JP5830828B2 - Backlight device and liquid crystal display - Google Patents

Description

  The present invention relates to a backlight device and a liquid crystal display, and is particularly suitable for application to a backlight device in a liquid crystal display for information display.

  Liquid crystal displays are used as image display means in various electronic and industrial equipment such as mobile phones, smartphones, tablet terminals, cameras, personal computers, CAD monitors, medical monitors, automobile monitors, and television receivers. The amount of usage and applications are expected to expand. In this liquid crystal display, illumination light is indispensable, and a backlight that illuminates light using a cold cathode fluorescent lamp (CCFL) or a light emitting diode (LED) as a light source on the back side of the display panel. A device is provided.

  As this backlight device, there are roughly classified two types, an edge light type and a direct type (Patent Document 1). In the edge light type backlight device, a light source is provided at an edge portion of a light guide plate made of a transparent plate, and light is emitted from the edge portion through a pattern or the like provided on the back surface. On the other hand, the direct type backlight device arranges a large number of light sources such as LEDs on the back surface of the liquid crystal panel, and emits light from each light source.

  The edge-light type backlight device has an advantage that the number of LEDs to be used can be reduced. On the other hand, in order to make the brightness of the display surface uniform by using the light guide plate, it is reflected on the back surface of the light guide plate. The pattern is complicated by silk printing, etc., the reflector is placed under the light guide plate, the diffuser plate and the prism are provided above, and the structure becomes complicated and the light utilization efficiency is also deteriorated. There's a problem. Also, even in direct type backlight devices, it is necessary to overlap the light from the LEDs in order to achieve uniform brightness, and because many LEDs are arranged side by side, the power consumption is large and the light utilization efficiency There is a problem that is bad. Further, the direct type backlight device has a problem that it is difficult to reduce the thickness because it is necessary to arrange a large number of LEDs and make the luminance uniform by overlapping before the light enters the liquid crystal panel.

JP 2007-264111 A JP 2007-240965 A

  The light use efficiency and energy efficiency for realizing uniform luminance in such a backlight device have a great influence on the power consumption of the liquid crystal display. The reduction in power consumption in liquid crystal displays is required to be further improved along with the improvement in image quality, and there is a demand for improvement in light use efficiency and energy efficiency in a backlight device. Therefore, the inventor made a prototype of the backlight device described in Patent Document 2 and conducted various studies. However, the backlight device described in Patent Literature 2 has not been ready for operation.

  In addition, it is known that it is effective to use a light source with low power consumption such as an LED as a light source of the backlight device in order to reduce power consumption of the backlight device. In addition, the development of a technique for minimizing the number of LEDs used as a light source has been demanded.

  The present invention has been made in view of the above, and an object of the present invention is to improve the light utilization efficiency, thereby minimizing the use of the light source and reducing the power consumption. It is to provide an apparatus and a liquid crystal display.

  In order to solve the above-described problems and achieve the above object, a backlight device according to the present invention includes a two-dimensional light source having a predetermined light intensity distribution in a plane, a first condensing optical system having a focal length f1, And a two-sided telecentric optical system formed from a second condensing optical system having a focal length f2 greater than the focal length f1, and the first condensing optical system side of the two-dimensional light source with respect to the second condensing optical system The light beam emitted from the two-dimensional light source, passed through the first light collecting optical system and traveled to the second light collecting optical system is emitted as the light beam from the second light collecting optical system, and the second light collecting optics. The light beam emitted from the system is configured to be emitted to the outside.

  The backlight device according to the present invention further includes an optical path changing unit that changes the optical path of the light beam emitted from the second light collecting optical system and that receives the light beam emitted from the second light collecting optical system. It is characterized by providing.

  In the backlight device according to the present invention, in the above invention, the optical path changing means includes a reflecting member configured to be able to reflect the light beam emitted from the second condensing optical system, and the reflecting surface of the reflecting member is the second collection. Inclined at a predetermined angle with respect to the optical axis of the light beam emitted from the optical optical system.

  In the backlight device according to the present invention, the emission direction of the light beam emitted from the second light collecting optical system is inclined at a predetermined angle with respect to the optical axis of the light beam that has passed through the first light collecting optical system. It is characterized by that.

  The backlight device according to the present invention is characterized in that, in the above invention, the second condensing optical system is constituted by a mirror system having at least one reflecting mirror.

In the backlight device according to the present invention, the light beam emitted from the two-dimensional light source and traveling through the first light collecting optical system is converted into the second light collecting optical system by the second light collecting optical system. An image is formed on the focal position at an area approximately (f2 / f1) ² times the area of the cross section perpendicular to the optical axis of the light beam emitted from the two-dimensional light source.

  In the backlight device according to the present invention, in the above invention, the distance between the principal points of the first condensing optical system and the second condensing optical system facing each other is such that the focal distance f1 of the first condensing optical system and the It is characterized by being approximately equal to the sum of the focal lengths f2 of the two condensing optical systems.

  The backlight device according to the present invention is characterized in that, in the above invention, the first condensing optical system includes at least four lenses.

  In the backlight device according to the present invention, in the above invention, the first condensing optical system is provided with at least one blocking member that blocks a part of the light beam emitted from the two-dimensional light source, and the blocking member is two-dimensional. It has at least one aperture through which an effective light beam out of the light beam emitted from the light source passes.

  In the above-described invention, the backlight device according to the present invention includes: a light source that emits light; and a light shaping unit that shapes light emitted from the light source and emits the light as a light beam. The area of the cross section perpendicular to the optical axis of the light beam at the end where the light emitted from the light source of the shaping means is incident is the optical axis of the light beam at the end where the light beam of the light shaping means is emitted. It is characterized by being smaller than the area of a cross section perpendicular to it.

  The backlight device according to the present invention, in the above invention, has a rectangular cross-sectional shape perpendicular to the optical axis of the light beam at the end of the light shaping means on the side where light from the light source is incident, A cross-sectional shape perpendicular to the optical axis of the light beam at the end of the light shaping unit on the side from which the light beam is emitted is rectangular.

  In the backlight device according to the present invention, the area of the cross section perpendicular to the optical axis of the light beam at the end of the light shaping unit on the side from which the light beam is emitted is from the light source of the light shaping unit. It is characterized in that it is not less than 3 times and not more than 5 times the area of the cross section perpendicular to the optical axis of the light flux at the end on the light incident side.

  The backlight device according to the present invention is characterized in that, in the above invention, the light shaping means is composed of a plurality of rods connected to each other or rods integrally formed with each other.

  The backlight device according to the present invention is characterized in that, in the above invention, the light emitting source is a light emitting diode.

  A liquid crystal display according to the present invention includes the backlight device according to the above-described invention and a flat plate-like liquid crystal panel having at least liquid crystals sandwiched between a plurality of light distribution layers, and emits a light beam emitted from the backlight device. The liquid crystal panel is incident substantially perpendicular to one surface.

