Backlight module and display device

A backlight module includes an optical plate, a light source, and at least one optical film. The optical plate includes a light-emitting surface, a bottom surface and a side surface. The light source faces to the bottom surface or the side surface. The optical film is disposed above the light-emitting surface and includes a main body and at least one refractive part disposed on an end surface of the main body. The refractive part has a plurality of microstructures. The refractive part has non-uniform thickness relative to the end surface along a side direction. A refractive index of the refractive part is different from a refractive index of the main body, such that a plurality of light rays are deflected toward different directions after passing through the refractive part.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates to a backlight module and a display device, and more particularly, to a backlight module capable of avoiding forming bright lines in an edge area thereof and a display device having the same.

2. Description of the Prior Art

With the advancement of science and technology, electronics with liquid crystal display devices, such as cell phones, tablets, laptops, etc., have become indispensable items in modern life. Since the liquid crystal itself does not emit light, the liquid crystal display device requires a backlight module to provide light source.

Please refer toFIG. 1, which is a cross-sectional view showing a conventional backlight module1. The light source3cannot be seen in this view angle. Herein, the light source3is drawn in dotted line for showing the relative positions of the light source3and the optical plate2. The backlight module1includes an optical plate2, a light source3, at least one optical film5and an outer frame6. Herein, the light source3is a LED light bar which includes a plurality of LEDs4. Most of the light rays emitted from the LEDs are guided by the optical plate2to uniformly emit from a light-emitting surface S1of the optical plate2. However, a few light rays, such as the light ray L0, emit from a side surface S2of the optical plate2and are reflected by the outer frame6to pass through the optical film5from an end surface S3of the optical film5to a surface S4of the optical film5. As a result, a bright line is formed in an edge area E of the optical film5, and the image quality of the liquid crystal display device is affected thereby.

SUMMARY OF THE INVENTION

According to an embodiment of the present disclosure, a backlight module includes an optical plate, a light source and at least one optical film. The optical plate includes a light-emitting surface, a bottom surface and a side surface. The bottom surface is opposite to the light-emitting surface. The side surface is connected between the light-emitting surface and the bottom surface. The light source faces to the bottom surface or the side surface of the optical plate. The optical film is disposed above the light-emitting surface and includes a main body and at least one refractive part. The main body includes a first surface, a second surface and at least one end surface. The second surface is opposite to the first surface. The end surface is connected between the first surface and the second surface. The refractive part is disposed on the end surface and includes a plurality of microstructures. The refractive part has non-uniform thickness relative to the end surface along a side direction. A refractive index of the refractive part is different from a refractive index of the main body, such that a plurality of light rays are deflected toward different directions after passing through the refractive part.

According to another embodiment of the present disclosure, a display device includes the aforementioned backlight module and a display panel. The display panel is disposed above the backlight module.

DETAILED DESCRIPTION

In the following detailed description of the embodiments, reference is made to the accompanying drawings which form a part thereof, and in which is shown by way of illustration specific embodiments in which the disclosure may be practiced. In this regard, directional terminology, such as up, down, left, right, front, back, bottom, top, etc., is used with reference to the orientation of the Figure(s) being described. As such, the directional terminology is used for purposes of illustration and is in no way limiting. In addition, identical numeral references or similar numeral references are used for identical elements or similar elements in the following embodiments.

According to the present disclosure, when two elements are substantially parallel, it refers that an angle is between the two elements, and the angle is 0±10 degrees. Preferably, the angle is 0±5 degrees. More preferably, the angle is 0±3 degrees. Alternatively, the angle is 180±10 degrees. Preferably, the angle is 180±5 degrees. More preferably, the angle is 180±3 degrees.

According to the present disclosure, a backlight module can be used to provide light source for the liquid crystal display (LCD) panel. Each element of the backlight module includes a bottom surface and a top surface. The bottom surface and the top surface are defined based on the LCD panel. A surface of each element away from the LCD panel is defined as the bottom surface, and a surface of each element facing toward the LCD panel is defined as the top surface. Moreover, when an element is disposed above another element, it refers that the element is disposed on a top surface of the another element or disposed above the top surface of the another element.

Please refer toFIG. 2, which is an exploded schematic diagram showing a side view of a display device10according to one embodiment of the present disclosure. The display device10includes a backlight module30and a display panel20. The display panel20is disposed above the backlight module30. The backlight module30is used to provide light rays for the display panel20. The display panel20can be a LCD panel.

The backlight module30includes an optical plate100, a light source200and at least one optical film300. The optical plate100includes a light-emitting surface110, a bottom surface120and a side surface130. The bottom surface120is opposite to the light-emitting surface110. The side surface130is connected between the light-emitting surface110and the bottom surface120.

