JPH0615007U - Surface light source - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to provide a surface light source device having high brightness and less uneven brightness. According to the surface light source device of the present invention, diffused light is emitted from a flat emission surface, and a transparent sheet of quadrangular pyramid or cone having a curved apex angle is arranged in front of the emission surface to eliminate bright and uneven brightness. It was done.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a surface light source device used for a backlight of a liquid crystal display device.

[0002]

[Prior art]

 As a surface light source device used for a backlight of a liquid crystal display device, there are, for example, one using a light guide as shown in FIG. 7 and one using a reflecting member as shown in FIG.

The surface light source device shown in FIG. 7 allows light from the light source 11 to enter the light guide body 12 made of a transparent member through the incident end face 12a, and emits it as diffused light through the diffusion plate 13 arranged on the surface thereof. The surface light source device is thus obtained.

The liquid crystal display panel 10 is arranged on the front surface of the diffusion plate 13 of this surface light source device to illuminate it.

In FIG. 8, the light source 11 is arranged on the reflecting surface 14a side of the reflecting plate 14 having an appropriate shape, and the diffusing plate 13 is further arranged. After being reflected by 14, the light reaches the diffuser plate 13 and passes through it to become diffused light, which is used as a surface light source. In the surface light source device shown in FIG. 8 as well, for example, the liquid crystal display panel 10 is arranged on the surface thereof to illuminate it.

Among these surface light source devices, there is known one in which a transparent sheet having a prism-shaped surface is arranged between the surface light source device and the liquid crystal display plate in order to increase brightness. That is, in the surface light source device of FIGS. 8 and 9, in front of the surface light source device having a structure in which a sheet 31 having a sectional shape as shown in FIG. 9 and a shape as shown in FIG. The display plate 10 is placed, and the liquid crystal display plate 10 is illuminated by diffused light from the surface light source device including the sheet 31.

In such a surface light source device in which the sheet 31 is arranged, the brightness is increased by the action of the sheet 31, and in particular, the brightness in the direction perpendicular to the surface of the sheet 31, that is, the direction perpendicular to the surface of the liquid crystal display panel 10. Becomes big. Also, as shown in FIG. 10, the lengthwise direction 32 of the prism is inclined with respect to the frame side of the liquid crystal display panel 10 and thus with respect to the bus line of the liquid crystal display panel to prevent stripes from appearing. You can

[0008]

[Problems to be solved by the device]

 The surface light source device provided with the above-mentioned sheet has a certain role in increasing the brightness, but it is still insufficient. In addition, uneven brightness may occur at the apex of the prism shape.

The present invention provides a surface light source device that is brighter and has no uneven brightness by changing the surface shape of the sheet.

[0010]

[Means for Solving the Problems]

 The surface light source device of the present invention is a surface light source device that emits diffused light through the surface of a diffuser plate such as a device using a light guide or a device using a curved reflector as described above. A sheet is arranged to increase the number of prisms, and the surface shape of this sheet is arranged with a large number of prism-shaped microprotrusions adjacent to each other. It was done. That is, in the surface light source device of the present invention, by making the shape of the projection a cone or a pyramid, the number of surfaces having the effect of refracting light by the projection and directing the light in a specific direction is increased. It was made uniform in each direction so as to be uniformly bright as a whole. Furthermore, by making the apex angle of each projection a curved surface, uneven brightness (locally brightening, etc.) due to a sudden change in the direction of the prismatic surface is eliminated, and the direction of the array of minute projections is changed to the liquid crystal. By making it oblique to the bus line or frame in the display panel, it was possible to prevent the occurrence of striped patterns when used as a backlight of a liquid crystal display panel.

The minute projections of the sheet used in the surface light source device of the present invention are not limited to cones and quadrangular pyramids, and the surfaces of prisms (projections) that eventually contribute to refraction are arranged in a relatively well-balanced direction and area. If

Further, it is more preferable that the portion where the adjacent protrusions of the sheet are connected to each other (the deepest portion of the concave portion) is a curved surface. That is, even in this concave portion, the direction of the surface changes abruptly, which may cause uneven brightness. However, if the surface is curved, this uneven brightness can be completely prevented.

[0013]

【Example】

 Next, an embodiment of the surface light source device of the present invention will be described.

