JP2748344B2 - Flat light source device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a flat lighting and a flat light source, and particularly to a flat light source device suitable for a thin advertising sign, a display device, a flat lighting device and the like. .

(Prior Art) Conventionally, particularly large-scale advertising signs and lighting devices that have been put into practical use have one or two or more fluorescent lamps installed in a housing and diffuse at an appropriate distance from the fluorescent lamps. The thing of the structure which arranged the board has become mainstream. However, in such an apparatus, if the distance between the fluorescent lamp and the diffuser plate is not sufficient, the bright line of the fluorescent lamp, which is called a slim line, can be seen, and it is inevitable to ensure uniform brightness. It is necessary to increase the depth of the device. In order to reduce the depth with such a device, it is inevitable to increase the diffusion performance of the diffusion plate, but this causes a decrease in light transmittance and darkens, so in order to maintain the same brightness, The number of fluorescent lamps must be increased, and problems such as an increase in power consumption and a measure against a rise in temperature have arisen.

Many proposals have been made for a long time to solve these problems (Japanese Utility Model Publication No. 42-18278, Japanese Patent Application Laid-Open No. 55-1).
No. 5126, Japanese Unexamined Patent Publication No. 55-133008, Japanese Utility Model Publication No. 56-35667
And Japanese Patent Application Laid-Open No. 59-22493), most of which are designed to shield the upper part of the light source and eliminate the bright line, so that the level is adjusted to the dark part of the surface to make it uniform, and the use of light amount It is not preferable from the viewpoint of efficiency.

In principle, it is possible to use a point light source approximation to place a lamp at the focal point of a convex lens, and to apply parallel light to the light passing through the convex lens. However, since a fluorescent lamp is not a so-called point light source, the reproducibility of the principle is poor and the fluorescent lamp cannot be put to practical use at present.

(Problems to be Solved by the Invention) In view of such circumstances, the present inventors have found that bright lines appear when a linear light source such as a fluorescent lamp is brought close to an illuminating surface, and that such bright lines are eliminated. In other words, the use of a shielding member lowers the brightness as a whole and reduces the efficiency of using the amount of light, and similarly, the surface becomes darker when trying to achieve uniformity by using a diffusion plate with high diffusion performance. Recognizing that this is a "trail" phenomenon in which the device is made thinner without lowering the brightness, we worked diligently to achieve a thinner device while making effective use of the light energy emitted by the light source as much as possible. The inventors have found that this can be achieved by controlling light and using a unique multi-prism sheet, and completed the present invention.

(Means for Solving the Problems) That is, the present invention has been made to solve the above problems, and the gist of the present invention is to incorporate a linear light source, provide a reflection surface on the back surface, and The front surface is a box-type flat light source device provided with a multi-prism sheet, wherein the reflection surface has a flat surface in which the linear light source is arranged at the center and two inclined surfaces connected to both sides of the flat surface. And the distance (R) from the center to the end of the flat surface
Is R <2D or R with respect to the diameter (D) of the linear light source.
> 3D, has the function of making the majority of the light reflected on the surface obliquely incident on the multi-prism sheet, and is arranged parallel to the light source on the inner surface of the multi-prism sheet. A prism group is formed, and the prism group is a series of prisms having the same shape repeatedly, and the prism group is directly reflected from the light source or reflected on the reflection surface and is directed to a slope facing the center side of the prism. A flat light source device having a function of deflecting the light that has entered and reaches the outwardly facing slope so that the traveling direction thereof approaches a predetermined direction, and emits the light from the multi-prism sheet.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to the drawings of Examples and Reference Examples.

Embodiment 1 and Reference Example 1: Embodiment and Reference Example in which the Reflection Surface is a Flat Surface FIG. 1 shows the appearance of a reference example for explaining an embodiment of the present invention, and FIG. The figure is a sectional view taken along the line II-II, in which 1 is a light source, 2 is a reflection surface, 3 is a multi-prism sheet, 4 is a dark part removal sheet, and 5 is a housing.

