JP5005117B2 - Lighting device - Google Patents

Description

  The present invention relates to a lighting device used for the purpose of illuminating an object.

In recent years, reduction of carbon dioxide emissions has been demanded from the viewpoint of preventing global warming, and in addition to conventional incandescent bulbs and fluorescent lamps, light emitting diodes (Light Emitting Diodes: LEDs) that have low power consumption and long life. Illumination devices using a light source as a light source have been widely used.
In particular, since the improvement in luminous efficiency is remarkable, the spread of lighting devices using LED light sources is rapidly progressing.

  In an illuminating device using a so-called point light source such as an LED, there is a problem that glare enters the eyes when the light source is viewed directly. In order to suppress this glare, conventionally, a technique of arranging a diffusing member on the light exit surface has been adopted. In this way, when the method of arranging the diffusing member on the light emitting surface is employed, there is a problem that the light amount generally decreases with diffusion. Therefore, in order to solve the problem of decrease in the light amount due to diffusion, An illuminating device using a diffusion cover with a changed transmittance is disclosed (for example, see Patent Documents 1 and 2).

However, when a point light source such as an LED is used, since there is a light component that emits light from a region having a high light transmittance of the diffusion cover whose transmittance is partially changed as described above, depending on the angle at which the light source is viewed, glare May become very strong.
Especially for lighting devices such as downlights, base lights and ceiling lights installed on the ceiling surface, there are many opportunities for the lighting devices to enter the eyes from diagonally below, and diffusion with partially changed transmittance as described above. In the cover, the effect of simultaneously eliminating the glare directly in the downward direction of the lighting device (frontal glare) and the glare downward in the oblique direction (diagonal glare) is small.

  On the other hand, as a technique for suppressing glare, there is a technique in which a light shielding member is arranged on the light exit surface, but there is still a problem that glare is still strong in a light component that emits light from an angle where light is not shielded.

  In order to solve the above-described problems, an illumination device having a configuration in which a light source is combined with a diffusion plate and a louver, and an illumination device having a configuration in which a light source is combined with a diffusion plate and a reflector have been proposed (for example, Patent Document 3). 4).

JP 2009-48955 A JP 2003-281923 A JP 2008-270096 A JP 2008-251279 A

However, in the lighting devices disclosed in Patent Documents 3 and 4, it is necessary to design a light shielding member such as a louver or a reflector, resulting in an increase in cost due to an increase in the number of members, or an increase in the size of the lighting device body. There is a problem that.
In addition, when the louver is used, since the louver physically blocks light emitted in an oblique direction, the oblique glare is satisfactorily suppressed, but there is a problem that glare in an angular range that is not shielded by the louver, particularly front glare remains. .

  In addition, regarding a light source unit for a liquid crystal display device, a technique has been proposed in which a glare eliminating effect is obtained by combining a diffusion plate having a light diffusion function and a diffusion sheet in which the diffusion angle of emitted light is changed in the plane. However, the total luminous flux is remarkably reduced, and the practically sufficient function cannot be exhibited as a light source unit for an illuminating device used for the purpose of illuminating an object.

  Therefore, in the present invention, it is used for the purpose of illuminating an object that has a small number of parts, can avoid an increase in size, can suppress a decrease in total luminous flux, and can eliminate front glare and oblique glare by controlling the light emission range. It is an object to provide a lighting device.

As a result of intensive studies in order to solve the problems of the prior art in the lighting device as described above, the inventor formed a concavo-convex structure on the surface as the diffusion sheet in the lighting device including the point light source and the diffusion sheet. When the light is incident in a direction perpendicular to the surface on which the uneven structure of the diffusion sheet is formed, the diffusion angle of the emitted light is one change in the diffusion angle within the surface of the diffusion sheet. The absolute value A of the angle formed by the normal line direction of the light exit surface of the diffusion sheet and the direction of the light beam emitted from the light exit surface is used as the horizontal axis. And the above-mentioned problems of the prior art can be solved by the illumination device having a predetermined light distribution characteristic in the light distribution characteristic diagram in which the luminous intensity B of the light emitted from the diffusion sheet is the vertical axis. Out, it has led to the completion of the present invention.
That is, the present invention is as follows.

[1]
A point light source,
A diffusion sheet provided in the direction of light emission from the point light source;
Comprising
The diffusion sheet has a light incident surface on which light from the point light source is incident and a light exit surface from which light from the point light source is emitted, and an uneven structure is formed on the light incident surface and / or the light exit surface. And
In the diffusion sheet, when light is incident in a direction perpendicular to the surface of the diffusion sheet on which the concavo-convex structure is formed, the diffusion angle of the emitted light is one of the diffusion angles in the plane of the diffusion sheet. It has the characteristic that it increases according to the distance from the minimum position in one change pattern,
A light distribution with the horizontal axis representing the absolute value A of the angle between the normal direction of the light exit surface of the diffusion sheet and the direction of the light beam emitted from the light exit surface, and the light intensity B of the light exiting from the diffusion sheet as the vertical axis In the characteristic diagram, the light intensity B decreases as the absolute value A of the angle increases.
[2]
A point light source,
A diffusion sheet provided in the direction of light emission from the point light source;
Comprising
The diffusion sheet has a light incident surface on which light from the point light source is incident and a light exit surface from which light from the point light source is emitted, and an uneven structure is formed on the light incident surface and / or the light output surface. And
In the diffusion sheet, when light is incident in a direction perpendicular to the surface of the diffusion sheet on which the concavo-convex structure is formed, the diffusion angle of the emitted light is one of the diffusion angles in the plane of the diffusion sheet. It has the characteristic that it increases according to the distance from the minimum position in one change pattern,
A light distribution with the horizontal axis representing the absolute value A of the angle between the normal direction of the light exit surface of the diffusion sheet and the direction of the light beam emitted from the light exit surface, and the light intensity B of the light exiting from the diffusion sheet as the vertical axis In the characteristic diagram,
A first angle region in which the luminous intensity B increases as the absolute value A of the angle increases;
A second angle region in which the luminous intensity B decreases as the absolute value A of the angle increases;
Have
The illuminating device in which the difference between the minimum luminous intensity and the maximum luminous intensity in the first angle region in which the luminous intensity B increases is 5% or less of the luminous intensity in the vertical direction of the light exit surface of the diffusion sheet.
[3]
The diffusion angle is minimum in the vicinity of the intersection of the diffusion sheet and a perpendicular drawn from the point light source to the diffusion sheet,
The illumination device according to [1] or [2], wherein a difference between a minimum value and a maximum value of the diffusion angle in the diffusion sheet surface is in a range of 30 ° to 90 °.
[4]
The illumination device according to any one of [1] to [3], wherein a diffusion angle of the diffusion sheet is in a range of 0.1 ° to 100 °.
[5]
The illumination device according to any one of [1] to [4], wherein a minimum value of a diffusion angle of the diffusion sheet is in a range of 0.1 ° to 30 °.
[6]
The illuminating device according to any one of [1] to [5], wherein a diffusion angle of the diffusion sheet is periodically changed in a specific direction within the surface of the diffusion sheet.
[7]
The illumination according to any one of [1] to [6], wherein the diffusion angle changes concentrically around an intersection of a perpendicular line dropped from the point light source to the diffusion sheet and the diffusion sheet. apparatus.
[8]
The said diffusion angle is changing to the concentric polygonal shape centering | focusing on the intersection of the perpendicular drawn from the said point light source to the said diffusion sheet, and the said diffusion sheet, It is any one of said [1] thru | or [6]. Lighting device.
[9]
[1] to [8], wherein the ratio of the total luminous flux of the illuminating device in which the diffusion sheet is arranged on the light output side of the point light source is 90% or more with respect to the total luminous flux value of the light directly emitted from the point light source. The lighting device according to any one of the above.
[10]
In the light distribution characteristic diagram,
For the maximum luminous intensity value in the range where the absolute value A of the angle is 0 ° or more and less than 40 °,
The lighting device according to any one of [1] to [9], wherein a ratio of luminous intensity when the absolute value A of the angle is in a range of 40 ° to 60 ° is in a range of 10% to 70%.
[11]
A plurality of the point light sources are arranged on the substrate,
The lighting device according to any one of [1] to [10], wherein a distance between the substrate surface and the diffusion sheet is smaller than a shortest arrangement interval between the plurality of point light sources.
[12]
The illumination device according to any one of [1] to [11], further including a reflection member and / or a light shielding member.
[13]
The lighting device according to [12], wherein the reflecting member is installed on the substrate surface.
[14]
The lighting device according to any one of [1] to [13], wherein the lighting device is disposed so as to irradiate a floor from a ceiling.
[15]
The illuminating device according to any one of [1] to [13], wherein the illuminating device is attached to an exterior of a vehicle and arranged so that light is emitted to the periphery of the vehicle.

  According to the present invention, there is provided an illuminating device that is used for the purpose of illuminating an object that has a small number of parts, can avoid an increase in size, can suppress a decrease in total luminous flux, and can eliminate front glare and oblique glare. it can.

