KR20200123353A - Light guide plate and backlight unit having the same - Google Patents

Abstract

The present invention relates to a direct-lighting type backlight device using a plurality of LEDs as a light source to be used as a surface light source for the backlighting of a display device. The light guide plate, which is a square plate made of transparent acrylic resin and having four corners rounded, includes: a light source hole penetrated on the center of a lower surface of the plate to accept a light source; a shielding member combined to shield an upper opening part of the light source hole; a first light output surface inclined downwards toward an edge around the upper opening part of the light source hole, and formed radially around the shielding member; and a second light output surface forming an edge side of the plate, which is extended from the first light output surface, into a curved shape. Therefore, the light of the light source accepted in the light source hole can be outputted to the first and second light output surfaces. According to the present invention, a light source hole having a hole structure is formed at the central part of a light guide plate such that the thickness of the central part can be formed to be thinner, thereby making it possible to manufacture a slim backlight device.

Description

Light guide plate and backlight unit having the same

The present invention relates to a backlight device, and more particularly, to a backlight device of a direct illumination method used as a surface light source for backlighting of a display device by employing a plurality of LEDs as light sources.

A liquid crystal display device (hereinafter referred to as'LCD'), which is a flat display device, does not emit light on its own unlike other display devices, and therefore requires a separate external light source to realize high-quality images. To Accordingly, the LCD further includes a backlight device of a surface light source in addition to the liquid crystal panel, and the backlight device realizes an image by uniformly supplying a high-intensity light source to the liquid crystal panel.

As described above, the backlight device refers to a lighting device for realizing an image of a display device such as an LCD, and is classified into an edge lighting type or a direct lighting type backlight device according to a position where a light source is disposed. In addition, as a light source of a backlight device, a light emitting diode (hereinafter referred to as'LED') having advantages such as small size, low power consumption, and high reliability is mainly used.

In the direct type backlight device, a plurality of LED light sources are arranged to face upward, a diffusion plate and an optical sheet are arranged at a predetermined distance from the LED light source, and light from the LED light source is emitted directly upward through the diffusion plate and optical sheet. do. Such a direct type backlight device is advantageous for a large-screen backlight device because there is no limitation on the arrangement area of the LED light source. On the other hand, in order to solve the hot spot caused by the point light source due to the characteristics of the LED having a point light source, the direct type backlight device has a minimum optical distance (OD) that allows sufficient light mixing between the LED light source and the diffusion plate. Since it must be secured, there is a disadvantage in slimming.

In order to solve this problem, a direct type backlight device having a light guide has been proposed by the present applicant in Korean Patent Publication No. 10-2019-0021522, and the main configuration of the backlight device of the prior document is shown in FIG. 1.

Referring to the drawings, in a conventional backlight device, an LED light source 12 is mounted on a substrate 11, and the light guide 13 is coupled to the substrate 11 while covering the LED light source 12, and the light guide body ( 13) A diffuser plate 14 and an optical sheet 15 are disposed on the top, and a reflective sheet 16 intervenes between the substrate 11 and the light guide 13. Here, the light guide body 13 has a light source groove 13a in which the LED light source 12 is disposed in the central portion of the lower surface, the upper surface forms a light exit surface 13b through which light is emitted, and the central portion of the upper surface has a concave shape. The slope 13c is formed, and a reflective layer 13d is formed on the reflective surface 13c.

In the backlight device having the above configuration, since the light of the LED light source 12 is reflected laterally through the light guide 13 and is emitted at a wide beam angle, the distance between the LED light source 12 and the diffusion plate 14 ( Even if OD) is reduced, uniform luminance is exhibited, which is advantageous for slimming the backlight device. For example, in the backlight device of the prior literature, when a light guide having a size of about 75 mm is disposed at 100 mm intervals, the optical distance OD may be reduced to 9 mm.

