KR20200024380A - Backlight unit - Google Patents

Abstract

The present invention relates to a backlight apparatus which provides light of a surface light source to a liquid crystal panel. The backlight apparatus comprises: a cover bottom having a bottom surface of an upward inclined structure while forming an accommodating space inside; a light source module comprising a substrate, an LED light source mounted on the substrate, and an anisotropic optical lens covering the LED light source, and disposed on one side of the accommodating space of the cover bottom to provide light into a light diffusion space; and a diffusion plate seated while covering an upper opening portion of the cover bottom to emit light distributed in the light diffusion space. The light emitted from the LED light source is collected and diffused by the optical lens, and is guided to an area of a carrying light portion.

Description

Backlight unit

The present invention relates to a backlight device for providing light of a surface light source to the liquid crystal panel.

Display devices are widely used in devices such as TVs, smartphones, laptops, and tablets, and include liquid crystal displays (LCDs), organic light-emitting displays (OLEDs), and plasma displays (PDPs); Various kinds such as Plasma Display Panel) are used.

Here, the liquid crystal display (hereinafter, referred to as 'LCD') does not emit light in itself, unlike other display devices, and requires an external light source to realize an image. Therefore, the LCD further includes a backlight device as a light source in addition to the liquid crystal panel, and the backlight device uniformly supplies high brightness light to the liquid crystal panel, thereby realizing high quality images.

As such, the backlight device refers to a surface light source assembly installed on a rear surface of a liquid crystal panel to realize an image of a display device such as an LCD. As the light source of the backlight device, a light emitting diode (LED) is mainly used, and the backlight of the direct lighting type or the edge lighting type is determined depending on the position of the LED light source. It is divided into devices. The direct method is a method in which the LED light source is disposed below the diffuser plate to illuminate the light directly through the diffuser plate, and the side method is a method in which the LED light source is disposed at the light guide plate side to indirectly illuminate the light through the light guide plate.

On the other hand, in recent years, the light guide plate has been deleted to minimize the number of parts of the device and the backlight device which is advantageous for slimming is introduced in Korea Patent Publication No. 10-2013-0104560. In the backlight device of the prior art, the LED light source is disposed at one side of the space inside the cover bottom, and the diffusion plate is disposed at the upper opening of the cover bottom. The inner surface of the cover bottom may be a light reflection treatment or a reflection sheet may be combined.

In the conventional backlight device, the light emitted from the LED light source is totally reflected in the light diffusion space inside the cover bottom and is emitted to the surface light source through the upper diffusion plate. At this time, the distance between the cover bottom and the diffusion plate is narrowed away from the LED light source by giving an inclination to the bottom surface of the cover bottom, thereby minimizing the distribution density and luminance variation of the light according to the distance of the LED light source.

The backlight device in which the light guide plate is removed has an effect of improving the luminance deviation of the light diffusion space by giving the cover bottom an inclination, but the light incident region still exhibits low brightness so that the brightness variation of the light incident region and the light incident region is reduced. There is a limit to total improvement. The light incident portion refers to one side in the cover bottom in which the light source is disposed, and the light incident portion refers to the opposite side facing the light incident portion.

In addition, the backlight device from which the light guide plate is removed has a disadvantage in that the size of the backlight device is disadvantageous due to the luminance deviation according to the distance of the light source.

Korea Patent Publication 10-2013-0104560 (published Sep. 25, 2013, backlight assembly and display device including the same)

The present invention has been proposed to solve the above problems, and in the side type backlight device from which the light guide plate is removed, by condensing and diffusing the light of the LED light source to induce it to easily reach the region of the incoming light, thereby improving luminance deviation. It is an object of the present invention to provide a backlight device which can reduce the number of LEDs and is advantageous in size.

The backlight device of the present invention for achieving the above object, the cover bottom having an upwardly inclined structure while forming a storage space therein, a substrate, an LED light source mounted on the substrate and an anisotropic optical covering the LED light source A light source module formed of a lens and disposed on one side of the storage space of the cover bottom to provide light into the light diffusion space, and seated while covering an upper opening of the cover bottom to distribute light distributed in the light diffusion space. It includes a diffuser plate for emitting, the light emitted from the LED light source is characterized in that it is guided to the light-receiving portion area while being focused and diffused by the optical lens.

