JP6888501B2 - 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 the surface light source device.

A surface light source device that emits light in a planar shape 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. Surface light source devices for liquid crystal display devices are 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 under the optical member. As the light source, for example, a light emitting diode (LED) is used.

In an in-vehicle liquid crystal display device, an edge light type surface light source device has been conventionally used as a backlight because it is easy to reduce the thickness. In such an in-vehicle liquid crystal display device, it is required to display brightly in order to ensure visibility under external light shining through a window. In order to obtain the brightest possible display 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, an in-vehicle liquid crystal display device is often arranged in a narrow space, and if a large number of light sources are densely arranged in this narrow space, the heat generated from the light sources cannot be sufficiently dissipated. That is, when an edge light type surface light source device is used as the backlight of an in-vehicle liquid crystal display device, if sufficient brightness is to be obtained, the heat generated from the light source cannot be sufficiently dissipated and the liquid crystal is displayed. There is a risk that the display device will become hot and 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, so that the heat generated from the light sources can be appropriately dissipated. Therefore, in an in-vehicle liquid crystal display device, it is required to reduce the thickness of the surface light source device 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 even image while making the surface light source device thinner, an illuminance distribution adjustment plate is arranged between the light source and the liquid crystal display panel, and the surface is formed by this illuminance distribution adjustment plate. A technique for adjusting the illuminance distribution in the light emitting surface of a light source device is known.

Patent Document 1 discloses a lighting unit including an LED light source and a reflection plate made of a material that reflects light without transmitting light. A plurality of light passing holes arranged in a matrix are formed in the reflection plate. The opening area of each of the plurality of light passing holes becomes smaller as the distance from the facing portion facing the LED light source becomes shorter. According to such a lighting unit, the light passing amount is smaller as the light passing hole is closer to the position where the light directly arriving from the LED light source is denser, and the light passing hole is located at the position where the light directly arriving from the LED light source is less dense. Increases the amount of light passing through. As a result, 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 lighting device can be made close to uniform.

Japanese Unexamined Patent Publication No. 2012-174372

In the lighting unit disclosed in Patent Document 1, the reflection plate is formed so as to have a square shape in a plan view. Therefore, the plan-view shape of the entire lighting unit formed by arranging the reflection plates in the vertical and horizontal directions is limited to a shape in which the ratio of the length in the vertical direction to the length in the horizontal direction is an integer ratio. To. That is, in the lighting unit disclosed in Patent Document 1, there is a limit in the design of the plan view shape of the entire lighting unit.

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

The surface light source device of the present invention
A light source and an illuminance distribution adjusting plate arranged to face the light source and adjusting the illuminance distribution of the light emitted from the light source are provided.
The illuminance distribution adjustment plate is
A base material having a plurality of light transmitting holes through which the light is transmitted is provided.
The substrate has one or more compartments and
Each compartment has a rectangular shape with long and short sides in plan view.
In each compartment area
The partition area is further divided into a plurality of regularly arranged element areas.
One light transmission hole is formed in each element region located in a region other than a predetermined region that overlaps with the light source when projected onto the light source along the normal direction of the base material.
The light transmitting hole has a predetermined aperture ratio with respect to the area of the element region in which the light transmitting hole is formed.
A virtual equal opening assuming that the center of any of the light transmitting holes has an aperture ratio equal to the opening ratio of the light transmitting hole or the center of another light transmitting hole having an aperture ratio equal to the opening ratio of the light transmitting hole. The aperture ratio line passing through the rate point has an elliptical shape having a long axis extending parallel to the long side in a plan view.

The illuminance distribution adjusting plate of the present invention
An illuminance distribution adjusting plate that is arranged facing the light source and adjusts the illuminance distribution of the light emitted from the light source.
A base material having a plurality of light transmitting holes through which the light is transmitted is provided.
The substrate has one or more compartments and
Each compartment has a rectangular shape with long and short sides in plan view.
In each compartment area
The partition area is further divided into a plurality of regularly arranged element areas.
One light transmission hole is formed in each element region located in a region other than a predetermined region that overlaps with the light source when projected onto the light source along the normal direction of the base material.
The light transmitting hole has a predetermined aperture ratio with respect to the area of the element region in which the light transmitting hole is formed.
A virtual equal opening assuming that the center of any of the light transmitting holes has an aperture ratio equal to the opening ratio of the light transmitting hole or the center of another light transmitting hole having an aperture ratio equal to the opening ratio of the light transmitting hole. The aperture ratio line passing through the rate point has an elliptical shape having a long axis extending parallel to the long side in a plan view.

According to the present invention, it is possible to improve the degree of freedom in designing the plan view shape of the surface light source device.

