WO2008093970A1

WO2008093970A1 - Led surface-lighting apparatus

Info

Publication number: WO2008093970A1
Application number: PCT/KR2008/000499
Authority: WO
Inventors: Young Ho Yoo
Original assignee: Fawoo Techmology Co., Ltd.
Priority date: 2007-01-30
Filing date: 2008-01-28
Publication date: 2008-08-07
Also published as: TW200901812A

Abstract

An LED surface-lighting apparatus converts point light into surface light while guiding and diffusing light to radiate it in a specific direction, thereby preventing glare and providing high quality lighting, which does not have an adverse effect on the eyes, using LEDs, which have excellent energy conversion efficiency. The surface lighting apparatus of the invention uses the LEDs, mounted on a PCB, as a light source, and includes a heat radiator connected to the printed circuit board and a light guide and diffuser for guiding light from the LED. The light guide and diffuser is formed of a single body, and includes a light-receiving part, which is disposed opposite the LED, and an outer surface light-radiating part, wherein the light-radiating part guides incident light, introduced by the light-receiving part, through a transparent resin portion of the body, to radiate it as surface light.

Description

LED SURFACE-LIGHTING APPARATUS

Technical Field

[1] The present invention relates to an LED lighting apparatus, and more particularly, to an LED surface-lighting apparatus, which converts point light into surface light while guiding and diffusing light to radiate it in a specific direction, thereby preventing glare and providing high quality lighting that does not have an adverse effect on the eyes, using LEDs, which have excellent energy conversion efficiency. Background Art

[2] LEDs (Light Emitting Diodes) have various advantages over conventional light sources, such as small size, long lifetime, low power consumption and excellent energy efficiency, owing to the direct conversion of electric energy into light energy, and high speed response. Accordingly, various lighting apparatuses using LEDs are under development.

[3] However, LEDs are a point source of light and produce high glare due to the straight traveling characteristic of light, which may damage the eyesight. Accordingly, LEDs are generally used for special lighting in exhibition halls or as headlights for vehicles, but there are problems with the implementation of LEDs in general lighting apparatuses.

[4] Multiple filters may be used to prevent glare. However, these filters entail problems of low brightness and reduced electric energy efficiency. Disclosure of Invention Technical Problem

[5] The present invention has been made to solve the foregoing problems with the prior art, and therefore the present invention provides an LED surface-lighting apparatus, which converts point light into surface light while guiding and diffusing light to radiate it in a specific direction, thereby preventing glare and providing high quality lighting, which does not have an adverse effect on the eyes, using LEDs, which have excellent energy conversion efficiency.

Technical Solution

[6] According to an aspect of the invention for realizing the foregoing object, the surface lighting apparatus of the invention uses at least one LED, mounted on a Printed Circuit Board (PCB), as a light source, and includes a heat radiator connected to the printed circuit board and a light guide and diffuser for guiding light from the LED.

[7] In the surface lighting apparatus of the invention, the light guide and diffuser is fo rmed of a single body, and includes a light-receiving part, which is disposed opposite the LED, and an outer surface light-radiating part, wherein the light-radiating part guides incident light, introduced by the light-receiving part, through a transparent resin portion of the body, to radiate it as surface light.

Advantageous Effects

[8] The LED surface-lighting apparatus of the invention has excellent effects. That is, the LED surface-lighting apparatus converts point light into surface light while guiding and diffusing light to radiate it in a specific direction, thereby preventing glare and providing high quality lighting, which does not have an adverse effect on the eyes, using LEDs, which have excellent energy conversion efficiency.

Brief Description of the Drawings [9] FIG. 1 is a perspective view illustrating the construction of an embodiment of the invention; [10] FIG. 2 is a perspective view illustrating an example of the structure of the light guide and diffuser of FIG. 1 ; [11] FIG. 3 is a perspective view illustrating another example of the structure of the light guide and diffuser of FIG. 1 ; [12] FIG. 4 is a bottom view of FIG. 2;

