JP2003217326A - Lighting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem in a conventional lighting system using a point source of light provided in a liquid crystal display device, wherein uniform illumination can not be materialized by diffusing illuminating light, because lack of luminance is caused and drop of visibility is caused by a straight scattered light. <P>SOLUTION: In this lighting system, many prisms are arranged in a horizontal direction, an optical member in which the prism rows are disposed so as to be laminated in the form of a wedge with respect to a vertical direction is disposed in the immediate front of the incident surface of a light guiding plate, a beam of illuminating light emitted from a point source of light while having a expanse is made to enter into the light guide by converting its light intensity distribution to diffuse it so as to make it uniform to the entrance surface of the light guide plate by refracting it in response to its incident angle. In addition, this lighting system illuminates a display screen with uniform brightness by illuminating light having high luminance and no scattered light, because many point sources of light are disposed in it. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device used in a reflective liquid crystal display device.

[0002]

2. Description of the Related Art Generally, a liquid crystal display device for displaying characters, numbers, patterns and the like is equipped with various types of illumination devices so that it can be used even in dark surroundings. These illuminating devices are roughly classified into a backlight illuminating device that illuminates from the back side of a transmissive liquid crystal display device and a front light illuminating device that illuminates from the front side of a reflective liquid crystal display device.

Since a normal small portable device is required to be small and lightweight and have low power consumption, a reflection type liquid crystal display device is often used for display, and a front light type illumination capable of illuminating when necessary. The device is installed.

In the conventional front light type illuminator, a light guide plate is arranged in front of the liquid crystal display screen, and illumination light is taken into the light guide plate from the lateral direction to make the entire screen bright. Therefore, it is desired to make the entire screen uniform in brightness, and a linear light source such as a fluorescent lamp is arranged on the side surface of the screen to irradiate the illumination light.

However, when a fluorescent lamp is used, there is a problem that the thickness of the illuminating device itself increases, and for a small portable device for which further miniaturization and low power consumption are desired, a light emitting diode ( It is considered to use a point light source such as an LED).

[0006]

However, when a point light source is used for illumination, the size and thickness and the power consumption can be reduced, but the difference in light intensity (luminance unevenness) on the display screen is in the vicinity of the light source. There is a problem in that unnecessary light that does not include display information is generated because it becomes large in the surrounding area. In order to solve such a problem, various attempts have been made to dispose a plurality of point light sources or to dispose a diffusion plate between the point light source and the light guide plate to reduce the peak of brightness.

For example, in Japanese Unexamined Patent Publication No. 2000-11723, a rod-shaped light guide plate is arranged between a point light source and a light guide plate, and a light beam diverging from the point light source is converted into a linear shape by the rod light guide plate. A technique for making the light incident on is disclosed. In the technology according to this publication, since the point light sources are arranged in the lateral direction,
The space is required and it becomes larger than before. In addition, the number of point light sources arranged is limited due to the configuration in which light is refracted and incident from the lateral direction, and there is a problem in that luminance is insufficient when adopted in an illumination device having a large display area.

In order to make the illumination light uniform,
Problems in an illumination device that forms an oblique reflection surface on the upper side in the light guide plate as shown in FIGS. 14 and 15 and performs illumination by a point light source will be described.

Most of the spread light beam group 54 emitted from the point light source 51 enters the light guide plate 52 from an oblique direction and propagates while repeating total reflection in the light guide plate. Therefore, there is a light ray that directly travels in the direction A of the observer without being reflected by the liquid crystal element 53.

This light ray does not include display information of the liquid crystal element 53, that is, it does not illuminate the display section, so it is unnecessary light for the observer and causes a reduction in display contrast. This unnecessary light is 2
There are various types, and the first one is a light beam that does not reflect on the reflection surface 55 provided on the surface of the light guide plate 52 and that is transmitted like the light beam 54a shown in FIG. This occurs for rays whose angle of incidence at the reflecting surface is less than the critical angle. The emission direction of the light ray 54a from the light guide plate 52 is mainly in the range of 45 to 90 degrees when the direction perpendicular to the display surface is 0 degree.

