KR101265518B1 - backlight unit - Google Patents

Abstract

The present invention relates to a side dimming type backlight device in which a light emitting diode light source is disposed at both ends of a plurality of bar-shaped light guides, the cover bottom having an accommodation space therein; One or more bar-shaped light guide members arranged in the cover bottom; An LED light source disposed on at least one side of a length direction of the light guide; A fixing hook for pressing the light guide member to fix it to the cover bottom; And a diffuser plate disposed on the light guide body.

Description

BACKLIGHT UNIT}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight device, and more particularly, to a side dimming backlight device in which a light emitting diode light source is disposed at both ends of a plurality of bar-shaped light guides.

Since a liquid crystal display (LCD) itself is non-luminescent, a backlight device for uniformly irradiating the information display panel with light is indispensably required. In general, a backlight device employed in a liquid crystal display device is classified into an edgy type and a direct type backlight device according to a position of a light source.

In the side backlight device, a light source is disposed at a side of the light guide plate to irradiate light into the light guide plate. This structure is advantageous for slimming of the backlight device, but has a disadvantage in that the backlight device is implemented in a large screen. On the other hand, the direct type backlight device has a structure in which a light source is disposed below the diffuser plate to irradiate light to the diffuser plate entirely. Such a structure is advantageous for a large screen backlight device, but has a disadvantage in that the thickness of the backlight device is increased and a plurality of light sources are required.

Recently, a light emitting diode (LED) light source is disposed on a side of a bar-shaped light guide, and thus, a backlight device that can compensate for the disadvantages of a side type backlight device and a direct type backlight device. Is being presented. For example, the present invention has been disclosed in the side dimming backlight device using an LED bar (LED Bar) in Korea Patent No. 10-093163.

1 is a perspective view illustrating a side dimming backlight device using an LED bar according to the related art. As illustrated, a plurality of bar-shaped light guides 30 having a longitudinal direction are arranged inside the cover bottom 10 to which the reflecting plate 20 is attached, and a substrate (on the side surface of the light guide 30) is provided. The LED array 40 in which the plurality of LEDs 41 are mounted is disposed at 42. At this time, the light exit surface of each LED 41 corresponds to the light incident surface of each light guide 30, and the light guide 30 and the corresponding LED 41 constitute an LED bar. Further, a diffusion plate 50 and various optical sheets 60 are disposed above the light guide 30.

In the side type backlight device using the LED bar as described above, the LED 41 is disposed on the side of the light guide 30 having the longitudinal direction, so that the light guide 30 functions as a line light source such as a fluorescent lamp. In addition, the scanning effect may be realized by individual driving of the LEDs 41 disposed on the light guides 30. In addition, the size of the light guide plate and the number of LEDs can be reduced compared to the conventional side-type or direct-type backlight device, and thus, there is an advantage in terms of manufacturing cost.

However, the plurality of light guide members 30 accommodated in the cover bottom 10 easily flow due to external impact. Due to this flow, the characteristics of the light incident to the light guide 30 and the light emitted from the light guide 30 are changed, which is a problem of deteriorating the quality of the backlight device. In addition, inside the cover bottom 10, high heat is generated by the light emission of the LED 41, and the light guide 30 is thermally expanded by the heat. At this time, the interval between the light incident surface of the light guide 30 and the light exit surface of the LED 41 becomes narrow, and there is a fear that the light guide 30 and the LED 41 come into contact with each other. Therefore, the thermal expansion also changes the characteristics of the light incident to the light guide 30 and the light emitted from the light guide 30, resulting in deterioration of the quality of the backlight device. That is, in the backlight device using the LED bar according to the related art, there is no means for stably fixing the light guide 30 to the inside of the cover bottom 10 in consideration of the flow and thermal expansion of the light guide 30. There was a difficulty.

In addition, the bar-shaped light guide 30 has a rectangular cross section in a short axis direction and is easy to assemble a backlight device. However, since the light guide body 30 has a narrow light exit angle, a dark portion is generated between the light guides 30. In order to remove the dark portion, when the distance between the light guide 30 is narrowed, a relatively large number of light guide 30 is applied to induce manufacturing costs, and the distance between the light guide 30 and the diffusion plate 50 is increased. In this case, the luminance decreases and the thickness of the backlight device increases.