FIG. 1 is a diagram for explaining an embodiment according to 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 a 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 diagram showing a cross section of a surface light source device corresponding to the IV-IV line of FIG. FIG. 5 is a plan view showing one section region of the illuminance distribution adjusting plate, and is a diagram showing an example of an arrangement pattern of an element region and a light transmitting hole. FIG. 6 is a diagram showing an example of an aperture ratio line passing through a plurality of light transmission holes. FIG. 7 is a diagram showing an example of an aperture ratio line passing through a light transmission hole and a virtual aperture ratio point. FIG. 8 is a diagram for explaining a method of calculating the position of the virtual 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, the scale, aspect ratio, etc. are appropriately changed from those of the actual product and exaggerated for the convenience of illustration and comprehension.

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

Further, the "plate surface (sheet surface, film surface)" is a plate-like member (sheet-like) that is a target when the target plate-like (sheet-like, film-like) member is viewed as a whole and from a broad perspective. A surface that coincides with the plane direction of a member or film-like member). In the present specification, the normal direction of the surface and the plate-shaped (sheet-shaped, film-shaped) member is the normal direction to the plate surface of the target surface and the plate-shaped (sheet-shaped, film-shaped) member. Refers to the direction.

Furthermore, as used in the present specification, the terms such as "parallel", "orthogonal", and "identical" and the values of length and angle that specify the shape and geometric conditions and their degrees are strictly used. Without being bound by meaning, we will interpret it including the range in which similar functions can be expected.

1 to 8 are diagrams for explaining one embodiment according to the present invention. Of 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 of 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. In the present embodiment, an example in which the display device 10 is an in-vehicle liquid crystal display device will be described, but the display device 10 of the present invention is not limited to this, and the display device 10 of the present invention can be used for advertisements, presentations, and televisions 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 has a surface light source device 20 having an light emitting surface 20a and a display panel 15 arranged so as to face the light emitting surface 20a. In the illustrated example, the display panel 15 is configured as a liquid crystal display panel, and therefore 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 observer 5.

In the illustrated example, the display panel 15 is arranged so that the display surface 15a on which the 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, and a part of the light incident on the display panel 15 is transmitted from the surface light source device 20 to display 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 functioning polarizer. The liquid crystal cell has a pair of support plates and a liquid crystal arranged between the pair of support plates. In the liquid crystal cell, an electric field can be applied to each region forming one pixel, and the orientation of the liquid crystal of the liquid crystal cell to which the electric field is applied changes. As an example, 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 a liquid crystal cell to which an electric field is not applied. The polarization direction is rotated by 90 ° when passing through the liquid crystal cell, and the polarization direction is maintained when passing through the liquid crystal cell to which an electric field is applied. As a result, depending on whether or not an electric field is applied to the liquid crystal cell, the polarized light 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 surface light source device 20 of the liquid crystal cell. It is possible to control whether the other polarizing plate is further transmitted or absorbed by the other polarizing plate and blocked.

The surface light source device 20 has a light emitting surface 20a that emits planar light, and 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, which is a so-called direct type. It is configured as a backlight. The surface light source device 20 of the present embodiment includes a light source 22 and an illuminance distribution adjusting plate 40 which is arranged 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, a spacer 23, a diffuser plate 26, a first optical sheet 27, and a second optical sheet 28 that support the light source 22. In the illustrated example, the spacer 23 and the illuminance distribution adjusting plate 40 are laminated in this order on the base laminate 30, and the diffuser plate 26, the first optical sheet 27, and the first optical sheet 27 are separated from the illuminance distribution adjusting plate 40 by a predetermined distance. 2 Laminates of optical sheets 28 are 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 this embodiment, as it is best shown in FIG. 3, the light source 22, while being differentially i.e. sequences arranged along the surface light source device first direction d ₁ parallel to the plate surface 20, the surface 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. In particular, 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 arranged two-dimensionally along _{the first direction d 1} and the second direction d _2. Not limited to this, the surface light source device 20 may have a plurality of light sources 22 arranged in a row along _{the first direction d 1} or the second direction d _{2, or only one light source 22.} May have. 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 of each light source 22 at the time of lighting can be adjusted independently of 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 parallel to one side of the rectangular shape contouring the illuminance distribution adjustment plate 40. Defined so that the second direction d ₂ is parallel to the other side orthogonal to the one side. In particular, in the illustrated example, the first direction d ₁ is defined to be parallel to the long side of the rectangular shape contouring the illuminance distribution adjustment plate 40, and the second direction d ₂ is parallel to the short side of the rectangular shape. Is defined to form.

The spacer 23 is a member that supports the illuminance distribution adjusting plate 40, and has a function of keeping 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 between two adjacent light sources 22, whereby the spacer 23 is surrounded by the wall portion 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 so as to form a grid pattern. The opening 25 is provided corresponding to the arrangement pattern of the light source 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 a plan view. Such spacers 23 include, for example, polycarbonate resin, acrylonitrile-butadiene-styrene copolymer resin (ABS resin), acrylonitrile-styrene-acrylate copolymer resin (ASA resin), and acrylonitrile-ethylene-propylene-diene-styrene copolymer resin (Acrylonitrile-ethylene-propylene-diene-styrene copolymer resin). It can be formed of AES resin), 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 to light in the visible light wavelength range.

