U.S. patent application number 11/119488 was filed with the patent office on 2005-11-10 for organic electroluminescence device.
This patent application is currently assigned to CANON KABUSHIKI KAISHA. Invention is credited to Kanai, Masahiro, Koike, Atsushi, Mitsui, Mutsuo.
Application Number | 20050248272 11/119488 |
Document ID | / |
Family ID | 35238848 |
Filed Date | 2005-11-10 |
United States Patent
Application |
20050248272 |
Kind Code |
A1 |
Koike, Atsushi ; et
al. |
November 10, 2005 |
Organic electroluminescence device
Abstract
The present invention provides an excellent organic EL device
with a glass substrate and a sealing glass sheet which are thinned
for weight reduction while avoiding lowering the durability and
impact resistance of the device. The organic luminescence device is
characterized in that sealing is performed at the space between a
face of the sealing glass sheet along the outer edge and a face of
the device substrate with a low melting point metal.
Inventors: |
Koike, Atsushi;
(Kawasaki-shi, JP) ; Mitsui, Mutsuo; (Tokyo,
JP) ; Kanai, Masahiro; (Tokyo, JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Assignee: |
CANON KABUSHIKI KAISHA
Tokyo
JP
|
Family ID: |
35238848 |
Appl. No.: |
11/119488 |
Filed: |
May 2, 2005 |
Current U.S.
Class: |
313/512 ;
313/504 |
Current CPC
Class: |
H01L 51/524 20130101;
H01L 51/5259 20130101; H01L 51/5243 20130101; H01L 51/5246
20130101 |
Class at
Publication: |
313/512 ;
313/504 |
International
Class: |
H01J 063/04; H01J
001/62 |
Foreign Application Data
Date |
Code |
Application Number |
May 7, 2004 |
JP |
2004-138410 |
Claims
What is claimed is:
1. An organic electroluminescence device including an organic
luminescence element portion having a pair of electrodes and an
organic conductive layer placed between the pair of electrodes, and
a substrate carrying the organic luminescence element portion
thereon, comprising a sealing member covering the organic
luminescence element portion, wherein no adhesive as an
interstitial object is provided on a surface at which the sealing
member and the organic luminescence element portion are in contact
with each other, and wherein a low melting point metal fixes the
sealing member to the substrate along an outer periphery of the
sealing member.
2. The organic electroluminescence device according to claim 1,
wherein a passivation layer containing at least silicon is placed
between the sealing member and the substrate.
3. The organic electroluminescence device according to claim 1,
wherein a laminated structure of a passivation layer containing at
least silicon and a moisture absorption layer is placed between the
sealing member and the substrate.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a thin, light-weight
organic electroluminescence device which has excellent durability
and is impact-resistant.
[0003] 2. Related Background Art
[0004] Display devices using electroluminescence (hereinafter
abbreviated as EL) materials can be made thinner and lighter in
weight than conventional CRTs, and are being applied to more and
more various uses. Since cellular phones, portable information
terminals and the like have obtained Internet connections, there is
a drastic increase in amount of graphically displayed information,
which raises the demand for display panels to display in color and
high definition.
[0005] For display devices that are mounted to portable information
terminals and the like, being light-weight is considered to be more
important. On the cellular phone market, for example, there are
products that weigh less than 70 g. Almost all parts employed
including individual electronic parts, casings, and batteries are
reviewed to make a portable information terminal or the like
lighter in weight. However, in order to achieve further weight
reduction, display devices, too, have to be lighter in weight.
[0006] Display devices in general are made using glass substrates.
One way to reduce the weight of display devices is to make the
glass substrates thinner. A thinner glass substrate, however,
increases the flexibility of a display device in which the
substrate is used, and causes the display device to warp easily
when a slight force is applied. The warping, in some cases,
instantly separates the glass substrate away from a sealing glass
sheet that constitutes the display device together with the glass
substrate. The separation generates high voltage (electrostatic
charge induced by the separation, which can cause a breakdown of
the display device or a driving TFT that drives the display device.
Decrease in impact resistance is fatal for cellular phones. It is
therefore an important subject how a glass substrate should be
bonded to a sealing glass sheet in order to achieve weight
reduction and impact resistance at the same time. A technique of
enclosing a light transmissive portion with glass or transparent
resin has been proposed in, for example, Japanese Patent
Application Laid-Open No. H10-305620.
