Optical film, backlight module and display device

Abstract

The invention relates to an optical film, which comprises a base material and a plurality of incident light microstructures arranged on the incident light surface of the base material, the substrate is defined to have a first extension direction and a second extension direction perpendicular to the first extension direction. The section shape of the light incidence microstructure in the first extension direction is different from the section shape of the light incidence microstructure in the second extension direction. Each light incidence microstructure is provided with a plurality of optical surfaces and a boundary line connected with the optical surfaces, and the boundary line is a straight line and is parallel to the light incidence surface of the base material. Through the structural design of the light incidence microstructure of the optical film, the light field of the light source can be expanded, so that the purpose of emitting light at a specific angle is achieved. The invention further provides a backlight module comprising the optical film and a display device.

Description

Optical film, backlight module and display device Technical Field

[0001] The present invention relates to an optical device, in particular to an optical film with a specific light output angle, a backlight module and a display device. Background Art

[0002] With the upgrade of vehicle features, existing in-vehicle displays, such as those in the center console, require a very wide horizontal viewing angle. However, some vehicles also include screens for the front passenger or other passengers. For safety reasons, display panels not intended for driver viewing require anti-peeping features to avoid interfering with driving. Furthermore, in certain situations, such as digital virtual rearview mirrors (VEMs), which capture the image from the exterior door mirrors and project it onto screens on either side of the door, the viewing angle is highly concentrated on one side. However, existing backlight module architectures cannot meet the specialized viewing angle requirements of in-vehicle displays.

[0003] Summary of the Invention

[0004] Therefore, an object of the present invention is to provide an optical film that can generate light at a specific angle.

[0005] The optical film of the present invention includes a substrate, and a plurality of light-incident microstructures arranged on the substrate. The substrate has a light-incident surface and a light-emitting surface opposite to the light-incident surface. The substrate is defined as having a first extension direction and a second extension direction perpendicular to the first extension direction. The light-incident microstructure is arranged on the light-incident surface of the substrate, and the cross-sectional shape of the light-incident microstructure in the first extension direction is different from the cross-sectional shape in the second extension direction. Each of the light-incident microstructures has a plurality of optical surfaces and a boundary line connecting the plurality of optical surfaces, and the boundary line is a straight line and parallel to the light-incident surface of the substrate.

[0006] Another technical means of the present invention is to define a first projection surface that is perpendicular to the first extension direction, and to define a second projection surface that is perpendicular to the second extension direction. Each of the light-entering microstructures has two first optical surfaces arranged along the second extension direction and opposite to each other, and a second optical surface and a third optical surface arranged along the first extension direction and opposite to each other, wherein the shape of each first optical surface projected onto the second projection surface is an asymmetric triangle, and the two sides are respectively connected to the second optical surface and the third optical surface, the shape of the second optical surface and the third optical surface projected onto the first projection surface is a trapezoid, and the slope of the second optical surface is greater than the slope of the third optical surface, and the boundary line of each of the light-entering microstructures is the connecting edge of the second optical surface and the third optical surface.

[0007] Another technical means of the present invention is that there is an air gap between the first optical surface of any of the light incident microstructures and the first optical surface of the adjacent light incident microstructure, and there is also an air gap between the second optical surface of any of the light incident microstructures and the third optical surface of the adjacent light incident microstructure.

[0008] Another technical means of the present invention is that the shape of each of the first optical surfaces of each of the light incident microstructures projected onto the second projection surface is a right triangle, wherein one base angle is a right angle.

[0009] Another technical means of the present invention is that the second optical surface and the third optical surface of each of the light incident microstructures have two side edges, wherein the side edges are not parallel to the boundary line and are connected to the light incident surface of the substrate.

[0010] Another technical means of the present invention is that the second optical surface of each of the light-incident microstructures is perpendicular to the light-incident surface of the substrate, and the area of ​​the second optical surface of each of the light-incident microstructures projected onto the first projection surface is equal to the area of ​​the second optical surface itself.