The present invention has been proposed to solve the above problems, the backlight device using an LED bar that can be uniformly fixed to the cover bottom by fixing a plurality of bar-shaped light guides arranged inside the cover bottom to the cover bottom. The purpose is to provide.

Another object of the present invention is to provide a backlight device using an LED bar by arranging the light guides in consideration of thermal expansion, thereby preventing the breakage of the LED and the change of the optical characteristics caused by thermal expansion of the LGP. .

In addition, the present invention is to provide a backlight device using an LED bar that can improve the brightness and uniformity of brightness by forming an optical pattern of various shapes on the upper or lower surface of the light guide.

The present invention for achieving the above object, the cover bottom formed therein storage space; One or more bar-shaped light guide members arranged in the cover bottom; An LED light source disposed on at least one side of a length direction of the light guide; A fixing hook pressing the light guide to fix the light guide to an upper cover bottom; And a diffusion plate disposed on the light guide, and a stopper for preventing the light guide from contacting the LED.

Here, the fixing hook is a light-transmissive resin material, the pressing portion for pressing the upper surface of the light guide, the lower portion extending from both ends of the pressing portion to be fastened to the cover bottom and the diffusion plate to support the It consists of a support part which protrudes upwards of a press part.

In addition, the light guide member may have a wedge shape in which the thickness becomes thinner toward the center portion, or may be formed in a separate form in which a center in the longitudinal direction is cut, or a plurality of light guide members may be integrally formed in the transverse direction.

In addition, the light guide member may have an upper surface formed in a round shape with respect to the light incident surface, and an optical pattern may be formed on the upper surface or the lower surface.

The backlight device of the present invention can reduce the manufacturing cost by reducing the size of the light guide plate and the number of LEDs by using an LED bar having an LED light source disposed on a side of a bar-shaped light guide, and the LEDs disposed on each light guide. The scanning effect can be realized by individual driving of.

In addition, the fixing hook stably fixes the light guide to the cover bottom to prevent the light guide from flowing, thereby exhibiting uniform optical characteristics.

In addition, by arranging the light guide members in consideration of thermal expansion, it is possible to prevent a change in the optical properties due to thermal expansion of the light guide body.

In addition, various shapes of optical patterns may be formed on the upper or lower surface of the light guide to improve brightness and uniformity of brightness.

1 is an exploded perspective view illustrating a conventional backlight device,
2 is an exploded perspective view illustrating a backlight device according to an embodiment of the present invention;
3 is a perspective view showing a coupling state of the light guide, which is a main part of FIG.
4 is a cross-sectional view illustrating an AA structure of the light guide coupled state of FIG. 3;
5 is a front sectional view showing a coupling state of a backlight device according to an embodiment of the present invention;
FIG. 6 is a sectional front view showing an arrangement of light guides and stoppers, which are main parts of FIG. 5; FIG.
7 is a front view showing a light guide according to an embodiment of the present invention;
8 is a side view showing a light guide according to an embodiment of the present invention;
9 is a side view showing a light collecting pattern of a light guide member according to an embodiment of the present invention;
10 is a front view showing a scattering pattern of the light guide according to the embodiment of the present invention;
11 is a plan view showing the optical characteristics of a backlight device according to the prior art, and
12 is a plan view illustrating optical characteristics of a backlight device according to an exemplary embodiment of the present invention.

The technical problem achieved by the present invention and the practice of the present invention will be apparent from the preferred embodiments described below. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is an exploded perspective view illustrating a backlight device according to an exemplary embodiment of the present invention. FIG. 3 is a perspective view illustrating a coupling state of a light guide, which is a main part of FIG. 2, and FIG. 4 is an AA of the light guide coupling state of FIG. 3. A cross section showing the structure.

As can be seen in these figures, in the backlight device of the present invention, the reflective sheet 200 and the plurality of light guide members 300 are seated in the inner space of the cover bottom 100, and one side of the light guide member 300 or LED array 400 is disposed on both sides. In this case, the light guide 300 is fixedly coupled to the cover bottom 100 by the fixing hook 800. In addition, after the diffusion plate 500 and the optical sheet 600 are stacked on the light guide 300, the guide panel 700 is fastened to the cover bottom 100. In the present invention, the cover bottom 100, the reflective sheet 200, the diffuser plate 500, the optical sheet 600 and the guide panel 700 in a general known configuration constituting the side or direct backlight device Detailed description will be omitted.

