Backlight module and display device

Abstract

A backlight module comprises: a light guide plate having a light incident surface; the light-emitting mechanism is positioned on one side of the light incident surface; the haze value of the first prismatic lens is not zero, the first prismatic lens is located above the light guide plate and provided with a plurality of first prism structures, and the first prism structures are of asymmetric structures; and the second prismatic lens is positioned above the first prismatic lens and is provided with a plurality of second prism structures, and the second prism structures are asymmetric structures. The invention further provides a display device comprising the backlight module.

Description

Backlight module and display device Technical Field

[0001] The present application mainly relates to a backlight module, and more particularly to a backlight module capable of effectively concentrating light to improve brightness, and a display device using the backlight module. Background Art

[0002] Conventional backlight modules utilize different optical film combinations to create different light emission patterns, such as a uniform light emission pattern across the entire optical surface or a concentrated light emission pattern that focuses light on specific areas within the optical surface. These backlight modules with different light emission patterns can be used in different display applications, such as automotive displays. For example, a display mounted on the passenger seat typically avoids angling its light toward the driver's seat to avoid disturbing the driver and thus ensure driving safety.

[0003] This conventional backlight module has two prism sheets arranged in the light-emitting direction of a light guide plate. By staggering the long prism structures of the two prism sheets, the brightness of the conventional backlight module can be enhanced. However, when the prism structures of the two prism sheets are symmetrical and the angle between the prism structures of the two prism sheets is 90°, the conventional backlight module is more likely to emit stray light, thereby reducing the overall light extraction efficiency.

[0004] In view of this, it is necessary to provide a backlight module to solve the above problems.

[0005] Summary of the Invention

[0006] The purpose of this application is to provide a backlight module that can effectively concentrate light to increase brightness and thereby enhance overall light output efficiency.

[0007] A second object of the present application is to provide a display device having the above-mentioned backlight module, which can meet the application type of a high-brightness concentrated light-emitting area.

[0008] To achieve the above-mentioned purpose, the present application provides a backlight module, comprising: a light guide plate having a light incident surface and a light exiting surface connected to each other; a light-emitting mechanism located on one side of the light incident surface of the light guide plate; a first prism sheet having a non-zero haze value, the first prism sheet being located above the light exiting surface of the light guide plate and having a first light incident surface and a first light exiting surface relatively arranged, the first light incident surface facing the light exiting surface of the light guide plate, the first light exiting surface being provided with a plurality of first prism structures, and the first prism structure being an asymmetric structure; and a second prism sheet being located above the first prism sheet and having a second light incident surface and a second light exiting surface relatively arranged, the second light incident surface facing the first light exiting surface of the first prism sheet, the second light exiting surface being provided with a plurality of second prism structures, and the second prism structure being an asymmetric structure.

[0009] In some embodiments, the haze value of the first prism sheet is between 10% and 30%, inclusive.

[0010] In some embodiments, the haze value of the second prism sheet is less than 20%, inclusive.

[0011] In some embodiments, the haze value of the second prism sheet is zero.

[0012] In some embodiments, the first prism structure is a strip structure formed by a first side surface and a second side surface, and the second prism structure is a strip structure formed by a third side surface and a fourth side surface, the first side surface and the third side surface are respectively closer to the light incident surface than the second side surface and the fourth side surface, the first side surface and the first light output surface have a first angle, the second side surface and the first light output surface have a second angle, the first angle is greater than the second angle, the third side surface and the second light output surface have a third angle, the fourth side surface and the second light output surface have a fourth angle, and the third angle is greater than the fourth angle.

[0013] In some embodiments, the backlight module further includes a diffusion sheet located above the second prism structure.

[0014] The present application further provides a display device, comprising: the aforementioned backlight module; and a display panel located above the backlight module.

[0015] The backlight module and display device of the present application have the following characteristics: at least two optical films with asymmetric microstructures, such as a first prism sheet and a second prism sheet, are stacked, and in the asymmetric microstructures of each of the first prism sheet and the second prism sheet, the steeper slope is inclined toward the light incident surface, while the slope of the slope facing the light from the light guide plate below is gentler, thereby effectively concentrating the light and achieving the effect of improving the brightness efficiency of the backlight module. The optical surface of the backlight module of the present application presents a specific concentrated light-emitting area, which is beneficial for application in scenes such as automotive displays. Furthermore, the present application can also achieve a better light-emitting uniformity effect in the optical surface of the backlight module by matching optical films with different haze values. For example, when the haze value of the first prism sheet is not zero, the backlight module of the present application can effectively cover blemishes and improve the problem of severe color deviation. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG1 is a side view of the backlight module of the present application;

[0017] [Figure 2] is a light shape simulation diagram of Figure 1;

[0018] Figure 3 is a diagram showing the relationship between the light output angle and the luminance shown in Figure 1.

