JP2004171870A - Lighting system and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting system with low power consumption capable of preventing the occurrence of a dark part in the vicinity of a side end face of a light guide plate on the side of a light source, of preventing the occurrence of a bright line or a rainbow-like moire, and of evenly and brightly illuminating an illumination region. <P>SOLUTION: This front light (lighting system) 10 is equipped with: the light guide plate 12; an intermediate light guide body 13 installed along one-side end face 12a of the guide plate 12; and a light emitting element 15 installed on a longitudinal end face 13g of the guide body 13. A side face of the guide body 13 facing to the light entering surface 12a of the guide plate 12 is used as an emission surface 13k for emitting light to the guide plate 12; a fine uneven part 40 for diffusing and reflecting the light emitted from the element 15 and propagating in the intermediate light guide body is formed on an outside surface 13j opposite to the emission surface 13k; and the uneven part 40 is so formed that the reflection angle of the light reflected toward the entering surface 12a of the guide plate 12 is controlled according to the distance from the element 15. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an illuminating device and a liquid crystal display device, and more particularly to an illuminating device capable of improving the uniformity of the luminance distribution of a light guide plate even with a single light source, and a configuration of a liquid crystal display device using the same.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a unit including a light source, an intermediate light guide, a light guide plate, and a case body having an inner surface that reflects the light source, an intermediate light guide, and an inner surface thereof, has been used as a front light of a reflective liquid crystal display device.
FIG. 16A is a perspective configuration diagram showing a conventional liquid crystal display device, and FIG. 16B is a plan view when a front light provided in the liquid crystal display device shown in FIG. 16A is viewed from an observation side. The liquid crystal display device shown in these figures includes a liquid crystal display unit 120 and a front light 110 arranged on the front side of the liquid crystal display unit 120 (for example, see Patent Document 1). Although not shown in detail, the liquid crystal display unit 120 is a reflection-type liquid crystal display unit that performs display by reflecting light incident from the front side thereof, and includes an upper substrate 121 and a lower substrate that are arranged to face each other. A liquid crystal layer is sandwiched between the liquid crystal layer 122 and the liquid crystal layer 122. By controlling the alignment state of the liquid crystal layer, display is performed by changing the light transmission state.
[0003]
The front light 110 includes a flat light guide plate 112, a rod-shaped intermediate light guide 113 disposed on a side end surface (light incident surface) 112 a of the light guide plate 112, and one end surface of the intermediate light guide 113. The light emitting element 115 is a point light source such as a white LED (Light Emitting Diode) disposed at 113 g (left end face in the figure). On the upper surface side of the light guide plate 112, a plurality of wedge-shaped prism grooves 114 are formed as reflection surfaces 112c formed in a stripe shape in a plan view in parallel with each other, and the lower surface is used for illuminating the liquid crystal display unit 120. An emission surface 112b from which illumination light is emitted is provided. Each prism groove 114 includes a gentle slope portion 114a and a sharp slope portion 114b formed at a steeper inclination angle than the gentle slope portion 114a.
These prism grooves 114 are formed slightly inclined with respect to the light guide plate side end surface 112a for the purpose of preventing moire.
The intermediate light guide 113 is provided to uniformly and efficiently emit light from the light emitting element 115 to the light guide plate 112 along the light incident surface of the light guide plate 112, and has an outer surface (the light guide plate 112). A prism surface 113f is formed on the outer surface 113a along the length direction of the outer surface 113a (from the end surface 113g on the light emitting element 115 side to the end surface 113h on the opposite side) 113a. .
The prism surface 113f is formed by forming a plurality of wedge-shaped grooves 113b parallel to each other in a plan view (transverse cross section). These wedge-shaped grooves 113b are provided so that the pitch and the depth are uniform. I have.
[0004]
In the front light 110 having such a configuration, the light emitted from the light emitting element 115 is introduced into the intermediate light guide 113, its propagation direction is changed by the prism surface 113 f, and the light is emitted from the light incident surface 112 a of the light guide plate 112. The light is introduced into the light guide plate 112, and this light is reflected on the reflection surface (inner surface) side of the upper surface of the light guide plate 112 in which the prism groove is formed, thereby changing the propagation direction of the light, and from the emission surface (lower surface) of the light guide plate 112 The light is emitted toward the liquid crystal display unit 120.
[0005]
[Patent Document 1]
Japanese Patent Application No. 10-19213
[0006]
[Problems to be solved by the invention]
In portable electronic devices such as portable information terminals and portable game machines, the battery drive time greatly affects the usability, and the liquid crystal display device used as these display units aims to reduce the power consumption of the front light. As in the case of a front light 110 shown in FIG. 16, a one-light type front light having only one light-emitting element 115 has been used. That is, it is intended to realize low power consumption by omitting the light emitting element. In addition, with the miniaturization of portable electronic devices, it is required to reduce the thickness of the front light 110 to about 1 mm.
[0007]
However, in such a single-lamp front light, a display area (illuminated area) having a wide area of several inches or more on a diagonal is uniformly and brightly illuminated by a combination of a thin light guide plate and a single light-emitting element. It was almost impossible to do. That is, in the case where the light emitting element 115 is provided on one side in the front light 110 shown in FIG. 16, in order to uniformly guide the light from the light emitting element 115 to the light guide It is necessary to equalize the incident light in the length direction of the light incident surface of the light guide plate 112 by the body 113, but it is difficult to equalize the incident light to the light guide plate 112 by the intermediate light guide 113 itself. In addition, it is difficult to obtain uniform outgoing light over the entire surface of the outgoing surface 112b, it is difficult to uniformly irradiate the display area of the liquid crystal display unit 120 without luminance unevenness, and the display visibility may be reduced. Was. For this reason, in a particularly prominent case, a dark portion 128 having a triangular shape in plan view as shown in FIG. A problem of variation in emitted light may occur, which may reduce the visibility of the liquid crystal display device.
Further, in the front light 110 provided with the intermediate light guide 113 having the prism surface 113f in which the plurality of wedge-shaped grooves 113b are regularly formed as described above, uniform light emission is provided over the entire exit surface 112b. It is difficult to obtain the light, and the prism effect is manifested by light dispersion at the two slopes constituting the wedge-shaped groove 113b and the apex angle thereof, so that a bright line or a rainbow-like moire may be generated.
[0008]
In a two-lamp type front light in which a light emitting element is also provided on the other end surface 113h side (right side in the figure) of the intermediate light guide 113, the light emitted from the light emitting element on the end surface 113h side causes the left side of the light guide plate 112 to be left. Although the light amount near the end face 112g is compensated for and becomes brighter, power consumption is increased as compared with the single-lamp type.
As described above, although the demand for a front light using one light emitting element as a light source is increasing, a front light capable of illuminating a large area uniformly and brightly while being thin has not been realized. Was.
[0009]
The present invention has been made in order to solve the above problems, the use efficiency of the light emitted from the light source is good, it is possible to prevent the occurrence of a dark portion near the light guide side edge of the light source side, In addition, it is an object to provide a low-power-consumption lighting device that can prevent the occurrence of a bright line or a rainbow-like moiré, and can uniformly and brightly illuminate an illuminated area.
Another object of the present invention is to provide a liquid crystal display device including the above lighting device and having high luminance and excellent display quality.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present invention employs the following configurations.
A lighting device according to the present invention includes a light guide plate, an intermediate light guide disposed along one end surface of the light guide plate, and a light source disposed on a longitudinal end surface of the intermediate light guide. With
The light guide plate has a side end surface into which light is introduced as a light incident surface, and introduces light emitted from the light source from the light incident surface of the light guide plate into the light guide plate through the intermediate light guide. An illumination device that emits light propagating inside the light guide plate from one surface side of the light guide plate,
A side surface of the intermediate light guide opposed to one end surface of the light guide plate is an emission surface for emitting light to the light guide plate, and the intermediate surface is emitted from the light source to an outer surface opposite to the emission surface. A minute uneven portion for diffusing and reflecting light propagating inside the light guide is formed, and the minute uneven portion reflects a reflection angle of light reflected toward a light incident surface of the light guide plate according to a distance from the light source. Is controlled.
[0011]
According to the illumination device having such a configuration, the light is reflected toward the light incident surface of the light guide plate by changing the formation conditions of the minute uneven portion formed on the outer surface of the intermediate light guide according to the distance from the light source. The reflection angle of the generated light is controlled in accordance with the distance from the light source, so that the brightness distribution of the light guide plate when viewed in a plan view can be made uniform, and the light guide plate can be made uniform from one surface side (emission surface). Outgoing light can be emitted.
