JPH1164641A - Illuminator by upward irradiation and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an illuminator by upper irradiation whose constitution is simple and which has the satisfactory illuminating efficiency and in which groove stirpes are not conspicuous by emitting the major portion of lights propagating in the inside of a light transmission body from the light transmission body to illuminate a reflection surface (subject to be illuminated). SOLUTION: A light source 1 is arranged at the side face of a light transmission body 3. Moreover, plural lines of V-shaped grooves 4 are formed on the upper surface of the light transmission body 3. The grooves 4 are formed so as to prolong roughly parallelly with the longitudinal direction of the light sauce 1 and are formed in V-shapes in a cross section. Flat plane parts being parts in which the grooves 4 are not present of the upper surface of the light transmission body 3 constitute one parts of the upper surface being one flat plane. An observoer 6 sees a subject to be illuminated 5 through the light transmission body 3. The light emitted from a light source 1 is made incident on the light transmission body 3 and propagates the inside of the body while repeating total reflections. At this time, since light beams are totally reflected by the grooves 4 being on the upper surface of the body 3 and angles of the light beams are changed to be made to be smaller than those in the total reflections, they are emitted from the bottom surface side to illuminate the subject to be irradiated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to printed materials such as books and photographs, OA equipment such as personal computers, screen display devices such as portable information terminals and portable video tape recorders, and reflection type liquid crystal displays used for various monitors. The present invention relates to an illumination device for upward irradiation used in a device and the like, and a liquid crystal display device using the illumination device.

[0002]

2. Description of the Related Art In recent years, personal computers, portable information terminals, video tape recorders, and the like have been reduced in size and portability, and reduction of power consumption of image display apparatuses has become an important issue. For this reason, there are many image display devices using a reflective liquid crystal display device. The reflection type liquid crystal display element obtains the brightness of the screen by reflecting external light such as sunlight and indoor light. However,
In a place with little external light, sufficient brightness cannot be obtained on the screen. Therefore, there is a demand for a lighting device that illuminates the reflective liquid crystal when there is little external light and does not hinder the observer when there is little external light, and that does not hinder the observer. Has been invented. 1 shows an example of a lighting device for upward illumination attached to a reflective liquid crystal display element. FIG. 17 is a schematic cross-sectional view of a conventional lighting device. As shown in FIG. 17, the conventional lighting device includes a light source 10
1, a reflector 102, a light guide 103, and a compensator 105. The reflector 102 extends the distance from the light source 101 to the side surface of the light guide 103 in order to collimate the light emitted from the light source 101. The light guide 103 has a function of propagating the light ray introduced from the reflector 102 by total reflection, and a function of totally reflecting the light ray by the slope of the groove on the upper surface and illuminating the reflection surface 104 by changing the ray angle. The compensator 105 has a function of correcting distortion generated when light reflected from the reflection surface 104 passes through the light guide 103.

[0003]

However, the conventional illuminating device has two light guides 103 and a compensating plate 105, and the light guide 103 and the compensating plate 105 have the same groove shape and are bonded together. Since the configuration is such that alignment is performed, it is difficult to perform alignment and the like, and there is a problem that manufacturing costs are increased. Therefore, an object of the present invention is to solve the above-described problems, and provide a lighting device that uses a simple configuration, has good lighting efficiency, has inconspicuous groove lines, and is illuminated by upward irradiation, and a liquid crystal display device that uses the lighting device. The purpose is to do.

[0004]

In order to achieve the above object, the present invention is configured as follows. First of the present invention
According to the aspect, the light source and the light source are arranged on the side surface, and a plurality of grooves at a predetermined interval are arranged on the upper surface in a direction parallel to the longitudinal direction of the light source, and the upper surface is arranged between the adjacent grooves. And at least a transparent plate-shaped light guide on which a flat portion constituting a part of the light guide is arranged, and observes an illuminated object arranged from the upper surface side of the light guide to the lower surface side of the light guide. The present invention provides an illumination device by upward irradiation, characterized in that the illumination device is configured to perform illumination. According to a second aspect of the present invention, each of the grooves of the light guide has a V-shape having a first slope located closer to the light source and a second slope located farther from the light source. a groove type, the total reflection angle of the light guide and theta _c, when the angle between the lower surface of the flat portion and the light guide has a theta _3, the first inclined surface and the light guide angle theta ₁ formed by the above-mentioned lower surface to provide a lighting device according to the top illumination according to the first embodiment in a range of _{θ 1 ≦ 90 ° -θ c +} 2θ 3 of. According to a third aspect of the present invention, each of the grooves of the light guide has a V-shape having a first slope located closer to the light source and a second slope located farther from the light source. The groove of the mold, the refractive index of the light guide is n, the angle between the flat portion and the lower surface of the light guide is θ ₃ , the perpendicular of the lower surface of the light guide and the direction of the observer when the the angle between beta, the angle theta ₁ formed by the above lower surface of the first inclined surface and the light guide _{body, θ 1 ≒ 45 + θ 3} - (1/2) sin -1 (1 / n * sin
β) The illumination device according to the first or second aspect, wherein the illumination device is provided by upward irradiation.

[0005] According to a fourth aspect of the present invention, each of the grooves of the light guide has a first slope located closer to the light source and a second slope located farther from the light source. Having V
An angle θ ₂ between the second slope and the lower surface of the light guide, where n is the refractive index of the light guide,
First to third satisfies θ ₂ ≦ (1/2) sin ⁻¹ (1 / n)
An illumination device by top illumination according to any of the aspects is provided. According to a fifth aspect of the present invention, there is provided the lighting device by upward irradiation according to any one of the first to fourth aspects, wherein in the light guide, the pitch of the grooves is equal to or less than the dot pitch of the illuminated object. . According to a sixth aspect of the present invention, each of the grooves of the light guide has a first position located closer to the light source.
A V-shaped groove having an inclined surface and a second inclined surface located on a side far from the light source, wherein, in the light guide, an observer observing the illuminated object and the upper surface of the light guide. Is L, the length of the first slope is ΔL *
(0.5 / 60) * The lighting device by upward irradiation according to any one of the first to fifth aspects, which is not more than π / 180 °, is provided. According to a seventh aspect of the present invention, in cross section, the lower surface, a convex portion having a slope angle theta ₄ with respect to the upper surface, a plurality placed transparent prisms across the plane substantially parallel to the lower surface The lighting device according to any one of the first to sixth aspects, in which a sheet is disposed on the upper surface of the light guide, by the upward irradiation. According to the eighth aspect of the present invention, the angle θ _{4 of the} slope of the prism sheet is 30 ° ≦ θ ₄ ≦ 50 °.
The illumination device by upward irradiation according to the seventh aspect of the present invention is provided.

