WO2012060247A1 - Light-control element, display device, and illumination device - Google Patents

Abstract

This light-control element is provided with: a plurality of light-emitting elements that are configured in a manner so as to control the amount of light that is radiated; a light-guide body that has a plurality of light extraction regions that extract any of the plurality of light beams to the outside while the light is being propagated; a first prism structure that transmits light entering from at least one of the plurality of light-emitting elements and radiates the light to the light-guide body; and a low-refractive-index body that has a lower refractive index than the refractive index of the light-guide body and that suppresses the entrance of light propagating within the light-guide body to the first prism structure. The first prism structure has at least one tilted surface having at least one type of tilt angle; the pathway of at least a portion of the plurality of light radiated from the plurality of light-emitting elements passes through the tilted surface; at least two light extraction regions from among the plurality of light extraction regions have mutually different ranges of angle of incidence at which light propagating within the light-guide body can be extracted to the outside; and each of the plurality of light beams radiated from the plurality of light-emitting elements is propagated at a different angle of propagation within the light-guide body.

Description

Dimmer element, display device, and illumination device

The present invention relates to a light control element, a display device, and a lighting device.
The present application claims priority based on Japanese Patent Application No. 2010-246675 filed in Japan on November 2, 2010, the contents of which are incorporated herein by reference.

As an example of a display device, a transmissive liquid crystal display device that performs display using light emitted from a lighting device is known. This type of liquid crystal display device has a liquid crystal panel and an illumination device arranged on the back side of the liquid crystal panel. A conventional lighting device includes a light source such as a light emitting diode (hereinafter abbreviated as LED) and a light guide plate, and propagates light emitted from the light source inside the light guide plate, and from the entire surface of the light guide plate. It was common to inject uniformly.
Hereinafter, in this specification, the illumination device provided on the back side of the display panel as described above may be referred to as a backlight.

On the other hand, an illuminating device that selectively emits light from a specific region within the surface of the light guide plate has been developed. In a liquid crystal display device equipped with this type of lighting device, for example, if there is a region where black is locally displayed on the liquid crystal panel, light is not emitted from the lighting device in the black display region, and other colors are displayed. In the area where light is emitted, light is emitted from the lighting device. In this way, whether or not light is emitted from the illumination device is controlled for each region. When this type of control is performed by the lighting device, a phenomenon in which a portion that should become black appears to be whitish, that is, a so-called black floating phenomenon is suppressed, and display contrast can be improved. In addition to controlling lighting / non-lighting for each area, it is possible to add a function of adjusting the amount of emitted light from each area, a so-called dimming function, to the lighting device. In this case, the contrast range that can be expressed can be expanded by dimming the illumination device according to the image displayed on the liquid crystal panel, and a powerful image can be created.

For example, as an example of a method for dimming illumination light, a display device having a configuration in which a light control panel having a light control layer such as a polymer-dispersed liquid crystal is adhered to the lower surface of a light guide plate that guides illumination light from a light source. It is disclosed (see Patent Document 1 below). The light control panel provided in this display device has a configuration in which a polymer dispersed liquid crystal is sandwiched between a translucent glass substrate having a transparent electrode formed on the entire surface and another substrate having a grid electrode. Have. Then, by applying a voltage to the polymer dispersed liquid crystal using the transparent electrode and the grid electrode and electrically changing the light scattering degree of the polymer dispersed liquid crystal, the extraction of light from the light guide plate is controlled. Yes. In addition, a display device is disclosed in which a light control layer made of liquid crystal with hybrid alignment is disposed on the lower surface of a light guide plate (see Patent Document 2 below).

JP 2002-296591 A JP 2001-108972 A

The light control mechanism of the display device described in Patent Document 1 is a combination of a light guide plate and a polymer dispersed liquid crystal. This light control mechanism controls the amount of light extracted from the light guide plate depending on whether the polymer-dispersed liquid crystal is in a scattering state or a transparent state. In this case, the role of the light guide plate is to propagate the light incident from the end face to the opposite end face while totally reflecting the light. The polymer-dispersed liquid crystal plays all the roles of extracting light from one surface of the light guide plate to the outside. However, this type of light control mechanism has a limit in the amount of light that can be extracted to the outside, and it is difficult to realize a bright illumination device.
The reason is that the amount of light that can be extracted from the light guide plate depends greatly on the performance of the polymer-dispersed liquid crystal. That is, if the scattering power of the polymer-dispersed liquid crystal is low, the amount of light that can be taken out from the light guide plate when the polymer-dispersed liquid crystal is in a scattering state is reduced. On the other hand, if even a small amount of scattering occurs when the polymer-dispersed liquid crystal is in a transparent state, light leaks from a portion where light should not be extracted and contrast is lowered. In order not to cause such a phenomenon, a polymer-dispersed liquid crystal having sufficiently high contrast and scattering characteristics is required. However, such polymer-dispersed liquid crystals are difficult to obtain and expensive. Also, liquid crystal is used in the light control mechanism of the liquid crystal display device described in Patent Document 2, and the same phenomenon as described above may occur.

An object of one embodiment of the present invention is to provide a light control element that can obtain a sufficient amount of light by efficiently extracting light from a light source from a light guide, has a simple structure, and is inexpensive. Another object is to provide a display device that can display brightly and with high contrast by using the light control element. Another object is to provide a lighting device that can obtain sufficient brightness by using the light control element.

A dimming element according to an aspect of the present invention propagates a plurality of light-emitting elements configured to control the amount of emitted light and a plurality of lights emitted from the plurality of light-emitting elements while being totally reflected internally. A light guide having a plurality of light extraction regions for extracting any one of the plurality of lights to the outside while the plurality of lights are propagated; A prism structure that is disposed on the first main surface of the light body and transmits the light incident from at least one of the plurality of light emitting elements to the light guide body; and the prism structure body and the light guide body A low refractive index body that has a refractive index lower than the refractive index of the light guide, and suppresses the light propagating through the light guide to the prism structure, The prism structure has one or more tilt angles with one or more tilt angles. A plurality of lights emitted from the plurality of light emitting elements, at least part of the light path passes through the inclined surface, and the light guide is provided between the prism structure and the light guide. A low refractive index body having a refractive index lower than the refractive index of the light body and suppressing the light propagating through the light guide to the prism structure is provided, and the plurality of light extraction regions At least two of the light extraction regions have different incident angle ranges in which light propagating inside the light guide can be extracted to the outside, and each of the plurality of lights emitted from the plurality of light emitting elements is Propagates the light guide at different propagation angles.

In the light control device according to one aspect of the present invention, at least one of the plurality of light emitting devices is disposed on the inclined surface of the prism structure, and is emitted from the light emitting device disposed on the inclined surface. Light may enter the light guide from the inclined surface through the prism structure and propagate through the light guide.

In the light control device according to an aspect of the present invention, at least one of the plurality of light emitting devices is disposed on an end surface of the light guide, and light emitted from the light emitting device disposed on the end surface is The light may enter the light guide from the end face and propagate through the light guide.

In the light control device according to one aspect of the present invention, the plurality of light emitting devices are respectively arranged on a plurality of inclined surfaces having different inclination angles of the prism structure, and emitted from the light emitting devices arranged on the plurality of inclined surfaces. The incident light may enter the light guide through the inclined surface through the prism structure and propagate through the light guide.

In the light control device according to an aspect of the present invention, at least one of the plurality of light emitting devices is a second main light guide member on the side opposite to the first main surface on which the prism structure is disposed. The light emitted from the light emitting element disposed on the surface and disposed on the second main surface is incident on the prism structure through the light guide and reflected by the inclined surface, and then the prism structure. May be incident on the light guide and propagate through the light guide.

In the light control device according to one aspect of the present invention, at least one of the plurality of light emitting devices is disposed on an end surface of the light guide, and light emitted from the light emitting device disposed on the end surface is emitted. The light may enter the light guide from the end face and propagate through the light guide.

In the light control device according to one aspect of the present invention, the plurality of light emitting devices are disposed on a second main surface of the light guide opposite to the first main surface on which the prism structure is disposed, Light emitted from the plurality of light emitting elements arranged on the main surface is incident on the prism structure through the light guide, reflected by the inclined surface, and then transmitted through the prism structure to guide the light. It may be incident on a light body and propagate inside the light guide.

The light control device according to one aspect of the present invention may include a plurality of the prism structures, and the plurality of prism structures may have inclined surfaces having different inclination angles.

In the light control device according to one aspect of the present invention, at least one of the plurality of prism structures is disposed on one of the first main surface and the second main surface of the light guide, and the rest The prism structure may be disposed on the other of the first main surface and the second main surface of the light guide.

A display device according to one embodiment of the present invention includes the light control element and a display element that performs display using light emitted from the light control element.

