KR20140121756A - Side emitting light emitting diode lens - Google Patents

Abstract

The present invention relates to a side emitting type light emitting diode lens capable of evenly emitting lights emitted from a light emitting diode by scattering lights emitted toward sides in a circumference direction by forming a curve part on the side and reducing material costs by reducing the whole volume. The side emitting type light emitting diode lens according to the present invention emitting lights emitted from the light emitting diode toward the sides comprises: a bottom surface having an entering surface in which lights emitted from the light emitting diode enter; an upper surface reflecting lights entered the entering surface; a side surface emitting lights reflected from the upper surface; and the curve part for curving lights in a circumference direction emitted from the side surface and emitting the lights, arranged on the outer surface of the side surface.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a side-emitting type light emitting diode (LED)

The present invention relates to a lens for a side-emitting type light emitting diode which emits light emitted from a light emitting diode (LED) to a side surface.

2. Description of the Related Art Generally, a liquid crystal display (LCD) is provided in a display device used for a computer monitor or a TV. However, such a liquid crystal display device requires a separate light source because it can not emit light by itself .

As a light source for a liquid crystal display device, a plurality of fluorescent lamps such as CCFL (Cold Cathode Fluorescent Lamp) and EEFL (External Electrode Fluorescent Lamp) are used, or a plurality of light emitting diodes (LED) Such a light source is provided in a backlight unit (BLU) together with a light guide plate, a plurality of optical sheets, and a reflection plate.

In recent years, light emitting diodes among these light sources have been attracting attention as a next generation light source because they have low power consumption, good durability, and low manufacturing cost. However, when a light emitting diode is used as a light source, light tends to concentrate and diverge into a narrow area. In order to apply this to a surface light source such as a display device, it is necessary to distribute light evenly over a wide area.

In recent years, studies on a lens for a light-emitting diode that performs such a function are actively under way. A representative example of the conventional technology is disclosed in US Patent No. 6679621, entitled " SIDE EMITTING LED LENS " There is a problem that it is not easy.

Korean Patent No. 10-0639873 (hereinafter referred to as " Prior Art ") discloses a side-emitting light emitting diode and a lens suitable for the same.

1 is a view showing a lens according to the prior art.

1, the lens 1 according to the prior art consists of an incidence surface, an upper surface 2 and a side surface 3, the incidence surface being a convex surface 4, incident surfaces 5 And lower total reflection slopes 6.

The light emitted from the LED 7 and incident on the convex surface 4 of the incident surface is incident on the upper surface 2 in a state of being substantially perpendicular to the convex surface 4 and is incident on the incident surfaces 5 The light is incident on the upper surface 2 in a substantially perpendicular state through the lower total reflection surfaces 6. Then, the light incident on the upper surface 2 in the substantially vertical state as described above is totally reflected on the upper surface 2 and exits through the side surface 3 to the outside.

However, as in the case of the lens 1 according to the prior art, the total height of the lens 1 is very large because it must be inclined upwardly in order to totally reflect the incident light with the top surface 2 being substantially vertical, There is a problem that the overall volume of the lens 1 becomes very large. Further, if the total volume of the lens 1 is increased as described above, the material cost for manufacturing the lens 1 increases, and the manufacturing cost increases.

SUMMARY OF THE INVENTION The present invention provides a lens for a side-emitting type light emitting diode capable of reducing a total volume.

Further, the present invention provides a lens for a side-emitting type light emitting diode capable of diffusing light emitted from a light emitting diode more evenly as a whole by dispersing light emitted to a side surface in a circumferential direction of the lens in a planar direction.

According to an aspect of the present invention, there is provided a side-emitting type light emitting diode lens for emitting light emitted from a light emitting diode (LED) to a side surface, wherein the light emitted from the light emitting diode is incident A bottom surface having an incident surface; An upper surface reflecting light incident on the incident surface; A side surface on which the light reflected from the upper surface is emitted; And a refracting portion provided on an outer circumferential surface of the side surface to refract and emit light incident on the side surface in a circumferential direction on a plane.

Preferably, the side surface includes an upper exit surface through which light reflected from the upper surface is emitted, and a lower exit surface through which light incident on the entrance surface enters and exits directly to the side surface, And the lower emission surface.

