KR20120088273A - Back light unit and menufacturing method thererof - Google Patents

Abstract

PURPOSE: A backlight unit and a manufacturing method thereof are provided to easily generate white light even though an inexpensive blue LED is used. CONSTITUTION: A light source(101) emits blue light. A light guide plate(130) makes the blue light of the light source toward a liquid crystal panel. First quantum dots(151) of a quantum dot layer(140) absorb a portion of the blue light and emit red light. Second quantum dots(152) of the quantum dot layer absorb and emit a portion of the blue light and emit green light. A sealing portion(160) seals the quantum dot layer.

Description

BACK LIGHT UNIT AND MENUFACTURING METHOD THEREROF}

The present invention relates to a backlight unit and a method of manufacturing the same.

Liquid crystal displays have a very large share in information display technology. The LCD displays information by inserting a liquid crystal between both glass plates, injecting electrodes through a power supply above and below the glass plate, converting them in each liquid crystal, and emitting light. In this case, the LCD does not emit light from itself but emits light through 'backlight'.

The backlight is directly related to the brightness and power consumption of the panel. In addition, the cost savings of the backlight also have a significant impact on the demand for LCD, as it is the most expensive component among the complete display module. CCFL, EEFL, FFL, LED and the like are used as the light source of the backlight unit. Recently, the LED light source has a higher response rate, excellent color expression, and eco-friendliness than CCFL.

1 is a cross-sectional view of a white LED light source using a fluorescent material according to the prior art. Referring to FIG. 1, in a white LED light source 10 using a fluorescent material according to the related art, a blue LED 11 is mounted on a light emitting element frame 12, and the blue LED 11 is embedded with a polymer to form a polymer phase. The phosphor contains a YAG (Yttrium Aluminum Garnet) -based phosphor 13 that emits a fluorescent material, for example, yellow (wavelength 560 nm). As a result, a mixture of the blue light 22 emitted from the blue LED 11, which is a nitride-based semiconductor element, and the yellow light in which the YAG-based phosphor 13 coated on the polymer material absorbs part of the blue light 33 to excite and emit light White light 30 is realized by the light. The blue light 22 from the GaN blue LED 11 itself and the YAG-based phosphor 13 absorbing the blue light from the GaN blue LED (light emitting diode) 11 serving as the excitation light source are yellow, thereby combining white light 30. This method is low cost and simple power supply circuit, while low luminous efficiency, wide wavelength spacing of blue (23) and yellow light (21) is easy to cause a glare effect due to color separation, the same color coordinate white Mass production of LED is difficult.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and an object of the present invention is to provide a backlight unit and a method of manufacturing the same, which are vivid in color, have high color reproducibility, and can be produced at low cost.

The backlight unit according to the present invention for solving the above problems is a light source for emitting blue light; A light guide plate for directing blue light emitted from the light source to the liquid crystal panel; A quantum dot layer disposed on the light guide plate and including first quantum dots absorbing a portion of blue light emitted from the light guide plate to emit red light and second quantum dots absorbing a portion of the blue light to emit green light; And a sealing part sealing the quantum dot layer.

Preferably, the size of the second quantum dot is smaller than the size of the first quantum dot.

It is preferable that the diameter of the said 1st and 2nd quantum dot is 2 nm-5 nm.

The first or second quantum dots may have one or more shapes of a circle, a triangle, a rectangle, and an oval.

The quantum dot layer may be formed by embedding the first and second quantum dots in a polymer material.

The polymer material may include at least one of a silicone resin, an epoxy resin, and an acrylic resin.

The backlight unit is preferably a side type backlight unit.

The backlight unit may further include a diffusion plate that evenly spreads irregular light generated by the quantum dot layer.

The quantum dot layer is disposed on the light guide plate and includes a first quantum dot layer including first quantum dots that absorbs a portion of the blue light emitted from the light guide plate and emits red light, and a portion of the blue light. It may include a second quantum dot layer including a second quantum dots that absorbs to emit green light.

The backlight unit manufacturing method according to the present invention provides a light guide plate; First quantum dots absorbing blue light and emitting red light and second quantum dots absorbing blue light and emitting green light are mixed with a polymer material to form a quantum dot layer on the light guide plate; Curing the quantum dot layer and cutting to a desired shape and size; Sealing the quantum dot layer.

