyl-1,4-phenylenediamine
(abbreviation: 2DPAPA),
N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthryl]-N,N',N'-triphenyl-1,4-phenylen-
ediamine (abbreviation: 2DPABPhA),
9,10-bis(1,1'-biphenyl-2-yl)-N-[4-(9H-carbazol-9-yl)phenyl]-N-phenylanthr-
acen-2-amine (abbreviation: 2YGABPhA),
N,N,9-triphenylanthracen-9-amine (abbreviation: DPhAPhA), coumarin
545T, N,N-diphenylquinacridone (abbreviation: DPQd), rubrene,
5,12-bis(1,1'-biphenyl-4-yl)-6,11-diphenyltetracene (abbreviation:
BPT),
2-(2-{2-[4-(dimethylamino)phenyl]ethenyl}-6-methyl-4H-pyran-4-ylidene)pro-
panedinitrile (abbreviation: DCM1),
2-{2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethen-
yl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCM2),
N,N',N'-tetrakis(4-methylphenyl)tetracene-5,11-diamine
(abbreviation: p-mPhTD),
7,14-diphenyl-N,N,N',N'-tetrakis(4-methylphenyl)acenaphtho[1,2--
a]fluoranthene-3,10-dia mine (abbreviation: p-mPhAFD),
{2-isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]-
quinolizin-9-yl) ethenyl]-4H-pyran-4-ylidene}propanedinitrile
(abbreviation: DCJTI),
{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij-
]quinolizin-9-yl) ethenyl]-4H-pyran-4-ylidene}propanedinitrile
(abbreviation: DCJTB), 2-(2,6-bis
{2-[4-(dimethylamino)phenyl]ethenyl}-4H-pyran-4-ylidene)propanedinitrile
(abbreviation: BisDCM), and
2-{2,6-bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benz-
o[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile
(abbreviation: BisDCJTM).
[0079] Examples of the light-emitting substance converting triplet
excitation energy into luminescence include a substance emitting
phosphorescence and a theimally activated delayed fluorescence
(TADF) material. Note that "delayed fluorescence" exhibited by the
TADF material refers to light emission having the same spectrum as
normal fluorescence and an extremely long lifetime. The lifetime is
10.sup.-6 seconds or longer, preferably 10.sup.-3 seconds or
longer.
[0080] Examples of the substance emitting phosphorescence include
bis{2-[3',5'-bis(trifluoromethyl)phenyl]pyridinato-N,C.sup.2'}iridium(III-
) picolinate (abbreviation: Ir(CF.sub.3ppy).sub.2(pic)),
bis[2-(4',6'-difluorophenyl)pyridinato-N,C.sup.2']iridium(III)
acetylacetonate (abbreviation: FIracac),
tris(2-phenylpyridinato)iridium(III) (abbreviation: Ir(ppy).sub.3),
bis(2-phenylpyridinato)iridium(III) acetylacetonate (abbreviation:
Ir(ppy).sub.2(acac)), tris(acetylacetonato)
(monophenanthroline)terbium(III) (abbreviation:
Tb(acac).sub.3(Phen)), bis(benzo[h]quinolinato)iridium(III)
acetylacetonate (abbreviation: Ir(bzq).sub.2(acac)),
bis(2,4-diphenyl-1,3-oxazolato-N,C.sup.2')iridium(III)
acetylacetonate (abbreviation: Ir(dpo).sub.2(acac)),
bis{2-[4'-(perfluorophenyl)phenyl]pyridinato-N,C.sup.2'}acetylacetonate
(abbreviation: Ir(p-PF-ph).sub.2(acac)),
bis(2-phenylbenzothiazolato-N,C.sup.2')iridium(III) acetylacetonate
(abbreviation: Ir(bt).sub.2(acac)),
bis[2-(2'-benzo[4,5-a]thienyl)pyridinato-N,C.sup.3']iridium(III)
acetylacetonate (abbreviation: Ir(btp).sub.2(acac)),
bis(1-phenylisoquinolinato-N,C.sup.2')iridium(III) acetylacetonate
(abbreviation: Ir(piq).sub.2(acac)),
(acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III)
(abbreviation: Ir(Fdpq).sub.2(acac)),
(acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III)
(abbreviation: [Ir(mppr-Me).sub.2(acac)]),
(acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III)
(abbreviation: [Ir(mppr-iPr).sub.2(acac)]),
(acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III)
(abbreviation: Ir(tppr).sub.2(acac)),
bis(2,3,5-triphenylpyrazinato) (dipivaloylmethanato)iridium(III)
(abbreviation: [Ir(tppr).sub.2(dpm)],
(acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III)
(abbreviation: [Ir(tBuppm).sub.2(acac)]),
(acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III)
(abbreviation: [Ir(dppm).sub.2(acac)]),
2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II)
(abbreviation: PtOEP), tris(1,3-diphenyl-1,3-propanedionato)
(monophenanthroline)europium(III) (abbreviation:
Eu(DBM).sub.3(Phen)), and
tris[1-(2-thenoyl)-3,3,3-trifluoroacetonato]
(monophenanthroline)europium(III) (abbreviation:
Eu(TTA).sub.3(Phen)).
[0081] Preferable examples of the substance (i.e., host material)
used for dispersing the light-emitting substance converting triplet
excitation energy into luminescence include compounds having an
arylamine skeleton, such as
2,3-bis(4-diphenylaminophenyl)quinoxaline (abbreviation: TPAQn) and
NPB, carbazole derivatives such as CBP and
4,4',4''-tris(carbazol-9-yl)triphenylamine (abbreviation: TCTA),
and metal complexes such as bis[2-(2-hydroxyphenyl)pyridinato]zinc
(abbreviation: Znpp.sub.2),
bis[2-(2-hydroxyphenyl)benzoxazolato]zinc (abbreviation:
Zn(BOX).sub.2),
bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum
(abbreviation: BAlq), and tris(8-quinolinolato)aluminum
(abbreviation: Alq.sub.3). Alternatively, a high molecular compound
such as PVK can be used.
[0082] Examples of the TADF material includes fullerene, a
derivative thereof, an acridine derivative such as proflavine, and
eosin. Other examples include a metal-containing porphyrin, such as
a porphyrin containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin
(Sn), platinum (Pt), indium (In), or palladium (Pd). Examples of
the metal-containing porphyrin include a protoporphyrin-tin
fluoride complex (SnF.sub.2(Proto IX)), a mesoporphyrin-tin
fluoride complex (SnF.sub.2(Meso IX)), a hematoporphyrin-tin
fluoride complex (SnF.sub.2(Hemato IX)), a coproporphyrin
tetramethyl ester-tin fluoride complex (SnF.sub.2(Copro III-4Me)),
an octaethylporphyrin-tin fluoride complex (SnF.sub.2(OEP)), an
etioporphyrin-tin fluoride complex (SnF.sub.2(Etio I)), and an
octaethylporphyrin-platinum chloride complex (PtCl.sub.2OEP).
Alternatively, a heterocyclic compound including a n-electron rich
heteroaromatic ring and a .pi.-electron deficient heteroaromatic
ring can be used, such as
2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-tri-
azine (PIC-TRZ). Note that a material in which the .pi.-electron
rich heteroaromatic ring is directly bonded to the .pi.-electron
deficient heteroaromatic ring is particularly preferably used
because both the donor property of the .pi.-electron rich
heteroaromatic ring and the acceptor property of the .pi.-electron
deficient heteroaromatic ring are increased and the energy
difference between the S.sub.1 level and the T.sub.1 level becomes
small.
[0083] When a host material and any of the light-emitting
substances converting singlet excitation energy into luminescence
or any of the light-emitting substances converting triplet
excitation energy into luminescence (i.e., a guest material) are
contained in the light-emitting layer 113, light emission with high
emission efficiency can be obtained from the light-emitting layer
113.
[0084] The electron-transport layer 114 is a layer containing a
substance with a high electron-transport property. For the
electron-transport layer 114, a metal complex such as Alq.sub.3,
tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq.sub.3),
bis(10-hydroxybenzo[h]quinolinato)beryllium (abbreviation:
BeBq.sub.2), BAlq, Zn(BOX).sub.2, or
bis[2-(2-hydroxyphenyl)benzothiazolato]zinc (abbreviation:
Zn(BTZ).sub.2) can be used. heteroaromatic compound such as
2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole
(abbreviation: PBD),
1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene
(abbreviation: OXD-7),
3-(4-tert-butylphenyl)-4-phenyl-5-(4-biphenylyl)-1,2,4-triazole
(abbreviation: TAZ),
3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole
(abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: Bphen),
bathocuproine (abbreviation: BCP), or
4,4'-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs) can
also be used. A high molecular compound such as
poly(2,5-pyridinediyl) (abbreviation: PPy),
poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)]
(abbreviation: PF-Py) or
poly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2'-bipyridine-6,6'-diyl)]
(abbreviation: PF-BPy) can also be used. The substances listed here
are mainly ones that have an electron mobility of 1.times.10.sup.-6
cm.sup.2/Vs or higher. Note that any substance other than the
substances listed here may be used for the electron-transport layer
114 as long as the electron-transport property is higher than the
hole-transport property.