[0007] Self-luminous display devices for full-color display can be
produced from organic EL materials. However, organic EL devices
have various confirmed degradation mechanisms, which are obstacles
to practical applications and urgent problems to be solved. Heat,
light, moisture, oxygen, etc. fasten degradation of an EL layer in
an organic EL device.
[0008] A common material used for a cathode to cause an organic EL
layer to emit light is alkaline metal or alkaline earth metal which
is low in work function. It is a known fact that the metal is very
reactive with oxygen or water and is easily oxidized. When a
cathode which injects electrons into an organic EL layer is
oxidized, the material of the cathode loses electrons. Also, an
oxide film is formed on the oxidized cathode material. The
reduction in number of electrons and influences due to the oxide
film are thought to lower the luminance of light emitted from the
EL layer.
[0009] Dark spots are dot defects in a pixel portion which fail to
emit light, and considered a problem that seriously lowers the
display quality. Dark spots are progressive defects and are said to
increase in number even when EL devices are not in operation if
moisture is present. The cause of dark spots is thought to be the
oxidization reaction of a cathode formed of alkaline metal or
alkaline earth metal. The current countermeasure against dark spots
is to enclose an organic EL device and add a desiccating agent
thereto.
[0010] Those many factors that lead to oxidization, including low
heat resistance of organic EL devices and heat which may cause
further oxidization, present great obstacles to practical
applications of organic EL devices.
[0011] Thus, while being very effective for weight reduction and
thinning of display devices, employing a thinner glass substrate
and sealing glass sheet leaves problems to be solved in order to
ensure the reliability of organic EL devices.
SUMMARY OF THE INVENTION
[0012] The present invention relates to a technique that solves
those problems, and an object of the present invention is to
provide a highly reliable organic EL device.
[0013] Therefore, the present invention provides an organic
electroluminescence device including an organic luminescence
element portion having a pair of electrodes and an organic
conductive layer placed between the pair of electrodes, and a
substrate carrying the organic luminescence element portion
thereon, comprising a sealing member covering the organic
luminescence element portion, wherein no adhesive as an
interstitial object is provided on a surface at which the sealing
member and the organic luminescence element portion are in contact
with each other, and wherein a low melting point metal fixes the
sealing member to the substrate along an outer periphery of the
sealing member.
[0014] In further aspect of the organic electroluminescence device,
a passivation layer containing at least silicon is placed between
the sealing member and the substrate.
[0015] In further aspect of the organic electroluminescence device,
a laminated structure of a passivation layer containing at least
silicon and a moisture absorption layer is placed between the
sealing member and the substrate.
[0016] The present invention can provide an excellent organic EL
device (organic electroluminescence device) with a glass substrate
and a sealing glass sheet which are thinned for weight reduction
while avoiding lowering the durability and impact resistance of the
device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a schematic diagram showing a laminated structure
of a luminescence device of the present invention; and
[0018] FIG. 2 is a schematic diagram showing in section a device
structure of the present invention which includes an organic EL
pixel and a part of a TFT.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] The present invention relates to an organic
electroluminescence device including an organic luminescence
element portion having a pair of electrodes and an organic
conductive layer placed between the pair of electrodes, and a
substrate carrying the organic luminescence element portion
thereon, comprising a sealing member covering the organic
luminescence element portion, wherein no adhesive as an
interstitial object is provided on a surface at which the sealing
member and the organic luminescence element portion are in contact
with each other, and wherein a low melting point metal fixes the
sealing member to the substrate along an outer periphery of the
sealing member.
[0020] In the organic electroluminescence device, a passivation
layer containing at least silicon is placed between the sealing
member and the substrate.
[0021] In the organic electroluminescence device, in which a
laminated structure of a passivation layer containing at least
silicon and a moisture absorption layer is placed between the
sealing member and the substrate.
[0022] The present invention provides a self-luminous display
device with a glass substrate where the device is formed and a
sealing glass sheet serving as a cover member for enclosure. In the
self-luminous display device according to the present invention,
the glass substrate is joined to the sealing glass sheet in a
reduced pressure atmosphere without fixing them with an adhesive,
which contains a large amount of moisture, or the like. A space
between a face along the outer edge of the sealing glass sheet and
a glass substrate face is enclosed in the reduced pressure
atmosphere with an sealing member formed from a low melting point
metal material to thereby remove moisture and oxygen and other
gases that can cause degradation of the device as much as possible
from the enclosed space. The enclosed space kept in this state is
completely shut off of the outside with the use of a low melting
point metal material.