[0011] Another technical means of the present invention is that the third optical surface of each of the light-incident microstructures is inclined to the light-incident surface of the substrate, and the area of ​​the third optical surface of each of the light-incident microstructures projected onto the first projection surface is smaller than the area of ​​the third optical surface itself.

[0012] Another technical means of the present invention is that the optical film further includes a plurality of prism structures disposed on the light-emitting surface of the substrate, wherein the prism structures extend along the second extension direction.

[0013] Another technical means of the present invention is that the cross-sectional shape of each of the prism structures in the second extension direction is an isosceles triangle with a right angle as the vertex.

[0014] Another technical means of the present invention is that the cross-sectional shape of each of the prism structures in the second extension direction is a non-isosceles triangle.

[0015] Another technical means of the present invention is that the cross-sectional shape of each of the prism structures in the first extension direction has a first active surface and a second active surface connected to each other, a first angle is formed between the first active surface and the light-emitting surface, and a second angle is formed between the second active surface and the light-emitting surface, the first angle is smaller than the second angle, and the shape of each of the first optical surfaces of each of the light-incident microstructures projected onto the second projection surface is a right triangle, one of the base angles being a right angle, and the first angle and the right angle being located on the same side.

[0016] Another technical means of the present invention is that each of the prism structures is a strip-shaped structure that is concave or convex from the light-emitting surface.

[0017] Another object of the present invention is to provide a backlight module comprising an optical film as described above, and a pair of light-emitting units for projecting light onto the light incident surface of the optical film.

[0018] Another object of the present invention is to provide a display device comprising a backlight module as described above, and a display panel disposed on the backlight module.

[0019] The effectiveness of the present invention lies in utilizing the intersection line of each of the light-entering microstructures to simultaneously connect the multiple optical surfaces and be parallel to the light-entering surface of the substrate. This causes a portion of the light entering from the light-entering surface of the substrate to directly pass through the intersection line without being split, while the other portion of the light is split to both sides. This allows the light to expand the viewing angle along the same axis. Furthermore, the cross-sectional shape of the light-entering microstructure in the first extension direction is different from the cross-sectional shape in the second extension direction. This allows the light to expand the viewing angle along a certain axis while being deflected toward one side to achieve the purpose of emitting light at a specific angle. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG1 is a perspective view of a preferred embodiment of an optical film according to the present invention, wherein the optical film includes a plurality of light-incident microstructures;

[0021] FIG2 is a perspective view showing another perspective of FIG1 flipped 180 degrees vertically to assist in explaining FIG1;

[0022] FIG3 is a top view illustrating FIG2 from another angle;

[0023] FIG4 is a side view illustrating the shape of a first optical surface of the light incident microstructure of the optical film on a second projection surface;

[0024] FIG5 is a side view illustrating the shape of a second optical surface of the light incident microstructure of the optical film on a first projection surface;

[0025] FIG6 is a side view illustrating the shape of a third optical surface of the light incident microstructure of the optical film on the first projection surface;

[0026] FIG7 is a side view of a preferred embodiment of the backlight module of the present invention;

[0027] FIG8 is a simulated energy distribution diagram illustrating the deflection of the energy and viewing angle of light after passing through the optical film of FIG2;

[0028] FIG9 is a schematic diagram illustrating the viewing angle specification of a digital rearview mirror for a vehicle;

[0029] FIG10 is a side view illustrating another form of the multiple prism structures of the optical film in the preferred embodiment;

[0030] FIG11 is a schematic diagram illustrating an enlargement of the area indicated by the box in FIG9 ;

[0031] FIG12 is a simulated energy distribution diagram illustrating the deflection of the energy and viewing angle of light after passing through the optical film of FIG10; and

[0032] FIG13 is a side view of a preferred embodiment of the display device of the present invention. DETAILED DESCRIPTION

[0033] The features and technical content of the related patent applications of this invention will be clearly presented in the following detailed description of the preferred embodiments with reference to the accompanying drawings. Before proceeding with the detailed description, it should be noted that similar components are represented by the same reference numerals. Directional terms mentioned in the following embodiments, such as "up," "down," "left," "right," "front," "back," "bottom," and "top," are merely references to the directions in the accompanying drawings. Therefore, the directional terms used are for illustrative purposes only and are not intended to limit the present invention.

