Optical film, optical film group, backlight module and display device

Abstract

The invention relates to an optical film, an optical film set, a backlight module and a display device. The optical film comprises a body, a plurality of first prism structures and a plurality of second prism structures. The body has a first optical surface and a second optical surface opposite to each other. The first prism structure is arranged on the first optical surface. Each first prism structure has a first extension direction. The second prism structure is arranged on the second optical surface. Each second prism structure has a second extension direction. The first extension direction is different from the second extension direction.

Description

Technical Field

[0001] The present disclosure relates to an optical film and its applications, and particularly to an optical film, an optical film group, a backlight module using the optical film and the optical film group, and a display device that can generate a larger light-emitting viewing angle. Background Art

[0002] For vehicle-mounted displays defined by the European Union, considering the viewing angles of the driver and co-driver, a viewing angle specification (Deutsches Flachdisplay Forum) has been established, and current in-vehicle product specifications are designed with reference to this specification.

[0003] Currently, the prism sheets used in backlight modules are mainly used to concentrate the light to emit in the direction of the normal viewing angle. However, since vehicle-mounted displays are installed below the line of sight and the Center Informative Display (CID) needs to be designed so that both the driver and co-driver can view it. Therefore, the viewing angle specification shows a distribution with a relatively narrow upper viewing angle (within 20 degrees for the upper viewing angle and within 15 degrees for the lower viewing angle) and a relatively wide left and right viewing angle (within 50 degrees for the left and right viewing angles), which is very different from the viewing angle requirements of general tablet computers or notebook computers.

[0004] Generally speaking, although the viewing angle can be reduced by an anti-peeping film, the energy loss of the anti-peeping film is quite large. If only by increasing the overall brightness can the brightness at a large viewing angle reach the desired value, there is also a problem of power consumption. Therefore, how to develop an optical film that meets specific viewing angles and brightness when applied to a display device and can achieve power-saving purposes is the motivation for the invention of this case. Summary of the Invention

[0005] Therefore, an object of the present disclosure is to provide an optical film and an optical film group that can be applied to a backlight module and a display device to meet specific viewing angles.

[0006] According to the above object of the present disclosure, an optical film is proposed. This optical film includes a body, a plurality of first prism structures, and a plurality of second prism structures. The body has opposite first and second optical surfaces. The first prism structures are disposed on the first optical surface, and each of the first prism structures has a first extending direction. The second prism structures are disposed on the second optical surface, and each of the second prism structures has a second extending direction. Wherein, the first extending direction is different from the second extending direction.

[0007] According to an embodiment of the present disclosure, the above-mentioned first prism structure has an arrangement density Y, and each first prism structure has a first side surface and a second side surface that are connected to each other, and there is an included angle X between the first side surface and the second side surface, where the arrangement density Y and the included angle X satisfy a relational expression, and the relational expression is Y≥-0.88 + 0.064X - 9.77778×10 -4 X 2 + 4.44444×10 -6 X 3 。

[0008] According to an embodiment of the present disclosure, there is a blank portion between the above-mentioned first prism structures, and the arrangement density Y is calculated according to a function, where the function is Y = (P1 - W1) / P1. Wherein, P1 is the distance between any two adjacent first prism structures, and W1 is the width of each blank portion.

[0009] According to an embodiment of the present disclosure, each of the above-mentioned first prism structures is a strip structure that is recessed or protruded from the first optical surface.

[0010] According to an embodiment of the present disclosure, the included angle between the above-mentioned first extension direction and the second extension direction is 90 degrees.

[0011] According to an embodiment of the present disclosure, when a light ray enters the body from one of the first optical surface and the second optical surface and exits from the other of the first optical surface and the second optical surface, the exit angle of a part of the light rays falls between -10 degrees and +10 degrees with respect to the normal direction of the light ray exit surface, and the exit angle of another part of the light rays falls between -40 degrees and +40 degrees with respect to the normal direction of the light ray exit surface. The ratio of the light output amount with the exit angle falling between -10 degrees and +10 degrees to the light output amount with the exit angle falling between -40 degrees and +40 degrees is greater than 0.57, including the end point values.

[0012] According to an embodiment of the present disclosure, when a light ray enters the body from one of the first optical surface and the second optical surface and exits from the other of the first optical surface and the second optical surface, most of the light rays exit along a front view direction, and this front view direction is parallel to the normal direction of the light ray exit surface, and a small part of the light rays exit along a side view direction, and the included angle between this side view direction and the front view direction is greater than 30 degrees, including the end point values.

[0013] According to the above object of the present disclosure, another backlight module is proposed. The backlight module includes a light guide plate, a light source, the above-mentioned optical film, and a film group. The light guide plate has a light incident surface and a light exit surface. The light source is adjacent to the light incident surface. The optical film is disposed in front of the light exit surface. The film group is located between the optical film and the light guide plate.