  The liquid crystal display according to the present invention is characterized in that, in the above-described invention, the light beam emitted from the second condensing optical system is reflected by the reflecting member to emit the light beam from the backlight device.

  According to the backlight device and the liquid crystal display according to the present invention, it is possible to reduce the power consumption by minimizing the use of the light source by improving the light utilization efficiency.

FIG. 1 is a side view in the X direction of a liquid crystal display according to a first embodiment of the present invention. FIG. 2 is a plan view of the liquid crystal display according to the first embodiment of the present invention in the Y direction. FIG. 3 is a perspective view showing a light shaping rod according to the first embodiment of the present invention. FIG. 4 is a side view in the X direction of the light shaping rod and lens system according to the first embodiment. FIG. 5 is a Y direction plan view of the light shaping rod and lens system according to the first embodiment. FIG. 6 is a schematic diagram corresponding to FIG. 1 for explaining the double-sided telecentric optical system. FIG. 7 is a schematic diagram corresponding to FIG. 2 for explaining the double-sided telecentric optical system. FIG. 8A is a schematic diagram for explaining the principle of a double-sided telecentric optical system. FIG. 8B is a schematic diagram for explaining the principle of the double-sided telecentric optical system. FIG. 9 is a schematic diagram for explaining a case where the paraxial image point position is positioned approximately in the middle between the lens system and the mirror system in the first embodiment of the present invention. FIG. 10 is a sectional view showing a reflective prism sheet according to the first embodiment of the present invention. FIG. 11 is a plan view showing the in-plane light intensity distribution emitted from the backlight device according to the first embodiment of the present invention. FIG. 12 shows a simulation result of the one-dimensional intensity distribution along the X direction when the in-plane intensity distribution of the light beam emitted from the rod tip surface is uniform in the backlight device according to the first embodiment of the present invention. It is a graph to show. FIG. 13 shows the simulation result of the one-dimensional intensity distribution along the Z direction when the in-plane intensity distribution of the light beam emitted from the rod tip surface is uniform in the backlight device according to the first embodiment of the present invention. It is a graph to show. FIG. 14 shows the simulation result of the one-dimensional intensity distribution along the X direction when the in-plane intensity distribution of the light beam emitted from the rod tip surface is uniform in the backlight device according to the second embodiment of the present invention. It is a graph to show. FIG. 15 shows a simulation result of the one-dimensional intensity distribution along the Z direction when the in-plane intensity distribution of the light beam emitted from the rod tip surface is uniform in the backlight device according to the second embodiment of the present invention. It is a graph to show. FIG. 16 shows a simulation result of the one-dimensional intensity distribution along the X direction when the in-plane intensity distribution of the light beam emitted from the rod tip surface is uniform in the backlight device according to the third embodiment of the present invention. It is a graph to show. FIG. 17 shows the simulation result of the one-dimensional intensity distribution along the Z direction when the in-plane intensity distribution of the light beam emitted from the rod tip surface is uniform in the backlight device according to the third embodiment of the present invention. It is a graph to show. FIG. 18 is a side view in the X direction of a liquid crystal display according to the fourth embodiment of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, this invention is not limited by the following embodiment. In the drawings, the same or corresponding elements are denoted by the same reference numerals as appropriate, and repeated descriptions are omitted as appropriate. Furthermore, it should be noted that the drawings are schematic, and dimensional relationships between elements may differ from actual ones. Even between the drawings, there are cases in which portions having different dimensional relationships and ratios are included.

(First embodiment)
First, a liquid crystal display provided with a backlight device according to the present invention will be described as a first embodiment of the present invention. FIG. 1 and FIG. 2 are a side view seen from the X direction and a plan view seen from the Y direction, respectively, showing the configuration of the liquid crystal display according to the first embodiment. 1 and 2, the direction perpendicular to the XY plane is taken as the Z direction.

  As shown in FIGS. 1 and 2, the backlight device 10 according to the first embodiment includes a light emitting diode (LED) 11, a light shaping rod 12, a lens system 13, a reflective prism sheet 14, and a mirror system 15. It is configured. In addition, a liquid crystal panel 16 is provided substantially parallel to the reflecting prism surface facing the optical axis side in the reflecting prism sheet 14 of the backlight device 10. The backlight device 10 and the liquid crystal panel 16 constitute the liquid crystal display 1.

  The LED 11 as a light source is composed of, for example, a white LED. The LED 11 is configured so that the color gamut is as wide as possible in order to improve color reproducibility. Here, when the LED 11 is constituted by a single LED, it is preferable to use an LED having a diameter φ of 2 mm or more and 4 mm or less (2 mm ≦ φ ≦ 4 mm) on the light emission end face side. In the first embodiment, an LED having a diameter φ of, for example, 3 mm is used as the LED 11. Moreover, the space | interval of the LED chip in LED11 and a cover glass (all are not shown) is about 0.28 mm, for example. The LED 11 is preferably a surface light source, and the intensity distribution of light emitted from the LED 11 is preferably a light distribution of a uniform diffusion surface (Lambertian).

  The light shaping rod 12 as the light shaping means is a rod for shaping the light beam emitted from the LED 11. FIG. 3 shows a perspective view of the light shaping rod 12. As shown in FIG. 3, the light shaping rod 12 includes a first rectangular parallelepiped first rod 12 a and a trapezoidal plate-shaped first rod 12 a that are different in shape from the light incident side end and the light emission side end. 2 rods 12b. That is, as for the 1st rod 12a, the cross section (henceforth XY cross section), YZ cross section, and XZ cross section along the surface prescribed | regulated from a X direction and a Y direction are all formed in the substantially rectangular shape. The second rod 12b is formed so that the XY section and the YZ section are substantially rectangular, and the XZ section is substantially trapezoidal. And the rectangular surface (Z direction rear end surface) of the end portion on the side where the LED 11 of the first rod 12a is installed is a light beam incident side end surface, and is configured to be able to closely contact the cover glass of the LED 11. The light shaping rod 12 is made of an optical material such as glass or resin such as borosilicate glass (product name BK7) or fused silica, which is transparent to the light beam emitted from the LED 11, but other various materials are used. Is possible.

