TWI393927B - Light guide panel comprising asymmetric front prism for lcd - Google Patents

Description

Light guide panel for a liquid crystal display including an asymmetric front sill

The present invention relates to a light guide panel of a backlight unit of a liquid crystal display (LCD), and more particularly to an area having an asymmetric front and can be adjusted at a specific position by controlling a cross-sectional shape of the front side of the light guide panel The light guide panel of the LCD backlight unit with the viewing angle and brightness.

Generally, a liquid crystal display (LCD) refers to an intermediate phase material that is applied between a liquid and a solid by applying an electric field to a liquid crystal, and is arranged between two glass substrates as electrodes to display numbers or images. s installation.

Since the LCD device is not a self-illuminating device, it must have a backlight unit as a light source that emits light. Then, an image or the like is displayed on the liquid crystal panel, which has liquid crystals arranged in a predetermined pattern and adjusts the transmittance of light emitted from the backlight unit.

Figure 1 is an exploded perspective view of a conventional LCD backlight unit.

The backlight unit 10 of the liquid crystal display can be classified into a direct type backlight unit according to the position of the light source that emits light, wherein the light source is directly placed on the rear side of the LCD panel 100, and the edge type backlight unit, wherein the light source is placed The side of the LCD panel 100. FIG. 1 shows an edge type backlight unit 10.

Referring to FIG. 1 , a conventional LCD backlight unit includes a light source 105 , a light guide panel 110 , a reflector 115 , a diffusion sheet 120 , a cymbal 125 , and a protection sheet 130 .

The light source 105 is used to start emitting light in the liquid crystal display. Although different Types of light sources can be used, however, LCDs typically employ a cold cathode fluorescent lamp (CCFL) that experiences very low power consumption and emits very high brightness white light.

The light guide panel 110 is disposed on one side of the light source 105 under the LCD panel 100 and is used to project light to the front of the light guide panel after converting the collected light of the light source 105 into planar light.

A reflection plate 115 is disposed on the rear side of the light guide panel 110 and serves to reflect light emitted from the light source 105 toward the LCD panel 100 placed in front of the reflection plate.

The diffusion sheet 120 is disposed on the upper side of the light guide panel 110 and serves to provide uniform light passing through the light guide panel 110.

The ruthenium sheet 125 serves to refract and collect light, which tends to improve brightness by rapidly reducing the brightness in the two directions (i.e., horizontal and vertical directions) when passing through the diffusion sheet 120.

The protective sheet 130 is disposed on the cymbal sheet and serves to protect the cymbal sheet 125 from being scratched and to prevent the occurrence of the Moire phenomenon when the cymbal sheet 125 stacked in two layers in the horizontal and vertical directions is used.

Although not shown in FIG. 1, the backlight unit 10 further includes: a mold frame or a casing for fixing components of the backlight unit 10, so that the backlight unit 10 can be an integral component; and a back cover or a lamp cover for The backlight unit 10 is protected and supported while maintaining the strength of the backlight unit 10.

2 and 3 are enlarged cross-sectional views of the light guide panel 110 illustrating the progress of light emitted from the light source 105 and passing through the light guide panel 110.

As shown in FIG. 2, the light source 105 is generally disposed near the backlight unit 10 One edge (for LCD TVs, just behind the LCD panel). Therefore, the light emitted from the light source 105 is not uniformly transmitted through the entire surface of the backlight unit, and the edge of the backlight unit tends to be brighter than the other portions. Light guide panel 110 is used to prevent such problems. The light guide panel 110 is usually made of a transparent acrylic resin, which ensures high strength of the light guide panel. Therefore, the light guide panel 110 is less likely to be broken or deformed and has a light weight and a high transmittance.

The light guide panel 110 is used to guide the light emitted from the light source 105 to uniformly advance in front of the light guide panel. However, actually, when light is emitted from a light source in which the light guide panel near which the backlight unit 10 is removed is disposed, it can be observed that the light guide panel does not exhibit uniform brightness, and light is concentrated at the opposite ends of the light guide panel. This is because the light guide panel 110 directs light from the light source 105 in the opposite direction.

Therefore, as shown in FIG. 3, a special process is performed on the rear side of the light guiding panel 110 to cause scattering reflection therefrom, so that the entire light guiding panel uniformly transmits light. Specifically, protrusions and depressions 113 each having a predetermined shape designed in consideration of the distance from the light source 105 are formed on the rear side. By such a patterning process of forming the protrusions and depressions 113, planar light having higher brightness and uniformity can be obtained on the LCD panel.

