Novel collimation high-brightness backlight module

Abstract

The invention relates to the technical field of semiconductor display, in particular to a novel collimation high-brightness backlight module. The backlight module comprises a light guide plate, a light source, a reflecting film and an optical laminated layer arranged on the light-emitting surface of the light guide plate. The light-emitting surface of the light guide plate is provided with a continuous columnar curved surface microstructure, and the lattice point surface is provided with triangular prism lattice point structures arranged according to a specific rule. The core of the invention is that the optical laminated layer comprises at least four prism film layers, the prism extension directions of at least two of the film layers are orthogonally arranged, and multi-stage beam splitting and precise collimation are performed on light through the synergistic effect of the light guide plate microstructure and the plurality of orthogonal prism film layers. On the premise that brightness is not obviously sacrificed, the visual angle of emergent light rays can be greatly contracted in the horizontal direction and the vertical direction at the same time, the excellent all-dimensional peep-proof effect is achieved, the structure is compact, and the side-in type display device is particularly suitable for side-in type display equipment with high requirements for privacy protection and lightening and thinning.

Description

Technical Field

[0001] This invention relates to the field of semiconductor display technology, and more specifically to a novel collimated high-brightness backlight module. Background Technology

[0002] With the widespread use of mobile electronic devices and the increasing public awareness of privacy protection, the demand for privacy-protecting display devices is becoming increasingly prominent in business, finance, and personal privacy protection scenarios. The core of privacy-protecting display technology lies in controlling the viewing angle of the display, so that the screen content is only visible within a small angle directly in front, thereby preventing onlookers from peeping from the side.

[0003] Currently, one of the mainstream technologies for achieving privacy protection in displays is to add a privacy film to the backlight module or panel of a liquid crystal display (LCD). This privacy film is typically based on the principle of a micro-louver grating, using built-in black light-absorbing strips or microstructures at specific angles to block light at wide angles, thus limiting the viewing angle. For example, a typical privacy film can achieve a viewing angle limitation of approximately ±30° in the left and right directions (with a brightness reduction to 5% as the viewing angle boundary). However, this technical solution has significant drawbacks: First, the grating structure blocks and absorbs most of the light, resulting in a significant decrease in the brightness of the front of the display (typically a loss of more than 50%). To maintain the perceived brightness, the backlight power must be increased, thus increasing overall power consumption and cost. Second, traditional privacy films are usually only effective in a single direction (such as the horizontal direction), with limited privacy protection in the vertical direction, making it difficult to achieve comprehensive privacy protection. Furthermore, the additional film layer also increases the module thickness, which is detrimental to the design of thinner and lighter devices.

[0004] Another technical approach starts with the backlight module itself, achieving light collimation through optical design. This involves directing the light beams towards a direction nearly perpendicular to the screen, naturally creating a narrow viewing angle. One existing collimation backlight solution uses direct backlighting combined with a complex multi-layer brightness enhancement film (BEF) and a focusing lens structure. While this solution achieves good collimation, its complex structure, large thickness, and high cost make it difficult to apply to edge-lit backlight modules where thickness is strictly limited.

[0005] For edge-lit backlight modules, achieving light collimation and privacy protection is more challenging. Edge-lit backlights rely on a light guide plate (LGP) to transform side-incident line light sources into surface light sources. The LGP's optical design aims to ensure uniform light output and a certain degree of diffusion to meet the demands of wide-viewing-angle displays. To achieve privacy protection, current technologies typically involve simply layering these privacy films onto conventional films (such as diffuser films and brightness enhancement films) in edge-lit backlight modules. This also leads to significant brightness loss and only unidirectional privacy protection. Although some research has attempted to use special designs on the dot matrix or light-emitting microstructures of the light guide plate to converge light—for example, by setting prism structures on the light-emitting surface or designing reflection structures at specific angles on the dot matrix surface—these solutions often only initially compress the viewing angle in a certain direction. The collimation of the emitted light is insufficient, the viewing angle contraction is limited, and it is difficult to effectively match the downstream optical films to achieve coordinated collimation in all directions (horizontal and vertical). This results in poor privacy protection, decreased brightness uniformity, or difficulties in process control.