[0034] Referring to Figures 1 and 2, a preferred embodiment of the optical film 2 of the present invention is shown. The optical film 2 includes a substrate 21, and a plurality of light-incident microstructures 22 and a plurality of prism structures 23 disposed on the substrate 21. It should be noted that Figure 2 is an angle after Figure 1 is reversed, and Figure 3 is a top view of Figure 2, which is used to more clearly show the detailed structure of the light-incident microstructure 22. The substrate 21 has a light-incident surface 211 and a light-emitting surface 212 opposite to the light-incident surface 211. The light-incident microstructure 22 is disposed on the light-incident surface 211, and the prism structure 23 is disposed on the light-emitting surface 212. The substrate 21 is defined to have a first extension direction E1 and a second extension direction E2 perpendicular to the first extension direction E1. The cross-sectional shape of the light-incident microstructure 22 in the first extension direction E1 is different from the cross-sectional shape in the second extension direction E2. Each of the light-entering microstructures 22 has a plurality of optical surfaces and a boundary line 220 connecting the plurality of optical surfaces. The boundary line 220 is a straight line and is parallel to the light-entering surface 211 of the substrate 21. The boundary line 220 of each of the light-entering microstructures 22 is used to simultaneously connect the plurality of optical surfaces and is parallel to the light-entering surface 211 of the substrate 21. This causes a portion of the light (as shown by L1 in FIG. 7 ) to directly pass through the boundary line 220 without being split after entering the light-entering surface 211 of the substrate 21, while another portion of the light (as shown by L2 in FIG. 7 ) is split to both sides. This allows the light to expand the viewing angle on the same axis. Furthermore, the cross-sectional shape of the light-entering microstructure 22 in the first extension direction E1 is different from the cross-sectional shape in the second extension direction E2, so that the light can expand the viewing angle on a certain axis while being deflected toward one side to achieve the purpose of emitting light at a specific angle.

[0035] As shown in Figures 2 and 3, each of the light-incident microstructures 22 has two first optical surfaces 221 disposed along the second extension direction E2 and opposite to each other, and a second optical surface 222 and a third optical surface 223 disposed along the first extension direction E1 and opposite to each other. As shown in Figure 3, the two sides of each first optical surface 221 are connected to the second optical surface 222 and the third optical surface 223, respectively.

[0036] Referring to FIG. 1 , a first projection plane P1 is defined as being perpendicular to the first extension direction E1, and a second projection plane P2 is defined as being perpendicular to the second extension direction E2. Referring to FIG. 1 and FIG. 4 , the shape of each first optical surface 221 of each light-incident microstructure 22 projected onto the second projection plane P2 is an asymmetric triangle. Referring to FIG. 1 and FIG. 5 , the shape of the second optical surface 222 projected onto the first projection plane P1 is a trapezoid. Referring to FIG. 1 and FIG. 6 , the shape of the third optical surface 223 projected onto the first projection plane P1 is also a trapezoid. As shown in FIG. 4 , the slope of the second optical surface 222 is greater than the slope of the third optical surface 223. Due to the trapezoidal design, as shown in the second optical surface 222 of Figure 2 or the third optical surface 223 of Figure 3, in addition to generating a top edge of the trapezoid (intersection line 220) parallel to the light incident surface 211 of the substrate 21, there are also side edges 224 of the trapezoid inclined to the light incident surface 211 of the substrate 21. Therefore, it is easier to cause a portion of the light to pass directly through the top edge of the trapezoid without being split, while the other portion of the light is split to both sides by the side edges 224 of the trapezoid on both sides. This allows the light to produce a splitting effect on the same axis (for example, the second extension direction E2) and expand the viewing angle. On the other axis (for example, the first extension direction E1), because the cross-sectional shape of the light incident microstructure 22 in the first extension direction E1 (the first optical surface 221 in FIG. 2 is an asymmetric triangle) is different from the cross-sectional shape in the second extension direction E2 (the second optical surface 222 in FIG. 2 is a trapezoid), the light does not produce a splitting effect on the other axis (for example, the first extension direction E1). Instead, the asymmetric triangle design is used to produce a light deflection effect, so that the light can expand the viewing angle on a certain axis and be deflected toward one side at the same time.