An example of the dimensions of the first rod 12a and the second rod 12b in the light shaping rod 12 configured as described above will be given. First, the X direction dimension Lx0 of the XY cross section at the light beam incident side end of the first rod 12a is preferably greater than 2.6 mm and less than 3.6 mm, and the Y direction dimension Ly0 is preferably greater than 1.0 mm and less than 2.4 mm. That is, it is preferable that the following expressions (1) and (2) are satisfied.
2.6 mm <Lx0 <3.6 mm (1)
1.0 mm <Ly0 <2.4 mm (2)

Further, considering the emission of the light beam from the light shaping rod 12 described later and the spread of the light beam toward the mirror system 15, the XY cross section of the light beam incident side end has a long side in the X direction and a short side in the Y direction. Is preferred. That is, it is preferable that the following expression (3) holds.
Ly0 ≦ Lx0 (3)

Further, the X direction dimension Lx1 and the Y direction dimension Ly1 in the XY cross section on the light beam exit side, which is the light exit side of the first rod 12a, are greater than 2.6 mm and less than 3.6 mm, and greater than 1.0 mm, respectively. Less than 2.4 mm is preferable. Further, the light beam emitting side end portion from which the light beam is emitted from the first rod 12a and the light beam incident side end portion from which the light beam is incident at the second rod 12b are connected, or the first rod 12a and the second rod 12b are connected. Are considered to be integrally molded, their XY cross sections have the same dimensions. That is, it is preferable that the XY cross section of the light beam emitting side end of the first rod 12a and the light beam incident side end of the second rod 12b have the same shape, and the following expressions (4) and (5) are satisfied. .
2.6 mm <Lx1 <3.6 mm (4)
1.0 mm <Ly1 <2.4 mm (5)
The first rod 12a has a substantially rectangular parallelepiped shape, and it is preferable to satisfy the following formulas (6) and (7) in order to perform shaping of the incident light beam without deviation, but it is not necessarily limited. Absent. The length L ₀ along the Z direction of the first rod 12a is, for example, 60 mm.
Lx0 = Lx1 (6)
Ly0 = Ly1 (7)

Similarly to the case described above, considering that light from the first rod 12a is appropriately incident on the second rod 12b, it is preferable that the following expression (8) corresponding to the expression (3) is satisfied. .
Ly1 ≦ Lx1 (8)

Further, the X-direction dimension Lx2 and the Y-direction dimension Ly2 of the rod front end surface 12c, which is the light beam exit side end from which the light beam is emitted from the second rod 12b, are greater than 12.0 mm and less than 13.2 mm, respectively. More than 1.0 mm and less than 2.4 mm are preferable. That is, it is preferable that the following expressions (9) and (10) are satisfied.
12.0mm <Lx2 <13.2mm (9)
1.0 mm <Ly2 <2.4 mm (10)

Further, considering that the light beam emitted from the second rod 12b is appropriately incident on the lens system 13, the XZ cross section of the second rod 12b has a trapezoidal shape in which the rod end surface 12c side is widened. In the second rod 12b, the X-direction dimension Lx2 of the rod tip surface 12c is preferably about 3 to 5 times the X-direction dimension Lx1 of the light beam incident side end. The Y-direction dimension Ly2 of the rod tip surface 12c is preferably larger than the Y-direction dimension Ly1 of the light beam incident side end of the second rod 12b. By making Ly2 larger than Ly1, in principle, the light beam emitted from the rod front end surface 12c becomes narrow, and the possibility that most of the light beam will enter the lens system 13 increases, so that energy loss can be reduced. Therefore, although it is preferable that the following formulas (11) and (12) are satisfied, it is not necessarily limited. The area of the XY cross section of the rod front end surface 12c is preferably 3 to 11 times the area of the XY cross section of the light beam incident side end of the first rod 12a. The length L ₁ along the Z direction of the second rod 12b is, for example, 30 mm.
3Lx1 ≦ Lx2 ≦ 5Lx1 (11)
Ly1 ≦ Ly2 (12)

  In the light shaping rod 12 described above, the X-direction dimensions Lx0, Lx1, Lx2 and the Y-direction dimensions Ly0, Ly1, Ly2 are not limited to the numerical ranges described above, and various values can be selected depending on the ratio of these dimensions. Can be adopted. That is, based on the ratio of the X direction dimensions Lx0, Lx1, Lx2 and the Y direction dimensions Ly0, Ly1, Ly2, it is possible to enlarge or reduce the above dimensions.

Specifically, instead of the above-described formulas (1) and (2), the ratio of the X-direction dimension Lx0 of the light incident side end of the first rod 12a to the Y-direction dimension Ly0 is larger than 1.1. It is also possible to make it less than .6. That is, the first rod 12a can be configured such that the following expression (13) is established.
1.1 <Lx0 / Ly0 <3.6 (13)

Similarly, instead of the above-described formulas (4) and (5), the Y-direction dimension Ly1 of the X-direction dimension Lx1 at the connecting portion of the light shaping rod 12 or the portion where the width expansion along the X-direction starts. The ratio to can also be greater than 1.1 and less than 3.6. That is, the first rod 12a and the second rod 12b can be configured so that the following expression (14) is established.
1.1 <Lx1 / Ly1 <3.6 (14)

Furthermore, instead of the above-described equations (9) and (10), the ratio of the second rod 12b and the X-direction dimension Lx2 to the Y-direction dimension Ly2 may be greater than 5.0 and less than 13.2. It is. That is, the second rod 12b can be configured so that the following expression (13) is established.
5.0 <Lx2 / Ly2 <13.2 (15)

  Even when the light shaping rod 12 is configured so that the expressions (13), (14), and (15) are established, the expressions (3), (6) to (8), (11 ) And (12) are preferably configured to hold together.

  By defining the shape of the light shaping rod 12 as described above, when uniformity is required in the illumination area of the backlight device 10 described later, the uniformity can be maintained and the light utilization efficiency can be improved. The LED 11 and the light shaping rod 12 described above constitute a two-dimensional light source, and a light beam having a predetermined in-plane intensity distribution is emitted from the rod front end surface 12 c of the light shaping rod 12. At this time, since the shape of the light shaping rod 12 is defined as described above, the in-plane intensity distribution on the rod tip surface 12 c is more uniform than the in-plane intensity distribution of the light beam emitted from the LED 11. Becomes extremely high.

  Next, the lens system 13 as the first condensing optical system and the mirror system 15 as the second condensing optical system will be described. As will be described later, the lens system 13 and the mirror system 15 form a double-sided telecentric optical system.

  As shown in FIGS. 1 and 2, the lens system 13 as the first condensing optical system maintains the in-plane intensity distribution of the light beam emitted from the light shaping rod 12, such as a uniform in-plane intensity distribution. While enlarging and shaping, it is made incident on the mirror system 15 provided oppositely.

  4 and 5 are a side view of the light shaping rod 12 and the lens system 13 viewed from the X direction and a plan view viewed from the Y direction, respectively. As shown in FIGS. 4 and 5, the light beam emitted from the LED 11 and shaped by the light shaping rod 12 is emitted from the rod front end surface 12c as a two-dimensional light source. Since the lens system 13 forms a mirror system 15 and a both-side telecentric optical system, which will be described later, the light emitted from the rod tip surface 12c can be regarded as approximately parallel to the optical axis and the principal ray by the both-side telecentric optical system. Converted into a thing.

  The lens system 13 is composed of at least four lenses and has a predetermined focal length f1. In the first embodiment, the lens system 13 is a so-called bright lens system that includes, for example, five lenses 13a, 13b, 13c, 13d, and 13e, and has an F value (F number) of about 1.1, for example. And these five lenses 13a-13e are arrange | positioned so that those principal points may pass on the central axis O of the XY cross section of LED11 and the light shaping rod 12, ie, on an optical axis. The aberration of the lens system 13 is corrected in the same manner as in a general imaging system, and the chromatic aberration is also sufficiently corrected. If all the lenses constituting the lens system 13 are spherical lenses, the lens system 13 is preferably composed of five lenses 13a to 13e, but is not necessarily limited to this number. In addition, by using at least one lens among the lenses constituting the lens system 13 as an aspherical lens, the lens system 13 can be constituted by four lenses.

