KR20220072070A - Backlight unit capable of socal dimming - Google Patents

Abstract

A backlight unit capable of local dimming is disclosed. The local dimming backlight unit may include: a light source unit including a circuit board and light sources arranged at regular intervals in longitudinal and transverse directions on the circuit board; a reflective sheet laminated on the circuit board and including a plurality of light source accommodating holes for accommodating the respective light sources; a resin molding filled in the light source accommodating hole to cover the light source in the light source accommodating hole; a plurality of light reflective barrier ribs arranged along the longitudinal direction and the lateral direction to form a grid structure, wherein the plurality of light reflective barrier ribs include a reflective member surrounding each of the light source accommodating holes; a diffusion plate disposed above the reflective member; and an optical sheet portion disposed on the diffusion plate.

Description

Local dimming backlight unit {BACKLIGHT UNIT CAPABLE OF SOCAL DIMMING}

The present invention relates to a backlight unit, and to a backlight unit capable of implementing local dimming.

Recently, as we enter the information age, the field of display that visually expresses electrical information signals has developed rapidly, and in response to this, various display devices (Display Apparatus) with excellent performance of thinness, light weight, and low power consumption have been developed. is being developed Specific examples of such a display device include a liquid crystal display device, a field emission display device, and a light emitting display device.

On the other hand, the image quality of the liquid crystal display is influenced by the contrast characteristic. There is a limit to improving the contrast characteristic only by modulating the light transmittance of the liquid crystal layer by controlling the data voltage applied to the liquid crystal layer. In order to improve contrast characteristics, various methods for controlling backlight dimming of adjusting the luminance of a backlight unit according to an image have been tried.

The backlight dimming control method may reduce power consumption by adjusting the luminance of the backlight unit according to the input image.

The backlight dimming method includes a global dimming method for adjusting the luminance of the entire display surface and a local dimming method for locally adjusting the luminance of the display surface.

The global dimming method may improve the dynamic contrast ratio measured between the previous frame and the next frame. The local dimming method can improve static contrast, which is difficult to improve with the global dimming method, by locally controlling the luminance of the display surface within one frame period.

However, the conventional local dimming method not only causes a difference in luminance and flicker between a plurality of blocks partitioned within the display surface, but also requires many circuit elements in the local dimming circuit, so that the circuit configuration is complicated and the algorithm thereof is complicated.

In addition, the local dimming method has a problem that is implemented only in a liquid crystal display using a direct backlight unit. However, the direct backlight unit has a problem in that it is difficult to reduce the thickness of the backlight unit because it has to have a diffuser plate disposed at a predetermined distance from the light source in order to diffuse the light incident from the lamp to uniform the luminance of the display surface.

Recently, due to the thinning trend of liquid crystal display devices, the distance between the diffuser plate and the light sources is narrowing, but the light from the light source is not sufficiently diffused. There is a problem with falling.

Therefore, the problem to be solved by the present invention is that the light emitted from the light source is controlled to have uniform luminance in the plane direction, so that the contrast ratio can be improved when realizing local dimming through inter-block lighting control, and the arrangement of a small number of light sources An object of the present invention is to provide a backlight unit capable of locally dimming that can increase luminance and reduce the number of light sources for local dimming.

A backlight unit capable of locally dimming according to an embodiment of the present invention includes: a light source unit including a circuit board and light sources arranged at regular intervals in longitudinal and transverse directions on the circuit board; a reflective sheet laminated on the circuit board and including a plurality of light source accommodating holes for accommodating the respective light sources; a resin molding filled in the light source accommodating hole to cover the light source in the light source accommodating hole; a plurality of light reflecting barrier ribs arranged in the longitudinal direction and the transverse direction to form a grid structure, wherein the plurality of light reflecting barrier ribs include a reflective member surrounding each of the light source accommodating holes; a diffusion plate disposed above the reflective member; and an optical sheet portion disposed on the diffusion plate.

In one embodiment, the light source may be a light emitting diode package.

In one embodiment, the light emitting diode chip may include one or more light emitting diode chips.

In one embodiment, the thickness of the reflective sheet may have a thickness of 0.1 to 0.5t.