(A), (b) It is a schematic perspective view which shows the specific structure of the principal part of the illuminating device of this embodiment. (C) It is a schematic front view which shows the specific structure of the principal part of the illuminating device of said (b). (A)-(c) It is a schematic sectional drawing which shows the specific structure of the principal part of the illuminating device of this embodiment. (A) The specific example of the light distribution characteristic of the illuminating device in 1st Embodiment is shown. (B) The specific example of the light distribution characteristic of the illuminating device in 2nd Embodiment is shown. It is explanatory drawing which shows the light emission component of the perpendicular direction radiate | emitted from the irradiation apparatus of this embodiment, and the light emission component of a wide angle direction. It is explanatory drawing which shows the definition of the diffusion angle of a diffusion sheet. It is explanatory drawing which shows the definition of the diffusion angle in a diffusion sheet. (A)-(f) The example of the diffusion angle distribution in the diffusion sheet which comprises the illuminating device of this embodiment is shown. It is a typical schematic perspective view of an example of the illuminating device which comprises the diffusion sheet from which the diffusion angle is changing concentrically. It is explanatory drawing of the direction where a diffusion angle changes in the diffusion sheet from which the diffusion angle is changing concentrically. (A), (b) About the diffusion angle distribution in the surface of a diffusion sheet, it is the schematic diagram which showed that a diffusion angle became so low that a color became white, and a diffusion angle became high, so that it became black. It is a typical schematic perspective view of an example of the illuminating device which comprises the diffusion sheet which the diffusion angle is changing to concentric square shape. It is explanatory drawing of the direction where a diffusion angle changes in the diffusion sheet from which a diffusion angle changes to concentric square shape. (A)-(e) It is the schematic diagram which showed that a diffusion angle became so low that a color became white, and a diffusion angle became so high that it became black about the diffusion angle distribution in the diffusion sheet surface. (A), (b) The state of the change of the diffusion angle in the predetermined direction of the diffusion sheet in which a diffusion angle changes to a concentric polygonal shape is shown. (A)-(f) The example of light source arrangement | positioning in the case of comprising a some point light source is shown. It is a schematic sectional drawing which shows the specific structure of the principal part of the illuminating device of this embodiment. It is a schematic perspective view of an example of a light shielding member (louver).

DESCRIPTION OF EMBODIMENTS Hereinafter, modes for carrying out the present invention (hereinafter referred to as the present embodiment) will be described with reference to the drawings.
In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.
Further, in each drawing, unless otherwise specified, the positional relationship such as up, down, left, and right is based on the positional relationship shown in the drawing, and the dimensional ratio in the drawing is not limited to the illustrated ratio.
Further, in this specification, the term with “abbreviation” indicates the meaning of the term excluding the “abbreviation” within the technical common sense of those skilled in the art. Shall also be included.

[Lighting device]
The illuminating device of this embodiment comprises a point light source and a diffusion sheet provided in the direction of light emission from the point light source.
The diffusion sheet has a light incident surface on which light from the point light source is incident and a light exit surface from which light from the point light source is emitted.
The diffusion sheet has a concavo-convex structure formed on the light incident surface and / or the light exit surface.
The diffusion sheet has a diffusion angle of light emitted from a surface opposite to the incident surface of the diffusion sheet when light is incident in a direction perpendicular to the surface on which the uneven structure of the diffusion sheet is formed. In the plane of the diffusion sheet, the diffusion angle increases according to the distance from the minimum position in one change pattern of the diffusion angle.
Therefore, when a single light source is used, it increases in accordance with the distance from the position where the diffusion angle is minimum in the plane of the diffusion sheet corresponding to the light source. In the surface of the diffusion sheet corresponding to the above, it is assumed that the diffusion angle is increased according to the distance from the position where the diffusion angle is minimum, that is, the position where the diffusion angle takes the minimum value in one change pattern.
Here, the minimum value is the minimum value in the change pattern of the diffusion angle of the diffusion sheet corresponding to one light source.
Further, when the illumination device of the present embodiment includes a plurality of light sources, the change in the diffusion angle in the diffusion sheet surface can be designed to be a periodic change, and the cycle is also arbitrarily designed. Can do.
Note that the term “periodic” as used herein refers to a constant change pattern of the diffusion angle in a specific direction within the diffusion sheet surface, for example, a combination of monotonous decrease and monotonous increase, curvilinear, linear, or stepwise decrease. This means that the combination of and increase is repeated a plurality of times, and this is not the case when the diffusion angle changes randomly within ± 10% of the average value.
The point light source may be a single light source or a plurality of light sources. In particular, in an illuminating device having a plurality of point light sources, it is preferable that the period in which the diffusion angle in the plane of the diffusion sheet changes corresponds to the arrangement interval of the point light sources, and the period and the arrangement of the point light sources More preferably, the interval is equal. This makes it easy to control the light distribution of the lighting device and suppress glare in the intended direction.

  In the illumination device of the present embodiment, the horizontal axis is the absolute value A of the angle formed by the normal direction of the light exit surface of the diffusion sheet and the direction of the light beam emitted from the light exit surface of the diffusion sheet, and from the light exit surface of the diffusion sheet When the luminous intensity B of the emitted light is taken as the vertical axis and a light distribution characteristic diagram is created, the relationship between the absolute value A of the angle and the luminous intensity B is as follows in the first embodiment and the second embodiment. Divided.

Although details will be described later, the illumination device of the first embodiment uses the absolute value A of the angle formed by the normal direction of the light exit surface of the diffusion sheet and the direction of the light emitted from the light exit surface as the horizontal axis, In the light distribution characteristic diagram in which the vertical axis is the luminous intensity B of light emitted from the diffusion sheet which is the light emitting surface of the illumination apparatus, the luminous intensity B decreases as the absolute value A of the angle increases.
Although the details will be described later, the illumination device of the second embodiment uses the absolute value A of the angle formed by the normal direction of the light exit surface of the diffusion sheet and the direction of the light emitted from the light exit surface as the horizontal axis. In the light distribution characteristic diagram in which the vertical axis is the luminous intensity B of the light emitted from the diffusion sheet that is the light emitting surface of the illumination device, the first angular region in which the luminous intensity B increases as the absolute value A of the angle increases. And the second angle region in which the light intensity B decreases as the absolute value A of the angle increases, and the difference between the minimum light intensity and the maximum light intensity in the first angle region in which the light intensity B increases Is an illuminating device that is 5% or less of the luminous intensity in the vertical direction of the light exit surface of the diffusion sheet.

  Although details will be described later, in this specification, the diffusion angle of emitted light when light is incident in a direction perpendicular to the surface on which the uneven structure of the diffusion sheet is formed is the transmitted light intensity is the peak intensity. An angle that is twice as large as an angle (half-value angle) that attenuates to half (full width half maximum, hereinafter sometimes referred to as FWHM).

(Point light source)
Although it does not specifically limit as a point light source which comprises the illuminating device of this embodiment, For example, an incandescent lamp, a mini krypton bulb, a xenon lamp, a metal halide lamp, an LED light source, etc. are mentioned.
The LED light source may be an LED chip alone or a single light source such as a COB type (Chip On Board type) LED, or may be a plurality of light sources such that a plurality of LED chips are mounted. The LED light source has a strong directivity, and it is easy to control the light distribution characteristics by combining with a lens, a reflecting member, or a diffusion sheet, and therefore, it is preferable as a light source constituting the illumination device of the present embodiment.

(Diffusion sheet)
The diffusion sheet has a function of diffusing and emitting light emitted from the point light source in the illumination device of the present embodiment.
Hereinafter, the diffusion sheet will be described with reference to the drawings.
Fig.1 (a) (b) is a schematic perspective view of the principal part of an example of the illuminating device of this embodiment. FIG.1 (c) is a schematic front view which shows the specific structure of the principal part of the illuminating device of FIG.1 (b).
As shown in FIGS. 1A to 1C, the point light source 11 is two-dimensionally formed in an inner region of a frame 13 as a substrate having a bottom surrounded by a wall portion having a predetermined height. Has been placed.
The diffusion sheet 12 is provided in a direction in which light is emitted from the point light source 11.
The optical axis of the light emitted from the point light source to the diffusion sheet 12 and the normal direction of the diffusion sheet are not necessarily parallel, and may be attached obliquely. However, usually, the optical axis and the normal direction are substantially parallel.

As for the diffusion sheet 12 which comprises the illuminating device of this embodiment, the uneven structure is formed in the light-incidence surface of the light from the said point light source 11, and / or the light-emitting surface.
When a conventionally known diffusion plate containing a diffusing agent is used, the total luminous flux of the light emitted from the point light source 11 and transmitted through the diffusion plate may be greatly reduced. In the diffusion sheet 12 that constitutes the illumination device, light is diffused by the concavo-convex structure, so that the light use efficiency can be increased and the decrease in the total luminous flux of transmitted light can be effectively suppressed.
In the diffusion sheet 12, the concavo-convex structure may be formed on at least one of a light incident surface on which light from the point light source 11 enters and a light exit surface on which light from the point light source 11 exits, It may be formed on both the light incident surface and the light exit surface.
In particular, it is arranged so that the surface on which the concavo-convex structure is formed becomes a light exit surface, and by retroreflection, the light emitted from the point light source 11 in an oblique direction is raised in the front direction, and the transmitted image of the point light source 11 is blurred. It is preferable to make it faint from the viewpoint of obtaining the effect of suppressing glare.

