KR102353715B1 - Quantom dot film and liquid crystal display device with the same - Google Patents

Abstract

The present invention relates to a quantum dot film 150 and a liquid crystal display having the same, wherein the spacer 157 for maintaining the thickness of the quantum dot material 155 is a different material, the core 158 and the shell 159 surrounding it. is composed of, the refractive index of the core 158 is greater than that of the shell 159, and the surface of the core 158 and the shell 159 is characterized in that they are curved, thereby improving the color of the liquid crystal display and improving the luminance. and the thickness of the quantum dot film 150 may be thinned.

Description

QUANTOM DOT FILM AND LIQUID CRYSTAL DISPLAY DEVICE WITH THE SAME

The present invention relates to a quantum dot film having a spacer of a core-shell structure and a liquid crystal display including the same.

In general, a liquid crystal display (LCD) is one of the flat panel display devices that display an image using liquid crystal, and has advantages of being thin and light compared to other display devices, and having a low driving voltage and low power consumption. It is widely used throughout.

Such a liquid crystal display device requires a backlight unit including a light source for supplying light because the liquid crystal display panel for displaying an image is a non-luminous element that does not emit light by itself.

As a light source, a light emitting diode (LED), which has a faster response speed, superior color expression, and environmental friendliness compared to a Cold Cathode Fluorescent Lamp (CCFL), is widely used.

In particular, in recent years, an image is implemented on a liquid crystal display panel using a quantum dot film on which quantum dots are formed and white light generated through an LED. The quantum dot film includes a plurality of quantum dots emitting light of different wavelength bands, and wavelength-converted light irradiated from the backlight unit through a quantum dot effect is emitted.

1 is a cross-sectional view showing a conventional quantum dot film (50). Referring to FIG. 1 , the quantum dot film 50 is an upper film 51 , a lower film 52 , a barrier layer 53 , and a quantum dot material layer 55 disposed between the upper film 51 and the lower film 52 . ) and a partition wall 56 . The barrier rib 56 is formed on the lower film 52 , has a constant height h, and serves to uniformly maintain the thickness of the quantum dot material layer 55 over the entire area of the quantum dot film 50 .

2a to 2b are diagrams illustrating a method of manufacturing the barrier rib 56 in the conventional quantum dot film 50 . First, referring to FIG. 2A , a resin 60 , which is a light-transmitting material such as _{SiO 2 , is coated on the lower film 52 .} Next, as shown in FIG. 2B , the barrier layer 53 and the partition wall 56 are formed by molding the applied resin 60 using a mold 62 having a mold in the shape of the partition wall 56 .

However, in the process of forming the partition wall 56 using the mold 62, the partition wall 56 is not formed or broken after molding, etc. There is a problem in that the thickness of the quantum dot material layer 55 is not maintained uniformly because the height of the barrier rib 56 is not constant. If the thickness of the quantum dot material layer 55 is not maintained uniformly, the quantum dot concentration becomes non-uniform at various positions in the phosphor film 50, so that the probability that the light incident from the light source is emitted through the quantum dot is also non-uniform, and thus finally A phenomenon in which the color is different occurs at each flat position of the panel displaying the screen.

In addition, the light emitted from the light source is incident on the quantum dot film 50 through the light guide plate. As seen above, the barrier rib 56 is formed by molding the resin 60, so it is composed of a material having light transmittance such as _{SiO 2 .} , even if it is a translucent material, it does not transmit all of the incident light, but reflects a part. Furthermore, as the barrier rib 56 has a height h as much as the required thickness to be maintained by the quantum dot material layer 55, the amount of light incident from the light guide plate is increased, and thus luminance loss occurs. .

