Backlight module and display device

Abstract

The backlight module comprises a light guide plate having a light incident surface, a light-emitting mechanism located on the side of the light incident surface, a first prism sheet located above the light guide plate with a haze value of non-zero and provided with a plurality of asymmetrical first prism structures, and a second prism sheet located above the first prism sheet and provided with a plurality of asymmetrical second prism structures. The present invention further provides a display device comprising the backlight module.

Description

Technical Field

[0001] The present invention mainly relates to a backlight module, and particularly to a backlight module capable of effectively concentrating light rays to improve brightness, and a display device applying the backlight module.

Background Art

[0002] Conventional backlight modules can form different light-emitting tendencies through combinations of different optical films. For example, the entire optical surface has a uniform light-emitting mode, or the light rays are in a concentrated light-emitting mode where they are concentrated on a specific area of the optical surface. The above-mentioned backlight modules with different light-emitting modes can be respectively applied to different display devices such as vehicle displays. For example, a vehicle display installed on the passenger seat usually needs to avoid the injection angle facing the driver's seat so as not to interfere with the driver and ensure driving safety.

[0003] Conventional backlight modules have two prism sheets in the light-emitting direction of the light guide plate. By staggering the long prism structures of the two prism sheets, the brightness improvement effect of the conventional backlight module can be achieved. However, when the prism structures of both prism sheets are symmetric structures and the included angle in the extending direction of each prism structure of the two prism sheets is 90°, the conventional backlight module is likely to generate stray light and reduce the overall light-emitting effect.

[0004] In view of this, it is necessary to provide a backlight module for solving the above problems. <00​​​​​​​A further object of the present invention is to provide a display device having the above-described backlight module that is suitable for application forms of a high-brightness concentrated light-emitting region.

[0006] To achieve the above objective, the present invention provides a backlight module comprising a light guide plate, a light-emitting mechanism, a first prism sheet, and a second prism sheet, wherein the light guide plate has a light-incident surface and a light-emitting surface connected to each other, the light-emitting mechanism is located on the side of the light-incident surface of the light guide plate, the first prism sheet has a non-zero haze value, the first prism sheet 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 positioned opposite each other, the first light-incident surface is directed toward the light-emitting surface of the light guide plate, the first light-emitting surface is provided with a plurality of first prism structures, the first prism structure is asymmetrical and is a strip structure formed by a first side surface and a second side surface, a first vertex angle is formed between the first side surface and the second side surface, within the range of 60 to 90 degrees, including the endpoint value, and a first bounding angle is formed between the first side surface and the first light-emitting surface, within the range of 50 to 80 degrees, including the endpoint value. A second prism angle is formed between the second side surface and the first light-emitting surface. The second prism sheet is located above the first prism sheet and has a second light-incident surface and a second light-emitting surface that are positioned opposite each other. The second light-incident surface is directed toward the first light-emitting surface of the first prism sheet. The second light-emitting surface is provided with a plurality of second prism structures, each of which is asymmetric and a strip-like structure formed by a third side surface and a fourth side surface. A second vertex angle is formed between the third side surface and the fourth side surface, within the range of 60 to 90 degrees, including the endpoint value. A third prism angle is formed between the third side surface and the second light-emitting surface, within the range of 50 to 80 degrees, including the endpoint value. A fourth prism angle is formed between the fourth side surface and the second light-emitting surface. The first side surface and the third side surface are each closer to the light-incident surface than the second side surface and the fourth side surface. The refractive indices of the first and second prism sheets are 1.5 to 1.The microstructure is located within a range of 7, including the endpoint value, and has an extension angle between the first extension direction of the first prism structure and the second extension direction of the second prism structure, within a range of 0 to 40 degrees, including the endpoint value. The first prism structure has a first spacing, within a range of 15 μm to 55 μm, including the endpoint value, and the second prism structure has a second spacing, within a range of 15 μm to 55 μm, including the endpoint value, and the first spacing is not equal to the second spacing.

[0007] In some embodiments, the haze value of the first prism sheet is in the range of 10% to 30%, including the endpoint value.

