JP4394977B2 - Surface light source device - Google Patents

Description

The present invention relates to an edge light type surface light source device that emits light incident from a point light source arranged at one end of a light guide in a planar shape, and more specifically, irradiates a display surface of a liquid crystal display device. The present invention relates to a lighting device with high brightness and high degree of uniformity. The surface light source device of the present invention is particularly suitable as a surface light source device using a point light source such as a light emitting diode (LED).

  Liquid crystal display devices are widely used as display devices for liquid crystal televisions, computers, word processors, mobile phones, and other information devices. The liquid crystal display device basically includes a backlight unit and a liquid crystal display element unit. As the backlight unit, an edge light type is often used from the viewpoint of making the liquid crystal display device compact. This edge light system is a backlight of a system in which a light source is disposed on a side surface portion of a plate-shaped light guide to emit light on the entire surface of the light guide.

  The backlight propagates light incident from a light source close to the side surface of the light guide from the light source side to the non-light source side while repeating total reflection in the light guide using the refractive index difference between the light guide and air. There are two methods for extracting light propagating in the light guide in a planar shape, one of which is reflected and refracted by dots of ink containing highly reflective particles printed on the light exit side of the light guide. In this method, light is emitted from the emission surface. In this method, the light emitted from the emission surface is made uniform by using a diffusion plate or a condensing prism sheet to erase the dot pattern or condensing it, and the liquid crystal display device as light in a desired direction Is used for lighting. However, in this method, since the light reflected by the printing dots of the highly reflective ink becomes scattered light, there is a problem that the light is diffused in an unnecessary direction and the light use efficiency is likely to be lowered. Furthermore, a lens sheet for distributing light to desired light is required.

  The other method is a method in which a prism-shaped uneven surface for reflecting incident light is provided on the side opposite to the light emitting surface of the light guide to emit light by reflection and refraction from the light emitting surface side.

  As a light guide technique capable of reducing power consumption, a prism having an unequal triangular shape is used from the viewpoint that a light refraction method mainly using a prism shape rather than a diffusion method increases light utilization efficiency (see Patent Document 1). A prism angle (see Patent Document 2), a circular arc groove (see Patent Document 3), etc., which are critical angles of the light guide, have been proposed. Further, as a method for preventing a large amount of light from being emitted in the vicinity of the incident portion, a contrivance such as a method of shortening the prism period as the distance from the incident portion (see Patent Document 1) has been elaborated. However, both of these have the problem that the light use efficiency tends to be lowered when trying to obtain uniform planar brightness.

  In order to increase the brightness of the liquid crystal display surface and reduce power consumption by a refraction method mainly composed of a prism shape, a light guide body is arranged such that a prism sheet having a large number of prism rows is arranged on the light guide body side. Has been proposed (see Patent Document 4). However, this method tends to increase the front luminance, but there is a problem in the uniformity of light in a point light source described later.

  On the other hand, conventionally, a light source for an edge light has been provided with a linear or rod-like light source such as a straight tube fluorescent lamp along the incident end face, and the emitted light has been guided to a light guide. However, in recent years, a liquid crystal display device having a relatively small screen of portable electronic devices such as a mobile phone, a portable information terminal, and a portable game machine has been used with an LED that can be expected to be reduced in size and power consumption. It has increased. In addition, there is an increasing demand for both the brightness of the display screen and the reduction in power consumption.

In order to transfer a linear light source to a point light source with low power consumption, a method of arranging a plurality of LEDs along the light incident surface of a light guide (see Patent Document 5) has been proposed. If the diffusion effect is reduced so as to increase the uniformity, the uniformity of the light between the LEDs is impaired. On the other hand, if the uniformity is obtained, the utilization efficiency decreases.
In order to improve the utilization efficiency and uniformity of the LED, there is an apparatus (see Patent Document 6) in which a lens having a prism shape is roughened by a method of emitting light from a light guide by refraction or reflection mainly using the prism shape described above. Although it has been proposed, a roughening process is required, which not only complicates the manufacturing process, but also results in diffused light, resulting in reduced efficiency and increased cost.
Japanese Patent No. 2925530 Japanese Patent No. 3012462 JP 2000-98383 A Japanese Patent Laid-Open No. 10-268138 JP 7-270624 A JP 2003-144325 A

In view of the above circumstances, even in low power punctiform light source, avoiding the scattering and diffusion of electrode force light, and an object thereof is to provide a highly uniform surface light source device luminance.

