CN115145072A - Backlight module and display device - Google Patents

Abstract

The invention relates to a backlight module and a display device. The backlight module includes: a light source; the light guide plate is arranged on one side of the light source and is provided with a first optical surface and a second optical surface; the first prism film is provided with a first light inlet surface and a first light outlet surface, the first light outlet surface is provided with a first prism angle, the first prism angle is formed by a first side surface and a second side surface, a first included angle formed by the first side surface and the first light inlet surface is larger than a second included angle formed by the second side surface and the first light inlet surface, and the first included angle and the second included angle are not obtuse angles; the second prism film is provided with a second light-emitting surface and a second light-entering surface, and the second light-emitting surface is provided with a second prism angle; the first light incident surface of the first prism film sheet faces the second optical surface of the light guide plate, and the second light incident surface of the second prism film sheet is opposite to the first prism structure of the first prism film sheet.

Description

Backlight module and display device

Technical Field

The present invention relates to a backlight module and a display device, and more particularly, to a backlight module having a two-layer prism film structure with asymmetric prism angles, which is formed by designing a prism film adjacent to a light guide plate, and a display device using the same.

Background

With the development of semiconductor technology, electronic products play an increasingly important role in human life, and products such as mobile phones, computers, televisions, intelligent watches \8230, and the like have more and more functions and are lighter and thinner in frames. However, energy consumption is required when various functions of electronic products are used, and therefore, how to reduce energy consumption of electronic products is a very important issue. In an electronic product having a display device, a backlight module of the display device often consumes a lot of energy in order to display a picture with sufficient brightness. In some specific electronic products (such as mobile phones, tablet computers, etc.), if the power consumption of the display device is too high, the electronic products are prone to have insufficient endurance.

The traditional side projection type backlight module is designed by applying a two-layer staggered prism Film structure (Cross Bright Enhancement Film, cross BEF) arranged in the light-emitting direction of the light guide plate, and the emitted light can obtain a better brightening effect by utilizing the mutually staggered arrangement of the strip-shaped prism structures in the two layers of prism films. However, in consideration of cost, most of the two prism films are designed in a forward configuration in which the prism angle of the upper layer and the prism angle of the lower layer are symmetrical, and the cross included angle between the extending directions of the two prism films is 90 degrees. However, this architecture is prone to stray light at light exit viewing angles other than-20 to 20 degrees. In another conventional structure, as shown in fig. 1, a configuration is adopted in which the lower film 11 has a symmetric prism angle and the upper film 12 has an asymmetric prism angle, when light enters the lower film 11, a part of interference light is generated, and the part of interference light enters an adjacent prism structure, thereby reducing the overall light-emitting efficiency. In view of the above, it is therefore necessary to redistribute the light incident from the light guide plate to enhance the brightness for a particular viewing angle or angular range.

Disclosure of Invention

The invention aims to provide a backlight module applying two stacked prism diaphragms, wherein the prism diaphragm close to the light-emitting surface of the light guide plate adopts the design of an asymmetric prism angle so as to improve the luminance of the backlight module.

In order to achieve the above object, the present invention provides a backlight module, comprising: a light source; the light guide plate is arranged on one side of the light source and is provided with a first optical surface and a second optical surface which are opposite; the first prism film is provided with a first light inlet surface and a first light outlet surface opposite to the first light inlet surface, a plurality of first prism structures are arranged on the first light outlet surface, each first prism structure is provided with a first prism angle, the first prism angle is formed by a first side surface and a second side surface, a first included angle formed by the first side surface and the first light inlet surface is larger than a second included angle formed by the second side surface and the first light inlet surface, and the first included angle and the second included angle are not obtuse angles; the second prism film is provided with a second light-emitting surface and a second light-entering surface opposite to the second light-emitting surface, the second light-emitting surface is provided with a plurality of second prism structures, and each second prism structure is provided with a second prism angle; the first prism film is arranged on one side of the light guide plate, the first light incident surface of the first prism film faces the second optical surface of the light guide plate, and the second light incident surface of the second prism film is opposite to the first prism structure of the first prism film so as to receive the light from the first light emergent surface.

In some embodiments of the present invention, the second prism angle of the second prism film is formed by two side surfaces, and the two side surfaces respectively form an equal included angle with the second light incident surface.

In some embodiments of the present invention, the second prism angle of the second prism film is 90 degrees.

In some embodiments of the present invention, the first included angle of each of the first prism angles is located closer to the light source than the second included angle.