In addition, the optical lens has an anisotropic structure in which the width in the vertical direction is narrower than the width in the left and right directions with respect to the direction in which light travels.

The optical lens may further include a first light emitting surface adjacent to a bottom surface and extending in a plane, and a second light emitting surface extending in a curved shape from the first light emitting surface to form a dome structure.

In addition, the optical lens is characterized in that the width of the first light emitting surface increases in the direction of the light travels, and has the largest width at the end of the first light emitting surface.

In addition, the optical lens has a ratio Hd / Hu of the length Hd of the first light emitting surface and the length Hu of the second light emitting surface of 0.8 to 0.9, and the width Lv of the vertical direction and the horizontal direction The ratio (Lv / Lh) of the width (Lh) is characterized in that 0.7 to 0.8.

In addition, the diffusion plate is characterized in that the reflective pattern is formed on the bottom surface.

The present invention can improve the light distribution density and luminance deviation in the entire region of the backlight device by condensing the optical lens of the anisotropic structure so that the light emitted from the LED light source can reach the light incident portion.

In addition, the present invention by the optical lens of the anisotropic structure diffuses the light emitted from the LED light source in the left and right direction, it is possible to reduce the number of LEDs to reduce the manufacturing cost.

In addition, according to the present invention, the light emitted from the LED light source is reflected to the entire region of the light diffusion space by the reflection pattern of the diffusion plate, thereby improving the luminance and the uniformity of the luminance.

1 is a cross-sectional view showing the main configuration of a backlight device according to an embodiment of the present invention;
2 is an exploded view showing a light source module which is a main part of FIG. 1;
3 and 4 is a view showing the optical lens and the light induction characteristics of the main part of FIG.
5 is a cross-sectional view illustrating light output characteristics of the backlight device of FIG. 2;
6 is a plan view showing optical characteristics of the backlight device according to the prior art and the present invention.

The technical problem achieved by the present invention and the practice of the present invention will be apparent from the preferred embodiments described below. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Differences between the embodiments of the present invention described below are to be understood as not mutually exclusive. That is, without departing from the spirit and scope of the present invention, the specific shapes, structures, and characteristics described may be implemented in other embodiments with respect to one embodiment, and the location of individual components within each disclosed embodiment. Or it should be understood that the arrangement may be changed, and like reference numerals in the drawings refer to the same or similar functions throughout the several aspects, the length and area, the thickness and the like may be exaggerated for convenience.

1 is a cross-sectional view showing a main configuration of a backlight device according to an embodiment of the present invention, FIG. 2 is an exploded view showing a light source module which is a main part of FIG. 1, and FIGS. 3 and 4 are an optical lens and a light which are main parts of FIG. 1. The induction characteristics are shown for the long side and the short side, respectively, Figure 5 is a cross-sectional view showing the light emission characteristics of the backlight device of FIG.

First, referring to FIG. 1, the backlight device according to the present embodiment includes a cover bottom 100 forming an accommodation space therein, a light source module 200 disposed at one side of the cover bottom inner space, and an upper opening of the cover bottom. It includes a diffuser plate 300 coupled to cover the cover sheet and a reflective sheet 400 seated inside the cover bottom. The reflective sheet 400 and the diffuser plate 300 are spaced at predetermined intervals, and a light diffusion space S in which light emitted from the light source module 130 is scattered and dispersed is formed.

In addition, although not shown, a guide panel may be fastened along the edge of the cover bottom 100 to fix the diffusion plate 300, and a liquid crystal panel is stacked on the diffusion plate 300 to implement a display device. .