Therefore, when the observer looks at a range of about 30 degrees from the direction perpendicular to the display surface, which is the general viewing direction, it does not have much adverse effect. Observing the display surface obliquely, the display quality deteriorates only when the display surface faces the light ray 13a. Further, a light beam that is reflected by the reflection surface 55 on the upper side of the light guide plate 52 and once headed for the liquid crystal element 53 is slightly reflected on the boundary surface 56 on the lower side of the light guide plate, and is reflected on the display surface without reflecting the liquid crystal element 53. On the other hand, there is a light ray 54b traveling in a relatively vertical direction. In order to reduce as much as possible the light rays 54b that cause deterioration of display quality, it is common practice to perform antireflection treatment on the liquid crystal side surface 56 of the light guide plate.

However, the ratio of these rays 54b and the rays 54c containing display information is the reflectance R1 after the antireflection treatment.
And the reflectance R2 of the liquid crystal surface are uniquely determined, and considering the scattering of the liquid crystal surface, if coefficient K = regular reflection / total reflection,
The contrast of unnecessary light is expressed by the following formula. R1 / (R1 + 2 × K × R2) According to this, the greater the reflection / scattering degree of the liquid crystal element, the greater the unnecessary light contrast and the worse the visibility. Under normal external light illumination, the larger the viewing angle of the liquid crystal element is, the better it is. Therefore, the unnecessary light contrast tends to increase. Therefore, further removal of unnecessary light is required as the viewing angle characteristics of the liquid crystal are improved.

Here, the direction of the unnecessary light toward the observer will be described. As shown by the light rays 54b and 54c shown in FIG. 15, the light rays reflected by the reflecting surface 55 of the light guide plate 52 are
Heading toward the liquid crystal element 53 side. Here, in the coordinate system defined in FIG. 12, the ray reflected by the reflecting surface 55 does not have a component in the x direction, and if it is in the yz plane, it faces the liquid crystal and is partly on the lower surface of the light guide plate. The ray that reflects and goes back up is also in the same yz plane. Therefore, the observation angle that can be recognized as unnecessary light by the observer is also the direction from the light guide plate information in the same yz plane as the light beam.

On the other hand, the ray group 61a shown in FIG.
Since each of 61b, 61c, and 61d has a component in the x direction as a directional component on the reflecting surface, the light guide plate 52
After being reflected by the lower side surface 56, when going upward, it also goes diagonally with the x component. Therefore, the observer does not observe this ray group even when seen from the vertical direction of the light guide plate 52, and observes it when the viewpoint is tilted until it becomes parallel to the direction of the x component of the ray. That is, when viewed from directly above the light guide plate 52 in the xy plane, the light ray group 61e is observed as oblique scattered rays, and the light rays 61a to 61d are observed as linear scattered light, respectively, which causes a reduction in visibility. Becomes

A solution to this problem is described in, for example, Japanese Patent Application Laid-Open No. 10-188636. In order to solve the problems described in this publication, a large number of columnar protrusions are formed on the reflecting surface of the light guide plate,
An illumination device has been proposed which diffuses incident light from a point light source and suppresses the generation of continuous bright lines to realize uniform illumination. This technique is effective in suppressing the generation of the above-described bright lines (scattered light) that appear as linear streaks, but since the cylindrical protrusions are arranged discretely, the illumination of the table itself It is difficult to improve the display quality because the light becomes non-uniform and the efficiency of reflection on the display body is disadvantageous, resulting in a large projection shape.

Therefore, according to the present invention, an increase in the number of constituent parts is suppressed, a large number of light sources can be arranged, and a large brightness can be obtained, and scattering in the display direction peculiar to the point light source is removed to obtain uniform brightness. An object of the present invention is to provide a lighting device in which display quality is improved by using a display screen.

[0017]

In order to achieve the above object, the present invention provides a point light source for irradiating illumination light, and a light guide plate having a reflecting portion for reflecting the illumination light from the point light source toward the illuminated body. In the illuminating device including, by refracting the illumination light from the light source according to the incident angle, the emission direction and the light intensity distribution of the illumination light is converted, and an optical member is provided to emit to the light guide plate, There is provided an illuminating device in which the distance from the light source to the incident end surface of the light guide plate or the incident direction varies depending on the location of the incident end surface of the light guide plate.

Further, according to the present invention, a point light source for irradiating a light beam having a spread in the emission direction and an incident light for internally reflecting the light beam and irradiating the light beam on the display section of the liquid crystal display device are used to display the display. A light guide plate for illuminating a section, and a plurality of prisms arranged vertically between the point light source and the light guide plate. An optical member, which is formed by stacking and refracts a light beam emitted so as to spread from a point light source in a direction according to an incident angle thereof, wherein the optical member is refracted according to an incident direction, Provided is an illuminating device which emits a light beam uniformly diffused to an incident end surface of a light plate to illuminate a display unit of the liquid crystal display device with uniform brightness.

