Light guide film, front light module and display device
By employing optical material layers with different refractive indices and complementary light-guiding microstructure design in e-paper readers, the problem of poor visibility of e-paper readers against dark backgrounds has been solved, and brightness and contrast have been improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- NICROTEK CO LTD
- Filing Date
- 2025-07-11
- Publication Date
- 2026-07-21
AI Technical Summary
E-paper readers have poor visibility in dark backgrounds, and existing front light modules cause energy decay, reducing display brightness and contrast, especially in color displays.
By employing first and second optical material layers with different refractive indices, combined with complementary light-guiding microstructure design, the light energy utilization rate is improved, the ineffective light emission is reduced, and the effective light emission is enhanced.
It improves the brightness and contrast of display devices, especially in color electronic paper displays, significantly enhancing light energy utilization and display effects.
Smart Images
Figure CN224536203U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of display technology, and in particular to a light guide film, a front light module, and a display device. Background Technology
[0002] Electronic Paper Display (EPD) is a reflective display technology with advantages such as low power consumption, bistable operation, wide viewing angle, high contrast under strong light, lightweight portability, and eye protection. It has been widely applied in various fields, including shelf labels, e-readers, smart healthcare, smart offices, and outdoor displays. EPD works by displaying images and text through the movement of tiny charged white and black particles under the influence of an electric field. Due to its excellent reading experience and low power consumption, EPD has become the mainstream technology in the e-book reading market. Compared to traditional LCD screens, EPD, being a reflective display technology, achieves display by reflecting ambient light, thus offering better visibility in direct sunlight; however, its visibility is significantly reduced against dark backgrounds. To address this visibility issue in dark backgrounds, a front light source, i.e., a front light guide film (or light guide plate), is typically added to provide illumination. However, due to the low reflectivity of the EPD itself, the light emitted from the lower surface of the front light source and illuminating the EPD, then passing through the front light module, and finally exiting from the light-emitting surface, inevitably experiences energy attenuation during this process. This reduces the brightness and contrast of the display module, especially when used for color EPD displays. Summary of the Invention
[0003] To solve at least one of the above-mentioned technical problems, this application provides a light guide film, a front light module, and a display device.
[0004] In a first aspect, a light guide film is proposed, comprising a first optical material layer and a second optical material layer directly stacked on the first optical material layer, wherein the refractive index of the first optical material layer is 1.48 to 1.70, the refractive index of the second optical material layer is 1.30 to 1.48, and the refractive index of the first optical material layer is greater than the refractive index of the second optical material layer;
[0005] At the interface between the first optical material layer and the second optical material layer, the first optical material layer has a first light-guiding microstructure, and the second optical material layer has a second light-guiding microstructure whose shape is complementary to that of the first light-guiding microstructure.
[0006] In some possible implementations, the first light-guiding microstructure includes a first recess recessed into the first optical material layer, and the second light-guiding microstructure includes a first protrusion protruding from the second optical material layer and filling the first recess.
[0007] In some possible implementations, the second light-guiding microstructure includes a second recess recessed into the second optical material layer, and the first light-guiding microstructure includes a second protrusion protruding from the first optical material layer and filling the second recess.
[0008] In some possible implementations, the second optical material layer has a third light-guiding microstructure on the surface of the second optical material layer opposite to the stacking interface.
[0009] In some possible implementations, the third light-guiding microstructure is formed as a concave prism shape.
[0010] In some possible implementations, the thickness of the first optical material layer is 0.1 to 0.5 mm, and the thickness of the second optical material layer is 0.002 to 0.03 mm.
[0011] In some possible implementations, the first optical material layer is formed of one of the following materials: PMMA, PC, MS, PET, PS.
[0012] In some possible implementations, the refractive index of the first optical material layer is 0.05 to 0.35 greater than that of the second optical material layer.