  Below, the specific example of each lens 13a-13e which comprises the lens system 13 in this 1st Embodiment is given. First, the lens 13a is made of an optical glass made of, for example, heavy barium crown glass (for example, product name BACD16 (HOYA)), and has a radius of curvature (hereinafter referred to as a rear surface radius of curvature) of the light incident side surface and a center of Z. 929.57 mm on the rear side in the direction (hereinafter, “-” is attached in the case of the rear side in the Z direction, and it is assumed to be −929.57 mm, etc.), the thickness is 7.5 mm, the diameter is 27 mm, and the light emission side The curvature radius of the surface (hereinafter referred to as the front surface curvature radius) is −20.004 mm. The distance between the lens 13a and the lens 13b along the central axis O is 0.12 mm. Next, the lens 13b is made of, for example, an optical glass having the product name BACD16, and has a rear surface curvature radius of 37.52 mm, a thickness of 7.0 mm, a diameter of 27 mm, and a front surface curvature radius of −42.1 mm. . The distance between the lens 13b and the lens 13c along the central axis O is 0.12 mm. Next, the lens 13c is made of optical glass made of, for example, heavy flint glass (for example, product name SF2 (SCHOTT)), has a rear surface radius of curvature of 15.1 mm, a thickness of 6.6 mm, a diameter of 22 mm, and a front. The direction radius of curvature is 10.2 mm. The distance between the lens 13c and the lens 13d along the central axis O is 6.9 mm, and the maximum diameter of the XY cross section in the space forming this distance is 15 mm. Next, the lens 13d is made of, for example, an optical glass having the product name SF2, and has a rear surface curvature radius of −9.71 mm, a thickness of 4.5 mm, a diameter of 22 mm, and a front surface curvature radius of −13.495 mm. is there. The distance between the lens 13c and the lens 13d along the central axis O is 0.42 mm. Next, the lens 13e is made of, for example, an optical glass having a product name BACD16, and has a rear surface radius of curvature of -450 mm, a thickness of 4.5 mm, a diameter of 24 mm, and a front surface radius of curvature of -29.465 mm. The distance on the central axis O between the lens 13d and the lens 13e is 6.9 mm, and the maximum diameter of the XY cross section in the space having this distance is 15 mm.

  Further, the lens system 13 is provided with blocking plates 17 and 18 as blocking members for blocking a part of the light beam other than the effective light beam at least at one place, and in two places in the first embodiment. Yes. Among these, the blocking plate 17 is provided between the lens 13 b and the lens 13 c in the lens system 13. For example, a rectangular opening 17a is formed in the blocking plate 17 in the plane. And it is comprised so that an effective light beam can pass through this opening 17a. Further, a blocking plate 18 similar to the blocking plate 17 is provided on the light emission side of the lens system 13. The blocking plate 18 is formed with, for example, a rectangular opening 18a in the surface so that an effective light beam can pass through the opening 18a. The in-plane shapes of the openings 17a and 18a are not limited to a rectangular shape, and may be various shapes such as an elliptical shape, a circular shape, a trapezoidal shape, or a parallelogram shape as necessary. In addition, a shielding plate 19 is also provided for blocking leakage light that has not entered the light beam incident side end of the light shaping rod 12 out of the light emitted from the LED 11.

  Here, the distance between the lens 13a closest to the light shaping rod 12 among the lenses 13a to 13e constituting the lens system 13 and the rod front end surface 12c of the light shaping rod 12 is 9.74 mm, for example. The distance between the lens 13e closest to the mirror system 15 among the lenses 13a to 13e constituting the lens system 13 and the mirror system 15 is, for example, 582.6 mm.

  The mirror system 15 as the second condensing optical system is composed of at least one reflecting mirror, specifically, for example, a concave mirror that is a reflecting mirror having a predetermined focal length f2. Here, an example of the dimensions of the mirror system 15 is a rectangular partial spherical surface whose rear surface curvature radius is -1200 mm, the dimension along the X direction is 400 mm, for example, and the dimension along the Y direction is 65 mm, for example. . Further, the mirror system 15 is inclined at a predetermined inclination angle θ with respect to the Y direction so that the reflection surface thereof faces the lower surface side of the reflective prism sheet 14 (see FIG. 1). Here, in the first embodiment, the inclination angle θ of the mirror system 15 correlates with the area forming the irradiation area of the backlight device 10 as will be described later, specifically, 2 degrees or more and 4 degrees or less. It is preferable to do this.

  Here, as described above, the mirror system 15 and the lens system 13 are combined to form a double-sided telecentric optical system. In the first embodiment, the double-sided telecentric optical system forms a finite optical system. In addition, although mentioned later for details, one side of the irradiation area | region of the backlight apparatus 10 has a substantially imaging relationship with the long side along the X direction of the rod front end surface 12c of the light shaping rod 12, The magnification is constant. .

  The double telecentric optical system will be described below. 6 and 7 are schematic diagrams corresponding to FIGS. 1 and 2 for describing the double-sided telecentric optical system, respectively. In FIGS. 6 and 7, for the sake of explanation, the same reference numerals as those in the first embodiment are used. However, unlike the first embodiment, the mirror system is assumed not to be inclined. 6 is a YZ plane view, and FIG. 7 is an XZ plane view. Further, in FIGS. 6 and 7, for the description of the both-side telecentric optical system, the distance d between the rod tip surface 12c of the light shaping rod 12 and the lens 13a of the lens system 13 is set to 9.355 mm, for example. It differs from the configuration of the first embodiment in that the position of the surface 12c is a paraxial object point position.

As shown in FIGS. 6 and 7, the light beam L emitted from the rod tip surface 12c of the light shaping rod 12 as a two-dimensional light source enters the lens system 13 so that the principal ray thereof is substantially parallel to the optical axis. This light beam is substantially collimated in the Z direction by the lens system 13. The collimated light beam L is reflected by a mirror system 15 comprising a concave mirror. The principal rays of the parallel light beam L _R after being reflected by the mirror system 15 are parallel to the optical axis and substantially parallel to each other, and the parallel light beam L _R is connected between the lens system 13 and the mirror system 15. Image. In addition, it is desirable that the principal rays of the respective parallel light beams L _R after reflection are substantially parallel to each other.

  8A and 8B are schematic diagrams illustrating the principle of a double-sided telecentric optical system, respectively. 8A and 8B, for ease of understanding, the lens system 13 having a focal length f1 is simplified and described, and the mirror system 15 is replaced with a lens system 15A having a similar focal length f2. It is described. Here, FIG. 8A corresponds to FIGS. 1 and 6, and FIG. 8B corresponds to FIGS. 2 and 7.

