KR20120002267A - Backlight unit including quantum dots - Google Patents

Abstract

PURPOSE: A backlight unit including a quantum dot is provided to reduce the phenomenon of yellowish generated in a photo converter form including a quantum dot. CONSTITUTION: A backlight unit includes a light guide plate(200), a plurality of light sources, and a photo converter(300). A plurality of light sources is located in the side of the light guide plate and emits the light of a specific wavelength band. The photo converter is inserted between the light source and the light guide plate. The photo converter is charged in the quantum dot for converting the wavelength of the light. The photo converter is formed in a hemi-cylinder shape.

Description

BACKLIGHT UNIT INCLUDING QUANTUM DOTS}

The present invention relates to a backlight unit, and more particularly, by changing the shape of a light conversion part filled with a quantum dot, the amount of light incident on the light guide plate increases, thereby reducing a yellowing phenomenon occurring on the light incident surface of the light guide plate. It is about.

Generally, a white LED used as a light source of a backlight unit is a method of implementing white by combining three LEDs of red, green, and blue, which are three primary colors of light, but this method creates a white light source. There are disadvantages in that it is necessary to use two LEDs, and a technology for controlling each LED has to be developed. Recently, a method of implementing white by exciting a phosphor using a blue LED as a light source has been spotlighted for its excellent luminous efficiency.

However, the spectrum of the light emitted from the white LED is excellent in the color of the blue region, while the color of the green and red is significantly low, there is a problem that the color reproduction rate is lowered.

In order to solve such a problem, a technique for implementing white light using the quantum dots (QDs) has recently been active.

Since the quantum dots have excellent light emission characteristics, when the white light is implemented using quantum dots (QDs), the color reproducibility of green and red is higher than that of conventional white LEDs.

However, when the backlight is formed by using the quantum dots as shown in FIG. 1, the light incident at the center of the fluorescent film 20 among the light emitted from the light source 10 has a substantially uniform RGB value while the fluorescent film 20 The light incident on the edge of the light is insufficient and is mostly converted into green light and red light. In this case, since light incident on the edge of the fluorescent film 20 is totally reflected at the light incident surface of the light guide plate 30, a yellowing phenomenon occurs in the vicinity of the light incident surface of the light guide plate 30.

In addition, as the light totally reflected on the light incident surface of the light guide plate 30 increases, the amount of light decreases, thereby decreasing the brightness of the backlight.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to reduce a yellowing phenomenon occurring at the light incident surface of the light guide plate by changing the shape of the light conversion unit.

Another object of the present invention is to improve the brightness of the backlight by increasing the amount of light incident to the light guide plate.

One feature of the present invention for achieving the above object is a light guide plate, a plurality of light sources positioned on the side of the light guide plate to emit light of a specific wavelength band, and mounted between the light source and the light guide plate of the light emitted from the light source It includes a light conversion unit filled with a quantum dot converting the wavelength band to a long wavelength, the light conversion unit is configured to have a curvature formed on at least one surface.

The light conversion portion is formed in a semicircular columnar shape or a trapezoidal columnar shape. At this time, the curvature surface of the semi-circle pillar is configured to have a curvature of 180mm ~ 500mm, the gradient angle of the trapezoidal pillar shape is configured to have a 35 ° ~ 50 ° relative to the horizontal plane.

Another feature of the present invention for achieving the above object is a light guide plate provided with a first lens having at least one convex surface, and a light guide plate having a second lens having one surface convex on the surface on which the light emitted from the light source is incident; It includes a light conversion unit inserted between the light source and the light guide plate and formed at least one surface concave.

According to the present invention, the amount of light passing through the light conversion part is incident on the light guide plate to increase the yellowing phenomenon occurring at the light incident surface of the light guide plate.

In addition, the brightness of the backlight is improved by increasing light incident on the light guide plate.

