JP2011159631A - Light guide, backlight apparatus and light source apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light guide that can enhance light utilization efficiency while having the capability of conducting light from a light source to a thin light guide plate, a backlight apparatus, and light source apparatus using the same. <P>SOLUTION: The light coming from an edge of a YZ plane and traveling along the YZ plane is reflected by a top face 4A at a point A and then is reflected by a bottom face 4b at a point B different from a point B' but the point B is not present in the YZ plane. In other words, the light reflected by the top face 4A at the point A has an X-directional component orthogonal to the YZ plane to go in the direction leaving from the YZ plane and to enter into the point B away from the point B'. Accordingly, when the incident angles θ1 at the point A are the same, the incident angle θ2 at the point B becomes smaller than the incident angle θ2' at the point B'. This enhances the possibility of satisfying full reflect conditions even if reflection is repeated. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a light guide, a backlight device, and a light source device, and more particularly, to a light guide for guiding light from a light source to a light guide plate and the like, and a backlight device and a light source device having the light guide.

  In a liquid crystal display device provided in a mobile phone, a portable information terminal, or the like, a backlight device for illuminating a display unit is used. The backlight device includes a light guide plate disposed on the back surface of a liquid crystal panel as a display unit, a light source such as a light emitting element (LED) or a cold cathode tube disposed on the side of the light guide plate, and light from the light source. It is comprised by the light guide for guiding to a light-guide plate. Since the backlight device having such a configuration allows light to be incident from the side surface of the light guide plate, there is no need to arrange a light source in the thickness direction of the light guide plate, so that the entire device can be reduced in thickness. is there.

  Incidentally, in recent years, liquid crystal display devices are often mounted on thin mobile phones, digital cameras, and the like, and the demand for downsizing of backlight devices has become strict. Accordingly, the light guide plate has been made thinner. However, it is difficult to downsize the LED used as the light source to the same extent as the thickness of the light guide plate. However, the light emission characteristics of LEDs are generally low in directivity, and some of the emitted light spreads radially at a wide angle, so it is a problem how to efficiently make the emitted light from the LED enter the thin light guide plate. It has become.

  Here, Patent Document 1 discloses a backlight device provided with a light receiving portion on which an inclined surface is formed that is inclined at an angle of 45 degrees or less upward from the main body portion of the light guide plate. Also disclosed is a technology for reducing the thickness of the backlight device by providing a light-receiving surface inclined substantially at right angles to the inclined surface, and inclining the light-emitting surface of the light source in parallel with the light-receiving surface. Has been.

JP 2003-121840 A

  However, in the former case, the light incident on the inclined surface is not necessarily totally reflected. Therefore, in order to increase the reflectance on the inclined surface, the inclined surface is covered with a reflective film. However, when the reflective film is coated, the manufacturing process of the light guide plate becomes complicated. Further, due to the characteristics of the reflective film, there is a problem that the light utilization efficiency is lowered because a lot of light is absorbed. Furthermore, in the latter case, it can contribute to reducing the thickness of the backlight device. However, in order to further reduce the thickness of the main body of the light guide plate, the number of times of reflection of incident light is increased in the light receiving portion. However, there is a problem that the light utilization efficiency is lowered.

  The present invention has been made in view of the problems of the prior art, and a light guide capable of enhancing the light use efficiency despite being able to conduct light from a light source to a thin light guide plate, and An object is to provide a backlight device and a light source device used.

The light guide according to claim 1, wherein the light guide is disposed between a light source and a light guide plate, and guides light from the light source to the light guide plate.
An incident surface for incident light from the light source;
An exit surface for emitting light to the light guide plate;
Extending in a direction intersecting the entrance surface and the exit surface, and having a top surface and a bottom surface facing each other,
One surface of the top surface and the bottom surface is relative to the other surface so that the size of the exit surface in the thickness direction of the light guide plate is smaller than the size of the entrance surface in the thickness direction of the light guide plate. Is inclined,
At least one of the top surface and the bottom surface is provided with a structure having a light leakage reduction shape for suppressing the amount of light emitted from a surface other than the light exit surface out of the light incident from the light incident surface. It is characterized by.
Further, in the light guide, when the light leakage reduction shape is arranged (virtual), a plane extending from the incident surface side toward the emission surface side and extending along the thickness direction of the light guide plate is disposed. When the light emitted from the light source and traveling along the plane enters the light leakage reduction shape, it has a shape having a plurality of reflection surfaces that give a direction component such that the reflected light leaves the plane. Is preferred.

  According to the light guide of the present invention, one of the top surface and the bottom surface is such that the size of the exit surface in the thickness direction of the light guide plate is smaller than the size of the entrance surface in the thickness direction of the light guide plate. Since this surface is inclined with respect to the other surface, light from a light source having a thickness larger than that of the light guide plate can be guided well. On the other hand, when the light emission characteristics of the light source are low, a part of the light emitted from the light source does not satisfy the total reflection condition while repeating the reflection between the top surface and the bottom surface inclined to each other, and the top surface Or there is a risk of leaking outward from the bottom surface. On the other hand, in the present invention, light leakage is reduced by suppressing the amount of light emitted from a surface other than the light exit surface out of the light incident from the light incident surface on at least one of the top surface and the bottom surface. Since a structure having a shape is provided, it becomes easy for light incident from the incident surface to satisfy the total reflection condition even if the light is repeatedly reflected on the top surface and the bottom surface inclined with respect to each other. Light utilization efficiency can be improved by suppressing light leaking outward from the bottom surface.

  According to a second aspect of the present invention, in the light guide according to the first aspect, the light leakage reduction shape extends from the incident surface side toward the emission surface side and extends along the thickness direction of the light guide plate. When the plane extending in this manner is a virtual plane, the direction component is such that when the light emitted from the light source and traveling along the virtual plane enters the light leakage reduction shape, the reflected light leaves the virtual plane. It is easy to satisfy the total reflection condition.

