KR20080022717A - Back light unit - Google Patents

Abstract

A backlight unit is provided to arrange light sources at a light guide plate and to form light scattering patterns only on upper ends of the light sources, thereby reducing the number of the light sources and decreasing the thickness of the light guide plate. A backlight unit comprises a light guide plate(231), multiple grooves(233), light sources(234), and optical sheet parts(290). The light guide plate uniformly scatters the light. The light sources are respectively placed in the grooves. The optical sheet parts are laid on the light guide plate. The light scattering patterns(235) are placed above the light sources and formed at straight light regions where the light is straightly reached. A reflecting plate is formed at the rear surface of the light guide plate to project the light from the light sources into the light guide plate. Thereby, the number of the light sources is reduced, and the thickness of the light guide plate decreases.

Description

Backlight Unit {BACK LIGHT UNIT}

1 is a configuration diagram of an embodiment of a general edge type backlight unit.

2 is a configuration diagram of an embodiment of a general direct type backlight unit.

Figure 3 is a configuration diagram of an embodiment of a backlight unit using a conventional light guide plate.

4 is an exemplary view illustrating a state in which light is emitted from a light source in a conventional backlight unit;

5 is a configuration diagram of an embodiment of a backlight unit according to the present invention;

FIG. 6 is a cross-sectional view of the backlight unit of FIG. 5 according to one embodiment of the present invention. FIG.

7 is an exemplary view illustrating a state in which light is emitted from a light source in the backlight unit according to the present invention.

<Explanation of symbols for main parts of the drawings>

131, 231: light guide plate 132: auxiliary plate

133, 233: groove 134, 234: light source

135, 235: light scattering pattern 136, 236: reflector

238: pattern mountain

The present invention relates to a backlight unit, and more particularly, to a backlight unit combining the advantages of an edge type backlight unit and a direct type backlight unit.

In recent years, as the society enters the information age, the display industry that processes and displays a large amount of information has been rapidly developed.

As a result, a liquid crystal display device (LCD device) is being developed that can meet various demands of the user, such as thinning, light weight, and low power consumption, and replaces a conventional cathode-ray tube (CRT). It is attracting attention as the next generation display device.

In general, a liquid crystal display may be classified into a liquid crystal panel displaying an image largely seen by a user, and a back light unit for increasing the brightness of the image.

In this case, the backlight unit may be classified into an edge type and a direct type according to the arrangement of light sources, and among these, a direct type backlight unit capable of high brightness to be suitable for large size and large screen is widely used. In the following description, the lamp, the light source, and the backlight are used in the same sense.

1 is a configuration diagram of an exemplary edge type backlight unit, and a general edge type backlight unit includes a light emitting part, a waveguide part, and an optical sheet part.

The light emitting portion is composed of a lamp 8 and a lamp housing 7 for protecting the lamp.

The waveguide is located on the light guide panel 2 which makes the light emitted from the lamp 8 into a uniform surface light source, and is located on the rear surface of the light guide plate to reflect the light from the lamp and concentrate it toward the liquid crystal panel side (front). It consists of a reflecting plate (1) that serves to prevent the loss of light from the back or side of the light guide plate.

An optical sheet unit is disposed on the light guide plate to diffuse light from the light guide plate to improve the brightness of the light (diffuser sheet) (3), located on the top of the diffusion sheet to collect light from the light guide plate to improve the viewing angle It is composed of a prism sheet (4, 5) and a protector sheet (6) to be located on the top layer of the backlight unit to prevent damage to the diffusion sheet and prism sheet and to secure a desired viewing angle. have.

In this case, as shown in FIG. 1, the edge type backlight unit must include two prism sheets 4 and 5 to obtain a desired viewing angle. Therefore, as the number of prism sheets increases, there is a problem that not only light loss occurs due to the feedback of light emitted from the light guide plate, but also disadvantages in terms of cost reduction. Recently, luminance, light uniformity, and color purity are higher than those of the edge type method. High direct type backlight units are becoming more popular around LCD TVs. That is, the high brightness of the light source (backlight) is required due to the market trend requiring the size and slimming of the liquid crystal display device. Is being applied.

2 is a configuration diagram of an embodiment of a general direct type backlight unit.