Further, in a conventional illumination device provided with an intermediate light guide provided with a prism surface in which a plurality of wedge-shaped grooves are regularly formed, a discontinuity at an interface between two slopes forming each wedge-shaped groove is provided. The surfaces are regularly present, and bright lines and rainbow-like moire are generated due to these discontinuous surfaces. However, in the present invention, the conditions for forming the minute uneven portions formed on the outer surface of the intermediate light guide are limited. Since it is changed according to the distance from the light source, the discontinuous surface between the convex portions of the minute concave / convex portions or between the concave portions and the concave portions is irregularly present, and furthermore, the intermediate light guide. Since the uneven portion formed on the outer surface of the body is very small and functions as a continuous diffusion surface, it is possible to prevent the occurrence of bright lines and rainbow-like moire.
Therefore, according to the present invention, even if the light source is provided on one end face of the intermediate light guide, the use efficiency of the light emitted from the light source is good, and the light guide plate side end face on the light source side is good. Since it is possible to prevent the generation of a dark portion in the vicinity and to prevent the occurrence of a bright line or a rainbow-like moiré, the uniformity of the luminance distribution of the light guide plate can be improved. It is possible to provide a low-power-consumption illuminating device capable of improving the uniformity of the emitted light and illuminating the illuminated area uniformly and brightly.
[0012]
Further, the lighting device according to the present invention is provided with a light guide plate, an intermediate light guide disposed along one end face of the light guide plate, and an end face in a longitudinal direction of the intermediate light guide. With a light source,
The light guide plate has a side end surface into which light is introduced as a light incident surface, and introduces light emitted from the light source from the light incident surface of the light guide plate into the light guide plate through the intermediate light guide. A lighting device for emitting light propagating inside the light guide plate from one surface side of the light guide plate, wherein a side surface of the intermediate light guide facing one end surface of the light guide plate emits light to the light guide plate. An exit surface is formed, and a prism surface including a plurality of wedge-shaped grooves is formed on an outer surface opposite to the exit surface, and emitted from the light source on the surface of the prism surface and propagates inside the intermediate light guide. Micro-irregularities for diffusing and reflecting light to be emitted are formed, and the angle of reflection of the light reflected toward the light-incident surface of the light guide plate is controlled in accordance with the distance from the light source. May be characterized.
[0013]
According to the illuminating device having such a configuration, in particular, since the above-described minute irregularities are formed on the surface of the prism surface formed on the outer surface of the intermediate light guide, the light is dispersed by the prism surface. The luminance distribution of the light emitted from the intermediate light guide can be made substantially uniform, and the light can be diffused when reflected by the minute unevenness due to the diffuse reflection action of the minute unevenness.
[0014]
Further, in the lighting device of the present invention having any one of the above-described structures, the fine unevenness as described above is also formed on the end surface of the intermediate light guide in the longitudinal direction opposite to the end surface on which the light source is provided. This has the effect of preventing loss of light emitted from the light source.
[0015]
Further, in the lighting device of the present invention having any one of the above structures, the minute concave-convex portion has a plurality of concave portions, and the plurality of concave portions each have a specific vertical cross section passing through the deepest point of the concave portion. Each of the concave portions may be such that the inclination angle of the cross section curve of the specific vertical cross section is controlled according to the distance from the light source.
[0016]
Further, in the lighting device of the present invention having any one of the above structures, the minute uneven portion has a plurality of convex portions, and each of the plurality of convex portions has a specific vertical cross section passing through the top of the convex portion. Each of the projections may be such that the inclination angle of the sectional curve of the specific longitudinal section is controlled in accordance with the distance from the light source.
[0017]
Further, in the lighting device of the present invention having any one of the above structures, the minute uneven portion has a plurality of convex portions or concave portions, and the pitch of the convex portions or concave portions is such that the side farther from the light source is the light source. Being smaller than the side closer to the light source, the light emitted from the intermediate light guide can be efficiently supplied to the light guide plate, and the uniformity of the light emitted from the intermediate light guide can be improved. This is preferable in that the amount of light emitted from the emission surface of the light guide plate and its uniformity can be improved.
[0018]
Further, in the lighting device of the present invention having any one of the above structures, the minute uneven portion has a plurality of convex portions or concave portions, and the height of the convex portions or the depth of the concave portions is farther from the light source. The light emitting device is configured to be larger than the light source closer to the light source, so that the light emitted from the intermediate light guide can be efficiently supplied to the light guide plate, and the uniformity of the light emitted from the intermediate light guide is improved. This is preferable in that the amount of light emitted from the emission surface of the light guide plate and its uniformity can be improved.
[0019]
Further, in the lighting device of the present invention having any one of the above structures, the light emitting angle of light emitted from the light emitting surface of the intermediate light guide toward the light input surface of the light guide plate is such that the lighting device is viewed in a plan view. In this case, the angle within ± 10 degrees with respect to the direction perpendicular to the light incident surface can efficiently supply the light emitted from the intermediate light guide to the light guide plate, and is emitted from the light emission surface of the light guide plate. This is preferable in that the amount of light and the uniformity can be improved.
Further, in the lighting device of the present invention having any one of the above structures, the light output angle of the light emitted from the output surface of the intermediate light guide toward the light input surface of the light guide plate is such that the lighting device has a cross-sectional view. In this case, the angle within ± 20 degrees with respect to the direction perpendicular to the light incident surface can efficiently supply the light emitted from the intermediate light guide to the light guide plate, and is emitted from the light emission surface of the light guide plate. This is preferable in that the amount of light and the uniformity can be improved.
[0020]
Further, in the lighting device of the present invention having any one of the above configurations, the emission direction of light emitted from the emission surface of the intermediate light guide toward the light incidence surface of the light guide plate is such that the illumination device is viewed in a plan view. In this case, the direction closer to the light source than the direction orthogonal to the light incident surface on the side near the light source, the direction opposite to the light source relative to the direction orthogonal to the light incident surface on the side farther from the light source, preferably Is a direction substantially perpendicular to an extending direction of a prism groove of a light guide plate to be described later, and an intermediate portion between a side near and far from the light source is a direction substantially perpendicular to the light incident surface. This is preferable because the light emitted from the light guide plate can be efficiently supplied to the light guide plate, and the amount of light emitted from the emission surface of the light guide plate and its uniformity can be improved.
[0021]
Further, in the lighting device of the present invention having any one of the above structures, the thickness of the intermediate light guide between the light exit surface and a surface (outer surface) opposite to the light exit surface is farther from the light source. Is smaller than the side closer to the light source, the light emitted from the intermediate light guide can be efficiently supplied to the light guide plate, and the amount of light emitted from the emission surface of the light guide plate and its uniformity Is preferred in that it can increase the
Further, in the lighting device of the present invention having any one of the above structures, the distance between the minute uneven portion of the intermediate light guide and the light incident surface of the light guide plate is such that the side farther from the light source is closer to the light source. It is preferable that the width is smaller than that in that the light emitted from the intermediate light guide can be efficiently supplied to the light guide plate, and the amount of light emitted from the emission surface of the light guide plate and its uniformity can be improved. .
[0022]
Further, in the lighting device of the present invention having any one of the above structures, the fact that the metal reflection film is formed on the surface of the minute uneven portion of the intermediate light guide increases the reflectance on the minute uneven surface, This is preferable in that the amount of light reflected toward the exit surface of the light body can be increased.
[0023]
In the lighting device of the present invention having any one of the above structures, the light source disposed on the longitudinal end face of the intermediate light guide may be a substantially point light source such as a light emitting element.
In the lighting device of the present invention having any one of the above structures, the other surface of the light guide plate is formed of a gentle slope portion and a sharp slope portion having a steeper inclination angle than the gentle slope portion. It is preferable that the plurality of prism grooves are formed in a stripe shape in a plan view, since the amount of emitted light is uniform in the light guide plate surface, and the use efficiency of the light source is high and a high-luminance illuminating device can be obtained.
Further, in the lighting device of the present invention having any one of the above configurations, the extending direction of the prism groove of the light guide plate may be set to a direction intersecting the light incident surface. When the illuminated object illuminated by the illuminating device has a periodic shape or pattern (regular pattern) at predetermined intervals, the prism groove of the light guide plate and the shape or pattern of the illuminated object are used. Direction of the prism groove depending on the pitch of the periodic shape or pattern (regular pattern) at predetermined intervals on the illuminated object in order to prevent the occurrence of a moiré pattern due to optical interference with the prism groove. It is preferable to set the intersection angle between the light source and the light incident surface so that the direction in which the prism groove extends and the direction in which the regular pattern of the illuminated object is repeated are not parallel.
