AU2016238924B2

AU2016238924B2 - Light-emitting device, integrated light-emitting device, and light-emitting module

Info

Publication number: AU2016238924B2
Application number: AU2016238924A
Authority: AU
Inventors: Motokazu Yamada; Yuichi Yamada
Original assignee: Nichia Corp
Current assignee: Nichia Corp
Priority date: 2015-10-08
Filing date: 2016-10-07
Publication date: 2021-06-10
Anticipated expiration: 2036-10-07
Also published as: AU2016238924A1; RU2018112372A3; BR112018006931B1; TWI799754B; RU2018112372A; BR112018006931A2; KR20170044032A; TW201724554A; CN106571421B; JP2021170688A; CN106571421A; JP7175099B2; TWI712181B; JP7252483B2; TW202112181A; RU2717381C2; CA2999401A1; JP2018139303A; JP2017073549A; KR102632427B1

Abstract

A light-emitting device includes a base including a conductive wiring; a light-emitting element mounted on the base and configured to emit light; a light reflective film provided on an upper surface of the light-emitting element; and a encapsulant covering the light-emitting element and the light reflective film. A ratio (H/W) of a height (H) of the encapsulant to a width (W) of a bottom surface of the encapsulant is less than 0.5. Fig.1 100 102 - - - --108 - - r 101 105 1 4H 103 W Fig.2 100 - 80 S60 Co E 40 20 0 -90 -60 -30 0 30 60 90 Incident angle (deg.)

Description

Fig.1 100 102 -- - - - 108 - - r

101 105 1 4H

103 W

Fig.2 100

- 80

S60

Co E 40

20

0 -90 -60 -30 0 30 60 90 Incident angle (deg.)

LIGHT-EMITTING DEVICE, INTEGRATED LIGHT-EMITTING DEVICE, AND LIGHT-EMITTING MODULE CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to Japanese

Patent Application No. 2015-200445, filed on October 8, 2015,

and Japanese Patent Application No. 2016-197968, filed on

October 6, 2016, the disclosures of which are hereby

incorporated by reference in their entirety.

BACKGROUND

[0002] The present disclosure relates to light-emitting

devices, integrated light-emitting devices, and

light-emitting modules.

[0003] In recent years, various electronic components

have been proposed and put into practical use, and they are

required to exhibit higher performance. In particular, some

electronic components need to maintain their performance for

a long period of time under a harsh usage environment. Such

requirements can apply to light-emitting devices using

semiconductor light-emitting elements, including a

light-emitting diode (i.e., LED). That is, in the fields of

general illumination and interior and exterior lighting for

vehicles, the light-emitting devices have been increasingly

required day by day to demonstrate higher performance, specifically, higher output (i.e., higher luminance) and higher reliability. Furthermore, the light-emitting devices are requested to be supplied at low costs while maintaining high performance.

Backlights used in liquid crystal televisions, general

lighting devices, and the like are developed by focusing on

their designs, which leads to a high demand for thinning.

[0004] For example, Japanese Unexamined Patent

Application Publication No. 2008-4948 discloses a

light-emitting device in which a reflector is provided on the

upper surface of a light-emitting element mounted on a submount

in a flip-chip manner to thereby achieve thinning of the

backlight.[

[0005] Japanese Unexamined Patent Application

PublicationNo.2008-4948 canachieve the light-emittingdevice

with wide light distribution. However, with further thinning

of the backlight, a light-emitting device capable of achieving

much wider light distribution has been required.

SUMMARY

[0006] Embodiments of the present disclosure have been

made in view of the foregoing circumstances, and it is an object

of the embodiments of the present disclosure to provide a

light-emitting device that enables wide light distribution

without using a secondary lens.

[0007] A light-emitting device according to an embodiment

includes: a base including a conductive wiring; a

light-emitting element mounted on the base and adapted to emit

light; a light reflective film provided on an upper surface of

the light-emitting element; and a encapsulant covering the

light-emitting element and the light reflective film, in which

a ratio (H/W) of a height (H) of the encapsulant to a width (W)

a bottom surface of of the encapsulant is less than 0.5.

[0008] Accordingly, the embodiment of the present

disclosure enables the wide light distribution without using

a secondary lens.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]

Fig. 1 is a cross-sectional view showing an example of

a light-emitting device according to a first embodiment.

Fig. 2 is a diagram showing incident-angle dependence of

a light transmissivity of a light reflective film in the

embodiment.

Fig. 3 is a diagram showing a relationship between a

wavelength range of a light reflective film and an emission

wavelength of a light-emitting element in the light-emitting

device of the embodiment.

Fig. 4 is a light distribution characteristic diagram of

the light-emitting device in the embodiment.

Fig. 5 is a light distribution characteristic diagram of

a light-emitting device using a secondary lens in Comparative

Example.

Fig. 6 shows Experimental Examples according to the

embodiment.

Fig. 7 is a cross-sectional view showing an example of

a light-emitting module in a second embodiment.

Figs. 8A and 8B show an example of a light reflective

plate.

