WO2012030085A1

WO2012030085A1 - Backlight unit and method for manufacturing the same

Info

Publication number: WO2012030085A1
Application number: PCT/KR2011/006056
Authority: WO
Inventors: Kyoung Soo Ahn; Sang Jun Park; Kyoung Jong Yoo; Jong Sun Kim
Original assignee: Lg Innotek Co., Ltd.
Priority date: 2010-09-03
Filing date: 2011-08-17
Publication date: 2012-03-08
Also published as: KR20120023345A; TW201215968A; TWI450001B

Abstract

Provided are a backlight unit and a method for manufacturing the backlight unit. The backlight unit includes a light guide plate in which a plurality of grooves are formed, a plurality of side emitting type light emitting devices inserted in the grooves, respectively, and optical path shift layers disposed in the grooves to shift optical paths of light emitted from the side emitting type light emitting devices.

Description

[Rectified under Rule 91 05.12.2011] BACKLIGHT UNIT AND METHOD FOR MANUFACTURING THE SAME

The present disclosure relates to a backlight unit and a method for manufacturing the backlight unit.

Cold cathode fluorescent lamps had been widely used as backlight light sources of liquid crystal displays (LCDs) owing to their inexpensive prices and easy-to-assemble characteristics. However, cold cathode fluorescent lamps have demerits such as mercury-related environmental problems, low response time, and poor color reproduction characteristics.

Due to such demerits of cold cathode fluorescent lamps, light emitting diodes (LEDs) had been proposed as backlight light sources.

Recently, much research is being conducted on backlight units using LEDs as light sources, and manufacture of such backlight units is largely increasing.

Backlight units can be classified into edge type backlight units and direct type backlight units. In edge type backlight units, light is incident on a side of a light guide plate, and the light is guided to a panel through the top surface of the light guide plate.

In direct type backlight units, an LED is disposed at a backside of a diffusion plate, and light emitted from the LED is supplied to a panel through the diffusion plate.

Although edge type backlight units can be easily made in thin shapes, it is difficult to ensure light uniformity if the size of a liquid crystal panel is large.

On the other hand, it is difficult to make direct type backlight units into thin shapes due to a distance between an LED and a diffusion plate although direct type backlight units can be easily made in large sizes.

Embodiments provide a backlight unit configured to prevent locally concentrated light emission from a light guide plate.

In one embodiment, a backlight unit including: a light guide plate in which a plurality of grooves are formed; a plurality of side emitting type light emitting devices inserted in the grooves, respectively; and optical path shift layers disposed in the grooves to shift optical paths of light emitted from the side emitting type light emitting devices.

In another embodiment, a backlight unit including: a light guide plate in which a plurality of openings are formed; a plurality of side emitting type light emitting devices inserted in the openings, respectively; and optical path shift layers configured to seal the openings and shift optical paths of light emitted from the side emitting type light emitting devices.

The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims.

As described above, in the backlight unit of the embodiments, the optical path shift layers are disposed in the grooves where the side emitting type light emitting devices are inserted, so as to shift optical paths of light emitted from the side emitting type light emitting devices. This prevents locally concentrated emission of light from the light guide plate, and thus brightness irregularity can be reduced.

In addition, beads may be dispersed in the optical path shift layers to irregularly reflect light emitted from the side emitting type light emitting devices and thus to prevent locally concentrated light emission from the light guide plate. Therefore, hot spots can be reduced.

Fig. 1 is a schematic sectional view illustrating a backlight unit according to an embodiment.

Fig. 2 is a schematic sectional view illustrating a comparison example of the backlight unit of the embodiment.

Fig. 3 is a schematic sectional view for explaining light propagation paths in the comparison example of the backlight unit of the embodiment.

Fig. 4 is a schematic sectional view for explaining light propagation paths in the backlight unit of the embodiment.

Fig. 5 is a schematic partial sectional view illustrating a backlight unit according to a first embodiment.

Fig. 6 is a schematic partial sectional view illustrating a backlight unit according to a second embodiment.

Fig. 7 is a schematic partial sectional view illustrating a backlight unit according to a third embodiment.

Figs. 8A to 8C are schematic partial sectional views illustrating a backlight unit according to a fourth embodiment.

Fig. 9 is a schematic partial sectional view illustrating a backlight unit according to a fifth embodiment.

Figs. 10A to 10D are schematic sectional views for explaining a method for manufacturing a backlight unit according to an embodiment.

