JPH07141908A - Prism member and lighting apparatus using prism member - Google Patents

Abstract

PURPOSE: To obtain a prism member and a lighting system by using it, capable of maintaining a luminance increase effect and a visual field angle regulation effect of the prism member, and simultaneously capable of removing bright and dark stripes caused by asymmetry of a luminance distribution of a prism surface. CONSTITUTION: Light sources 1, 2 are disposed on one side of a diffusion plate 3, and a prism member 4 is disposed on the opposite side of the light sources 1, 2 of the diffusion plate 3 so that the prism forming surface is positioned outside. And besides, in this lighting system having such a section shape of each prism that the section is roughly triangular and the right and left base angles are in the range of 10-50 deg., the prism member 4 is so constituted that the distances between the prism are in the range of 20-100 μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prism member suitable for an illuminating device for a backlight in a display device using liquid crystal and an illuminating device using the prism member.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices used in laptop computers and the like have been particularly strongly required to be lightweight and thin, and with full-color liquid crystal display, The backlight device is required to be thinner and brighter. As an example of such a device, as shown in Japanese Patent Laid-Open No. 63-318003, a light and thin illumination device as shown in FIG. 3 is known. That is, the reflector 3
A linear light source 34 such as a fluorescent tube on the side of the first reflecting surface 31a,
, 34 are arranged, a prism film 32 is further installed above the light sources 34, ..., 34, and a transparent film 3 for protecting the prisms of the prism film 32 is provided thereon.
3 are arranged and configured. Then, the light directly arriving from the light sources 34, ..., 34 or the light reflected by the reflecting plate 31 is used as illumination light through the prism film 32. In such a configuration, for example, when the apex angle of each prism of the prism film 32 is 90 °, the prism film 3 is formed at an angle other than the angle close to the vertical from the horizontal plane.
The light incident on 2 is remarkably directional by being refracted by the prism, and the light incident on the prism film 32 at an angle nearly perpendicular to the horizontal plane is totally reflected by the prism and returns to the light source side. Therefore, the light source 34,
The luminance directly above 34 does not become too large, and uniform illumination can be obtained from the light emitting surface of the illumination device.

Further, as disclosed in Japanese Patent Laid-Open No. 2-257188, an illuminating device as shown in FIG. 4 is also known. That is, one linear light source 42 such as a fluorescent lamp is arranged on the reflection surface 41a side of the reflection plate 41, and further, this light source 42
The diffusing plate 43 is installed above the diffusing plate 43, and the regulating plate 44 with the horizontal surface facing the diffusing plate 43 side is installed directly above the diffusing plate 43. Then, the spread of light diffused from each point on the diffusion plate 43 is regulated by the regulation plate 44. When acrylic resin is selected as an example of the material of the regulation plate 44 and the apex angle of the prism formed on the surface of the regulation plate 44 on the side opposite to the horizontal plane is set to 90 °, the viewing angle is about 35 degrees. It is known that the upper luminance is increased by 30% as compared with that without the regulation plate 44. In addition, "regulation plate" here
Means that one side is smooth and the other side has an apex angle of 60
It is a transparent plate in which prisms having an angle of ° to 180 ° are continuously arranged.

In the illuminating device using such a regulating plate (prism film), the diffused light obtained from the diffuser 43 is quite close to the perfect diffused light. Therefore, FIG.
As shown in FIG.
The luminance distribution on 1 and the luminance distribution on the downward-sloping surface 52 are not bilaterally symmetrical, and are in the relationship of specular reflection images. For example, when the observation direction is tilted to the right in FIG. 5 from above the diffusion plate 44 vertically, the prism surface 51 is observed as a dark stripe because the brightness on the prism surface 51 is smaller than the brightness on the prism surface 52. I will end up. Such stripes cause the image quality of the liquid crystal display device installed above the illumination device to be significantly impaired. Therefore, the present invention provides a prism member and a prism member capable of eliminating the bright and dark fringes caused by the asymmetry of the brightness distribution of the prism surface of the prism member while maintaining the brightness increasing effect and the viewing angle regulating effect of the prism member. It is an object to provide a lighting device used.

[0005]

In order to achieve the above object, a prism member according to the present invention is a prism member having a plurality of prisms formed on one surface thereof. "Pitch") is 20 to 100 [mu] m. In a preferred aspect of the present invention, the prism member is made of polycarbonate resin or acrylic resin, and the prism of the prism member has a substantially triangular cross-sectional shape, and the base angle on the left and right of the triangle is 10 to 50 °. Such a configuration can be adopted.