Figs. 9A and 9B show luminance distribution

characteristics ofa light-emittingmodule according to Example

2.

DETAILED DESCRIPTION

[0010] Embodiments of the present disclosure will be

described below with reference to the accompanying drawings as

appropriate. A light-emitting device to be described below is

to embody the technical idea of the present disclosure and is

not intended to limit the present invention unless otherwise

specified. The contents of the description regarding one

embodiment or example can also be applied to other embodiments

and examples.

Furthermore, in the description below, the same names or

reference characters denote the same or similar members, and

thus a detailed description thereof will be omitted as appropriate. Moreover, regardingeachelement configuring the present invention, a plurality of elements may be formed by the same member, thereby allowing this one member to function as these elements. Conversely, the function of one member can be shared and achieved by a plurality of members.

[0011]

[First Embodiment]

Fig. 1 is a schematic configuration diagram showing one

example of a light-emitting device according to a first

embodiment.

As shownin Fig.1, in this embodiment, the light-emitting

device includes a base 101 with conductive wirings 102, and a

light-emitting element 105 mounted on the base 101. The

light-emitting element 105 is mounted in a flip-chip manner via

bonding members 103 to straddle at least a region between a pair

of conductive wirings 102 provided at the surface of the base

101. Alight reflective film106 is formedona light extraction

surface side of the light-emitting element 105 (i.e., upper

surface of the light-emitting element 105). At least a part

of each conductive wiring may be provided with an insulating

member 104. A region of the upper surface of the conductive

wiring102 electrically connected to the light-emittingelement

105 is exposed from the insulating member 104.

[0012] The light transmissivity of the light reflective

film 106 is dependent on an angle of incidence of the light incident from the light-emitting element 105. Fig. 2 is a diagram showing incident-angle dependence of the light transmissivity of the light reflective film 106 in this embodiment. The light reflective film 106 hardly allows the light to pass therethrough in the direction perpendicular to the upper surface of the light-emitting element 105, but increases the amount of the light transmitted as the angle of incidence increases relative to the perpendicular direction.

Specifically, when the incident angle is in a range of -300 to

300, the light transmissivity is approximately 10%. When the

incident angle becomes smaller than -30°, the light

transmissivity gradually becomes larger. Further, when the

incident angle becomes smaller than -50°, the light

transmissivity increases drastically. Likewise, when the

incident angle becomes larger than 300, the light

transmissivity gradually becomes larger. Further, when the

incident angle becomes larger than 500, the light

transmissivity increases drastically. That is, the light

transmissivity of the light reflective film for said light

increases as an absolute value of an incident angle increases.

The formation of such a reflective film can achieve the batwing

light distribution characteristics shown in Fig. 4.

The term "batwing light distribution characteristics" as

used herein means the light distribution characteristics

exhibiting a first peak in a first region with a light distribution angle of less than 900, the first peak having a higher intensity than that at the light distribution angle of

900, as well as a second peak in a second region with a light

distribution angle of more than 90, the second peak having a

higher intensity than that at the light distribution angle of

900.

[0013] The light-emitting element 105 is covered with a

light transmissive encapsulant 108. The encapsulant 108 is

disposed on the base to cover the light-emitting element 105

in order to protect the light-emitting element 105 from an

external environment and to optically control the light output

from the light-emittingelement. The encapsulant108 is formed

substantially in the dome shape. The encapsulant 108 covers

the light-emitting element 105 with the light reflective film

106 disposed thereto, the surfaces of the conductive wirings

102 located around the light-emitting element 105, and

connection portions between the light-emitting element 105

including the bonding members 103 and the conductive wirings

102. That is, the upper surface and lateral surfaces of the

light reflective film 106 are in contact with the encapsulant

108, and the lateral surfaces of the light-emitting element 105

not covered with the light reflective film 106 are also in

contact with the encapsulant 108. The connection portions may

be covered with an underfill, not with the encapsulant 108. In

this case, the encapsulant 108 is formed to cover the upper surface of the underfill and the light-emitting element. In this embodiment, the light-emitting element 105 is directly covered with the encapsulant 108.

[0014] The encapsulant 108 is preferably formed to have

a circular or ellipsoidal outer shape in the top view, with the

ratio of a height (H) of the encapsulant in an optical-axis

direction to a diameter (width: W) of the encapsulant in the

top view set to a value less than 0.5. For the encapsulant 108

having the ellipsoidal shape, there are a major axis and a minor

axis that can be considered as the length of the width, but the

minor axis is defined as a diameter (W) of the encapsulant 108

in the present specification. The upper surface of the

encapsulant 108 is formed in a convex curved shape.

With this arrangement, the light emitted from the

light-emitting element 105 is refracted at an interface between

the encapsulant 108 and air, which can achieve the wider light

distribution.

Here, the height (H) of the encapsulant indicates the

height from a mounting surface for the light-emitting element

105 as shown in Fig. 1. The width (W) of the encapsulant

indicates its diameter when the encapsulant has a circular

bottom surface as mentioned above, or alternatively indicates

the length of the shortest part thereof when the encapsulant

has any shape other than the circle.