FIG. 3 is a plan view showing an illuminance distribution adjusting plate 40 incorporated in the surface light source device 20. In FIG. 3, the positions of the openings 25 of the light source 22 and the spacer 23 arranged on the back side of the illuminance distribution adjusting plate 40 are shown by broken lines. The illuminance distribution adjusting plate 40 includes a base material 41 in which a plurality of light transmitting holes 45 for transmitting light emitted from the light source 22 are formed. In FIG. 3, the light transmission hole 45 is not shown. The base material 41 of the illuminance distribution adjusting plate 40 has one or more compartment regions Aa corresponding to each light source 22. That is, the base material 41 is provided with one partition region Aa 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 regions defined by the alternate long and short dash lines on the base material 41 indicate the respective compartmentalized areas Aa.

Each compartment area Aa has a rectangular shape (rectangular shape) having a long side 42 and a short side 43 in a 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. Therefore, the long side 42 of the partition area Aa and the long side of the illuminance distribution adjusting plate 40 are parallel to each other, and the short side 43 of the partition 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 partition area Aa and the short side of the illuminance distribution adjustment plate 40 are parallel, and the short side 43 of the partition area Aa and the long side of the illuminance distribution adjustment plate 40 are parallel. Each partition area Aa is further divided into a plurality of element areas Ab that are regularly arranged. The specific shape and arrangement pattern of the element region Ab will be described later.

In the example shown in FIG. 3, the division line La that partitions the adjacent division regions Aa of the base material 41 is defined along the wall portion 24 of the spacer 23. In other words, the lane marking La is defined 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 lane marking La is defined so as to form a grid pattern. 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 Consists of a part of. In the illustrated example, each compartment area Aa has a width W _{1 along the first direction d 1} and a width W ₂ along 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 compartment area Aa, and the width W ₂ corresponds to the length along the short side 43 of the compartment 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 partition region Aa has a rectangular shape having a long side 42 and a short side 43 in a plan view, and the lengths of the long side 42 and the short side 43 are set to each other. It can be changed independently. Therefore, the illuminance distribution adjusting plate 40 can be configured by arranging the compartmentalized regions Aa having a rectangular shape composed of the long side 42 and the short side 43 having an arbitrary length. Therefore, the lengths of the long side and the short side of the illuminance distribution adjustment plate 40 can be adjusted with a high degree of freedom as compared with the conventional illuminance distribution adjustment plate formed by arranging the division regions having a square shape in a plan view. Can be set. That is, it is possible to improve the degree of freedom in designing the plan view shape of the surface light source device 10.

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

The base laminate 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 reflecting 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 reflecting 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 reflecting layer 36, but for example, a metal or a resin may be used. Can be done. In particular, when a base material 31 made of a metal material having good thermal conductivity such as aluminum is used, the heat generated by the light source 22 can be dissipated toward the back surface side of the surface light source device 20 via the base material 31. It is more preferable because it can be done. 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, 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 substrate thinner than the conventional rigid substrate as the film substrate 33, the surface light source device 20 can be made thinner. The material of the film substrate 33 can be appropriately selected in consideration of insulation, heat resistance, durability, dimensional stability during heating, mechanical strength, etc., and is, for example, polyimide (PI) or polyethylene terephthalate ( PEN) and polyethylene terephthalate (PET) can be used.

The film substrate 33 is fixed to the substrate 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 substrate 31. As an example, double-sided tape can be used as the bonding layer 32. In addition, 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. 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 using the subtract method. That is, the wiring layer 34 having a desired pattern can be formed by patterning the metal layer such as copper foil arranged on the film substrate 33 by etching using a photolithography technique. Not limited to this, the wiring layer 34 may be formed by using another method such as an additive method or a semi-additive method. An electrode portion is provided at a connection portion of the wiring layer 34 with the light source 22 and other wiring or a 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 serving as the electrode portion 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 the material of the resist layer 35, for example, a resin material such as a polyester resin, an epoxy resin, an epoxy resin and a phenol resin, an epoxy acrylate resin, or a silicone resin can be used. As an example, the resist layer 35 is provided with a resin layer so as to cover the entire wiring layer 34 and the film substrate 33, and the electrode portion is exposed at a portion to 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 reflecting 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 to direct the light path to the light reflecting layer 36 side. It has a function of reflecting the light bent toward the illuminance 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 region. Further, the light reflecting layer 36 is arranged on the same side of the illuminance distribution adjusting plate 40 as the light source 22 so as to be parallel to 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 where the light source 22 should be arranged. In the illustrated example, the light reflecting layer 36 is arranged so as to surround the light source 22 in a plan view. Further, in the illustrated example, the light reflecting layer 36 is provided so as to expose the inner peripheral edge portion surrounding the light source 22 of the resist layer 35. Not limited to this, in the light reflecting layer 36, for example, the inner peripheral edge portion of the resist layer 35 and the inner peripheral edge portion of the light reflecting layer 36 coincide with each other so that the inner peripheral edge portion surrounding the light source 22 of the resist layer 35 is not exposed. It may be provided in this way. As the light reflecting layer 36, for example, a layer made 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, whereby the in-plane distribution of illuminance is made uniform, and the light transmitting hole 45 of the illuminance distribution adjusting plate 40 The image can be made inconspicuous. The diffusion plate 26 can be used without particular limitation as long as it is a member having a light diffusion function. For example, a resin plate or a glass plate having fine irregularities on the surface, or a resin plate having diffusion 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 and emits it from the display panel 15 side to intensively improve the illuminance in the normal direction of the first optical sheet 27. It is a condensing sheet for making the light source. The condensing sheet of the present embodiment is a sheet having a plurality of unit prisms arranged along a certain direction on the sheet surface. As the condensing sheet, for example, "BEF" (registered trademark) available from 3M, Inc. of the United States can be used.