1 is a cross-sectional view of a conventional backlight,
2 is a combined perspective view of a backlight according to a first embodiment of the present invention;
3 is a cross-sectional view of a backlight according to a first embodiment of the present invention;
4 is a graph showing a change in illuminance uniformity according to the change in curvature of the light conversion unit according to the first embodiment of the present invention;
5 is a cross-sectional view of a backlight according to a second embodiment of the present invention;
6 is a graph showing a change in roughness uniformity according to the light conversion part gradient angle of the second embodiment of the present invention;
7 is a schematic diagram of a backlight unit according to a third embodiment of the present invention;
FIG. 8 is a spot diagram of a light guide plate according to a change in the radius of curvature of the lens of the third exemplary embodiment of the present invention. FIG.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description.

However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.

In the present application, the terms "comprises", "having", and the like are used to specify that a feature, a number, a step, an operation, an element, a component, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

In addition, it is to be understood that the accompanying drawings in the present application are shown enlarged or reduced for convenience of description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the drawings. Like reference numerals designate like elements throughout, and duplicate descriptions thereof will be omitted.

The backlight according to the embodiment of the present invention is largely a light guide plate 200, a plurality of light sources 100 positioned on the side of the light guide plate 200 and emitting light of a specific wavelength band, and the light source 100 and the light guide plate 200 It is configured to include a light conversion unit 300 is mounted between the quantum dots filled between the wavelength band of the light emitted from the light source 100 to the long wavelength.

The light guide plate 200 is an optical sheet for converting the point light source 100 incident from the light source 100 into the surface light source 100, and may be variously changed according to the embodiment as well as the shape of the general light guide plate 200. . For example, when the light guide plate 200 is formed as a wedge or the like, the shape of the light guide plate 200 may be appropriately determined, and any suitable surface shape such as a straight surface or a curved surface may be applied to the light guide plate 200 at the edge portion.

In addition, although not shown in the drawings, the prism-shaped unevenness may be formed on the upper surface of the light guide plate 200, and the unevenness of the prism-shaped may be formed in any surface form such as a straight surface, a refractive surface, a curved surface, or the like.

The light source 100 may be formed in plural on the side surface of the light guide plate 200 and may be formed of an LED element. At this time, the light source 100 may be composed of a blue LED or a UV LED having a wavelength of 430 ~ 470nm.

The light conversion unit 300 serves to convert light of a single wavelength emitted from the light source 100 into various wavelengths, and quantum dots (QDs) having different sizes are injected into a capillary made of transparent glass. Both ends are sealed.

Quantum dots (QDs) refer to particles of a predetermined size having a quantum confinement effect and have a size of about 2 to 15 nm.

The quantum dots (QDs) generate strong fluorescence in a narrow wavelength band, and the light emitted by the quantum dots (QDs) is generated as electrons in an unstable (excited) state fall from the conduction band to the valence band. .

In this case, the smaller the particles of the quantum dots QDs generate light having a shorter wavelength, and the larger the particles produce light having a longer wavelength.

In particular, since the quantum dots (QDs) have excellent light emission characteristics, when the white light is implemented using the quantum dots (QDs), the color reproducibility of green and red is higher than that of conventional white LEDs.

When the blue LED is used as the light source 100, the quantum dot size of the quantum dot absorbs light in the blue wavelength band and emits light in the green wavelength band, and the quantum dot QD2 emits light in the red wavelength band. ) May be included at random.

Accordingly, as the light emitted from the light source 100 passes through the light conversion unit 300, the quantum dots QDs randomly absorb blue light and convert the light into green or red wavelength band light, and as a result, blue, green, and red light. As the light of the wavelength is mixed with each other, white light is made to be incident to the light guide plate 200.

In contrast, when the UV light source 100 is used, quantum dots (QDs) having a size that absorbs light in the ultraviolet wavelength band and emits light in the blue, green, or red wavelength band should be selected. Of course, the following description will be made based on the blue LED for convenience of description.

Photocurable resin is applied between the light source 100 and the light conversion unit 300 and between the light conversion unit 300 and the light guide plate 200, and irradiates and cures UV light to light source 100 and the light conversion unit ( 300 and the light guide plate 200 may be indexed in place.

Referring to FIG. 3, the light conversion unit 300 according to the first exemplary embodiment of the present invention may have one surface having a curvature surface 301, and the other surface may have a flat semi-circular column shape. However, the present invention is not limited thereto, and the curvature of the one surface and the other surface may be formed differently or may be formed in the form of a light conversion film.

