KR100701318B1 - Light emitting unit and back light apparatus using the same - Google Patents

Abstract

Disclosed is a light emitting unit having a structure capable of increasing luminance.

The disclosed light emitting unit includes a base; A light emitting diode mounted on the base and emitting light; A first refraction portion installed on the base and drawn in a conical groove shape for refraction and transmission of light incident from the light emitting diode, and a second refraction portion for refraction and transmission of incident light formed at a predetermined curvature around the first refraction portion. And a lens formed in a cylindrical shape around the second refraction portion and having a transmission portion for transmitting incident light, wherein the light emitted from the light emitting diode is emitted through the first, second refraction portion or transmission portion. It is done.

Description

Light emitting unit and back light apparatus using the same

1 is a schematic cross-sectional view showing a conventional edge-emitting backlight device.

Figure 2 is a schematic cross-sectional view showing a light emitting unit according to an embodiment of the present invention.

3 is a partial cross-sectional perspective view of FIG. 2.

4 is a view showing an optical path of the illumination light at the first refractive portion.

5 is a view showing the optical path of the illumination light when the right angle of the first refraction portion is less than 80 °.

6 is a view showing the optical path of the illumination light when the right angle of the first refraction portion exceeds 120 °.

7 is a view showing an optical path of the illumination light when the radius of curvature of the second refractive portion exceeds 3mm.

8 is a view showing a direction angle distribution of illuminated light in the light emitting unit according to the embodiment of the present invention.

9 is a schematic cross-sectional view showing a backlight device according to an embodiment of the present invention.

FIG. 10 is a view illustrating a luminance distribution of illuminated light in the backlight device of FIG. 9. FIG.

Explanation of symbols on the main parts of the drawings

20 ... Light emitting unit 21 ... Light emitting diode

31.Base 35 ... Protective

37.Adhesive 40 ... Lens

41 First Refraction 43 Second Refraction

45 ... transmitter 61 ... reflective plate

63.Diffusion Plate 65 ... Prism Sheet

70 ... LCD panel

The present invention relates to a light emitting unit using a light emitting diode and a backlight device employing the same. More particularly, the present invention relates to a light emitting unit having a structure capable of increasing luminance and a direct light emitting backlight device employing the same.

In general, a liquid crystal display device, which is a kind of light receiving type flat panel display, does not have its own light emitting capability, and thus forms an image by selectively transmitting illumination light emitted from the outside. To this end, a backlight device for illuminating light is provided on the back of the liquid crystal display.

The backlight device is classified into a direct light type and an edge light type according to the arrangement of the light sources. The direct emission type is a method in which a lamp installed directly below the liquid crystal panel directly irradiates light directly onto the liquid crystal panel. On the other hand, the edge emitting type is a method in which a lamp installed at an edge of a light guide panel (LGP) irradiates light and transmits the irradiated light to the liquid crystal panel through the light guide plate.

1 is a schematic cross-sectional view showing a conventional edge-emitting backlight device. Referring to the drawings, cold cathode fluorescent lamps (CCFLs) are provided at both edges of the light guide plate 3. The bottom of the light guide plate 3 is formed with a reflector 9 for emitting light incident from the CCFL 1 toward the liquid crystal display device (hereinafter referred to as LCD) panel 10. Therefore, the light irradiated from the CCFL 1 is incident on the light guide plate 3 through the edge. The incident light is converted into surface light by the light guide plate 3 and the reflecting plate 9 and is emitted to the upper surface of the light guide plate 3.

The diffusion plate 5 and the optical prism sheet 7 are disposed on the upper surface of the light guide plate 3. Therefore, the light emitted to the upper surface of the light guide plate 3 is diffused by the diffuser plate 5, and then travels toward the LCD panel 10 with the path corrected by the optical prism sheet 7. .

On the other hand, the conventional backlight device described above has the advantage that by adopting the CCFL (1) as a light source, it is possible to obtain a strong white light of high brightness, high uniformity, it is possible to design a large area. However, since the CCFL 1 uses mercury as the discharge gas, it cannot be free from environmental problems. In addition, since the light guide plate 3 and the optical prism sheet 7 are used to change the light illuminated at the edge in the vertical direction, and the light guide plate 3 and the optical prism sheet 7 are used to correct the path of the illumination light, it is necessary to secure a space occupied by these optical elements. The disadvantage is that there is a limit to reducing the overall thickness of the backlight device. In addition, there is a problem that the color reproduction rate is very low at about 74% level compared to the standard of the National Television System Committee (NTSC).