[0014] According to the above object of the present disclosure, a backlight module is provided. The backlight module includes a light source and the above optical film. The light source includes a substrate and a plurality of light-emitting units arranged on the substrate. The optical film is disposed in front of the light source.

[0015] According to the above object of the present disclosure, a display device is provided. The display device includes the above backlight module and a display panel. The display panel is disposed in front of the backlight module.

[0016] According to the above object of the present disclosure, an optical film group is provided. The optical film group includes a first film and a second film. The first film has a first optical surface and a plurality of first prism structures, wherein the first prism structures are disposed on the first optical surface, and each first prism structure has a first extending direction. The second film has a second optical surface and a plurality of second prism structures, wherein the first optical surface and the second optical surface face opposite directions respectively, the second prism structures are disposed on the second optical surface, and each second prism structure has a second extending direction. Wherein the first extending direction is different from the second extending direction.

[0017] According to an embodiment of the present disclosure, the above first prism structure has an arrangement density Y, and each first prism structure has a first side surface and a second side surface connected to each other, and there is an included angle X between the first side surface and the second side surface, wherein the arrangement density Y and the included angle X satisfy a relational expression, and the relational expression is Y≥-0.88 + 0.064X - 9.77778×10 -4 X 2 + 4.44444×10 -6 X 3 。

[0018] According to an embodiment of the present disclosure, there is a blank portion between any two adjacent first prism structures, and the arrangement density Y is calculated according to a function, where the function is Y=(P1 - W1) / P1, where P1 is the distance between any two adjacent first prism structures, and W1 is the width of each blank portion.

[0019] According to an embodiment of the present disclosure, each of the above first prism structures is a strip structure recessed or protruding from the first optical surface.

[0020] According to an embodiment of the present disclosure, the included angle between the first extending direction and the second extending direction is 90 degrees.

[0021] According to an embodiment of the present disclosure, when light enters from one of the first optical surface and the second optical surface and exits from the other of the first optical surface and the second optical surface, the exit angles of a part of the light fall between -10 degrees and +10 degrees relative to the normal direction of the light exit surface, and the exit angles of another part of the light fall between -40 degrees and +40 degrees relative to the normal direction of the light exit surface. The ratio of the light output with exit angles between -10 degrees and +10 degrees to the light output with exit angles between -40 degrees and +40 degrees is greater than 0.57, including the endpoint values.

[0022] According to an embodiment of the present disclosure, when light enters from one of the first optical surface and the second optical surface and exits from the other of the first optical surface and the second optical surface, most of the light exits along a front view direction, and this front view direction is parallel to the normal direction of the light exit surface, and a small part of the light exits along a side view direction, and the included angle between this side view direction and the front view direction is greater than 30 degrees, including the endpoint values.

[0023] For the above purpose of the present disclosure, a backlight module is further proposed. The backlight module includes a light guide plate, a light source, the above optical film stack, and a film stack. The light guide plate has a light incident surface and a light exit surface. The light source is adjacent to the light incident surface. The optical film stack is disposed in front of the light exit surface. The film stack is located between the optical film and the light guide plate.

[0024] For the above purpose of the present disclosure, a backlight module is proposed. The backlight module includes a light source and the above optical film stack. The light source includes a substrate and a plurality of light emitting units arranged on the substrate. The optical film is disposed in front of the light source.

[0025] For the above purpose of the present disclosure, a display device is proposed. The display device includes the above backlight module and a display panel. The display panel is disposed in front of the backlight module.

[0026] As can be seen from the above, the present disclosure mainly designs the first prism structure and the second prism structure on the optical film or the optical film stack, which can convert part of the direct light into other viewing angle directions, thereby improving the overall viewing range. Without increasing the current to improve the overall brightness, it can meet a specific viewing angle. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] To more fully understand the embodiments and their advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which:

[0028] Figure 1 A schematic diagram showing an optical film applied to a direct-lit backlight module according to an embodiment of the present disclosure;

[0029] Figure 2Partial schematic diagram of an optical film according to an embodiment of the present disclosure;

[0030] Figure 3 Schematic diagram showing the viewing angle specification of a conventional EU-defined vehicle display;

[0031] Figure 4 Graph showing the relationship between the included angle (X) and the arrangement density (Y) of a first prism structure according to an embodiment of the present disclosure;

[0032] Figure 5 Schematic diagram showing the ratio of the side-view light output to the front-view light output generated by an optical film using first prism structures with different angles and different arrangement densities according to an embodiment of the present disclosure;

[0033] Figure 6A Schematic diagram of the simulated light output brightness of each viewing angle of a conventional optical film;

[0034] Figure 6B Schematic diagram of the simulated light output brightness of each viewing angle of an optical film with a first prism structure according to an embodiment of the present disclosure;

[0035] Figure 7 Graph showing the relationship between the viewing angle and the brightness simulated using an optical film according to an embodiment of the present disclosure and an optical film of a comparative example;

