Privacy backlight module

Abstract

This backlight module is made by laminating an upper backlight module, a lower backlight module, and a reflective film disposed below the lower backlight module, wherein the upper backlight module is a transparent module, the lower backlight module is a transparent or opaque module, the upper backlight module is a collimating or diffusing backlight module, and the lower backlight module is a collimating or diffusing backlight module, and the upper and lower backlight modules have different characteristics. It has the advantages of being able to simultaneously achieve two light emission directions, beam splitting and collimation, being applicable to multiple types of backlight modules, and having adjustable beam splitting angles, high efficiency, and individual control.

Description

Technical Field

[0001] The present invention relates to a backlight module of a liquid crystal display, and particularly to a backlight module for preventing peeping.

Background Art

[0002] In recent years, liquid crystal displays have been widely applied to various display devices, and their relevance to people's lives has been increasing. Since a liquid crystal display itself cannot emit light, it is necessary to arrange a backlight module that can provide a backlight. When all special usage scenarios or users attach importance to privacy and do not want others to see the content on their screens, a peeping prevention screen is applied. Currently, there are two modes for peeping prevention screens. One is realized by a juxtaposed grid structure, which is static peeping prevention where the transmitted light is blocked by the grid and does not exit at a certain angle. With such a structure, a peeping prevention effect at a certain angle can be obtained, but overall, the transmittance is low and it is dark, resulting in a poor user experience, and it is impossible to achieve both peeping prevention and wide-angle display. The second is dynamic peeping prevention, which mainly includes the following.

[0003] 1) Mount a 3M anti-peeping film on a general backlight module, and mount a PDLC, a smectic phase light modulating film, etc. between the 3M anti-peeping film and the display, and switch between the fully transparent state and the scattered state using the light modulating film to switch between the privacy state and the shared state. This solution has problems such as the high price of the 3M anti-peeping film, the poor viewing angle in the fully transparent state of the PDLC, which has an adverse effect on the privacy state effect, and the high driving voltage of the smectic phase light modulating film and the too slow response speed at low temperatures.

[0004] 2) Mount a PDLC, a smectic phase light modulating film, etc. on a collimated backlight module. This solution has problems such as the high cost of the collimated backlight and the low yield. <>

[0005] 3) A privacy display system based on a liquid crystal light bulb, which displays a rapid switch between privacy and shared states by providing two pairs of electrodes of different shapes on both sides of the liquid crystal light bulb. This solution has efficiency losses because it requires a specific angle of incident light.

[0006] With the above solutions, the emission angle can only be fixed within a certain range in essentially one dimension, without considering two dimensions, and the angle range cannot be adjusted, thus limiting its usability. [Overview of the project] [Problems that the invention aims to solve]

[0007] The technical problem that this invention aims to solve is to provide a privacy backlight module that can perform two-dimensional anti-peeping with adjustable angle, can efficiently switch between two display modes, anti-peeping and wide-angle, without response time, and has high overall transmittance. [Means for solving the problem]

[0008] The technical solution used in the present invention to solve the above technical problems is as follows: A privacy backlight module, The device is constructed by laminating an upper backlight module, a lower backlight module, and a reflective film provided below the lower backlight module. The upper backlight module is a transparent module, and the lower backlight module is either a transparent or opaque module. The upper backlight module is either a collimated or diffused backlight module, and the lower backlight module is either a collimated or diffused backlight module. The upper and lower backlight modules have different characteristics.

[0009] The collimated backlight module includes a first light guide plate, a first light source provided on the side surface of the first light guide plate, and a first microprism array provided on the upper surface of the first light guide plate, wherein the first microprism array is arranged along the light transmission direction of the first light source. The diffuse backlight module includes a second light guide plate, a second light source provided on the side surface of the second light guide plate, and a second microprism array provided on the upper surface of the second light guide plate, wherein the second microprism array is arranged along the light transmission direction of the second light source.