[0008] In some embodiments, the haze value of the second prism sheet is 20% or less, including the endpoint value.

[0009] In some embodiments, the haze value of the second prism sheet is zero.

[0010] In some embodiments, the refractive index of the second prism sheet is greater than or equal to the refractive index of the first prism sheet.

[0011] In some embodiments, the first vertex angle is greater than the second vertex angle.

[0012] In some embodiments, the peak value of the light rays emitted from the backlight module in the first direction is less than 10 degrees.

[0013] In some embodiments, in a first direction, the light rays emitted from the backlight module have a first half-width angle, and in a second direction, the light rays emitted from the backlight module have a second half-width angle, the second direction being perpendicular to the first direction, and the ratio of the second half-width angle to the first half-width angle being in the range of 1.65 to 3.69, including the endpoint value.

[0014] In some embodiments, the second full width at half maximum angle is in the range of 28 to 59 degrees, including the endpoint value.

[0015] In some embodiments, the backlight module further includes a diffusion sheet located above the second prism structure.

[0016] The present invention further provides a display device comprising the backlight module and a display panel located above the backlight module.

[0017] The backlight module and display device of the present invention have the following features. At least two optical film sheets with asymmetric microstructures, such as a first prism sheet and a second prism sheet having an asymmetric structure, are laminated and utilized. In the asymmetric microstructures of the first and second prism sheets, steep slopes are inclined toward the light incident surface, while the slope receiving light rays from the lower light guide plate has a gentle slope. This efficiently concentrates the light rays, achieving an effect of improving the brightness gain of the backlight module. The optical surface of the backlight module of the present invention exhibits a specific concentrated light emission region, making it suitable for applications such as vehicle displays. Furthermore, the present invention can achieve a good uniform light emission effect on the optical surface of the backlight module through a combination of optical films having different haze values. For example, if the haze value of the first prism sheet is not zero, the backlight module of the present invention can effectively mask scratches and defects, improving the problem of severe color misalignment. [Brief explanation of the drawing]

[0018] [Figure 1] This is a side view of the backlight module of the present invention. [Figure 2] Figure 1 is a simulation diagram of the light distribution. [Figure 3] Figure 1 is a phase diagram including the emission angle and brightness. [Figure 4] This is a simulation diagram of the light distribution of a conventional backlight module. [Figure 5]This is a schematic diagram of the angle of attachment in the extension direction of the prism structure of the first prism sheet and the second prism sheet of the backlight module of the present invention. [Figure 6] This is a side view of another conventional backlight module. [Figure 7] Figure 6 is a simulation diagram of the light distribution. [Figure 8] This is a side view of a display device including the backlight module of the present invention. [Modes for carrying out the invention]

[0019] Embodiments of the present invention will be described in detail with reference to the drawings. The following drawings are mainly simplified schematic diagrams and only provide a general overview of the basic structure of the present invention. Therefore, these drawings only show elements relevant to the present invention, and the elements shown are not depicted in the actual number, shape, dimensional ratio, etc., of the actual implementation. Actual specifications and dimensions are based on a selective design, and the layout of the elements may be more complex.

[0020] The following descriptions of each embodiment are intended to illustrate specific embodiments in which the present invention can be implemented, with reference to the accompanying drawings. Directional terms used in the present invention, such as “up,” “down,” “front,” and “back,” refer to directions with reference to the accompanying drawings. Therefore, directional terms are for illustrative purposes and not to limit the present invention. In this specification, the term “includes” is understood to mean including the elements described, unless explicitly stated otherwise, but does not exclude other elements.

[0021] Referring to FIG. 1, it is a side view of a preferred embodiment of the backlight module of the present invention, which includes 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.

[0022] Referring to FIG. 2, it is a light distribution simulation diagram of the backlight module of the present invention, which can deflect and concentrate the light rays from the light guide plate 1 in the directly upward direction, and can make the light rays from the light guide plate 1 approach the normal direction of the optical surface as much as possible. As can be seen from FIG. 3, since the range of the injection angle is between -40 degrees and +40 degrees, the optical surface of the backlight module of the present invention has more prominent light condensing characteristics.

