WO2011125479A1 - Polarizing light guide plate, illuminating device, and projection display device - Google Patents

Abstract

Disclosed is a polarizing light guide plate which comprises: a light guide body (10) which has opposing surfaces, wherein one of the surfaces serves as an emitting surface (10a); a reflective layer (12) provided on the other surface of the opposing surfaces of the light guide body (10); a plurality of half-wavelength plates (11) formed on the emitting surface (10a) of the light guide body (10) at regular intervals in a certain direction; and a plurality of anisotropic refraction portions (13) formed along the other surface at regular intervals in the certain direction within the light guide body (10). The anisotropic refraction portion (13) is provided such that a refractive index with respect to a first polarized light is smaller than that of the light guide body (10) and a refractive index with respect to a second polarized light is larger than that of the light guide body (10).

Description

Polarized light guide plate, illumination device, and projection display device

The present invention relates to a polarization light guide plate from which light having polarization properties is emitted, and more particularly, to a polarization light guide plate of a projection display device typified by a liquid crystal projector.

Patent Document 1 discloses a light guide plate that emits light having polarization. The light guide plate includes a first layer having an incident end face on which light from a light source is incident and an emission surface from which the light is emitted, a second layer formed on the emission surface side of the first layer, and a second layer. A third layer made of an anisotropic material is formed, and a plurality of light distribution adjusting units are formed in an interface between the second layer and the first layer. A polarization conversion plate and a reflection plate are formed on the surface of the first layer opposite to the exit surface.

The surface of the second layer opposite to the first layer is a prism surface. The prism surface is formed by repeatedly arranging prism structures having a triangular wave cross section.

The width of the light distribution adjusting unit becomes smaller as the distance from the light source increases. The interval between the light distribution adjusting units increases as the distance from the light source increases. These light distribution adjusting units are configured such that the amount of reflected light gradually decreases as the distance from the light source increases.

The third layer is configured such that the first refractive index for P-polarized light and the second refractive index for S-polarized light are different. The first refractive index of the third layer is substantially the same as the refractive index of the first layer and the second layer. The second refractive index of the third layer is larger than the refractive indexes of the first layer and the second layer.

In the above light guide plate, among the light incident from the incident end face, the P-polarized light passes through the boundaries of the first layer, the second layer, and the third layer as they are. The P-polarized light incident on the third layer from the second layer is reflected in the direction of the first layer by the surface of the third layer opposite to the second layer.

The P-polarized reflected light incident on the second layer from the third layer is reflected in the direction of the third layer by the light distribution adjusting unit, or is transmitted through the first layer and the polarization conversion plate and is reflected by the reflecting plate. Reflected in the direction of one layer. As described above, the P-polarized light is guided between the third layer and the reflection plate, and is converted into S-polarized light by passing through the polarization conversion plate in the light guide process.

On the other hand, the S-polarized light traveling from the first layer to the second layer passes through the boundary between the first layer and the second layer as it is. The S-polarized light traveling from the second layer to the third layer is refracted at the boundary between the second layer and the third layer, and enters the third layer. Of the S-polarized light that has entered the third layer from the second layer, light that is incident on the prism surface of the second layer at a predetermined incident angle (an angle that satisfies the total reflection condition) is reflected by the prism surface. Then, the light is emitted from the third layer to the outside.

JP 2008-117766 Gazette

In the light guide plate described in Patent Document 1, S-polarized light incident at a predetermined incident angle with respect to the prism surface of the second layer is emitted from the light guide plate. On the other hand, the P-polarized light is not emitted from the light guide plate, but is guided between the third layer and the reflecting plate, and passes through the polarization conversion plate in the light guide process, thereby being converted into S-polarized light. Is done. That is, unless the P-polarized light is converted into S-polarized light by the polarization conversion plate, the P-polarized light continues to be guided through the light guide plate and is not emitted from the light guide plate.

Usually, when light is guided, a part of the light is absorbed by the member during the light guiding process, resulting in light loss. In the light guide plate described in Patent Document 1, P-polarized light is always guided through the light guide plate without being emitted from the light guide plate, so that light loss occurs in the light guide process.

Further, as shown in FIG. 18 of Patent Document 1, since the emission angle distribution of the light guide plate is about ± 90 °, the following problems occur.

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

An object of the present invention is to provide a polarizing light guide plate that can reduce light loss in the light guide process and solves the problems due to the etendue restrictions and suppresses the spread of the emission angle. Another object of the present invention is to provide a lighting device and a projection display device.

In order to achieve the above object, the polarizing light guide plate of the present invention comprises:
A light guide including opposing surfaces, and one of these surfaces being an exit surface;
A reflective layer provided on the other surface of the opposing surface of the light guide;
Phase difference means provided on the exit surface of the light guide;
A plurality of anisotropic refracting portions periodically formed in a certain direction along the other surface in the light guide;
Each of the plurality of anisotropic refracting portions has a refractive index with respect to the first polarized light that is smaller than a refractive index of the light guide and has a polarization state different from that of the first polarized light. The refractive index is configured to be larger than the refractive index of the light guide,
The phase difference unit changes the phase of at least one of the first and second polarized lights emitted from the emission surface, and emits circularly polarized light having the same rotation direction or linearly polarized light having the same polarization direction. .

