WO2019059060A1 - Area light source device and luminance distribution adjusting plate - Google Patents

Abstract

[Problem] To improve the freedom of design of the plan-view shape of an area light source device. [Solution] A base material (41) of a luminance distribution adjusting plate (40) of an area light source device (20) includes one or more compartment regions (Aa). Each of the compartment regions has a rectangular shape having long sides (42) and short sides (43) in plan view. In each compartment region, the compartment region is further divided into a plurality of element regions (Ab) that are regularly arranged. Each of element regions that are positioned in regions other than a predetermined region overlapping a light source when projected onto the light source in a direction normal to the base material has a light transmitting hole (45). The light transmitting hole has a predetermined opening ratio with respect to the area of the element region in which the light transmitting hole is formed. An equi-opening ratio line (50) passing between the center of an arbitrary light transmitting hole and the center of another light transmitting hole having an opening ratio equal to the opening ratio of the light transmitting hole, or a virtual equi-opening ratio point (P) assumed to have an opening ratio equal to the opening ratio of the light transmitting hole has, in plan view, the shape of an ellipse having a major axis (52) extending in parallel with the long sides.

Description

Surface light source device and illuminance distribution adjustment plate

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

A surface light source device that emits planar light is widely used, for example, 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 disposed on the side of an optical member and a direct type in which a light source is disposed directly below an optical member. For example, a light emitting diode (LED) is used as the light source.

In a liquid crystal display device for vehicles, an edge light type surface light source device has conventionally been used as a back light from the viewpoint of easy thinning. In such a liquid crystal display device for vehicles, in order to secure visibility under the external light which inserts from a window, displaying brightly is called for. In order to obtain as bright a display as possible with an edge light type surface light source device, it is necessary to closely arrange a large number of light sources on the side of the optical member. Here, liquid crystal display devices for vehicles are often disposed in a narrow space, and if a large number of light sources are densely disposed in this narrow space, it is not possible to sufficiently dissipate the heat generated from the light sources. That is, when an edge light type surface light source device is used as a backlight of a liquid crystal display device for a vehicle, if it is intended to obtain sufficient brightness, the heat generated from the light source can not be sufficiently dissipated. The display device may be heated to a high temperature, which may cause a malfunction. On the other hand, if a direct type surface light source device can be used as a backlight, a plurality of light sources can be arranged separately from each other, so heat generated from the light sources can be properly dissipated. Therefore, in a liquid crystal display device for vehicles, it is required to make the surface light source device thinner while using a direct type surface light source device as a backlight.

In the direct type surface light source device, in order to display an image without unevenness while thinning the surface light source device, an illuminance distribution adjustment plate is disposed between the light source and the liquid crystal display panel, and the surface is made by the illuminance distribution adjustment plate. There is known a technique for adjusting the illuminance distribution in the light emitting surface of the light source device.

JP2012-174372A discloses a lighting 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 in the reflection plate. The opening area of each of the plurality of light passing holes is smaller as the distance from the facing portion facing the LED light source is shorter. According to such a lighting unit, the light passing hole decreases as the light passing hole is closer to a position where the density of light directly arriving from the LED light source is high, and the light passing hole at a position where the density of light directly arriving from the LED light source is low Will increase the amount of light passing. As a result, the distribution of light passing through the reflection plate can be made to approach uniformly, and the distribution of illumination light of the illumination device can be made to approach uniform.

In the lighting unit disclosed in JP2012-174372A, the reflection plate is formed to have a square shape in plan view. Therefore, the plan view shape of the entire lighting unit formed by arranging the reflection plates in the longitudinal direction and the lateral direction is limited to a shape in which the ratio of the longitudinal length to the lateral length is an integer ratio. Ru. That is, in the lighting unit disclosed in JP2012-174372A, there is a limit to the design of the plan view shape of the whole lighting unit.

The present invention has been made in view of these points, and it is an object of the present invention to improve the degree of freedom in the design of the plan view shape of the surface light source device.

The surface light source device of the present invention is
A light source, and an illuminance distribution adjusting plate disposed opposite to the light source and adjusting an illuminance distribution of light emitted from the light source;
The illuminance distribution adjustment plate is
The substrate includes a plurality of light transmission holes for transmitting the light.
The substrate has one or more compartmental areas,
Each divided region has a rectangular shape having a long side and a short side in plan view,
In each compartment area,
The divided area is further divided into a plurality of regularly arranged element areas,
One light transmission hole is formed in each of the element regions located in a region other than the predetermined region overlapping with the light source when projected onto the light source along the normal direction of the substrate;
The light transmission hole has a predetermined aperture ratio to the area of the element region in which the light transmission hole is formed,
A virtual equal aperture assumed to have the center of any light transmitting hole and the centers of other light transmitting holes having an opening ratio equal to the opening ratio of the light transmitting hole or the opening ratio equal to the opening ratio of the light transmitting hole The iso-aperture line passing through the curvature point has an elliptical shape having a major axis extending parallel to the long side in a plan view.

The illuminance distribution adjustment board of the present invention is
An irradiance distribution adjusting plate disposed opposite to a light source and adjusting an irradiance distribution of light emitted from the light source,
The substrate includes a plurality of light transmission holes for transmitting the light.
The substrate has one or more compartmental areas,
Each divided region has a rectangular shape having a long side and a short side in plan view,
In each compartment area,
The divided area is further divided into a plurality of regularly arranged element areas,
One light transmission hole is formed in each of the element regions located in a region other than the predetermined region overlapping with the light source when projected onto the light source along the normal direction of the substrate;
The light transmission hole has a predetermined aperture ratio to the area of the element region in which the light transmission hole is formed,
A virtual equal aperture assumed to have the center of any light transmitting hole and the centers of other light transmitting holes having an opening ratio equal to the opening ratio of the light transmitting hole or the opening ratio equal to the opening ratio of the light transmitting hole The iso-aperture line passing through the curvature point has an elliptical shape having a major axis extending parallel to the long side in a plan view.

[Effect of the invention]
According to the present invention, it is possible to improve the degree of freedom in designing the planar light source shape of the surface light source device.