The light guide according to claim 3, wherein the light guide is disposed between a light source and a light guide plate, and guides light from the light source to the light guide plate.
An incident surface for incident light from the light source;
An exit surface for emitting light to the light guide plate;
Extending in a direction intersecting the entrance surface and the exit surface, and having a top surface and a bottom surface facing each other,
One surface of the top surface and the bottom surface is relative to the other surface so that the size of the exit surface in the thickness direction of the light guide plate is smaller than the size of the entrance surface in the thickness direction of the light guide plate. Is inclined,
When at least one of the top surface and the bottom surface extends from the incident surface side toward the exit surface side and extends along the thickness direction of the light guide plate as a virtual plane, the light source emits light. A structure having a light leakage reduction shape having a directional component such that reflected light of light traveling along the virtual plane is separated from the virtual plane is provided. The operational effects of the present invention are the same as those of the first and second aspects of the invention.

  According to a fourth aspect of the present invention, in the light guide according to any one of the first to third aspects, the light leakage reduction shape is a streak-like unevenness extending from the incident surface side toward the emission surface side. Therefore, mass production is possible by molding, for example. The light leakage reduction shape may be formed integrally with the top surface and / or the bottom surface, or may be formed separately and adhered to the top surface and / or the bottom surface.

  According to a fifth aspect of the present invention, in the light guide according to the fourth aspect, the light leakage reduction shape includes a plurality of pairs of inclined surfaces, and the intersection of the pair of inclined surfaces is from the incident surface side. It extends toward the exit surface side.

  The light guide according to claim 6 extends in a direction intersecting the entrance surface, the exit surface, the top surface, and the bottom surface in the invention according to any one of claims 1 to 5, and faces each other. And the distance between the pair of side surfaces is wider on the exit surface side than the entrance surface side, so that the light incident on the side surface satisfies the total reflection condition Since it becomes easy, it is preferable.

  A light guide according to a seventh aspect of the present invention is the light guide according to any one of the first to fourth aspects, wherein a pair of side surfaces extending in a direction intersecting the incident surface and the emission surface and facing each other are provided. And the distance between the pair of side surfaces is wider on the exit surface side than the entrance surface side, and the light leakage reduction shape extends from the entrance surface side toward the exit surface side. The incident surface has a plurality of pairs of inclined surfaces having intersecting portions, and an interval between adjacent intersecting portions on the incident surface side is smaller than an interval on the exit surface side. It is easier to control the traveling direction of incident light, and various characteristics such as illuminance distribution and luminance distribution on the exit surface can be controlled according to the purpose, reducing illuminance unevenness on the exit surface. Is done. In addition, since light incident from the incident surface easily satisfies the total reflection condition, the light use efficiency can be increased.

The light guide according to claim 8 is characterized in that, in the invention according to claim 5 or 7, the following conditional expression (4) is satisfied, where β is an angle formed by the pair of inclined surfaces at the intersection. And
100 ° ≦ β ≦ 170 ° (4)

When the angle β formed by the pair of inclined surfaces at the intersecting portion satisfies the conditional expression (4), the light incident on the light guide can easily satisfy the total reflection condition, so that the light use efficiency can be improved. Compared to the case where there is no light, the light utilization efficiency is about 1.2 times or more. In particular, if β is 170 ° or less, the effect of controlling the traveling direction of the light can be enhanced, and sufficient light utilization efficiency can be obtained. On the other hand, if β is 100 ° or more, the tip portion of each inclined surface becomes a shape that is difficult to be chipped and manufacturing is easy, and fragments and the like are not easily attached to the light guide, so that the influence of unnecessary scattering is suppressed, Sufficient light utilization efficiency can be obtained. Preferably, if β satisfies the following formula, light utilization efficiency of about 1.3 times or more can be realized as compared with the case where there is no inclined surface.
116 ° ≦ β ≦ 165 ° (4 ′)

  According to a ninth aspect of the present invention, in the light guide according to any of the first to eighth aspects, the light leakage reducing shape is provided so as to protrude from the incident surface of the light guide plate. Thus, even when the light guide plate is thin, it is possible to ensure the strength of the light guide on the exit surface side.

  A light guide according to a tenth aspect is the light guide according to any one of the first to eighth aspects, wherein a part of the light leakage reduction shape protrudes from the incident surface of the light guide plate on the emission surface. Therefore, even when the light guide plate is thin, it is possible to ensure the strength of the light guide on the exit surface side.

  The light guide according to claim 11 is the invention according to any one of claims 1 to 10, wherein the dimension of the exit surface in the thickness direction of the light guide plate is equal to or less than the thickness of the entrance surface of the light guide plate. Therefore, even when the light guide plate is thin, it is possible to ensure the strength of the light guide on the exit surface side.

  A light guide according to a twelfth aspect is the invention according to any one of the first to eleventh aspects, wherein a dimension of the light leakage reduction shape in the thickness direction of the light guide plate is from the incident surface side to the emission surface side. It is easy to control the traveling direction of light incident from the entrance surface, and for various characteristics such as illuminance distribution and luminance distribution on the exit surface. Since it can be controlled together, illuminance unevenness on the emission surface is reduced. In addition, since light incident from the incident surface easily satisfies the total reflection condition, the light use efficiency can be increased.

  A light guide according to a thirteenth aspect is the light guide according to any one of the first to eleventh aspects, wherein a dimension of the light leakage reduction shape in the thickness direction of the light guide plate is from the incident surface side to the output surface side. Since it gradually increases and then decreases gradually, the light utilization efficiency can be further increased.

  A light guide according to a fourteenth aspect is the invention according to any one of the first to thirteenth aspects, wherein the light leakage reducing shape is a plurality of pairs of inclined surfaces, and is an intersection of the pair of inclined surfaces. Is between the inclined surface extending from the incident surface side toward the output surface side and the two inclined surfaces forming a valley, and along the bottom surface on the output surface side. And a gap surface extending in the direction.

  For example, even when the light guide plate having a small thickness is used, in order to ensure the strength of the light guide, the exit surface cannot be thinned, and as a result, the top surface side of the exit surface protrudes from the entrance surface of the light guide plate. May end up. In such a case, the light traveling in the ride guide may leak out of the light guide plate from the protruding exit surface, and the light may not be used appropriately. On the other hand, according to the present invention, a gap surface extending between the two inclined surfaces forming a valley and extending along the bottom surface is provided on the emission surface side, and the light The light can be used appropriately by reflecting light from the inside of the guide and thereby suppressing light leaking. The gap surface may be a flat surface or a curved surface.