According to a first aspect of the present invention for solving the above problems, a point light source, an incident surface composed of one end face of a light guide opposed to the light source, a reflecting surface positioned substantially perpendicular to the incident surface, and an exit surface In the surface light source device constituted by the above, a large number of lens arrays (A) having convex and / or concave curved surfaces extending in a direction substantially perpendicular to the incident surface are formed on the emission surface or the reflection surface, and further on the incident surface. On the other hand, a large number of asymmetric lens rows or prism rows (B) extending in a substantially parallel direction is opposite to a large number of lens rows (A) having convex and / or concave curved surfaces extending in a direction substantially perpendicular to the incident surface. 0.1 to 5 so that the asymmetric lens array or prism array (B) receives light toward the light source side with respect to the reflection surface or the exit surface positioned substantially perpendicular to the entrance surface. the surface light source device characterized by having an inclined surface of every angle α And content.

According to a second aspect of the present invention, the shape of a large number of lens arrays (A) having convex and / or concave curved surfaces extending in a direction substantially perpendicular to the incident surface is a cross-sectional shape in a direction parallel to the incident surface. , claim 1, the ratio H / W of the width W of the maximum height and / or the maximum low H and 1 unit of lens recess of the protrusion is equal to or within a range of 1 / 2-1 / 10 the serial placement of the surface light source device and the contents.

According to a third aspect of the present invention, as the shape of a large number of lens arrays (A) having convex and / or concave curved surfaces extending in a direction substantially perpendicular to the incident surface is separated from the incident surface, the cross-section of the convex or concave portions is increased. The surface light source device according to claim 2 , which has a large shape.

According to a fourth aspect of the present invention, an asymmetric lens array or prism array (B) extending substantially parallel to the incident surface is a reflective surface or an output surface substantially perpendicular to the asymmetric lens array or prism array (B1) and the entrance surface. The surface light source device according to any one of claims 1 to 3 , wherein the surface light source device is formed by a row (B2) of flat portions parallel to the surface.

According to a fifth aspect of the present invention, a large number of lens arrays (A) having convex and / or concave curved surfaces extending in a direction substantially perpendicular to the incident surface and an asymmetric lens array extending in a direction substantially parallel to the incident surface. or at least one of the prism row (B) are produced in sheet form, a surface light source according to any one of claims 1 to 4, characterized in that bonded to the light guide having at least one plane The contents are equipment.

A surface light source device according to the present invention includes a point light source, an incident surface composed of one end face of a light guide opposed to the light source, a reflective surface positioned substantially perpendicular to the incident surface, and an output surface. , A large number of lens arrays (A) having convex and / or concave curved surfaces extending in a direction substantially perpendicular to the incident surface are formed on the exit surface or reflecting surface, and further, a large number extending in a direction substantially parallel to the incident surface. The asymmetric lens array or prism array (B) is formed on a surface opposite to a large number of lens arrays (A) having convex and / or concave curved surfaces extending in a direction substantially perpendicular to the incident surface, An inclined surface having an angle α of 0.1 to 5 degrees so that the asymmetric lens array or prism array (B) receives light toward the light source side with respect to the reflection surface or the exit surface positioned substantially perpendicular to the entrance surface. by having, efficiently guiding the light emitted from the point light source It can be uniformly emitted across the exit surface of the body, in particular useful for a liquid crystal display device.

Having adopted LED point light source of low power as the light source, a cellular phone, portable information terminals, such as in a portable game machine, light weight, can be achieved thin, low power consumption.
Further, a light guide body in which a lens portion and a prism portion requiring precise processing are mass-produced separately from the main body portion of the light guide body, and these are combined with the light guide body main body portion is easy to manufacture and suitable.

  A surface light source device usually includes a light source such as a cold cathode tube or a light-emitting diode that is disposed in the vicinity of a side surface of the light guide, and the back surface of the light source is surrounded by a reflector or the like, It is configured to receive light from the end face.

  As shown in FIG. 1, when the light guide 2 is a parallel plane, light is incident on the light guide 2 from the incident surface 2 a of the light guide 2 from the light source 1 collected from the reflector 5. As the incident light, light 01 parallel to the light guide 2 travels straight, and light 02 smaller than the critical angle of the light guide 2 is emitted to the outside of the light guide 2. On the other hand, the light beams 03 and 04 that are equal to or larger than the critical angle of the light guide 2 are guided without changing the direction and angle while repeating total reflection on the upper and lower surfaces of the light guide 2.

