KR101472338B1 - Backlight Unit - Google Patents

Abstract

The present invention relates to a side dimming type backlight device capable of showing high brightness and uniform brightness at the same time by controlling a light emitting path with a light pattern formed on a light guide plate and a prism sheet. The backlight device comprises; a plat type light guide plate wherein a prism shaped reflection pattern of a single angle is formed on the lower side and a line shaped condensing pattern is formed on a light emitting side in a direction is aligned with a progressing direction of light and a diffusion pattern of a longitudinal direction is formed on light incident side; an Led array which is arranged on the light incident side of the light guide plate; and a prism sheet which forms a prism pattern on the lower side and is arranged on the upper side of the light guide plate. The present invention of the composition as above improves condensing efficiency of the light which is emitted to the upper side and shows high brightness and light property in which the uniformity of the brightness is excellent because uniform light is emitted to all over the whole areas.

Description

BACKLIGHT UNIT}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight device, and more particularly, to a side-illuminated backlight device capable of exhibiting high brightness and exhibiting uniform brightness by controlling a light emission path with a light pattern formed on a light guide plate and a prism sheet.

Background Art [0002] A backlight device is an illumination device for realizing an image of a display device such as a liquid crystal display device. Recently, a light emitting diode (LED) has been spotlighted as a light source of a backlight device. Such a backlight device is classified into a direct lighting type or an edge lighting type backlight device according to the position of a light source. The direct-type backlight device illuminates light directly on a liquid crystal panel through an optical sheet in a lower light source. In a side-type backlight device, a light source is disposed on a side of a light guide plate, and indirectly illuminates light through a light guide plate and an optical sheet. .

1 is an exploded perspective view showing a main structure of a conventional side-type backlight device. As shown in the figure, the side-type backlight device has a structure in which the LED array 20 is disposed on one side of the rectangular light guide plate 10 and the prism sheet 30 is stacked on the upper side of the light guide plate 10.

In the backlight device according to the related art, a wedge-shaped light pattern 11 is formed on the lower surface of the light guide plate 10 in a direction perpendicular to the traveling direction of light, A downward prism pattern 31 is formed in one direction. In the backlight device having such a structure, the light emitted from the light guide plate 10 has a predetermined exit angle with respect to the vertical direction, and the exit angle is changed while passing through the prism sheet 30 to condense the light in the vertical direction. The light pattern 12 formed on the upper surface of the light guide plate 10 condenses the incident light so that light is emitted through the prism sheet 30 at a high luminance. Such a backlight device does not include a separate diffusion sheet by the light patterns 11 and 12 formed on the light guide plate 10 and the downward prism pattern 31 of the prism sheet 30 so that the backlight device can be made slim, And at the same time, emits light of high luminance.

However, in the conventional backlight device, the light pattern 11 formed on the lower surface of the light guide plate 10 has a single wedge (prism) shape and the light incident into the light guide plate is reflected on the reflection surface 11a of the light pattern 11, And is guided to the opposite light surface. At this time, the light is totally reflected by the reflective surface 11a having a predetermined horizontal inclination angle, and proceeds in the direction of the light surface. Accordingly, most of the light incident into the light guide plate is concentrated on the side of the light-receiving surface, and exhibits high luminance on the side of the light-receiving surface. However, darkness occurs due to a relatively small distribution of light on the light-entering surface side (see Table 2). Accordingly, in the backlight device according to the related art, there is a problem in uniformly distributing the light between the light-incident surface and the light-incident surface, and thus there is a problem that the uniform luminance can not be displayed as a whole.

In order to solve this problem, a light guide plate in which longitudinal light patterns are applied to the light incidence plane is proposed, but the light pattern on the light incidence plane is rather a light incidence phenomenon in relation to the light pattern on the light incidence plane A light guide plate in which a light pattern is formed on the light entrance surface and the light exit surface at the same time is not practically developed.

SUMMARY OF THE INVENTION The present invention has been proposed in order to solve the above problems, and it is an object of the present invention to improve the light collecting efficiency of light emitted to the upper side, The present invention also provides a backlight device in which the above-mentioned problems are solved.

Another object of the present invention is to provide a backlight device which can exhibit high luminance and uniformity even when a small number of light emitting diode packages are used, thereby reducing manufacturing costs.

According to an aspect of the present invention, there is provided a backlight device in which a prism-shaped reflection pattern is formed on a lower surface, a line-shaped light-collecting pattern is formed on a light- A planar light guide plate on which a diffusion pattern in the vertical direction is formed on the light incidence surface; An LED array disposed on the light-entering surface side of the light guide plate; And a prism sheet on which a prism pattern is formed and disposed on the upper side of the light guide plate.