[0013] Secondly, a light guide film is proposed, comprising a first optical material layer and a second optical material layer directly stacked on the first optical material layer, wherein the refractive index of the first optical material layer is 1.48 to 1.70, the refractive index of the second optical material layer is 1.30 to 1.48, and the refractive index of the first optical material layer is greater than the refractive index of the second optical material layer;
[0014] On the surface opposite to the first optical material layer of the second optical material layer, the second optical material layer has a third light-guiding microstructure.
[0015] In some possible implementations, the third light-guiding microstructure is formed as a concave prism shape.
[0016] Thirdly, a front-light module is proposed, including:
[0017] The light guide film as described in the first or second aspect has a side surface that serves as the light incident surface, and the surface of the first optical material layer opposite to the first optical material layer is configured as the light emitting surface facing the observer.
[0018] A light source is disposed on the light-incident surface side of the light guide film.
[0019] Fourthly, a display device is proposed, comprising:
[0020] As described in the third aspect, the front light module;
[0021] An EPD panel is disposed on the side of the first optical material layer opposite to the second optical material layer.
[0022] The light guide film provided in this application includes a first optical material layer and a second optical material layer directly stacked on the first optical material layer. The refractive index of the first optical material layer is 1.48–1.70, and the refractive index of the second optical material layer is 1.30–1.48, with the refractive index of the first optical material layer being greater than that of the second optical material layer. At the interface between the first and second optical material layers, the first optical material layer has a first light-guiding microstructure, and the second optical material layer has a second light-guiding microstructure with a shape complementary to the first light-guiding microstructure. Through this design, the light guide film has high light energy utilization, thereby helping to improve the brightness and contrast of the front light module and display device equipped with the light guide film. Attached Figure Description
[0023] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings of the embodiments will be briefly described below. Obviously, the drawings described below only relate to some embodiments of this application, and are not intended to limit this application.
[0024] Figure 1 This is a side view schematic diagram of a part of the display module provided in the embodiments of this application.
[0025] Figure 2 yes Figure 1 A side view of the front light module in the diagram.
[0026] Figure 3 This is a schematic diagram of light passing through a traditional light guide film.
[0027] Figure 4 This is a schematic diagram showing the transmission of light through the light guide film provided in the embodiments of this application.
[0028] Figure 5 It is light through Figure 3 The simulation results of the propagation path of a traditional light guide film are shown.
[0029] Figure 6 It is light through Figure 4 The simulation results of the propagation path of the light guide film are shown.
[0030] Figure 7 This is a side view schematic diagram of the front light module provided in the embodiment of this application.
[0031] The light transmission through these two light guide films was simulated respectively.
[0032] Explanation of reference numerals in the attached figures:
[0033] 100 - Display device;
[0034] 10-Front light module;
[0035] 1,1'-Light guide film;
[0036] 2-Light source;
[0037] 3-EPD panel;
[0038] 4-Cover plate;
[0039] 5-First optical material layer, 51-First light-guiding microstructure, 51a-First recess, 51b-Second protrusion;
[0040] 6-Second optical material layer, 61-Second light-guiding microstructure, 61a-First protrusion, 61b-Second recess, 62-Third light-guiding microstructure;
[0041] 7-First OCA layer;
[0042] 8-Second OCA layer;
[0043] S1, S1' - light-incident surface, S2, S2' - light-outceasing surface, S3, S3' - opposing surface, S4 - layered interface. Detailed Implementation
[0044] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the described embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. It is understood that, without conflict, some technical means of the various embodiments described herein can be substituted for or combined with each other.
[0045] In the description of this application, the terms "first," "second," etc., are used only to distinguish the described objects and have no sequential or technical meaning. Therefore, objects specified with "first," "second," etc., may explicitly or implicitly include one or more of those objects, and, for example, the term "first element" itself does not imply the existence of a "second element," nor does the term "second element" itself imply the existence of a "first element." Furthermore, words such as "a" or "one" do not indicate a quantity limitation, but rather indicate the presence of at least one, while "multiple" indicates not less than two.
