U.S. patent application number 15/538253 was filed with the patent office on 2017-12-07 for wavelength converting member and method of producing the same.
This patent application is currently assigned to NS MATERIALS INC.. The applicant listed for this patent is NS MATERIALS INC.. Invention is credited to Eiichi KANAUMI, Akiharu MIYANAGA.
Application Number | 20170352789 15/538253 |
Document ID | / |
Family ID | 56150420 |
Filed Date | 2017-12-07 |
United States Patent
Application |
20170352789 |
Kind Code |
A1 |
MIYANAGA; Akiharu ; et
al. |
December 7, 2017 |
WAVELENGTH CONVERTING MEMBER AND METHOD OF PRODUCING THE SAME
Abstract
Provided is a wavelength converting member which can reduce
change in the light emission intensity over time as compared with
conventional members and a method of producing the wavelength
converting member. A wavelength converting member (1) includes a
quantum dot layer (2) having quantum dots, barrier layers (3, 4)
formed on at least both sides of the quantum dot layer (2). The
moisture vapor transmission rate of the barrier layer is lower than
9 g/(m.sup.2d). Thus, change in the light emission intensity over
time can be effectively inhibited.
Inventors: |
MIYANAGA; Akiharu; (Fukuoka,
JP) ; KANAUMI; Eiichi; (Fukuoka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NS MATERIALS INC. |
Fukuoka |
|
JP |
|
|
Assignee: |
NS MATERIALS INC.
Fukuoka
JP
|
Family ID: |
56150420 |
Appl. No.: |
15/538253 |
Filed: |
December 21, 2015 |
PCT Filed: |
December 21, 2015 |
PCT NO: |
PCT/JP2015/085632 |
371 Date: |
June 21, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 33/508 20130101;
B82Y 20/00 20130101; H01L 33/648 20130101; H01L 2924/0001 20130101;
H01L 33/504 20130101; H01L 33/50 20130101; H01L 33/502
20130101 |
International
Class: |
H01L 33/50 20100101
H01L033/50; B82Y 20/00 20110101 B82Y020/00; H01L 33/64 20100101
H01L033/64 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 26, 2014 |
JP |
2014-263785 |
Claims
1. A wavelength converting member comprising: a quantum dot layer
having quantum dots; and at least one organic layer formed on an
outer side of the quantum dot layer, wherein a moisture vapor
transmission rate of the organic layer is lower than 9
g/(m.sup.2d).
2. The wavelength converting member according to claim 1, wherein
the moisture vapor transmission rate is 0.1 g/(m.sup.2d) or
less.
3. The wavelength converting member according to claim 1, wherein
the organic layer is formed around the entire periphery of the
quantum dot layer.
4. The wavelength converting member according to claim 3, wherein a
wrap starting end and a wrap finishing end of the organic layer are
joined at an edge on one side of the quantum dot layer.
5. The wavelength converting member according to claim 3, wherein
the organic layers are placed on both the top and bottom of the
quantum dot layer and are joined at edges on sides of the quantum
dot layer.
6. The wavelength converting member according to claim 1, wherein
the quantum dot layer is formed from a molding or formed by inkjet
printing.
7. The wavelength converting member according to claim 1, wherein a
layered structure, having a moisture vapor transmission rate that
is less than 9 g/(m.sup.2d), is formed on the outer side of the
quantum dot layer, and wherein, out of the layered structure, the
organic layer is formed at the innermost layer facing the quantum
dot layer.
8. (canceled)
9. The wavelength converting member according to claim 7, wherein
in the layered structure, an inorganic layer is provided on, an
outer side of the innermost layer.
10. The wavelength converting member according to claim 7, wherein
the layered structure comprises a plurality of the organic layers,
and an inorganic layer is sandwiched between the organic
layers.
11. The wavelength converting member according to claim 9, wherein
the inorganic layer is formed from a SiO.sub.2 layer.
12. The wavelength converting member according to claim 7, wherein
the organic layer is formed in contact with the quantum dot
layer.
13. The wavelength converting member according to claim 7, wherein
the organic layer is formed from a PET film.
14. The wavelength converting member according to claim 1, wherein
the quantum dot layer contains a thickening agent.
15. The wavelength converting member according to claim 1, wherein
the quantum dot layer contains a light-scattering agent.
16. The wavelength converting member according to claim 1, wherein
a surface of the organic layer is matted.
17. A method of producing a wavelength converting member,
comprising: forming an organic layer, having a moisture vapor
transmission rate of less than 9 g/(m.sup.2d), on an outer side of
a quantum dot layer having quantum dots.
18. The method of producing a wavelength converting member,
according to claim 17, wherein the entire periphery of the quantum
dot layer is covered by the organic layer.
19. The method of producing a wavelength converting member,
according to claim 18, further comprising: forming a plurality of
the quantum dot layers at intervals on a lower organic layer;
forming an upper organic layer over a surface of the lower organic
layer and surfaces of the plurality of the quantum dot layers; and
isolating the quantum dot layers by cutting the lower organic layer
and the upper organic layer between the quantum dot layers.
20. The method of producing a wavelength converting member,
according to claim 17, further comprising forming the quantum dot
layer from a molding or forming by inkjet printing.
21. The method of producing a wavelength converting member,
according to claim 17, further comprising: forming a layered
structure, having a moisture vapor transmission rate that is less
than 9 g/(m.sup.2d), on the outer side of the quantum dot layer,
and forming, out of the layered structure, the organic layer at an
innermost side facing the quantum dot layer.
22. The method of producing a wavelength converting member,
according to claim 17, further comprising: forming the layered
structure to have a plurality of organic layers and an inorganic
layer sandwiched between the organic layers, wherein the innermost
layer, of the layered structure, that faces the quantum dot layer
and the outermost layer, of the layered structure, are constituted
by the organic layers.
23. The method of producing a wavelength converting member,
according to claim 17, wherein the quantum dot layer includes a
thickening agent.
Description
TECHNICAL FIELD
[0001] The present invention relates to a wavelength converting
member used for a back light etc. and to a method of producing the
same.
BACKGROUND ART
[0002] For example, JP 2013-544018 A (PTL 1) below discloses an
invention relating to quantum dot films and lighting devices using
the same.
[0003] For example, PTL 1 discloses in FIG. 6A, a lighting device
600 having a QD (quantum dot) phosphor material 604 and barrier
layers 620 and 622 placed on both sides of the material. The
barrier layers are provided, thereby ensuring the photostability of
QDs and protecting the QDs from elevated temperatures, moisture,
and other harmful environmental conditions (see etc. of PTL 1).
CITATION LIST
Patent Literature
[0004] PTL 1: JP 2013-544018 A
SUMMARY OF INVENTION
Technical Problem
[0005] However, the invention according to PTL 1 does not refer in
particular to the relationship between the structure of the barrier
layers and change in the light emission intensity over time. In
other words, PTL 1 does not limit the structure of the barrier
layers in terms of change in the light emission intensity over
time.
[0006] The present invention is made in consideration of the above,
in particular with a view to providing a wavelength converting
member which can reduce change in the light emission intensity over
time as compared with conventional members and a method of
producing the wavelength converting member.
Solution to Problem
[0007] A wavelength converting member according to the present
invention includes a quantum dot layer having quantum dots; and at
least one barrier layer formed on at least both sides of the
quantum dot layer. The moisture vapor transmission rate of the
barrier layer is lower than 9 g/(m.sup.2d). Thus, change in the
light emission intensity over time can be effectively inhibited as
compared with conventional techniques.
[0008] In the present invention, the moisture vapor transmission
rate is preferably 0.1 g/(m.sup.2d) or less.
[0009] Further, in the present invention, the barrier layer is
preferably formed around the entire periphery of the quantum dot
layer.
[0010] Preferably, in the present invention, a wrap starting end
and a wrap finishing end of the barrier layer are joined at edge on
one side of the quantum dot layer.
[0011] Preferably, in the present invention, barrier layers are
placed on both the top and bottom of the quantum dot layer and are
joined at edges on sides of the quantum dot layer.
[0012] Further, in the present invention, the quantum dot layer is
preferably formed from a molding or formed by inkjet printing.
[0013] Further, in the present invention, the barrier layer is
preferably formed to have at least an organic layer. This
facilitates the handling of the barrier layer (improvement in the
handling).
[0014] Preferably, in the present invention, the barrier layer has
a layered structure, in which the organic layer is formed as the
innermost layer facing the quantum dot layer. This allows the
quantum dot layer to be easily formed on the barrier layer, and the
adhesion between the barrier layer and the quantum dot layer can be
improved.
[0015] Preferably, in the present invention, in the barrier layer,
an inorganic layer is provided outside the innermost layer. This
can effectively improve the barrier properties of the barrier
layer.
[0016] Preferably, in the present invention, a plurality of the
organic layers are provided, and an inorganic layer is sandwiched
between the organic layers. With such a structure including three
or more layers in which the innermost layer and the outermost layer
in the barrier layer are organic layers and an inorganic layer is
sandwiched between the organic layers, the handling, the barrier
properties, the adhesion between the barrier layer and the quantum
dot layer, etc. can effectively be improved. In the present
invention, the inorganic layer is preferably formed from a
SiO.sub.2 layer.
[0017] Further, in the present invention, the organic layer is
preferably formed in contact with the quantum dot layer.
[0018] Further, in the present invention, the organic layer is
preferably formed from a PET film.
[0019] Further, in the present invention, the quantum dot layer
preferably contains a thickening agent. For example, since the
viscosity would likely be reduced when a dispersant is added to
improve the dispersibility of quantum dots, a thickening agent is
added to adjust the viscosity. This allows the quantum dot layer to
be formed with a certain uniform thickness, thereby achieving good
fluorescence properties.
[0020] Further, in the present invention, the quantum dot layer may
contain a light-scattering agent. Further, a surface of the barrier
layer may be matted. Thus, adding a light-scattering agent to the
quantum dot layer or matting a surface of the barrier layer can
promote light scattering.
[0021] In a method of producing a wavelength converting member
according to the present invention, the barrier layer made of a
material having a moisture vapor transmission rate of less than 9
g/(m.sup.2d) is formed on at least both sides of a quantum dot
layer having quantum dots. In the present invention, the barrier
layer made of a material having a moisture vapor transmission rate
of less than 9 g/(m.sup.2d) is prepared, and the barrier layer is
formed on at least both sides of the quantum dot layer. This makes
it possible to produce a wavelength converting member which allows
for easier production process and allows change in the light
emission intensity to be effectively inhibited as compared with
conventional techniques.
[0022] Further, in the method of producing a wavelength converting
member of the present invention, the entire periphery of the
quantum dot layer having quantum dots is covered by the barrier
layer. This makes it possible to produce a wavelength converting
member which allows change in the light emission intensity to be
more effectively inhibited as compared with conventional
techniques.
[0023] Further, in the present invention, the method preferably
includes the steps of: forming a plurality of the quantum dot
layers at intervals on a lower barrier layer; forming an upper
barrier layer over a surface of the lower barrier layer and
surfaces of the plurality of the quantum dot layers; and isolating
the quantum dot layers by cutting the lower barrier layer and the
upper barrier layer between the quantum dot layers. Thus, a
plurality of wavelength converting members can be obtained at the
same time.