FIG. 1 is a view for explaining an embodiment according to the present invention, and is a perspective view schematically showing an example of a display device provided with a display panel and a surface light source device. FIG. 2 is a perspective view schematically showing an example of a surface light source device. FIG. 3 is a plan view showing an example of the illuminance distribution adjustment plate incorporated in the surface light source device. FIG. 4 is a cross-sectional view of the surface light source device corresponding to the line IV-IV in FIG. FIG. 5 is a plan view showing one sectioned area of the illuminance distribution adjusting plate, showing an example of an arrangement pattern of element areas and light transmission holes. FIG. 6 is a diagram showing an example of equal aperture ratio lines passing through a plurality of light transmission holes. FIG. 7 is a diagram showing an example of equal aperture ratio lines passing through light transmission holes and imaginary equal aperture ratio points. FIG. 8 is a diagram for explaining a method of calculating the position of the virtual equal aperture ratio point.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings attached to the present specification, for the sake of easy illustration and understanding, the scale, vertical and horizontal dimensional ratios, etc. are exaggerated and changed from those of a real thing as appropriate.

In the present specification, the terms "plate", "sheet" and "film" are not distinguished from one another based only on the difference in designation. For example, "plate" is a concept that also includes members that may be called "sheets" and "films". Therefore, for example, "illuminance distribution adjustment plate" may be "illuminance distribution adjustment sheet" or "illuminance distribution adjustment" It can not be distinguished only by the difference of a name and the member called film.

In addition, “plate surface (sheet surface, film surface)” refers to a plate-shaped member (sheet-shaped member (sheet-shaped member) when the target plate-shaped (sheet-shaped, film-shaped) member is viewed globally and generally. It refers to the surface that coincides with the planar direction of the member (film-like member). In this specification, the normal direction of the surface and plate-like (sheet-like, film-like) members means the normal to the surface of the object and plate-like (sheet-like, film-like) members. It points to the direction.

Furthermore, as used herein, the terms such as “parallel”, “orthogonal”, “identical”, values of length and angle, etc., which specify the shape and geometrical conditions and their degree, etc. Without being bound by the meaning, it shall be interpreted including the extent to which the same function can be expected.

1 to 8 are diagrams for explaining an embodiment according to the present invention. Among these, FIG. 1 is a view schematically showing an example of a display device provided with a display panel and a surface light source device, and FIG. 2 is a perspective view schematically showing an example of the 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, text information, and a video composed of a combination of these on the display panel 15. In the present embodiment, an example in which the display device 10 is a vehicle-mounted liquid crystal display device will be described. However, the present invention is not limited to this. It can be used for various applications 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 exit surface 20a, and a display panel 15 disposed to face the light exit 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 backlight, and illuminates the display panel 15 from the back side of the display panel 15, that is, the side opposite to the observer 5.

In the illustrated example, the display panel 15 is disposed such that the display surface 15 a on which an image is displayed faces the opposite side of the surface light source device 20. Thereby, the display surface 15 a of the display panel 15 forms the display surface 10 a of the display device 10. The display panel 15 is formed in a rectangular shape when viewed in 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, transmits part of light incident from the surface light source device 20 to the display panel 15, 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 in accordance with 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) disposed between the pair of polarizing plates can be used. In this liquid crystal display panel, the polarizing plate separates incident light into two orthogonal polarization components, transmits polarization components in one direction, and absorbs polarization components in the other direction orthogonal to the one direction. It has a polarizer with a function. The liquid crystal cell has a pair of support plates and a liquid crystal disposed between the pair of support plates. The liquid crystal cell is configured such that an electric field can be applied to each region forming one pixel, and the alignment of liquid crystals of the liquid crystal cell to which the electric field is applied is changed. 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 disposed on the surface light source device 20 side of the liquid crystal cell is, for example, a liquid crystal cell not applied with an electric field. When passing through the liquid crystal cell, the polarization direction is rotated by 90.degree., And when passing through a liquid crystal cell to which an electric field is applied, the polarization direction is maintained. Thereby, the polarization component in the specific direction transmitted through the polarizing plate disposed on the surface light source device 20 side of the liquid crystal cell is disposed on the opposite side to the surface light source device 20 of the liquid crystal cell depending on the presence or absence of the electric field application to the liquid crystal cell. It is possible to control whether the light is further transmitted through another polarizing plate or absorbed and blocked by the other polarizing plate.

The surface light source device 20 has a light emitting surface 20a for emitting planar light, and is a so-called direct type in which a 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 back light. The surface light source device 20 of the present embodiment includes a light source 22 and an illuminance distribution adjusting plate 40 which is disposed to face the light source 22 and adjusts the illuminance distribution of the light emitted from the light source 22. In the example shown in FIG. 2, the surface light source device 20 further includes a base laminate 30 supporting the light source 22, a spacer 23, a diffusion plate 26, a first optical sheet 27, and 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 separated from the illuminance distribution adjusting plate 40 by a predetermined distance, and the diffusion plate 26, the first optical sheet 27 and the first A stack of two optical sheets 28 is arranged in order. The second optical sheet 28 forms the light exit surface 20 a of the surface light source device 20.

The light source 22 is configured of, for example, a light emitting diode (LED) or the like, and is disposed to face the illuminance distribution adjustment plate 40. In the present embodiment, as well illustrated in FIG. 3, the light sources 22 are arranged or aligned along the first direction d ₁ parallel to the plate surface of the surface light source device 20, and It is arranged along the second direction d ₂ intersecting the parallel and the first direction d ₁ to the plate surface of the light source device 20. Especially in this embodiment, the first direction d ₁ and the second direction d ₂ are orthogonal. Nachi Suwa, in the present embodiment, a plurality of light sources 22 are two-dimensionally arranged along the first direction d ₁ and the second direction d _2. Incidentally, not limited to this, a surface light source device 20 may have a plurality of light sources 22 arranged in a row along the first direction d ₁ and the second direction d _2, one light source 22 only May be included. It is preferable that the output of each light source 22, that is, the lighting and extinguishing of each light source 22, and / or the brightness at the time of lighting each light source 22 can be adjusted independently from the outputs of the other light sources 22.