[0085] The electron-transport layer 114 is not limited to a single
layer, but may be a stack of two or more layers each containing any
of the substances listed above.
[0086] The electron-injection layer 115 is a layer containing a
substance with a high electron-injection property. For the
electron-injection layer 115, an alkali metal, an alkaline earth
metal, or a compound thereof, such as lithium fluoride (LiF),
cesium fluoride (CsF), calcium fluoride (CaF.sub.2), or lithium
oxide (LiO.sub.x) can be used. A rare earth metal compound like
erbium fluoride (ErF.sub.3) can also be used. An electride may also
be used for the electron-injection layer 115. Examples of the
electride include a substance in which electrons are added at high
concentration to calcium oxide-aluminum oxide. Any of the
substances for forming the electron-transport layer 114, which are
given above, can be used.
[0087] A composite material in which an organic compound and an
electron donor (donor) are mixed may also be used for the
electron-injection layer 115. Such a composite material is
excellent in an electron-injection property and an
electron-transport property because electrons are generated in the
organic compound by the electron donor. In this case, the organic
compound is preferably a material that is excellent in transporting
the generated electrons. Specifically, for example, the substances
for forming the electron-transport layer 114 (e.g., a metal complex
or a heteroaromatic compound), which are given above, can be used.
As the electron donor, a substance showing an electron-donating
property with respect to the organic compound may be used. Specific
examples are an alkali metal, an alkaline earth metal, and a rare
earth metal are preferable, and lithium, cesium, magnesium,
calcium, erbium, and ytterbium. In addition, an alkali metal oxide
or an alkaline earth metal oxide is preferable, and lithium oxide,
calcium oxide, and barium oxide are given. A Lewis base such as
magnesium oxide can also be used. An organic compound such as
tetrathiafulvalene (abbreviation: FIF) can also be used.
[0088] Note that each of the above-described hole-injection layer
111, hole-transport layer 112, light-emitting layer 113,
electron-transport layer 114, and electron-injection layer 115 can
be formed by a method such as an evaporation method (e.g., a vacuum
evaporation method), an ink jet method, or a coating method.
[0089] In the above-described light-emitting element, current flows
because of a potential difference generated between the first
electrode 101 and the second electrode 103 and holes and electrons
are recombined in the EL layer 102, whereby light is emitted. Then,
the emitted light is extracted outside through one or both of the
first electrode 101 and the second electrode 103. Thus, one or both
of the first electrode 101 and the second electrode 103 are
electrodes having light-transmitting properties.
[0090] Note that the light-emitting element described in this
embodiment is an example of a light-emitting element in which the
dibenzo[f,h]quinoxaline derivative obtained by the synthesis method
of one embodiment of the present invention is used as an EL
material. As a light-emitting device including the above-described
light-emitting element, a passive matrix light-emitting device and
an active matrix light-emitting device can be fabricated. It is
also possible to fabricate a light-emitting device including a
light-emitting element having a microcavity structure. Each of the
light-emitting devices is one embodiment of the present
invention.
[0091] Note that there is no particular limitation on the structure
of the transistor (FET) in the case of fabricating the active
matrix light-emitting device. For example, a staggered FET or an
inverted staggered FET can be used as appropriate. A driver circuit
formed over a FET substrate may be formed of both an n-type FET and
a p-type FET or only either an n-type FET or a p-type FET.
Furthermore, there is no particular limitation on the crystallinity
of a semiconductor film used for the FET. For example, either an
amorphous semiconductor film or a crystalline semiconductor film
can be used. Examples of a semiconductor material include Group IV
semiconductors (e.g., silicon), Group III semiconductors (e.g.,
gallium), compound semiconductors (including oxide semiconductors),
and organic semiconductors.
[0092] Note that the structure described in this embodiment can be
combined as appropriate with any of the structures described in the
other embodiments.
Embodiment 3
[0093] Described in this embodiment is a case of fabricating a
light-emitting element (hereinafter, a tandem light-emitting
element) that has a structure in which a charge-generation layer is
provided between a plurality of EL layers and the
dibenzo[f,h]quinoxaline derivative obtained by the synthesis method
of one embodiment of the present invention is used as an EL
material in the EL layers.
[0094] A light-emitting element described in this embodiment is a
tandem light-emitting element including a plurality of EL layers (a
first EL layer 202(1) and a second EL layer 202(2)) between a pair
of electrodes (a first electrode 201 and a second electrode 204) as
illustrated in FIG. 2A.
[0095] In this embodiment, the first electrode 201 functions as an
anode, and the second electrode 204 functions as a cathode. Note
that the first electrode 201 and the second electrode 204 can have
structures similar to those described in Embodiment 2. In addition,
all or any of the plurality of EL layers (the first EL layer 202(1)
and the second EL layer 202(2)) may have structures similar to
those described in Embodiment 2. In other words, the structures of
the first EL layer 202(1) and the second EL layer 202(2) may be the
same or different from each other and can be similar to those of
the EL layers described in Embodiment 2.
[0096] In addition, a charge-generation layer 205 is provided
between the plurality of EL layers (the first EL layer 202(1) and
the second EL layer 202(2)). The charge-generation layer 205 has a
function of injecting electrons into one of the EL layers and
injecting holes into the other of the EL layers when voltage is
applied between the first electrode 201 and the second electrode
204. In this embodiment, when voltage is applied such that the
potential of the first electrode 201 is higher than that of the
second electrode 204, the charge-generation layer 205 injects
electrons into the first EL layer 202(1) and injects holes into the
second EL layer 202(2).
[0097] Note that in terms of light extraction efficiency, the
charge-generation layer 205 preferably has a property of
transmitting visible light (specifically, the charge-generation
layer (I) 205 has a visible light transmittance of 40% or more).
The charge-generation layer 205 functions even when it has lower
conductivity than the first electrode 201 or the second electrode
204.
[0098] The charge-generation layer 205 may have either a structure
in which an electron acceptor (acceptor) is added to an organic
compound having a high hole-transport property or a structure in
which an electron donor (donor) is added to an organic compound
having a high electron-transport property. Alternatively, both of
these structures may be stacked.
[0099] In the case of the structure in which an electron acceptor
is added to an organic compound having a high hole-transport
property, as the organic compound having a high hole-transport
property, for example, an aromatic amine compound such as NPB, TPD,
TDATA, MTDATA, or
4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl
(abbreviation: BSPB), or the like can be used. The substances
listed here are mainly ones that have a hole mobility of 10.sup.-6
cm.sup.2/Vs or higher. Note that any organic compound other than
the compounds listed here may be used as long as the hole-transport
property is higher than the electron-transport property.
[0100] As the electron acceptor,
7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation:
F.sub.4-TCNQ), chloranil, and the like can be given. Transition
metal oxides can also be given. Oxides of metals belonging to
Groups 4 to 8 of the periodic table can also be given.
Specifically, vanadium oxide, niobium oxide, tantalum oxide,
chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide,
and rhenium oxide are preferable because of their high
electron-accepting properties. Among these, molybdenum oxide is
especially preferable because it is stable in the air, has a low
hygroscopic property, and is easy to handle.
[0101] On the other hand, in the case of the structure in which an
electron donor is added to an organic compound having a high
electron-transport property, as the organic compound having a high
electron-transport property, for example, a metal complex having a
quinoline skeleton or a benzoquinoline skeleton, such as Alq,
Almq.sub.3, BeBq.sub.2, or BAlq, or the like can be used.
Alternatively, a metal complex having an oxazole-based ligand or a
thiazole-based ligand, such as Zn(BOX).sub.2 or Zn(BTZ).sub.2 can
be used. Alternatively, in addition to such a metal complex, PBD,
OXD-7, TAZ, Bphen, BCP, or the like can be used. The substances
listed here are mainly ones that have an electron mobility of
10.sup.-6 cm.sup.2/Vs or higher. Note that any organic compound
other than the compounds listed here may be used as long as the
electron-transport property is higher than the hole-transport
property.
[0102] As the electron donor, it is possible to use an alkali
metal, an alkaline earth metal, a rare earth metal, metals
belonging to Groups 2 and 13 of the periodic table, or an oxide or
carbonate thereof. Specifically, lithium (Li), cesium (Cs),
magnesium (Mg), calcium (Ca), ytterbium (Yb), indium (In), lithium
oxide, cesium carbonate, or the like is preferably used.
Alternatively, an organic compound such as tetrathianaphthacene may
be used as the electron donor.
[0103] Note that forming the charge-generation layer 205 by using
any of the above materials can suppress a drive voltage increase
caused by the stack of the EL layers.