  In order to extract the light taken into the light guide 2 to the exit surface 2d by light-reflective reflection and refraction with good light efficiency instead of scattered light, for example, as shown in FIG. There is a method of providing prism rows of unequal triangles arranged in the vertical direction. In this method, as shown in FIG. 2, when the angle (hereinafter referred to as the light receiving angle) α formed between the light receiving / reflecting surface of the prism array and the linearly traveling direction of the incident light is relatively large, the 03, 04 light is reflected on the reflecting surface 2cA. And is emitted at an angle substantially perpendicular to the emission surface 2d. However, as shown in FIG. 3, the 05 light reflected by the reflecting surface 2cB other than the reflecting surface 2cA has a drawback that it changes its direction and becomes close to the straight 01 light. And since light is likely to be emitted in a location near the light source, in order to improve the uniformity of the light, not only the emission near the light source is suppressed, but if the emission is not suppressed as a whole, the uniformity of the emission Is difficult to keep.

  In FIG. 3, as in FIG. 2, an unequal triangular prism array arranged in a direction perpendicular to the direction of the incident light is provided on the reflecting surface 2 c side. If the light receiving angle α is small, the light source position shown in FIG. 2 is reversed. The incident light is reflected by the inclined surface 2cB having a small light receiving angle, and the 03, 04 light is directed toward the light exit surface 2d. The light is emitted at a low angle. And 05 light close to a straight line can be emitted while the direction is changed by the reflecting surface 2cB and reflected several times. In addition, the difference in intensity of the emission between the location near the light source and the location far from the light source is small, and even when the emission intensity is increased, the uniformity of the emission is easily maintained. The reason is that if the light receiving angle α of the prism array is increased in order to increase the emission intensity, a large amount of light is reflected and refracted in the vicinity of the light source as shown in FIG. 2, whereas as shown in FIG. This is because if the light receiving angle α is reduced, the light receiving / reflecting surface can be made large from the beginning, so that the emission intensity can be increased and the uniformity of the emission can be sufficiently maintained.

  In order to increase the outgoing light having a low outgoing angle with respect to the outgoing surface in the direction perpendicular to the outgoing surface, a method using a concavo-convex structure or a coated surface of high refractive index particles on the outgoing surface 2d has been often used. As described above, a decrease in light efficiency due to scattering is inevitable. To solve this problem, if a large number of lens arrays having convex and / or concave curved surfaces extending in a direction substantially perpendicular to the incident surface are arranged on the exit surface, the exit light is emitted while suppressing light scattering. It was found that the height can be increased in the direction perpendicular to the surface.

Further, as the light source shifts to a point light source of LED with low power consumption, in order to spread the light from the point light source uniformly in the width direction of the incident surface of the light guide, it is particularly a point due to the installation of a plurality of point light sources. In order to make the intensity of light between the light sources uniform, it is extremely effective to arrange a large number of lens rows on the exit surface that extend in a direction substantially perpendicular to the entrance surface and have convex and / or concave curved surfaces. I found out. In particular, it has been found that a curved surface has a great effect of making the intensity of light between point light sources uniform.
The present invention has been completed based on the above findings.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 4 is a schematic perspective view showing an embodiment of the surface light source device according to the present invention.
In the figure, two LEDs as a plurality of point-like light sources 1 are provided close to an incident surface 2 a formed from one end surface of the light guide 2.
The light guide 2 has two surfaces, an emission surface 2d and a reflection surface 2c, substantially perpendicular to the incident surface 2a. A large number of lens rows (A) having convex and / or concave curved surfaces extending in a direction substantially perpendicular to the incident surface 2a are set on the exit surface 2d. In this lens array (A), the ridges of the curved surface may be adjacent to each other, or may be set intermittently, that is, intermittently through a flat surface. Furthermore, the curved ridgelines may be parallel to each other, but they are non-parallel and narrow at locations close to the light source, and become wider as the distance increases, that is, the curved cross-sectional shape increases as the distance from the incident surface increases. Can be set as follows.
In the present invention, the “substantially perpendicular direction with respect to the incident surface 2a” refers to about ± 5 degrees in the perpendicular direction. The same applies to the following.