However, in the conventional backlight device, a concave groove for the reflective surface 13c is formed on the upper surface of the light guide 13 and the light source groove 13a must be simultaneously formed on the lower surface of the same central axis, so that the grooves are formed on the upper and lower surfaces. Since the light guide plate 13 must have a minimum thickness, it is limited in reducing the overall thickness of the backlight device.

In addition, in recent years, with the slimming of the backlight device, the thickness of the light guide 13 has also been reduced by several mm units, for example, 5 mm or less, so that the shapes of the light source groove 13a and the reflective surface 13c are respectively formed in the light guide plate 13. There is a disadvantage that it is very difficult to process accurately. The light emitted from the LED light source 12 greatly depends on the characteristics of the light emitted to the light emitting surface 13b depending on the shape of the light source groove 13a and the reflective surface 13c, and the light source groove 13a and the reflective surface ( If 13c) is not accurately processed, the optical characteristics are changed and the desired optical characteristics cannot be displayed.

Korean Patent Publication No. 10-2019-0021522 (published on Mar. 6, 2019, a light guide and a backlight device having the same)

The present invention has been proposed in order to solve the above problems, and an object of the present invention is to provide a light guide that is more advantageous in slimming by improving the structure of the light guide and a backlight device having the same.

In addition, it is an object of the present invention to provide a light guide capable of facilitating shape processing even for a thinner light guide, and a backlight device including the same.

The light guide of the present invention for achieving the above object is a rectangular plate having four corners curved with a transparent acrylic resin, a light source hole penetrating to accommodate a light source at a central lower surface of the plate, and an upper side of the light source hole A light blocking member coupled to shield the opening, a first light-emitting surface formed radially around the light-blocking member and formed in a downward slope around the upper opening of the light source hole, and the first light-emitting surface extending from the first light-emitting surface The plate is configured to emit light from a light source accommodated in the light source hole to the first and second light emitting surfaces, including a second light emitting surface having a curved edge side surface.

Here, the light source hole is characterized in that it is formed to have a narrower width toward the top.

In addition, the light blocking member is characterized in that it has a reflectance of 70 to 95%.

In addition, the light blocking member is characterized in that it has a thickness of 50㎛ to 300㎛.

In addition, the first light exit surface is formed of four unit light exit surfaces that are radially symmetric about the light blocking member, and a connection surface to which the neighboring unit light exit surfaces are connected is curved.

In addition, the connection surface is characterized in that it forms a curved shape in which a radius of curvature increases from a central portion of the plate to an edge.

In addition, the backlight device of the present invention includes a cover bottom forming an accommodation space therein, the light guide body seated in the accommodation space of the cover bottom, a light source accommodated in the light source hole of the light guide body, and the upper part of the light guide body. It includes a laminated diffusion plate.

In addition, a plurality of the light guides are disposed at predetermined intervals within the receiving space of the cover bottom, and the size of the light guide (L), the distance between the light guides (P), and the light exit angle of the light guide With respect to (θ), the optical distance OD between the bottom surface of the cover bottom and the diffusion plate is set by OD = (PL) x tan (90°-θ).

According to the present invention, by forming a light source hole having a hole structure in the central portion of the light guide, the thickness of the central portion can be made thinner, thereby making the backlight device slimmer.

In addition, according to the present invention, shape processing can be easily performed even for a light guide having a thinner structure by forming a hole in the center portion of the light guide.

1 is a cross-sectional view showing a main configuration of a backlight device according to the prior art;
2 is a perspective view showing a main configuration of a backlight device according to the present invention;
3 is a cross-sectional view showing the backlight device of FIG. 2;
4 is an enlarged view showing a light source unit that is a main part of FIG. 3;
5 is a perspective view showing the main part of FIG. 2, a light guide.