The lighting device of the present invention is
The polarizing light guide plate,
And at least one light source for supplying light to an end 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. FIG. 2 is a perspective view schematically showing a part of the polarization light guide plate shown in FIG. 1. It is a schematic diagram for demonstrating the emission conditions of the polarizing light-guide plate shown in FIG. It is a schematic diagram for demonstrating the light guide conditions of the polarizing light-guide plate shown in FIG. It is a schematic diagram for demonstrating another light guide condition of the polarizing light guide plate shown in FIG. It is a schematic diagram for demonstrating the conditions (thickness and width) of the magnitude | size of the anisotropic refractive part of the polarizing light-guide plate shown in FIG. It is a schematic diagram for demonstrating the magnitude | size of the anisotropic refractive part of the polarizing light-guide plate shown in FIG. It is a schematic diagram for demonstrating the space | interval of the anisotropic refractive part of the polarizing light-guide plate shown in FIG. It is a schematic diagram which shows the 1st Example of the polarization light-guide plate shown in FIG. It is a schematic diagram which shows the 2nd Example 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 which shows a part of prism sheet 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 1/2 wavelength plate 12 Reflective layer 13 Anisotropic refractive part

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a cross-sectional view showing a configuration of a polarizing light guide plate according to the first embodiment of the present invention. FIG. 2 is a perspective view of the polarizing light guide plate shown in FIG.

As shown in FIGS. 1 and 2, the polarization light guide plate is used in a projection display device typified by a liquid crystal projector, and is provided on the light guide 10 and one surface of the light guide 10. A plurality of anisotropies provided on the boundary surface between the half-wave plate 11 formed, the reflective layer 12 provided on the other surface of the light guide 10, and the reflective layer 12 in the light guide 10 And a refracting portion 13.

The light guide 10 is plate-shaped and 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 the 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 half-wave plate 11 is almost equal to the refractive index n0 of the light guide 10. The half-wave plate 11 has a rectangular shape and is periodically formed in a direction intersecting the longitudinal direction. Here, the longitudinal direction is a direction along the long side of the half-wave plate. The direction intersecting the longitudinal direction is, for example, a direction perpendicular to the end surface where the light source of the light guide 10 is provided.

The anisotropic refracting portion 13 is made of a material having an anisotropic refractive index. 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 is n1, and the refractive index for the second polarized light is n2. The anisotropic refracting portion 13 is configured to satisfy the condition of n1 <n0 <n2.

The anisotropic refracting portion 13 has a rectangular parallelepiped shape and is periodically arranged in a direction intersecting with the longitudinal direction (the same as the longitudinal direction of the half-wave plate 11).

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

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

In the polarization light guide plate of the present embodiment, a part of light (non-polarized light) incident on the first end surface of the light guide 10 from the light source is reflected between the emission surface 10a and the reflective layer 12 and guided. The light propagates in the light body 10 toward the second end face facing the first end face. In this propagation process, a part of the light enters the anisotropic refracting portion 13.

The anisotropic refracting unit 13 includes first and second emission conditions between the emission surface 10a and the reflective layer 12 and emission conditions for emitting the first and second polarized lights from different regions of the emission surface 10a. The light guide condition for guiding the polarized light is satisfied.

First, the emission conditions of the anisotropic refracting unit 13 will be described.

FIG. 3 is a diagram for explaining the emission conditions of the anisotropic refracting unit 13 with respect to the first and second polarized lights. A part of the polarization light guide plate shown in FIG. It is the schematic diagram of the cross section cut | disconnected by the plane perpendicular | vertical to 1 end surface (end surface provided with the light source) and the output surface 10a. In FIG. 3, an arrow indicated by a solid line indicates P-polarized light, and an arrow indicated by a broken line indicates S-polarized light. In this example, the refractive index for P-polarized light is n1, and the refractive index for S-polarized light is n2.

In the anisotropic refracting unit 13, the S-polarized light incident at an angle φ0 formed with the surface 13a with respect to the surface 13a located on the light exit surface 10a side of the light guide 10 is refracted at an angle θ1 and is surface 13a. It reaches the surface 13b opposite to. Here, the incident angle of the S-polarized light with respect to the surface 13a is given by “90 ° −φ0”, which is larger than the angle θ1.

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

The incident angle θ2 (= 90 ° −θ1) of the S-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). For this reason, the S-polarized light incident on the side surface 13c from the surface 13b is refracted at an angle φ1 (> θ2) and reaches the output surface 10a of the light guide 10.

Since the refractive index of the half-wave plate 11 is substantially equal to the refractive index of the light guide 10, the S-polarized light from the side surface 13 c passes through the surface 10 a without being refracted and passes through the half-wave plate 11. Incident in. In the half-wave plate 11, the incident light reaches the surface 11 a opposite to the light guide 10. When the incident angle (90 ° −θ1) of the incident light with respect to the surface 11a is smaller than the critical angle, the incident light is emitted from the surface 11a at the emission angle β. The light emitted from the surface 11a is P-polarized light.

