Light source module, backlight module and display device

A light source module includes a back plate and light-emitting units. The back plate includes a bottom plate and a sidewall. An included angle is formed between an outer side surface of the sidewall and a horizontal plane where the bottom plate is located, and the included angle is an acute angle. An optical distance is defined between a top end of the sidewall and the horizontal plane. The light-emitting units are arranged in the back plate. The light-emitting units which are closest to the sidewall are defined as target light-emitting units, and each of the target light-emitting units has a radiation angle, and each of the target light-emitting units is separated from the sidewall by a distance. The first horizontal distance is determined by a tangent function of a complementary angle of the radiation angle, the second horizontal distance is determined by a tangent function of the included angle.

BACKGROUND

Field of Invention

The present disclosure relates to a light source module. More particularly, the present disclosure relates to a light source module having improved luminance uniformity and its applications to a backlight module and a display device.

Description of Related Art

Generally, a light source module which is used for a direct type backlight module includes a substrate and plural light-emitting units arranged on the substrate at equal intervals. Light generated by the light-emitting units can be further mixed by an optical film to form a surface light source.

In order to reduce the cost and weight of the overall light source module, usually the number of light-emitting units is reduced. However, if the light-emitting units near a sidewall of a backplate are disposed too far from the sidewall, light generated by the light-emitting unit cannot be efficiently reflected by sidewall of the backplate, which causes dark shadow formed on a light-emitting surface near the edge of the sidewall. On the contrary, if the number of the light-emitting units is increased to solve the problem of dark shadow formed on the edges or corners of the sidewall, this will increase the weight and cost of the overall light source module.

SUMMARY

The invention provides a light source module which has good luminance uniformity, thereby improving the overall optical taste of a backlight module and a display device.

According to the aforementioned object, a light source module is provided. The light source module includes a back plate and plural light-emitting units. The back plate includes a bottom plate and a sidewall standing on the bottom plate, in which an included angle (θslope) is formed between an outer side surface of the sidewall and a horizontal plane where the bottom plate is located, and the included angle is an acute angle, and an optical distance (OD) is defined between a top end of the sidewall and the horizontal plane. The light-emitting units are arranged in the back plate, in which the light-emitting units which are closest to the sidewall are defined as plural target light-emitting units, and each of the target light-emitting units has a radiation angle (θLED), and each of the target light-emitting units is separated from the sidewall by a distance (d). The distance (d) is a difference between a first horizontal distance and a second horizontal distance, and the first horizontal distance is formed between each of the target light-emitting units and a predetermined location of the sidewall, and the second horizontal distance is formed between a bottom edge of the sidewall and the predetermined location of the sidewall. The first horizontal distance is calculated according to a first function F1, and the first function F1 is determined by a tangent function of a complementary angle of the radiation angle (θLED), the second horizontal distance is calculated according to a second function F2, and the second function F2 is determined by a tangent function of the included angle (θslope).

According to an embodiment of the present invention, the aforementioned radiation angle (θLED) is a half viewing angle or a half light-intensity angle of each of the target light-emitting units, and light emitted by each of the target light-emitting units at the radiation angle (θLED) is directed to the predetermined location of the sidewall.

According to an embodiment of the present invention, a portion of a surface of the sidewall which ranges from the predetermined location to a top edge of the sidewall can reflect more than 50% of light generated by each of the target light-emitting units.

According to an embodiment of the present invention, the aforementioned predetermined location is a midpoint of the sidewall or a position lower than the midpoint of the sidewall to which the light emitted by each of the target light-emitting units at half viewing angle or a half light-intensity angle is able to reach.

According to an embodiment of the present invention, the first function F1 is defined by the following equation:

F⁢⁢1=P·(1tan⁡(90⁢°-θLED)).
The second function F2 is defined by the following equation:

F⁢⁢2=P·(1tan⁡(θslope)).
P represents a vertical distance between the horizontal plane and the predetermined location on the sidewall.

According to an embodiment of the present invention, a vertical distance P between the horizontal plane and the predetermined location on the sidewall is greater than or equal to 20% of the optical distance (OD) and is smaller than or equal to 50% of the optical distance (OD).

According to an embodiment of the present invention, the relationship between the included angle (θslope) and the radiation angle (θLED) is defined by an inequality: (90−θLED)<θslope≤90.