The LCD panel can be classified into a twisted nematic (TN) type and an in-plane switching (IPS) type depending on the arrangement of the liquid crystals. The TN type LCD provides a poor viewing angle compared to an IPS type LCD. However, because of its excellent transmittance, the TN type LCD is suitable for LCDs that require frontal visibility. On the other hand, although the IPS type LCD provides an excellent viewing angle than the TN type LCD, it has a low transmittance, which deteriorates the overall brightness.

Depending on the operating environment, the type of LCD panel associated with the liquid crystal alignment, and other external factors, it is often desirable to improve the brightness of the LCD at a particular angle or at a particular location.

Traditionally, reflective polarizing brightness enhancement films (DBEF) and non-multilayer film reflective polarizing brightness enhancement films (DRPF) have been used to improve brightness or viewing angle. However, these films lead to an increase in the total thickness of the backlight unit and an increase in manufacturing cost, thereby reducing the competitiveness of the LCD product including such a film.

The brightness uniformity-viewing-dependent item control in TCO'03 is controlled to fall within a specific range with respect to the degree of brightness uniformity of the horizontal and vertical fields of view of a general visual display unit. Figure 4 shows the measurement locations defined in the TCO'03 standard for the evaluation of the characteristics of a typical visual display unit.

Figures 5 and 6 show on brightness uniformity - TCO'03 viewing angle dependence of the standard, wherein the degree of uniformity of brightness based on the horizontal and vertical field of view are defined and L _H L _V, and is controlled to have 1.7 or smaller. The TCO'03 standard is a serious obstacle in the development of TN mode liquid crystal displays (LCDs) with a large limitation in the viewing angle of the display, and a component or technology that controls the viewing angle at a specific position and the angle in the backlight unit of the LCDs. Has been developed.

Therefore, there is a need for a technique for improving the brightness and viewing angle of an LCD without using a film.

In view of the above problems, it is an object of the present invention to provide a light guide panel of an LCD backlight unit that can not only adjust visibility at a specific position. And at a specific angle of view, it also meets the TCO'03 standard.

According to a feature of the present invention, a light guide panel of an LCD backlight unit includes a main body having an outer side for receiving incident light, a front side for emitting light, and a rear side, wherein the front side is formed by a triangular cross section. An asymmetric front ridge is formed with one slanted side treated to have a smooth mirrored surface and the other slanted side treated to have a rough diffusing surface.

According to another feature of the present invention, a light guide panel of an LCD backlight unit includes a body having an outer side for receiving incident light, a front side for emitting light, and a rear side, wherein the front side has a trapezoidal cross section The asymmetric front ridge is formed with one slanted side treated to have a smooth mirrored surface and the other slanted side treated to have a rough diffusing surface.

According to the present invention, the light guide panel of the LCD backlight unit optimizes the distribution of the viewing angle corresponding to the display, so that the light source of the backlight unit can be effectively used. Further, according to the present invention, the light guide panel can be formed to have a slim thickness and a low manufacturing cost by eliminating the DBEF and the DRPF used for the conventional light guide panel, and particularly satisfy the optical characteristics under the TCO'03 standard, At the same time ensure high brightness and good viewing angle characteristics.

According to a feature of the present invention, a light guide panel of an LCD backlight unit includes a main body having an outer side for receiving incident light, a front side for emitting light, and a rear side, wherein the front side is formed by a triangular cross section. An asymmetrical front ridge is formed with one sloping side of the front sill being treated to have a smooth mirrored surface and the other sloping side being treated to have a rough diffusing surface.

According to another feature of the present invention, a light guide panel of an LCD backlight unit includes a body having an outer side for receiving incident light, a front side for emitting light, and a rear side, wherein the front side has a trapezoidal cross section The asymmetric front ridge is formed with one slanted side of the front sill being treated to have a smooth mirrored surface and the other sloping side being treated to have a rough diffusing surface.

7 is a perspective view of a light guide panel of an LCD backlight unit according to an embodiment of the present invention.

Referring to FIG. 7, a light guide panel 30 of an LCD backlight unit according to an embodiment of the present invention is generally made of a transparent acrylic material, which has high strength and is not easily broken or deformed, and is light in weight and exhibits high transmission of visible light. rate. The light guide panel 30 includes a main body 300, an asymmetric front bezel 310, and a rear sill 320.

The main body 300 includes an outer side 301 for receiving incident light, a front side 303 connected to the outer side 301 and facing the LCD panel (not shown), and a rear side 305 connected to the outer side 301 and facing the front side. 303.

The term "outer side 301" vocabularily refers to one side of the object, but is defined herein as a surface through which light emitted from the source 306 enters the light guide panel. In Figure 7, the outer side 301 represents the opposite sides of the adjacent light source 306.

