Side edge type surface emitting device

Abstract

To provide a side edge type surface light-emitting device that can be reduced in manufacturing cost.SOLUTION: A side edge type surface light-emitting device comprises: a light guide plate 1 which has an emission surface Se on an upper side, a light distribution control surface Sd on a lower side, and an incidence surface Sin on a side surface connecting the emission surface Se and the light distribution control surface Sd; a light source which is provided on the incidence surface Sin side of the light guide plate 1, for example, a plurality of light-emitting diodes (LED) elements 2; an upper prism sheet 3 which has a plurality of prisms provided opposite the emission surface Se side of the light guide plate 1 along a parallel direction (Y direction) of the incidence surface Sin and an emission surface provided on an upper side; and a lower prism sheet 4A which has a plurality of triangular prisms 41A provided on an upper side opposite the light distribution control surface Sd of the light guide plate 1 along a right-angled direction (X direction) of the incidence surface Sin of the light guide plate 1 and a flat surface 42A provided on a lower side.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a side-edge type surface emitting device. [Background technology]

[0002] A side-edge type surface emitting device is made up of a light guide plate and a light source, such as a light-emitting diode (LED) element, provided on one side of the light guide plate. Since it is thin and lightweight, it is used as a backlight for a display device, such as a liquid crystal display (LCD) device. When such a display device is used in a public place, it is required to have a narrow light distribution characteristic, i.e., a narrow viewing angle characteristic, to prevent others from peeking at the display. This is called the privacy characteristic (effect) of the backlight.

[0003] FIG. 48 is a perspective view showing a conventional side-edge type surface emitting device (see Patent Documents 1 and 2).

[0004] In FIG. 48, the side edge type surface emitting device has an emission surface S on the upper side. e , and the light distribution control surface S on the bottom d , exit surface S e and light distribution control surface S d The incident surface S on one side of in and an incident surface S of the light guide plate 1. in A light source, such as a plurality of light emitting diode (LED) elements 2, is provided on the side of the light guide plate 1. e The incident surface S in The upper prism sheet 3 has a plurality of prisms provided on the lower side along the parallel direction (Y direction) of the light guide plate 1 and an exit surface on the upper side. d The light guide plate 1 has a flat surface 42 and an incident surface S in The light guide plate 1 includes a lower prism sheet 4 having a plurality of triangular prisms 41 provided on the lower side along the direction perpendicular to the light guide plate 1 (X direction), and a light absorbing sheet 5 for absorbing leaked light, provided opposite the triangular prisms 41 of the lower prism sheet 4. The light guide plate 1 has the same structure as the light guide plate 1 shown in Fig. 2 described later. That is, as shown in Fig. 2, the light guide plate 1 has a double-sided prism structure, and the entrance surface S inalong the perpendicular direction (X direction) of the exit surface S e A plurality of upper prisms 11 and an entrance surface S in Along the parallel direction (Y direction) of the light distribution control surface S d The upper prism sheet 3 is made up of a plurality of lower prisms 12 provided on the upper prism sheet 3. An air layer is provided between the lower prism sheet 4 and the light absorbing sheet 5 to ensure total reflection of the triangular prisms 41 of the lower prism sheet 4. In other words, the light absorbing sheet 5 and the lower prism sheet 4 are spaced apart. An LCD panel (not shown) is provided on the outer side of the upper prism sheet 3. Note that I1 and I2 indicate absolute luminance at viewing angles θ=±35° and ±45°.

[0005] FIG. 49 is a cross-sectional view in the horizontal direction (Y direction) of the lower prism sheet 4 in FIG.

[0006] As shown in FIG. 49, the triangular prisms 41 are arranged at equal intervals and have symmetric linear inclined surfaces 41-1, 41-2 along the X direction facing the light absorbing sheet 5 in FIG. 48. In this case, the apex angle α formed by the linear inclined surfaces 41-1, 41-2 is, for example, 90°.

[0007] FIG. 50 is a lateral (Y direction) sectional view for explaining the operation of the lower prism sheet 4 in FIG.

[0008] In FIG. 50, the light distribution control surface S d The light L2 leaking from the lower prism sheet 4 is incident on the flat surface 42 of the lower prism sheet 4.

[0009] Of the light L2, light L21 having a small angle of incidence with respect to the flat surface 42 of the lower prism sheet 4 is totally reflected by the linearly inclined surfaces 41-1 and 41-2 of the triangular prism 41 and returns to the light guide plate 1. In this case, the angle of incidence of the light L21 with respect to the linearly inclined surfaces 41-1 and 41-2 is larger than the critical angle of the lower prism sheet 4. As a result, the light L2 51A. More than 90% of this light is emitted by the upper prism sheet 3 at a viewing angle θ=−35° to 35°, thereby increasing the absolute luminance I0 at a viewing angle θ=0° in the horizontal (Y direction) light distribution according to the absolute luminance I shown in FIG.

[0010] On the other hand, light L22 having a large angle of incidence with respect to the flat surface 42 of the lower prism sheet 4 among the light L2 is refracted and emitted from the linearly inclined surfaces 41-1 and 41-2 of the triangular prism 41, and is absorbed by the light absorbing sheet 5. In this case, the angle of incidence of the light L22 with respect to the linearly inclined surfaces 41-1 and 41-2 is smaller than the critical angle of the lower prism sheet 4. As a result, the luminance I1 at the viewing angle θ=±35° and the absolute luminance I2 at the viewing angle θ=±45° can be reduced, and therefore, small luminance factors (privacy effect) I1 / I0 and I2 / I0 can be realized in the horizontal (Y direction) light distribution by the relative luminance I / I0 shown in FIG. 51B. In other words, the privacy effect can be improved.

[0011] Furthermore, light L23 of light L2 having an intermediate angle of incidence with respect to the flat surface 42 of the lower prism sheet 4 has an angle of incidence at the linearly inclined surfaces 41-1 and 41-2 of the triangular prism 41 that just barely exceeds the critical angle of the lower prism sheet 4. In this case, the total reflection light at the linearly inclined surface 41-1 or 41-2 generates a light distribution wider than the viewing angle θ=-35° to 35°. The light rays with this light distribution deteriorate the luminance factors (privacy effect) I1 / I0 and I2 / I0. The privacy effect is greater as the luminance factors I1 / I0 and I2 / I0 are both closer to 0.

[0012] Fig. 52 is a graph showing the relationship between the apex angle α of the prisms 41 of the lower prism sheet 4 in Figs. 49 and 50 and the total luminous flux (%) and the luminance factor (privacy effect) I1 / I0. In Fig. 52, the total luminous flux is set to 100% when the apex angle α of the prism 41 is 90°.

[0013] As shown in Fig. 52, when the apex angle α is between 70° and 110°, the total luminous flux is 88% or more, and when the apex angle α is between 85° and 100°, the total luminous flux is 90% or more. The luminance factor (privacy effect) I1 / I0 is somewhat worse, but is tolerable. In other words, the luminance factor (privacy effect) can be adjusted by the apex angle α, but preferably the apex angle α is 90°.

[0014] In the above, the privacy characteristics (effects) have been explained using the horizontal (Y direction) light distribution, but the same applies to the vertical (X direction) light distribution. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] JP 2019-212387 A [Patent Document 2] US10684405B2 [Patent Document 3] JP 2012-8600 A (Patent No. 5346066 A) Summary of the Invention [Problem to be solved by the invention]

[0016] 48, an air layer exists between the lower prism sheet 4 and the light absorbing sheet 5, and the apex angle of the triangular prism 41 of the lower prism sheet 4 faces the light absorbing sheet 5, making handling difficult in the manufacturing process, and foreign matter may get mixed in between the lower prism sheet 4 and the light absorbing sheet 5, or the triangular prism 41 of the lower prism sheet 4 and / or the light absorbing sheet 5 may come into contact and be scraped by external force, vibration, etc. during member transportation work, etc., resulting in minute defects. In particular, since the light absorbing sheet 5 is black, the above-mentioned foreign matter or defects may act as a reflecting member for white spots or bright spots, causing defects in the side edge type surface emitting device, reducing the yield and thus increasing the manufacturing cost. [Means for solving the problem]

[0017] In order to solve the above-mentioned problems, a side-edge type surface emitting device according to the present invention includes a light guide plate having an exit surface on an upper side, a light distribution control surface on a lower side, and an entrance surface on a side surface connecting the exit surface and the light distribution control surface, a light source provided on the entrance side of the light guide plate, an upper prism sheet having a plurality of first prisms provided on the lower side along a direction parallel to the entrance surface of the light guide plate and facing the exit surface side of the light guide plate, and an exit surface on the upper side, and a lower prism sheet having a plurality of second prisms provided on the upper side along a direction perpendicular to the entrance surface of the light guide plate and facing the light distribution control surface of the light guide plate, and a flat surface provided on the lower side. a light absorbing sheet provided opposite to and spaced apart from the first flat surface of the first lower prism sheet; It is equipped with the following. Effect of the Invention

[0018] According to the present invention, since the lower surface of the lower prism sheet is flat, foreign matter or defects do not occur and act as white or bright spots, so that defects of the side edge type surface emitting device can be prevented, the yield can be improved, and the manufacturing cost can be reduced. Even if a light absorbing sheet is provided opposite the flat lower surface of the lower prism sheet, the flat surfaces of the lower prism sheet and the light absorbing sheet face each other, so that handling is easy in the manufacturing process and foreign matter is unlikely to get mixed between the lower prism sheet and the light absorbing sheet, and fine defects are unlikely to occur due to the lower prism sheet and / or the light absorbing sheet being scraped by external force, vibration, etc. during the member transportation work, etc. As a result, the yield of the side edge type surface emitting device can be improved, and therefore the manufacturing cost can be reduced. [Brief description of the drawings]