2A to 2C are schematic cross-sectional views of the main part of an example of the illumination device of the present embodiment.
In these, as shown in FIG. 1, the point light source 11 is disposed on the bottom of a frame 13 having walls on all sides, and the diffusion sheet 12 faces the light exit surface side of the point light source 11, that is, the light source 11 described above. It is provided in the position to do.
In the example of FIG. 2A, the surface side on which the uneven structure of the diffusion sheet 12 is formed is the light exit surface of the diffusion sheet 12, and in the example of FIG. 2B, the uneven structure is formed. The light surface side is the light incident surface of the diffusion sheet 12. The surface on which the uneven structure is not formed, that is, the light exit surface, may be subjected to a predetermined antireflection treatment or the like within a range that does not impair the desired light distribution characteristics in order to suppress glare.
Further, as shown in FIG. 2C, the concavo-convex structure may be formed on both sides.

By forming many concavo-convex structures on the surface of the diffusion sheet 12, the diffusibility of light from the diffusion sheet can be controlled as will be described later.
The concavo-convex structure of the diffusion sheet 12 is a structure in which a large number of protrusions are provided on the surface, and the shape of the protrusions is approximately conical, approximately spherical, approximately elliptical, approximately lenticular lens, approximately free. Any protrusion may be used, and the protrusions may be arranged regularly or irregularly.
Moreover, between each projection part which comprises an uneven structure may be connected with the continuous curved surface.
Furthermore, a pseudo-random structure in which irregular irregularities are connected by a continuous curved surface can be preferably used.
The concavo-convex structure can be formed using a speckle pattern by interference exposure, and can be made into a fine three-dimensional structure by this method.
A three-dimensional structure formed using a speckle pattern by interference exposure can be a fine uneven structure of 20 μm or less, which was difficult by machining.
In particular, the method of forming a concavo-convex structure using a speckle pattern by interference exposure is a manufacturing method suitable for manufacturing diffusion sheets having different diffusion angles in a predetermined region within the diffusion sheet surface.
In addition, according to the method of forming a concavo-convex structure using a speckle pattern by interference exposure, an isotropic shape such as a microlens or an anisotropic shape such as a lenticular lens can be easily formed. This is a suitable method for forming the concavo-convex structure.

The shape of the concavo-convex structure provided on the light entrance surface and / or the light exit surface of the diffusion sheet 12 can be arbitrarily designed according to the width and shape of the target irradiation range, thereby widening the irradiation range. The height and shape can be controlled.
In an illuminating device that shows an isotropic light emission pattern without providing the diffusion sheet 12, when the diffusion sheet 12 is provided, in order to make the irradiation range circular or square, the concavo-convex structure is isotropic, for example, It is preferable to have an uneven shape such that a sphere is embedded on the surface, or an uneven shape such that an oblate or oblate is embedded on the surface in a random direction, and in order to make the irradiation range elliptical or rectangular It is preferable that the concavo-convex structure has an anisotropic shape, for example, an concavo-convex shape in which an oblate or oblate sphere is embedded in a specific angle range, a lenticular shape, or the like.
The pitch and height of the concavo-convex structure of the diffusion sheet 12 are preferably less than the resolution of the human eye, that is, 20 μm or less, because it becomes difficult to stand out, and as a result, the aesthetic appearance of the target irradiation device is not impaired.
In addition, the uneven structure is preferably an irregular uneven structure formed by a continuous curved surface from the viewpoint of suppressing moire, surface glare, and viewing angle dependency of luminance on the light emitting surface of the lighting device.

Specifically, the diffusion sheet having the concavo-convex structure formed on the light incident surface and / or the light outgoing surface can be produced as follows.
First, a sub-master type in which a speckle pattern is formed by preliminarily irradiating a photosensitive material or a photoresist with laser light through a lens, a diffusion plate, an aperture, a mask or the like by interference exposure.
A submaster mold having a desired concavo-convex structure is produced by adjusting the size, shape and direction of the speckle pattern by changing the distance and size between members constituting the laser irradiation system, and will be described later using this submaster mold. Thus, a metal master mold is prepared, and further, a diffusion sheet is manufactured using the metal master mold.

In general, the diffusion angle of light transmitted through the diffusion sheet depends on the average size and shape of the speckle pattern.
The higher the speckle pattern height and the narrower the pitch, that is, the higher the aspect ratio, the larger the diffusion angle.
The size of the speckle pattern can be measured by, for example, an SEM (scanning electron microscope) or an ultra-deep microscope.
Further, the unit structure constituting the concavo-convex structure of the diffusion sheet is not limited to an isotropic one, and an anisotropic one can be formed, and a concavo-convex structure in which isotropic and anisotropy are combined. You can also
If the speckle pattern is an ellipse with the horizontal axis as the major axis, anisotropic diffusivity is obtained, and the vertical diffusion angle is increased.
As described above, by using a speckle pattern formed by interference exposure, it is also possible to manufacture a sub-master type capable of manufacturing a diffusion sheet whose diffusion angle varies depending on the position.
The detailed manufacturing method of the submaster type is disclosed in Japanese Patent No. 3341519 and Japanese Patent No. 3390954.

As described above, a metal master mold to which the speckle pattern is transferred is manufactured by applying a metal to the sub master mold on which the speckle pattern is formed by interference exposure by a method such as electroforming.
Next, a photosensitive resin is applied onto a light-transmitting base material sheet, and ultraviolet rays are irradiated using the master mold, thereby transferring and forming a concavo-convex structure with a speckle pattern.
Ultraviolet rays are irradiated from the back surface of the substrate sheet having light transmittance, thereby forming a cured photosensitive resin layer having a concavo-convex structure transferred to the boundary surface between the substrate sheet and the master mold.
As the base sheet having light transmittance, a material that transmits ultraviolet rays can be used. For example, a glass sheet or a resin sheet made of polyester, polycarbonate, triacetyl cellulose, or the like is preferably used.
The diffusion angle of the diffusion sheet can be controlled by changing the pitch, height, and aspect ratio of the concavo-convex structure, but can also be controlled by changing the refractive index of the photosensitive resin layer that is cured by ultraviolet rays.

After obtaining the base material sheet having the concavo-convex structure as described above, the base material sheet is used for a predetermined support made of a light-transmitting material, using a predetermined adhesive material, or performing thermal transfer or the like. Depending on the situation, they may be bonded together.
As the support, for example, glass, polyethylene terephthalate, polymethyl methacrylate, polycarbonate, or the like can be preferably used as long as it is a translucent material having a total light transmittance of 70% or more as defined in JIS K7361-1.
The diffusion sheet can also be manufactured by placing the above-described master mold in a predetermined molding machine and using this molding machine to perform injection molding with a transparent resin such as polymethyl methacrylate, polycarbonate, polystyrene, or cycloolefin polymer. it can. According to this injection molding method, a bonding step to a support is not required, the transfer rate of the concavo-convex structure is high, and the strength of the molded product is high.

(Optical characteristics of lighting device)
The diffusion sheet constituting the illuminating device of the present embodiment has a diffusion angle of one in the plane of the diffusion sheet when light is incident in a direction perpendicular to the surface of the diffusion sheet on which the concavo-convex structure is formed. It is characterized in that it increases in accordance with the distance from the minimum position in one change pattern.
Therefore, when a single light source is used, the diffusion angle increases in accordance with the distance from the position where the diffusion angle is minimum in the plane of the diffusion sheet corresponding to the light source. Corresponding to the light source, the diffusion angle increases in accordance with the distance from the position where the diffusion angle is minimum, that is, the position where the minimum value in the diffusion angle change pattern is obtained, in the diffusion sheet surface. Specifically, as shown in FIGS. 7A, 7 </ b> B, and 7 </ b> D, in addition to the change pattern in which the diffusion angle monotonously increases according to the distance, FIGS. 7C, 7 </ b> E, and 7 </ b> F are used. As shown in FIG. 5, it is assumed that a change pattern in which the diffusion angle is constant in the short section but increases in the long section is included. Here, the long section refers to a section corresponding to half of the cycle, and the short section refers to a section shorter than that.
In either case of a single light source or a plurality of light sources, the intersection of the perpendiculars drawn from the light source to the diffusion sheet and the position where the diffusion angle shows the minimum value (the position showing the minimum value in the change pattern of the diffusion angle) are , Do not have to match exactly.
When a plurality of light sources are used, the change in the diffusion angle can be designed as a periodic change in a specific direction.
“Periodic change in a specific direction” refers to a specific direction in a diffusion sheet surface, for example, when a line connecting positions corresponding to a plurality of point light sources is a specific direction, according to the position along the specific direction. That is, the diffusion angle of the diffusion sheet is changed, and the change of the diffusion angle is repeated as a cycle.
A specific example will be described. For example, first, when focusing on the first light source, the diffusion angle of the diffusion sheet near the light source (perpendicular direction) is the smallest, and the diffusion angle increases with increasing distance from the light source. After the diffusion angle becomes maximum at a predetermined position along the line, the diffusion angle becomes smaller as the second light source is approached from there, and the diffusion angle becomes near the second light source (vertical direction). A configuration example in which the cycle of minimizing is repeated is given. Here, near the light source (in the vertical direction) means that the distance between the position where the diffusion angle shows the minimum value and the position directly under the light source is within 5% of the light source interval.
Note that “the diffusion angle changes periodically” in the diffusion sheet constituting the illumination device of the present embodiment is not limited to the above specific example.
In the plane of the diffusion sheet, the diffusion angle is increased according to the distance from the position where the diffusion angle is minimum in one change pattern of the diffusion angle. While sufficient illuminance in the irradiation direction can be secured, glare in a specific direction can be suppressed.
Conventionally, a diffusion plate containing a diffusion agent inside is used, and the concentration of the diffusion agent is changed depending on the position of the diffusion plate, or a diffusion sheet having a uniform diffusion direction in a plane is partially laminated. As a result, the light diffusion angle is distributed. However, when such a diffusion plate is used, there is a problem that the total luminous flux is greatly reduced. In addition, since it is difficult to smoothly change the diffusion angle in the surface, the design property when the light exit surface of the lighting device is directly viewed is deteriorated, or the light distribution characteristic design of the lighting device is limited. There is also a problem. In the illuminating device of this embodiment, since the diffuser plate as described above is not used, it is possible to effectively prevent a decrease in total luminous flux and a decrease in designability and to have a high degree of freedom in designing light distribution characteristics. ing.

