U.S. patent number RE45,442 [Application Number 13/085,129] was granted by the patent office on 2015-03-31 for multiple wavelength light emitting device, electronic apparatus, and interference mirror.
This patent grant is currently assigned to Cambridge Display Technology Limited, Seiko Epson Corporation. The grantee listed for this patent is Jeremy Henley Burroughes, Takeo Kaneko, Tomoko Koyama, Tatsuya Shimoda. Invention is credited to Jeremy Henley Burroughes, Takeo Kaneko, Tomoko Koyama, Tatsuya Shimoda.
United States Patent |
RE45,442 |
Shimoda , et al. |
March 31, 2015 |
Multiple wavelength light emitting device, electronic apparatus,
and interference mirror
Abstract
A multiple wavelength light emitting device is provided
wherewith the resonance strength and directivity between colors can
be easily adjusted for balance. This light emitting device
comprises a light emission means 4 for emitting light containing
wavelength components to be output, and a semi-reflecting layer
group 2 wherein semi-reflecting layers 2R, 2G, and 2B that transmit
some light having specific wavelengths emitted from the light
emission means and reflect the remainder are stacked up in order in
the direction of light advance in association with wavelengths of
light to be output. Light emission regions A.sub.R, A.sub.G, and
A.sub.B are determined in association with the wavelengths of light
to be output. The configuration is such that, in the light emission
regions, the distances L.sub.R, L.sub.G and L.sub.B between a
reflecting surface for fight from the light emission means side of
the semi-reflecting layers 2R, 2G, and 2B that reflect light output
from those light emission regions and a point existing in an
interval from the end of the light emitting layer on the
semi-reflecting layer group side to the reflecting layer are
adjusted so as to have an optical path length at which that light
resonates.
Inventors: |
Shimoda; Tatsuya (Suwa,
JP), Koyama; Tomoko (Suwa, JP), Kaneko;
Takeo (Suwa, JP), Burroughes; Jeremy Henley
(Godmanchester Cambs, GB) |
Applicant: |
Name |
City |
State |
Country |
Type |
Shimoda; Tatsuya
Koyama; Tomoko
Kaneko; Takeo
Burroughes; Jeremy Henley |
Suwa
Suwa
Suwa
Godmanchester Cambs |
N/A
N/A
N/A
N/A |
JP
JP
JP
GB |
|
|
Assignee: |
Seiko Epson Corporation (Tokyo,
JP)
Cambridge Display Technology Limited (Cambridge,
GB)
|
Family
ID: |
10854631 |
Appl.
No.: |
13/085,129 |
Filed: |
April 12, 2011 |
PCT
Filed: |
June 02, 2000 |
PCT No.: |
PCT/GB00/02143 |
371(c)(1),(2),(4) Date: |
March 08, 2002 |
PCT
Pub. No.: |
WO00/76010 |
PCT
Pub. Date: |
December 14, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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11520860 |
Sep 14, 2006 |
Re. 44164 |
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Reissue of: |
09980100 |
Jun 2, 2000 |
6791261 |
Sep 14, 2004 |
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Reissue of: |
09980100 |
Jun 2, 2000 |
6791261 |
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Foreign Application Priority Data
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Jun 2, 1999 [GB] |
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9912850.6 |
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Current U.S.
Class: |
313/506; 359/584;
313/113; 313/112; 359/577; 359/885 |
Current CPC
Class: |
H01L
27/3211 (20130101); H01L 51/5036 (20130101); G02B
5/285 (20130101); H01L 51/5265 (20130101); H01L
27/3281 (20130101) |
Current International
Class: |
H05B
33/00 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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A 8-248276 |
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WO |
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Other References
Sep. 16, 2011 Office Action issued in U.S. Appl. No. 13/016,767.
cited by applicant .
Office Action issued in JP Application No. 2001-502181 on Oct. 14,
2010 (with English translation). cited by applicant .
David G. Lidzey et al., "Pixelated Multicolor Microcavity Displays"
IEEE Journal of Selected Topics Quantum Electronic, IEEE Service
Center, Piscataway, NJ, US, vol. 4, No. 1, Feb. 1998, XP011062343.
cited by applicant .
Office Action issued in U.S. Appl. No. 11/520,860 on May 11, 2011.
cited by applicant .
Aug. 3, 2012 Office Action issued in U.S. Appl. No. 11/520,860.
cited by applicant .
Nakayama et al., "Organic Luminescent Devices with Optical
Microcavity Structure", Shingaku Gihou, OME 94-79, Mar. 1995, pp.
7-12. (w/abstract). cited by applicant .
Dodabalapur et al., "Physics and applications of organic
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15, 1996, pp. 6954-6964. cited by applicant.
|
Primary Examiner: Patel; Ashok
Attorney, Agent or Firm: Oliff PLC
Parent Case Text
.Iadd.Notice: More than one reissue application has been filed for
the reissue of U.S. Pat. No. 6,791,261. The reissue application are
application Ser. No. 11/520,860, filed on Sep. 14, 2006, now issued
as U.S. Pat. No. Re. 44,164, application Ser. No. 13/016,767, filed
on Jan. 28, 2011, now issued as U.S. Pat. No. Re. 43,759, which is
a divisional of application Ser. No. 11/520,860, application Ser.
No. 13/085,129 (the present application), filed on Apr. 12, 2011,
which is a continuation reissue of application Ser. No. 11/520,860.
.Iaddend.
.Iadd.This application is a reissue continuation of application
Ser. No. 11/520,860, filed on Sep. 14, 2006, which is an
application for reissue of U.S. Pat. No. 6,791,261. .Iaddend.
Claims
What is claimed is:
.[.1. A multiple wavelength light emitting device for emitting
light of a plurality of differing wavelengths comprising: light
emission means for emitting light containing wavelength components
to be output; a reflecting layer placed in proximity to said light
emission means; a semi-reflecting layer group opposite said
reflecting layer with said light emission means therebetween, the
semi-reflecting layer group having semi-reflecting layers that
reflect some light emitted from said light emission means having
specific wavelengths and that transmit the remainder of the light
emitted from said light emission means, stacked in order, in a
direction of light advance so as to correspond with light
wavelengths to be output; and two or more light emission regions
wherein the wavelength of the output light differs wherein: the
distance between the reflecting layer for light from the light
emission means side of the semi-reflecting layer group that
partially reflects light output from that light emission region and
a point at which light is emitted, existing in an interval from an
end surface of said light emission means on the semi-reflecting
layer group side to a surface of said reflecting layer, is adjusted
so as to have an optical path length such that light of the
wavelength output from that light emission region resonates,
wherein said point in the interval from the end surface of said
light emission means on the semi-reflecting layer group side to the
surface of said reflecting layer is a light emission point in said
light emission means..].
.[.2. A multiple wavelength light emitting device according to
claim 1, wherein said semi-reflecting layer group has a plurality
of types of semi-reflecting layers responsive to light of a
plurality differing wavelengths that are placed uniformly without
any separation between light emission regions..].
.[.3. A multiple wavelength light emitting device according to
claim 1, wherein said reflecting surface for light from light
emission means side of semi-reflecting layer in said
semi-reflecting layer group is in a different position in thickness
direction for each light emission region of different light
emission wavelength..].
.[.4. A multiple wavelength light emitting device according to
claim 1, wherein said point existing in interval from end of said
light emission means on semi-reflecting layer group side to said
reflecting layer is on reflecting surface of said reflecting
layer..].
.[.5. A multiple wavelength light emitting device according to
claim 4, wherein, in a light emission region that outputs light of
wavelength .lamda., distance L between a reflecting surface for
light from light emission means side of said semi-reflecting layer
of said plurality of semi-reflecting layers that reflects light of
wavelength .lamda. and a point existing in interval from end of
said light emission means on semi-reflecting layer group side
thereof to said reflecting layer is adjusted so that L=.SIGMA.di
.SIGMA.(nidi)+m.sub.1(.PHI./2.pi.)=m.sub.2.lamda./2 where ni is
refractive index of i'th substance between said semi-reflecting
layer and said light emitting surface, di is thickness thereof,
.PHI. is phase shift occurring at said reflecting surface in said
reflecting layer, and m.sub.1 and m.sub.2 are natural
numbers..].
.[.6. A multiple wavelength light emitting device according to
claim 1, wherein a point where an electric field becomes maximized
between electrodes in an organic electro-luminescence layer
coincides with said point at which light is emitted..].
.[.7. A multiple wavelength light emitting device according to
claim 1, wherein, in a light emission region that outputs light of
wavelength .lamda., distance L between a reflecting surface for
light from light emission means side of said semi-reflecting layer
of said plurality of semi-reflecting layers that reflects light of
wavelength .lamda. and a light emission point existing in interval
from end of said light emission means on semi-reflecting layer
group side thereof to said reflecting layer is adjusted so that
L=.rho.di .SIGMA.(nidi)=m.sub.2.lamda./2+(2m.sub.3+1).lamda./4
where ni is refractive index of the i'th substance between said
reflective surface and said light emission point, di is thickness
thereof, m.sub.2 is a natural number, and m.sub.3 is an integer
greater than 0..].
.[.8. A multiple wavelength light emitting device according to
claim 1, wherein, in said semi-reflecting layer group, said
semi-reflecting layer that reflects light of longer wavelength is
positioned on side nearer to said light emitting device..].
.[.9. A multiple wavelength light emitting device according to
claim 1, wherein semi-reflecting layers configuring said
semi-reflecting layer group are configured with two layers of
different refractive index stacked alternately..].
.[.10. A multiple wavelength light emitting device according to
claim 9, wherein said semi-reflecting layers are adjusted so as to
satisfy the relationship n1d1=n2d2=(1/4+m/2).lamda. where n1 is
refractive index of one of said two layers having different
refractive indexes, d1 is thickness thereof, n2 is refractive index
of other layer, d2 is thickness thereof, .lamda. is wavelength of
light reflected in that semi-reflecting layer, and m is 0 or a
natural number..].