[0036] Figure 8 Schematic diagram showing an optical film according to an embodiment of the present disclosure applied to a direct-lit backlight module;

[0037] Figure 9 Schematic diagram showing an optical film according to an embodiment of the present disclosure applied to a side-lit backlight module;

[0038] Figure 10 Schematic diagram of a display device according to an embodiment of the present disclosure;

[0039] Figure 11 Schematic diagram showing an optical film group according to an embodiment of the present disclosure applied to a direct-lit backlight module;

[0040] Figure 12 Partial schematic diagram of an optical film group according to an embodiment of the present disclosure;

[0041] Figure 13 Schematic diagram showing an optical film group according to an embodiment of the present disclosure applied to a side-lit backlight module; and

[0042] Figure 14A schematic diagram of a display device according to another embodiment of the present disclosure is shown. Detailed Embodiment

[0043] Please refer to Figure 1 , which is a schematic diagram showing an optical film applied to a direct-lit backlight module according to an embodiment of the present disclosure. The optical film 100 of this embodiment can be mainly applied to the direct-lit backlight modules 200 and 500 as shown in Figure 1 and Figure 8 , or applied to the edge-lit backlight module 300 as shown in Figure 9 to increase the light-emitting viewing angle of the backlight module 200 or the backlight module 300. In the backlight module 200 shown in Figure 1 , the optical film 100 is disposed in front of the light source 210. Among them, the light source 210 includes a substrate 211 and a plurality of light-emitting units 212 arrayed on the substrate 211. Thereby, the light provided by the light source 210 can directly pass through the optical film 100 and exit from the optical film 100.

[0044] As shown in Figure 1 , the optical film 100 of this embodiment includes a body 110, a plurality of first prism structures 120, and a plurality of second prism structures 130. Among them, the body 110 has a first optical surface 111 and a second optical surface 112. The first prism structures 120 are disposed on the first optical surface 111, and the second prism structures 130 are disposed on the second optical surface 112. As shown in Figure 1 , the first prism structure 120 has a first extension direction D1, and the second prism structure 130 has a second extension direction D2, where the first extension direction D1 is different from the second extension direction D2. Thereby, when light enters the optical film 100 from the first optical surface 111, the first prism structure 120 can convert some of the direct light into light in other directions, and then the deflected light exits through the second prism structure 130 on the second optical surface 112. Specifically, as shown in Figure 1As shown, when light passes through the optical film 100, a part of the light (such as light L1) can pass through the blank part S1 between the first prism structures 120 and exit light along the front view direction, and a part of the light (such as light L2) can pass through the action of the first prism structure 120 and exit light along the side view direction. Among them, the front view direction referred to here means that the light is parallel to the normal direction of the optical film 100, and there is an angle θ between the side view direction and the front view direction, where. More specifically, the front view direction is parallel to an exit light normal of the optical film 100, and the angle θ between the side view direction and the exit light normal is greater than 40 degrees, including the end point values. In this way, the optical film 100 of the present embodiment can further convert part of the direct light into other viewing angle directions, adjust the size of the horizontal viewing angle, expand the viewing angle, and meet specific viewing angles and brightness without increasing the current to improve the overall brightness, while achieving the purpose of power saving.

[0045] In this embodiment, each first prism structure 120 is a strip structure protruding from the first optical surface 111. In other embodiments, the first prism structure 120 may also be a strip structure recessed from the first optical surface 111. In some embodiments, the included angle between the first extension direction D1 and the second extension direction D2 is 90 degrees. Please also refer to Figure 2 , Figure 2 is a partial schematic diagram of an optical film according to an embodiment of the present disclosure. In one embodiment, each first prism structure 120 has a first side surface 121 and a second side surface 122 connected to each other, and there is an included angle X between the first side surface 121 and the second side surface 122. The first prism structure 120 has an arrangement density, and there is a spacing P1 between any two adjacent first prism structures 120, and the blank part S1 has a width W1. Among them, the arrangement density is calculated according to a function, and the function is expressed as follows: Y=(P1-W1) / P1.

[0046] In this embodiment, when the light passes through the optical film 100 and the ratio of the light output amount of the light L2 exiting from the side view direction to the light output amount of the light L1 exiting from the front view direction is greater than or equal to 0.4, that is, when the ratio of the side view light output amount to the front view light output amount of the optical film 100 needs to be 40% or more, the design of the first prism structure 120 must satisfy a relational expression: This relational expression is Y≥0.441+0.01249X-3.2875*10 -4 X 2 +1.95833*10 -6 X 3 .

