Backlight module, visual angle switching method thereof and display device comprising backlight module

Abstract

The invention relates to a backlight module, a visual angle switching method thereof and a display device comprising the backlight module. The invention discloses a backlight module which can be switched between a partial view angle mode and a narrow view angle mode. The backlight module has a first partial view angle brightness LAS1 and a first positive view angle brightness LAN1 in the partial view angle mode, and LAS1 / LAN1gt; and 50%. The backlight module has a second partial viewing angle luminance LAS2 and a second positive viewing angle luminance LAN2 in the narrow viewing angle mode, and LAS2 / LAN2lt; and 0.5%. The first partial view angle and the second partial view angle occur in a slope direction, and the first positive view angle and the second positive view angle occur in a positive direction. When a partial viewing angle execution step is executed, an upper backlight unit and a lower backlight unit are both turned on to be in the partial viewing angle mode. When a narrow viewing angle execution step is executed, the upper backlight unit is turned off and the lower backlight unit is turned on to be in the narrow viewing angle mode. The invention further provides a display device comprising the backlight module.

Description

Technical Field

[0001] The invention relates to an optical device, in particular to a backlight module and a display device capable of generating different viewing angle modes. Background Art

[0002] With the advancement of technology, electronic devices equipped with liquid crystal displays have become an indispensable item in modern people's lives. However, users have different requirements for the viewing angle of display devices in different occasions. For example, if a user wants to share the 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, that is, the display device is in sharing mode; if the user wants to maintain privacy when handling personal affairs, the display screen is expected to be visible only to the user, and the display product needs to have a narrow viewing angle function, that is, anti-peeping mode.

[0003] As the number of in-car display applications increases, in-car displays other than dashboards should also be able to switch viewing angles to avoid distraction and affect driving safety. If traditional display devices need to be protected from peeping, the simplest way is to add a privacy film on the outermost layer, but the disadvantage of this is that the brightness is usually significantly reduced. If different viewing angles are controlled through a display panel, an active display panel dedicated to different viewing angle modes is required, which is more expensive to manufacture.

[0004] Especially for displays in front of the passenger seat of a vehicle, a narrow viewing angle function is required to prevent the light and shadow emitted by the screen from affecting the driver or reflecting on the window. However, sometimes it is necessary to share information with the driver without letting the light reflect on the window, so a biased viewing angle function to one side is required. Summary of the invention

[0005] Therefore, an object of the present invention is to provide a backlight module that can switch between a narrow viewing angle and a biased viewing angle.

[0006] The backlight module of the present invention can switch between a bias viewing angle mode and a narrow viewing angle mode. In the bias viewing angle mode, the backlight module has a first bias viewing angle luminance LAS1 and a first normal viewing angle luminance LAN1, wherein LAS1 / LAN1>50%. In the narrow viewing angle mode, the backlight module has a second bias viewing angle luminance LAS2 and a second normal viewing angle luminance LAN2, wherein LAS2 / LAN2<0.5%. The first bias viewing angle and the second bias viewing angle occur in an oblique direction, and the first normal viewing angle and the second normal viewing angle occur in a forward direction.

[0007] Another technical means of the present invention is that the backlight module includes an upper backlight unit and a lower backlight unit located below the upper backlight unit. The upper backlight unit includes an upper light source and an upper light guide plate for receiving light emitted by the upper light source, and the upper light guide plate has at least one first side and at least one second side, the first side is substantially parallel to a first axial direction, the second side is substantially parallel to a second axial direction, and the second axial direction is not parallel to the first axial direction. The first axial direction is between +90° and -90°, and the upper light source is arranged on the side of the first axial direction adjacent to +90° and extends along the second axial direction.

[0008] Another technical means of the present invention is that the upper light guide plate is roughly rectangular, the first side is one of the long sides of the rectangle, and the second side is one of the short sides of the rectangle, and the upper light source is adjacent to the short side.

[0009] Another technical means of the present invention is that the upper light guide plate has a light emitting surface, a reflection surface, and a plurality of mesh dot structures formed on the reflection surface. The light emitting surface is located on a plane defined by the first axial direction and the second axial direction, the light emitting surface and the reflection surface are located on opposite sides of the upper light guide plate, each of the mesh dot structures has a central area and an outer ring area surrounding the central area, the height h of the central area is greater than 1 μm, and the diameter of the outer ring area is greater than 1 μm. Is greater than 2h.

