Light guide plate and backlight module

Abstract

The present application provides a light guide plate and a backlight module, which are applied to a narrow frame display. The light guide plate comprises a substrate, a plurality of ribs and at least one self-limiting structure. The substrate is made of a first material and has an incident light side and an opposite side. The ribs are made of a second material with a low coefficient of thermal expansion, embedded in the substrate and adjacent to the bottom surface, and extend along the incident light side to the opposite side. The self-limiting structure is integrally formed with at least one rib and protrudes from the opposite side of the substrate. Through the design of the low thermal expansion ribs and the self-limiting structure, the thermal expansion and displacement of the light guide plate can be effectively limited; in combination with the cross-sectional shape of the ribs and the density compensation design of the dots, the optical path interference can be reduced, and excellent optical performance can be achieved under the condition of extremely narrow frame.

Description

Technical Field

[0001] This invention relates to a light guide plate, and more particularly to a light guide plate with a composite structure having low thermal expansion characteristics and a self-limiting structure for use in a backlight module of a narrow bezel display. Background Technology

[0002] In recent years, with the continuous increase in screen ratio requirements for terminal products such as automotive displays, desktop displays, commercial displays, and televisions, the design of backlight modules is developing towards extremely narrow bezels or even bezel-less designs. As the core light transmission component of edge-lit backlight modules, the stability of the light guide plate's dimensions directly affects the bezel width and overall optical performance.

[0003] Currently, narrow-bezel, high-brightness displays primarily use polymethyl methacrylate (PMMA) as the substrate for their light guide plates. However, PMMA has a relatively high coefficient of thermal expansion (typically approximately 7.2 × 10⁻⁶). −5 / ℃). Within the normal operating temperature and humidity range of the backlight module (e.g., between 25℃ and 85℃), the light guide plate will experience significant thermal and hygroscopic expansion along its length. For example, a 150 mm long PMMA light guide plate will expand by 6.75 mm under storage conditions of 60℃ and 90% relative humidity.

[0004] To accommodate the aforementioned expansion and prevent the light guide plate from bulging due to impact with the frame and causing optical problems, existing designs generally reserve sufficient expansion space between the light guide plate and the frame. However, there is an inherent contradiction between the reserved gap and the requirements of the narrow bezel mechanism. If the reserved space is forcibly reduced, the expanded light guide plate will compress against the frame, causing the light guide plate to warp and the optical coupling surface to shift, which in turn leads to optical problems such as bright spots, shadows, and reduced image uniformity on the light-incident side. In addition, the heat distortion temperature of PMMA material is approximately 90°C to 105°C. When the product's operating temperature reaches 85°C, there is also a risk of thermal deformation on the light-incident side of the internal light guide plate.

[0005] On the other hand, if glass with a smaller coefficient of thermal expansion is used as the substrate for the light guide plate (the typical value of the coefficient of thermal expansion of glass is approximately 7.2 × 10⁻⁶), −6 / ℃, heat distortion temperature is about 700℃). Although it can reduce the coefficient of thermal expansion by 10 times and eliminate the problem of heat deformation, the manufacturing cost of glass substrate light guide plate is high, and it has disadvantages such as fragility, difficulty in assembly and transportation.

[0006] Therefore, how to design a light guide plate structure that can effectively meet the limitations of thermal expansion and thermal deformation of the light guide plate under extremely narrow bezel conditions, without sacrificing optical performance and is easy to manufacture and assemble, is an issue that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] The purpose of this invention is to provide a light guide plate and a backlight module. By embedding ribs with a low coefficient of thermal expansion into the substrate and combining them with a self-limiting structure, it helps to limit the thermal expansion and displacement of the light guide plate under extremely narrow bezel conditions, while taking into account both excellent optical performance and manufacturing cost.

[0008] To achieve the above objectives, the present invention provides a light guide plate, comprising: a substrate, a plurality of ribs, and at least one self-limiting structure. The substrate is made of a first material and has a top surface, a bottom surface opposite the top surface, and a plurality of side edges connecting the top surface and the bottom surface. The side edges include a light-incident side edge and a counter-side edge opposite the light-incident side edge. The plurality of ribs are made of a second material, the linear coefficient of thermal expansion of which is lower than that of the first material. The ribs are embedded within the substrate and adjacent to the bottom surface, extending along the light-incident side edge toward the counter-side edge. The at least one self-limiting structure is integrally formed with at least one of the ribs and protrudes from the counter-side edge of the substrate.