In this reference example, a fluorescent light “FL-10W” (100 V AC, 10 W, 25 mmφ) manufactured by Toshiba Corporation was used as the light source 1, and the reflecting surface 2 was formed on a surface of a 0.5 mm thick aluminum sheet with a thickness of 25 μm.
Used were laminated silver-evaporated polyester films. The multi-prism sheet 3 is obtained by using a colorless and transparent acrylic resin plate (thickness: 1 mm) and subjecting it to hot pressing together with a mold. The pitch P is 0.38 m as shown in FIG.
m, the prism angles α ₁ and α ₂ are both 31.5 ° and the vertex angle α is 6
A sheet was used in which prism groups each having a substantially equilateral triangular shape of 3 ° were arranged so as to extend in parallel. Further, as will be described later, the dark portion removal sheet 4 is made of various synthetic resin translucent plates (2 mm thick, 1 m thick).
m) was used. Then, the housing 5 was assembled in a box shape using a synthetic resin plate. Further, the dimensions of the device at this time is, l ₁ is 6 times the 150mm diameter of the fluorescent lamp, l ₂ is 350 mm, the gap d ₁ of the opening surface of the fluorescent lamp and the housing 5 was 5 mm.

(1) Measurement of Luminance Distribution as Light Box Among the devices configured as described above, first, in order to grasp the light amount of the housing having the light source and the reflecting surface, the multi-prism sheet 3 and the dark part removing sheet shown in FIG. 4 except here by placing a colorless transparent acrylic resin plate with a thickness of 3mm and light box (using the light box for the convenience of later also experiments), l ₂ direction of light box brightness of the surface It measured at equally spaced points on at 10mm intervals in the longitudinal l ₁ direction in the center of. The brightness was measured using a Minolta nt-1 brightness meter at a viewing angle of 1 ° and a spot diameter of 7 mmφ. The results are as shown in Table 1. The maximum difference between light and dark was more than 20 times.

(2) Measurement of luminance of multi-prism sheet Next, the above-mentioned multi-prism sheet is placed on the above-mentioned light box with the prism group facing the light source. The brightness was measured. Table 2 shows this result. Although a band-shaped dark part (about 20 mm in width) is formed in the center corresponding to the position immediately above the fluorescent lamp,
There were no places with extremely low luminance, and the ratio of light and dark was 3.75 or less, indicating that it could be used in some applications.

(3) the distance between the fluorescent lamp tube surface and the multi-prism sheet;
Investigation of dark area generation In the configuration of the flat light source device measured in Table 2, the distance between the fluorescent lamp tube surface and the multi-prism sheet is 8 mm. How it changes.

First, except for the transparent acrylic resin plate having a thickness of 3 mm above the light box, as shown in FIG. 4, a spacer 6 made of a transparent acrylic resin plate for setting an interval in the fluorescent lamp 1 is interposed. The measurement was performed by changing the interval of d ₂ by changing.

 Table 3 shows the results.

As is clear from this result, it was found that when the distance of d ₂ was reduced, the width of the dark portion was gradually reduced, and it was confirmed that the device in this configuration should be put to practical use with reference to this. .

However, practically, it is desirable to eliminate such a dark portion. Therefore, further investigation is performed, and the multi-prism sheet is directly contacted with the tube surface of the fluorescent lamp (ie, d ₂ = 0)
The dark part disappeared, and conversely, a band with a higher luminance than the surroundings with a width of 3 to 5 mm appeared.

From this, it was found that there was a distance where the luminance difference disappeared between d ₂ = 0 to 1 mm. When the polyester film having a thickness of 0.1 mm was used as the spacer 6, it was observed that d ₂ = 0.3 mm and 0.4 mm. And a uniform state with no luminance difference was obtained. Therefore, it was confirmed that the use of a spacer capable of maintaining this distance or the use of a multi-prism sheet made of inorganic glass having high rigidity can also be used in this configuration.

(4) Examination of a member for removing dark portions As described above, it was confirmed that a surface having uniform brightness could be obtained by using the multi-prism sheet alone. However, the fluorescent lamp and the multi-prism sheet were separated at a small interval as described above. Since assembling has practically difficult aspects, the removal of the dark part was examined by using other members.