In one embodiment, the resin molding may be silicon-based.

In one embodiment, the resin molding is silicone-based, shore hardness A25 or more, transmittance 70% or more, viscosity 30 Pa ^. s or more.

In an embodiment, the reflective member is attached to the upper surface of the reflective sheet, and may be attached by any one of hook fastening, double-sided tape, and epoxy molding.

In one embodiment, the inner surface of each light reflective barrier rib surrounding the four light source accommodating holes may be formed to be inclined in a direction away from the light source accommodating hole.

In one embodiment, the angle of the inner surface of each of the light reflection barrier ribs may be set to an angle within 60 to 150.

In one embodiment, the reflective member may be a PA or PC material.

In an embodiment, the reflective member may be made of a PA or PC material, and may have a reflectance of 90% or more and a flexural strength of 1000 kgf/cm 2 or more.

In one embodiment, the reflective member may have a characteristic that the luminance decrease is 5% or less in an environment where 170° C. is continued for 5 hours (hrs), and the luminance decrease is 10% or less in an environment where 120° C. is continued for 400 hours (hrs). .

In an embodiment, the reflective member may include a support protrusion protruding from an upper end of some of the plurality of barrier ribs, and the diffusion plate may be supported on the support protrusion.

In an embodiment, the reflective member may include an IC escape space concave inwardly on the bottom surface, and the IC escape space may be set to a position and number corresponding to the position and number of IC chips provided on the circuit board. have.

According to the backlight unit capable of local dimming according to the present invention, the light emitted from the light source is controlled to have uniform luminance in the plane direction, so that the contrast ratio can be improved when implementing local dimming through lighting control between blocks. .

In addition, since the light emitted from the light source is guided in the direction of the diffusion plate without loss by the light reflecting barrier rib of the reflective member, the luminance can be increased only by arranging a small number of light sources, and the number of light sources for local dimming can be reduced. There is an advantage that can reduce the manufacturing cost of the unit and the display device.

In addition, since the luminance can be increased by the light reflecting barrier rib of the reflective member, there is an advantage that blocks partitioned for local dimming can be partitioned to include only one light source.

1 is a cross-sectional view illustrating a configuration of a backlight unit capable of local dimming according to an embodiment of the present invention.
FIG. 2 is a partially enlarged cross-sectional view of FIG. 1 .
3 is a partially enlarged cross-sectional view illustrating a state in which a plurality of light sources shown in FIG. 1 are provided in a light source accommodating hole.
4 is a partially enlarged cross-sectional view illustrating another embodiment of the resin molding shown in FIG. 1 .
FIG. 5 is a perspective view showing the state of the reflective member shown in FIG. 1 .
6 is a partially enlarged perspective view illustrating an IC escape space of the bottom surface of the reflective member shown in FIG. 1 .
7 is a view illustrating a result of a light efficiency evaluation for confirming a luminance increasing effect of a backlight unit capable of local dimming according to an embodiment of the present invention.
FIG. 8 is a partially enlarged cross-sectional view for explaining the structure of the backlight unit of the comparative example of FIG. 7 .
9 is a view showing the results of measuring the luminance and PSF (Point Spread Function) for one block of each of the Example and Comparative Example of FIG. 7 .

Hereinafter, a backlight unit capable of local dimming according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Since the present invention can have various changes and can have various forms, specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to the specific disclosed form, it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention. In describing each figure, like reference numerals have been used for like elements. In the accompanying drawings, the dimensions of the structures are enlarged than the actual size for clarity of the present invention.

Terms such as first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present application, terms such as "comprise" or "have" are intended to designate that a feature, number, step, operation, component, part, or a combination thereof described in the specification exists, but one or more other features It is to be understood that it does not preclude the possibility of the presence or addition of numbers, steps, operations, components, parts, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and should not be interpreted in an ideal or excessively formal meaning unless explicitly defined in the present application. does not

1 is a cross-sectional view showing the configuration of a backlight unit capable of local dimming according to an embodiment of the present invention, FIG. 2 is a partially enlarged cross-sectional view of FIG. 1, and FIG. 3 is a plurality of light sources shown in FIG. is a partially enlarged cross-sectional view showing a state provided as 6 is a partially enlarged perspective view illustrating the IC escape space of the bottom surface of the reflective member shown in FIG. 1 .