[0009] In one embodiment of the present invention, the first material is polymethyl methacrylate (PMMA), and the second material is a polymer composite material including glass fiber or carbon fiber.

[0010] In one embodiment of the invention, each of the ribs has a triangular cross-section.

[0011] In one embodiment of the invention, the top height of each of the ribs is less than one-third of the thickness of the substrate.

[0012] In one embodiment of the present invention, the sides further include a first side and a second side that respectively connect the light-incident side and the opposing side, and the arrangement spacing of the ribs in the central region near the substrate is smaller than the arrangement spacing near the first side and the second side.

[0013] In one embodiment of the present invention, the spacing between adjacent ribs is 5 mm to 20 mm.

[0014] In one embodiment of the present invention, the self-limiting structure extends outward from the opposite side along the extension direction of the ribs, and one end of the self-limiting structure extends toward both sides perpendicular to the extension direction.

[0015] In one embodiment of the present invention, the sides further include a first side and a second side that respectively connect the light-incident side and the opposing side, and the ribs include two outermost ribs that are closest to the first side and the second side, and only the two outermost ribs are provided with the self-limiting structure.

[0016] In one embodiment of the present invention, the light guide plate further includes a plurality of dots disposed on the bottom surface of the substrate, and the distribution density of the dots around the ribs is lower than the distribution density of the dots away from the ribs.

[0017] To achieve the above objectives, the present invention further provides a backlight module, including a frame and the aforementioned light guide plate. The frame has at least one slot; the light guide plate is disposed within the frame, wherein the self-limiting structure forms a limiting engagement with the slot of the frame.

[0018] Through the above structure, the light guide plate and backlight module of the present invention can achieve the following effects: the rib design with a low coefficient of thermal expansion reduces the overall thermal expansion and moisture absorption deformation of the light guide plate; the cooperation between the self-limiting structure and the frame slot restricts the displacement of the light guide plate and the expansion of the ribs; the compensation design of the triangular cross-section and dot density of the ribs guides the light upward and reduces the interference of the ribs on the light path, thereby achieving a uniform light effect for the entire image. Furthermore, the present invention can be manufactured through insert injection molding or co-extrusion processes, is compatible with existing production lines, and helps to reduce manufacturing costs. Attached Figure Description

[0019] To gain a more complete understanding of the embodiments and their advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, wherein:

[0020] Figure 1 This is a top view schematic diagram of a light guide plate according to an embodiment of the present invention;

[0021] Figure 2 This is a partial three-dimensional schematic diagram of a light guide plate according to an embodiment of the present invention;

[0022] Figure 3 This is a schematic diagram of the AA-line cross-section of a light guide plate according to an embodiment of the present invention;

[0023] Figure 4 This is a schematic diagram of the dot distribution of a light guide plate according to an embodiment of the present invention; recalling

[0024] Figure 5 This is a partial top view of a backlight module according to an embodiment of the present invention.

[0025] In the attached figures, the following labels are used:

[0026] 10: Backlight Module

[0027] 20: Frame

[0028] 21: Card slot

[0029] 100: Light guide plate

[0030] 110: Substrate

[0031] 111: Top surface

[0032] 112 : Bottom

[0033] 113: Side of incoming light

[0034] 114: Opposite side

[0035] 115: First side

[0036] 116: Second side

[0037] 120: Ribs

[0038] 121: Outermost rib

[0039] 122: Triangle

[0040] 123: Top

[0041] 130: Self-limiting structure

[0042] 131: End

[0043] 140: Outlets

[0044] d: Spacing

[0045] h: height

[0046] t: thickness Detailed Implementation

[0047] The embodiments of the present invention are discussed in detail below. However, it will be understood that the embodiments provide many applicable concepts that can be implemented in a wide variety of specific contexts. The discussed and disclosed embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0048] In the accompanying drawings, the thicknesses of layers, films, panels, regions, etc., are enlarged for clarity. Throughout the specification, the same reference numerals denote the same elements. It should be understood that although the terms "first," "second," etc., may be used herein to describe various elements, components, regions, layers, and / or portions, these elements, components, regions, layers, and / or portions should not be limited by these terms. These terms are used only to distinguish one element, component, region, layer, or portion from another element, component, region, layer, or portion. Therefore, the "first element," "component," "region," "layer," or "part" discussed below may be referred to as "second element," "component," "region," "layer," or "part" without departing from the teachings herein.