[0019] FIG4 is a light pattern simulation diagram of a conventional backlight module;

[0020] FIG5 is a side view of another conventional backlight module;

[0021] Figure 6 is a simulated diagram of the light shape in Figure 5;

[0022] [Figure 7] is a side view of the display device of the present application including the above-mentioned backlight module. DETAILED DESCRIPTION

[0023] The embodiments of the present application are described in detail below with reference to the accompanying drawings. The accompanying drawings are mainly simplified schematic diagrams that only illustrate the basic structure of the present application in a schematic manner. Therefore, only elements related to the present application are marked in these drawings, and the elements shown are not drawn based on the number, shape, size ratio, etc. during implementation. The specifications and dimensions during actual implementation are actually a selective design, and the component layout may be more complex.

[0024] The following descriptions of the various embodiments are made with reference to the accompanying drawings to illustrate specific embodiments in which the present application may be implemented. Directional terms mentioned in this application, such as "upper", "lower", "front", "back", etc., are only used with reference to the directions in the accompanying drawings. Therefore, the directional terms used are used to illustrate and understand the present application, rather than to limit the present application. In addition, in the specification, unless explicitly described to the contrary, the word "comprising" will be understood to mean including the stated elements, but not excluding any other elements.

[0025] Please refer to Figure 1, which is a side view of a preferred embodiment of the backlight module of the present application, comprising: a light guide plate 1, a light-emitting mechanism 2, a first prism sheet 3 and a second prism sheet 4. The light guide plate 1, the first prism sheet 3 and the second prism sheet 4 are stacked in sequence, the light-emitting mechanism 2 is located on one side of the light guide plate 1, the haze value of the first prism sheet 3 is not zero, and the prism structures of the first prism sheet 3 and the second prism sheet 4 are both asymmetric structures.

[0026] Please refer to Figure 2, which is a light shape simulation diagram of the backlight module of the present application. It can deflect and concentrate the light from the light guide plate 1 toward the upper side, and make the light from the light guide plate 1 as close to the normal direction of the optical surface as possible. And it can be seen from Figure 3 that the range of light output angle falls between -40 degrees and +40 degrees. Therefore, the convergent light output characteristics of the optical surface of the backlight module of the present application are more obvious.

[0027] In this application, a backlight module comprising two asymmetric microstructured prism sheets (i.e., the first prism sheet 3 and the second prism sheet 4) is provided. Its luminance can be greater than that of conventional backlight modules; more preferably, it can reach approximately 1.6 times the luminance of conventional backlight modules. Thus, compared to conventional backlight modules, the backlight module of this application can achieve the effect of concentrating light and improving the backlight module's luminance. Thus, when the backlight module of this application is applied to a vehicle display, the driver's view is not disturbed by the display image in front of the passenger seat, ensuring driving safety.

[0028] The present application is a backlight module with two asymmetric microstructure prism sheets. In comparison, the conventional backlight module has two symmetrical microstructure prism sheets. Since the single symmetrical microstructure prism sheet of the conventional backlight module can cause the incident light angle to be deflected toward the forward direction at a larger angle, the conventional backlight module will increase the degree of light deflection after using two symmetrical microstructure prism sheets to collect light, causing the peak of the light to deviate from the forward direction. Referring to Figure 4, the conventional backlight module with two symmetrical microstructure prism sheets produces a light peak at about -6 degrees on the Y axis, rather than in the forward direction of 0 degrees. Furthermore, there will be local light scattered in the +Y axis and -Y axis directions, resulting in the inability to effectively concentrate the light in one place. Compared with the backlight module of the present application, the conventional backlight module cannot effectively concentrate the light in one place. Therefore, when the conventional backlight module is used in a car display, the display light in front of the passenger seat will be projected toward the driver's seat, disrupting the driver's vision and increasing the risk of driving accidents.

[0029] 1 , in the backlight module of the present application, the light guide plate 1 has a light incident surface 11 and a light emitting surface 12, and the light incident surface 11 is connected to the light emitting surface 12. The light guide plate 1 also has a bottom surface 13 opposite to the light emitting surface 12, and the bottom surface 13 is connected to the light incident surface 11.

[0030] The light emitting mechanism 2 is located on one side of the light incident surface 11 of the light guide plate 1 and is used to emit light toward the light incident surface 11 of the light guide plate 1 . For example but not limited to, the light emitting mechanism 2 can be a light emitting diode.

