KR20220030398A - Back light unit and display apparatus having the same - Google Patents

Abstract

A backlight unit according to an embodiment of the present invention includes: a light guide plate which extracts light from a light source; a light extraction device which is provided on one surface of the light guide plate, to vertically extract light of a specific wavelength region from the light guided by the light guide plate; and a light absorbing film which is disposed on one surface of the light guide plate, to absorb light that is not in a vertical direction of the light extracted from the light guide plate to the light extraction device.

Description

A backlight unit and a display device having the same

The present invention relates to a backlight unit and a display device having the same, and more particularly, it is possible to emit light of a specific wavelength from a light source in a vertical direction by means of a light extraction device, and not in a vertical direction by a light absorption film The present invention relates to a backlight unit capable of improving color gamut by absorbing and removing light emitted in a direction, and a display device having the same.

A display device, which is a type of device for displaying an image, is a device for displaying an image using a display panel and is used in various devices such as a television, a computer monitor, a smart phone, and various smart pads.

However, since a general display device cannot emit light by itself, a separate light source such as a backlight unit is required, and the backlight unit is generally disposed behind the display panel.

The backlight unit may be classified into an edge type type that requires a light guide panel (LGP) that uniformly guides light emitted from a light source to a display panel, and a direct type type that does not require a light guide panel. The direct backlight unit in which the light source is disposed directly below the display panel may not use a light guide plate.

However, in response to consumer demand for display devices that are thin and have almost no bezels, edge-type backlight units capable of slimming the display devices by arranging the light sources on the side of the light guide plate have been widely used.

In a conventional backlight unit, a diffraction grating for selectively diffracting only light having a wavelength corresponding to the RGB tri-color light among incident light irradiated from an external light source is formed on the light guide plate.

However, the backlight technology, which implements high color reproduction by applying the diffraction grating as a light extraction element, lacks the ability to selectively extract only RGB specific light due to the color dispersion characteristics of the diffraction grating, and thus implements the function of a high-color reproduction backlight. There is a limit to what is difficult to do.

Accordingly, the development of a backlight unit having a new configuration capable of realizing a high color reproduction function is required.

As a related prior art, there is Republic of Korea Patent Publication No. 10-2017-0112586 (name of the invention: light guide plate with integrated color compensation function, manufacturing method thereof, and backlight unit including the same).

The embodiment of the present invention can emit light of a specific wavelength from the light source in the vertical direction by the light extraction device, as well as absorb and remove the light emitted in the non-vertical direction by the light absorption film, so that the color gamut To provide a backlight unit capable of improving the display device and a display device having the same.

The problem to be solved by the present invention is not limited to the problem(s) mentioned above, and another problem(s) not mentioned will be clearly understood by those skilled in the art from the following description.

A backlight unit according to an embodiment of the present invention includes: a light guide plate for extracting light from a light source; and a light absorbing film disposed on one surface of the light guide plate to absorb light that is not in a vertical direction among light extracted from the light guide plate to the light extraction device.

A plurality of light absorbers may be regularly provided inside the light absorption film according to an embodiment of the present invention.

The light absorber according to an embodiment of the present invention is a porous carbon nano body capable of absorbing at least one region of a visible light region, or is prepared through a process of printing, etching and deposition using a pigment or dye including carbon black. It can be a structure.

The light absorber according to an embodiment of the present invention may have a thickness of 50 to 300 micrometers (μm) and a continuous width of 10 to 30 micrometers.

The light extraction device according to an embodiment of the present invention is a thin diffraction grating provided on one surface of the light guide plate, and the diffraction grating may emit incident light that is totally internally reflected in the light guide plate in a vertical direction with respect to the light guide plate. .

The diffraction grating according to an embodiment of the present invention has a grating period of 320 to 480 nanometers (nm), and may have a diffraction efficiency range of 10 to 80%.

Meanwhile, a display device according to an embodiment of the present invention includes a backlight unit and a display panel coupled to the backlight unit, wherein the backlight unit includes a light guide plate for extracting light from a light source, and one surface of the light guide plate. A light extraction element for vertically extracting light of a specific wavelength region from among the light guided by the light guide plate, and a light extraction element disposed on one surface of the light guide plate to absorb light that is not in a vertical direction among the light extracted from the light guide plate to the light extraction element It may include a light absorbing film.