According to a ninth aspect of the present invention, there is provided the illuminating device according to the seventh or eighth aspect, wherein a pitch of the inclined surface of the prism sheet is equal to or less than a dot pitch of the illuminated object. According to the tenth aspect of the present invention, when a distance between an observer observing the illuminated object and the upper surface of the light guide is L, the length of the slope of the prism sheet is ΔL * ( 0.5 / 60) * π / 180 °. The lighting device according to any one of the seventh to ninth aspects, wherein the lighting device is provided by upward irradiation. According to the eleventh aspect of the present invention, in the cross-sectional shape, a transparent prism in which a plurality of convex portions having an inclined surface at an angle θ ₄ with respect to the lower surface are arranged on the upper surface with a plane substantially parallel to the upper surface interposed therebetween. The lighting device according to any one of the first to sixth aspects, in which a sheet is disposed on the upper surface of the light guide, by the upward irradiation. According to a twelfth aspect of the present invention, the angle θ _{4 of the} slope of the prism sheet is 3
The lighting device according to the eleventh aspect, in which 0 ° ≦ θ ₄ ≦ 50 °, is provided. According to a thirteenth aspect of the present invention, there is provided the illumination device by upward irradiation according to the eleventh or twelfth aspect, wherein a pitch of the grooves of the prism sheet is equal to or less than a dot pitch of the illuminated object. According to a fourteenth aspect of the present invention, in the prism sheet, when a distance between an observer observing the illuminated object and the upper surface of the light guide is L, the length of the slope is ΔL *. (0.
(5/60) * π / 180 ° The illumination device according to any one of the eleventh to thirteenth aspects, wherein the illumination device is provided by upward irradiation.

According to a fifteenth aspect of the present invention, there is provided the light guide according to the first to sixth aspects, wherein a plurality of grooves are arranged at predetermined intervals in a direction orthogonal to a longitudinal direction of the light source on the upper surface of the light guide. An illumination device according to any one of the above aspects is provided. According to a sixteenth aspect of the present invention, the groove provided in the direction orthogonal to the longitudinal direction of the light guide is a V-shaped groove,
The lighting device by upward irradiation according to the fifteenth aspect, wherein the V-shaped apex angle θ ₅ is in the range of 80 ° ≦ θ ₅ ≦ 120 °. According to a seventeenth aspect of the present invention, the light guide is formed of a wedge-shaped plate, and the light source is disposed on a side having a larger thickness. To provide a lighting device by irradiating the upper part of the lighting device. According to an eighteenth aspect of the present invention, there is provided a liquid crystal display device for illuminating a liquid crystal screen using the illumination device for upward irradiation according to any one of the first to seventeenth aspects.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a lighting device using upward irradiation according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 and FIG. 14 are a schematic diagram and a more detailed schematic diagram of a cross section of an illuminating device by upward irradiation according to the first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a light source, for example, a fluorescent lamp such as a hot cathode tube or a cold cathode tube, or a plurality of light emitting diodes arranged, or an incandescent lamp, or a linearly formed organic light emitting material, It is arranged on the side surface of the light guide 3. In FIG. 1, 2 is a reflector,
It is arranged so as to cover the light source 1, and the inner surface is configured to have high reflectance and low diffusivity. For example, a reflector 2 is formed by depositing a material having a high reflectance such as silver or aluminum on a resin sheet and bonding the sheet to a thin metal plate or a resin sheet. When the light source 1 is a fluorescent lamp, it is desirable that the gap between the light source 1 and the reflector 2 is filled with a material having a refractive index close to 1.5 of glass. Further, it is desirable that the side surface thickness of the light guide 3 on the light source 1 side and the height of the reflector 2 be the same. In FIG. 1, the light guide 3 is, for example, a transparent substrate ( hereinafter, simply referred to as a “light guide”), and is made of quartz, glass, or a transparent resin such as an acrylic resin or polycarbonate. As shown in FIG. 2, the light guide 3 is equivalent to the size of the illuminated object. The lower surface 32 of the light guide 3 and the incident surface 33 make an angle of substantially 90 degrees. The light guide 3 has a substantially wedge shape as a whole, and the upper surface 31 of the light guide 3
It is inclined so as to gradually approach the lower surface 32 of the light guide 3 toward the side opposite to the light source 1. That is, the light guide 3
When the thickness of the side surface 33 on the light source side is d1 and the thickness of the side surface on the side opposite to the light source 1 is d2, d1 ≧ d2. Here, the relationship between the thicknesses may be basically d1 = d2, but if d1> d2, the brightness is kept uniform and the brightness is further improved. A plurality of V-shaped grooves 4 are formed on the upper surface 31 of the light guide 3.

FIG. 3 shows a detailed view of the groove 4. Groove 4 is light source 1
Are formed so as to extend substantially in parallel with the longitudinal direction (the direction penetrating the drawing), and have a V-shaped cross section. The slope on the light source side of the groove 4 is referred to as a first slope 41. The slope of the groove 4 opposite to the light source 1 is referred to as a second slope 42. A portion of the light guide upper surface 31 where the groove 4 is not provided is referred to as a flat portion 43. The plane portion 43 is an upper surface 3 which is one plane.
1 is a part of the first embodiment. Light guide lower surface 32 and groove 4
The first angle theta ₁ between the inclined surface 41 of θ ₁ ≦ 90 ° -θ of
in the range of _c + 2 [Theta] _3, and _{θ 1 ≒ 45 ° + θ 3} -
(1/2) sin ^-1 (1 / n * sinβ). Here, θ _c is the total reflection angle, and θ ₃ is the plane portion 43 and the light guide lower surface 32.
Is the angle between the perpendicular of the lower surface 32 of the light guide 3 and the direction of the observer. In FIG. 3, reference numeral 132 denotes a virtual plane parallel to the lower surface 32. Also, the light guide lower surface 32
And the angle θ ₂ between the second slope 42 of the groove 4 and θ ₂ ≦
(1/2) sin ^-1 (1 / n). Here, n is the refractive index of the light guide 3. However, as shown in FIG.
Both the pitch p and the depth h of the groove 4 have the upper surface 31 as a reference surface. On the other hand, in FIG. 1, 5 is a reflection surface. The reflective surface 5 is, for example, a printed matter such as a book or a photograph, an OA device such as a personal computer, a portable information terminal, a screen display device such as a portable video tape recorder, a reflective liquid crystal display device used for various monitors, and the like. . In FIG. 1, reference numeral 6 denotes an observer (more precisely, an observer's eye).
It is. The observer 6 looks at the reflection surface 5 through the light guide 3.