Here, the reflection pattern is characterized in that the first inclination angle? 1 with respect to the horizontal is? 1? 42 degrees and the second inclination angle? 2 is between 1 °?? 2? 5 °.

The diffusion pattern is a spherical or aspherical shape and is characterized in that a ratio of a height H to a width W (R1 = H / W) is R1? 0.2.

The diffusing pattern has a V-groove shape and has a vertex angle? 1 of 50 占?? 3? 80 占 and a ratio (R2 = L1 / L2) of the pattern portion L1 and the specular surface portion L2 is 1/3? R1 < / = 1.

In addition, the light converging pattern is a prism having a rounded vertex angle, and neighboring patterns are different in height.

According to the present invention having the above-described structure, the combination of the light pattern formed on the light guide plate and the downward prism pattern of the prism sheet improves the light collection efficiency of the light emitted to the image side and exhibits high brightness, And exhibits optical characteristics excellent in luminance uniformity.

In addition, the present invention eliminates the diffusion sheet and exhibits high luminance and uniformity even when a small number of light emitting diode packages are used, thereby reducing the manufacturing cost.

1 is an exploded perspective view showing a main structure of a backlight device according to a conventional technique,
FIG. 2 is an exploded perspective view showing a main configuration of a backlight device according to an embodiment of the present invention,
FIG. 3 is a side enlarged view showing in detail the reflection pattern of the light guide plate, which is the main part of FIG. 2,
FIG. 4 is a front sectional view showing in detail the condensing pattern of the light guide plate, which is the main part of FIG. 2,
FIG. 5 is a plan sectional view showing an example of a diffusion pattern of the light guide plate, which is a main part of FIG. 2, and FIG.
6 is a plan sectional view showing another example of the diffusion pattern of the light guide plate, which is the main part of FIG. 2, in detail.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: FIG. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is an exploded perspective view showing a main configuration of a backlight device according to an embodiment of the present invention.

2, the side-type backlight device of the present invention includes a light guide plate 100, an LED array 200 disposed on the side of the light guide plate 100, and a prism sheet 300 disposed on the upper side of the light guide plate 100 ). The light guide plate 100, the LED array 200 and the prism sheet 300 are stably fixed by a guide panel (not shown) that is seated on a cover bottom (not shown) and fastened to the cover bottom from above the cover bottom . Further, a reflective sheet (not shown) may be further disposed under the light guide plate 100.

Here, the light guide plate 100 converts the light of a plurality of point light sources incident from the LED array 200 into total light through total internal reflection, and emits the light to the upper side. The light guide plate 100 may be made of a transparent acrylic resin having a square plate shape, for example, a PMMA panel. A reflection pattern 110 for reflecting the light to the upper prism sheet 300 is formed on the reflection surface of the lower surface of the light guide plate 100. A condensing pattern 120 for condensing the light emitted from the light- And a diffusing pattern 130 for diffusing light incident to the inside is formed on the light-incident surface of the side surface.

The LED array 200 includes an array of a plurality of LED packages 220 mounted on a substrate 210 at regular intervals. The substrate 210 has a predetermined width and length, and a circuit pattern for driving the LED package 220 is printed. The LED package 220 emits light to a window region of one side as a light source of the backlight device and is incident into the light guide plate 100. The LED package 220 may have a window region formed by a top view method or a side view method.

The prism sheet 300 functions to improve the optical characteristics of the backlight unit by condensing the light of the surface light source emitted from the light guide plate 100 and controlling the traveling direction of the light by being stacked on the light guide plate 100. [ The prism sheet 300 may be formed of a sheet or a film using transparent acrylic resin, and a prism pattern 310 for condensing light is formed on the bottom surface.

In this backlight device, light from the LED array 200 is diffused by the diffusion pattern 130 and enters the inside of the light guide plate 100. While passing through the light guide plate 100 and the prism sheet 300, 110, the light condensing pattern 120, and the prism pattern 310, the outgoing angle is controlled so as to provide a high brightness together with high light condensation. Hereinafter, the specific configuration of each of these patterns and the light emission characteristics thereof will be described.

Fig. 3 is a side view enlarged view showing in detail the reflection pattern of the light guide plate, which is the main part of Fig. 2, and is a detailed view of part A. Fig. As can be seen from the drawing, the reflection pattern 110 of the light guide plate 100 is a light pattern formed on the reflection surface, which is the lower surface of the light guide plate, and has a prism shape in which one side and the other side are tilted. The reflection pattern 110 functions to improve the light collection efficiency of the light emitted upward along with the prism pattern 310 of the prism sheet 300.