Preferably, the refracting portions may be provided continuously or at regular intervals on the outer circumferential surface of the side surface, and more preferably, the refracting portions are provided so as to face each other in a plane so as to refract light emitted to the side surface in opposite directions And may include a pair of refracting surfaces.

Preferably, a stepped portion that is stepped in the inward direction may be provided between the upper emitting surface and the lower emitting surface.

According to the present invention, there is provided a lens for a side-emitting type LED having the above-described structure, wherein a refracting portion is provided on a planar side surface, and light emitted from the side surface is dispersed in a circumferential direction of the lens to emit light, The light uniformity of the backlight unit and the display device can be improved.

According to the lens for a side-emitting type LED according to the present invention, the height of the lens can be reduced by the central region of the incident surface, and the width of the lens can be reduced by the peripheral region of the incident surface, The volume can be further reduced, thereby reducing the material cost and reducing the manufacturing cost.

1 is a vertical sectional view showing a lens according to the prior art,
2 is a perspective view showing a lens for a side-emitting light emitting diode according to an embodiment of the present invention,
Figure 3 is a vertical cross-sectional view of the lens according to Figure 2,
Fig. 4 is a plan view of the lens according to Fig. 2,
5 to 7 are views for explaining various forms of the refracting portion,
8 is a view for explaining the optical condition of the upper surface,
Fig. 9 is a view for explaining the optical condition of the side surface,
10 is a perspective view illustrating a lens for a side-emitting light emitting diode according to another embodiment of the present invention,
11 is a vertical sectional view of the lens according to Fig. 10,
12 is a plan view of the lens according to Fig. 10,
13 and 14 are plan views schematically showing a lens according to still another embodiment of the present invention,
15 is a vertical sectional view showing a lens according to another embodiment of the present invention,
Fig. 16 is a view for explaining the configuration and action of the central region of the lens incident surface according to Fig. 15,
17 is a diagram for explaining the configuration and operation of the peripheral region,
18 is a vertical sectional view showing a lens according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. Rather, the intention is not to limit the invention to the particular forms disclosed, but rather, the invention includes all modifications, equivalents and substitutions that are consistent with the spirit of the invention as defined by the claims.

In the accompanying drawings, the thickness and the size are exaggerated for clarity of description and the present invention is not limited by the relative size or thickness shown in the attached drawings.

The present invention can reduce the overall volume to reduce the material cost and diffuse light emitted to the side surface in the tangential component of the lens by providing a refracting portion on the planar side to emit light from the light emitting diode To a side-emitting type light emitting diode lens which can diffuse the light emitted from the light emitting diode more uniformly as a whole.

FIG. 2 is a perspective view showing a lens for a side-emitting type LED according to an embodiment of the present invention, FIG. 3 is a vertical cross-sectional view of the lens according to FIG. 2, and FIG. 4 is a plan view of the lens according to FIG.

2 to 4, a lens 10 for a light emitting diode (LED) according to an embodiment of the present invention includes a bottom surface 20, an upper surface 30 and a bottom surface 20, And a side surface 40 connecting the upper surface 30.

The bottom surface 20 is provided with an incident surface 100 on which light emitted from a light emitting diode (LED) 11 is incident and an incident surface 100 is formed on the center of the bottom surface 20 And the inner surface of the groove 21.

The upper surface 30 reflects light incident on the incident surface 100 and directly incident on the upper surface 30 to the side surface 40. The upper surface 30 emits light directly incident using a coating or a separate member But it is preferably optically designed to totally reflect the incident light L1. For this, the upper surface 30 may have a central groove 32 having a depressed shape as it approaches the optical axis 12 of the LED 11, so that the shape of the upper surface 30 on the vertical cross- And may be formed in a convex curved shape directed upward in the direction away from the optical axis 12 as the distance from the optical axis 12 increases. The optical condition for totally reflecting the light L1 directly incident on the upper surface 30 will be described later in detail.

The side surface 40 is configured to emit the light L1 reflected from the upper surface 30 to the outside of the lens 10. The side surface 40 is provided with a light L2 that is directly incident on the side surface 40 of the light emitted from the LED 11 and incident on the incident surface 100 as well as the light L1 reflected from the top surface 30, (Not shown). The optical condition for emitting the light L2 directly incident on the side surface 40 to the outside of the lens 10 will be described later in detail.