According to an embodiment of the present invention, the relationship between the included angle (θslope) and the radiation angle (θLED) is defined by an equation:

According to an embodiment of the present invention, a distance (D) is calculated by subtracting a third horizontal distance from the difference between the first horizontal distance and the second horizontal distance. The third horizontal distance is a distance between a center and an edge of each of the target light-emitting units, wherein the third horizontal distance is calculated according to a third function F3, and the third function F3 is determined by a tangent function of a complementary angle of the radiation angle (θLED).

According to an embodiment of the present invention, the first function F3 is defined by the following equation:

F⁢⁢3=Htan⁡(90⁢°-θLED),
in which H represents a height of each of the target light-emitting units.

According to an embodiment of the present invention, the relationship among the height (H) of each of the target light-emitting units, the optical distance (OD), the included angle (θslope) and the radiation angle (θLED) is defined by an inequality:

According to an embodiment of the present invention, the relationship among the height (H) of each of the target light-emitting units, the optical distance (OD), the included angle (θslope) and the radiation angle (θLED) is defined by an inequality:

According to an embodiment of the present invention, the height (H) of each of the target light-emitting units is in a range from 0.5 mm to 1.5 mm.

According to an embodiment of the present invention, the optical distance (OD) is in a range from 3 mm to 10 mm.

According to the aforementioned object, a backlight module is provided. The backlight module includes a light source module and at least one optical film. The optical film is disposed on the light source module.

According to the aforementioned object, a display device is provided. The display device includes a light source module, at least one optical film and display panel. The optical film is disposed on the light source module. The display panel is disposed on the optical film.

According to the aforementioned embodiments of the present invention, the inclined angle of the sidewall of the back plate of the present disclosure is defined by the radiation angle of each of the light-emitting units. In addition, the first function and the second function are used to calculate the distance between each of the target light-emitting units and the sidewall of the back plate according to light-emitting amount and radiation angle of each of the light-emitting units. Therefore, light generated from the light-emitting units can be efficiently reflected by the sidewall of the back plate and is further emitted upwards, so that the amount of light can meet the requirements for use in the backlight module and the luminance uniformity of an area near the sidewall can be increased.

DETAILED DESCRIPTION

Referring toFIG. 1,FIG. 1is a schematic diagram showing a display device100in accordance with a first embodiment of the present disclosure. The display device100mainly includes a light source module200, at least one optical film300disposed on the light source module200and a display panel400disposed on the optical film300. The light source module200includes a back plate210and plural light-emitting units220. The back plate210includes a bottom plate211and a sidewall212standing on the bottom plate211. The light-emitting units220are arranged in the back plate210. Therefore, light generated by the light-emitting units220can be mixed by the optical film300to form a surface light source so as to emit out from the display panel400. The light-emitting units220which are closest to the sidewall212are defined as target light-emitting units220′ among all the light-emitting units220. After emitting towards the sidewall212, light generated by the target light-emitting units220′ will be reflected by the sidewall212and then emit towards the optical film300. In order to avoid too much or too little of light emitted from the edge of the sidewall212, a distance d between each of the target light-emitting units220′ and a bottom edge of the sidewall212needs to be designed.

In the present embodiment, as shown inFIG. 1, the distance d between each of the target light-emitting units220′ and the bottom edge of the sidewall212is a difference between a first horizontal distance d1 and a second horizontal distance d2. The first horizontal distance d1 is a horizontal distance between each of the target light-emitting units220′ and a predetermined location A1 of the sidewall212. The second horizontal distance d2 is a horizontal distance between the bottom edge of the sidewall212and the predetermined location A1 of the sidewall212. In the present embodiment, the predetermined location A1 can be determined by a reflection amount of light emitted by each light-emitting unit, a half viewing angle of each light-emitting unit, or a half light-intensity angle of each light-emitting unit. The “predetermined location A1” as referred herein refers to any positions on an inclined surface of the sidewall212, and light emitted towards the predetermined location A1 can be reflected by the sidewall212to be emitted from a position near a top edge of the sidewall212. Therefore, the distance d of each of the target light-emitting units220′ and the bottom edge of sidewall212is designed to direct the light generated by each of the target light-emitting units220′ to the predetermined location A1. For example, the back plate210have a function of supporting components which are used in the light-emitting units220and the light source module200, and the sidewall212of the back plate210has the function of reflecting light. Therefore, In order to improve the luminous efficiency of the overall display device, the top edge of the sidewall212is taken as a reference, and a portion of the surface of the sidewall212near the predetermined location A1 to the top edge of the sidewall212can reflect at least 50% (preferably more than 90%) of light generated by the light-emitting units220to emit upwards. Accordingly, the predetermined location A1 referred in the present disclosure can be defined as long as the required amount of reflection light can be achieved. On the other hand, in terms of utilization efficiency of the light emitted by light-emitting units, light emitted by the light-emitting units at the half viewing angles or the half light-intensity angles can be directed to the midpoint of the sidewall212or a position below the midpoint of the sidewall212, and is further emitted upwards.