A plurality of light absorbers may be regularly provided inside the light absorption film according to an embodiment of the present invention.

The light absorber according to an embodiment of the present invention is a porous carbon nano body capable of absorbing at least one region of a visible light region, or is prepared through a process of printing, etching and deposition using a pigment or dye including carbon black. It is a structure, and may be provided to have a thickness of 50 to 300 micrometers and a continuous width of 10 to 30 micrometers.

The light extraction device according to an embodiment of the present invention is a thin diffraction grating provided on one surface of the light guide plate, and the diffraction grating emits incident light that undergoes total internal reflection within the light guide plate in a vertical direction with respect to the light guide plate, The diffraction grating has a grating period of 320 to 480 nanometers, and may have a diffraction efficiency range of 10 to 80%.

According to an embodiment of the present invention, light of a specific wavelength can be emitted from the light source in the vertical direction by the light extraction device, and light emitted in a non-vertical direction can be absorbed and removed by the light absorption film. Color gamut can be improved.

In addition, the extraction wavelength region can be adjusted by adjusting the grating period of the diffraction grating, and the absorption wavelength region can be adjusted by adjusting the absorption region of the light absorber, thereby realizing a desired color gamut.

1 is a diagram schematically illustrating a partial configuration of a backlight unit according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating the principle of configuring a narrowband wavelength spectrum by the backlight unit of FIG. 1 .

Advantages and/or features of the present invention, and methods for achieving them, will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be embodied in various different forms, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the art to which the present invention pertains It is provided to fully inform those who have the scope of the invention, and the present invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout.

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

1 is a diagram schematically illustrating a partial configuration of a backlight unit according to an embodiment of the present invention.

First, although not shown as a whole, the display apparatus according to an embodiment of the present invention may include the backlight unit 100 schematically illustrated in FIG. 1 and a display panel coupled thereto.

Although not shown here, the display panel may include, for example, a first substrate and a second substrate having a stacked structure, and a liquid crystal layer may be included between the substrates.

In other words, signal lines such as a data line and a gate line may be formed on the first substrate, and a thin film transistor may be formed at an intersection of the data line and the gate line.

A color filter, a common electrode, and a black matrix may be provided on the second substrate, and a polarizing member may be provided on the second substrate so that an external user can view an image.

With this configuration, the amount of transmitted light can be adjusted while the liquid crystal has a different arrangement structure according to the light provided from the backlight unit 100, and various colors can be realized through RGB mixing while the adjusted light passes through the transparent substrates. .

A plurality of optical sheets 150 may be interposed between the display panel and the backlight unit 100 to be described later. The optical sheet 150 is placed on the light guide plate 120 , and can collect and diffuse the planar light provided from the light guide plate 120 in one direction, that is, in the display panel direction. For this purpose, the optical sheet 150 ) may include a plurality of sheets.

By the configuration of the display device, the light passing through the backlight unit 100 transmits through the optical sheets and the display panel, for example, BT.2020 (4K recommended by the International Broadcasting Standards Organization, ITU, a narrowband spectrum). /UHD standard) high color reproduction corresponding to an overlap ratio of 90 to 98%, which is a standard, is possible according to the configuration of the backlight unit 100 to be described later.

Referring to FIG. 1 , a backlight unit 100 according to an embodiment of the present invention includes a light source 110 , a light guide plate 120 for extracting light from the light source 110 , and one surface of the light guide plate 120 . A light extraction device provided to extract light of a specific wavelength region from among the light guided by the light guide plate 120 in a vertical direction, and the light disposed on one surface of the light guide plate 120 and extracted from the light guide plate 120 to the light extraction device It may include a light absorbing film 140 that absorbs light in a non-vertical direction.

And, although not shown, it may further include a cover bottom and a guide panel that cover the above-described components.

First, the light source 110 may include a plurality of light emitting diodes (LEDs) having white light and a printed circuit board to which they are electrically connected. The light source 110 is provided on the side of the light guide plate 120 , and may provide light in the direction of the light guide plate 120 . Due to the structure of the light source 110 , it can be implemented as an edge-type backlight unit 100 capable of slimming the display device.