.[.11. A multiple wavelength light emitting device according to
claim 1, wherein said semi-reflecting layer group comprises gap
adjustment layers, between semi-reflecting layers thereof, for
adjusting distance between reflecting surface for light from said
light emission means side of semi-reflecting layer other than that
semi-reflecting layer closest to said light emission means and a
point existing interval from end of said light emission means on
semi-reflecting layer group side to said reflecting layer..].
.[.12. A multiple wavelength light emitting device according to
claim 9, wherein, in order to adjust distance between reflecting
surface for light from said light emission means said of
semi-reflecting layer other than that semi-reflecting layer closest
to said light emission means and a point existing in interval from
end of said light emission means on semi-reflecting layer group
side to said reflecting layer, thickness of one layer in laminar
structure wherein said layers of different refractive index
configure said semi-reflecting layers is altered..].
.[.13. A multiple wavelength light emitting device according to
claim 1, wherein multiple types of light emission means for
emitting a relatively large amount of light having light components
of wavelengths corresponding to said light emission regions are
provided so that they are associated with said light emission
regions..].
.[.14. A multiple wavelength light emitting device according to
claim 1, wherein light emission means capable of emitting light
having wavelength components associated with all said light
emission regions are provided commonly for all said light emission
regions..].
.[.15. A multiple wavelength light emitting device according to
claim 1, wherein said light emission means are an organic
electro-luminescence layer sandwiched between electrode layers, and
electrode provided on back side thereof corresponds to said
reflecting layer..].
.[.16. A multiple wavelength light emitting device according to
claim 15, wherein said light emission means comprise a hole
transport layer on positive electrode side of said organic
electro-luminescence layer..].
.[.17. A multiple wavelength light emitting device according to
claim 15, wherein said light emission means comprises an electron
transport layer on negative electrode side of said organic
electro-luminescence layer..].
.[.18. A multiple wavelength light emitting device according to
claim 15, wherein distance between reflecting surface for light
from light emission means side of said semi-reflecting layers and a
point existing in interval from end of said light emission means on
semi-reflecting layer side thereof to said reflecting layer is
adjusted with thickness of positive electrode positioned on
semi-reflecting layer group side of said light emission
means..].
.[.19. A multiple wavelength light emitting device according to
claim 15, comprising a layer on semi-reflecting layer group side of
said light emission means for purpose of adjusting distance between
reflecting surface for light from light emission means side of said
semi-reflecting layers and a point existing in interval from end of
said light emission means on semi-reflecting layer side thereof to
said reflecting layer..].
.[.20. A multiple wavelength light emitting device according to
claim 15, wherein said negative electrode is made of a material
exhibiting light reflectance..].
.[.21. A multiple wavelength light emitting device according to
claim 15, wherein at least one of electrode films sandwiched around
said organic electro-luminescence layer is formed separately and is
independently, associated with said light emission regions..].
.[.22. A multiple wavelength light emitting device according to
claim 21, wherein one or other of said electrode films is separated
by a partition member that partitions said light emission regions
from one another..].
.[.23. A multiple wavelength light emitting device according to
claim 21, wherein, of said electrode films, the negative electrode
is separated in association with said light emission regions, and
thickness of said positive electrode is altered in association with
said light emission regions in order to adjust distance between
reflecting surface for light from light emission means side of said
semi-reflecting layers and a point existing in interval from end of
said light emission means on semi-reflecting layer side thereof to
said reflecting layer..].
.[.24. A multiple wavelength light emitting device according to
claim 21, wherein, of said electrode films, the positive electrode
is separated in association with said light emission regions, and
thickness thereof is altered in association with said light
emission regions in order to adjust distance between reflecting
surface for light from light emission means side of said
semi-reflecting layers and a point existing in interval from end of
said light emission means on semi-reflecting layer side thereof to
said reflecting layer..].
.[.25. A multiple wavelength light emitting device according to
claim 21, comprising drive circuits for individually driving said
electrically separated electrode films..].
.[.26. An electronic apparatus comprising: the multiple wavelength
light emitting device claimed in claim 25..].
.[.27. A electronic apparatus according to claim 26, wherein said
light emission regions in said multiple wavelength light emitting
device are formed as pixels for displaying images, and function as
display elements configured so that the driving of pixels can be
controlled in response to image information..].
.[.28. An interference mirror comprising: a plurality of
interference reflecting layers, configured so that some light of
mutually different wavelength can be reflected, positioned
sequentially in the direction of the optical axis; and a plurality
of gap adjacent layers, each of which has a different thickness
with respect to one another, in the direction of the optical axis,
positioned between said interference reflecting layers..].
.Iadd.29. A multiple wavelength light emitting device that
comprises a plurality of light emission regions that emit lights of
wavelengths corresponding to mutually different colors, comprising:
a first light emission means provided in a first light emission
region, the first light emission means emitting a first color light
that has a first wave length; a second light emission means
provided in a second light emission region, the second light
emission means emitting a second color light that has a second wave
length which is different from the first wave length; a reflecting
layer placed opposite to the first and second light emission means;
a semi-reflecting layer group placed so as to be opposite to the
first and second light emission means on a side opposite to the
reflecting layer with respect to the first and second light
emission means, and formed by stacking a first semi-reflecting
layer and a second semi-reflecting layer, the first semi-reflecting
layer having a first reflecting surface configured to reflect
primarily the first color light emitted by the first light emission
means, the second semi-reflecting layer having a second reflecting
surface configured to reflect primarily the second color light
emitted by the second light emission means; a first distance
between the first reflecting surface of the first semi-reflecting
layer in the first light emission region and a first point in the
first light emission means being a distance that resonates the
first color light to be emitted by the first light emission region;
and a second distance between the second reflecting surface of the
second semi-reflecting layer in the second light emission region
and a second point in the second light emission means being a
distance that resonates the second color light to be emitted by the
second light emission region, the first point existing in an
interval from an end surface of the first light emission means on
the semi-reflecting layer group side to a surface of the reflecting
layer, the second point existing in an interval from an end surface
of the second light emission means on the semi-reflecting layer
group side to the surface of the reflecting layer. .Iaddend.
.Iadd.30. The multiple wavelength light emitting device according
to claim 29, wherein the distance L between the first reflecting
surface of the first semi-reflecting layer and the first point in
the first light emission means is adjusted so that L=.SIGMA.di
.SIGMA.(nidi)=m.sub.2.lamda./2+(2m.sub.3+1).lamda./4 where .lamda.
is the wavelength, ni is refractive index of i'th substance between
the first reflecting surface of the first semi-reflecting layer and
the first point in the first light emission means, di is thickness
of the i'th substance, m.sub.2 is a natural number, and m.sub.3 is
an integer greater than 0. .Iaddend.
.Iadd.31. The multiple wavelength light emitting device according
to claim 29, wherein the semi-reflecting layer group comprises a
gap adjustment layer between each of the first and second
semi-reflecting layers for adjusting distance between the first
reflecting surface for light from the first light emission means in
a semi-reflecting layer other than that semi-reflecting layer
closest to the first light emission means and the first point in
the first light emission means. .Iaddend.
.Iadd.32. The multiple wavelength light emitting device according
to claim 31, wherein in order to adjust distance between a
reflecting surface for light from the first light emission means
side in a semi-reflecting layer other than that semi-reflecting
layer closest to the first light emission means and the first point
in the first light emission means, thickness of one layer in a
laminar structure wherein the layers of different refractive index
that configure the first and second semi-reflecting layers are
altered. .Iaddend.
.Iadd.33. The multiple wavelength light emitting device according
to claim 29, wherein the first light emission means includes a
luminescence layer provided between a first electrode provided on
the semi-reflecting layer group side with respect to the first
light emission means and a second electrode provided on a side
opposite to the semi-reflecting layer group with respect to the
first light emission means, and the second electrode corresponds to
the reflecting layer. .Iaddend.
.Iadd.34. The multiple wavelength light emitting device according
to claim 33, wherein in the first light emission means, a point
where an electric field becomes maximized between the first
electrode and the second electrode and the first point in the first
light emission means coincide. .Iaddend.
.Iadd.35. The multiple wavelength light emitting device according
to claim 34, wherein one of the first electrode or the second
electrode is formed separately and independently associated with
each of the plurality of light emission regions. .Iaddend.
.Iadd.36. The multiple wavelength light emitting device according
to claim 33 wherein the distance between the first reflecting
surface of the first semi-reflecting layer and the first point in
the first light emission means is adjusted with thickness of the
first electrode. .Iaddend.
.Iadd.37. The multiple wavelength light emitting device according
to claim 36, wherein one of the first electrode or the second
electrode is formed separately and independently associated with
each of the plurality of light emission regions. .Iaddend.
.Iadd.38. The multiple wavelength light emitting device according
to claim 33, comprising a layer on the semi-reflecting layer group
side of said first light emission means for purpose of adjusting
the distance between the first reflecting surface of the first
semi-reflecting layer and the first point in the first light
emission means. .Iaddend.
.Iadd.39. The multiple wavelength light emitting device according
to claim 38, wherein one of the first electrode or the second
electrode is formed separately and independently associated with
each of the plurality of light emission regions. .Iaddend.
.Iadd.40. The multiple wavelength light emitting device according
to claim 33, wherein the first electrode is separated in
association with the first and second light emission regions, and
the distance between the first reflecting surface of the first
semi-reflecting layer and the first point in the first light
emission means is adjusted by thickness of the first electrode.
.Iaddend.
.Iadd.41. The multiple wavelength light emitting device according
to claim 40, comprising drive circuits for individually driving the
first electrode or the second electrode. .Iaddend.
