TWI890647B - Display device - Google Patents

Abstract

A display device includes a cover plate, an optical module, and a color electrophoresis display module. The optical module is located under the cover plate and includes a light guide plate, a first optical layer, a second optical layer, and a light source. The light guide plate has a first main surface and a second main surface opposite to each other. The first main surface faces the cover plate and is provided with a plurality of concave microstructures having non-gradient shapes. The first optical layer is located on the first main surface. The second optical layer is located on the second main surface. The light source is disposed on a lateral side of the light guide plate. The color electrophoretic display module is located under the optical module. A refractive index of the second optical layer is smaller than a refractive index of the light guide plate and larger than a refractive index of the first optical layer. A ratio of an ideal interface reflectivity between the first optical layer and the first main surface to an ideal interface reflectivity between the second optical layer and the second main surface is about 3 to about 13.

Description

Display device

The present disclosure relates to a display device, and more particularly to a display device with a front light module.

E-book readers utilize bi-stable display technology, consuming power only when the display changes. This reduces power consumption by over 90% compared to conventional self-luminous displays, achieving environmental benefits in terms of energy conservation and power saving. Furthermore, replacing traditional paper books with e-books can reduce carbon emissions from deforestation, demonstrating sustainable value through green technology.

Currently, e-book readers use front-lit displays to allow users to clearly see the content displayed in dark or bright environments. A front-lit display includes a front-lit module and a display panel. The front-lit module includes a light guide plate and a light-emitting unit arranged adjacent to each other. The light guide plate has a light-emitting surface. Light emitted by the light-emitting unit enters one end of the light guide plate and is refracted by the light guide plate to propagate to the display panel. The display panel then reflects the light through the light guide plate and reaches the user's eyes. Front-lit displays form images by reflecting light, so unlike self-luminous display panels, the display image is not disturbed by light in bright environments.

Existing solutions typically coat the top and bottom of the light guide plate with a low-refractive-index material, allowing light to be fully internally reflected within the plate. This allows light to be transmitted from the light source end of the light guide plate to the opposite end with minimal energy loss, similar to fiber optic transmission. While designs with a large refractive index difference between the light guide plate and its upper and lower layers can better ensure total internal reflection, it can also hinder light traveling through the light guide plate from exiting the front light, resulting in insufficient effective light reaching the display panel. Furthermore, because the refractive index of the light guide plate is much higher than that of the low-refractive-index material at the interface below it, the light incident on the display panel through the light guide plate will deviate significantly from the normal direction of the interface, making it difficult for it to enter the display panel. Consequently, the light that is not modulated by the display panel becomes noise light, which causes a whitened image.

Therefore, how to come up with a display device that can solve the above problems is one of the issues that the industry is eager to invest research and development resources to solve.

In view of this, one purpose of the present disclosure is to provide a display device that can solve the above-mentioned problems.

In order to achieve the above-mentioned purpose, according to one embodiment of the present disclosure, a display device includes a cover plate, an optical module and a color electrophoretic display module. The optical module is located under the cover plate and includes a light guide plate, a first optical layer, a second optical layer and a light source. The light guide plate has a first main surface and a second main surface relative to each other. The first main surface faces the cover plate and is provided with a plurality of concave microstructures with non-gradient shapes. The first optical layer is located on the first main surface. There is a first ideal interface reflectivity R _0-1 between the first optical layer and the first main surface. The second optical layer is located on the second main surface. There is a second ideal interface reflectivity R _0-2 between the second optical layer and the second main surface. The light source is arranged on the side of the light guide plate. The color electrophoretic display module is located under the optical module. The light guide plate has a refractive index _nLG of approximately 1.55 to approximately 1.65. The first optical layer has a refractive index _n1 of approximately 1.38 to approximately 1.41. The second optical layer has a refractive index _n2 of approximately 1.48 to approximately 1.52. The ratio of the first ideal interface reflectivity _R0-1 to the second ideal interface reflectivity _R0-2 is approximately 3 to approximately 13. The first ideal interface reflectivity _R0-1 and the second ideal interface reflectivity _R0-2 are calculated by the following formula: , .