Here, the prism pitch is 20 to 100.
The reason why μm is preferable is as follows. For example, when observing a liquid crystal display device of about 10 inches, a person having normal eyesight often sees the display surface from a distance of about 40 cm to 80 cm. It is very difficult for a human eye to identify a fine pattern of about 100 μm or less when seeing a subject separated by such a distance. Therefore, when the prism pitch of the diffuser plate is set to 100 μm or less, a striped pattern due to the asymmetry of the luminance distribution of the left downward surface 51 and the right downward surface 52 of the prism in FIG. It becomes very difficult and, fortunately, people can barely see the stripes. Furthermore, by limiting the pitch of the prisms in this way, the brightness increasing effect and the viewing angle regulating effect of the diffuser plate are not impaired at all. On the other hand, if the pitch of the prisms is made too small, moire fringes may be observed due to the relationship with the cell pitch of the liquid crystal display device. Therefore, while preventing moire fringes from occurring, light diffraction occurs and the liquid crystal display device It is necessary to prevent such a phenomenon that the white light required for the above cannot be obtained.

Therefore, it is necessary to regulate the pitch of the prism to 20 μm or more and 100 μm or less. Polycarbonate resin or acrylic resin is preferable as the material of the prism member because it has a high light transmittance because of its excellent transparency, and has an appropriate hardness, and also has excellent heat resistance and processability. This is because it is suitable for a lighting device. Furthermore,
The cross-sectional shape of the prism is generally triangular, and it is preferable that the left and right base angles of this triangle are 10 to 50 ° in consideration of the refractive index of the material, the viewing angle, and the rate of increase in luminance. Here, the viewing angle and the rate of increase in luminance are closely related to the refractive index of the material and the left and right base angles of the triangle, and when an appropriate polycarbonate resin or acrylic resin is used as the material of the prism, The ratio is in the range of 1.4 to 1.7, and in this range, the base angles of the left and right sides of the triangle are 10 to 10.
This is because when it is set to 50 °, a practically appropriate increase in viewing angle and brightness can be obtained. That is, if the base angle is less than 10 °, sufficient luminance cannot be obtained, and if the base angle exceeds 50 °, the viewing angle is conversely narrowed.

Further, in order to achieve the above object, the illuminating device according to the present invention is configured to include the prism member, the diffusing plate, and the light source portion. Such an illuminating device is suitable for use as a backlight in a display device using liquid crystal, for example. In such an illuminating device, it is desirable that the diffusion plate be disposed between the prism member and the light source portion. This is because the diffusion plate effectively diffuses the light from the light source portion into the prism to enhance the illumination effect. In addition, the light source,
It is not particularly limited, and for example, one or more fluorescent tubes, electric bulbs, halogen lamps, tungsten lamps,
Alternatively, a light emitting diode or the like can be used. Furthermore,
Although the configuration of the light source portion is not particularly limited,
In order to increase the degree of freedom in designing as an illuminating device, the light source portion may include a light source and a light guide member. Here, the light guide member means a member for efficiently guiding the light of the light source to a predetermined position, and for example, a light guide tube made of a hollow or filled acrylic resin is preferable.

In addition, as another preferable aspect of the light source portion of the present invention, the light source portion is composed of a light source, a reflector and a light guide member. This is because the reflection plate can more effectively supply the light from the light source to the diffusion plate or the prism member. In the present invention, it is necessary to fix each component in actual use, but the fixing method is not particularly limited, and even if the entire component is externally caulked using a jig. Alternatively, it is also possible to fix it by using an adhesive or the like.

[0010]

According to the structure of the prism member of the present invention, the prism pitch is limited within a predetermined range so as to maintain the brightness increasing effect and the viewing angle regulating effect of the prism member. It is possible to eliminate the bright and dark fringes caused by the asymmetry of the brightness distribution on the prism surface while maintaining the effect of increasing the brightness of the member and the effect of restricting the viewing angle. In this prism member, the shape of each prism is substantially triangular in cross section, and further, the apex angle of the prism is further limited within a predetermined range so as to maintain the brightness increasing effect and the viewing angle regulating effect of the prism member. With this structure, the bright and dark fringes caused by the asymmetry of the luminance distribution on the prism surface can be further eliminated while maintaining the luminance increasing effect and the viewing angle regulating effect of the prism member.

Further, according to the structure of the illuminating device of the present invention, the prism member is structured so as to limit the pitch of the prism within a predetermined range so as to maintain the brightness increasing effect and the viewing angle regulating effect of the prism member. By arranging this prism member with respect to the light source through a diffusion plate, a brighter illuminating device can be obtained as an illuminating device, and when the viewing direction of the illuminating device is changed to the prism vertical direction. The light and dark streaks seen in can be obscured. Further, in this illuminating device, each prism of the prism member in which the prism member is arranged with respect to the light source via the diffuser plate has a substantially triangular cross-sectional shape, and further, the brightness increasing effect and the viewing angle regulating effect of the prism member are provided. To maintain the prism pitch, if necessary the apex angle,
If it is configured to be limited to within a predetermined range, while maintaining the brightness increasing effect and viewing angle regulating effect of the prism member,
The bright and dark fringes caused by the asymmetry of the luminance distribution on the prism surface can be eliminated.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A prism member and an illuminating device using the prism member according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of an illuminating device using a prism member according to a first embodiment of the present invention, in which 1 is a reflection plate, 2 is a W-shaped fluorescent tube, 3 is a diffusion plate, and 4 is a prism plate. . The fluorescent tube 2 is disposed on one side of the diffusion plate 3, and the diffusion plate 3 is provided.
The prism plate 4 is disposed on the side opposite to the fluorescent tube 2 such that the prism forming surface is on the outside. Therefore, the light from the fluorescent tube 2 enters the diffuser plate 3 directly or after being reflected by the reflector plate 1, passes through the diffuser plate 3, and enters the prism plate 4. The cross-sectional shape of each prism is approximately an isosceles triangle, and the left and right base angles thereof are 45 °.