Further, in the illumination device of the present embodiment, the absolute value A of the angle formed by the normal direction of the light exit surface of the diffusion sheet and the direction of the light beam emitted from the light exit surface, and the luminous intensity B emitted from the diffusion sheet, Has a predetermined relationship.
First, as the illumination device according to the first embodiment, the horizontal axis represents the absolute value A of the angle formed between the normal direction of the light exit surface of the diffusion sheet and the direction of the light beam emitted from the light exit surface. When a light distribution characteristic diagram is created with the luminous intensity B of the light emitted from the vertical axis as the vertical axis, it is assumed that there is a diffusion sheet in which the luminous intensity B decreases as the absolute value A of the angle increases.
In the lighting device of this embodiment, when measuring the light distribution characteristic and creating the light distribution characteristic diagram, the diffusion sheet is rotated by rotating around the rotation axis in the light exit surface of the lighting device to be measured. Measured by changing the angle formed between the normal direction of the light exit surface and the direction of the light beam emitted from the light exit surface and entering the illuminometer. At this time, the rotation axis and the direction in which the light exit surface of the illumination device is rotated are selected according to the shape of the light exit surface of the illumination device to be measured.
For example, when the shape of the light exit surface is a square, a line segment passing through the center of the square and parallel to any of the four sides is measured as the rotation axis. When the shape of the light exit surface is a circle, measurement is performed using an arbitrary diameter of the circle as a rotation axis. When the shape of the light exit surface is a rectangle, the line segment passing through the center of the rectangle and parallel to the short side is the rotation axis 1, and the line segment passing through the center of the rectangle and parallel to the long side Two sets are measured using the minute as the rotation axis 2.
When the light exit surface is elliptical, two sets are measured with the major axis of the ellipse as the rotation axis 1 and the minor axis as the rotation axis 2.
In measuring the light distribution characteristics, it is generally necessary to measure a rotation angle range of −90 to 0 ° and a range of 0 to 90 °, but the light distribution characteristics are symmetric with respect to the rotation axis. In the case of an illuminating device having a, it is only necessary to measure one side.
3A, the absolute value A (0 degrees) of the angle formed by the normal direction of the light exit surface of the diffusion sheet constituting the illumination device in the first embodiment and the direction of the light beam emitted from the light exit surface. A light distribution characteristic diagram in which the horizontal axis is (-90 degrees) and the luminous intensity B of light emitted from the diffusion sheet is the vertical axis, is shown in an orthogonal coordinate system.
As shown in FIG. 3A, when the absolute value A of the angle increases, that is, when the illuminating device is viewed directly from an oblique direction, the luminous intensity is decreased, so that glare is effectively suppressed. .
Further, as the distance between the surface provided with the point light source and the diffusion sheet becomes smaller, it becomes easier to realize the light distribution characteristic diagram in the illumination device of the first embodiment.

Next, in the illumination device of the second embodiment, the horizontal axis represents the absolute value A of the angle formed between the normal direction of the light exit surface of the diffusion sheet and the direction of the light beam emitted from the light exit surface, and the diffusion When creating a light distribution characteristic diagram with the luminous intensity B of the light emitted from the sheet as the vertical axis, the first angular area where the luminous intensity B increases as the absolute value A of the angle increases, and the absolute value of the angle A second angle region in which the light intensity B decreases as the value A increases, and the difference between the minimum light intensity and the maximum light intensity in the first angle region in which the light intensity B increases is the diffusion sheet. It is assumed that it has a diffusion sheet that is 5% or less of the luminous intensity in the normal direction of the light exit surface.
In particular, the low angle side and the high angle side of the first angle region where the luminous intensity B increases as the absolute value A of the angle between the normal direction of the light exit surface of the diffusion sheet and the direction of the light beam emitted from the light exit surface increases. It is preferable to have the 2nd angle area | region where the said luminous intensity B decreases as the absolute value A of the said angle increases on both angle sides.
In FIG.3 (b), the absolute value A (0 degree ~) of the angle which the normal line direction of the light emission surface of the said diffusion sheet which comprises the illuminating device in 2nd Embodiment, and the direction of the light ray radiate | emitted from the said light emission surface make. An example of the light distribution characteristic diagram with the horizontal axis of 90 degrees) and the luminous intensity B of the light emitted from the diffusion sheet as the vertical axis is shown in an orthogonal coordinate system.
In the case where there are a plurality of angle areas where the luminous intensity increases (the first angular area) in the light distribution characteristic diagram, the angular area where the difference between the minimum luminous intensity and the maximum luminous intensity is maximum is within the first angular area. It is sufficient to satisfy the above condition that the difference between the minimum luminous intensity and the maximum luminous intensity is 5% or less of the luminous intensity in the normal direction of the light exit surface of the diffusion sheet.
Thereby, the diagonal glare resulting from the light which radiate | emits the wide angle side rather than the perpendicular direction of the said illuminating device can be suppressed effectively.

  Further, the illumination device of the present embodiment emits light directly from the point light source when the predetermined optical sheet (including a diffusion sheet and a reflection sheet) is not disposed on the light exit surface side from the point light source. The ratio of the total luminous flux in the illuminating device having a diffusion sheet on the light exit surface side of the point light source is preferably 90% or more, and preferably 95% or more with respect to the total luminous flux value of the emitted light. Thereby, a glare can be suppressed, maintaining the illumination intensity of the target irradiation surface.

The irradiation apparatus of the present embodiment uses the absolute value A of the angle formed by the normal direction of the light exit surface of the diffusion sheet and the direction of the light beam emitted from the light exit surface as the horizontal axis, and the light emitted from the diffusion sheet. In the light distribution characteristic diagram with the luminous intensity B as the vertical axis, the luminous intensity in the range where the absolute value A of the angle is 40 ° to 60 ° with respect to the maximum luminous intensity value in the range where the absolute value A of the angle is 0 ° or more and less than 40 °. Is preferably in the range of 10% to 70%. In particular, it is preferably in the range of 20% to 60%, more preferably in the range of 30% to 60%.
FIG. 4 is an explanatory diagram showing the light output component in the vertical direction and the light output component in the wide-angle direction that are emitted from the irradiation apparatus of the present embodiment.
By defining the relationship between the absolute value A of the angle and the luminous intensity B as described above, glare from an angle at which the light exit surface easily enters the field of view when the light exit surface of the illuminating device is directly viewed is effective. The light emission component in the vertical direction and the light emission component in the wide angle direction are well balanced, and a wide range from the vertical direction to the wide angle direction can be irradiated.

In the illuminating device of this embodiment, it is preferable that the diffusion angle in the area | region in which the uneven structure of the said diffusion sheet was formed is the range of 0.1 degrees-100 degrees.
In particular, in order to control the light distribution while suppressing the decrease in the total luminous flux, it is preferably in the range of 0.1 ° to 90 °, more preferably in the range of 0.1 ° to 80 °.
By controlling the diffusing angle of the diffusing sheet within the above range, the 1/2 beam angle of the light emitted from the illumination device is controlled, and the amount of light emitted to a wide angle outside the target irradiation surface is reduced to suppress oblique glare. can do.
In this specification, the ½ beam angle means that the rotation direction of the light emitting surface of the illuminating device is rotated to both sides around the rotation axis so that the normal direction of the light emitting surface of the diffusion sheet and the light emitting surface When the angle between the direction of the light entering the light meter and entering the illuminometer is changed, and the axis where the luminous intensity from the illuminating device is maximized is taken as the maximum luminous intensity axis, the luminous intensity from the illuminating device is ½ of the maximum luminous intensity. The angle formed by the direction.
Specifically, the direction in which the luminous intensity from the illumination device is ½ of the maximum luminous intensity is a direction of 0 to 90 ° with respect to the maximum luminous intensity axis when having the light distribution characteristic as shown in FIG. In each range of 0 to −90 °, there are one direction, that is, two directions in total. In this case, the angle formed by these two directions is a 1/2 beam angle.
On the other hand, when having the light distribution characteristics as shown in FIG. 3B, the direction in which the luminous intensity from the lighting device is ½ of the maximum luminous intensity is a direction of 0 to 90 ° with respect to the maximum luminous intensity axis, There may be two or more directions in each of the directions of 0 to -90 °. In this case, the absolute value of the angle is the smallest in each of the direction of 0 to 90 ° and the direction of 0 to −90 ° among the directions in which the luminous intensity from the lighting device is ½ of the maximum luminous intensity. The angle formed by the directions becomes a 1/2 beam angle.
Further, in the lighting device of the present embodiment, when measuring the 1/2 beam angle, the rotation axis and the direction in which the light emitting surface of the lighting device is rotated are selected according to the shape of the light emitting surface of the lighting device to be measured. To do.
For example, when the shape of the light exit surface is a square, a line segment passing through the center of the square and parallel to any of the four sides is measured as the rotation axis. When the shape of the light exit surface is a circle, measurement is performed using an arbitrary diameter of the circle as a rotation axis. When the shape of the light exit surface is a rectangle, the line segment passing through the center of the rectangle and parallel to the short side is the rotation axis 1, and the line segment passing through the center of the rectangle and parallel to the long side Two sets are measured using the minute as the rotation axis 2.
When the light exit surface is elliptical, two sets are measured with the major axis of the ellipse as the rotation axis 1 and the minor axis as the rotation axis 2.
In measuring the 1/2 beam angle, it is generally necessary to measure the rotation angle in the range of -90 to 0 ° and in the range of 0 to 90 °. In the case of an illuminating device having light characteristics, an angle in a direction in which the absolute value of the angle with the maximum luminous intensity axis is the smallest in a direction that is ½ of the maximum luminous intensity in a range of 0 to 90 ° is obtained. , Double that.