.Iadd.42. The multiple wavelength light emitting device according
to claim 33, wherein the second electrode is separated in
association with the first and second light emission regions, and
the distance between the first reflecting surface of the first
semi-reflecting layer and the first point in the first light
emission means is adjusted by thickness of the first electrode.
.Iaddend.
.Iadd.43. The multiple wavelength light emitting device according
to claim 42, comprising drive circuits for individually driving the
first electrode or the second electrode. .Iaddend.
.Iadd.44. The multiple wavelength light emitting device according
to claim 33, wherein one of the first electrode or the second
electrode is formed separately and independently associated with
each of the plurality of light emission regions. .Iaddend.
.Iadd.45. The multiple wavelength light emitting device according
to claim 29 wherein, in the semi-reflecting layer group, the first
and second semi-reflecting layers are placed successively over the
plurality of light emission regions. .Iaddend.
.Iadd.46. The multiple wavelength light emitting device according
to claim 29, wherein the first light emission means includes a
luminescence layer, and the luminescence layer is provided
discretely for each of the plurality of light emission regions.
.Iaddend.
.Iadd.47. The multiple wavelength light emitting device according
to claim 29, wherein the first light emission means includes a
luminescence layer, and the luminescence layer is provided commonly
for the plurality of light emission regions. .Iaddend.
.Iadd.48. A display comprising a multiple wavelength light emitting
device claimed in claim 29. .Iaddend.
.Iadd.49. An electric apparatus comprising a multiple wavelength
light emitting device claimed in claim 29. .Iaddend.
.Iadd.50. The electronic apparatus according to claim 49, wherein
the plurality of light emission regions are formed as pixels for
displaying images, and function as display elements configured so
that the driving of pixels can be controlled in response to image
information. .Iaddend.
Description
This invention relates to improvements in a light emitting device
capable of emitting multiple colors suitable for application for
example in organic electro-luminescence(=EL) devices.
The art of combining a reflective layer with a multi-layer
dielectric film wherein layers having differing refractive indexes
are alternately stacked, and therewith reflecting light of specific
wavelengths is known. In Shingaku Gihou, OME 94-79 (March, 1995),
pp 7-12, the concept is set forth of using very small resonance
structures based on such multi-layer dielectric films to emit
multiple light colors. According to this literature, by adjusting
the positions of the light emission layer and the reflective
surface where reflection occurs in these very small resonance
structures, resonant light can be output having any of the
wavelengths contained in the light output by the emission
layers.
In Japanese Patent Laid-open No. 275381/1994, for example, a light
emitting device having the layer structure illustrated in FIG. 13
is disclosed. This light emitting device comprises a transparent
substrate 100, a very small resonance structure 102, a positive
electrode 103, a hole transport layer 106, an organic EL layer 104,
and negative electrodes 105. The wavelengths are selected by
altering each of the thicknesses of the positive electrodes
103.
In the article written by members of Bell laboratory, J. Appl.
Phys. 80(12), Dec. 15, 1996, a light emitting device having the
layer structure illustrated in FIG. 14 is disclosed. This light
emitting device comprises a transparent substrate 100, a very small
resonance structure 102, SiO.sub.2 film 108, a positive electrode
103, a hole transport layer 106, an organic EL layer 104, and
negative electrodes 105. The thicknesses of the negative electrodes
103 are the same, but the optical path lengths are altered,
respectively, by an SiO.sub.2 layer, to select the resonant light
wavelength.
With light emitting devices having the structure set forth in the
publicized literature noted above, however, there is a problem in
that it is very difficult to design light emitting devices
optimized for all of a plurality of wavelengths. In other words,
the very small resonance structure and gap adjustment materials are
optimized for a specific wavelength dispersion. Wherefore, with a
very small resonance structure designed so that it is compatible
with one of the plurality of light colors having a range of
wavelengths, adequate reflectance cannot be achieved relative to
other wavelength dispersions. In a color display apparatus, for
example, it is necessary to balance the resonance intensity and
color purity of each of the colors R (red), G (green), and B (blue)
according to the characteristics of human vision. Such balancing
adjustments are difficult with conventional light emitting
devices.
That having been said, it is nevertheless very difficult in actual
manufacturing practice to make the structure of the multi-layer
dielectric film different for each pixel (light emission region)
unit, therefor this is a difficult method to realise industrially,
and hence an expensive process.
Thereupon, a first object of the present invention is to provide a
multiple wavelength light emitting device that is balanced and
optimized for a plurality of wavelengths.
A second object of the present invention is to provide a multiple
wavelength light emitting device wherewith optimization for a
plurality of wavelengths is easy, and the manufacture thereof is
easy.
A third object of the present invention is to provide an electronic
apparatus capable of emitting light of a plurality of optimized
wavelengths.
A fourth object of the present invention is to provide an
interference mirror capable of sharpening and emitting a multiple
wavelength light spectrum.
An invention that realizes the first object noted above is a
multiple wavelength light emitting device for emitting multiple
light beams having differing wavelengths, comprising: 1) light
emission means for emitting light containing the wavelength
components to be output; 2) a reflecting layer positioned in
proximity to the light emission means; and 3) a semi-reflecting
layer group that is positioned so as to be in opposition with the
reflecting layer with the light emission means sandwiched
therebetween, wherein semi-reflecting layers that reflect some of
the light emitted from the light emission means having specific
wavelengths, while transmitting the remainder, are stacked up in
order in the direction of light travel corresponding to the light
wavelengths to be output.
The present invention is also a multiple wavelength light emitting
device that comprises at least two but possibly more light emission
regions such that the wavelengths of the output light differ,
structured so that the distance between a reflecting surface for
light from the light emission means side on the semi-reflecting
layers that reflect some of the light output from one of the
plurality of light emission regions and a point that exists in the
interval from the end of the light emission means on the
semi-reflecting layer group side to the reflecting layer is
adjusted so that it becomes an optical path length at which light
of the wavelength output from that light emission region
resonates.
Based on the structure described above, the semi-reflecting layer
group is optimized for all light wavelengths that are to be
emitted, in any of the light emission regions. By adjusting the
distance between the reflecting surface of the semi-reflecting
layers for the light from the light emission means side and the
point existing in the interval from the end of the semi-reflecting
layer group side of the light emission means to the reflecting
layer, and preferably the distance between the light emission
points within the light emission means and the surface (reflecting
surface) on the light emission means side of the reflecting layer,
according to the light emission means and reflecting layer used,
which optimized light is output is determined. The semi-reflecting
layers other than those optimized for light of wavelengths other
than those output merely function commonly as semi-transparent
layers exhibiting a certain attenuation factor, wherefore it is
possible to maintain balance between light of multiple
wavelengths.
There is no limitation on the "light emission means," as used here,
but it is at least necessary that the wavelength component be
generated for the light that one wishes to output. The "reflective
layer" should form a flat surface, but it does not necessarily have
to have a uniform flat surface. The language "in proximity to"
includes cases where there is contact with the light emission
means, and cases where the positioning results in a slight gap
therebetween. So long as a reflective action is exhibited, this may
be something that is not closely and indivisibly connected to the
light emission means. The "light emission region" is a domain for
outputting light having some wavelength dispersion, and signifies
that light of different wavelengths is output in each light
emission region. "Wavelength" is inclusive of a wide range of
wavelengths, including ultraviolet and infrared radiation in
addition to wavelengths in the visible light region.
"Semi-reflecting layers" include structures such as half mirrors or
polarizing panels in addition to interfering laminar structures
wherein multiple film layers having different refractive indexes
are stacked in layers. In the case of a very small dielectric-based
resonating structure, "reflecting surface" refers to the surface on
the side toward the light emission means. "Optical path length"
corresponds to the product of the medium's refractive index and
thickness.
The specification of the "point existing in the interval from the
semi-reflecting layer group side of the light emission means to the
surface of the reflecting layer" is for the purpose of adjusting
the position in the thickness direction where resonance conditions
will be satisfied by the light emission means configuration. Here,
the positional relationship in the thickness direction (light axis)
is defined, and a plane that emits light or reflects light (in the
case of a reflecting layer) is formed by the set of "points" that
satisfy the resonance conditions in the light emission means
overall. Here, when the point existing in the interval from the end
of the light emission means on the semi-reflecting layer group side
to the reflecting layer is on the reflecting surface of the
reflecting layer, the distance L between the reflecting surface on
the light emission means side in the semi-reflecting layer of the
plurality of semi-reflecting layers that reflects light of
wavelength .lamda., in the light emission region wherein light of
wavelength .lamda. is output, and the point existing in the
interval from the end of the semi-reflecting group side in the
light emission means to the surface of the reflecting layer is
adjusted so as to satisfy the relationship L=.SIGMA.di Eq. 1
.SIGMA.(nidi)+m.sub.1(.PHI./2.pi.).lamda.=m.sub.2.lamda./2 where ni
is the refractive index of the i'th substance between the
semi-reflecting layer and the light emitting surface, di is the
thickness thereof, .PHI. is the phase shift occurring at the
reflecting surface in the reflecting layer, and m.sub.1 and m.sub.2
are natural numbers. L corresponds to the actual distance, while
.SIGMA. (nidi) corresponds to the optical path length. It is a
necessary condition for resonance between the semi-reflecting
surface and the reflecting surface placed on the side opposite
thereto that the sum of the optical path length and the phase shift
be a natural multiple of the half-wavelength.
