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WO2007029961A1 - Light emitting unit and direct light type back light apparatus using the same - Google Patents

Light emitting unit and direct light type back light apparatus using the same Download PDF

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Publication number
WO2007029961A1
WO2007029961A1 PCT/KR2006/003527 KR2006003527W WO2007029961A1 WO 2007029961 A1 WO2007029961 A1 WO 2007029961A1 KR 2006003527 W KR2006003527 W KR 2006003527W WO 2007029961 A1 WO2007029961 A1 WO 2007029961A1
Authority
WO
WIPO (PCT)
Prior art keywords
light
light emitting
lens
emitting unit
incident
Prior art date
Application number
PCT/KR2006/003527
Other languages
French (fr)
Inventor
Yong-Suk Kim
Original Assignee
Luxpia Co., Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Luxpia Co., Ltd. filed Critical Luxpia Co., Ltd.
Publication of WO2007029961A1 publication Critical patent/WO2007029961A1/en

Links

Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B19/00—Condensers, e.g. light collectors or similar non-imaging optics
    • G02B19/0033—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use
    • G02B19/0047—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with a light source
    • G02B19/0071—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with a light source adapted to illuminate a complete hemisphere or a plane extending 360 degrees around the source
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B19/00—Condensers, e.g. light collectors or similar non-imaging optics
    • G02B19/0004—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed
    • G02B19/0028—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed refractive and reflective surfaces, e.g. non-imaging catadioptric systems
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B19/00—Condensers, e.g. light collectors or similar non-imaging optics
    • G02B19/0033—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use
    • G02B19/0047—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with a light source
    • G02B19/0061—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with a light source the light source comprising a LED
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B3/00—Simple or compound lenses
    • G02B3/02—Simple or compound lenses with non-spherical faces
    • G02B3/04—Simple or compound lenses with non-spherical faces with continuous faces that are rotationally symmetrical but deviate from a true sphere, e.g. so called "aspheric" lenses
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/48—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
    • H01L33/58—Optical field-shaping elements
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/1336—Illuminating devices
    • G02F1/133602—Direct backlight
    • G02F1/133603—Direct backlight with LEDs
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/48—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
    • H01L33/58—Optical field-shaping elements
    • H01L33/60—Reflective elements

Definitions

  • the present invention relates to a light emitting unit using a light emitting diode and a backlight apparatus employing the light emitting unit, and more particularly, to a light emitting unit having improved brightness, wherein formation of dark portions in and around the center of a lens can be prevented, and a direct light type backlight apparatus employing the light emitting unit.
  • the LGP 3 and the optical prism sheet 7 are used to convert the light transmitted through the edges of LGP 3 to be transmitted in a perpendicular direction and to correct the path of the illumination light, the number of components is great and space for the components is needed, which creates a limitation in reducing the total thickness of the backlight apparatus.
  • the color gamut of the conventional backlight apparatus is very low, about 74 % of the National Television System Committee (NTSC) standard.
  • LED light emitting units using light emitting diodes
  • the LEDs are point light sources unlike the CCFLs which are line light sources.
  • the LEDs have longer lifetime, are environmentally-friendly, have high color gamut, and the range of operation of the LED is wider. Moreover, the LEDs can illuminate highly bright light.
  • the present invention provides a light emitting unit with increased brightness and a structure in which formation of dark portions in the center of the upper portion of the light emitting unit are prevented.
  • the present invention also provides a direct light type backlight apparatus employing the light emitting unit without a light guide panel (LGP), to be made thin and have uniform illumination over a large surface.
  • LGP light guide panel
  • a light emitting unit comprising: a base; a light emitting diode that is mounted on the base and emits light; a cup member formed around the light emitting diode on the base to a predetermined height; and a lens installed on the base and including an incident portion that is disposed toward the light emitting diode and onto which light is incident, a first refraction portion that is formed flat in the center of a surface of the lens opposite the incident portion and refracts and transmits incident light, and a second refraction portion that is formed from the first refraction portion to have a predetermined curvature and refracts and transmits incident light, wherein light emitted by the light emitting diode is illuminated uniformly over a wide range of angles through the lens.
  • a direct light type backlight apparatus comprising: a reflection panel reflecting incident light; a light source including a plurality of light emitting units each according to one of claims 1 through 7 and emitting light; a diffusion plate that is disposed on the light source and diffuses the light irradiated from the light emitting units; and a prism sheet converting the path of the light diffused by the diffusion plate by refracting and transmitting the light.
  • the backlight apparatus according to the present invention includes a plurality of light emitting units having the above-described structure to illuminate light under the LCD panel. Accordingly, the backlight apparatus according to the present invention can be applied to a large-sized display device according to the arrangement and number of the light emitting units. Moreover, since light having desired uniform brightness can be obtained without using a light guiding panel, the backlight apparatus can be made light and thin, and the manufacturing costs and production time of the backlight apparatus can be reduced.
  • FIG. 1 is a cross-sectional view of a conventional edge emitting type light emitting backlight apparatus
  • FIG. 2 is a cross-sectional view illustrating a light emitting unit according to an embodiment of the present invention
  • FIG. 4 illustrates paths of light L1 and L2 emitted from a light emitting diode when the refractive index of a dispensing member is greater than the refractive index of a lens;
  • FIG. 12 illustrates a light emitting unit in which the diameter W of a first refraction portion is one third of the diameter R of the lens or smaller, and FIGS. 13 and 14 illustrate brightness distribution of the light transmitting the lens in FIG. 12;
  • FIG. 15 illustrates an air layer formed between the lens and the dispensing member;
  • FIG. 20 is a cross-sectional view illustrating the a light emitting unit according to another embodiment of the present invention.
  • FIGS. 21 and 22 illustrate a angle distribution and uniformity of emitted light when a surface of the lens is polished
  • FIGS. 23 and 24 illustrate an angle distribution and uniformity of emitted light when the surface of the lens is Matte-treated
  • FIG. 27 is a graph showing luminescence of the polished lens and of the Matte-treated lens according to an embodiment of the present invention.
  • FIG. 28 is a schematic view of a cross-sectional curve for explaining the surface roughness.
  • FIG. 2 is a cross-sectional view illustrating a light emitting unit according to an embodiment of the present invention.
  • the light emitting unit includes a base 31 , a light emitting diode 40 mounted on the base 31 , a cup member 33 formed around the light emitting diode 40 on the base 31 , and a lens 50 that is installed on the base 31 and changes the direction of light emitted from the light emitting diode 40.
  • the light emitting diode 40 is a point light source and radiates light having a predetermined wavelength from a surface facing the lens 50.
  • a lead frame 35 is formed in the base 31 to supply power to the light emitting diode 40, and the light emitting diode 40 is mounted on the lead frame 35 or is electrically connected to the lead frame 35 by wires.
  • the cup member 33 is formed around the light emitting diode 40 on the base to a predetermined height.