Next, the diffusion angle of the diffusion sheet constituting the lighting device of the present embodiment will be described in detail.
FIG. 5 is an explanatory diagram of the definition of the diffusion angle in the diffusion sheet constituting the lighting device of the present embodiment.
As described above, the diffusion angle is twice the angle at which the transmitted light intensity (the vertical axis in FIG. 5 indicates the relative value of the light intensity) attenuates to half the peak intensity (half-value angle). It refers to the angle (Full Width Half Maximum: FWHM).
The diffusion angle is determined by using, for example, a goniophotometer (manufactured by Nippon Denshoku Industries Co., Ltd., GC 5000L), with the surface on which the uneven structure of the diffusion sheet is formed (hereinafter referred to as an uneven surface) as a light incident surface. It is obtained by measuring the angular distribution of transmitted light intensity with respect to light incident in the normal direction of the surface.
Here, the normal direction of the diffusion sheet refers to a direction perpendicular to the uneven surface of the diffusion sheet, as shown in FIG.
In FIG. 6, among the light in various directions that pass through the diffusion sheet, the light that is incident in the normal direction of the concavo-convex surface passes through the light from the intersection with the diffusion sheet in the vertical direction (reference angle 0 °). Highest strength. The angle twice when the transmitted light intensity is half of the highest transmitted light intensity (peak intensity) (angle from the reference angle) is the diffusion angle (FWHM).
It is preferable that the diffusion angle in the diffusion sheet constituting the illuminating device of the present embodiment is minimized at the intersection of the perpendicular line drawn from the point light source to the diffusion sheet and the diffusion sheet.
Thereby, in the lighting device of the present embodiment, the luminous intensity of the light that irradiates the vertical direction from the point light source is maximized, for example, when the lighting device is installed on a ceiling surface or the like, while illuminating the intended surface, the perpendicular line It is easy to suppress oblique glare when the direction is used as a reference.
Note that, in the illumination device of the present embodiment, as described above, the intersection of the perpendicular line dropped from the light source to the diffusion sheet, and the position where the diffusion angle shows the minimum value (the position showing the minimum value in the change pattern of the diffusion angle) However, in the case of a single light source, it may be shifted by about 1 to 2 mm, and in the case of a plurality of light sources, it may be shifted within about 5% of the distance between the light sources.

The difference between the minimum diffusion angle and the maximum diffusion angle in the diffusion sheet constituting the lighting device of the present embodiment is preferably in the range of 30 ° to 90 °.
In particular, in order to suppress glare in a lighting device using a light source with a small light emitting area and strong directivity, the difference between the minimum diffusion angle and the maximum diffusion angle is within a range of 40 ° to 80 °. Preferably, it is in the range of 40 ° to 70 °.
By making the difference between the minimum diffusion angle and the maximum diffusion angle of the diffusion sheet within the above range, an effective glare suppression effect can be achieved, and particularly when the illuminance distribution on the irradiated surface is uneven and the illuminance difference becomes large. In the case where a thin lighting device having a short distance between the light source and the diffusion sheet is manufactured, a high effect can be obtained.

In the illumination device of the present embodiment, it is preferable that the minimum diffusion angle of the diffusion sheet is in the range of 0.1 ° to 30 °.
In particular, in order to suppress glare in the front direction and glare in the oblique direction at the same time, the minimum diffusion angle of the diffusion sheet is preferably in the range of 1 ° to 25 °, and is preferably in the range of 1 ° to 15 °. It is more preferable.
This also has the effect of suppressing the decrease in total luminous flux.

  As a method of changing the diffusion angle depending on the position in the surface of the diffusion sheet, control of the spraying amount by the sand blast method, control of the coating amount by a method of forming a concavo-convex structure by applying resin beads on the sheet surface, bead diameter The diffusion angle may be controlled by adjusting the angle, etc. In particular, a method using a speckle pattern by interference exposure is preferable because it becomes easy to set the strict diffusion angle as described above.

As the diffusion sheet, there are an isotropic diffusion sheet in which the light emitted in any direction on the surface of the diffusion sheet has an equal diffusion angle, and an anisotropic diffusion sheet having a diffusion angle different depending on the light emission direction. Any of them can be used.
In particular, an anisotropic diffusion sheet is preferably used in order to realize an asymmetric light distribution characteristic depending on the application.
For the isotropic diffusion sheet, based on the result of measuring the diffusion angle by the above-described measurement method, for example, 60 °, 60 ° × 60 °, etc., and the anisotropic diffusion sheet has the maximum diffusion angle. And a diffusion angle in two directions, ie, a direction orthogonal to the direction in which the diffusion angle is maximum, are measured and expressed as, for example, 60 ° × 10 °, 90 ° × 30 °, or the like.

The diffusion angle of the diffusion sheet in the illuminating device of the present embodiment is continuously changed in order to eliminate the cut-off line on the irradiation surface or to prevent the deterioration of the design when the light exit surface of the illuminating device is directly viewed. Also good.
A case where the diffusion angle of the diffusion sheet continuously changes and a case where the diffusion angle changes discontinuously will be described. Examples of the diffusion angle distribution of the diffusion sheet are shown in FIGS.
7A to 7F, the position in a specific direction in the diffusion sheet surface is the horizontal axis, the diffusion angle (FWHM) is the vertical axis, and the position corresponding to the vertical direction of the light exit surface when viewed from the light source. The diffusion angle distribution for one period centered is shown.
In the above, “one cycle” includes both a single light source and a plurality of light sources. When attention is paid to a specific light source, it is one of the change patterns of the diffusion angle of the diffusion sheet facing the light source. Shall say one.
Here, when the diffusion angle continuously changes, the diffusion angle is linear as shown in FIG. 7A, the diffusion angle is curved as shown in FIG. 7B, and FIG. As shown in c), (d), and (f), any of those in which the diffusion angle changes in a mixed form of a straight line and a curve may be used.
The case where the diffusion angle changes discontinuously includes a case where the diffusion angle in the diffusion sheet changes stepwise with a predetermined position range as a partition, as shown in FIG. 7 (e).

  Further, as shown in FIG. 7 (e), by changing the diffusion angle in the plane of the diffusion sheet discontinuously, it is possible to selectively irradiate a specific part or to glare in a specific direction. Can be selectively suppressed.

FIG. 8 is a schematic schematic perspective view of an example of a lighting device including a diffusion sheet whose diffusion angle changes continuously or discontinuously.
In FIG. 8, a state in which the diffusion angle is changed in a concentric manner centering on the intersection of the perpendicular line dropped from each of the light sources arranged in a square lattice shape to the diffusion sheet and the diffusion sheet is schematically illustrated. Represents.
FIG. 9 is an explanatory diagram of the direction in which the diffusion angle changes.
As indicated by the arrows in FIG. 9, the diffusion angle changes from the center of the concentric circle toward the end of the circle. That is, the diffusion angles are distributed concentrically from the center of the circle. That is, the diffusion angles are equal on the circles passing through the tips of the arrows shown in FIG.
FIG. 10 is a schematic diagram showing the diffusion angle distribution in the surface of the diffusion sheet, in which the diffusion angle decreases as the color becomes white, and the diffusion angle increases as the color becomes black.
FIG. 10A shows a front view of the diffusion sheet when the light sources are arranged in a square lattice pattern as shown in FIGS.
FIG. 10B shows a front view of the diffusion sheet when the light sources are arranged in a staggered pattern.
By diffusing the diffusion angle concentrically in the diffusion sheet, the diffusibility from the center of the diffusion sheet to all directions can be made uniform, so that the light output control in the illumination device of this embodiment is facilitated.
In particular, when the point light sources are arranged in a square lattice pattern or a staggered lattice pattern, the concentric distribution of the diffusion angles can be brought into a preferable state. Further, depending on the arrangement interval of the point light sources, a concentric elliptical diffusion angle distribution can be formed.