Further, the second optical sheet 28 in the present embodiment is a reflective polarizing plate that transmits a polarizing component in a direction parallel to the transmission axis and reflects a polarization component in a direction parallel to the reflection axis orthogonal to the transmission axis. Is. According to this reflective polarizing plate, it is possible to prevent light of a polarizing component emitted from the surface light source device 20 and not effectively used by the display panel 15 from being incident on 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 the reflective polarizing plate, for example, "DBEF" (registered trademark) available from 3M, Inc. of the United States can be used.

As the diffuser plate 26, the first optical sheet 27, and the second optical sheet 28, it is preferable to use one having a high visible light transmittance 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 section region Aa of the illuminance distribution adjusting plate 40, and is a diagram showing an example of an arrangement pattern of the element region Ab and the light transmission hole 45. The illuminance distribution adjusting plate 40 includes a base material 41 in which a plurality of light transmitting 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 to direct the optical path toward the light reflecting 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 to light in the visible light wavelength region. 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 transmission, and the light transmission hole 45 is a physical hole formed in the base material 41, that is, It is formed as a through hole extending from one main surface of the two main surfaces of the opposing base materials 41 to the other main surface, but 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 in the normal direction to the plate surface of the illuminance distribution adjustment plate 40. For example, the illuminance distribution adjustment plate 40 is formed with light. It has a transparent plate-shaped transparent base material having transparency and a light reflecting layer provided on the transparent base material, particularly on the main surface of the transparent base material on the light source 22 side, and the light transmitting hole 45 is formed by the light. It may be configured as an opening provided in the reflective layer. In this case, the transparent base material does not have to 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 reflecting layer 36 is reflected by the light reflecting layer 36 and travels toward the illuminance distribution adjusting plate 40. When light that repeats this process enters any of the light transmission holes 45 of the illuminance distribution adjustment plate 40, the light passes through the light transmission holes 45 and is transmitted from the illuminance distribution adjustment plate 40 to the display panel 15 side (diffusion plate in FIG. 4). It emits toward the 26 side). At this time, the direction emitted from the light source 22 is substantially parallel to the plate surface of the illuminance distribution adjusting plate 40 while repeating reflection between the illuminance distribution adjusting plate 40 and the light reflecting layer 36 (as an example, the first direction d in FIG. 4). _The illuminance of the light traveling to 1) decreases as the distance from the light source 22 increases. However, the illuminance distribution adjusting plate 40 of the present embodiment, as described above, a plurality of light transmitting holes 45, the opening area farther from the center O ₁ of the divided area Aa facing directly above the light sources 22 becomes larger Arranged in a pattern. As a result, the illuminance of the light transmitted through the light transmitting holes 45 and emitted is made uniform. When the spacer 23 is made of a material having high reflectivity to light in the visible light wavelength region, it travels in a direction substantially parallel to the plate surface of the illuminance distribution adjusting plate 40 and is incident on the wall portion 24 of the spacer 23. The resulting 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 partition area Aa is further divided into a plurality of element areas Ab that are regularly arranged. The element region Ab and the light transmission holes 45 formed in each element region Ab will be described with reference to FIGS. 5 to 7. FIG. 5 is a plan view showing one section region Aa of the illuminance distribution adjusting plate 40, and is a diagram showing an example of an arrangement pattern of the element region Ab and the light transmission hole 45.