[0010] The upper backlight module is a collimated backlight module, the lower backlight module is a diffuse backlight module, and the first microprism array and the second microprism array are orthogonal to each other or parallel to each other.

[0011] The upper backlight module is a diffuse backlight module, the lower backlight module is a collimated backlight module, and the first microprism array and the second microprism array are orthogonal to each other or parallel to each other.

[0012] The first light guide plate is a parallel plate, the first light source is provided on one side of the first light guide plate, and the first reflective surface is provided on the side opposite to the first light source.

[0013] The first light guide plate is a parallel plate, the first light source is provided on one side of the first light guide plate, and the first auxiliary light source is provided on the side opposite to the first light source.

[0014] The first light guide plate is a wedge-shaped plate, and the first light source is provided on the thick end side of the wedge-shaped plate. The wedge angle of the wedge-shaped plate is 5° or less.

[0015] A reflective surface is provided on the end side of the wedge-shaped plate.

[0016] The first light guide plate is a bidirectional wedge-shaped plate, and the first light source is provided on the two thick end surfaces of the wedge-shaped plate.

[0017] The first microprism array has a trapezoidal or cup-shaped structure, and the first microprism array and the first light guide plate are integrated with each other.

[0018] The first microprism array is arranged uniformly or unevenly.

[0019] The first microprism array focuses and refracts the light incident from the first light guide plate outwards.

[0020] The second light guide plate is a parallel plate, the second light source is provided on one side of the second light guide plate, and the second reflective surface is provided on the side opposite to the second light source.

[0021] The second light guide plate is a parallel plate, the second light source is provided on one side of the second light guide plate, and the second auxiliary light source is provided on the side opposite to the second light source.

[0022] The second microprism array refracts and radiates the light incident from the second light guide plate outwards.

[0023] A privacy film is in close contact with the upper surface of the lower backlight module, and there is an air gap between the privacy film and the lower surface of the upper backlight module.

[0024] The lower interface of the bidirectional wedge-shaped light guide plate may be linear or nonlinear.

[0025] The side contours of the first microprism array and the second microprism array may be straight lines, curved lines, or multiple line segments.

[0026] Contours such as the arcs and multiple line segments may be concave (converging) on the inside, convex (diverging) on the inside, or a combination of concave and convex.

[0027] The upper backlight module is a diffusive backlight module, the lower backlight module is a collimating backlight module, the collimating backlight module includes a first light guide plate and a first light source, the diffusive backlight module includes a second light guide plate and a second light source, the second light guide plate is a parallel flat plate, a second micro prism array is provided on the upper surface of the second light guide plate, the second micro prism array is arranged along the light transmission direction of the second light source, the second light source is provided on one side surface of the second light guide plate, a second auxiliary light source is provided on the side surface opposite to the second light source, the first light guide plate is a wedge-shaped plate, the first light source is provided on the thick end side surface of the wedge-shaped plate, and a rhombic prism film is provided between the first light guide plate and the second light guide plate.

[0028] The upper backlight module is a diffusive backlight module, the lower backlight module is a collimating backlight module, the collimating backlight module includes a first light guide plate and a first light source, the diffusive backlight module includes a second light guide plate and a second light source, the second light guide plate is a parallel flat plate, a second micro prism array is provided on the upper surface of the second light guide plate, the second micro prism array is arranged along the light transmission direction of the second light source, the second light source is provided on one side surface of the second light guide plate, a second auxiliary light source is provided on the side surface opposite to the second light source, the first light guide plate is a wedge-shaped plate, the first light source is provided on the thick end side surface of the wedge-shaped plate, and an inverse prism film is provided between the first light guide plate and the second light guide plate.

[0029] An anti-peeping film is provided between the inverse prism film and the second light guide plate.