In some embodiments of the present invention, the first included angle of the first prism film is greater than 45 degrees and less than or equal to 90 degrees.

In some embodiments of the present invention, the second included angle of the first prism film sheet is 45 degrees.

In some embodiments of the present invention, the second prism structures of the second prism film extend along a first direction, the first prism structures of the first prism film extend along a second direction, and an included angle between the first direction and the second direction is in a range of 0 degrees to 50 degrees inclusive.

In some embodiments of the present invention, any two adjacent first prism structures are staggered with respect to the peak height of the first light incident surface.

In some embodiments of the invention, the first prism structures on the first light emitting surface are staggered in a group of higher heights and a group of lower heights relative to the peak heights of the first light incident surface.

Another objective of the present invention is to provide a display device, which employs the backlight module with the above technical features to enhance the luminance of the display device.

In order to achieve the above object, the present invention provides a display device, comprising: such as the backlight module; and a liquid crystal module disposed above the second light-emitting surface of the second prism film.

The invention has at least the following characteristics: the light guide plate is provided with two layers of prism diaphragms, wherein the lower layer of prism diaphragm, namely the prism diaphragm close to the light-emitting surface of the light guide plate, is arranged in a forward direction, and the prism angle of the lower layer of prism diaphragm is designed in an asymmetric mode, so that more light rays with a positive visual angle can be provided; in addition, compared with the configuration mode that the prism film sheet with the asymmetric prism angle is arranged on the upper layer and the prism film sheet with the symmetric prism angle is arranged on the lower layer, the configuration mode that the prism film sheet with the symmetric prism angle is arranged on the upper layer and the prism film sheet with the asymmetric prism angle is arranged on the lower layer achieves higher luminance which can reach 10 percent, so that the light rays emitted by the light guide plate can be more effectively utilized.

Drawings

FIG. 1 is a schematic front view of a prior art crossed double-layer prism film structure;

FIG. 2 is a front view of a backlight module according to an embodiment of the present invention;

FIG. 3 is a schematic front view of the arrangement of the first prismatic film and the second prismatic film of the embodiment shown in FIG. 2;

FIG. 4a is a schematic diagram of an optical path of a first layer of prism film of a prior art double-layer prism film structure using a symmetrical prism structure;

FIG. 4b is a schematic diagram of a light path of light emitted from the light guide plate entering the first prism structure according to an embodiment of the backlight module of the present invention;

FIG. 5a is a simulated light shape adjusted by the second prism structure of the backlight module according to the embodiment of the present invention;

FIG. 5b is a schematic diagram of light shape adjusted by two sides of the second prism angle according to an embodiment of the present invention

FIG. 6 is a graph of light distribution for a structure according to an embodiment of the present invention and the structure shown in FIG. 1;

FIG. 7 is a top view of an included angle between extending directions of a first prism structure and a second prism structure according to an embodiment of the present invention;

FIG. 8 is a light distribution diagram of the first prism structure and the second prism structure at different arrangement angles according to an embodiment of the present invention;

FIG. 9 is a schematic front view of a first prism structure with staggered high and low peak heights according to an embodiment of the present invention;

FIG. 10 is a schematic front view of a first prism structure with a set of high peak heights alternating with a set of low peak heights according to an embodiment of the present invention; and

fig. 11 is a front view of a display device according to an embodiment of the invention.

Detailed Description

Now, the embodiments of the present invention will be described in detail with reference to the accompanying drawings, which are mainly simplified schematic diagrams illustrating the basic structure of the invention only in a schematic way, so that only the elements related to the invention are labeled in the drawings, and the illustrated elements are not drawn in terms of number, shape, size ratio and the like in the implementation, and the specification and the size in the actual implementation are actually a selective design, and the layout of the elements may be more complicated.

The following description of the embodiments refers to the accompanying drawings in order to illustrate specific embodiments in which the invention may be practiced. The directional terms used in the present invention, such as "up", "down", "front", "back", etc., refer to the directions of the drawings. Accordingly, the directional terms used are used for illustration and understanding of the present application, and are not used to limit the present application. In addition, in the description, unless explicitly described to the contrary, the word "comprise" will be understood to mean that the recited elements are included, but not to exclude any other elements.

