KR20120037642A - Light emitting device array, and backlight unit and display having the same - Google Patents

Abstract

PURPOSE: A backlight unit and a display device with the same are provided to prevent lowering of reliability of a light source due to expansion of a light guide plate. CONSTITUTION: A light source unit(111) includes a substrate and a plurality of light emitting devices. The light emitting devices are separated from the substrate. A light guide plate(120) is adjacent to the light source unit. The light guide plate guides light emitted from the light source unit toward a light emitting side. The light source unit includes a protrusion part.

Description

Backlight unit and display device including same {Light emitting device array, and backlight unit and display having the same}

The present invention relates to a backlight unit and a display device including the same.

In general, liquid crystal displays have better visibility than cathode ray tubes (CRTs), are smaller than cathode ray tubes with the same screen size, and have a smaller calorific value. It is widely used as a display device of a mobile phone, a computer monitor, or a television.

The liquid crystal display device arranges two substrates on which electrodes are formed so that the surfaces on which the two electrodes are formed face each other, injects a liquid crystal material between the two substrates, and then applies a voltage to the two electrodes to form a liquid crystal. By moving a molecule, it is an apparatus which expresses an image by the transmittance | permeability of light which changes accordingly.

Since the liquid crystal is thin and long in structure, the liquid crystal has directivity in the arrangement of molecules, and the direction of the arrangement of molecules can be controlled by artificially applying an electric field to the liquid crystal. Therefore, if the molecular arrangement direction of the liquid crystal is arbitrarily adjusted, the molecular arrangement of the liquid crystal is changed, and light is refracted in the molecular arrangement direction of the liquid crystal due to optical anisotropy to express image information.

However, since the liquid crystal display is a light-receiving element that does not emit light by itself, a separate light source is required, and a backlight unit is used as the light source. That is, the light emitted from the backlight unit disposed under the liquid crystal panel is incident on the liquid crystal panel to adjust the amount of light transmitted according to the arrangement of the liquid crystals to display an image.

The backlight unit includes a backlight assembly including a reflector, a light guide plate, an optical sheet, a light source, and the like, and a frame and a cover in which the backlight assembly is accommodated.

In the backlight unit, a light guide plate is disposed at the rear of the liquid crystal panel and a light source is disposed at the side of the light guide plate to send light emitted from the light source to the liquid crystal panel through the light guide plate, and a light source is disposed at the rear of the liquid crystal panel to There is a direct type that sends the light of the light directly to the liquid crystal panel.

In recent years, the backlight unit is becoming more compact, and in the case of the edge type backlight unit, the distance between the light guide plate and the light source is becoming narrower. A lot of heat is generated during operation of the display device, and as the light guide plate is expanded by the heat, reliability of the light source is deteriorated due to the pressing of the light source disposed on the side of the light guide plate.

An embodiment of the present invention is to provide a backlight unit and a display device having the same that can prevent the reliability of the light source due to the expansion of the light guide plate in the edge type backlight unit.

In one embodiment, a backlight unit includes: a light source unit including a substrate and a plurality of light emitting devices disposed spaced apart from the substrate; A light guide plate disposed adjacent to the light source unit and configured to guide light emitted from the light source unit toward an emission surface; The light source unit includes a protrusion protruding a predetermined distance from the end of the light emitting device.

The light source unit may be disposed on a side surface of the light guide plate.

In addition, the protrusion is disposed between the light emitting elements.

In addition, the protrusion may be reflective or translucent.

In addition, a plurality of the protrusions are spaced apart along the longitudinal direction of the substrate.

The end of the protrusion also has a flat surface.

In addition, the protrusion is screwed to the substrate.

In addition, the protrusion is a 0 ohm resistor attached to the substrate.

The 0 ohm resistor is also attached to the substrate by surface mount technology.

In addition, the protrusion protrudes by 0.3 to 1 mm from the light emitting device.

The display device of the embodiment includes an image display member; And the backlight unit radiating light to the image display member. .

The embodiment can provide a backlight unit and a display device having the same that can prevent a decrease in reliability of a light source due to expansion of the light guide plate in the backlight unit.

