U.S. patent application number 11/325529 was filed with the patent office on 2006-10-19 for light emitting diode element.
This patent application is currently assigned to Asahi Glass Company, Limited. Invention is credited to Satoshi Fujimine, Tomoyuki Kobayashi, Syuji Matsumoto, Nobuhiro Nakamura, Naoki Sugimoto.
Application Number | 20060231737 11/325529 |
Document ID | / |
Family ID | 37107613 |
Filed Date | 2006-10-19 |
United States Patent
Application |
20060231737 |
Kind Code |
A1 |
Matsumoto; Syuji ; et
al. |
October 19, 2006 |
Light emitting diode element
Abstract
A light emitting diode element having a light emitting diode
sealed by glass, wherein the glass consists essentially of, as
represented by mol % based on the following oxides, from 30 to 70%
of SnO, from 15 to 50% of P.sub.2O.sub.5, from 0.1 to 20% of ZnO,
from 0 to 10% of SiO.sub.2+GeO.sub.2, from 0 to 30% of
Li.sub.2O+Na.sub.2O+K.sub.2O, and from 0 to 20% of MgO+CaO+SrO+BaO.
Glass for covering a light emitting diode element, which has an
internal transmittance of at least 80% with thickness of 1 mm for a
light having a wavelength of 405. nm and which consists essentially
of, as represented by mol % based on the following oxides, from 40
to 53% of TeO.sub.2, from 0 to 10% of GeO.sub.2, from 5 to 30% of
B.sub.2O.sub.3, from 0 to 10% of Ga.sub.2O.sub.3, from 0 to 10% of
Bi.sub.2O.sub.3, from 3 to 20% of ZnO, from 0 to 3% of
Y.sub.2O.sub.3, from 0 to 3% of La.sub.2O.sub.3, from 0 to 7% of
Gd.sub.2O.sub.3 and from 0 to 5% of Ta.sub.2O.sub.5, and
TeO.sub.2+B.sub.2O.sub.3 is at most 75 mol %.
Inventors: |
Matsumoto; Syuji;
(Yokohama-shi, JP) ; Kobayashi; Tomoyuki;
(Yokohama-shi, JP) ; Sugimoto; Naoki;
(Yokohama-shi, JP) ; Fujimine; Satoshi;
(Yokohama-shi, JP) ; Nakamura; Nobuhiro;
(Yokohama-shi, JP) |
Correspondence
Address: |
C. IRVIN MCCLELLAND;OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
Asahi Glass Company,
Limited
Chiyoda-ku
JP
|
Family ID: |
37107613 |
Appl. No.: |
11/325529 |
Filed: |
January 5, 2006 |
Current U.S.
Class: |
250/208.1 ;
257/E33.059; 257/E33.073 |
Current CPC
Class: |
H01L 2924/00 20130101;
H01L 33/56 20130101; H01L 2924/0002 20130101; C03C 3/19 20130101;
H01L 2924/0002 20130101; C03C 3/122 20130101; H01L 33/00 20130101;
H01L 33/54 20130101 |
Class at
Publication: |
250/208.1 |
International
Class: |
H01L 27/00 20060101
H01L027/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 15, 2005 |
JP |
2005-118413 |
Sep 2, 2005 |
JP |
2005-254906 |
Claims
1. A light emitting diode element having a light emitting diode
sealed by glass, wherein the glass consists essentially of, as
represented by mol % based on the following oxides, from 30 to 70%
of SnO, from 15 to 50% of P.sub.2O.sub.5, from 0.1 to 20% of ZnO,
from 0 to 10% of SiO.sub.2+GeO.sub.2, from 0 to 30% of
Li.sub.2O+Na.sub.2O+K.sub.2O, and from 0 to 20% of
MgO+CaO+SrO+BaO.
2. A light emitting diode element having a light emitting diode
sealed by glass, wherein the glass consists essentially of, as
represented by mol % based on the following oxides, from 20 to 55%
of B.sub.2O.sub.3, from 1 to 20% of Bi.sub.2O.sub.3, from 0 to 30%
of ZnO, from 0 to 20% of SiO.sub.2+GeO.sub.2, from 0 to 30% of
Li.sub.2O+Na.sub.2O+K.sub.2O, and from 0 to 30% of
MgO+CaO+SrO+BaO.
3. A light emitting diode element having a light emitting diode
sealed by glass, wherein the glass consists essentially of, as
represented by mol % based on the following oxides, from 20 to 70%
of TeO.sub.2, from 3 to 30% of ZnO, from 0 to 55% of
B.sub.2O.sub.3, from 0 to 10% of SiO.sub.2+GeO.sub.2, from 0 to 30%
of Li.sub.2O+Na.sub.2O+K.sub.2O, and from 0 to 20% of
MgO+CaO+SrO+BaO.
4. The light emitting diode element according to claim 3, wherein
ZnO is from 5 to 30 mol %.
5. The light emitting diode element according to claim 1, wherein
the glass has a refractive index of at least 1.6 at a wavelength of
400 nm.
6. The light emitting diode element according to claim 2, wherein
the glass has a refractive index of at least 1.6 at a wavelength of
400 nm.
7. The light emitting diode element according to claim 3, wherein
the glass has a refractive index of at least 1.6 at a wavelength of
400 nm.
8. The light emitting diode element according to claim 1, wherein
the glass has a refractive index of at least 1.7 at a wavelength of
633 nm.
9. The light emitting diode element according to claim 2, wherein
the glass has a refractive index of at least 1.7 at a wavelength of
633 nm.
10. The light emitting diode element according to claim 3, wherein
the glass has a refractive index of at least 1.7 at a wavelength of
633 nm.
11. The light emitting diode element according to claim 1, wherein
the glass has an average linear expansion coefficient of from
75.times.10.sup.-7 to 140.times.10.sup.-7/.degree. C. within a
range of from 50 to 300.degree. C.
12. The light emitting diode element according to claim 2, wherein
the glass has an average linear expansion coefficient of from
75.times.10.sup.-7 to 140.times.10.sup.-7/.degree. C. within a
range of from 50 to 300.degree. C.
13. The light emitting diode element according to claim 3, wherein
the glass has an average linear expansion coefficient of from
75.times.10.sup.-7 to 140.times.10.sup.-7/.degree. C. within a
range of from 50 to 300.degree. C.
14. The light emitting diode element according to claim 1, wherein
the glass has a crystallization temperature of higher than
400.degree. C.
15. The light emitting diode element according to claim 2, wherein
the glass has a crystallization temperature of higher than
400.degree. C.
16. The light emitting diode element according to claim 3, wherein
the glass has a crystallization temperature of higher than
400.degree. C.
17. A light emitting diode element having a substrate having an
average linear expansion coefficient of from 70.times.10.sup.-7 to
90.times.10.sup.-7/.degree. C. within a range of from 50 to
300.degree. C., wherein the substrate is covered with glass which
has a softening point of at most 500.degree. C., an average linear
expansion coefficient of from 65.times.10.sup.-7 to
95.times.10.sup.-7/.degree. C. within a range of from 50 to
300.degree. C., an internal transmittance of at least 80% with a
thickness of 1 mm for a light having a wavelength of 405 nm and a
refractive index of at least 2.0 for the same light.
18. The light emitting diode element according to claim 17, wherein
the glass contains no PbO.
19. A light emitting diode element having a substrate having an
average linear expansion coefficient of from 70.times.10.sup.-7 to
90.times.10.sup.-7/.degree. C. within a range of from 50 to
300.degree. C., wherein the substrate is covered with glass which
has a softening point of at most 500.degree. C., an average linear
expansion coefficient of from 65.times.10.sup.-7 to
95.times.10.sup.-7/.degree. C. within a range of from 50 to
300.degree. C., an internal transmittance of at least 80% with a
thickness of 1 mm for a light having a wavelength of 405 nm and a
refractive index of at least 1.7 for the same light and which
contains no PbO.
20. The light emitting diode element according to claim 17, wherein
the substrate is a sapphire substrate.
21. The light emitting diode element according to claim 19, wherein
the substrate is a sapphire substrate.
22. The light emitting diode element according to claim 17, wherein
the glass is a TeO.sub.2-B.sub.2O.sub.3--ZnO glass, which contains
TeO.sub.2 in an amount of from 40 to 53 mol %.
23. The light emitting diode element according to claim 19, wherein
the glass is a TeO.sub.2-B.sub.2O.sub.3--ZnO glass, which contains
TeO.sub.2 in an amount of from 40 to 53 mol %.
