JP2010027573A - Light guide plate, light emitting device, and light guiding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light guide plate and a light emitting device with good light distribution characteristics as well as a light guiding method. <P>SOLUTION: The light guide plate is equipped with an incident face for incidence of light, a diffusion face to diffuse the light, and a light outgoing face to emit the light, and the diffusion face includes a plurality of diffusing surface dots of truncated cone shape or of spherical cone shape. Or, the light guide plate is equipped with the incident face for incidence of light, the diffusion face to diffuse the light, and the outgoing face to emit the light, and the diffusion face includes a plurality of diffusing surface dots of cone shape, of truncated cone shape, or of spherical cone shape, and the basic angle of diffusing surface dots is in a range 45 degrees or more and 60 degrees or less. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light guide plate, a light emitting device, and a light guide method, and more particularly to a light guide plate having a diffusion surface for diffusing light, a light emitting device including the light guide plate, and a light guide method.

In recent years, thin light-emitting backlights have been widely provided in guide lights, mobile phones, car navigation systems, and the like. There are various types of backlights and light guide plates used therefor. For example, in a light guide plate formed by molding a thermoplastic resin and having a light incident surface, a light reflecting surface, and a light emitting surface, the light emitting surface. A light guide plate having a convex portion of a certain size or a concave portion of a certain size, and a reflection sheet is laminated on a light reflection surface of the light guide plate, and a downward prism sheet and a diffusion sheet are provided on a necessary emission surface. A backlight characterized by being laminated has been proposed (Patent Document 1).
JP 2005-209558 A

  The present invention provides a light guide plate, a light emitting device, and a light guide method that can obtain good light distribution characteristics.

  According to one aspect of the present invention, the light has an incident surface on which light is incident, a diffusion surface that diffuses light, and an exit surface that emits light. There is provided a light guide plate having a plurality of diffusing surface dots.

  According to another aspect of the present invention, the light source includes an incident surface on which light is incident, a diffusion surface that diffuses light, and an output surface that emits light. There is provided a light guide plate characterized by having a plurality of diffusing surface dots that are dots in the form of a sphere or a cone, and the base angle of the diffusing surface dots is in the range of 45 degrees or less and 60 degrees or less.

  According to another aspect of the present invention, the light-receiving surface has a light incident surface, a light diffusing surface for diffusing light, and a light emitting surface for emitting light, and the diffusing surface is a spherical dot. A light guide plate having a diffusing surface dot and having a height / curvature radius which is a ratio of a height to a radius of curvature of the diffusing surface dot is in a range of 0.375 to 0.825. The

  According to another aspect of the present invention, any one of the light guide plates described above, a housing that stores the light guide plate, and a side that is inside the housing and faces the incident surface. There is provided a light-emitting device comprising: a light source; and a display plate provided as at least a part of a surface of the housing that faces the emission surface.

  According to another aspect of the present invention, there is provided a light guide method characterized in that light is incident on the incident surface of any one of the light guide plates and light is extracted from the output surface.

  ADVANTAGE OF THE INVENTION According to this invention, the light guide plate, light-emitting device, and light guide method with which a favorable light distribution characteristic is acquired are provided.

Embodiments of the present invention will be described below with reference to the drawings. In addition, in each drawing, the same code | symbol is attached | subjected to the same component and detailed description is abbreviate | omitted suitably.
FIG. 1 is a schematic cross-sectional view illustrating an example (specific example 1) of a light guide plate, a light emitting device, and a light guide method according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along line AA ′ of the light emitting device 2 according to the first specific example.
The light guide plate 40 according to the first specific example includes an incident surface 42 on which light is incident, a diffusion surface 44 that diffuses light, and an output surface 46 that emits light. It has the dot 44p with the shape to do.
In addition, the light emitting device 2 according to the first specific example is provided on the light guide plate 40, the housing 10 that stores the light guide plate 40, and the inner surface of the housing 10 that faces the incident surface 42 (light source surface 14). And the display board 60 provided as a part of the surface of the housing 10 that faces the emission surface 46. In addition, the light emitting device 2 may include a reflective sheet 30 between the light guide plate 40 and the bottom wall surface 16 which is the inner surface 12 of the housing 10 and is in the direction opposite to the direction in which the viewer exists. . Further, the light emitting device 2 may include a diffusion sheet 50 between the light guide plate 40 and the display plate 60.

1 and 2, the light emitting device 2 and each component have a square shape, but the shape is not limited thereto, and may be any shape without departing from the spirit of the present embodiment. It can be.
The light emitting device 2 according to the specific example 1 can be used as a backlight for, for example, a guide light, a mobile phone, and a car navigation system.

Next, each component of the light emitting device 2 according to the specific example 1 will be described.
Here, the side or direction where the viewer is present when viewed from the light emitting device 2 (the direction of “y” in FIG. 1) may be referred to as “front”, “front side”, or “front direction”. A plane parallel to the display panel 60 is defined as a “main surface”.

