JP7445579B2 - backlight module - Google Patents

Description

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

A high-collimation surface light source can improve the brightness in the positive direction and suppress the luminous flux at large angles by limiting its emission angle to one relatively small range. Therefore, power consumption can be reduced and the generation of stray light can be avoided. Generally speaking, highly collimated surface light sources usually have the following applications:

(1) Highly collimated surface light sources have a relatively small light cone angle, so if the human eye is not within the angle of the emitting light cone, the display will not show up. Since the image cannot be viewed, it can be applied to a display device with a privacy function. Switch the orientation of the emissive light cone so that the light cone faces the user's eyes and a bystander away from the user cannot clearly see the displayed image when the person's eyes are at different angles to the display There is a need.

(2) Applied to near-eye displays that can switch the direction of the backlight light cone according to the position of the person's eyes. Because it uses a light guide plate with a V-shaped microstructure arranged in concentric circles, it is difficult to realize a large area, but it is suitable for small displays that require a backlight (for example, liquid crystal displays). very suitable. Therefore, the highly collimated surface light source is suitable as a backlight module for virtual reality, head-mounted displays, and near-eye displays. These systems are prone to stray light if the NA value of the illumination system is larger than that required for imaging. On the other hand, by reducing the size of the light emitting light cone, it is possible to reduce power consumption and further reduce weight. If the illumination system's NA value is smaller than that required for imaging, multiple differently oriented light cones can be used and superimposed to achieve the required NA value for imaging. At this time, the orientation and size of the superimposed light cones can be further adjusted depending on the position of the person's eyes and the content of the image. In this way, stray light can be reduced, contrast increased and power consumption reduced.

(3) Since the light field display is a light field display consisting of a sub-image and a microlens array, and the NA value required for its imaging is relatively small, the generation of stray light and ghost images can be avoided. By changing the direction of the emitting light cone, energy can be transferred in different visible regions. In this way, the image light can be focused on the person's eyes according to the position of the person's eyes, and the range in which the eyes can move can be increased.

However, commercially available highly collimated surface light sources usually have the problem of asymmetrical light emitting light cones. In order to achieve a symmetrical light shape, it is necessary to add an optical film, such as a lenticular film. However, the cost increases as the number of optical films installed increases.

There are also backlight modules on the market that use holograms instead of V-shaped microstructures to guide light flux from a light guide plate. Its holographic pattern is concentric circles, and when used with a point light source, a relatively uniform light cone can be obtained, but its application to white light is difficult due to its holographic dispersion properties. be.

Therefore, how a surface light source can simultaneously control the size and shape of the light cone to generate a uniform light cone and also switch the direction of the light cone is an issue that needs to be overcome as soon as possible. It has become.

Please note that this "Background Art" section is only for helping people understand the content of the present invention, and therefore the content disclosed in this "Background Art" section may not be known to those skilled in the art. May involve technology. Therefore, the content disclosed in this "Background Art" section is based on the fact that the content or the problem to be solved by one or more embodiments of the present invention was already well known to a person skilled in the art before the filing of the present invention. does not mean it has been.

An object of the present invention is to provide a backlight module that can generate a uniform light cone and also switch the direction of the light emitting light cone.

Other objects and advantages of the present invention can be further understood from the technical features disclosed in the present invention.

According to one embodiment of the present invention, a backlight module is provided, which includes a light guide plate, a first light source and a first optical film. The light guide plate has a light input surface, a light output (also referred to as light extraction or light emission) surface, and a bottom surface, of which the light input surface is connected between the light output surface and the bottom surface, and the light output surface is opposite to the bottom surface. The bottom surface has a plurality of concentric annular first V-shaped microstructures. The first light source is installed on one side of the light incident surface of the light guide plate, and the centers of the first V-shaped microstructures are aligned with the first light source. The first optical film is installed on one side of the light exit surface of the light guide plate. The first optical film has a plurality of concentric annular second V-shaped microstructures.

As described above, in the backlight module according to the embodiment of the present invention, the bottom surface of the light guide plate has a plurality of concentric annular first V-shaped microstructures, and the center of the first V-shaped microstructure is the first light source. Since the first optical film is aligned and has a plurality of concentric annular second V-shaped microstructures, the backlight module has a highly collimated light output shape (also referred to as a light shape). .

In order to make the above-mentioned features and advantages of the present invention more clear, the present invention will be described in detail by way of examples and with reference to the accompanying drawings.

