Patent Application
20160259113
1. Technical Field
The present invention relates to an illuminating device provided with a light-guide plate and a light-emitting element, a display device, and a mobile electronic apparatus.
2. Related Art
In a display device provided with a reflective display panel, an illuminating device referred to as a so-called front light is used because transmitted light is not able to be used. The illuminating device described above allows light to enter from a side surface of the light-guide plate and emit illumination light from a surface of the light-guide plate on one side in a thickness direction toward the display panel. In the display device used in a mobile electronic apparatus, a light-emitting element such as a light-emitting diode is used as a light source. In such a case, an image display area of the display panel needs to be illuminated uniformly with a small number of the light-emitting elements from a viewpoint of power saving or the like.
JP-A-2013-88501 is an example of the related art.
As illustrated in
An advantage of some aspects of the invention is to provide an illuminating device configured to reduce intensity variations of illumination light emitted from a light-guide plate even in a case where a curved surface is provided on a side surface of the light-guide plate, a display device including the illuminating device, and a mobile electronic apparatus including such a display device.
An illuminating device according to an aspect of the invention includes a first light-emitting element; and a light-guide plate including on a side surface a first light-incident portion opposing the first light-emitting element and configured to emit illumination light from a surface on one side in a thickness direction, in which the light-guide plate in plan view has a curved surface on the side surface thereof at a distance from the first light-incident portion, and a plurality of first bevels facing the first light-incident portion at a certain angle exceeding (90°—critical angle) with respect to a virtual line extending from a center of the first light-incident portion are formed in at least part of an area of the curved surface in a circumferential direction in plan view.
In the aspect, the plan view of the light-guide plate represents a shape of the light-guide plate when viewed from a direction perpendicular to a first surface.
In the aspect, although a curved surface is provided on the side surface of the light-guide plate, the plurality of first bevels facing the first light-incident portion at the certain angle exceeding (90°—critical angle) with respect to the corresponding virtual line extending from the center of the first light-incident portion are formed in at least part of the area of the curved surface in the circumferential direction in plan view. Therefore, light travelling linearly from the center of the first light-incident portion toward an area where the first bevels are provided is partly transmitted through the first bevels. Even though the rest of the light is reflected by the first bevels, such light is less likely to converge on a specific area inside the light-guide plate. In particular, since the plurality of first bevels each form a certain angle with respect to the corresponding virtual line, a direction in which the light reflected from the first bevel travels can be easily determined. Therefore, since intersection of the light reflected from the first bevels inside the light-guide plate can be easily avoided, concentration of the light reflected from the first bevels on a specific area inside the light-guide plate is reliably suppressed. Therefore, the occurrence of an event in which the illumination light exits from a specific area on one surface of the light-guide plate at an extremely high light intensity is reliably suppressed, and thus intensity variations of the illumination light are alleviated.
Preferably, the plurality of first bevels are each at a right angle with respect to the corresponding virtual line. In other words, preferably, the plurality of first bevels each form an angle of 90° with respect to the corresponding virtual line. In this configuration, when light travels linearly toward an area where the first bevels are formed, some of the light is reliably transmitted through the first bevels irrespective of the position of the first light-incident portion from which light travels. The light reflected from the first bevels travels toward the first light-incident portion, and thus the occurrence of an event in which the reflected light concentrates at a specific area inside the light-guide plate is reliably suppressed. Therefore, the illumination light that exits from one surface of the light-guide plate is reliably prevented from having an extremely high intensity in a specific area, and thus intensity variations of the illumination light are reliably alleviated.
Preferably, among the plurality of first bevels, end portions of the first bevels adjacent to each other in the circumferential direction are connected via a linear portion parallel to the virtual line. In this configuration, the first bevels can be easily designed. In addition, even when light travels linearly from the first light-incident portion toward points between the first bevels, the light is less likely to be reflected from the points between the first bevels.
Preferably, in plan view, all of the plurality of first bevels have the same length. In this configuration, the first bevels can be easily designed.
