Backlight device and display device

A backlight device comprises a plurality of point light sources, a luminance uniformity sheet, a light diffusion sheet, a plurality of lenses, and a partition wall. The luminance uniformity sheet includes transmission portions that are arranged opposite the point light sources. The light diffusion sheet is disposed on an opposite side of the luminance uniformity sheet relative to the point light sources. The lenses are disposed between the light diffusion sheet and the luminance uniformity sheet. The partition wall is disposed at least one of between the point light sources and the luminance uniformity sheet and between the luminance uniformity sheet and the lenses and is disposed between adjacent point light sources in a plan view or between adjacent lenses in the plan view.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No. 2022-64794 filed in Japan on Apr. 8, 2022. The entire disclosure of Japanese Patent Application No. 2022-64794 is hereby incorporated herein by reference.

BACKGROUND

Field of the Invention

The present invention generally relates to a backlight device and a display device. More specifically, the present invention relates to a backlight device and a display device equipped with lenses.

Background Information

Conventionally, backlight devices and display devices equipped with lenses are known (see Japanese Laid-Open Patent Application Publication No. 2007-80755 (Patent Literature 1), for example).

The above-mentioned Patent Literature 1 discloses a lighting device (a backlight device) having light sources, a first optical sheet, and a second optical sheet. The first optical sheet of the lighting device has apertures through which at least the light from the light sources passes and a region that blocks the light from the light sources. The second optical sheet of the lighting device has lenses that align the direction of the light rays of the light incident through the apertures of the first optical sheet.

SUMMARY

However, the lighting device described in the above-mentioned Patent Literature 1 is considered to have a problem in that the contrast of the region corresponding to the adjacent light sources on the emission surface side of the second optical sheet is decreased due to the spreading of the light from the light sources. In addition, although not disclosed in the above-mentioned Patent Literature 1, it is desired to efficiently emit the diffused light when the diffused light is emitted from the lighting device. For these reasons, it is desired to effectively emit the diffused light while suppressing the decrease in the contrast.

One object of this disclosure is to provide a backlight device and a display device capable of effectively emitting diffused light while suppressing a decrease in contrast.

In view of the state of the known technology, a backlight device according to a first aspect of this disclosure is a backlight device that comprises a plurality of point light sources, a luminance uniformity sheet configured to uniform luminance of light from the point light sources and including transmission portions that are arranged opposite the point light sources and are configured to transmit the light from the point light sources, a light diffusion sheet disposed on an opposite side of the luminance uniformity sheet relative to the point light sources and configured to diffuse the light from the point light sources, a plurality of lenses disposed between the light diffusion sheet and the luminance uniformity sheet and configured to convert light transmitted through the transmission portions of the luminance uniformity sheet into parallel light or light that is slightly diffused over a range smaller than a range of an incident angle of the light transmitted through the transmission portions, and a partition wall disposed at least one of between the point light sources and the luminance uniformity sheet and between the luminance uniformity sheet and the lenses and disposed between adjacent point light sources in a plan view or between adjacent lenses in the plan view.

DETAILED DESCRIPTION OF EMBODIMENTS

Configuration of Display Device100

Referring toFIGS.1to6, the configuration of a display device100according to one embodiment will be described. In the drawings, a left and right direction when the display device100is viewed from a front side is referred to as an X direction. Also, an up and down direction when the display device100is viewed from the front side is referred to as a Y direction. Also, a direction connecting a rear side and the front side of the display device100is referred to as a Z direction.

The backlight1is equipped with a plurality of LED (Light Emitting Diode) light sources10, a substrate20, a reflective sheet30, a luminance uniformity sheet40, first partition walls50, a lens sheet60with a plurality of lenses61, and a light diffusion sheet70. In the backlight1, the LED light source10and the reflection sheet30on the substrate20, the luminance uniformity sheet40, the first partition walls50, the lens sheet60, and the light diffusion sheet70are arranged in this order inside the frame3. The backlight1is configured to irradiate the display2with the light from the rear side of the display2. The LED light sources10are an example of “point light sources” of the present disclosure, and the first partition walls50are an example of a “partition wall” of the present disclosure.

The LED light sources10are arranged on the substrate20. The LED light sources10are arranged in a grid in the X direction and in the Y directions. In other words, the LED light sources10are arranged in an array or matrix. The LED light sources10include point light sources, respectively. The LED light sources10include light emitting portions11, respectively. In this embodiment, the light emitting portions11of the LED light sources10have a substantially rectangular shape in a plan view. The luminance of the LED light sources10is configured to be adjusted by current value. The LED light sources10each are individually controllable. The LED light sources10are disposed on the rear side (Z2direction side) of the display2. Therefore, the display device100is a so-called direct lighting type display device. The term “point light source” means a light source whose light emitting portion has a very small area that is close to a point.

The substrate20is disposed on the rear side (Z2direction side) of the reflective sheet30. The substrate20is a printed circuit board. The substrate20has a circuit that electrically connects the LED light sources10.

The reflective sheet30is disposed on the substrate20via an adhesive layer (not shown). The reflective sheet30is disposed on the LED light source10side with respect to the luminance uniformity sheet40and is arranged to surround each of the LED light sources10. The reflective sheet30includes a plurality of apertures31(seeFIG.4) for the LED light sources10. The reflective sheet30is configured to re-reflect reflected return light from a reflective portion42(seeFIG.3) of the luminance uniformity sheet40back to the luminance uniformity sheet40side. The reflective sheet30is made, for example, of foamed polyethylene terephthalate.

