JPWO2011118563A1 - Polarized light guide plate, illumination device, and projection display device - Google Patents

Abstract

The polarizing light guide plate includes a light guide 10 through which light incident from an end surface propagates, a quarter-wave plate 11 formed on one surface of the light guide 10, and the other surface of the light guide 10. The reflective layer 12 is provided, and a plurality of refracting portions 13 and 14 provided in the light guide 10 so as to face the one surface. The refractive unit 13 has a refractive index for the first polarized light larger than the refractive index of the light guide 10 and a refractive index for the second polarized light whose polarization state is different from that of the first polarized light. It is the same as. The refractive unit 14 has a refractive index for the first polarized light that is smaller than the refractive index of the light guide 10, and a refractive index for the second polarized light is the same as the refractive index of the light guide 10. The refracting portions 13 and 14 are alternately arranged in a first direction intersecting with a direction perpendicular to the end face.

Description

  The present invention relates to a polarizing light guide plate from which light having polarization properties is emitted, and more particularly to a polarizing light guide plate of a projection display device represented by a display device such as a mobile phone or a liquid crystal projector.

  Patent Document 1 discloses an illumination device that emits light having polarization. The illumination device includes an isotropic waveguide, a lamp provided on an end face of the waveguide, a reflector provided on an end face opposite to the side provided with the lamp of the waveguide, and a waveguide. And an anisotropic layer provided on the road through an adhesive layer.

  In the anisotropic layer, the waveguide side surface is the first prism surface, and the opposite surface is the second prism surface. The first prism surface is formed by periodically forming a microstructure having a triangular wave cross section along the first direction. The second prism surface is an exit surface of the illumination device, and a fine structure whose cross section is a triangular wave shape is periodically formed along a second direction orthogonal to the first direction.

  According to the above illumination device, the first polarized light out of the light traveling from the waveguide toward the anisotropic layer is refracted by the first prism surface, but the polarization state is different from that of the first polarized light. The second polarized light passes through the first prism surface as it is. That is, the first prism surface has an action of separating incident light (unpolarized light) into first and second polarized light.

  The first polarized light refracted by the first prism surface is emitted from the second prism surface. The second prism surface has a function of collimating the emitted first polarized light in a predetermined direction. On the other hand, the second polarized light transmitted through the first prism surface is reflected by the second prism surface toward the waveguide side.

JP 2008-542991 Gazette

  In the illumination device described in Patent Document 1, not only collimated light (emitted light near the front surface) but also divergent light is emitted from the second prism surface (emitted surface). For example, in FIG. 4a of Patent Document 1, in addition to the collimated light, as the outgoing light, divergent light with a horizontal angle of 60 ° to 70 ° and a vertical angle of 20 ° to 40 °, and a horizontal angle of −60 °. A divergent light with a vertical angle of 20 ° to 40 ° at ˜−70 ° is shown. As described above, the illumination device described in Patent Document 1 has the following problems because the angular spread (outgoing angle) of outgoing light due to divergent light is large.

  In general, in a projection display device that irradiates a display element with light from a light source and projects an image formed by the display element by a projection optical system, an etendue determined by the light emission cross-sectional area of the light source and the divergence angle of the emitted light. Design that takes into account the constraints imposed by That is, in order to use all of the light emitted from the light source as projection light, the product value of the light emission cross-sectional area of the light source and the divergence angle of the emitted light is expressed by the display area of the display element and the F number of the projection optical system. It is necessary to make the value less than the product of the determined capture angle (solid angle). If this condition is not satisfied, part of the light from the light source is not used as projection light.

  When the illumination device described in Patent Document 1 is applied to a projection display device, a part of the light emitted from the illumination device (diverging light) is not used as projection light, and thus is emitted from the illumination device accordingly. Light utilization efficiency is reduced.

  Furthermore, divergent light emitted from the illumination device becomes stray light and leaks out of the device, or the stray light enters the projection optical system, thereby degrading the image quality of the projected image. For this reason, it is necessary to provide a member that absorbs or blocks such stray light in the projection display device, and the cost of the device increases accordingly.

  The object of the present invention is to solve the above-mentioned problems due to etendue restrictions and the problem of viewing angle dependence, and to suppress the spread of the emission angle, a polarizing light guide plate using the same, an illumination device using the same, and a projection type It is to provide a display device.

In order to achieve the above object, the polarizing light guide plate of the present invention comprises:
A light guide through which light incident from the end face propagates,
A quarter wave plate formed on one surface of the light guide;
A reflective layer provided on the other surface facing the one surface of the light guide;
A plurality of refractive indexes with respect to a first polarized light that is larger than a refractive index of the light guide, and a refractive index with respect to a second polarized light having a polarization state different from that of the first polarized light is the same as the refractive index of the light guide. A first refracting portion of
A plurality of second refracting sections having a refractive index with respect to the first polarized light smaller than a refractive index of the light guide and a refractive index with respect to the second polarized light being the same as the refractive index of the light guide; Have
The plurality of first and second refracting portions are provided in the light guide so as to face the one surface, and at least in a first direction intersecting a direction perpendicular to the end surface, The first refracting portions and the second refracting portions are alternately arranged.

The lighting device of the present invention is
The polarizing light guide plate,
And at least one light source provided on an end surface of the polarizing light guide plate.

The projection display device of the present invention is
The above lighting device;
A display element irradiated with light emitted from the illumination device;
A projection optical system for projecting an image formed by the display element.

Another projection display device of the present invention is
A lighting device of each color of red, green, and blue composed of the lighting device described above,
A first display element irradiated with red light emitted from the red illumination device;
A second display element irradiated with green light emitted from the green illumination device;
A third display element irradiated with blue light emitted from the blue illumination device;
A projection optical system for projecting each color image displayed on the first to third display elements.

It is a schematic diagram which shows the structure of the polarizing light-guide plate which is the 1st Embodiment of this invention. It is a schematic diagram which shows an example of the two-dimensional arrangement | positioning of the refractive part of the polarizing light-guide plate shown in FIG. It is a schematic diagram for demonstrating the emission conditions with respect to the 1st polarized light in the 1st refractive part of the polarizing light-guide plate shown in FIG. It is a schematic diagram for demonstrating the 1st light guide condition with respect to the 1st polarized light in the 1st refractive part of the polarizing light-guide plate shown in FIG. It is a schematic diagram for demonstrating the 2nd light guide condition with respect to the 1st polarized light in the 1st refractive part of the polarizing light guide plate shown in FIG. It is a schematic diagram for demonstrating the 3rd light guide condition with respect to the 1st polarized light in the 1st refractive part of the polarizing light-guide plate shown in FIG. It is a schematic diagram for demonstrating the emission conditions with respect to the 1st polarized light in the 2nd refractive part of the polarizing light-guide plate shown in FIG. It is a schematic diagram for demonstrating the 1st light guide condition with respect to the 1st polarized light in the 2nd refractive part of the polarizing light-guide plate shown in FIG. It is a schematic diagram for demonstrating the 2nd light guide condition with respect to the 1st polarized light in the 2nd refractive part of the polarization light guide plate shown in FIG. It is a schematic diagram for demonstrating the 3rd light guide conditions with respect to the 1st polarized light in the 2nd refractive part of the polarizing light-guide plate shown in FIG. It is a schematic diagram for demonstrating the 4th light guide condition with respect to the 1st polarized light in the 2nd refractive part of the polarizing light-guide plate shown in FIG. It is a schematic diagram for demonstrating the operation | movement with respect to the light of each polarization | polarized-light component of S polarized light and P polarized light in the polarizing light-guide plate which has the matrix-shaped arrangement | positioning shown in FIG. It is a schematic diagram for demonstrating the angle conversion conditions in the polarizing light-guide plate shown in FIG. It is a schematic diagram for demonstrating the magnitude | size and space | interval of the refractive part which satisfy | fill the angle conversion conditions shown in FIG. It is a schematic diagram for demonstrating the conditions for suppressing the angular spread in the refractive part of the polarizing light-guide plate shown in FIG. It is a schematic diagram which shows an example of a structure of the refractive part which satisfy | fills the conditions shown to FIG. 8A. It is a schematic diagram for demonstrating another condition for suppressing the angular spread in the refractive part of the polarizing light-guide plate shown in FIG. It is a schematic diagram which shows an example of a structure of the refractive part which satisfy | fills the conditions shown to FIG. 9A. It is a schematic diagram for demonstrating the conditions of the magnitude | size of the 1st refractive part for increasing the emitted light quantity of the polarizing light-guide plate shown in FIG. It is a schematic diagram for demonstrating the conditions of the space | interval of the 1st refractive part for increasing the emitted light quantity of the polarizing light-guide plate shown in FIG. 1, and the refractive part adjacent to this. It is a schematic diagram for demonstrating the conditions of the magnitude | size of the 2nd refractive part for increasing the emitted light quantity of the polarizing light-guide plate shown in FIG. It is a schematic diagram for demonstrating the conditions of the space | interval of the 2nd refractive part for increasing the emitted light quantity of the polarizing light guide plate shown in FIG. 1, and the refractive part adjacent to this. It is a schematic diagram which shows one Example of arrangement | positioning of the 1st and 2nd refractive part of the polarizing light-guide plate shown in FIG. It is a schematic diagram for demonstrating the luminance distribution of the emitted light when the refracting parts of the polarization light guide plate shown in FIG. 1 are arranged at equal intervals. It is a schematic diagram for demonstrating the brightness | luminance distribution of the emitted light in case the space | interval of the refractive part of the polarizing light-guide plate shown in FIG. 1 becomes large gradually as it leaves | separates from an end surface. It is a schematic diagram which shows the modification of the polarizing light-guide plate shown in FIG. It is a schematic diagram which shows the cross-sectional shape of the prism sheet of the polarizing light guide plate shown to FIG. 14B. It is a schematic diagram which shows another modification of the polarizing light-guide plate shown in FIG. It is a schematic diagram which shows the structure of the polarizing light-guide plate which is the 2nd Embodiment of this invention. It is a schematic diagram for demonstrating the emission conditions with respect to the 1st polarized light in the 1st refractive part of the polarizing light-guide plate shown in FIG. It is a schematic diagram for demonstrating the 1st light guide condition with respect to the 1st polarized light in the 1st refractive part of the polarizing light guide plate shown in FIG. It is a schematic diagram for demonstrating the 2nd light guide conditions with respect to the 1st polarized light in the 1st refractive part of the polarization light guide plate shown in FIG. It is a schematic diagram for demonstrating the 3rd light guide conditions with respect to the 1st polarized light in the 1st refractive part of the polarizing light-guide plate shown in FIG. It is a schematic diagram for demonstrating the 4th light guide condition with respect to the 1st polarized light in the 1st refractive part of the polarizing light-guide plate shown in FIG. It is a schematic diagram for demonstrating the 5th light guide condition with respect to the 1st polarized light in the 1st refractive part of the polarization light guide plate shown in FIG. It is a schematic diagram for demonstrating the 1st output conditions with respect to the 1st polarized light in the 2nd refractive part of the polarizing light-guide plate shown in FIG. It is a schematic diagram for demonstrating the 2nd output conditions with respect to the 1st polarized light in the 2nd refractive part of the polarizing light-guide plate shown in FIG. It is a schematic diagram for demonstrating the 1st light guide condition with respect to the 1st polarized light in the 2nd refractive part of the polarizing light-guide plate shown in FIG. It is a schematic diagram for demonstrating the 2nd light guide condition with respect to the 1st polarized light in the 2nd refractive part of the polarization light guide plate shown in FIG. It is a schematic diagram for demonstrating the 3rd light guide condition with respect to the 1st polarized light in the 2nd refractive part of the polarizing light-guide plate shown in FIG. It is a schematic diagram for demonstrating the 4th light guide condition with respect to the 1st polarized light in the 2nd refractive part of the polarizing light-guide plate shown in FIG. It is a schematic diagram for demonstrating the 5th light guide condition with respect to the 1st polarized light in the 2nd refractive part of the polarizing light-guide plate shown in FIG. It is a schematic diagram which shows the modification of the polarization light-guide plate shown in FIG. It is a schematic diagram which shows an example of an illuminating device provided with the polarizing light-guide plate of this invention. It is a schematic diagram which shows the structure of the projection type display apparatus using an illuminating device provided with the polarizing light-guide plate of this invention.

DESCRIPTION OF SYMBOLS 10 Light guide 11 1/4 wavelength plate 12 Reflection layers 13 and 14 Refraction part

  Next, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic diagram showing a configuration of a polarizing light guide plate according to the first embodiment of the present invention.

  As shown in FIG. 1, the polarization light guide plate is used in a projection display device typified by a liquid crystal projector, and is provided with a light guide 10 and a quarter provided so as to sandwich the light guide 10. A plurality of refraction portions 13 (first refraction portions) and a plurality of refraction portions 14 (second refraction portions) provided along a boundary surface between the wave plate 11 and the reflection layer 12 and the reflection layer 12 in the light guide 10. Refraction part). The cross section shown in FIG. 1 is a surface obtained by cutting the polarizing light guide plate along the first direction. Here, the first direction is a direction intersecting or orthogonal to a direction perpendicular to a predetermined end surface of the light guide 10 (an end surface on the side where the light source is disposed).

  The light guide 10 has a plate shape and is made of a material having an isotropic refractive index. Refractive index isotropic means that the refractive indexes for the first and second polarized lights (P-polarized light and S-polarized light) having different polarization states are the same. Here, the refractive index of the light guide 10 is n0.

  The light guide 10 has a plurality of end faces (usually four end faces), and light from the light source is incident on at least one of these end faces. The light source is, for example, a semiconductor light source such as a light emitting diode (LED) or a semiconductor laser (LD), or a light source called a solid light source.

  The refractive index of the quarter wave plate 11 is substantially equal to the refractive index n0 of the light guide 10. The surface of the quarter-wave plate 11 opposite to the light guide 10 is an emission surface 11a.