[0023] In the present invention, the brightness of the backlight module having two asymmetric fine structure prism sheets (i.e., the first prism sheet 3 and the second prism sheet 4) may be greater than that of the conventional backlight module, and more preferably, it is about 1.6 times that of the conventional backlight module. Thereby, the backlight module of the present invention can achieve the effects of concentrating light rays and improving the brightness of the backlight module compared with the conventional backlight module. Thus, when the backlight module of the present invention is applied to a vehicle display, it can ensure that the driver's field of vision is not blocked by the screen of the display in front of the passenger seat, and ensure driving safety.

[0024] The present invention is a backlight module having two asymmetric microstructure prism sheets, whereas conventional backlight modules have two symmetric microstructure prism sheets. In conventional backlight modules, one symmetric microstructure prism sheet deflects the light at a large angle when the incident angle is directed in the positive direction. Therefore, when a conventional backlight module uses two symmetric microstructure prism sheets to focus the light, the degree of light deflection increases, and the peak of the light ray shifts from the positive direction. Referring to Figure 4, a conventional backlight module with two symmetric microstructure prism sheets generates the peak of the light ray at approximately -6 degrees along the Y axis, rather than in the positive direction of 0 degrees. In addition, localized light rays are scattered in the +Y axis direction and the -Y axis direction, making it impossible to efficiently concentrate the light ray to one location. This conventional backlight module is less able to efficiently concentrate the light ray to one location compared to the backlight module of the present invention. Therefore, when conventional backlight modules are applied to vehicle displays, the light from the display in front of the passenger seat is directed towards the driver's seat, obstructing the driver's field of vision and increasing the risk of accidents while driving.

[0025] Referring to Figure 1, in the backlight module of the present invention, the light guide plate 1 has a light incident surface 11 and a light emission surface 12, and the light incident surface 11 and the light emission surface 12 are connected to each other. The light guide plate 1 further has a bottom surface 13 facing the light emission surface 12, and the bottom surface 13 is connected to the light incident surface 11.

[0026] The light-emitting mechanism 2 is located on the side of the light incident surface 11 of the light guide plate 1 and is used to emit light rays toward the light incident surface 11 of the light guide plate 1. For example, the light-emitting mechanism 2 may be a light-emitting diode, although this is not limited to the light-emitting mechanism 2.

[0027] 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 that are positioned opposite each other. Here, the first light-incident surface 31 is directed toward 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, the first prism structures 33 having an asymmetric structure. In this embodiment, the refractive index of the first prism sheet 3 is in the range of 1.5 to 1.7, including the endpoint value.

[0028] The second prism sheet 4 is located above the first prism sheet 3 and has a second light incident surface 41 and a second light emission surface 42 that are positioned opposite each other. Here, the second light incident surface 41 is directed toward the first light emission surface 32 of the first prism sheet 3, and the second light emission surface 42 is provided with a plurality of second prism structures 43, the second prism structures 43 having an asymmetric structure. In this embodiment, the refractive index of the second prism sheet 4 is between 1.5 and 1.7, including the endpoint value. Preferably, the refractive index of the second prism sheet 4 is greater than or equal to the refractive index of the first prism sheet 3.

[0029] In this embodiment, the first prism structure 33 of the first prism sheet 3 is a strip structure formed by a first side surface 331 and a second side surface 332, and the second prism structure 43 of the second prism sheet 4 is a strip 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 incident surface 11 / light emission mechanism 2 than the second side surface 332 and the fourth side surface 432, respectively. A first angle θ1 is formed between the first side surface 331 and the first light emission surface 32, and is in the range of 50 to 80 degrees, including the endpoint value. A second angle θ2 is formed between the second side surface 332 and the first light emission surface 32. A third angle θ3 is formed between the third side surface 431 and the second light emission surface 42, and is in the range of 50 to 80 degrees, including the endpoint value. A fourth angle θ4 is formed between the fourth side surface 432 and the second light emission surface 42. Furthermore, a first vertex angle φ1 is formed between the first side surface 331 and the second side surface 332, and is within the range of 60 to 90 degrees, including the endpoint value. A second vertex angle φ2 is formed between the third side surface 431 and the fourth side surface 432, and is within the range of 60 to 90 degrees, including the endpoint value. Preferably, the first vertex angle φ1 is larger than the second vertex angle φ2.

