RU2717381C2 - Light-emitting device, integrated light-emitting device and light-emitting module - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: light-emitting device includes: a base containing current-conducting paths; a light emitting element mounted on the base and configured to emit light radiation; light-reflecting film located on the upper surface of the light-emitting element; and a coating covering the light emitting element and the light-reflecting film. Ratio (H/W) of shell height (H) to width (W) of shell bottom surface is less than 0.5.

EFFECT: invention provides wide distribution of light radiation without using a secondary lens.

17 cl, 9 dwg, 1 tbl

Description

FIELD OF THE INVENTION

Link to a related application

This application claims priority in accordance with Japanese Patent Application No. 2015-200445 of October 08, 2015, and Japanese Patent Application No. 2016-197968 of October 6, 2016, which are incorporated herein by reference in their entirety.

State of the art

The present invention relates to light emitting devices, integrated light emitting devices, and light emitting modules.

In recent years, various electronic components have been proposed and found practical application, and it is necessary that they demonstrate higher performance. In particular, some electronic components must maintain their performance over a long period of time under harsh operating conditions. Such requirements can be applied to light emitting devices that use semiconductor light emitting elements, including LEDs (i.e., LEDs). That is, in the field of general lighting and internal and external lighting for vehicles, it is necessary that the light-emitting devices from day to day show higher performance, in particular, higher power (i.e., higher brightness) and higher reliability. Moreover, light-emitting devices having a low cost and at the same time maintaining high performance are required.

The backlight used in LCD televisions, general lighting devices, etc. are developed with a focus on their design, which leads to a high demand for their refinement.

For example, Japanese Patent Application Publication No. 2008-4948 describes a light-emitting device in which a reflector is formed on an upper surface of a light-emitting element mounted on a substrate by an inverted crystal method to thereby make the backlight thinner.

The publication of Japanese Unexamined Patent Application No. 2008-4948 provides a light emitting device with a wide distribution of light radiation. However, with further refinement of the backlight, a light-emitting device was required, capable of providing a much wider distribution of light radiation.

SUMMARY OF THE INVENTION

The objects of the invention were developed taking into account the above circumstances, and the objective of the present invention is to provide a light emitting device that provides a wide distribution of light radiation without the use of a secondary lens.

The light emitting device in accordance with the invention includes: a base comprising conductive paths; a light emitting element mounted on the base and adapted to emit light radiation; a reflective film located on the upper surface of the light emitting element; and a casing covering the light emitting element and the retroreflective film, wherein the ratio (H / W) of the height (H) of the casing to the width (W) of the lower surface of the casing is less than 0.5.

Accordingly, the invention provides a wide distribution of light radiation without the use of a secondary lens.

Brief Description of the Drawings

(Fig. 1)

In FIG. 1 is a sectional view showing an example of a light emitting device in accordance with a first embodiment.

(Fig. 2)

In FIG. 2 is a diagram showing the dependence of the transmittance of light radiation of a reflective film as a function of the angle of incidence in this embodiment.

(Fig. 3)

In FIG. 3 is a diagram showing the relationship between the wavelength range of the reflective film and the radiation wavelength of the light emitting element in the light emitting device in accordance with an embodiment of the invention.

(Fig. 4)

In FIG. 4 is a light distribution diagram of a light emitting device according to an embodiment of the invention.

(Fig. 5)

In FIG. 5 is a light distribution diagram of a light emitting device using a secondary lens in a comparative example.

(Fig. 6)

In FIG. 6A-6I show experimental examples in accordance with an embodiment of the invention.

(Fig. 7)

In FIG. 7 is a cross-sectional view showing an example of a light emitting module in a second embodiment of the invention.

(Fig. 8A)

In FIG. 8A shows an example of a reflective plate.

(Fig. 8B)

In FIG. 8B shows an example of a reflective plate.

(Fig. 9A)

In FIG. 9A shows the luminance distribution characteristics of a light emitting module in accordance with Example 2.

(Fig. 9B)

In FIG. 9A shows the luminance distribution characteristics of a light emitting module in accordance with Example 2.

Description of Embodiments

Embodiments of the present invention will be described below with reference to the accompanying drawings. The light emitting device, which is described below, implements the technical idea of the present invention, and it is not intended to limit the present invention unless otherwise indicated. The contents of the description regarding one embodiment or example can also be applied to other embodiments or examples.

Moreover, in the description below, the same names or reference numbers indicate the same or similar elements, and thus, their detailed description will be accordingly omitted. Moreover, with respect to each element constituting the present invention, several elements can be formed by one element, thereby allowing this one element to function as these elements. Conversely, the function of one element can be divided and obtained by several elements.

First option

In FIG. 1 is a schematic configuration diagram showing one example of a light emitting device in accordance with the first embodiment.

