KR20180036216A - Back light unit and display device having the same - Google Patents

Abstract

The present invention discloses a backlight unit capable of preventing an image defect and a reliability defect caused by a reflection plate by application of a reflection coating layer with excellent reflection efficiency instead of deleting the reflection plate, and a display device having the same. To this end, the back light unit and the display device having the same according to the present invention design the reflection coating layer with high reflectance which includes a white resin and a bead distributed and located within the white resin on a LED substrate instead of deleting the reflection plate. Therefore, the backlight unit and the display device having the same according to the present invention add the bead to the white resin mixed with a white pigment in a photo solder resist (PSR) as the reflection coating layer, thereby improving brightness and image quality by improvement of a surface scattering property of the reflection coating layer by bead addition. The backlight unit comprises: an LED package module; and an optical member.

Description

BACKLIGHT UNIT AND DISPLAY DEVICE HAVING THE SAME [0002]

The present invention relates to a backlight unit and a display device having the same.

Representative large-sized display devices include a liquid crystal display (LCD) device and a plasma display device (Plasma Display Device). Unlike a self-luminous type plasma display device, a liquid crystal display device essentially requires a separate backlight unit because of its own light emitting device.

BACKGROUND ART [0002] A backlight unit used in a liquid crystal display device is classified into an edge type backlight unit and a direct-type backlight unit according to the position of a light source.

In the edge method, since the light source is disposed on the right and left sides or the upper and lower sides of the liquid crystal panel and the light is uniformly dispersed on the front side by using the light guide plate, uniformity of light is good and the panel thickness can be made extremely thin.

The direct-type method is generally used for a display having a size of 20 inches or more. Since the light source is disposed at a lower portion of the panel, the light efficiency is higher than that of the edge type.

A CCFL (Cold Cathode Fluorescent Lamp) is mainly used as a light source used in a conventional backlight unit of an edge type or a direct-down type. However, since a backlight unit using a CCFL is always powered on a CCFL, a considerable amount of power is consumed. , The color reproduction rate of about 70% and the environmental pollution problems caused by the addition of mercury have been pointed out as disadvantages.

In order to solve such a problem, recently, a backlight unit using a light emitting diode (LED) has been actively studied.

In a liquid crystal display device using an LED as a backlight unit, a structure is generally used in which an LED package module is mounted on a cover bottom, and a reflector separately manufactured on the LED package module is laminated. However, in the case of a structure in which a separately manufactured reflector is laminated, the price of the reflector is relatively high, and image defects and reliability defects due to the reflector have been raised as problems.

Particularly, in recent years, the number of LED packages has increased to about 500 or more, in order to meet the trend of realizing high brightness with the display panel becoming larger than 60 inches. Accordingly, it is necessary to design an LED package hole penetrating the LED package according to the number of the LED package. In this case, when the reflector plate for designing the LED package hole is punched, the LED package hole becomes too large, Are frequently occurring, which increases the cost of repairing wood.

The present invention provides a backlight unit and a display device having the backlight unit that can prevent image defects and reliability defects due to a reflection plate by applying a reflection coating layer having excellent reflection efficiency instead of deleting the reflection plate.

To this end, the backlight unit and the display device having the same according to the present invention have designed a reflective coating layer having high reflectance including a white resin and beads dispersed in a white resin on an LED substrate instead of deleting the reflector.

As a result, the backlight unit and the display device having the same according to the present invention can improve the surface scattering characteristics of the reflective coating layer by adding beads to the white resin mixed with the white pigment in the PSR as the reflective coating layer, .

A backlight unit and a display device having the same according to the present invention include an LED package module having an LED substrate disposed on a cover bottom, an LED package mounted on the LED substrate, and a reflective coating layer disposed on the LED substrate, And an optical member mounted on the spaced apart upper part.

At this time, the reflective coating layer includes a white resin and beads dispersed and disposed in the white resin.

Therefore, the backlight unit and the display device having the same according to the present invention can improve the brightness and image quality by improving the surface scattering property of the reflective coating layer by adding beads by adding beads to the white resin mixed with the white pigment in PSR as the reflective coating layer .

Further, the backlight unit and the display device having the same according to the present invention are designed such that the LED package module and the optical member are spaced apart from each other by an interval of 25 to 40 mm to secure a sufficient light distance, It is possible to prevent a defect from being recognized visually.

The backlight unit and display device having the same according to the present invention can improve brightness and image quality by improving the surface scattering property of the reflective coating layer by adding beads by adding beads to a white resin mixed with PSR and white pigment as a reflective coating layer .