There are also cases where a resonance condition is set, setting
the point in the interval from the end of the light emission means
on the semi-reflecting layer group side to the reflecting layer as
the light emission point in the light emission means. In such cases
as this, the distance L between the reflecting surface on the light
emission means side in the semi-reflecting layer of the plurality
of semi-reflecting layers that reflects light of wavelength
.lamda., in the light emission region wherein light of wavelength
.lamda. is output, and the point existing in the interval from the
end of the semi-reflecting group side in the light emission means
to the surface of the reflecting layer is adjusted so as to satisfy
the relationship L=.SIGMA.di Eq. 2
.SIGMA.(nidi)=m.sub.2.lamda./2+(2m.sub.3+1).lamda./4 where ni is
the refractive index of the i'th substance between the reflective
surface and the point, di is the thickness thereof, m.sub.2 is a
natural number, and m.sub.3 is an integer greater than 0.
The semi-reflecting layer group here is placed evenly so that
multiple types of semi-reflecting layers having differing
wavelengths corresponding to the plurality of light wavelengths are
not separated by a light emission region. The reflecting surface
for the light from the light emission means side of the
semi-reflecting layer in the semi-reflecting layer group is in a
different position in the thickness direction for each light
emission region having a different light emission wavelength.
It is to be preferred that the semi-reflecting layer group be
arranged so that the semi-reflecting layer reflecting light of
longer wavelength is on the side nearer to the light emitting
device. This is because it is harder for light of short wavelength
to be reflected by a semi-reflecting layer optimized for light of
longer wavelength.
More specifically, the semi-reflecting layers making up the
semi-reflecting layer group are configured such that two layers of
differing refractive index are stacked up alternately. If we have
two semi-reflecting layers having different refractive indexes, for
example, and take n1 as the refractive index of one layer, d1 as
the thickness thereof, n2 as the refractive index of the other
layer, and d2 as the thickness thereof, then, when the wavelength
of the light reflected in that semi-reflecting layer is .lamda. and
m is made 0 or a natural number, then an adjustment is made to
satisfy the relationship n1d1=n2d2=(1/4+m/2).lamda. Eq. 3 This is
an interference condition in this resonance structure. It
corresponds to the half-wavelength in one combination of two
layers. Reflection occurs when light from a layer of low refractive
index is incident on a layer of high refractive index, wherefore it
is desirable that the arrangement be high refractive index) layer,
low layer, high layer, low layer, etc., stacking from the light
emission means.
In the invention that realizes the second object noted above, the
distance from the reflecting surface for light from the light
emission means side of the semi-reflecting layer closest to the
light emission means to a point existing in the interval from the
end of the light emission means on the semi-reflecting layer group
side to the reflecting layer, and preferably the distance from the
light emission point in the light emission means and the surface on
the light emission means side of the reflecting layer, according to
light emission means and reflecting layer used, are maintained at
optical path lengths that satisfy Equations 1 and 2 above. And a
gap adjustment layer is comprised, between the semi-reflecting
layers, for adjusting the distance between the reflecting surface
for light from the light emission means side in a semi-reflecting
layer other than the semi-reflecting layer closest to the light
emission means and the point existing in the interval from the end
of the light emission means on the semi-reflecting layer group side
to the reflecting layer. The light emission means can be provided
flat, without making the height thereof different in the thickness
direction, wherefore the complex process of changing the layer
thickness in each light emission region during manufacture can be
omitted. The "gap adjustment means" need only exhibit light
transmissivity, and may be freely selected from among resins or
dielectric materials.
In the present invention, moreover, the distance from the
reflecting surface for light from the light emission means side of
the semi-reflecting layer closest to the light emission means to a
point existing in the interval from the end of the light emission
means on the semi-reflecting layer group side to the reflecting
layer, and preferably the distance from the light emission point in
the light emission means and the surface on the light emission
means side of the reflecting layer, according to light emission
means and reflecting layer used, are maintained at lengths that
satisfy Equations 1 and 2 above. And, in order to adjust the
distance between the reflecting surface for light from the light
emission means side in a semi-reflecting layer other than the
semi-reflecting layer closest to the light emission means and the
point existing in the interval from the end of the light emission
means on the semi-reflecting layer group side to the reflecting
layer, the thickness of one layer, in the laminar structure
configuring the semi-reflecting layers wherein layers of different
refractive index are stacked up, is altered. The gap is adjusted at
the layer at the boundary with the semi-reflecting layer, wherefore
the quantity of materials used can be cut back, and it is only
necessary, in terms of fabrication process, to control the film
thickness when forming the layer the thickness thereof is to be
adjusted, so the fabrication process can be omitted. It is
preferable that the layer used for adjusting the thickness be the
layer of high refractive index that is closest among the
semi-reflecting layers to the light emission means.
In one aspect of the light emission means, multiple types of light
emission means that emit a relatively large number of light
components having wavelengths associated with light emission
regions are provided so that they are associated with the light
emission regions. This applies to cases where optimal light
emitting materials are used which contain the wavelength components
for the light output in each light emission region.
In another aspect of the light emission means, light emission means
are provided, common to each light emission region, capable of
emitting light including all components of wavelengths associated
with the light emission regions. If light emitting materials can be
used which contain all of the light wavelength components to be
output, then there is no need to prepare different light emitting
material in each light emitting region.
In concrete terms, the light emission means may comprise an organic
electro-luminescence layer sandwiched between electrode layers,
wherein the electrode provided at the back surface thereof
corresponds to the reflection layer. In an organic
electro-luminescence layer such as this, there are cases where the
point where the electric field reaches maximum between the
electrodes coincides with the light emission point in the light
emitting layer. It is preferable here that the light emission means
be provided with a hole transport layer on the side toward the
positive electrode. The light emission means may also be provided
with an electron transport layer on the side of the organic
electro-luminescence layer toward the negative electrode.
When an organic electro-luminescence device is used, the distance
between the reflecting surface for light from the light emission
means side of the semi-reflecting layers and a point existing in
the interval from the end of the light emission means on the
semi-reflecting layer side to the reflecting layer is adjusted by
the thickness of the positive electrode located on the
semi-reflecting layer group side of the light emission means.
When an organic electro-luminescence device is used, moreover, a
layer for adjusting the distance between the reflecting surface for
light from the light emission means side of the semi-reflecting
layers and a point existing in the interval from the end of the
light emission means on the semi-reflecting layer side to the
reflecting layer (such as a hole transport layer) may be provided
on the side of the light emission means toward the semi-reflecting
layer group.
The negative electrode is configured of a material exhibiting light
reflectance. If some degree of light reflectance is exhibited, then
it can be used as a reflecting surface for the semi-reflecting
layer.
When the configuration is made to enable light emission by the
light emission region, at least one or other of the electrode films
sandwiching the organic electro-luminescence layers is formed
separately and independently in correspondence with the light
emission region. If one or other of the electrode layers is
separated, an active matrix drive configuration is formed, whereas
if both electrodes are separated, a passive matrix drive
configuration is formed.
In terms of a concrete aspect, it is desirable that the electrodes
be separated by a partitioning material and, if necessary, that the
organic electro-luminescence layer also be partitioned off. Such a
partitioning material would consist of an insulator material.
In another possible aspect, of the electrode films, the negative
electrode is made to correspond to the light emission region and
separated, while the positive electrode, in order to adjust the
distance from the reflecting surface for light from the light
emission means side of the semi-reflecting layer closest to the
light emission means to a point existing in the interval from the
end of the light emission means on the semi-reflecting layer group
side to the reflecting layer, has the thickness thereof changed and
made to correspond to the light emission region.
In yet another possible aspect, of the electrode films, the
positive electrode is made to correspond to the light emission
region and separated, and also, in order to adjust the distance
from the reflecting surface for light from the light emission means
side of the semi-reflecting layer closest to the light emission
means to a point existing in the interval from the end of the light
emission means on the semi-reflecting layer group side to the
reflecting layer, has the thickness thereof changed and made to
correspond to the light emission region.
When such independent electrodes are provided, drive circuits are
provided separately for driving the electrically separated
electrode films.
An invention that realizes the third object noted above is an
electronic apparatus that is equipped with the multiple wavelength
light emitting device of the present invention, as described in the
foregoing. One possible concrete aspect thereof is an electronic
apparatus that functions as a display element, configured such that
the light emission regions in the multiple wavelength light
emitting device are formed as pixels for displaying images, and
such that the drive of each pixel can be controlled in response to
pixel information.
An invention that realizes the fourth object noted above is an
interference mirror, configured so as to be able to partially
reflect light of mutually differing wavelengths, and comprising a
plurality of interference reflecting layers arrayed sequentially in
the optical axis direction, and gap adjustment layers positioned
between the interference reflecting layers.
Embodiments of the present invention will now be described by way
of further example only and with reference to the accompanying
drawings; in which:
FIG. 1 is a cross-sectional diagram of the layer structure of a
multiple wavelength light emitting device in a first embodiment of
the present invention;
FIG. 2 is a diagram for explaining the interference conditions in a
semi-reflecting layer;
FIG. 3 is a cross-sectional diagram of the layer structure of a
multiple wavelength light emitting device in a second embodiment of
the present invention;
FIG. 4 is a cross-sectional diagram of the layer structure of a
multiple wavelength light emitting device in a third embodiment of
the present invention;
FIG. 5 is a cross-sectional diagram of the layer structure of a
multiple wavelength light emitting device in a fourth embodiment of
the present invention;
FIG. 6 is a cross-sectional diagram of the layer structure of a
multiple wavelength light emitting device in a fifth embodiment of
the present invention;
FIG. 7 is a cross-sectional diagram of the layer structure of a
multiple wavelength light emitting device in a sixth embodiment of
the present invention;
FIG. 8 is a cross-sectional diagram of the layer structure of a
multiple wavelength light emitting device in a seventh embodiment
of the present invention;
FIG. 9 is a cross-sectional diagram of the layer structure of a
multiple wavelength light emitting device in an eighth embodiment
of the present invention;
FIG. 10 is a cross-sectional diagram of the layer structure of a
multiple wavelength light emitting device in a ninth embodiment of
the present invention;
FIG. 11 is a cross-sectional diagram of the layer structure of a
multiple wavelength light emitting device in a tenth embodiment of
the present invention;
FIG. 12 is a cross-sectional diagram of the layer structure of a
multiple wavelength light emitting device in an eleventh embodiment
of the present invention;
FIG. 13 is a cross-sectional diagram of the layer structure in a
positive electrode gap adjustment type of light emitting device
equipped with a conventional single semi-reflecting layer; and
FIG. 14 is a cross-sectional diagram of the layer structure in a
dielectric gap adjustment type of light emitting device equipped
with a conventional single semi-reflecting layer.