[0049] Furthermore, relative terms such as “lower” or “bottom” and “upper” or “top” may be used herein to describe the relationship between one element and another, as illustrated in the figures. It should be understood that relative terms are intended to include different orientations of the device beyond those shown in the figures. For example, if a device in one of the figures is flipped, an element described as being “lower” than other elements would be oriented “upper” than other elements. Therefore, the exemplary term “lower” can include both “lower” and “upper” orientations, depending on the specific orientation of the figure.

[0050] Please refer to Figure 1 , Figure 1 This is a top view schematic diagram of a light guide plate according to an embodiment of the present invention. The present invention provides a light guide plate 100, mainly used in displays or backlight modules with narrow bezels or bezel-less designs. The light guide plate 100 includes a substrate 110. The substrate 110 is the main structure of the light guide plate 100, and it is made of a first material. In this embodiment, the first material is, for example, a polymer material with good light transmittance such as polymethyl methacrylate (PMMA).

[0051] The substrate 110 has a top surface 111 and a bottom surface 112 opposite to the top surface 111 (the relative positions of the top surface 111 and the bottom surface 112 are shown in the reference). Figure 2 and Figure 3 ), and multiple sides connecting the top surface 111 and the bottom surface 112. In practical applications, the top surface 111 usually faces the display panel (i.e., the light-emitting surface direction), while the bottom surface 112 faces the reflector of the backlight module.

[0052] The substrate 110 has a plurality of sides including a light-incident side 113, a opposing side 114 opposite to the light-incident side 113, and a first side 115 and a second side 116 respectively connecting the light-incident side 113 and the opposing side 114. In other words, the first side 115 and the second side 116 are two other opposing sides of the substrate 110. It is worth noting that... Figure 1 In the illustrated embodiment, the light-incident side 113 and the opposing side 114 are taken as examples of the short side of the substrate 110; however, the present invention is not limited thereto. In other embodiments, to meet the ultra-narrow bezel design requirements of different models, the light-incident side 113 may also be the long side of the substrate 110, while the opposing side 114 may be another long side. Such variations in geometric direction are all within the scope of the present invention.

[0053] Please continue to refer to Figure 1 The light guide plate 100 also includes multiple ribs 120. The multiple ribs 120 are embedded within the substrate 110 and adjacent to the bottom surface 112 (the embedding depth and cross-sectional characteristics will be discussed later). Figure 3(Detailed explanation follows). Multiple ribs 120 are made of a second material, and the linear coefficient of thermal expansion of the second material is lower than that of the first material of the substrate 110. In this embodiment, the second material is, for example, a polymer composite material containing glass fibers or carbon fibers. By adding varying numbers of these low-thermal-expansion ribs 120, the overall coefficient of thermal expansion of the light guide plate 100 can be effectively reduced to 7.2 × 10⁻⁶. −6 / ℃ to 7.2×10 −5 Within a range of / ℃, this overcomes the problem that pure PMMA substrates are prone to severe thermal expansion and moisture absorption deformation in high temperature or high humidity environments.

[0054] In terms of geometric layout, multiple ribs 120 extend along the light-incident side 113 toward the opposite side 114. This extension configuration, which follows the direction of light travel, not only reduces the interference of the ribs 120 on the light path, but also effectively suppresses the thermal expansion of the light guide plate 100 in this direction.

[0055] Furthermore, to address the thermal stress distribution within the light guide plate 100, the plurality of ribs 120 employ an asymmetrical compensation design in terms of arrangement density. Specifically, the substrate 110 has a central region located between the first side 115 and the second side 116. The spacing between the plurality of ribs 120 near the central region is smaller than the spacing near the first side 115 and the second side 116. In other words, the ribs 120 exhibit a "dense in the middle and sparse on the sides" distribution. Due to the greater expansion stress in the central region of the light guide plate 100, the denser ribs 120 help enhance the suppression effect; while the sparser ribs 120 on the sides can further reduce interference to the optical paths on both sides. In a specific embodiment, the spacing between adjacent ribs 120 (i.e., Figure 1 The spacing d) indicated in the middle mark can be designed from 5 mm to 20 mm.