[0104] Although the light-emitting element including two EL layers
is described in this embodiment, the present invention can be
similarly applied to a light-emitting element in which n EL layers
(202(1) to 202(n)) (n is three or more) are stacked as illustrated
in FIG. 2B. In the case where a plurality of EL layers are included
between a pair of electrodes as in the light-emitting element
according to this embodiment, by providing charge-generation layers
(205(1) to 205(n-1)) between the EL layers, light emission in a
high luminance region can be obtained with current density kept
low. Since the current density can be kept low, the element can
have a long lifetime. When the light-emitting element is applied to
lighting, voltage drop due to resistance of an electrode material
can be reduced, which results in homogeneous light emission in a
large area. In addition, a low-power-consumption light-emitting
device that can be driven at low voltage can be achieved.
[0105] When the EL layers have different emission colors, a desired
emission color can be obtained from the whole light-emitting
element. For example, in the light-emitting element having two EL
layers, when an emission color of the first EL layer and an
emission color of the second EL layer are made to be complementary
colors, a light-emitting element emitting white light as a whole
light-emitting element can also be obtained. Note that
"complementary colors" refer to colors that can produce an
achromatic color when mixed. In other words, emission of white
light can be obtained by mixture of light emitted from substances
whose emission colors are complementary colors.
[0106] The same can be applied to a light-emitting element having
three EL layers. For example, the light-emitting element as a whole
can provide white light emission when the emission color of the
first EL layer is red, the emission color of the second EL layer is
green, and the emission color of the third EL layer is blue.
[0107] Note that the structure described in this embodiment can be
combined as appropriate with any of the structures described in the
other embodiments.
Embodiment 4
[0108] Described in this embodiment is a light-emitting device that
includes a light-emitting element in which the
dibenzo[f,h]quinoxaline derivative obtained by the synthesis method
of one embodiment of the present invention is used as an EL
material in a light-emitting layer.
[0109] The light-emitting device may be either a passive matrix
type light-emitting device or an active matrix type light-emitting
device. Note that any of the light-emitting elements described in
the other embodiments can be used for the light-emitting device
described in this embodiment.
[0110] In this embodiment, an active matrix light-emitting device
is described with reference to FIGS. 3A and 3B.
[0111] Note that FIG. 3A is a top view illustrating a
light-emitting device and FIG. 3B is a cross-sectional view taken
along the chain line A-A' in FIG. 3A. The active matrix
light-emitting device according to this embodiment includes a pixel
portion 302 provided over an element substrate 301, a driver
circuit portion (a source line driver circuit) 303, and driver
circuit portions (gate line driver circuits) 304a and 304b. The
pixel portion 302, the driver circuit portion 303, and the driver
circuit portions 304a and 304b are sealed between the element
substrate 301 and a sealing substrate 306 with a sealant 305.
[0112] In addition, over the element substrate 301, a lead wiring
307 for connecting an external input terminal, through which a
signal (e.g., a video signal, a clock signal, a start signal, a
reset signal, or the like) or electric potential from the outside
is transmitted to the driver circuit portion 303 and the driver
circuit portions 304a and 304b, is provided. Here, an example is
described in which a flexible printed circuit (FPC) 308 is provided
as the external input terminal. Although only the FPC is
illustrated here, the FPC may be provided with a printed wiring
board (PWB). The light-emitting device in this specification
includes, in its category, not only the light-emitting device
itself but also the light-emitting device provided with the FPC or
the PWB.
[0113] Next, a cross-sectional structure is described with
reference to FIG. 3B. The driver circuit portion and the pixel
portion are formed over the element substrate 301; the driver
circuit portion 303 that is the source line driver circuit and the
pixel portion 302 are illustrated here.
[0114] The driver circuit portion 303 is an example in which an FET
309 and an FET 310 are combined. Note that the driver circuit
portion 303 may be formed with a circuit including transistors
having the same conductivity type (either an n-channel transistor
or a p-channel transistor) or a CMOS circuit including an n-channel
transistor and a p-channel transistor. Although this embodiment
shows a driver integrated type in which the driver circuit is
formed over the substrate, the driver circuit is not necessarily
formed over the substrate, and may be formed outside the
substrate.
[0115] The pixel portion 302 includes a plurality of pixels each of
which includes a switching FET 311, a current control FET 312, and
a first electrode (anode) 313 that is electrically connected to a
wiring (a source electrode or a drain electrode) of the current
control FET 312. Although the pixel portion 302 includes two FETs,
the switching FET 311 and the current control FET 312, in this
embodiment, one embodiment of the present invention is not limited
thereto. The pixel portion 302 may include, for example, three or
more FETs and a capacitor in combination.
[0116] As the FETs 309, 310, 311, and 312, for example, a staggered
transistor or an inverted staggered transistor can be used.
Examples of a semiconductor material that can be used for the FETs
309, 310, 311, and 312 include Group IV semiconductors (e.g.,
silicon), Group III semiconductors (e.g., gallium), compound
semiconductors, oxide semiconductors, and organic semiconductors.
In addition, there is no particular limitation on the crystallinity
of the semiconductor material, and an amorphous semiconductor or a
crystalline semiconductor can be used. In particular, an oxide
semiconductor is preferably used for the FETs 309, 310, 311, and
312. Examples of the oxide semiconductor include an In--Ga oxide
and an In-M-Zn oxide (M is Al, Ga, Y, Zr, La, Ce, or Nd). For
example, an oxide semiconductor that has an energy gap of 2 eV or
more, preferably 2.5 eV or more, further preferably 3 eV or more is
used for the FETs 309, 310, 311, and 312, so that the off-state
current of the transistors can be reduced.
[0117] In addition, an insulator 314 is formed to cover end
portions of the first electrode (anode) 313. In this embodiment,
the insulator 314 is formed using a positive photosensitive acrylic
resin. The first electrode 313 is used as an anode in this
embodiment.
[0118] The insulator 314 preferably has a curved surface with
curvature at an upper end portion or a lower end portion thereof.
This enables the coverage with a film to be formed over the
insulator 314 to be favorable. The insulator 314 can be formed
using, for example, either a negative photosensitive resin or a
positive photosensitive resin. The material of the insulator 314 is
not limited to an organic compound and an inorganic compound such
as silicon oxide, silicon oxynitride, or silicon nitride can also
be used.
[0119] An EL layer 315 and a second electrode (cathode) 316 are
stacked over the first electrode (anode) 313. In the EL layer 315,
at least a light-emitting layer is provided. In the EL layer 315, a
hole-injection layer, a hole-transport layer, an electron-transport
layer, an electron-injection layer, a charge-generation layer, and
the like can be provided as appropriate in addition to the
light-emitting layer.
[0120] A light-emitting element 317 is formed of a stack of the
first electrode (anode) 313, the EL layer 315, and the second
electrode (cathode) 316. For the first electrode (anode) 313, the
EL layer 315, and the second electrode (cathode) 316, any of the
materials given in Embodiment 2 can be used. Although not
illustrated, the second electrode (cathode) 316 is electrically
connected to the FPC 308 which is an external input terminal.
[0121] Although the cross-sectional view of FIG. 3B illustrates
only one light-emitting element 317, a plurality of light-emitting
elements are arranged in matrix in the pixel portion 302.
Light-emitting elements that emit light of three kinds of colors
(R, G, and B) are selectively formed in the pixel portion 302,
whereby a light-emitting device capable of full color display can
be obtained. In addition to the light-emitting elements that emit
light of three kinds of colors (R, G, and B), for example,
light-emitting elements that emit light of white (W), yellow (Y),
magenta (M), cyan (C), and the like may be formed. For example, the
light-emitting elements that emit light of a plurality of kinds of
colors are used in combination with the light-emitting elements
that emit light of three kinds of colors (R, G, and B), whereby
effects such as an improvement in color purity and a reduction in
power consumption can be obtained. Alternatively, a light-emitting
device that is capable of full color display may be fabricated by
combination with color filters.
[0122] Furthermore, the sealing substrate 306 is attached to the
element substrate 301 with the sealant 305, whereby a
light-emitting element 317 is provided in a space 318 surrounded by
the element substrate 301, the sealing substrate 306, and the
sealant 305. Note that the space 318 may be filled with an inert
gas (such as nitrogen and argon) or the sealant 305.
[0123] An epoxy-based resin or glass frit is preferably used for
the sealant 305. The material preferably allows as little moisture
and oxygen as possible to penetrate. As the sealing substrate 306,
a glass substrate, a quartz substrate, or a plastic substrate
formed of fiber-reinforced plastic (FRP), polyvinyl fluoride)
(PVF), polyester, acrylic, or the like can be used. In the case
where glass frit is used as the sealant, the element substrate 301
and the sealing substrate 306 are preferably glass substrates for
high adhesion
[0124] As described above, an active matrix light-emitting device
can be obtained.
[0125] Note that the structure described in this embodiment can be
combined as appropriate with any of the structures described in the
other embodiments.