A predetermined shape of the rear cymbal 320 is formed on the rear side 305 and has a longitudinal direction perpendicular to the incident direction (Q direction) of the light from the light source 306. That is, when the helium 320 is set perpendicular to the incident direction (Q) of the light emitted from the light source 306, they may cause effective diffraction, refraction, and diffusion of the light. The collection of the posterior condyles 320 may constitute a predetermined dot pattern or stripe pattern.

The front side 303 is formed by an asymmetric front bead 310 having a predetermined cross-sectional shape and used to cause diffraction, refraction, and diffusion of light emitted by the body 300.

The asymmetrical front sill 310 is formed at a certain interval on the front side 303 and has a longitudinal direction disposed parallel to the incident direction of light emitted from the light source, that is, in the Q direction in FIG.

Unlike conventional front sills, each asymmetric front sill 310 has a slanted side that is treated to have a rough diffusing surface 307, and another slanted side that is treated to have a smooth mirrored surface 308 (although The term "mirror surface" generally means a mirrored or smooth plane, and the "front mirrored surface" of the asymmetric front is referred to herein.

The mirror surface 308 preferably has an Ra value of 0.2 μm or less, which corresponds to the surface roughness of the grinding treatment under the Korean Standard (KS), and the diffusion surface 307 preferably has an Ra value of 6.3 μm or more. It corresponds to the surface roughness of the general treatment under KS.

In this embodiment, referring to the rule of surface roughness under KS, the mirror surface 308 and the diffusion surface 307 are suggested to have Ra values of 0.2 μm and 6.3 μm, respectively. In this regard, in the experimental test of the present invention, when both the mirror surface 308 and the diffusion surface 307 have an Ra value of about 0.2 μm, the TH'03 standard L _H system is about 1.9. Furthermore, when the diffusion surfaces 307 each have an Ra value of about 5 μm, the TH'03 standard L _H system is about 1.7, and when the diffusion surface 307 has an Ra value of about 10 μm, the TCO'03 standard L _H The system is about 1.4. That is, in the case where the diffusion surface 307 is an Ra value of about 5 μm or less, considering the brightness uniformity-viewing dependence of the TCO'03 standard, although the light guiding panel does not exhibit a remarkable improvement effect, the light guiding light The panel also meets the TCO'03 standard. However, in order to obtain further improvement effects, it is preferable that the diffusion surface 307 has a Ra value as low as possible.

8 is a side cross-sectional view of a light guide panel of an LCD backlight unit in accordance with an embodiment of the present invention.

Referring to FIG. 8, an asymmetric front sill 310 is disposed on the front side such that the mirror surface 308 of the current cymbal 310 faces the right and left sides of the light guide panel and the diffusion surface of the front cymbal 310 faces the light guide panel. central. This arrangement is designed to improve viewing angle characteristics and to meet the TCO'03 standard by enhancing side visibility.

In other words, the right and left sloping sides of the asymmetric front sill 310 have optically distinct surface features such that the mirrored surface 308 of the front sill 310 provides a generally optical function and the diffusing surface 307 provides diffusion. And the general optical function of the cockroach. Therefore, when the asymmetric front bead 310 causes diffraction, refraction, and diffusion of light emitted from the main body 300 in a direction inclined to the LCD panel (not shown) facing the light guiding panel 30, the asymmetric front edge The structure of the mirror 310 can further improve the uniformity of light reaching the LCD panel (not shown).

In FIG. 8, the asymmetrical front sill 310 has a vertical cross section of an asymmetrical triangle, and the mirrored surface 308 is disposed to oppose the right and left sides of the light guide panel 30 in opposite directions. However, the structure of the asymmetric front sill 310 satisfies the most suitable viewing distribution under the TCO '03 standard and can be modified to have right and left faces disposed to face the light guide panel 30. Diffusion surface 307.

9 is a side cross-sectional view of a light guide panel of an LCD backlight unit in accordance with another embodiment of the present invention.

In contrast to the embodiment of Figure 8, the mirrored surface 308 of Figure 9 is disposed to face the center of the light guide panel. The configuration of this mirrored surface 308 improves the visibility of the front side of the display. In other words, the improvement in the visibility of the outside or the improvement in the visibility of the front side can be selected via the mirroring surface as shown in FIG. 8 or FIG. 9 depending on the kind of display.

Figure 10 is a side cross-sectional view of a light guiding panel of an LCD backlight unit in accordance with still another embodiment of the present invention.

Referring to Figure 10, the separation space is defined between turns to form a separation face 315 from which light can be directed perpendicular to the LCD panel (not shown) to further improve the uniformity of light reaching the LCD unit (not shown).