Specifically, the cover bottom 100 is configured to form the rear housing of the backlight device while accommodating and fixing the reflective sheet 400, the light source module 200, and the diffusion plate 300 therein. The cover bottom 100 has a vertical side wall extending from the bottom side of the bottom plate while the square plate on the plate is formed on the bottom side, the inside is formed with a storage space with an open top. The cover bottom 100 may be manufactured by injection molding using a metal having excellent heat dissipation such as aluminum. In particular, the cover bottom 100 of the present invention forms an inclined structure that the plate constituting the bottom surface is bent upward as the plate away from the light incident portion. That is, the cover bottom 100 has a wedge shape in which the thickness becomes thinner from the light incident part to the light incident part.

The light source module 200 is a light source of a backlight device that provides light to the light diffusion space S between the diffuser plate 300 and the reflective sheet 400, and is provided on the substrate 210 as illustrated in FIG. 2. LED 220 is mounted, and includes an optical lens 230 coupled to the substrate 210 while covering each LED (220).

The light source module 200 is disposed so that the light exit surface of the LED 220 faces the light diffusion space S at one side of the cover bottom 100 receiving space. The light of the light source module 200 is reflected and reflected by the reflective sheet 400 while being scattered and dispersed in the light diffusion space S, and exits in the form of a surface light source while passing through the diffuser plate 300. In addition, the light emitted from the individual LEDs 220 are collected and diffused by the optical lens 230 and distributed evenly to the incoming light receiving region.

The optical lens 230 has a dome shape of an anisotropic structure in which the cross section (yz plane) of the light propagation direction (x direction) is elliptical. That is, the optical lens 230 has a relatively long width in the left-right direction (y direction) and a relatively short width in the up-down direction (z direction).

In addition, the optical lens 230 forms a concave light source groove 231 on the bottom surface, and the inner surface of the light source groove 231 constitutes a light incident surface 232 on which the light of the LED 220 is incident. A coupling protrusion 233 may be formed on the bottom surface of the optical lens 230 to be coupled to the substrate 210.

In addition, the surface of the optical lens 230 constitutes a light exit surface 234 through which light is emitted, and the light exit surface 234 includes a first light exit surface 234a extending linearly from the bottom surface in the exit direction, and the first light exit surface 234a. The second light exit surface 234b extends in a dome shape from the light exit surface 234a. That is, the optical lens 230 has an elliptical shape having a relatively long left and right width, and the surface includes a first light emitting surface 234a having a planar structure and a second light emitting surface 234b having a curved structure.

The first light emitting surface 234a has a bar shape having an inclined structure in which the width thereof increases with respect to the direction in which light travels (x direction). The second light exit surface 234b has a dome shape having a curved structure whose width decreases with respect to the direction in which light travels. Therefore, the optical lens 230 has a maximum width at the end of the first light exit surface 234a as the width gradually increases, and then gradually decreases along the second light exit surface 234b of the dome structure. The light incident into the optical lens 230 is first collected and diffused at the first light emitting surface 234a of the plane while totally reflected and refracted, and is secondly collected and diffused at the second light emitting surface 234b of the curved surface.

The optical lens 230 according to the present exemplary embodiment condenses light in the vertical direction and diffuses the light in the left and right directions so that light of uniform brightness is emitted in the entire region of the light diffusion space. The light condensation and diffusion of the light are relatively narrow in the vertical direction and wide in the left and right direction, and the lens shape of the anisotropic structure, the first light emitting surface 234a of the planar structure, and the second light emitting surface 234b of the curved structure By a continuous configuration.

The light condensing and diffusion of the light by the optical lens 230 may be performed by the lengths of the first light emitting surface 234a and the second light emitting surface 234b (the length of the light traveling direction), the long side (the width of the left and right directions) and the short side (up and down). Direction width).

3 and 4, in the optical lens 230, the length Hd of the first light emitting surface 234a and the length Hu of the second light emitting surface 234b have a ratio Hd / of about 0.8 to 0.9. Hu). When the ratio (Hd / Hu) of the length ratio Hd / Hu of the first light emitting surface 234a and the second light emitting surface 234b is less than 0.8 or more than 0.9, the directivity angle due to total reflection and refraction between the plane and the curved surface is distorted, thereby condensing efficiency. Is lowered.