1 and 2 , the backlight unit capable of locally dimming according to an embodiment of the present invention includes a light source unit 110 , a reflective sheet 120 , a resin molding 130 , a reflective member 140 , and a diffuser plate ( 150 ) and an optical sheet unit 160 .

The light source unit 110 may include a circuit board 111 and a plurality of light sources 112 arranged at regular intervals in the longitudinal and transverse directions on the circuit board 111 .

Each of the light sources 112 may be a light emitting diode package. The light emitting diode package may include one or more light emitting diode chips, and may include a distributed bragg reflector (DBR) layer covering an upper surface of the light emitting diode chip. The distributed Bragg reflector layer may reflect light emitted from the light emitting diode chip in a lateral direction of the light emitting diode chip.

The reflective sheet 120 is stacked on the circuit board 111 and may include a plurality of light source accommodating holes 121 for accommodating each light source 112 . The light source accommodating hole 121 may be formed to be larger than the size of the light source 112 . For example, the light source accommodating hole 121 may have a rectangular shape, and may have a size capable of accommodating two or more light sources 112 as shown in FIG. 3 .

The reflective sheet 120 may have a thickness of 0.1 to 0.5t, and the thickness may increase in response to an increase in the size of the circuit board 111 .

The resin molding 130 may be filled in the light source accommodating hole 121 to cover the light source in the light source accommodating hole 121 of the reflective sheet 120 , and the light emitted from the light source 112 may be diffused around the light source 112 . can do it For example, the resin molding may be silicone-based, shore hardness A25 or more, transmittance 70% or more, viscosity 30 Pa ^. It may be provided to have a characteristic of s or more.

For example, the upper surface of the resin molding 130 may be on the same plane as the plane of the reflective sheet 120 as shown in FIGS. 1 and 2 .

As another example, the upper surface of the resin molding 130 may be formed to be more convex than the plane of the reflective sheet 120 as shown in FIG. 4 . For example, the upper surface of the resin molding 130 may have a spherical shape. In this case, the light emitted from the light source 112 may be further diffused.

As shown in FIG. 5 , the reflective member 140 may include a plurality of light reflective barrier ribs 141 that are arranged along the longitudinal and lateral directions of the circuit board 111 to form a lattice structure. The reflective member 140 may be attached to the upper surface of the reflective sheet 120 so that each light reflective barrier rib 141 surrounds the light source accommodating hole 121 in all directions. Each of the light reflective barrier ribs 141 decreases in width in the upward direction, and the inner surface of each light reflective barrier rib 141 is formed to be inclined in a direction away from the light source accommodating hole 121, so that the light source accommodating hole ( The inner surfaces surrounding the 121) may form an obtuse angle with the reflective layer (). For example, the angle of the inner surfaces surrounding the light source accommodating hole 121 may be set to an angle within 60 to 150 degrees.

There is no particular limitation on the means by which the reflective member 140 is attached on the reflective sheet 120, and for example, it may be attached by any one of hook fastening, double-sided tape, and epoxy molding.

In an embodiment, the reflective member 140 may be provided to have a reflectance of 90% or more and a flexural strength of 1000 kgf/cm 2 or more, and if these characteristics are provided, there is no particular limitation in material. For example, it may be a PA or PC material having the above characteristics.

In another embodiment, the reflective member 140 has a luminance decrease of 5% or less in an environment where 170° C. is maintained for 5 hours (hrs), and a luminance decrease of 10% or less in an environment where 120° C. is continued for 400 hours (hrs). It can be provided to have, and if it has these characteristics, there is no particular limitation of the material. For example, it may be injection molded as a PA or PC material to have the above properties.

The reflective member 140 may include a support protrusion 142 protruding from an upper end of some of the plurality of light reflective barrier ribs 141 . For example, the support protrusion 142 may protrude from the upper end of the intersection of some of the light reflective barrier ribs 141 among the plurality of light reflective barrier ribs 141 .