Next, the operation of the lighting device according to the first embodiment of the present invention will be described. Light incident on the light guide 3 from the light source 1 through the incident surface 33 has a refractive index of the light guide 3 of n.
Then, according to Snell's law, the radiation distribution becomes ± sin ⁻¹ (1 / n) light centered on the 0 ° direction. Light guide 3
Most materials have a refractive index of 1.42 or more, so the radiation distribution is in the range of ± 44.77 °. Therefore, the incident light beam propagates in the light guide 3 with a radiation distribution of ± 44.77 °. The light incident on the light guide lower surface 32 has an incident angle of 90 ° -44.77 ° = 45.23 ° or more, which is larger than the total reflection angle.
The light is totally reflected. Next, the operation of light on the light guide upper surface 31 will be described with reference to the drawings. The upper surface 31 of the light guide has a structure in which a plurality of flat portions 43 and a plurality of grooves 4 formed by the first slope 41 and the second slope 42 are arranged. As shown in FIGS. 4 (a) to 4 (e), they are classified into the following five patterns. The first pattern (a) is light incident on the plane portion 43. The second pattern (b) is light incident on the first slope 41. The third pattern (c) is light incident on the second slope 42. In the following description, α is an angle between the light guide lower surface 32 and the light beam reaching the light guide upper surface 31. Light guide upper surface 3
The light reaching 1 is ± sin ^-1 (1/1 /
α is 0 ° or more, and has the maximum radiation distribution at 0 ° because the light of the radiation distribution of n) is the light of the distribution in the plus direction.

In the first pattern (a), light enters the plane portion 43 at an incident angle of {90 ° -α-θ ₃ }. Since θ ₃ is small, most light is reflected. The light reflected by the plane portion 43 has an angle of {−α−2 * θ ₃ }. In the second pattern (b), light is incident on the first slope 41 at an incident angle of {90 ° -α-θ ₁ }. Of the light incident on the first slope 41, part is reflected by Fresnel reflection, but part is transmitted and lost. The light reflected by the first slope 41 has a ray angle of {−α−2 * θ ₁ }. In the third pattern (c), light is incident on the second slope 42 at an incident angle of {90 ° −α + θ ₂ }. In addition, the light reflected by the second slope 42 has a ray angle of {−α + 2 * θ ₂ }. Therefore, when θ ₂ is small, the reflected light becomes light more parallel than before the reflection. The light is actually reflected as a combination of the first to third patterns. Although not limited because it depends on the size of the lighting device, the groove height h is about 5 μm to 25 μm and the pitch p is about 100 μm to 250 μm. There is also a large number of light reflected by (a composite of the first pattern and the second pattern). This pattern is referred to as a fourth pattern (d).

In the fourth pattern (d), light is incident on the first slope 41 at an incident angle of {90 ° − (− α−2 * θ ₃ ) −θ ₁ }.
Incident on. At this time, θ ₁ is θ ₁ ≦ 90 ° −θ _c + 2θ ₃
Therefore, the angle of incidence on the first slope 41 is 90 °
− (− Α−2 * θ ₃ ) −θ ₁ ≧ α + θ _c (where θ _c is the total reflection angle). Since α is 0 ° or more, it is preferable that all rays are larger than the total reflection angle and are totally reflected. Note that if θ ₁ is less than 20 °, the observer 6 will not easily see it, so it is preferable to set the angle to more than 20 °. The light reflected from the first slope 41 is ｛α + 2 * θ
The light beam angle becomes ₃ −2 * θ ₁ }, and the incident angle on the light guide lower surface 32 is {90 ° + α + 2 * θ ₃ −2 * θ ₁ }. At this time, θ ₁ becomes θ ₁ ≒ 45 ° + θ ₃ − (1/2) sin ⁻¹
(1 / n * sin β), the incident angle on the light guide lower surface 32 is 90 ° + α + 2 * θ ₃ -2 * θ ₁ ≒ α + si
n ⁻¹ (1 / n * sinβ). Here, β is as shown in FIG.
As shown in FIG. 5, the angle formed between the direction perpendicular to the reflection surface 5 and the observation direction of the observer 6, in other words, the direction of the observer 6. Since α is 0 ° at the maximum, the ray is
The light enters the lower surface with an angular distribution centered at n ^-1 (1 / n * sinβ). Therefore, since the light is emitted from the light guide lower surface 32 with an angle distribution centered on the angle β, it is favorable when observing from the angle β direction, and can be adjusted to a direction that is easy for the observer to see. Α is preferably closer to 0 ° because the radiation angle distribution centered on the angle β direction becomes narrower. If θ ₂ is small, the light beam is
After that, there is also a lot of light (composite of the first, second, and third patterns) that is reflected by the flat surface portion 43 and enters the first slope 41. This pattern is referred to as a fifth pattern (e).

In the fifth pattern (e), the second slope 4
The light reflected at 2 is {−α + 2 * θ ₂ }, so if θ ₂ is small, the reflected light is more parallel than before the reflection. Therefore, the light reflected by the second slope 42 is transmitted to the flat portion 43 and the first portion 43 as described in the fourth pattern (d).
Light guide body lower surface 32 after total reflection at slope 41 of
This is preferable because the radiation angle distribution from the object becomes narrow. Specific values of theta ₂ is not limited because depending on the size of the lighting device is an angle of light into at least a second inclined surface 42 reaches to a parallel beam direction. Therefore, θ ₂ is the angle at which the light ray having the maximum angle sin ⁻¹ (1 / n) of α is reflected in the direction of 0 °, and θ ₂ ≦ (１ ／) sin ⁻¹ (1 / n). In addition, assuming that there is no flat portion 43, the necessity of the flat portion 43 will be described below. Of the light that reaches the light guide upper surface 31, the light of 0 <α <θ ₂ cannot reach the second slope 42 as easily understood, so the first slope 41.
To reach. For this reason, part of the light is reflected by Fresnel reflection, but part of the light is transmitted and lost. Also,
When the light having the angle θ ₂ <α <2θ ₂ is reflected by the second slope 42, the light having the angle α becomes the light having the angle −α + 2θ ₂ as described in the third pattern, so that 0 <α <a θ _2. Therefore, Fresnel reflection occurs on the first slope 41,
Transmitted and lost. Also, 2θ ₂ <α <｛sin-1
The light of (1 / n)｝ is reflected by the second slope 42 and is
in−1 (1 / n) + 2θ ₂ ｝ <α <0. Part of the light reflected on the second slope 42 is the first slope 4
1 is good, but another part is the first slope 41.
To the light guide lower surface 32. Therefore, 0 <
Since the ratio of light of α <θ ₂ increases, the probability of transmission through the first slope 41 and loss increases. Therefore, the plane portion 4
No. 3 is necessary. As a result, the light reflected by the groove 4 is emitted from the lower surface 32 of the light guide 3. The emission angle is not limited because it varies depending on the characteristics of the reflection plate 5. However, it is desirable that the emission angle is the direction β that the observer 6 normally observes.