[0023] The glass substrate and the sealing glass sheet are joined
to each other in a reduced pressure atmosphere in order to utilize,
for press-fit, the difference in pressure between the sealing
atmosphere pressure and the normal pressure (1 atm.), which is used
environment, without using an adhesive of a large water content or
the like. Usually, when the dew point of a reduced atmosphere
pressure under operation is 80.degree. C. or lower, the operating
pressure is around {fraction (1/10)} atm to {fraction (1/100)} atm,
so that exposure for a few minutes does not raise a problem. While
a manufacturer may choose, if possible, to employ a method capable
of fixing a sealing glass sheet and a glass substrate to each other
in an atmospheric pressure environment without the fear of
separation, a reduced pressure atmosphere that does not reduce to
take generation of bubbles into consideration is preferable from
the viewpoint of manufacturing technique.
[0024] In the case where an organic EL material that is
particularly responsive to moisture is used, a layered (or
non-layered) moisture absorbent may be placed in advance on the
device substrate. A preferable absorbent is of the type that
chemically reacts with moisture to keep absorbed moisture inside
and never release, and that maintains its solid state after
absorbing moisture. Absorbent examples that meet the requirements
include, alkaline metal oxides, alkaline earth metal oxides,
sulfates, metal halides, perchlorates, and organic substances.
[0025] The low melting point metal material in the above refers to
indium (melting point: 157.degree. C.), tin (melting point:
232.degree. C.), or thallium (melting point: 271.degree. C.), or
alloys thereof. How the wettability with a glass surface is
enhanced is particularly important in sealing using the low melting
point metal material. One way to enhance the wettability
satisfactorily while preventing the element portion of the glass
substrate from reaching a temperature of 100.degree. C., at which
device characteristics are adversely affected, or higher, is to
dispense the low melting point metal material melted by applying
ultrasonic waves over the enclosed portion while the glass
substrate and the sealing glass sheet are heated at 70 to
80.degree. C.
[0026] There is no particular limitation on the material of the
sealing glass sheet. However, taking into account slightly
remaining moisture in the glass even after a dehydration process
and the possibility of long-term exposure to high temperature and
high humidity, it is desirable to form a passivation film from
silicon nitride or silicon oxynitride on the face inside the
enclosed space. The passivation film prevents degradation of the
device due to the diffusion of moisture, ious, etc. from the glass.
When the passivation film is a silicon nitride film, it is enough
to take about 50 to 100 nm in film thickness. In order to enhance
the short wavelength transmittance, a silicon oxynitride film with
a thickness of about 100 to 200 nm is employed as the passivation
film.
[0027] Now, an embodiment of the present invention will be
described in detail with reference to the accompanying drawings.
First, reference symbols in the drawings are explained.
[0028] `1` denotes a glass substrate.
[0029] `A` represents an anode.
[0030] `101` denotes a hole-transporting layer.
[0031] `102` denotes a luminescence layer.
[0032] `103` denotes an electron injection layer.
[0033] `K` represents a cathode.
[0034] `F` represents a sealing glass sheet.
[0035] `M` represents a low melting point metal sealing
material.
[0036] `2` denotes a gate electrode.
[0037] `3` denotes a gate insulating layer.
[0038] `4` denotes a semiconductor layer.
[0039] `5` denotes an interlayer insulating film.
[0040] `9` denotes another interlayer insulating film.
[0041] `D` represents a drain.
[0042] `S` represents a source.
[0043] FIG. 1 is a sectional view showing the basic structure of a
top emission type organic EL device according to the present
invention.
[0044] The organic EL device is composed of an anode A, a cathode
K, and an organic EL layer 10 held between the two. The organic EL
layer 10 contains a luminescence layer 102, which emits light when
holes supplied from the anode A are recombined with electrons
supplied from the cathode K. The organic EL layer 10 also contains
a hole-transporting layer 101 and an electron injection electrode
layer 103.