[0006] Therefore, there is a lack of efficient and compact collimating optical solutions in the existing technology that can achieve excellent all-around privacy protection without significantly sacrificing brightness for side-lit backlight modules. Summary of the Invention

[0007] To address the challenges of existing side-lit backlight modules in achieving high brightness, all-around privacy protection, and compact structure, this invention provides a novel collimated high-brightness backlight module and its core light guide plate. The aim is to achieve directional guidance and precise collimation of light from the light source end through the synergistic design of the light guide plate microstructure and multi-layer prism film.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a novel collimated high-brightness backlight module. The module includes a light guide plate, multiple light sources, a reflective film, and an optical stack disposed outside the light-emitting surface of the light guide plate. The light guide plate has a light-incident surface, a dotted surface adjacent to the light-incident surface, and a light-emitting surface disposed opposite to the dotted surface; multiple light sources are disposed on one side of the light-incident surface of the light guide plate; and the reflective film is disposed outside the dotted surface of the light guide plate.

[0009] The core improvement of this invention lies in the optical stack, which includes at least four prism film layers. These four prism films are orthogonally stacked, with the bottommost prism film inverted according to the direction of the LED light-incident face perpendicular to the light guide plate (prism facing the light guide plate). The remaining prism films are orthogonally stacked in pairs, with the orientation of the inverted prism film as a reference. This unique optical stack performs multi-stage beam splitting and coordinated collimation on the light emitted from the light guide plate's light-emitting surface, ultimately reducing the light emission angle to an extremely small range in the direction perpendicular to the light-emitting surface, thereby achieving excellent all-around privacy protection in both horizontal and vertical directions.

[0010] Preferably, a specific configuration of the optical stack is as follows: a first prism film, a second prism film, a third prism film, and a microstructure film are sequentially arranged along the light emission direction.

[0011] Specifically, the first prism film has its prism surface facing the light guide plate (i.e., "inverted"), and its prism extension direction is perpendicular to the entrance end face of the light guide plate; the second prism film is conventionally placed face up, and its prism extension direction is orthogonal to the first prism film. The microstructure film is disposed on the outermost side of the optical stack, and its first surface (light-emitting surface) has a periodically arranged concave pyramid microprism structure; the extension direction of the bottom edge of the single concave pyramid forms a 45° angle with the edge of the microstructure film; the second surface (light-incident surface) of the microstructure film is a haze surface with a preset haze value of <30%. The microstructure film is used to slightly fog the light and achieve the final contraction and deflection of the viewing angle, resulting in light emission characteristics with excellent uniformity and collimation.

[0012] Secondly, this invention provides a novel light guide plate for the aforementioned backlight module. This light guide plate features a specially designed optical microstructure, with a continuous columnar curved surface microstructure on its light-emitting surface for initial focusing and angle control of light before it leaves the light guide plate. Its dot surface has multiple inwardly recessed specific triangular prism dot structures, and light-guiding groove structures distributed in areas other than the triangular prism dot structures on the dot surface. The bevel angle of the triangular prism dot structures is precisely designed to efficiently reflect light propagating within the light guide plate towards the light-emitting surface, giving it a specific emission angle.

[0013] Preferably, these triangular prism dot structures are arranged on the dot surface according to a preset mathematical rule (such as based on Bessel equation, offset rectangular array, radial polynomial, etc.) to ensure the uniformity of the brightness of the light-emitting surface of the light guide plate, laying a good foundation for the precise collimation of the downstream optical stack.

[0014] The beneficial effects of this invention are as follows: This invention employs a systematic optical design of "preliminary convergence of a special light guide plate microstructure + cascaded collimation of multiple orthogonal prism films." This invention can simultaneously and significantly reduce the angle of the emitted light in both the horizontal and vertical directions (for example, the full width at half maximum (FWHM) can be controlled within 40° in all directions), achieving an all-around privacy protection effect that is difficult to achieve with traditional single privacy films, and greatly improving the security of privacy protection.

[0015] Unlike traditional privacy films that rely on absorbing or blocking light, this invention primarily redistributes the direction of light through optical principles such as reflection and refraction. The vast majority of light is guided to emerge within the frontal viewing angle, avoiding unnecessary light loss. Therefore, while achieving a narrow viewing angle, it maintains high frontal brightness and optical efficiency, resolving the conflict between privacy and brightness.