In addition, the optical lens 230 has an anisotropic structure, and the width (short side Lv) in the vertical direction and the width (long side Lh) in the left and right directions are configured to have a ratio (Lv / Lh) of about 0.7 to 0.8. When the width ratios of the vertical direction and the left and right directions are less than 0.7 or more than 0.8, the emission directivity angle of the light is distorted, and condensing and diffusing efficiency is lowered.

In addition, in the optical lens 230, the first light emitting surface 234a has an inclination in which the width thereof increases with respect to the traveling direction of the light, and the inclination angle θ1 is preferably 1 ° to 3 °. In addition, in the optical lens 230, the inclination angle θ2 with respect to the tangent is preferably 20 ° to 30 ° at a position where the second light exit surface 234b has a curved shape and is connected to the first light exit surface 234a. When the inclination angles θ1 and θ2 of the first light emitting surface 234a and the second light emitting surface 234b are outside the above ranges, the light collecting efficiency is reduced.

In the optical lens 230 having the above-described configuration, as shown in FIG. 3B, light in the vertical direction is focused to increase the straightness of the light. As a result, the light reaches a far distance from the light source. At this time, the half width is narrowly formed within about 20 degrees with respect to the up-down direction. In addition, the optical lens 230, as shown in Figure 4 (b) increases the light diffusion in the left and right direction, and eventually, the number of LEDs are reduced. At this time, the full width at half maximum is approximately 40 ° or more with respect to the left and right directions.

As the optical lens 230, a transparent resin having excellent light transmittance may be used, and a resin such as polymethylmethacrylate (PMMA), polystyrene (PS), meta styrene (MS), or polycarbonate (PC), which is not easily deformed or broken due to its high strength. It can be prepared by injection molding using.

Referring back to FIG. 1, the diffusion plate 300 is a light control member that diffuses light emitted upward from the light diffusion space S so that light having uniform luminance is emitted. In particular, the diffusion plate 300 has a reflection pattern 310 formed on the bottom surface (light diffusion space surface) for guiding light from the light incident region to the light incident region. The reflective pattern 310 reflects the light emitted from the LED 220 and the light distributed in the light diffusion space S between the reflective sheet 400 and the diffuser plate 300, and particularly, the light of the light incident region is imported. Reflect to the miner area. The reflective pattern 310 is printed on the surface of the diffusion plate 300, the ink is added to the light reflecting agent, the resin is added to the light reflecting material is coated, the sheet of light reflecting material is laminated, or various shapes of the pattern is imprinted Can be formed.

In addition, the reflective pattern 310 is formed while the area is reduced as the distance from the light source module 200. That is, the diffuser plate 300 has a reflective pattern 310 formed in a relatively large area in the light incident region, and its area gradually decreases toward the light incident region. This is because the amount of light distributed in the light incident portion is the largest, so that a relatively large amount of light is reflected so that the light is uniformly distributed throughout the light diffusion space (S). The area of the reflective pattern 310 can be varied by adjusting the size or density of the pattern.

In addition, the reflective pattern 310 may be formed in a positive manner in which printing is performed in a specific pattern region or in a negative manner in which printing is performed in a portion except for the specific pattern region.

In addition, the reflective pattern 310 is formed from a position spaced a predetermined distance (a) from the light source module. Since the LED 220 emits light at a predetermined direction angle θ, when considering the thickness T of the light diffusion space S, the reflective pattern 310 is separated from the LED 220 by a = (2 * It is preferably formed from positions spaced apart by a distance of T) / (* tanθ). Therefore, it is possible to prevent waste of material for unnecessary areas and to prevent contradictions in which dark portions are generated in areas adjacent to the light source by the reflection pattern.

Reflective sheet 400 is a configuration for reflecting the light emitted from the light source module 200 distributed in the light diffusion space (S) to the upper side, made of a metal sheet with excellent light reflectance or light reflective material such as Ag on the surface It may be made of a coated sheet. The reflective sheet 400 may be formed by laminating a sheet or a film on the bottom surface of the cover bottom 100, and may be formed by coating a resin of a light reflective material on the bottom surface of the cover bottom 100.