Embodiment 1
The first embodiment of the present invention pertains to a basic
structure in a case where three basic colors of light can be
emitted, as necessary for a color display, and gap adjustments are
made with the positive electrode. The layer structure of the
multiple wavelength light emitting device in the first embodiment
is illustrated in FIG. 1. This multiple wavelength light emitting
device, as depicted in FIG. 1, comprises a substrate 1, a
semi-reflecting layer group 2, a positive electrode 3, a light
emitting layer 4, and a negative electrode 5.
The substrate 1, which serves as the base during fabrication, is
made of a material that exhibits light transmissivity and certain
mechanical strengths, and that can withstand heat treatment during
fabrication. Such materials as glass, quartz, or resins are
suitable for this substrate.
The semi-reflecting layer group 2 is configured by a stack of
semi-reflecting layers 2R, 2G, and 2B, optimized for light of a
certain wavelength. The semi-reflecting layer 2R is optimized to
interfere with a red emitted light wavelength (in vicinity of 625
nm). The semi-reflecting layer 2G is optimized to interfere with a
green emitted light wavelength (in vicinity of 525 nm). And the
semi-reflecting layer 2B is optimized to interfere with a blue
emitted light wavelength (in vicinity of 450 nm). The
semi-reflecting layers are arrayed with the semi-reflecting layer
2R that resonates with light of longer wavelength (red) placed on
the side closer to the light emitting layer 4, the semi-reflecting
layer 2G that resonates with light of a shorter wavelength (green)
placed below that (lower down in FIG. 1), and with the
semi-reflecting layer 2B that resonates with light of the shortest
wavelength (blue) placed below that. It is difficult for light of
short wavelength to be reflected by a semi-reflecting layer
optimized for light of a longer wavelength. Thus, by ordering the
layers in this way, a more efficient light emitting device can be
configured.
FIG. 2 is a diagram for explaining the interference conditions
together with an expanded view of the layer structure in the
semi-reflecting layers. Each semi-reflecting layer is configured as
an alternate stack of two layers having different refractive index,
namely a first layer 21 and a second layer 22. In terms of the
interference conditions as relating to the refractive index and
thickness, adjustments are made so as to satisfy the relationship
n1d1=n2d2=(1/4+m/2).lamda. Eq. 3 where n1 is the refractive index
of the first layer 21, d1 is the thickness thereof, n2 is the
refractive index of the second layer 22, and d2 is the thickness
thereof. Also, .lamda. is the wavelength of light reflected in that
semi-reflecting layer and m is an integer greater than 0. This
corresponds to the half-wavelength of light in one two-layer
combination. Reflection occurs when light from a layer of low
refractive index is incident in a layer of high refractive index.
Therefore it is desirable that the layers be stacked up, from the
side toward the light emission means, as a high (refractive index)
layer, low layer, high layer, low layer, etc.; set, in other words,
so that n1>n2
As to the specific materials used for the semi-reflecting layers
2R, 2G, and 2B, dielectric materials having differing refractive
indexes are stacked up so as to satisfy the relationship
represented in Equation 3. TiO.sub.2 having a refractive index of
2.4 may be used for the first layer 21, for example, and SiO.sub.2
having a refractive index of 1.44 as the second layer 22.
Alternatively, ZnS having a refractive index of 2.37 may be used
for the first layer 21, and MgF.sub.2 having a refractive index of
1.38 as the second layer 22. The layers configuring the
semi-reflecting layers are not limited to dielectric materials,
however, and, for example, a laminar structure formed of resins or
liquid crystals, as disclosed in Japanese Patent Laid-open No.
H10-133222/1998, may be employed. In the semi-reflecting layers,
the thicknesses of the first and second layers are adjusted to
agree with the wavelength in that semi-reflecting layer. When the
difference in refractive index is small between the first and
second layers, the reflectance will decline, wherefore many layers
are stacked up.
The positive electrode 3 is provided so as to exhibit light
transmissivity. The material of the positive electrode is used as
the positive electrode in an organic EL element, wherefore a metal,
alloy, electrically conductive compound, or mixture thereof is used
which exhibits a large work function (4 eV or greater). ITO is a
preferable choice. If it is made thin to such degree that optical
transmissivity can be secured, then other materials such as gold
metal, CuI, SnO.sub.2, and ZnO may be used. Here, the thickness of
the positive electrode is adjusted for optical path length so that
light resonates in each light emission region and so that light
transmissivity is exhibited. With the optical path length, it is
necessary to define two surfaces for causing light to resonate. One
surface is a reflecting surface for the light from the light
emitting layer side of the semi-reflecting layer that partially
reflects light output from that light emission region. The other
surface is variously altered by the morphology of the light
emission means that contain the light emitting layer. Specifically,
this surface will either be a surface that is perpendicular to the
light axis and contains a point in the interval from the end of the
light emitting layer on the semi-reflecting layer group side to the
negative electrode surface (this surface hereinafter expressed by
the term "light emitting surface") or the reflecting surface on the
negative electrode side. In each drawing, the position of the other
surface is shown at the interface between the negative electrode
and light emitting layer. However, as noted above, these positions
can be set in the interval from the surface of the light emitting
layer (or hole transport layer in cases where such is provided) on
the semi-reflecting layer group side to the negative electrode
(reflecting layer). In the red light emission region A.sub.R, the
distance L.sub.R is adjusted so that the optical path distance
between the boundary surface between the light emitting layer 4R
and negative electrode, and the reflecting surface of the
semi-reflecting layer 2R, satisfies the resonance conditions for
red light. In the green light emission region A.sub.G, the distance
L.sub.G is adjusted so that the optical path distance between the
boundary surface between the light emitting layer 4G and the
negative electrode, and the reflecting surface of the
semi-reflecting layer 2G, satisfies the resonance conditions for
green light. And in the blue light emission region A.sub.B, the
distance L.sub.b is adjusted so that the optical path distance
between the boundary surface between the light emitting layer 4B
and the negative electrode, and the reflecting surface of the
semi-reflecting layer 2B, satisfies the resonance conditions for
green light.
Turning to the resonance conditions, as illustrated in FIG. 2, if
.lamda. is taken as the wavelength of the light that is output in
that light emission region, then the distance L between the
interface between the light emitting layer and the negative
electrode, and the reflecting surface for the light from the light
emitting layer of the semi-reflecting layer having a structure that
reflects light of that wavelength .lamda. is adjusted so as to
satisfy the relationship L=.SIGMA.di Eq. 1 (as above)
.SIGMA.(nidi)+m.sub.1(.PHI./2.pi.).lamda.=m.sub.2.lamda.2 where ni
is the refractive index of the i'th substance (including the
dielectric layers in the semi-reflecting layers for other
wavelengths) between the reflecting surface of that semi-reflecting
layer and the light emitting surface 40, di is the thickness
thereof, and m.sub.1 and m.sub.2 are natural numbers. When
reflection is caused at the negative electrode surface, the phase
shift that develops during reflection at the reflecting surface is
given as .PHI.. Red light in the light emission region A.sub.R does
not pass through the other semi-reflecting layer or layers along
the way, wherefore adjustments are made so that the value of the
product of the thickness and refractive index of the positive
electrode 3 becomes a natural multiple of the half-wavelength.
As to the resonance conditions, as described in the foregoing, when
a light emitting surface is set with one point in the light
emitting layers 4R, 4G, and 4B as the light emission point, the
distances L (L.sub.R, L.sub.G, L.sub.B) between the reflecting
surface on the light emitting layer side in the semi-reflecting
layers 2R, 2G, and 2B that reflect light of wavelength .lamda. and
a point existing in interval from the end of the semi-reflecting
layer side in the light emitting layers 4R, 4G, and 4B to the
reflecting layer (that is, the interface between the light emitting
layer 4 and negative electrode 5) is adjusted so as to satisfy the
relationship L=.SIGMA.di Eq. 2 (as above)
.SIGMA.(nidi)=m.sub.2.lamda./2+(2m.sub.3+1).lamda./4 where ni is
the refractive index of the i'th substance between the reflecting
surface and the point, di is the thickness thereof, m.sub.2 is a
natural number, and m.sub.3 is an integer greater than 0.
The light emitting layers 4R, 4G, and 4B are formed, respectively,
of organic EL materials. The organic EL materials used emit light
containing a relatively high amount of light components of
wavelengths associated with the light emission regions. The light
emitting surface changes depending on whether or not a charge
transport layer exists, as will be described in conjunction with a
subsequent embodiment. The thickness of each light emitting layer
is determined according to the relationship between the negative
electrode that is the reflecting surface and the light emission
wavelength. For the material of the light emitting layer it is
possible to employ materials being researched and developed as
organic electro-luminescence device materials, such as those set
forth in Japanese Patent Laid-open No. 163967/1998 and Japanese
Patent Laid-open No. 248276/1996. Specifically, the materials used
for the red light emitting layer 4R include cyanopolyphenylene
vinyline precursor,
2-1,3',4'-dihydroxyphenyl-3,5,7-trihydroxy-1-benzopolyriumperchlorate,
or PVK doped with DCM1. The materials used for the green light
emitting layer 4G include polyphenylene vinyline precursor,
2,3,6,7-tetrahydro-11-oxo-1H,5H,11H-(1)penzopyrano6,7,8-ij-quinolidine-10-
-carbonate, and PVK doped with quotamine 6. And the materials used
for the blue light emitting layer 4B include aluminum quinolinol
complex, pyrozoline dimer,
2,3,6,7-tetrahydro-9-methyl-11-oxo1H,5H,11H-(1)
penzopyrano6,7,8-ij-quinolidine, distyro derivative, and PVK doped
with 1,1,4,4-triphenyl-1,3-butadiene.