The light source200can face to the bottom surface120or the side surface130of the optical plate100. Specifically, the light source200can be disposed under the bottom surface120or adjacent to the side surface130of the optical plate100. That is, the backlight module30can be a direct-type backlight module or a side-type backlight module. Herein, the light source200is exemplarily disposed adjacent to the side surface130of the optical plate100, and thus the backlight module30is exemplarily a side-type backlight module. The light source200can be, but is not limited to, a cold cathode fluorescent lamp (CCFL) or a LED light bar. Herein, the light source200is exemplarily a LED light bar which includes a plurality of LEDs210.

The optical film300is disposed above the light-emitting surface110of the optical plate100. The optical film300includes a main body310and at least one refractive part320. Please also refer toFIG. 6, which is a three-dimensional exploded diagram showing the backlight module30inFIG. 2. The main body310includes a first surface311, a second surface312, a first end surface313, a second end surface314, a third end surface315and a fourth end surface316. The second surface312is opposite to the first surface311. Each of the first end surface313, the second end surface314, the third end surface315and the fourth end surface316is connected between the first surface311and the second surface312. The first end surface313is opposite to the third end surface315. The second end surface314is opposite to the fourth end surface316and is connected between the first end surface313and the third end surface315. The first end surface313faces toward the light source200. Herein, the number of the refractive part320is one and the refractive part320is disposed on the second end surface314, which is exemplary and the present disclosure is not limited thereto.

Please refer toFIG. 3, which is an enlarged view of a portion A inFIG. 2. To clearly illustrate, the directions inFIG. 3are based on an XYZ rectangular coordinate system, wherein the X direction is perpendicular to and pointing out of the plane of the paper. In the main body310of the optical film300, the first surface311is parallel to the XY-plane, and the second end surface314is parallel to the XZ-plane. In the embodiment, the refractive part320includes a plurality of microstructures321. The microstructures321are stacked from the second end surface314as a datum level and are stacked along a side direction D1away from the second end surface314, wherein the side direction D1is parallel to the Y direction. The refractive part320has non-uniform thickness (i.e., the left end points of the refractive part320have different Y coordinates) relative to the second end surface314along the side direction D1. For example, the thickness T1is different from the thickness T2. Further, a refractive index of the refractive part320is different from a refractive index of the main body310, such that a plurality of light rays, such as light rays L1, L2and L3, are deflected toward different directions after passing through the refractive part320. For example, the structure that the refractive part320has non-uniform thickness relative to the second end surface314along the side direction D1can be achieved by stacking the microstructures321with substantially identical size or different sizes.

InFIG. 3, the microstructures321have substantially identical size. With the stacking method of the microstructures321, the microstructures321are located at different heights to allow the refractive part320to have non-uniform thickness relative to the second end surface314along the side direction D1, such as the unequal thicknesses T1and T2. Herein, a direction of the height is parallel to the Y direction. As such, the plurality of light rays have different light paths in the refractive part320due to non-uniform thickness, which is favorable for the plurality of light rays to emit out the refractive part320at different positions. Taking the light rays L1and L2as an example, the light path of the light ray L1in the refractive part320is the straight-line distance from the point P1to the point P2, and the light path of the light ray L2in the refractive part320is the straight-line distance from the point P3to the point P4. The light path of the light ray L2in the refractive part320is longer than that of the light ray L1in the refractive part320. Moreover, compared with the optical film without the refractive part320(not shown), the number of deflections of the light rays can be increased when the light rays pass through both the refractive part320and the main body310, which can owe to the refractive indices of the refractive part320and the main body310being different. Taking the light ray L2as an example, the first deflection occurs when the light ray L2travels from the air to the refractive part320at the point P3, the second deflection occurs when the light ray L2travels from the refractive part320to the main body310at the point P4, and the third deflection occurs when the light ray L2travels from the main body310to the air at the point P5. As a comparison, when the optical film is not disposed with the refractive part320, the first deflection occurs when the light ray L2travels from the air to the main body310, and the second deflection occurs when the light ray L2travels from the main body310to the air. Therefore, with the refractive part320and the main body310having different refractive indices, the number of deflections of the light rays can be increased, which can disperse a light ray into a plurality of light rays that emit out at different positions of the main body310. Accordingly, the bright line generated by the light rays emitting out at the same position can be avoided, and the effect of softening the light rays can be achieved. As such, the image quality of the display device10can be enhanced, and it is beneficial to configure the display device10as a narrow border display device.

Please refer toFIG. 4, which is an enlarged view of the portion A inFIG. 2according to another embodiment of the present disclosure. Similar toFIG. 3, the directions inFIG. 4are based on the XYZ rectangular coordinate system. Compared toFIG. 3, the plurality of microstructures321have different sizes in the embodiment. For example, the plurality of microstructures321have at least two sizes. Taking the microstructures321being ball-shaped and having different sizes as an example, the curvature of the spherical surface allows the plurality of light rays, such as the light rays L4, L5and L6, to be deflected toward different directions after passing through the refractive part320.