[0010] Another technical means of the present invention is that the height h of the central area of ​​each of the dot structures is 3-7 μm, including the end value, and the diameter of the outer ring area is 15-35 μm, inclusive.

[0011] Another technical means of the present invention is that the central area of ​​each of the dot structures is concave relative to the reflective surface, and the outer ring area is an annular convex wall relative to the reflective surface.

[0012] Another technical means of the present invention is that the central area of ​​each of the dot structures is convex relative to the reflective surface, and the outer ring area is concave relative to the reflective surface.

[0013] Another technical means of the present invention is that the backlight module further includes an upper light-controlling film disposed on the light-emitting side of the upper backlight unit, for collecting the light emitted by the backlight module along the second axis to a positive viewing angle.

[0014] Another technical means of the present invention is that the backlight module also includes at least one lower light-controlling film arranged between the upper backlight unit and the lower backlight unit, wherein the upper light-controlling film and the lower light-controlling film regulate light in different directions, and the lower light-controlling film is used to collect the light output of the backlight module along the first axis to a positive viewing angle.

[0015] Another technical means of the present invention is that the backlight module also includes two prism sheets arranged between the upper backlight unit and the lower backlight unit, wherein each prism sheet has a plurality of strip microstructures arranged in parallel and facing the upper backlight unit, and the extension directions of the strip microstructures of the two prism sheets are perpendicular to each other.

[0016] Another technical means of the present invention is that the lower backlight unit includes a lower light source, a lower light guide plate receiving light from the lower light source, and at least one optical film located on a light-emitting side of the lower light guide plate. The lower light guide plate has a light-entering side connected to the light-emitting side, and the light-entering side receives light emitted by the lower light source, wherein the lower light source is extended along the first axial direction.

[0017] Another technical means of the present invention is that the lower backlight unit includes a lower light source, a diffusion plate for receiving light from the lower light source, and at least one optical film located on a light-emitting side of the diffusion plate. The diffusion plate has a light-entering side, opposite to the light-emitting side, and the light-entering side receives light emitted by the lower light source.

[0018] Another technical means of the present invention is that the forward direction is located at a substantially 0° viewing angle position of the first axis, and the oblique direction is located at a substantially -45° viewing angle position of the first axis.

[0019] Another object of the present invention is to provide a viewing angle switching method of a backlight module, which is used to switch the viewing angle of the aforementioned backlight module. The viewing angle switching method includes a bias viewing angle execution step and a narrow viewing angle execution step. When the bias viewing angle execution step is executed, the upper backlight unit and the lower backlight unit are both turned on to the bias viewing angle mode. When the narrow viewing angle execution step is executed, the upper backlight unit is turned off and the lower backlight unit is turned on to the narrow viewing angle mode.

[0020] Another technical means of the present invention is that the backlight module is applied to an in-vehicle display, and the viewing angle switching method further includes a sensing step to determine whether to execute the biased viewing angle execution step or the narrow viewing angle execution step according to the vehicle speed or the driver's eye tracking gaze.

[0021] Another object of the present invention is to provide a display device, comprising a backlight module as described above, and a display panel disposed on the backlight module.

[0022] The effect of the present invention is that when applied to the in-car display set at the front passenger seat, in the narrow viewing angle mode, LAS2 / LAN2<0.5%, the lateral light brightness is reduced to less than 0.5% of the second front viewing angle brightness LAN2, and the brightness is concentrated in the front viewing direction, so that it can only be viewed by the front passenger, avoiding the side light from affecting the front driver, and achieving the effect of narrow viewing angle. In the offset viewing angle mode, LAS1 / LAN1>50%, so that the brightness required for the lateral viewing angle is at least 50% relative to the first front viewing angle brightness LAN1, which can be viewed by both the front driver and the front passenger at the same time, and has sufficient brightness for the front driver to watch, achieving the effect of offset viewing angle. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a side view of a preferred embodiment of the backlight module of the present invention, wherein an upper light source and a lower light source are both edge-entry light sources;

