TWI895231B - Touch display - Google Patents

Abstract

A touch display includes a cover plate, a chassis, a front light module, a touch module, and a reflective display module. The cover plate is provided with an ink layer. The front light module includes a light guide plate and a light source module including a light-emitting diode, a first reflective layer, and a second reflective layer. The touch module has a side facing the light source module, and the light guide plate has an extension portion outside the vertical projection range of the touch module. The extension portion has an exposed part that is not covered and is exposed to air. The reflective display module includes a reflective display and a light-blocking element. The reflective display does not overlap with the light-emitting diode in the vertical projection of the cover plate. The light-emitting diode, the first reflective layer, the second reflective layer, and a side entry light surface of the light guide plate form a first light mixing area. The side of the touch module, the ink layer, the chassis, and the light-blocking element form a second light mixing area, with the extension portion located within the second light mixing area.

Description

touch display device

This disclosure relates to a touch display device, and in particular to a reflective touch display device.

E-book readers utilize bi-stable display technology, consuming power only when changing screens. 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.

Generally speaking, reflective displays often feature a front light guide plate (LGP) to provide display functionality even in dark or dimly lit areas. However, this also hinders the need for thinner designs when integrating a touch panel into a touch display. Existing technologies have attempted to address this issue by reducing the LGP's thickness. However, thinning the LGP can lead to other issues, such as optical defects in touch displays, such as hot spots.

To improve the optical issues caused by thinning the light guide plate (LGP), the prior art TWI855599 proposed several solutions. For example, by placing a light-shielding film on top of the light-emitting element and the LGP, and deploying a flexible circuit board on the bottom, the optical performance of the thinned LGP was improved. Light coupling efficiency was also enhanced by adjusting the thickness ratio of the light-emitting element to the LGP. However, covering the light-emitting element with a light-shielding film in this prior art absorbs some light, reducing overall light utilization efficiency. Furthermore, this prior art did not further consider the changes in light mixing effects as the LGP thickness was reduced. As a result, the light uniformity at the end of the LGP closest to the light source was poor, potentially causing localized hot spots (light spots) or uneven illumination. Therefore, how to balance the thinness of touch display design and light uniformity is a direction worth researching.

According to some embodiments of the present disclosure, a touch display device includes a cover plate, a housing, a front light module, a touch module, and a reflective display module. The cover plate has a visible area and a peripheral area, and the peripheral area is provided with an ink layer. The housing and the cover plate together form a storage space. The front light module includes a light guide plate and a light source module. The light guide plate has a side light incident surface. The light source module includes a plurality of light-emitting diodes, a first reflective layer, and a second reflective layer. Each light-emitting diode has a light-emitting surface facing the side light incident surface, a reflective surface opposite to the light-emitting surface, and a continuous uniform light surface surrounding the light-emitting surface and the reflective surface. The first reflective layer covers a portion of the light guide plate. The second reflective layer supports a portion of the light guide plate. The touch module is located between the cover plate and the front light module and has a touch module side facing the light source module. The light guide plate has an extension beyond the vertical projection of the touch module onto the light guide plate. The extension has an exposed portion that is not covered by the first reflective layer or the second reflective layer, and the exposed portion is exposed to air. The reflective display module includes a reflective display and a light shielding element. The vertical projection of the reflective display onto the cover plate does not overlap with the vertical projection of the light-emitting diode onto the cover plate. The light shielding element is connected to the reflective display. The light-emitting diode, the first reflective layer, the second reflective layer, and the side light-incident surface of the light guide plate form a first light mixing area. The touch module side, ink layer, housing, and light-shielding element form a second light-mixing area, and the extended portion of the light guide plate is located in the second light-mixing area.

In some embodiments of the present disclosure, the light guide plate has an upper surface and a lower surface opposite to the upper surface, and the exposed portion on the upper and lower surfaces is a substantially flat surface that is in direct contact with air.

In some embodiments of the present disclosure, the light guide plate has an upper surface and a lower surface opposite to the upper surface, and the length of the exposed portion on the upper surface is shorter than the length of the exposed portion on the lower surface.

In some embodiments of the present disclosure, the continuous, evenly lit surface is a light-transmitting matte surface.

In some embodiments of the present disclosure, the frontlight module further includes a first optical adhesive layer and a second optical adhesive layer. The first optical adhesive layer is located between the first reflective layer and the light guide plate, and the second optical adhesive layer is located between the second reflective layer and the light guide plate. The total thickness of the light guide plate, the first optical adhesive layer, and the second optical adhesive layer is less than the thickness of each light-emitting diode.

In some embodiments of the present disclosure, the bottom surface of the second optical adhesive layer is flush with the bottom surface of each light-emitting diode.

In some embodiments of the present disclosure, the light transmittance of the first optical adhesive layer and the second optical adhesive layer is 91% to 99.9%.

In some embodiments of the present disclosure, the vertical projection of the side-lighting surface of the light guide plate on the cover plate does not overlap with the vertical projection of the reflective display on the cover plate.

In some embodiments of the present disclosure, the reflective display has a display side facing the light-emitting surface of each light-emitting diode, and the vertical projection of the display side on the light guide plate falls within the exposed portion.

In some embodiments of the present disclosure, the first reflective layer, the second reflective layer, the light-incident side surface of the light guide plate, and the light-emitting surface of each light-emitting diode enclose an air cavity, and the first reflective layer has a sloped surface at a position corresponding to the air cavity.

According to the above-described embodiments of the present disclosure, by providing dual light mixing zones and extending the light guide plate with the extended portion positioned within the light mixing zones, it is possible to ensure that thinning the light guide plate to accommodate the thinner design of the touch display device will not affect the overall optical performance of the touch display device.

