JPH1039302A - Surface illumination system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illumination system which has high efficiency and high luminance, less consumes electric power and features high mass productivity. SOLUTION: Plural pieces of grooves 6 having a triangular shape in section are formed on the rear surface of a parallel flat planar light transmission body 1. A wire-shaped light source 4 is arranged in parallel with these grooves 6 on the one flank of the light transmission body 1 and a reflector 5 is so disposed as to cover the wire-shaped light source 4. The angle ϕ1 of the slope on the wire-shaped light source 4 side of the grooves 6 is set like the equation, where the refractive index of the light transmission body 1 is defined as (n) and the central angle of a radiation luminance distribution as α. ϕ1 =53 deg.-sin<-1> (1/n)sin α}A light diffusion plate 2 is arranged atop the light transmission body 1 and a reflection plate 3 is arranged to cover the rear surface and the other flank of the light transmission body 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar illumination system used as a backlight for a liquid crystal display or the like.

[0002]

2. Description of the Related Art In recent years, liquid crystal displays have been widely used as display devices for personal computers and portable terminals. The planar illumination system as the backlight is required to have high luminance and low power consumption.

Hereinafter, an example of a conventional planar illumination system will be described.
This will be described with reference to FIG. 34 (see JP-A-5-127159). FIG. 34 is a sectional view showing a planar illumination system according to the related art. As shown in FIG. 34, the conventional planar illumination system includes:
A parallel plate-shaped light guide 131, and a linear light source 13 provided near the side surface of the light guide 131 and parallel to the side surface of the light guide 131.
4, a reflecting plate 135 provided so as to cover the linear light source 134, a light diffusing substance 136 formed on the back surface (lower surface) of the light guide 131, and a back surface (lower surface) of the light guide 131. ), A light diffusion sheet 132 provided on the surface (upper surface) of the light guide 131, and a prism sheet 13 provided immediately above the light diffusion sheet 132.
7.

In this conventional planar illumination system, light from a linear light source 134 is made incident on a side surface of a light guide 131 and light propagating in the light guide 131 by total reflection is transmitted to the light guide 1.
The light is diffused by the light diffusion material 136 formed on the back surface of the base 31. This breaks the conditions for total reflection of light,
Light is emitted to the outside of the light guide 131. The light emitted from the light guide 131 is reflected by the reflection sheet 133 provided on the back surface of the light guide 131, and exits from the surface of the light guide 131. Since light is emitted obliquely from the surface of the light guide 131, the light is directed in the front direction by the refraction effect of the prism sheet 137 provided on the light diffusion sheet 132. In this case, since the light diffusion sheet 132 is provided on the surface of the light guide 131, the pattern of the light diffusion material 136 formed on the back surface of the light guide 131 can be seen from the front side of the light guide 131. There is no.

[0005]

However, in the above-mentioned conventional planar illumination system, since multiple reflection occurs between the prism sheet 137 and the reflection sheet 133, the light diffusion material 136 and the light diffusion sheet 132 are not reflected. And reflection sheet 13
3, there is a problem that the light absorption is increased and the light efficiency as a planar illumination system is reduced. Further, since a large number of sheets are used (reflection sheet 133, light diffusion sheet 13
2, the prism sheet 137), and the alignment of the sheets is misaligned, and the display quality is deteriorated due to mixing of dust between the sheets.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the prior art, and has as its object to provide a high-efficiency, high-luminance, low-power-consumption, and excellent mass-productivity planar illumination system. Aim.

[0007]

To achieve the above object, a first configuration of a planar illumination system according to the present invention comprises a light guide and a light source disposed on a side surface of the light guide. A planar illumination system configured to emit light incident on the light guide from the light source from an upper surface of the light guide, wherein a plurality of grooves are spaced apart on a lower surface of the light guide. And at least a surface of the groove on the light source side is inclined. According to the first configuration of the planar illumination system, the light can be emitted from the upper surface of the light guide by two total reflections at the flat portion and the groove inclined portion on the lower surface of the light guide. The sheet and the light diffusing material on the lower surface of the light guide become unnecessary. For this reason, light absorption by the prism sheet and the light diffusing material is eliminated, and light efficiency is improved, so that high luminance and low power consumption can be achieved. Further, the number of sheets can be reduced, and the step of forming the light diffusing material on the lower surface of the light guide can be omitted, so that the assembling property and mass productivity are improved.

Further, in the first configuration of the planar illumination system according to the present invention, it is preferable that a cross section of the light guide is wedge-shaped. According to this preferred example, the weight can be reduced. Further, light reflected on the side of the light guide opposite to the light source does not return to the light source again, so that light can be efficiently extracted from the light guide.

In the first configuration of the planar illumination system according to the present invention, it is preferable that the groove width is smaller than the groove interval. According to this preferred example, the light propagating in the light guide is totally reflected at a portion of the light guide where the groove is not formed, and is totally reflected at the inclined surface of the groove, so that only the light guide is used. Since light can be emitted in a direction substantially perpendicular to the upper surface of the light guide, a prism sheet is not required. As a result, it is possible to prevent a decrease in the amount of light due to multiple reflections in the prism sheet. Also, it is not necessary to apply a light diffusing substance to the lower surface of the light guide to extract light from the light guide, and light absorption by the light diffusing substance does not occur, so that a high-luminance planar illumination system is realized. Can be.

Further, in the first configuration of the planar illumination system according to the present invention, it is preferable that the cross-sectional shape of the groove is trapezoidal or triangular. In the first configuration of the planar illumination system of the present invention, when the refractive index of the light guide is n and the central angle of the radiance distribution is α, the inclination angle of the light source side surface of the groove is as follows. It is preferably given by (Equation 2).

[0011]

(Equation 2)

According to this preferred example, the center of the radiance distribution can be directed in any direction α. Further, in the first configuration of the planar illumination system of the present invention, each groove is
It is preferable that it is composed of a plurality of adjacent groove groups. According to this preferred example, it is possible to further increase the luminance.

In the first configuration of the planar illumination system according to the present invention, the lower surface of the light guide has a stepped shape,
Preferably, at least one groove is formed for each step.

Further, in the first configuration of the planar illumination system according to the present invention, it is preferable that at least the inclined surface on the light source side of the groove is a curved surface. According to this preferred example, the radiance distribution of the light emitted from the light guide can be broadened.
It can correspond to a liquid crystal display having a wide viewing angle.

Further, in the first configuration of the planar illumination system according to the present invention, it is preferable that at least the inclined surface on the light source side of the groove is a rough surface. According to this preferred example, since the reflected light can be diffused to broaden the radiance distribution of the light emitted from the light guide, it is possible to cope with a liquid crystal display having a wide viewing angle.

Further, in the first configuration of the planar illumination system according to the present invention, a polarizer is provided above the light guide, and a polarization conversion plate for rotating a polarization direction is provided below the light guide. Is preferred. According to this preferred example, it is possible to prevent light absorption by the incident-side polarizer of the liquid crystal display.
Light efficiency can be improved up to twice. As a result, it is possible to significantly increase luminance and reduce power consumption. In this case, the cross-sectional shape is triangular and the apex angle is approximately 9
A polarization conversion plate having a 0 ° groove is used, and the polarization conversion plate is oriented such that the direction of the groove is approximately 45 ° with respect to the transmission axis of the polarizer.
It is preferable to arrange them at an angle of °. According to this preferred example, the polarization direction of the light incident on the polarization conversion plate can be rotated.

Further, in the first configuration of the planar illumination system according to the present invention, a polarizer is provided above the light guide, and a phase difference of a quarter wavelength is provided below the light guide. Preferably, a plate is provided, and the retardation plate is disposed such that its optical axis direction forms an angle of approximately 45 ° with the transmission axis of the polarizer. According to this preferred example, the polarization direction of the light incident on the retardation plate can be rotated to prevent light absorption by the polarizer on the incident side of the liquid crystal display. As a result, the light efficiency can be improved by a factor of up to two times, so that a significant increase in luminance and low power consumption can be achieved.

In the first configuration of the spread illuminating system according to the present invention, it is preferable that a light diffusing plate is provided above the light guide and a reflector is provided below the light guide. According to this preferred example, the light emitted from the lower surface of the light guide can be reflected by the reflection plate and re-entered into the light guide, and the light emitted from the upper surface of the light guide can be reflected by the light diffusion plate. Diffusion can prevent bright lines due to the grooves.

A second configuration of the spread illuminating system according to the present invention includes a light guide, and a light source disposed on a side surface of the light guide, and the light enters the light guide from the light source. A planar illumination system configured to emit light from the upper surface of the light guide, wherein a plurality of linear protrusions are formed at intervals on the lower surface of the light guide, and the linear protrusions At least the surface opposite to the light source is inclined. According to the second configuration of the planar illumination system, light can be emitted from the upper surface of the light guide by total reflection at the inclined portion of the linear projection on the lower surface of the light guide. The light diffusing material on the lower surface of the light guide becomes unnecessary. For this reason, light absorption by the prism sheet and the light diffusing material is eliminated, and light efficiency is improved, so that high luminance and low power consumption can be achieved. Further, the number of sheets can be reduced, and the step of forming the light diffusing material on the lower surface of the light guide can be omitted, so that the assembling property and mass productivity are improved.

In the second configuration of the planar illumination system according to the present invention, it is preferable that the light guide has a wedge-shaped cross section. In the second configuration of the planar illumination system of the present invention, it is preferable that the lower surface of the light guide has a stepped shape, and a linear projection is formed at each step.

In the second configuration of the planar illumination system according to the present invention, a polarizer is provided above the light guide, and a polarization conversion plate for rotating the polarization direction is provided below the light guide. Is preferred. Further, in this case, a cross-sectional shape is triangular, and a polarization conversion plate having a groove with an apex angle of approximately 90 ° is used, and the polarization conversion plate is oriented with respect to the transmission axis of the polarizer. Preferably, they are arranged at an angle of approximately 45 °.

Further, in the second configuration of the planar illumination system according to the present invention, a polarizer is provided above the light guide, and a phase difference of a quarter wavelength is provided below the light guide. Preferably, a plate is provided, and the retardation plate is disposed such that its optical axis direction forms an angle of approximately 45 ° with the transmission axis of the polarizer.