That is, the general direct type backlight unit as shown in FIG. 2 includes a cover bottom 10 on a plate made of metal or a synthetic resin material, and a white or silver metal material seated on the cover bottom. And a reflector 20 on the plate, a cold cathode fluorescent lamp 30 arranged in parallel on the reflecting plate, and an optical sheet portion 90 seated on the plurality of cold cathode fluorescent lamps.

The optical sheet unit 90 includes a diffusion plate 40 seated on a vertical upper end of the cold cathode fluorescent lamp (hereinafter, simply referred to as a 'lamp'), a diffusion sheet 50 seated on an upper end of the diffusion plate, and the diffusion. It comprises a prism sheet 60 seated on the top of the sheet and a reflective polarizing film (MOF) 70 of a multi-layer structure seated on the top of the prism sheet.

In this case, the general direct-backlit backlight unit illustrated in FIG. 2 is widely used due to the large size of the liquid crystal display, the market trend requiring slimness, and high brightness. However, since a plurality of lamps are used, power consumption is increased. In addition, since the distance between the lamp 30 and the diffuser plate 40 must be secured, it is difficult to slim down, and sagging of the diffuser plate is caused due to heat and support force, resulting in poor luminance at the edge of the backlight unit. . Among the above problems, a plurality of lamps should be used in the direct type backlight unit, and a problem in which the distance between the lamp and the diffusion plate should be secured will be described with reference to FIG. 4 below.

That is, as described above, the edge type backlight unit uses one or two lamps, but the light efficiency is worse than that of the direct type, and the direct type backlight has not only a large number of lamps but also luminance uniformity and lamps. The thickness of the backlight becomes thick because the gap between the diffuser plate and the lamp is kept constant in order to prevent the human eye from being visible, and the diffuser plate sags due to heat and self-supporting force, thereby degrading the function of diffusing light. have. Therefore, in order to solve the above problems, a backlight unit using a light guide plate as shown in FIG. 3 has been proposed.

3 is a configuration diagram of a backlight unit using a conventional light guide plate.

That is, as shown in FIG. 3, the backlight unit using the conventional light guide plate includes a plurality of auxiliary plates 132 formed on the top of the light guide plate 131 and a plurality of rear surfaces formed at regular intervals on the rear surface of the light guide plate 131. The groove 133 and the light source 134 formed in the groove 133 are included.

In the backlight unit using the conventional light guide plate having the above configuration, a plurality of light scattering patterns 135 are formed on the surface of the auxiliary plate 132 between the light guide plate 131 and the auxiliary plate 132 and are emitted from the light source 134. The light to be scattered or diffused.

In addition, in the backlight unit using the conventional light guide plate, the light emitted from the light source 134 is formed inside the light guide plate 131 by forming a reflecting plate 136 on the rear surface of the light guide plate 131 including the light source 134. To be incident.

That is, the light emitted from the light source 134 is incident on the light guide plate 131, and after scattering in the light guide plate 131, illuminates the entire liquid crystal panel through the auxiliary plate 132 on which the light scattering pattern 135 is formed. Done.

However, since the backlight unit using the light guide plate as described above uses the auxiliary plate 132 in addition to the light guide plate 131, the manufacturing cost increases and the manufacturing process becomes complicated.

In addition, in the backlight unit using the light guide plate, since the light scattering pattern 135 formed on the auxiliary plate 132 is distributed over the entirety of the auxiliary plate 132 as shown in FIG. 3, the light is concentrated on the light source 134. There is a problem in that it does not diffuse and scatter them to other parts, there is a problem that the brightness of the backlight unit as a whole is poor. This will be described with reference to FIG. 4 below.

FIG. 4 is an exemplary view illustrating a state in which light is emitted from a light source in a conventional backlight unit, and illustrates a state in which light is emitted from a light source of a backlight unit using a light guide plate as shown in FIG. 3 and a general direct type backlight unit. However, in particular, as shown in FIG. 3, the light scattering pattern 135 shows a state in which light is emitted from the backlight unit in which the whole is evenly distributed on the auxiliary plate 132.

That is, as shown in FIG. 4, the light emitted from the two light sources 134 is diverged at a predetermined angle α to reach the auxiliary plate 132 or the diffusion plate 40, and then the auxiliary plate 132. Or scattered or diffused by the diffusion plate 40.