In some embodiments, the first horizontal distance d1 is calculated according to a first function F1, and the second horizontal distance d2 is calculated according to a second function F2. The first function F1 is determined by a tangent function of a complementary angle of a radiation angle (θLED) of each of the target light-emitting units220′. In one example, the first function F1 is defined by the following equation (1):

wherein “P” represents a vertical distance P between a horizontal plane HP where the bottom plate211is located and the predetermined location A1 on the sidewall212; θLEDrepresents the half viewing angle or the half light-intensity angle of each of the target light-emitting units220′. In the present embodiments, light emitted by the target light-emitting units220′ at the radiation angle θLEDcan emit to the predetermined location A1 of the sidewall212.

In the present embodiment, there is an included angle θslopeformed between an outer side surface of the sidewall and the horizontal plane HP where the bottom plate211is located, and the included angle θslopeis an acute angle. In the present embodiment, and the second function F2 is determined by a tangent function of the included angle θslope. In one example, the second function F2 is defined by the following equation (2):

On the condition that the included angle θslopebetween the sidewall212and the horizontal plane HP, the vertical distance P between the horizontal plane HP and the predetermined location A1 of the sidewall212, and the radiation angle θLEDof each of the target light-emitting units220′ are known, the distance d between each of the target light-emitting units220′ and the bottom edge of sidewall212can be obtained by calculating the difference between the equation (1) and the equation (2).

As shown inFIG. 1, an optical distance OD is formed between a top end of the sidewall212and the horizontal plane HP where the bottom plate211is located. The optical distance OD as referred herein refers to a light-mixing distance of the light-emitting units220. In some embodiments, the vertical distance P in the first function F1 and the second function F2 is greater than or equal to 20% of the optical distance OD and is smaller than or equal to 50% of the optical distance OD. For example, the distance between each of the target light-emitting units220′ and the bottom edge of sidewall212can be determined by reflection amount of light emitted by each of the target light-emitting units, so that light emitted by the light-emitting units at the half viewing angle or the half light-intensity angle can be directed to the predetermined location A1 and further emit upwards. Therefore, light emitted by the light-emitting units should be directed to the midpoint of the sidewall212or the position below the midpoint of the sidewall212. In other words, when the bottom edge of the sidewall212is taken as a reference, the vertical distance P is designed to be 20%-50% of the optical distance OD so as to direct the light emitted by the light-emitting units to sidewall212.

Simultaneously referring toFIG. 1,FIG. 2AandFIG. 2B,FIG. 2Ais a diagram showing a simulation of optical trends for a light source module in accordance with the first embodiment of the present disclosure, andFIG. 2Bis a reference curve showing a relationship between luminance of light generated according to the first embodiment and X-axis positions. It is noted that, the original photos of the optical trends simulation shown in this disclosure (for example,FIG. 2A,FIG. 4A, andFIG. 5A) are color images. When the optical trends simulation diagrams are presented in a grayscale, gray level from lighter to darker regions represents value variation of the optical trends from a small value to large value. In the first embodiment, the optical distance OD is 10 mm, the vertical distance P is 20% of the optical distance OD, the distance d between each of the target light-emitting units220′ and the bottom edge of the sidewall212is 1.4 mm. It can be seen from the graph inFIG. 2Bthat the luminance emitted from the light source module200near the center of the back plate210is smaller than the luminance emitted from the light source module200near the sidewall212of the back plate210. In addition, the curve of brightness inFIG. 2Bis a relatively smooth curve, which meets the requirements of common backlight modules.

Simultaneously referring toFIG. 1,FIG. 3AandFIG. 3B,FIG. 3Ais a diagram showing a simulation of optical trends for a light source module in accordance with a second embodiment of the present disclosure, andFIG. 3Bis a reference curve showing a relationship between luminance of light generated according to the second embodiment and X-axis positions. In the second embodiment, the optical distance OD is 10 mm, the vertical distance P is 50% of the optical distance OD, and the distance d between each of the target light-emitting units220′ and the bottom edge of the sidewall212is 4.9 mm. It can be seen from the graph inFIG. 3Bthat the luminance emitted from the light source module200near the center of the back plate210is smaller than the luminance emitted from the light source module200near the sidewall212of the back plate210. In addition, the curve of brightness inFIG. 3Bis a relatively smooth curve, which meets the requirements of common backlight modules.