[0019] [Figure 1] 1 is a perspective view showing a first embodiment of a side-edge type surface emitting device according to the present invention. [Diagram 2] FIG. 2 is a perspective view of the light guide plate of FIG. [Diagram 3] FIG. 3 is a cross-sectional view of one of the upper prisms of FIG. 2. [Figure 4] 3 shows the lower prism of FIG. 2, in which (A) is a bottom view and (B) is a partial cross-sectional view of (A). [Diagram 5] 3 is a cross-sectional view for explaining the operation of the light guide plate of FIG. 2. [Figure 6] 2 is a cross-sectional view showing details of the upper prism sheet in FIG. [Figure 7] 2 is a cross-sectional view showing details of the lower prism sheet in FIG. 1. [Figure 8] 2A and 2B are cross-sectional views for explaining the operation of the side-edge type surface emitting device of FIG. 1, where (A) is a cross-sectional view showing the operation in the horizontal direction (Y direction), and (B) is a cross-sectional view showing the operation in the vertical direction (X direction). [Figure 9] 8A shows the results of simulation operation in the horizontal direction (Y direction), where (A) is a graph showing the horizontal absolute luminance distribution, (B) is a graph showing the horizontal relative luminance distribution, which is a partial enlargement of (A), and (C) is a table showing the horizontal privacy effect. [Figure 10] 9 is a graph showing the total luminous flux and the lateral privacy effect of the side-edge type surface emitting device based on the results of simulation operation in the lateral direction (Y direction) of FIG. 8(A). [Figure 11] 8B shows the results of simulation operation in the vertical direction (X direction), in which (A) is a graph showing the vertical absolute luminance distribution, (B) is a graph showing the vertical relative luminance distribution, which is a partial enlargement of (A), and (C) is a table showing the vertical privacy effect. [Figure 12] 9 is a graph showing the total luminous flux and vertical privacy effect of the side-edge type surface emitting device based on the simulation operation results in the vertical direction (X direction) of FIG. 8(B). [Figure 13] FIG. 2 is a perspective view showing a second embodiment of a side-edge type surface emitting device according to the present invention. [Figure 14] 14A and 14B are cross-sectional views for explaining the operation of the side-edge type surface emitting device of FIG. 13, where (A) is a cross-sectional view showing the operation in the horizontal direction (Y direction), and (B) is a cross-sectional view showing the operation in the vertical direction (X direction). [Figure 15] 14A shows the results of simulation operation in the horizontal direction (Y direction), where (A) is a graph showing the horizontal absolute luminance distribution, (B) is a graph showing the horizontal relative luminance distribution, which is a partial enlargement of (A), and (C) is a table showing the horizontal privacy effect. [Figure 16]15 is a graph showing the total luminous flux and lateral privacy effect of the side-edge type surface emitting device based on the results of simulation operation in the lateral direction (Y direction) of FIG. 14(A). [Figure 17] 14B shows the results of simulation operation in the vertical direction (X direction), in which (A) is a graph showing the vertical absolute luminance distribution, (B) is a graph showing the vertical relative luminance distribution, which is a partial enlargement of (A), and (C) is a table showing the vertical privacy effect. [Figure 18] 15 is a graph showing the total luminous flux and vertical privacy effect of the side-edge type surface emitting device based on the simulation operation results in the vertical direction (X direction) of FIG. 14(B). [Figure 19] FIG. 11 is a perspective view showing a side-edge type surface emitting device as a comparative example. [Figure 20] 20A and 20B are cross-sectional views for explaining the operation of the side-edge type surface emitting device of FIG. 19, where (A) is a cross-sectional view showing the operation in the horizontal direction (Y direction), and (B) is a cross-sectional view showing the operation in the vertical direction (X direction). [Figure 21] 20(A) shows the results of simulation operation in the horizontal direction (Y direction), where (A) is a graph showing the horizontal absolute luminance distribution, (B) is a graph showing the horizontal relative luminance distribution, which is a partial enlargement of (A), and (C) is a table showing the horizontal privacy effect. [Figure 22] 21 is a graph showing the total luminous flux and lateral privacy effect of the side-edge type surface emitting device based on the results of simulation operation in the lateral direction (Y direction) of FIG. 20(A). [Figure 23] 20B shows the results of simulation operation in the vertical direction (X direction), in which (A) is a graph showing the vertical absolute luminance distribution, (B) is a graph showing the vertical relative luminance distribution, which is a partial enlargement of (A), and (C) is a table showing the vertical privacy effect. [Figure 24] 21 is a graph showing the total luminous flux and vertical privacy effect of the side-edge type surface emitting device based on the simulation operation results in the vertical direction (X direction) of FIG. 20(B). [Diagram 25] FIG. 11 is a perspective view showing a third embodiment of a side-edge type surface emitting device according to the present invention. [Figure 26] 26A and 26B show the lower prism sheet added in FIG. 25, in which (A) is a cross-sectional view and (B) is a cross-sectional view showing a contact portion between the lower prism sheets. [Figure 27] 26A and 26B are cross-sectional views for explaining the operation of the side-edge type surface emitting device of FIG. 25, where (A) is a cross-sectional view showing operation in the horizontal direction (Y direction), and (B) is a cross-sectional view showing operation in the vertical direction (X direction). [Figure 28] 27(A) shows the results of simulation operation in the horizontal direction (Y direction), where (A) is a graph showing the horizontal absolute luminance distribution, (B) is a graph showing the horizontal relative luminance distribution, which is a partial enlargement of (A), and (C) is a table showing the horizontal privacy effect. [Figure 29] 28 is a graph showing the total luminous flux and lateral privacy effect of the side-edge type surface emitting device based on the results of simulation operation in the lateral direction (Y direction) of FIG. 27(A). [Diagram 30] 27B shows the results of simulation operation in the vertical direction (X direction), in which (A) is a graph showing the vertical absolute luminance distribution, (B) is a graph showing the vertical relative luminance distribution, which is a partial enlargement of (A), and (C) is a table showing the vertical privacy effect. [Diagram 31] 27B is a graph showing the total luminous flux and vertical privacy effect of the side-edge type surface emitting device based on the simulation operation results in the vertical direction (X direction) of FIG. [Diagram 32] FIG. 11 is a perspective view showing a fourth embodiment of a side-edge type surface emitting device according to the present invention. [Diagram 33] 33A and 33B are cross-sectional views for explaining the operation of the side-edge type surface emitting device of FIG. 32, where (A) is a cross-sectional view showing operation in the horizontal direction (Y direction), and (B) is a cross-sectional view showing operation in the vertical direction (X direction). [Diagram 34] 33(A) shows the results of simulation operation in the horizontal direction (Y direction), where (A) is a graph showing the horizontal absolute luminance distribution, (B) is a graph showing the horizontal relative luminance distribution, which is a partial enlargement of (A), and (C) is a table showing the horizontal privacy effect. [Diagram 35]34 is a graph showing the total luminous flux and lateral privacy effect of the side-edge type surface emitting device based on the lateral (Y direction) simulation operation results of FIG. 33(A). [Diagram 36] 33B shows the results of simulation operation in the vertical direction (X direction), in which (A) is a graph showing the vertical absolute luminance distribution, (B) is a graph showing the vertical relative luminance distribution, which is a partial enlargement of (A), and (C) is a table showing the vertical privacy effect. [Figure 37] 34 is a graph showing the total luminous flux and vertical privacy effect of the side-edge type surface emitting device based on the simulation operation results in the vertical direction (X direction) of FIG. 33(B). [Figure 38] FIG. 11 is a perspective view showing a fifth embodiment of a side-edge type surface emitting device according to the present invention. [Figure 39] 39A and 39B are cross-sectional views for explaining the operation of the side-edge type surface emitting device of FIG. 38, where (A) is a cross-sectional view showing operation in the horizontal direction (Y direction), and (B) is a cross-sectional view showing operation in the vertical direction (X direction). [Diagram 40] 39(A) shows the results of simulation operation in the horizontal direction (Y direction), where (A) is a graph showing the horizontal absolute luminance distribution, (B) is a graph showing the horizontal relative luminance distribution which is a partial enlargement of (A), and (C) is a table showing the horizontal privacy effect. [Diagram 41] 40 is a graph showing the total luminous flux and lateral privacy effect of the side-edge type surface emitting device based on the results of simulation operation in the lateral direction (Y direction) of FIG. 39(A). [Diagram 42] 39B shows the results of simulation operation in the vertical direction (X direction), in which (A) is a graph showing the vertical absolute luminance distribution, (B) is a graph showing the vertical relative luminance distribution, which is a partial enlargement of (A), and (C) is a table showing the vertical privacy effect. [Diagram 43] 40 is a graph showing the total luminous flux and vertical privacy effect of a side-edge type surface emitting device based on the results of simulation operation in the vertical direction (X direction) of FIG. 39(B). [Diagram 44]FIG. 39 is a cross-sectional view showing a modification of the side-edge type surface emitting devices of FIGS. 25, 32 and 38, illustrating a contact portion between lower prism sheets. [Diagram 45] 45 is a table for explaining the average luminance and privacy effect of a modification of the side-edge type surface emitting device of FIG. 38 that employs the integrated lower prism sheet of FIG. 44. [Figure 46] This graph shows the results of simulating the total luminous flux and relative luminance I1 / I0 and I2 / I0 at viewing angles θ=±35° and ±45° when the apex angle αB of the triangular prism 41B of the lower prism sheet 4B in the side edge type surface emitting device of Figure 38 is fixed at 90° and the apex angle αA of the triangular prism 41A of the lower prism sheet 4A is changed to 90°, 80°, 85°, 95°, 100°, 110°, 120°, and 125°. [Figure 47] This graph shows the results of simulating the total luminous flux and relative luminance I1 / I0 and I2 / I0 at viewing angles θ=±35° and ±45° when the apex angle αA of the triangular prism 41A of the lower prism sheet 4A in the side edge type surface emitting device of Figure 38 is fixed at 90° and the apex angle αB of the triangular prism 41B of the lower prism sheet 4B is changed to 90°, 95°, 100°, 85°, 80°, 110°, and 120°. [Figure 48] FIG. 1 is a perspective view showing a conventional side-edge type surface emitting device. [Figure 49] 49 is a cross-sectional view of the lower prism sheet in FIG. 48 taken along the lateral direction (Y direction). [Figure 50] 50 is a lateral (Y direction) cross-sectional view illustrating the operation of the lower prism sheet in FIG. 49. FIG. [Figure 51] 49 shows the light distribution in the lateral direction (Y direction) of the side-edge type surface emitting device of FIG. 48, where (A) is a graph of absolute luminance, and (B) is a graph of relative luminance (luminance ratio). [Figure 52] 51 is a graph showing the relationship between the apex angle of the prisms of the lower prism sheets of FIGS. 49 and 50 and the total luminous flux (%) and the luminance factor (privacy effect). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] FIG. 1 is a perspective view showing a side-edge type surface emitting device according to a first embodiment of the present invention.

[0021] In Fig. 1, a lower prism sheet 4A is provided instead of the lower prism sheet 4 in Fig. 48. Also, the light absorbing sheet 5 is not provided.

[0022] The lower prism sheet 4A is a light distribution control surface S of the light guide plate 1. d The incident surface S of the light guide plate 1 faces the in The lower prism sheet 4A has a plurality of triangular prisms 41A provided on the upper side along the perpendicular direction (X direction) of the light emitting device, and a flat surface 42A provided on the lower side. By making the lower side of the lower prism sheet 4A a flat surface, in other words, by making the surface opposite to the emission surface of the side-edge type surface light emitting device flat, handling in the manufacturing process becomes easier, yields are improved, and manufacturing costs can be reduced.

[0023] Each part of the side-edge type surface emitting device of FIG. 1 will be described in detail below.

[0024] FIG. 2 is a perspective view of the light guide plate 1 of FIG.