The present invention and the technical problem achieved by the implementation of the present invention will be clarified by the preferred embodiments described below. Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

It should be understood that the differences between the present embodiments described below are not mutually exclusive. That is, without departing from the spirit and scope of the present invention, specific shapes, structures, and characteristics described may be implemented in other embodiments in relation to one embodiment, and the location of individual components within each disclosed embodiment. Alternatively, it should be understood that the arrangement may be changed, and similar reference numerals in the drawings refer to the same or similar functions over various aspects, and the length, area, thickness, and the like may be exaggerated for convenience. In the description of the present embodiment, expressions such as up, down, inside, outside, before, after, etc. represent a relative order, position, direction, and the like, and the technical meaning is not necessarily bound to the dictionary meaning.

FIG. 2 is a perspective view showing a main configuration of a backlight device according to the present invention, FIG. 3 is a cross-sectional view illustrating the backlight device of FIG. 2, and FIG. 4 is an enlarged view illustrating a light source part of FIG. 3.

As shown in these drawings, the backlight device 100 of the present embodiment has a reflective member 130 mounted while exposing the LED light source 110 on a substrate 120 on which a plurality of LED light sources 110 are mounted, The light guide 140 is coupled to the substrate 120 such that the LED light source 110 is positioned at the center thereof, and the diffusion plate 150 and the optical sheet 160 are disposed on the light guide 140. These optical elements are assembled to each other while being accommodated in the cover bottom 170 of a square plate having an accommodation space therein, and the assembly is fixed by a guide panel (not shown) fastened to the cover bottom 170 from the top. The space between the reflective member 130 or the light guide 140 and the diffusion plate 150 forms a light mixing space S in which the light emitted from the light guide 140 is mixed.

Specifically, a plurality of LED light sources 110 may be arranged on the substrate 120 on which the circuit is printed at predetermined intervals in a horizontal, vertical, diagonal or arbitrary direction, and a backlight that emits light to the top or side It functions as a light source for the device. The substrate 120 on which the LED light source 110 is mounted is mounted on the bottom surface of the cover bottom 170. At this time, the LED light source 110 is assembled to be positioned in the light source hole 141 of the light guide body 140 while being exposed to the upper portion of the reflective member 130. In addition, the LED light source 110 is composed of a CSP (chip scale package) type LED device that emits light to the top and four sides.

The reflective member 130 reflects light leaking below the light guide or distributed in the light mixing space S upwardly to improve the brightness of the backlight device. The reflective member 130 has a sheet hole 131 exposing the LED light source 110 and may be formed of a sheet or film having excellent reflectivity.

The diffusion plate 150 and the optical sheet 160 are light control members that are stacked on the light guide body 140 to improve brightness and uniformity of light emitted upward. The diffusion plate 150 diffuses light emitted from the light guide 140 to improve uniformity, and the optical sheet 160 condenses the light emitted upward to improve brightness. The optical sheet 160 may be composed of a pair of prism sheets.

In the backlight device 100 of the present embodiment, the substrate 120 including the cover bottom and the guide panel, the LED light source 110, the reflective member 130, the diffusion plate 150 and the optical sheet 160 have a known configuration. Can be applied.

The light guide 140 is a light conversion device that converts the light of a point light source provided from the LED light source 110 into a surface light source by total reflection and refracting therein, and is composed of a transparent acrylic resin having a predetermined refractive index. For example, it may be composed of a resin such as polymethylmethacrylate (PMMA), poly styrene (PS), meta styrene (MS), or polycarbonate (PC). The light guide 140 has a substantially square plate shape, and four corners of the square plate are curved.

The light guide body 140 has a light source hole 141 in which the LED light source 110 is accommodated in a central portion. The light source hole 141 forms a hole structure that penetrates the light guide member 140 having a thin thickness in a vertical direction. The light source hole 141 may have a circular plane, and may have a polygonal shape such as a square according to the shape of the LED light source 110. In addition, the light source hole 141 may have a shape whose diameter becomes narrower toward the top, and the light source hole 141 of this shape transmits a relatively large amount of light among the light emitted from the LED light source 110. 140) It can be directly incident inside.