[0045] A description is given on a sealing glass sheet F and the
low melting point metal sealing material M, which are features of
the present invention. Soda lime glass or other materials that have
satisfactory visible light transmittance can basically be used for
the sealing glass sheet F. The thinner the sealing glass sheet F,
the lighter the device weighs. However, a too thin glass sheet
makes it difficult to handle. It is therefore preferable for the
sealing glass sheet F to have a thickness of about 0.1 to 0.5
mm.
[0046] The low melting point metal sealing material M is preferably
made from one of indium (In, melting point: 157.degree. C.), tin
(Sn, melting point: 232.degree. C.), and thallium (Tl, melting
point: 271.degree. C.), which are not poisonous and which are
air-stable, or alloys thereof. In these three metals may be added
such elements as lithium (Li, melting point: 179.degree. C.),
sodium (Na, melting point: 98.degree. C.), potassium (K, melting
point: 64.degree. C.), cesium (Cs, melting point: 29.degree. C.),
gallium (Ga, melting point: 30.degree. C.), and rubidium (Rb,
melting point: 39.degree. C.), which cannot be used alone. The
sealing member performs sealing at the space between a face along
the edge of the sealing glass sheet and a glass substrate face by
bringing the glass substrate and the glass sheet enclosure into
close contact with each other. Since the present invention does not
take the conventional organic EL device structure in which an
adhesive is sandwiched between the glass substrate and the sealing
glass sheet, the cross-sectional area of a path through which
moisture and oxygen and other gases permeate from the outside of
the device is greatly reduced. This and the fact that the present
invention employs a metal sealing member of very low gas
permeability in place of an organic adhesive ensure substantially
complete air-tightness. After the sealing process, owing to the
difference in the pressure inside the device and the atmospheric
pressure, the glass substrate and the sealing glass sheet do not
separate from each other when warped a little in an atmospheric
pressure environment. The glass substrate and the sealing glass
sheet remain tightly fit to each other and thus the impact
resistance is improved.
[0047] The anode A desirably has a large work function. For
instance, gold (Au), platinum (Pt), chromium (Cr), palladium (pd),
selenium (Se), iridium (Ir), and copper iodide, and alloys thereof
can be employed for the anode A.
[0048] Organic compounds that can be used for the hole-transporting
layer 101 include, but not limited to, triphenyl diamine
derivatives, oxadiazole derivatives, polyphyrin derivatives, and
stillbene derivatives.
[0049] Examples of organic compounds that can serve as the material
of the luminescence layer 102 include triarylamine derivatives,
stillbene derivatives, polyarylenes, aromatic condensed polycyclic
compounds, aromatic heterocyclic compounds, aromatic condensed
heterocyclic compounds, and metal complex compounds, and single or
complex oligomers thereof. One or more kinds of the above
luminescent materials may be used to dope a hole injection layer, a
hole-transporting layer, or an electron-transporting layer. The
luminescence layer 102 of the present invention is not limited to
the above materials configurations.
[0050] For the electron injection electrode layer 103, organic
compounds doped with carbonates including cesium carbonate and
lithium carbonate are suitable. A known example of such organic
compounds is Alq.sub.3. Iuorganic mixed layers are also applicable,
for which layers Lif etc. can be employed.
[0051] A magnetron sputtering apparatus is preferably employed to
form the cathode K by deposition. Specifically, transparent
conductive film materials such as ITO and IWO arranged in the same
deposition space are used as targets to form a transparent
conductive film containing H on a device substrate in an atmosphere
of a gas mixture of Ar, O.sub.2 and H.sub.2O by intense magnetic
field sputtering (target surface horizontal magnetic field: 1200
G). During the deposition, the flow rate of H.sub.2O gas is lowered
toward the end of the deposition time. Alternatively, a
concentration gradient of H is created in the film thickness
direction of the cathode K by increasing the power applied to the
transparent conductive film targets. Other than magnetron
sputtering, a deposition method using an electron gun, an ion
plating method using a plasma gun may be employed to form the
cathode K by deposition.
[0052] Any thin film forming method can be employed to form the
hole-transporting layer 101, the luminescence layer 102, and the
electron injection electrode layer 103. Options include deposition,
sputtering, CVD, molecular beam epitaxy (MBE), dipping, spin
coating, casting, bar coating, and roll coating. Preferably, a
deposition apparatus that uses resistance heating or Knudsen cells
is employed. Co-deposition in which a dopant and an organic
compound are simultaneously heated and deposited is suitable for
forming the electron injection layer.
