JP5510038B2 - Collimated light source and surface light source device - Google Patents

Description

  The present invention relates to a collimated light source and a surface light source device, and more particularly to a collimated light source for allowing parallel light to enter a light guide plate of the surface light source device and a surface light source device using the collimated light source.

  FIG. 1 shows a surface light source device that selectively emits light from a plurality of light emitting areas 14 a and 14 b in a light guide plate 14. In this surface light source device, when the light source unit 11a emits light, only the front light emitting area 14a emits light by the light emitted from the light source unit 11a. Further, when the light source unit 11b is caused to emit light, only the light emitting area 14b in front of the light emitting area 14b emits light by the light emitted from the light source unit 11b.

  However, in such a surface light source device, for example, when the spread of light emitted from the light source unit 11a is large, the light emitted from the light source unit 11a in an oblique direction enters the light emitting area 14b as indicated by an arrow in FIG. Then, the light is emitted to another light emitting area 14b that should not emit light. Therefore, in this surface light source device, collimated light sources that emit parallel light are used as the light source units 11a and 11b.

  FIG. 2 is a perspective view showing the structures of the collimated light source 11 and the light guide plate 14 used in the surface light source device. 3A and 3B are a plan view and a schematic cross-sectional view of the collimated light source 11 and the light guide plate 14, respectively. The collimating light source 11 includes a plurality of light sources 12 and a plate-like collimating lens array 13 having translucency. The collimating lens array 13 is formed by integrally arranging a plurality of collimating lenses 15 in the shape of a biconvex lens composed of an entrance side lens 16 and an exit side lens 17. The collimating lens array 13 is arranged with the emission side lens 17 facing the incident end face 18 of the light guide plate 14, and the light source 12 is arranged at a position facing the incident side lens 16 of each collimating lens 15. As shown in FIG. 3B, a number of triangular prism-shaped deflection patterns 19 are recessed on the lower surface of the light emitting area of the light guide plate 14.

  As shown in FIG. 3A, when the light source 12 is turned on, the light emitted from the light source 12 is converted into parallel light by passing through each collimator lens 15, and from the incident end face 18 of the light guide plate 14. The light enters the light guide plate 14. The light incident on the light guide plate 14 is guided while repeating total reflection between the front and back surfaces of the light guide plate 14 as shown in FIG. The light emitting area emits light from the light emitting surface 20 (the surface of the light guide plate 14).

  However, when the collimated light source 11 having the structure as shown in FIGS. 2 and 3 is used, a straight line (hereinafter referred to as “lens”) passing through the center between adjacent collimating lenses 15 and parallel to the optical axis of the collimating lens 15. The ratio of the amount of light distributed in the vicinity of the joint between the lenses is small compared to the area in front of the central portion of the collimating lens 15, and a dark line is generated at the joint between the lenses. There has been a problem that luminance unevenness occurs in the light emitting area and the appearance of the surface light source device is deteriorated. Specifically, the luminance distribution in front of the two collimating lenses 15 is as shown in FIG. In the luminance distribution K shown in FIG. 4, the lower the dot density, the lower the luminance, and the higher the dot density, the higher the luminance. According to the luminance distribution K, it can be seen that the luminance is high in front of the central portion of each collimating lens 15 and the luminance is low near the joint between the lenses. FIG. 5 is a graph showing the luminance distribution along the line AA in FIG. 4 (luminance distribution on the light emitting surface 20), and the horizontal axis in FIG. 5 indicates the position on the AA line (Y direction position). Represents. The width W of one collimating lens 15 is 10 mm, and the joint C between the lenses is the origin of the Y-direction position (0 mm position). In this specification, a direction parallel to the width direction or the arrangement direction of the collimating lens is referred to as a Y direction, and a direction parallel to the optical axis direction of the collimating lens is referred to as an X direction. According to FIG. 5, it can be clearly seen that the luminance is high in front of the central portion of the collimating lens 15 and the luminance is low at the joint between the lenses.

  Patent Document 1 discloses a light emitting module that emits parallel light. In this light emitting module, a Fresnel lens-like lens member is provided in front of a light source, and light emitted from the light source is converted into parallel light by passing through the lens member. However, even in such a light emitting module, sufficient light cannot be distributed to the end of the lens member, so that the amount of light at the end is insufficient compared to the center of the lens member, and it tends to be dark.

