WO2013039339A2

WO2013039339A2 - Lighting device

Info

Publication number: WO2013039339A2
Application number: PCT/KR2012/007351
Authority: WO
Inventors: Eun Hwa Kim
Original assignee: Lg Innotek Co., Ltd.
Priority date: 2011-09-14
Filing date: 2012-09-13
Publication date: 2013-03-21
Also published as: WO2013039339A3; KR20130029202A

Abstract

A lighting device may be provided that includes: a light source disposed on a substrate; a light guide which is disposed on the substrate and surrounds the light source; and a reflector which is formed on an upper portion of the light guide and reflects light incident from the light source.

Description

LIGHTING DEVICE

This embodiment relates to a lighting device.

A light emitting diode (LED) is a semiconductor element for converting electric energy into light. As compared with existing light sources such as a fluorescent lamp and an incandescent electric lamp and so on, the LED has advantages of low power consumption, a semi-permanent span of life, a rapid response speed, safety and an environment-friendliness. For this reason, many researches are devoted to substitution of the existing light sources with the LED. The LED is now increasingly used as a light source for lighting devices, for example, various lamps used interiorly and exteriorly, a liquid crystal display device, an electric sign and a street lamp and the like.

However, the LED generates much heat when turned on. If the heat is not readily radiated, the life span and illuminance of the LED are reduced and quality characteristic is remarkably deteriorated. Therefore, advantages of the LED lighting device can be obtained under the condition that the heat radiation of the LED is easily done.

The objective of the present invention is to provide a lighting device capable of guiding a path of light.

The objective of the present invention is to provide a lighting device having excellent rear light distribution.

One embodiment is a lighting device including: a light source disposed on a substrate; a light guide which is disposed on the substrate and surrounds the light source; and a reflector which is formed on an upper portion of the light guide and reflects light incident from the light source.

The light source includes at least one light emitting device.

The reflector is formed to have a conical shape.

The reflector includes a reflective surface made of glass.

A reflective surface of the reflector is formed to be flat.

An angle formed by a reflective surface of the reflector and an upper horizontal surface of the reflector is from 43 degree to 48 degree.

The light guide includes an acrylic resin (PMMA).

The reflector has a shape projecting toward the light source.

The light source includes a light emitting device and a fluorescent substance applied on the light emitting device.

The reflector has a reflective surface formed to reflect the light to the shape.

The lighting device further includes a cover which is disposed on the substrate and covers the light source, the light guide and the reflector.

An opalescent pigment is disposed on an inner surface of the cover.

The pigment further includes a diffusion agent which causes light transmitting through the cover to be diffused into the inner surface of the cover.

Another embodiment is a lighting device including: a light source disposed on a substrate; a light guide which is disposed on the substrate and surrounds the light source, and of which both ends thereof are opened in such a manner that the light source is exposed; and a reflector which is disposed on an upper portion of the light guide and reflects light irradiated in one direction by the light guide, and reflects light irradiated in the one direction by the light source in a reverse direction to the one direction.

The light guide reflects all of the light irradiated from the light source and allows the light to reach the reflector.

A lighting device in accordance with this embodiment has a light emitting point which moves without optical loss.

A lighting device in accordance with this embodiment has excellent rear light distribution by using a surface-mounted light emitting device.

Fig. 1a is a plan view of a lighting device according to a first embodiment;

Fig. 1b is a side view of the lighting device shown in Fig. 1a;

Figs. 2a and 2b are views showing light irradiated from a light source of the lighting device according to the first embodiment;

Fig. 3 is a view showing a simulation result of light distribution of an LED light source shown in Figs. 2a and 2b;

Fig. 4 is a perspective view showing a lighting device according to a second embodiment;

Figs. 5a to 5c are views showing a traveling direction of light from the lighting device employing a light guide 20;

Fig. 6 is a view showing a light distribution of the lighting device shown in Fig. 4;

Fig. 7 is a view showing a lighting device and a traveling direction of light in accordance with a third embodiment;

Fig. 8 is a sectional perspective view of the lighting device shown in Fig. 7;

Fig. 9 is a cross sectional view of the lighting device shown in Fig. 7;

Figs. 10a to 10e are views showing traveling paths of light as γ changes from 43 degree to 48 degree when α is 55 degree;

Fig. 11 is a view showing a traveling direction of light in a state where a body is coupled to the lighting device shown in Fig. 7;

Fig. 12 is a view showing a cover which is fastened to the lighting device shown in Fig. 7;

Fig. 13 is a front view showing the lighting device to which the cover and the body are coupled;

Fig. 14 is a view showing a traveling path of light irradiated from the lighting device shown in Fig. 13; and

Fig. 15 is a view showing a light distribution by the lighting device according to the embodiment of the present invention.

