JP4038055B2 - Surface lighting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a planar lighting device used for lighting means such as a signboard and various reflective display devices, and particularly to lighting means for a liquid crystal display device.
[0002]
[Prior art]
Liquid crystal display devices, which are characterized by being thin, occupying a small volume, and being light, are used in many electric products such as mobile phones and personal computers, and the demand for them is increasing. By the way, since the liquid crystal itself of the liquid crystal display device does not emit light itself, the liquid crystal is irradiated separately from the liquid crystal display device when used in a dark place where the brightness of sunlight or room illumination cannot be taken in sufficiently. A lighting means is required.
Therefore, it is desired that the illumination means for irradiating the liquid crystal is also small and consumes little power. In recent years, a planar illumination device of a thin side light type (light guide plate type) is often used as the means.
[0003]
FIG. 12 shows an example of a conventional example of a planar illumination device that uses a sidelight system. FIG. 13 shows the reflection direction dispersion surface 31 in a state in which the plate-shaped light guide in the conventional planar illumination device is turned upside down. As shown in FIG. 12, the planar lighting device 1 ′ includes a plate-shaped light guide 2, a light source unit 5 that is disposed close to one end face 8 of the plate-shaped light guide 2, and light reflection. A member (also referred to as a frame) 13 is generally configured. In addition, a light reflection pattern 19 is formed on the upper surface (observation side surface) 15 of the plate-like light guide 2, and the light reflection pattern 19 makes an incident from one side end face 8 of the plate-like light guide 2. The light from the light source unit 5 is uniformly emitted to the liquid crystal display device L disposed on the lower surface 16 side of the plate-like light guide 2 without being affected by the distance from the light source unit 5.
[0004]
The light source unit 5 includes a rod-shaped light guide 3 made of a translucent material, and point light sources 4 and 4 disposed to face the end surfaces 6 and 7 of the rod-shaped light guide 3. An optical path changing means 12 is formed on the opposite surface of the one side surface 9 of the third lens 3. Moreover, the light reflection member 13 is formed in a substantially U shape, and is disposed so as to cover the rod-shaped light guide 3 when the planar lighting device 1 ′ is combined.
[0005]
The light reflection pattern 19 includes a groove portion 17 having a substantially triangular cross section as a prism and a flat portion 18 adjacent to the groove portion, and is parallel to the axial direction of the light source portion 5 (also referred to as the axial direction of the rod-shaped light guide 3). Is formed.
[0006]
The lower surface 16 of the plate-like light guide 2 is provided with a reflection direction dispersion surface 31 having a reflection direction dispersion pattern 21, and a non-reflection coating (not shown) is applied to the surface. The reflection direction dispersion pattern 21 is formed in parallel to the axial direction of the light source unit 5, similarly to the light reflection pattern 19 formed on the upper surface 15 of the plate-like light guide 2. By making the reflection direction dispersion pattern 21 into a lenticular shape, the reflection direction dispersion surface 31 can be easily manufactured by injection molding or the like. Note that the lenticular shape refers to the form of a small lens group having a kamaboko shape.
[0007]
By providing this reflection direction dispersion pattern 21, the direction of the light reflected by the reflection direction dispersion pattern 21 is made irregular so that there is no angle region where light does not come out from the light reflection pattern 19, and the observer's viewpoint The occurrence of bright and dark stripes whose positions and intervals change with the movement of the light is suppressed. The content of this reflection direction dispersion pattern is proposed in Japanese Patent Application No. 2001-391963.
[0008]
However, by providing the reflection direction dispersion pattern 21 on the lower surface of the plate-like light guide, a new interference fringe is generated when the light reflected by the reflection direction dispersion pattern 21 passes through the light reflection pattern 19 again and exits. A malfunction occurred.
[0009]
[Problems to be solved by the invention]
This interference fringe is caused by the difference in intensity of each emitted light with respect to the viewpoint when the reflected light from the reflection direction dispersion pattern is emitted from the light reflection pattern due to the positional relationship between the light reflection pattern and the reflection direction dispersion pattern. Turned out to be.
Therefore, in order to reduce the reflected light in the reflection direction dispersion pattern, an antireflection coating has been applied to the lower surface of the reflection direction dispersion pattern. However, as described in Japanese Patent Application No. 2001-391963, it covers the entire visible range. Therefore, the reflection cannot be completely suppressed, and there is usually a reflected light of a level of 0.2%, and the reflected light is a cause of interference fringes.
