WO2012043361A1

WO2012043361A1 - Illumination device and display device

Info

Publication number: WO2012043361A1
Application number: PCT/JP2011/071576
Authority: WO
Inventors: 國政文枝; 石田壮史
Original assignee: シャープ株式会社
Priority date: 2010-09-29
Filing date: 2011-09-22
Publication date: 2012-04-05

Abstract

The disclosed illumination device (3) is provided with a light-emitting diode (light source) (4) and a light guide plate (5). The light guide plate (5) is provided with a light guide body (6), a first prism (optical path changer) (10) which gradually changes the angle of the light guided through the inside of the light guide body (6), a low refractive index layer (7) with a refractive index lower than that of the light guide body (6), and a prism layer (8) with a refractive index higher than that of the low refractive index layer (7). The prism layer (8) is provided with multiple prisms (8a) having three faces (P1-P3), wherein said three faces (P1-P3) are provided such that light incident from the low refractive index layer (7) is completely reflected in the prisms (8a) sequentially by the three faces (P1-P3) and is emitted from the emitting face (6b) of the light guide body (6) towards a liquid crystal panel (2).

Description

Lighting device and display device

The present invention relates to a lighting device, particularly a lighting device including a light guide plate, and a display device using the same.

In recent years, for example, liquid crystal display devices have been widely used in liquid crystal televisions, monitors, mobile phones and the like as flat panel displays having features such as thinness and light weight compared to conventional cathode ray tubes. Such a liquid crystal display device includes an illumination device (backlight) that emits light and a liquid crystal panel that displays a desired image by serving as a shutter for light from a light source provided in the illumination device. It is.

In addition, the illumination device is roughly classified into a direct type and an edge light type depending on the arrangement of the light source with respect to the liquid crystal panel as an object to be irradiated with light, but the liquid crystal display device has recently been made thinner than the direct type. An edge light type that is easy to draw is generally used. That is, in the edge light type lighting device, the light source is arranged on the side of the liquid crystal panel to reduce the thickness, and a light guide plate having an emission surface arranged to face the non-display surface of the liquid crystal panel is provided. The light from the light source is converted into planar illumination light and applied to the liquid crystal panel.

In addition, in a conventional lighting device, for example, as described in Patent Document 1 below, a light guide body into which light from a light source enters, an air layer on the opposite side of the light guide body from the liquid crystal panel A light guide plate having a first light transmission layer, a second light transmission layer, and a micro mirror that are sequentially provided integrally without using a light source is used, and the light use efficiency of the light source can be improved. It was.

That is, as the light guide of this conventional lighting device, the one having a wedge-shaped cross section in which the thickness dimension between the top surface and the bottom surface becomes smaller as the distance from the light source is increased. In this conventional lighting device, the first light transmission layer has a refractive index smaller than that of the light guide, and the second light transmission layer has a refractive index substantially the same as that of the light guide. It was. Further, a plurality of concave portions (prisms) having inclined surfaces are formed on the micro mirror side of the second light transmission layer, and the second light transmission layer is embedded so that the micro mirror embeds the plurality of concave portions. Are integrally provided.

In this conventional lighting device, light from the light source is guided while being repeatedly reflected between the top surface and the bottom surface in the light guide. At this time, the incident angle of the light with respect to the bottom surface of the light guide is changed so as to be gradually reduced, and the guided light enters the first light transmission layer. Thereafter, the light incident on the first light transmission layer is incident on the second light transmission layer, and then is collected by the micro mirror and reflected to the liquid crystal panel side.

JP 2001-110218 A

However, in the conventional lighting apparatus as described above, the light from the light source is reflected using a micro mirror made of a metal film such as aluminum or nickel, and is emitted to the liquid crystal panel (irradiated object) as emitted light. It was. For this reason, in this conventional illumination device, the light absorption (loss) generated by the micro mirror cannot be reduced, and the light use efficiency of the light source is significantly reduced.

In view of the above problems, an object of the present invention is to provide an illuminating device excellent in light utilization efficiency capable of reducing an optical loss and obtaining emitted light, and a display device using the illuminating device.

In order to achieve the above object, an illumination device according to the present invention includes a light source and a light guide plate that guides light from the light source in a predetermined propagation direction and emits the light to an object to be irradiated. Because
The light guide plate is
A light guide including a light incident surface for receiving light from the light source, an emission surface for emitting light incident from the light incident surface to the irradiated object side, and a facing surface facing the emission surface. When,
An optical path changing unit that is provided on the light exit surface side or the opposing surface side of the light guide and gradually changes the angle of light guided through the light guide;
A low refractive index layer having a refractive index lower than the refractive index of the light guide, and provided on the opposite surface side of the light guide;
The low refractive index layer is provided on the opposite side of the light guide, and includes a prism layer having a refractive index higher than the refractive index of the low refractive index layer,
The prism layer is provided with a plurality of prisms having at least three surfaces,
In the prism, at least the light incident from the low refractive index layer side is sequentially totally reflected by the at least three surfaces and emitted from the emission surface of the light guide to the irradiated object side. Three surfaces are provided.