The method of manufacturing the backlight unit further includes forming a diffusion plate on the quantum dot layer to uniformly diffuse irregular light emitted from the quantum dot layer.

The polymer material may include at least one of a silicone resin, an epoxy resin, and an acrylic resin.

The forming of the quantum dot layer may include forming a first quantum dot layer including first quantum dots absorbing the blue light on the light guide plate and emitting red light, and absorbing the blue light on the first quantum dot layer to form green light. The method may include forming a second quantum dot layer including second quantum dots to emit light.

According to the present invention, even when using an inexpensive blue LED, white light can be easily implemented, and an existing light guide plate and a blue LED can be used as it is. In addition, since the quantum dot is used, the color is clearer and the color reproducibility is excellent than that of the conventional phosphor.

1 is a cross-sectional view of a white LED light source using a fluorescent material according to the prior art.
2 is a cross-sectional view of the backlight unit according to the first embodiment of the present invention.
3 is a sectional view of a backlight unit according to a second embodiment of the present invention.
Figure 4 shows a spectral distribution graph for comparing the performance of the backlight unit according to the present invention and the backlight unit using a fluorescent material according to the prior art.
5 is a cross-sectional view of a liquid crystal display according to an exemplary embodiment of the present invention.
** detailed description of the symbols in the drawings **
101: light source 102: light source housing
130: light guide plate 140, 170: quantum dot layer
151: first quantum dot 152: second quantum dot
160: sealing part

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Hereinafter, a member for a backlight unit using a quantum dot according to a preferred embodiment and a method of manufacturing the same will be described in detail with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail to avoid unnecessarily obscuring the subject matter of the present invention.

First, there are generally two types of backlight, firstly, a light source is provided on the side of the liquid crystal panel to provide light to the liquid crystal layer, and secondly, the light source provides light directly from the bottom of the liquid crystal panel. It is a direct type backlight. The side backlight may be installed on the side of the liquid crystal panel to supply light to the liquid crystal layer through the reflection plate and the light guide plate. Therefore, since the thickness can be made thin, it is mainly used in notebooks and the like which require a thin display device. The present invention is applied to side backlights.

The present invention relates to a backlight unit using a quantum dot (Quantum Dot) in place of the phosphor in the LED backlight unit and a method of manufacturing the same. The backlight unit according to the present invention includes a quantum dot layer made of a light guide plate and a polymer material stacked on the light guide plate and containing quantum dots, or is implemented by coding a polymer material containing quantum dots on the light guide plate.

In addition, the method of manufacturing a backlight unit according to the present invention may include mixing a quantum dot with a polymer material, applying the mixture to a predetermined thickness on a light guide plate, curing the coded mixture and cutting it into a predetermined shape.

2 is a cross-sectional view of the backlight unit according to the first embodiment of the present invention.

Referring to FIG. 2, a backlight unit using a quantum dot according to a first embodiment of the present invention includes a light source 101 and a light source housing 102 for receiving the light source. In addition, the backlight unit includes a light guide plate 130 for directing light emitted from the light source 101 to the liquid crystal panel, and a sealing portion for sealing the quantum dot layer 140 and the quantum dot layer 140 coded on the light guide plate 130. And 170. The light source 101 is housed in the light source housing 102 and is embodied as a blue LED according to this embodiment. Light from the light source 101 is directed to the upper and lower portions of the light guide plate 130 uniformly along the plate surface of the light guide plate 130. At this time, the light directed to the lower portion of the light guide plate 130 is reflected by a reflecting plate (not shown) disposed below the light guide plate 130 and directed to the upper portion of the light guide plate 130. As such, light directed toward the upper portion of the light guide plate 130 is incident on the quantum dot layer 140.

The quantum dot layer 140 is made of a polymer material. For example, a silicone resin, an epoxy resin, and an acrylic resin may be used alone, or may be mixed. A plurality of quantum dots 151 and 152 are embedded in the polymer material.