  • the cup member 33 is formed to surround the light emitting diode 40 with a dispensing member 61 which will be described later, and for installing the lens 50.
  • the height of the cup member 33 should be such that the light path passing through the lens 50 is not interrupted.
  • the height of the cup member 33 is set as high as the light emitting diode 40 or is slightly higher than the light emitting diode 40.
  • the lens 50 has a structure to refract the emitted light in a perpendicular direction to the upper surface of the base 31 or in a direction almost perpendicular of the light from the light emitting diode 40 to the side.
  • an incident portion 52 may be formed of a protruding surface protruding towards the light emitting diode 40 with a predetermined curvature.
  • the incident portion 52 has a predetermined curvature, thereby functioning as a directional controlling element for light transmitted through the lens 50 together with the first and second refraction portion 53 and 55. Accordingly, the direction of light can be efficiently controlled when a lens is included.
  • a dispensing member 61 may be further included inside the cup member 33.
  • the dispensing member 61 is a transparent member and is interposed between the light emitting diode 40 and the lens 50 to protect the light emitting diode 40.
  • the dispensing member 61 blocks heat, which is generated during emission of light from the light emitting diode 40, from being directly transferred to the lens 50, thereby preventing yellowing of the lens 50.
  • FIG. 4 illustrates paths of light L1 and L2 emitted from the light emitting diode 40 when the refractive index of a dispensing member 61' is greater than the refractive index of the lens 50. Referring to FIG.
  • L3 proceeds in a more upward direction of the lens 50 than L4.
  • the difference between the refractive indices of the lens 50 and the dispensing member 61" is small or zero, light proceeds at a greater refraction angle, and thus can be spread to a wider region entirely.
  • the higher the refractive index of the lens 50 the greater the final refraction angle of light emitted from the lens 50. Therefore, the lens 50 and the dispensing member 61 " may have the same refractive index, which is preferably large.
  • the lens 50 may be formed of a material satisfying Inequality 1: [Inequality 1 ] 1.4 ⁇ n ⁇ ⁇ 1.65
  • Examples of a transparent material forming the lens 50 may be epoxy resin, polymethylmethacrylate (PMMA), polycarbonate (PC), acrylic resin, silicone resin, etc. having a d-line refractive index nd1 of 1.54.
  • the dispensing member 61 is formed of a material satisfying Inequality 2: [Inequality 2]
  • An example of the material forming the dispensing member 61 is silicone resin having a d-line refractive index nd2 of 1.41.
  • the first refraction portion 53 has a structure that is formed flat in the center of the surface opposite to the incident portion 51.
  • the refraction angle at which light is transmitted through the lens 50 increases and thus dark portions in a position where brightness is measured can be removed.
  • the lens having a first refraction portion 53 with a flat structure and the lens according to Comparative Example as illustrated in FIGS. 6 and 7 are compared to describe the advantage of the first refraction portion 53 having a flat structure.
  • FIGS. 6 and 7 illustrate a light emitting unit and a backlight apparatus disclosed in Korean Patent Application No.
  • the lens 20 includes a first refraction portion 21 that is engraved in a cone form in the upper center of the lens 20 and a second refraction portion 23 formed from the first refraction portion 21 with a predetermined curvature.
  • the distributions A and B of light transmitted through respectively the first refraction portion 21 and the second refraction portion 23 are observed when the lens 20 is formed as described above.
  • the distribution B of the light transmitted through the second refraction portion 23 is uniform with relatively small interval difference.
  • the distribution A of the light transmitted through the first refraction portion 21 increases from the center of the first refraction portion 21 to the second refraction portion 23, and thus, the intensity of light increases towards the center of the first refraction portion 21.
  • the refraction angle rapidly increases according to the distance variation of the incident angle.
  • the first refraction portion 53 is formed of a flat structure in order to remove the dark portions.
  • the incident angle in the center increases proportionally on the whole, and thus dark portions generated at the portion where brightness is measured (or at the position of the LCD when the light emitting unit is employed as a light source of the backlight apparatus) can be removed.
  • the diameter w of the first refraction portion 53 may satisfy Inequality 3 below with respect to the total diameter R of the lens 50. [Inequality 3]
  • FIG. 8 illustrates a light emitting unit in which the diameter W of a first refraction portion is one third of the diameter R of the lens or greater
  • FIGS. 9, 10, and 11 illustrate the brightness distribution of the light transmitting the lens of FIG. 8.
  • the brightness distribution C of the light transmitted through the first refraction portion 53 is of higher intensity than the brightness distribution of the light transmitted through the surrounding portions. This is because the refraction angle is low since the first refraction portion 53 is formed of a flat structure, and the number of light beams proceeding in a straight line through the center is increased. Having such a structure, the brightness distribution of light transmitted through the lens 50 is not uniform, and thus the light emitting unit according to the current embodiment of the present invention cannot be used as a light source for a light emitting unit.
  • FIG. 12 illustrates a light emitting unit in which the diameter w of a first refraction portion is one third of the diameter R of the lens or smaller
  • FIGS. 13 and 14 illustrate brightness distribution of the light transmitting the lens of FIG. 12.
  • the second refraction portion 55 has predetermined curvature to refract and transmit light that is emitted by the light emitting diode 40 to a side.
  • the second refraction portion 55 may be a spherical surface having a radius of curvature of 2 to 10 mm.
  • the radius of curvature is greater than 10 mm, the refraction angle of the light emitted by the light emitting diode 40 and incident on the second refraction portion 55 becomes smaller. Accordingly, the illumination surface of light is reduced.
  • the curvature radius of the second refraction portion 55 is 2 mm or smaller, sufficient size of the second refraction portion 55 cannot be secured, and the first refraction portion 53 cannot be arranged properly.
  • the lens 50 can be formed using projection molding, injection molding, transfer molding, diamond turning processing, etc.
  • the lens 50 can be installed on the base 31 using an adhesive agent 63.
  • the adhesive agent 63 may be epoxy resin or silicone resin which is identical to the medium of the lens 50. As illustrated in FIG. 2, when the lens 50 is bonded to the base 31 , the interface between the lens 50 and the dispensing member 61 may be separated and an air layer may be formed therebetween, as illustrated in FIG. 15.
  • the light emitting unit may have a bonding structure as illustrated in FIG. 16.
  • the lens 50 is installed on the base 31 , wherein a portion of the lens 50 is bonded to the cup member 35.
  • the first bonding portion formed in the lens 50 and the second bonding portion 35a formed in the cup member 35 are formed as uneven shapes corresponding to each other such that the surface area of the first and second bonding portions 57 and 35a facing each other is large, and bonded to each other using an adhesive agent 65.
  • the adhesive agent 65 may be formed of epoxy which is identical to the material of the lens 50.
  • the bonding structure is improved as described above, even when the lens 50 and the dispensing member 61 are not bonded to each other due to the characteristic of the material, the lens 50 is strongly bonded to the cup member 35, and thus the thermal expansion of the dispensing member 61 , which is generated during the operation of the light emitting unit 40, can be suppressed. Accordingly, air from the outside does not flow into the cup members 35 during the on/off operation of the light emitting unit 40, thereby fundamentally blocking formation of an air layer.