Embodiment 5
[0126] In this embodiment, examples of an electronic appliance
manufactured using a light-emitting device in which the
dibenzo[f,h]quinoxaline derivative obtained by the synthesis method
of one embodiment of the present invention is used as an EL
material are described with reference to FIGS. 4A to 4D.
[0127] Examples of electronic appliances including the
light-emitting device include television devices (also referred to
as TV or television receivers), monitors for computers and the
like, cameras such as digital cameras and digital video cameras,
digital photo frames, cellular phones (also referred to as portable
telephone devices), portable game machines, portable information
terminals, audio playback devices, and large game machines such as
pachinko machines. Specific examples of the electronic appliances
are illustrated in FIGS. 4A to 4D.
[0128] FIG. 4A illustrates an example of a television device. In
the television device 7100, a display portion 7103 is incorporated
in a housing 7101. Images can be displayed by the display portion
7103, and the light-emitting device can be used for the display
portion 7103. In addition, here, the housing 7101 is supported by a
stand 7105.
[0129] The television device 7100 can be operated by an operation
switch of the housing 7101 or a separate remote controller 7110.
With operation keys 7109 of the remote controller 7110, channels
and volume can be controlled and images displayed on the display
portion 7103 can be controlled. Furthermore, the remote controller
7110 may be provided with a display portion 7107 for displaying
data output from the remote controller 7110.
[0130] Note that the television device 7100 is provided with a
receiver, a modem, and the like. With the use of the receiver,
general television broadcasts can be received. Moreover, when the
television device is connected to a communication network with or
without wires via the modem, one-way (from a sender to a receiver)
or two-way (between a sender and a receiver or between receivers)
information communication can be performed.
[0131] FIG. 4B illustrates a computer, which includes a main body
7201, a housing 7202, a display portion 7203, a keyboard 7204, an
external connection port 7205, a pointing device 7206, and the
like. Note that this computer can be manufactured using the
light-emitting device for the display portion 7203.
[0132] FIG. 4C illustrates a smart watch, which includes a housing
7302, a display panel 7304, operation buttons 7311 and 7312, a
connection terminal 7313, a band 7321, a clasp 7322, and the
like.
[0133] The display panel 7304 mounted in the housing 7302 serving
as a bezel includes a non-rectangular display region. The display
panel 7304 can display an icon 7305 indicating time, another icon
7306, and the like.
[0134] The smart watch illustrated in FIG. 4C can have a variety of
functions, for example, a function of displaying a variety of
information (e.g., a still image, a moving image, and a text image)
on a display portion, a touch panel function, a function of
displaying a calendar, date, time, and the like, a function of
controlling processing with a variety of software (programs), a
wireless communication function, a function of being connected to a
variety of computer networks with a wireless communication
function, a function of transmitting and receiving a variety of
data with a wireless communication function, and a function of
reading program or data stored in a recording medium and displaying
the program or data on a display portion.
[0135] The housing 7302 can include a speaker, a sensor (a sensor
having a function of measuring force, displacement, position,
speed, acceleration, angular velocity, rotational frequency,
distance, light, liquid, magnetism, temperature, chemical
substance, sound, time, hardness, electric field, current, voltage,
electric power, radiation, flow rate, humidity, gradient,
oscillation, odor, or infrared rays), a microphone, and the like.
Note that the smart watch can be manufactured using the
light-emitting device for the display panel 7304.
[0136] FIG. 4D illustrates an example of a mobile phone. A mobile
phone 7400 includes a housing 7401 provided with a display portion
7402, a microphone 7406, a speaker 7405, a camera 7407, an external
connection portion 7404, an operation button 7403, and the like. In
the case where the light-emitting element of one embodiment of the
present invention is formed over a flexible substrate, the
light-emitting element can be used for the display portion 7402
having a curved surface as illustrated in FIG. 4D.
[0137] When the display portion 7402 of the mobile phone 7400
illustrated in FIG. 4D is touched with a finger or the like, data
can be input to the mobile phone 7400. In addition, operations such
as making a call and composing an e-mail can be performed by touch
on the display portion 7402 with a finger or the like.
[0138] There are mainly three screen modes of the display portion
7402. The first mode is a display mode mainly for displaying an
image. The second mode is an input mode mainly for inputting data
such as characters. The third mode is a display-and-input mode in
which two modes of the display mode and the input mode are
combined.
[0139] For example, in the case of making a call or creating
e-mail, a character input mode mainly for inputting characters is
selected for the display portion 7402 so that characters displayed
on the screen can be input. In this case, it is preferable to
display a keyboard or number buttons on almost the entire screen of
the display portion 7402.
[0140] When a detection device including a sensor for detecting
inclination, such as a gyroscope or an acceleration sensor, is
provided inside the mobile phone 7400, display on the screen of the
display portion 7402 can be automatically changed by determining
the orientation of the mobile phone 7400 (whether the mobile phone
is placed horizontally or vertically for a landscape mode or a
portrait mode).
[0141] The screen modes are changed by touch on the display portion
7402 or operation with the button 7403 of the housing 7401. The
screen modes can be switched depending on the kind of images
displayed on the display portion 7402. For example, when a signal
of an image displayed on the display portion is a signal of moving
image data, the screen mode is switched to the display mode. When
the signal is a signal of text data, the screen mode is switched to
the input mode.
[0142] Moreover, in the input mode, if a signal detected by an
optical sensor in the display portion 7402 is detected and the
input by touch on the display portion 7402 is not performed for a
certain period, the screen mode may be controlled so as to be
changed from the input mode to the display mode.
[0143] The display portion 7402 may function as an image sensor.
For example, an image of a palm print, a fingerprint, or the like
is taken by touch on the display portion 7402 with the palm or the
finger, whereby personal authentication can be performed. In
addition, when a backlight or a sensing light source that emits
near-infrared light is provided in the display portion, an image of
a finger vein, a palm vein, or the like can be taken.
[0144] As described above, the electronic appliances can be
obtained using the light-emitting device that includes the
light-emitting element fabricated by the fabrication method of one
embodiment of the present invention. Note that the light-emitting
device can be used for electronic appliances in a variety of fields
without being limited to the electronic appliances described in
this embodiment.
[0145] Note that the structure described in this embodiment can be
combined as appropriate with any of the structures described in the
other embodiments.
Embodiment 6
[0146] In this embodiment, examples of a lighting device that
includes a light-emitting device containing the
dibenzo[f,h]quinoxaline derivative obtained by the synthesis method
of one embodiment of the present invention are described with
reference to FIG. 5.
[0147] FIG. 5 illustrates an example in which the light-emitting
device is used as an indoor lighting device 8001. Since the
light-emitting device can have a large area, it can be used for a
lighting device having a large area. In addition, a lighting device
8002 in which a light-emitting region has a curved surface can also
be obtained with the use of a housing with a curved surface. A
light-emitting element included in the light-emitting device
described in this embodiment is in a thin film form, which allows
the housing to be designed more freely. Thus, the lighting device
can be elaborately designed in a variety of ways. In addition, a
wall of the room may be provided with a large-sized lighting device
8003.
[0148] When the light-emitting device is used for a table by being
used as a surface of a table, a lighting device 8004 that has a
function as a table can be obtained. When the light-emitting device
is used as part of other furniture, a lighting device that
functions as the furniture can be obtained.
[0149] As described above, a variety of lighting devices that
include the light-emitting device can be obtained. Note that these
lighting devices are also embodiments of the present invention.
[0150] Note that the structure described in this embodiment can be
combined as appropriate with any of the structures described in the
other embodiments.
Example 1
Synthesis Example 1
[0151] In this example, a method of synthesizing
2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline
(abbreviation: 2mDBTBPDBq-II) (Structural Formula (200)) is
described as a synthesis method of one embodiment of the present
invention. Note that a structure of 2mDBTBPDBq-II is shown
below.
##STR00020##
Step 1: Synthesis of 2-(3-chlorophenyl)dibenzo[f,h]quinoxaline
[0152] First, 19.9 g (75 mmol) of 2-chlorodibenzo[f,h]quinoxaline
(Structural Formula (301)), 12.9 g (82.5 mmol) of 3-chlorophenyl
boronic acid, 31.1 g (225 mmol) of potassium carbonate, 380 mL of
toluene, 100 mL of ethanol, and 115 mL of water were put in a 1-L
three-neck flask, and the air in the flask was replaced with
nitrogen. This mixture was degassed by being stirred under reduced
pressure.
[0153] Then, 0.51 g (2.25 mmol) of palladium(II) acetate
(abbreviation: Pd(OAc).sub.2) and 1.53 g (4.5 mmol) of
tris(2-methylphenyl)phosphine were added to the mixture. This
mixture was stirred at approximately 80.degree. C. under a nitrogen
stream for 6 hours to precipitate a gray solid. The gray solid was
separated by suction filtration and washed with ethanol, water, and
ethanol in this order. The obtained solid was dried at 70.degree.
C. under reduced pressure to give 24.3 g of an objective substance
in a yield of 95%.