In one or more embodiments of the present disclosure, each concave microstructure includes two connected inclined surfaces, which are recessed from the first main surface.

In one or more embodiments of the present disclosure, a color electrophoretic display module includes a microcapsule electrophoretic display (MEPD) and a color pixel array. The MEPD is located beneath an optical module. The color pixel array can be printed on a substrate to form a color filter, which is then placed between the optical module and the MEPD. Alternatively, a color filter pattern can be printed directly on the front plane laminate (FPL) of the electronic paper, replacing the separate color filter on the MEPD.

In one or more embodiments of the present disclosure, the color electrophoretic display module is a microcup color electrophoretic display.

In one or more embodiments of the present disclosure, the display device further includes a touch-sensitive layer located between the cover plate and the optical module.

In one or more embodiments of the present disclosure, the light transmittance of the touch sensing layer is 85-98%.

In one or more embodiments of the present disclosure, the first optical layer is directly connected between the touch sensing layer and the first main surface.

In one or more embodiments of the present disclosure, the first optical layer is a low-reflection index coating formed on the first major surface.

In one or more embodiments of the present disclosure, the first optical layer completely fills the concave microstructures, and forms a substantially flat surface on a side of the first optical layer away from the light guide plate.

In one or more embodiments of the present disclosure, the first optical layer is directly connected between the cover plate and the first main surface.

In summary, in the display device disclosed herein, by making the refractive index of the first optical layer disposed on the first principal surface of the light guide plate smaller than the refractive index of the light guide plate, and the difference is relatively large, noise light emitted from the first principal surface can be effectively reduced. By making the refractive index of the second optical layer disposed on the second principal surface of the light guide plate smaller than the refractive index of the light guide plate, and the difference is relatively small, the effective light transmitted to the color electrophoretic display module can be effectively increased by designing unequal refractive index differences between the upper and lower interfaces of the light guide plate and its adjacent materials. Furthermore, by providing a concave microstructure with a non-gradient shape disposed on the first principal surface, the direction of incident light can be precisely modulated toward the color electrophoretic display module.

The above description is merely intended to illustrate the problems to be solved by the present disclosure, the technical means for solving the problems, and the resulting effects, etc. The specific details of the present disclosure will be described in detail in the following embodiments and related drawings.

The following figures illustrate various embodiments of the present disclosure. For clarity, numerous practical details are included in the following description. However, it should be understood that these practical details are not intended to limit the present disclosure. In other words, these practical details are not essential to some embodiments of the present disclosure. Furthermore, to simplify the drawings, some commonly used structures and components are depicted in simplified schematic form.

Please refer to FIG. 1 , which is a schematic diagram illustrating a display device 100 according to an embodiment of the present disclosure. As shown in FIG. 1 , in this embodiment, the display device 100 includes a cover plate 110, an optical module 120, a color electrophoretic display module 130, and an optical adhesive layer 140. The optical module 120 is located below the cover plate 110 and is connected to the cover plate 110 via the optical adhesive layer 140. The color electrophoretic display module 130 is located below the optical module 120. The optical module 120 is configured to emit light toward the color electrophoretic display module 130. The color electrophoretic display module 130 is configured to modulate the light emitted by the optical module 120 and reflect the modulated light, which then passes through the optical module 120 and the cover 110 to reach the user's eyes. Therefore, the display device 100 of this embodiment is a front-lit electronic paper display (EPD).

As shown in FIG. 1 , in this embodiment, the optical module 120 includes a light guide plate 121, a first optical layer 122, a second optical layer 123, and a light source 124. The light guide plate 121 has a first principal surface 121a and a second principal surface 121b that are opposed to each other. The first principal surface 121a faces the cover plate 110. The first optical layer 122 is located on the first principal surface 121a. The second optical layer 123 is located on the second principal surface 121b. The light source 124 is disposed on a side of the light guide plate 121 and is configured to emit light from the side of the light guide plate 121 into the light guide plate 121.