[0037] Furthermore, the shape of each of the first optical surfaces 221 of each of the light incident microstructures 22 projected onto the second projection plane P2 is a right triangle, with one base angle being a right angle, as shown in FIG. 4 .

[0038] Through the above-mentioned right-angled triangle design, the light will hardly be deflected on the right-angled surface, while the light deflection effect will be produced at the oblique angle surface with the maximum proportion. In this way, the light can be deflected toward one side with the maximum proportion and greater advantage in the axial direction where no splitting effect is produced (that is, the first extension direction E1).

[0039] 1 and 4 , the second optical surface 222 of each light-incident microstructure 22 is perpendicular to the light-incident surface 211 of the substrate 21, while the first projection plane P1 is perpendicular to the first extension direction E1 and also perpendicular to the light-incident surface 211 of the substrate 21. Therefore, the area of ​​the second optical surface 222 of each light-incident microstructure 22 projected onto the first projection plane P1 is equal to the area of ​​the second optical surface 222 itself. Furthermore, the third optical surface 223 of each light-incident microstructure 22 is inclined relative to the light-incident surface 211 of the substrate 21, and the area of ​​the third optical surface 223 of each light-incident microstructure 22 projected onto the first projection plane P1 is smaller than the area of ​​the third optical surface 223 itself.

[0040] 2 and 3 , the boundary line 220 of each of the light-incident microstructures 22 is the connecting edge between the second optical surface 222 and the third optical surface 223. Furthermore, the second optical surface 222 and the third optical surface 223 of each of the light-incident microstructures 22 have two side edges 224, wherein the side edges 224 are not parallel to the boundary line 220 and are connected to the light-incident surface 211 of the substrate 21.

[0041] 2 , an air gap 24 is formed between the first optical surface 221 of any light-incident microstructure 22 and the first optical surface 221 of an adjacent light-incident microstructure 22. An air gap 24 is also formed between the second optical surface 222 of any light-incident microstructure 22 and the third optical surface 223 of an adjacent light-incident microstructure 22. With this design, all the light-incident microstructures 22 are separated from each other and not connected together, whether in the first extension direction E1 or the second extension direction E2. This facilitates the generation of light-splitting or light-deflecting effects without interference from other strip-shaped structures that could affect the optical effect.

[0042] 1 and 4 , in this embodiment, the cross-sectional shape of each of the prism structures 23 in the second extension direction E2 (equivalent to the shape projected onto the second projection plane P2) is an isosceles triangle with a right-angled vertex. This design enhances the brightness enhancement effect when light leaves the light-emitting surface 212.

[0043] Referring to FIG7 , the backlight module of the present invention comprises a light source 3, a diffuser plate 4 arranged on the light-emitting side of the light source 3, a plurality of films 5, and the aforementioned optical film 2. The light from the light source 3 first passes through the diffuser plate 4 to form a relatively uniform surface light source 3 and then passes through the optical film 2. Referring to FIG5 , after the light passes through the optical film 2, a portion of the light (such as the light L1) will pass through the intersection line 220 of the light-entering microstructure 22 and exit along the front-viewing direction, while a portion of the light (such as the light L2) can exit along the side-viewing direction through the action of the light-entering microstructure 22. The front-viewing direction referred to here refers to the direction in which the light is parallel to the normal of the optical film 2, and there is an angle between the side-viewing direction and the front-viewing direction. In this way, part of the straight light can be converted into other viewing directions to expand the size of the viewing angle in a certain direction (such as the vertical direction). In addition, referring to FIG. 4 , in the first extension direction E1, each of the light-entering microstructures 22 is asymmetrical. The second optical surface 222 is a vertical trapezoidal surface, while the third optical surface 223 is an inclined trapezoidal surface. Therefore, when a portion of light passes through the light-entering microstructure 22, the third optical surface 223 of the light-entering microstructure 22 effectively deflects the light toward a specific lateral direction. Furthermore, because the second optical surface 222 is perpendicular to the light-entering surface 211 and the light source 3 below, it hardly refracts the light, effectively suppressing the light extraction efficiency of the second optical surface 222 and generating a maximum deflection effect on the third optical surface 223. This allows light to be concentrated toward one side in the axial direction (i.e., the first extension direction E1) where no light splitting effect occurs, with the greatest possible advantage. Through the above design, referring to the simulated energy distribution diagram in Figure 8, the optical film 2 of this preferred embodiment can generate stronger energy in the dark area between ±20 degrees in the vertical direction, while generating the strongest light energy in the dark area near -10 degrees horizontally. In addition to being able to adjust the vertical viewing angle, it can further guide and deflect light to a specific angle.