Further, the backlight unit and the display device having the backlight unit according to the present invention have a four-layer structure in which the diffusion plate, the first prism sheet, the second prism sheet, and the brightness enhancing sheet are sequentially stacked with the optical member, The luminance reduction was compensated.

Accordingly, in the backlight unit and the display device having the same according to the present invention, a reflective coating layer having high reflectance with beads added to a white resin is applied, and a diffusion plate, first and second prism sheets, and brightness enhancing sheet By applying a four-layer structure that is stacked in order, luminance compensation can be performed without a reflector.

As a result, the backlight unit according to the present invention and the display device having the backlight unit can eliminate the reflection plate, so that the punching operation is unnecessary, and therefore, the problem of reliability lowering due to poor punching can be prevented. .

Further, the backlight unit and the display device having the same according to the present invention are designed such that the LED package module and the optical member are spaced apart from each other by an interval of 25 to 40 mm to secure a sufficient light distance, It is possible to prevent a defect from being recognized visually.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an assembled sectional view showing a part of a display device according to an embodiment of the present invention; Fig.
2 is a schematic diagram showing an enlarged view of the backlight unit of Fig.
Fig. 3 is an enlarged view of a portion A in Fig. 2; Fig.
FIG. 4 is an enlarged plan view of the LED package module of FIG. 1; FIG.
5 is a photograph showing the image quality measurement results for Comparative Example 1 and Examples 1 to 3;
6 is a photograph showing the image quality measurement results for Examples 4 to 7. Fig.
7 is a graph showing the image quality measurement results for Examples 8 to 9 and Comparative Examples 2 to 3. Fig.

The above and other objects, features, and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings, which are not intended to limit the scope of the present invention. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to denote the same or similar elements.

Hereinafter, a backlight unit according to a preferred embodiment of the present invention and a display device having the same will be described in detail with reference to the accompanying drawings.

1 is an assembled cross-sectional view showing a part of a display device according to an embodiment of the present invention.

1, a display device 100 according to an exemplary embodiment of the present invention includes a display panel 110, a main supporter 120, a cover bottom 130, a backlight unit 140, and a top case 150 do.

The display panel 110 plays a key role in realizing an image. Although not shown in detail in the drawings, the display panel 110 includes first and second substrates (not shown) spaced apart from each other by a predetermined distance, a liquid crystal layer interposed between the first and second substrates, Time). At this time, various wirings and pixel electrodes are arranged on the first substrate in addition to the thin film transistor, and a color filter layer and a black matrix for displaying RGB primary colors are arranged on the second substrate.

The main supporter 120 is disposed under the display panel 110 to support the edge of the display panel 110. [ For this purpose, the main supporter 120 may have a rectangular frame shape.

The cover bottom 130 is coupled to the lower portion of the main supporter 120. The cover bottom 130 may have a shape in which both side edges are bent upward so as to have sides. Accordingly, the side surface of the cover bottom 130 can be set to abut the side surface of the main supporter 120.

The backlight unit 140 is mounted on the cover bottom 130. This backlight unit 140 includes an LED package module 145 and an optical member 146.

The LED package module 145 includes an LED substrate 141 disposed on the cover bottom 130, an LED package 142 mounted on the LED substrate 141, and a reflective coating layer 142 disposed on the LED substrate 141 143).

The LED substrate 141 may be any substrate capable of mounting the LED package 142 at a high density, and a lead frame may be used.

The LED package 142 emits light having colors of red (R), green (G), and blue (B) in the direction of the display panel (110). By simultaneously lighting the LED package 142, white light can be realized by color combination.

In the case of the display device 100 of the direct-type structure shown in FIG. 1, light emitted from neighboring LED packages 142 is superimposed and mixed with each other, and then directly incident on the display panel 110 to provide a surface light source . At this time, the direct display type display device 100 sequentially drives the LED package 142 on / off to display a more vivid image, and supplies light to specific areas of the display panel 110 A local dimming scheme may be used. Accordingly, the contrast ratio can be improved by making the bright image brighter or the dark image darker, thereby realizing a more vivid image.

The reflective coating layer 143 includes a white resin 143a and beads dispersed in the white resin 143a (143b in Fig. 2). At this time, the white resin 143a includes a PSR (photo solder resist) and a white pigment mixed with PSR.

The reflective coating layer 143 is disposed to cover the upper surface of the LED substrate 141 except for the LED package 142 and has a thickness lower than the thickness of the LED package 142. [

As described above, in the present invention, by adding beads to the white resin 143a in which the white pigment is mixed with the PSR as the reflective coating layer 143, a separate reflector (not shown) is mounted for improvement of surface scattering characteristics by bead addition It is possible to improve the luminance and the image quality.

