KR101047754B1 - Side Dimming Backlight Unit - Google Patents

Abstract

The present invention provides a functional light pattern for guiding a point light source incident in a diagonal line in a straight line, thereby enabling a scanning structure or a dimming structure during individual on / off driving of light sources, thereby improving image quality. A light guide plate, wherein a plurality of light emitting diode light sources are arranged on a side surface of the light guide plate, and the light guide plate of the side dimming type backlight device is configured to emit light from a point light source incident from the light emitting diode light source into a surface light source. A dot pattern for scattering and dispersing the light of the point light source incident therein is emitted to the upper surface of the light guide plate, and a prism shape having a rounded vertex of a cross section is formed on the upper surface of the light guide plate to induce the straightness of the light of the point light source incident therein; Aspherical cylindrical or round cylindrical The light pattern is formed, and guides the light traveling in the left and right diagonal lines with respect to the traveling direction in the light guide plate to the straight light, characterized in that configured to enable the scanning structure during the on-off driving.

Backlight, Light Guide Plate, LED, Optical Interference, Scanning

Description

Side illuminated backlight unit {EDGE LIGHTING BACK LIGHT UNIT}

The present invention relates to a side-illumination backlight device, and more particularly, a functional light pattern for inducing a linearly incident point light source light is formed to enable a scanning structure or a dimming structure during individual on / off driving of light sources. It relates to a light guide plate of the side dimming backlight device that can improve the image quality.

In general, a liquid crystal display (LCD) is widely used as a flat panel display because it can be driven using low power and has a vivid color reproduction ability. However, unlike CRTs and PDPs, LCDs are non-light-emitting devices that do not emit light directly, and require a separate backlight unit using fluorescent lamps to irradiate light from the back of the LCD panel to the panel. do.

Back light used in the liquid crystal display is classified into a front dimming type (or direct type) and a side dimming type (or edge type) according to a method of disposing a light source. Direct-lighting is to place the light source on the lower side of the flat plate. Since the shape of the light source is shown on the liquid crystal panel, the space between the light source and the liquid crystal should be secured and maintained. Since the light scattering means must be installed separately, there is a limit to thinning. Edge-lighting is a method of distributing light to the entire surface by using a light guide panel after installing a light source on the outside of a flat plate, which has a problem of low luminance and highly optical processing technology for the light guide plate. Is required.

At this time, the light source of the back light device may be a fluorescent lamp such as CCFL (Cot Cathode Fluorescent Lamp), HCFL (Hot Cathode Fluorescent Lamp), EEFL (External Electrode Fluorescent Lamp), LED (Light Emitting Diode) device, EL (Electro) Luminescence element is mainly used.

As shown in FIG. 1, the conventional side-illuminated backlight device basically has a structure in which a plurality of LED 10 arrays, which are light sources, are disposed on one side or both sides of the light guide plate 20. Optical sheets, such as a diffusion sheet and a prism sheet, are arrange | positioned, and the structure below arranges a reflecting sheet.

The light of the point light source emitted from the LED light source 10 by the structure as described above is scattered and totally reflected inside the light guide plate 20 is converted into a surface light source, the light of the surface light source is emitted to the upper side of the light guide plate 20, the backlight device Function as.

However, in the side dimming type backlight device using the LED according to the related art, the light of the point light source incident into the light guide plate 20 spreads in the diagonal direction on the left and right sides by scattering phenomenon. In this case, as shown in FIG. 2, light is also emitted to a region where the LEDs 10 that are turned off with respect to the plurality of LEDs 10 are disposed. As shown in FIG. 3, the characteristics of the light paths control the scanning or dimming effects such that light is emitted from a wide area from the upper side to the left side of the light guide plate so that the light is emitted only to each area. Difficult problems arise. That is, the scanning structure or the dimming structure is difficult due to the interference of light during the on / off driving of the LED, which finally degrades the image quality of the LCD.

The side dimming backlight device according to the prior art has a problem that the light of the point light source proceeds obliquely by the interference of light in the light guide plate, which makes it difficult to control the scanning or dimming for LEDs individually driven on and off. have.