  • FIG. 17 is a cross-sectional view illustrating a light emitting unit according to another embodiment of the present invention.
  • the light emitting unit includes a base 31 , a light emitting diode 40 mounted on the base 31 , a cup member 35 formed around the light emitting diode 40 on the base 31 , a lens 150 that is installed on the base 31 and changes the direction of light emitted by the light emitting diode 40, and a dispensing member 161.
  • the lens 150 includes a first refraction portion 153 having a flat structure and a second refraction portion 155 having a predetermined curvature.
  • the lens 150 has the substantially same structure as the lens 50, thus detailed description of the lens 150 will be omitted.
  • the lens 150 and the dispensing member 161 are formed of silicone resin and as a single unit using a direct molding process.
  • the number of assembly processes can be reduced.
  • the lens 150 and the dispensing member 161 formed as a single unit are formed of silicone resin, yellowing can be prevented, which occurs when the lens 150 and the dispensing member 161 are formed of epoxy resin, and decrease in luminous flux due to the yellowing can be prevented.
  • FIG. 20 is a cross-sectional view of a light emitting unit according to another embodiment of the present invention.
  • the light emitting unit includes a base 31 , a light emitting diode 40 mounted on the base 31 , a cup member 35 formed around the light emitting diode 40 on the base 31 , a lens 250 that is installed on the base 31 and changes the direction of light emitted by the light emitting diode 40, and a dispensing member 61.
  • the lens 250 includes a first refraction portion 253 having a flat structure and a second refraction portion 255 having a predetermined curvature, wherein a surface 250a of the lens 250 is Matte-treated.
  • the lens 250 has the same structure as the lens 150 except that the surface 250a is Matte-treated, thus detailed description of the lens 250 will be omitted.
  • the surface of a lens of a conventional light emitting unit is polished, concerning the brightness.
  • the lens 250 is polished, as illustrated in FIG. 21 , the light intensity does not vary smoothly with angle, and thus bright lines in a ring form are generated as illustrated in FIG. 22, thereby causing a decrease in uniformity of brightness of illumination light.
  • the surface 250a of the lens 250 is Matte-treated, light transmitting the lens 250 is scattered at the first and second refraction portions 253 and 255, and light having uniform light distribution without bright lines in a ring form can be obtained, as illustrated in FIGS. 23 and 24.
  • FIG. 25 shows a angle distribution of light emitted by a conventional light emitting unit, which has a maximum light intensity at 0 degrees.
  • a considerable amount of scattered light beams show up as a dotted line in FIG. 25.
  • the light intensity of the dotted line is 0.5 times or less of the maximum light intensity, and the light beams in the area of the dotted line do not illuminate but disappear when the light emitting unit is driven.
  • the Matte-treatment of the surface 250a of the lens refers to processing the surface of the lens to have a predetermined roughness.
  • the surface roughness refers to the degree of unevenness of the surface indicating the precision of the surface.
  • FIG. 28 is a schematic view of a cross-sectional curve for explaining the surface roughness.
  • the cross-sectional curve refers to the shape of a cross-section of the processed surface cut perpendicularly.
  • Rmax refers to maximum roughness
  • Ra refers to the average of the center line, that is, roughness.
  • Rmax refers to the distance between two parallel lines which are parallel to the center line of the cross-sectional curve and contact respectively the highest point of the plot and the lowest point of the plot when picking a reference line from the plot.
  • Ra according to the current embodiment of the present invention may be in the range of 0.8 ⁇ m through 1.8 ⁇ m.
  • Ra When Ra is less than 0.8 ⁇ m, the lens surface becomes as if polished, and thus bright lines in a ring form are formed.
  • Ra When Ra is greater than 1.8 ⁇ m, light is scattered excessively, thus the luminous flux is decreased.
  • FIG. 29 is a cross-sectional view of an edge emitting type light emitting backlight apparatus according to an embodiment of the present invention.
  • the edge emitting type light emitting backlight apparatus includes a reflection panel 71 , light source 100 that is formed on the reflection panel 71 and irradiates light, a diffusion plate 73 disposed on the light source 100, and a prism sheet 75 refracting and transmitting emitted light in the direction of an LCD panel 77.
  • the reflection panel 71 reflects light emitted from the light source 100 to the diffusion plate 73.
  • the light source 100 includes a plurality of light emitting units which have been described with reference to FIGS. 2 through 28, each light emitting unit emits light having a maximum light intensity at +/- 75 degrees.
  • the light emitting unit has the configuration as described above, thus detailed description thereof will not be repeated.
  • the diffusion plate 73 diffuses and transmits the light emitted by the light source 100.
  • the prism sheet 75 refracts the light refracted and transmitted by the diffusion plate 73 to guide the light to the LCD panel 77.
  • the backlight apparatus as described above can emit light having predetermined brightness to the LCD panel 70 without a light guide panel (LGP) (reference numeral 3 of FIG. 1 ) using a direct light type light emitting light source.
  • LGP light guide panel
  • the light emitting unit according to the present invention includes an improved bonding structure of a lens and a base to prevent formation of an air layer between the lens and the dispensing member, thereby fundamentally preventing decrease in light uniformity due to the air layer.
  • the light emitting unit according to the present invention includes a lens having a Matte-treated surface to scatter emission light on the surface of the lens, thereby reducing bright lines which are caused when the surface of the lens is polished.
  • the backlight apparatus according to the present invention includes a plurality of light emitting units having the above-described structure to illuminate light onto a lower surface of the LCD panel. Accordingly, the backlight apparatus according to the present invention can be applied to a large-sized display device according to the arrangement and number of the light emitting units. Moreover, since light having desired uniform brightness can be obtained without using a light guiding panel, the backlight apparatus can be made light and thin, and the manufacturing costs and production time of the backlight apparatus can be reduced.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Nonlinear Science (AREA)
  • Computer Hardware Design (AREA)
  • Power Engineering (AREA)
  • Mathematical Physics (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Planar Illumination Modules (AREA)

Abstract

Provided are a light emitting unit and a direct light type backlight apparatus employing the light emitting unit. The light emitting unit includes: a base; a light emitting diode that is mounted on the base and emits light; a cup member formed around the light emitting diode on the base to a predetermined height; and a lens installed on the base and including an incident portion that is disposed toward the light emitting diode and onto which light is transmitted, a first refraction portion that is formed flat in the center of a surface of the lens opposite the incident portion and refracts and transmits incident light, and a second refraction portion that is formed from the first refraction portion to have a predetermined curvature and refracts and transmits incident light, wherein the light emitting unit emits light uniformly over a wide range of angles by allowing light emitted by the light emitting diode to be transmitted through the lens. The direct light type backlight apparatus includes: a reflection panel reflecting incident light; a light source including a plurality of the light emitting units emitting light; a diffusion plate that is disposed on the light source and diffuses the light irradiated from the light emitting unit; and a prism sheet converting the path of the light diffused by the diffusion plate by refracting and transmitting the light.