As described above, the vertical cross section of the asymmetric front sill 310 has an asymmetrical triangle in the embodiment of Figures 7-10. However, it should be noted that the present invention is not limited to this structure. For example, the vertical cross section of the asymmetric front sill 310 may have a trapezoidal shape or an inverted trough shape having a pointed apex and a predetermined radius of curvature on each side.

Figures 11 through 14 are cross-sectional views of different examples of asymmetric front ridges.

Referring to Figures 11 and 12, the asymmetric front cymbal 310 has a triangular shape and a corner angle (θ 1 + θ 2) in the range of 40 to 140 degrees. In the asymmetric front 图 of Fig. 11, θ 1 and θ 2 are different values, and for the asymmetric front 图 of Fig. 12, θ 1 and θ 2 are the same value.

Referring to Figures 13 and 14, the asymmetric front cymbal 310 has a trapezoidal shape and a corner angle (θ 1 + θ 2) in the range of 20 to 70 degrees. In the opposite of Figure 13 In the front sill, θ 1 and θ 2 are different values, and for the asymmetrical front 图 of Fig. 14, θ 1 and θ 2 are the same value.

As described above, the asymmetric front sill 310 can be modified to a different shape.

In other words, when the asymmetric front cymbal 310 has the trapezoidal shape shown in Figs. 13 and 14, the ratio of the short side to the long side parallel to each other is preferably 0.5 or less. If the ratio of the short side to the long side of the trapezoid is larger than 0.5, the area ratio of the flat surface of the entire shape becomes excessively increased, resulting in deterioration of luminance.

30‧‧‧Light guide panel

300‧‧‧ Subject

301‧‧‧ outside

303‧‧‧ front side

305‧‧‧ Back side

306‧‧‧Light source

307‧‧‧Diffusion surface

308‧‧‧Mirror surface

310‧‧‧Asymmetric front

315‧‧‧Separation surface

320‧‧‧ After

1 is an exploded perspective view of a conventional LCD backlight unit; FIGS. 2 and 3 are enlarged cross-sectional views of the light guide panel, showing the progress of light emitted from the light source and passing through the light guide panel; FIG. 4 is shown for a general visual display unit. The feature is evaluated at the measurement position defined in the TCO '03 standard; FIGS. 5 and 6 show the TCO'03 standard regarding brightness uniformity-viewing dependence; FIG. 7 is an LCD backlight unit according to an embodiment of the present invention. FIG. 8 is a side cross-sectional view of a light guide panel of an LCD backlight unit according to an embodiment of the present invention; FIG. 9 is a light guide panel of an LCD backlight unit according to another embodiment of the present invention. Side view; FIG. 10 is a guide of an LCD backlight unit according to still another embodiment of the present invention. A side cross-sectional view of the light panel; Figures 11 through 14 are cross-sectional views of different examples of asymmetric front ridges.

Claims (10)

A light guide panel of an LCD backlight unit includes a main body having an outer side for receiving incident light, a front side for emitting light, and a rear side, wherein the front side is an asymmetric front side having a triangular cross section Formed, an inclined side of each asymmetric front bead is treated to have a smooth mirrored surface, and the other inclined side is treated to have a rough diffusing surface. A light guide panel of an LCD backlight unit includes a main body having an outer side for receiving incident light, a front side for emitting light, and a rear side, wherein the front side is an asymmetric front side having a trapezoidal cross section Formed, an inclined side of each asymmetric front bead is treated to have a smooth mirrored surface, and the other inclined side is treated to have a rough diffusing surface. The light guide panel of claim 1 or 2, wherein the asymmetric front bezel is configured to have a mirrored surface facing the center of the light guide panel. The light guide panel of claim 1 or 2, wherein the asymmetric front sill is configured to have a diffusing surface facing the center of the light guide panel. The light guide panel of claim 1, wherein the angle between the inclined side and the vertical line of the asymmetric front sill is equal to the angle between the other inclined side and the vertical line. The light guide panel of claim 2, wherein the angle between the inclined side and the vertical line of the asymmetric front sill is equal to the other inclined side The angle between the edge and the vertical line. The light guide panel of claim 1 or 5, wherein the asymmetric front sill has an apex angle in a range of 40 to 140 degrees. The light guide panel of claim 2, wherein the asymmetric front sill has an angle defined in a range of 20 to 70 degrees between each inclined side and a vertical line. The light guide panel of claim 1 or 2, wherein the asymmetric front rafts are separated from each other by a predetermined distance to have a separation surface therebetween. The light guide panel of claim 2, wherein the ratio of the short side (a) of the asymmetric front sill to the long side (b) is 0.5 or less.