[13] FIG. 5 is a half cross-sectional view illustrating a light guide and diffuser according to an embodiment of the invention; [14] FIG. 6 is a half cross-sectional view illustrating a light guide and diffuser according to another embodiment of the invention; [15] FIG. 7 is a cross-sectional view illustrating a light guide and diffuser according to a further embodiment of the invention; [16] FIG. 8 is a half cross-sectional view illustrating a light guide and diffuser according to still a further embodiment of the invention; [17] FIG. 9 is a perspective view illustrating a light guide and diffuser according to still another embodiment of the invention; [18] FIG. 10 is an exploded perspective view illustrating the construction of an embodiment of the invention;

[19] FIG. 11 is a bottom view illustrating the PCB of FIG. 1 ;

[20] FIG. 12 is a view illustrating an example of the construction of light guide and diffusers of the invention; [21] FIG. 13 is a view illustrating the refraction of incident light in an acryl plate, which is used as a light guide and diffuser in the invention; [22] FIG. 14 is a view illustrating the refraction of incident light in an example of a light guide and diffuser of the invention; [23] FIG. 15 is a plan view illustrating the refraction of light toward the outer cir- cumference in an example of a light guide and diffuser of the invention;

[24] FIG. 16 is a view illustrating an example of the construction of the invention; and

[25] FIG. 17 is a view illustrating another example of the construction of the invention.

[26] <Major Reference Signs of Drawings>

[27] 1: LED surface-lighting apparatus

[28] 2: screw-thread socket 10: housing

[29] 11 : screw-thread connector 21 : transformer

[30] 23: PCB 25: LED

[31] 30: light guide and diffuser 30a: light-receiving part

[32] 30b: light-radiating part 30c: inner recess

[33] 31: lens part 32: scratch

[34] 33: perpendicular groove 34: bottom

[35] 34a: inclined surface 37: reflector sheet

[36] 39: light-refracting recess 40: heat radiator

[37] 30s: multiple light guide and diffuser

Mode for the Invention

[38] Hereinafter, exemplary embodiments of the LED surface-lighting apparatus of the present invention will be described more fully in conjunction with the accompanying drawings.

[39] FIG. 1 is a perspective view illustrating the construction of an embodiment of the invention.

[40] As shown in FIG. 1, an LED surface-lighting apparatus 1 according to this embodiment of the invention includes one or more LEDs 25, which are mounted on a PCB 23 and are used as a light source, a heat radiator 40, connected to the PCB 23, and a light guide and diffuser 30 for guiding light from the LEDs 25.

[41] The light guide and diffuser 30 is made of a single body, and includes a light- receiving part 30a, which is disposed opposite the LEDs 25 to introduce light, and an outer surface light-radiating part 30b. The light-radiating part 30b guides the incident light through a transparent resin portion of the body, and radiates the incident light as surface light through the outer surface thereof.

[42] Preferably, the light guide and diffuser 30 is provided with at least one component selected from the group comprising V-shaped grooves, dots, a sanded surface and scratches 32 (see FIGS. 1 to 4).

[43] The sanded surface is produced by abrading the surface of the light-radiating part with a sheet of sandpaper, so that the surface becomes translucent.

[44] Desirably, the light guide and diffuser 30 is made of a light-transmitting resin molding, in which the light-receiving part 30a, contacting the LEDs 25, and an inner recess 30c is formed. [45] As shown in several drawings including FIG. 5, the inner recess 30c desirably has a

V-shaped cross section. [46] The light guide and diffuser 30 may also have a light-diffusing lens part 31 in the light-receiving part 30a. [47] The lens part 31 may have formed therein a plurality of recesses 31a, each of which acts as a concave lens (see FIG. 2), or a circular groove 31b, which is formed in a concentric circle drawn around the center of the light guide and diffuser (see FIG. 3). [48] Desirably, light-diffusing grooves 33 are formed in the outer circumference of the light guide and diffuser 30, in the direction perpendicular to the light emitting direction of the LEDs. [49] The farther the perpendicular groove 33 is from the LEDs 25, the larger its depth

33d or width 33a may be. [50] This is because the perpendicular groove 33 having a larger depth 33d or width 33a can diffuse more LED light, thereby producing smooth light, so that a point source of light is not seen from below. [51] The light guide and diffuser 30 may have various outer configurations, such as a cylinder (see FIG. 1), a cone (see FIG. 6), or a frustum of a cone in which the bottom

