JP2002373518A - Flat illumination equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide flat illumination equipment which has a sufficient contrast characteristic. SOLUTION: A light source, which consists of a bar-like light guide body and a point-like light source, is arranged in a vicinity of a set of side surfaces of a transparent board 2 which counters, respectively. Light reflective patterns 19 are formed on the upper surface (surface of observer side) of the transparent board 2 along with a direction of an axis of the light guide body. The light reflective pattern 19 consists of groove parts 17 and flat parts 18, which adjoin the groove parts. Each the sections of the groove parts 17 have almost trapezoidal shapes, and circular projections 34 are formed on the bottoms 33. The light, which has advanced in the direction of an arrow P, among the light, which is incident into the transparent board 2 from the light guide body, advances to the direction of arrow P and penetrates a slope surface 31. The light, which has advanced to the exterior of the transparent board 2, reflects at the projection 34 and advances to the direction of arrow B'. By forming the projection 34, the light, which penetrates the slope surface 31, reflects in the slope surface 32 of the opposite side, and advances in the direction of the observer direction (the direction of arrow A) can be lost. Then, the contrast characteristic is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar illuminating device used as an illuminating device such as a signboard or various reflection type display devices, and more particularly to an illuminating device for a liquid crystal display device.

[0002]

2. Description of the Related Art Liquid crystal display devices, which are characterized by being thin, occupying a small volume, and being lightweight, are used in many electric appliances such as mobile phones and personal computers. I have. By the way, since the liquid crystal itself of the liquid crystal display device does not emit light by itself, when used in a dark place where the brightness of sunlight or room lighting cannot be sufficiently captured, the liquid crystal is irradiated separately from the liquid crystal display device. Lighting means is required. Therefore, it is desired that the illuminating means for irradiating the liquid crystal is also small in size and low in power consumption, and in recent years, a thin plate-shaped sidelight type (light guide plate type) planar illuminating device is often used as the means. The inventors of the present application have proposed the following conventional example in Japanese Patent Application No. 2000-268517 as such a sidelight type surface illumination device.

FIG. 3 shows an embodiment of a conventional planar lighting device. As shown in the figure, a spread illuminating device 1 includes a transparent substrate 2 made of a translucent material, light sources 5a and 5b arranged along one side surface 8a and 8b of the transparent substrate 2, and a light reflecting member. (Frames) 13a and 13b. Then, light emitted from the light source units 5a and 5b enters the transparent substrate 2 and irradiates a liquid crystal display (not shown) arranged below the transparent substrate 2.

The light sources 5a and 5b are composed of light guides 3a and 3b made of a rod-shaped transparent member and a point light source (for example, light emitting diode) 4 disposed at one end of the light guides 3a and 3b.
a and 4b. In addition, the light guides 3a, 3
b is provided with optical path changing means 12a and 12b. The light path changing means 12a and 12b are formed by forming a large number of light scattering portions, for example, step-like or groove-like, on the side opposite to the surfaces 9a and 9b facing the one side end surfaces 8a and 8b of the transparent substrate 2. It has a function of causing light emitted from the shape light sources 4a and 4b to enter the one end surfaces 8a and 8b of the transparent substrate 2 almost uniformly. The light guides 3a, 3b
Are arranged such that one side surface 9a, 9b of the light guide 3a, 3b faces the one side end surface 8a, 8b of the transparent substrate 2 at a predetermined distance from the one side end surface 8a, 8b of the transparent substrate 2. ing.

In order to make the light emitted from the point light sources 4a and 4b efficiently enter the transparent substrate 2, light reflecting members (frames) 13a and 13a are provided around the light guides 3a and 3b.
3b is provided. The light reflecting members 13a, 13b are formed in a substantially U-shape, and cover the periphery of the light guides 3a, 3b in the longitudinal direction other than the surfaces 9a, 9b facing the transparent substrate 2.
A film on which a metal such as silver is deposited is provided on the side (inner surface) of the light reflecting members 13a and 13b covering the light guides 3a and 3b.
Hard resin products to which a white film or the like is attached, or those obtained by bending a metal plate such as an aluminum plate or a stainless steel plate are used.