[0031] The first prism sheet 3 is located above the light emitting surface 12 of the light guide plate 1 and has a first light incident surface 31 and a first light emitting surface 32 arranged opposite to each other, wherein the first light incident surface 31 faces the light emitting surface 12 of the light guide plate 1, and the first light emitting surface 32 is provided with a plurality of first prism structures 33, and the first prism structure 33 is an asymmetric structure.

[0032] The second prism sheet 4 is above the first prism sheet 3 and has a second light incident surface 41 and a second light emitting surface 42 arranged opposite to each other, wherein the second light incident surface 41 faces the first light emitting surface 32 of the first prism sheet 3, and the second light emitting surface 42 is provided with a plurality of second prism structures 43, and the second prism structure 43 is also an asymmetric structure.

[0033] In this embodiment, the first prism structure 33 of the first prism sheet 3 is a strip-shaped structure formed by a first side surface 331 and a second side surface 332, while the second prism structure 43 of the second prism sheet 4 is a strip-shaped structure formed by a third side surface 431 and a fourth side surface 432. The first side surface 331 and the third side surface 431 are closer to the light-emitting mechanism 2 than the second side surface 332 and the fourth side surface 432, respectively. Furthermore, the first side surface 331 and the first light-emitting surface 32 form a first angle θ1, the second side surface 332 and the first light-emitting surface 32 form a second angle θ2, the third side surface 431 and the second light-emitting surface 42 form a third angle θ3, and the fourth side surface 432 and the second light-emitting surface 42 form a fourth angle θ4.

[0034] In the present application, the first prism structure 33 and the second prism structure 43 are both strip-shaped structures extending inwardly from the drawing. Furthermore, the first angle θ1 of the first prism structure 33 and the third angle θ3 of the asymmetric microstructure of the second prism structure 43 are relatively close to the light incident surface 11 of the light guide plate 1. Furthermore, the first angle θ1 is greater than the second angle θ2, and the third angle θ3 is greater than the fourth angle θ4. Consequently, the first side surface 331 and the third side surface 431, which have steeper slopes, are relatively close to the light incident surface 11, while the second side surface 332 and the fourth side surface 432, which have gentler slopes, are relatively far from the light incident surface 11.

[0035] In the present application, a single prism sheet with an asymmetric microstructure has a microstructure side surface with a steeper slope that is relatively close to the light incident surface, that is, the slope of the inclined surface that receives the light from the light guide plate 1 below is gentler, so that the incident light angle is deflected toward the forward direction at a smaller angle. Therefore, when two prism sheets with an asymmetric microstructure are used (i.e., the first prism sheet 3 and the second prism sheet 4), since the first side surface 331 and the third side surface 431 with a steeper slope are relatively close to the light incident surface 11, that is, the gentle slope of the second side surface 332 and the fourth side surface 432 can deflect the incident light angle toward the forward direction at a smaller angle. Therefore, after the effects of the first prism sheet 3 and the second prism sheet 4 deflecting the light toward the forward direction are superimposed, the peak of the light is precisely concentrated in the forward direction, achieving the purpose of effective light collection. Furthermore, as can be seen from FIG. 2 , the light is concentrated in one place. Thus, when the backlight module of the present application is applied to a car display, it can ensure that the sight line of the driver's seat will not be disturbed by the display screen in front of the passenger seat, thereby ensuring driving safety.

[0036] Please refer to Figure 5, which is a side view of another conventional backlight module, which has two asymmetric microstructure prism sheets, and the inclination direction of this asymmetric microstructure is different from the inclination direction of the asymmetric microstructure of the present application. In detail, the conventional backlight module includes a lower prism sheet 91 and an upper prism sheet 92, wherein the lower prism sheet 91 has a first angle θ1' and a second angle θ2', and the first angle θ1' is smaller than the second angle θ2'. The upper prism sheet 92 has a third angle θ3' and a fourth angle θ4', and the third angle θ3' is smaller than the fourth angle θ4'. The first angle θ1' and the third angle θ3' are both relatively close to a light incident surface. Therefore, a first side surface 911 and a third side surface 921 with a gentler slope are relatively close to the light incident surface, while a second side surface 912 and a fourth side surface 922 with a steeper slope are relatively far away from the light incident surface.