[0025] In FIG. 2, the light guide plate 1 is composed of a base portion 10 and upper prism 11 and lower prism 12 other than the base portion 10. The base portion 10 of the light guide plate 1 is made of a light-transmitting material such as acrylic resin or polycarbonate resin, and the upper prism 11 and lower prism 12 are made of a light-transmitting material such as UV resin. In the light guide plate 1 according to the embodiment of the present invention, the base portion 10 is made of polycarbonate, and the upper prism 11 and lower prism 12 are made of UV-cured polymer-type acrylate. In the embodiment of the present invention, the base portion 10 of the light guide plate 1 is made of polycarbonate resin. The light guide plate 1 has a double-sided prism structure, and the incident surface S in along the perpendicular direction (X direction) of the exit surface S e A plurality of upper prisms 11 and an entrance surface S in Along the parallel direction (Y direction) of the light distribution control surface S dThe LED element 2 in FIG. in When light is incident on the light guide plate 1, the light propagates through the light guide plate 1, is reflected by the lower prism 12, and travels toward the upper prism 11. e It is emitted from

[0026] FIG. 3 is a cross-sectional view of one of the upper prisms 11 of FIG.

[0027] 3, the upper prism 11 protrudes in the Z direction and is therefore convex, that is, each prism of the upper prism 11 has a rounded tip 11a with an apex angle β of 80 to 110° and a radius of curvature R of 0 to 25 μm.

[0028] The cross-sectional shape of each prism of the upper prism 11 may be other shapes, such as a semicircle, a trapezoid, an isosceles triangle, etc. Also, hemispherical protrusions and hemispherical recesses may be arranged in the X and Y directions, semicylindrical recesses may extend in the X direction, and quadrangular pyramidal protrusions may be arranged in the X and Y directions.

[0029] FIG. 4 shows the details of the lower prism 12 in FIG. 2, where (A) is a bottom view and (B) is a partial cross-sectional view of (A).

[0030] As shown in the bottom view of FIG. 4A, a plurality of flat mirror surfaces 13 are arranged on the light distribution control surface S d The flat mirror surface portion 13 is disposed on the light source 10 along the X direction. The flat mirror surface portion 13 is intended to make the light uniform to the depth. The width of the flat mirror surface portion 13 in the Y direction is equal to the width of the incident surface S. in On the other hand, each prism of the lower prism 12 has an entrance surface S in The angle becomes larger as it gets farther away from the center. This allows more light to be emitted from the surface more uniformly toward the back. Also, as shown in the partial cross-sectional view of FIG. 4B, each prism of the lower prism 12 is composed of an asymmetric upward inclined surface 12-1 with an inclination angle γ1 and a downward inclined surface 12-2 with an inclination angle γ2 (<γ1). In this case, the light distribution control is mainly performed by the downward inclined surface 12-2.

[0031] FIG. 5 is a cross-sectional view for explaining the operation of the light guide plate 1 of FIG.

[0032] In FIG. 5, a certain light is emitted from the exit surface S e and light distribution control surface S d Then, the light is reflected by the exit surface S e Or, the light is refracted and emitted from the downward inclined surface 12-2 of the lower prism 12. In this case, the Y-direction width of each prism of the flat mirror surface portion 13 and the lower prism 12 changes along the X-direction, so that the light is refracted and emitted from the emission surface S e The light L1 emitted from the exit surface S e In this way, the light output surface S e The light L1 emitted from the exit surface S e On the other hand, the light is emitted at a certain angle to the normal of the light distribution control surface S d The light L2 leaking from the lens 10 leaks into the lower prism sheet 4A in FIG.

[0033] FIG. 6 is a cross-sectional view showing the details of the upper prism sheet 3 of FIG.

[0034] In FIG. 6, the upper prism sheet 3 is composed of a base portion 30 and a modified triangular prism 31, and has an entrance surface S in (FIG. 1) A plurality of deformed triangular prisms 31 are arranged on the lower side at equal distances from the center of the prism 31, and a flat surface S is arranged on the upper side of the prism 31. e3 Each of the modified triangular prisms 31 has an entrance surface S in The straight inclined surface 31-1 and the entrance surface S in 3, and has a curved inclined surface 31-2 on the opposite side. The upper prism sheet 3 has a base portion 30 made of a light-transmitting resin such as polyethylene terephthalate, polycarbonate, or polymethyl methacrylate. The modified triangular prisms 31 are made of a UV-curable resin, for example, a polymer type acrylate. In the upper prism sheet 3 according to the embodiment of the present invention, the base portion 30 is made of polyethylene terephthalate, and the triangular prisms 31 are made of a UV-cured polymer type acrylate. Each modified triangular prism 31 faces the exit surface S of the light guide plate 1. e (FIG. 1). Each deformed triangular prism 31 has a width W U is, for example, 18 to 25 μm, and the height HU The width W of each of the deformed triangular prisms 31 is, for example, 15 to 18 μm. U or height H U may be changed as necessary to eliminate moire that occurs when a backlight and liquid crystal are combined. In this case, each modified triangular prism 31 is determined by the angle δ1 of the linear inclined surface 31-1, the angle δ2 of the curved inclined surface 31-2, and the radius of the curved inclined surface 31-2. However, the curved inclined surface 31-2 may be any curve such as a straight line, a spline curve, or a parabola. e When the inclined light L1 from the upper prism sheet 3 enters the modified triangular prism 31 of the upper prism sheet 3, the light L1 is refracted at the linear inclined surface 31-1 and then totally reflected at the curved inclined surface 31-2. e3 From the flat surface S e3 Light L3 is emitted in the normal direction.

[0035] FIG. 7 is a cross-sectional view of the lower prism sheet 4A of FIG.

[0036] 7, the lower prism sheet 4A is composed of a base portion 40A and triangular prisms 41A. The lower prism sheet 4A is arranged at equal intervals and has an entrance surface S in The lower prism sheet 4A has a plurality of triangular prisms 41A-1 provided on the upper side along a direction perpendicular to the light distribution control surface S of the light guide plate 1 (X direction), and a flat surface 42A provided on the lower side. The lower prism sheet 4A has a base portion 40A made of a light-transmitting resin such as polyethylene terephthalate, polycarbonate, or polymethyl methacrylate. The triangular prisms 41A other than the base portion 40A are made of a UV-curable resin, for example, a polymer type acrylate. The lower prism sheet 4A in the embodiment of the present invention uses polyethylene terephthalate for the base portion 40A and a UV-cured polymer type acrylate for the triangular prisms 41A. Each triangular prism 41A is aligned with the light distribution control surface S of the light guide plate 1. d In this case, the apex angle αA formed by the linear inclined surfaces 41A-1 and 41A-2 is in the range of 85° to 95°, and is, for example, 90°.D is 25 to 30 μm, and the height H D is, for example, 10 to 16 μm, and the height H U The width W of the lower prism sheet 4A is smaller than that of the lower prism sheet 4A. D Or height H D may be changed as necessary to eliminate moire that occurs when a backlight and liquid crystal are combined.

[0037] 8A and 8B are cross-sectional views for explaining the operation of the side-edge type surface emitting device of FIG. 1, where (A) is a cross-sectional view showing operation in the horizontal direction (Y direction), and (B) is a cross-sectional view showing operation in the vertical direction (X direction).

[0038] As shown in (A) and (B) of FIG. 8, light L21 having a large angle of incidence with respect to the linearly inclined surfaces 41A-1 and 41A-2 of the triangular prisms 41A of the lower prism sheet 4A is totally reflected by the flat surface 42A of the lower prism sheet 4A and is reflected by the flat surface S of the upper prism sheet 3. e That is, the light L21 can increase the luminance I at a viewing angle θ of -35° to 35°.

[0039] On the other hand, as shown in (A) and (B) of FIG. 8, light L22 having a small angle of incidence with respect to the linearly inclined surfaces 41A-1 and 41A-2 of the triangular prism 41A of the lower prism sheet 4A among the light L2 is refracted and emitted from the flat surface 42A of the lower prism sheet 4A, and does not return to the upper prism sheet 3. That is, the light L22 can reduce the luminance I outside the viewing angle θ=-35° to 35°, that is, the relative luminance (privacy effect) I1 / I0. However, a part of the light refracted and emitted from the flat surface 42A of the lower prism sheet 4A is reflected by the housing (reflector) of the device, and becomes return light. This return light increases the total luminous flux of the device, but deteriorates the privacy effect.

[0040] 8A and 8B, the light L23 having an intermediate angle of incidence with respect to the linearly inclined surfaces 41A-1 and 41A-2 of the triangular prism 41A of the lower prism sheet 4A has an angle of incidence that just barely exceeds the critical angle of the flat surface 42A of the lower prism sheet 4A. e This causes the light to be inclined from the normal direction, resulting in a light distribution wider than the viewing angle θ = -35° to 35°. The light rays of this light distribution deteriorate the luminance factor (privacy effect) I1 / I0.

[0041] FIG. 9 shows the results of a simulation of the horizontal (Y direction) operation of (A) in FIG. 8, where (A) is a graph showing the horizontal absolute luminance distribution, (B) is a graph showing the horizontal relative luminance distribution, which is a partial enlargement of (A), and (C) is a table showing the horizontal privacy effect. In the following explanation, the simulation software used is Solid Work Light Simulation SREOS by OPTISWORKS (now ANSYS, Inc.). Also, unless otherwise specified, the upper prism sheet 3 is a prism having a width W of each deformed triangular prism 31. U 21μm, height H U The lower prism sheet 4A has a width W D 27μm, height H D The thickness of the light guide plate 1 was set to 14 μm. The light guide plate 1 shown in FIG.

[0042] 9 shows the results of a simulation of the horizontal (Y direction) operation of FIG. 8(A), comparing the side-edge type surface emitting device shown in FIG. 1 with the side-edge type surface emitting device shown in FIG. 48, and the structures are the same in that the light guide plate 1 and the deformed triangular prism 31 of the upper prism sheet 3 face downward. On the other hand, the triangular prism 41A of the lower prism sheet 4A of FIG. 1 faces upward, whereas the triangular prism 41 of the lower prism sheet 4 of FIG. 48 faces downward, and FIG. 48 differs in that the lower prism sheet 4 includes a light absorbing sheet 5 in the direction facing the light guide plate 1. According to the horizontal (Y direction) absolute luminance distribution obtained by the side-edge type surface emitting device of FIG. 1 shown in FIG. 9(A), it is almost the same as the horizontal (Y direction) absolute luminance distribution obtained by the conventional side-edge type surface emitting device of FIG. 48, but the total luminous flux in the horizontal and vertical directions is slightly increased. This is due to return light that is emitted from the lower flat surface 42A of the lower prism sheet 4A and is reflected by the surrounding housing or the like and re-enters the lower prism sheet 4A. On the other hand, referring to the relative luminance light distribution in Fig. 9(B), which is a partially enlarged view of Fig. 9(A), and the horizontal privacy effect table in Fig. 9(C), outside the viewing angle θ=-35° to 35°, the relative luminance I1 / I0 at θ=±35° and the relative luminance I2 / I0 at θ=±45° are slightly larger than those of the conventional side-edge type surface emitting device in Fig. 48, and therefore the privacy effect is slightly worse, but within an acceptable range.