As shown inFIG. 4, the microstructures321have different sizes, and the microstructures321are stacked from the second end surface314(i.e., XZ-plane) as a datum level along the side direction D1away from the second end surface314to allow the refractive part320to have non-uniform thickness relative to the second end surface314along the side direction D1, such as the unequal thicknesses T3and T4. As such, the plurality of light rays have different light paths in the refractive part320. For example, the light path of the light ray L5in the refractive part320is longer than the light path of the light ray L4in the refractive part320. Accordingly, it is favorable for the plurality of light rays to emit out the refractive part320at different positions. Moreover, with the refractive part320and the main body310having different refractive indices, when the light rays pass through both the refractive part320and main body310, the number of deflections of the light rays can be increased. For details ofFIG. 4, references can be made to the related description ofFIG. 3. Moreover, the microstructures321with different sizes can also have different refractive indices, which can enhance the random degree of the deflections of the light rays. Accordingly, the bright line generated by the light rays emitting out at the same position can be avoided, and the effect of softening the light rays can be achieved. InFIG. 4, the thickness of the refractive part320along the side direction D1can also be adjusted by changing the stacking method of the microstructures321. In the embodiment, the refractive index of the main body310can be 1 to 3, and the refractive index of the refractive part320can be 1 to 3. In summary, with the microstructures321having different sizes or having identical size but being stacked by different methods, the refractive part320is allowed to have non-uniform thickness on the XZ-plane, so as to increase the number of deflections of the light rays. Accordingly, the bright line generated by the light rays emitting out at the same position can be avoided, and the effect of softening the light rays can be achieved.

As shown inFIGS. 3 and 4, the refractive part320can further include a substrate322, the microstructures321are distributed in the substrate322. The substrate322can be an adhesive to adhere the microstructures321on the second end surface314. However, it is only exemplary, and the present disclosure is not limited thereto. In other embodiment, the substrate322can be omitted, and the microstructures321can be attached on the second end surface314directly. Moreover, a refractive index of the substrate322can be the same as or different from that of the microstructures321. When the refractive indices of the substrate322and the microstructures321are different, it is favorable for increasing the number of the deflections of the light rays. As such, the effect of dispersing the light rays can be enhanced. Taking the light ray L3shown inFIG. 3as an example, the first deflection occurs when the light ray L3travels from the air to the microstructures321at the point P6, the second deflection occurs when the light ray L3travels from the microstructures321to the substrate322at the point P7, the third deflection occurs when the light ray L3travels from the substrate322to the microstructures321at the point P8, the fourth deflection occurs when the light ray L3travels from the microstructures321to the main body310at the point P9, and the fifth deflection occurs when the light ray L3travels from the main body310to the air at the point P10. Similarly, as shown inFIG. 4, the light ray L6passes through the substrate322, but the light rays L4and L5do not pass through the substrate322. As a result, the number of the deflections of the light rays L6is more than that of the light rays L4and L5.

The microstructures321have light transmitting property. The microstructures321can be made of TiO2, SiO2, Ta2O5, poly(methyl methacrylate) (PMMA) or a combination thereof. The microstructures321can be microparticles, nanoparticles or a combination thereof. For example, the size of the microstructures321can be, but is not limited to, 0.1 μm to 20 μm. The shape of the microstructures321is exemplarily ball-shaped. The normal direction of each of the points on the spherical surface varies along the spherical surface, which is favorable for changing the travel directions of the plurality of light rays. Taking the light rays L1and L2shown inFIG. 3as an example, the travel directions of the light rays L1and L2are substantially parallel to each other before entering into the refractive part320. Because the positions where the light rays L1and L2entering into the microstructures321are different (i.e., the position of the point P1on the spherical surface is different from the position of the point P3on the spherical surface), the incident angles of the light ray L1and L2into the microstructures321are different, which affects the subsequent deflection angles thereof. In other embodiment, the microstructures321can be polyhedral structures, such as cubes, cuboids, etc. Different normal directions can be provided by different planes. As such, different incident angles can be formed when a plurality of light rays parallel to each other project on the different planes. It is also beneficial to change the travel directions of the plurality of light rays. Herein, the microstructures321are solid particles. However, the present disclosure is not limited thereto. For example, in other embodiments, the microstructures321can be hollow particles, composite particles or a combination thereof. Each of the hollow particles (not shown) can include a hollow portion (the refractive index of air equals to 1) and a shell portion (the refractive index thereof is greater than 1). The shell portion can be made of TiO2, SiO2, Ta2O5, resin (such as PMMA) or a combination thereof. Each of the composite particles (not shown) can be, but is not limited to, a core-shell structure. The core-shell structure can include a core portion and a shell portion. The core portion can be made of TiO2, SiO2or Ta2O5, and the shell portion can be made of resin, such as PMMA. Alternatively, the core portion and the shell portion can be made of different resins. As such, each of the microstructures321can provide two different refractive indices, the effect of dispersing the light rays can be enhanced thereby.