  The refracting portions 13 and 14 are made of a material having refractive index anisotropy, and the cross-sectional shape thereof is a rectangular shape. The refractive index anisotropy indicates that the refractive indexes for the first and second polarized lights are different. Here, the refractive index for the first polarized light in the refracting section 13 is n1, and the refractive index for the second polarized light is n2. In the refracting section 14, the refractive index for the first polarized light is n1 ', and the refractive index for the second polarized light is n2'. The refracting unit 13 satisfies the refractive index condition of n1> n0 and n2 = n0. On the other hand, the refracting unit 14 satisfies the refractive index condition of n1 '<n0 and n2' = n0.

  The refracting parts 13 and the refracting parts 14 are provided alternately and periodically in at least the first direction. The arrangement of the refracting portions 13 and 14 may be a one-dimensional arrangement or a two-dimensional arrangement.

  FIG. 2 schematically shows a two-dimensional arrangement of the refractive portions 13 and 14. In this example, the refracting portions 13 and 14 are alternately arranged in the first direction described in FIG. 1 and are alternately arranged in a second direction intersecting or orthogonal to the first direction. In the two-dimensional arrangement, the refracting portions 13 and 14 may be alternately arranged only in the first direction.

  The size (height, length and width) of the refracting portions 13 and 14 and the interval between the refracting portions 13 and 14 are appropriately set in consideration of the light guide conditions and the emission conditions. Here, the height is a thickness in a direction perpendicular to the surface 10a on the side where the quarter wavelength plate 11 is provided. The length and width are the lengths of two intersecting sides when the refracted portion is viewed from a direction perpendicular to the surface 10a.

  Next, the operation of the polarizing light guide plate of this embodiment will be described.

  In the polarization light guide plate of this embodiment, a part of the light (non-polarized light) incident on the first end face of the light guide 10 from the light source is emitted from the output surface 11a of the quarter wavelength plate 11 and the reflection layer 12. And propagates in the light guide 10 toward the second end face facing the first end face. In this propagation process, a part of the light enters the refracting parts 13 and 14.

  The refracting units 13 and 14 are the first and second polarized light between the emission condition for emitting the first polarized light from the emission surface 11a and between the emission surface 11a of the quarter-wave plate 11 and the reflective layer 12. Although it is configured to satisfy the light guide condition for guiding light, the conditions are different from each other.

  First, the light guide conditions and emission conditions of the refraction part 13 will be described.

  FIG. 3A is a diagram for explaining the emission conditions of the refracting unit 13 with respect to the first polarized light, and a part of the polarization light guide plate shown in FIG. 2 is a schematic diagram of a cross section cut along a plane perpendicular to the emission surface 11a of the quarter-wave plate 11).

  In the refracting portion 13, the first polarized light incident at an angle φ0 formed with the surface 13a with respect to the surface 13a located on the quarter wavelength plate 11 side is refracted at an angle θ1 and faces the surface 13a. 13b is reached. Here, the incident angle of the first polarized light with respect to the surface 13a is given by “90 ° −φ0”, which is larger than the angle θ1.

  The surface 13 b is an interface between the refracting portion 14 and the reflective layer 12. The first polarized light incident from the surface 13a and reaching the surface 13b is reflected by the surface 13b. The first polarized light reflected by the surface 13b reaches the side surface 13c.

  The incident angle θ2 (= 90 ° −θ1) of the first polarized light reflected by the surface 13b with respect to the side surface 13c is smaller than the critical angle (the smallest incident angle at which total reflection occurs). Therefore, the first polarized light incident on the side surface 13c from the surface 13b is refracted at an angle φ1 (> θ2) and reaches the surface 10a of the light guide 10.

  Since the refractive index of the ¼ wavelength plate 11 is substantially equal to the refractive index of the light guide 10, the first polarized light from the side surface 13c passes through the surface 10a without being refracted and is ¼ wavelength. It reaches the exit surface 11a of the plate 11. Since the first polarized light that has passed through the surface 10a passes through the quarter-wave plate 11 once, the light that reaches the exit surface 11a is circularly polarized light.

  When the incident angle (90 ° −φ1) of the circularly polarized light incident on the emission surface 11a is smaller than the critical angle, the circularly polarized light is emitted from the emission surface 11a at the emission angle β.

  As described above, in the refracting unit 13, the first polarized light that satisfies the condition of being incident from the surface 13 a and emitted from the side surface 13 c (outgoing condition) is converted into circularly polarized light by the quarter wavelength plate 11. Then, the light is emitted from the emission surface 11a.

  Further, as shown in FIG. 3A, after the first polarized light that enters the refracting portion 13 from the surface 13a and is emitted from the side surface 13c is reflected by the reflective layer 12, the quarter-wave plate 11 is The condition of passing through and exiting from the exit surface 11a is also established as the exit condition.

  FIG. 3B is a diagram for explaining the first light guide condition of the refracting unit 13 for the first polarized light, and a part of the polarization light guide plate shown in FIG. FIG. 6 is a schematic view of a cross section cut along a plane perpendicular to the end face and the exit face 11 a of the quarter-wave plate 11.

  As in the case of the emission condition, in the refracting unit 13, the first polarized light that is incident on the surface 13a at an angle φ0 with the surface 13a is refracted at an angle θ1 and reaches the surface 13b. The first polarized light incident from the surface 13a and reaching the surface 13b is reflected by the surface 13b. The first polarized light reflected by the surface 13b reaches the surface 13a.

  The incident angle (same as θ1) of the first polarized light reflected by the surface 13b with respect to the surface 13a is smaller than the critical angle. For this reason, the first polarized light incident on the surface 13 a from the surface 13 b is refracted and reaches the surface 10 a of the light guide 10. Here, the angle between the first polarized light emitted from the surface 13a and the surface 13a is φ0.

  Since the refractive index of the quarter-wave plate 11 is substantially equal to the refractive index of the light guide 10, the first polarized light from the surface 13a passes through the surface 10a without being refracted and is ¼. It reaches the emission surface 11 a of the wave plate 11. Since the first polarized light that has passed through the surface 10a passes through the quarter-wave plate 11 once, the light that reaches the exit surface 11a is circularly polarized light.

  The incident angle (90 ° −φ0) of the circularly polarized light incident on the exit surface 11a is larger than the critical angle. Therefore, the circularly polarized light is reflected in the direction of the light guide 10 at the emission surface 11a. Since the circularly polarized light reflected by the emission surface 11a passes through the quarter-wave plate 11, the light incident on the surface 10a of the light guide 10 is the second polarized light. The second polarized light incident from the surface 10 a propagates through the light guide 10.

  As described above, in the refracting unit 13, the first polarized light that satisfies the first light guide condition that is incident from the surface 13a, reflected by the surface 13b, and emitted from the surface 13a is emitted from the emission surface 11a. Instead, after being converted into the second polarized light by the quarter wavelength plate 11, the light propagates through the light guide 10.

  FIG. 3C is a diagram for explaining the second light guide condition of the refracting unit 13 for the first polarized light, and a part of the polarization light guide plate shown in FIG. FIG. 6 is a schematic view of a cross section cut along a plane perpendicular to the end face and the exit face 11 a of the quarter-wave plate 11.

  In the refracting unit 13, the first polarized light incident at the incident angle φ0 with respect to the side surface 13d is refracted at the angle θ1 and reaches the surface 13b.

  The first polarized light incident from the side surface 13d and reaching the surface 13b is reflected by the surface 13b. The first polarized light reflected by the surface 13b reaches the surface 13a.

  The incident angle θ2 of the first polarized light reflected by the surface 13b with respect to the surface 13a is smaller than the critical angle. For this reason, the first polarized light incident on the surface 13 a from the surface 13 b is refracted and reaches the surface 10 a of the light guide 10. Here, the angle between the first polarized light emitted from the surface 13a and the surface 13a is φ1.

  Since the refractive index of the quarter-wave plate 11 is substantially equal to the refractive index of the light guide 10, the first polarized light from the surface 13a passes through the surface 10a without being refracted and is ¼. It reaches the emission surface 11 a of the wave plate 11. Since the first polarized light that has passed through the surface 10a passes through the quarter-wave plate 11 once, the light that reaches the exit surface 11a is circularly polarized light.

  The incident angle (90 ° −φ1) of circularly polarized light incident on the exit surface 11a is larger than the critical angle. Therefore, the circularly polarized light is reflected in the direction of the light guide 10 at the emission surface 11a. Since the circularly polarized light reflected by the emission surface 11a passes through the quarter-wave plate 11, the light incident on the surface 10a of the light guide 10 is the second polarized light. The second polarized light incident from the surface 10 a propagates through the light guide 10.

  Thus, in the refracting portion 13, the first polarized light that satisfies the second light guiding condition that is incident from the side surface 13d, reflected by the surface 13b, and emitted from the surface 13a is emitted from the emission surface 11a. Instead, after being converted into the second polarized light by the quarter wavelength plate 11, the light propagates through the light guide 10.

  3D is a diagram for explaining a third light guide condition of the refracting unit 13 with respect to the first polarized light, and a part of the polarization light guide plate shown in FIG. FIG. 6 is a schematic view of a cross section cut along a plane perpendicular to the end face and the exit face 11 a of the quarter-wave plate 11.

  In the refracting unit 13, the first polarized light incident at the incident angle φ0 with respect to the side surface 13d is refracted at the angle θ1 and reaches the surface 13b.

  The first polarized light incident from the side surface 13d and reaching the surface 13b is reflected by the surface 13b. The first polarized light reflected by the surface 13b reaches the side surface 13c.

  The incident angle (same as θ1) of the first polarized light reflected by the surface 13b with respect to the side surface 13c is smaller than the critical angle. For this reason, the first polarized light incident on the side surface 13 c from the surface 13 b is refracted and reaches the surface 10 a of the light guide 10. Here, the angle between the first polarized light emitted from the side surface 13c and the side surface 13c is φ0.

  Since the refractive index of the quarter-wave plate 11 is substantially equal to the refractive index of the light guide 10, the first polarized light from the side surface 13c passes through the surface 10a without being refracted, and becomes 1/4. It reaches the emission surface 11 a of the wave plate 11. Since the first polarized light that has passed through the surface 10a has passed through the quarter-wave plate 11 once, the light that reaches the exit surface 11a is circularly polarized light.

  The incident angle (90 ° −φ0) of the circularly polarized light incident on the exit surface 11a is larger than the critical angle. Therefore, the circularly polarized light is reflected in the direction of the light guide 10 at the emission surface 11a. Since the circularly polarized light reflected by the exit surface 11a passes through the quarter-wave plate 11, the light incident on the light guide 10 from the exit surface 11a is second polarized light. The second polarized light incident from the surface 10 a propagates through the light guide 10.

  Thus, in the refracting section 13, the first polarized light that satisfies the third light guiding condition, which is incident from the side surface 13d, reflected by the surface 13b, and emitted from the side surface 13c, is emitted from the emission surface 11a. Instead, after being converted into the second polarized light by the quarter wavelength plate 11, the light propagates through the light guide 10.

  Next, light guide conditions and emission conditions of the refracting unit 14 will be described.

  FIG. 4A is a diagram for explaining the emission condition of the refraction unit 14 with respect to the first polarized light, and a part of the polarization light guide plate shown in FIG. FIG. 6 is a schematic view of a cross section cut along a plane perpendicular to the end surface provided with) and the emission surface 11a.

  In the refracting unit 14, the first polarized light incident on the side surface 14d located on the first end surface side at the incident angle φ0 is refracted at the angle θ1 ′ (> φ0) and reaches the surface 14b.

  The surface 14 b is an interface between the refracting portion 14 and the reflective layer 12. The first polarized light incident from the surface 14d and reaching the surface 14b is reflected by the surface 14b. The first polarized light reflected by the surface 14b reaches the surface 14a (the surface located on the quarter wavelength plate 11 side).

  The incident angle θ2 ′ (= 90−θ1 ′) of the first polarized light reflected by the surface 14b with respect to the surface 14a is smaller than the critical angle. For this reason, the first polarized light reflected by the surface 14b and incident on the surface 14a is refracted at an angle φ1 'and reaches the surface 10a. The relationship between the incident angle θ2 ′ and the angle φ1 ′ is given by “θ2 ′> 90 ° −φ1 ′”.

  Since the refractive index of the quarter-wave plate 11 is substantially equal to the refractive index of the light guide 10, the first polarized light from the surface 14a passes through the surface 10a without being refracted and is ¼ wavelength. It reaches the exit surface 11a of the plate 11. Since the first polarized light that has passed through the surface 10a passes through the quarter-wave plate 11 once, the light that reaches the exit surface 11a is circularly polarized light.

  When the incident angle (90 ° −φ1 ′) of the circularly polarized light incident on the exit surface 11a is smaller than the critical angle, the circularly polarized light is emitted from the exit surface 11a at the exit angle β.

  As described above, in the refracting unit 14, the first polarized light that satisfies the condition (outgoing condition) that is incident from the side surface 14 d and is emitted from the surface 14 a is converted into circularly polarized light by the quarter-wave plate 11. Then, the light is emitted from the emission surface 11a.

  As shown in FIG. 4A, the first polarized light that enters the refracting portion 14 from the side surface 14d and exits from the surface 14a passes through the quarter-wave plate 11 and exits from the exit surface 11a. The above condition is also established as the emission condition.

  4B is a diagram for explaining the first light guide condition of the refracting unit 14 for the first polarized light, and a part of the polarization light guide plate shown in FIG. FIG. 6 is a schematic view of a cross section cut along a plane perpendicular to the end face and the exit face 11 a of the quarter-wave plate 11.

  As in the case of the emission condition, in the refracting unit 14, the first polarized light incident at the incident angle φ0 with respect to the side surface 14d is refracted at the angle θ1 ′ and reaches the surface 14b. The first polarized light incident from the side surface 14d and reaching the surface 14b is reflected by the surface 14b. The first polarized light reflected by the surface 14b reaches the side surface 14c.

  The incident angle (same as θ1 ′) of the first polarized light reflected by the surface 14b with respect to the side surface 14c is smaller than the critical angle. Therefore, the first polarized light incident on the side surface 14c from the surface 14b is refracted at an angle φ0 and reaches the surface 10a of the light guide 10.

  Since the refractive index of the quarter-wave plate 11 is substantially equal to the refractive index of the light guide 10, the first polarized light from the side surface 14c passes through the surface 10a without being refracted, and becomes 1/4. It reaches the emission surface 11 a of the wave plate 11. Since the first polarized light that has passed through the surface 10a passes through the quarter-wave plate 11 once, the light that reaches the exit surface 11a is circularly polarized light.

