Backlight module and display device

Abstract

The utility model relates to backlight module and display device. The backlight module contains light guide plate, a plurality of light emitting unit, optical film piece, first prism piece and second prism piece. Light guide plate has the light entrance surface and the light exit surface, these light emitting units are arranged on the light entrance surface along the arrangement direction. Optical film piece has opposite first surface and second surface, and the first surface faces on the light exit surface. First prism piece is superimposed on the second surface and contains the first prism strip along the first direction extension, second prism piece is superimposed on first prism piece and contains the second prism strip along the second direction extension perpendicular to the first direction, and second direction has the angle theta with the arrangement direction. The angle theta is configured to make the Y1 of backlight module 0.07, Y1=L1 / L2, L1 is the brightness of backlight module at 45 degrees viewing angle, and L2 is the brightness of backlight module at 0 degrees viewing angle.

Description

[0001] This application claims priority to Chinese Patent Application No. 202521648060.4, filed on August 5, 2025, entitled “Backlight Module and Display Device”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates to a backlight module and a display device comprising the aforementioned backlight module. Background Technology

[0003] With technological advancements, display devices equipped with LCD panels have become indispensable items in modern life. However, users have different requirements for the viewing angle of display devices in different situations. For example, if a user wants to share information on the screen with others, the display device needs to have a wide viewing angle so that multiple people can see the content on the screen from different angles, which is to make the display device a sharing mode; if a user wants to maintain privacy while handling personal matters, they want the display to be visible only to themselves, which requires the display product to have a narrow viewing angle, which is a privacy mode.

[0004] In the current architecture, optical films such as privacy filters are placed between the backlight module and the LCD panel to guide the light emitted from the backlight module and block wide-angle light. However, privacy filters and other optical films affect light utilization, causing problems such as insufficient brightness and excessive power consumption. In addition, the use of privacy filters and other optical films also increases costs and the thickness of the backlight module.

[0005] Therefore, developing a backlight module that can achieve privacy mode without affecting light utilization when applied to display devices, thereby increasing brightness and reducing power consumption, while also reducing costs and not increasing the thickness of the backlight module, is one of the goals that those skilled in the art wish to achieve. Utility Model Content

[0006] The purpose of this disclosure is to provide a backlight module and a display device including the aforementioned backlight module. By configuring the angle between the extension direction of the prism strip of the prism sheet and the arrangement direction of the light-emitting unit, the ratio of the luminance of the backlight module at a 45-degree viewing angle to the luminance at a 0-degree viewing angle is less than 0.07. Therefore, when applied to a display device, a privacy mode can be achieved without affecting the light utilization rate, which helps to improve the privacy effect, increase the brightness and reduce the power consumption, and can reduce the cost without increasing the thickness of the backlight module.

[0007] This disclosure discloses at least one embodiment of a backlight module comprising a light guide plate, a plurality of light-emitting units, an optical film, a first prism sheet, and a second prism sheet. The light guide plate has a light-incident surface and a light-emitting surface. The light-emitting units are arranged along an arrangement direction and disposed on the light-incident surface. The optical film has opposing first and second surfaces, with the first surface facing the light-emitting surface. The first prism sheet is stacked on the second surface and includes a plurality of first prism strips extending along a first direction. The second prism sheet is stacked on the first prism sheet and includes a plurality of second prism strips extending along a second direction. The second direction is perpendicular to the first direction, and the second direction forms an angle θ with the arrangement direction. The angle θ is configured such that Y1 of the backlight module is less than 0.07, Y1 = L1 / L2, where L1 is the luminance of the backlight module at a 45-degree viewing angle, and L2 is the luminance of the backlight module at a 0-degree viewing angle.

[0008] This disclosure discloses a display device according to at least another embodiment, comprising the backlight module and a display panel. The display panel is stacked on a second prism sheet and includes a first substrate, a second substrate, and a liquid crystal layer sandwiched between the first substrate and the second substrate. Attached Figure Description

[0009] Figure 1 This is a perspective schematic diagram of a backlight module according to at least one embodiment disclosed herein.