On the other hand, as a light source replacing the above-described CCFL, a light emitting unit using a light emitting diode (LED) is emerging. Unlike the CCFL, which is a linear light source, the light emitting diode is a point light source, and has the advantages of longer life, wider operating temperature range, environmental friendliness, and high color reproducibility than the CCFL. In addition, there is an advantage that it is possible to illuminate the light of a high luminance depending on the structure.

However, when the backlight unit is configured by arranging such a high brightness light emitting unit at the edge of the light guide plate, light is not sufficiently transmitted to the center portion of the LCD panel in illuminating light over the entire large area of the LCD panel. Accordingly, there is a problem in that the dark portion is formed in the portion. In addition, since the backlight device having such a structure employs both the light guide plate and the optical prism sheet, there is a limit in thickness reduction compared to the case where the CCFL is used as the light source.

Accordingly, an object of the present invention is to provide a light emitting unit having an improved structure to reduce the bright lines by increasing the luminance and changing the path of light beams vertically directed by the light emitting device. There is this.

In addition, another object of the present invention is to provide a backlight device capable of implementing thinner and larger screen illumination by excluding a light guide plate by employing the light emitting unit described above.

In order to achieve the above object, a light emitting unit according to the present invention includes a base; A light emitting diode mounted on the base and emitting light; A first refraction portion installed on the base and formed in a conical groove shape to refractively transmit the light incident from the light emitting diode, and a refraction transmission of incident light having a predetermined curvature around the first refraction portion. And a lens including a second refractive portion and a transmissive portion formed in a cylindrical shape around the second refractive portion to transmit incident light, wherein the light irradiated from the light emitting diodes is exposed to the first, second refractive portion, or transmissive portion. Characterized in that to be emitted through.

In addition, the backlight device according to the present invention in order to achieve the above another object, and a reflecting plate for reflecting the incident light; A light source including a plurality of light emitting units on the reflecting plate to illuminate light; A diffuser plate disposed on the light source to diffusely transmit light illuminated by the light emitting unit; And a prism sheet for converting the propagation path by refracting the light diffused through the diffusion plate.

Hereinafter, a light emitting unit and a backlight device employing the same according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2 and 3, the light emitting unit according to the embodiment of the present invention includes a base 31, a light emitting diode 21 mounted on the base 31, and a light emitting unit 21 mounted on the base 31. It includes a lens 40 for determining the emission direction of the light illuminated from the light emitting diode (21).

The light emitting diode 21 is a point light source, and illuminates light having a predetermined wavelength at a wide radiation angle on the surface facing the lens 40.

The lens 40 has a structure in which the light emitted from the light emitting diode 21 can be deflected laterally to the light which is illuminated in a direction perpendicular to or close to the top surface of the base 31. That is, the lens 40 has a structure recessed in the shape of a conical groove, and has a first refractive portion 41 for refractive-transmitting incident light and a predetermined curvature around the first refractive portion 41 to generate incident light. The second refraction portion 43 for refractive transmission and the transmission portion 45 is formed in a cylindrical shape around the second refraction portion 43 to transmit incident light.

The first refraction portion 41 is disposed above the center of the light emitting diode 21 and has a structure in which the first refraction portion 41 is drawn in a conical groove shape. Therefore, the light incident on the first refractive surface 41a of the first refractive portion 41 in the light emitting diode 21 is spread at a larger exit angle than the angle of incidence at the first refractive portion 41 so that the light is wide. Spread at even intervals.

Referring to FIG. 4, an optical path according to an incident position of light incident on the first refractive portion 41 will be described. In the drawing, only the first to third incident light 51a, 51b, and 51c of the light rays incident on the first refractive surface 41a are illustrated. Here, the first incident light 51a, the second incident light 51b, and the third incident light 51c are arranged in a direction far from the side close to the center 42 of the first refractive portion 41.