[0024]
Next, a liquid crystal display device of the present invention includes the lighting device of the present invention having any one of the above-described structures, and a liquid crystal display unit illuminated by the lighting device.
Since the liquid crystal display device of the present invention includes the lighting device of the present invention, the display region (illuminated region) can be uniformly and brightly illuminated even when the lighting device has one light emitting element. A liquid crystal display device with good display visibility, high luminance and excellent display quality, and low power consumption can be obtained.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(1st Embodiment)
[Overall configuration of liquid crystal display device]
FIG. 1 is a perspective configuration diagram of a liquid crystal display device according to a first embodiment of the present invention, FIG. 2 is a plan configuration diagram of the liquid crystal display device shown in FIG. 1, and FIG. 3 is a liquid crystal display device shown in FIG. FIG. 3 is a sectional view taken along line III-III of the device. 4 is an enlarged plan view showing a front light (illumination device) provided in the liquid crystal display device shown in FIG. 2, and FIG. 5 is a front view III of the front light provided in the liquid crystal display device shown in FIG. FIG. 3 is a sectional view taken along line III.
As shown in FIGS. 1 to 3, the liquid crystal display device of the present embodiment includes a front light (illumination device) 10 and a reflective liquid crystal display unit 20 disposed on the back side (the lower side in the figure). It is configured.
[0026]
As shown in FIG. 1, the front light 10 includes a substantially flat transparent light guide plate 12, an intermediate light guide 13 disposed along a side end surface (one side end surface) 12 a, and the intermediate light guide 13. A light emitting element (light source) 15 disposed on one end surface 13g in the length direction of the body 13 and an intermediate light guide so as to cover one end of the intermediate light guide 13, the light emitting element 15 and the light guide plate 12. And a case body (light shielding and reflecting body) 19 attached from the 13 side.
That is, in the front light 10 according to the present embodiment, the side end surface 12a of the light guide plate 12 is a light incident surface of the light guide plate. As shown in FIG. 2, a plurality of light guide plates 12 are provided on the upper surface side (another surface side) of the light guide plate 12 at a tilt angle α with respect to the light incident surface 12a on which the intermediate light guide 13 is disposed. The prism grooves 14 are arranged and formed. In FIGS. 1 and 2, reference numeral 12 d denotes a side end surface (another side end surface) of the light guide plate 12 opposite to the light incident surface 12 a.
[0027]
The liquid crystal display unit 20 includes an upper substrate 21 and a lower substrate 22 that are arranged to face each other. A rectangular area 20D indicated by a dotted line in FIG. 1 is a display area of the liquid crystal display unit 20, and FIG. As shown in FIG. 2, pixels 20c are formed in a matrix in the display area 20D.
In the liquid crystal display device having the above configuration, the light guide plate 12 is disposed on the display area 20D of the liquid crystal display unit 20, and the display of the liquid crystal display unit 20 can be visually recognized through the light guide plate 12. In a dark place where external light cannot be obtained, the light emitting element 15 is turned on, and light emitted from the light emitting element 15 is transmitted from the light incident surface 12a of the light guide plate 12 to the inside of the light guide plate via the intermediate light guide 13. The light is propagated inside the light guide plate and emitted from the lower surface (one surface) 12b side of the light guide plate 12 toward the liquid crystal display unit 20 to illuminate a display area (illuminated area) 20D. I have.
[0028]
Next, the configuration of each part of the liquid crystal display device of the present embodiment will be described in detail with reference to the drawings.
[Front light]
The light guide plate 12 of the front light 10 is a plate-shaped member that is disposed on the display area 20D of the liquid crystal display unit 20 and emits light emitted from the light emitting element 15 to the liquid crystal display unit 20 from the lower surface 12b side. It is composed of an acrylic resin or the like. As shown in the partial cross-sectional view of FIG. 3, the upper surface of the light guide plate 12 (the other surface, in other words, the surface on the side opposite to the liquid crystal display unit 20) has a plurality of prism grooves 14 in a stripe shape in parallel with each other. The lower surface (surface on the side of the liquid crystal display unit 20) 12b is an emission surface from which illumination light for illuminating the liquid crystal display unit 20 is emitted.
[0029]
The prism groove 14 is a wedge-shaped longitudinal section formed by a pair of slopes formed to be inclined with respect to the reference surface Sa of the reflection surface 12c, and one of these slopes is a gentle slope 14a. The other is a steep slope 14b formed at a steeper inclination angle than the gentle slope 14a. As shown in FIGS. 1 and 2, the prism groove 14 is formed so as to be inclined so that the extending direction thereof and the light incident surface 12 a of the light guide plate 12 intersect. In FIG. 3, light propagating from the right side to the left side (light propagating from the light incident surface 12a to the other side end surface 12d) inside the light guide plate 12 is directed toward the light emitting surface 12b by the steep slope portion 14b of the reflecting surface 12c. The light is reflected and emitted toward the liquid crystal display unit 20 arranged on the lower surface side of the light guide plate 12.
[0030]
In the front light 10, the inclination angle θ of the gentle slope portion 14a shown in FIG. ₁ Is in the range of 1 ° to 5 ° with respect to the reference surface Sa of the reflection surface 12c, and the inclination angle θ of the steep slope portion 14b ₂ Is in the range of 41 ° or more and 45 ° or less. With such a range, light propagating in the plane of the light guide plate 12 can be efficiently emitted to the liquid crystal display unit 20, and a liquid crystal display device capable of bright display can be configured.
The reference surface Sa of the reflection surface 12c is a surface including the top portion 14d between the adjacent prism grooves 14 of the light guide plate 12.
[0031]
In the front light 10 of the present embodiment, the pitch P of the prism grooves 14 (the distance between the tops 14d or the distance between the bottoms of the prism grooves 14) is constant within the reflection surface 12c of the light guide plate. Further, in the case of the front light 10 of the present embodiment, the depth d of the prism groove 14 (the distance between the reference surface Sa and the bottom top of the prism groove 14) is also constant.
Note that the pitch P and the depth d of the prism grooves 14 are not necessarily required to be constant, and even if these are changed to form the prism grooves 14, it does not exceed the technical scope of the present invention. Also, the inclination angle θ of each prism groove 14 ₁ And θ ₂ Even if the prism groove 14 is formed by changing the above, it does not exceed the technical scope of the present invention.
[0032]
2, the inclination angle α of the prism groove 14 given by the angle formed by the prism groove 14 and the light incident surface 12a is in a range of more than 0 ° and 15 ° or less, as shown in FIG. It is preferable that it is formed as follows. The inclination angle α is more preferably in the range of 6.5 ° to 8.5 °, and by setting it in such a range, a moiré pattern hardly occurs and the front light is excellent in uniformity of emitted light. It can be.
[0033]
The light guide plate 12 may be formed of a transparent resin material such as a polycarbonate resin or an epoxy resin, glass, or the like, in addition to an acrylic resin.
Further, the light guide plate 12 can make the amount of emitted light uniform as the light guide plate as a whole increases in thickness, so that the plate thickness is preferably 0.8 mm or more, and more preferably 1.0 mm or more. More preferred. Further, when the plate thickness is 1.2 mm or more, since the luminance is not much different from that of the plate having a thickness of 1.0 mm to 1.5 mm, the upper limit of the plate thickness is 1.5 mm from the viewpoint of thinning the front light 10. Good to do.
[0034]
The intermediate light guide 13 is a quadrangular prism-shaped transparent member along the light incident surface 12a of the light guide plate 12. The light emitting element 15 is provided on one end face 13 g of the intermediate light guide 13.
As shown in FIGS. 1 and 4, the intermediate light guide 13 has a side end surface facing the light incident surface 12 of the light guide plate 12, and the light emitted from the light emitting element 15 is used as the light guide plate. An emission surface 13k for emitting the light to the light source 12 is provided.
Further, as shown in FIG. 4, an outer surface 13j of the intermediate light guide 13 opposite to the emission surface 13k is provided for diffusing and reflecting light emitted from the light emitting element 15 and propagating inside the intermediate light guide. The minute uneven portion 40 is formed. The minute uneven portion 40 has a plurality of convex portions 41. The plurality of convex portions 41 are provided so as to be convex inside the intermediate light guide 13. Each of the plurality of convex portions 41 has a specific vertical cross section that passes through the top 41 a of the convex portion 41. The shape of the convex portion that can be used for the minute concave / convex portion 40 of the present embodiment will be described later in detail. Further, minute uneven portions 40 are also formed on the end face 13h of the intermediate light guide 13 opposite to the end face 13g on which the light emitting element 15 is provided, for the reason described above.
