KR100657580B1 - Light Guide Plate for Backlight unit - Google Patents

Abstract

A light guide plate for a backlight unit that realizes low power consumption and high brightness is disclosed. Comprising a transparent body having a constant width and length, the lamp insertion groove is formed in the longitudinal center of the rear surface of the body is inserted into the lamp over the entire width, the light emitted from the lamp along the bottom surface of the lamp insertion groove A prism that totally reflects a part is integrally formed to protrude.

LGP, LGP, Slot, Luminance, Light Intensity, Wedge, Uniformity

Description

Light guide plate for backlight unit {Light Guide Plate for Backlight unit}             

1 is a perspective view illustrating a light guide plate according to an exemplary embodiment of the present invention.

FIG. 2 is a partially enlarged view showing the lamp insertion groove of FIG. 1 in detail.

3 is an explanatory diagram illustrating an operation principle of a light guide plate according to the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light guide plate for a backlight unit applied to a display device, and more particularly, to a light guide plate of a direct type that can realize low power consumption and high brightness.

The development of display devices in the information society is developing remarkably and its role is also important. In particular, a liquid crystal display device, which is spotlighted as a flat panel display, does not emit light by itself, and thus requires a backlight unit. The performance of the liquid crystal display device depends not only on the liquid crystal display device itself but also on the performance of the backlight unit used. The bar is big.

The backlight unit is largely composed of a light guide plate, an optical film, a lamp assembly, and a mold frame. Such a liquid crystal display is classified into a direct method and an edge method according to the lamp position of the backlight unit.

In the edge type backlight unit, a lamp assembly is installed on the side of the light guide plate, and includes a lamp that emits light and a lamp reflector that reflects the light emitted from the lamp to the light guide plate by surrounding the lamp so that the side opposite to the light guide plate is opened. .

However, in the edge method, there is a limit in using the light beam from the light source efficiently. Therefore, the loss ratio of the light beam emitted in the reflector direction to increase the light efficiency is high, so high power is required to emit the light beam having a desired efficiency. .

In addition, the edge method has a limit in reducing the size of the liquid crystal display. That is, since the lamp assembly is installed on the light guide plate side, a lamp insertion space is required on the light guide plate side. In addition, in order to realize a thinner liquid crystal display device, it is necessary to reduce the diameter of the lamp and the thickness of the light guide plate. At this time, the diameter of the lamp can no longer be reduced due to a decrease in brightness and uniformity of light of the liquid crystal display device. Since the thickness cannot be smaller than the lamp diameter in order to improve the light efficiency, the liquid crystal display cannot be made thin.

In order to overcome this drawback, a direct type backlight unit has been proposed. However, in the direct method, a plurality of lamps are inevitably used to increase the brightness and ensure the uniformity of the brightness, thereby increasing the power consumption.

In order to overcome this problem, a light guide plate structure capable of increasing luminance and obtaining uniformity of luminance while reducing power consumption by using a single lamp has been proposed.

For example, Korean Patent Laid-Open Publication No. 1998-82344 (hereinafter referred to as '344') is installed in a mold frame and a mold frame, and the thickness becomes thinner from the bottom center to both sides and the lamp is inserted in the center of the bottom surface. A light guide plate is formed in which a groove is formed and a locking step is formed in a predetermined region between an insertion groove and both side surfaces thereof.

In addition, Korean Utility Model Publication No. 1998-63693 (hereinafter referred to as '693') has a flat front surface and a rear surface of which has a thinner thickness from the center to both end portions, and a lamp insertion groove having a rear side opened in the center of the rear surface. When the light guide plate is formed, a light absorbing part for absorbing light from the lamp is provided on the bottom surface of the lamp insertion groove, and a lamp protection plate for protecting the lamp is provided at a portion opposite to the opening of the lamp insertion groove. have.

However, according to No. 344, forming a dot-shaped reflective pattern in the rounded portion inside the insertion groove is practically ineffective because there is no processing technology for maintaining reproducibility, and light is emitted in the form of diffused light by the reflective pattern itself. There is a problem that the luminance of the center is relatively high. In addition, there is a problem that the light is lost due to the locking step to reduce the efficiency of the light source.

In addition, according to No. 693, there is a problem that the light efficiency is lowered by the light absorbing portion present in the lamp insertion groove, may cause heat generation.

Accordingly, the present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a light guide plate capable of realizing high brightness while minimizing power consumption.

Other objects and features of the present invention will be clearly understood through the preferred embodiments described below.

According to the present invention, the light guide plate for the backlight unit is made of a transparent material body having a constant width and length, and a lamp insertion groove is formed in which the lamp is inserted over the entire width in the longitudinal center of the rear surface of the body, A prism integrally reflects a portion of the light emitted from the lamp along the bottom surface is integrally formed.

Preferably, the cross-sectional shape of the prism may be polygonal. In a preferred embodiment, the height of the prism is 0.5 to 2.5mm, the width of the lamp insertion groove may be 1 to 5mm.

In addition, the body may have a cross-sectional profile in which the thickness decreases toward both sides from the longitudinal center of the rear surface, and may further include a diffusion part formed by cutting a portion of the apex portion of the prism by cutting the cross section to form a square or round shape. .

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

1 is a perspective view illustrating a light guide plate according to an exemplary embodiment of the present invention.

As shown, the light guide plate 100 is composed of a body 110 of a transparent material. For example, the material of the body 110 may be polycarbonate (PC) or poly methylmethacrylate (PMMA).