[0024] Further, in the present invention, the quantum dot layer is
preferably formed from a molding or formed by inkjet printing.
[0025] Preferably, in the present invention, the barrier layer has
an organic layer, and the organic layer is provided on the
innermost side to face the quantum dot layer. Thus, while the
adhesion between the barrier layer and the quantum dot layer can be
improved, high wettability of a surface of the organic layer can be
achieved, and the quantum dot layer can be formed more easily.
[0026] Preferably, in the present invention, the barrier layer has
a plurality of organic layers and an inorganic layer sandwiched
between the organic layers, and the innermost layer of the barrier
layer facing the quantum dot layer and the outermost layer thereof
are constituted by the organic layers. The organic layers on both
sides of the barrier layer allows for good handling, making it
easier to form the quantum dot layer. Further, the inclusion of
inorganic layer allows the barrier properties of the barrier layer
to be effectively improved.
[0027] Further, in the present invention, the quantum dot layer
preferably contains a thickening agent. This allows the viscosity
of the quantum dot layer to be adjusted, which facilitates the
formation of the quantum dot layer having a given thickness on the
surface of the barrier layer.
Advantageous Effects of Invention
[0028] Thus, in accordance with the wavelength converting member of
the present invention, change in the light emission intensity over
time can effectively be inhibited as compared with conventional
techniques.
BRIEF DESCRIPTION OF DRAWINGS
[0029] In the accompanying drawings:
[0030] FIGS. 1A to 1C are longitudinal sectional views each showing
a wavelength converting member exemplifying a first embodiment of
the present invention;
[0031] FIG. 2 is a longitudinal sectional view of a wavelength
converting member exemplifying a second embodiment of the present
invention;
[0032] FIG. 3 is a longitudinal sectional view of a wavelength
converting member exemplifying a third embodiment of the present
invention;
[0033] FIGS. 4A and 4B are longitudinal sectional views each
showing a wavelength converting member exemplifying a fourth
embodiment of the present invention;
[0034] FIG. 5 is a longitudinal sectional view of a wavelength
converting member exemplifying a fifth embodiment of the present
invention;
[0035] FIG. 6 is a longitudinal sectional view of a wavelength
converting member exemplifying a sixth embodiment of the present
invention;
[0036] FIG. 7 is a longitudinal sectional view of a wavelength
converting member exemplifying a seventh embodiment of the present
invention;
[0037] FIG. 8 is a longitudinal sectional view of a wavelength
converting member exemplifying an eighth embodiment of the present
invention;
[0038] FIG. 9 is a longitudinal sectional view of a wavelength
converting member exemplifying a ninth embodiment of the present
invention;
[0039] FIG. 10 is a longitudinal sectional view of a wavelength
converting member exemplifying a tenth embodiment of the present
invention;
[0040] FIG. 11 is a longitudinal sectional view of a wavelength
converting member exemplifying an eleventh embodiment of the
present invention;
[0041] FIG. 12 is a longitudinal sectional view of a wavelength
converting member exemplifying a twelfth embodiment of the present
invention;
[0042] FIG. 13 is a longitudinal sectional view of a wavelength
converting member exemplifying a thirteenth embodiment of the
present invention;
[0043] FIG. 14 is a perspective view of a wavelength converting
member of the embodiments;
[0044] FIG. 15 is a longitudinal sectional view of a display device
using a wavelength converting member of the embodiments;
[0045] FIG. 16 is a longitudinal sectional view of a display device
using a wavelength converting member of the embodiments, different
from FIG. 15;
[0046] FIG. 17 is a longitudinal sectional view of a light guide
member using a wavelength converting member of the embodiments;
[0047] FIG. 18 is a conceptual diagram of an apparatus for
producing a wavelength converting member of the embodiments;
[0048] FIG. 19 is a conceptual diagram for illustrating a method of
producing a wavelength converting member of the eighth embodiment
of the present invention;
[0049] FIG. 20 is a conceptual diagram for illustrating a method of
producing a wavelength converting member of the ninth embodiment of
the present invention;
[0050] FIGS. 21A and 21B are a conceptual diagram for illustrating
a method of producing a wavelength converting member of the tenth
embodiment of the present invention;
[0051] FIG. 22 is a schematic view of a light emission testing unit
used in experiments;
[0052] FIG. 23 is a graph showing the relationship between the
elapsed time and the blue light intensity (450 nm area) for each
sample;
[0053] FIG. 24 is a graph showing the relationship the elapsed time
and the green light intensity (green area) for each sample;
[0054] FIG. 25 is a graph showing the relationship the elapsed time
and the x-coordinate of the CIE color space chromaticity diagram
for each sample;
[0055] FIG. 26 is a graph showing the relationship the elapsed time
and the y-coordinate of the CIE color space chromaticity diagram
for each sample;
[0056] FIG. 27 is a graph showing the relationship the elapsed time
and the normalized illumination for each sample;
[0057] FIG. 28 is a graph showing the relationship the elapsed time
and the x-coordinate of the CIE color space chromaticity diagram
for each sample;
[0058] FIG. 29 is a graph showing the relationship the elapsed time
and the y-coordinate of the CIE color space chromaticity diagram
for each sample;
[0059] FIG. 30 is a graph showing the relationship the elapsed time
and the normalized illumination for each sample;
[0060] FIG. 31 is a graph showing the relationship the elapsed time
and the blue light intensity (450 nm area) for Sample 9 to Sample
11;
[0061] FIG. 32 is a graph showing the relationship the elapsed time
and the green light intensity (green area) for Sample 9 to Sample
11;
[0062] FIG. 33 is a graph showing the relationship the elapsed time
and the red light intensity (red area) for Sample 9 to Sample
11;
[0063] FIG. 34 is a graph showing the relationship the elapsed time
and the x-coordinate of the CIE color space chromaticity diagram
for Sample 9 to Sample 11;
[0064] FIG. 35 is a graph showing the relationship the elapsed time
and the y-coordinate of the CIE color space chromaticity diagram
for Sample 9 to Sample 11;
[0065] FIG. 36 is a graph of the measurements of the relationship
the elapsed time and the blue light intensity (450 nm area) for
Sample 12 to Sample 14;
[0066] FIG. 37 is a graph showing the relationship the elapsed time
and the green light intensity (green area) for Sample 12 to Sample
14;
[0067] FIG. 38 is a graph showing the relationship the elapsed time
and the red light intensity (red area) for Sample 12 to Sample
14;
[0068] FIG. 39 is a graph showing the relationship the elapsed time
and the x-coordinate of the CIE color space chromaticity diagram
for Sample 12 to Sample 14;
[0069] FIG. 40 is a graph showing the relationship the elapsed time
and the y-coordinate of the CIE color space chromaticity diagram
for Sample 12 to Sample 14;
[0070] FIG. 41 shows the light emission spectrum for Sample 9;
[0071] FIG. 42 shows the light emission spectrum for Sample 10;
[0072] FIG. 43 shows the light emission spectrum for Sample 11;
[0073] FIG. 44 shows the light emission spectrum for Sample 12;
[0074] FIG. 45 shows the light emission spectrum for Sample 13;
and
[0075] FIG. 46 shows the light emission spectrum for Sample 14.
DESCRIPTION OF EMBODIMENTS
[0076] Embodiments of the present invention (hereinafter simply
referred to as "(disclosed) embodiments") will now be described in
detail. The present invention is not limited to the following
embodiments and can be variously altered without departing from the
spirit of the present invention.
[0077] FIGS. 1A to 1C are longitudinal sectional views of a
wavelength converting member exemplifying a first embodiment of the
present invention. As shown in FIG. 1A, a wavelength converting
member 1 includes a quantum dot layer 2 having quantum dots,
barrier layers 3 and 4 formed on both sides of the quantum dot
layer 2. As shown in FIG. 14, the wavelength converting member 1 is
for example a sheet member shaped like a thin plate. In general, a
"sheet" is defined as a structure having a thickness that is small
relative to the length and the width. The wavelength converting
member 1 may or may not be flexible, but is preferably flexible.
The wavelength converting member 1 is sometimes simply called a
sheet, or may be called a film or a film sheet. However, a "film"
herein is defined as a flexible sheet product. Further, the
wavelength converting member 1 may be formed with a uniform
thickness, or may have a structure in which the thickness varies
from point to point in the member, varies gradually in the length
direction or the width direction, or varies in stages. The length
dimension L, the width dimension W, and the thickness dimension T
of the wavelength converting member 1 are not limited, and may be
varied depending on the product. For example, the wavelength
converting member can be used for a back light of a large product
such as a TV set, or can be used for a back light of a small
portable device such as a smartphone. Accordingly, the size of the
wavelength converting member is determined in accordance with the
size of the product.
[0078] The quantum dot layer 2 includes numerous quantum dots, and
may also include a fluorescent pigment, a fluorescent dye, or the
like in addition to the quantum dots.
[0079] The quantum dot layer 2 is preferably formed from a resin
composition in which quantum dots are dispersed. Examples of resins
(binders) that can be used include: polypropylene, polyethylene,
polystyrene, AS resin, ABS resin, acrylic resin, methacrylate
resin, polyvinyl chloride, polyacetal, polyamide, polycarbonate,
modified polyphenylene ether, polybutylene terephthalate,
polyethylene terephthalate, polysulfone, polyethersulfone,
polyphenylene sulfide, polyamide-imide, polymethylpentene, liquid
crystal polymers, epoxy resin, phenol resin, urea formaldehyde
resin, melamine resin, diallyl phthalate resin, unsaturated
polyester resin, polyimide, polyurethane, silicone resin, a
styrene-based thermoplastic elastomer, and mixtures thereof. For
example, a urethane-acrylic resin, urethane acrylate, a
styrene-based thermoplastic elastomer, etc. can be used preferably.
HYBRAR.RTM. available from KURARAY CO., LTD. can be given as an
example of a styrene-based thermoplastic elastomer.
[0080] Although the structure and the material of the quantum dots
are not limited; for example, a quantum dot in this embodiment can
have a semiconductor core having a diameter of two nanometers to
several tens of nanometers. Further, a quantum dot can have, in
addition to the core consisting of a semiconductor particle, a
shell part covering the circumference of the core. The diameter of
the core consisting of a semiconductor particle may be 2 nm to 20
nm, preferably, 2 nm to 15 nm. This does not limit the material of
the core. For example, the core can use a core material containing
at least Zn and Cd; a core material containing Zn, Cd, Se, and S;
ZnCuInS; CdS; ZnSe; ZnS; CdSe; InP; CdTe; or a composite
thereof.
[0081] The quantum dots include, for example, quantum dots having a
fluorescence wavelength of approximately 520 nm (green) and those
having a fluorescence wavelength of approximately 660 nm (red).
Accordingly, when blue light enters the light entrance plane 1a as
shown in FIGS. 1A to 1C, the quantum dots convert part of the blue
light into green or red light. Thus, white light can be obtained
from the light exit plane 1b.
[0082] For example, the quantum dot layer 2 is formed by coating
the surface of a film like barrier layer with a resin composition
in which quantum dots are dispersed, or by previously shaping the
resin composition into a predetermined shape.