[0010] Figure 2 The graph shows the relationship between the included angle θ and the luminance gain, and the relationship between the noise ratio at a 45-degree viewing angle, using at least one embodiment of the backlight module disclosed herein.

[0011] Figure 3 This is a graph showing the relationship between the included angle θ and the noise ratio at an 85-degree viewing angle for a backlight module using at least one embodiment of this disclosure.

[0012] Figure 4 This is a three-dimensional schematic diagram of an optical film according to at least one embodiment disclosed herein.

[0013] Figure 5A and Figure 5B These are, respectively, a perspective view and a cross-sectional view of a light guide plate according to at least one embodiment of the present disclosure.

[0014] Figure 6 This is a perspective view of a display device according to at least one embodiment of the present disclosure.

[0015] Figure 7 and Figure 8 This is a perspective view of a display device according to at least another embodiment of the present disclosure.

[0016] Figure 9A and Figure 9B These are perspective schematic diagrams of the compensation diaphragm in sharing mode and privacy mode, representing at least one embodiment of the present disclosure.

[0017] Figure 10A and Figure 10B These are light transmission images from various angles simulated in privacy mode using the compensation film and backlight module of at least one embodiment of this disclosure. Detailed Implementation

[0018] In the following description, to clearly present the technical features of this disclosure, the dimensions (e.g., length, width, thickness, and depth) of the elements (e.g., layers, films, substrates, and regions) in the accompanying drawings will be enlarged proportionally, and the number of some elements may be reduced. Therefore, the description and explanation of the embodiments below are not limited to the number of elements in the accompanying drawings and the size and shape of the elements, but should cover the dimensions, shapes, and deviations from both caused by actual manufacturing processes and / or tolerances.

[0019] Secondly, the terms "approximately," "about," or "substantially" used in this disclosure not only cover explicitly stated numerical values ​​and ranges, but also the permissible deviation range understood by someone skilled in the art to which this utility model pertains. This deviation range can be determined by errors generated during measurement, which may be caused by limitations of the measurement system or process conditions. For example, two objects (e.g., planes or traces of a substrate) are "substantially parallel" or "substantially perpendicular," where "substantially parallel" and "substantially perpendicular" respectively represent that the parallelism and perpendicularity between the two objects may include non-parallelism and non-perpendicularity caused by permissible deviation ranges.

[0020] Furthermore, "about" can mean within one or more standard deviations of the aforementioned values, such as ±30%, ±20%, ±10%, or ±5%. Terms such as "about," "approximately," or "substantially" used in this disclosure may be chosen based on the optical, etching, mechanical, or other properties to select an acceptable range of deviations or standard deviations, and are not applied to all of the aforementioned optical, etching, mechanical, and other properties using only one standard deviation.

[0021] The spatial relative terms used in this disclosure, such as "below," "under," "above," and "above," are for the convenience of describing the relative relationship between one element or feature and another, as illustrated in the accompanying drawings. The true meaning of these spatial relative terms includes other orientations. For example, when the drawings are shown rotated 180 degrees vertically, the relationship between one element and another may change from "below" or "under" to "above" or "above." Furthermore, the spatial relative descriptions used in this disclosure should be interpreted in the same way.

[0022] It should be understood that although this disclosure may use terms such as "first," "second," and "third" to describe various elements or features, these elements or features should not be limited by these terms. These terms are primarily used to distinguish one element from another, or one feature from another. Furthermore, the term "or" as used in this disclosure may, as appropriate, include any combination of one or more of the associated listed items.

[0023] Please see Figure 1 The backlight module 100 includes a light guide plate 102, a plurality of light-emitting units 104, an optical film 106, a first prism sheet 108, and a second prism sheet 110. The light guide plate 102 has an incident light surface IS and an exit light surface ES. The light-emitting units 104 are arranged along the arrangement direction AD and disposed on the incident light surface IS. The optical film 106 has a first surface S1 and a second surface S2 facing each other, and the first surface S1 faces the exit light surface ES.

