Backlight module and display device

Abstract

A backlight module is provided and comprises a back frame, a light guide plate, a light source mounted on the back frame and faces toward one surface of the light guide plate, and optical films positioned on an upper surface of the light guide plate. The back frame includes a back plate and a side wall extending upward from edges of the back plate, each of side wall has an upper flange with free end extends from the end of the side wall far from the back plate toward the interior of the back frame. The light guide plate is positioned above the back plate, with protruding strips formed on its surface along its thickness direction, creating a stepped profile in the cross-section of the light guide plate. These protruding strips are confined between the free ends and the back plate.

Description

[Technical Field]

[0001] This invention relates to a side-lit display backlight module, and more precisely, to a backlight module capable of forming a narrow bezel. [Previous Technology]

[0002] Narrow bezel display devices are currently a trend, necessitating changes to the internal structure. Referring to Figures 1 and 2, a conventional display device structure is shown. The internal chamber of the display device 100 is defined by a lower cover 10. The open end face of the lower cover 10 has a front frame to support the back cover of the display module 20, and the interior of the chamber is used to install the backlight module. The conventional backlight module includes at least a light source (not shown), a light guide plate 32, and an optical film 36, which are clamped together by the back frame 31 and the upper frame 80 to form the module. If the display device uses a side-lit backlight, a reflector 37 is also provided between the light guide plate 32 and the upper surface of the back frame 31 to project the light from inside the light guide plate 32 onto the optical film 36, and then towards the rear of the display module 20. A buffer 40 is provided on the vertical surface of the back frame 31 and faces the edges of the light guide plate 32, optical film 36, and reflector 37 to reduce impact on the internal components of the back frame 31.

[0003] A portion of the upper frame 80 of the backlight module rests on top of the optical film. The display module 20 above the upper frame 80 cannot receive light, becoming an ineffective area 90, which is also the main reason why a narrow bezel cannot be constructed. In some assembly structure designs, the front frame can be omitted, and the opening end face of the lower cover 10 directly supports the display module 20. If the upper frame 80 of the backlight module can be omitted under such circumstances, the side bezel can be further reduced to achieve the purpose of a narrow bezel. However, omitting the upper frame will directly cause the light guide element to be unable to be effectively positioned, resulting in functional failure. [Summary of the Invention]

[0004] To achieve the above objectives, a backlight module is provided, installed inside a lower cover of a display device, comprising a back frame, a light guide plate, a light source, and an optical film. The back frame has a back plate and a side wall extending upward from the edge of the back plate. The side wall has an upper edge, and the free end of the upper edge extends from the end of the side wall away from the back plate toward the interior of the back frame. The light guide plate is disposed above the back plate, and a protrusion is formed outward along a surface in a thickness direction of the light guide plate, so that the cross-section of the light guide plate in the thickness direction forms a stepped profile. The protrusion is located below the upper edge, so that the protrusion is confined between the free end and the back plate. The light source is mounted on the back frame and faces a surface of the light guide plate in the thickness direction. The optical film is positioned on the upper surface of the light guide plate.

[0005] Preferably, a reflective sheet is provided between the lower surface of the light guide plate and the back plate.

[0006] Preferably, the reflective sheet is larger than the upper surface of the light guide plate.

[0007] Preferably, the upper surface of the light guide plate is an upper surface that is higher than the upper edge.

[0008] Preferably, a buffer is fitted on the free end of the upper edge.

[0009] Preferably, the upper surface of the light guide plate has a protrusion to match a groove of the optical film, the protrusion being adjacent to the light source relative to the convex strip.

[0010] Preferably, the groove of the optical film has an opening facing another pair of sidewalls of the back frame, which are parallel to the sidewalls.

[0011] Preferably, at least one of the length of the protrusion or the length of the upper edge is shorter than the length of one side of the light guide plate.

[0012] The present invention further provides a display device comprising the aforementioned backlight module, lower cover, and display module. The lower cover has a chamber formed by a bottom surface and an outer wall. The backlight module is mounted in the chamber along a thickness direction of the backlight module, and the top surface of the backlight module is lower than an opening end face of the outer wall. The display module is mounted on the opening end face to close the chamber.

Implementation Method

[0013] The following description is based on the top of the module shown in Figure 4 (i.e., the positive Z-axis direction) to conform to the common understanding of those skilled in the art.

[0014] Please refer to Figures 3 and 4, which illustrate a backlight module 30 installed inside the lower cover 10 of the display device 100. The lower cover 10 has a chamber 15 formed by a bottom surface 11 and an outer wall 12. The backlight module 30 is installed in the chamber 15 along the thickness direction (Z-axis direction) of the backlight module 30. The display module 20 is installed on the open end face of the outer wall 12 of the lower cover 10 to close the chamber 15.