In the example shown in FIG. 3, the contour of the illuminance distribution adjusting plate 40 has a rectangular shape in plan view. Although the first direction d ₁ and the second direction d ₂ can be arbitrarily defined, in the example shown, so that the first direction d ₁ forms a parallel to the one side of the rectangular shape forming the contour of the illuminance distribution adjusting plate 40 is defined, the second direction d ₂ is defined as to be parallel with other one side perpendicular to the one side. Especially in the illustrated example, the first direction d ₁ is defined so as to form a parallel to the long sides of the rectangular shape forming the contour of the illuminance distribution adjusting plate 40, the second direction d ₂ is parallel to the short sides of the rectangular Defined to make

The spacer 23 is a member for supporting the illuminance distribution adjusting plate 40, and has a function of keeping the 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 24 that divides between two adjacent light sources 22, whereby the spacer 23 is surrounded by the wall 24 corresponding to each light source 22. The 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 A plurality of extending wall portions 24 are arranged in a grid shape. The openings 25 are provided corresponding to the arrangement pattern of the light sources 22. That is, the spacer 23, while being arranged in the first direction d _1, arranged in the second direction d _2, has a plurality of openings 25. In the present embodiment, each opening 25 is formed in a rectangular shape in plan view. Such a spacer 23 may be, for example, polycarbonate resin, acrylonitrile-butadiene-styrene copolymer resin (ABS resin), acrylonitrile-styrene-acrylate copolymer resin (ASA resin), acrylonitrile-ethylene-propylene-diene-styrene copolymer resin AES resin), polymethyl methacrylate 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 can be used. In particular, the spacer 23 is preferably made of a material having high reflectivity to light in the visible light wavelength range.

FIG. 3 is a plan view showing the illuminance distribution adjustment plate 40 incorporated in the surface light source device 20. As shown in FIG. In FIG. 3, the positions of the light source 22 disposed on the back side of the illuminance distribution adjustment plate 40 and the openings 25 of the spacer 23 are indicated by broken lines. The illuminance distribution adjusting plate 40 includes a base 41 on which a plurality of light transmission holes 45 for transmitting light emitted from the light source 22 are formed. In FIG. 3, the light transmission holes 45 are not shown. The base material 41 of the illuminance distribution adjusting plate 40 has one or more divided areas Aa corresponding to the light sources 22. That is, one division area Aa is provided in the base 41 for one light source 22. Accordingly, the substrate 41 has while being arranged along the first direction d _1, arranged along the second direction d _2, a plurality of divided areas Aa. In FIG. 3, the area | region divided by the dashed-dotted line in the base material 41 has shown each division area Aa.

Each divided area Aa has a rectangular shape (rectangular shape) having a long side 42 and a short side 43 in plan view. The long side 42 and the short side 43 have different lengths from each other, and the long side 42 has a length larger than the length of the short side 43. In the example shown in FIG. 3, the long side 42 of the partition area Aa extends along the first direction d _1, the short side 43 of the partition area Aa extends along the second direction d _2. Accordingly, the long side 42 of the divided area Aa and the long side of the illuminance distribution adjustment plate 40 are parallel to each other, and the short side 43 of the divided area Aa and the short side of the illuminance distribution adjusting plate 40 are parallel to each other. Note that the present invention is not limited thereto, long side 42 of the partition area Aa extends along the second direction d _2, the short side 43 of the partition area Aa may extend along the first direction d _1. In this case, the long side 42 of the divided area Aa is parallel to the short side of the illuminance distribution adjustment plate 40, and the short side 43 of the divided area Aa is parallel to the long side of the illuminance distribution adjustment plate 40. 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 region Ab will be described later.

In the example shown in FIG. 3, division lines La that define adjacent division areas Aa of the base material 41 are defined along the wall 24 of the spacer 23. In other words, the dividing line La is defined to be located in a region facing the wall 24 of the spacer 23 along the normal direction of the illuminance distribution adjustment 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 lines La are defined to form a grid. In the illustrated example, the long sides 42 of the partition area Aa is made from a portion of the division line La extending in a first direction d _1, the short side 43 of the partition area Aa is division line La extending in a second direction d ₂ It consists of a part of In the illustrated example, the partitioned regions Aa has a width W ₁ in the first direction d _1, and a width W ₂ in the second direction d _2. In the example shown in FIG. 3, the width W ₁ corresponds to the length along the long side 42 of the partition area Aa, the width W ₂ corresponding to the length along the short side 43 of the partition area Aa. The width W ₁ and the width W ₂ can be, for example, 5 mm or more and 50 mm or less.

In the illuminance distribution adjusting plate 40 of the present embodiment, each divided area Aa has a rectangular shape having the long side 42 and the short side 43 in plan view, and the lengths of the long side 42 and the short side 43 It is possible to change independently. Therefore, the illuminance distribution adjusting plate 40 can be configured by arranging the divided areas Aa having a rectangular shape configured by the long side 42 and the short side 43 of an arbitrary length. Therefore, the lengths of the long side and the short side of the illuminance distribution adjusting plate 40 can be increased with a high degree of freedom, respectively, as compared to the conventional illuminance distribution adjusting plate configured by arranging the divided areas having a square shape in plan view. It can be set. That is, it is possible to improve the degree of freedom in designing the planar light source shape of the surface light source device 20.

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

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

The base 31 is a member that functions as a base 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 the film substrate 33, the wiring layer 34, the resist layer 35, and the light reflecting layer 36 can be properly held, but, for example, metal or resin may be used. Can. In particular, when using a substrate 31 formed of a metal material with good thermal conductivity such as aluminum, the heat generated by the light source 22 can be dissipated toward the back side of the surface light source device 20 via the substrate 31. It is more preferable because it can. The thickness of the base 31 can be, for example, 0.5 mm or more and 10 mm or less. The base 31 may be a part of the housing of the surface light source device 20.