In this embodiment, the light guide plate 121 has a refractive index n _LG . The first optical layer 122 has a refractive index n ₁ . The second optical layer 123 has a refractive index n ₂ . By making the refractive index n ₁ of the first optical layer 122 smaller than the refractive index n _LG of the light guide plate 121, and by making the difference between the refractive indices n ₁ and n _LG larger than the difference between the refractive indices n ₂ and n _LG , according to Snell's law, most incident light rays between the first optical layer 122 and the light guide plate 121 will be totally reflected at angles greater than the critical angle. This effectively reduces noise rays that escape from the first principal surface 121a and do not carry image information. In addition, by making the refractive index _n2 of the second optical layer 123 smaller than the refractive index _nLG of the light guide plate 121, and the difference between the refractive index _n2 and the refractive index _nLG smaller than the difference between the refractive index _n1 and the refractive index _nLG , fewer incident light rays between the first optical layer 122 and the light guide plate 121 are totally reflected at a greater angle than the critical angle. Therefore, light rays are more easily transmitted from the second main surface 121b of the light guide plate 121 into the color electrophoretic display module 130, thereby increasing the effective light (image ray) that has been modulated and carries image information. In other words, because the refractive index _n2 is greater than the refractive index _n1 , the proportion of light rays propagating within the light guide plate 121 that undergoes total internal reflection at the interface between the second optical layer 123 and the second principal surface 121b is less than the proportion that undergoes total internal reflection at the interface between the first optical layer 122 and the first principal surface 121a. In other words, between the upper and lower principal surfaces, the light rays propagating within the light guide plate 121 are significantly more inclined to depart from the second principal surface 121b, which has a smaller refractive index difference with the light guide plate 121. This makes it easier for light rays in the optical module 120 of this embodiment to propagate toward the color electrophoretic display module 130, thereby being modulated by the color electrophoretic display module 130 into effective light.

In some embodiments, the refractive index _nLG of the light guide plate 121 is approximately 1.55 to approximately 1.65. The refractive index _n1 of the first optical layer 122 is approximately 1.38 to approximately 1.41. The refractive index _n2 of the second optical layer 123 is approximately 1.48 to approximately 1.52. Furthermore, a first ideal interface reflectivity _R0-1 is present between the first optical layer 122 and the first principal surface 121a. A second ideal interface reflectivity _R0-2 is present between the second optical layer 123 and the second principal surface 121b. The ratio of the first ideal interface reflectivity _R0-1 to the second ideal interface reflectivity _R0-2 is approximately 3 to approximately 13. The first ideal interface reflectivity _R0-1 and the second ideal interface reflectivity _R0-2 can be calculated by the following formulas (1) and (2), respectively: (1) (2)

It should be noted that when the refractive index n _LG of the light guide plate 121, the refractive index n ₁ of the first optical layer 122, the refractive index n ₂ of the second optical layer 123, the first ideal interface reflectivity R _0-1 between the first optical layer 122 and the first principal surface 121a, and the second ideal interface reflectivity R _0-2 between the second optical layer 123 and the second principal surface 121b are within the aforementioned ranges, significant effects can be achieved in reducing noise light emitted from the first principal surface 121a and increasing effective light transmitted from the second principal surface 121b of the light guide plate 121 to the color electrophoretic display module 130.