100: Touch display device

110: Cover plate

111: Edge

112: Ink layer

120: Shell

121: Inner surface

140: Touch Module

141: Touch module side

150: Display module

151: Boundary

152: Reflective Display

153: Display side

154: Shading element

160: Frame adhesive

170: Flexible circuit board

180: Flexible circuit board

190, 190a, 190b, 190c: Optical adhesive layer

191:Side

200: Front light module

210: Light guide plate

210P: Extension

210N: Exposed parts

210M: Optical Microstructures

211: Upper surface

213: Lower surface

215: Side entry glossy surface

220: Light source module

222: LED

223: Shiny surface

224: First reflective layer

224I: Medial wall

225: Reflective surface

227: Continuous smooth finish

226: Second reflective layer

226I: Medial wall

228: Light-blocking layer

229: Surface

230: Flexible circuit board

240: First optical adhesive layer

250: Second optical adhesive layer

251:Side

253: Lower surface

300: Support structure

310: Direct bonding structure

320: Ground wire

VA: Viewing Area

PA: Peripheral Area

Y: Storage space

P: Pitch

S: Air cavity

A1: First light mixing area

A2: Second mixed light zone

d1~d6: horizontal distance

H1~H4, T1~T3: Thickness

L1~L2: Length

R1: Area

Q: Inclined surface

To make the above and other objects, features, advantages, and embodiments of the present disclosure more clearly understood, the accompanying drawings are described as follows: FIG1 is a schematic cross-sectional view of a touch display device according to some embodiments of the present disclosure; FIG2 is a schematic partial enlarged view of region R1 in FIG1; and FIG3 is a schematic top view of certain components of a touch display device according to some embodiments of the present disclosure.

The following drawings illustrate various embodiments of the present disclosure. For the sake of clarity, numerous practical details are included in the following description. However, these practical details should not be construed as limiting the present disclosure. Furthermore, for ease of reading, the dimensions of the elements in the drawings are not drawn to scale. Furthermore, relative terms such as "lower" and "upper" may be used herein to describe the relationship of one element to another, as shown in the drawings. It should be understood that relative terms are intended to encompass different orientations of the device in addition to the orientation depicted in the drawings. Furthermore, terms such as "first" and "second" mentioned in the specification or patent application are used only to name different components or to distinguish different embodiments or scopes. They are not intended to limit the upper or lower limit on the number of components, nor are they intended to define the manufacturing or installation sequence of the components.

Please refer to Figure 1, which is a schematic cross-sectional view of a touch display device 100 according to some embodiments of the present disclosure. The touch display device 100 includes a cover plate 110, a housing 120, a front light module 200, a touch module 140, and a reflective display module 150. In other words, the touch display device 100 of the present disclosure is a reflective touch display device. In the following description, each of the aforementioned components will be described in detail.

The cover plate 110 has a visible area VA and a peripheral area PA. An ink layer 112 is provided on the peripheral area PA on the side of the cover plate 110 facing the touch module 140 to prevent light leakage. In some embodiments, the ink layer 112 may extend from the edge 111 of the cover plate 110 toward the visible area VA, creating a boundary between the peripheral area PA and the visible area VA. In some embodiments, the ink layer 112 may include three stacked layers: a black ink layer located on the side relatively close to the touch module 140, and two white ink layers located on the side relatively close to the cover plate 110. In some embodiments, the cover plate 110 is made of a material with a certain degree of rigidity, such as glass, quartz, or a suitable polymer (e.g., polycarbonate, polymethyl methacrylate), to provide protection for the touch display device 100.

The housing 120 and the cover 110 together form a housing space Y, in which the frontlight module 200, the touch module 140, and the reflective display module 150 are located. In some embodiments, the housing 120 and the cover 110 together enclose a rectangular housing space Y. In some embodiments, the housing 120 can be attached to the cover 110 via a sealant 160 disposed on the peripheral area PA of the cover 110. In some embodiments, the inner surface 121 of the housing 120 can be made of stainless steel, which has the property of reflecting light; that is, the inner surface 121 of the housing 120 can be a reflective surface.

The frontlight module 200 is configured to provide frontlight illumination for the touch display device 100 and includes a light guide plate 210 and a light source module 220. The light source module 220 is used to provide light to the light guide plate 210 and cooperates with the light guide plate 210 to improve light uniformity. The light guide plate 210 has an upper surface 211, a lower surface 213, and a sidelighting surface 215. The upper surface 211 is opposite the lower surface 213, and the sidelighting surface 215 connects the upper surface 211 and the lower surface 213 and faces the light-emitting diode 222 in the light source module 220. In other words, the light emitted by the light-emitting diode 222 enters the light guide plate 210 in the form of sidelight. In some embodiments, the light guide plate 210 may include polycarbonate, polymethacrylate, polyolefin, or a combination thereof, and is preferably designed to be flexible.

To accommodate the thinner design of the frontlight module 200, the thickness H1 of the light guide plate 210 disclosed herein can be designed to be between 0.1 mm and 0.25 mm (e.g., 0.15 mm or 0.20 mm). However, while thinning the light guide plate 210 contributes to the thinner design of the frontlight module 200, it can also lead to other problems, potentially causing optical defects in the frontlight module 200. For example, a thinner light guide plate 210 shortens the optical path, resulting in less light mixing space, which can cause uneven light distribution (i.e., hotspots). To address this issue, the present disclosure not only thins the light guide plate 210 to accommodate the thinner design of the frontlight module 200, but also utilizes at least a dual light mixing mechanism to improve the uneven light distribution resulting from the thinning of the light guide plate 210, thereby also taking into account the overall applicability of the touch display device 100. Detailed implementation methods will be described later.

