KR20070001429A - Back-light unit - Google Patents

Abstract

A back light unit is provided to distribute beads in a light guide plate such that the light guide plate has a diffusing function and a light-focusing function. A back light unit includes at least one lamp(111) emitting light, a light guide plate(113), a reflection pattern(120), and a case. The light guide plate is arranged at one side of the lamp and includes a plurality of diffusing beads(115) and light-focusing beads(116). The reflection pattern is formed on the backside of the light guide plate. The case houses the lamp, the light guide plate and the reflection pattern. The light guide plate is fabricated by dispersing the diffusing beads and the light-focusing beads in a thermal-hardened transparent resin and hardening the resin.

Description

Backlight Unit {BACK-LIGHT UNIT}

1 is a cross-sectional view of a backlight unit according to the prior art.

2 is a rear view of a light guide plate according to the prior art;

3 is a cross-sectional view of the backlight unit according to the present invention.

4 is a view showing an optical path in the light guide plate according to the present invention.

5 is a cross-sectional view of various types of diffused beads and condensed beads according to the present invention.

6 is a backlight rear view showing a reflection pattern according to the present invention;

<Description of Symbols for Main Parts of Drawings>

111 light emitting lamp 113 light guide plate

115: diffused beads 116: condensed beads

120: reflection pattern

The present invention relates to a backlight unit, and more particularly, to a backlight unit having a light guide plate that simultaneously performs a diffusion function and a light condensing function.

Recently, researches on flat panel displays have been actively conducted, and among them, liquid crystal display devices (LCDs), field emission display devices (FEDs), electro-luminescence display devices (ELDs), and PDPs (PDPs) Plasma Display Panels).

Among these, liquid crystal display devices have a large contrast ratio, are suitable for gray scale display or moving image display, and have low power consumption. Therefore, the area of the liquid crystal display device has been expanded to notebook PCs, desktop monitors, and liquid crystal TVs.

However, since the liquid crystal display itself is non-luminescent, a separate external light source for irradiating light is required. In particular, in the case of a transmissive liquid crystal display, a separate dimming device that emits light and guides the back of the LCD panel is necessary.

Hereinafter, a conventional backlight unit will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view of a backlight unit according to the prior art, and FIG. 2 is a rear view of the light guide plate according to the prior art.

In general, a backlight unit that provides light to a display device (eg, a liquid crystal panel) includes a light emitting lamp 11 which is installed at one corner and emits light as shown in FIG. 1, and the light emitting lamp 11. A light guide plate 13 for converting the line light source irradiated from the light source into a uniform surface light source, a reflecting plate 12 positioned below the light guide plate 13 to reflect light leaking downward to the top, and the light guide plate 13 Diffusion Sheet 15 positioned at the upper part to uniformly diffuse the light from the light guide plate 13 and Light diffused at the diffusion part located at the upper part of the diffusion sheet 15 to condense into a liquid crystal panel. The upper and lower prism sheets 16a and 16b are transferred, and a protective sheet 17 that protects the prism sheets on the prism sheets 16a and 16b. Although not shown, the components of the backlight are housed by a main support that holds them.

The backlight is condensed by the light emitted from the light emitting lamp 11 to the light-receiving portion of the light guide plate 13, passes through the light guide plate, and then passes through the diffusion sheet 15, the prism sheets 16a and 16b, and the protective sheet 17 in order. It is transmitted to the information display surface.

In this case, as shown in FIGS. 1 and 2, the light pattern 13 is periodically arranged with a dot pattern 20 having a predetermined shape such as a circle, a rectangle, or a hexagon, and the brightness concentration phenomenon in a region close to the lamp is performed. To prevent.

In general, the dot pattern is a screen printing method of forming a light scattering ink pattern is most widely used, and a method of injecting the surface of the light guide plate using a transfer film or by processing the uneven surface directly into the mold when the plastic or resin injection; It is formed by a method of directly processing a dot pattern on the injected acrylic plate.

Here, the size of the dot pattern is formed larger as the lamp approaches, and smaller as it moves away from the lamp, thereby reducing the intensity of light reflected from the light guide plate, thereby solving the luminance concentration, thereby obtaining a uniform brightness on the liquid crystal panel. We plan to improve.