  The housing 10 has a function of supporting each component such as the light source 20, the reflection sheet 30, and the light guide plate 40, and can be made of any material as long as this function can be achieved. All or part of the inner surface 12 of the housing 10 can be configured to reflect light. For example, the light emitted from the light source 20 is favorably guided toward the light guide plate 40 by imparting reflectivity to the peripheral surface of the light source 20. Further, by providing reflectivity to the surface facing the light source surface 14 (light source facing surface 17), the light emitted from the light source 20 and reaching the light source facing surface 17 is reflected by the light source facing surface 17 and guided well. Guided in the direction of the light plate 40. Further, by providing reflectivity to the inner surface 12 that is in a direction opposite to the front direction (bottom wall surface 16), the light emitted from the light source 20 and traveling toward the bottom wall surface 16 is reflected by the bottom wall surface 16. Then, it is guided in the direction of the light guide plate 40 satisfactorily. In this case, the reflection sheet 30 is unnecessary.

  The light source 20 is an object or device serving as a light source. For example, a linear light source such as a cold cathode tube or a point light source such as a light emitting diode (LED) can be used. Alternatively, a surface light source may be used. In the case of using a point light source, the number of light sources is not particularly limited, and may be singular or plural. It can be selected as appropriate in consideration of the trade-off between obtaining good light distribution characteristics and cost. In addition, in order to appropriately diffuse the light, for example, a light source that emits Lambert diffuse radiation or radiation close thereto can be used.

  The reflection sheet 30 is provided to reflect light in the front direction and has a reflection surface 32 that reflects light. The reflection surface 32 is disposed so as to face the diffusion surface 44. The reflection sheet 30 can be made of any material as long as this function can be achieved. For example, a plate whose reflection surface 32 is finished so as to perform Lambertian diffuse reflection or reflection similar thereto can be used. In the specific example 1, the reflection sheet 30 is provided in parallel to the diffusion surface 44 (that is, inclined with respect to the main surface), but is not limited to this configuration. The reflection sheet 30 may be on the main surface, or may be provided in another manner as long as light is reflected in the front direction. From the viewpoint of luminous efficiency, the reflective sheet 30 is preferably provided in parallel with the diffusing surface 44, and from the viewpoint of ease of processing, the reflective sheet 30 is preferably on the main surface. Further, as described above, when the bottom wall surface 16 is configured to have reflectivity, it is not necessary to provide the reflection sheet 30.

The diffusion sheet 50 is provided for diffusing the light emitted from the light guide plate 40, and is made of, for example, a translucent sheet.
The display board 60 is provided to display a display target, and a display panel, a liquid crystal unit, or the like can be used according to the purpose of use of the light emitting device 2.

Next, the light guide plate 40 will be described.
The light guide plate 40 is provided to guide light in the front direction, and can be made of, for example, a transparent resin. The size is appropriately selected according to the purpose of use, and the thickness can be set to, for example, several mm. In the first specific example, the thickness of the light guide plate 40 is not uniform and has a shape (so-called tapered shape) that is continuously thinned in one direction starting from the incident surface 42. It is not something that can be done. The thickness of the light guide plate 40 may be uniform, or may be another shape as long as light is diffused in the front direction. From the viewpoint of luminous efficiency, the light guide plate 40 preferably has a tapered shape, and from the viewpoint of ease of processing, the thickness of the light guide plate 40 is preferably uniform.

  Further, in the light emitting device 2, the diffusing surface 44 is provided so as to approach the display plate 60 as the distance from the incident surface 42 increases, but the configuration is not limited thereto. The diffusing surface 44 may be on the main surface, or may be provided in another manner as long as light is diffused in the front direction. From the viewpoint of luminous efficiency, it is preferable that the diffusing surface 44 is provided so as to approach the display plate 60 as the distance from the incident surface 42 increases. From the viewpoint of ease of processing, the thickness of the light guide plate 40 is uniform. The diffusing surface 44 is preferably provided on the main surface.

  Here, the light guide plate 40 has concave dots 44 p having a certain shape on the diffusion surface 44. The arrangement of the dots 44p is appropriately selected so that light is emitted substantially uniformly on the main surface (emission surface 46) of the light guide plate 40. For example, the arrangement may be an arrangement as shown in FIG. 2 or a random arrangement. The interval (pitch) L between the dots 44p may be the same or different. Further, when the pitch L is different, the arrangement may or may not be regular. If the pitch L is periodic, moire (interference fringes) may occur. However, if the pitch L is randomly arranged, this is suppressed. Further, the density of the dots 44p (the ratio of the area occupied by the dots 44p to the unit area) may be partially modulated. Thereby, uneven brightness can be suppressed. Moreover, when using a point light source for the light source 20, patterning can be changed with arrangement | positioning of a light source.

Next, the shape of the dot 44p will be described with reference to FIGS.
FIG. 3 is a schematic diagram illustrating the shape of the dot 44p according to the first specific example. In FIG. 3, (a), (c), (e), and (g) are schematic cross-sectional views showing examples of the dots 44p, and (b), (d), (f), and (h) These are schematic plan views of the respective examples.