By the way, it is considered that the above-described interference fringes are generated by the following mechanism.
An example of the light reflection pattern 29 composed of stepped prisms will be described with reference to FIG.
[0010]
In the conventional structure shown in FIG. 9, the light 22 a emitted from the light source portion travels in the plate-shaped light guide 2 and is reflected by the prism step portion 27, and the reflected light 22 b is directed toward the lower surface 26. The light travels through the light guide 2 and is reflected near the center of the reflection direction dispersion pattern 21 formed on the lower surface 26 of the plate light guide 2. The reflected light 22c (Q) passes through the plate-like light guide 2 again, passes through the light reflection pattern 29 formed by the step portion 27 and the gentle slope portion 28, and is emitted to the outside. The light 22d emitted from one light source portion travels in the plate-shaped light guide 2 and is reflected by the prism step portion 27, and the reflected light 22e travels in the plate-shaped light guide 2 toward the lower surface 26. Further, the light is reflected in the vicinity of the end of the reflection direction dispersion pattern 21 formed on the lower surface 26 of the plate-like light guide 2. The reflected light 22f (R) passes through the plate-like light guide 2 again at an angle different from that of the light Q, passes through the light reflection pattern 29 formed by the step portion 27 and the gentle slope portion 28, and then passes through the outside. To exit. When the light R passes through the plate-shaped light guide plate and is emitted to the outside, the direction and intensity of the emitted light with respect to the viewpoint 25 are different from those of the light Q. FIG. 10 schematically shows the intensities of the light Q and R emitted from the light reflection pattern 29. The light Q is indicated by an ellipse, and the light R is an ellipse with diagonal lines. As shown in the figure, since the light Q and the light R are alternately generated on the entire surface of the light reflection pattern, the intensity of the light emitted from the light reflection pattern 29 is not uniform. Therefore, interference fringes are generated.
Therefore, the present invention suppresses the interference fringes generated by the patterns of the upper and lower surfaces of the plate-shaped light guide without generating bright and dark stripes that change in position and interval as the observer's viewpoint moves. An object of the present invention is to provide a planar illumination device that can suppress the generation of interference fringes without increasing the number of components to be used and without reducing the light use efficiency. .
[0011]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the invention of claim 1 is characterized in that a plate-shaped light guide made of a light-transmitting material that disposes a liquid crystal display device on the lower surface side, and a side surface of the plate-shaped light guide. In the side light type planar lighting device, the plate-like light guide is provided with a light reflection pattern formed by a plurality of prisms on the upper surface of the plate-like light guide. A reflection direction dispersion pattern made of lenticular is formed on the surface opposite to the surface on which the light reflection pattern is formed, and the microlenses constituting the lenticular are arranged with respect to the horizontal surface of the plate-like light guide. The maximum angle of the tangent line on the outer peripheral surface is formed to be 3 degrees or less, and the reflection direction dispersion pattern is formed to have a predetermined angle with respect to the length direction of the prism of the light reflection pattern. To do In the present invention, since the reflection direction dispersion pattern formed on the lower surface of the plate-shaped light guide is inclined with respect to the length direction of the prism of the light reflection pattern, it is partially in the direction of the light reflection pattern. The intensity of light emitted along can be changed. This schematic diagram is shown in FIG. The light Q is indicated by an ellipse and a circle, and the light R is a hatched circle. In this case, unlike the pattern of the emitted light shown in FIG. 10, the light Q and the light R are not generated alternately, so that the intensity of the light emitted from the light reflection pattern can be made uniform as a whole. As a result, the intensity of each emitted light with respect to the viewpoint becomes uniform, and the generation of interference fringes can be suppressed. (FIGS. 10 and 11 are images representing the pattern of the emitted light, and do not represent an accurate pattern.)
[0012]
In order to solve the above-mentioned problems, the invention according to claim 2 is the reflection direction dispersion formed on the surface opposite to the surface on which the light reflection pattern of the plate-like light guide is formed in the invention according to claim 1. pattern, characterized in that inclined 35 degrees angle from 10 degrees to the length direction of the prisms of the light reflection pattern.
[0013]
In order to solve the above-mentioned problem, the invention of claim 3 is characterized in that, in the invention of claim 1 or 2 , flat portions are disposed between the microlenses constituting the lenticular. Is.
[0014]
In order to solve the above-mentioned problem, the invention of claim 4 is characterized in that, in the invention of claim 1 or 2, the edge portion of the microlens constituting the lenticular is rounded. It is.