The following provides a comparison table 1 of the measurements after actual experiments of an embodiment of the present disclosure and comparative examples 1 and 2. Table 1 Embodiment Comparative example 1 Comparative example 2 Optical adhesive layer (n) 1.48 1.405 1.41 First optical layer (n ₁ ) 1.39 NA NA Light guide plate (n _LG ) 1.58 1.58 1.58 Second optical layer (n ₂ ) 1.48 1.405 1.41 Contrast (light source OFF) 17.3 16.9 16.2 Contrast (light source ON) 16.8 (-2.9%) 14.7 (-13%) 15.3 (-5.6%) Ideal interface reflectivity ratio 3.832 1 1

As shown in Table 1 above, in Comparative Examples 1 and 2, where both the first optical layer 122 above the light guide plate 121 and the second optical layer 123 below it adopt a low refractive index design, the contrast ratio decreases significantly after the light source 124 is turned on (13% and 5.6%, respectively) compared to the present embodiment (2.9%). This indicates that the designs employed in Comparative Examples 1 and 2 are not conducive to effective light entering the color electrophoretic display module 130 from the second principal surface 121b of the light guide plate 121 and also increase light leakage from the first principal surface 121a of the light guide plate 121.

In some embodiments, the material of the light guide plate 121 includes, for example, polycarbonate (PC), polymethyl methacrylate (PMMA) or a composite material thereof, but the present disclosure is not limited thereto.

In some embodiments, the first optical layer 122 is a low-reflection index coating formed on the first main surface 121a of the light guide plate 121, but the present disclosure is not limited thereto. That is, the first optical layer 122 can be formed on the first main surface 121a by a coating or deposition process.

In some embodiments, the material of the first optical layer 122 includes a fluorine-containing resin, such as a fluorine-containing acrylic resin, but the present disclosure is not limited thereto.

In some embodiments, the thickness of the optical adhesive layer 140 connected between the optical module 120 and the cover plate 110 is about 175 μm.

In some embodiments, the thickness of the second optical layer 123 is about 300 μm.

In some embodiments, the second optical layer 123 is an optical adhesive layer. The material of the second optical layer 123 includes, for example, acrylic resin or silicone resin, but the present disclosure is not limited thereto.

Please refer to FIG. 2, which is a partial schematic diagram illustrating a light guide plate 121 and a first optical layer 122 according to an embodiment of the present disclosure. As shown in FIG. 1 and FIG. 2, in this embodiment, a plurality of concave microstructures 121c having non-gradient shapes are provided on the first main surface 121a of the light guide plate 121. By providing the concave microstructures 121c, the direction of light can be accurately modulated toward the color electrophoretic display module 130. In other words, the incident light has a consistent angle on the light-facing surface of the non-gradient concave microstructure 121c, and the light modulated by the plane will be directed toward the color electrophoretic display module 130 at its designed modulation angle, that is, the refracted light emitted by the light source 124 after being modulated by the non-gradient concave microstructure 121c has good directionality. If the concave microstructure 121c has a gradient shape (e.g., a hemispherical shape), the light emitted by the light source 124 is incident on the microstructure's gradient light-facing surface. Therefore, the modulated light will be refracted in different directions as the angle between the light-facing surface and the incident light changes. Although this can increase light uniformity, the light entering the color electrophoretic display module 130 comes from different incident directions, resulting in lower contrast and color saturation than when using a concave microstructure 121c with a non-gradient shape.

As shown in FIG. 2 , in this embodiment, each concave microstructure 121c includes two connected inclined surfaces 121c1 and 121c2. The two inclined surfaces 121c1 and 121c2 are recessed from the first main surface 121a. Specifically, the inclined surface 121c1 of each concave microstructure 121c serves as a light-facing surface closer to the light source 124, while the inclined surface 121c2 of each concave microstructure 121c serves as a light-reflecting surface farther from the light source 124. The area of the inclined surface 121c1 serving as the light-facing surface is larger than the area of the inclined surface 121c2 serving as the light-reflecting surface. Thereby, the amount of incident light modulated and redirected by the concave microstructures 121 c on the first main surface 121 a of the light guide plate 121 can be effectively increased, and the amount of light guided from the first main surface 121 a to the color electrophoretic display module 130 can be effectively increased.

In some embodiments, the angle between the two inclined surfaces 121c1 and 121c2 of each concave microstructure 121c is approximately 40 degrees to approximately 70 degrees. This effectively allows the first main surface 121a to redirect incident light from the light source 124 vertically into the color electrophoretic display module 130.