The light emitted from the light source 100 is emitted in the range of 180 ° from the exit surface of the light source 100 and is incident on the light conversion part 300, but the blue light emitted from the light source 100 is lighter as it moves away from the optical axis. Will be reduced.

Therefore, the light passing through the center of the light conversion unit 300 (close to the optical axis) of the light emitted from the light source 100 has a large amount of light, some of which are converted into green light and red light by quantum dots, and some of the blue light The light is incident on the light incidence surface 210 of the light guide plate 200 while maintaining the light uniformity.

On the other hand, among the light emitted from the light source 100, the blue light incident on the edge of the light conversion unit has a small amount of light, and thus is converted into green light and red light and emitted in the direction of the light guide plate 200.

In this case, since the curvature surface 301 of the light conversion unit 300 serves as a convex lens, the light incident on the edge of the light conversion unit 300 is focused in the direction of the light guide plate 200 so that the light guide plate 200 It can be easily incident on.

Therefore, the yellowing phenomenon in which the green light and the red light emitted from the edge of the conventional light conversion unit 300 are observed around the incident surface of the light guide plate 200 is eliminated.

In addition, since the green light and the red light converted at the edge of the light conversion unit 300 are incident on the light guide plate 200, the color uniformity and brightness of the white light are increased as a whole.

4 is a graph showing a change in illuminance uniformity according to the curvature change of the light conversion unit of the first embodiment of the present invention.

Referring to FIG. 4, the illuminance uniformity was measured while continuously changing the curvature radius of the light conversion unit 300. The illuminance uniformity was significantly lowered until the curvature radius was 180 mm or less, and then rapidly increased at 180 mm or more. After 500mm or more it can be confirmed that the roughness uniformity is reduced to about 60 or less.

Therefore, since the roughness uniformity required in the backlight is generally about 60, the radius of curvature is preferably 180 mm to 500 mm, more preferably 190 mm to 300 mm.

Although the light conversion unit 300 has been described as having the curvature surface 301 facing the light source 100 in FIG. 3, the light conversion unit 300 is not limited thereto. It was experimentally confirmed that the curvature surface 301 had a similar roughness uniformity even when facing the light guide plate 200.

In addition, the light conversion unit 300 may be formed long in the longitudinal direction to cover all of the plurality of light sources 100, but may be formed in the same number as each of the light sources 100 and mounted at corresponding positions. .

FIG. 5 is a cross-sectional view of the backlight unit according to the second embodiment of the present invention, and FIG. 6 is a graph showing a change in illuminance uniformity according to the gradient angle of the light conversion unit according to the second embodiment of the present invention.

Since the backlight unit according to the second embodiment of the present invention has a difference in the shape of the light conversion unit 310, other configurations are the same, and detailed descriptions of the same parts will be omitted in order to avoid duplication of description.

In the light conversion unit 310 according to the second embodiment of the present invention, the cross section is formed in a trapezoidal shape, and when referring to FIG. 6, the draft angle of the trapezoidal oblique surface 312 is 50 ° from 35 ° based on the horizontal plane (or optical axis). In the case of °, roughness uniformity becomes good.

Referring to FIG. 5, the light incident on the trapezoidal oblique surface 312 of the light conversion unit 310 is refracted and incident perpendicularly to the light guide plate 200, thereby eliminating the yellowing phenomenon and increasing luminance as described above. It has an effect.

In addition, in FIG. 5, the upper side 311 of the trapezoid is illustrated to face the light source 100, but is not necessarily limited thereto. The upper side 311 of the trapezoid may be configured to face the light guide plate 200. Is defined as shorter than the lower side (313).)

FIG. 7 is a schematic diagram of a backlight unit according to a third embodiment of the present invention, and FIG. 8 is a spot diagram of the light guide plate 200 according to a change in the curvature radius of the lens of the third embodiment of the present invention.

According to an embodiment of the present invention, a backlight unit includes a light source 100 including a first lens 400 having at least one convex surface, a light conversion unit 340 having at least one surface concave, and a second lens having at least one surface convex. 500 is provided with a light guide plate 200.