  The incident angle (90 ° −φ0) of the circularly polarized light incident on the exit surface 11a is larger than the critical angle. Therefore, the circularly polarized light is reflected in the direction of the light guide 10 at the emission surface 11a. Since the circularly polarized light reflected by the exit surface 11a passes through the quarter wavelength plate 11 again, the light incident on the surface 10a from the exit surface 11a is the second polarized light. The second polarized light incident from the surface 10 a propagates through the light guide 10.

  As described above, in the refracting unit 14, the first polarized light that satisfies the first light guiding condition that is incident from the side surface 14d, reflected by the surface 14b, and output from the side surface 14c is output from the output surface 11a. Instead, after being converted into the second polarized light by the quarter wavelength plate 11, the light propagates through the light guide 10.

  FIG. 4C is a diagram for explaining the second light guide condition of the refracting unit 14 with respect to the first polarized light, and a part of the polarization light guide plate shown in FIG. FIG. 6 is a schematic view of a cross section cut along a plane perpendicular to the end face and the exit face 11 a of the quarter-wave plate 11.

  In the refracting unit 14, the first polarized light incident on the surface 14a at an angle φ0 with the surface 14a is refracted at an angle θ1 ′ and reaches the surface 14b.

  The first polarized light incident from the surface 14a and reaching the surface 14b is reflected by the surface 14b. The first polarized light reflected by the surface 14b is incident on the side surface 14c at an incident angle θ2 ′. The incident angle θ2 ′ is smaller than the critical angle. Therefore, the first polarized light incident on the side surface 14c from the surface 14b is refracted at an angle φ1 'and reaches the surface 10a.

  Since the refractive index of the quarter-wave plate 11 is substantially equal to the refractive index of the light guide 10, the first polarized light from the side surface 14c passes through the surface 10a without being refracted and is ¼ wavelength. It reaches the exit surface 11a of the plate 11. Since the first polarized light that has passed through the surface 10a passes through the quarter-wave plate 11 once, the light that reaches the exit surface 11a is circularly polarized light.

  The incident angle (90 ° −φ1 ′) of circularly polarized light incident on the exit surface 11a is larger than the critical angle. Therefore, the circularly polarized light is reflected in the direction of the light guide 10 at the emission surface 11a. Since the circularly polarized light reflected by the emission surface 11a passes through the quarter-wave plate 11, the light incident on the surface 10a of the light guide 10 is the second polarized light. The second polarized light incident from the surface 10 a propagates through the light guide 10.

  Thus, in the refracting section 14, the first polarized light that satisfies the second light guide condition that is incident from the surface 14a, reflected by the surface 14b, and emitted from the side surface 14c is emitted from the emission surface 11a. Instead, after being converted into the second polarized light by the quarter wavelength plate 11, the light propagates through the light guide 10.

  4D is a diagram for explaining a third light guide condition of the refracting unit 14 with respect to the first polarized light, and a part of the polarization light guide plate shown in FIG. FIG. 6 is a schematic view of a cross section cut along a plane perpendicular to the end face and the exit face 11 a of the quarter-wave plate 11.

  In the refracting unit 14, the first polarized light incident on the surface 14a at an angle φ0 with the surface 14a is refracted at an angle θ1 ′ and reaches the surface 14b.

  The first polarized light incident from the surface 14a and reaching the surface 14b is reflected by the surface 14b. The first polarized light reflected by the surface 14b reaches the surface 14a.

  The incident angle (same as θ1 ′) of the first polarized light reflected by the surface 14b with respect to the surface 14a is smaller than the critical angle. For this reason, the first polarized light incident on the surface 14 a from the surface 14 b is refracted and reaches the surface 10 a of the light guide 10. Here, the angle between the first polarized light emitted from the surface 14a and the surface 14a is φ0.

  Since the refractive index of the quarter-wave plate 11 is substantially equal to the refractive index of the light guide 10, the first polarized light from the surface 14a passes through the surface 10a without being refracted, and becomes 1/4. It reaches the emission surface 11 a of the wave plate 11. Since the first polarized light that has passed through the surface 10a passes through the quarter-wave plate 11 once, the light that reaches the exit surface 11a is circularly polarized light.

  The incident angle (90 ° −φ0) of the circularly polarized light incident on the exit surface 11a is larger than the critical angle. Therefore, the circularly polarized light is reflected in the direction of the light guide 10 at the emission surface 11a. Since the circularly polarized light reflected by the emission surface 11a passes through the quarter-wave plate 11, the light incident on the surface 10a of the light guide 10 is the second polarized light. The second polarized light incident from the surface 10 a propagates through the light guide 10.

  Thus, in the refraction part 14, the 1st polarization light which satisfies the 3rd light guide condition which enters from surface 14a, is reflected by surface 14b, and is emitted from surface 14a is emitted from output surface 11a. Instead, after being converted into the second polarized light by the quarter wavelength plate 11, the light propagates through the light guide 10.

  FIG. 4E is a diagram for explaining the fourth light guide condition of the refracting unit 14 for the first polarized light, and a part of the polarization light guide plate shown in FIG. FIG. 6 is a schematic view of a cross section cut along a plane perpendicular to the end face and the exit face 11 a of the quarter-wave plate 11.

  In the refracting section 14, the first polarized light that is incident on the surface 14a at an angle φ with the surface 14a is reflected by the surface 14a.

  The first polarized light reflected by the surface 14 a reaches the surface 10 a of the light guide 10. Since the refractive index of the quarter-wave plate 11 is substantially equal to the refractive index of the light guide 10, the first polarized light from the surface 14a passes through the surface 10a without being refracted, and becomes 1/4. It reaches the emission surface 11 a of the wave plate 11. Since the first polarized light that has passed through the surface 10a passes through the quarter-wave plate 11 once, the light that reaches the exit surface 11a is circularly polarized light.

  The incident angle (90 ° −φ) of circularly polarized light incident on the exit surface 11a is larger than the critical angle. Therefore, the circularly polarized light is reflected in the direction of the light guide 10 at the emission surface 11a. Since the circularly polarized light reflected by the emission surface 11a passes through the quarter-wave plate 11, the light incident on the surface 10a of the light guide 10 is the second polarized light. The second polarized light incident from the surface 10 a propagates through the light guide 10.

  Thus, in the refracting section 14, the first polarized light that satisfies the fourth light guide condition of being reflected by the surface 14a is not emitted from the emission surface 11a, but is secondly emitted by the quarter wavelength plate 11. After being converted into the polarized light, the light propagates through the light guide 10.

  As described above, according to the polarization light guide plate of the present embodiment, only the first polarized light that satisfies the emission conditions of the refraction units 13 and 14 is emitted as circularly polarized light from the emission surface 11a, and the emission angle spread is The angle β is controlled within a possible range. Here, the emission angle β is taken in the in-plane direction of the first plane intersecting (or orthogonal to) each of the first end face (end face on the side where the light source is disposed) of the light guide 10 and the emission face 11a. The first emission angle to be obtained.

  More specifically, when the angle φ0 is 48.1 ° and the angle φ1 is 52.0 ° in the emission condition shown in FIG. 3A, the emission angle β is 67.3 °. When the angle φ0 is 45.0 ° and the angle φ1 is 48.9 °, the emission angle β is 80.5 °. When the angle φ0 is 44.3 ° and the angle φ1 is 48.2 °, the emission angle β is 89.8 °. When the maximum angle of light incident on the light guide 10 from the light source with respect to the plane parallel to the exit surface 11a of the quarter-wave plate 11 is 48.1 ° or less, the exit angle width is 22.5 °. . Here, the emission angle width is an angle width given by the maximum angle and the minimum angle of the emission angle β, and is an angular spread of the first emission angle of the outgoing light of the polarizing light guide plate of the present embodiment.

  Further, according to the polarization light guide plate of the present embodiment, light is circulated between the ¼ wavelength plate 11 and the reflection layer 12, and in the circulation process, polarization separation by the refracting portions 13 and 14 and a ¼ wavelength plate are performed. The light can be reused by performing the polarization conversion according to 11. Thereby, the light utilization efficiency can be further improved.

  FIG. 5 schematically shows the operation of the S-polarized light and the P-polarized light with respect to the light in the polarization light guide plate having the matrix arrangement shown in FIG. In FIG. 5, the dashed arrow indicates S-polarized light, and the solid arrow indicates P-polarized light. As the refracting portion 14, a solid-line rectangular portion and a broken-line rectangular portion are described, but the broken-line rectangular portion is located on the back side of the refracting portion 13 toward the drawing, and the solid-line rectangular portion faces the drawing. And located in front of the refracting portion 13.

  In the example shown in FIG. 5, the refractive index for P-polarized light is n1, the refractive index for S-polarized light is n2, and the refracting unit 13 satisfies the refractive index condition of n1> n2 and n2 = n0. The refractive index for P-polarized light is n1 ', the refractive index for S-polarized light is n2', and the refracting unit 14 satisfies the refractive index condition of n1 '<n2' and n2 '= n0.

  In the refracting portion 13, P-polarized light that satisfies the emission condition of entering from the surface 13 a and exiting from the side surface 13 c is emitted from the emission surface 11 a of the quarter-wave plate 11. In addition, in the refracting unit 14, only P-polarized light that satisfies the emission condition of entering from the side surface 14d and exiting from the surface 14a is emitted from the exit surface 11a of the quarter-wave plate 11.

  On the other hand, the S-polarized light is transmitted as it is without being refracted by the refraction portions 13 and 14. Part of the S-polarized light is reflected by the reflective layer 12, and the reflected S-polarized light enters the quarter-wave plate 11 from the surface 10 a of the light guide 10. The light that has entered the quarter-wave plate 11 is reflected by the exit surface 11a, and the reflected light is incident on the surface 10a of the light guide 10 again. In this case, the light incident on the quarter wavelength plate 11 from the light guide 10 passes through the quarter wavelength plate 11 twice. That is, the S-polarized light incident on the quarter-wave plate 11 from the surface 10a of the light guide 10 passes through the quarter-wave plate 11 twice, and thus is converted into P-polarized light.

  Although not shown in the drawing, the P-polarized light that does not satisfy the emission condition in the refracting portions 13 and 14 propagates through the light guide 10 while being reflected by the emission surface 11 a of the quarter-wave plate 11 and the reflection layer 12. To do. In this propagation process, the P-polarized light incident on the quarter-wave plate 11 from the surface 10a of the light guide 10 passes through the quarter-wave plate 11 twice, and thus is converted into S-polarized light.

  In addition, in the refracting portions 13 and 14, a part of the light guided through the light guide 10 undergoes angle conversion. For example, according to the emission condition shown in FIG. 3A, when the angle φ1 is larger than the angle φ0 and the incident angle (90−φ1) with respect to the emission surface 11a is smaller than the critical angle, the first polarized light is emitted from the emission surface 11a. It is emitted from. However, even when the angle φ1 is larger than the angle φ0, if the incident angle (90−φ1) is greater than or equal to the critical angle, the first polarized light is reflected by the emission surface 11a and is guided to the light guide 10. Guide the light inside. In this case, as the light to be guided is guided, the angle φ gradually increases. As a result, the incident angle (90−φ1) becomes smaller than the critical angle, and the light to be guided exits from the exit surface 11a. Is done. In the angle conversion by the refracting unit 13, the angle φ 0 is increased in such a light guide process, and the light propagating through the light guide 10 while being reflected by the output surface 11 a of the quarter-wave plate 11 and the reflection layer 12. Among them, the first polarized light satisfying the emission condition can be obtained.

  In the example shown in FIG. 5, the refractive indexes for S-polarized light may be n1 and n1 ', and the refractive indexes for P-polarized light may be n2 and n2'. In this case, only S-polarized light satisfying the emission condition is emitted from the emission surface 11 a of the quarter-wave plate 11.

  Moreover, according to the polarizing light guide plate of the present embodiment, not only the first emission angle described above is controlled, but also the first plane described above (the first end surface of the light guide 10 and each of the emission surfaces 11a). It is also possible to control the second emission angle that can be taken in the in-plane direction of the second plane intersecting or orthogonal to each of the intersecting or orthogonal surfaces and the exit surface 11a.

  FIG. 6 is a schematic diagram showing how the second emission angle is limited. FIG. 6 shows a state in which adjacent refracting portions 13 and 14 are viewed from a direction perpendicular to the emission surface 11 a of the quarter-wave plate 11.

  The refracting portion 13 has four side surfaces 13c to 13f. The side surfaces 13c and 13d are parallel, and the side surfaces 13e and 13f are parallel. The refracting portion 14 has four side surfaces 14c to 14f. The side surfaces 14c and 14d are parallel, and the side surfaces 14e and 14f are parallel. The side surface 13e of the refracting portion 13 is parallel to the side surface 14f of the refracting portion 14.

  In the refracting portion 13, the first polarized light enters from the side surface 13d and exits from the side surface 13e. In this case, the angle φ1 between the first polarized light emitted from the side surface 13e and the perpendicular drawn with respect to the side surface 13d (or the side surface 13c) is the perpendicular of the first polarized light incident on the side surface 13d. Is smaller than the angle φ0.

  A part of the first polarized light emitted from the side surface 13e of the refracting unit 13 enters from the side surface 14f of the refracting unit 14 and exits from the side surface 14c of the refracting unit 14. In this case, the angle φ1 ′ formed between the first polarized light emitted from the side surface 14c and the perpendicular line is smaller than the angle φ1 formed between the first polarized light emitted from the side face 13e and the perpendicular line described above.

  In this way, the first polarized light is incident from the side surface 13d of the refracting portion 13 and is emitted from the side surface 13e, and the emitted first polarized light is incident from the side surface 14f of the refracting portion 14 and the side surface. When the angle conversion condition of being emitted from 14c is satisfied, the second emission angle can be narrowed.

