JPH0237604A - Thin type light box - Google Patents

Abstract

PURPOSE:To make a lighting surface uniformly bright by providing a light transmitting member with an irregular reflection pattern between a light diffusing/transmitting member and multiple fluorescent tubes and providing a reflecting member with light diffusion transmission property between the adjacent fluorescent tubes. CONSTITUTION:Multiple fluorescent tubes 2 and 2 are arranged in a flat frame 6 with a reflecting face on the inside, a light diffusing/transmitting member 5, e.g., obscure glass, covering the opening face is provided on the opening face 7 of the frame 6 to form a lighting face 8. A light transmitting member 4 with an irregular reflecting pattern 9 is provided between the light diffusing/ transmitting member 5 and the fluorescent tubes 2, a reflecting member 3 with light diffusion permeability is provided between the adjacent fluorescent tubes 2 and 2. The light received by the light transmitting member is reflected by the irregular reflecting pattern in accordance with the strength of the light and reaches the light diffusing/transmitting member at the opening face as the light with constant intensity, thereby the lighting surface with uniform intensity is obtained.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a light box used for -gA lighting equipment, illuminated signboards, tracing stands, back lighting equipment for liquid crystal display devices, etc. This paper is concerned with improving the luminance distribution and efficiency of the illumination surface in a thin light box.

[Conventional technology 1] Light boxes with built-in fluorescent tubes are provided with a light diffusing and transmitting member on the opening surface of the casing as an illumination surface, and there has been a strong demand for thinning them depending on the application, but the depth relative to the width of the casing In a thin light box where the ratio of the tube diameter of the fluorescent tube to the depth of the housing is 0.3 or less and the ratio of the tube diameter of the fluorescent tube to the depth of the housing is 0.5 or more, the light received by the light diffusing and transmitting member on the illumination surface is intense directly above the fluorescent tube. Since the light has a uneven intensity distribution, the following various methods have been proposed to make the brightness of the illumination surface uniform.

(a) A method in which a large number of fluorescent tubes are placed at intervals inside a flat housing.

10) The inner surface of the housing is used as a reflective surface, and a light-transmitting member having a reflective film-like shape is provided between the illumination surface and the fluorescent tube,
A method of uniformizing the brightness of the illuminated surface by sending light from bright areas to dark areas by avoiding repeated reflections (for example, Japanese Patent Application Laid-open No. 18533/1983) 4 (c) Semi-cylindrical opaque member with partial cutouts A method of attenuating the light directly above the fluorescent tube by covering the fluorescent tube with the cutout, and reflecting the light leaking from the cutout on the reflective surface of the inner surface of the housing to make the brightness of the illumination surface uniform (for example, Japanese Patent Publication No. 44-84
No. 21).

2) The so-called edge light method, in which light introduced from the side of a flat housing is uniformly distributed and reflected onto the illumination surface using a curved reflecting member.

[Problem to be solved by the invention l Among the various conventional methods mentioned above (in the detective method,
The disadvantage of using a large number of fluorescent tubes is that power consumption is large and costs increase, and method (0) has the disadvantage that light with an intensity distribution that has a strong peak directly above the fluorescent tubes is reflected in an uneven pattern. Since the light is uniformly adjusted by repeated reflection between the light-transmitting member having the light-transmitting member and the inner surface of the casing, a slight positional shift in the reflection pattern significantly impairs the uniformity of the light. As the width of the illumination surface increases, there is a drawback that light loss increases due to an increase in the number of reflections.

Next, in method (c), because the strong light directly above the fluorescent tube is attenuated by the semi-cylindrical opaque member, (b)
This method has the disadvantage that the effective use of light is poorer than that of the previous method, and the illumination surface becomes dark. It was difficult to increase the size of the illumination surface.

In addition, when using multiple fluorescent tubes in methods (b) and (c), it is possible to increase the light intensity between adjacent fluorescent tubes by selecting the shape and reflection characteristics of the reflective surface on the inner surface of the housing. However, since conventional reflecting surfaces have so-called surface reflectivity in which light is reflected only from the surface, the light intensity distribution between the fluorescent tubes is uniquely determined by the shape of the reflecting surface. Therefore, if the housing is thin, a reflecting surface of a desired shape cannot be formed, and therefore sufficient light intensity cannot be obtained, and the light intensity directly above the fluorescent tube may be increased.

Further, in this case, since the reflected light has a directivity determined by the reflecting surface, there is a drawback that so-called parallax occurs on the illumination surface, in which the brightness varies depending on the viewing angle.

The present invention eliminates such drawbacks in the prior art, and
To provide a thin light box that has excellent light utilization efficiency, has a bright and uniform illumination surface, is easy to assemble, and is inexpensive.

