JP2009134922A - Surface light source device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface light source device capable of emitting uniform light in the front face direction at high luminance even though the number of arrangements of light sources is lessened. <P>SOLUTION: In the surface light source device 1 in which a plurality of light sources 2 are mutually arranged to space in certain spacings and each deflection structure plate 3 changing the direction of light emitted from the light source is arranged at the front side of the light source 2, the deflection structure plate 3 is formed to emit light directly incident from two adjacent light sources toward the front face side direction a of the normal direction of the deflection structure plate 3 at a range corresponding to a range between two adjacent light sources 2, 2 in the deflection structure plate, and a reflective surface section 7 for reflecting light emitted from the light source 2 to a back side to the light source 2 or in the direction passing a near position of the light source 2 is arranged at the back side of the light source 2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a surface light source device capable of emitting uniform light in the front direction with high brightness even when the number of light sources is small, and a transmission type image display capable of displaying a uniform and bright image toward the front direction even when the number of light sources is small. Relates to the device.

As a transmissive image display device, for example, a configuration in which a direct type surface light source device is disposed as a backlight on the back side of a transmissive image display unit configured using, for example, a transmissive liquid crystal cell is known. . As the surface light source device, a plurality of light sources are arranged in the lamp box at intervals, a light diffusion plate is arranged on the front side of these light sources, and a prism member is arranged on the front side of the light diffusion plate. A surface light source device having the above-described configuration is known (see Patent Document 1).
Japanese Unexamined Patent Publication No. 7-141908 (paragraph 0012, FIG. 1)

  By the way, it is needless to say that it is preferable to reduce the number of light sources constituting the surface light source device as much as possible in terms of power saving. However, if the number of light sources is reduced, the luminance decreases. What is required is one that can emit uniform light with high luminance even if the number of light sources is small.

  On the other hand, in the surface light source device described in the above-mentioned Patent Document 1, the deflecting structure portion formed of the prism member transmits light from one of the light sources closer to the normal direction (vertical direction) between two adjacent light sources. ) Is configured so that the light can be emitted toward the front side, but the direction in which light is emitted from the other light source is not considered at all. It was not possible to ensure a sufficiently high brightness.

  The present invention has been made in view of such a technical background, and even if the number of light sources is small, the surface light source device that can emit uniform light in the front direction with high luminance and the number of light sources are small. Another object of the present invention is to provide a transmissive image display device capable of displaying a uniform and high-luminance image in the front direction.

  In order to achieve the above object, the present invention provides the following means.

[1] A surface light source device in which a plurality of light sources are arranged at intervals, and a deflection structure plate that changes the direction of light emitted from the light sources is arranged on the front side of these light sources,
The deflecting structure plate is configured such that the light directly incident from the two adjacent light sources is incident on a region corresponding to the region between the two adjacent light sources in the deflecting structure plate in the direction of the front side in the normal direction of the deflecting structure plate. Configured to be emitted toward
A reflection surface part is provided on the back side of the light source, and reflects light emitted from the light source toward the back side toward the light source or in a direction passing through a position near the light source. Surface light source device.

[2] The reflective surface portion is
One or a plurality of curved reflecting surfaces whose curvature centers are present in the light source region or in the vicinity of the light source, and / or a plurality of planar reflecting surfaces arranged so as to surround the light source on the back side of the light source, In a cross-sectional view in a plane orthogonal to the length direction of the light source, the center of the smallest virtual circle that includes all of the vertices at both ends of the planar reflecting surface is present in the light source region or in the vicinity of the light source. 2. The surface light source device according to item 1, further comprising a planar reflection surface.

  [3] The reflection surface portion is formed to extend from the rear side region of the light source to a substantially lateral region on the left side of the light source and a substantially lateral region on the right side of the light source. The surface according to the preceding item 1 or 2, wherein the light emitted toward the direction is reflected by the reflecting surface portion and reflected toward the light source or in a direction passing through a position near the light source. Light source device.

  [4] The surface according to any one of items 1 to 3, wherein the reflection surface portion reflects light emitted from the light source toward the back side in a direction passing through a position near the light source. Light source device.

[5] The range of the position near the light source is:
When the distance between the deflection structure plate and the light source is “H” and the distance between the centers of adjacent light sources is “L”, it passes through the center position of the light source parallel to the normal direction of the deflection structure plate. The vertical distance to the first virtual straight line is 0.15 L or less, and the vertical distance to the second virtual straight line that is parallel to the deflection structure plate and passes through the center position of the light source is 0.15 H or less. The surface light source device according to any one of the preceding items 1 to 4, which is a range excluding a light source region in which a distance from a center position of the light source is equal to or less than a radius of the light source.