The film substrate 33 is a member that functions as a base for holding 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, whereby the film substrate 33 forms a flexible printed wiring board together with the wiring layer 34. The thickness of the film substrate 33 can be, for example, 10 μm or more and 500 μm or less. By using a thinner substrate 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 may be appropriately selected in consideration of insulation, heat resistance, durability, dimensional stability at heating, mechanical strength and the like, and examples thereof include polyimide (PI) and polyethylene naphthalate ( PEN), polyethylene terephthalate (PET) can be used.

The film substrate 33 is fixed to the base 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 31. As an example, a double-sided tape can be used as the bonding layer 32. Besides, an appropriate adhesive or 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 highly conductive metal material. As a metal material which forms the wiring layer 34, metal materials, such as copper, aluminum, gold, silver etc. or these alloys, can be mentioned, for example. As an example, the wiring layer 34 can be formed using a subtraction method. That is, the wiring layer 34 having a desired pattern can be formed by patterning a metal layer such as copper foil disposed on the film substrate 33 by etching using a photolithographic 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 part is provided in the connection part with the light source 22 and other wiring or connectors in the wiring layer 34.

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 portions to be the electrode portions of the wiring layer 34. The resist layer 35 has a function of protecting the wiring layer 34 and preventing a short circuit between the wiring layer 34 and other members. As a material of the resist layer 35, for example, resin materials such as polyester resin, epoxy resin, epoxy resin and phenol resin, epoxy acrylate resin, silicone resin can be used. As an example, the resist layer 35 is provided with a resin layer so as to cover the whole of the wiring layer 34 and the film substrate 33, and the electrode portion is exposed at a portion to be the electrode portion of the wiring layer 34 by etching using photolithography technology. 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, and the light path thereof is directed to the light reflection layer 36 side. It has a function of reflecting the light bent toward the illumination distribution adjusting plate 40 again. Therefore, the light reflecting layer 36 is preferably a layer having high reflectivity to light in the visible light wavelength range. The light reflecting layer 36 is disposed on the same side as the light source 22 of the illuminance distribution adjusting plate 40 in parallel with the illuminance distribution adjusting plate 40. In the example shown in FIG. 4, the light reflecting layer 36 is laminated on the resist layer 35 except for the place where the light source 22 is to be disposed. In the illustrated example, the light reflecting layer 36 is disposed so as to surround the light source 22 in plan view. Further, in the illustrated example, the light reflection layer 36 is provided to expose the inner peripheral edge portion surrounding the light source 22 of the resist layer 35. The light reflection layer 36 is not limited to this, for example, the inner peripheral edge of the resist layer 35 matches the inner peripheral edge of the light reflection layer 36 so that the inner peripheral edge of the resist layer 35 surrounding the light source 22 is not exposed. It may be provided as such. 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 diffusion plate 26 is a plate-like member having a function of diffusing the light incident on the diffusion plate 26, whereby the in-plane distribution of the illuminance is made uniform, and the light transmitting holes 45 of the illuminance distribution adjusting plate 40 are made. It can make the image unnoticeable. The diffusion plate 26 is not particularly limited as long as it is a member having a light diffusion function, and for example, a resin plate or a glass plate having fine irregularities on the surface, and a resin plate having diffusion particles inside And glass plates can be used.

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

In addition, the second optical sheet 28 in the present embodiment transmits a polarization component in a direction parallel to the transmission axis, and reflects the polarization component in a direction parallel to a reflection axis orthogonal to the transmission axis. It is. According to this reflection type polarizing plate, light of a polarization component which is emitted from the surface light source device 20 and can not be effectively used in the display panel 15 is prevented from being incident on the display panel 15 and being absorbed by the polarizing plate can do. Therefore, the utilization efficiency of the light source light can be improved, and the illuminance characteristic can be improved. As this reflection type polarizing plate, for example, "DBEF" (registered trademark) available from 3M Company in the United States can be used.

From the viewpoint of securing sufficient illuminance of the surface light source device 20, it is preferable to use one having a high visible light transmittance as each of the diffusion plate 26, the first optical sheet 27 and the second optical sheet 28. .

Next, the illuminance distribution adjustment plate 40 will be described in detail. FIG. 5 is a plan view showing one sectioned area Aa of the illuminance distribution adjusting plate 40, and showing an example of an arrangement pattern of the element area Ab and the light transmission holes 45. As shown in FIG. The illuminance distribution adjusting plate 40 includes a base 41 on which a plurality of light transmission holes 45 for transmitting light emitted from the light source 22 are formed. 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 so that the light path is directed to the light reflecting layer 36 side. It is configured to be able to bend. For this reason, it is preferable that the base material 41 of the illuminance distribution adjusting plate 40 be a layer having high reflectivity to light in the visible light wavelength range. The base 41 is formed of, for example, a white resin material. As an example, the substrate 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 41 formed of a material having low light transmittance, and the light transmitting holes 45 are physical holes formed in the base 41, that is, Although it is formed as a through hole extending from one of the two main surfaces of the opposing base material 41 to the other main surface, the specific configuration of the light transmission hole 45 is not limited to this. The light transmission hole 45 may be formed as a portion through which light can be transmitted from one side to the other side of the normal direction to the plate surface of the illuminance distribution adjustment plate 40, for example, the illuminance distribution adjustment plate 40 The light transmitting hole 45 has a transparent plate-like transparent substrate, and a light reflecting layer provided on the transparent substrate, particularly on the main surface of the transparent substrate on the light source 22 side. 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 adjustment plate 40 is reflected by the illuminance distribution adjustment plate 40 and travels toward the light reflecting layer 36 side. The light incident on the light reflecting layer 36 is reflected by the light reflecting layer 36 and travels toward the illuminance distribution adjustment plate 40. When light repeating this is incident on any of the light transmission holes 45 of the illuminance distribution adjustment plate 40, the light passes through the light transmission holes 45 and the illuminance distribution adjustment plate 40 to the display panel 15 side (the diffusion plate in FIG. 4) 26) and emit. At this time, a direction substantially parallel to the plate surface of the illuminance distribution adjustment plate 40 while emitting light from the light source 22 and repeating reflection between the illuminance distribution adjustment plate 40 and the light reflection layer 36 (as an example, a first direction d in FIG. _The light traveling to ₁ ) decreases in illuminance as it gets away from the light source 22. However, in the illuminance distribution adjusting plate 40 according to the present embodiment, as described above, the more the light transmission holes 45 are away from the center O ₁ of the section area Aa facing immediately above the light source 22, the larger the opening area becomes. It is arranged in a pattern. Thereby, the illuminance of the light transmitted through each light transmission hole 45 and emitted can be made uniform. When the spacer 23 is made of a material having high reflectivity to light in the visible light wavelength range, it travels in a direction substantially parallel to the plate surface of the illuminance distribution adjustment plate 40 and is incident on the wall 24 of the spacer 23 The reflected light is reflected by the spacer 23 and bent toward the light source 22 side. Thereby, the utilization efficiency of the light radiate | emitted from the light source 22 can further be improved.