[0024] Figure 2 is a top view illustrating the shape of an upper light guide plate;

[0025] Figure 3 It is a side view, illustrating a dot structure in a partially enlarged manner;

[0026] Figure 4 It is a side view, illustrating another form of the dot structure;

[0027] Figure 5 is a side view, which is another form of the preferred embodiment, wherein the upper light source is an edge-entry light source, and the lower light source is a direct-entry light source;

[0028] Figure 6 is a side view of a preferred embodiment of the display device of the present invention;

[0029] Figure 7 is a graph illustrating luminance distribution in a bias viewing mode; and

[0030] Figure 8 It is a simulated energy distribution diagram, which illustrates the deflection of the energy and viewing angle of light in this deflection angle mode. DETAILED DESCRIPTION

[0031] The features and technical contents of the related patent applications of the present invention will be clearly presented in the following detailed description of the preferred embodiments with reference to the drawings. It should be noted before the detailed description that similar components are represented by the same number. The directional terms mentioned in the following embodiments, such as: up, down, left, right, front, back, bottom, top, etc., are only referenced to the directions of the attached drawings. Therefore, the directional terms used are for illustration, not for limitation of the present invention.

[0032] In the following description, the terms "about", "substantially", "roughly" or "same" generally indicate a range within 10%, within 5%, within 3%, within 2%, within 1%, or within 0.5% of a given value. The quantities given here are approximate quantities, that is, in the absence of specific description of "about", "substantially", "roughly" or "same", the meaning of "about", "substantially", "roughly" or "same" can still be implied.

[0033] The backlight module of the present invention can switch between a bias viewing angle mode and a narrow viewing angle mode. The backlight module has a first bias viewing angle luminance LAS1 and a first normal viewing angle luminance LAN1 in the bias viewing angle mode, wherein LAS1 / LAN1>50%. The backlight module has a second bias viewing angle luminance LAS2 and a second normal viewing angle luminance LAN2 in the narrow viewing angle mode, wherein LAS2 / LAN2<0.5%. The first bias viewing angle and the second bias viewing angle occur in an oblique direction, and the first normal viewing angle and the second normal viewing angle occur in a forward direction. In this way, when the present invention is applied to an in-vehicle display arranged on a co-pilot seat, LAS2 / LAN2<0.5% in the narrow viewing angle mode, reducing the lateral light luminance to less than 0.5% of the second normal viewing angle luminance LAN2, and concentrating the luminance in the normal viewing angle direction, so that it can only be viewed by the co-pilot, avoiding the lateral light luminance from affecting the driver, and achieving the effect of a narrow viewing angle. In the offset viewing mode, LAS1 / LAN1>50%, which means that the brightness required for the lateral viewing angle is at least 50% of the brightness LAN1 of the first straight viewing angle. It can be viewed by both the pilot and the co-pilot at the same time, and has sufficient brightness for the pilot to view, thus achieving the effect of the offset viewing angle.

[0034] See also Figure 1 , which is a preferred embodiment of the backlight module of the present invention. The backlight module comprises an upper backlight unit 2 and a lower backlight unit 3 located below the upper backlight unit 2. The upper backlight unit 2 comprises an upper light source 21 and an upper light guide plate 22 receiving light emitted by the upper light source 21.

[0035] like Figure 2 As shown, the upper light guide plate 22 has at least one first side 221 and at least one second side 222, the first side 221 is substantially parallel to a first axial direction X, the second side 222 is substantially parallel to a second axial direction Y, and the second axial direction Y is not parallel to the first axial direction X. The first axial direction X is between +90° and -90°, and the upper light source 21 is disposed on a side of the first axial direction X adjacent to +90° and extends along the second axial direction Y.