On the outer surface of the minute uneven portion 40 formed on the outer surface 13j and the end surface 13h of the intermediate light guide 13, a metal reflection film made of a metal thin film of high reflectivity such as Al or Ag is used for the reason described above. 47 may be formed.
[0035]
Pitch P of convex portions 41 constituting minute concave / convex portions 40 formed on outer side surface 13j ₂ (The distance between the adjacent convex portions 41 and the tops of the convex portions 41 or the distance between the adjacent convex portions 41 and the center of the convex portions) is reduced as the distance from the light emitting element 15 increases, for the reason described above. That is, the pitch P of the projection 41 ₂ Is smaller on the side farther from the light emitting element 15 than on the side closer to the light emitting element 15. Also, the height d of the convex portion 41 ₂ Is higher as the distance from the light emitting element 15 increases, that is, the height d of the protrusion 41 is increased. ₂ Is larger on the side farther from the light emitting element 15 than on the side closer to the light emitting element 15. Further, the distance between the minute uneven portion 40 of the intermediate light guide 13 and the light incident surface 12a of the light guide plate 12 (the distance between the top of the convex portion 41 and the light incident surface 12a in the present embodiment) is closer to the light emitting element 15. The side may be smaller than the side closer to the light emitting element 15.
[0036]
The reflection angle of the light reflected toward the light incident surface 12a of the light guide plate 12 is controlled in accordance with the distance from the light emitting element 15 to the minute uneven portion 40 formed on the outer side surface 13j. State.
In FIG. 4, a region surrounded by a dotted line a is a region of the intermediate light guide 13 near the light emitting element, a region surrounded by a dotted line c is a region of the intermediate light guide 13 far from the light emitting element, and is surrounded by a dotted line b. The shaded area is an intermediate area between the area of the intermediate light guide 13 near the light emitting element and the area far from the light emitting element. FIG. 6 is an explanatory diagram showing an example of the position of the outer surface 13j of the intermediate light guide 13 and the angle of light from the light emitting element reaching each position. In FIG. 6, illustration of the minute uneven portion 40 is omitted.
[0037]
As shown in FIG. 6A, the light L reaching the portion of the outer surface 13j near the light emitting element (the outer surface 13j in the region a in FIG. 4) is such that the light emitted from the light emitting element 15 has an emission surface 13k at an initial stage. Many are reflected by These lights L are incident on the outer surface 13j at an angle θ close to 90 degrees. ₅ By controlling the inclination angle of the cross-sectional curve of the specific vertical cross section passing through the top 41a of the convex portion 41 in the area a in FIG. 4, the light R (light guide plate) reflected toward the emission surface 13k Of the light R emitted from the light exit surface 13k to the light incident surface 12a. ₆ When the front light 10 is viewed in a plan view as shown in FIG. 4, the angle is within ± 10 degrees with respect to a direction M perpendicular to the light incident surface 12a, and the light emission angle θ of the light R. ₆ When the front light 10 is viewed in cross section as shown in FIG. 5, the angle is within ± 20 degrees with respect to a direction M perpendicular to the light incident surface 12a.
[0038]
Further, as shown in FIG. 6C, the light L arriving at a portion of the outer surface 13j farther from the light emitting element (the outer surface 13j in the region c in FIG. 4) is the light L emitted from the light emitting element 15 in the horizontal direction. There are many things. These lights L impinge on the outer surface 13j at a small angle θ. ₅ By controlling the inclination angle of the cross-sectional curve of the specific longitudinal section passing through the top 41a of the convex portion 41 in the area c of FIG. 4, the light R reflected toward the emission surface 13k (light guide plate) Of the light R emitted from the light exit surface 13k to the light incident surface 12a. ₆ When the front light 10 is viewed in a plan view as shown in FIG. 4, the angle is within ± 10 degrees with respect to a direction M perpendicular to the light incident surface 12a, and the light emission angle θ of the light R. ₆ When the front light 10 is viewed in cross section as shown in FIG. 5, the angle is within ± 20 degrees with respect to a direction M perpendicular to the light incident surface 12a.
[0039]
Further, as shown in FIG. 6B, light L arriving at an intermediate portion (outer surface 13j in region b in FIG. 4) of the outer surface 13j on the near side and far side of the light emitting element is the light emitted from light emitting element 15 Many are repeatedly reflected in the intermediate light guide 13. These lights L are applied to the outer surface 13j at various angles (wide angle range) θ. ₅ The light R (light guide plate) reflected toward the emission surface 13k is controlled by controlling the inclination angle of a cross-sectional curve of a specific vertical cross-section passing through the top 41a of the convex portion 41 in the region b in FIG. Of the light R emitted from the light exit surface 13k to the light incident surface 12a. ₆ When the front light 10 is viewed in a plan view as shown in FIG. 4, the angle is within ± 10 degrees with respect to a direction M perpendicular to the light incident surface 12a, and the light emission angle θ of the light R. ₆ When the front light 10 is viewed in cross section as shown in FIG. 5, the angle is within ± 20 degrees with respect to a direction M perpendicular to the light incident surface 12a.
[0040]
Next, another example in which the reflection angle of light reflected from the minute uneven portion 40 toward the light incident surface from the emission from the minute uneven portion 40 is controlled according to the distance from the light emitting element 15 will be described.
The reflection angle of the light R reflected toward the light entrance surface 12a of the light guide plate 12 by controlling the inclination angle of the cross-sectional curve of the specific vertical cross section passing through the top 41a of the convex portion 41 in the region a of FIG. And the light emission angle θ of the light R as shown in FIG. 7A. ₇ May be a direction closer to the light emitting element 15 than the direction M.
Further, by controlling the inclination angle of the cross-sectional curve of the specific vertical cross section passing through the top 41a of the convex portion 41 in the region c of FIG. 4, the light R reflected toward the light entrance surface 12a of the light guide plate 12 is controlled. The reflection angle is controlled, and as shown in FIG. ₇ May be a direction opposite to the light emitting element 15 side with respect to the direction M, preferably a direction substantially orthogonal to the extending direction of the prism groove 14 of the light guide plate 12.
Further, by controlling the inclination angle of the cross-sectional curve of the specific longitudinal section passing through the top 41a of the convex portion 41 in the region b of FIG. 4, the light R reflected toward the light incident surface 12a of the light guide plate 12 is controlled. The reflection angle is controlled, and as shown in FIG. ₇ Is a substantially direction M (a direction substantially orthogonal to the light incident surface 12a).
[0041]
The intermediate light guide 13 may be made of a transparent resin material such as a polycarbonate resin or an epoxy resin, glass, or the like, in addition to an acrylic resin. The light emitting element (point light source) 15 is not particularly limited as long as it can be disposed on the end face of the intermediate light guide 13, and a white LED (Light Emitting Diode), an organic EL element, or the like can be used.
In addition, the minute uneven portion 40 formed on the end face 13h of the intermediate light guide 13 does not reflect the inside of the intermediate light guide, and prevents a light component propagating in a horizontal direction in a sectional view from leaking from the end face 13h. ing.
[0042]
In the front light 10 of the present embodiment, the light emitted from the light emitting element 15 propagates inside the intermediate light guide 13 in the length direction of the intermediate light guide 13, and diffuses and reflects on the surface of the minute uneven portion 40. However, at this time, the light reflected on the surface of the minute uneven portion 40 is emitted toward the light incident surface 12 a of the light guide plate 12 with the reflection angle controlled according to the distance from the light emitting element 15. I have.
[0043]
As shown in FIG. 1, a case body 19 is attached to the front light 10 on the side of the intermediate light guide 13. A reflection film (not shown) made of a metal thin film having a high reflectance such as Al or Ag is formed on the inner surface side of the case body 19, and light leaking outward from the intermediate light guide 13 and the light guide plate 12 is formed. In the case where there is, the light is reflected by the reflection film, so that the light enters the intermediate light guide 13 again and can be used as illumination light.