FIG. 11 is a schematic schematic perspective view of another example of a lighting device including a diffusion sheet whose diffusion angle changes continuously or discontinuously.
In FIG. 11, the diffusion angle changes continuously or discontinuously in a concentric quadrangular shape centering on the intersection of the perpendicular line drawn from the light sources arranged in a square lattice shape to the diffusion sheet and the diffusion sheet. The state is shown schematically.
In FIG. 11, a diffusion sheet whose diffusion angle continuously or discontinuously changes in a concentric quadrangular shape is shown, but the diffusion sheet constituting the illumination device of the present embodiment is limited to this example. Instead, a diffusion sheet whose diffusion angle continuously or discontinuously changes in a triangular shape to an arbitrary polygonal shape can be applied.
FIG. 12 is an explanatory diagram of the direction in which the diffusion angle changes.
As shown in FIG. 12, the diffusion angle changes continuously or discontinuously from the center of the concentric rectangle toward the end of the rectangle. That is, the diffusion angles are distributed in a concentric quadrilateral shape, and as shown by the arrows in FIG. 12, the diffusion angles are equal on a quadrilateral passing through the end of the arrow from the center of the concentric quadrangle.
FIGS. 13A to 13E are schematic views showing that the diffusion angle distribution in the surface of the diffusion sheet is such that the diffusion angle becomes smaller as the color becomes white and the diffusion angle becomes larger as the color becomes black.
FIG. 13A shows a front view of the diffusion sheet when the light sources are arranged in a square lattice pattern as shown in FIGS.
FIG. 13B shows a front view of the diffusion sheet when the light sources are arranged in a staggered pattern.
FIG.13 (c) shows the front view of a diffusion sheet when the light source is arranged in the shape of a square lattice using the diffusion sheet whose diffusion angle changes continuously or discontinuously in a concentric rhombus shape.
FIG.13 (d) shows the front view of a diffusion sheet when the light source is arranged in zigzag form using the diffusion sheet which a diffusion angle changes to a concentric rhombus shape continuously or discontinuously.
FIG.13 (e) shows the front view of a diffusion sheet when the light source is arranged in a zigzag form using the diffusion sheet whose diffusion angle changes continuously or discontinuously in a concentric hexagonal shape.
In FIG. 12, in the direction x of a → b and the direction z of a → c, where the intersection of the perpendicular line drawn from the three point light sources (a, b, c) to the diffusion sheet and the diffusion sheet are the base points, respectively. FIGS. 14A and 14B show the distribution of the diffusion angle.
14A and 14B, the horizontal axis indicates the relative distance in the x direction and the z direction, and the vertical axis indicates the diffusion angle.
Since the diffusion sheet has a concentric quadrangular diffusion angle distribution as shown in FIG. 12, adjacent point light sources (a and b, a and c) as shown in FIGS. ), The shape of the diffusion angle distribution with the relative distance as the horizontal axis is the same in the x and z directions.
Similarly, in the direction of the arrow y in FIG. 12, the shape of the diffusion angle distribution is the same as the shape of the diffusion angle distribution in the x direction and the z direction.
As shown in FIGS. 11 to 14 above, the diffusion angle changes to a concentric quadrangular shape (or other concentric polygonal shape) centering on the intersection of the perpendicular line from the point light source to the diffusion sheet and the diffusion sheet. By arranging the light sources in a square lattice pattern or a staggered lattice pattern, it is preferable that the difference in appearance depending on the direction can be reduced when the light emitting surface of the illumination device of this embodiment is directly viewed.

In the diffusion sheet constituting the illumination device of the present embodiment, the total light transmittance as defined in JIS K7361-1 is preferably 70% or more when light is incident from the surface on which the concavo-convex structure is formed, and more preferably. Is 80% or more, more preferably 90% or more.
By setting the total light transmittance in the diffusion sheet to 70% or more, the light emitted from the light source can be effectively used, which is preferable from the viewpoint of power saving.
The thickness of the diffusion sheet is preferably 0.1 mm to 5 mm from the viewpoints of handleability and cost.

A preferred configuration example of the illumination device of the present embodiment will be described with reference to FIGS. 15 and 16.
FIGS. 15A to 15F are schematic front views in which a plurality of point light sources 11 are arranged on the substrate 14.
The point light source 11 has a concentric shape as shown in FIGS. 15A and 15B, a lattice shape as shown in FIGS. 15C and 15D, and a linear shape as shown in FIGS. 15E and 15F. It may be arranged in accordance with the application such as the irradiation range and the installation location.
The point light source 11 has a concentric shape as shown in FIGS. 15A and 15B, a lattice shape as shown in FIGS. 15C and 15D, a straight shape as shown in FIG. It may be arranged stepwise as in f), and can be designed according to the application such as the irradiation range and installation location.

FIG. 16 is a schematic cross-sectional view of an example of an illumination device including a plurality of point light sources 11.
In the illuminating device of FIG. 16, a plurality of point light sources 11 are arranged on a substrate, and a diffusion sheet 12 is provided in the light output direction of the light sources.
In FIG. 16, p represents the arrangement interval of the point light sources 11, and h represents the distance between the substrate surface on which the point light sources 11 are arranged and the diffusion sheet 12.
In the illumination device of the present embodiment, it is preferable that the separation distance h between the surface of the substrate 14 and the diffusion sheet 12 is smaller than the shortest arrangement interval p between the plurality of point light sources.
When the angle formed by the perpendicular line and the straight line connecting the other adjacent point light source and the intersection point at the intersection point of the perpendicular line dropped from one point light source 11 to the diffusion sheet 12 is θ as described above. As described above, the distance h between the substrate surface and the diffusion sheet (denoted as the distance h between the substrate and the diffusion sheet in FIG. 16) is smaller than the shortest arrangement interval (p in FIG. 16) between the plurality of point light sources. Thus, the angle θ can be made larger than 45 degrees.
In general, the amount of light emitted from the point light source 11 decreases as the light emission angle with respect to the perpendicular direction becomes larger. Therefore, by increasing the angle θ, the perpendicular dropped from the point light source 11 to the diffusion sheet 12. The light emission component from the point light source adjacent to the point light source at the intersection of the diffusion sheet 12 and the glare can be reduced.
Note that it is also possible to control the light distribution characteristics by changing the separation distance h within the range where the oblique glare does not appear, and to adjust the irradiation range and illuminance on the irradiation surface.

The illuminating device of this embodiment is good also as a structure combined with at least any one of the predetermined | prescribed reflecting member and light-shielding member other than the point light source 11 and the diffusion sheet 12. FIG.
For example, by using the frame 13 shown in FIG. 1 as a reflecting member, the light emitted from the light source in the lighting device and retroreflected by the diffusion sheet 12 is reflected by the reflecting member and is emitted to the front surface of the light source again. The reduction of the total luminous flux can be suppressed by the recycling effect.
Further, for example, combining with a light shielding member such as a louver or a baffle is preferable because not only the light emission in a specific direction is limited to suppress glare but also the 1/2 beam angle can be further narrowed.
The illuminating device of this embodiment can also be made into the form with which the reflection member was installed in the board | substrate surface which arrange | positions the said point light source. As the reflection member, a metal sheet or a white diffuse reflection sheet is preferably used.
The lighting device shown in FIG. 1 (a) is called a base light and is mainly installed on the ceiling. In the conventional base light, glare is very high by providing a reflecting member around the light source. Although there has been a problem of becoming stronger, glare can be prevented by using the diffusion sheet of the present embodiment without using a shielding member such as a louver.
The lighting device shown in FIG. 1 (b) is called a downlight, and has a form in which holes are mainly formed in the ceiling and installed therein. Conventionally known downlights have a structure in which the periphery of the light source is surrounded by a concave reflector in order to control the light distribution characteristics and suppress glare. However, the height (depth) is inevitably due to the use of such a structure. The degree of freedom during construction is reduced. Furthermore, it is necessary to shield light with a baffle or the like, but when the diffusion sheet of this embodiment is used, glare and light distribution characteristics can be controlled without using a reflector or baffle, and the number of parts is reduced. Reduction and thickness reduction can be achieved.
In addition, the lighting device of the present embodiment is used for a device that is arranged so as to irradiate the floor from the ceiling, such as the above-described base light, downlight, and ceiling light inside the vehicle.
Moreover, the illumination device of the present embodiment can be used for the purpose of irradiating the surroundings of the vehicle as a headlight or a rear lamp of the vehicle.
When used as a lighting device for a vehicle, in addition to a method of disposing a diffusion sheet constituting the lighting device of the present embodiment described above inside a light or lamp, the present embodiment described above is provided on the surface of a lamp cover or an inner lens. There is also a method of providing an uneven shape similar to the uneven shape of the diffusion sheet constituting the illumination device. In this case, an uneven shape similar to the uneven shape of the diffusion sheet described above is formed on the surface of the mold for molding the lamp cover and the inner lens.
In the case of a lamp cover, the uneven shape is preferably formed on the inner surface of the cover component in order to prevent functional deterioration due to dirt. In the case of an inner lens, the concavo-convex structure may be shaped on either the inner surface or the outer surface.

  Examples of the present invention and comparative examples will be specifically described below.