The light guide 300 constituting the backlight device of the present invention is made of a transparent resin such as PMMA, and in particular, the present invention forms a bar shape having a rectangular cross section having a predetermined length. The light guide 300 has both end faces in the longitudinal direction forming a light incident surface (see 300a in FIG. 5), and a light source is disposed in front of the light incident surface 300a. In addition, the cross-section in the longitudinal direction of the light guide 300 has a rectangular shape, but may be formed in a variety of shapes, such as circular, elliptical, semicircular.

As illustrated in FIGS. 2 and 3, a plurality of light guides 300 are disposed at predetermined intervals in an inner space of the cover bottom 100, and the LED array 400 is disposed at both sides of each light guide 300. Is placed. In the LED array 400, a plurality of LEDs 410 are disposed on the substrate 420 at predetermined intervals, and each LED 410 is positioned in front of the light incident surface 300a of each light guide 300. The light guide 300 and the LED 410 disposed at the side thereof form an LED bar module, and the light emitted from the LED 410 passes through the light guide 300 and is emitted to the upper surface of the light guide 300. . At this time, the light emitted from one light guide 300 forms a line light source having a longitudinal direction. That is, the module consisting of a bar-shaped light guide 300 and a light source of the LED 410 disposed on the side thereof functions as a line light source.

Meanwhile, the bar-shaped light guide member 300 is fixedly coupled to the cover bottom 100 by the fixing hook 800. As shown in FIG. 4, the fixing hooks 800 are fastened to the cover bottom 100 at both ends of the fixing hooks 800 while enclosing the outer circumferential surface of the light guide 300. The sieve 300 is fixed to the cover bottom 100. A plurality of fixing hooks 800 may be fastened to one light guide 300 according to the length of the light guide 300. The cover bottom 100 and the reflective sheet 200 are formed with a through hole for fastening the fixing hook 800.

As shown in (a) of FIG. 4, the fixing hook 800 is bent downward from both ends of the pressing portion 810 and the pressing portion 810 having a length corresponding to the unidirectional width of the light guide 300. It consists of a fixed portion 820 extending. At the end of the fixing part 820, a hook-shaped locking protrusion 821 for hooking the cover bottom 100 is formed. The pressing unit 810 presses the light guide 300 so that the light guide body 300 may be in close contact with the cover bottom 100, and the fixing part 820 may have a fixing hook 800 by a locking protrusion 821. It is to be fastened to the cover bottom 100. In addition, as shown in FIG. 4B, the pressing part 810 of the fixing hook 800 may be formed to have a length capable of receiving two light guides 300.

In addition, the fixing hook 800 further includes a support part 830 for supporting the diffusion plate 500 stacked on the upper side. The support part 830 protrudes upward from the upper surface of the pressing part 810 in a conical shape at a predetermined length. The diffusion plate 500 and the optical sheet 600 may be formed at a predetermined size or more, or the center may be struck downward by heat generated inside the cover bottom. The supporting part 830 supports the bottom surface of the diffusion plate 500 to prevent the diffusion plate 500 and the optical sheet 600 from hitting downward (see FIG. 5).

On the other hand, the light emitted from the light guide 300 is blocked by the fixing hook 800 may cause a dark portion, in order to prevent this, the fixing hook 800 is preferably made of a resin material excellent in light transmittance.

FIG. 5 is a front sectional view schematically illustrating a coupling state of a backlight device according to an exemplary embodiment of the present invention, and FIG. 6 is a front sectional view showing an arrangement of light guides and stoppers, which are main parts of FIG. 5.

As shown in FIG. 5, a stopper 110 is provided between the light emitting surface 410a of the LED 410 and the light receiving surface 300a of the light guide 300. As the light guide 300, PMMA resin is generally used, and the PMMA resin is expanded by heat. In particular, in the case of forming a bar shape as in the present invention, thermal expansion is mainly performed in the longitudinal direction. In this case, the light incident surface 300a of the light guide 300 may be in contact with the light emitting surface 410a of the LED 410. have. The stopper 110 supports the light incident surface 300a of the light guide 300 to prevent the stopper 110 from contacting the light exit surface 410a of the LED 410.