In the second structure of the planar illumination system according to the present invention, it is preferable that a light diffusing plate is provided above the light guide, and a reflecting plate is provided below the light guide.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically with reference to embodiments. <First Embodiment> FIG. 1 is a sectional view showing a spread illuminating system according to a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a light guide, and the light guide 1 is formed of quartz, glass, a transparent resin (for example, an acrylic resin, polycarbonate), or the like. The upper surface and the lower surface of the light guide 1 are substantially parallel, and the shape of the light guide 1 is substantially rectangular when viewed from the upper surface side. Further, the side surface and the upper and lower surfaces of the light guide 1 form an angle of about 90 °. A plurality of grooves 6 are formed on the lower surface of the light guide 1. Reference numeral 2 denotes a light diffusion plate, and the light diffusion plate 2 is disposed above the upper surface of the light guide 1. The light diffusing plate 2 is formed by dispersing a material having a different refractive index inside a sheet such as a transparent resin, dispersing a transparent spherical material on a transparent sheet, or forming irregularities on the surface of the transparent sheet. It is constituted by doing. Reference numeral 3 denotes a reflection plate, and the reflection plate 3 is disposed so as to cover the lower surface of the light guide 1 and the side surface opposite to the side of the linear light source 4 described later. The reflection plate 3 may, for example, densely disperse bubbles of several μm to several tens μm inside a transparent resin sheet,
It is constituted by depositing a material having high reflectance such as silver or aluminum on a resin sheet, a metal plate or the like. Thereby, the reflectance of the reflection plate 3 is high at least on the surface facing the light guide 1. Reference numeral 4 denotes a linear light source. The linear light source 4 is disposed near one side surface of the light guide 1.
As the linear light source 4, for example, a fluorescent lamp such as a hot cathode tube or a cold cathode tube, a linearly arranged light emitting diode, an incandescent lamp, or a linearly formed organic light emitting material is used. Reference numeral 5 denotes a reflector, which is arranged so as to cover the linear light source 4. Reflector 5
Is configured such that its inner surface has a high reflectance and a low diffusivity. The reflector 5 having such characteristics can be obtained, for example, by depositing a material having high reflectance such as silver or aluminum on a resin sheet and bonding the sheet to a thin metal plate or a resin sheet.

FIG. 2 shows a cross-sectional shape of the reflector according to the present embodiment. In FIG. 2, 7 and 8 are reflectors 5
And an elliptical cross section (hereinafter referred to as “elliptical portion 7” and “elliptical portion 8”). One of the focal points of the elliptical portion 7 is the center point O of the linear light source 4, and the other focal point is a point P located between the linear light source 4 and the upper surface of the reflector 5.
It is. Similarly, one of the focal points of the elliptical portion 8 is the center point O of the linear light source 4, and the other focal point is a point Q located between the linear light source 4 and the lower surface of the reflector 5. Oval part 7,
It is desirable that the elliptical radius of 8 is small. When the linear light source 4 is a fluorescent lamp, the gap between the linear light source 4 and the reflector 5 is
Preferably, it is filled with a transparent material having a refractive index close to the refractive index of glass 1.5.

It is desirable that the thickness of the side surface of the light guide 1 on the side of the linear light source 4 and the height of the reflector 5 be the same. The size (diameter) of the linear light source 4 is 80 times the height of the reflector 5.
% Or less, and more preferably 70% or less of the height of the reflector 5. Thereby, a gap between the linear light source 4 and the reflector 5 is secured, and the linear light source 4
This is because the rear emission light can be efficiently guided to the light guide 1.

FIG. 3 shows a cross-sectional shape (a portion A in FIG. 1) of the light guide in the planar illumination system in FIG. In FIG. 3, the linear light source 4 is located on the left side. As shown in FIG. 3, the lower surface of the light guide 1 includes a flat portion 11 substantially parallel to the upper surface 15 of the light guide 1 and a plurality of grooves 6 having a trapezoidal cross section. The groove 6 has a slope 12 on the side of the linear light source 4, a bottom surface 14 substantially parallel to the upper surface 15 of the light guide 1, and a slope 13 on the opposite side to the linear light source 4. In order to make the center of the radiance distribution of the light emitted from the light guide 1 substantially perpendicular to the upper surface 15 of the light guide 1, the angle φ ₁ of the slope 12 of the groove 6 on the side of the linear light source 4 should be set. The angle may be set to approximately 53 °. Also,
The center of the radiance distribution, in order to fit within ± 10 ° with respect to the normal direction of the top surface 15 of the light guide 1, the angle phi ₁ of the linear light source 4 side inclined surface 12 of about 46 ° <phi ₁ may be set in the range of about 60 °. Further, in order to direct the center of the radiance distribution in an arbitrary direction α in the plane of FIG. 3 by setting the central angle of the radiance distribution to α, the angle φ ₁ of the inclined surface 12 on the side of the linear light source 4 is represented by the following ( What is necessary is just to set like Formula 3).

[0028]

(Equation 3)

The slope 1 of the groove 6 on the side opposite to the linear light source 4.
The radiance from the light guide 1 increases as the angle φ _{2 of} 3 becomes closer to 90 °. The slope 13 is an incident portion of the light guide 1. Therefore, the slope 13 is the same as the incident portion (side surface) from the linear light source 4 and has an angle φ _{2 with} respect to the upper surface 15 and the lower surface.
Is set to about 90 °, the incident light from the inclined surface 13 can be totally reflected in the light guide 1, and as a result, the light emitted from the light guide 1 in the oblique direction can be prevented. Thus, the luminance in the front direction (upper direction 15) can be increased. Practically, the slope 1 opposite to the linear light source 4
The angle φ ₂ of 3 is preferably in the range of 60 ° <φ ₂ <90 °. Considering that the light guide 1 is manufactured by press molding, injection molding, roller molding, or the like, it is desirable to provide a draft angle of about 3 °, so that the angle φ ₂ of the slope 13 on the opposite side to the linear light source 4 is About 87 ° or 87 °
It is desirable to set smaller.

FIGS. 4A and 4B show the arrangement (groove distribution) of grooves formed in the light guide in the planar illumination system of the present embodiment. The direction of the groove 6 is substantially parallel to the longitudinal direction of the linear light source 4. The pitch p of the groove 6 is constant, and the width H of the groove 6 decreases as the distance from the linear light source 4 decreases, and the width H of the groove 6 increases as the distance from the linear light source 4 increases.

The distance from the side surface of the light guide 1 on the side of the linear light source 4 is x, the area ratio of the groove 6 at the distance x is S (the area of the flat portion 11 near the distance x is s ₁ , the area of the groove 6 is the case of a s _2, if _{S = s 2 / (s 1} + s 2)), the length of the light guide body 1 is L, holds the relationship of the following equation (4).

[0032]

(Equation 4)

In this case, S is desirably in the range of 0 <S <1/2, and β is desirably in the range of 1.0 <β <4.0. In order to make the luminance distribution of the light emitted from the light guide 1 uniform, α should be about 0.04 and β should be about 3.0.

The finer the pitch p of the groove 6, the less noticeable the groove line, and the better the visibility of the display. Also,
When the pitch p of the grooves 6 is small, a light diffusing plate 2 having a small diffusivity can be used, so that the luminance in the front direction (the upper surface direction of the light guide 1) can be increased. As a result of conducting a visual experiment by changing the pitch p, it was found that the groove streaks became inconspicuous by setting the pitch p to 1 mm or less. Preferably, the pitch p is set to 0.
It is better to set it to 5 mm or less. Further, if the pitch p is set to one third or less of the pixel pitch of the liquid crystal display, the light diffusion plate 2 becomes unnecessary.

Next, the operation of the planar illumination system configured as described above will be described. First, as shown in FIG. 2, the light emitted from the linear light source 4 directly enters the light guide 1 like a light ray 10 or is reflected by a reflector 5,
The light enters the light guide 1. Most of the backward emission light (light emitted to the side opposite to the light guide 1) from the linear light source 4 enters the elliptical portions 7 and 8 of the reflector 5. One of the focal points of the elliptical portion 7 (8) is the center point O of the linear light source 4, and the other focal point is a point P (point) located between the linear light source 4 and the upper surface (lower surface) of the reflector 5. Q). In the case of an elliptical mirror such as the elliptical portions 7 and 8, light emitted from one focal point has a characteristic of being condensed on the other focal point. Therefore, most of the backward emission light emitted from the linear light source 4 is: The light enters the light guide 1 through the elliptical portions 7 and 8. In general, when the linear light source 4 is a fluorescent lamp, about half of the re-incident light to the fluorescent lamp is absorbed by the fluorescent material of the fluorescent lamp. Can be reduced. Further, as the elliptical radius of the elliptical portions 7 and 8 is smaller, the ratio of the reflected light at the elliptical portions 7 and 8 is increased, so that the light efficiency is improved. When the linear light source 4 is a fluorescent lamp, the light emitting portion of the fluorescent lamp, that is, the phosphor is formed inside the fluorescent tube, so that the gap between the linear light source 4 and the reflector 5 is made of the material of the fluorescent tube. By filling with a transparent material having a refractive index close to the refractive index, the diameter of the fluorescent tube can be substantially reduced. As a result, the gap between the linear light source 4 and the reflector 5 can be increased, so that the light efficiency can be improved.