The lighting device according to one embodiment of the present invention includes the light control element.

According to the aspect of the present invention, it is possible to obtain a light control device that can obtain a sufficient amount of light by efficiently taking out light from a light source from a light guide, has a simple structure, and is inexpensive. In addition, by using the dimming element, a display device that can display brightly and with high contrast can be realized. In addition, an illumination device that can obtain sufficient brightness can be realized by using the above light control element.

It is a perspective view which shows the liquid crystal display device and backlight of 1st Embodiment. It is a figure for demonstrating the principle in which light inject | emits from each light extraction area | region in the backlight of 1st Embodiment. It is a figure for demonstrating the principle in which light inject | emits from each light extraction area | region in the backlight of 1st Embodiment. It is a figure for demonstrating the backlight of a 1st comparative example. It is sectional drawing which shows the backlight of 2nd Embodiment. It is sectional drawing which shows the backlight of 2nd Embodiment. It is sectional drawing which shows the backlight of 2nd Embodiment. It is a figure for demonstrating the backlight of a 2nd comparative example. It is sectional drawing which shows the backlight of the 1st modification of 2nd Embodiment. It is sectional drawing which shows the backlight of the 2nd modification of 2nd Embodiment. It is sectional drawing which shows the backlight of 3rd Embodiment. It is sectional drawing which shows the backlight of 3rd Embodiment. It is a figure for demonstrating the backlight of a 3rd comparative example. It is a figure for demonstrating the backlight of a 3rd comparative example. It is sectional drawing which shows the backlight of 4th Embodiment. It is sectional drawing which shows the backlight of 4th Embodiment. It is sectional drawing which shows the backlight of 4th Embodiment. It is sectional drawing which shows the backlight of the 1st modification of 4th Embodiment. It is sectional drawing which shows the backlight of the 2nd modification of 4th Embodiment. It is a schematic block diagram which shows the example of 1 structure of a liquid crystal display device. It is a figure which shows the example of arrangement | positioning of the backlight in a liquid crystal display device. It is a figure which shows the example of arrangement | positioning of the backlight in a liquid crystal display device. It is a figure which shows the example of arrangement | positioning of the backlight in a liquid crystal display device. It is a figure which shows the example of arrangement | positioning of the backlight in a liquid crystal display device. It is sectional drawing which shows an example of an illuminating device. It is a top view which shows an example of an illuminating device. It is sectional drawing which follows the A-A 'line of FIG. 17A which is an example of an illuminating device.

[First Embodiment]
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
In the present embodiment, a liquid crystal display device using a liquid crystal panel as a display element is illustrated.
FIG. 1 is a perspective view showing a liquid crystal display device and a backlight according to the present embodiment. 2A and 2B are diagrams for explaining the principle of light emitted from each light extraction region in the backlight according to the present embodiment. FIG. 2A shows a case where light is emitted from the second light extraction region RB. FIG. 2B shows a case where light is emitted from the first light extraction area RA. FIG. 3 is a diagram for explaining the backlight of the first comparative example.
In the following drawings, in order to make each component easy to see, the scale of the size may be varied depending on the component.

As shown in FIG. 1, the liquid crystal display device 1 (display device) of the present embodiment includes a liquid crystal panel 2 (display element), a backlight 3 (light control element) disposed on the back side of the liquid crystal panel 2, have. The liquid crystal panel 2 is a transmissive liquid crystal panel that performs display using light emitted from the backlight 3. The user views the display from the opposite side of the backlight 3, that is, from the upper side of the liquid crystal panel 2 in FIG.

In the present embodiment, the configuration of the liquid crystal panel 2 is not particularly limited, and may be an active matrix type liquid crystal panel provided with a switching thin film transistor (hereinafter abbreviated as TFT) for each pixel. A simple matrix type liquid crystal panel that does not include a TFT may be used. The liquid crystal panel is not limited to a transmissive liquid crystal panel, and may be a transflective liquid crystal panel. The display mode is not particularly limited, and there are various display modes such as VA (Vertical Alignment) mode, TN (Twisted Nematic) mode, STN (Super Twisted Nematic) mode, IPS (In-Plane Switching) mode, etc. A liquid crystal panel can be used.

The backlight 3 of the present embodiment does not emit light uniformly from the entire surface of the light guide described later, but emits light for each light extraction region in which the entire surface is divided into a plurality (four in this embodiment). The amount of light to be controlled can be controlled. That is, in the backlight 3 of the present embodiment, each of the plurality of light extraction regions has a dimming function, and the backlight 3 as a whole emits light only in a specific light extraction region or does not emit light. be able to. Alternatively, the amount of light emitted from a specific light extraction region can be changed with respect to the amount of light emitted from another light extraction region.

Next, the configuration of the backlight 3 of the present embodiment will be described in detail.
As shown in FIG. 1, the backlight 3 of the present embodiment includes two backlight units 4 having the same dimensions, shape, and configuration. The two backlight units 4 are arranged in a direction orthogonal to the longitudinal direction of the light guide 5 described later, that is, a direction orthogonal to the direction in which the two light extraction regions RA and RB of the light guide 5 are arranged (y in FIG. 1). Are arranged adjacent to each other in the axial direction).
Accordingly, the backlight 3 has a total of four light extraction regions RA and RB, two in the horizontal direction and two in the vertical direction on the screen of the liquid crystal display device 1. Each backlight unit 4 includes two LEDs 7 a and 7 b (light emitting elements) and a light guide 5. The light guide 5 is composed of a parallel plate made of a resin having optical transparency such as acrylic resin. Here, although the backlight 3 shows an example in which the light guide is composed of two separate backlight units 4, the light guide having a total of four light extraction regions RA and RB is shown. An integral structure may be used. Even in this structure, it is possible to select the light extraction areas RA and RB from which light is emitted by using a highly directional LED.

Of the two main surfaces of the light guide 5, a triangular prism-shaped prism structure 6 is provided on the first main surface 5 a facing the liquid crystal panel 2. The prism structure 6 has an inclined surface 6a inclined with respect to the first main surface 5a (reference horizontal plane) of the light guide 5 when a plane parallel to the first main surface 5a of the light guide 5 is set as a reference horizontal plane. 6b. As shown in FIGS. 2A and 2B, the cross-sectional shape when the prism structure 6 is cut along the xz plane is an unequal triangular shape, and the two inclined surfaces 6a and 6b with respect to the first main surface 5a of the light guide 5 The inclination angles are different from each other. The prism structure 6 is for causing the light emitted from the LED 7a installed on one inclined surface 6a to enter the light guide 5 at a predetermined angle. Between the light guide 5 and the prism structure 6, a prism low refractive index body 8 p described later is provided.

On one inclined surface 6a of the prism structure 6 (left inclined surface in FIGS. 2A and 2B), one LED 7a of the two LEDs 7a and 7b has the light emission side facing the prism structure 6 side. It is fixed by an optical adhesive. The other LED 7b is fixed to one first end face 5c of the light guide 5 with an optical adhesive with the light emission side facing the light guide 5 side. The end surface 5c of the light guide 5 on which the LED 7b is installed is not perpendicular to the first main surface 5a but is inclined at a predetermined inclination angle. The light guide 5 totally reflects internally the light emitted from the LEDs 7a and 7b, and the second end surface 5d opposite to the first end surface 5c side where the LED 7b is installed (-x in FIGS. 2A and 2B). It has a function of propagating light from the direction toward + x direction) and extracting it to the external space during that time. Further, the two LEDs 7a and 7b can be independently turned on and off, and further can control the amount of emitted light.

Although not shown in FIG. 1, the backlight 3 includes a printed wiring board on which the LEDs 7a and 7b are mounted, a control unit including a driving IC for driving and controlling the LEDs 7a and 7b, and the like. . In this embodiment, it is preferable to use LEDs 7a and 7b having high directivity. For example, the half-value width of the intensity distribution with respect to the spread angle of the emitted light while the light is guided through the light guide 5 is about 5 °. Things can be used.

In the following description, for the sake of convenience, the respective light extraction areas are referred to as a first light extraction area RA and a second light extraction area RB from the side closer to the LEDs 7a and 7b to the side farther from the side. The main surface of the light guide 5 provided with the prism structure 6 is the first main surface 5a, the main surface opposite to the first main surface 5a is the second main surface 5b, and the light guide is provided with the LED 7b. The end face 5 is referred to as a first end face 5c, and the end face opposite to the first end face 5c is referred to as a second end face 5d. The LED installed on the inclined surface 6a of the prism structure 6 is referred to as a first LED 7a, and the LED installed on the first end surface 5c of the light guide 5 is referred to as a second LED 7b.

