Light guide film, front light module and reflective display

Abstract

The invention relates to a light guide film, a front light module and a reflective display. The light guide film comprises: a substrate layer having a light incident surface; the upper ultraviolet adhesive layer is arranged above the base material layer; the lower ultraviolet adhesive layer is arranged below the base material layer; the two optical adhesive layers are respectively arranged above the upper ultraviolet adhesive layer and below the lower ultraviolet adhesive layer; and the incident light microstructure unit is provided with a first microstructure area, and the first microstructure area is arranged on the incident light surface of the base material layer.

Description

[0001] This application claims the benefit of Chinese patent application No. 202311321405.0 filed on October 12, 2023, with invention name “Light-guiding film, front light module and reflective display”, the entire contents of which are hereby incorporated by reference into this application. Technical Field

[0002] The invention mainly relates to a light-guiding film, in particular to a light-guiding film capable of reducing incident light halo, a front light module with the light-guiding film, and a reflective display using the front light module. Background Art

[0003] In order to meet the requirements of thin design, the front light module of conventional e-books adopts a relatively thin light guide plate, but the thickness of the LED is greater than the thickness of the light guide plate. Therefore, in order to improve its light coupling efficiency and solve the problem of bright spots, the front light module of conventional e-books usually needs to make a thicker light entrance part to increase the light coupling effect, and set a light entrance microstructure near the light source to solve the problem of LED hotspots.

[0004] However, when light enters the light guide plate through the light-entering microstructure, the light is easily refracted and reflected due to the existence of the structure with varying thickness and the light-entering microstructure, which increases the probability of destroying total reflection. Therefore, the light easily produces a bright halo, which in turn causes the light-emitting surface to have a poor appearance. Furthermore, if the problem of poor light entry is to be improved, the shielding area must be increased, resulting in more ineffective areas of the front light module, which cannot meet the current narrow frame requirements.

[0005] In view of this, it is necessary to provide a light guide film to solve the above problems. Summary of the invention

[0006] The object of the present invention is to provide a light-guiding film, which can be provided with a light-incident microstructure only on the light-incident surface of a substrate layer, thereby reducing the probability of causing damage to total reflection.

[0007] Another object of the present invention is to provide a front light module having the above-mentioned light-guiding film, which can reduce the generation of bright halos and has the effect of reducing the poor appearance of the light-emitting surface.

[0008] 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 frame module design.

[0009] In order to achieve the above-mentioned purpose, the present invention provides a light-guiding film, comprising: a substrate layer having a light incident surface; an upper UV adhesive layer disposed above the substrate layer; a lower UV adhesive layer disposed below the substrate layer; two optical adhesive layers disposed above the upper UV adhesive layer and below the lower UV adhesive layer, respectively; and a light incident microstructure unit having a first microstructure region disposed on the light incident surface of the substrate layer.

[0010] In some embodiments, the light incident microstructure unit further has a second microstructure region, and the second microstructure region is disposed on the end surfaces of the upper UV adhesive layer and the lower UV adhesive layer, respectively, and is closer to the light incident surface of the substrate layer.

[0011] In some embodiments, the light incident microstructure unit is composed of a plurality of microstructures, each microstructure in the first microstructure region has a first depth, each microstructure in the second microstructure region has a second depth, and the first depth is greater than the second depth.

[0012] 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.

[0013] In some embodiments, the absolute value of the difference between the refractive index of the lower UV adhesive layer and the refractive index of the adjacent optical adhesive layer is D2, 0≦D2 <D1。

[0014] 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.

[0015] In some embodiments, the refractive index of the lower UV adhesive layer is less than the refractive index of the upper UV adhesive layer.

[0016] In some embodiments, 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 a direction away from the light incident surface of the substrate layer.

[0017] The present invention further provides a front light module, comprising: the aforementioned light guide film, the upper UV adhesive layer of the light guide film having a plurality of reflective microstructures; and a light emitting unit, which is arranged on the light incident side of the light guide film.

[0018] The present invention further 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.

[0019] In some embodiments, the optical component is a touch sensor.