  [6] A transmissive image display device, wherein the surface light source device according to any one of items 1 to 5 is arranged on the back side of the transmissive image display unit.

  In the invention of [1], light (direct light that is directly incident without being reflected) directly from the two adjacent light sources into a region corresponding to a region between the two adjacent light sources in the deflecting structure plate. Since both can be emitted toward the front side of the normal direction of the deflection structure plate, uniform light can be emitted with high luminance even if the number of light sources is small. That is, it can illuminate sufficiently brightly in the front direction.

  Furthermore, a reflection surface portion is provided on the back side of the light source to reflect light emitted from the light source toward the back side toward the light source or in a direction passing through a position near the light source. The reflected light formed by the light emitted toward the back side being reflected by the reflecting surface portion is deflected by a path close to the path of the light emitted from the light source toward the front side and directly incident on the deflection structure plate. Since the light is incident on the plate, the reflected light is emitted toward the front side of the normal direction of the deflection structure plate. In this way, not only light that is emitted from the light source toward the front surface and directly incident on the deflecting structure plate, but also light that is emitted from the light source toward the back surface side is reflected by the reflecting surface portion, and thus the deflection structure plate Since the light can be emitted toward the front side in the normal direction (that is, the reflected light can also be effectively emitted to the front side), the luminance in the front direction of the surface light source device can be further improved. it can.

  On the other hand, in the configuration in which the reflection surface portion according to the above configuration is not provided, the light emitted from the light source toward the back side cannot be sufficiently effectively used. That is, the light emitted from the light source toward the back side can be effectively used and emitted toward the front side of the normal direction of the deflecting structure plate, and thus sufficient luminance can be obtained in the front direction. I can't.

  On the other hand, in the present invention, high-intensity light can be emitted in the front direction by providing the reflection surface portion as described above.

  In the invention of [2], the reflecting surface portion is a) one or more curved reflecting surfaces whose center of curvature is present in the light source region or in the vicinity of the light source, and / or b) the light source on the back side of the light source. A plurality of planar reflection surfaces arranged so as to surround the center of the smallest virtual circle including all of the vertices at both ends of the planar reflection surface in a cross-sectional view in a plane orthogonal to the length direction of the light source However, since the light source region or the plurality of planar reflecting surfaces present in the vicinity of the light source are provided, the luminance in the front direction can be further improved.

  In the invention of [3], the light source is formed so as to extend from the rear side region of the light source to a substantially lateral region on the left side of the light source and a substantially lateral region on the right side of the light source. Since the light emitted toward the light source is reflected by the reflection surface part and reflected toward the light source or in a direction passing through the vicinity of the light source, the light source is directed toward the back side. Not only the emitted light but also the light emitted toward almost the left and right sides of the light source can be emitted toward the front side of the normal direction of the deflecting structure plate, and thereby the brightness in the front direction Can be further improved.

  In the invention of [4], the reflection surface portion reflects light emitted from the light source toward the back side in a direction passing through a position in the vicinity of the light source, so that the luminance in the front direction is further improved. be able to.

  In the invention of [5], since the range of the position near the light source is limited to a specific range that is particularly close to the light source, the luminance in the front direction can be further improved.

  In the invention of [6], a transmissive image display device capable of displaying a bright image in the front direction even when the number of light sources arranged is small is provided.

  1 to 4 show a liquid crystal display device according to one embodiment (first embodiment) of a transmissive image display device (10) of the present invention. In FIG. 1, (10) is a liquid crystal display device, (11) is a liquid crystal cell, (12) and (13) are polarizing plates, and (1) is a surface light source device. Polarizing plates (12) and (13) are respectively arranged on the upper and lower sides of the liquid crystal cell (11), and a transmissive image display section (14) is constituted by these constituent members (11), (12) and (13).

  The said surface light source device (1) is arrange | positioned at the lower surface side (back side) of the said lower polarizing plate (13). The surface light source device (1) is a thin box-shaped lamp box (5) having a rectangular shape in plan view and having an open upper surface (front surface), and a lamp box (5) spaced apart from each other. A plurality of light sources (2) and a deflection structure plate (3) disposed above (front side) the plurality of light sources (2). The deflection structure plate (3) is placed and fixed to the lamp box (5) so as to close its open surface.

  In the present embodiment, a fluorescent tube is used as the light source (2), but the present invention is not particularly limited to this. In the present embodiment, for convenience of explanation, as the light source (2), a first light source (21), a second light source (22), a third light source (23), a fourth light source (24), and a fifth light source ( 25) shows a configuration in which five light sources are used. However, the number of light sources is not particularly limited, and two or more light sources may be used. .

