TWI743897B - Backlight module - Google Patents

Abstract

A backlight module including a light guide plate, a first light source and a first optical film is provided. The light guide plate has a light incident surface, a light exiting surface and a bottom surface, wherein the light incident surface is connected between the light exiting surface and the bottom surface, the light exiting surface is opposite to the bottom surface, and the bottom surface has a plurality of concentric ring-shaped first V-shaped microstructures. The first light source is disposed on a side of light incident surface of the light guide plate, wherein a center of a circle of the first V-shaped microstructures is aligned with the first light source. The first optical film is disposed on a side of the light exiting surface of the light guide plate. The first optical film has a plurality of concentric ring-shaped second V-shaped microstructures.

Description

Backlight module

The present invention relates to an optical module, and particularly relates to a backlight module.

The high-collimation plane light source limits its light-emitting angle to a small range, which can increase the forward brightness and suppress large-angle light. For certain imaging devices, it can reduce power consumption and avoid stray light. Generally speaking, flat light sources with high collimation usually have the following applications.

(1) The flat light source with high collimation degree is small because the light cone angle of the light source is small, so that the human eye must fall within the luminous light cone angle to clearly see the image displayed by the display, so it is suitable for application in privacy function monitor. When the angles of the human eyes to the display are different, the direction of the luminous light cone angle must be switched so that the light cone angle can face the user's eyes, and onlookers away from the user cannot see the displayed image clearly.

(2) Applied to near-eye displays that can switch the direction of the backlight light cone according to the position of the human eye. Since it is difficult to achieve a large area by using a light guide plate with a V-shaped microstructure distributed in concentric circles, it is very suitable for small displays that require backlighting (such as liquid crystal displays). Therefore, a flat light source with high collimation is suitable for virtual reality. Environment, head-mounted display The backlight module of the near-eye display. In these systems, if the NA value of the illumination system is greater than that required for imaging, stray light is easily caused. On the other hand, shrinking the light cone can reduce power consumption and further reduce weight. If the NA value of the illumination system is less than that required for imaging, multiple light cones in different directions can be used to superimpose to achieve the required NA value for imaging. At this time, the direction and size of the superimposed light cone can be further adjusted according to the position of the human eye and the content of the image. In this way, stray light can be reduced, contrast can be increased, and power consumption can be reduced.

(3) The light field display is a light field display composed of sub-images and a microlens array. The NA value required for imaging is relatively small, so the generation of stray light and ghost images can be avoided. By changing the direction of the light-emitting light cone, energy can be transferred in different visible areas. In this way, the image light can be concentrated on the human eye according to the position of the human eye to increase the movable range of the eye.

However, the planar light source with high collimation on the market usually has the problem of asymmetry of the light cone. To achieve a symmetrical light shape, an additional optical film is needed, such as a lenticular film. However, the more optical films are installed, the cost will be further increased.

In addition, there are backlight modules on the market that use holograms instead of V-shaped microstructures to guide light out of the light guide plate. Although its holographic pattern is concentric circles and matched with a point-shaped light source, a relatively uniform light cone can be obtained, but its holographic dispersion characteristics make it difficult to apply to white light.

Therefore, how the planar light source can simultaneously control the size and shape of the light-emitting cone, generate a uniform light cone, and further switch the direction of the light-emitting cone, has become an urgent problem to be overcome.

The present invention provides a backlight module, which can switch the direction of the light-emitting light cone while generating a uniform light cone.

An embodiment of the present invention provides a backlight module, which includes a light guide plate, a first light source, and a first optical film. The light guide plate has a light incident surface, a light exit surface and a bottom surface. The light incident surface is connected between the light exit surface and the bottom surface. The light exit surface is opposite to the bottom surface, and the bottom surface has a plurality of first V-shaped microstructures in a concentric ring shape. The first light source is arranged on one side of the light incident surface of the light guide plate, wherein the centers of the first V-shaped microstructures are aligned with the first light source. The first optical film is arranged on one side of the light emitting surface of the light guide plate. The first optical film has a plurality of second V-shaped microstructures in a concentric ring shape.