The luminance uniformity sheet40(seeFIG.5) is disposed opposite the LED light sources10in the Z direction. The luminance uniformity sheet40is disposed between the reflective sheet30and the lens sheet60. The luminance uniformity sheet40is used to make the luminance distribution substantially uniform, thereby making the luminance substantially uniform across the entire display screen. As shown inFIG.3, the luminance uniformity sheet40includes a plurality of transmission portions41that transmit the light emitted from the LED light sources10and the reflective portion42that reflects the light emitted from the LED light sources10. The transmission portions41include through holes that penetrate in the thickness direction (the Z direction). The plurality of transmission portions41are provided. The reflective portion42is an entire portion other than portions where the through holes (i.e., the transmission portions41) are provided (e.g., a portion of the luminance uniformity sheet other than the through holes). The reflective portion42is configured to reflect light incident on the reflective portion42toward the reflective sheet30side. The luminance uniformity sheet40is configured to make the luminance distribution in the plane direction (XY directions) substantially uniform by transmitting the light through the transmission portions41that are provided in advance. The luminance uniformity sheet40is made of a resin having a property of reflecting light. The luminance uniformity sheet40is made, for example, of foamed polyethylene terephthalate. A peripheral edge portion of the luminance uniformity sheet40is supported by spacers (not shown) provided in the frame3. InFIG.3, the LED light sources10(seeFIG.2), which are not supposed to be seen and are located at the back side of the paper, are illustrated for convenience of explanation.

In other words, the luminance uniformity sheet40is provided between the LED light sources10and the emission surface of the backlight1. The luminance uniformity sheet40is formed by a sheet having reflective characteristics. The luminance uniformity sheet40is provided with the transmission portions41whose position and size are appropriately set according to the arrangement of the LED light sources10, the light distribution of the LED light sources10, and the structure of the frame3(housing). The luminance uniformity sheet40is an optical sheet for making the luminance on the emission surface of the backlight1uniform.

FIG.2is a schematic diagram showing the arrangement of the LED light sources10, the transmission portions41, the lenses61, and the first partition walls50as viewed from the Z direction. InFIG.2, the LED light sources10are shown by thin solid lines, the transmission portions41are shown by hatched lines, the first partition walls50are shown by thick solid lines, and the lenses61are shown by dashed lines. The transmission portions41are each offset, in the plan view, with respect to the light emitting portions11of the LED light sources10(seeFIG.1) so as not to overlap with the light emitting portions11of the LED light sources10. In other words, the transmission portions41are each disposed with respect to the LED light sources10at positions that are not directly above the light emitting portions11in the Z direction. The transmission portions41are arranged in a grid along the X direction and the Y direction. The transmission portions41have a substantially square shape. The shape of the transmission portions41is similar to the shape of the lenses61of the lens sheet60in the plan view. The size D2of each of the transmission portions41is smaller than the size D1of the light emitting portions11of the LED light sources10.

As shown inFIG.1, the lens sheet60is disposed between the luminance uniformity sheet40and the light diffusion sheet70. As shown inFIG.6, the lens sheet60has the lenses61. The lenses61are collimator lenses. As shown inFIG.3, the lenses61are configured to convert light incident through the through holes of the luminance uniformity sheet40into parallel light parallel to the Z direction and are configured to emit the light. The light transmitted through the lenses61reaches the light diffusion sheet70. By making the emission light converted into the parallel light by the lenses61be incident on the light diffusion sheet70, the light can be appropriately converted into light that has a peak of diffusion in a specific direction in the light diffusion sheet70and whose diffusion is suppressed in directions other than the specific direction, as compared to the case in which diffused light is incident on the light diffusion sheet70.

As shown inFIG.6, the lenses61each have a convex lens formed in a square shape in the plan view. The lenses61have the same shape as each other. The lenses61are arranged with each other in the X direction and in the Y direction. As shown inFIG.2, the lenses61are provided one for each of the transmission portions41of the luminance uniformity sheet40. The lenses61are arranged in a matrix in the same manner as the arrangement of the transmission portions41. As shown inFIG.3, the transmission portions41of the luminance uniformity sheet40are arranged on the optical axes L of the lenses61, respectively. The reflective portion42of the luminance uniformity sheet40is not disposed on the optical axes L of the lenses61.

The LED light sources10are arranged one for at least two lenses61of the lenses61. In this embodiment, as shown inFIG.2, the LED light sources10are arranged one for four lenses61of the lenses61. As viewed from the Z direction, the region in which the four lenses61are arranged has a substantially square shape. As viewed from the Z direction, the LED light sources10are each arranged to straddle the four lenses61of the lenses61. As viewed from the Z direction, the LED light sources10are each disposed in a center portion of the substantially square-shaped region formed by the four lenses61.

The lenses61are made of a resin that transmits light. The lenses61are made of a transparent resin, such as polycarbonate, acrylic resin, or polyolefin, for example. The lens sheet60has an area that is larger than the bottom surface inside the frame3. Holding portions62(seeFIG.6) of the lens sheet60are supported by protrusions (not shown) provided on the inner surface of the frame3.

As shown inFIG.1, the light diffusion sheet70is disposed on the opposite side of the lens sheet60with respect to the luminance uniformity sheet40. The light diffusion sheet70is configured to diffuse the light transmitted through the lens sheet60. The light diffusion sheet70has an asymmetric fine pattern formed on the surface on the display side. The light diffusion sheet70is made, for example, of polyethylene terephthalate or polycarbonate.