Partition area Aa is further partitioned into a plurality of regularly arranged element regions Ab. The element regions Ab and the light transmission holes 45 formed in the element regions Ab will be described with reference to FIGS. 5 to 7. FIG. 5 is a plan view showing one sectioned area Aa of the illuminance distribution adjusting plate 40, and showing an example of an arrangement pattern of the element area Ab and the light transmission holes 45. As shown in FIG.

In the illustrated example, the element region Ab, as well are arranged along the first direction d _1, it is arranged along the second direction d _2. Nachi Suwa, in the present embodiment, a plurality of element regions Ab are two-dimensionally arranged along the first direction d ₁ and the second direction d _2. In FIG. 5, the regions partitioned by two-dot chain lines indicate the respective element regions Ab. In the illustrated example, each element region Ab has an outline of a rectangular shape, especially a square shape in plan view, but the shape of the element region Ab is not limited thereto. For example, each element region Ab may have an outline having another shape such as a triangle or a hexagon in a plan view. Note that, in the present specification, that “a plurality of element areas Ab are“ ordered regularly ”” means that a plurality of element areas Ab having the same shape and size are arranged at the same pitch. ing. In the example shown in FIG. 5, although all of the plurality of element regions Ab have the same shape and size, the present invention is not limited thereto, and the plurality of element regions Ab may have two or more types of shapes, sizes or It may have an orientation.

In FIG. 5, the position of the light source 22 disposed on the back side of the illuminance distribution adjustment plate 40 is indicated by a broken line. The plurality of element areas Ab include element areas Ab ₀ overlapping with the light source 22 when projected onto the light source 22 along the normal direction of the substrate 41. The element region Ab ₀ overlaps with the light source 22 when projected onto the light source 22 along the normal direction of the substrate 41 if at least a part of the element region Ab ₀ is along the normal direction of the substrate 41 When projected onto the light source 22, the light source 22 overlaps with the light source 22. For example, as the vertices are shared by a plurality of element regions Ab ₀ and / or sides overlaps the center of the light source 22 when projected to the light source 22 along the normal direction of the substrate 41, a plurality of element regions Ab In the case where the plurality of element regions Ab ₀ including the apexes and / or sides are respectively projected onto the light source 22 along the normal direction of the base 41, the light source 22 overlaps with the light source 22. .

In the example shown in FIG. 5, the element regions Ab ₀ other element regions Ab, one of the light transmitting hole 45 are respectively formed. In other words, each element area Ab other than the element area Ab ₀ is defined such that one light transmission hole 45 is included. Thus, in the example shown, between two light transmitting hole 45 adjacent in the first direction d _1, and, between two light transmitting hole 45 adjacent in the second direction d _2, element regions adjacent each The dividing line Lb which divides Ab comes to be located. As a result, in the example shown, lane lines Lb as a whole, a plurality of partition lines Lb extending in the second direction d ₂ is arranged in the first direction d _1, the first direction is arranged in the second direction d ₂ A plurality of division lines Lb extending to d ₁ are defined to form a lattice. Each element region Ab has a width _{W 3} in the first direction _{d 1,} and a width _{W 4} in the second direction _{d 2.} The width _{W 3} and a width _{W 4} may be, for example 0.2mm or 10mm or less.

In the element area Ab ₀ and the element area Ab located in the vicinity of the element area Ab ₀ , an element area Ab in which the light transmission hole 45 is not formed may be present. That is, in the planar view of the illuminance distribution adjustment plate 40, in the element area Ab located in the predetermined area overlapping the light source 22 when projected onto the light source 22 along the normal direction of the substrate 41, light transmission There may be an element region Ab in which the hole 45 is not formed. In other words, one light transmission hole 45 is formed in each of the element regions Ab located in a region other than the predetermined region overlapping the light source 22 when projected onto the light source 22 along the normal direction of the substrate 41. In the example shown in FIG. 5, the element region Ab ₀ no light transmitting hole 45 is formed, the element region Ab other than element regions Ab _0, one of the light transmitting hole 45 are respectively formed. Not limited thereto, the light transmitting hole 45 in the element region Ab ₀ may be formed. That is, all elements region Ab including element regions Ab _0, may be one of the light transmitting hole 45 are formed respectively. Here, that the element area Ab is located in an area other than the predetermined area means that the center of the element area Ab (in the present embodiment, the center of the light transmission hole 45 formed in the element area Ab) is the predetermined area. It means to be located in the area other than. The predetermined area is, for example, a point in the divided area Aa that overlaps the center of the light source 22 when projected onto the light source 22 along the normal direction of the base material 41, that is, in the present embodiment, It can be an area at a distance of 5 mm or less from the center O ₁ along the surface direction of the base 41. In this case, the predetermined region is the outline and the inside of a circle with a radius of 5 mm centered on the center O ₁ in a plan view of the base 41.