The light source module 220 includes a plurality of light-emitting diodes 222, a first reflective layer 224, and a second reflective layer 226. Each light-emitting diode 222 is disposed adjacent to the light guide plate 210 and has a light-emitting surface 223 facing the light-incident surface 215 of the light guide plate 210. Furthermore, each light-emitting diode 222 has a reflective surface 225 (see FIG. 2 ) facing the light-emitting surface 223 and a continuous light-homogenizing surface 227 (see FIG. 2 ) surrounding the light-emitting surface 223 and the reflective surface 225. In some embodiments, the continuous light-homogenizing surface 227 can be a light-transmitting matte surface, such as a matte-treated surface or a light-transmitting material having a microstructure. In some embodiments, the continuous homogenous surface 227 may be made of a material with partial light transmittance and high haze, such as a translucent, milky white, soft, hazy, heat-resistant polymer. In some embodiments, the light source module 220 may include a housing (e.g., a packaging housing) that completely encapsulates the LED 222, and the continuous homogenous surface 227 of the LED 222 may be made of the material of the housing. In other words, light not only passes through a two-dimensional, translucent haze surface, but also passes through a translucent haze structure having a certain thickness (e.g., the thickness of a single side of the housing). When the continuous homogenizing surface 227 is a translucent matte surface, it diffuses light that is not directly emitted from the light-emitting surface 223, thereby reducing localized overbrightness or light spots (hot spots). In contrast, with a commonly used parabolic reflector lampshade, when the continuous homogenizing surface 227 is a non-translucent reflective surface, the light that is not directly emitted from the light-emitting surface 223 is concentrated by the reflective surface. While this improves light efficiency, it also over-concentrates the light entering the light guide plate 210, resulting in uneven brightness distribution.

In some embodiments, the LED 222 may have an elongated light-emitting surface 223, such as a rectangular one. Compared to point light sources, an elongated light-emitting surface 223 can reduce light diffraction and provide a more uniform light distribution. Furthermore, by elongating the light-emitting surface 223 so that it extends horizontally, combined with a continuous light-transmitting, soft-mist-like surface 227, the pitch between adjacent LEDs 222 can be effectively blurred, reducing the apparent bright-dark boundary caused by the light source arrangement and the hotspots caused by optical interference due to the regularly spaced point light sources, thereby improving overall optical uniformity. In some embodiments, the LED 222 uses the SSWM31CQ2-NAA LED (available from Seoul Semiconductor), with dimensions of 3.0 mm (width) × 0.85 mm (length) × 0.3 mm (thickness H4, see FIG. 2 ).

Please refer to Figures 1 and 3 , with Figure 3 being a schematic top view of some components of the touch display device 100 according to some embodiments of the present disclosure. In some embodiments, a plurality of LEDs 222 are arranged spaced apart from one another on the second reflective layer 226 along the side-light-incident surface 215 of the light guide plate 210. The spacing P between two adjacent LEDs 222 is 12 mm to 15 mm (e.g., 12.5 mm, 13 mm, 13.5 mm, 14 mm, or 14.5 mm), where the spacing P refers to the distance between the center points of two adjacent LEDs 222. In some embodiments, the horizontal distance d1 between the light-emitting surface 223 of the LED 222 and the side light-entering surface 215 of the light guide plate 210 can be 0.1275 mm to 0.850 mm. This horizontal distance d1 allows light to propagate through the air and diffuse appropriately before entering the light guide plate 210. Furthermore, the light-emitting surface 223 of the LED 222 is kept at equal distances from the first reflective layer 224, the second reflective layer 226, and the side light-entering surface 215. This creates a structure similar to a photographic light box in the space between the LED 222 and the light guide plate 210, thereby achieving a uniform light distribution effect and avoiding overbrightness or bright/dark edges. If the horizontal distance d1 is too small, light may be overly concentrated in a local area, resulting in uneven brightness. This can also create overly bright spots (hot spots) in specific areas due to diffraction from the light source. If the horizontal distance d1 is too large, some light may be excessively diverged before entering the light guide plate 210, potentially causing light to escape beyond the side light-entering surface 215. This can lead to unintended illumination and reduce the amount of light entering the light guide plate 210, thereby lowering overall illumination brightness. In some embodiments, the lower limit of the horizontal distance d1 can be calculated as follows: (thickness H1 of the light guide plate 210 + thickness H2 of the first optical adhesive layer 240 + thickness H3 of the second optical adhesive layer 250)/2. This design takes into account the distance between the light source (LED 222) and each reflective wall, ensuring that the amount of light reflected back in different directions is similar. This prevents excessive concentration of reflected light in a single direction, thereby improving the uniformity of light distribution.