Preferably, the side surface 40 may have a shape inclined inward by a predetermined angle? As it goes downward. For example, as shown in FIG. 3, the side surface 40 may be an inclined surface tilted inward at a predetermined slope toward the lower side with respect to the optical axis 12 of the LED 11, ≪ / RTI > Thus, not only the entire volume of the lens 10 can be reduced, but also the lower mold can be easily separated when the lens 10 is manufactured by injection molding, thereby making it easy to manufacture.

The light-emitting diode lens is a transparent material having excellent transmittance such as glass, acrylic resin, polymethylmethacrylate (PMMA), polycarbonate (PC), and polyethyleneterephthalate (PET) However, since the lens 10 according to the present invention is formed in a shape in which the side surface 40 is inclined inward, it is difficult to form the upper mold 30. Therefore, Injection molding is possible with only two molds of the lower mold and the lower mold can be easily separated downward.

Therefore, as shown in FIG. 2, the vertical cross-sectional shape of the lens 10 according to the present invention may be an inverted trapezoidal shape having a depressed central portion of the upper surface 30. [

The lens according to the present invention includes a refracting portion 200 provided on the outer circumferential surface of the side surface 40 to refract light L3 emitted to the side surface 40 in a planar tangential component T, . The light L3 emitted to the side surface 40 may be the light that is reflected by the upper surface 30 and emitted from the side surface 40. The light L3 emitted from the side surface 40 may be incident on the incident surface 100 Or light emitted directly from the side surface 40 and incident on the side surface 40 may be emitted. That is, in the present invention, the light L3 emitted to the side surface 40 may be all the light emitted from the LED 11 and incident into the lens 10 out of the lens 10. According to the configuration of the refracting portion 200, the light L3 emitted to the side surface 40 is refracted by the refracting portion 200 to be further dispersed in the circumferential direction T in a plane on the plane and emitted to the outside of the lens 10 So that the lens 10 according to the present invention can diffuse the light emitted from the LED 11 more uniformly as a whole. This is because the backlight unit (back light unit) provided with the lens 10 according to the present invention Unit, BLU) and the display device.

In the lens 10 according to the present invention, the upper surface 30 is formed so as to reflect light directly incident on the LED 11 in a direction away from the optical axis 12 of the LED 11, that is, in a radial component (R) And the refracting unit 200 may be configured to totally reflect the light incident on the side surface 40 in the circumferential direction T of the lens 10 in order to more evenly diffuse the light emitted from the LED 11. [ As shown in FIG.

The lens 10 according to the present invention may further include a leg 50 extending downward from a predetermined position of the bottom surface 20 to support the lens 10. 4, the legs 50 may be provided at a predetermined distance from the LED 11 at predetermined angular intervals, or may be provided continuously at a constant distance from the LEDs 11, that is, in a substantially circular band shape .

Hereinafter, various forms of the refracting section 200 will be described in detail.

Fig. 4 is a plan view of the lens according to Fig. 2, and Figs. 5 to 7 are views for explaining various forms of the refracting portion.

4 to 7, the refracting portion 200 may be continuously provided on the outer circumferential surface of the side surface 40. As shown in FIG. Also, although not shown in the drawings, the refracting portions 200 may be provided at regular intervals on the outer circumferential surface of the side surface 40. When the refracting portion 200 is provided continuously or at regular intervals on the outer circumferential surface of the side surface 40 as described above, the light L3 incident on the side surface 40 is projected in the circumferential direction T of the planar lens 10 So that it is possible to distribute it more uniformly.

Preferably, the refracting portion 200 includes a pair of refracting surfaces 210 that are provided to face each other in the planar view and refract light L3 emitted to the side surface 40 in opposite directions to each other. The light L3 emitted to the side surface 40 is refracted in opposite directions to each other by the pair of refracting surfaces 210 of the refracting portion 200 and is emitted to the outside of the lens 10, The light can be diffused more widely in the direction T, and thus the light emitted from the LED 110 can be more evenly diffused.

4, the refracting portion 200 may have a convex shape outwardly from the outer circumferential surface of the side surface 40. As shown in FIG. 5, the refracting portion 200 may have a concave shape inward from the outer circumferential surface It is possible. 4, in the case where the refracting portion 200 is formed in a convex shape, the light L3 emitted to the side surface 40 is emitted from the pair of refracting surfaces 210, , As shown in FIG. 5, when the refracting portion 200 is formed in a concave shape, the light L3 emitted to the side surface 40 is emitted away from the beginning.