24. The light emitting diode element according to claim 22, wherein
the glass consists essentially of, as represented by mol % based on
the following oxides, from 42 to 58% of TeO.sub.2+GeO.sub.2, from
15 to 35% of B.sub.2O.sub.3+Ga.sub.2O.sub.3+Bi.sub.2O.sub.3, from 3
to 20% of ZnO and from 1 to 15% of
Y.sub.2O.sub.3+La.sub.2O.sub.3+Gd.sub.2O.sub.3+Ta.sub.2O.sub.5, and
TeO.sub.2+B.sub.2O.sub.3 is at most 75 mol %.
25. The light emitting diode element according to claim 23, wherein
the glass consists essentially of, as represented by mol % based on
the following oxides, from 42 to 58% of TeO.sub.2+GeO.sub.2, from
15 to 35% of B.sub.2O.sub.3+Ga.sub.2O.sub.3+Bi.sub.2O.sub.3, from 3
to 20% of ZnO and from 1 to 15% of
Y.sub.2O.sub.3+La.sub.2O.sub.3+Gd.sub.2O.sub.3+Ta.sub.2O.sub.5, and
TeO.sub.2+B.sub.2O.sub.3 is at most 75 mol %.
26. The light emitting diode element according to Claim 17, wherein
the glass consists essentially of, as represented by mol % based on
the following oxides, from 40 to 53% of TeO.sub.2, from 0 to 10% of
GeO.sub.2, from 5 to 30% of B.sub.2O.sub.3, from 0 to 10% of
Ga.sub.2O.sub.3, from 0 to 10% of Bi.sub.2O.sub.3, from 3 to 20% of
ZnO, from 0 to 3% of Y.sub.2O.sub.3, from 0 to 3% of
La.sub.2O.sub.3, from 0 to 7% of Gd.sub.2O.sub.3 and from 0 to 5%
of Ta.sub.2O.sub.5, and TeO.sub.2+B.sub.2O.sub.3 is at most 75 mol
%.
27. The light emitting diode element according to claim 19, wherein
the glass consists essentially of, as represented by mol % based on
the following oxides, from 40 to 53% of TeO.sub.2, from 0 to 10% of
GeO.sub.2, from 5 to 30% of B.sub.2O.sub.3, from 0 to 10% of
Ga.sub.2O.sub.3, from 0 to 10% of Bi.sub.2O.sub.3, from 3 to 20% of
ZnO, from 0 to 3% of Y.sub.2O.sub.3, from 0 to 3% of
La.sub.2O.sub.3, from 0 to 7% of Gd.sub.2O.sub.3 and from 0 to 5%
of Ta.sub.2O.sub.5, and TeO.sub.2+B.sub.2O.sub.3 is at most 75 mol
%.
28. Glass for covering a light emitting diode element, which has an
internal transmittance of at least 80% with thickness of 1 mm for a
light having a wavelength of 405 nm and which consists essentially
of, as represented by mol % based on the following oxides, from 40
to 53% of TeO.sub.2, from 0 to 10% of GeO.sub.2, from 5 to 30% of
B.sub.2O.sub.3, from 0 to 10% of Ga.sub.2O.sub.3, from 0 to 10% of
Bi.sub.2O.sub.3, from 3 to 20% of ZnO, from 0 to 3% of
Y.sub.2O.sub.3, from 0 to 3% of La.sub.2O.sub.3, from 0 to 7% of
Gd.sub.2O.sub.3 and from 0 to 5% of Ta.sub.2O5, and
TeO.sub.2+B.sub.2O.sub.3 is at most 75 mol %.
29. The glass for covering a light emitting diode element according
to claim 28, which comprises from 42 to 58% of TeO.sub.2+GeO.sub.2,
from 15 to 35% of B.sub.2O.sub.3+Ga.sub.2O.sub.3+Bi.sub.2O.sub.3,
from 3 to 20% of ZnO and from 1 to 15% of
Y.sub.2O.sub.3+La.sub.2O.sub.3+Gd.sub.2O.sub.3+Ta.sub.2O.sub.5.
30. The glass for covering a-light emitting diode element according
to claim 28, which contains no PbO.
31. The glass for covering a light emitting diode element according
to claim 28, which has a softening. point of at most 500.degree.
C., an average linear expansion coefficient of from
65.times.10.sup.-7 to 95.times.10.sup.-7/.degree. C. within a range
of from 50 to 300.degree. C. and a refractive index of at least 1.7
for a light having a wavelength of 405 nm.
32. The glass for covering a light emitting diode element according
to claim 31, wherein the refractive index is at least 2.0.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a light emitting diode
element (hereinafter referred to as a LED element) having a light
emitting diode (hereinafter referred to LED) sealed by glass.
[0003] 2. Discussion of Background
[0004] Heretofore, as a white light source, an incandescent bulb, a
fluorescent lamp or the like has been widely used. In recent years,
as a new type of white light source, a so-called white LED element
has been developed, and its application to e.g. a backlight for
liquid crystal display has been rapidly progressing.
[0005] In a presently commercially available typical one chip type
white LED element, LED of a quantum well structure having a
luminous layer of InGaN having In added to GaN, is sealed by a
resin having a YAG phosphor.
[0006] This white LED element functions as a white light source as
follows. Namely, when a direct current is conducted to LED, a blue
light will be emitted from LED. On the other hand, the YAG phosphor
will be excited by a part of the blue light, and a yellow light
(fluorescence) will be emitted from this phosphor. Such blue light
and yellow light are in a relation of complementary colors, and
when they enter into human eyes in a mixed state, s they will be
observed as white light by the principle of an additive color
mixture.
[0007] However, such a white LED element having LED sealed by a
resin has had a problem such that when it is used for a long period
of time, moisture tends to penetrate into the resin, whereby the
operation of LED will be hindered, and by ultraviolet-rays
discharged from LED, the resin undergoes a color change, whereby
its light transmittance tends to decrease.
[0008] As a white LED element to solve such a problem,
JP-A-2002-203989 proposes at pages 2 to 7 one having LED formed on
a substrate in a flip chip form, and such LED is sealed by
sol-gel-glass.
[0009] However, in such sol-gel glass, pores are present or tend to
remain, whereby the hindrance by moisture of the LED operation may
not sufficiently be suppressed. To solve such a problem of pores,
heat treatment at 1,300.degree. C. may typically be carried out,
but there has been a problem that heat treatment at a very high
temperature like 1,300.degree. C. can not be applied to the
production of a LED element.
SUMMARY OF THE INVENTION
[0010] It is an object of the present invention to provide a LED
element which does not bring about such problems.
[0011] The present invention provides a LED element having LED
sealed by glass, wherein the glass consists essentially of, as
represented by mol % based on the following oxides, from 30 to 70%
of SnO, from 15 to 50% of P.sub.2O.sub.5, from 0.1 to 20% of ZnO,
from 0 to 10% of SiO.sub.2+GeO.sub.2, from 0 to 30% of
Li.sub.2O+Na.sub.2O+K.sub.2O, and from 0 to 20% of MgO+CaO+SrO+BaO
(first aspect).
[0012] Further, the present invention provides a LED element having
LED sealed by glass, wherein the glass consists essentially of, as
represented by mol % based on the following oxides, from 20 to 55%
of B.sub.2O.sub.3, from 1 to 20% of Bi.sub.2O.sub.3, from 0 to 30%
of ZnO, from 0 to 20% of SiO.sub.2+GeO.sub.2, from 0 to 30% of
Li.sub.2O+Na.sub.2O+K.sub.2O, and from 0 to 30% of MgO+CaO+SrO+BaO
(second aspect).
[0013] Further, the present invention provides a LED element having
LED sealed by glass, wherein the glass consists essentially of, as
represented by mol % based on the following oxides, from 20 to 70%
of TeO.sub.2, from 3 to 30% of ZnO, from 0 to 55% of
B.sub.2O.sub.3, from 0 to 10% of SiO.sub.2+GeO.sub.2, from 0 to 30%
of Li.sub.2O+Na.sub.2O+K.sub.2O, and from 0 to 20% of
MgO+CaO+SrO+BaO (third aspect).