[0056] Furthermore, the plurality of ribs 120 includes two outermost ribs 121 closest to the first side 115 and the second side 116, respectively. The light guide plate 100 further includes at least one self-limiting structure 130, which is integrally formed with at least one of the plurality of ribs 120. Figure 1 In the illustrated embodiment, self-limiting structures 130 are provided only on the two outermost ribs 121 (in principle, providing them only on the two outermost sides is sufficient to meet the limiting requirements); however, the present invention is not limited thereto. In other embodiments, depending on the design of the mechanism or the requirements of the limiting strength, self-limiting structures 130 may also be added to other ribs 120 located in the central region.

[0057] Please refer to the above as well. Figure 1 and Figure 2 . Figure 2This is a partial three-dimensional schematic diagram of a light guide plate according to an embodiment of the present invention, which mainly presents the three-dimensional geometric features of a self-limiting structure.

[0058] like Figure 2 As shown, the self-locking structure 130 protrudes from the opposing side 114 of the substrate 110. Specifically, the self-locking structure 130 extends outward from the opposing side 114 along the extending direction of the rib 120 (e.g., the outermost rib 121), and the self-locking structure 130 has an end 131. The end 131 extends outward to both sides perpendicular to the aforementioned extending direction, so that the self-locking structure 130 has an overall T-shaped appearance. This geometric feature of extending vertically to both sides helps to increase the engagement area of ​​the structure, so as to form a stable locking fit with the subsequent backlight module components (to be referred to later). Figure 5 (Detailed explanation follows).

[0059] Furthermore, it is worth noting that the self-limiting structure 130 protrudes only toward the opposing side 114, and not toward the light-incident side 113. This configuration avoids interference between the self-limiting structure 130 and light-emitting elements (such as LED strips) that are typically located next to the light-incident side 113, ensuring the stability of the optical coupling.

[0060] In terms of manufacturing process, the light guide plate 100 can be manufactured by insert molding or co-extrusion. For example, a rib 120 made of a second material (including a self-limiting structure 130 integrally formed therewith) can be placed into a mold as an insert, and then the first material can be injection molded into a substrate 110, so that the two are tightly bonded into a composite structure. The advantage of using insert molding or co-extrusion is that it is highly compatible with existing light guide plate production lines, without the need for major replacement of equipment, thereby effectively reducing the cost of production line modification.

[0061] Please refer to the above as well. Figure 1 , Figure 3 and Figure 4 . Figure 3 This is a schematic diagram of the AA-line cross-section of a light guide plate according to an embodiment of the present invention. Figure 4 This is a schematic diagram of the dot distribution of a light guide plate according to an embodiment of the present invention. It should be noted that, in order to clearly show the technical features to be described, Figure 3 and Figure 4 This is only a schematic diagram; details such as the number and spacing of ribs 120 are not shown in the original text. Figure 1 There are omissions and simplifications.

[0062] like Figure 3As shown, ribs 120 are embedded inside the substrate 110 and adjacent to the bottom surface 112. In terms of cross-sectional shape, each rib 120 has a triangular cross-section 122 (e.g., a prism triangle). The inclined structure of the triangle 122 guides light and creates an upward focusing effect, thereby reducing light loss during transmission. In addition, each rib 120 has a top 123, and the height h of the top 123 is designed to be less than one-third of the thickness t of the substrate 110. This height ratio design ensures that the core optical path region inside the light guide plate 100 (i.e., the upper two-thirds of the substrate 110) is free of ribs, thereby reducing the impact of the ribs 120 on the main optical path transmission.

[0063] Next, please refer to Figure 4 The light guide plate 100 further includes multiple dots 140. These dots 140 are arranged on the bottom surface 112 of the substrate 110 to disrupt total internal reflection and guide light out of the light guide plate 100. To accommodate the ribs 120, the distribution of the dots 140 employs a compensation design. Specifically, the density of dots 140 near the ribs 120 is lower than the density of dots 140 farther from the ribs 120. In other words, the dots 140 around the ribs 120 are more sparse, while those farther from the ribs 120 are more dense. This dot compensation design further reduces the interference of the ribs 120 on the light path, resulting in a more uniform light distribution across the entire image.

[0064] Please refer to the following at the same time Figure 1 , Figure 2 and Figure 5 . Figure 5 This is a partial top view of a backlight module according to an embodiment of the present invention.

[0065] Based on the light guide plate 100 described above, the present invention further provides a backlight module 10. The backlight module 10 includes a frame 20 and a light guide plate 100 disposed within the frame 20. The frame 20 has at least one slot 21, the position of which corresponds to the self-limiting structure 130 of the light guide plate 100.