The quantum dot (quantum dot) is a result of research on 'nano' material, which means a small particle of 1 billionth of a meter, and is one of the nano materials recently attracting attention. The quantum dot is composed of a shell composed of a centroid of about 2-10 nm (nanometer) and a ZnS (zinc sulfide), and usually has a nanoparticle having a size of 10-15 nm because a polymer is applied to the outer surface of the shell. CdSe (cadmium selenide), CdTe (cadmium telluride), and CdS (cadmium sulfide) are mainly used as quantum dots.

Quantum dots generate strong light in a narrow wavelength range. The light emitted by the quantum dots is generated by unstable electrons falling from the conduction band to the valence band. In this case, the quantum dot has a very special property that the smaller the particles generate light of a short wavelength, the larger the particles, the longer wavelength light. Therefore, if the size of the quantum dot is adjusted, it can emit all the light in the visible light region of the desired wavelength. Also, when quantum dots of different sizes are present together, light can be emitted at one wavelength and can produce many colors at once.

The plurality of quantum dots 151 and 152 in the polymer material include red quantum dots 151 and green quantum dots 152. The red quantum dots 151 and the green quantum dots 152 absorb a portion of the blue light emitted from the light source 101 implemented as the blue LED. Red quantum dots 151 absorb a portion of blue light to emit red light, and green quantum dots 152 absorb a portion of blue light to emit green light. The red light emitted from the red quantum dots 151 and the green light emitted from the green quantum dots 152 are mixed to generate yellow light, which is a complementary color of blue. The yellow light thus generated is mixed with the remaining blue light not absorbed by the red quantum dots 151 and the green quantum dots 152 to generate white light.

The size of these quantum dots (151, 152) is preferably 2nm to 5nm. On the other hand, since the quantum dots are smaller particles generate light of a shorter wavelength, the larger particles are longer wavelength light, and the red light is shorter than the green light, the size of the green quantum dot 152 is red quantum dot 151 It is desirable to be smaller than the size of.

In addition, the shape of the quantum dot 60 may have a circular and triangular shape as shown, but is not necessarily limited thereto, and may have another shape such as a square or an ellipse as necessary.

The sealing unit 160 may seal the quantum dot layer 140 so that the quantum dot layer 140 is not separated on the light guide plate 130.

The present invention includes a method of manufacturing a backlight unit according to the first embodiment of the configuration as described above.

First, the light guide plate 130 is prepared. Next, the quantum dot solution is mixed with the polymer material so that the quantum dots are dispersed in the polymer material. The polymer material may be, for example, a silicone resin. The mixing may be performed by a mixer or shaker well known to those skilled in the art. The quantum dot layer 140 is formed by coding a polymer material having mixed quantum dots on a light guide plate 130 in a predetermined thickness according to the present invention. The polymer material may include one or more of a silicone resin, an epoxy resin, and an acrylate resin.

 The predetermined thickness is preferably about 100 μm. Subsequently, the quantum dot layer 140 coded on the light guide plate 130 is cured at a predetermined temperature for a predetermined time. The predetermined temperature is approximately 150 ° C., and the predetermined time is approximately 1 hour. The cured quantum dot layer 140 is cut to have a desired shape and size. Subsequently, the sealing unit 160 is formed by sealing the coded quantum dot layer 140 on the light guide plate 130. Then, the light source 101 and the light source housing 102 are added to form a backlight unit.

3 is a cross-sectional view of a backlight unit using a quantum dot according to the second embodiment of the present invention. In this embodiment, it demonstrates mainly different from 1st embodiment, and the part which is not described follows 1st embodiment. Like numbers refer to like elements.

Referring to FIG. 3, the backlight unit according to the second exemplary embodiment of the present invention includes a light source 101, a light source housing 102 accommodating the light source, and a light guide plate 130 for directing light from the light source 101 to the liquid crystal panel. And a sealing unit 170 sealing the quantum dot layer 170 and the quantum dot layer 170 coded on the light guide plate 130.

The quantum dot layer 170 includes a first quantum dot layer 171 and a second quantum dot layer 172. The first quantum dot layer 171 is made of a polymer material, and a plurality of first quantum dots 151 having one color are embedded. The second quantum dot layer 172 is also made of a polymer material, and a plurality of second quantum dots 152 having a color different from the color of the quantum dot 151 embedded in the first quantum dot layer 171 is embedded. The first quantum dot 151 has one of red and green colors, and the second quantum dot 152 has one of red and green colors.