In an embodiment of the present invention, the above-mentioned light guide plate and the first optical film are arranged in an arrangement direction, the light guide plate has a direction of a central axis, and the first light source is arranged on the central axis of the light guide plate And the central axis direction is perpendicular to the arrangement direction.

In an embodiment of the present invention, the backlight module further includes at least one second light source. At least one second light source is arranged on one side of the light incident surface of the light guide plate. At least one second light source is arranged spaced apart from the first light source on the light incident surface perpendicular to the arrangement direction.

In an embodiment of the present invention, at least one of the first light source and the at least one second light source is turned on, so that the light shape of the backlight module falls within a specific viewing angle range.

In an embodiment of the present invention, the number of the above-mentioned at least one second light source It is an even number, and at least one second light source is arranged at intervals with the first light source as the center.

In an embodiment of the present invention, the centers of the aforementioned second V-shaped microstructures are aligned with the first light source.

In an embodiment of the present invention, the second V-shaped microstructures of the above-mentioned first optical film are arranged on the surface close to the light emitting surface of the light guide plate.

In an embodiment of the present invention, the backlight module further includes a second optical film. The second optical film is arranged between the light guide plate and the first optical film, and has a plurality of third V-shaped microstructures in a concentric ring shape.

In an embodiment of the present invention, the centers of the aforementioned third V-shaped microstructures are aligned with the first light source.

In an embodiment of the present invention, the third V-shaped microstructures of the above-mentioned second optical film are arranged on the surface away from the light emitting surface of the light guide plate.

In an embodiment of the present invention, the light incident surface of the above-mentioned light guide plate has a diffusion structure. The diffusion structure is an air column or a microstructure array.

In an embodiment of the present invention, the light incident mask of the above-mentioned light guide plate has a light-scattering structure. The astigmatism structure is a divergent lens.

Based on the above, in the backlight module of the embodiment of the present invention, since the bottom surface of the light guide plate has a plurality of first V-shaped microstructures in a concentric ring shape, the center of the first V-shaped microstructure is aligned with the first light source, and A first optical film with a plurality of second V-shaped microstructures in a concentric ring shape is provided, so that the backlight module can have a highly collimated light shape.

100: Backlight module

110: The first light source

112A, 112B, 114A, 114B: second light source

120, 120A, 120B, 120C: light guide plate

120S1: Glossy surface

120S2: bottom surface

120S3: Glossy surface

120S4: side

122, 122A: the first V-shaped microstructure

122C, 130C, 140C: center of circle

130: The first optical diaphragm

132: Second V-shaped microstructure

140: second optical diaphragm

142: The third V-shaped microstructure

150: reflective sheet

B: beam

L: propagation distance

P: Pitch

r: radius

W: effective area

θ: Angle of view

FIG. 1 is a schematic cross-sectional view of a backlight module according to an embodiment of the present invention.

2 is a bottom view of the light guide plate of the backlight module according to an embodiment of the present invention.

3 is a bottom view of the first optical film of the backlight module according to an embodiment of the present invention.

4 is a top view of the second optical film of the backlight module according to an embodiment of the present invention.

5A to 5C are respectively different examples of the light output shape of the backlight module according to an embodiment of the present invention.

FIG. 6 is a curve diagram of the light output brightness of the backlight module with respect to the viewing angle according to an embodiment of the present invention.

7A to 7C are respectively different examples in which the light guide plate of the backlight module according to an embodiment of the present invention has a diffusion structure on the light incident surface.

FIG. 7D is an example of light beam propagation according to the diffusion structure of FIG. 7A.

FIG. 8 is a graph of the light intensity versus angle of the backlight module according to the embodiment of the present invention when the light guide plate has a diffusion structure on the light incident surface.