In some embodiments, the distribution density of the concave microstructures 121c disposed on the first major surface 121a is exponentially related to the distance from the light source 124. For example, the distribution density of the concave microstructures 121c is proportional to the square of the distance from the light source 124, but the present disclosure is not limited thereto.

In some embodiments, the upper surface of the first optical layer 122 covering the concave microstructure 121c is substantially flat to prevent the effective light reflected by the color electrophoretic display module 130 from being disturbed in its traveling direction or attenuated in its energy when propagating through an uneven interface.

In some embodiments, the refractive index of the first optical layer 122 covering the concave microstructure 121c is smaller than that of the light guide plate 121, and the difference is relatively large. Compared to selecting an optical layer with a smaller refractive index difference from the light guide plate 121, the probability of total internal reflection occurring between the two inclined surfaces 121c1 and 121c2 of the concave microstructure 121c and the optical layer is higher. In other words, at the interface between the concave microstructure 121c and the optical layer, light propagates primarily in a specific direction modulated by the tilt angles of the inclined surfaces 121c1 and 121c2 due to total internal reflection. This enhances the directivity of the modulated light, ensuring that as much incident light from the light source 124 as possible enters the color electrophoretic display module 130. In some embodiments, the first optical layer 122 completely fills the concave microstructures 121c, leaving no air gaps, and forms a substantially flat surface on the side of the first optical layer 122 facing away from the light guide plate 121. In some embodiments, after the first optical layer 122 completely fills the concave microstructures 121c, the substantially flat surface formed has a thickness T of approximately 10 µm from the first major surface 121a (see FIG. 2 ). In some embodiments, the first optical layer 122 is formed on the first major surface 121a by coating or deposition.

As shown in FIG. 1 , in this embodiment, the color electrophoretic display module 130 includes a microcapsule electrophoretic display 131 and a color pixel array 132 . The microcapsule electrophoretic display 131 is located below the optical module 120 . The color pixel array 132 is located between the optical module 120 and the microcapsule electrophoretic display 131 . The color pixel array 132 includes multiple sub-pixel regions with different colors (e.g., red, green, and blue). The microcapsule electrophoretic display 131 includes multiple black and white electronic ink capsules. By controlling the grayscale changes of the electronic ink capsules located below different sub-pixel regions, the color electrophoretic display module 130 can produce a full-color image effect.

Because the secondary pixel region of the color pixel array 132 absorbs a portion of the wavelength of white light to display the remaining colors, and because external light must pass back and forth through the color pixel array 132, the color pixel array 132 significantly reduces energy efficiency. As a result, under normal conditions, the color electrophoretic display module 130 appears dimmer than a black and white electrophoretic display module. Therefore, compared to black and white electrophoretic display modules, color electrophoretic display modules 130 require a frontlight module to improve the brightness of the display screen. In particular, the frontlight module interface reflectivity design disclosed herein reduces noise light and increases effective light after being irradiated by the frontlight module. Furthermore, the reflected light modulated by sub-pixel areas of different colors does not mix, thereby improving the overall image display quality.

In some embodiments, the microcapsule electrophoretic display 131 includes a barrier layer (not shown). The barrier layer has a refractive index of approximately 1.6. Because the barrier layer and the materials at its upper and lower interfaces have similar refractive indices, most light between these interfaces can continue to propagate through the interfaces between the different materials without being reflected and attenuated by the interface due to the refractive index difference. Therefore, light exiting the second main surface 121b of the light guide plate 121 can enter the microcapsule electrophoretic display 131 as much as possible. For example, the ideal interface reflectivity between the barrier layer and the second optical layer 123 is 0.15%.

In some embodiments, a color filter pattern may be provided in the front plane laminate (FPL) of the electronic paper to replace the color filter separately provided on the microcapsule electrophoretic display 131.