Referring to the drawings, the angle of incidence at the first refractive portions 41 of each of the first to third incident lights 51a, 51b, and 51c is u ₁ , u ₂ , u ₃ , and the angles of refraction u ₁ ′, u _{In the case of 2} ', u ₃ ', the incident angle increases in the order of u ₁ <u ₂ <u ₃ , and the magnitude of the refractive angle increases in the order of u ₁ '<u ₂ '<u ₃ '. As described above, as the angle of refraction of the light incident on the first refraction portion 41 increases toward the farther from the side closer to the center 42, the distribution of the emitted light is distributed outward relative to the center.

In order to have a larger refractive angle than the incident angle as described above, the d-line refractive index n _d1 of the lens 40 is preferably made of a transparent material satisfying Equation 1 below.

Examples of the transparent material constituting the lens 40 may include plastic materials such as epoxy resin having a d-line refractive index of 1.54, polymethyl methacrylate (PMMA), polycarbonate (PC), and acrylic resin.

As such, the reason why the light distribution in the center of the lens 40 is reduced by using the first refraction portion 41 is that the light emitting unit 20 according to the present embodiment is generally fixed to a certain area when the light emitting unit 20 is applied to the display unit. To bend.

That is, when applied to the display unit, when looking at the light path from the light emitting diode 21 to the diffusion plate, the distance of the outside light is far longer than the light close to the center, the configuration such as the lens 40 is excluded If so, it can lead to uneven brightness. By employing the lens 40 to reduce the light distribution in the center of the lens 40, it is possible to have a constant brightness.

To this end, the right angle θ of the conical groove of the first refractive portion 41 preferably satisfies Equation 2 below.

When the right angle θ of the conical groove is smaller than 130 °, as shown in FIG. 5, the light rays 51 'directed to the first refractive surface 41a among the light rays emitted from the light emitting diodes 21 do not refractory and are totally reflected and effective. It becomes impossible to use it as light, which causes a problem of reducing light efficiency. Here, the right angle condition of the conical groove to be total reflection is determined from the relationship between the right angle θ and the critical angle θ _c according to the difference in refractive index of the lens 40 and the refractive index of the surrounding medium (for example, air). That is, by making the right angle θ larger than 130 °, the incident angles u ₁ , u ₂ , u ₃ of the incident light with respect to the first refractive surface 41a may be set to be smaller than the critical angle θ _c , and thus the first refractive surface 41 a. Can be prevented from total reflection. The critical angle θ _c is defined by Equation 3 below.

Here, n ₀ is the refractive index of the air outside the lens 40, n is the refractive index of the lens 40.

On the other hand, when the right angle θ of the conical groove is greater than 160 °, as shown in FIG. 6, the incident angles u ₁ , u ₂ , u ₃ of the light illuminated by the light emitting diodes 21 and directed toward the first refractive surface 41 a are As a result, the refraction angles u ₁ ′, u ₂ ′, and u ₃ ′ are also reduced, resulting in a narrow orientation angle. In this case, there is a problem that a bright line may be observed in the LCD panel when the LED panel is employed in a direct light emitting unit that illuminates light on the LCD panel.

The second refractive portion 43 has a second refractive surface 43a having a predetermined curvature so as to deflect and transmit the light ray 53 directly incident on the light emitting diode 21 to the side. Here, the second refractive surface 43a is preferably a spherical surface having a radius of curvature of 1 mm to 3 mm. In this case, when the radius of curvature is greater than 3 mm, as shown in FIG. 7, the light incident from the light emitting diode 21 and incident on the second refractive portion 43 has a large refractive angle at the second refractive surface 43a. Don't have Therefore, when illuminating light on the LCD panel, a problem arises that the illumination area is narrowed.

On the other hand, when the curvature of the refracting surface 43a is less than 1 mm, it is difficult to secure a sufficient size of the refracting surface 43a, and it is difficult to properly arrange the first refraction portion 41 and the transmission portion 45.

The transmission part 45 is a tapered cylindrical structure having no curvature structure. In this way, the transmissive portion 45 is formed in a planar manner, so that the light is emitted from the light emitting diode 21 at a large radial angle 55 so as to travel at a desired orientation angle, for example, in the range of approximately 50 ° to 70 °.