Advantages of the Invention

[0030] Compared to conventional technology, the advantages of the present invention are as follows: It can simultaneously achieve two light emission directions, beam splitting and collimation, and can be applied to multiple types of backlight modules. The beam splitting is angle-adjustable, highly efficient, and individually controllable. The beam splitting function is realized by the design of the double-sided light receiving head, and furthermore, the design of the microprism structure on the light emission surface allows for uniform light emission, for example, with increasing density from the edge towards the center, thereby avoiding the problem of pale color and insufficient brightness in the center of conventional panels. [Brief explanation of the drawing]

[0031] [Figure 1] This is a schematic diagram of the optical path of the first structure of a single light source collimated backlight module in Example 1 of the embodiment of the present invention. [Figure 2] This is a schematic diagram of the optical path of the second structure of a single light source collimated backlight module in Example 1 of the embodiment of the present invention. [Figure 3] This is a schematic diagram of the optical path of the third structure of a single light source collimated backlight module in Example 1 of the embodiment of the present invention. [Figure 4] This is a schematic diagram of the structure of a single light source diffuse backlight module in Example 1 of the present invention. [Figure 5] This is a schematic diagram of the optical path of the first structure of a dual light source collimated backlight module in Example 2 of the embodiment of the present invention. [Figure 6] This is a schematic diagram of the optical path of the second structure of a dual light source collimated backlight module in Example 2 of the embodiment of the present invention. [Figure 7] This is a schematic diagram of the optical path of the third structure of the dual light source collimated backlight module in Example 2 of the embodiment of the present invention. [Figure 8] This is a schematic diagram of the structure of a dual light source diffuse backlight module in Example 2 of the embodiment of the present invention. [Figure 9] This is a schematic diagram of the first structure of a dual light source backlight module in Example 3 of the present invention. [Figure 10] This is a schematic diagram of the second structure of a dual light source backlight module in Example 3 of the present invention. [Figure 11] This is a schematic diagram of the optical path of a specific combination of a diffuse backlight module and a collimated backlight module in the second structure of a dual light source backlight module in Example 3 of the embodiment of the present invention. [Figure 12] This is a schematic diagram of the optical path of a specific diffuse backlight module, an anti-peeping film, and a collimated backlight module in the second structure of the dual light source backlight module in Example 3 of the embodiment of the present invention. [Figure 13] This is a schematic plan view of a dual light source backlight module in Example 3 of the present invention, where the upper backlight module and the lower backlight module are arranged vertically. [Figure 14] This is a schematic diagram of the three-dimensional structure of a first structure in which an upper backlight module and a lower backlight module are arranged vertically in a dual light source backlight module according to Example 3 of the embodiment of the present invention. [Figure 15] This is a schematic diagram of the three-dimensional structure of a second structure in which the upper backlight module and the lower backlight module are arranged vertically in a dual light source backlight module according to Example 3 of the embodiment of the present invention. [Figure 16] This is a schematic diagram of the three-dimensional structure when an anti-peeping film is added to the first structure in which the upper backlight module and the lower backlight module are vertically arranged in the dual light source backlight module of Example 3 of the embodiment of the present invention. [Figure 17] This is a schematic diagram of the first structure of a backlight module in Example 4 of the embodiment of the present invention. [Figure 18] This is a schematic diagram of the second structure of the backlight module in Example 4 of the embodiment of the present invention. [Figure 19] This is a schematic diagram of the emitted light spectrum of a dual light source backlight module in an embodiment of the present invention. [Modes for carrying out the invention]

[0032] The present invention will be described in more detail below with reference to the drawings and examples.

[0033] Examples A backlight module capable of controlling the angle of light, comprising an upper backlight module, a lower backlight module, and a reflective film provided below the lower backlight module, wherein the upper backlight module is a transparent module, and the lower backlight module may be a transparent module or an opaque module, and the upper backlight module may be a collimated backlight module or a diffuse backlight module, and the upper backlight module and the lower backlight module have different characteristics. A collimated backlight module includes a first light guide plate, a first light source provided on the side of the first light guide plate, and a first microprism array provided on the top surface of the first light guide plate, wherein the first microprism array is arranged along the light transmission direction of the first light source. A diffuse backlight module includes a second light guide plate, a second light source provided on the side of the second light guide plate, and a second microprism array provided on the top surface of the second light guide plate, wherein the second microprism array is arranged along the light transmission direction of the second light source.