  The cross-sectional shape of a large number of lens arrays (A) having convex and / or concave curved surfaces extending in a direction substantially perpendicular to the incident surface 2a is an arc shape, an elliptical shape, a parabolic shape, or an apex portion of a triangular prism. Can be selected from shapes such as curved curves. At this time, a left-right asymmetrical shape as viewed from a direction perpendicular to the incident surface 2a may be used, but a symmetric shape is preferable because light emission tends to be symmetrical.

  Further, the cross-sectional shape of the lens array (A) has a maximum height H when it has a convex structure, a maximum height H when it has a concave structure, and a ratio H of the lens width W of one unit. / W affects the emission direction of light and the distribution of emission, and this ratio H / W is preferably in the range of 1/2 to 1/10. When H / W is larger than 1/2 or smaller than 1/10, the point light source becomes beam-shaped and hardly spreads to the width of the incident surface of the light guide.

On the opposite surface on which a large number of lens arrays (A) having convex and / or concave curved surfaces extending in a substantially right angle direction with respect to the incident surface 2a are formed, a large number extending in a direction substantially parallel to the incident surface 2a Asymmetric lens rows or prism rows (B).
In the present invention, the “substantially parallel direction with respect to the incident surface 2a” refers to about ± 5 degrees in the parallel direction. The same applies to the following.

The cross-sectional shape of the asymmetric lens array or prism array (B) is, as shown in the enlarged view in a circle in FIG. 4, the light source side with the reflecting surface 2 c or the exit surface 2 d positioned substantially perpendicular to the entrance surface 2 a as the base. An inclined surface S1 having an angle (light receiving angle) α of 0.1 to 5 degrees is essential, and the other surface is arranged based on a prism row (B) composed of an inclined surface S2 having an arbitrary angle β. The
Note that the apex angle or valley angle formed by the inclined surface S1 having an angle α of 0.1 to 5 degrees toward the light source and the inclined surface S2 having another arbitrary angle β is 0.1 to 5 degrees. As long as the inclined surface S1 having the angle α is substantially maintained, the top or the valley may be rounded and a lens array showing a curvature or the like may be used.

  The asymmetric lens array or prism array (B) is guided by the inclined surface S1 having an angle α of 0.1 to 5 degrees toward the light source side while the light incident from the light source is refracted or reflected to change the direction. Light with higher uniformity can be emitted from the emission surface 2d of the light body 2.

  In the lens array or prism array (B) having the inclined surface S1 having an angle α of 0.1 to 5 degrees toward the light source side, long edges or valley edges may be adjacent to each other, and substantially the same as the incident surface 2a. It may be intermittently arranged via a flat surface substantially parallel to the vertical emitting surface 2d or reflecting surface 2c. The period in which the lens rows or prism rows are arranged is arbitrary, but is usually in the range of 20 to 300 μm. Furthermore, the arranged period may be changed according to the distance from the light source.

  The light guide 2 may be a parallel plate in which the reflection surface 2c and the emission surface 2d are parallel to each other, or may be a wedge shape that becomes thinner as the distance from the incidence surface 2a increases. In many cases, the incident surface 2a is arranged perpendicularly to the reflecting surface 2c or the exit surface 2d. However, the incident surface 2a may be inclined to adjust the direction of incident light.

Although the incident surface 2a has many mirror surfaces for efficient incidence, it is possible to dent the place where the point light source is installed or to spread the light beam by placing a projection. Further, it is possible to provide a diffusing means on the incident surface 2a.

  The light guide is made of a transparent material. A transparent synthetic resin is suitable for mass production with a precise shape. This material is optional, but is selected from durable synthetic resins because it must withstand use as a surface light source device. Examples of such synthetic resins include acrylic resins, polyester resins, polycarbonates, polyolefins, epoxy resins, acrylic UV curable resins, and the like.

The molding method is arbitrary, but when a synthetic resin is used, injection molding, compression molding, etc., and a combination of these methods are employed. Further, the lens array (A) and the lens array or prism array (B) can be created separately from the light guide body, and can be created by combining them. As an example, a method in which a lens array or a prism array is formed into a continuous sheet by extrusion molding or a coating method, and this is combined with the main body is suitable for mass production. Furthermore, the coating method is suitable for creating a wide variety of light guides in that a simple mold can be used, and a method of curing and bonding using a UV curable resin or the like on the light guide body is suitable. ing.
As described above, the light guide may be a one-component integral type or a multilayer body. In the case of a multilayer body, a material having a close refractive index is preferred.