[0043] Figure 10 is a graph of the total luminous flux and lateral privacy effects I1 / I0 and I2 / I0 of the side-edge type surface-emitting device of Figure 1 based on the results of the lateral simulation operation of Figure 8(A). In Figure 10, the total luminous flux is represented by black dots, and the privacy effect is represented by white dots. In this graph, the higher the total luminous flux (lm), the higher the luminance of the light-emitting device, and the smaller the values ​​of I1 / I0 and I2 / I0, the higher the privacy effect. In other words, the higher the plot on the graph, the higher the total luminous flux and the higher the privacy effect.

[0044] As shown in Fig. 10, in the side-edge type surface emitting device of Fig. 1, the total luminous flux is slightly increased due to the return light within the device compared to the side-edge type surface emitting device of Fig. 48, but the privacy effects I1 / I0 and I2 / I0 are slightly decreased. However, this deterioration in the privacy effect is within an acceptable range.

[0045] FIG. 11 shows the results of simulation operation in the vertical direction (X direction) of (B) in FIG. 8, where (A) is a graph showing the vertical absolute luminance distribution, (B) is a graph showing the vertical relative luminance distribution, which is a partial enlargement of (A), and (C) is a table showing the vertical privacy effect.

[0046] According to the vertical direction (X direction) absolute luminance distribution obtained by the side edge type surface light emitting device of FIG. 1 shown in FIG. 11A, it is almost the same as the vertical direction (X direction) absolute luminance distribution obtained by the conventional side edge type surface light emitting device of FIG. 48, but the total luminous flux in the horizontal and vertical directions is slightly increased. This is also because the light emitted from the lower flat surface 42A of the lower prism sheet 4A is reflected from the surrounding housing and the like and re-enters the lower prism sheet 4A. On the other hand, referring to the relative luminance distribution in FIG. 11B, which is a partially enlarged view of FIG. 11A, and the vertical direction privacy effect table in FIG. 11C, outside the viewing angle θ=-35° to 35°, the relative luminance I1 / I0 at θ=±35° and the relative luminance I2 / I0 at θ=±45° are slightly larger than those of the conventional side edge type surface light emitting device of FIG. 48, and therefore the privacy effect is slightly worse, but within an acceptable range.

[0047] FIG. 12 is a graph showing the total luminous flux and the vertical privacy effects I1 / I0 and I2 / I0 of the side-edge type surface emitting device of FIG. 1 based on the results of the vertical simulation operation of FIG. 8(B).

[0048] As shown in Fig. 12, in the side-edge type surface emitting device of Fig. 1, the total luminous flux is slightly increased compared to the side-edge type surface emitting device of Fig. 48, but the privacy effects I1 / I0 and I2 / I0 are slightly worse. However, the vertical privacy effect tends to be higher than the horizontal privacy effect, and is still within the acceptable range.

[0049] Thus, according to the first embodiment shown in Figure 1, the lower surface of the outer lower prism sheet 4A is flat, making it easy to handle during the manufacturing process, reducing the risk of foreign matter being mixed in, and also reducing the occurrence of fine defects during component transportation operations, etc.

[0050] Fig. 13 is a perspective view showing a second embodiment of a side-edge type surface emitting device according to the present invention. In Fig. 13, a light absorbing sheet 5 is added to the side-edge type surface emitting device of Fig. 1 so as to face the triangular prisms 41A of the lower prism sheet 4A. In this case, an air layer is provided between the lower prism sheet 4A and the light absorbing sheet 5. In other words, the lower prism sheet 4A and the light absorbing sheet 5 are spaced apart. The light absorbing sheet 5 is made of, for example, polyethylene terephthalate (PET) coated with black ink.

[0051] Figure 14 is a cross-sectional view for explaining the operation of the side-edge type surface emitting device of Figure 13, where (A) is a cross-sectional view showing operation in the horizontal direction (Y direction), and (B) is a cross-sectional view showing operation in the vertical direction (X direction).

[0052] As shown in (A) and (B) of FIG. 14, as in (A) and (B) of FIG. 8, of the light L2, the light L21 having a large angle of incidence with respect to the linearly inclined surfaces 41A-1 and 41A-2 of the triangular prism 41A of the lower prism sheet 4A is totally reflected by the flat surface 42A of the lower prism sheet 4A and is reflected by the flat surface S of the upper prism sheet 3. e That is, the light L21 can increase the luminance I at a viewing angle θ of -35° to 35°.

[0053] 14A and 14B, light L22 having a small angle of incidence with respect to the linearly inclined surfaces 41A-1 and 41A-2 of the triangular prism 41A of the lower prism sheet 4A is refracted and emitted from the flat surface 42A of the lower prism sheet 4A, and is absorbed by the light absorbing sheet 5. Therefore, the light L22 does not return at all to the upper prism sheet 3. In other words, the light L22 can improve the luminance I outside the viewing angle θ=-35° to 35°, that is, the relative luminance (privacy effect) I1 / I0, but the total luminous flux of the device is reduced.

[0054] 14A and 14B, as in the case of FIG. 8A and 8B, the light L23 of the light L2 having an intermediate angle of incidence with respect to the linearly inclined surfaces 41A-1 and 41A-2 of the triangular prism 41A of the lower prism sheet 4A has an angle of incidence that just barely exceeds the critical angle of the flat surface 42A of the lower prism sheet 4A. e This causes the light to be inclined from the normal direction, resulting in a light distribution wider than the viewing angle θ = -35° to 35°. The light rays of this light distribution deteriorate the luminance factor (privacy effect) I1 / I0.

[0055] FIG. 15 shows the results of simulation operation in the horizontal direction (Y direction) of (A) in FIG. 14, where (A) is a graph showing the horizontal absolute luminance distribution, (B) is a graph showing the horizontal relative luminance distribution, which is a partial enlargement of (A), and (C) is a table showing the horizontal privacy effect.

[0056] According to the absolute luminance distribution in the horizontal direction (Y direction) obtained by the side-edge type surface emitting device of FIG. 13 shown in FIG. 15(A), it is almost the same as the absolute luminance distribution in the horizontal direction (Y direction) obtained by the conventional side-edge type surface emitting device of FIG. 48, but the total luminous flux in the horizontal direction and the vertical direction is slightly reduced. This is because the light emitted from the lower flat surface 42A of the lower prism sheet 4A is absorbed by the light absorbing sheet 5. On the other hand, referring to the relative luminance distribution in FIG. 15(B) which is a partially enlarged view of FIG. 15(A) and the horizontal privacy effect table in FIG. 15(C), outside the viewing angle θ=-35° to 35°, the relative luminance I1 / I0 at θ=±35° and the relative luminance I2 / I0 at θ=±45° are slightly larger than those of the conventional side-edge type surface emitting device of FIG. 48, and therefore the privacy effect is slightly worse, but is better than that of the side-edge type surface emitting device of FIG. 1. This is also because the light emitted from the lower flat surface 42A of the lower prism sheet 4A is absorbed by the light absorbing sheet 5.

[0057] FIG. 16 is a graph showing the total luminous flux and the lateral privacy effects I1 / I0 and I2 / I0 of the side-edge type surface emitting device of FIG. 13 based on the lateral simulation operation results of FIG. 14(A).

[0058] As shown in FIG. 16, in the side edge type surface emitting device of FIG. 13, the total luminous flux is slightly reduced compared to the side edge type surface emitting device of FIG. 1, but it is understood that the privacy effects I1 / I0 and I2 / I0 are good.

[0059] FIG. 17 shows the results of simulation operation in the vertical direction (X direction) of FIG. 14(B), in which (A) is a graph showing the vertical absolute luminance distribution, (B) is a graph showing the vertical relative luminance distribution, which is a partial enlargement of (A), and (C) is a table showing the vertical privacy effect.

[0060] According to the absolute luminance distribution in the vertical direction (X direction) obtained by the side-edge type surface emission device of Fig. 13 shown in Fig. 17(A), it is almost the same as the absolute luminance distribution in the vertical direction (X direction) obtained by the conventional side-edge type surface emission device of Fig. 48, but the total luminous flux in the horizontal and vertical directions is slightly increased. On the other hand, referring to the relative luminance distribution in Fig. 17(B) which is a partially enlarged view of Fig. 17(A) and the vertical privacy effect table in Fig. 17(C), outside the viewing angle θ=-35° to 35°, the relative luminance I1 / I0 at θ=±35° and the relative luminance I2 / I0 at θ=±45° are slightly smaller than those of the conventional side-edge type surface emission device of Fig. 48, and therefore the privacy effect is good.

[0061] FIG. 18 is a graph showing the total luminous flux and the vertical privacy effects I1 / I0 and I2 / I0 of the side-edge type surface emitting device of FIG. 13 based on the results of the vertical simulation operation of FIG. 14(B).

[0062] As shown in Fig. 18, in the side-edge type surface emitting device of Fig. 13, the total luminous flux is slightly reduced compared to the side-edge type surface emitting device of Fig. 48, but the vertical privacy effects I1 / I0 and I2 / I0 are slightly better. However, the vertical privacy effect tends to be higher than the horizontal privacy effect.

[0063] Fig. 19 is a perspective view showing a side-edge type surface emission device as a comparative example. In Fig. 19, a light absorbing layer 5' is provided instead of the light absorbing sheet 5 in the side-edge type surface emission device of Fig. 13. In this case, the lower prism sheet 4A and the light absorbing layer 5' are in contact with each other. The light absorbing layer 5' can be realized by painting a resin containing black ink, for example.

[0064] Figure 20 is a cross-sectional view for explaining the operation of the side-edge type surface emitting device of Figure 19, where (A) is a cross-sectional view showing operation in the horizontal direction (Y direction), and (B) is a cross-sectional view showing operation in the vertical direction (X direction).

[0065] 20A and 20B, light L21 having a large angle of incidence with respect to the linearly inclined surfaces 41A-1 and 41A-2 of the triangular prisms 41A of the lower prism sheet 4A is absorbed in the light absorbing layer 5' without being reflected by the flat surface 42A of the lower prism sheet 4A. In other words, the light L21 reduces the luminance I at viewing angles θ of -35° to 35°.

[0066] 20A and 20B, light L22 having a small angle of incidence with respect to the linearly inclined surfaces 41A-1 and 41A-2 of the triangular prism 41A of the lower prism sheet 4A is refracted and emitted from the flat surface 42A of the lower prism sheet 4A, but is still absorbed by the light absorbing layer 5'. Therefore, the light L22 does not return to the upper prism sheet 3 at all. In other words, the light L22 can improve the luminance I outside the viewing angle θ=-35° to 35°, that is, the relative luminance (privacy effect) I1 / I0, but the total luminous flux of the device is significantly reduced.

[0067] 20A and 20B, similarly to Fig. 14A and 14B, light L23 of light L2 having an intermediate angle of incidence with respect to linearly inclined surfaces 41A-1 and 41A-2 of triangular prism 41A of lower prism sheet 4A has an angle of incidence that just barely exceeds the critical angle of flat surface 42A of lower prism sheet 4A. In this case, light L23 is also absorbed by light absorbing layer 5', improving the luminance factor (privacy effect) I1 / I0.

[0068] FIG. 21 shows the results of simulation operation in the horizontal direction (Y direction) of (A) in FIG. 20, where (A) is a graph showing the horizontal absolute luminance distribution, (B) is a graph showing the horizontal relative luminance distribution, which is a partial enlargement of (A), and (C) is a table showing the horizontal privacy effect.