[0015] Fig. 4 shows an example of changes in the light distribution characteristics depending on the presence or absence of the encapsulant 108. In Fig. 4, the solid line shows the light distribution characteristic of a light-emitting device 100 in the first embodiment. On the other hand, the dotted line shows the light distribution characteristic of a light-emitting device fabricated in the same way as in the first embodiment except that the encapsulant 108 is not formed.

As can be seen from Fig. 4 according to the light-emitting

device in the first embodiment, the first peak moves in the

direction that decreases the light distribution angle as well

as the second peak moving in the direction that increases the

light distribution angle, as compared with a light-emitting

device without the encapsulant 108. Therefore, the

light-emitting device in the first embodiment can achieve the

wider light distribution.

[0016] The use of both the light reflective film 106 and

the encapsulant 108 in this way can achieve the desired light

distribution characteristics without using the secondary lens.

That is, the formation of the light reflective film 106 can

reduce the luminance directly above the light-emitting element

105, while the encapsulant 108 can concentrate on widening the

distribution of the light from the light-emitting element 105,

which enables significant downsizing of the encapsulant with

a lens function.

In other words, conventionally, reduction in luminance directly above the light-emitting element while widening the light distribution is possible only by adjusting a height of the encapsulant, as a result, the height of the encapsulant must be increased In contrast, the light-emitting device in this embodiment includes the light reflective film 106 having reducedluminance directlyabove the light-emittingelement105, thereby achieving the batwing light distribution characteristics. Thereby, the encapsulant 108 can be configured to focus on the function of widening the light distribution. Thus, this embodiment can achieve downsizing of the light-emitting device.

This arrangement can achieve a thinned backlight module

(i. e. , light-emitting module) with which non-uniform luminance

is reduced, as will be mentioned later. Fig. 5 shows the light

distribution characteristics obtained by using the secondary

lensas acomparativeexample. Evenwithoutusingany secondary

lens, the light-emitting device in this embodiment can achieve

substantially the same light distribution characteristics as

when using a secondary lens.

[0017] Nine light-emittingdevices withdifferentheights

(H) in the optical axis direction of the encapsulants 108 and

different diameters (widths: W) of the encapsulants in the top

view were fabricated. The results of their light distribution

characteristics are shown in Figs. 6A-6I. The light-emitting

element used therein was a blue LED having a substantially square shape with one side of 600 pm in length in the planar view and a thickness of 150 pm. The light reflective film 106 formed on the main surface of the light-emitting element 105 is configuredofelevenlayersby repeatedly formingaSiO 2 layer

(82 nm in thickness) and a ZrO 2 layer (54 nm in thickness).

Regarding each of the nine light-emitting devices No. 1

to No. 9, the ratio of the height (H) of the encapsulant to the

diameter (width: W) of the encapsulant is shown in Table 1.

[Table 1]

No.1 No.2 No.3 No.4 No.5 No.6 No.7 No.8 No.9

H(mm) 0.70 0.89 0.92 0.79 0.93 1.09 0.74 1.00 1.18

W(mm) 2.76 2.78 2.56 3.06 3.14 3.11 3.40 3.28 3.29

H/W 0.25 0.32 0.36 0.26 0.30 0.35 0.22 0.30 0.36

Result Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig.

6A 6B 6C 6D 6E 6F 6G 6H 61

As can be seen from the experimental results, the light

distribution characteristics did not change so much due to the

difference in the diameter of the encapsulant. However, the

ratio of the height (H) of the encapsulant to the diameter

(width: W) of the encapsulant affected the light distribution

characteristics.

The graphs of Figs. 6A-6I show that the ratio (H/W) of

the height (H) to the width (W) of the encapsulant is preferably

0.3 or less in order to achieve a wider light distribution.

[0018] Preferred examples of the light-emitting device

100 in this embodiment will be described below.

(Base 101)

The base 101 is a member for mounting the light-emitting

element 105. The base 101 has the conductive wirings 102 on

its surface to supply electric power to the light-emitting

element 105.

Examples of a material for the base 101 can include

ceramics, and resins such as a phenol resin, an epoxy resin,

a polyimide resin, a BT resin, polyphthalamide (PPA), and

polyethylene terephthalate (PET). Among them, the resin is

preferably selected as the material in terms of low cost and

formability. The thickness of the base can be selected as

appropriate. The base may be either a rigid base or a flexible

base manufacturable by a roll-to-roll system. The rigid base

may be a thinned rigid base that is bendable.

[0019] To obtain the light-emitting device with high

resistance to heat and light, ceramics are preferably selected

as the material for the base 101. Examples of ceramics can

include alumina, mullite, forsterite, glass-ceramics,

nitride-based (e.g., AlN) ceramics, and carbide-based (e.g.,

SiC) ceramics. Among them, ceramics made of alumina or mainly

containing alumina are preferable.