1 is a perspective view illustrating a display device according to an exemplary embodiment.
2 is a cross-sectional view illustrating a backlight unit according to an embodiment.
3 is a cross-sectional view showing a general light emitting device package.
4 is a plan view illustrating a light source unit and a light guide plate of a backlight unit according to another exemplary embodiment.
5 is a plan view illustrating a light source unit and a light guide plate of a backlight unit according to another exemplary embodiment.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention that can specifically realize the above object will be described.

In the description of the above embodiments, each layer (film), region, pattern or structures may be on or "below" or "bottom on" the substrate, each layer (film), region, pad or pattern. under "," on "and" under "are" directly "or" indirectly "formed. It includes everything. In addition, the criteria for the top or bottom of each layer will be described with reference to the drawings.

In the drawings, the thickness or size of each layer is exaggerated, omitted, or schematically illustrated for convenience and clarity of description. In addition, the size of each component does not necessarily reflect the actual size.

1 is a perspective view illustrating a display device according to an exemplary embodiment.

The display device 100 includes an image display member 190 and a backlight unit. Here, the image display member 190 refers to a member configured to display an image by receiving light such as a liquid crystal panel. Hereinafter, a liquid crystal panel will be described as an example of the image display member 590.

The liquid crystal panel 190 is formed by injecting a liquid crystal layer between the TFT substrate and the color filter substrate. The liquid crystal panel 190 arranges two substrates on which electrodes are formed so that the surfaces on which the electrodes are formed face each other, injects a liquid crystal material between the two substrates, and then applies an electric voltage generated by applying a voltage to the two electrodes. By moving the liquid crystal molecules, the image is represented by the transmittance of light that varies accordingly.

The backlight unit is a light source device that emits light behind the liquid crystal panel 190 so that the liquid crystal panel 190 can display an image. The backlight unit may include a backlight assembly 110 having a light source 111, a light guide plate 120, an optical sheet 130, and a reflective sheet 140, and a storage device having a frame 150 and a lower cover 170. Can be.

The light source unit 111 is formed by mounting a light emitting device (or a light emitting device package) such as a light emitting diode (LED) or a cold cathode fluorescent lamp (CCFL) on a substrate, and a main substrate (not shown). ) Is electrically connected. A plurality of light emitting elements are arranged spaced apart from the substrate. The light source unit 111 may be arranged on the side surface of the light guide plate 120.

The light guide plate 120 guides the light emitted from the light source unit 111 toward the emission surface (the direction in which the liquid crystal panel 190 is located) to distribute the light evenly throughout the light emitting area. A plurality of reflective dots may be formed on the rear surface of the light guide plate 120 to diffuse the light emitted from the light source unit 111.

The optical sheet 130 is disposed on the light guide plate 120, and the light emitted from the light guide plate 120 undergoes diffusion and refraction to improve brightness and light efficiency. The optical sheet 130 may be composed of one or a plurality. For example, the optical sheet 130 may include a diffusion sheet and a prism sheet, or may be configured as one optical sheet having a function of a diffusion sheet and a function of a prism sheet. have. The type and number of optical sheets 130 may be variously selected depending on the required luminance characteristics.

The reflective sheet 140 may be positioned under the light guide plate 120. The reflective sheet 140 reflects the light leaking backward from the light guide plate 120 toward the exit surface.

The liquid crystal panel 190 and the backlight assembly 110 should be accommodated and fixed, and a frame 150, an upper cover 160, and a lower cover 170 are used for this purpose.

The frame 150 and the lower cover 170 serve to receive the backlight assembly 110. The backlight assembly 110 may include only the light source 111 and the light guide plate 120, and may further include one or more of the optical sheet 130 and the reflective sheet 140. The range of components included in the backlight assembly 110 may be appropriately selected by those skilled in the art and does not limit the present invention.

The liquid crystal panel 190 may be mounted on the frame 150. The liquid crystal panel 190 is supported and received between the upper cover 160 and the frame 150. The frame 150, the upper cover 160 and the lower cover 170 may be formed of a metal or plastic material.