As described above, in the anisotropic refraction unit 13, S-polarized light that satisfies the condition of being incident from the surface 13 a and emitted from the side surface 13 c (emission condition) is P-polarized light by the half-wave plate 11. After being converted to, the light is emitted at an emission angle β.

Although not shown in FIG. 3, the S-polarized light incident from the surface 13 a and emitted from the side surface 13 c is reflected by the reflective layer 12 and then passes through the half-wave plate 11. The condition of emission is also established as the emission condition.

Further, in the anisotropic refracting unit 13, the P-polarized light incident at the incident angle φ0 with respect to the side surface 13d located on the first end surface side of the light guide 10 is refracted at the angle θ1 (> φ0). , Reach the surface 13b.

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

The incident angle θ2 (= 90−θ1) of the P-polarized light reflected by the surface 13b with respect to the surface 13a is smaller than the critical angle. For this reason, the P-polarized light is refracted at an angle φ1 with respect to the surface 13a and reaches the output surface 10a.

When the incident angle (90 ° −φ1) of the P-polarized light from the surface 13a with respect to the emission surface 10a is smaller than the critical angle, the P-polarized light is emitted from the emission surface 10a at the emission angle β.

As described above, in the anisotropic refracting portion 13, the P-polarized light that satisfies the condition (exit condition) that is incident from the side surface 13d and emitted from the surface 13a is emitted from the output surface 10a at the output angle β.

Although not shown in FIG. 3, the condition that the P-polarized light incident from the side surface 13d is directly emitted from the surface 13a without passing through the reflective layer 12 is also satisfied as the emission condition.

When viewed from a direction perpendicular to the exit surface 10a of the light guide 10 without the half-wave plate 11, the region where the S-polarized light is emitted from the exit surface 10a is the P-polarized light of the exit surface 10a. It is different from the region where light is emitted. The half-wave plate 11 is formed on a region of the emission surface 10a where S-polarized light is emitted.

The half-wave plate 11 may be formed not on the area of the emission surface 10a where S-polarized light is emitted but on the area where P-polarized light is emitted. In this case, light emitted from the polarization light guide plate is S-polarized light.

Next, the light guide conditions of the anisotropic refraction part 13 will be described.

FIG. 4 is a diagram for explaining the light guide conditions of the anisotropic refracting portion 13, and a part of the polarization light guide plate shown in FIG. 1 is replaced with the first end face of the light guide 10 and the exit face 10 a. It is a schematic diagram of the cross section cut | disconnected by the plane perpendicular | vertical to.

In the anisotropic refracting portion 13, the S-polarized light incident on the surface 13a at an angle φ0 ′ formed with the surface 13a is refracted at an angle θ1 ′ and reaches the surface 13b. The S-polarized light incident from the surface 13a and reaching the surface 13b is reflected by the surface 13b. The S-polarized light reflected by the surface 13b reaches the side surface 13c.

The incident angle θ2 ′ (= 90 ° −θ1 ′) of the S-polarized light reflected by the surface 13b with respect to the side surface 13c is smaller than the critical angle. For this reason, the S-polarized light incident on the side surface 13 c from the surface 13 b is refracted and reaches the output surface 10 a of the light guide 10. Here, the angle between the S-polarized light emitted from the side surface 13c and the side surface 13c is φ1 '.

The incident angle (90 ° −φ1 ′) of the S-polarized light from the side surface 13c with respect to the emission surface 10a is larger than the critical angle. Therefore, the S-polarized light is reflected by the emission surface 10a.

In this way, in the anisotropic refracting portion 13, the S-polarized light that satisfies the light guide condition of entering from the surface 13a, reflected by the surface 13b, and emitted from the side surface 13c is reflected by the exit surface 10a. And propagates in the light guide 10.

Further, in the anisotropic refracting unit 13, the P-polarized light incident at the incident angle φ0 ′ on the side surface 13d is refracted at the angle θ1 ′ and reaches the surface 13b.

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

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

The incident angle (90 ° −φ1 ′) of the P-polarized light from the surface 13a with respect to the emission surface 10a is larger than the critical angle. Therefore, the P-polarized light is reflected by the exit surface 10 a and propagates through the light guide 10.

As described above, in the anisotropic refraction unit 13, the P-polarized light that satisfies the light guide condition of entering from the side surface 13d, reflected by the surface 13b, and emitted from the surface 13a is reflected by the emission surface 10a. And propagates in the light guide 10.

FIG. 5 is a diagram for explaining another light guide condition of the anisotropic refracting portion 13, 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 the surface 10a.

In the anisotropic refracting unit 13, the S-polarized light incident at the incident angle φ0 ′ on the side surface 13d is refracted at the angle θ1 ′ and reaches the surface 13b.