In the illuminating device configured as described above, the light guide having the light incident surface, the light exit surface, and the opposing surface, and an optical path changing unit that gradually changes the angle of light guided through the inside of the light guide. The light guide plate is provided with a low refractive index layer having a refractive index lower than the refractive index of the light guide while being provided on the opposite surface side of the light guide. Thereby, in the light guide plate, the light from the light source that has entered from the light entrance surface can be guided in a predetermined propagation direction away from the light entrance surface, and the light from the light source from the entire light exit surface of the light guide. Can be emitted. The light guide plate is provided with a prism layer having a refractive index higher than that of the low refractive index layer on the side opposite to the light guide of the low refractive index layer. It is possible to limit the angle range of light entering the light. As a result, light in a limited angle range is reflected to the exit surface side, so that a prism with little light loss can be formed. Further, the prism layer is provided with a plurality of prisms having at least three surfaces. In the prism, light incident from the low refractive index layer side is sequentially totally reflected by at least three surfaces, and the light exit surface of the light guide The at least three surfaces are provided so as to be emitted to the irradiated object side. Thus, unlike the conventional example, it is possible to configure an illumination device with excellent light utilization efficiency that can reduce the light loss and obtain outgoing light.

In the illumination device, it is preferable that the angles of the surfaces are set so that the incident angle of light is not less than a critical angle on the at least three surfaces.

In this case, the light loss can be reduced and the light emitted to the irradiated object can be obtained more reliably.

In the illumination device, it is preferable that a plurality of the prisms are continuously formed in the normal direction of the light incident surface of the light guide in the prism layer.

In this case, the emitted light to the irradiated object can be emitted more uniformly, and it is possible to reliably prevent uneven brightness from occurring in the emitted light to the irradiated object.

In the illumination device, it is preferable that in the prism layer, the plurality of prisms have substantially the same shape and have the same size.

In the illumination device, the low refractive index layer is attached to the facing surface of the light guide,
The prism layer may be attached to a surface of the low refractive index layer opposite to the light guide.

In this case, the light guide plate can be easily thinned, and a compact lighting device can be easily configured.

Further, in the illumination device, a prism integrally formed on the light exit surface of the light guide may be used as the optical path changing unit.

In this case, a light guide plate that is easy to manufacture can be configured.

In the illumination device, in each of the plurality of prisms, a surface on which light incident from the low refractive index layer side is first totally reflected may be set at an angle of 90 degrees or less with respect to the propagation direction. Good.

In this case, the prism layer can be easily formed.

In the illumination device, the prism layer may be provided with a light scattering function for scattering light.

In this case, the angle range of the emitted light can be widened and the viewing angle can be increased.

Further, in the illumination device, it is preferable that a reflection portion that reflects light emitted from the prism layer to the prism layer side is provided on the opposite side of the prism layer from the low refractive index layer.

In this case, the light utilization efficiency of the light source can be further improved.

Moreover, in the said illuminating device, While providing the reflective polarizing plate provided in the said to-be-irradiated object side of the said light-guide plate,
In each of the plurality of prisms, one surface included in the at least three surfaces may be provided in parallel to the reflecting portion.

In this case, the brightness of the emitted light to the irradiated object can be improved by the reflective polarizing plate. In addition, since one surface included in the at least three surfaces is provided in parallel to the reflecting portion, the front luminance in the emitted light can be reliably improved, and the emitted light by the reflective polarizing plate can be improved. The brightness improvement effect can be increased.

Further, in the illumination device, a first light diffusion unit that diffuses light from the light source in a direction orthogonal to the propagation direction is provided on the emission surface side or the opposed surface side of the light guide. Also good.

In this case, more uniform outgoing light can be emitted, and it is possible to more surely prevent uneven brightness in the outgoing light to the irradiated object.

Further, in the illumination device, a second light diffusion unit that diffuses light from the light source in a direction orthogonal to the propagation direction may be provided on the light incident surface of the light guide.

Further, the display device according to the present invention is characterized by using any one of the lighting devices described above.

In the display device configured as described above, a lighting device with excellent light utilization efficiency that can reduce the light loss and obtain the emitted light is used. Therefore, the display device has high brightness and labor saving. Can be configured easily.

In the display device, a liquid crystal panel may be used as the irradiated object.

In this case, a high-brightness and labor-saving liquid crystal display device can be easily configured.

According to the present invention, it is possible to provide an illuminating device excellent in light utilization efficiency capable of reducing light loss and obtaining outgoing light, and a display device using the same.

FIG. 1 is a diagram for explaining an illumination device and a liquid crystal display device according to a first embodiment of the present invention. FIG. 2 is a perspective view illustrating a main configuration of the lighting device illustrated in FIG. 1. FIG. 3 is a side view illustrating a specific configuration of the illumination device illustrated in FIG. 1. FIG. 4 is an enlarged side view showing a main part configuration of the light guide plate of the illumination device shown in FIG. 1. FIG. 5 is a diagram illustrating the configuration of the second prism provided on the light exit surface of the light guide in the illumination device illustrated in FIG. 1. FIG. 6 is a diagram illustrating a configuration of a third prism provided on the light incident surface of the light guide in the illumination device illustrated in FIG. 1. FIG. 7 is a diagram illustrating an illumination device and a liquid crystal display device according to the second embodiment of the present invention. FIG. 8 is an enlarged side view showing the main configuration of the light guide plate of the illumination device shown in FIG. FIG. 9A and FIG. 9B are diagrams for explaining an operation example in the illumination devices of the first and second embodiments, respectively. FIG. 10 is an enlarged side view showing the main configuration of the light guide plate of the illumination device according to the third embodiment of the present invention. Fig.11 (a) and FIG.11 (b) are the figures explaining the operation example in the illuminating device of 1st and 3rd embodiment, respectively.