In the surface light source device, the light source 1 and the periphery of the light source 1 are covered with a reflector 5 as necessary. Light source 1 is a low power punctiform light source of Ru is used. Although there is a method in which a point light source is linearized by installing a linear light guide, it is often installed directly because it tends to reduce the light use efficiency. Further, there are many cases where a plurality of display screens are installed according to the brightness requirement of the display screen.

  In the light guide 2, a surface provided with a large number of lens rows (A) having convex and / or concave curved surfaces extending in a direction substantially perpendicular to the incident surface 2 a is incorporated in the display device as an output surface. On the contrary, the surface provided with a large number of asymmetric lens rows or prism rows (B) extending in a direction substantially parallel to the incident surface 2a may be incorporated in the display device as an exit surface. Since the opposite surface incorporated as the emitting surface becomes a reflecting surface, it is preferable to install a reflecting plate (not shown) facing the reflecting surface.

  The reflector is a white reflector with particles with different refractive indexes embedded in it, a diffuse reflector that uses a concavo-convex structure on the surface, a reflector that has a thin film or layer of metal such as silver or aluminum, and a multilayer reflector that has multiple layers of different refractive indexes. A board etc. can be used.

  In order to condense the emitted light in the direction of the liquid crystal panel, a prism film is usually installed on the exit surface 2d. When the direction of the light emitted from the light guide 2 includes a relatively large angle with respect to the light exit surface 2d, for example, an angle of 30 degrees or more is included, a prism array having a triangular section with an apex angle of about 90 degrees is adjacently arranged. The formed film can be installed so that the prism surface is on the light exit side. In this case, it is often the case that the same kind of film is installed in such a manner that the prism rows are overlapped so as to be close to each other so that the prism surface is on the exit side.

  When the direction of the outgoing light with respect to the outgoing surface 2d is relatively small, for example, an angle of 30 degrees or less is large, the prism surface becomes the incident side of a film in which prism rows with a triangular triangle having an acute angle are arranged adjacent to each other. In many cases, the prism rows are arranged so as to be parallel to the incident surface of the light guide. In addition, in order to illuminate the display surface of the liquid crystal panel uniformly and with high quality, finally, various diffusion plates can be installed on a light guide or a prism film.

  A light source with a light source and a surface light source device incorporating optical members such as reflectors, prism films, diffusers, and various polarizing films and retardation plates, if necessary, are incorporated as backlights for liquid crystal display devices. It is. In the liquid crystal display device, a liquid crystal panel, upper and lower polarizing plates, and RGB three primary color panels are incorporated.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited only to this Example.

In the following examples and comparative examples, brightness, uniformity, and lens shape were measured by the following methods.
“Measurement of brightness and leveling”
Using a two-dimensional color distribution measuring device CA-1500 manufactured by Minolta Co., Ltd., the measurement location was determined according to the size of the surface light source from a distance of 400 mm above the light guide surface. Specifically, in the case of a size of 50 mm × 35.5 mm, the measurement surface was divided into nine and the luminance at the center of the division was measured. The luminance was expressed in cd / m ² . In the case of 70 mm × 45 mm size, the measurement point was divided into 25 and the luminance at the center of the division was measured. The degree of uniformity was expressed as a percentage (%) obtained by dividing the minimum value of luminance measured by dividing by the maximum value.

"Lens shape measurement"
Using an ultra-deep shape measuring microscope VK-8500 manufactured by Keyence Co., Ltd., the angle and the height H of the convex portion or the height H of the concave portion and the lens width W of one unit are measured from the shape chart. Asked.