[0044]
In the front light 10 of the present embodiment, the light entrance surface of the light guide plate 12 is changed by changing the formation conditions of the minute uneven portion 40 formed on the outer surface 13j of the intermediate light guide 13 according to the distance from the light emitting element 15. The reflection angle of the light reflected toward the light guide plate 12a is controlled in accordance with the distance from the light emitting element 15, and the brightness distribution of the light guide plate 12 when viewed in a plan view can be made uniform. Emitted light can be emitted uniformly from the emission surface 12b. In addition, the discontinuous surface between the convex portions 41 of the minute concave / convex portions 40 is irregular, and the concave / convex portions formed on the outer surface 13j of the intermediate light guide 13 are minute. Therefore, since it functions as a continuous diffusion surface, it is possible to prevent the occurrence of bright lines and rainbow-like moire.
Therefore, according to the front light 10 of the present embodiment, the utilization efficiency of the light emitted from the light emitting element 15 is good, and it is possible to prevent a dark portion from being generated near the light guide plate side end surface 12g on the light emitting element 15 side. Moreover, it is possible to prevent the occurrence of bright lines and rainbow-like moiré, to uniformly and brightly illuminate the display area 20D of the liquid crystal display unit 20, and to reduce power consumption.
[0045]
In the present embodiment, a single-lamp front light in which the light emitting element 15 is provided on one end face in the length direction of the intermediate light guide 13 has been described. Of course, 15 may be provided.
Also, a case has been described where the thickness between the outer surface 13j of the intermediate light guide 13 (the surface on which the minute uneven portions are not formed, that is, the reference surface S of the outer surface 13j) and the emission surface 13k is uniform. The thickness (distance) between the outer side surface 13j and the emission surface 13k may be smaller on the side farther from the light emitting element 15 than on the side closer to the light emitting element 15; Pitch P of convex part 41 ₂ And height d ₂ May be constant.
[0046]
[Liquid crystal display unit]
The liquid crystal display unit 20 is a reflective passive matrix type liquid crystal display unit capable of color display. As shown in FIG. 3, a liquid crystal layer is provided between an upper substrate 21 and a lower substrate 22 which are arranged to face each other. 23, a plurality of strip-shaped transparent electrodes 26a and an alignment film 26b are sequentially formed on the inner surface side (the liquid crystal layer 23 side) of the upper substrate 21 and extend in the left-right direction in the drawing. A reflection layer 25, a color filter layer 29, a plurality of strip-shaped transparent electrodes 28a in plan view, and an alignment film 28b are sequentially formed on the inner surface side (the liquid crystal layer 23 side) of 22.
The transparent electrode 26a of the upper substrate 21 and the transparent electrode 28a of the lower substrate 22 are both formed in a strip-like planar shape, and are arranged in a stripe shape in plan view. The extending direction of the transparent electrode 26a and the extending direction of the transparent electrode 28a are arranged so as to be orthogonal to each other in plan view. Therefore, one dot of the liquid crystal display unit 20 is formed at a position where one transparent electrode 26a and one transparent electrode 28a intersect, and three colors (red, green, and blue) described later correspond to each dot. One color filter of the filters is arranged. Then, the three dots emitting R (red), G (green) and B (blue) constitute one pixel 20c of the liquid crystal display unit 20, as shown in FIG. Further, as shown in FIG. 2, when viewed in a plan view, a large number of pixels 20c are arranged in a matrix in the display area 20D.
[0047]
The color filter layer 29 has a structure in which red, green, and blue color filters 29R, 29G, and 29B are periodically arranged, and each color filter is provided below the corresponding transparent electrode 28a. A set of color filters 29R, 29G, and 29B is formed for each pixel 20c. The display color of the pixel 20c is controlled by controlling the driving of the electrodes corresponding to the color filters 29R, 29G, and 29B.
[0048]
In the liquid crystal display device of the present embodiment, the direction in which the prism grooves 14 formed in the light guide plate 12 of the front light 10 extend and the direction in which the pixels of the liquid crystal display unit 20 are arranged intersect. That is, by preventing the repetition direction of RGB of the color filter layer 29 that gives a periodic pattern to the liquid crystal display unit 20 and the extending direction of the prism groove 14 from becoming parallel, the moire pattern due to optical interference between the two. Is to prevent the occurrence of.
[0049]
FIG. 8 is an enlarged plan view showing an adjacent pixel group of the liquid crystal display unit 20 shown in FIG. As shown in this figure, the liquid crystal display unit 20 has a plurality of pixels 20c formed in a matrix in a plan view, and each pixel 20c has a set of red, green, and blue color filters 29R, 29G. , 29B.
As shown in FIG. 8, in the liquid crystal display device of the present embodiment, the extending direction of the prism groove 14 of the front light 10 indicated by the two-dot chain line in FIG. (Horizontal direction in the drawing) and are inclined at an inclination angle β.
The inclination angle β of the prism groove 14 with respect to the arrangement direction (the horizontal direction in the drawing) of the pixels 20c is preferably in the range of more than 0 ° and 15 ° or less, and more preferably 6.5 ° or more and 8.5 °. The range is as follows. With such a range, it is possible to prevent a moire pattern from being generated due to optical interference with the periodic structure of the pixels of the liquid crystal display unit 20. Outside the above range, the effect of reducing the moiré pattern tends to decrease. Further, the inclination angle β is more preferably in the range of 6.5 ° to 8.5 °. By setting such a range, the effect of preventing a moiré pattern becomes higher. When there is no possibility that a moiré pattern is generated, the inclination angle β may be 0 °.
[0050]
In the liquid crystal display device of the present embodiment, as shown in FIG. 2, since the light guide plate side end surface 12a of the front light 10 and the pixel array direction of the liquid crystal display unit 20 are arranged in parallel, The angle α formed between the extending direction of the prism groove 14 and the light guide plate side end surface 12a and the angle β formed between the extending direction of the prism groove 14 and the arrangement direction of the pixels 20c coincide with each other, but the light guide plate side end surface. When the arrangement direction of 12c and the pixel 20c is not parallel, the inclination angles α and β are different angles. In this case, in order to reduce the moiré pattern, it is preferable that the inclination angle β is set to the above-mentioned range by giving priority to the inclination angle α. When the inclination angle β is determined, the extending direction of the prism groove 14 is determined. Therefore, in order to make the distribution of the amount of light emitted from the light guide plate 12 uniform, the angle of the light guide plate side end face 12 c with respect to the angle of the prism groove 14 is determined. May be adjusted so as to fall within the range of the inclination angle α.
[0051]
The reflection layer 25 is composed of an organic film made of an acrylic resin material or the like, and a metal reflection film of high reflectivity such as Al or Ag formed on the organic film. A plurality of concave portions having a property are provided. The organic film is for giving the metal reflective film a predetermined surface shape.
[0052]
Since the liquid crystal display device of the present embodiment includes the front light 10 that can illuminate a large area uniformly and brightly, the entire area of the display area 20D is irradiated with high brightness and uniform brightness. Excellent display quality can be obtained. Further, even when the front light 10 has one light emitting element 15, the uniformity of brightness does not decrease, so that the visibility of the display is good, and therefore the display quality is excellent and the power consumption is low. Is obtained.
[0053]
[Active matrix liquid crystal display unit]
In the above embodiment, the liquid crystal display unit 20 is of a passive matrix type. However, an active matrix type liquid crystal display unit can be applied to the liquid crystal display device according to the present invention. Also in this case, since the planar configuration of the liquid crystal display unit is the same as that of the liquid crystal display unit 20 of the previous embodiment shown in FIG. 2, FIG. 2 is also used in the following description. That is, the liquid crystal display unit of this configuration includes a plurality of pixels 20c arranged in a matrix in a plan view.
[0054]
FIG. 9 shows a plan view of a pixel 20c formed in the liquid crystal display unit having this configuration, and FIG. 10 shows a cross-sectional view taken along line IX-IX of FIG. The liquid crystal display unit shown in FIGS. 9 and 10 has a configuration in which a liquid crystal layer 33 is sandwiched between an upper substrate 31 and a lower substrate 32 which are arranged to face each other. 33), a plurality of substantially rectangular transparent electrodes 36 arranged in a matrix in a plan view and pixel switching transistor elements T formed for each of the transparent electrodes 36 are provided. A reflection layer 35, a color filter layer 39 formed on the reflection layer 35, and a transparent electrode 38 formed on the entire surface of the color filter layer 39. I have. A region where three transparent electrodes 36 corresponding to R, G, and B are formed corresponds to one pixel 20c. In FIG. 9, the transistor element T is an equivalent circuit diagram for easy understanding of the drawing.