  As shown in FIG. 3, the dot 44p according to the first specific example has a concave shape, the conical shape shown in FIGS. 3A and 3B, and the dots 44p shown in FIGS. 3C and 3D. A truncated cone shape, as shown in FIGS. 3E and 3F, a cone shape whose upper end is like a spherical crown (a part of a sphere generated when a sphere is cut into a plane) (hereinafter referred to as “spherical cone shape”). And a shape selected from the spherical crown shape (hereinafter referred to as “spherical shape”) shown in FIGS. The shape of the upper end of the spherical cone shape shown in FIGS. 3E and 3F is close to the spherical crown, such as a spherical crown, and an elliptical crown (a part of a spherical shape generated when the elliptical ball is cut into a plane). Shape is also included. Hereinafter, the dots having the respective shapes are referred to as “conical dots”, “conical truncated dots”, “spherical cone dots”, and “spherical dots”, and the former three may be collectively referred to as “conical dots”. .

  Unlike the V-groove, these shaped dots 44p have an action of spreading light horizontally and an action of raising the light vertically, so that light can be effectively extracted to the front of the light emitting device 2.

4 and 5 are schematic cross-sectional views for deriving a preferable shape of the dot 44p.
First, a preferable shape of the conical dot 44p will be described. FIGS. 4A, 4B, and 4C are schematic cross-sectional views for deriving a preferable shape for the conical, frustoconical, and spherical conical dots 44p, respectively.

  When these conical dots 44p are used, as a result of a simulation experiment (simulation) by the inventor described later, the light distribution on the front side varies depending on the value of the angle (base angle) θ formed between the side surface and the bottom surface. It was found. In order to obtain a good light distribution, the lower limit of the θ value is preferably 45 degrees, more preferably 50 degrees, and the upper limit is preferably 60 degrees, more preferably 55 degrees. Further, since the same result was obtained even when the bottom surface radius R was different, it is considered that the light distribution on the front side does not depend on the R value, that is, the size of the dot 44p.

Next, a preferable shape of the spherical dot 44p will be described. FIG. 5 is a schematic cross-sectional view for deriving a preferable shape of the spherical dot 44p.
When a spherical dot 44p is used, as a result of a simulation experiment by the inventor described later, it is found that the light distribution on the front side varies depending on the ratio of the height D to the radius of curvature R (D / R ratio). It was done. In order to obtain a good light distribution, the lower limit of the D / R ratio is preferably 0.375, more preferably 0.5, and the upper limit is preferably 0.825, more preferably 0.625. is there. Moreover, since the same result was obtained even if the curvature radius R was different, it is considered that the light distribution on the front side does not depend on the R value, that is, the size of the dot 44p. In other words, if the shapes of the dots 44p are similar, almost the same light distribution characteristics can be obtained regardless of the size of the dots 44p.

  The bottom radius R of the conical dots, the radius of curvature R of the spherical dots, and the interval (pitch) L of the dots 44p are preferably sufficiently large with respect to the wavelength of the light, for example, 10 times or more of the wavelength of the light. Is preferred.

Note that when conical dots are used, light directivity is higher than when spherical dots are used, and higher front luminous intensity is obtained.
In addition, the truncated cone dot, the spherical cone dot, and the spherical dot are easier to process than the conical dot having a sharp shape at the upper end.

Next, the effect of this embodiment will be described with reference to FIG.
FIG. 6 is a schematic cross-sectional view showing a light guide plate 70 and a light emitting device 4 according to a comparative example compared with the present embodiment. The shape of the dot 74p provided on the diffusion surface 74 of the light guide plate 70 does not necessarily match the shape of the dot 44p according to the specific example 1 described above. The light emitting device 4 is a conventional light emitting device and has basically the same structure as the light emitting device 2 according to the first specific example of the present embodiment, but further includes a prism sheet 80.

First, the effect of this embodiment will be described in relation to the presence or absence of a prism sheet.
In the light emitting device 4 according to the comparative example, since the shape of the dot 74p does not necessarily match the shape of the dot 44p according to the specific example 1, it is considered that the light emitted from the light guide plate 70 does not necessarily have good light distribution characteristics. It is done. For this reason, the prism sheet 80 is introduced, and the light scattered by the dots 74p is refracted by the prism surface of the prism sheet 80 so that the light is emitted well in the front direction. The prism sheet 80 is effectively used particularly when spherical dots 74p are used. Spherical dots have a characteristic that light directivity is weak, and thus light is diffused widely and luminance unevenness is small. Therefore, there is a problem that light cannot be sufficiently emitted in the front direction. For this reason, it is necessary to guide the emitted light in the front direction using the prism sheet 80.

  On the other hand, the light emitting device 2 according to the specific example 1 does not include the prism sheet 80. This is because, by using the light guide plate 40 provided with dots 44p having a specific shape, light is emitted in the front direction with a good light distribution characteristic without using the prism sheet 80, as shown in a simulation example described later. This is because it is not necessary to introduce the prism sheet 80. Thus, the following effects are acquired by making the prism sheet 80 unnecessary.