  The deflection structure plate (3) is a plate having a function of changing the direction of light emitted from the light source (2) and incident on the deflection structure plate (3). In the present invention, the deflecting structure plate (3) has two adjacent light sources (2) in a region corresponding to a region between the two adjacent light sources (2) and (2) in the deflecting structure plate (3). (2) The light that is directly incident (for example, the light that passes through the optical path indicated by the solid line in FIG. 2) can be emitted toward the front side direction (a) in the normal direction of the deflection structure plate (3). Has been.

  Describing individually with reference to FIG. 2, the adjacent 2 in the region (91) corresponding to the region between the adjacent first light source (21) and the second light source (22) in the deflection structure plate (3). Both light (F1) and (F2) directly incident from the two light sources (21) and (22) can be emitted toward the front side direction (a) in the normal direction of the deflection structure plate (3). Yes. Similarly, the two adjacent light sources (22) (22) in the region (92) corresponding to the region between the adjacent second light source (22) and the third light source (23) in the deflection structure plate (3). 23) The light (F2) and (F3) which are directly incident from 23) can be emitted toward the front side direction (a) in the normal direction of the deflection structure plate (3). Further, the same configuration is adopted for the other regions (93) and (94) in the deflection structure plate (3).

  As shown in FIG. 3, the back surface (light source side surface) (light incident surface) (3b) of the deflection structure plate (3) is formed as a smooth surface.

  As shown in FIGS. 1 and 2, the deflection structure plate (3) has a front surface (surface on the image display unit side) (light emission surface) (3 a) as shown in FIGS. 1 and 2. ), A region (91) corresponding to a region between the second light source (22) and the third light source (23), a region (92) corresponding to a region between the second light source (23) and the third light source (23), It consists of four regions, a region (93) corresponding to the region between the four light sources (24) and a region (94) corresponding to the region between the adjacent fourth light source (24) and the fifth light source (25). These four regions (91), (92), (93), and (94) each have 30 small regions (Am; m = 0, 1, 2, 3, 4, 5,..., 27, 28, 29) (see FIG. 2). Each of the small regions (Am; m = 0 to 29) has a width of 1000 μm (1 mm).

  The light exit surface (3a) of the small region (A0) located immediately above the light source (2) among the small regions is formed as a smooth surface as shown in FIG. Accordingly, the light incident on the small area (A0) from the light source (2) directly below has both the light incident surface (3b) and the light emitting surface (3a) as smooth surfaces. The light is emitted toward the front side direction (a) in the normal direction of 3).

Further, in the remaining 29 small areas (Am; m = 1 to 29) excluding the small area (A0) in the deflection structure plate (3), the light exit surface (3a) is as shown in FIG. The cross-sectional shape is a triangular prism. Each small region (Am; m = 1 to 29) has 20 prisms (triangles). Further, the intervals (t ₁ , t ₂ ,..., T ₂₈ , t ₂₉ ) between the prisms (triangles) are all 50 μm. Further, the angles (αm, βm) formed by the two hypotenuses of the triangles constituting the prism in each small region (Am; m = 1 to 29) and the normal line (a) are set to the values shown in Table 1. . Note that the angles αm and βm of the triangles in the same small region are the same. That is, the triangles in the same small region all have the same cross-sectional shape. For example, all triangles (prisms) in the small area A1 are set to α = 85.1 degrees, β = 24.2 degrees, and t = 50 μm.

  As described above, the light incident surface (3b) of the deflection structure plate (3) is formed as a smooth surface over the entire surface, and the prism having a specific configuration as described above including Table 1 includes the deflection structure plate (3). Are formed on the light exit surface (3a) of the light source, so that the light directly incident from the two adjacent light sources is deflected to the region corresponding to the region between the two adjacent light sources in the deflection structure plate (3). It can radiate | emit toward the front side direction (a) of the normal line direction of a structure board (3). Therefore, even if the number of the light sources (2) is small, the emitted light can be emitted with high luminance in the front direction, whereby a high-luminance image can be generated in the front direction via the transmissive image display unit (14). Can be displayed.

  The transmissive image display device (10) of the present invention further comprises the following configuration. That is, in the lamp box (5), the light emitted from the second light source (22) toward the back side is directed toward the second light source (22) toward the back side of the second light source (22). Or a reflecting surface portion (7) that reflects toward the direction passing through the position near the second light source (22) (see FIGS. 1 and 2). In the present embodiment, the reflecting surface portion (7) extends from the back side of the second light source (22) to a substantially lateral side of the second light source (22) on the left side of the front view and a substantially lateral side of the right side of the front view. (See FIG. 2). The reflection surface portion (7) includes a first curved reflection surface (7a) having a center of curvature (Y1) in the vicinity of the second light source (22) and a center of curvature (Y2) in the vicinity of the second light source (22). It has a reflection surface formed by connecting the second curved reflection surface (7b) existing at the position (see FIGS. 2 and 4). The reflection surface portion (7) includes a first curved reflection surface (7a) in which the center of curvature (Y1) exists in the region (Z) of the second light source (22), and a center of curvature (Y2) of the second light source ( The configuration may include a reflection surface formed by connecting the second curved reflection surface (7b) existing in the region (Z) of 22).