The optical member 146 is mounted on the upper portion spaced apart from the LED package module 145. At this time, the optical member 146 may be mounted on the main supporter 120, but is not limited thereto. The optical member 146 refracts or scatters light incident from the LED package module 145 to widen the viewing angle of the display device 100 and increase the brightness.

At this time, the optical member 146 preferably has a four-layer structure to compensate for the decrease in luminance due to the elimination of the reflection plate.

To this end, the optical member 146 has a four-layer structure in which a diffusion plate 146a, a first prism sheet 146b, a second prism sheet 146c, and a brightness enhancement sheet 146d are sequentially stacked.

The diffuser plate 146a is disposed at an upper portion spaced apart from the LED package module 145 and disposed in the closest position to the LED package module 145. [ The diffusion plate 146a spreads the light emitted from the LED package 142 along the surface to make the color and brightness of the display device 100 uniform. In addition, the diffusion plate 146a serves as a support for maintaining the optical distance so that the optical member 146 is not sagged.

The first prism sheet 146b is stacked on the diffusion plate 146a and functions to increase the brightness by refracting or condensing the light diffused by the diffusion plate 146a.

The second prism sheet 146c is stacked on the first prism sheet 146b and functions to increase the brightness by refracting or condensing the light passing through the first prism sheet 146b.

The brightness enhancement sheet 146d is stacked on the second prism sheet 146c to improve brightness. The brightness enhancement sheet 146d is a type of polarizing film and is referred to as a reflective polarizing film. The brightness enhancement sheet 146d transmits polarized light in a direction parallel to the polarization direction of the brightness enhancement sheet 146d out of the light emitted from the LED package 142 and transmits polarized light in a direction different from the polarization direction of the brightness enhancement sheet 146d The brightness is improved.

The top case 150 is mounted on the display panel 110, and is coupled to the main supporter 120 and the display panel 110.

FIG. 2 is an enlarged view of the backlight unit of FIG. 1, and FIG. 3 is an enlarged view of a portion A of FIG. 2, which will be described in detail in connection with FIG.

1 to 3, a backlight unit 140 according to an embodiment of the present invention includes an LED substrate 141 disposed on a cover bottom 130, an LED package 142 mounted on an LED substrate 141, ), And a reflective coating layer 143 disposed on the LED substrate 142.

The LED substrate 141 may be any substrate capable of mounting the LED package 142 at a high density, and a lead frame may be used.

The LED package 142 emits light having colors of red (R), green (G), and blue (B) in the direction of the display panel (110). By simultaneously lighting the LED package 142, white light can be realized by color combination.

It is preferable that the LED package 142 maintains a light distance D at a certain interval from the optical member 146. This is because when the light distance D is 25 mm or more, This is because it is possible to prevent occurrence of gaps between the LED substrates 141, and a detailed description thereof will be described later.

The reflective coating layer 143 includes a white resin 143a and a bead 143b dispersed in the white resin 143a.

The white resin 143a includes PSR (photo solder resist) and a white pigment mixed with PSR.

The reflective coating layer 143 is disposed to cover the upper surface of the LED substrate 141 except for the LED package 142 and preferably has a thickness lower than the thickness of the LED package 142.

The beads 143b are randomly distributed in the white resin 143a so that the light emitted from the LED package 142 can not pass through the optical member 146 and is reflected toward the cover bottom 130, (146) direction to improve the surface scattering characteristics and improve the brightness.

The beads 143b may have a circular shape or an elliptical shape when viewed in cross section, but are not limited thereto, and any shape can be used as long as the beads 143b can maintain a constant shape in the white resin 143a.

This bead (143b) has silica (SiO _2), calcium carbonate (CaCO _3), barium sulfate (BaSO _4), titanium (TiO _2), aluminum hydroxide {Al (OH) _3}, magnesium oxide (MgO) oxide, Zinc (ZnO ₂ ), and the like may be used, but the present invention is not limited thereto.

At this time, the bead 143b is preferably added in a content ratio of 1 to 10% by weight of the total weight of the reflective coating layer 143. If the addition amount of the beads 143b is less than 1% by weight of the total weight of the reflective coating layer 143, the surface scattering effect can not be properly exhibited and the effect of improving brightness and image quality may be insignificant. Conversely, if the amount of the beads 143b added exceeds 10% by weight of the total weight of the reflective coating layer 143, there is a problem that the brightness is lowered due to the addition of a large amount of glass beads 143b in terms of image quality. Also, a large amount of the bead 143b, which is relatively expensive, can be added to increase the manufacturing cost.

The principle of brightness improvement of the above-described backlight unit will be briefly described below.