On the upper surface (viewer-side surface) 6 of the transparent substrate 2, light incident from one side surface 8a, 8b is uniformly emitted from the entire lower surface 24 of the transparent substrate 2 to the liquid crystal display device (not shown). For this purpose, a light reflection pattern 29 is formed.
The light reflection pattern 29 includes a groove 27 and a flat portion 28 adjacent to the groove, and is formed in a plurality along the axial direction of the light guides 3a and 3b. The groove 27 has a substantially inverted trapezoidal shape. That is, the short side of the trapezoid is connected to the bottom surface of the groove (the lower surface 24).
Side), and the long side is formed as the upper surface 6 side. The groove 27 is formed such that the depth of the groove 27 increases as the distance from the light guides 3a and 3b increases. That is, the depths of the adjacent groove portions 27 are formed to be different from each other, and the groove portions 27 close to the light guides 3a and 3b are formed.
The depth of the groove 27 formed near the center of the transparent substrate 2 becomes deeper, and conversely, the depth of the groove 27 formed farther from the light guides 3a and 3b becomes deeper. It is formed as follows.

FIG. 4 schematically shows a state in which light incident on the transparent substrate 2 is reflected by the groove of the light reflection pattern 29 and irradiates the liquid crystal display device. At this time, the inclined surface 21 and the bottom surface 2 are formed in the hatched trapezoidal groove 27.
3 is an outer angle of θ1, the inclined surface 22 and the bottom surface 2
In the case where the outer angle of the angle formed by 3 is θ2, the outer angles θ1 and θ2 are set to angles at which more light is totally reflected by the inclined surfaces 21 and 22. Further, if the angles are limited so that the screen becomes the brightest, the outer angles θ1 and θ2 become 3
It is set in the range of 5 ° to 55 °.

[0008]

By the way, even in the planar illuminating device having the above-described configuration, actually, bright and dark fringes as shown in FIG. 4 were generated. And the groove 2
The light reflected on the inclined surfaces 21 and 22 of No. 7 generated bright portions of light and dark stripes. However, since the shape of the groove 27 has a trapezoidal shape, the ratio of the pitch P of the light and dark fringes to the groove pitch L becomes smaller than the conventional ratio of the pitch, the difference in the light and dark of the light and dark fringes is inconspicuous, and the illumination quality is reduced. Somewhat good.

However, the light incident on the inclined surface 21 of the groove 27 includes light transmitted through the inclined surface 21 as shown in FIG. That is, the light A traveling in the transparent substrate 2 and hitting the inclined surface 21 includes the light A traveling in the direction of the lower surface 24 and irradiating the liquid crystal display device and then traveling in the direction of the observer (upward in the figure), After passing through the surface 21, there is light B which is reflected by the inclined surface 22 on the opposite side of the groove portion 27 and travels toward the observer (note that the light B travels in the transparent substrate 2 from the right direction in FIG. The same applies to incident light). For this reason, on the screen, the contrast characteristics as shown in FIG. 6 occur and there is a problem that the illumination quality deteriorates.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an improvement in a light reflection pattern formed on a transparent substrate allows a uniform surface brightness and dense illumination over the entire display screen. It is intended to provide a lighting device.

[0011]

In order to solve the above-mentioned problems, a first aspect of the present invention is to dispose a linear light source close to each other along two opposing side surfaces of a transparent substrate made of a translucent material. In a sidelight type planar lighting device in which a light reflection pattern composed of a plurality of grooves and a flat portion adjacent to the grooves is formed on the transparent substrate, the grooves forming the light reflection pattern have a cross-sectional shape of Are formed in a substantially inverted trapezoidal shape, and a projection is provided on the bottom surface of the groove toward the observer.

The light emitted from the light source enters the transparent substrate and is reflected on the inclined surface of the groove, the bottom surface of the groove, and the flat portion forming the light reflection pattern. Most of the light reflected on the inclined surface travels toward the liquid crystal display device disposed below the transparent substrate and irradiates the display pixels. A part of the light hitting the inclined surface passes through the inclined surface and travels in the groove, but is reflected by the protrusion formed in the groove and is defined as a direction perpendicular to the transparent substrate (observer direction). Proceed in different directions.
By thus refracting the light transmitted through the inclined surface by the projections and preventing the light from traveling in the vertical direction, the contrast characteristics on the screen are improved.

