Light guide film, front light module and reflective display

Abstract

A light guide film includes: a substrate layer having a light-incident surface; an upper ultraviolet adhesive layer disposed above the substrate layer; a lower ultraviolet adhesive layer disposed below the substrate layer; two optical adhesive layers disposed above the upper ultraviolet adhesive layer and below the lower ultraviolet adhesive layer, respectively; and a light-incident microstructure unit having a first microstructure region disposed on the light-incident surface of the substrate layer. The present invention also provides a front light module and a reflective display incorporating the light guide film.

Description

Technical Field

[0001] The present invention is mainly about a light guide film, and more particularly about a light guide film that can reduce the brightness halo of incident light, a front light module having the light guide film, and a reflective display using the front light module. Prior Technology

[0002] To achieve a thin design, the front light module of a Xizhi e-reader uses a relatively thin light guide plate, but the thickness of the LED is greater than the thickness of the light guide plate. Therefore, to improve light coupling efficiency and solve problems such as bright spots, the light guide plate of the Xizhi e-reader's front light module usually needs to have a larger light-incident section to increase the light coupling effect, and light-incident microstructures need to be set near the light source to deal with the LED hotspot problem.

[0003] However, when light enters the light guide plate through the light-incident microstructure, the varying thickness of the structure and the microstructure itself easily causes refraction and reflection, increasing the probability of total internal reflection failure. This results in a bright halo effect on the light-emitting surface, leading to an undesirable appearance. Furthermore, improving the light-incident quality would necessitate increasing the shielding area, resulting in more ineffective areas in the front light module and failing to meet current narrow bezel requirements.

[0004] In view of this, it is necessary to provide a light guide film to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a light guide film that can have light incident microstructures set only on the light incident surface of the substrate layer, thereby reducing the probability of causing total internal reflection.

[0006] A further objective of the present invention is to provide a front light module having the aforementioned light guide film, which can reduce the generation of halos and reduce the undesirable appearance of the light-emitting surface.

[0007] Another object of the present invention is to provide a reflective display having the above-mentioned front light module, which can meet the requirements of narrow bezel module design.

[0008] To achieve the above objectives, the present invention provides a light guide film comprising: a substrate layer having a light-incident surface; an upper ultraviolet adhesive layer disposed above the substrate layer; a lower ultraviolet adhesive layer disposed below the substrate layer; two optical adhesive layers disposed above the upper ultraviolet adhesive layer and below the lower ultraviolet adhesive layer, respectively; and a light-incident microstructure unit having a first microstructure region disposed on the light-incident surface of the substrate layer, wherein the material of the first microstructure region is the same as the material of the substrate layer.

[0009] In some embodiments, the light-incident microstructure unit further has a second microstructure region disposed on the end face of the upper ultraviolet adhesive layer and the lower ultraviolet adhesive layer, and is closer to the light-incident surface of the substrate layer.

[0010] In some embodiments, the incident light microstructure unit is composed of a plurality of microstructures, each of the microstructures in the first microstructure region has a first depth, each of the microstructures in the second microstructure region has a second depth, and the first depth is greater than the second depth.

[0011] In some embodiments, the refractive index of the substrate layer is greater than the refractive index of the lower UV adhesive layer, and the difference is D1.

[0012] In some embodiments, the absolute value of the difference between the refractive index of the lower ultraviolet adhesive layer and the refractive index of the adjacent optical adhesive layer is D2, where 0 ≤ D2. <D1。

[0013] In some embodiments, the refractive index of the substrate layer is less than or equal to the refractive index of the upper UV adhesive layer.

[0014] In some embodiments, the refractive index of the lower ultraviolet adhesive layer is less than the refractive index of the upper ultraviolet adhesive layer.

[0015] In some embodiments, the lower UV adhesive layer has an inclined portion and a flat portion, the inclined portion being closer to the light-incident surface of the substrate layer, and the flat portion extending from the inclined portion toward the light-incident surface away from the substrate layer.

[0016] The present invention also provides a front light module, comprising: the aforementioned light guide film, wherein the upper ultraviolet adhesive layer of the light guide film has a plurality of reflective microstructures; and a light-emitting unit disposed on a light-incident side of the light guide film.

[0017] The present invention also provides a reflective display, comprising: the aforementioned front light module; an optical component disposed above the light guide film; and a display panel disposed below the light guide film.

[0018] In some embodiments, the optical component is a touch sensor.