Hereinafter, preferred embodiments of the illumination device of the present invention and a display device using the same will be described with reference to the drawings. In the following description, the case where the present invention is applied to a transmissive liquid crystal display device will be described as an example. Moreover, the dimension of the structural member in each figure does not faithfully represent the actual dimension of the structural member, the dimensional ratio of each structural member, or the like.

[First Embodiment]
FIG. 1 is a diagram for explaining an illumination device and a liquid crystal display device according to a first embodiment of the present invention. FIG. 2 is a perspective view illustrating a main configuration of the lighting device illustrated in FIG. 1. 1, the liquid crystal display device 1 according to the present embodiment includes a liquid crystal panel 2 in which the upper side of FIG. 1 is installed as a viewing side (display surface side), and a non-display surface side of the liquid crystal panel 2 (lower side of FIG. 1). And an illuminating device 3 of the present invention that generates illumination light for illuminating the liquid crystal panel 2. In the present embodiment, the liquid crystal panel 2 and the illumination device 3 are integrally assembled to constitute a transmissive liquid crystal display device 1.

The liquid crystal panel 2 includes a color filter substrate 2a and an active matrix substrate 2b constituting a pair of substrates, and constitutes an object to be irradiated with planar illumination light from the illumination device 3. Further, the color filter substrate 2a and the active matrix substrate 2b are made of a transparent synthetic resin such as a flat transparent glass material or an acrylic resin, and between the color filter substrate 2a and the active matrix substrate 2b. The liquid crystal layer (not shown) is sandwiched.

The active matrix substrate 2b constitutes one of the pair of substrates. In the active matrix substrate 2b, pixel electrodes or thin film transistors (thin film transistors (thin film transistors)) are formed in accordance with a plurality of pixels included in the display surface of the liquid crystal panel 2. A TFT (Thin Film Transistor) or the like is formed between the liquid crystal layer (not shown). On the other hand, the color filter substrate 2a constitutes the other of the pair of substrates, and the color filter substrate 2a has a color filter, a counter electrode, and the like formed between the liquid crystal layer (not shown). )

Further, the liquid crystal panel 2 is provided with a control device (not shown) that controls the driving of the liquid crystal panel 2, and operates the liquid crystal layer in units of pixels to drive the display surface in units of pixels. A desired image is displayed on the display surface.

The liquid crystal mode and pixel structure of the liquid crystal panel 2 are arbitrary. Moreover, the drive mode of the liquid crystal panel 2 is also arbitrary. That is, as the liquid crystal panel 2, any liquid crystal panel that can display information can be used. Therefore, the detailed structure of the liquid crystal panel 2 is not shown in FIG.

Referring also to FIG. 2, the illumination device 3 includes a light emitting diode 4 as a light source and a light guide plate 5 disposed to face the light emitting diode 4. In the illumination device 3, a plurality of, for example, three light emitting diodes 4 are arranged on a straight line along a direction (X direction) perpendicular to the paper surface of FIG. 1. Each of these light-emitting diodes 4 includes, for example, a blue light-emitting diode and a white light-emitting diode that emits white light with a phosphor, or red (R), green (G), and blue (B) light-emitting diodes. A so-called 3 in 1 white light emitting diode is used. The light emitting diode 4 may not be white.

The light guide plate 5 is configured in a substantially rectangular parallelepiped shape, and receives light from the light emitting diode 4. Further, the light guide plate 5 is configured to guide light from the light emitting diode 4 in a predetermined propagation direction (Z direction) and to emit the light to the liquid crystal panel (object to be irradiated) 2. Further, as will be described later in detail, the light guide plate 5 collects light while concentrating the light emitted to the liquid crystal panel 2 while preventing the occurrence of luminance unevenness as much as possible. The liquid crystal panel 2 is irradiated with emitted light having a luminance or higher. Thereby, in the illuminating device 3 of this embodiment, installation of optical sheets, such as a diffusion plate and a condensing lens, can be abbreviate | omitted between the liquid crystal panel 2 and the light-guide plate 5. FIG.

Here, the illumination device 3 of the present embodiment will be specifically described with reference to FIGS.

FIG. 3 is a side view illustrating a specific configuration of the lighting device shown in FIG. FIG. 4 is an enlarged side view showing a main part configuration of the light guide plate of the illumination device shown in FIG. 1. FIG. 5 is a diagram illustrating the configuration of the second prism provided on the light exit surface of the light guide in the illumination device illustrated in FIG. 1. FIG. 6 is a diagram illustrating a configuration of a third prism provided on the light incident surface of the light guide in the illumination device illustrated in FIG. 1. In FIGS. 1 and 3, the second and third prisms are not shown for the sake of simplicity. In FIG. 5, the third prism is not shown for simplification of the drawing. In FIG. 6, the first and second prisms are not shown for simplification of the drawing.

As illustrated in FIG. 3, in the illumination device 3 of the present embodiment, the light emitting diode 4 is disposed to face one side surface of the light guide plate 5. And in the illuminating device 3, as illustrated by arrow L1 of FIG. 3, the light from the light emitting diode 4 is guide | induced to the said propagation direction (Z direction), and it radiate | emits suitably to the liquid crystal panel 2 (FIG. 1) side. (Details will be described later). In the illuminating device 3, the reflection plate 9 as a reflection portion is disposed below the light emitting diode 4 and the light guide plate 5 (lower side in the Y direction), and reflects light from the light guide plate 5 to the light guide plate 5. Is configured to do. For example, a dielectric multilayer mirror, a silver-coated reflector, or a reflector made of white PET resin is used as the reflector 9.