Returning to Figure 1, the first reflective layer 224 covers a portion of the upper surface 211 of the light guide plate 210, while the second reflective layer 226 supports a portion of the lower surface 213 of the light guide plate 210. In some embodiments, the first reflective layer 224 further extends to the upper surface of the LED 222 (i.e., the continuous uniform light surface 227 at the top in Figure 2) to cover the entire LED 222, and the second reflective layer 226 further extends to the lower surface of the LED 222 (i.e., the continuous uniform light surface 227 at the bottom in Figure 2) to support the entire LED 222. In terms of the overall structure, the light-incident side surface 215 of the light guide plate 210, the light-emitting surface 223 of the light-emitting diode 222, the first reflective layer 224 and the second reflective layer 226 together enclose an air cavity S. The arrangement of the first reflective layer 224 and the second reflective layer 226 constrains the reflection direction of light, allowing it to escape from the light-emitting surface 223 and enter the air cavity S. Within the air cavity S, the light is then reflected by the first and second reflective layers 224, 226, adjusting its direction before entering the light guide plate 210. This mechanism reduces the directivity of light emitted by the highly directional light-emitting diode 222 by reflecting it through the structure surrounding the air cavity S (i.e., increasing the degree of light dispersion upon entering the light guide plate 210 through reflection). This homogenization process occurs before the light is transmitted through the light guide plate 210. Consequently, the light traveling through the light guide plate 210 is more evenly distributed, reducing localized hot spots and thereby improving overall optical uniformity. In some embodiments, the first reflective layer 224 covers all LEDs 222 and the spaces between adjacent LEDs 222 (i.e., at the spacing P shown in FIG. 3 ). In some embodiments, the second reflective layer 226 may be an opaque, reflective surface of the flexible circuit board 230 connected to the LEDs 222, such as the opaque, reflective surface located above the flexible circuit board 230 in FIG. 2 . In some embodiments, the second reflective layer 226 may be an ink-coated film, a chemically plated film, or an electroplated film, or the white surface of the flexible circuit board 230 itself (i.e., the white flexible circuit board 230 provides the reflective function). In some embodiments, the light reflectivity of the first reflective layer 224 may be 60% to 80% (e.g., 65%, 70%, or 75%), and the light reflectivity of the second reflective layer 226 may be 55% to 75% (e.g., 60%, 65%, or 70%).

In some embodiments, the light source module 220 may further include a light shielding layer 228. The light shielding layer 228 is superimposed on a surface 229 of the first reflective layer 224 that faces away from the LED 222 and the light guide plate 210. In some embodiments, both the first reflective layer 224 and the light shielding layer 228 extend from the upper surface of the LED 222 (i.e., the continuous homogenous surface 227 at the top in FIG. 2 ) to the upper surface 211 of the light guide plate 210, completely covering the air cavity S between the LED 222 and the light guide plate 210. In some embodiments, the light shielding layer 228 may completely overlap with the first reflective layer 224. Because the light-shielding layer 228 is closer to the user than the first reflective layer 224, it absorbs or blocks any outgoing light from the peripheral area PA, preventing it from affecting the user's vision. For example, the light-shielding layer 228 absorbs or blocks light that directly penetrates the first reflective layer 224.

Please first refer to Figure 2, which is a partially enlarged schematic diagram of region R1 in Figure 1. In some embodiments, the light source module 220 may further include a first optical adhesive layer 240. The first optical adhesive layer 240 is located between the first reflective layer 224 and the light guide plate 210. More specifically, the first optical adhesive layer 240 is located below the first reflective layer 224 and covers a portion of the upper surface 211 of the light guide plate 210 and the entire upper surface of the light-emitting diode 222 (i.e., the continuous uniform light surface 227 at the top). In some embodiments, the first optical adhesive layer 240 may completely overlap the light-shielding layer 228 and the first reflective layer 224. That is, the first optical adhesive layer 240 may span the air cavity S between the LED 222 and the light guide plate 210, forming a continuous covering layer thereon. In some embodiments, the light-incident side surface 215 of the light guide plate 210, the light-emitting surface 223 of the LED 222, the first optical adhesive layer 240, and the second reflective layer 226 collectively enclose the air cavity S. In some embodiments, the first optical adhesive layer 240, the first reflective layer 224, and the light-shielding layer 228 can be three layers of a single piece of black and white tape. For example, the first reflective layer 224 can be formed of a white polyethylene terephthalate (PET) substrate, and black ink is applied to one side of the white PET substrate to form the light-shielding layer 228. The other side of the white PET substrate is coated with an adhesive with high light transmittance to form the first optical adhesive layer 240. These tapes can be easily obtained from commercial products, such as the black and white tape model 550P5 BSFX produced by Sekisui Chemical Co., Ltd. In some embodiments, the material of the first optical adhesive layer 240 may be an acrylic adhesive, which may have a light transmittance of 91% to 99.9% (e.g., 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%). In some embodiments, the thickness H2 of the first optical adhesive layer 240 may be 0.01 mm to 0.1 mm, preferably 0.03 mm to 0.065 mm (e.g., 0.055 mm).

In some embodiments, the light source module 220 may further include a second optical adhesive layer 250. The second optical adhesive layer 250 is positioned between the second reflective layer 226 (flexible circuit board 230) and the light guide plate 210, allowing the light guide plate 210 to be disposed on the second reflective layer 226 (flexible circuit board 230) through the second optical adhesive layer 250. In some embodiments, the side surface 251 of the second optical adhesive layer 250 and the light-entering side surface 215 of the light guide plate 210 may be on different planes. More specifically, the side surface 251 of the second optical adhesive layer 250 may be indented relative to the light-entering side surface 215 of the light guide plate 210 (e.g., by approximately 0.1-0.3 micrometers). In some embodiments, the lower surface 253 of the second optical adhesive layer 250 can be substantially flush with the lower surface of the LED 222 (i.e., the continuous uniform light surface 227 at the bottom). In some embodiments, the side light-incoming surface 215 of the light guide plate 210, the light-emitting surface 223 of the LED 222, the first optical adhesive layer 240, the second optical adhesive layer 250, and the second reflective layer 226 collectively define an air cavity S. In some embodiments, the second optical adhesive layer 250 can be made of Nitto No. 5605 optical adhesive (available from Nitto Denko Corporation). In some embodiments, the second optical adhesive layer 250 may be made of an acrylic adhesive having a light transmittance of 91% to 99.9% (e.g., 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%). In some embodiments, the thickness H3 of the second optical adhesive layer 250 may be 0.02 mm to 0.08 mm (e.g., 0.03 mm, 0.04 mm, 0.05 mm, 0.06 mm, or 0.07 mm).