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

The incident angle θ2 ′ (= 90 ° −θ1 ′) of the S-polarized light reflected by the surface 13b with respect to the surface 13a is smaller than the critical angle. For this reason, the S-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 S-polarized light emitted from the surface 13a and the surface 13a is φ1 '.

The incident angle (90 ° −φ1 ′) of the S-polarized light from the surface 13a with respect to the emission surface 10a is larger than the critical angle. Therefore, the S-polarized light is reflected by the emission surface 10 a and propagates through the light guide 10.

As described above, in the anisotropic refracting portion 13, the S-polarized light that satisfies the light guide condition of entering from the side surface 13d, reflected by the surface 13b, and emitted from the surface 13a is reflected by the emission surface 10a. And propagates in the light guide 10.

Further, in the anisotropic refracting portion 13, the P-polarized light incident on the surface 13a at an angle φ0 ′ formed with the surface 13a is refracted at an angle θ1 ′ and reaches the surface 13b.

The P-polarized light incident from the surface 13a and reaching the surface 13b is reflected by the surface 13b. The P-polarized light reflected by the surface 13b is incident on the side surface 13c at an incident angle θ2 ′. The incident angle θ2 ′ is smaller than the critical angle. Therefore, the P-polarized light incident on the side surface 13c from the surface 13b is refracted at an angle φ1 'and reaches the output surface 10a.

The incident angle (90 ° -φ1 ') of the P-polarized light incident on the exit surface 10a is larger than the critical angle. Therefore, the P-polarized light is reflected by the emission surface 10 a and propagates through the light guide 10.

As described above, in the anisotropic refraction unit 13, the P-polarized light that satisfies the light guide condition of entering from the surface 13a, reflected by the surface 13b, and emitted from the side surface 13c is reflected by the emission surface 11a. And propagates in the light guide 10.

As described above, according to the polarization light guide plate of the present embodiment, the first and second polarized lights (S-polarized light and P-polarized light) satisfying the emission condition of the anisotropic refracting unit 13 are emitted from the emission surface 10a. Emitted. One of the first and second polarized light emitted from the emission surface 10 a is polarized and converted by the half-wave plate 11. As a result, one of the first and second polarized light is emitted from the polarization light guide plate, and the spread of the emission angle is controlled within a range that the angle β can take. 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 output angle to obtain.

More specifically, when the angle φ0 is 48.1 ° and the angle φ1 is 52.0 ° in the S-polarized light emission condition shown in FIG. 3, the emission angle β is 67.3 °. is there. 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 emission surface 10a is 48.1 ° or less, the emission 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 emission angle of the outgoing light of the polarizing light guide plate of the present embodiment.

In the examples shown in FIGS. 3 to 5, the magnitude relationship between the refractive indexes of S-polarized light and P-polarized light and the region where the half-wave plate 11 is formed can be changed as appropriate.

In the polarization light guide plate of the present embodiment, in order for only one of the first and second polarized light to be emitted as the emitted light, the first polarized light on the emission surface 10a of the light guide 10 is used. The first region from which the light is emitted and the second region from which the second polarized light is emitted need to be completely separated.

Hereinafter, the size and interval of the anisotropic refracting portion 13 capable of separating the region where the first and second polarized lights are emitted from the emission surface 10a will be described.

FIG. 6 is a diagram for explaining the size conditions (thickness and width) of the anisotropic refracting portion 13 and is cut along a plane perpendicular to the first end face of the light guide 10 and the exit face 10a. FIG. In FIG. 6, the arrow indicated by a broken line is S-polarized light, and the arrow indicated by a solid line is P-polarized light.

The width of the anisotropic refracting portion 13 (the length of the surfaces 13a and 13b) is B, the thickness of the anisotropic refracting portion 13 (the length of the side surfaces 13c and 13d) is H, and the thickness of the light guide 10 is as follows. Is D.

The maximum angle of the P-polarized light incident from the surface 13a and emitted from the side surface 13c with the perpendicular of the side surface 13c is φ1max, and the maximum angle φ1max is given to the P-polarized light incident on the surface 13a. An angle formed with the surface 13a is set to φ0max.

The minimum angle of the S-polarized light incident from the side surface 13d and emitted from the surface 13a with the surface 13a is φ1min, and the side surface 13d of the S-polarized light incident on the side surface 13d is given the minimum angle φ1min. The angle formed by the perpendicular to is φ0 min. Also, let X be the shortest distance from the exit point of the S-polarized light emitted at the minimum angle φ1 min on the surface 13a to the end of the surface 13a on the side surface 13c side.

By forming the anisotropic refracting portion 13 so as to satisfy the following formulas (1) to (4), a region where the first and second polarized lights are emitted from the exit surface 10a (the exit region of S-polarized light and P-polarized light emission area) can be separated.

FIG. 7 is a diagram for explaining the interval between the anisotropic refracting portions, and is a schematic diagram of a cross section cut along a plane perpendicular to the first end face of the light guide 10 and the emission face 10a. In FIG. 7, the arrow indicated by a broken line is S-polarized light, and the arrow indicated by a solid line is P-polarized light.