In the illuminating device having the above-described structure, when the illuminating light, which is composed of the light rays expanded from the point light source, is incident on the optical member, the illuminating light is incident on the wedge-shaped optical member having a plurality of centrally protruding prisms. After being refracted in various directions depending on the incident angle, it is incident on the light guide plate, propagates while being totally reflected inside the light guide plate, and is provided on a part of the plane on the viewer side of the light guide plate. Rays are reflected by the reflective surface, which is then reflected by the liquid crystal display element surface and evenly exits to the viewing surface side, eliminating unnecessary light in the display direction specific to the point light source, resulting in a uniform display screen brightness. It becomes

[0020]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. As a first embodiment of the lighting device of the present invention, a lighting device including a point light source will be described. FIG. 1 shows the configuration of the liquid crystal display device as viewed from the observer's viewing direction, that is, from above, and FIG.
The cross-sectional structure seen from the direction is shown. The arrow indicates the traveling direction of the light beam.

This lighting device is arranged in a U-shaped casing 5 and is driven by a light emission control circuit (not shown) to emit light. For example, light emitting diodes (LED) 1a, 1b, 1
a point light source 1 using c, an optical member 2 that receives a light beam emitted so as to spread from the point light source 1 and refracts the light beam according to the incident angle, a reflective liquid crystal display element (hereinafter, referred to as a liquid crystal element). (Referred to as 4) above the display surface, and is configured by the light guide plate 3 that uniformly illuminates the display surface by the light rays incident from the optical member 2. Here, in order to simplify the description, an example in which three point light sources are used has been described, but the number of point light sources is an arbitrary number in consideration of the required brightness value and power consumption. Further, the light emitting diodes are linearly arranged in the housing 5 so that they are equidistant from the incident end surface 3d of the light guide plate 3.

The optical member 2 includes an incident end surface 3 of the light guide plate 3.
Prism rows 6a, 6b, 6 arranged immediately before d and having a large number of micro prisms (triangular prisms) arranged in the horizontal direction
6n are stacked so as to project in a "wedge shape" in a plurality of stages in the vertical direction, and the light spread from the point light source 1 is refracted by the respective prisms according to the incident angle to the light guide plate 3. Make it incident. The optical member 2 is made of transparent resin, glass, or the like. Here, the prism apex angle is set to 90 degrees, but it can be variously changed according to the design. Such an optical member 2 is characterized in that each prism has a different distance from the point light source 1 or an incident angle.

The inside of the casing 5 also functions as a reflection plate for efficiently emitting the illumination light having the spread of the point light source to the light guide plate 3, and on the inner surface thereof, aluminum or white Teflon is used. (Registered trademark), barium sulfate, or
A high-reflectance member made of powder such as magnesium oxide is provided. Further, these light reflecting members may be formed in a sheet shape and attached to the inner wall of the housing 5.

On the upper surface side of the light guide plate 3, a large number of minute V
One wall surface of the V groove on the side of the point light source 1 on which the groove is formed serves as a reflecting surface 3a for reflecting a light ray. The material of the light guide plate 3 is made of a transparent resin, such as acrylic, polycarbonate, or polyolefin material, and has a refractive index of about 1.5. Among the light rays incident on the light guide plate 3, the light rays having an incident angle equal to or greater than the critical angle propagate inside the light guide plate 3 while totally irradiating the flat portion 3c and the bottom surface 3b facing the flat portion 3c. The critical angle is calculated from the refractive index of the material.
Calculated with sin (1 / 1.5), it is about 42 degrees. A part of a light ray propagating in the light guide plate 3 and having an incident angle equal to or greater than the critical angle is reflected toward the display element 4 by the minute reflection surface 3a, and the display surface is changed according to the reflectance of the display element 4. By reflecting the light and transmitting it through the light guide plate 3 toward the observer side, the information displayed on the display element 4 can be observed brightly.

