KR100603636B1 - 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, 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 disposed on the upper portion of the lamp, the diffuser plate is configured to disperse light at a central portion of the lamp and with neighboring lamps. A continuous triangular prism pattern of embossed or intaglio is formed on one surface of the diffusion plate to gradually concentrate light toward the boundary portion. At this time, the depth of the pattern is thin in the center portion of the lamp and gradually deepens toward the boundary surface, is formed on the back or front of the diffusion plate.

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.

LCD, Backlight, Diffusion Plate, Pattern, Injection Molding, Prism

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 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 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 a reflecting plate (1) for preventing, a diffusion plate (3) for diffusing light from the upper part of the lamp (2), and emitting a uniform light, and a diffusion 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 central portion of the pattern is characterized in that the light is distributed and gradually concentrated to the boundary portion with the neighboring lamp.

In addition, the pattern is a continuous triangular prism pattern of the embossed or intaglio, the depth of the prism pattern is a thin structure in the central portion of the lamp gradually deeper toward the interface, the embossed triangular prism pattern is formed on the back of the diffuser plate The negative triangular prism pattern is formed on the front surface 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 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 density d are constant, and only the depth h changes.

[First Embodiment]

4A to 4C illustrate a first embodiment of a diffuser plate of a direct backlight assembly according to the present invention, in which a continuous embossed prism pattern is formed on the rear surface of the diffuser plate at different depths (h) according to a distance from the lamp 12. 13B). FIG. 4A is a view illustrating a diffuser plate 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 a view illustrating an example of an optical path in an embossed prism pattern. to be.

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. Deepen the depth of 41). That is, when the distance between the lamp and the lamp is P, the depth h1 of the prism pattern at the center position where the lamp 12 is located is the thinnest, and the depth of the prism pattern 41 gradually moves toward both sides of the lamp 12. (h) is deepened (ie h ₁ <h ₂ <h ₃ .... <h _n ) and deepest at the P / 2 position, which is the boundary to the neighboring ramp. 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 at the boundary of the embossed prism pattern according to the incident angle. For incident light incident on the prism pattern 41 having the vertex angle α, the incident light is incident at the incident angle θ ₁ and bent at an angle of θ ₂ to θ ₃ at the boundary of the prism. It can be seen that it is reflected at an angle and directed forward.

Second Embodiment

5A to 5C illustrate a second embodiment of the diffuser plate of the direct type backlight assembly according to the present invention, in which a continuous engraved prism pattern 51 is formed by varying the depth h according to the distance from the lamp 12. This is the case formed on the front surface 13F. 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. In this case, the intaglio prism pattern 51 deepens the depth of the intaglio prism pattern 51 as it moves away from the center of the lamp in order to disperse the light in the central portion where the lamp is located and 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 depth h1 of the intaglio prism pattern 51 at the center position where the lamp 12 is located is the thinnest, and the intaglio prism pattern gradually moves toward both sides of the lamp 12. The depth h of 51 is deep (ie h ₁ <h ₂ <h ₃ ... <H _n ) and deepest at the P / 2 position, which is the boundary with the neighboring ramp. 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, in which a continuous prism pattern is formed on the back surface 13B of the diffuser plate by varying the depth h according to the distance from the lamp 12. In the first embodiment formed, a small amount (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 continuous triangular prism pattern 41 is formed on the back surface 13B of the diffusion plate. At this time, the prism pattern 41 deepens the depth of the prism pattern as it moves away from the center of the lamp in order to disperse the light at the center portion of the lamp and 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 depth h1 of the prism pattern at the center position of the lamp is the thinnest, and the prism depth h becomes deeper (i.e., h) as it gradually moves to both sides of the lamp. ₁ <h ₂ <h ₃ .... <h _n ), deepest at the P / 2 position, which is the boundary to a neighboring lamp. 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, if a prism pattern is formed on one surface of the diffusion plate, the depth of the pattern is changed so that the light is dispersed in the central portion where the lamp is located and gradually condensed as it moves away from the lamp. In addition, there is an effect that can improve the uniformity of the luminance distribution. 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.

Claims (5)

delete 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, In the central portion of the lamp on one surface of the diffuser plate is formed a pattern in the form of dispersing light and gradually concentrating light toward the boundary with the neighboring lamp, The pattern is An embossed or engraved continuous triangular prism pattern, wherein the depth of the prism pattern is thin in the central portion of the lamp and gradually deepens toward the boundary surface. The method of claim 2, wherein the embossed triangular prism 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 negative triangular prism pattern 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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