The light guide member 140 having the light source hole 141 at the center may have a thickness around the thickest light source hole 141 as thin as the thickness of the LED light source 110, so that the backlight device can be manufactured more slimly. do.

In addition, the light guide member 140 is coupled to an upper opening of the light source hole 141 to block light from the LED light source 110. Light emitted from the LED light source 110 in the upward direction is directly incident on the diffusion plate 150 and appears as a hot spot on the top of the backlight device.

The light blocking member 142 blocks light emitted upward from the LED light source 110 to prevent a hot spot phenomenon. For this purpose, the light blocking member 142 is formed of a sheet or film material having a thickness of 50 μm to 300 μm and reflectance of 70 to 95%. In addition, it is preferable that the light blocking member 142 has a diameter of at least 1.1 times the opening so that the opening of the light source hole 141 can be completely shielded.

In addition, the light guide member 140 forms a dome or pyramid structure with a central portion of an upper surface thicker than an edge, and includes a first light exit surface 143 on an upper surface and a second light exit surface 144 on a side surface.

The first light-exiting surface 143 is inclined downward from the center of the light guide member 140 toward the edge. The first light exit surface 143 emits light directly emitted from the LED light source 110 or reflected from the light blocking member 142 and distributed in the light guide body 140 upward. The light emitted from the first light exit surface 143 is mixed in the light mixing space S and is emitted through the diffusion plate 150. The first light exit surface 143 may be divided into a unit light exit surface of four regions that are radially symmetric about the light blocking member 142 with respect to the upper surface of the light guide member 140 in the shape of a square plate, and the neighboring unit light exit surface is The connecting surface 145 to be connected forms a smooth curved surface shape. In addition, the connection surface 145 has a curved shape in which the radius of curvature increases from the center to the edge.

The second light exit surface 144 forms a curved surface at the side of the edge of the light guide body 140. The second light exit surface 144 extends from the edge of the first light exit surface 143 in a convex curved shape and is connected to the lower surface of the light guide body 140. Accordingly, the convexly curved second light exit surface 144 emits light distributed inside the light guide 140 evenly to the upper side and the side surface.

In this way, the light of the LED light source 110 is emitted to form an even distribution over the entire area of the light mixing space (S) through the first light exit surface 143 and the second light exit surface 144 of the light guide body 140. .

In addition, the light guide member 140 has a light scattering pattern 146 formed on a lower surface of the light source hole 141 for scattering and diffusely reflecting light totally reflected therein. The light scattering pattern 146 may form a convex structure or a concave groove structure, and scatter and scatter light inside the light guide 140 to improve luminance and at the same time make the light uniformly inside the light guide. Distributed so as to be evenly emitted from the first light exit surface 143 and the second light exit surface 144. The light scattering pattern 146 may have various shapes such as a fine dot or pyramid shape.

In the backlight device 100 of the present embodiment, as shown in FIG. 2, a plurality of light guide members 140 are disposed to constitute one backlighting module. That is, a plurality of light guide members 140 may be disposed at predetermined intervals in a horizontal, vertical or arbitrary direction according to the size of the backlight device 100. At this time, the LED light source 110 is disposed together in the light source hole 141 of each light guide 140, and the light blocking member 142 is coupled to the upper opening. In this way, the backlight device 100 having a plurality of light guides 140 may implement local dimming by individually driving the LED light sources 110 accommodated in each of the light guides 140.

On the other hand, in the backlight device 100 of the present embodiment, the optical distance OD may be determined by the size L of the light guide 140, the distance P between the light guides 140, and the light exit angle θ. have. 2 and 3, when a plurality of light guides 140 having a predetermined size (L) are disposed at a predetermined interval (P), tan (90°-θ) with respect to the light exit angle (θ) ) = OD / (PL), so the diffuser plate is determined by the optical distance (OD) = (PL) x tan(90°-θ) from the bottom of the cover.