In the quantum dot, the smaller the particle, the shorter the wavelength of light, and the larger the particle, the longer the light. Accordingly, light of various wavelengths such as red, green, and blue can be easily obtained by adjusting the size of the quantum dots. For example, when a light emitting device emitting blue light is used as a light source and white light is emitted through the quantum dot material layer 55 , the quantum dot material layer 55 absorbs light in the blue wavelength band to emit light in the green wavelength band. It includes a quantum dot of a size that emits light and a quantum dot of a size that emits light in a red wavelength band. Accordingly, while the blue light emitted from the light source passes through the quantum dot material layer 55 , the quantum dots absorb blue light and convert it into light of a green or red wavelength band, and as a result, blue, green, and red wavelengths Light is mixed with each other to emit white light. However, in order to emit white light using these quantum dot characteristics and to have high color reproducibility of green and red, the quantum dot material layer 55 must include a certain concentration of quantum dots and, accordingly, have a certain thickness. Therefore, the backlight unit including the quantum dot film 50 has a loss in thickness than the conventional liquid crystal display having a white light emitting light source, and furthermore, the current quantum dot is an expensive material, and the quantum dot material layer 55 is a quantum dot of a certain concentration. There is a problem of cost increase when manufacturing a backlight unit including the need to include.

The present invention is to solve the above problems, and the present invention is a quantum dot film capable of improving color difference, improving luminance, and reducing the thickness of a quantum dot material layer, and a liquid crystal display having the same, compared to a conventional barrier rib structure. is to provide

In order to achieve the above object, the quantum dot film and the display device having the same according to the present invention maintain the thickness of the quantum dot material layer through a spacer having a core-shell structure rather than a barrier rib, and the refractive index of the core is greater than that of the shell, The core and shell have surfaces that are curved.

The liquid crystal display device of the present invention maintains the thickness of the quantum dot material layer of the quantum dot film through a spacer having a double refractive index as a core-shell structure, thereby improving color and improving luminance compared to the conventional barrier rib structure, and the core and shell are curved By having a surface, the thickness of the quantum dot film can be made thin.

1 is a cross-sectional view showing a conventional quantum dot film.
2a to 2b is a view showing a conventional method for manufacturing a barrier rib of a quantum dot film.
3 is an exploded perspective view illustrating a liquid crystal display device of the present invention.
4 is a cross-sectional view showing the quantum dot film of the present invention.
5 is a cross-sectional view of the interface between the core and the shell for explaining the luminance improvement process of the present invention.
6 is an exploded perspective view of the quantum dot film 150 for explaining the spacer arrangement of the present invention.
7 is a view for explaining a luminance test result of a liquid crystal display according to the related art and the present invention.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

3 is an exploded perspective view illustrating a liquid crystal display device of the present invention.

Referring to FIG. 3 , the liquid crystal display may include a backlight unit 10 and a display unit 20 . Since the components shown in FIG. 3 are not essential, the display device according to the exemplary embodiments of the present invention may include more or fewer components.

The backlight unit 10 includes a light guide plate 110 , a light source module 120 disposed on a side surface of the light guide plate 110 to provide light, a reflective sheet 130 disposed under the light guide plate 110 , and the light guide plate 110 . It may include a quantum dot film 150 disposed on the quantum dot film 150 , and at least one optical sheet 160 disposed on the quantum dot film 150 . In addition, the backlight unit 10 may include the light guide plate 110 , the light source module 120 , and the cover bottom 140 accommodating the reflective sheet 130 .

The light guide plate 110 serves to diffuse the incident light emitted from the light source module 120 through total reflection or the like to form a surface light source. The light diffused by the light guide plate 110 is irradiated toward the display unit 20 .

The light guide plate 110 may be made of a transparent material. For example, the light guide plate 110 may include one of an acrylic resin series such as PMMA (polymethyl metaacrylate), polyethylene terephthlate (PET), poly carbonate (PC), cycloolefin copolymer (COC), and polyethylene naphthalate (PEN) resins. have.

The light source module 120 is coupled to at least one side surface of the light guide plate 110 , and may include a substrate 121 , a light emitting device package 122 disposed on the substrate 121 at predetermined intervals, and the like.