On the first main surface 5 a of the light guide 5, two light extraction areas RA and RB having a rectangular planar shape are provided along the longitudinal direction of the light guide 5 (x-axis direction in FIG. 1). . In the light extraction region RA, a low refractive index body 8a and a light scattering body 10 are stacked in this order from the light guide 5 side. The low refractive index body 8 a has a refractive index lower than that of the light guide 5. The light scatterer 10 scatters the light emitted from the low refractive index body 8a. In the light extraction region RB, the refractive index body 9 and the light scattering body 10 are stacked in this order from the light guide 5 side. The refractive index body 9 has a refractive index equal to the refractive index of the light guide 5. The light scatterer 10 scatters the light emitted from the refractive index body 9.

The low refractive index body 8p for the prism provided on the lower surface of the prism structure 6 and the low refractive index body 8a provided in the light extraction region RA are both lower than the refractive index of the light guide 5 and equal to each other. It has a refractive index. The refractive index body 9 has a refractive index equal to the refractive index of the light guide 5.
The low refractive index body 8 and the refractive index body 9 provided in the light extraction regions RA and RB have a relative refractive index along the light propagation direction (from the −x direction to the + x direction in FIG. 1). They are arranged in order from low to high refractive index. As an example of the present embodiment, the refractive index nWG of the light guide 5 is 1.5, the refractive index nLP of the low refractive index body 8p provided on the lower surface of the prism structure 6 is 1.3, and the first light extraction The refractive index nA of the low refractive index body 8a provided in the region RA is set to 1.3, and the refractive index nB of the refractive index body 9 provided in the second light extraction region RB is set to 1.5.
The refractive index nP of the prism structure 6 is equal to the refractive index nWG of the light guide 5 and is set to 1.5.

As a method of forming the low refractive index bodies 8p and 8a and the refractive index body 9 having different refractive indexes, for example, the following two methods can be cited.
The first method is to form the low refractive index bodies 8p and 8a and the refractive index body 9 using different materials. For example, acrylic resin is used as the material of the light guide 5, and amorphous fluororesin “AF1600” (registered trademark, refractive index: n _A = 1.29 to 1) manufactured by DuPont is used as the material of the low refractive index bodies 8 p and 8 a. .31), each liquid material of methacrylic resin “Parapet (optical grade)” (registered trademark, refractive index: n _C = 1.49) manufactured by Kuraray Co., Ltd. is selected on the light guide body 5 This can be realized by applying and curing the resin.
Since the refractive index body 9 has the same refractive index as that of the light guide body 5, it is not always necessary to form the refractive index body 9 on the light guide body 5 in the second light extraction region RB. For example, the light scatterer 10 may be merely disposed on the light guide 5.

The second technique is to use a material containing a low refractive index material in a predetermined substrate and adjust the refractive index by varying the concentration of the low refractive index material. For example, a methacrylic resin “Parapet (Optical Grade)” (registered trademark, refractive index: n _C = 1.49) manufactured by Kuraray Co., Ltd. used as a material for the refractive index body 9 is used as a base material, and Ardrich is included therein Low refractive index materials such as mesoporous silica nanopowder (registered trademark, refractive index: 1.27) manufactured by Nikon Corporation, or airgel (registered trademark, refractive index: 1.27) manufactured by Jason Wells are included. Liquid materials having different concentrations of the rate material are prepared. Each liquid material can be selectively applied on the light guide 5 and cured.

A light scatterer 10 is laminated on the low refractive index body 8a and the refractive index body 9 provided in each of the light extraction regions RA and RB. The light scatterer 10 has a function of scattering the light incident from the low refractive index body 8 a and the refractive index body 9 and extracting it to the external space of the backlight 3. Specifically, as the light scatterer 10, a commercially available light scattering film in which scattering beads or the like are coated on a base film can be used. By sticking a light scattering film on the low refractive index body 8a and the refractive index body 9, the light scattering body 10 can be formed. As the light scatterer 10 of this embodiment, it is desirable to use a light scattering film with high light scattering ability.

Hereinafter, the operation of the backlight of the present embodiment will be described.
2A and 2B respectively show cross-sectional views taken along the line AA ′ of FIG.
In the present embodiment, as an example, as shown in FIG. 2A, the angle β formed by the first end surface 5c of the light guide 5 and the first main surface 5a is set to 75 °. Since the second LED 7b is fixed so that light enters perpendicularly to the first end face 5c, the angle formed by the central axis of the light propagating in the light guide 5 with respect to the reference horizontal plane X is the propagation angle φ. If defined, the propagation angle φB of light from the second LED 7b can be expressed as φB = 90 ° −β, and the propagation angle φB is 15 °. That is, the light Lb emitted from the second LED 7b repeats total reflection between the first main surface 5a and the second main surface 5b of the light guide 5, and from the first end surface 5c side to the second end surface 5d side. Is propagated at a propagation angle φB = 15 °.

In the case of this embodiment, as an example, as shown in FIG. 2B, the angle α formed by the first main surface 5a (reference horizontal plane) of the light guide and the inclined surface 6a of the prism structure 6 is set to 55 °. Yes.
Since the first LED 7a is fixed so that light enters perpendicularly to the inclined surface 6a, the light propagation angle φA from the first LED 7a can be expressed as φA = 90 ° −α, and the propagation angle φA is 35. °. That is, the light La emitted from the first LED 7a is propagated at a propagation angle φA = 35 ° inside the prism structure 6 and travels toward the low refractive index body 8p.

Here, the light La, Lb from each LED 7a, 7b is the interface between the light guide 5 and the low refractive index body 8a in each light extraction area RA, RB, the interface between the light guide 5 and the refractive index body 9, The critical angle at the time of incidence on the interface between the prism structure 6 and the low refractive index body 8p for the prism will be considered.
The interface between the light guide 5 and the low refractive index body 8a in the first light extraction region RA is a light guide with a refractive index n _WG = 1.5 and a low refractive index body 8a with a refractive index n _A = 1.3. From Snell's law, the critical angle γ _A is 60.1 °. Therefore, in the first light extraction region RA, light incident from the light guide 5 to the low refractive index body 8a with an incident angle of less than 60.1 ° is transmitted through the interface, and the incident angle is 60.1 ° or more. The light incident on is totally reflected at the interface.

On the other hand, the interface between the light guide 5 and the refractive index body 9 in the second light extraction region RB is a refraction having a refractive index n _WG = 1.5 and a refractive index n _B = 1.5. Since it becomes an interface with the index body 9, light passes through the interface at all incident angles.

Thus, the two low-refractive-index bodies 8a and the refractive-index bodies 9 provided in the two light extraction regions RA and RB of the present embodiment have a relatively low refractive index along the light propagation direction. To those having a relatively high refractive index. Based on such a difference in refractive index, the two light extraction regions RA and RB have different incident angle ranges in which light can be extracted to the outside. Further, the two light extraction regions RA and RB are light extraction regions having a relatively wide incident angle range that can be extracted from a light extraction region having a relatively narrow incident angle range along the light propagation direction. They are arranged in order. Specifically, the incident angle range that can be extracted in the first light extraction region RA is less than 60.1 °, and the incident angle range that can be extracted in the second light extraction region RB is a full angle range.

The critical angle at the interface between the prism structure 6 and the low refractive index body 8p for the prism is the same as the critical angle at the interface between the light guide 5 and the low refractive index body 8a. In other words, the interface between the prism structure 6 and the low refractive index body 8p for the prism is between the light guide having the refractive index n _WG = 1.5 and the low refractive index body 8p for the prism having the refractive index n _p = 1.3. Since it becomes an interface, the critical angle γ _P is 60.1 ° according to Snell's law. Therefore, light incident from the prism structure 6 with respect to the interface at an incident angle of less than 60.1 ° is transmitted through the interface, and light incident at an incident angle of 60.1 ° or more is totally reflected at the interface.

Here, as shown in FIG. 2B, when the first LED 7a fixed to the inclined surface 6a of the prism structure 6 is turned on, the propagation angle φA inside the prism structure 6 is 35 ° as described above. Since the incident angle θP of the light with respect to the low refractive index body 8p for the prism can be expressed as θP = 90 ° −φA, the incident angle θP is 55 °. When the light La from the first LED 7a enters the interface between the prism structure 6 and the low refractive index body 8p for the prism at an incident angle θP = 55 °, the critical angle γ _P here is 60.1 °. The light La enters the prism low refractive index body 8p from the interface between the prism structure 6 and the prism low refractive index body 8p, passes through the prism low refractive index body 8p, and enters the light guide 5. At this time, the light La is 2 when incident on the interface between the prism structure 6 and the low refractive index body 8p for prism and when emitted from the interface between the low refractive index body 8p for prism and the light guide 5. Although the light is refracted, the refraction angle is canceled out by the two refractions, so that the light La emitted from the first LED 7a maintains the propagation angle inside the prism structure 6 also inside the light guide 5, Propagated at a propagation angle φA = 35 °.