JP 2008-141152 A

  The present invention has been made in view of the technical problems as described above, and its object is to increase the amount of light distributed between the collimating lenses or in the region corresponding to the side surface of the collimating lens. An object of the present invention is to provide a collimated light source and a surface light source device that can reduce luminance unevenness and dark lines of the surface light source device.

A collimating light source according to the present invention comprises a plurality of light sources and a plurality of collimating lenses arranged in parallel along the width direction for collimating the light emitted from each of the light sources into parallel light. A collimating light source comprising an array , wherein the collimating lens includes a lens incident surface facing the light source, and a reflecting wall extending from both ends of the lens incident surface toward the opposite side of the light source. And a step surface extending from the end of the reflecting wall on the side far from the light source, and a convex lens-shaped exit side lens provided on the opposite side of the lens entrance surface, the lens entrance surface Is provided with a diffusion region in which a plurality of diffusion patterns for diffusing incident light toward the side are formed, and the reflection walls are inclined so that the distance between the reflection walls increases toward the emission side lens side. and, before Step surface is characterized in that extending in parallel with the lens light incident surface.

  According to the collimated light source of the present invention, the light of the light source incident from the diffusion region of the lens incident surface is diffused and spread in the lateral direction (side direction), and the light diffused in the lateral direction at a large angle is reflected by the reflecting wall. By doing so, the light emitted from the collimated light source is collimated by the emission side lens and emitted forward as parallel light. According to such a collimated light source, the light in the central part can be diffused in the diffusion region and distributed to the edge part, so that the light quantity over the width direction can be obtained without impairing the parallelism of the light emitted from the collimated light source. Can be made uniform. Therefore, when used as a surface light source device in combination with a light guide plate, it is possible to prevent dark lines from being generated in the light guide plate in a region facing the side surface of the collimating lens, and to reduce unevenness in luminance.

Furthermore, the collimating light source according to the present invention includes a collimating lens array in which a plurality of the collimating lenses are continuously arranged along the width direction thereof, and the plurality of light sources are respectively provided with a lens incident surface of each collimating lens. Therefore, it is possible to irradiate a wide light emitting area with parallel light. In addition, since the width can be increased without increasing the length (depth) of the collimated light source, it is possible to avoid an increase in the size of the collimated light source. Further, in the collimating lens, since the step surface extending in parallel with the lens light incident surface is provided from the end of the reflecting wall far from the light source, the length of the joint portion between the collimating lenses can be increased. In the collimating lens array, it is possible to prevent the joint portion between the collimating lenses from being damaged.

Certain embodiments of the collimated light source according to the present invention, the diffusion region is characterized by being configured by arranging said diffusion pattern and the flat surface alternately. According to this embodiment, only a part of the light incident on the diffusion region can be diffused, and the light distribution in the collimator lens can be adjusted by changing the area ratio between the diffusion pattern and the flat surface.

Another embodiment of the collimated light source according to the present invention is characterized in that a flat surface region having no diffusion pattern is formed on both sides of the diffusion region on the lens incident surface. According to such an embodiment, since the light incident on the side end portion of the lens light incident surface is not diffused, it is possible to prevent the light at both end portions from being diffused to reduce the light amount.

  Yet another embodiment of the collimated light source according to the present invention is characterized in that the diffusion pattern is a V-groove recessed in the lens light incident surface. According to the V-groove-shaped diffusion pattern, light incident on the diffusion pattern can be spread toward both sides.

  Further, if the inclination angle of the slope of the diffusion pattern having a V-groove shape with respect to the lens incident surface is 33 ° or more and 62 ° or less, the effect of preventing luminance unevenness in the light emitting area of the light guide plate can be enhanced.

  Yet another embodiment of the collimated light source according to the present invention is characterized in that an angle between the reflection wall and a surface obtained by extending the lens light incident surface is 52 ° or more and 64 ° or less. According to such an embodiment, it is possible to reduce the amount of light emitted in an oblique direction out of the direction of the parallel light, and to reduce luminance unevenness in the light emitting area of the light guide plate.