[0020] In the use of a resin as the material for the base

101, an inorganic filler such as glass fiber, SiO 2 , TiO 2 , or

A1 2 0 3 , is mixed into the resin, thereby allowing the base to

have improved mechanical strength and improved optical

reflectance, reduced thermalexpansion rate, and the like. The

base 101 may be any other member as long as it can separate and

insulate a pair of conductive wirings 102 from each other. The

base 101may employ a so-called metalbase that includes a metal

member with an insulating layer formed therein.

[0021]

(Conductive Wiring 102)

The conductive wirings 102 are members electrically

connected to electrodes of the light-emitting element 105 and

adapted to supply current (electric power) from the outside to

the light-emitting element. That is, the conductive wiring

serves as an electrode or a part thereof for energization with

the power from the outside. Normally, the conductive wirings

are formed of at least two wirings, namely, positive and

negative wirings spaced apart from each other.

[0022] Each conductive wiring 102 is formed over at least

an upper surface of the base that serves as a mounting surface

for the light-emitting element 105. Material for the

conductive wiring 102 can be selected as appropriate, depending

on material used for the base 101, a manufacturing method

thereof, and the like. For example, when ceramic is used as

the material for the base 101, the conductive wirings 102 are

preferably made of material having a high melting point that can withstand the sintering temperature of a ceramic sheet.

Specifically, metal with a high melting point, such as tungsten

or molybdenum, is preferably used as the material for the

conductive wiring. Further, other metal materials, such as

nickel, gold, or silver may be formed to cover the

above-mentioned surface of the conductive wiring by plating,

sputtering, vapor deposition, etc.

[0023] When the glass epoxy resin is used as the material

for the base 101, the material for the conductive wiring 102

is preferably made of material that is easy to process. In the

case of using the epoxy resin injection-molded, the conductive

wiring 102 is made of material that can be easily processed by

punching, etching, bending, etc., and has a relatively high

mechanical strength. Specifically, examples of the conductive

wiring can include metals, such as copper, aluminum, gold,

silver, tungsten, iron, and nickel, and a metal layer or lead

frame made of an iron-nickel alloy, phosphor bronze, an

iron-copper alloy, molybdenum, and the like. The surface of

the lead frame may be coated with a metal material other than

that of a lead frame main body. Such metal materials can be

appropriately selected, for example, silver alone, or an alloy

ofsilver and copper, gold, aluminumor rhodium. Alternatively,

the conductive wiring can be formed of multiple layers using

silver or eachalloy. Suitable methods for coatingwithametal

materialcaninclude sputtering, vapor deposition, and the like as well as the plating.

[0024]

(Bonding member 103)

The bonding members 103 are members for fixing the

light-emitting element 105 onto the base 101 or conductive

wirings102. In the flip-chipmounting, conductive members are

used as the bonding members in the same manner as in this

embodiment. Specifically, suitable materials for the bonding

member can include an Au-containing alloy, an Ag-containing

alloy, a Pd-containing alloy, an In-containing alloy, a Pb-Pd

containing alloy, an Au-Ga containing alloy, an Au-Sn

containing alloy, an Sn-containing alloy, an Sn-Cu containing

alloy, anSn-Cu-Ag containing alloy, anAu-Ge containing alloy,

an Au-Si containing alloy, an Al-containing alloy, a Cu-In

containing alloy, and a mixture of metal and a flux.

[0025] Suitable forms of the bondingmember103 caninclude

a liquid-type, a paste-type, and/or a solid-type (e.g.,

sheet-shaped, block-shaped, wire-shaped and/or powder-form).

The form of the bonding member can be selected based on the

composition thereof, the shape of the base, and the like, as

appropriate. These bonding members 103 may be formed of a

single member or a combination of several kinds of members.

[0026]

(Insulating Member 104)

The conductive wirings 102 are preferably covered with the insulatingmember104 except forparts thereofelectrically connected to the light-emitting element 105 and other materials.

That is, as shown in the respective figures, a resist for

insulating and covering the conductive wirings 102 may be

disposed over the base. The insulating member 104 can function

as such a resist.

[0027] In the case of disposing the insulating member 104,

a white-based filler can be contained in the insulating member.

The white-based filler contained in the insulating member can

reduce leakage and absorption of light, thereby enabling

improvement of the light extraction efficiency of the

light-emitting device 100 as well as insulating the conductive

wirings 102.

Material for the insulating member 104 can be

appropriately selected on the basis that the material is less

likely to absorb the light from the light-emitting-element and

have an insulating property. Examples of the material for the

insulating member can include epoxy, silicone, modified

silicone, urethane, oxetane, acrylic, polycarbonate, and

polyimide resins.

[0028]

(Light-Emitting Element 105)

The light-emitting element 105 mounted on the base can

be one known in the art. In this embodiment, a light-emitting

diode is preferably used as the light-emitting element 105.

A light-emitting element 105 that emits light at an

appropriate wavelength can be selected. For example, a blue

or green light-emitting element can utilize ZnSe, a

nitride-based semiconductor (InxAlyGai_x_yN, 0 X, 0 Y, X

+ Y 1), or GaP. A light transmissive sapphire substrate and

the like canbeusedas agrowthsubstrate. Aredlight-emitting

element can use GaAlAs, AlInGaP, etc. Moreover, semiconductor

light-emitting elements made of any material other than the

materials mentioned above can also be used. The composition,

emission color, and size of the light-emitting element for use,

and the number of light-emitting elements for use, and the like

can be selected as appropriate in accordance with the purpose.