[0037] Since the side surface of the conventional backlight module with a gentler slope of the microstructure is relatively close to the light incident surface, that is, the slope of the inclined surface that receives the light from the light guide plate below is steeper, the incident angle of the conventional backlight module is greater than the incident angle of the aforementioned backlight module with a symmetrical microstructure, and the light is deflected in the forward direction to a greater extent. As a result, when two prism sheets with asymmetric microstructures whose side surfaces with a gentler slope are relatively close to the light incident surface are used, the deflection angle is too large and the light cannot be effectively collected. Furthermore, it can be seen from FIG6 that the peak of the light is dispersed and presents two light-emitting surfaces with higher peaks. Compared with the backlight module of the present application, the conventional backlight module cannot effectively concentrate the light in one place. Therefore, when the conventional backlight module is used for a car display, the display light in front of the passenger seat will be projected toward the driver's seat, interfering with the driver's line of sight and increasing the risk of traffic accidents.

[0038] In other words, whether the conventional backlight module uses two prism sheets with symmetrical microstructures or two prism sheets with asymmetric microstructures whose microstructure sides are gently sloped and relatively close to the light-entering surface, neither can achieve the effect of focusing light in a single location. Therefore, when the conventional backlight module is used in an automotive display, the light from the display in front of the passenger seat will be projected toward the driver's seat, obstructing the driver's vision and increasing the risk of accidents.

[0039] In this embodiment, the haze value of the second prism sheet 4 can be zero or non-zero. In order to achieve a balance between high brightness and light uniformity, in this application, the first prism sheet 3 or the second prism sheet 4 respectively adds the following haze value conditions.

[0040] For example, compared to a conventional backlight module with two symmetrical microstructured prism sheets, in the present application, the backlight module luminance performance of the first prism sheet 3 with a haze value of 30% is improved by approximately 3%. When the haze value is below 30%, the improvement is close to 60%, and the improvement increases as the haze value decreases. However, if the haze value of the first prism sheet 3 is 40%, the luminance improvement effect is lower than that of the conventional backlight module design with two symmetrical microstructured prism sheets, and is actually reduced by 6%. Therefore, it is preferred that the haze value of the first prism sheet 3 is below 30%, inclusive.

[0041] Looking at the effect of improving color difference, the haze value of the first prism sheet 3 needs to be designed to be non-zero, as described below. When the haze value of the first prism sheet 3 is 30% and the haze value of the second prism sheet 4 is zero, the color difference of the backlight module of the present application can be calculated to be 0.0067. However, when the haze value of the first prism sheet 3 is zero and the haze value of the second prism sheet 4 is 30%, the color difference of the backlight module of the present application can be calculated to be 0.0076, which increases the color deviation by about 13%. Therefore, if the haze value of the first prism sheet 3 is not zero, the backlight module can be effectively shielded and the problem of severe color deviation can be improved.

[0042] Preferably, the haze value of the second prism sheet 4 can also be less than 20%, including the endpoint value. If the haze value of the second prism sheet 4 exceeds 20%, the overall brightness of the backlight module will decrease. On the other hand, when the haze value of the second prism sheet 4 is less than 20% (not zero), for example: the haze value of the second prism sheet 4 is 20%, and the haze value of the first prism sheet 3 is 10%, the haze value of the second prism sheet 4 is greater than the haze value of the first prism sheet 3; or the haze value of the second prism sheet 4 is 10%, and the haze value of the first prism sheet 3 is 20%, the haze value of the second prism sheet 4 is less than the haze value of the first prism sheet 3, the color difference of the backlight module of the present application falls near 0.0073, which is still an acceptable value.

[0043] Furthermore, when the haze value of the first prism sheet 3 is 30% and the haze value of the second prism sheet 4 is zero, the color difference of the backlight module of the present application can be calculated to be 0.0067, which has the smallest color difference. That is, the haze value of the second prism sheet 4 is zero, which can produce the best color difference improvement effect. It is worth noting that the color difference is obtained using CIE 1976LAB calculation. The addition of the haze value in this embodiment can also be achieved by adding diffusion particles to the light incident surface of the first prism sheet 3 and the light incident surface of the second prism sheet 4. This can help achieve a better light uniformity effect on the optical surface.

[0044] 1 , the backlight module of the present application further includes a diffuser 5 located above the second prism sheet 4. This diffuser 5 is an upper diffuser. It is worth noting that, in order to achieve the requirement for a thinner backlight module, the backlight module of the present application can also omit the lower diffuser in conventional backlight modules.

[0045] Specifically, in conventional backlight modules, light diffuses after passing through the lower diffuser, preventing it from being effectively concentrated. Therefore, the backlight module of the present application can further omit the lower diffuser and utilize the asymmetrical first prism sheet 3 and second prism sheet 4 to concentrate the light and thereby improve the brightness of the backlight module.

