Display device and light enhancement film of the display device

A light enhancement film provided in the disclosure includes a substrate and an optical microstructure having a plurality of hexagonal cylindrical lenses inseparably arranged on a surface of the substrate in accordance with a honeycombed arrangement. Each of the hexagonal cylindrical lenses has different cross-sectional areas that are gradually narrowed from the surface of the substrate in a direction away from the substrate, and every two adjacent lenses have a gap therebetween. Furthermore, a display device having the light enhancement film is provided as well.

RELATED APPLICATIONS

This application claims priority to Taiwan Application Serial Number 99104819, filed Feb. 12, 2010, which is herein incorporated by reference.

BACKGROUND

1. Technical Field

The disclosure relates to a display device, more particularly to a display device and its light enhancement film.

2. Description of Related Art

A traditional electrophoretic display (EPD) has an upper substrate, a lower substrate, and an electrophoretic film arranged between the upper substrate and the lower substrate. If the electrophoretic display does not have a brightness enhancement film (BEF) arranged thereon, after external lights arrive the electrophoretic film via the upper substrate, because reflected lights from the electrophoretic film cannot be effectively transmitted outwards the electrophoretic display by the upper substrate, the light intensity of the reflected lights from the electrophoretic film for a viewer is degraded.

Therefore, the brightness enhancement film (BEF) can be arranged in the electrophoretic display to enhance the light intensity thereof, in which the brightness enhancement film (BEF) normally has a micro structural layer thereon. The micro structural layer has a plurality of microstructures. The microstructures are presented as pillars which are lain parallel and interspaced on a surface of the brightness enhancement film.

When an incident light from an external light source is transmitted into the electrophoretic display and travels to the electrophoretic film in a direction parallel to the parallel pillars, the light intensity of the electrophoretic display can be improved positively, so as to upgrade the quality of the display for the viewer. However, when another incident light from the external light source is transmitted into the electrophoretic display and travels to the electrophoretic film in another direction perpendicular to the parallel pillars, the light intensity of the electrophoretic display cannot be improved, and degrades the quality of the display for the viewer

Therefore, how to develop a brightness enhancement film (BEF) for improving the mentioned disadvantages and inconveniences shall be concerned.

SUMMARY

Therefore, an aspect of the present disclosure is to present a display device and its light enhancement film, which enables different directional incident lights to be respectively reflected outward from the display device after the lights move into the light enhancement film, so as to increase the light intensity of the display device.

In a practice of the disclosure, the light enhancement film has a substrate and an optical microstructure. The optical microstructure has a plurality of hexagonal cylindrical lenses (hexagonal pillar lenses or hexagonal prisms) inseparably arranged on a surface of the substrate in accordance with a honeycombed arrangement. Each of the hexagonal cylindrical lenses is gradually narrowed in girth or cross-section area from the substrate in a direction away from the substrate. Thus, each of the hexagonal cylindrical lenses has a largest cross-sectional area on the surface of the substrate, and each of the hexagonal cylindrical lenses has a smallest cross-sectional area furthest away from the substrate. Also, two corresponding surfaces of every two adjacent hexagonal cylindrical lenses are spaced by a gap between the two adjacent hexagonal cylindrical lenses. In another practice of the disclosure, the display device has a reflective display module, a light enhancement film, and a transparent adhesive layer. The optical microstructure has a plurality of hexagonal cylindrical lenses inseparably arranged on a surface of the substrate in accordance with a honeycombed arrangement. Each of the hexagonal cylindrical lenses is gradually narrowed in girth or cross-section area from the substrate in a direction away from the substrate. Thus, each of the hexagonal cylindrical lenses has a largest cross-sectional area on the surface of the substrate, and each of the hexagonal cylindrical lenses has a smallest cross-sectional area furthest away from the substrate. Also, two corresponding surfaces of every two adjacent hexagonal cylindrical lenses are spaced by a gap between the two adjacent hexagonal cylindrical lenses. The light-transmissive adhesive layer is sandwiched between the reflective display module and the light enhancement film for sticking and fixing the hexagonal cylindrical lenses on the reflective display module.