Please refer toFIG. 7, which is a cross-sectional view showing a display device10′ according to another embodiment of the present disclosure. The light source200cannot be seen in this view angle. Herein, the light source200is drawn in dotted line for showing the relative positions of the light source200and the optical plate100. Compared with the display device10inFIG. 2, the backlight module30′ further includes a frame400. The frame400includes a back plate410and a lateral wall420. The lateral wall420surrounds the back plate410. The optical plate100, the light source200and the optical film300are carried by the back plate410. A top424of the lateral wall420is configured to carry the display panel20, and a top surface T of the optical film300is not shielded by the lateral wall420. In other words, the display device10′ is a display device without plastic frame. The number of deflections of the light rays reflected by the frame400can be increased via passing through the refractive part320. As such, the bright line generated by the light rays concentrated at the same position can be avoided. Accordingly, it is not required to use the lateral wall420to shield the top surface T of the optical film300to cover the bright line, and the display device10′ can be configured as a display device without plastic frame.

InFIG. 7, an inner surface423of the lateral wall420includes a first area421and a second area422. For clearly distinguishing the first area421and the second area422, the first area421and the second area422are sprinkled with different dots. The first area421is corresponding to the optical film300, and the second area422is corresponding to the optical plate100. A surface roughness of the first area421can be greater than a surface roughness of the second area422, and/or a reflectivity of the first area421can be smaller than a reflectivity of the second area422. Specifically, when the first area421is arranged with a smaller reflectivity, it can ensure that less light rays are reflected by the first area421to the optical film300; when the first area421is arranged with a greater roughness, it can provide the light rays reflected by the first area421a higher random degree of reflection directions. As such, it can ensure that the inner surface423of the lateral wall420is able to reflect the light rays back to the optical plate100for reuse, while avoiding the light rays from being concentrated at the same position of the optical film300, which can further soften the light rays.

Please referFIGS. 2 and 6. In the embodiment, the optical film300only has a refractive part320disposed on the second end surface314. However, the present disclosure is not limited thereto. In other embodiment, when the light source is also disposed on the side surface of the optical plate and corresponds to the first end surface of the optical film, the backlight module can preferably include two refractive parts disposed on the second end surface and the fourth end surface, respectively. Alternatively, the backlight module can only include one refractive part disposed on the first end surface or the third end surface. Alternatively, the backlight module can include three refractive parts disposed on the second end surface, the third end surface and the fourth end surface, respectively. In other words, the number and/or the position of the refractive part can be adjusted according to practical demands, such as the arrangement of the optical elements in the backlight module or the desired optical properties of the backlight module. Moreover, in the embodiment, the backlight module30includes an optical film300, which is only exemplary. In other embodiment, the backlight module30can include a plurality of optical films, and at least one of the optical films is disposed with the refractive part.

Please refer toFIG. 5, which is a schematic diagram showing an optical film300′ according to another embodiment of the present disclosure. Compared to the optical film300, the refractive part320of the optical film300′ has a first extending portion320aand a second extending portion320b. The first extending portion320aextends from the second end surface314to the first surface311of the main body310, and the second extending portion320bextending from the second end surface314to the second surface312of the main body310. With the arrangement, the light rays (not shown) reflected by the frame can further pass through the first extending portion320aand/or the second extending portion320bafter passing through and deflected by the refractive part320on the second end surface314. It is favorable for increasing the number of deflections of the light rays and enhancing the effect of dispersing the light rays. According to one embodiment, when a length of the first extending portion320aparallel to the side direction D1is M1, the following relationship can be satisfied: 0<M1≤2 mm; when a length of the second extending portion320bparallel to the side direction D1is M2, the following relationship can be satisfied: 0<M2≤2 mm. M1 and M2 can be the same or different. According to another embodiment, the refractive part320can be arranged with one of the first extending portion320aand the second extending portion320bto solve the problem of the bright line resulted from the light rays reflected by other components, such as a upper plastic frame the or a lower optical plate.

Compared to the prior art, the backlight module of the present disclosure includes an optical film disposed with at least one refractive part on at least one end surface thereof, which allows a plurality of light rays deflected toward different directions after passing through the refractive part. The bright line generated by the light rays concentrated at the same position can be avoided, and the effect of softening the light rays can be achieved. Accordingly, the image quality of the display device can be enhanced, and it is beneficial to the application of the display device without plastic frame or the narrow border display device.