[0016] This invention is based on a mature side-lit backlight architecture. It achieves functionality by optimizing the light guide plate's structure and adding specific film layers, eliminating the need for a bulky external collimating lens assembly. The specially designed light guide plate combined with multi-layered films enables complex light control functions within a limited space, which is beneficial for applications in thinner products such as mobile devices.

[0017] The arrangement of the dot structure, the angle of the slope, and the number of films, the angle of the prisms and the placement method in the optical stack of the light guide plate of this invention can all be adjusted and matched according to specific performance requirements such as privacy angle and brightness uniformity, providing a flexible technical means for product customization. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a three-dimensional structural diagram of the novel light guide plate provided in an embodiment of the present invention.

[0020] Figure 2 for Figure 1 The diagram shows the principle of light propagation trajectory inside the light guide plate.

[0021] Figure 3 This is a partial top view of the dotted surface of the light guide plate in one embodiment of the present invention.

[0022] Figure 4 This is a schematic diagram showing the arrangement of triangular prism dots in an offset rectangle manner in an embodiment of the present invention.

[0023] Figure 5 for Figure 1 Enlarged cross-sectional view of the continuous columnar curved surface structure on the light-emitting surface of the light guide plate.

[0024] Figure 6 This is an exploded structural diagram of a basic backlight module embodiment of the present invention.

[0025] Figure 7 For corresponding Figure 6 3D view distribution of light emission obtained from structural simulation.

[0026] Figure 8 This is a preferred optical stack configuration diagram according to an embodiment of the present invention.

[0027] Figure 9 This is a configuration diagram of the optical stack of the present invention, which consists of four standard brightness enhancement films (BEF).

[0028] Figure 10 yes Figure 8 A simulation diagram of the configuration structure.

[0029] Figure 11 yes Figure 9 A simulation diagram of the configuration structure.

[0030] The labels in the diagram represent: 100-Light Guide Plate 101-Light-receiving surface 102-Network Surface 103 - Emitting Surface 110-Continuous cylindrical curved surface structure 111, 112 - Circular arc segments forming a continuous cylindrical surface 120-Triangular Prism Dot Structure 130-Dot Structure Profile 200-Light Source 201-Reflective film 300-First Prism Film 500-Second Prism Film 600-Microstructure Membrane 700-Third Prism Film 800-Fourth prism film. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] See Figures 1 to 6 This invention provides a novel functional light guide plate 100 specifically designed for narrow-angle light emission. The light guide plate 100 is generally flat and mainly includes three functional surfaces: an incident surface 101 for receiving line light sources, a dotted surface 102 with precise microstructures, and an emitting surface 103 disposed opposite to the incident surface. The incident surface 101 and the dotted surface 102 are perpendicularly connected.

[0033] The core feature of the light guide plate 100 lies in its surface microstructure design: 1. Microstructure of the light-emitting surface: such as Figure 1 and Figure 6 As shown, a continuous cylindrical curved surface structure 110 is formed on the light-emitting surface 103. This structure is composed of a series of closely arranged cylindrical lens units extending along a specific direction (e.g., parallel to the light-incident surface 101). Its cross-sectional curve is formed by the continuous alternation and smooth connection of arcs 111 (R1, R2) and arcs 112 (R3) with different radii. The center of arc 111 is located inside the light guide plate 100, while the center of arc 112 is located outside the light guide plate 100. This asymmetrical composite curved surface design can perform initial convergence and angle filtering of the light reflected from the dot surface 102 to the light-emitting surface, effectively converging the light-emitting angle perpendicular to the extension direction of the cylindrical lens (e.g., the D2 direction).

[0034] 2. Microstructure of dot surfaces: such as Figures 2 to 5 As shown, two main types of microstructures are distributed on the dot surface 102: Triangular prism dot structure 120: (e.g., ...) Figure 4 As shown, the structure is a triangular prism-shaped groove recessed inside the light guide plate 100 (in the -D3 direction). Its key geometric parameters include: the angles between the two reflective sides and the dot surface 102 (bottom surface) are α and β, respectively, satisfying the relationship: 90°>β>α>0°. The dot height H can range from 1 micrometer to 20 micrometers. The lengths of the prism's base, L1 and L2, satisfy the relationship: L2=b×L1, where b>0. The precise design of the inclined angles α and β determines the specific exit angle at which light, after total internal reflection within the light guide plate 100, is reflected towards the light-emitting surface 103 upon impact with the inclined surface. A smaller α angle helps guide the light closer to the normal (D3).