  According to a fifteenth aspect of the present invention, in the invention according to the fourteenth aspect, an intersection line of the two inclined surfaces intersecting the gap surface is gradually separated from the incident surface side toward the emission surface side. It is characterized by.

  A light guide according to a sixteenth aspect is characterized in that, in the invention according to the fourteenth or fifteenth aspect, the gap surface is in contact with the emission surface, but is not in contact with the incident surface.

  A light guide according to claim 17 is the light guide according to any one of claims 1 to 16, wherein the light leakage reduction shape is a plurality of pairs of inclined surfaces, and is an intersection of the pair of inclined surfaces. Each intersects with the inclined surface extending from the incident surface side toward the output surface side and the two inclined surfaces forming a mountain, and is in contact with the output surface and with respect to the output surface. It has a tapered surface inclined toward the incident surface side at a predetermined angle.

  According to the present invention, a tapered surface that intersects each of the two inclined surfaces that form a mountain and is in contact with the emission surface and inclined toward the incident surface side at a predetermined angle with respect to the emission surface is provided. By reflecting light from the inside of the light guide and thereby suppressing light leaking out, it is possible to use light appropriately. The tapered surface may be a flat surface or a curved surface.

  The light guide according to claim 18 is the invention according to any one of claims 5, 7, and 14 to 17, wherein the angle of the intersecting portion of the pair of inclined surfaces is constant over the entire length of the intersecting portion. It is characterized by being.

  The light guide according to claim 19 is the invention according to any one of claims 1 to 18, wherein the top surface and the bottom surface are assembled so as to be inclined with respect to the bottom surface of the light guide plate. Therefore, the light use efficiency can be increased.

  The light guide according to claim 20 is the invention according to any one of claims 1 to 18, wherein the bottom surface is assembled so as to be positioned on the same plane with respect to the bottom surface of the light guide plate. Therefore, it becomes easy to manufacture a backlight device including the light guide.

  The light guide according to claim 21 is characterized in that, in the invention according to any one of claims 1 to 20, the light guide has a plurality of the incident surfaces. Is easy to manufacture.

  A light guide according to a twenty-second aspect is the light-emitting device according to any one of the first to twenty-first aspects, wherein the light source is an LED.

  A backlight device according to a twenty-third aspect has the light guide according to any one of the first to twenty-second aspects.

The backlight device according to claim 24, which is disposed between a light source and a liquid crystal element, emits light from the light source, and light that has passed through the light guide toward the liquid crystal element. A backlight device comprising a light guide plate that
The light guide is
An incident surface for incident light from the light source;
An exit surface for emitting light to the light guide plate;
Extending in a direction intersecting the entrance surface and the exit surface, and having a top surface and a bottom surface facing each other,
One surface of the top surface and the bottom surface is relative to the other surface so that the size of the exit surface in the thickness direction of the light guide plate is smaller than the size of the entrance surface in the thickness direction of the light guide plate. Is inclined,
At least one of the top surface and the bottom surface is provided with a structure having a light leakage reduction shape that suppresses the amount of light emitted from a surface other than the light exit surface out of the light incident from the light incident surface. It is characterized by being. The operational effects of the present invention are the same as those of the first aspect of the present invention.

The backlight device according to claim 25, wherein a light source and a light guide disposed between the light source and the light guide plate, and a light guide for guiding light from the light source to the light guide plate are integrally attached. A device,
The light guide is
An incident surface for incident light from the light source;
An exit surface for emitting light to the light guide plate;
Extending in a direction intersecting the entrance surface and the exit surface, and having a top surface and a bottom surface facing each other,
One surface of the top surface and the bottom surface is relative to the other surface so that the size of the exit surface in the thickness direction of the light guide plate is smaller than the size of the entrance surface in the thickness direction of the light guide plate. Is inclined,
At least one of the top surface and the bottom surface is provided with a structure having a light leakage reduction shape that suppresses the amount of light emitted from a surface other than the light exit surface out of the light incident from the light incident surface. It is characterized by being. The operational effects of the present invention are the same as those of the first aspect of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, although the light from a light source can be easily conducted also with respect to a thin light-guide plate, the light guide which can improve the utilization efficiency of light, and a backlight apparatus and a light source device using the same Can be provided.

It is sectional drawing of the backlight apparatus containing the light guide concerning this Embodiment. It is the figure which cut | disconnected the backlight apparatus of FIG. 1 by the II-II line | wire, and looked at the arrow direction. 3 is a schematic perspective view of a light guide 4. FIG. It is a figure for demonstrating the light leakage reduction shape. It is a figure which shows the simulation result which this inventor performed. 6 (a) is a side view of the light guide 4, FIG. 6 (b) is a top view of the light guide 4, and FIG. 6 (c) shows a pair of inclined surfaces 4g and 4h on the exit surface side. It is the enlarged view seen. It is a side view of the light guide concerning the modification of this Embodiment. It is a figure which expands and shows the prism of the light guide concerning the modification of this Embodiment. It is a top view of the light guide concerning the modification of this Embodiment. It is a perspective view of the light guide concerning another embodiment. It is a top view of the light guide shown in FIG. It is a figure which shows the result of the simulation which the inventor performed. It is a side view which shows the light guide 4 and the light-guide plate 3 concerning this Embodiment. It is a perspective view which shows the light guide 4 and light-guide plate 3 concerning another embodiment. It is the figure which looked at embodiment shown in FIG. 14 from the side. It is a graph which shows the result of the simulation which this inventor performed. It is a perspective view which shows the light guide 4 and the light-guide plate 3 concerning another embodiment. It is the figure which looked at embodiment shown in FIG. 17 from the side. It is a graph which shows the result of the simulation which this inventor performed. It is a side view of the light guide 4 concerning another modification. It is a side view of the light guide 4 and the light-guide plate 3 concerning another modification.

  Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings. FIG. 1 is a cross-sectional view of a backlight device BL including a light guide and a light source device LA according to the present embodiment. FIG. 2 is a sectional view of the backlight device of FIG. FIG. In FIGS. 1 and 2, an LED 2 that is three light sources and a thin plate-shaped light guide plate 3 are disposed in a housing 1, and three (see FIG. 2) light guides 4 are disposed therebetween. A fine convex portion (or concave portion) 3 a is formed on the upper surface of the light-transmitting light guide plate 3. The convex portion 3a, which is a light scattering portion, becomes larger (higher) as the distance from the LED 2 increases, and the arrangement interval thereof is narrowed, so that the light irradiated from the upper surface of the light guide plate 3 is brought closer to the entire surface. be able to. Further, a diffusion plate 5 is disposed on the upper surface of the light guide plate 3, and a liquid crystal display element 6 is disposed on the upper surface of the diffusion plate 5. The light source device LA can be configured by integrally attaching the LED 2 to the light guide 4. The backlight device BL includes an LED 2, a light guide 4, a light guide plate 3, and a diffusion plate 5.

  1 and 2, the light emitted from the LED 2 is guided into the light guide plate 3 by the light guide 4, and is uniformly irradiated from the upper surface thereof to the lower surface of the liquid crystal display element 6 through the diffusion plate 5. It is like that.

  FIG. 3 is a schematic perspective view of the light guide 4. In FIG. 3, the thickness direction of the light guide plate 3 is the vertical direction (Y direction), and the width direction of the light guide plate 3 is the left and right direction (X direction). The light guide 4 integrally formed from a transparent resin such as PC or PMMA has a top surface 4a, a bottom surface 4b, side surfaces 4c and 4d, and an incident surface 4e and an output surface 4f intersecting these. ing.

  The incident surface 4e is in contact with or close to the exit surface 2a (see FIG. 1) of the LED 2, and the exit surface 4f is in contact with or in close proximity to the entrance surface 3b (see FIG. 1) of the light guide plate 3. The vertical dimension D1 of the entrance surface 4e is larger than the vertical dimension D2 of the exit surface 4f, and the lateral dimension L1 of the entrance surface 4e is greater than the lateral dimension L2 of the exit surface 4f. It is getting smaller. Since it has such a shape, the light guide 4 can guide the light emitted from the LED 2 to the thin light guide plate 3.

  Furthermore, the light guide 4 forms a light leakage reduction shape 4M on the top surface 4a. Here, the vertical dimension D1 of the incident surface 4e represents the vertical dimension on the incident surface 4e side of the light guide 4 excluding the light leakage reduction shape, and the vertical dimension D2 of the emission surface 4f is The vertical dimension on the light exit surface 4f side of the light guide 4 excluding the light leakage reduction shape is shown.

  FIG. 4 is a diagram for explaining a light leakage reduction shape. In FIG. 4, a YZ plane (imaginary plane) is defined as a plane orthogonal to the bottom surface 4b. The YZ plane passes through the center of the LED 2 in the width direction of the light guide plate 3 and extends along the thickness direction of the light guide plate 3. Here, it is assumed that the top surface 4A 'indicated by the dotted line is inclined so as to become narrower toward the exit surface side (the back side in FIG. 4) with respect to the bottom surface 4b. In such a case, the light that is emitted from the front edge of the YZ plane and travels along the YZ plane satisfies the total reflection condition while the incident angle is small. It is reflected and subsequently reflected by the bottom surface 4b at the point B ′, and does not leave the YZ plane even after reflection. However, since the top surface 4A 'is inclined toward the exit surface with respect to the bottom surface 4b, the incident angle θ2' at the point B is larger than the incident angle θ1 at the point A. Therefore, if one of the incident angles exceeds the threshold value during repeated reflection, the total reflection condition is lost, and light may leak to the outside through the top surface 4A 'or the bottom surface 4b.

  Here, as a light leakage reduction shape, a configuration is considered in which a top surface 4A that is not only inclined toward the exit surface side with respect to the bottom surface 4b but also inclined toward the left side surface side is provided (see solid line). . In the example of FIG. 4, it is assumed that the YZ planes intersect at the intersection positions of the top surfaces 4A 'and 4A. According to such a configuration, the light emitted from the front edge of the YZ plane and traveling along the YZ plane is reflected by the top surface 4A at the point A as shown by the solid arrow, and is subsequently different from the point B ′. Although reflected by the bottom surface 4b at the point B, the point B does not exist in the YZ plane. In other words, the light reflected by the top surface 4A at the point A has an X direction component orthogonal to the YZ plane, proceeds in a direction away from the YZ plane, and enters a point B far from the point B ′. Become. Therefore, when the top surface 4A ′ is used and when the top surface 4A is used, when the incident angle θ1 at the point A is the same, the incident angle θ2 at the point B is equal to the incident angle θ2 at the point B ′. Thus, when the top surface 4A is used, the possibility of satisfying the total reflection condition is increased even when reflection is repeated, compared with the case where the top surface 4A 'is used.

  However, this effect is limited to rays incident on the light leakage reduction shape along the YZ plane or along a plane parallel to the YZ plane, that is, incident rays having only components in the Y and Z directions. is not. Similar effects can be obtained with respect to incident rays having components in the X direction in addition to the Y and Z directions. That is, a part or all of the Y direction component of the incident light beam is converted into the X direction or the Z direction by the top surface 4A, so that the possibility that the light beam satisfies the total reflection condition is increased.

  As described above, the light leakage reduction shape is such that one of the top surface 4a and the bottom surface 4b of the light guide 4 is uniformly inclined in the direction in which the width in the vertical direction (height direction) of the side surface 4c or 4d becomes narrow. Can only demonstrate its function. Furthermore, in the present embodiment, as shown in FIG. 3, a part of the top surface 4a is deformed, and a plurality of pairs of intersecting long and slender inclined surfaces (referred to as line-like irregularities or prisms) 4g, 4h are provided. Since an intersection (which is called the apex of the prism) 4i of the pair of inclined surfaces 4g and 4h extends from the entrance surface 4e toward the exit surface 4f, the light guide 4 is arranged in the vertical direction. The dimensions can be reduced, which can contribute to the downsizing of the backlight device. In the present embodiment shown in FIGS. 3 to 13, the pair of inclined surfaces 4g and 4h constitute the light leakage reduction shape 4M. Although not shown in some drawings, when a gap surface 4k is formed between a pair of inclined surfaces 4g and 4h as will be described later, the gap surface 4k is also formed into a light leakage reduction shape 4M. In addition, when the tapered surface 4p connected to the pair of inclined surfaces 4g and 4h is formed as described later, the tapered surface 4p is also included in the light leakage reduction shape 4M.