In the embodiment of the present invention, it is preferable that the cup member 32 formed at a predetermined height around the light emitting diode 21 on the base 31 is further provided. The cup member 32 is provided to surround the light emitting diode 21 with a protective member 35 to be described later. The height of the cup member 32 should be formed to a height that does not interfere with the path of the light traveling to the transmission portion 45. If a part of the light directed to the transmission part 45 is incident on the cup member 32, the incident light is reflected by the cup member 32 and is directed to a path other than the desired traveling path, causing performance degradation. Let's do it. In view of this, the height of the cup member 32 is formed to be equal to or slightly higher than the height of the light emitting diode 21. More preferably, it is formed to a height of about 0.6 mm or less.

It is preferable that the protection member 35 is further provided in the inner space of the cup member 32. The protection member 35 is made of a transparent material that transmits incident light to protect the light emitting diode 21 and the lens 40.

The protection member 35 is installed on the base 31 and is located between the light emitting diode 21 and the lens 40. By placing the protective member 35 on the light emitting diode 21, the wires connected to the light emitting diode 21 and the base 31 can be protected. In addition, the heat generated during the illumination of the light emitting diode 21 may be blocked from being directly transmitted to the lens 40, thereby preventing yellowing of the lens 40 due to heat.

The protection member 35 may be made of the same material as the lens 40 or may be made of a transparent material having a relatively low refractive index than the lens 40. When the protective member 35 is formed of a material having a lower refractive index than the lens 40, the light illuminated by the light emitting diodes 21 is an interface between the protective member 35 and the lens 40. To prevent total reflection. That is, since total reflection occurs when a material having a high refractive index is incident to an angle greater than a critical angle, when the protective member 35 is made of a material having a lower refractive index than the refractive index of the lens 40 as described above, the boundary surface It can fundamentally prevent total reflection from.

More preferably, the protection member 35 is made of a material satisfying Equation 4 below, for example, a silicon material having a d-line refractive index of 1.42. Here, n _d2 represents the d-line refractive index of the protective member.

The lens 40 configured as described above may be molded through injection molding, injection molding, transfer molding, or diamond turning.

In addition, the installation of the lens 41 to the base 31 may be performed using the adhesive (37). Here, as an example of the adhesive agent 37, the same epoxy resin as the medium of the lens 41 can be mentioned.

8 shows the light intensity distribution of the light emitted from the light emitting unit according to the embodiment of the present invention configured as described above.

Referring to the drawing, the range of the directivity angle at which most of the light beams are emitted is approximately 50 ° to 70 °, and the light rays emitted toward the center have luminous intensity values of about 10% compared to the light beams having the highest luminous angle. Able to know. That is, it can be seen that the luminance value near 0 ° decreases and the luminance of the side-illuminated light increases. Therefore, it is possible to suppress the generation of bright lines when employed in the direct emission type backlight device.

In addition, by having the above-described direct angle distribution, a light emitting unit having a lens is provided for each of the light emitting diodes corresponding to the red, blue, and green wavelengths, and when the light emitting units are arranged in sequence, color synthesis problems and color reproducibility All of them can be satisfied.

9 is a schematic cross-sectional view showing an edge-emitting backlight device according to an embodiment of the present invention. Referring to the drawings, a reflector 61, a light source provided on the reflector 61 to illuminate light, a diffuser plate 63 disposed on the light source, and illumination light are directed toward the LCD panel 70. And a prism sheet 65 for refractive transmission. The reflecting plate 61 reflects the light incident from the light source to the diffuser plate 63.

The light source includes a plurality of light emitting units 20 described with reference to FIGS. 2 and 3, and each light emitting unit 20 illuminates most of the light at a direction angle of 50 ° to 70 °. Since the configuration itself of this light emitting unit 20 is as described above, its detailed description will be omitted.

The diffusion plate 63 diffuses and transmits the light illuminated by the light emitting unit 20. The prism sheet 65 is directed toward the LCD panel 70 by refracting and transmitting the light diffused and transmitted by the diffusion plate 63.

