KR20120019784A - Backlight unit - Google Patents

Abstract

PURPOSE: A direct type backlight device is provided to convert the light of a spot light source emitted from an LED(Light Emitting Diode) into the light of a surface light source, thereby recycling the surface light source by a diffusion plate. CONSTITUTION: A plurality of grooves is formed on the bottom of a light guide plate(120). An LED is inserted into the grooves. The light guide plate is laminated on the top of an LED array. A prism pattern with a round vertex angle is formed on the top of a plurality of diffusion plates. The diffusing plates are laminated on the top of the light guide plate so that prism patterns cross each other. An optical sheet(140) is laminated on the top of the diffusing plates.

Description

Direct type backlight unit {Backlight unit}

The present invention relates to a backlight device, and more particularly, to a direct type backlight device in which a light guide plate and a diffusion plate provided with a recycling function are stacked on a light emitting diode to emit light with a uniform light distribution while reducing the thickness of the backlight device. will be.

Since liquid crystal displays (LCDs) are non-luminescent in themselves, a backlight device for irradiating light onto the information display panel is required.

Such a backlight device is classified into an edgy type and a direct type backlight device according to the position of the light source. In addition, as a light source used in a backlight device, a light emitting diode (LED) having a low power consumption, a long lifespan, and emitting light of various colors is mainly used. Since LEDs exhibit the characteristics of a point light source, they are generally used together with a light guide plate or a diffusion plate when used as a light source of a backlight device.

In the case of the side type backlight device, a plurality of LEDs are arranged on the side of the light guide plate to inject light into the light guide plate, which is advantageous in slimming the backlight device, but is disadvantageous in terms of luminance due to incident light from the side. On the other hand, in the direct type backlight device, a plurality of LEDs are disposed under the diffuser plate to exhibit high brightness, but a limited space must be secured between the light source and the diffuser plate, thereby limiting the slimming of the backlight device.

1 is an exploded perspective view illustrating a direct backlight device according to the related art, and FIG. 2 is a plan view illustrating optical characteristics of the backlight device of FIG. 1. In the conventional backlight device, an LED array 11 having a plurality of LEDs 2 mounted on a substrate 1 is disposed below the diffusion plate 12, and various optical sheets 13 are disposed on the diffusion plate 12. ) Are stacked. In this structure, the light emitted from the LED 2 passes through the functional optical sheet 13 such as the diffusion plate 12, the prism sheet, and the diffusion sheet, and is converted into a surface light source to function as backlighting.

However, in the conventional direct type backlight device, as shown in FIG. 2, a spot is generated by a point light source, and thus light emitted to the outside of the direct type backlight device causes stains to damage the appearance. In order to prevent such spots, a constant distance must be maintained between the LED array 11 and the diffusion plate 12. For example, in the structure in which the distance d between the LED array 11 and the diffuser plate 12 is 20 mm or more, unevenness does not appear, and uniformity is guaranteed to some extent, but when it is narrowed below, unevenness occurs as shown in FIG. 2. Therefore, in the conventional direct type backlight device, there is a limit in ensuring the uniformity of light and at the same time slimming the thickness.

The present invention has been proposed to solve the above problems, the light of the point light source emitted from the LED is converted to the surface light source by the light guide plate, and is configured to be recycled (recycling) by the diffuser plate, which is emitted upward An object of the present invention is to provide a direct backlight device capable of making the light distribution uniform and at the same time slimming the thickness.

The present invention for achieving the above object is a LED array mounted with a plurality of LEDs on the substrate; A light guide plate formed on a lower surface of the LED array and having a plurality of grooves into which the LED is inserted; A plurality of diffuser plates having a rounded vertex prism pattern formed on an upper surface thereof and stacked on top of the light guide plate such that each prism pattern crosses each other; And an optical sheet laminated on an upper side of the diffusion plate.

In the above-described configuration, the prism pattern is formed to have a vertex angle α of 60 ° to 110 ° and a radius of curvature R of 0.2 x P to 0.7 x P with respect to the spacing P of the pattern. It features.

In the above configuration, the plurality of diffusion plate is characterized in that the prism pattern is laminated at an intersection angle of 80 ° to 100 °.

In the direct type backlight device having the above configuration, a light guide plate is disposed on the upper side of the LED array to convert light of a point light source into a surface light source, and two diffuser plates having a prism pattern are arranged on the upper side of the light guide plate to be emitted upward. By recycling the light again, the light distribution can be made uniform, and at the same time, the backlight device can be made slim by minimizing the distance between the LED light source and the diffusion plate.