The light guide plate 5 has a substantially rectangular parallelepiped light guide 6 made of a transparent material having a refractive index n1, and a refractive index n2 attached to the lower surface (opposing surface 6c) of the light guide 6 without an air layer. A low refractive index layer 7 made of a transparent material and a transparent material having a refractive index n3 attached to the lower surface of the low refractive index layer 7 (surface 7a opposite to the light guide 6) without an air layer. A prism layer 8 is provided.

Specifically, the light guide 6 is made of a transparent synthetic resin such as polycarbonate resin or acrylic resin. The low refractive index layer 7 is made of a transparent synthetic resin having a refractive index n2 lower than the refractive index n1 of the light guide 6, such as a fluorine-based acrylate resin. The prism layer 8 is made of a transparent synthetic resin having a refractive index n3 higher than the refractive index n2 of the low refractive index layer 7, such as a polycarbonate resin or an acrylic resin. Furthermore, although the light guide 6, the low refractive index layer 7, and the prism layer 8 use a sheet that is an integral unit of three layers, they may be attached sequentially by a UV curable resin or an adhesive layer (not shown).

The light guide 6 opposes the light incident surface 6a for receiving light from the light emitting diode 4, the light emitting surface 6b for emitting light incident from the light incident surface 6a to the liquid crystal panel 2 side, and the light emitting surface 6b. The counter surface 6c is provided.

Further, the normal direction of the light incident surface 6 a of the light guide 6 so that the plurality of prisms 8 a covers the light exit surface 6 b of the light guide 6 on the surface of the prism layer 8 opposite to the low refractive index layer 7. They are continuously formed in the (Z direction) with no gaps on the surface. These prisms 8a are formed by imprinting, injection, or the like, and the plurality of prisms 8a are formed in substantially the same shape and in the same size. Further, as will be described in detail later, each of the plurality of prisms 8a is provided with three surfaces. The light incident from the low refractive index layer 7 side is totally totally reflected and emitted to the liquid crystal panel 2 side. It is like that.

In addition, a first prism (prism) 10 is integrally formed on the light exit surface 6 b of the light guide 6 as an optical path changing portion that gradually changes the angle of light guided through the light guide 6. Has been. Specifically, as shown in FIG. 4, the exit surface 6b is inclined at an inclination angle φ1 with respect to the parallel portion 10a parallel to the propagation direction (Z direction) and the parallel portion 10a (propagation direction). A plurality of first prisms 10 having vertical portions 10c erected with respect to the inclined portion 10b are formed along the Z direction so as to be parallel to the inclined portion 10b and the Y direction. Further, the first prism 10 is configured to overlap with a later-described second prism 11 formed in the X direction on the emission surface 6b. In the light guide 6, the angle of light guided through the inside of the light guide 6 is gradually changed by the first prism 10 as illustrated by the arrow L <b> 1 in FIG. 4. .

Further, as illustrated in FIG. 5, the light guide 6 is provided with a second prism 11 that is formed in a concave shape on the light exit surface 6 b and is configured integrally with the first prism 10. ing. The second prism 11 constitutes a first light diffusion portion that diffuses light from the light emitting diode 4 in a direction (X direction) orthogonal to the propagation direction, and is inclined obliquely downward to the right in FIG. It has the inclined part 11a and the inclined part 11b inclined in the diagonally lower left direction in FIG. Further, since the second prism 11 is configured integrally with the first prism 10, it is divided by the vertical portion 10c of the first prism 10 in the Z direction (direction perpendicular to the paper surface of FIG. 5). ing.

Further, as illustrated in FIG. 6, the light guide 6 is provided with a third prism 12 which is formed in a concave shape and integrally with the light incident surface 6 a. The third prism 12 constitutes a second light diffusion portion that diffuses light from the light emitting diode 4 in a direction (X direction) orthogonal to the propagation direction, and is inclined in the diagonally upper right direction in FIG. It has the inclined part 12a and the inclined part 12b inclined in the diagonally upward left direction in FIG.

Further, as shown in FIG. 4, three surfaces P1, P2, and P3 are formed on each prism 8a of the prism layer 8. In these three surfaces P1 to P3, as illustrated by an arrow L1 in FIG. 4, light incident from the low refractive index layer 7 side is sequentially totally reflected in the order of the surface P3, the surface P2, and the surface P1. It is like that. That is, on the three surfaces P1 to P3, the angles of the surfaces are set so that the incident angle of light is not less than the critical angle. Specifically, as shown in FIG. 4, the plane P1 is configured to have an inclination angle of φP1 with respect to the propagation direction (Z direction). Further, the plane P2 is configured to have an inclination angle of φP2 with respect to the propagation direction (Z direction), and the plane P3 is configured to have an inclination angle of φP3 with respect to the propagation direction (Z direction). On the surface P3 where light incident from the low refractive index layer 7 side is first totally reflected, the inclination angle φP3 is set to an angle of 90 degrees or less with respect to the propagation direction (Z direction).

Hereinafter, the operation in which light from the light emitting diode 4 is guided through the light guide plate 5 and emitted to the liquid crystal panel 2 will be described in detail with reference to FIG.