[Means for Solving the Problems] The present invention provides that when a reflective member having light diffusing and transmitting properties, such as a porous member formed by fixing and molding transparent plastic beads, is irradiated with light, rather than from the surface thereof, It aims to make light uniform by utilizing the complex reflection from inside during diffuse transmission, and specifically, the configuration shown in FIG. 1, which is an embodiment of the present invention, is used. have.

That is, in the figure, a plurality of fluorescent tubes 2.2 are arranged inside a flat housing 6 whose inner surface is a reflective surface l, and the opening surface 7 of the housing 6 is covered with a layer of, for example, frosted glass. An illumination surface 8 is formed by providing a light diffusing and transmitting member 5 as shown in FIG. A reflective member 3 having light diffusing and transmitting properties is provided between adjacent fluorescent tubes 2.2.

[For production] Next, the operation of the present invention will be explained.

FIG. 2 is a diagram showing the intensity distribution of light received by a light transmitting member having an uneven reflection pattern provided between the illumination surface and the fluorescent tube in the thin light box of the present invention, and FIG. FIG. 3 is a diagram showing the luminance distribution on the illumination surface of the thin light box.

According to the above-mentioned structure, (1) in the thin light box of the present invention, since the reflective member provided between the adjacent fluorescent tubes is a reflective member with light diffusing and transmitting properties, the light from the fluorescent tubes that is irradiated onto the reflective member from both sides; is complexly reflected from within during diffuse transmission rather than from its surface. Therefore, the secondary light composed of reflected light and transmitted light emitted from the reflective member is not directed in a specific direction, but becomes so-called omnidirectional light, which illuminates the reflective member and turns it into a pseudo light source.

The non-directional secondary light from the reflective member, which has become a pseudo light source in this way, is irradiated onto the opposing surface of the light transmitting member located above and having an uneven reflection pattern, increasing the light intensity there. Because I will.

As shown by curve a in FIG. 2, the light intensity distribution on the light-transmitting member is at a higher level and gentler than in the conventional case (curve C).

In this way, the light received by the light transmitting member is firstly reflected by the non-uniform reflection pattern according to the intensity of the light, becomes light with a constant intensity, reaches the light diffusing transmitting member on the aperture surface, and is transmitted to the third light transmitting member. As shown by a in the figure, the illumination surface has uniform brightness.

[Example 11 In the example shown in Fig. 1, the flat housing 6 has a long side of 160 m-1
A straight-tube cold cathode fluorescent tube 2.2 with a trapezoidal cross section of 110 m5 on the short side and 9III in height, the inner surface of which is painted white to serve as a reflective surface 1, and a tube diameter of 8+m-1 and a length of 275 mm.
are placed inside the housing 6 at a distance of 6 mm from the bottom surface by 0.5 mm.
A light diffusing and transmitting member 5 arranged at a length of 4 m and having a thickness of 21111 mm.
(Mitsubishi Rayon ■ Milky white translucent acrylic plate 435#
) is provided to cover the opening surface 7 of the housing 6 to form the illumination surface 8, and the thickness is 188 μm between the fluorescent tube 2 and the light diffusing and transmitting member 5.
A light-transmissive member 4 is provided by vapor-depositing a dot-shaped non-uniform reflective pattern 9 on a transparent polyester film with a pitch of 0.8++v+. Set so that the transmittance of
The surface of the vapor deposition surface was coated with a transparent resin protective film having a thickness of 1.5 μI.

The light diffusing and transmitting reflective member 3 provided between the fluorescent tubes 2.2 is a breathable member made of granular polypropylene fixed and molded with a diameter of 70 μm, and has an isosceles triangular shape with a base of 40 mm and a height of 7+s*. are doing.

When this thin light box was placed in an environment of 25° C., the intensity distribution of light received by the surface of the light-transmitting member 4 was first examined, and the result was as shown by curve a in FIG. 2.

The light intensity at the midpoint XS between the fluorescent tube positions x1 and x2 increases compared to the case where the reflective member 3 of the present invention is not used (curve b), and the luminance distribution of the illumination surface at this time is shown in Figure 3. a′
As shown in FIG. 2, it was extremely uniform, and its value increased by about 25% compared to the case (b!) in which the reflective member 3 of the present invention was not used, and there was no parallax at all.

Next, when a surface reflection type reflective member of the same shape was used in place of the reflective member 3 of the present invention, the light intensity distribution received by the light transmitting member 4 and the luminance distribution on the illumination surface were respectively shown in FIG.
and the middle point X of the fluorescent tube as shown in FIG. 3C' compared to the present invention.

The light intensity was low and the illuminated surface was dark.

Furthermore, in this embodiment, the tolerance range of accuracy for attaching the light transmitting member 4 to the fluorescent tube 2 is approximately 0.5 mm, which is a significant relaxation of the tolerance range of 0.1 mm+ in the conventional method. It is.