FIG. 1 is a schematic cross-sectional view of a backlight module according to an embodiment of the present invention. Please refer to FIG. 1, an embodiment of the present invention provides a backlight module 100, which includes It includes a light guide plate 120, a first light source 110, and a first optical film 130, wherein the light guide plate 120 and the first optical film 130 are arranged along an arrangement direction (the Z axis direction in FIG. 1).

2 is a bottom view of the light guide plate of the backlight module according to an embodiment of the present invention. Please refer to FIG. 1 and FIG. 2 at the same time. In this embodiment, the material of the light guide plate 120 may be plastic, glass or other suitable materials for the light beam to penetrate, but the present invention is not limited to this. The light guide plate 120 has a light-incident surface 120S1, a bottom surface 120S2, and a light-emitting surface 120S3. The light-incident surface 120S1 is connected between the light-emitting surface 120S3 and the bottom surface 120S2, and the light-emitting surface 120S3 is opposite to the bottom surface 120S2. In this embodiment, the light guide plate 120 further has a plurality of side surfaces 120S4. The side surface 120S4 can be connected to the light incident surface 120S1, the bottom surface 120S2, and the light exit surface 120S3, or the side surface 120S4 can be connected to the bottom surface 120S2 and the light exit surface 120S3.

In this embodiment, the bottom surface 120S2 of the light guide plate 120 has a plurality of first V-shaped microstructures 122 in a concentric ring shape. In other words, the plurality of first V-shaped microstructures 122 have the same center 122C located at the same position. In this embodiment, the bottom surface 120S2 of the light guide plate 120 also has a flat area between the light incident surface 120S2 and the first V-shaped microstructure 122A, wherein the first V-shaped microstructure 122A is a plurality of first V-shaped microstructures. The structure 122 that is closest to the center 122C. The flat area is adjacent to the light incident surface 120S1 of the light guide plate 120, and the first V-shaped microstructure 122 is not disposed in the flat area. In an embodiment, the radius r of the flat area is, for example, 10 mm. However, the present invention is not limited to this. The radius r of the flat area or the ratio between the area of the flat area and the area of the area where the first V-shaped microstructure 122 is provided should be determined according to design requirements. In the embodiment of the present invention In the backlight module 100 of, since the light guide plate 120 may include a flat area, the problem of the mura hot spot on the side of the light incident surface 120S1 of the light emitting type of the backlight module 100 can be effectively improved.

In addition, in this embodiment, the first light source 110 may be a light-emitting diode (LED) or other suitable light sources. The first light source 110 is preferably a light source with a high Lumen value. The first light source 110 is arranged on one side of the light incident surface 120S1 of the light guide plate 120, the light guide plate 120 has a central axis (not shown) in the direction (the Y-axis direction in FIG. 1), and the first light source 110 is arranged on the light guide plate The center axis direction of 120 is in the direction of the center axis and the center axis direction is perpendicular to the arrangement direction, wherein the center 122C of the first V-shaped microstructure 122 is aligned and corresponds to the first light source 110.

In one embodiment, the backlight module 100 further includes at least one second light source 112A, 112B, 114A, 114B. The second light sources 112A, 112B, 114A, and 114B may be light-emitting diodes (LEDs) or other suitable light sources. The second light source 112A, 112B, 114A, 114B is preferably a light source with a high Lumen value. Furthermore, the second light sources 112A, 112B, 114A, and 114B are arranged on one side of the light incident surface 120S1 of the light guide plate 120. The second light sources 112A, 112B, 114A, and 114B are arranged at intervals with a pitch P as an interval from the first light source 110 on the light incident surface 120S1 perpendicular to the arrangement direction. That is, the first light source 110 and the second light source 112A, 112B, 114A, and 114B are arranged in the X-axis direction.

In this embodiment, the first light source 110 and the second light source 112A, 112B, 114A, 114B are used to emit the light beam B. After penetrating the light incident surface 120S1 of the light guide plate 120, the light beam B is transmitted in the light guide plate 120 in a manner of total reflection. When beam B passes When the first V-shaped microstructure 122 reaches the first V-shaped microstructure 122, the first V-shaped microstructure 122 destroys the total reflection of the light beam B, and makes the light beam B penetrate the light surface 120S3 and pass toward the first optical film 130.