[0030] Referring to Figure 5, in this embodiment, the microstructure has an extension angle φ3 between the first extension direction D1 of the first prism structure 33 and the second extension direction D2 of the second prism structure 43, which is within the range of 0 to 40 degrees and includes the endpoint value. On the other hand, the first prism structure 33 has a first spacing S1 which is within the range of 15 μm to 55 μm and includes the endpoint value. The second prism structure 43 has a second spacing S2 which is within the range of 15 μm to 55 μm and includes the endpoint value. Here, the reason why the first spacing S1 is not equal to the second spacing S2 is that if the first spacing S1 is equal to the second spacing S2, a moiré pattern may occur. For example, the first spacing S1 of the first prism structure 33 or the second spacing S2 of the second prism structure 43 may be 18 μm, 24 μm, or 50 μm, as long as the first spacing S1 is not equal to the second spacing S2.

[0031] In this invention, both the first prism structure 33 and the second prism structure 43 are strip-shaped structures that extend toward the drawing. On the other hand, the first binding angle θ1 of the first prism structure 33 and the third binding angle θ3 of the asymmetric microstructure of the second prism structure 43 are located relatively close to the light incident surface 11 of the light guide plate 1, and the first binding angle θ1 is larger than the second binding angle θ2, and the third binding angle θ3 is larger than the fourth binding angle θ4. The steeply sloping first side surface 331 and the third side surface 431 are located relatively close to the light incident surface 11, while the gently sloping second side surface 332 and the fourth side surface 432 are located relatively far from the light incident surface 11.

[0032] In this invention, a single prism sheet with an asymmetric microstructure has sides with steeply sloping microstructures that are relatively close to the light incident surface. That is, the slope of the inclined surface that receives the light rays from the lower light guide plate 1 is gentle, so the light is deflected at a small angle with the incident angle directed in the positive direction. Therefore, when using two prism sheets with asymmetric microstructures (i.e., a first prism sheet 3 and a second prism sheet 4), the steeply sloping first side surface 331 and third side surface 431 are located relatively close to the light incident surface 11. That is, the gentle slopes of the second side surface 332 and fourth side surface 432 deflect the light at a small angle with the incident angle directed in the positive direction. As a result, the positive deflection effects of the first prism sheet 3 and the second prism sheet 4 overlap, concentrating the peak of the light rays precisely in the positive direction and enabling efficient light collection. As can be seen from Figure 2, by concentrating the light rays in one place, when the backlight module of the present invention is applied to a vehicle display, it is possible to ensure that the driver's field of view is not obstructed by the display screen in front of the passenger seat, thereby ensuring driving safety.

[0033] Referring to Figure 6, which is a side view of another conventional backlight module, it has two asymmetric microstructure prism sheets, but the inclination direction of this asymmetric microstructure is different from the inclination direction of the asymmetric microstructure of the present invention. Specifically, the conventional backlight module includes a lower prism sheet 91 and an upper prism sheet 92, the lower prism sheet 91 has a first binding angle θ1' and a second binding angle θ2', the first binding angle θ1' is smaller than the second binding angle θ2'. The upper prism sheet 92 has a third binding angle θ3' and a fourth binding angle θ4', the third binding angle θ3' is smaller than the fourth binding angle θ4'. Since the first and third included angles θ1' and θ3' are both relatively close to the plane of incident light, the first and third sides 911 and 921, which have gentle slopes, are relatively close to the plane of incident light, while the second and fourth sides 912 and 922, which have steep slopes, are relatively far from the plane of incident light.