[0044] Refer to Figure 9, which illustrates the viewing angle specifications for automotive digital rearview mirrors. Depending on the viewing position, a digital rearview mirror can be divided into Area A+, Area A, and Area B, with different light output requirements for each area. Therefore, when the preferred embodiment of the optical film of the present invention is applied to an automotive digital rearview mirror, the simulated energy distribution diagram in Figure 8 can meet the viewing angle specifications for Area A+ and Area A. The darker area near -10 degrees in Area A+ produces the strongest light energy, while the lighter area extends to nearly -40 degrees in Area A, meeting the light output requirements.

[0045] Referring to Figures 10 and 11 , in some embodiments, the cross-sectional shape of each prismatic structure 23 in the second extension direction E2 is a non-isosceles triangle. The cross-sectional shape of each prismatic structure 23 in the first extension direction E1 includes a first active surface 231 and a second active surface 232 connected to each other. The first active surface 231 forms a first angle θ1 with the light-emitting surface 212, and the second active surface 232 forms a second angle θ2 with the light-emitting surface 212. The first angle θ1 is smaller than the second angle θ2. As previously described, from the perspective of Figure 11 , one of the base angles of each of the first optical surfaces 221 of each of the light-incident microstructures 22 is a right angle, and the first angle θ1 and the right angle are located on the same side. That is, in the first extension direction E1, the tip of each prismatic structure 23 and the tip of each of the light-incident microstructures 22 face different directions. This design allows light to be deflected and emitted in a controlled manner after passing through the optical film 2. As shown in the simulated energy distribution in Figure 12, the light energy is adjusted to be strongest in the darker areas near 0 degrees in Area A+, reducing the deflection effect of light in Area A+ toward the left of the negative horizontal value. However, all light energy above 20 degrees on the right side of the horizontal direction is shifted to the left of the negative horizontal value, extending the light-colored area further to Area B near -50 degrees, more closely meeting the viewing angle specifications for Areas A+, A, and B in automotive digital rearview mirrors.

[0046] It should be noted that, in this embodiment, each of the prism structures 23 is a strip-shaped structure protruding from the light-emitting surface 212. In some embodiments, each of the prism structures 23 may also be a strip-shaped structure recessed into the light-emitting surface 212.

[0047] 13 , a display panel 6 is disposed on the backlight module, which is the display device of the present invention.

[0048] In summary, the present invention primarily utilizes the design of the light-entering microstructures 22 on the optical film 2 to redirect some direct light into alternate viewing angles, thereby enhancing the overall field of view. Furthermore, light can be deflected toward specific angles to meet the viewing angle requirements of various in-vehicle display devices, effectively achieving the present invention's objectives.

[0049] However, the above is only a preferred embodiment of the present invention and should not be used to limit the scope of implementation of the present invention. In other words, simple equivalent changes and modifications made according to the claims and the description of the invention are still within the scope of the patent of the present invention.