[0066] like Figure 5As shown, when the light guide plate 100 is assembled within the frame 20, the self-limiting structure 130 (especially its vertically extending ends 131) engages with the slots 21 of the frame 20, forming a stable limiting fit. Under extremely narrow bezel design conditions, only a very small gap can be reserved between the light guide plate 100 and the frame 20. When the light guide plate 100 undergoes thermal expansion or moisture absorption expansion under normal operating temperature (e.g., 85°C) or high humidity conditions, the engagement of the self-limiting structure 130 and the slots 21 effectively limits the overall displacement of the light guide plate 100, while also limiting the excessive expansion of the internal ribs 120. This mechanism design prevents the light guide plate 100 from warping and deforming due to insufficient space for expansion and impact with the frame 20, thereby preventing the optical coupling surface from shifting.

[0067] In summary, the light guide plate 100 and backlight module 10 provided in this embodiment of the invention have the following multiple benefits. In terms of thermodynamics and dimensional stability, by embedding ribs 120 with a low coefficient of thermal expansion, the thermal expansion and moisture absorption deformation of the PMMA substrate 110 are significantly reduced, resolving the structural contradiction of insufficient space reserved in the ultra-narrow bezel. In terms of optical performance, the ribs 120 extend along the light path, and with the triangular cross-section design 122 and height limitation, they can guide light upwards for focusing; simultaneously, the density compensation design of the dot matrix 140 on the bottom surface 112 effectively reduces the interference of the ribs 120 on the light path, ensuring the uniformity of the emitted light image and achieving the goal of not sacrificing optical performance. In terms of structure and assembly, the integrated self-limiting structure 130, in conjunction with the slot 21 of the frame 20, provides enhanced limiting functionality; and the overall composite structure can be manufactured through insert injection molding or co-extrusion processes, making it highly compatible with existing production lines and helping to control manufacturing costs.

[0068] Although the present invention has been disclosed above by way of embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make some modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A light guide plate, characterized in that, include: A substrate made of a first material, the substrate having a top surface, a bottom surface opposite the top surface, and a plurality of side edges connecting the top surface and the bottom surface, the plurality of side edges including a light-incident side edge and a pair of opposing side edges opposite the light-incident side edge; Multiple ribs, made of a second material having a lower linear thermal expansion coefficient than the first material, are embedded in the substrate and adjacent to the bottom surface, extending along the light-incident side toward the opposing side; and at least one self-limiting structure is integrally formed with at least one of the multiple ribs and protrudes from the opposing side of the substrate.

2. The light guide plate as described in claim 1, characterized in that, The first material is polymethyl methacrylate, and the second material is a polymer composite material including glass fiber or carbon fiber.

3. The light guide plate as described in claim 1, characterized in that, Each of the plurality of ribs has a triangular cross-section.

4. The light guide plate as described in claim 3, characterized in that, The top height of each of the plurality of ribs is less than one-third of the thickness of the substrate.

5. The light guide plate as described in claim 1, characterized in that, The plurality of sides further includes a first side and a second side that respectively connect the light-incident side and the opposing side, and the arrangement spacing of the plurality of ribs in the central region near the substrate is smaller than the arrangement spacing near the first side and the second side.

6. The light guide plate as described in claim 5, characterized in that, The spacing between adjacent ribs is 5 mm to 20 mm.

7. The light guide plate as described in claim 1, characterized in that, The self-limiting structure extends outward from the opposite side along the extension direction of the plurality of ribs, and one end of the self-limiting structure extends toward both sides perpendicular to the extension direction.

8. The light guide plate as described in claim 1, characterized in that, The plurality of sides further includes a first side and a second side that respectively connect the light-incident side and the opposing side, and the plurality of ribs includes two outermost ribs that are closest to the first side and the second side, and only the two outermost ribs are provided with the self-limiting structure.

9. The light guide plate as described in claim 1, characterized in that, Further, including: Multiple dots are arranged on the bottom surface of the substrate, and the distribution density of the multiple dots around the multiple ribs is lower than the distribution density of the multiple dots away from the multiple ribs.

10. A backlight module, characterized in that, include: A plastic frame with at least one card slot; And a light guide plate as described in any one of claims 1 to 9, disposed within the frame, wherein the self-limiting structure forms a limiting engagement with the slot of the frame.

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