As shown in FIG. 1, in this embodiment, the light emitting device includes a base 101 with conductive paths 102 and a light emitting element 105 mounted on the base 101. The light emitting element 105 is installed by the inverted crystal method using the connecting elements 103 so as to lean at least on the area between a pair of conductive paths 102 made on the surface of the base 101. The reflective film 106 is made on the side of the light-emitting surface of the light-emitting element 105 (ie, on the surface of the light emitting element 105). At least a portion of each conductive path may comprise an insulating member 104. An area of the upper surface of the conductive path 102 electrically connected to the light emitting element 105 is not covered by the insulating member 104.

The light transmittance of the light reflecting film 106 depends on the angle of incidence of the light incident from the light emitting element 105. In FIG. 2 is a diagram showing the dependence of the light transmittance of the reflective film 106 on the angle of incidence in this embodiment. The reflective film 106 almost does not pass light radiation through itself in a direction perpendicular to the upper surface of the light emitting element 105, but increases the amount of transmitted light radiation if the angle of incidence relative to the perpendicular direction increases. In particular, if the angle of incidence is in the range from -30 ° to 30 °, the transmittance of light radiation is approximately 10%. If the angle of incidence becomes less than -30 °, then the transmittance of light radiation gradually increases. In addition, if the angle of incidence becomes less than -50 °, the transmittance of light radiation increases sharply. Similarly, if the angle of incidence becomes greater than 30 °, then the transmittance of light radiation gradually increases. In addition, if the angle of incidence becomes greater than 50 °, the transmittance of light radiation increases sharply. That is, the transmittance of the light radiation of the reflective film increases with an increase in the absolute value of the angle of incidence of the light radiation. The formation of such a reflective film can provide a characteristic of the distribution of light radiation in the form of bat wings, as shown in FIG. 4.

As used herein, the term “characteristic of the distribution of light radiation in the form of bat wings” means a characteristic of the distribution of light radiation having a first peak in the first region with a light distribution angle of less than 90 °, the first peak having a higher intensity than when the angle of light distribution is 90 °, as well as a second peak in the second region with a light distribution angle of more than 90 °, the second peak having a higher intensity than with a light distribution angle new radiation equal to 90 °.

The light-emitting element 105 is covered with a light-conductive sheath 108. The sheath 108 is located on the base, covering the light-emitting element 105, to protect the light-emitting element 105 from the external environment and to optically control the light emission emitted by the light-emitting element. Shell 108 is made essentially dome-shaped. The sheath 108 covers the light emitting element 105 with a reflective film 106 located thereon, the surfaces of the conductive paths 102 located around the light emitting element 105, and the connecting portions between the light emitting element 105, including the connecting elements 103 and the conductive paths 102. That is, the upper surface and the side surfaces of the reflective film 106 are in contact with the sheath 108, and the side surfaces of the light-emitting element 105 not covered by the reflective film 106 are also in contact with sheath 108. The connecting portions may be coated with the interlayer rather than the sheath 108. In this case, the sheath 108 is formed so that it covers the upper surface of the interlayer and the light emitting element. In this embodiment, the light emitting element 105 is directly covered by a sheath 108.

The shell 108 is preferably made so that it has a round or ellipsoidal external shape in a plan view, wherein the ratio of the height (H) of the shell in the direction of the optical axis to the diameter (width W) of the shell in the top view is less than 0.5. For the shell 108, having an ellipsoidal shape, there is a main axis and a minor axis, which can be considered as length and width, but in the present description by the diameter (W) of the shell 108 we mean the minor axis. The upper surface of the shell 108 is made in a convex curved shape.

With such a device, the light radiation emitted by the light emitting element 105 is refracted at the boundary between the cladding 108 and the air, so that a wider distribution of light radiation can be obtained.

Here, the height (H) of the casing means the height from the mounting surface for the light emitting element 105, as shown in FIG. 1. The width (W) of the shell means its diameter if the shell has a circular bottom surface, as mentioned above, or, alternatively, means the length of its shortest part, if the shell has a shape other than round.

In FIG. 4 shows an example of a change in the distribution characteristic of light radiation depending on the presence or absence of cladding 108. FIG. 4, the solid line shows a light distribution characteristic of the light emitting device 100 in the first embodiment. On the other hand, the dashed line shows the light distribution characteristic of the light emitting device manufactured in the same way as in the first embodiment except that there is no cladding 108.

As seen in FIG. 4, for the light-emitting device in the first embodiment, the first peak moves in a direction that decreases the angle of distribution of light radiation, just as the second peak moves in a direction that increases the angle of distribution of light radiation, compared with a light-emitting device without a clad 108. Therefore, the light emitting device in the first embodiment can give a wider distribution of light radiation.