As shown in the stopper 110, a portion of the bottom surface of the cover bottom 100 may be cut and bent upward, and a separate protrusion may be formed on the bottom surface of the cover bottom 100. In addition, it is also possible to form a projection toward the light incident surface 300a of the light guide 300 on the substrate 420 of the LED array 400.

Meanwhile, the stopper 110 may be formed at a position where a predetermined distance d is secured to the light incident surface of the light guide 300 in consideration of thermal expansion of the light guide 300. That is, the light guide 300 should be disposed at a predetermined distance d from the stopper 110. Referring to FIG. 6, the distance L2 between the stoppers 110 on both sides of the light guide 300 is L1 ≦ L2 ≦ L1 * (1 + 100 * α) with respect to the length L1 of the light guide 300. It is formed between. That is, the distance L2 between the stoppers 110 should be at least longer than the length L1 of the light guide 300, but if it is too long, there is an unreasonable point that the light emitted from the LED 410 is lost. Therefore, the light guide 300 is disposed such that the distance d between the stopper 110 and the light guide 300 of the light guide 300 is less than 0.5 * L1 * (1 + 100 * α). desirable. Here, α is the linear expansion coefficient of the light guide 300. '100' is the maximum value of the temperature change and is represented by twice the temperature change value at the time of high temperature operation. Since the change in temperature during the high temperature operation in a general state is 53 ° C., it can be converted to '100' which is approximately twice.

7 and 8 are front and side views illustrating a light guide according to various embodiments of the present disclosure.

First, the light guide according to the embodiment of the present invention may form various shapes. That is, as shown in FIG. 7, the bar-shaped light guide 300 has a predetermined cross-sectional length of a square shape (a), or forms a symmetrical wedge shape that becomes thinner toward the center portion (b). ), It is possible to achieve a separate type in which the center part is cut (c, d). The wedge-shaped light guide (b) is a shape in consideration of the distance to the light source, the light intensity is weakened away from the light source, the uniform light can be emitted to the entire upper surface of the light guide. In addition, the light guides (c, d) of the split type light guides having the central portion cut off are blocked at the central cut portion. Therefore, the dimming effect can be realized by split driving of LEDs on both sides.

In addition, the upper light emitting surface 300b of the light guide 300 through which light is emitted also forms various shapes. That is, as shown in FIG. 8, the short-axis cross section of the light exit surface 300b may be semicircular (a), or both corners may have a round shape (b). In addition, two light guides 300 having such a shape may form an integrated body connected in the lateral direction (c, d), and a plurality of light guide bodies 300 may be integrally connected in a horizontal direction. When the light exit surface 300b is formed in a round shape, the light exit angle is wider than that of the planar shape to remove the dark portion between the light guides 300 and to improve uniformity. Therefore, it is possible to reduce the material cost by widening the interval between the light guide 300 or by using a light guide 300 having a thin thickness. In addition, the thickness of the light guide 300 may be reduced, or the distance between the light guide 300 and the diffusion plate 500 may be reduced to reduce the size of the backlight device.

9 is a side view showing a light collecting pattern of a light guide according to an embodiment of the present invention, Figure 10 is a front view showing a scattering pattern. As can be seen in these figures, in the light guide 300 according to the embodiment of the present invention, a light collecting pattern 310 is formed on an upper light emitting surface, and a scattering pattern 320 is formed on a lower reflective surface.

That is, condensing patterns 310 having various shapes are formed on the upper surface of the light guide 300. For example, as illustrated in FIG. 9, a prism shape (a), a prism shape with rounded vertices (b), and a lenticular shape are illustrated. The condensing pattern 310 of (c) is formed. The condensing pattern 310 improves luminance by inducing a traveling direction of light emitted to the light guide upper surface in a vertical direction.

Since the light characteristics vary according to the specific shape of the light collecting pattern 310, in the present invention, the light collecting pattern 310 of the prism shape (a) has a vertex angle A1 of 80 ° to 130 ° and a width W1 of 5. The micrometers 100 micrometers-100 micrometers, depth H1 are formed in 5 micrometers-100 micrometers, and in the prism shape b with rounded vertex, the curvature radius R1 is formed by 5 micrometers-20 micrometers. In addition, the light collecting pattern 310 of the lenticular shape c has a width W2 of 5 μm to 1000 μm and a depth H2 of 5 μm to 500 μm.