  The reflection surface portion (7) extends along the length direction of the light source (22) (the depth direction in FIG. 1) on the back side of the second light source (22). That is, the long reflective surface portion (7) is arranged in a manner covering from the back side of one end portion in the length direction of the second light source (22) to the back side of the other end portion.

  As for the first and third to fifth light sources (21), (23), (24), and (25), the reflection surface portion having the same configuration as described above is provided on the back side of each light source (21), (23), (24), and (25). (7) are similarly arranged (see FIGS. 1 and 2).

  Adjacent reflecting surface portions (7) and (7) are all connected by a flat connecting reflector (8). In the present embodiment, the entire front surface (surface on the deflection structure plate side) of the reflective surface portion (7) is a white reflective surface. In addition, the entire front surface (surface on the deflection structure plate side) of the articulated reflecting plate (8) is a white reflecting surface.

  Thus, in the surface light source device (1), the light emitted from the light source (2) toward the back side is directed toward the light source (2) or the light source (2). ) Is provided so that the light reflected from the light source (2) toward the back side is reflected by the reflective surface ((2)) as shown in FIG. The reflected light (dotted line with an arrow in FIG. 2) reflected by 7) is emitted directly from the light source (2) toward the front surface and directly enters the deflection structure plate (3) (in FIG. 2). Since the light enters the deflecting structure plate (3) through a path close to the path indicated by the solid line with the arrow, the reflected light can also be emitted toward the front side direction (a) in the normal direction of the deflecting structure plate (3). it can. Thus, not only the light emitted from the light source (2) toward the front side but directly incident on the deflecting structure plate (3), but also the light emitted from the light source (2) toward the back side is reflected on the reflection surface portion. Since it can radiate | emit toward the front side direction (a) of the normal direction of a deflection | deviation structure board (3) through reflection in (7), the brightness | luminance of the front direction of a surface light source device (1) is improved more. be able to.

  Furthermore, the reflection surface portion (7) extends not only from the back side region of the light source (2) but also from the back side to the substantially lateral region on the left side and the substantially lateral region on the right side of the light source (2). The light that is formed and emitted from the light source (2) toward the substantially lateral sides of the left and right sides is also reflected by the reflecting surface portion (7) toward the light source (2) or the light source (2 ) Is reflected toward the direction passing through the position near the light source (2), so that not only the light emitted from the light source (2) toward the back side, but also from the light source (2) to substantially the left and right sides. The light emitted toward the front can also be emitted toward the front side direction (a) in the normal direction of the deflecting structure plate (3), whereby the luminance in the front direction can be further improved. Therefore, according to the transmissive image display device (10), it is possible to display a uniform and high-brightness image in the front direction.

  In addition, in the surface light source device having the configuration not including the reflection surface portion (7), as shown in FIG. 10, the light emitted from the light source (2) toward the back side and the substantially right and left sides is a lamp. The light is reflected by the inner surface of the box (5) and enters the deflecting structure plate (3). The deflection structure plate (3) is formed from the two adjacent light sources (2) and (2) in a region corresponding to a region between the two adjacent light sources (2) and (2) in the deflection structure plate (3). It is designed to emit both directly incident light (for example, light passing through an optical path shown by a solid line in FIG. 10) toward the front side direction (a) of the normal direction of the deflection structure plate (3). From FIG. 10, the reflected light (shown by dotted lines with arrows) reflected in a disordered direction and incident on the deflecting structure plate (3) is directed toward the front side in the normal direction of the deflecting structure plate (3). It is difficult to emit light toward (a). That is, when the reflection surface portion (7) is not provided, the reflected light is emitted in a disordered direction after passing through the deflecting structure plate (3), and the reflected light is emitted in the front direction. It is difficult. As described above, in the configuration not provided with the reflection surface portion (7), although the emission direction of the light directly incident on the deflection structure plate (3) from the light source (2) can be controlled, it is reflected from the light source (2). Thus, since the outgoing direction of the reflected light entering the deflecting structure plate (3) in a disordered direction cannot be controlled, it is not possible to obtain sufficient luminance in the front direction.

  In the present invention, as the reflection surface portion (7), the light emitted from the light source (2) toward the back side is directed toward the light source (2) or in a direction passing through a position near the light source (2). The shape, structure, etc. are not particularly limited as long as they fulfill the function of reflecting light.