Using both the retroreflective film 106 and the sheath 108 in this way, the desired light distribution characteristic can be obtained without using a secondary lens. That is, the formation of the retroreflective film 106 can reduce the brightness directly above the light emitting element 105, while the shell 108 can focus on expanding the distribution of light radiation from the light emitting element 105, which can significantly reduce the lens function shell.

In other words, usually a decrease in brightness directly above the light emitting element when expanding the distribution of light radiation is possible only by adjusting the height of the shell, as a result of which the height of the shell should be increased. In contrast, the light-emitting device in this embodiment includes a reflective film 106 having a reduced brightness directly above the light-emitting element 105, thereby achieving the distribution characteristics of light radiation in the form of bat wings. Thus, the cladding 108 may be configured to focus on the expansion function of the light distribution. Thus, this embodiment can reduce the size of the light emitting device.

Such a device can provide a thinner backlight module (i.e., a light emitting module), which allows to reduce uneven brightness, as will be described below. In FIG. 5, as a comparative example, a light distribution characteristic obtained using a secondary lens is shown. Even without the use of a secondary lens, the light emitting device in this embodiment can give substantially the same light emission distribution characteristic as when using the secondary lens.

Nine light-emitting devices were manufactured having different heights (H) of the cladding 108 in the direction of the optical axis and different diameters (width: W) of the cladding in a plan view. The light distribution characteristics obtained for them are shown in FIG. 6A-6I. The light emitting element used was a blue LED having a substantially square shape with a side of 600 μm in plan view and a thickness of 150 μm. A reflective film 106 formed on the main surface of the light emitting element 105 is made of eleven layers by repeatedly depositing a SiO ₂ layer (82 nm thick) and a ZrO ₂ layer (54 nm thick).

For each of the nine light-emitting devices No. 1-9, the ratio of the height (H) of the shell to the diameter (width W) of the shell is shown in Table 1.

Table 1

Number 1 Number 2 Number 3 Number 4 Number 5 Number 6 Number 7 Number 8 Number 9 N (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.
6A FIG.
6B FIG. 6C FIG. 6D FIG. 6E FIG. 6F FIG. 6g FIG. 6H FIG.
6I

As can be seen from the experimental results, the characteristics of the distribution of light radiation due to differences in the diameter of the shell do not change much. However, the ratio of the height (H) of the cladding to the diameter (width: W) of the cladding affects the light distribution properties.

The graphs in FIG. 6A-6I show that in order to obtain a wider distribution of light radiation, the ratio (H / W) of the height (H) to the width (W) of the cladding should preferably be 0.3 or less.

Preferred examples of the light emitting device 100 in this embodiment will be described below.

Base 101

The base 101 is an element on which the light emitting element 105 is mounted. The base 101 contains conductive tracks 102 on its surface to supply electric power to the light emitting element 105.

Examples of materials from which base 101 is made may include ceramics and resins such as phenolic resin, epoxy resin, polyimide resin, BT resin, polyphthalamide (PPA) and polyethylene terephthalate (PET). Among them, the resin is preferably selected as a material having a low cost and shapeability. The thickness of the base can be selected appropriately. The base can be either a rigid base or a flexible base made using a roll system. The rigid base may be a thin rigid base that can be bent.

In order to obtain a light-emitting device resistant to heat and light radiation, ceramics are preferably selected as the base material 101. Examples of ceramics may include alumina, mullite, forsterite, glass ceramics, nitride-based ceramics (e.g., AlN) and carbide-based ceramics (e.g., SiC). Among them, ceramic made of aluminum or containing aluminum is preferable.

When using the resin as the material for the base 101, an inorganic filler such as fiberglass, SiO ₂ , TiO ₂ or Al ₂ O ₃ is mixed with the resin, thereby allowing the base to have increased mechanical strength and increased optical reflectivity, reduced coefficient of thermal expansion and etc. The base 101 can be any other element if it can separate and isolate a pair of conductive paths 102 from each other. The base 101 can use a so-called metal base, which includes a metal element with an insulating layer formed on it.

Conductors 102

The conductive paths 102 are elements electrically connected to the electrodes of the light emitting element 105, and they are adapted to supply current (electricity) from the outside to the light emitting element. That is, the conductive tracks serve as electrodes or parts thereof for supplying power from the outside. Typically, the conductive tracks are made of at least two tracks, namely, positive and negative, located at a distance from each other.