  Yet another embodiment of the collimated light source according to the present invention is characterized in that the emission side lens is formed of a Fresnel lens. According to this embodiment, the length (depth) of the collimated light source can be shortened, and the collimated light source can be further downsized.

  A surface light source device according to the present invention includes a light guide plate and one or a plurality of collimated light sources according to the present invention. According to the surface light source device of the present invention, it is possible to prevent dark lines from being generated in a region corresponding to the edge of the collimating lens or a region corresponding to a joint between the collimating lenses, and uneven luminance of the surface light source device can be reduced.

  The means for solving the above-described problems in the present invention has a feature in which the above-described constituent elements are appropriately combined, and the present invention enables many variations by combining such constituent elements. .

FIG. 1 is a plan view showing a conventional surface light source device having two light source units. FIG. 2 is a perspective view showing a conventional surface light source device including one collimated light source and a light guide plate. 3A and 3B are a plan view and a schematic sectional view showing the surface light source device of FIG. FIG. 4 is a plan view of the surface light source device showing the luminance distribution in front of the collimating lens array. FIG. 5 is a diagram showing the luminance distribution along the line AA in FIG. FIG. 6 is a perspective view of a collimated light source according to Embodiment 1 of the present invention. FIG. 7A is a plan view of the collimated light source of Embodiment 1, and FIG. 7B is a side view thereof. FIG. 8 is an enlarged perspective view of a diffusion region provided on the lens incident surface of the collimator lens. FIG. 9 (A) is a diagram illustrating a rounded corner formed between the lens incident surface of the collimator lens and the reflection wall. FIG. 9 (B) is a diagram showing the rounds that occur at the end of the diffusion pattern in the diffusion region. FIG. 10 is a plan view of the surface light source device including the collimated light source and the light guide plate according to the first embodiment. 11A and 11B are a plan view and a cross-sectional view of a deflection pattern provided on the back surface of the light guide plate. 12 shows the luminance distribution in the front of one collimating lens in the collimating lens array shown in FIG. 2 (in the case of a conventional lens) and the luminance distribution in the front of the collimated light source according to the first embodiment of the present invention (first embodiment). It is the figure which compared and showed. FIG. 13A is a diagram for explaining a chip pitch of a light source having a blue LED chip, a red LED chip, and a green LED chip, and FIG. 13B shows a pattern pitch of a diffusion pattern provided in the diffusion region. It is a figure explaining. FIG. 14 is a perspective view showing a surface light source device according to Embodiment 2 of the present invention. FIG. 15 is a plan view showing a collimated light source used in the surface light source device of the second embodiment. FIG. 16 is a perspective view of a collimating lens array used in the collimating light source of FIG. FIG. 17 is a graph showing the luminance distribution along the line AA of FIG. 14 in front of two collimating lenses in the collimating lens array of Embodiment 2, and is the luminance distribution of the conventional example shown in FIG. Is also shown. FIG. 18 is a diagram illustrating the Y direction directivity immediately after passing through the collimating lens. FIG. 19 is a graph showing the relationship between the slope inclination angle β of the diffusion pattern and the luminance unevenness ratio Q with the conventional example. FIG. 20 is a diagram for explaining the definition of the side lobe rate. FIG. 21 is a diagram showing the relationship between the angle α of the reflecting wall, the side lobe ratio, and the luminance unevenness ratio of the conventional example when the slope inclination angle β of the diffusion pattern is 33 °. FIG. 22 is a diagram showing the relationship between the angle α of the reflecting wall, the side lobe ratio, and the luminance unevenness ratio of the conventional example when the slope inclination angle β of the diffusion pattern is 52 °. FIG. 23 is a diagram showing the relationship between the angle α of the reflection wall, the side lobe ratio, and the luminance unevenness ratio of the conventional example when the slope inclination angle β of the diffusion pattern is 62 °. FIG. 24 is a diagram illustrating the relationship between the height of the reflecting wall, the side lobe ratio, and the luminance unevenness ratio of the conventional example. FIG. 25 is a plan view showing a collimated light source of a comparative example. FIG. 26 is a perspective view of a collimating lens array used in the collimating light source of FIG. FIG. 27 is a perspective view showing a modification of the collimating lens array in the comparative example of FIG. FIG. 28 is a perspective view showing a collimated light source according to Embodiment 3 of the present invention. FIG. 29 is a plan view of a collimated light source according to the third embodiment.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments, and various design changes can be made without departing from the gist of the present invention.