[0029] Various emission wavelengths can be selected

dependingon the materialof the semiconductor layer andamixed

crystal ratio thereof. The light-emitting element may have

positive and negative electrodes on the same surface side to

enable the flip-chip mounting, or may alternatively have

positive and negative electrodes on its different surfaces.

[0030] The light-emitting element 105 in this embodiment

has a light transmissive substrate, and a semiconductor layer

stacked on the substrate. The semiconductor layer includes an

n-type semiconductor layer, an active layer, and a p-type

semiconductor layer formed in this order. An n-type electrode

is formed on the n-type semiconductor layer, and a p-type

electrode is formed on a p-type semiconductor layer.

[0031] As shown in Fig. 1, the light-emitting element 105

is mounted in a flip-chip manner on the conductive wirings 102

disposed on the surface of the base 101 via the bonding members

103. A surface of the light-emitting element 105 opposed to

the surface thereof with the electrodes formed thereon, that

is, a main surface of the light transmissive substrate would

serve as a light extraction surface. However, in this

embodiment, the light reflective film106 is formed on the light

extraction surface, and thus the lateral surface of the

light-emitting element 105 practically serves as the light

extraction surface. That is, part of the light emitted from

the light-emitting element 105 and directed toward the main

surface of the light-emitting element 105 is returned to the

light-emitting element 105 by the light reflective film 106,

thenrepeatedly reflectedinside the light-emittingelement105,

and eventually output from the lateral surfaces of the

light-emitting element 105. Therefore, the light distribution

characteristics of the light-emitting device 100 (see the

dotted line in Fig. 4) exhibit the characteristics of a

combination of the light passing through the light reflective

film 106 and the light emitted from the lateral surfaces of the

light-emitting element 105.

[0032] The light-emitting element 105 is disposed to

straddle the region between the two conductive wirings 102 that

are isolated and insulated on positive and negative sides. The light-emitting element 105 is electrically connected and mechanically fixed to the conductive wirings via the conductive bonding members 103. To mount the light-emitting element 105, a method using bumps can be employed as well as a method using solder paste. As a light-emitting element 105, a small-sized package product which includes the light-emitting element encapsulated with a resin or the like can also be used. The shape or structure of the light-emitting element 15 can be appropriately selected.

[0033] As will be described below, in the case of the

light-emitting device including a wavelength conversionmember,

the light-emitting element suitably uses a nitride

semiconductor (InxAlyGai_x_yN, 0 X, 0 Y, X + Y 1) capable

of emitting light with a short wavelength that can efficiently

excite a wavelength conversion layer.

[0034] Although an embodiment using flip-chip mounting

has been described as an example, certain embodiments of the

present invention may employ a mounting state in which an

insulating base side of a light-emitting element serves as the

mounting surface, and electrodes formed on the upper surface

of the light-emitting element are connected to wires. In this

case, the upper surface of the light-emitting element is an

electrode-formed surface side, and the light reflective film

is positioned on the electrode-formed surface side.

[0035]

(Light Reflective Film 106)

The light reflective film 106 is formed on the light

extraction surface side, which is the main surface of the

light-emitting element 105.

Material for the light reflective film may be one which

reflects at least the light emitted from the light-emitting

element 105, for example, metal or resin containing a white

filler.

A dielectric multilayer film can be used to produce the

reflective film with less light absorption. Additionally, the

reflectance of the light reflective film can be suitably

adjusted by designing the dielectric multilayer film, or its

reflectance can also be controlled by adjusting the angle of

the light. In particular, the reflectance is increased in the

direction perpendicular to the light extraction surface (also

called the optical axis direction), and decreased at a large

angle relative to the optical axis due to increase of the light

transmissivity of the reflective film, which can control the

shape of the batwing light distribution.

[0036] Regarding a reflection wavelength range in the

optical axis direction of the dielectric multilayer film, i.e.

in the direction perpendicular to the upper surface of the

light-emitting element, as shown in Fig. 3, it is preferable

to widen a region on a long wavelength side of the reflection

wavelength range, with respect to the emission peak wavelength of the light-emitting element 105.

This is because as the angle from the optical axis is

varied, in other words, as the angle from the optical axis of

the incident light is increased, the reflection wavelength

range of the dielectric multilayer film is shifted to the short

wavelength side. By widening the reflection wavelength range

toward the long wavelength side with respect to the emission

wavelength, the adequate reflectance can be maintained up to

a wide angle, that is, for light incident from the

light-emitting element at a large angle relative to the optical

axis.

Materials suitable for use in the dielectric multilayer

film can be a metal oxide film material, a metal nitride film,

an oxynitride film, or the like. Organic materials, such as

a silicone resinor a fluorine resin, can alsobe used. However,

the material for the dielectric multilayer can be selected from

ones other than those described above.