[0034] Example 1: Collimated backlight module or diffused backlight module with a single light source structure Figure 1 is a schematic diagram of the first structure of a single-light source collimated backlight module. The first light guide plate 32 is a parallel plate, the first microprism array 33 is provided on the surface of the first light guide plate 32, the first light source 31 is provided on one side surface 321 of the first light guide plate 32, and the first reflective film 34 is provided on the side surface 324 opposite to the first light source 31, the surface of the first reflective film 34 is a first reflective surface having a predetermined reflectivity, and the substrates of the first light guide plate 32 and the first microprism array 33 are made of optical material.

[0035] As shown in the figure, when light 301 emitted from the first light source 31 enters the first light guide plate 32 from the end face 321, according to Snell's law (n1sinθ1=n2sinθ2, where n1 is the refractive index of medium 1, θ1 is the angle of incidence, n2 is the refractive index of medium 2, and θ2 is the angle of refraction), the trajectory of the light path is such that the light 301 travels forward while being continuously reflected between the upper interface 322 and the lower interface 323, and finally enters the lower opening of the first microprism array 33, is refracted by one of its microprisms 331, is refracted by the side surface 3311 of the microprism 331, and exits outside the surface 333 of the microprism 331 of the first microprism array 33. When another beam of light 302 emitted from the first light source 31 enters the first light guide plate 32, according to Snell's law, the trajectory of the light path is similar: the light 302 travels forward while being continuously reflected between the upper interface 322 and the lower interface 323, and as it travels, it does not hit the first microprism array 33, so it is reflected by the first reflective film 34 at the side surface 324 and travels in the opposite direction inside the first light guide plate 32. The reflected light 302 hits the lower end of the microprism 332 on its return path and enters the microprism 332, where it is refracted by the side surface 3321 of the microprism 332 and exits the surface 333 of the first microprism array 33.

[0036] Figure 2 is a schematic diagram of the second structure of a single-source collimated backlight module. The first light guide plate 53 employs a wedge-shaped structure, and the first light source 51 is provided on the thicker side (wedge-shaped) of the wedge-shaped plate. If the refractive index of the first light guide plate 53 is 1.58, then the angle range of light incident on the wedge-shaped plate is α = ±arcsin(1 / 1.58) = ±40°. When light propagates within the wedge-shaped plate, the angle 90-α made with the normals of the upper and lower reflective surfaces of the wedge-shaped plate is 50° or more. On the other hand, the total reflection angle is γ = arcsin(1 / 1.58) = 40°, and if 90-α is greater than γ, the total reflection condition is met and no light is emitted. When the angle of the wedge plate is β, each time light is reflected by the upper interface 531 or the lower interface 532, the angle that the wedge plate makes with the normal to the upper interface 531 or the lower interface 532 decreases by β, and light is emitted only when the emission condition is met. In such a solution, the wedge angle β of the first light guide plate 53 is extremely small, and the light energy (e.g., light 501) almost satisfies the total internal reflection condition as it travels, so it is confined by the upper interface 531 and the lower interface 532. In this example, since the light travels in one direction, the first microprism array 52 is arranged in one direction (asymmetrically), and the light is refracted at one side 521 of the microprism and exits the backlight module only when it is irradiated onto the lower aperture of the microprism structure, and is not refracted at the other side 522 of the microprism.