Next, the propagation of light in the light guide 1 will be described with reference to FIG. When the refractive index of the light guide 1 is n, the light incident on the light guide 1 has a radiation distribution of ± sin ^-1 (1 / n) according to Snell's law. Most of the materials of the light guide 1 have a refractive index n of 1.42 or more, so that the radiation distribution is in a range of ± 44.77 °. By the way, since the upper surface and the lower surface of the light guide 1 are substantially parallel and the angle between the upper surface and the lower surface and the side surface which is the incident surface to the light guide 1 is approximately 90 °, the side surface of the light guide 1 is Is incident on the upper or lower surface of the light guide 1, the incident angle θ
Is the minimum value of (90 ° −44.77 °) = 45.23 °.
Becomes When the refractive index n of the light guide 1 is 1.42 or more, the total reflection angle is 44.77 ° or less, so that light incident from the side surface of the light guide 1 It will be totally reflected. Of the light propagating in the light guide 1, the light totally reflected by the flat portion 11 other than the vicinity of the groove 6, such as the light ray 16, propagates while repeating the total reflection in the light guide 1. Similarly, light totally reflected on the bottom surface 14 of the groove 6, such as the light ray 17, propagates in the light guide 1 while repeating total reflection. Light totally reflected by the flat portion 11 near the groove 6 and totally reflected by the inclined surface 12 of the groove 6 on the side of the linear light source 4 like the light beam 18 changes the optical path greatly, and reaches the upper surface 15 of the light guide 1. Incident. At this time, since the optical path is greatly changed by the two total reflections, the incident angle becomes equal to or smaller than the total reflection angle, and most of the light exits the light guide 1. Most of the light directly incident on the inclined surface 12 of the groove 6 on the side of the linear light source 4 such as the light beam 19,
The light passes through the slope 12, is refracted by the slopes 12 and 13, returns to the light guide 1 again, and propagates in the light guide 1 while repeating total reflection. A part of the light transmitted through the slope 12 is reflected by the reflector 3 (FIG. 1) and returns to the inside of the light guide 1. As described above, of the light propagating in the light guide 1, the flat portion 1
The light totally reflected twice by the light guide 1 and the slope 12 of the groove 6 on the side of the linear light source 4 is emitted from the upper surface 15 of the light guide 1 to the outside.

FIG. 5 shows the result of obtaining the radiance distribution of the light emitted from the light guide 1 by ray tracing. The horizontal axis in FIG. 5 represents the radiance distribution in the paper of FIG. 1, and the negative direction is toward the linear light source 4. The vertical axis in FIG. 5 represents the normalized luminance. Figure 5 is a radiance distribution when set angle phi ₁ to 53 ° of the linear light source 4 side inclined surface 12 of the groove 6, the angle phi ₂ of the linear light source 4 and the opposite side of the slope 13 to 87 ° . In this case, it can be seen that the center of the radiance distribution is substantially perpendicular to the upper surface 15 of the light guide 1. The light path of the light emitted from the upper surface 15 of the light guide 1 is changed by the total reflection on the inclined surface 12 of the groove 6 on the side of the linear light source 4. Therefore, by changing the angle φ _{1 of the} inclined surface 12, the central angle of the radiance distribution is changed. α can be controlled.

Since the following relationship (Equation 5) is established according to Snell's law, α and φ ₁ are represented by the following (Equation 6) and (Equation 7).
It is written as follows.

[0039]

(Equation 5)

[0040]

(Equation 6)

[0041]

(Equation 7)

For example, when the light guide 1 is made of acrylic material and its refractive index n is 1.49, the groove 6 is required to keep the central angle α of the radiance distribution within the range of ± 10 °.
The angle φ ₁ of the slope 12 on the side of the linear light source 4 is 46 ° <φ ₁ <
What is necessary is just to set in the range of 60 degrees.

The closer to the linear light source 4, the greater the amount of light in the light guide 1, and the farther from the linear light source 4, the smaller the amount of light in the light guide 1. Therefore, as shown in FIGS. 4A and 4B, the width H of the groove 6 with respect to the flat portion 11 decreases as the distance from the linear light source 4 decreases, and the groove 6 with respect to the flat portion 11 decreases as the distance from the linear light source 4 increases. By increasing the width H, it is possible to obtain a planar illumination system with a small variation in the amount of light emitted from the upper surface 15 of the light guide 1.

Light emitted from the upper surface 15 of the light guide 1 enters the light diffusion plate 2 (FIG. 1) and is diffused. By this diffusion, it is possible to prevent a bright line due to the groove 6 formed on the lower surface of the light guide 1.

As described above, according to the present embodiment, the linear light source 4 is disposed on the side surface of the parallel-plate light guide 1, and a plurality of trapezoidal cross-sections are formed on the lower surface of the light guide 1. The groove 6 is formed substantially parallel to the linear light source 4, and the light totally reflected twice by the flat portion 11 on the lower surface of the light guide 1 and the inclined surface 12 of the groove 6 on the linear light source 4 side is formed by the light guide 1. Since the light is emitted from the upper surface 15, the prism sheet and the light diffusing material on the lower surface of the light guide 1 are not required. Accordingly, light absorption by the prism sheet and the light diffusing material is eliminated, and light efficiency is improved, so that high luminance and low power consumption can be achieved. Further, the number of sheets can be reduced, and the step of forming the light diffusing material on the lower surface of the light guide 1 can be omitted, so that the assemblability and mass productivity are improved.

In the present embodiment, the sectional shape of the groove 6 is trapezoidal, but it is not necessarily limited to this configuration. As shown in FIG. 6, the cross-sectional shape of the groove 6 may be triangular.

<Second Embodiment> FIG. 7 shows a second embodiment of the present invention.
It is sectional drawing which shows the light guide of the planar illumination system in embodiment. The planar illumination system in the present embodiment has basically the same configuration as that of the first embodiment, but the light guide 1
Are different from each other in the shape of the groove formed on the lower surface. Note that FIG.
, The linear light source 4 is located on the left side.

As shown in FIG. 7, the lower surface of the light guide 1 is
A flat portion 11 substantially parallel to the upper surface 15 of the light body 1;
From the slope 20 on the side 4 and the slope 21 on the side opposite to the linear light source 4
A third groove having a triangular cross-sectional shape and slopes 22, 2
3 and a second groove similarly formed by the slopes 24 and 25.
And one groove. The first to third grooves
They are located adjacent to each other. Slope 2 on the linear light source 4 side of the groove
Angle φ of 0, 22, 24 ₁Are almost the same, and
Of the slopes 21, 23, 25 on the opposite side of the linear light source 4 of FIG.
_TwoIs almost the same. That is, the first to third grooves
Is almost similar. Radiance of light emitted from light guide 1
The center of the distribution is substantially perpendicular to the upper surface 15 of the light guide 1
To do this, the slopes 20, 22 of the groove 6 on the side of the linear light source 4,
24 angle φ₁May be set to about 50 °. Also, release
Center the radiance distribution in the direction normal to the upper surface 15 of the light guide 1
To keep it within ± 10 °, the angle φ₁And about
43 ° <φ₁It may be set in a range of about 57 °. Further
, The central angle of the radiance distribution is α, and
To direct the center of the radiance distribution in the direction α of
φ₁May be set as in the following (Equation 8).

[0049]

(Equation 8)

The slope 2 of the groove 6 on the side opposite to the linear light source 4.
The closer the angle φ ₂ of 1, 23, 25 is to 90 °, the higher the radiance from the light guide 1. In practice, the angle phi ₂ is desirably in the range of _{60 ° <φ 2 <90 °} . Considering that the light guide 1 is manufactured by press molding, injection molding, roller molding, or the like, it is desirable to provide a draft angle of about 3 °, so the angle φ ₂ is about 87 °, or
It is desirable that the angle is set smaller than 87 °.

The width of the first, second and third grooves is defined as h₁,
h_Two, H_ThreeAnd h₁> H_Two> H _ThreeMeet the relationship
Is desirable. That is, the groove width becomes closer to the linear light source 4.
Is desirably smaller. For example, the groove of the first groove
When the ratio of the groove width of the n-th groove to the width is hn
Where hn = γ^n-1And it is sufficient. In this case, γ is 0.5
Preferably in the range of ~ 1.0, more preferably about 0.8
Desirably degrees.

Next, the operation of the planar illumination system configured as described above will be described. Of the light propagating in the light guide 1, the light incident on the flat portion 11 other than near the groove is
The light propagates while turning back the total reflection in the light guide 1. Light incident on the flat portion 11 near the third groove formed by the slopes 20 and 21 is totally reflected by the flat portion 11 and further reflected by the slope 20, so that the optical path is largely changed and the upper surface 15 of the light guide 1 is changed. Incident on. Most of the light incident on the upper surface 15 in this way has an incident angle equal to or less than the total reflection angle on the upper surface 15,
Light is emitted from the upper surface 15 of the light guide 1 to the outside. Also, slope 2
Most of the light that has directly entered 0 passes through the slope 20, a part of the light enters the light guide 1 again from the opposite slope 21, and the remaining part is reflected by the reflector 3 (FIG. 1). The light is reflected and enters the light guide 1 again. Part of the light that has reentered the light guide 1 from the slope 21 is totally reflected by the slope 22 of the second groove on the side of the linear light source 4, passes through the upper surface 15, and exits the light guide 1. . The remaining part of the light that has reentered the light guide 1 from the slope 21 passes through the slope 22, reenters the light guide 1 from the opposite slope 23, and the linear light source of the first groove is formed. The light is emitted from the upper surface 15 of the light guide 1 by total reflection on the slope 24 on the fourth side. Slopes 22, 24 of the second groove and the first groove on the side of linear light source 4
The same applies to light that is directly incident on.

FIG. 8 shows the result of obtaining the radiance distribution of the light emitted from the light guide 1 by ray tracing. The horizontal axis in FIG. 8 represents the radiance distribution in the paper plane of FIG. 7, and the negative direction is the linear light source 4 side. The vertical axis of FIG. 8 represents the normalized luminance. In FIG. 8, 27 (broken line) indicates
5 is a radiance distribution in the first embodiment,
6 (solid line) indicates that the angle φ ₁ in the present embodiment is 50
°, a radiance distribution when setting the angle phi ₂ to 87 °. In this case, it can be seen that the center of the radiance distribution is substantially perpendicular to the upper surface 15 of the light guide 1.
Also, the center luminance of the planar illumination system in the present embodiment is:
By arranging three grooves per pitch, the first
This is about 40% higher than that of the embodiment. Light emitted from the light guide 1, the optical path is changed by total reflection at inclined surfaces 20, 22, 24 of the linear light source 4 side of the groove, the center of the radiance distribution by varying the angle phi ₁ of the slope The angle α can be controlled.

According to Snell's law, the following relationship (Equation 9) holds, so that α and φ ₁ are represented by (Equation 10) and (Equation 1).
It is written as 1).