[0037]

(Encapsulant 108)

Materials suitable for use in the encapsulant 108 can be

light transmissive materials, including an epoxy resin, a

silicone resin, a mixed resin thereof, or glass. Among them,

the silicone resin is preferably selected by taking into

consideration the resistance to light and the formability.

[0038] The encapsulant 108 can contain: a light diffusion material, a wavelength conversion material, such as phosphors or quantum dots that absorbs part of light from the light-emitting element 105 to output light with a different wavelength from that of the light emitted from the light-emitting element; and a colorant corresponding to the color of emitted light from the light-emitting element.

In the case of adding these materials to the encapsulant

108, itispreferable touse ones less likely toaffect the light

distribution characteristics. For example, the material

having a particle size of 0.2 pm or less is preferable because

it less likely to affects the light distribution

characteristics. The term "particle size" as used in the

present specification means an average particle size, and the

average particle size is measured based on a

Fisher-SubSieve-Sizers-No. (F.S.S.S.No) using an air

permeability method.

[0039] The encapsulant 108 can be formed by compression

molding or injection molding to cover the light-emitting

element 105. Alternatively, the material for the encapsulant

108 is optimized its viscosity to be dropped or drawn on the

light-emitting element 105, thereby controlling the shape of

the encapsulant 108 by the surface tension of the material

itself.

[0040] In the latter formation method, a mold is not

required, so that the encapsulant can be formed by a simpler method. Other thanadjusting theviscosityof thebasematerial of the encapsulant 108, the viscosity of the encapsulant material can be adjusted by using the above-mentioned light diffusion material, wavelength conversion material, and/or colorant to form the encapsulant 108 with a desired level of viscosity.

[0041]

[Second Embodiment]

Fig. 7 is a cross-sectional view of a light-emitting

module 300 including a light-emitting device 200 in a second

embodiment. In this embodiment, a plurality of the

light-emitting elements 105 is mounted at predetermined

intervals on thebase101. At leastone light reflectivemember

110 is disposed between the adjacent light-emitting elements

105 so as to reflect the light emitted at a small angle relative

to the upper surface of the light-emitting element (i.e., upper

surface of the base 101). That is, the light-emitting device

200 is an integrated light-emitting device that includes a

plurality of the light-emitting devices 100 of the first

embodiment and the light reflective member110 disposedbetween

the respective light-emitting devices 100. A light diffusion

plate 111 for diffusing the light from the light-emitting

element 105 is disposed above the light-emitting devices 100

and the light reflective member 110 and substantially in

parallelwith the upper surfaces of the light-emitting elements.

A wavelength conversion layer 112 for converting part of the

light emitted from the light-emittingelements105 to light with

a different wavelength is disposed above the light diffusion

plate111and substantiallyinparallelwith the light diffusion

plate 111.

[0042] In general, as the ratio of a distance between the

base 101 and the light diffusion plate 111 (hereinafter maybe

referred to as an optical distance: OD) to a distance between

the adjacent light-emitting elements (hereinafter may be

referred to as apitch) is decreased, the amount oflight between

the light-emitting elements 105 on the surface of the light

diffusion plate 111 becomes small, causing a dark space.

However, with the arrangement including the light

reflective member 110 disposed in this way, the light reflected

by the light reflective member 110 compensates for the amount

of light between the light-emitting elements, whereby the

non-uniform luminance on the surface of the light diffusion

plate 111 can be reduced even in a region with a smaller ratio

of OD/Pitch.

Specifically, in the light-emitting device 200 of the

second embodiment, an inclination angle 0 of a light reflective

surface of the light reflective member 110 relative to the base

101 is set such that the non-uniform luminance on the surface

of the light diffusion plate 111 is reduced taking into

consideration the light distribution characteristics of the respective light-emitting devices 100. Regarding the light distribution characteristics of the plurality of light-emitting devices 100 arranged, each light-emitting device 100 preferably has the light distribution characteristics that the amount of light becomes large in a region with a large light distribution angle, i.e., in a region at alight distribution angle ofaround 900, in order to reduce the non-uniformluminance on the surface of the light diffusion plate 111 and to achieve the thinned light-emitting device 200.

[0043] When the ratio of OD/Pitch is small, for example,

0.2 or less, an elevation angle at which the incident light

enters the light reflective member110is less than220 relative

to the light-emitting surface of the light-emitting element 105.

Thus, to increase the reflectance of the light by the light

reflective member 110 at the low OD/Pitch of 0.2 or less, the

light distribution characteristics of the light-emitting

device 100 preferably has the feature that, for example, the

amount oflight at the elevation angle ofless than 200 relative

to the upper surface of the base is large. Specifically, the

first and second peaks of the emission intensity are preferably

positioned in a range of the elevation angle of less than 200.

Here, the elevation angle of 200 corresponds to the light

distribution angles of -70° and+700 in Fig. 4. In other words,

the first peak of emission intensity is positioned in a range

ofless than -700 of the lightdistributionangle, and the second peak of emission intensity is positioned in a range of greater than +700 of the light distribution angle, as shown in Fig. 4.