The reflective pattern 110 has a reflective surface 110b opposite to the inclined surface 110a on the light incidence surface side and has a plurality of reflective surfaces 110a at predetermined intervals in the direction parallel to the light incidence surface Respectively. The distance between the first pattern and the second pattern on the side of the light incidence surface having the largest interval is set to be shorter than the interval between the second pattern and the liquid crystal panel (not shown) The pixel size is smaller than the pixel size. Moire can be observed outside the liquid crystal panel due to the pattern when the interval between the reflective patterns 120 is equal to or larger than the pixels of the liquid crystal panel.

 Particularly, the reflection pattern 110 of the present invention is formed such that the inclined plane 110a and the reflection plane 110b have a single angle (? 1,? 2) structure with respect to the horizontal plane. The reflection pattern 110 having a single angle structure can use an injection mold having a simple structure in manufacturing a light guide plate using injection molding as compared with the multiple angle structure and can simplify the injection process and reduce the defect rate due to burrs and the like . At this time, it is preferable that the inclined surface 110a with respect to the horizontal plane is formed to have an inclination angle alpha 1 of at least 42 degrees, and the inclination angle alpha 2 of the reflective surface 110b is formed to be between 1 and 5 degrees. When the inclination angle alpha 1 of the inclined plane 110a is less than 42 degrees, the total reflection by the inclined plane 110a affects the light control characteristic. When the inclination angle alpha 2 of the reflective surface 110b is less than 1 deg., The light emission control effect toward the upper side is weakened. When the inclination angle alpha 2 is more than 5 deg., Light is emitted and light leakage may occur . As a result, the inclination angle alpha 2 of the reflection surface 110b can exhibit a good light condensing efficiency when it is formed between 1 and 5 degrees.

FIG. 4 is a front sectional view showing in detail the condensing pattern of the light guide plate, which is the main part of FIG. 2, and is an enlarged sectional view taken along the line B-B. As shown in the figure, the light collecting pattern 120 of the light guide plate 100 is a light pattern formed on the light emitting surface, which is the upper surface of the light guide plate, and has a prism shape with a vertex angle rounded. The light condensing pattern 120 condenses light emitted to the upper side of the light guide plate 100 and controls the light to pass through the prism sheet 300.

The condensing patterns 120 are formed in a direction (y direction) parallel to the traveling direction of light, and are formed in a continuous manner with respect to the arrangement direction (x direction) of the light sources. In particular, the light collecting patterns 120 in the present invention are formed so as to have shapes different from each other with respect to the neighboring patterns. That is, as shown in the drawing, neighboring condensing patterns 120 are different in height (D1> D2), and patterns having different heights are randomly arranged. In addition, the neighboring condensing patterns 120 may be different in height and width. If the adjacent condensing patterns 120 have different heights, it is possible to prevent a wet out phenomenon that may occur due to the patterned pattern.

FIG. 5 is a plan sectional view showing in detail a diffusion pattern of the light guide plate which is a main part of FIG. 2, FIG. 6 is a plan view of another example of the diffusion pattern of the light guide plate which is a main part of FIG. 2, to be.

First, as shown in FIG. 5, the diffusion pattern 130 of the light guide plate 100 is formed as a light pattern formed on a light incident surface of a light incident side of a light guide plate, and protruding as a spherical surface or an aspheric surface. The diffusion pattern 130 diffuses light incident into the light guide plate 100 to control the distribution of a large amount of light in the light incident surface area of the light guide plate 100.

The light diffused by the diffusion pattern 130 is controlled again by the condensing pattern 120 on the light exiting surface. That is, the optical characteristics are controlled by the combination of the diffusion pattern 130 and the condensing pattern 120. The diffusion pattern 130 of the present invention is formed to have a predetermined height and width, and the light emitted to the light- Distribution.

The diffusing pattern 130 for the diffusing pattern 130 may be formed by continuously forming the diffusing patterns 130 in a spherical or aspherical shape as shown in FIG. . Particularly, in the present invention, the height H and the width W of the spherical or aspherical diffusion pattern 130 have a constant ratio. The ratio (R1 = H / W) of the height H to the width W at this time is preferably 0.2 or less. Even when the ratio of the spherical or aspherical shape is more than 0.2, the incident light diffusing effect is excellent, but hot spot is generated again in the light incidence surface area by the light condensing pattern 120.