  More specifically, when the angle φ0 is 48.1 ° and the angle φ1 is 44.2 ° in the angle conversion condition shown in FIG. 6, the angle φ1 ′ is 40.4 °. If the angle φ0 is 30.0 ° and the angle φ1 is 25.3 °, the angle φ1 ′ is 20.0 °. If the angle φ0 is 20.0 ° and the angle φ1 is 12.8 °, the angle φ1 ′ is 12.8 °. As described above, when the maximum incident angle φ0 of the light incident on the end surface of the light guide 10 from the light source to the side surfaces of the refractive portions 13 and 14 is 48.1 °, the light is incident on a predetermined surface of the refractive portion 13. Then, the angle can be narrowed by about 4 °. Subsequently, when the light from the refracting portion 13 enters the predetermined surface of the refracting portion 14, the angle can be further narrowed by about 4 °. Accordingly, the refraction portions 13 and 14 can be narrowed by about 8 degrees.

  When the angle φ0 is 30 °, the refracting portions 13 and 14 can narrow the angle by about 5 °. Therefore, the refracting portions 13 and 14 can be narrowed by about 10 degrees.

  In the polarizing light guide plate of the present embodiment, the effect of narrowing the angle of the second emission angle varies depending on the number of times of passing through the predetermined surfaces of the refracting portions 13 and 14.

  In order to sufficiently obtain the effect of limiting the second emission angle, the size and interval of the refracting portions 13 and 14 are appropriately set so as to satisfy the angle conversion condition shown in FIG. FIG. 7 shows an example of the sizes and intervals of the refraction parts 13 and 14 that satisfy the angle conversion condition shown in FIG.

  FIG. 7 shows a state in which the adjacent refracting portions 13 and 14 are viewed from a direction perpendicular to the emission surface 11a of the quarter-wave plate 11. In FIG. 7, the symbol A indicates the length of the short side (side surfaces 13 c and 13 d) of the refracting portion 13, and the symbol B indicates the length of the long side (side surfaces 13 e and 13 f) of the refracting portion 13. The symbol b indicates the length of the side (side surfaces 14e, 14f) of the refracting unit 14 parallel to the long side of the refracting unit 13, and the symbol a indicates the side (side surface) of the refracting unit 14 parallel to the short side of the refracting unit 13. 14c, 14d). Reference sign D indicates a distance between a plane including the side surface 13d of the refracting portion 13 and a plane including the side surface 13d of the refracting portion 14. The symbol P indicates the distance between the side surface 13e of the refracting portion 13 and the side surface 14f of the refracting portion 14.

  Conditions for the first polarized light to enter the side surface 13d of the refracting portion 13 at an angle φ0, to exit from the side surface 13e at an angle φ1, and for the emitted first polarized light to enter the side surface 14f of the refracting portion 14 Is given by the following equations (1) to (3).

なお、上記の式（１）〜（３）の条件を満たす場合であっても、屈折部１３、１４の第１の偏光光の入射方向や入射位置によっては、一部の光の出射角が広がる場合がある。

Even when the conditions of the above expressions (1) to (3) are satisfied, depending on the incident direction and the incident position of the first polarized light of the refracting units 13 and 14, the emission angle of some of the light may be May spread.

  For example, as shown in the left part of FIG. 8A, when the first polarized light is incident from the side surface 13e of the refracting unit 13 and is emitted from the side surface 13c, the second emission angle described above is widened. As shown in the right portion of FIG. 8A, such an angular spread is suppressed by increasing the long side of the refracting portion 13 so that the first polarized light incident from the side surface 13e is emitted from the side surface 13f. be able to.

  FIG. 8B shows an example of conditions for suppressing the above-described angular spread. In the refracting portion 13, the first polarized light enters from the side surface 13e and exits from the side surface 13f. The first polarized light is refracted when passing through each of the side surfaces 13e and 13f. The angle of the first polarized light incident on the side surface 13e with respect to the side surface 13e is φ0. The angle between the first polarized light passing through the side surface 13e and the perpendicular to the side surface 13e is defined as θ3.

  In the above case, when the length B of the long side of the refracting portion 13 satisfies the following expression (4), the above-described angular spread can be suppressed.

また、図９Ａの左側下部に示すように、第１の偏光光が、屈折部１４の側面１４ｄから入射して、側面１４ｆから出射する場合、上述した第２の出射角度が広がる。加えて、この側面１４ｆから出射した第１の偏光光が、屈折部１３の側面１３ｅから入射して、側面１３ｃから出射すると、上述した第２の出射角度はさらに広がる。

9A, when the first polarized light is incident from the side surface 14d of the refracting unit 14 and is emitted from the side surface 14f, the above-described second emission angle is widened. In addition, when the first polarized light emitted from the side surface 14f enters from the side surface 13e of the refracting portion 13 and exits from the side surface 13c, the second emission angle described above further increases.

  As a method for suppressing the above-described angular spread, there is a method of shortening the lengths of the side portions of the side surfaces 14c and 14d of the refracting portion 14 and reducing the distance from the refracting portion 13 as shown in the upper left part of FIG. 9A. (First method).

  Further, as another method for suppressing the above-described angular spread, as shown in the upper right part of FIG. 9A, the side portions 13c and 13d of the refracting portion 14 are increased in the length of the side portions and the interval between the refracting portions 13 is increased. There is a technique (second technique).

  In the second method, the first polarized light is prevented from entering from the side surface 14d of the refracting unit 14 and exiting from the side surface 14f. The conditions for this suppression will be described with reference to FIG. 9B.

  In the refracting section 14, the first polarized light enters from the side surface 14d and exits from the side surface 14c. The first polarized light is refracted when passing through each of the side surfaces 14c and 14d. The angle of the first polarized light incident on the side surface 14d with respect to the perpendicular of the side surface 14d is φ1. The angle of the first polarized light that has passed through the side surface 14d with respect to the side surface 14d is defined as θ1 '.

  In the above case, the angular spread can be suppressed when the length b of the side portions 14e and 14f of the refracting portion 14 satisfies the following formula (5).

また、本実施形態の偏光導光板において、１／４波長板１１の出射面１１ａから出射される光の光量は、屈折部１３、１４の間隔や大きさ（長さおよび高さ）によって変化する。

In the polarization light guide plate of the present embodiment, the amount of light emitted from the exit surface 11a of the quarter-wave plate 11 varies depending on the spacing and size (length and height) of the refracting portions 13 and 14. .

  The size of the refracting portion 13 for increasing the amount of emitted light will be described with reference to FIG. 10A. In FIG. 10, the symbol B indicates the length of the long side of the refracting portion 13 (the length of the surfaces 13a and 13b), and the symbol H indicates the thickness of the refracting portion 13 (the length of the side surfaces 13c and 13d). .

  In the refracting unit 13, the first polarized light is incident from the surface 13a and reflected by the surface 13b, and the reflected light is emitted from the side surface 13c. The first polarized light is refracted when passing through the surface 13a and the side surface 13c. The angle of the first polarized light incident from the surface 13a with respect to the surface 13b is θ2, and the angle between the first polarized light emitted from the side surface 13c and the perpendicular of the side surface 13c is φ1. In this case, the amount of light emitted from the exit surface 11a of the quarter-wave plate 11 can be increased by setting the length B of the refracting portion 13 to satisfy the following formula (6).

出射光量を増大するための屈折部１３とこれに隣接する屈折部との間隔を、図１０Ｂを参照して説明する。図１０Ｂにおいて、符号Ｂ、Ｈは、図１０Ａで説明したとおり、屈折部１３の長さおよび厚さを示す。符号Ｑは、屈折部１３とこれに隣接する屈折部（屈折部１３または屈折部１４）との間隔を示す。

The interval between the refracting portion 13 for increasing the amount of emitted light and the refracting portion adjacent thereto will be described with reference to FIG. 10B. In FIG. 10B, symbols B and H indicate the length and thickness of the refracting portion 13 as described in FIG. 10A. The symbol Q indicates the distance between the refracting portion 13 and the refracting portion (refractive portion 13 or refracting portion 14) adjacent thereto.

  The first polarized light emitted from the side surface 13 c of the refracting unit 13 is reflected by the reflective layer 12. The angle between the first polarized light emitted from the side surface 13c and the perpendicular of the side surface 13c is φ1. In this case, the amount of light emitted from the emission surface 11a of the quarter-wave plate 11 can be increased by setting the interval Q so as to satisfy the following expression (7).

出射光量を増大するための屈折部１４の大きさを、図１１Ａを参照して説明する。図１１Ａにおいて、符号ｂは、屈折部１４の長さ（面１４ａ、１４ｂの長さ）を示し、符号ｈは、屈折部１４の厚さ（側面１４ｃ、１４ｄの長さ）を示す。

The size of the refracting portion 14 for increasing the amount of emitted light will be described with reference to FIG. 11A. In FIG. 11A, the symbol b indicates the length of the refracting portion 14 (the length of the surfaces 14a and 14b), and the symbol h indicates the thickness of the refracting portion 14 (the length of the side surfaces 14c and 14d).

  In the refracting section 14, the first polarized light is incident from the side surface 14d and reflected by the surface 14b, and the reflected light is emitted from the surface 14a. The first polarized light is refracted when passing through each of the surface 14a and the side surface 14d. The angle of the first polarized light incident from the side surface 14d with respect to the surface 14b is θ2 ′. In this case, the amount of light emitted from the exit surface 11a of the quarter-wave plate 11 can be increased by setting the length b of the refracting portion 14 to satisfy the following formula (8).

出射光量を増大するための屈折部１４とこれに隣接する屈折部との間隔を、図１１Ｂを参照して説明する。図１１Ｂにおいて、符号ｂ、ｈは、図１１Ａで説明したとおり、屈折部１４の長さおよび厚さを示す。符号ｑは、屈折部１４とこれに隣接する屈折部（屈折部１３または屈折部１４）との間隔を示す。

An interval between the refracting portion 14 for increasing the amount of emitted light and the refracting portion adjacent thereto will be described with reference to FIG. 11B. In FIG. 11B, symbols b and h indicate the length and thickness of the refracting portion 14 as described in FIG. 11A. The symbol q indicates the distance between the refracting part 14 and the refracting part (refractive part 13 or refracting part 14) adjacent thereto.

  The first polarized light is reflected by the reflective layer 12, and the reflected light enters the side surface 14 d of the refracting unit 14. The angle of the first polarized light incident on the reflective layer 12 with respect to the surface of the reflective layer 12 is φ0. In this case, the amount of light emitted from the emission surface 11a of the quarter-wave plate 11 can be increased by setting the interval q so as to satisfy the following expression (9).

なお、１／４波長板１１の出射面１１ａの面内方向における出射光の輝度分布を均一にする場合は、長さＢ、ｂおよび間隔Ｑ、ｑをそれぞれ３０〜１００μｍの範囲に設定することが出射光の均一化、また実用上好ましい。

When the luminance distribution of the emitted light in the in-plane direction of the emission surface 11a of the quarter wavelength plate 11 is made uniform, the lengths B and b and the intervals Q and q should be set in the range of 30 to 100 μm, respectively. Is preferable from the viewpoint of making the emitted light uniform and practical.

  Hereinafter, specific numerical examples of the interval and size of the refractive portions 13 and 14 of the polarizing light guide plate of the present embodiment will be given.

Example 1
In FIG. 12, an example of arrangement | positioning of the refractive parts 13 and 14 is shown. In FIG. 12, the upper part is a top view and the lower part is a cross-sectional view. Symbols A, B, and H respectively indicate the length, width, and height of the refracting portion 13, and symbols a, b, and h indicate the length, width, and height of the refracting portion 14, respectively. Reference sign Q indicates the distance between the refracting portion 13 and the refracting portion 13 adjacent thereto. Reference symbol P indicates the distance between the refracting portion 13 and the refracting portion 14. Reference sign D indicates the length between the end faces located on the side where the light source is disposed, among the side surfaces of the refracting portions 13 and 14.

  The refractive index n0 of the light guide 10 is 1.50. The refractive indexes n1 and n2 of the refracting portion 13 are 1.55 and 1.50, respectively. The refractive indices n1 'and n2' of the refracting section 14 are 1.45 and 1.50, respectively. The length D between the side surfaces of the refracting portions 13 and 14 is 10.2 μm.

  The interval P is 10.0 μm and the interval Q is 46.1 μm. The width A, length B, and height H of the refracting portion 13 are 36.4 μm, 50.0 μm, and 29.5 μm, respectively. The width a, length b, and height h of the refracting portion 14 are 20.0 μm, 22.1 μm, and 19.5 μm, respectively.

  The angle of light incident on the light guide 10 from the light source with respect to the plane parallel to the exit surface 11a of the quarter-wave plate 11 is 48.1 ° or less. In this case, the angular spread of the first emission angle emitted from the emission surface 11a of the quarter wavelength plate 11 is 22.7 °. Further, the angular spread of the second emission angle emitted from the emission surface 11a of the quarter-wave plate 11 is set to about 7 ° to 18 ° with respect to the angular spread of the light incident into the light guide 10 from the light source. Can.

  The first emission angle is taken in the in-plane direction of the first plane that intersects (or is orthogonal to) the end surface of the light guide 10 on the side where the light source is disposed and the emission surface 11a of the quarter-wave plate 11. The output angle to obtain. The second emission angle is an emission angle that can be taken in the in-plane direction of the second plane parallel to the emission surface 11a of the quarter-wave plate 11 and intersecting the first plane.

(Example 2)
The polarizing light guide plate of this embodiment also has the arrangement shown in FIG.

  The refractive index n0 of the light guide 10 is 1.50. The refractive indexes n1 and n2 of the refracting portion 13 are 1.55 and 1.50, respectively. The refractive indices n1 'and n2' of the refracting section 14 are 1.45 and 1.50, respectively. The length D between the side surfaces of the refracting portions 13 and 14 is 10.2 μm.

  The interval P is 10.0 μm and the interval Q is 75.1 μm. The width A, length B, and height H of the refracting portion 13 are 50.0 μm, 67.6 μm, and 37.0 μm, respectively. The width a, length b, and height h of the refracting portion 14 are 20.0 μm, 22.1 μm, and 13.3 μm, respectively.

  The angle of light incident on the light guide 10 from the light source with respect to the plane parallel to the exit surface 11a of the quarter-wave plate 11 is 48.1 ° or less.

  The polarized light guide plate of the present embodiment has a first polarized light on the light source side end face of the refracting portion 13 by an amount corresponding to the width A of the refracting portion 13 larger than that of the polarizing light guide plate of the first embodiment. More light can be incident.