The amount of light in a range of the elevation angle of less

than 200 is preferably 30% or more of the whole amount of light,

and more preferably 40% or more thereof.

[0044]

(Light Reflective Member 110)

The light reflective member 110 is provided between the

adjacent light-emitting elements 105.

The light reflective member may be formed of a material

that reflects at least light with the emission wavelength of

the light-emitting element 105. For example, a metal plate or

resin containing a white filler can be suitably used for the

light reflective member.

A dielectric multilayer film can be used as a reflective

surface of the light reflectivemember toproduce the reflective

surface with less light absorption. Additionally, the

reflectance of the light reflective member can be appropriately

adjusted by designing the dielectric multilayer film, or its

reflectance can also be controlled by the angle of the light.

[0045] The height of the light reflective member 110 and

the inclinationangle 0of the light reflective surface relative

to the surface of the base 101 can be set to appropriate values.

The reflective surface of the light reflective member 110 may

be a planar surface or a curved surface. To obtain the desired light distribution characteristics, the suitable inclination angle 0 and shape of the reflective surface can be set. The height of the light reflective member 110 is preferably set at

0.3 times or less and more preferably 0.2 times or less the

distance between the adjacent light-emitting elements. This

arrangement can provide the thinned light-emitting module 300

with less non-uniform luminance.

[0046] For the light-emitting device 200 used in an

environment where the use temperature tends to change

significantly, the linear expansion coefficient of the light

reflective member 110 needs to be close to that of the base 101.

In the case where the light reflective member 110 significantly

differs from the base 101 in the linear expansion coefficient,

warpage might occur in the light-emitting device 200 due to the

change in temperature, or otherwise the positionalrelationship

between the components, especially, between the light-emitting

device100 and the light reflective member110might shift, thus

possibly failing to obtain the desired optical properties.

However, the linear expansion coefficient is a physical

property and thus there are not somany alternatives in reality.

For this reason, the light reflective member 110 is preferably

formedby a filmmoldedcomponent thatis elastically deformable

in order to reducing the occurrence of warpage of the

light-emitting device 200 even in the case where the light

reflective member significantly differs from the base in the linear expansion coefficient. This is because the light reflective member 110 made of a less elastically deformable material, such as solid material tends to expand while maintaining its shape, but the film-shaped light reflective member can be appropriately deformed to compensate its expansion.

[0047] Preferably, a plurality of the light reflective

members 110 is coupled together into a plate shape to have

through holes 113 where the light-emitting devices 200 are

disposed. Fig. 8 shows such a plate-shaped light reflective

plate 110'. Fig. 8A is a top view of the light reflective plate

110', and FIGT. 8B is a cross-sectional view taken along the

line A-A of Fig. 8A. Such a light reflective plate 110' can

be formed by metal molding, vacuum forming, pressure molding,

press forming, and the like. The light reflective plate 110'

is disposed on the base 101. The light reflective member 110

may be formed by a method which involves drawing a light

reflective resin directly on the base 101, and the like. The

height of the light reflective member 110 is preferably set at

0.3 times or less the distance between the adjacent

light-emitting elements, and for example, more preferably 0.2

times or less the distance between the adjacent light-emitting

elements.

[0048]

[Example 1]

In this example, as shown in Fig. 1, a glass-epoxy-based

material is used for the base 101, and a Cu material of 35 pm

in thickness is used as the conductive wiring.

Anitride-basedblue LEDmay be used as the light-emitting

element 105. The LED has an approximately square shape with

one side of 600 pm in length in the planar view and a thickness

of 150 pm. An epoxy-based white solder resist may be used as

the insulating member 104.

The light reflective film 106 formed on the main surface

of the light-emittingelement105 is configuredofelevenlayers

by repeatedly forming a SiO 2 layer (82 nm in thickness) and a

ZrO 2 layer (54 nm in thickness).

At this time, the light transmissivity of the light

reflective film 106 is shown in Fig. 2. The light

transmissivity in the direction perpendicular to the main

surface side of the light-emittingelement (i.e., in the optical

axis direction) is low, and the light transmissivity of the

light reflective film is increased as an angle away from the

optical axis increases.

The light-emitting element 105 is covered with the

encapsulant 108. The encapsulant 108 is formed of a silicone

resin and has a height (H) of 1. 0 mm and a diameter of the bottom

surface (W) of 3.0 mm.

With this arrangement, the light emitted from the

light-emitting element 105 is refracted at an interface between the encapsulant 108 and air, which widens the range of the light distributionangles. The light distribution characteristicof the light-emitting device 100 obtained by this arrangement is indicated by the solid line in Fig. 4. The light distribution characteristic obtained by a light-emitting device without the encapsulant 108 is indicated by the dotted line in Fig. 4. In this way, the encapsulant 108 is used together with the light reflective film 106, which can achieve the lower OD/Pitch.

[0049]

[Example 2]

In Example 2, a plurality of light-emitting elements 105

of Example 1 are mounted on the base 101, and the at least one

light reflective member 110 is disposed between the adjacent

light-emitting elements. Here, Pitch is set at 12.5 mm.