The interval between two adjacent anisotropic refracting portions 13A and 13B is P. The anisotropic refracting portion 13 </ b> A is disposed on the first end surface (end surface on the side where the light source is provided) side of the light guide 10.

The maximum angle formed by the surface 13a of the S-polarized light that is reflected by the reflective layer 12, is incident from the side surface 13d of the anisotropic refracting portion 13B, and is emitted from the surface 13a of the anisotropic refracting portion 13B is φ1max. To do.

The minimum angle formed by the reflection layer 12 of the P-polarized light that is incident from the surface 13a of the anisotropic refraction unit 13A, is emitted from the side surface 13c of the anisotropic refraction unit 13A, and is reflected by the reflection layer 12 is determined. φ1 min.

The shortest distance from the point through which the P-polarized light from the reflective layer 12 giving the minimum angle φ1 min passes on the plane including the surface 13a of the anisotropic refracting portion 13B to the end of the surface 13a (side surface 13d side). Y.

By forming the anisotropic refracting portions 13A and 13B so as to satisfy the following expressions (5) to (6), a region where the first and second polarized lights are emitted from the emission surface 10a (emission of S-polarized light) Region and the exit region of P-polarized light) can be separated.

Further, in the polarization light guide plate of the present embodiment, the distance between the anisotropic refracting portions 13 is narrowed so that the light is reflected by the reflective layer 12 and enters from the side surface 13d of the anisotropic refracting portion 13 and exits from the surface 13a. The first polarized light and the second polarized light that is incident from the surface 13a of the anisotropic refracting portion 13 and is emitted from the side surface 13c are not emitted from the emission surface 10a, but are guided through the light guide 10. It can also be configured to shine.

Hereinafter, the interval between the anisotropic refracting portions 13 for realizing the above-described light guide will be described.

FIG. 8 is a diagram for explaining the interval between the anisotropic refracting portions, and is a schematic diagram of a cross section cut along a plane perpendicular to the first end face of the light guide 10 and the emission face 10a. In FIG. 8, the arrow indicated by a broken line is S-polarized light, and the arrow indicated by a solid line is P-polarized light.

The interval between two adjacent anisotropic refracting portions 13A and 13B is P. The anisotropic refracting portion 13 </ b> A is disposed on the first end surface (end surface on the side where the light source is provided) side of the light guide 10. The width (length of the surfaces 13a and 13b) of each of the anisotropic refracting portions 13A and 13B is B, and the thickness (the length of the side surfaces 13c and 13d) is H. Let D be the thickness of the light guide 10.

The maximum angle of the S-polarized light incident on the reflective layer 12 without passing through the anisotropic refracting portion 13A and the reflective layer 12 is φ0max. In the anisotropic refracting portion 13B, the maximum angle of the S-polarized light incident from the side surface 13d and emitted from the surface 13a with the surface 13a is φ1max. In the anisotropic refracting portion 13A, the minimum angle of the angle formed by the perpendicular of the side surface 13c of the P-polarized light incident from the surface 13a, reflected by the surface 13b (interface with the reflective layer 12), and emitted from the side surface 13c. Is φ1 min.

By setting the interval P between the anisotropic refracting portions 13A and 13B so as to satisfy the following expressions (7) to (8), the light is reflected by the reflective layer 12 and is incident from the side surface 13d of the anisotropic refracting portion 13B. The S-polarized light emitted from the surface 13a and the P-polarized light incident from the surface 13a of the anisotropic refracting portion 13A, reflected by the surface 13b, and emitted from the side surface 13c can be guided.

Example 1
FIG. 9 is a schematic diagram for explaining the configuration of the polarizing light guide plate according to the first embodiment of the present invention.

In FIG. 9, the arrow indicated by a broken line is S-polarized light, and the arrow indicated by a solid line is P-polarized light. The width of the anisotropic refracting portion 13 is B, and the thickness is H. Let D be the thickness of the light guide 10. The width of the half-wave plate 11 is b. P-polarized light from the anisotropic refracting portion 13 that enters the half-wave plate 11 directly or through the reflective layer 12 enters the P-polarized light that enters from the surface on the exit surface 10a side and exits from the side surface. Let L be the shortest distance between the plane including the emitted side surface and the end of the half-wave plate 11. Let P be the distance between the anisotropic refracting portions 13.

The interval P between the anisotropic refracting portions 13 satisfies the conditions of the above-described formulas (1) to (6). The refractive index n0 of the light guide 10 is 1.50, and the refractive indexes n1 and n2 of the anisotropic refracting portion 13 are 1.45 and 1.55, respectively. The thickness D of the light guide 10 is 1 mm. The anisotropic refractive portion 13 has a width B of 300 μm and a thickness H of 100 μm. The spacing P between the anisotropic refracting portions 13 is 300 μm. The width b of the half-wave plate 11 is 285 μm. The shortest distance L is 701 μm.