The light emitted from the light guide lower surface 32 reaches the reflecting plate 5 and is reflected. The reflected light passes through the light guide 3 again and reaches the observer 6. At this time, the groove 4 of the light guide 3
If the strain caused by the swelling is large, the groove streaks are conspicuous and unsuitable. However, if the grooves 4 are provided to such an extent that moire fringes cannot be formed at a pitch p equal to or less than the minimum resolution (dot pitch) of the reflection plate 5, the light transmittance of each dot only affects the image quality, and The distortion does not affect the image quality. Further, although it depends on the application, it is not limited, but the distance when viewing the normal screen (the observer 6 and the upper surface 31 of the light guide 3).
And the minimum resolution of the human eye is 0.5
Therefore, if the length x of the first slope 41 of the groove 4 is not more than {L * (0.5 / 60) * π / 180},
Grooves are not noticeable. For example, if L is 35 cm, {35 * (0.5 / 60) * π / 180} = 50 μ
It can be said that the groove streak less than m is inconspicuous. As described above, if the pitch p is equal to or smaller than the dot pitch of the reflector 5 or the distance at which the observer 6 looks at the normal screen (the distance between the observer 6 and the upper surface 31 of the light guide 3) is L, the first Length x of slope 41
= H / tan (θ ₁ ) is ΔL * (0.5 / 60) * π /
When the angle is 180 ° or less, the groove line is not conspicuous, which is preferable.

As described above, the light emitted from the light source 1 is emitted from the lower surface 32 of the light guide by the first slope 41 of the groove 4 and illuminates the reflecting plate 5. The density decreases and the luminance distribution becomes non-uniform. However, the thickness d of the side surface of the light guide 3 on the light source 1 side
1 and the thickness d2 of the side surface opposite to the light source 1, d1
Since there is a relationship of ≧ d2, the light density is kept constant and the luminance distribution is kept constant. Further, it is preferable that the pitch p be reduced as the distance from the light source 1 increases, so that the luminance distribution becomes more uniform. Further, at a position far from the light source 1, the depth h
Is preferable, since the brightness distribution becomes more uniform. As described above, according to the above-described first embodiment, it is possible to provide an illuminating device that has a simple configuration, has high illumination efficiency, has no noticeable groove streak, has a uniform luminance distribution, and is illuminated by upward irradiation.

A specific numerical example of the first embodiment can be configured as follows. From the viewpoint of setting to be equal to or smaller than the critical angle, θ ₁ ≦ 90 ° −θ _c + 2θ
_{In 3} , the luminance is improved by setting θ ₁ ≦ 49.8 °. Also, θ ₁ ≒ 45 ° + θ _3- (1/2) sin ^-1 (1 / n
* Sinβ), when β = 30 °, θ ₁ ≒ 4
The emission angle is set to 6.2 °. Also, θ ₂ ≦
At (1/2) sin ^-1 (1 / n), from the viewpoint of improving the reflectance on the first slope 41 of the groove 4 of the light guide 3 by parallelizing the light rays, θ ₂ ≦ 20. The brightness is improved to 9 °. Further, the pitch p of the groove 4 is set to 250 μm or less so as to be equal to or less than the dot pitch of the reflection plate 5 so as to reduce the groove stripe. Also, the length of the first slope 41 of the groove 4 x ≦ の L *
For (0.5 / 60) * π / 180 °, x ≦ 5
The groove width is set to 0.9 μm to reduce groove streaks. Here,
Refractive index n = 1.5 of light guide 3, angle θ ₃ = 0.8 ° between upper surface 31 and lower surface 32 of light guide 3, upper surface 31 of light guide 3
It is assumed that the distance L between the object and the observer 6 is L = 350 mm. In addition,
In the first embodiment, as a result of a simulation experiment,
It was found that if the length of the flat portion was about 5 times the length of the first slope, the number of rays in the fifth pattern increased, which was preferable.

The present invention is not limited to the first embodiment, but can be embodied in various other modes. For example, it is preferable to provide a protective film on the surface of the light guide 3 of the first embodiment, since deterioration of the appearance due to scratches or the like can be prevented. For example, as a hard coat agent as an example of a material for forming the protective film, there are a thermosetting silicone system emphasizing a coating function, a UV curing acrylic system emphasizing a coating workability, and a UV curing silicon system. Further, in the first embodiment, a transparent sheet such as acrylic or polycarbonate may be disposed instead of the protective film. Further, a protective film may be provided on these transparent sheets. Further, the light guide 3 of the first embodiment described above.
It is preferable to provide an anti-reflection film on the upper surface 31 because the image from the reflection plate 5 becomes clear. Further, a collimator for collimating light in a direction parallel to the light source 1 may be provided on the light source side surface 33 of the light guide 3 of the first embodiment. The radiation distribution of the light emitted from the light source 1 spreads not only in a direction perpendicular to the light source 1 but also in a horizontal direction. For this reason, it can be used effectively by suppressing the light in the horizontal direction by the collimator. In other words, the front luminance is increased by narrowing the radiance distribution in the left-right direction.

As a modification of the first embodiment,
For a reflector having a large screen with a diagonal of 13 inches or more, luminance is maintained and good by using two or more fluorescent lamps. An example is shown in FIG. For example, there is a method of arranging two or more lamps in the light source 1 as shown in FIG.
Alternatively, as shown in FIG. 5B, there is a method in which two light guides 3 of the first embodiment are prepared and small-diameter side surfaces are brought into contact with each other and arranged to face each other. According to this configuration, the light emitted from the right light source 11 is internally reflected by the upper surface 311 of the right light guide 3 and is emitted from the lower surface 321, and the light emitted from the left light source 12 is the left light guide 3
Since the light is internally reflected by the upper surface 312 and emitted from the lower surface 322, the brightness is preferably maintained for a large screen. Also,
As shown in FIG. 5C, the light guide 3 of the first embodiment is
There is a method in which individual pieces are prepared, and the side faces having a large thickness are brought into contact with each other and arranged back to back. According to this configuration,
The light emitted from the right light source 11 is internally reflected by the upper surface 312 of the left light guide 3 and is emitted from the lower surface 322, and the light emitted from the left light source 12 is the upper surface 3 of the right light guide 3.
Since the light is internally reflected at 11 and is emitted from the lower surface 321, the brightness is preferably maintained for a large screen. Further, for a reflector having a small screen with a diagonal of 4 inches or less, if a light emitting diode or the like is used as the light source 1, it is more suitable for further miniaturization, which is preferable. In this case, since the radiation distribution of the light emitting diode has a certain degree of directivity, the reflector 2 may be omitted.