Hereafter, an embodiment of this art will be described in detail with reference to accompanying drawings. However, the accompanied drawings are provided only for more easily describing the present invention. It is easily understood by those skilled in the art that the spirit and scope of the present invention is not limited to the scope of the accompanied drawings.

A criterion for “on” and “under” of each layer will be described based on the drawings. A thickness or a size of each layer may be magnified, omitted or schematically shown for the purpose of convenience and clearness of description. The size of each component may not necessarily mean its actual size.

In description of embodiments of this art, when it is mentioned that an element is formed “on” or “under” another element, it means that the mention includes a case where two elements are formed directly contacting with each other or are formed such that at least one separate element is interposed between the two elements. The “on” and “under” will be described to include the upward and downward directions based on one element.

Further, throughout the specification, when it is mentioned that a portion is “connected” to another portion, it includes not only “is directly connected” but also “electrically connected” with another element placed therebetween. Additionally, when it is mentioned that a portion “includes” an element, it means that the portion does not exclude but further includes other elements unless there is a special opposite mention.

Fig. 1a is a plan view of a lighting device according to a first embodiment. Fig. 1b is a side view of the lighting device shown in Fig. 1a.

Referring to Figs. 1a and 1b, a light emitting device substrate 11 has a chip on board (COB) type on which an LED chip is mounted or is formed by a surface molding device (SMD) method. A light source 10 emitting a desired color can be formed by applying a circular fluorescent substance on the substrate 11 having a light emitting device formed therein. The substrate may include a printed circuit board (PCB), a metal core PCB (MCPCB), a flexible PCB (FPCB) or a ceramic substrate. Here, while the light source 10 is formed by applying the circular fluorescent substance, there is no limit to this.

Figs. 2a and 2b are views showing light irradiated from a light source of the lighting device according to the first embodiment. Fig. 3 is a view showing a simulation result of light distribution of an LED light source shown in Figs. 2a and 2b.

Referring to Figs. 2a, 2b and 3, the light source 10 has front light distribution and there is little rear light distribution.

Fig. 4 is a perspective view showing a lighting device according to a second embodiment.

Referring to Fig. 4, the lighting device includes a substrate 11, a light source 10 disposed on the substrate 11, and a light guide 20 formed on the light source 10 formed on the substrate 11.

In the embodiment, the substrate 11 may be a PCB and the like. Also, the substrate may include a printed circuit board (PCB), a metal core PCB (MCPCB), a flexible PCB (FPCB) or a ceramic substrate.

In the embodiment, the light source 10 may be an MCP type light emitting device package or may be formed by applying a fluorescent substance on the at least one light emitting device.

The light guide 20 may be disposed on the light source 10 and may be formed on the upper portion of the light source 10 in the form of a cylinder of which the outside diameter is “D” and the inside diameter is “2a”. The diameter of the light guide 20 may be the same as or slightly greater than that of the light source 10. The bottom surface of the light source 10 should not necessarily have a circular shape and may have an elliptical shape or a polygonal shape in accordance with a designed light distribution.

The light guide 20 is formed of a transparent material allowing light to transmit through. The refractive index of the light guide 20 should be greater than that of air in order that the light emitted from the light emitting device is totally reflected into the inside of the light guide 20 by the light guide 20.

Figs. 5a to 5c are views showing a traveling direction of light from the lighting device employing a light guide 20.

Hereafter, travel of the light emitted from the light emitting device will be described with reference to Figs. 4 and 5a to 5c.

As shown in Fig. 5a, the light irradiated from the light source 10 is divided into two kinds of light. One is light which travels straight forward and is irradiated in front of the light source 10 without being reflected by the light guide 20 (see

reference numerals

0, 1, 2 and 3). The other is light which is totally reflected by the light guide 20 (see

reference numerals

4, 5, 6, 7 and 8).