  FIG. 5 is a diagram showing a simulation result performed by the present inventor. 5A shows a state in which the light guide 4 is projected in the Z-axis direction in FIG. 3, and FIG. 5B shows a state in which the light guide 4 is projected in the X-axis direction in FIG. . According to FIG. 5, it is understood that the light incident on the light guide 4 travels to the exit surface while being reflected in the order of R1 to R10 between the prism on the top surface 4a and the bottom surface 4b.

Here, the preferable form of the light guide 4 is described. 6A is a side view of a portion of the light guide 4 excluding the light leakage reduction shape, FIG. 6B is a top view of the light guide 4, and FIG. 6C is a light leakage. It is the figure which took out only the part of a reduced shape, and is the enlarged view which looked at a pair of inclined surface 4g, 4h toward the output surface side. The height dimension on the incident surface 4e is D1, the height direction dimension on the exit surface 4f is D2, the distance (full length) between the entrance surface 4e and the exit surface 4f is L3, and the entrance surface 4e and the top surface 4a. When the angle between the incident surface 4e and the bottom surface 4b is θ2, the smaller one of the angles θ1 and θ2 falls below the upper limit value of the following formula (1), It is preferable to reduce the total length L3 of the guide 4 and to exceed the lower limit value because the total reflection condition is easily satisfied.
70 ° <θ <90 ° (1)

Moreover, it is preferable that the area of the incident surface 4e is larger than the area of the output surface 4f because light can be efficiently distributed. That is, it is preferable to design the light guide 4 so that the following formula is established, where L1 is the dimension in the width direction on the incident surface 4e and L2 is the dimension in the width direction on the exit surface 4f.
L1 × D1 ≦ L2 × D2 (2)

In FIG. 6B, it is preferable that the angle γ formed by the center line of the light guide 4 and the apex of the prism having the light leakage reduction shape satisfy the following expression, because the total reflection condition is easily satisfied. The angle γ is effective even at 0 °.
0 ° ≦ γ ≦ 40 ° (3)

The angle β formed by the inclined surfaces 4g and 4h in FIG. 6 (c) is more than the lower limit value of the following expression, so that the total reflection condition can be easily satisfied. The height can be suppressed.
100 ° ≦ β ≦ 170 ° (4)

  FIG. 7 is a side view of a light guide according to a modification of the present embodiment. As shown in FIG. 7A, the angle θ1 formed by the top surface 4a of the light guide 4 with respect to the incident surface of the light guide 4 facing the emission surface of the LED 2 and the bottom surface 4b of the light guide 4 are formed. The angle θ1 formed by the top surface 4a of the light guide 4 with respect to the incident surface of the light guide 4 and the bottom surface of the light guide 4 as shown in FIG. The angle θ2 formed with 4b may be varied. Further, as shown in FIG. 7C, an angle θ1 (or θ2) formed by the top surface 4a (or the bottom surface 4b) of the light guide 4 with respect to the incident surface of the light guide 4 can be an obtuse angle. .

  FIG. 8 is an enlarged view showing an enlarged top surface of the light guide according to the modification of the present embodiment. As shown in FIG. 8A, the inclined surfaces 4g and 4h may stand up at different angles as shown in FIG. 8B, as well as when they stand up at the same angle with respect to the horizontal plane. Further, as shown in FIG. 8 (c), a plane 4j may be arranged between adjacent prisms, or as shown in FIG. 8 (d), the intersection 4i of the inclined surfaces 4g and 4h may be a plane. good. Furthermore, as shown in FIG. 8E, the surface of the prism may be a curved surface. In such a case, the inclined surfaces 4g and 4h are smoothly connected at the intersection. Moreover, the shape of these modified examples can be configured to appear in the middle of the length direction (depth direction) of the light guide 4, for example, or can be configured to be combined from a plurality of shapes by switching from the middle.

  FIG. 9 is a top view of a light guide according to a modification of the present embodiment. As shown in FIG. 9 (a), the intersection 4i, which is the apex of the prism, extends not only when inclined to both sides with respect to the center line of the light guide 4, but also as shown in FIG. 9 (b). The light guide 4 may extend parallel to the center line of the light guide 4 or may extend in a direction inclined with respect to the center line of the light guide 4 as shown in FIG. Furthermore, as shown in FIG. 9D, the intersecting portions 4i may extend radially, or may extend so as to draw a curve instead of a straight line. Further, as shown in FIGS. 9E and 9F, the side surfaces 4c and 4d of the light guide may be curved surfaces. The dotted lines in FIGS. 9B, 9C, and 9D represent prism valleys (valley ridge lines). For example, in FIG. 9A, the prism valleys are omitted. Yes.

  FIG. 10 is a perspective view of a light guide according to another embodiment, and FIG. 11 is a top view of the light guide shown in FIG. Similarly, in FIG. 10, the thickness direction of the light guide plate 3 is defined as the vertical direction (Y direction), and the width direction of the light guide plate 3 is defined as the horizontal direction (X direction). The light guide 4 integrally formed from a transparent resin such as PC, PMMA, or cycloolefin polymer has a top surface 4a, a bottom surface 4b, side surfaces 4c and 4d, and an incident surface 4e and an output surface 4f intersecting these. And have. Furthermore, a part of the top surface 4a is deformed, and a plurality of pairs of a pair of slender inclined surfaces (which are referred to as streaky irregularities or prisms) 4g and 4h are provided, and an intersection of the pair of inclined surfaces 4g and 4h. 4i (referred to as the apex of the prism) extends from the entrance surface 4e toward the exit surface 4f. Further, an intersection between adjacent pairs of inclined surfaces 4h and 4g is defined as a valley ridge line 4j.