In the light guide plate 5, the light from the light emitting diode 4 entering from the light incident surface 6 a of the light guide 6 reaches the interface between the light guide 6 and the low refractive index layer 7 as illustrated in FIG. 4. At this interface, light whose incident angle θ1 is larger than the critical angle θ expressed by the following equation (1) is reflected to the inner side of the light guide 6, and as shown by an arrow L1 in FIG. The light guide 6 is guided inside.

θ = arcsin (n2 / n1) ――― (1)
Further, when the light guided inside the light guide 6 reaches the inclined portion 10b of the first prism 10, the angle of light guided by the inclined portion 10b is changed, and the inside of the light guide 6 is changed. Is reflected. When the light is incident on the interface between the light guide 6 and the low refractive index layer 7 at an angle equal to or smaller than the critical angle θ, the light enters the low refractive index layer 7 as indicated by an arrow L1 in FIG. After entering the light, the light enters the prism layer 8. Then, the direction of light is converted to the direction of the emission surface 6b by the prism 8a of the prism layer 8, and the light is emitted from the emission surface 6b. In other words, the angle range of light entering the prism layer 8 can be limited by the low refractive index layer 7.

Specifically, the angle range of the angle (incident angle) θ2 of the light incident on the low refractive index layer 7 is expressed by the following inequality (1) using the tilt angle φ1.

θ-2 × φ1 ≦ θ2 ≦ θ ――― (1)
Further, the angle range of the angle (incident angle) θ2 ′ of the light entering the prism layer 8 is represented by the following inequality (2).

arcsin (n1 × sin (θ−2 × φ1) / n3 ≦ θ2 ′ ≦ arcsin (n1 × sin (θ) / n3) ――― (2)
In the prism 8a, as described above, the angles of the surfaces are set so that the light incident angle is equal to or larger than the critical angle on the three surfaces P1 to P3. For this reason, the light incident from the low refractive index layer 7 side first strikes the surface P3 and is totally reflected. Thereafter, the totally reflected light strikes the surface P2 and is totally reflected, and further strikes the surface P1 to be totally reflected, changes the angle in the direction of the exit surface 6b, and exits from the exit surface 6b.

Further, when the refractive index n3 of the prism layer 8 satisfies the following inequality (3), even if the inclination angle φP3 of the surface P3 is 90 degrees or less, the incident angle of light on the surface P3 becomes a critical angle or more, The surface P3 can be a total reflection surface.

90 ° -θ2 '≧ arcsin (1 / n3) ――― (3)
In the illuminating device 3 of the present embodiment configured as described above, the light guide 6 having the light incident surface 6 a, the light exit surface 6 b, and the facing surface 6 c, and the light guided through the light guide 6. A first prism (optical path changing portion) 10 that gradually changes the angle and a low refractive index layer 7 that is provided on the facing surface 6 c side of the light guide 6 and has a lower refractive index than the refractive index of the light guide 6. Are provided on the light guide plate 5. Thereby, in the light guide plate 5 of the present embodiment, the light from the light emitting diode (light source) 4 entering from the light incident surface 6a can be guided in a predetermined propagation direction away from the light incident surface 6a. Light from the light emitting diode 4 can be emitted from the entire emission surface 6 b of the light guide 6. Further, the brightness of the emitted light can be made uniform by adjusting the density of the first prism 10 in the plane.

In the light guide plate 5 of the present embodiment, a prism layer 8 having a refractive index higher than the refractive index of the low refractive index layer 7 is provided on the side opposite to the light guide 6 of the low refractive index layer 7. Therefore, the angle range of light entering the prism layer 8 by the low refractive index layer 7 can be limited. As a result, in the illuminating device 3 of the present embodiment, the light from the light exit surface 6b of the light guide 6, that is, the light emitted from the light guide plate 5 to the liquid crystal panel (object to be irradiated) 2 can be condensed, so that high luminance is achieved. Obtainable.

Further, the prism layer 8 of the present embodiment is provided with a plurality of prisms 8a having three surfaces P1 to P3. In the prism 8a, light incident from the low refractive index layer 7 side is sequentially applied to the three surfaces P1 to P3. The three surfaces P1 to P3 are provided so as to be totally reflected and emitted from the emission surface 6b of the light guide 6 to the liquid crystal panel 2 side. In other words, unlike the above-described conventional example, the illumination device 3 of the present embodiment emits light by sequentially performing total reflection on the three surfaces P1 to P3 of the prism layer 8 without providing a micro mirror made of a metal film. Light from the diode 4 is condensed and emitted to the liquid crystal panel 2 side. Thereby, in this embodiment, unlike the above-described conventional example, it is possible to configure the illumination device 3 excellent in light utilization efficiency that can reduce the light loss and obtain the emitted light.

In this embodiment, the angles of the surfaces are set so that the incident angle of light is not less than the critical angle on the three surfaces P1 to P3 of the prism 8a. Thereby, in this embodiment, light loss can be reduced and the emitted light to the liquid crystal panel 2 can be obtained more reliably.

In the present embodiment, since the plurality of prisms 8a are continuously formed in the normal direction of the light incident surface 6a of the light guide 6, the light emitted to the liquid crystal panel 2 is emitted more uniformly. It is possible to reliably prevent uneven brightness in the light emitted to the liquid crystal panel 2.

In the present embodiment, the plurality of prisms 8a have substantially the same shape and are formed to have substantially the same size, so that the light emitted to the liquid crystal panel 2 is emitted more uniformly. Therefore, it is possible to reliably prevent uneven brightness from occurring in the light emitted to the liquid crystal panel 2.