Thereafter, the light La emitted from the first LED 7a repeats total reflection between the first main surface 5a and the second main surface 5b of the light guide 5, but the light guide plate 5 of the present embodiment is configured by parallel plates. because they are, even after repeated many times totally reflected light La is from the 1LED7a, the incident angle theta _a with respect to the first major surface 5a is always 55 °. When the light La from the first LED 7a reaches the first light extraction region RA and enters the interface between the light guide 5 and the low refractive index body 8a at an incident angle θ _A = 55 °, the critical angle γ here _{Since A} is 60.1 °, the light La passes through the interface between the light guide 5 and the low refractive index body 8a and is incident on the low refractive index body 8a. To be taken out. In this way, substantially the entire amount of light La emitted from the first LED 7a can be extracted from the first light extraction area RA.

Next, as shown in FIG. 2A, if the second LED 7b fixed to the first end face 5c of the light guide 5 is turned on, the propagation angle φB of the light emitted from the second LED 7b is 15 °, and the low refractive index Since the incident angle θB of light with respect to the body 8a can be expressed as θB = 90 ° −φB, the incident angle θB is 75 °. When the light Lb from the second LED 7b reaches the first light extraction region RA and enters the interface between the light guide 5 and the low refractive index body 8a at an incident angle θB = 75 °, the critical angle γ _A here Is 60.1 °, the light Lb cannot be transmitted through the interface between the light guide 5 and the low refractive index body 8a, and is totally reflected. Next, when the light Lb from the second LED 7b reaches the second light extraction region RB, the light Lb passes through the interface between the light guide 5 and the refractive index body 9 and enters the refractive index body 9, and then the light Lb. It is taken out from the scatterer 10 to the outside. In this way, substantially the entire amount of the light Lb emitted from the second LED 7b can be extracted from the second light extraction region RB.

If the light La emitted from the first LED 7a enters the second light extraction region RB, the light La is extracted from the second light extraction region RB. However, almost the entire amount of the light La emitted from the first LED 7a is extracted in the first light extraction area RA before reaching the second light extraction area RB, and therefore almost reaches the second light extraction area RB. There is no.
Therefore, actually, the light La emitted from the first LED 7a is not extracted from the second light extraction region RB, and the light Lb emitted from the second LED 7b is extracted from the second light extraction region RB. Based on such a principle, the backlight 3 of the present embodiment can extract light emitted from a predetermined LED only from a predetermined light extraction area.

As described above, according to the backlight 3 of the present embodiment, depending on which of the two LEDs 7a and 7b of each backlight unit 4 is lit, of the two light extraction areas RA and RB It is possible to appropriately select which light extraction area to extract light from, that is, which light extraction area RA, RB emits light. Further, by controlling the amount of light emitted from each LED 7a, 7b, the amount of light extracted from the selected light extraction area RA, RB, that is, the brightness of the selected light extraction area can be adjusted. it can.

In the conventional backlight, whether or not light is emitted from each region is controlled by electrically switching the light scattering degree of the polymer dispersed liquid crystal and the light transmittance of the hybrid alignment liquid crystal.
Therefore, if the optical properties of these liquid crystals are inferior even a little, light cannot be extracted sufficiently. Alternatively, the light leaks from other than the desired region and the contrast is lowered. On the other hand, the backlight 3 of the present embodiment can control whether or not light is emitted from the light extraction areas RA and RB by simply switching the LEDs 7a and 7b to be lit without using liquid crystal. Therefore, by efficiently taking out the light emitted from each LED from the light guide 5, a sufficient amount of light can be obtained and a backlight with high contrast can be realized. Furthermore, the structure can be simplified, the thickness can be reduced, and the inexpensive backlight 3 can be realized. In addition, by using the backlight 3 described above, it is possible to realize the liquid crystal display device 1 that can display brightly and with high contrast.

Further, if there is no low refractive index body between the prism structure 6 and the light guide 5 as in the backlight 301 of the first comparative example shown in FIG. 3, the light Lb emitted from the second LED 7b is When the light enters the interface between the prism structure 6 and the light guide 5 while propagating through the light guide 5, the light Lb passes through the interface and exits to the external space through the prism structure 6. Such light becomes leakage light, and the light that should originally be emitted from the second light extraction region RB decreases, and a desired light amount cannot be obtained. In that respect, according to the backlight 3 of the present embodiment, the prism low refractive index body 8p is provided between the prism structure 6 and the light guide 5, so that the light guide 5 is propagated. Incidence of light to the prism structure 6 is suppressed by the prism low refractive index body 8p.
As a result, the occurrence of leakage light as described above is suppressed, and a desired amount of light can be obtained.

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described with reference to FIGS. 4A to 4C.
The basic configuration of the backlight of the present embodiment is the same as that of the first embodiment, and the number of LEDs and light extraction areas is three, the shape of the prism structure and the installation position of the LEDs are the first implementation. It is different from the form. Therefore, in this embodiment, the description regarding the basic configuration of the backlight is omitted.
4A to 4C are diagrams showing how light is emitted from each light extraction region in the backlight according to the present embodiment. FIG. 5 is a diagram for explaining the backlight of the second comparative example.
4A to 4C and FIG. 5, the same reference numerals are given to the same components as those used in the first embodiment, and the detailed description thereof will be omitted.

The backlight of the first embodiment includes two LEDs, and two light extraction areas RA and RB are provided on the light guide 5. On the other hand, as shown in FIGS. 4A to 4C, the backlight 12 of this embodiment includes three LEDs 7a, 7b, and 7c, and three light extraction regions RA and RB on the light guide 5. , RC are provided.

In the first light extraction region RA, the first low refractive index body 8a and the light scatterer 10 are stacked in this order from the light guide 5 side. The first low refractive index body 8 a has a refractive index lower than that of the light guide 5. The light scatterer 10 scatters the light emitted from the first low refractive index body 8a. In the second light extraction region RB, the second low refractive index body 8b and the light scatterer 10 are stacked in this order from the light guide 5 side. The second low refractive index body 8 b has a refractive index lower than the refractive index of the light guide 5. The light scatterer 10 scatters the light emitted from the second low refractive index body 8b. In the third light extraction region RC, the refractive index body 9 and the light scatterer 10 are stacked in this order from the light guide 5 side. The refractive index body 9 has a refractive index equal to the refractive index of the light guide 5. The light scatterer 10 scatters the light emitted from the refractive index body 9.

The first low-refractive index body 8a, the second low-refractive index body 8b, and the refractive index body 9 provided in the three light extraction regions RA, RB, and RC are along the light propagation direction (the −x direction in FIG. 1). From the relatively low refractive index to the relatively high refractive index.
As an example of this embodiment, the refractive index nWG of the light guide 5 is 1.5, the refractive index nA of the first low refractive index body 8a provided in the first light extraction region RA is 1.3, and the second light extraction. The refractive index nB of the second low refractive index body 8b provided in the region RB is set to 1.4, and the refractive index nC of the refractive index body 9 provided in the third light extraction region RC is set to 1.5.

The prism structure 13 of the present embodiment has three inclined surfaces 13a, 13b, 13c facing the second end surface 5d side of the light guide 5. The LEDs 7a, 7b, and 7c are fixed to the inclined surfaces 13a, 13b, and 13c by optical adhesives, respectively. The three inclined surfaces 13 a, 13 b, and 13 c are gradually inclined with respect to the reference horizontal plane from the far side to the near side with respect to the light guide 5. Hereinafter, the inclined surface 13a farthest from the light guide 5 (the upper inclined surface in FIGS. 4A to 4C) is referred to as a first inclined surface, and the LED 7a installed on the first inclined surface 13a is referred to as a first LED. . The inclined surface 13b (the intermediate inclined surface in FIGS. 4A to 4C) that is the next farthest from the light guide 5 is referred to as a second inclined surface, and the LED 7b installed on the second inclined surface 13b is referred to as a second LED. The inclined surface 13c (lower inclined surface in FIGS. 4A to 4C) on the side closest to the light guide 5 is referred to as a third inclined surface, and the LED 7c installed on the third inclined surface 13c is referred to as a third LED.

In the case of the present embodiment, as an example, the angle α1 formed between the first major surface 5a (reference horizontal plane) of the light guide 5 and the first inclined surface 13a of the prism structure 13 is 55 °, and the first of the light guide 5 The angle α2 formed between the main surface 5a (reference horizontal plane) and the second inclined surface 13b of the prism structure 13 is 65 °, and the first main surface 5a (reference horizontal plane) of the light guide 5 and the third inclination of the prism structure 13 The angle α3 formed with the surface 13c is set to 75 °.