[0036] like Figure 1As shown, the upper light guide plate 22 has a light emitting surface 223, a reflecting surface 224, and a plurality of mesh structures 23 formed on the reflecting surface 224. The mesh structure 23 can destroy the total reflection of light, so that the light can evenly penetrate from the light emitting surface 223 of the upper light guide plate 22. The light emitting surface 223 and the reflecting surface 224 are respectively located on opposite sides of the upper light guide plate 22. The light emitting surface 223 is located on a plane defined by the first axial direction X and the second axial direction Y. In this embodiment, if a display with a rectangular shape and a long side in the horizontal direction is used, the upper light guide plate 22 is roughly rectangular, the first side 221 is one of the long sides of the rectangle, and the second side 222 is one of the short sides of the rectangle, the upper light source 21 is adjacent to the second side 222, the first axial direction X is the horizontal direction of the long side, and the second axial direction Y is the vertical direction of the short side. In other words, the upper light source 21 is disposed on the side adjacent to +90° on the first axis X, or on the right side in the horizontal direction of the long side, and extends along the second axis Y, which is the vertical direction of the short side. Therefore, the light emitted by the upper light source 21 will advance to the left side in the horizontal direction of the long side and emit light through the light emitting surface 223 of the upper light guide plate 22.

[0037] Since no other prism sheets for changing the direction of light travel are disposed above the light emitting surface 223 of the upper light guide plate 22 in the present embodiment, the light will not be reversed when traveling toward the left side in the horizontal direction of the long side, but will still be emitted from the light emitting surface 223 of the upper light guide plate 22 with a negative slope between 0° and -90°, so that in the offset viewing angle mode, the brightness required for the lateral viewing angle is at least 50% of the maximum brightness of the front viewing angle, thereby achieving the offset viewing angle effect.

[0038] Compared with the prior art, if the upper light source is set on one side of the second axis and along the horizontal direction of the long side, its light field distribution will be more spread out instead of falling on the first axis, and the light cannot be concentrated on the lateral viewing angle. The brightness of the lateral viewing angle relative to the maximum brightness of the front viewing angle will not reach the minimum required level of 50%.

[0039] See also Figure 3 Each of the dot structures 23 of the upper light guide plate 22 has a central region 231 and an outer ring region 232 surrounding the central region 231. The height h of the central region 231 is greater than 1 μm, and the diameter of the outer ring region 232 is In this embodiment, each of the mesh structures 23 may be as follows: Figure 3 As shown in FIG. 2 , the central area 231 is convex relative to the reflective surface 224, and the outer ring area 232 is concave relative to the reflective surface 224. With this design, each of the mesh structures 23 will appear as follows. Figure 3The lower arc-shaped protrusion shown (or Figure 4 The invention can not only achieve the basic effect in narrow viewing angle mode and offset viewing angle mode, but also improve the efficiency and difficulty of laser processing on the mold. In order to improve the brightness required for the lateral viewing angle, reduce energy consumption, and improve the display quality (front-of-screen, FOS), this embodiment can be as follows Figure 3 As shown, the protrusion height of each dot structure 23 is further increased (or as shown in Figure 4 The depth of the concave hole of each dot structure 23 is further deepened as shown). The height h of the central area 231 of each dot structure 23 is 3-7 μm, including the end value. The diameter of the outer ring area 232 It should be noted that, in other embodiments, each of the dot structures 23 may also be as follows: Figure 4 As shown, the central area 231 is concave relative to the reflective surface 224 , and the outer ring area 232 is an annular convex wall relative to the reflective surface 224 .

[0040] Also, see Figure 1 The backlight module also includes an upper light-controlling film 4 disposed on the light-emitting side of the upper backlight unit 2, two lower light-controlling films 5 disposed between the upper backlight unit 2 and the lower backlight unit 3, and two prism sheets 6 disposed between the upper backlight unit 2 and the lower backlight unit 3. The upper light-controlling film 4 and the lower light-controlling film 5 regulate light in different directions. The upper light-controlling film 4 is used to collect the light emitted by the backlight module along the second axial direction Y to a positive viewing angle, so that when applied to vehicle-mounted products, such as the center console (Center Information Display, CID) or the display in front of the co-pilot (Passenger Information Display, PID), the vertical light can be converged to the center to avoid the light being reflected by the windshield. As for the lower light-controlling film 5, it is used to collect the light emitted by the backlight module along the first axis X to the positive viewing angle, thereby converging the light field distribution generated by the lower backlight unit 3 from the left and right horizontal directions to the center, so as to enhance the narrow viewing angle effect and prevent excessively expanded and diffused light from passing through the upper backlight unit 2 and affecting the basic effects of the narrow viewing angle mode and the offset viewing angle mode.