In this embodiment, in each of the plurality of prisms 8a, the surface P3 on which the light incident from the low refractive index layer 7 side is first totally reflected is set at an angle of 90 degrees or less with respect to the propagation direction (Z direction). Has been. Accordingly, when the prism 8a is formed on the prism layer 8 using imprint or injection, the mold can be easily separated, and the prism layer 8 can be easily formed.

In the present embodiment, a reflecting plate (reflecting portion) 9 that reflects the light emitted from the prism layer 8 toward the prism layer 8 is provided on the opposite side of the prism layer 8 from the low refractive index layer 7. Therefore, the light use efficiency of the light emitting diode 4 can be further improved.

In the present embodiment, a second prism (first light diffusion portion) 11 that diffuses light from the light emitting diode 4 in a direction orthogonal to the propagation direction is provided on the light exit surface 6 b side of the light guide 6. Therefore, it is possible to emit more uniform outgoing light, and more reliably prevent luminance unevenness from occurring in the outgoing light to the liquid crystal panel 2.

In the present embodiment, the light incident surface 6 a of the light guide 6 is provided with a third prism (second light diffusion portion) 12 that diffuses the light from the light emitting diode 4 in a direction orthogonal to the propagation direction. Therefore, it is possible to emit more uniform outgoing light, and more reliably prevent luminance unevenness from occurring in the outgoing light to the liquid crystal panel 2.

In the present embodiment, the illumination device 3 with excellent light utilization efficiency capable of reducing the optical loss and obtaining the emitted light is used. Therefore, the liquid crystal display device 1 with high luminance and labor saving can be obtained. It can be easily configured.

[Second Embodiment]
FIG. 7 is a diagram illustrating an illumination device and a liquid crystal display device according to the second embodiment of the present invention. FIG. 8 is an enlarged side view showing the main configuration of the light guide plate of the illumination device shown in FIG. In the figure, the main difference between this embodiment and the first embodiment is that a reflective polarizing plate is provided on the liquid crystal panel (illuminated object) side of the light guide plate, and each of the prisms includes the three This is that one surface included in the surface is provided in parallel to the reflecting plate (reflecting portion). In addition, about the element which is common in the said 1st Embodiment, the same code | symbol is attached | subjected and the duplicate description is abbreviate | omitted.

That is, as shown in FIG. 7, in the liquid crystal display device 1 of the present embodiment, a reflective polarizing plate 13 is provided between the liquid crystal panel 2 and the illumination device 3. As shown by the arrow L2 or the arrow L3 in FIG. 7, the reflective polarizing plate 13 transmits or reflects light according to the polarization axis of light, and increases the luminance of light emitted to the liquid crystal panel 2. It functions as a brightness enhancement film.

Further, as illustrated in FIG. 8, in the illumination device 3 of the present embodiment, in each prism 18 a of the prism layer 18, one surface P2 among the three surfaces P1 to P3 is parallel to the reflecting plate 9. It is formed as follows. That is, the surface P2 is configured by a horizontal plane parallel to the propagation direction (Z direction). Thereby, in the illuminating device 3 of this embodiment, the front brightness | luminance with the emitted light to the liquid crystal panel 2 can be improved reliably.

Here, with reference to FIG. 9 (a) and FIG. 9 (b), the effect obtained by setting the surface P2 to the horizontal plane will be described in detail.

FIG. 9A and FIG. 9B are diagrams for explaining an operation example in the illumination devices of the first and second embodiments, respectively.

As illustrated by the arrow L4 in FIG. 9A, when the light reflected by the reflective polarizing plate 13 is incident on the light guide 6 near 90 degrees, the light is converted into a prism. At layer 8 the direction is changed. For this reason, as illustrated by the arrow L4 in FIG. 9A, even when reflected by the reflecting plate 9, there is little light returning to the front direction (90-degree direction, that is, Y direction) of the emission surface 6b, and the front luminance is reduced. Improvement effect is small.

On the other hand, in this embodiment, since the surface P2 is configured in the horizontal plane, as illustrated by the arrow L5 in FIG. 9B, the light is emitted from the surface P2 in the direction of the reflecting plate 9, When the light reflected by the reflecting plate 9 enters the prism layer 18 from the surface P2, it is emitted from the emission surface 6b at an angle in the vicinity of 90 degrees and can be reused. For this reason, in this embodiment, front luminance can be improved and the luminance improvement effect by the reflective polarizing plate 13 can be increased.

With the above configuration, the present embodiment can achieve the same operations and effects as the first embodiment. In the present embodiment, the reflective polarizing plate 13 is provided on the light guide plate 5 on the liquid crystal panel (irradiated object) 2 side. Thereby, the brightness | luminance of the emitted light to the liquid crystal panel 2 can be improved. Further, in each of the plurality of prisms 18a of the present embodiment, the surface P2 is provided in parallel to the reflecting plate 9, so that the front luminance with the emitted light can be improved reliably, and the output from the reflective polarizing plate 13 can be improved. The effect of improving the brightness of incident light can be increased.

[Third Embodiment]
FIG. 10 is an enlarged side view showing the main configuration of the light guide plate of the illumination device according to the third embodiment of the present invention. In the figure, the main difference between the present embodiment and the first embodiment is that a light scattering function for scattering light is added to the prism layer. In addition, about the element which is common in the said 1st Embodiment, the same code | symbol is attached | subjected and the duplicate description is abbreviate | omitted.

