KR100557449B1 - Diffusion Plate Of Backlight Assembly - Google Patents

Abstract

The present invention relates to a diffuser plate of a direct type backlight used in a liquid crystal display (LCD).

In the diffuser plate of the present invention, a plurality of lamps are arranged in a plane with respect to the display surface, and in a direct backlight assembly having a diffuser plate on the upper portion of the lamp, a portion corresponding to the central position of the lamp on one surface of the diffuser plate In the microlens pattern of the structure that is dense and gradually decreases toward the portion corresponding to the boundary position is formed to disperse the light at the center portion of the lamp and to concentrate the light toward the boundary portion with the neighboring lamp. Here, the micro lens pattern is a hemispherical, square, triangular embossed or intaglio pattern, and is formed on the back of the diffusion plate or the front of the diffusion plate.

Therefore, according to the present invention, the microlens pattern is formed on one surface of the diffuser plate, but the depth of the pattern is changed, thereby dispersing the light in the center portion where the lamp is located and gradually condensing the light as the light is distributed away from the lamp. Can improve the uniformity.

LCD, Backlight, Diffusion Plate, Pattern, Injection Molding, Micro Lens

Description

Diffusion Plate Of Backlight Assembly}             

1 is a first example showing a conventional diffuser in a direct backlight;

2 is a second example of a conventional diffuser plate in a direct backlight;

3 is an overall configuration diagram of a direct backlight suitable for applying the present invention,

Figure 4 is a first embodiment of the diffuser plate of the direct type backlight assembly according to the present invention,

Figure 5 is a second embodiment of the diffuser plate of the direct type backlight assembly according to the present invention,

6 is a third embodiment of the diffuser plate of the direct type backlight assembly according to the present invention;

7 is a fourth embodiment of the diffuser plate of the direct type backlight assembly according to the present invention;

8 is a fifth embodiment of a diffuser plate of a direct backlight assembly according to the present invention;

9 is a graph showing the luminance characteristics of the direct type backlight assembly to which the present invention is applied.

* Explanation of symbols for main parts of the drawings

10: backlight assembly 11: reflector

12: lamp 13: diffuser plate

13B: Back side of diffuser plate 13F: Front side of diffuser plate

14: diffusion sheet 20: liquid crystal panel

41: back pattern 51: front pattern

The present invention relates to a backlight used in a liquid crystal display (LCD), and more particularly, to a diffuser plate of a direct backlight having a micro lens pattern formed on one surface thereof.

Recently, a liquid crystal display (LCD), which is widely used as a flat panel display device, is a passive optical device that does not emit light by itself. Therefore, a backlight assembly is attached to a rear surface of the liquid crystal panel as a light source to display an image. Therefore, the characteristics of the entire liquid crystal display device are affected by the backlight assembly structure.

Such a backlight assembly has an edge type that requires a light guide plate that is located on the side of the lamp according to the position of the light source with respect to the display surface, and converts the lamp beneficiation into a surface light, and directly under the display surface where the lamp is not needed. It is divided into forms. Among these, the direct type backlight assembly is widely used in large liquid crystal display devices because of high light utilization efficiency, simple configuration, and no limitation on the size of the display surface.

As shown in FIGS. 1 and 2, the direct type backlight assembly reflects a plurality of lamps 2 disposed below the display surface and the light emitted from the lamps 2 to the display surface to reduce the loss of light. It consists of the reflecting plate 1 which prevents, the diffuser plate 3 which diffuses light in the upper part of the lamp 2, and distributes uniform light, and the diffuser sheet 4.

On the other hand, the direct type backlight assembly has a lamp on the plane, so that the shape of the lamp appears on the liquid crystal panel, so that the gap between the lamp and the liquid crystal panel must be kept considerably, resulting in limitations in thinning and causing unevenness in the overall luminance of the panel. There is this. That is, in the direct type backlight assembly, since a large number of lamps are located under the display surface, the light density on the back of the diffuser plate positioned perpendicular to the lamp and the back of the diffuser plate located between the lamp and the lamp is changed, thereby inevitably causing unevenness of luminance. Will result.