Simultaneously referring toFIG. 1,FIG. 4AandFIG. 4B,FIG. 4Ais a diagram showing a simulation of for a light source module in accordance with a first comparative example, andFIG. 4Bis a reference curve showing a relationship between luminance of light generated according to the first comparative example and X-axis positions. In the first comparative example, the optical distance OD is 10 mm and the vertical distance P is 10% of the optical distance OD, the distance d between each of the target light-emitting units220′ and the bottom edge of the sidewall212is 0.3 mm. However, the curve of brightness inFIG. 4Bshows that the luminance emitted from the light source module200near the sidewall212is particularly high, and does not meet the requirements of common backlight modules.

Simultaneously referring toFIG. 1,FIG. 5AandFIG. 5B,FIG. 5Ais a diagram showing a simulation of optical trends for a light source module in accordance with a second comparative example, andFIG. 5Bis a reference curve showing a relationship between luminance of light generated according to the second comparative example and X-axis positions. In the second comparative example, the optical distance OD is 10 mm and the vertical distance P is 80% of the optical distance OD, the distance d between each of the target light-emitting units220′ and the bottom edge of the sidewall212is 6.1 mm. However, the curve of brightness inFIG. 5Bshows that the luminance emitted from the light source module200near the sidewall212is particularly low, and does not meet the requirements of common backlight modules. Accordingly, by designing the vertical distance P of light-emitting units220from the predetermined location A1 to the bottom edge of the sidewall212to be greater than or equal to 20% of the optical distance OD and to be smaller than or equal to 50% of the optical distance OD, the light source module has improved luminance uniformity. In some examples, the optical distance OD is in a range from 3 mm to 10 mm.

Referring toFIG. 1again, in one embodiment, the included angle θslopeis formed between the sidewall212and the horizontal plane HP. The relationship between the included angle θslopeand the radiation angle θLEDof each of the target light-emitting units220′ can be defined by an equation (3) or an equation (4):

Therefore, on the condition that the radiation angle θLEDis known, the included angle θslopeof the sidewall212can be calculated by using the equation (3) and the equation (4).

It is noted that, it is assumed that the light-emitting units220in the light source module200shown inFIG. 1are point light sources, so there is no need to consider the heights of the light-emitting units220. In other embodiments, light-emitting units having heights also can be applied to the light source module. Referring toFIG. 6,FIG. 6is a schematic diagram showing a display device500in accordance with a second embodiment of the present disclosure. The structure of the display device500shown inFIG. 6is similar to that of the display device100shown inFIG. 1, and the main difference therebetween is that a light source module600of the display device500has different designs. The light source module600shown inFIG. 6mainly includes a back plate610and plural light-emitting units620. The back plate610includes a bottom plate611and a sidewall612standing on the bottom plate611, and the light-emitting units620are arranged in the back plate610. Therefore, light generated by the light-emitting units620can be mixed by the optical film300to form a surface light source to emit out from the display panel400. The light-emitting units620which are closest to the sidewall612are defined as target light-emitting units620′ among the light-emitting units620. There is a distance D between each of the target light-emitting units620′ and a bottom edge of the sidewall612.

As shown inFIG. 6, in the present embodiment, the distance D is calculated by subtracting a third horizontal distance D3 from a difference between the first horizontal distance D1 and the second horizontal distance D2. The first horizontal distance D1 is a horizontal distance between each of the target light-emitting units620′ and a predetermined location A1 on the sidewall612. The second horizontal distance D2 is a horizontal distance between the bottom edge of the sidewall612and the predetermined location A1 on the sidewall612. The third horizontal distance D3 is a distance between a center and a side edge of each of the target light-emitting units620′. In other words, in a case of each of the light-emitting units620′ having a height H, the height H of each of the light-emitting units620′ has to be considered while calculating the distance D between each of the target light-emitting units620′ and the bottom edge of the sidewall212. In one embodiment, the first horizontal distance D1 is calculated according to the aforementioned first function F1, and the first function F1 is defined by the aforementioned equation (1). In addition, the second horizontal distance D2 is calculated according to the aforementioned first function F2, and the first function F2 is defined by the aforementioned equation (2). In the equation (1), “P” represents a vertical distance P between a horizontal plane HP where the bottom plate611is located and the predetermined location A1 of the sidewall612, and “θLED” represents a radiation angle of each of the target light-emitting units620′, for example, the half viewing angle or the half light-intensity angle of each of the target light-emitting units620′. In the equation (2), “θslope” represents an included angle formed between an outer side surface of the sidewall612and the horizontal plane HP where the bottom plate611is located.