  Further, by setting the length D between the side surfaces of the refracting portions 13 and 14, the length B and height H of the refracting portion 13, and the length b and height h of the refracting portion 14 to the values described above. Further, the angular spread in the in-plane direction of the plane parallel to the emission surface 11a of the quarter wavelength plate 11 can be suppressed.

  Also in the polarizing light guide plate of the present embodiment, the angular spread of the first emission angle emitted from the emission surface 11a of the quarter-wave plate 11 is 22.7 °. The angular spread of the second emission angle emitted from the emission surface 11a of the quarter wavelength plate 11 can be set to about 7 to 18 °.

(Example 3)
The polarizing light guide plate of this embodiment also has the arrangement shown in FIG.

  The refractive index n0 of the light guide 10 is 1.50. The refractive indexes n1 and n2 of the refracting portion 13 are 1.55 and 1.50, respectively. The refractive indices n1 'and n2' of the refracting section 14 are 1.45 and 1.50, respectively. The length D between the side surfaces of the refracting portions 13 and 14 is 16.0 μm.

  The interval P is 10.0 μm, and the interval Q is 101.0 μm. The width A, length B, and height H of the refracting portion 13 are 40.0 μm, 83.5 μm, and 49.1 μm, respectively. The width a, length b, and height h of the refracting portion 14 are 20.0 μm, 48.0 μm, and 29.5 μm, respectively.

  The angle of light incident on the light guide 10 from the light source with respect to the plane parallel to the exit surface 11a of the quarter-wave plate 11 is 48.1 ° or less.

  Also in the polarizing light guide plate of the present embodiment, the angular spread of the first emission angle emitted from the emission surface 11a of the quarter-wave plate 11 is 22.7 °. In addition, the angular spread of the second emission angle emitted from the emission surface 11a of the quarter-wave plate 11 is 7 ° to 18 ° with respect to the angular spread of the light incident into the light guide 10 from the light source. It can be fitted to the extent.

Example 4
The polarizing light guide plate of this embodiment also has the arrangement shown in FIG.

  The refractive index n0 of the light guide 10 is 1.50. The refractive indexes n1 and n2 of the refracting portion 13 are 1.60 and 1.50, respectively. The refractive indexes n1 'and n2' of the refracting section 14 are 1.40 and 1.50, respectively. The length D between the side surfaces of the refracting portions 13 and 14 is 11.8 μm.

  The interval P is 10.0 μm, and the interval Q is 74.0 μm. The width A, length B, and height H of the refracting portion 13 are 36.3 μm, 50.0 μm, and 32.0 μm, respectively. The width a, length b, and height h of the refracting portion 14 are 20.0 μm, 28.5 μm, and 18.8 μm, respectively.

  The angle of light incident on the light guide 10 from the light source with respect to the plane parallel to the exit surface 11a of the quarter-wave plate 11 is 48.1 ° or less.

  According to the polarizing light guide plate of the present embodiment, the angular spread of the first emission angle emitted from the emission surface 11a of the quarter wavelength plate 11 is 33.6 °. Further, the angular spread of the second emission angle emitted from the emission surface 11a of the quarter wavelength plate 11 is set to about 12 to 26 ° with respect to the angular spread of the light incident into the light guide 10 from the light source. be able to.

  According to the polarizing light guide plate of the present embodiment described above, the angular spread of the first emission angle can be reduced and the angular spread of the second emission angle can be reduced. Therefore, the spread of the emission angle of the light emitted from the polarizing light guide plate can be kept within the light usable range based on the etendue constraint.

  Moreover, since the light propagating in the light guide 10 can be used by circulating light between the quarter-wave plate 11 and the reflective layer 12, the light utilization efficiency can be improved.

  Furthermore, the problem of stray light due to diverging light and viewing angle dependency, which has occurred in the illumination device described in Patent Document 1, by enabling polarization conversion and narrowing the emission angle without using a prism surface, Does not occur.

  In the polarization light guide plate of the present embodiment, the refracting parts 13 and 14 may be arranged at equal intervals.

  Further, as the distance from the end surface of the light guide 10 on the side where the light source is disposed (as the distance from the end surface becomes longer), the interval between the refractive portions 13 and 14 may be gradually increased. In this case, the luminance distribution in the in-plane direction of the exit surface 11a of the quarter wavelength plate 11 can be made uniform as compared with the case where the refracting portions 13 and 14 are arranged at equal intervals.

  FIG. 13A schematically shows the luminance distribution of the emitted light when the refracting portions 13 are arranged at equal intervals, and FIG. 13B shows the emitted light when the interval between the refracting portions 13 is gradually increased as the distance from the end face increases. The luminance distribution of is schematically shown. 13A and 13B, a part of the polarizing light guide plate is cut along a plane perpendicular to the first end face of the light guide 10 (end face provided with the light source) and the exit face 11a of the quarter-wave plate 11. A first end face (not shown) is arranged on the right side of the drawing.

  In the configuration shown in FIG. 13A (with the refracting portions 13 arranged at equal intervals), the closer to the first end face side, the more emitted light 100 and guided light 101 are generated. For this reason, the brightness | luminance of the light radiate | emitted from the output surface 11a of the quarter wavelength plate 11 becomes so large that it is near the 1st end surface side.

  On the other hand, in the configuration shown in FIG. 13B (in which the interval between the refracting portions 13 is increased as the distance from the first end surface increases), the interval between the refracting portions 13 is small on the first end surface side. For this reason, on the first end face side, the reflected light 102 from the reflective layer 12 (in the configuration of FIG. 13A, the reflected light 102 becomes outgoing light) is incident on the side surface of the refracting portion 13, and The light is emitted from the surface on the emission surface 11 a side of the quarter-wave plate 11. The light emitted from the refracting unit 13 then becomes the light guide light 101, is reflected by the emission surface 11 a of the quarter-wave plate 11 and the reflection layer 12, and propagates through the light guide 10.

  Since the distance between the refracting portions 13 increases as the distance from the first end surface increases, the amount of reflected light 102 incident on the side surface (side surface on the first end surface side) of the refracting portion 13 also moves away from the first end surface. It becomes small according to. As a result, the luminance distribution of the light emitted from the emission surface 11a is more uniform than the configuration of FIG. 13A.

  In the configuration shown in FIGS. 13A and 13B, the refracting portions 13 are arranged in one direction. However, the refracting portions 14 are arranged in one direction, or the refracting portions 13 and 14 are alternately arranged in one direction. For the ones arranged in the direction, the luminance distribution of the emitted light can be made uniform as described above.

  Further, the luminance distribution of the emitted light can be made uniform by gradually increasing the refracting portions 13 and 14 as they move away from the first end face. In this case, the size of the refracting portions 13 and 14 is defined by one or more of the length, width, and height of the refracting portions.

  Furthermore, by combining the method of gradually widening the interval between the refracting portions 13 and 14 with increasing distance from the first end surface, and the method of gradually increasing the refracting portions 13 and 14 with increasing distance from the first end surface, The luminance distribution of the emitted light can be made more uniform.

  In the polarization light guide plate of this embodiment, as shown in FIGS. 3A and 4A, the light emitted from the emission surface 11a of the quarter-wave plate 11 has an inclination with respect to the normal of the emission surface 11a. . A prism sheet may be used to emit light in a direction perpendicular to the emission surface 11a.

  FIG. 14A shows a configuration using a prism sheet. As shown in FIG. 14A, the plurality of vertices of the prism sheet 15 are provided so as to face the emission surface 11 a of the quarter-wave plate 11.

  As shown in FIG. 14B, the prism sheet 15 has a prism surface 15a having a triangular cross-sectional shape arranged two-dimensionally. The apex angle of the prism surface 15a is determined based on the angle of light emitted from the emission surface 11a (for example, the emission angle β shown in FIGS. 3A and 4A).

  For example, the refractive index n0 of the light guide 10 is 1.50, the refractive indexes n1 and n2 of the refracting part 13 are 1.55 and 1.50, respectively, and the refractive indices n1 ′ and n2 ′ of the refracting part 14 are When they are 1.45 and 1.50, respectively, the emission angle β is larger than 67 ° and smaller than 90 °. In this case, if the refractive index of the prism sheet 15 is 1.50, the apex angle of the prism surface 15a is 70 °.

  As shown in FIG. 14B, the prism sheet 15 having a prism surface 15a having an apex angle of 70 ° has an angle δ formed by a surface parallel to a surface forming one side of the prism surface 15a and the emission surface 11a. It arrange | positions on the output surface 11a so that it may become 55 degrees. According to this arrangement, it is possible to obtain outgoing light having an angular spread of ± 12 ° with respect to a direction perpendicular to the outgoing surface 11a.

  In the polarization light guide plate of the present embodiment, the light emitted from the emission surface 11a of the quarter wavelength plate 11 is circularly polarized light. In order to obtain the first or second polarized light (specifically, S-polarized light or P-polarized light) as the outgoing light of the polarizing light guide plate, the light emitted from the outgoing surface 11a of the quarter-wave plate 11 Another quarter wave plate may be arranged in the traveling direction.

  FIG. 15 shows a configuration including another quarter-wave plate. In FIG. 15, except for the quarter-wave plate 16, it is the same as that shown in FIG. 14A. The quarter wavelength plate 16 is provided so as to face the surface of the prism sheet 15 opposite to the surface on the quarter wavelength plate 11 side.

  According to the configuration shown in FIG. 15, the circularly polarized light emitted from the quarter wavelength plate 11 passes through the quarter wavelength plate 16 after passing through the prism sheet 15. When the polarization light guide plate is configured so that the first polarized light passes through the quarter wavelength plate 11, the second polarized light is emitted from the quarter wavelength plate 16. On the other hand, when the polarization light guide plate is configured so that the second polarized light passes through the quarter wavelength plate 11, the first polarized light is emitted from the quarter wavelength plate 16. As described above, the first or second polarized light (specifically, S-polarized light or P-polarized light) can be obtained as the emitted light from the polarization light guide plate.

  Next, a method for producing the polarizing light guide plate of this embodiment will be described.

  First, a light guide having a concave portion in a region to be the refractive portions 13 and 14 is created. The light guide can be created for mold forming, cutting and the like.

  Next, an alignment film is applied to the surface of the light guide where the concave portion is formed and one surface of the reflective layer (reflecting plate), and an alignment process is performed. Next, a UV curable liquid crystal monomer is embedded in the recess by screen printing. Thereafter, the surface of the light guide body on which the concave portion is formed and one surface of the reflective layer are bonded together.

  The bonded light guide and reflective layer are heated and then cooled to align the UV curable liquid crystal monomer. Finally, UV light is irradiated to cure the aligned UV curable liquid crystal monomer, and then a quarter-wave plate is attached to the surface of the light guide opposite to the reflective layer. Thereby, the polarization light guide plate of the first embodiment is obtained.

(Second Embodiment)
FIG. 16 is a schematic diagram showing a configuration of a polarizing light guide plate according to the second embodiment of the present invention.

  In the polarization light guide plate of the present embodiment, a plurality of refracting portions 13 and 14 are provided inside the light guide 10, and other configurations are the same as those of the first embodiment.

  Also in this embodiment, the refracting portion 13 satisfies the refractive index condition of n1> n2 and n2 = n0, and the refracting portion 14 satisfies the refractive index condition of n1 ′ <n2 ′ and n2 ′ = n0. .

  The refracting parts 13 and 14 are periodically arranged inside the light guide 10 so as to face the quarter-wave plate 11, and the refracting parts 13 and 14 are alternately arranged in at least one direction. . The arrangement of the refracting portions 13 and 14 is as described in the first embodiment.

  Next, the operation of the polarizing light guide plate of this embodiment will be described.

  Also in the polarization light guide plate of the present embodiment, a part of the light (unpolarized light) incident on the first end surface of the light guide 10 from the light source is a quarter wavelength plate 11 as in the first embodiment. The light is reflected between the light exit surface 11a and the reflective layer 12, and propagates in the light guide 10 toward the second end surface facing the first end surface. In this propagation process, a part of the light enters the refracting parts 13 and 14.

  The refracting units 13 and 14 are the first and second polarized light between the emission condition for emitting the first polarized light from the emission surface 11a and the emission surface 11a of the quarter-wave plate 11 and the reflective layer 12. Although it is configured to satisfy the light guide condition for guiding light, the conditions are different from each other.

  First, the light guide conditions and emission conditions of the refraction part 13 will be described.

  FIG. 17A is a diagram for explaining the emission conditions of the refraction unit 13 with respect to the first polarized light, and a part of the polarization light guide plate shown in FIG. 2 is a schematic diagram of a cross section cut along a plane perpendicular to the emission surface 11a of the quarter-wave plate 11).

  In the refracting portion 13, the first polarized light incident at an angle φ0 formed with the surface 13a with respect to the surface 13a located on the quarter wavelength plate 11 side is refracted at an angle θ1 and faces the surface 13a. It is emitted from 13b. Here, the incident angle of the first polarized light with respect to the surface 13a is given by “90 ° −φ0”. The incident angle of the first polarized light with respect to the surface 13b is given by “90 ° −θ1”.

  The 1st polarized light radiate | emitted from the surface 13b is reflected in the reflection layer 12, and injects into the light guide 10 again from the surface 13b. Here, the incident angle of the first polarized light reflected by the reflective layer 12 with respect to the surface 13b is smaller than the critical angle.

  The first polarized light entering the light guide 10 from the surface 13b reaches the side surface 13c. The incident angle θ2 of the first polarized light incident from the surface 13b with respect to the side surface 13c is smaller than the critical angle. Therefore, the first polarized light incident on the side surface 13 c is refracted at an angle φ1 and reaches the surface 10 a of the light guide 10.

  Since the refractive index of the ¼ wavelength plate 11 is substantially equal to the refractive index of the light guide 10, the first polarized light from the side surface 13c passes through the surface 10a without being refracted and is ¼ wavelength. It reaches the exit surface 11a of the plate 11. Since the first polarized light that has passed through the surface 10a passes through the quarter-wave plate 11 once, the light that reaches the exit surface 11a is circularly polarized light.