[0020] The light-guiding film, front light module and reflective display of the present invention have the following characteristics: since a light-entering microstructure unit is designed on the light-entering surface of the substrate layer, the upper UV adhesive layer and the lower UV adhesive layer are not necessarily designed with a light-entering microstructure unit. The design of this local light-entering microstructure can reduce the probability of damaging the total reflected light at the light-entering surface closer to the substrate layer, and can locally adjust the probability of changing the light track in the light-entering area, thereby achieving the effect of avoiding the occurrence of the bright halo phenomenon, but at the same time the light-entering microstructure unit can still deal with the problem of LED hot spots, meeting the requirements of narrow-frame module design. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to make the above and other objects, features, advantages and embodiments of the present invention more understandable, the accompanying drawings are now described as follows:

[0022] Figure 1 is a side cross-sectional view of a light guide film according to a first embodiment of the present invention;

[0023] Figure 2 A top view of a substrate layer of a light guide film according to a first embodiment of the present invention;

[0024] Figure 3 is a side cross-sectional view of a light guide film according to a second embodiment of the present invention;

[0025] Figure 4 is a side cross-sectional view of the front light module of the first embodiment of the present invention; and

[0026] Figure 5 FIG. 4 is a schematic diagram of a reflective display according to a first embodiment of the present invention. DETAILED DESCRIPTION

[0027] The embodiments of the present invention are described in detail as follows with reference to the accompanying drawings. The accompanying drawings are mainly simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner. Therefore, only elements related to the present invention are marked in the accompanying drawings, and the elements shown are not drawn in terms of the number, shape, size ratio, etc. during implementation. The specifications and dimensions during actual implementation are actually a selective design, and the element layout may be more complicated.

[0028] The following descriptions of the embodiments refer to the accompanying drawings to illustrate specific embodiments in which the present invention can be implemented. The directional terms mentioned in the present invention, such as "upper", "lower", "front", "back", etc., refer only to the directions of the accompanying drawings. Therefore, the directional terms used are used to illustrate and understand the present application, rather than to limit the present application. In addition, in the specification, unless explicitly described to the contrary, the word "comprising" will be understood to mean including the elements described, but not excluding any other elements.

[0029] Please refer to Figure 1, is a side cross-sectional view of a first embodiment of the light guide film of the present invention, comprising: a substrate layer 1, an upper UV adhesive layer 2, a lower UV adhesive layer 3, two optical adhesive layers 4 and a light incident microstructure unit 5, wherein the substrate layer 1 has a light incident surface 11, the upper UV adhesive layer 2 is arranged above the substrate layer 1, the lower UV adhesive layer 3 is arranged below the substrate layer 1, and the two optical adhesive layers 4 are respectively arranged above the upper UV adhesive layer 2 and below the lower UV adhesive layer 3, please refer to Figure 2 The light incident microstructure unit 5 has a first microstructure region 51 , which is disposed on the light incident surface 11 of the substrate layer 1 .

[0030] Please refer to Figure 5 A light incident microstructure unit 5 is designed on the light incident surface 11 of the substrate layer 1, and the upper UV adhesive layer 2 and the lower UV adhesive layer 3 are not necessarily designed with a light incident microstructure unit 5. With the design of this local light incident microstructure, the light will not pass through the light incident microstructure unit 5 before entering the lower UV adhesive layer 3, but will directly enter the lower UV adhesive layer 3, making it less likely to produce light refraction and reflection. Therefore, the light incident surface 11 closer to the substrate layer 1 can reduce the probability of causing damage to total reflection, thereby reducing the generation of bright halos, which has the effect of reducing the poor appearance of the luminous surface. At the same time, the light incident microstructure unit 5 can still deal with the problem of LED hot spots, thereby meeting the requirements of narrow frame module design.

[0031] 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 a thermoplastic material. Therefore, compared with the substrate layer 1, the upper UV adhesive layer 2 and the lower UV adhesive layer 3 are not easy to be cured and formed after being heated and the mold is molded and warmed up, and are still easy to return to the original unmolded state, making it more difficult to emboss the light-entering microstructure unit 5. However, after the substrate layer 1 is heated and the mold is molded and warmed up, it will be cured and formed to retain the shape of the light-entering microstructure unit 5.

[0032] In more detail, the refractive index of the lower UV adhesive layer 3 is smaller than that of the upper UV adhesive layer 2, the refractive index of the substrate layer 1 is larger than that of the lower UV adhesive layer 3, and the refractive index of the substrate layer 1 is smaller than or equal to that of the upper UV adhesive layer 2. Therefore, the light reflected from the lower UV adhesive layer 3 to the substrate layer 1 and the upper UV adhesive layer 2 gradually enters the optically dense medium from the optically sparse medium, thereby reducing the probability of returning to the optically sparse medium, that is, the lower UV adhesive layer 3, thereby improving the brightness of the light.