It is worth noting that the first and second optical adhesive layers 240, 250 serve to increase the light-incident surface area of the light guide plate 210. Specifically, because the first and second optical adhesive layers 240, 250 have high light transmittance, even higher than that of the light guide plate 210 in some embodiments, and because the first and second optical adhesive layers 240, 250 are disposed on the upper and lower surfaces 211, 213, respectively, of the light guide plate 210, they can be considered extensions of the light-incident side surface 215 of the light guide plate 210. Furthermore, the thickness H3 of the second optical adhesive layer 250 (0.05 mm to 0.15 mm) serves to elevate the light guide plate 210, aligning the side light incident surface 215 of the light guide plate 210 roughly with the center of the light-emitting surface 223 of the LED 222. This adjusts the angle of light incidence and increases the proportion of light entering the light guide plate 210, thereby improving light utilization. Furthermore, by ensuring that the total thickness (H1 + H2 + H3) of the light guide plate 210, the first optical adhesive layer 240, and the second optical adhesive layer 250 is less than the thickness H4 of the LED 222, the light-emitting surface 223 of the LED 222 is elevated relative to the entire light incident surface. This design can guide the light emitted by the LED 222 into the light guide plate 210 in a "cohesive" manner, reducing light loss caused by light divergence.

Please return to Figure 1. Overall, in the present disclosure, multiple LEDs 222, a first reflective layer 224, a second reflective layer 226, and the light-incident surface 215 of the light guide plate 210 form a first light-mixing region A1. This arrangement allows light to undergo moderate reflection within the region, reducing its directivity and making it uniform before entering the light guide plate 210. Specifically, the continuous light-distributing surface 227 (see Figure 2) within the LED 222 promotes uniform light diffusion during initial emission, minimizing the occurrence of localized glare or dark areas. After preliminary homogenization, the light enters the air cavity S. Some of the light enters the light guide plate 210 directly through its side light-incoming surface 215, while another portion is first reflected and mixed by the first reflective layer 224 and the second reflective layer 226 for further homogenization. This homogenization mechanism is similar to the light processing mechanism in a photographic light box. Ultimately, the light, conditioned by the first light mixing area A1, is uniformly focused and enters the light guide plate 210, thereby improving light consistency and uniformity. The present disclosure implements the first light mixing mechanism through the provision of the first light mixing area A1. In particular, because the LED 222 of the present disclosure is taller than the light guide plate 210, the first reflective layer 224 extending from the light guide plate 210 to the LED 222 has a slope Q at the location corresponding to the air cavity S. This slope Q gradually decreases from the LED 222 to the light guide plate 210 (gradually approaching the second reflective layer 226), thereby helping to "cohesively" concentrate light entering the light guide plate 210 and reducing light loss caused by light divergence.

Before explaining the second light mixing mechanism, let's first introduce the touch module 140 and reflective display module 150 of this disclosure.

Please continue referring to Figure 1. The touch module 140 is located between the cover 110 and the front light module 200, and on the side of the upper surface 211 of the light guide plate 210. It has a touch module side 141 facing the light source module 220. In some embodiments, the touch module 140 may include a sensing layer and control circuitry (not shown) to detect user touch operations and convert them into corresponding output signals. In some embodiments, to achieve signal transmission, the touch module 140 may be electrically connected to the driver circuit via a flexible circuit board 170 to stably transmit touch data to the system control unit for further processing and execution of corresponding display or input commands.

The reflective display module 150 includes a reflective display 152 and a light shielding element 154. The reflective display module 150 is located on the side of the lower surface 213 of the light guide plate 210 and between the light guide plate 210 and the housing 120. Specifically, the light guide plate 210 is located between the touch module 140 and the reflective display module 150. The reflective display 152 has a display side 153 facing the light-emitting surface 223 of the light-emitting diode 222. The light shielding element 154 is connected to the reflective display 152, and the entire light source module 220 is located between the flexible circuit board 170 and the light shielding element 154. In some embodiments, the light shielding element 154 may be an opaque surface of the flexible circuit board 180 and may be, for example, a smooth, glossy black plastic material.

To accommodate the thinner design of the frontlight module 200 (i.e., a thinner light guide plate 210), the present disclosure further optimizes the structure of the light guide plate 210. Generally speaking, as the light guide plate 210 becomes thinner, its internal light mixing area is relatively reduced, potentially leading to a decrease in the uniformity of light before entering the viewing area (VA), thereby affecting display quality. Therefore, unlike conventional frontlight modules where the edge of the light guide plate (e.g., the side-lighting surface) falls within the peripheral area of the reflective display, the present disclosure further extends the length of the light guide plate 210 to be greater than the entire length of the reflective display 152. More specifically, as shown in FIG. 1 , the light guide plate 210 extends beyond the entire outline dimension of the reflective display 152, that is, beyond the entire display side surface 153 of the reflective display 152. In other words, the vertical projection of the side light input surface 215 of the light guide plate 210 onto the cover plate 110 does not fall within the vertical projection of the reflective display 152 onto the cover plate 110. In other words, the vertical projection of the side light input surface 215 of the light guide plate 210 onto the cover plate 110 does not overlap with the vertical projection of the reflective display 152 onto the cover plate 110. By extending the light guide plate 210 beyond the display side 153 of the reflective display 152, even with a thinner light guide plate 210, more space for light mixing can be provided. This allows the light from the light source module 220 to be fully evenly distributed before entering the viewing area VA, thereby reducing localized brightness unevenness or hot spots.