Referring to FIG. 7, light having a predetermined angle among the light emitted from the light source 100 is collected while passing through the first first lens 400, diverged while passing through the light conversion unit 340, and then again, the light guide plate. The light is refracted while passing through the second lens 500 formed on the light incident surface 210 of 200, and finally enters the light guide plate 200 vertically. In this case, reference numeral P denotes an optical axis of the light source.

The first lens 400 and the second lens 500 may be formed so that one surface has a curvature or both surfaces thereof may have a curvature. In addition, the lens may be separately formed and mounted to the light source 100 and the light guide plate 200, respectively, but is not limited thereto. The lens may be integrally formed with the light source 100 and the light guide plate 200.

The spot diagram of FIG. 8 tests the incident angle of the red light at 0 °, the incident angle of the green light at 14 °, and the incident angle of the blue light at 20 ° to pass through each lens to the light incident surface of the light guide plate 200. It is an experiment to see if the incident points are the same.

Referring to 8, the green light and the blue light can be seen that the light receiving points S coincide with each other on the light receiving surface of the light guide plate 200. It can be seen that the aberration is small.

At this time, the spec of each lens in order of light incident, the light incident surface 410 of the first lens 400 has a radius of curvature of 21mm, the light emitting surface 411 is formed flat, the light conversion The light incident surface 341 of the part 340 is concavely formed at −19 mm, and the light emitting surface 342 is convexly formed at 22 mm. Further, the light incident surface 510 of the second lens 500 is convexly formed with a radius of curvature of 328 mm, and the light emitting surface 520 is concavely formed with -16 mm.

Therefore, considering the optical error of the lens, the curvature range of each lens may be determined as shown in Table 1 below.

First lens Light conversion unit 2nd lens Light incident 11 to 31mm -9 to -29 mm 318 to 338 mm Light emitting surface ∞ 12 to 32mm -6 to -26 mm

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

100: light source 200: light guide plate
300: light conversion unit 311: curvature plane
400: first lens 500: second lens

Claims (11)

Light guide plate;
A plurality of light sources positioned on side surfaces of the light guide plate to emit light of a specific wavelength band; And
And a light conversion part inserted between the light source and the light guide plate and filled with a quantum dot converting a wavelength band of light emitted from the light source into a long wavelength.
The light conversion unit is a backlight unit formed in a semi-circular column shape or trapezoidal column shape. The backlight unit of claim 1, wherein a curvature surface of the semi-circular column faces the light source. The backlight unit of claim 1, wherein a curvature surface of the semi-circular column faces the light guide plate. The backlight unit of claim 2 or 3, wherein the curvature surface of the semi-circular column has a curvature of 180 mm to 500 mm. The backlight unit of claim 4, wherein the light conversion unit is formed in plural and formed at positions corresponding to the light sources, respectively. The backlight unit of claim 4, wherein the light conversion unit extends to a predetermined length corresponding to the plurality of light sources. The backlight unit of claim 1, wherein the light source is a blue LED, and the quantum dots filled in the light conversion part absorb blue light and emit green light or red light. The backlight unit of claim 1, wherein the light source is a UV LED, and the quantum dot filled in the light conversion unit absorbs an ultraviolet wavelength and emits at least one of blue light, green light, and red light. The backlight unit of claim 1, wherein a gradient angle of the trapezoidal pillar shape is 35 ° to 50 ° based on a horizontal plane. A light source including at least one convex first lens;
A light guide plate having a second lens having one surface convex on a surface on which light emitted from the light source is incident; And
And a light conversion part inserted between the light source and the light guide plate and formed at least one surface of the light guide plate. The light incident surface of the first lens has a radius of curvature of 11 to 31 mm, and a light emitting surface is flat, and the light incident surface of the first lens is concave to have a diameter of -9 to -29 mm. The light emitting surface of the backlight unit is formed convexly (12 ~ 32mm), the light incident surface of the second lens is formed convexly curvature radius of 318 ~ 338mm and the light emitting surface is concave -6 ~ -26mm.

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