  (1) First, according to the specific example 1, a light-emitting device with a wide viewing angle is provided. When the prism sheet 80 is used, since the viewing angle depends on the apex angle of the prism, the horizontal viewing angle or the vertical viewing angle is limited to about ± 55 degrees depending on the direction of the prism slope. However, in the first specific example, since the prism sheet 80 is not used, there is no such restriction, and both the horizontal viewing angle and the vertical viewing angle can be secured to ± 75 degrees. Therefore, the light emitting device 2 according to the specific example 1 is useful when a wide field of view is required.

  (2) Next, according to Specific Example 1, a thin light-emitting device is provided. The thickness of the prism sheet 80 is generally about 100 μm to 200 μm, but by not using this, the light emitting device can be thinned.

  (3) Next, according to Specific Example 1, a relatively inexpensive light emitting device is provided. In general, since the prism sheet 80 is expensive, the light emitting device 2 of the specific example 1 that does not use the prism sheet 80 is relatively inexpensive. Further, the manufacturing process is simplified, and the cost is reduced from this point.

  In the present embodiment, the use of the prism sheet 80 is not limited, and the prism sheet 80 may be used as necessary.

Next, the effect of this embodiment will be discussed in relation to the dot shape.
In the light guide plate 40 according to the first specific example, the dots 44p have the specific shape described above. Accordingly, the following effects can be obtained in addition to the effects described above in relation to the prism sheet as compared with the light guide plate 70 provided with the dots 74p having no such shape.

  According to the specific example 1, manufacture of the light guide plate 40 and the light emitting device 2 is facilitated. In the comparative example, it is considered that the size of the dot 74p needs to be relatively small in order to obtain good light distribution characteristics. On the other hand, according to the first specific example, since the light distribution is determined by the θ value or the D / R ratio without depending on the size of the dots 44p, relatively large dots 44p can be used. For example, for the conical dot 44p, the bottom surface radius R or the bottom base radius R can be about 10 μm to 400 μm, and for the spherical dot 44p, the bottom surface radius R can be about 10 μm to 400 μm. Can do. For this reason, the influence of the shape error (height and roundness) of the mold used when patterning the dots 44p can be reduced, and the accuracy of the shape can be ensured appropriately. That is, processing becomes easy.

  As described above, according to the light guide plate, the light emitting device, and the light guide method according to the present embodiment, a good light distribution characteristic with a wide viewing angle and little luminance unevenness can be obtained. In addition, processing of the light guide plate and the light emitting device is facilitated, and a thin and inexpensive light emitting device is provided.

(Other configuration examples)
Next, another configuration according to the present embodiment will be described with reference to FIGS.
FIG. 7 is a schematic cross-sectional view illustrating another example (specific example 2) of the light guide plate, the light emitting device, and the light guide method according to the present embodiment. The light emitting device 2 according to the specific example 2 has the same configuration as the light emitting device 2 of the specific example 1, but does not include the reflection sheet 30 and the diffusion sheet 50. In the specific example 2, the main surface portion (bottom wall surface 16) of the inner surface 12 of the housing 10 is configured to reflect light (for example, to perform Lambert diffuse reflection or reflection close thereto). For this reason, the reflection sheet 30 is unnecessary. The display board 60 is made of a milky white material having the property of diffusing light, and thus the diffusion sheet 50 is not necessary.

  Even with this configuration, as in the first specific example, good light distribution characteristics can be obtained, and processing of the light guide plate is facilitated. Further, by eliminating the need for the reflection sheet 30 or the diffusion sheet 50, the processing of the light emitting device is further facilitated, and the light emitting device is further reduced in thickness.

  FIG. 8 is a schematic cross-sectional view illustrating another example (specific example 3) of the light guide plate, the light emitting device, and the light guide method according to the present embodiment. FIG. 8A is a schematic cross-sectional view of the light emitting device 2 according to the specific example 3 cut along the main surface between the light guide plate 40 and the display plate 60. FIG. 8B is a cross-sectional view taken along line B-B ′ of FIG. The light emitting device 2 according to the third specific example has the same configuration as the light emitting device 2 according to the second specific example, but the shape is also patterned on the incident surface 42 of the light guide plate 40. As this shape, it can be set as the dot 42p which consists of cylindrical concave shape, cylindrical convex shape, V-groove shape etc., for example. In this case, the light emitted from the light source 20 is scattered by the dots 42p. Thereby, even when a plurality of point light sources are used as the light source 20, the luminance unevenness is suppressed regardless of the interval (pitch) L2 of the light sources 20, and the light is guided to the diffusion surface 44 satisfactorily.

  In this case, the light guide plate 40 may have a dot non-formation region 44 b in which the dots 44 p are not patterned in a certain region near the incident surface 42 of the diffusion surface 44. Thereby, the light emitted from the light source 20 is guided to the region (dot formation region 44a) where the dots 44p are more satisfactorily patterned.