However, when reducing the number of lamps for cost reduction or reducing the thickness of the backlight unit for improving the brightness, the auxiliary plate 132 or the diffusion of light emitted from the two light sources 134 does not overlap. Since the light reaches the plate 40, even if light is scattered or diffused by the light scattering pattern or the diffuser plate 20 evenly distributed on the auxiliary plate 132 or the diffuser plate 40, the light is scattered or diffused evenly. As a result, the upper portion of the light source 134 (direct light area A) has a higher luminance than the portion between the light source and the light source (indirect area B), resulting in a problem that luminance is uneven when viewed as a whole of the backlight unit. do.

Therefore, due to the above problems, a conventional general direct type backlight unit and a backlight unit using a light guide plate as shown in FIG. 3 must use a plurality of lamps (light sources), while a lamp (light source) and an auxiliary plate (or diffuser). There is a problem that it is difficult to slim because sufficient separation distance must be maintained between the plates).

Accordingly, an object of the present invention for solving the above problems is to arrange the light source in a direct type on the light guide plate used for the edge type, while forming a light scattering pattern only on the upper end of the light source of the light guide plate, the number of the light guide plate It is to provide a backlight unit that can reduce the thickness of.

In order to achieve the above object, the backlight unit according to an embodiment of the present invention, the light guide plate for uniformly scattering light; A plurality of grooves formed at regular intervals on a rear surface of the light guide plate; Light sources disposed in the plurality of grooves, respectively; And an optical sheet disposed on an upper end of the light guide plate, wherein a light scattering pattern is formed in a direct light region in which the light emitted from the light source is directly located on the top of the light source. do.

In addition, the present invention further includes a reflecting plate formed on a rear surface of the light guide plate including the light source to allow the light source emitted from the light source to be incident into the light guide plate.

In addition, the lower surface of the light guide plate is characterized in that the reflective pattern for reflecting the light emitted from the light source to the upper surface is formed.

In addition, the lower surface of the light guide plate is characterized in that the pattern mountain for reflecting the light emitted from the light source to the upper surface is formed.

Other objects and features of the present invention in addition to the above objects will become apparent from the description of the embodiments with reference to the accompanying drawings.

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

5 is a configuration diagram of a backlight unit according to an exemplary embodiment of the present invention, and FIG. 6 is a cross-sectional view of the backlight unit illustrated in FIG. 5 according to the CC ′ of FIG. 5.

The backlight unit according to the present invention uses the optical characteristics of the edge type backlight unit structure by arranging a plurality of light sources on the light guide plate used in the edge type backlight unit, thereby reducing the size of a large liquid crystal display device using a smaller number of light sources. spec) can be implemented, slimming is possible, and the luminance non-uniformity problem of the edge portion can be improved, and the light guide plate region (hereinafter, simply referred to as 'direct light region') where the light emitted from the light source is directly reached. Light scattering pattern By selectively printing and forming, it is possible to prevent luminance unevenness caused by the direct light of the lamp. Can be.

As shown in FIGS. 5 and 6, a backlight unit according to the present invention having the above characteristics includes a light guide panel 231 for uniformly scattering light, and a constant distance on a rear surface of the light guide plate. And a plurality of grooves 233 formed therein, a light source 234 disposed in each of the grooves, and an optical sheet portion 290 disposed on an upper end of the light guide plate. In this case, a light scattering pattern 235 is formed in the direct light region of the surface of the light guide plate 231 where the light emitted from the light source is directly reached and is emitted from the light source 234. Scatters direct sunlight.

The optical sheet unit 290 may be composed of a diffusion sheet, a prism sheet, a polarizing film, and the like, and the light scattered and diffused through the light guide plate 231 and the light scattering pattern 235 as a surface light source having a uniform distribution. Change and diverge vertically. That is, a liquid crystal panel (not shown) manufactured through a separate process is seated on the upper end of the optical sheet unit 290, and the surface light source passing through the optical sheet unit 290 is incident to the liquid crystal panel.

The light guide plate 231 is a wave guide that scatters the light emitted from the light source 234 to diverge upward, and the same material as the light guide plate used for the edge type backlight unit may be used. For example, a polymethyl methacrylate (PMMA) resin having excellent light transmittance may be used. As described above, a plurality of grooves 233 are formed in the light guide plate, and light sources (lamps) 234 are arranged in the grooves.