[0024] A first prism sheet 108 is stacked on a second surface S2 and includes a plurality of first prism strips P1 extending along a first direction D1. A second prism sheet 110 is stacked on the first prism sheet 108 and includes a plurality of second prism strips P2 extending along a second direction D2. The second direction D2 is perpendicular to the first direction D1, and the second direction D2 forms an angle θ with the arrangement direction AD. The angle θ is configured such that Y1 of the backlight module 100 is less than 0.07, Y1 = L1 / L2, where L1 is the luminance of the backlight module 100 at a 45-degree viewing angle, and L2 is the luminance of the backlight module 100 at a 0-degree viewing angle.

[0025] By configuring the extension direction of the first prism strip P1 (i.e., the first direction D1) to be perpendicular to the extension direction of the second prism strip P2 (i.e., the second direction D2), and the extension direction of the second prism strip P2 to have an angle θ with the arrangement direction AD of the light-emitting unit 104, the distribution of light in the horizontal direction can be controlled. Most of the light can be adjusted to be emitted in the direction perpendicular to the light-emitting surface ES of the light guide plate 102, so that the light is concentrated in the 0-degree viewing angle (i.e., the frontal viewing angle), the luminance can be further improved, and the luminance at the 45-degree viewing angle (i.e., the side viewing angle) can be reduced. This makes the ratio of the luminance of the backlight module 100 at the 45-degree viewing angle to the luminance at the 0-degree viewing angle less than 0.07. Therefore, when applied to a display device, a privacy mode can be achieved without affecting the light utilization rate, which helps to improve the privacy effect, increase the brightness and reduce the power consumption, and can reduce the cost without increasing the thickness of the backlight module 100.

[0026] Specifically, Y1 represents the light leakage level of the backlight module 100 at a 45-degree viewing angle.

[0027] The Y1 and included angle θ of the backlight module 100 satisfy the function n1 is the refractive index of the first prism (108), n2 is the refractive index of the second prism (110), and n3 is... The refractive index of the optical film 106. In some embodiments, n1, n2, and n3 are 1.45 to 1.6. This function allows for precise configuration of the angle θ between the extension direction of the second prism strip P2 and the arrangement direction AD of the light-emitting unit 104, ensuring that the ratio of the luminance of the backlight module 100 at a 45-degree viewing angle to its luminance at a 0-degree viewing angle is less than 0.07. Therefore, when applied to a display device, it can achieve a better privacy mode without affecting light utilization, thus helping to improve the privacy protection effect.

[0028] like Figure 2 As shown, when the included angle θ is between 20 degrees and 160 degrees, the luminance gain curve C1 of the backlight module 100 remains above 80%, and the noise ratio curve C2 of the backlight module 100 at a 45-degree viewing angle is less than 7%, meaning the ratio of the luminance of the backlight module 100 at a 45-degree viewing angle to its luminance at a 0-degree viewing angle is less than 0.07. In short, by applying the optical film 106 disclosed herein, more than 80% of the energy of the backlight module 100 can be directed at a 0-degree viewing angle, while the 45-degree viewing angle direction exhibits low noise (less than 7%). Therefore, when the backlight module 100 is applied to a display device, it can achieve a better privacy mode without affecting light utilization, helping to improve privacy protection, increase brightness, and reduce power consumption.

[0029] In some embodiments, Y2 represents the light leakage level of the backlight module 100 at an 85-degree viewing angle, which is the ratio of the brightness of the backlight module 100 at an 85-degree viewing angle to its brightness at a 0-degree viewing angle. Furthermore, the Y2 of the backlight module 100 and the included angle θ satisfy the function n1 is the refractive index of the first prism sheet 108, n2 is the refractive index of the second prism sheet 110, and n3 is the refractive index of the optical film 106. This function allows for the appropriate configuration of the angle θ between the extension direction of the second prism strip P2 (i.e., the second direction D2) and the arrangement direction AD of the light-emitting unit 104. By limiting this angle θ to between 20° and 160°, within this range, it can be ensured that the Y2 of the backlight module 100 is ≤0.5, meaning the ratio of the backlight module 100's luminance at an 85-degree viewing angle to its luminance at a 0-degree viewing angle is not greater than 0.5. This avoids significant light leakage at large viewing angles when the display device is in privacy mode, further enhancing the privacy protection effect.