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 the alternate long and short dash lines indicate the respective element regions Ab. In the illustrated example, each element region Ab has a rectangular shape, particularly a square shape, in a plan view, but the shape of the element region Ab is not limited to this. For example, each element region Ab may have a contour having another shape such as a triangle or a hexagon in a plan view. In addition, in this specification, "regular arrangement" of a plurality of element regions Ab means that a plurality of element regions Ab having the same shape and size are arranged at the same pitch. ing. In the example shown in FIG. 5, the plurality of element regions Ab are all having the same shape and size, but the plurality of element regions Ab are not limited to this, 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 arranged on the back side of the illuminance distribution adjusting plate 40 is shown by a broken line. _{The plurality of element regions Ab include an element region Ab 0} that overlaps with the light source 22 when projected onto the light source 22 along the normal direction of the base material 41. When the element region Ab ₀ overlaps with the light source 22 when projected onto the light source 22 along the normal direction of the base material 41, at least a part of the _{element region Ab 0 is along the normal direction of the base material 41.} It means that it overlaps with the light source 22 when projected onto the light source 22. For example, the plurality of element regions Ab ₀ so that the vertices and / or sides shared by the plurality of element regions Ab 0 overlap the center of the light source 22 when projected onto the light source 22 along the normal direction of the base material 41. Is arranged, each of the plurality of element regions Ab ₀ including the apex and / or side overlaps with the light source 22 when projected onto the light source 22 along the normal direction of the base material 41. ..

In the example shown in FIG. 5, one light transmission hole 45 is formed in each of the element regions Ab other than the element region Ab _0. In other words, _{each element region Ab other than the element region Ab 0} is defined so as to include one light transmission hole 45. Therefore, in the illustrated example, the element regions adjacent to each other are between the two light transmitting holes 45 adjacent to each other _{in the first direction d 1} and between the two light transmitting holes 45 adjacent to each other in the second direction d _2. The lane marking Lb that divides Ab will 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 lane markings Lb extending to d 1} are defined to form a grid pattern. Each element region Ab has a width W _{3 along the first direction d 1} and a width W ₄ along the second direction d ₂ . The width W ₃ and the width W ₄ can be, for example, 0.2 mm or more and 10 mm or less.

In the element region Ab ₀ and the element region Ab _{located in the vicinity of the element region Ab 0} , there may be an element region Ab in which the light transmission hole 45 is not formed. That is, in the plan view of the illuminance distribution adjusting plate 40, light is transmitted into the element region Ab located in a predetermined region that overlaps with the light source 22 when projected onto the light source 22 along the normal direction of the base material 41. There may be an element region Ab in which the holes 45 are not formed. In other words, one light transmission hole 45 is formed in each element region Ab located in a region other than a predetermined region that overlaps with the light source 22 when projected onto the light source 22 along the normal direction of the base material 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 to this, the light transmission hole 45 may be formed in _{the element region Ab 0 as well.} That is, one light transmission hole 45 may be formed in each of all the element regions Ab including the _{element region Ab 0.} Here, when the element region Ab is located in a region other than the predetermined region, the center of the element region Ab (in the present embodiment, the center of the light transmission hole 45 formed in the element region Ab) is a predetermined region. It means that it is located in an area other than. As an example, the predetermined region overlaps with the center of the light source 22 when projected onto the light source 22 along the normal direction of the base material 41 in the compartment region Aa, that is, the compartment region Aa in the present embodiment. It can be a region within 5 mm from the center O ₁ along the plate surface direction of the base material 41. In this case, a predetermined region in a plan view of the base member 41, the contour and inside of the circle of radius 5mm around the center O _1.

In the example shown in FIG. 5, the center of each light transmitting hole 45 coincides with the center of the element region Ab in which the light transmitting hole 45 is arranged. 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 the light transmitting holes 45 is isotropically emitted from the light transmitting holes 45 in the plate surface direction of the base material 41. Therefore, it is possible to improve the in-plane uniformity of the illuminance of the illumination light emitted from the surface light source device 20. However, the present invention is not limited to this, and each light transmission hole 45 may be formed so as 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 compartment 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 transmitting hole 45 is the area S of the element region Ab in which the light transmitting hole 45 is formed in _{the area S a of the light transmitting hole 45 in the plan view of the illuminance distribution adjusting plate 40.} Refers to the ratio to _{b (S a} / S _b ).

The size of the light transmitting hole 45 _{changes so as to increase from the element region Ab 0} toward the peripheral edge of the compartment region Aa. On the other hand, in the plan view of the illuminance distribution adjusting plate 40, the plurality of element regions Ab have the same area as each other. Therefore, the aperture ratio of the light transmitting hole 45 _{changes so as to increase from the element region Ab 0} toward the peripheral edge of the compartment region Aa. However, in the example shown in FIG. 5, there is a region where the aperture ratio of the light transmission hole 45 is constant in the vicinity of the peripheral edge of the compartmentalized area Aa, particularly in the vicinity of the corner of the compartmentalized area Aa.

It is assumed that the center of an arbitrary light transmitting hole 45 has an aperture ratio equal to the opening ratio of the center of another light transmitting hole 45 having an aperture ratio equal to the opening ratio of the light transmitting hole 45 or the opening ratio of the light transmitting hole 45. The line passing through the virtual equal aperture ratio point P is defined as the equal aperture ratio line 50. FIG. 5 shows an example of the equal aperture ratio line 50 as a alternate long and short dash line.