In this embodiment, the light diffusion sheet70is an anisotropic light diffusion sheet that diffuses the light from LED light sources10anisotropically. The light diffusion sheet70is configured to emit light that has a peak of diffusion in a specific direction and whose diffusion is suppressed in directions other than the specific direction. The light diffusion sheet70is configured to have a wide diffusion angle in the X direction and a narrow diffusion angle in the Y direction with respect to the incident light from the lenses61. For example, the light diffusion sheet70is configured so that the diffusion angle in the X direction is about ±50 degrees and the diffusion angle in the Y direction is about ±30 degrees. Alternatively, the light diffusion sheet70is configured so that, for example, the diffusion angle in the X direction is about ±50 degrees and the diffusion angle in the Y direction is about ±20 degrees. Alternatively, the light diffusion sheet70is configured so that, for example, the diffusion angle in the X direction is about ±50 degrees and the diffusion angle in the Y direction is about ±10 degrees. The diffusion angle in the X direction and the diffusion angle in the Y direction of the light diffusion sheet70are not particularly limited.

The first partition walls50are disposed between the luminance uniformity sheet40and the lens sheet60. As shown inFIG.2, the first partition walls50are formed in a grid shape partitioning compartments in the X direction and in the Y direction. The first partition walls50are formed to partition each compartment into a substantially rectangular shape. The first partition walls50are disposed between adjacent LED light sources10in the plan view. In other words, the first partition walls50divide between the LED light sources10so that the LED light sources10are each arranged in a different compartment from each other. The first partition walls50are each configured to be disposed along an outer periphery of a placement region of the lenses61corresponding to one LED light source10in the plan view. In this embodiment, the first partition walls50are each disposed along the outer periphery of the placement region of four lenses61corresponding to one LED light source10in the plan view. The display device100supports a local dimming, in which the luminance is controlled for each compartment partitioned by the first partition walls50. The display device100adjusts the luminance of each LED light source10according to the color of the image. The local dimming is a technique that divides the entire screen of the display device into a plurality of regions and adjusts the luminance of the light sources for each region.

As shown inFIG.3, one ends of the first partition walls50in the Z direction are in contact with the luminance uniformity sheet40, and the other ends of the first partition walls50in the Z direction is in contact with the lens sheet60. No partition wall is disposed between the reflective sheet30and the luminance uniformity sheet40. With this configuration, the light from the LED light sources10is repeatedly reflected between the reflective portion42of the luminance uniformity sheet40and the reflective sheet30, and thus the light from the LED light sources10can be effectively mixed.

The first partition walls50are formed of resin. The first partition walls50are configured to absorb the light emitted from the LED light sources10. The first partition walls50preferably have lower brightness, and for example, it is made of a resin having a black color.

As shown inFIG.1, the display2is arranged opposite the light diffusion sheet70and is disposed on an opposite side relative to the LED light sources10. The display2is, for example, a liquid crystal panel. The display2includes a plurality of pixels. The display2displays an image by changing the transmittance of the light emitted from the LED light sources10by each of the pixels. The display2is driven based on image signals. The display2includes a liquid crystal cell.

The frame3has a box shape with an opening on the front side. In this embodiment, the bottom surface inside the frame3has a rectangular shape.

Effect of this Embodiment

The following effects can be achieved in this embodiment.

As described above, this embodiment comprises the light diffusion sheet70, the lenses61that convert light into the parallel light or the light that is slightly diffused, and the first partition walls50disposed between the luminance uniformity sheet40and the lenses61and disposed between adjacent LED light sources10in the plan view. With this configuration, the decrease in contrast on the emission surface side of the lenses61can be suppressed because the spreading of the light from the LED light sources10can be suppressed by the first partition walls50disposed between the luminance uniformity sheet40and the lenses61. In addition, since the parallel light and the slightly diffused light can be incident on the light diffusion sheet70from the lenses61, the diffused light can be efficiently emitted from the light diffusion sheet70, unlike when light that is not the parallel light or the slightly diffused light is incident on the light diffusion sheet70. For these reasons, the diffused light can be efficiently emitted while suppressing the decrease in contrast.

With this embodiment, as described above, the transmission portions41of the luminance uniformity sheet40are offset with respect to the light emitting portions11of the LED light sources10so as not to overlap with the light emitting portions11in the plan view. With this configuration, unlike when the transmission portions41of the luminance uniformity sheet40are disposed directly above the light emitting portions11of the LED light sources10, direct light from the LED light sources10can be suppressed from transmitting through the transmission portions41, and thus chromaticity irregularities caused by chromaticity variations between individual LED light sources can be suppressed.

As described above, this embodiment further comprises the reflective sheet30that is disposed on the LED light source10side of the luminance uniformity sheet40, is arranged to surround each of the LED light sources10, and reflects the light emitted from the LED light sources10, and the luminance uniformity sheet40further includes the reflective portion42that reflects the light emitted from the LED light sources10. With this configuration, the light from the LED light sources10is repeatedly reflected between the reflective portion42of the luminance uniformity sheet40and the reflective sheet30, and thus the light from the LED light sources10is mixed (blended). This allows the mixed light to transmit through the transmission portions41, and thus the chromaticity irregularities caused by the chromaticity variations between individual LED light sources10can be further suppressed. In addition, the illuminance distribution of the light emitted from the lenses61can be made uniform, and the luminance can be made high due to the light collecting effect of each of the lenses61.

With this embodiment, as described above, the lenses61are arranged one for each of the transmission portions41of the luminance uniformity sheet40, and the LED light sources10are arranged one for at least two lenses61of the lenses61. With this configuration, the mixed light transmitted through the transmission portions41can be incident on the lenses61arranged one for each of the transmission portions41, and the light can be emitted from the lenses61in the region of one LED light source10. As a result, the illuminance distribution of the light emitted from the lenses61can be made more uniform and the luminance can be made higher.

With this embodiment, as described above, the LED light sources10are arranged in an array, and the LED light sources10are each arranged to straddle the at least two lenses61in the plan view. With this configuration, the luminance uniformity can be further improved because the LED light source10can be disposed about the center portion of the region of one LED light source10.

With this embodiment, as described above, the first partition wall50is disposed along the outer periphery of the placement region of the at least two lenses61in the plan view. With this configuration, the decrease in contrast in the region corresponding to the adjacent LED light sources10on the emission surface side of the lenses61can be more suppressed.

With this embodiment, as described above, the size D2of the transmission portions41of the luminance uniformity sheet40is smaller than the size D1of the light emitting portions11of the LED light sources10in the plan view. With this configuration, the size of the reflective portion42of the luminance uniformity sheet40can be made larger, compared to a case in which the size D2of the transmission portions41of the luminance uniformity sheet40is larger than the size D1of the light emitting portions11of the LED light sources10. This allows more light from the LED light sources10to be repeatedly reflected between the reflective portion42of the luminance uniformity sheet40and the reflective sheet30, and thus the light from the LED light sources10can be more effectively mixed. As a result, the chromaticity irregularities can be further suppressed and the luminance uniformity can be further improved.

With this embodiment, as described above, the light diffusion sheet70is an anisotropic light diffusion sheet that diffuses the light from the light sources anisotropically. With this configuration, the light incident on the anisotropic light diffusion sheet can be emitted as light that has a peak of diffusion in a specific direction and whose diffusion is suppressed diffusion in directions other than the specific direction. Therefore, for example, the display device100can be made to perform high luminance display in the specific direction.

With this embodiment, as described above, the transmission portions41of the luminance uniformity sheet40are located on the optical axes L of the lenses61. With this configuration, it is possible to suppress an increase of light that does not pass through centers of the lenses61out of the light transmitted through the luminance uniformity sheet40. Therefore, for example, blurring of the displayed image on the display device100can be suppressed.

MODIFICATION EXAMPLES

The embodiments disclosed here should be considered in all respects to be illustrative and not restrictive. The scope of the invention is indicated by the claims, not by the description of the embodiments described above, and furthermore includes all changes (modification examples) within the meaning and scope equivalent to the claims.

For example, in the embodiment, as described above, an example is shown in which the reflective sheet30is provided, the luminance uniformity sheet40includes the reflective portion42, the transmission portions41of the luminance uniformity sheet40are offset with respect to the light emitting portions11of the LED light sources10so as not to overlap with the light emitting portions11in the plan view, the LED light sources10are arranged one for four lenses61of the lenses61, and the first partition walls50are disposed between the luminance uniformity sheet40and the lenses61, but the present invention is not limited to this.

For example, as shown inFIGS.7and8, it can be configured such that the reflective sheet30is not provided, the luminance uniformity sheet40does not include the reflective portion42, the transmission portions41of the luminance uniformity sheet40are arranged to overlap the light emitting portions11of the LED light sources10in the plan view, the LED light sources10are arranged one for one lens61of the lenses61, and second partition walls51are further provided the LED light sources10and the luminance uniformity sheet40.

As shown inFIG.8, the second partition walls51are disposed between the LED light sources10and the luminance uniformity sheet40. One ends of the second partition walls51in the Z direction are in contact with the substrate20, and the other ends of the second partition walls51in the Z direction are in contact with the luminance uniformity sheet40. As shown inFIG.7, the second partition walls51are arranged in the same position as the first partition walls50so as to overlap with the first partition walls50in the plan view. The first and second partition walls50and51are each disposed along the outer periphery of the placement region of one lens61corresponding to one LED light source10in the plan view. The display device100supports a local dimming in which the luminance is controlled for each compartment partitioned by the first and second partition walls50and51. The second partition walls51are configured to absorb the light emitted from the LED light sources10. Specifically, the second partition walls51are made of a resin having a color such as black. It can also be configured such that either one ends of the second partition walls51in the Z direction are in contact with the substrate20, or the other ends of the second partition walls51in the Z direction are in contact with the luminance uniformity sheet40.

Even with this configuration, the first and second partition walls50and51can suppress the spread of the light from the LED light sources10.

In the embodiment, as described above, an example is shown in which the lenses61include collimator lenses, and the lenses61are configured to convert the light incident through the through holes of the luminance uniformity sheet40into the parallel light parallel to the Z direction and are configured to emit the light, but the present invention is not limited to this. For example, the lenses61can be configured to convert light into light that is slightly diffused over a range smaller than a range of an incident angle of the light transmitted through the transmission portions41of the luminance uniformity sheet40and incident on the lenses61and be configured to emit the light. In this case, for example, the lenses61can be configured to convert the light incident through the through holes of the luminance uniformity sheet40into light that diffuses about ±10 degrees in the Z direction and be configured to emit the light. Even if the lenses61are configured to convert light into the light that is slightly diffused and are configured to emit the light, the same effect can be obtained as when the lenses61are configured to convert light into the parallel light and are configured to emit the light.

In the embodiment, as described above, an example is shown in which the light diffusion sheet70is an anisotropic light diffusion sheet that diffuses the light from the LED light sources10anisotropically, but the present invention is not limited to this. For example, the light diffusion sheet70can be an isotropic light diffusion sheet that diffuses the light from the LED light sources10isotropically. In this case, for example, the light diffusion sheet70can be configured to convert light incident from the lenses61to diffuse about ±30 degrees in the Z direction and be configured to emit the light.

In the embodiment, as described above, an example is shown in which the lenses61each have a substantially square shape in the plan view and have the same shape as each other, and the LED light sources10are configured to be arranged one for four lenses61of the lenses61, but the present invention is not limited to this. The LED light sources10can be arranged one for two, three, or five or more lenses61of the lenses61.

