KR100820975B1 - Planar light source, backlight unit and liquid crystal display having the same - Google Patents

Abstract

The present invention relates to a surface light source device capable of providing planar light, a backlight unit having the surface light source device, and a liquid crystal display device. In a surface light source device for outputting light provided to a liquid crystal panel, a surface light source device according to an exemplary embodiment of the present invention includes a light source unit including one or more light emitting elements arranged at predetermined intervals and a light incident surface from the light source unit. And a light conversion unit reflecting and exiting from the light conversion unit, wherein the light conversion unit includes a light incidence unit having a plurality of surfaces on which light emitted from the light source unit is incident or reflected, and a plane on which the light incident unit is incident or reflected is flat Or a curved surface. The present invention has the advantage that one light source can serve as a plurality of light sources by using reflection and refraction of light. In addition, the present invention has a merit that one light source serves as a plurality of light sources, thereby reducing power consumption and heat generation.

Surface light source device, backlight unit, liquid crystal display device

Description

Surface light source device, backlight unit and liquid crystal display device having same {PLANAR LIGHT SOURCE, BACKLIGHT UNIT AND LIQUID CRYSTAL DISPLAY HAVING THE SAME}

1 is a perspective view illustrating a conventional liquid crystal display device.

2 is a cross-sectional view illustrating a liquid crystal display device according to an exemplary embodiment of the present invention.

3A to 3C are perspective views of a surface light source device according to preferred embodiments of the present invention.

4A to 4C are cross-sectional views of a surface light source device according to preferred embodiments of the present invention.

5 is a view for explaining the process of the light in the surface light source device according to an embodiment of the present invention.

FIG. 6 is an enlarged view of a portion A of FIG. 5.

The present invention relates to a surface light source device, a backlight unit having the surface light source device, and a liquid crystal display device.

In general, a liquid crystal display device is an electronic device that transmits various electrical information generated by various devices to visual information by using a change in light transmittance of a liquid crystal according to an applied voltage.

1 is a perspective view illustrating a conventional liquid crystal display device.

Referring to FIG. 1, the liquid crystal display device 100 includes a liquid crystal panel 150 and a backlight unit 110 disposed on a rear surface of the liquid crystal panel.

In understanding and practicing the present invention, the specific structure of the liquid crystal panel 150 is not important. Therefore, the basic structure of the liquid crystal panel 150 will be described within the range necessary for understanding the present invention.

The liquid crystal panel 150 generally includes a pair of transparent substrates, a liquid crystal layer interposed between the transparent substrates, a color filter layer formed on each of the transparent substrates, a black matrix, a pixel electrode, a common electrode, and a TFT array.

The backlight unit 110 includes a light source unit 120, a light guide plate 130, a reflective sheet 140, and an optical sheet 112.

The light source unit 120 includes a light source 120a and a light source reflector 120b.

Generally as the light source 120a, a cold cathode fluorescent lamp or an external electrode fluorescent lamp is used.

The light source 120a is disposed in parallel with the light guide plate 130 at one side of the light guide plate 130 in a state of being accommodated inside the light source reflecting plate 120b.

The light source reflector 120b is disposed along the outer circumferential surface of the light source 120a and reflects the light generated from the light source 120a to the side of the light guide plate 130 to improve the efficiency of light incident to the light guide plate 130.

The side surface of the light guide plate 130 disposed adjacent to the light source unit 120 becomes a light incident surface for light to be incident thereon, and the light incident through the light incident surface is mixed inside the light guide plate 130 to allow the light incident. Light is emitted toward the liquid crystal panel 150 disposed above through the light emitting surface disposed in a substantially perpendicular relationship with the surface.

The reflective sheet 140 reflects the light emitted to the rear surface of the light guide plate 130 back toward the light guide plate 130 to improve light utilization efficiency.

The optical sheet 112 may include a plurality of optical films such as the diffusion sheet 112a, the prism sheet 112b, and the protective sheet 112c.

In the edge-light type backlight unit having the above structure, not only the light efficiency is lowered because only light incident through one side of the light guide plate 130 is used, but also the light loss occurs considerably in the light guide plate 130 itself. have.