As shown in FIGS. 8A and 8B, the lens system 13 forms an object-side telecentric optical system for the light beam emitted from the rod front end surface 12c of the light shaping rod 12, and proceeds while the optical path is bent by the lens system 13. Thus, the traveling direction of the light beam L is expanded. The light beam L is converted into a parallel light beam L _R by the lens system 15A constituting the imaging side telecentric optical system, and is imaged at a paraxial image point located on the right side of the lens system 15A on the paper surface. Therefore, the in-plane intensity distribution along the XY section of the light beam L emitted from the rod front end surface 12c of the light shaping rod 12 is similar to the in-plane intensity distribution along the XY section of the parallel light beam L _R that is reflected light as it is. Is reflected. That is, by emitting the light beam L having a uniform in-plane intensity distribution from the rod tip surface 12c of the light shaping rod 12, the intensity distribution of the parallel light beam L _R can be made uniform.

Further, as shown in FIG. 8B, the parallel light beam expanded about (f2 / f1) times along the X direction with respect to the X-direction dimension Lx2 of the light beam L emitted from the rod front end surface 12c of the light shaping rod 12. _LR is formed. Therefore, by adjusting the shape (curvature or the like) of the lens system 15A (corresponding to the mirror system 15) to increase or decrease the focal length f2, the width Wx of the irradiation area can be enlarged or reduced. Similarly, as shown in FIG. 8A, the parallel light beam L _R is approximately (f2 / f1) along the Y direction with respect to the Y-direction dimension Ly2 of the light beam L emitted from the rod tip surface 12c of the light shaping rod 12. ) Enlarged twice. Therefore, at the focal position of the lens system 15A (corresponding to the mirror system 15), the area is approximately (f2 / f1) ² times the area of the cross section perpendicular to the optical axis of the light beam emitted from the rod tip surface 12c. Imaged. Then, in the region between the lens system 13 and the lens system 15A, the parallel light beam L _R is expanded to the width Wx along the X direction as shown in FIG. 8A, and in the Y direction as shown in FIG. 8B. Enlarged to a width Wy along. Also, the widths Wx and Wy of the irradiation area can be reduced and enlarged by increasing or decreasing the focal length f1 of the lens system 13, respectively. In these cases, the in-plane intensity distribution along the XY cross section of the light beam L emitted from the rod front end surface 12c is similarly reflected in the intensity distribution along the XY cross section of the parallel light beam L _R. That is, assuming a plane including the parallel light beam L _R (the cut surface) while inclined with respect to the optical axis of the collimated light beam L _R, setting this cutting plane how the optical axis, the cutting The intensity distribution of the parallel light beam L _{R on} the surface is in a state in which the in-plane intensity distribution along the XY cross section of the light beam L emitted from the rod tip surface 12c is reflected.

8A and 8B, in order to form such a double-sided telecentric optical system, the rear principal point of the lens system 13 and the front principal point of the lens system 15A opposite to the rear principal point the distance D _lm, preferably substantially equal to the sum of the focal length f1 and the focal length f2 of the lens system 15A of the lens system 13. That is, it is preferable that the following expression (16) holds.
f1 + f2 = D _lm (16)
Specifically, when the focal length f1 of the lens system 13 is, for example, 21.17 mm and the focal length f2 of the lens system 15A (corresponding to the mirror system 15) is, for example, 600 mm, the rear principal point of the lens system 13 is interval D _lm of the lens system 15A (corresponding to the mirror system 15) is preferably in the (600 + 21.17 =) 621.17mm. In the optical systems shown in FIGS. 8A and 8B, when the distance d between the rod tip surface 12c and the lens 13a of the lens system 13 is changed, the paraxial focal position of the lens system 15A (corresponding to the mirror system 15) becomes Z. It changes along the direction.

Further, as shown in FIG. 1, in the backlight device 10, the mirror system 15 is tilted by a tilt angle θ as a predetermined angle with respect to the Y direction so that the reflecting surface thereof faces the reflective prism sheet 14 side. Let As a result, as shown in FIG. 1, the expanded light beam L travels in a direction inclined with respect to the optical axis of the light beam L by the mirror system 15 and is reflected as a parallel light beam L _R from the mirror system 15. 14 is irradiated on the reflecting prism surface. In this case, the outgoing direction of the reflected parallel light beam L _R forms a predetermined angle of 2θ with respect to the principal ray of the light beam L from the lens system 13. Further, by adjusting the inclination angle θ of the mirror system 15, the irradiation width Wz along the Z direction of the parallel light beam L _R irradiated to the reflective prism sheet 14, that is, the irradiation area of the parallel light beam L _R is adjusted and controlled. Can do. That is, the mirror system 15 has a function of expanding the irradiation area along the Z direction, and reflects the intensity distribution of the light beam emitted from the light shaping rod 12 in the irradiation area to the reflective prism sheet 14. It is possible.

Next, FIG. 9 is a schematic diagram corresponding to FIGS. 2, 7, and 8A, showing the paraxial image point position in the first embodiment. In FIG. 9, the distance d ₁ between the rod tip surface 12c of the light shaping rod 12 and the lens 13a of the lens system 13 is 9.74 mm, which is larger than the distance d ₀ (9.355 mm) in FIGS. 6 and 7 described above. The position of the rod tip surface 12c is a paraxial object point position. As shown in FIGS. 8 and 9, when the distance d between the light shaping rod 12 and the lens 13a of the lens system 13 is increased, the paraxial image point position by the combined optical system of the lens system 13 and the mirror system 15 is increased. Move to the mirror system 15 side. In the case where the distance d ₁ is about 9.7 mm, for example, the paraxial image point position is an approximately intermediate position between the lens system 13 and the mirror system 15. This paraxial image point position corresponds to the paraxial image point position in the combined optical system of the lens system 13 and the mirror system 15. In addition, it is _preferable that the reflecting prism surface irradiated with the parallel light beam L _R in the reflective prism sheet 14 intersects with a plane including the paraxial image point position (a plane perpendicular to the optical axis of the parallel light beam L _R ). That is, it is desirable to perform alignment between the reflective prism sheet 14 and the mirror system 15 so that the paraxial image point position exists on the reflective prism surface of the reflective prism sheet 14. Thereby, in the irradiated region of the reflective prism sheet 14, the degree of blur of light irradiation can be made similar at the near point and the far point with respect to the mirror system 15.

Further, the reflective prism sheet 14 as a reflecting member which is an optical path changing means is provided so that the reflecting prism surface is substantially parallel to the central axis O and substantially parallel to the XZ plane. This reflection type prism sheet 14 is for further reflecting the parallel light beam L _R reflected by the mirror system 15 to change the optical path of the parallel light beam L _R so as to be emitted to the outside as a reflected parallel light beam L _r. It is. In the first embodiment, the reflected parallel light beam L _r is applied to the back surface (upper side surface in FIG. 1) of the liquid crystal panel 16. FIG. 10 is a partial YZ sectional view of the reflective prism sheet 14.