In order to solve this problem, the conventional direct type backlight assembly uses a diffusion plate to which a diffusion agent is added as shown in FIG. 1 or screen-prints a pattern on the back of the diffusion plate to which the diffusion agent is added as shown in FIG. Uniformity was matched overall.

FIG. 1 is a view illustrating a conventional diffuser plate to which a diffuser is added in a direct backlight, (a) is a schematic configuration diagram of a backlight assembly, and (b) a diffuser inserted into a diffuser plate 3 FIG. 3 is a view showing a phenomenon in which light is diffused by beads 3a, and (c) is a diagram showing a luminance distribution curve according to a distance from the center position c of the lamp 2.

Referring to FIG. 1, a diffuser 3a is added to a conventional diffuser plate 3 so that light emitted from a lamp 2 is diffused so that the lamp center position c as shown in the curve graph shown in FIG. It can be seen that the luminance distribution curve G1 having the maximum luminance b1 is lowered to the luminance distribution curve G2 having the maximum luminance b1 '.

FIG. 2 is a view illustrating a conventional diffuser plate screen-printed with a pattern 3b on the back surface of the diffuser plate 3 to which a diffuser 3a is added in a direct backlight. (B) is a view showing a phenomenon in which light is dispersed by the diffusing agent (3a) and the print pattern (3b), (c) is a distance from the central position (c) of the lamp A diagram showing a luminance distribution curve.

Referring to Fig. 2, the conventional diffusion plate 3 is added with a diffusing agent 3a and a print pattern 3b so that the light emitted from the lamp 2 is emitted so that the curved graph shown in Similarly, it can be seen that the luminance distribution curve G1 having the maximum luminance b2 at the lamp center position c is significantly lowered to the luminance distribution curve G2 having the maximum luminance b2 '.

However, the direct type backlight assembly employing the conventional diffuser plate as described above, as shown in the luminance distribution characteristic graphs shown in FIGS. 1 (c) and 2 (c), has a central position (c) of the lamp 2. As the distance from the both sides is farther away, the luminance is remarkably lowered, so that the overall uniformity is lowered, and the overall luminance is also greatly lowered by blocking the transmitted light. In addition, high brightness is required in a large-screen display device, and a conventional diffuser plate is difficult to provide high brightness by blocking transmitted light.

The present invention has been made to solve the above problems, by forming a pattern for light scattering and condensing on the back or front of the diffuser plate to prevent the brightness is lowered and the uniformity of the luminance distribution as a whole, the direct type The purpose is to provide a diffuser plate of the backlight assembly.

In order to achieve the above object, the apparatus of the present invention is a direct type backlight assembly having a plurality of lamps arranged in a plane with respect to a display surface and having a diffuser plate on the upper portion of the lamp, wherein the lamp is provided on one surface of the diffuser plate. In the part corresponding to the center position of, the micro lens pattern of the structure is closed and gradually decreases toward the part corresponding to the boundary position. The light is dispersed in the center part of the lamp and gradually gets light toward the boundary with the neighboring lamp. It is characterized by focusing.

Here, the micro lens pattern is a hemispherical, square, triangular embossed or intaglio pattern, and is formed on the back of the diffusion plate or the front of the diffusion plate.

And the diffusion plate may be added with a small amount of scattering agent, the pattern may be formed by injection molding or by a sanding process.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a cross-sectional view schematically showing the overall configuration of a direct backlight suitable for applying the present invention. In FIG. 3, the display screen side is referred to as 'front', and the mold frame side is referred to as 'back'.

Referring to FIG. 3, the direct type backlight assembly 10 to which the present invention is applied includes a plurality of lamps 12 that generate light, and positioned under the lamps 12 to reflect the light of the lamps 12 to the front. Liquid crystal panel 20 composed of a reflecting plate 11, a diffusion plate 13 positioned above the lamp 12 to diffuse light, and a diffusion sheet 14 placed on the diffusion plate 13 to display an image. It is positioned below the light supply to the liquid crystal panel 20.

The reflecting plate 11 is usually located at the bottom of the mold frame, on which the lamp 12 is located. Accordingly, the reflecting plate 11 reflects the light emitted from the lamp 12 toward the bottom (back) back toward the diffuser plate 13 to improve the efficiency of the light generated from the lamp 12.