Between the prism structure 13 and the light guide 5, the first low refraction for a prism having a refractive index equal to the refractive index of the first low refractive index body 8a on the optical path of the light La emitted from the first LED 7a. A rate body 14a is provided. Further, between the prism structure 13 and the light guide 5, a second prism for prism having a refractive index equal to the refractive index of the second low refractive index body 8 b on the optical path of the light Lb emitted from the second LED 7 b. A low refractive index body 14b is provided.
Therefore, the refractive index nPA of the first low refractive index body for prism 14a is 1.3, and the refractive index nPB of the second low refractive index body for prism 14b is 1.4. A low refractive index body is not provided on the optical path of the light Lc emitted from the third LED 7c.

Hereinafter, the operation of the backlight 12 of the present embodiment will be described.
In this embodiment, the inclination angle α1 of the first inclined surface 13a where the first LED 7a is installed is 55 °, the inclination angle α2 of the second inclined surface 13b where the second LED 7b is installed is 65 °, and the third LED 7c is installed. The inclination angle α3 of the three inclined surfaces 13c is 75 °. Therefore, the propagation angle φA of the light La emitted from the first LED 7a is 35 °, the propagation angle φB of the light Lb emitted from the second LED 7b is 25 °, and the propagation angle φC of the light Lc emitted from the third LED 7c is 15 °. Become.

Regarding the critical angle at each interface, at the interface between the light guide 5 and the first low refractive index body 8a in the first light extraction region RA, the critical angle γ _A is 60.1 ° as in the first embodiment. It is. The interface between the light guide 5 and the second low refractive index body 8b in the second light extraction region RB is the second of the light guide 5 having a refractive index n _WG = 1.5 and the refractive index n _B = 1.4. Since it becomes an interface with the low refractive index body 8b, the critical angle γ _B is 69.0 ° according to Snell's law. Accordingly, in the second light extraction region RB, light incident from the light guide 5 to the second low refractive index body 8b with an incident angle of less than 69.0 ° is transmitted through the interface, and the incident angle is 69.0. Light incident at or above ° is totally reflected at the interface. As with the second light extraction region RB of the first embodiment, the light is transmitted through the interface between the light guide 5 and the refractive index body 9 in the third light extraction region RC.

Thus, the first low refractive index body 8a, the second low refractive index body 8b, and the refractive index body 9 provided in the three light extraction areas RA, RB, RC of the present embodiment are divided into the light extraction areas RA, Along the propagation direction of the light incident on RB and RC, the light beams are arranged in the order from a relatively low refractive index to a relatively high refractive index. Based on such a difference in refractive index, the three light extraction regions RA, RB, and RC can be extracted from the light extraction region having a relatively narrow incident angle range along the propagation direction of incident light. The light extraction regions are arranged in order of a relatively wide incident angle range. Specifically, the incident angle range that can be extracted in the first light extraction region RA is less than 60.1 °, the incident angle range that can be extracted in the second light extraction region RB is less than 69.0 °, and the third light. The incident angle range that can be extracted in the extraction region RC is the entire angle range.

The critical angle at the interface between the prism structure 13 and the first low refractive index body 14a for prism and the second low refractive index body 14b for prism is the same as the critical angle at the interface in each light extraction region RA, RB, RC. is there. That is, the critical angle γ _PA at the interface between the prism structure 13 and the first prism low refractive index body 14a is 60.1 °, and the interface between the prism structure 13 and the second prism low refractive index body 14b. The critical angle γ _{E at} is 69.0 °.

Here, as shown in FIG. 4C, when the first LED 7a is turned on, as described above, the propagation angle φA of the light La emitted from the first LED 7a is 35 °. 1 The incident angle θPA of light with respect to the interface with the low refractive index body 14a is 55 °. When light La from the 1LED7a incident on the interface at an incident angle θPA = 55 °, because here the critical angle gamma _PA in is 60.1 °, the light La passes through the first low refractive index member 14a prism , Enters the light guide 5. The light La emitted from the first LED 7a is propagated at the propagation angle φA = 35 ° also inside the light guide 5.

Thereafter, when the light La from the first LED 7a is incident on the interface between the light guide 5 and the first low refractive index body 8a at the incident angle θA = 55 °, the critical angle γ _A here is 60.1 °. Therefore, the light La passes through the interface between the light guide 5 and the first low refractive index body 8a and is incident on the first low refractive index body 8a. Thereafter, the light is scattered by the light scatterer 10 and taken out to the external space. In this way, substantially the entire amount of light La emitted from the first LED 7a can be extracted from the first light extraction area RA.

Next, as shown in FIG. 4B, if the second LED 7b is turned on, the propagation angle φB of the light Lb emitted from the second LED 7b is 25 °, so that the prism structure 13 and the second low-refractive-index body for prism are used. The incident angle θPB of the light Lb with respect to the interface with 14b is 65 °. When the light Lb from the second LED 7b is incident on the interface at an incident angle θDPB = 65 °, the critical angle γ _PA here is 69.0 °, so that the light Lb is transmitted through the second low-refractive index body for prism 14b. , Enters the light guide 5. The light Lb emitted from the second LED 7b is also propagated at the propagation angle φB = 25 ° inside the light guide 5.

Thereafter, when the light Lb from the second LED 7b is incident on the interface between the light guide 5 and the first low refractive index body 14a for the prism at an incident angle θPB = 65 °, the critical angle γ _PB here is 60.1 °. Therefore, the light Lb cannot be transmitted through this interface and is totally reflected. Even in the next first light extraction area RA, the critical angle γ _A is 60.1 °. Therefore, even if the light Lb from the second LED 7b reaches the first light extraction area RA, the light guide 5 and the first low light extraction area RA The light cannot be transmitted through the interface with the refractive index body 8a and is totally reflected. Next, when the light Lb from the second LED 7b reaches the second light extraction region RB, the critical angle γ _B here is 69.0 °, so that the light Lb is the light guide 5 and the second low refractive index body. 8b is transmitted through the interface with the second low-refractive index body 8b and transmitted through the second low-refractive index body 8b to be extracted from the light scatterer 10 to the outside. In this way, substantially the entire amount of the light Lb emitted from the second LED 7b can be extracted from the second light extraction region RB.

Next, as shown in FIG. 4A, if the third LED 7c is turned on, the light emitted from the third LED 7c passes through the prism structure 13 as it is and propagates in the light guide 5 at a propagation angle φC = 15 °. Is done. The incident angle θC with respect to each interface of the light Lc emitted from the third LED 7c is 75 °, and the interface between the light guide 5 and the second low refractive index body 14b for prism, the first low refractive index for the light guide 5 and prism. The interface between the light guide 5 and the first low refractive index body 8a in the first light extraction region RA, and the light guide 5 and the second low refractive index body 8b in the second light extraction region RB. Since the interfaces each have a critical angle of 60.1 ° or 69.0 °, the light Lc emitted from the third LED 7c cannot be transmitted through all these interfaces and is totally reflected. When the light Lc from the third LED 7c reaches the third light extraction region RB, it passes through the refractive index body 9 and is extracted from the light scatterer 10 to the outside. In this way, substantially the entire amount of the light Lc emitted from the third LED 7c can be extracted from the third light extraction region RB.

As described above, according to the backlight 12 of the present embodiment, which of the three light extraction areas RA, RB, RC depends on which of the three LEDs 7a, 7b, 7c is lit. It is possible to appropriately select whether to extract light from the light extraction region. Further, by controlling the amount of light emitted from each LED 7a, 7b, 7c, the amount of light extracted from the selected light extraction area RA, RB, RC, that is, the brightness of the selected light extraction area is controlled. Can be adjusted.

Also in the present embodiment, it is possible to obtain the same effect as in the first embodiment that a sufficient amount of light is obtained, a high contrast, a simple structure, a thin and inexpensive backlight can be obtained. In the configuration of the present embodiment, since it is not necessary to install the LED on the end face of the light guide 5, for example, when the thickness of the light guide is thin, it is difficult to install the LED on the end face of the light guide. It is suitable for.

FIG. 5 shows the backlight 302 of the second comparative example. The backlight 302 does not have a low refractive index body between the prism structure 13 and the light guide 5. In the backlight 302, light emitted from any of the LEDs 7 a, 7 b, and 7 c is transmitted through the interface when entering the interface between the prism structure 13 and the light guide 5 while propagating through the light guide 5. Then, it goes out to the external space through the prism structure 13. Such light becomes leakage light, and the light that should be emitted from the light extraction area is reduced, and a desired light amount cannot be obtained. In that respect, according to the backlight 12 of the present embodiment, the first low refractive index body for prism 14a and the second low refractive index body for prism 14b are provided between the prism structure 13 and the light guide 5. Yes. Therefore, the light propagating through the light guide 5 is prevented from entering the prism structure 13 by the low refractive index members 14a and 14b. As a result, the occurrence of leakage light as described above is suppressed, and a desired amount of light can be obtained.