  For example, you may employ | adopt the structure (2nd Embodiment) provided with the reflective surface part (7) as shown in FIGS. In the second embodiment, light emitted from the light source (2) toward the back side is directed toward the light source (2) or in the vicinity of the light source (2). Is the same as in the first embodiment in that a reflecting surface portion (7) that reflects in a direction passing through is provided, but in the second embodiment, the reflecting surface portion (7) has a center of curvature ( A configuration is adopted in which Y) is composed of one curved reflecting surface existing in the vicinity of the light source (2) (see FIG. 7). In addition, the said reflective surface part (7) may be the structure which consists of one curved reflective surface in which the curvature center (Y) exists in the said light source area | region (Z). 5-7, the same code | symbol is attached | subjected about the component same as 1st Embodiment of the said FIGS. 1-4, and the description is abbreviate | omitted.

  Or you may employ | adopt the structure (3rd Embodiment) provided with the reflective surface part (7) as shown in FIG. In the third embodiment, light emitted from the light source (2) toward the back side is directed toward the light source (2) or in the vicinity of the light source (2). Is the same as in the first and second embodiments in that a reflective surface portion (7) that reflects toward the direction passing through is provided, but in the third embodiment, the reflective surface portion (7) A plurality of planar reflecting surfaces (7c) arranged so as to surround the light source (2) on the back side of the light source (2) are connected to each other, and are surfaces orthogonal to the length direction of the light source (2). In the cross-sectional view, the apex (9) connecting the adjacent plane reflecting surfaces (7c) and (7c), the non-joining apex (9A) of the leftmost plane reflecting surface (7c), and the rightmost plane reflecting surface (7c). The center (Y3) of the smallest virtual circle (U) containing all of the non-connected vertices (9B) of Configuration present in the vicinity of the source region (Z) or the light source (2) is adopted. In the third embodiment, the minimum virtual circle (U) containing all the vertices (9), (9), (9), (9), (9), (9A), and (9B) (9) (9) (9) (9) (9) (9A) (9B) It is a circle which passes. That is, the inner surface shape of the reflection surface portion (7) is the same shape as one shape obtained by dividing the regular dodecagon into two equal parts. In FIG. 8, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  Or you may employ | adopt the structure (4th Embodiment) provided with the reflective surface part (7) as shown in FIG. In the fourth embodiment, light emitted from the light source (2) toward the back side is directed toward the light source (2) or in the vicinity of the light source (2). The reflective surface part (7) which reflects toward the direction which passes is provided, and the said reflective surface part (7) is arrange | positioned so that the said light source (2) may be surrounded in the back side of the said light source (2) A plurality of planar reflection surfaces (7c) are connected to each other, and a vertex (9) connecting the adjacent planar reflection surfaces (7c) and (7c) in a cross-sectional view in a plane orthogonal to the length direction of the light source (2). )... And the smallest virtual circle (U) including all of the non-connected vertex (9A) of the leftmost plane reflecting surface (7c) and the non-connected vertex (9B) of the rightmost plane reflecting surface (7c). Center (Y4) of the light source exists in the light source region (Z) or in the vicinity of the light source (2). In this fourth embodiment, the smallest virtual circle that includes all of the vertices (9), (9), (9), (9A), and (9B) is the same as the third embodiment. (U) is different from the third embodiment in that it is a circle passing through some of the vertices (9), (9), (9), (9A), and (9B). That is, the smallest virtual circle (U) including all the vertices does not pass through the vertex at the lowest position in the center (the position farthest from the deflection structure plate), and the remaining four vertices (9) and (9). (9A) A circle that passes through (9B). In FIG. 9, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  As the reflection surface portion (7), as in the first and second embodiments described above, one or a plurality of curved reflection surfaces having a center of curvature at the light source region (Z) or a position near the light source (2) are provided. The configuration provided is preferable in that the luminance in the front direction can be further improved.

  Further, as the reflection surface portion (7), as in the third and fourth embodiments described above, a plurality of planar reflection surfaces arranged to surround the light source (2) on the back side of the light source (2). (7c), which includes all the vertices (9), (9A), and (9B) at both ends of the planar reflecting surface (7c) in a cross-sectional view on a plane orthogonal to the length direction of the light source (2). The center (Y3) (Y4) of the smallest virtual circle (U) includes a plurality of planar reflection surfaces (7c) existing in the light source region (Z) or in the vicinity of the light source (2). This is preferable in that the luminance in the front direction can be further improved.