Each conductive path 102 is performed at least on the upper surface of the base, which serves as the mounting surface for the light emitting element 105. The material for the conductive paths 102 can be selected appropriately depending on the material used for the base 101, their manufacturing method, and t .P. For example, if ceramic was used as the material for the base 101, the conductive paths 102 are preferably made of a material having a high melting point, which can withstand the sintering temperature of the ceramic sheet. In particular, a metal having a high melting point, such as tungsten or molybdenum, is preferably used as the material for the conductive tracks. In addition, other materials such as nickel, gold or silver may be used to cover the aforementioned surface of the conductive tracks by coating, spraying, vapor deposition, etc.

If epoxy fiberglass is used as the base material 101, a material that is easily processed is preferably used as the material for the conductive paths 102. In the case of using pressure-molded epoxy, the conductive paths 102 are made of material that can be easily processed by punching, etching, bending, etc. and has a relatively high mechanical strength. In particular, examples of conductive paths may include metals such as copper, aluminum, gold, silver, tungsten, iron and nickel, as well as a metal layer or lead frame of iron-nickel alloy, phosphor bronze, iron-copper alloy, molybdenum, etc. . The surface of the lead frame may be coated with a metal material other than the metal material of the main body of the lead frame. Such metallic materials can be suitably selected, for example, only silver or an alloy of silver and copper, gold, aluminum or rhodium. Alternatively, the conductive tracks may be made of several layers using silver or each alloy. Suitable coating methods for the metal material may include spraying, vapor deposition, and the like, as well as coating.

The connecting element 103

The connecting elements 103 are elements designed to fix the light emitting element 105 on the base 101 or the conductive tracks 102. When installed using the inverted crystal method, the conductive elements are used as the connecting elements in the same way as in this embodiment. In particular, suitable materials for the connecting elements may include a gold-containing alloy containing silver alloy containing palladium alloy containing indium alloy, lead-palladium alloy, gold-gallium alloy, gold-tin alloy, tin alloy, tin-copper alloy, tin-copper-silver alloy, gold-germanium alloy, gold-silicon alloy containing aluminum alloy, copper-indium alloy, and a mixture of metal and flux,

Suitable forms of the connecting element 103 may include the following: liquid type, paste type and / or solid type (eg, in the form of a sheet, in the form of a block, in the form of a wire and / or in the form of a powder). The shape of the connecting element may be suitably selected based on its composition, base shape, etc. These connecting elements 103 may be made of a single element or a combination of several types of elements.

Insulating element 104

The conductive paths 102 are preferably coated with an insulating element 104, with the exception of parts electrically connected to the light emitting element 105 and other materials. That is, as shown in the respective figures, resistance for insulation and coating of the conductive paths 102 can be applied to the base. The insulating element 104 may function as such a resistance.

In the case of applying the insulating element 104, a white filler may be contained in the insulating element. The white filler contained in the insulating element can reduce leakage and absorption of light radiation, thereby allowing to increase the efficiency of light radiation of the light emitting device 100, as well as isolate the conductive tracks 102.

The material for the insulating element 104 can be appropriately selected based on the fact that this material does not absorb light from the light-emitting element and has insulating properties. Examples of material for the insulating element may include epoxy, silicone, modified silicone, urethane, oxetane, acrylic, polycarbonate and polyimide resin.

Light Emitting Element 105

A light emitting element 105 mounted on the base may be known in the art. In this embodiment, an LED is preferably used as the light emitting element 105.

X, 0

Y, X + Y

1) или GaP. В качестве подложки для выращивания можно применять светопроводящую сапфировую подложку и т.п. В красном светодиоде может быть использован GaAlAs, AlInGaP, и т.д. Более того, можно применять полупроводниковые светоизлучающие элементы, выполненные из любого материала, отличающегося от материалов, упомянутых выше. Состав, цвет излучения и размер светоизлучающего элемента, а также число используемых светоизлучающих элементов и т.п. можно выбрать подходящим образом в соответствии с целями.You can select the light emitting element 105, which emits light radiation of the appropriate wavelength. For example, in a blue or green light-emitting element, ZnSe, a nitride semiconductor (In _x Al _y Ga _1-xy N, 0

X, 0

Y, X + Y

1) or GaP. As a growth substrate, a light guide sapphire substrate and the like can be used. GaAlAs, AlInGaP, etc. can be used in the red LED. Moreover, semiconductor light emitting elements made of any material other than the materials mentioned above can be used. The composition, color of the radiation and size of the light emitting element, as well as the number of light emitting elements used, etc. can be selected appropriately according to purpose.

You can choose different lengths of the emitted waves depending on the material of the semiconductor layer and its ratio of mixed crystals. The light emitting element may contain positive and negative electrodes on the same surface so that it can be installed by the inverted crystal method, or, alternatively, it may have positive and negative electrodes on its different surfaces.