As shown in FIG. 10, the reflection-type prism sheet 14 liquid crystal panel 16 side of the reflecting prism face on, parallel to the X direction, i.e. extends in the direction perpendicular to the optical path direction of the parallel light beam L _R as viewed from the Y direction A plurality of reflective convex portions 14a are provided. The reflection convex portion 14a has, for example, a triangular shape whose YZ cross section has a width l ₀ and a height t ₀ , and is provided at a predetermined interval l ₁ . At least the mirror system 15 side of the surface of the reflective protrusion 14a is composed of a reflection can mirror the parallel light beam L _R. The parallel light flux L _R from the mirror system 15 is reflected by adjusting the width l ₀ or height t ₀ of the triangular base of the reflective convex portion 14a and the interval l ₁ between the adjacent reflective convex portions 14a. It can be prevented from reaching the surface of the reflective prism sheet 14 between the convex portions 14a. Therefore, the parallel light beam L _R from the mirror system 15 can reach only the slope formed by the mirror surface of the reflection convex portion 14a, and the parallel light beam L _R can be reflected by this slope. Thereby, since the light flux that reaches the surface of the reflective prism sheet 14 and is scattered in a direction different from the desired direction can be minimized, the light utilization efficiency can be improved. Furthermore, the area spacing l ₁ between the reflecting convex portion 14a adjacent Since a plane mirror, it is possible to re-enter the reflected light of the reflected parallel light beam L _r incident on the liquid crystal panel 16.

Further, by adjusting the shapes of the reflective prism sheet 14 and the reflective convex portion 14a and the inclination angle with respect to the Z direction according to the optical path of the parallel light beam L _R from the mirror system 15, the parallel light beam L _{R is obtained.} Can be reflected in a desired direction while maintaining a predetermined in-plane intensity distribution. As shown in FIG. 1, the LED 11, the light shaping rod 12, the lens system 13, the reflective prism sheet 14, and the mirror system 15 constitute the backlight device 10 of the liquid crystal display 1. Further, as described above, the backlight device 10 as a whole is configured such that the both-side telecentric optical system is a finite optical system, whereby parallel light beams can be emitted from the backlight device 10.

  Further, as the liquid crystal panel 16, a conventionally known flat plate-like liquid crystal panel can be used. That is, the liquid crystal panel 16 is composed of a laminated body in which, for example, a polarizing filter, a glass substrate, a liquid crystal sandwiched between light distribution layers, and a diffusion plate are laminated. The parallel light beam emitted from the backlight device 10 is configured to enter the back surface, which is one surface of the liquid crystal panel 16, substantially perpendicularly to the back surface, whereby the liquid crystal display 1 according to the first embodiment. Is configured.

The inventor made a prototype of the backlight device 10 configured as described above, and emitted the light from the rod front end surface 12c of the light shaping rod 12 despite using the LED 11 composed of a single LED. It was confirmed that the in-plane intensity distribution of the luminous flux L to be made uniform. Specifically, the light beam was able to diverge uniformly from the entire surface of the rod tip surface 12c. And this inventor measured the intensity distribution of the light emitted from the backlight apparatus 10 in this case. FIG. 11 is a diagram showing an in-plane light intensity distribution emitted from the backlight device 10. In FIG. 11, the irradiation area is about 450 mm × 600 mm, and the closer the light intensity is, the closer to black, and the higher the intensity, the closer to white. Further, αE-β in the following drawings means α × 10 ^−β . From FIG. 11, it can be seen that light can be irradiated almost uniformly over the entire irradiation region of the backlight device 10.

FIGS. 12 and 13 respectively show the in-plane intensity distribution of the light beam L emitted from the rod tip surface 12c with the power of light output from the LED chip of the LED 11 being 1 W in the backlight device 10 configured as described above. 3 is a graph showing a simulation result of light intensity distribution along the X direction and the Z direction in FIG. From FIG. 12 and FIG. 13, the light intensity along the X direction and the Z direction of the backlight device 10 is 1.13 × 10 ⁻⁴ W · cm ⁻² or more in a wide region, and the sufficient light intensity (luminance) ) Can be obtained. Then, when the above-described backlight device 10 is prototyped and measured, the uniform in-plane intensity distribution of the light beam emitted from the light shaping rod 12 is reflected in the in-plane intensity distribution of the light emitted from the backlight device 10, It was confirmed that an in-plane light intensity distribution with extremely high uniformity was realized. Furthermore, according to the backlight device 10 according to the first embodiment described above, it was confirmed that the light emission energy utilization efficiency was about 38.8% with respect to the energy of the light emitted from the LED 11. Here, the light emission energy utilization efficiency is a ratio of the number of light beams reaching the irradiation area to the number of light beams diverged from the LED 11 in the light beam simulation. Further, according to the knowledge of the present inventor, the energy utilization efficiency is determined by the shape of the LED chip, the shape of the irradiation side of the first rod 12a, the shape of the emission side of the rod tip surface 12c, the F value (NA) of the lens system 13, It depends on the absorption and reflection of the entire optical system and the distance between the LED chip and the cover glass. Here, in the utilization as described above, as the energy of the parallel light beam L _R, and using the value calculated based on the intensity distribution of the parallel light beam L _R calculated in the previous reflection prism sheet 14. In the backlight device 10 according to the first embodiment, by appropriately designing the reflective prism sheet 14, the reflected parallel light beam L _r is transmitted to the outside with a light emission energy utilization efficiency similar to the light emission energy utilization efficiency described above. Can be emitted.

  According to the first embodiment of the present invention described above, it is possible to illuminate a conventional illumination area more uniformly by using the LED 11 composed of a single LED, so that power consumption is reduced. be able to. In addition, since the light shaping rod 12 and the lens system 13 and the mirror system 15 linked with the lens system 13 constitute a double-sided telecentric optical system, the light emitted from the backlight device 10 can be made into parallel light, While maintaining low power consumption, a backlight having an in-plane intensity distribution reflecting the light intensity distribution on the light emitting surface of the light shaping rod 12 in a wide area can be obtained. According to the first embodiment, the lens system 13 and the mirror system 15 are basically an infinite system, and the position of the rod front end surface 12c, which is the exit end surface of the light shaping rod 12, is determined by the lens system. By arranging them before and after the 13 focal positions, the illumination uniformity of the backlight is ensured. Thereby, by making the light intensity distribution on the light emitting surface of the light shaping rod 12 uniform in the light emitting surface, a uniform backlight reflecting the uniformity can be obtained in a wide illumination region.

  Moreover, according to the backlight device 10 in the first embodiment described above, the thickness of the backlight device 10 is set to the length along the Z direction or the width along the X direction of the irradiation region of the backlight device 10. It was confirmed that the thickness could be 10% or less. Thereby, the backlight device can be thinned, narrowed, and downsized.