Description

LIGHT EMITTING UNIT AND DIRECT LIGHT TYPE BACK LIGHT APPARATUS
USING THE SAME
TECHNICAL FIELD
The present invention relates to a light emitting unit using a light emitting diode and a backlight apparatus employing the light emitting unit, and more particularly, to a light emitting unit having improved brightness, wherein formation of dark portions in and around the center of a lens can be prevented, and a direct light type backlight apparatus employing the light emitting unit.
BACKGROUND ART
In general, liquid crystal displays, which are flat panel displays, are light receiving devices which do not form images using light emitted by themselves form images by transmitting selectively illumination light irradiated from outside. A backlight unit is installed behind a liquid crystal display to emit light.
According to the arrangement of a light source, the backlight apparatus can be classified as a direct light type backlight apparatus in which a plurality of lamps installed directly under a liquid crystal display emit light directly to a liquid crystal panel, and an edge emitting type backlight apparatus in which a lamp installed at an edge of a light guide panel (LGP) emits light and the light is transferred to a liquid crystal panel. FIG. 1 is a cross-sectional view illustrating a conventional edge emitting type backlight apparatus. Referring to FIG. 1 , cold cathode fluorescent lamps (CCFL) 1 are disposed at both edges of an LGP 3. Then a reflection panel 9 is disposed below the LGP 3 to reflect light emitted by the CCFLs 1 to a liquid crystal display (LCD) panel 10. Thus the light emitted by the CCFLs 1 is incident on the LGP 3 and is transmitted through the edges of the LGP 3. The incident light is converted into surface light by the LGP 3 and the reflection panel 9 and is transmitted through an upper surface of the LGP 3. A diffusion plate 5 and an optical prism sheet 7 are disposed on the upper surface of the LGP 3. Accordingly, light transmitted through the upper surface of the LGP 3 is diffused by the diffusion plate 5 and the path of the light is corrected by the optical prism sheet 7 to proceed toward the LCD panel 10. Since the conventional backlight apparatus uses CCFLs 1 as light sources, intense white light having high brightness, high uniformity and large surface size can be obtained. However, the CCFLs 1 use mercury as discharging gas and thus create environmental problems. Also, as the LGP 3 and the optical prism sheet 7 are used to convert the light transmitted through the edges of LGP 3 to be transmitted in a perpendicular direction and to correct the path of the illumination light, the number of components is great and space for the components is needed, which creates a limitation in reducing the total thickness of the backlight apparatus. In addition, the color gamut of the conventional backlight apparatus is very low, about 74 % of the National Television System Committee (NTSC) standard.
Meanwhile, light emitting units using light emitting diodes (LED) have been replacing the CCFLs recently. The LEDs are point light sources unlike the CCFLs which are line light sources. The LEDs have longer lifetime, are environmentally-friendly, have high color gamut, and the range of operation of the LED is wider. Moreover, the LEDs can illuminate highly bright light.
However, when a backlight apparatus is formed by disposing such light emitting units having high brightness at edges of the LGP, light is irradiated onto the entire surface of the LCD panel and thus light is not sufficiently irradiated onto the center of the LCD panel. Accordingly, dark portions are formed in the center of the LCD panel. Also, the backlight apparatus with the above described structure employs both the LGP and the optical prism sheet, and thus cannot be made as thin as the backlight apparatus employing CCFLs as light sources.
DETAILED DESCRIPTION OF THE INVENTION TECHNICAL PROBLEM
The present invention provides a light emitting unit with increased brightness and a structure in which formation of dark portions in the center of the upper portion of the light emitting unit are prevented.
The present invention also provides a direct light type backlight apparatus employing the light emitting unit without a light guide panel (LGP), to be made thin and have uniform illumination over a large surface.
TECHNICAL SOLUTION According to an aspect of the present invention, there is provided a light emitting unit comprising: a base; a light emitting diode that is mounted on the base and emits light; a cup member formed around the light emitting diode on the base to a predetermined height; and a lens installed on the base and including an incident portion that is disposed toward the light emitting diode and onto which light is incident, a first refraction portion that is formed flat in the center of a surface of the lens opposite the incident portion and refracts and transmits incident light, and a second refraction portion that is formed from the first refraction portion to have a predetermined curvature and refracts and transmits incident light, wherein light emitted by the light emitting diode is illuminated uniformly over a wide range of angles through the lens.
According to an aspect of the present invention, there is provided a direct light type backlight apparatus comprising: a reflection panel reflecting incident light; a light source including a plurality of light emitting units each according to one of claims 1 through 7 and emitting light; a diffusion plate that is disposed on the light source and diffuses the light irradiated from the light emitting units; and a prism sheet converting the path of the light diffused by the diffusion plate by refracting and transmitting the light.
ADVANTAGEOUS EFFECTS The light emitting unit according to the current embodiment of the present invention changes the path of the light emitted in an upper vertical direction of the light emitting diode using a lens including a first refraction portion having a flat structure and a second refraction portion having predetermined curvature to emit light having a light intensity in angle distribution of +/- 75 degree range. Accordingly, when the light emitting unit according to the present invention is employed as a light source of the backlight apparatus of an LCD panel, bright lines which appear around the light emitting diode are prevented, and furthermore, dark portions, which are likely to be formed when cone-shaped intruding grooves are formed in the center of the lens, can be prevented. In addition, the light emitting unit according to the present invention includes an improved bonding structure of a lens and a base to prevent formation of an air layer between the lens and the dispensing member, thereby fundamentally preventing decrease in light uniformity due to the air layer. Also, the light emitting unit according to the present invention includes a lens having a Matte-treated surface to scatter emission light on the surface of the lens, thereby reducing bright lines which are caused when the surface of the lens is polished.