[0030] like Figure 3As shown, the noise ratio curve C3 of the backlight module 100 at an 85-degree viewing angle is close to 90%, or greater than 50%, when the included angle θ is 90 degrees. In other words, when the included angle θ is 90 degrees, the ratio of the backlight module 100's luminance at an 85-degree viewing angle to its luminance at a 0-degree viewing angle is greater than 0.5. This means that the noise at large viewing angles is higher than 50%. Therefore, in the backlight module 100, the included angle θ is not configured to be 90 degrees to ensure that the ratio of the backlight module 100's luminance at an 85-degree viewing angle to its luminance at a 0-degree viewing angle is not greater than 0.5. This avoids significant light leakage at large viewing angles when the display device is in privacy mode, further improving the privacy protection effect.

[0031] Please see Figure 4 The optical film 106 includes a plurality of strip-shaped microstructures SM and a plurality of cone-shaped microstructures CM. The strip-shaped microstructures SM are arranged parallel to each other on a first surface S1, and the cone-shaped microstructures CM are located on a second surface S2. In some embodiments, each cone-shaped microstructure CM is a pyramid structure with multiple facets, and the extension direction E1 of each strip-shaped microstructure SM intersects the arrangement direction AD of the light-emitting units 104; for example, the extension direction E1 of the strip-shaped microstructure SM is perpendicular to the arrangement direction AD of the light-emitting units 104.

[0032] By utilizing these strip-shaped microstructures SM and these cone-shaped microstructures CM, light emitted from the light-emitting surface ES of the light guide plate 102 first passes through the strip-shaped microstructures SM of the optical film 106, producing an effect of improved directivity. Then, it passes through the cone-shaped microstructures CM of the optical film 106 to maintain concealing properties. This concealing effect is mainly due to the fact that the cone-shaped microstructures CM have multiple facets, which can deflect light through multiple facets and guide it to multiple light-emitting directions, preventing light energy from being too concentrated directly above the cone-shaped microstructures CM, thereby maintaining the concealing effect. In contrast, ordinary dot microstructures or diffused particles only scatter light in an uncertain direction and cannot effectively control the concealing direction. In this way, the optical film 106 can still promote concentrated light emission while maintaining concealing capabilities, thereby improving the light-emitting angle focus and positive angle brightness of the backlight module 100.

[0033] Please see Figure 5A and Figure 5BThe light guide plate 102 is a highly directional light guide plate, comprising a body BD, multiple strip lens structures LM, and multiple dimming structures DM. The body BD has an incident surface IS, an exit surface ES, and an optical surface LS. The incident surface IS is connected to the optical surface LS and the exit surface ES, and the optical surface LS and the exit surface ES are arranged opposite to each other. The strip lens structures LM are disposed on the optical surface LS. The dimming structures DM are disposed between these strip lens structures LM. Each dimming structure DM has a connected first light-acting surface F1 and a second light-acting surface F2. The first light-acting surface F1 is an inclined surface facing the incident surface IS, and the second light-acting surface F2 is an inclined surface facing the side of the body BD opposite to the incident surface IS. The inclination directions of the first light-acting surface F1 and the second light-acting surface F2 are different and asymmetrical.

[0034] Because the light guide plate 102 has a dimming structure DM between the strip lens structures LM, and the strip lens structure LM is used directly as the side of the dimming structure DM, the side of the dimming structure DM is not joined to the optical surface LS of the light guide plate 102, thus avoiding the problem of light leakage from the side of conventional microstructures. By using different inclinations of the first light-acting surface F1 and the second light-acting surface F2 of the dimming structure DM, the amount of light reflection or the guidance of light output can be increased, thereby improving the efficiency of light utilization. In terms of processing, using the strip lens structure LM directly as the side of the dimming structure DM not only reduces processing time but also allows for precise control of the inclination angles of the first light-acting surface F1 and the second light-acting surface F2 to produce the desired optical effect. Compared to traditional light guide plates, the highly directional light guide plate 102 disclosed in this paper can more effectively guide light to the positive viewing angle, reduce the generation of lateral light, and thus reduce the dependence on privacy films, achieving the goal of excellent privacy effect without using privacy films.