  When the incident angle (90 ° −φ1) of the circularly polarized light incident on the emission surface 11a is smaller than the critical angle, the circularly polarized light is emitted from the emission surface 11a at the emission angle β.

  Thus, in the refracting unit 13, the first polarized light that satisfies the condition (exit condition) that enters from the surface 13a and exits from the surface 13b, and then enters from the surface 13b and exits from the side surface 13c, After being converted into circularly polarized light by the quarter-wave plate 11, the light is emitted from the emission surface 11a.

  In addition, as shown in FIG. 17A, after the first polarized light that enters the refracting portion 13 from the surface 13a and is emitted from the side surface 13c is reflected by the reflective layer 12, the quarter-wave plate 11 is The condition of passing through and exiting from the exit surface 11a is also established as the exit condition.

  FIG. 17B is a diagram for explaining the first light guide condition of the refracting unit 13 for the first polarized light, and a part of the polarization light guide plate shown in FIG. FIG. 6 is a schematic view of a cross section cut along a plane perpendicular to the end face and the exit face 11 a of the quarter-wave plate 11.

  In the refracting unit 13, the first polarized light that is incident on the surface 13a at an angle φ0 with the surface 13a is refracted at an angle θ1 and is emitted from the surface 13b. The first polarized light emitted from the surface 13 b is reflected by the reflective layer 12 and then reaches the surface 10 a of the light guide 10. The angle of the first polarized light reflected by the reflective layer 12 with respect to the reflective layer 12 is the same as the angle φ0.

  Since the refractive index of the quarter-wave plate 11 is substantially equal to the refractive index of the light guide 10, the first polarized light from the reflective layer 12 passes through the surface 10a without being refracted, and 1 / It reaches the emission surface 11a of the four-wavelength plate 11. Since the first polarized light that has passed through the surface 10a passes through the quarter-wave plate 11 once, the light that reaches the exit surface 11a is circularly polarized light.

  The incident angle (90 ° −φ0) of the circularly polarized light incident on the exit surface 11a is larger than the critical angle. Therefore, the circularly polarized light is reflected in the direction of the light guide 10 at the emission surface 11a. Since the circularly polarized light reflected by the emission surface 11a passes through the quarter-wave plate 11, the light incident on the surface 10a of the light guide 10 is the second polarized light. The second polarized light incident from the surface 10 a propagates through the light guide 10.

  As described above, in the refracting portion 13, the first light guide condition is satisfied that the light enters the surface 13 a, exits from the surface 13 b, is reflected by the reflective layer 12, and then reaches the surface 10 a of the light guide 10. The first polarized light is not emitted from the emission surface 11 a, and is propagated through the light guide 10 after being converted into second polarized light by the quarter-wave plate 11.

  FIG. 17C is a diagram for explaining the second light guide condition of the refracting unit 13 with respect to the first polarized light, and a part of the polarization light guide plate shown in FIG. FIG. 6 is a schematic view of a cross section cut along a plane perpendicular to the end face and the exit face 11 a of the quarter-wave plate 11.

  In the refracting unit 13, the first polarized light that is incident on the surface 13a at an angle φ0 with the surface 13a is refracted at an angle θ1 and emitted from the surface 13b. The 1st polarized light radiate | emitted from the surface 13b is reflected in the reflection layer 12, and injects into the light guide 10 again from the surface 13b.

  The first polarized light entering the light guide 10 from the surface 13b reaches the surface 13a. The incident angle (same as θ1) of the first polarized light incident from the surface 13b with respect to the surface 13a is smaller than the critical angle. Therefore, the first polarized light incident on the surface 13a is refracted at an angle φ0 and reaches the surface 10a of the light guide 10. Here, the angle between the first polarized light emitted from the surface 13a and the surface 13a is φ0.

  Since the refractive index of the quarter-wave plate 11 is substantially equal to the refractive index of the light guide 10, the first polarized light from the surface 13a passes through the surface 10a without being refracted and is ¼. It reaches the emission surface 11 a of the wave plate 11. Since the first polarized light that has passed through the surface 10a passes through the quarter-wave plate 11 once, the light that reaches the exit surface 11a is circularly polarized light.

  The incident angle (90 ° −φ0) of the circularly polarized light incident on the exit surface 11a is larger than the critical angle. Therefore, the circularly polarized light is reflected in the direction of the light guide 10 at the emission surface 11a. Since the circularly polarized light reflected by the emission surface 11a passes through the quarter-wave plate 11, the light incident on the surface 10a of the light guide 10 is the second polarized light. The second polarized light incident from the surface 10 a propagates through the light guide 10.

  Thus, in the refracting unit 13, the first polarized light that satisfies the second light guide condition of entering from the surface 13a and exiting from the surface 13b and then entering from the surface 13b and exiting from the surface 13a is obtained. The light is not emitted from the emission surface 11 a but is converted into the second polarized light by the quarter-wave plate 11 and then propagates through the light guide 10.

  FIG. 17D is a diagram for explaining a third light guide condition of the refracting unit 13 for the first polarized light, and a part of the polarization light guide plate shown in FIG. FIG. 6 is a schematic view of a cross section cut along a plane perpendicular to the end face and the exit face 11 a of the quarter-wave plate 11.

  In the refracting unit 13, the first polarized light incident at the incident angle φ0 with respect to the side surface 13d is refracted at the angle θ1 and is emitted from the surface 13b. Here, the incident angle of the first polarized light with respect to the surface 13b is given by “90 ° −θ1”.

  The 1st polarized light radiate | emitted from the surface 13b is reflected in the reflection layer 12, and injects into the light guide 10 again from the surface 13b.

  The first polarized light entering the light guide 10 from the surface 13b reaches the surface 13a. The incident angle (same as θ1) of the first polarized light incident from the surface 13b with respect to the surface 13a is smaller than the critical angle. Therefore, the first polarized light incident on the surface 13a is refracted at an angle φ0 and reaches the surface 10a of the light guide 10. Here, the angle between the first polarized light emitted from the surface 13a and the surface 13a is φ0.

  Since the refractive index of the quarter-wave plate 11 is substantially equal to the refractive index of the light guide 10, the first polarized light from the surface 13a passes through the surface 10a without being refracted and is ¼. It reaches the emission surface 11 a of the wave plate 11. Since the first polarized light that has passed through the surface 10a passes through the quarter-wave plate 11 once, the light that reaches the exit surface 11a is circularly polarized light.

  The incident angle (90 ° −φ0) of the circularly polarized light incident on the exit surface 11a is larger than the critical angle. Therefore, the circularly polarized light is reflected in the direction of the light guide 10 at the emission surface 11a. Since the circularly polarized light reflected by the emission surface 11a passes through the quarter-wave plate 11, the light incident on the surface 10a of the light guide 10 is the second polarized light. The second polarized light incident from the surface 10 a propagates through the light guide 10.

  As described above, in the refracting unit 13, the first polarized light that satisfies the third light guide condition of entering from the side surface 13d and exiting from the surface 13b and then entering from the surface 13b and exiting from the surface 13a is obtained. The light is not emitted from the emission surface 11 a but is converted into the second polarized light by the quarter-wave plate 11 and then propagates through the light guide 10.

  FIG. 17E is a diagram for explaining the fourth light guide condition of the refracting unit 13 for the first polarized light, and a part of the polarization light guide plate shown in FIG. FIG. 6 is a schematic view of a cross section cut along a plane perpendicular to the end face and the exit face 11a of the quarter-wave plate 11.

  In the refracting unit 13, the first polarized light incident at the incident angle φ0 with respect to the side surface 13d is refracted at the angle θ1 and is emitted from the surface 13b. Here, the incident angle of the first polarized light with respect to the surface 13b is given by “90 ° −θ1”.

  The first polarized light emitted from the surface 13 b is reflected by the reflective layer 12 and then reaches the surface 10 a of the light guide 10. The angle of the first polarized light reflected by the reflective layer 12 with respect to the reflective layer 12 is φ1.

  Since the refractive index of the quarter-wave plate 11 is substantially equal to the refractive index of the light guide 10, the first polarized light from the reflective layer 12 passes through the surface 10a without being refracted, and 1 / It reaches the emission surface 11a of the four-wavelength plate 11. Since the first polarized light that has passed through the surface 10a passes through the quarter-wave plate 11 once, the light that reaches the exit surface 11a is circularly polarized light.

  The incident angle (90 ° −φ1) of circularly polarized light incident on the exit surface 11a is larger than the critical angle. Therefore, the circularly polarized light is reflected in the direction of the light guide 10 at the emission surface 11a. Since the circularly polarized light reflected by the emission surface 11a passes through the quarter-wave plate 11, the light incident on the surface 10a of the light guide 10 is the second polarized light. The second polarized light incident from the surface 10 a propagates through the light guide 10.

  As described above, in the refracting portion 13, the fourth light guide condition that the light enters from the side surface 13 d, exits from the surface 13 b, is reflected by the reflective layer 12, and reaches the surface 10 a of the light guide 10 is satisfied. The first polarized light is not emitted from the emission surface 11 a, and is propagated through the light guide 10 after being converted into second polarized light by the quarter-wave plate 11.

  FIG. 17F is a diagram for explaining the fifth light guide condition of the refracting unit 13 with respect to the first polarized light, and a part of the polarization light guide plate shown in FIG. FIG. 6 is a schematic view of a cross section cut along a plane perpendicular to the end face and the exit face 11 a of the quarter-wave plate 11.

  In the refracting unit 13, the first polarized light incident at the incident angle φ0 with respect to the side surface 13d is refracted at the angle θ1 and is emitted from the surface 13b. The 1st polarized light radiate | emitted from the surface 13b is reflected in the reflection layer 12, and injects into the light guide 10 again from the surface 13b.

  The first polarized light entering the light guide 10 from the surface 13b reaches the side surface 13c. The incident angle (same as θ1) of the first polarized light incident from the surface 13b with respect to the side surface 13c is smaller than the critical angle. Therefore, the first polarized light incident on the side surface 13 c is refracted at an angle φ0 and reaches the surface 10 a of the light guide 10.

  Since the refractive index of the quarter-wave plate 11 is substantially equal to the refractive index of the light guide 10, the first polarized light from the side surface 13c passes through the surface 10a without being refracted, and becomes 1/4. It reaches the emission surface 11 a of the wave plate 11. Since the first polarized light that has passed through the surface 10a has passed through the quarter-wave plate 11 once, the light that reaches the exit surface 11a is circularly polarized light.

  The incident angle (90 ° −φ0) of the circularly polarized light incident on the exit surface 11a is larger than the critical angle. Therefore, the circularly polarized light is reflected in the direction of the light guide 10 at the emission surface 11a. Since the circularly polarized light reflected by the exit surface 11a passes through the quarter-wave plate 11, the light incident on the light guide 10 from the exit surface 11a is second polarized light. The second polarized light incident from the surface 10 a propagates through the light guide 10.

  In this way, in the refracting unit 13, the first polarized light that satisfies the fifth light guiding condition is incident from the side surface 13d and emitted from the surface 13b, and then incident from the surface 13b and emitted from the side surface 13c. The light is not emitted from the emission surface 11 a but is converted into the second polarized light by the quarter-wave plate 11 and then propagates through the light guide 10.

  Next, light guide conditions and emission conditions of the refracting unit 14 will be described.

  FIG. 18A is a diagram for explaining the first emission condition of the refracting unit 14 for the first polarized light, and a part of the polarization light guide plate shown in FIG. It is a schematic diagram of the cross section cut | disconnected by the plane perpendicular | vertical to an end surface (end surface provided with the light source) and the output surface 11a.

  In the refracting unit 14, the first polarized light incident on the side surface 14d at the incident angle φ0 is refracted at the angle θ1 ′ and is emitted from the surface 14b. Here, the incident angle of the first polarized light with respect to the surface 14b is given by “90 ° −θ1 ′”.

  The first polarized light emitted from the surface 14b is reflected by the reflective layer 12, and then enters the refracting portion 14 again from the surface 14b and reaches the surface 14a. The incident angle θ2 ′ of the first polarized light incident from the surface 14b with respect to the surface 14a is smaller than the critical angle. For this reason, the first polarized light is refracted at an angle φ1 ', exits from the surface 14a, and then reaches the surface 10a.

  Since the refractive index of the quarter-wave plate 11 is substantially equal to the refractive index of the light guide 10, the first polarized light from the surface 14a passes through the surface 10a without being refracted and is ¼ wavelength. It reaches the exit surface 11a of the plate 11. Since the first polarized light that has passed through the surface 10a passes through the quarter-wave plate 11 once, the light that reaches the exit surface 11a is circularly polarized light.

  When the incident angle (90 ° −φ1 ′) of the circularly polarized light incident on the emission surface 11a is smaller than the critical angle, the circularly polarized light is emitted from the emission surface 11a at the emission angle β.

  As described above, in the refracting unit 14, the first polarized light that satisfies the first emission condition of entering from the side surface 14d and exiting from the surface 14b, and then entering from the surface 14b and exiting from the surface 14a is: After being converted into circularly polarized light by the quarter-wave plate 11, the light is emitted from the emission surface 11a.

  As shown in FIG. 18A, the first polarized light that enters the refracting portion 14 from the side surface 14d and exits from the surface 14a passes through the quarter-wave plate 11 and exits from the exit surface 11a. The above condition is also established as the emission condition.

  18B is a diagram for explaining the second emission condition of the refracting unit 14 with respect to the first polarized light, and a part of the polarization light guide plate shown in FIG. It is a schematic diagram of the cross section cut | disconnected by the plane perpendicular | vertical to an end surface and the output surface 11a.

  In the refracting unit 14, the first polarized light incident at the incident angle φ0 with respect to the side surface 14d is refracted at the angle θ1 ′ and emitted from the surface 14b. Here, the incident angle of the first polarized light with respect to the surface 14b is given by “90 ° −θ1 ′”.

  The first polarized light emitted from the surface 14 b is reflected by the reflective layer 12 and then reaches the surface 10 a of the light guide 10. The angle of the first polarized light reflected by the reflective layer 12 with respect to the reflective layer 12 is φ1 ′.