(First embodiment)
Hereinafter, a collimated light source and a surface light source device according to Embodiment 1 of the present invention will be described with reference to FIGS.

  FIG. 6 is a perspective view showing the collimated light source 21 according to Embodiment 1 of the present invention, in which the light source 22 and the collimating lens 23 are drawn slightly apart. FIG. 7A is a plan view of the collimating light source 21, and also shows a part of the collimating lens 23 (diffusion pattern 30) enlarged sequentially. FIG. 7B is a side view of the collimated light source 21.

  The collimating light source 21 includes a light source 22 and a collimating lens 23 (dark line erasing lens). The light source 22 incorporates one or a plurality of LED chips therein, and usually emits white light from the front surface. The collimating lens 23 has a plate shape with a uniform thickness, and the upper and lower surfaces thereof are smooth surfaces parallel to each other. The collimating lens 23 is manufactured by injection molding, cutting, or the like using a transparent resin having a large refractive index such as polycarbonate resin, acrylic resin, or polymethyl methacrylate resin (PMMA) as a raw material.

  The collimating lens 23 includes a lens incident surface 24 for making the light source 22 face each other. A diffusion region 25 (pattern formation surface) is formed at the center of the lens incident surface 24, and a flat surface region 24 a having no pattern is formed on both sides of the diffusion region 25. As shown in FIGS. 7A and 8, the diffusion region 25 is formed by arranging the diffusion patterns 30 at a constant pitch with the flat surface 25a interposed therebetween. The diffusion pattern 30 has a V-groove shape and extends in the thickness direction of the lens light incident surface 24 with a uniform cross-sectional shape. The slope inclination angle β of the diffusion pattern 30 having the V-groove shape (isosceles triangle shape) is preferably 33 ° or more and 62 ° or less as described later. The light source 22 is disposed in opposition to the lens incident surface 24 in the vicinity thereof.

  Side portions extending forward from both ends of the lens light incident surface 24 include a reflection wall 26, a step surface 27, and a side wall surface 28, respectively. The reflection wall 26 forms an angle α with respect to the lens light incident surface 24, and the space between the left and right reflection walls 26 increases toward the front. The angle α of the reflecting wall 26 is preferably 52 ° or more and 64 ° or less as will be described later. The step surface 27 is a surface parallel to the lens light incident surface 24. The left and right side wall surfaces 28 are parallel to each other. The front surface of the collimator lens 23 is configured by an exit side lens 29 (convex lens) that has an arc shape in plan view.

  According to the collimated light source 21 having the above-described structure, the light incident on both ends (flat surface region 24a) of the lens incident surface 24 out of the light emitted from the light source 22 is refracted by the flat surface region 24a. The light enters the collimating lens 23. On the other hand, the light incident on the central portion (diffusion region 25) of the lens light incident surface 24 is diffused by the diffusion pattern 30 and spread left and right when entering the collimator lens 23, and spread to both sides. The light is totally reflected by the reflection wall 26 and directed forward. Then, the light emitted from the collimating lens 23 is collimated by the emission side lens 29 and becomes almost parallel light. Accordingly, the amount of light distributed in the central portion of the collimating lens 23 is reduced because light is diffused, and the amount of light distributed is increased in both sides of the collimating lens 23 because light is diffused in the diffusion region 25. In addition, the amount of light is made uniform over the entire width of the collimating lens 23.

  Further, since the diffusion region 25 is constituted by the flat surface 25a and the diffusion pattern 30, only a part of the light incident on the diffusion region 25 can be diffused by the diffusion pattern 30, and the pitch of the diffusion pattern 30 is adjusted. Thus, the ratio of the amount of light diffused by the diffusion pattern 30 can be adjusted. Further, by adjusting the slope inclination angle β of the diffusion pattern 30, the direction in which light is diffused by the diffusion pattern 30 can also be adjusted.

  The light emitted from the collimated light source 21 is desirably as close to perfect parallel light as possible. However, the light distribution characteristic of the light emitted from the collimated light source 21 is such that the half-value one-side angle is within ± 12 °. There is no problem.