[0069] According to the absolute luminance distribution in the horizontal direction (Y direction) obtained by the side-edge type surface light emitting device of FIG. 14 shown in FIG. 21A, the total luminous flux in the horizontal direction and the vertical direction is significantly reduced compared to the absolute luminance distribution in the horizontal direction (Y direction) obtained by the conventional side-edge type surface light emitting device of FIG. 48. This is because the light emitted from the lower flat surface 42A of the lower prism sheet 4A is absorbed by the light absorbing layer 5'. On the other hand, referring to the relative luminance distribution in FIG. 21B, which is a partially enlarged view of FIG. 21A, and the horizontal privacy effect table in FIG. 21C, outside the viewing angle θ=-35° to 35°, the relative luminance I1 / I0 at θ=±35° and the relative luminance I2 / I0 at θ=±45° are slightly smaller than those of the conventional side-edge type surface light emitting device of FIG. 48, and therefore the privacy effect is slightly better than that of the side-edge type surface light emitting device of FIG. 13. This is also because the light emitted from the lower flat surface 42B of the lower prism sheet 4B is absorbed by the light absorbing layer 5'.

[0070] FIG. 22 is a graph showing the total luminous flux and the lateral privacy effects I1 / I0 and I2 / I0 of the side-edge type surface emitting device of FIG. 19 based on the lateral simulation operation results of FIG. 20(A).

[0071] As shown in FIG. 22, in the side edge type surface emitting device of FIG. 19, the total luminous flux is significantly reduced compared to the side edge type surface emitting device of FIG. 13, but the privacy effects I1 / I0 and I2 / I0 are good.

[0072] FIG. 23 shows the results of simulation operation in the vertical direction (X direction) of (B) in FIG. 20, in which (A) is a graph showing the vertical absolute luminance distribution, (B) is a graph showing the vertical relative luminance distribution, which is a partial enlargement of (A), and (C) is a table showing the vertical privacy effect.

[0073] According to the absolute luminance distribution in the vertical direction (X direction) obtained by the side-edge type surface emission device of Fig. 19 shown in Fig. 23(A), the total luminous flux in the horizontal and vertical directions is significantly reduced compared to the absolute luminance distribution in the vertical direction (X direction) obtained by the conventional side-edge type surface emission device of Fig. 48. On the other hand, referring to the relative luminance distribution in Fig. 23(B) which is a partially enlarged view of Fig. 23(A) and the vertical privacy effect table in Fig. 23(C), outside the viewing angle θ=-35° to 35°, the relative luminance I1 / I0 at θ=±35° and the relative luminance I2 / I0 at θ=±45° are slightly smaller than those of the conventional side-edge type surface emission device of Fig. 48, and therefore the privacy effect is good.

[0074] FIG. 24 is a graph showing the total luminous flux and the vertical privacy effects I1 / I0 and I2 / I0 of the side-edge type surface emitting device of FIG. 19 based on the results of the vertical simulation operation of FIG. 20(B).

[0075] As shown in Figure 24, in the side-edge type surface-emitting device of Figure 19, the total luminous flux is significantly reduced compared to the side-edge type surface-emitting device of Figure 48, but the vertical privacy effects I1 / I0 and I2 / I0 are slightly better.

[0076] Thus, the side edge type surface emitting device of FIG. 19 as a comparative example can tolerate the privacy effect, but since the total luminous flux is significantly reduced by the light absorbing layer 5', it is not preferable as a surface emitting device.

[0077] FIG. 25 is a perspective view showing a side-edge type surface emitting device according to a third embodiment of the present invention.

[0078] In FIG. 25, a lower prism sheet 4B is added below the lower prism sheet 4A in FIG.

[0079] The lower prism sheet 4B has the same structure as the lower prism sheet 4A. That is, as shown in FIG. 26A, the lower prism sheet 4B faces the flat surface 42A of the lower prism sheet 4A and has an incident surface S of the light guide plate 1. inThe lower prism sheet 4A has a plurality of triangular prisms 41B provided on the upper side along the right angle direction (X direction) of the lower prism sheet 4A and a flat surface 42B provided on the lower side. Each triangular prism 41B has symmetrical linear inclined surfaces 41B-1 and 41B-2 along the X direction. In this case, the apex angle αB formed by the linear inclined surfaces 41B-1 and 41B-2 is in the range of 85° to 95°, for example, 90°. In addition, since the lower prism sheets 4A and 4B are made of a transparent resin with a medium hardness, as shown in FIG. 26B, the flat surface 42A of the lower prism sheet 4A and the triangular prisms 41B of the lower prism sheet 4B are in contact with each other due to their weights. At this time, the tips of the triangular prisms 41B of the lower prism sheet 4B are slightly rounded. As a result, it is expected that the privacy effect will be improved by refracting light that would otherwise be totally reflected by flat surface 42A of lower prism sheet 4A, which would deteriorate the privacy effect, into the rounded tips of triangular prisms 41B of lower prism sheet 4B.

[0080] Figure 27 is a cross-sectional view for explaining the operation of the side-edge type surface emitting device of Figure 25, where (A) is a cross-sectional view showing operation in the horizontal direction (Y direction), and (B) is a cross-sectional view showing operation in the vertical direction (X direction).

[0081] As shown in (A) and (B) of FIG. 27, similarly to (A) and (B) of FIG. 8, the light distribution control surface S d Of the light L2 coming from the upper prism sheet 3, light L21 having a large angle of incidence with respect to the linearly inclined surfaces 41A-1 and 41A-2 of the triangular prisms 41A of the lower prism sheet 4A is totally reflected by the flat surface 42A of the lower prism sheet 4A and is incident on the flat surface S of the upper prism sheet 3. e That is, the light L21 can increase the luminance I at a viewing angle θ of -35° to 35°.

[0082] On the other hand, as shown in (A) and (B) of FIG. 27, the light L22 having a small angle of incidence with respect to the linearly inclined surfaces 41A-1 and 41A-2 of the triangular prism 41A of the lower prism sheet 4A is refracted and emitted from the flat surface 42A of the lower prism sheet 4A, enters the lower prism sheet 4B, and does not return to the upper prism sheet 3. That is, the light L22 can reduce the luminance I outside the viewing angle θ=-35° to 35°, that is, the relative luminance (privacy effect) I1 / I0. However, a part of the light refracted and emitted from the flat surface 42B of the lower prism sheet 4B is reflected by the housing (reflector) of the device and becomes return light. This return light increases the total luminous flux of the device, but deteriorates the privacy effect.

[0083] Furthermore, as shown in (A) and (B) of FIG. 27, the light L23 of the light L2 having an intermediate angle of incidence with respect to the linearly inclined surfaces 41A-1 and 41A-2 of the triangular prism 41A of the lower prism sheet 4A has an angle of incidence that just barely exceeds the critical angle of the flat surface 42A of the lower prism sheet 4A. Even in this case, if a part of the light is at the tip of the triangular prism 41B of the lower prism sheet 4B, it enters the lower prism sheet 4B and does not return to the upper prism sheet 3. This improves the privacy effect. However, even in this case, a part of the light refracted and emitted from the flat surface 42B of the lower prism sheet 4B is reflected by the housing (reflector) of the device and becomes return light, which increases the total luminous flux of the device while worsening the privacy effect.

[0084] FIG. 28 shows the results of simulation operation in the horizontal direction (Y direction) of (A) in FIG. 27, where (A) is a graph showing the horizontal absolute luminance distribution, (B) is a graph showing the horizontal relative luminance distribution which is a partial enlargement of (A), and (C) is a table showing the horizontal privacy effect.

[0085] According to the absolute luminance distribution in the horizontal direction (Y direction) obtained by the side-edge type surface light emitting device of FIG. 25 shown in FIG. 28A, it is almost the same as the absolute luminance distribution in the horizontal direction (Y direction) obtained by the conventional side-edge type surface light emitting device of FIG. 48, but the total luminous flux in the horizontal direction and the vertical direction is slightly increased. This is due to the return light that is reflected from the surrounding housing and the like and re-enters the lower prism sheets 4B and 4A after the light that has been emitted from the lower flat surface 42B of the lower prism sheet 4B. On the other hand, referring to the relative luminance distribution in FIG. 28B, which is a partially enlarged view of FIG. 28A, and the horizontal privacy effect table in FIG. 28C, outside the viewing angle θ=-35° to 35°, the relative luminance I1 / I0 at θ=±35° and the relative luminance I2 / I0 at θ=±45° are slightly larger than those of the conventional side-edge type surface light emitting device of FIG. 48, and therefore the privacy effect is worse, but within an acceptable range.

[0086] FIG. 29 is a graph showing the total luminous flux and the lateral privacy effects I1 / I0 and I2 / I0 of the side-edge type surface emitting device of FIG. 25 based on the lateral simulation operation results of FIG. 27(A).

[0087] As shown in Fig. 29, in the side-edge type surface emitting device of Fig. 25, the total luminous flux is slightly increased compared to the side-edge type surface emitting device of Fig. 48 due to the return light within the device, but the privacy effects I1 / I0 and I2 / I0 are reduced. However, this deterioration in the privacy effect is within an acceptable range.

[0088] FIG. 30 shows the results of simulation operation in the vertical direction (X direction) of (B) in FIG. 27, in which (A) is a graph showing the vertical absolute luminance distribution, (B) is a graph showing the vertical relative luminance distribution, which is a partial enlargement of (A), and (C) is a table showing the vertical privacy effect.

[0089] The diagram shown in FIG. 25According to the vertical direction (X direction) absolute luminance distribution obtained by the side edge type surface light emitting device of FIG. 48, it is almost the same as the vertical direction (X direction) absolute luminance distribution obtained by the conventional side edge type surface light emitting device of FIG. 48, but the total luminous flux in the horizontal and vertical directions is slightly increased. This is also because the light emitted from the lower flat surface 42B of the lower prism sheet 4B is reflected from the surrounding housing, etc. and re-enters the lower prism sheets 4B and 4A. On the other hand, referring to the relative luminance distribution in FIG. 30B, which is a partially enlarged view of FIG. 30A, and the vertical direction privacy effect table in FIG. 30C, outside the viewing angle θ=-35° to 35°, the relative luminance I1 / I0 at θ=±35° and the relative luminance I2 / I0 at θ=±45° are larger than those of the conventional side edge type surface light emitting device of FIG. 48, and therefore the privacy effect is worse, but within an acceptable range.

[0090] FIG. 31 is a graph showing the total luminous flux and the vertical privacy effects I1 / I0 and I2 / I0 of the side-edge type surface emitting device of FIG. 25 based on the results of the vertical simulation operation of FIG. 27(B).

[0091] As shown in Fig. 31, in the side-edge type surface emitting device of Fig. 25, the total luminous flux is slightly increased compared to the side-edge type surface emitting device of Fig. 48, but the privacy effects I1 / I0 and I2 / I0 are worse. However, the vertical privacy effect tends to be higher than the horizontal privacy effect, and is still within the acceptable range.