As shown inFIG. 6, the third horizontal distance D3 is a distance between the center and the side edge of each of the target light-emitting units620′. In one example, the third horizontal distance D3 is half the width of each of the target light-emitting units620′. The third horizontal distance D3 is calculated according to a third function F3. The third function F3 is determined by a tangent function of a complementary angle of a radiation angle θLEDof each of the target light-emitting units620′. In one example, the third function F3 is defined by the following equation (5):

wherein “H” in the equation (5) represents the height H of each of the target light-emitting units620′. In some embodiments, the height H is in a range from 0.5 mm to 1.5 mm.

As shown inFIG. 6, an optical distance OD is formed between a top end of the sidewall612and the horizontal plane HP where the bottom plate611is located. In some embodiments, the relationship among the height H of each of the target light-emitting units620′, the optical distance between the top end of the sidewall612and the horizontal plane HP where the bottom plate611, the included angle θslopebetween the outer side surface of the sidewall612and the horizontal plane HP where the bottom plate611is located, and the radiation angle θLEDof each of the target light-emitting units620′ can be defined by an inequality (6) or an inequality (7):

Simultaneously referring to Table 1 andFIG. 6, Table 1 shows the relationship between the optical distance OD and the distance D which is formed between each of the target light-emitting units620′ and the bottom edge of sidewall612when the radiation angle θLEDof each of the target light-emitting units620′ is 60 degrees, the height H of each of the target light-emitting units620′ is 0.5 mm, the included angle θslopebetween the outer side surface of the sidewall612and the horizontal plane HP is 60 degrees.

Simultaneously referring to Table 2 andFIG. 6, Table 2 shows the relationship between the optical distance OD and the distance D which is formed between each of the target light-emitting units620′ and the bottom edge of sidewall612when the radiation angle θLEDof each of the target light-emitting units620′ is 60 degrees, the height H of each of the target light-emitting units620′ is 0.2 mm, the included angle θslopebetween the outer side surface of the sidewall612and the horizontal plane HP is 60 degrees.

Simultaneously referring to Table 3 andFIG. 6, Table 3 shows the relationship between the optical distance OD and the distance D which is formed between each of the target light-emitting units620′ and the bottom edge of sidewall612when the radiation angle θLEDof each of the target light-emitting units620′ is 75 degrees, the height H of each of the target light-emitting units620′ is 0.5 mm, the included angle θslopebetween the outer side surface of the sidewall612and the horizontal plane HP is 52.5 degrees.

Simultaneously referring to Table 4 andFIG. 6, Table 4 shows the relationship between the optical distance OD and the distance D which is formed between each of the target light-emitting units620′ and the bottom edge of sidewall612when the radiation angle θLEDof each of the target light-emitting units620′ is 75 degrees, the height H of each of the target light-emitting units620′ is 1 mm, the included angle θslopebetween the outer side surface of the sidewall612and the horizontal plane HP is 52.5 degrees.

From Tables 1-4, on the condition that the included angle θslopebetween the sidewall612and the horizontal plane HP, the radiation angle θLEDof each of the target light-emitting units620′, the height H of each of the target light-emitting units620′ and the optical distance OD between the top end of the sidewall612and the horizontal plane HP where the bottom plate611is located are known, the distance D between each of the target light-emitting units620′ and the bottom edge of the sidewall612can be calculated by using the equation (1), equation (2) and the equation (5).

According to the aforementioned embodiments of the present invention, the inclined angle of the sidewall of the back plate of the present disclosure is defined by the radiation angle of each of the light-emitting units. In addition, the first function and the second function are used to calculate the distance between each of the target light-emitting units and the sidewall of the back plate according to light-emitting amount and radiation angle of each of the light-emitting units. Therefore, light generated from the light-emitting units can be efficiently reflected by the sidewall of the back plate and is further emitted upwards, so that the amount of light can meet the requirements for use in the backlight module and the luminance uniformity of an area near the sidewall can be increased.