Refraction when a light beam from a point light source enters the optical member 2 will be described below. FIG. 3 is an enlarged configuration diagram of a part of the prism array of the optical member 2 as seen obliquely from above, and FIG. 4 is a diagram of the incident surface side of the optical member 2 as seen from the front. Further, FIG. 5A is an enlarged configuration diagram of a part of the prism row viewed from above, and FIG. 5B is an enlarged configuration diagram of a part of the prism row in cross section. The arrow in the figure
A light beam emitted from one point light source 1 is shown with a width, and in order to facilitate understanding of the description, one of the prisms 5a to 5n on the upper side of the optical member 2 has two prisms.
The light rays incident on the surface will be described. Hereinafter, FIG. 3 and FIG.
6 and 6, it is shown that two light rays are incident, but this shows that the light ray from one point light source has a width, and two light rays from two light sources are incident. It does not indicate that it is in a working state.

The rays 7 and 8 emitted from the point light source 1 (not shown) and spreading in the vertical direction have an emission angle of approximately 0 degrees (incident end face 3).
(in the direction perpendicular to d) from the incidence planes 5a1, 5b1, 5c1, ... 5n1 and 5a2, 5b2, 5c2 of the prism rows 5a-5n,
… Injects into 5n2 and refracts each.

For example, in the light ray 7, the light ray 7a which is incident in the vicinity of the emission angle of 0 degree, that is, in the horizontal direction (z-axis direction) is shown in FIG.
As shown in (b), when incident on the incident surface 5a (5a1), the y-axis direction is maintained as it is and refracted only in the x-axis direction as shown in FIG. 5 (a). Further, when the light beam 7b having an emission angle from the point light source in the upward direction (y-axis direction) is incident on the incident surface 5b (5b1) at the upper stage of the incident surface 5a,
As shown in (b), the light is refracted in the x-axis direction while having an inclination in the y-axis direction, that is, it is refracted in a slightly obliquely upward direction.

As described above, the light rays 7 (7a to 7n) incident on the respective incident surfaces of the optical member 2 are refracted in a fixed direction in the x-axis direction, but upward in accordance with the radiation angle of the light ray 7. Since it is also refracted, it is refracted in an obliquely upward direction according to the radiation angle.

As shown in FIG. 6A, the light rays which are simultaneously refracted in the y-axis direction and the x-axis direction according to the angle (radiation angle) incident on the incident surface of the optical member 2 are guided by the light guide plate 3. When viewed from the incident end face B side, the light beam distribution is as shown in FIG. 6B, and the light beam behaves like a curved light source.

Further, although an example in which there is no divergence in the x-axis has been described so far, in reality, many light rays also have divergence in the x-axis direction due to the point light source, and these rays are shown in FIG. The light is refracted as shown in FIG.
The group of refracted rays is as shown in (b). Similar to FIG. 6B, when viewed from the incident end surface C side of the light guide plate 3, these rays also become a light ray group in a state of being spread over the entire incident end surface C as shown in FIG. 7C. This is a locus whose phase is shifted by a half cycle from the locus shown in FIG. 6B, and when these are combined, the locus shown in FIG. 8 is obtained.

6 (a) and 6 (b) are diagrams showing a ray having a specific emission direction from the point light source 1, but in reality, the angle distribution as a point light source is further continuously changed. Since it is a group of rays that have, when observed from different angles in the xz plane, not from the direction of the incident end faces B and C,
Further, the curve group is out of phase with FIG. 6B and FIG. 7B, and is converted into a group of light rays close to the surface light source as a whole.

From the above, in the illuminating device according to the first embodiment, a prism row in which a large number of microprisms (triangular prisms) are arranged is laminated in a large number of stages so as to vertically project in a "wedge shape". By arranging the formed optical member 2 immediately in front of the light guide plate, a wide light beam emitted from a point light source is refracted in accordance with each incident angle to the prism and a light beam group is distributed in a plane. Then, since the light is incident on the light guide plate, bright lines due to scattered light can be prevented and the display surface of the display element can be uniformly illuminated.

Next, the illumination device of the second embodiment will be described. 9 shows the configuration of the liquid crystal display device viewed from the observer's viewing direction, that is, from above, and FIG. 10 shows the cross-sectional configuration of FIG. 9 viewed from the D direction. The arrow indicates the traveling direction of the light beam.