According to a second aspect of the present invention, in order to solve the above-mentioned problem, the light reflection pattern is parallel or constant at an angle to an axial direction of the light source. It is characterized by being formed.

[0014] In order to solve the above problems, the invention of claim 3 is directed to the invention according to claim 1 or 2, wherein
An outer angle of an inclination angle formed by the inclined surface and the bottom surface of the trapezoidal groove portion is formed at an angle of 35 ° to 55 °. By forming the inclination angle of the inclined surface of the groove constituting the light reflection pattern at a predetermined angle, it is possible to obtain a favorable light distribution characteristic on the observer side.

According to a fourth aspect of the present invention, in order to solve the above-mentioned problem, in the third aspect of the present invention, the angle of the outer angle is formed symmetrically in each groove. Things. By forming the left and right inclined surface angles of the groove symmetrically, better light distribution characteristics can be obtained.

According to a fifth aspect of the present invention, in order to solve the above-mentioned problem, the depth of each groove constituting the light reflection pattern is constant. It is characterized by being. By forming a light reflection pattern in which the depth of the groove is constant, further excellent light distribution characteristics are obtained.

According to a sixth aspect of the present invention, the distance between adjacent grooves of the light reflection pattern is as follows:
It is characterized by being constant.

According to a seventh aspect of the present invention, the height of the projection provided on the bottom surface of the groove is 3 mm.
It is not less than μm and not more than the depth of the groove. According to an eighth aspect of the present invention, in the invention according to any one of the first to seventh aspects, the cross-sectional shape of the protrusion is any one of an arc shape, a rectangular shape, and a triangular shape. Things. By setting the height of the projection provided on the bottom surface of the groove to a predetermined height according to the depth of the groove, and by forming the groove portion in a predetermined shape, light transmitted through the inclined surface of the groove portion is opposite. Ensure that the side slope is not reached.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a spread illuminating apparatus according to the present invention will be described below with reference to the accompanying drawings. Note that the present planar illumination device is an improvement of the shape of the light reflection pattern formed on the transparent substrate of the planar illumination device described as a conventional example, more specifically, the shape of the groove that constitutes the light reflection pattern. The same reference numerals are given to the same members as those of the spread illuminating device described above, and the detailed description thereof is omitted.

FIG. 1A is a diagram (side view of a transparent substrate) showing one form of a light reflection pattern formed on a transparent substrate 2 of the spread illuminating apparatus according to the present invention. Transparent substrate 2 (FIG. 3
On the upper surface 6 (the surface on the observer side) of the
There is provided a light reflection pattern 19 composed of a flat portion 18 adjacent to the groove 17. The light reflection pattern 19 is formed along the longitudinal direction of the light guides 3a and 3b, and the depth of the groove 17 constituting the light reflection pattern 19 and the distance between adjacent grooves are set to be constant.
Note that light sources 5a and 5b are arranged on opposing side surfaces (one side surface 8a and 8b) of the transparent substrate 2. In FIG. 1A, the light source units 5a and 5b are arranged in the left-right direction.

Each groove 17 has a shape in which a projection 34 (for example, an arc-shaped projection in this embodiment) is provided on the bottom surface 33 of the inverted trapezoidal groove toward the observer along the axis of the light source. are doing. That is, the short side of the trapezoid is formed on the bottom side (lower side 24 side) of the groove, the long side of the trapezoid is formed on the upper side 6, and the projection 34 extending on the upper side 6 is provided on the bottom 33. The projection 34 has a function of preventing light from transmitting through one inclined surface of the groove 17 and traveling toward the opposite inclined surface of the groove 17. Arrows in FIG. 1A schematically show light traveling in the transparent substrate 2. Hereinafter, light reflected on the inclined surface of the groove 17 will be described.