[0014] Further, as an embodiment suitable in a case where it is
desired to prevent a problem occurring during the sealing or
thereafter due to mismatching with the expansion coefficient of
e.g. sapphire which is commonly used as a LED substrate (the
average linear expansion coefficient within a range of from 50 to
300.degree. C. (hereinafter this linear expansion coefficient will
be referred to as .alpha.) is typically 80.times.10.sup.-7/.degree.
C.), the present invention provides a LED element having a
substrate having .alpha. of from 70.times.10.sup.-7 to
90.times.10.sup.-7/.degree. C., wherein the substrate is covered
with glass which has a softening point of at most 500.degree. C.,
.alpha. of from 65.times.10.sup.-7 to 95.times.10.sup.-7/.degree.
C., an internal transmittance with a thickness of 1 mm for a light
having a wavelength of 405 nm (hereinafter, this internal
transmittance will be referred to as T.sub.405) being at least 80%
and a refractive index for the same light being at least 2.0
(fourth aspect).
[0015] Further, as another preferred embodiment in a similar case,
the present invention provides a LED element having a substrate
having .alpha. of from 70.times.10.sup.-7 to
90.times.10.sup.-7/.degree. C., wherein the substrate is covered
with glass which has a softening point of at most 500.degree. C.,
.alpha. of from 65.times.10.sup.-7 to 95.times.10.sup.-7/.degree.
C., T.sub.405 of at least 80% and a refractive index of at least
1.7 for the same light and which contains no PbO (fifth
aspect).
[0016] Further, as glass for covering a LED element suitable in a
case where it is desired to prevent a problem occurring during the
sealing or thereafter due to mismatching of the expansion
coefficient with the expansion coefficient of e.g. sapphire which
is commonly used as a substrate for LED, the present invention
provides glass for covering a LED element (hereinafter this glass
will be referred to as the glass of the present invention), which
has T.sub.405 of at least 80% and which consists essentially of, as
represented by mol % based on the following oxides, from 40 to 53%
of TeO.sub.2, from 0 to 10% of GeO.sub.2, from 5 to 30% of
B.sub.2O.sub.3, from 0 to 10% of Ga.sub.2O.sub.3, from 0 to 10% of
Bi.sub.2O.sub.3, from 3 to 20% of ZnO, from 0 to 3% of
Y.sub.2O.sub.3, from 0 to 3% of La.sub.2O.sub.3, from 0 to 7% of
Gd.sub.2O.sub.3 and from 0 to 5% of Ta.sub.2O.sub.5, and
TeO.sub.2+B.sub.2O.sub.3 is at most 75 mol %.
[0017] According to the present invention, LED can be sealed or
covered by glass without employing a sol-gel method, whereby
hindrance of the operation of LED due to moisture scarcely takes
place.
[0018] Further, it becomes possible to-cover LED by glass having a
refractive index being large and a small difference in the
expansion coefficient from the sapphire substrate, without
impairing the light-emitting function of LED.
[0019] With a LED element covered by such glass or with the LED
element of the present invention, the light-withdrawing efficiency
from such a glass-covered portion will be high.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a view showing one embodiment of the LED element
of the present invention in cross section.
[0021] FIG. 2 is a schematic view showing the cross section of
another embodiment of the LED element of the present invention.
[0022] FIG. 3 is a cross-sectional schematic view illustrating a
method for producing the LED element of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] In the LED element of the present invention, in each case,
LED is sealed or covered by glass, and in each case, such glass is
one which can not be prepared by a sol-gel method, i.e. such glass
is not sol-gel glass in each case.
[0024] In the LED element of the present invention, LED is sealed,
for example, by placing a glass block having a proper shape on LED
and letting this glass block soften and flow; LED is sealed by
means of glass in a molten state; or LED is sealed by densely
covering LED with glass in a powder state and then letting glass in
a powder state soften and flow. Usually, a phosphor is added to the
above glass block, the above glass in a molten state or the above
glass in a powder state. Hereinafter, the glass which seals LED
(including one having a phosphor dispersed therein) may sometimes
be referred to as the sealing glass.
[0025] Now, the present invention (mainly the first, second and
third aspects of the present invention) will be described with
reference to FIG. 1, but the present invention is by no means
thereby restricted.
[0026] FIG. 1 shows an embodiment of the LED element of the present
invention in cross section. Reference numeral 1 indicates LED, 2a
and 2b electrodes, 3a and 3b lead frames, 4 a housing, 5 an
insulating layer, 6 a mount section, and 7 the sealing glass.
[0027] LED1 is typically LED which emits ultraviolet light or blue
light having a wavelength of from 360 to 480 nm, and it may, for
example, be LED (InGaN LED) of a quantum well structure having a
luminous layer made of InGaN having In added to GaN. In a case
where LED1 is InGaN LED, the portions in contact with electrodes 2a
and 2b are a n-type semiconductor and a p-type semiconductor,
respectively. Further, on LED1, a substrate made of e.g. sapphire
is present, but such a substrate is not shown.
[0028] The electrodes 2a and 2b are to conduct a direct current to
LED1, and they are usually made of gold, platinum or the like and
will be formed by a plating method, a vapor deposition method or
the like on the surface of lead frames 3a and 3b of a thin plate
shape.
[0029] The lead frames 3a and 3b are electrically connected to the
electrodes 2a and 2b, respectively, by bonding or close contact and
will function as terminals for external connection. The lead frames
3a and 3b are preferably thin plates of a conductive material,
whereby bonding or close contact with the electrodes 2a and 2b can
easily be made, and they are excellent in the heat dissipation
property. The conductive material is typically a metal, which may,
for example, be aluminum or an aluminum alloy.
[0030] The housing 4 is usually one having an aperture formed at
the center of a metal plate. The inner surface of this aperture is
preferably made to have a tapered shape as shown in FIG. 1 so that
light emitted in a horizontal direction from LED1 is reflected and
efficiently taken out from the top of the LED element. Further, the
shape of such an aperture is typically circular, but is not limited
thereto, and it may be oval, square or the like.
[0031] The metal plate is required to be one capable of maintaining
the shape stably even when the temperature is raised at the time of
sealing LED1 by the glass. Such a temperature is, for example, at
most 450.degree. C., and as a metal plate suitable in such a case,
an aluminum plate or an aluminum alloy plate may, for example, be
mentioned.
[0032] In a case where an aluminum plate or an aluminum alloy plate
is employed as the metal plate, the reflectance to ultraviolet
light and visible light is at least 90%, whereby the
light-withdrawing efficiency from the LED element can be made
high.
[0033] Of the surface of the housing 4, the surface constituting
the outer surface of the LED element is preferably excellent in the
electrical insulating properties. Otherwise, through the surface,
the electrode 2a and the electrode 2b may likely be short-circuited
or electrically connected. In order to increase the electrical
insulating properties of the above surface, such surface may be
subjected to oxidation treatment to convert it to alumite, in the
case where the housing 4 is aluminum or an aluminum alloy.
[0034] The insulating layer 5 is to electrically insulate the
housing 4 from the electrodes 2a and 2b, and one made of a resin,
ceramic, glass or the like may, for example, be mentioned. However,
it is required to be one capable of maintaining the shape stably
even when the temperature is raised at the time of sealing.
[0035] As the mount section 6, one made of a resin, ceramics, glass
or the like which is excellent in the electrical insulating
properties, may, for example, be mentioned. In a case where the
mount section 6 is already formed at the time of sealing, it is
required to be one capable of maintaining the shape stably even
when the temperature is raised at the time of sealing, and one made
of alumina is, for example, preferred.
[0036] The sealing glass 7 is to seal LED1 not to let the surface
of LED1 be exposed to the atmosphere.
[0037] The softening point (T.sub.S) of the glass to be used for
the sealing glass 7 is preferably at most 500.degree. C. If it
exceeds 500.degree. C., the temperature to let this glass soften
and flow to seal LED1, tends to be too high, and there may be a
problem such that the light-emitting properties of LED1 will
deteriorate, the emission wavelength will change, or no emission
will take place. It is more preferably at most 450.degree. C.,
further preferably at most 400.degree. C., particularly preferably
at most 350.degree. C., most preferably at most 330.degree. C.
[0038] The refractive index at a wavelength of 400 nm (hereinafter,
this refractive index will be referred to as n) of the glass to be
used for the sealing glass 7 is preferably at least 1.6. If it is
less than 1.6, the light-withdrawing efficiency from the high
refractive index substrate (such as a sapphire substrate having n
of 2.5) at the top of LED1, may likely deteriorate. It is more
preferably at least 1.7, particularly preferably at least 1.85,
most preferably at least 2.0. Further, n of such glass is typically
at most 2.3.