Please refer to fig. 2 and fig. 3. The backlight module 2 of the present embodiment mainly includes: a light source 21, a light guide plate 22, a first prism film 23, and a second prism film 24. The light source 21 may provide light, which may be, for example, a light emitting diode. The light guide plate 22 is disposed at one side of the light source 21 and can guide the light emitted from the light source 21 to form a surface light source, the light guide plate 22 has a first optical surface 221 and a second optical surface 222 opposite to the first optical surface 221, in this embodiment, the first optical surface 221 is a reflection surface of the light guide plate 22, and the second optical surface 222 is a light emitting surface of the light guide plate 22. In the present embodiment, the first prism film 23 and the second prism film 24 are disposed on the same side of the light guide plate 22.

As shown in fig. 3, the first prism film 23 is disposed on one side of the light guide plate 22. The first prism film 23 has a first light incident surface 231 and a first light emitting surface 232 opposite to the first light incident surface 231, the first light incident surface 231 faces the second optical surface 222 of the light guide plate 22, and the first light emitting surface 232 is provided with a plurality of first prism structures 233, in this embodiment, each of the first prism structures 233 has a first prism angle 234. As shown in fig. 3, the first prism angle 234 is formed by a first side surface 2341 and a second side surface 2342, the first side surface 2341 forms a first included angle α with an imaginary plane P1 parallel to the first light incident surface 231, that is, the first side surface 2341 forms a first included angle α with the first light incident surface 231; the second side surface 2342 and the imaginary plane P1 parallel to the first light incident surface 231 form a second included angle β, that is, the second side surface 2342 and the first light incident surface 231 form a second included angle β, the first included angle α and the second included angle β are not obtuse angles, and the first included angle α is greater than the second included angle β.

As shown in fig. 3, the second prism film 24 has a second light incident surface 241 and a second light emitting surface 242 opposite to the second light incident surface 241, the second light emitting surface 242 is provided with a plurality of second prism structures 243, in this embodiment, the number of the second prism structures 243 is plural, and each second prism structure 243 has a second prism angle 244. Generally, the two side surfaces forming the second prism angle 244 respectively form an included angle γ with the second light incident surface 241, for example, the included angles formed by the two side surfaces of the second prism angle 244 of fig. 3 respectively and an imaginary plane P2 parallel to the second light incident surface 241 are generally equal, for example, 45 degrees, that is, the included angles between the two side surfaces of the second prism angle 244 respectively and the second light incident surface 241 are both 45 degrees, in this case, the second prism angle 244 is 90 degrees. However, the present invention is not limited to the included angle γ being 45 degrees, and the included angle γ may be implemented with equal angles but not 45 degrees.

It is noted that the first prism structure 233 of the present invention is mainly used to reduce the interference problem caused by non-forward light emission (e.g., light emission in the 20-70 degree region). Referring to fig. 4a, the conventional backlight module structure includes a conventional prism film having a symmetrical prism structure, and an interference light L exists in light from a lower light guide plate, and the interference light L enters an adjacent symmetrical prism structure, so that light originally emitting in a forward direction is influenced by interference, thereby reducing the overall light-emitting efficiency.

Referring to fig. 4b, each of the first prism structures 233 of the present invention has an asymmetric structure, the first included angle α of the first prism angle 234 is located at a side close to the light source 21 than the second included angle β, the first included angle α is greater than the second included angle β, and both the first included angle α and the second included angle β are non-obtuse angles. More specifically, the incident angle of the light emitted from the light guide plate 22 entering the first light incident surface 231 of the first prism film 23 is not 90 degrees, when the light enters the first light incident surface 231 of the first prism film 23, most of the light is deflected firstly, then hits the second side surface 2342 (i.e. the light facing surface of the first prism film 23) and is deflected for the second time, and is guided to the forward light emitting direction as much as possible, and at this time, another part of the interference light L hits the second side surface 2342 and is reflected to the first side surface 2341, and the light emitting direction of the light emitting light is deflected for the second time, so that the degree of interference of the adjacent first prism structures 233 by the interference light L can be reduced, and the maximum benefit of disposable light emitting can be achieved as much as possible.

Referring to the light shape simulation diagram of fig. 5a, the light shape adjusted by the first prism film 23 is flat, and after entering the second prism film 24, the light shape adjusted by the two side surfaces of the second prism angle is as shown in fig. 5b, so as to provide a better light-emitting viewing angle.