The substrate 121 may include a printed circuit board (PCB) including a circuit pattern for supplying an electric signal to the light emitting device package 122 .

The light emitting device package 122 is electrically connected to a circuit pattern formed on the substrate 121 and operates as a light source of the display device. That is, the light emitting device package 122 receives an electric signal from the circuit pattern of the substrate 121, converts it into an optical signal, and outputs it.

Meanwhile, the light emitting device package 122 may be provided on the side surface of the cover bottom 140 or on a heat dissipation plate (not shown). In this case, the substrate 121 for supporting the light emitting device package 122 may be omitted.

A reflective sheet 130 may be disposed under the light guide plate 110 . The reflective sheet 130 may improve the brightness of the backlight unit 210 by reflecting the light incident on the lower surface of the light guide plate 110 and directing it upward.

The reflective sheet 130 is not limited thereto, but may be formed of PET, PC, PVC resin, or the like.

The cover bottom 140 may be made of metal or the like, and may have a box shape with an open top. For example, the cover bottom 140 may be formed by bending or bending a metal plate or the like.

The light source module 120 , the light guide plate 110 , the reflective sheet 130 , and the optical sheet 160 are accommodated in a space formed by bending or bending the cover bottom 140 . In addition, the cover bottom 140 supports the liquid crystal display panel 210 .

A quantum dot film 150 is disposed on the light guide plate 110 .

The quantum dot film 150 includes a plurality of quantum dots emitting light of different wavelength bands, and converts the wavelength of light irradiated from the light source module 120 through the quantum dot effect and emits it.

The quantum dot film 150 may include a plurality of quantum dots and a resin material. The resin material may include epoxy, silicone, and the like.

At least one optical sheet 160 having light-transmitting properties may be disposed on the quantum dot film 150 .

The optical sheet 160 may include, for example, a diffusion sheet 161 , a polarizing sheet 162 , a prism sheet 163 , and the like.

The diffusion sheet 161 directs the light incident from the light source module 120 to the front of the liquid crystal display panel 210 and diffuses the light to have a uniform distribution in a wide range to irradiate the liquid crystal display panel 210 . .

The polarizing sheet 162 performs a function of polarizing the obliquely incident light from among the light incident on the polarizing sheet 162 to be vertically emitted. At least one polarizing sheet 162 may be disposed under the liquid crystal display panel 210 to vertically change the light emitted from the diffusion sheet 161 .

The prism sheet 163 transmits light parallel to its own transmission axis and makes it incident on the liquid crystal display panel 210 , and reflects light perpendicular to the transmission axis.

The display unit 20 may include a liquid crystal display panel 210 and a driving circuit unit 220 . In addition, the display unit 20 may further include a guide panel 230 supporting the display panel 210 , a top case 240 surrounding the edge of the liquid crystal display panel 210 and coupled to the guide panel 230 , etc. have.

The liquid crystal display panel 210 is a display unit of a liquid crystal display and may include a thin film transistor (TFT) substrate, a color filter substrate, and a liquid crystal layer interposed between the two substrates. The thin film transistor substrate includes a plurality of gate lines, a plurality of data lines intersecting the plurality of gate lines, and a thin film transistor (TFT) formed in a region where each gate line and the data lines intersect.

A driving circuit unit 220 may be connected to one side of the liquid crystal display panel 210 . The driving circuit unit 220 includes a printed circuit board (PCB) 221 that supplies a scan signal to the gate line of the thin film transistor substrate, and a printed circuit board 222 that supplies a data signal to the data line. .

The light emitted from the light source module 120 is diffused by the light guide plate 110 and proceeds in various paths with various orientation angles. Some of them are wavelength-converted and emitted by the quantum dots included in the quantum dot film 150 , and some of them are emitted without passing through the quantum dots. Accordingly, when the concentration of the quantum dot material layer 155 is uniformly maintained over the entire area of the quantum dot film 150 , the color of the liquid crystal display panel 210 can be recognized uniformly.