[0033] In addition, since the lower UV adhesive layer 3 is generally rolled onto the substrate layer 1 using a roller, the structure and defects on the roller will be transferred to the substrate layer 1, and the defects of poor transfer will have an adverse effect on 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, and the difference is 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 is D2, 0≦D2 <D1。

[0034] Thus, the refractive index of the lower UV adhesive layer 3 is closer to that of the adjacent optical adhesive layer 4, so that the surface defects of the lower UV adhesive layer 3 are almost filled by the optical adhesive layer 4 of a material having a similar or same refractive index, so that the light travels almost in the same layer of medium without being affected by the defects. In this way, the light deflected toward the lower UV adhesive layer 3 is more likely to penetrate the lower UV adhesive layer 3 and the optical adhesive layer 4 and reach the display panel of the reflective display of the present invention disposed below the light guide film, and is not easily reflected to the substrate layer 1 and emitted from the upper UV adhesive layer 2, thereby having the effect of reducing the probability of light emission and avoiding the occurrence of the bright halo phenomenon.

[0035] Specifically, the lower UV 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, and the flat portion 32 extends from the inclined portion 31 to a direction away from the light incident surface 11 of the substrate layer 1. Thus, the thickness of the inclined portion 31 is greater than that of the flat portion 32, so as to increase the luminous flux of light entering the lower UV adhesive layer 3, thereby improving the light coupling efficiency of the lower UV adhesive layer 3.

[0036] However, the inclined portion 31 easily increases the probability of light trace refraction and reflection, thereby destroying total reflection and causing bright halo. Therefore, in this embodiment, the light-entering microstructure unit 5 is only formed on the substrate layer 1 and does not extend to the upper UV adhesive layer 2 and the lower UV adhesive layer 3, so that the probability of changing the light trace in the light-entering area can be locally adjusted, and at the same time, the probability of the inclined portion 31 destroying total reflection can be reduced. The light will penetrate the inclined portion 31 and is not easily reflected to the substrate layer 1, and the light will be emitted from the upper UV adhesive layer 2, thereby avoiding the bright halo phenomenon.

[0037] Please refer to Figure 3, is a side cross-sectional view of the second embodiment of the light-guiding film of the present invention. Compared with the first embodiment, the difference is that the upper UV adhesive layer 2 and the lower UV adhesive layer 3 are made of materials different from those of the first embodiment, and their thermal curing ability is smaller than that of the substrate layer 1. The light-entering microstructure unit 5 also has a second microstructure region 52, which is arranged on the end faces of the upper UV adhesive layer 2 and the lower UV adhesive layer 3, respectively, and is closer to the light-entering 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 heat-press transfer the microstructure to the light-entering surface 11 of the substrate layer 1 and the end faces of the upper UV adhesive layer 2 and the lower UV adhesive layer 3, respectively, and are closer to the light-entering surface 11 of the substrate layer 1.

[0038] In view of the above, in order to avoid the light incident microstructure units 5 being fully arranged on the light incident surface 11, which would easily cause the destruction of total reflection and light output as mentioned in the previous technology, and then produce a bright halo phenomenon, in the present embodiment, the light incident microstructure unit 5 is designed to be composed of a plurality of microstructures, each microstructure of the first microstructure area 51 has a first depth, and each of the microstructures of the second microstructure area 52 has a second depth. Since the upper UV adhesive layer 2 and the lower UV adhesive layer 3 are UV-cured, and the substrate layer 1 is a thermoplastic material, when heated, the mold is easier to form the microstructure on the substrate layer 1 by hot pressing, so that the microstructure transferred to the substrate layer 1 by hot pressing is relatively deep. As for the upper UV adhesive layer 2 and the lower UV adhesive layer 3, the microstructure transferred to the upper UV adhesive layer 2 and the lower UV adhesive layer 3 by hot pressing is relatively shallow because their thermal curing capabilities are smaller than those of the substrate layer 1. Therefore, the first depth is greater than the second depth, so that the effect of the substrate layer 1 adjusting and changing the light trace of the light incident area is greater than the effect of the upper UV adhesive layer 2 and the lower UV adhesive layer 3 adjusting and changing the light trace of the light incident area. In this way, the probability of light being reflected by the inclined portion 31 to the substrate layer 1 and emitting from the upper UV adhesive layer 2 can be reduced, thereby avoiding the occurrence of a bright halo phenomenon.