Also, as shown in FIG. 6, the refracting unit 200 may be formed of only a pair of refracting surfaces 210 that are opposed to each other with respect to the center axis 201 and are symmetrical to each other.

As shown in FIG. 7, the refracting portion 200 may be configured such that the first refracting portion 202 having a concave shape and the second refracting portion 203 having a convex shape are alternately connected to each other. In this case, A part of the light L3 emitted to the side surface 40 is emitted in a direction away from each other by the pair of refracting surfaces 211 of the first refracting part 202 and the other part is emitted from the second refracting part 203 Are brought close to each other by a pair of refracting surfaces (212), and are emitted in a direction to move away from each other. In addition, alternate shapes of the first refracting portion 202 and the second refracting portion 203 may be formed continuously or at regular intervals.

Therefore, the present invention is not limited to the specific shape of the refracting portion 200. The refracting portion 200 is provided on the outer peripheral surface of the side surface 40 and is provided with a light L3 emitted to the side surface 40 in the circumferential direction So that it can be refracted evenly.

Meanwhile, it is preferable that the upper surface 30 is optically designed to totally reflect incident light directly. Hereinafter, optical conditions of the upper surface 30 will be described in detail with reference to the drawings.

8 is a view for explaining the optical condition of the upper surface.

8, when an intersection point between the optical axis 12 of the LED 11 and the LED 11 is defined as a reference point P, an arbitrary point P ₁ on the upper surface 30 is connected to the reference point P linear with the optical axis (12) forming for the distance of any point (P ₁₎ and a reference point (P) on each of the α _1, the upper surface (30) R _1, increment of the α ₁ on Δα _1, Δα ₁ of of R ₁ increment (decrease or increase) the ΔR _1, any point on the upper surface (30) (P ₁₎ normal 13 and the straight line that is, any point on the upper surface (30) (P ₁₎ and a reference point in the When the make up each straight line connecting the (P) and the refractive index of the material of the β _1, the lens 10 by n, the upper surface 30 is _{ΔR 1 / (R 1 Δα 1} )> 1 / √ (n 2 - 1) < / RTI > conditions. The above condition becomes an optical condition for optically totally reflecting the light L1 directly incident on the upper surface 30. [

Likewise, it is preferable that the side surface 40 is also optically designed so that the direct incident light L2 is emitted to the outside of the lens 10. The optical conditions of this side surface 40 will now be described in detail with reference to the drawings.

Fig. 9 is a view for explaining the optical condition of the side surface. Fig.

9, when a point of intersection between the optical axis 12 and the LED 11 is defined as a reference point P, a straight line connecting an arbitrary point P ₂ on the side surface 40 and the reference point P and an optical axis 12 ) and the a horizontal axis (16) forms a vertical angle α _2, an arbitrary point (P ₂₎ and the increment of the distance between the reference point (P) R _2, wherein the α ₂ on the side 40 to the Δα _2, Δα ₂ Letting the increment of R ₂ for R _{2 be} ΔR ₂ and the refractive index of the material of the lens 10 be n, the side surface 40 satisfies the condition ΔR ₂ / (R ₂ Δα ₂ ) <1 / √ (n ² -1) . The above condition becomes an optical condition for optically emitting the light L2 directly incident on the side surface 40 to the outside of the lens 10. [

FIG. 10 is a perspective view showing a lens according to another embodiment of the present invention, FIG. 11 is a vertical sectional view of the lens according to FIG. 10, and FIG. 12 is a plan view of the lens according to FIG.

The lens 10 according to the present embodiment differs from the lens 40 according to the above embodiment in the configuration of the side surface 40. Therefore, The description and the reference numerals are used.

10 to 12, the side surface 40 according to the present embodiment includes an upper exit surface 42 through which the light L1 reflected from the upper surface 30 is emitted, And a lower exit surface 44 for direct entry into and exit from the side surface 40.

The side surface 40 may be further provided with a step 45 which is inwardly stepped between the upper exit surface 42 and the lower exit surface 44. [ Thus, when the step portion 45 is provided on the side surface 40, the overall volume of the lens 10 can be further reduced, so that the material cost can be reduced.