The lamps 12 are fixed by a lamp holder (not shown) and are arranged in plural on the lower plane of the display surface. As such a lamp, a cold cathode fluorescent lamp (CCFL) is mainly used.

Light emitted from the lamp 12 is incident on the diffuser plate 13 positioned above the lamp 12. The diffusion plate 13 is usually made of PMMA resin and directs the light emitted from the lamp 12 toward the front side of the liquid crystal panel 20 and can be incident at a wide range of angles. The diffusion sheet 14 is positioned on the diffusion plate 13 to improve luminance. Since the light emitted from the diffuser plate 13 is a diffused light having a large viewing angle, the viewing angle is narrowed using the diffusion sheet 14 to improve the front luminance of the liquid crystal display and reduce power consumption.

The diffusion plate 13 of the present invention applied to such a direct backlight assembly is formed by injection molding (or forming by sanding) a micro lens pattern on the back surface 13B or the front surface 13F of the diffusion plate, and the lamp 12 The number of microlenses per unit distance of the microlens pattern (i.e. density n / cm) varies depending on the distance from the lens, and the light is dispersed in the center portion of the lamp 12 and focused when it is far from the lamp 12 to reduce the brightness. As a result, the overall uniformity of the luminance distribution is improved.

For ease of understanding, the first embodiment in which the microlens pattern is formed on the back surface 13B of the diffusion plate and the second embodiment in which the microlens pattern is formed on the front surface 13F of the diffusion plate, the microlens patterns of different shapes are The third embodiment formed on the rear surface, the fourth embodiment in which the micro lens patterns having different shapes are formed on the rear surface and the diffusion agent is added, and the fifth embodiment in which the micro lens patterns of the different shapes are formed on the front surface will be described. do.

[First Embodiment]

4A to 4C illustrate a first embodiment of the diffuser plate of the direct type backlight assembly according to the present invention, and are sequentially embossed by varying the number of microlenses per unit distance (n / cm) according to the distance from the lamp 12. This is the case where the microlens pattern is formed on the back surface 13B of the diffusion plate. 4A is a view showing a diffuser plate having a pattern formed on its rear surface, and FIG. 4B is an enlarged view of an embossed micro lens pattern 41 formed on the rear surface, and FIG. 4C shows an example of an optical path in an embossed micro lens pattern. One drawing. In Figure 4a (a) is a perspective view of the diffusion plate shown to aid in understanding the micro lens pattern, (b) is a cross-sectional view of the diffusion plate.

4A to 4C, an embossed microlens pattern 41 is formed on the back surface 13B of the diffusion plate in which the number of microlenses per unit length is different. At this time, the embossed microlens pattern 41 per unit area is further away from the center of the lamp (c) to disperse the light in the central portion (c) where the lamp 12 is located and to concentrate the light when away from the lamp (12). The number of micro lens patterns 41 is reduced. That is, when the distance between the lamp and the lamp is P, the number of microlenses per unit length of the microlens pattern at the center position where the lamp 12 is located is large, and the microlenses gradually move toward both sides of the lamp 12. The number of microlenses per unit length of the pattern 41 becomes small (i.e., n ₁ > n ₂ > n ₃ ....> n _n ), which is the smallest at the P / 2 position, which is a boundary with a neighboring lamp. In terms of the distance between the micro lenses, the distance d ₁ between the micro lenses at the center of the lamp 12 is narrower, and the distance d _n is wider as it is farther from the center (d ₁ <d ₂ <... < d _n ). Therefore, in the diffusion plate 13 of the first embodiment, light at the center portion where the lamp 12 is located tends to be dispersed and light at the boundary portion between the lamps is concentrated, so that the luminance distribution is uniform without lowering the overall luminance. I can keep it.

In FIG. 4C, incident light is bent according to the incident angle at the boundary surface of the embossed micro lens pattern, and incident light incident on the micro lens pattern 41 is incident at the incident angle θ ₁ and bent forward at an angle of θ ₂ at the boundary surface of the micro lens and is directed forward. It can be seen that.