First, some light L1 may be reflected in the direction of the cover bottom 130 without passing through the optical member 146 out of the light emitted from the LED package 142. At this time, the light L1 reflected in the direction of the cover bottom 130 is reflected by the principle that the light L2 refracted by the bead 143b of the reflection coating layer 143 is reflected again toward the optical member 146, The characteristics can be improved and the luminance can be increased.

FIG. 4 is an enlarged plan view of the LED package module of FIG. 1, which will be described in conjunction with FIG.

As shown in FIGS. 1 and 4, in order to meet the trend of realizing high brightness with the display panel 110 becoming larger than 60 inches, the number of LED packages 142 is increased to about 500 or more .

Accordingly, the LED package module 145 is mounted in a plate type detachable structure in which a plurality of LED package modules 145 are spaced apart in a matrix form on the cover bottom 130.

That is, it is preferable that the display device 100 according to the present invention is applied with a plate type as the LED package module 145. This is because when the bar type LED package module 145 is applied, Even when the reflective coating layer 143 having the above-mentioned reflective coating layer 143 is applied, the light reflection area is small and it is difficult to achieve the luminance improving effect. In addition, when the bar type LED package module 145 is applied, since the cover bottom 130 disposed at the portion where the LED substrate 141 is not present is exposed to the outside, light reflection is not performed, It can act as a factor for drastically lowering the image quality.

Each of the plurality of LED package modules 145 is further mounted on the LED substrate 141 and further includes an LED connector 144 for supplying power to the LED package 142. At this time, the LED connector 144 may be disposed at one side edge of the LED substrate 141, but is not limited thereto. That is, the LED connector 144 may be designed and modified in various forms such as one long side edge and both short side edges of the LED substrate 141.

The LED connector 144 may be mounted on the upper surface and the lower surface of the LED substrate 141 so as to partially protrude from the upper surface.

As described above, in the display device 100 of the large model of 60 inches or more, the LED substrate 141 is divided into a matrix and mounted. In this case, when the plurality of LED package modules 145 are disposed in close contact with each other without maintaining a constant interval, the LED substrate 141 is expanded by thermal expansion during the high temperature test, Twisting or deforming may cause defects.

In order to solve this problem, the plurality of LED package modules 145 are spaced apart from each other by a first distance d1 and a second distance d2 in the horizontal and vertical directions. At this time, the first and second spacings d1 and d2 are designed to be 1.5 to 2.5 mm, respectively.

Accordingly, in the case of the display apparatus 100 according to the present invention, when the light distance of a predetermined distance or more can not be secured, the deterioration of the connector 144 due to the erasure of the reflector, Can be caused.

The LED package module 145 includes the optical member 146 and the LED module 144 in a thickness of 25 to 40 mm to prevent the LED connector 144 from being visually observed and the gap between the plurality of LED substrates 141 to be visible. So that a sufficient light distance is secured.

As described above, the display device according to the embodiment of the present invention improves surface scattering characteristics of a white resin through beads by adding beads to a white resin mixed with a white pigment in PSR as a reflective coating layer, Can be improved.

In addition, the display device according to the embodiment of the present invention has a four-layer structure in which a diffusion plate, a first prism sheet, a second prism sheet, and a brightness enhancement sheet are sequentially stacked on an optical member, Can be compensated.

Therefore, in the display device according to the embodiment of the present invention, a reflective coating layer having high reflectance with beads added to a white resin is applied, and a diffusion plate, first and second prism sheets, and a brightness enhancement sheet are sequentially laminated It is possible to compensate the brightness without using the reflector.

As a result, since the display device according to the embodiment of the present invention can eliminate the reflector, it is unnecessary to perform the punching operation, so that the problem of reliability lowering due to poor punching can be prevented at its source, .

In addition, the display device according to the embodiment of the present invention is designed such that the LED package module and the optical member are spaced apart from each other by an interval of 25 to 40 mm to secure a sufficient light distance, Thereby making it possible to prevent the defect from being recognized.

Example

Hereinafter, the configuration and operation of the present invention will be described in more detail with reference to preferred embodiments of the present invention. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

The contents not described here are sufficiently technically inferior to those skilled in the art, and a description thereof will be omitted.

1. Specimen Manufacturing

A reflective coating layer according to Examples 1 to 9 and Comparative Examples 1 to 3 was prepared with the compositions shown in Table 1.

[Table 1] (unit:% by weight)

2. Property evaluation

Table 2 shows the results of measurement of luminance and luminance uniformity for a display device to which the reflective coating layer according to Examples 1 to 7 and Comparative Example 1 was applied. 5 is a photograph showing the image quality measurement results for Comparative Example 1 and Examples 1 to 3, and FIG. 6 is a photograph showing the image quality measurement results for Examples 4 to 7. FIG. 5 (a), 5 (b) and 5 (d) show the image quality measurement results for Examples 1 to 3, and FIGS. 6 (a) to 6 The image quality measurement results for Examples 4 to 7 are shown.