[0083] As shown in FIG. 1A, the barrier layers 3 and 4 are
individually placed on both sides of the quantum dot layer 2. As
shown in FIG. 1B, the barrier layers 3 and 4 can be joined to both
surfaces of the quantum dot layer 2 with adhesive layers 7 provided
therebetween. Thus provided barrier layers 3 and 4 protect both
surfaces of the quantum dot layer 2, leading to improved resistance
to environment (durability). Such a structure in which barrier
layers are placed on both sides of a quantum dot layer has
conventionally been studied (PTL 1). However, the structure does
not limit the structure of the barrier layers in terms of
inhibiting change in the light emission intensity of the wavelength
converting member over time.
[0084] This being the case, in this embodiment, the moisture vapor
transmission rate of the barrier layers 3 and 4 is set to lower
than 9 g/(m.sup.2d). Here, the "moisture vapor transmission rate"
can be measured based on JIS K7129 (:2008). Specifically, the
moisture vapor transmission rate can be measured using, without
limitation, a humidity sensor method, an infrared sensor method, or
a gas chromatography method. In this embodiment, the moisture vapor
transmission rate of the barrier layers 3 and 4 is preferably 5
g/(m.sup.2d) or less, more preferably 3 g/(m.sup.2d) or less, still
more preferably 1 g/(m.sup.2d) or less, yet more preferably 0.1
g/(m.sup.2d) or less, and even more preferably 0.01 g/(m.sup.2d) or
less. The moisture vapor transmission rate is most preferably
6.times.10.sup.-3 g/(m.sup.2d) or less.
[0085] Thus, change in the light emission intensity over time can
be effectively inhibited as compared with conventional techniques
by controlling the moisture vapor transmission rate of the barrier
layers 3 and 4. For example, as shown in the experimental results
described below, when quantum dots having a green fluorescence
wavelength were used, for a sample in which barrier layers having a
moisture vapor transmission rate of 9 g/(m.sup.2d) were used, the
light emission intensity of the blue fluorescence wavelength
(incident light) gradually increased over time while the light
emission intensity of the green fluorescence wavelength decreased
rapidly. For endurance test conditions, the temperature was set at
60.degree. C., and the humidity was set at 90%.
[0086] The high moisture vapor transmission rate of the barrier
layers 3 and 4 increases the amount of water vapor reaching the
quantum dot layer 2, so that the quantum dots contained in the
quantum dot layer 2 are likely to deteriorate. To address this
problem, in this embodiment, the moisture vapor transmission rate
of the barrier layers 3 and 4 is set to lower than 9 g/(m.sup.2d)
so as to protect the quantum dots from the adverse environment or
rapid changes in the environment. Thus, deterioration of the
quantum dots can be suppressed and change in the light intensity
over time can be effectively inhibited. The experiments described
below proved that change in the light emission intensity over time
could effectively be inhibited when the moisture vapor transmission
rate of the barrier layers 3 and 4 was 0.1 g/(m.sup.2d) or
less.
[0087] In FIG. 1B, the quantum dot layer 2 is joined to the barrier
layers 3 and 4 with the adhesive layers 7 therebetween;
alternatively, as shown in FIG. 1C, the barrier layers 3 and 4 can
be directly jointed to both sides of a quantum dot layer 2' without
providing the adhesive layers 7.
[0088] In the structure of FIG. 1C, for example, when an adhesive
component is contained in the quantum dot layer 2', the barrier
layers 3 and 4 can be joined to both surfaces of the quantum dot
layer 2'. This makes it possible to reduce the sheet thickness of
the wavelength converting member 1; for example, the thickness can
be adjusted to 100 .mu.m or less.
[0089] Even for the structure in which the adhesive layers 7 are
provided as shown in FIG. 1B, for example, when the quantum dot
layer 2 is formed by calendaring a substrate for supporting the
quantum dot layer 2 is not required; in addition, the quantum dot
layer 2 can be formed with a thin sheet thickness, specifically of
approximately 70 .mu.m or less, which allows the wavelength
converting member 1 to be formed with a thin sheet thickness.
[0090] Next, in addition to the fact that the moisture vapor
transmission rate of the barrier layers 3 and 4 is less than 9
g/(m.sup.2d), the material and structure of the barrier layers 3
and 4 that are preferred in this embodiment will be described. Note
that the following embodiment does not limit the presence or
absence of the adhesive layers or the state of the quantum dot
layer to those in FIG. 1B and FIG. 1C.
[0091] In FIG. 2, the barrier layers 3 and 4 are each formed as a
single layer of an organic layer 5. The organic layer 5 constitutes
a resin film, and the barrier layers 3 and 4 are present as resin
films, which results in easier handling of the barrier layers 3 and
4. Further, in FIG. 2, the organic layer 5 abuts the quantum dot
layer 2. Here, since the surface of the organic layer 5 is
excellent in wettability, when the quantum dot layer 2 is formed by
application, the quantum dot layer 2 can easily be formed with a
given thickness on the surfaces of the barrier layers 3 and 4.
Further, the adhesion between the quantum dot layer 2 and the
organic layer 5 can be improved by thermocompression bonding, etc.
In this embodiment, the organic layer 5 is preferably a PET
(polyethylene terephthalate) film. This allows for high light
transmittance, and can effectively improve the above-described
handling and the adhesion between the organic layer and the quantum
dot layer 2.
[0092] Further, in FIG. 3, the barrier layers 3 and 4 are each
formed to have a layered structure composed of the organic layer 5
and an inorganic layer 6. In this case, the organic layers 5 are
formed as the innermost layers in the barrier layers 3 and 4 that
are in contact with the quantum dot layer 2, and the inorganic
layers 6 are formed on the outer sides of the innermost layers (as
the outermost layers). The organic layers 5 are preferably PET
(polyethylene terephthalate) films. The inorganic layers 6 are
preferably SiO.sub.2 layers. Further, the inorganic layer 6 may be
a layer of silicon nitride (SiN.sub.x), aluminum oxide
(Al.sub.2O.sub.3), titanium oxide (TiO.sub.2), or silicon oxide
(SiO.sub.2), or a laminate thereof. The provision of such organic
layers 5 facilitates the handling of the barrier layers 3 and 4.
Further, since the organic layers 5 are placed inside in the
barrier layers 3 and 4, the organic layers 5 can abut the quantum
dot layer 2. Accordingly, as with FIG. 2, when the quantum dot
layer 2 is formed by application, the formation can be facilitated,
and the adhesion between the quantum dot layer 2 and the organic
layers 5 can be improved. Further, in FIG. 3, the inorganic layers
6 are provided in the barrier layers 3 and 4, resulting in
excellent barrier properties even when the barrier layers 3 and 4
are thin. The barrier properties here refer to water vapor
transmission properties and gas barrier properties. In this
embodiment, the moisture vapor transmission rate of the barrier
layers 3 and 4 can be made lower than 9 g/(m.sup.2d) even when the
thickness of the barrier layers 3 and 4 is as small as several tens
of micrometers. The gas barrier properties may be evaluated with
oxygen transmission rate. In FIG. 3, the barrier layers 3 and 4
each have a two-layer structure having a single layer of the
organic layer 5 and a single layer of the inorganic layer 6;
alternatively, they may each have a structure in which a plurality
of the organic layers 5 and a plurality of the inorganic layers 6
alternately stacked (provided that the innermost layers of the
barrier layers 3 and 4 are preferably the organic layers 5).
[0093] In FIG. 4A, the barrier layers 3 and 4 are each formed with
a layered structure composed of a plurality of the organic layers 5
and the inorganic layer 6 sandwiched between the organic layers 5.
The organic layers 5 are preferably PET (polyethylene
terephthalate) films. Further, the organic layers 5 preferably
contain a diffusion agent. Alternatively, a diffusion promoting
layer can be formed between the quantum dot layer 2 and the organic
layers 5. The inorganic layer 6 is preferably a SiO.sub.2 layer.
Further, the inorganic layer 6 may be a layer of silicon nitride
(SiN),), aluminum oxide (Al.sub.2O.sub.3), titanium oxide
(TiO.sub.2), or silicon oxide (SiO.sub.2), or a laminate thereof.
In FIG. 4A, the barrier layers 3 and 4 each have a three-layer
structure composed of two organic layers 5 and one inorganic layer
6; alternatively, they may each have a structure composed of five
or more layers.
[0094] In FIG. 4A, both the benefits from the barrier structure
shown in FIG. 2 and the benefits from the barrier structure shown
in FIG. 3 can be achieved. Specifically, as shown in FIG. 4A, the
innermost layers and the outermost layers in the barrier layers 3
and 4 are formed from the organic layers 5. Accordingly, the
handling of the barrier layers 3 and 4 can be more effectively
facilitated. In addition, this makes it possible to effectively
achieve higher adhesion between the barrier layers 3 and 4 and the
quantum dot layer 2, easier formation of the quantum dot layer 2,
and higher barrier properties of the barrier layers 3 and 4.
[0095] Note that as an alternative to the structure in FIG. 4A, for
example, the barrier layers 3 and 4 may each have a layered
structure of inorganic layer 6-organic layer 5-inorganic layer 6.
In this geometry, a plurality of the inorganic layers 6 are placed
in each of the barrier layers 3 and 4, which allows the barrier
layers 3 and 4 to have more excellent barrier properties.
[0096] In the above structure, the barrier layers 3 and 4 are each
placed on either side of the quantum dot layer 2. Specifically, the
barrier layers 3 and 4 can each have a different layered structure
such as the single layer structure shown in FIG. 2 or the layered
structures shown in FIG. 3 and FIG. 4A; and the barrier properties,
typified by the moisture vapor transmission rate, of the barrier
layers 3 and 4 may have the nominal values, for example.
[0097] On the other hand, in FIG. 4B, a plurality of barrier layers
3, 4, 7, and 8 are stacked on both sides of the quantum dot layer
2. For example, the barrier layers 3, 4, 7, and 8 are each formed
with a single layer structure or a layered structure shown in FIG.
2, FIG. 3, and FIG. 4A. The barrier layer 3 is joined to the
barrier layer 7 and the barrier layer 4 is joined to the barrier
layer 8 using an adhesive or the like. For example, the barrier
layers 3, 4, 7, and 8 each have a layered structure of organic
layer (for example, a PET film)-inorganic layer (for example,
SiO.sub.2). In the laminate, the inorganic layers are provided
inside to be closer to the quantum dot layer 2, whereas the organic
layers are provided on the outer sides. Specifically, in FIG. 4B,
for example, the laminate has barrier layer 8 (organic
layer-inorganic layer)-barrier layer 4 (organic layer-inorganic
layer)-quantum dot layer 2-barrier layer 7 (inorganic layer-organic
layer)-barrier layer 3 (inorganic layer-organic layer) stacked in
this order from the lower side to the upper side in the
diagram.
[0098] When the plurality of the barrier layers 3, 4, 7, and 8 are
stacked as described above, variations can be reduced and the
barrier properties can be steadily improved even when the barrier
layers 3, 4, 7, and 8 used have low barrier properties.
[0099] Further, in the above structures, the barrier layers placed
on both sides of the quantum dot layer 2 have symmetric layered
structures; alternatively, the barrier layers may have asymmetric
structures.