FIG. 6 is a diagram showing an example of an equal aperture ratio line 50 passing through a plurality of light transmission holes 45, and FIG. 7 is an example of an equal aperture ratio line 50 passing through the light transmission hole 45 and the virtual equal aperture ratio point P. It is a figure which shows. As shown in FIGS. 5 to 7, the equal aperture ratio line 50 has an elliptical shape in a plan view. In particular, the equiaper aperture ratio line 50 has an elliptical shape having a long axis 52 extending parallel to the long side 42 of the partition region Aa in a plan view. More specifically, the equal aperture ratio 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 from each other, and the major axis 52 has a length larger than the length of the minor axis 53.

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

In the example shown in FIG. 7, the ellipse passing through the four light transmission holes 452 having the same aperture ratio is not fixed to one. In this case, the position of the virtual equal aperture ratio point P assuming that the light transmission hole 452 has an aperture ratio equal to that of the light transmission hole 452 is calculated in the partition region Aa, and the center of the light transmission hole 452 and the virtual equal aperture ratio point P pass through. Let the curve be the equal aperture ratio line 50. Assuming that the virtual equal aperture ratio point P has a light transmitting hole centered on the point P, it can be assumed that the light transmitting hole has an aperture ratio equal to the opening ratio of the light transmitting hole 452. It is a point. When the equal aperture ratio line 50 has an elliptical shape in a plan view, it is assumed that the equal aperture ratio line 50 passing through the center of an 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 aperture ratio point P will be described with reference to FIG. FIG. 8 is an enlarged view of the portion surrounded by the alternate long and short dash line in FIG. 7 with VIII. First, there are two adjacent light transmitting holes 453a and 453b located in the partition region Aa, the opening ratio of one light transmitting hole 453a is smaller than the opening ratio of the light transmitting hole 452, and the other light transmitting hole 453b. Two light transmitting holes 453a and 453b are specified, in which the opening ratio of the light transmitting holes 452 is larger than the opening ratio of the light transmitting holes 452.

The virtual equal opening rate point P exists at a position separated by a distance a from the center Oa toward the center Ob on the line segment Lc connecting the center Oa of the light transmission hole 453a and the center Ob of the light transmission hole 453b. And. At this time, the distance a is calculated 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 be done.
a = (Rb / (Ra + Rb)) × D ・ ・ ・ Equation (1)

Using the virtual equal aperture ratio point P whose position is calculated in this way, it is assumed that the center of an arbitrary light transmission hole 452 has an aperture ratio equal to the aperture ratio of the light transmission hole 452 in a plan view. When the imaginary aperture ratio point P passing through the virtual equal aperture ratio point P is determined to be one, the equal aperture ratio line 50 composed of the ellipse is defined. That is, the center of the arbitrary light transmission hole 452 and the equal aperture ratio line 50 passing through the virtual equal aperture ratio point P assuming that the light transmission hole 452 has an aperture ratio equal to the aperture ratio of the light transmission hole 452 have an elliptical shape in a plan view. Having it can be said to mean that an ellipse passing through the center of the light transmission hole 452 and the virtual aperture ratio point P is determined as one.

In the example shown in FIG. 5, there is no light transmission hole 45 having an aperture ratio larger than the aperture ratio in the equivalent aperture ratio line L inside the arbitrary aperture ratio line L. Further, outside the arbitrary aperture ratio line L, there is no light transmission hole 45 having an aperture ratio smaller than the aperture ratio in the equal aperture ratio line L.

In the conventional lighting unit disclosed in Patent Document 1, a plurality of light transmitting holes are arranged so as to form an equiaper aperture ratio line having a perfect circular shape. Here, when a plurality of light transmission holes are arranged so as to form an equal aperture ratio line having a perfect circle shape in the compartmentalized region having a rectangular shape, the aperture ratio of the light transmission holes near the long side of the compartmentalized region is increased. It will be significantly different from the aperture ratio of the light transmission hole near the short side. Specifically, the aperture ratio of the light transmitting holes near the long side of the partition region, particularly near the center of the long side, is smaller than the aperture ratio of the light transmitting holes near the short side of the partition region. As a result, the illuminance of the light emitted from the illuminance distribution adjusting plate may be uneven between the vicinity of the long side and the vicinity of the short side of the partition region. 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 equiaper aperture ratio line L has an elliptical shape having a long axis 52 extending parallel to the long side 42 of the partition region Aa in a plan view. The difference between the aperture ratio of the light transmitting hole 45 near the long side 42 and the opening ratio of the light transmitting hole 45 near the short side 43 of the partition region Aa can be reduced. Therefore, it is possible to suppress the illuminance unevenness of the light emitted from the illuminance distribution adjusting plate 40, which may occur between the vicinity of the long side 42 and the vicinity of the short side 43 of the partition region Aa. That is, it is possible to effectively suppress the uneven illuminance in the light emitting surface 20a of the surface light source device 20 provided with the illuminance distribution adjusting plate 40.

