KR20080046313A - Lgp structure of edge-type backlight unit - Google Patents

Abstract

A light guide plate structure of an edge-type backlight unit is provided to improve brightness and uniformity of emitted light by focusing the light from a linear optical source and emitting the focused light upward. A light guide plate structure(10) of an edge-type backlight unit converts a linear optical source into a surface optical source and emits the light. A microlens pattern(20) is embossed or depressed on a lower surface of a light guide plate with a density increasing from an incident surface(11a) to a non-incident surface(11b). An aspherical cylinder lens pattern(30) is formed to be normal to the incident surface in a direction from the incident surface to the non-incident surface. The light which is incident on the light guide plate from a linear optical source, is focused and the focused light is uniformly emitted upward.

Description

Light guide plate structure of side type backlight device {LGP structure of edge-type Backlight unit}

1 is a view showing a general structure of a side type backlight device,

2 is a perspective view showing a light guide plate structure of a side type backlight device according to an embodiment of the present invention;

3 is a bottom view showing a microlens pattern according to an embodiment of the present invention;

4 is a detailed view showing a microlens pattern according to an embodiment of the present invention;

5 is a plan view showing a cylinder lens pattern according to an embodiment of the present invention,

6 is a detailed view showing a cylinder lens pattern according to an embodiment of the present invention;

7 is a view for explaining the aspherical shape pattern of the cylinder lens according to the embodiment of the present invention;

8 is a view showing an optical path of a light guide plate according to the prior art;

9 is a view showing an optical path of a light guide plate according to an embodiment of the present invention.

** Description of symbols for the main parts of the drawing **

10: light guide plate

11a: entrance face 11b: entrance face

20: microlens pattern 30: aspherical cylinder lens pattern

R, R _S : radius of curvature

The present invention relates to a backlight device for a liquid crystal display device, and more particularly, a microlens pattern is formed on a lower surface of a light guide plate, and an aspherical cylinder lens pattern is formed on an upper surface thereof so as to uniformly emit high brightness light to the upper side. It relates to a light guide plate structure of a type backlight device.

Recently, as the information society develops, the demand for display devices is increasing in various forms. Accordingly, liquid crystal display (LCD), plasma display panel (PDP), electro luminescent display (ELD), and vacuum fluorescent display (VFD) Various flat panel display devices have been researched and developed. Here, LCD is widely used as a mobile flat panel display device because of its excellent image quality, light weight, thinness, and low power consumption, and is particularly used as a laptop, computer monitor, and TV monitor.

However, LCDs do not emit light by themselves and require a separate external light source to realize high quality images. Therefore, the LCD structure further includes a backlight device as a light source of the liquid crystal display panel in addition to the liquid crystal display panel, so that the backlight device uniformly supplies a high brightness light source to the liquid crystal display panel to realize a high quality image.

In general, a backlight device of a liquid crystal display is a cylindrical light source such as a Cold Cathode Fluorescent Lamp (CCFL), a Hot Cathode Fluorescent Lamp (HCFL), an External Electrode Fluorescent Lamp (EEFL), or a Light Emitting Diode (LED). EL (Electro Luminescence) devices are mainly used, and are classified into edge-lighting and direct-lighting backlight devices according to the way light sources are arranged.

Due to its relatively thin thickness, the side backlight device is mainly used for LCDs for thinning of portable communication devices, and the direct type backlight device is mainly used for LCDs for large screens such as notebooks and TV monitors due to its high light efficiency. do.

As shown in FIG. 1, in the side backlight device, a fluorescent lamp 2, which is a light source, is positioned on a side of a light guide plate 1 that converts light of a linear light source into a surface light source, and the fluorescent lamp 2 is a lamp reflector 3. The light emitted from the fluorescent lamp 2 is directly or reflected by the lamp reflector 3 to be incident on the light guide plate 1. The reflective plate 4 is positioned below the light guide plate 1, and the optical sheet 5 and the protective sheet 6 are positioned above the light guide plate.