On the other hand, because the light-emitting surface 223 of the LED 222 and the side-light-incident surface 215 of the light guide plate 210 face each other, the LED 222 of the present disclosure also extends beyond the entire display side surface 153 of the reflective display 152. In other words, the vertical projection of the reflective display 152 on the cover plate 110 does not overlap with the vertical projection of the LED 222 on the cover plate 110. Overall, the vertical projection of the side-light-incident surface 215 of the light guide plate 210 on the cover plate 110 can be located between the vertical projection of the display side surface 153 of the reflective display 152 on the cover plate 110 and the vertical projection of the light-emitting surface 223 of the LED 222 on the cover plate 110.

Please refer to Figure 3 for the relative positions of the light guide plate 210, LED 222, reflective display 152, and touch module 140. The light guide plate 210's light-incident side surface 215 serves as its dimensional boundary, the reflective display 152's display-side surface 153 serves as its dimensional boundary, and the touch module 140's touch module-side surface 141 serves as its dimensional boundary. In the present disclosure, the LED 222 is located outside the light guide plate 210's light-incident side surface 215, and the light guide plate 210's light-incident side surface 215 is located outside the reflective display 152's display-side surface 153. Furthermore, the touch module side surface 141 of the touch module 140 may be located between the viewing area boundary 151 of the reflective display 152 and the display side surface 153 of the reflective display 152 , that is, located in the peripheral area of the reflective display 152 .

In some embodiments, the horizontal distance d2 between the light-incident side surface 215 of the light guide plate 210 and the display side surface 153 of the reflective display 152 may be 2.6 mm to 3.4 mm, and the horizontal distance d3 between the display side surface 153 of the reflective display 152 and the touch module side surface 141 of the touch module 140 may be 4.6 mm to 5.6 mm. In some embodiments, the horizontal distance d4 between the display side surface 153 of the reflective display 152 and the viewing area boundary 151 of the reflective display 152 may be 16.54 mm to 17.14 mm.

Please return to Figure 2. Based on the relative positional relationship between the light guide plate 210, light-emitting diode 222, reflective display 152, and touch module 140 described above, the light guide plate 210 of the present disclosure has an extended portion 210P outside the vertical projection of the touch module 140 onto the light guide plate 210. This extended portion 210P has an exposed portion 210N that is not covered by the first reflective layer 224 or the second reflective layer 226, and this exposed portion 210N is exposed to air. Specifically, because the extended portion 210P of the light guide plate 210 has a portion that is not covered by any layer (e.g., a reflective layer, a light-shielding layer, or an optically transparent adhesive layer), this portion forms the exposed portion 210N that is in direct contact with air. It should be understood that if the extended portion 210P of the light guide plate 210 is completely covered by a reflective layer or a light-shielding layer, while this may help improve the light efficiency of the light guide plate 210, it will cause light that enters the light guide plate 210 but does not meet the requirements for total reflection to propagate further within the light guide plate 210, further disrupting the light's direction of travel and thus affecting the final display effect. Therefore, the present disclosure exposes a portion of the extended portion 210P. This allows light that does not meet the requirements for total reflection to escape from the exposed portion 210N through the interface with the air, reducing the disordered propagation of light within the light guide plate 210 and further improving the image display effect. In addition, the direct contact between the exposed portion 210N and the air provides additional optical advantages. Specifically, due to the significant difference in refractive index between air (refractive index 1) and the light guide plate 210 (refractive index approximately 1.6), the interface between air and the light guide plate 210 increases the probability of total internal reflection of light within the light guide plate 210. This allows some light that meets the requirements for total internal reflection to continue to propagate within the light guide plate 210, thereby improving light utilization efficiency. In some embodiments, the vertical projection of the display side 153 of the reflective display 152 onto the light guide plate 210 falls within the exposed portion 210N.

Please refer to Figures 1 and 2 together. Overall, the touch module side surface 141, ink layer 112, housing 120, and light-shielding element 154 form a second light-mixing area A2, with the extended portion 210P of the light guide plate 210 located within this area. Specifically, the upper boundary of the second light-mixing area A2 is formed by the ink layer 112, the lower boundary is formed by the light-shielding element 154, one side boundary is formed by the housing 120, and the other side boundary is at least partially formed by the touch module side surface 141. Furthermore, the boundaries of the second light-mixing area A2 may also include the upper surface 211 and lower surface 213 of the light guide plate 210 on its extended portion 210P. In some embodiments, the touch display device 100 further includes an optical adhesive layer 190 disposed between the touch module 140 and the light guide plate 210, and between the light guide plate 210 and the reflective display 152. In this case, a side boundary of the second light mixing area A2 is formed by the touch module side surface 141 and the side surface 191 of the optical adhesive layer 190. In some embodiments, the light source module 220 (including the light-emitting diode 222, the first reflective layer 224, the second reflective layer 226, the light-shielding layer 228, the first optical adhesive layer 240, and the second optical adhesive layer 250), the extended portion 210P of the light guide plate 210, and the flexible circuit board 170 are all located within the second light mixing area A2. Areas without components in the second light mixing area A2 are filled with air.