[0055]

(Equation 9)

[0056]

(Equation 10)

[0057]

[Equation 11]

For example, when the light guide 1 is made of acrylic material and has a refractive index n of 1.49, the groove angle must be adjusted to keep the central angle α of the radiance distribution within the range of ± 10 °. The angle φ ₁ of the slopes 20, 22, 24 on the side of the light source 4
It suffices to set the angle in the range of ° <φ ₁ <57 °.

As described above, according to the present embodiment, the linear light source 4 is arranged on the side surface of the parallel-plate light guide 1, and the triangular groove is formed on the lower surface of the light guide 1. 3 per pitch
Since the light guides are formed adjacent to each other and light is emitted from the upper surface 15 of the light guide 1 by total reflection in each groove, the same effect as in the first embodiment can be obtained. Further, as described above, it is possible to further increase the luminance.

In the present embodiment, three grooves are formed per pitch. However, the present invention is not limited to this configuration, and two or four or more grooves are formed per pitch. It may be formed. The greater the number of grooves per pitch, the higher the luminance. However, considering the ease of processing, the number of grooves is desirably about three per pitch.

Further, in the first and second embodiments, the shape of the light guide 1 is a parallel plate, but it is not necessarily limited to this configuration. In order to reduce the weight or to efficiently extract the light from the light guide 1, the shape of the light guide 1 may be a straight or curved wedge having a thinner side on the side opposite to the linear light source 4. Good.

<Third Embodiment> FIG. 9 shows a third embodiment of the present invention.
FIG. 10 is a cross-sectional view showing a planar illumination system according to the embodiment.
FIG. 10 is an enlarged sectional view of a portion A in FIG. 9. The planar illumination system in the present embodiment has basically the same configuration as that of the second embodiment, but differs in the shape of the lower surface of the light guide.
As shown in FIGS. 9 and 10, the lower surface of the light guide 28 has a step shape, and a groove 29 is formed adjacent to a step portion of the step. That is, one stepped portion on the lower surface of the light guide 28 is a third groove having a triangular cross-sectional shape including the flat portion 11, the slope 20 on the side of the linear light source 4, and the slope 21 on the side opposite to the linear light source 4. , A second groove also including the slopes 22 and 23, a first groove also including the slopes 24 and 25, and a slope 30 of the step portion. The flat portion 11 is substantially parallel to the upper surface 15 of the light guide 28, and the first to third grooves are arranged adjacent to each other. Slopes 20, 22, 2
The angles φ ₁ of the angles 4 and 30 are almost the same, and the slope 2
The angles φ _{2 of 1,} 23 and 25 are almost the same. That is, the first to third grooves are substantially similar in shape. The center of the radiance distribution of the light emitted from the light guide 28 is
To substantially perpendicular to the upper surface 15 of the angle phi ₁
May be set to about 50 °. Further, the center of the radiance distribution is set to ± 10 with respect to the normal direction of the upper surface 15 of the light guide 28.
° to fit within the angle phi _1, about 43 ° <phi ₁
It may be set in a range of about 57 °. Further, to set the center angle of the radiance distribution to α and direct the center of the radiance distribution in an arbitrary direction α in the plane of FIG. 9, the angle φ ₁ is set as shown in the following (Equation 12). Good.

[0063]

(Equation 12)

Further, as the angle φ ₂ is closer to 90 °, the radiance from the light guide 28 becomes higher. Practically, the angle φ
₂ is preferably in the range of 60 ° <φ ₂ <90 °.
Considering that the light guide 28 is manufactured by press molding, injection molding, roller molding, etc., it is desirable to provide a draft angle of about 3 °, so the angle φ ₂ is about 87 ° or smaller than 87 °. It is desirable to be set.

The width of the first, second and third grooves is defined as h₁,
h_Two, H_ThreeAnd h₁> H_Two> H _ThreeMeet the relationship
Is desirable. That is, the groove width becomes closer to the linear light source 4.
Is desirably smaller. For example, the groove of the first groove
When the ratio of the width of the n-th groove to the width is hn,
hn = γ^n-1And it is sufficient. In this case, γ is 0.5 to
It is desirable to be in the range of 1.0, more preferably about 0.8
It is desirable that

The closer the light guide 28 is to the linear light source 4, the thicker the light guide 28 becomes.
Is thicker and thinner as the distance from the linear light source 4 increases. Stairs
Is a constant value, and the envelope of the light guide 28 is a flat surface.
Thus, the light guide 28 has a wedge shape. Opposite side to linear light source 4
Thickness t of the side surface of the light guide 28 _TwoIs smaller, the light guide 2
The radiance from 8 is higher. Light guide 2 on the side of linear light source 4
8 thickness t₁, Then t_Two/ T₁Is less than 0.5
It is desirable to have. When the length of the light guide 28 is L,
And the wedge angle of the light guide 28 is tan^-1｛(T _Two−
t₁) / L}.

In the planar illumination system configured as described above, similarly to the case of the second embodiment, the light guide 2
The light that has entered the inside 8 is inclined by the slopes 20 and 2 on the side of the linear light source 4 in the groove.
The light exits from the upper surface 15 of the light guide 28 by total reflection on the slopes 30 of the steps 2 and 24 and the step. Further, since the light guide 28 becomes thinner as the distance from the linear light source 4 increases, the linear light source 4
Is reflected on the side of the light guide 28 opposite to the linear light source 4 and does not return to the linear light source 4 again. As a result, light efficiency is increased.

FIG. 11 shows the result of obtaining the radiance distribution of the light emitted from the light guide 28 by ray tracing. FIG.
The horizontal axis indicates the radiance distribution in the plane of FIG. 9, and the negative direction is the linear light source 4 side. The vertical axis in FIG.
It represents the normalized luminance. In FIG. 11, 32
(Dashed line) is the radiance distribution in the second embodiment, 31 (solid line), the angle phi ₁ of the present embodiment 50 °, the angle phi ₂ to 87 °, the wedge of the light guide body 28 It is a radiance distribution when the angle is set to 1.83 °.
In this case, it can be seen that the center of the radiance distribution is substantially perpendicular to the upper surface 15 of the light guide 28. Further, the center luminance of the planar illumination system in the present embodiment is 1
By arranging three grooves in the pitch and setting the wedge angle of the light guide 28 to 1.83 °, it is improved by about 20% as compared with the case of the second embodiment. Light guide 28
The light emitted from the optical path changes its optical path due to the total reflection on the slopes 20, 22, 24, and 30, so that the angle φ _{1 of} these slopes
Can be controlled to control the central angle α of the radiance distribution.

Since the following relationship (Equation 13) holds according to Snell's law, α and φ ₁ are expressed as (Equation 14) and (Equation 15) below.

[0070]

(Equation 13)

[0071]

[Equation 14]

[0072]

(Equation 15)

For example, the light guide 28 is made of acrylic material.
Radiance when the refractive index n is 1.49
In order to keep the central angle α of the distribution within the range of ± 10 °, the angle
Degree φ ₁Is 43 ° <φ₁Set it to <57 °
No.

As described above, according to the present embodiment, the linear light source 4 is disposed on the side surface of the light guide 28, and the thickness of the light guide 28 is reduced according to the distance from the linear light source 4. For this purpose, the lower surface is formed in a stepped shape, and three grooves each having a triangular cross section are formed adjacent to each other on the lower surface of the light guide 28 so as to be adjacent to each other. By emitting light, the same effect as in the second embodiment can be obtained. Further, as described above, it is possible to further increase the luminance.

In the present embodiment, three grooves are formed per pitch. However, the present invention is not limited to this configuration, and one, two, four or more grooves are formed per pitch. A groove may be formed. The greater the number of grooves per pitch, the higher the luminance. However, considering the ease of processing, the number of grooves is desirably about three per pitch.

Further, in the present embodiment, the step Δt of the stairs is a constant value. However, the present invention is not necessarily limited to this configuration, and the value of the step Δt is changed according to the distance from the linear light source 4. You may. For example, slope 24,
The value of the step Δt may be determined in accordance with the depth of the first groove including 25. In this case, the cross-sectional shape of the envelope on the lower surface of the light guide 28 is a curve connecting the lower end of the side surface on the side of the linear light source 4 to the end on the upper surface opposite to the linear light source 4.

In the present embodiment, a groove is formed for each step. However, the present invention is not necessarily limited to this configuration, and a step portion having no groove may be provided.

<Fourth Embodiment> FIG. 12 is a sectional view showing a planar illumination system according to a fourth embodiment of the present invention.
FIG. 3 is an enlarged sectional view of a portion A in FIG. The planar illumination system in this embodiment has basically the same configuration as that of the third embodiment, except that the shape of the lower surface of the light guide and the reflection plate 3 are removed, and the light guide is replaced. The difference is that the back of the body is covered with a highly reflective material.

As shown in FIGS. 12 and 13, the light guide 33
Has a stepped shape, and a slope 35 on the linear light source 4 side and a slope 36 on the opposite side to the linear light source 4
A linear projection having a triangular cross section is formed. Here, the step difference Δt of the stairs is a constant value. Light guide 3
Assuming that the refractive index of 3 is n, the angle φ ₃ of the slope 35 on the side of the linear light source 4 is set so as to satisfy the following (Equation 16).

[0080]

(Equation 16)

The flat part 11 on the lower surface of the light guide 33 is substantially parallel to the upper surface 15 of the light guide 33. A reflection film 34 is formed on the lower surface of the light guide 33 by depositing a material having high reflectance, for example, silver, aluminum, or a dielectric multilayer film. Thereby, light is reflected on the flat portion 11 on the lower surface of the light guide 33 and the slopes 35 and 36.

Next, the operation of the planar illumination system configured as described above will be described. Of the light propagating inside the light guide 33, the light 38 incident on the flat portion 11 propagates while repeating total reflection in the light guide 33. Light 37 incident on the slope 36 on the opposite side of the linear projection 4 from the linear light source 4
Changes the light path by total reflection on the slope 36, and the light guide 3
3 is emitted to the outside from the upper surface 15. The light propagating in the light guide 33 has an incident angle on the upper surface 15 or the lower surface of the light guide 33 of {90 ° −sin ⁻¹ (1 / n)} at the maximum. On the other hand, since the angle φ ₃ of the slope 35 of the linear projection on the side of the linear light source 4 is less than or equal to {90 ° −sin ⁻¹ (1 / n)}, there is almost no incident light on the slope 35.