(Second Embodiment)
Next, a backlight device according to a second embodiment of the present invention will be described. In the second embodiment, in the first rod 12a of the light shaping rod 12, the X-direction dimensions Lx0 and Lx1 of the incident-side end portion and the emission-side end portion are, for example, 3 mm and the Y-direction dimensions Ly0 and Ly1, respectively. For example, it is 1 mm. The X-direction dimension Lx2 of the second rod 12b on the rod front end surface 12c is, for example, 12 mm, the Y-direction dimension Ly2 is, for example, 2 mm, and the second rod 12b has a so-called trumpet shape. Then, the dimensions of the LED 11 are set such that the dimension in the X direction is 3 mm and the dimension in the Y direction is 1 mm (3 mm × 1 mm). Since other configurations are the same as those of the first embodiment, description thereof is omitted. And when this inventor calculated the light emission energy efficiency by setting the sensor pitch which measures light intensity to 750x1000, it was confirmed that the light emission energy utilization efficiency from LED11 improves to about 68.8%. . In other words, it was confirmed that the loss of light energy can be reduced geometrically and optically on the emission side of the light shaping rod 12 and the incident side of the lens system 13 by making the shape of the light shaping rod 12 a trumpet shape.

FIGS. 14 and 15 respectively show the in-plane intensity distribution of the light beam L emitted from the rod tip surface 12c in the backlight device 10 configured as described above, assuming that the power of the light output from the LED chip of the LED 11 is 1W. 3 is a graph showing a simulation result of a one-dimensional intensity distribution along the X direction and the Z direction in FIG. 14 and 15, the light intensity along the X direction and the Z direction of the backlight device 10 is 2.16 × 10 ⁻⁴ W · cm ⁻² or more in a wide area, and the light intensity is uniform and sufficient. It can be seen that (luminance) is obtained. Furthermore, it can be seen that approximately twice the light intensity is obtained as compared with the backlight device 10 according to the first embodiment.

  According to the second embodiment, the same effects as those of the first embodiment can be obtained, and the energy utilization efficiency of light can be further improved. That is, as described in the second embodiment, by changing the size and shape of the LED 11 and configuring the light shaping rod 12 in a trumpet shape according to the size and shape, for example, use of light emitted from the LED 11 Efficiency can be improved. Further, by defining the correlation between the size of the LED 11 and the shape of the light shaping rod 12 as in the first and second embodiments, it becomes possible to significantly improve the energy utilization efficiency of light.

(Third embodiment)
Next, a backlight device according to a third embodiment of the present invention will be described. In the third embodiment, the shape of the light shaping rod 12 is the same as that of the second embodiment. Then, the LED chip (not shown) provided in the chip cover of the LED 11 is configured to be closer to the chip cover. Specifically, the distance between the diode chip and the chip cover (both not shown) in the LED 11 is made smaller than 0.28 mm in the first embodiment, for example, about 0.2 mm. Moreover, the dimension of the part closely_contact | adhered to the light shaping rod 12 of LED11 shall also be 3x1 mm similar to 2nd Embodiment. When the present inventor confirmed the light emission energy efficiency in the case of using such an LED 11, it was confirmed that the light emission energy utilization efficiency can be improved to about 75.5% with respect to the light emission from the LED 11.

  According to the third embodiment, the same effects as those of the second embodiment can be obtained, and the light energy utilization efficiency can be further improved. In the simulation result of the one-dimensional intensity distribution along the X direction and the Z direction in FIG. 2 when the in-plane intensity distribution of the light beam L emitted from the rod tip surface 12c is uniform, the second embodiment It was confirmed that sufficient light intensity (luminance) was obtained with the same high uniformity.

(Fourth embodiment)
Next, a backlight device according to a fourth embodiment of the present invention will be described. In the fourth embodiment, the shape of the light shaping rod 12 is the same as in the second and third embodiments. Then, the LED chip (not shown) provided in the chip cover of the LED 11 is configured to be closer to the chip cover. Specifically, the distance between the diode chip and the chip cover (both not shown) in the LED 11 is made smaller than 0.2 mm in the third embodiment, for example, about 0.1 mm. Moreover, the dimension of the part closely_contact | adhered to the light shaping rod 12 of LED11 shall also be 3x1 mm similar to 2nd Embodiment. When the present inventor confirmed the light emission energy efficiency in the case of using such an LED 11, it was confirmed that the light emission energy utilization efficiency can be improved to about 84.4% with respect to the light emission from the LED 11.

FIGS. 16 and 17 each illustrate a light beam emitted from the rod tip surface 12c with the power of light output from the LED chip of the LED 11 being 1 W in the backlight device 10 according to the fourth embodiment configured as described above. It is a graph which shows the simulation result of the intensity distribution along the X direction and Z direction of FIG. 2 when the intensity distribution of L is made uniform. 16 and 17 that the intensity distribution along the X direction and the Z direction of the backlight device 10 is substantially uniform at 2.61 × 10 ⁻⁴ W · cm ⁻² or more in a wide region. Furthermore, it can be seen that the light intensity can be improved by 20% or more compared to the backlight device 10 according to the second embodiment.

  According to the fourth embodiment, the same effects as those of the first to third embodiments can be obtained, and the light energy utilization efficiency can be further improved.

(Fifth embodiment)
Next, a liquid crystal display provided with a backlight device according to a fifth embodiment of the present invention will be described. FIG. 18 is a side view of the liquid crystal display according to the fifth embodiment viewed from the X direction.

  As shown in FIG. 18, the backlight device 20 according to the fifth embodiment differs from the first embodiment in that it is a plate-like resin that is molded by a resin molding method such as injection molding, for example. It has a body 26. And LED21, the light shaping rod 22, and the lens system 23 are embedded at the time of the shaping | molding of the resin body 26, for example in the state positioned previously. Here, the light shaping rod 22 and the lens system 23 are preferably formed so as to be in contact with at least air, but are not necessarily limited to such a configuration. Further, the resin body 26 is formed in a flat plate shape, and a recess 26a is formed on one surface side. The reflective prism sheet 24 and the mirror system 25 are integrally formed by depositing a metal such as aluminum (Al) or copper (Cu) on the resin body 26. At this time, since the metal is embedded in the concave portion 26a, the reflective member 24a having the same effect as the reflective convex portion 14a of the reflective prism sheet 14 according to the first embodiment is formed. The backlight device 20 is configured as described above. The liquid crystal display 16 according to the fifth embodiment is configured by providing the liquid crystal panel 16 illuminated by the backlight device 20 at a predetermined position on the other surface of the resin body 26. In addition, this liquid crystal display 2 can be used conveniently as liquid crystal displays, such as a smart phone and a portable terminal.

  According to the backlight device 20 according to the fifth embodiment, the resin body 26 can be molded by embedding the LED 21, the light shaping rod 22, and the lens system 23 in a state in which the resin body 26 is positioned in advance. Since the reflective prism sheet 24 and the mirror system 25 can be integrally formed by depositing metal on one main surface and one end, respectively, mass production is possible even when the liquid crystal display 2 is downsized. And the productivity can be improved, so that the cost can be reduced.