In the above-described first embodiment, the optical member whose light-receiving surface side projects in a "wedge shape" is used. On the contrary, in this embodiment, the "reverse wedge" shown in FIG. 10 is used. This is an example in which an incident surface having a concave shape is formed and is integrally formed on the incident end surface of the light guide plate. This is because the metal mold for resin-molding the light guide plate 11 has a "wedge-shaped" projecting shape in the part which becomes the incident end face, and the "reverse shape" is produced by the mold processing accompanying resin molding of the light guide plate 11. It forms a large number of prisms arranged in a wedge shape. Here, each prism formed on the incident end face 12 of the light guide plate 11 corresponds to the optical member 2 in the first embodiment described above.
It has the exact same shape as the prism.

Therefore, a trajectory equivalent to the trajectory of the light beam described with reference to FIGS. 6A and 7B is drawn, and the divergent light beam emitted from the point light source corresponds to each incident angle to the prism. It becomes a group of rays that are refracted and distributed over the surface,
The same effect as that of the first embodiment can be obtained.

Next, an illumination device according to the third embodiment will be described. FIG. 11 shows the configuration of the liquid crystal display device viewed from the observer's viewing direction, that is, from above, and FIG.
FIG. 13 is a cross-sectional view seen from the direction, and FIG. 13 is an enlarged view showing a part of the prism array of the optical member as seen obliquely from above. The arrow in the figure indicates the traveling direction of the light beam.

In the above-described first and second embodiments, the prism arrays in the horizontal direction are laminated in a "wedge shape" in a plurality of upper and lower stages, but in the present embodiment, immediately before the light guide plate 3, the upper and lower sides are arranged. This is an example using an optical member 31 having a “wedge” shape in which triangular prisms obliquely inclined are arranged laterally (x-axis direction) so that the center projects in the direction (y-axis direction). This optical member 3
The tip portion of 1 is cut so as to be a flat surface along the y-axis direction. These triangular prisms are
As in the above embodiment, the vertical angle or the side (one side of the side)
Are arranged so that they face the front.

Also in this embodiment, as shown in FIG.
The divergent light beam from the point light source is refracted by the optical member in the direction according to the incident direction, and the effect that the light beam group becomes a planar distribution in the light guide plate is obtained, and the bright line due to scattered light as in the past is obtained. It is possible to prevent this and illuminate the display surface of the display element more uniformly.

In this embodiment, the optical member is the light guide plate.
Although described as a separate body, it may be formed integrally with the light guide plate as in the second embodiment described above. Incidentally, the triangular prism incident surface of the optical member may be not only a linear flat surface but also a curved surface, and not only a linear wedge shape when viewed from the lateral direction, but also an intensity distribution function of a point light source, Considering the visual characteristics when changing the viewing angle of the display surface, for example, sin
It is also possible to arbitrarily set a curve, a quadratic function shape, a parabolic shape, or the like.

It should be noted that in the above-described embodiment, the optical members are prism rows in which prisms of the same shape are evenly arranged in one row. However, the present invention is not limited to this, and for example, a prism facing a point light source directly. As the largest one, as the distance from the point light source recedes to both sides, that is, the longer the distance to the prism, the narrower the prism angle (apex angle) viewed from the front side may be, and many prisms may be provided. Similarly, in the vertical direction, the prism angle may be narrowed and a large number may be arranged. Further, not only the angle of the prisms but also the number of prisms may be increased by downsizing.

[0041]

As described in detail above, according to the present invention, an increase in the number of constituent parts is suppressed, and the distance from the light source to the incident end face of the light guide plate varies depending on the position of the incident end face of the light guide plate. As a result, it is possible to provide a lighting device with improved display quality by eliminating scattering in the display direction, which is specific to the point light source, and providing a display screen with uniform brightness.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a liquid crystal display device in a lighting device of a first embodiment.

FIG. 2 is a diagram showing a cross-sectional configuration of the liquid crystal display device shown in FIG.

FIG. 3 is an enlarged configuration diagram showing a part of the optical member shown in FIG. 1 as seen from an obliquely upper direction.

FIG. 4 is a front view of the incident surface side of the optical member shown in FIG.

5A is an enlarged configuration diagram of a part of a prism row viewed from above, and FIG. 5B is an enlarged configuration diagram of a cross section of a part of the prism row.

FIG. 6 (a) is a view showing a light beam which is vertically incident on an optical member, and FIG. 6 (b) is a view showing a light beam distribution.

FIG. 7 (a) is a diagram showing a light beam incident on an optical member from an oblique direction, and FIG. 7 (b) is a diagram showing a light beam distribution.
FIG. 6C is a diagram showing a light ray group in a state of being spread over the entire incident end face.