In an embodiment, the number of the second light sources 112A, 112B, 114A, and 114B may be an even number, and the second light sources 112A, 112B, 114A, and 114B are arranged at intervals with the first light source 110 as the center. In addition, FIG. 1 illustrates four second light sources 112A, 112B, 114A, and 114B. However, the present invention is not limited to this. The number of the second light sources 112A, 112B, 114A, and 114B of the backlight module 100 should be set according to the design requirements of the light output shape of the backlight module 100.

In an embodiment, the backlight module 100 further includes a reflective sheet 150. The reflective sheet 150 is disposed on one side of the bottom surface 120S2 of the light guide plate 120. Since a part of the light beam B will be emitted from the bottom surface 120S2 of the light guide plate 120 during the process of passing through the light guide plate 120, the light energy will be lost. Therefore, through the arrangement of the reflective sheet 150, the light beam B emitted from the bottom surface 120S2 of the light guide plate 120 can be reflected and transmitted back to the light guide plate 120, so as to improve the utilization rate of light energy. The reflective sheet 150, the light guide plate 120, and the first optical film 130 are arranged along an arrangement direction (the Z-axis direction in FIG. 1).

3 is a bottom view of the first optical film of the backlight module according to an embodiment of the present invention. Please refer to FIGS. 1 and 3 at the same time. In this embodiment, the first optical film 130 is disposed on one side of the light emitting surface 120S3 of the light guide plate 120. The first optical film 130 is, for example, an optical inverse prism (Turning Film). In addition, the first optical film 130 has a plurality of second V-shaped microstructures 132 in a concentric ring shape, and the second V-shaped microstructures 132 are disposed on a surface close to the light emitting surface 120S3 of the light guide plate 120. Second V The center 130C of the microstructure 132 is aligned and corresponds to the first light source 110.

4 is a top view of the second optical film of the backlight module according to an embodiment of the present invention. Please refer to FIGS. 1 and 4 at the same time. In one embodiment, the backlight module 100 further includes a second optical film 140. The second optical film 140 is, for example, a Brightness Enhancement Film (BEF). Furthermore, the second optical film 140 is disposed between the light guide plate 120 and the first optical film 130, and has a plurality of third V-shaped microstructures 142 in a concentric ring shape. The third V-shaped microstructure 142 of the second optical film 140 is disposed on a surface away from the light emitting surface 120S3 of the light guide plate 120, and the circle center 140C of the third V-shaped microstructure 142 is aligned and corresponds to the first light source 110.

5A to 5C are respectively different examples of the light output shape of the backlight module according to an embodiment of the present invention. FIG. 5A shows the light shape of the backlight module 100 after only the first light source 110 is turned on, and FIG. 5B shows the light shape of the backlight module 100 after only the second light source 112A is turned on, and FIG. After the two light sources 114A, the light shape of the backlight module 100 is emitted. FIG. 6 is a curve diagram of the light output brightness of the backlight module with respect to the viewing angle according to an embodiment of the present invention.

Please refer to FIGS. 5A to 6, when only the first light source 110 is turned on, the first light source 110 is used to make the light shape of the backlight module 100 symmetrically fall within a specific viewing angle range perpendicular to the light emitting surface 120S3 as the center Inside. For example, in FIG. 6, the viewing angle is 0 degrees as the center, and the viewing angle range is 2.5 degrees or less and -2.5 degrees or more. That is, in the above-mentioned embodiment of the present invention, the first light source 110 is arranged on the center of the light incident surface 120S1 in the direction perpendicular to the arrangement direction, the circle center 122C of the first V-shaped microstructure 122 is aligned with the first light source 110, and the first light source 110 The center of the two V-shaped microstructure 132 Under the condition that 130C is aligned with the first light source 110, the light shape of the backlight module 100 is centered at a viewing angle of 0 degrees. However, the present invention is not limited to this, and the position where the first light source 110 is set should be determined by the design of the light output shape of the backlight module 100.