[0100] In addition, the following processes may be performed to
improve the light scattering capability of the wavelength
converting member 1. Specifically, in the embodiment shown in FIG.
5, surfaces of the barrier layers 3 and 4 are matted. For example,
the barrier layers 3 and 4 can be each formed as a laminate of
inorganic layer-organic layer-matted layer. In such a structure,
surfaces 3a and 4a of the respective barrier layers 3 and 4 have
irregularities. Alternatively, a surface of one of the barrier
layer 3 and the barrier layer 4 may be matted. Yet alternatively, a
light-scattering agent 8 may be contained in the quantum dot layer
2 as shown in FIG. 6. Examples of the material of the
light-scattering agent 8 can include, but not limited to, fine
particles of SiO.sub.2, BN, AlN, or the like. By way of example,
the light-scattering agent 8 may be contained at 1 wt % to 10 wt %
with respect to the quantum dot layer 2. Further, the
light-scattering agent 8 may be contained in the barrier layers 3
and 4. In this case, the concentration of the light-scattering
agent 8 contained in the quantum dot layer 2 may be equal to or
different from the concentration of the light-scattering agent
contained in the barrier layers 3 and 4. The barrier layers 3 and 4
shown in FIG. 5 and FIG. 6 may have any one of the structures in
FIG. 2 to FIG. 4B. For example, a surface of one of the barrier
layer 3 and the barrier layer 4 may be matted; the quantum dot
layer 2 may contain the light-scattering agent 8; and the barrier
layer 3 or the barrier layer 4 may contain the light-scattering
agent 8.
[0101] In another embodiment shown in FIG. 7, the quantum dot layer
2 contains a thickening agent 9. Examples of the thickening agent 9
can include, but not limited to, carboxyvinyl polymers-based,
carboxymethyl cellulose-based, methyl ether acrylate
copolymers-based; and bentonite (aluminum silicate)-based or
hectorite (magnesium silicate)-based additives. When the thickening
agent 9 is contained, the viscosity of the resin composition
forming the quantum dot layer 2 can be appropriately adjusted, and
the quantum dot layer 2 can easily be formed with a given thickness
and a given shape.
[0102] In FIG. 6 and FIG. 7, the barrier layers 3 and 4 may be
matted as in FIG. 5.
[0103] Further, in this embodiment, the quantum dot layer 2
preferably contains a dispersant to improve the dispersibility of
the quantum dots contained in the quantum dot layer 2. Examples of
the material of the dispersant used include, but not limited to,
additives of epoxy resins, polyurethanes, polycarboxylates,
acid-formaldehyde condensate polymers of naphthalenesulfonic,
polyethylene glycols, compounds of partial alkyl ester of a
polycarboxylic acid, polyethers, polyalkylene polyamines, alkyl
sulfonate salts, quaternary ammonium salts, higher alcohol alkylene
oxides, polyhydric alcohol esters, alkyl polyamines, or
polyphosphates. DISPERBYK.RTM. available from BYK Japan KK can be
given as a specific example.
[0104] As shown in Table 1 below, when quantum dots were mixed and
dispersed in a liquid resin, the viscosity was found to decrease.
When the viscosity was measured, the shear rate was 15/s to 500/s.
The unit of the viscosity shown in the table is (mPas).
TABLE-US-00001 TABLE 1 Resin only (without quantum dots) Quantum
dots mixed in Resin 6603 3170 8906 3367
[0105] Accordingly, in order to keep the viscosity within a
predetermined range for facilitating the formation of the quantum
dot layer 2, the viscosity is preferably adjusted for example by
adding the above thickening agent. Note that the values of the
viscosity shown in Table 1 are mere examples, and the viscosity can
be adjusted to a required level as appropriate.
[0106] In the embodiments shown in FIG. 1A to FIG. 7, the barrier
layers are placed at least on both the top and bottom of the
quantum dot layer 2, and no limitation is placed on the provision
of the barrier layers at edges on the sides of the quantum dot
layer 2 (the right and left sides of the quantum dot layer 2 in the
diagram). On the other hand, in structures described below, a
barrier layer is formed around the entire periphery of the quantum
dot layer 2. FIG. 8 is a longitudinal sectional view of a
wavelength converting member exemplifying an eighth embodiment of
the present invention. The entire periphery of the quantum dot
layer 2 is covered with the barrier layer 81, which allows the
entire periphery of the quantum dot layer 2 to be protected.
Accordingly, the durability can be improved as compared with the
case where only both the top and bottom of the quantum dot layer 2
are protected as shown in FIGS. 1A to 1C. Thus, deterioration of
the quantum dot layer 2 can suitably be suppressed. As shown in
FIG. 8, a wrap starting end 82 and a wrap finishing end 83 of the
barrier layer 81 overlap on a top surface 80 of the quantum dot
layer 2. It will be appreciated that the position where the wrap
starting end 82 and the wrap finishing end 83 overlap may be on any
one of the top surface 80, the bottom surface, the right side, and
the left side of the quantum dot layer 2. For the region where the
wrap starting end 82 and the wrap finishing end 83 overlap, the
wrap starting end 82 and the wrap finishing end 83 are joined for
example by thermocompression bonding and bonding. In the structure
shown in FIG. 8, the wrap starting end 82 and the wrap finishing
end 83 overlap in a position facing one face of the quantum dot
layer 2, so that the barrier layer 81 can be used without
waste.
[0107] Without limiting the overall shape of a wavelength
converting member 60 shown in FIG. 8, the wavelength converting
member 60 may be shaped like a stick, a block, or a chip, or may be
shaped like a sheet obtained by extending the length dimension of
the quantum dot layer 2 in the lateral direction in the diagram
shown in FIG. 8.
[0108] FIG. 9 is a longitudinal sectional view of a wavelength
converting member exemplifying a ninth embodiment of the present
invention. In FIG. 9, the barrier layer 81 covers the entire
periphery of the quantum dot layer 2, and the wrap starting end 82
and the wrap finishing end 83 of the barrier layer 81 are joined
for example by thermocompression bonding at an edge on one side of
the quantum dot layer 2 (the right side of the quantum dot layer 2
in the diagram). Thus, the structure in which the wrap starting end
82 and the wrap finishing end 83 of the barrier layer 81 are joined
at an edge on one side of the quantum dot layer 2 allows the wrap
starting end 82 and the wrap finishing end 83 to be joined in a
region without affecting the quantum dot layer 2. For example, when
the wrap starting end 82 and the wrap finishing end 83 are joined
by thermocompression bonding, the quantum dot layer 2 can be
prevented from being heated, and thermal effects on the quantum dot
layer 2 can be suppressed. Alternatively, the wrap starting end 82
and the wrap finishing end 83 may be joined by bonding.
[0109] FIG. 10 is a longitudinal sectional view of a wavelength
converting member exemplifying a tenth embodiment of the present
invention. In FIG. 10, the quantum dot layer 2 is provided on a
lower barrier layer 85, and an upper barrier layer 86 is provided
to cover the lower barrier layer 85 and the quantum dot layer 2.
The barrier layers 85 and 86 placed on both the top and bottom of
the quantum dot layer 2 are joined to each other at edges on the
sides of the quantum dot layer 2 (the right and left sides of the
quantum dot layer 2 in the diagram) for example by bonding or
thermocompression bonding. Since the barrier layers 85 and 86 are
joined to each other at the edges of the quantum dot layer 2,
effects of the joining process on the quantum dot layer 2 can be
suppressed. Further, in the structure of FIG. 10, unlike in FIG. 8
and FIG. 9, the barrier layers 85 and 86 are two separate layers,
and the quantum dot layer 2 is sandwiched between the barrier
layers 85 and 86. Accordingly, it is not necessary to wrap the
entire periphery of the quantum dot layer 2 with the barrier layer
81 as in the structures shown in FIG. 8 and FIG. 9. Therefore, the
wavelength converting member 60 can easily be formed with the
barrier layers being formed on the entire periphery of the quantum
dot layer 2, and the structure shown in FIG. 10 is suitable for
mass production of the wavelength converting member 60.
[0110] In FIG. 1A to FIG. 10, for example, the quantum dot layer 2
is formed from a molding. Specifically, the quantum dot layer 2 is
formed for example by injection molding, and the barrier layer(s)
are provided on the molding of the quantum dot layer 2. When the
quantum dot layer 2 is formed from a molding, wavelength converting
members having various shapes can be easily and suitably formed. In
this embodiment, the quantum dot layer 2 is not necessarily formed
from a molding, and may be formed by application. In the case of
application, a barrier layer is previously prepared, and the
quantum dot layer 2 is applied to the barrier layer. The
application can be performed for example by inkjet printing or a
dispenser method. In particular, inkjet printing is preferred.
[0111] In FIG. 11 to FIG. 13, a quantum dot layer 62 is formed by
inkjet printing. In a wavelength converting member 61 shown in FIG.
11, the quantum dot layer 62 is formed by inkjet printing, and the
structure of the barrier layer 81 provided on the quantum dot layer
62 is the same as that in FIG. 8. Further, in the wavelength
converting member 61 shown in FIG. 12, the quantum dot layer 62 is
formed by inkjet printing, and the structure of the barrier layer
81 provided on the quantum dot layer 62 is the same as that in FIG.
9. Further, in the wavelength converting member 61 shown in FIG.
13, the quantum dot layer 62 is formed by inkjet printing, and the
structure of the barrier layers 81 provided on the quantum dot
layer 62 is the same as that in FIG. 10.
[0112] When the quantum dot layer 62 is formed by inkjet printing,
the quantum dot layer 62 can be formed with a significantly thin
thickness. As a result, as shown in FIG. 11 to FIG. 13, a surface
61a of the wavelength converting member 61 can be planarized.
[0113] For example, the wavelength converting members 1, 60, and 61
of the disclosed embodiments can each be incorporated into a back
light unit 55 shown in FIG. 15. In FIG. 15 to FIG. 17, the
wavelength converting member 1 is illustrated as an example. In
FIG. 15, the back light unit 55 is configured to have a plurality
of light emitting devices 20 (LEDs) and the wavelength converting
member 1 of this embodiment that faces the light emitting devices
20. As shown in FIG. 15, the light emitting devices 20 are
supported on a surface of a support 52. In FIG. 15, the back light
unit 55 is placed on the back side of a display area 54 of, for
example, a liquid crystal display, and constitutes part of a
display device 50.
[0114] Although not shown in FIG. 15, in addition to the wavelength
converting member 1, a diffuser panel for diffusing light, and
other sheets may be provided between the light emitting devices 20
and the display area 54.
[0115] When the wavelength converting member 1 is formed like a
sheet as shown in FIG. 14, the wavelength converting member 1 in
the form of a single sheet may be placed between the light emitting
devices 20 and the display area 54 as shown in FIG. 15.
Alternatively, for example, a plurality of the wavelength
converting members 1 may be joined together to achieve a
predetermined size. A structure in which the plurality of
wavelength converting members 1 are joined together by tiling is
hereinafter referred to as a compound wavelength converting
member.