[0055]
One end of the transistor element T for switching the transparent electrode 36 is connected to the transparent electrode 36, and the other two ends of the transistor element T are connected to a scanning line G extending between the transparent electrodes 36 in the left-right direction in the figure. ₁ ~ G ₃ And a signal line S extending vertically in the drawing. ₁ ~ S ₂ It is connected to the. The color filters 39R, 39G, and 39B are disposed on the color filter layer 39 at positions corresponding to the transparent electrodes 36 on the lower substrate 32, and a black matrix 39M is provided between the adjacent color filters 39R, 39G, and 39B. It is formed in a lattice shape in plan view. Although not shown, a black matrix having a lattice shape in a plan view is formed on the inner surface side of the upper substrate 31 so as to surround the periphery of the transparent electrode 36. , Are not incident on the scanning lines or signal lines connected thereto.
Further, as the reflection layer 35 of the liquid crystal display unit of this example, the same reflection layer 25 as the configuration described in the above embodiment can be applied.
[0056]
The liquid crystal display unit having the above configuration controls the electric potential of the transparent electrode 36 by the transistor element T, and controls the light transmission state of the liquid crystal layer 33 between the transparent electrode 36 and the transparent electrode 38 of the lower substrate 32 to perform display. It is supposed to do.
[0057]
In the active matrix type liquid crystal display unit, a light-shielding black matrix is formed in a lattice shape in plan view so as to surround the transparent electrode 36, and the contrast of display can be increased. Also, the periodic pattern of the pixel 20c tends to be clear. That is, optical interference between the periodic arrangement of the pixels 20c and the prism grooves 14 of the front light 10 tends to occur. In the liquid crystal display device of the present embodiment, the prism grooves 14 are arranged in the same direction as the arrangement direction of the pixels 20c. By being formed to extend in the intersecting direction, it is possible to suppress the interference and effectively prevent the visibility from being lowered due to the moiré pattern. As described above, even when the liquid crystal display device according to the present invention is configured using the active matrix type liquid crystal display unit, a display quality in which a moiré pattern does not occur in the display region and a uniform and bright display is possible. And a liquid crystal display device excellent in the above.
[0058]
Although FIG. 10 shows a case where the color filter layer 39 is formed on the reflective layer 35 side, a pixel switching electrode is formed on the lower substrate 32 side, and this electrode also serves as a reflective layer. A color filter layer may be formed on the upper substrate 31 side.
[0059]
(Second embodiment)
Next, a liquid crystal display device according to a second embodiment of the present invention will be described with reference to FIG. FIG. 11 is an enlarged plan view illustrating a front light (illumination device) provided in the liquid crystal display device according to the second embodiment.
The difference between the front light 50 provided in the liquid crystal display device of the second embodiment and the front light 10 used in the first embodiment is that the unevenness formed on the outer surface 13j of the intermediate light guide 13 is small. This is a point that the shape of the portion is different, that is, the minute uneven portion 80 formed on the outer surface 13j of the intermediate light guide 13 in the present embodiment has a plurality of concave portions 81. Since the configuration is the same as that of the front light 10 shown in FIGS. 1 to 3, a detailed description thereof will be omitted below. The basic structure of the liquid crystal display unit is the same as that of the liquid crystal display unit shown in FIGS. 1 and 3, and a detailed description thereof will be omitted.
[0060]
The plurality of concave portions 81 constituting the minute concave-convex portion 80 are provided such that the concave portions face the inside of the intermediate light guide 13. The plurality of concave portions 81 have a specific vertical cross section that passes through the deepest point 81 a of the concave portion 81. The shape of the concave portion that can be employed in the minute concave and convex portion 80 of the present embodiment will be described in detail later. Further, minute unevenness portions 80 are also formed on the end surface 13h of the intermediate light guide 13 opposite to the end surface 13g on which the light emitting element 15 is provided, for the reason described above.
The metal reflection film 47 is formed on the outer surface of the minute uneven portion 80 formed on the outer surface 13j and the end surface 13h of the intermediate light guide 13 for the reason described above.
[0061]
Pitch P of concave portion 81 forming minute concave-convex portion 80 formed on outer side surface 13j ₃ The distance between the adjacent recesses 81 and the tops of the recesses 81 is reduced as the distance from the light emitting element 15 increases, that is, the pitch P of the recesses 81 is reduced. ₃ Is smaller on the side farther from the light emitting element 15 than on the side closer to the light emitting element 15. Also, the depth d of the concave portion 81 ₃ Is higher as the distance from the light emitting element 15 is increased, that is, the depth d of the concave portion 81 is increased. ₃ Is larger on the side farther from the light emitting element 15 than on the side closer to the light emitting element 15.
Further, the distance between the minute uneven portion 80 of the intermediate light guide 13 and the light incident surface 12a of the light guide plate 12 (the distance between the bottom of the concave portion 81 and the light incident surface 12a in this embodiment) is closer to the light emitting element 15. May be smaller than the side closer to the light emitting element 15.
[0062]
The reflection angle of the light reflected toward the light entrance surface 12a of the light guide plate 12 is controlled in accordance with the distance from the light emitting element 15 to the minute uneven portion 80 formed on the outer side surface 13j.
In the front light 50 of the present embodiment, the light emitted from the light emitting element 15 propagates inside the intermediate light guide 13 in the length direction of the intermediate light guide 13 and diffuses and reflects on the surface of the minute uneven portion 80. However, at this time, the light reflected on the surface of the minute uneven portion 80 is emitted toward the light incident surface 12 a of the light guide plate 12 with the reflection angle controlled according to the distance from the light emitting element 15. I have.
In the front light 50 of the present embodiment, the same effects as those of the front light 10 of the first embodiment can be obtained.
[0063]
(Third embodiment)
Next, a liquid crystal display device according to a third embodiment of the present invention will be described.
FIG. 12 is an enlarged plan view illustrating a main part of a front light provided in the liquid crystal display device according to the third embodiment.
The difference between the front light 60 provided in the liquid crystal display device of the third embodiment and the front light 10 used in the first embodiment is that a prism surface 13 a is formed on the outer surface 13 j of the intermediate light guide 13. On the surface of the prism surface 13a, a minute uneven portion 40 is formed, and on the outer surface of the minute uneven portion 40, a metal reflection film (not shown) made of a metal thin film of high reflectivity such as Al or Ag is formed. Since it is formed, since the configuration other than the above is the same as that of the front light 10 shown in FIGS. 1 to 3, detailed description thereof will be omitted below. Further, the liquid crystal display unit is equivalent to the liquid crystal display unit shown in FIGS. 1 and 3, and a detailed description thereof will be omitted.
[0064]
The prism surface 13a is formed by forming a plurality of wedge-shaped grooves 13b in a plan view (transverse section) parallel to each other. The wedge-shaped groove 13b has a pair of slopes 13b1 and 13b2 for reflecting light.
Depth d of wedge-shaped groove 13b ₄ Are formed so as to increase exponentially or cubically toward the side opposite to the light emitting element side. In the present embodiment, the grooves formed farther from the light emitting element 15 have a deeper groove (from the light emitting element). The more distant grooves 13b protrude from the inside of the intermediate light guide 13), so that light can be uniformly applied to the side end surface 12a of the light guide plate 12.
Also, the pitch P of the wedge-shaped groove 13b ₄ (Or the distance between the bottoms of the grooves 13) is formed so as to decrease exponentially or quadratically toward the side opposite to the light emitting element side. It is preferable in that the emitted light quantity and its uniformity can be improved. For example, the pitch P ₄ May be formed small.
[0065]
Further, it is preferable that the angle θa formed by the two slopes 13b1 and 13b2 forming the wedge-shaped groove 13b is set to 105 degrees or more and 115 degrees or less. It is preferable that each of the angle θb of the slope 13b1 and the angle θc of the slope 13b2 is not less than 37.5 degrees and not more than 32.5 degrees. The angle θb of the slope 13b1 and the angle θc of the slope 13b2 may be the same or different.
[0066]
The micro uneven portion 40 of this embodiment is the same as the micro uneven portion 40 of the first embodiment except that it is provided on the surface of the prism surface 13a. The reflection angle of the light reflected toward the light incident surface 12a is controlled.
[0067]
In the front light 60 of the present embodiment, the brightness distribution of the light emitted from the intermediate light guide 13 can be made substantially uniform by the light dispersing action of the prism surface 13a. When the light is reflected by the uneven portion 40, the light can be diffused. At this time, the light reflected on the surface of the minute uneven portion 40 enters the light guide plate 12 by controlling the reflection angle according to the distance from the light emitting element 15. The light is emitted toward the light surface 12a.