Also, a direct backlight unit configured by placing a plurality of light sources, for example, cold cathode fluorescent lamps or external electrode fluorescent lamps, directly below the liquid crystal panel, a diffuser plate on the front side of the light source, and a reflective sheet on the rear side thereof. Even if the light emitted from the light source passes through the diffuser plate, there is a problem that the luminance uniformity is low.

In addition, when a plurality of light sources are disposed adjacent to each other, heat convection occurs in a limited space of the liquid crystal display, thereby deforming the optical sheet disposed thereon, and adversely affects the display quality of the liquid crystal display.

It is a first object of the present invention to provide a surface light source device which is advantageous in terms of power consumption and heat generation by using fewer light sources than conventional backlight units.

A second object of the present invention is to provide a surface light source device having a structure capable of providing more uniform plane light.

A third object of the present invention is to provide a backlight unit and a liquid crystal display device having such a surface light source device.

In order to achieve the above object, the surface light source device according to an embodiment of the present invention, the surface light source device for outputting light provided to the liquid crystal panel, comprising one or more light emitting elements arranged at predetermined intervals And a light conversion unit reflecting light emitted from the light source unit from the inner surface and exiting the light source unit, wherein the light conversion unit includes a light incidence unit having a plurality of surfaces on which light emitted from the light source unit is incident or reflected. The surface on which the negative light is incident or reflected is characterized in that the plane or curved surface.

In addition, the backlight unit according to an embodiment of the present invention is a backlight unit for illuminating a liquid crystal panel from the rear, the surface light source device for illuminating the liquid crystal panel and the side surface light source device is disposed on one side, the surface light source And at least one optical sheet for receiving light output from the device and outputting the light to the liquid crystal panel, wherein the surface light source device includes: a light source unit including at least one light emitting element disposed at predetermined intervals; And a light conversion unit reflecting and exiting from the light conversion unit, wherein the light conversion unit includes a light incidence unit having a plurality of surfaces on which light emitted from the light source unit is incident or reflected, and a plane on which the light incident unit is incident or reflected is flat Or a curved surface.

In addition, the liquid crystal display device according to an embodiment of the present invention, the liquid crystal panel and the liquid crystal for displaying an image by controlling the amount of light transmitted by changing the arrangement of the liquid crystal molecules of the liquid crystal layer in accordance with an electrical signal applied from the outside And a backlight unit configured to provide light input to the liquid crystal panel from a rear side of the panel, wherein the backlight unit is disposed on one side of the surface light source device and the surface light source device for illuminating the liquid crystal panel, and the surface light source device. At least one optical sheet for receiving the light output from the output to the liquid crystal panel, the surface light source device, the light source including at least one light emitting element disposed at a predetermined interval and the light incident from the light source in the inner surface It includes a light conversion unit for reflecting and exiting, the light conversion unit from the light source unit If the exported and the light includes a light incident surface having a plurality of impinging or reflected, that is the light incident or reflected light incident portion is characterized in that a plane or curved surface.

The present invention has the advantage that one light source can serve as a plurality of light sources by using the reflection of light. In addition, the present invention has a merit that one light source serves as a plurality of light sources, thereby reducing power consumption and heat generation.

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

2 is a cross-sectional view illustrating a liquid crystal display device according to an exemplary embodiment of the present invention. Here, the backlight unit used in the liquid crystal display is a direct type.

Referring to FIG. 2, the liquid crystal display 200 may display a liquid crystal panel 270 and a liquid crystal panel 270 that display a predetermined image according to an electrical signal including display information applied from the outside. And a backlight unit 210 disposed at the rear of the 270.

The liquid crystal panel 270 may include a pair of transparent substrates, a liquid crystal layer interposed between the transparent substrates, a color filter layer formed on each of the transparent substrates, a black matrix, a pixel electrode, a common electrode, and a TFT array.

The color filter includes color filters corresponding to red (R), green (G), and blue (B), and when light is applied, the color filter generates an image corresponding to the color of red, green, or blue.

The TFT array switches the pixel electrode as a switching element.

The common electrode and the pixel electrode convert the arrangement of the molecules of the liquid crystal layer according to a predetermined voltage applied from the outside.

The liquid crystal layer is composed of a plurality of liquid crystal molecules, the liquid crystal molecules change the arrangement corresponding to the voltage difference generated between the pixel electrode and the common electrode, whereby the light provided from the backlight unit 210 is the liquid crystal layer The incident on the color filter corresponds to the change in the molecular arrangement of the.