For example, as shown inFIG.9, the lenses61can each have a substantially hexagonal shape in the plan view and have the same shape as each other, and the LED light sources10can be arranged one for three lenses61of the lenses61. In this case, the first partition walls50are each disposed along the outer periphery of the placement region of three adjacent lenses61corresponding to one LED light source10in the plan view. The shape of the transmission portions41of the luminance uniformity sheet40can be a rectangular shape or other shapes such as a substantially hexagonal shape.

As shown inFIG.10, for example, the lenses61can each have a substantially triangular shape in the plan view and have the same shape as each other, and the LED light sources10can be arranged one for six lenses61of the lenses61. In this case, the first partition walls50are each disposed along the outer periphery of the placement region of six adjacent lenses61corresponding to one LED light source10in the plan view. The shape of the transmission portions41of the luminance uniformity sheet40can be a triangular shape or other shapes such as a rectangular shape.

As shown inFIG.11, for example, the lenses61can each have a substantially square shape in the plan view and have the same shape as each other, and the LED light sources10can be arranged one for each of sixteen lenses61of the lenses61. The size of the lenses61can be smaller than the size of the lenses61in the above embodiment. The lenses61in portions that do not overlap with the LED light sources10in the plan view can be notched to the extent that does not affect optical performance. Therefore, the lenses61in the portions that do not overlap with the LED light sources10in the plan view can be notched. With this configuration, even when the outer shape of the display device100is required to be different from the rectangular shape, the display device100can be appropriately provided in a different shape by notching some lenses61that do not overlap the LED light sources10in the plan view and are located in the periphery of the lens sheet60. The sizes of the transmission portions41of the luminance uniformity sheet40can differ from each other according to the distance from the LED light sources10.

In the embodiment, as described above, an example is shown in which the LED light sources10are arranged one for four lenses61of the lenses61, and the lenses61each have the same shape as each other, but the present invention is not limited to this. For example, as shown inFIGS.12and13, the LED light sources10can be arranged one for four lenses61of the lenses61, and the lenses61can each have a different shape from each other.

As shown inFIG.12, the LED light sources10are arranged one for four lenses61of the lenses61. The portion formed by the four lenses61has a substantially rectangular shape. The light amount of the light transmitted through the transmission portions41of the luminance uniformity sheet40and incident on the lenses61near four corners of the substantially rectangular shape formed by the four lenses61can be larger than in other portions, due to repeated reflection.

Therefore, as shown inFIG.13, the four lenses61can each be configured to slope from a position closer to the center portion of the substantially rectangular shape formed by the four lenses61than the center portion of each of the four lenses61toward the rear side and toward the corners of the substantially rectangular shape formed by the four lenses61.FIG.13is a cross-sectional view taken along1200A-1200A line inFIG.12as well as a cross-sectional view taken along1200B-1200B line inFIG.12. With this configuration, the light emission can be suppressed at the four corners of the substantially rectangular shape formed by the four lenses61, and thus uneven luminance can be suppressed. As long as the light emission can be suppressed, the four lenses61can each be configured to protrude further from a position closer to the center portion of the substantially rectangular shape formed by the four lenses61than the center portion of each of the four lenses61toward the front side and toward the four corners of the substantially rectangular shape formed by the four lenses61. Furthermore, the modification example, as described above, is not limited to the portion formed by the four lenses61of the lenses61. The number of lenses61for one LED light source10is not particularly limited, and the portion can be formed by six lenses61or the portion can be formed by sixteen lenses61.

In the embodiment, as described above, an example is shown in which the first partition walls50are provided that are disposed between the luminance uniformity sheet40and the lens sheet60and made of a resin having a color such as black, but the present invention is not limited to this. The first partition walls50can be made of a resin having a high bright color, such as white or milky white, and reflect the light emitted from the LED light sources10. With this configuration, the light reflected by the first partition walls50can be utilized, and thus the light utilization efficiency can be improved.

In the embodiment, as described above, an example is shown in which the first partition walls50are provided that are disposed between the luminance uniformity sheet40and the lens sheet60and made of a resin having a color such as black, but the present invention is not limited to this. For example, it can be further provided with either third partition walls52(seeFIG.14) or fourth partition walls53(seeFIG.15), which are disposed between the LED light sources10and the luminance uniformity sheet40and has a color such as white or milky white.

As shown inFIG.14, the third partition walls52are disposed between the LED light sources10and the luminance uniformity sheet40. The third partition walls52are formed to be in contact with the luminance uniformity sheet40and separated (S1) from the reflective sheet30. The third partition walls52are disposed in the same position as the first partition walls50so as to overlap the first partition walls50in the plan view. The first and third partition walls50and52are disposed along the outer periphery of the placement region of the lenses61corresponding to one LED light source10in the plan view. The display device100supports a local dimming, in which brightness is controlled for each compartment partitioned by the first and third partition walls50and52. The third partition walls52are configured to reflect the light emitted from the LED light sources10. Specifically, the third partition walls52is made of a resin having a color such as white or milky white. InFIG.14, as inFIG.3, the LED light source10(seeFIG.2), which are not supposed to be seen and are located at the back side of the paper, are also illustrated for convenience of explanation.