The light from the light guides 3a and 3b is
a and 8b enter the transparent substrate 2 and travel toward the opposing surfaces 8b and 8a while repeating reflection. Transparent substrate 2
Some of the light traveling inside travels in the direction of arrow P or arrow Q, for example, and reaches the inclined surface 31 or 32 of the groove 17. For the sake of explanation, the arrow P indicates the light guide 3
The light incident from a and the arrow Q are light incident from the light guide 3b. Of the light traveling in the direction of arrow P, the slope 31
The light reflected at travels in the direction of the lower surface 24 of the transparent substrate 2, that is, in the direction of arrow C. Then, a liquid crystal display device disposed below the transparent substrate 2 is irradiated, and the reflected light is reflected by an arrow A.
It proceeds in the direction, that is, in the observer direction.

On the other hand, of the light traveling in the direction of arrow P, light incident on the inclined surface 31 at a critical angle or less passes through the inclined surface 31 and travels outside the transparent substrate 2. Then, the light that has traveled to the outside is reflected on the projection 34 formed on the bottom surface 33 of the groove 17 and travels in the direction of arrow B ′. Thus, conventionally (when the projections 34 are not provided on the bottom surface 33), after transmitting through the inclined surface 31, the light is reflected by the opposite inclined surface 32 in the same groove 17 and travels toward the observer. Light (light B shown in FIG. 5) can be eliminated, and the contrast characteristics on the screen (the characteristics shown in FIG. 6) can be improved.

FIG. 2 shows a projection 34 on the bottom surface 33 of the groove 17.
FIG. 7 is a diagram showing contrast characteristics on a screen when a pattern is formed. In FIG. 6, the uneven contrast characteristic (decrease in contrast at the emission angle of 0 °) existing near the emission angle of 0 ° can be improved, and the contrast in the observer direction, that is, the emission angle of 0 ° direction can be improved. At the highest, a clear image can be reproduced.

As the specific size of the projection formed on the bottom surface of the groove, for example, the length of the transparent substrate in the longitudinal direction of the light guide is 100 mm, and the length in the short direction is 80 mm.
The depth of the groove is about 8 μm, and the distance between adjacent grooves is about 15
In order to prevent light from transmitting through one inclined surface of the groove portion 17 and traveling toward the opposite inclined surface of the groove portion 17 when formed to have a thickness of 3 μm, the protrusion should be 3 μm to 3 μm from the bottom surface.
It is desirable to form it at an arc height of 8 μm.

The inclined surfaces 31 and 3 forming the groove 17
The inclination angle of 2 is set as follows. The inclined surface 31 and the bottom surface 33 in the hatched groove 17 in FIG.
Is the external angle of the angle formed by θ1, the inclined surface 32 and the bottom surface 33.
The outer angle of the angle formed by is defined as θ2. Outside angles θ1 and θ2
Is set to an angle such that more light is reflected by the inclined surfaces 31 and 32. Further, the angle is limited so that the screen becomes the brightest. Considering these facts, in the transparent substrate 2 in this embodiment, light can be reflected most efficiently when the external angle θ1 and the external angle θ2 are both 45 °. However, it is desirable to appropriately set the shape according to the shape and purpose of use of the transparent substrate.
The outer angle θ2 is set in the range of 35 ° to 55 °.

The shape of the projection formed on the bottom surface 33 of the groove 17 is not limited to the arcuate shape shown in this embodiment. It has a shape that can prevent the light from reaching the inclined surface and reflect the light reflected by the projection in a direction different from the observer direction (the direction of arrow A in FIG. 1A). For example, a rectangular shape (FIG. 1)
(B)), a triangular shape (FIG. 1 (c)), and the like. Also, the position of the protrusion formed on the bottom surface may be any position on the bottom surface as long as it can prevent light traveling on the opposite inclined surface. Further, the light reflection pattern may be formed at a predetermined angle with respect to the axial direction of the light source.

In the above embodiment, the light of the arrow P incident from the light guide 3a has been described with reference to FIG.
The same applies to the light of the arrow Q incident from the light guide 3b. The light transmitted through the inclined surface 32 can be reflected by the projection 34 in a direction different from the observer direction, and a clear image with good contrast characteristics can be obtained. Can be reproduced.