[0034] In conventional backlight modules, the sides of the microstructure with a gentle slope are relatively close to the light incidence surface. In other words, the slope of the inclined surface that receives light rays from the light guide plate below is steep. Therefore, the incidence angle of conventional backlight modules deflects the light at a larger angle toward the positive direction than that of backlight modules with the aforementioned symmetrical microstructure. Consequently, when using two prism sheets with asymmetrical microstructures where the sides of the microstructure with a gentle slope are relatively close to the light incidence surface, the deflection angle becomes too large, and the light cannot be effectively focused. Furthermore, as can be seen from Figure 7, the peaks of the light rays are dispersed, resulting in a light emission surface with two high peaks. Thus, conventional backlight modules cannot effectively concentrate light rays to one location compared to the backlight module of the present invention. Therefore, when a conventional backlight module is applied to a vehicle display, the light rays from the display in front of the passenger seat are directed toward the driver's seat, obstructing the driver's field of view and increasing the risk of driving accidents.

[0035] In other words, the conventional backlight modules described above, whether using two prism sheets with symmetrical microstructures or two prism sheets with gently sloping microstructures, are unable to achieve the effect of concentrating light rays to a single point compared to two prism sheets with asymmetrical microstructures relatively close to the light incidence surface. Therefore, when the conventional backlight modules described above are applied to vehicle displays, the light rays from the display in front of the passenger seat are directed towards the driver's seat, obstructing the driver's field of vision and increasing the risk of driving accidents.

[0036] In this embodiment, the haze value of the second prism sheet 4 may or may not be zero. Considering the balance between high brightness and uniform light emission, the present invention adds the following haze value conditions to either the first prism sheet 3 or the second prism sheet 4, respectively.

[0037] For example, compared to a conventional backlight module having two symmetrical microstructure prism sheets, the brightness of the backlight module with the first prism sheet 3 having a haze value of 30% in the present invention is improved by approximately 3%, and when the haze value is 30% or less, an improvement of nearly 60% is observed, with the improvement being greater as the haze value decreases. However, taking the case where the haze value of the first prism sheet 3 is 40% as an example, the brightness improvement effect is lower than that of a conventional backlight module design having two symmetrical microstructure prism sheets, and is actually reduced by 6%. Therefore, it is preferable that the haze value of the first prism sheet 3 be 30% or less.

[0038] From the perspective of improving color difference, the haze value of the first prism sheet 3 needs to be designed to be other than zero, and the details are as follows. 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 invention was 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 invention was calculated to be 0.0076, and the color shift phenomenon increased by about 13%. Therefore, by setting the haze value of the first prism sheet 3 to something other than zero, the effect of masking scratches and defects in the backlight module can be enhanced, and the problem of severe color shift can be improved.

[0039] The haze value of the second prism sheet 4 is preferably 20% or less. If the haze value of the second prism sheet 4 exceeds 20%, the overall brightness of the backlight module decreases. On the other hand, if the haze value of the second prism sheet 4 is 20% or less (not zero), for example, if the haze value of the second prism sheet 4 is 20% and the haze value of the first prism sheet 3 is 10%, and the haze value of the second prism sheet 4 is greater than the haze value of the first prism sheet 3, or if the haze value of the second prism sheet 4 is 10% and the haze value of the first prism sheet 3 is 20%, and 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 invention is approximately 0.0073 in all cases, which is within the acceptable range.

[0040] 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 invention is calculated to be 0.0067, which is the minimum color difference. In other words, by setting the haze value of the second prism sheet 4 to zero, the optimal color difference improvement effect can be obtained. This color difference was calculated based on CIE1976LAB. The application of the haze value in this embodiment may also be achieved by adding diffusing particles to the light incident surfaces of the first prism sheet 3 and the second prism sheet 4, which can help to obtain a good effect of light emission uniformity on the optical surface.