[0035] Light guide trench structure: such as Figure 3 and Figure 5 As shown, auxiliary light-guiding groove structures (not separately marked in the figure) are distributed in the remaining area between the triangular prism dot structures 120. These grooves mainly serve to disrupt the optical path, suppress bright spots, and further improve the uniformity of light output.

[0036] Branch network layout: such as Figure 5 As shown, the spatial distribution of the triangular prism dot structure 120 on the dot surface 102 is not random, but rather optimized according to preset mathematical rules, such as offset rectangular arrays, grid arrays, pseudo-random distributions based on the Bessel equation, radial multinomial distributions, or custom list distributions. This orderly arrangement, combined with the gradual design of dot size and density, ensures that light rays incident from the light-incident surface 101 are uniformly guided to the entire light-exit surface 103, achieving excellent brightness uniformity and providing a uniform "light field input" for the back-end processing of collimating optics.

[0037] See Figure 6 Based on the light guide plate 100 of Embodiment 1, a basic collimated backlight module is constructed. This module includes: The novel light guide plate 100.

[0038] Multiple light sources (LEDs) 200 are arranged in a straight line and closely attached to the outside of the light incident surface 101 of the light guide plate 100.

[0039] A reflective film 201 is attached to the outside of the dotted surface 102 of the light guide plate 100. Its properties can be specular reflection or diffuse reflection. It is used to reflect the downward-leaking light back into the light guide plate 100 to improve the light utilization rate.

[0040] In this basic configuration, the light emitted by LED200 enters the light guide plate 100 from the light incident surface 101 and propagates through internal total internal reflection. When the light encounters the triangular prism dot structure 120 on the dot surface 102, it is directionally reflected towards the light emitting surface 103 according to its slope angle α. After further collimation by the continuous cylindrical curved surface structure 110 of the light emitting surface 103, it is emitted. Figure 7 The simulation results show that the basic module can achieve a more concentrated viewing angle distribution than the traditional side-lit backlight in both the D1 and D2 directions, forming a "light lobe" with specific directionality, which lays the foundation for subsequent all-round collimation.

[0041] To achieve synchronous and efficient viewing angle contraction in both the horizontal (D1) and vertical (D2) directions and to achieve all-around privacy protection, a specific optical film layer stack needs to be added to the basic module. Figure 8 A preferred optical stack configuration is shown.

[0042] In this embodiment, the following film layers are sequentially stacked on the light-emitting surface 103 of the light guide plate 100 along the light emission direction (+D3 direction): 1. First prism film (inverted BEF) 300: Its prism-structured side (prism surface) faces the light guide plate 100 (i.e., "inverted"). The extension direction of its prism is parallel to the D2 direction. The function of this film is to "cut" and deflect the light emitted from the light guide plate, which has been initially converged in the D2 direction, so that it spreads out in the D1-D3 plane.

[0043] 2. Second prism film 500 (BEF): Its prism face faces upward, and the extension direction of the prism is orthogonal to the first prism film 300, that is, parallel to the D1 direction. It is responsible for collimating the light rays processed by the first prism film 300 in the D2-D3 plane.

[0044] 3. Microstructure film 600: Located on the outermost side. In this embodiment, one side of the film is a functional surface with a micro pyramid structure, and the other side may have a coating haze. The pyramid structure can perform final micro-diffusion and angle fine-tuning of the collimated light from the prism film below, which helps to eliminate moiré patterns, improve viewing comfort, and optimize front brightness.

[0045] This configuration of "inverted BEF + orthogonal BEF + microstructure film" achieves precise optical path control through matching the light output angle of the light guide plate 100 itself (determined by the dot angle α).