[0053] FIG. 2 schematically shows the cross-sectional structure of
a TFT substrate used in manufacture of an organic EL device which
includes a part of an organic EL pixel and a TFT. A luminescent
pixel portion is obtained by laying the anode A, the organic EL
layer 10, and the cathode K on top of one another in this order.
The anode A is independently provided for each pixel. The anode A
is formed of Cr, for example, and is basically reflective. The
cathode K is shared between pixels, and is basically
light-transmissive. The TFT is composed of a gate electrode 2,
which is formed on a substrate 1 composed of glass or the like, a
gate insulating film 3, which is overlaid on a top face of the gate
electrode 2, and a semiconductor thin film 4, which is placed above
the gate electrode 2 with the gate insulating film 3 interposed
between 2 and 4. The semiconductor thin film 4 is, for example, a
polycrystalline silicon thin film. The TFT also has a source S, a
channel Ch, and a drain D which serve as passages of a current
supplied to the pixel electrode. The TFT, having the bottom gate
structure, is covered with a interlayer insulating film 5, on which
the source electrode S and the drain electrode D are formed.
Another interlayer insulating film 9 is placed on the source and
drain electrodes, and the pixel electrode (anode A) is formed on
the interlayer insulating film 9.
[0054] Described below are Examples of the present invention.
EXAMPLE 1
[0055] Formation of a Cr Electrode
[0056] DC sputtering was conducted using a Cr target on a glass
substrate to form as an anode A a Cr film to a thickness of 100 nm.
A deposition mask was used during the sputtering to obtain a
striped pattern of 3-mm stripes. The sputtering employs Ar gas and
was conducted at a pressure of 0.2 Pa and a discharge power of 2.5
W/cm
[0057] Formation of an Insulating Layer
[0058] Reactive DC sputtering was conducted using a Si target over
a portion on the Cr electrode pattern that was to be enclosed, to
thereby form as an insulating layer (not shown in the drawing) a
SiNx film to a thickness of 200 nm. The SiNx film was to prevent a
low melting point metal sealing material from short-circuiting the
Cr electrode upon sealing. The reactive DC sputtering used a
deposition mask to pattern the film. The reactive DC sputtering
employed Ar and N.sub.2 gas, and was conducted at a flow rate ratio
of Ar:N.sub.2=2:1, a pressure of 0.2 Pa, and a discharge power of
6.5 W/cm.sup.2.
[0059] Exposure to Air
[0060] Next, the substrate was taken out of the sputtering
apparatus, and was subjected to ultrasonic cleaning with acetone
and then isopropyl alcohol (IPA). The ultrasonic cleaning was
followed by washing in boiling IPA and drying, and further UV/ozone
cleaning.
[0061] Pre-Treatment
[0062] The substrate was moved into an organic EL deposition
apparatus, which was then exhausted until a vacuum state was
obtained. In a pre-treatment chamber, an RF power of 50 W was
applied to a ring-shaped electrode near the substrate to conduct an
oxygen plasma cleaning process. The oxygen pressure was set to 0.6
Pa, and the process time was set to 40 seconds.
[0063] Formation of a Hole-Transporting Layer
[0064] The substrate was moved from the pre-treatment chamber to a
deposition chamber, which was exhausted until a pressure of
1.times.10E.sup.(-4) Pa was reached. Thereafter, .alpha.NPD capable
of transporting holes was deposited by resistance heating
deposition at a deposition rate of 0.2 to 0.3 nm/sec to form the
hole transporting layer 101 with a thickness of 35 nm. The
hole-transporting layer 101, the luminescence layer 102, and the
electron injection layer 103 were deposited on a given portion with
the use of the same deposition mask. The given portion was a
portion on the substrate where Cr was exposed (pixel
electrode).
[0065] Formation of a Luminescence Layer
[0066] On the hole-transporting layer 101, Alq.sub.3 which is an
alkylate complex was deposited by resistance heating deposition
under the same deposition conditions that have been employed to
form the hole-transporting layer 101. The Alq.sub.3 film had a
thickness of 15 nm which serves as the luminescence layer 102.