[0154] Synthesis Scheme (a-1) of Step 1 is shown below.
##STR00021##
[0155] Analysis results by nuclear magnetic resonance (.sup.1H-NMR)
spectroscopy of the gray solid obtained in Step 1 are described
below. FIGS. 6A and 6B are .sup.1H-NMR charts. FIG. 6B is a chart
where the range from 6.5 (ppm) to 10 (ppm) on the horizontal axis
(.delta.) in FIG. 6A is enlarged. The charts show that
2-(3-chlorophenyl)dibenzo[f,h]quinoxaline (Structural Formula
(100)) was obtained in Step 1.
[0156] .sup.1H NMR (CDCl.sub.3, 500 MHz): .delta. (ppm)=7.50-7.57
(m, 2H), 7.74-7.85 (m, 4H), 8.20 (td, J=7.5 Hz, 1.5 Hz, 1H), 8.38
(t, J=2.0 Hz, 1H), 8.66 (d, J=8.0 Hz, 2H), 9.23 (dd, J=8.0 Hz, 2.0
Hz, 1H), 9.36 (s, 1H), 9.40 (dd, J=8.5 Hz, 2.0 Hz, 1H).
Step 2: Synthesis of
2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline
(abbreviation: 2mDBTBPDBq-II)
[0157] Next, 23.9 g (70 mmol) of
2-(3-chlorophenyl)dibenzo[f,h]quinoxaline obtained in Step 1, 23.4
g (77 mmol) of 3-(dibenzothiophen-4-yl)phenylboronic acid, 44.6 g
(210 mmol) of tripotassium phosphate, 15.6 g (210 mmol) of
t-butanol, and 470 mL of dioxane were put in a 1-L three-neck
flask, and the air in the flask was replaced with nitrogen. This
mixture was degassed by being stirred under reduced pressure.
[0158] Then, 157 mg (0.70 mmol) of palladium(II) acetate, 502 mg
(1.4 mmol) of di(1-adamantyl)-n-butylphosphine (abbreviation:
cataCXium.RTM.), and 2-(3-chlorophenyl)dibenzo[f,h]quinoxaline were
added to the mixture. This mixture was stirred at approximately
100.degree. C. under a nitrogen stream for 14 hours. After
reaction, a precipitated gray solid was separated by suction
filtration to give a solid. The solid was washed with ethanol,
water, ethanol, and toluene in this order. The obtained solid was
dried at 100.degree. C. under reduced pressure to give 37.6 g of an
objective substance in a yield of 95%.
[0159] By a train sublimation method, 35 g of the objective solid,
which was the objective substance, was purified. In the
purification by sublimation, the objective substance was heated at
325.degree. C. under a pressure of 2.7 Pa. After cooling, 29.6 g of
a pale yellow solid was obtained in a yield of 84%. Synthesis
Scheme (a-2) of Step 2 is shown below.
##STR00022##
[0160] Analysis results by nuclear magnetic resonance (.sup.1H-NMR)
spectroscopy of the pale yellow solid obtained in Step 2 are
described below. FIGS. 7A and 7B are .sup.1H-NMR charts. FIG. 7B is
a chart where the range from 6.5 (ppm) to 10 (ppm) on the
horizontal axis (.delta.) in FIG. 7A is enlarged. The charts show
that
2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline
(abbreviation: 2mDBTBPDBq-II) (Structural Formula (200)) was
obtained in Step 1.
[0161] .sup.1H NMR (CDCl.sub.3, 500 MHz): .delta. (ppm)=7.44-7.52
(m, 2H), 7.62 (d, J=5.0 Hz, 2H), 7.68-7.75 (m, 3H), 7.75-7.89 (m,
7H), 8.18 (s, 1H), 8.19-8.24 (m, 2H), 8.35 (d, J=7.0 Hz, 1H), 8.67
(d, J=8.0 Hz, 2H), 8.70 (s, 1H), 9.26 (d, J=7.5 Hz, 1H), 9.45 (d, J
8.0 Hz, 1H), 9.48 (s, 1H).
[0162] Here, the purity of 2-chlorodibenzo[f,h]quinoxaline
(Structural Formula (301)), which was used as a source material in
Step 1, was analyzed by ACQUITY Ultra Performance LC (hereinafter,
ACQUITY UPLC). According to the analysis, in addition to
2-chlorodibenzo[f,h]quinoxaline (Structural Formula (301)),
substances with m/z (i.e., mass-to-charge ratio) of 231 and 299
were contained as impurities with area ratios of 0.3% and 0.8%,
respectively, and the purity was calculated to be 98.7%. The
impurities with m/z of 231 and 299 are presumed to be
dibenzo[f,h]quinoxaline (Structural Formula (302)) and a
monochlorinated 2-chlorodibenzo[f,h]quinoxaline (Structural Formula
(303)) shown below, respectively.
##STR00023##
[0163] The above results indicate that the
2-chlorodibenzo[f,h]quinoxaline derivative (General Formula (A1)),
which was used as a source material in a synthesis method
(Synthesis Scheme (A-1)) in Embodiment 1, generally contains a
chlorinated (monochlorinated or dichlorinated)
2-chlorodibenzo[f,h]quinoxaline derivative represented by General
Formula (A1') as an impurity.
##STR00024##
[0164] Note that in General Formula (A1'), R.sup.1 to R.sup.8
separately represent hydrogen, an alkyl group having 1 to 6 carbon
atoms, a phenyl group, or a phenyl group having an alkyl group
having 1 to 6 carbon atoms as a substituent.
[0165] Next, the purity of
2-(3-chlorophenyl)dibenzo[f,h]quinoxaline (Structural Formula
(100)), which was the compound (i.e., intermediate) obtained in
Step 1, was analyzed similarly. According to the analysis, in
addition to 2-(3-chlorophenyl)dibenzo quinoxaline (Structural
Formula (100)), substances with m/z (i.e., mass-to-charge ratio) of
265, 307, 417, and 493 were contained as impurities with area
ratios of 0.1%, 0.3%, 0.3%, and 0.1%, respectively, and the purity
was calculated to be 99.2%. The impurities with in/z of 265, 307,
417, and 493 are presumed to be 2-chlorodibenzo[f,h]quinoxaline,
2-phenyldibenzo[f,h]quinoxaline,
2-[3-(3'-chlorophenyl)-phenyl]dibenzo[f,h]quinoxaline, and
2-{3-[3'-(3''-chlorophenyl)-phenyl]-phenyl}dibenzo[f,h]quinoxaline,
respectively. Note that these impurities are consumed in subsequent
reaction or can be removed by purification. In addition, the
results of the purity analysis indicate that an impurity (i.e., a
chloride (a monochloride or a dichloride)) originating from the
monochlorinated 2-chlorodibenzo[f,h]quinoxaline (Structural Formula
(303)), which is an impurity that can be contained in the source
material, i.e., 2-chlorodibenzo[f,h]quinoxaline (Structural Formula
(301)), is hardly detected in the synthesis method.
[0166] Even when the 2-chlorodibenzo[f,h]quinoxaline derivative
(General Formula (A1)), which is used as a source material,
contains a chlorinated (monochlorinated or dichlorinated)
2-chlorodibenzo[f,h]quinoxaline derivative represented by General
Formula (A1') as an impurity in the synthesis method (Synthesis
Scheme (A-1)) described in Embodiment 1, a substance produced in
addition to an intermediate is only a monochloride that can be
removed; thus, an objective substance can be purified easily.
[0167] The chlorine content of 2mDBTBPDBq-II, which is an objective
substance in this embodiment, was measured by combustion-ion
chromatography. According to the measurement, the chlorine content
of 2mDBTBPDBq-II was 1 ppm (.mu.g/g), which was very small.
Example 2
[0168] In this example, a light-emitting element 1 of one
embodiment of the present invention, and a comparative
light-emitting element 2 and a comparative light-emitting element
3, which were fabricated for comparison, are described with
reference to FIG. 8. Chemical formulae of materials used in this
example are shown below.
##STR00025## ##STR00026##
<<Fabrication of Light-Emitting Element 1, Comparative
Light-Emitting Element 2, and Comparative Light-Emitting Element
3>>
[0169] First, indium tin oxide containing silicon oxide (ITSO) was
deposited over a glass substrate 800 by a sputtering method,
whereby a first electrode 801 functioning as an anode was formed.
The thickness was 110 nm and the electrode area was 2 mm.times.2
mm.
[0170] Next, as pretreatment for fabricating the light-emitting
element 1, the comparative light-emitting element 2, and the
comparative light-emitting element 3 over the substrate 800, UV
ozone treatment was performed for 370 seconds after washing of a
surface of the substrate with water and baking that was performed
at 200.degree. C. for 1 hour
[0171] After that, the substrate was transferred into a vacuum
evaporation apparatus where the pressure had been reduced to
approximately 10.sup.-4 Pa, and subjected to vacuum baking at
170.degree. C. for 30 minutes in a heating chamber of the vacuum
evaporation apparatus, and then the substrate 800 was cooled down
for approximately 30 minutes.