Second Embodiment

5A to 5C illustrate a second embodiment of the diffuser plate of the direct type backlight assembly according to the present invention, wherein the number of microlenses per unit length (n / cm) is varied depending on the distance from the lamp 12. This is the case where the pattern 51 is formed on the front surface 13F of the diffusion plate. FIG. 5A is a view showing a diffuser plate 13 having a negative pattern formed on the front surface, and FIG. 5B is an enlarged view of the negative micro lens pattern 51 formed on the front surface 13F, and FIG. 5C is a negative micro lens pattern. In Fig. 51, an example of the optical path is shown.

5A to 5C, a hemispherical micro lens pattern 51 is formed on the front surface 13F of the diffusion plate in an intaglio. At this time, the negative microlens pattern 51 has a smaller number per unit length of the negative microlens pattern 51 as it moves away from the center of the lamp in order to disperse the light at the central part where the lamp is located and to concentrate the light when it is far from the lamp. (I.e. n ₁ > n ₂ > n ₃ ....> n _n ). That is, when the distance between the lamp and the lamp is P, the distance d ₁ between the negative microlens patterns 51 at the center position where the lamp 12 is located is the shortest, and gradually increases to both sides of the lamp 12. As a result, the distance d of the intaglio microlens pattern 51 becomes long (that is, d ₁ <d ₂ <d ₃ .... <d _n ), which is the longest at the P / 2 position, which is a boundary with a neighboring lamp. . Therefore, the diffusion plate 13 of the second embodiment tends to disperse the light at the center portion where the lamp 12 is located and to concentrate the light at the boundary portion between the lamps, thereby reducing the luminance distribution without lowering the overall luminance. It can be made uniform.

In FIG. 5C, the incident light is bent at an angle of incidence at the interface of the microlenses. In the case of incident light incident on the hemispherical microlens pattern 51, the incident light is bent at an angle of incidence θ ₁ and is bent at an angle of θ ₂ to face forward from the boundary of the microlens. It can be seen that.

Third Embodiment

FIG. 6 is a third embodiment of the diffuser plate of the direct type backlight assembly according to the present invention, in which the microlens pattern is formed on the back surface 13B of the diffuser plate by varying the shape of the microlens pattern according to the distance from the lamp 12. If formed. In FIG. 6, (a) is a perspective view of the diffusion plate 13 shown to help understand the microlens pattern, and (b) is a cross-sectional view of the diffusion plate 13.

Referring to FIG. 6, as the microlens pattern is densely formed at the center position of the lamp and gradually moves away from the lamp, the number of n / cm per unit length of the microlens pattern decreases. The shape of the microlens pattern at the center position is hemispherical or spherical and triangular toward the periphery. That is, when the distance between the lamp and the lamp is P, the number per unit length of the microlens pattern at the center position of the lamp is the highest, and the number per unit length of the microlens pattern gradually goes away from both sides of the lamp (n / cm) is lowered (i.e., n ₁ > n ₂ > n ₃ ....> n _n ) and lowest at the P / 2 position, which is the boundary to the neighboring ramp.

Therefore, in the diffusion plate of the third embodiment, light in the center portion where the lamp 12 is located tends to be dispersed and light at the boundary portion between the lamps tends to be concentrated, so that the luminance distribution can be made uniform without lowering the overall luminance. .

[Example 4]

7 is a fourth embodiment of the diffuser plate of the direct type backlight assembly according to the present invention, in which the microlens pattern is formed on the back surface 13B of the diffuser plate by varying the shape of the microlens pattern according to the distance from the lamp 12. It is a case where a scattering agent is added to the diffuser plate of the fourth embodiment formed. In Figure 7 (a) is a perspective view of the diffusion plate 13 shown to help understand the micro lens pattern, (b) is a cross-sectional view of the diffusion plate (13).

Referring to FIG. 7, the diffusion plate 13 of the fourth embodiment is a case in which a small amount (approximately about 2%) of scattering agent is added to the diffusion plate 13 in the third embodiment. Therefore, the diffuser plate 13 of the fourth embodiment tends to scatter a little as a whole, and the light at the center portion where the lamp is located tends to be dispersed and the light at the boundary portion between the lamps is concentrated, without lowering the overall luminance. The luminance distribution can be made uniform.