[0067] Formation of an Electron Injection Electrode
[0068] Layer
[0069] Formed on the luminescence layer 102 by resistance heating
deposition was the electron injection layer 103 with a thickness of
35 nm. The electron injection layer 103 was composed of an
Alq.sub.3 layer and a cesium carbonate (Cs.sub.2CO.sub.3) layer.
The deposition rates of the materials were adjusted such that the
thickness ratio of the Alq.sub.3 layer and the cesium carbonate
layer became 9:1. Specifically, the materials set in their
respective deposition boats were deposited by resistance heating
while the deposition rate of the organic layer was set lower than 5
A/S and the overall deposition rate of the co-deposition layer was
set lower than 5 A/S by adjusting the current values of the
boats.
[0070] Formation of a Cathode (Transparent Conductive Film)
[0071] The substrate was moved to another deposition chamber where
an ITO target was used to form the cathode K with a thickness of
130 nm on the electron injection layer 103 by DC magnetron
sputtering. The DC magnetron sputtering used a mask so that the Cr
pixel electrode was covered and the cathode K intersected the Cr
stripes.
[0072] As described above, since a magnet capable of creating a
strong magnetic field was placed on the backside of the ITO target,
low voltage sputtering could be performed.
[0073] The cathode K was formed by room temperature deposition, in
which the substrate was not heated, at a deposition pressure of 1.0
Pa. The deposition employed Ar and O.sub.2 gas of which flow rates
were set to 500 sccm and 5.0 sccm, respectively. A discharge power
of 500 W was applied to the ITO target. The transmittance was 85%
(at 450 nm) and the specific resistivity was 8.0 E.sup.-4
.OMEGA.cm.
[0074] Seal
[0075] The substrate was lastly moved to a glove box having an
N.sub.2 atmosphere with a dew point controlled to -80 to
-85.degree. C. A sealing glass sheet made of soda lime glass and
having a thickness of 0.3 mm (the sealing glass sheet has already
been dehydrated at 120.degree. C. for 120 min in a glove box
atmosphere) was joined to the substrate. In this state, the
pressure in the glove box was reduced to 1000 Pa by a vacuum pump.
Then at the space between a face along the edge of the sealing
glass sheet and a glass substrate face sealing was performed with
indium by a sealing robot equipped with an ultrasonic solder
iron.
[0076] Device Evaluation
[0077] The anode A, the hole-transporting layer 101, the
luminescence layer 102, the electron injection electrode layer 103,
and the cathode K were thus formed on the glass substrate and a
sealing process was performed to obtain a luminescence device.
[0078] a) Durability Characteristics: the obtained luminescence
device was subjected to a 23-hour accelerated endurance test under
a constant current with the Cr electrode as an anode A, the
transparent conductive film as a cathode K, and with the current
density set to 100 A/cm.sup.2. The durability of the device was
expressed in percentage how much the luminance was lowered after 23
hours from the initial luminance of 100% (`-` means a reduction,
`+` means an increase). The results are shown in Table 1.
[0079] b) Impact Resistance: a device for an impact test was
manufactured. The layer structure, deposition conditions of the
layers, and sealing conditions that were employed for the test
device were identical to those shown in FIG. 1 and described above,
except for the deposition mask. In the test device, one
50.times.150 .mu.m luminescent portion was formed at the center of
a 45.times.55 mm glass substrate, a 35.times.45 mm sealing glass
sheet was joined onto the top of the luminescent portion and the
face along the edge of the sealing glass sheet was sealed. Five
samples of such devices were manufactured, and each of them was
fixed and housed in a plastic case (50.times.90.times.25 mm,
partially metal) that weighed 80 g. The case was dropped from a 2-m
height onto an urethane foam mat having a thickness of 50 mm. Each
device was dropped five times while emitting light, and then
dropped five more times while emitting no light to check whether
the device operated normally after having been dropped ten times in
total. Dropping in this manner ten times total made one set. Ten
sets were carried out until the device broke, and the set at which
the device was broken was used as an indicator of the impact
resistance of the device (if a device is broken at the end of the
fifth set, the indicator is "5"). Of the five devices, the average
value of the middle three devices excluding the smallest indicator
and the largest indicator was calculated. The result is shown in
Table 1.