[Diffusion sheet]
The speckle pattern was controlled by interference exposure, and laser light was irradiated to the photoresist through a lens, a diffuser plate, an aperture, and a mask to produce a sub-master type in which various uneven structures were formed on the surface. Further, a master mold was produced from this sub-master mold through an electroforming process.
Next, using the master mold, a concavo-convex structure made of an ultraviolet curable resin was formed on a 188 μm thick polyester resin film to prepare a diffusion sheet.

[Angle distribution of transmitted light intensity of diffusion sheet]
As shown in FIG. 16, the surface on which the concavo-convex structure of the diffusion sheet produced as described above was formed was used as the light exit surface of the lighting device.
The angular distribution of the transmitted light intensity with respect to the light incident in the normal direction of the surface on which the uneven structure of the diffusion sheet was formed was measured with a goniophotometer (GC 5000L, manufactured by Nippon Denshoku Industries Co., Ltd.).
Moreover, in order to obtain the diffusion angle for one period in the surface of the diffusion sheet, the diffusion angle at each measurement point was measured while shifting the position.

  About Example 1- Example 4 and Comparative Example 1- Comparative Example 5, it measured and evaluated using the illuminating device A described below.

[Lighting device A]
A white polyester resin reflective sheet (Furukawa Electric Co., Ltd., trade name: MCPET) is pasted on the aluminum die-cast substrate surface, and a wall surface made of a reflective sheet having a predetermined height is formed on the periphery of the substrate surface. The frame shape shown in FIG.
As the point light source 11, 196 LED light sources were arranged in a square lattice pattern at intervals of 22.5 mm on the substrate surface.
Further, as shown in FIG. 16, a diffusing sheet described later is disposed at a predetermined distance h from the substrate surface, and the overall illumination device is about 30 cm × 30 cm.

[Light distribution characteristics measurement]
(1/2 beam angle)
The light distribution characteristics were measured using a lux high tester (manufactured by Hioki Electric Co., Ltd.) as an illuminance meter.
The absolute value of the angle formed between the normal direction of the light emitting surface of the lighting device and the direction of the light beam emitted from the light emitting surface of the lighting device is as follows with respect to the center position of the light emitting surface of the lighting device. Set by rotating.
Specifically, the illuminance meter is arranged with a horizontal distance d = 4000 mm apart from the center position of the light exit surface of the illumination device to be measured, and the illumination device is rotated horizontally every 5 ° while moving the light exit surface. The illuminance value E measured in the range where the horizontal rotation angle γ is −90 ° to 90 ° with the vertical direction being 0 ° is converted to luminous intensity I by the following (Equation 1), and the light distribution characteristic of the lighting device is calculated. Obtained.
I = E · d ² (Formula 1)
Here, an angle that is twice the absolute value of the angle between the normal direction of the light exit surface of the illumination device and the direction in which the luminous intensity is ½ of the luminous intensity in the normal direction is defined as a ½ beam angle. .
The 1/2 beam angle was measured while rotating the illuminating device every 1 ° so that the illuminance value in the normal direction of the light emitting surface of the illuminating device was halved.
In this case, when the light distribution characteristic and the 1/2 beam angle are measured, the shape of the light exit surface of the illumination device A is a square, and thus is a line segment passing through the center of the square and parallel to any of the four sides. A straight line was measured as the rotation axis.
(Total luminous flux)
Further, based on the light distribution characteristics, the total luminous flux φ is calculated by the following (Equation 2) according to the “spherical band coefficient method”, and in the illumination device, the optical sheet is not disposed on the light exit surface side from the light source. Evaluation was made as a relative value when the total luminous flux was 100.
Z (r) in the following (Formula 2) is a spherical zone coefficient, and is a value unrelated to the luminous intensity.
I (r) is the luminous intensity when the illumination device (light source) is set at the rotation angle r.
φ = ΣZ (r) · I (r) (Formula 2)

[Glare evaluation]
Glare was evaluated while rotating the lighting device in the same manner as the light distribution characteristic measurement.
The front glare looks directly at the lighting device from a distance of 4000 mm in the vertical direction (0 °) of the light emitting surface of the lighting device, and the oblique glare is a distance of 4000 mm in the diagonal direction of the light emitting surface (azimuth angle of 30 ° to 60 °). The lighting device was directly viewed and evaluated visually.
◎: Not uncomfortable (withstands direct view)
○: Slightly uncomfortable (LED bright spots are slightly blurred)
×: Uncomfortable (LED bright spots are conspicuous and cannot withstand direct viewing)

〔Comprehensive judgment〕
The evaluation results of total luminous flux, 1/2 beam angle, front glare and oblique glare were used as judgment factors, and comprehensive judgment was made according to the following criteria.
(Judgment element)
Total luminous flux (relative value): less than 90
1/2 beam angle: 100 ° or more
Glare evaluation: Front glare or diagonal glare
(Criteria)
A determination: None of the above determination elements apply.
B determination: Only one of the above determination elements is applicable.
C determination: Two or more of the above determination elements are applicable.

[Example 1]
In the illuminating device of Example 1, the minimum diffusion angle of the diffusion sheet is 1 degree and the maximum diffusion angle is 60 degrees, and the diffusion angle is continuous as shown in FIG. 7B for each position corresponding to each point light source. It was changing.
Here, the distance h of the diffusion sheet from the substrate surface was set to 15 mm.
In the illuminating device of Example 1, the luminous intensity decreased as the absolute value of the angle increased in the light distribution characteristic diagram in which the vertical direction of the light exit surface was 0 degree.
The evaluation results of the 1/2 beam angle, total luminous flux, and glare of Example 1 are shown in Table 1 below.
In Example 1, it can be seen that oblique glare can be suppressed while suppressing a decrease in total luminous flux as compared with the case where no diffusion sheet is provided, and it has practically good characteristics as a lighting device. It was.

[Example 2]
In the lighting device of Example 2, the minimum diffusion angle of the diffusion sheet is 1 degree and the maximum diffusion angle is 60 degrees, and the diffusion angle is continuous as shown in FIG. 7B for each position corresponding to each point light source. It was changing.
The distance h of the diffusion sheet from the substrate surface was adjusted, and the light incident angle from the adjacent light source was changed at a position on the diffusion sheet viewed perpendicularly from the light source to control the light distribution characteristics in the lighting device.
In this example, the distance h from the substrate surface to the diffusion sheet was set to 10 mm.
In the light distribution characteristic diagram in which the vertical direction of the light exit surface is set to 0 degree, the lighting apparatus of Example 2 includes, in order from the low angle side, a second angle region in which the light intensity decreases as the absolute value of the angle increases, The minimum luminous intensity in the first angle area having the first angle area where the luminous intensity increases as the absolute value increases and the second angular area where the luminous intensity decreases as the absolute value of the angle increases. The difference between the maximum luminous intensity and the maximum luminous intensity was 1% of the luminous intensity in the vertical direction of the light exit surface of the diffusion sheet.
The evaluation results of the 1/2 beam angle, total luminous flux, and glare of Example 2 are shown in Table 1 below.
In Example 2, it can be seen that oblique glare can be suppressed while suppressing a decrease in the total luminous flux, compared with the case where no diffusion sheet is used, and it has practically good characteristics as a lighting device. It was.

Example 3
In the illuminating device of Example 3, the diffusion sheet has a minimum diffusion angle of 1 degree and a maximum diffusion angle of 55 degrees, and the diffusion angle is continuous as shown in FIG. 7B for each position corresponding to each point light source. It was changing.
Here, the distance h of the diffusion sheet from the substrate surface was set to 15 mm.
In the illuminating device of Example 3, the luminous intensity decreased as the absolute value of the angle increased in the light distribution characteristic diagram in which the vertical direction of the light exit surface was 0 degree.
The evaluation results of 1/2 beam angle, total luminous flux and glare of Example 3 are shown in Table 1 below.
In Example 3, as compared with the case where a diffusion sheet is not used, it is found that oblique glare can be suppressed while suppressing the decrease in total luminous flux, and it has practically good characteristics as a lighting device. It was.

Example 4
In the illumination device of Example 4, the diffusion sheet has a minimum diffusion angle of 15 degrees and a maximum diffusion angle of 55 degrees, and the diffusion angle is continuous as shown in FIG. 7B for each position corresponding to each point light source. It was changing.
The distance h of the diffusion sheet from the substrate surface was adjusted, and the light incident angle from the adjacent light source was changed at a position on the diffusion sheet viewed perpendicularly from the light source to control the light distribution characteristics in the lighting device.
In this example, the distance h from the substrate surface to the diffusion sheet was set to 25 mm.
In the light distribution characteristic diagram in which the vertical direction of the light exit surface is 0 degree, the illumination device of Example 4 includes, in order from the low angle side, a second angle region in which the light intensity decreases as the absolute value of the angle increases, The minimum luminous intensity in the first angle area having the first angle area where the luminous intensity increases as the absolute value increases and the second angular area where the luminous intensity decreases as the absolute value of the angle increases. And the maximum luminous intensity was 0.9% of the luminous intensity in the vertical direction of the light exit surface of the diffusion sheet.
The evaluation results of the 1/2 beam angle, total luminous flux, and glare of Example 4 are shown in Table 1 below.
In Example 4, it can be seen that oblique glare can be suppressed while suppressing a decrease in total luminous flux as compared with the case where a diffusion sheet is not used, and it has practically good characteristics as a lighting device. It was.