  The incident surface 4e is in contact with or close to the exit surface 2a (see FIG. 1) of the LED 2, and the exit surface 4f is in contact with or in close proximity to the entrance surface 3b (see FIG. 1) of the light guide plate 3. The vertical dimension D1 on the incident surface 4e side of the side surfaces 4c and 4d is larger than the vertical dimension D2 on the output surface 4f side, and the horizontal dimension L1 of the incident surface 4e is equal to that of the output surface 4f. It is smaller than the dimension L2 in the left-right direction. In addition, the interval W1 between the adjacent intersecting portions 4i on the incident surface 4e side is smaller than the interval W2 on the exit surface 4f side. Further, the number of streaky irregularities on the incident surface 4e side is equal to the number of streaky irregularities on the exit surface 4f side. In the present embodiment, the dimensions of the pair of inclined surfaces 4g and 4h forming the light leakage reduction shape in the thickness direction of the light guide plate 3 gradually increase from the incident surface 4e side to the output surface 4f side. ing.

Here, in FIG. 10, when the angle formed by the pair of inclined surfaces 4g and 4h at the intersecting portion 4i is β, the following conditional expression (4) is satisfied.
100 ° ≦ β ≦ 170 ° (4)

  Since it has such a shape, it is easy to control the traveling direction of light incident from the incident surface 4e, and various characteristics such as illuminance distribution and luminance distribution on the output surface 4f can be controlled according to the purpose. Therefore, the illuminance unevenness on the exit surface 4f is reduced. Moreover, since the light incident from the incident surface 4e easily satisfies the total reflection condition, the light use efficiency can be improved.

  FIG. 12 is a diagram showing the results of a simulation performed by the inventor. 12, in the embodiment shown in FIGS. 10 and 11, the angle θ <b> 1 between the incident surface and the top surface is 89.6 ° as an example of a range satisfying 70 ° <θ <b> 1 <90 °, and the refractive index 1. When the light guide is configured using the resin material of 525, the result of an example in which the apex angle β of the prism which is a light leakage reduction shape is changed from 90 ° to 180 ° is shown. The apex angle β of 180 ° means that the prism has no light leakage reduction shape and the top surface is flat. In FIG. 12, the vertical axis represents the light efficiency, and the horizontal axis represents the apex angle β of the prism. According to the results shown in FIG. 12, the light use efficiency of 0.44 or more can be ensured when β is in the range of 100 ° to 170 °. Furthermore, in the range where β is 116 ° or more and 165 ° or less, the light use efficiency can be secured 0.52 or more.

  By the way, in the backlight device, the light guide plate 3 having a relatively small thickness may be used. However, if the thickness of the light exit surface 4f of the light guide 4 is reduced in accordance with the thickness of the light incident surface 3b of the light guide plate 3, the strength of the light guide 4 is insufficient, which may cause bending or breakage. In addition, problems such as molding defects due to a decrease in rigidity also occur. Therefore, in order to ensure the strength of the light guide 4 on the exit surface 4 f side, the top surface 4 a side of the exit surface 4 f may protrude from the entrance surface 3 b of the light guide plate 3.

  In such a case, as shown in FIG. 13, the light traveling in the ride guide 4 enters the diffusion plate 5 located above the light guide plate 3 from the protruding area of the emission surface 4 f and enters from the side surface. There is a possibility that the intensity distribution of the light emitted from the diffusion plate 5 may be non-uniform. In the following embodiments, such problems can be alleviated or eliminated.

  FIG. 14 is a perspective view showing a light guide 4 and a light guide plate 3 according to another embodiment, and shows an assembled state. In the present embodiment, when the thickness direction is the vertical direction, the thickness T2 of the incident surface 3b of the light guide plate 3 is thinner than the maximum thickness T1 on the light exit surface 4f side of the light guide 4 including the light leakage reduction shape. It has become. Further, the dimension D2 in the height direction on the exit surface of the light guide is smaller than the thickness T2 of the incident surface 3b of the light guide plate 3. Accordingly, on the light exit surface 4f side of the light guide 4, a part of the crest formed by the inclined surfaces 4g and 4h (that is, the light leakage reduction shape) protrudes upward from the incident surface 3b (on all inclined surfaces). It is sufficient if a part of it is not limited. It should be noted that even from the crest formed by the inclined surfaces 4g and 4h to the intersecting lines 4m and 4n where each of the inclined surfaces 4g and 4h intersect the gap surface 4k (that is, the entire light leakage reduction shape) protrudes from the incident surface 3b. However, in order to obtain the effect of the present invention, it is sufficient that at least a part of the light leakage reducing shape protrudes from the incident surface 3b.

  Further, in the present embodiment, the gap surface 4k, which is a plane extending between the two inclined surfaces 4h and 4g forming the valleys among the plurality of pairs of inclined surfaces and extending along the bottom surface 4b, is formed. Provided. The gap surface 4k and the intersecting lines 4m and 4n of the two inclined surfaces 4h and 4g intersecting with the gap surface 4k are gradually separated from the entrance surface 4e side to the exit surface 4f side, so that manufacture is easy. That is, the gap surface 4k has a triangular shape as viewed from above. Further, the gap surface 4k is formed so as to be in contact with the emission surface 4f but not to be in contact with the incident surface 4e. The gap surface 4k is preferably terminated in the incident surface 3b. Since the gap surface 4k is formed, the dimensions of the inclined surfaces 4g and 4h constituting the light leakage reduction shape in the thickness direction of the light guide plate 3 gradually increase from the incident surface 4e side to the output surface 4f side. After that, it gradually decreases (see FIG. 15). Since the angle β formed by the pair of inclined surfaces 4g and 4h is constant over the entire length of the intersecting portion 4i, the manufacture is easy. Other configurations are the same as those in the embodiment shown in FIG. In the present embodiment shown in FIGS. 14 to 16, the pair of inclined surfaces 4g and 4h and the gap surface 4k constitute the light leakage reduction shape 4M.

  FIG. 15 is a side view of the embodiment shown in FIG. According to the present embodiment, a part of the light that passes through the vicinity of the top surface 4a out of the light incident from the incident surface 4e of the light guide 4 is totally reflected by the gap surface 4k, whereby the light guide plate 3 It is oriented so as to pass through the incident surface 3b. Thereby, the light leaking out of the light guide plate 3 from the region on the exit surface 4f side of the light leakage reduction shape protruding from the incident surface 3b can be suppressed.