To sum up, by the appearance of the hexagonal cylindrical lenses of the light enhancement film, the disclosure of the display device and its light enhancement film provide lights to travel within the display device via the hexagonal cylindrical lenses on one side, and enhance light intensity to a viewer by adjusting the traveling path of the reflective lights to the viewer on the other side. Thus, the display device can further provide better brightness of reflective lights and displaying performances.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Refer toFIG. 1,FIG. 2andFIG. 3.FIG. 1is a schematic view of a display device and its light enhancement film and an enlarged view of a hexagonal cylindrical lens (hexagonal pillar lenses or hexagonal prisms) in accordance with one embodiment of the present disclosure.FIG. 2is a schematic view of the optical microstructure observed from a direction from the light-transmissive adhesive layer ofFIG. 1.FIG. 3is a cross-sectional view along a line3-3inFIG. 2and a schematic view of light traveling.

The present disclosure provides a display device100and its light enhancement film200. The display device100has a light enhancement film200, a reflective display module300and a light-transmissive adhesive layer400.

The “reflective liquid crystal display module” has a lot of types or kinds, and one of them is on a reflective material installed below an LCD panel of the reflective liquid crystal display module so as to replace irradiation material or the back light module of the transmissive liquid crystal display to provide lights by reflecting ambient light when the ambient light is sufficiently intense. Since the reflective liquid crystal display module only provides passive reflective lights, the reflective liquid crystal display module is also named “passive liquid crystal display module”. Accordingly, the reflective liquid crystal display is also called “passive liquid crystal display”.

The “electrophoretic display module” is a reflective display relating to the migration of particles (micro-particles). The operating principle of the electrophoretic display module relies on the migration of charged micro-particles within a clear or color light-transmitting fluid. Generally, the charged micro-particles, when subjected to an electric field, swarm toward the electrode with the opposite polarity. The rotation or translation of such micro-particles within the fluid may cause the pixels of the display to be switched between the on and off statuses. The electrophoretic display module may be made on a glass substrate, a metal substrate or a plastic substrate.

The light enhancement film200at least has a substrate210and an optical microstructure220. The substrate210is shaped as a plate, has a first surface211and a second surface212opposite with each other. The first surface211of the substrate210is neighbored with an ambient light source or an external light source L (FIG. 3) and is opposite to the optical microstructure220. Therefore, the first surface211is an outward surface and the second surface212is an inward surface. The optical microstructure220is positioned on the second surface212of the substrate210, and includes a plurality of hexagonal cylindrical lenses (hexagonal pillar lenses or hexagonal prisms)221. In an option, these hexagonal cylindrical lenses221have the same dimension or volume, or are regular hexagonal cylindrical lenses, or are regular hexagonal cylindrical lenses with the same dimension or volume. Also, these hexagonal cylindrical lenses221are arranged on the second surface212of the substrate210in accordance with a honeycombed arrangement (FIG. 2).

These hexagonal cylindrical lenses221are inseparably connected with each other by edges226thereof, or every two adjacent hexagonal cylindrical lenses221have a same edge226(or share the same edge). The edges226of the same hexagonal cylindrical lens221are grouped together in the shape of a hexagon. The edges226are just on the second surface212.

Other polyhedron lenses or alike also can inseparably connect with each other by theirs edges thereof or share the same edge, however, the optical performance of the polyhedron lenses is worse than the optical performance of the hexagonal cylindrical lenses.