[0172] Next, the substrate 800 was fixed to a holder provided in
the vacuum evaporation apparatus so that a surface of the substrate
1100 over which the first electrode 801 was formed faced downward.
In this example, a case is described in which a hole-injection
layer 811, a hole-transport layer 812, a light-emitting layer 813,
an electron-transport layer 814, and an electron-injection layer
815, which are included in an EL layer 802, are sequentially formed
by a vacuum evaporation method.
[0173] After reducing the pressure in the vacuum evaporation
apparatus to 10.sup.-4 Pa, 1,3,5-tri(dibenzothiophen-4-yl)benzene
(abbreviation: DBT3P-II) and molybdenum(VI) oxide were deposited by
co-evaporation so that the mass ratio of DBT3P-II to molybdenum
oxide was 4:2, whereby the hole-injection layer 811 was formed over
the first electrode 801. The thickness was 20 nm. Note that
co-evaporation is an evaporation method in which a plurality of
different substances are concurrently vaporized from different
evaporation sources.
[0174] Next, 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine
(abbreviation: BPAFLP) was deposited by evaporation to a thickness
of 20 nm, whereby the hole-transport layer 812 was formed.
[0175] Next, the light-emitting layer 813 was formed on the
hole-transport layer 812. The light-emitting layer 813 that had a
stacked-layer structure and a thickness of 40 nm was formed as
follows:
2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline
(abbreviation: 2mDBTBPDBq-II),
4,4'-di(1-naphthyl)-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine
(abbreviation: PCBNBB), and
(acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III)
(abbreviation: [Ir(dppm).sub.2(acac)]) were deposited by
co-evaporation so that the mass ratio of 2mDBTBPDBq-II to PCBNBB
and [Ir(dppm).sub.2(acac)] was 0.7:0.3:0.05 to a thickness of 20
nm, and then 2mDBTBPDBq-II, PCBNBB, and [Ir(dppm).sub.2(acac)] were
deposited by co-evaporation so that the mass ratio of 2mDBTBPDBq-II
to PCBNBB and [Ir(dppm).sub.2(acac)] was 0.8:0.2:0.05 to a
thickness of 20 nm.
[0176] Next, on the light-emitting layer 813, 2mDBTBPDBq-II was
deposited by evaporation to a thickness of 20 nm and then
bathophenanthroline (abbreviation: Bphen) was deposited by
evaporation to a thickness of 10 nm, whereby the electron-transport
layer 814 was formed. Furthermore, lithium fluoride was deposited
by evaporation to a thickness of 1 nm on the electron-transport
layer 814, whereby the electron-injection layer 815 was formed.
[0177] Note that 2mDBTBPDBq-II used for the light-emitting element
1 (the light-emitting layer 813 and the electron-transport layer
814) was synthesized by the synthesis method of one embodiment of
the present invention, specifically, the synthesis method described
in Example 1; on the other hand, 2mDBTBPDBq-II that was used for
the comparative light-emitting element 2 and the comparative
light-emitting element 3 was synthesized by a conventional
synthesis method, specifically, a comparative synthesis method
described in this example.
[0178] Finally, aluminum was deposited to a thickness of 200 nm on
the electron-injection layer 815, whereby a second electrode 803
functioning as a cathode was formed. Through the above-described
steps, the light-emitting element 1, the comparative light-emitting
element 2, and the comparative light-emitting element 3 were
fabricated. Note that in all the above evaporation steps,
evaporation was performed by a resistance-heating method.
[0179] Table 1 shows element structures of the light-emitting
element 1, the comparative light-emitting element 2, and the
comparative light-emitting element 3 that were fabricated as
described above.
TABLE-US-00001 TABLE 1 Hole- Light- Electron- First Hole-injection
transport emitting injection Second electrode layer layer layer
Electron-transport layer layer electrode Light-emitting ITSO
DBT3P-II:MoOx BPAFLP * ** 2mDBTBPDBq-II Bphen LiF (1 nm) Al (200
nm) element 1 (110 nm) (4:2 20 nm) (20 nm) (Synthesis method (10
nm) of the present invention) (20 nm) Comparative ITSO
DBT3P-II:MoOx BPAFLP *** **** 2mDBTBPDBq-II Bphen LiF (1 nm) Al
(200 nm) light-emitting (110 nm) (4:2 20 nm) (20 nm) (Conventional
(10 nm) element 2 synthesis method) (20 nm) Comparative ITSO
DBT3P-II:MoOx BPAFLP *** **** 2mDBTBPDBq-II Bphen LiF (1 nm) Al
(200 nm) light-emitting (110 nm) (4:2 20 nm) (20 nm) (Conventional
(10 nm) element 3 synthesis method) (20 nm) * 2mDBTBPDBq-II
(Synthesis method of the present
invention):PCBNBB:[Ir(dppm).sub.2(acac)] (0.7:0.3:0.05 20 nm) **
2mDBTBPDBq-II (Synthesis method of the present
invention):PCBNBB:[Ir(dppm).sub.2(acac)] (0.8:0.2:0.05 20 nm) ***
2mDBTBPDBq-II (Conventional synthesis
method):PCBNBB:[Ir(dppm).sub.2(acac)] (0.7:0.3:0.05 20 nm) ****
2mDBTBPDBq-II (Conventional synthesis
method):PCBNBB:[Ir(dppm).sub.2(acac)] (0.8:0.2:0.05 20 nm)
[0180] The fabricated light-emitting element 1, comparative
light-emitting element 2, and comparative light-emitting element 3
were each sealed in a glove box containing a nitrogen atmosphere so
as not to be exposed to the air (specifically, a sealant was
applied onto outer edges of the elements, and at the time of
sealing, UV treatment was performed first and then heat treatment
was performed at 80.degree. C. for 1 hour).
<<Operation Characteristics of Light-Emitting Element 1,
Comparative Light-Emitting Element 2, and Comparative
Light-Emitting Element 3>>
[0181] Operation characteristics of the fabricated light-emitting
element 1, comparative light-emitting element 2, and comparative
light-emitting element 3 were measured. Note that the measurement
was carried out at room temperature (in an atmosphere kept at
25.degree. C.).
[0182] FIG. 9 shows current density-luminance characteristics of
the light-emitting element 1, the comparative light-emitting
element 2, and the comparative light-emitting element 3. In FIG. 9,
the vertical axis represents luminance (cd/m.sup.2) and the
horizontal axis represents current density (mA/cm.sup.2). FIG. 10
shows current voltage-luminance characteristics of the
light-emitting element 1, the comparative light-emitting element 2,
and the comparative light-emitting element 3. In FIG. 10, the
vertical axis represents luminance (cd/m.sup.2) and the horizontal
axis represents voltage (V).
[0183] Table 2 shows initial values of main characteristics of the
light-emitting element 1, the comparative light-emitting element 2,
and the comparative light-emitting element 3 at a luminance of
approximately 1000 cd/m.sup.2. Note that orange light emission
originating from [Ir(dppm).sub.2(acac)] was obtained from each of
the light-emitting elements.
TABLE-US-00002 TABLE 2 Current Volt- Cur- density Lumi- Current
Power age rent (mA/ nance efficiency efficiency (V) (mA) cm.sup.2)
(cd/m.sup.2) (cd/A) (lm/W) Light-emitting 2.8 0.032 0.81 620 76 86
element 1 Comparative 3.0 0.054 1.4 1200 86 90 light-emitting
element 2 Comparative 2.9 0.049 1.2 1000 84 91 light-emitting
element 3
[0184] FIG. 11 shows results of reliability tests of the
light-emitting element 1, the comparative light-emitting element 2,
and the comparative light-emitting element 3. In FIG. 11, the
vertical axis represents normalized luminance (%) with an initial
luminance of 100% and the horizontal axis represents driving time
(h) of the elements. Note that in the reliability tests, the
light-emitting element 1, the comparative light-emitting element 2,
and the comparative light-emitting element 3 were driven under the
conditions where the initial luminance was set to 5000 cd/m.sup.2
and the current density was constant.
[0185] The light-emitting element 1 is a light-emitting element in
which the EL layer contains, as an EL material, 2mDBTBPDBq-II
synthesized by the synthesis method of one embodiment of the
present invention, that is, a synthesis method in which a
2-(chloroaryl)dibenzo[f,h]quinoxaline derivative that can be
separated and removed by purification by sublimation is used as a
synthetic intermediate in a synthetic pathway. In contrast, the
comparative light-emitting element 2 and the comparative
light-emitting element 3 are light-emitting elements in which the
EL layer contains, as an EL material, 2mDBTBPDBq-II synthesized by
the conventional synthesis method described as a reference example
in this example. The results show that the light-emitting element 1
fabricated using, as the EL material, 2mDBTBPDBq-II synthesized by
the synthesis method of one embodiment of the present invention has
higher reliability and a longer lifetime than the comparative
light-emitting element 2 and the comparative light-emitting element
3.