[0015]
In order to solve the above-mentioned problems, a fifth aspect of the present invention provides the microlens having the lenticular shape with respect to the horizontal surface of the plate-like light guide according to any one of the first to fourth aspects. The outer peripheral surface is composed of a plurality of planes whose angles change stepwise.
[0016]
In order to solve the above-mentioned problem, the invention of claim 6 is the invention according to any one of claims 1 to 5 , wherein an arc-shaped groove is formed instead of the microlens constituting the lenticular. It is characterized by.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a planar lighting device according to the present invention will be described below with reference to the accompanying drawings. In addition, this planar illuminating device has a reflection direction dispersion pattern for irregularly reflecting light formed on the lower surface of the plate-like light guide of the planar illuminating device described as the conventional example, and a prism having a light reflecting pattern. It is characterized by being formed to be inclined with respect to the length direction and the shape of the reflection direction dispersion pattern. The same members as those of the conventional planar illumination device are denoted by the same reference numerals, and detailed descriptions thereof are provided. Description is omitted.
[0018]
FIG. 1 is an exploded perspective view showing an embodiment of a planar lighting device according to the present invention.
FIG. 2 shows the reflection direction dispersion surface 31 of the present invention in a state where the plate-like light guide is turned over. As shown in FIG. 1, the planar illumination device 1 includes a plate-shaped light guide 2, a light source unit 5 that is disposed close to one end face 8 of the plate-shaped light guide 2, and a light reflecting member. (Also referred to as a frame) 13. In addition, a light reflection pattern 19 is formed on the upper surface (observation side surface) 15 of the plate-like light guide 2, and the light reflection pattern 19 makes an incident from one side end face 8 of the plate-like light guide 2. The light from the light source unit 5 is uniformly emitted to the liquid crystal display device L disposed on the lower surface 16 side of the plate-like light guide 2 without being affected by the distance from the light source unit 5.
[0019]
The light source unit 5 includes a rod-shaped light guide 3 made of a translucent material, and point light sources 4 and 4 disposed to face the end surfaces 6 and 7 of the rod-shaped light guide 3. An optical path changing means 12 is formed on the opposite surface of the one side surface 9 of the third lens 3. Moreover, the light reflection member 13 is formed in a substantially U shape, and is disposed so as to cover the rod-shaped light guide 3 when the planar lighting device 1 is combined.
[0020]
The light reflection pattern 19 includes a groove portion 17 having a substantially triangular cross section as a prism and a flat portion 18 adjacent to the groove portion, and is parallel to the axial direction of the light source portion 5 (also referred to as the axial direction of the rod-shaped light guide 3). Is formed. Further, the interval between the light reflection patterns 19, that is, the interval between adjacent groove portions 17 (also referred to as a groove pitch) is set to the same interval. Further, the depth of the groove 17 is shallow on the one side end face 8 side (light source part 5 side) of the plate-like light guide 2 and deep on the one side end face 10 side. That is, the groove portion 17 is formed so that its depth gradually increases as the distance from the light source portion 5 increases.
[0021]
The lower surface 16 of the plate-like light guide 2 is provided with a reflection direction dispersion surface 31 having a reflection direction dispersion pattern 21, and a non-reflection coating (not shown) is applied to the surface. By providing this reflection direction dispersion pattern 21, the occurrence of bright and dark stripes in which the position and interval that occur with the movement of the observer's viewpoint changes is suppressed.
Furthermore, by forming the reflection direction dispersion pattern 21 at a predetermined angle (Φ) with respect to the length direction of the prism of the light reflection pattern 19, the generation of interference fringes due to the upper and lower surface patterns as described above. It is possible to hold down.
[0022]
FIG. 8 shows the interference fringes when the reflection direction dispersion pattern formed on the surface opposite to the surface on which the light reflection pattern is formed is changed in angle (Φ) with respect to the length direction of the prism of the light reflection pattern. The generation result (visual observation) is shown. From this result, it is possible to suppress the occurrence of interference fringes when the angle (Φ) of the reflection direction dispersion pattern is from 10 degrees to 35 degrees. The angle (Φ) of the reflection direction dispersion pattern can be practically selected in the range of 10 degrees to 35 degrees, but a better form is selected from 20 degrees to 25 degrees.
[0023]
In the above-described embodiment, the case where the light reflection pattern 19 of FIG. 1 is configured by the groove portion 17 and the flat portion 18 has been described. However, the present invention is not limited to this embodiment, and a stepped prism as described later is used. In the case where the groove portion is configured, the groove portion has a substantially trapezoidal shape, the groove portion has a plurality of steps, or the cross-sectional shape may have a curve.
[0024]
Moreover, in the above-mentioned form, although the case where two point light sources 4 were arrange | positioned close to the end surfaces 6 and 7 of the rod-shaped light guide 3 was demonstrated, it is not limited to this form, A rod-shaped light guide It may be a case where one point light source 4 is arranged only on one end face of the end face 6 or the end face 7 of the body 3. Furthermore, the light source unit 5 may be a case where a fluorescent lamp which is a rod-shaped light source is used instead of the combination of the rod-shaped light guide 3 and the point light source 4. Furthermore, although the light source part 5 is arrange | positioned close to the one side end surface 8 of the plate-shaped light guide 2, it is not limited to this, Both the side surfaces of the plate-shaped light guide 2, That is, the case where it arrange | positions close to the one side end surface 8 and the one side end surface 10 may be sufficient respectively.
[0025]
In addition, the reflection direction dispersion pattern 21 formed on the lower surface 16 of the plate-like light guide 2 has a kamaboko shape with the outer peripheral surface facing the liquid crystal display device L side (downward in the drawing), that is, a lenticular shape, The light reflecting pattern 19 is disposed with an inclination in the length direction of the prism (left and right in the figure). Here, the lenticular-shaped reflection direction dispersion pattern 21 will be described with reference to FIG. 3, which is a schematic diagram. In the reflection direction dispersion pattern, the tangent S on the outer peripheral surface of the lenticular-shaped microlens is the horizontal surface of the plate-shaped light guide. It is desirable to form it to be 3 degrees or less with respect to T. Further, since it has been proved from the experimental results that the luminance is lowered at 3 degrees or more, it is desirable that the maximum angle θmax formed by the tangent S and the horizontal surface T is 3 degrees or less.
[0026]
In this way, by forming the lenticular-shaped reflection direction dispersion pattern 21 in which the angle θi formed with respect to the horizontal plane T continuously changes, the light reflected in the same angular direction at each step portion is different. It can be advanced in the angular direction.
[0027]
4 is an enlarged view of a dotted line portion B in FIG. As shown in the figure, by processing the edge portion 51 of the reflection direction dispersion pattern 21 in a round shape, the presence of the reflection direction dispersion pattern 21 becomes inconspicuous when viewed from the observation surface side, and visibility can be improved.
[0028]
The reflection direction dispersion pattern 21 is not limited to the lenticular shape as shown in FIG. 2 described above, and may have a form as shown in FIGS. 5 to 7, for example.
The reflection direction dispersion pattern 21 ′ shown in FIG. 5 has an arc shape with the inner peripheral surface facing the liquid crystal display device L side (downward direction in the figure). Even in the case of this shape, since the angle of the light reflection direction dispersion pattern can be continuously changed, the same effect as described above can be obtained.
[0029]
The reflection direction dispersion pattern 21 ″ shown in FIG. 6 has a shape constituted by a large number of planes 61 to 68. Even in this shape, the angles θA, θB, and θC of the surfaces 61 to 68 that disperse the light reflection direction with respect to the horizontal surface T can be changed stepwise (the planes 64 and 68 are the horizontal planes). Therefore, the same effect as described above can be obtained. The angles θA, θB, and θC are preferably set so that the maximum angle θA is 3 degrees or less. Moreover, the structure without the plane 68 may be sufficient.
[0030]
The reflection direction dispersion pattern 21 ′ ″ shown in FIG. 7 is composed of lenticular microlenses 71 and 72 and a flat portion 73 of the reflection direction dispersion pattern disposed between these reflection portions. Even in the case of this shape, since the angle of the light reflection direction dispersion pattern can be continuously changed, the same effect as described above can be obtained.
In this case, since the flat portion 73 of the reflection direction dispersion pattern is disposed between the minute lens 71 and the minute lens 72, it is manufactured more than the reflection direction dispersion pattern in which only the minute lens is continuously disposed. Has the advantage of being easy. Further, the same effect can be obtained even if a flat portion is provided in the reflection direction dispersion pattern 21 ′ having the form shown in FIG.
[0031]
【The invention's effect】
According to the planar illumination device according to the present invention, the present invention provides a plate-shaped light guide that has a surface facing the surface on which the light reflection pattern is formed, and is 10 in the length direction of the prism of the light reflection pattern. By forming a plurality of reflection direction dispersion patterns inclined by 35 degrees from the angle, interference fringes caused by reflected light on the upper and lower surfaces of the plate-like light guide can be suppressed, and the number of parts to be used can be reduced. It is possible to suppress the occurrence of interference fringes without increasing it and without reducing the light utilization efficiency.