The negative electrode 5 functions as the negative electrode of the
organic EL element, so a metal, alloy, electrically conductive
compound, or mixture thereof having a small work function (4 eV or
below) is used. It is particularly desirable, in the interest of
enhancing the efficiency of the light emitting layer and causing
the light to strongly resonate, that a material of high reflectance
be used. Specifically, such substances include diamond, aluminum
nitride, boron nitride, sodium, sodium-potassium alloys, magnesium,
lithium, magnesium-copper mixtures, magnesium-silver mixtures,
magnesium-aluminum mixtures, magnesium-indium mixtures,
aluminum-aluminum oxide mixtures, indium, lithium-aluminum
mixtures, and rare earth metals lithium fluride-aluminum, ie add
flurides with A1 as either bilayer or Alloy.
In the configuration described above, when a certain voltage is
applied across the positive electrode 3 and negative electrode 5,
current flows to the light emitting layers, inducing an
electro-luminescence effect, whereupon light containing wavelength
components in the spectrum defined by the light emitting material
is emitted on both sides of the layer. The light emitted on the
side of the negative electrode 5 is reflected, interferes either
with the direct light from the light emitting surface or with the
light reflected on the negative electrode side, and is ejected to
the ejection side (downward in FIG. 1). At this time, there is a
refractive index differential in the dielectric layers configuring
the semi-reflecting layer, wherefore reflection occurs at the
interface of the dielectric layers having different refractive
indexes. According to the interference conditions of Equation 3
exhibited by the dielectric layers, there is either a mutual
canceling or mutual reinforcing effect, and only that light having
the wavelength optimized in the dielectric material is reflected
with high efficiency. This interferes with the light from the light
emitting layer side, that is, with the light reflected by the
negative electrode surface and the direct light from the light
emitting layer, and only light having a wavelength that coincides
with the resonance conditions expressed above in Equation 1 or 2,
for example, resonates between the reflecting surface and the light
emitting surface. As to the light having other wavelength
components, when light from the light emitting layer is incident on
the semi-reflecting layer corresponding to those wavelength
components, the phase does not match and resonance does not occur,
wherefore such light is relatively weakened. As a consequence, that
wavelength spectrum is sharpened, and high-intensity light passes
through the semi-reflecting layer and is ejected. The other
semi-reflecting layers that do not match the resonance conditions
function merely as semitransparent films, and the light attenuation
and other effects resulting thereby are roughly the same in every
wavelength domain. For this reason, light of a plurality of
wavelengths, balanced in terms of intensity and color purity, will
be output from each light emission region.
As based on the first embodiment described in the foregoing,
resonance structures for each of three basic colors are stacked up,
and resonance conditions are determined by adjusting the distance
between the reflecting surface for light from the light emission
means side of the semi-reflecting layers to a point existing in the
interval from the end of the light emitting layer on the
semi-reflecting layer side to the reflecting layer, wherefore it is
possible to eject balanced light of a plurality of wavelengths.
As based on this embodiment, moreover, a semi-reflecting layer
optimized for longer wavelengths is provided on the light emitting
layer side, wherefore light can be emitted without affecting the
light of other wavelengths.
As based on this embodiment, furthermore, an organic EL element is
adopted as the light emission means, making it possible to select a
material having suitable wavelength dispersion from among many
different materials.
As based on this embodiment, moreover, the light emitting material
is changed in light emission wavelength units, wherefore light of
higher purity and intensity can be output.
As based on this embodiment, furthermore, the negative electrode is
formed of a light-reflecting material, thus making it possible to
effect resonance efficiently.
Embodiment 2
A second embodiment of the present invention pertains to a
configuration wherein a hole transport layer is provided in the
organic EL element of the first embodiment. In FIG. 3 is
illustrated the layer structure of the multiple wavelength light
emitting device of the second embodiment. This multiple wavelength
light emitting device, as illustrated in FIG. 3, comprises a
substrate 1, a semi-reflecting layer group 2, a positive electrode
3, a hole transport layer 6, a light emitting layer 4, and a
negative electrode 5.
The hole transport layer 6, also called a hole injection layer, is
made of an organic or inorganic material exhibiting either a hole
injection function or an electron barrier-forming function.
Materials disclosed in Japanese Patent Laid-open No. 163967/1988 or
Japanese Patent Laid-open No. 248276/1996, for example, may be
used. More specifically, the substances that may be used include
triazole derivatives, oxadiazole derivatives, polyaryl alcane
derivatives, pyrazoline derivatives, pyrazolone derivatives,
phenylene diamine derivatives, arylamine derivatives,
amino-substitution chalcone derivatives, oxazole derivatives,
styrylanthracene derivatives, fluoronolene derivatives, hydrazone
derivatives, stilbene derivatives, silazane derivatives, polysilane
copolymers, aniline copolymers, and electrically conductive complex
oligomers. The thickness thereof is made just sufficient to support
the hole carrier function. However, when a hole transport layer is
used, it is possible for the light emitting surface to be close to
the interface between the hole transport layer 6 and the light
emitting layer 4. Accordingly, in the interest of efficient light
emission, thickness conditions are set for the light emitting layer
and the hole transport layer such that mutual cancellation will not
result from reflection by the negative electrode 5.
Other than this, the layer structure is the same as in the first
embodiment and no further description is made here. When providing
the hole transport layer, depending on the materials used in the
light emitting layer and hole transport layer, the thicknesses
thereof are adjusted so as to optimally obtain the desired
wavelength characteristics.
As based on the second embodiment, in addition to realizing the
same benefits as with the first embodiment, the addition of the
hole transport layer enables the light emission efficiency of the
organic EL element to be enhanced, resulting in an even brighter
light emitting device.
Embodiment 3
A third embodiment pertains to a configuration wherein an electron
transport layer is provided in the organic EL element in the second
embodiment. The layer structure of the multiple wavelength light
emitting device in the third embodiment is illustrated in FIG. 4.
As illustrated in FIG. 4, a substrate 1, a semi-reflecting layer
group 2, a positive electrode 3, a hole transport layer 6, a light
emitting layer 4, an electron transport layer 7, and a negative
electrode 5 are provided.
The electron transport layer, also called an electron injection
layer, has a function whereby it takes electrons injected from the
negative electrode and conveys them efficiently to the light
emitting layer. Materials disclosed in Japanese Patent Laid-open
No. 163967/1988, Japanese Patent Laid-open No. 248276/1996 or
Japanese Patent Laid-open No. 194393, for example, may be used.
More specifically, the substances that may be used include
nitro-substitution fluorolene derivatives, anthraquinodimethane
derivatives, diphenylquinone derivatives, thiophan dioxide
derivatives, naphthalene perilene and other heterocyclic
tetracarbonate anhydrides, carbodiimide, freolenidine methan
derivatives, anthraquinodimethanne and anthrolone derivatives,
oxadiazole derivatives, and quinoxaline derivatives. The thickness
thereof is made just sufficient to support the electron carrier
function.
In other respects the layer structure is the same as in the second
embodiment described above, so no further description is given
here. However, the hole transport layer may be provided, or
omitted, with the decision as to whether to provide it or not being
based on a balance with the organic EL material.
As based on this third embodiment, in addition to realizing the
same benefits as with the second embodiment described earlier, the
addition of the electron transport layer enables the light emission
efficiency of the organic EL element to be enhanced, resulting in
an even brighter light emitting device.
Embodiment 4
A fourth embodiment of the present invention pertains to a
configuration wherein the adjustment of the optical path length
that is a resonance condition in the organic EL element in the
first embodiment is performed with insulators. In FIG. 5 is
illustrated the layer structure of the multiple wavelength light
emitting device in the fourth embodiment. This multiple wavelength
light emitting device, as illustrated in FIG. 5, comprises a
substrate 1, a semi-reflecting 2, a positive electrode 3,
insulators 8G and 8B, a light emitting layer 4, and a negative
electrode 5.
In this fourth embodiment, the positive electrode 3 is matched with
the resonance conditions in the red light emission region A.sub.R
and formed in the same thickness in the other light emission
regions also. On the other hand, however, in the green light
emission region A.sub.G and the blue light emission region A.sub.B,
respectively, insulators 8G and 8B are provided, in different
thicknesses, so as to satisfy the resonance conditions in Equations
1 and 2. However, in this embodiment, all that has been done is to
adjust the optical path length in order to cause resonance in the
green and blue light emission regions, and an insulator may be
placed in the red domain. The insulators 8G and 8B may be made of
an organic or inorganic substance exhibiting light transmissivity.
A dielectric such as SiO.sub.2, Si.sub.3N.sub.4, or TiO.sub.2 may
be used, for example. However, there is a difference in refractive
index between the dielectric and the positive electrode, wherefore
the distances L.sub.G and L.sub.B from the semi-reflecting layers
2G and 2B to the light emitting surface will differ slightly from
the first embodiment. In other respects the layer structure is the
same as in the embodiments described earlier. When the charge
carrier capability in the light emitting layer is low, moreover, a
hole transport layer or an electron transport layer, or both, may
be provided as in the second and third embodiments.
As based on this fourth embodiment, in addition to realizing the
same benefits as in the embodiments described earlier, since the
positive electrode can be formed with a uniform thickness, light
emitting devices can be provided which are easier to fabricate when
using a positive electrode material wherewith it is difficult to
impart thickness differences.