The light emitted from the light emitting device of the light source 10 transmits through an air layer surrounding the light emitting device and is irradiated. Here, since the refractive index of the air layer within the light source 10 is different from that of the light guide 20, the light emitted from the light emitting device is refracted at an interface between two media by Snell’s law. In other words, since the refractive index of the air is less than that of the light guide 20, an angle formed within the light source between the light and a normal is greater than an angle formed in the light guide 20 between the light and the normal. Therefore, when the light emitted from the light source 10 is incident on the light guide 20, an angle formed by the interface and the normal is, as shown in Fig. 5b, reduced. Further, as shown in Fig. 5c,

lights

0, 1, 2 and 3, which are emitted from the light source 10 and form a relatively small angle with the normal of the interface, do not meet a side of the light guide 20 and transmits to the upper portion of the light guide 20.

However, the

lights

4, 5, 6, 7 and 8, which are emitted from the light source 10 and form a relatively large angle with the normal of the interface, meet the side of the light guide 20. Here, the refractive index of the light guide 20 is greater than that of outside air of the light guide 20. Therefore, when an incident angle of light incident on the light guide 20 is greater than a critical angle, total internal reflection (TIR) occurs on all of the incident lights. For example, when the light guide 20 is formed of an acrylic resin (PMMA) having a refractive index of about 1.5, a critical angle for the total internal reflection is 42.03 degree. The refractive index of the light guide 20 should be from 1.4 to 2.0 for the total internal reflection. When the incident angle of the light emitted from the light emitting device of the light source 10 is less than the critical angle, the light may not be totally reflected by the light guide 20 and may be transmitted into the air. Therefore, for the purpose of the total internal reflection of all of the lights incident from the light source 10 to the light guide 20, the refractive index of the medium may be increased.

Fig. 6 is a view showing a light distribution of the lighting device shown in Fig. 4.

Referring to Fig. 6, it can be found that there is no big difference from the light distribution of the light source of Fig. 1a. That is, the light guide 20 guides the light emitted from the light source 10 to the upper portion thereof without having an influence on the light distribution of the light emitted from the light source 10. Here, the light guide 20 guides most of the light without loss through the total internal reflection (TIR). Through this, in the lighting device according to the embodiment of the present invention, the light which is actually emitted from the light source is emitted to the upper portion of the light guide 20.

Next, a structure for increasing the rear light distribution of the lighting device according to the second embodiment will be described.

Fig. 7 is a view showing a lighting device according to a third embodiment.

Referring to Fig. 7, the lighting device employs a reflector 30. Fig. 7 shows that the light from the light source 10 is reflected by the reflector 30. The light distribution efficiency of the reflector 30 may be changed according to the shape of the reflector 30. The reflector 30 may have various shapes, for example, a trigonal pyramidal shape, a poly pyramidal shape, a conical shape, an elliptical shape and the like. Particularly, when the reflector 30 has a polygonal shape, the light distribution efficiency may be changed according to an angle (γ of the following Fig. 9) formed by a reflective surface of the reflector 30 and the top surface of the reflector 30, i.e., an opposite surface to a projecting portion of the reflector 30. Further, when the reflector 30 has an elliptical shape, the light distribution efficiency may be changed in response to an angle formed by a tangent line contacting with the top surface of the reflector 30 and a tangent line contacting with the reflective surface of the reflector 30.

In the lighting device, the reflector 30 is formed on the upper portion of the light guide 20. It can be seen that the light emitted from the light source 10 directly reaches the reflector 30 or is totally internally reflected by the light guide 20, and then reaches the reflector 30. The light which has been incident on the reflector 30 is reflected at the same reflection angle as the incident angle of the light. Also, in the lighting device, an emission point of the light may be moved to the reflector 30 from the light source 10 by the reflector 30. Here, the light guide 20 is able to totally reflect the light irradiated from the light source 10, so that optical loss may be prevented.

Fig. 8 is a sectional perspective view of the lighting device shown in Fig. 7.

As shown in Fig. 8, the light guide 20 covers the entire top surface of the light source 10. Also, the bottom surface of the light guide 20 may be greater than the top surface of the light guide 20. The light guide 20 may include the reflector 30 projecting toward the light source 10. As described above, the light source 10 may be a light emitting device package comprised of a plurality of the light emitting devices or may be formed by applying a fluorescent substance on a single LED chip.

Fig. 9 is a cross sectional view of the lighting device shown in Fig. 7.

Referring to Fig. 9, it can be seen that the height “H” of the light guide 20 is changed according to an angle “γ” formed by the reflective surface of the reflector 30 and the upper horizontal surface of the reflector 30. That is, the more the angle “γ” increases, the more the depth “c” of the reflector 30 and the height “H” of the light guide 20 increase.