For example, the first included angle α of the first prism film 23 of the present invention may be greater than 45 degrees and less than or equal to 90 degrees, and by using this structure, the light entering the first prism film 23 can be effectively utilized, and more light-emitting angles with positive viewing angles can be provided. The second included angle β of the first prism film 23 may be fixed, for example, the second included angle β may be 45 degrees, but not limited thereto. The larger the first included angle α is, the larger the exit angle of the light from the first prism film 23 is, so that the interference of the original most light can be reduced, and the maximum benefit of disposable light emission can be achieved. When the first included angle α is equal to 45 degrees, which is equivalent to the conventional structure shown in fig. 1 and 4a, the interference light L enters the adjacent first prism structure 233, and the overall light-emitting efficiency is reduced. When the first included angle α is smaller than 45 degrees, more interference light L may enter the adjacent first prism structures 233, thereby reducing the efficiency of forward light emission. On the other hand, when the first included angle α is greater than 90 degrees, the second included angle β is smaller than 45 degrees, and the light collection effect of the second side 2342 at the position of-20 degrees to 20 degrees is reduced, and further, when the first included angle α is equal to 90 degrees, the light collection effect at the position of-20 degrees to 20 degrees is the best, and the interference light L entering the adjacent first prism structure 233 is the least.

Therefore, compared with the prior art, the luminance of the present invention can be improved by using the two-layer structure of the first prism film 23 and the second prism film 24. Further, the light distribution diagram generated by both the structure of the present invention and the structure of the prior art is shown in fig. 6, where the vertical axis of fig. 6 is luminance (nits) and the horizontal axis is angle of view (angularity) and degree. By comparing the two-layer prism film structure of the present invention (including the second optical surface 222 side disposed near the light guide plate 22 for emitting light, the first prism film 23 as a non-equiangular prism, and the second prism film 24 as an equiangular prism) with the inverted structure shown in fig. 1 (i.e., the first film 11 as an equiangular prism is disposed near the light guide plate, and the second film 12 as a non-equiangular prism is disposed at the light emitting side of the first film 11), it can be seen that the luminance of the present invention is 10% higher than that of the conventional structure shown in fig. 1 at the viewing angle of 0 degree, and the present invention can improve the luminance of the light emitting angle falling between-20 degrees and 20 degrees, while suppressing the luminance of the light emitting angle falling between 20 degrees and 70 degrees, as shown by the arrows in fig. 6.

Referring to fig. 7, in the present embodiment, the first prism structures 233 of the first prism film 23 extend along the first direction a, and the second prism structures 243 of the second prism film 24 extend along the second direction B, and preferably, an included angle δ between the first direction a and the second direction B is within a range from 0 degree to 50 degrees and includes an endpoint value. Referring to fig. 8 again, fig. 8 is a light distribution diagram when the direction angle δ of the second prism film 24 relative to the first prism film 23 changes when the first prism film 23 is fixed, and the vertical axis of fig. 8 is luminance (nits) and the horizontal axis is the angle of the viewing angle, and the unit is degree. As can be seen from fig. 8, when the included angle δ between the first prism film 23 and the second prism film 24 is between 0 degree and 50 degrees, the luminance is best at 0 degree, the luminance is worse at 50 degrees, and when the included angle δ is larger than 50 degrees, the required luminance cannot be achieved.

As shown in fig. 9, in another embodiment, under the condition that the angles of the first included angle α and the second included angle β of the first prism film 23 embodiment are kept unchanged, in another aspect of the first prism film 23', the second prism structures 233a' have a peak height H1 relative to the first light incident surface 231', the second prism structures 233b' have a peak height H2 relative to the first light incident surface 231', and H1 is not equal to H2, so that any two adjacent second prism structures 233a', 233b 'are in a staggered arrangement formed by connecting a higher second prism structure 233a' to a lower second prism 233b 'relative to the first light incident surface 231'.

As shown in fig. 10, in the present embodiment, under the condition that the angles of the first included angle α and the second included angle β of the first prism film 23 are kept unchanged, in another aspect of the first prism film 23", the plurality of first prism structures 233a" on the first light emitting surface 232 "have a peak height H1 relative to the first light incident surface 231", the plurality of first prism structures 233b "have a peak height H2 relative to the first light incident surface 231", and H1 is not equal to H2, so that the plurality of first prism structures 233a ", 233b" on the first light emitting surface 232 "form a staggered arrangement structure formed by connecting a group of higher first prism structures 233a" with a group of lower first prism structures 233b "relative to the first light incident surface 231". By using the structure in which the higher first prism structures 233a 'are staggered with the lower first prism structures 233b' as shown in fig. 9, or the structure in which a set of higher second prism structures 233a ″ is staggered with a set of lower second prism structures 233b ″ as shown in fig. 10, the gap between the first prism film 23 and the second prism film 24 can be increased to prevent the occurrence of the adsorption phenomenon.