  The reflective surface portion (7) reflects light emitted from the light source (2) toward the back side toward the light source (2) or in a direction passing through a position near the light source (2). Although it is necessary to be configured, as the range (area) (W) of the vicinity position of the light source (2), the separation interval between the deflection structure plate (3) and the light source (2) is set to “H”, When the center-to-center distance between the adjacent light sources (2) and (2) is “L”, the distance between the light source (2) and the center position (G) is parallel to the normal direction of the deflection structure plate (3). A vertical distance to the first virtual line (Q) is 0.15 L or less, and a second virtual line (J) passing through the center position (G) of the light source (2) parallel to the deflection structure plate (3). ) Is a range in which the vertical distance is 0.15H or less, and the distance from the center position (G) of the light source (2) is the light. A it is preferably a range in which the light source region excluding (i.e. light source areas existing) (Z) is the radius less (2) (see FIG. 4,7). When the reflected light reflected by the reflecting surface portion (7) is configured to pass through the light source vicinity position in such a specific range, the luminance in the front direction can be further improved.

  Moreover, in the said embodiment, although the front surface of the reflective surface part (7) was formed in the white reflective surface, it is not specifically limited to such a structure, For example, you may form in a mirror-reflection surface.

  The thickness (S) of the deflection structure plate (3) is not particularly limited, but is usually set to 0.1 to 15 mm, preferably 0.5 to 10 mm, and more preferably 1 to 5 mm. It is.

  As the deflection structure plate (3), a transparent plate made of a transparent material such as transparent resin or transparent glass is usually used. The transparent resin is not particularly limited. For example, polycarbonate resin, ABS resin (acrylonitrile-butadiene-styrene copolymer resin), methacrylic resin, MS resin (methyl methacrylate-styrene copolymer resin), Examples include polystyrene resin, AS resin (acrylonitrile-styrene copolymer resin), polyolefin resin (for example, polyethylene, polypropylene, etc.), and the like. A light diffusing agent (light diffusing particles) may be dispersed and contained in the deflection structure plate (3).

  The method for forming the prism (triangle) is not particularly limited, and examples thereof include an extrusion method, a press method, a cutting method, and an injection molding method. Especially, it is preferable to manufacture by an extrusion method from a viewpoint of production efficiency.

  The light source (2) is not particularly limited, and examples thereof include a fluorescent tube (cold cathode ray tube), a straight tube lamp such as a halogen lamp and a tungsten lamp, and a point light source such as a light emitting diode (LED).

  The distance (L) between the centers (G) and (G) of the adjacent light sources (2) and (2) is preferably set to 15 to 150 mm from the viewpoint of power saving. The distance (H) between the deflection structure plate (3) and the light source (2) is preferably set to 5 to 50 mm from the viewpoint of reducing the thickness.

  The surface light source device (1) and the transmissive image display device (10) according to the present invention are arranged on the back side of at least one light source (2) among the plurality of light sources constituting the surface light source device (1). The structure provided with the reflective surface part (7) which reflects toward the direction which passes the light which was emitted toward toward the said light source (2) or the vicinity position of the said light source (2) is also included. Of course, the light source (2) is released from the light source (2) toward the back side of each of the plurality of light sources constituting the surface light source device (1) and the transmissive image display device (10). Needless to say, it is preferable to employ a configuration in which a reflecting surface portion (7) is provided that reflects the slanted light toward the light source (2) or in a direction passing through a position near the light source (2). .

  Further, as the reflection surface portion (7), for example, when a plurality of straight tubular lamps arranged in parallel with each other is used as the light source (2), the center in the length direction of the plurality of straight tubular light sources (2) is used. A configuration (a configuration in which a reflective surface portion is disposed only on the back side of the central portion in the length direction of each light source) may be employed in a state of being orthogonal to the light source (2) so as to be connected to each other. .

  2 and 6 may be designed such that the horizontal direction in FIGS. 2 and 6 is the horizontal direction (horizontal direction) of the surface light source device (1) and the transmissive image display device (10), or FIG. , 6 may be designed to be the vertical direction (vertical direction) of the surface light source device (1) and the transmissive image display device (10), and is not particularly limited. For example, the transmissive image display device (10) may be designed with a wide viewing angle in the left-right direction (horizontal direction) and a narrow viewing angle in the vertical direction (vertical direction). In such a case, for example, the horizontal direction in FIGS. 2 and 6 may be designed to be the vertical direction (vertical direction) of the surface light source device (1) and the transmissive image display device (10).

  The surface light source device (1) and the transmissive image display device (10) according to the present invention are not particularly limited to those of the above embodiment, and do not depart from the spirit as long as they are within the scope of the claims. Any design changes are allowed as far as possible.

  Next, specific examples of the present invention will be described, but the present invention is not particularly limited to these examples.