The backlight unit 210 is located at the rear of the liquid crystal panel 270 and provides light, for example, white light, to the liquid crystal panel 270.

The backlight unit 210 includes an optical sheet 220, a surface light source device 230, and a frame 260 that provide sufficient planar light to illuminate the visible surface of the liquid crystal panel 270.

The optical sheet 220 is disposed between the liquid crystal panel 270 and the surface light source device 230, and may include a diffusion sheet 220a, a prism sheet 220b, and a protective sheet 220c.

The light emitted through the surface light source device 230 passes through the diffusion sheet 220a, and the diffusion sheet 220a diffuses or condenses the incident light to make the luminance uniform and widen the viewing angle.

On the other hand, the light passing through the diffusion sheet 220a is sharply reduced in brightness, the prism sheet 220b is used to compensate for this. Since the prism sheet 220b refracts the light emitted from the diffusion sheet 220a and concentrates the light incident at a low angle toward the front side, the luminance increases in the effective viewing angle range.

The light passing through the diffusion sheet 220a is incident on the protective sheet 220c disposed thereon, and the viewing angle reduced by the prism sheet 220b is re-expanded within a predetermined range to enter the liquid crystal panel 270. Done.

The liquid crystal panel 270 implements a predetermined image by changing the molecular arrangement of the liquid crystal layer according to an electrical signal including image information applied from the outside to control the light transmittance.

In understanding and practicing the present invention, the precise structural and material properties of the optical sheet 220 are not critical, and the backlight unit employing the optical sheet using any structure and material commonly used in the backlight unit is not limited to the present invention. Ideas can be applied broadly.

The surface light source device 230 includes a light source unit 240 including at least one light emitting element disposed at predetermined intervals, and a light conversion unit 250 which reflects and emits light incident from the light source unit 240 from an inner surface thereof.

The light conversion unit 250 has a shape in which light emitted from the light source unit 240 protrudes from one end of the light incidence unit 252 and the light incidence unit 252 having a plurality of surfaces on which the light is incident or reflected. And a plurality of light output units 254 and 256 having a plurality of surfaces on which light transmitted from the unit 252 reflects or emits light.

According to the exemplary embodiment of the present invention, as illustrated in FIG. 2, the light conversion unit 250 may be configured to have a Y shape when viewed from the front. Details of the configuration and shape of the light conversion unit 250 will be described later.

Meanwhile, in FIG. 2, the surface light source device 230 is composed of twelve, which is arbitrarily determined for the purpose of description, and the number thereof is determined by the size of the liquid crystal panel 270, the degree of luminance required, and the light emitted from the light emitting device. In consideration of the calorific value and the like, it can be adjusted to an appropriate number.

The frame 260 may provide a space for accommodating the surface light source device 230, and a reflective sheet 280 may be disposed thereon.

The reflective sheet 280 reflects the light emitted from the surface light source device 230 to the bottom and enters the surface light source device 230 to improve light utilization efficiency.

In one embodiment of the present invention, the reflective sheet 280 is coated with silver (Ag) on a sheet made of SUS, Brass, aluminum, PET, and the like, and even if the heat is generated fine titanium coating to prevent deformation due to endotherm for a long time Can be produced. In addition, in another embodiment of the present invention, the reflective sheet 280 may be manufactured by dispersing bubbles for scattering light on a sheet made of synthetic resin such as PET.

3A to 3C are perspective views illustrating a surface light source device according to preferred embodiments of the present invention.

3A to 3C, the surface light source device 330 of the present invention includes light emitting devices 340, 342, and 346 and a light conversion unit 350.

The light converter 350 includes a light incident part 352 and light exit parts 354 and 356.

In FIG. 3A, the light emitting device 340 may be configured of a cold cathode fluorescent lamp or an external electrode fluorescent lamp.

The cold cathode fluorescent lamp has electrodes at both ends of the glass tube, and contains a certain amount of mixed gas such as mercury, argon, and neon, and a phosphor is coated on the inner surface of the glass tube.

When a high voltage electric field is applied to two electrodes of a cold cathode fluorescent lamp, electron emission occurs. Then, when electron emission begins, mercury is excited to emit ultraviolet light, which emits visible light as it collides with the phosphor on the glass tube wall.