[0046] In the description of this application, the terms "comprising" or "having" indicate the presence of the said features, numbers, operations, elements, and / or combinations thereof, but do not exclude the presence or addition of one or more other features, numbers, operations, elements, and / or combinations thereof.
[0047] In the description of this application, references to "one embodiment" or "some embodiments" mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized.
[0048] Figure 1 A portion of a display device 100 provided in an embodiment of this application is shown. The display device 100 includes a front light module 10, an EPD panel 3, and a cover plate 4.
[0049] Figure 2 Showing more details Figure 1 The front light module 10 includes a light guide film 1 and a light source 2. The light guide film 1 has a side surface that serves as a light incident surface S1, and a light emitting surface S2 and an opposing surface S3 disposed opposite each other in its thickness direction. The light source 2 is disposed on the light incident surface S1 side of the light guide film 1 to generate light rays incident on the light incident surface S1 of the light guide film 1; therefore, the light source 2 is a side-illuminated light source 2. The light source 2 can be an LED.
[0050] The EPD panel 3 is bonded to the opposing surface S3 side of the light guide film 1 via a first OCA (Optically Clear Adhesive) layer 7. The transparent cover plate 4 is bonded to the light-emitting surface S2 side of the light guide film 1 via a second OCA layer 8. When this display device 100 is applied to an electronic device, the cover plate 4 becomes a component facing the observer and in contact with the environment.
[0051] The light guide film 1 includes a first optical material layer 5 and a second optical material layer 6 directly stacked on the first optical material layer 5. At the stacking interface S4 of the first optical material layer 5 and the second optical material layer 6, the first optical material layer 5 has a first light-guiding microstructure 51, and the second optical material layer 6 has a second light-guiding microstructure 61 with a shape complementary to the first light-guiding microstructure 51. Thus, the first light-guiding microstructure 51 and the second light-guiding microstructure 61 constitute an embedded light-guiding microstructure. The surface of the second optical material layer 6 opposite to the stacking interface S4 is configured as the aforementioned light-emitting surface S2 facing the observer, and the surface of the first optical material layer 5 opposite to the stacking interface S4 is configured as the aforementioned opposing surface S3 facing away from the observer (facing the EPD panel 3). The refractive index of the first optical material layer 5 is 1.48 to 1.70, and the refractive index of the second optical material layer 6 is 1.30 to 1.48, with the refractive index of the first optical material layer 5 being greater than that of the second optical material layer 6.
[0052] Please see again. Figure 1 In practice, light from the light source 2 enters the light guide film 1, particularly the first optical material layer of the light guide film 1, through the light incident surface S1. When the light irradiates the embedded light guide microstructure at the interface S4 between the second optical material layer 6 and the first optical material layer 5, most of the light is reflected to the opposing surface S3 of the optical film and refracted to the EPD panel 3 through the opposing surface S3. Then, it is reflected back to the light guide film 1 through the EPD panel 3 and finally exits from the cover plate 4 and enters the observer's eye, thereby observing the image (e.g., text) information on the EPD panel 3.
[0053] The reflected light from the EPD panel 3 cannot all pass through the light guide film 1. Instead, it will reflect back towards the EPD panel at the relevant interface of the light guide film 1. In order to improve the utilization rate of light energy by the front light module 10 and the display device 100, the amount of light reflected at the light guide film 1 can be reduced, so that as much light as possible is emitted from the light-emitting surface S2 of the light guide film 1.