[0041] Referring to Figure 1, the backlight module of the present invention further includes an optical film 5 located above the second prism sheet 4. The optical film 5 may be a film having a light atomization effect, for example, a film containing diffusing particles, or a multi-functional brightness-enhancing film having a diffusing layer or a rough surface layer. In order to achieve the need for a thinner backlight module, the backlight module of the present invention may omit the lower diffusing sheet found in conventional backlight modules.

[0042] Specifically, in conventional backlight modules, when light rays pass through the lower diffusion sheet, they are actually diffused by the module, making it impossible to effectively concentrate the light rays. Therefore, the backlight module of the present invention further omits the lower diffusion sheet and concentrates the light rays using a first prism sheet 3 and a second prism sheet 4 that form an asymmetrical structure with respect to each other, thereby achieving the effect of improving the brightness of the backlight module.

[0043] The backlight module of the present invention may further have a reflective sheet 6 on the bottom surface 13 side of the light guide plate 1. This has the effect of improving the light utilization rate of the light-emitting mechanism 2, as light rays emitted from the bottom surface 13 of the light guide plate 1 are reflected by the reflective sheet 6 and returned to the light guide plate 1.

[0044] Referring to Tables 1 to 3, each represents an embodiment of the backlight module of the present invention, having an upper diffusion sheet but omitting the lower diffusion sheet. Tables 1 to 3 show a comparison of luminance gains when the refractive index of the first prism sheet 3 is adjusted and a second prism sheet 4 with a different refractive index is compared. Here, luminance gain comparison (1) is an estimation of the luminance gain values ​​of the other experimental groups based on the luminance values ​​of the experimental group with the first prism sheet 3 having a relatively low refractive index, as shown in Table 1. Furthermore, luminance gain comparison (2) is an estimation of luminance gain values ​​obtained by swapping the second prism sheet 4 with a different refractive index with the first prism sheet 3 having the same refractive index.

[0045] [Table 1] [Table 2] [Table 3]

[0046] First, referring to the nine sets of examples in Tables 1 to 3, if the refractive indices of the first prism sheet 3 and the second prism sheet 4 are within the range of 1.5 to 1.7, and include the endpoint values, then regardless of whether the refractive index of the second prism sheet 4 is greater than, less than, or equal to that of the first prism sheet 3, the peak value of the light rays emitted from the backlight module in the first direction (Y-axis direction) can be maintained at less than 10 degrees, thereby achieving the effect of ensuring high light output efficiency in the true viewing angle.

[0047] Next, in the optical simulation diagrams measured under the conditions of these nine sets of embodiments, in the first direction (Y-axis direction), the light rays emitted from the backlight module have a first full width at half maximum (FWHM) angle, and in the second direction (X-axis direction), the light rays emitted from the backlight module have a second FWHM angle, the second direction is perpendicular to the first direction, and the ratio of the second FWHM angle to the first FWHM angle is in the range of 1.65 to 3.69, including the endpoint value. For example, the first direction (Y-axis direction) is approximately parallel to the path of the light rays emitted from the light source, the second direction (X-axis direction) is approximately parallel to the light incident surface of the light guide plate, and the ratio of the FWHM angles along the second direction and the first direction, i.e., the ratio of the second FWHM angle to the first FWHM angle, is 4 or less. This ensures that the light field of view of the entire backlight module is within the normal viewing range of the display device user. In the embodiments illustrated in the present invention, the second half-width angle is in the range of 28 to 59 degrees, including the endpoint value.

[0048] In the nine sets of examples shown in Tables 1 to 3, the second prism sheet 4 with a high refractive index selected in Table 3 ensures that the peak value of the light rays emitted from the backlight module in the first direction (Y-axis direction) is closer to the true viewing angle (0 degrees) compared to the second prism sheet 4 with a low refractive index selected in Table 1, and also exhibits superior luminance gain in the luminance gain comparison (1). However, considering material cost conditions, the second prism sheet 4 with a low refractive index selected in Table 1 is more advantageous.