[0092] Thus, according to the third embodiment shown in Figure 25, the lower surface of the outer lower prism sheet 4B is flat, making it easy to handle during the manufacturing process, reducing the risk of foreign matter being mixed in, and also reducing the occurrence of fine defects during component transportation operations, etc.

[0093] Fig. 32 is a perspective view showing a fourth embodiment of a side-edge type surface emitting device according to the present invention. In Fig. 32, a light absorbing sheet 5 is added to the side-edge type surface emitting device of Fig. 25 so as to face the triangular prisms 41B of the lower prism sheet 4B. In this case, an air layer is provided between the lower prism sheet 4B and the light absorbing sheet 5. In other words, the lower prism sheet 4B and the light absorbing sheet 5 are spaced apart. The light absorbing sheet 5 is made of, for example, polyethylene terephthalate (PET) coated with black ink.

[0094] Figure 33 is a cross-sectional view for explaining the operation of the side-edge type surface emitting device of Figure 32, where (A) is a cross-sectional view showing operation in the horizontal direction (Y direction), and (B) is a cross-sectional view showing operation in the vertical direction (X direction).

[0095] As shown in (A) and (B) of FIG. 27 As in (A) and (B) of FIG. 1, light L21 having a large angle of incidence with respect to the linearly inclined surfaces 41A-1 and 41A-2 of the triangular prism 41A of the lower prism sheet 4A is totally reflected by the flat surface 42A of the lower prism sheet 4A and is incident on the flat surface S of the upper prism sheet 3. e That is, the light L21 can increase the luminance I at a viewing angle θ of -35° to 35°.

[0096] 33A and 33B, light L22 having a small angle of incidence with respect to the linearly inclined surfaces 41A-1 and 41A-2 of the triangular prism 41A of the lower prism sheet 4A among the light L2 is refracted and emitted from the flat surface 42A of the lower prism sheet 4A, enters the lower prism sheet 4B, is further refracted and emitted, and is finally absorbed by the light absorbing sheet 5. Therefore, the light L22 does not return to the upper prism sheet 3 at all. In other words, the light L22 can improve the luminance I outside the viewing angle θ=-35° to 35°, that is, the relative luminance (privacy effect) I1 / I0, but the total luminous flux of the device is reduced.

[0097] Furthermore, as shown in (A) and (B) of FIG. 27As in (A) and (B) of the above, the light L23 having an intermediate angle of incidence with respect to the linearly inclined surfaces 41A-1 and 41A-2 of the triangular prism 41A of the lower prism sheet 4A of the light L2 has an angle of incidence that just barely exceeds the critical angle of the flat surface 42A of the lower prism sheet 4A. In this case, if a part of the light L2 is at the tip of the triangular prism 41B of the lower prism sheet 4B, it enters the lower prism sheet 4B and does not return to the upper prism sheet 3. Therefore, the amount of light that is totally reflected by the air layer without coming into contact with the tip of the triangular prism 41B of the lower prism sheet 4B from the lower prism sheet 4A, which causes the privacy effect to deteriorate, is relatively reduced, improving the privacy effect. However, in this case, a part of the light that is refracted and emitted from the flat surface 42B of the lower prism sheet 4B is reflected by the housing (reflector) of the device and becomes return light, but the amount of light is small. The light is inclined from the normal direction of the flat surface Se of the upper prism sheet 3, generating a light distribution wider than the viewing angle θ=-35° to 35°. The light rays with this light distribution deteriorate the luminance factor (privacy effect) I1 / I0. However, in FIG. 32, due to the presence of the light absorbing sheet 5, the light that would cause the light distribution wider than the viewing angle θ=-35° to 35° is absorbed by the light absorbing sheet 5. Therefore, the light distribution narrower than the viewing angle θ=-35° to 35° is relatively unaffected by the absorption by the black sheet, and the privacy effect is improved while maintaining the front luminance.

[0098] FIG. 34 shows the results of simulation operation in the horizontal direction (Y direction) of (A) in FIG. 33, where (A) is a graph showing the horizontal absolute luminance distribution, (B) is a graph showing the horizontal relative luminance distribution which is a partial enlargement of (A), and (C) is a table showing the horizontal privacy effect.

[0099] According to the absolute luminance distribution in the horizontal direction (Y direction) obtained by the side-edge type surface emitting device of FIG. 32 shown in FIG. 34(A), it is almost the same as the absolute luminance distribution in the horizontal direction (Y direction) obtained by the conventional side-edge type surface emitting device of FIG. 48, and the total luminous flux in the horizontal direction and the vertical direction is also almost the same. This is because the light emitted from the lower flat surface 42B of the lower prism sheet 4B is absorbed by the light absorbing sheet 5, but the amount is small. On the other hand, referring to the relative luminance distribution in FIG. 34(B), which is a partially enlarged view of FIG. 34(A), and the horizontal privacy effect table in FIG. 34(C), outside the viewing angle θ=-35° to 35°, the relative luminance I1 / I0 at θ=±35° and the relative luminance I2 / I0 at θ=±45° are slightly larger than those of the conventional side-edge type surface emitting device of FIG. 48, and therefore the privacy effect is slightly worse, but is better than that of the side-edge type surface emitting device of FIG. 25. This is because the light emitted from the lower flat surface 42B of the lower prism sheet 4B is absorbed by the light absorbing sheet 5.

[0100] FIG. 35 is a graph showing the total luminous flux and the lateral privacy effects I1 / I0 and I2 / I0 of the side-edge type surface emitting device of FIG. 32 based on the lateral simulation operation results of FIG. 33(A).

[0101] As shown in FIG. 35, in the side edge type surface emitting device of FIG. 32, the total luminous flux is slightly reduced compared to the side edge type surface emitting device of FIG. 25, but it can be seen that the privacy effects I1 / I0 and I2 / I0 are good.

[0102] FIG. 36 shows the results of simulation operation in the vertical direction (X direction) of FIG. 33(B), in which (A) is a graph showing the vertical absolute luminance distribution, (B) is a graph showing the vertical relative luminance distribution, which is a partial enlargement of (A), and (C) is a table showing the vertical privacy effect.

[0103] According to the absolute luminance distribution in the vertical direction (X direction) obtained by the side-edge type surface emission device of Fig. 32 shown in Fig. 36(A), it is almost the same as the absolute luminance distribution in the vertical direction (X direction) obtained by the conventional side-edge type surface emission device of Fig. 48, but the total luminous flux in the horizontal and vertical directions is slightly increased. On the other hand, referring to the relative luminance distribution in Fig. 36(B) which is a partially enlarged view of Fig. 36(A) and the vertical privacy effect table in Fig. 36(C), outside the viewing angle θ=-35° to 35°, the relative luminance I1 / I0 at θ=±35° and the relative luminance I2 / I0 at θ=±45° are comparable to those of the conventional side-edge type surface emission device of Fig. 48, and therefore the privacy effect is also comparable.

[0104] FIG. 37 is a graph showing the total luminous flux and the vertical privacy effects I1 / I0 and I2 / I0 of the side-edge type surface emitting device of FIG. 32 based on the results of the vertical simulation operation of FIG. 33(B).

[0105] As shown in Fig. 37, in the side-edge type surface emitting device of Fig. 32, the total luminous flux is slightly reduced compared to the side-edge type surface emitting device of Fig. 48, but the vertical privacy effects I1 / I0 and I2 / I0 are about the same, and it is slightly better than the side-edge type surface emitting device of Fig. 25. However, the vertical privacy effect tends to be higher than the horizontal privacy effect.

[0106] Fig. 38 is a perspective view showing a fifth embodiment of a side-edge type surface emitting device according to the present invention. In Fig. 38, a light absorbing layer 5' is provided instead of the light absorbing sheet 5 in the side-edge type surface emitting device of Fig. 25. In this case, the lower prism sheet 4A and the light absorbing layer 5' are in contact with each other. The light absorbing layer 5' can be realized by painting a resin containing black ink, for example.

[0107] Figure 39 is a cross-sectional view for explaining the operation of the side-edge type surface emitting device of Figure 38, where (A) is a cross-sectional view showing operation in the horizontal direction (Y direction), and (B) is a cross-sectional view showing operation in the vertical direction (X direction).

[0108] As shown in (A) and (B) of FIG. 39, light L21 having a large angle of incidence with respect to the linearly inclined surfaces 41A-1 and 41A-2 of the triangular prisms 41A of the lower prism sheet 4A is totally reflected by the flat surface 42A of the lower prism sheet 4A and is reflected by the flat surface S of the upper prism sheet 3. e That is, the light L21 increases the luminance I at a viewing angle θ of -35° to 35°.

[0109] On the other hand, as shown in Fig. 39(A) and (B), the light L22 having a small angle of incidence with respect to the linearly inclined surfaces 41A-1 and 41A-2 of the triangular prism 41A of the lower prism sheet 4A is refracted and emitted from the flat surface 42A of the lower prism sheet 4A, enters the lower prism sheet 4B, and is finally absorbed by the light absorbing layer 5'. Therefore, the light L22 does not return to the upper prism sheet 3 at all. In other words, the light L22 can improve the luminance I outside the viewing angle θ = -35° to 35°, that is, the relative luminance (privacy effect) I1 / I0, but the total luminous flux of the device is slightly reduced.

[0110] 39A and 39B, the light L23 of the light L2 having an intermediate angle of incidence with respect to the linearly inclined surfaces 41A-1 and 41A-2 of the triangular prism 41A of the lower prism sheet 4A has an angle of incidence that just barely exceeds the critical angle of the flat surface 42A of the lower prism sheet 4A. In this case, if a part of the light L2 is at the tip of the triangular prism 41B of the lower prism sheet 4B, it enters the lower prism sheet 4B and does not return to the upper prism sheet 3. Therefore, the amount of light that is totally reflected by the air layer without coming into contact with the tip of the triangular prism 41B of the lower prism sheet 4B from the lower prism sheet 4A, which causes a deterioration in the privacy effect, is relatively reduced, and the luminance factor (privacy effect) I1 / I0 is improved. In addition, in the side edge type surface emitting device of FIG. 39, the light absorbing layer 5' is present, and light that causes a light distribution wider than the viewing angle θ=-35° to 35° is absorbed by the light absorbing layer 5'. Therefore, the light distribution narrower than the viewing angle θ=-35° to 35° is relatively not affected by the absorption of the light absorbing layer 5', and the privacy effect is improved while maintaining the front brightness. Here, the side edge type surface emitting device of FIG. 38 does not have an air layer between the lower prism sheet 4B and the light absorbing layer 5' compared to the side edge type surface emitting device of FIG. 32. With this structure, the light that travels from the lower prism sheet 4B to the light absorbing layer 5' is reflected at the interface between the lower prism sheet 4B and the light absorbing layer 5' relatively reduced, and is absorbed by the light absorbing layer 5'. Therefore, the privacy effect is better than that of the side edge type surface emitting device of FIG. 32 while maintaining the front brightness.