[0116] Here, a structure in which the compound wavelength
converting member is placed instead of the wavelength converting
member 1 of the display device 50 in FIG. 15, and a diffuser panel
is placed between the light emitting devices 20 and the compound
wavelength converting member, that is, a structure of light
emitting devices 20-diffuser panel-compound wavelength converting
member-display area 54 will be discussed. With such a structure,
light emitted from the light emitting devices 20 and diffused by
the diffuser panel enters the compound wavelength converting
member. Since the light diffused by the diffuser panel enters the
compound wavelength converting member, the distribution of the
light intensity depending on the distance from the light emitting
devices 20 can be reduced. The distance between the light emitting
devices 20 and the compound wavelength converting member is longer
than in the case where the diffuser panel is not provided, which
reduces effects of heat radiated from the light emitting devices 20
on the quantum dots contained in the compound sheet.
[0117] On the other hand, as shown in FIG. 16, the structure may
have light emitting devices 20-compound wavelength converting
member 21-diffuser panel 22-display area 54 placed in this order.
Accordingly, even when irregular reflection occurs at the joints
between the wavelength converting members 1 or the emission color
varies due to deterioration of quantum dots caused by water vapor
having entered through the joints, color unevenness in the display
of the display area 54 can be suitably reduced. Specifically, since
the light output from the compound wavelength converting member 21
is diffused by the diffuser panel 22 and then enters the display
area 54, color unevenness in the display of the display area 54 can
be reduced.
[0118] When the compound wavelength converting member 21 is used, a
diffuser panel is preferably placed on the light emission side of
the compound wavelength converting member 21 not only when the
compound wavelength converting member 21 is used for the display
device shown in FIG. 16, but also when the compound wavelength
converting member 21 is used for example for a lighting.
[0119] Alternatively, as shown in FIG. 17, the wavelength
converting member 1 of this embodiment may be provided at least
either on a surface of a light guide plate 40 or between the light
guide plate 40 and light emitting devices 20 to serve as a light
guide member. As shown in FIG. 17, the light emitting devices 20
(LEDs) are placed to face the light guide plate 40. Note that the
use of the wavelength converting member 1 of the embodiments is not
limited to those shown in FIG. 15, FIG. 16, and FIG. 17.
[0120] In the disclosed embodiments, change in the light emission
intensity of the wavelength converting member 1 over time can
effectively be reduced as compared with conventional techniques.
Accordingly, when the wavelength converting member 1 of the
disclosed embodiments is used for the back light unit 55, the light
guide member, etc., the wavelength conversion characteristics can
be made stable and the lifespan of the back light unit 55 and the
light guide member can be extended.
[0121] Further, the wavelength converting member 1 of this
embodiment can be flexible. This allows the wavelength converting
member 1 to be suitably placed for example on a curved surface.
[0122] Note that the wavelength converting member 1 of this
embodiment can also be used for a lighting device, a light source
unit, a light diffusion apparatus, a light reflector system, etc.
other than the back light unit or the light guide member described
above.
[0123] Further, in FIG. 15, FIG. 16, and FIG. 17, a wavelength
converting member 61 in which one of the quantum dot layers 62
shown in FIG. 11 to FIG. 13 is formed by inkjet printing can be
used. The wavelength converting members 1, 60, and 61 shown in FIG.
1 to FIG. 13 may each be placed inside a glass capillary.
[0124] FIG. 18 is a conceptual diagram for illustrating apparatus
for producing a wavelength converting member of this embodiment. A
shown in FIG. 18, the apparatus is configured to have a first web
roll 30 for feeding a resin film 10 to be the barrier layer 3 and a
second web roll 31 for feeding a resin film 11 to be a barrier
layer 4, a take-up roll 32, and a pressure contact portion 35
composed of a pair of nip rolls 33 and 34, a coating means 36, and
a heating unit 38.
[0125] As shown in FIG. 18, the resin film 10 having a moisture
vapor transmission rate of less than 9 g/(m.sup.2d) is fed from the
first web roll 30, and a surface of the resin film 10 is coated
with a resin composition 37 containing quantum dots using the
coating means 36. The resin composition 37 can be applied for
example by an application method using a known application coater
or an impregnation coater. Examples of the coater include a gravure
coater, a dip coater, and a comma knife coater. Alternatively, the
resin composition 37 can be applied by inkjet printing.
[0126] As shown in FIG. 18, the resin film 10 of which surface is
coated with the resin composition 37 is heated by the heating unit
38 provided with heaters, etc. This leads to evaporation of a
solvent contained in the resin composition 37, and the quantum dot
layer 2 is solidified to a certain extent at this time.
[0127] Subsequently, as shown in FIG. 18, the resin film 11 having
a moisture vapor transmission rate of less than 9 g/(m.sup.2d) fed
from the second web roll 31 abuts an exposed surface of the quantum
dot layer 2, and a layered structure of resin film 11-quantum dot
layer 2-resin film 10 is pressured and welded between the nip rolls
33 and 34 composing the pressure contact portion 35. In the
pressure contact portion 35, the boundaries of the quantum dot
layer 2 and the resin films 10 and 11 are fixed by
thermocompression bonding.
[0128] A sheet member 39 composed of resin film 11-quantum dot
layer 2-resin film 10 is wound on the take-up roll 32. The wound
sheet member 39 is cut into a predetermined size, thereby obtaining
the wavelength converting member 1 shaped like a sheet.
[0129] In the above production method, the quantum dot layer 2 is
formed by application on the resin film 10, and the thickness of
the quantum dot layer 2 formed can be roughly from 10 .mu.m to 500
.mu.m. Further, the thickness of the resin films 10 and 11 is
roughly from a few tens of micrometers to 1000 micrometers, so that
the thickness of the wavelength converting member 1 is roughly from
50 .mu.m to 2500 .mu.m. Note that the thickness of the quantum dot
layer 2 and the thickness of the wavelength converting member 1 are
not limited.
[0130] The resin films 10 and 11 illustrated in FIG. 18 each have a
single layer of the organic layer 5 shown in FIG. 2 or a layered
structure having the organic layer 5 and the inorganic layer 6
shown in one of FIG. 3 and FIGS. 4A and 4B. Preferably, the
inorganic layer 6 is provided between the plurality of organic
layers 5 as shown in FIG. 4A. Specifically, the resin films 10 and
11 preferably each have a layered structure of PET film-SiO.sub.2
layer-PET film.
[0131] Alternatively, a stack of a plurality of resin films can be
fed to be placed on both surfaces of the quantum dot layer to
provide a structure in which the a plurality of barrier layers are
placed on both sides of the quantum dot layer as shown in FIG.
4B.
[0132] The matting process shown in FIG. 5 is performed on one or
both of the surfaces of the sheet member 39 wound on the take-up
roll 32 shown in FIG. 18 or is performed on both surfaces of the
wavelength converting member 1 shown in FIG. 14, formed by cutting
the sheet member 39 into a predetermined size.
[0133] The matting process can be performed for example by
sandblasting the sheet surface, or by coating the sheet surface
with a mat layer, but is not limited thereto. Further, as shown in
FIG. 6, in order to obtain the quantum dot layer 2 containing the
light-scattering agent 8, the light-scattering agent 8 can be added
to the resin composition 37 to be applied with the coating means 36
shown in FIG. 18. When the thickening agent 9 is contained in the
resin composition 37 to be applied with the coating means 36 shown
in FIG. 18, the viscosity of the resin composition 37 can be
suitably adjusted. The viscosity can be adjusted to, for example,
around several hundreds of mPas to several thousands of mPas,
without limitation. Suitably adjusting the viscosity of the resin
composition 37 to optimize the fluidity of the resin composition 37
allows for the formation of the quantum dot layer 2 with a
generally uniform thickness on a surface of the resin film 10.
[0134] In the production process shown in FIG. 18, the quantum dot
layer 2 is formed by application to a surface of the resin film 10;
alternatively, the resin films 10 and 11 may be stuck to both
surfaces of the molding of the quantum dot layer 2 having
previously been formed. The quantum dot layer 2 may be formed using
a method such as injection molding, extrusion molding, blow
molding, thermoforming, compression molding, calendaring, blown
film extrusion, or casting. The thickness of the molding of the
quantum dot layer 2 can be around 10 .mu.m to 500 .mu.m. For
example, the molding of the quantum dot layer 2 can be formed with
a thickness of approximately 300 .mu.m. The resin films 10 and 11
can be stuck to both sides of the molding of the quantum dot layer
2 by thermocompression bonding, etc. Note that adhesive layers may
be provided between the quantum dot layer 2 and the resin films 10
and 11.
[0135] Methods for making the wavelength converting member 1 into a
film include methods using a coating machine and methods using a
molding machine. Curing methods using a coating machine include UV
curing and heat curing.
[0136] In this embodiment, the resin films 10 and 11 having a
moisture vapor transmission rate of less than 9 g/(m.sup.2d) can
suitably and easily be placed on both sides of the quantum dot
layer 2. This makes it possible to easily produce a wavelength
converting member 1 which allows change in the light emission
intensity to be effectively inhibited as compared with conventional
techniques.
[0137] Next, a method of producing the wavelength converting member
in FIG. 8 will be described with reference to FIG. 19. FIG. 19 is a
conceptual diagram for illustrating a method of producing a
wavelength converting member of the eighth embodiment of the
present invention. As shown in the left diagram in FIG. 19, for
example, the quantum dot layer 2 is formed from a molding. Next, in
the middle diagram in FIG. 19, the barrier layer 81 is placed on
the entire periphery of the quantum dot layer 2. Further, as shown
in the right diagram in FIG. 19, the wrap starting end 82 and the
wrap finishing end 83 overlap on one side (top surface 80 in FIG.
19) of the quantum dot layer 2 and the wrap starting end 82 and the
wrap finishing end 83 are thermocompression bonded using a
thermocompression bonding member 90. Thermocompression bonding can
be performed for example by while heating, pressing the wrap
starting end 82 and the wrap finishing end 83 or joining them under
pressure using rollers. Alternatively, the wrap starting end 82 and
the wrap finishing end 83 can be joined using an adhesive instead
of thermocompression bonding. The production method shown in FIG.
19 enables easily and suitably covering the entire periphery of the
quantum dot layer 2 with the barrier layer 81.
[0138] A method of producing the wavelength converting member in
FIG. 9 will be described with reference to FIG. 20. FIG. 20 is a
conceptual diagram for illustrating a method of producing a
wavelength converting member of the ninth embodiment of the present
invention. As shown in the left diagram in FIG. 20, for example,
the quantum dot layer 2 is formed from a molding. In the middle
diagram in FIG. 20, with the wrap starting end 82 of the barrier
layer 81 being located at an edge on one side of the quantum dot
layer 2, the barrier layer 81 is wrapped around the quantum dot
layer 2, and the wrap starting end 82 and the wrap finishing end 83
overlap at the edge of the quantum dot layer 2 as shown in the
right diagram of FIG. 20. The wrap starting end 82 and the wrap
finishing end 83 are then thermocompression bonded using
thermocompression bonding member 90. As shown in FIG. 20, the wrap
starting end 82 and the wrap finishing end 83 of the barrier layer
81 overlap at an edge on one side of the quantum dot layer 2, which
can reduce effects caused by joining the wrap starting end 82 and
the wrap finishing end 83 for example by thermocompression bonding
on the quantum dot layer 2 (thermal effects, etc.). Thus, the
quantum dot layer 2 can be prevented from being deteriorated in the
step of forming the barrier layer 81. Note that the wrap starting
end 82 and the wrap finishing end 83 may be joined by bonding.