The present invention has been proposed to solve the above problems, in the side-illumination type backlight device is connected to a plurality of light guide plate, the lower surface of each light guide plate is formed with a dot pattern for efficiently scattering and total reflection of the light guide plate A light pattern is formed on the upper surface to improve the linearity of light incident into the light guide plate, thereby minimizing light interference when driving individual LEDs on and off, thereby enabling more than one scanning structure or dimming structure in one light guide plate. It is an object of the present invention to provide a side-illuminated backlight device that can improve the image quality of the.

The present invention for achieving the above object, a side light type backlight including a plate-shaped light guide plate, a plurality of LED light source disposed along the longitudinal direction of at least one side edge of the light guide plate and an optical sheet disposed on the light guide plate. In the apparatus, the light guide plate is formed in a vertical direction with respect to the light incident surface at the upper surface, and has a rounded vertex prism shape or cylinder, which guides the light of the LED light source traveling in a left-right diagonal from the inside to proceed straight. Shaped light induction pattern; And a dot-shaped light scattering pattern formed on a lower surface to scatter and totally reflect light incident therein, and to emit upwardly, wherein the light induction pattern of a prism shape having a rounded vertex is provided between 60 ° and 100 °. Has a radius of curvature R1 of 0.2 x P1 to 0.7 x P1 with respect to the vertex angle α1 of the pattern and the spacing P1 of the pattern, and the light guide pattern of the cylinder shape is 0.4 x with respect to the spacing P2 of the pattern. It has a height (H2) of P2 to 1.0 x P2.

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The side dimming type backlight device according to the present invention has improved linearity with respect to the light of the point light source incident into the light guide plate by the light pattern formed on the upper side, and even in the light guide plate structure in which a plurality of light guide plate structures are connected to each other, the interference of light during the on / off operation of individual LEDs is improved. It can be minimized, and efficient scanning and dimming effects can be displayed and controlled.

In addition, the image quality of the liquid crystal display may be improved by inducing scanning or dimming effects by inducing linearity of light incident into the light guide plate.

The technical problems achieved by the present invention and the practice of the present invention will be more clearly understood by the preferred embodiments of the present invention described below. The following examples are merely illustrative of the present invention and are not intended to limit the scope of the present invention. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

4 to 6 are a perspective view, a plan view and a bottom view of the light guide plate of the side-illuminated backlight device according to an embodiment of the present invention, respectively.

Referring to the drawings, the side-illuminated backlight device according to an embodiment of the present invention forms a structure in which a plurality of LEDs 10 as light sources are disposed on both sides of the light guide plate. In this case, the light source 10 may be disposed only on one side of the light guide plate 20, but may be disposed on both sides in order to be applied to a large screen or to efficiently implement a scanning or dimming effect. In addition, the light guide plate 20 according to the exemplary embodiment of the present invention has a prism shape or a cylindrical pattern (hereinafter referred to as an “light pattern”) formed on an upper surface thereof, and a dot pattern (hereinafter referred to as a “dot pattern”) formed thereon. ) Is formed.

In more detail, the above-described LED 10 is a light source of a backlight device, a plurality of LEDs are arranged in an array (array) on both sides of the light guide plate, and one or several LEDs to exhibit a scanning or dimming effect in the side-illuminated backlight device Are individually configured to be driven off and on.

The light guide plate 20 is configured to convert the light of the point light source incident from the LED 10 to the surface light source through the entire light guide plate, and a resin material having excellent light transmittance is mainly used. In the light guide plate is made of a resin material of any one of polymethylmethacrylate (PMMA), poly stylene (PS), meta stylene (MS), PC (poly carbonate) showing a light transmittance of 95% or more. In addition, an optical pattern 21 such as a prism shape is formed on the upper surface of the light guide plate 20, and a dot pattern 22 is formed on the lower surface of the light guide plate 20.

In this case, the light pattern 21 on the upper surface of the light guide plate 20 totally reflects the light of the point light source incident through the light incident part so as to be transmitted to a region deep inside the light guide plate 20. At this time, the light of the point light source incident into the light guide plate 20 proceeds while being spread in a left and right diagonal direction at a predetermined angle with respect to a traveling direction, as shown in FIG. 2, wherein the light pattern 21 is incident light. Induces the light to proceed straight.