Embodiment 5
In the embodiments described above, a different light emitting
layer is provided in each light emission region. In a fifth
embodiment of the present invention, however, the same light
emitting layer is provided for all of the light emission regions.
In FIG. 6 is illustrated the layer structure of the multiple
wavelength light emitting device in the fifth embodiment. This
multiple wavelength light emitting device, as illustrated in FIG.
6, comprises a substrate 1, semi-reflecting layer group 2, positive
electrode 3, light emitting layer 4, and negative electrode 5.
In this embodiment, the light emitting layer 4 is provided commonly
for all of the light emitting layers. It is desirable that the
light emitting layer be made of a wide-band light emitting material
containing in good balance the wavelength components of the light
supplied from the light emission regions in an intensity more than
the predetermined level. The materials which may be used for this
purpose include, for example, aluminum chelate (Alq.sub.3) and
polyparaphenylene vinyline. The distance between the reflecting
surface of the semi-reflecting layer and the light emitting surface
is considered to be the same as in the first embodiment. When the
charge carrier capability in the light emitting layer is low,
moreover, a hole transport layer or an electron transport layer, or
both, may be provided as in the second and third embodiments. It is
also permissible to adjust the optical path length with insulators
as in the fourth embodiment. A diamine derivative (TAD) might be
used for the hole transport layer used together with Alq.sub.3.
In this configuration, light containing all of the wavelength
components to be output is ejected from the light emitting layer 4.
For this reason, in any of the semi-reflecting layers, light having
a wavelength optimized for that reflecting layer will be reflected.
However, the distance between the reflecting surface of the
semi-reflecting layer and either the light emission point (light
emitting surface) in the light emitting layer or the reflecting
surface of the negative electrode is optimized so as to match the
resonance conditions for a wavelength associated with each light
emission region, wherefore only light having a wavelength within
those resonance conditions is ejected with a sharpened
spectrum.
As based on this fifth embodiment, in addition to realizing the
same benefits as with the other embodiments, there is no need to
fabricate a light emitting layer separately for each light emission
region, wherefore manufacture is simplified.
Embodiment 6
In the embodiments described in the foregoing, different resonance
conditions are set for each light emission region with the positive
electrode or insulators. In a sixth embodiment, however, the
resonance conditions are altered while keeping the thickness of
every layer uniform. In FIG. 7 is illustrated the layer structure
of the multiple wavelength light emitting device of this sixth
embodiment. This multiple wavelength light emitting device, as
illustrated in FIG. 7, comprises a substrate 1, a semi-reflecting
layer group 2 provided with spacers 9G and 9B, a positive electrode
3, a light emitting layer 4, and a negative electrode 5.
The spacers 9G and 9B are layers provided for adjusting the gaps
between the semi-reflecting layers. These spacers should be made of
a material such as a resin or dielectric that exhibits high light
transmissivity and that bonds well with the semi-reflecting layers.
If it is possible to maintain the distance between the
semi-reflecting layers, needless to say, these layers may be
configured of a gas, a liquid, or a liquid crystal, etc. The
spacers 9G and 9B may be made of different materials having
different refractive indexes. The materials for the light emitting
layers are selected so that in the light emitting layer 2R in the
red light emission region A.sub.R more red light wavelength
components are present, so that in the light emitting layer 2G in
the green light emission region A.sub.G more green light wavelength
components are present, so that in the light emitting layer 2B in
the blue light emission region A.sub.B more blue light wavelength
components are present, and so that comparatively few other
wavelength components are present. In this embodiment, the layer
structure is the same in every light emission region, it being
necessary to define the light emitting wavelength by the
characteristics of the light emitting layer itself. In terms of
resonance conditions, all of the light emission regions are set at
uniform thickness with the positive electrode 5. That is, the
optical path length between the light emitting surface of the light
emitting layer 4R and the reflecting surface in the semi-reflecting
layer 2R that is closest to the light emitting layer is maintained
so as to correspond to a natural number multiple of the
half-wavelength of the light (red light) reflected in that
semi-reflecting layer. The thicknesses of the spacers 9G and 9B are
adjusted so that the optical path length between the reflecting
surface in the semi-reflecting layer 9G or 9B and the light
emitting surface of the light emission means satisfies the
resonance conditions expressed in Equation 2. More specifically,
for the green light emission region A.sub.g, an optical path length
corresponding to the product of the refractive index n.sub.9G and
the thickness d.sub.9G of the spacer 9G is added to Equation 2, and
material having a refractive index so as to satisfy the resonance
conditions is selected and the thickness set. And for the blue
light emission region A.sub.B, the optical path length
(n.sub.9Gd.sub.9G+n.sub.9B d.sub.9B) for both the spacer 9B and the
spacer 9G is added to Equation 2, and material having a refractive
index so as to satisfy the resonance conditions is selected and the
thickness set. When the charge carrier capability in the light
emitting layer is low, moreover, a hole transport layer or an
electron transport layer, or both, may be provided as in the second
and third embodiments.
In the configuration described in the foregoing, when light is
ejected from the light emitting layer, for the red light
semi-reflecting layer 2R closest to the light emitting layer,
resonance and light emission occurs as in the first embodiment. For
the other light emission regions also, since the optical path
length thereof is adjusted so as to coincide with a natural number
multiple of the half-wavelength, resonance occurs, and a sharpened
spectrum of the resonant wavelength is output.
As based on this sixth embodiment, in addition to realizing the
same benefits as in the other embodiments, the layers inclusive of
the positive electrode and light emitting layer may all be formed
flat and of uniform thickness, wherefore such complex process steps
as patterning can be omitted and, hence, manufacturing costs
reduced.
Embodiment 7
A seventh embodiment pertains to a modification of the gap
adjustment method employed in the sixth embodiment. In FIG. 8 is
illustrated the layer structure of the multiple wavelength light
emitting device in this seventh embodiment. This multiple
wavelength light emitting device, as illustrated in FIG. 8,
comprises a substrate 1, a semi-reflecting layer group 2 equipped
with gap adjustment layers 21G and 21B, a positive electrode 3, a
light emitting layer 4, and a negative electrode 5.
The gap adjustment layer 21G is a layer for adjusting the gap
between the semi-reflecting layers, altering the thickness of the
first layer 21 that is the closest to the light emitting layer of
the green semi-reflecting layers 2G. The gap adjustment layer 21B
is a layer for adjusting the gap between the semi-reflecting
layers, altering the thickness of the first layer 21 that is
closest to the light emitting layer of the blue semi-reflecting
layers 2B. Because the layers configuring the semi-reflecting
layers are themselves dielectric materials, when the thickness of
one layer is made different, that layer ceases to be a layer that
produces interference, and, with the refractive index and thickness
thereof, it will contribute to an increase in the optical path
length given. More specifically, with respect to the green light
emission region A.sub.G, an optical path length corresponding to
the product of the refractive index n1 and thickness d.sub.21G of
the gap adjustment layer 21G is added to Equation 2, and material
having a refractive index that satisfies the resonance conditions
is selected and its thickness set. With respect to the light
emission region A.sub.B, an optical path length
n1(d.sub.21G+d.sub.21B) for both of the gap adjustment layers 21B
and 21G is added to Equation 2, and material having a refractive
index that satisfies the resonance conditions is selected and its
thickness set.
In other respects the configuration is the same as in the sixth
embodiment.
As based on this seventh embodiment, the gap is adjusted with the
layer at the interface with the semi-reflecting layer, wherefore
savings in materials used can be realized, and, when forming the
gap adjustment layer in the process of fabricating the
semi-reflecting layers, it is only necessary to control the film
thickness, thus making it possible to reduce the number of
manufacturing steps.
Embodiment 8
An eighth embodiment pertains to a structure wherewith it is
possible to make a light emitting layer emit light in each light
emission region. The layer structure of the multiple wavelength
light emitting device in this eighth embodiment is illustrated in
FIG. 9. This multiple wavelength light emitting device, as
illustrated in FIG. 9, comprises a substrate 1, a semi-reflecting
layer group 2, a positive electrode 3, a light emitting layer 4, an
electrically divided negative electrode 5, a substrate 11, and
banks 10. Also provided are drive circuits (not shown) for
separately and independently applying control voltages V.sub.R,
V.sub.G, and V.sub.B, to the electrodes 5R, 5G, and 5B that are
electrically separated by the banks 10, together with
interconnecting wiring therefor.
In this embodiment, the banks 10 are provided at the interfaces of
the light emission regions, with negative electrodes formed so that
they are electrically separated in the domains partitioned by the
banks. The substrate 11 is also provided for forming the banks 10
and the negative electrode patterns. A suitable material for the
banks 10 would be polyimide, for example, or another organic or
inorganic substance that is an insulator and that can be patterned
and formed with a fixed height matched with the light emission
region. In addition to electrically separating the negative
electrode, as illustrated, the banks may also be formed so that
they electrically separate the light emitting layer together with
the negative electrode. When configured thusly, the layer structure
corresponding to the organic EL element is sequentially formed on
the base provided by the substrate 11. The substrate 11 need only
exhibit mechanical strength and thermal strength. The drive
circuits may be configured with TFTs, etc., so that they can drive
each light emission region. Since the positive electrode is a
common substrate, it forms an active matrix type of drive scheme.
When the charge carrier capability in the light emitting layer is
low, moreover, a hole transport layer or an electron transport
layer, or both, may be provided as in the second and third
embodiments. The positive electrode may also comprise a structure
wherein insulators are stacked, as indicated in the fourth
embodiment. The light emitting layers may all be provided commonly
also, as in the fifth embodiment.