1 is a cross-sectional view of a backlight module according to an embodiment of the present invention. FIG. 3 is a bottom view of a light guide plate of a backlight module according to an embodiment of the present invention. FIG. 3 is a bottom view of a first optical film of a backlight module according to an embodiment of the present invention. FIG. 3 is a top view of a second optical film of a backlight module according to an embodiment of the present invention. FIG. 3 is a diagram showing an example of a light output shape of a backlight module according to an embodiment of the present invention. FIG. 3 is a diagram showing an example of a light output shape of a backlight module according to an embodiment of the present invention. FIG. 3 is a diagram showing an example of a light output shape of a backlight module according to an embodiment of the present invention. FIG. 3 is a curve diagram of light output brightness versus viewing angle of a backlight module according to an embodiment of the present invention. FIG. 3 is a diagram illustrating an example in which a light guide plate of a backlight module according to an embodiment of the present invention has a diffusion structure on a light incident surface. FIG. 3 is a diagram illustrating an example in which a light guide plate of a backlight module according to an embodiment of the present invention has a diffusion structure on a light incident surface. FIG. 3 is a diagram illustrating an example in which a light guide plate of a backlight module according to an embodiment of the present invention has a diffusion structure on a light incident surface. 7A is a diagram showing an example of light flux propagation by the diffusion structure shown in FIG. 7A. FIG. FIG. 6 is a curve diagram of light output intensity versus angle of the backlight module according to an embodiment of the present invention when the light guide plate has a diffusion structure on the light incident surface.

The above-mentioned and other technical contents, features, functions and effects of the present invention will become clearer from the detailed description of the preferred embodiments as follows, based on the accompanying drawings. It should be noted that terms regarding directions mentioned in the following embodiments, such as top, bottom, left, right, front, back, etc., refer only to the directions in the attached drawings. Accordingly, the directional terminology used is for the purpose of describing the invention only and is not intended to limit the invention.

FIG. 1 is a cross-sectional view of a backlight module according to an embodiment of the present invention. Referring to FIG. 1, in one embodiment of the present invention, a backlight module 100 is provided, which includes a light guide plate 120, a first light source 110 and a first optical film 130, among which the light guide plate 120 is the first light source. The optical films 130 are arranged along the arrangement direction (for example, the Z-axis direction in FIG. 1).

FIG. 2 is a bottom view of a light guide plate of a backlight module according to an embodiment of the present invention. Referring to FIGS. 1 and 2 at the same time, in this embodiment, the material of the light guide plate 120 may be plastic, glass, or other suitable material in order to pass the light beam. The invention is not limited to this. The light guide plate 120 has a light entrance surface 120S1, a bottom surface 120S2, and a light exit surface 120S3, among which the light entrance surface 120S1 is connected between the light exit surface 120S3 and the bottom surface 120S2, and the light exit surface 120S3 faces the bottom surface 120S2. do. In this embodiment, the light guide plate 120 further includes a plurality of side surfaces 120S4. The side surface 120S4 may be connected to the light entrance surface 120S1, the bottom surface 120S2, and the light exit surface 120S3, or the side surface 120S4 may 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 concentric annular first V-shaped microstructures 122. In other words, the plurality of first V-shaped microstructures 122 have the same center of circle 122C located at the same position. In this embodiment, the bottom surface 120S2 of the light guide plate 120 further has a flat area between the light incident surface 120S2 and the first V-shaped microstructure 122A, of which the first V-shaped microstructure 122A is Among the plurality of first V-shaped fine structures 122, this is the one closest to the center 122C. The flat area is close to the light incident surface 120S1 of the light guide plate 120, and the first V-shaped microstructure 122 is not installed in the flat area. In one embodiment, the radius r of the flat area is, for example, 10 mm, but the present invention is not limited to this, and the radius r of the flat area or the area of the flat area and the first V-shaped microstructure 122 are The proportion between the area of the area and the area of the area to be covered should be determined according to the needs of the design. In the backlight module 100 according to the embodiment of the present invention, the light guide plate 120 may include a flat area, so that the light incident surface of the light output shape of the backlight module 100 (i.e., the shape of the light emitted from the backlight module 100) The problem of unevenness (hot spot) on one side of 120S1 can be effectively improved.