[0047] Please refer to Figure 3 and Table 1, Figure 3To illustrate a schematic diagram of the viewing angle specification for a vehicle-mounted display defined by the European Union. In a viewing angle specification for a vehicle-mounted display defined by the European Union (Deutsches Flachdisplay Forum), in order to simultaneously consider the viewing angles of the driver and co-driver seats, for example Figure 3 In the shown regions A+, A, and B, it is stipulated that the ratio of the light output amount of the light emitted from the side view direction (i.e., the luminance of region B) to the light output amount of the light emitted from the front view direction (i.e., the luminance of region A+) of the vehicle-mounted display should be at least greater than 37.5%. And in this embodiment, a higher standard than the viewing angle specification for a vehicle-mounted display defined by the European Union is adopted, requiring that the ratio of the light output amount of the light emitted from the side view direction to the light output amount of the light emitted from the front view direction is greater than or equal to 40% (i.e., greater than 37.5%). Therefore, using the relational expression of this embodiment to design the optical film 100 can expand the light output viewing angle and meet the requirement of the vehicle-mounted display defined by the European Union that the luminance ratio of region B must be greater than 37.5%.

[0048] Table 1 Figure 3 The viewing angle range of each region in and the European Union viewing angle specification

[0049]

[0050] Please also refer to Figure 4 and Figure 5 , where Figure 4 is a relational curve diagram showing the relationship between the angle (X) and the arrangement density (Y) of a first prism structure according to an embodiment of the present disclosure, Figure 5 is a schematic diagram showing the ratio of the side view light output amount to the front view light output amount generated by the optical film using the first prism structures with different angles and different arrangement densities according to an embodiment of the present disclosure. From Figure 4 and Figure 5 it can be seen that when the ratio of the side view light output amount to the front view light output amount of the optical film 100 is required to be 40%, the angle X of the first prism structure 120 can be set to 40 degrees and the arrangement density to 54%, or the angle X of the first prism structure 120 can be set to 60 degrees and the arrangement density to 43%, or the angle X of the first prism structure 120 can be set to 90 degrees and the arrangement density to 33%, or the angle X of the first prism structure 120 can be set to 120 degrees and the arrangement density to 59%, so as to generate the required specific light output viewing angle.

[0051] Please also refer to Figure 6A and Figure 6B , Figure 6A is a schematic diagram of the simulated light output luminance of each viewing angle of a conventional optical film, Figure 6B is a schematic diagram of the simulated light output luminance of each viewing angle of the optical film with the first prism structure according to an embodiment of the present disclosure. Compared with Figure 6ASchematic diagram of brightness simulation of a conventional optical film, it can be clearly seen that Figure 6B In the embodiment of Figure 6B , the dark area will be separated into two areas, reducing the light emission brightness in the front view angle to reduce the light emission energy loss in the front view angle, and increasing the side view angle brightness of the driver's and passenger's seats. As for the general prism sheet or the film sheet comparative example that does not meet the relational expression, the dark area cannot be separated into two areas and the object of the present invention cannot be achieved.

[0052] It should be noted that the present disclosure is not limited to the above angles and arrangement densities. Using the relational expression of the present disclosure, the included angle X and the arrangement density of the corresponding first prism structure 120 can be calculated according to the ratio requirement of the light emission amount. For example, Figure 4 The curve in Figure 4 represents the relationship curve of the included angle X and the arrangement density of the first prism structure 120 when the ratio of the side view light emission amount to the front view light emission amount of the optical film 100 is equal to 40%. The range above this curve represents the relationship of the included angle X and the arrangement density of the first prism structure 120 corresponding to a higher ratio of the side view light emission amount to the front view light emission amount. Taking the point with the included angle X of 90 degrees as an example, when the included angle X of the first prism structure 120 is 90 degrees, the arrangement density is 33%, and at this time the ratio of the side view light emission amount to the front view light emission amount is 40%. When a higher ratio of the side view light emission amount to the front view light emission amount is required, under the same condition that the included angle X of the first prism structure 120 is 90 degrees, by increasing the arrangement density of the first prism structure 120, for example, setting the arrangement density to be greater than 33%, the purpose of increasing the ratio of the side view light emission amount to the front view light emission amount can be achieved.

[0053] Please also refer to Figure 7 , Figure 7 Figure 7 is a graph showing the relationship between the viewing angle and the brightness simulated by using the optical film 100 of an embodiment of the present disclosure and the optical film of the comparative example. Among them, the optical film of the comparative example is a general single-sided prism sheet. As can be seen from Figure 7 Figure 7 , when the light passes through the general single-sided prism sheet and emits light, the light emission amount is relatively high in the light emission viewing angle range between -40 degrees and +40 degrees; and when the light passes through the optical film 100 of the embodiment of the present disclosure and emits light, although the brightness in the front view angle range from -30 degrees to +30 degrees of the light emitted from the optical film 100 is lower than the front view light emission brightness of the optical film of the comparative example, the light emission amount at the viewing angle positions outside the range of more than -40 degrees to +40 degrees is significantly increased. For example, the relative brightness in the viewing angle ranges of -50 degrees and +50 degrees increases from 0.3 to 0.5. This indicates that the optical film 100 of the present embodiment can reduce the light emission brightness in the front view angle to reduce the light emission energy loss in the front view angle, and increase the side view angle brightness of the driver's and passenger's seats to meet the use requirements of vehicle-mounted displays.