1 is an exploded perspective view showing a direct backlight device according to the prior art;
2 is a plan view showing the optical characteristics of a direct type backlight device according to the prior art,
3 is an exploded perspective view showing a direct backlight device according to an embodiment of the present invention;
4 is an exploded perspective view showing a main part of a direct backlight device according to an embodiment of the present invention;
5 is a partially enlarged cross-sectional view of a diffusion plate according to an embodiment of the present invention;
6A and 6B are plan views illustrating optical characteristics of a diffuser plate of a direct type backlight device according to an embodiment of the present invention;
7 is a plan view showing the optical characteristics of the direct type backlight device according to an embodiment of the present invention, and
8 is a graph showing the light directing angle of the direct type backlight device according to the embodiment of 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. The following examples are merely illustrated to illustrate the present invention and are not intended to limit the scope of the present invention. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is an exploded perspective view illustrating a direct type backlight device according to an exemplary embodiment of the present invention. In the direct type backlight device of the present invention, the light guide plate 120, the lower diffuser plate 130d, the upper diffuser plate 130u, and the plurality of optical sheets 140 are sequentially stacked, and an LED array (below) of the light guide plate 120 is provided. 110 is arranged to form a structure.

In detail, the light guide plate 120 is configured to convert light of a point light source into a surface light source, and is configured to have a predetermined thickness with a flat acrylic material such as polymethylmetacrylate (PMMA). A plurality of light receiving grooves 121 recessed inwardly are formed on the bottom surface of the light guide plate 120 at predetermined intervals in the horizontal and vertical directions. The LEDs 112 are inserted into the grooves 121, and the light emitted from the LEDs 112 is incident into the light guide plate 120 through each wall surface of the grooves 121.

The LED array 110 is configured to function as a light source of a backlight device, and a plurality of LEDs 112 are arranged on a substrate 111 on which a predetermined circuit is printed. The LEDs 112 are arranged in the horizontal and vertical directions at positions corresponding to each light receiving groove 121 formed in the light guide plate 120. The LED array 110 is coupled such that one LED 112 is inserted into each light receiving groove 31 of the light guide plate 120 under the light guide plate 120. The LED 112 may be a side siew type or a top view type LED, and a light emitting LED may be used if it emits light to both side and top surfaces.

Meanwhile, the light guide plate 120 and the LED array 110 are separately configured as described above, and the light guide plate 120 may be disposed on the upper side of the LED array 110, but the light guide plate 120 and the LED array 110 may be disposed on the LED array 110. ) May be integrally formed. That is, the plurality of LEDs 112 are mounted on the substrate 111 at regular intervals, and the molding part is formed by applying a transparent acrylic resin to the entire upper surface of the substrate 111 to seal the LEDs 112, thereby forming the light guide plate. It may be configured to perform a function.

The diffusion plate 130 is configured to uniform the light distribution of the light emitted from the light guide plate 120, and a diffusion agent such as TiO 2, SiO 2, or the like is added to the transparent acrylic resin. In particular, in the present invention, the diffusion plate 130 is composed of two sheets of the lower diffusion plate 130d and the upper diffusion plate 130u. In addition, a prism-shaped pattern 131 is formed on the upper surface of each diffusion plate 130, and the pattern 131u of the upper diffusion plate 130u and the pattern 131d of the lower diffusion plate 130d are illustrated in FIG. 4. As described above, the diffusion plates 130 are stacked to cross each other.

The optical sheet 140 performs a function of controlling the light emission direction of the light emitted from the upper diffusion plate 130u and optical characteristics such as brightness and uniformity. The optical sheet 140 may be composed of a plurality of sheets including sheets in which a prism shape pattern is formed in the horizontal and vertical directions.

In the direct type backlight device having such a configuration, the light of the point light source emitted from the LED 112 passes through the light guide plate 120 and is repeatedly converted to the surface light source by repeating total reflection and scattering. The light of the surface light source emitted from the light guide plate 120 passes through the lower diffusion plate 130d and the upper diffusion plate 130u. At this time, the light passing through the lower diffusion plate 130d is recycled in the x (or y) direction by the y (or x) direction prism pattern 131d. In addition, light passing through the upper diffusion plate 130u is recycled in the y (or x) direction by the x (or y) direction prism pattern 131u. That is, the light of the surface light source emitted from the light guide plate 120 is recycled in the xy direction while passing through the lower diffuser plate 130d and the upper diffuser plate 130u and emitted in a uniform light distribution.