[0139] A method of producing the wavelength converting member in
FIG. 10 will be described with reference to FIG. 21. FIG. 21 is a
conceptual diagram for illustrating a method of producing a
wavelength converting member of the tenth embodiment of the present
invention. In the step shown in FIG. 21A, a plurality of the
quantum dot layers 2 are placed at intervals on the barrier layer
85. For example, the quantum dot layers 2 are each formed from a
molding, and the plurality of the quantum dot layers 2 are arranged
on the barrier layer 85. Here, the quantum dot layers 2 are
preferably fixed to the barrier layer 85 by bonding.
[0140] Subsequently, in the step shown in FIG. 21B, the barrier
layer 86 is placed over the surface of the barrier layer 85 and the
quantum dot layers 2. Preferably, an adhesive layer is previously
applied to the inner surface of the barrier layer 86 (facing the
barrier layer 85 and the quantum dot layers 2), and the barrier
layer 85 is stuck to the barrier layer 86 with the quantum dot
layers 2 therebetween. Alternatively, the barrier layer 85 and the
barrier layer 86 can be stuck together by thermocompression
bonding. As shown by the chain lines in FIG. 21B, the joined
barrier layers 85 and 86 are cut between the adjacent quantum dot
layers 2 thereby isolating the quantum dot layers 2. Thus, a
plurality of the wavelength converting members 60 can be obtained
at the same time.
[0141] According to the method of producing the wavelength
converting member 60 shown in FIG. 21, since the barrier layers 85
and 86 overlap, the barrier layers can be placed on the entire
periphery of the quantum dot layers 2, so that the wavelength
converting members 60 in each of which the barrier layer is formed
on the entire periphery of the quantum dot layers 2 can be easily
and suitably produced, and the method is suitable for mass
production of the wavelength converting members 60.
[0142] Using the production methods shown in FIG. 19 to FIG. 21,
the entire periphery of the quantum dot layer(s) 2 can be covered
by the barrier layer, the entire periphery of the quantum dot
layer(s) 2 can be suitably protected by the barrier layer(s), and
the durability can be more effectively improved. Thus,
deterioration of the quantum dot layer(s) 2 can be more suitably
suppressed.
[0143] For example, the quantum dot layers(s) 2 shown in FIG. 19 to
FIG. 21 are formed from a molding; alternatively, the quantum dot
layer(s) 2 may be formed by inkjet printing as shown in FIG. 11 to
FIG. 13. In the case of inkjet printing, a resin composition in
which quantum dots are dispersed is discharged onto the top of the
barrier layer by inkjet printing. The discharged resin composition
is preferably heated for stabilization. The heating temperature is
preferably 30.degree. C. to 80.degree. C. and more preferably
30.degree. C. to 50.degree. C.
[0144] In this embodiment, the resin films 10 and 11 (barrier
layers) each have an organic layer, and it is preferable that the
organic layer abuts the quantum dot layer(s) 2 in the production
process. Thus, the quantum dot layer(s) 2 can be formed on a
surface of the organic layer with high wettability, the quantum dot
layer(s) 2 can be formed more easily, and the adhesion between the
barrier layer and the quantum dot layer(s) 2 can be improved due to
the affinity therebetween.
[0145] Further, the layered structure of the resin films 10 and 11
each having a plurality of organic layers and an inorganic layer
provided between the organic layers allows the organic layers to be
placed on both surfaces of the resin films 10 and 11. This improves
handling, and allows for easier formation of the quantum dot layer
2 on the surfaces of the resin films 10 and 11. In addition, the
inorganic layers included in the barrier layers make it possible to
effectively improve barrier properties of the resin films 10 and 11
(barrier layers).
[0146] Alternatively, the resin films 10 and 11 can each have a
layered structure composed of a plurality of inorganic layers and
an organic layer provided between the inorganic layers. Further, a
plurality of resin films can be placed by being stacked. In this
case, the resin films 10 and 11 can be joined by sticking them
together using an adhesive or by thermocompression bonding.
EXAMPLES
[0147] The present invention will be described in detail below with
Examples and Comparative Examples performed to demonstrate the
effects of the present invention. Note that the present invention
is not limited to the following examples.
[0148] In Sample 1 to Sample 8 of Examples, an elastomer was
dissolved in organosilane, thereby obtaining a QD ink (resin
composition) in which quantum dots having a fluorescence wavelength
of approximately 520 nm (green)(also referred to as "green quantum
dots") were dispersed. For the elastomer, HYBRAR.RTM. 7311 from
KURARAY CO., LTD. was used.
[0149] A laminate of glass-QD ink-barrier layer was obtained. Heat
treatment was performed to evaporate the solvent of the QD ink,
thereby obtaining a quantum dot layer. In this case, the following
structure was employed for the barrier layer.
<Sample 1>
[0150] A barrier layer formed as a film having a three-layer
structure of PET film-SiO.sub.2 layer-PET film with a moisture
vapor transmission rate of 6.times.10.sup.-3 g/(m.sup.2d). The
thickness of the barrier layer was 49 .mu.m.
<Sample 2>
[0151] A barrier layer having a three-layer structure of PET
film/SiO.sub.2 layer/PET film with a moisture vapor transmission
rate of 9 g/(m.sup.2d). The thickness of the barrier layer was 50
.mu.m.
<Sample 3>
[0152] A cyclic olefin-based film.
[0153] Laminates using the barrier layers of Sample 1 to Sample 3
above were subjected to an endurance test under conditions of
temperature: 60.degree. C. and humidity: 90%. The light emission
intensity was measured using a total luminous flux measurement
system available from Otsuka Electronics Co., Ltd. by measuring the
total luminous flux of the light caused in each sample by blue
(wavelength: 450 nm) LED excitation light.
[0154] FIG. 23 is a graph showing the relationship the elapsed time
and the blue light intensity (450 nm area) for each sample. Here,
the blue light intensity corresponds to the area of the emission
peak observed at a wavelength of 450 nm.
[0155] As shown in FIG. 23, the blue light intensity (450 nm area)
was found to gradually increase over time in Sample 2 and Sample 3.
In other words, that the intensity of blue light was found to
increase over time in Sample 2 and Sample 3. On the other hand, it
was found that the blue light intensity (450 nm area) was constant
in Sample 1, and the light intensity of blue light did not change
over time. Further, it was found for Sample 1 that while the
initial blue light intensity (time: 0 h) and the blue light
intensity after 150 hours were 0.0075 (time: 0 h) and 0.0070 (150
h), respectively; thus, the blue light intensity hardly changed,
and the change in the blue light intensity was within 10%. Here,
the change in the blue light intensity is represented by [(initial
blue light intensity-blue light intensity after 150 hours)/initial
blue light intensity].times.100(%)(absolute value).
[0156] FIG. 24 is a graph showing the relationship the elapsed time
and the green light intensity (green area) for each sample. Here,
the green light intensity corresponds to the area of the emission
peak observed at a wavelength of 520 nm. As shown in FIG. 24, in
Sample 2 an Sample 3, the green light intensity (green area) was
found to rapidly decrease over time. The increased blue light
intensity and the reduced green light intensity as in Sample 2 and
Sample 3 mean that the green quantum dots deteriorated over time.
On the other hand, it was found for Sample 1 that the blue light
intensity (450 nm area) did not change over time, and the reduction
in the green light intensity (green area) over time was
successfully made smaller compared with Sample 2 and Sample 3.
Further, it was found for Sample 1 that the initial green light
intensity (time: 0 h) and the green light intensity after 150 hours
were 0.0078 (time: 0 h) and 0.0039 (150 h), respectively; thus, the
change over time was smaller compared with Sample 2 and Sample 3,
and the change in the green light intensity was within 50%. Here,
the change in the green light intensity is represented by [(initial
green light intensity-green light intensity after 150
hours)/initial green light intensity].times.100(%)(absolute
value).
[0157] The measurement results presented in FIG. 23 and FIG. 24
show that deterioration of the quantum dots can be suitably
suppressed with the use of the barrier layer of Sample 1, thereby
effectively inhibiting the change in the light emission intensity
over time. Based on the measurement results shown in FIG. 23 and
FIG. 24, the moisture vapor transmission rate of the barrier layer
was set to a value lower than 9 g/(m.sup.2d). Further, the moisture
vapor transmission rate range of the barrier layer of Sample 1,
that is, 6.times.10.sup.-3 g/(m.sup.2d) or less is assumed to be
the most preferable range.
[0158] Subsequently, the barrier films were evaluated. In the
evaluation, barrier layers of Sample 1 above, Sample 5 in which the
moisture vapor transmission rate was 1.6.times.10.sup.-2
g/(m.sup.2d), and Sample 6 in which the moisture vapor transmission
rate was 8.4.times.10.sup.-3 g/(m.sup.2d) were used. The light
transmittance (%) was 86.8 (total light) for Sample 1, 92.5
(wavelength: 450 nm) for Sample 5, and 90.6 (wavelength: 450 nm)
for Sample 6.
[0159] FIG. 25 is a graph showing the relationship the elapsed time
and the x-coordinate of the CIE color space chromaticity diagram
for each sample. Sample 4 is a sample without barrier layers (the
quantum dot layer formed from a molding).
[0160] In the evaluation, both sides of the quantum dot layer were
sandwiched between the barrier films of the above samples, and
light emitting devices (LEDs) were placed on the side of one of the
barrier films with a diffuser panel provided therebetween.
Measurements were performed from the side of the other barrier film
using a spectrometer.
[0161] FIG. 22 is a schematic view of a light emission testing unit
used in experiments. Part of the light emission testing unit is
shown by a longitudinal sectional view. As shown in FIG. 22, a
light emission testing unit 56 was provided with the light emitting
devices 20 (LEDs) and Sample S being placed in a position facing
the light emitting devices 20. Each sample in the experiments was a
sheet, in which a quantum dot layer was sandwiched between the
above barrier films, and the end faces of the barrier films were
bonded for example with an epoxy bond and stuck together using
aluminum tape. The light emitting devices 20 were supported on a
surface of the support 52, and a diffuser panel 22 was provided
between the light emitting devices 20 and Sample S. All sides of
the light emitting devices 20 were surrounded by a cylindrical
reflective sheet 23, and the diffuser panel 22 was placed on the
top of the reflective sheet 23. The light emitted from the light
emitting devices 20 was diffused by the diffuser panel 22 and
entered Sample S. The reflective sheet 23 had a box shape with an
opening of for example 3 cm square, and the reflective sheet 23 had
a height (distance of the diffuser panel 22 from the support 52) of
for example 4 cm. The light emitted from the light emitting devices
20 was then made to enter Sample S through the diffuser panel 22,
and the light output from the top of Sample S was measured using
the total luminous flux measurement system. Note that the
experiment was performed under conditions of temperature:
60.degree. C. and humidity: 90%. Using the light emission testing
unit 56 shown in FIG. 22, the light emission intensity of the light
emitting devices 20 through Sample S can be accurately
measured.