In the above conditions, when the angle φ0 is 48.1 ° and the angle φ1 is 52.0 °, 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 the light incident on the light guide 10 from the light source with respect to the plane parallel to the output surface 10a is 48.1 ° or less, the angular spread of the output angle of the output light of the polarizing light guide plate is 22.7 °. Can be about.

(Example 2)
FIG. 10 is a schematic diagram for explaining a configuration of a polarizing light guide plate according to the second embodiment of the present invention.

In FIG. 10, an arrow indicated by a broken line is S-polarized light, and an arrow indicated by a solid line is P-polarized light. The width of the anisotropic refracting portion 13 is B, and the thickness is H. Let D be the thickness of the light guide 10. The width of the half-wave plate 11 is b. P-polarized light from the anisotropic refracting portion 13 that enters the half-wave plate 11 directly or through the reflective layer 12 enters the P-polarized light that enters from the surface on the exit surface 10a side and exits from the side surface. Let L be the shortest distance between the plane including the emitted side surface and the end of the half-wave plate 11. Let P be the distance between the anisotropic refracting portions 13. The interval P between the anisotropic refracting portions 13 satisfies the conditions of the expressions (7) to (8) described above.

The refractive index n0 of the light guide 10 is 1.50, and the refractive indexes n1 and n2 of the anisotropic refracting portion 13 are 1.45 and 1.55, respectively. The thickness D of the light guide 10 is 1 mm. The anisotropic refractive portion 13 has a width B of 300 μm and a thickness H of 100 μm. The spacing P between the anisotropic refracting portions 13 is 80 μm. The width b of the half-wave plate 11 is 196 μm. The shortest distance L is 701 μm.

In the above conditions, when the angle φ0 is 48.1 ° and the angle φ1 is 52.0 °, 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 the light incident on the light guide 10 from the light source with respect to the plane parallel to the output surface 10a is 48.1 ° or less, the angular spread of the output angle of the output light of the polarizing light guide plate is 22.7 °. Can be about.

(Example 3)
The polarizing light guide plate of the third embodiment of the present invention is also configured as shown in FIG.

In the polarizing light guide plate of this example, the refractive index n0 of the light guide 10 is 1.50, and the refractive indexes n1 and n2 of the anisotropic refracting portion 13 are 1.45 and 1.55, respectively. The light guide 10 has a thickness D of 500 μm. The anisotropic refracting portion 13 has a width B of 260 μm and a thickness H of 100 μm. The spacing P between the anisotropic refracting portions 13 is 80 μm. The width b of the half-wave plate 11 is 50 μm. The shortest distance L is 310 μm.

Also in the above conditions, when the angle φ0 is 48.1 ° and the angle φ1 is 52.0 °, 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 °. Also in this case, the angular spread of the outgoing angle of the outgoing light from the polarizing light guide plate can be set to about 22.7 °.

According to the polarization light guide plate of the present embodiment described above, it is possible to keep the spread of the emission angle of light emitted from the polarization light guide plate within a light usable range based on etendue restrictions.

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

Furthermore, according to the polarizing light guide plate of the present embodiment, the following operational effects can be obtained.

Generally, in a light guide plate used in an illuminating device, angle conversion means is provided in order to effectively use incident light having a certain degree of emission angle distribution from a light source. Examples of the angle conversion means include a method of making the light guide plate a wedge shape, a method of providing a prism portion in the light guide plate, and the like. By providing such an angle conversion means, the light guide angle of the light incident on the light guide plate (more specifically, the angle formed with the surface on the exit side of the incident light) gradually increases in the light guide process. Thus, the light satisfying the emission condition can be increased.

Since the light guide plate used in the projector illumination device is small, for example, if the wedge angle of the wedge-shaped structure (angle formed by the reflecting surface and the exit surface) is small, the incident light reaches the surface facing the entrance surface. By this time, a sufficient change in the light guide angle cannot be obtained, and the effect of increasing the amount of light by the wedge-shaped structure is halved. For this reason, the wedge-shaped structure has a wedge angle that is somewhat large.

In the light guide plate described in Patent Document 1 described above, it is desirable to apply the angle conversion means in order to effectively use incident light. In this case, the angle conversion means is realized by, for example, a configuration in which the thickness of the first layer is gradually reduced as the distance from the incident surface increases.

In the light guide plate described in Patent Document 1, only the S-polarized light that satisfies the angle condition of entering the prism surface of the second layer at a predetermined incident angle is emitted from the light guide plate, and the P-polarized light is Even when such an angle condition is satisfied, light is guided between the third layer and the reflection plate without being emitted from the light guide plate.

The P-polarized light that satisfies the angle condition and is reflected by the prism surface of the second layer passes through the first layer and the polarization conversion plate and is reflected in the direction of the first layer by the reflecting plate. At this time, the P-polarized light is converted into S-polarized light by the polarization conversion plate, and the light guide angle is changed by the wedge-shaped structure. In this case, if the wedge angle is small to some extent, the S-polarized light reflected by the reflecting plate is emitted from the exit surface of the light guide plate in order to satisfy the angle condition.