By these measures, even when the pitch L2 of the light sources 20 composed of point light sources is different, the same light guide plate 40 can be used, and the cost can be reduced.
Thus, according to the specific example 3, the light distribution characteristic is further improved. Further, similarly to the second specific example, a thin light emitting device is provided.

  FIG. 9 is a schematic cross-sectional view showing another example (specific example 4) of the light guide plate, the light emitting device, and the light guide method according to the present embodiment. The light emitting device 2 according to the specific example 4 has the same configuration as that of the light emitting device 2 of the specific example 1, but the dots 44p are not on the surface (rear surface 44) in the direction opposite to the front direction in the light guide plate 40. , And provided in a convex shape on the surface in the front direction (front surface 46). In this case, the front surface 46 is an exit surface as well as a diffusion surface. The shape of the dot 44p in the specific example 4 is the same as the shape of the dot 44p described above with respect to the specific example 1.

  Even with such a configuration, it is expected that the same effect as in the first specific example can be obtained. That is, it is expected that a good light distribution characteristic can be obtained, the processing of the light guide plate and the light emitting device is facilitated, and a thin and inexpensive light emitting device is provided.

(Example)
Next, an example (simulation) for examining the effect of the present embodiment will be described with reference to FIGS.
First, the light guide plate 40 and the light emitting device 2 used in this embodiment will be described.
The light guide plate 40 used in the example is the same as that described above with respect to the specific example 3 (FIG. 8). The diffusing surface 44 has a dot formation region 44a and a dot non-formation region 44b, and concave dots 44p are patterned in the dot formation region 44a. The dots 42p are patterned on the incident surface 42.

  The interval (pitch) L between the dots 44p is randomly modulated at a constant rate. Thereby, generation | occurrence | production of a moire is suppressed. Further, the density of the dots 44p (the ratio (%) of the area occupied by the dots 44p to the unit area) is partially changed in the range of 15 to 50%. Thereby, the brightness | luminance nonuniformity of LED which is a point light source can be corrected. The pitch L is on average 1.8 times the bottom radius R (for conical dots) or the radius of curvature R (for spherical dots).

The light-emitting device 2 used in the example is basically the same as that described above with reference to the specific example 3, but further includes a reflection sheet 30 and a diffusion sheet 50. The reflection sheet 30 and the diffusing surface 44 are inclined with respect to the main surface. However, in Experimental Example 8, the diffusion sheet 50 is not used. “Toray E60L” was used for the reflection sheet 30 and “Tsujiten D114” was used for the diffusion sheet 50. An LED is used as the light source 20.
Next, the orientation angle serving as a reference for the light distribution is described.
FIG. 10 is a schematic diagram for explaining the light distribution angle. FIG. 10A is a schematic perspective view showing the horizontal light distribution angle α and the vertical light distribution angle β. FIG. 10B is a schematic plan view showing the horizontal light distribution angle α. FIG. 10C is a schematic left side view showing the vertical light distribution angle β.

  As shown in FIG. 10A, the light emitting device 2 was installed so that the main surface of the light guide plate 40 was vertical with the light source 20 facing upward. In FIG. 10, the Y axis is an axis that passes through the center of gravity of the main surface of the light guide plate 40 and goes straight to the main surface of the light guide plate 40, and the front side is a positive direction. The X axis is a horizontal axis passing through the display panel 60 and intersecting with the Y axis, and the left side is positive when viewed from the viewer. The Z-axis is an axis that is orthogonal to the X-axis and the Y-axis and whose upper side is positive. An intersection point of the X axis, the Y axis, and the Z axis is defined as an origin O.

  The horizontal light distribution angle α is an angle on the XY plane, and is an angle formed by a straight line connecting the origin O and the observation point between the negative axis of the Y axis and a clockwise angle when viewed from above. . The vertical light distribution angle β is an angle on the YZ plane, and is an angle formed between the straight line connecting the origin O and the observation point with the negative axis of the Z axis, and is a counterclockwise angle when viewed from the left side. is there. The straight front direction of the light guide plate 40 is the Y-axis direction, which is a direction in which “α = 180 degrees” and “β = 90 degrees”.

(Experimental example 1)
In the present experimental example, the relationship between the R value and θ value and the light distribution when a conical dot was used as the dot 44p was examined.
FIG. 11 is a graph showing the experimental results. A plurality of base radii R and base angles θ of the conical dots 44p were selected (table in the figure), and the light distribution in the horizontal direction and the vertical direction was measured.

  FIG. 11A shows the light distribution in the horizontal direction, the horizontal axis represents the horizontal light distribution angle α (unit: degree, deg), and the vertical axis represents the light intensity (unit: candela, cd). . FIG. 11B shows the light distribution in the vertical direction, the horizontal axis represents the vertical light distribution angle β (unit: degree, deg), and the vertical axis represents the light intensity (unit: candela, cd). .

  As shown in FIGS. 11A and 11B, if the θ value is the same, the light distribution characteristics are almost the same even if the R values are different.