[0054] Please refer to Figure 3, in at least one embodiment of the present invention, when light acts on the optical film 100, when the light output amount between -10 degrees and +10 degrees relative to the normal direction of the light exit surface (i.e., the luminance of region A) and the light output amount between -40 degrees and +40 degrees relative to the normal direction of the light exit surface (i.e., the luminance of region A+) have a ratio greater than or equal to 0.57, that is, when the optical film 100 requires the ratio of the light output amount between -10 degrees and +10 degrees (relative to the normal direction of the light exit surface) to the light output amount between -40 degrees and +40 degrees to be more than 57%, the design of the first prism structure 120 must satisfy a relational expression: this relational expression is Y≥-0.88 + 0.064X - 9.77778*10 -4 X 2 +4.44444*10 -6 X 3 . In this way, it can meet the requirement of the luminance ratio of region A being greater than 56.3% defined by the European Union for vehicle-mounted displays.

[0055] In the embodiment that satisfies the above relational expression, when light acts on the optical film 100, most of the light (such as light L1) can pass through the blank part S1 between the first prism structures 120 and exit along the front view direction (i.e., region A+ between -10 degrees and +10 degrees), and a small part of the light (such as light L2) can exit along the side view direction (i.e., region A between -40 degrees and +40 degrees) through the action of the first prism structure 120. Therefore, at this time, the angle θ between the side view direction and the front view direction is greater than 30 degrees, including the end point values. In this way, the optical film 100 of this embodiment can further convert part of the direct light into other viewing angle directions, adjust the size of the horizontal viewing angle, expand the viewing angle, and meet the specific viewing angle and luminance without increasing the current to improve the overall luminance, thereby achieving the purpose of power saving.

[0056] Please also refer to Figure 8 , Figure 8 , which is a schematic diagram showing an optical film applied to a direct-lit backlight module according to an embodiment of the present disclosure. The backlight module 500 of this embodiment includes a light source 210, a diffusion film 510, a diffusion plate 520, and an optical film 100. In Figure 8 the shown backlight module 500, the optical film 100 is disposed in front of the light source 210. The diffusion film 510 and the diffusion plate 520 are disposed between the light source 210 and the optical film 100. Thereby, the light provided by the light source 210 can pass through the diffusion film 510 and the diffusion plate 520, and then enter the optical film 100, and form a wide viewing angle light output through the action of the optical film 100.

[0057] Please also refer to Figure 9 , Figure 9Schematic diagram of an optical film applied to a side - entry backlight module according to an embodiment of the present disclosure. The optical film 100 of the present embodiment can also be applied to the side - entry backlight module 300. Among them, the backlight module 300 includes a light source 310, a light guide plate 320, a film group 330, and an optical film 100. Among them, the light source 310 is adjacent to the light incident surface 321 of the light guide plate 320, and the optical film 100 is disposed in front of the light exit surface 322 of the light guide plate 320. The film group 330 is disposed between the light guide plate 320 and the optical film 100. Thus, the light provided by the light source 310 can enter the light guide plate 320 to form a surface light source. After exiting, it can pass through the film group 330 and then enter the optical film 100, and form a wide - viewing - angle light output through the action of the optical film 100.

[0058] Please also refer to Figure 10 , which is a schematic diagram of a display device according to an embodiment of the present disclosure. The display device 400 of the present embodiment includes a backlight module 200 as shown in Figure 1 and a display panel 410. The display panel 410 is disposed in front of the backlight module 200. Thus, the display device 400 achieves the purpose of reducing the light output in the front - view angle and increasing the light output in the side - view angle through the design of the optical film 100 in the backlight module 200, so it will not be elaborated here. Among them, in this embodiment, the backlight module 200 as shown in Figure 1 is applied to the display device 400 only for illustrative purposes and is not used to limit the present disclosure. The backlight modules of the foregoing other embodiments (such as Figure 9 the backlight module 300 as shown) can be applied to the display device to produce the same effect of expanding the viewing angle.

[0059] Please refer to Figure 11 , which is a schematic diagram of an optical film group applied to a direct - type backlight module according to an embodiment of the present disclosure. The optical film group 600 of the present embodiment can be mainly applied to a direct - type backlight module 700 as shown in Figure 11 , or applied to a side - entry backlight module 800 as shown in Figure 13 to increase the light - output viewing angle of the backlight module 700 or the backlight module 800. In the Figure 11 shown backlight module 700, the optical film group 600 is disposed in front of the light source 710. Among them, the light source 710 includes a substrate 711 and a plurality of light - emitting units 712 arrayed on the substrate 711. Thus, the light provided by the light source 710 can directly pass through the optical film group 600 and exit from the optical film group 600.