That is, as shown in FIG. 10, in the illuminating device 3 of this embodiment, in each prism 28a of the prism layer 28, for example, the surfaces P1 and P3 are configured as curved surfaces, thereby providing a light scattering function for scattering light. Has been. Thereby, in the illuminating device 3 of this embodiment, generation | occurrence | production of the brightness nonuniformity by the emitted light to the liquid crystal panel 2 can be prevented more reliably. Further, since the angle range of the emitted light can be widened, the liquid crystal panel 2 can have a wide viewing angle.

Here, with reference to FIG. 11A and FIG. 11B, the effect of making the surfaces P1 and P3 curved surfaces will be described in detail.

FIG. 11 (a) and FIG. 11 (b) are diagrams for explaining an operation example in the illumination devices of the first and third embodiments, respectively.

When the surfaces P1 and P3 are configured as mirror surfaces instead of curved surfaces, the light that is sequentially totally reflected by the surfaces P1 to P3 and emitted to the liquid crystal panel 2 is indicated by arrows L6 and L6 ′ in FIG. As illustrated, the light is emitted to the liquid crystal panel 2 without substantially spreading. Specifically, when the angle θ2 of the light entering the low refractive index layer 7 satisfies the following inequality (4):
θ ≦ θ2 ≦ θ-2 × φ1 ――― (4)
The angular spread θw of the light returning to the low refractive index layer 7 is expressed by the following equation (2).

θw = 2 × φ1 ――― (2)
On the other hand, by forming the surfaces P1 and P3 into curved surfaces, the angle spread θw of the light returning to the low refractive index layer 7 is set to 2 as illustrated by arrows L7 and L7 ′ in FIG. It can be made larger than xφ1.

With the above configuration, the present embodiment can achieve the same operations and effects as the first embodiment. Further, in the present embodiment, in each prism 28a of the prism layer 28, the surfaces P1 and P3 are curved so that a light scattering function for scattering light is given to the surfaces P1 and P3. Thereby, in the present embodiment, it is possible to emit more uniform emitted light, and more reliably prevent uneven brightness from occurring in the emitted light to the liquid crystal panel (object to be irradiated) 2, and The angle range of incident light can be expanded. As a result, in this embodiment, the viewing angle characteristics of the liquid crystal panel 2 can be expanded (wide viewing angle), and the display quality of the liquid crystal display device 1 can be improved.

In addition, it may replace with said curved surface, and the structure which provides a light-scattering function to the said surfaces P1 and P3 may be given to the surfaces P1 and P3, for example by carrying out embossing and uneven | corrugated formation on the surface.

It should be noted that all of the above embodiments are illustrative and not restrictive. The technical scope of the present invention is defined by the claims, and all modifications within the scope equivalent to the configurations described therein are also included in the technical scope of the present invention.

For example, in the above description, the case where the present invention is applied to a transmissive liquid crystal display device has been described. However, the lighting device of the present invention is not limited to this, and a transflective liquid crystal display device or a liquid crystal display device is not limited thereto. The present invention can be applied to various display devices such as a projection display device using a panel as a light valve.

In addition to the above explanation, the present invention is installed on a light box for illuminating X-ray film or photographic negatives for irradiating light to make it easy to see, or on a signboard or a wall in a station. It can be suitably used as a lighting device for a light emitting device that illuminates advertisements and the like.

In the above description, the light emitting diode is used as the light source. However, the light source of the present invention is not limited to this, and a discharge tube such as a cold cathode fluorescent tube or a hot cathode fluorescent tube is used. You can also

In the above description, the low refractive index layer is attached to the opposite surface of the light guide without an air layer, and the prism layer is a light guide with a low refractive index layer without an air layer. The case where it affixed on the surface on the opposite side to was demonstrated. However, in the lighting device of the present invention, the low refractive index layer having a lower refractive index than the refractive index of the light guide is provided on the opposite surface side of the light guide, and the refractive index higher than the refractive index of the low refractive index layer. The prism layer is not limited as long as the prism layer is provided on the side opposite to the light guide of the low refractive index layer.

Specifically, a transparent intermediate layer made of a material having a refractive index lower than that of the light guide and greater than that of the low refractive index layer may be provided between the light guide and the low refractive index layer. Good. Further, a transparent intermediate layer made of a material having a refractive index lower than that of the prism layer and larger than that of the low refractive index layer may be provided between the low refractive index layer and the prism layer. Furthermore, an air layer can also be used as the low refractive index layer.

However, in the case where the light guide, the low refractive index layer, and the prism layer are integrally formed with each other as in each of the above embodiments, the light guide plate can be easily made thinner. This is preferable in that a compact lighting device can be easily configured.

In the above description, the case where the prism layer is provided with a prism having three surfaces has been described. However, the prism layer of the present invention includes a plurality of prisms having at least three surfaces. The at least three surfaces are provided so that light incident from the low refractive index layer side is sequentially totally reflected by at least three surfaces and emitted from the light emitting surface to the irradiated object side. Any prism may be used. For example, a prism having four surfaces that can sequentially reflect light incident from the low refractive index layer side and emit the light toward the irradiated object side may be used.

In the above description, the case where the first prism (prism) formed integrally with the light exit surface of the light guide is used as the optical path changing unit has been described. There is no limitation as long as it is provided on the light exiting surface side or the opposing surface side of the light guide and the angle of light guided through the light guide is gradually changed.