  11A, when the θ value is 45 to 60 degrees, the frontal light intensity in the horizontal direction (the light intensity when α = 180 degrees) is high, and the θ value is 50 to 55 degrees. In some cases, the front brightness is the highest. That is, the lower limit of the θ value is preferably 45 degrees, more preferably 50 degrees, and the upper limit of the θ value is preferably 60 degrees, and more preferably 55 degrees.

  Further, as shown in FIG. 11B, the same can be said for the relationship between the θ value and the frontal luminous intensity in the vertical direction (luminous intensity when β = 90 degrees). That is, when the θ value is within the above preferable range, the frontal luminous intensity in the vertical direction is good.

(Experimental example 2)
In this experimental example, the relationship between the R value and θ value and the light distribution when the conical dot, the truncated cone dot, and the spherical conical dot (conical dot) were used as the conical dot 44p was examined.
FIG. 12 is a graph showing the experimental results. The bottom surface radius R and the base angle θ of the conical dot 44p were selected (table in the figure), and the light distribution in the horizontal direction and the vertical direction was measured. For the conical dot 44p, R is 79 μm. Regarding the truncated cone dot 44p, the lower base R is 150 μm and the upper base R2 is 71 μm. For the spherical conical dot 44p, R is 100 μm and the radius of curvature R3 is 50 μm. The θ value is 51.7 degrees for all shapes. The height H is 100 μm in any shape. The reason why the height H is set to the same condition is to make the emission efficiency of the emitted light uniform.

12 (a) and 12 (b) represent the light distribution in the horizontal and vertical directions, respectively, and the horizontal and vertical axes are the same as those described above with reference to FIG.
As shown in FIGS. 12 (a) and 12 (b), almost all of these three cases exhibited the same light distribution characteristics. From this, it is considered that if the θ values are the same, almost the same light distribution characteristics can be obtained regardless of the shape near the apex of the cone and the size of the dot 44p. Further, if the θ value is within the preferred range described above with respect to Experimental Example 1 including the value (51.7 degrees) used in this Experimental Example, it is considered that the front luminous intensity is secured well in the horizontal direction and the vertical direction. .
In the case of the spherical conical dots 44p, it is considered that the light distribution characteristics of the spherical dots 44p described in the following Experimental Example 3 become closer as the proportion of the spherical shape increases.

(Experimental example 3)
In this experimental example, the relationship between the R value, the D / R ratio, and the light distribution when a spherical dot was used as the dot 44p was examined.
FIG. 13 is a graph showing the experimental results. The bottom surface radius R of the spherical dot 44p and the ratio (D / R ratio) between the heights D and R (D / R ratio) were selected (table in the figure), and the light distribution in the horizontal and vertical directions was measured. 13 (a) and 13 (b) represent the light distribution in the horizontal direction and the vertical direction, respectively, and the horizontal and vertical axes are the same as those described above with reference to FIG.

As shown in FIGS. 13A and 13B, if the D / R ratio is the same (that is, if the dot shapes are similar), the light distribution characteristics even if the R values are different. Are almost identical.
Further, as shown in FIG. 13A, when the D / R ratio is 0.375 to 0.825, the frontal luminous intensity in the horizontal direction (luminous intensity when α = 180 degrees) is increased, and the D / R ratio is increased. When the ratio is 0.5 to 0.625, the front brightness is the highest. That is, the lower limit of the D / R ratio is preferably 0.375, more preferably 0.5, and the upper limit of the D / R ratio is preferably 0.825, more preferably 0.625. I can say that.

Further, as shown in FIG. 13B, the same can be said for the relationship between the D / R ratio and the frontal luminous intensity in the vertical direction (luminous intensity when β = 90 degrees). That is, when the D / R ratio is within the above preferable range, the frontal luminous intensity in the vertical direction is good. When the D / R ratio is less than 0.375, light is emitted only to a relatively low position. On the other hand, as the D / R ratio increases, the light intensity peak approaches the front (β = 90 degrees), but the light distribution increases and the light intensity at the front decreases. From this, it is considered that when the D / R ratio is larger than 0.825, sufficient front luminance cannot be obtained.
As for the curvature radius R, good results are obtained in the range of 10 μm to 400 μm, but the radius of curvature R is not limited to this range.

(Experimental example 4)
In this experimental example, the light emitting device 2 according to the present embodiment and the light emitting device 4 according to the comparative example were compared, and the relationship between the presence / absence of the prism sheet 80 and the light distribution was examined. The light guide plate 40 and the light guide plate 70 used for the light emitting device 2 and the light emitting device 4 respectively have spherical dots. The base angle θ is 52 degrees, the base radius R is 78 μm, and the height H is 100 μm. The light emitting device 4 is basically the same as the light emitting device 2, but further includes a prism sheet 80. The apex angle of the prism is 90 degrees.

The number of LEDs is 5, and the luminous flux per one is 1 (lm: lumen). The size of the light guide plate 40 and the light guide plate 70 is 200 mm × 215 mm.
FIG. 14 is a graph showing the experimental results. 14 (a) and 14 (b) represent the light distribution in the horizontal and vertical directions, respectively, and the horizontal and vertical axes are the same as those described above with reference to FIG.