[0050] [Explanation of Symbols] 2 Optical film 21 Substrate 211 Light incident surface 212 Light exit surface 22 Light incident microstructure 220 Boundary line 221 First optical surface 222 Second optical surface 223 Third optical surface 224 Side 23 Prism structure 24 Air gap 3 Light source 4 Diffuser plate 5 Film 6 Display panel A+ Area A Area B Area E1 First extension direction E2 Second extension direction L1 Light L2 Light P1 First projection surface P2 Second projection surface Angle θ1 First angle θ2 Second angle

Claims

1. An optical film, comprising: The substrate has a light incident surface and a light emitting surface opposite to the light incident surface, wherein The substrate is defined to have a first extension direction and a second extension direction perpendicular to the first extension direction; and A plurality of light incident microstructures are disposed on the light incident surface of the substrate, wherein the cross-sectional shape of the light incident microstructure in the first extension direction is different from the cross-sectional shape in the second extension direction, wherein each of the light incident microstructures has a plurality of optical surfaces and a boundary line connecting the plurality of optical surfaces, and the boundary line is a straight line and parallel to the light incident surface of the substrate.

2. The optical film according to claim 1, wherein: A first projection plane is defined to be perpendicular to the first extension direction, and a second projection plane is defined to be perpendicular to the second extension direction. Each of the light-entering microstructures has two first optical surfaces arranged along the second extension direction and opposite to each other, and a second optical surface and a third optical surface arranged along the first extension direction and opposite to each other, wherein the shape of each of the first optical surfaces projected onto the second projection plane is an asymmetric triangle, and the two sides are respectively connected to the second optical surface and the third optical surface, the shape of the second optical surface and the third optical surface projected onto the first projection plane is a trapezoid, and the slope of the second optical surface is greater than the slope of the third optical surface, and the boundary line of each of the light-entering microstructures is the connecting edge of the second optical surface and the third optical surface.

3. The optical film according to claim 2, wherein: An air gap is formed between the first optical surface of any light incident microstructure and the first optical surface of an adjacent light incident microstructure, and an air gap is formed between the second optical surface of any light incident microstructure and the third optical surface of an adjacent light incident microstructure.

4. The optical film according to claim 2, wherein: The shape of each of the first optical surfaces of each of the light-incident microstructures projected onto the second projection surface is a right triangle, wherein one base angle is a right angle.

5. The optical film according to claim 2, wherein: The second optical surface and the third optical surface of each of the light incident microstructures have two side edges, wherein the side edges are not parallel to the boundary line, and the side edges are connected to the light incident surface of the substrate.

6. The optical film according to claim 2, wherein: The second optical surface of each of the light incident microstructures is perpendicular to the light incident surface of the substrate, and the area of ​​the second optical surface of each of the light incident microstructures projected onto the first projection surface is equal to the area of ​​the second optical surface itself.

7. The optical film according to claim 6, wherein: The third optical surface of each of the light incident microstructures is inclined to the light incident surface of the substrate, and the area of ​​the third optical surface of each of the light incident microstructures projected onto the first projection surface is smaller than the area of ​​the third optical surface itself.

8. The optical film according to any one of claims 1 to 7, further comprising a plurality of prism structures disposed on the light-emitting surface of the substrate, wherein: The prism structure extends along the second extension direction.

9. The optical film according to claim 8, wherein: The cross-sectional shape of each of the prism structures in the second extension direction is an isosceles triangle with a right angle at the top.

10. The optical film according to claim 8, wherein: The cross-sectional shape of each of the prism structures in the second extension direction is a non-isosceles triangle.

11. The optical film according to claim 10, wherein: The cross-sectional shape of each of the prism structures in the first extension direction comprises a first active surface and a second active surface which are connected, a first angle being formed between the first active surface and the light emitting surface, a second angle being formed between the second active surface and the light emitting surface, the first angle being smaller than the second angle, and the shape of each of the first optical surfaces of each of the light incident microstructures projected onto the second projection surface is a right triangle, one of the base angles being a right angle, and the first angle and the right angle being located on the same side.

12. The optical film according to claim 8, wherein: Each of the prism structures is a strip-shaped structure concave or convex from the light-emitting surface. 13 . A backlight module, comprising the optical film according to claim 1 , and a light-emitting unit, wherein the light-emitting unit projects light onto a light incident surface of the optical film.

14. A display device, comprising the backlight module as claimed in claim 13, and a display panel arranged on the backlight module.

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