Examples 1-5 and Comparative Examples 1-2
A wedge-shaped acrylic plate having a long side of 50 mm, a short side of 35.5 mm, the short side as the incident surface 2a, a thickness of the incident surface 2a of 0.8 mm along the long side, and a thickness of the counter-incident surface 2b of 0.57 mm is prepared. did.
On the exit surface side of the acrylic plate, a lens shape having an arc shape with a central angle of about 146 degrees with a curvature of 24 μm and a convex height of 17 μm at a pitch of 48 μm is adjacent to the lens ridge line and parallel to the long side. A UV curable resin (GA4100RL-A, manufactured by Jujo Chemical Co., Ltd.) was used to make it adhere to the exit surface side of the acrylic plate, and then cured and adhered through a UV irradiator.
Subsequently, as shown in Table 1, the opposite reflecting surface 2c has a light receiving angle α, but the other inclined surface facing the reflecting surface has a constant angle β of 45 degrees and a pitch of 190 μm. 6 types of prism sheets were produced using the same UV curable resin as the exit surface, and a light guide integrated with the reflective surface side of the acrylic plate was produced.
Next, as shown in FIG. 5, an isosceles prism film 6 having an apex angle of 65 degrees with a pitch of 50 μm is disposed on the light exit surface 2d of the light guide so that the apex ridge is parallel to the incident surface 2a. Further, a surface light source in which a lens surface is disposed so as to face the exit surface 2d of the light guide 2 and an Ag reflection sheet 7 (75W 05 manufactured by Reiko Co., Ltd.) is disposed on the surface of the light guide 2 facing the reflection surface 2c. Created a device.
In addition, as Comparative Example 1, a light guide sample without an unequal side prism array was also prepared.

Subsequently, four LED lamps are wired in series as the light source 1 on the short side (incident surface side) of the acrylic plate having a thickness of 0.8 mm and lighted under a current condition of 15 mA. And the degree of uniformity was measured.
Table 1 shows the measurement results. The luminance value in Table 1 is an average value of the luminance of 9 divisions.

  From Table 1, it can be seen that in the examples of the present invention having a light receiving angle α of 0.1 to 5 degrees, the brightness and the uniformity are high, and the surface light source is bright and uniform. On the other hand, Comparative Example 1 in which the light receiving angle α is 0 degrees has a high degree of uniformity but low brightness, and Comparative Example 2 in which the light receiving angle α is as large as 5.5 degrees has a low degree of uniformity and the light receiving angle α is 0. It can be seen that the brightness or the degree of uniformity is inferior outside the range of 1 to 5 degrees.

Examples 6-7 and Comparative Examples 3-5
A wedge-shaped acrylic plate having a long side of 70 mm, a short side of 45 mm, the short side as the incident surface 2a, the incident surface 2a as the thickness of 0.8 mm, and the counter-incident surface 2b as the thickness of 0.5 mm was prepared.
In Comparative Example 3, a prismatic shape of an isosceles triangle having an apex angle of 90 degrees at a pitch of 50 μm on the exit surface is made of UV curable resin (GA4100RL-A manufactured by Jujo Chemical Co., Ltd.) so that the prism ridge line is parallel to the long side. The prism shape produced using this was adhered to an acrylic plate and then cured and adhered through a UV irradiator. In the case of the 90-degree right triangle of Comparative Example 3, H / W is ½.

  In Comparative Example 4, a lens shape having a curved triangle-shaped tip of the prism shape of Comparative Example 3 was used on the exit surface. When this lens shape was measured with a shape measuring machine, the height H of the convex portion was 17 μm, and the width W of one unit of lens was 48 μm. Accordingly, the H / W in this case is 1 / 2.8.

  In Comparative Example 5, the same prism shape as that used for the reflecting surface in Example 3 was used for the reflecting surface, and a plane without a lens array was used for the emitting surface.

  In Example 6, the same lens shape as that of Comparative Example 4 was used on the exit surface, and the same prism shape as that of Comparative Example 5 was used on the reflecting surface.

  In Example 7, when the lens shape used on the exit surface was measured with a shape measuring machine, the height H of the convex portion was 11 μm and the width W of one unit of lens was 48 μm. Therefore, H / W in this case is 1 / 4.4.

The surface light source device was created by the same method as in Examples 1 to 6, and turned on by the same method to measure the luminance.
The measurement results are shown in Table 2. The luminance values in Table 2 are average values of the luminance in 25 divisions.

  From the results of Table 2, it can be seen that Examples 6 and 7 have high brightness and high level of uniformity. On the other hand, in Comparative Examples 3 and 4, it can be seen that both the luminance and the degree of uniformity are low. Further, in Comparative Example 3, the bright and dark lines of four beams from the LED were conspicuous. In Comparative Example 5, the bright and dark lines of the four beams were more conspicuous, and it was judged impossible to measure the luminance and obtain the average luminance, so that the measurement was impossible.