  Further, when the collimating lens 23 is manufactured by injection molding, in order to make it easy to remove the collimating lens 23 from the molding die, the exit side lens 29 is inclined by about 1 ° in the thickness direction (drawing taper angle). May be. Similarly, in order to make it easy to take out the collimating lens 23 from the molding die, the lens light incident surface 24 and the like may be provided with a larger angle, for example, an inclination (extraction taper angle) of about 3 to 5 ° in the thickness direction. . In the case of molding, as shown in FIG. 9A, a corner having a radius of curvature of about 0.2 mm may be formed at the corner between the lens light incident surface 24 and the reflecting wall 26, as shown in FIG. As shown in (B), there may be a rounded radius of curvature of about 0.2 mm at the end of the diffusion pattern 30, but this level of rounded is not a problem in the performance of the collimating lens 23.

  FIG. 10 is a plan view of the surface light source device 31 in which the collimated light source 21 and the light guide plate 32 are combined. The light guide plate 32 is formed into a plate shape by a transparent resin having a high refractive index such as polycarbonate resin or acrylic resin, and has a thickness equal to or greater than the thickness of the collimating lens 23. Yes. The collimated light source 21 is disposed to face the light incident end surface 33 of the light guide plate 32. The light guide plate 32 has a light emitting area 32a. A large number of deflection patterns 34 are provided in the light emitting area 32a on the back surface of the light guide plate 32. As shown in FIGS. 11A and 11B, the deflection pattern 34 is a triangular prism-shaped recess formed on the back surface of the light guide plate 32, and is opposite to the deflection reflection surface 35 facing the light source side and the light source. It has a back surface 36 facing sideways. The tilt angle γ of the deflecting and reflecting surface 35 is 42 °, and the tilt angle ε of the back surface 36 is 60 ° or more and 90 ° or less. Since the deflection pattern 34 is to be emitted from the surface (light emission surface) of the light guide plate 32 by totally reflecting the light guided in the light guide plate 32 with the deflection reflection surface 35, the deflection pattern is formed on the entire light emitting area 32a. By arranging 34, the light emitting area 32a can emit light.

  The light emitting area 32a has a width equal to the width W of the collimating lens 23, and the amount of parallel light emitted from the collimating light source 21 is made uniform in the Y direction. The light emission brightness at is uniform. In particular, dark lines are less likely to occur at both ends in the Y direction of the light emitting area 32a.

  The graph of FIG. 12 represents the luminance distribution when the surface light source device 31 of FIG. 10 is used, and also shows the luminance distribution in the case of the conventional example for comparison. The position in the Y direction on the horizontal axis in FIG. 12 is a position along the line BB in FIG. 10, and the optical axis of the collimating lens is the origin of the Y direction position (position of 0 mm). In addition, the vertical axis indicates the luminance (light emission luminance) of light emitted from the surface of the light guide plate 32.

  The collimating lens 23 of Embodiment 1 used for measuring the luminance distribution in FIG. 12 has a length L = 11 mm, a width W = 10.5 mm, a radius of curvature R = 5.8 mm of the exit side lens 29, and an angle of the reflecting wall 26. α = 58 °, the height of the reflecting wall 26 (the step distance between the lens incident surface 24 and the step surface 27) D = 3 mm. The luminance was measured along the line BB in the light emitting area 32a having a width of 10.5 mm.

  The luminance distribution of the conventional example in FIG. 12 is the same as that of the collimating lens 15 (with a width of 10.5 mm) in the collimating lens array 13 having the shape shown in FIGS. The light emission luminance along the BB line was measured using the same light source 22 and light guide plate 32 as used.

  In the luminance distribution in the case of the conventional example in FIG. 12, the luminance is maximum at the center in the Y direction of the light emitting area 32a, and the luminance gradually decreases toward the end of the light emitting area 32a in the Y direction. On the other hand, in the luminance distribution in the first embodiment, substantially uniform luminance is obtained over the entire Y direction of the light emitting area 32a. Therefore, according to FIG. 12, it can be seen that dark lines are unlikely to occur in the light emitting area 32a in the regions corresponding to both side surfaces of the collimated light source 21.

  The light source 22 may emit white light by a combination of a blue LED chip and a yellow phosphor. However, when the surface light source device 31 is combined with a color liquid crystal, three colors of red, green, and blue are used. The display color becomes brighter when white light is emitted using the LED chip. In addition, if there are three color LED chips, colored light can be emitted by emitting only one color LED chip or only two color LED chips, and the collimating light source 21 has a color rendering effect. It can also be made.

  FIG. 13A shows a light source 22 in which blue LED chips 22B, red LED chips 22R, and green LED chips 22G are arranged at a constant pitch (chip pitch) Pc, and a diffusion region 25 that faces the light source 22. When such a light source 22 is used, the pitch (pattern pitch) Pp of the diffusion pattern 30 shown in FIG. 13B is ½ of the chip pitch Pc, and the two diffusion patterns 30 are opposed to each other between the LED chips. It is preferable to make it. For example, when the chip pitch Pc is 0.58 mm, the pattern pitch Pp of the diffusion pattern 30 is 0.29 mm. It is desirable to provide six diffusion patterns 30 for one light source 22.

(Second Embodiment)
FIG. 14 is a perspective view showing a surface light source device 41 according to Embodiment 2 of the present invention. FIG. 15 is a plan view of the collimated light source 42 used in the surface light source device 41. FIG. 16 is a perspective view of a collimating lens array 43 used for the collimating light source 42. The collimating lens array 43 used in the second embodiment is an array in which a plurality of the collimating lenses 23 of the first embodiment are arranged in the width direction. The light source 22 is disposed at a position facing each lens light incident surface 24 of the collimating lens array 43. By using such a collimated light source 42, it is possible to widen the light emitting area and deal with a wide light emitting area. In the case of the collimating lens array 43, the V-groove portion formed between the end portions of the adjacent emission side lenses 29 may be rounded with a radius of curvature of about 0.2 mm.

  The characteristics of the surface light source device 41 will be described. FIG. 17 is a graph showing the luminance distribution along the line AA in FIG. 14 (line segment in the Y direction at a position 18 mm from the light incident end face 33) in front of the two collimating lenses 23. The horizontal axis of FIG. 17 represents the position on the AA line (Y direction position), and the vertical axis represents the luminance of the light emitted from the surface (light emitting surface) of the light guide plate 32. The width W of one collimating lens 23 is 10 mm, and the joint between the lenses is the origin in the Y direction position (0 mm position). The dimensions of the collimating lens 23 are the same as those of the collimating lens 23 shown in FIG. FIG. 17 also shows the luminance distribution of the conventional example shown in FIG. 5 for comparison. In the case of the conventional example, the brightness is high near the optical axis of the collimating lens 15 (position in the Y direction is ± 5 mm), and the brightness is high near the joint between the lenses (positions in the Y direction are 0 mm and ± 10 mm). As a result, the luminance unevenness is significantly generated in the light guide plate. On the other hand, in the case of the surface light source device 41 of the second embodiment, the luminance is almost uniform in the entire Y direction. Therefore, according to the surface light source device 41 of Embodiment 2, it turns out that the dark line which generate | occur | produced in the prior art example is lose | eliminated, and the brightness nonuniformity in a light emission area is improved significantly.

  FIG. 18 is a diagram showing the directivity in the Y direction immediately after passing through the collimator lens 23. The directivity in the Y direction immediately after passing through the collimating lens is the directivity of light emitted from a certain collimating lens 23 when a plurality of light sources 22 emit light, and as shown in FIG. The angle measured from the optical axis is θ, and the amount of light immediately after passing through the lens in the direction of the angle θ is measured. According to FIG. 18, the half-value one-side angle in the Y direction directivity of the emitted light, that is, the angle θ when the luminous intensity becomes ½ of the maximum value is ± 6 °, which is good parallel from the collimated light source 42. Light is emitted. Therefore, according to the surface light source device 41 of the second embodiment, dark lines are less likely to be generated in the light emitting area, the effect of improving the luminance unevenness is increased, and the collimated light source 42 can emit parallel light with a small spread. Even when a plurality of light emitting areas are formed on the light guide plate 32 (see FIG. 1), the other light emitting areas are less likely to shine. If interference between the light emitting areas is less likely to occur in this way, the light emitting areas can be brought closer to each other than before, and a fine display is also possible.