[0035] Please see Figure 6 The display device 10 includes the aforementioned backlight module 100 and display panel 200. The display panel 200 is stacked on the second prism sheet 110 and includes a first substrate 202, a second substrate 204, and a liquid crystal layer 206 sandwiched between the first substrate 202 and the second substrate 204. By employing the backlight module 100 disclosed herein, the display device 10 can achieve high brightness and excellent privacy protection without using a traditional privacy film, and the display device 10 can switch between shared mode and privacy mode.

[0036] In addition to the above embodiments, please refer to Figure 7 and Figure 8 In other embodiments disclosed herein, display devices 10A and 10B further include a compensation film 300 located on one side of the display panel 200. For example... Figure 7As shown, the compensation film 300 of the display device 10A is located between the backlight module 100 and the display panel 200. Figure 8 As shown, the compensation film 300 of the display device 10B is stacked on the display panel 200.

[0037] Please see Figure 9A and Figure 9B The compensation film 300 includes a liquid crystal retardation film 302 and a passive retardation film 304. The liquid crystal retardation film 302 includes a guest material M1 and a host material M2. The guest material M1 is an anisotropic material, and the host material M2 is a liquid crystal material. The volume or weight of the guest material M1 is smaller than that of the host material M2.

[0038] More specifically, the liquid crystal delay film 302 further includes a first electrode plate EP1 and a second electrode plate EP2, with the guest material M1 and the host material M2 sandwiched between the first electrode plate EP1 and the second electrode plate EP2. The first electrode plate EP1 and the second electrode plate EP2 each include an alignment layer (not shown in the figure). The alignment layer is disposed on the surfaces of the first electrode plate EP1 and the second electrode plate EP2 facing the guest material M1 and the host material M2, and provides alignment for the host material M2, such as vertical alignment.

[0039] The host material M2 primarily provides the alignment direction of liquid crystal molecules to determine the overall optical properties and responds to electric field control to change its alignment state under voltage. More importantly, it carries the guest material M1, serving as a carrier and orientation medium for dye molecules. The guest material M1 provides angle-selective absorption, which is the main mechanism by which the compensation film 300 produces a privacy effect. In shared mode, both polarization components are allowed to pass through, while in privacy mode, one polarization component is reflected while the other passes through.

[0040] As mentioned above, the design of object material M1 and subject material M2, compared with traditional technologies for achieving privacy mode, can achieve dynamic switching, that is, unlike louver film which is fixed, and can avoid interference with the pixel array, so no moiré pattern is generated, and no special production is required for different resolutions, thus reducing costs and improving efficiency.

[0041] In summary, the host material M2 is responsible for providing a controllable molecular arrangement structure, while the guest material M1 is responsible for providing the actual angle-selective optical effect. The two work together to enable the compensation film 300 to produce a privacy effect.

[0042] In this embodiment, the passive retardation film 304 is a negative C-plate retardation film. The negative C-plate retardation film may have an optical material layer containing a layer of birefringent material, and the optical axis of the optical material layer is perpendicular to the plane of the optical material layer. The Δn of the negative C-plate retardation film is negative, and Δn is defined as the difference between the extraordinary index of refraction (ne) and the ordinary index of refraction (no).

[0043] In shared mode, the negative C-plate retardation film is designed to compensate for the retardation effect of the liquid crystal retardation film 302 in the off-axis direction. For light rays perpendicular to the film plane or incident at an acute angle, there will be no overall polarization state conversion. This means that the brightness of display devices 10A and 10B is essentially unaffected by the viewing angle, and the high transmittance at the central viewing position allows multiple users to comfortably view the display over a wide range of viewing angles.

[0044] In privacy mode, the combination of the negative C-plate retardation film and the liquid crystal retardation film 302 causes a change in the polarization state of off-axis light. This polarization state change reduces the brightness of light in the tilted axis (off-axis) direction, while the brightness in the positive axis (directly in front) direction is not significantly reduced. Compared to using the liquid crystal retardation film 302 alone, combining it with the negative C-plate retardation film can further increase the field of view for reducing off-axis brightness.