Further, when a plurality of light transmitting holes are arranged so as to form an equiaper aperture ratio line having a perfect circular shape in the compartmentalized region having a rectangular shape, the length of the compartmentalized region in which the aperture ratio of the light transmitting holes is relatively small. In the vicinity of the sides, the width of the base material existing between the adjacent light transmitting holes along the direction connecting the centers of the adjacent light transmitting holes becomes relatively large. On the other hand, in the vicinity of the short side of the partition region where the aperture ratio of the light transmitting holes is relatively large, the base material existing between the adjacent light transmitting holes follows the direction connecting the centers of the adjacent light transmitting holes. The width is relatively small. Therefore, when an external force, vibration, etc. is applied to the illuminance distribution adjustment plate, the stress caused by the external force, vibration, etc. is compared with the base material existing between the adjacent light transmission holes in the vicinity of the short side of the partition region. It concentrates on a part having a small width, and damage such as cracks and breaks may occur in this part.

On the other hand, in the illuminance distribution adjusting plate 40 of the present embodiment, the equi-opening ratio line L has an elliptical shape having a long axis 52 extending parallel to the long side 42 of the partition region Aa in a plan view. The width of the base material 41 existing between the adjacent light transmitting holes 45 in the vicinity of the long side 42 of the partition region Aa and the base material 41 existing between the adjacent light transmitting holes 45 in the vicinity of the short side 43 of the partition region Aa. The difference from the width of can be reduced. Therefore, when an external force, vibration, or the like is applied to the illuminance distribution adjusting plate 40, stress caused by the external force, vibration, or the like exists between the adjacent light transmitting holes 45 in the vicinity of the short side 43 of the partition region Aa. Concentration on the base material 41 can be suppressed. That is, when an external force, vibration, or the like is applied to the illuminance distribution adjusting plate 40, it is possible to effectively prevent the illuminance distribution adjusting plate 40 from being damaged.

The ratio (W ₆ / W _{5 ) of the length W 6} of the minor axis of the ellipse forming the equal opening ratio line 50 to _{the length W 5} of the major axis is the length _{W 2} of the short side 43 of the partition region Aa. The ratio of the long side 42 to the length W ₁ (W ₂ / W ₁ ) is preferably 0.8 times or more and 1.2 times or less. More preferably, the ratio (W ₆ / W ₅ ) is 0.9 times or more and 1.1 times or less the ratio (W ₂ / W _1). That is,
(W ₂ / W ₁ ) × 0.8 ≦ (W ₆ / W ₅ ) ≦ (W ₂ / W ₁ ) × 1.2 ・ ・ ・ Equation (2)
Is preferable
(W ₂ / W ₁ ) × 0.9 ≦ (W ₆ / W ₅ ) ≦ (W ₂ / W ₁ ) × 1.1 ・ ・ ・ Equation (3)
Is more preferable.

In this case, the difference between the aperture ratio of the light transmitting hole 45 near the long side 42 and the opening ratio of the light transmitting hole 45 near the short side 43 of the partition region Aa can be further reduced. Further, the width of the base material 41 existing between the adjacent light transmitting holes 45 in the vicinity of the long side 42 of the partition region Aa and the group existing between the adjacent light transmitting holes 45 in the vicinity of the short side 43 of the partition region Aa. The difference from the width of the material 41 can be further reduced.

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 the light emitted from the light source 22, and the illuminance distribution adjusting plate 40 is provided. A base material 41 having a plurality of light transmitting holes 45 through which light is transmitted is provided, the base material 41 has one or more compartment regions Aa, and each compartment region Aa has a long side 42 and a short side in a plan view. It has a rectangular shape with sides 43, and in each compartment area Aa, the compartment area Aa is further divided into a plurality of regularly arranged element regions Ab, and the light source 22 is along the normal direction of the base material 41. One light transmission hole 45 was formed in each of the element regions Ab located in a region other than a predetermined region that overlaps with the light source 22 when projected onto the light transmission hole 45, and the light transmission hole 45 was formed in the light transmission hole 45. The center of an arbitrary light transmitting hole 45 having a predetermined opening ratio with respect to the area of the element region Ab, and the center of another light transmitting hole 45 having an opening ratio equal to the opening ratio of the light transmitting hole 45 or the light transmitting The equal opening ratio line L passing through the virtual equal opening ratio point P assuming that the opening ratio is equal to the opening ratio of the hole 45 has an elliptical shape having a long axis 52 extending parallel to the long side 42 in a plan view. Have.