[0037] Figure 3 is a schematic diagram of the third structure of a single-source collimated backlight module. A first reflective film 55 is provided at the end of a wedge-shaped light guide plate, forming a backlight module that emits light in two directions. The first microprism array 54 is arranged symmetrically, and the emission process of light 502 emitted from the light source 51 is similar to that of light 501 in Figure 2. However, light that does not hit the lower aperture of the first microprism array 54 as it travels (e.g., light 503) is reflected back to the wedge-shaped plate by the first reflective film 55 at the end face of the wedge-shaped plate, and travels while being reflected between the upper reflective surface 531 and the lower reflective surface 532 of the wedge-shaped plate. This process is the opposite of the reverse process (inverted wedge shape), and each time the light is reflected at the upper interface 531 or the lower interface 532, the angle between the light and the normal to the upper interface 531 or the lower interface 532 of the wedge-shaped plate increases by β. As a result, the angle between the light and the normal to the interface increases, and the returned light hits the lower aperture of the first microprism array 54 and is then reflected from the first microprism array 54 by the side surface 523 of the microprism.

[0038] Figure 4 is a schematic diagram of the structure of a single-source diffuse backlight module. The two sides of the microprisms in the second microprism array 43 are designed to radiate the light refracted at the sides in different directions that are symmetrical (or asymmetrical) with respect to the normal to the surface of the prism array. Light 401 and 402 emitted from the second light source 41 enter the second light guide plate 42 from the side 421 and travel through the second light guide plate 42. Of these, light 401 strikes the lower opening of the microprism, is refracted at the side 432, and exits the backlight module. On the other hand, light 402 does not strike the lower opening of the microprism as it travels, so it is reflected by the second light guide plate 42 by the second reflective film 44 at another side 423 of the second light guide plate 42, travels in the opposite direction, strikes the lower opening of the microprism as it travels opposite light 401, is refracted at the side 431 of the microprism, and exits the backlight module. By changing the side profile of the microprism, the opposing light beams 401 and 402 are refracted by the microprism in two different directions. As a result, there is no light in the direction of the normal 434 to the surface 433 of the second microprism array 43, and light is distributed on both sides in the direction of the normal 434. The degree (range) of beam dispersion can be controlled by changing the side profile of the microprism.

[0039] Example 2: Collimated or diffused backlight module with a dual light source structure Figure 5 is a schematic diagram of the first structure of a dual light source collimated backlight module. The first light guide plate 32 is a parallel plate, the first microprism array 33 is provided on the surface of the first light guide plate 32, the first light source 31 is provided on one side surface 321 of the first light guide plate 32, and the first auxiliary light source 35 is provided on the side surface 324 opposite to the first light source 31. The substrates of the first light guide plate 32 and the microprism array 33 are manufactured from optical materials.

[0040] As shown in the figure, the light from the two light sources travels in opposite directions, and these light emission mechanisms are the same as in Figure 2. In Figure 6, the side surface of the microprism is designed so that the emitted light is distributed around the normal 334 of the light emission surface 333, that is, the light emission ranges of the light traveling in the two directions overlap. For example, the distribution ranges of light 301, 302 and 303, 304 shown in Figure 6 overlap.

[0041] Figure 6 is a schematic diagram of the second structure of a dual light source collimated backlight module. The first light guide plate 57 is configured as two linear wedge-shaped plate structures with their thin sides connected, forming a bidirectional light emission module, in which case the first microprism array is arranged symmetrically. A specific implementation solution is that when light 504 emitted from the first auxiliary light source 56 is incident on the linear wedge-shaped plate, it first hits the structure (wedge shape) where the thickness decreases, and proceeds while being reflected between the upper interface 571 and the lower interface 572. If the angle of the wedge-shaped plate is β, each time the light is reflected at the upper interface 571 or the lower interface 572, the angle between the wedge-shaped plate and the normal to the upper interface 571 or the lower interface 572 decreases by β, and the light is emitted only when the emission condition is met. In this solution, the wedge angle β of the wedge-shaped light guide plate is extremely small, and the light energy (e.g., light 504) almost satisfies the total internal reflection condition as it propagates, so it is confined by the upper interface 571 and the lower interface 572, and the light is refracted by the side surface 522 of the microprism and exits the backlight module only when it irradiates the lower aperture of the first microprism array. Light that does not hit the lower aperture of the first microprism array in the wedge-shaped structure with decreasing thickness continues to propagate and enters the wedge-shaped structure with increasing thickness (inverted wedge), and this process is the same as in the case of the inverted wedge, for example, the exit point of light 505 from the first microprism array is in the inverted wedge portion. The same applies to the first light source 51 corresponding to the first auxiliary light source 56.