Next, the basis for the appropriate angle (33 ° or more and 62 ° or less) of the slope inclination angle β of the diffusion pattern 30 will be described. First, the luminance unevenness ratio Q with the conventional example is defined as follows.
Luminance unevenness ratio Q = (luminance difference in the embodiment of the present invention) / (luminance difference in the conventional example)
Here, the luminance difference in the embodiment of the present invention is a difference N between the maximum luminance and the minimum luminance in the luminance distribution of the surface light source device 41 of the embodiment of the present invention (Embodiment 2), as shown in FIG. Further, the luminance difference in the conventional example is a difference M between the maximum luminance and the minimum luminance in the luminance distribution of the conventional example. Therefore, as the luminance unevenness ratio Q = N / M is smaller, dark lines are less likely to occur and the effect of improving the luminance unevenness is enhanced. However, if the luminance unevenness ratio Q with the conventional example is 0.4 or less, the luminance unevenness is improved. The effect is sufficient.

  FIG. 19 is a graph showing the luminance unevenness ratio Q obtained by changing the slope inclination angle β of the diffusion pattern 30 in the range of 20 ° to 75 °. If the brightness unevenness ratio Q with the conventional example is 40% or less, the effect of improving brightness unevenness is sufficient. Therefore, when the slope inclination angle β at which the brightness unevenness ratio Q is 40% or less is obtained from FIG. For this purpose, it is understood that the slope inclination angle β should be in the range of 33 ° to 62 °.

Next, the basis of the appropriate angle (52 ° or more and 64 ° or less) of the angle α of the reflection wall 26 will be described. First, the side lobe rate of Y direction directivity immediately after lens transmission is defined. For example, in the Y-direction directivity immediately after passing through the lens as shown in FIG. When the lobe intensity is S, S / T. That is,
Side lobe ratio = side lobe intensity S / peak intensity T
It is. A large side lobe rate means that light having a high luminous intensity (side lobe light) is guided in an oblique direction to light other light emitting areas (see FIG. 1), thereby deteriorating the appearance of the surface light source device. Therefore, the performance of the collimated light source 42 is higher when the side lobe ratio is smaller.

  Since the slope inclination angle β is preferably 33 ° or more and 62 ° or less as described above, the case where the slope inclination angle β is 33 °, 52 °, or 62 ° is selected as a value approximately equal to the values at both ends. Then, in each case of β = 33 °, 52 °, and 62 °, changes in the side lobe ratio with respect to the angle α of the reflection wall 26 and the luminance unevenness ratio Q with the conventional example were examined. FIG. 21 is a graph showing the results of measuring changes in the side lobe ratio and the luminance unevenness ratio Q with respect to the conventional example with respect to the angle α of the reflecting wall 26 when the slope inclination angle β is 33 °. FIG. 22 is a graph showing the results of measuring the change in the side lobe ratio with respect to the angle α of the reflection wall 26 and the luminance unevenness ratio Q with the conventional example when the slope inclination angle β is 52 °. FIG. 23 is a graph showing results of measuring changes in the side lobe ratio and the luminance unevenness ratio Q with respect to the conventional example with respect to the angle α of the reflecting wall 26 when the slope inclination angle β is 62 °.

  As the characteristics of the surface light source device 41, it is preferable that the luminance unevenness ratio Q is 60% or less and the side lobe ratio is 5% or less. When the range of the angle α of the reflecting wall 26 satisfying such conditions is obtained from FIGS. 21 to 23, the optimal range of the angle α is 52 ° or more and 64 ° or less. More desirably, the luminance unevenness ratio Q is 50% or less and the side lobe ratio is 3% or less. In the case of this condition, according to FIGS. 21 to 23, the optimum range of the angle α is 56 ° or more and 62 ° or less.

  Next, the function of the step surface 27 will be described. FIG. 24 shows the case where the width of the lens incident surface 24 is 3.68 mm, the angle α of the reflection wall 26 is 58 °, the slope inclination angle β of the diffusion pattern 30 is 37 °, and the arrangement pitch of the collimating lenses 23 is 10.5 mm. 4 is a graph showing changes in the side lobe ratio and the luminance unevenness ratio Q depending on the height D of the reflecting wall 26 in FIG. As described above, the smaller the side lobe ratio, the better. However, if it is 5% or less, there is no problem in use. Further, the luminance unevenness ratio Q is preferably 60% or less, and particularly preferably 40% or less. In FIG. 24, the side lobe rate is minimized when the height D of the reflecting wall 26 is maximized at 5.4 mm. At this time, since the luminance unevenness ratio Q with the conventional example is also 40% or less, it can be said that it is optimal in terms of performance.