The light emitting element 105 in this embodiment comprises a light guide substrate, and a semiconductor layer is provided on the substrate. The semiconductor layer includes an n-type semiconductor layer, an active layer and a p-type semiconductor layer, made in this order. The n-type electrode is performed on the n-type semiconductor layer, and the p-type electrode is performed on the p-type semiconductor layer.

As shown in FIG. 1, the light emitting element 105 is mounted by the inverted crystal method on the conductive paths 102 located on the surface of the base 101 by the connecting elements 103. The surface of the light emitting element 105, opposite to its surface on which the electrodes are made, that is, the main surface of the light guide substrate, will serve as a light emitting surface. However, in that embodiment of the invention, the reflective film 106 is formed on the light emitting surface, and thus, the side surface of the light emitting element 105 practically serves as the light emitting surface. That is, a portion of the light emitted by 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 reflecting film 106, then is reflected again inside the light emitting element 105, and finally exits through the side surfaces of the light emitting element 105 Therefore, the distribution properties of the light radiation of the light emitting device 100 (see the dashed line in FIG. 4) demonstrate the combination properties of light radiation, seated through a reflective film 106, and light radiation emitted from the side surfaces of the light emitting element 105.

The light emitting element 105 is located so as to cover the area between two conductive paths 102, which are isolated and separated on the positive and negative sides. The light emitting element 105 is electrically connected and mechanically fixed to the conductive paths using the conductive connecting elements 103. To install the light emitting element 105, it is possible to apply a method using prepress, as well as a method using solder paste. As the light emitting element 105, you can also use a small product that includes a light emitting element enclosed in a resin or the like. The shape and structure of the light emitting element 105 can be selected accordingly.

X, 0

Y, X + Y

1), способный излучать световое излучение, имеющее короткую длину волны, которое может эффективно возбуждать слой преобразования длины волны.As will be described below, in the case of a light-emitting device including a wavelength conversion element, a nitride semiconductor is suitably used in the light-emitting element (In _x Al _y Ga _1-xy N, 0

X, 0

Y, X + Y

1) capable of emitting light radiation having a short wavelength, which can effectively excite a wavelength conversion layer.

Although an example has been described in which an inverted crystal installation is used, in some embodiments of the present invention, an installation can be used in which the base side insulation of the light emitting element serves as a mounting surface and the electrodes formed on the upper surface of the light emitting element are connected with the tracks. In this case, the upper surface of the light emitting element is a side with electrodes, and a reflective film is arranged on the side with electrodes.

Reflective Film 106

The reflective film 106 is formed on the side of the light emitting surface, which is the main surface of the light emitting element 105.

The material for the retroreflective film may be a material that reflects at least the light radiation emitted by the light emitting element 105, for example, a metal or resin containing a white filler.

For the manufacture of a reflective film having a lower ability to absorb light radiation, a dielectric multilayer film can be used. In addition, the reflection coefficient of the reflective film can be adjusted accordingly by designing the dielectric multilayer film, or its reflection coefficient can also be controlled by adjusting the angle of light emission. In particular, the reflection coefficient increases in the direction perpendicular to the light emitting surface (also called the direction of the optical axis) and decreases at a large angle relative to the optical axis due to an increase in the transmittance of the light radiation of the reflective film, which can give the distribution of light radiation in the form of bat wings.

Regarding the length range of the reflected waves in the direction of the optical axis of the dielectric multilayer film, i.e. in a direction perpendicular to the upper surface of the light emitting element, as shown in FIG. 3, it is preferable to expand the region on the long wavelength side of the reflected wavelength range with respect to the peak radiation wavelength of the light emitting element 105.

The reason for this is a change in the angle from the optical axis, in other words, when the angle from the optical axis of the incident light increases, the range of reflected wavelengths of the dielectric multilayer film is shifted toward short wavelengths. By expanding the range of reflected wavelengths towards longer wavelengths relative to the emitted wavelength, it is possible to maintain an adequate reflection coefficient up to a wide angle, that is, when light radiation is incident from the light emitting element at a large angle relative to the optical axis.

Materials suitable for use in a dielectric multilayer film may be a metal oxide film, a metal nitride film, an oxynitride film, and the like. Organic materials such as silicone resin or fluoroplastic resin can also be used. However, the material for the dielectric multilayer film can be selected from materials other than those described above.

Shell 108

Materials suitable for use as cladding 108 may be photoconductive materials including epoxy resin, silicone resin, a mixture thereof, or glass. Among them, silicone resin is preferably selected, taking into account the resistance to light radiation and the ability to shape.

Shell 108 may comprise: a light scattering material, a wavelength converting material, such as a phosphor or quantum impurities, which absorb part of the light radiation from the light emitting element 105 to emit light radiation whose wavelength is different from the wavelength of the light radiation emitted by the light emitting element; and a pigment corresponding to the color of the light emitted by the light emitting element.