[0019] The light guide film, front light module, and reflective display of the present invention have the following characteristics: Since the light-incident microstructure unit is designed on the light-incident surface of the substrate layer, the upper ultraviolet adhesive layer and the lower ultraviolet adhesive layer do not necessarily have the light-incident microstructure unit designed. This local light-incident microstructure design can reduce the probability of destroying total internal reflection light emission on the light-incident surface closer to the substrate layer, and can locally adjust and change the light trace in the light-incident area, thus avoiding the phenomenon of bright halo. At the same time, the light-incident microstructure unit can still deal with the problem of LED hot spots and meet the requirements of narrow bezel module design. Simple Explanation of the Diagram

[0020] [Figure 1] is a side sectional view of the light guide film according to the first embodiment of the present invention; [Figure 2] is a top view of the substrate layer of the light guide film according to the first embodiment of the present invention; [Figure 3] is a side sectional view of the light guide film according to the second embodiment of the present invention; [Figure 4] is a side sectional view of the optical module prior to the first embodiment of the present invention; and [Figure 5] is a schematic diagram of a reflective display according to the first embodiment of the present invention. Implementation

[0021] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The accompanying drawings are mainly simplified schematic diagrams, which are only used to illustrate the basic structure of the present invention. Therefore, only the elements related to the present invention are marked in these drawings, and the elements shown are not drawn according to the number, shape, size ratio, etc. of the implementation. The actual specifications and dimensions of the implementation are a selective design, and the layout of the elements may be more complex.

[0022] The following descriptions of the embodiments are with reference to the accompanying drawings, illustrating specific embodiments in which the invention may be practiced. Directional terms used in this invention, such as "up," "down," "front," and "back," are merely directional references to the accompanying drawings. Therefore, the directional terms used are for illustration and understanding of this application, and not for limiting this application. Furthermore, in this specification, unless explicitly stated otherwise, the word "comprising" will be understood to mean including the stated elements, but does not exclude any other elements.

[0023] Please refer to Figure 1, which is a side sectional view of the first embodiment of the light guide film of the present invention. It includes: a substrate layer 1, an upper ultraviolet adhesive layer 2, a lower ultraviolet adhesive layer 3, two optical adhesive layers 4, and a light-incident microstructure unit 5. The substrate layer 1 has a light-incident surface 11. The upper ultraviolet adhesive layer 2 is disposed above the substrate layer 1, and the lower ultraviolet adhesive layer 3 is disposed below the substrate layer 1. The two optical adhesive layers 4 are respectively disposed above the upper ultraviolet adhesive layer 2 and below the lower ultraviolet adhesive layer 3. Please also refer to Figure 2. The light-incident microstructure unit 5 has a first microstructure region 51 disposed on the light-incident surface 11 of the substrate layer 1. The material of the first microstructure region 51 is the same as the material of the substrate layer 1.

[0024] Please refer to Figure 5. Here, the light-incident microstructure unit 5 is designed on the light-incident surface 11 of the substrate layer 1. The upper UV adhesive layer 2 and the lower UV adhesive layer 3 do not necessarily have the light-incident microstructure unit 5 designed. With this local light-incident microstructure design, the light does not pass through the light-incident microstructure unit 5 before entering the lower UV adhesive layer 3, but directly enters the lower UV adhesive layer 3. This makes it less likely to cause light refraction and reflection. The probability of total internal reflection damage can be reduced by placing the light-incident surface 11 closer to the substrate layer 1, thereby reducing the generation of halos and reducing the appearance of the light-emitting surface. At the same time, the light-incident microstructure unit 5 can still deal with the problem of LED hot spots and meet the requirements of narrow bezel module design.

[0025] This is mainly because the upper UV adhesive layer 2 and the lower UV adhesive layer 3 are UV-cured, while the substrate layer 1 is thermo-cured. As a result, the upper UV adhesive layer 2 and the lower UV adhesive layer 3 are not easy to cure and form after heating and mold molding, and are more likely to return to their original unshaped state. It is even more difficult to imprint the light-incident microstructure unit 5. However, the substrate layer 1 will cure and form after heating and mold molding, thus retaining the shape of the light-incident microstructure unit 5.

[0026] More specifically, the refractive index of the lower UV adhesive layer 3 is less than that of the upper UV adhesive layer 2, the refractive index of the substrate layer 1 is greater than that of the lower UV adhesive layer 3, and the refractive index of the substrate layer 1 is less than or equal to that of the upper UV adhesive layer 2. Therefore, the light reflected by the lower UV adhesive layer 3 and entering the substrate layer 1 and the upper UV adhesive layer 2 gradually enters the optically denser medium from the optically less dense medium, reducing the probability of returning to the optically less dense medium, i.e., the lower UV adhesive layer 3, thereby improving the brightness.