In FIG. 3, although the first quantum dot 151 has a red color and the second quantum dot 152 has a green color, the present invention is not limited thereto.

Hereinafter, a method of manufacturing the backlight unit according to the second embodiment of the configuration as described above will be described.

First, the light guide plate 130 is prepared. Next, the quantum dot solution is mixed with the polymer material so that the quantum dots are dispersed in the polymer material. The quantum dot layer 170 is formed by coding a polymer material mixed with quantum dots to a predetermined thickness on the light guide plate 130 according to the present invention.

The quantum dot layer 170 according to the second embodiment of the present invention includes a plurality of quantum dot layers. Therefore, in the first embodiment, the quantum dot layer 140 may be formed by one coating. However, when the quantum dot layer 170 according to the second embodiment includes a plurality of quantum dot layers, the coating and curing are performed a plurality of times. It can be formed by. Therefore, when forming different quantum dot layers including different types of quantum dots, a first mixed liquid obtained by mixing a plurality of first quantum dots with a first polymer material is prepared, and the first mixed liquid is prepared on the light guide plate 130. It is applied to one predetermined thickness and cured to form a first quantum dot layer 171.

Subsequently, a second mixed solution obtained by mixing a plurality of second quantum dots with a second polymer material is prepared, and the second quantum dot layer 172 is coated on the first quantum dot layer 171 to a second predetermined thickness and cured. 2 quantum dot layer 172 is formed. The first quantum dot has a different color than the second quantum dot. The color obtained by mixing the color of the first quantum dot and the color of the second quantum dot is complementary to the color of light emitted from the light source 101. The first polymer material and the second polymer material may be the same. The first predetermined thickness and the second predetermined thickness may be the same. That is, the first quantum dot layer 171 and the second quantum dot layer 172 may be coated on the light guide plate 130 and the first quantum dot layer 171 with the same thickness. In addition, the temperature at which the first quantum dot layer 171 and the second quantum dot layer 172 are cured is approximately 150 ° C., and the curing time is approximately 1 hour.

In addition, the quantum dot layer 170 formed as described above is cut to have a desired shape and size. Next, the sealing unit 160 is formed by sealing the quantum dot layer 170. Then, the light source 101 and the light source housing 102 are added to form a backlight unit.

The backlight unit according to the first embodiment or the second embodiment as described above emits high quality white light and can obtain higher spectroscopic color reproducibility than the conventional backlight unit.

Figure 4 shows a spectral distribution graph for comparing the performance of the backlight unit according to the present invention and the backlight unit using a fluorescent material according to the prior art.

As shown in FIG. 4, when the YAG fluorescent material is used for a conventional blue LED in the backlight unit according to the related art, the wavelength of the blue light B has a peak at 450 nm. Further, the interval of the wavelength of the yellow light Y is about 555 nm to 560 nm, which is a very wide range. Therefore, color reproduction of red light or green light cannot be reproduced clearly.

On the other hand, looking at the spectral distribution of the light emitted from the backlight unit according to the present invention, the blue light (B) may be implemented by a blue LED as described above. The green light G has a wavelength range of about 555 nm to 560 nm, and the red light R has a wavelength interval of about 620 nm to 630 nm. That is, it can be seen that the green light and the red light have narrow wavelength spacings, and thus show a more vivid color reproduction rate than when using the backlight of the prior art shown in FIG. In particular, by adjusting the amount of use of the green quantum dots and red quantum dots can be further increased the size of these peaks.

Next, a liquid crystal display employing a backlight unit according to the present invention will be described with reference to FIG. 5.

5 is a cross-sectional view of a liquid crystal display according to an exemplary embodiment of the present invention.

Referring to FIG. 5, the liquid crystal display includes a light source 101, a light source housing 102, a reflective sheet 120, a reflective pattern 120, a light guide plate 130, a quantum dot layer 140, a diffusion plate 180, The prism sheet 190 and the liquid crystal panel 200 are included.

