KR101844360B1 - Display device - Google Patents

Abstract

A display device is started. The display device includes an optical sheet; A reflective sheet disposed under the optical sheet and directly opposed to the optical sheet; A display panel disposed on the optical sheet; And a light source for emitting light between the optical sheet and the reflection sheet, wherein the reflection sheet includes a diffraction pattern for diffracting light from the light source.

Description

Display device {DISPLAY DEVICE}

The embodiment relates to a display device.

Recently, flat panel display devices such as a liquid crystal display (LCD), a plasma display panel (PDP), and an organic light emitting diode (OLED) have been developed in place of the conventional CRT.

The liquid crystal display device includes a thin film transistor substrate, a color filter substrate, and a liquid crystal display panel in which liquid crystal is injected between both substrates. Since the liquid crystal display panel is a non-light emitting device, a backlight unit for supplying light to the bottom surface of the thin film transistor substrate is positioned. The amount of light irradiated from the backlight unit is adjusted according to the alignment state of the liquid crystal.

The backlight unit is divided into edge type and direct type according to the position of the light source. The edge type is a structure in which a light source is provided on a side surface of the light guide plate.

The direct type is a structure that is mainly developed with the size of a liquid crystal display device being enlarged. One or more light sources are arranged on the lower surface of the liquid crystal display panel to supply light to the liquid crystal display panel.

The direct-type backlight unit has advantages in that it can utilize a larger number of light sources than the edge-type backlight unit and can secure a high luminance, but has a disadvantage that the thickness becomes thicker than the edge type in order to ensure uniformity of brightness have.

Such a liquid crystal display device is disclosed in Korean Patent Laid-Open Publication No. 10-2011-0068110.

The embodiment is intended to provide a display device having a slim structure and improved color uniformity.

A display device according to an embodiment includes an optical sheet; A reflective sheet disposed under the optical sheet and directly opposed to the optical sheet; A display panel disposed on the optical sheet; And a light source for emitting light between the optical sheet and the reflection sheet, wherein the reflection sheet includes a diffraction pattern for diffracting light from the light source.

A display device according to an embodiment includes an optical sheet; A reflective sheet disposed under the optical sheet and directly opposed to the optical sheet; A display panel disposed on the optical sheet; And a light source that emits light between the optical sheet and the reflective sheet, and the reflective sheet reflects light from the light source at a reflection angle larger than the incident angle.

The display device according to the embodiment can directly face the optical sheet and the reflective sheet. Accordingly, the display device according to the embodiment can omit the light guide plate. Therefore, the display device according to the embodiment has a slim structure and can be light.

Further, the reflection sheet includes a diffraction pattern. Accordingly, the reflection sheet can reflect the incident light at a reflection angle larger than the incident angle. Accordingly, the light emitted from the light source may travel further, then pass through the optical sheet, and be incident on the display panel. Therefore, the display apparatus according to the embodiment can prevent the luminance of the portion adjacent to the light source from increasing, and can improve the luminance uniformity as a whole.

Further, the light source generates blue light, and the blue light is converted into green light and red light by the light converting member, and the white light formed thereby can be incident between the optical sheet and the reflective sheet.

At this time, the green light and the red light may have a wide directivity angle as compared with the blue light. At this time, since the green light and the red light have a larger wavelength than the blue light, the directivity angle of the green light and the red light can be narrowed more by the diffraction pattern than the directivity angle of the blue light.

Accordingly, the blue light, the red light, and the green light may have similar directivity angles. Thus, the display device according to the embodiment can have improved color uniformity.

1 is an exploded perspective view showing a liquid crystal display device according to an embodiment.
2 is a cross-sectional view showing one end surface of the liquid crystal display device according to the embodiment.
3 is a view illustrating a process in which light is reflected from a light emitting diode onto a reflective sheet.
4 is a view illustrating a process in which light is reflected from a light emitting diode to a reflective portion.
Figs. 5 to 7 are diagrams showing diffraction patterns. Fig.
8 is a view showing a light emitting diode, a light converting member, and a reflecting sheet according to another embodiment.

In the description of the embodiments, it is described that each substrate, frame, sheet, layer or pattern is formed "on" or "under" each substrate, frame, sheet, In this case, "on" and "under " all include being formed either directly or indirectly through another element. In addition, the upper or lower reference of each component is described with reference to the drawings. The size of each component in the drawings may be exaggerated for the sake of explanation and does not mean the size actually applied.