2 is a cross-sectional view illustrating a backlight unit according to an embodiment.

The backlight unit 200 includes a frame 250, a lower cover 270, a light source 211, a light guide plate 220, an optical sheet 230, a reflective sheet 240, and the like.

The light source 211 may be disposed at both sides of the space formed by the frame 250 and the lower cover 270. In the light source unit 211, a plurality of light emitting devices (or light emitting device packages) 211b may be spaced apart from each other along the longitudinal direction of the substrate 211a (the direction in or out of the drawing).

The light guide plate 220 is disposed adjacent to the light source unit 211. The light guide plate 220 guides the light emitted from the light emitting element 211b of the light source unit 211 to an emission surface (the direction in which the optical sheet 230 is located in the drawing).

The optical sheet 230 may be disposed on the light guide plate 220. A reflecting sheet 240 may be disposed under the light guide plate 220 to reflect light leaking backward from the light guide plate 220 toward the emission surface. A buffer 275 may be positioned between the reflective sheet 240 and the lower cover 270.

When the display device is being driven, a lot of heat is generated from the light emitting element 211b of the light source unit 211. In particular, recently, since the number of light emitting elements disposed in the light source unit is reduced and the light quantity of the light emitting elements is higher, more heat is generated, and the light guide plate 220 is expanded by such heat. Since the light guide plate 220 has a much larger expansion in the width direction than the thickness direction, the light guide plate 220 expands toward the light emitting device 211b and the light emitting device 211b is pressed. Pressing of the light emitting element 211b adversely affects the reliability of the light emitting element 211b.

3 is a cross-sectional view showing a general light emitting device package. The light emitting device package 1 includes a package body 11, lead frames 13 and 14, a light emitting device 20, a resin layer 25, and the like.

The package body 11 may be formed using alumina, quartz, or the like, and the cavity C may be formed at a predetermined depth on the upper body 12. The lead frames 13 and 14 are used as electrodes and are electrically separated from each other. The light emitting element 20 is mounted on the lead frames 13 and 14. The light emitting device 20 is electrically connected to the lead frames 13 and 14 by a wire 22.

The resin layer 25 is laminated in the cavity C region on the light emitting element 20. The resin layer 25 includes a transparent silicone or epoxy material. Phosphor may be added to the resin layer 25. Alternatively, a separate phosphor layer including phosphors may be formed between the light emitting device 20 and the resin layer 25. The phosphor absorbs the light emitted from the light emitting device 20 to emit light of a desired color. For example, when the light emitting element 20 emits blue light and the phosphor is yellow, the light emitted through the phosphor becomes white light.

As described above, since the light emitting device package 1 gathers several parts to form a single package, when the light emitting device package 1 is pressurized, various parts including the light emitting device 20 may be damaged and adversely affect reliability.

Referring back to FIG. 2, when the light guide plate 220 is expanded by heat while the backlight unit 200 is being driven, the side surface of the light guide plate 220 exerts a pressure on the light emitting device 211b. Since the long-term reliability of the backlight unit 200 is very important, repeated expansion and contraction of the light guide plate 220 has a fatal effect on the reliability of the light emitting device 211b.

4 is a plan view illustrating a light source unit and a light guide plate of a backlight unit according to another exemplary embodiment.

The backlight unit 300 includes a light source 311 and a light guide plate 320 disposed adjacent to the light source 311.

The light source unit 311 includes a substrate 311a and a plurality of light emitting devices 311b spaced apart from the substrate 311a. Here, the light emitting device 311b means not only a light emitting device having a narrow meaning, such as an LED chip, but also a light emitting device package packaged including an LED chip. The light source 311 may be disposed on at least one side surface among the four side surfaces of the light guide plate 320.

As the substrate 311a, a printed circuit board (PCB) printed with circuit wiring may be used. The light emitting device package may be mounted on the substrate 311a by Surface Mount Technology (SMT) (POB type). Alternatively, the light emitting device may be disposed on the substrate 311a by die bonding an LED chip (light emitting device) on the substrate 311a and making electrical connection by wire bonding (COB type).