[0045] Furthermore, the compensation film 300 further includes a first polarizer 306 and a second polarizer 308. A passive retardation film 304 is sandwiched between the first polarizer 306 and the liquid crystal retardation film 302, and the liquid crystal retardation film 302 is sandwiched between the passive retardation film 304 and the second polarizer 308. The polarization directions of the first polarizer 306 and the second polarizer 308 are parallel to each other. In some embodiments, the second polarizer 308 can serve as the lower polarizer of the display panel 200.

[0046] like Figure 9A As shown, when display devices 10A and 10B are used in shared mode, the voltage difference between the first electrode plate EP1 and the second electrode plate EP2 of the liquid crystal delay film 302 is zero. For example, no voltage is applied to the first electrode plate EP1 and the second electrode plate EP2. The guest material M1 and the host material M2 of the liquid crystal delay film 302 are not deflected. Therefore, the light emitted by the backlight module 100 enters the compensation film 300 and the transmission pattern is transmitted through the entire viewing angle.

[0047] like Figure 9BAs shown, when display devices 10A and 10B are used in privacy mode, the voltage difference between the first electrode plate EP1 and the second electrode plate EP2 of the liquid crystal delay film 302 is not zero, causing the guest material M1 and the host material M2 of the liquid crystal delay film 302 to deflect. Therefore, the transmission pattern of the light emitted by the backlight module 100 after entering the compensation film 300 is as follows. Figure 10A The light transmission diagram shown is shown.

[0048] like Figure 10A As shown, the transmittance pattern generated by the compensation diaphragm 300 has a first distribution mode DS1 and a second distribution mode DS2 in privacy mode. The first distribution mode DS1 extends along a first axis, and the second distribution mode DS2 is located along a second axis. The first axis intersects with the second axis, and the luminance of the first distribution mode DS1 is greater than the luminance of the second distribution mode DS2.

[0049] like Figure 10B As shown, the transmittance pattern generated by the backlight module 100 has a positive distribution mode ND, a weak distribution mode WD, and a strong distribution mode SD in privacy mode. The weak distribution mode WD and the strong distribution mode SD are located on mutually orthogonal axes, and the positive distribution mode ND is located at the intersection of the mutually orthogonal axes. The luminance of the positive distribution mode ND is greater than that of the strong distribution mode SD, and the luminance of the strong distribution mode SD is greater than that of the weak distribution mode WD. Furthermore, the strong distribution mode SD is misaligned with the aforementioned second distribution mode DS2.

[0050] For example, in privacy mode, such as Figure 10B As shown, most of the light from the backlight module 100 is emitted from the central position to form the positive distribution mode (ND), a small portion of the light is emitted from both ends of the axis between 157.5 degrees and 337.5 degrees to form the strong distribution mode (SD), and an even smaller portion of the light is emitted from both ends of the axis between 67.5 degrees and 247.5 degrees to form the weak distribution mode (WD). Figure 10A As shown, after the light emitted from the backlight module 100 passes through the compensation film 300, most of the light is emitted along the axial direction of 120 degrees to 300 degrees to form the first distribution mode DS1, and a small portion of the light is emitted at both ends of the axial direction of 30 degrees to 210 degrees to form the second distribution mode DS2.

[0051] In other words, in privacy mode, the strong distribution mode SD formed by the light emitted from the backlight module 100 is blocked by the compensation film 300, and the second distribution mode DS2 formed by the light emitted from the compensation film 300 is prevented from light leakage because the backlight module 100 below emits only weak light or even no light at the corresponding position. Therefore, by using the staggered combination design of the strong distribution mode SD and the second distribution mode DS2, it can be ensured that the display screen of the display devices 10A and 10B in privacy mode is only visible to the user located in the center of the display devices 10A and 10B, thereby avoiding obvious light leakage from other viewing positions of the display devices 10A and 10B in privacy mode, further improving the privacy effect. It is even more difficult for people looking from the side to see the screen content. Unlike general privacy laptops that require a privacy screen protector, it can achieve high brightness and good privacy effect.