  FIG. 16 is a graph showing the results of a simulation performed by the present inventor. The vertical axis represents the light leakage rate, and the horizontal axis represents the light guide including the light leakage reduction shape with respect to the incident surface thickness T2 of the light guide plate. This is the maximum thickness T1 on the exit surface side. The inventor changed the inclination angle of the gap surface 4k with respect to a horizontal plane (here, a plane parallel to the bottom surface of the light guide plate 3) to 0 °, 0.1 °, 0.2 °, and 0.3 °. As a result, it was found that the light leakage rate increases as T1 / T2 is increased under any condition. In addition, according to another examination result, it is known that the light use efficiency is high when T1 / T2 is in the range of 1.1 to 1.5.

  FIG. 17 is a perspective view showing a light guide 4 and a light guide plate 3 according to still another embodiment, and shows an assembled state. In the present embodiment, out of a plurality of pairs of inclined surfaces, the two inclined surfaces 4g and 4h that form a mountain intersect with each other and are in contact with the emitting surface 4f and at a predetermined angle with respect to the emitting surface 4f. A tapered surface 4p inclined to the incident surface 4e side is provided. The tapered surface 4p can be formed by scraping a plurality of pairs of inclined surfaces 4g and 4h together by a virtual plane Q inclined at an angle δ with respect to the emission surface 4f. You may make it mutually differ. In the present embodiment, the maximum thickness T1 on the light exit surface 4f side of the light guide 4 and the thickness of the entrance surface 3b of the light guide plate 3 are equal. Since the tapered surface 4p is formed, the dimensions of the inclined surfaces 4g and 4h constituting the light leakage reduction shape in the thickness direction of the light guide plate 3 gradually increase from the incident surface 4e side to the output surface 4f side. After that, it gradually becomes smaller (see FIG. 18). The angle β formed by the pair of inclined surfaces 4g and 4h is constant over the entire length of the intersection 4i. Other configurations are the same as those in the embodiment shown in FIG. In the present embodiment shown in FIGS. 17 to 19, the pair of inclined surfaces 4g and 4h and the tapered surface 4p constitute the light leakage reduction shape 4M.

  FIG. 18 is a side view of the embodiment shown in FIG. According to the present embodiment, among the light incident from the incident surface 4 e of the light guide 4, a part of the light passing through the vicinity of the top surface 4 a is totally reflected by the tapered surface 4 p, whereby the light guide plate 3. It is oriented so as to pass through the incident surface 3b. Thereby, the light leaking out of the light guide plate 3 from the surface other than the emission surface 4f can be suppressed. Note that a gap surface 4k shown in FIGS. 14 and 15 may be added to the present embodiment.

  FIG. 19 is a graph showing the results of a simulation performed by the present inventor. In (a), the vertical axis represents the light utilization efficiency, and the horizontal axis represents the angle formed between the tapered surface of the light guide and the exit surface. In (b), the vertical axis is the light leakage rate, and the horizontal axis is the angle δ between the tapered surface of the light guide and the exit surface shown in FIG. As is clear from FIG. 19, it was found that the tapered surface 4p has the lowest light leakage rate and the highest light utilization efficiency in the range of 75 ° to 85 °.

  FIG. 20 is a side view of a light guide 4 according to another modification. As shown in FIG. 20, the inclined surfaces 4g and 4h constituting the light leakage reduction shape may be provided on the top surface 4a on the emission surface 4e side and on the bottom surface 4b on the incident surface 4f side. At this time, it is desirable that the inclined surfaces 4g and 4h on the top surface 4a side and the inclined surfaces 4g and 4h on the bottom surface 4b side do not overlap in the vertical direction.

  FIG. 21 is a side view of a light guide 4 and a light guide plate 3 according to another modification. As shown in FIG. 21A, when the light guide 4 is assembled so that the exit surface 4 f of the light guide 4 and the entrance surface 3 b of the light guide plate 3 are in close contact with each other, the bottom surface 4 b of the light guide 4 is relative to the bottom surface 3 c of the light guide plate 3. If it is arranged so as to be inclined, the amount of light taken in from the incident surface 3b increases, and the light utilization efficiency increases.

  On the other hand, as shown in FIG. 21B, the bottom surface 4 b of the light guide 4 is brought into contact with the bottom surface 3 c of the light guide plate 3 when assembled so that the light exit surface 4 f of the light guide 4 and the light incident surface 3 b of the light guide plate 3 are closely attached. On the other hand, if it arrange | positions on the same plane, an assembly property will improve.

  The present invention has been described above with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be modified or improved as appropriate. For example, the prism may be provided only on the bottom surface 4b, or may be formed on both the top surface 4a and the bottom surface 4b. Alternatively, the top surface 4a and / or the bottom surface 4b may be planar and a sheet on which a prism is formed may be attached.

1 housing 2 LED
3 light guide plate 4 light guide 4A, 4A ', 4a top surface 4b bottom surface 4c, 4d side surface 4e incident surface 4f exit surface 4g, 4h inclined surface 4i intersecting portion 4k gap surface 4p taper surface 5 diffuser plate 6 liquid crystal display element

Claims (25)