Light from the light source 101 is directed to the upper and lower portions of the light guide plate 130 uniformly along the plate surface of the light guide plate 130. In this case, the light directed to the lower portion of the light guide plate 130 is reflected by the pattern 120 disposed under the light guide plate 130 and directed to the upper portion of the light guide plate 130. In addition, the reflective sheet 120 is disposed on the lower surface of the light guide plate 130 to be substantially equal to the area of the light guide plate 130 to prevent light from leaking to the lower surface of the light guide plate 130. That is, when a part of the light emitted from the light source 101 is directed to the reflective sheet 120, it is reflected by the reflective sheet 120 again and directed to the quantum dot layer 140 through the light guide plate 130.

As described above, blue light emitted from the light source 101 is incident on the quantum dot layer 140, and white light is emitted by the quantum dots 151 and 152. The quantum dot layer 140 is sealed by a seal, but the illustration of the seal is omitted in FIG. 5.

The diffusion plate 180 evenly spreads irregular light generated by the quantum dot layer 140 arranged at the bottom of the backlight unit, and supports various optical sheets. According to the prior art, the diffusion plate 180 is generally used in a direct type backlight unit, but the backlight unit of the present invention is used to evenly diffuse the light emitted from the quantum dot layer 140.

After the light passes through the diffuser plate 180, the light luminance is diffused in both the horizontal and vertical directions perpendicular to the plane, and the light luminance rapidly drops.

The prism sheet 190 is used to refocus this light to raise the light brightness. Prism sheet 190 is a strip-type micro-prism is formed on the base material (PET) base material, and most of the horizontal and vertical sheets (191,192) are used as one set. Finally, the viewing angle and luminance of the light passing through the prism sheet 190 are improved.

In the foregoing detailed description of the present invention, specific examples have been described. However, various modifications are possible within the scope of the present invention. The technical spirit of the present invention should not be limited to the above-described embodiments of the present invention, but should be determined by the claims and equivalents thereof.

Claims (13)

A light source emitting blue light;
A light guide plate for directing blue light emitted from the light source to the liquid crystal panel;
A quantum dot layer disposed on the light guide plate and including first quantum dots absorbing a portion of blue light emitted from the light guide plate to emit red light and second quantum dots absorbing a portion of the blue light to emit green light; And
And a sealing unit sealing the quantum dot layer. The method of claim 1,
And the size of the second quantum dot is smaller than the size of the first quantum dot. The method of claim 1,
The diameter of the first and second quantum dots is 2nm to 5nm backlight unit. The method of claim 1,
The first or second quantum dot is a backlight unit having a shape of at least one of circular, triangular, square, oval. The method of claim 1,
And the quantum dot layer is formed by embedding the first and second quantum dots in a polymer material. The method of claim 5,
The polymer material may include at least one of a silicone resin, an epoxy resin, and an acrylic resin. The method of claim 1,
The backlight unit is a backlight unit is a side type backlight unit. The method of claim 7, wherein
The backlight unit further comprises a diffuser plate to evenly diffuse the irregular light generated by the quantum dot layer. The method of claim 1,
The quantum dot layer is disposed on the light guide plate and includes a first quantum dot layer including first quantum dots that absorbs a portion of the blue light emitted from the light guide plate and emits red light, and a portion of the blue light. And a second quantum dot layer including second quantum dots to absorb green light and emit green light. Providing a light guide plate;
First quantum dots absorbing blue light and emitting red light and second quantum dots absorbing blue light and emitting green light are mixed with a polymer material to form a quantum dot layer on the light guide plate;
Curing the quantum dot layer and cutting to a desired shape and size;
A backlight unit manufacturing method comprising sealing the quantum dot layer. The method of claim 10,
And forming a diffuser plate on the quantum dot layer to uniformly diffuse irregular light emitted from the quantum dot layer. The method of claim 10,
The polymer material may include at least one of a silicone resin, an epoxy resin, and an acrylic resin. The method of claim 10,
Forming the quantum dot layer is
Forming a first quantum dot layer including first quantum dots absorbing the blue light and emitting red light on the light guide plate;
And forming a second quantum dot layer on the first quantum dot layer, the second quantum dot layer including second quantum dots to absorb green light and emit green light.

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