The light guide plate 320 guides the light emitted from the light source unit 311 toward the emission surface (direction coming out of the ground) to distribute the light evenly throughout the light emitting area. A plurality of reflective dots may be formed on the rear surface of the light guide plate 320 to diffuse the light emitted from the light source unit 311.

As a material of the light guide plate 320, a transparent acrylic resin (PMMA) may be used. PMMA has the advantage of high visible light transmittance due to high mechanical strength, not broken or deformed, light, strong chemical resistance, and transparent.

When the backlight unit 300 is being driven, heat is generated from the light emitting element 311b or the like to about 60 to 80 ° C. and transferred to the light guide plate 220. The light guide plate 320 generally has a rectangular parallelepiped shape, and the expansion in the width direction or the longitudinal direction is much larger than that in the thickness direction. In recent years, the distance between the light emitting element and the light guide plate is further reduced (for example, about 0.5 to 1 mm) to increase the light emission efficiency. Thus, when the light guide plate 320 is expanded, the end of the light guide plate 320 is moved to the light emitting element 311b. By pressing, the light emitting element 311b may be damaged.

In this embodiment, in order to prevent the light guide plate 320 from expanding and pressurizing the light emitting device 311b, the light source 311 includes a protrusion 311c protruding a predetermined distance from the end of the light emitting device 311b. . The protrusion 311c may protrude about 0.3 to 1 mm from the end of the light emitting device 311b.

The protrusion 311c may have a flat surface to widen the contact area with the light guide plate 320. This allows the pressing force applied from the light guide plate 320 to be well distributed throughout the protrusion 311c.

The protrusion 311c may be made of metal or plastic. The protrusion 311c may be made of any material as long as the protrusion 311c is in contact with the light guide plate 320 that is expanded to protect the light emitting device 311b from the pressing force of the light guide plate 320.

The protrusion 311c may be disposed between the light emitting elements 311b spaced apart from each other in the longitudinal direction of the substrate 311a. The number of protrusions 311c disposed on the substrate 311a may be appropriately selected to effectively protect the light emitting device 311b from the expansion of the light guide plate 320.

The protrusion 311c may be screwed to the substrate 311a. To this end, the protrusion 311c has a male screw shape having a flat head portion, and the substrate 311a is provided with a groove having a spiral. By rotating the protrusion 311c with respect to the groove of the substrate 311a, the protrusion 311c may be screwed to the substrate 311a.

The protrusion 311c may be made of a reflective or translucent material. Since a part of the light emitted from the light emitting element 311b is reflected back to the substrate 311a from the light guide plate 320, the light is reflected or transmitted by hitting the surface or the protrusion 311c of the substrate 311a and the light guide plate 320 again. It is desirable to be able to be guided to.

The light source unit 311 of the present embodiment may be used as the light source unit 111 in the display device shown in FIG. 1.

5 is a plan view illustrating a light source unit and a light guide plate of a backlight unit according to another exemplary embodiment.

The backlight unit 400 may include a light source 411 and a light guide plate 420 disposed adjacent to the light source 411.

The light source unit 411 includes a substrate 411a and a plurality of light emitting devices 411b spaced apart from the substrate 411a. Here, the light emitting device 411b is meant to include not only a light emitting device having a narrow meaning, such as an LED chip, but also a light emitting device package packaged including an LED chip. The light source unit 411 may be disposed on at least one side surface among the four side surfaces of the light guide plate 420.

As the board 411a, a printed circuit board (PCB) printed with circuit wiring may be used. The light emitting device package may be mounted on the substrate 411a by Surface Mount Technology (SMT) (POB type). Alternatively, the light emitting device may be disposed on the substrate 411a by die bonding an LED chip (ie, a light emitting device) on the substrate 411a and making electrical connection by wire bonding (COB type). .