[0027] In addition, since the lower UV adhesive layer 3 is typically rolled onto the substrate layer 1 using a roller, any structures or defects on the roller are transferred to the substrate layer 1. Poorly transferred defects can negatively impact the light-emitting surface. Therefore, in this embodiment, the refractive index of the substrate layer 1 is designed to be greater than the refractive index of the lower UV adhesive layer 3, with a difference of D1. Preferably, the absolute value of the difference between the refractive index of the lower UV adhesive layer 3 and the refractive index of the adjacent optical adhesive layer 4 can also be D2, where 0 ≤ D2. <D1。

[0028] Therefore, the refractive index of the lower ultraviolet adhesive layer 3 is closer to that of the adjacent optical adhesive layer 4, so that the surface defects of the lower ultraviolet adhesive layer 3 are almost filled by the optical adhesive layer 4, which is made of a material with a similar or the same refractive index. This allows light to travel in the same medium without being affected by defects. As a result, light that is deflected towards the lower ultraviolet adhesive layer 3 can more easily penetrate the adjacent lower ultraviolet adhesive layer 3 and the optical adhesive layer 4 and reach the display panel of the reflective display of the present invention, which is disposed under the light guide film, and is less likely to be reflected to the substrate layer 1 and emitted from the upper ultraviolet adhesive layer 2. This has the effect of reducing the probability of light emission and avoiding the occurrence of halos.

[0029] Specifically, the lower ultraviolet adhesive layer 3 has an inclined portion 31 and a flat portion 32, wherein the inclined portion 31 is closer to the light-incident surface 11 of the substrate layer 1. The flat portion 32 extends from the inclined portion 31 away from the light-incident surface 11 of the substrate layer 1. Therefore, the thickness of the inclined portion 31 is greater than that of the flat portion 32, thereby increasing the light flux entering the lower ultraviolet adhesive layer 3 and improving the light coupling efficiency of the lower ultraviolet adhesive layer 3.

[0030] However, the tilted portion 31 increases the probability of total internal reflection being disrupted due to light refraction and reflection, resulting in a bright halo. Therefore, in this embodiment, the light-incident microstructure unit 5 is only formed on the substrate layer 1 and does not extend to the upper ultraviolet adhesive layer 2 and the lower ultraviolet adhesive layer 3. This allows for local adjustment and alteration of the light trajectory in the light-incident area, while also reducing the probability of total internal reflection being disrupted by the tilted portion 31. Light will pass through the tilted portion 31 and is less likely to be reflected back to the substrate layer 1, instead exiting from the upper ultraviolet adhesive layer 2, thus avoiding the bright halo phenomenon.

[0031] Please refer to Figure 3, which is a side sectional view of the second embodiment of the light guide film of the present invention. The difference between this second embodiment and the first embodiment is that the upper ultraviolet adhesive layer 2 and the lower ultraviolet adhesive layer 3 are made of materials different from those in the first embodiment, and their thermosetting ability is less than that of the substrate layer 1. The light-incident microstructure unit 5 also has a second microstructure region 52, disposed on the end faces of the upper ultraviolet adhesive layer 2 and the lower ultraviolet adhesive layer 3, and adjacent to the light-incident surface 11 of the substrate layer 1. Specifically, the first microstructure region 51 and the second microstructure region 52 are formed by using a mold to hot-press transfer the microstructure onto the light-incident surface 11 of the substrate layer 1, and the end faces of the upper ultraviolet adhesive layer 2 and the lower ultraviolet adhesive layer 3, and adjacent to the light-incident surface 11 of the substrate layer 1.

[0032] As mentioned above, to avoid the light-incident microstructure unit 5 being fully distributed on the light-incident surface 11, which could easily cause total internal reflection to be disrupted and light to be emitted, resulting in a bright halo phenomenon, as mentioned in the prior art, in this embodiment, the light-incident microstructure unit 5 is designed to be composed of a plurality of microstructures. Each microstructure in the first microstructure region 51 has a first depth, and each microstructure in the second microstructure region 52 has a second depth. This is because the upper ultraviolet adhesive layer 2 and the lower ultraviolet adhesive layer 3 are UV-cured, while the substrate layer 1 is thermosetting. When heated, the mold can more easily form the microstructure on the substrate layer 1 by hot pressing, making the microstructure transferred to the substrate layer 1 by hot pressing relatively deep. As for the upper UV adhesive layer 2 and the lower UV adhesive layer 3, because their heat curing ability is less than that of the substrate layer 1, the microstructure transferred to the upper UV adhesive layer 2 and the lower UV adhesive layer 3 by hot pressing is relatively shallow. Therefore, the first depth is greater than the second depth, so the effect of adjusting and changing the light trail in the light-incident area on the substrate layer 1 is greater than the effect of adjusting and changing the light trail in the light-incident area on the upper UV adhesive layer 2 and the lower UV adhesive layer 3. In this way, the probability of light being reflected by the inclined part 31 to the substrate layer 1 and escaping from the upper UV adhesive layer 2 can be reduced, and the phenomenon of bright halo can also be avoided.