The body 110 is a plate shape having a constant length and width, preferably the body 110 has a cross-sectional profile of the thickness decreases toward both sides from the longitudinal center of the rear surface.

In the longitudinal center of the rear surface of the body 110, a lamp insertion groove 120 into which a lamp 200, for example, a cold cathode fluorescent lamp is inserted, is formed, and a lamp ( Prisms 112 for internal reflection or total reflection of light emitted from 120 are integrally formed.

Here, the internal reflection refers to a form in which the emitted light is partially passed through the prism 112 to the surface and the other is reflected from the prism 112, and total reflection reflects all of the emitted light from the prism 112. Say the form.

In this embodiment, the cross-sectional shape of the prism 112 is shown as a triangle, but may be another polygon. In the following description, a triangle is taken as an example.

FIG. 2 is a partially enlarged view showing the lamp insertion groove of FIG. 1 in detail.

The width w of the lamp insertion groove 120 is about 1 to 5 mm, and the height hp of the prism 112 is 0.5 to 2.5 mm, which is about 1/2 of the width w. Along with this, the vertex vertices α of the triangular cross section constituting the prism 112 are preferably in the range of about 70 to 120 degrees. In another form, the vertex portion of the triangular cross section may be formed as a curved portion having a predetermined curvature.

On the other hand, as described above, the body 110 has a cross-sectional profile of the thickness decreases toward both sides from the longitudinal center of the rear surface, the angle θ for this is preferably about 35 degrees or less.

An operation principle of the light guide plate according to the present invention having such a structure will be described with reference to FIG. 3.

As shown in FIG. 3, light emitted from the lamp 200, which is a light source, proceeds in about four types.

First, the light going straight to the side of the lamp insertion groove 120 proceeds as indicated by the path R1.

Further, light traveling straight to the upper portion of the lamp insertion groove 120 travels to the surface of the body 110 via the prism 112 as indicated by the path R2.

The path R4 represents a path of light obliquely traveling from the lamp 200 to the side of the lamp insertion groove 120 and is bent at the interface between the lamp insertion groove 120 and the body 110 but similarly travels through the body 110. do.

On the other hand, the light traveling obliquely to the prism 112, as indicated by the path R3, the total reflection occurs when the internal reflection or the critical angle or more and the light is reflected from the surface of the prism 112 to proceed into the body 110.

According to such a configuration, most of the light emitted locally through the surface of the body 110 corresponding to the lamp insertion groove 120 into which the lamp 200 is inserted may be used for the internal reflection and total reflection of the body 110. It can be emitted to the front of the surface, increasing the overall light efficiency and consequently increasing brightness while lowering power consumption.

According to the measurement results of the actual optical properties, it can be seen that the luminance and the light intensity at a certain distance, the luminance relative to the viewing angle, and the light intensity at the surface of the light guide plate are all improved.

In addition, by using total reflection by the prism, the local luminance of the body portion corresponding to the lamp insertion groove 120 into which the lamp is inserted may not be greatly increased, thereby achieving uniformity of the overall luminance.

4 is a partially enlarged view showing a modification of the present invention.

In this embodiment, the diffusion portion 114 is formed at the apex of the prism 112. As shown in FIG. 4, the diffusion part 114 is formed by cutting and removing a portion of the vertex to form a square, and may be formed in a round shape in addition to the square.

Light emitted from the lamp by the diffuser 114 is diffused and emitted to the surface, thereby preventing the surface of the body 110 corresponding to the lamp insertion groove 120 from being too dark by internal reflection and total reflection.

According to this configuration, there is an advantage that the local brightness of the body portion corresponding to the lamp insertion groove can be compensated for at the same time as the overall brightness increase by the prism 112 is maximized.

Although the above has been described with reference to the preferred embodiments of the present invention, various changes and modifications can be made without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be limited to the above embodiments, but should be determined by the claims described below.

As described above, according to the present invention, most of the light emitted locally through the surface of the body corresponding to the lamp insertion groove into which the lamp is inserted can be emitted to the front surface of the body using internal reflection and total reflection. There is an advantage of increasing the overall light efficiency and consequently increasing the brightness while lowering the power consumption.

Further, by using total reflection by the prism, the local luminance of the body portion corresponding to the lamp insertion groove into which the lamp is inserted does not greatly increase, thereby achieving uniformity of the overall luminance.

In particular, by forming the diffusion portion at the apex of the prism, there is an advantage that the local luminance decrease of the body portion corresponding to the lamp insertion groove can be compensated while maximizing the overall luminance increase by the prism.

Claims (6)

It is made of a transparent material having a constant width and length, the lamp insertion groove is formed in the longitudinal center of the rear surface of the body is inserted into the lamp over the entire width, and is emitted from the lamp along the bottom surface of the lamp insertion groove A light guide plate for a backlight unit, characterized in that the prism for totally reflecting a part of the light is formed integrally. The light guide plate of claim 1, wherein the cross-sectional shape of the prism is a polygon. The light guide plate according to claim 1 or 2, wherein the prism has a height of 0.5 to 2.5 mm. The light guide plate of claim 1, wherein the width of the lamp insertion groove is 1 to 5 mm. The light guide plate according to claim 1 or 2, wherein the body has a cross-sectional profile whose thickness decreases from the center in the longitudinal direction of the rear surface to both sides. The light guide plate according to claim 1 or 2, further comprising a diffusion part formed by cutting a portion of the apex portion of the prism so as to have a square or round cross section.

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