[0039] The refractive index at a wavelength of 633 nm of the glass
to be used for the sealing glass 7 is preferably at least 1.7.
[0040] The temperature T.sub.F at which the viscosity of the glass
to be used for the sealing glass 7 becomes 10.sup.5P, is preferably
at most 500.degree. C. If it exceeds 500.degree. C., bubbles
remaining in the sealing glass 7 obtained by softening and flowing
this glass to seal LED 1, tend to be many, and the light
transmittance may likely deteriorate. It is more preferably at most
450.degree. C., particularly preferably at most 400.degree. C.,
most preferably at most 380.degree. C.
[0041] It is preferred that .alpha. of the glass to be used for the
sealing glass 7 is from 75.times.10.sup.-7 to
140.times.10.sup.-7/.degree. C. If it is outside this range, it may
likely be difficult to let the expansion match, for example, when
LED1 is InGaN LED, a thereof is typically
85.times.10.sup.-7/.degree. C. It is more preferably at most
135.times.10.sup.-7/.degree. C.
[0042] It is preferred that the crystallization temperature
(T.sub.C) of the glass to be used for the sealing glass 7 is more
than 400.degree. C. If T.sub.C is 400.degree. C. or lower, crystals
tend to be precipitated in a large amount in the glass at the time
of sealing which is typically carried out at a temperature of at
most 450.degree. C., whereby the light transmittance may likely
deteriorate. It is more preferably at least 420.degree. C., further
preferably at least 450.degree. C., particularly preferably at
least 550.degree. C., most preferably higher than 600.degree. C.
Here, in the present invention, the crystallization temperature is
meant for the crystallization initiation temperature at the time
when the crystallization peak is observed when the glass is
powdered and subjected to a differential thermal analysis from room
temperature to 600.degree. C. at a temperature raising rate of
10.degree. C./min, and a case wherein no crystallization peak is
observed, is designated as "higher than 600.degree. C.".
[0043] T.sub.C is higher than (T.sub.S+60.degree. C.), more
preferably higher than (T.sub.S+90.degree. C.).
[0044] Further, T.sub.C of the glass to be used for the sealing
glass 7 is preferably higher than T.sub.F, more preferably higher
than (T.sub.F+40.degree. C.), particularly preferably higher than
(T.sub.F+60.degree. C.)
[0045] The light transmittance (internal transmittance) at a
wavelength of from 400 to 750 nm with a thickness of 2 mm, of the
glass to be used for the sealing glass 7, is preferably at least
70%. The light transmittance at a wavelength of 360 to 750 nm with
a thickness of 2 mm, of the glass to be used for the sealing glass
7, is more preferably at least 70%.
[0046] Now, the components of the glass to be used for the sealing
glass 7 in the first aspect of the present invention will be
described. Here, unless otherwise specified, "mol %" will be
represented simply by "%" to describe the glass composition
below.
[0047] SnO is a network former of glass and is essential. If it is
less than 30%, the glass tends to be instable. It is preferably at
least 45%. If it exceeds 70%, the glass rather tends to be
instable, or T.sub.S or T.sub.F tends to be so high that sealing of
LED1 tends to be difficult.
[0048] P.sub.2O.sub.5 is a network former of the glass and is
essential. If it is less than 15%, the glass tends to be instable.
If it exceeds 50%, the glass rather tends to be instable. In a case
where the sealing glass 7 will be in contact with the atmosphere,
it is preferred to adjust P.sub.2O.sub.5 to be preferably at most
45%, more preferably at most 40%, to improve the water
resistance.
[0049] ZnO is a component incorporated, for example, to stabilize
the glass and is essential. If it is less than 0.1%, the glass
tends to be instable. It is preferably at least 3%. If it exceeds
20, T.sub.S tends to be high. It is preferably at most 13%.
[0050] The total of the contents of SnO and ZnO is preferably from
1.8 to,2.2 times the content of P.sub.2O.sub.5. If the total
content is outside this range, the glass tends to be instable, and
it is more preferably from 1.9 to 2.1 times.
[0051] Each of SiO.sub.2 and GeO.sub.2 is not essential, but they
may be incorporated in a total amount of up to 10% to stabilize the
glass, to improve the water resistance, etc. If they exceed 10%,
T.sub.S is likely to be high.
[0052] Each of Li.sub.2O, Na.sub.2O and K.sub.2O is not essential,
but they may be incorporated in a total amount of up to 30%, for
example, to lower T.sub.S. If they exceed 30%, the glass is likely
to be instable. In a case where the sealing glass 7 will be in
contact with the atmosphere, it is preferred to adjust the total
content of Li.sub.2O, Na.sub.2O and K.sub.2O to be at most 10%
thereby to improve the water resistance.
[0053] Each of MgO, CaO, SrO and BaO is not essential, but they may
be incorporated in a total amount of up to 20% to stabilize the
glass, to improve the water resistance, etc. If they exceed 20%, Ts
is likely to be high.
[0054] The glass to be used for the sealing glass 7 in the first
aspect of the present invention, consists essentially of the above
components, but it may contain other components within a range not
to impair the purpose of the present invention. In a case where
such other components are incorporated, their total amount is
preferably at most 15%, more preferably at most 7%.
[0055] The first aspect of the present invention is suitable when
it is desired to shift the ultraviolet absorption end of the glass
to be used for the sealing glass 7 to a shorter wavelength side
(for example, at most 350 nm), to bring the internal transmittance
to be at least 80% or to make Ts to be lower.
[0056] The following glass A may, for example, be mentioned as
glass to be used for the sealing glass 7 in the first aspect of the
present invention. Here, the refractive index at a wavelength of
633 nm was measured as follows. Namely, a plate sample having both
sides mirror-polished and having a size of 2 cm.times.2 cm and a
thickness of 1 mm, was prepared, and the refractive index was
measured by using a refractive index measuring apparatus Model
12010 PRISM COUPLER (tradename), manufactured by Metricon. GLASS
A
[0057] Composition: SnO 62%, P.sub.2O.sub.5 33%, ZnO 5%.
[0058] Glass transition point (TG): 262.degree. C.
[0059] T.sub.S: 322.degree. C.
[0060] n: 1.8 (estimated value).
[0061] Refractive index at a wavelength of 633 nm: 1.77.
[0062] T.sub.F: 360.degree. C. (estimated value)
[0063] .alpha.: 135.times.10-7/.degree. C.
[0064] T.sub.C: higher than 600.degree. C.
[0065] Internal transmittance at a wavelength of 400 nm with a
thickness of 2 mm: 97%.
[0066] Now, components of glass to be used for the sealing glass 7
in the second aspect of the present invention will be
described.
[0067] B.sub.2O.sub.3 is a network former of the glass and is
essential. If it is less than 20%, the glass tends to be instable.
If it exceeds 55%, T.sub.S tends to be so high that sealing of LED1
tends to be difficult.
[0068] Bi.sub.2O.sub.3 is a network former of the glass and is a
component to increase n and thus essential. If it is less than 1%,
the glass tends to be instable, or n tends to be low. If it exceeds
20%, the above-mentioned light transmittance, particularly the
internal transmittance at a wavelength of 380 nm, tends to be low,
for example is likely to be less than 70%.
[0069] ZnO is not essential, but may be incorporated up to 30%, for
example, to stabilize the glass. If it exceeds 30%, T.sub.S tends
to be high.
[0070] Each of SiO.sub.2 and GeO.sub.2 is not essential, but they
may be incorporated in a total amount of up to 20%, for example, to
stabilize the glass or to improve the water resistance. If they
exceed 20%, T.sub.S is likely to be high.
[0071] Each of Li.sub.2O, Na.sub.2O and K.sub.2O is not essential,
but they may be incorporated in a total amount of up to 30%, for
example, to lower T.sub.S. If they exceed 30%, the glass is likely
to be instable. In a case where the sealing glass 7 will be in
contact with the atmosphere, it is preferred to adjust the total
content of Li.sub.2O, Na.sub.2O and K.sub.2O to be at most 10%
thereby to improve the water resistance.
[0072] Each of MgO, CaO, SrO and BaO is not essential, but they may
be incorporated in a total amount of up to 30%, for example, to
stabilize the glass or to improve the water resistance. If they
exceed 30%, T.sub.S is likely to be high.