As described above, according to the present embodiment, the linear light source 4 is disposed on the side surface of the light guide 33, and the linear projection composed of the inclined surfaces 35 and 36 is provided on the lower surface of the light guide 33. Further, a reflection film 34 is formed on the lower surface of the light guide 33, and the light guide 3 is formed by total reflection of the linear projections on the slope 36 opposite to the linear light source 4.
By emitting light from the upper surface 15 of the third embodiment, the same effect as in the third embodiment can be obtained. Furthermore, since the number of sheets can be reduced by removing the reflection plate 3 (FIG. 9), assemblability and mass productivity are improved.

In this embodiment, the light guide 33 is used.
Is formed in a stepped shape, but is not necessarily limited to this configuration, and a step Δt = 0 may be set. <Fifth Embodiment> FIG. 14 is a sectional view showing a planar illumination system according to a fifth embodiment of the present invention. As shown in FIG. 14, the planar illumination system according to the present embodiment has basically the same configuration as that of the first embodiment, but each of the first illumination system is symmetrical with respect to the center axis. The difference is that the planar illumination system according to the embodiment is arranged, and the side opposite to the linear light source 4 is coupled at the center.

According to the above configuration, the same effect as that of the first embodiment can be obtained. Further, since the number of the linear light sources 4 is two, the luminance can be doubled. In this embodiment, the configuration of the groove formed on the lower surface of the light guide 1 is the same as the configuration of the groove in the first embodiment, but is not necessarily limited to this configuration. Not
The configuration of the groove in the second embodiment may be adopted.

<Sixth Embodiment> FIG. 15 is a sectional view showing a planar illumination system according to a sixth embodiment of the present invention. As shown in FIG. 15, the planar illumination system according to the present embodiment has basically the same configuration as the third embodiment, but the third illumination system is symmetrical with respect to the central axis. The difference is that the planar illumination system according to the embodiment is arranged, and the side opposite to the linear light source 4 is coupled at the center.

With the above configuration, the same effects as those of the third embodiment can be obtained. Further, since the number of linear light sources 4 is two, the luminance can be doubled. As shown in FIG. 16, the planar illumination systems according to the third embodiment are arranged symmetrically with respect to the central axis, and the envelopes on the lower surfaces of the two light guides 28 are flat. Alternatively, a configuration may be adopted in which the side surface opposite to the linear light source 4 is coupled at the center.

<Seventh Embodiment> FIG.
(B) is a planar illumination system according to the seventh embodiment of the present invention.
FIG. 6 is a diagram showing a groove distribution on the lower surface of the light guide of FIG. As shown in FIG.
As described above, the planar illumination system in the present embodiment is basically
The configuration is the same as that of the first embodiment, but the light guide 1
Are different from each other in the distribution of grooves formed on the lower surface. Groove 6
The direction is substantially parallel to the longitudinal direction of the linear light source 4,
The width H is constant, and the pitch p (p₁, P_Two, P _Three, P
_Four) Changes. The pitch p of the groove 6 becomes closer to the linear light source 4.
And the pitch of the groove 6 increases as the distance from the linear light source 4 increases.
Chip p becomes smaller.

The distance from the side surface of the light guide 1 on the side of the linear light source 4 is x, the area ratio of the groove at the distance x is S (the area of the flat portion 11 near the distance x is s ₁ , and the area of the groove 6 is If s ₂ , S = s ₂ / (s ₁ + s ₂ )), and if the length of the light guide 1 is L, as in the case of the first embodiment,
The following relationship (Equation 17) holds.

[0090]

[Equation 17]

In this case, S is desirably in the range of 0 <S <1/2, and β is desirably in the range of 1.0 <β <4.0. In order to make the luminance distribution of the light emitted from the light guide 1 uniform, α should be about 0.04 and β should be about 3.0.

According to the present embodiment, the same effects as those of the first embodiment can be obtained. <Eighth Embodiment> FIGS. 18A and 18B are views showing the groove distribution on the lower surface of a light guide of a planar illumination system according to an eighth embodiment of the present invention. As shown in FIGS. 18A and 18B, the planar illumination system according to the present embodiment has basically the same configuration as that of the first embodiment, but the lower surface of the light guide 1. Are different in the distribution of the grooves formed.

The direction of the groove 6 is substantially parallel to the longitudinal direction of the linear light source 4, and the width H and the pitch p of the groove 6 in the direction perpendicular to the longitudinal direction of the linear light source 4 are constant. Linear light source 4
The length of the groove 6 in the longitudinal direction becomes shorter as the distance from the linear light source 4 increases, and becomes longer as the distance from the linear light source 4 increases. The pitch q of the groove 6 in the longitudinal direction of the linear light source 4 is
It is desirable that the pitch is substantially equal to the pitch p of the groove 6 in a direction perpendicular to the longitudinal direction of the linear light source 4.

The distance from the side of the light guide 1 on the side of the linear light source 4 is x, the area ratio of the groove at the distance x is S (the area of the flat portion 11 near the distance x is s ₁ , and the area of the groove 6 is If s ₂ , S = s ₂ / (s ₁ + s ₂ )), and if the length of the light guide 1 is L, as in the case of the first embodiment,
The following relationship (Equation 18) holds.

[0095]

(Equation 18)

In this case, S is preferably in the range of 0 <S <1/2, and β is preferably in the range of 1.0 <β <4.0. In order to make the luminance distribution of the light emitted from the light guide 1 uniform, α should be about 0.04 and β should be about 3.0.

According to this embodiment, the same effects as those of the first embodiment can be obtained. <Ninth Embodiment> FIG. 19 is a sectional view showing a groove shape on the lower surface of a light guide of a planar illumination system according to a ninth embodiment of the present invention. The planar illumination system in the present embodiment has basically the same configuration as that of the first embodiment, but differs in the shape of the groove formed on the lower surface of the light guide 1. FIG.
As shown in FIGS. 9A and 9B, the radiance distribution of the light emitted from the light guide 1 can be broadened by making the slope 12 of the groove 6 on the side of the linear light source 4 curved. FIG.
As shown in (c), the inclined surface 12 of the groove 6 on the side of the linear light source 4 is roughened so that the reflected light is diffused and the light guide 1 is diffused.
The radiance distribution of the light emitted from the light source can be broadened.

With the above configuration, the same effect as that of the first embodiment can be obtained. Further, the groove slope 12 on the side of the linear light source 4 can be curved or the groove slope 12 can be roughened. In addition, the radiance distribution can be widened to support a liquid crystal display having a wide viewing angle.

In the first to ninth embodiments, the angle between the upper surface and the side surface of the light guide is set to 90 °, but the present invention is not necessarily limited to this configuration.
The upper surface of the light guide may be inclined within a range that satisfies the condition that light incident from the side surface of the light guide is totally reflected inside the light guide.
For example, the angle between the upper surface and the side surface of the light guide is 80 ° to 10 °.
The angle may be set to 0 °, or a curved surface may be provided on the side surface.

In the first to ninth embodiments, the distribution of the grooves formed on the lower surface of the light guide is given by an exponential function, but is given by a polynomial represented by the following (19). You may.

[0101]

[Equation 19]

In the first to ninth embodiments, the reflector 5 has a sectional shape having two elliptical portions. However, the present invention is not necessarily limited to this configuration. May be U-shaped or semicircular.

In the first to ninth embodiments, one linear light source 4 is used. However, as shown in FIG. Elliptical portions 7 and 8 may be provided for the linear light source 4 respectively. The same applies to a case where three or more linear light sources 4 are provided.

In the third and sixth embodiments, the groove on the lower surface of the light guide is formed adjacent to the step portion having the step shape. However, the present invention is not necessarily limited to this configuration. The groove on the lower surface of the light guide may be formed at any position.

The distribution of the grooves in the seventh and eighth embodiments may be applied to the second to sixth embodiments. Further, in the first to ninth embodiments, the first, fifth, and the fifth, the fifth, and the fifth embodiments can be performed within a range that satisfies the conditional expression of the groove area ratio S at a distance x from the side surface of the light guide body on the linear light source 4 side. The distribution of the grooves in the sixth embodiment may be combined.

The shape of the groove in the ninth embodiment may be applied to the second to eighth embodiments. <Tenth Embodiment> FIG. 21 is a sectional view showing a planar illumination system according to a tenth embodiment of the present invention, and FIG. 22 is a perspective view of a light guide.

In FIGS. 21 and 22, reference numeral 101 denotes a light guide, which is formed of quartz, glass, transparent resin (for example, acrylic resin, polycarbonate) or the like. Here, in order to simplify the description, the light guide 101
Are parallel plates, the angle between the side surface and the upper and lower surfaces of the light guide 101 is 90 °, and the refractive index n of the light guide 101 is 1.5. Reference numeral 104 denotes a linear light source. As the linear light source 104, a fluorescent light, an incandescent light, an arrangement of LEDs, or the like is used. The linear light source 104 is arranged substantially parallel to the side surface of the light guide 101. Reference numeral 105 denotes a reflector, which is disposed so as to cover the linear light source 104 (see FIG. 22). A material having high reflectivity such as silver or aluminum is deposited on a surface of the reflector 105 facing the linear light source 104, thereby realizing high reflectivity. Two recesses are formed in the rear end face of the reflector 105. The cross-sectional shape of the depression is preferably a shallow ellipse or a sector.

The linear light source 104 is provided on the lower surface of the light guide 101.
A plurality of grooves 106 are formed in parallel. That is,
The lower surface of the light guide 101 has a portion where the groove 106 is formed,
It is composed of a portion (flat portion) where the groove 106 is not formed. The pitch p of the groove 106 (FIG. 25) is constant, and the groove width is smaller than the pitch p. Here, in order to simplify the description, the cross-sectional shape of the groove 106 is an isosceles triangle, and the apex angle is β (see FIG. 25).