1) Brightness and luminance uniformity

After applying the reflective coating layers according to Examples 1 to 7 and Comparative Example 1 to a 75-inch direct-type display device (LG Display LD750DUP-SEH1), luminance and luminance uniformity were measured using a luminance meter.

[Table 2]

As shown in Tables 1 and 2 and FIGS. 5 to 6, when the reflective coating layer according to Comparative Example 1 in which SiO ₂ was not added was used, the luminance and luminance uniformity were only 2,499 nit and 89.8% .

In contrast, when the reflective coating layer according to Examples 1 to 7 was applied, the image quality was improved as the addition amount of SiO ₂ increased. At this time, it can be seen that as the addition amount of SiO ₂ increases, the luminance value increases and then the luminance value tends to slightly decrease again after exceeding 5 wt%.

On the other hand, Fig. 7 is a diagram showing the image quality measurement results for Examples 8 to 9 and Comparative Examples 2 to 3. Fig.

As shown in FIG. 7, in the case of Embodiments 8 to 9, when the light distance is designed to be 25 mm or more without applying a lens, it is confirmed that the image quality is good without deteriorating the visibility of the connector and the gap between the LED substrates .

On the other hand, in the case of the comparative example 2 in which the light distance is 23 mm without applying the lens, it can be seen that the clearance between the connector view and the LED substrate is visible.

Also, in the case of the comparative example 3 in which the light distance was applied to 15.2 mm by the lens application, it was confirmed that the visibility of the connector and the clearance between the LED substrates were more clearly visible than in the comparative example 2, .

While the present invention has been particularly shown and described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. It is therefore to be understood that such changes and modifications are intended to be included within the scope of the present invention unless they depart from the scope of the present invention.

100: display device 110: display panel
120: main supporter 130: cover bottom
140: backlight unit 141: LED substrate
142: LED package 143: reflective coating layer
143a: white resin 143b: bead
145: LED package module 146: optical member
146a: diffusion plate 146b: first prism sheet
146c: second prism sheet 146d: brightness enhancing sheet

Claims (9)

An LED package module having an LED substrate disposed on a cover bottom, an LED package mounted on the LED substrate, and a reflective coating layer disposed on the LED substrate; And
An optical member mounted above the LED package module and spaced apart from the optical member; / RTI >
Wherein the reflective coating layer comprises a white resin and a bead dispersed in the white resin.
The method according to claim 1,
The white resin
A backlight unit comprising a PSR (photo solder resist) and a white pigment mixed with the PSR.
The method according to claim 1,
The reflective coating layer
And a backlight unit disposed to cover an upper surface of the LED substrate excluding the LED package, the backlight unit having a thickness lower than a thickness of the LED package.
The method according to claim 1,
The bead
And 1 to 10% by weight of the total weight of the reflective coating layer.
The method according to claim 1,
The bead
Of silica (SiO _2), calcium carbonate (CaCO _3), barium sulfate (BaSO _4), titanium oxide (TiO _2), aluminum hydroxide {Al (OH) _3}, magnesium oxide (MgO) and zinc oxide (ZnO ₂₎ A backlight unit comprising at least one selected.
The method according to claim 1,
The optical member
A diffusion plate disposed at an upper portion spaced apart from the LED package module,
A first prism sheet laminated on the diffusion plate,
A second prism sheet laminated on the first prism sheet,
And a brightness enhancing sheet laminated on the second prism sheet.
A display panel;
A main supporter disposed under the display panel and supporting an edge of the display panel;
A cover bottom coupled to a lower portion of the main supporter; And
And a backlight unit mounted on the cover bottom,
The backlight unit includes:
An LED package module having an LED substrate disposed on the cover bottom, an LED package mounted on the LED substrate, and a reflective coating layer disposed on the LED substrate, and an optical member / RTI >
Wherein the reflective coating layer comprises a white resin and a bead dispersed and disposed in the white resin.
8. The method of claim 7,
The LED package module
A plurality of plate-type separable structures spaced apart in a matrix form on the cover bottom,
Wherein each of the plurality of LED package modules further comprises an LED connector mounted on the LED substrate for supplying power to the LED package.
9. The method of claim 8,
In order to prevent the appearance of the LED connector and the gap between the plurality of LED substrates,
Wherein the LED package module is spaced apart from the optical member by an interval of 25 to 40 mm.

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