  However, when the height D of the reflecting wall 26 is the maximum value of 5.4 mm, the collimating lens array 43 has the reflecting walls 26 of the adjacent collimating lenses 23 meeting each other as shown in FIGS. The shape has no step surface 27. In addition, the length d of the joint portion between the collimating lenses 23 is as short as about 2 mm. Therefore, the collimating lens array 43 may be damaged at the joint portion. However, when only one collimating lens 23 is used, there is no risk of breakage, and the shape without the step surface 27 may be used.

  Further, when the height D of the reflection wall 26 is the maximum value of 5.4 mm, the length d of the joint portion between the collimating lenses 23 is set to 0 mm in order to shorten the length L of the collimating lens array 43. The shape of the collimating lens array 43 is as shown in FIG. In this case, since the directivity in the Y direction of the collimating lens array 43 is expanded to ± 12.5 °, the parallelism of the emitted light is lowered, which is not preferable as the collimating light source 42.

  Therefore, the actually used collimating lens array 43 is designed so that the luminance unevenness ratio Q is close to the minimum value at a slight sacrifice of the side lobe ratio, and the height D of the reflecting wall 26 is 3 mm or more and 4 mm or less. As shown in FIGS. 15 and 16, the step surface 27 is bridged between the reflecting walls 26.

(Third embodiment)
FIG. 28 is a perspective view showing a collimated light source 51 according to Embodiment 3 of the present invention. FIG. 29 is a plan view of the collimated light source 51. The collimating light source 51 is characterized in that a Fresnel lens is used as each exit side lens 53 of the collimating lens array 52. In this collimated light source 51, since the Fresnel lens is used for the exit side lens 53, the length L of the collimated lens array 52 can be shortened, and the occupied area when the collimated light source 51 is built in can be reduced. .

21, 42, 51 Collimated light source 22 Light source 23 Collimating lens 24 Lens incident surface 24a Flat surface region 25 Diffusion region 25a Flat surface 26 Reflecting wall 28 Side wall surface 29, 53 Emission side lens 30 Diffusion pattern 31, 41 Surface light source device 32 Optical plate 32a Light emitting area 34 Deflection pattern 43, 52 Collimator lens array α Reflecting wall angle β Slope inclination angle

Claims (8)

A plurality of light sources, the at collimated light source and a collimating lens array configured by consecutively provided along the width direction a plurality of collimating lenses for emitting collimated the light emitted from the light sources There,
The collimating lens includes a lens incident surface facing the light source, reflection walls extending from opposite ends of the lens incident surface toward the opposite side of the light source, and a side of the reflection wall far from the light source. A step surface extended from the end of the lens, and a convex lens-shaped exit side lens provided on the opposite side of the lens incident surface,
The lens incident surface is provided with a diffusion region in which a plurality of diffusion patterns for diffusing incident light to the side are formed,
The reflection wall is inclined so that the space between the reflection walls spreads toward the exit side lens side ,
The collimating light source , wherein the step surface extends parallel to the lens light incident surface .   The collimating light source according to claim 1, wherein the diffusion region is configured by alternately arranging the diffusion patterns and flat surfaces.   2. The collimated light source according to claim 1, wherein a flat surface region having no diffusion pattern is formed on both sides of the diffusion region on the lens incident surface.   The collimating light source according to claim 1, wherein the diffusion pattern is a V-groove recessed in the lens light incident surface. 5. The collimated light source according to claim 4 , wherein an inclination angle of the inclined surface of the diffusion pattern having a V-groove shape with respect to the lens incident surface is not less than 33 ° and not more than 62 °.   2. The collimated light source according to claim 1, wherein an angle between the reflection wall and a surface obtained by extending the lens incident surface is 52 ° or more and 64 ° or less.   The collimating light source according to claim 1, wherein the emission side lens is formed of a Fresnel lens. A surface light source device comprising a light guide plate and one or a plurality of collimated light sources according to claim 1 .

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