FIG. 1 is a diagram showing an example of using the light guide of the surface light source device of the present invention and showing a configuration when used as a backlight of a liquid crystal display panel, where 1 is a light source and 2 is a light guide. An optical body, a diffusion plate 3 and a reflection plate 4 have substantially the same structure as a surface light source device using a general light guide. 5 is a sheet used in the present invention, the surface of which is arranged with minute projections 6 as shown in FIG. A large number of the minute projections 6 of the sheet 5 are arranged side by side in the directions of arrows A and B, and one row thereof is enlarged and shown in FIGS. 3 and 4. As can be seen from this figure, each minute protrusion 6 has a quadrangular pyramid shape, and its apex angle portion 6a is a curved surface (convex surface).

The surface light source device of this embodiment in which the sheet 5 having the above-described shape is arranged becomes an extremely bright light source by the sheet 5, and the brightness in the direction perpendicular to the surface is particularly increased. Further, the respective protrusions 6 are arranged in the A direction or the B direction, and when the liquid crystal display plate 10 is arranged as shown in FIG. 1, the direction in which the protrusions 6 are arranged becomes an oblique direction with respect to the frame of the liquid crystal display plate 10. . That is, the protrusions 6 are arranged obliquely with respect to the bus line of the liquid crystal display panel. As a result, it is possible to prevent the striped pattern due to the sheet having the protrusions from appearing.

FIG. 5 is a view showing a sheet of another embodiment of the surface light source device of the present invention, in which the minute projections have a curved apex angle of the cone.

Also in this embodiment, the number of refracting surfaces is increased and the refracting surfaces are substantially evenly distributed in all directions, so that the surface light source becomes more uniform and the brightness is increased. Further, if the arrangement direction of the cones is oriented in the frame direction of the liquid crystal display panel or in an oblique direction with respect to the bus line of the liquid crystal display panel, it is possible to prevent a striped pattern from appearing.

In each of the above-described embodiments, the connecting portion of the adjacent small protrusions is as shown by the chain line C 1 in FIG. Therefore, the direction of the refracting surface changes abruptly here, and a phenomenon similar to that at the apex angle of a cone or a pyramid occurs, which may be a factor that slightly hinders the uniformity of brightness. Therefore, it is more desirable to make the connection portion (the portion of the chain line C in FIG. 6) of the conical or pyramid-shaped minute projections indicated by the reference symbol D for uniform brightness.

In the above embodiment, the present invention is applied to a surface light source device using a light guide, but other surface light source devices such as a surface light source device using a reflecting member as shown in FIG. Can also be applied to.

[0020]

[Effect of device]

 In the surface light source device of the present invention, the brightness can be increased and uniform brightness can be obtained by arranging the transparent sheet having a large number of minute protrusions having a curved tip in front of the emitting surface. It has a so-called effect. If the connection between adjacent protrusions is curved, it is possible to obtain more uniform brightness. Further, when this is used as a backlight of a liquid crystal display panel in combination to form a liquid crystal display device, the arrangement direction of the minute protrusions of the sheet should be oblique to the bus line or frame side of the liquid crystal display panel. By doing so, it is possible to prevent unnecessary striped patterns from appearing on the display plate.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of a surface light source device of the present invention.

FIG. 2 is a plan view of a transparent sheet used in the above embodiment.

FIG. 3 is an enlarged view of the surface shape of the transparent sheet.

FIG. 4 is an enlarged cross-sectional view of minute protrusions on the transparent sheet.

FIG. 5 is a plan view of a transparent sheet according to another embodiment of the present invention.

FIG. 6 is a view showing another example between the minute protrusions of the transparent sheet used in the present invention.

FIG. 7 is a sectional view of a conventional example of a surface light source device using a light guide.

FIG. 8 is a sectional view of a conventional example of a surface light source device using a reflector.

FIG. 9 is a sectional view of a transparent sheet used in a conventional surface light source device.

FIG. 10 is a plan view of a transparent sheet of the above conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source 2 Light guide 3 Diffusion plate 5 Sheet having fine protrusions 6 Fine protrusions 7 Liquid crystal display plate

Claims (4)

[Scope of utility model registration request] 1. A surface light source device in which a sheet having an emission surface for emitting diffused light from a plane emission surface and having a large number of minute projections on one surface thereof is arranged in front of the emission surface, the projection of the sheet. Is a surface light source device having a quadrangular pyramid or a conical shape whose apex angle is a curved surface. 2. The surface light source device according to claim 1, wherein the protrusions adjacent to each other of the sheet are connected by a curved surface. 3. A liquid crystal display plate is arranged in front of the surface light source device, and a projection of the sheet of the surface light source device is obliquely arranged with respect to a bus line or a frame of the liquid crystal display plate. The liquid crystal display device according to claim 1. 4. The liquid crystal display device according to claim 3, wherein the protrusions are arranged in a direction of 45 ° with respect to a bus line or a frame of the liquid crystal display plate.