KR20050087097A - 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 part of the lamp, the gap between the patterns on the rear surface of the diffuser plate is the center of the lamp. In the part, an embossed triangular prism pattern is formed that is narrow and gradually widens toward the boundary surface, so that light is dispersed in the center portion of the lamp, and the light is gradually concentrated toward the boundary portion with the neighboring lamp. In addition, in the apparatus of the present invention, a negative triangular prism pattern is formed on the front surface of the diffuser plate in which the spacing between the patterns is wide at the center of the lamp and gradually narrows toward the interface.

Therefore, according to the present invention, a prism pattern is formed on one surface of the diffuser plate, but the depth of the pattern is changed to disperse light at the center portion where the lamp is located and gradually condense as it moves away from the lamp, thereby reducing the overall luminance. Uniformity can be improved.

Description

Diffusion Plate Of Backlight Assembly}

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 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, in the apparatus of the present invention, in a direct type backlight assembly having a plurality of lamps arranged in a plane with respect to a display surface and having a diffusion plate on the top of the lamp, a pattern is provided on the rear surface of the diffusion plate. The gap between them is narrow in the center of the lamp, and an embossed triangular prism pattern is formed that gradually widens toward the boundary, dispersing the light in the center of the lamp and focusing the light gradually toward the boundary with the neighboring lamps. It features.

In addition, the device of the present invention is formed in the front of the diffusion plate is formed with an intaglio triangle prism pattern in which the distance between the pattern is wider at the center of the lamp and gradually narrower toward the boundary surface, so that light is distributed at the center of the lamp and adjacent lamps The light is gradually concentrated toward the boundary of.

The diffusion plate may be added with a small amount of scattering agent, the pattern may be formed by injection molding or mechanical processing.

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 mechanical processing) a prism pattern on the rear surface 13B or the front surface 13F of the diffusion plate, By varying the depth (h) of the prism pattern according to the distance of the light is distributed in the center portion of the lamp 12, and when it is far away from the lamp 12 to focus the light intensity is lowered while improving the overall uniformity of the luminance distribution. For ease of understanding, the first embodiment in which the prism pattern is formed on the back surface 13B of the diffuser plate, and the second embodiment in which the prism pattern is formed on the front surface 13F of the diffuser plate, the prism pattern is formed on the back or front surface and diffused. It will be described separately by the third embodiment I added. At this time, in the embossed or intaglio prism pattern of the present invention, the angle α and the depth h are constant, and only the distance d between the patterns, that is, the density changes.

[First Embodiment]

4A to 4C illustrate the first embodiment of the diffuser plate of the direct backlight assembly according to the present invention, in which the embossed prism pattern 41 diffuses by varying the distance d between the patterns according to the distance from the lamp 12. This is the case formed in the back surface 13B of a board. 4A is a view showing a diffuser plate 13 having a pattern formed on a rear surface thereof, and FIG. 4B is an enlarged view of an embossed prism pattern 41 formed on a rear surface thereof, and FIG. 4C is an example of an optical path in the embossed prism pattern. Figure is shown.

4A to 4C, a continuous triangular embossed prism pattern 41 is formed on the back surface 13B of the diffusion plate. At this time, the embossed prism pattern 41 disperses the light in the central portion (c) where the lamp 12 is located, and moves away from the center position (c) of the lamp to concentrate the light when it is far from the lamp 12. Increase the distance d of 41). In other words, when the distance between the lamp and the lamp is P, the distance d1 between the prism patterns at the center position where the lamp 12 is located is the smallest, and gradually moves away from both sides of the lamp 12 between the prism patterns 41. The spacing d of d is gradually larger (i.e., d ₁ <d ₂ <d ₃ .... <d _n ) and becomes larger at the P / 2 position, which is the boundary with neighboring ramps (the pattern density as opposed to the spacing between patterns). Decreases further away from center). 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, the incident light is bent according to the angle of incidence at the boundary surface of the embossed prism pattern. In the case of incident light incident on the prism pattern 41 having a vertex angle of α, the incident light is incident at the incident angle θ ₁ and then bent at an angle of θ ₂ at the boundary surface of the prism and is forward. You can see that heading to.