[0073] The glass to be used for the sealing glass 7 in the second
aspect of the present invention, consists essentially of the above
components. However, it may contain other components within a range
not to impair the purpose of the present invention. In a case where
such other components are incorporated, their total content is
preferably at most 15%, more preferably at most 7%.
[0074] The second aspect of the present invention is suitable in a
case where it is desired to shift the ultraviolet absorption end of
the glass to be used for the sealing glass 7 to a short wavelength
side (for example at most 380 nm), to bring the above internal
transmittance to be at least 70% or to increase n, for example, to
a level of 1.6.
[0075] Now, components of the glass to be used for the sealing
glass 7 in the third aspect of the present invention will be
described.
[0076] TeO.sub.2 is a network former of the glass and is essential.
If it is less than 20%, it tends to be difficult to obtain glass
having large n. It is preferably at least 40%. If it exceeds 70%,
vitrification rather tends to be difficult.
[0077] ZnO is a component, for example, to stabilize the glass and
is essential. If it is less than 3%, it tends to be difficult to
obtain homogeneous glass. It is preferably at least 5%, more
preferably at least 11%. If it exceeds 30%, T.sub.S tends to be
high.
[0078] B.sub.2O.sub.3 is not essential, but may be incorporated up
to 55%, for example, to stabilize the glass or to increase the
internal transmittance at a wavelength of 380 nm. If it exceeds
55%, T.sub.S tends to be high, and sealing of LED1 tends to be
difficult.
[0079] Each of SiO.sub.2 and GeO.sub.2 is not essential, but they
may be incorporated in a total amount of up to 10%, for example, to
stabilize the glass or to improve the water resistance. If they
exceed 10%, T.sub.S is likely to be high.
[0080] Each of Li.sub.2O, Na.sub.2O and K.sub.2O is not essential,
but they may be incorporated in a total amount of up to 30%, for
example, to lower T.sub.S. If they exceed 30%, the glass is likely
to be instable. In a case where the sealing glass 7 will be in
contact with the atmosphere, it is preferred to adjust the total
content of Li.sub.2O, Na.sub.2O and K.sub.2O to be at most 10%
thereby to improve the water resistance.
[0081] Each of MgO, CaO, SrO and BaO is not essential, but they may
be incorporated in a total amount of up to 20%, for example, to
stabilize the glass or to improve the water resistance. If they
exceed 20%, T.sub.S is likely to be high.
[0082] The glass to be used for the sealing glass 7 in the third
aspect of the present invention, consists essentially of the above
components, but it may contain other components within a range not
to impair the purpose of the present invention. In a case where
such other components are to be incorporated, their total amount is
preferably at most 15%, more preferably at most 7%.
[0083] For example, Y.sub.2O.sub.3 may be incorporated up to 5% for
the purpose of making n to be higher.
[0084] The third aspect of the present invention is suitable in a
case where it is desired to increase n of the glass to be used for
the sealing glass 7, for example, to a level of at least 1.65.
[0085] Glasses B1 to B4 as identified in Table 1 may, for example,
be mentioned as the glass to be used for the sealing glass 7 in the
third aspect of the present invention. The lines from TeO.sub.2 to
Y.sub.2O.sub.3 show the composition as represented by mol %; the
units for T.sub.G and T.sub.C are .degree. C.; the unit for .alpha.
is 10.sup.-7/.degree. C.; and the internal transmittance is a value
(unit: %) at a wavelength of 400 nm with a thickness of 2 mm.
Further, T.sub.C and .alpha. are estimated values calculated from
the composition. TABLE-US-00001 TABLE 1 B1 B2 B3 B4 TeO.sub.2 57 65
65 65 ZnO 27 17.5 15 12.5 GeO.sub.2 5 5 5 5 Na.sub.2O 8 5 5 5 BaO 0
5 7.5 10 Y.sub.2O.sub.3 3 2.5 2.5 2.5 T.sub.G 335 335 335 335 n
2.02 2.08 2.08 2.08 Refractive index 1.93 1.98 1.98 1.98
(wavelength 633 nm) .alpha. 115 130 130 130 T.sub.C 550 500 500 500
Internal 97 97 97 97 transmittance
[0086] The LED element of the present invention preferably takes a
flip chip system as shown in FIG. 1 and is preferably one not
taking a wire bonding system.
[0087] The following test was carried out to ascertain whether or
not there is a problem when the above glass A is used for sealing
of LED having sapphire as the substrate.
[0088] Firstly, the glass A was melted, and a small portion thereof
was dropped on a carbon plate and cooled to obtain a glass ball
having a diameter of about 4 mm.
[0089] On the other hand, a Petri dish-form aluminum pan (diameter:
5 mm, height 5 mm) as an attachment to a is differential thermal
analysis apparatus TG/DTA6300 manufactured by Seiko Instruments
Inc., was ready, and at its center, an alumina plate simulating LED
(size: 2 mm.times.2 mm, thickness: 1 mm) was placed, and the above
glass ball was mounted on the alumina plate.
[0090] Then, using an electric furnace, the set was maintained at
400.degree. C. for 1 hour and then cooled naturally. After the
cooling, the aluminum pan was taken out, and it was found that the
glass ball was softened and flowed to seal the alumina plate, and
the sealed glass had an extremely high transparency and no bubbles
or cracks were observed therein.
[0091] Further, the above alumina plate was made of highly pure
alumina, and its .alpha. was 85.times.10.sup.-7/.degree. C. which
was close to .alpha. of sapphire to be used for the substrate of
LED, and it is considered sufficient as a simulation of LED.
[0092] Now, the fourth and fifth aspects of the present invention
directed to a LED element wherein .alpha. of the substrate is from
70.times.10 to 90.times.10.sup.-7/.degree. C., whereby a problem
due to mismatching of the expansion coefficient scarcely occurs
(hereinafter these aspects of the present invention may be
sometimes generally referred to as the present invention), and the
glass of the present invention suitable as glass for covering a LED
element in these aspects of the present invention, will be
described.
[0093] FIG. 2 is a schematic view of the cross section of the LED
element of the present invention, and FIG. 3 is a schematic view
illustrating an example of the method for preparing the LED element
of the present invention, and they show the disposition and cross
sections of the respective components. Hereafter, the present
invention will be described with reference to these Figs., but it
should be understood that present invention is by no means thereby
restricted.
[0094] As illustrated in FIG. 2, the glass-covered LED element of
the present invention comprises a LED element 10 and glass (LED
element-covering glass) 7 covering it.
[0095] The LED element 10 comprises a substrate 10S, LED 10L, p
electrode 10P and n electrode 10N, as constituting, components.
[0096] LED10L is typically LED which emits ultraviolet light or
blue light having a wavelength of from 360 to 480 nm and may, for
example, be LED of a quantum well structure (InGaN LED) having a
luminous layer made of InGaN having In added to GaN. In a case
where LED 10L is InGaN LED, the portions in contact with the p
electrode 10P and the n electrode 10N are a p-type semiconductor
and a n-type semiconductor, respectively.
[0097] LED10L is formed on one side of the substrate 10S. In FIG.
2, the side of LED10L opposite to the side on which the p electrode
10P and the n electrode 10N are formed, is in contact with the
substrate 10S.
[0098] The substrate 10S has .alpha. of from 70.times.10.sup.-7 to
90.times.10.sup.-7/.degree. C., but typically, .alpha. is from
75.times.10.sup.-7 to 85.times.10.sup.-7/.degree. C. Usually, as
the substrate 10S, a sapphire substrate having .alpha. of about
80.times.10.sup.-7/.degree. C. is used.
[0099] Each of the p electrode 10P and the n electrode 10N is
typically made of gold and electrically connected to a p electrode
portion and a n electrode portion (not shown) of LED10L usually via
a buffer layer.
[0100] T.sub.S of the glass 7 is at most 500.degree. C. If it
exceeds 500.degree. C., the temperature for the heat treatment to
cover the LED element 10 by the glass 7 will be too high, and the
light-emitting function of the LED element 10 is likely to be
impaired. It is preferably at most 490.degree. C.
[0101] For the same reason, Tg of the glass 7 is preferably at most
450.degree. C.
[0102] The glass 7 has .alpha. of from 65.times.10.sup.-7 to
95.times.10.sup.-7/.degree. C. If .alpha. is outside this range,
mismatching in the expansion coefficient with the substrate 10S
tends to be too large. In a case where the substrate 10S is one
having .alpha. of from 75.times.10.sup.-7 to
85.times.10.sup.-7/.degree. C. such as a sapphire substrate,
.alpha. of the glass 7 is preferably from 70.times.10.sup.-7 to
90.times.10.sup.-7/.degree. C.