Specifically, as the optical path changing unit, a saw-shaped prism array or a lenticular lens configured separately from the light guide, or a lens array such as a V-shaped groove, the light exit surface of the light guide or A rough surface having a dot shape or the like on the opposite surface can also be used.

However, the case where the first prism formed integrally on the light exit surface of the light guide is used as in each of the above embodiments is preferable in that a light guide plate that can be easily manufactured can be configured.

In the above description, the case where a reflecting plate is used as the reflecting portion has been described. However, the reflecting portion of the present invention is provided on the opposite side of the low refractive index layer of the prism layer and is emitted from the prism layer. There is no limitation as long as it reflects light toward the prism layer. Specifically, for example, the bottom surface of the housing of the lighting device that houses the light source and the light guide plate can be used as the reflecting portion.

In the above description, as the first light diffusing portion, the second prism that is formed in a concave shape on the light exit surface of the light guide and is configured integrally with the first prism is used. explained. However, the first light diffusion portion of the present invention is not limited as long as it is provided on the light exit surface side or the opposite surface side of the light guide and diffuses light from the light source in a direction orthogonal to the propagation direction. . Specifically, a prism array configured separately from the light guide and the first prism may be used. Moreover, the prism formed in convex shape may be sufficient with respect to the output surface of a light guide. Further, it may be a curved surface.

Further, in the above description, a case has been described in which the third prism formed integrally with the concave shape on the light incident surface of the light guide is used as the second light diffusion portion. However, the second light diffusion portion of the present invention is not limited as long as it is provided on the light incident surface of the light guide and diffuses light from the light source in a direction orthogonal to the propagation direction. Specifically, a prism array configured separately from the light guide may be used. Moreover, the prism formed in the convex shape may be sufficient with respect to the light-incidence surface of a light guide. Further, it may be a curved surface.

The present invention is useful for an illuminating device excellent in light utilization efficiency that can reduce light loss and obtain outgoing light, and a display device using the same.

1 Liquid crystal display device 2 Liquid crystal panel (object to be irradiated)
3 Lighting device 4 Light emitting diode (light source)
DESCRIPTION OF SYMBOLS 5 Light guide plate 6 Light guide 6a Light-incidence surface 6b Outgoing surface 6c Opposite surface 7 Low refractive index

layer 7a Surface

8, 18, 28

Prism layer

8a, 18a, 28a Prism P1, P2, P3 surface 9 Reflector (reflective part)
10 First prism (optical path changing section)
11 Second prism (first light diffusion portion)
12 3rd prism (2nd light-diffusion part)

Claims

A light source and a lighting device including a light guide plate that guides light from the light source in a predetermined propagation direction and emits the light to an irradiated object,
The light guide plate is
A light guide including a light incident surface for receiving light from the light source, an emission surface for emitting light incident from the light incident surface to the irradiated object side, and a facing surface facing the emission surface. When,
An optical path changing unit that is provided on the light exit surface side or the opposing surface side of the light guide and gradually changes the angle of light guided through the light guide;
A low refractive index layer having a refractive index lower than the refractive index of the light guide, and provided on the opposite surface side of the light guide;
The low refractive index layer is provided on the opposite side of the light guide, and includes a prism layer having a refractive index higher than the refractive index of the low refractive index layer,
The prism layer is provided with a plurality of prisms having at least three surfaces,
In the prism, at least the light incident from the low refractive index layer side is sequentially totally reflected by the at least three surfaces and emitted from the emission surface of the light guide to the irradiated object side. Three faces are provided,
A lighting device characterized by that.
The lighting device according to claim 1, wherein the angle of each of the at least three surfaces is set so that an incident angle of light is not less than a critical angle.
The lighting device according to claim 1, wherein a plurality of the prisms are continuously formed in the prism layer in a normal direction of the light incident surface of the light guide.
The lighting device according to any one of claims 1 to 3, wherein in the prism layer, the plurality of prisms have substantially the same shape and the same size.
The low refractive index layer is attached to the facing surface of the light guide,
The lighting device according to any one of claims 1 to 4, wherein the prism layer is affixed to a surface of the low refractive index layer opposite to the light guide.
The illumination device according to any one of claims 1 to 5, wherein a prism formed integrally with the light exit surface of the light guide is used as the optical path changing portion.
7. In each of the plurality of prisms, a surface on which light incident from the low refractive index layer side is first totally reflected is set at an angle of 90 degrees or less with respect to the propagation direction. The lighting device according to claim 1.
The lighting device according to any one of claims 1 to 7, wherein the prism layer is provided with a light scattering function for scattering light.
The reflective portion that reflects light emitted from the prism layer to the prism layer side is provided on the opposite side of the prism layer from the low refractive index layer. Lighting equipment.
While including a reflective polarizing plate provided on the irradiated object side of the light guide plate,
The lighting device according to claim 9, wherein each of the plurality of prisms is provided with one surface included in the at least three surfaces in parallel to the reflecting portion.
11. The first light diffusion portion for diffusing light from the light source in a direction orthogonal to the propagation direction is provided on the light exit surface side or the opposed surface side of the light guide. The lighting device according to any one of the above.
The second light diffusing section for diffusing light from the light source in a direction orthogonal to the propagation direction is provided on the light incident surface of the light guide. The lighting device described.
A display device using the illumination device according to any one of claims 1 to 12.
The display device according to claim 13, wherein a liquid crystal panel is used as the irradiation object.