The more the angle “γ” decreases, the more an angle formed by a tangent line of the reflector 30 and the light incident on the reflector 30 decreases. Therefore, the light incident on the reflector 30 is reflected again toward the light source 10, and the amount of the light reflected to the side of the light guide 20 is reduced. That is, optical loss occurs due to the repetitive internal reflections. Therefore, the more the angle “γ” increases, the more the amount of the light which is reflected by the reflector 30 and is emitted to the outside of the light guide 20 increases.

The following Table 1 and Table 2 show relationship between numerals shown in Fig. 9.

Table 1

part	-	Length	Unit
a	Source/2	10.00	mm
b	α	11.92	mm
	β	14.28	mm
	α
		50	degree
β
	60	degree
D	Diameter	22.00	mm

Table 2

	γ	C	H
	degree	Height
	50	55	60
1	43	9.33	21.24	23.61	26.65
2	45	10.00	21.92	24.28	27.32
3	46	10.36	22.27	24.64	27.68
4	47	10.72	22.64	25.01	28.04
5	48	11.11	23.02	25.39	28.43

When the angle “γ” increases greater than 60 degree, a magnitude of “α” is excessively reduced. As a result, the light is not emitted to the outside of the light guide 20 and the amount of the light coming and going between the reflector 30 and the light source 10, so that optical loss becomes increased. Therefore, the angle “γ” is required to be from 43 degree to 48 degree so as to obtain the optimum rear light distribution.

Figs. 10a to 10e are views showing traveling paths of light as γ changes from 43 degree to 48 degree when α is 55 degree. In Fig. 10a, when “α” is 55 degree and “γ” is 43 degree, “H” may be 23.61 as shown in Table 2. In Fig. 10b, when “α” is 55 degree and “γ” is 45 degree, “H” may be 24.28 as shown in Table 2. In Fig. 10c, when “α” is 55 degree and “γ” is 46 degree, “H” may be 24.64 as shown in Table 2. In Fig. 10d, when “α” is 55 degree and “γ” is 47 degree, “H” may be 25.01 as shown in Table 2. In Fig. 10e, when “α” is 55 degree and “γ” is 48 degree, “H” may be 25.39 as shown in Table 2.

Fig. 11 is a view showing a traveling direction of light in a state where a body is coupled to the lighting device shown in Fig. 7.

Referring to Fig. 11, a body 40 may be coupled to the lower portion of the substrate 11 on which the light source 10 is formed. The light emitted from the light source 10 may be divided into two lights. One is reflected by the reflector 30 and the other transmits through the light guide 20. Particularly, it can be found that a large amount of the light emitted from the light source 10 travels toward the rear of the lighting device. That is, the lighting device having excellent rear light distribution can be provided. Also, the light emitted from the light source 10 may collide with the body 40 of the lighting device and be refracted.

Fig. 12 is a view showing a cover which is fastened to the lighting device shown in Fig. 7.

Referring to Fig. 12, the cover 50 surrounds and protects the light source 10, the light guide 20 and the reflector 30, and allows the light emitted from the light guide 20 to be distributed to the front or rear of the lighting device through reflection and refraction.

The cover 50 may have a bulb-shaped appearance. The inner surface of the cover 50 may be coated with an opalescent pigment. The pigment may include a diffusion agent which causes light transmitting through the cover 50 to be diffused into the inner surface of the cover 50.

The cover 50 may be made of glass. However, the glass is vulnerable to weight or external impact. Therefore, it is recommended that the cover 50 is made of plastic, polypropylene (PP), polyethylene (PE) and the like. More preferably, it is recommended that the cover 50 is made of polycarbonate (PC) and the like which has excellent light resistance, thermal resistance and impact strength and is used for light distribution.

The roughness of the inner surface of the cover 50 may be larger than that of the outer surface of the cover 50. This intends that the light generated from the light source 10 is irradiated to the inner surface of the cover 50 and then sufficiently scattered and diffused and is emitted outwardly. Accordingly, light emitting property is enhanced.

Fig. 13 is a front view showing the lighting device to which the cover and the body are coupled.

Referring to Fig. 13, the lighting device includes the substrate 11, the light source 10 disposed on the substrate 11, the light guide 20 which is formed on the substrate 11 and surrounds the light source 10, the reflector 30 which is formed in the upper portion of the light guide 20 and has a depressed-shape, the cover 50 which is formed on the substrate 11 and surrounds all of the light source 10, the light guide 20 and the reflector 30, and the body 40 which is disposed beneath the substrate 11 and includes a heat sink of the lighting device.