In the side type backlight device having such a structure, light emitted from the fluorescent lamp 2 is incident on the side incident surface of the light guide plate 1, and in the light guide plate 1, the light of the fluorescent lamp that is incident on the light source is subjected to total internal reflection and refraction. The light is uniformly converted to the surface light source, and the light emitted downward is reflected by the reflector 4 onto the light guide plate 1. On the upper side of the light guide plate 1, an optical sheet 5 such as a diffusion sheet, a downward prism sheet, an upward prism sheet, and a protective sheet 6 are laminated, and the liquid crystal positioned at the upper side by diffusing and condensing the light emitted from the light guide plate again. By emitting to a display panel (not shown), it serves as a backlight. Here, the light guide plate is to convert the light of the linear light source incident from the fluorescent lamp into total internal reflection, refraction, and the like and convert the light into a surface light source, which is a main component of the backlight device.

In particular, in the recent liquid crystal display devices, a backlight device having a thin thickness is required due to a high luminance and uniformity of light emitted to the front surface (upper side) of the backlight device, and a slimness. However, the light guide plate and the backlight device according to the related art have a structure in which various kinds of optical sheets including a diffusion sheet are stacked on the light guide plate. In this case, a problem arises in that the overall thickness of the backlight device is increased by many optical sheets, and consequently, the liquid crystal display device is thick.

The present invention is proposed to solve the above problems, the light pattern is formed on the upper and lower surfaces of the light guide plate, respectively, by efficiently reflecting and refracting the light of the line light source incident from the incident surface to be emitted to the upper side, An object of the present invention is to provide a light guide plate structure of a side type backlight device that can improve the brightness and uniformity of the light emitting device, and can reduce the thickness of the backlight device by removing the diffusion sheet stacked on the upper side.

The present invention for achieving the above object is in the light guide plate structure of the side-type backlight device for converting the light of the line light source to the surface light source, the density of the microlens pattern on the lower surface of the light guide plate from the incident surface to the incident surface It is embossed or engraved with dense density at, and the aspherical cylinder lens pattern is formed on the upper surface as the incident surface from the incident surface perpendicular to the incident surface, so as to condense the light incident from the light source to the light guide plate and to emit it uniformly upward. It is characterized in that the configuration.

In the above-described configuration, the aspherical microlens pattern of the lower surface of the light guide plate has a curvature radius R _M of 5 μm ≦ R _M ≦ 50 μm and a height H of 0.5 μm ≦ H ≦ ₂₀ μm. do.

In the above-described configuration, the cylindrical lens pattern on the upper surface of the light guide plate has a width W of 20 µm ≤ W ≤ 100 µm, and a distance P between vertices of the lens is 1 W ≤ P ≤ 4 W with respect to the width, The radius of curvature R _S is 0.5W ≦ R _S ≦ 1.5W with respect to the width W of the pattern, characterized in that it is formed continuously or discontinuously.

In addition, the cylindrical lens pattern is characterized in that the conic constant (K, conic constant) is formed K≤-0.5.

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

2 is a view illustrating a light guide plate structure of a backlight device according to an exemplary embodiment of the present invention, FIGS. 3 and 4 are views illustrating a lower structure of a light guide plate, and FIGS. 5 and 6 are views illustrating an upper structure of a light guide plate.

Referring to FIG. 2, one side of the light guide plate 100 of the side type backlight device according to the embodiment of the present invention forms an incident surface 11a, and the thickness thereof becomes thinner from the incident surface 11a to the incident surface 11b. Losing in the shape of a cube.

Referring to the operation of the light guide plate having such a structure, a light source (not shown) such as a fluorescent lamp is disposed on the incident surface 11a side, and the line light source of the fluorescent lamp is incident into the light guide plate 10 through the incident surface 11a. . The incident light is uniformly emitted to the upper side of the light guide plate 10 through total internal reflection and refraction inside the light guide plate. In this case, the light emitted through the light guide plate 10 forms a surface light source.