1 is an exploded perspective view showing a liquid crystal display device according to an embodiment. 2 is a cross-sectional view showing one end surface of the liquid crystal display device according to the embodiment. 3 is a view illustrating a process in which light is reflected from a light emitting diode onto a reflective sheet. 4 is a view illustrating a process in which light is reflected from a light emitting diode to a reflective portion. Figs. 5 to 7 are diagrams showing diffraction patterns. Fig. 8 is a view showing a light emitting diode, a light converting member, and a reflecting sheet according to another embodiment.

1 to 7, a liquid crystal display according to an embodiment includes a backlight unit 10 and a liquid crystal panel 20.

The backlight unit 10 emits light to the liquid crystal panel 20. The backlight unit 10 is a surface light source and can uniformly irradiate the bottom surface of the liquid crystal panel 20 with light.

The backlight unit 10 is disposed under the liquid crystal panel 20. The backlight unit 10 includes a bottom cover 100, a plurality of light emitting diodes 200, a printed circuit board 201, a plurality of optical sheets 300, a reflective sheet 400, and a reflective unit 500 .

The bottom cover 100 has a top opened shape. The bottom cover 100 accommodates the light emitting diodes 200, the printed circuit board 201, the reflection sheet 400, the reflection unit 500, and the optical sheets 300.

The light emitting diodes 200 are light sources for generating light. The light emitting diodes 200 are disposed between the reflective sheet 400 and the optical sheets 300. That is, the light emitting diodes 200 are disposed corresponding to the space between the reflective sheet 400 and the optical sheets 300. The light emitting diodes 200 generate light and emit light between the reflective sheet 400 and the optical sheets 300.

The light emitting diodes 200 may be white light emitting diodes for generating white light.

The light emitting diodes 200 are mounted on the printed circuit board 201. The light emitting diodes 200 are disposed under the printed circuit board 201. The light emitting diodes 200 are driven by receiving a driving signal through the printed circuit board 201.

The printed circuit board 201 is electrically connected to the light emitting diodes 200. The printed circuit board 201 may mount the light emitting diodes 200. The printed circuit board 201 is disposed inside the bottom cover 100.

The optical sheets 300 are disposed on the reflective sheet 400. The optical sheets 300 change or enhance the characteristics of incident light and supply the light to the liquid crystal panel 20. [

The optical sheets 300 may be a diffusion sheet 301, a first prism sheet 302, and a second prism sheet 303.

The diffusion sheet 301 is disposed on the reflective sheet 400. The diffusion sheet 301 is directly opposed to the reflective sheet 400. That is, no other member is interposed between the diffusion sheet 301 and the reflection sheet 400. Only an empty space 110 is formed between the diffusion sheet 301 and the reflective sheet 400.

The diffusion sheet 301 improves the uniformity of the transmitted light. The diffusion sheet 301 may include a plurality of beads.

The first prism sheet 302 is disposed on the diffusion sheet 301. The second prism sheet 303 is disposed on the first prism sheet 302. The first prism sheet 302 and the second prism sheet 303 increase the straightness of light passing therethrough.

The reflective sheet 400 is disposed in the bottom cover 100. More specifically, the reflective sheet 400 is disposed on the bottom surface of the bottom cover 100. The reflective sheet 400 reflects upward the light incident between the diffusion sheet 301 and the reflective sheet 400.

3, the reflection sheet 400 may reflect light from the light emitting diodes 200 at an angle of reflection 2 larger than the incident angle? 1. More specifically, the reflective sheet 400 can reflect visible light with a reflection angle larger than the incident angle. More specifically, the reflective sheet 400 can reflect light of a wavelength band of about 400 nm to about 700 nm at a reflection angle larger than the incident angle. That is, when light from the light emitting diodes 200 is reflected by the reflective sheet 400, it may be closer to the optical axis.

Referring to FIG. 5, the reflective sheet 400 includes a reflective layer 410 and a diffraction pattern 420.

The reflective layer 410 has a high reflectivity. The reflective layer 410 may be formed of a material having a high refractive index. The reflective layer 410 may be a white paint layer. The reflective layer 410 may be an aluminum layer. In addition, the reflective layer 410 may be a resin layer containing titanium oxide particles.

The diffraction pattern 420 is disposed on the reflective layer 410. The diffraction pattern 420 may protrude upward from the upper surface of the reflective layer 410. In addition, the diffraction pattern 420 may expose a part of the upper surface of the reflective layer 410. The upper surface of the reflective layer 410 may be a reflective surface.

The diffraction pattern 420 diffracts light incident on the reflective sheet 400. The diffraction pattern 420 may diffract and reflect the light incident on the reflective sheet 400. Accordingly, the diffraction pattern 420 can make the reflection angle of the light incident on the reflection sheet 400 larger than the incident angle.