The lens 10 according to the present embodiment is provided with the refracting portion 200 provided only on the lower exit surface 44 of the side surface 40 but the present invention is not limited thereto, May be provided on at least one of the upper exit surface (42) and the lower exit surface (44).

Figs. 13 and 14 are plan views schematically showing a lens according to another embodiment of the present invention, Fig. 13 is a plan view showing an embodiment in which the refracting portion 200 is provided only on the upper exit surface 42, Fig. 14 Is a plan view showing an embodiment in which the refracting portion 200 is provided on both of the upper exit surface 42 and the lower exit surface 44.

15 is a vertical sectional view showing a lens according to another embodiment of the present invention. The lens 10 according to the present embodiment differs from the above-described embodiments in the configuration of the incident surface 100, and thus the detailed description and the reference numerals of the same configuration are the same as those of the above- I will.

15, the incident surface 100 according to the present embodiment includes light L4 and L5 diverging within a predetermined angle range with respect to the optical axis 12 among the light emitted from the LED 11, And a side incidence surface 120 that allows the light L6 outside the light incident on the upper incidence surface 110 of the light emitted from the LED 11 to enter the side surface 40 Lt; / RTI &gt;

The upper incident surface 110 includes a central region 112 including the optical axis 12 of the LED 11 and refracting light emitted from the LED 11 in a direction away from the optical axis 12 and making the light enter the upper surface 30 And a peripheral region 114 connected to the central region 112 and refracting the light emitted from the LED 11 in a direction approaching the optical axis 12 and causing the light to enter the top surface 30. [

The central region 112 is formed in a direction away from the optical axis 12 by the light L4 near the optical axis 12, that is, the light L4 diverging toward the center of the upper incident plane 110, And the peripheral region 114 makes the light L5 diverging to the peripheral portion of the upper incident plane 110 among the light emitted from the LED 11 to be incident on the upper surface 30, And incident on the upper surface 30. The side incident face 120 connects the peripheral region 114 and the bottom face 20 and refracts the light L6 outside the light incident on the upper incident face 110 to enter the side face 40. [

The lens 10 according to the present invention having such a structure can reduce the height H of the lens 10 by the central region 112 and reduce the width H of the lens 10 by the peripheral region 114 W) can be reduced.

Fig. 16 is a view for explaining the configuration and action of the central region of the lens incident surface according to Fig. 15;

16, the central region 112 of the incident surface 100 is divided into the light L4 diverging near the optical axis 12 of the LED 11, that is, the light diverging toward the center of the upper incident surface 110 The light L4 is refracted in the direction away from the optical axis 12 in the direction of the arrow and is incident on the upper surface 30. When the light L4 is incident on the upper surface 30, And therefore the upward slope of the top surface 30 for total reflection of such light L4 can be made small. On the other hand, when the light is diverted from the LED 11 as in the prior art and is incident on the upper surface 30 in a state substantially parallel to the optical axis 12, The slope should be very large. That is, as shown in the drawing, the lens 10 according to the present invention can reduce the height of the lens 10 by approximately H by the central region 112.

The central region 112 is formed so as to refract in the direction away from the optical axis 12 the light L4 incident at an arbitrary point P ₃ on the central region 112, The intersection P ₄ between the central region 112 and the peripheral region 114 is the lowest end of the central region 112. In this case,

For example, as shown in the figure, the central region 112 may be a curved line having a peak point in the vertical section on the optical axis 12, and in another embodiment may be a straight line inclined downwardly at a predetermined angle, Or may be formed in a convex shape. In addition, there may be any inflection point P ₅ on the central region 112 so that the central region 112 can be in the form of a smooth curve at the intersection P ₄ .

17 is a diagram for explaining the configuration and operation of the peripheral region,

As seen in Figure 17, the incident surface direction approaching the light (L5) to the peripheral region 114 of the system 100 is incident on the arbitrary point (P ₆₎ on the peripheral region 114 on the optical axis 12 (arrow The light L5 is made closer to the optical axis 12 when it is incident on the upper surface 30 so that the width of the lens 10 . In particular, edge end point of the peripheral region (114) (P ₇₎ by the incident light (L8) is the end point (P _7), the upper surface of the lens 10 according to the present invention is the point where incident on the upper surface 30 is refracted on the 30, the edge end points (P ₈₎ there is formed to, when the peripheral area 114 as shown in the figure thereby refracting the light (L8) in the optical axis 12 direction, and the upper surface 30, edge end point P ₈ 'To P ₈ so that the width of the lens 10 can be reduced by approximately W. [ Therefore, the peripheral region 114, the width of the peripheral region 114, any point (P _6), the light (L5) As to the refractive much in the direction approaching the optical axis 12 lens 10 is incident to the is that much more The width of the lens 10 can be directly reduced as the angle of refraction increases toward the edge of the peripheral region 114.