Also, the backlight apparatus according to the present invention includes a plurality of light emitting units having the above-described structure to illuminate light under the LCD panel. Accordingly, the backlight apparatus according to the present invention can be applied to a large-sized display device according to the arrangement and number of the light emitting units. Moreover, since light having desired uniform brightness can be obtained without using a light guiding panel, the backlight apparatus can be made light and thin, and the manufacturing costs and production time of the backlight apparatus can be reduced.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view of a conventional edge emitting type light emitting backlight apparatus; FIG. 2 is a cross-sectional view illustrating a light emitting unit according to an embodiment of the present invention;
FIG. 3 is a schematic view illustrating another embodiment of an incident portion of the light emitting unit of FIG. 2;
FIG. 4 illustrates paths of light L1 and L2 emitted from a light emitting diode when the refractive index of a dispensing member is greater than the refractive index of a lens;
FIG. 5 illustrates a path of light L3 when the refractive index of the dispensing member is smaller than the refractive index of the lens and the difference between the refractive indices of the dispensing member and of the lens is great, and a path of light L4 when the refractive indices of the dispensing member and of the lens are identical; FIGS. 6 and 7 illustrate a light emitting unit according to Comparative Example; FIG. 8 illustrates a light emitting unit wherein the diameter W of a first refraction portion is one third of the diameter R of the lens or greater, and FIGS. 9, 10, and 11 illustrate brightness distribution of the light transmitting the lens of FIG. 8; FIG. 12 illustrates a light emitting unit in which the diameter W of a first refraction portion is one third of the diameter R of the lens or smaller, and FIGS. 13 and 14 illustrate brightness distribution of the light transmitting the lens in FIG. 12; FIG. 15 illustrates an air layer formed between the lens and the dispensing member;
FIG. 16 is a cross-sectional view illustrating a light emitting unit according to another embodiment of the present invention; FIG. 17 is a cross-sectional view illustrating a light emitting unit according to another embodiment of the present invention;
FIG. 18 is a graph illustrating yellowing generated when the lens is formed of epoxy resin;
FIG. 19 is a graph illustrating whether yellowing is generated or not when the lens is formed of silicone resin;
FIG. 20 is a cross-sectional view illustrating the a light emitting unit according to another embodiment of the present invention;
FIGS. 21 and 22 illustrate a angle distribution and uniformity of emitted light when a surface of the lens is polished; FIGS. 23 and 24 illustrate an angle distribution and uniformity of emitted light when the surface of the lens is Matte-treated;
FIG. 25 illustrates an angle distribution of emitted light of a general light emitting unit, which has a maximum light intensity at 0 degrees;
FIG. 26 illustrates an angle distribution of emitted light of the light emitting unit according to an embodiment of the present invention, which has a maximum light intensity at +/-75 degrees;
FIG. 27 is a graph showing luminescence of the polished lens and of the Matte-treated lens according to an embodiment of the present invention;
FIG. 28 is a schematic view of a cross-sectional curve for explaining the surface roughness; and
FIG. 29 is a schematic view of a direct light type backlight apparatus according to an embodiment of the present invention.
MODE OF THE INVENTION The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown.
FIG. 2 is a cross-sectional view illustrating a light emitting unit according to an embodiment of the present invention. The light emitting unit includes a base 31 , a light emitting diode 40 mounted on the base 31 , a cup member 33 formed around the light emitting diode 40 on the base 31 , and a lens 50 that is installed on the base 31 and changes the direction of light emitted from the light emitting diode 40. The light emitting diode 40 is a point light source and radiates light having a predetermined wavelength from a surface facing the lens 50. A lead frame 35 is formed in the base 31 to supply power to the light emitting diode 40, and the light emitting diode 40 is mounted on the lead frame 35 or is electrically connected to the lead frame 35 by wires. The cup member 33 is formed around the light emitting diode 40 on the base to a predetermined height. The cup member 33 is formed to surround the light emitting diode 40 with a dispensing member 61 which will be described later, and for installing the lens 50. The height of the cup member 33 should be such that the light path passing through the lens 50 is not interrupted. When a portion of the light emitted from the light emitting diode 40 is incident on the cup member 33, the incident light is reflected by the cup member 33 and proceeds in a different path which is not wanted, thereby decreasing the performance of the light emitting unit. Thus the height of the cup member 33 is set as high as the light emitting diode 40 or is slightly higher than the light emitting diode 40. The lens 50 has a structure to refract the emitted light in a perpendicular direction to the upper surface of the base 31 or in a direction almost perpendicular of the light from the light emitting diode 40 to the side. That is, for a light source of a direct light type backlight apparatus, the lens 50 refracts the light so that the maximum intensity of light is at an angle of approximately +/- 75 degrees and so that the intensity of the light at the center of the lens 50 is lower than the maximum intensity to maintain uniform bright light.
For this, the lens 50 includes an incident portion 51 through which light is incident, a first refraction portion 53 that is formed flat in the center of an opposite surface to the incident portion 51 , and a second refraction portion 55 that is formed with predetermined curvature from the first refraction portion 53. The incident portion 51 is disposed at side of the light emitting diode 40, and light is incident to the lens 50 through the incident portion 51. Referring to FIG. 2, the incident portion 51 according to an embodiment of the present invention may have a plane structure parallel to the light emission surface of the light emitting diode 40. Referring to FIG. 3, an incident portion 52 according to another embodiment of the present invention may be formed of a protruding surface protruding towards the light emitting diode 40 with a predetermined curvature. In this case, the incident portion 52 has a predetermined curvature, thereby functioning as a directional controlling element for light transmitted through the lens 50 together with the first and second refraction portion 53 and 55. Accordingly, the direction of light can be efficiently controlled when a lens is included.
Referring to FIGS. 2 and 3, a dispensing member 61 may be further included inside the cup member 33. The dispensing member 61 is a transparent member and is interposed between the light emitting diode 40 and the lens 50 to protect the light emitting diode 40. In addition, the dispensing member 61 blocks heat, which is generated during emission of light from the light emitting diode 40, from being directly transferred to the lens 50, thereby preventing yellowing of the lens 50. FIG. 4 illustrates paths of light L1 and L2 emitted from the light emitting diode 40 when the refractive index of a dispensing member 61' is greater than the refractive index of the lens 50. Referring to FIG. 4, light L1 having an incident angle smaller than a critical angle θc[= sin-1(nd1/nd2)] at the interface between the lens 50 and the dispensing member 61' is refracted and transmitted through the incident portion 51 , while light L2 having an incident angle that is greater than the critical angle θc is totally internally reflected at the incident portion 51. nd1 and nd2 denote respectively the d-line refractive index of the lens and the d-line refractive index of the dispensing member 61. That is, since total internal reflection occurs when light is incident from a medium having a higher refractive index to a medium having a lower refractive index at an angle greater than a critical angle, and in order to prevent this total internal reflection, the dispensing member 61 may be formed of the same material as that of the lens 50 or may be formed of a transparent material having a refractive index that is relatively lower than that of the lens 50. Meanwhile, FIG. 5 illustrates a path of light L3 when the refractive index of the dispensing member 61 " is smaller than the refractive index of the lens 50 and the difference between the refractive indices of the dispensing member 61 " and that of the lens 50 is great, and a path of light L4 when the refractive index of the dispensing member 61" is identical to the refractive index of the lens 50. Referring to FIG. 5, in both cases, light emitted from the light emitting diode 40 is transmitted to the lens 50. However, light L3 is refracted at the surface of the incident portion 51 initially, whereas light L4 is not refracted as it is transmitted, and thus, is transmitted straight through the surface of the incident portion 51. Thus, comparing the paths of the light transmitted through the lens 50, L3 proceeds in a more upward direction of the lens 50 than L4. In other words, when the difference between the refractive indices of the lens 50 and the dispensing member 61" is small or zero, light proceeds at a greater refraction angle, and thus can be spread to a wider region entirely. Also, the higher the refractive index of the lens 50, the greater the final refraction angle of light emitted from the lens 50. Therefore, the lens 50 and the dispensing member 61 " may have the same refractive index, which is preferably large. The lens 50 may be formed of a material satisfying Inequality 1: [Inequality 1 ] 1.4 < nΛ < 1.65
Examples of a transparent material forming the lens 50 may be epoxy resin, polymethylmethacrylate (PMMA), polycarbonate (PC), acrylic resin, silicone resin, etc. having a d-line refractive index nd1 of 1.54.