Referring to FIG. 6, the diffusion pattern 130 of the light guide plate 100 may be recessed in a V-groove shape. As can be seen in the drawing, the V-groove shaped diffusion patterns 130 are formed to have a predetermined apex angle, and at the same time, a plurality of patterns are formed while maintaining predetermined spacing. The apex angle alpha 3 at this time is formed in a range of 50 DEG to 80 DEG and the ratio (R2 = L1 / L2) of the pattern portion L1 to the mirror surface portion L2 is preferably 1/3 to 1 or less Do. Even when the apex angle 3 is out of the above range or the ratio R2 between the pattern portion L1 and the mirror surface portion L2 is out of the above range in the V groove shaped diffusion pattern 130, The hot spot is generated again in the light incidence surface area by the condensing pattern 120. [

Table 1 shows the occurrence of hot spots according to the shape of the diffusion pattern formed on the light incident side of the light guide plate.

Conventional general
Diffusion pattern Spherical or aspherical
Diffusion pattern V-shaped
Diffusion pattern

[Table 1] shows the light characteristics of a light guide plate to which a general diffusion pattern is applied to a light incidence plane according to a conventional technique, a diffusion pattern of a spherical or aspherical shape according to the present invention, and a diffusion pattern of a V- Respectively. Here, the conventional diffusion pattern has an aspheric shape having a height H of 25 占 퐉 and a width W of 50 占 퐉, and a pattern having a height-width ratio (R1 = H / W) of 0.5 is applied. The spherical or aspheric diffusing pattern according to the first embodiment of the present invention is aspherical shape having a height H of 50 mu m and a width W of 500 mu m and a ratio of height to width (R1 = H / W) of 0.5 The V-groove-shaped diffusion pattern according to the second embodiment is a V-shaped diffusion pattern having a vertex angle? 3 of 50 degrees, a pattern portion L1 of 50 mu m, and a mirror surface portion L2 of 100 mu m. A pattern having a ratio of the pattern portion to the mirror surface portion (R2 = L1 / L2) of 0.5 in the groove shape was applied.

 As can be seen from Table 1, it can be seen that a clear hot spot is observed in the light incident surface area in the light guide plate having a general diffusion pattern according to the related art. However, as in the present invention, it can be seen that the hot spot is not observed at all in the light guide plate using the diffuse pattern of spherical or aspherical surface, and it is only very weak at the light guide plate using the V groove type diffusion pattern.

Meanwhile, the optical characteristics of the backlight device according to the prior art and the backlight device according to the embodiment of the present invention are compared in Table 2. In the conventional backlight device, only a single reflection pattern is formed on the lower surface of the light guide plate. In the backlight device of the present invention, a single reflection pattern is formed on the lower surface of the light guide plate, and a spherical diffusion pattern is formed on the light entrance surface.

According to the prior art
Reflection pattern of single angle structure The reflection pattern &
Light-incoming surface diffusion pattern

입광면 측Light side

Light-incoming surface side Light side

Light-incoming surface side

As can be seen from [Table 1], when a diffusion pattern is not formed on the light incidence plane of the light guide plate and only a reflection pattern of a single angle structure is formed on the lower face, most of the incident light is concentrated on the light- Darkness is observed on the light-incident surface side. This is because most of the light incident on the lower surface of the light guide plate for concentrating the light is guided to go straight toward the light surface. However, when a diffusion pattern is formed on the light incident surface of the light guide plate, uniform light is emitted from the entire region of the backlight device. This is because the diffusion pattern uniformly diffuses the light incident into the light guide plate so that the light in the light guide plate can be sufficiently distributed to the light entrance surface.

As described above, the backlight device of the present invention improves the light collecting efficiency of the light emitted by the reflection pattern of the lower surface of the light guide plate, the light collecting pattern of the upper surface, and the downward prism sheet laminated on the upper surface of the light guide plate, Can be improved.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.

100: light guide plate 110: reflection pattern
110a: an inclined surface 110b:
120: condensing pattern 130: diffusion pattern
200: LED array
300: prism sheet 310: prism pattern

Claims (5)

A prism-shaped reflection pattern of a single angle is formed on the lower surface, a line-shaped light-converging pattern is formed on the light-exiting surface in a direction parallel to the traveling direction of light, and a diffusing pattern of spherical or aspherical shape protruding in the longitudinal direction is formed on the light- A light guide plate on the plate;
An LED array disposed on the light-entering surface side of the light guide plate; And
And a prism sheet having a prism pattern formed on the lower surface thereof and disposed on the upper side of the light guide plate,
Wherein the reflection pattern has a first inclination angle alpha 1 with respect to a horizontal direction of? 1? 42 degrees and a second inclination angle? 2 with respect to a horizontal direction of 1 °?
Wherein the diffusion pattern has a ratio (R1 = H / W) of a height (H) to a width (W) of R1? 0.2. delete delete delete The light-emitting device according to claim 1,
Characterized in that the vertex angle is a prism shape having a rounded vertex and the neighboring patterns have different heights.

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