  From FIG. 14A, in the case of the light emitting device 4, light is not irradiated at a position where the horizontal light distribution angle α is 120 degrees or less and 240 degrees or more in the horizontal direction. If the front is 0 degree, the horizontal viewing angle is ± 60 degrees. On the other hand, in the case of the light emitting device 2, the light intensity is ensured uniformly throughout the wide position range where the horizontal light distribution angle α is 90 to 270 degrees. If the front is 0 degree, the horizontal viewing angle is ± 75 degrees.

  Further, from FIG. 14B, in the case of the light emitting device 4, the light intensity is remarkably reduced at positions where the vertical light distribution angle β is 45 degrees or less and 135 degrees or more in the vertical direction. If the front is 0 degree, the vertical viewing angle is ± 45 degrees. On the other hand, in the case of the light-emitting device 2, the luminous intensity is uniformly ensured uniformly in a wide position range where the vertical light distribution angle β is 0 to 180 degrees. If the front is 0 degree, the vertical viewing angle is ± 75 degrees.

  From the above, it can be said that the light emitting device 2 according to the present embodiment is wider in both the horizontal viewing angle and the vertical viewing angle than the light emitting device 4 according to the comparative example including the prism sheet 80.

(Experimental example 5)
In this experimental example, the case where the conical dot 44p was used was compared with the case where the spherical dot 44p was used. For the conical dot 44p, θ = 52 degrees, R = 78 μm, and H = 100 μm. For the spherical dot 44p, D / R = 0.5.

The number of LEDs is 5, and the luminous flux per one is 1 (lm: lumen). The size of the light guide plate 40 is 200 mm × 215 mm.
FIG. 15 is a graph showing the experimental results. FIGS. 15A and 15B show the light distribution in the horizontal direction and the vertical direction, respectively, and the horizontal and vertical axes are the same as those described above with reference to FIG.

  From FIG. 15A and FIG. 15B, when the conical dot 44p is used, the directivity of light is strong in both the horizontal direction and the vertical direction and the front luminous intensity is high compared to the case where the spherical dot 44p is used. I understand that. For this reason, the light guide plate 40 and the light emitting device 2 using the conical dots 44p can be effectively used for a mobile phone, a security display device, and the like that require light directivity.

(Experimental example 6)
In the present experimental example, the light distribution when the milky white plate was used as the display plate 60 was examined. As the light guide plate 40, one having spherical dots 44p (D / R ratio is 0.5) was used. The light emitting device 2 includes a display plate 60 made of a milky white plate and does not include the diffusion sheet 50.

The number of LEDs is 3, and the luminous flux per one is 1 (lm: lumen). The size of the light guide plate 40 is 145 mm × 130 mm.
FIG. 16 is a graph showing the experimental results. 16 (a) and 16 (b) represent the light distribution in the horizontal direction and the vertical direction, respectively, and the horizontal and vertical axes are the same as those described above with reference to FIG.
From FIG. 16A and FIG. 16B, it can be seen that a good light distribution can be obtained even when a milky white plate is used as the display plate 60.

(Experimental example 7)
In this experimental example, the relationship between the luminous flux of the light source 20 and the light distribution was examined. As the light guide plate 40, one having spherical dots 44p (D / R ratio is 0.5) was used.
The number of LEDs is five. The luminous flux per LED is 19.5 (lm: lumen), which is larger than other experimental examples. The size of the light guide plate 40 is 215 mm × 200 mm.

FIG. 17 is a graph showing the experimental results. FIGS. 17A and 17B show the light distribution in the horizontal direction and the vertical direction, respectively, and the horizontal and vertical axes are the same as those described above with reference to FIG.
17A and 17B show that a good light distribution can be obtained even when the luminous flux of the light source 20 is relatively large (the frontal luminous intensity in the horizontal direction is 33 cd).

(Experimental example 8)
In this experimental example, the light distribution was examined when the luminous flux of the light source 20 was relatively high and the number of light sources 20 was relatively small. As the light guide plate 40, one having spherical dots 44p (D / R ratio is 0.5) was used.
The number of LEDs is 3, and the luminous flux per one is 19.5 (lm: lumen). The size of the light guide plate 40 is 145 mm × 130 mm. The diffusion sheet 50 is not used.
FIG. 18 is a graph showing the experimental results. 18 (a) and 18 (b) represent the light distribution in the horizontal and vertical directions, respectively, and the horizontal and vertical axes are the same as those described above with reference to FIG.
From FIG. 18A and FIG. 18B, it can be seen that a good light distribution can be obtained even in this experimental example (front light intensity, 12 to 13 cd).