On the other hand, the light guide plate 10 according to the embodiment of the present invention, as shown, the light induction of the micro lens pattern (20, micro lens pattern) on the lower surface and the aspherical cylindrical lens pattern (30, semi-cylindrical lens pattern) on the upper surface Each pattern is formed.

Specifically, as shown in FIG. 3, the microlens pattern 20 of the lower surface of the light guide plate 10 has a dense density at a small density toward an incidence surface 11b from the incident surface 11a. It is formed to gradually increase.

In addition, as shown in FIG. 4, the microlens pattern 20 has a radius of curvature R of 5 μm to 50 μm, and a height H of 0.5 μm to 20 μm. In this case, the lower surface of the light guide plate 10 may be formed in the shape of embossed (a) or intaglio (b).

As shown in FIG. 5, the above-described cylinder lens pattern 30 on the upper surface of the light guide plate 10 is formed in the direction of the incident surface 11b from the incident surface 11a in a direction perpendicular to the light source of the incident surface 11a. The cross section forms an aspherical hyperbolic surface and an elongated ellipsoidal shape, and preferably forms a semi-cylindrical lens pattern. The cylinder lens pattern 30 is a pattern that is formed to collect light that is incident from the incident surface 11a of the light guide plate and is distributed to the left and right and outputs the light toward the image side.

To this end, looking at the cross section of the aspherical cylinder lens pattern 30 according to an embodiment of the present invention with reference to Figure 6, the distance in the vertical direction from the incident optical axis, that is, the diameter (W) of the lens pattern 30 is 20㎛ To 100 μm, and the distance P between the vertices of the lens pattern 30 is W relative to the diameter W of the lens pattern. To between 4 W, to be formed continuously or discontinuously. In addition, the radius of curvature R _S of the apex of the cylinder lens pattern 30 is preferably formed to be 0.5W to 1.5W with respect to the diameter (W) of the lens pattern 30.

On the other hand, the cylindrical lens pattern 30 is aspherical in this case, the conic constant (K, conic constant) of the aspherical lens is to be formed to be -0.5 or less (K≤-0.5). Conic constants and aspheric coefficients for aspherical lenses are calculated by the aspherical equation as shown in Equation 1 below.

Where D _n is the distance from the lens vertex to the optical axis direction, W _n / 2 is the distance from the lens axis perpendicular to the optical axis, R is the radius of curvature at the lens vertex, K is the conic constant, A, B, C, D Denotes aspherical coefficients respectively.)

At this time, the shape of the lens pattern according to the conic constant K of the aspherical lens has a variety of shapes as shown in FIG. In other words, if the value of the Koenic constant is K> 0, it becomes a flat ellipsoid, if K = 0, it is spherical, if -1 <K <0, it is a long ellipsoid, if K = -1, it is a parabolic, K <- If 1, it will be hyperbolic.

Therefore, the aspherical cylindrical lens pattern according to the embodiment of the present invention is preferably formed as a long ellipsoid or hyperbolic surface with a conic constant K of -0.5 or less (K≤-0.5).

The light incident on the incident surface 11a of the light guide plate 10 by the above structure is uniformly focused to the image side by the microlens pattern 20 on the lower surface, and by the aspherical cylinder lens pattern 30 on the upper surface. By condensing again and exiting upward, high luminance light is emitted.

8 and 9 are views illustrating a light path by a conventional light guide plate and a light guide plate according to an embodiment of the present invention.