[0060] Such as Figure 11As shown, the optical film stack 600 of the present embodiment includes a first film 610 and a second film 620. Among them, the first film 610 has a first optical surface 612 and a plurality of first prism structures 611, and the second film 620 has a second optical surface 622 and a plurality of second prism structures 621. The first prism structures 611 are disposed on the first optical surface 612, and the second prism structures 621 are disposed on the second optical surface 622. As Figure 11 shown, the first prism structure 611 has a first extension direction D1, and the second prism structure 621 has a second extension direction D2, wherein the first extension direction D1 is different from the second extension direction D2. Thereby, when light enters the optical film stack 600 from the first optical surface 612, the first prism structure 611 can convert part of the direct light into light in other directions, and then the light after turning exits through the second prism structure 621 on the second optical surface 622. Specifically, as Figure 11 shown, when the light is affected by the optical film stack 600, a part of the light (such as light L1) can exit along the front view direction through the blank portion S2 between the first prism structures 611, and a part of the light (such as light L2) can exit along the side view direction after being affected by the first prism structure 611. Among them, the front view direction herein refers to the direction in which the light is parallel to the normal direction of the optical film stack 600, and there is an included angle θ between the side view direction and the front view direction, where. More specifically, the front view direction is parallel to an outgoing light normal of the optical film stack 600, and the included angle θ between the side view direction and the outgoing light normal is greater than 40 degrees, including the end values. In this way, the optical film stack 600 of the present embodiment can further convert part of the direct light into light in other viewing angle directions, adjust the size of the horizontal viewing angle, expand the viewing angle, and meet specific viewing angles and brightness without increasing the current to improve the overall brightness, while achieving the purpose of power saving.

[0061] In this embodiment, each first prism structure 611 is a strip structure protruding from the first optical surface 612. In other embodiments, the first prism structure 611 may also be a strip structure recessed from the first optical surface 612. In some embodiments, the included angle between the first extension direction D1 and the second extension direction D2 is 90 degrees. Please also refer to Figure 12 , Figure 12 is a partial schematic diagram of an optical film stack according to an embodiment of the present disclosure. In one embodiment, each first prism structure 611 has a first side surface 611a and a second side surface 611b connected to each other, and there is an included angle X between the first side surface 611a and the second side surface 611b. The first prism structure 611 has an arrangement density Y, and there is a spacing P1 between any two adjacent first prism structures 611, and the blank portion S2 has a width W1. Among them, the arrangement density is calculated according to a function, and the function is expressed as follows: Y = (P1 - W1) / P1.

[0062] In this embodiment, when the light acts on the optical film group 600, when the ratio of the light output amount of the light L2 emitted from the side view direction to the light output amount of the light L1 emitted from the front view direction is greater than or equal to 0.4, that is, when the ratio of the side view light output amount to the front view light output amount of the optical film group 600 needs to be more than 40%, the design of the first prism structure 611 must satisfy a relational expression: this relational expression is Y≥0.441+0.01249X-3.2875*10 -4 X 2 +1.95833*10 -6 X 3 。

[0063] Similarly, when the light acts on the optical film group 600, when the ratio of the light output amount between -10 degrees and +10 degrees with respect to the normal direction of the light output surface of the light (that is, the luminance of area A) to the light output amount between -40 degrees and +40 degrees with respect to the normal direction of the light output surface of the light (that is, the luminance of area A+) is greater than or equal to 0.57, that is, when the ratio of the light output amount between -10 degrees and +10 degrees (with respect to the normal direction of the light output surface) to the light output amount between -40 degrees and +40 degrees of the optical film group 600 needs to be more than 57%, the design of the first prism structure 611 must satisfy a relational expression: this relational expression is Y≥-0.88+0.064X-9.77778*10 -4 X 2 +4.44444*10 -6 X 3 。Thus, it can meet the requirement of the vehicle-mounted display defined by the EU that the luminance ratio of area A must be greater than 56.3%.

[0064] In the embodiment that satisfies the above relational expression, when the light acts on the optical film group 600, most of the light (such as the light L1) can pass through the blank part S2 between the first prism structures 611 and be emitted along the front view direction (that is, the area A+ between -10 degrees and +10 degrees), and a small part of the light (such as the light L2) can pass through the action of the first prism structure 611 and be emitted along the side view direction (that is, the area A between -40 degrees and +40 degrees). Therefore, at this time, the included angle θ between the side view direction and the front view direction is greater than 30 degrees, including the end point values. In this way, the optical film group 600 of the present embodiment can further convert part of the direct light into other viewing angle directions, adjust the size of the horizontal viewing angle, expand the viewing angle, and meet the specific viewing angle and luminance without increasing the current to improve the overall luminance, while achieving the purpose of power saving.