Please refer to FIG. 2 and FIG. 5A to FIG. 6. In FIG. 2, when the first light source 110 and the second light source 112A, 112B, 114A, 114B are all turned on, the light shape of the backlight module 100 can symmetrically fall on Within another specific viewing angle range centered on the light-emitting surface 120S3. For example, in FIG. 6, the viewing angle is 0 degrees as the center, and the viewing angle range is 10 degrees or less and -10 degrees or more. That is, compared to only turning on the first light source 110, when all the light sources are turned on, the light shape of the backlight module 100 falls within a larger viewing angle range.

In another embodiment, at least one of the first light source 110 and the second light source 112A, 112B, 114A, 114B is turned on, so that the light shape of the backlight module 100 falls within another specific viewing angle range. In other words, according to the relative position or angle between the backlight module 100 and the user's line of sight, the user can adjust which light sources need to be turned on so that the light shape of the backlight module 100 falls within the viewing angle range required by the user. Inside. Therefore, the backlight module 100 of the embodiment of the present invention makes the user experience better.

7A to 7C are respectively different examples in which the light guide plate of the backlight module according to an embodiment of the present invention has a diffusion structure on the light incident surface. FIG. 7D is an example of light beam propagation according to the diffusion structure of FIG. 7A. As shown in FIG. 7D, when the light beam B projected by the first light source 110 enters the light guide plate 120A (having a diffusion structure 124A) through the light incident surface 120S1, since the refraction of the light beam B complies with Snell's law, the light beam B After entering the light guide plate 120, the cone angle of the light becomes larger, so that the propagation distance of the light beam B (representing the entrance The distance L) from the light surface 120S1 to the boundary of the effective area W is shortened to increase the effective light emitting area W of the light guide plate 120A. Compared with a light guide plate without a diffusion structure, a too small light cone angle will require a longer light beam B propagation distance, which will reduce the size of the effective area W.

FIG. 8 shows the light intensity distribution of the light cone angle after the light beam B is guided into the light guide plate 120 when the light guide plate has different diffusion structures on the light incident surface. Please refer to FIGS. 7A to 8, in an embodiment, the light incident surface 120S1 of the light guide plate 120A, 120B, 120C has a diffusion structure 124A, 124B, 124C, wherein the diffusion structure 124A is a (semi) air column, and the diffusion structure 124A refers to a groove formed by the light guide plate 120A. The diffusion structures 124B and 124C are microstructure arrays. Furthermore, the material of the diffusion structure 124C is, for example, a material with a high refractive index.

Referring to FIGS. 7A and 8, when the light incident surface 120S1 of the light guide plate 120A of the embodiment of the present invention has a (half) air column diffusion structure 124A, the light cone introduced into the light guide plate 120A is relatively large.

Referring to FIGS. 7B and 8, when the light incident surface 120S1 of the light guide plate 120B of the embodiment of the present invention has the diffusion structure 124B of the microstructure array, the light cones introduced into the light guide plate 120B are more concentrated.

Referring to FIGS. 7C and 8, when the light incident surface 120S1 of the light guide plate 120C of the embodiment of the present invention has the diffusion structure 124C of the microstructure array, the light cone introduced into the light guide plate 120C is relatively uniform.

In another embodiment, the light incident surface 120S1 of the light guide plate 100 may have a diffusive structure, and the diffusive structure is a divergent lens. In other words, when the embodiment of the present invention The backlight module 100 has a diffuser structure 124A, 124B, 124C or a diffuser structure on the light incident surface 120S1 of the light guide plate. The size of the backlight module 100 and the light guide plate 120 can be effectively reduced (under the same effective area size, due to the light The cone becomes larger and has a shorter propagation distance L, as shown in Figure 7D).