In the aspect, the illuminating device may have a configuration including a second light-emitting element, in which the light-guide plate includes a second light-incident portion opposing the second light-emitting element at a distance from the first light-incident portion on the side surface thereof, and includes a plurality of second bevels in at least part of the curved surface in a circumferential direction in plan view, and the second bevels each form a certain angle exceeding (90°—critical angle) with respect to a virtual line extending from a center of the second light-incident portion and face the second light-incident portion. In this configuration, light entering from the second light-incident portion is less likely to concentrate on a specific area of the light-guide plate. Therefore, the occurrence of an event in which the illumination light exits at an extremely high intensity from a specific area on one surface of the light-guide plate is avoided, and thus intensity variations of the illumination light are reliably alleviated.
Preferably, the light-emitting element is a light-emitting diode.
A display device provided with the illuminating device of the invention includes a display panel opposing the one surface of the light-guide plate.
In this case, a mode in which the display panel is a reflective display panel may be employed.
The display device of the invention may be used in various electronic apparatuses such as mobile electronic apparatuses.
The invention will be described with reference to accompanying drawings, wherein like numbers reference like elements.
Embodiments of the invention will be described with reference to the drawings. In the drawing referred to in the following description, layers and members are not drawn in actual sizes so that the layers and members are large enough to be recognizable in the drawings. In the following descriptions, the term “plan view of a light-guide plate 50” means a shape of the light-guide plate 50 when viewed from a right angle with respect to a first surface 51 of the light-guide plate 50.
A display device 1 illustrated in
In the first embodiment, the display panel 10 is a reflective display panel such as an electrophoretic panel, a reflective liquid-crystal panel, a MEMS device, or a light interference device and includes a first substrate 11, a light-transmissive second substrate 12 arranged so as to oppose the first substrate 11, and a display layer 13 provided between the first substrate 11 and the second substrate 12. A surface of the first substrate 11 opposing the second substrate 12 and a surface of the second substrate 12 opposing the first substrate 11 are provided with electrodes (not illustrated) configured to drive the display layer 13.
In the reflective display panel 10 described above, as illustrated by arrow P in
The illuminating device 30 is configured as a so-called front light and includes light-emitting elements 40 and a light-transmissive light-guide plate 50 having on a side surface 54 light-incident portions 55 opposing the light-emitting elements 40. In the first embodiment, the light-guide plate 50 is adhered to the second substrate 12 of the display panel 10 with a light-transmissive adhesive layer 20. The light-guide plate 50 is formed of a light-transmissive resin having a refractive index of 1.5 to 1.6, and in the first embodiment, the light-guide plate 50 is formed of a resin polycarbonate mold (refractive index=1.59).
In the illuminating device 30 as described above, light emitted from the light-emitting elements 40 enters the inside of the light-guide plate 50 from the light-incident portions 55 of the light-guide plate 50 and travels in the light-guide plate 50 while generating repeated reflections between a first surface 51 and a second surface 52 opposed in a thickness direction of the light-guide plate 50, and the illumination light is emitted toward the display panel 10 from the first surface 51 (one surface in the thickness direction), which is one of the first surface 51 and the second surface 52 and is located on the display panel 10 side. The illumination light is modulated by the display panel 10, enters the inside of the light-guide plate 50 from the first surface 51 of the light-guide plate 50, and then exits from the second surface 52, so that an image is displayed. In the first embodiment, at least one of the first surface 51 and the second surface 52 of the light-guide plate 50 has a light scattering portion 59 including projections and depressions at a predetermined distribution. In the first embodiment, the light scattering portion 59 includes a plurality of semi-spherical projections having, for example, a radius of 60 μm and a height of 10 μm and arranged at pitches of 0.2 mm on the second surface 52 of the light-guide plate 50. Only an area in which the light scattering portion 59 is formed is illustrated in
In the first embodiment, the light-guide plate 50 has a substantially circular shape in plan view, and part of the light-guide plate 50 in the circumferential direction is a projecting portion 53 projecting radially outward. Therefore, substantially the entire part of the light-guide plate 50 in the circumferential direction except the projecting portion 53 has a curved surface 540 protruding radially outward. In the first embodiment, the light-guide plate 50 has a thickness of 0.4 mm and a diameter of 32 mm.