To this end, the light pattern 21 may be formed in a prism shape or a cylinder shape in a direction parallel to the light propagation direction, and a cross section thereof may be formed in a prism shape having a rounded vertex angle, a cylindrical shape of an aspherical surface, a round cylinder shape, or the like. have.

The dot pattern 22 of the lower surface of the light guide plate 20 is configured to scatter and totally reflect the light of the point light source passing through the inside of the light guide plate so that the light is emitted to the upper surface of the light guide plate as a surface light source. In this case, the dot pattern 22 may be formed on the light incident portion side where the LED is disposed in consideration of the amount of light, and may be formed densely away from the light incident portion.

7 is a cross-sectional view showing in detail the light pattern of the light guide plate according to the embodiment of the present invention, Figures 8 and 9 are views showing the optical characteristics of the light guide plate according to the embodiment of the present invention.

Looking at the light pattern 21 of the upper surface of the light guide plate according to an embodiment of the present invention in detail with reference to Figure 7, it is formed as a prism pattern or a cylinder pattern convex upward in the longitudinal direction parallel to the light traveling direction, the cross section (AA ) Is formed in the shape of a round prism with a vertex angle as shown in (A), or as a cylindrical shape aspherical as shown in (B), or a round cylindrical shape as a sphere as shown in (C). Can be.

Here, the angle α1 of the vertex angle of which the prism-shaped light pattern 21 having a rounded vertex angle is between 60 ° and 100 °, and the radius of curvature R1 of the rounded vertex angle is the interval P1 at which the pattern is formed. It is preferably formed between 0.2 * P1 to 0.7 * P1.

In addition, it is preferable that the cross-sectional aspherical or round cylinder-shaped light pattern 21 is formed between 0.4 * P2-1.0 * P2 with respect to the space | interval P2 in which the height H2 of a cross section is formed.

As shown in FIG. 8, the light characteristic of the light guide plate having the above-described structure is that the light emitted from the LED in the on state is significantly reduced in the left and right inclination angle θb with respect to the traveling direction inside the light guide plate as compared with FIG. 2. It can be seen that it shows a relatively good straightness, and as a result, as shown in Figure 9 it can be seen that the left and right width (d) of the light is significantly narrow compared to FIG. The left and right inclination angle with respect to the traveling direction of the light inside the light guide plate is about 40 ° (θa in FIG. 2) for the light guide plate according to the prior art, and about 10 ° (FIG. 8) for the light guide plate according to the embodiment of the present invention. Θb) is shown.

 Therefore, in the light guide plate according to the embodiment of the present invention, an excellent scanning or dimming effect can be realized by minimizing the interference of light with respect to the individual driving of the LED in the on state and the off state by the linear light. As a result, excellent image quality can be exhibited in the liquid crystal display device.

FIG. 10 is a diagram illustrating an optical interference index of a light guide plate according to an exemplary embodiment of the present invention. Table 1 shows an optical interference index for a light pattern having a rounded vertex shape, and Table 2 shows an aspherical surface having an aspheric surface or a cross section. The optical interference index for the round cylindrical light pattern is shown.

The graph of FIG. 10 is a graph obtained by measuring the luminance of light along a vertical line of a central portion of the light guide plate through which light travels, and the optical interference index is calculated as (Im_min / Im_max) * (I1 / I2). In general, the case where the optical interference index is less than 40% is regarded as a very good condition.

Optical interference index according to the embodiment of the present invention measured by the above method is as shown in Table 1 and Table 2.