In the backlight device of this embodiment, as shown in FIG. 5, light emitted from the LED 220 is collected and diffused while passing through the optical lens 230, and is distributed in the light diffusion space S in the light incident area. Some of the light is emitted through the non-patterned region of the diffuser plate 300, and some of the light is reflected by the reflective pattern 310 to be guided to the incident-light incidence region. Therefore, the amount of light emitted from the diffusion plate 300 in the light incident region is relatively increased, so that light having a uniform luminance is emitted.

In the description of the present invention, a configuration in which the light source module is disposed on one side of the cover bottom is illustrated, but the light source module is disposed on both sides facing each other, and the bottom surface of the cover bottom may be configured to have an upward slope toward the center. At this time, both sides constitute the light incident portion, and the central region constitutes the light incident portion.

6 is a plan view showing optical characteristics of the backlight device of the prior art and the present embodiment.

In the backlight device according to the related art, the bottom surface of the cover bottom has an inclined structure upward, and the backlight device according to the present embodiment has an inclined structure with the bottom surface of the cover bottom, and the optical lens is coupled to the LED and reflected on the diffuser plate. When the pattern was formed, the optical properties emitted from the diffusion plate were respectively measured. The optical lens 230 has the lengths Hd and Hu of the first light emitting surface 234a and the second light emitting surface 234b of 3.26 mm and 2.73 mm, respectively, with a ratio Hd / Hu of 0.84, and the vertical direction and the left and right directions. A lens having a ratio (Lv / Lh) of 0.77 was used as the widths (Lv, Lh) of the directions were 7.68 mm and 5.95 mm, respectively.

First, as shown in (a), in the conventional backlight device, most of the light is distributed near the light source module to show high brightness, but as the distance from the light source module increases, the brightness is significantly decreased. Therefore, in the conventional backlight device, the luminance deviation still appears in the light incident region and the light incident region.

However, in the backlight device of the present embodiment, it can be seen that the overall luminance is high and the luminance is uniform regardless of the distance from the light source module. This is because a sufficient amount of light emitted from the LED reaches and is distributed to the light incident region by the optical lens and the reflection pattern.

While illustrative embodiments of the present invention have been illustrated and described as described above, various modifications and other embodiments may be made by those skilled in the art. Such modifications and other embodiments are all considered and included in the appended claims without departing from the true spirit and scope of the invention.

100: cover bottom
200: light source module 210: substrate
220: LED 230: optical lens
300: diffusion plate 310: reflection pattern
400: reflective sheet

Claims (7)

A cover bottom having an upwardly inclined structure while forming a storage space therein;
A light source module comprising a substrate, an LED light source mounted on the substrate, and an anisotropic optical lens covering the LED light source, the light source module being disposed at one side of the storage space of the cover bottom to provide light into the light diffusion space; And
And a diffuser plate seated while covering the upper opening of the cover bottom to emit light distributed in the light diffusion space.
The light emitted from the LED light source is collected and diffused by the optical lens is led to the light incident region. The method of claim 1, wherein the optical lens,
And an anisotropic structure in which the width in the vertical direction is narrower than the width in the horizontal direction with respect to the direction in which light travels. The method of claim 2, wherein the optical lens,
And a second light emitting surface adjacent to the bottom surface and extending in a plane and a second light emitting surface extending in a curved shape from the first light emitting surface to form a dome structure. The method of claim 3, wherein the optical lens
The width of the first light emitting surface is increased with respect to the direction of the light, so that the backlight device having the largest width at the end of the first light emitting surface. The method of claim 4, wherein the optical lens,
The ratio Hd / Hu of the length Hd of the first light emitting surface to the length Hu of the second light emitting surface is 0.8 to 0.9. The method of claim 4, wherein the optical lens,
A ratio (Lv / Lh) of the width Lv in the vertical direction and the width Lh in the left and right directions is 0.7 to 0.8. The diffusion plate according to any one of claims 1 to 6, wherein
A backlight device, characterized in that the reflective pattern is formed on the bottom surface.

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