[0015] Please refer to Figures 5 to 7 together. The backlight module 30 includes a back frame 31, a light guide plate 32, a light source 35, and an optical film 36. The back frame 31 has a back plate 311, a pair of sidewalls 312A and 312B, and another pair of sidewalls 316. The pair of sidewalls 312A and 312B and the other pair of sidewalls 316 extend upward (positive Z-axis) from the edge of the back plate 311. As an example, the pair of sidewalls 312A and 312B encapsulate the long side direction of the light guide plate 32, and the other pair of sidewalls 316 encapsulates the short side direction of the light guide plate 32. One of the sidewalls 312A and 312B has an upper edge 313 parallel to the back panel 311. The free end 314 of the upper edge 313 extends from the end of the sidewall 312A away from the back panel 311 toward the interior of the back frame 31 and is located above the back panel 311.

[0016] A light guide plate 32 is disposed above a back plate 311, and an optical film 36 is positioned on the upper surface 313a of the light guide plate 32. The light guide plate 32 has outwardly formed protrusions 325 along its thickness direction, so that the light guide plate 32 forms a stepped profile in its cross-section (i.e., the YZ plane) in the thickness direction. Correspondingly, the lower surface 32b of the light guide plate 32 is larger than the upper surface 32a of the light guide plate 32.

[0017] In this structural design, the light guide plate 32 is first tilted so that the protrusion 325 enters between the free end 314 of the upper edge 313 and the back plate 311. Then, the side of the light guide plate 32 without the protrusion 325 is placed downwards (negative Z-axis direction) so that the light guide plate 32 is placed flat in the back frame 31. In this way, the displacement of the backlight module 30 can be restricted solely through the back plate 311. At the same time, the absence of the upper frame 80 in this structure (as shown in Figure 2) reduces the ineffective area 90 of the display device, allowing the display device to be constructed with a narrow bezel structure.

[0018] In this embodiment, the light source 35 is mounted on the sidewall 312B along the long side of the back frame 31, facing a surface of the light guide plate 32 along its thickness direction. Specifically, the surface of the light guide plate 32 along its thickness direction can be divided into a surface parallel to the YZ plane and a surface parallel to the XZ plane. One of the XZ-plane-parallel surfaces of the light guide plate 32 has a stepped profile and is confined between the free end 314 of the upper edge 313 and the back plate 311. The other XZ-plane-parallel surface of the light guide plate 32 serves as the light incident surface of the light source 35. The light emitting surface of the backlight module 30 is parallel to the XY plane. However, in other embodiments, the light source 35 may also be mounted on the sidewall 316 along the short side of the back frame 31, facing a surface of the light guide plate 32 parallel to the YZ plane.

[0019] The optical film 36 and the light guide plate 32 can be positioned by bonding the lower surface of the optical film 36 to the upper surface 32a of the light guide plate 32 with optical adhesive. Alternatively, the upper surface 32a of the light guide plate 32 can be provided with a positioning structure to limit the optical film 36 and position it on the upper surface of the light guide plate 32. In this embodiment, the upper surface 32a of the light guide plate 32 has a protrusion 321 to match a groove 361 of the optical film 36, and the protrusion 321 is adjacent to the light source 35 relative to the protrusion 325. The groove 361 of the optical film 36 has an opening facing the other sidewalls 316 of the back frame.

[0020] In this embodiment, there is a gap between the upper surface 36a of the optical film 36 and the rear side of the display module 20 to ensure sufficient light mixing.

[0021] Under the premise of using a side-lit light source, a reflector 37 can also be provided between the lower surface 32b of the light guide plate 32 and the back plate 311 to project the light inside the light guide plate 32 onto the optical film 36, and then project it toward the rear side of the display module 20.

[0022] Furthermore, corresponding to the structure of the light guide plate 32, the size of the reflective sheet 37 can be larger than the upper surface 32a of the light guide plate 32 and equal to the lower surface 32b of the light guide plate 32. Even, in other embodiments, it can be larger than the lower surface 32b of the light guide plate 32.

[0023] It is worth mentioning that the upper edge 313 can be as low as possible, reserving the space above the upper edge 313 for the remaining mounting components. In this embodiment, the upper surface 32a of the light guide plate 32 is used to support the optical film 36, and the upper surface 32a of the light guide plate 32 is higher than the upper surface 313a of the upper edge 313, so that the optical film 36 is completely located above the upper edge 313. In this embodiment, since the optical film 36 is confined to the upper surface 32a of the light guide plate 32, the positioning of the internal light guiding element (e.g., the optical film 36) can be ensured as long as the light guide plate 32 is confined to the back frame 31.

[0024] Please refer to Figures 7 and 8. Figure 8 illustrates another embodiment of the backlight module. The difference from the embodiment in Figure 7 is that a buffer member 40 is fitted onto the free end 314 of the upper edge 313 in Figure 8. The buffer member 40 faces the concave portion of the surface of the light guide plate 32 in the thickness direction, is located above the protrusion 325, or further presses against the surface of the protrusion 325 to prevent the light guide plate 32 from vibrating or producing abnormal noise due to impact. It is worth mentioning that the upper surface of the buffer member 40 can be designed not to be higher than the upper surface 32a of the light guide plate 32.

[0025] In the embodiment shown in FIG5, the protrusion 325 of the light guide plate 32 and the upper edge 313 of the sidewall 312A both extend from one end to the other along the long side direction of the light guide plate 32. However, based on the design concept of this embodiment, the length of the protrusion 325 may be shorter than the length of the long side direction of the light guide plate.