34 is wider than the light-receiving part 30a (see FIGS. 7 and 8). [52] Alternatively, the light guide diffuser 30 may have an inclined bottom surface 34 for radiating light (see FIG. 9). [53] The light guide and diffuser 30 may also include a reflector sheet 37, which is provided on a portion of the inner circumference or the outer surface of the inner recess 30c. [54] The reflector sheet 37, provided on the outer circumference, is used to radiate light in one direction. [55] Especially, since light exits to the rear of the inclined surface 34 when reflected from the inclined surface 34 at an angle smaller than a critical angle, the reflector sheet

37 is desirably provided on the entire outer surface, except for the inclined surface 34a, in order to radiate light through only the inclined surface (see FIG. 9). [56] According to the exemplary embodiment of the invention shown in FIG. 10, a plurality of light guides and diffusers 30 is provided on one PCB 23, and the light- receiving part 30a of each light guide and diffuser 30 is circularly shaped. [57] On the PCB 23, a plurality of LEDs 25 is arranged so as to correspond to the array of the light guide and diffusers 30 (see FIG. 11). [58] As an alternative, the light guide and diffusers 30 may be connected with each other, thereby forming a single body of multiple light guide and diffuser 30s (see FIG.

12). [59] The light guide and diffuser 30 may be provided with lugs 36 for coupling with the heat radiator 40.

[60] According to another embodiment of the invention as shown in FIG. 17, the light guide and diffuser 30 may have a light-refracting recess 39, which is formed in the bottom thereof, and is concave from below, thereby forming an inverted V-shaped (i.e., Λ-shaped) cross section.

[61] Desirably, the light-refracting recess 39 is configured as a single cone-shaped recess having an inverted V shape, and the diameter 39a of the bottom circle of the cone- shaped recess has the maximum size that can be obtained from the bottom of the light guide and diffuser 30.

[62] Below, a description will be made of the operation of the LED surface-lighting apparatus 1 of the invention, which has the above-described construction.

[63] First, the light refracting properties of acryl, which is used for the light guide and diffuser of the invention, will be discussed with reference to FIG. 13.

[64] In theory, the refractive index n of acryl is 1.49 and the total reflection angle θc thereof is 42.155°.

[65] The total reflection condition is θ>θc. That is, total reflection occurs when the refraction angle is larger than 42.155°.

[66] In FIG. 13, when the incidence angle is α, refraction occurs on 'Surface 1' according to the following relationships.

[67] sin(90-α) = nDsin(90-θ)

[68] => cosα = nDcosθ

[69] ^ θ = cos-l(l/nDcosθ)

[70] In the above relationships, 47.84° < θ < 90° is produced from 0° < α <90°.

[71] Since this necessarily satisfies the relationship θ > θc, total reflection always occurs in acryl. Accordingly, incident light cannot exit through 'Surface 2' unless a scratch is formed in the surface, through which light may exit.

[72] The invention utilizes the light refracting properties of acryl in order to guide and diffuse LED light not only in the straight emission direction but also through the entire 360° circumference and the entire area of the bottom 34, thereby preventing glare and converting point light into surface light in a desired specific direction.

[73] Furthermore, the light guide and diffuser 30 of the invention is provided with the lens part 31 in the light-receiving part 30a and the inner recess 30c in the inner portion thereof, so that straight rays from the LEDs can refract successively at the lens part 31, the outer circumference of the light guide and diffuser 30, and the inner circumference of the inner recess 30c, thereby performing diffusion by refraction while traveling through the inner circumference and the outer circumference of the light guide and diffuser. Accordingly, the rays, generated from a point source of light, are converted into surface light (see FIGS. 14 and 15).

[74] That is, when light from the LEDs 25 enters the light-receiving part 30a, it is diffused to the inner circumference and the outer circumference by the lens part 31, which is configured to refract and diffuse light at various angles. During the diffusion, the incident light is refracted successively along the inner circumference and the outer circumference.

[75] The inner recess 30c having a V-shaped cross section performs an important function of refracting again the incident light, which enters from the LEDs or through the outer circumference, so that the incident light can successively refract.

[76] Moreover, the light-receiving part 30a of the light guide and diffuser 30 is provided with the light-diffusing lens part 31, which increases the diffusion angle of light in the light guide and diffuser, thereby further enhancing the diffusion effect.