[0042] Figure 7 is a schematic diagram of the third structure of the dual light source collimated backlight module. In the solution of the bidirectional wedge-shaped light guide plate, the lower interface 571 of the wedge-shaped plate may be a plurality of nonlinear line segments. Its operating principle is the same as in Figure 7.

[0043] Figure 8 is a schematic diagram of the structure of a dual light source diffuse backlight module, which is the same as in Figure 5 except that the second reflective film 44 has been replaced with a second auxiliary light source 45.

[0044] Example 3 As shown in Figure 9, a double-incident (dual light source) backlight module 1 that can provide two forms of collimation and large-angle (diffuse) light emission includes a collimated backlight module 11 as the upper backlight module responsible for collimated light emission, a diffuse backlight module 12 as the lower backlight module responsible for diffuse light emission, and a reflective film 13 positioned below the lower backlight module that reflects stray light reflected downward from the optical interface in the direction of light emission, thereby reusing the stray light and increasing the light efficiency of the backlight module.

[0045] As shown in Figure 10, a double-incident backlight module 2, which can provide two forms of light emission—collimated and large-angle (diffuse) light emission—includes a diffuse backlight module 12 as the upper backlight module responsible for diffuse light emission, a collimated backlight module 11 as the lower backlight module responsible for collimated light emission, and a reflective film 13 positioned below the lower backlight module. In Example 3 of Figures 10 and 11, the upper and lower backlight modules are positioned in the same direction, i.e., the light sources on the same side of two upper and lower backlight modules are stacked vertically, for example, 111 and 121, 112 and 122, etc.

[0046] As shown in Figure 11, the dual light source diffusion backlight module 15 is the upper backlight module, and the bidirectional wedge-shaped collimated backlight module 16 is the lower backlight module. The upper backlight module 15 and the lower backlight module 16 are arranged on a combined reflective film 17. Taking the lower backlight module 16 as an example, the light 601 and 602 emitted from the light sources 621 and 622 enter the wedge-shaped light guide plate, travel in opposite directions, and are refracted when they hit the lower opening of the microprism before exiting into the lower backlight module 16. The light 601, 602, 603, and 604 emitted from the collimated backlight module 16 pass through the upper backlight module 15 and become a beam in the collimated direction. However, when passing through the upper backlight module, a portion of the collimated beam is dispersed by the haze effect caused by the microprism structure of the upper backlight module 15. Similarly, light emitted from the two light sources 611 and 612 of the upper backlight module 15, for example, light 605 and 606, enters the parallel light guide plate, travels in opposition to each other, and when it hits the lower opening of the microprism, it is refracted at a large angle by the side of the microprism and exits the diffuse backlight module 15. Such light 601, 602, 605, and 606 become full-angle beams, and when the upper backlight module 15 is closed, the beam range is limited to the collimated portions 601 and 602. The viewing angle of the beam can be switched by controlling the on / off state of the light sources of the upper backlight module 15. In this example, the reflective film 17 located below reflects light leaking from below the wedge-shaped light guide plate and light reflected downward from different interfaces of the backlight module structure, reusing the light emitted downward to improve the overall light efficiency of the backlight module. In this technological solution, the upper backlight module is a parallel plate and the lower backlight module is wedge-shaped, but the following combinations are also possible: The upper backlight module is wedge-shaped and the lower backlight module is a parallel plate. Both the upper and lower backlight modules are parallel plates, and both the upper and lower backlight modules are wedge-shaped.