[0103] The glass 7 covers at least the substrate 10S.
[0104] Since n of the glass 7 is at least 1.7 in the LED element of
the fifth aspect of the present invention (hereinafter referred to
as the second LED element) and at least 2.0 in the LED element of
the fourth aspect of the present invention (hereinafter referred to
as the first LED element), return of light to the substrate 10S by
reflection is suppressed even in a case where the substrate 10S has
large n like a sapphire substrate (n: about 2.5), whereby the
light-withdrawing efficiency from the substrate 10S can be made
high.
[0105] In the second LED element, n of the glass 7 is preferably at
least 1.9, more preferably at least 2.0.
[0106] T.sub.405 of the glass 7 is at least 80%, whereby it is
possible to suppress the reduction of light quantity by light
absorption and to increase the light-withdrawing efficiency. It is
preferably at least 85%, more preferably at least 90%, particularly
preferably at least 93%.
[0107] The glass 7 is one containing no PbO in the second LED
element. Also in the first LED element, it is preferably one
containing no PbO.
[0108] The glass 7 may, for example, be a
TeO.sub.2-B.sub.2O.sub.3--ZnO type is glass which contains
TeO.sub.2 in an amount of from 40 to 53%.
[0109] In the TeO.sub.2-B.sub.2O.sub.3--ZnO type glass, if
TeO.sub.2 is less than. 40%, n tends to be small, or T.sub.S tends
to be high. It is preferably at least 43%. If it exceeds 53%,
.alpha. tends to be large. It is typically at most 51%.
[0110] The above exemplified TeO.sub.2-B.sub.2O.sub.3--ZnO type
glass is preferably the glass of the present invention. Otherwise,
it is preferably glass which consists essentially of, based on the
following oxides, from 42 to 58% of TeO.sub.2+GeO.sub.2, from 15 to
35% of B.sub.2O.sub.3+Ga.sub.2O.sub.3+Bi.sub.2O.sub.3, from 3 to
20% of ZnO, and from 1 to 15% of
Y.sub.2O.sub.3+La.sub.2O.sub.3+Gd.sub.2O.sub.3+Ta.sub.2O.sub.5,
wherein TeO.sub.2+B.sub.2O.sub.3 is at most 75 mol %.
[0111] Now, an example of the method for producing one as shown in
FIG. 2 which is a LED element of the present invention, will
described with reference to FIG. 3.
[0112] Firstly, glass 7 having a shape as shown in FIG. 3 i.e.
glass 7 having a shape such that a part of a ball is cut off so
that the cut surface is flat, is prepared as follows. Namely, on a
heat resistant plate, a release agent powder is sprayed to form a
release agent layer. On such a release agent layer, a small piece
of glass 7 is placed and heated to a temperature of at least
T.sub.S of the glass 7 to soften and flow the glass 7 so that it
will be substantially-spherical by the surface tension.
Substantially spherical glass 7 thus obtained is flat at the
portion in contact with the release agent layer, and its shape is
one having a part of a ball cut off, so that the cut surface is
flat. Here, the heat resistant plate may, for example, be a silicon
wafer, and the release agent powder may, for example, be a boron
nitride powder.
[0113] Then, on the release agent layer 30 formed on the heat
resistant plate 20, the LED element 10 is placed so that the
substrate 10S faces upward. Here, one having the release agent
layer 30 formed on the heat resistant plate 20 may be one used to
prepare the glass 7 having the above-mentioned shape.
[0114] On the LED element 10, the glass 7 having the
above-mentioned shape prepared as described above, is placed and
heated to a temperature of at least T.sub.S of the glass 7 to
soften and flow the glass 7 to cover at least the portion of the
substrate 10S of the LED element 10. In FIG. 3, the side surface of
the LED element 10 is also covered.
[0115] Now, the glass of the present invention will be
described.
[0116] T.sub.405 of the glass of the present invention is
preferably at least 85%, more preferably at least 90%, particularly
preferably at least 93%.
[0117] T.sub.S of the glass of the present invention is preferably
at most 500.degree. C., more preferably at most 490.degree. C.
[0118] .alpha. of the glass of the present invention is preferably
from 65.times.10.sup.-7 to 95.times.10.sup.-7/.degree. C.,
typically from 75.times.10.sup.-7 to 85.times.10.sup.-7/.degree.
C.
[0119] n of the glass of the present invention is preferably at
least 1.7, more preferably at least 1.9, particularly preferably at
least 2.0.
[0120] The glass of the present invention preferably has T.sub.S of
at most 500.degree. C., .alpha. of from 65.times.10.sup.-7 to
95.times.10.sup.-7/.degree. C. and n of at least 1.7.
[0121] The glass of the present invention is preferably one which
can be prepared by melting at a temperature of at most 980.degree.
C. Otherwise, it will be difficult to melt the glass by using a
metal crucible (melting point: 1,063.degree. C.), and it will be
required to carry out melting by means of a crucible made of
platinum or a platinum alloy, and consequently, platinum will be
dissolved in the glass, whereby T.sub.405 tends to be low.
[0122] Now, the composition of the glass of the present invention
will be described.
[0123] TeO.sub.2 is a network former of the glass and is essential.
If it is less than 40%, n tends to be small, or T.sub.S tends to be
high. It is preferably at least 43%. If it exceeds 53%, .alpha.
tends to be large. It is preferably at most 51%.
[0124] GeO.sub.2 is not essential, but may be incorporated up to
10% to form the glass skeleton, to increase T.sub.405, to stabilize
the glass or to suppress devitrification. If it exceeds 10%,
T.sub.S tends to be high. It is preferably at most 7%. When
GeO.sub.2 is contained, its content is preferably at least 1%, more
preferably at least 3%.
[0125] The total content of TeO.sub.2 and GeO.sub.2 is preferably
from 42 to 58%. If it is less than 42%, the glass is likely to be
instable. It is more preferably at least 45%. If it exceeds 58%,
.alpha. tends to be large, or T.sub.S tends to be high. It is more
preferably at most 55%.
[0126] B.sub.2O.sub.3 is a component to form-the glass skeleton and
is essential. If it is less than 5%, the glass tends to be
instable. It is preferably at least 10%. If it exceeds 30%, n tends
to be small, or chemical durability such as water resistance tends
to be low. It is preferably at most 20%.
[0127] The total content of TeO.sub.2 and B.sub.2O.sub.3 is at most
75%. If it exceeds 75%, .alpha. tends to be large. It is preferably
at most 70%.
[0128] Ga.sub.2O.sub.3 is not essential, but may be incorporated up
to 10% to increase n. If it exceeds 10%, the glass tends to be
instable. It is preferably at most 8%. When Ga.sub.2O.sub.3 is
contained, its content is preferably at least 1%, more preferably
at least 3%.
[0129] Bi.sub.2O.sub.3 is not essential, but may be incorporated up
to 10% to increase n. If it exceeds 10%, T.sub.405 tends to be low.
It is preferably at most 5%. When Bi.sub.2O.sub.3 is contained, its
content is preferably at least 0.1%, more preferably at least
0.5%.
[0130] The total content of B.sub.2O.sub.3, Ga.sub.2O.sub.3 and
Bi.sub.2O.sub.3 is preferably from 15 to 35%. If it is less than
15%, vitrification is likely to be difficult. It is more preferably
at least 20%. If it exceeds 35%, the glass is likely to be
instable. It is more preferably at most 30%.
[0131] ZnO is a component to stabilize-the glass and is essential.
If it is less than 3%, the glass tends to be instable. It is
preferably at least 5%, more preferably at least 10%. If it exceeds
20%, it will be required to melt it at a temperature exceeding
980.degree. C. It is preferably at most 19%.
[0132] Y.sub.2O.sub.3 is not essential, but may be incorporated up
to 3%, for example, to suppress devitrification. If it exceeds 3%,
n tends to be small. It is preferably at most 1%. When
Y.sub.2O.sub.3 is contained, its content is preferably at least
0.1%, more preferably at least 0.5%.
[0133] La.sub.2O.sub.3 is not essential, but may be incorporated up
to 3%, for example, to suppress devitrification. If it exceeds 3%,
n tends to be small. It is preferably at most 1%. When
La.sub.2O.sub.3 is contained, its content is preferably at least
0.1%, more preferably at least 0.5%.