[0049] Furthermore, the luminance gain comparison (2) compares Tables 1, 2, and 3 independently and individually. As mentioned above, in each table, the first prism sheet 3 with the same refractive index is used as the reference for luminance gain. If the refractive index of the second prism sheet 4 is higher than that of the first prism sheet 3, the gain value in the luminance gain comparison (2) can be improved. For example, as a compromise considering material costs, it is preferable to select one of the three example configurations in Table 1. However, if there is a specific requirement for high brightness, it is possible to obtain a better luminance gain value and light output efficiency at the true viewing angle by preferentially selecting the first prism sheet 3, which has a higher refractive index than Table 1, and combining it with an example configuration in which the refractive index of the second prism sheet is greater than or equal to that of the first prism sheet (for example, a combination of Tables 2 and 3 with a luminance gain of 100% or more in the luminance gain comparison (2)).

[0050] Referring to Figure 8, which is a partial cross-sectional view of the display device of the present invention, the display device comprises the aforementioned backlight module and a display panel 7 located above the backlight module. More specifically, the display panel 7 is located above the diffusion sheet 5.

[0051] As described above, the backlight module and display device of the present invention utilize at least two optical film sheets with asymmetric microstructures, such as a first prism sheet and a second prism sheet, which have an asymmetric structure. In the asymmetric microstructures of the first and second prism sheets, steep slopes are inclined toward the light incident surface, while slopes receiving light rays from the lower light guide plate have a gentle slope. This efficiently concentrates the light rays and improves the brightness gain of the backlight module. The optical surface of the backlight module of the present invention exhibits a specific concentrated light emission region, making it suitable for applications such as vehicle displays. Furthermore, the present invention can achieve a good uniform light emission effect on the optical surface of the backlight module through a combination of optical films having different haze values. For example, if the haze value of the first prism sheet is not zero, the backlight module of the present invention can effectively mask scratches and defects and improve the problem of severe color misalignment.

[0052] The embodiments described above are for illustrative purposes only to illustrate the principles, features and effects of the present invention and do not limit the scope of the invention. Those skilled in the art can modify and change the embodiments described above without departing from the spirit and scope of the invention. All equivalent modifications and changes made using the disclosures of the present invention should be included in the claims. [Explanation of symbols]

[0053] 1...Light guide plate 11...Light incidence surface 12...Light exit surface 13…Bottom 2…Light-emitting mechanism 3…First prism sheet 31...First light incidence surface 32...First light exit surface 33…First prism structure 331…1st side 332…Second side 4…Second prism sheet 41…Second light incidence surface 42…Second light-emitting surface 43…Second prism structure 431…Third side surface 432…Fourth side surface 5…Diffusion sheet 6…Reflection sheet 7…Display panel θ1…First included angle θ2…Second included angle θ3…Third included angle θ4…Fourth included angle φ1…First apex angle φ2…Second apex angle φ3…Included angle of the extension of the microstructure D1…First extension direction D2…Second extension direction S1…First interval S2…Second interval 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 included angle θ2’…Second included angle θ3’…Third included angle θ4’…Fourth included angle

Claims

1. It is a backlight module, It comprises a light guide plate, a light-emitting mechanism, a first prism sheet, and a second prism sheet. The light guide plate has a light incident surface and a light emission surface that are connected to each other. The light-emitting mechanism is located on the side of the light incident surface of the light guide plate, The first prism sheet has a non-zero haze value, 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 positioned opposite each other, the first light-incident surface is directed toward the light-emitting surface of the light guide plate, and the first light-emitting surface is provided with a plurality of first prism structures, the first prism structures having an asymmetric structure. The second prism sheet is located above the first prism sheet and has a second light incident surface and a second light emission surface that are positioned opposite each other. The second light incident surface is directed toward the first light emission surface of the first prism sheet, and the second light emission surface is provided with a plurality of second prism structures, the second prism structures having an asymmetric structure. Backlight module.

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

3. The haze value of the second prism sheet is 20% or less, including the endpoint value. The backlight module according to claim 2.

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

5. 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 each closer to the light incident surface than the second side surface and the fourth side surface, the first side surface and the first light emission surface have a first binding angle, the second side surface and the first light emission surface have a second binding angle, the first binding angle is larger than the second binding angle, the third side surface and the second light emission surface have a third binding angle, and the fourth side surface and the second light emission surface have a fourth binding angle, the third binding angle is larger than the fourth binding angle. The backlight module according to claim 1.