[0054] In some embodiments, the first light-guiding microstructure 51 includes a first recess 51a recessed into the first optical material layer 5, the second light-guiding microstructure 61 includes a first protrusion 61a protruding from the second optical material layer 6 and filling the first recess 51a, and the second light-guiding microstructure 61 includes a second recess 61b recessed into the second optical material layer 6, and the first light-guiding microstructure 51 includes a second protrusion 51b protruding from the first optical material layer 5 and filling the second recess 61b. In manufacturing, a first light-guiding microstructure 51 can be formed on the upper surface of the first optical material layer 5 by hot stamping or UV stamping. Then, a second optical material layer 6 is formed on the upper surface of the first optical material layer 5 with the first light-guiding microstructure 51. When the second optical material layer 6 is formed on the upper surface of the first optical material layer 5, a portion of the material of the second optical material layer 6 fills the first recess 51a of the first light-guiding microstructure 51 to obtain the first protrusion 61a. A portion of the material of the second optical material layer 6 is pushed open by the second protrusion 51b of the first light-guiding microstructure 51 to obtain the second recess 61b.
[0055] In other embodiments, the first light-guiding microstructure 51 may be formed as a simple recess without a protrusion, and correspondingly the second light-guiding microstructure 61 may be formed as a simple protrusion without a recess, or vice versa.
[0056] Now, please see Figure 3 and Figure 4 , Figure 3 This is a schematic diagram showing light being directed onto a light guide film 1', a traditional single-layer optical film structure, and then exiting through that light guide film 1'. Figure 4 This is a schematic diagram showing light rays striking the optical film, which is composed of a first light-emitting material layer and a second optical material layer, as described in this embodiment of the application, and exiting through the light guide film 1. For simplicity, the drawing of the light reflection portion at the interface has been omitted.
[0057] for Figure 3 The traditional light guide film 1' is formed entirely of an optical material such as PC. If the absorption characteristics of the material itself are ignored, the light transmittance T of the light guide film 1' in air is mainly related to the reflectance R of light at the two interfaces where the PC material and air meet. Moreover, the reflectance R at the two interfaces is mainly determined by the refractive index n1 of the material forming the light guide film 1'. The light transmittance T of the traditional light guide film 1' in air is:
[0058] T = 1 - (R1 + R2) (1)
[0059] Wherein, R1 is the reflectivity of the light incident on the interface S3' (light-emitting surface) of the light guide film 1', and R2 is the reflectivity of the light incident on the interface S2' (opposite surface) of the light guide film 1'. Since the interfaces S3' and S2' are defined by the same material, R1 = R2.
[0060] And approximately:
[0061]
[0062] Where n1 is the refractive index of the material, n0 is the refractive index of air, and n0 = 1.
[0063] When formed Figure 3 When the material of the light guide film 1' is PC, n1 = 1.58, then the interface reflectivity R1 = R2 = 5.05%. Neglecting the absorption of light by the material, its light transmittance T = 89.9%.
[0064] Please see Figure 4 As shown, for a specific example of the light guide film 1 provided in this application embodiment, its first material layer is PC with a refractive index n1 = 1.58, and its second material layer is other transparent optical material with a refractive index n2 = 1.36. According to the above formula (2), the reflectivities at the three interfaces S3, S2, and S4 are R1 = 5.05%, R2 = 0.56%, and R3 = 2.33%, respectively. Therefore, the total reflectivity R = R1 + R2 + R3 = 7.94%. Neglecting material absorption, the transmittance T = 92.06%. Compared with the traditional PC material light guide film 1', the transmittance increases by 2.16%. Therefore, when this light guide film 1 of the present application embodiment is used in a display device 100, especially a reflective front light display device 100, the light energy utilization and brightness of the device can be significantly improved.