[0134] Gd.sub.2O.sub.3 is not essential, but may be incorporated up
to 7%, for example, to suppress devitrification. If it exceeds 7%,
T.sub.S tends to be high. It is preferably at most 5%. When
Gd.sub.2O.sub.3 is contained, its content is preferably at least
1%, more preferably at least 3%.
[0135] Ta.sub.2O.sub.5 is not essential, but may be incorporated up
to 5% to increase n. If it exceeds 5%, T.sub.S tends to be high. It
is preferably at most 4%. When Ta.sub.2O.sub.5 is contained, its
content is preferably at least 1%, more preferably at least 2%.
[0136] The total content of Y.sub.2O.sub.3, La.sub.2O.sub.3 ,
Gd.sub.2O.sub.3 and Ta.sub.2O.sub.5 is preferably from 1 to 15%. If
it is less than 1%, devitrification is likely to take place. It is
more preferably at least 3%. If it exceeds 15%, vitrification is
likely to be difficult. It is more preferably at most 10%.
[0137] It is preferred that TeO.sub.2+GeO.sub.2 is from 42 to 58%,
B.sub.2O.sub.3+Ga.sub.2O.sub.3+Bi.sub.2O.sub.3 is from 15 to 35%,
and Y.sub.2O.sub.3+La.sub.2O.sub.3+Gd.sub.2O.sub.3+Ta.sub.2O.sub.5
is from 1 to 15%.
[0138] The glass of the present invention consists essentially of
the above components, but may contain other components within a
range not to impair the purpose of the present invention. In a case
where such components are incorporated, the total content of such
components is preferably at most 10%, more preferably at most 5%.
As such other components, TiO.sub.2 may, for example, be mentioned.
TiO.sub.2 may be incorporated when it is desired to adjust n or to
prevent solarization. If its content exceeds 2%, T.sub.405 tends to
be low, or .alpha. tends to be large. It is typically at most
1.3%.
[0139] Further, the glass of the present invention may contain an
alkali metal oxide, for example, to lower T.sub.S. However, such an
alkali metal oxide is likely to cause an electrical problem, and
its content is preferably less than 1%, and usually, no alkali
metal oxide is incorporated.
[0140] Further, the glass of the present invention preferably
contains no PbO.
[0141] Now, the present invention will be described in further
detail with reference to Examples. However, it should be understood
that the present invention is by no means thereby restricted.
[0142] With respect to Examples 1 to 13, raw materials were blended
to prepare 450 g of a blend material having a composition shown by
mol % in the lines from TeO.sub.2 to Na.sub.2O in the Tables, and
the blend material was put into a gold crucible having a capacity
of 300 cc and melted at 950.degree. C. for 2.5 hours. At that time,
stirring was carried out for 1 hour by a gold stirrer to homogenize
the molten glass. The homogenized molten glass was cast in a carbon
mold to form it into a plate shape.
[0143] With respect to Example 11, after casting the molten glass,
glass deposited on the inner wall of the gold crucible was
naturally cooled in the atmosphere, and small glass pieces
deposited on the inner wall were then collected.
[0144] With respect to Example 14, the molten glass was formed into
a plate shape in the same manner as in Example 1 to 13, but
devitrification was remarkable. Therefore, melting was carried out
as follows. Namely, 100 g of a blend material was prepared, put
into a gold crucible having a capacity of 100 cc and melted at
995.degree. C. for 1 hour. At that time, no stirring by a gold
stirrer was carried out, since the melting temperature was close to
the melting point of gold, and it was feared that the shape might
not be maintained. The inadequately homogenized molten glass thus
obtained was cast to form it into a plate shape, followed by
annealing.
[0145] Examples 1 to 12 represent Examples for the glass of the
present invention, and Examples 13 and 14 represent Comparative
Examples to the glass of the present invention.
[0146] With respect to each glass obtained, T.sub.S (unit: .degree.
C.), T.sub.g (unit: .degree. C.), a (unit: 10.sup.-7/.degree. C.),
n and T.sub.405 (unit: %) were measured. The measurement methods
thereof will be described below.
[0147] T.sub.S: A sample processed into a cylinder having a
diameter of 5 mm and a length of 20 mm was measured at a
temperature raising rate of 5.degree. C./min by means of a
thermomechanical analyzer DILATOME5000 (tradename), manufactured by
McScience. With respect to Example 7, not a measured value, but a
value estimated from the composition is shown together with an
estimated precision. With respect to Example 14, neither
measurement nor estimation was carried out.
[0148] Tg: 150 mg of a sample processed into a powder was packed
into a platinum pan and measured by means of a thermal analyzer
TG/DTA6300 (tradename), manufactured by, Seiko Instruments,
Inc.
[0149] .alpha.: A sample processed into a cylinder having a
diameter of 5 mm and a length of 20 mm was measured at a
temperature raising rate of 5.degree. C./min by means of the
above-mentioned thermomechanical analyzer. The expansion
coefficient was obtained every 25.degree. C. within a range of from
50 to 300.degree. C., and the average value was taken as .alpha..
With respect to-Example 7, not measured value, but a value
estimated from the composition is shown together with an estimated
precision.
[0150] n: Glass is processed into a triangular prism having 30 mm
on a side and 10 mm in thickness and measured by means of a
precision spectrometer GMR-1 (tradename) manufactured by Kalnew
Optical.
[0151] T.sub.405: Two plate-shaped glass samples having thicknesses
of 1 mm and 5 mm and a size of 2 cm.times.2 cm and having each side
mirror-polished, were prepared, and the transmittance for light
having a wavelength of 405 nm was measured by means of a
spectrophotometer U-3500 (tradename) manufactured by Hitachi Ltd.
The transmittances of the plate shaped samples-having thicknesses
of 1 mm and 5 mm obtained by the measurements are represented by T1
and T5, respectively, and T.sub.405 (unit: %) is calculated by the
following formula. T.sub.405=100.times.exp [(2/3).times.log.sub.e
(T5/T1)]
[0152] Further, with respect to Examples 9, 11, 13 and 14, in
accordance with the evaluation method prescribed by Japan Optical
Glass Industry Association, water resistance RW and acid resistance
RA were evaluated as follows. The grades are shown in the
corresponding columns in the Tables.
[0153] RW: Glass particles having a diameter of from 420 to 600
.mu.m were prepared, and the mass reduction ratio when they were
immersed in 80 ml of pure water at 100.degree. C. for 1 hour, was
measured. The mass reduction ratio being less than 0.05 was rated
as grade 1; at least 0.05 and less than 0.10 as grade 2; at least
0.10 and less than 0.25 as grade 3; at least 0.25 and less than
0.60 as grade 4; at least 0.60 and less than 1.10 as grade 5; and
at least 1.10 as grade 6. RW is preferably grade 1.
[0154] RA: Glass particles having a diameter of from 420 to 600
.mu.m were prepared, and the mass reduction ratio when they were
immersed in 80 ml of a 0.01 N nitric acid aqueous solution at
100.degree. C. for 1 hour, was measured. The mass reduction ratio
being less than 0.20 was rated as grade 1; at least 0.20 and less
than 0.35 as grade 2; at least 0.35 and less than 0.65 as grade 3;
at least 0.65 and less than 1.20 as grade 4; at least 1.20 and less
than 2.20 as grade 5: and at least 2.20 as grade 6. RA is
preferably grade 1. TABLE-US-00002 TABLE 2 Ex. 1 Ex. 2 Ex. 3 Ex. 4
Ex. 5 Ex. 6 Ex. 7 TeO.sub.2 51.0 47.0 46.8 46.0 45.0 46.0 47.0
GeO.sub.2 4.0 3.0 3.0 3.0 5.0 5.0 5.0 B.sub.2O.sub.3 19.0 19.0 19.0
19.0 19.0 19.0 19.0 Ga.sub.2O.sub.3 5.0 5.0 5.0 5.0 6.0 6.0 6.0
Bi.sub.2O.sub.3 0 5.0 5.0 5.0 4.0 3.0 2.0 ZnO 15.0 15.0 15.0 15.0
15.0 15.0 15.0 Y.sub.2O.sub.3 0.5 0.5 0.5 0.5 0.5 0.5 0.5
La.sub.2O.sub.3 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Gd.sub.2O.sub.3 3.0 3.0
3.0 3.0 3.0 3.0 3.0 Ta.sub.2O.sub.3 2.0 2.0 2.0 2.0 2.0 2.0 2.0
TiO.sub.2 0 0 0.2 1.0 0 0 0 Na.sub.2O 0 0 0 0 0 0 0 T.sub.S 476 478
478 479 487 486 485 .+-. 10 Tg 430 430 430 435 440 440 440 .alpha.