As described above, according to the first embodiment,
Light emitted from the light source 1 enters the light guide 3 and is
Propagation while repeating total reflection within. At this time, the light beam is totally reflected by the grooves 4,..., 4 on the upper surface of the light guide 3, and is emitted to the lower surface side because the angle of the light beam is changed and becomes smaller than the total reflection angle. Light up. The reflection at each groove 4 is reflected on the first slope 41, the second slope 42, and the plane portion 43 in a complex manner. Therefore, the first slope 4
If the angle of 1 is {90 ° −θ _c + 2θ ₃ } or less, the reflectance increases and the illumination efficiency improves. Also, the first slope 4
1 changes the angle of the light beam emitted from the light guide 3.
Therefore, the angle of the first slope 41 is {45 ° + θ ₃ −
(1/2) sin ^-1 (1 / n * sinβ)｝
The angle of the emitted light becomes the β direction, and the angle of the emitted light can be adjusted to an angle that is easy for the observer 6 to see. The angle of the second slope 42 is {(1/2) sin ^-1 (1 / n)}.
In the following case, the light reflected by the second slope 42 becomes more parallel light. For this reason, the reflectance of light that reaches the first slope 41 or the flat portion 43 after being reflected by the second slope 42 increases. Therefore, lighting efficiency is improved. If the pitch of the grooves 4,..., 4 is less than or equal to the dot pitch of the illuminated object 5, the groove stripes are not conspicuous and do not hinder the observer 6. When the distance between the observer 6 and the upper surface of the light guide 3 is L, the length x of the first slope 41 is ΔL * (0.5 / 6).
0) * π / 180 ° or less, since the resolving power of the human eye is 0.5 minutes, the groove is not noticeable and does not hinder the observer 6. As described above, it is possible to provide an illuminating device that has a simple configuration, has high illumination efficiency, and irradiates upward with less noticeable groove streaks.

Next, an illumination device using upward irradiation according to a second embodiment of the present invention will be described with reference to the drawings. Second embodiment of the present invention
The structure of the lighting device of the embodiment is almost the same as that of the lighting device of the first embodiment, except that the transparent substrate 7 is arranged on the light guide 3. 6 and 15, reference numeral 7 denotes a transparent substrate (hereinafter, referred to as a prism sheet) made of quartz, glass, or a transparent resin, for example, an acrylic resin, polycarbonate, or the like. Especially when it is a transparent resin,
It may be a sheet made of a soft material.
One surface of the prism sheet 7 is a flat surface 71, and the other surface is a prism surface 72 having a triangular wedge-shaped cross section. The shape of the prism sheet 7 is substantially the same size as the light guide 3 when viewed from above. As shown in FIG. 7, the prism surface 72 of the prism sheet 7 has at least a combination of a wedge-shaped convex portion 73 (hereinafter, referred to as a prism portion) of an isosceles triangle (or an equilateral triangle) and a plane portion 74. A plurality of the wedge-shaped prism portions 73 having an isosceles triangular cross section extend in a direction parallel to the longitudinal direction of the light source 1 and are arranged at a pitch P in a direction perpendicular to the longitudinal direction. Prism 73 with an isosceles triangular cross section
Is the angle between each of the slopes and a virtual plane parallel to the plane 71.
When _4, theta ₄ in order to function effectively the prism sheet 7 is preferably in the range from 30 ° to 50 °.
The prism sheet 7 is disposed on the upper surface of the light guide 3 with the prism surface 72 facing downward.

Next, the operation of the lighting device according to the second embodiment will be described. Among the light incident on the light guide 3 from the light source 1, there is a light transmitted through the first slope 41 of the groove 4. This light beam has a large exit angle with respect to the upper surface 31 of the light guide 3.
For example, in the first embodiment, the light is emitted in a direction around 80 °. FIG. 8 is a graph showing the characteristics of light emitted from the light guide upper surface 31 when θ ₁ = 40 ° and θ ₂ = 10 °. In FIG. 8, it can be seen that the amount of light leakage increases at an emission angle of about 70 ° to 80 °. Therefore, when the light reaches the prism surface 72 of the prism sheet 7, the light is reflected by the triangular prism portion 73 as shown in FIG. 9, reenters the light guide 3, passes through the light guide 3, and reaches the reflector 5. . At this time, according to experiments and simulations, the slope angle θ ₄
It was found that the efficiency was good when the angle was in the range of 30 ° to 50 °. As a result, the light irradiation efficiency is improved and the brightness is increased. The light (image) reflected by the reflection plate 5 is distorted when passing through the light guide 3 and the prism sheet 7, but the cross section of the prism sheet 7 has a flat portion 74. If the length ratio of the slope portion of the prism portion 73 is large and the pitch P of the prism portion 73 is small, the distortion is small. In other words, the minimum resolution (dot pitch) of the reflector
If the prism portions 73 are provided at the following pitch, the light transmittance of each dot only affects the image quality, and the distortion of each dot does not affect the image quality. Although it is not limited because it differs depending on the application, the length of the slope is ΔL * (0.5 / 60)
If it is less than * π / 180 °, the streak of the prism portion is not conspicuous. For example, if L is 35 cm, it can be said that the streak of the prism portion of 50 μm or less is inconspicuous.

As described above, when the pitch P of the prism portion 73 is equal to or less than the dot pitch of the reflector, or the distance at which the observer looks at the normal screen is L (= the distance between the observer and the upper surface of the prism sheet), When the length of the slope of the portion 73 is not more than {L * (0.5 / 60) * π / 180},
The streaks of the convex portion 73 are suitable because they are not noticeable. As a specific numerical example, the angle θ ₄ of the inclined surface is set in the range of 30 ° to 50 ° to reuse the leaked light, and the pitch P
In order to reduce the streak of the prism portion, the dot pitch is set to 250 μm or less. In addition, since the length of the slope of the prism portion is set to {L * (0.5 / 60) * π / 180} or less, the streak length of the prism portion is reduced to 50.9 μm or less. The purpose of the prism sheet 7 is to reflect light leaked from the light guide 3 on a slope and reuse the same, and therefore, the prism sheet 7 can be realized even in other shapes as long as the slope and the flat portion are the same as those in the above embodiment. is there. FIGS. 10A and 10B show examples of other shapes. For example, as shown in FIG.
10 in which a plurality of triangular grooves 76 are arranged, FIG.
As shown in FIG. 15B, a plurality of peaks 77 having a trapezoidal cross section are arranged (see FIG. 15). Also,
The radiation distribution of the light beam emitted from the light source 1 spreads not only in a direction perpendicular to the light source but also in a horizontal direction. For this reason, by arranging the prism sheet 7 such that the projections extend in the direction of the prism in a direction perpendicular to the longitudinal direction of the light source 1, light having a component in a direction parallel to the light source 1 is reflected on the slope, and again. Illuminating the reflection surface 5 through the light guide 3 can improve the illumination efficiency.