In summary, in the backlight module of the embodiment of the present invention, since the bottom surface of the light guide plate has a plurality of first V-shaped microstructures in a concentric ring shape, the center of the first V-shaped microstructure is aligned with the first light source , And a first optical film with a plurality of second V-shaped microstructures in a concentric ring shape is provided. Therefore, the light shape of the backlight module can be symmetrically concentrated in a specific viewing angle range centered on a viewing angle of 0 degrees .

However, the above are only preferred embodiments of the present invention, and should not be used to limit the scope of implementation of the present invention, that is, all simple equivalent changes and modifications made in accordance with the scope of the patent application of the present invention and the content of the description of the invention are all It still falls within the scope of the patent for the present invention. In addition, any embodiment of the present invention or the scope of the patent application does not have to achieve all the objectives or advantages or features disclosed in the present invention. In addition, the abstract part and title are only used to assist in patent search, and are not used to limit the scope of rights of the present invention. In addition, the terms "first" and "second" mentioned in this specification or the scope of the patent application are only used to name the element (element) or to distinguish different embodiments or ranges, and are not used to limit the number of elements. Upper or lower limit.

100: Backlight module

110: The first light source

120: light guide plate

120S1: Glossy surface

120S2: bottom surface

120S3: Glossy surface

122: The first V-shaped microstructure

130: The first optical diaphragm

132: Second V-shaped microstructure

140: second optical diaphragm

142: The third V-shaped microstructure

150: reflective sheet

B: beam

θ: Angle of view

Claims (12)

A backlight module, characterized in that the backlight module comprises: a light guide plate having a light incident surface, a light exit surface and a bottom surface, wherein the light incident surface is connected between the light exit surface and the bottom surface, the The light-emitting surface is opposite to the bottom surface, and the bottom surface has a plurality of concentric ring-shaped and continuous first V-shaped microstructures; a first light source is arranged on one side of the light-incident surface of the light guide plate, wherein the first The center of the V-shaped microstructure is aligned with the first light source; and a first optical film is arranged on one side of the light emitting surface of the light guide plate, and the first optical film has a plurality of concentric rings and continuous The second V-shaped microstructure, wherein the light beam projected by the first light source sequentially passes through the light guide plate and penetrates the first optical film. The backlight module according to claim 1, wherein the light guide plate and the first optical film are arranged in an arrangement direction, the light guide plate has a direction of a central axis, and the first light source is arranged on the light guide plate. The direction of the central axis and the direction of the central axis are perpendicular to the arrangement direction. The backlight module according to claim 2, further comprising: at least one second light source, the number of the at least one second light source is an even number, and is arranged on one side of the light incident surface of the light guide plate, and the at least one second light source The two light sources are arranged at intervals with the first light source as the center on the light incident surface perpendicular to the arrangement direction. The backlight module according to claim 3, wherein at least one of the first light source and the at least one second light source is turned on so that the light shape of the backlight module falls within a specific viewing angle range. The backlight module according to claim 1, wherein the centers of the second V-shaped microstructures are aligned with the first light source. The backlight module according to claim 1, wherein the second V-shaped microstructures of the first optical film are arranged on a surface close to the light emitting surface of the light guide plate. The backlight module according to claim 1, further comprising: a second optical film, which is arranged between the light guide plate and the first optical film, and has a plurality of third V-shaped micro structure. The backlight module according to claim 7, wherein the centers of the third V-shaped microstructures are aligned with the first light source. The backlight module according to claim 7, wherein the third V-shaped microstructures of the second optical film are arranged on a surface away from the light emitting surface of the light guide plate. The backlight module according to claim 1, wherein the light incident mask of the light guide plate has a diffusion structure, and the diffusion structure is an air column or a microstructure array. The backlight module according to claim 1, wherein the light-incident mask of the light guide plate has an astigmatism structure, and the astigmatism structure is a divergent lens. The backlight module according to claim 1, wherein the bottom surface of the light guide plate further has a flat area, and the flat area is located between the first V-shaped microstructure and the center of the first V-shaped microstructures. Between the light-incident surface.

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