However, in order to apply to a projector, it is necessary to increase the wedge angle to some extent. In this case, since the S-polarized light reflected by the reflecting plate as described above does not satisfy the angle condition, the light is guided between the third layer and the reflecting plate without being emitted from the light guiding plate. For this reason, the effect of increasing the amount of light by the wedge-shaped structure is halved.

Thus, in the light guide plate described in Patent Document 1, when applied to a projector, it is difficult to realize a projector with high brightness because the effect of increasing the amount of light by the angle conversion means cannot be obtained sufficiently. is there.

On the other hand, according to the polarizing light guide plate of the present embodiment, the light satisfying the angle condition (emission condition) is emitted from the emission surface 10a of the light guide 10 regardless of the polarization state. Further, since the light guide angle of the incident light is changed by passing through the anisotropic refracting portion 13, it is not necessary to use an angle conversion means such as a wedge structure. Therefore, according to the polarizing light guide plate of the present embodiment, it is possible to realize a projector having a large amount of emitted light and a high brightness as compared with the light guide plate described in Patent Document 1.

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 anisotropic refracting portion 13 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 treatment 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 half-wave plate is attached to a predetermined region on 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)
In the polarization light guide plate of the first embodiment described above, the outgoing light has an inclination with respect to the normal of the outgoing surface 10a. Here, a mode capable of emitting light in a direction perpendicular to the emission surface 10a will be described.

FIG. 11 is a cross-sectional view showing a configuration of a polarizing light guide plate according to the second embodiment of the present invention.

As shown in FIG. 11, the polarizing light guide plate of this embodiment is obtained by adding a prism sheet 15 to the polarizing light guide plate of the first embodiment. The configuration other than the prism sheet 15 is the same as that of the polarizing light guide plate of the first embodiment.

The plurality of apex angles of the prism sheet 15 are provided so as to face the light exit surface 10 a of the light guide 10. FIG. 12 shows an enlarged view in which a part of the prism sheet 15 is enlarged.

As shown in FIG. 12, the prism sheet 15 is formed by two-dimensionally arranging prism surfaces 15a having a triangular cross-sectional shape. The apex angle of the prism surface 15a is determined based on the angle of light emitted from the emission surface 10a and the half-wave plate 11 (for example, the emission angle β shown in FIG. 3). For example, when the emission angle β is larger than 67 ° and smaller than 90 °, assuming that the refractive index of the prism sheet 15 is 1.50, the apex angle of the prism surface 15a is about 70 °.

The prism sheet 15 having the 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 triangular shape of the prism surface 15a and the emission surface 10a, so that 55 °. It arrange | positions on the output surface 10a. According to this arrangement, it is possible to obtain outgoing light with an angular spread of ± 12 ° with respect to a direction perpendicular to the outgoing surface 10a.

(Other embodiments)
In any one of the first and second embodiments described above, the half-wave plate 11 is a first quarter-wave plate, and a second quarter-wave plate is interposed between the first quarter-wave plates. May be provided. The first and second quarter-wave plates are alternately and periodically arranged in a fixed direction (the direction in which the anisotropic refracting portions 13 are arranged). The optical axis of the first quarter-wave plate is orthogonal to the optical axis of the second quarter-wave plate.

According to the polarization light guide plate of the other embodiment, for example, among the S-polarized light and the P-polarized light emitted from the emission surface 10a, the S-polarized light passes through the first quarter-wave plate, and the P-polarized light. Light passes through the second quarter-wave plate. Then, circularly polarized light in the same rotational direction (clockwise or counterclockwise circularly polarized light) is emitted from each of the first and second quarter wavelength plates.

By providing a third quarter-wave plate in the optical path of circularly polarized light emitted from the polarizing light guide plate of this other embodiment, it is possible to obtain light of one of P-polarized light and S-polarized light. it can.

The polarizing light guide plate of the other embodiment also satisfies the conditions for the emission condition, the light guide condition, the size of the anisotropic refracting portion 13 (thickness and width), and the interval described in the first embodiment. .

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

FIG. 13 shows an example of a cross-sectional structure of an illuminating device provided with the polarizing light guide plate of the present invention.

The illumination device shown in FIG. 13 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, 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, and is provided so as to face the end face 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.

The light (unpolarized 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 body 10 from the light source 20 is reflected by the exit surface 10a and the reflective layer 12, and in the light guide body 10 toward the end surface 10c facing the end surface 10b. Propagate toward. In this propagation process, a part of the light enters the anisotropic refracting portion 13.

In the anisotropic refracting unit 13, the first and second polarized light satisfying the emission condition are emitted from the emission surface 10a. In the emission surface 10, the region where the first polarized light is emitted is different from the region where the second polarized light is emitted. The half-wave plate 11 is provided in a region where the first polarized light is emitted, and the first polarized light emitted from the emission surface 10 a is converted into the second polarized light by the half-wave plate 11. Converted. In FIG. 13, the half-wave plate 11 is provided in a region where S-polarized light is emitted, and the S-polarized light emitted from the emission surface 10 a is converted into P-polarized light by the half-wave plate 11. Is converted to

According to the present illuminating device, the angular spread (outgoing angle) of the outgoing light by the anisotropic refracting unit 13 can be kept within the usable range of light based on etendue restrictions.