In order to prevent the light guide plate 420 from expanding and driving the light emitting device 411b by driving the backlight unit 400, the light source part 41 protrudes a predetermined distance from the end of the light emitting device 411b. ). The protrusion 411c may protrude from about 0.3 mm to about 1 mm from the end of the light emitting device 311b.

In this embodiment, this protrusion 411c may be an ohmic resistance. The 0 ohm resistor is a resistor with a resistance of 0 ohm (actually having a resistance value close to 0 ohm), and can be manufactured in various shapes.

Since a plurality of light emitting elements 411b are disposed on the substrate 411a, circuit wirings for supplying power to the light emitting elements 411b are printed on the substrate 411a. The protrusion 411c is disposed between the light emitting elements 411b. Since the circuit wiring often passes through the light emitting element 411b, such a protrusion 411c is provided so as not to affect the existing circuit. It is using a 0 ohm resistor.

If the protrusion 411c, that is, the position where the ohmic resistance is to be attached is determined on the substrate 411a, the protrusion 411c may be attached onto the substrate 411a by surface mount technology (SMT). Surface mount technology refers to a process or system that places components on an electromagnetic plate. Surface-mount technology can be done automatically or semi-automatically, which makes it possible to miniaturize packages and reduce manufacturing costs.

In the present embodiment, since the protrusion 411c is formed of an ohmic resistance, the protrusion 411c is moved to the substrate 411a without affecting the position where the protrusion 411c is attached to the substrate 411a or the circuit wiring disposed adjacent thereto. ) Can be placed.

The light source unit 411 of the present exemplary embodiment may be used as the light source unit 111 in the display device illustrated in FIG. 1.

Although the configuration of the protrusion attached to the substrate of the light source unit has been described above, the protrusion may have various shapes and materials as long as it can prevent the light emitting device from being pressed by the expansion of the light guide plate.

Features, structures, effects, and the like described in the above embodiments are included in at least one embodiment of the present invention, and are not necessarily limited to only one embodiment. Furthermore, the features, structures, effects, and the like illustrated in the embodiments may be combined or modified with respect to other embodiments by those skilled in the art to which the embodiments belong. Therefore, it should be understood that the present invention is not limited to these combinations and modifications.

In addition, the above description has been made with reference to the embodiment, which is merely an example, and is not intended to limit the present invention. Those skilled in the art to which the present invention pertains will be illustrated as above without departing from the essential characteristics of the present embodiment. It will be appreciated that various modifications and applications are possible. For example, each component specifically shown in the embodiment can be modified. And differences relating to such modifications and applications will have to be construed as being included in the scope of the invention defined in the appended claims.

100 display device 110 backlight assembly
111 light source unit 120 light guide plate
130: optical sheet 140: reflective sheet
150: frame 160: top cover
170: lower cover 190: liquid crystal panel
211: light source 211a: substrate
211b: light emitting element 311: light source
311a: substrate 311b: light emitting element
311c: protrusion 320: light guide plate

Claims (11)

A light source unit having a substrate and a plurality of light emitting elements disposed spaced apart from the substrate;
A light guide plate disposed adjacent to the light source unit and configured to guide light emitted from the light source unit toward an emission surface;
Including,
The light source unit includes a backlight unit protruding a predetermined distance from the end of the light emitting device. The method of claim 1,
The light source unit is a backlight unit disposed on the side of the light guide plate. The method of claim 1,
The protrusion unit is disposed between the light emitting elements. The method of claim 1,
The projection unit has a reflective or translucent backlight unit. The method of claim 1,
And a plurality of protrusions spaced apart from each other along the longitudinal direction of the substrate. The method of claim 1,
An end of the protrusion has a flat surface. The method of claim 1,
The protrusion unit is screwed coupled to the substrate. The method of claim 1,
The protrusion unit is a 0 ohm resistor attached to the substrate. The method of claim 8,
And the 0 Ohm resistor is attached to the substrate by surface mount technology. The method of claim 1,
The protrusion unit protrudes 0.3 to 1 mm from the light emitting device. An image display member; And
A backlight unit according to any one of claims 1 to 10 for irradiating light to the image display member;
Display device comprising a.

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