FIG. 8 is a diagram showing a state in which the ray groups shown in FIGS. 6B and 7C are combined.

FIG. 9 is a diagram showing a configuration of a liquid crystal display device in the lighting device of the second embodiment.

FIG. 10 is a diagram showing a cross-sectional configuration of an illumination device according to a second embodiment.

FIG. 11 is a diagram showing a configuration of a liquid crystal display device in an illumination device of a third embodiment.

FIG. 12 is a diagram showing a cross-sectional configuration of an illumination device according to a third embodiment.

FIG. 13 is an enlarged configuration diagram showing a part of the optical member shown in FIG. 11 as seen from an obliquely upper direction.

FIG. 14 is a diagram showing paths of light rays in a light guide plate for explaining problems in the conventional lighting device.

15 is a diagram showing a cross-sectional configuration of the illumination device in FIG.

[Explanation of symbols]

1 ... Point light source 1a, 1b, 1c ... Light emitting diode (LED) 2 ... Optical member 3 ... Light guide plate 3d ... Incident end face 4 ... Reflective liquid crystal display element (display element) 5 ... Case 6, 6a, 6b, 6c, 6n ... Prism row

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Claims (6)

[Claims] 1. An illuminating device comprising: a point light source that illuminates illumination light; and a light guide plate that has a reflecting portion that reflects the illumination light from the point light source toward an object to be illuminated. An optical member is provided which converts the emission direction and the light intensity distribution of the illumination light by refracting according to the angle and emits it to the light guide plate, and the distance or the incident direction from the light source to the light guide plate incident end face. Is different depending on the location of the incident end face of the light guide plate. 2. A point light source for irradiating a light ray having a spread in an emission direction, and illuminating the light ray by irradiating the light ray on a display portion of a liquid crystal display device by injecting the light ray and internally reflecting the light ray. A light guide plate, and a prism row formed by arranging a number of prisms in a horizontal direction, which is arranged between the point light source and the light guide plate, in a vertical direction,
Formed by stacking in multiple stages so that it projects in a wedge shape,
An optical member that refracts a light beam emitted so as to spread from a point light source in a direction according to an incident angle of the light source, and the optical member is refracted according to the incident direction, so that the incident end face of the light guide plate is uniform. An illuminating device, which emits a light beam that is diffused to illuminate a display portion of the liquid crystal display device with uniform brightness. 3. The lighting device further accommodates a plurality of the point light sources arranged on a straight line so as to have a constant distance from an incident end surface of the light guide plate, and reflects the light on an inner wall surface thereof. A U-shaped casing provided with a use portion is provided, and the casing houses the optical member on an opening side and is attached to an incident end surface of the light guide plate. Illumination device described. 4. A point light source for irradiating a light beam having a divergence in an emission direction, and the light beam being incident on the light beam, internally reflected, and irradiating the light beam on a notation displayed on a display unit of a liquid crystal display device, A light guide plate for illuminating the notation, wherein the incident end face of the light guide plate has a plurality of prisms formed by arranging a number of prisms in a horizontal direction in a reverse wedge shape in which the prism rows are vertically wedged. The light emitted from the point light source so as to spread out is refracted in a direction according to the incident angle, and the light uniformly diffused into the light guide plate is emitted, and the liquid crystal An illuminating device, which illuminates a notation displayed on a display unit of the display device with uniform brightness. 5. A point light source for irradiating a light beam having a divergence in an emission direction, and the light beam being incident on the light beam, internally reflected, and irradiating the light beam on a notation displayed on a display unit of a liquid crystal display device, A light guide plate for illuminating the notation, and a prism array formed by arranging a large number of diagonally inclined triangular prisms in the lateral direction are laminated so as to vertically project in a wedge shape, and the point light source and the light guide plate are formed. It is arranged between the incident end face and the light emitted from the point light source to spread out,
An optical member refracting in a direction according to the incident angle, the optical member refracting according to the incident direction to emit a light beam uniformly diffused to the incident end face of the light guide plate, and the liquid crystal. An illuminating device, which illuminates a notation displayed on a display unit of the display device with uniform brightness. 6. The illumination device according to claim 5, wherein the shape of the optical member is formed on an incident end surface of the light guide plate, and the optical member and the light guide plate are integrated. Lighting equipment.