As shown in fig. 11, the structure of the display device 3 of the present embodiment includes: the backlight module 2 according to any of the above embodiments; and a liquid crystal module 31 disposed above the second light emitting surface 242 of the second prism film 24. The display device 3 can receive the most effective disposable light-emitting and light rays with narrower light-emitting angles of the backlight module 2 through the design of the backlight module 2, and therefore the detailed description is omitted here.

In summary, in the backlight module of the present invention, by the overlapped design of the first and second prism films, the prism film close to the light-emitting surface of the light guide plate is disposed in the forward direction (i.e. the prism structure faces away from the light-emitting surface of the light guide plate), the prism angle thereof is designed in an asymmetric manner, and the included angle between the first and second prism films is matched, so that the light rays with the light-emitting angle deviating from the normal viewing angle to a certain extent can be suppressed, and at the same time, more light rays with the light-emitting angle with the normal viewing angle can be provided, and the display device using the backlight module can also have more light rays with the normal viewing angle (e.g. the light-emitting angle with the viewing angle of-20 degrees to 20 degrees), thereby enhancing the luminance performance and suppressing the luminance with the viewing angle of 20 degrees to 70 degrees.

The above-described embodiments are merely illustrative of the principles, features and effects of the present invention, and it is not intended to limit the scope of the invention, and those skilled in the art can modify and change the above-described embodiments without departing from the spirit and scope of the present invention. Any equivalent changes and modifications made using the teachings of the present invention should still be covered by the appended claims.

[ List of reference numerals ]

1: display film

11: first film

12: second film

2: backlight module

21: light source

22: light guide plate

221: first optical surface

222: second optical surface

23. 23', 23": first prism film

231. 231': first light incident surface

232. 232': the first light emitting surface

233. 233a ', 233b', 233a ", 233b": first prism structure

234: first prism angle

2341: first side surface

2342: the second side surface

24: second prism film

241: second light incident surface

242: the second light emitting surface

243: second prism structure

244: second prism angle

3: display device

31: liquid crystal module

A: a first direction

B: second direction

H1, H2: peak height

P1, P2: imaginary plane

α: first included angle

Beta: second included angle

γ: included angle

δ: the included angle of the direction.

Claims (10)

1. A backlight module, comprising:

a light source;

the light guide plate is arranged on one side of the light source and is provided with a first optical surface and a second optical surface which are opposite;

the first prism film is provided with a first light inlet face and a first light outlet face opposite to the first light inlet face, a plurality of first prism structures are arranged on the first light outlet face, each first prism structure is provided with a first prism angle, the first prism angle is formed by a first side face and a second side face, a first included angle formed by the first side face and the first light inlet face is larger than a second included angle formed by the second side face and the first light inlet face, and the first included angle and the second included angle are not obtuse angles; and

the second prism film is provided with a second light-emitting surface and a second light-entering surface opposite to the second light-emitting surface, the second light-emitting surface is provided with a plurality of second prism structures, and each second prism structure is provided with a second prism angle;

the first prism film is disposed on one side of the light guide plate, the first light incident surface of the first prism film faces the second optical surface of the light guide plate, and the second light incident surface of the second prism film is opposite to the first prism structure of the first prism film to receive light from the first light emitting surface.

2. The backlight module as claimed in claim 1, wherein the second prism angle of the second prism film is formed by two side surfaces, and the two side surfaces respectively form an equal included angle with the second light incident surface.

3. The backlight module according to claim 2, wherein the second prism angle of the second prism film is 90 degrees.

4. The backlight module according to claim 1, wherein the first angle of each of the first prism angles is closer to the light source than the second angle.

5. The backlight module as claimed in claim 1, wherein the first included angle of the first prism film is greater than 45 degrees and less than or equal to 90 degrees.

6. The backlight module as claimed in claim 5, wherein the second included angle of the first prism film is 45 °.

7. The backlight module according to claim 1, wherein the second prism structures of the second prism film extend along a first direction, the first prism structures of the first prism film extend along a second direction, and an included angle between the first direction and the second direction is in a range of 0 degrees to 50 degrees, inclusive.

8. The backlight module as claimed in claim 1, wherein any two adjacent first prism structures are staggered with respect to a height of a peak of the first light incident surface.

9. The backlight module as claimed in claim 1, wherein the first prism structures on the first light emitting surface are staggered with respect to the peak heights of the first light incident surface.

10. A display device, comprising:

a backlight module according to any one of claims 1 to 9; and

and the liquid crystal module is configured above the second light-emitting surface of the second prism film.

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