  Since the refractive index of the quarter-wave plate 11 is substantially equal to the refractive index of the light guide 10, the first polarized light from the reflective layer 12 passes through the surface 10a without being refracted and is ¼. It reaches the emission surface 11 a of the wave plate 11. Since the first polarized light that has passed through the surface 10a passes through the quarter-wave plate 11 once, the light that reaches the exit surface 11a is circularly polarized light.

  When the incident angle (90 ° −φ1 ′) of the circularly polarized light incident on the exit surface 11a is smaller than the critical angle, the circularly polarized light is emitted from the exit surface 11a at the exit angle β.

  As described above, in the refracting unit 14, the first polarized light that satisfies the second emission condition of entering from the side surface 14d and exiting from the surface 14b and then reflected by the reflective layer 12 and reaching the surface 10a is After being converted into circularly polarized light by the quarter-wave plate 11, the light is emitted from the emission surface 11a.

  FIG. 18C is a diagram for explaining the first light guide condition of the refracting unit 14 with respect to the first polarized light, and a part of the polarization light guide plate shown in FIG. FIG. 6 is a schematic view of a cross section cut along a plane perpendicular to the end face of FIG.

  In the refracting unit 14, the first polarized light incident on the side surface 14d at the incident angle φ0 is refracted at the angle θ1 ′ and is emitted from the surface 14b. Here, the incident angle of the first polarized light with respect to the surface 14b is given by “90 ° −θ1 ′”.

  The first polarized light emitted from the surface 14b is reflected by the reflection layer 12, and then enters the refracting unit 14 from the surface 14b again. The first polarized light incident from the surface 14b reaches the side surface 14c. The incident angle (same as θ1 ′) of the first polarized light with respect to the side surface 14c is smaller than the critical angle. Therefore, the first polarized light exits from the side surface 14c and is refracted at an angle φ0. The first polarized light emitted from the side surface 14 c reaches the surface 10 a of the light guide 10.

  Since the refractive index of the quarter-wave plate 11 is substantially equal to the refractive index of the light guide 10, the first polarized light from the side surface 14c passes through the surface 10a without being refracted, and becomes 1/4. It reaches the emission surface 11 a of the wave plate 11. Since the first polarized light that has passed through the surface 10a passes through the quarter-wave plate 11 once, the light that reaches the exit surface 11a is circularly polarized light.

  The incident angle (90 ° −φ0) of the circularly polarized light incident on the exit surface 11a is larger than the critical angle. Therefore, the circularly polarized light is reflected in the direction of the light guide 10 at the emission surface 11a. Since the circularly polarized light reflected by the exit surface 11a passes through the quarter wavelength plate 11 again, the light incident on the surface 10a from the exit surface 11a is the second polarized light. The second polarized light incident from the surface 10 a propagates through the light guide 10.

  As described above, in the refracting unit 14, the first polarized light that satisfies the first light guide condition of entering from the side surface 14d and exiting from the surface 14b and then entering from the surface 14b and exiting from the side surface 14c is obtained. The light is not emitted from the emission surface 11 a but is converted into the second polarized light by the quarter-wave plate 11 and then propagates through the light guide 10.

  18D is a diagram for explaining the second light guide condition of the refracting unit 14 for the first polarized light, and a part of the polarization light guide plate shown in FIG. FIG. 6 is a schematic view of a cross section cut along a plane perpendicular to the end face of FIG.

  In the refracting unit 14, the first polarized light incident on the surface 14a at an angle φ0 with the surface 14a is refracted at an angle θ1 ′ and emitted from the surface 14b. Here, the incident angle of the first polarized light with respect to the surface 14a is given by “90 ° −φ0”.

  The first polarized light emitted from the surface 14 b is reflected by the reflective layer 12. The first polarized light reflected by the reflective layer 12 is incident on the refraction part 14 again from the surface 14b. The first polarized light incident from the surface 14b is incident on the side surface 14c at an incident angle θ2 ′. The incident angle θ2 ′ is smaller than the critical angle. For this reason, the first polarized light incident on the side surface 14c is emitted from the side surface 14c and refracted at an angle φ1 'to reach the surface 10a.

  Since the refractive index of the quarter-wave plate 11 is substantially equal to the refractive index of the light guide 10, the first polarized light from the side surface 14c passes through the surface 10a without being refracted and is ¼ wavelength. It reaches the exit surface 11a of the plate 11. Since the first polarized light that has passed through the surface 10a passes through the quarter-wave plate 11 once, the light that reaches the exit surface 11a is circularly polarized light.

  The incident angle (90 ° −φ1 ′) of circularly polarized light incident on the exit surface 11a is larger than the critical angle. Therefore, the circularly polarized light is reflected in the direction of the light guide 10 at the emission surface 11a. Since the circularly polarized light reflected by the emission surface 11a passes through the quarter-wave plate 11, the light incident on the surface 10a of the light guide 10 is the second polarized light. The second polarized light incident from the surface 10 a propagates through the light guide 10.

  Thus, in the refracting section 14, the first polarized light that satisfies the second light guide condition that is incident from the surface 14a, reflected by the surface 14b, and emitted from the side surface 14c is emitted from the emission surface 11a. Instead, after being converted into the second polarized light by the quarter wavelength plate 11, the light propagates through the light guide 10.

  18E is a diagram for explaining the third light guide condition of the refracting unit 14 for the first polarized light, and a part of the polarization light guide plate shown in FIG. FIG. 6 is a schematic view of a cross section cut along a plane perpendicular to the end face of FIG.

  In the refracting unit 14, the first polarized light incident on the surface 14a at an angle φ0 with the surface 14a is refracted at an angle θ1 ′ and emitted from the surface 14b. Here, the incident angle of the first polarized light with respect to the surface 14a is given by “90 ° −φ0”.

  The first polarized light emitted from the surface 14 b is reflected by the reflective layer 12 and then reaches the surface 10 a of the light guide 10. The angle of the first polarized light reflected by the reflective layer 12 with respect to the reflective layer 12 is φ0.

  Since the refractive index of the quarter-wave plate 11 is substantially equal to the refractive index of the light guide 10, the first polarized light from the reflective layer 12 passes through the surface 10a without being refracted and is ¼. It reaches the emission surface 11 a of the wave plate 11. Since the first polarized light that has passed through the surface 10a passes through the quarter-wave plate 11 once, the light that reaches the exit surface 11a is circularly polarized light.

  The incident angle (= 90 ° −φ0) of the circularly polarized light incident on the exit surface 11a is larger than the critical angle. Therefore, the circularly polarized light is reflected in the direction of the light guide 10 at the emission surface 11a. Since the circularly polarized light reflected by the emission surface 11a passes through the quarter-wave plate 11, the light incident on the surface 10a of the light guide 10 is the second polarized light. The second polarized light incident from the surface 10 a propagates through the light guide 10.

  Thus, in the refracting section 14, the first polarized light that satisfies the second light guide condition that is incident from the surface 14a, reflected by the surface 14b, and emitted from the side surface 14c is emitted from the emission surface 11a. Instead, after being converted into the second polarized light by the quarter wavelength plate 11, the light propagates through the light guide 10.

  FIG. 18F is a diagram for explaining the fourth light guide condition of the refracting unit 14 for the first polarized light, and a part of the polarization light guide plate shown in FIG. FIG. 6 is a schematic view of a cross section cut along a plane perpendicular to the end face of FIG.

  In the refracting unit 14, the first polarized light incident on the surface 14a at an angle φ0 with the surface 14a is refracted at an angle θ1 ′ and emitted from the surface 14b. Here, the incident angle of the first polarized light with respect to the surface 14a is given by “90 ° −φ0”.

  The first polarized light emitted from the surface 14 b is reflected by the reflective layer 12. The first polarized light reflected by the reflective layer 12 is incident on the refraction part 14 again from the surface 14b. The first polarized light incident from the surface 14b is emitted from the surface 14a and then reaches the surface 10a. Here, the angle of the first polarized light emitted from the surface 14a with respect to the surface 14a is φ0.

  Since the refractive index of the quarter-wave plate 11 is substantially equal to the refractive index of the light guide 10, the first polarized light from the surface 14a passes through the surface 10a without being refracted and is ¼ wavelength. It reaches the exit surface 11a of the plate 11. Since the first polarized light that has passed through the surface 10a passes through the quarter-wave plate 11 once, the light that reaches the exit surface 11a is circularly polarized light.

  The incident angle (90 ° −φ0) of the circularly polarized light incident on the exit surface 11a is larger than the critical angle. Therefore, the circularly polarized light is reflected in the direction of the light guide 10 at the emission surface 11a. Since the circularly polarized light reflected by the emission surface 11a passes through the quarter-wave plate 11, the light incident on the surface 10a of the light guide 10 is the second polarized light. The second polarized light incident from the surface 10 a propagates through the light guide 10.

  As described above, in the refracting unit 14, the first polarized light that satisfies the fourth light guide condition that is incident from the surface 14a, reflected by the surface 14b, and emitted from the side surface 14c is emitted from the emission surface 11a. Instead, after being converted into the second polarized light by the quarter wavelength plate 11, the light propagates through the light guide 10.

  18G is a diagram for explaining the fifth light guide condition of the refracting unit 14 for the first polarized light, and a part of the polarization light guide plate shown in FIG. FIG. 6 is a schematic view of a cross section cut along a plane perpendicular to the end face of FIG.

  In the refracting unit 14, the first polarized light is incident on the surface 14a at an angle φ formed with the surface 14a. Here, the incident angle of the first polarized light with respect to the surface 14a is given by “90 ° −φ”. The first polarized light is reflected by the surface 14a.

  The first polarized light reflected by the surface 14 a reaches the surface 10 a of the light guide 10. Since the refractive index of the quarter-wave plate 11 is substantially equal to the refractive index of the light guide 10, the first polarized light from the surface 14a passes through the surface 10a without being refracted, and becomes 1/4. It reaches the emission surface 11 a of the wave plate 11. Since the first polarized light that has passed through the surface 10a passes through the quarter-wave plate 11 once, the light that reaches the exit surface 11a is circularly polarized light.

  The incident angle (90 ° −φ) of circularly polarized light incident on the exit surface 11a is larger than the critical angle. Therefore, the circularly polarized light is reflected in the direction of the light guide 10 at the emission surface 11a. Since the circularly polarized light reflected by the emission surface 11a passes through the quarter-wave plate 11, the light incident on the surface 10a of the light guide 10 is the second polarized light. The second polarized light incident from the surface 10 a propagates through the light guide 10.

  Thus, in the refracting section 14, the first polarized light that satisfies the fifth light guide condition of being reflected by the surface 14a is not emitted from the emission surface 11a, but is secondly emitted by the quarter wavelength plate 11. After being converted into the polarized light, the light propagates through the light guide 10.

  The same effects as those of the first embodiment can also be obtained by the polarizing light guide plate of the present embodiment described above.

  Also in the present embodiment, the same modifications as those in the first embodiment are made with respect to the size and interval of the refracting parts 13 and 14 and the way of arranging the refracting parts 13 and 14 (one-dimensional arrangement and two-dimensional arrangement). It can be carried out.

  Further, in the present embodiment, the same modification as that of the first embodiment can be performed with respect to the prism sheet, another quarter wave plate, and the like.

  Next, the manufacturing procedure of the polarizing light guide plate of this embodiment will be described.

  The polarizing light guide plate of this embodiment can be manufactured by changing the step of forming the recess in the procedure for manufacturing the polarizing light guide plate of the first embodiment. Specifically, a recess is formed in a region of the surface of the first light guide that becomes the refracting portions 13 and 14, and UV curable liquid crystal monomer is embedded in the recess by screen printing. And the surface in which the recessed part of the 1st light guide was formed and one surface of the 2nd light guide are bonded together. Other steps are the same as those in the first embodiment.

  The polarizing light guide plate of each embodiment described above is an example of the present invention, and the configuration thereof can be changed as appropriate. For example, in the polarization light guide plate of the second embodiment, as shown in FIG. 19, the polarization light guide plate is cut at a plane orthogonal to each of the end surface where the light source is provided and the exit surface of the quarter wavelength plate 11. The cross-sectional shape of the light guide 10 may be a wedge shape. The wedge-shaped light guide 10 is configured such that the light source side is thick and gradually becomes thinner as the distance from the end surface on the light source side increases. According to this configuration, it is possible to change the incident angle of the light reflected between the exit surface of the quarter-wave plate 11 and the reflection layer 12 and propagating through the light guide 10 to the refraction portions 13 and 14. . Thereby, compared with the structure shown in FIG. 16, the light which satisfy | fills the emission conditions of the refractive parts 13 and 14 can be obtained efficiently.

  The wedge-shaped light guide described above can also be applied to the polarizing light guide plate of the first embodiment. In this case, the refraction parts 13 and 14 have an inclination with respect to the exit surface of the quarter-wave plate 11, but the inclinations of the refraction parts 13 and 14 are the same. Therefore, the angular spread of the light emitted from the emission surface of the quarter-wave plate 11 in this case is the same as that described in the first embodiment.

(Lighting device)
Next, an illuminating device provided with the polarizing light-guide plate of this invention is demonstrated.

  FIG. 20 shows an example of a cross-sectional structure of an illumination device including the polarizing light guide plate of the present invention.

  The illumination device shown in FIG. 20 includes the polarization light guide plate shown in FIG. This illuminating device can be used as an illuminating device for a liquid crystal display device such as a mobile phone or a projection display device represented by a liquid crystal projector.

  The light source 20 is a semiconductor light source such as a light emitting diode (LED) or a semiconductor laser (LD), or a light source called a solid light source, and is provided so as to face the end surface 10 b of the light guide 10. As long as the light from the light source 20 can be efficiently incident on the light guide 10, the light source 20 may be arranged in any manner with respect to the end face 10b. For example, the light emitting unit of the light source 20 may be disposed close to the end surface 10b, and an optical member (prism or lens) for causing light from the light emitting unit to enter the end surface 10b between the light emitting unit and the end surface 10b. ) May be arranged.

  Light (non-polarized light) emitted from the light source 20 enters the light guide 10 from the end face 10b. Light (non-polarized light) incident on the end surface 10b of the light guide 10 from the light source 20 is reflected between the exit surface 11a of the quarter-wave plate 11 and the reflection layer 12, and the end surface in the light guide 10 is also obtained. Propagates toward the end face 10c facing 10b. In this propagation process, a part of the light enters the refracting parts 13 and 14.