[77] That is, the recesses 31a of the lens part 31, in contact with the LEDs 25, act as a concave lens, so that light can widely refract and diffuse in all directions, including the inner and outer circumferences of the light guide and diffuser 30.

[78] In addition, the circular groove 31b of the lens part 31, formed in a circle concentric to the outer circumference of the light guide and diffuser, is devised to act as a concave lens but not to interfere with the LEDs 25 when the light guide diffuser 30 rotates to engage with a housing 10.

[79] The reflector sheet 37, applied to the inner recess 30c of the light guide and diffuser

30, can reflect incident light entering through the outer circumference or the bottom 34 even if the incidence angle is larger than the reflection angle. This, as a result, prevents any loss of brightness.

[80] The scratches 32, such as a V-shaped groove, formed in the outer circumference of the light guide and diffuser 30, act as a light diffusing channel, which scatters light to increase the light diffusion rate, thereby providing more smooth lighting.

[81] The perpendicular grooves 33, formed in the outer circumference of the light guide and diffuser 30, act to block and radiate strong rays, which are directed straight to the inner or outer circumference. The transmission of light is partially interrupted, and the rays further diffuse while scattering to the outside, thereby being radiated smoothly.

[82] When the depth 33d or the width 33a of a perpendicular groove 33 is set to be larger as the perpendicular groove 33 is located farther from the LEDs 25, the diffusion of light can be maximized to the extent that a point source of light is not seen from the bottom 34. This represents high quality light irradiation, which ensures high luminance but prevents glare.

[83] In the case where the outer shape of the light guide and diffuser 30 is a cylinder having parallel top and bottom surfaces, or a cone, as shown in FIG. 6, which has V- shaped grooves, sanded scratches or perpendicular grooves 33 formed therein, the entire 360° circumference and the bottom 34 of the light guide and diffuser 30, that is, all of the outer surfaces of the lighting apparatus, act as a light-radiating part. The frustum of the cone concentrically radiates light in one direction through the bottom 34 (see FIG. 7). In a combination of the cone and the frustum of the cone (see FIG. 8), light can be radiated through the bottom and a conical portion.

[84] In the case where the inclined bottom surface 34 is provided (see FIG. 9), light is guided and diffused by only the inclined bottom surface 34, and thus is radiated in one direction. This structure is effective in a case, such as a desk lamp, in which lighting concentrated in one direction is required.

[85] Accordingly, the shape of the light guide and diffuser 30 can be suitably set according to the use of lighting or the location of the lighting apparatus.

[86] Furthermore, the light guide and diffuser 30, which has a greater length from the light-receiving part to the bottom 34, can further enhance light refraction and scattering, thereby preventing glare and improving light quality.

[87] The size of the lighting apparatus can be set variously from a small capacity to a large capacity by increasing the size of the PCB 23 and mounting a plurality of the light guides and diffusers 30 on the PCB 23.

[88] The light guide and diffusers 30 can be configured as a plurality of light guides and diffusers 30 in order to facilitate ease of assembly.

[89] The perpendicular grooves 33, formed in the outer circumference of the light guide and diffuser 30, may cause a decrease in brightness owing to the accumulation of dust or foreign materials as time passes.

[90] As shown in FIG. 17, the cone-shaped light-refracting recess 39, which is concave from the bottom of the light guide and diffuser 30, can prevent dust or foreign materials from accumulating while diffusing light to the circumference.

[91] That is, the inclined surface 39b of the light-refracting recess 39 causes a portion of incident light from the LEDs to enter at an angle greater than a critical angle, so that the light portion refracts and is radiated through the outer circumference instead of traveling straight.

[92] As set forth above, the invention converts point light from the LEDs into surface light in order to prevent glare and also guide and diffuse light to radiate it in a specific direction. As a result, the invention can provide high quality lighting, which does not have an adverse effect on the eyes, using LEDs, which have excellent energy conversion efficiency.

[93] Furthermore, the size of the lighting apparatus can be set variously, from a small size to a large size.

[94] As shown in FIG. 16, a transformer 21, which converts AC to DC, is connected to the PCB 23, and the transformer 21 and the PCB 23 are provided inside a separate housing 10, which is provided with a screw-thread connector 11 corresponding to a typical screw-thread socket 2, which conducts AC power. The lighting apparatus of the invention has general usability, that is, it is usable with both AC power and DC power.