Fig. 11 is a schematic partial sectional view illustrating a backlight unit according to a sixth embodiment.

Reference will now be made in detail to the embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings.

The backlight unit of the embodiment includes: a light guide plate 100 in which a plurality of grooves 110 are formed; a plurality of side emitting type light emitting devices 310 inserted in the grooves 110, respectively; and optical path shift layers 200 disposed at the grooves 110 to shift optical paths of light emitted from the side emitting type light emitting devices 310.

The light guide plate 100 may be formed of a transparent material. For example, the light guide plate 100 may be formed of one of an acrylic resin-based material such as polymethylmethacrylate (PMMA), a polyethylene terephthalate (PET) resin, a poly carbonate (PC) resin, and a polyethylene naphthalate (PEN) resin.

The side emitting type light emitting devices 310 may include light emitting diodes (LEDs).

The LEDs may be color LEDs capable of emitting at least one of red light, blue light, green light, and white light, or may be ultraviolet (UV) LEDs. For example, the color LEDs may include a combination of red, blue, green, and white LEDs. Arrangement of the color LEDs and light types of the color LEDs may be changed within the technical scope of the embodiment.

A printed circuit board (PCB) 300 on which the side emitting type light emitting devices 310 are disposed may be disposed under the light guide plate 100.

The PCB 300 may be a metal core PCB, an FR-4 PCB, a general PCB, a flexible PCB, or a ceramic PCB. However, the PCB 300 is not limited thereto, but may be any other PCB in the technical scope of the embodiments.

Furthermore, in the backlight unit of the current embodiment, the grooves 110 are formed in the bottom surface of the light guide plate 100 to receive the side emitting type light emitting devices 310, and the optical path shift layers 200 are disposed on the inner walls of the grooves 110.

Optical paths of light emitted from the side emitting type light emitting devices 310 are shifted (i.e., changed) at the optical path shift layers 200, and then the light is incident on the light guide plate 100. Thereafter, the light is guide to the outside through the light guide plate 100.

At this time, the light the light paths of which are shifted at the optical path shift layers 200 is uniformly distributed throughout the light guide plate 100 and is then guided to the outside. Therefore, the light discharged from the light guide plate 100 does not cause a hot spot, and thus brightness irregularity can be reduced.

That is, in the backlight unit of the current embodiment, the optical path shift layers 200 is disposed at the grooves 110 where the side emitting type light emitting devices 310 are inserted, so as to shift optical paths of light emitted from the side emitting type light emitting devices 310. This prevents locally concentrated emission of light from the light guide plate 100. Therefore, brightness irregularity can be reduced.

The optical path shift layers 200 may be formed of a resin such as an acryl-containing resin and a silicon-containing resin.

The optical path shift layers 200 may have a refractive index different from that of the light guide plate 100. Light emitted from the side emitting type light emitting devices 310 may be incident onto the optical path shift layers 200 through air layers and be refracted at the optical path shift layers 200. In this way, optical paths of light emitted from the side emitting type light emitting devices 310 are shifted.

The refractive index of the optical path shift layers 200 may be larger or smaller than that of the light guide plate 100.

As shown in Fig. 2, in the comparison example of the backlight unit of the present disclosure, an optical path shift layer is not disposed at grooves 110 where side emitting type light emitting devices 310 are inserted.

In the comparison example, when light emitted from the side emitting type light emitting devices 310 propagates through air layers and a light guide plate 100, the light is concentrated at regions close to the side emitting type light emitting devices 310. This causes hot spots.

That is, as shown in Fig. 3, rays A and B emitted from the side emitting type light emitting device 310 are incident onto the light guide plate 100 through an air layer and are discharged to the outside through a region (K).

Therefore, light emitted from the comparison example may have brightness irregularity due to a hot spot.

However, in the backlight unit of the current embodiment, since the optical path shift layers 200 are disposed at the grooves 110 of the light guide plate 100, light rays A1 and B1 emitted from the side emitting type light emitting device 310 propagate through an air layer and are refracted at the optical path shift layer 200. That is, the optical paths of the light rays A1 and B1 are shifted at the optical path shift layer 200, and thus the light rays A1 and B1 are not concentrated at a region of the light guide plate 100 as shown in Fig. 4.

That is, when the light rays A1 and B1 are discharged through the light guide plate 100, the light rays A1 and B1 are not concentrated at a specific region of the light guide plate 100. Accordingly, when light is emitted from the backlight unit, hot spots can be reduced, and thus brightness irregularity can be prevented.