[First Modification of Second Embodiment]
In the above-described embodiment, one prism structure is provided on the light guide. However, instead of this configuration, a plurality of prism structures may be provided on the light guide.

As shown in FIG. 6, the backlight 16 according to this modification includes two prism structures 17 and 18 arranged on the first main surface 5 a of the light guide 5 along the light propagation direction. Yes. In the first prism structure 17 disposed on the side far from the first end surface 5c of the light guide 5, the first LED 7a is provided on one inclined surface 17a. Between the 1st prism structure 17 and the light guide 5, the 1st low refractive index body 14a for prisms which has a refractive index (n = 1.3) equal to the refractive index of the 1st low refractive index body 8a is provided. Is provided. In the second prism structure 18 disposed on the side of the light guide 5 close to the first end surface 5c, the second LED 7b and the third LED 7c are provided on the two inclined surfaces 18b and 18c, respectively. Between the second prism structure 18 and the light guide 5, on the optical path of the light emitted from the second LED 7b, a refractive index equal to the refractive index of the second low refractive index body 8b (n = 1.4). A second low-refractive-index body 14b for a prism having the above is provided. No low refractive index body is provided on the optical path of the light emitted from the third LED 7c. Other configurations are the same as those of the backlight according to the second embodiment.

In other words, the backlight 16 of this modification includes a portion corresponding to the first inclined surface 13a of the prism structure 13 in the backlight 12 of the second embodiment shown in FIGS. 4A to 4C, and the second and third inclined surfaces. It can be said that the portion corresponding to the surfaces 13b and 13c is divided into two prism structures 17 and 18.

Also in this embodiment, it is possible to obtain the same effects as the first and second embodiments that a sufficient amount of light is obtained, a high contrast, a simple structure, a thin and inexpensive backlight can be obtained. In particular, according to the configuration of the backlight 16 of the present modification, the size in the direction (z-axis direction) perpendicular to the first main surface 5a of the light guide 5 of each prism structure 17, 18 can be reduced. The light can be made thinner.

[Second Modification of Second Embodiment]
The two prism structures in the first modification may be arranged on different main surfaces of the light guide. That is, the prism structure does not necessarily have to be arranged on the side where the light extraction region is provided.

In the backlight 20 of this modification, as shown in FIG. 7, the second prism structure 18 is provided on the first main surface 5 a of the light guide 5, and the second main surface 5 b of the light guide 5 is the second main surface 5 b. One prism structure 17 is provided. Other configurations are the same as those of the first modified example.

Also in this embodiment, it is possible to obtain the same effects as the first and second embodiments that a sufficient amount of light is obtained, a high contrast, a simple structure, a thin and inexpensive backlight can be obtained.

[Third Embodiment]
Hereinafter, a third embodiment of the present invention will be described with reference to FIGS. 8A and 8B.
The basic configuration of the backlight of the present embodiment is the same as that of the first embodiment, and the point where the inclined surface of the prism structure is a reflecting surface and the LED installation position are different from those of the first embodiment. Therefore, in this embodiment, the description regarding the basic configuration of the backlight is omitted.
8A and 8B are diagrams illustrating a state in which light is emitted from each light extraction region in the backlight according to the present embodiment. 9A and 9B are diagrams for explaining the backlight of the third comparative example.
In FIG. 8A, FIG. 8B, FIG. 9A, and FIG. 9B, the same code | symbol is attached | subjected to the same component as drawing used in 1st Embodiment, and the detailed description is abbreviate | omitted.

In the backlight 22 of the present embodiment, as shown in FIGS. 8A and 8B, a mirror 23 is formed on the inclined surface 6a of the prism structure 6 provided on the first main surface 5a of the light guide 5. The inclined surface 6a functions as a light reflecting surface. The first LED 7a is disposed at a position on the second main surface 5b of the light guide 5 facing the light reflecting surface. The second LED 7b is disposed on the first end face 5c of the light guide 5 as in the first embodiment. Between the prism structure 6 and the light guide 5, a prism low refractive index body 8 p having a refractive index lower than that of the light guide 5 is provided.
Between the 1st LED7a and the light guide 5, the low refractive index body 24 for LED which has a refractive index lower than the refractive index of the light guide 5 is provided.

In the present embodiment, the low refractive index body 8p provided between the prism structure 6 and the light guide 5 and the LED low refractive index body 24 provided between the first LED 7a and the light guide 5 are as follows. The refractive index is equal, and is also equal to the refractive index of the low refractive index body 8a in the first light extraction region RA. Therefore, in the example of the first embodiment, the refractive indexes of these low refractive index bodies 8p, 24, 8a are all 1.3. Other configurations are the same as those of the first embodiment.

The behavior of the light emitted from the second LED 7b is the same as that of the first embodiment as shown in FIG. 8A. That is, the angle β formed by the first end surface 5c of the light guide 5 and the first main surface 5a is set to 75 °, and the light emitted from the second LED 7b is the first main surface 5a of the light guide 5. Is transmitted at a propagation angle φB = 15 ° from the first end surface 5c side to the second end surface 5d side while repeating total reflection between the first end surface 5b and the second main surface 5b. The light Lb emitted from the second LED 7b is incident on the first main surface 5a of the light guide 5 at an incident angle θB = 75 °. Therefore, the light Lb is totally reflected in the first light extraction area RA and enters the second light extraction area RB. When it reaches, it passes through the refractive index body 9 and the light scattering body 10 and is taken out to the external space.

On the other hand, the light La emitted from the first LED 7a is emitted in the direction perpendicular to the second main surface 5b of the light guide 5 as shown in FIG. 8B. Body 5 and low-refractive-index body 8p for prism to be incident on prism structure 6 and reflected by mirror 23 on inclined surface 6a, and again transmitted to low-refractive-index body 8p for prism and incident on light guide 5 To do. In the case of the first embodiment, the relationship between the inclination angle α of the inclined surface 6a of the prism structure 6 and the light propagation angle φA is φA = 90 ° −α, whereas in the present embodiment, the prism structure Since the light La is reflected by the inclined surface 6a of the body 6, the relationship between the inclination angle α of the inclined surface 6a of the prism structure 6 and the light propagation angle φA is different from the first embodiment, and φA = 90 ° − 2α. Therefore, for example, when the inclination angle α of the inclined surface 6a is 27.5 °, the propagation angle φA of the light La emitted from the first LED 7a is 35 °, which is the same as in the first embodiment, from the above relational expression.

When the propagation angle φA of the light La emitted from the first LED 7a is 35 °, the incident angle of the light La emitted from the first LED 7a to the interface between the prism structure 6 and the low refractive index body 8p for the prism, and the first The incident angle θA to the interface between the light guide 5 and the low refractive index body 8a in the light extraction region RA is 55 °. Since the critical angle at these interfaces is 60.1 °, the light La emitted from the first LED 7a can pass through these interfaces and is extracted from the first light extraction region RA to the external space.

In this way, according to the backlight 22 of the present embodiment, which light extraction area RA or RB is selected depending on which of the two LEDs 7a and 7b is lit. It is possible to appropriately select whether to extract light from the light source. Further, by controlling the amount of light emitted from each LED 7a, 7b, the amount of light extracted from the selected light extraction area RA, RB, that is, the brightness of the selected light extraction area can be adjusted. it can.

Also in this embodiment, the same effects as those of the first and second embodiments can be obtained in that a sufficient amount of light is obtained, a high contrast, a simple structure, a thin and inexpensive backlight can be obtained.

9A and 9B show a backlight 303 of a third comparative example. The backlight 303 does not have a low refractive index body between the prism structure 6 and the light guide 5 and between the first LED 7 a and the light guide 5. In the backlight 303, when the light Lb emitted from the second LED 7b is incident on the interface between the prism structure 6 and the light guide 5 while propagating through the light guide 5, the light Lb is transmitted through the interface, and the prism structure It goes out to external space through 6. Also, when the light Lb emitted from the second LED 7b enters the interface between the first LED 7a and the light guide 5, the light Lb passes through the interface and exits to the external space through the first LED 7a. Such light becomes leakage light, and there is a problem that the light that should be emitted from the light extraction area is reduced and a desired light quantity cannot be obtained.

In that respect, according to the backlight 22 of the present embodiment, the low refractive index body 8p for the prism, the low refractive index for the LED, between the prism structure 6 and the light guide 5, and between the first LED 7a and the light guide 5. Since the index body 24 is provided, incidence of light propagating through the light guide 5 to the prism structure 6 or the first LED 7a is suppressed by the low refractive index bodies 8p and 24. As a result, the occurrence of leakage light as described above is suppressed, and a desired amount of light can be obtained.