Since the light guide 140 of the present embodiment exhibits a light exit angle θ of 70° with respect to the vertical direction, for example, when applied to a 55" display device, the size (L) and the spacing (P) of the light guide body 140 ), the optical distance and the number of LEDs as shown in [Table 1] below are required.

Size(mm) Spacing(mm) OD(mm) LED quantity(ea) 49.0 60 4 240 55.3 80 9 135 75.3 100 9 84

As can be seen in [Table 1], the light guide of the present invention can adjust the optical distance and the required number of LEDs by appropriately selecting the size and arrangement interval of the light guide for a display device of a specific size.

In addition, [Table 2] compares the light characteristics of the backlight device for a light guide having no light scattering pattern (Experimental Example 1) and a light guide having a light scattering pattern (Experimental Example 2) in the backlight device of this embodiment. Shown. In the experiment of [Table 2], three LED light sources and light guides were arranged in a 3 x 3 array in the horizontal and vertical directions at 50mm intervals. As the LED light source, a general CSP structure LED having a size of 1.3 (horizontal) x 1.3 (vertical) x 0.4 (thick) was used, and a diffusion plate and a pair of prism sheets were stacked on the top of the light guide. As the light scattering pattern, a circular dot pattern was applied.

division Experimental Example 1 Experimental Example 2 Map Data

Contrast 0.767 0.220

As can be seen in [Table 2], when the light scattering pattern is formed on the lower surface of the light guides of Experimental Examples 1 and 2, uniform luminance over the entire area of each light guide and backlight device You can see that it represents light.

Although the exemplary embodiments of the present invention have been shown and described as described above, various modifications and other embodiments may be made by those skilled in the art. These modifications and other embodiments are all considered and included in the appended claims and will not depart from the true spirit and scope of the present invention.

110: LED light source
120: substrate
130: reflective member
140: light guide
141: light source hole 142: light blocking member
143: first exit surface 144: second exit surface
145: connecting surface 146: light scattering pattern
150: diffuser plate
160: optical sheet
170: cover bottom

Claims (8)

It is a square plate with four corners treated with a transparent acrylic resin.
A light source hole through which a light source is received at a central portion of the lower surface of the plate;
A light blocking member coupled to shield the upper opening of the light source hole;
A first light-exiting surface inclined downward toward an edge around an upper opening of the light source hole and formed radially around the light blocking member; And
Including; a second light exit surface formed in a curved shape at the edge side of the plate extending from the first light exit surface,
A light guide for emitting light of a light source accommodated in the light source hole to the first light-emitting surface and the second light-emitting surface. The method of claim 1, wherein the light source hole,
A light guide, characterized in that it is formed to have a narrower width toward the top. The method of claim 1, wherein the light blocking member,
A light guide, characterized in that it has a reflectance of 70 to 95%. The method of claim 1, wherein the light blocking member,
A light guide, characterized in that it has a thickness of 50㎛ to 300㎛. The method of claim 1, wherein the first light exit surface,
A light guide comprising four unit light exit surfaces that are radially symmetric about the light blocking member, and a connection surface to which the neighboring unit light exit surfaces are connected is curved. The method of claim 1, wherein the connection surface,
A light guide, characterized in that the plate has a curved shape in which a radius of curvature increases from the center to the edge. A cover bottom forming an accommodation space therein;
The light guide according to any one of claims 1 to 6 seated in the receiving space of the cover bottom;
A light source accommodated in a light source hole of the light guide body; And
And a diffusion plate stacked on the light guide. The method of claim 7, wherein the light guide,
A plurality of the cover bottoms are arranged at predetermined intervals in the receiving space,
The optical distance (OD) between the bottom surface of the cover bottom and the diffusion plate with respect to the size (L) of the light guide, the distance P between the light guides, and the light exit angle (θ) of the light guide,
Backlight device, characterized in that set by OD = (PL) x tan(90°-θ).

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