However, since it is difficult to solve the problem of luminance uniformity only with a dot pattern, as described above, a plurality of optical sheets such as a diffusion sheet, an upper and lower prism sheet, and a protective sheet are further provided on the light guide plate.

However, the conventional backlight unit as described above has the following problems.

According to the conventional backlight unit, since the number of parts is increased by being separately provided and assembled together with the diffusion sheet and the prism sheet, it is difficult to reduce the thickness of the backlight unit, and the number of assembling processes increases due to the increase in the number of parts, thereby increasing the defective rate. There is a problem that the production cost as a whole rises.

An object of the present invention devised to solve the above problems is to distribute the beads in the light guide plate to perform the diffusion function and the condensing function at the same time by using a backlight unit, characterized in that not using a separate diffusion sheet and prism sheet To provide.

According to an aspect of the present invention, there is provided a backlight unit including at least one light emitting lamp for providing a light source, a light guide plate provided on one side of the light emitting lamp, and including a plurality of diffused beads and condensed beads; And a reflective pattern formed on the rear surface of the light guide plate and a case accommodating the components.

At this time, the light guide plate according to the present invention is prepared by dispersing and mixing the diffusion type beads and the light collection type beads in a transparent resin substrate which is a thermosetting resin.

Hereinafter, the backlight unit according to the present invention will be described in detail with reference to the accompanying drawings.

3 is a cross-sectional view of a backlight unit according to the present invention, FIG. 4 is a view showing an optical path in a light guide plate according to the present invention, and FIG. 5 is a cross-sectional view of various types of diffused beads and condensed beads according to the present invention. 6 is a backlight rear view showing a reflection pattern according to the present invention.

The backlight unit according to the present invention is characterized by having a light guide plate including diffused beads and condensed beads. Specifically, as shown in FIG. 3, the backlight unit is installed at an edge of the backlight unit to emit light. At least one light emitting lamp 111, the light guide plate 113 for converting the line light source irradiated from the light emitting lamp 111 into a uniform surface light source, and the light leaking to the lower portion located in the lower light guide plate 113 A reflection pattern 120 reflecting upward, a diffused beads 115 mixed in the light guide plate 113 to scatter light emitted from the light emitting lamp to mitigate light non-uniformity, and a diffused beads inside the light guide plate. The light concentrating beads 116 are disposed on the upper side and collect light in the up, down, left and right directions to increase luminance and transmit the light to the liquid crystal panel. In this case, although not shown, a protective sheet may be further provided to protect the light guide plate having beads mixed on the light guide plate and to increase the viewing angle.

As a result, the diffuser beads 115 perform a conventional diffuser sheet function, and the condensed beads 116 perform a conventional prism sheet function so that the light guide plate itself performs a diffuser function and a light condensing function at the same time. There is no need to provide a separate diffusion sheet and a prism sheet. In addition, since the number of mixed diffused beads varies according to the thickness of the light guide plate, the thickness of the light guide plate or the number of diffused beads may be changed so that a desired light scattering state may be achieved.

In this case, the light collecting beads 116 are mixed to be located at an upper point inside the light guide plate, and the diffusion bead 115 is positioned above the height of the light emitting lamp 111 in the light guide plate. It is possible to mix evenly in the part where the mold beads are not formed.

In addition, an upper surface of the light guide plate 113 through which light exits to the liquid crystal panel is formed in a concave lens shape, thereby increasing light efficiency by preventing light from exiting to the side.

On the other hand, the light emitting lamp 111 emits white light, may be located on one side edge of the light guide plate, may be located on both edges of the light guide plate, respectively, using a cold cathode fluorescent lamp (Cold Cathode Fluorescence Lamp) is generally low heat generation Doing. When the light emitting lamps are positioned at both edges of the light guide plate, it is preferable that the upper surface of the light guide plate has a concave lens shape. However, when the light emitting lamps are positioned only at one edge of the light guide plate, the light distribution by the light emitting lamps is different so that the top surface of the light guide plate is inclined. It would be more desirable to have a form.

As shown in FIG. 6, the reflection pattern 120 has a larger size and a smaller distance as the lamp approaches the lamp. The reflection pattern 120 reduces the intensity of light reflected from the light guide plate to solve the luminance concentration phenomenon. Ensure uniform brightness.