[0041] Furthermore, each prism sheet 6 has a plurality of strip microstructures 61 arranged in parallel and facing the upper backlight unit 2, and the extension directions of the strip microstructures 61 of the two prism sheets 6 are perpendicular to each other. The prism sheet 6 directly faces the upper light guide plate 22 of the upper backlight unit 2, and there are no other opaque components between the two to block the light path. Therefore, the light emitted by the lower backlight unit 3 can penetrate the lower light-control film 5 and the prism sheet 6 and directly enter the upper backlight unit 2, without being blocked by other opaque components to reduce the light transmittance, and there will not be a large proportion of light reflected back to the lower backlight unit 3, which helps to improve the brightness of the light output in the narrow viewing angle mode and the offset viewing angle mode.

[0042] As for the lower backlight unit 3, its style and light source placement are not limited. Figure 1 As shown, the lower backlight unit 3 is an edge-entry light source and includes a lower light source 31, a lower light guide plate 32 receiving light from the lower light source 31, at least one optical film 33 located on a light exit side 322 of the lower light guide plate 32, and a reflective sheet 34. The lower light guide plate 32 has a light entrance side 321 connected to the light exit side 322. The light entrance side 321 receives light emitted by the lower light source 31, and the lower light source 31 is extended along the first axial direction X. In some embodiments, the lower backlight unit 3 may also be as follows Figure 5 The direct-down light source is shown, and includes a lower light source 31, a diffuser 35 receiving light from the lower light source 31, at least one optical film 33 located on a light-emitting side 352 of the diffuser 35, and a reflector 34. The diffuser 35 has a light-entering side 351, opposite to the light-emitting side 352, and the light-entering side 351 receives light emitted by the lower light source 31. Figure 6 A display panel 7 is arranged on the aforementioned backlight module to form the display device of the present invention. Figure 6 In Figure 1 The backlight module shown in FIG. 1 is used as an example. In some embodiments, the display panel 7 is disposed on Figure 5 On the backlight module shown.

[0043] The present invention also provides a method for switching the viewing angle of a backlight module, which is used to switch the viewing angle of the aforementioned backlight module. The viewing angle switching method includes a bias viewing angle execution step and a narrow viewing angle execution step. When the bias viewing angle execution step is executed, the upper backlight unit 2 and the lower backlight unit 3 are both turned on to the bias viewing angle mode. When the narrow viewing angle execution step is executed, the upper backlight unit 2 is turned off and the lower backlight unit 3 is turned on to the narrow viewing angle mode.

[0044] As mentioned above, the backlight module has a first bias angle brightness LAS1 and a first normal angle brightness LAN1 in the bias angle mode, wherein LAS1 / LAN1>50%. The backlight module has a second bias angle brightness LAS2 and a second normal angle brightness LAN2 in the narrow viewing angle mode, wherein LAS2 / LAN2<0.5%. It should be particularly noted that the first bias angle and the second bias angle occur in an oblique direction, and the first normal viewing angle and the second normal viewing angle occur in a forward direction. Figure 2 , the forward direction is located at a substantially 0° viewing angle position of the first axis X, and the oblique direction is located at a substantially -45° viewing angle position of the first axis X. For example, when the backlight module is applied to an in-car display and is arranged directly in front of the front passenger seat, the forward direction (0° viewing angle) corresponds to the position of the front passenger seat, and the oblique direction (-45° viewing angle) corresponds to the position of the front passenger seat. Furthermore, if Figure 1 As shown, the upper light source 21 must be disposed at a short side position of the upper light guide plate 22 away from the driver's seat so that the light of the upper light source 21 is projected toward the driver's seat.