The external electrode fluorescent lamp has a brightness of 400 nit or more, which is more than 60% higher than that of a cold cathode fluorescent lamp, which makes it possible to further spread the application of TFT LCD, such as a TV requiring high brightness, and the cold cathode fluorescent lamp with the electrode inside the lamp. Unlike the electrodes, the electrodes are external and operate in parallel, reducing the voltage deviation between the glass and the lamp, enabling even brightness.

In FIG. 3B, the light emitting element 342 may be configured as a light emitting diode. In addition, the surface light source device 330 may further include a light emitting element accommodating part 344 to fix the light emitting elements 342 arranged in a line.

Light emitting diodes are semiconductor devices that emit light by passing a current through a compound such as gallium arsenide. Its low power consumption and lifespan reaches 100,000 hours, so once installed, it requires little replacement or maintenance.

Since the light emitting diodes are point light sources, the plurality of light emitting diodes may be arranged in a line at predetermined intervals to obtain an effect similar to a linear light source.

In FIG. 3C, the light emitting device 346 may be configured of an organic electroluminescent display.

The organic electroluminescent device is a self-luminous display device using a phenomenon in which light is generated when electrons and holes recombine in an organic compound layer when a current flows through a fluorescent organic compound thin film. Such an organic EL device is structurally thin, lightweight, has a simple component, and has a simple manufacturing process. In addition, it is applicable to high-definition display devices by securing wide viewing angles, perfect video, and high color purity, and has low power consumption and low voltage DC driving characteristics.

In the case of the organic electroluminescent device, it may be configured to have a predetermined width (W) and length (L) corresponding to the shape and size of the light conversion unit 350.

4A to 4C are cross-sectional views of a surface light source device according to preferred embodiments of the present invention.

4A and 4B, the surface light source devices 410 and 440 include light source units 420 and 450 and light conversion units 430 and 460.

The light sources 420 and 450 may be configured as light emitting devices, and the light emitting devices may be cold cathode fluorescent lamps, external electrode fluorescent lamps, light emitting diodes, or organic electroluminescent devices.

The light converters 430 and 460 include light incident parts 432 and 462 and light exit parts 434, 436, 464, and 466.

According to an embodiment of the present invention, the material of the light conversion units 430 and 460 may be a thermoplastic resin material having good light transmittance and having a good balance of mechanical properties (particularly impact resistance), heat resistance, and electrical properties. Preferably, the light conversion units 430 and 460 may be made of polyethylene terephthalate (PET), polycarbonate (PC), or polymethyl methacrylate (PMMA). Most preferably, the light conversion units 430 and 460 may be made of polymethyl methacrylate. Polymethyl methacrylate is high in strength and therefore not easily broken and easily deformed. In addition, the visible light transmittance is high, making it suitable as a light source material.

In one embodiment of the present invention, the light conversion unit 430 and 460 may be manufactured by a conventional plastic molding method known in the art such as injection or extrusion. Those skilled in the art will be able to manufacture the light conversion portion of the present invention from the above-mentioned materials using these molding methods without further explanation.

The light incident parts 432 and 462 include surfaces 432a and 462a on which light emitted from the light sources 420 and 450 are incident, and surfaces 432b, 432c, 462b and 462c on which the incident light is reflected. In the case of FIG. 4A, the surface 432a on which light is incident and the surfaces 432b and 432c on which light is reflected are all composed of planes. Surfaces 462b and 462c are configured in a plane.

According to an embodiment of the present invention, in addition to the configuration illustrated in FIGS. 4A and 4B with respect to the light incident portions 432 and 462, the surface on which the light is incident or reflected may be configured in various combinations of flat or curved surfaces. . In addition, the curved surface may be configured in a convex or concave shape, the degree of curvature of the curved surface may be determined in various ways depending on the purpose of light condensation or dispersion.

The light exit portions 434, 436, 464, and 466 have a shape protruding from one end of the light incident portions 432 and 462 and reflect the light transmitted through the light incident portions 432 and 462. 434b, 436a, 436b, 464a, 464b, 466a and 466b) and exit faces 434c, 436c, 464c and 466c. In the case of Fig. 4A, the surfaces 434a, 434b, 436a, and 436b on which light is reflected and the surfaces 434c and 436c on which light is emitted are all composed of planes. The curved surface, and the exiting surfaces 464c and 466c are configured in a plane.