The light reflective member 110 is a plate-shaped light

reflective plate, which is formed using a polypropylene sheet

containing a TiO 2 filler (having a thickness (t) of 0.2 mm) by

the vacuum forming method so as to have a reflection angle 0

(i.e., elevation angle) of 550 and a height of 2.4 mm. The light

reflective member 110 is a plate-shaped light reflective plate

shown in Fig. 8 and disposed on the insulating member 104.

Over the light reflective member110, amilky-white light

diffusion plate 111 and a wavelength conversion layer 112 are

disposed to form a liquid crystal backlight (i.e.,

light-emitting module). In this arrangement, Figs. 9A and 9B show the result of comparison of the non-uniform luminance on the surface of the light diffusion plate 111 between the presence and absence of the light reflective member 110. Fig.

9A shows a light-emitting module without light reflective

member, and Fig. 9B shows a light-emitting module in the

presence of the light reflective member. As shown in Figs. 9A

and 9B, in the case where the light reflective member is not

disposed, the relative luminance is decreased to in a range of

about 0.6 to about 0.7 within a region where the relative

luminance tended to be high (i.e., in a range of the number of

pixels between about 250 pixels to about 720 pixels). On the

other hand, in the case where the light reflective member is

disposed, the relative luminance isnot decreased tobelow about

0.8 within the region where the relatively luminance tended to

be high (i.e., at the number of pixels between about 250 pixels

to about 720 pixels). In other words, it can be seen the effect

that non-uniform luminance is improved by providing the light

reflective member.

[0050] The light-emitting device and light-emitting

module of the present embodiments can be used in backlight light

sources forliquidcrystaldisplays, various lighting fixtures,

and the like.

[0051] Throughout this specification and the claims which

follow, unless the context requires otherwise, the word

"comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0052] The reference toanypriorartin this specification

is not, and should not be taken as, an acknowledgement or any

form of suggestion that the prior art forms part of the common

general knowledge in Australia.

Claims

WHAT IS CLAIMED IS:

1. A light-emitting device comprising:

a base including a conductive wiring;

a light-emitting element mounted on the base and

configured to emit light;

a light reflective film provided on an upper surface

of the light-emitting element; and

a encapsulant covering the light-emitting element and

the light reflective film, wherein the encapsulant has a

upper surface with a convex curved shape,

characterized in that a ratio (H/W) of a height (H) of

the encapsulant to a width (W) of a bottom surface of the

encapsulant is 0.3 or less.

2. The light-emitting device according to claim 1,

wherein the light reflective film is configured such that a

light transmissivity of the light reflective film for said

light has incident-angle dependence.

3. The light-emitting device as in claim 1 or 2,

wherein a light transmissivity of the light reflective film

for said light increases as an absolute value of an incident

angle of said light increases.

4. The light-emitting device as in one of claims 1

to 3, wherein the light reflective film is formed of a

dielectric multilayer film.

5. The light-emitting device as in one of claims 1

to 4, wherein:

a reflection wavelength range of the light reflective

film for light perpendicularly incident on the light

reflective film includes an emission peak wavelength of the

light-emitting element, and

in the reflection wavelength range, a region on a

longer wavelength side of the emission peak wavelength is

wider than a region on a shorter wavelength side of the

emission peak wavelength.

6. The light-emitting device as in one of claims 1

to 5, wherein 30% or more of total light emitted from the

light-emitting device is emitted in a direction at an

elevation angle of less than 200 relative to an upper surface

of the base.

7. The light-emitting device as in one of claims 1

to 5, wherein 40% or more of total light emitted from the

light-emitting device is emitted in a direction at an

elevation angle of less than 200 relative to an upper surface

of the base.

8. The light-emitting device as in one of claims 1

to 7, wherein the light-emitting element is mounted in a

flip-chip manner.

9. A light-emitting module comprising:

the light-emitting device as in one of claims 1 to 8;

and a wavelength conversion member located at a light extraction surface side of the light-emitting device, the wave length conversion member being configured to absorb part of the light emitted from the light-emitting element and to convert the absorbed light to light with a wavelength different from an emission wavelength of the light-emitting element.

10. An integrated light-emitting device comprising:

a plurality of the light-emitting devices as in one of

claims 1 to 8,

wherein at least one light reflective member is

disposed between adjacent ones of the light-emitting devices.

11. The integrated light-emitting device according

to claim 10, wherein the light reflective member has a height

that is 0.3 times or less than a distance between the

adjacent light-emitting devices.

12. The integrated light-emitting device according

to claim 10, wherein the light reflective member has a height

0.2 times or less a distance between the adjacent light

emitting devices.

13. A light-emitting module comprising:

the integrated light-emitting device as in one of

claims 10 to 12; and

a wavelength conversion member located at a light

extraction surface side of the integrated light-emitting

device, the wavelength conversion member being configured to absorb part of light from the light-emitting element and to convert absorbed light to light with a wavelength different from an emission wavelength of the light-emitting element.

-60

Pitch