[0045] As mentioned above, the narrow viewing angle mode is when the upper backlight unit 2 is turned off and the lower backlight unit 3 is turned on. At this time, the relationship between the second oblique viewing angle luminance LAS2 and the second normal viewing angle luminance LAN2 is LAS2 / LAN2<0.5%. In other words, the luminance (LAS2) in the oblique direction is quite low at this time to avoid interfering with normal driving. In more detail, when the lower backlight unit 3 is turned on, the light incident side 321 of the lower light guide plate 32 receives the light emitted by the lower light source 31, and emits light through the light emitting side 322. Since the lower light control film 5 is used to collect the light emitted along the first axial direction X to the normal viewing angle (that is, to concentrate the light on the left and right sides to the central position), the light is emitted in a direction close to the normal direction, providing collimated normal light of sufficient intensity at the viewing angle of 0 degrees, such as Figure 1 As shown by the arrow A in the middle. Therefore, in the narrow viewing angle mode, people on the left and right sides can be prevented from seeing the content displayed on the screen, which has a peeping effect. When applied to vehicle-mounted devices other than the dashboard (such as the screen set in front of the co-pilot seat), switching to the narrow viewing angle mode can prevent the driver from being distracted by watching the screen, thereby improving driving safety.

[0046] In the slant viewing mode, both the upper backlight unit 2 and the lower backlight unit 3 are turned on. At this time, the relationship between the first slant viewing angle luminance LAS1 and the first normal viewing angle luminance LAN1 is LAS1 / LAN1>50%. Therefore, the luminance (LAS1) of the slant viewing angle mode in the oblique direction is sufficient for viewing by the driver. In more detail, when both the upper backlight unit 2 and the lower backlight unit 3 are turned on, the light of the lower backlight unit 3 directly enters the upper backlight unit 2 after being converged by the prism sheet 6 and the lower light-control film 5. Since the upper light source 21 of the upper backlight unit 2 is arranged at a short side position of the upper light guide plate 22 away from the driver's seat, the light of the upper light source 21 is projected in the direction of the driver's seat. When both the upper backlight unit 2 and the lower backlight unit 3 are turned on, as Figure 1 As shown, in addition to providing collimated forward light of sufficient intensity at the position of 0 degree of viewing angle (arrow A), it also provides light of sufficient intensity at the position of -45 degree of viewing angle (arrow B), so that the co-pilot and the driver can watch at the same time. The upper light-controlling film 4 arranged in the light-emitting direction of the upper backlight unit 2 is used to collect the light emitted by the backlight module along the second axial direction Y to the positive viewing angle to prevent the light from being reflected through the windshield.

[0047] See also Figure 7 , is a horizontal luminance distribution diagram of the bias viewing mode, and is a comparison of dot structures 23 of different sizes. The dotted line represents that the height h of the central area 231 of each of the dot structures 23 is 1 μm, and the diameter of the outer ring area 232 is The solid line represents that the height h of the central area 231 of each of the dot structures 23 is 5 μm, and the diameter of the outer ring area 232 is 25μm. Figure 7 It can be seen that compared to the case where the height h of the central area 231 of each of the dot structures 23 is 1μm, when the height h of the central area 231 of each of the dot structures 23 is 5μm, the first positive viewing angle luminance LAN1 in the forward direction (0° viewing angle) and the first bias viewing angle luminance LAS1 in the oblique direction (-45° viewing angle) can be improved. That is, the co-pilot and the driver can watch at the same time. At the same time, the luminance distribution between -10° and -45° can be improved to reduce the visual difference. In addition, the luminance can be reduced at viewing angles below -45° and above +45°, reducing unnecessary light output and saving energy. Refer to Figure 8 , is the spatial brightness distribution diagram under the partial viewing angle mode. It should be noted that the spatial brightness distribution diagram is a computer simulation diagram, and was originally a color diagram, but in this case it is presented as a grayscale diagram. Figure 8It can be seen from the spatial brightness distribution diagram that in the biased viewing angle mode, energy concentration can be observed in the center and the left side. In addition, when the height h of the central area 231 of each of the dot structures 23 is 5 μm, the power consumed for viewing angle control is about 50% of that when the height h of the central area 231 of each of the dot structures 23 is 1 μm, which has the effect of saving power and is also conducive to application in the use environment of electric vehicles.