[Example 5]

8 is a fifth embodiment of the diffuser plate of the direct type backlight assembly according to the present invention, in which the shape of the microlens pattern varies according to the distance from the lamp 12 so that the microlens pattern is formed on the front surface 13F of the diffuser plate. If formed on. In FIG. 8, (a) is a perspective view of the diffusion plate 13 shown to help understand the microlens pattern, and (b) is a cross-sectional view of the diffusion plate 13.

Referring to FIG. 8, the microlens pattern is densely formed at the center position of the lamp and the number per unit length (n / cm) of the microlens pattern is gradually increased from the lamp on the front surface 13F of the fifth embodiment. Decreases. In addition, the shape of the microlens pattern at the center position is hemispherical, or it can be seen that toward the periphery becomes a square, a triangle. That is, when the distance between the lamp and the lamp is P, the number per unit length of the microlens pattern at the center position of the lamp is the highest, and the number per unit length of the microlens pattern gradually goes away from both sides of the lamp (n / cm) is lowered (i.e., n ₁ > n ₂ > n ₃ ....> n _n ) and lowest at the P / 2 position, which is the boundary with the neighboring ramp.

Therefore, in the diffusion plate of the fifth embodiment, light in the center portion where the lamp 12 is located tends to be dispersed and light at the boundary portion between the lamps tends to be concentrated, so that the luminance distribution can be uniform without lowering the overall luminance. .

Meanwhile, although not shown in the drawing, in the fifth embodiment in which the microlens pattern is formed on the entire surface of the diffusion plate, a small amount of scattering agent may be added to the diffusion plate in the same manner.

FIG. 9 is a graph illustrating a luminance distribution curve in a direct backlight assembly to which the present invention is applied, and representatively illustrates characteristics of one lamp.

Referring to Fig. 9, the horizontal axis represents the relative distance to both sides from the center (c) position of the lamp, and the vertical axis represents the luminance level. The first curve G1 shows the luminance distribution of the pure lamp without considering the influence of the diffuser plate 13, and has the maximum luminance b4 at the central position c of the lamp 12 and the lamp 12. It can be seen that the luminance gradually decreases as it moves away from it. The second curve G2 shows the luminance distribution passing through the diffuser plate 13 according to the present invention. The second curve G2 is the maximum luminance b4 'at the central position c of the lamp 12 and gradually increases as it moves away from the lamp 12. It can be seen that the luminance is lowered.

In addition, when comparing the first curve G1 and the second curve G2, the luminance at the center portion c is significantly lowered and the luminance at the boundary portion is slightly higher due to the diffusion plate 13 according to the present invention. It can be seen that the uniformity of the overall luminance distribution is greatly improved without significantly lowering the overall luminance.

As described above, according to the present invention, the microlens pattern is formed on one surface of the diffuser plate, but the depth of the pattern is varied so that the light is dispersed in the central part where the lamp is located and the light is gradually collected as it moves away from the lamp. There is an effect that can improve the uniformity of the luminance distribution without. In particular, the diffusion plate according to the present invention can be produced simply by injection molding or sanding process can reduce the cost of production.

Claims (5)

In a direct backlight assembly in which a plurality of lamps are arranged in a plane with respect to a display surface and a diffuser plate is placed on top of the lamps, On one surface of the diffusion plate In the part corresponding to the center position of the lamp, the micro lens pattern of the structure is formed that is dense and gradually disappears to the part corresponding to the boundary position. The diffuser plate of the direct type backlight assembly, characterized in that the central portion of the lamp to disperse light and to concentrate the light gradually toward the boundary with the neighboring lamp. The method of claim 1, wherein the pattern is A diffuser plate of a direct type backlight assembly, characterized by a hemispherical, square or triangular embossed or engraved pattern. The method of claim 2, wherein the micro lens pattern is The diffuser plate of the direct backlight assembly, characterized in that formed on the back of the diffuser plate. The method of claim 2, wherein the micro lens pattern is The diffuser plate of the direct type backlight assembly, characterized in that formed on the front of the diffuser plate. The method of claim 3 or 4, wherein the diffusion plate is A diffuser plate of a direct type backlight assembly, wherein a small amount of scattering agent is added.

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