The strip-shaped dark portion is caused by a small amount of light emitted in the direction of the normal line (FIG. 3L) of the prism at a position directly above the fluorescent lamp (light incident from the normal direction is generally emitted from 60 to 80 °). Therefore, the light emitted at an angle deviated from the normal direction can be eliminated by collecting the light at the dark portion. As a sheet having such a function, a translucent plate having a certain degree of diffusivity, that is, a milk half-plate was considered to be suitable. First, each grade (six types) of an acrylic resin milk half-plate was prepared. The performance was measured. The used milk half plates are as follows.

・ Mitsubishi Rayon acrylic resin milk plate “Acrylite # 432” (2mm thick) ・ Mitsubishi Rayon acrylic resin milk plate “Acrylite # 422” (2mm thickness) ・ Mitsubishi Rayon acrylic resin milk Half plate "Acrylite # 609" (2mm thick) ・ Mitsubishi Rayon company acrylic resin milk plate "Acrylite # 610" (2mm thickness) ・ Mitsubishi Rayon company acrylic resin milk plate "Acrylite # 613" (Thickness 2mm) ・ Acrylic resin milk plate "Acrylite # M3" (thickness 1mm) manufactured by Mitsubishi Rayon Co., Ltd. The distribution of the incident angle and the outgoing angle is measured using a goniometer manufactured by Murakami Color Research Laboratory. changing the light beam incident angle with respect to each sample, and measuring the transmission light distribution, beam emission angle and for each angle of incidence and the angular width when the intensity is reduced to _^1/2 of the peak emission intensity (half-value) I asked. The total light transmittance was measured according to JIS-K7105.

 Table 4 shows the results.

(5) Evaluation of the performance when using the dark part removal sheet A light box (with a multi-prism sheet provided through a transparent acrylic resin plate having a thickness of 3 mm) when measuring the brightness of the multi-prism sheet was used. The above-mentioned milk half plate was further placed thereon, and the luminance was measured (referred to as Case A). For comparison, measurements were also taken for a case where only the multi-prism sheet was placed on the light box (case B) and a case where only the milk half-plate was placed (referred to as case C).

FIG. 6 to FIG. 11 show this result, and it was confirmed that the uniformity effect by the dark portion removal sheet was remarkable. In the graphs of these figures, case A is indicated by +, case B is indicated by □, and case C is indicated by Δ.

(6) Confirmation of Function of Reflection Surface In the above reference example, the reflection surface 2 is provided at an angle as shown in FIG. 2 or FIG. In order to make the light enter the multi-prism sheet 3 obliquely, more specifically, with respect to the normal line of the prism
It is configured to be incident at about 50 to 80 °, which is one condition for achieving the function of the present invention.
In order to confirm this point, a study was conducted using a reflective surface 2 having a flat portion on the bottom surface as shown in FIG. 5 (FIG. 5 shows an embodiment of the present invention, and in this embodiment, The configuration is the same as that of the above-described reference example except for the shape of the reflecting surface 2).
When 2D or R = 3D, this R portion becomes dark, and it was found that uniformity could not be achieved.

Reference Example 2: Reference Example in which Reflection Surface is Curved Surface FIG. 12 is a cross-sectional view of a reference example of the present invention. here,
1 is a light source, 2 is a reflection surface, 3 is a multi prism sheet, 4
Denotes a dark portion removal sheet, and 5 denotes a housing.

The reference example 2 is different from the reference example 1 of FIGS. 1 and 2 mainly in the shape of the reflection surface 2, but the other parts are almost the same. Incidentally, l ₁ the direction of the cross-sectional shape of the reflecting surface 2, an arc of radius of curvature r.

In FIG. 12, prism groups are formed on the lower surface of the multi-prism sheet 3 in the same manner as in FIG. 2, but the prism groups are not shown.

(1) Comparison of Luminance Uniformity According to Shape of Reflecting Surface The multi-prism sheet and the dark part removal sheet described in Reference Example 1 were placed in this order on the light box described in (1) of Reference Example 1 above. Acrylite # 609, Acrylite # 432, and Acrylite # M3
Were used. Ex3-
A, Ex1-B, Ex1-C.