The ink layer 112 and the light-shielding element 154 are light-absorbing, effectively reducing the impact of stray light. The housing 120 is reflective, partially directing the propagation of light. Therefore, when light that doesn't meet the total internal reflection (TRI) criteria escapes from the exposed portion 210N of the extension 210P and enters the second light-mixing area A2, the majority of the light is absorbed by the ink layer 112 or the light-shielding element 154, preventing it from returning to the light guide plate 210 and causing light turbulence. A small amount of light may be reflected back to the light guide plate 210 via the housing 120. If the reflected light meets the TIR criteria, it can still be effectively utilized, avoiding additional light loss. This design prevents excessively turbulent light from re-entering the light guide plate 210, thereby improving light uniformity and ensuring a more stable display. On the other hand, because the refractive indices of the light guide plate 210 (approximately 1.6), the optical adhesive layer 190 (approximately 1.49), and the touchscreen module 140 (approximately 1.6 for the touchscreen substrate) are all higher than the refractive index of air (approximately 1), when light escapes from the light guide plate 210 to the second light mixing area A2 and attempts to re-enter these high-refractive-index media, if the incident angle is small, the light will propagate closer to the normal direction of the material, allowing it to quickly penetrate the medium along a shorter path, reducing interference with the light within the light guide plate 210.

It's worth noting that after the light emitted by the LED 222 enters the light guide plate 210, some of the light fails to meet the requirements for total internal reflection. If the light guide plate 210 does not extend into the second light mixing area A2, this light will easily form stray light on the side of the light guide plate 210 near the side light input surface 215, thereby affecting the image display quality and user visual experience. By designing the extended portion 210P of the light guide plate 210, the light guide plate 210 is extended into the second light mixing area A2. This allows these light rays that fail to meet the requirements for total internal reflection to escape into the second light mixing area A2 (air) through the exposed portion 210N of the extended portion 210P, preventing them from re-entering the light guide plate 210 and causing confusion, thereby improving overall optical uniformity. Therefore, the light guide plate 210 needs to extend beyond the display side 153 of the reflective display 152 to form a sufficiently long extension portion 210P, thereby ensuring that the light guide plate 210 can extend into the second light mixing area A2. For example, if the extension portion 210P is not long enough, it will be difficult to form a sufficiently long exposed portion 210N. As a result, light that does not meet the total reflection conditions cannot effectively escape into the second light mixing area A2 and remains within the light guide plate 210, resulting in reduced optical uniformity.

In particular, because the flexible circuit board 170 can be made of a translucent orange-brown plastic material, when a white light-emitting diode 222 is used as the LED 222, the light escaping from the exposed portion 210N of the light guide plate 210 enters the second light mixing area A2 and passes through the flexible circuit board 170. The translucent orange-brown material of the flexible circuit board 170 can contribute to a color-adjusting effect that enhances the color temperature of the light transmitted therethrough.

Please refer to Figure 2. In some embodiments, a plurality of optical microstructures 210M are disposed on the upper surface 211 or lower surface 213 of the light guide plate 210. The optical microstructures 210M are used to disrupt total internal reflection of light within the light guide plate 210, allowing the light guide plate 210 to adjust and refract (guide) some light toward the reflective display 152. This in turn refracts light reflected from the reflective display 152, allowing the user to view the image. In some embodiments, the exposed portion 210N of the light guide plate 210 is not provided with the optical microstructures 210M on the upper surface 211 and lower surface 213. In other words, the exposed portion 210N is a substantially flat surface on the upper surface 211 and lower surface 213, and is in direct contact with the air. Because the optical microstructures 210M are not disposed on the upper and lower surfaces 211 and 213 of the exposed portion 210N, interference with the light propagation direction caused by the optical microstructures 210M is avoided, reducing additional light scattering in the exposed portion 210N. This allows light that does not meet the requirements for total internal reflection to smoothly pass from the exposed portion 210N into the second light mixing area A2 (air).

In some embodiments, the length L1 of the exposed portion 210N of the light guide plate 210 on the top surface 211 is different from the length L2 of the exposed portion 210N on the bottom surface 213 of the light guide plate 210. Specifically, the length L1 of the exposed portion 210N of the light guide plate 210 on the top surface 211 may be smaller than the length L2 of the exposed portion 210N on the bottom surface 213 of the light guide plate 210. In other words, the horizontal distance d5 between the inner sidewall 224I of the first reflective layer 224 and the side surface 191 of the optical adhesive layer 190 disposed on the top surface 211 of the light guide plate 210 may be smaller than the horizontal distance d6 between the inner sidewall 226I of the second reflective layer 226 and the side surface 191 of the optical adhesive layer 190 disposed on the bottom surface 213 of the light guide plate 210. This is because light escaping from above the light guide plate 210 is closer to the user. Therefore, compared to light escaping from directions away from the user, a more stringent light shielding device is required above the light guide plate 210 to avoid affecting the user's viewing experience. In some embodiments, the difference between the length L1 (horizontal distance d5) and the length L2 (horizontal distance d6) can be 1.305 mm to 1.595 mm (e.g., 1.35 mm, 1.40 mm, 1.45 mm, 1.50 mm, or 1.55 mm).

Overall, the present disclosure implements a second light-mixing mechanism through the provision of the second light-mixing area A2, and achieves a dual light-mixing mechanism by combining the first and second light-mixing areas A1 and A2. Specifically, because the first light-mixing area A1 is located within the second light-mixing area A2, light within the exposed portion 210N of the light guide plate 210 that does not meet the total internal reflection conditions can also escape into the air cavity S within the first light-mixing area A1 and into the space between the LEDs 222 (i.e., the spacing P shown in Figure 3).