As shown inFIG.15, the fourth partition walls53are disposed between the LED light sources10and the luminance uniformity sheet40. The fourth partition walls53are formed to be in contact with the reflective sheet30and separated (S2) from the luminance uniformity sheet40. The fourth partition walls53are disposed in the same position as the first partition walls50so as to overlap the first partition walls50in the plan view. The first and fourth partition walls50and53are disposed along the outer periphery of the placement region of the lenses61corresponding to one LED light source10in the plan view. The display device100supports a local dimming in which the brightness is controlled for each compartment partitioned by the first and fourth partition walls50and53. The fourth partition walls53are configured to reflect the light emitted from the LED light sources10. Specifically, the fourth partition walls53are made of a resin having a color such as white or milky white. InFIG.15, as inFIG.3, the LED light sources10(seeFIG.2), which are not supposed to be seen and are located at the back side of the paper, are also illustrated for convenience of explanation.

In the modification examples further with the third partition walls52or the fourth partition walls53, the third partition walls52or the fourth partition walls53are provided that are disposed between the LED light sources10and the luminance uniformity sheet40, the third partition walls52are formed to be in contact with the luminance uniformity sheet40and separated (S1) from the reflective sheet30, and the fourth partition walls53are formed to be in contact with the reflective sheet30and separated (S2) from the luminance uniformity sheet40. With this configuration, both mixing of the light from the LED light sources10between the luminance uniformity sheet40and the reflective sheet30and suppression of the decrease in contrast are appropriately achieved.

In the modification examples further with the third partition walls52or the fourth partition walls53, the third partition walls52and the fourth partition walls53may not be disposed in the same position as the first partition walls50in the plan view. For example, the third partition walls52and the fourth partition walls53can be disposed along the outer periphery of the placement region of the lenses61corresponding to at least two LED light sources10in the plan view. With this configuration, the light from the LED light sources10can be effectively mixed between the luminance uniformity sheet40and the reflective sheet30while suppressing the decrease in contrast.

In the embodiment, as described above, an example is shown in which the transmission portions41of the luminance uniformity sheet40are disposed on the optical axes L of the lenses61, respectively, but the present invention is not limited to this. For example, the transmission portions41of the luminance uniformity sheet40can be disposed at positions that are offset from the optical axes L of the lenses61.

In the embodiment, as described above, an example is shown in which the shape of the transmission portions41is similar to the shape of the lens61in the plan view, the present invention is not limited to this. For example, the shape of the transmission portions41does not have to be similar to the shape of the lens61in the plan view. For example, the shape of the transmission portions41can be polygonal, circular, elliptical, or the like, regardless of the shape of the lens61in the plan view.

In the embodiment, as described above, an example is shown in which the size D2of each of the transmission portions41is smaller than the size D1of the light emitting portions11of the LED light sources10, but the present invention is not limited to this. For example, the size D2of each of the transmission portions41can be the same as the size D1of the light emitting portions11of the LED light sources10, or the size D2of each of the transmission portions41can be larger than the size D1of the light emitting portions11of the LED light sources10.

In the embodiment, as described above, an example is shown in which the transmission portions41include the through holes, but the present invention is not limited to this. For example, the transmission portions41can include a member with high transmittance, such as a transparent member.

In the embodiment, as described above, an example is shown in which the display2is disposed opposite the light diffusion sheet70, but the present invention is not limited to this. For example, a direction changing sheet (not shown), which has a prism shape with a saw-tooth cross-sectional shape and is used to change the viewing angle, can be further provided between the display2and the light diffusion sheet70. The direction changing sheet refers to a sheet that changes the direction of incident light and transmits it. Furthermore, a viewing angle limiting film (not shown) can be further provided between the display2and the direction changing sheet. The viewing angle limiting film refers to a film that narrows the light distribution of the light emitted from the direction changing sheet in one direction.

In the embodiment, as described above, an example is shown in which the first partition walls50are provided that are disposed between adjacent LED light sources10in the plan view, but the present invention is not limited to this. For example, as shown inFIGS.16to18, it can be provided with fifth partition walls54disposed between adjacent lenses61in the plan view.

FIG.16is a schematic diagram showing the arrangement of the LED light sources10, the transmission portions41, the lenses61, and the fifth partition walls54as viewed from the Z direction. InFIG.16, the LED light sources10are shown by thin solid lines, the transmission portions41are shown by hatching, and the fifth partition walls54are shown by thick solid lines. The fifth partition walls54are disposed between adjacent lenses61in the plan view. In other words, the fifth partition walls54partition the lenses61so that the lenses61are placed in different compartments from each other in the plan view.

As shown inFIGS.17and18, one ends of the fifth partition walls54in the Z direction are in contact with the luminance uniformity sheet40, and the other ends of the fifth partition walls54in the Z direction are in contact with the lens sheet60. No partition wall is disposed between the reflective sheet30and the luminance uniformity sheet40. The fifth partition walls54is formed of resin. The fifth partition walls54are configured to absorb the light emitted from the LED light sources10. The fifth partition walls54can be configured to reflect the light emitted from the LED light sources10. InFIG.17, as inFIG.3, the LED light sources10(seeFIG.16), which are not supposed to be seen and are located at the back side of the paper, are also illustrated for convenience of explanation.

The modification example, as described above, comprises the light diffusion sheet70, the lenses61that convert light into the parallel light or the slightly diffused light, and the fifth partition walls54that are disposed between the luminance uniformity sheet40and the lenses61and between adjacent lenses61in the plan view. With this configuration, the fifth partition walls54that are disposed between the luminance uniformity sheet40and the lenses61can suppress the spreading of the light from the LED light sources10, and thus the decrease in contrast on the emission surface side of the lenses61can be suppressed. In addition, since the parallel light and the slightly diffused light can be incident from the lenses61on the light diffusion sheet70, the diffused light can be efficiently emitted from the light diffusion sheet70, unlike when light that is not the parallel light or the slightly diffused light is incident on the light diffusion sheet70. For these reasons, the diffused light can be efficiently emitted while suppressing the decrease in contrast.