The light scattering pattern 235 is to allow light emitted to the direct light region to scatter or diffuse more than the surface of the light guide plate 231 other than the direct light region (hereinafter, simply referred to as an indirect region). The light guide plate 231 may be formed on a surface of the light guide plate 231 by printing or sanding, and may be formed in various shapes in addition to the shape shown in FIG. 5.

The light source 234 may be a cold cathode fluorescent lamp (CCFL) or an external electrode fluorescent lamp (EEFL).

That is, when the light emitted from the light source 234 is incident on the light guide plate 231, the backlight unit according to the present invention having the configuration as described above may emit light scattered in the light guide plate 231. After passing through 290, the entire liquid crystal panel is illuminated. In this case, since the light scattering pattern 235 is formed in the direct light region located directly on the light source 234 of the light guide plate 231, the present invention provides more direct light directly received from the light source 234. By scattering and diffusing, a small number of light sources 234 are used to maintain uniform brightness of the surface of the light guide plate 231 even when the distance between the light source and the light source is high or the light guide plate 231 is formed slim. It has the feature to make it. At this time, the features of the present invention as described above will be described in detail with reference to FIG.

Meanwhile, the backlight unit according to the present invention may further include a reflecting plate 236 on the rear surface of the light guide plate 231 including the light source 234, and the reflecting plate 236 may be a light source emitted from the light source 234. The light guide plate 231 may function to be incident into the light guide plate 231.

In addition, the backlight unit according to the present invention, by forming a reflective pattern on the lower surface of the light guide plate 231, so that the light emitted from the light source 234 is well reflected on the lower surface of the light guide plate 231 more. Light may be directed toward the liquid crystal panel. In this case, instead of forming a reflective pattern on the lower surface of the light guide plate 231, a pattern mountain 238 is formed on the lower surface of the light guide plate 231 to perform a function similar to the reflective pattern. It may be.

FIG. 7 is an exemplary view illustrating a state in which light is emitted from a light source in the backlight unit according to the present invention, and illustrates the function of the light scattering pattern 235.

That is, the present invention is to provide a backlight unit that can reduce the number of the light source 234, while slimming, and if the number of the light source 234 is reduced and the height of the light guide plate 231 is slimmed, as shown in FIG. As described above, the light emitted from the light sources 234 reaches the surface of the light guide plate 231 without overlapping each other.

In this case, when using the light scattering pattern 135 which is uniformly distributed on the upper part of the light guide plate as in the conventional backlight unit illustrated in FIG. 3, the scattering on the upper part of the light guide plate also has the same distribution. The light density of the corresponding portion is inevitably smaller than the light density of the portion corresponding to the indirect region (B).

Therefore, in order to solve the above problems, the light scattering pattern 235 is formed only in a portion of the light guide plate 231 corresponding to the direct light region A, as shown in FIG. Since light reaching (A) can be scattered or diffused more and reach the indirect region B, more uniform luminance can be obtained when viewed on the entire surface of the light guide plate 231.

As described above, the backlight unit according to the present invention can use a smaller lamp (light source) as compared to a general direct-type backlight even when applied to a large inch, thereby simplifying the manufacturing process, and using manufacturing costs and lamps. There is an excellent effect that can reduce the power consumption by.

In addition, since the height of the light guide plate can be reduced by the light scattering pattern partially formed, the present invention has an excellent effect of slimming as a whole.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (5)

A light guide plate for uniformly scattering light; A plurality of grooves formed at regular intervals on a rear surface of the light guide plate; Light sources disposed in the plurality of grooves, respectively; And It includes an optical sheet portion placed on the top of the light guide plate, And a light scattering pattern is formed in a direct light region of the surface of the light guide plate directly above the light source and directly reaching the light emitted from the light source. The method of claim 1, And a reflective plate formed on a rear surface of the light guide plate including the light source to allow the light source emitted from the light source to be incident into the light guide plate. The method of claim 1, And a reflective pattern is formed on a lower surface of the light guide plate to reflect light emitted from the light source to the upper surface. The method of claim 1, The lower surface of the light guide plate is formed with a pattern mountain for reflecting the light emitted from the light source to the upper surface. The method of claim 1, The light scattering pattern is, The backlight unit is formed by a printing method or a sanding method.

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