If these materials are added to the sheath 108, it is preferable to use those that will not adversely affect the light distribution properties. For example, a material having a particle size of 0.2 μm or less is preferred since it is less likely to adversely affect the light distribution properties. The term “particle size” as used in this specification refers to the average particle size, and the average particle size is measured using a Fisher-SubSieve-Sizers (F.S.S.S.. No) using the method of breathability.

The sheath 108 may be formed by compression molding or injection molding to close the light emitting element 105. Alternatively, the material for the sheath 108 has an optimum viscosity so that it can be applied in the form of a drop or applied to the light emitting element 105, thereby controlling the shape of the sheath 108 through the surface tension of the material itself.

In the latter method of formation, a mold is not required, so that the shell can be made in a simpler way. In addition to adjusting the viscosity of the base material of the sheath 108, the viscosity of the sheath material can be adjusted using the aforementioned light-scattering material, wavelength converting material and / or pigment to form the sheath 108 with a desired viscosity level.

Second option

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, based on 101, several light emitting elements 105 are installed at predetermined intervals. At least one light reflecting element 110 is disposed between adjacent light emitting elements 105 to reflect light emitted at a slight angle relative to the upper surface of the light emitting element (i.e., the upper surface of the base 101). That is, the light-emitting device 200 is an integrated light-emitting device that includes several light-emitting devices 100 of the first embodiment and a light-reflecting element 110 located between the respective light-emitting devices 100. The light-diffusing plate 111, designed to diffuse light radiation from the light-emitting element 105, is located above light emitting devices 100 and retroreflective element 110 and is essentially parallel to the upper surface there are light emitting elements. A wavelength conversion layer 112 for converting a portion of the light emitted by the light emitting elements 105 into light having a different wavelength is located above the light scattering plate 111 and is substantially parallel to the light scattering plate 111.

In general, since the ratio of the distance between the base 101 and the light diffusing plate 111 (hereinafter referred to as the optical distance: OD) to the distance between adjacent light emitting elements (hereinafter referred to as the pitch) decreases, the amount of light radiation between the light emitting elements 105 on the surface of the diffusing plate 111 becomes small, causing a dark space.

However, when the device comprises a retroreflective element 110 arranged in such a way, the light radiation reflected by the retroreflective element 110 compensates for the amount of light radiation between the light emitting elements, as a result of which the unevenness of the brightness on the surface of the diffuser plate 111 can be reduced even in the region with a lower OD / step ratio.

In particular, in the light emitting device 200 according to the second embodiment of the invention, the inclination angle θ of the reflective surface of the reflective element 110 relative to the base 101 is set so that the unevenness of brightness on the surface of the diffuser plate 111 is reduced taking into account the light distribution properties of the respective light emitting devices 100. With regard to the distribution properties light emission of several light emitting devices 100, each light emitting device 100 preferably having m such distribution characteristics of light radiation, that the amount of light emission becomes large in a region with a large angle distribution of the light emission, i.e., in the region with the angle of distribution of light radiation of about ± 90 °, in order to reduce the unevenness of brightness on the surface of the diffuser plate 111 and to obtain a thin light-emitting device 200.

If the OD / step ratio is small, for example 0.2 or less, then the angle of inclination at which the incident light enters the light reflecting element 110 is less than 22 ° with respect to the light emitting surface of the light emitting element 105. Thus, in order to increase the light reflectance emitted by the light reflecting element 110 at a low OD / pitch ratio of 0.2 or less, the light distribution characteristic of the light emitting device 100 is preferably such that, for example, the amount of light emitted under glom inclination less than 20 ° relative to the upper surface of the base is large. In particular, the first and second peaks of radiation intensity are preferably located in a tilt range of less than 20 °. Here, an inclination angle of 20 ° corresponds to the angles of light distribution of 20 ° and 160 ° in FIG. 4. In other words, the first peak in radiation intensity is located in the range of angles of light distribution less than 20 °, and the second peak in radiation intensity is located in the range of angles of distribution of light radiation greater than 160 °, as shown in FIG. 4. The amount of light radiation in the range of inclination angles less than 20 ° is preferably 30% or more of the total amount of light radiation, and more preferably 40% or more.

Reflective Element 110

A reflective element 110 is disposed between adjacent light emitting elements 105.

The reflective element may be made of a material that reflects at least light radiation having a radiation wavelength of the light emitting element 105. For example, a metal plate or resin containing a white filler may be used for the reflective element.

For the manufacture of a reflective surface having a lower ability to absorb light radiation, a dielectric multilayer film can be used as a reflective surface with less absorption of light radiation. In addition, the reflection coefficient of the reflective element can be adjusted accordingly by designing a dielectric multilayer film, or its reflection coefficient can also be controlled by the angle of light emission.