[0039] Please refer to Figure 4 The front light module of the present invention comprises: the aforementioned light guide film, on which the UV adhesive layer 2 has a plurality of reflective microstructures; and a light emitting unit 6, which is disposed on the light incident side of the light guide film.

[0040] Please refer to Figure 5 The reflective display of the present invention comprises: the front light module mentioned above; 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 electronic book mentioned in the background technology, and the optical component 7 is a touch sensor.

[0041] As described above, in 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 emboss the light incident microstructure units on the upper ultraviolet glue layer and the lower ultraviolet glue layer compared to the substrate layer using heat curing. Therefore, the upper ultraviolet glue layer and the lower ultraviolet glue layer do not necessarily need to be designed with light incident microstructure units. This local design of the 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 path in the light incident area can be locally adjusted and changed, thus having the effect of avoiding the generation 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 adjacent optical glue layer be D2, where 0 ≤ D2 < D1, the light rays deflected towards the lower ultraviolet glue layer are more likely to penetrate the optical glue layer adjacent to the lower ultraviolet glue layer and reach the display panel, rather than being reflected to the substrate layer and emitting light from the upper ultraviolet glue layer. Therefore, it also has the effect of reducing the light emission probability. At the same time, the light incident microstructure units can still handle the problem of LED hot spots, meeting the requirements of the narrow bezel module design. Therefore, it can be applied to the front light module used in e-books, meeting the forward-looking requirements of future color electronic paper and module thinning.

[0042] 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 the present invention that can be implemented. Any person skilled in the 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 using the content disclosed in the present invention should still be covered by the scope of the following claims.

[0043]

List of Reference Numerals

[0044] 1: Substrate layer

[0045] 11: Light incident surface

[0046] 2: Upper ultraviolet glue layer

[0047] 3: Lower ultraviolet glue layer

[0048] 31: Tilted portion

[0049] 32: Flat portion

[0050] 4: Optical glue layer

[0051] 5: Light incident microstructure unit

[0052] 51: First microstructure region

[0053] 52: Second microstructure region

[0054] 6: Light emitting unit

[0055] 7: Optical components

[0056] 8: Display panel.

Claims

1. A light guide film, characterized in that: Include: A substrate layer having a light incident surface; an upper UV adhesive layer, which is disposed above the substrate layer; A lower ultraviolet adhesive layer, which is disposed below the substrate layer; Two optical adhesive layers, which are respectively arranged above the upper UV adhesive layer and below the lower UV adhesive layer; and The light incident microstructure unit has a first microstructure region, and the first microstructure region is arranged on the light incident surface of the substrate layer.

2. The light guide film according to claim 1, characterized in that: The light incident microstructure unit further has a second microstructure region, which is disposed on the end surfaces of the upper ultraviolet adhesive layer and the lower ultraviolet adhesive layer, respectively, and is closer to the light incident surface of the substrate layer.

3. The light guide film according to claim 2, characterized in that: The light incident microstructure unit is composed of a plurality of microstructures. Each microstructure in the first microstructure region has a first depth. Each microstructure in the second microstructure region has a second depth. The first depth is greater than the second depth.

4. The light guide film according to claim 1, characterized in that: The refractive index of the substrate layer is greater than the refractive index of the lower ultraviolet adhesive layer, and the difference is D1.

5. The light guide film according to claim 4, characterized in that: The absolute value of the difference between the refractive index of the lower UV adhesive layer and the refractive index of the adjacent optical adhesive layer is D2, 0≦D2 <D1。 6. The light guide film according to claim 1, characterized in that: The refractive index of the substrate layer is less than or equal to the refractive index of the upper UV adhesive layer.

7. The light guide film according to claim 1, characterized in that: The refractive index of the lower UV adhesive layer is smaller than the refractive index of the upper UV adhesive layer.

8. The light guide film according to claim 1, characterized in that: The lower ultraviolet 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 to a direction away from the light incident surface of the substrate layer.

9. A front light module, characterized in that: Include: The light guide film according to any one of claims 1 to 8, wherein the upper UV adhesive layer of the light guide film has a plurality of reflective microstructures; and The light-emitting unit is arranged on the light-incident side of the light-guiding film.

10. A reflective display, characterized in that: Include: The front light module according to claim 9; an optical component disposed above the light guide film; and The display panel is arranged below the light guide film.

11. The reflective display according to claim 10, characterized in that: The optical component is a touch sensor.

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