In the first embodiment, a distal end portion 530 of the projecting portion 53 has a linear shape, and the distal end portion 530 of the projecting portion 53 on the side surface 54 of the light-guide plate 50 has the light-incident portions 55. In the first embodiment, the light-incident portions 55 include a first light-incident portion 55a and a second light-incident portion 55b at positions adjacent to each other on the distal end portion 530 of the projecting portion 53. Therefore, the light-emitting elements 40 include a first light-emitting element 40a opposing the first light-incident portion 55a and a second light-emitting element 40b opposing the second light-incident portion 55b. In a width direction orthogonal to a direction in which the light-emitting elements 40 and the light-incident portions 55 oppose each other, the maximum width of the light-guide plate 50 is significantly larger than an area in which the light-incident portions 55 are provided.
The display panel 10 includes a substantially circular shape in plan view in the same manner as the light-guide plate 50 and includes a projecting portion 15 that overlaps the projecting portion 53 of the light-guide plate 50. However, the shape of the display panel 10 in plan view is not limited to the substantially circular shape and may be a rectangular shape. In any case, part of the area where the display panel 10 and the light-guide plate 50 overlap each other is used as an image display area 1a. In the first embodiment, the image display area 1a is configured as a circular area having a slightly smaller outer diameter than that of the light-guide plate 50.
In the first embodiment, the light-emitting elements 40 are, for example, light-emitting diodes 41 which emit white light. The light-emitting diodes 41 excite a yellow phosphor with blue light and generate white light. Therefore, the light-emitting elements 40 function as substantially oval-shaped surface light sources. The light-emitting elements 40 are arranged so that a short axis extends in the thickness direction of the light-guide plate 50 and a long axis extends in a direction of extension of the side surface 54 (the light-incident portions 55) of the light-guide plate 50.
As illustrated in
In the first embodiment, the area where the plurality of first bevels 541 are formed corresponds to an area in which part of light that has entered the light-guide plate 50 from the first light-incident portion 55a enters at an angle larger than a critical angle with respect to the curved surface 540 of the light-guide plate 50 illustrated in
When setting the area as described above, first, the center C1 of the first light-incident portion 55a is assumed to be positioned on an exact circle which constitutes part of the curved surface 540 as illustrated in
Therefore, in the first embodiment, the first bevels 541 illustrated in
In plan view of the light-guide plate 50, all of the plurality of first bevels 541 illustrated in
As illustrated in
In the first embodiment, all of the plurality of first bevels 541 have the same length, and in the first embodiment, all of the plurality of first bevels 541 have, for example, a predetermined dimension. Among the plurality of first bevels 541, end portions of the first bevels 541 adjacent to each other in the circumferential direction are connected via linear portions 546 parallel to the virtual lines L0.
In order to set the first bevels 541 as described above, first, a first bevel 541a having a predetermined dimension which forms an angle of 90° with respect to a virtual line L0a is set as illustrated in
The area in which second bevels 542 are formed illustrated in
As described thus far, in the illuminating device 30 and the display device 1 of the first embodiment, although the curved surface 540 is provided on the side surface 54 of the light-guide plate 50, a plurality of first bevels 541 facing the first light-incident portion at a certain angle exceeding (90°—critical angle) with respect to a virtual line L0 extending from a center C1 of the first light-incident portion 55a are formed in at least part of an area of the curved surface 540 in a circumferential direction in plan view. Therefore, even if light travels linearly from the center C1 of the first light-incident portion 55a toward an area where the first bevels 541 are formed, the light is partly transmitted through the first bevels 541. Even though remaining parts of the light reflect from the first bevels 541, such parts of the light are less likely to converge on a specific area of the light-guide plate 50.