In addition, in this illuminating device, although the polarization light guide plate of 1st Embodiment is used, it may replace with this and the polarization light guide plate of 2nd Embodiment or the polarization light guide plate of other embodiment may be used. .

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.

(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. 14 is a schematic diagram showing a configuration of a projection display device using an illumination device including the polarization light guide plate of the present invention. Referring to FIG. 14, the projection display device includes illumination devices 300 to 302, liquid crystal elements 303 to 305 as display elements, a cross dichroic mirror 306, and a projection optical system 307.

All of the lighting devices 300 to 302 are constituted by the lighting devices described above. 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.

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.

The 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 type 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 projection display device described above.

The present invention has been described above with reference to the embodiments, but 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 priority based on Japanese Patent Application No. 2010-080792 filed on Mar. 31, 2010, the entire disclosure of which is incorporated herein.

Claims (12)

1. A light guide including opposing surfaces, and one of these surfaces being an exit surface;
   A reflective layer provided on the other surface of the opposing surface of the light guide;
   Phase difference means provided on the exit surface of the light guide;
   A plurality of anisotropic refracting portions periodically formed in a certain direction along the other surface in the light guide;
   Each of the plurality of anisotropic refracting portions has a refractive index with respect to the first polarized light that is smaller than a refractive index of the light guide and has a polarization state different from that of the first polarized light. The refractive index is configured to be larger than the refractive index of the light guide,
   The phase difference unit changes the phase of at least one of the first and second polarized lights emitted from the emission surface, and emits circularly polarized light having the same rotation direction or linearly polarized light having the same polarization direction. , Polarized light guide plate.
2. 2. The polarizing light guide plate according to claim 1, wherein the phase difference means has a plurality of half-wave plates periodically formed in the fixed direction.
3. Each of the plurality of anisotropic refracting portions has a rectangular parallelepiped shape, and is incident from a first surface located on the emission surface side of the light guide and is adjacent to the first surface. The polarizing light guide plate according to claim 2, wherein the first polarized light emitted from the surface is formed to pass through any of the plurality of half-wave plates.
4. Each of the plurality of anisotropic refracting portions is incident from a third surface facing the second surface, and the second polarized light emitted from the first surface is the plurality of the plurality of anisotropic surfaces. The polarizing light guide plate according to claim 3, wherein the polarizing light guide plate is formed so as to pass through a region where the half-wave plate is not formed.
5. The phase difference means has a plurality of first quarter-wave plates and a plurality of second quarter-wave plates formed alternately in the fixed direction, and the first quarter-wave plates. The polarizing light guide plate according to claim 1, wherein an optical axis of the plate is orthogonal to an optical axis of the second quarter-wave plate.
6. Each of the plurality of anisotropic refracting portions has a rectangular parallelepiped shape, and is incident from a first surface located on the emission surface side of the light guide and is adjacent to the first surface. The polarizing light guide plate according to claim 5, wherein the first polarized light emitted from the surface is formed so as to pass through any of the plurality of first quarter-wave plates.
7. Each of the plurality of anisotropic refracting portions is incident from a third surface facing the second surface, and the second polarized light emitted from the first surface is converted into the plurality of second The polarizing light guide plate according to claim 6, wherein the polarizing light guide plate is formed so as to pass through any one of the quarter-wave plates.
8. The length of each of the plurality of anisotropic refracting portions in the predetermined direction is B, the height in the direction perpendicular to the emission surface is H, and the distance between the opposing surfaces of the light guide is D. age,
   The refractive index of the light guide is n0, and the refractive indexes of the plurality of anisotropic refracting portions with respect to the first and second polarized lights are n1 and n2, respectively.
   The maximum angle of the first polarized light incident from the first surface and emitted from the second surface with the perpendicular of the second surface is φ1max, and the maximum angle is given. The angle between the first polarized light incident on the first surface and the first surface is φ0max,
   The minimum angle of the second polarized light incident from the third surface and emitted from the first surface with the first surface is φ1 min, and the third angle is given. The angle between the second polarized light incident on the surface and the perpendicular of the third surface is φ0 min,
   When the shortest distance from the exit point of the second polarized light emitted at the minimum angle on the first surface to the end on the second surface side of the first surface is X,
   

   

   The polarizing light guide plate according to claim 4 or 7, which satisfies the following condition.
9. 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 8, wherein the prism sheet is disposed so as to face the emission surface of the light guide.
10. The polarizing light guide plate according to any one of claims 1 to 9,
    And at least one light source for supplying light to an end of the polarizing light guide plate.
11. A lighting device according to claim 10;
    A display element irradiated with light emitted from the illumination device;
    A projection optical system that projects an image formed by the display element.
12. A lighting device of each color of red, green, and blue, comprising the lighting device according to claim 10;
    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