The hexagonal cylindrical lenses221respectively extend from the substrate210in a direction away from the substrate210. Each hexagonal cylindrical lens221is not equivalently sized in girth or cross-section area, each hexagonal lens221are gradually narrowed in girth or cross-section area from the second surface212of the substrate210in a direction away from the substrate210, or towards the light-transmissive adhesive layer400. Therefore, each of the hexagonal cylindrical lenses221has a largest hexagonal girth or cross-sectional area on the second surface212of the substrate210, and a smallest hexagonal girth or cross-sectional area on a distal surface225of the hexagonal cylindrical lens221furthest away from the substrate210. In view of that, it implies that two corresponding surfaces222of every two adjacent hexagonal cylindrical lenses221are spaced by a gap223between the two adjacent hexagonal cylindrical lenses221(FIG. 3). The light-transmissive adhesive layer400lies on a surface of the reflective display module300and sticks the distal surfaces (tip surfaces or end surfaces)225of the hexagonal cylindrical lenses221to fix the optical microstructure220on the reflective display module300. Thus, the light-transmissive adhesive layer400is sandwiched between the reflective display module300and the light enhancement film200(FIG. 3). The light-transmissive adhesive layer400is made of the following materials, for example, ultraviolet curable adhesive or epoxy. Therefore, refer toFIG. 3again, after different directional ambient incident lights from an external light source L travel into the reflective display module300, due to the appearance of the hexagonal cylindrical lenses221, the disclosure of the light enhancement film200directs the directional incident lights within the display device100via the hexagonal cylindrical lenses221compulsorily, and adjusts a traveling path that the lights reflected to a viewer V on the other side to further enhance light intensity thereof to the viewer V. Thus, the display device100can further provide better brightness of reflective lights and improve the display performance.

In an optional embodiment of the disclosure, refer toFIG. 3again, the substrate210and the optical microstructure220of the light enhancement film200are formed integrally in one, and made of light-transmissive plastic material.

The ends of these hexagonal cylindrical lenses221with the largest hexagonal cross-sectional area are inseparably arranged on the second surface212of the substrate210in accordance with a honeycombed arrangement shown inFIG. 2. The hexagonal distal surfaces225of these hexagonal cylindrical lenses221with the smallest hexagonal cross-sectional areas are interspaced and arranged on a surface of the light-transmissive adhesive layer400or embedded in the light-transmissive adhesive layer400in accordance with the honeycombed arrangement shown inFIG. 2. The light-transmissive plastic material is, for example, polymethyl methacrylate (PMMA), polystyrene (PS), polycarbonate (PC), polyethylene Terephthalate (PET) or polyimides.

Refer toFIG. 4.FIG. 4is a partial schematic view of a light enhancement film in accordance with another embodiment of the present disclosure. In an optional embodiment of the disclosure, the substrate210and the optical microstructure220of the light enhancement film200may not be formed integrally but formed separately and combined later.

The ends of these hexagonal cylindrical lenses221with the largest hexagonal cross-sectional areas are inseparably arranged in a honeycomb pattern, and connected on the second surface212of the substrate210(FIG. 4). The hexagonal distal surfaces225of these hexagonal cylindrical lenses221with the smallest hexagonal cross-sectional areas are interspaced and arranged on a surface of the light-transmissive adhesive layer400or embedded in the light-transmissive adhesive layer400in the honeycomb pattern shown inFIG. 2orFIG. 3.

In the embodiment, we can say that the optical microstructure220is additionally formed on the substrate210. The substrate210, for example, has light-transmissive plastic material such as polyethylene Terephthalate (PET), polycarbonate (PC) or other light-transmissive plastic materials. The optical microstructure220, for example, has ultraviolet curable material such as polymethacrylic acid or resin.

Exemplarily, substrate210can be a polyethylene Terephthalate (PET) film, and the optical microstructure220is an ultraviolet curable material layer which is embossed a plurality of hexagonal cylindrical lenses221thereon.

Refer toFIG. 2andFIG. 3orFIG. 4again. In the other optional embodiment of the disclosure, the varied dimension or volume of the hexagonal cylindrical lenses221can be:

(1) An included angle θ of any value in a range from 10 degrees to 45 degrees (e.g. 10, 11, 12 . . . or 45 degrees) can be formed between the two corresponding surfaces of every two adjacent hexagonal cylindrical lenses121having the gap223.