Near the upper surface of the light guide 101, the light guide 10
The light diffusion sheet 102 is disposed so as to cover the upper surface of the light diffusion sheet 1. In addition, a reflection sheet 103 is disposed near the lower surface of the light guide 101 so as to cover the lower surface of the light guide 101. A material having high reflectivity such as silver or aluminum is deposited on a surface of the reflective sheet 103 facing the groove 106 of the light guide 101, thereby realizing high reflectivity.

The operation of the planar illumination system configured as described above will be described below with reference to FIGS. 21, 23 to 25. FIG. 23 is a diagram of optical path tracing with a linear light source and a reflector, FIG. 24 is a diagram of optical path tracing in a light guide, and FIG. 25 is a diagram of optical path tracing in a groove formed in the light guide.

As shown in FIG. 23, the light emitted from the linear light source 104 directly enters the light guide 101 or is reflected by the reflector 105 and then enters the light guide 101.
By forming two depressions in the reflector 105,
The light reflected at the concave portion is reflected by the linear light source 104 and the reflector 10.
5 and enters the light guide 101. When light reenters the linear light source 104, light absorption occurs. However, by forming a depression in the reflector 5, light absorption in the linear light source 104 can be reduced.

Light that has entered the side surface of the light guide 101 at an angle η ₁ is refracted at an angle η ₂ when entering the light guide 101.
Since the following relationship (Equation 20) holds according to Snell's law, the refraction angle η ₂ is expressed as the following (Equation 21).

[0113]

(Equation 20)

[0114]

(Equation 21)

When the maximum value η _2max of the refraction angle η ₂ is obtained, the following _expression (22) is obtained.

[0116]

(Equation 22)

For example, if the refractive index n of the light guide 101 is 1.5
In this case, η _2max is 41.8 °. As shown in FIG. 24, of the light that has entered the light guide 101, the light guide 101
The incident angle η ₃ of the light incident on the flat portion other than the vicinity of the groove 106 on the lower surface of is expressed by the following (Equation 23).

[0118]

(Equation 23)

On the other hand, the total reflection angle at the boundary when traveling from a medium having a refractive index n (n> 1) into the air (refractive index 1) is calculated as sin ⁻¹ (1/1) using Snell's law. n). Light incident from the side surface of the light guide 101 is
In order to propagate while repeating total reflection in a flat portion other than the vicinity of the upper and lower surfaces of the groove 106, the angle η ₃ only needs to be larger than the total reflection angle sin ⁻¹ (1 / n). That is, the following relationship (Equation 24) may be satisfied.

[0120]

(Equation 24)

From the above (Equation 22) and (Equation 23), the angle η
Minimum eta _{3min 3} is as follows (Equation 25).

[0122]

(Equation 25)

Therefore, when the above (Equation 24) and (Equation 25) are used, refraction for propagating light while repeating total reflection in flat portions other than the vicinity of the groove 106 on the upper surface and the lower surface of the light guide 101 is used. The condition of the rate n is as follows (Equation 26).

[0124]

(Equation 26)

In the present embodiment, since the refractive index n of the light guide 101 is set to 1.5, this condition is satisfied.
In general, materials such as quartz, glass, acrylic resin, and polycarbonate have a refractive index of ^21/2 or more.
This condition is satisfied. Therefore, light incident on a flat portion other than near the groove 106 on the lower surface of the light guide 101 is
The light propagates while repeating total reflection within 1.

Next, FIG. 25 shows that light incident on the light guide 101 is emitted from the upper surface of the light guide 101 in a direction substantially perpendicular to the groove 106 formed on the lower surface of the light guide 101. It will be described using FIG.

In FIG. 25, the direction parallel to the upper surface of the light guide 101 is the x-axis direction, and the direction perpendicular to the upper surface of the light guide 101 is the y-axis direction. The angle between the direction of light propagating inside the light guide 101 and the x-axis is η ₂ .

From the condition of incidence on the light guide 101, the maximum value of η ₂ becomes sin as given by the above (Equation 22).
^-1 (1 / n). As shown in FIG. 25, a part of the light totally reflected at the portion (flat portion) where the groove 106 is not formed enters the slope of the groove 106. This light beam is defined as a.

The light ray a enters the portion (flat portion) where the groove 106 is not formed at an incident angle η ₃ . Since the refractive index n of the light guide body 101 satisfies the condition of the above (Equation 26), the light is totally reflected. Next, this light beam a is incident on the slope of the groove 106. Since the cross-sectional shape of the groove 106 is an isosceles triangle and the vertex angle is β, the slope γ of the slope is given by the following (Equation 27).

[0130]

[Equation 27]

The angle of incidence η ₄ on the slope of the groove 106 is shown in FIG.
It is given by the following (Equation 28).

[0132]

[Equation 28]

Here, the condition of total reflection on the slope of the groove 106 is obtained as shown in the following (Equation 29).

[0134]

(Equation 29)

The light rays totally reflected on the slope of the groove 106 enter the upper surface of the light guide 101. The incident angle η _{6 at} this time is
It is given by the following (Equation 30).

[0136]

[Equation 30]

The emission angle η ₇ from the light guide 101 is given by the following (Equation 31) according to Snell's law.

[0138]

(Equation 31)

(Equation 22), (Equation 28), (Equation 29)
Therefore, the range of η ₂ is given by the following (Equation 32).

[0140]

(Equation 32)

For example, if the apex angle β of the groove 106 is 60 ° and the refractive index n of the light guide 101 is 1.5, the above (Equation 32) is obtained.
Thus, 11.8 ° <η ₂ <41.8 °, and from the above (Equation 31), −27.9 ° <η ₇ <17.9 °.
Therefore, according to this configuration, when light propagating in the light guide 101 exits from the light guide 101, the center of the radiation distribution is located in a direction substantially perpendicular to the upper surface of the light guide 101.

If the vertex angle β of the groove 106 is slightly increased to 65 ° and the refractive index n of the light guide 101 is set to 1.5, 9.3 ° <η ₂ from the above (Equation 32). <41.8 °
From the above (Equation 31), −23.9 ° <η ₇ <2
5.7 °. Therefore, according to this configuration, the light guide 1
The symmetry of the radiation distribution from 01 is good.

If the refractive index n of the light guide 101 is increased to 1.6 and the apex angle β of the groove 106 is set to 70 °, then 3.7 ° <η ₂ < 38.7 °, and from the above (Equation 31), −26.7 ° <η ₇ <30.
9 °. Therefore, according to this configuration, the light guide 101
The angle of spread of the light emitted from the camera can be changed.

As described above, the refractive index n of the light guide 101,
By changing the apex angle β of the groove 106, the directivity and spread angle of the light emitted from the light guide 101 can be controlled. Light emitted from the upper surface of the light guide 101 is diffused by the light diffusion sheet 102 (FIG. 21), and has a predetermined viewing angle,
And a radiation distribution without unevenness is obtained.

Of the light propagating in the light guide 101, the light directly incident on the slope of the groove 106 returns to the light guide 1 again across the groove 106 or is reflected by the reflection sheet 103. Thereafter, the light returns to the inside of the light guide 101.

Further, by arranging the grooves 106 at regular intervals and changing the depth of the grooves 106, the amount of light emitted from the light guide 101 is adjusted, and the amount of light emitted from a location on the light guide 101 is adjusted. Variation can be suppressed. That is,
When the depth of the groove 106 is small, the area of the slope of the groove 106 is small, so that the amount of light totally reflected on the slope of the groove 106 is small, and the amount of light emitted from the light guide 101 is also small. Conversely, when the depth of the groove 106 is large, the area of the slope of the groove 106 becomes large, so that the amount of light totally reflected on the slope of the groove 106 increases, and the amount of light emitted from the light guide 101 also increases. Become. Therefore, inside the light guide 101, the amount of light increases as the distance from the linear light source 104 increases, and the amount of light decreases as the distance from the linear light source 104 increases.
, The depth of the groove 106 becomes shallower as the distance from the linear light source 104 increases, and the depth of the groove 106 gradually increases as the distance from the linear light source 104 increases.
1 can be constant irrespective of the location above.

If the ratio of the depth of the groove 106 to the distance between the grooves 106 is a predetermined value, the distance between the grooves 106 may not be equal. For example, the distance between the grooves 106 on the side of the linear light source 104 is increased, and
06 may be narrowed.

In the present embodiment, the parallel-plate light guide 101 is used, but the present invention is not necessarily limited to this configuration. In order to reduce the weight or to efficiently extract light from the light guide 101, the light guide 1
The shape of 01 may be a straight or curved wedge section in which the side opposite to the linear light source 104 is thinned. Further, the light guide 101 may have a hollow shape.

Further, in the present embodiment, the light guide 1
The angle formed between the upper and lower surfaces of the light guide 101 and the side surface is set to 90 °, but is not necessarily limited to this configuration.
If the condition for total internal reflection is satisfied, an angle other than 90 ° may be provided, or a curved surface may be provided on the side surface.

Further, in the present embodiment, the groove 106
Is a isosceles triangle, but is not necessarily limited to this configuration. When one linear light source 104 is arranged on one side surface of the light guide 101, the groove 1
06 may be an arbitrary triangle. Further, the tip of the groove 106 may be slightly rounded.

In order to widen the viewing angle, a part of the slope of the groove 106 may be roughened. Although one linear light source 104 is used in this embodiment, a plurality of linear light sources 104 are connected to the light guide 101 in order to achieve high luminance.
May be arranged on each side surface.

In the present embodiment, the light guide 1
The refractive index n of the light guide 10 is set to 1.5.
The refractive index n of 1 is not necessarily limited to this value, and may be a value of 1.41 or more.

In the present embodiment, the groove 106
Are formed in parallel with the linear light source 104, but are not necessarily limited to this configuration.
As shown in FIG. 6, a plurality of grooves 106 may be formed to cross. With such a configuration, moire fringes with the pixel array of the liquid crystal panel can be prevented.

<Eleventh Embodiment> FIG. 27 is a sectional view showing a planar illumination system according to an eleventh embodiment of the present invention.
FIG. 28 is a diagram of optical path tracking in the planar illumination system, and FIG.
FIG. 29A is a plan view of a polarization conversion plate, and FIG.
29A is a sectional view taken along the line AA, FIG. 29C is a sectional view taken along the line BB of FIG. 29A, FIG. 29D is a sectional view taken along the line CC of FIG. 29A, and FIG. It is explanatory drawing of conversion.