[0111] FIG. 40 shows the results of simulation operation in the horizontal direction (Y direction) of (A) in FIG. 39, where (A) is a graph showing the horizontal absolute luminance distribution, (B) is a graph showing the horizontal relative luminance distribution which is a partial enlargement of (A), and (C) is a table showing the horizontal privacy effect.

[0112] According to the absolute luminance distribution in the horizontal direction (Y direction) obtained by the side-edge type surface light emitting device of FIG. 38 shown in FIG. 40(A), the total luminous flux in the horizontal direction and the vertical direction is slightly decreased compared to the absolute luminance distribution in the horizontal direction (Y direction) obtained by the conventional side-edge type surface light emitting device of FIG. 48. This is because the light emitted from the lower flat surface 42A of the lower prism sheet 4A is absorbed by the light absorbing layer 5'. On the other hand, referring to the relative luminance distribution in FIG. 40(B), which is a partially enlarged view of FIG. 40(A), and the horizontal privacy effect table in FIG. 40(C), outside the viewing angle θ=-35° to 35°, the relative luminance I1 / I0 at θ=±35° and the relative luminance I2 / I0 at θ=±45° are comparable to those of the conventional side-edge type surface light emitting device of FIG. 48, and therefore the privacy effect is comparable and better than that of the side-edge type surface light emitting device of FIG. 32. This is also because the light emitted from the lower flat surface 42B of the lower prism sheet 4B is absorbed by the light absorbing layer 5'.

[0113] FIG. 41 is a graph showing the total luminous flux and the lateral privacy effects I1 / I0 and I2 / I0 of the side-edge type surface emitting device of FIG. 38 based on the lateral simulation operation results of FIG. 39(A).

[0114] As shown in FIG. 41, in the side edge type surface emitting device of FIG. 38, the total luminous flux is slightly lower than that of the side edge type surface emitting device of FIG. 32, but the privacy effects I1 / I0 and I2 / I0 are good.

[0115] FIG. 42 shows the results of simulation operation in the vertical direction (X direction) of (B) in FIG. 39, in which (A) is a graph showing the vertical absolute luminance distribution, (B) is a graph showing the vertical relative luminance distribution which is a partial enlargement of (A), and (C) is a table showing the vertical privacy effect.

[0116] According to the absolute luminance distribution in the vertical direction (X direction) obtained by the side-edge type surface emission device of Fig. 38 shown in Fig. 42(A), the total luminous flux in the horizontal and vertical directions is slightly lower than the absolute luminance distribution in the vertical direction (X direction) obtained by the conventional side-edge type surface emission device of Fig. 48. On the other hand, referring to the relative luminance distribution in Fig. 42(B) which is a partially enlarged view of Fig. 42(A) and the vertical privacy effect table in Fig. 42(C), outside the viewing angle θ=-35° to 35°, the relative luminance I1 / I0 at θ=±35° and the relative luminance I2 / I0 at θ=±45° are slightly smaller than those of the conventional side-edge type surface emission device of Fig. 48, and therefore the privacy effect is good.

[0117] FIG. 43 is a graph showing the total luminous flux and the vertical privacy effects I1 / I0 and I2 / I0 of the side-edge type surface emitting device of FIG. 38 based on the results of the vertical simulation operation of FIG. 39(B).

[0118] As shown in Figure 43, in the side-edge type surface-emitting device of Figure 38, the total luminous flux is slightly reduced compared to the side-edge type surface-emitting device of Figure 48, but the vertical privacy effects I1 / I0 and I2 / I0 are significantly better.

[0119] Thus, according to the side edge type surface emitting device of FIG. 38 which is the fifth embodiment, although the total luminous flux is slightly reduced by the light absorbing layer 5', the privacy effect can be significantly improved.

[0120] 25, 32 and 38, the flat surface 42A of the lower prism sheet 4A and the tips of the triangular prisms 41B of the lower prism sheet 4B are in contact with each other due to their weight, but the flat surface 42A of the lower prism sheet 4A and the tips of the triangular prisms 41B of the lower prism sheet 4B can also be bonded to each other using a light-transmitting adhesive layer to integrate the lower prism sheet 4A and the lower prism sheet 4B. This will be explained using FIG.

[0121] FIG. 44 shows a modification of the side-edge type surface emitting device of FIG. 25, FIG. 32 and FIG. 38, and is a sectional view showing the contact portion between lower prism sheets 4A and 4B.

[0122] As shown in Fig. 44, a light-transmitting adhesive layer 6 having adhesive force for the lower prism sheets 4A and 4B is provided on the flat surface 42A of the lower prism sheet 4A, and the tips of the triangular prisms 41B of the lower prism sheet 4B are inserted into the light-transmitting adhesive layer 6. D The thickness of the light-transmitting adhesive layer 6 including the wicking amount 6a is, for example, about 20% or less of the height of the triangular prism 41B, for example, about 2 μm. The material of the light-transmitting adhesive layer 6 is, for example, a UV-curable resin urethane or epoxy that can be partially crosslinked before bonding and completely crosslinked after bonding (see Patent Document 3).

[0123] According to the modified example of Figures 25, 32 and 38 shown in Figure 44, by using lower prism sheets 4A and 4B that are integrated in advance in the manufacturing process, handling becomes easier and the inclusion of foreign matter and the occurrence of defects are reduced.

[0124] In this way, when the integrated lower prism sheets 4A, 4B of Fig. 44 are used in the side-edge type surface emitting device of Fig. 38, there is almost no decrease in the total luminous flux (or average luminance), and the privacy effect can be improved. Similarly, when the integrated lower prism sheets 4A, 4B of Fig. 44 are used in the side-edge type surface emitting devices of Figs. 25 and 32, there is almost no decrease in the total luminous flux (or average luminance), and the privacy effect can be improved.

[0125] The total luminous flux (or average luminance) and privacy effect of a modified example in which the lower prism sheets 4A and 4B of Fig. 44 are adopted in the side-edge type surface emitting device of Fig. 38 will be described. In this case, since the contact area between the lower prism sheet 4A and the lower prism sheet 4B is increased by the light-transmitting adhesive layer 6, it was difficult to simulate the optical characteristics. Therefore, Fig. 45 shows the experimental results of the average luminance (corresponding to the total luminous flux) and privacy effect of a modified example of the side-edge type surface emitting device of Fig. 38 in which the integrated lower prism sheets 4A and 4B of Fig. 44 are adopted, and the average luminance (corresponding to the total luminous flux) and privacy effect of the conventional side-edge type surface emitting device of Fig. 48.

[0126] As shown in Fig. 45(A), the average luminance of absolute luminance at 81 points in the modified example of the side edge type surface emitting device of Fig. 38 using the integrated lower prism sheets 4A and 4B of Fig. 44 was almost identical at 97.7% of the average luminance (corresponding to the total luminous flux) of absolute luminance at 81 points in the conventional side edge type surface emitting device of Fig. 48. The simulated total luminous flux of the side edge type surface emitting device of Fig. 38 was also almost identical at 99.9% of the simulated total luminous flux of the conventional side edge type surface emitting device of Fig. 48.

[0127] As shown in (B) of Figure 45, the average values ​​of relative luminance I1 / I0 and I2 / I0 at horizontal (Y direction) viewing angles θ=±35° and ±45° in a modified example of the side-edge type surface-emitting device of Figure 38 using the integrated lower prism sheets 4A and 4B of Figure 44 were improved by 16.19% and 12.135% compared to the average values ​​of the relative luminance I1 / I0 and I2 / I0 at horizontal (Y direction) viewing angles θ=±35° and ±45° in the conventional side-edge type surface-emitting device of Figure 48. The relative luminances I1 / I0 and I2 / I0 at simulated viewing angles θ=±35° and ±45° in the horizontal direction (Y direction) in the side-edge type surface emission device of FIG. 38 were improved by 0% and -21.15% compared to the relative luminances I1 / I0 and I2 / I0 at simulated viewing angles θ=±35° and ±45° in the horizontal direction (Y direction) in the conventional side-edge type surface emission device of FIG. 48. As a result, it can be seen that the modified example of the side-edge type surface emission device of FIG. 38 using the integrated lower prism sheets 4A and 4B of FIG. 44 is extremely superior in terms of privacy effect in the horizontal direction (Y direction) compared to the side-edge type surface emission device of FIG. 38. The improvement rates are {(conventional value in FIG. 48)-(value in the embodiment)} ÷(the previous value in Figure 48) × 100% The calculation is as follows.

[0128] As shown in (C) of Figure 45, the average values ​​of relative luminance I1 / I0 and I2 / I0 at viewing angles θ=±35° and ±45° in the vertical direction (X direction) in the modified example of the side-edge type surface-emitting device of Figure 38 using the integrated lower prism sheets 4A and 4B of Figure 44 were improved by 28.19% and 31.715% compared to the average values ​​of the relative luminance I1 / I0 and I2 / I0 at viewing angles θ=±35° and ±45° in the vertical direction (X direction) in the conventional side-edge type surface-emitting device of Figure 48. The relative luminances I1 / I0 and I2 / I0 at the simulated viewing angles θ=±35° and ±45° in the vertical direction (X direction) in the side edge type surface emitting device of FIG. 38 were improved by 27.42% and 26.09% compared to the relative luminances I1 / I0 and I2 / I0 at the simulated viewing angles θ=±35° and ±45° in the vertical direction (X direction) in the conventional side edge type surface emitting device of FIG. 48. As a result, it can be seen that the modified example of the side edge type surface emitting device of FIG. 38 using the integrated lower prism sheets 4A and 4B of FIG. 44 is superior in terms of privacy effect in the vertical direction (X direction) compared to the side edge type surface emitting device of FIG. 38. Therefore, as shown in the side edge type surface emitting device of the fifth embodiment, even when the lower prism sheet 4A and the lower prism sheet 4B are integrated by the light-transmitting adhesive layer 6, the privacy effect can be significantly improved while maintaining almost the same front luminance as the conventional side edge type surface emitting device shown in FIG. 48.

[0129] Next, the setting of the apex angles αA, αB of the triangular prisms 41A, 41B of the lower prism sheets 4A, 4B in the side-edge type surface emitting device of FIG. 38 will be described.

[0130] FIG. 46 shows a side-edge type surface emitting device of FIG. 38 in which the apex angle αB of the triangular prism 41B of the lower prism sheet 4B is fixed to 90° and the width W D The figure shows the results of simulating the total luminous flux and the relative luminance I1 / I0 and I2 / I0 at viewing angles θ=±35° and ±45° when the apex angle αA is changed to 90°, 80°, 85°, 95°, 100°, 110°, 120°, and 125° while keeping the width W of the triangular prism 41A constant.D Since the height H of the triangular prism 41A is constant, D The more acute the apex angle, the higher the value, and the more obtuse the apex angle, the lower the value. The simulation setting in FIG. 46 is the simulation of the side edge type surface emitting device in FIG. 38 with a width W D is kept constant, and only the apex angle αA is changed. In FIG. 46, the total luminous flux is plotted relatively upward, and the privacy effect is plotted relatively downward. The total luminous flux plotted relatively upward is expressed by connecting the plots with a line, and the privacy effect plotted relatively downward is also expressed by connecting the plots with a line. In this graph, the larger the total luminous flux (lm) is, the higher the luminance of the light-emitting device is, and the smaller the relative luminances I1 / I0 and I2 / I0 are, the higher the privacy effect is. In other words, the higher the plot on the graph, the higher the total luminous flux and the higher the privacy effect.