The illuminance distribution adjusting plate 40 of the present embodiment is an illuminance distribution adjusting plate 40 that is arranged to face the light source 22 and adjusts the illuminance distribution of the light emitted from the light source 22, and is a plurality of light transmitting holes that transmit light. A base material 41 on which 45 is formed is provided, the base material 41 has one or more compartment regions Aa, and each compartment region Aa has a rectangular shape having a long side 42 and a short side 43 in a plan view. In each compartment area Aa, the compartment area Aa is further divided into a plurality of element regions Ab that are regularly arranged and overlaps with 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 located in the region other than the region of No. 1, and the light transmission hole 45 has a predetermined opening ratio with respect to the area of the element region Ab in which the light transmission hole 45 is formed. The center of any light transmitting hole 45 and the center of another light transmitting hole 45 having an opening ratio equal to the opening ratio of the light transmitting hole 45 or the opening ratio equal to the opening ratio of the light transmitting hole 45. The equal aperture ratio line L passing through the virtual equal opening ratio point P assumed to have has an elliptical shape having a long axis 52 extending parallel to the long side 42 in a plan view.

According to the surface light source device 20 and the illuminance distribution adjusting plate 40, each partition region Aa has a rectangular shape having a long side 42 and a short side 43 in a plan view, and the long side 42 and the short side 43. It is possible to change the length of each of them independently of each other. Therefore, the illuminance distribution adjusting plate 40 can be configured by arranging the compartmentalized regions Aa having a rectangular shape composed of the long side 42 and the short side 43 having an arbitrary length. Therefore, the lengths of the long side and the short side of the illuminance distribution adjustment plate 40 can be adjusted with a high degree of freedom as compared with the conventional illuminance distribution adjustment plate formed by arranging the division regions having a square shape in a plan view. Can be set. That is, it is possible to improve the degree of freedom in designing the plan view shape of the surface light source device 10.

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

Further, since the equi-opening ratio line L has an elliptical shape having a long axis 52 extending parallel to the long side 42 of the partition region Aa in a plan view, adjacent light transmission holes in the vicinity of the long side 42 of the compartment region Aa. The difference between the width of the base material 41 existing between the 45 and the width of the base material 41 existing between the adjacent light transmitting holes 45 in the vicinity of the short side 43 of the partition region Aa can be reduced. Therefore, when an external force, vibration, or the like is applied to the illuminance distribution adjusting plate 40, stress caused by the external force, vibration, or the like exists between the adjacent light transmitting holes 45 in the vicinity of the short side 43 of the partition region Aa. Concentration on the base material 41 can be suppressed. That is, when an external force, vibration, or the like is applied to the illuminance distribution adjusting plate 40, it is possible to effectively prevent the illuminance distribution adjusting plate 40 from being damaged.

10 Display device 15 Display panel 20 Surface light source device 22 Light source 23 Spacer 26 Diffuse plate 27 1st optical sheet 28 2nd optical sheet 30 Base laminate 31 Base material 32 Bonding layer 33 Film substrate 34 Wiring layer 35 Resist layer 36 Light reflection layer 37 Conductive connection layer 40 Illuminance distribution adjustment plate 41 Base material 42 Long side 43 Short side 45 Light transmission hole 50 Equal aperture ratio line 52 Long axis 53 Short axis Aa Partition area Ab Element area P Virtual equal aperture ratio point

Claims (2)

A surface light source device including a light source and an illuminance distribution adjusting plate arranged to face the light source and adjusting the illuminance distribution of light emitted from the light source.
The illuminance distribution adjustment plate is
A base material having a plurality of light transmitting holes through which the light is transmitted is provided.
The substrate has one or more compartments and
Each compartment has a rectangular shape with long and short sides in plan view.
In each compartment area
The partition area is further divided into a plurality of regularly arranged element areas.
One light transmission hole is formed in each element region located in a region other than a predetermined region that overlaps with the light source when projected onto the light source along the normal direction of the base material.
The light transmitting hole has a predetermined aperture ratio with respect to the area of the element region in which the light transmitting hole is formed.
A virtual equal opening assuming that the center of any of the light transmission holes has an aperture ratio equal to the opening ratio of the light transmission hole or the center of another light transmission hole having an aperture ratio equal to the opening ratio of the light transmission hole. A surface light source device having an elliptical shape having a long axis extending parallel to the long side in a plan view. An illuminance distribution adjusting plate that is arranged facing the light source and adjusts the illuminance distribution of the light emitted from the light source.
A base material having a plurality of light transmitting holes through which the light is transmitted is provided.
The substrate has one or more compartments and
Each compartment has a rectangular shape with long and short sides in plan view.
In each compartment area
The partition area is further divided into a plurality of regularly arranged element areas.
One light transmission hole is formed in each element region located in a region other than a predetermined region that overlaps with the light source when projected onto the light source along the normal direction of the base material.
The light transmitting hole has a predetermined aperture ratio with respect to the area of the element region in which the light transmitting hole is formed.
A virtual equal opening assuming that the center of any of the light transmitting holes has an aperture ratio equal to the opening ratio of the light transmitting hole or the center of another light transmitting hole having an aperture ratio equal to the opening ratio of the light transmitting hole. The aperture ratio line passing through the rate point is an illuminance distribution adjusting plate having an elliptical shape having a long axis extending parallel to the long side in a plan view.

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