<Example 1>
The angular distribution of the luminance of light emitted from the deflection structure plate (3) toward the observer when the liquid crystal display device (10) having the configuration of the first embodiment (see FIGS. 1 to 4) is configured. It was calculated by simulation using the ray tracing method. The result of this simulation is shown by a solid line in FIG. Various design conditions were the same as described above (see Table 1 etc.). The distance (L) between the adjacent light sources (2) and (2) is 30 mm, the distance (H) from the light source (2) to the deflection structure plate (3) is 19 mm, and the diameter (2r) of the light source (2) is The radius of curvature (R) of the first curved surface reflecting surface (7a) and the second curved surface reflecting surface (7b) of the reflecting surface portion (7) made of a white reflecting plate was set to 3 mm. The deflecting structure plate (3) is made of a resin plate made of MS resin (transparent resin) with a refractive index of 1.57 and a thickness (S) of 2 mm. The center of curvature (Y1) of the first curved reflecting surface (7a) moves 1 mm from the center position (G) of the light source (2) along the first imaginary straight line (Q) in the front direction, and further the second imaginary. It exists at a position moved 1 mm in the left direction of the drawing parallel to the straight line (J). Further, the center of curvature (Y2) of the second curved reflecting surface (7b) moves from the center position (G) of the light source (2) by 1 mm along the first virtual straight line (Q) to the front surface, and further the second virtual It exists in the position which moved 1 mm in the drawing right direction in parallel with the straight line (J).

  The ray tracing simulation is a Monte Carlo stochastic simulation based on geometric optics, and the shape, refractive index, and interface reflection characteristics of each model component of the model to be simulated are set, and a sufficiently large number of occurrences occur. Each transmission and reflection is tracked for the light beam being repeated and this is repeated until the result is sufficiently converged.

<Comparative Example 1>
The deflection structure plate (3) in the liquid crystal display device (10) of the first embodiment in which the reflection surface portion (7) is not provided (the other configuration and setting conditions are the same as those in the first embodiment) (see FIG. 10). ) To calculate the angular distribution of the brightness of the light emitted toward the observer. The result of this simulation is shown by a dotted line in FIG. The distance (h) between the light source (2) and the white reflector (5a) on the bottom of the lamp box was set to 4 mm.

  From the graph of FIG. 11, in Example 1, the emitted light is sufficiently condensed within a range of ± 12 ° centered on the front side direction (a) in the normal direction of the deflection structure plate (3). In contrast, in Comparative Example 1, the emitted light is only within a range of ± 5 ° centered on the front side direction (a) in the normal direction of the deflection structure plate (3). The light is not sufficiently condensed and the luminance in the front direction is insufficient.

  FIG. 12 shows an emission within an arbitrary emission angle range (angle range on both sides of + and −) centering on the front side direction (a) in the normal direction of the deflection structure plate (3) based on the simulation result. It is the graph which showed the ratio (%) with respect to the energy of all the emitted light of the energy of light to be performed. The result of Example 1 is indicated by a solid line, and the result of Comparative Example 1 is indicated by a dotted line. From the graph of FIG. 12, in Comparative Example 1, about 42% of the total emitted light is in a direction within a range of ± 10 ° with respect to the front side direction (a) in the normal direction of the deflection structure plate (3). In contrast, in Example 1, about 63% of all the emitted light is emitted in a direction within a range of ± 10 ° with respect to the front side direction (a) in the normal direction of the deflection structure plate (3). I found out that

  In general, in a liquid crystal television or the like, it is considered that the viewer should watch at a position about three times as high as the screen height from the liquid crystal television. In this case, the viewer can view the screen of the liquid crystal television. In the evaluation of the graph of FIG. 12, the angle when viewing the uppermost position is about 10 ° upward from the horizontal and the angle when viewing the lowermost position of the screen is about 10 ° downward from the horizontal. The light emitted in the direction within a range of ± 10 ° around the front-side direction (a) in the normal direction of the deflection structure plate (3) is regarded as “front-side light” and subjected to a comparative evaluation. .

  The surface light source device of the present invention is suitably used as a backlight for a transmissive image display device, but is not particularly limited to such applications.