Also in the front light 60 of the present embodiment, the efficiency of use of the light emitted from the light emitting element 15 is good, and it is possible to prevent a dark portion from being generated in the vicinity of the light guide plate side end face 12g on the light emitting element side, and to further obtain a bright line or a rainbow. It is possible to prevent the occurrence of moiré-like shapes, to uniformly and brightly illuminate the display area of the liquid crystal display unit, and to provide a front light with low power consumption.
[0068]
(Embodiment of convex part of fine uneven part)
An example of a large number of protrusions 41 employed in the fine unevenness according to the first or third embodiment will be described.
FIG. 13A is an enlarged perspective view showing one of the projections 119 of the first example employed as the large number of projections 41. The surface of the projection 119 has a first curved surface having a small curvature and a curvature. And a second curved surface having a large diameter. Each of the first curved surface and the second curved surface is smoothly continuous with the first curve A extending from one peripheral portion S1 of the convex portion 119 to the top portion 119a and the first curve A in the specific longitudinal section X shown in FIG. 13B. And a second curve B extending from the top 119a to the other peripheral portion S2.
[0069]
The top portion 119a is located at a position shifted in the x direction from the center O of the convex portion 119 in plan view, and has a reference surface S of the first curve (first section curve) A (in the first embodiment, the intermediate light guide 13 On the outer side surface 13j, the surface on which the fine unevenness is not formed, that is, the reference surface S of the intermediate light guide, and in the third embodiment, the surface of the prism surface 13a on which the fine unevenness is not formed) Tilt angle θ _h And the inclination angle θ of the second curve (second sectional curve) B _h Are set, for example, in an angular range of 1 ° to 89 ° and 0.5 ° to 88 °, respectively. _h Is larger than that of the second curve B. In addition, the inclination angle δa in the peripheral portion S1 of the first curve A indicating the maximum inclination angle varies in each of the protrusions 119, for example, within a range of approximately 4 ° to 35 °. Thereby, the height d of each convex portion 119 is obtained. ₂ (The height from the reference surface S of the intermediate light guide 13 of the first embodiment to the top 41a of the convex portion 41, and the height of the surface of the prism surface 13a of the third embodiment from the surface where the fine unevenness is not formed. The height of the top 41 to the top 41a varies, for example, in the range of 0.25 μm to 3 μm.
[0070]
In addition, the first curved surface and the second curved surface both have substantially symmetrical shapes in the Y section shown in FIG. 13C, and the inclination angle θ of the outer peripheral surface. _g Is set, for example, in the range of −18 ° to + 18 °.
Note that the “inclination angle” of a curve or a curved surface is defined as a reference surface S of a curve or a curved surface within a minute range, for example, when a minute range of 0.5 μm width is taken at an arbitrary position on the curve or the curved surface. Means the angle with respect to
As shown in FIGS. 4 and 5, a plurality of the above-mentioned protrusions 119 are formed on the outer side surface 13j of the intermediate light guide 13 as the plurality of protrusions 41. At this time, these protrusions 119 are formed by light emitting elements. The inclination angles of the cross-sectional curves A and B when cross-sectioned at the specific vertical cross-section X are controlled in accordance with the distance from 15.
[0071]
Further, the pitch of the protrusions 119 (the interval between the centers O of the adjacent protrusions 119) may be smaller on the side farther from the light emitting element 15 than on the side closer to the light emitting element 15, as shown in FIG. Also, the height d of the projection 119 ₂ As shown in FIG. 4, the side of the front light 10 that is farther from the light emitting element 15 may be larger than the side that is closer to the light emitting element 15.
[0072]
FIG. 14A is an enlarged perspective view showing one of the projections 219 of the second example employed as the large number of projections 41. In this example, the surface shape of the projections 119 shown in FIG. Is modified to change the directivity.
The convex portion 219 is composed of a first curved surface having a small curvature and a second curved surface having a large curvature, similarly to the convex portion 119 described above, and the first curved surface and the second curved surface are each a specific longitudinal section shown in FIG. 14B. At X, a first curve (first sectional curve) A ′ from one peripheral portion S1 of the convex portion 219 to the top portion 219a, and the other from the top portion 219a of the convex portion 219 smoothly to the first curve A ′. It has a shape indicated by a second curve (second cross-sectional curve) B ′ reaching the peripheral portion S2.
[0073]
The top 219 a is located at a position shifted in the x direction from the center O of the projection 219, and the inclination angle θ of the first curve A ′ with respect to the reference plane S. _h And the inclination angle θ of the second curve B ′ _h The average value of the absolute values is set in a range of 2 ° to 90 ° and 1 ° to 89 °, for example, and the inclination angle θ of the first curve A ′ is set. _h Is larger than that of the second curve B '. In addition, the inclination angle δa at the peripheral portion S1 of the first curve A ′ indicating the maximum inclination angle varies in each of the convex portions 219, for example, within a range of approximately 4 ° to 35 °. Thereby, the height d of each convex portion 219 ₂ Are configured to vary within a range of, for example, 0.25 μm to 3 μm.
[0074]
On the other hand, both the first curved surface and the second curved surface are substantially symmetrical with respect to the center O in the Y section shown in FIG. 14C. The shape of this Y section is a curve E having a large curvature (that is, a gentle curve close to a straight line) around the top 219a, and its inclination angle θ with respect to the reference plane S. _g Is configured to be, for example, approximately 10 ° or less. Further, the inclination angle θ of the deep curves F and G with respect to the reference plane S _g Are varied within a range of, for example, 2 ° to 9 °. Further, the height d of the top 219a ₂ Are configured to vary within a range of, for example, 0.1 μm to 3 μm.
As shown in FIGS. 4 and 5, a plurality of the above-described protrusions 219 are formed as the plurality of protrusions 41 on the outer side surface 13j of the intermediate light guide 13. The inclination angles of the cross-sectional curves A ′ and B ′ when crossing at the specific vertical cross-section X are controlled in accordance with the distance from 15.
Further, the pitch of the protrusions 219 (the interval between the centers O of the adjacent protrusions 219) may be smaller on the side farther from the light emitting element 15 than on the side closer to the light emitting element 15, as shown in FIG. Also, the height d of the convex portion 219 ₂ As shown in FIG. 4, the side of the front light 10 that is farther from the light emitting element 15 may be larger than the side that is closer to the light emitting element 15.
[0075]
FIG. 15 is an enlarged cross-sectional view when one of the protrusions 319 of the third example employed as the plurality of protrusions 41 is cut along a specific vertical section X.
The surface of the convex portion 319 is formed of one curved surface, and this curved surface is gentle in the specific longitudinal section X from one peripheral portion S1 of the convex portion 319 to the other peripheral portion S2 through the top 319a. It has the shape shown by the curve A. The convex portions are set with the depth thereof varied in the range of 0.1 μm to 3 μm, and the pitch of the adjacent concave portions 319 (the interval between the centers O of the adjacent convex portions 319) is set in the range of 5 μm to 100 μm. , The inclination angle θ of the inner surface of the recess 319. _h Is set in the range of −18 ° to + 18 °.
As shown in FIGS. 4 and 5, a plurality of the above-described protrusions 319 are formed as the plurality of protrusions 41 on the outer side surface 13j of the intermediate light guide 13. The inclination angle of the cross-sectional curve A when cross-sectioned at the specific vertical cross-section X is controlled in accordance with the distance from 15.
[0076]
In addition, as shown in FIGS. 4 and 5, one of the protrusions of the first to third examples is one of the protrusions employed as the plurality of protrusions 41 on the outer surface 13j of the intermediate light guide 13. Not limited to the type, two or more of the first to third convex portions may be employed. In this case, different types of these convex portions are arranged according to the distance from the light emitting element 15. Further, the inclination angle of the cross-sectional curve when cross-sectioned at the specific vertical cross-section X may be controlled according to the distance from the light-emitting element 15.
Further, in the above embodiment, at least one of the projections 119, 219, 319 of the first to third examples is used as the multiple projections 41 constituting the fine unevenness according to the first or third embodiment. Although the case of adoption has been described, if at least one of the convex portions 119, 219, and 319 of the first to third examples is formed on the outer surface 13j such that the concave side is inside the intermediate light guide 13, It can be adopted as a large number of concave portions 81 constituting the fine concave-convex portion 80 according to the second embodiment. In that case, each top of the projections of the first to third examples is the deepest point.