[0047] As shown in Figure 12, an anti-peeping film 18 may be added to the structure in Figure 12 to further improve the blackness (module contrast) of the collimated (angle) cutoff area. In such a configuration, in order to reduce light loss at the interface, the lower surface 181 of the anti-peeping film 18 is in optical contact with the light-emitting surface 641 of the lower backlight module 64, and the upper surface 182 of the anti-peeping film 18 must not be in contact with the lower surface 631 of the diffuse backlight module 63, maintaining non-optical contact.

[0048] As shown in Figure 13, the upper and lower backlight modules are arranged orthogonally, that is, the light sources of one backlight module, e.g., 72 and 73, are positioned horizontally, while the light sources of the other backlight module, 71 and 74, are positioned vertically. The two modules, positioned orthogonally, are more tightly coupled, and the arrangement of the light sources does not interfere with each other. This reduces the actual haze on the lower backlight module caused by the microprism structure of the upper module while achieving a compact structural design. The beam rules for the combination of orthogonal backlight modules are the same as those for a combination of parallel backlight modules.

[0049] Figure 14 shows a configuration with the collimated backlight module 81 positioned below and the diffused backlight module 82 positioned above, arranged orthogonally. Figure 15 shows a combination with the diffused backlight module 82 below and the collimated backlight module 81 above.

[0050] As shown in Figure 16, in a configuration with a collimated backlight module 81 at the bottom and a diffused backlight module 82 at the top, an anti-peeping film 84 may be added between 81 and 82 to further improve the blackness of the collimated (angle) cutoff area (contrast of the backlight module). In such a configuration, the lower surface 841 of the anti-peeping film 84 is in optical contact with the light-emitting surface 811 of the lower backlight module 81 in order to reduce light loss at the interface. Also, the upper surface 842 of the anti-peeping film 84 must not be in contact with the lower surface 821 of the diffused backlight module 82, and non-optical contact must be maintained.

[0051] Example 4 As shown in Figure 17, the backlight module consists of an opaque all-wedge collimated backlight module 92 as the lower backlight module and a transparent diffuse backlight module 91 as the upper backlight module. The upper and lower backlight modules are arranged in the same direction, meaning that the light sources 911 and 924 of the two backlight modules are stacked vertically. Unlike the integrated wedge module structure, in Figure 17, the rhombic prism film 922, the wedge-shaped light guide plate 921, and the reflective film 923 are all separate devices, and the refractive indices of the two materials used in the rhombic prism film 922 and the wedge-shaped light guide plate 921 are the same or similar. The principle of operation is as follows. Light 901 and 902 emitted from the light source 924 enter through the tip of the wedge-shaped light guide plate 921 and propagate through the wedge-shaped light guide plate 921 (for example, n=1.58), following Snell's law of refraction n1sinθ1=n2sinθ2. In the formula, n1 is the refractive index of medium 1, θ1 is the angle of incidence, n2 is the refractive index of medium 2, and θ2 is the angle of refraction.

[0052] The angular range after light enters the wedge-shaped light guide plate 921 is α = ±arcsin(1 / 1.58) = ±40°. When light propagates within the wedge-shaped light guide plate 921, the angle 90-α between the normal to the upper reflective surface 9211 and the lower reflective surface 9212 of the wedge-shaped light guide plate 921 is 50° or greater. On the other hand, the total reflection angle is γ = arcsin(1 / 1.58) = 40°. If 90-α is greater than γ, the total reflection condition is met and no light is emitted. When the angle of the wedge-shaped plate is β, each time light is reflected, the angle between the normal to the emission surface 9211 of the wedge-shaped light guide plate 921 decreases by β, and light is emitted only when the emission condition is met. To make it easier to understand, all the light emitted from the emission surface 9211 and entering the upper rhombic prism film 922 is emitted when it is approximately at the total reflection angle, and the direction of the light is almost coincidental. That is, regardless of the initial direction of light 901 and 902 in the wedge-shaped light guide plate 921, the incident directions of these rhombic prism films 922 are almost coincidental. Therefore, after the beam is refracted by the rhombic prism film 922, the degree of convergence in a given direction is good. Such a configuration is particularly important in applications where a high degree of collimation is required. Here, the operating principle of module 91 of the upper diffusion light guide plate 921 is the same as in each of the above examples, but because the collimation of the all-wedge collimated backlight module is superior, the light emission range of the diffusion backlight module is also expanded accordingly to form a seamless full cover with the emitted beam of the collimated backlight module.