(1) In view of the state of the known technology, a backlight device according to a first aspect of this disclosure is a backlight device that comprises a plurality of point light sources, a luminance uniformity sheet configured to uniform luminance of light from the point light sources and including transmission portions that are arranged opposite the point light sources and are configured to transmit the light from the point light sources, a light diffusion sheet disposed on an opposite side of the luminance uniformity sheet relative to the point light sources and configured to diffuse the light from the point light sources, a plurality of lenses disposed between the light diffusion sheet and the luminance uniformity sheet and configured to convert light transmitted through the transmission portions of the luminance uniformity sheet into parallel light or light that is slightly diffused over a range smaller than a range of an incident angle of the light transmitted through the transmission portions, and a partition wall disposed at least one of between the point light sources and the luminance uniformity sheet and between the luminance uniformity sheet and the lenses and disposed between adjacent point light sources in a plan view or between adjacent lenses in the plan view.

The backlight device according to the first aspect of this disclosure, as described above, comprises the light diffusion sheet, the lenses configured to convert the light into the parallel light or the light that is slightly diffused, and the partition wall disposed at least one of between the point light sources and the luminance uniformity sheet and between the luminance uniformity sheet and the lenses and disposed between adjacent point light sources in the plan view or between adjacent lenses in the plan view. With this configuration, a decrease in contrast on an emission surface side of the lenses can be suppressed because the spreading of the light from the point light sources can be suppressed by the partition wall disposed at least one of between the point light sources and the luminance uniformity sheet and between the luminance uniformity sheet and the lenses. In addition, since the parallel light and the slightly diffused light can be incident on the light diffusion sheet from the lenses, the diffused light can be efficiently emitted from the light diffusion sheet, unlike when light that is not the parallel light or the slightly diffused light is incident on the light diffusion sheet. For these reasons, the diffused light can be efficiently emitted while suppressing the decrease in contrast.

(2) In accordance with a preferred embodiment according to the backlight device mentioned above, the transmission portions of the luminance uniformity sheet are offset with respect to light emitting portions of the point light sources so as not to overlap with the light emitting portions in the plan view. With this configuration, unlike when the transmission portions of the luminance uniformity sheet are disposed directly above the light emitting portions of the point light sources, direct light from the point light sources can be suppressed from transmitting through the transmission portions, and thus chromaticity irregularities caused by chromaticity variations between individual point light sources can be suppressed.

(3) In accordance with a preferred embodiment according to any one of the backlight devices mentioned above, the size of the transmission portions of the luminance uniformity sheet is smaller than the size of the light emitting portions of the point light sources in the plan view. With this configuration, the size of the reflective portion of the luminance uniformity sheet can be made larger, compared to a case in which the size of the transmission portions of the luminance uniformity sheet is larger than the size of the light emitting portions of the point light sources. This allows more light from the point light sources to be repeatedly reflected between the reflective portion of the luminance uniformity sheet and the reflective sheet, and thus the light from the point light sources can be more effectively mixed. As a result, chromaticity irregularities can be further suppressed and luminance uniformity can be further improved.

(4) In accordance with a preferred embodiment according to any one of the backlight devices mentioned above, the lenses are arranged one for each of the transmission portions of the luminance uniformity sheet, and the point light sources are arranged one for at least two lenses of the lenses. With this configuration, the mixed light transmitted through the transmission portions can be incident on the lenses arranged one for each of the transmission portions, and the light can be emitted from the lenses in a region of one point light source. As a result, the illuminance distribution of the light from the lenses can be made more uniform and the luminance can be made higher.

(5) In accordance with a preferred embodiment according to any one of the backlight devices mentioned above, the point light sources are arranged in an array, and the point light sources are each arranged to straddle the at least two lenses of the lenses in the plan view. With this configuration, the luminance uniformity can be further improved because the point light source can be disposed about a center portion of the region of one point light source.

(6) In accordance with a preferred embodiment according to any one of the backlight devices mentioned above, the partition wall is disposed along an outer periphery of a placement region of the at least two lenses of the lenses. With this configuration, the decrease in contrast in the region corresponding to adjacent point light sources on an emission surface side of the lenses can be more suppressed.

(7) In accordance with a preferred embodiment according to any one of the backlight devices mentioned above, the light diffusion sheet is an anisotropic light diffusion sheet that is configured to diffuse the light from the point light sources anisotropically. Here, “anisotropic” means that the physical quantity or physical property changes depending on the direction. With this configuration, the parallel light or the slightly diffused light incident on the anisotropic light diffusion sheet can be emitted as light that has a peak of diffusion in a specific direction and whose diffusion is suppressed in directions other than the specific direction. Therefore, for example, a display device can be made to perform high luminance display in the specific direction.

(8) In accordance with a preferred embodiment according to any one of the backlight devices mentioned above, the backlight device further comprises a reflective sheet disposed on a point light source side of the luminance uniformity sheet, arranged to surround each of the point light sources, and configured to reflect the light from the point light sources, the luminance uniformity sheet further including a reflective portion that is configured to reflect the light from the point light sources. With this configuration, the light from the point light sources is repeatedly reflected between the reflective portion of the luminance uniformity sheet and the reflective sheet, and thus the light from the point light sources is mixed (blended). This allows the mixed light to transmit through the transmission portions, and thus the chromaticity irregularities caused by the chromaticity variations between individual point light sources can be suppressed. In addition, the illuminance distribution of the light from the lenses can be made uniform, and the luminance can be made high due to the light collecting effect of each of the lenses.