Also, in this embodiment, the first light source 110 may be a light-emitting diode (LED) or other suitable light source. The first light source 110 is preferably selected as a light source with a high lumen value. The first light source 110 is installed on one side of the light incident surface 120S1 of the light guide plate 120, and the light guide plate 120 has a central axis (not shown) direction (for example, the Y-axis direction in FIG. One light source 110 is installed in the direction of the central axis of the light guide plate 120, the direction of the central axis is perpendicular to the arrangement direction, and the center 122C of the first V-shaped microstructure 122 is the first light source 110 and corresponds to it.

In one embodiment, the backlight module 100 further includes at least second light sources 112A, 112B, 114A, and 114B. The second light sources 112A, 112B, 114A, 114B may be light-emitting diodes (LEDs) or other suitable light sources. The second light sources 112A, 112B, 114A, 114B are preferably selected to have high lumen values. Further, the second light sources 112A, 112B, 114A, and 114B are installed on one side of the light entrance surface 120S1 of the light guide plate 120. The second light sources 112A, 112B, 114A, and 114B are arranged at intervals of a pitch P from the first light source 110 along the direction in which the light entrance surface 120S is perpendicular to the arrangement direction. In other words, the first light source 110 and the second light sources 112A, 112B, 114A, and 114B are arranged at intervals along the X-axis direction in FIG.

In this embodiment, the first light source 110 and the second light sources 112A, 112B, 114A, and 114B are used to emit the luminous flux B. After passing through the light incident surface 120S1 of the light guide plate 120, the light beam B propagates within the light guide plate 120 by total reflection. When the luminous flux B propagates to the first V-shaped microstructure 122, the first V-shaped microstructure 122 destroys the total reflection of the luminous flux B and allows the luminous flux B to pass through the light output surface 120S3 and enter the first optic. The light can be propagated toward the film 130.

In one embodiment, the number of second light sources 112A, 112B, 114A, 114B may be an even number, and the second light sources 112A, 112B, 114A, 114B are arranged at intervals around the first light source 110. be done. Furthermore, although four second light sources 112A, 112B, 114A, and 114B are shown in FIG. The number of lights to be installed should be determined depending on the design needs of the light output shape of the backlight module 100.

In one embodiment, the backlight module 100 further includes a reflective sheet 150. The reflective sheet 150 is installed on one side of the bottom surface 120S2 of the light guide plate 120. A part of the light beam B may be emitted from the bottom surface 120S2 of the light guide plate 120 in the process of propagating through the light guide plate 120, resulting in a loss of optical energy. Therefore, by installing the reflective sheet 150, the light beam B emitted from the bottom surface 120S2 of the light guide plate 120 can be reflected and propagated to the light guide plate 120, so that the utilization rate of light energy can be improved. The reflective sheet 150, the light guide plate 120, and the first optical film 130 are arranged along an arrangement direction (for example, the Z-axis direction in FIG. 1).

FIG. 3 is a bottom view of a first optical film of a backlight module according to an embodiment of the present invention. Referring to FIGS. 1 and 3 at the same time, in this embodiment, the first optical film 130 is installed on one side of the light exit surface 120S3 of the light guide plate 120. The first optical film 130 is, for example, an optical turning film. In addition, the first optical film 130 has a plurality of concentric annular second V-shaped microstructures 132, and the second V-shaped microstructures 132 are installed on the surface of the light exit surface 120S3 close to the light guide plate 120. Ru. The center 130C of the second V-shaped microstructure 132 is aligned with and corresponds to the first light source 110.

FIG. 4 is a top view of a second optical film of a backlight module according to an embodiment of the present invention. Referring 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, an optical brightness enhancement film (BEF). In addition, the second optical film 140 is installed between the light guide plate 120 and the first optical film 130, and has a plurality of concentric ring-shaped third V-shaped microstructures 142. The third V-shaped microstructure 142 of the second optical film 140 is installed on the surface of the light exit surface 120S3 leaving the light guide plate 120, and the center 140C of the third V-shaped microstructure 142 is connected to the first light source 110. Aligned and corresponding.

5A to 5C are diagrams showing examples of different light output shapes of a backlight module according to an embodiment of the present invention. 5A shows the light output shape of the backlight module 100 after turning on only the first light source 110, for example, and FIG. 5B shows the light output shape of the backlight module 100 after turning on only the second light source 112A, for example. For example, FIG. 5C shows the light output shape of the backlight module 100 after only the second light source 114A is turned on. FIG. 6 is a curve diagram of luminance versus viewing angle of light output (ie, light emitted from the backlight module) of a backlight module according to an embodiment of the present invention.