EXAMPLE 2
[0080] Two types of luminescence devices are manufactured under the
same conditions as Example 1 except that the low melting point
metal sealing material was made of tin. The thus obtained devices
are evaluated for durability characteristics and impact resistance
in the same manner employed in Example 1. The result is shown in
Table 1.
COMPARATIVE EXAMPLE 1
[0081] Two types of luminescence devices were manufactured under
the same conditions as Example 1 except that the sealing atmosphere
was changed to a normal pressure N.sub.2 atmosphere (dew point: -80
to -85.degree. C.) from the reduced pressure environment. The thus
obtained devices were evaluated for durability characteristics and
impact resistance in the same manner employed in Example 1. The
result is shown in Table 1.
EXAMPLE 3
[0082] Formation of a Passivation Film
[0083] A passivation film (not shown in the drawing) with a
thickness of 100 nm was formed on a face of the sealing glass sheet
that was nearer toward the EL device by conducting reactive DC
sputtering using a Si target (sealing glass
sheet/SiNx/cathode/organic layer/anode/glass substrate). The
passivation film prevents deterioration of the device due to the
diffusion of moisture ions, etc. from the sealing glass sheet. The
deposition employed Ar and N.sub.2 gas, and was conducted at a flow
rate ratio of Ar:N.sub.2=2:1, a pressure of 0.2 Pa, and a discharge
power of 6.5 W/cm.sup.2.
[0084] The thus obtained devices were evaluated for durability
characteristics and impact resistance in the same manner employed
in Example 1. The result is shown in Table 1.
EXAMPLE 4
[0085] Formation of a Moisture Absorption Layer
[0086] It is practically impossible to completely remove water
molecules from the interior of the device during the sealing
process no matter how low the moisture pressure in the sealing
atmosphere is. In order to deal with a small amount of moisture
permeated, a moisture absorption layer (not shown in the drawing)
was formed in advance on the cathode K by sputtering (sealing glass
sheet/SiNx/SrO/cathode/organic layer/anode/glass substrate). The
moisture absorbing film was an SrO film, which was obtained by
subjecting an SrO.sub.2 target to RF sputtering, and by setting the
flow rate of Ar to 20 sccm, the pressure to 0.45 Pa, and the
discharge power to 2.5 W/cm.sup.2.
[0087] Two types of luminescence devices were manufactured under
the same conditions as Example 3 except that the moisture
absorption layer was added in advance. The thus obtained devices
were evaluated for durability characteristics and impact resistance
in the same manner employed in Example 1. The result is shown in
Table 1.
COMPARATIVE EXAMPLE 2
[0088] Two types of luminescence devices were manufactured under
the same conditions as Example 4 except that the sealing atmosphere
was changed to a normal pressure N.sub.2 atmosphere (dew point: -80
to -85.degree. C.) from the reduced pressure environment, and that
an adhesive layer was formed in advance on the sealing glass sheet.
The adhesive layer was formed from a two-pack epoxy adhesive which
cures at room temperature to a thickness of 10 .mu.m on SiNx by
spin coating (sealing glass sheet/SiNx/adhesive
layer/SrO/cathode/organic layer/anode/glass substrate). The thus
obtained devices were evaluated for durability characteristics and
impact resistance in same the manner employed in Example 1. The
result is shown in Table 1.
1 TABLE 1 Durability (%) ([post-endurance test luminance] / Impact
initial luminance) Resistance Example 1 -9 .gtoreq.11 Example 2 -10
.gtoreq.11 Comparative Example 1 -9 5.7 Example 3 -3 .gtoreq.11
Example 4 -5 .gtoreq.11 Comparative Example 2 -27 .gtoreq.11
[0089] As is obvious from Table 1, the luminescence devices of the
present invention exhibit remarkable durability despite having no
adhesive between the glass substrate and the sealing glass sheet.
In addition, the passivation layer and the moisture absorption
layer have recognizable effects. Table 1 clearly shows the
effectiveness of the reduced pressure sealing atmosphere in terms
of impact resistance, suggesting that adhesion force effectively
acts between the glass substrate and the sealing glass sheet.
[0090] This application claims priority from Japanese Patent
Application No. 2004-138410 filed May 7, 2004, which is hereby
incorporated by reference herein.
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