According to another embodiment of the present invention, in addition to the configuration shown in FIGS. 4A and 4B with respect to the light output units 434, 436, 464, and 466, the surface on which the light is reflected or emitted is in various combinations of flat or curved surfaces. Can be configured. In addition, the number of the light output units 434, 436, 464, and 466 may be further added in consideration of light efficiency, brightness, size of the surface light source devices 410 and 440, and the like.

Referring to FIG. 4C, the surface light source device 460 of the present invention includes a light source unit 470 and a light conversion unit 480. The light source unit 470 includes a light emitting element 472 and a cap 474.

The light converter 480 includes a light incident part 482 and light exit parts 484 and 486.

4A and 4B, the light source 470 further includes a cap 474.

The cap 474 may be disposed above the light emitting device 472 to narrow the angle α of the light emitted from the light emitting device 472. Accordingly, the amount of light incident from the light emitting element 472 to the light conversion unit 480 increases, and thus, the light efficiency can be improved.

5 is a view for explaining the process of the light in the surface light source device according to an embodiment of the present invention. In this case, the light conversion unit omits the cross section or hatching in order to clearly display the line through which the light travels.

FIG. 6 is an enlarged view of a portion A of FIG. 5.

5 and 6, the light L ₁ emitted from the light emitting element 520 at a predetermined angle is incident through one surface 532a of the light incident part 532. Here, due to the difference in refractive index between the medium (small medium) between the light emitting element 520 and the light conversion unit 530 and the medium (dense medium) constituting the light incident part 532, the light is emitted from the light emitting element 520. The light L ₁ is refracted and proceeds to the light output part 534 (L ₂ ).

In FIG. 5, although light is incident through one surface 532a of the light incident part 532, it is shown to proceed directly to the light exit parts 534 and 536, but according to an angle at which light is incident, the light incident part ( After being reflected at the other sides 532b and 532c of 532, it may proceed to light exit portions 534 and 536.

Subsequently, the advanced light L ₂ causes reflection on one surface 534b of the light output part 534, and an angle greater than or equal to a critical angle that satisfies the total reflection condition according to Snell's law, which is well known in the art. When incident on (θ _a ), light causes total reflection and progresses in the light output portion 534 (L ₃ ).

Subsequently, when the advanced light L ₃ is incident on the other surface 534a of the light output part 534 at an angle θ _b or more than a critical angle, total reflection occurs again, and in the light output part 534. Proceed (L ₄ ).

Subsequently, when the advanced light L ₄ is incident on another surface 534c of the light output part 534 at an angle θ _c below the critical angle, the light causes refraction and the light conversion part 530. It is emitted from.

The above-described process also occurs on the surfaces 536a, 536b, and 536c of the other light output units 536 of the light conversion unit 530, so that one light emitting device 520 may serve as two light sources. have.

Therefore, when the backlight unit 210 is configured using the surface light source device 510 of the present invention, the number of light emitting devices 520 used in the backlight unit 210 can be reduced, so that the backlight unit 210 can be reduced. It is possible to reduce the power consumption and the amount of heat generated.

According to the exemplary embodiment of the present invention, the light output units 534 and 536 of the light conversion unit 530 may be configured in a symmetrical manner to generate plane light having uniform luminance.

In the above-described surface light source device 510, the light causes total reflection twice and is emitted from the light conversion unit 530, but the angle of light incident from the light emitting element 520 to the light conversion unit 530, Depending on the shape of the surface on which the light is reflected, the refractive index of the material constituting the light conversion unit 530, etc. may cause total reflection several times, and may be emitted from the light conversion unit 530.

Preferred embodiments of the present invention described above are merely disclosed for purposes of illustration, and those skilled in the art having various ordinary knowledge of the present invention will be able to make various modifications, changes, additions within the spirit and scope of the present invention. And additions should be considered to be within the scope of the following claims.

The present invention has the advantage that it is possible to provide a plurality of plane light with uniform luminance from one light source by using the reflection of light.

In addition, since the present invention emits a plurality of plane light using one light source, there is an advantage that can reduce the power consumption and the amount of heat generated.