The height of the reflective element 110 and the angle θ of the inclination of the reflective surface relative to the surface of the base 101 can be set equal to the corresponding value. The reflective surface of the reflective element 110 may be a flat surface or a curved surface. To obtain the required properties of the distribution of light radiation, you can set the appropriate angle θ of inclination and the shape of the reflecting surface. The height of the light reflecting element 110 is preferably set equal to 0.3 or less, more preferably 0.2 or less, from the distance between adjacent light emitting elements. Such an arrangement may produce a thin light emitting module 300 with less uneven brightness.

For the light-emitting device 200 used in an environment where the temperature of use tends to change significantly, the linear expansion coefficient of the retro-reflecting element 110 should be close to the corresponding coefficient of the base 101. In the case where the linear expansion coefficient of the retro-reflecting element 110 is significantly different from the corresponding coefficient of the base 101 , warping may occur in the light emitting device 200 due to a change in temperature or, otherwise, the relative position of the components In particular, the light emitting device 100 and the retroreflective element 110 may shift, thereby possibly preventing the desired optical properties from being obtained. However, the linear expansion coefficient is a physical property and, therefore, in reality there are not many alternatives. For this reason, the reflective element 110 is preferably made of a film molded component that is elastically deformable to reduce the possibility of warping of the light emitting device 200 even when the linear expansion coefficient of the reflective element is significantly different from the corresponding base coefficient. This is because a retroreflective element 110 made of a less elastic deformable material, for example, a solid material, tends to expand while maintaining its shape, but the reflective element in the form of a film can be deformed accordingly to compensate for its expansion.

Preferably, several retroreflective elements 110 are connected together in a plane so that there are through holes 113 where the light emitting devices 200 are located. In FIG. 8 shows such a flat reflective plate 110 '. In FIG. 8A is a plan view of the reflective plate 110 ′, and FIG. 8B is a cross-sectional view taken along line AA shown in FIG. 8A. Such a retroreflective plate 110 'may be made by metal casting, vacuum molding, pressing, and the like. The reflective plate 110 'is located on the base 101. The reflective element 110 may be made by a method that includes applying a reflective resin directly to the base 101 and the like. The height of the light-reflecting element 110 is preferably set equal to 0.3 or less from the distance between adjacent light-emitting elements, and, for example, more preferably 0.2 or less, from the distance between the adjacent light-emitting elements.

Example 1

In this example, as shown in FIG. 1, epoxy fiberglass was used for base 101, and copper material 35 μm thick was used as conductive paths.

As the light emitting element 105, a nitride blue LED can be used. The LED has an approximately square shape with a side of 600 microns in a plan view and a thickness of 150 microns. As the insulating element 104, an epoxy white solder resist can be used.

A reflective film 106 formed on the main surface of the light emitting element 105 is made of eleven layers by repeatedly depositing a SiO ₂ layer (82 nm thick) and a ZrO ₂ layer (54 nm thick).

Currently, the transmittance of light radiation of the reflective film 106 is shown in FIG. 2. The transmittance of the light radiation in the direction perpendicular to the main surface of the light emitting element (ie, in the direction of the optical axis) is low, and the transmittance of the light radiation of the reflective film increases as the angle of deviation from the optical axis increases.

The light emitting element 105 is coated with a sheath 108. The sheath 108 is made of silicone resin and has a height (H) of 1.0 mm and a diameter of the lower surface (W) of 3.0 mm.

With such a device, the light radiation emitted by the light emitting element 105 is refracted at the boundary between the cladding 108 and the air, which broadens the range of angles of distribution of light radiation. The light distribution characteristic of the light emitting device 100 thus obtained is shown by the solid line in FIG. 4. The light emission distribution characteristic obtained for a light-emitting device without cladding 108 is shown by a dashed line in FIG. 4. Thus, the sheath 108 is used together with the reflective film 106, whereby a lower OD / pitch ratio can be achieved.

Example 2

In Example 2, several light-emitting elements 105 of Example 1 are mounted on the base 101, and at least one light-reflecting element 110 is located between adjacent light-emitting elements. In this case, the pitch is 12.5 mm.

The reflective element 110 has a flat shape in the form of a reflective plate, which is made using a polypropylene sheet containing a TiO ₂ filler (thickness (t) 02 mm) by vacuum molding to obtain a reflection angle θ (i.e., tilt angle) of 55 ° and a height of 2.4 mm. The reflective element 110 is a flat reflective plate shown in FIG. 8 and located on the insulating element 104.