Fig. 5 is a schematic partial sectional view illustrating a backlight unit according to a first embodiment, and Fig. 6 is a schematic partial sectional view illustrating a backlight unit according to a second embodiment.

In the backlight unit of the first embodiment, as shown in Fig. 5, optical path shift layers 211 and 212 are disposed in partial regions of a groove 110 of a light guide plate 100.

That is, the optical path shift layers 211 and 212 are disposed in predetermined regions of the groove 110 of the light guide plate 100. For example, the optical path shift layers 211 and 212 may be coated on predetermined regions of the inner wall of the groove 110 of the light guide plate 100.

The predetermined regions of the groove 110 of the light guide plate 100 may be partial regions of the groove 110. For example, the predetermined regions of the groove 110 may be inner wall regions of the groove 110 that are spaced apart from each other.

For example, the optical path shift layers 211 and 212 may cover mutually-facing corners of the groove 110 as shown in Fig. 5.

As described above, the optical path shift layers 211 and 212 are disposed in partial regions of the groove 110 of the light guide plate 100. However, the positions of the optical path shift layers 211 and 212 are not limited to the positions shown in Fig. 5. That is, the optical path shift layers 211 and 212 may be disposed at any positions so long as hot spots and brightness irregularity of light emitted from the backlight unit can be reduced.

In the backlight unit of the second embodiment, as shown in Fig. 6, an uneven pattern 201 is formed on an optical path shift layer 200.

The uneven pattern 201 may change optical paths of light emitted from a side emitting type light emitting device 310. That is, light may be variously scattered according to the shape of the uneven pattern 201, and thus optical paths may also be variously changed to reduce hot spots when light is discharged from the backlight unit.

In the backlight unit of the third embodiment, beads 220 are dispersed in an optical path shift layer 200.

The beads 220 irregularly reflects light emitted from a side emitting type light emitting device 310 so that locally concentrated emission from a light guide plate 100 can be prevented. Therefore, hot spots can be reduced.

The beads 220 may be formed of at least one of acryl, silicon, glass, and polystyrene.

Figs. 8A to 8C are schematic partial sectional views illustrating a backlight unit according to a fourth embodiment, and Fig. 9 is a schematic partial sectional view illustrating a backlight unit according to a fifth embodiment.

The backlight unit of the fourth embodiment includes: a light guide plate 100 in which a plurality of openings 111 are formed; a plurality of side emitting type light emitting devices 310 inserted in the openings 111, respectively; and optical path shift layers 200 sealing the openings 111 and shifting optical paths of light emitted from the side emitting type light emitting devices 310.

Since the openings 111 of the light guide plate 100 are closed by the optical path shift layers 200, light emitted from the side emitting type light emitting devices 310 is discharged to the outside through the optical path shift layers 200 or the light guide plate 100.

Referring to Fig. 8A, the optical path shift layers 200 may be spaced apart from the side emitting type light emitting devices 310 so that air layers can be formed between the optical path shift layers 200 and the side emitting type light emitting devices 310.

Alternatively, the optical path shift layers 200 may be in contact with the side emitting type light emitting devices 310, and thus air layers may not be formed among the side emitting type light emitting devices 310, the optical path shift layers 200, and the light guide plate 100.

In this case, the optical path shift layers 200 may partially cover the side emitting type light emitting devices 310 as shown in Fig. 8B or entirely cover the side emitting type light emitting devices 310 as shown Fig. 8C.

Referring to Fig. 9, the backlight unit of the fifth embodiment may include: a light guide plate 100 in which a plurality of grooves 110 are formed; a plurality of side emitting type light emitting devices 310 inserted in the grooves 110, respectively; and optical path shift layers 200 covering the side emitting type light emitting devices 310 and shifting optical paths of light emitted from the side emitting type light emitting devices 310. Referring to Fig. 9, the optical path shift layer 200 covers the surface of the side emitting type light emitting device 310 and is spaced a predetermined distance from the sidewall of the groove 110 of the light guide plate 100 so that an air layer can be formed between the optical path shift layer 200 and the light guide plate 100.

According to the backlight unit manufacturing method of the embodiment, first, a plurality of side emitting type light emitting devices 310 are disposed on a PCB 300 as shown in Fig. 10A.

Next, a light guide plate 100 in which a plurality of grooves 110 are formed is prepared (refer to Fig. 10B).