Therefore, according to the second embodiment, the light emitted from the light source 1 enters the light guide 3 and propagates in the light guide 3 while repeating total reflection. At this time, the light beam is totally reflected by the grooves 4,..., 4 on the upper surface 31 of the light guide 3, and is emitted to the lower surface side because the angle of the light beam is changed and becomes smaller than the total reflection angle. To illuminate. The reflection at each groove 4 is reflected on the first slope 41, the second slope 42, and the plane portion 43 in a complex manner. Therefore, a part of the light beam is emitted from the upper surface 31 of the light guide 3 at the first slope 41. The light emitted from the upper surface 31 of the light guide is reflected by the slope on the lower surface of the prism sheet 7 and reenters the light guide 3,
The illumination target 5 is illuminated. Thereby, the lighting efficiency is improved. The angle θ ₄ of the slope of the prism sheet 7 is 30.
When the angle is in the range of 50 ° to 50 °, illumination can be performed more efficiently. If the pitch P of the inclined surface of the prism sheet 7 is equal to or less than the dot pitch of the illuminated object 5, the streaks of the prism sheet 7 are inconspicuous and do not hinder the observer 6. The observer 6 and the upper surface 7 of the prism sheet 7
Assuming that the distance from the slope is L, the length of the slope is ΔL * (0.
If it is 5/60) * π / 180 ° or less, the streak of the prism portion is not conspicuous because the resolution of the human eye is 0.5 minutes, and does not hinder the observer 6. As described above, it is possible to provide an illuminating device that has a simple configuration, has high illumination efficiency, and irradiates the prism portion with inconspicuous stripes.

Next, an illumination device using upward irradiation according to a third embodiment of the present invention will be described. The structure of the lighting device according to the third embodiment of the present invention is substantially the same as that of the lighting device according to the second embodiment, except for the method of arranging the prism sheet. The prism sheet 7 in the present embodiment is disposed with the prism surface 72 facing upward. The operation at this time is shown in FIG.
This will be described with reference to FIG. Although the reflected light depends on the characteristics of the reflection plate 5, the light diffused as a whole is emitted. Therefore, the light is also emitted in directions other than the viewing angle. Light other than the viewing angle is condensed by the prism surface 72 of the prism sheet 7 to improve the front luminance. The reflected light is substantially perpendicular to the light guide 3 and the prism sheet 7 (0 °).
Direction). The reflected light passes through the light guide 3 and enters from the flat portion 74 of the prism sheet 7. Assuming that the reflection plate 5 is a perfect diffusion plate, the distribution of light after entering the prism sheet 7 is distributed at ± sin ^-1 (1 / n ₁ ) around the 0 ° direction. Here, n ₁ is the refractive index of the prism sheet 7. As shown in FIG. 11, assuming that the angle between the flat surface 71 of the prism sheet 7 and the slope of the projection 73 is θ ₄ , the emission angle is Δθ ₄ + sin.
⁻¹ (n * sin (α−θ ₄ ))}. θ ₄ is 50 °,
If n ₁ = 1.5, the maximum value of α + sin ⁻¹ (1 /
n ₁ ) is 41.8 °, the emission angle is 37.7 °,
It becomes smaller than ± 90 ° before entering the prism sheet. For this reason, the radiation distribution of the reflected light is narrowed by the inclined surface of the prism sheet 7. From experiments and simulations, it was found that the efficiency was good when the angle θ ₄ of the slope was in the range of 30 ° to 50 °. That is, within this range, the emission angle distribution of the reflected light can be narrowed, and the front luminance can be improved.

As described above, the front luminance is improved by disposing the prism surface 72 with the upper surface facing upward. Even if the reflection surface 5 is not a perfect diffusion surface and the emission angle of the light guide 3 is not 0 °, the radiation distribution can be similarly narrowed,
It is suitable. The light (image) reflected by the reflection plate 4 is distorted when passing through the light guide 3 and the prism sheet 7, but the cross section of the prism sheet 7 has a flat portion 74 and the flat portion 74. The ratio of the length of the slope portion of the prism portion 73 is large, and if the pitch is small, the distortion is small. That is, if grooves are provided at a pitch equal to or less than the minimum resolution (dot pitch) of the reflector, the light transmittance of each dot only affects the image quality, and the distortion of each dot does not affect the image quality. Absent. Although it is not limited because it differs depending on the application, the length of the slope is ΔL * (0.5 / 60) * π / 180 ° or less, the streak of the prism portion is inconspicuous. For example, if L is 35c
If it is m, it can be said that the streak of the prism part of 50 μm or less is inconspicuous. As described above, the pitch P is equal to or less than the dot pitch of the reflector, or the length of the slope is ΔL * (0.5 / 6) where L is the distance at which the observer views the normal screen.
0) * π / 180 ° or less is preferable because the streak of the prism portion is not noticeable. Specific numerical examples are the same as in the second embodiment.

In the third embodiment, the prism sheet 7 is intended to improve the front luminance by condensing the light other than the viewing angle by the prism surface 72 of the prism sheet 7. This can be realized if there is a slope and a plane portion similar to those in the third embodiment. FIG. 16 shows an example of another shape. For example, of the three types of prism sheets 7 in FIG.
The upper right prism sheet has a plurality of triangular grooves 76 on its upper surface. In the lower right prism sheet, a plurality of peaks 77 having a trapezoidal cross section are arranged on the upper surface thereof. A similar function can be achieved with these prism sheets.
Further, as can be easily determined from the above description, the longitudinal direction of the prism of the prism sheet 7 is not limited. Therefore, according to the third embodiment, in the cross-sectional shape, a plurality of convex portions 73 having an inclined surface at an angle θ ₄ with respect to the lower surface are arranged on the upper surface with a plane (74) substantially parallel to the upper surface interposed therebetween. Prism sheet 7 made of a transparent substrate
By arranging on the light guide 3, the radiation distribution of the reflected light from the illuminated object 5 can be narrowed, and the front luminance can be improved. If the pitch P of the slope of the prism sheet 7 is equal to or less than the dot pitch of the illuminated object 5,
The streaks of the prism sheet 7 are not noticeable, and do not hinder the observer 6. When the distance between the observer 6 and the upper surface of the prism sheet 7 is L, the length of the slope is ΔL * (0.5
/ 60) * π / 180 ° or less, since the resolving power of the human eye is 0.5 minutes, the groove is not noticeable and does not hinder the observer 6. As described above, it is possible to provide an illuminating device that has a simple configuration, has high illumination efficiency, and irradiates upward with less noticeable groove streaks.