[Display Device of Fourth Embodiment]
Hereinafter, a fourth embodiment of the present invention will be described with reference to FIGS. 10A to 10C.
The basic configuration of the backlight of the present embodiment is the same as that of the second embodiment, and the point where the inclined surface of the prism structure is a reflecting surface and the LED installation position are different from those of the second embodiment. Therefore, in this embodiment, the description regarding the basic configuration of the backlight is omitted.
FIG. 10A to FIG. 10C are diagrams showing a state in which light is emitted from each light extraction region in the backlight according to the present embodiment.
10A to 10C, the same reference numerals are given to the same components as those used in the second embodiment, and the detailed description thereof will be omitted.

As shown in FIGS. 10A to 10C, the backlight 26 of the present embodiment includes a first inclined surface 13a, a second inclined surface 13b, and a first inclined surface 13b of the prism structure 13 provided on the first main surface 5a of the light guide 5. A mirror 23 is formed on each of the third inclined surfaces 13c, and these inclined surfaces 13a, 13b, and 13c function as light reflecting surfaces. A first LED 7a, a second LED 7b, and a third LED 7c are disposed at a position on the second main surface 5b of the light guide 5 facing these light reflecting surfaces. Between the prism structure 13 and the light guide 5, the first low refractive index body 8a of the first light extraction region RA is disposed on the optical path of the light La emitted from the first LED 7a and reflected by the first inclined surface 13a. A first low-refractive-index body for prism 14a having a refractive index equal to (n = 1.3) is provided.

For a prism having a refractive index (n = 1.4) equal to the second low refractive index body 8b of the second light extraction region RB on the optical path of the light Lb emitted from the second LED 7b and reflected by the second inclined surface 13b. A second refractive index body 14b is provided. A low refractive index body is not provided on the optical path of the light Lc emitted from the third LED 7c and reflected by the third inclined surface 13c. Further, between the first LED 7 a, the second LED 7 b, the third LED 7 c, and the light guide 5, an LED low refractive index body 24 having a refractive index lower than that of the light guide 5 is provided.

As an example of this embodiment, the inclination angle α1 of the first inclined surface 13a is 27.5 °, the inclination angle α2 of the second inclined surface 13b is 32.5 °, and the inclination angle α3 of the third inclined surface 13c is 37.5. Set to °. As described in the third embodiment, the relationship between the inclination angle α of the inclined surfaces 13a, 13b, and 13c of the prism structure 13 and the light propagation angle φ is φ = 90 ° −2α. The propagation angle φA of the light La emitted from the first inclined surface 13a and reflected by the first inclined surface 13a is 35 °, the propagation angle φB of the light Lb emitted from the second LED 7b and reflected by the second inclined surface 13b is 25 °, and emitted from the third LED 7c. The propagation angle φC of the light Lc reflected by the third inclined surface 13c is 35 °, which is the same as in the second embodiment. Therefore, the behavior of the light emitted from each LED 7a, 7b, 7c is the same as in the second embodiment. That is, substantially the entire amount of light emitted from the first LED 7a is extracted from the first light extraction area RA, and substantially the entire amount of light emitted from the second LED 7b is extracted from the second light extraction area RB and emitted from the third LED 7c. Substantially the entire amount of light is extracted from the third light extraction region RC.

Also in this embodiment, it is possible to obtain the same effects as those in the first to third embodiments that a sufficient amount of light is obtained, a high contrast, a simple structure, a thin and inexpensive backlight can be obtained. In particular, in the case of the present embodiment, since the three LEDs 7a, 7b, 7c are all installed on the second main surface 5b of the planar light guide 5, it is easy to mount the LEDs including wiring and driving circuits. Become.

[First Modification of Fourth Embodiment]
In the above-described embodiment, one prism structure is provided on the light guide. However, instead of this configuration, a plurality of prism structures may be provided on the light guide.

As shown in FIG. 11, the backlight 28 of the present modification includes two prism structures 17 and 18 arranged on the first main surface 5 a of the light guide 5 along the light propagation direction. Yes. In the first prism structure 17 disposed on the far side from the first end surface 5 c of the light guide 5, a mirror 23 is provided on one inclined surface 17 a, and the inclined surface on the second main surface 5 b of the light guide 5. The first LED 7a is provided at a position facing the 17a. Between the 1st prism structure 17 and the light guide 5, the 1st low refractive index body 14a for prisms which has a refractive index (n = 1.3) equal to the refractive index of the 1st low refractive index body 8a is provided. Is provided.

In the second prism structure 18 disposed on the side close to the first end surface 5c of the light guide 5, mirrors 23 are provided on the two inclined surfaces 18b and 18c, and the second main surface 5b of the light guide 5 is provided. 2nd LED7b and 3rd LED7c are each provided in the position facing each inclined surface 18b, 18c. Between the second prism structure 18 and the light guide 5, a refractive index equal to the refractive index of the second low refractive index body 8 b (on the optical path of the light emitted from the second LED 7 b and reflected by the inclined surface 18 b ( A second low-refractive-index body 14b for prism having n = 1.4) is provided. No low refractive index body is provided on the optical path of the light emitted from the third LED 7c. Other configurations are the same as those of the backlight according to the fourth embodiment.

In other words, the backlight 28 of this modification includes a portion corresponding to the first inclined surface 13a of the prism structure 13 in the backlight 26 of the fourth embodiment shown in FIGS. 10A to 10C, and the second and third inclined surfaces. A portion corresponding to the surfaces 13 b and 13 c is divided into two prism structures 17 and 18.

Also in this embodiment, it is possible to obtain the same effects as those in the first to fourth embodiments that a sufficient amount of light is obtained, a high contrast, a simple structure, a thin and inexpensive backlight can be obtained. In particular, according to the configuration of this modification, the size of the individual prism structures 17 and 18 in the direction perpendicular to the first main surface 5a of the light guide 5 (z-axis direction) can be reduced. Can be planned.

[Second Modification of Fourth Embodiment]
The two prism structures in the first modification may be arranged on different main surfaces of the light guide. That is, the prism structure does not necessarily have to be arranged on the side where the light extraction region is provided.

In the backlight 30 of the present modification, the second prism structure 18 is provided on the first main surface 5a of the light guide 5 as shown in FIG. Further, the first prism structure 17 is provided on the second main surface 5 b of the light guide 5. Correspondingly, the first LED 7 a is provided at a position facing the first inclined surface 17 a of the first prism structure 17 on the first main surface 5 a of the light guide 5. In addition, the second LED 7b and the third LED 7c are provided at positions on the second main surface 5b of the light guide 5 facing the inclined surfaces 18b and 18c of the second prism structure 18, respectively. Other configurations are the same as those of the first modified example.

Also in this embodiment, it is possible to obtain the same effects as those in the first to fourth embodiments that a sufficient amount of light is obtained, a high contrast, a simple structure, a thin and inexpensive backlight can be obtained.

[Configuration example of display device]
Hereinafter, one configuration example of the display device will be described with reference to FIGS. 13 to 15B.
FIG. 13 is an exploded perspective view showing a schematic configuration of a liquid crystal display device which is a configuration example of the display device. FIG. 14A, FIG. 14B, FIG. 15A, and FIG. 15B are diagrams showing examples of backlight arrangement in the liquid crystal display device.

As shown in FIG. 13, the liquid crystal display device 121 of this configuration example includes a lower case 122, a reflection plate 123, a backlight 3 (light control element), a diffusion plate 124, and a liquid crystal panel 2 (display element). And an upper case 125. That is, a laminated body of the reflecting plate 123, the backlight 3, the diffusion plate 124, and the liquid crystal panel 2 is accommodated in the lower case 122 and the upper case 125. By disposing the reflector 123 on the opposite side of the backlight 3 from the liquid crystal panel 2, light leaking from the backlight 3 to the opposite side of the liquid crystal panel 2 can be reflected and contributed to display. Further, by disposing the diffusion plate 124 between the backlight 3 and the liquid crystal panel 2, luminance unevenness of the backlight 3 can be reduced. However, the reflecting plate 123 and the diffusing plate 124 are not necessarily used.

As shown in FIG. 14A, a configuration in which a plurality of backlights 3 are arranged in the screen of the liquid crystal display device 121 so that the light extraction regions RA, RB, RC are arranged in the vertical direction of the screen can be employed. . Alternatively, as shown in FIG. 14B, a configuration in which a plurality of backlights 3 are arranged in the screen of the liquid crystal display device 127 so that the light extraction areas RA, RB, RC are arranged in the horizontal direction of the screen is adopted. Can do.

Alternatively, as shown in FIGS. 15A and 15B, light extraction areas RA, RB, RC are provided only in a part of the longitudinal direction, and the other parts are elongated bar-shaped light guides that are areas where light is guided. A backlight 137 combining a plurality of 135 (three in this example) 135 may be used. In the plurality of light guides 135, regions where the light extraction regions RA, RB, RC are provided are shifted in the longitudinal direction. Therefore, when a plurality of light guides 135 are combined, the light extraction regions RA, RB, and RC are arranged along the longitudinal direction of the light guide 135.