Next, optical path shift layers 200 are formed in the grooves 110 of the light guide plate 100 to shift optical paths of light emitted from the side emitting type light emitting devices 310 (refer to Fig 10C).

At this time, the optical path shift layers 200 may be formed on the entire inner walls of the grooves 110 as shown in Fig. 1 or partial regions of the inner walls of the grooves 110 as shown in Fig. 5. In the latter case, the optical path shift layers 200 may be formed on mutually-facing corner regions of the inner walls of the grooves 110. In addition, the optical path shift layers 200 may have uneven surfaces as shown in Fig. 6.

The optical path shift layers 200 may be formed ofoneoftheabove-describedmentionedmaterials.

Then, the light guide plate 100 is aligned with the PCB 300 so that the side emitting type light emitting devices 310 can be inserted into the grooves 110 of the light guide plate 100 (refer to Fig. 10D).

When or after the light guide plate 100 is aligned with the PCB 300, a fixation process such as a coupling or bonding process may be performed to fix the light guide plate 100 to the PCB 300.

In the backlight unit of the sixth embodiment, a pattern 101 is disposed on a light guide plate 100 facing a PCB 300 to discharge light incident onto the light guide plate 100.

As shown in Fig. 11, the backlight unit includes: a shift layer 200 on the inner wall of a groove 110 formed in the light guide plate 100; and a reflection plate 320 on the bottom surface of the light guide plate 100.

That is, the pattern 101 is formed on the light guide plate 100, and the reflection plate 320 is disposed on the bottom surface of the light guide plate 100. Therefore, light incident onto the reflection plate 320 and light reflected from the reflection plate 320 to the light guide plate 100 can be scattered at the pattern 101. Therefore, light can be discharged from the backlight unit without hot spots.

Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.

Claims

A backlight unit comprising:

a light guide plate in which a plurality of grooves are formed;

a plurality of side emitting type light emitting devices inserted in the grooves, respectively; and

optical path shift layers disposed in the grooves to shift optical paths of light emitted from the side emitting type light emitting devices.
The backlight unit according to claim 1, wherein the optical path shift layers are formed of a resin.
The backlight unit according to claim 1, wherein the optical path shift layers have a refractive index different from that of the light guide plate.
The backlight unit according to claim 1, wherein the side emitting type light emitting devices are light emitting diodes (LEDs).
The backlight unit according to claim 1, wherein the optical path shift layers are disposed in partial regions of the grooves.
The backlight unit according to claim 1, wherein the optical path shift layers are disposed in corner regions of the grooves.
The backlight unit according to claim 1, wherein uneven patters are disposed on the optical path shift layers.
The backlight unit according to claim 1, wherein beads are dispersed in the optical path shift layers.
The backlight unit according to claim 8, wherein the beads are formed of at least one of acryl, silicon, glass, and polystyrene.
The backlight unit according to claim 1, wherein the side emitting type light emitting devices are disposed on a printed circuit board (PCB), and a reflection plate is disposed between the light guide plate and the PCB.
The backlight unit according to claim 11, wherein an uneven pattern is disposed on a surface of the light guide plate that makes contact with the reflection plate.
A backlight unit comprising:

a light guide plate in which a plurality of openings are formed;

a plurality of side emitting type light emitting devices inserted in the openings, respectively; and

optical path shift layers configured to seal the openings and shift optical paths of light emitted from the side emitting type light emitting devices.
The backlight unit according to claim 12, wherein air layers formed between the optical path shift layers and the side emitting type light emitting devices.
The backlight unit according to claim 12, wherein the optical path shift layers are disposed to cover partial regions of the side emitting type light emitting devices.
The backlight unit according to claim 12, wherein the optical path shift layers have a refractive index different from that of the light guide plate.
The backlight unit according to claim 12, wherein the side emitting type light emitting devices are LEDs.
The backlight unit according to claim 12, wherein the optical path shift layers are formed of a resin.
A method for manufacturing a backlight unit, the method comprising:

disposing a plurality of side emitting type light emitting devices on a PCB;

preparing a light guide plate in which a plurality of grooves are formed;

forming optical path shift layers in the grooves of the light guide plate to shift light emitted from the side emitting type light emitting devices; and

aligning the light guide plate with the PCB to insert the side emitting type light emitting devices into the grooves of the light guide plate.
The method of claim 18, wherein the forming of the optical path shift layers is performed such that the optical path shift layers are formed on partial regions of inner walls of the grooves.
The method of claim 18, wherein the optical path shift layers are formed in corner regions of the grooves.