The diffusion plate 150 may be disposed above the reflective member 140 . In this case, the diffusion plate 150 may be supported on the upper end of the support protrusion 142 of the reflective member 140 above the reflective member 140 . The diffusion plate 150 may diffuse the light reflected from the reflective member 140 along the surface of the diffusion plate 150 .

The optical sheet unit 160 may be disposed on the diffusion plate 150 , and may collect the light diffused from the diffusion plate 150 so that the light travels in a direction away from the diffusion plate 150 . For example, the optical sheet unit 160 may include a plurality of prism sheets and a protective sheet. As another example, when the light source 112 is implemented with blue light, it may include a fluorescent sheet or a quantum dot sheet disposed on the diffusion plate 150 .

Meanwhile, as shown in FIG. 6 , the reflective member 140 may include an IC escape space 143 concave inwardly on the bottom surface thereof. The IC escape space 143 accommodates an IC chip when an IC chip (not shown) is provided on the circuit board 111 , and corresponds to the position and number of IC chips provided on the circuit board 111 . It can be set by position and number.

Hereinafter, a light diffusion path of a backlight unit capable of local dimming according to an embodiment of the present invention will be described.

First, light emitted from the light source 112 of the light source unit 110 may be emitted in a lateral direction of the light source 112 .

Light emitted in the lateral direction of the light source 112 may be widely diffused around the light source 112 by the resin molding 130 while passing through the resin molding 130 .

A part of the light that has passed through the resin molding 130, for example, a part of the light far from each light reflective barrier rib 141 of the reflective member 140 travels toward the diffusion plate 150, and the reflective member 140 The remaining light adjacent to each light reflecting barrier rib 141 of the reflective member 140 proceeds toward the reflective member 140 and reaches the inner surface of each of the barrier ribs 141 of the reflective member 140 surrounding the four sides of the light source accommodating hole 121 And, the light is reflected from the inner surface of each barrier rib 141 in the direction of the diffusion plate 150 to guide the light to the upper direction of the light source 112 , and the inner surface of each light reflective barrier rib 141 of the reflective member 140 is Since the width decreases toward the top, the light may travel away from the light source 112 .

At this time, a portion of the light emitted from the light source 112 may proceed in the direction of the reflective sheet 120 , that is, the inner surface of the light source accommodating hole 121 . In this case, the light source 112 is reflected from the inner surface of the light source accommodating hole 121 . ( can

Light reaching the diffusion plate 150 is condensed by the diffusion plate 150 , diffuses in the direction of the surface of the diffusion plate 150 , and proceeds in the direction of the optical sheet unit 160 .

The light traveling in the direction of the optical sheet unit 160 may be further condensed by the optical sheet unit 160 and then emitted in the front direction of the backlight, that is, in the direction of the display panel (not shown).

7 is a view illustrating a result of a light efficiency evaluation for confirming a luminance increasing effect of a backlight unit capable of local dimming according to an embodiment of the present invention.

The light efficiency was evaluated by measuring the luminance distribution of light in the direction of the display panel from which the light is finally emitted, and was measured while gradually increasing the emitted area among the total area of the display panel. In the evaluation result of FIG. 7, the number of channels indicates the number of blocks partitioned for local dimming, Window 1% to 100% indicates the ratio of the total area of the display panel, and the number of partitioned blocks is the same in both Comparative Examples and Examples, The light efficiency of each of Comparative Examples and Examples was evaluated by making the number of light emitting diode packages in each block the same.

7 , the embodiment is a display device including the backlight unit of the present invention, the comparative prior art is a display device including the backlight unit structure shown in FIG. 8 , and as shown in FIG. 8 , the backlight unit of the comparative example A plurality of light emitting diode chips 12 are arranged on the circuit board 11 , the entire plurality of light emitting diode chips 12 are covered with resin molding 13 , and there is no reflective member 140 of the present invention. .

7, in the case of Window 1%, the light efficiency of the embodiment increased by 76%, in the case of Window 100%, the light efficiency of the embodiment increased by about 22%, and even in the section between Window 1% and Window 100%, the light efficiency of the embodiment It was confirmed that this increased.

9 is a view showing the results of measuring the luminance and PSF (Point Spread Function) for one block of each of the Example and Comparative Example of FIG. 7 .