Meanwhile, in FIG. 3 , the edge type backlight unit 10 is illustrated as an example, but the present invention is not limited thereto. According to the present invention, the backlight unit may be implemented as a direct type. In this case, if a diffuser plate is applied to the backlight unit 10 instead of the light guide plate 110 , the quantum dot film 150 may be disposed on or below the diffuser plate or may be implemented integrally with the diffuser plate.

Hereinafter, the quantum dot film 150 of the present invention will be described in detail with reference to the necessary drawings.

4 is a cross-sectional view showing the quantum dot film 150 of the present invention.

Referring to FIG. 4 , the quantum dot film 150 includes an upper film 151 , a lower film 152 , a barrier layer 153 positioned on the lower film 152 , an upper film 151 and a barrier layer 153 . It may include a quantum dot material layer 155 disposed therebetween, and a spacer 157 between the upper film 151 and the barrier layer 153 to maintain a uniform thickness of the quantum dot material layer 155 .

The upper film 151 and the lower film 152 may be made of various materials having light-transmitting properties. For example, the upper film 151 and the lower film 152 are not limited thereto, but may be made of PET.

_{The barrier layer 153 is formed by applying a light-transmitting material such as SiO 2} , which is not limited thereto, to the upper portion of the lower film 152 , and may have grooves in which the spacers 157 can be accommodated.

The upper film 151 , the lower film 152 , the barrier layer 153 , and the quantum dot material layer 155 may be compressed to have a film-like structure. When the quantum dot material layer 155 comes into contact with oxygen, moisture, etc., the lifetime is reduced. In order to prevent this, the upper film 151 , the lower film 152 and the barrier layer 153 protect and seal the quantum dot material layer 155 . do.

The quantum dot material layer 153 exists in the form of a thin film between the upper film 151 and the lower film 152, and converts the wavelength of incident light.

The quantum dot material layer 153 may include a plurality of quantum dots and the same.

Quantum dots refer to particles of a predetermined size (eg, about 2 to 15 nm) having a quantum confinement effect, and are composed of a core and a shell made of ZnS (zinc sulfide). Examples of the quantum dot core include CdSe (cadmium selenide), CdTe (cadmium telluride), and CdS (cadmium sulfide).

Quantum dots can be synthesized by a chemical wet method. The chemical wet method is a method of growing particles by putting a precursor material in an organic solvent, and the chemical wet method for synthesizing quantum dots may be accomplished by various existing methods.

The spacer 157 may include a core 158 and a shell 159 surrounding it. The spacer 157 may have a ball shape because the core 158 and the shell 159 have a ball shape, but is not limited thereto and can be deformed into various shapes having a curved surface, such as an ellipse or a lenticular, and the core A shape in which the 158 is formed on the barrier layer 153 and the shell 159 covers it is also possible.

The core 158 may be made of various materials having light-transmitting properties. For example, the core 158 may be formed of one _{of TiO 2} , ZrO _{2 , and ZnO.}

The shell 159 may be made of various materials having light-transmitting properties. For example, the shell 159 may be made of SiO ₂ .

As described above, since the core 158 and the shell 159 constituting the spacer 157 are formed of different materials, the refractive indices of the core 158 and the shell 159 have different values. _{The refractive index n 2} of the material constituting the core 158 may have a greater value than _{the refractive index n 2} of the material constituting the shell 159 . Some of the light emitted from the light source module 120 is incident on the spacer 157 , and is refracted at an incident angle more perpendicular to the upper film 151 as it is emitted from the core 158 to the shell 159 .

5 is a cross-sectional view of the interface between the core and the shell for explaining the luminance improvement process of the present invention.