[0065] Please also refer to Figure 13 , Figure 13Schematic diagram showing an optical film stack applied to a side - lit backlight module according to an embodiment of the present disclosure. The optical film stack 600 of the present embodiment can also be applied to the side - lit backlight module 800. Among them, the backlight module 800 includes a light source 810, a light guide plate 820, a film stack 830, and an optical film stack 600. Among them, the light source 810 is adjacent to the light incident surface 821 of the light guide plate 820, and the optical film stack 600 is disposed in front of the light exit surface 822 of the light guide plate 820. The film stack 830 is disposed between the light guide plate 820 and the optical film stack 600. Thus, after the light provided by the light source 810 enters the light guide plate 820 to form a surface light source for light output, it can pass through the film stack 830 and then enter the optical film stack 600, and form a wide - viewing - angle light output through the action of the optical film stack 600.

[0066] Please also refer to Figure 14 , which is a schematic diagram of a display device according to another embodiment of the present disclosure. The display device 900 of the present embodiment includes a backlight module 700 as shown in Figure 11 and a display panel 910. The display panel 910 is disposed in front of the backlight module 700. Thus, through the design of the optical film stack 600 in the backlight module 700 of the display device 900, the purpose of reducing the light output in the front - view angle and increasing the light output in the side - view angle is also achieved, so it will not be elaborated here. Among them, in this embodiment, the backlight module 700 as shown in Figure 11 is applied to the display device 900 only for illustrative purposes and is not intended to limit the present disclosure. The backlight modules of the foregoing other embodiments (such as Figure 13 the backlight module 800 as shown in) can all be applied to the display device to produce the same effect of expanding the viewing angle.

[0067] As can be seen from the above - mentioned embodiments of the present disclosure, the present disclosure mainly designs the first prism structure and the second prism structure on the optical film or the optical film stack, which can convert part of the direct light into other viewing - angle directions, thereby improving the overall viewing range. Without increasing the current to improve the overall brightness, it can meet a specific viewing angle. On the other hand, the relationship formula of the present disclosure can also be used to design the angle change and arrangement density of the first prism structure and the second prism structure to meet the viewing - angle requirements of different in - vehicle display devices.

[0068]

Symbol Description

[0069] 100: Optical film

[0070] 110: Body

[0071] 111: First optical surface

[0072] 112: Second optical surface

[0073] 120: First prism structure

[0074] 121: First side

[0075] 122: Second side

[0076] 130: Second prism structure

[0077] 200: Backlight module

[0078] 210: Light source

[0079] 211: Substrate

[0080] 212: Light-emitting unit

[0081] 300: Backlight module

[0082] 310: Light source

[0083] 320: Light guide plate

[0084] 321: Light incident surface

[0085] 322: Light exit surface

[0086] 330: Film stack

[0087] 400: Display device

[0088] 410: Display panel

[0089] 500: Backlight module

[0090] 510: Diffusion film

[0091] 520: Diffusion plate

[0092] 600: Optical film stack

[0093] 610: First film

[0094] 611: First prism structure

[0095] 611a: First side

[0096] 611b: Second side

[0097] 611: First optical surface

[0098] 620: Second film

[0099] 621: Second prism structure

[0100] 622: Second optical surface

[0101] 700: Backlight module

[0102] 710: Light source

[0103] 711: Substrate

[0104] 712: Light-emitting unit

[0105] 800: Backlight module

[0106] 810: Light source

[0107] 820: Light guide plate

[0108] 821: Light-incident surface

[0109] 822: Light-emitting surface

[0110] 830: Film stack

[0111] 900: Display device

[0112] 910: Display panel

[0113] A: Region

[0114] B: Region

[0115] A+: Region

[0116] D1: First extension direction

[0117] D2: Second extension direction

[0118] L1: Light ray

[0119] L2: Light ray

[0120] P1: Spacing

[0121] S1: Blank part

[0122] S2: Blank part

[0123] W1: Width

[0124] θ: Included angle

[0125] X: Included angle.

Claims

1. An optical film, characterized in that, Comprising: A body having opposite first and second optical surfaces; A plurality of first prism structures disposed on the first optical surface, wherein each of the plurality of first prism structures has a first extending direction; And A plurality of second prism structures disposed on the second optical surface, wherein each of the plurality of second prism structures has a second extending direction; Wherein the first extending direction is different from the second extending direction.

2. The optical film according to claim 1, wherein The plurality of first prism structures have an arrangement density Y, and each of the plurality of first prism structures has a first side surface and a second side surface connected to each other, and there is an included angle X between the first side surface and the second side surface, wherein the arrangement density Y and the included angle X satisfy a relational expression, and the relational expression is: Y ≥ -0.88 + 0.064X - 9.77778×10 -4 X 2 + 4.44444×10 -6 X 3 。 3. The optical film according to claim 2, wherein There is a blank portion between any two adjacent ones of the plurality of first prism structures, and the arrangement density Y is calculated according to a function, wherein the function is Y = (P1 - W1) / P1, where P1 is the spacing between any two adjacent ones of the plurality of first prism structures, and W1 is the width of each of the plurality of blank portions.