[0065] Furthermore, most of the light entering the light guide film 1 from the light incident surface S1 is reflected by the embedded light guide microstructure and then exits from the opposing surface S3 of the light guide film 1. A small portion exits directly from the upper surface (layer interface S4) of the first optical material layer 5 and then from the light emitting surface S2. When the light guide film 1 is used as the front light guide film 1 in the front light module 10, only the light emitted from the opposing surface S3 of the light guide film 1 can illuminate the EPD panel 3; this portion of light energy can be called effective light (Image). The light emitted directly from the light emitting surface S2 not only cannot illuminate the EPD panel 3 but also becomes ineffective light (Noise). Definition: The ratio of effective light emitted from the opposing surface S3 of the light guide film to ineffective light emitted from the light emitting surface S2 is the beam splitting ratio of the light guide film. A lower beam splitting ratio will reduce the contrast ratio (the ratio of effective light emitted to ineffective light emitted by the entire display device 100) and the display effect. To better discuss... Figure 3 Traditional light guide film 1' and Figure 4The light guide film 1 provided in a specific example of the embodiment of this application has a difference in the beam splitting ratio. The light transmission through the two light guide films was simulated respectively, and the light transmission simulation diagrams are as follows: Figure 5 and Figure 6 The simulation results are shown in Table 1 below.
[0066] Table 1:
[0067] Effective light output intensity (relative value) Ineffective light emission intensity (relative value) spectral ratio Traditional light guide film 10667 2910 3.67 The light guide film in this embodiment 10579 2432 4.35
[0068] Table 1 shows that, compared to Figure 3 The conventional light guide film 1' shown is shown. Figure 4 The light guide film 1 in the middle has a higher spectral ratio.
[0069] In this embodiment, because the light guide film 1 itself has a higher beam splitting ratio, when it is configured in the front light module 10 of the reflective display device 100, more reflected light energy will be reflected after the effective light is reflected by the EPD panel. After passing through the light guide film 1, the OCA layer for full lamination, and the full lamination cover plate 4, it will be emitted from the light-emitting side of the display device 100. Simultaneously, because the light guide film 1 in this embodiment has higher light transmittance, the emitted light intensity will be further enhanced, and the display contrast of the display device will also be further improved. To better discuss the configuration... Figure 3 The display device 100 with the traditional light guide film 1' and configured with Figure 4 The difference in effective light emission intensity of the display device 100 with light guide film 1 on the light emission side of cover plate 4 was simulated and calculated for the light transmission through the two display devices 100 respectively, and the results are shown in Table 2.
[0070] Table 2:
[0071] Effective light emission intensity (relative value) of the display device Traditional light guide film 8320 The light guide film in this embodiment 13095
[0072] Table 2 illustrates the differences between the configurations. Figure 3 The front light module of the traditional light guide film 1' is configured with Figure 4 The brightness gain of the front light module 10 of the central light guide film 1 reaches about 157%.
[0073] The preceding text, based on a principle introduction and simulation calculations, discussed in detail the case where the refractive indices of the first optical material layer 5 and the second optical material layer 6 are 1.48 and 1.36, respectively. It was found that in this case, the light guide film 1, the front light module 10 on which the light guide film 1 is disposed, and the further display device 100 exhibit higher brightness gain and contrast. However, the inventors have discovered that when the refractive index of the first optical material layer 5 of the light guide film 1 is 1.48–1.70, the refractive index of the second optical material layer 6 is 1.30–1.48, and the refractive index of the first optical material layer 5 is greater than that of the second optical material layer 6, the light guide film 1, the front light module 10 on which the light guide film 1 is disposed, and the further display device 100 also exhibit excellent optical performance. Furthermore, when the refractive index of the first optical material layer 5 is 0.05 to 0.35 greater than that of the second optical material layer 6, the light transmittance of the light guide film 1 in this embodiment can be increased by 0.6% to 3% in air compared to the conventional light guide film 1'. For example, regarding the light transmittance, it can be increased from 89.9% of the conventional PC light guide film 1' to 92%, or from 92% of the conventional PMMA light guide film 1' to 93.7%, or from 88.2% of the conventional PET light guide film 1' to 90.9%. This improves the light energy utilization of the entire front light module 10, thereby improving the brightness and contrast of the front light module 10, especially when used in a color electronic paper display device 100.
[0074] The first optical material layer 5, with a refractive index of 1.48 to 1.70, can be formed from any of the following materials: PMMA, PC, MS, PET, PS.