Similarly, for the configuration of Reference Example 2, three types of light boxes were similarly formed, and a plasma sheet and a dark part removal sheet were similarly placed in this order. here,
The radius of curvature r of the reflecting surface was 100 mm. Acrylite # 609 and Acrylite # 43 are used as the dark part removal sheet.
2 and Acrylite # M3. These three
The types of devices are referred to as Ex2-A, Ex2-B, and Ex2-C, respectively.

For each of the above devices, the luminance was measured as described in (1) of Reference Example 1, and the maximum difference between all the measurement points was examined. As a result, the uniformity of luminance can be understood.

 The results are shown in Table 5 below.

As is clear from the above results, the uniformity of luminance could be improved by forming the reflecting surface from a curved surface, as compared with a device having a reflecting surface from a flat surface.

(2) Relationship between distance between lamp and multi-prism sheet and effective width of apparatus Next, it was examined how the uniformity of luminance changes by changing the distance between the lamp and the multi-prism sheet.

Here, the fluorescent light “FL-10W” manufactured by Toshiba Corporation is used as the light source 1.
(AC 100V, 10W, 25mmφ) and fluorescent lamp “FL-3 manufactured by NEC Corporation”
0SEX-N "(AC100V, 30W, 32mmφ) was used. These lamps are referred to as La-1 and La-2, respectively. As the multi-prism sheet 3 and the dark part removing sheet 4, the same ones as in the above-mentioned Reference Example 1 were used. However, the type of light source used (lamp), and by setting the size and magnitude of l ₁ of d _1, and uniquely determine the radius of curvature r of the reflecting surface 2. In addition, l ₂ was 300mm.

Table 6 below shows each specific configuration example of the apparatus of FIG.
D ₁ , l ₁ , r in _{1 to} Con-9, the type of light source used, and l ₁
Indicates / D. Here, D is the diameter of the light source lamp.

With respect to each of the above configuration examples, the luminance was measured as described in (1) of Reference Example 1 above. In addition, there is a case where the dark portion removal sheet is replaced with the same configuration example.

In Table 7 below, for each of the configuration examples Con-1 to Con-9, the used dark area removal sheet, the average luminance value, and the luminance uniformity are shown. Here, the brightness uniformity was calculated by the following equation.

Luminance uniformity = ± (maximum luminance value-minimum luminance value) / average luminance value x (1 /
2) x 100 [%] Among the above configuration example Con-1~Con-9, the device Ex2-A thing with ACRYLITE # 609 as a dark portion removed sheet and the (1), is a plot of the relation between d ₁ and r 13 is a graph of FIG.

Assuming that the luminance uniformity is within about ± 10% as an allowable range, the relationship between r and d ₁ within the allowable range was approximated by the following cubic equation (1) by the least square method.

_{r ≦ 22.12 + 11.33d 1 -20.94d 1} 2/10 2 + 1.747d 1 3/10 3 (1) This range corresponds to a portion below the curve C ₁ in FIG. 13.

By using this equation (1) is used when determining the diameter D and the distance d ₁ of the lamp, the upper limit of r is set to within the allowable range brightness uniformity, thus uniquely width
The maximum value of l ₁ is found.

After all, if you set the lamp used and the housing depth,
The maximum width of the housing that can maintain the luminance uniformity is calculated, and the design of the light source device becomes extremely easy.

For both cases where the lamp diameter D is 25 mmφ and 32 mmφ, the relationship between d ₁ and l ₁ was approximated by the following cubic expressions (2) and (3), corresponding to the above expression (1).

For _{· D = 25mmφ l 1 ≦ 78.75} + 10.58d 1 -17.79d 1 2/10 2 + 2.029d 1 3/10 3 (2) · D = For _{32mmφ l 1 ≦ 100.35 + 9.03d 1} -9.16d ^{_{1 2/10 2 + 0.693d 1}} 3/10 3 (3) these ranges, respectively, the curve C ₂ in Figure 14, C
It corresponds to the part below ₃ .