[0026] Please refer to Figure 9. In the embodiment shown in Figure 9, there may be two protrusions 325. These protrusions 325 are located along the long side and are close to the two ends of the other pair of sidewalls 316. The number and length of the protrusions 325 can be adjusted according to the stability of the installation. Correspondingly, a portion of the sidewall 312A is folded inward to form an upper edge 313, which covers part of the protrusions 325. This structure can also achieve a similar effect.

[0027] In this embodiment, the middle portion of the light guide plate 32 is the portion without the protrusion 325. The surface of the middle portion along the thickness direction is substantially flush with and connected to the outermost surface of the protrusion 325. The upper surface of the middle portion is connected to the upper surface 32a of the light guide plate 32. That is, the cross-section of this portion is rectangular, and the middle portion can also form the light-emitting surface of the backlight module 30. In other embodiments, the upper edge 313 of the sidewall 312A can also completely cover the protrusion 325 of the light guide plate 32.

[0028] Please refer to Figure 10, which illustrates another embodiment of the back frame of the backlight module. The back frame 31 has a back plate 311, a pair of sidewalls 312A, 312B, and another pair of sidewalls 316. The pair of sidewalls 312A, 312B and the other pair of sidewalls 316 extend upward (in the positive Z-axis direction) from the edge of the back plate 311, and the end faces of the pair of sidewalls 312A, 312B and the other pair of sidewalls 316 are at the same height. The pair of sidewalls 312A, 312B encapsulate the long side direction of the light guide plate 32, and the other pair of sidewalls 316 encapsulates the short side direction of the light guide plate 32.

[0029] By stamping, a tongue plate is formed on the wall surface of the side wall 312A. Then, the tongue plate is folded inward to form an upper edge 313 and cover the protrusion 325. This structure can also achieve a similar effect. With such a structure, a reflective sheet can also be installed on the inner side of the side wall 312A to cover the hollow part of the side wall 312A caused by the folding of the tongue plate, so that the light source is concentrated towards the light-emitting surface of the backlight module 30. [Simplified Explanation of the Diagram]

[0030] Figure 1 is a schematic diagram of the appearance of the display device.

[0031] Figure 2 is a cross-sectional schematic diagram of the display device.

[0032] Figure 3 is a schematic diagram of the appearance of the display device.

[0033] Figure 4 is a cross-sectional schematic diagram of the embodiment of Figure 3.

[0034] Figure 5 is an exploded view of the components of the backlight module in the embodiment of Figure 3.

[0035] Figure 6 is a partial enlarged view of Figure 5.

[0036] Figure 7 is a cross-sectional schematic diagram of the backlight module of the embodiment shown in Figure 3.

[0037] Figure 8 is a cross-sectional schematic diagram of another embodiment of the backlight module.

[0038] Figure 9 is a schematic diagram of some components of a backlight module in another embodiment.

[0039] Figure 10 is a schematic diagram of the back frame of another embodiment of the backlight module.

Claims

1. A backlight module, installed inside a lower cover of a display device, comprising: a back frame having a back plate and a side wall extending upward from an edge of the back plate, the side wall having an upper edge, a free end of the upper edge extending from an end of the side wall away from the back plate toward the interior of the back frame; a light guide plate disposed above the back plate, the light guide plate having a protrusion formed outwardly along a surface in a thickness direction such that the light guide plate forms a stepped profile in a cross-section in the thickness direction, the protrusion being located below the upper edge and confined between the free end and the back plate; a light source mounted on the back frame and facing the surface of the light guide plate in the thickness direction; and an optical film positioned on an upper surface of the light guide plate; wherein... The upper surface of the light guide plate is higher than the upper edge.

2. The backlight module as described in claim 1, wherein a reflective sheet is provided between the lower surface of the light guide plate and the back plate.

3. The backlight module as described in claim 2, wherein the reflector is larger than the upper surface of the light guide plate.

4. The backlight module as described in claim 1, wherein a buffer is fitted at the free end of the upper edge, and the protrusion is limited between the buffer and the back plate.

5. The backlight module as claimed in claim 1, wherein the upper surface of the light guide plate has a protrusion to match a groove of the optical film, the protrusion being adjacent to the light source relative to the ridge.

6. The backlight module as claimed in claim 5, wherein the groove of the optical film has an opening facing another pair of sidewalls of the back frame, the other pair of sidewalls being parallel to the sidewalls.

7. The backlight module as claimed in claim 1, wherein at least one of the length of the protrusion or the length of the upper edge is shorter than the length of one side of the light guide plate.

8. A display device comprising: a backlight module as claimed in any one of claims 1 to 7; a cover having a bottom surface and an outer wall forming a chamber, the backlight module being disposed in the chamber along a thickness direction of the backlight module, the top surface of the backlight module being lower than an open end face of the outer wall; and a display module mounted on the open end face to close the chamber.

9. The display device as claimed in claim 8, wherein the backlight module does not include a top frame pressing against the uppermost surface of the backlight module.

Images