For example, as shown in FIG. 15A, a plurality of backlights 137 may be arranged in the screen of the liquid crystal display device 131 so that the light extraction areas RA, RB, RC are arranged in the vertical direction of the screen. Alternatively, as shown in FIG. 15B, a plurality of backlights 137 may be arranged in the screen of the liquid crystal display device 133 so that the light extraction areas RA, RB, RC are arranged in the horizontal direction of the screen.

[Configuration example of lighting device]
Hereinafter, two configuration examples of the lighting device will be described with reference to FIGS. 16 to 17B.
FIG. 16 is a cross-sectional view of a lighting device which is a first configuration example. FIG. 17A and FIG. 17B are diagrams showing a lighting apparatus as a second configuration example, FIG. 17A is a plan view, and FIG. 17B is a cross-sectional view taken along the line AA ′ in FIG. 17A.

For example, in the illumination device 201 shown in FIG. 16, the first low refractive index body 8a having a refractive index of 1.3 is formed on the first main surface 5a side of the light guide 5 and the refractive index is on the second main surface 5b side. A second low refractive index body 8b of 1.4 is formed. A light scatterer 10 is stacked on the first low refractive index body 8a and the second low refractive index body 8b. Other configurations are the same as those of the first embodiment.

In the illumination device 201, the first main surface 5a depends on which of the two LEDs 7a and 7b provided on the first end surface 5c of the light guide 5 or the inclined surface 6a of the prism structure 6 is lit. It is possible to switch between emitting light from the side and emitting light from the second main surface 5b side. Therefore, it is possible to realize an illumination device that can switch the light emitting surface.

Further, in the lighting device 203 shown in FIG. 17A, a character portion 204 written “SHARP” is formed on one surface of the light guide 5. Corresponding to the character portion 204, as shown in FIG. 17B, a first low refractive index body 8a having a refractive index of 1.3 is formed on the first main surface 5a side of the light guide 5, and the character portion 204 is formed. The first low refractive index body 8a is not formed in any other part. A light scatterer 10 is stacked on the first low refractive index body 8a. That is, the character part 204 is a light extraction area in the above embodiment. Other configurations are the same as those of the first embodiment.

In this illuminating device 203, the light from the character portion 204 depends on which of the two LEDs 7a and 7b provided on the first end surface 5c of the light guide 5 or the inclined surface 6a of the prism structure 6 is lit. Or whether light is emitted from other than the character portion 204 can be switched. Therefore, according to this structure, the illuminating device which can be utilized as electronic signage apparatuses, such as a digital signage which can blink the character part 204, for example is realizable.

Note that the technical scope of the aspect of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the aspect of the present invention. For example, in the above embodiment, the light scatterer is provided on the low refractive index body in order to extract the light to the external space. Instead of this configuration, the light scatterer particles are dispersed inside the low refractive index body. Also good. Alternatively, a configuration may be adopted in which unevenness processing is performed on the upper surface of the low refractive index body and light is scattered by the unevenness. When this type of configuration is employed, a light scatterer on the low refractive index body is not necessary.

Further, for example, in the above-described embodiment, the light guide made of parallel plates is used, but instead of this configuration, a prism structure is formed on a part of the first main surface or the second main surface of the light guide. Or it is good also as a structure of making a part of 1st main surface or 2nd main surface of a light guide into an inclined surface. When this type of configuration is employed, when light propagating through the light guide is totally reflected by the prism structure or the inclined surface, the light propagation angle changes before and after that. Along with this, the incident angle of light to each light extraction region also changes before and after incidence on the prism structure and the inclined surface, so even if a low refractive index body having the same refractive index is used in a plurality of light extraction regions. , Light can be selectively extracted. According to this structure, the kind of material which comprises a low refractive index body can be reduced.

As an overall configuration of the liquid crystal display device, an optical member such as a light diffusion film or a prism sheet may be appropriately disposed between the liquid crystal panel and the backlight. By using these optical members, it is possible to further reduce luminance unevenness and adjust the light diffusion angle and direction. In addition, the specific configurations of the constituent elements in the backlight and the liquid crystal display device exemplified in the above embodiments, such as the material, dimensions, number, and manufacturing method, can be changed as appropriate. For example, instead of using a plate-like member as the light guide, a rod-like member may be used.

The aspect of the present invention can be used for a liquid crystal display device, various display devices that perform display using a dimmer element, and various illumination devices that perform illumination using a dimmer element.

DESCRIPTION OF SYMBOLS 1,121,127,131,133 ... Liquid crystal display device (display device), 2 ... Liquid crystal panel (display element), 3, 12, 16, 20, 22, 26, 28, 30, 137 ... Backlight (light control) Element), 5, 135 ... light guide, 6, 13 ... prism structure, 7a ... first LED (light emitting element), 7b ... second LED (light emitting element), 7c ... third LED (light emitting element), 8a ... first. Low refractive index body, 8b ... second low refractive index body, 8p ... low refractive index body for prism, 9 ... refractive index body, 14a ... first low refractive index body for prism, 14b ... second low refractive index body for prism , 17 ... 1st prism structure, 18 ... 2nd prism structure, 23 ... Mirror, 24 ... Low refractive index body for LED, 201, 203 ... Illumination device.

Claims (11)

A plurality of light emitting elements configured to control the amount of light emitted;
A light guide configured to propagate a plurality of light emitted from the plurality of light emitting elements while totally reflecting the light internally. While the plurality of lights are propagated, any one of the plurality of lights A light guide having a plurality of light extraction areas for extracting the light to the outside;
A prism structure that is disposed on the first main surface of the light guide, transmits light incident from at least one of the plurality of light emitting elements, and emits the light to the light guide;
Between the prism structure and the light guide, the refractive index is lower than the refractive index of the light guide, and the light propagating through the light guide is prevented from entering the prism structure. A low refractive index body,
The prism structure has one or more inclined surfaces having one or more types of inclination angles;
Among the plurality of light emitted from the plurality of light emitting elements, at least a part of the light path passes through the inclined surface,
At least two light extraction regions of the plurality of light extraction regions have different incident angle ranges in which light propagating through the light guide can be extracted to the outside,
A dimming element in which each of a plurality of lights emitted from the plurality of light emitting elements propagates in the light guide at different propagation angles. Among the plurality of light emitting elements, at least one light emitting element is disposed on the inclined surface of the prism structure,
The light according to claim 1, wherein light emitted from the light emitting element disposed on the inclined surface is incident on the light guide through the prism structure through the prism structure, and propagates inside the light guide. Optical element. Of the plurality of light emitting elements, at least one light emitting element is disposed on an end surface of the light guide,
The light control element according to claim 2, wherein light emitted from the light emitting element disposed on the end face enters the light guide from the end face and propagates through the light guide. The plurality of light emitting elements are respectively disposed on a plurality of inclined surfaces having different inclination angles of the prism structure,
The light emitted from the light emitting elements arranged on the plurality of inclined surfaces is incident on the light guide through the prism structure from the inclined surfaces, and propagates inside the light guide. Dimmer element. Among the plurality of light emitting elements, at least one light emitting element is disposed on the second main surface of the light guide opposite to the first main surface on which the prism structure is disposed,
The light emitted from the light emitting element disposed on the second main surface is incident on the prism structure through the light guide, reflected by the inclined surface, and then transmitted through the prism structure. The light control element according to claim 1, wherein the light control element is incident on a light guide and propagates through the light guide. Of the plurality of light emitting elements, at least one light emitting element is disposed on an end surface of the light guide,
The light control element according to claim 5, wherein light emitted from the light emitting element disposed on the end face enters the light guide from the end face and propagates through the light guide. The plurality of light emitting elements are disposed on a second main surface of the light guide opposite to the first main surface on which the prism structure is disposed,
Light emitted from the plurality of light emitting elements disposed on the second main surface is incident on the prism structure through the light guide, is reflected by the inclined surface, and then passes through the prism structure. The light control device according to claim 5, wherein the light control element is incident on the light guide and propagates through the light guide. The light control device according to claim 1, wherein a plurality of the prism structures are provided, and the plurality of prism structures have inclined surfaces having different inclination angles. Of the plurality of prism structures, at least one prism structure is disposed on one of the first main surface and the second main surface of the light guide, and the remaining prism structures are the ones of the light guide. The light control element of Claim 8 arrange | positioned at the other of the 1st main surface and the said 2nd main surface. A display device comprising: the light control element according to claim 1; and a display element that performs display using light emitted from the light control element. A lighting device comprising the light control device according to claim 1.

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