<Change of Optical Coefficient of Interference According to Vertex Angle α1 and Curvature Radius R1 for a Prismatic Light Pattern with Rounded Angles (P1 = 50 μm) division α1 = 60 ° α1 = 70 ° α1 = 80 ° α1 = 90 ° α1 = 95 ° α1 = 100 ° α1 = 110 ° α1 = 120 ° R1 = 5 μm - - 34.77% 42.94% 42.91% 48.09% 51.27% 77.91% R1 = 10 μm 25.39% 25.72% 32.94% 41.41% 41.85% 44.94% 50.27% 76.26% R1 = 15 μm - - 32.08% 39.77% 39.83% 43.65% 47.07% 69.49% R1 = 20 μm 23.18% 25.23% 32.44% 36.05% 39.06% 39.85% 55.69% 74.60% R1 = 25 μm 22.21% 23.40% - - - - - - R1 = 30㎛ - 38.20% - - - - - -

<Results of change of optical interference index according to distance P2 and height H2 for spherical (round) or aspherical cylindrical light pattern> division Round Aspheric surface P2 25 μm 40 μm 50 탆 H2 3.35 μm 10 탆 20 탆 25 μm 40 μm 45㎛ 50 탆 55 μm result 139.4% 40.41% 16.25% 10.54% 32.62% 28.65% 10.48% 40.45%

Referring to Table 1, in the case of a prism-shaped light pattern having a rounded vertex, when the distance P1 of the pattern is 50 μm and the radius of curvature R1 is 20 μm, the vertex angle α1 is very good up to 100 °. The interference index (39.85%) is shown, and the smaller the radius of curvature R1 is, the smaller the curvature radius R1 is for the same vertex angle (α1 = 100 °). Until now, a relatively good optical interference index (44.94%) is shown.

In addition, referring to Table 2, in the case of the spherical or aspherical cylindrical light pattern, the height H2 of the cross section is 20 µm to 50 µm (that is, 0.4 * P2 to 1.0 *) when the pattern interval P2 is 50 µm. It can be seen that P2) shows a very good optical interference index.

As described above, it can be seen that the inclination angle with respect to the propagation direction of the light incident from the light incident part proceeds with excellent linearity of about 10 ° due to the functional light induction pattern formed on the upper surface of the light guide plate according to the embodiment of the present invention. . Such optical characteristics make it possible to efficiently display and control a scanning effect or a dimming effect during individual on / off driving of LEDs.

The present invention has been described above with reference to one embodiment shown in the drawings, but those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom.

1 is a plan view showing a partial structure of a side-illumination backlight device according to the prior art,

2 and 3 is a view showing the optical characteristics for the light guide plate according to the prior art,

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

5 is a plan view showing a light guide plate of the side-illuminated backlight device according to an embodiment of the present invention;

6 is a bottom view of a light guide plate of a side-illuminated backlight device according to an embodiment of the present invention;

7 is a cross-sectional view showing in detail the light pattern of the light guide plate according to the embodiment of the present invention;

8 and 9 illustrate optical characteristics of the light guide plate according to the embodiment of the present invention;

10 is a view for showing the optical interference index of the light guide plate according to the embodiment of the present invention.

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

10: LED (light source)

20 light guide plate

21: light pattern

22: dot pattern

Claims (5)

The side light guide plate comprising a plate-shaped light guide plate, a plurality of LED light sources disposed along a length direction of at least one edge of the light guide plate, and an optical sheet disposed on the light guide plate, wherein the light guide plate is A light incidence pattern having a rounded prism shape or a cylinder shape, which is formed in a vertical direction with respect to the light incident surface at an upper surface and induces the light of the LED light source to proceed in a straight line from the inside to a straight line; And A dot-shaped light scattering pattern formed on a lower surface and scattering and totally reflecting light incident therein, and exiting upward; The light-guiding pattern having a rounded vertex shape has a radius of curvature R1 of 0.2 x P1 to 0.7 x P1 with respect to a vertex angle α1 of 60 ° to 100 ° and a gap P1 of the pattern, And the light guide pattern having a cylinder shape has a height H2 of 0.4 x P2 to 1.0 x P2 with respect to the interval P2 of the pattern. delete delete The method of claim 1, wherein the light scattering pattern, A side dimming backlight device formed by printing or laser processing. The method of claim 1, wherein the light guide plate, A side dimming backlight device comprising at least one resin of polymethylmethacrylate (PMMA), poly stylene (PS), meta stylene (MS), and polycarbonate (PC) having a light transmittance of 95% or more.

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