Also, the dispensing member 61 is formed of a material satisfying Inequality 2: [Inequality 2]
1.4 < n& < 1.65
An example of the material forming the dispensing member 61 is silicone resin having a d-line refractive index nd2 of 1.41.
Referring to FIG. 2, the first refraction portion 53 has a structure that is formed flat in the center of the surface opposite to the incident portion 51. When the first refraction portion 53 is formed as a flat structure as described above, the refraction angle at which light is transmitted through the lens 50 increases and thus dark portions in a position where brightness is measured can be removed. Hereinafter, the lens having a first refraction portion 53 with a flat structure and the lens according to Comparative Example as illustrated in FIGS. 6 and 7 are compared to describe the advantage of the first refraction portion 53 having a flat structure. FIGS. 6 and 7 illustrate a light emitting unit and a backlight apparatus disclosed in Korean Patent Application No. 10-2004-0113927, filed on 28 December 2004 by the present applicant, under the title of "Light emitting unit and backlight apparatus employing the same". Referring to FIGS. 6 and 7, the lens 20 includes a first refraction portion 21 that is engraved in a cone form in the upper center of the lens 20 and a second refraction portion 23 formed from the first refraction portion 21 with a predetermined curvature. The distributions A and B of light transmitted through respectively the first refraction portion 21 and the second refraction portion 23 are observed when the lens 20 is formed as described above. First, the distribution B of the light transmitted through the second refraction portion 23 is uniform with relatively small interval difference. On the other hand, the distribution A of the light transmitted through the first refraction portion 21 increases from the center of the first refraction portion 21 to the second refraction portion 23, and thus, the intensity of light increases towards the center of the first refraction portion 21. This is because the refraction angle rapidly increases according to the distance variation of the incident angle. When the number of incident light beams per unit surface in the first refraction portion 21 is smaller than that of the second refraction portion 23, as illustrated in FIG. 7, dark portions are generated in a ring form at the interface between the first refraction portion 21 and the second refraction portion 23.
It is a characteristic of the present invention that the first refraction portion 53 is formed of a flat structure in order to remove the dark portions. When the first refraction portion 53 is formed of a flat structure, the incident angle in the center increases proportionally on the whole, and thus dark portions generated at the portion where brightness is measured (or at the position of the LCD when the light emitting unit is employed as a light source of the backlight apparatus) can be removed. Also, the diameter w of the first refraction portion 53 may satisfy Inequality 3 below with respect to the total diameter R of the lens 50. [Inequality 3]
xxr ^T- ^ O FIG. 8 illustrates a light emitting unit in which the diameter W of a first refraction portion is one third of the diameter R of the lens or greater, and FIGS. 9, 10, and 11 illustrate the brightness distribution of the light transmitting the lens of FIG. 8. Referring to FIGS. 8, 9, 10 and 11 , the brightness distribution C of the light transmitted through the first refraction portion 53 is of higher intensity than the brightness distribution of the light transmitted through the surrounding portions. This is because the refraction angle is low since the first refraction portion 53 is formed of a flat structure, and the number of light beams proceeding in a straight line through the center is increased. Having such a structure, the brightness distribution of light transmitted through the lens 50 is not uniform, and thus the light emitting unit according to the current embodiment of the present invention cannot be used as a light source for a light emitting unit.
FIG. 12 illustrates a light emitting unit in which the diameter w of a first refraction portion is one third of the diameter R of the lens or smaller, and FIGS. 13 and 14 illustrate brightness distribution of the light transmitting the lens of FIG. 12.
Referring to FIGS. 12, 13 and 14, since the first refraction portion 53 is formed of a flat structure, dark portions in the center can be removed. Also, the diameter w of the first refraction portion 53 is formed to be relatively narrow to reduce the number of light beams proceeding in a straight line through the center, and thus radical increase of brightness in the first refraction portion 53 can be suppressed. Accordingly, light transmitted through the lens 50 can have generally uniform brightness distribution. Accordingly, when the light emitting unit according to the current embodiment of the present invention is employed as a light source of a backlight apparatus for a display device, light having generally uniform brightness can be irradiated on a predetermined surface.
The second refraction portion 55 has predetermined curvature to refract and transmit light that is emitted by the light emitting diode 40 to a side. The second refraction portion 55 may be a spherical surface having a radius of curvature of 2 to 10 mm. When the radius of curvature is greater than 10 mm, the refraction angle of the light emitted by the light emitting diode 40 and incident on the second refraction portion 55 becomes smaller. Accordingly, the illumination surface of light is reduced. When the curvature radius of the second refraction portion 55 is 2 mm or smaller, sufficient size of the second refraction portion 55 cannot be secured, and the first refraction portion 53 cannot be arranged properly.
The lens 50 can be formed using projection molding, injection molding, transfer molding, diamond turning processing, etc.
Also, the lens 50 can be installed on the base 31 using an adhesive agent 63. The adhesive agent 63 may be epoxy resin or silicone resin which is identical to the medium of the lens 50. As illustrated in FIG. 2, when the lens 50 is bonded to the base 31 , the interface between the lens 50 and the dispensing member 61 may be separated and an air layer may be formed therebetween, as illustrated in FIG. 15.
In particular, when the lens 50 and the adhesive agent 63 are formed of epoxy resin or silicone resin and the dispensing member 61 is formed of silicone resin, there is no adhesive force between the epoxy resin and the silicone resin, and thus an air layer is more likely to be formed. In this case, in detail, heat is generated when the light emitting diode 40 operates and the dispensing member 61 formed of silicone resin thermally expands. Then the lens 50 may spontaneously loosen upwards. Meanwhile, when the light emitting diode 40 is turned off, the dispensing member 61 cools down and contracts, and thus an air layer is generated in the interface between the dispensing member 61 and the lens 50. When an air layer is formed as described above, light beams are refracted at the interface in an improper manner, thereby causing not uniform brightness distribution.
Thus the light emitting unit according to another embodiment of the present invention may have a bonding structure as illustrated in FIG. 16. Referring to FIG. 16, the lens 50 is installed on the base 31 , wherein a portion of the lens 50 is bonded to the cup member 35. Here, the first bonding portion formed in the lens 50 and the second bonding portion 35a formed in the cup member 35 are formed as uneven shapes corresponding to each other such that the surface area of the first and second bonding portions 57 and 35a facing each other is large, and bonded to each other using an adhesive agent 65. Here, the adhesive agent 65 may be formed of epoxy which is identical to the material of the lens 50.