In some embodiments, the stacking design of light exiting the second main surface 121b of the light guide plate 121 and entering the color electrophoretic display module 130 is intended to achieve an optical energy cascade. Specifically, the energy loss between each stacking layer between the light guide plate 121 and the reflective particles in the color electrophoretic display module 130 is similar; in other words, the direction of light travel is not significantly changed along the light path. For example, each stacking layer between the light guide plate 121 and the color electrophoretic display module 130 is constructed using materials with similar properties, such as materials with similar refractive indices. For example, the ideal interface reflectivity between the stacked layers is less than 0.15%. For example, the ideal interface reflectivity between the second optical layer 123 and the protective layer (not shown) of the color electrophoretic display module 130 is less than 0.15%. Another example is the ideal interface reflectivity between the protective layer of the color electrophoretic display module 130 and the internal drive electrode backplane (not shown) of the color electrophoretic display module 130 is less than 0.15%, but the present invention is not limited to this. In some embodiments, through this energy crosstalk stacking design, 90-99% of the light exiting the second main surface 121b of the light guide plate 121 can enter the color electrophoretic display module 130.

Please refer to FIG. 3 , which is a schematic diagram illustrating a display device 200 according to another embodiment of the present disclosure. As shown in FIG. 3 , in this embodiment, display device 200 includes a cover plate 110 , an optical module 120 , a color electrophoretic display module 230 , and an optical adhesive layer 140 . The cover plate 110 , optical module 120 , and optical adhesive layer 140 are identical to those in the embodiment shown in FIG. Therefore, reference may be made to the aforementioned descriptions and will not be repeated here. This embodiment differs from the embodiment shown in FIG. 1 in that the color electrophoretic display module 230 in this embodiment is a microcup color electrophoretic display. A microcup color electrophoretic display is composed of numerous tiny cup-shaped structures, each filled with charged particles of a different color. When an electric field is applied to the microcup, the charged particles are affected by the electric field force and move up and down in the liquid. By controlling the electric field force, the position of particles of different colors in the microcup can be positioned, thereby displaying the desired color. However, the wall of the cup-shaped structure of the microcup color electrophoretic display has a certain thickness. If the incident light is not perpendicular to the display surface of the cup-shaped structure (that is, the side facing the user), the light may be refracted by the material of the wall of the cup-shaped structure before reaching the charged particles, resulting in poor display effect. Therefore, through the reflectivity design of the front light module interface disclosed in the present invention, the incident light entering the color electrophoretic display module 130 is made more perpendicular to the display surface of the color electrophoretic display module 130, thereby improving the overall image display quality.

Please refer to FIG. 4 , which is a schematic diagram illustrating a display device 300 according to another embodiment of the present disclosure. As shown in FIG. 4 , in this embodiment, the display device 300 includes a cover plate 110, an optical module 120, a color electrophoretic display module 130, optical adhesive layers 321 and 322, and a touch-sensitive layer 310. The cover plate 110, optical module 120, and color electrophoretic display module 130 are identical to those in the embodiment shown in FIG. Therefore, reference may be made to the aforementioned descriptions and will not be repeated here. This embodiment differs from the embodiment shown in FIG. 1 in that the display device 300 of this embodiment includes a touch-sensitive layer 310 between the cover plate 110 and the optical module 120. The first optical layer 122 is connected to the touch-sensitive layer 310 via the optical adhesive layer 321. The cover plate 110 is connected to the touch-sensitive layer 310 via the optical adhesive layer 322. Thus, the display device 300 of this embodiment can provide an additional touch function.