However, the light source 110 is not limited thereto, and it is of course that a light emitting diode or a laser diode of RGB wavelength may be used.

On the other hand, as shown in FIG. 1 , the light guide plate 120 of this embodiment converts point or line light provided from the light source 110 into a planar shape and provides it in the direction of the display panel, from the light source 110 . Light may be extracted through the upper surface of the light guide plate 120 facing the display panel while causing total internal reflection within the light guide plate 120 .

However, when light is guided through the upper surface of the light guide plate 120 , that is, the exit surface, light must be extracted in a vertical direction. function may be impaired.

To this end, in this embodiment, light of each color is vertically extracted through the light extraction device 130 , and light can be absorbed in a non-vertical direction by the light absorbing film 140 to obtain high color reproducibility. can

First, as shown in FIG. 1 , the light extraction device 130 of this embodiment has thin diffraction gratings 130a and 130b for emitting incident light that undergoes total internal reflection within the light guide plate 120 in the vertical direction of the light guide plate 120 . , 130c) may include. In the diffraction gratings 130a, 130b, and 130c, as shown in FIGS. 1 and 2, bars having a cross section of a grating shape are spaced apart from each other on the upper surface of the light guide plate 120, and for extracting red light (R) in the vertical direction. A diffraction grating 130a, a diffraction grating 130b for extracting green light G in a vertical direction, and a diffraction grating 130c for extracting blue light B in a vertical direction may be provided.

The diffraction gratings 130a, 130b, and 130c of this embodiment, for example, in the light guide plate 120 having a refractive index of 1.59, blue light of 450 nm (nm), green light of 520 nm, 638 of white light having a central angle of 60 degrees Red light of nanometers may be emitted in a vertical direction to the light guide plate 120 through a grating period of 320 to 480 nanometers, such as 331 nanometers, 383 nanometers, and 470 nanometers, respectively.

By adjusting the grating period of the diffraction gratings 130a, 130b, and 130c, the extraction wavelength region can be adjusted.

Here, the grating period of the diffraction gratings 130a, 130b, and 130c of this embodiment can be obtained through Equation 1 below.

[Formula 1]

The diffraction gratings 130a, 130b, and 130c may exhibit a diffraction efficiency range of 10 to 80%. Equation 2 to obtain the diffraction efficiency is as follows.

[Equation 2]

However, although the above-described light extraction device 130 is provided, as shown in FIG. 1 , light directed in an oblique direction instead of a vertical direction may be generated, which causes a decrease in color gamut. Looking at the rightmost side of FIG. 1 , red light is emitted in a vertical direction by the diffraction grating 130a of the light extraction element 130 , but green light and blue light are directed in an oblique direction.

To this end, in the present embodiment, the light absorbing film 140 may be provided on the light guide plate 120 to absorb light directed in a direction other than the vertical direction. Through this, only light in a vertical direction is transmitted through the light absorbing film 140 , thereby improving the color gamut of the display device.

As shown in FIG. 1 , a plurality of light absorbers 141 may be regularly provided inside the light absorption film 140 of the present embodiment. Due to the spaced apart structure of the light absorber 141 , light having a vertical direction may pass between the light absorbers 141 , and the light absorber 141 absorbs light that is not in a vertical direction, so that red light having a vertical direction is absorbed. , green light, and blue light may be provided in the direction of the display panel, thereby increasing color gamut.

Here, the light absorber 141 may be a porous carbon nano body capable of absorbing at least one region of the visible light region, or a structure prepared through a process of printing, etching, and deposition using a pigment or dye including carbon black. there is.

The light absorber 141 may have a thickness of 50 to 300 micrometers and a continuous width of 10 to 30 micrometers, but is not limited thereto.

The absorption wavelength region may be adjusted by adjusting the number and region of the light absorbers 141 of the light absorbing film 140 .

Meanwhile, an operating principle of the backlight unit 100 according to the present embodiment will be described with reference to FIG. 2 .

FIG. 2 is a diagram illustrating a principle of configuring a spectrum of a narrow band wavelength by the backlight unit of FIG. 1 .