As shown in FIG. 27, the configurations of the light source 4, the reflector 5, and the light guide 28 are the same as those of the third embodiment, and the description is omitted. A light diffusion plate 42 is provided near the upper surface of the light guide 28. Thereby, the light emitted from the upper surface of the light guide 28 can be diffused while maintaining the polarization state. That is, when linearly polarized light enters the light diffusion plate 42, the polarization of the emitted diffused light is substantially linearly polarized, and the polarization direction is substantially parallel to the incident light. A polarizer 40 is provided near the upper surface of the light diffusion plate 42. The polarizer 40 transmits only polarized light in a specific direction, and reflects polarized light orthogonal to the polarization direction of transmitted light. The polarizer 40 is arranged so that its transmission axis is parallel to the transmission axis of the incident-side polarizer of the liquid crystal display. A polarization conversion plate 41 is provided near the lower surface of the light guide 28. When linearly polarized light having a specific polarization direction is incident, the polarization conversion plate 41 rotates the polarization direction by approximately 90 ° and emits light in a direction opposite to the incident direction.

The following describes the structure of the polarization conversion plate 41.
This will be described with reference to FIG. As shown in FIGS. 29A and 29D, a plurality of narrow slit-shaped grooves 41b are formed in the polarization conversion plate 41 along the longitudinal direction. As shown in FIGS. 29 (a), (b) and (c), the polarization conversion plate 41 has a V-shaped groove 41c at an angle of approximately 45 ° with the slit-shaped groove 41b so as to be orthogonal to each other. , 41
d is formed in plurality. V-grooves 41c, 41
The vertex angles δ ₁ and δ ₂ of d are each approximately 90 °. The depths of the slit-shaped groove 41b and the V-shaped grooves 41c and 41d are substantially the same. The polarization conversion plate 41 is arranged so that the groove forming portion is downward in FIG. Further, a reflection film 41a is formed in the groove forming portion of the polarization conversion plate 41 by evaporating a material having a high reflectance such as silver or aluminum.

Hereinafter, the operation of the planar illumination system configured as described above will be described with reference to FIGS. 28 and 30. As shown in FIG. 28, the light 4 propagating in the light guide 28
The light 3 is emitted from the upper surface of the light guide 28 by total reflection in the groove 29 formed on the lower surface of the light guide 28. In general, the light emitted from the linear light source 4 is randomly polarized light, so that the light emitted from the light guide 28 is also randomly polarized light. Light guide 28
Out of the light reaching the polarizer 40 after exiting from the upper surface, the polarized light 44 in the transmission axis direction of the polarizer 40 transmits through the polarizer 40,
Polarized light 45 orthogonal to polarized light 44 is reflected by polarizer 40. The polarized light 45 reflected by the polarizer 40 passes through the light guide 28 and reaches the polarization conversion plate 41.

Then, the light is reflected by the polarizer 40 and
The polarization direction of the light that has reached 1 is 90
The rotation will be described with reference to FIG. FIG. 30 shows three grooves 41 b, 41 c and 41 of the polarization conversion plate 41.
3 shows three surfaces formed by d. In FIG. 30, a light ray 47 is light incident on the polarization conversion plate 41, and is a linearly polarized light whose polarization direction is the x-axis direction. The light ray 47 is reflected on the surface 51 to become a light ray 48. The polarization direction of the light ray 48 is also parallel to the x-axis. Light ray 48 is reflected at surface 52 to become light ray 49. The polarization direction of the light beam 49 is parallel to the y-axis. Further, the light beam 49 is reflected by the surface 53 to become a light beam 50. The polarization direction of the light beam 50 is also parallel to the y-axis.
Therefore, the polarization direction of light beam 50 is 90
° is rotating. Here, the polarization direction of the light ray 47 is parallel to the x-axis, but the polarization direction of the light ray 50 is rotated by 90 ° with respect to the light ray 47 regardless of the polarization direction of the light ray 47 in any direction in the xy plane. Since the polarization direction is rotated by 90 ° by the polarization conversion plate 41, the polarization direction of the reflected light 46 on the polarization conversion plate 41 becomes parallel to the transmission axis direction of the polarizer 40, as shown in FIG. The reflected light 46 is the polarizer 4
Transmit 0.

As described above, according to the present embodiment, 3
By using the polarization conversion plate 41 that rotates the polarization direction by reflection on three surfaces formed by the three grooves 41b, 41c, and 41d, light absorption by the incident-side polarizer of the liquid crystal display can be prevented. Light efficiency can be improved up to twice. Therefore, it is possible to significantly increase luminance and reduce power consumption.

<Twelfth Embodiment> FIG. 31A is a partial perspective view showing a polarization converter of a planar illumination system according to a twelfth embodiment of the present invention, and FIG. FIG. 32 shows the relationship between the transmission axis direction and the groove direction of the polarization conversion plate.
(A), (b) is explanatory drawing of the polarization conversion in a polarization conversion plate. The planar illumination system according to the present embodiment has basically the same configuration as that of the eleventh embodiment, except for the structure of the polarization conversion plate.

As shown in FIG. 31A, the polarization conversion plate 5
In FIG. 9, a plurality of grooves 59a having a triangular cross section and an apex angle δ ₃ of about 90 ° are continuously formed. The reflection film 58 is formed on the groove forming portion of the polarization conversion plate 59 by depositing a material having high reflectance such as silver or aluminum. The polarization conversion plate 59 is arranged so that the groove forming portion faces down in the planar illumination system (see 41 in FIG. 28).
An angle δ ₄ between the groove direction of the polarization conversion plate 59 and the transmission axis direction of the polarizer 40 (see FIG. 27) is about 45 °. FIG.
As shown in (b), for example, if the transmission axis direction of the polarizer 40 is 54, the direction of the groove 59a of the polarization conversion plate 59 is
The direction is 57 or 56.

Next, the polarization direction is changed to 9 by the polarization conversion plate 59.
The rotation by 0 ° will be described with reference to FIG.
FIG. 32A shows an adjacent groove portion of the polarization conversion plate. FIG. 32 (b) shows D in FIG.
It is a figure when it sees from E and F direction. When viewed in the direction of the arrow D, the polarization direction of the light ray 60 incident on the slope of the groove 59a is:
It forms an angle of 45 ° with the direction of the groove 59a, that is, the x-axis direction. The ray 60 is reflected by the slope and is reflected by the ray 61
Becomes The polarization direction of the light ray 61 is x
At an angle of 45 ° to the x-axis in the z-plane. Also, when viewed in the view from the arrow F, the light beam 61 appears to be rotated by 90 ° because it is viewed from the side opposite to the view in the direction of arrow E. Further, the light ray 61 is reflected on the other slope to become a light ray 62. As viewed from the arrow D, the polarization direction of the light beam 62 is rotated by 90 ° with respect to the polarization direction of the light beam 60. Therefore, the polarization direction is changed by 90 ° by the polarization conversion plate 59.
Can be rotated.

As described above, according to the present embodiment, the polarization conversion plate 59 in which the triangular groove 59a having the apex angle δ ₃ of 90 ° is formed can be adjusted so that the direction of the groove 59a is in the transmission axis direction of the polarizer 40. By arranging them so as to form an angle of about 45 ° with respect to that, the polarization direction can be rotated by the polarization conversion plate 59, and the same effect as in the eleventh embodiment can be obtained.

<Thirteenth Embodiment> FIG. 33 (a) is a sectional view showing a planar illumination system according to a thirteenth embodiment of the present invention, and FIG. 33 (b) is a diagram showing a transmission axis direction and a position of a polarizer. It is a figure showing relation with the direction of an optical axis of a phase difference plate. The planar illumination system according to the present embodiment has basically the same configuration as that of the above-described eleventh embodiment, but instead of the polarization conversion plate 41,
The difference is that a phase difference plate 63 and a reflection plate 64 are used.

The retardation plate 63 is a plate having uniaxial birefringence, for example, quartz, calcite, or a transparent resin sheet that is stretched to have birefringence is used. The phase difference of the phase difference plate 63 is set so as to be shifted by a quarter wavelength with respect to the vertically incident light. It is desirable to use a material having a large wavelength dispersion as the material of the phase difference plate 63, so that the phase difference can be made constant within the wavelength range of the linear light source 4. The phase difference plate 63 is arranged such that its optical axis forms an angle of approximately 45 ° with the transmission axis of the polarizer 40. For example, 54 in FIG.
In this case, the optical axis of the phase difference plate 63 is set to the direction of the azimuth 65 or azimuth 66. Here, the direction 54 of the transmission axis of the polarizer 40 and the azimuth 65 or azimuth 6
Angle [delta] ₅ with 6 is 45 °.

A phase difference plate 63 having a phase difference of 波長 wavelength
When light whose polarization direction forms an angle of 45 ° with the optical axis of the phase difference plate 63 enters, the light emitted from the phase difference plate 63 becomes circularly polarized light. When this circularly polarized light is reflected by the reflecting plate 64 and enters the retardation plate 63 again, it returns to linearly polarized light. At this time, the polarization direction is shifted by 90 ° from the polarization direction of the linearly polarized light incident on the phase difference plate 63.

As described above, according to the present embodiment, the phase difference plate 63 having a quarter wavelength retardation is used, and the direction of the optical axis of the phase difference plate 63 is changed to the transmission axis of the polarizer 40. The same effect as in the eleventh embodiment can be obtained by arranging at an angle of approximately 45 ° with respect to the direction.

Although the eleventh, twelfth, and thirteenth embodiments are based on the configuration of the third embodiment, the present invention is not necessarily limited to this configuration. The configuration according to the first, second, or fourth to tenth embodiments may be used.

In the eleventh, twelfth, and thirteenth embodiments, the transmitted polarized light and the reflected polarized light at the polarizer 40 are linearly polarized light. However, the present invention is not limited to this configuration. It may be polarized light.