[0029]

According to the planar lighting device of the present invention, by providing a projection on the bottom surface of the groove having a substantially trapezoidal cross section, light transmitted through one inclined surface of the groove can be transmitted to the other inclined surface. , And a clear image with good contrast characteristics can be realized. In addition, by limiting the inclination angle of the inclined surface forming the groove to a predetermined angle, light incident on the transparent substrate from the light guide can be efficiently emitted from the lower surface of the transparent substrate. Even when the depth of the groove and the distance between adjacent grooves are constant, the light from the transparent substrate irradiating the liquid crystal display device can be made uniform over the entire substrate, thereby improving the yield in the manufacturing process. Can be done. Furthermore, by limiting the height of the protrusion formed on the bottom surface of the groove to a predetermined value, it is possible to more reliably block light transmitted through one inclined surface from reaching the other inclined surface, and to improve contrast. A clear image with good characteristics can be realized.

[Brief description of the drawings]

FIG. 1A is a side view showing one embodiment of a light reflection pattern formed on a transparent substrate of a spread illuminating apparatus according to the present invention. (B), (c) is a figure which shows another form of the protrusion part formed in a groove | channel.

FIG. 2 is a diagram showing contrast characteristics obtained by the light reflection pattern shown in FIG.

FIG. 3 is an exploded perspective view showing one embodiment of a conventional planar illumination device.

FIG. 4 is a side view showing a light reflection pattern formed on a transparent substrate of the spread illuminating apparatus shown in FIG.

FIG. 5 is a view showing light reflected by a groove of the light reflection pattern shown in FIG. 4;

6 is a diagram showing contrast characteristics obtained by the light reflection pattern shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Planar illumination device 2 Transparent board 3a, 3b Light guide 4a, 4b Point light source 5a, 5b Light source part 6 Upper surface (viewer side surface) 8a, 8b One side surface 12a, 12b Optical path conversion means 13a, 13b Light reflection Member 17 Groove 18 Flat portion 19 Optical path conversion means 24 Lower surface 31, 32 Inclined surface 33 Bottom surface 34 Projection

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) F21Y 103: 00 F21Y 103: 00 (72) Inventor Tomoyuki Kawashima 174-1 Asana-cho, Asaba-cho, Iwata-gun, Shizuoka Minebe A Hamamatsu Corporation F-term (reference) 2H038 AA52 AA55 BA06 2H091 FA14Z FA23Z FA41Z FD04 FD06 LA17 5G435 AA02 BB12 BB16 EE22 FF08 GG24 KK07

Claims (8)

[Claims] 1. A light reflection pattern comprising a plurality of grooves and a flat portion adjacent to the grooves, wherein linear light sources are respectively arranged close to each other along two opposing side surfaces of a transparent substrate made of a translucent material. In the side-light type planar illumination device formed on the transparent substrate, the groove constituting the light reflection pattern has a substantially inverted trapezoidal cross-sectional shape, and is formed on the bottom surface of the groove toward the observer. A planar lighting device comprising a projection. 2. The spread illuminating apparatus according to claim 1, wherein the light reflection pattern is formed so as to be parallel or at a certain angle to an axial direction of the light source. 3. The planar state according to claim 1, wherein an outer angle of an inclination angle formed by the inclined surface and the bottom surface of the trapezoidal groove portion is formed at an angle of 35 ° to 55 °. Lighting equipment. 4. The angle of the outer angle is formed symmetrically in each groove portion.
A spread illuminating device according to claim 1. 5. The light reflection pattern according to claim 1, wherein the depth of each of the grooves constituting the light reflection pattern is constant.
5. The spread illuminating device according to any one of items 1 to 4. 6. The spread illuminating apparatus according to claim 1, wherein an interval between adjacent grooves of the light reflection pattern is constant. 7. The spread illuminating apparatus according to claim 1, wherein the height of the projection provided on the bottom surface of the groove is not less than 3 μm and not more than the depth of the groove. 8. The spread illuminating apparatus according to claim 1, wherein a cross-sectional shape of the protrusion is any one of an arc, a rectangle, and a triangle.