The backlight device configured as described above can illuminate the LCD panel 70 with light having a constant luminance even by eliminating the use of the light guide plate (3 in FIG. 1) by disposing a light source in a direct light emission type.

FIG. 10 illustrates luminance measured at a position spaced a predetermined distance from the LCD panel 70 of FIG. 9. Referring to the drawings, it can be seen that the color is the same from the center to the vicinity of the + /-40mm area. Therefore, when the backlight device is configured as described above, it can be seen that the light having uniform luminance is illuminated.

The light emitting unit according to the present invention configured as described above uses a lens including a first refraction portion of a conical groove structure and a second refraction portion having a predetermined curvature to change a path of light irradiated in the vertically upward direction of the light emitting diode. It is possible to illuminate light having a directivity distribution in the range of approximately 50 ° to 70 °. Therefore, when employed as a light source of the backlight device of the LCD panel, it is possible to prevent the bright line that the light emitting diode mounting portion appears brighter than the surroundings.

In addition, the backlight device according to the present invention can be provided with a plurality of light emitting units having the above-described structure to illuminate the light from below the LCD panel. Therefore, there is an advantage that it can be applied to a large display according to the alignment position and the number of light emitting units. In addition, since the desired luminance can be obtained without using the light guide plate and the optical prism sheet, it is possible to reduce the thickness, reduce the manufacturing cost, and reduce the production time.

The above embodiments are merely exemplary, and various modifications and equivalent other embodiments are possible from those skilled in the art. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the invention described in the claims below.

Claims (15)

A base; A light emitting diode mounted on the base and emitting light; A first refraction portion installed on the base and formed in a conical groove shape to refractively transmit the light incident from the light emitting diode, and a refraction transmission of incident light having a predetermined curvature around the first refraction portion. And a lens including a second refractive portion and a transmission portion formed in a cylindrical shape around the second refractive portion to transmit incident light. And the light emitted from the light emitting diode is emitted through the first, second refractive or transmissive portion. The method of claim 1, And a cup member formed at a predetermined height around the light emitting diode on the base. The method of claim 2, And a protective member filled in the cup member and positioned between the light emitting diode and the lens to protect the light emitting diode and the lens. The method of claim 3, The protective member is a light emitting unit, characterized in that made of a transparent material having a relatively low refractive index compared to the refractive index of the lens. The method of claim 4, wherein The protective member is a light emitting unit, characterized in that made of a material that satisfies the following Conditional Expression 1. Here, n _d2 represents the d-line refractive index of the protective member. <Condition 1>

The method of claim 5, The protective member is a light emitting unit, characterized in that made of a silicon material. The method according to any one of claims 1 to 6, The right angle θ of the conical groove of the first refraction portion satisfies Conditional Expression 2 below, so that the light incident from the light emitting diode can be refracted in a direction away from the center of the first refraction portion. <Condition 2>

The method according to any one of claims 1 to 6, The second refractive portion is a light emitting unit, characterized in that the spherical surface having a radius of curvature of 1mm to 3mm. The method according to any one of claims 1 to 6, The lens is a light emitting unit, characterized in that made of a transparent material satisfying the following Conditional Expression 3. Where n _d1 represents the d-line refractive index of the lens. <Condition 3>

The method of claim 9, The lens is a light emitting unit, characterized in that made of epoxy resin or plastic material. A reflector for reflecting incident light; A light source having a plurality of light emitting units according to any one of claims 1 to 6 on the reflecting plate to illuminate light; A diffuser plate disposed on the light source and configured to diffuse light illuminated by the light emitting unit; And a prism sheet for converting the propagation path by refracting and transmitting the light diffused through the diffusion plate. The method of claim 11, And a right angle θ of the conical groove of the first refraction portion is set in a range of 130 ° to 160 °. The method of claim 11, And the second refraction portion is a spherical surface having a radius of curvature of 1 mm to 3 mm. The method of claim 11, The lens is a backlight device, characterized in that made of a transparent material that satisfies the condition 4. Where n _d1 represents the d-line refractive index of the lens. <Condition 4>

The method of claim 14, The lens is a backlight device, characterized in that made of epoxy resin or plastic material.

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