(9) In accordance with a preferred embodiment according to any one of the backlight devices mentioned above, the partition wall is disposed between the point light sources and the luminance uniformity sheet, and the partition wall is either formed in contact with the luminance uniformity sheet and separated from the reflective sheet, or formed in contact with the reflective sheet and separated from the luminance uniformity sheet. With this configuration, mixing of the light from the point light sources between the luminance uniformity sheet and the reflective sheet and suppression of the decrease in contrast can be appropriately balanced.

(10) In accordance with a preferred embodiment according to any one of the backlight devices mentioned above, the transmission portions of the luminance uniformity sheet are located on optical axes of the lenses. With this configuration, it is possible to suppress an increase of light that does not pass through centers of the lenses out of the light transmitted through the luminance uniformity sheet. Therefore, for example, blurring of displayed images on a display device can be suppressed.

(11) In accordance with a preferred embodiment according to any one of the backlight devices mentioned above, the transmission portions include through holes, respectively.

(12) In accordance with a preferred embodiment according to any one of the backlight devices mentioned above, the luminance uniformity sheet further includes a reflective portion that is a portion of the luminance uniformity sheet other than the through holes.

(13) In accordance with a preferred embodiment according to any one of the backlight devices mentioned above, the partition wall is disposed along an outer periphery of a placement region of one or more lenses of the lenses arranged corresponding to one point light source.

(14) In accordance with a preferred embodiment according to any one of the backlight devices mentioned above, the lenses have a triangular shape, a rectangular shape or a hexagonal shape.

(15) In view of the state of the known technology, a display device according to a second aspect of this disclosure is a display device that comprises any one of the backlight devices mentioned above, and a display arranged opposite the light diffusion sheet and disposed on an opposite side relative to the point light sources.

The display device according to the second aspect of this disclosure, as described above, comprises the light diffusion sheet, the lenses configured to convert the light into the parallel light or the light that is slightly diffused, and the partition wall disposed at least one of between the point light sources and the luminance uniformity sheet and between the luminance uniformity sheet and the lenses and disposed between adjacent point light sources in the plan view or between adjacent lenses in the plan view. With this configuration, a decrease in contrast on an emission surface side of the lenses can be suppressed because the spreading of the light from the point light sources can be suppressed by the partition wall disposed at least one of between the point light sources and the luminance uniformity sheet and between the luminance uniformity sheet and the lenses. In addition, since the parallel light and the slightly diffused light can be incident on the light diffusion sheet from the lenses, the diffused light can be efficiently emitted from the light diffusion sheet, unlike when light that is not the parallel light or the slightly diffused light is incident on the light diffusion sheet. For these reasons, the diffused light can be efficiently emitted while suppressing the decrease in contrast.

(16) In accordance with a preferred embodiment according to any one of the backlight devices mentioned above, the partition wall is disposed between the luminance uniformity sheet and the lenses such that the partition wall is formed in contact with the luminance uniformity sheet and the lenses.

(17) In accordance with a preferred embodiment according to any one of the backlight devices mentioned above, the backlight device further comprises an additional partition wall disposed between the point light sources and the luminance uniformity sheet.

(18) In accordance with a preferred embodiment according to any one of the backlight devices mentioned above, the additional partition wall is arranged to overlap the partition wall as viewed in the plan view.

(19) In accordance with a preferred embodiment according to any one of the backlight devices mentioned above, the backlight device further comprises a substrate on which the point light sources are mounted, the additional partition wall being formed in contact with the luminance uniformity sheet and the substrate.

(20) In accordance with a preferred embodiment according to any one of the backlight devices mentioned above, the backlight device further comprises a reflective sheet disposed on a point light source side of the luminance uniformity sheet, arranged to surround each of the point light sources, and configured to reflect the light from the point light sources, the additional partition wall being either formed in contact with the luminance uniformity sheet and separated from the reflective sheet, or formed in contact with the reflective sheet and separated from the luminance uniformity sheet.

According to the present disclosure, as described above, it is possible to provide a backlight device and a display device that can effectively emit diffused light while suppressing a decrease in contrast.

As used herein, the following directional terms “forward”, “rearward”, “front”, “rear”, “up”, “down”, “above”, “below”, “upward”, “downward”, “top”, “bottom”, “side”, “vertical”, “horizontal”, “perpendicular” and “transverse” as well as any other similar directional terms refer to those directions of a display device in an upright position on a horizontal surface. Accordingly, these directional terms, as utilized to describe the display device should be interpreted relative to a display device on a horizontal surface. The terms “left” and “right” are used to indicate the “right” when referencing from the right side as viewed from the front side of the display device, and the “left” when referencing from the left side as viewed from the front side of the display device.

The phrase “at least one of” as used in this disclosure means “one or more” of a desired choice. For one example, the phrase “at least one of” as used in this disclosure means “only one single choice” or “both of two choices” if the number of its choices is two. For another example, the phrase “at least one of” as used in this disclosure means “only one single choice” or “any combination of equal to or more than two choices” if the number of its choices is equal to or more than three. Also, the term “and/or” as used in this disclosure means “either one or both of”.

The term “attached” or “attaching”, as used herein, encompasses configurations in which an element is directly secured to another element by affixing the element directly to the other element; configurations in which the element is indirectly secured to the other element by affixing the element to the intermediate member(s) which in turn are affixed to the other element; and configurations in which one element is integral with another element, i.e. one element is essentially part of the other element. This definition also applies to words of similar meaning, for example, “joined”, “connected”, “coupled”, “mounted”, “bonded”, “fixed” and their derivatives. Finally, terms of degree such as “substantially”, “about” and “approximately” as used herein mean an amount of deviation of the modified term such that the end result is not significantly changed.