[0075] In another embodiment, such as Figure 7 As shown, on the surface of the second optical material layer 6 opposite to the lamination interface S4, i.e., the light-emitting surface S2 of the light guide film 1, the second optical material layer 6 has a third light-guiding microstructure 62. In this case, the third light-guiding microstructure 62 can further reflect the ineffective light that is to be emitted from the light-emitting surface S2 of the light guide film 1 back to the light guide film 1, reducing the emission of ineffective light and increasing the energy of the effectively emitted light, thereby further improving the contrast. Preferably, the third light-guiding microstructure 62 can be formed into a concave prism shape, such as a triangular prism shape. It should be understood that even... Figure 7 The light guide film 1 in the figure omits the embedded light guide microstructures 51 and 61 at the layer interface S4, but since the light-emitting surface S3 has a third light guide microstructure 62, and the refractive index of the first optical material layer 5 is 1.48 to 1.70, and the refractive index of the second optical material layer 6 is 1.30 to 1.48, which is smaller than the refractive index of the first optical material layer 5, it still has a relatively high light energy utilization rate.
Claims
1. A light guide film, characterized in that, It includes a first optical material layer and a second optical material layer directly stacked on the first optical material layer. The refractive index of the first optical material layer is 1.48 to 1.70, and the refractive index of the second optical material layer is 1.30 to 1.
48. The refractive index of the first optical material layer is greater than that of the second optical material layer. At the interface between the first optical material layer and the second optical material layer, the first optical material layer has a first light-guiding microstructure, and the second optical material layer has a second light-guiding microstructure whose shape is complementary to that of the first light-guiding microstructure.
2. The light guide film according to claim 1, characterized in that, The first light-guiding microstructure includes a first recess recessed into the first optical material layer, and the second light-guiding microstructure includes a first protrusion protruding from the second optical material layer and filling the first recess.
3. The light guide film according to claim 1 or 2, characterized in that, The second light-guiding microstructure includes a second recess recessed into the second optical material layer, and the first light-guiding microstructure includes a second protrusion protruding from the first optical material layer and filling the second recess.
4. The light guide film according to claim 1, characterized in that, On the surface of the second optical material layer opposite to the stacked interface, the second optical material layer has a third light-guiding microstructure.
5. The light guide film according to claim 4, characterized in that, The third light-guiding microstructure is formed into a concave prism shape.
6. The light guide film according to claim 1, characterized in that, The thickness of the first optical material layer is 0.1 to 0.5 mm, and the thickness of the second optical material layer is 0.002 to 0.03 mm.
7. The light guide film according to claim 1, characterized in that, The first optical material layer is formed of one of the following materials: PMMA, PC, MS, PET, PS.
8. The light guide film according to any one of claims 1 to 2, 4 to 7, characterized in that, The refractive index of the first optical material layer is 0.05 to 0.35 greater than that of the second optical material layer.
9. A light guide film, characterized in that, It includes a first optical material layer and a second optical material layer directly stacked on the first optical material layer. The refractive index of the first optical material layer is 1.48 to 1.70, and the refractive index of the second optical material layer is 1.30 to 1.
48. The refractive index of the first optical material layer is greater than that of the second optical material layer. On the surface opposite to the first optical material layer of the second optical material layer, the second optical material layer has a third light-guiding microstructure.
10. The light guide film according to claim 9, characterized in that, The third light-guiding microstructure is formed into a concave prism shape.
11. A front light module, characterized in that, include: The light guide film according to any one of claims 1 to 10 has a side surface as a light incident surface, and the surface of the second optical material layer opposite to the first optical material layer is configured as a light emitting surface facing the observer; A light source is disposed on the light-incident surface side of the light guide film.
12. A display device, characterized in that, include: The front light module as described in claim 11; An EPD panel is disposed on the side of the first optical material layer opposite to the second optical material layer.