  In the refracting sections 13 and 14, only the first polarized light that satisfies the emission condition passes through the quarter-wave plate 11 and is emitted from the emission surface 11a. The outgoing light from this outgoing face 11a is circularly polarized light.

  The circularly polarized light emitted from the emission surface 11 a passes through the prism sheet 15 and the quarter wavelength plate 16. By the prism sheet 15, the outgoing light from the outgoing surface 11a is aligned in a direction substantially perpendicular to the outgoing surface 11a. The quarter-wave plate 16 converts the circularly polarized light that has passed through the prism sheet 15 into second polarized light.

  According to this illuminating device, the refracting portions 13 and 14 can make the angular spread (outgoing angle) of the emitted light fall within the usable range of light based on etendue restrictions. Therefore, when this illuminating device is applied to a projection display device, the problem of stray light due to divergent light that occurs in the illuminating device described in Patent Document 1 does not occur.

  In addition, since the angular spread of the emission angle can be reduced, the viewing angle that occurs in the illumination device described in Patent Document 1 when the illumination device is applied to a liquid crystal display device such as a mobile phone. There is no dependency problem.

  In the present illumination device, the polarizing light guide plate is not limited to the configuration shown in FIG. The polarization light guide plate may be any of the polarization light guide plate described in the first and second embodiments and its modification.

  Moreover, the some light source 20 may be provided with respect to the end surface 10b.

  Furthermore, at least one light source 20 may be provided on both of the end faces 10b and 10c.

  In the configuration in which the light source 20 is provided on both of the end faces 10b and 10c, when the wedge-shaped light guide 10 is applied, the thickness of the central portion (the intermediate position between the end face 10b and the end face 10c) is the smallest, and the end face The light guide 10 may be formed so that the thickness gradually increases toward the 10b and 10c sides.

  In addition, in the above configuration, the distance between the refracting portions 13 and 14 is gradually increased or the refracting portions 13 and 14 are gradually increased between the end surfaces 10b and 10c and the central portion as the distance from the end surfaces 10b and 10c increases. You may enlarge it.

(Projection type display device)
The illumination device including the polarization light guide plate of the present invention described above can be applied to a projection display device typified by a liquid crystal projector.

  FIG. 21 is a schematic diagram illustrating a configuration of a projection display device using an illumination device including the polarization light guide plate of the present invention. Referring to FIG. 21, the projection display device includes illumination devices 300 to 302, liquid crystal elements 303 to 305 that are display elements, a cross dichroic mirror 306, and a projection optical system 307.

  All of illuminating devices 300 to 302 are configured by the above-described illuminating device (having two quarter-wave plates). A blue LED is used as the light source of the illumination device 300. A green LED is used as the light source of the illumination device 301. A red LED is used as the light source of the illumination device 302.

  In addition, when what has one quarter wavelength plate is used as a polarization light-guide plate of the illuminating devices 300-302, between the output surface of the illuminating device 300 and the liquid crystal element 303, the output surface of the illuminating device 301 is used. And a liquid crystal element 304, and between the exit surface of the illumination device 302 and the liquid crystal element 305, separate quarter-wave plates are provided.

  The blue light emitted from the illumination device 300 is applied to the liquid crystal element 303. The liquid crystal element 303 is driven by a liquid crystal driving circuit (not shown) and forms a blue image based on a video signal supplied from the outside.

  Green light emitted from the illumination device 301 is applied to the liquid crystal element 304. The liquid crystal element 304 is driven by a liquid crystal driving circuit (not shown) and forms a green image based on a video signal supplied from the outside.

  The red light emitted from the illumination device 302 is applied to the liquid crystal element 305. The liquid crystal element 305 is driven by a liquid crystal drive circuit (not shown), and forms a red image based on a video signal supplied from the outside.

  The image light of each color formed by the liquid crystal elements 303 to 305 enters the projection optical system 307 via the cross dichroic mirror 306. The projection optical system 307 projects each color image formed by the liquid crystal elements 303 to 305 onto a screen (or a member replacing the screen) (not shown).

  Another projection display device uses an illuminating device including light sources of red, green, and blue colors on the end face of the polarizing light guide plate of the present invention. In this case, light (corresponding to white light) of predetermined polarized light (P-polarized light or S-polarized light) of red, green, and blue is emitted from the illumination device. Light emitted from the illumination device is irradiated onto a display element (for example, a liquid crystal element). The display element displays red, green, and blue images based on an external video signal in a time division manner. The light emission timing of the light source is controlled in synchronization with the time division display. Each color image formed on the display element is projected by the projection optical system.

  The polarizing light guide plate of the present invention and the illumination device including the same can be used as a backlight of a liquid crystal display in addition to the above-described projection display device.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited to the above-described embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and operation of the present invention without departing from the spirit of the present invention.

  This application claims the priority on the basis of Japanese application Japanese Patent Application No. 2010-072945 for which it applied on March 26, 2010, and takes in those the indications of all here.

Claims (28)

A light guide through which light incident from the end face propagates,
A quarter wave plate formed on one surface of the light guide;
A reflective layer provided on the other surface facing the one surface of the light guide;
A plurality of refractive indexes with respect to a first polarized light that is larger than a refractive index of the light guide, and a refractive index with respect to a second polarized light having a polarization state different from the first polarized light is the same as the refractive index of the light guide. A first refracting portion of
A plurality of second refracting sections having a refractive index with respect to the first polarized light smaller than a refractive index of the light guide and a refractive index with respect to the second polarized light being the same as the refractive index of the light guide; Have
The plurality of first and second refracting portions are provided in the light guide so as to face the one surface, and at least in a first direction intersecting a direction perpendicular to the end surface, A polarization light guide plate in which the first refracting portions and the second refracting portions are alternately arranged.   The polarizing light guide plate according to claim 1, wherein the first and second refracting portions have a rectangular parallelepiped shape and are formed on the other surface of the light guide.   In the first refracting portion, the light satisfies the emission condition of being incident from the first surface located on the one surface side of the light guide and being emitted from the second surface adjacent to the first surface. The polarization light guide plate according to claim 2, wherein the first polarized light passes through the ¼ wavelength plate. The length of the first refracting portion in the direction perpendicular to the end surface when the first refracting portion is viewed from a direction perpendicular to a plane orthogonal to each of the one surface and the end surface of the light guide. Is B, the height of the first refracting portion in the direction perpendicular to the one surface is H, and the first polarized light is incident from the first surface in the first refracting portion. When the angle of the light of the first polarized light with respect to the reflective layer when exiting from the second surface through the reflective layer is θ2,

The polarizing light guide plate according to claim 3, wherein the condition is satisfied. When the first refracting portion is viewed from a direction perpendicular to a plane orthogonal to each of the one surface and the end surface of the light guide, the first refracting portion in a direction perpendicular to the one surface The height is H, the distance between the first refracting part and the refracting part adjacent to the first refracting part in the direction perpendicular to the end face is Q, and the first refracting part has the first refracting part When the exit angle when polarized light is incident from the first surface and exits from the second surface is φ1,

The polarizing light guide plate according to claim 3, wherein the condition is satisfied.   In the second refracting portion, an emission condition that enters from the first surface facing the end surface of the light guide and exits from the second surface located on the one surface side of the light guide is satisfied. The polarization light guide plate according to claim 2, wherein the first polarized light passes through the ¼ wavelength plate. The length of the second refracting portion in the direction perpendicular to the end surface when the second refracting portion is viewed from a direction perpendicular to a plane orthogonal to each of the one surface and the end surface of the light guide. Is b, and the height of the second refracting portion in the direction perpendicular to the one surface is h. In the second refracting portion, the first polarized light is incident from the first surface. When the angle of the light of the first polarized light with respect to the reflective layer when exiting from the second surface through the reflective layer is θ2 ′,

The polarizing light guide plate according to claim 6, wherein the condition is satisfied. When the second refracting portion is viewed from a direction perpendicular to a plane orthogonal to each of the one surface and the end surface of the light guide, the second refracting portion in the direction perpendicular to the one surface The height is h, the distance between the second refracting part and the refracting part adjacent to the second refracting part in the direction perpendicular to the end face is q, and the first polarized light passes through the reflective layer. When the angle of the light of the first polarized light with respect to the reflective layer when entering from the first surface of the second refractive part through

The polarizing light guide plate according to claim 6, wherein the condition is satisfied.   2. The polarization light guide plate according to claim 1, wherein the first and second refracting portions have a rectangular parallelepiped shape and are formed between the one surface and the other surface inside the light guide.   In the first refracting portion, the light is incident from the first surface located on the one surface side of the light guide, is emitted from the second surface facing the first surface, and then the reflection is performed. The light of the first polarization that satisfies the emission condition of entering from the second surface through the layer and exiting from the third surface adjacent to the first and second surfaces is the 1 / The polarizing light guide plate according to claim 9, which passes through a four-wave plate.   In the first refracting section, an emission condition that the light enters from the first surface located on the one surface side of the light guide and exits from the second surface adjacent to the first surface is satisfied. The polarization light guide plate according to claim 9, wherein the first polarized light passes through the quarter-wave plate.   In the second refracting portion, an emission condition that enters from the first surface facing the end surface of the light guide and exits from the second surface located on the one surface side of the light guide is satisfied. The polarization light guide plate according to claim 9, wherein the first polarized light passes through the quarter-wave plate.   In the second refracting portion, a third surface that enters from the first surface facing the end surface of the light guide and faces the second surface located on the one surface side of the light guide. The polarization light guide plate according to claim 9, wherein the first polarized light satisfying an emission condition of being emitted from the light passes through the quarter-wave plate.   In the second refracting portion, a third surface that enters from the first surface facing the end surface of the light guide and faces the second surface located on the one surface side of the light guide. The light of the first polarization that satisfies the emission condition of being emitted from the first surface and then incident from the third surface through the reflective layer and emitted from the second surface is the quarter wavelength. The polarizing light guide plate according to claim 9, which passes through the plate.   2. The polarizing light guide plate according to claim 1, wherein an interval between the first and second refracting portions in a direction perpendicular to the end face increases as the distance from the end face increases.   2. The polarizing light guide plate according to claim 1, wherein lengths of the first and second refracting portions in a direction perpendicular to the end face increase as the distance from the end face increases.   2. The polarizing light guide plate according to claim 1, wherein thicknesses of the first and second refracting portions in a direction perpendicular to the one surface increase with increasing distance from the end surface.   The length of the first refracting portion in the direction perpendicular to the end face is longer than the length of the second refracting portion in the direction perpendicular to the end face, and the length of the first refracting portion in the first direction is longer. The polarizing light guide plate according to claim 2 or 9, wherein a length is longer than a length of the second refracting portion in the first direction.   When the first and second refracting portions adjacent to each other in the first direction are viewed from a direction perpendicular to the one surface of the light guide, the first refracting portion of the light guide 19. The polarization guide according to claim 18, wherein the second refracting portion is disposed between a line extending from the first side on the end face side and a second side facing the first side. Light board. When the first and second refracting portions adjacent to the first direction are viewed from a direction perpendicular to the one surface of the light guide, the first and second in the first direction The lengths of the refracting portions are A and a, respectively, the interval between the first side surfaces of the first and second refracting portions facing each other is P, and on the end face side of the first and second refracting portions. The distance between the second side surfaces is D, the refractive index of the light guide is n0, the refractive index of the first refracting part with respect to the first polarized light is n1, and the first refracting part. The angle of the incident light with respect to the second side surface is φ0 when the light of the first polarized light is incident from the second side surface and is emitted from the first side surface, When the angle to the side is φ1,

The polarizing light guide plate according to claim 2 or 9, which satisfies the following condition. When the first and second refracting parts adjacent to the first direction are viewed from a direction perpendicular to the one surface of the light guide, the first refracting part in the first direction The length is A, the length of the first refracting part in the second direction orthogonal to the first direction is B, and the first side surface between the first and second refracting parts is opposed to each other. P is the distance between the second side surfaces located on the end face side of the first and second refracting parts, and D is the distance between the first and second refracting parts. When the incident light is incident from the first side surface and is emitted from the third side surface facing the first side surface, the angle of the incident light with respect to the second side surface is φ0, and the incident light is incident from the second side surface and When the angle formed by the first direction of light propagating in the first refracting portion is θ3,

The polarizing light guide plate according to claim 2 or 9, which satisfies the following condition. When the first and second refracting portions adjacent to the first direction are viewed from a direction perpendicular to the one surface of the light guide, the second direction is perpendicular to the first direction. The length of the second refracting portion is b, and in the second refracting portion, the first polarized light is incident from the first side surface located on the end surface side, and the first side surface. When the light beam is emitted from the second side surface adjacent to the first side surface, the angle formed by the direction perpendicular to the end surface of the incident light is φ1, and the light that is incident from the first side surface and propagates through the second refracting portion When the angle with respect to the first side is θ1 ′,

The polarizing light guide plate according to claim 2 or 9, which satisfies the following condition.   The cross-sectional shape of the light guide when viewed from a direction perpendicular to a plane intersecting each of the one surface and the end surface of the light guide is a wedge shape. The polarizing light guide plate according to claim 1. A prism sheet in which a plurality of prism portions having a triangular cross-sectional shape are formed on a plane;
The polarizing light guide plate according to any one of claims 1 to 23, wherein the prism sheet is disposed so as to face a surface of the quarter wavelength plate opposite to the light guide side. .   The polarizing light guide plate according to any one of claims 1 to 24, further comprising another quarter-wave plate provided in a traveling direction of light emitted from the quarter-wave plate. The polarizing light guide plate according to any one of claims 1 to 25;
And at least one light source provided on an end face of the polarizing light guide plate. An illumination device according to claim 26;
A display element irradiated with light emitted from the illumination device;
A projection optical system that projects an image formed by the display element. A lighting device of each color of red, green, and blue, comprising the lighting device according to claim 26;
A first display element irradiated with red light emitted from the red illumination device;
A second display element irradiated with green light emitted from the green illumination device;
A third display element irradiated with blue light emitted from the blue illumination device;
A projection optical system that projects an image of each color displayed on the first to third display elements.

Images