Each prism has a striped shape in plan view, and the distance between adjacent apex angles is 50 μm. Polycarbonate resin is used as a material for the prism plate, and the size is 99 mm in length, 66 mm in width, and 5 mm in thickness (from the top to the back). Such a prism plate is produced by injection-molding an original plate and then cutting the prism with a diamond blade. In such an illumination device, not only bright and dark fringes are not observed, but so-called moire fringes are not observed even when used as a backlight of a liquid crystal display device, and a very bright image with good image quality is obtained. The brightness at this time is about 38% higher than when there is no prism plate, and the viewing angle is about 60 ° (± 30 ° when the vertical upward direction is 0 °) in the direction perpendicular to the prism groove. It is equal to or wider than about 80 ° in the parallel direction (± 40 ° when the vertical upward direction is 0 °).

FIG. 2 is a sectional view of an illuminating device using a prism member according to the second embodiment of the present invention. In the second embodiment, a prism plate is applied to a lighting device using an acrylic resin, which is well known as a light source system, as a light guide. In FIG. 2, 21 is a reflection plate, 22 is a linear fluorescent tube, 23 is a diffusion plate, 24 is a prism plate, and 25 is an acrylic resin light guide. The second embodiment differs from the first embodiment in that the light source is not composed of the fluorescent tube 2 and the reflector 1 as in the first embodiment, but instead of the two fluorescent tubes 22 and 22. Two reflectors 21 and 21 that reflect the light of the fluorescent tubes 22 and 22, and a light guide 25 that guides the light from each fluorescent tube 22 and the reflected light from the reflector 21 to a predetermined portion.
And another reflecting plate 26 such as a reflecting plate for preventing light from leaking downward on the lower surface of the light guide 25. Also at this time, the diffused light emitted from the diffusion plate 23 is
It is close to perfect diffused light (Lambertian). Acrylic resin is used as an example of the material of the prism plate 24, the apex angle of the prism is set to 110 °, and the pitch of the prism is set to 50 μm. At this time, the viewing angle is about 80 ° (0 ° above the vertical.
Is ± 40 °), and the rate of increase in luminance is about 25%.

As is apparent from the above-mentioned two embodiments, the characteristics obtained depending on the angle of the apex angle of the prism and the material (that is, the refractive index) are different, and it is necessary to appropriately determine them depending on the purpose of use. Therefore, according to the above-mentioned embodiment, by limiting the apex angle and pitch of the prism within the predetermined range so as to maintain the brightness increasing effect and the viewing angle regulating effect of the prism plate, the asymmetry of the brightness distribution of the prism surface It is possible to eliminate the bright and dark stripes caused. Therefore,
In addition to obtaining a brighter illuminator, the bright and dark stripes seen when changing the viewing direction of the illuminator to the prism vertical direction can be obscured. The present invention can be applied to, for example, an internally-illuminated signboard other than the above-mentioned embodiments.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an illumination device using a prism member according to a first embodiment of the present invention.

FIG. 2 is a sectional view of an illuminating device using a prism member according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view of a conventional lighting device.

FIG. 4 is a cross-sectional view of another conventional lighting device.

5 is an enlarged explanatory view of a prism portion of the lighting device of FIG.

[Explanation of symbols]

1, 2, 26 ... Reflector, 2, 22 ... Fluorescent tube, 3, 23
... Diffusion plate, 4, 24 ... Prism plate, 25 ... Light guide.

Claims (5)

[Claims] 1. A prism member having a plurality of prisms formed on one surface thereof, wherein the prism pitch is 20 to 10
A prism member having a thickness of 0 μm. 2. The prism member is made of polycarbonate or acrylic resin, and the prism has a substantially triangular cross-sectional shape, and the left and right base angles of the triangle are 10 to 50.
The prism member according to claim 1, wherein the prism member has an angle of 0 °. 3. A lighting device in which a prism member, a diffusion plate, and a light source portion are arranged in this order, and the prism member according to claim 1 or 2 is used as the prism member. . 4. The illumination device according to claim 3, wherein the light source portion includes a light source and a light guide member that guides light from the light source to the diffusion plate. 5. The light source section, wherein the light source portion guides the light source, a reflection plate that reflects the light from the light source, and the light from the light source and the light reflected by the reflection plate to the diffusion plate. The lighting device according to claim 3, further comprising: