JP6748950B2 - Surface light source device and illuminance distribution adjustment plate - Google Patents

Description

The present invention relates to a surface light source device and an illuminance distribution adjusting plate used in this surface light source device.

2. Description of the Related Art A surface light source device that emits light in a planar manner is widely used as a backlight that illuminates a liquid crystal display panel incorporated in a liquid crystal display device from the back side. The surface light source device for a liquid crystal display device is roughly classified into an edge light type in which a light source is arranged on the side of an optical member and a direct type in which a light source is arranged directly below the optical member. As the light source, for example, a light emitting diode (LED) is used.

In a vehicle-mounted liquid crystal display device, an edge light type surface light source device has been conventionally used as a backlight because it can be easily made thin. In such a vehicle-mounted liquid crystal display device, it is required to display brightly in order to ensure visibility under the external light that is inserted through the window. In order to obtain as bright a display as possible with an edge light type surface light source device, it is necessary to densely arrange a large number of light sources on the side of the optical member. Here, the on-vehicle liquid crystal display device is often arranged in a narrow space, and when a large number of light sources are densely arranged in this narrow space, it becomes impossible to sufficiently dissipate heat generated from the light sources. That is, when an edge light type surface light source device is used as a backlight of a vehicle-mounted liquid crystal display device, when trying to obtain sufficient brightness, the heat generated from the light source cannot be sufficiently dissipated and the liquid crystal The display device may become hot and may malfunction. On the other hand, if a direct type surface light source device can be used as the backlight, a plurality of light sources can be arranged apart from each other, and thus heat generated from the light sources can be appropriately radiated. Therefore, in a vehicle-mounted liquid crystal display device, it is required to reduce the thickness of the surface light source device while using the direct surface light source device as a backlight.

In a direct type surface light source device, an illuminance distribution adjusting plate is arranged between the light source and the liquid crystal display panel in order to display a uniform image while reducing the thickness of the surface light source device. A technique for adjusting the illuminance distribution in the light emitting surface of a light source device is known.

JP2012-274372A discloses an illumination unit having an LED light source and a reflection plate made of a material that reflects light without transmitting light. A plurality of light passage holes arranged in a matrix are formed on the reflection plate. The opening area of each of the plurality of light passage holes is smaller as the distance from the facing portion facing the LED light source is shorter. According to such an illumination unit, the closer to the position where the density of the light directly reaching from the LED light source is higher, the smaller the light passing amount is, and the light passing hole at the position where the density of the light directly reaching from the LED light source is low. Has more light passing through it. Thereby, the distribution of the light passing through the reflection plate can be made close to uniform, and the distribution of the irradiation light of the illumination device can be made close to uniform.

Further, JP45386675B discloses a surface illumination unit including a light source and a bottom surface portion and an optical reflection plate arranged at a predetermined interval in the light emission direction. In the vicinity of the center of the optical reflector, a plurality of concentric, annular, non-penetrating holes centered on the center of the optical reflector are formed. A large number of concentric and discontinuous narrow arc-shaped narrow holes are formed outside the non-through holes. Outside the arcuate hole, a large number of round holes are arranged in a bag shape in a plan view. The hole farthest from the center of the optical reflection plate among the arc-shaped holes is located on the straight line connecting the center of the optical reflection plate and the hexagonal vertex where the circular hole adjacent to the arc-shaped hole is arranged. By arranging the arc-shaped hole farthest from the center on the straight line connecting the apex and the center of the hexagon in this manner, the distance between the apex and the arc-shaped hole is narrowed. This makes it easier for light from the round holes and the arc-shaped holes to hit the upper portion between the apex and the arc-shaped holes, and uniform illumination can be obtained.

In the lighting unit disclosed in JP2012-274372A, since the plurality of light passage holes are arranged in a matrix, the aperture ratio of the light passage holes is limited in the peripheral portion of the reflection plate, and the light transmittance in the peripheral portion is limited. Could not be made large enough. As a result, the illuminance of the light emitted from the reflection plate is reduced at the peripheral edge of the reflection plate, and the illuminance distribution in the light emitting surface of the illumination unit is uneven. Further, if the light passage hole is too large in the peripheral edge portion of the reflection plate, the portion of the reflection plate remaining between the adjacent light passage holes becomes thin, which may lead to a reduction in the strength of the reflection plate.

Further, in the surface lighting unit disclosed in JP45386675B, the hole farthest from the center of the optical reflection plate among the arc-shaped holes is defined as the hexagonal vertex where the round holes adjacent to the arc-shaped hole are arranged and the optical reflection plate. Even if it is arranged on the straight line connecting the centers of the circles, there is still a region where no hole is formed between the arc-shaped hole and the round hole arranged at the apex of the hexagon, and the optical reflection plate is present in that region. The illuminance of the light emitted from the device is reduced, and the illuminance distribution in the light emitting surface of the surface illumination unit is uneven.

The present invention has been made in view of the above circumstances, and an object thereof is to suppress uneven illuminance in the light exit surface of a direct type surface light source device.

The surface light source device of the present invention is
A light source; and an illuminance distribution adjusting plate that is arranged to face the light source and adjusts an illuminance distribution of light emitted from the light source,
The illuminance distribution adjustment plate,
A base material on which a plurality of light transmitting holes for transmitting the light are formed,
The substrate has one or more compartments,
In each division area,
The divided area is further divided into a plurality of regularly arranged element areas,
Each element region has a hexagonal shape in plan view,
At least one light transmission hole is formed in each of the element regions adjacent to the element region overlapping with the light source when projected onto the light source along the normal direction of the substrate.

In the surface light source device of the present invention,
The illuminance distribution adjusting plate may have a curved surface shape that is bent in a first direction along the plate surface.

In the surface light source device of the present invention,
Each element region has three pairs of opposite sides in plan view,
The two opposite sides are parallel to each other,
Two sides forming a pair of opposite sides of the three pairs of opposite sides may be orthogonal to the first direction.

The illuminance distribution adjusting plate of the present invention,
An illuminance distribution adjusting plate arranged to face a light source and adjusting the illuminance distribution of light emitted from the light source,
A base material on which a plurality of light transmitting holes for transmitting the light are formed,
The substrate has one or more compartments,
In each division area,
The divided area is further divided into a plurality of regularly arranged element areas,
Each element region has a hexagonal shape in plan view,
At least one light transmission hole is formed in each of the element regions adjacent to the element region overlapping with the light source when projected onto the light source along the normal direction of the substrate.

The surface light source device of the present invention is
A surface light source device comprising: a light source; and an illuminance distribution adjusting plate that is arranged to face the light source and adjusts an illuminance distribution of light emitted from the light source,
The illuminance distribution adjustment plate,
A base material on which a plurality of light transmitting holes for transmitting the light are formed,
The substrate has one or more compartments,
In each of the divided areas, when the surface light source device is observed from the normal direction of the substrate, one light transmitting hole is formed at each vertex of a hexagon surrounding the light source.

[Effect of the invention]
According to the present invention, it is possible to suppress uneven illuminance in the light exit surface of the direct type surface light source device.

FIG. 1 is a diagram for explaining one embodiment of the present invention and is a perspective view schematically showing an example of a display device including a display panel and a surface light source device. FIG. 2 is a perspective view schematically showing an example of the surface light source device. FIG. 3 is a plan view showing an example of an illuminance distribution adjusting plate incorporated in the surface light source device. FIG. 4 is a view showing a cross section of the surface light source device, which corresponds to line IV-IV in FIG. 3. FIG. 5 is a plan view showing one divided area of the illuminance distribution adjusting plate, and is a view showing an example of an arrangement pattern of element areas and light transmission holes. FIG. 6 is a diagram for explaining the aperture ratio in the element region. FIG. 7 is a diagram for explaining the aperture ratio in the element region. FIG. 8 is a diagram for explaining the minimum clearance between the contour of the light transmitting hole and the contour of the element region. FIG. 9 is a diagram for explaining a modification of the illuminance distribution adjusting plate, and is a perspective view showing the bent illuminance distribution adjusting plate. FIG. 10 is a plan view showing one element region in the illuminance distribution adjusting plate of FIG. FIG. 11 is a diagram for explaining another modified example of the illuminance distribution adjusting plate, and is a plan view showing one sectioned region of the illuminance distribution adjusting plate. FIG. 12 is a graph showing the distribution of the aperture ratio in the partitioned area of FIG. FIG. 13 is a plan view showing a modification of the shape of the element region.

An embodiment of the present invention will be described below with reference to the drawings. In addition, in the drawings attached to the present specification, for convenience of illustration and understanding, the scale, the vertical and horizontal dimension ratios, etc. are appropriately changed and exaggerated from the actual ones.

In the present specification, the terms “plate”, “sheet” and “film” are not distinguished from each other based only on the difference in designation. For example, a “plate” is a concept that includes members that can also be called “sheets” or “films”. Therefore, for example, “illuminance distribution adjustment plate” means “illuminance distribution adjustment sheet” or “illumination distribution adjustment sheet”. It cannot be distinguished from the member called "film" only by the difference in designation.

The term “plate surface (sheet surface, film surface)” means the target plate-shaped member (sheet-shaped member) when the target plate-shaped (sheet-shaped, film-shaped) member is viewed as a whole and comprehensively. (A member, a film-like member) refers to a surface that coincides with the plane direction. In the present specification, the normal direction of the surface and plate-shaped (sheet-shaped, film-shaped) member means the normal to the plate surface of the target surface- and plate-shaped (sheet-shaped, film-shaped) member. Refers to the direction.

In the present specification, “plan view” refers to a state in which a symmetrical plate-shaped (sheet-shaped or film-shaped) member is viewed from the normal line direction of the member. For example, "a plate-shaped member is formed in a rectangular shape in a plan view" means that the member is formed in a rectangular shape when the member is viewed from a direction normal to the plate surface. Refers to.

Further, as used in the present specification, the shape and geometric conditions and the degree thereof are specified. For example, terms such as “parallel”, “orthogonal”, “identical”, and values of length and angle are strict. Without being bound by the meaning, it should be interpreted including the range to the extent that similar functions can be expected.

1 to 12 are views for explaining one embodiment of the present invention. Among these, FIG. 1 is a diagram schematically showing an example of a display device including a display panel and a surface light source device, and FIG. 2 is a perspective view schematically showing an example of a surface light source device.

The display device 10 according to the present embodiment is a device that displays, for example, a moving image, a still image, character information, or an image composed of a combination thereof on the display panel 15. Although an example in which the display device 10 is a vehicle-mounted liquid crystal display device will be described in the present embodiment, the display device 10 of the present invention is not limited to this, and the display device 10 according to the present invention can be used for advertisement, presentation, or television indoors or outdoors. It can be used for various purposes such as displaying images and various information. The display device 10 shown in FIG. 1 includes a surface light source device 20 having a light emitting surface 20a and a display panel 15 arranged to face the light emitting surface 20a. In the illustrated example, the display panel 15 is configured as a liquid crystal display panel, and thus the display device 10 is configured as a liquid crystal display device. In the present embodiment, the surface light source device 20 constitutes a so-called direct type backlight, and illuminates the display panel 15 from the back side of the display panel 15, that is, the side opposite to the viewer 5.

In the illustrated example, the display panel 15 is arranged such that the display surface 15 a on which an image is displayed faces the opposite side of the surface light source device 20. As a result, the display surface 15a of the display panel 15 forms the display surface 10a of the display device 10. The display panel 15 is formed in a rectangular shape when viewed from the normal direction of the display panel 15, that is, in a plan view.

The display panel 15 of the present embodiment is a transmissive liquid crystal display panel, which transmits a part of the light that has entered the display panel 15 from the surface light source device 20 and displays an image on the display surface 15a. The display panel 15 includes a liquid crystal layer having a liquid crystal material, and the light transmittance of the display panel 15 changes according to the strength of the electric field applied to the liquid crystal layer. As an example of such a display panel 15, a liquid crystal display panel having a pair of polarizing plates and a liquid crystal cell (liquid crystal layer) arranged between the pair of polarizing plates can be used. In this liquid crystal display panel, the polarizing plate decomposes the incident light into two orthogonal polarization components, transmits the polarization component in one direction, and absorbs the polarization component in the other direction orthogonal to the one direction. It has a polarizer having a function. The liquid crystal cell has a pair of support plates and liquid crystal arranged between the pair of support plates. An electric field can be applied to each region of the liquid crystal cell forming one pixel, and the alignment of the liquid crystal of the liquid crystal cell to which the electric field is applied changes. The polarization component in a specific direction (direction parallel to the transmission axis) emitted from the surface light source device 20 and transmitted through the polarizing plate arranged on the surface light source device 20 side of the liquid crystal cell is, for example, a liquid crystal cell to which an electric field is not applied. When passing through a liquid crystal cell to which an electric field is applied, the polarization direction is rotated by 90° and the polarization direction is maintained. As a result, depending on whether or not an electric field is applied to the liquid crystal cell, the polarization component in a specific direction transmitted through the polarizing plate arranged on the surface light source device 20 side of the liquid crystal cell is arranged on the opposite side of the liquid crystal cell surface light source device 20. It is possible to control whether the light is further transmitted through another polarizing plate or is absorbed and blocked by the other polarizing plate.

The surface light source device 20 has a light emitting surface 20a that emits planar light, and is a so-called direct type in which the light source 22 is provided in a region facing the light emitting surface 20a in the normal direction of the light emitting surface 20a. It is configured as a backlight. As shown in FIG. 2, the surface light source device 20 of the present embodiment includes a base laminated body 30, which supports the light source 22, a spacer 23, an illuminance distribution adjusting plate 40, a diffusion plate 26, a first optical sheet 27, and It has a second optical sheet 28. In the illustrated example, the spacer 23 and the illuminance distribution adjusting plate 40 are sequentially stacked on the base laminate 30, and are spaced apart from the illuminance distribution adjusting plate 40 by a predetermined distance to form the diffusion plate 26, the first optical sheet 27, and the first optical sheet 27. The laminated body of the two optical sheets 28 is arranged in order. The second optical sheet 28 forms the light emitting surface 20a of the surface light source device 20.

The light source 22 is composed of, for example, a light emitting diode (LED) or the like, and is arranged so as to face the illuminance distribution adjusting plate 40. In the present embodiment, as well shown in FIG. 3, the light sources 22 are arranged or arranged side by side along the first direction d ₁ parallel to the plate surface of the surface light source device 20, and The light source devices 20 are arranged in parallel with a plate surface of the light source device 20 and along a second direction d ₂ that intersects the first direction d ₁ . Particularly in the present embodiment, the first direction d ₁ and the second direction d ₂ are orthogonal to each other. That is, in the present embodiment, the plurality of light sources 22 are two-dimensionally arranged along the first direction d ₁ and the second direction d ₂ . However, the present invention is not limited to this, and the surface light source device 20 may have a plurality of light sources 22 arranged in a line along the first direction d ₁ or the second direction d ₂ , or only one light source 22. May have. In addition, it is preferable that the output of each light source 22, that is, the lighting and extinction of each light source 22 and/or the brightness when each light source 22 is turned on can be adjusted independently from the output of the other light source 22.

In the example shown in FIG. 3, the contour of the illuminance distribution adjusting plate 40 has a rectangular shape in a plan view. The first direction d ₁ and the second direction d ₂ can be arbitrarily defined, but in the illustrated example, the first direction d ₁ is set to be parallel to one side of the rectangular shape that forms the contour of the illuminance distribution adjusting plate 40. The second direction d ₂ is defined to be parallel to the other side that is orthogonal to the one side. Particularly, in the illustrated example, the first direction d ₁ is defined to be parallel to the long side of the rectangular shape forming the contour of the illuminance distribution adjusting plate 40, and the second direction d ₂ is parallel to the short side of the rectangular shape. Is defined as

The spacer 23 is a member that supports the illuminance distribution adjusting plate 40, and has a function of maintaining a predetermined distance between the base laminate 30 and the illuminance distribution adjusting plate 40. As shown in FIG. 2, the spacer 23 has a wall portion 24 that partitions the space between two adjacent light sources 22, so that the spacer 23 is surrounded by the wall portion 24 corresponding to each light source 22. An opening 25 is formed. In the illustrated example, the spacer 23, in plan view, a plurality of wall portions 24 which are arranged in a first direction d ₁ extending in the second direction d _2, in the first direction d ₁ are arranged in the second direction d ₂ The plurality of extending wall portions 24 are arranged so as to form a lattice shape. The openings 25 are provided corresponding to the arrangement pattern of the light sources 22. That is, the spacer 23 has a plurality of openings 25 arranged in the first direction d ₁ and arranged in the second direction d ₂ . In the present embodiment, each opening 25 is formed to have a rectangular shape, particularly a square shape in a plan view, but the present invention is not limited to this, and each opening 25 has another shape such as a triangle, a hexagon, or a circle in a plan view. May be done. Such a spacer 23 includes, for example, polycarbonate resin, acrylonitrile-butadiene-styrene copolymer resin (ABS resin), acrylonitrile-styrene-acrylate copolymer resin (ASA resin), acrylonitrile-butadiene-styrene copolymer resin (AES resin), It can be formed of polymethylmethacrylate resin (PMMA resin), polyacetal resin, polyvinyl chloride resin, polyethylene resin, polypropylene resin, polyethylene terephthalate resin, or a mixture of two or more of these resins. In particular, the spacer 23 is preferably made of a material having high reflectivity for light in the visible light wavelength range.

FIG. 3 is a plan view showing the illuminance distribution adjusting plate 40 incorporated in the surface light source device 20. In FIG. 3, the positions of the light source 22 and the opening 25 of the spacer 23 arranged on the back side of the illuminance distribution adjusting plate 40 are indicated by broken lines. The illuminance distribution adjusting plate 40 includes a base material 41 having a plurality of light transmission holes 45 for transmitting the light emitted from the light source 22. In addition, in FIG. 3, the illustration of the light transmission hole 45 is omitted. The base material 41 of the illuminance distribution adjusting plate 40 has one or more divided areas Aa corresponding to the respective light sources 22. That is, the base material 41 is provided with one divided area Aa for one light source 22. Therefore, the base material 41 has a plurality of partitioned areas Aa arranged along the first direction d ₁ and arranged along the second direction d ₂ . In FIG. 3, the regions of the base material 41 partitioned by the alternate long and short dash lines indicate the respective partitioned regions Aa. In the illustrated example, each divided area Aa is formed in a rectangular shape in a plan view, but the shape of the divided area Aa is not limited to this. Each divided area Aa is further divided into a plurality of regularly arranged element areas Ab. The specific shape and arrangement pattern of the element area Ab will be described later.

In the example shown in FIG. 3, the division line La that divides the adjacent division areas Aa of the base material 41 is defined along the wall portion 24 of the spacer 23. In other words, the demarcation line La is defined so as to be located in a region facing the wall portion 24 of the spacer 23 along the normal direction of the illuminance distribution adjusting plate 40. As a result, partition lines La, as a whole, a plurality of partition lines La extending in a second direction d ₂ is arranged in the first direction d _1, of the plurality extending in a first direction d ₁ are arranged in the second direction d ₂ The division line La is defined so as to form a grid pattern. In the illustrated example, each partitioned area Aa has a width W ₁ along the first direction d ₁ and a width W ₂ along the second direction d ₂ . The width W ₁ and the width W ₂ can be, for example, 5 mm or more and 50 mm or less.

FIG. 4 shows a cross section of the surface light source device 20 corresponding to line IV-IV in FIG. In particular, FIG. 4 shows a cross section of the surface light source device 20 corresponding to one divided area Aa in the base material 41 of the illuminance distribution adjusting plate 40.

The base laminated body 30 has a function of supporting the light source 22 and supplying power to the light source 22. In the example shown in FIG. 3, the base laminate 30 has a base material 31, a bonding layer 32, a film substrate 33, a wiring layer 34, a resist layer 35, and a light reflection layer 36.

The base material 31 is a member that functions as a base material that holds the film substrate 33, the wiring layer 34, the resist layer 35, and the light reflection layer 36. The material of the base material 31 is not particularly limited as long as it can appropriately hold the film substrate 33, the wiring layer 34, the resist layer 35, and the light reflection layer 36, but for example, metal or resin is used. You can In particular, when the base material 31 formed of a metal material having good thermal conductivity such as aluminum is used, the heat generated in the light source 22 can be radiated toward the back side of the surface light source device 20 through the base material 31. It is more preferable because it can. The thickness of the base material 31 can be, for example, 0.5 mm or more and 10 mm or less. The base material 31 may form a part of the housing of the surface light source device 20.

The film substrate 33 is a member that functions as a base material that holds the wiring layer 34, and forms a printed wiring board together with the wiring layer 34. The film substrate 33 shown in FIG. 4 is formed of a flexible resin film, and thus the film substrate 33 forms a flexible printed wiring board together with the wiring layer 34. The film substrate 33 can have a thickness of, for example, 10 μm or more and 500 μm or less. By using a substrate thinner than the conventional rigid substrate as the film substrate 33, the surface light source device 20 can be thinned. The material of the film substrate 33 can be appropriately selected in consideration of insulation, heat resistance, durability, dimensional stability during heating, mechanical strength, and the like. For example, polyimide (PI) or polyethylene naphthalate ( PEN) and polyethylene terephthalate (PET) can be used.

The film substrate 33 is fixed to the base material 31 via the bonding layer 32. The bonding layer 32 is not particularly limited as long as the film substrate 33 can be appropriately fixed to the base material 31. As an example, a double-sided tape can be used as the bonding layer 32. Besides, an appropriate adhesive or pressure-sensitive adhesive may be used as the bonding layer 32.

The wiring layer 34 is provided on the film substrate 33 and has a function of supplying power to the light source 22. Therefore, the wiring layer 34 is preferably formed of a metal material having high conductivity. Examples of the metal material forming the wiring layer 34 include metal materials such as copper, aluminum, gold, silver, and the like, or alloys thereof. As an example, the wiring layer 34 can be formed by using the subtract method. That is, the wiring layer 34 having a desired pattern can be formed by patterning a metal layer such as a copper foil arranged on the film substrate 33 by etching using a photolithography technique. The wiring layer 34 is not limited to this, and may be formed using another method such as an additive method or a semi-additive method. In addition, an electrode portion is provided in the connection portion of the wiring layer 34 with the light source 22 or another wiring or connector.

A resist layer 35 is provided on the wiring layer 34 and the film substrate 33 exposed from the wiring layer 34. In particular, the resist layer 35 is provided so as to cover the wiring layer 34 and the film substrate 33 exposed from the wiring layer 34, except for the portion which becomes the electrode portion of the wiring layer 34. The resist layer 35 has a function of protecting the wiring layer 34 and also of preventing a short circuit between the wiring layer 34 and another member. As a material of the resist layer 35, for example, a resin material such as a polyester resin, an epoxy resin, an epoxy resin, a phenol resin, an epoxy acrylate resin, or a silicone resin can be used. As the resist layer 35, for example, a resin layer is provided so as to cover the wiring layer 34 and the film substrate 33 as a whole, and the electrode portion is exposed at a portion which will be an electrode portion of the wiring layer 34 by etching using a photolithography technique. It can be formed by providing an opening.

The light reflection layer 36 is a layer provided to improve the utilization efficiency of the light emitted from the light source 22, and is emitted from the light source 22 and reflected by the illuminance distribution adjusting plate 40 so that its optical path is directed to the light reflection layer 36 side. It has a function of reflecting the light bent toward the illuminance distribution adjusting plate 40 again. Therefore, the light reflection layer 36 is preferably a layer having high reflectivity for light in the visible light wavelength range. The light reflection layer 36 is arranged on the same side of the illuminance distribution adjusting plate 40 as the light source 22 and in parallel with the illuminance distribution adjusting plate 40. In the example shown in FIG. 4, the light reflection layer 36 is laminated on the resist layer 35 except the portion where the light source 22 is to be arranged. In the illustrated example, the light reflection layer 36 is arranged so as to surround the light source 22 in a plan view. In the illustrated example, the light reflection layer 36 is provided so as to expose the inner peripheral edge portion of the resist layer 35 surrounding the light source 22. However, the present invention is not limited to this, and in the light reflection layer 36, for example, the inner peripheral edge of the resist layer 35 and the inner peripheral edge of the light reflective layer 36 are aligned so that the inner peripheral edge of the resist layer 35 surrounding the light source 22 is not exposed. It may be provided in this way. As the light reflection layer 36, for example, a layer formed of a white resin material can be used.

The light source 22 is connected to the electrode portion of the wiring layer 34 via the conductive connection layer 37. As the conductive connection layer 37, for example, a layer made of solder, a conductive adhesive, or the like can be used.

The diffusing plate 26 is a plate-shaped member having a function of diffusing the light incident on the diffusing plate 26, and thereby makes the in-plane distribution of the illuminance uniform and allows the light transmitting holes 45 of the illuminance distribution adjusting plate 40 to be formed. The image can be made inconspicuous. The diffuser plate 26 can be used without particular limitation as long as it is a member having a light diffusing function. For example, a resin plate or a glass plate having fine irregularities on its surface, or a resin plate having diffusing particles inside. Or a glass plate can be used.

The first optical sheet 27 in the present embodiment changes the traveling direction of the light incident from the light source 22 side to emit the light from the display panel 15 side, and intensively improves the illuminance in the normal direction of the first optical sheet 27. It is a light-condensing sheet for making it. The light-condensing sheet according to the present embodiment is a sheet having a plurality of unit prisms arranged along a certain direction on the sheet surface. As this light-condensing sheet, for example, "BEF" (registered trademark) available from 3M Company in the United States can be used.

Further, the second optical sheet 28 in the present embodiment transmits a polarization component in the direction parallel to the transmission axis thereof and reflects a polarization component in the direction parallel to the reflection axis orthogonal to the transmission axis thereof. Is. According to this reflective polarizing plate, it is possible to prevent light having a polarization component that is emitted from the surface light source device 20 and cannot be effectively used in the display panel 15 from entering the display panel 15 and being absorbed by the polarizing plate. can do. Therefore, it is possible to improve the utilization efficiency of the light source light and improve the illuminance characteristics. As this reflective polarizing plate, for example, "DBEF" (registered trademark) available from 3M Company in the United States can be used.

As the diffusion plate 26, the first optical sheet 27, and the second optical sheet 28, those having a high visible light transmittance are preferably used from the viewpoint of ensuring sufficient illuminance of the surface light source device 20. ..

Next, the illuminance distribution adjusting plate 40 will be described in detail. FIG. 5 is a plan view showing one divided area Aa of the illuminance distribution adjusting plate 40, and is a view showing an example of an arrangement pattern of the element areas Ab and the light transmission holes 45. The illuminance distribution adjusting plate 40 includes a base material 41 in which a plurality of light transmitting holes 45 that transmit the light emitted from the light source 22 are formed. The plurality of light transmission holes 45 are arranged in each divided area Aa in a pattern in which the opening area increases as the distance from the center O _{1 of the} divided area Aa facing directly above the light source 22 increases. The illuminance distribution adjusting plate 40 also has a function of improving the utilization efficiency of the light emitted from the light source 22, and reflects the light incident on the illuminance distribution adjusting plate 40 to direct its optical path to the light reflection layer 36 side. It is configured so that it can be bent. Therefore, the base material 41 of the illuminance distribution adjusting plate 40 is preferably a layer having high reflectivity for light in the visible light wavelength range. The base material 41 is formed of, for example, a white resin material. As an example, the base material 41 may be formed of a foamed resin such as foamed polyethylene terephthalate (foamed PET).

In the present embodiment, the illuminance distribution adjusting plate 40 has a base material 41 formed of a material having low light transmittance, and the light transmission holes 45 are physical holes formed in the base material 41, that is, Although it is formed as a through hole extending from one main surface of the two main surfaces of the base material 41 facing each other to the other main surface, the specific configuration of the light transmission hole 45 is not limited to this. The light transmitting hole 45 may be formed as a portion through which light can be transmitted from one side in the direction normal to the plate surface of the illuminance distribution adjusting plate 40 to the other side. It has a transparent plate-shaped transparent substrate and a light-reflecting layer provided on the transparent substrate, in particular, on the main surface of the transparent substrate on the light source 22 side, and the light-transmitting holes 45 form the light-transmitting holes. It may be configured as an opening provided in the reflective layer. In this case, the transparent substrate may not be provided with physical holes.

As shown in FIG. 4, the light emitted from the light source 22 toward the illuminance distribution adjusting plate 40 is reflected by the illuminance distribution adjusting plate 40 and travels toward the light reflecting layer 36 side. The light incident on the light reflection layer 36 is reflected by the light reflection layer 36 and travels toward the illuminance distribution adjusting plate 40. When light that repeats this is incident on any of the light transmitting holes 45 of the illuminance distribution adjusting plate 40, the light passes through the light transmitting holes 45 and is transmitted from the illuminance distribution adjusting plate 40 to the display panel 15 side (in FIG. It is emitted toward the (26 side). At this time, the light emitted from the light source 22 is repeatedly reflected between the illuminance distribution adjusting plate 40 and the light reflecting layer 36, and the direction substantially parallel to the plate surface of the illuminance distribution adjusting plate 40 (as an example, the first direction d in FIG. 4). _The illuminance of the light that proceeds to ₁ ) decreases as the distance from the light source 22 increases. However, in the illuminance distribution adjusting plate 40 of the present embodiment, as described above, the opening area of the plurality of light transmitting holes 45 increases as the distance from the center O _{1 of the} divided area Aa facing directly above the light source 22 increases. Since they are arranged in a pattern, it is possible to make the illuminance of the light transmitted through each light transmission hole 45 uniform. When the spacer 23 is made of a material having high reflectivity for light in the visible light wavelength range, the spacer 23 advances in a direction substantially parallel to the plate surface of the illuminance distribution adjusting plate 40 and enters the wall portion 24 of the spacer 23. The reflected light is reflected by the spacer 23, and its optical path is bent toward the light source 22 side. Thereby, the utilization efficiency of the light emitted from the light source 22 can be further improved.

The divided area Aa shown in FIG. 5 is further divided into a plurality of regularly arranged element areas Ab. Each element region Ab has a hexagonal shape in plan view. Especially, each element region Ab has a regular hexagonal shape in a plan view. In the illustrated example, a plurality of element regions Ab having the same shape and size are arranged in the partitioned region Aa at the same pitch. Specifically, the plurality of element regions Ab have a gap in the partitioned region Aa such that two adjacent element regions Ab share one side with each other and three element regions Ab share one vertex with each other. It is lined up without. As a result, the plurality of element regions Ab are arranged in a so-called honeycomb shape.

In FIG. 5, the position of the light source 22 arranged on the back side of the illuminance distribution adjusting plate 40 is indicated by a broken line. The plurality of element regions Ab include an element region Ab1 that overlaps the light source 22 when projected onto the light source 22 along the normal direction of the base material 41. Particularly in the illustrated example, the element region Ab1 is located at the center O ₁ of the partitioned region Aa. Here, that the element region Ab1 overlaps the light source 22 when projected onto the light source 22 along the normal direction of the base material 41 means that at least a part of the element region Ab1 is in the normal direction of the base material 41. It refers to overlapping with the light source 22 when projected along the light source 22. For example, the plurality of element regions Ab are arranged such that the vertex shared by the three element regions Ab1 overlaps the center of the light source 22 when projected onto the light source 22 along the normal direction of the base material 41. In this case, each of the three element regions Ab1 including the apex overlaps the light source 22 when projected onto the light source 22 along the normal direction of the base material 41.

At least one light transmitting hole 45 is formed in each of the element regions Ab2 adjacent to the element region Ab1 overlapping the light source 22 when projected onto the light source 22 along the normal direction of the base material 41. In particular, one light transmission hole 45 is formed in each of the six element regions Ab2 that are adjacent to the element region Ab1 and share any one side. Therefore, in the illustrated example, one light transmission hole 45 is formed at each vertex of the hexagon surrounding the light source 22 in a plan view in each partitioned area Aa. In the illustrated example, one light transmission hole 45 is formed in each of all the element regions Ab except the element region Ab1 including the element region Ab2. In other words, each element area Ab other than the element area Ab1 is defined so as to include one light transmission hole 45. Therefore, the partition lines that partition the adjacent element regions Ab are located between the two adjacent light transmission holes 45. More specifically, the dividing line that divides the adjacent element regions Ab is one of the perpendicular bisectors along the plate surface of the base material 41 that is a line segment that connects the centers of two adjacent light transmitting holes 45. Can be defined as a department.

In addition, in the example shown in FIG. 5, the light transmission hole 45 is not formed in the element region Ab1, but the invention is not limited to this, and one light transmission hole 45 may be formed in the element region Ab1. .. That is, one light transmission hole 45 may be formed in each of the element regions Ab in the partitioned region Aa including the element region Ab2. In this case, each element region Ab1 is also defined so as to include one light transmitting hole 45.

Each light transmitting hole 45 has a circular contour in a plan view. In this case, the light emitted from the light source 22 and transmitted through each light transmission hole 45 is isotropically emitted from the light transmission hole 45 in the plate surface direction of the base material 41. Therefore, the in-plane uniformity of the illuminance of the illumination light emitted from the surface light source device 20 can be improved. However, the present invention is not limited to this, and each light transmission hole 45 may be formed to have another planar shape such as an elliptical shape, a triangular shape, a rectangular shape, or a hexagonal shape in a plan view.

The size of the light transmission hole 45 changes so as to increase from the element region Ab1 toward the peripheral edge of the partitioned region Aa. Here, that the dimension of the light transmitting hole 45 changes so as to increase from the element region Ab1 toward the peripheral edge of the partitioned region Aa means that the dimension of the light transparent hole 45 moves from the element region Ab1 toward the peripheral edge of the partitioned region Aa. In addition to the case where the size of the light transmission hole 45 changes so as to always increase, the case where the size of the light transmission hole 45 does not change in a part of the region is included. In other words, when the dimension of the light transmitting hole 45 changes so as to increase from the element region Ab1 toward the peripheral edge of the partition region Aa, the dimension of the light transmitting hole 45 moves from the element region Ab1 toward the peripheral edge of the partition region Aa. It means that there is no area that changes so as to become smaller. In the example shown in FIG. 5, the size of the light transmission hole 45 changes so as to always increase from the element region Ab1 toward the peripheral edge of the partitioned region Aa. In the illustrated example, the center of each light transmitting hole 45 and the center of the element region Ab2 in which the light transmitting hole 45 is arranged coincide with each other.

The surface light source device 20 of the present embodiment includes a light source 22 and an illuminance distribution adjusting plate 40 that is arranged to face the light source 22 and adjusts the illuminance distribution of light emitted from the light source 22. The base material 41 is provided with a plurality of light transmitting holes 45 that transmit light, and the base material 41 has one or more partitioned areas Aa. In each partitioned area Aa, the partitioned areas Aa are regularly arranged. Is further divided into a plurality of element regions Ab arranged in a line, and each element region Ab has a hexagonal shape in plan view, and at least when projected onto the light source 22 along the normal direction of the base material 41. One light transmission hole 45 is formed in each of the element regions Ab adjacent to the element region Ab overlapping with the light source 22.

Further, the illuminance distribution adjusting plate 40 of the present embodiment is an illuminance distribution adjusting plate 40 that is arranged so as to face the light source 22 and that adjusts the illuminance distribution of the light emitted from the light source 22. The base material 41 having the through holes 45 is provided, and the base material 41 has one or more partitioned areas Aa. In each partitioned area Aa, the partitioned areas Aa are a plurality of regularly arranged element areas. Each element region Ab is further divided into Abs, and each element region Ab has a hexagonal shape in a plan view, and at least the element region Ab overlapping the light source 22 when projected onto the light source 22 along the normal direction of the base material 41. One light transmission hole 45 is formed in each of the element regions Ab adjacent to.

Further, the surface light source device 20 of the present embodiment includes a light source 22 and an illuminance distribution adjusting plate 40 that is arranged so as to face the light source 22 and adjusts the illuminance distribution of light emitted from the light source 22. 40 includes a base material 41 in which a plurality of light transmitting holes 45 that transmit light are formed, and the base material 41 has one or more partitioned areas Aa. In each partitioned area Aa, the light source 22 is provided in plan view. One light transmission hole 45 is formed at each vertex of the surrounding hexagon.

According to the surface light source device 20 and the illuminance distribution adjusting plate 40 as described above, since the element region Ab has a hexagonal shape in a plan view, the element region Ab has a rectangular shape (square shape as an example). It is possible to increase the aperture ratio (area of the light transmitting hole 45/area of the element region Ab) in each element region Ab, as compared with the case of performing the above. This aperture ratio will be described with reference to FIGS. 6 and 7. FIG. 6 is a diagram for explaining a theoretical maximum aperture ratio when the element region Ab has a rectangular shape, and FIG. 7 shows a case where the element region Ab has a hexagonal shape. It is a figure for demonstrating the theoretical maximum aperture ratio.

Considering a circle that is inscribed in a polygon formed by demarcation lines that form the outline of the element region Ab, the hole having the circle as the outline is the maximum light transmission hole 45 that can be provided in the element region Ab. .. The maximum aperture ratio is defined as (area of light transmitting hole 45/area of element region Ab) when the maximum light transmitting hole 45 is formed in the element region Ab. When the element region Ab has a rectangular shape (square shape) (see FIG. 6), the maximum aperture ratio is about 0.785. On the other hand, when the element region Ab has a hexagonal shape (see FIG. 7), the maximum aperture ratio is about 0.915. That is, when the element region Ab has a rectangular shape, the light transmitting hole 45 cannot be formed in the element region Ab so as to have an aperture ratio exceeding about 0.785, but the element region Ab is not formed. When the element has a hexagonal shape, the light transmitting hole 45 can be formed in the element region Ab so as to have an aperture ratio of more than about 0.785. Therefore, when the element region Ab has a hexagonal shape in a plan view, the aperture ratio in each element region Ab is increased as compared with the case where the element region Ab has a rectangular shape. Is possible. This improves the degree of freedom in designing the aperture ratio in each element region Ab. In particular, it is possible to increase the aperture ratio of each element region Ab in the peripheral portion of the partitioned region Aa, and it is possible to emit more light to the viewer 5 side from each light transmission hole 45 in the peripheral portion. Therefore, it is possible to effectively suppress uneven illuminance within the light emitting surface 20a of the surface light source device 20.

Further, according to the surface light source device 20 and the illuminance distribution adjusting plate 40 as described above, as in the surface lighting unit disclosed in JP45386675B, between the arc-shaped hole and the round hole arranged at the apex of the hexagon. Since there is no region in which no hole is formed, it is possible to prevent the illuminance of the light emitted from the illuminance distribution adjusting plate from decreasing in the region, and to prevent unevenness in the illuminance distribution in the light emitting surface of the surface light source device. You can

The base material 41 of the illuminance distribution adjusting plate 40 has a relatively small thickness (0.05 mm or more and 1 mm or less, for example), and stress is applied to the base material 41 during handling of the illuminance distribution adjusting plate 40 in the manufacturing process. Can occur. Furthermore, especially when the surface light source device 20 is used for a vehicle, repeated stress may occur in the illuminance distribution adjusting plate 40 due to the vibration of the vehicle. Therefore, the illuminance distribution adjusting plate 40 is desired to have sufficient strength to withstand these stresses.

According to the surface light source device 20 and the illuminance distribution adjusting plate 40 of the present embodiment, when the element region Ab has a hexagonal shape in plan view, the element region Ab has a rectangular shape. Compared with, the minimum clearance C _min between the contour of the light transmission hole 45 and the contour of the element region Ab can be increased, and thus the strength of the illuminance distribution adjusting plate 40 can be improved. FIG. 8 is a diagram for explaining this minimum clearance C _min .

The portion of the illuminance distribution adjusting plate 40 that has the lowest strength against bending load, tensile load, twisting load, etc. is the portion of the base material 41 located between two adjacent light transmission holes 45. Here, the minimum gap between the contour of the light transmission hole 45 and the contour of the element region Ab in the portion of the base material 41 located between two adjacent light transmission holes 45 is defined as the minimum clearance C _min . In this case, when the minimum clearance C _min in the element area Ab is relatively large, it can be determined that the intensity of the illuminance distribution adjusting plate 40 having the element area Ab is high.

As shown in FIG. 8, the radius of the light transmitting hole 45 is r, the length of one side of the element region Ab ₁₀ having a square shape is a, and the distance between a pair of opposite sides of the element region Ab ₂₀ having a hexagonal shape. Be b. In addition, the light transmission hole 45 provided in the element region Ab ₁₀ and the light transmission hole 45 provided in the element region Ab ₂₀ have the same radius r. At this time, the minimum clearance C _min1 in the element region Ab ₁₀ and the minimum clearance C _min2 in the element region Ab ₂₀ can be expressed as follows.
_Cmin1 =(a/2)-r... Formula (1)
_Cmin2 =(b/2)-r... Formula (2)

Area _{S 2} of the surface area _{S 1} and element region _{Ab 20} of element regions _{Ab 10} can be expressed as follows.
S ₁ =a ² ... Formula (3)
^{_{S 2 = (3 1/2 / 2}} ) × b 2 ··· Equation (4)

When the element regions Ab ₁₀ and Ab ₂₀ have the same aperture ratio, the light transmission holes 45 provided in the element region Ab ₁₀ and the light transmission holes 45 provided in the element region Ab ₂₀ have the same area. And S ₁ =S ₂ . Therefore, it can be seen from Equations (3) and (4) that b=1.07×a, that is, b>a.

From equations (1) and (2) and b>a as described above, C _min2 >C _min1 is derived. That is, when the element region Ab ₂₀ having a hexagonal shape and the element region Ab ₁₀ having a square shape have the same aperture ratio, the minimum clearance C _min2 in the element region Ab ₂₀ is in the element region Ab ₁₀ . It becomes larger than the minimum clearance C _min1 . Therefore, the intensity of the illuminance distribution adjusting plate 40 having the element regions Ab ₂₀ having a hexagonal shape is higher than the intensity of the illuminance distribution adjusting plate having the element regions Ab ₁₀ having a square shape. That is, according to the illuminance distribution adjusting plate 40 of the present embodiment, even when a bending load, a tensile load, a torsion load, or the like is applied to the illuminance distribution adjusting plate 40, the illuminance distribution adjusting plate 40 is deformed by these loads. It is possible to effectively suppress the occurrence of cracks and cracks.

Various modifications can be made to the above-described embodiment. Modifications will be described below with reference to the drawings as necessary. In the following description and the drawings used in the following description, for the portions that can be configured in the same manner as the above-described embodiment, the same reference numerals as those used for the corresponding portions in the above-described embodiment are used. A duplicate description is omitted. Further, when it is clear that the operational effects obtained in the above-described embodiment can be obtained also in the modified example, the description thereof may be omitted.

FIG. 9 is a diagram for explaining a modified example of the illuminance distribution adjustment plate 40. Since the conventional edge light type backlight requires a light guide plate, it is not possible to bend the backlight itself to realize a usable backlight, that is, a flexible backlight. On the other hand, in the surface light source device 20 including the illuminance distribution adjusting plate 40 according to the present embodiment, each member forming the surface light source device 20 does not need a light guide plate and is configured by a member having flexibility. Therefore, it is possible to realize the surface light source device 20 that is flexible as a whole.

For example, when the surface light source device 20 is used for a vehicle, particularly when the surface light source device 20 is used as a backlight of a meter panel in which a speedometer, a tachometer, etc. are arranged, the surface light source device 20 of the present embodiment is used. It is possible to bend and arrange the curved surface. FIG. 9 shows an illuminance distribution adjusting plate 40 when the surface light source device 20 is bent and arranged in a curved shape. As the surface light source device 20 is curved, the illuminance distribution adjusting plate 40 is also curved and arranged. The illuminance distribution adjusting plate 40 shown in FIG. 9 has a curved surface shape curved in the first direction d ₁ along the plate surface.

When the illuminance distribution adjusting plate 40 formed in a flat shape is bent into a curved surface as shown in FIG. 9, stress is generated in the base material 41 of the illuminance distribution adjusting plate 40, and this stress causes Then, the base material 41 may be deformed or cracked. Therefore, the illuminance distribution adjusting plate 40 is required to have sufficient strength against the stress generated when it is bent into a curved surface.

In this modification, as shown in FIG. 10, each element region Ab of the illuminance distribution adjusting plate 40 has a hexagonal shape in plan view, and three pairs of opposite sides (47, 47), (48, 48) and (49, 49). The two sides forming the opposite sides (47, 47), (48, 48), (49, 49) are parallel to each other. That is, the opposite sides 47 and 47 are parallel to each other, the opposite sides 48 and 48 are parallel to each other, and the opposite sides 49 and 49 are parallel to each other. Of the three pairs of opposite sides (47, 47), (48, 48), (49, 49), two sides 47 forming a pair of opposite sides 47, 47 are orthogonal to the first direction d _1. There is. In other words, the two sides 47 forming the pair of opposite sides 47, 47 extend parallel to the second direction d ₂ orthogonal to the first direction d ₁ .

When the illuminance distribution adjusting plate 40 is bent in the first direction d ₁ along the plate surface, stress is generated in a cross section of the base material 41 in each element region Ab, which is orthogonal to the first direction d ₁ . Of these cross sections, the cross section in which the cross-sectional area of the base material 41 is the smallest is the cross section that passes through the center O ₂ of the light transmission hole 45. Therefore, the strength of the base material 41 in each element region Ab can be evaluated by the size of the area of the cross section that passes through the center O ₂ of the light transmission hole 45 in the base material 41 and is orthogonal to the first direction d ₁ . The cross-sectional area S ₃ of the cross section passing through the center O ₂ of the light transmission hole 45 in the base material 41 is defined as C, which is the distance (clearance) between the contour of the light transmission hole 45 and the contour of the element region Ab in the cross section. When the thickness of the material 41 is T, it can be expressed by the following formula.
_{S 3 = 2 × C × T} ··· Equation (5)

As illustrated, the clearance C has a maximum value C _max when it is defined along a straight line passing through the center O ₂ of the light transmission hole 45 and the apex of the hexagon forming the contour of the element region Ab. Take That is, the cross-sectional area S ₃ has the maximum value in a cross section defined along a straight line passing through the center O ₂ of the light transmitting hole 45 and the hexagonal apexes that form the contour of the element region Ab. Therefore, the cross section defined along the straight line passing through the center O ₂ of the light transmitting hole 45 and the apex of the hexagon forming the contour of the element region Ab is arranged so as to be orthogonal to the first direction d _1. If, namely, the two sides 47 that form the opposite sides 47, 47 of a pair, when both perpendicular to the first direction d _1, the most strength against bending of the first direction d ₁ of the illuminance distribution adjusting plate 40 Can be large.

Further, as shown in FIG. 9 in particular, when the illuminance distribution adjusting plate 40 is bent and used in the first direction d ₁ along the plate surface, the material of the base material 41 is 1.0×. It is preferable to use a material having an elastic modulus of 10 ⁴ kg/cm ² or more and 10.0×10 ⁴ kg/cm ² or less. When the elastic modulus of the base material 41 is 1.0×10 ⁴ kg/cm ² or more, it is possible to effectively suppress distortion of the illuminance distribution adjusting plate 40 due to vibration or the like. Further, when the elastic modulus of the base material 41 is 10.0×10 ⁴ kg/cm ² or less, when the illuminance distribution adjusting plate 40 is bent, the base material 41 is elastically deformed to become the base material 41. It is possible to suppress the occurrence of a large stress locally, and thereby prevent the base material 41 from cracking.

11 and 12 are diagrams for explaining another modification of the illuminance distribution adjusting plate 40. 11 is a plan view showing one divided area Aa of the illuminance distribution adjusting plate 40, and FIG. 12 is a graph showing an example of the distribution of the aperture ratio in the divided area Aa of FIG.

In the example shown in FIG. 11, in plan view, the partitioned area Aa is located outside the first area Ac1 adjacent to the first area Ac1 and the first area Ac1 that include the center O ₁ of the partitioned area Aa. It is divided into three regions, that is, a second region Ac2 and a third region Ac3 that is adjacent to the second region Ac2 and located outside the second region Ac2. The partition line Lb1 partitioning the first area Ac1 and the second area Ac2 and the partition line Lb2 partitioning the second area Ac2 and the third area Ac3 are centered on the center O ₁ of the partition area Aa. It is concentric.

The rectangular vertex forming the contour of the partitioned area Aa is taken as the boundary of the partitioned area Aa, and the distribution of the aperture ratio along the straight line Lc connecting the center O ₁ of the partitioned area Aa and the boundary of the partitioned area Aa in FIG. Shown in. In FIG. 12, the horizontal axis represents (distance from center/distance from center to boundary), and the vertical axis represents aperture ratio (%). The horizontal axis (distance from the distance / the center from the center to the boundary) is the distance from the center O ₁ of the divided area Aa in each element region Ab to the center of the element region Ab, the center O ₁ of the divided area Aa It is divided by the distance to the boundary of the partitioned area Aa. Further, the aperture ratio in FIG. 12 is defined by (area of light transmitting hole 45/area of element region Ab×100) in each element region Ab.

In the illustrated example, in the first area Ac1, the size of the light transmission hole 45 changes so as to increase from the center O ₁ of the partitioned area Aa toward the peripheral edge of the first area Ac1. Further, in the second region Ac2, the size of the light transmitting hole 45 changes so as to increase from the first region Ac1 side toward the third region Ac3 side. Further, the rate of change of the size of the light transmitting hole 45 in the second area Ac2 is larger than the rate of change of the size of the light transmitting hole 45 in the first area Ac1. On the other hand, the rate of change of the size of the light transmission hole 45 in the third area Ac3 is smaller than the rate of change of the size of the light transmission hole 45 in the second area Ac2. In the illustrated example, the dimensional change rate of the light transmission hole 45 in the third region Ac3 is the same as the dimensional change rate of the light transmission hole 45 in the first region Ac1 and the dimensional change rate of the light transmission hole 45 in the second region Ac2. It is smaller than the dimensional change rate. Particularly in the illustrated example, the size of the light transmitting hole 45 does not change, that is, the size of the light transmitting hole 45 is constant in the third region Ac3.

As described above, the intensity of the illuminance distribution adjusting plate 40 can be evaluated by the minimum clearance C _min . By setting the smallest minimum clearance C _min in the partitioned area Aa to be a predetermined value or more, it is possible to secure a desired strength of the illuminance distribution adjustment plate 40. If the element regions Ab have the same shape and size, the minimum clearance C _min is a function of the aperture ratio in the element region Ab. That is, as the aperture ratio in the element region Ab increases, the minimum clearance C _{min in the} element region Ab decreases. Therefore, the upper limit value of the aperture ratio in the element region Ab is determined corresponding to the smallest minimum clearance C _min in the partitioned region Aa.

FIG. 12 shows an example of the aperture ratio distribution when the dimensional change rate of the light transmitting hole 45 in the second area Ac2 and the dimensional change rate of the light transmitting hole 45 in the third area Ac3 are made equal. It shows with. In the aperture ratio distribution shown by the broken line, when the boundary of the partitioned region Aa, that is, (distance from center/distance from center to boundary) is 1, the aperture ratio in the element region Ab is the upper limit value (here, 70%).

As shown in FIG. 12, in the illuminance distribution adjusting plate 40 of the present modification, the rate of change of the size of the light transmitting hole 45 in the third region Ac3 is the size of the light transmitting hole 45 in the second region Ac2. And the change rate of the size of the light transmission hole 45 in the second area Ac2 is the same as the change rate of the light transmission hole 45 in the third area Ac3. By comparison, the aperture ratio in each element region Ab can be increased in the second region Ac2 and the third region Ac3. On the other hand, the upper limits of the aperture ratio are the same, that is, the smallest minimum clearance C _min in the partitioned area Aa is also the same. Therefore, according to the illuminance distribution adjusting plate 40 of the present modification, it is possible to increase the aperture ratio of the entire partitioned area Aa while securing the strength of the illuminance distribution adjusting plate 40. This improves the degree of freedom in designing the aperture ratio in each element region Ab. In particular, more light can be emitted to the observer 5 side from each light transmission hole 45 in the second region Ac2 and the third region Ac3. Therefore, it is possible to effectively suppress uneven illuminance within the light emitting surface 20a of the surface light source device 20.

FIG. 13 shows a modification of the shape of the element region Ab. In FIG. 13, the illustration of the light transmission hole 45 is omitted. In the illustrated example, each element region Ab has a pair of first opposite sides Si1 having a certain length, a pair of second opposite sides Si2 having a length shorter than the length of the first opposite side Si1, and a second opposite side Si2. And a pair of third opposite sides Si3 having a length shorter than the length of the hexagonal shape. The pair of first opposite sides Si1 have the same length, the pair of second opposite sides Si2 have the same length, and the pair of third opposite sides Si3 have the same length. In addition, each element region Ab has the same contour shape as each other. The element region Ab having such a contour shape also has the same effect as the element region Ab having the regular hexagonal contour described above with reference to FIG.

The element region Ab is not limited to the examples shown in FIGS. 5 and 13, and may have contours of various shapes. In particular, the element area Ab can have a hexagonal contour that can be filled in a plane.

Although some modifications of the above-described embodiment have been described above, it is of course possible to appropriately combine and apply a plurality of modifications.

Claims (5)

A surface light source device comprising: a light source; and an illuminance distribution adjusting plate that is arranged to face the light source and adjusts an illuminance distribution of light emitted from the light source,
The illuminance distribution adjustment plate,
A base material on which a plurality of light transmitting holes for transmitting the light are formed,
The substrate has one or more compartments,
In each division area,
The divided area is further divided into a plurality of regularly arranged element areas,
Each element region has a hexagonal shape in plan view,
A surface light source device in which at least one light transmission hole is formed in at least an element region adjacent to an element region overlapping the light source when projected onto the light source along a normal direction of the base material. The surface light source device according to claim 1, wherein the illuminance distribution adjustment plate has a curved surface shape that is curved in a first direction along the plate surface. Each element region has three pairs of opposite sides in plan view,
The two opposite sides are parallel to each other,
The surface light source device according to claim 2, wherein two sides forming a pair of opposite sides of the three pairs of opposite sides are orthogonal to the first direction. An illuminance distribution adjusting plate arranged to face a light source and adjusting the illuminance distribution of light emitted from the light source,
A base material on which a plurality of light transmitting holes for transmitting the light are formed,
The substrate has one or more compartments,
In each division area,
The divided area is further divided into a plurality of regularly arranged element areas,
Each element region has a hexagonal shape in plan view,
At least one light transmission hole is formed in each of element regions adjacent to an element region that overlaps the light source when projected onto the light source along the normal direction of the base material. .. A surface light source device comprising: a light source; and an illuminance distribution adjusting plate that is arranged to face the light source and adjusts an illuminance distribution of light emitted from the light source,
The illuminance distribution adjustment plate,
A base material on which a plurality of light transmitting holes for transmitting the light are formed,
The substrate has one or more compartments,
A surface light source device in which one light transmission hole is formed at each vertex of a hexagon surrounding the light source in a plan view in each partitioned region.

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