Next, an illumination device using upward irradiation according to a fourth embodiment of the present invention will be described with reference to the drawings. Fourth Embodiment of the Present Invention
The structure of the lighting device of the embodiment is almost the same as that of the lighting device of the first embodiment, except for the groove shape of the light guide 3. FIG.
FIG. 2 shows a view of the lighting device as viewed from above. A lateral groove 4 is provided in a direction parallel to the light source 1. A vertical groove 8 is provided in a direction perpendicular to the light source 1. The lateral groove 4 is the same as the groove 4 of the first embodiment. FIG. 13 shows a sectional view of the vertical groove 8. Flute 8
Is a V-shaped groove, and the vertical angle θ ₅ of the groove 8 is from 80 ° to 1
Between 20 ゜. The radiation distribution of the light emitted from the light source 1 spreads not only in a direction perpendicular to the light source 1 but also in a horizontal direction. For this reason, by arranging the vertical groove 8, light having a component in a direction parallel to the light source 1 is reflected on the inclined surface, and emitted from the light guide 3 to illuminate the reflection surface 5, thereby improving the illumination efficiency. Can be. The inventor
Repeated experiments and simulations, theta ₅ was found to be effective when in the range of 120 ° from 80 °.
That is, within this range, the luminance can be improved by effectively utilizing the light in the direction parallel to the light source 1. Examples of specific numerical values of pitch and slope length are
This is similar to the embodiment. Therefore, according to the fourth embodiment, the light emitted from the light source 1 enters the light guide 3,
The light propagates while repeating total reflection within the light guide 3. At this time, the light beam is totally reflected by the grooves 4,..., 4 on the upper surface 31 of the light guide 3, and is emitted to the lower surface side because the angle of the light beam is changed and becomes smaller than the total reflection angle. To illuminate. The radiation distribution of the light emitted from the light source 1 spreads not only in a direction perpendicular to the light source 1 but also in a horizontal direction. For this reason, by arranging the vertical grooves 8,..., 8, light having a component in a direction parallel to the light source 1 is reflected on the inclined surface, and emitted from the light guide 3 to illuminate the reflecting surface, thereby improving the illumination efficiency. Can be done. The shape of each vertical groove 8 is V-shaped, and the vertical angle θ ₅ of each vertical groove 8 is 80 °.
When the angle is in the range of 120 to 120 °, illumination can be performed more efficiently. As described above, with a simple configuration,
It is possible to provide an illuminating device that has high illumination efficiency and irradiates upward with inconspicuous groove lines.

[0028]

As described above, according to one aspect of the present invention, the light source and the light source are arranged on the side surface, and grooves at predetermined intervals are formed on the upper surface in a direction parallel to the longitudinal direction of the light source. A transparent plate-shaped light guide in which a plurality of the light guides are arranged, and a plane portion (43) constituting a part of the upper surface is arranged between the adjacent grooves; The illuminated object arranged on the lower surface side of the light guide is observed from the side. Therefore, most of the light propagating inside the light guide is emitted from the light guide by total reflection in the groove, and the reflection surface can be illuminated. If the angle of the first slope of the groove is θ ₁ ≦ 90−θ _c + 2θ ₃ , illumination can be performed more efficiently. Further, the angle θ ₁ of the first slope is θ ₁ ≒ 45 ° + θ ₃ − (1/2) si
n ^-1 (1 / n * sinβ), the observer's direction β
The emission angle can be adjusted to the above, which is good. Also,
The angle of the second slope of the groove is θ ₂ ≦ (1/2) sin
^{If -1} (1 / n), illumination can be performed more efficiently. Further, when the pitch of the grooves is set to be equal to or less than the dot pitch of the object to be illuminated, it is possible to make the groove lines inconspicuous. When the distance between the observer and the lighting device, specifically, the upper surface of the light guide is L, the length of the first slope is ΔL * (0.
5/60) * π / 180 ° or less, the groove streaks can be made less noticeable.

Further, according to the illumination device by upward irradiation of another aspect of the present invention, in the cross-sectional shape, a convex portion having an inclined surface at an angle θ ₄ with respect to the upper surface on the lower surface has a flat surface substantially parallel to the lower surface. By arranging a plurality of transparent prism sheets on the light guide, the light leaking from the light guide is reflected on the slope of the angle θ ₄ and passes through the light guide. To illuminate the reflector. When the angle θ _{4 of} the slope is in the range of 30 ° to 50 °, the illumination efficiency is further improved. When the pitch of the slope of the prism sheet is equal to or less than the dot pitch of the object to be illuminated, the groove lines can be made inconspicuous. When the distance between the observer and the lighting device is L, the length of the slope of the prism sheet is ΔL *.
(0.5 / 60) * π / 180 ° or less, the groove streaks can be made less noticeable. Furthermore, according to the illumination device by upward irradiation of still another aspect of the present invention, in the cross-sectional shape, the convex portion having the inclined surface at the angle θ ₄ with respect to the lower surface sandwiches the plane substantially parallel to the upper surface. By arranging a plurality of transparent prism sheets arranged on the light guide, the radiation distribution of the reflected light from the reflecting surface can be narrowed, and the front luminance can be improved.
When the pitch of the slope of the prism sheet is equal to or less than the dot pitch of the object to be illuminated, the groove lines can be made inconspicuous. Further, when the distance between the observer and the illumination device, specifically, the distance between the upper surface of the prism sheet is L and the length of the slope of the prism sheet is {L * (0.5 / 60) * π / 180} or less, Grooves can be made less noticeable. Furthermore, according to the illumination device by the upward irradiation of another aspect of the present invention, by arranging a plurality of grooves at predetermined intervals in a direction perpendicular to the light source on the upper surface of the light guide, a direction parallel to the light source is provided. The component light is reflected on the inclined surface and emitted from the light guide to illuminate the reflection surface, so that the illumination efficiency can be improved.
The groove provided in the vertical direction is V-shaped, be in the range of 120 ° from the vertical angle theta ₅ is 80 ° V-shaped, it is possible to further improve the illumination efficiency. Further, in a liquid crystal display device using the above-described lighting device, it is possible to achieve a liquid crystal display device that can inherit the advantages of the lighting device as it is.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a cross section of a lighting device using upward irradiation according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of a cross section of a light guide according to the first embodiment.

FIG. 3 is a schematic cross-sectional view showing details of a groove in the first embodiment.

FIG. 4 is a diagram for describing light reflection on the upper surface of the light guide according to the first embodiment.

FIG. 5 is a schematic cross-sectional view showing another example of the illumination device according to the first embodiment.

FIG. 6 is a schematic diagram of a cross section of a lighting device using upward irradiation according to a second embodiment of the present invention.

FIG. 7 is a schematic diagram of a cross section of a prism sheet according to a second embodiment.

FIG. 8 is a graph showing a radiation distribution of light emitted from the upper surface of the light guide according to the second embodiment.