In some embodiments, to minimize interface reflections along the optical path, the touch-sensing layer 310 may be made of a substrate with a refractive index similar to that of the optical adhesive layers 321 and 322. For example, the refractive index of the optical adhesive layers 321 and 322 is approximately 1.48, while the refractive index of the substrate of the touch-sensing layer 310 is approximately 1.6, but the present disclosure is not limited to this. For example, the ideal interface reflectivity between the optical adhesive layers 321 and 322 and the touch-sensing layer 310 is 0.15%. In some embodiments, the touch sensing layer 310 may be formed using a plastic substrate, particularly one with a refractive index similar to that of the optical adhesive layers 321 and 322. For example, PET may be used as the substrate for the touch sensing layer 310. In some embodiments, the touch sensing layer 310 may be formed using a transparent metal oxide as the electrode material, particularly one with a refractive index similar to that of the optical adhesive layers 321 and 322. For example, ITO may be used as the electrode material for the touch sensing layer 310. By selecting a material with an appropriate refractive index, the light transmittance through the touch sensing layer 310 can be increased to 85% to 98%.

In some implementations, the material of at least one of the optical adhesive layers 321 and 322 includes, for example, acrylic resin, but the present disclosure is not limited thereto.

Please refer to FIG. 5 , which is a schematic diagram illustrating a display device 400 according to another embodiment of the present disclosure. As shown in FIG. 5 , in this embodiment, the display device 400 includes a cover plate 110, an optical module 420, and a color electrophoretic display module 130. The cover plate 110 and the color electrophoretic display module 130 are identical to those in the embodiment shown in FIG. 1 , and thus, reference may be made to the aforementioned descriptions and will not be repeated here. This embodiment differs from the embodiment shown in FIG. 1 in that the display device 400 of this embodiment directly connects the first optical layer 422 of the optical module 420 between the cover plate 110 and the first major surface 121a of the light guide plate 121. Specifically, the first optical layer 422 is an optical adhesive layer, which is selected from an optical adhesive having a refractive index of approximately 1.38 to approximately 1.41. In some embodiments, the optical adhesive selected has a refractive index of 1.405. This approach not only achieves the aforementioned technical effects of increasing effective light and reducing light leakage, but also simplifies the manufacturing process.

Please refer to FIG. 6 , which is a schematic diagram illustrating a display device 500 according to another embodiment of the present disclosure. As shown in FIG. 6 , in this embodiment, the display device 500 includes a cover plate 110 , an optical module 520 , a color electrophoretic display module 130 , an optical adhesive layer 322 , and a touch-sensitive layer 310 . The cover plate 110 , the color electrophoretic display module 130 , the optical adhesive layer 322 , and the touch-sensitive layer 310 are the same as those in the embodiment shown in FIG. 4 . Therefore, reference may be made to the aforementioned related descriptions and will not be repeated here. This embodiment differs from the embodiment shown in FIG. 4 in that the display device 500 of this embodiment utilizes the first optical layer 522 of the optical module 520 directly connected between the touch sensor layer 310 and the first major surface 121a of the light guide plate 121. Specifically, the first optical layer 522 is an optical adhesive layer, which is made of an optical adhesive having a refractive index of approximately 1.38 to approximately 1.41. In some embodiments, the optical adhesive has a refractive index of 1.405. This approach not only achieves the aforementioned technical effects of increasing effective light and reducing light leakage, but also simplifies the manufacturing process.

From the above detailed description of the specific implementation methods of the present disclosure, it can be clearly seen that in the display device of the present disclosure, by making the refractive index of the first optical layer disposed on the first main surface of the light guide plate smaller than the refractive index of the light guide plate, and the difference is relatively large, the noise light emitted from the first main surface can be effectively reduced. By making the refractive index of the second optical layer disposed on the second main surface of the light guide plate smaller than the refractive index of the light guide plate, and the difference is relatively small, the effective light transmitted to the color electrophoretic display module can be effectively increased by designing the refractive index difference between the upper and lower interfaces of the light guide plate and its adjacent materials to be unequal. In addition, by providing a concave microstructure with a non-gradient shape on the first main surface, the direction of the incident light can be modulated accurately toward the color electrophoretic display module.

Although the present disclosure has been disclosed in the form of embodiments as described above, this is not intended to limit the present disclosure. Anyone skilled in the art may make various changes and modifications without departing from the spirit and scope of the present disclosure. Therefore, the scope of protection of the present disclosure shall be determined by the scope of the attached patent application.