1 is a schematic side view showing an embodiment of a transmissive image display device according to the present invention. 1 is a schematic side view showing an embodiment (first embodiment) of a surface light source device according to the present invention. In FIG. 2, the optical path of the light emitted from the light source to the front side and directly incident on the deflection structure plate and emitted from the deflection structure plate is indicated by a solid line with an arrow. Moreover, the optical path of the light emitted toward the back side from the light source is indicated by a dotted line with an arrow. It is a side view which expands and shows a part of deflection structure board of the surface light source device of FIG. It is a side view which expands and shows the light source of the surface light source device of FIG. 2, and its vicinity. It is a typical side view showing other embodiments of a transmission type image display device concerning this invention. It is a typical side view which shows other embodiment (2nd Embodiment) of the surface light source device which concerns on this invention. In FIG. 6, the optical path of light emitted from the light source to the front side and directly incident on the deflection structure plate and emitted from the deflection structure plate is indicated by a solid line with an arrow. Moreover, the optical path of the light emitted toward the back side from the light source is indicated by a dotted line with an arrow. It is a side view which expands and shows the light source and its vicinity of the surface light source device of FIG. It is a side view which expands and shows the reflective surface part in other embodiment (3rd Embodiment) of the surface light source device which concerns on this invention, and its vicinity. It is a side view which expands and shows the reflective surface part in other embodiment (4th Embodiment) of the surface light source device which concerns on this invention, and its vicinity. It is a typical side view which shows the structure of the surface light source device of the comparative example 1. In FIG. 10, the optical path of light emitted from the light source to the front side and directly incident on the deflection structure plate and emitted from the deflection structure plate is indicated by a solid line with an arrow. Moreover, the optical path of the light emitted toward the back side from the light source is indicated by a dotted line with an arrow. Angular distribution (indicated by a solid line) of the luminance of light emitted from the deflection structure plate in Example 1 toward the observer, and the luminance angle of the light emitted from the deflection structure plate in Comparative Example 1 toward the observer. It is a graph which shows distribution (it shows with a dotted line). The energy of light emitted within a specific emission angle range (angle range on both sides of + and-) centering on the front side direction (a) of the normal direction of the deflection structure plate is relative to the energy of all emission light. The result of Example 1 is indicated by a solid line, and the result of Comparative Example 1 is indicated by a dotted line.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Surface light source device 2 ... Light source 3 ... Deflection structure board 7 ... Reflective surface part 7a ... 1st curved surface reflective surface 7b ... 2nd curved surface reflective surface 7c ... Planar reflective surface 9, 9A, 9B ... Vertex 10 ... Liquid crystal display device (transmission) Type image display device)
DESCRIPTION OF SYMBOLS 14 ... Transmission-type image display part 21 ... 1st light source 22 ... 2nd light source 23 ... 3rd light source 24 ... 4th light source 25 ... 5th light source 91-94 ... Corresponding area a ... Front direction of normal direction G ... Light source Center position Q ... 1st virtual straight line J ... 2nd virtual straight line U ... Virtual circle Y, Y1, Y2 ... Center of curvature Y3, Y4 ... Center of virtual circle W ... Range (region) of position near light source
Z: Light source area

Claims (6)

A surface light source device in which a plurality of light sources are spaced apart from each other, and a deflection structure plate for changing the direction of light emitted from the light sources is disposed on the front side of these light sources,
The deflecting structure plate is configured such that the light directly incident from the two adjacent light sources is incident on a region corresponding to the region between the two adjacent light sources in the deflecting structure plate in the front side direction in the normal direction of the deflecting structure plate. Configured to be emitted toward
A reflection surface portion is provided on the back side of the light source, the reflection surface portion reflecting light emitted from the light source toward the back side toward the light source or in a direction passing through a position near the light source. Surface light source device. The reflective surface portion is
One or a plurality of curved reflecting surfaces whose curvature centers are present in the light source region or in the vicinity of the light source, and / or a plurality of planar reflecting surfaces arranged so as to surround the light source on the back side of the light source, In a cross-sectional view in a plane orthogonal to the length direction of the light source, the center of the smallest virtual circle that includes all of the vertices at both ends of the planar reflecting surface is present in the light source region or in the vicinity of the light source. The surface light source device according to claim 1, comprising a plane reflecting surface.   The reflective surface portion is formed to extend from the rear side region of the light source to the substantially lateral region on the left side of the light source and the substantially lateral region on the right side of the light source. The surface light source device according to claim 1, wherein the emitted light is reflected by the reflection surface portion and reflected toward the light source or in a direction passing through a position near the light source. .   The surface light source device according to any one of claims 1 to 3, wherein the reflection surface portion reflects light emitted from the light source toward the back side in a direction passing through a position near the light source. . The range of the vicinity of the light source is
When the distance between the deflection structure plate and the light source is “H” and the distance between the centers of adjacent light sources is “L”, it passes through the center position of the light source parallel to the normal direction of the deflection structure plate. The vertical distance to the first virtual straight line is 0.15 L or less, and the vertical distance to the second virtual straight line that is parallel to the deflection structure plate and passes through the center position of the light source is 0.15 H or less. 5. The surface light source device according to claim 1, wherein the surface light source device is a range excluding a light source region whose distance from the center position of the light source is equal to or less than a radius of the light source.   A transmissive image display device comprising the surface light source device according to any one of claims 1 to 5 arranged on the back side of a transmissive image display unit.

Images