4. The optical film according to claim 1, wherein, Each of the plurality of first prism structures is a strip structure recessed or protruding from the first optical surface.

5. The optical film according to claim 1, characterized in that, The included angle between the first extending direction and the second extending direction is 90 degrees.

6. The optical film according to claim 1, wherein When light enters the body from one of the first optical surface and the second optical surface and exits from the other of the first optical surface and the second optical surface, the exit angle of a part of the light falls between -10 degrees and +10 degrees with respect to the normal direction of the light exit surface, and the exit angle of another part of the light falls between -40 degrees and +40 degrees with respect to the normal direction of the light exit surface, wherein the ratio of the light output amount with the exit angle falling between -10 degrees and +10 degrees to the light output amount with the exit angle falling between -40 degrees and +40 degrees is greater than 0.57, including the end values.

7. The optical film according to claim 1, wherein When light enters the body from one of the first optical surface and the second optical surface and exits from the other of the first optical surface and the second optical surface, most of the light exits along the front view direction, and the front view direction is parallel to the normal direction of the light exit surface, and a small part of the light exits along the side view direction, and the included angle between the side view direction and the front view direction is greater than 30 degrees, including the end values.

8. A backlight module, characterized in that, Comprising: A light guide plate having a light incident surface and a light exit surface; A light source adjacent to the light incident surface; The optical film as described in any one of claims 1 to 7, disposed in front of the light exit surface; A film group located between the optical film and the light guide plate.

9. A backlight module, characterized in that, Comprising: A light source including a substrate and a plurality of light emitting units arranged on the substrate; and The optical film as described in any one of claims 1 to 7, disposed in front of the light source.

10. A display device, characterized in that, Comprising: The backlight module as described in claim 8 or claim 9; and A display panel disposed in front of the backlight module.

11. An optical film stack, characterized in that, Comprising a first film and a second film, wherein: The first film has a first optical surface and a plurality of first prism structures, wherein the plurality of first prism structures are disposed on the first optical surface, and each of the plurality of first prism structures has a first extending direction; The second diaphragm has a second optical surface and a plurality of second prism structures, wherein the first optical surface and the second optical surface face in opposite directions respectively, the plurality of second prism structures are disposed on the second optical surface, and each of the plurality of second prism structures has a second extending direction; and wherein the first extending direction is different from the second extending direction.

12. The optical film stack according to claim 11, wherein, The plurality of first prism structures have an arrangement density Y, and each of the plurality of first prism structures has a first side surface and a second side surface connected to each other, and there is an angle X between the first side surface and the second side surface, wherein the arrangement density Y and the angle X satisfy a relational expression, and the relational expression is: Y ≥ -0.88 + 0.064X - 9.77778×10 -4 X 2 + 4.44444×10 -6 X 3 。 13. The optical film stack according to claim 12, wherein There is a blank portion between any two adjacent ones of the plurality of first prism structures, and the arrangement density Y is calculated according to a function, wherein the function is Y = (P1 - W1) / P1, where P1 is the distance between any two adjacent ones of the plurality of first prism structures, and W1 is the width of each of the plurality of blank portions.

14. The optical film stack according to claim 11, wherein, Each of the plurality of first prism structures is a strip structure recessed or protruding from the first optical surface.

15. The optical film stack according to claim 11, characterized in that, The included angle between the first extending direction and the second extending direction is 90 degrees.

16. The optical film stack according to claim 11, wherein, When light enters from one of the first optical surface and the second optical surface and exits from the other of the first optical surface and the second optical surface, the exit angle of a part of the light falls between -10 degrees and +10 degrees with respect to the normal direction of the light exit surface, and the exit angle of another part of the light falls between -40 degrees and +40 degrees with respect to the normal direction of the light exit surface, wherein the ratio of the light exit amount with the exit angle falling between -10 degrees and +10 degrees to the light exit amount with the exit angle falling between -40 degrees and +40 degrees is greater than 0.57, including the end point values.

17. The optical film stack according to claim 11, wherein When light enters the body from one of the first optical surface and the second optical surface and exits from the other of the first optical surface and the second optical surface, most of the light exits along the front view direction, and the front view direction is parallel to the normal direction of the light exit surface, and a small part of the light exits along the side view direction, and the included angle between the side view direction and the front view direction is greater than 30 degrees, including the end point values.

18. A backlight module, characterized in that, Comprising: A light guide plate having a light incident surface and a light exit surface; A light source adjacent to the light incident surface; The optical film sheet group according to any one of claims 11 to 17, disposed in front of the light exit surface; A film sheet group located between the optical film sheet group and the light guide plate.

19. A backlight module, characterized in that, Comprising: A light source including a substrate and a plurality of light emitting units arranged on the substrate; and The optical film sheet group according to any one of claims 11 to 17, disposed in front of the light source.

20. A display device, characterized in that, Comprising: The backlight module according to claim 18 or claim 19; and A display panel disposed in front of the backlight module.

Images