Particularly, since the diffraction pattern 420 diffracts the light incident on the reflection sheet 400, a part of the incident light is reflected at a reflection angle larger than the incident angle, and a part of the incident light is reflected at a reflection angle smaller than the incident angle . At this time, the thickness and the pitch P of the diffraction pattern 420 can be adjusted so that the light reflected by the small reflection angle causes destructive interference and the light reflected by the large reflection angle causes the constructive interference.

For example, the pitch P of the diffraction pattern 420 is about 0.2 탆 to about 50 탆, the width W of the diffraction pattern 420 is about 0.1 탆 to about 25 탆, The height H of the diffraction pattern 420 may be about 0.2 μm to about 4 μm.

More specifically, the diffraction pattern 420 has a pitch P of about 0.3 탆 to about 1 탆, the diffraction pattern 420 has a width W of about 0.15 탆 to about 0.5 탆, the diffraction pattern 420 The reflection sheet 400 may have a larger reflection angle with respect to visible light when the height H of the reflective sheet 400 is about 0.4 mu m to about 1 mu m.

In addition, in order to obtain a desired reflection angle with respect to the incident angle, the pitch P of the diffraction pattern 420 may satisfy the following expression (1).

Equation 1

P = m? / (Sin? 1-sin? 2)

Here, P is a pitch P of the diffraction pattern 420, m is an integer,? Is a wavelength of incident light,? 1 is an incident angle, and? 2 is an angle of reflection. In particular, m may be 1, and lambda may be from about 400 nm to about 700 nm. In addition, the pitch P and the height H of the diffraction pattern 420 can be adjusted so that the angle of reflection is about 20 to about 55 when the incident angle is about 10 to about 45 degrees.

Referring to FIG. 6, the diffraction pattern 420 may include a curved surface. The diffraction pattern 420 may have a sin wave shape. That is, the diffraction pattern 420 may have a wave shape. The diffraction pattern 420 may be formed as a curved surface as a whole. Similarly, the reflection angle by the diffraction pattern 420 can be adjusted by the pitch of the diffraction pattern 420 and the height difference between the valley and the mountain.

Referring to FIG. 7, the diffraction pattern 420 may include an inclined surface. The inclined surface is inclined with respect to the optical axis of the light emitting diodes (200). The diffraction pattern 420 may have a saw-tooth shape. The reflection angle of the diffraction pattern 420 may be adjusted by the pitch of the diffraction pattern 420 and the inclination angle of the inclined plane.

The reflective portion 500 is disposed between the diffusion sheet 301 and the reflective sheet 400. The reflective portion 500 is disposed on the lower surface of the diffusion sheet 301. The reflective portion 500 is adjacent to the light emitting diodes 200. The reflective portion 500 may extend in a direction in which the light emitting diodes 200 are aligned in a line. The reflective portion 500 is disposed between the light emitting diodes 200 and the diffusion sheet 301. That is, the light emitting diodes 200 are disposed between the reflective portion 500 and the reflective sheet 400.

Referring to FIG. 4, the reflective portion 500 may have substantially the same characteristics as the reflective sheet 400. That is, the reflection unit 500 can reflect the light from the light emitting diodes 200 at an angle of reflection? 4 larger than the incident angle? 3. More specifically, the reflector 500 may reflect visible light with a reflection angle greater than the incident angle. More specifically, the reflector 500 can reflect light of a wavelength band of about 400 nm to about 700 nm at a reflection angle larger than the incident angle. That is, when light from the light emitting diodes 200 is reflected by the reflection unit 500, the light can be closer to the optical axis.

The reflective portion 500 may have substantially the same configuration as the reflective sheet 400. That is, the reflection unit 500 includes a reflection layer 410 and a diffraction pattern 420, like the reflection sheet 400.

Referring to FIG. 8, the liquid crystal display device according to the embodiment may further include a light conversion member 600. The light conversion member 600 is disposed on the exit surface of the light emitting diodes 200. The light conversion member 600 can convert the wavelength of incident light and emit the light upward.

For example, when the light emitting diodes 200 are a blue light emitting diode, the light converting member 600 may convert blue light emitted upward from the light emitting diodes 200 into green light and red light. That is, the light conversion member 600 converts a part of the blue light into green light having a wavelength band of about 520 nm to about 560 nm, and converts the other part of the blue light to a light having a wavelength range of about 630 nm to about 660 nm It can be converted into red light.

Accordingly, light passing through the light conversion member 600 without being converted and light converted by the light conversion member 600 can form white light. That is, the blue light, the green light, and the red light may be combined, and the white light may be incident on the liquid crystal panel 20.

The light conversion member 600 may include a plurality of light conversion particles (not shown).

The light conversion particles convert the wavelength of light emitted from the light emitting diodes (200). The light conversion particles receive light emitted from the light emitting diodes 200 and convert wavelengths. For example, the light conversion particles may convert blue light emitted from the light emitting diodes 200 into green light and red light. That is, some of the light conversion particles convert the blue light into green light having a wavelength band between about 520 nm and about 560 nm, and another portion of the light conversion particles convert the blue light into light having a wavelength between about 630 nm and about 660 nm It is possible to convert the red light into the red light having the wavelength band of.

The light conversion particles may include a phosphor. More specifically, the light conversion particles may include a green phosphor and a red phosphor.

In addition, the photoconversion particles may be a plurality of quantum dots (QDs). The quantum dot may include core nanocrystals and shell nanocrystals surrounding the core nanocrystals. In addition, the quantum dot may include an organic ligand bound to the shell nanocrystal. In addition, the quantum dot may include an organic coating layer surrounding the shell nanocrystals.

The shell nanocrystals may be formed of two or more layers. The shell nanocrystals are formed on the surface of the core nanocrystals. The quantum dot may convert the wavelength of the light incident on the core core crystal into a long wavelength through the shell nanocrystals forming the shell layer and increase the light efficiency.

The quantum dot may include at least one of a group II compound semiconductor, a group III compound semiconductor, a group V compound semiconductor, and a group VI compound semiconductor. More specifically, the core nanocrystals may include Cdse, InGaP, CdTe, CdS, ZnSe, ZnTe, ZnS, HgTe or HgS. The shell nanocrystals may include CuZnS, CdSe, CdTe, CdS, ZnSe, ZnTe, ZnS, HgTe or HgS. The diameter of the quantum dot may be 1 nm to 10 nm.

The wavelength of light emitted from the quantum dots can be controlled by the size of the quantum dots or the molar ratio of the molecular cluster compound and the nanoparticle precursor in the synthesis process. The organic ligand may include pyridine, mercapto alcohol, thiol, phosphine, phosphine oxide, and the like. The organic ligands serve to stabilize unstable quantum dots after synthesis. After synthesis, a dangling bond is formed on the outer periphery, and the quantum dots may become unstable due to the dangling bonds. However, one end of the organic ligand is in an unbonded state, and one end of the unbound organic ligand bonds with the dangling bond, thereby stabilizing the quantum dot.

Particularly, when the quantum dot has a size smaller than the Bohr radius of an exciton formed by electrons and holes excited by light, electricity or the like, a quantum confinement effect is generated to have a staggering energy level and an energy gap The size of the image is changed. Further, the charge is confined within the quantum dots, so that it has a high luminous efficiency.

Unlike general fluorescent dyes, the quantum dots vary in fluorescence wavelength depending on the particle size. That is, as the size of the particle becomes smaller, it emits light having a shorter wavelength, and the particle size can be adjusted to produce fluorescence in a visible light region of a desired wavelength. In addition, since the extinction coefficient is 100 to 1000 times higher than that of a general dye, and the quantum yield is also high, it produces very high fluorescence.

The quantum dot can be synthesized by a chemical wet process. Here, the chemical wet method is a method of growing particles by adding a precursor material to an organic solvent, and the quantum dots can be synthesized by a chemical wet method.

In this case, the blue light emitted from the light emitting diodes 200 is converted into red light and green light by the light conversion particles, and the red light and the green light are emitted in a random direction.

Accordingly, the red light and the green light emitted from the light conversion member 600 have a wide directivity angle, and the blue light passing through the light conversion member 600 can have a narrow directivity angle.

8, the reflection sheet 400 and the reflection unit 500 may reflect red light R and green light G having a large wavelength with a relatively large reflection angle. Accordingly, the red light R, the green light G and the blue light B can proceed between the diffusion sheet 301 and the reflection sheet 400 with a similar directivity as a whole.

Referring again to FIGS. 1 and 2, the liquid crystal panel 20 is disposed on the optical sheets 500. Further, the liquid crystal panel 20 is disposed on the panel guide 23. The liquid crystal panel 20 may be guided by the panel guide 23.

The liquid crystal panel 20 displays an image by adjusting the intensity of light passing through the liquid crystal panel 20. That is, the liquid crystal panel 20 is a display panel for displaying an image using light emitted from the backlight unit 10. [ The liquid crystal panel 20 includes a TFT substrate 21, a color filter substrate 22, and a liquid crystal layer interposed between the two substrates. In addition, the liquid crystal panel 20 includes polarizing filters.

Although not shown in detail in the drawings, the TFT substrate 21 and the color filter substrate 22 will be described in detail. The TFT substrate 21 defines pixels by intersecting a plurality of gate lines and data lines, A thin film transistor (TFT) is provided for each region and is connected in a one-to-one correspondence with the pixel electrodes mounted on the respective pixels. The color filter substrate 22 includes color filters of R, G and B colors corresponding to the respective pixels, a black matrix for covering the gate lines, the data lines, the thin film transistors, etc., .

And a driving PCB 25 for supplying a driving signal to the gate line and the data line is provided at an edge of the liquid crystal display panel 210.

The drive PCB 25 is electrically connected to the liquid crystal panel 20 by a chip on film (COF) 24. Here, the COF 24 may be changed to a TCP (Tape Carrier Package).

As described above, the liquid crystal display according to the embodiment can directly face the optical sheet and the reflective sheet 400. [ Accordingly, in the liquid crystal display device according to the embodiment, the light guide plate can be omitted. Therefore, the display device according to the embodiment has a slim structure and can be light.

In addition, the reflective sheet 400 includes the diffraction pattern 420. Accordingly, the reflective sheet 400 can reflect incident light at a reflection angle larger than the incident angle. Therefore, the light emitted from the light emitting diodes 200 may be further advanced, and then may be incident on the liquid crystal panel through the optical sheet. Accordingly, the liquid crystal display according to the embodiment can prevent the luminance of the portion adjacent to the light emitting diodes 200 from increasing and improve the luminance uniformity as a whole.

The light emitting diodes 200 emit blue light and the blue light is converted into green light and red light by the light converting member 600 and the white light thus formed is reflected by the optical sheet and the reflective sheet 400, Respectively.

At this time, the green light and the red light may have a wide directivity angle as compared with the blue light. At this time, since the green light and the red light have a larger wavelength than the blue light, the directivity angle of the green light and the red light can be narrowed more greatly than the directivity angle of the blue light by the diffraction pattern 420.

Accordingly, the blue light, the red light, and the green light may have similar directivity angles. Thus, the display device according to the embodiment can have improved color uniformity.

In addition, the features, structures, effects and the like described in the embodiments are included in at least one embodiment of the present invention, and are not necessarily limited to only one embodiment. Furthermore, the features, structures, effects and the like illustrated in the embodiments can be combined and modified by other persons skilled in the art to which the embodiments belong. Therefore, it should be understood that the present invention is not limited to these combinations and modifications.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood that various modifications and applications are possible. For example, each component specifically shown in the embodiments can be modified and implemented. It is to be understood that all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims (13)

Bottom cover;
An optical sheet disposed in the bottom cover;
A reflective sheet disposed in the bottom cover and disposed under the optical sheet, the reflective sheet facing the optical sheet;
A light conversion member disposed in the bottom cover, disposed between the optical sheet and the reflective sheet, the light conversion member including quantum dots and converting the wavelength of the emitted light;
A display panel disposed on the optical sheet; And
And a light source disposed on one inner side surface of the bottom cover inside the bottom cover and emitting light between the optical sheet and the reflective sheet,
The reflection sheet including a plurality of diffraction patterns including curved surfaces disposed on a reflection layer,
A part of the upper surface of the reflection layer is exposed between the diffraction pattern and another diffraction pattern adjacent to the diffraction pattern,
Wherein a part of the emitted light is diffracted in the direction of the display panel by the diffraction pattern and another part of the emitted light is reflected in the direction of the display panel by the reflection sheet. The method according to claim 1,
Wherein the reflection sheet reflects incident light at a reflection angle larger than an incident angle. delete The method according to claim 1,
And the diffraction pattern is protruded from the upper surface of the reflective layer. 5. The method of claim 4,
And the pitch of the diffraction pattern is 0.2 to 50 占 퐉. The method according to claim 1,
Wherein the diffraction pattern includes an inclined surface inclined with respect to the optical sheet. delete The method according to claim 1,
The light source generates blue light,
Wherein the light conversion member converts the blue light into green light and red light. 5. The method of claim 4,
And the diffraction pattern exposes a part of the upper surface of the reflection layer. 5. The method of claim 4,
And the width of the diffraction pattern is 0.1 mu m to 25 mu m. 5. The method of claim 4,
And the height of the diffraction pattern is 0.2 mu m to 4 mu m from the upper surface of the reflective layer. The method according to claim 1,
Wherein the light conversion member is disposed on a side surface of the light source. The method according to claim 1,
Wherein the light source, the optical sheet, and the reflective sheet are disposed apart from each other.

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