[95] The exemplary embodiments of the present invention have been described hereinbefore with reference to the accompanying drawings. The terms and language used in the description and the claims of the present application should be construed in view of the concept and the principle of the invention, but should not be limited to a typical or literal translation thereof. Accordingly, the embodiments described herein and the constructions illustrated in the drawings are intended to illustrate the most desirable embodiments of the invention, but not to represent all aspects of the principle. On the contrary, it should be understood that various equivalents and modifications, which can replace the above-described embodiments, may be possible when this invention is embodied. Industrial Applicability

[96] As set forth above, the LED surface lighting apparatus of the invention converts point light from the LEDs into surface light in order to prevent glare and also guide and diffuse light to radiate it in a specific direction. As a result, the LED surface lighting apparatus of the invention can provide high quality lighting, which does not have an adverse effect on the eyes, using LEDs, which have excellent energy conversion efficiency.

Claims

[1] A surface lighting apparatus using at least one light emitting diode, mounted on a printed circuit board, as a light source, the surface lighting apparatus comprising a heat radiator connected to the printed circuit board and a light guide and diffuser for guiding light from the light emitting diode, wherein the light guide and diffuser is formed of a single body, and includes a light-receiving part, which is disposed opposite the light emitting diode, and an outer surface light-radiating part, wherein the light-radiating part guides incident light, introduced by the light-receiving part, through a transparent resin portion of the body, to radiate it as surface light.

[2] The surface lighting apparatus according to claim 1, wherein the light-radiating part of the light guide and diffuser have at least one selected from the group consisting of a V-shaped groove, dots, a sanded surface portion and a scratch.

[3] The surface lighting apparatus according to claim 1, wherein the light guide and diffuser is made of a light-transmitting resin molding, and has an inner recess in an inner portion of the molding, and the light-receiving part contacts a plurality of the light emitting diodes.

[4] The surface lighting apparatus according to claim 3, wherein the inner recess of the light guide and diffuser has a V-shaped cross section.

[5] The surface lighting apparatus according to claim 1, wherein the light-receiving part of the light guide and diffuser has a lens part, which diffuses light.

[6] The surface lighting apparatus according to claim 5, wherein the lens part has individual concave recesses, each of which acts as a concave lens, or a circular groove, which is formed along a concentric circle drawn around the center of the light guide and diffuser.

[7] The surface lighting apparatus according to claim 1, wherein the light guide and diffuser has a perpendicular groove, which is formed in the outer circumference of the light guide and diffuser in a direction perpendicular to a light emitting direction of the light emitting diode, in order to diffuse light.

[8] The surface lighting apparatus according to claim 7, wherein a depth or a width of the perpendicular groove increases as the perpendicular groove is located farther away from the light emitting diode.

[9] The surface lighting apparatus according to any of the preceding claims 1 to 5 and 7, wherein the light guide and diffuser is shaped as a cylinder, a cone, or a frustum of a cone having a bottom wider than the light-receiving part.

[10] The surface lighting apparatus according to claim 9, wherein the light guide and diffuser has an inclined surface in the bottom, which radiates light.

[11] The surface lighting apparatus according to claim 1 or 2, wherein a reflector sheet is applied on a portion of the inner circumference or the outer surface of the inner recess.

[12] The surface lighting apparatus according to claim 1, wherein the light-receiving part of the light guide and diffuser is circularly shaped, and a plurality of the light guides and diffusers is mounted on a single printed circuit board.

[13] The surface lighting apparatus according to claim 12, wherein the light guide and diffusers are connected with each other, thereby forming a single body comprising a plurality of light guides and diffusers.

[14] The surface lighting apparatus according to claim 1, wherein the light guide and diffusers has a light-refracting recess, which is concave from a bottom thereof, thereby forming an inverted V-shaped cross section.

[15] The surface lighting apparatus according to claim 14, wherein the light-refracting recess is shaped as a single cone having an inverted V-shaped cross section, and a bottom circle of the cone-shaped recess has a maximum diameter that is obtainable from the bottom of the light guide and diffuser.