In the example shown in FIG. 5, the centers of the light transmission holes 45 coincide with the centers of the element regions Ab in which the light transmission holes 45 are disposed. Each light transmission hole 45 has a circular outline in plan view. In this case, light emitted from the light source 22 and transmitted through the light transmission holes 45 is isotropically emitted from the light transmission holes 45 in the surface direction of the base 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 ellipse, a triangle, a rectangle, or a hexagon in a plan view.

In the example shown in FIG. 5, the light transmitting hole 45 is not formed in the element region Ab _0, not limited to this, the light transmitting hole 45 in the element region Ab ₀ may be formed . That is, one light transmission hole 45 may be formed in each of all the element regions Ab included in the divided region Aa.

The light transmission hole 45 has a predetermined aperture ratio with respect to the area of the element region Ab in which the light transmission hole 45 is formed. In the present specification, the aperture ratio of the light transmission hole 45 means the area S of the element region Ab in which the light transmission hole 45 is formed in the area S _a of the light transmission hole 45 in plan view of the illuminance distribution adjustment plate 40 _It refers to the ratio to _b (S _a / S _b ).

Dimensions of the light transmitting hole 45 is changed so as to increase toward the element region Ab ₀ the peripheral divided area Aa. On the other hand, in plan view of the illuminance distribution adjustment plate 40, the plurality of element regions Ab have the same area. Accordingly, the aperture ratio of the light transmitting hole 45 is changed so as to increase toward the element region Ab ₀ the peripheral divided area Aa. However, in the example shown in FIG. 5, there is a region where the aperture ratio of the light transmission holes 45 is constant in the vicinity of the periphery of the divided region Aa, particularly in the vicinity of the corner of the divided region Aa.

It is assumed that the center of any light transmission hole 45 and the center of another light transmission hole 45 having an opening ratio equal to the opening ratio of the light transmission hole 45 or the opening ratio equal to the opening ratio of the light transmission hole 45 A line passing through the virtual equal aperture ratio point P is taken as an equal aperture ratio line 50. In FIG. 5, an example of the equal aperture ratio line 50 is shown by a dashed dotted line.

FIG. 6 is a diagram showing an example of equal aperture ratio lines 50 passing through a plurality of light transmission holes 45, and FIG. 7 shows an example of equal aperture ratio lines 50 passing light transmission holes 45 and virtual equal opening ratio point P. FIG. As shown in FIGS. 5 to 7, the equal aperture ratio line 50 has an elliptical shape in plan view. In particular, the equal aperture ratio line 50 has an elliptical shape having a major axis 52 extending in parallel with the long side 42 of the divided area Aa in plan view. More specifically, the iso-aperture line 50 has a major axis 52 and a minor axis 53 orthogonal to the major axis 52. The major axis 52 and the minor axis 53 have different lengths, and the major axis 52 has a length greater than the length of the minor axis 53.

A method of defining an equal aperture line 50 through the center of any light transmission hole will be described. In the example shown in FIG. 6, the curve passing through the center of any light transmission hole 451 and the centers of other light transmission holes 451 having the same aperture ratio as the light transmission hole 451 has an equal aperture ratio Line 50; When the equal aperture ratio line 50 has an elliptical shape in plan view, the equal aperture ratio line 50 passing through the center of any light transmission hole 451 has an elliptical shape. In other words, when an ellipse passing through the center of an arbitrary light transmission hole 451 and the center of another light transmission hole 451 having an aperture ratio equal to the aperture ratio of the light transmission hole 451 in a plan view is determined as one. Then, the equal aperture ratio line 50 consisting of the ellipse is defined. That is, the equal aperture ratio line 50 passing through the center of any light transmission hole 451 and the centers of other light transmission holes 451 having the same aperture ratio as the light transmission hole 451 has an elliptical shape in plan view It can also be said that an ellipse passing through the plurality of light transmission holes 451 having the same aperture ratio is determined as one.

In the example shown in FIG. 7, the number of ellipses passing through the four light transmission holes 452 having equal aperture ratios is not fixed. In this case, the position of a virtual equal opening ratio point P assumed to have an aperture ratio equal to that of the light transmission hole 452 is calculated in the divided area Aa, and the center of the light transmission hole 452 passes through the virtual equal opening ratio point P Let the curve be an equal aperture line 50. Assuming that a light transmission hole centered at the point P is present, it can be assumed that this light transmission hole will have an aperture ratio equal to the aperture ratio of the light transmission hole 452 It is a point. When the equal aperture ratio line 50 has an elliptical shape in plan view, the equal aperture ratio line 50 passing through the center of the arbitrary light transmission hole 452 and the virtual equal aperture ratio point P has an elliptical shape.

A method of calculating the position of the virtual equal aperture ratio point P will be described with reference to FIG. FIG. 8 is an enlarged view of a portion surrounded by an alternate long and short dash line indicated by VIII in FIG. First, in the two adjacent light transmission holes 453a and 453b located in the divided area Aa, the aperture ratio of one light transmission hole 453a is smaller than the aperture ratio of the light transmission aperture 452, and the other light transmission aperture 453b The two light transmission holes 453 a and 453 b having an opening ratio larger than the light transmission hole 452 are specified.

The virtual equal aperture ratio point P is located on a line segment Lc connecting the center Oa of the light transmission hole 453a and the center Ob of the light transmission hole 453b at a distance away from the center Oa toward the center Ob by a distance a I assume. At this time, the distance a is obtained by the following equation (1), where Ra is the aperture ratio of the light transmission hole 453a, Rb is the aperture ratio of the light transmission hole 453b, and D is the distance between the center Oa and the center Ob. Can.
a = (Rb / (Ra + Rb)) x D formula (1)

It is assumed that the center of any light transmission hole 452 has an opening ratio equal to the opening ratio of the light transmission hole 452 in plan view using the virtual equal opening ratio point P whose position is calculated in this manner. When an ellipse passing through the virtual equal aperture ratio point P is determined to be one, an equal aperture ratio line 50 consisting of the ellipse is defined. That is, the equal aperture ratio line 50 passing through the virtual equal aperture ratio point P assumed to have the center of an arbitrary light transmission hole 452 and the aperture ratio equal to the opening ratio of the light transmission hole 452 has an elliptical shape in plan view It can be said that having has a single ellipse which passes through the center of the light transmission hole 452 and the virtual equal aperture ratio point P.