_{The light l 1} incident at an angle of _{θ 1} with respect to the interface between the core 158 and the shell 159 is an example, and the light l ₁ incident from the core 158 is the core 158 and the shell 159 . ) _{is incident at an angle of θ 1} , and is again emitted at an angle of _{θ 2} with respect to the interface between the core 158 and the shell 159 . At this time, the refractive index (n _{1 ) of the material constituting the core 158 has a value greater than the refractive index (n 2} ) of the material constituting the shell 159, so _{that the θ 1} value is the θ ₂ value according to Snell's law. As it becomes smaller, the value of θ _{4 which is the incident angle of the outgoing light l 2} with respect to the horizontal plane of the upper film 151 is closer to _{θ 3} which is the incident angle of the incident _{light l 1 .} Accordingly, the emitted light l ₂ is refracted at a more perpendicular slope to the upper film 151 than the incident light l _{1 .}

The diffusion sheet 161 diffuses the light incident from the light source module 120 to irradiate the liquid crystal display panel 210 , and the emitted light l ₂ is more perpendicular to the upper film 151 than the incident light l _{1 .} As it is refracted at one slope and is incident on the diffusion sheet 161 , the ratio of the light that is directed toward the front of the liquid crystal display panel 210 out of the total light emitted from the diffusion sheet 161 is increased, and the As a result, the ratio of the polarized light also increases, which in turn increases the luminance of the liquid crystal display.

[Table 1] below is an experimental example for the light output amount of the quantum dot film.

[Table 1]

Sample 1 is an example of the conventional barrier rib structure quantum dot film of FIG. 1, and Sample 2 is an experimental example of the present invention. 7 is a view for explaining a luminance test result of a liquid crystal display according to the related art and the present invention. Referring to FIG. 7, in the case of Sample 1, a square having a length of 0.6 mm on one side and a height of 0.96 mm is _{a barrier rib structure of a SiO 2} material, and in the case of Sample 2, a core 158 _{of a TiO 2 material having a radius of 0.2 mm.} and a spacer 157 composed of a shell 159 _{of SiO 2} material having a radius of 0.48 mm. The partition wall and the spacers 157 were arranged at the same interval of 2.42 mm. When the amount of light incident on the lower film 152 is 683 lm, Sample 1 emits 309 lm, but Sample 2 emits 316 lm, which increases the output amount by about 2.3%.

6 is an exploded perspective view of the quantum dot film 150 for explaining the spacer 157 arrangement of the present invention.

_{The barrier layer 153 is formed by applying a light-transmitting material such as SiO 2} on the lower film 152, and may have grooves in which the spacers 157 can be accommodated. The spacers 157 are disposed in the grooves and can be fixed to the barrier layer 153 even when the liquid crystal display moves. In addition, a barrier layer having the same configuration may be additionally formed on the upper film 151 . At this time, the grooves of the barrier layer formed on the upper film 151 vertically overlap the grooves of the barrier layer 153 formed on the upper portion of the lower film 152 .

Accordingly, the thickness of the quantum dot material layer 55 is maintained uniformly and the quantum dot concentration is uniform over the entire area of the phosphor film 50 , so that the probability that the light incident from the light source is emitted through the quantum dots is also uniform. Accordingly, the present invention emits uniform white light over the entire area of the quantum dot film 150 compared to the conventional barrier rib structure, which has a high possibility of process defects, so that the color can be maintained uniformly at each flat position of the panel.

When the light source module 120 emits blue light, the light incident to the spacer 157 is blue light emitted from the light source module 120 . Since the surface of the core 158 and the shell 159 of the present invention has a curved shape, a ratio of light scattering from the surface is higher than that of a quantum dot film having a conventional barrier rib structure. Blue light incident on the spacer 157 is diffused in various directions on the curved surface of the core 158 or shell 159 , and some of the diffused light passes through the quantum dot material layer 155 and is a red or green quantum dot. It is converted into a wavelength in the red or green band by incident to

Therefore, as compared to the quantum dot film having a conventional barrier rib structure, some of the blue light incident to the spacer 157 also passes through the quantum dots, so that the quantum dots of the present invention convert more blue light into red or green light. Accordingly, the present invention can have a high color gamut of green and red while emitting white light even with a small number of quantum dots compared to the prior art, and accordingly, the thickness of the quantum dot film 150 can be reduced and manufacturing costs can be reduced.