As shown in FIG. 9 , as a result of measuring the luminance and PSF of one block of each of Comparative Example and Example of FIG. 7 , it was confirmed that the Example had high luminance and improved PSF characteristics by 22%.

In the backlight unit capable of local dimming according to an embodiment of the present invention, the light emitted from the light source 112 is controlled to have uniform luminance in the plane direction, and the contrast ratio is improved when local dimming is implemented through inter-block lighting control. There are advantages to being

In addition, since the light emitted from the light source 112 is guided in the direction of the diffusion plate 150 without loss by the light reflection barrier rib 141 of the reflective member 140, the luminance can be increased only by disposing a small number of light sources 112. Since the number of light sources 112 for local dimming can be reduced, there is an advantage in that the manufacturing cost of the backlight unit and the display device can be reduced.

In addition, since the luminance may be increased by the light reflection barrier rib 141 of the reflective member 140 , there is an advantage that blocks partitioned for local dimming may be partitioned to include only one light source 112 .

The description of the presented embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the scope of the invention. Thus, the present invention is not to be limited to the embodiments presented herein but should be construed in the widest scope consistent with the principles and novel features presented herein.

Claims (14)

a light source unit including a circuit board and light sources arranged at regular intervals in longitudinal and transverse directions on the circuit board;
a reflective sheet laminated on the circuit board and including a plurality of light source accommodating holes for accommodating each of the light sources;
a resin molding filled in the light source accommodating hole to cover the light source in the light source accommodating hole;
a plurality of light reflecting barrier ribs arranged in the longitudinal direction and the transverse direction to form a grid structure, wherein the plurality of light reflecting barrier ribs include a reflective member surrounding each of the light source accommodating holes;
a diffusion plate disposed above the reflective member; and
characterized in that it comprises an optical sheet portion disposed on the diffusion plate,
Backlight unit with local dimming. According to claim 1,
The light source is characterized in that the light emitting diode package,
Backlight unit with local dimming. 3. The method of claim 2,
wherein the light emitting diode chip comprises one or more light emitting diode chips,
Backlight unit with local dimming. According to claim 1,
The thickness of the reflective sheet is characterized in that it has a thickness of 0.1 to 0.5t,
Backlight unit with local dimming. According to claim 1,
The resin molding is characterized in that the silicone-based,
Backlight unit with local dimming. According to claim 1,
The resin molding is silicon-based,
Shore hardness A25 or more, transmittance 70% or more, viscosity 30 Pa ^. Characterized in that it has a characteristic of s or more,
Backlight unit with local dimming. According to claim 1,
The reflective member is attached to the upper surface of the reflective sheet,
It is characterized in that it is attached by means of any one of hook fastening, double-sided tape, and epoxy molding,
Backlight unit with local dimming. According to claim 1,
The inner surface of each light reflective barrier rib surrounding each of the light source accommodating holes is formed to be inclined in a direction away from the light source accommodating hole,
Backlight unit with local dimming. 9. The method of claim 8,
The angle of the inner surface of each of the light-reflecting barrier ribs is characterized in that it is set to an angle within 60 to 150,
Backlight unit with local dimming. According to claim 1,
The reflective member is characterized in that PA or PC material,
Backlight unit with local dimming. According to claim 1,
The reflective member is made of PA or PC material,
Characterized in that it has a reflectance of 90% or more and a flexural strength of 1000 kgf/cm 2 or more,
Backlight unit with local dimming. According to claim 1,
The reflective member is characterized in that it has a luminance decrease of 5% or less in an environment where 170° C. is maintained for 5 hours (hrs), and has a characteristic of 10% or less of a decrease in luminance in an environment where 120° C. is continued for 400 hours (hrs),
Backlight unit with local dimming. According to claim 1,
The reflective member includes a support protrusion protruding from an upper end of some of the plurality of partition walls,
The diffusion plate is characterized in that supported on the support projection,
Backlight unit with local dimming. According to claim 1,
The reflective member includes an IC escape space concave inwardly on the bottom portion,
wherein the IC escape space is set to a position and number corresponding to the position and number of IC chips provided on the circuit board;
Backlight unit with local dimming.

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