JPH02257188A - Illuminator - Google Patents

Abstract

PURPOSE:To obtain a thin and even brightness distribution by forming a regulating board which guides diffused lights emitted from each point on a diffusing board on a side opposite to the light source of the diffusing board so that the regulating board is provided in parallel or integrally with the diffusing board. CONSTITUTION:The regulating board 4 which respectively and overall guides lights diffused from each point on the diffusing board 3 in a direction vertical to the diffusing board 3 and regulates the spread of the diffusion is formed on the front face of the diffusing board 3 so that the regulating board is provided in parallel or integrally with the diffusing board. For the regulating board 4, a transparent board which is linear on the side of the diffusing board 3, provided with a cross sectional form of a saw tooth shape on the other side and arranged so that the length direction of the part of the saw tooth shape is aligned with the length direction of the linear light source is imagined. Thus since the lights diffused at a large angle can be used and an angle of the diffusing direction narrows, only the brightness is heightened with the brightness distribution kept even.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a lighting device suitable for use as a backlight for a display device using liquid crystal, for example.

[Prior Art] A display device using a liquid crystal needs to illuminate a display surface of a certain area with uniform brightness. Therefore, a lighting device that is thin and capable of uniformly illuminating within a certain plane is required. As a lighting device that satisfies such requirements, a lighting device as shown in FIG. 4 is conventionally known. That is, a linear light source 2 such as a fluorescent tube is placed on the opposite slope la side of the reflecting plate l, and a diffuser plate 3 is further placed. The light that reaches 3 is diffused by this diffuser plate 3 and used as illumination light.

Such illumination devices are known in which improvements have been made to the curved shape of the reflecting plate 2, etc. in order to obtain diffused light that is thin and has uniform brightness. A product that satisfies the above requirements to a large extent has been obtained.

[Problems to be Solved by the Invention] Such a lighting device is required not only to be thin and have a uniform luminance distribution, but also to be capable of bright lighting with as high luminance as possible.

Therefore, it is an object of the present invention to provide a thin, high-intensity lighting device that can provide a uniform brightness distribution.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the lighting device of the present invention includes a diffuser plate that diffuses light from each point on the diffuser plate in front of the diffuser plate of the conventional lighting device described above. A regulating plate is arranged to regulate its spread within a certain angular range centered on a direction perpendicular to the direction.

For example, in a display device using a liquid crystal, when viewing an image or the like on a display board, the image or the like is mostly viewed from a direction perpendicular to the display board.

The present invention was made based on the fact that light diffused by a diffuser plate at a large angle with respect to the perpendicular line contributes little or nothing to the observation of the display plate. In other words, the light diffused from each point on the diffuser plate is guided as a whole in a direction perpendicular to the diffuser plate, and a regulating plate for regulating the spread is installed in parallel or integrally with the front surface of the diffuser plate. be.

With these, the brightness of the light from the diffuser plate is increased by making use of light that is diffused at a large angle that has not been used conventionally. Moreover, since the spread of the light from above the diffuser plate is guided by the regulating plate so that the angle with respect to the vertical direction is small, the overall brightness can be achieved while maintaining the uniformity of the brightness distribution.

The regulating plate used in the present invention is a transparent plate having a straight line on the diffusion plate side and a serrated cross section on the other side, and the length direction of the serrated part is a straight line, as will be specifically explained later in the examples. It is conceivable that the light source is arranged in the longitudinal direction.

[Example] Next, an example of the lighting device of the present invention will be described based on the drawings. FIG. 1 is a sectional view of an embodiment of the present invention, in which 1 is a reflecting plate, 2 is a linear light beam, and 3 is a diffuser plate, which have the same structure as a conventional lighting device. Further, reference numeral 4 denotes a regulating plate arranged in parallel on the diffuser plate 3, which has a continuous cross-sectional shape as partially enlarged in FIG. 2 and has the same area as the diffuser plate 3. It is made of transparent plate.