[0046] The backlight module of the present application may further include a reflective sheet 6 located on one side of the bottom surface 13 of the light guide plate 1. Thus, light emitted from the bottom surface 13 of the light guide plate 1 can be reflected by the reflective sheet 6 and transmitted back to the light guide plate 1, thereby improving the light utilization efficiency of the light emitting mechanism 2.

[0047] 7 is a partial cross-sectional view of the display device of the present application, which includes: the aforementioned backlight module; and a display panel 7 located above the backlight module. More specifically, the display panel 7 is located above the diffuser 5.

[0048] As mentioned above, the backlight module and display device of the present application utilize a stack of at least two optical films with asymmetric microstructures, such as a first prism sheet and a second prism sheet, with an asymmetric structure. In the asymmetric microstructures of each of the first prism sheet and the second prism sheet, the steeper slope is inclined toward the light incident surface, while the slope facing the light from the light guide plate below is gentler, thereby effectively concentrating the light and achieving the effect of improving the brightness efficiency of the backlight module. The optical surface of the backlight module of the present application presents a specific concentrated light-emitting area, which is beneficial for applications such as automotive displays. Furthermore, the present application can also achieve a better light-emitting uniformity effect in the optical surface of the backlight module by matching optical films with different haze values. For example, when the haze value of the first prism sheet is not zero, the backlight module of the present application can effectively cover blemishes and improve the problem of severe color deviation.

[0049] The embodiments disclosed above are merely illustrative of the principles, features, and functions of this application and are not intended to limit the scope of application. Anyone skilled in the art may modify and alter the embodiments described above without departing from the spirit and scope of this application. Any equivalent changes and modifications resulting from the disclosure of this application are intended to be covered by the appended claims.

[0050]

Explanation of symbols

[0051] (This application) 1: Light guide plate 11: Light incident surface 12: Light emitting surface 13: Bottom surface 2: Light-emitting mechanism 3: First prism sheet 31: First light incident surface 32: First light emitting surface 33: First prism structure 331: First side surface 332: Second side surface 4: Second prism sheet 41: Second light incident surface 42: Second light emitting surface 43: Second prism structure 431: Third side surface 432: Fourth side surface 5: Diffuser sheet 6: Reflector sheet 7: Display panel θ1: First angle θ2: Second angle θ3: Third angle θ4: Fourth angle 91: Lower prism sheet 911: First side surface 912: Second side surface 92: Upper prism sheet 921: Third side surface 922: Fourth side surface θ1': First angle θ2': Second angle θ3': Third angle θ4': Fourth angle.

Claims

1. A backlight module, comprising: A light guide plate having a light incident surface and a light emitting surface connected to each other; A light-emitting mechanism, located on one side of the light incident surface of the light guide plate; A first prism sheet, whose haze value is not zero, is located above the light emitting surface of the light guide plate, and has a first light incident surface and a first light emitting surface that are oppositely arranged, the first light incident surface faces the light emitting surface of the light guide plate, and the first light emitting surface is provided with a plurality of first prism structures, and the first prism structures are asymmetric structures; and The second prism sheet is located above the first prism sheet and has a second light incident surface and a second light emitting surface which are arranged opposite to each other. The second light incident surface faces the first light emitting surface of the first prism sheet. The second light emitting surface is provided with a plurality of second prism structures, and the second prism structures are asymmetric structures.

2. The backlight module according to claim 1, in, The haze value of the first prism sheet is between 10% and 30%, including the end value.

3. The backlight module according to claim 2, in, The haze value of the second prism sheet is less than or equal to 20%, including the end point value.

4. The backlight module according to claim 2, in, The haze value of the second prism sheet is zero.

5. The backlight module according to claim 1, in, The first prism structure is a strip structure formed by a first side surface and a second side surface, and the second prism structure is a strip structure formed by a third side surface and a fourth side surface, the first side surface and the third side surface are respectively closer to the light incident surface than the second side surface and the fourth side surface, the first side surface and the first light emitting surface have a first angle, the second side surface and the first light emitting surface have a second angle, the first angle is greater than the second angle, the third side surface and the second light emitting surface have a third angle, the fourth side surface and the second light emitting surface have a fourth angle, and the third angle is greater than the fourth angle.

6. The backlight module according to claim 1, in, The backlight module also includes a diffusion sheet located above the second prism structure.

7. The backlight module according to claim 1, in, The light guide plate also has a bottom surface opposite to the light emitting surface, and the reflective sheet is located on one side of the bottom surface of the light guide plate.

8. A display device, comprising: The backlight module according to any one of claims 1 to 7; and The display panel is located above the backlight module.

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