[0053] As shown in Figure 18, in the structure of Figure 17, an anti-peeping film 93 is provided between the transparent diffuse backlight module 91 and the opaque collimated backlight module 92 to further improve the blackness of the collimated (angle) cutoff area (contrast of the backlight module). In this configuration, to reduce light loss at the interface, the lower surface 932 of the anti-peeping film 93 is in optical contact with the light emitting surface 9251 of the lower backlight module. Also, the upper surface 931 of the anti-peeping film 93 must not be in contact with the lower surface 9121 of the diffuse backlight module 912, and non-optical contact must be maintained. Here, in Figure 17, the rhombic prism film above the wedge-shaped light guide plate is replaced with an inverse prism film 925, and their operating principles are similar, refracting the light emitted from the wedge-shaped light guide plate in a specific direction by total internal reflection.

[0054] Figure 19 shows the emitted light spectrum of a dual-source backlight module in an embodiment of the present invention. As is clear from the figure, when the upper and lower backlight modules are operating simultaneously, the backlight modules provide a contour 23 of the light emission range that covers the entire field of view. When the radiating backlight module is turned off, the dotted line spectrum 21 does not appear, and the backlight module provides only the emitted light spectrum 22 in the collimation direction.

Claims

1. It is a privacy backlight module, The backlight module, which allows control of the angle of light, comprises an upper backlight module, a lower backlight module, and a reflective film provided below the lower backlight module, wherein the upper backlight module is a transparent module, the lower backlight module is a transparent module or an opaque module, the upper backlight module is a diffuse backlight module, and the lower backlight module is a collimated backlight module. The collimated backlight module includes a first light guide plate, a first light source provided on the side of the first light guide plate, a first auxiliary light source provided on the side of the first light guide plate opposite to the first light source, and a first microprism array provided on the upper surface of the first light guide plate, wherein the first microprism array is arranged along the light transmission direction of the first light source. The diffuse backlight module includes a second light guide plate, a second light source provided on the side of the second light guide plate, a second auxiliary light source provided on the side of the second light guide plate opposite to the second light source, and a second microprism array provided on the upper surface of the second light guide plate, wherein the second microprism array is arranged along the light transmission direction of the second light source. The privacy backlight module is characterized in that the upper backlight module and the lower backlight module are arranged so that the direction from the first light source to the first auxiliary light source and the direction from the second light source to the second auxiliary light source are orthogonal to each other, so that the arrangement of the first light source, the first auxiliary light source, the second light source and the second auxiliary light source does not interfere with each other.

2. The privacy backlight module according to claim 1, characterized in that the first light guide plate is a wedge-shaped plate, and the first light source is provided on the thick end side of the wedge-shaped plate.

3. The privacy backlight module according to claim 2, characterized in that the wedge angle of the wedge-shaped plate is 5° or less.

4. The privacy backlight module according to claim 1, characterized in that the first microprism array has a trapezoidal or cup-shaped structure, and the first microprism array and the first light guide plate are integrated with each other.

5. The privacy backlight module according to claim 1, characterized in that the first microprism array focuses and refracts light incident from the first light guide plate outwards.

6. The privacy backlight module according to claim 1, characterized in that the second microprism array refracts and radiates light incident from the second light guide plate outwards.

7. The privacy backlight module according to claim 1, characterized in that a privacy film is in close contact with the upper surface of the lower backlight module, and there is an air gap between the privacy film and the lower surface of the upper backlight module.

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