4 is an exploded perspective view illustrating main parts of a direct type backlight device according to an exemplary embodiment of the present invention, and FIG. 5 is a partially enlarged cross-sectional view of the diffuser plate. As shown in FIG. 4, the lower diffusion plate 130d and the upper diffusion plate 130u are stacked such that the prism patterns formed on the upper surface cross each other. At this time, it is preferable that the crossing angle θ of each prism pattern 131u and 131d forms an angle of 80 ° to 100 °. When out of the range of the crossing angle θ, the recycling may be biased in one direction in the x or y direction, so that the light distribution may be biased.

In addition, the prism pattern 131 formed on the upper surface of each diffusion plate 130 is formed in a prism shape having a rounded vertex as shown in FIG. 5. At this time, the angle α of the vertex angle is 60 ° to 110 °, the curvature radius (R) is preferably formed from 0.2 x P to 0.7 x P with respect to the interval (P) of the pattern. Within this range of shapes, light passing through each diffusion plate 130 can be efficiently recycled.

In particular, in the direct type backlight device of the present invention, the distance d between the LED array 110 as the light source and the upper diffusion plate 130u may be reduced to about 10 mm. Even if the interval is narrowed, since the light is emitted in a uniform distribution as will be described later, the thickness of the overall backlight device can be reduced.

FIG. 6 is a plan view illustrating optical characteristics of a diffuser plate of a direct type backlight device according to an exemplary embodiment of the present invention, FIG. 6A is a photograph illustrating optical characteristics emitted from a lower diffuser plate, and FIG. 6B is emitted from an upper diffuser plate. It is a photograph showing the optical characteristics. 7 is a plan view illustrating optical characteristics of the direct type backlight device according to the embodiment of the present invention, and FIG. 8 is a graph showing the light directing angle of the direct type backlight device according to the embodiment of the present invention.

First, referring to FIGS. 6A and 6B, light emitted through the lower diffuser 130d is dimly observed by a point light source (FIG. 6A), but passes through the upper diffuser 130u. The light emitted is not observed by the spot light source. That is, it can be seen that the light of the point light source is recycled in the xy direction while passing through both the lower diffusion plate 130d and the upper diffusion plate 130u to completely remove the spot.

In addition, referring to Figure 7, the light emitted to the upper portion of the backlight device by removing the spot is emitted with a uniform light distribution over the entire surface, compared with the appearance of the direct type backlight device according to the prior art of Figure 2 You can see that it has been completely removed.

This is because the lower diffuser 130d and the upper diffuser 130u which are stacked to intersect on the upper side of the light guide plate 120 according to the exemplary embodiment of the present invention recycle the light emitted from the light guide plate 120 in the xy direction. .

Referring to FIG. 8, the directivity angle of the light emitted to the upper side of the diffuser plate in the backlight device according to the present invention is compared with the directivity angle of the light emitted to the upper side of the diffuser plate in the conventional backlight device. In comparison, it can be seen that a part of the component C of the light emitted in the vertical direction (z direction) is recycled to the component D of the light having a wide direction angle in the horizontal direction (xy direction).

Therefore, the backlight device of the present invention, in which a light guide plate and two diffuser plates having a prism pattern formed on the light guide plate intersect with each other, narrows the distance between the light source of the LED array and the diffuser plate and at the same time achieves uniform light. The appearance can improve the appearance of the backlight device.

Although the embodiments of the present invention have been described with reference to the present invention, those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom.

110: LED array 111: substrate
112: LED 120: light guide plate
121: light receiving groove 130: diffuser plate
131: prism pattern 140: optical sheet

Claims (3)

An LED array having a plurality of LEDs mounted on a substrate;
A light guide plate formed on a lower surface of the LED array and having a plurality of grooves into which the LED is inserted;
A plurality of diffuser plates having a rounded vertex prism pattern formed on an upper surface thereof and stacked on top of the light guide plate such that each prism pattern crosses each other; And
The direct type backlight device including a; optical sheet laminated on the diffusion plate. The method of claim 1, wherein the prism pattern,
A direct backlight unit having a vertex angle (α) of 60 ° to 110 ° and a radius of curvature (R) of 0.2 x P to 0.7 x P with respect to the spacing P of the pattern. The method of claim 1 or 2, wherein the plurality of diffusion plates,
A prism pattern is laminated at an intersection angle of 80 ° to 100 °.

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