Referring to FIGS. 5A to 6, when only the first light source 110 is turned on, the first light source 110 changes the light output shape of the backlight module 100 to a specific direction centered on the direction perpendicular to the light output surface 120S3. It is used to position the camera symmetrically within the viewing angle range. For example, in FIG. 6, the viewing angle range is 2.5 degrees or less and -2.5 degrees or more, centered on the viewing angle of 0 degrees. In other words, the first light source 110 in the embodiment of the present invention described above is installed at the center of the direction in which the light incident surface 120S1 is perpendicular to the arrangement direction, and the center 122 of the first V-shaped microstructure 122 is located at the center of the first V-shaped microstructure 122. Under the conditions that the light source 110 is aligned and the center 130C of the second V-shaped microstructure 132 is aligned with the first light source 110, the light output shape of the backlight module 100 has a viewing angle of 0 degrees. Center. Note that the present invention is not limited thereto, and the position where the first light source 110 is installed should be determined according to the design of the light output shape of the backlight module 100.

Referring to FIGS. 2 and 5A to 6, in FIG. 2, when the first light source 110 and the second light sources 112A, 112B, 114A, and 114B are all turned on, the light output shape of the backlight module 100 is as follows. It can be located symmetrically within another specific viewing angle range centered on a direction perpendicular to the light exit surface 120S3. For example, in FIG. 6, the viewing angle range is 10 degrees or less and -10 degrees or more, centered on the viewing angle of 0 degrees. In other words, when all the light sources are turned on, the light output shape of the backlight module 100 is located within a larger viewing angle range than when only the first light source 110 is turned on.

In another embodiment, at least one of the first light source 110 and the second light sources 112A, 112B, 114A, 114B is turned on to change the light output shape of the backlight module 100 to another specific viewing angle. position within range. In other words, based on the relative position or angle between the backlight module 100 and the user's line of sight, the user can adjust which light source(s) should be turned on to The light output shape of the light module 100 can be positioned within the viewing angle range required by the user. Therefore, the backlight module 100 according to the embodiment of the present invention can provide a better user experience.

7A to 7C are diagrams each showing an example in which a light guide plate of a backlight module according to an embodiment of the present invention has different diffusion structures on a light incident surface. FIG. 7D is a diagram showing an example of light flux propagation by the diffusion structure shown in FIG. 7A. As shown in FIG. 7D, when the luminous flux B projected by the first light source 110 enters the light guide plate 120A (having the diffusing structure 124A) via the light entrance surface 120S1, the refraction of the luminous flux B is determined by Snell's law ( Snell's law), the angle of the light cone after the light flux B enters the light guide plate 120 increases, and this causes the propagation distance of the light flux B (represents the distance L from the light entrance surface 120S1 to the boundary of the effective area W). ) can be shortened and the effective light output area W of the light guide plate 120A can be increased. On the other hand, in the case of a light guide plate without a diffusion structure, the propagation distance of the light beam B needs to be made longer due to the too small angle of the light cone, so the size of the effective area W is made smaller.

FIG. 8 is a diagram showing the light intensity distribution at the angle of the light cone after the light beam B is introduced into the light guide plate 120 when the light guide plate has a different diffusion structure on the light entrance surface. Referring to FIGS. 7A to 8, in one embodiment, the light incident surfaces 120S1 of the light guide plates 120A, 120B, and 120C have diffusion structures 124A, 124B, and 124C, among which the diffusion structure 124A is a (semi-) The diffusion structure 124A refers to a groove formed in the light guide plate 120A. Diffusion structures 124B, 124C are microstructure arrays. Further, 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 in the embodiment of the present invention has a (semi) air column diffusion structure 124A, the light cone introduced into the light guide plate 120A is relatively small. big.

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

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

In another embodiment, the light entrance surface 120S1 of the light guide plate 100 may have a light diverging structure, and the light diverging structure is a diverging lens. In other words, in the backlight module 100 according to the embodiment of the present invention, the size of the backlight module 100 and the light guide plate 120 is reduced by having the diffusion structures 124A, 124B, 124C or the light divergence structure on the light incident surface 120S1 of the light guide plate. It can be effectively reduced (as shown in Figure 7D, under the condition of the same effective area size, the light cone becomes larger and therefore has a relatively short propagation distance L).