A scattering pattern 320 having various shapes is formed on the lower surface of the light guide 300. For example, as illustrated in FIG. 10, a prism shape (a), an embossed or intaglio dot shape (b) is formed, or a dot shape. The printed pattern c is formed. The scattering pattern 320 scatters the light traveling through the light guide 300 by total reflection to improve the uniformity of the light. In particular, the scattering pattern 320 is preferably formed such that the density or size of the pattern increases as the distance from the light source.

Since the optical properties vary according to the specific shape of the scattering pattern 320, in the present invention, the scattering pattern 320 of the prism shape a has a vertex angle A3 of 80 ° to 130 ° and a width W3 of 5. The micrometers-100 micrometers, the depth H3 are 5 micrometers-100 micrometers, and the space | interval P3 of a pattern is 5 micrometers-5000 micrometers. In addition, the embossed or intaglio dot shape b is formed to have a width W4 of 10 µm to 2000 µm and a height H4 of 5 µm to 100 µm. In addition, the dot-shaped printed pattern c has a width W5 of 10 µm to 2000 µm and a thickness H5 of 5 µm to 20 µm.

FIG. 11 is a plan view illustrating optical characteristics of a backlight device according to the related art, and FIG. 12 is a plan view illustrating optical characteristics of a backlight device according to an exemplary embodiment of the present invention. FIG. 11 illustrates the characteristics of light emitted from the upper part of the diffuser plate after arranging a plurality of light guide members of which the upper light emitting surface forms a plane, and FIG. 12 illustrates a plurality of light guide members of which the upper light emitting surface has a round shape. It showed the characteristics of light emitted to the upper part of the diffusion plate.

First, in the backlight device according to the related art, as shown in FIG. 11, dark portions are generated between the light guides in both the illuminance characteristic (a) and the luminance characteristic (b), and the appearance uniformity is 89%. However, in the backlight device according to the embodiment of the present invention, as shown in FIG. 12, in the illuminance characteristic (a) and the luminance characteristic (b), the dark portion is removed between the light guide members, and the appearance uniformity is 96%. . In general, when the uniformity is 95% or more, the appearance level is evaluated to be good, and thus, the backlight device of the present invention exhibits excellent uniformity.

Although the embodiments of the present invention have been described with reference to the present invention, those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom.

100: cover bottom 110: stopper
200: reflective sheet
300: light guide
300a: light guide surface 300b: light guide surface
310: light collecting pattern 320: scattering pattern
400: LED array 410: LED
420: substrate 410a: LED light emitting surface
500: diffuser plate
600: Optical Sheet
700: guide panel
800: fixed hook 810: pressing portion
820: fixing part 830: supporting part

Claims (10)

A cover bottom in which a storage space is formed;
One or more bar-shaped light guide members arranged in the cover bottom;
An LED light source disposed on at least one side of a length direction of the light guide;
A diffusion plate disposed above the light guide; And
Pressing portion for pressing the upper surface of the light guide, extending from both ends of the pressing portion to the lower side, a hook-shaped locking projection is formed at the end, the fixing portion fastened to the cover bottom, and to support the diffusion plate And a plurality of fixing hooks configured to support the projecting portion protruding upward from the pressing portion to fix the light guide to the cover bottom. delete delete The method of claim 1, wherein the fixing hook,
A backlight device comprising a light transmitting resin. The method of claim 1,
And a stopper provided on the LED substrate or the cover bottom to prevent the light guide from being in contact with the LED light source. The method of claim 1, wherein the light guide is
Backlight device, characterized in that forming a wedge shape becomes thinner toward the center portion. The method of claim 1, wherein the light guide is
A backlight device, characterized in that the center of the longitudinal direction is formed into a cut off. The method of claim 1, wherein the light guide is
A backlight device, characterized in that a plurality of light guides are integrally formed in the transverse direction. The light guide according to any one of claims 1 to 6, wherein the light guide is
An upper surface is formed in a round shape with respect to the light incident surface. The light guide according to any one of claims 1 to 6, wherein the light guide is
An optical pattern is formed on at least one surface of the upper surface or the lower surface.

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