A milk-white light-diffusing plate 111 and a wavelength conversion layer 112 are arranged above the light reflecting element 110 to obtain a liquid crystal backlight (i.e., a light emitting module). With such a device in FIG. 9A and 9B show the result of comparing the unevenness of brightness on the surface of the diffuser plate 111 for the presence and absence of the reflective element 110. FIG. 9A shows a light emitting module without a reflective element, and in FIG. 9B shows a light emitting module comprising a reflective element. As shown in FIG. 9A and 9B, when there is no reflective element, the relative brightness decreases to a range of from about 0.6 to 0.7 in a region where the relative brightness tends to be high (i.e., in the range of the number of pixels from about 250 to about 720). On the other hand, when there is a reflective element, the relative brightness does not decrease below 0.7 in the region where the relative brightness tends to be high (i.e., in the range of the number of pixels from about 250 to about 720). In other words, it is seen that in the presence of a reflective element, the unevenness of brightness is reduced.

The light emitting device and the light emitting module according to the present embodiments can be used as a backlight for liquid crystal displays, various lighting devices, and the like.

Claims (33)

1. A light emitting device comprising: a base including conductive paths; a light emitting element mounted on the base and configured to emit light radiation; a reflective film located on the upper surface of the light emitting element; and a shell covering the light-emitting element and the reflective film, and the ratio (H / W) of the height (H) of the shell to the width (W) of the lower surface of the shell is less than 0.5. 2. The light emitting device according to claim 1, in which the upper surface of the shell has a convex curved shape. 3. The light emitting device according to claim 1, in which the reflective film is made so that the transmittance of the light radiation of the reflective film for the specified light radiation depends on the angle of incidence. 4. The light emitting device according to claim 1, in which the transmittance of light radiation of the reflective film for the specified light radiation increases as the absolute value of the angle of incidence of the specified light radiation increases. 5. The light emitting device according to claim 1, in which the reflective film is formed of a dielectric multilayer film. 6. The light emitting device according to claim 1, in which: the wavelength range reflected by the reflective film for light radiation incident perpendicular to the reflective film includes the wavelength of the peak radiation of the light-emitting element, and in the indicated range of reflection wavelengths, the region on the side of longer wavelengths with respect to the emission peak is wider than the region on the side of shorter wavelengths with respect to the radiation peak. 7. The light emitting device according to claim 1, wherein 30% or more of the total light radiation emitted by the light emitting device is emitted in a direction at an inclination angle of less than 20 ° with respect to the upper surface of the base. 8. The light emitting device according to claim 1, wherein 40% or more of the total light emitted by the light emitting device is emitted in a direction at an angle of inclination of less than 20 ° with respect to the upper surface of the base. 9. The light emitting device according to claim 1, wherein the ratio (H / W) of the height (H) of the casing to the width (W) of the lower surface of the casing is 0.3 or less. 10. The light emitting device according to claim 1, wherein the light emitting element is installed by the inverted crystal method. 11. A light emitting module comprising: light emitting device according to any one of paragraphs. 1-10; and a wavelength conversion element located on the side of the light-emitting surface of the light-emitting device, wherein the wavelength conversion element is configured to absorb part of the light radiation emitted by the light-emitting element and convert the absorbed light radiation into light radiation with a wavelength different from the wavelength of the light radiation emitted by the light-emitting device an element. 12. An integrated light emitting device, comprising: multiple light emitting devices according to any one of paragraphs. 1-10, wherein at least one retroreflective element is located between adjacent said light emitting devices. 13. The integrated light emitting device according to claim 12, in which the reflective element has a height of 0.3 or less from the distance between adjacent light emitting devices. 14. The integrated light emitting device according to claim 12, in which the reflective element has a height of 0.2 or less from the distance between adjacent light emitting devices. 15. A light emitting module containing: an integrated light emitting device according to claim 12; and a wavelength conversion element located on the side of the light output surface of the integrated light emitting device, wherein the wavelength conversion element is configured to absorb part of the light radiation emitted by the light-emitting element and convert the absorbed light radiation into light radiation with a wavelength different from the wavelength of the light radiation emitted light emitting element. 16. A light emitting module containing: an integrated light emitting device according to claim 13; and a wavelength conversion element located on the side of the light output surface of the integrated light emitting device, wherein the wavelength conversion element is configured to absorb part of the light radiation emitted by the light-emitting element and convert the absorbed light radiation into light radiation with a wavelength different from the wavelength of the light radiation emitted light emitting element. 17. A light emitting module comprising: an integrated light emitting device according to claim 14; and a wavelength conversion element located on the side of the light output surface of the integrated light emitting device, wherein the wavelength conversion element is configured to absorb part of the light radiation emitted by the light-emitting element and convert the absorbed light radiation into light radiation with a wavelength different from the wavelength of the light radiation emitted light emitting element.

Images