100, 200, 300, 400, 500: Display device 110: Cover plate 120, 420, 520: Optical module 121: Light guide plate 121a: First principal surface 121b: Second principal surface 121c: Concave microstructure 121c1, 121c2: Inclined surface 122, 422, 522: First optical layer 123: Second optical layer 124: Light source 130, 230: Color electrophoretic display module 131: Microcapsule electrophoretic display 132: Color pixel array 140, 321, 322: Optical adhesive layer 310: Touch sensor layer T: Thickness

To facilitate understanding of the above and other objects, features, advantages, and embodiments of the present disclosure, the accompanying drawings are described as follows: Figure 1 is a schematic diagram illustrating a display device according to an embodiment of the present disclosure. Figure 2 is a partial schematic diagram illustrating a light guide plate and a first optical layer according to an embodiment of the present disclosure. Figure 3 is a schematic diagram illustrating a display device according to another embodiment of the present disclosure. Figure 4 is a schematic diagram illustrating a display device according to another embodiment of the present disclosure. Figure 5 is a schematic diagram illustrating a display device according to another embodiment of the present disclosure. Figure 6 is a schematic diagram illustrating a display device according to another embodiment of the present disclosure.

Domestic Storage Information (Please enter in order by institution, date, and number) None International Storage Information (Please enter in order by country, institution, date, and number) None

100: Display device

110: Cover plate

120: Optical module

121: Light guide plate

121a: First main surface

121b: Second main surface

121c: Concave microstructure

122: First optical layer

123: Second optical layer

124: Light Source

130: Color electrophoretic display module

131: Microcapsule electrophoresis display

132: Color pixel array

140: Optical adhesive layer

Claims (10)

A display device comprises: a cover plate; an optical module disposed below the cover plate and comprising: a light guide plate having a first main surface and a second main surface opposite to each other, the first main surface facing the cover plate and provided with a plurality of concave microstructures having non-gradient shapes; a first optical layer disposed on the first main surface, wherein a first ideal interface reflectivity R _0-1 is provided between the first optical layer and the first main surface; a second optical layer disposed on the second main surface, wherein a second ideal interface reflectivity R _0-2 is provided between the second optical layer and the second main surface; and a light source disposed on a side of the light guide plate; and a color electrophoretic display module disposed below the optical module, wherein the light guide plate has a refractive index n _LG of approximately 1.55 to approximately 1.65. The first optical layer has a refractive index n ₁ of about 1.38 to about 1.41, and the second optical layer has a refractive index n ₂ of about 1.48 to about 1.52. The ratio of the first ideal interface reflectivity R _0-1 to the second ideal interface reflectivity R _0-2 is about 3 to about 13. The first ideal interface reflectivity R _0-1 and the second ideal interface reflectivity R _0-2 are calculated by the following formula: , . The display device as described in claim 1, wherein each of the concave microstructures includes two connected inclined surfaces, and the two inclined surfaces are recessed from the first main surface. The display device of claim 1, wherein the color electrophoretic display module comprises: a microcapsule electrophoretic display located below the optical module; and a color pixel array located between the optical module and the microcapsule electrophoretic display. The display device as described in claim 1, wherein the color electrophoretic display module is a microcup color electrophoretic display. The display device as described in claim 1 further includes a touch sensing layer located between the cover plate and the optical module. The display device as described in claim 5, wherein the light transmittance of the touch sensing layer is 85-98%. The display device of claim 5, wherein the first optical layer is directly connected between the touch sensing layer and the first main surface. The display device as described in claim 1, wherein the first optical layer is a low reflection index coating formed on the first major surface. The display device as described in claim 1, wherein the first optical layer completely fills the plurality of concave microstructures and forms a substantially flat surface on a side of the first optical layer away from the light guide plate. The display device of claim 1, wherein the first optical layer is directly connected between the cover plate and the first main surface.