[0131] First, because it has a large effect on the backlight output efficiency, in (A), (B), (C), and (D) of FIG. αA The apex angle αA of the triangular prism 41A having a total luminous flux of 90% or less when the total luminous flux is 90° is excluded. Therefore, the backlight output efficiency is high when the backlight output efficiency exceeds L90%. αA=90°, 80°, 85°, 95°, 120° The following is the target.

[0132] Next, the horizontal relative luminance I1 / I0 at the viewing angle θ=±35° in FIG. 46(A) is observed, and the apex angle αA having the horizontal relative luminance I1 / I0 at the viewing angle θ=±35° that is greater than the level IRA when the apex angle αA of the triangular prism αA is 90° is deemed to have a low privacy effect and is excluded. Therefore, αA=90°, 80°, 100°, 110°, 120°, 125° In this case, taking into consideration the total luminous flux, it is determined that αA=90° and 120° are superior. In this case, it is determined that αA=120° is particularly superior.

[0133] Next, the horizontal relative luminance I2 / I0 at the viewing angle θ=±45° in FIG. 46B is observed, and the apex angle αA having the horizontal relative luminance I2 / I0 at the viewing angle θ=±45° that is greater than the level IRB when the apex angle αA of the triangular prism αA is 90° is deemed to have a low privacy effect and is excluded. Therefore, αA=90°, 80°, 110°, 120° In this case, taking into account the total luminous flux, it is determined that αA=90° is superior.

[0134] Next, the vertical relative luminance I1 / I0 at the viewing angle θ=±35° in FIG. 46C is observed, and the apex angle αA having the vertical relative luminance I1 / I0 at the viewing angle θ=±35° that is greater than the level IRC when the apex angle αA of the triangular prism αA is 90° is deemed to have a low privacy effect and is excluded. Therefore, αA=90°, 110°, 120°, 125° In this case, taking into account the total luminous flux, it is determined that αA=90° is superior.

[0135] Next, the vertical relative luminance I2 / I0 at the viewing angle θ=±45° in FIG. 46(D) is observed, and the apex angle αA having the vertical relative luminance I2 / I0 at the viewing angle θ=±45° that is greater than the level IRD when the apex angle αA of the triangular prism αA is 90° is deemed to have a low privacy effect and is excluded. Therefore, αA=90°, 85° In this case, taking into account the total luminous flux, it is determined that αA=90° and 85° are superior. In this case, it is determined that αA=85° is particularly superior.

[0136] In this way, when the apex angle αB of the triangular prism 4B is fixed at 90°, the apex angle αA of the triangular prism 4A is advantageously set to 90°, 85°, or 120°, but overall, αA = 90° is the best. Therefore, it is best to set αA = 85° to 95° with αA = 90° as the center.

[0137] FIG. 47 shows a side-edge type surface emitting device of FIG. 38 in which the apex angle αA of the triangular prism 41A of the lower prism sheet 4A is fixed at 90°, and the width W D The figure shows the results of simulating the total luminous flux and the relative luminance I1 / I0 and I2 / I0 at viewing angles θ=±35° and ±45° when the apex angle αB is changed to 90°, 95°, 100°, 85°, 80°, 110°, and 120° while keeping the width W of the triangular prism 41B constant. D Since the height H of the triangular prism 41B is constant, D The more acute the apex angle, the higher the value, and the more obtuse the apex angle, the lower the value. The simulation setting in FIG. 47 is the simulation of the side edge type surface emitting device in FIG. 38 with a width W D is kept constant, and only the apex angle αB is changed. In FIG. 47, the total luminous flux is plotted relatively upward, and the privacy effect is plotted relatively downward. The total luminous flux plotted relatively upward is expressed by connecting the plots with a line, and the privacy effect plotted relatively downward is also expressed by connecting the plots with a line. In this graph, the larger the total luminous flux (lm) is, the higher the luminance of the light-emitting device is, and the smaller the values ​​of I1 / I0 and I2 / I0 are, the higher the privacy effect is. In other words, the higher the plot is on the graph, the higher the total luminous flux and the higher the privacy effect is.

[0138] First, because it has a significant effect on the backlight output efficiency, in (A), (B), (C), and (D) of Figures 47, the apex angle αB of triangular prism 41B having a total luminous flux below the 90% level L90% of the total luminous flux when αB = 90° is excluded. However, in this case, the total luminous flux is 99.9% to 100.4% of the total luminous flux when αA = 90°, so all are included.

[0139] Next, the horizontal relative luminance I1 / I0 at the viewing angle θ=±35° in FIG. 47(A) is observed, and the apex angle αB having the horizontal relative luminance I1 / I0 at the viewing angle θ=±35° that is greater than the level IRA when the apex angle αB of the triangular prism αA is 90° is deemed to have a low privacy effect and is excluded. Therefore, αB=90° The following is the target.

[0140] Next, the horizontal relative luminance I2 / I0 at the viewing angle θ=±45° in FIG. 47B is observed, and the apex angle αA having the horizontal relative luminance I2 / I0 at the viewing angle θ=±45° that is greater than the level IRB when the apex angle αB of the triangular prism αA is 90° is deemed to have a low privacy effect and is excluded. Therefore, αB=90°, 95° In this case, αB=95° is considered to be the most advantageous.

[0141] Next, the vertical relative luminance I1 / I0 at the viewing angle θ=±35° in FIG. 47C is observed, and the apex angle αB having the vertical relative luminance I1 / I0 at the viewing angle θ=±35° that is greater than the level IRC when the apex angle αB of the triangular prism α4B is 90° is deemed to have a low privacy effect and is excluded. Therefore, the privacy effect is high. αA=90°, 95° The following is the target.

[0142] Next, the vertical relative luminance I2 / I0 at the viewing angle θ=±45° in FIG. 47(D) is observed, and the apex angle αB having the vertical relative luminance I2 / I0 at the viewing angle θ=±45° that is greater than the level IRD when the apex angle αB of the triangular prism αB is 90° is deemed to have a low privacy effect and is excluded. Therefore, the privacy effect is high. αA=90°, 100°, 85°, 120° In this case, taking into account the total luminous flux, it is determined that αA=90° and 85° are superior. In this case, it is determined that αB=85° is particularly superior.

[0143] In this way, when the apex angle αA of the triangular prism 4A is fixed at 90°, the apex angle αB of the triangular prism 4A is advantageously set to 90°, 95°, or 85°, but overall, αB = 90° is the best. Therefore, it is best to set αB = 85° to 95° with αB = 90° as the center.

[0144] In the side edge type surface emitting devices of Fig. 25 and Fig. 32, the apex angles αA and αB of the triangular prisms 41A and 41B of the lower prism sheets 4A and 4B are preferably 85° to 95°. In this case, the apex angles αA and αB of the prisms 41A and 41B may be the same or different. Furthermore, each side of the triangular prisms 41A and 41B may not be straight, but may be a curved shape with any number of points, such as a parabola. Furthermore, the material of the lower prism sheet 4A and the material of the lower prism sheet 4B may be the same or different.

[0145] In the above embodiment, the ridges of the triangular prisms 41A and 41B are straight, but they do not have to be straight.

[0146] Furthermore, the present invention can be applied to any modifications within the obvious scope of the above-described embodiment. [Industrial Applicability]

[0147] The side-edge type surface-emitting device of the present invention can be used in LCD panels for notebook computers, monitor display devices used in ATMs and public institutions, lighting devices with switchable light distribution characteristics, LCD panels for car navigation systems, car interior display devices, etc. [Explanation of symbols]

[0148] 1: Light guide plate 11: Upper prism 12: Lower prism S in :Incidence plane S e : Exit surface S d :Light distribution control surface 13:Flat mirror surface part 2: LED element 3: Upper prism sheet 4, 4A, 4B: Lower prism sheet 41, 41A, 41B: Triangular prism 41-1, 41-2, 41A-1, 41A-2, 41B-1, 41B-2: Straight inclined surface 42, 42A, 42B: Flat surface 5: Light absorbing sheet 5': Light absorbing layer 6: Light-transparent adhesive layer

Claims

1. A light guide plate having an emission surface on an upper side, a light distribution control surface on a lower side, and an entrance surface on a side connecting the emission surface and the light distribution control surface; a light source provided on the light incident surface side of the light guide plate; an upper prism sheet having a plurality of first prisms provided on a lower side along a direction parallel to the incident surface of the light guide plate so as to face the exit surface side of the light guide plate and an exit surface on an upper side; a first lower prism sheet having a plurality of second prisms provided on an upper side along a direction perpendicular to the incident surface of the light guide plate and facing the light distribution control surface of the light guide plate, and a first flat surface provided on a lower side; a light absorbing sheet provided opposite to and spaced from the first flat surface of the first lower prism sheet; A side edge type surface emitting device comprising:

2. A light guide plate having an emission surface on an upper side, a light distribution control surface on a lower side, and an entrance surface on a side connecting the emission surface and the light distribution control surface; a light source provided on the light incident surface side of the light guide plate; an upper prism sheet having a plurality of first prisms provided on a lower side along a direction parallel to the incident surface of the light guide plate so as to face the exit surface side of the light guide plate and an exit surface on an upper side; a first lower prism sheet having a plurality of second prisms provided on an upper side along a direction perpendicular to the incident surface of the light guide plate and facing the light distribution control surface of the light guide plate, and a first flat surface provided on a lower side; a second lower prism sheet having a plurality of third prisms provided on an upper side along a direction perpendicular to the incident surface of the light guide plate, the second lower prism sheet being opposed to and in contact with the first flat surface of the first lower prism sheet, and a second flat surface provided on a lower side; A side edge type surface emitting device comprising:

3. 3. The side-edge type surface emitting device according to claim 2, further comprising a light absorbing sheet disposed opposite to and spaced from said second flat surface of said second lower prism sheet.

4. 3. The side-edge type surface emitting device according to claim 2, further comprising a light absorbing layer provided opposite to and in contact with said second flat surface of said second lower prism sheet.

5. a light-transmitting adhesive layer provided on the first flat surface of the first lower prism sheet; 3. A side-edge type surface emitting device as described in claim 2, wherein the tip portions of the third prisms of the second lower prism sheet penetrate the light-transmitting adhesive layer and contact the first flat surface of the first lower prism sheet.

6. 2. The side-edge type surface emitting device according to claim 1, wherein each of the first prisms is a triangular prism having an apex angle of 85° to 95°.

7. 3. The side-edge type surface emitting device according to claim 2, wherein each of the second prisms is a triangular prism having an apex angle of 85° to 95°.

8. A liquid crystal display device comprising the side edge type surface emitting device according to claim 1 .

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