In particular, since the plurality of first bevels 541 each form a certain angle with respect to the corresponding virtual line L0, a direction in which light reflected from the first bevel 541 travels can be easily determined. Therefore, intersection of the light reflected from the first bevels 541 inside the light-guide plate 50 can be easily avoided. Therefore, the occurrence of an event in which concentration of the light reflected from the first bevels 541 on the specific area inside the light-guide plate 50 is reliably suppressed. Further, the plurality of first bevels 541 form a certain angle with respect to the virtual lines L0. Therefore, total reflection can advantageously be prevented even though the angles formed with respect to the virtual lines L0 are not set in accordance with the position in the circumferential direction for each of the first bevels 541. Specifically, in the first embodiment, the plurality of first bevels 541 form an angle of 90° with respect to the virtual lines L0. Therefore, irrespective of the position in the first light-incident portion 55a from which light travels linearly toward an area where the first bevels 541 are formed, part of light is reliably transmitted therethrough. In addition, since the plurality of first bevels 541 each form an angle of 90° with respect to the corresponding virtual line L0, the light reflected from the first bevels 541 travels toward the first light-incident portion 55a. Therefore, the occurrence of an event in which concentration of the light reflected from the first bevels 541 on the specific area inside the light-guide plate 50 is reliably suppressed.
In addition, the curved surface 540 of the light-guide plate 50 is provided with the second bevels 542, which are similar to the first bevels 541.
Therefore, as will be described later with reference to
Since the lengths of the plurality of first bevels 541 are the same, the first bevels 541 can be easily designed. Among the plurality of first bevels 541, the end portions of the first bevels 541 adjacent to each other in the circumferential direction are connected via linear portions 546 parallel to the virtual lines L0. Therefore, the first bevels 541 can be easily designed. In addition, even when light travels linearly from the first light-incident portion 551 to points between the first bevels 541, the light is less likely to be reflected from the points between the first bevels 541.
As illustrated in
The light-guide plate 50 illustrated in
Therefore, as illustrated in
The light-guide plate 50 illustrated in
In the same manner as the first embodiment, the light-guide plate 50 having the configuration described above is provided with the plurality of first bevels 541 facing a center C1 of the first light-incident portion 55a and formed continuously in at least part of the curved surface 540 in the circumferential direction. In the second embodiment, the first bevels 541 are formed on the curved surface 540 of the light-guide plate 50 on both sides with respect to the first light-incident portion 55a in the widthwise direction, and the first bevels 541 face the first light-incident portion 55a at a certain angle exceeding (90°—critical angle) with respect to the virtual lines L0 extending from the center C1 of the first light-incident portion 55a as described in conjunction with the first embodiment irrespective of the side where the first bevels 541 are arranged. In the second embodiment as well, in the same manner as the first embodiment, all of the plurality of first bevels 541 face the first light-incident portion 55a at an angle of 90° with respect to the virtual lines L0 extending from the center C1 of the first light-incident portion 55a. Therefore, in the second embodiment as well, in the same manner as the first embodiment, the occurrence of an event in which the illumination light has an extremely high light intensity from a specific area on the light-guide plate 50 is avoided, and thus intensity variations of the illumination light are alleviated.
For example, as illustrated in
In the embodiments described above, the lengths of the plurality of first inclined surfaces 541 are the same. However, a mode in which the lengths of the plurality of the first inclined surfaces 541 are different may be employed. In the embodiments described above, the angles formed between the virtual lines L0 adjacent each other are different. However, the angles formed between the virtual lines L0 adjacent to each other may be the same. In this case, the shorter the distance between the first inclined surfaces 541 and the light source C1 becomes, the shorter the length of the first inclined surfaces 541. In the above embodiments, the light-guide plate 50 has a substantially circular shape in plan view. However, the invention may be applied in the case where the light-guide plate 50 has an ellipsoidal shape or an oval shape. Furthermore, although the entire shape has a rectangular shape, the invention may be applied to the case where the light-guide plate 50 provided with the curved surface partly in the circumferential direction is used. In the above embodiments, since the display panel 10 is the reflective display panel, the illuminating device 30 is used as a front light. However, a configuration in which a light-transmissive display panel is used as the display panel 10 and the illuminating device 30 is used as a back light is also applicable. In addition, the illuminating device 30 of the invention may be used in photo frames configured to accommodate photos for exhibition, or in advertising displays, instrument used in automobiles or the like. Configuration Example of Mobile Electronic Apparatus
The display device 1 of the invention may be used as display devices for mobile phones, Personal Digital Assistants, camera finders, or electronic papers in addition to the mobile electronic apparatus 100 illustrated in
The entire disclosure of Japanese Patent Application No. 2015-044367, filed Mar. 6, 2015 is expressly incorporated by reference herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-044367 | Mar 2015 | JP | national |