[0162] As shown in FIG. 25, the x-coordinate did not change over
time for Samples 1, 5, and 6 except for Sample 4 without barrier
layers. In Sample 1 and Sample 5, the initial x-coordinate (time: 0
h) and the x-coordinate after 200 hours were 0.208 (time: 0 h) and
0.210 (200 h), respectively; thus, the change in the x-coordinate
was found to be within 1%. In Sample 6, the initial x-coordinate
(time: 0 h) and the x-coordinate after 200 hours were 0.210 (time:
0 h) and 0.213 (200 h), respectively; thus, the change in the
x-coordinate was found to be within 2%. Here, the x-coordinate
change is represented by [(initial x-coordinate-x-coordinate after
200 hours)/initial x-coordinate].times.100(%)(absolute value).
[0163] FIG. 26 is a graph showing the relationship the elapsed time
and the y-coordinate of the CIE color space chromaticity diagram
for each sample. As shown in FIG. 26, the y-coordinate did not
change over time in Samples 1, 5, and 6 except for Sample 4 without
barrier layers. In Sample 1 and Sample 5, the initial y-coordinate
(time: 0 h) and the y-coordinate after 200 hours were 0.170 (time:
0 h) and 0.190 (200 h), respectively; thus, the change in the
y-coordinate was found to be within 15%. In Sample 6, the initial
y-coordinate (time: 0 h) and the y-coordinate after 200 hours were
0.170 (time: 0 h) and 0.195 (200 h), respectively; thus, the change
in the y-coordinate was found to be within 15%. Here, the
y-coordinate change is represented by [(initial
y-coordinate-y-coordinate after 200 hours)/initial
y-coordinate].times.100(%)(absolute value).
[0164] FIG. 27 is a graph showing the relationship the elapsed time
and the normalized illumination for each sample. As shown in FIG.
27, the normalized illumination did not change over time in Samples
1, 5, and 6 except for Sample 4 without barrier layers. In this
result, the normalized illumination changed by .+-.30% over 200
hours.
[0165] Next, a barrier layer having a moisture vapor transmission
rate of 10.sup.-2 g/(m.sup.2d) was used as Sample 7, and a barrier
layer having a moisture vapor transmission rate of 10.sup.-1
g/(m.sup.2d) was used as Sample 8. The moisture vapor transmission
rates of the barrier layers had the nominal values. Further, a
sheet described in the description of FIG. 22 above was formed and
the spectrum was measured over time using the light emission
testing unit of FIG. 22.
[0166] FIG. 28 is a graph showing the relationship the elapsed time
and the x-coordinate of the CIE color space chromaticity diagram
for each sample. In the experiments, in addition to Sample 7 and
Sample 8, Sample 1 and Sample 2 described above were used.
[0167] As shown in FIG. 28, in Sample 2 having a barrier layer with
a moisture vapor transmission rate of 9 g/(m.sup.2d), the
x-coordinate changed immediately after the start of the experiment.
In Sample 1, Sample 7, an Sample 8, in each of which the barrier
layer had a moisture vapor transmission rate of 10.sup.-1
g/(m.sup.2d) or less, change in the x-coordinate over time was not
observed or was very small. In Sample 1 and Sample 8, the initial
x-coordinate (time: 0 h) and the x-coordinate after 1100 hours were
0.220 (time: 0 h) and 0.225 (1100 h), respectively; thus, the
change in the x-coordinate was found to be within 5%. In Sample 7,
the initial x-coordinate (time: 0 h) and the x-coordinate after
1100 hours were 0.219 (time: 0 h) and 0.219 (1100 h), respectively;
thus, the change in the x-coordinate was found to be 0%. Here, the
x-coordinate change is represented by [(initial
x-coordinate-x-coordinate after 1100 hours)/initial
x-coordinate].times.100(%)(absolute value).
[0168] FIG. 29 is a graph showing the relationship the elapsed time
and the y-coordinate of the CIE color space chromaticity diagram
for each sample. As shown in FIG. 29, change in the y-coordinate
over time was not observed or was very small in Samples 1, 7, and 8
except for Sample 2 having a barrier layer with a moisture vapor
transmission rate of 9 g/(m.sup.2d). In Sample 1 and Sample 8, the
initial y-coordinate (time: 0 h) and the y-coordinate after 1100
hours were 0.190 (time: 0 h) and 0.210 (1100 h), respectively;
thus, the change in the y-coordinate was found to be within 15%. In
Sample 7, the initial y-coordinate (time: 0 h) and the y-coordinate
after 1100 hours were 0.160 (time: 0 h) and 0.195 (1100 h),
respectively; thus, the change in the y-coordinate was found to be
within 25%. Here, the y-coordinate change is represented by
[(initial y-coordinate-y-coordinate after 1100 hours)/initial
y-coordinate].times.100(%)(absolute value).
[0169] FIG. 30 is a graph showing the relationship the elapsed time
and the normalized illumination for each sample. As shown in FIG.
30, change in the normalized illumination over time was not
observed or was very small in Samples 1, 7, and 8 except for Sample
2 having a barrier layer with a moisture vapor transmission rate of
9 g/(m.sup.2d). In this result, the normalized illumination changed
by .+-.30% over 200 hours.
[0170] From the above experiments, barrier layer(s) having a
moisture vapor transmission rate of approximately 0.1 g/(m.sup.2d)
or more were found to sufficiently improve durability. Based on the
above, the moisture vapor transmission rate of the barrier layer(s)
was preferably set to 0.1 g/(m.sup.2d) or less.
[0171] Next, experiments were performed using samples in which the
barrier layer was formed around the entire periphery of the quantum
dot layer(s). In Sample 9 to Sample 14, a QD ink (resin
composition) obtained by dissolving an elastomer in organosilane
and dispersing quantum dots having a fluorescence wavelength of
approximately 520 nm (green) and quantum dots having a fluorescence
wavelength of approximately 650 nm (red)(also referred to as "red
quantum dots") therein. For the elastomer, HYBRAR.RTM. 7311 from
KURARAY CO., LTD. was used. Heat treatment was performed to
evaporate the solvent of the QD ink, thereby obtaining a quantum
dot layer. For the quantum dot layers used in the experiments, high
concentration layers and low concentration layers were prepared.
For the barrier layer, a sheet member in which a SiO.sub.2 layer
was formed on a PET film that had a moisture vapor transmission
rate of approximately 10.sup.-3 g/(m.sup.2d) was used. The samples
(wavelength converting members) used in the experiments had the
following structures.
<Sample 9>
[0172] A wavelength converting member constituted by only a quantum
dot layer without barrier layers.
<Sample 10>
[0173] The wavelength converting member shown in FIG. 8. Note that
the wrap starting end and the wrap finishing end of the barrier
layer were thermocompression bonded in an overlapping manner on the
top surface of the quantum dot layer.
<Sample 11>
[0174] The wavelength converting member shown in FIG. 10. Note that
the wrap starting end and the wrap finishing end of the barrier
layer were thermocompression bonded in an overlapping manner at
edges on the sides of the quantum dot layer.
[0175] The above samples were subjected to an endurance test under
conditions of temperature: 60.degree. C. and humidity: 90%. The
light emission intensity was measured using a total luminous flux
measurement system available from Otsuka Electronics Co., Ltd. by
measuring the total luminous flux of the light caused in each
sample by blue (wavelength: 450 nm) LED excitation light. First,
the experimental results for Sample 9 to Sample 11 using the low
concentration quantum dot layers are described.
[0176] FIG. 31 is a graph showing the relationship the elapsed time
and the blue light intensity (450 nm area) for Sample 9 to Sample
11. Here, the blue light intensity corresponds to the area of the
emission peak observed at a wavelength of 450 nm.
[0177] As shown in FIG. 31, the blue light intensity (450 nm area)
was found to gradually increase over time in Sample 9. In other
words, the intensity of blue light was found to increase over time
in Sample 9. On the other hand, it was found that the blue light
intensity (450 nm area) stayed constant in Sample 10 and Sample 11,
and the light intensity of blue light was kept unchanged over time.
Further, the initial blue light intensity (time: 0 h) and the blue
light intensity after 450 hours were 0.0049 (time: 0 h) and 0.0056
(450 h), respectively in Sample 10 and were 0.0053 (time: 0 h) and
0.0053 (450 h), respectively in Sample 11. It was found for Sample
10 and Sample 11 that the blue light intensity after 450 hours
hardly changed from the initial blue light intensity (time: 0 h),
and the change in the blue light intensity was within 15%. Here,
the change in the blue light intensity is represented by [(initial
blue light intensity-blue light intensity after 450 hours)/initial
blue light intensity].times.100(%)(absolute value).
[0178] FIG. 32 is a graph showing the relationship the elapsed time
and the green light intensity (green area) for Sample 9 to Sample
11. Here, the green light intensity corresponds to the area of the
emission peak observed at a wavelength of 520 nm. As shown in FIG.
32, in Sample 9, the green light intensity (green area) was found
to rapidly decrease in 100 hours from the start of the experiment.
The increased blue light intensity and the reduced green light
intensity as in Sample 9 mean that the green quantum dots
deteriorated over time. On the other hand, it was found that the
blue light intensity (450 nm area) did not change over time in
Sample 10 and Sample 11, and the reduction in the green light
intensity (green area) over time was made smaller compared with
Sample 9. Further, the initial green light intensity (time: 0 h)
and the green light intensity after 450 hours were 0.0017 (time: 0
h) and 0.0016 (450 h), respectively in Sample 10 and were 0.0022
(time: 0 h) and 0.0023 (450 h), respectively in Sample 11. Further,
it was found for Sample 10 and Sample 11 that the change from the
initial green light intensity (time: 0 h) to the green light
intensity after 450 hours was smaller compared with Sample 9, and
the change in the green light intensity was within 10%. Here, the
change in the green light intensity is represented by [(initial
green light intensity-green light intensity after 450
hours)/initial green light intensity].times.100(%)(absolute
value).
[0179] FIG. 33 is a graph showing the relationship the elapsed time
and the red light intensity (red area) for Sample 9 to Sample 11.
Here, the red light intensity corresponds to the area of the
emission peak observed at a wavelength of 650 nm. As shown in FIG.
33, in Sample 9, the red light intensity (red area) was found to
rapidly decrease in 50 hours from the start of the experiment. The
increased blue light intensity and the reduced red light intensity
as in Sample 9 mean that the red quantum dots deteriorated over
time. On the other hand, it was found that the blue light intensity
(450 nm area) did not change over time in Sample 10 and Sample 11,
and the reduction in the red light intensity (red area) over time
was successfully made smaller compared with Sample 9. Further, the
initial red light intensity (time: 0 h) and the red light intensity
after 450 hours were 0.0017 (time: 0 h) and 0.0014 (450 h),
respectively in Sample 10 and were 0.0022 (time: 0 h) and 0.0018
(450 h), respectively in Sample 11. It was found for Sample 10 and
Sample 11 that the change from the initial red light intensity
(time: 0 h) to the red light intensity after 450 hours was smaller
compared with Sample 9, and the change in the red light intensity
was within 25%. Here, the change in the red light intensity is
represented by [(initial red light intensity-red light intensity
after 450 hours)/initial red light intensity].times.100(%)(absolute
value).