Please return to Figure 1. In some embodiments, the optical adhesive layer 190 of the touch display device 100 may include an optical adhesive layer 190a disposed between the upper surface 211 of the light guide plate 210 and the touch module 140, an optical adhesive layer 190b disposed between the lower surface 213 of the light guide plate 210 and the reflective display 152, and an optical adhesive layer 190c disposed between the cover plate 110 and the touch module 140. In some embodiments, to accommodate the thinner design of the touch display device 100, the thicknesses of the optical adhesive layers 190a, 190b, and 190c may be reduced. For example, the thickness T3 of optical adhesive layer 190c and the thickness T1 of optical adhesive layer 190a can each be 75 microns to 150 microns, while the thickness T2 of optical adhesive layer 190b can be 50 microns to 100 microns. In some embodiments, the side surface 191 of optical adhesive layer 190 (including the side surfaces of optical adhesive layers 190a, 190b, and 190c) is flush with the touch module side surface 141.

In some embodiments, the touch display device 100 may further include a support structure 300 and a direct surface attachment (DSA) structure 310. The direct surface attachment structure 310 can attach the touch module 140 to the support structure 300, and the support structure 300 can provide mechanical strength and stability. In some embodiments, the support structure 300 can also serve as part of the electrical connection. For example, the flexible circuit board 170, 230 and the grounding wire 320 thereon can be connected to the support structure 300 to provide a stable electrical ground.

According to the above-described embodiments of the present disclosure, by providing dual light mixing zones and extending the light guide plate with the extended portion positioned within the light mixing zones, it is possible to ensure that thinning the light guide plate to accommodate the thinner design of the touch display device will not affect the overall optical performance of the touch display device.

Although this disclosure has been disclosed above in terms of implementation, it is not intended to limit this disclosure. Anyone skilled in the art may make various modifications and improvements without departing from the spirit and scope of this disclosure. Therefore, the scope of protection of this disclosure shall be determined by the scope of the attached patent application.

100: Touch display device

110: Cover plate

111: Edge

112: Ink layer

120: Shell

121: Inner surface

140: Touch Module

141: Touch module side

150: Display module

152: Reflective Display

153: Display side

154: Shading element

160: Frame adhesive

170: Flexible circuit board

180: Flexible circuit board

190, 190a, 190b, 190c: Optical adhesive layer

191:Side

200: Front light module

210: Light guide plate

211: Upper surface

213: Lower surface

215: Side entry glossy surface

220: Light source module

222: LED

223: Shiny surface

224: First reflective layer

226: Second reflective layer

228: Light-blocking layer

229: Surface

300: Support structure

310: Direct bonding structure

320: Ground wire

VA: Viewing Area

PA: Peripheral Area

Y: Storage space

S: Air cavity

A1: First light mixing area

A2: Second mixed light zone

H1, T1~T3: Thickness

Q: Inclined surface

Claims (10)

A touch display device includes: a cover having a visible area and a peripheral area, wherein the peripheral area is provided with an ink layer; a housing, which forms a receiving space together with the cover; a front light module, which includes: a light guide plate having a side light incident surface; and a light source module, which includes: a plurality of light emitting diodes, wherein each of the light emitting diodes has a side light incident surface. a light-emitting surface, a reflective surface opposite to the light-emitting surface, and a continuous uniform light surface surrounding the light-emitting surface and the reflective surface; a first reflective layer covering a portion of the light guide plate; and a second reflective layer supporting a portion of the light guide plate; a touch module located between the cover and the front light module and having a touch module side facing the light source module, wherein the light guide plate is disposed between the touch module and the front light module. The module has an extension outside the vertical projection range of the light guide plate, and the extension has an exposed portion that is not covered by the first reflective layer and the second reflective layer, and the exposed portion is exposed to the air; a reflective display module includes: a reflective display, wherein the vertical projection of the reflective display on the cover plate and the vertical projection of the light-emitting diodes on the cover plate do not overlap; and a shading element connected to the reflective display; wherein: the light-emitting diodes, the first reflective layer, the second reflective layer and the side light-incident surface of the light guide plate form a first light mixing area; and the side surface of the touch module, the ink layer, the housing and the shading element form a second light mixing area, and the extension of the light guide plate is in the second light mixing area. The touch display device as described in claim 1, wherein the light guide plate has an upper surface and a lower surface opposite to the upper surface, and the exposed portion is a substantially flat surface on the upper surface and the lower surface and directly contacts the air. The touch display device as described in claim 1, wherein the light guide plate has an upper surface and a lower surface opposite to the upper surface, and the length of the exposed portion on the upper surface is smaller than the length of the exposed portion on the lower surface. The touch display device as described in claim 1, wherein the continuous smooth surface is a light-transmitting matte surface. A touch display device as described in claim 1, wherein the front light module further includes a first optical adhesive layer and a second optical adhesive layer, the first optical adhesive layer is located between the first reflective layer and the light guide plate, the second optical adhesive layer is located between the second reflective layer and the light guide plate, and the total thickness of the light guide plate, the first optical adhesive layer and the second optical adhesive layer is less than the thickness of each of the light-emitting diodes. The touch display device of claim 5, wherein the bottom surface of the second optical adhesive layer is flush with the bottom surface of each of the light-emitting diodes. The touch display device as described in claim 5, wherein the transmittance of the first optical adhesive layer and the second optical adhesive layer is 91% to 99.9%. The touch display device as described in claim 1, wherein the vertical projection of the side light surface of the light guide plate on the cover plate does not overlap with the vertical projection of the reflective display on the cover plate. The touch display device as described in claim 1, wherein the reflective display has a display side facing the light-emitting surface of each of the light-emitting diodes, and the vertical projection of the display side on the light guide plate falls in the exposed portion. The touch display device as described in claim 1, wherein the first reflective layer, the second reflective layer, the side light incident surface of the light guide plate and the light emitting surface of each of the light emitting diodes enclose an air cavity, and the first reflective layer has a slope at a position corresponding to the air cavity.