(2) A first length (pitch) P between every two parallel edges226of the largest cross-sectional area (FIG. 2) of each hexagonal cylindrical lens221on the second surface212of the substrate210can be any value in a range from 30 μm to 160 μm (e.g. 30, 31, 32 . . . or 160 μm). A second length (width) W between every two parallel edges of the hexagonal distal surfaces225, having the smallest cross-sectional area, of each hexagonal cylindrical lens221can be any value in a range from 12 μm to 96 μm (e.g. 12, 13, 14 . . . or 96 μm).

(3) A ratio of the first length (pitch) P thereof and the second length (width) W thereof can be any value in a range from 0.4 to 0.6 (e.g. 0.4, 0.5 or 0.6).

The hexagonal cylindrical lenses221of the other optional embodiment can cooperate with any of the embodiments mentioned above to adopt the substrate210and the optical microstructure220formed integrally in one or assembled together, when the hexagonal cylindrical lenses221relates the dimension or volume of the length P, W and the included angle θ.

Furthermore, since the light-transmissive adhesive layer400tightly adheres the hexagonal distal surfaces225of the hexagonal cylindrical lenses221to the reflective display module300, no space exists between the light-transmitting adhesive layer400and the hexagonal distal surfaces225thereof so as to prevent the lights operating from total internal reflection phenomenon, and to further retain the light intensity of the reflected lights from the reflective display module300for the viewer V.

Specifically, a refractive index of the hexagonal cylindrical lenses221and a refractive index of the light-transmissive adhesive layer400respectively can be any one value in a range from 1.4 to 1.7 (e.g. 1.4, 1.5, 1.6 or 1.7).

More particularly when there is barely a space between the reflective display module300and the hexagonal distal surfaces225of the hexagonal cylindrical lenses221, the light-transmissive adhesive layer400and the hexagonal cylindrical lenses221have the same or almost the same refractive index once the light-transmissive adhesive layer400and the hexagonal cylindrical lenses221are grouped in one. Then, the embodiment can prevent the total internal reflection phenomenon caused by the reflected lights from the reflective display module300, and further retain the light intensity of the reflected lights from the reflective display module300for the viewer V.

Refer toFIG. 1andFIG. 5in whichFIG. 5is an illumination gain chart of the disclosed light enhancement film and conventional light enhancement films.

A curve A ofFIG. 5is made according to a testing result of a conventional display module without a conventional light enhancement film to receive incident lights having a 45 degree included angle between the X axis, the Y axis and the Z axis, separately. A curve B ofFIG. 5is made according to a testing result of a conventional display module equipped with a conventional light enhancement film to receive incident lights having a 45 degree included angle between the X axis, the Y axis and the Z axis, separately. A curve C ofFIG. 5is made according to a testing result of the display device100of the disclosure equipped the light enhancement film200having the hexagonal cylindrical lenses221to receive incident lights having a 45 degree included angle with the X axis, the Y axis and the Z axis, separately.

As learned from the curve A and curve B, when a conventional display module is not equipped with a conventional light enhancement film the light intensity of the conventional display module at zero degree of view angle is worse than the light intensity of another conventional display module with the conventional light enhancement film at zero degree of view angle. However, when the display module100of the disclosure is equipped with the light enhancement film200having the hexagonal cylindrical lenses221, the light intensity of the display module100of the disclosure at zero degree of view angle is greater than the light intensity of the other conventional display module with the conventional light enhancement film at zero degree of view angle.

Therefore, it can be inferred that the light enhancement film200having the hexagonal cylindrical lenses221provides better light intensity for viewer V (FIG. 3) at zero degree of view angle compared with that provided from the conventional light enhancement film.

To sum up, when the light enhancement film200of the disclosure receives different directional incident lights traveling into the light enhancement film200, because of the appearance of the hexagonal cylindrical lenses221, the disclosure of the light enhancement film200directs the directional incident lights within the display device100via the hexagonal cylindrical lenses221compulsorily, and adjusts a traveling path that the lights reflected to a viewer V to further enhance light intensity thereof to the viewer V. Thus, the display device100can further provide better brightness of reflective lights and displaying performances.