In a light guide that is disposed between a light source and a light guide plate and guides light from the light source to the light guide plate,
An incident surface for incident light from the light source;
An exit surface for emitting light to the light guide plate;
Extending in a direction intersecting the entrance surface and the exit surface, and having a top surface and a bottom surface facing each other,
One surface of the top surface and the bottom surface is relative to the other surface so that the size of the exit surface in the thickness direction of the light guide plate is smaller than the size of the entrance surface in the thickness direction of the light guide plate. Is inclined,
At least one of the top surface and the bottom surface is provided with a structure having a light leakage reduction shape for suppressing the amount of light emitted from a surface other than the light exit surface out of the light incident from the light incident surface. Light guide characterized by.   The light leakage reduction shape is emitted from the light source when the plane extending from the incident surface side toward the emission surface side and extending along the thickness direction of the light guide plate is a virtual plane. The light guide according to claim 1, wherein the light guide has a shape having a directional component such that when the light traveling along the light enters the light leakage reduction shape, the reflected light leaves the virtual plane. In a light guide that is disposed between a light source and a light guide plate and guides light from the light source to the light guide plate,
An incident surface for incident light from the light source;
An exit surface for emitting light to the light guide plate;
Extending in a direction intersecting the entrance surface and the exit surface, and having a top surface and a bottom surface facing each other,
One surface of the top surface and the bottom surface is relative to the other surface so that the size of the exit surface in the thickness direction of the light guide plate is smaller than the size of the entrance surface in the thickness direction of the light guide plate. Is inclined,
When at least one of the top surface and the bottom surface extends from the incident surface side toward the exit surface side and extends along the thickness direction of the light guide plate as a virtual plane, the light source emits light. A light guide having a light leakage reduction shape having a directional component such that reflected light of light traveling along the virtual plane is separated from the virtual plane.   The light guide according to any one of claims 1 to 3, wherein the light leakage reduction shape is a streak-like unevenness extending from the incident surface side toward the emission surface side.   5. The light leakage reduction shape includes a plurality of pairs of inclined surfaces, and an intersection of the pair of inclined surfaces extends from the incident surface side toward the emission surface side. Light guide as described.   The incident surface, the exit surface, the top surface, and the bottom surface extend in a direction intersecting with each other and have a pair of side surfaces facing each other, and the distance between the pair of side surfaces is greater than the exit surface side than the exit surface side. 6. The light guide according to claim 1, wherein the light guide is widened on the surface side. It has a pair of side surfaces that extend in a direction intersecting the entrance surface and the exit surface and face each other, and the distance between the pair of side surfaces is wider on the exit surface side than the entrance surface side. And
The light leakage reduction shape has a plurality of pairs of inclined surfaces having intersections extending from the incident surface side toward the emission surface side, and an interval between the adjacent intersection portions on the incident surface side is: The light guide according to claim 1, wherein the light guide is smaller than an interval on the emission surface side. 8. The light guide according to claim 5, wherein the following conditional expression (4) is satisfied, where β is an angle formed by a pair of inclined surfaces at the intersection.
100 ° ≦ β ≦ 170 ° (4)   9. The light guide according to claim 1, wherein the light leakage reduction shape is provided so as to protrude from the incident surface of the light guide plate.   9. The light guide according to claim 1, wherein a part of the light leakage reduction shape is provided on the light exit surface so as to protrude from the light entrance surface of the light guide plate. 10.   The light guide according to any one of claims 1 to 10, wherein a dimension of the emission surface in the thickness direction of the light guide plate is equal to or less than a thickness of the incident surface of the light guide plate.   The size of the light leakage reduction shape in the thickness direction of the light guide plate is gradually increased from the incident surface side toward the emission surface side. Light guide.   The dimension of the light leakage reduction shape in the thickness direction of the light guide plate gradually increases from the incident surface side toward the exit surface side, and then gradually decreases. The light guide according to any one of 11. The light leakage reducing shape is
A plurality of pairs of inclined surfaces, wherein an intersection of the pair of inclined surfaces extends from the incident surface side toward the emission surface side; and
14. A gap surface extending between the two inclined surfaces forming a valley and extending in a direction along the bottom surface on the emission surface side. Light guide according to Crab.   The light guide according to claim 14, wherein an intersection line between the two inclined surfaces intersecting with the gap surface is gradually separated from the incident surface side toward the emission surface side.   The light guide according to claim 14, wherein the gap surface is in contact with the emission surface, but is not in contact with the incident surface. The light leakage reducing shape is
A plurality of pairs of inclined surfaces, wherein an intersection of the pair of inclined surfaces extends from the incident surface side toward the emission surface side; and
2. A tapered surface that intersects each of the two inclined surfaces forming a mountain and is in contact with the emission surface and is inclined toward the incident surface side at a predetermined angle with respect to the emission surface. The light guide in any one of -16.   18. The light guide according to claim 5, wherein an angle of the intersecting portion of the pair of inclined surfaces is constant over the entire length of the intersecting portion.   The light guide according to any one of claims 1 to 18, wherein the top surface and the bottom surface are assembled so as to be inclined with respect to the bottom surface of the light guide plate.   The light guide according to claim 1, wherein the bottom surface is assembled so as to be positioned on the same plane with respect to the bottom surface of the light guide plate.   21. The light guide according to claim 1, comprising a plurality of the incident surfaces.   The light guide according to claim 1, wherein the light source is an LED.   A backlight apparatus comprising the light guide according to claim 1. A backlight device that is disposed between a light source and a liquid crystal element, and includes a light guide that receives light from the light source and a light guide plate that emits light that has passed through the light guide toward the liquid crystal element. There,
The light guide is
An incident surface for incident light from the light source;
An exit surface for emitting light to the light guide plate;
Extending in a direction intersecting the entrance surface and the exit surface, and having a top surface and a bottom surface facing each other,
One surface of the top surface and the bottom surface is relative to the other surface so that the size of the exit surface in the thickness direction of the light guide plate is smaller than the size of the entrance surface in the thickness direction of the light guide plate. Is inclined,
At least one of the top surface and the bottom surface is provided with a structure having a light leakage reduction shape that suppresses the amount of light emitted from a surface other than the light exit surface out of the light incident from the light incident surface. A backlight device characterized by comprising: A light source device that is disposed between a light source and a light guide that is disposed between the light source and the light guide plate and guides light from the light source to the light guide plate.
The light guide is
An incident surface for incident light from the light source;
An exit surface for emitting light to the light guide plate;
Extending in a direction intersecting the entrance surface and the exit surface, and having a top surface and a bottom surface facing each other,
One surface of the top surface and the bottom surface is relative to the other surface so that the size of the exit surface in the thickness direction of the light guide plate is smaller than the size of the entrance surface in the thickness direction of the light guide plate. Is inclined,
At least one of the top surface and the bottom surface is provided with a structure having a light leakage reduction shape that suppresses the amount of light emitted from a surface other than the light exit surface out of the light incident from the light incident surface. A light source device characterized by comprising:

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