Although described in detail according to the examples and reference examples,
The content of the present invention is not limited to these examples,
Various modifications are possible. For example, as the light source 1 of the present invention, a linear light source such as an LED array, a link lamp or a quenching lamp can be used in addition to a linear light source such as a fluorescent lamp.

The reflecting surface 2 can also be selected from an appropriate metal reflecting surface or the like. If the reflecting surface 2 has a function of reflecting light from the light source 1 and making most of the light obliquely enter the multi-prism sheet 3, for example, The shape is not limited, such as forming an upwardly concave surface composed of a combination of planes.

As the multi-prism sheet 3 used in the present invention,
In addition to the acrylic resin, a synthetic resin such as a polycarbonate resin, a styrene resin, and a vinyl chloride resin, or an inorganic glass can be used. The multi-prism sheet 3 can be used not only in a plate shape (thickness of about 0.5 to 5 mm) but also in a thin film shape. The shape of the prism may be changed according to the direction of the direct light from the linear light source or the direction in which the light once reflected and incident in an oblique direction is orthogonal to the multi-prism sheet 3 or the direction in which the light is concentrated and emitted in an arbitrary direction. Should be set.

Further, as the dark part removing sheet 4, besides the acrylic resin semi-transparent plate used in the reference example, a sheet or a film having the same performance can be used. An appropriate one may be selected in consideration of the peak emission angle and the angular width at that time.

When a thin plate or a film is used as the multi-prism sheet 3 or the dark portion removing sheet 4, if necessary, a transparent plate for preventing bending is used.
And the light source 1.

(Effect of the Invention) Since the present invention has the configuration as described in detail above, a flat light source device that is bright, has high uniformity, and can be made sufficiently thin by effectively utilizing light from the light source. There are benefits that can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a reference example of the present invention, and FIG.
FIG. 3 is a partial enlarged view of the multi-prism sheet, FIG. 4 is a partial sectional view of an example used for examining the width of a band-shaped dark portion, and FIG. FIG. 6 is a sectional view of a light box according to an embodiment of the invention,
FIG. 11 is a graph evaluating the performance in the reference example of the present invention,
FIG. 12 is a sectional view showing one embodiment of the present invention, and FIGS.
FIG. 14 is a graph showing the characteristics of the reference example of the present invention. DESCRIPTION OF SYMBOLS 1 ... Light source 2 ... Reflection surface 3 ... Multi-prism sheet 4 ... Dark part removal sheet 5 ... Housing

────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code FI G09F 9/00 336 G09F 9/00 336F (56) References JP-A-61-15104 (JP, A) JP-A-61-158367 (JP, A) Japanese Utility Model Showa 59-194208 (JP, U) Japanese Utility Model Showa 60-51812 (JP, U) Japanese Utility Model Showa 60-105012 (JP, U)

Claims (3)

(57) [Claims] 1. A box-type flat light source device having a linear light source built-in, a reflection surface on the back surface, and a multi-prism sheet on the front surface, wherein the reflection surface is formed by the linear light source. It has a flat surface arranged in the center and two slopes connected to both sides of the flat surface, and the distance (R) from the center to the end of the flat surface is larger than the diameter (D) of the linear light source. R <
In the relationship of 2D or R> 3D, it has a function to make most of the light reflected on the surface obliquely incident on the multi-prism sheet, and the inner surface of the multi-prism sheet is parallel to the light source. An extended prism group is formed, and the prism group is formed by repeatedly arranging prisms of the same shape. The prism group is directly reflected from the light source or reflected by the reflection surface and directed toward the center of the prism. A flat light source device having a function of deflecting light incident on the inclined surface and arriving at the outwardly directed inclined surface so that the traveling direction thereof approaches a predetermined direction, and outputs the light from the multi-prism sheet. 2. The flat light source device according to claim 1, wherein a dark portion removing sheet for eliminating a dark portion immediately above the light source is disposed on the front side of the multi-prism sheet. 3. The flat light source device according to claim 1, wherein a distance between the linear light source and the multi-prism sheet is 0.3 to 0.4 mm.