From the above, in the backlight module according to the embodiment of the present invention, the bottom surface of the light guide plate has a plurality of concentric annular first V-shaped microstructures, and the center of the first V-shaped microstructure is the first V-shaped microstructure. Since the first optical film is aligned with the light source and has a plurality of concentric annular second V-shaped microstructures, the light output shape of the backlight module has a specific shape centered at the viewing angle of 0 degrees. It can be focused symmetrically within the viewing angle range.

Although the present invention has been disclosed above based on the preferred embodiments described above, the preferred embodiments described above are not intended to limit the present invention, and those skilled in the art will understand the technical concept of the present invention. Since minor changes and embellishments may be made to the present invention without departing from its scope, the scope of protection of the present invention shall be based on that defined in the appended claims. Moreover, it is not necessary for any embodiment of the invention or the claims to achieve all objects or advantages or features disclosed in the invention. Furthermore, the part of the abstract and the title of the invention are only for assisting in searching for documents, and do not limit the technical scope of the present invention. Additionally, terms such as "first," "second," and the like used herein or in the claims name elements or distinguish between other embodiments or scopes. It is not intended to limit the upper or lower limits on the number of elements.

100: Backlight module
110: First light source
112A, 112B, 114A, 114B: Second light source
120, 120A, 120B, 120C: Light guide plate
120S1: Light entrance surface
120S2: Bottom
120S3: Light output surface
120S4: Side
122, 122A: First V-shaped microstructure
122C, 130C, 140C: Enshin
130: Daiichi Optical Film
132: Second V-shaped fine structure
140: Second optical film
142: Third V-shaped fine structure
150: Reflective sheet
B: Luminous flux
L: Propagation distance
P: Pitch
r: radius
W: Effective area θ: Viewing angle

Claims (12)

A backlight module including a light guide plate, a first light source , a first optical film, and a second optical film ,
The light guide plate has a light entrance surface, a light exit surface, and a bottom surface, the light entrance 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 concentric having an annular first V-shaped microstructure;
The first light source is installed on one side of the light incident surface of the light guide plate, and the centers of the plurality of concentric annular first V-shaped microstructures are aligned with the first light source,
the first optical film is installed on one side of the light exit surface of the light guide plate, and the first optical film has a plurality of concentric annular second V-shaped microstructures;
The second optical film is disposed between the light guide plate and the first optical film, and has a plurality of concentric ring-shaped third V-shaped microstructures . The backlight module according to claim 1,
The light guide plate and the first optical film are arranged along an arrangement direction, the light guide plate has a central axis direction, the first light source is installed in the direction of the central axis of the light guide plate, A backlight module, wherein the direction of the central axis is perpendicular to the arrangement direction. The backlight module according to claim 2,
further comprising at least one second light source installed on one side of the light input surface of the light guide plate,
The at least one second light source is a backlight module, wherein the light incident surface is arranged at a distance from the first light source in a direction perpendicular to the arrangement direction. The backlight module according to claim 3,
A backlight module, wherein at least one of the first light source and the at least one second light source is turned on, thereby positioning a light output shape of the backlight module within a specific viewing angle range. The backlight module according to claim 3,
The backlight module, wherein the number of the at least one second light source is an even number, and the at least one second light source is arranged at intervals around the first light source. The backlight module according to claim 1,
The backlight module, wherein a center of the plurality of concentric annular second V-shaped microstructures is aligned with the first light source. The backlight module according to claim 1,
The first optical film has a surface close to the light exit surface of the light guide plate, and the plurality of concentric annular second V-shaped microstructures are disposed on the surface of the first optical film. light module. The backlight module according to claim 1,
The backlight module, wherein a center of the plurality of concentric annular third V-shaped microstructures is aligned with the first light source. The backlight module according to claim 1,
The second optical film has a surface leaving the light exit surface of the light guide plate, and the plurality of concentric annular third V-shaped microstructures are installed on the surface of the second optical film. light module. The backlight module according to claim 1,
The light incident surface of the light guide plate has a diffusing structure, and the diffusing structure is an air column or a microstructure array. The backlight module according to claim 1,
The light incident surface of the light guide plate has a light diverging structure, and the light diverging structure is a diverging lens. The backlight module according to claim 1,
The bottom surface of the light guide plate further has a flat area, and the flat area is located between the first V-shaped microstructures closest to the center of the plurality of concentric annular first V-shaped microstructures, and A backlight module located between the input light surface.

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