  As mentioned above, although embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, Various deformation | transformation based on the technical idea of this invention is possible. For example, the numerical values and materials given in the above-described embodiments are merely examples, and different numerical values and materials may be used as necessary.

  In the above-described embodiment, as a backlight device, a backlight device of a liquid crystal display in which the light intensity distribution in the illumination area is uniformed is taken as an example, but not only a general liquid crystal display but also a smartphone, a tablet terminal, etc. The present invention can be applied to a backlight device in any information display. Moreover, it can also be applied to lighting-type signboards, posters and painting lighting, and general lighting with uniform surface luminance, if necessary.

  Further, in the first embodiment described above, the shape of the XY cross section of the rod front end surface 12c, which is the light beam exit side end of the light shaping rod 12, is rectangular, but it is not necessarily limited to a rectangular shape. Various shapes such as a circular shape, an elliptical shape, a trapezoidal shape, and a parallelogram shape are possible. A known homogenizer may be used in place of the light shaping rod 12. Further, if the light source can emit light having a uniform in-plane intensity distribution within a desired range, the two-dimensional light source may be configured without using the light shaping means.

Further, in the first embodiment described above, the parallel light beam L _R reflected by the mirror system 15 is further reflected by the reflective prism sheet 14 to change the optical path, thereby emitting the light beam to the outside. However, it is not necessarily limited to the reflective prism sheet 14, and various members can be used as long as they are members that can change the optical path of a light beam such as a prism. Further, for example, the parallel light beam L _R reflected by the mirror system 15 may be directly output to the outside and used as illumination light.

  In the first embodiment described above, the mirror system 15 as the second condensing optical system is constituted by a concave mirror. In order to planarize the mirror system 15, the mirror system 15 constituted by a concave mirror is used. Instead, a Fresnel lens and a reflection mirror or a reflection type Fresnel lens may be used.

  In the first embodiment described above, a single white LED is used as the LED 11, but an RGBLED array or a vertical cavity surface emitting laser (VCSEL) can also be used. In addition, when LED11 is comprised from single LED, white LED is preferable, and when using several LED, these LED may be comprised from white LED, but it is comprised from RGBLED array etc. Also good.

The material of each lens 13a~13e of the lens system 13 used in the first embodiment described above, not necessarily limited to the material described above, the refractive index N _d and the Abbe number [nu _d is defined If it is a value, it is possible to employ | adopt various materials.

  In the first embodiment described above, the X-direction dimension Lx0 of the light incident side end of the first rod 12a is equal to or larger than the Y direction dimension Ly0. The X-direction dimension Lx0 may be smaller than the Y-direction dimension Ly0 (Lx0 <Ly0). Similarly, Lx1 <Ly1 and Lx2 <Ly2 may be set.

1, 2 Liquid crystal display 10, 20 Backlight device 11, 21 Light emitting diode (LED)
DESCRIPTION OF SYMBOLS 12, 22 Light shaping rod 12a 1st rod 12b 2nd rod 12c Rod front end surface 13, 23 Lens system 13a, 13b, 13c, 13d, 13e Lens 14, 24 Reflective prism sheet 14a Reflective convex part 15, 25 Mirror system 16 LCD panels 17, 18 blocking plate 17a, 18a opening 19 the shielding plates 24a reflecting member 26 resin body 26a concave L light beam L _R parallel beam L _r reflected parallel light beam

Claims (11)

A light emitting source comprising light emitting diodes (11, 21);
A two-dimensional light source that have a light shaping means for emitting a light beam to shape the light emitted from the light source,
A double-sided telecentric optical system formed by a first condensing optical system having a focal length f1 and a second condensing optical system having a focal length f2 larger than the focal length f1 ,
Furthermore, an optical path changing means,
A backlight device comprising :
The end of the light shaping means on the side where the light emitted from the light source enters is the end of the light shaping means on the side where the light flux is emitted. Smaller than the area of the cross section perpendicular to the optical axis of the luminous flux in
The first condensing optical system is a lens system (13, 23) provided on the two-dimensional light source side with respect to the second condensing optical system;
The second condensing optical system includes a mirror system (15, 25),
The emission direction of the light beam emitted from the second light collecting optical system is inclined with respect to the optical axis of the light beam that has passed through the first light collecting optical system;
Furthermore, the optical path changing means comprises a reflective prism sheet (14, 24) that changes the optical path of the light beam emitted from the second condensing optical system.
A backlight device characterized by that. The light shaping means is a light shaping rod (12, 22), and the first condensing optical system is a lens system (13, 23) having at least four lenses. The backlight device according to claim 1.   The mirror system (15, 25) has its reflecting surface facing the incident surface, which is the lower surface side of the reflecting prism sheet (14, 24), and the thickness direction of the reflecting prism sheet (14, 24). The backlight device according to claim 1, wherein the backlight device is inclined at an inclination angle θ = 2 ° to 4 °. The light beam emitted from the two-dimensional light source and traveling through the first condensing optical system is moved from the two-dimensional light source to the focal position of the second condensing optical system by the second condensing optical system. the backlight according to any one of claims 1 to 3, characterized in that focusing substantially (f2 / f1) ² times the area of the area of the cross section perpendicular to the optical axis of the emitted light beam apparatus. The distance between the principal points of the first condensing optical system and the second condensing optical system facing each other is the focal length f1 of the first condensing optical system and the focal length f2 of the second condensing optical system. the backlight device according to any one of claims 1-4, characterized in that substantially equal to the sum of. The first condensing optical system is provided with at least one blocking member that blocks a part of the light beam emitted from the two-dimensional light source, and the blocking member is effective among the light beams emitted from the two-dimensional light source. the backlight device according to any one of claims 1 to 5, characterized in that it has at least one opening for passing the light beam. At the end of the light shaping means on the side where light from the light source is incident, the cross-sectional shape perpendicular to the optical axis of the light flux is rectangular, and the light shaping means emits the light flux. The backlight device according to any one of claims 1 to 6 , wherein a cross-sectional shape perpendicular to the optical axis of the light beam at the end is rectangular. The area of the cross section perpendicular to the optical axis of the light beam at the end of the light shaping unit on the side from which the light beam is emitted is the end of the light shaping unit at the side on which light from the light source is incident. The backlight device according to claim 1, wherein the backlight device has a cross-sectional area perpendicular to the optical axis of the luminous flux that is 3 to 5 times. The backlight device according to any one of claims 1 to 8 , wherein the light shaping means includes a plurality of rods connected to each other or rods integrally formed with each other. The backlight device according to any one of claims 1 to 9 ,
A flat plate-like liquid crystal panel having at least a liquid crystal sandwiched between a plurality of light distribution layers,
A liquid crystal display, wherein a light beam emitted from the backlight device is incident substantially perpendicular to one surface of the liquid crystal panel. The backlight device according to any one of claims 1 to 9 , wherein a light beam emitted from the second condensing optical system is reflected by the reflective prism sheet (14, 24) , thereby the backlight. The liquid crystal display according to claim 10 , wherein a light beam is emitted from the device.