In the example shown in FIG. 5, the light transmission hole 45 having an aperture ratio larger than the aperture ratio at the equal aperture ratio line 50 does not exist inside the arbitrary equal aperture ratio line 50. Moreover, the light transmission hole 45 having an aperture ratio smaller than the aperture ratio at the equal aperture ratio line 50 does not exist outside the arbitrary equal aperture ratio line 50.

In the conventional illumination unit disclosed in JP2012-174372A, the plurality of light transmission holes are arranged to form an equal aperture ratio line having a perfect circular shape. Here, in the case where a plurality of light transmission holes are arranged so as to form an equal aperture ratio line having a perfect circular shape in the rectangular region, the aperture ratio of the light transmission holes near the long side of the partition region is The aperture ratio of the light transmission holes in the vicinity of the short side is largely different. Specifically, the aperture ratio of the light transmission holes in the vicinity of the long side of the divided region, in particular, in the vicinity of the center of the long side is smaller than the aperture ratio of the light transmission holes in the vicinity of the short side of the divided region. Thereby, unevenness may occur in the illuminance of light emitted from the illuminance distribution adjustment plate near the long side and near the short side of the divided area. That is, illuminance unevenness may occur in the light emitting surface of the surface light source device provided with the illuminance distribution adjusting plate.

On the other hand, in the illuminance distribution adjusting plate 40 of the present embodiment, the equal aperture ratio line 50 has an elliptical shape having a major axis 52 extending parallel to the long side 42 of the divided area Aa in plan view, The difference between the aperture ratio of the light transmission holes 45 near the long side 42 of the divided area Aa and the aperture ratio of the light transmission holes 45 near the short side 43 can be reduced. Therefore, it is possible to suppress uneven illuminance of light emitted from the illuminance distribution adjustment plate 40 which may occur between the vicinity of the long side 42 and the vicinity of the short side 43 of the divided area Aa. That is, it is possible to effectively suppress the illuminance unevenness in the light emitting surface 20 a of the surface light source device 20 provided with the illuminance distribution adjusting plate 40.

In addition, when a plurality of light transmission holes are arranged so as to form a true circular shape equal opening ratio line in a divided region having a rectangular shape, the length of the divided region having a relatively small opening ratio of light transmission holes In the vicinity of the side, the width along the direction connecting the centers of the adjacent light transmission holes of the base material present between the adjacent light transmission holes is relatively large. On the other hand, in the vicinity of the short side of the divided area where the aperture ratio of the light transmission holes is relatively large, the base material existing between the adjacent light transmission holes is along the direction connecting the centers of the adjacent light transmission holes. The width is relatively small. Therefore, when an external force or vibration is applied to the illuminance distribution adjusting plate, the base material existing between adjacent light transmission holes in the vicinity of the short side of the divided area is compared with the stress caused by the external force or vibration. It concentrates on a portion having a very small width, and in this portion, breakage such as cracking or breakage may occur.

On the other hand, in the illuminance distribution adjusting plate 40 of the present embodiment, the equal aperture ratio line 50 has an elliptical shape having a major axis 52 extending parallel to the long side 42 of the divided area Aa in plan view, The width of the base material 41 existing between the adjacent light transmission holes 45 in the vicinity of the long side 42 of the divided area Aa and the base material 41 existing between the adjacent light transmission holes 45 in the vicinity of the short side 43 of the divided area Aa The difference between the width and the width can be reduced. Therefore, when an external force, vibration or the like is applied to the illuminance distribution adjusting plate 40, a stress caused by the external force or vibration is present between adjacent light transmission holes 45 in the vicinity of the short side 43 of the divided area Aa. Concentration on the substrate 41 can be suppressed. That is, when external force or vibration is applied to the illuminance distribution adjusting plate 40, the illuminance distribution adjusting plate 40 can be effectively prevented from being damaged.

Incidentally, the ratio of length _{W 5} of the major axis of length _{W 6} of the minor axis of the ellipse forming the equivalent aperture ratio line 50 _(W 6 / W ₅₎ is of the short side 43 of the partition area Aa of the length _{W 2} The ratio (W ₂ / W ₁ ) to the length W ₁ of the long side 42 is preferably 0.8 times or more and 1.2 times or less. More preferably, the ratio (W ₆ / W ₅ ) is not less than 0.9 times and not more than 1.1 times the ratio (W ₂ / W ₁ ). That is,
(W ₂ / W ₁ ) × 0.8 ≦ (W ₆ / W ₅ ) ≦ (W ₂ / W ₁ ) × 1.2 Formula (2)
Is preferably
(W ₂ / W ₁ ) × 0.9 ≦ (W ₆ / W ₅ ) ≦ (W ₂ / W ₁ ) × 1.1 Formula (3)
It is further preferred that

In this case, the difference between the aperture ratio of the light transmission holes 45 near the long side 42 of the divided area Aa and the aperture ratio of the light transmission holes 45 near the short side 43 can be further reduced. Further, the width of the base material 41 existing between the adjacent light transmission holes 45 in the vicinity of the long side 42 of the divided area Aa and the group existing between the adjacent light transmission holes 45 in the vicinity of the short side 43 of the divided area Aa. The difference with the width of the material 41 can be further reduced.

The surface light source device 20 according to the present embodiment includes a light source 22 and an illuminance distribution adjusting plate 40 which is disposed to face the light source 22 and adjusts the illuminance distribution of light emitted from the light source 22. A plurality of light transmission holes 45 for transmitting light, the base material 41 has one or more divided regions Aa, and each divided region Aa has a long side 42 and a short length in plan view In each divided area Aa, the divided area Aa is further divided into a plurality of regularly arranged element areas Ab, and the light source 22 is arranged along the normal direction of the base 41. Each light transmission hole 45 is formed in each of the element regions Ab located in a region other than the predetermined region overlapping with the light source 22 when projected onto the light transmission hole 45, and the light transmission hole 45 is formed in the light transmission hole 45. The place for the area of the element region Ab And the center of any light transmission hole 45 and the center of another light transmission hole 45 having an opening ratio equal to that of the light transmission hole 45 or equal to the opening ratio of the light transmission hole 45 An equal aperture ratio line 50 passing through a virtual equal aperture ratio point P assumed to have an aperture ratio has an elliptical shape having a major axis 52 extending parallel to the long side 42 in plan view.