When the bonding structure is improved as described above, even when the lens 50 and the dispensing member 61 are not bonded to each other due to the characteristic of the material, the lens 50 is strongly bonded to the cup member 35, and thus the thermal expansion of the dispensing member 61 , which is generated during the operation of the light emitting unit 40, can be suppressed. Accordingly, air from the outside does not flow into the cup members 35 during the on/off operation of the light emitting unit 40, thereby fundamentally blocking formation of an air layer.
Also, as illustrated in FIG. 3, when the incident portion 52 is curved, the space between the incident portion 52 and the dispensing member 61 becomes small, and thus thermal expansion of the dispensing member 61 can be suppressed more efficiently. FIG. 17 is a cross-sectional view illustrating a light emitting unit according to another embodiment of the present invention.
Referring to FIG. 17, the light emitting unit according to the current embodiment of the present invention includes a base 31 , a light emitting diode 40 mounted on the base 31 , a cup member 35 formed around the light emitting diode 40 on the base 31 , a lens 150 that is installed on the base 31 and changes the direction of light emitted by the light emitting diode 40, and a dispensing member 161. The lens 150 includes a first refraction portion 153 having a flat structure and a second refraction portion 155 having a predetermined curvature. The lens 150 has the substantially same structure as the lens 50, thus detailed description of the lens 150 will be omitted. The lens 150 and the dispensing member 161 are formed of silicone resin and as a single unit using a direct molding process. When the lens 150 and the dispensing member 161 are formed as a single unit using a direct molding process, the number of assembly processes can be reduced.
Also, as the lens 150 and the dispensing member 161 formed as a single unit are formed of silicone resin, yellowing can be prevented, which occurs when the lens 150 and the dispensing member 161 are formed of epoxy resin, and decrease in luminous flux due to the yellowing can be prevented.
In other words, when the lens 150 of the light emitting unit is formed of epoxy resin using a direct molding process, the light emitting unit can operate at low current. However, at high current, the temperature of the light emitting diode increases, thus causing decrease in luminous flux. FIG. 18 is a graph showing the yellowing of a lens formed of epoxy resin. Referring to the graph of FIG. 18, the transmittance is about 80 % or greater than with respect to light of a wavelength of about 350 nm or greater initially. Then, over time, the wavelength band with transmittance of about 80 % or greater is gradually shifted, and after 14 days, only light of a wavelength of about 450 nm or greater has transmittance of 80 % or greater. Accordingly, as represented as a region D, the lens is yellowed.
Meanwhile, when the lens 150 is formed of silicone resin, as illustrated in FIG. 19, light of a wavelength of about 350 nm still has transmittance of about 80 % or greater even after 14 days as initially, thus yellowing of the lens 150 does not occur. FIG. 20 is a cross-sectional view of a light emitting unit according to another embodiment of the present invention. Referring to FIG. 20, the light emitting unit includes a base 31 , a light emitting diode 40 mounted on the base 31 , a cup member 35 formed around the light emitting diode 40 on the base 31 , a lens 250 that is installed on the base 31 and changes the direction of light emitted by the light emitting diode 40, and a dispensing member 61. The lens 250 includes a first refraction portion 253 having a flat structure and a second refraction portion 255 having a predetermined curvature, wherein a surface 250a of the lens 250 is Matte-treated. The lens 250 has the same structure as the lens 150 except that the surface 250a is Matte-treated, thus detailed description of the lens 250 will be omitted.
Regarding the surface treatment of the lens, the surface of a lens of a conventional light emitting unit is polished, concerning the brightness. When the lens 250 is polished, as illustrated in FIG. 21 , the light intensity does not vary smoothly with angle, and thus bright lines in a ring form are generated as illustrated in FIG. 22, thereby causing a decrease in uniformity of brightness of illumination light. Thus, when the surface 250a of the lens 250 is Matte-treated, light transmitting the lens 250 is scattered at the first and second refraction portions 253 and 255, and light having uniform light distribution without bright lines in a ring form can be obtained, as illustrated in FIGS. 23 and 24.
When a conventional lens is Matte-treated, the overall luminous flux is decreased. However, in the case of the light emitting unit having a maximum light intensity at about +/- 75 degrees, luminous flux is not decreased significantly. This will be described in detail hereinafter. FIG. 25 shows a angle distribution of light emitted by a conventional light emitting unit, which has a maximum light intensity at 0 degrees. When a surface of the light emitting unit is Matte-treated, a considerable amount of scattered light beams show up as a dotted line in FIG. 25. The light intensity of the dotted line is 0.5 times or less of the maximum light intensity, and the light beams in the area of the dotted line do not illuminate but disappear when the light emitting unit is driven. FIG. 26 shows a angle distribution of light emitted by the light emitting unit according to the current embodiment having an approximate maximum light intensity at +/- 75 degrees. In this case, since light irradiated in the entire region of the light emitting unit is used as illumination light, light scattered by the Matte-treated surface is also counted as effective illumination light. Accordingly, decrease in luminous flux is not significant. FIG. 27 shows luminescence of the polished lens and of the Matte-treated lens according to an embodiment of the present invention. As illustrated in FIG. 27, luminescence of both lenses similarly increases when the current applied to the light emitting diode is increased.
The Matte-treatment of the surface 250a of the lens refers to processing the surface of the lens to have a predetermined roughness. The surface roughness refers to the degree of unevenness of the surface indicating the precision of the surface. FIG. 28 is a schematic view of a cross-sectional curve for explaining the surface roughness. The cross-sectional curve refers to the shape of a cross-section of the processed surface cut perpendicularly. Rmax refers to maximum roughness, and Ra refers to the average of the center line, that is, roughness. In addition, Rmax refers to the distance between two parallel lines which are parallel to the center line of the cross-sectional curve and contact respectively the highest point of the plot and the lowest point of the plot when picking a reference line from the plot. Ra according to the current embodiment of the present invention may be in the range of 0.8 μm through 1.8 μm. When Ra is less than 0.8 μm, the lens surface becomes as if polished, and thus bright lines in a ring form are formed. When Ra is greater than 1.8 μm, light is scattered excessively, thus the luminous flux is decreased.
FIG. 29 is a cross-sectional view of an edge emitting type light emitting backlight apparatus according to an embodiment of the present invention. Referring to FIG. 29, the edge emitting type light emitting backlight apparatus includes a reflection panel 71 , light source 100 that is formed on the reflection panel 71 and irradiates light, a diffusion plate 73 disposed on the light source 100, and a prism sheet 75 refracting and transmitting emitted light in the direction of an LCD panel 77. The reflection panel 71 reflects light emitted from the light source 100 to the diffusion plate 73. The light source 100 includes a plurality of light emitting units which have been described with reference to FIGS. 2 through 28, each light emitting unit emits light having a maximum light intensity at +/- 75 degrees. The light emitting unit has the configuration as described above, thus detailed description thereof will not be repeated. The diffusion plate 73 diffuses and transmits the light emitted by the light source 100. The prism sheet 75 refracts the light refracted and transmitted by the diffusion plate 73 to guide the light to the LCD panel 77.