FIG. 9 is a diagram for describing light reflection of a prism unit in the second embodiment.

FIG. 10 is a schematic cross-sectional view illustrating another example of the prism sheet according to the second embodiment.

FIG. 11 is a diagram for explaining light propagation in a prism sheet according to the second embodiment.

FIG. 12 is a diagram of a third embodiment of the present invention when viewed from above a lighting device by upward irradiation.

FIG. 13 is a schematic diagram of a cross section of a light guide according to a third embodiment.

FIG. 14 is a more detailed schematic diagram of a cross section of the illumination device for upward irradiation in the first embodiment.

FIG. 15 is a more detailed schematic diagram of a cross section of a lighting device by upward irradiation in the second embodiment.

FIG. 16 is a more detailed schematic diagram of a cross section of a lighting device by upward irradiation in the second embodiment.

FIG. 17 is a schematic cross-sectional view of a conventional lighting device.

[Explanation of symbols]

 Reference numerals 1, 11, 12 Light source 2 Reflector 3 Light guide 4, 8 Groove 5 Reflecting surface 6 Observer 7 Prism sheet 31, 311, 312 Upper surface 32, 321, 322 Lower surface 33 Incident surface 41 First slope 42 Second slope 43 Plane part 71 Plane 72 Prism surface 73 Prism part 74 Plane part 76 Groove 77 Mountain

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Watanabe 1006 Kazuma Kadoma, Kadoma City, Osaka Inside Matsushita Electric Industrial Co., Ltd.

Claims (18)

[Claims] 1. A light source (1) and the light source are arranged on a side surface, and a plurality of grooves (4) at a predetermined interval are arranged on an upper surface (31) in a direction parallel to a longitudinal direction of the light source. ,
A transparent plate-shaped light guide (3) in which a flat portion (43) constituting a part of the upper surface is disposed between the adjacent grooves; and the light guide is provided from the upper surface side of the light guide. An illumination device for upward irradiation, characterized in that an object to be illuminated (5) arranged on a lower surface side of a light body is observed. 2. The groove (4) of the light guide (3),
A V-shaped groove having a first slope (41) located closer to the light source and a second slope (42) located farther from the light source, and a total reflection angle of the light guide; Is θ _c , and the angle between the flat portion and the lower surface (32) of the light guide is θ ₃ , the angle θ ₁ between the first slope and the lower surface of the light guide is θ ₁ The lighting device by upward irradiation according to claim 1, wherein a range of ≦ 90 ° −θ _c + 2θ ₃ is satisfied. 3. The grooves (4) of the light guide (3) are:
A V-shaped groove having a first slope (41) located closer to the light source and a second slope (42) located farther from the light source; n, and the angle formed by the plane portion and the lower surface (32) of the light guide is θ.
₃ , and the angle between the perpendicular of the lower surface of the light guide and the direction of the observer (6) is β, the angle θ ₁ between the first slope and the lower surface of the light guide is: θ ₁ ≒ 45 + θ _3- (1/2) sin ^-1 (1 / n * sin
The lighting device by upward irradiation according to claim 1 or 2, wherein β). 4. The groove (4) of the light guide (3)
A V-shaped groove having a first slope (41) located closer to the light source and a second slope (42) located farther from the light source; n, an angle θ between the second slope and the lower surface of the light guide.
_The illumination device by upward irradiation according to any one of claims 1 to 3, wherein ₂ satisfies θ ₂ ≦ (１ ／) sin ⁻¹ (1 / n). 5. The illumination device according to claim 1, wherein a pitch (p) of the grooves in the light guide is equal to or less than a dot pitch of the illuminated object. 6. The grooves (4) of the light guide (3)
A V-shaped groove having a first slope (41) located closer to the light source and a second slope (42) located farther from the light source; When the distance between the observer (6) observing the illuminated object and the upper surface of the light guide is L, the length of the first slope is ΔL *.
(0.5 / 60) * π / 180 ° or less.
5. The illumination device according to any one of claims 5, wherein the illumination device is configured to perform upward illumination. 7. A transparent section having a plurality of projections (73) having an inclined surface at an angle θ ₄ with respect to the upper surface on the lower surface thereof with a plane (74) substantially parallel to the lower surface interposed therebetween. The illumination device according to any one of claims 1 to 6, wherein a prism sheet (7) is disposed on the upper surface of the light guide. 8. The angle θ of the slope of the prism sheet
_The illumination device according to claim 7, wherein ₄ is in a range of 30 ° ≦ θ ₄ ≦ 50 °. 9. The illumination device according to claim 7, wherein a pitch (P) of the inclined surface of the prism sheet is equal to or less than a dot pitch of the illuminated object. 10. An observer observing the object to be illuminated (6).
When the distance between the prism sheet and the upper surface of the light guide is L, the length of the slope of the prism sheet is ΔL * (0.5 / 6).
0) The lighting device by upward irradiation according to any one of claims 7 to 9, wherein the angle is not more than * π / 180 °. 11. A cross-sectional transparent shape in which a plurality of convex portions (73) having an inclined surface at an angle θ ₄ with respect to the lower surface are arranged on the upper surface with a plane (74) substantially parallel to the upper surface interposed therebetween. The illumination device according to any one of claims 1 to 6, wherein a prism sheet (7) is disposed on the upper surface of the light guide. 12. The illumination device according to claim 11, wherein the angle θ _{4 of the} inclined surface of the prism sheet is in a range of 30 ° ≦ θ ₄ ≦ 50 °. 13. The illumination device according to claim 11, wherein a pitch of the grooves of the prism sheet is equal to or less than a dot pitch of the object to be illuminated. 14. In the prism sheet, when a distance between an observer (6) observing the object to be illuminated and the upper surface of the light guide is L, the length of the slope is ΔL *.
(0.5 / 60) * π / 180 ° or less.
14. The illumination device according to any one of claims 13 to 13, wherein the illumination device is configured to perform upward illumination. 15. The light guide according to claim 1, wherein a plurality of grooves (8) are arranged on the upper surface of the light guide at predetermined intervals in a direction orthogonal to a longitudinal direction of the light source. Illumination device by top irradiation. 16. The groove (8) provided in a direction perpendicular to the longitudinal direction of the light guide is a V-shaped groove.
It is the apex angle theta ₅ of shape, the illumination device according to the top illumination according to claim 15 in the range of _{80 ° ≦ θ 5 ≦ 120 °} . 17. The upper part according to claim 1, wherein the light guide is formed of a wedge-shaped plate, and the light source is disposed on a side surface (33) having a larger thickness. Illumination device by irradiation. 18. A liquid crystal display device for illuminating a liquid crystal screen using the illumination device for upward irradiation according to any one of claims 1 to 17.