The illuminance distribution adjusting plate 40 of the present embodiment is an illuminance distribution adjusting plate 40 which is disposed to face the light source 22 and adjusts the illuminance distribution of the light emitted from the light source 22, and a plurality of light transmission holes for transmitting light. The substrate 41 includes a base 41 formed with 45. The base 41 has one or more partition areas Aa, and each partition area Aa has a rectangular shape having a long side 42 and a short side 43 in plan view, In each divided area Aa, the divided area Aa is further divided into a plurality of regularly arranged element areas Ab, and when projected onto the light source 22 along the normal direction of the base material 41, the divided area Aa is overlapped with the light source 22 One light transmission hole 45 is formed in each of the element regions Ab located in the regions other than the region, and the light transmission hole 45 has a predetermined aperture ratio to the area of the element region Ab in which the light transmission holes 45 are formed. Have any light transmission A virtual equal aperture ratio point assumed to have a center of 45 and a center of another light transmission hole 45 having an aperture ratio equal to the aperture ratio of the light transmission hole 45 or an aperture ratio equal to the aperture ratio of the light transmission hole 45 The equal aperture ratio line 50 passing through P has an elliptical shape having a major axis 52 extending in parallel with the long side 42 in a plan view.

According to such a surface light source device 20 and the illuminance distribution adjusting plate 40, each divided area Aa has a rectangular shape having the long side 42 and the short side 43 in plan view, and the long side 42 and the short side 43 It is possible to change the lengths of the two independently of one another. Therefore, the illuminance distribution adjusting plate 40 can be configured by arranging the divided areas Aa having a rectangular shape configured by the long side 42 and the short side 43 of an arbitrary length. Therefore, the lengths of the long side and the short side of the illuminance distribution adjusting plate 40 can be increased with a high degree of freedom, respectively, as compared to the conventional illuminance distribution adjusting plate configured by arranging the divided areas having a square shape in plan view. It can be set. That is, it is possible to improve the degree of freedom in designing the planar light source shape of the surface light source device 20.

Further, since the equal aperture ratio line 50 has an elliptical shape having a major axis 52 extending in parallel to the long side 42 of the divided area Aa in plan view, the opening of the light transmission hole 45 near the long side 42 of the divided area Aa The difference between the ratio and the aperture ratio of the light transmission holes 45 near the short side 43 can be reduced. Therefore, it is possible to suppress uneven illuminance of light emitted from the illuminance distribution adjustment plate 40 which may occur between the vicinity of the long side 42 and the vicinity of the short side 43 of the divided area Aa. That is, it is possible to effectively suppress the illuminance unevenness in the light emitting surface 20 a of the surface light source device 20 provided with the illuminance distribution adjusting plate 40.

Furthermore, since the equal aperture ratio line 50 has an elliptical shape having a major axis 52 extending in parallel to the long side 42 of the divided area Aa in plan view, adjacent light transmission holes in the vicinity of the long side 42 of the divided area Aa The difference between the width of the base material 41 present between 45 and the width of the base material 41 present between the adjacent light transmission holes 45 in the vicinity of the short side 43 of the divided area Aa can be reduced. Therefore, when an external force, vibration or the like is applied to the illuminance distribution adjusting plate 40, a stress caused by the external force or vibration is present between adjacent light transmission holes 45 in the vicinity of the short side 43 of the divided area Aa. Concentration on the substrate 41 can be suppressed. That is, when external force or vibration is applied to the illuminance distribution adjusting plate 40, the illuminance distribution adjusting plate 40 can be effectively prevented from being damaged.

Claims (2)

1. A surface light source device comprising: a light source; and an illuminance distribution adjusting plate disposed opposite to the light source and adjusting an illuminance distribution of light emitted from the light source,
   The illuminance distribution adjustment plate is
   The substrate includes a plurality of light transmission holes for transmitting the light.
   The substrate has one or more compartmental areas,
   Each divided region has a rectangular shape having a long side and a short side in plan view,
   In each compartment area,
   The divided area is further divided into a plurality of regularly arranged element areas,
   One light transmission hole is formed in each of the element regions located in a region other than the predetermined region overlapping with the light source when projected onto the light source along the normal direction of the substrate;
   The light transmission hole has a predetermined aperture ratio to the area of the element region in which the light transmission hole is formed,
   A virtual equal aperture assumed to have the center of any light transmitting hole and the centers of other light transmitting holes having an opening ratio equal to the opening ratio of the light transmitting hole or the opening ratio equal to the opening ratio of the light transmitting hole An iso-aperture line passing through a point point has an elliptical shape having a major axis extending parallel to the long side in a plan view.
2. An irradiance distribution adjusting plate disposed opposite to a light source and adjusting an irradiance distribution of light emitted from the light source,
   The substrate includes a plurality of light transmission holes for transmitting the light.
   The substrate has one or more compartmental areas,
   Each divided region has a rectangular shape having a long side and a short side in plan view,
   In each compartment area,
   The divided area is further divided into a plurality of regularly arranged element areas,
   One light transmission hole is formed in each of the element regions located in a region other than the predetermined region overlapping with the light source when projected onto the light source along the normal direction of the substrate;
   The light transmission hole has a predetermined aperture ratio to the area of the element region in which the light transmission hole is formed,
   A virtual equal aperture assumed to have the center of any light transmitting hole and the centers of other light transmitting holes having an opening ratio equal to the opening ratio of the light transmitting hole or the opening ratio equal to the opening ratio of the light transmitting hole An illuminance distribution adjusting plate, wherein an equal aperture ratio line passing through the index point has an elliptical shape having a major axis extending parallel to the long side in a plan view.

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