In the configuration described in the foregoing, when drive
voltages V.sub.R, V.sub.G, and V.sub.B are applied so as to control
the drive circuits in each light emission region, current flows
only in the corresponding light emitting layer, and only the hue of
that light emission region is output. If the light emission regions
are formed so that they are associated with color pixels in a color
display apparatus, and the drive voltage in each light emission
region controlled with a correspondence established with RGB
signals in color image data, the whole will function as a color
display apparatus. In addition, the configuration is such as to
permit the light emission color to be freely altered even when used
as a light emitting device.
As based on the eighth embodiment described in the foregoing, the
configuration is made so that the negative electrode is
electrically separated into units that can be driven separately.
Thus, in addition to realizing the benefits provided by the other
embodiments, it is possible to make the multiple wavelength light
emitting device of the present invention function as a display
apparatus or other electronic apparatus.
Embodiment 9
A ninth embodiment pertains to a modification of the eighth
embodiment wherein the negative electrode is separated by
patterning. The layer structure of the multiple wavelength light
emitting device in this ninth embodiment is illustrated in FIG. 10.
This multiple wavelength light emitting device, as illustrated in
FIG. 10, comprises a substrate 1, a semi-reflecting layer group 2,
a positive electrode 3, a light emitting layer 4, a patterned
negative electrode 5, and a substrate 11. Also provided are drive
circuits (not shown) for separately and independently applying
control voltages V.sub.R, V.sub.G, and V.sub.B, to the electrically
separated negative electrodes 5R, 5G, and 5B, together with
interconnecting wiring therefor.
In this embodiment, the negative electrode 5 is patterned in
association with the light emission regions. The light emitting
layer 4 is provided commonly for all of the light emission regions,
as described in conjunction with the fourth embodiment. The
material for the light emitting layer is the same as in the fourth
embodiment. The substrate 11 is necessary when configuring the
negative electrode by patterning so that it is electrically
separated. In this embodiment also it is preferable that
fabrication begin from the substrate 11. The drive circuits can
separately and independently drive the electrically separated
negative electrodes 5R, 5G, and 5B. In other respects the
configuration is the same as in the first embodiment. If the
positive electrode 3 is also patterned, and fashioned so as to
configure the negative electrode 5 and matrix wiring, then this
light emitting device can be driven as a passive matrix type of
display apparatus.
In this configuration, when drive voltages V.sub.R, V.sub.G, and
V.sub.B are applied to control the drive circuits for each light
emitting domain, current flows only in the corresponding light
emitting layer, and only the hue of that light emission region is
output. If the light emission regions are formed so that they are
associated with color pixels in a color display apparatus, and the
drive voltage in each light emission region controlled with a
correspondence established with RGB signals in color image data,
the whole will function as a color display apparatus. In addition,
the configuration is such as to permit the light emission color to
be freely altered even when used as a light emitting device.
As based on the ninth embodiment described in the foregoing, the
configuration is made so that the negative electrode is
electrically separated into units that can be driven separately.
Thus, in addition to realizing the benefits provided by the other
embodiments, it is possible to provide a multiple wavelength light
emitting device having a comparatively simple layer structure that
can be easily fabricated.
Embodiment 10
A tenth embodiment pertains to a configuration wherein, contrary to
the eighth embodiment, the positive electrode is separated by
banks. The layer structure of the multiple wavelength light
emitting device in this tenth embodiment is illustrated in FIG. 11.
This multiple wavelength light emitting device, as illustrated in
FIG. 11, comprises a substrate 1, a semi-reflecting layer group 2,
a positive electrode 3 separated by banks 10, a light emitting
layer 4, a negative electrode 5, and a substrate 11. Also provided
are drive circuits (not shown) for separately and independently
applying control voltages V.sub.R, V.sub.G, and V.sub.B, to the
electrically separated positive electrodes 3R, 3G, and 3B, together
with interconnecting wiring therefor.
In this embodiment, banks 10 are provided so that they can separate
the light emitting layer and the positive electrode in each light
emitting domain. The same materials and formation method can be
used for the banks 10 and the substrate 11 as set forth in
conjunction with the eighth embodiment. It is particularly
desirable that the ink jet method set forth in Japanese Patent
Laid-open No. H10-153967/1998 be used as the fabrication method for
forming the banks on the substrate and pattern-forming the
electrodes and light emitting layer. As to the drive scheme, when
the negative electrode 5 is made a common electrode as in this
embodiment, it is possible to provide a TFT on the side of the
positive electrode 3, thereby permitting operation as an active
matrix drive scheme. Also, by electrically separating the negative
electrode side also, using banks and patterning, and forming a
matrix-form electrode structure above and below the light emitting
layer, it is possible to effect operation as a simple matrix drive
scheme.
When the charge carrier capability in the light emitting layer is
low, moreover, a hole transport layer or an electron transport
layer, or both, may be provided as in the second and third
embodiments, The positive electrode may also comprise a structure
wherein insulators are stacked, as indicated in the fourth
embodiment. The light emitting layers may all be provided commonly
also, as in the fifth embodiment.
In this configuration, when drive voltages V.sub.R, V.sub.G, and
V.sub.B are applied to control the drive circuits for each light
emitting domain, current flows only in the corresponding light
emitting layer, and only the hue of that light emission region is
output. If the light emission regions are formed so that they are
associated with color pixels in a color display apparatus, and the
drive voltage in each light emission region controlled with a
correspondence established with RGB signals in color image data,
the whole will function as a color display apparatus. In addition,
the configuration is such as to permit the light emission color to
be freely altered even when used as a simple light emitting
device.
As based on the tenth embodiment described in the foregoing, the
configuration is made so that the positive electrode is
electrically separated into units that can be driven separately.
Thus, in addition to realizing the benefits provided by the other
embodiments, it is possible to make the multiple wavelength light
emitting device of the present invention function as a display
apparatus or other electronic apparatus.
Embodiment 11
An eleventh embodiment pertains to a modification of the tenth
embodiment wherein the positive electrode is separated by
patterning. The layer structure of the multiple wavelength light
emitting device in this eleventh embodiment is illustrated in FIG.
12. This multiple wavelength light emitting device, as illustrated
in FIG. 12, comprises a substrate 1, a semi-reflecting layer group
2, a patterned positive electrode 3, a light emitting layer 4, a
negative electrode 5, and a substrate 11. Also provided are drive
circuits (not shown) for separately and independently applying
control voltages V.sub.R, V.sub.G, and V.sub.B, to the electrically
separated positive electrodes 3R, 3G, and 3B, together with
interconnecting wiring therefor.
In this embodiment, the positive electrode 3 is patterned in
association with the light emitting domains. The polarity of the
drive circuits is opposite to the polarity in the eighth and ninth
embodiments described earlier. The drive circuits, moreover, are
fashioned so that they can individually and independently drive the
electrically separated positive electrodes 3R, 3G, and 3B. In other
respects, the configuration is the same as that of the eighth
embodiment. In this embodiment, because the negative electrode side
is not formed so as to be separate and independent, it is possible
to form the laminar structure from the side of the semi-reflecting
layer group 2. When forming the positive electrode 3, it is only
necessary to perform patterning coordinated with the light emitting
domains.
In this configuration, when drive voltages V.sub.R, V.sub.G, and
V.sub.B are applied to control the drive circuits for each light
emitting domain, current flows only in the corresponding light
emitting layer, and only the hue of that light emission region is
output. If the light emission regions are formed so that they are
associated with color pixels in a color display apparatus, and the
drive voltage in each light emission region controlled with a
correspondence established with RGB signals in color image data,
the whole will function as a color display apparatus. In addition,
the configuration is such as to permit the light emission color to
be freely altered even when used as a simple light emitting
device.
As based on the eleventh embodiment described in the foregoing, the
configuration is made so that the positive electrode is
electrically separated into units that can be driven separately.
Thus, in addition to realizing the benefits provided by the other
embodiments, it is possible to provide a multiple wavelength light
emitting device having a comparatively simple layer structure that
can be easily fabricated.
Other Modifications
The present invention is not limited to or by the embodiments
described in the foregoing, but may be configured in various
suitable modifications so long as the scope of the basic concept
thereof is not exceeded. The organic EL layer was used merely as
representative of light emission means, for example, and some other
known light emission means having a different structure may be used
instead. As to the light emission effect, moreover, optical light
emission may be used in addition to electric field light
emission.
For the semi-reflecting layers, a multiple-layer dielectric film is
used in the embodiments described in the foregoing, but this is not
a limitation. It is also permissible to install a thin film or
optical element functioning as a half mirror so that the resonance
conditions are satisfied, or to use polarizing panels as the
semi-reflecting layers while controlling the polarization.
There is also no limitation on the electronic apparatus in which
the multiple wavelength light emitting device of the present
invention may be applied. It may be employed in display or
illumination devices in watches, calculators, portable telephones,
pagers, electronic notebooks, notebook personal computers, and
other portable information terminal apparatuses, as well as in
camera viewfinders and large displays.
As based on the present invention, the configuration is made so
that the wavelength output can be selected by adjusting the
distance between the reflecting surface for light from the light
emission means side of the semi-reflecting layer that partially
reflects light output from the light emission region and a point
existing in the interval from the end of the light emission means
on the semi-reflecting layer group side to the reflecting layer,
wherefore a multiple wavelength light emitting device can be
provided wherewith light can be ejected that is optimized for any
of a plurality of wavelengths.
As based on the present invention, the configuration is made so
that the distance from the light emission means can be adjusted by
the gap between the semi-reflecting layers. Therefore a multiple
wavelength light emitting device can be provided wherewith
optimization for a plurality of wavelengths is easy and which is
easy to fabricate.
As based on the present invention, a multiple wavelength light
emitting device is provided which outputs light of a plurality of
optimized wavelengths, wherefore electronic apparatuss can be
provided wherein the balance between light emission colors can be
perfectly adjusted.
* * * * *