[0052] The following table shows a comparative example 1 of a display device using a conventional backlight module and a conventional privacy screen in privacy mode; a comparative example 2 of a display device using a conventional backlight module and the compensation film 300 disclosed herein; and a comparative example 3 of a display device using a conventional backlight module and the compensation film 300 disclosed herein. Figure 1 Measurement data from an embodiment of a display device using the backlight module and the compensation film 300 disclosed herein:

[0053] As shown in the table above, the noise ratio of this embodiment at a 45-degree viewing angle is 0.4%, which is comparable to Comparative Example 1 and superior to Comparative Example 2. The noise ratio of this embodiment at a 65-degree viewing angle is 2.7%, which is higher than 0.5% of Comparative Example 1, but still superior to Comparative Example 2. However, in terms of brightness gain, the brightness gain of this embodiment is 137%, which is significantly better than Comparative Example 1 and Comparative Example 2.

[0054] In summary, in the backlight module and display device including the aforementioned backlight module of at least one embodiment disclosed above, the angle between the prism strip extension direction of the prism sheet and the light-emitting unit arrangement direction is configured such that the ratio of the luminance of the backlight module at a 45-degree viewing angle to the luminance at a 0-degree viewing angle is less than 0.07. Therefore, when applied to a display device, a privacy mode can be achieved without affecting the light utilization rate, which helps to improve the privacy effect, increase brightness and reduce power consumption, and can reduce costs without increasing the thickness of the backlight module. Furthermore, by applying the backlight module with a compensation film to the display device, the misalignment design of the transmission pattern of the backlight module and the compensation film ensures that the display screen in privacy mode is only visible to the user located in the center of the display device, thereby avoiding obvious light leakage at other viewing positions in privacy mode and further improving the privacy effect.

[0055] Although this disclosure has been disclosed above through embodiments, it is not intended to limit this disclosure. Those skilled in the art should be able to make some modifications and refinements without departing from the spirit and scope of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope defined in the appended claims.

[0056] [List of Labels in the Attached Image]

[0057] 10, 10A, 10B: Display devices

[0058] 100: Backlight Module

[0059] 102: Light guide plate

[0060] 104: Light-emitting unit

[0061] 106: Optical films

[0062] 108: First Prism Slide

[0063] 110: Second Prism Slide

[0064] 200: Display panel

[0065] 202: First substrate

[0066] 204: Second substrate

[0067] 206: Liquid Crystal Layer

[0068] 300: Compensation diaphragm

[0069] 302: Liquid Crystal Delay Film

[0070] 304: Passive Delay Membrane

[0071] 306: First polarizer

[0072] 308: Second polarizer

[0073] AD: Arrangement Direction

[0074] BD: Ontology

[0075] C1: Brightness gain curve

[0076] C2: Noise ratio curve at 45-degree viewing angle

[0077] C3: Noise ratio curve for 85-degree viewing angle

[0078] CM: Conical microstructure

[0079] D1: First Direction

[0080] D2: Second Direction

[0081] DM: Dimming Structure

[0082] DS1: First distribution mode

[0083] DS2: Second distribution mode

[0084] E1, E2: Extension direction

[0085] EP1: First electrode plate

[0086] EP2: Second electrode plate

[0087] ES: Light-emitting surface

[0088] F1: First light-acting surface

[0089] F2: Second light-acting surface

[0090] IS: Light-receiving surface

[0091] LM: Strip lens structure

[0092] LS: Optical surface

[0093] M1: Object Material

[0094] M2: Main material

[0095] ND: Forward distribution mode

[0096] P1: First Prism Strip

[0097] P2: Second Prism Strip

[0098] S1: First surface

[0099] S2: Second surface

[0100] SD: Strongly Distributed Mode

[0101] SM: Strip-shaped microstructure

[0102] WD: Weakly distributed mode

[0103] θ: included angle.