(Reference Synthesis Method: Conventional Synthesis Method)
[0186] As a reference synthesis method, the conventional method of
synthesizing
2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline
(abbreviation: 2mDBTBPDBq-II) is described below.
##STR00027##
<<Synthesis of 2mDBTBPDBq-II>>
[0187] Synthesis Scheme (b-1) of 2mDBTBPDBq-II is shown.
##STR00028##
[0188] In a 200-mL three-neck flask were put 0.83 g (3.2 mmol) of
2-chlorodibenzo[f,h]quinoxaline, 1.3 g (3.5 mmol) of
3'-(dibenzothiophen-4-yl)-3-biphenylboronic acid, 40 mL of toluene,
4 mL of ethanol, and 5 mL of a 2M aqueous potassium carbonate
solution. This mixture was degassed by being stirred under reduced
pressure, and the air in the flask was replaced with nitrogen. To
this mixture was added 80 mg 70 .mu.mol) of
tetrakis(triphenylphosphine)palladium(0). This mixture was stirred
at 80.degree. C. under a nitrogen stream for 16 hours. After a
predetermined period of time had elapsed, the precipitated solid
was separated by filtration to give a yellow solid. Ethanol was
added to this solid, followed by irradiation with ultrasonic waves.
The solid was suction filtered to give a solid. The obtained solid
was dissolved in toluene, and the toluene solution was suction
filtered through alumina and Celite (produced by Wako Pure Chemical
Industries, Ltd., Catalog No. 531-16855), and the filtrate was
concentrated to give a yellow solid. Furthermore, this solid was
recrystallized from toluene to give 1.1 g of yellow powder in a
yield of 57%.
[0189] By a train sublimation method, 40.3 g of yellow powder,
which was obtained by increasing the reaction scale in the
above-described synthesis method, was purified. In the purification
by sublimation, the yellow powder was heated at 350.degree. C.
under a pressure of 7.6 Pa with an argon flow rate of 100 mL/min.
By the purification by sublimation, 6.4 g of the yellow powder,
which was an objective substance, was obtained in a yield of 15.9%
in a region heated at a temperature higher than 310.degree. C. and
lower than or equal to 345.degree. C. in an apparatus (hereinafter,
a high-temperature region) and 2.9 g of the yellow powder was
obtained in a yield of 7.2% in a region heated at 310.degree. C. in
the apparatus (hereinafter, a middle-temperature region).
[0190] Here, the purity of 2-chlorodibenzo[f,h]quinoxaline, which
was a source material, was analyzed by ACQUITY Ultra Performance LC
(ACQUITY UPLC). According to the analysis, in addition to
2-chlorodibenzoquinoxaline, substances with m/z (i.e.,
mass-to-charge ratio) of 232 and 299 were contained as impurities
with area ratios of 0.4% and 0.9%, respectively, and the purity was
calculated to be 98.7%. These impurities with m/z of 232 and 299
are presumed to be dibenzo[f,h]quinoxaline and monochlorinated
2-chlorodibenzo[f,h]quinoxaline (Structural Formula (303)).
Structural Formula (303) is shown below, respectively. The above
results indicate that the 2-chlorodibenzo[f,h]quinoxaline
derivative such as 2-chlorodibenzo[f,h]quinoxaline that was a
source material generally contains a dihalide represented by
Structural Formula (303) as an impurity.
##STR00029##
[0191] The purity of 2mDBTBPDBq-II obtained by the above synthesis
and purification methods was analyzed by high performance liquid
chromatography (UPLC). In the purity analysis, as an impurity, a
substance with m/z (i.e., mass-to-charge ratio) of 599 was detected
from a sample collected in the high-temperature region in the
purification by sublimation with an area ratio lower than 0.1% and
detected from a sample collected in the middle-temperature region
with an area ratio of 0.1%.
[0192] In addition, when chlorine was quantified by a
combustion-ion chromatography method in order to measure the
halogen concentration of 2mDBTBPDBq-II, 63 ppm of chlorine was
detected in the sample collected in the high-temperature region in
the purification by sublimation and 276 ppm of chlorine was
detected in the sample collected in the middle-temperature region
in the purification by sublimation.
[0193] From the above results, the impurity is presumed to be
monochlorinated 2mDBTBPDBq-II (Structural Formula (304)).
Structural Formula (304) is shown below. The above results show
that monochlorinated 2-chlorodibenzo[f,h]quinoxaline (Structural
Formula (303)), which is contained in the source material, reacts
with one equivalent of a boronic acid, so that the EL material
(2mDBTPDBq-II that is the objective substance) containing chlorine
as a substituent remains as an impurity. In addition, the above
data on the comparative light-emitting element 2 and the
comparative light-emitting element 3 indicate that a chloride of
the EL material that contains chlorine as a substituent adversely
affects the reliability of the elements. The above data also
indicate that the luminance of the comparative light-emitting
element 3 that used the sample collected in the middle-temperature
region in the purification by sublimation and had a high chlorine
content of the EL material of 276 ppm decays faster than the
luminance of the comparative light-emitting element 2 that used the
sample collected in the high-temperature region in the purification
by sublimation and had a chlorine content of the EL material of 63
ppm.
[0194] Thus, it is indicated that the chlorine content of the EL
material quantitatively correlates with the reliability
(deterioration rate) of the element and that the synthesis method
of one embodiment of the present invention that can decrease the
chlorine content to be lower than or equal to 10 ppm can minimize
the deterioration rate of the element and achieve high reliability
of the element.
##STR00030##
[0195] It was found from the above results that, as described in
Embodiment 1, when reaction shown in Synthesis Scheme (B-1) is
performed using a 2-chlorodibenzo[f,h]quinoxaline derivative
(General Formula (A1)) containing a chlorinated (monochlorinated or
dichlorinated) 2-chlorodibenzo[f,h]quinoxaline derivative (General
Formula (A1')), a chlorinated dibenzo[f,h]quinoxaline derivative
(General Formula (G1')) is generated as shown in Synthesis Scheme
(B-1'). It was also found that the chlorinated
dibenzo[f,h]quinoxaline derivative (General Formula (G1')) has a
significant adverse effect on the reliability of a light-emitting
element.
<<Chlorine Content of EL Material and Operation
Characteristics of Light-Emitting Element>>
[0196] Furthermore, a correlation between the chlorine content of
an EL material and the reliability of a light-emitting element was
examined in detail.
[0197] Samples of 2mDBTBPDBq-II, which was used for the
light-emitting element in this example, were synthesized in a
plurality of lots, and the chlorine contents of the samples were
measured by a combustion-ion chromatography method.
[0198] Four kinds of samples (samples 1 to 4) that are
2mDBTBPDBq-II synthesized by the synthesis method of one embodiment
of the present invention all had a very small chlorine content of 1
ppm (.mu.g/g). In addition, six kinds of samples (samples 5 to 10)
that are 2mDBTBPDBq-II synthesized by a conventional synthesis
method described below had chlorine contents shown in Table 3.
TABLE-US-00003 TABLE 3 Sample Normalized Chlorine No. luminance (%)
content (ppm) Light-emitting element Sample 1 94.13 1
Light-emitting element 1 Sample 2 93.66 1 Light-emitting element 2
Sample 3 91.97 1 Light-emitting element 3 Sample 4 95.63 1
Light-emitting element 4 Sample 5 81.96 45 Light-emitting element 5
Sample 6 82.16 63 Light-emitting element 6 Sample 7 80.38 71
Light-emitting element 7 Sample 8 72.16 137 Light-emitting element
8 Sample 9 65.02 208 Light-emitting element 9 Sample 10 60.66 276
Light-emitting element 10
[0199] Light-emitting elements (light-emitting elements 1 to 10)
were fabricated using these samples (samples 1 to 10) and subjected
to reliability tests for 450 hours. Note that structures of the
fabricated light-emitting elements and conditions of the
reliability tests are the same as those described above.
[0200] In FIG. 13, the normalized luminance (%) of the
light-emitting elements after 450 hours and the chlorine contents
(ppm) in the samples used for the light-emitting elements were
plotted on the horizontal axis and the vertical axis, respectively,
and an approximate curve obtained from the plot is shown. The
approximate curve shows that the reliability increases as the
chlorine content decreases in the region where the chlorine content
is higher than approximately 10 ppm to 20 ppm, meanwhile the
reliability is close to or reaches the saturation point when the
chlorine content is lower than or equal to 10 ppm. This means that
stable high reliability can be obtained by decreasing the chlorine
content of an EL material to be less than or equal to 10 ppm.
Example 3
Synthesis Example 2
[0201] In this example, a method of synthesizing
2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline
(abbreviation: 2mDBTBPDBq-II) (Structural Formula (200)) is
described as a synthesis method of one embodiment of the present
invention. In the method described in this example, reaction
conditions are different from those in Example 1. Note that a
structure of 2mDBTBPDBq-II is shown below.