86 91 90 89 87 86 86 .+-. 3 n 1.972 2.034 2.034 2.038 2.008 1.997
1.986 T.sub.405 99 96.7 95.9 91.3 98.4 99.0 98.7 RW -- -- -- -- --
-- -- RA -- -- -- -- -- -- --
[0155] TABLE-US-00003 TABLE 3 Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex.
13 Ex. 14 TeO.sub.2 45.2 45.0 44.8 45.0 45.0 51.0 54.0 GeO.sub.2
5.0 5.0 5.0 5.0 3.0 0 5.0 B.sub.2O.sub.3 19.0 19.0 19.0 18.0 19.0
29.0 0 Ga.sub.2O.sub.3 6.0 6.0 6.0 6.0 5.0 0 0 Bi.sub.2O.sub.3 3.0
3.0 3.0 3.0 5.0 0 0 ZnO 15.0 15.0 15.0 15.0 15.0 15.0 30.0
Y.sub.2O.sub.3 0.5 0.5 0.5 0.5 0.5 2.0 3.0 La.sub.2O.sub.3 0.5 0.5
0.5 0.5 0.5 2.0 0 Gd.sub.2O.sub.3 3.0 3.0 3.0 3.0 3.0 1.0 0
Ta.sub.2O.sub.3 2.0 2.0 2.0 3.0 2.0 0 0 TiO.sub.2 0.8 1.0 1.2 1.0
2.0 0 0 Na.sub.2O 0 0 0 0 0 0 8.0 T.sub.S 485 490 489 490 485 465
-- Tg 440 440 440 445 445 420 335 .alpha. 85 86 86 86 87 105
>120 n 2.001 2.001 2.001 2.011 2.041 1.948 2.01 T.sub.405 94.2
94.9 93.6 95.2 86.6 99 98.0 RW -- 1 -- 1 -- 1 3 RA -- 1 -- 1 -- 2
3
EXAMPLE 1
[0156] Using the above-mentioned small pieces of glass in Example
11, a LED element covered with glass was prepared by the method as
described above with reference to FIG. 3.
[0157] As a heat resistant plate, a 6 inch silicon wafer
manufactured by Osaka Titanium was used, and as a release agent
powder, boron nitride powder Boron Spray manufactured by Kaken
Kogyo Co., Ltd. was sprayed thereon. The boron nitride powder layer
was made to have a thickness such that the silicon wafer surface
was not seen.
[0158] A small piece of glass having a weight of about 30 mg was
placed on the boron nitride powder layer on the silicon wafer and
heated form 25.degree. C. to 610.degree. C. at a rate of 5.degree.
C. per minute by means of a muffle furnace FP41 manufactured by
Yamato Scientific Co., Ltd. and maintained at that temperature for
15 minutes. Then, it was cooled at a rate of 5.degree. C. per
minute to obtain glass B having a shape as shown by symbol 7 in
FIG. 3. With this glass, the height was 1.9 mm, the maximum value
of the width in a horizontal direction was 2.0 mm, and the diameter
of the flat portion (circular shape) of the bottom surface was 0.8
mm.
[0159] Then, on the silicon nitride powder layer on the silicon
wafer, many blue emitting LED bare chips GB-3070 manufactured by
Showa Denko K.K. were applied from a height of about 3 cm.
[0160] The LED bare chip is one having InGaN formed as a
semiconductor layer on a sapphire substrate, and its size is 300
.mu.m.times.300 .mu.m, and the thickness is 80 .mu.m. On the side
opposite to the sapphire substrate, a p electrode and a n
electrode, each having the surface made of gold, are formed, and
each electrode is circular with a diameter of 110 .mu.m.
[0161] Among the applied bare chips, one having the
electrode-forming side in contact with the boron nitride powder
layer and having the sapphire substrate at the top, is selected,
and the above-mentioned glass B is placed so that the center of the
bottom surface thereof will be located on the sapphire substrate,
followed by the same heat treatment as in the case of preparing the
above glass B. As a result, a glass-covered LED element having the
sapphire substrate covered by glass as-shown in FIG. 2 and having
the bare chip embedded in the glass, was obtained. The dimensions
such as the height and the maximum value of width in the horizontal
direction, of the covered glass, were substantially the same as the
glass B, and no glass was deposited on the electrode-formed
surface.
[0162] Across the p electrode and the n electrode of this glass
covered LED element, a voltage of 3.5 V was applied by a manual
prova by means of a DC power source MC35-1A manufactured by Kikusui
Electronics Corp., whereby light emission was observed.
EXAMPLE 2
[0163] A LED element covered with glass was prepared by a method
different from Example 1.
[0164] Firstly, on an alumina substrate (thickness: 1 mm, size: 50
mm.times.100 mm) having a gold circuit pattern formed, LED
manufactured by Toyoda Gosei Co., Ltd. (tradename: E1C60-0B011-03)
was flip chip-mounted.
[0165] On the other hand, a glass plate of Example 11 having a
thickness of 1.5 mm and a size of 3 mm.times.3 mm, was prepared,
and its both sides were mirror-polished.
[0166] This mirror-polished glass plate was placed on LED on the
alumina substrate having the above LED flip chip-mounted, and the
temperature was raised to 610.degree. C. at a rate of 1.degree. C.
per minute and maintained at that level for 15 minutes to soften
and flow the glass plate to cover LED. Cooling was carried out at a
rate of 1.degree. C. per minute to about 400.degree. C., and at a
lower temperature range, the set was left to naturally cool in the
furnace.
[0167] The thickness of the cover glass of the obtained
glass-covered LED element was about 1.7 mm, and its maximum value
of width in the horizontal direction was 2.2 mm.
[0168] The cover glass and LED were found to be closely bonded by
visual observation. Further, bubbles in the cover glass were
little, and only a few having a diameter of about 10 .mu.m were
found as observed by an optical microscope.
[0169] With respect to this glass covered LED element, the emission
intensity was measured by a constant current measurement at 20 mA
by means of LED tester LX4681A (tradename) manufactured by
Teknologue Co., Ltd.
COMPARATIVE EXAMPLE 1
[0170] For the purpose of comparison, an alumina substrate having
the above LED flip chip-mounted, was separately prepared, and
without covering by glass, with respect to the LED, the emission
intensity was measured in the same manner as in Example 2, whereby
the ratio in the emission intensity of Comparative Example 1 to
Example 2 was 0.69:1.00. Namely, the emission intensity of the LED
element of the present invention covered by glass was 1.45 times
that of the non-covered LED element.
COMPARATIVE EXAMPLE 2
[0171] For the purpose of comparison, a resin covered LED element
was prepared as follows.
[0172] Firstly, an alumina substrate having the above LED flip
chip-mounted, was separately prepared.
[0173] Then, about 25 ml of a silicone resin precursor LPS3400
(tradename) for LED manufactured by Shin-Etsu Chemical Co., Ltd.
in: a gel form, was dropped on LED on the above alumina substrate
and thereafter maintained at 100.degree. C. for 1 hour and further
maintained at 150.degree. C. for 1 hour to let the silicone resin
precursor undergo a polymerization reaction thereby to have LED
covered by the silicone resin (n=1.410).
[0174] With respect to the resin covered LED element thus obtained,
the emission intensity was measured in the same manner as in
Example 2, whereby the ratio in the emission intensity of
Comparative Example 2 to Example 2 was 0.83:1.00. Namely, the
emission intensity of the glass covered LED element of the present
invention was 1.21 times that of the resin covered LED element.
[0175] The LED element of the present invention can be used as a
blue LED element. Further, it can be used as a white LED element if
a phosphor powder emitting a yellow fluorescence using a blue color
as excitation light, is incorporated into the glass.
[0176] The entire disclosures of Japanese Patent Application No.
2005-118413 filed on Apr. 15, 2005 and Japanese Patent Application
No. 2005-254906 filed on Sep. 2, 2005 including specifications,
claims, drawings and summaries are incorporated herein by reference
in their entireties.
* * * * *