Claims

1. A backlight module, characterized in that, include: A light guide plate, which has a light-incident surface and a light-exit surface; Multiple light-emitting units are arranged along an arrangement direction and disposed on the light-incident surface; An optical film having a first surface and a second surface opposite to each other, wherein the first surface faces the light-emitting surface; A first prism sheet is stacked on the second surface, the first prism sheet comprising a plurality of first prism strips extending along a first direction; as well as A second prism sheet is stacked on top of a first prism sheet. The second prism sheet includes a plurality of second prism strips extending along a second direction, wherein the second direction is perpendicular to the first direction and the second direction forms an angle θ with the arrangement direction. Wherein, the included angle θ is configured such that Y1 of the backlight module is less than 0.

07. Y1 = L1 / L2, Wherein, L1 is the luminance of the backlight module at a 45-degree viewing angle, and L2 is the luminance of the backlight module at a 0-degree viewing angle.

2. The backlight module according to claim 1, characterized in that, Where n1 is the refractive index of the first prism sheet, n2 is the refractive index of the second prism sheet, and n3 is the refractive index of the optical film.

3. The backlight module according to claim 2, characterized in that, The included angle θ is configured such that Y2 ≤ 0.5 for the backlight module. Where Y2 is the ratio of the brightness of the backlight module at an 85-degree viewing angle to the brightness at a 0-degree viewing angle.

4. The backlight module according to claim 3, characterized in that, The included angle θ is not 90 degrees, but is greater than 20 degrees and less than 160 degrees.

5. The backlight module according to claim 1, characterized in that, The optical film includes: Multiple strip-shaped microstructures are located on the first surface and arranged parallel to each other; and Multiple cone-shaped microstructures are located on the second surface.

6. The backlight module according to claim 5, characterized in that, Each of the conical microstructures is a pyramid structure with multiple facets, and the extension direction of each of the strip microstructures intersects with the arrangement direction.

7. The backlight module according to claim 1, characterized in that, The light guide plate includes: The body has the light-incident surface, the light-exit surface and the optical surface, wherein the light-incident surface is connected to the optical surface and the light-exit surface, and the optical surface and the light-exit surface are arranged opposite to each other; Multiple strip-shaped lens structures are disposed on the optical surface; and Multiple dimming structures are disposed between the multiple strip lens structures, wherein each of the dimming structures has a connected first light-acting surface and a second light-acting surface. The first light-acting surface is an inclined surface facing the light-incident surface, and the second light-acting surface is an inclined surface facing one side of the body relative to the light-incident surface. The first light-acting surface and the second light-acting surface have different inclination directions and are asymmetrical.

8. A display device, characterized in that, include: The backlight module according to any one of claims 1 to 7; as well as A display panel, which is stacked on the second prism sheet, the display panel comprising: First substrate; Second substrate; and A liquid crystal layer is sandwiched between the first substrate and the second substrate.

9. The display device according to claim 8, characterized in that, It further includes a compensation film located on one side of the display panel. The compensation film includes a liquid crystal delay film and a passive delay film. The liquid crystal delay film includes a guest material and a host material. The guest material is an anisotropic material, and the host material is a liquid crystal material. The volume or weight of the guest material is smaller than that of the host material.

10. The display device according to claim 9, characterized in that, The passive delay diaphragm is a negative C-plate delay diaphragm.

11. The display device according to claim 9, characterized in that, The display device is configured to operate in a shared mode or a privacy mode, wherein, in response to the privacy mode, the transmittance pattern generated by the compensation film has a first distribution mode and a second distribution mode in the privacy mode, the first distribution mode extending along a first axis and the second distribution mode located along a second axis, wherein the first axis intersects the second axis, the luminance of the first distribution mode is greater than the luminance of the second distribution mode, and the transmittance pattern generated by the backlight module has a positive distribution mode, a weak distribution mode and a strong distribution mode in the privacy mode, the weak distribution mode and the strong distribution mode being located on mutually orthogonal axes, the positive distribution mode being located at the intersection of mutually orthogonal axes, the luminance of the positive distribution mode being greater than the luminance of the strong distribution mode, the luminance of the strong distribution mode being greater than the luminance of the weak distribution mode, and the strong distribution mode being misaligned with the second distribution mode.

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