The backlight apparatus as described above can emit light having predetermined brightness to the LCD panel 70 without a light guide panel (LGP) (reference numeral 3 of FIG. 1 ) using a direct light type light emitting light source.
The light emitting unit according to the current embodiment of the present invention changes the path of the light emitted in an upper vertical direction of the light emitting diode using a lens including a first refraction portion having a flat structure and a second refraction portion having predetermined curvature to emit light having a light intensity in angle distribution of +/- 75 degree range. Accordingly, when the light emitting unit according to the present invention is employed as a light source of the backlight apparatus of an LCD panel, bright lines which appear from the light emitting diode are prevented, and furthermore, dark portions, which are likely to be formed when cone-shaped intruding grooves are formed in the center of the lens, can be prevented. In addition, the light emitting unit according to the present invention includes an improved bonding structure of a lens and a base to prevent formation of an air layer between the lens and the dispensing member, thereby fundamentally preventing decrease in light uniformity due to the air layer. Also, the light emitting unit according to the present invention includes a lens having a Matte-treated surface to scatter emission light on the surface of the lens, thereby reducing bright lines which are caused when the surface of the lens is polished.
Also, the backlight apparatus according to the present invention includes a plurality of light emitting units having the above-described structure to illuminate light onto a lower surface of the LCD panel. Accordingly, the backlight apparatus according to the present invention can be applied to a large-sized display device according to the arrangement and number of the light emitting units. Moreover, since light having desired uniform brightness can be obtained without using a light guiding panel, the backlight apparatus can be made light and thin, and the manufacturing costs and production time of the backlight apparatus can be reduced.
While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.

Claims

1. A light emitting unit comprising: a base; a light emitting diode that is mounted on the base and emits light; a cup member formed around the light emitting diode on the base to a predetermined height; and a lens installed on the base and including an incident portion that is disposed toward the light emitting diode and onto which light is incident, a first refraction portion that is formed flat in the center of a surface of the lens opposite the incident portion and refracts and transmits incident light, and a second refraction portion that is formed from the first refraction portion to have a predetermined curvature and refracts and transmits incident light, wherein light emitted by the light emitting diode is illuminated uniformly over a wide range of angles through the lens.
2. The light emitting unit of claim 1 , further comprising a dispensing member that is installed inside the cup members and protects the light emitting diode.
3. The light emitting unit of claim 2, wherein the dispensing member is formed of a material that has a lower refractive index than the refractive index of the lens or that has substantially the same refractive index as the lens.
4. The light emitting unit of claim 3, wherein the dispensing member is formed of a material satisfying the inequality below: <lnequality>
Ii < nΛ < Lffi where nd2 denotes the d-line refractive index of the dispensing member.
5. The light emitting unit of claim 4, wherein the dispensing member is formed of a silicone resin.
6. The light emitting unit of claim 2, wherein the lens and the dispensing member are formed of silicone resin and formed as a single unit through a direct molding process.
7. The light emitting unit of claim 1 , wherein the incident portion of the lens is formed flat or as a protruding surface protruding at a predetermined curvature.
8. The light emitting unit of one of claims 1 through 7, wherein the diameter of the first refraction portion is approximately one third of the total diameter of the lens or less.
9. The light emitting unit of one of claims 1 through 7, wherein the first refraction portion is a spherical surface having a radius of curvature in the range of 2 mm through 10 mm.
10. The light emitting unit of one of claims 1 through 6, wherein the lens is formed of a transparent material satisfying the inequality below:
<lnequality>
1.4 < ndl ≤ 1.65 where nd1 denotes the d-line refractive index of the lens.
11. The light emitting unit of claim 10, wherein the lens is formed of a material selected from the group consisting of epoxy resin, polymethylmethacrylate, polycarbonate, acrylic resin, and silicone resin.
12. The light emitting unit of one of claims 1 through 7, wherein a portion of the lens is bonded to the cup members to be installed on the base, wherein a bonding portion of the lens and a bonding portion of the cup members are formed to be non-flat shapes corresponding to each other such that the surface area of the bonding portions of the lens and of the cup members facing each other is large.
13. The light emitting unit of claim 12, wherein the bonding portion of the lens and the bonding portion of the cup members are bonded to each other using an adhesive agent formed of epoxy or silicone resin.
14. The light emitting unit of one of claims 1 through 7, wherein the surface of the lens is Matte-treated so that light passing through the lens is scattered by the first and second refraction portions.
15. The light emitting unit of claim 14, wherein the average roughness Ra of the surface of the lens is in the range of 0.8 μm through 1.8 m-
16. A direct light type backlight apparatus comprising: a reflection panel reflecting incident light; a light source including a plurality of light emitting units each according to one of claims 1 through 7 and emitting light; a diffusion plate that is disposed on the light source and diffuses the light irradiated from the light emitting units; and a prism sheet converting the path of the light diffused by the diffusion plate by refracting and transmitting the light .
17. The direct light type backlight apparatus of claim 16, wherein the diameter of the first refraction portion is approximately one third of the total diameter of the lens or less.
18. The direct light type light emitting unit of claim 16, wherein the first refraction portion is a spherical surface having a radius of curvature in the range of 2 mm through 10 mm.
19. The direct light type light emitting unit of claim 16, wherein the lens is formed of a transparent material satisfying the inequality below: <lnequality>
14 < ndi < 1.65 where nd1 denotes the d-line refractive index of the lens.
20. The direct light type light emitting unit of claim 16, wherein a portion of the lens is bonded to the cup members to be installed on the base, wherein a bonding portion of the lens and a bonding portion of the cup members are formed of non-flat shapes corresponding to each other such that the surface area of the bonding portions of the lens and of the cup members facing each other is large.
21. The direct light type light emitting unit of claim 20, wherein the bonding portion of the lens and the bonding portion of the cup members are bonded to each other using an adhesive agent formed of epoxy or silicone resin.
22. The direct light type light emitting unit of claim 16, wherein the surface of the lens is Matte-treated so that light passing through the lens is scattered by the first and second refraction portions, and the average roughness Ra of the surface of the lens is in the range of 0.8 μm through 1.8 μm.
PCT/KR2006/003527 2005-09-05 2006-09-05 Light emitting unit and direct light type back light apparatus using the same WO2007029961A1 (en)

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CN101994988A (en) * 2009-08-24 2011-03-30 恩普乐股份有限公司 Light flux controlling member, light emitting apparatus, surface light source apparatus and display apparatus
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CN101994988A (en) * 2009-08-24 2011-03-30 恩普乐股份有限公司 Light flux controlling member, light emitting apparatus, surface light source apparatus and display apparatus
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CN111897163A (en) * 2020-08-20 2020-11-06 安徽芯瑞达科技股份有限公司 Backlight module device for realizing ultra-low OD by matching LED with lens

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