Second Embodiment

5A to 5C illustrate a second embodiment of the diffuser plate of the direct backlight assembly according to the present invention, in which the negative prism pattern 51 diffuses by varying the distance d between the patterns according to the distance from the lamp 12. This is the case formed on the front surface 13F of the 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 prism pattern 51 formed on the front surface 13F, and FIG. 5C is a negative prism pattern 51. Is an example of an optical path.

5A to 5C, a continuous triangular prism pattern 51 is formed in an intaglio on the front surface 13F of the diffusion plate. At this time, the intaglio prism pattern 51 disperses the light at the center portion where the lamp is located, and decreases the distance d of the intaglio prism pattern 51 as it moves away from the center position of the lamp to concentrate the light when it is far from the lamp. That is, when the distance between the lamp and the lamp is P, the distance d1 between the intaglio prism pattern 51 at the center position where the lamp 12 is located is the largest, and the intaglio prism gradually moves toward both sides of the lamp 12. The spacing d between the patterns 51 is small (i.e., d ₁ > d ₂ > d _{3 ..} > d _n ) and is smallest at the P / 2 position, which is the boundary with the neighboring ramp (between the patterns In contrast to the spacing of, the pattern density increases the further away from the center). 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 so that the luminance distribution is uniform without lowering the overall luminance. can do.

In FIG. 5C, the incident light is bent at an angle of incidence at the boundary of the prism. In the case of incident light incident on the prism pattern 51 having a vertex angle of α, the incident light is bent at an angle of incidence θ ₁ and is bent at an angle of θ ₂ toward the front of the boundary of the prism. Able to know.

Third Embodiment

FIG. 6 is a third embodiment of the diffuser plate of the direct type backlight assembly according to the present invention, wherein the prism pattern is formed on the rear surface 13B of the diffuser plate by varying the distance d between the patterns according to the distance from the lamp 12. In the first embodiment formed in the present invention, a small amount (approximately about 2%) of the scattering agent 13a is added to the diffusion plate 13. Although not shown in the drawing, in the second embodiment in which the prism 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.

Referring to FIG. 6, a triangular prism pattern 41 is formed on the back surface 13B of the diffusion plate. At this time, the prism pattern 41 increases the distance between the prism patterns as it moves away from the center of the lamp in order to disperse the light at the center portion where the lamp is located and to concentrate the light when away from the lamp. That is, when the distance between the lamp and the lamp is P, the distance d1 between the prism patterns at the center position of the lamp is the smallest, and the distance d between the prisms becomes larger (ie, gradually away from both sides of the lamp). d ₁ <d ₂ <d ₃ .... <d _n ), which is greatest at the P / 2 position, which is the boundary to the neighboring ramp. In addition, a small amount of scattering agent 13a is added to the inside of the diffusion plate 13 made of PMMA resin. Therefore, the diffuser plate 13 of the third 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.

FIG. 7 is a graph illustrating a luminance distribution curve in a direct backlight assembly to which the present invention is applied, and illustrates a characteristic of one lamp.

Referring to Fig. 7, 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, a prism pattern is formed on one surface of the diffuser plate, but the spacing (density) between the patterns is changed, thereby dispersing light in the central part where the lamp is located and gradually condensing as it moves away from the lamp. There is an effect that can improve the uniformity of the luminance distribution without dropping. In particular, the diffusion plate according to the present invention can be produced simply by injection molding or mechanical processing can reduce the cost of production.

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 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

Claims (3)

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 the back of the diffusion plate An embossed triangular prism pattern is formed in which the spacing between the patterns is narrow at the center of the lamp and gradually widens toward the interface. The diffuser plate of the direct type backlight assembly, characterized in that the central portion of the lamp to distribute the light and to concentrate the light gradually toward the boundary with the neighboring lamp. 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 the front of the diffusion plate There is a negative triangular prism pattern between the patterns that is wider at the center of the lamp and narrower toward the interface. The diffuser plate of the direct type backlight assembly, characterized in that the central portion of the lamp to distribute the light and to concentrate the light gradually toward the boundary with the neighboring lamp. The method of claim 1 or 2, wherein the diffusion plate A diffuser plate of a direct type backlight assembly, wherein a small amount of scattering agent is added.