[0180] The experimental results presented in FIG. 31 to FIG. 33
show that deterioration of quantum dots can be suitably suppressed
by covering the entire periphery of the quantum dot layer with the
barrier layer, thereby effectively inhibiting the change in the
light emission intensity over time.
[0181] Subsequently, the barrier films were evaluated. FIG. 34 is a
graph showing the relationship the elapsed time and the
x-coordinate of the CIE color space chromaticity diagram for Sample
9 to Sample 11.
[0182] As shown in FIG. 34, the x-coordinate did not change
substantially over time in any of the samples. In Sample 10, the
initial x-coordinate (time: 0 h) and the x-coordinate after 450
hours were 0.2013 (time: 0 h) and 0.1892 (450 h), respectively;
thus, the change in the x-coordinate was found to be within 10%. In
Sample 11, the initial x-coordinate (time: 0 h) and the
x-coordinate after 450 hours were 0.2080 (time: 0 h) and 0.1998
(450 h), respectively; thus, the change in the x-coordinate was
found to be within 5%. Here, the x-coordinate change is represented
by [(initial x-coordinate-x-coordinate after 450 hours)/initial
x-coordinate].times.100(%)(absolute value).
[0183] FIG. 35 is a graph showing the relationship the elapsed time
and the y-coordinate of the CIE color space chromaticity diagram
for Sample 9 to Sample 11. As shown in FIG. 35, the y-coordinate of
Sample 9 that was not provided with barrier layers significantly
changed over time as compared with Sample 9 and Sample 10 in which
the entire periphery of the quantum dot layer was surrounded by the
barrier layer. In Sample 10, the initial y-coordinate (time: 0 h)
and the y-coordinate after 450 hours were 0.1428 (time: 0 h) and
0.1210 (450 h), respectively; thus, the change in the y-coordinate
was found to be within 20%. In Sample 11, the initial y-coordinate
(time: 0 h) and the y-coordinate after 450 hours were 0.1626 (time:
0 h) and 0.1635 (450 h), respectively; thus, the change in the
y-coordinate was found to be within 1%. Here, the y-coordinate
change is represented by [(initial y-coordinate-y-coordinate after
450 hours)/initial y-coordinate].times.100(%)(absolute value).
[0184] When Sample 10 and Sample 11 were compared, better results
were obtained overall with Sample 11 than with Sample 10. This is
probably because in Sample 11, the wrap starting end and the wrap
finishing end of the barrier layer were thermocompression bonded at
the edges of the quantum dot layer unlike in Sample 10, so that
thermal effects on the quantum dot layer were reduced as compared
with the structure of Sample 10.
[0185] Next, experimental results for Sample 12 to Sample 14 using
the high concentration quantum dot layers are described.
<Sample 12>
[0186] A wavelength converting member constituted by only a quantum
dot layer without barrier layers.
<Sample 13>
[0187] The wavelength converting member shown in FIG. 8. Note that
the wrap starting end and the wrap finishing end of the barrier
layer were thermocompression bonded in an overlapping manner on the
top surface of the quantum dot layer.
<Sample 14>
[0188] The wavelength converting member shown in FIG. 10. Note that
the wrap starting end and the wrap finishing end of the barrier
layer were thermocompression bonded in an overlapping manner at
edges on the sides of the quantum dot layer.
[0189] The above samples were subjected to an endurance test under
conditions of temperature: 60.degree. C. and humidity: 90%. The
light emission intensity was measured using a total luminous flux
measurement system available from Otsuka Electronics Co., Ltd. by
measuring the total luminous flux of the light caused in each
sample by blue (wavelength: 450 nm) LED excitation light.
[0190] FIG. 36 is a graph of the measurements of the relationship
the elapsed time and the blue light intensity (450 nm area) for
Sample 12 to Sample 14.
[0191] As shown in FIG. 36, the intensity of blue light was found
to increase over time in Sample 12. On the other hand, it was found
that the blue light intensity (450 nm area) stayed constant in
Sample 13 and Sample 14, and the light intensity of blue light was
kept unchanged over time. Further, the initial blue light intensity
(time: 0 h) and the blue light intensity after 189 hours were
0.0010 (time: 0 h) and 0.0013 (189 h), respectively in Sample 13
and were 0.0010 (time: 0 h) and 0.0009 (189 h), respectively in
Sample 14. It was found for Sample 13 and Sample 14 that the blue
light intensity after 189 hours hardly changed from the initial
blue light intensity (time: 0 h), or the change in the blue light
intensity was smaller than that in Sample 12, and the change in the
blue light intensity was within 30%. Here, the change in the blue
light intensity is represented by [(initial blue light
intensity-blue light intensity after 189 hours)/initial blue light
intensity].times.100(%)(absolute value).
[0192] FIG. 37 is a graph showing the relationship the elapsed time
and the green light intensity (green area) for Sample 12 to Sample
14. Here, the green light intensity corresponds to the area of the
emission peak observed at a wavelength of 520 nm. As shown in FIG.
36 and FIG. 37, it was found that changes in the blue light
intensity (450 nm area) and the green light intensity (green area)
over time in Sample 13 and Sample 14 were successfully made smaller
compared with Sample 12. Further, the initial green light intensity
(time: 0 h) and the green light intensity after 189 hours were
0.0017 (time: 0 h) and 0.0019 (189 h), respectively in Sample 13
and were 0.0015 (time: 0 h) and 0.0018 (189 h), respectively in
Sample 14. It was found for Sample 13 and Sample 14 that the change
from the initial green light intensity (time: 0 h) to the green
light intensity after 189 hours was within 20%. Here, the change in
the green light intensity is represented by [(initial green light
intensity-green light intensity after 189 hours)/initial green
light intensity].times.100(%)(absolute value).
[0193] FIG. 38 is a graph showing the relationship the elapsed time
and the red light intensity (red area) for Sample 12 to Sample 14.
Here, the red light intensity corresponds to the area of the
emission peak observed at a wavelength of 650 nm. As shown in FIG.
36 and FIG. 38, it was found that changes in the blue light
intensity (450 nm area) and the red light intensity (red area) over
time were successfully made smaller in Sample 13 and Sample 14
compared with Sample 12. Further, the initial red light intensity
(time: 0 h) and the red light intensity after 189 hours were 0.0038
(time: 0 h) and 0.0039 (189 h), respectively in Sample 13 and were
0.0037 (time: 0 h) and 0.0040 (189 h), respectively in Sample 14.
It was found for Sample 13 and Sample 14 that the change from the
initial red light intensity (time: 0 h) to the red light intensity
after 189 hours was within 10%. Here, the change in the red light
intensity is represented by [(initial red light intensity-red light
intensity after 189 hours)/initial red light
intensity].times.100(%)(absolute value).
[0194] The experimental results presented in FIG. 36 to FIG. 38
show that deterioration of the quantum dots can be suitably
suppressed by covering the entire periphery of the quantum dot
layer with the barrier layer, thereby effectively inhibiting the
change in the light emission intensity over time.
[0195] Subsequently, the barrier films were evaluated. FIG. 39 is a
graph showing the relationship the elapsed time and the
x-coordinate of the CIE color space chromaticity diagram for Sample
12 to Sample 14. In Sample 13, the initial x-coordinate (time: 0 h)
and the x-coordinate after 189 hours were 0.3729 (time: 0 h) and
0.3524 (189 h), respectively; thus, the change in the x-coordinate
was found to be within 10%. In Sample 14, the initial x-coordinate
(time: 0 h) and the x-coordinate after 189 hours were 0.3748 (time:
0 h) and 0.3811 (189 h), respectively; thus, the change in the
x-coordinate was found to be within 5%. Here, the x-coordinate
change is represented by [(initial x-coordinate-x-coordinate after
189 hours)/initial x-coordinate].times.100(%)(absolute value). FIG.
40 is a graph showing the relationship the elapsed time and the
y-coordinate of the CIE color space chromaticity diagram for Sample
12 to Sample 14. In Sample 13, the initial y-coordinate (time: 0 h)
and the y-coordinate after 189 hours were 0.3441 (time: 0 h) and
0.3301 (189 h), respectively; thus, the change in the y-coordinate
was found to be within 5%. In Sample 14, the initial y-coordinate
(time: 0 h) and the y-coordinate after 189 hours were 0.3347 (time:
0 h) and 0.3580 (189 h), respectively; thus, the change in the
y-coordinate was found to be within 5%. Here, the y-coordinate
change is represented by [(initial y-coordinate-y-coordinate after
189 hours)/initial y-coordinate].times.100(%)(absolute value). As
shown in FIG. 39 and FIG. 40, changes in the x-coordinate and the
y-coordinate over time were smaller in Sample 13 and Sample 14 in
which the entire periphery of the quantum dot layer was surrounded
by the barrier layer compared with Sample 12 that was not provided
with barrier layers.
[0196] When Sample 13 and Sample 14 were compared, better results
were obtained overall with Sample 13 than with Sample 14. This is
probably because in Sample 14, the wrap starting end and the wrap
finishing end of the barrier layer were thermocompression bonded at
the edges on the sides of the quantum dot layer unlike in Sample
13, so that thermal effects on the quantum dot layer were reduced
as compared with the structure of Sample 13.
[0197] FIG. 41 to FIG. 43 show the light emission spectrum of light
output when blue light of 450 nm was applied to Sample 9 to Sample
11. The horizontal axis represents the wavelength, and the vertical
axis represents the light intensity. Each diagram shows the spectra
after 0 hours (immediately after the start of the experiment) and
after 450 hours. As shown in FIG. 41, in Sample 9, significant
change in the spectrum was observed in 450 hours from 0 hours. On
the other hand, as shown in FIG. 42 and FIG. 43, in Sample 10 and
Sample 11, change in the spectrum in 450 hours from 0 hours was
smaller compared with Sample 9. It was found for Sample 10 and
Sample 11 that since the barrier layer covered the periphery of the
quantum dot layer, deterioration of quantum dots was suitably
suppressed; thus, change in the light emission intensity over time
was effectively inhibited.
[0198] FIG. 44 to FIG. 46 show the light emission spectrum of light
output when blue light of 450 nm was applied to Sample 12 to Sample
14. The horizontal axis represents the wavelength, and the vertical
axis represents the light intensity. Each diagram shows the spectra
after 0 hours (immediately after the start of the experiment) and
after 189 hours. As shown in FIG. 44, in Sample 12, significant
change in the spectra was observed in 189 hours from 0 hours. On
the other hand, as shown in FIG. 45 and FIG. 46, the change in the
spectrum in 189 hours from 0 hours was found to be smaller in in
Sample 13 and Sample 14 compared with Sample 12. It was found for
Sample 13 and Sample 14 that since the barrier layer covered the
periphery of the quantum dot layer, deterioration of quantum dots
was suitably suppressed; thus, change in the light emission
intensity over time was effectively suppressed.
INDUSTRIAL APPLICABILITY
[0199] The present invention can provide a wavelength converting
member which makes it possible to effectively inhibit change in the
light emission intensity over time; and a back light unit, a light
guide member, a display device, and the like that have stable
wavelength conversion characteristics can be obtained using the
wavelength converting member of the present invention.
[0200] This application is based on Japanese patent application No.
2014-263785 filed on Dec. 26, 2014, the content of which is hereby
incorporated in its entirety.
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