[Example 21 In the thin light box of the present invention shown in FIG.
A trapezoidal cross-section housing 6 with an area of 165 m5 inside the light-resolving surface and a height of 1111 m is molded with ABSP4 resin.
Two straight hot cathode fluorescent tubes 2.2 of IIm with a spacing of 66I
A transparent polyester film with a thickness of 188 μm was placed between the milk semi-acrylic plate 5 (CL-132 manufactured by Nitto Jijin ■) with a thickness of 2+ us, which forms the illumination surface 8, and the fluorescent tube 2.2. As in Example 1, a light transmitting member 4 having a dot-like non-uniform reflection pattern 9 formed by aluminum vapor deposition is provided, and a plate-like member has an opening angle θ=136° between the fluorescent tubes 2.2.
A light diffusive and transparent reflecting member 3 is formed by bending to a height of 6 degrees.
Sample A is made with E CB 1010), 87μm
Sample B is made from a diffusely transparent film (D105 manufactured by Kimoto Co., Ltd.), and Sample C is made from a white-painted aluminum plate, and the brightness on each illumination surface is compared with the case without reflective member 3. I obtained the following result.

Table-1 Sample Increase/decrease in brightness A +16% B +11% C-9% As can be seen from Table 1, both Sample A and Sample B of the present invention have increased brightness, but the shape of the reflective member is the same. However, the brightness of the illuminated surface of Sample C, which used a reflective member with surface reflection properties as in the prior art, decreased.

Further, in sample C, an attempt was made to improve the brightness by changing the opening angle θ, but even with the best opening angle θ=132°, the brightness was only improved by 15%.

Furthermore, for comparison, when a reflective member made of a specularly reflective aluminum plate with an electrolytically polished finish is used instead of the reflective member 3, the illumination surface brightness increases, but significant parallax occurs, and furthermore, the brightness decreases due to minute changes in the aperture angle. It was unsuitable for use as a backlight for display devices because it caused unevenness.

The light diffusing and transmitting reflective member of the present invention complexly reflects the primary light irradiated from the fluorescent tube from inside the reflective member during diffuse transmission, thereby creating a pseudo light source.The reflected light and transmitted light emitted from the reflective member are In addition to those shown in each example, since the secondary light consisting of
% of diffusely permeable materials.

The light diffusing and transmitting reflective member of the present invention may be composed of a single material, but it may also be constructed by mixing or laminating several materials with different diffuse transmittances and reflectances to partially change the internal reflectance. , and its shape may be as shown in FIGS. 5 and 6 (it can be arbitrarily designed depending on the required illumination surface, and the present invention is not limited to the shape of the reflecting member).

[Advantageous Effects of the Invention 1] As explained above, the thin light box of the present invention uses a light diffusing and transmitting reflective member with a simple structure as a pseudo light source in order to obtain uniform light, and does not use a large number of fluorescent tubes. Therefore, the cost is low, and since the secondary light from the reflecting member is non-directional, there is no parallax on the illumination surface.

In addition, since the light intensity between adjacent fluorescent tubes is increased by the reflective member, the light intensity distribution received by the light-transmitting member having an uneven reflection pattern becomes gentle, so that the installation of the light-transmitting member is difficult. Moreover, since there is no parallax, the assembly work of each member is easy, and the brightness of the illumination surface is also uniform and stable.

Furthermore, in the present invention, even if the distance between adjacent fluorescent tubes is large,
The light diffusive transmissive reflective member provided between them effectively introduces the light radiated laterally from the fluorescent tube to the illumination surface, and since a light attenuation member is not used as in the conventional method, the light in the present invention is Utilization efficiency is extremely high.

(Thus, the present invention achieves the intended purpose.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing one embodiment of the present invention, and FIGS. 2 and 3 are diagrams explaining its operation. FIG. 4 is a diagram showing a cross section of another embodiment of the present invention,
FIGS. 5 and 6 are cross-sectional views of other embodiments of the present invention. ■...Reflecting surface 2...Fluorescent tube 3...Light diffusing and transmitting reflective member 4...Light transmitting member 5...Light diffusing and transmitting member 6...Housing 7...Opening surface 8 ...Illumination surface 9...Reflection pattern lO...Reflector 11...Diffuse transmission material Patent applicant Ohno Technical Research Institute Ltd. 1) Figure 5

Claims (1)

[Claims] (1) A plurality of fluorescent tubes are arranged inside a flat housing whose inner surface is a reflective surface, and a light diffusing and transmitting member is provided covering the opening surface of the housing to serve as an illumination surface, and the light diffusing and transmitting member and the fluorescent A thin light box in which a light-transmitting member having a non-uniform reflective pattern is provided between tubes, characterized in that a reflecting member having light-diffusing and transmitting properties is provided between adjacent fluorescent tubes. .