A peripheral region (114) so as to bends in a direction to approach the light (L2) incident to an arbitrary point (P ₆₎ on the central region 114 in this manner to the optical axis 12, the farther from the optical axis 12 The intersection P ₄ between the central region 112 and the peripheral region 114 is at the lowest end of the central region 112 and at the same time the intersection P ₄ between the central region 112 and the peripheral region 114 And becomes the lowermost end of the peripheral region 114. That is, the intersection point P ₄ is the lowermost end of the upper incident surface 110.

For example, as shown in the figure, the peripheral region 114 may be curved upwardly away from the optical axis 12 in the vertical cross-section, and in another embodiment may have a straight or downwardly convex shape . Preferably, the peripheral region 114 may have a shape in which the inclination of the tangent line increases toward the edge. In this manner, the increasing rate of the upward inclination, that is, the inclination of the tangent line toward the edge of the peripheral region 114 increases The refraction angle in the direction of the optical axis 12 at the edge end point P ₇ of the peripheral region 114 is maximized and thus the width of the lens 10 can be directly and most greatly reduced.

18 is a vertical sectional view showing a lens according to another embodiment of the present invention.

Referring to FIG. 18, the lens 10 according to the present embodiment is configured such that the center region 112 is inclined downward as the vertical section is away from the optical axis 12, and is formed in a straight line inclined in a direction away from the optical axis 12 And the peripheral region 114 is formed in the form of a straight line that is inclined upward and away from the optical axis 12 as it moves away from the optical axis 12 in the vertical section. In this case, the central region 112 and the peripheral region The intersection point P _{4 of the} upper surface 114 is a discontinuous point and is the lowest end of the upper incident surface 110. As described above, the lens 10 according to the present invention is not limited to the specific shape of the central region 112 and the peripheral region 114, and may be formed by reducing the height H of the lens 10, W) can be reduced.

As described above, the present invention can reduce the overall volume and reduce the material cost, and it is possible to reduce the total volume by providing the refracting portion on the planar side surface and dispersing the light emitted to the side surface in the tangential component of the lens The present invention relates to a lens for a side-emitting type light emitting diode capable of diffusing light emitted from a light emitting diode more uniformly as a whole, and the embodiments can be modified in various forms. Accordingly, the present invention is not limited to the embodiments disclosed herein, and all changes which can be made by those skilled in the art are also within the scope of the present invention.

10: lens 11: light emitting diode (or LED)
12: optical axis 20: bottom surface
21: groove portion 30: upper surface
40: side 50: leg
100: incidence plane 110: upper incidence plane
112: center area 114: peripheral area
120: side incidence plane 200:
210: a pair of refracting surfaces

Claims (5)

A side-emitting type light emitting diode lens for emitting light emitted from a light emitting diode (LED) to a side surface,
A bottom surface having an incident surface on which light emitted from the light emitting diode is incident;
An upper surface reflecting light incident on the incident surface;
A side surface on which the light reflected from the upper surface is emitted; And
And a refracting portion provided on an outer peripheral surface of the side surface to refract and emit light emitted to the side surface in a circumferential direction on a plane. The method according to claim 1,
Wherein the side surface includes an upper exit surface through which light reflected from the upper surface is emitted and a lower exit surface through which light incident on the incident surface directly enters and exits from the side surface,
Wherein the refracting portion is provided on at least one of the upper emitting surface and the lower emitting surface. 3. The method according to claim 1 or 2,
Wherein the refracting portion is provided continuously or at regular intervals on an outer circumferential surface of the side surface. The method of claim 3,
Wherein the refracting portion includes a pair of refracting surfaces provided to face each other in a planar manner and to refract and emit light emitted to the side surface in opposite directions. 3. The method of claim 2,
And a stepped portion is formed between the upper emitting surface and the lower emitting surface so as to be stepped in the inward direction.

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