The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. In other words, those specific examples that have been appropriately modified by those skilled in the art are also included in the scope of the present invention as long as they have the characteristics of the present invention. For example, the elements included in each of the specific examples described above and their arrangement, materials, conditions, shapes, sizes, and the like are not limited to those illustrated, but can be changed as appropriate.
Moreover, each element with which each embodiment mentioned above is provided can be combined as long as technically possible, and the combination of these is also included in the scope of the present invention as long as it includes the features of the present invention.

It is a schematic cross section showing an example (specific example 1) of a light guide plate, a light emitting device, and a light guide method according to an embodiment of the present invention. It is A-A 'line sectional drawing of the light-emitting device 2 which concerns on the specific example 1. FIG. It is a schematic diagram showing the shape of the dot 44p concerning the specific example 1. It is a schematic cross section for deriving the desirable shape of dot 44p. It is a schematic cross section for deriving the desirable shape of dot 44p. It is a schematic cross section showing the light emitting device 4 according to a comparative example compared with the present embodiment. It is a schematic cross section showing other examples (specific example 2) of a light guide plate, a light emitting device, and a light guide method according to the present embodiment. It is a schematic cross section showing other examples (specific example 3) of a light guide plate, a light emitting device, and a light guide method according to the present embodiment. It is a schematic cross section showing other examples (specific example 4) of a light guide plate, a light emitting device, and a light guide method according to the present embodiment. It is a schematic diagram for demonstrating a light distribution angle. It is a graph showing an experimental result. It is a graph showing an experimental result. It is a graph showing an experimental result. It is a graph showing an experimental result. It is a graph showing an experimental result. It is a graph showing an experimental result. It is a graph showing an experimental result. It is a graph showing an experimental result.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 Light-emitting device 4 Light-emitting device 10 Case 12 Inner surface 14 Light source surface 16 Bottom wall surface 17 Light source opposing surface 20 Light source 30 Reflective sheet 32 Reflective surface 40 Light guide plate 42 Incident surface 42p Dot 44 Diffusion surface, rear surface 44a Dot formation area 44b Dot non-formation Area 44p dot, cone dot, truncated cone dot, sphere cone dot, sphere dot 46 exit surface, front face 46p dot 50 diffusion sheet 60 display plate 70 light guide plate 72 entrance surface 74 diffusion surface, rear surface 74p dot 76 exit surface, front face 80 prism Sheet D Height H Height L Pitch L2 Pitch O Origin R Bottom radius, bottom radius, curvature radius R2 Upper radius R3 curvature radius y Front direction α Horizontal light distribution angle β Vertical light distribution angle θ Base angle

Claims (16)

An incident surface for entering light, a diffusion surface for diffusing light, and an exit surface for emitting light;
A light guide plate having a plurality of diffusing surface dots which are frustoconical or spherical conical dots on the diffusing surface. An incident surface for entering light, a diffusion surface for diffusing light, and an exit surface for emitting light;
The diffusion surface has a plurality of diffusion surface dots that are conical, frustoconical, or spherical conical dots,
The light guide plate according to claim 1, wherein a base angle of the diffusing surface dots is in a range of 45 degrees or less and 60 degrees or less.   The light guide plate according to claim 2, wherein the base angle is in a range of 50 degrees to 55 degrees.   The light guide plate according to claim 1, wherein the bottom surface radius of the diffusing surface dots is in the range of 10 μm to 400 μm. An incident surface for entering light, a diffusion surface for diffusing light, and an exit surface for emitting light;
The diffusion surface has a diffusion surface dot that is a spherical dot,
A light guide plate, wherein a height / curvature radius, which is a ratio of a height to a curvature radius of the diffusing surface dots, is in a range of 0.375 to 0.825.   The light guide plate according to claim 5, wherein the height / curvature radius is in a range of 0.5 to 0.625.   The light guide plate according to claim 5 or 6, wherein a radius of curvature of the diffusing surface dots is in a range of 10 µm to 400 µm.   The light guide plate according to claim 1, wherein the diffusing surface dots have a concave shape.   9. The light guide plate according to claim 1, wherein the incident surface has incident surface dots that are cylindrical concave shapes, cylindrical convex shapes, or V-groove shaped dots.   The light guide plate according to claim 1, wherein the light guide plate has a region where the diffusion surface dots are not provided in the vicinity of the incident surface of the diffusion surface.   11. The light guide plate according to claim 1, wherein a ratio of an area occupied by the diffusion surface dots to a unit area is modulated on the diffusion surface.   The light guide plate according to claim 11, wherein the ratio is modulated in a range of 15 to 50%. The light guide plate according to any one of claims 1 to 12,
A housing for storing the light guide plate;
A light source provided inside the housing and on the side facing the incident surface;
A display board provided as at least a part of a surface of the housing and facing the emission surface;
A light-emitting device comprising:   14. The light emitting device according to claim 13, further comprising a reflection sheet provided between the light guide plate and a bottom wall surface on the inner surface of the housing opposite to the display plate. .   The light-emitting device according to claim 13, further comprising a diffusion sheet provided between the light guide plate and the display plate.   A light guide method, wherein light is incident on the incident surface of the light guide plate according to claim 1, and light is extracted from the output surface.

Images