In the eleventh, twelfth and thirteenth embodiments, the linearly polarized light is converted to 9 by the polarization conversion plate.
Although it is rotated by 0 °, the same applies to elliptically polarized light.

[0171]

As described above, according to the first configuration of the planar illumination system of the present invention, the light guide is formed by the total reflection twice at the flat portion and the groove inclined portion on the lower surface of the light guide. Since light can be emitted from the upper surface of the light guide, the prism sheet and the light diffusing material on the lower surface of the light guide are not required. For this reason, light absorption by the prism sheet and the light diffusing material is eliminated, and light efficiency is improved, so that high luminance and low power consumption can be achieved.
Further, the number of sheets can be reduced, and the step of forming the light diffusing material on the lower surface of the light guide can be omitted, so that the assembling property and mass productivity are improved.

According to the second configuration of the planar illumination system of the present invention, light can be emitted from the upper surface of the light guide by total reflection at the inclined portion of the linear projection on the lower surface of the light guide. Therefore, the prism sheet and the light diffusing material on the lower surface of the light guide are not required. For this reason, light absorption by the prism sheet and the light diffusing material is eliminated, and light efficiency is improved, so that high luminance and low power consumption can be achieved. Further, the number of sheets can be reduced, and the step of forming the light diffusing material on the lower surface of the light guide can be omitted, so that the assembling property and mass productivity are improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a planar illumination system according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a shape of a reflector of the planar illumination system according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a shape (a portion A in FIG. 1) of a light guide of the planar illumination system according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a groove distribution on the lower surface of the light guide of the planar illumination system according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a result of obtaining a radiance distribution of light emitted from the light guide using the planar illumination system according to the first embodiment of the present invention.

FIG. 6 is a cross-sectional view showing another configuration example of the light guide of the planar illumination system according to the first embodiment of the present invention.

FIG. 7 is a sectional view showing a light guide of a planar illumination system according to a second embodiment of the present invention.

FIG. 8 is a diagram illustrating a result of obtaining a radiance distribution of light emitted from a light guide using a planar illumination system according to the second embodiment of the present invention.

FIG. 9 is a sectional view showing a planar illumination system according to a third embodiment of the present invention.

FIG. 10 is an enlarged sectional view of a portion A in FIG. 9;

FIG. 11 is a diagram showing a result of obtaining a radiance distribution of light emitted from a light guide using a planar illumination system according to a third embodiment of the present invention.

FIG. 12 is a sectional view showing a planar illumination system according to a fourth embodiment of the present invention.

FIG. 13 is an enlarged sectional view of a portion A in FIG. 12;

FIG. 14 is a sectional view showing a planar illumination system according to a fifth embodiment of the present invention.

FIG. 15 is a sectional view showing a planar illumination system according to a sixth embodiment of the present invention.

FIG. 16 is a sectional view showing another example of the planar illumination system according to the sixth embodiment of the present invention.

FIG. 17 is a diagram illustrating a groove distribution on a lower surface of a light guide of a planar illumination system according to a seventh embodiment of the present invention.

FIG. 18 is a diagram showing a groove distribution on a lower surface of a light guide of a planar illumination system according to an eighth embodiment of the present invention.

FIG. 19 is a sectional view showing a shape of a groove on a lower surface of a light guide of a planar illumination system according to a ninth embodiment of the present invention.

FIG. 20 is a cross-sectional view showing another configuration example of the light source and the reflector used in the embodiment of the present invention.

FIG. 21 is a sectional view showing a planar illumination system according to a tenth embodiment of the present invention.

FIG. 22 is a perspective view showing a light guide of a planar illumination system according to a tenth embodiment of the present invention.

FIG. 23 is a diagram illustrating optical path tracing with a linear light source and a reflector of a planar illumination system according to a tenth embodiment of the present invention.

FIG. 24 is a diagram of optical path tracking in a light guide of a planar illumination system according to a tenth embodiment of the present invention.

FIG. 25 is a diagram of optical path tracking in a groove formed in a light guide of a planar illumination system according to a tenth embodiment of the present invention.

FIG. 26 is a perspective view showing another configuration example of the light guide of the planar illumination system according to the tenth embodiment of the present invention.

FIG. 27 is a sectional view showing a planar illumination system according to an eleventh embodiment of the present invention.

FIG. 28 is a diagram illustrating optical path tracking of a planar illumination system according to an eleventh embodiment of the present invention.

FIG. 29A is a plan view showing a polarization converter of a planar illumination system according to an eleventh embodiment of the present invention, FIG. 29B is a cross-sectional view taken along line AA of FIG. 29A, and FIG. (a) is a BB cross-sectional view, and (d) is a CC cross-sectional view of (a).

FIG. 30 is an explanatory diagram of polarization conversion of a planar illumination system according to an eleventh embodiment of the present invention.

FIG. 31 (a) is a partial perspective view showing a polarization conversion plate of a planar illumination system according to a twelfth embodiment of the present invention, and FIG. 31 (b) is a planar illumination system according to the twelfth embodiment of the present invention. FIG. 4 is a diagram showing the relationship between the transmission axis direction of the polarizer and the groove direction of the polarization conversion plate.

FIG. 32 is an explanatory diagram of polarization conversion by a polarization conversion plate of a planar illumination system according to an eleventh embodiment of the present invention.

FIG. 33 (a) is a sectional view showing a planar illumination system according to a thirteenth embodiment of the present invention, and FIG. 33 (b) is transmission of a polarizer of the planar illumination system according to the thirteenth embodiment of the present invention. FIG. 4 is a diagram illustrating a relationship between an axial direction and an azimuth of an optical axis of a phase difference plate.

FIG. 34 is a cross-sectional view showing a planar illumination system according to the related art.

[Explanation of symbols]

1, 28, 33, 101 Light guide 2 Light diffuser 3, 34, 58, 64 Reflector 4, 104 Linear light source 5, 105 Reflector 6, 29, 106 Groove on lower surface of light guide 7, 8 Elliptical portion 11 Flat portion on the lower surface of the light guide 12, 20, 22, 24, 35 Slope of the groove on the side of the linear light source 13, 21, 23, 25, 36 Slope of the groove opposite to the linear light source 14 Bottom of the groove 15 Upper surface of light guide 40 Polarizer 41, 59 Polarization conversion plate 42 Light diffusion plate 63 Phase difference plate 103 Reflection sheet

Continued on the front page (72) Inventor Masaya Ito 1006 Kazuma Kadoma, Osaka Pref.Matsushita Electric Industrial Co., Ltd. Inventor Ken Tadashi 1006, Kazuma, Kadoma, Osaka Pref., Matsushita Electric Industrial Co., Ltd. 1006 Kadoma, Matsushita Electric Industrial Co., Ltd.

Claims (20)

[Claims] 1. A light guide, and a light source disposed on a side surface of the light guide, wherein light incident on the light guide from the light source is emitted from an upper surface of the light guide. A planar illumination system, wherein a plurality of grooves are formed on a lower surface of the light guide at intervals, and at least a surface of the groove on the light source side is inclined. 2. The planar illumination system according to claim 1, wherein the light guide has a wedge-shaped cross section. 3. The planar illumination system according to claim 1, wherein the groove width is smaller than the groove interval. 4. The planar illumination system according to claim 1, wherein the cross-sectional shape of the groove is trapezoidal or triangular. 5. The inclination angle of the surface of the groove on the light source side is given by the following (Equation 1), where n is the refractive index of the light guide and α is the central angle of the radiance distribution. Planar lighting system. (Equation 1) 6. The planar illumination system according to claim 1, wherein each groove comprises a plurality of adjacent groove groups. 7. The light guide has a stepped lower surface,
2. The method according to claim 1, wherein at least one groove is formed for each step.
A planar illumination system according to any one of the above. 8. The planar illumination system according to claim 1, wherein at least the inclined surface on the light source side of the groove is a curved surface. 9. The planar illumination system according to claim 1, wherein at least the inclined surface on the light source side of the groove is a rough surface. 10. The planar illumination system according to claim 1, wherein a polarizer is provided above the light guide, and a polarization conversion plate for rotating the polarization direction is provided below the light guide. 11. A cross-sectional shape is triangular and a vertex angle is approximately 90.
° using a polarization conversion plate having a groove formed, the polarization conversion plate, the direction of the groove is approximately 45 ° to the transmission axis of the polarizer
The planar illumination system according to claim 10, wherein the surface illumination system is arranged so as to form an angle. 12. A polarizer is provided above the light guide, and a phase difference plate having a quarter wavelength is provided below the light guide,
2. The spread illuminating system according to claim 1, wherein the retardation plate is disposed such that its optical axis direction forms an angle of approximately 45 ° with respect to the transmission axis of the polarizer. 13. The spread illuminating system according to claim 1, wherein a light diffusion plate is provided above the light guide, and a reflection plate is provided below the light guide. 14. A light guide, and a light source disposed on a side surface of the light guide, wherein light incident on the light guide from the light source is emitted from an upper surface of the light guide. A planar illumination system, wherein a plurality of linear projections are formed at intervals on a lower surface of the light guide, and at least a surface of the linear projection opposite to the light source is inclined. Surface lighting system. 15. The planar illumination system according to claim 14, wherein the light guide has a wedge-shaped cross section. 16. The planar illumination system according to claim 14, wherein the lower surface of the light guide has a stepped shape, and a linear projection is formed for each step. 17. The planar illumination system according to claim 14, wherein a polarizer is provided above the light guide, and a polarization conversion plate for rotating a polarization direction is provided below the light guide. 18. A cross-sectional shape is triangular and a vertex angle is approximately 90.
° using a polarization conversion plate having a groove formed, the polarization conversion plate, the direction of the groove is approximately 45 ° to the transmission axis of the polarizer
The planar illumination system according to claim 17, wherein the surface illumination system is arranged so as to form an angle. 19. A polarizer is provided above the light guide, and a phase difference plate having a quarter wavelength is provided below the light guide,
15. The spread illuminating system according to claim 14, wherein the retardation plate is arranged such that its optical axis direction forms an angle of approximately 45 with respect to the transmission axis of the polarizer. 20. The planar illumination system according to claim 14, wherein a light diffusion plate is provided above the light guide, and a reflection plate is provided below the light guide.