Examples 8-9
The exit surface has the same lens shape as in Example 6 with a lens width W of 48 μm, a convex height H of 17 μm and a H / W of 1/2. It has a lens array arranged perpendicularly to the entrance surface, and the reflective surface has a 100 μm pitch receiving angle α of 1.6 degrees and a non-equal triangular prism array having a cross section with an angle β of 45 degrees of the other surface and 90 μm. A wedge-shaped light guide having the same long and short sides as in Examples 6 to 7 having a shape in which flat portions of pitch are alternately present was manufactured by injection molding using an acrylic resin.
A surface light source device was prepared for the light guide in the same manner as in Examples 1 to 6, and the brightness was measured by lighting in the same manner. Moreover, the measurement result was shown as Example 9 of Table 3 using the output surface and the reflective surface in reverse.

  From the results of Table 3, the brightness of Example 8 using a lens shape in which a convex portion extending in a direction perpendicular to the entrance surface is formed on the exit surface is higher than that of Example 9 using the same lens shape on the reflection surface. I understand that it is expensive. However, even in Example 9, a considerably high luminance is obtained, and thus it can be seen that the exit surface and the reflection surface may be interchanged.

It is the schematic which shows an optical path in case a light guide is a parallel plane. It is the schematic which shows the optical path at the time of providing the big light reception angle (alpha) in the reflective surface of a light guide. It is the schematic which shows the optical path at the time of providing the small light reception angle (alpha) in the reflective surface of a light guide. It is a typical perspective view which shows one embodiment of the surface light source device by this invention. It is the schematic of a surface light source device.

1- point light source 2 Light guide 2a Incident surface 2b Anti-incident surface 2c Reflective surface 2d Output surface 01-05 Optical path 5 Reflector 6 Prism film 7 Reflector (flat plate)
(A) Multiple lens rows having convex and / or concave curved surfaces extending in a direction substantially perpendicular to the incident surface (B) Multiple asymmetric lens rows or prism rows extending in a direction substantially parallel to the incident surface S1 Light source side An inclined surface having an angle α of 0.1 to 5 degrees to the angle S2 An inclined surface having an arbitrary angle β

Claims (5)

In a surface light source device including a point light source, an incident surface composed of one end face of a light guide facing the light source, a reflecting surface positioned substantially perpendicular to the incident surface, and an exit surface, substantially perpendicular to the incident surface A large number of lens arrays (A) having convex and / or concave curved surfaces extending in the direction are formed on the exit surface or the reflection surface, and a large number of asymmetric lens arrays or prism arrays extending in a direction substantially parallel to the entrance surface. (B) is formed on a surface opposite to a large number of lens arrays (A) having convex and / or concave curved surfaces extending in a direction substantially perpendicular to the incident surface, and the asymmetric lens array or prism array ( B) has an inclined surface with an angle α of 0.1 to 5 degrees so as to receive light toward the light source with respect to the reflecting surface or the emitting surface positioned substantially perpendicular to the incident surface. Light source device. The shape of a large number of lens arrays (A) having convex and / or concave curved surfaces extending in a direction substantially perpendicular to the incident surface is the maximum height of the convex portions in the cross-sectional shape in the direction parallel to the incident surface. / or recesses maximum low H and claim 1 Symbol placement of the surface light source device, characterized in that there the ratio H / W of the width W of one unit of lens is in the range of 1 / 2-1 / 10 of the. The shape of a large number of lens arrays (A) having convex and / or concave curved surfaces extending in a direction substantially perpendicular to the incident surface is such that the cross-sectional shape of the convex or concave portions increases as the distance from the incident surface increases. The surface light source device according to claim 2 . An asymmetric lens array or prism array (B) extending substantially parallel to the incident surface is an asymmetric lens array or prism array (B1) and an array of flat portions parallel to the reflecting surface or the exit surface substantially perpendicular to the incident surface. It is formed by (B2), The surface light source device of any one of Claims 1-3 characterized by the above-mentioned. At least one of a large number of lens arrays (A) having convex and / or concave curved surfaces extending in a direction substantially perpendicular to the incident surface and an asymmetric lens array or prism array (B) extending in a direction substantially parallel to the incident surface. any is produced in sheet form, a surface light source device according to any one of claims 1 to 4, characterized in that bonded to the light guide having at least one plane.

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