[0048] It should also be noted that the viewing angle switching method also includes a sensing step, which determines whether to execute the biased viewing angle execution step or the narrow viewing angle execution step based on the vehicle speed or the driver's eye tracking gaze. For example, when the sensing step detects that the vehicle speed is 0, or the driver does not need to look straight ahead, the biased viewing angle execution step is executed. At this time, the upper backlight unit 2 and the lower backlight unit 3 are both turned on to the biased viewing angle mode, allowing the driver to view the screen. If the vehicle speed is not 0, or the driver looks straight ahead, the narrow viewing angle execution step is executed. At this time, the upper backlight unit 2 is turned off and the lower backlight unit 3 is turned on to the narrow viewing angle mode, and the driver cannot clearly view the screen.

[0049] In summary, in the backlight module and the viewing angle switching method of the present invention, the upper backlight unit 2 and the lower backlight unit 3 are turned on at the same time to provide a bias viewing angle mode, and the lower backlight unit 3 is turned on and the upper backlight unit 2 is turned off to provide a narrow viewing angle mode. Therefore, the backlight module and the display device of the present invention have the function of switching between the bias viewing angle mode and the narrow viewing angle mode. At the same time, through the setting position of the upper light source 21, the light can be emitted toward the direction of the front driver's seat and the light can be prevented from being reflected through the window of the passenger seat. In addition, as the number of in-vehicle display applications increases, there is also a need for anti-peeping. In order to avoid affecting the driver's driving vision and improve driving safety, the present invention switches the light source to meet the narrow viewing angle mode (anti-peeping) and the offset viewing angle mode (sharing), so as to achieve multi-tasking use in different scene conditions. It is particularly suitable for vehicle displays, especially when used in the display in front of the passenger seat of the vehicle (Passenger Information Display, PID). In the offset viewing angle mode (sharing), the driver and the passenger can watch the screen content at the same time. In the narrow viewing angle mode (anti-peeping), the driver can be prevented from seeing the content of the display screen, which can avoid the driver's distraction and is conducive to protecting the privacy of the passengers. It can also further avoid the impact of side window reflected light on driving, which can ensure the advantage of driving safety, meet the PID screen's active switching requirements for privacy mode and sharing mode, and the light field in the sharing mode can be concentrated in a specific area, which can improve light utilization.

[0050] However, what is described above is only a preferred embodiment of the present invention, and should not be used to limit the scope of implementation of the present invention. That is, all simple equivalent changes and modifications made according to the claims and the invention description of the present invention are still within the scope of the patent of the present invention.

[0051]

Explanation of symbols

[0052] 2 Upper backlight unit

[0053] 21 Upper light source

[0054] 22 Upper light guide plate

[0055] 221 First side

[0056] 222 Second side

[0057] 223 Light emitting surface

[0058] 224 Reflective surface

[0059] 23 Network structure

[0060] 231 Central Area

[0061] 232 Outer Ring Area

[0062] 3 Lower backlight unit

[0063] 31 Lower light source

[0064] 32 Lower light guide plate

[0065] 321 Light incident side

[0066] 322 Light output side

[0067] 33 Optical film

[0068] 34 Reflective sheet

[0069] 35 Diffuser Plate

[0070] 351 Light incident side

[0071] 352 Light output side

[0072] 4 Upper light control film 5. Lower light control film 6 Prism

[0073] 61 Strip microstructure 7 Display Panel A Arrow B Arrow X First Axis Y Second Axis diameter h Height.

Claims

1. A backlight module, characterized in that: It can switch between the bias viewing angle mode and the narrow viewing angle mode. In the bias viewing angle mode, the backlight module has a first bias viewing angle luminance LAS1 and a first normal viewing angle luminance LAN1, wherein LAS1 / LAN1>50%. In the narrow viewing angle mode, the backlight module has a second bias viewing angle luminance LAS2 and a second normal viewing angle luminance LAN2, wherein LAS2 / LAN2<0.5%. The first bias viewing angle and the second bias viewing angle occur in an oblique direction, and the first normal viewing angle and the second normal viewing angle occur in a forward direction.

2. The backlight module according to claim 1, characterized in that: It comprises an upper backlight unit and a lower backlight unit located below the upper backlight unit, the upper backlight unit comprises an upper light source and an upper light guide plate receiving light emitted by the upper light source, the upper light guide plate has at least one first side and at least one second side, the first side is substantially parallel to a first axis, the second side is substantially parallel to a second axis, the second axis is not parallel to the first axis, the first axis is between +90° and -90°, the upper light source is arranged on a side of the first axis adjacent to +90° and extends along the second axis.