The above description is merely illustrative of the present invention, and various modifications may be made by those of ordinary skill in the art to which the present invention pertains without departing from the technical spirit of the present invention. Therefore, the embodiments disclosed in the specification of the present invention do not limit the present invention. The scope of the present invention should be interpreted by the following claims, and all technologies within the scope equivalent thereto should be construed as being included in the scope of the present invention.

10: backlight unit 110: light guide plate
120: light source module 130: reflective sheet
140: cover bottom 150: quantum dot film
151: upper film 152: lower film
153: barrier layer 155: quantum dot material layer
157: spacer 158: core
159: shell 160: optical sheet
161 diffusion sheet 162 polarizing sheet
163: light collecting sheet 20: display unit
210: liquid crystal display panel 220: driving circuit unit
221: gate signal printed circuit board 222: data signal printed circuit board
230: guide panel 240: top case

Claims (15)

an upper film 151 and a lower film 152 facing each other;
a first barrier layer 153 laminated on the lower film 152;
a quantum dot material layer 155 positioned between the upper film 151 and the first barrier layer 153;
a spacer 157 positioned between the upper film 151 and the lower film 152 and maintaining the thickness of the quantum dot material layer 155; and
and a first groove formed in the first barrier layer 153 to receive the spacer 157,
The spacer 157 is a quantum dot film 150 including a core 158 and a shell 159 surrounding the core 158 .
The method of claim 1,
Quantum dot film 150, characterized in that the core 158 and the shell 159 are different materials.
3. The method of claim 2,
Quantum dot film 150, characterized in that the refractive index of the core 158 is greater than the refractive index of the shell (159).
delete The method of claim 1,
The core 158 and the shell 159 are quantum dot film 150, characterized in that the surface is a curved surface.
6. The method of claim 5,
The core 158 and the shell 159 are quantum dot film 150, characterized in that the ball shape.
In the liquid crystal display device comprising a backlight unit (10) having a liquid crystal display panel (210) and a quantum dot film (150),
The quantum dot film 150 includes an upper film 151 and a lower film 152 facing each other, a quantum dot material layer 155 and the upper film 151 positioned between the upper film 151 and the lower film 152 . ) and a spacer 157 positioned between the lower film 152 and maintaining the thickness of the quantum dot material layer 155,
The backlight unit 10 includes a light source module 120 for emitting light,
The light incident on the spacer 157 is vertically refracted while exiting from the core 158 to the shell 159 at an angle of incidence with respect to the horizontal plane of the upper film 151,
The spacer (157) includes the core (158) and the shell (159) surrounding the core (158).
8. The method of claim 7,
The liquid crystal display device, characterized in that the core (158) and the shell (159) are made of different materials.
9. The method of claim 8,
The liquid crystal display device, characterized in that the refractive index of the core (158) is greater than the refractive index of the shell (159).
delete 8. The method of claim 7,
The quantum dot film 150 is laminated on the lower film 152 to further include a barrier layer 153 for positioning the quantum dot material layer 155 and the spacer 157 between the upper film 151 and the upper film 151 . includes,
The barrier layer (153) has a groove for accommodating the spacer (157).
8. The method of claim 7,
The surface of the core (158) and the shell (159) is a liquid crystal display, characterized in that the curved surface.
13. The method of claim 12,
The core (158) and the shell (159) is a liquid crystal display, characterized in that the ball shape.
14. The method of claim 13,
The backlight unit 10 includes a light source module 120 emitting blue light,
The quantum dot material layer 155 includes quantum dots that absorb the blue light and convert it into light of a green or red wavelength band.

The method of claim 1,
A second barrier layer is laminated on the upper film 151 to position the quantum dot material layer 155 and the spacer 157 between the lower film 152 and the second barrier layer,
The second barrier layer is a quantum dot film (150) having a second groove for receiving the spacer (157).

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