##STR00031##
Step 1: Synthesis of 2-(3-chlorophenyl)dibenzo[f,h]quinoxaline
[0202] First, 132.4 g (500 mmol) of 2-chlorodibenzo[f,h]quinoxaline
(Structural Formula (301)), 86.0 g (550 mmol) of 3-chlorophenyl
boronic acid, 159.0 g (1.5 mol) of potassium carbonate, 2.5 L of
toluene, 630 mL of ethanol, and 750 mL of water were put in a 1-L
three-neck flask. This mixture was degassed under reduced pressure,
and then the air in the flask was replaced with nitrogen.
[0203] Then, 2.23 g (10 mmol) of palladium(II) acetate
(abbreviation: Pd(OAc).sub.2) and 8.85 g (20 mmol) of
tris(2,6-dimethoxyphenyl)phosphine were added to the mixture, and
this mixture was heated and refluxed for approximately 4 hours.
After that, the temperature of the flask was cooled down to room
temperature, and a precipitate was separated by filtration. The
precipitate was washed with water, ethanol, and toluene. The
resulting residue was dissolved in heated toluene, and this
solution was filtered through Celite. The obtained filtrate was
cooled down to room temperature, and a precipitate was separated by
filtration. The resulting residue was dried at 100.degree. C. under
reduced pressure to give 149.5 g of a pale yellow solid, which was
an objective substance, in a yield of 88%.
[0204] Synthesis Scheme (c-1) of Step 1 is shown below.
##STR00032##
[0205] The pale yellow solid obtained in Step 1 was analyzed by
nuclear magnetic resonance (.sup.1H-NMR) spectroscopy to confirm
that 2-(3-chlorophenyl)dibenzo[f,h]quinoxaline (Structural Formula
(100)) was obtained in Step 1.
Step 2: Synthesis of
2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline
(abbreviation: 2mDBTBPDBq-II)
[0206] Next, 35.0 g (103 mmol) of
2-(3-chlorophenyl)dibenzo[f,h]quinoxaline obtained in Step 1, 33.5
g (110 mmol) of 3-(dibenzothiophen-4-yl)phenylboronic acid, 63.7 g
(300 mmol) of tripotassium phosphate, 29 mL of t-butanol, and 670
mL of diethylene glycol dimethyl ether were put in a 1-L three-neck
flask, and the air in the flask was replaced with nitrogen. This
mixture was degassed by being stirred under reduced pressure.
[0207] Then, 0.69 g (3.1 mmol) of palladium(II) acetate and 2.22 g
(6.2 mmol) of di(1-adamantyl)-n-butylphosphine (abbreviation:
cataCXium.RTM.) were added to the mixture, and this mixture was
heated and refluxed for approximately 8 hours. After that, the
temperature of the flask was cooled down to room temperature, and a
precipitate was separated by filtration. The precipitate was washed
with water, ethanol, and toluene. The resulting residue was
dissolved in heated toluene, and this solution was filtered through
Celite. The obtained filtrate was cooled down to room temperature,
and a precipitate was separated by filtration. The resulting
residue was dried at 100.degree. C. under reduced pressure to give
53.0 g of a pale yellow crystalline solid, which was an objective
substance, in a yield of 94%.
[0208] By a train sublimation method, 110 g of the objective solid,
which was obtained by increasing the reaction scale in the
synthesis method, was purified. In the purification by sublimation,
the objective substance was heated at 350.degree. C. under a
pressure of 5.6.times.10.sup.-3 Pa. After cooling, 67.2 g of a pale
yellow solid was obtained in a yield of 62%. Synthesis Scheme (c-2)
of Step 2 is shown below.
##STR00033##
[0209] The pale yellow solid obtained in Step 2 was analyzed by
nuclear magnetic resonance (.sup.1H-NMR) spectroscopy to confirm
that
2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline
(abbreviation: 2mDBTBPDBq-II) (Structural Formula (200)) was
obtained.
[0210] Next, purity analysis of
2-(3-chlorophenyl)dibenzo[f,h]quinoxaline (Structural Formula
(100)), which was the compound (i.e., intermediate) obtained in
Step 1, was performed similarly. According to the analysis, in
addition to 2-(3-chloropheny)dibenzo[f,h]quinoxaline (Structural
Formula (100)), substances with m/z (i.e., mass-to-charge ratio) of
265, 307, 417, 459, and 611 were contained as impurities with area
ratios of 0.2%, 0.2%, 0.1%, 0.1%, and 0.2%, respectively, and the
purity was calculated to be 99.2%. The impurities with m/z of 265,
307, 417, 459, and 611 are presumed to be
2-chlorodibenzo[f,h]quinoxaline, 2-phenyldibenzo[f,h]quinoxaline,
2-(3-chlorophenyl)dibenzo[f,h]quinoxaline,
2-(1,1':3',1''-terphenyl)dibenzo[f,h]quinoxaline, and
2,2'-(1,1'-biphenyl-3,3'-diyl)di(dibenzo[f,h]quinoxaline). Note
that these impurities are consumed in subsequent reaction or can be
removed by purification. In addition, the results of the purity
analysis indicate that an impurity (i.e., a chloride (a
monochloride or a dichloride)) originating from the monochlorinated
2-chlorodibenzo[f,h]quinoxaline (Structural Formula (303)), which
is an impurity that can be contained in the source material, i.e.,
2-chlorodibenzo[f,h]quinoxaline (Structural Formula (301)), is
hardly detected in the synthesis method.
[0211] The chlorine content of 2mDBTBPDBq-II, which is an objective
substance in this embodiment, was measured by combustion-ion
chromatography. According to the measurement, the chlorine content
of 2mDBTBPDBq-II was 1 ppm (.mu.g/g), which was very small. This
indicates that the present invention can be implemented even when
the reaction conditions are changed.
Example 4
Synthesis Example 3
[0212] A method of synthesizing
2-(4-chlorophenyl)dibenzo[f,h]quinoxaline represented by Structural
Formula (101) in Embodiment 1 is described as a specific method of
synthesizing a 2-(chloroaryl)dibenzo[f,h]quinoxaline derivative of
one embodiment of the present invention that is a synthetic
intermediate and can be separated and removed by purification by
sublimation. Note that a structure of
2-(4-chlorophenyl)dibenzo[f,h]quinoxaline is shown below.
##STR00034##
Step 2: Synthesis of 2-(4-chlorophenyl)dibenzo[f,h]quinoxaline
[0213] First, in a 200-mL three-neck flask were put 4.0 g (15 mmol)
of 2-chlorodibenzo[f,h]quinoxaline (Structural Formula (301)), 2.5
g (17 mmol) of 4-chlorophenyl boronic acid, 76 mL of toluene, 19 mL
of ethanol, and 22.7 mL of a 2M aqueous potassium carbonate
solution. This mixture was degassed by being stirred under reduced
pressure, and the air in the flask was replaced with nitrogen.
[0214] Then, 68 mg (15 mmol) of palladium(II) acetate
(abbreviation: Pd(OAc).sub.2) and 0.18 g (0.60 mmol) of
tris(2-methylphenyl)phosphine were added to the mixture. This
mixture was stirred at approximately 80.degree. C. under a nitrogen
stream for 8 hours. After a predetermined period of time had
elapsed, the precipitated solid was separated by filtration to give
a brown solid. The obtained solid was dissolved in toluene, and the
toluene solution was suction-filtered through alumina and Celite,
and the filtrate was concentrated to give a yellow solid.
Furthermore, this solid was recrystallized from toluene to give 3.8
g of the yellow solid in a yield of 75%.
[0215] Synthesis Scheme (d-1) of Step 2 is shown below.
##STR00035##
[0216] Analysis results by nuclear magnetic resonance (.sup.1H-NMR)
spectroscopy of the yellow solid obtained in Step 2 are described
below. FIGS. 12A and 12B are .sup.1H-NMR charts. FIG. 12B is a
chart where the range from 6.5 (ppm) to 10 (ppm) on the horizontal
axis (.delta.) in FIG. 12A is enlarged. The charts show that
2-(4-chlorophenyl)dibenzo[f,h]quinoxaline (Structural Formula
(101)) was obtained in Step 2.
[0217] .sup.1H NMR (CDCl.sub.3, 500 MHz): .delta. (ppm)=7.45-7.50
(m, 3H), 7.54-7.60 (m, 3H), 7.64 (d, J=8.5 Hz, 1H), 7.71 (dd, J=8.0
Hz, 1.7 Hz, 1H), 7.82-7.86 (m, 3H), 8.17 (dd, J=8.0 Hz, 1.8 Hz,
1H), 8.19-8.23 (m, 1H).
[0218] This application is based on Japanese Patent Application
serial No. 2013-190214 filed with the Japan Patent Office on Sep.
13, 2013 and Japanese Patent Application serial No. 2014-097738
filed with the Japan Patent Office on May 9, 2014, the entire
contents of which are hereby incorporated by reference.
* * * * *