[0077]
【The invention's effect】
As described above in detail, according to the present invention, the efficiency of use of light emitted from a light source is good, and it is possible to prevent a dark portion from being generated near a side end surface of a light guide plate on a light source side, and to further obtain a bright line or a rainbow-like shape. And a low-power illuminating device capable of uniformly and brightly illuminating the illuminated area.
[Brief description of the drawings]
FIG. 1 is a perspective configuration diagram of a liquid crystal display device according to a first embodiment of the present invention.
FIG. 2 is a plan view of the liquid crystal display device shown in FIG. 1;
FIG. 3 is a partial cross-sectional view of the liquid crystal display device shown in FIG. 2 taken along line III-III.
FIG. 4 is an enlarged plan view showing a front light (illumination device) provided in the liquid crystal display device shown in FIG. 2;
FIG. 5 is a sectional view taken along line III-III of a front light provided in the liquid crystal display device shown in FIG. 2;
FIG. 6 is an explanatory diagram showing an example of the position of the outer surface of the intermediate light guide shown in FIG. 2 and the angle of light from the light emitting element reaching each position.
FIG. 7 is an explanatory view showing an example of the positions of the minute uneven portions of the intermediate light guide shown in FIG. 2 and the direction in which light reflected by the minute uneven portions at each position exits to the light incident surface.
FIG. 8 is an enlarged plan view showing a pixel group of the liquid crystal display unit shown in FIG. 2;
FIG. 9 is an enlarged plan view showing pixels of an active matrix liquid crystal display unit.
FIG. 10 is a sectional view taken along the line IX-IX of FIG. 9;
FIG. 11 is an enlarged plan view showing a front light provided in a liquid crystal display device according to a second embodiment.
FIG. 12 is an enlarged plan view illustrating a front light provided in a liquid crystal display device according to a third embodiment.
FIG. 13 is a schematic view showing a first example of a convex portion of a fine concave-convex portion of an intermediate light guide provided in the front light according to the first embodiment, where A is a perspective view thereof and B is an X sectional view thereof. It is a figure and C is the Y sectional drawing.
FIG. 14 is a schematic view showing a second example of a convex portion of the fine concave-convex portion of the intermediate light guide provided in the front light according to the first embodiment, where A is a perspective view and B is an X section thereof. It is a figure and C is the Y sectional drawing.
FIG. 15 is an enlarged cross-sectional view of the third example of the fine irregularities of the intermediate light guide provided in the front light according to the first embodiment, taken along a specific vertical section X.
16A is a perspective view of a liquid crystal display device having a conventional configuration, and FIG. 16B is a plan view of a front light shown in FIG.
[Explanation of symbols]
10, 50, 60: front light (illumination device), 20: liquid crystal display unit, 12: light guide plate, 12a: side end surface (light entrance surface, one side end surface), 12b: lower surface (exit surface, one surface), 12c ... Top surface (reflection surface, other one surface), 12d ... side end surface (other side end surface), 12g ... side end surface, 12h ... side end surface, 13 ... intermediate light guide, 13a ... prism surface, 13b ... rust-shaped groove, 13b1, 13b2 ... slope, 13g ... end face, 13h ... end face, 13k ... emission face, 13j ... outer face, 14 ... prism groove, 14a ... gentle slope part, 14b ... steep slope part, 15 ... light emitting element (light source), 20D ... Display area (illuminated area), 40, 80 ... minute unevenness, 41, 119, 219, 319 ... convex, 41a, 119a, 219a, 319a ... top, 47 ... metal reflective film, 81 ... concave, 81a ... Deepest point, d ₂ … Height, d ₃ ... depth, L ... light, M ... direction perpendicular to the light incident surface, R ... reflected light, P ₂ , P ₃ … Pitch, θ _h … Inclination angle

Claims (15)

A light guide plate, an intermediate light guide disposed along one end surface of the light guide plate, and a light source disposed on a longitudinal end surface of the intermediate light guide,
The light guide plate has a light incident surface at a side end surface into which light is introduced, and introduces light emitted from the light source from the light incident surface of the light guide plate into the light guide plate through the intermediate light guide. A lighting device for emitting light propagating inside the light guide plate from one surface side of the light guide plate, wherein a side surface of the intermediate light guide opposed to one end surface of the light guide plate emits light to the light guide plate. An emission surface is formed on the outer surface on the opposite side to the emission surface, and minute uneven portions for diffusing and reflecting light emitted from the light source and propagated inside the intermediate light guide are formed. A lighting device, wherein a reflection angle of light reflected toward a light incident surface of the light guide plate is controlled according to a distance from a light source. A light guide plate, an intermediate light guide disposed along one end surface of the light guide plate, and a light source disposed on a longitudinal end surface of the intermediate light guide,
The light guide plate has a light incident surface at a side end surface into which light is introduced, and introduces light emitted from the light source from the light incident surface of the light guide plate into the light guide plate through the intermediate light guide. A lighting device for emitting light propagating inside the light guide plate from one surface side of the light guide plate, wherein a side surface of the intermediate light guide opposed to one end surface of the light guide plate emits light to the light guide plate. An exit surface is formed, and a prism surface including a plurality of wedge-shaped grooves is formed on an outer surface opposite to the exit surface, and the prism surface is emitted from the light source and propagates inside the intermediate light guide. Micro-irregularities for diffusing and reflecting light to be emitted are formed, and the angle of reflection of light reflected toward the light incident surface of the light guide plate is controlled in accordance with the distance from the light source. A lighting device characterized by the above-mentioned. The minute concave-convex portion has a plurality of concave portions, each of the plurality of concave portions has a specific vertical cross section passing through the deepest point of the concave portion, and each concave portion has a cross section of the specific vertical cross section according to a distance from a light source. 3. The lighting device according to claim 1, wherein an inclination angle of the curve is controlled. The micro uneven portion has a plurality of convex portions, each of the plurality of convex portions has a specific vertical section passing through the top of the convex portion, and each of the convex portions is the specific one according to a distance from a light source. 3. The lighting device according to claim 1, wherein an inclination angle of a cross-sectional curve of the vertical cross section is controlled. The said micro uneven | corrugated part has a several convex part or a recessed part, The pitch of the said convex part or a recessed part is smaller on the side farther to the light source than the side near the light source, The characterized by the above-mentioned. The lighting device according to any one of claims 1 to 4. The minute uneven portion has a plurality of convex portions or concave portions, and the height of the convex portions or the depth of the concave portions is larger on the side farther from the light source than on the side closer to the light source. The lighting device according to claim 1. The light exit angle of the light exiting from the exit surface of the intermediate light guide toward the light entrance surface of the light guide plate is ± 10 degrees with respect to a direction orthogonal to the light entrance surface when the lighting device is viewed in plan. The lighting device according to any one of claims 1 to 6, wherein: The light exit angle of light emitted from the exit surface of the intermediate light guide toward the light entrance surface of the light guide plate is ± 20 degrees with respect to a direction orthogonal to the light entrance surface when the illumination device is viewed in cross section. The lighting device according to any one of claims 1 to 7, wherein The emission direction of light emitted from the emission surface of the intermediate light guide toward the light entrance surface of the light guide plate is orthogonal to the light entrance surface near the light source when the illumination device is viewed in plan. The direction on the light source side than the direction, the direction opposite to the light source with respect to the direction orthogonal to the light incident surface on the side far from the light source, the intermediate part between the near side and the far side of the light source is the light incident surface. The lighting device according to claim 1, wherein the direction is substantially orthogonal. The distance between the minute uneven portion of the intermediate light guide and the light incident surface of the light guide plate is smaller on a side farther from the light source than on a side closer to the light source. The lighting device according to claim 1. The lighting device according to claim 1, wherein a metal reflection film is formed on a surface of the minute uneven portion of the intermediate light guide. The lighting device according to any one of claims 1 to 11, wherein the light source disposed on the longitudinal end face of the intermediate light guide is a substantially point-like light source. On another side of the light guide plate, a plurality of prism grooves formed by a gentle slope portion and a sharp slope portion having a steeper inclination angle than the gentle slope portion are formed in a stripe shape in a plan view. The lighting device according to any one of claims 1 to 12, wherein The lighting device according to any one of claims 1 to 13, wherein an extending direction of the prism groove of the light guide plate is set to a direction crossing the light incident surface. A liquid crystal display device comprising: the lighting device according to claim 1; and a liquid crystal display unit illuminated by the lighting device.

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