Referring to FIG. 7, the light pattern of the etching pattern 20 ′ is formed on the lower surface of the conventional light guide plate 1. Looking at the optical path in the light guide plate 1 of this structure, the light of the line light source incident on the incident surface (11a) is totally reflected and refracted to the upper surface of the light guide plate by the etching pattern 20 'of the lower surface of the light guide plate. At this time, the light that passes through the upper surface of the light guide plate and exits from the inside to the outside is refracted at a predetermined angle θ _E from the vertical normal again, and the refraction angle θ _E is remarkably laid out at about 55 ° or more. . In addition, the optical path viewed from the incident surface 11a side is not emitted vertically, but is refracted in the left and right directions and is emitted. Due to such refraction, the light in the normal direction cannot be efficiently concentrated in the upper direction of the light guide plate, so that the luminance is lowered, so that a separate diffusion sheet must be laminated.

On the other hand, referring to Figure 8, looking at the optical path of the light guide plate 10 according to an embodiment of the present invention, the light of the line light source incident on the incident surface (11a) is the microlens pattern 20 of the lower surface of the light guide plate 10 The total reflection and refraction are performed on the light guide plate 10 above. At this time, since the aspherical cylinder lens pattern 30 is formed on the upper surface of the light guide plate 10, the light collected by the microlens pattern 20 is once again focused on the aspherical cylinder lens pattern 30 on the upper surface and emitted to the upper side. do. In this case, the light emitted upwards of the light guide plate 10 is refracted at an angle of about 46 ° (θ _S ), and is emitted to have a small divergence angle (θ _E > θ _S ) from the normal line as compared with the conventional light guide plate. The brightness of the upper side of the light guide plate due to the emitted light can be improved.

That is, in the light guide plate 10 according to the embodiment of the present invention, the light condensed by the microlens pattern 20 on the lower surface is condensed by the aspherical cylinder lens pattern 30 on the upper surface, thereby having a double synergy effect of luminance. . For this reason, a separate diffusion sheet is not required on the light guide plate.

According to the light guide plate structure according to various embodiments of the present invention, the light path of the light emitted to the upper light guide plate is refracted by 40 ° to 50 ° from the normal on the light guide plate upper side than the conventional light guide plate, the light is efficiently focused upward In addition, the light is condensed efficiently in the left and right directions on the incident surface side.

Although the present invention has been described in detail through specific embodiments, the present invention is not limited to the above-described embodiments, and various changes may be made by those skilled in the art to which the present invention pertains without departing from the spirit and scope of the present invention. It may be changed and implemented.

As described above, according to the present invention, aspherical cylinder lens patterns and microlens patterns are formed on the upper and lower surfaces of the light guide plate, respectively, to efficiently condense the light of the line light source incident from the incident surface and to emit the light toward the upper side, thereby providing brightness and uniformity of light. In this case, the diffusion sheet, which is conventionally laminated on the light guide plate, can be removed, thereby making the thickness of the backlight device thinner.

Claims (4)

In the light guide plate structure of the side-type backlight device for converting the light of the line light source into a surface light source and emitting it, On the lower surface of the light guide plate, a microlens pattern is embossed or engraved with a dense density at a small density from the incident surface to the incident surface, An aspherical cylinder lens pattern is formed on the image surface as an incident surface from the incident surface perpendicular to the incident surface. A light guide plate structure of a side type backlight device, characterized in that it is configured to focus light incident on the light guide plate from the line light source and to emit it uniformly upward. The microlens pattern of the lower surface of the light guide plate has a radius of curvature R _M of 5 μm ≦ R _M ≦ 50 μm and a height H of 0.5 μm ≦ H ≦ ₂₀ μm. Light guide plate structure of side type backlight device. The cylinder lens pattern of the upper surface of the light guide plate has a diameter (W) of 20 μm ≦ W ≦ 100 μm, and a distance (P) between vertices of the lens is 1 W ≦ P ≦ 4 W with respect to a diameter. The curvature radius R _S is 0.5W ≦ R _S ≦ 1.5W with respect to the diameter W of the pattern, and is formed continuously or discontinuously. The light guide plate structure of claim 3, wherein the cylindrical lens pattern has a conic constant of K ≦ −0.5.

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