6. The backlight module further comprises a diffusion sheet located above the second prism structure. The backlight module according to claim 1.

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

8. A display device, A backlight module according to any one of claims 1 to 7, The system includes a display panel located above the backlight module. Display device.

9. It is a backlight module, It comprises a light guide plate, a light-emitting mechanism, a first prism sheet, and a second prism sheet. The light guide plate has a light incident surface and a light emission surface that are connected to each other. The light-emitting mechanism is located on the side of the light incident surface of the light guide plate, The first prism sheet has a haze value that is not zero, and 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 set opposite each other, the first light-incident surface is directed toward the light-emitting surface of the light guide plate, and the first light-emitting surface is provided with a plurality of first prism structures, the first prism structure is asymmetrical and is a strip structure formed by a first side surface and a second side surface, a first vertex angle is formed between the first side surface and the second side surface, within the range of 60 to 90 degrees, including the endpoint value, a first binding angle is formed between the first side surface and the first light-emitting surface, within the range of 50 to 80 degrees, including the endpoint value, and a second binding angle is formed between the second side surface and the first light-emitting surface. The second prism sheet is located above the first prism sheet and has a second light incident surface and a second light emission surface that are set opposite each other, the second light incident surface is directed toward the first light emission surface of the first prism sheet, and the second light emission surface is provided with a plurality of second prism structures, the second prism structures are asymmetric structures and are strip-like structures formed by a third side surface and a fourth side surface, a second vertex angle is formed between the third side surface and the fourth side surface, within the range of 60 to 90 degrees, including the endpoint value, a third binding angle is formed between the third side surface and the second light emission surface, within the range of 50 to 80 degrees, including the endpoint value, and a fourth binding angle is formed between the fourth side surface and the second light emission surface. The first and third sides are each closer to the light incident surface than the second and fourth sides, the refractive indices of the first and second prism sheets are in the range of 1.5 to 1.7, including the endpoint values, The microstructure has an extension angle between the first extension direction of the first prism structure and the second extension direction of the second prism structure, which is within the range of 0 to 40 degrees, including the endpoint value. The first prism structure has a first spacing, which is in the range of 15 μm to 55 μm and includes endpoint values, and the second prism structure has a second spacing, which is in the range of 15 μm to 55 μm and includes endpoint values, and the first spacing is not equal to the second spacing. Backlight module.

10. The haze value of the first prism sheet is in the range of 10% to 30%, including the endpoint value. The backlight module according to claim 9.

11. The haze value of the second prism sheet is 20% or less, including the endpoint value. The backlight module according to claim 9.

12. The haze value of the second prism sheet is zero. The backlight module according to claim 9.

13. The refractive index of the second prism sheet is greater than or equal to the refractive index of the first prism sheet. The backlight module according to claim 9.

14. The first vertex angle is greater than the second vertex angle. The backlight module according to claim 9.

15. The peak value of the light beam emitted from the backlight module in the first direction is less than 10 degrees. The backlight module according to claim 9.

16. In the first direction, the light rays emitted from the backlight module have a first half-width angle, and in the second direction, the light rays emitted from the backlight module have a second half-width angle, the second direction is perpendicular to the first direction, and the ratio of the second half-width angle to the first half-width angle is in the range of 1.65 to 3.69, including the endpoint value. The backlight module according to claim 9.

17. The second half-width angle is in the range of 28 to 59 degrees, including the endpoint values. The backlight module according to claim 16.

18. The backlight module further includes an optical film located above the second prism structure. The backlight module according to claim 9.

19. The light guide plate further has a bottom surface facing the light emitting surface, and the reflective sheet is located on the side of the bottom surface of the light guide plate. The backlight module according to claim 9.

20. A display device, A backlight module according to any one of claims 9 to 19, The system includes a display panel located above the backlight module. Display device.

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