The optical path of the backlight unit having the above-described configuration is the same as that of FIG. 4, wherein the line light source irradiated from the light emitting lamp 11 positioned at the side of the light guide plate 111 travels through the side of the light guide plate to the inside of the light guide plate. .

At this time, the line light source is refracted to the inner wall of the light guide plate in the light guide plate, and is vertically scattered on the surface of the diffusion beads 115 inside the light guide plate (II region of FIG. 4). At this time, some of the light traveling inside the light guide plate leaks between the spaced apart diffused beads, is reflected by the reflective pattern 120 on the bottom surface of the light guide plate, and then proceeds to the inside of the light guide plate again (region I of FIG. 4).

The light scattered vertically from the diffused beads 115 passes through the focused beads 116 and is condensed by the difference in refractive index between the focused beads and the light guide plate. Is detected. Here, the light exiting without passing through the light collecting beads extends the viewing angle while passing through the upper surface of the light guide plate having a concave lens shape (III region in FIG. 4).

Here, the diffused beads 115 and the condensed beads 116 can be selected from various forms according to the characteristics of the desired outgoing light, the cross-sectional view, as shown in Figure 5, spherical, oval, triangular It can be used that formed. That is, since the scattering angle or refraction angle of light varies depending on the shape of the beads, beads of a desired shape are selected and used. 5 shows the direction of the exit light according to the shape of the light collecting beads.

The diffused beads are formed of small grains, such as small glass ware, to scatter light, and the condensed beads are formed of transparent glass because they must pass light, and the size of the diffused beads is condensed. Smaller ones than the beads are selected and mixed in the light guide plate, and the number thereof is larger than that of the light collecting beads.

The light guide plate is formed by manufacturing a plastic or a resin such as polymethyl methacrylate (PMMA) in a flat or wedge type. The light diffusion plate and the light condensing beads are formed in a transparent resin substrate, which is the thermosetting resin. After dispersing and mixing, the thermosetting resin is heated to remove solvent and crosslink to form a light guide plate. At this time, during the process of pouring the uncured thermosetting resin into the mold for manufacturing the light guide plate and temporarily curing the light-curing plate, the light guide plate having both diffusion and condensing functions is selectively dispersed and mixed. This is done.

Therefore, the light guide plate according to the present invention can realize uniform and bright luminance without optical sheets.

On the other hand, the above embodiment is only a description of a preferred embodiment of the present invention, the scope of application of the present invention is not limited to such, the present invention can be appropriately changed within the scope of the same idea. For example, the shape and structure of each component specifically shown in the embodiment of the present invention can be modified.

The backlight unit according to the present invention as described above has the following effects.

That is, by dispersing beads in the light guide plate to simultaneously perform the diffusion function and the light condensing function, high brightness can be realized without using a separate diffusion sheet and a prism sheet.

Therefore, the number of parts such as a diffusion sheet and a prism sheet can be reduced, thereby reducing the number of assembly processes, a defective rate, and a process cost, and the light and small size of the backlight unit can be reduced.

Claims (8)

At least one light emitting lamp providing a light source, A light guide plate provided on one side of the light emitting lamp and including a plurality of diffused beads and condensed beads; A reflection pattern formed on a rear surface of the light guide plate; And a case accommodating the components. The method of claim 1, And a surface on which the light is emitted from the light guide plate has a concave lens shape. The method of claim 1, And a protective sheet on the upper part of the light guide plate. The method of claim 1, The light emitting lamp is a backlight unit, characterized in that the lamp for emitting a line light source. The method of claim 1, The light emitting lamp is disposed on one side edge of the light guide plate or the backlight unit, characterized in that disposed on both edges of the light guide plate. The method of claim 1, And the diffusion beads are uniformly mixed above the height at which the light emitting lamp is positioned. The method of claim 1, The diffusion unit or the condensed beads are selected from the cross-section is spherical, elliptical, triangular and used. The method of claim 1, The light guide plate is a backlight unit, characterized in that the diffusion-type beads and light-condensing beads are dispersed and mixed in a transparent resin substrate of a thermosetting resin.

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