[0032]
Also, the shape of the reflection direction dispersion pattern is formed into a lenticular shape in which the angle of the light reflecting surface changes continuously, and the angle of the surface of the reflection direction dispersion pattern is set with respect to the horizontal surface of the plate-shaped light guide. And the reflection direction dispersion pattern is composed of a lenticular microlens and a flat portion disposed adjacent to the microlens, or a horizontal surface of the plate-like light guide An effect similar to that described above can be obtained by using a plurality of planes in which the angle with respect to changes stepwise.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing an embodiment of a planar lighting device according to the present invention.
FIG. 2 shows a reflection direction dispersion surface of the present invention in a state where a plate-like light guide is turned over.
FIG. 3 is a schematic diagram showing another embodiment of a reflection direction dispersion pattern in the planar illumination device according to the present invention.
4 is a partially enlarged view of FIG. 3;
FIG. 5 is a diagram showing another embodiment of a reflection direction dispersion pattern in the planar illumination device according to the present invention.
FIG. 6 is a diagram showing another embodiment of a reflection direction dispersion pattern in the planar illumination device according to the present invention.
FIG. 7 is a diagram showing another embodiment of a reflection direction dispersion pattern in the planar illumination device according to the present invention.
FIG. 8 shows a result of suppressing interference fringes when the angle (Φ) of the reflection direction dispersion pattern of the planar illumination device according to the present invention is changed.
FIG. 9 is a view showing an embodiment of a reflection direction dispersion surface of a conventional planar illumination device.
FIG. 10 is a schematic diagram showing the intensity of light emitted from a light reflection pattern of a conventional planar illumination device.
FIG. 11 is a schematic diagram showing the intensity of light emitted from the light reflection pattern of the planar illumination device of the present invention.
FIG. 12 is an exploded perspective view showing one embodiment of a conventional planar illumination device.
FIG. 13 shows a reflection direction dispersion surface in a state where a plate-like light guide is turned over in a conventional planar illumination device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Planar illuminating device 2 Plate-shaped light guide 3 Rod-shaped light guide 4 Point light source 5 Light source part 6 and 7 End surface 8, 10 One side end surface 15 Upper surface 16, 26 Lower surface 17 Groove part 18 Flat part 19, 29 Light reflection pattern 21 Reflection direction dispersion pattern 27 Step portion 28 Slow slope portion 31 Reflection direction dispersion surfaces 61 to 68 Flat surfaces 71, 72 Micro lens 73 Flat portion L of reflection direction dispersion surface Liquid crystal display device

Claims (6)

A plurality of prisms each including a plate-like light guide made of a light-transmitting material on which a liquid crystal display device is arranged on the lower surface side, and a rod-like light source unit arranged close to the side surface of the plate-like light guide In a sidelight type planar illumination device in which a light reflection pattern constituted by is formed on the upper surface of the plate-like light guide,
On the surface opposite to the surface on which the light reflection pattern of the plate-shaped light guide is formed, a reflection direction dispersion pattern made of lenticular is formed ,
The microlens constituting the lenticular is formed such that the maximum angle of the tangent on the outer peripheral surface thereof is 3 degrees or less with respect to the horizontal surface of the plate-shaped light guide.
The planar illumination device, wherein the reflection direction dispersion pattern is formed at a predetermined angle with respect to a length direction of the prism of the light reflection pattern .   The reflection direction dispersion pattern formed on the surface of the plate-like light guide opposite to the surface on which the light reflection pattern is formed has an angle of 10 degrees with respect to the length direction of the prism of the reflection light reflection pattern. The planar illumination device according to claim 1, wherein the planar illumination device is inclined 35 degrees from the angle. The planar illumination device according to claim 1, wherein a flat portion is disposed between the microlenses constituting the lenticular . The planar illumination device according to claim 1 or 2, wherein an edge portion of the microlens constituting the lenticular is rounded . The planar lens according to any one of claims 1 to 4, wherein the microlens constituting the lenticular is composed of a plurality of planes whose angles with respect to a horizontal plane of the plate-like light guide change stepwise. Lighting device. 6. The planar illumination device according to claim 1, wherein an arc-shaped groove is formed instead of the microlens constituting the lenticular .

Images