Claims (21)

In the surface light source device for outputting light provided to the liquid crystal panel, A light source unit including one or more light emitting elements arranged at predetermined intervals; And It includes a light conversion unit for reflecting the light incident from the light source from the inner surface and exiting, The light conversion unit includes a light incidence unit having a plurality of surfaces on which light emitted from the light source unit is incident or reflected, Surface in which the light incident or reflected light incident portion is a plane or curved surface light source device. The method of claim 1, wherein the light source unit, And a cap disposed on the light emitting element, the cap narrowing an emission angle of light emitted from the light emitting element. The surface light source device according to claim 1, wherein the light emitting device is a cold cathode fluorescent lamp, an external electrode fluorescent lamp, a light emitting diode, or an organic electroluminescent device. The method of claim 1, wherein the light conversion unit, And a plurality of light output parts having a shape protruding from one end of the light incidence part and having a plurality of surfaces on which the light transmitted from the light incidence part reflects or exits. delete 5. The plane light source device according to claim 4, wherein the surface on which the light exit portion reflects or emits light is flat or curved. The plane light source device of claim 1, wherein the light conversion unit is made of polyethylene terephthalate, polycarbonate, or polymethyl methacrylate. A backlight unit for illuminating a liquid crystal panel from the rear, A surface light source device for illuminating the liquid crystal panel; And At least one optical sheet disposed on one side of the surface light source device and receiving the light output from the surface light source device and outputting the light to the liquid crystal panel, The surface light source device, A light source unit including one or more light emitting elements arranged at predetermined intervals; And It includes a light conversion unit for reflecting the light incident from the light source from the inner surface and exiting, The light conversion unit includes a light incidence unit having a plurality of surfaces on which light emitted from the light source unit is incident or reflected, The surface of the light incident part is incident or reflected, the backlight unit, characterized in that the flat or curved surface. The method of claim 8, wherein the light source unit, And a cap disposed on the light emitting device, the cap narrowing an emission angle of light emitted from the light emitting device. The backlight unit of claim 8, wherein the light emitting device is a cold cathode fluorescent lamp, an external electrode fluorescent lamp, a light emitting diode, or an organic electroluminescent device. The method of claim 8, wherein the light conversion unit, And a plurality of light emitting units having a shape protruding from one end of the light incidence unit and having a plurality of surfaces on which light transmitted from the light incidence unit reflects or exits. delete The backlight unit of claim 11, wherein a surface on which the light output part reflects or emits light is flat or curved. The backlight unit of claim 8, wherein the light conversion unit is made of polyethylene terephthalate, polycarbonate, or polymethyl methacrylate. A liquid crystal panel for displaying an image by controlling a transmission amount of light input by changing an arrangement of liquid crystal molecules of the liquid crystal layer according to an electrical signal applied from the outside; And It includes a backlight unit for providing light input to the liquid crystal panel from the rear of the liquid crystal panel, The backlight unit, A surface light source device for illuminating the liquid crystal panel; And At least one optical sheet disposed on one side of the surface light source device and receiving the light output from the surface light source device and outputting the light to the liquid crystal panel, The surface light source device, A light source unit including one or more light emitting elements arranged at predetermined intervals; And It includes a light conversion unit for reflecting the light incident from the light source from the inner surface and exiting, The light conversion unit includes a light incidence unit having a plurality of surfaces on which light emitted from the light source unit is incident or reflected, And a plane or a curved surface where light is incident or reflected on the light incident part. The method of claim 15, wherein the light source unit, And a cap disposed on the light emitting element, the cap narrowing an emission angle of light emitted from the light emitting element. The liquid crystal display of claim 15, wherein the light emitting device is a cold cathode fluorescent lamp, an external electrode fluorescent lamp, a light emitting diode, or an organic electroluminescent device. The method of claim 15, wherein the light change unit, And a plurality of light output parts having a shape protruding from one end of the light incident part and having a plurality of surfaces on which the light transmitted from the light incident part reflects or exits. delete 19. The liquid crystal display device according to claim 18, wherein the surface on which the light exit portion reflects or emits light is flat or curved. The liquid crystal display of claim 15, wherein the light conversion unit is made of polyethylene terephthalate, polycarbonate, or polymethyl methacrylate.

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