The reflector 30 may have a shape projecting from the uppermost portion of the light guide 20 in a direction in which the light source 10 is disposed. In the embodiment, the reflector 30 may have a conical shape. In the present specification, the conical shape includes not only a geometrically perfect cone but also a cone of which the bottom surface and conical surface, which form the cone, are curved in the outward or inward direction of the cone. The reflector 30 may have a funnel-shape or a trumpet-shape as well as the conical shape. However, there is no limit to the shape of the reflector 30.

The light via the light guide 20 from the light source 10 is incident on a reflective surface of the lower portion of the reflector 30. The incident light is reflected by the reflective surface and is emitted to the outside. The reflective surface of the reflector 30 may be made of glass and the like which causes specular reflection and may be flat or curved according to a reflection angle.

Fig. 14 is a view showing a traveling path of light irradiated from the lighting device shown in Fig. 13.

Referring to Fig. 14, it can be found that a large amount of the light emitted from the light source 10 travels toward the rear of the lighting device. That is, according to another embodiment of the present invention, the lighting device having excellent rear light distribution can be provided.

Referring to Fig. 15, it can be found that, in the lighting device according to the embodiment of the present invention, light is uniformly distributed to the entire surface of the lighting device and excellent rear light distribution is obtained.

The present invention is not limited to the embodiment described above and the accompanying drawings. The scope of rights of the present invention is intended to be limited by the appended claims. It will be understood by those skilled in the art that various substitutions, modification and changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims. The features, structures and effects and the like described in the embodiments are included in at least one embodiment of the present invention and are not necessarily limited to one embodiment. Furthermore, the features, structures, effects and the like provided in each embodiment can be combined or modified in other embodiments by those skilled in the art to which the embodiments belong. Therefore, contents related to the combination and modification should be construed to be included in the scope of the present invention.

Although embodiments of the present invention were described above, these are just examples and do not limit the present invention. Further, the present invention may be changed and modified in various ways, without departing from the essential features of the present invention, by those skilled in the art. That is, the components described in detail in the embodiments of the present invention may be modified. Further, differences due to the modification and application should be construed as being included in the scope and spirit of the present invention, which is described in the accompanying claims.

Claims

A lighting device comprising:

a light source disposed on a substrate;

a light guide which is disposed on the substrate and surrounds the light source, and of which both ends thereof are opened in such a manner that the light source is exposed; and

a reflector which is disposed on an upper portion of the light guide and reflects light incident from the light source,

wherein the light guide is made of a material having a refractive index greater than 1.4.
The lighting device of claim 1, wherein the light source comprises at least one light emitting device.
The lighting device of claim 1, wherein the reflector is formed to have a conical shape.
The lighting device of claim 1, wherein the reflector comprises a reflective surface made of glass.
The lighting device of claim 1, wherein a reflective surface of the reflector is formed to be flat.
The lighting device of claim 1, wherein an angle formed by a reflective surface of the reflector and an upper horizontal surface of the reflector is from 43 degree to 48 degree.
The lighting device of claim 1, wherein the light guide comprises an acrylic resin (PMMA).
The lighting device of claim 1, wherein the reflector has a shape projecting toward the light source.
The lighting device of claim 1, wherein the light source comprises a light emitting device and a fluorescent substance disposed on the light emitting device.
The lighting device of claim 8, wherein the reflector has a reflective surface formed to reflect the light to the shape.
The lighting device of claim 8, further comprising a cover which is disposed on the substrate and covers the light source, the light guide and the reflector.
The lighting device of claim 11, wherein an opalescent pigment is disposed on an inner surface of the cover.
The lighting device of claim 12, wherein the pigment further comprises a diffusion agent which causes light transmitting through the cover to be diffused into the inner surface of the cover.
A lighting device comprising:

a light source disposed on a substrate;

a light guide which is disposed on the substrate and surrounds the light source, and of which both ends thereof are opened in such a manner that the light source is exposed; and

a reflector which is disposed on an upper portion of the light guide and reflects light irradiated in one direction by the light guide, and reflects light irradiated in the one direction by the light source in a reverse direction to the one direction.
The lighting device of claim 14, wherein the light guide reflects all of the light irradiated from the light source and allows the light to reach the reflector.