[0046] The simulation parameters are as follows:

[0047] Simulation results ( Figure 10 This indicates that the emitted light energy of the module is highly concentrated within a very small solid angle centered on the normal (D3), and the full width at half maximum (FWHM) in both the D1 and D2 directions can be effectively compressed, for example, to within 40°, thereby achieving excellent omnidirectional privacy protection and high brightness at the front center.

[0048] Example 4: Another optical stack configuration See Figure 9 This illustrates another embodiment of the invention. In this embodiment, the optical stack consists of four standard brightness enhancement films (BEF), omitting the specific microstructure film.

[0049] The first BEF is placed upside down with the prism face down (extending in the same direction as D2).

[0050] The next three BEFs are stacked alternately orthogonally (for example, the extension directions are D1, D2, D1 in sequence).

[0051] This "four BEF orthogonally superimposed" scheme, through the repeated beam splitting and deflection of light by multiple layers of prisms, can also gradually collimate the light from the light guide plate in Embodiment 1 or 2.

[0052] The simulation parameters are as follows:

[0053] like Figure 11 The simulated viewing angle distribution diagram shows that this configuration can also achieve highly concentrated light emission characteristics. The two uppermost co-directional BEFs can be considered as two-stage collimation for light rays in a single direction, and their effect is equivalent to or can be replaced by the "BEF + microstructure film" combination in Example 3.

[0054] As can be seen from the above embodiments, the technical solution of the present invention systematically solves the problem of achieving all-around privacy protection in side-lit backlights by organically combining light control at the light guide plate source with collimation through multi-layer films at the back end. The unique triangular prism dot pattern and continuous cylindrical structure of the light guide plate provides controllable and uniform directional light output. Subsequently, four (or more) prism film layers, specially designed and arranged, act like a precise "optical processor," cascadingly splitting, deflecting, and collimating these directional lights in the horizontal and vertical directions, ultimately outputting a highly collimated beam of light, achieving a fundamental shift from wide-viewing-angle displays to narrow-viewing-angle privacy displays. This solution, while ensuring high luminous efficiency and high brightness, is structurally fully compatible with existing side-lit backlight processes, possessing extremely high industrial application value.

[0055] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A novel collimated high-brightness backlight module, characterized in that, include: A light guide plate has a light incident surface, a dotted surface adjacent to the light incident surface, and a light emitting surface disposed opposite to the dotted surface; Multiple light sources are disposed on one side of the light incident surface of the light guide plate; A reflective film is disposed on the outer side of the dotted surface of the light guide plate; An optical stack is disposed on the outer side of the light-emitting surface of the light guide plate; the optical stack includes at least four prism film layers, wherein at least two prism film layers are orthogonally stacked in their prism extension directions, for splitting and collimating the light from the light-emitting surface of the light guide plate, so as to achieve a reduction in the light emission angle in the direction perpendicular to the light-emitting surface.

2. The novel collimated high-brightness backlight module according to claim 1, characterized in that, The optical stack specifically includes a first prism film, a second prism film, a third prism film, and a microstructure film arranged sequentially along the light emission direction.

3. The novel collimated high-brightness backlight module according to claim 2, characterized in that, The prism extension direction of the first prism film is orthogonal to the prism extension direction of the second prism film, and the prism surface of the first prism film is disposed facing the light guide plate; the prism extension direction of the third prism film is the same as or orthogonal to the prism extension direction of the second prism film; the microstructure film is disposed on the outermost side of the optical stack.

4. The novel collimated high-brightness backlight module according to claim 3, characterized in that, The light-emitting surface of the light guide plate is provided with a continuous columnar curved surface microstructure; the dot surface has multiple inwardly recessed triangular prism dot structures arranged in a certain manner.

5. The novel collimated high-brightness backlight module according to claim 4, characterized in that, The triangular prism dot structure is arranged on the dot surface according to a preset mathematical rule.

6. The novel collimated high-brightness backlight module according to claim 3, characterized in that, The light-emitting surface of the microstructure film is provided with a pyramid-shaped microstructure, and the light-incident surface is provided with an optical film with a preset haze.

7. The novel collimated high-brightness backlight module according to claim 3, characterized in that, The angle of view of the light emitted by the backlight module is distributed such that the full width at half maximum (FWHM) in both the horizontal and vertical directions is no greater than 40°.

Images