As shown in FIG. 2, a transparent regulating plate 4 whose surface 4a on the side of the diffusion plate 3 is flat (straight in cross section) and whose surface 4b on the opposite side is sawtooth in cross section is placed on the diffusion plate. Then, the light f21 from the diffuser plate is refracted by the regulating plate 4 and then heads upward. At this time, the angle 01 when the light enters the surface 4a, that is, the angle θ1 of the light emitted from the diffuser plate 3, goes in the direction of an angle θ2 with respect to a line perpendicular to the diffuser plate 3 after exiting the surface 4b. Here, as is clear from the drawing, θ2<θ1. Therefore, the diffused light generated from points A, B, and C on the diffuser plate 3 in the conventional illumination device shown in FIG. 4 becomes as shown in the figure after exiting the surface 4b of the device of the present invention.

In this embodiment, when the angle O of the regulating plate 4 becomes large, as shown in FIG. side 4
Total reflection occurs at b. Therefore, if the angle θ is too large, the amount of light will be lost. Also, there is less light going diagonally,
Observation from an oblique direction becomes difficult. However, generally light source 2
Directly above, the diffuser plate 3 is closest to the light source 2, and therefore the brightness is higher than the other areas. Therefore, at the expense of some loss of light quantity, the above-mentioned total internal reflection is used inversely as a light source. By removing this, it is also possible to make the brightness uniform on the diffuser plate 3 without using other means or by using it in combination with other means. On the other hand, if θ is too small, the regulating plate 4 will become close to a parallel plane plate, and the effects of the present invention will hardly be obtained. Therefore, the value of θ needs to be selected within an appropriate range depending on the size (area), material (refractive index), etc. of the lighting device.

For example, in the case of a lighting device that uses PMMA (acrylic resin) as the material and has a size of 220 x 140 mm, θ=4
A relatively good effect was obtained when the angle was set to 5 degrees, and the viewing angle was about 35 degrees, and the brightness on the display surface was increased by 30% compared to the same device using a conventional device without a regulating plate.

As described above, the value of the angle θ of the surface 4b of the regulating plate 4 in this embodiment may be selected to be an appropriate value depending on the refractive index of the material, the purpose of use, etc. The refractive index of glass and plastic materials that can be used here ranges from 1.4 to 1.7. Therefore,
Considering this point, the range of the angle O mentioned above is Oo<
θ<60° is appropriate. The value of O is determined by setting conditions such as viewing angle and luminance efficiency.

Further, as described above, in order to lower the brightness at the center of the diffuser plate 3, which has high brightness, and to achieve a uniform brightness distribution as a whole, θ may be made larger only in the center than in other parts. It is also effective to vary the value of θ depending on the location, taking into consideration the purpose of use.

Furthermore, in the above embodiment, the diffusion plate 3 and the regulation plate 4 are installed side by side as separate objects. It may also be formed by body molding using two-color molding, with the regulating layer portion formed from a transparent resin material on the other side.

Furthermore, although each portion of the surface 4b has a straight cross section in the illustrated embodiment, it may also have a slightly convex or concave surface. Further, the apex portion may also have a rounded shape instead of a sharp shape.

[Effects of the Invention] The lighting device of the present invention makes it possible to utilize light that is diffused at a large angle, which would have been wasted depending on the purpose of use in the conventional lighting device. Therefore, it is possible to increase only the brightness while maintaining a uniform brightness distribution, and it is possible to obtain a bright and uniform brightness distribution9.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention, and FIG. 2 is a sectional view of an embodiment of the present invention. FIG. 3 is an enlarged sectional view of a part of the regulating plate used in the first embodiment, and FIG. 4 is a sectional view of a conventional lighting device. ■...Reflector, 2...Light source, 3...Diffusion plate, 4...
・Regulation board

Claims (2)

[Claims] (1) In an illumination device comprising a reflector, a linear light source disposed close to the reflector, and a diffuser disposed on the opposite side of the reflector with respect to the light source, the diffuser is located on the opposite side of the light source. 1. An illumination device characterized in that regulating plates are arranged side by side or integrally formed to guide each diffused light so as to regulate the spread of the diffused light emitted from each point on the diffuser plate. (2) The lighting device according to claim (1), wherein the regulating plate is a transparent plate having a straight line on the diffusion plate side and a sawtooth cross section on the other side.