Referring to the left drawing of FIG. 2 , it can be seen that the light totally internally reflected from the light guide plate 120 is emitted through the diffraction grating of the light extraction element 130 and is emitted in various directions. And it can be confirmed that the spectrum at this time is widely distributed.

However, looking at the right side view of FIG. 2 , when the light absorber 141 is disposed, the light in the vertical direction passes between the light absorbers 141, and the light that is not in the vertical direction is absorbed by the light absorber 141, It can be seen that the color gamut can be improved by the light absorber 141 . And it can be confirmed that the spectrum at this time is distributed at a specific wavelength.

As such, according to an embodiment of the present invention, light of a specific wavelength can be emitted from the light source 110 in the vertical direction by the light extraction device 130 , as well as the vertical direction by the light absorption film 140 . It is possible to absorb and remove light emitted in a direction other than that, thereby improving color gamut.

In addition, the extraction wavelength region can be adjusted by adjusting the grating period of the diffraction gratings 130a, 130b, and 130c, as well as the absorption wavelength region can be adjusted by adjusting the absorption region of the light absorber 141 to realize a desired color gamut. can

The display device having the above configuration may implement a high-efficiency display by matching with, for example, a holographic optical element used in a vehicle head-up display.

Although specific embodiments according to the present invention have been described so far, various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims described below as well as the claims and equivalents.

As described above, although the present invention has been described with reference to limited embodiments and drawings, the present invention is not limited to the above-described embodiments, which are various modifications and variations from these descriptions by those skilled in the art to which the present invention pertains. Transformation is possible. Accordingly, the spirit of the present invention should be understood only by the claims described below, and all equivalents or equivalent modifications thereof will fall within the scope of the spirit of the present invention.

100: backlight unit 110: light source
120: light guide plate 130: light extraction element
130a, 130b, 130c: diffraction grating 140: light absorption film
141: light absorber 150: optical sheet

Claims (10)

a light guide plate for extracting light from the light source;
a light extraction device provided on one surface of the light guide plate to vertically extract light of a specific wavelength region from among the light guided by the light guide plate; and
a light absorbing film disposed on one surface of the light guide plate to absorb light that is not in a vertical direction among light extracted from the light guide plate to the light extraction device;
A backlight unit comprising a. According to claim 1,
The backlight unit, characterized in that the plurality of light absorbers are regularly provided inside the light absorption film. The light absorber is a porous carbon nano body capable of absorbing at least one region of the visible light region, or a structure prepared through printing, etching, and deposition using a pigment or dye including carbon black. unit. 4. The method of claim 3,
The light absorber has a thickness of 50 to 300 micrometers (μm) and a continuous width of 10 to 30 micrometers. According to claim 1,
The light extraction element is a thin diffraction grating provided on one surface of the light guide plate,
wherein the diffraction grating emits incident light, which is totally internally reflected within the light guide plate, in a direction perpendicular to the light guide plate. 6. The method of claim 5,
The diffraction grating has a grating period of 320 to 480 nanometers (nm), and has a diffraction efficiency range of 10 to 80%. backlight unit; and
a display panel coupled to the backlight unit;
includes,
The backlight unit is
a light guide plate for extracting light from the light source;
a light extraction device provided on one surface of the light guide plate to vertically extract light of a specific wavelength region from among the light guided by the light guide plate; and
a light absorbing film disposed on one surface of the light guide plate to absorb light that is not in a vertical direction among light extracted from the light guide plate to the light extraction device;
A display device comprising a. 8. The method of claim 7,
A display device, characterized in that a plurality of light absorbers are regularly provided inside the light absorption film. 9. The method of claim 8,
The light absorber is a porous carbon nano body capable of absorbing at least one region of the visible light region, or a structure prepared through a process of printing, etching and deposition using a pigment or dye including carbon black, and is 50 to 300 micrometers. A display device, characterized in that it is provided to have a continuous width of 10 to 30 micrometers with a thickness of a meter. 8. The method of claim 7,
The light extraction element is a thin diffraction grating provided on one surface of the light guide plate,
The diffraction grating emits incident light, which is totally internally reflected within the light guide plate, in a direction perpendicular to the light guide plate,
The diffraction grating has a grating period of 320 to 480 nanometers, and a display device, characterized in that it has a diffraction efficiency range of 10 to 80%.

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