3. The backlight module according to claim 2, characterized in that: The upper light guide plate is roughly rectangular, the first side is one of the long sides of the rectangle, and the second side is one of the short sides of the rectangle, and the upper light source is adjacent to the short side.

4. The backlight module according to claim 2, wherein: The upper light guide plate has a light emitting surface, a reflecting surface, and a plurality of lattice structures formed on the reflecting surface. The light emitting surface is located on a plane defined by the first axial direction and the second axial direction. The light emitting surface and the reflecting surface are located on opposite sides of the upper light guide plate. Each of the lattice structures has a central area and an outer ring area surrounding the central area. The height h of the central area is greater than 1 μm, and the diameter of the outer ring area is greater than 1 μm. More than 2h.

5. The backlight module according to claim 4, characterized in that: The height h of the central area of ​​each of the dot structures is 3-7 μm, including the end value, and the diameter of the outer ring area is 15-35 μm, inclusive.

6. The backlight module according to claim 4, characterized in that: The central area of ​​each of the lattice dot structures is in a concave shape relative to the reflecting surface, and the outer ring area is in a ring-shaped convex wall shape relative to the reflecting surface.

7. The backlight module according to claim 4, characterized in that: The central area of ​​each of the lattice dot structures is convex relative to the reflective surface, and the outer ring area is concave relative to the reflective surface.

8. The backlight module according to claim 2, wherein: It also includes an upper light-controlling film arranged on the light-emitting side of the upper backlight unit, which is used to collect the light emitted by the backlight module along the second axis to a positive viewing angle.

9. The backlight module according to claim 8, characterized in that: It also includes at least one lower light-controlling film arranged between the upper backlight unit and the lower backlight unit, wherein the upper light-controlling film and the lower light-controlling film regulate light in different directions, and the lower light-controlling film is used to collect light emitted from the backlight module along the first axis to a positive viewing angle.

10. The backlight module according to claim 2, wherein: It also includes two prism sheets arranged between the upper backlight unit and the lower backlight unit, wherein each prism sheet has a plurality of strip microstructures arranged in parallel and facing the upper backlight unit, and the extension directions of the strip microstructures of the two prism sheets are perpendicular to each other.

11. The backlight module according to claim 2, wherein: The lower backlight unit includes a lower light source, a lower light guide plate that receives light from the lower light source, and at least one optical film located on the light output side of the lower light guide plate, wherein the lower light guide plate has a light input side connected to the light output side, and the light input side receives light emitted by the lower light source, wherein the lower light source is extended along the first axis.

12. The backlight module according to claim 2, wherein: The lower backlight unit includes a lower light source, a diffusion plate for receiving light from the lower light source, and at least one optical film located on the light-emitting side of the diffusion plate. The diffusion plate has a light-entering side, opposite to the light-emitting side, and the light-entering side receives light emitted by the lower light source.

13. The backlight module according to any one of claims 2 to 12, characterized in that: The forward direction is located at a viewing angle position of substantially 0° with respect to the first axis, and the oblique direction is located at a viewing angle position of substantially -45° with respect to the first axis.

14. A method for switching viewing angle of a backlight module, characterized in that: Used to switch the viewing angle of the backlight module as described in any one of claims 2 to 13, the viewing angle switching method includes a bias viewing angle execution step and a narrow viewing angle execution step. When the bias viewing angle execution step is executed, the upper backlight unit and the lower backlight unit are both turned on to the bias viewing angle mode. When the narrow viewing angle execution step is executed, the upper backlight unit is turned off and the lower backlight unit is turned on to the narrow viewing angle mode.

15. The viewing angle switching method of the backlight module according to claim 14, characterized in that: The backlight module is applied to an in-vehicle display, and the viewing angle switching method further comprises a sensing step, and determines whether to execute the bias viewing angle execution step or the narrow viewing angle execution step according to the vehicle speed or the driver's eye tracking gaze.

16. A display device, characterized in that: It comprises a backlight module as claimed in any one of claims 1 to 13, and a display panel arranged on the backlight module.

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