[0033] Referring to Figure 4, the front light module of the present invention includes: the aforementioned light guide film, wherein the ultraviolet adhesive layer 2 has a plurality of reflective microstructures; and a light-emitting unit 6, which is disposed on a light-incident side of the light guide film.

[0034] Referring to Figure 5, the reflective display of the present invention includes: the aforementioned front light module, an optical component 7 disposed above the light guide film, and a display panel 8 disposed below the light guide film. The reflective display is the e-book mentioned in the background art, and the optical component 7 is a touch sensor.

[0035] As described above, for the light guide film, front light module, and reflective display of the present invention, since the upper ultraviolet glue layer and the lower ultraviolet glue layer are cured by ultraviolet light, while the substrate layer is cured by heat, it is more difficult to imprint the light incident microstructure unit on the upper ultraviolet glue layer and the lower ultraviolet glue layer compared to the substrate layer by heat curing. Therefore, the upper ultraviolet glue layer and the lower ultraviolet glue layer do not necessarily need to be designed with the light incident microstructure unit. This design of the local light incident microstructure can reduce the probability of destroying total reflection light emission on the light incident surface closer to the substrate layer. Thereby, the probability of the light trace in the light incident area can be locally adjusted and changed, achieving the effect of avoiding the occurrence of bright halo phenomena. Furthermore, by making the refractive index of the substrate layer greater than that of the lower ultraviolet glue layer, with the difference being D1, and making the absolute value of the difference between the refractive index of the lower ultraviolet glue layer and the refractive index of the optically adjacent glue layer be D2, where 0 ≤ D2 < D1, the light rays deflected towards the lower ultraviolet glue layer can more easily penetrate the optically adjacent glue layer closer to the lower ultraviolet glue layer and reach the display panel, also achieving the effect of reducing the light emission probability. At the same time, the light incident microstructure unit can still handle the problem of LED hot spots, meeting the requirements of the narrow border module design. Therefore, it can be applied to the front light module used in e-books to meet the forward-looking requirements of future color electronic paper and module thinning.

[0036] The above-disclosed embodiments are only illustrative of the principles, features, and effects of the present invention, and are not intended to limit the scope of implementation of the present invention. Any person skilled in this art can modify and change the above embodiments without departing from the spirit and scope of the present invention. Any equivalent changes and modifications made by applying the content disclosed in the present invention should still be covered by the following patent application scope.

[0037] ﹝The present invention﹞ 1: Substrate layer 11: Light incident surface 2: Upper ultraviolet glue layer ​​​​​​​​​​​​​​​​​​​

Claims

1. A light guide film, comprising: a substrate layer having a light-incident surface; an upper ultraviolet adhesive layer disposed above the substrate layer; a lower ultraviolet adhesive layer disposed below the substrate layer; two optical adhesive layers disposed above the upper ultraviolet adhesive layer and below the lower ultraviolet adhesive layer, respectively; and a light-incident microstructure unit having a first microstructure region disposed on the light-incident surface of the substrate layer, wherein the material of the first microstructure region is the same as the material of the substrate layer; wherein... The lower UV adhesive layer has an inclined portion and a flat portion. The inclined portion is closer to the light-incident surface of the substrate layer, and the flat portion extends from the inclined portion toward the light-incident surface away from the substrate layer.

2. The light guide film as described in claim 1, wherein, The light-incident microstructure unit also has a second microstructure region disposed on the end face of the upper ultraviolet adhesive layer and the lower ultraviolet adhesive layer, and is closer to the light-incident surface of the substrate layer.

3. The light guide film as described in claim 2, wherein, The incident light microstructure unit is composed of a plurality of microstructures. Each of the microstructures in the first microstructure region has a first depth, and each of the microstructures in the second microstructure region has a second depth. The first depth is greater than the second depth.

4. The light guide film as described in claim 1, wherein, The refractive index of the substrate layer is greater than that of the underlying UV adhesive layer, and the difference is D1.

5. The light guide film as described in claim 4, wherein, The absolute value of the difference between the refractive index of the ultraviolet adhesive layer and the refractive index of the adjacent optical adhesive layer is D2, where 0 ≦ D2 < D1.

6. The light guide film as described in claim 1, wherein, The refractive index of the substrate layer is less than or equal to the refractive index of the UV adhesive layer.

7. The light guide film as described in claim 1, wherein, The refractive index of the lower UV adhesive layer is less than that of the upper UV adhesive layer.

8. A front light module comprising: a light guide film as described in any one of claims 1 to 7, the upper ultraviolet adhesive layer of the light guide film having a plurality of reflective microstructures; and a light-emitting unit disposed on a light-incident side of the light guide film.

9. A reflective display comprising: a front light module as described in claim 8; an optical component disposed above the light guide film; and a display panel disposed below the light guide film.

10. The reflective display as described in claim 9, wherein, The optical component is a touch sensor.

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