[Comparative Example 1]
In the lighting device of Comparative Example 1, no diffusion sheet was disposed. The other configuration is the same as that of the first embodiment.
The evaluation results of 1/2 beam angle, total luminous flux and glare in Comparative Example 1 are shown in Table 2 below.
In Comparative Example 1, it was found that the front glare and the oblique glare were strongly felt, and the lighting device did not have practically good characteristics.

[Comparative Example 2]
In the illuminating device of Comparative Example 2, louvers having a lattice structure with an interval equal to the arrangement interval of the light sources were arranged on the substrate.
Further, no diffusion sheet was disposed.
Other than that, the illuminating device was configured in the same manner as in Example 1.
FIG. 17 shows the structure of the louver used in Comparative Example 2.
Here, the louver intervals x and y were made equal to the LED light source arrangement interval, and the louver height l was 15 mm.
The louver material used was the same as the reflective sheet attached to the substrate surface.
The evaluation results of 1/2 beam angle, total luminous flux and glare in Comparative Example 2 are shown in Table 2 below.
In Comparative Example 2, since the louver physically blocks the outgoing light in the oblique direction, the oblique glare was satisfactorily suppressed. However, the glare in the angular range that is not shielded by the louver, particularly the front glare, was felt strongly, and as an illumination device Turned out to be undesirable.

[Comparative Example 3]
In the lighting device of Comparative Example 3, the diffusion sheet was changed to a diffusion plate (a diffusion plate having a thickness of 1.5 mm and containing 13,000 ppm of silicone fine particles having a particle size of 2 μm and a true specific gravity of 1.35). Other than that, the illuminating device was configured in the same manner as in Example 1.
Here, the distance h = 15 mm from the substrate surface to the diffusion plate.
The evaluation results of 1/2 beam angle, total luminous flux and glare in Comparative Example 3 are shown in Table 2 below.
In Comparative Example 3, front glare / diagonal glare was suppressed satisfactorily, but the total luminous flux was reduced by about 12% compared to the case where no optical sheet was disposed, which proved unfavorable as a lighting device. .

[Comparative Example 4]
In the illumination device of Comparative Example 4, the diffusion sheet has a minimum diffusion angle of 1 degree and a maximum diffusion angle of 60 degrees, and the diffusion angle continuously changes as shown in FIG.
Here, the distance h from the substrate surface to the diffusion sheet was set to 25 mm.
In the lighting device of Comparative Example 4, the light distribution characteristic diagram in which the vertical direction of the light exit surface is 0 degree, in order from the low angle side, the second angle region in which the light intensity decreases as the absolute value of the angle increases, The minimum luminous intensity in the first angle area having the first angle area where the luminous intensity increases as the absolute value increases and the second angular area where the luminous intensity decreases as the absolute value of the angle increases. And the maximum luminous intensity was 13% of the luminous intensity in the vertical direction of the light exit surface of the diffusion sheet.
The evaluation results of 1/2 beam angle, total luminous flux and glare of Comparative Example 4 are shown in Table 2 below.
In Comparative Example 4, the front glare was suppressed satisfactorily, but the oblique glare was strongly observed, indicating that the lighting device is not preferable.

[Comparative Example 5]
In the lighting device of Comparative Example 5, the diffusion sheet has a minimum diffusion angle of 1 degree and a maximum diffusion angle of 30 degrees, and the diffusion angle continuously changes as shown in FIG.
Here, the distance h from the substrate surface to the diffusion sheet was set to 25 mm.
In the light distribution characteristic diagram in which the vertical direction of the light exit surface is 0 degree, the illumination device of Comparative Example 5 has, in order from the low angle side, a second angle region in which the light intensity decreases as the absolute value of the angle increases, The minimum luminous intensity in the first angle area having the first angle area where the luminous intensity increases as the absolute value increases and the second angular area where the luminous intensity decreases as the absolute value of the angle increases. And the maximum luminous intensity was 13% of the luminous intensity in the vertical direction of the light exit surface of the diffusion sheet.
The evaluation results of 1/2 beam angle, total luminous flux and glare of Comparative Example 5 are shown in Table 2 below.
In Comparative Example 5, the front glare was suppressed satisfactorily, but the oblique glare was strongly observed, and it was found that the lighting device is not preferable.

  About Example 5-Example 7 and Comparative Example 6, it measured and evaluated using the illuminating device B described below.

[Lighting device B]
A reflective sheet made of white polyester resin (trade name MCPET manufactured by Furukawa Electric Co., Ltd.) is pasted on the substrate surface made of aluminum die-casting, and a wall surface made of a reflective sheet having a predetermined height is formed on the periphery of the substrate surface. The frame shape shown in FIG.
About the point light source 11, as shown in FIG.1 (c), six LED light sources were arrange | positioned at the said substrate surface at the interval of 17 mm at hexagonal shape.
Furthermore, in Examples 5 to 7 to be described later, a diffusion sheet to be described later is arranged at a predetermined distance h from the substrate surface.

[Light distribution characteristics measurement]
(1/2 beam angle)
The illuminometers were arranged with a horizontal distance d = 1000 mm apart from the center position of the light exit surface of the lighting device to be measured. Other conditions were measured by the same method as in the case of the lighting device A.

(Total luminous flux)
Further, based on the light distribution characteristics, the total luminous flux φ is calculated by the following (Equation 2) according to the “spherical band coefficient method”, and in the illumination device, the optical sheet is not disposed on the light exit surface side from the light source. Evaluation was made as a relative value when the total luminous flux was 100.
Z (r) in the following (Formula 2) is a spherical zone coefficient, and is a value unrelated to the luminous intensity.
I (r) is the luminous intensity when the illumination device (light source) is set at the rotation angle r.
φ = ΣZ (r) · I (r) (Formula 2)
The calculation method used was the same as that for the lighting device A.

(Glare evaluation)
Glare looked directly at the lighting device from a position at a distance of 1000 mm from the light emitting surface of the lighting device B. Other conditions were evaluated by the same method as in the case of the lighting device A.

Example 5
In the lighting device of Example 5, the minimum diffusion angle of the diffusion sheet is 2 degrees and the maximum diffusion angle is 42 degrees, and the diffusion angle is continuously as shown in FIG. 7B for each position corresponding to the light source. Assume that it is changing.
The distance h of the diffusion sheet from the substrate surface was adjusted, and the light incident angle was changed from the adjacent light source at a position on the diffusion sheet as viewed perpendicularly from the light source, thereby controlling the light distribution characteristics in the lighting device.
In this example, the distance h from the substrate surface to the diffusion sheet was set to 10 mm.
In the illuminating device of Example 5, the luminous intensity decreased as the absolute value of the angle increased in the light distribution characteristic diagram in which the vertical direction of the light exit surface was 0 degree.
The evaluation results of the 1/2 beam angle and the total luminous flux of Example 5 are shown in Table 3 below.
In the fifth embodiment, front glare and oblique glare can be suppressed while reducing the total luminous flux, and the 1/2 beam angle can be reduced to 60 °. It was found that it has practically good characteristics.

Example 6
In the illuminating device of Example 6, the diffusion sheet has a minimum diffusion angle of 1 degree and a maximum diffusion angle of 60 degrees, and the diffusion angle is continuously as shown in FIG. 7B for each position corresponding to the light source. Assume that it is changing.
The distance h of the diffusion sheet from the substrate surface was adjusted, and the light incident angle from the adjacent light source was changed at a position on the diffusion sheet viewed perpendicularly from the light source to control the light distribution characteristics in the lighting device.
In this example, the distance h from the substrate surface to the diffusion sheet was set to 10 mm.
In the illuminating device of Example 6, in the light distribution characteristic diagram in which the vertical direction of the light exit surface was 0 degree, the light intensity decreased as the absolute value of the angle increased.
The evaluation results of the 1/2 beam angle and the total luminous flux of Example 6 are shown in Table 3 below.
In the sixth embodiment, front glare and oblique glare can be suppressed while reducing the total luminous flux, and the 1/2 beam angle can be reduced to 52 °. It was found that it has practically good characteristics.

Example 7
In the illumination device of Example 7, the minimum diffusion angle of the diffusion sheet is 15 degrees and the maximum diffusion angle is 40 degrees, and the diffusion angle is continuously as shown in FIG. 7B for each position corresponding to the light source. Assume that it is changing.
The distance h of the diffusion sheet from the substrate surface was adjusted, and the light incident angle from the adjacent light source was changed at a position on the diffusion sheet viewed perpendicularly from the light source to control the light distribution characteristics in the lighting device.
In this example, the distance h from the substrate surface to the diffusion sheet was set to 10 mm.
In the illuminating device of Example 7, the luminous intensity decreased as the absolute value of the angle increased in the light distribution characteristic diagram in which the vertical direction of the light exit surface was 0 degree.
The evaluation results of the 1/2 beam angle and the total luminous flux of Example 7 are shown in Table 3 below.
In Example 7, although the glare is slightly felt, the front glare can be suppressed while suppressing the decrease in the total luminous flux, and the 1/2 beam angle can be reduced to 69 °. It has been found that it has practical characteristics.

[Comparative Example 6]
In the illumination device of Comparative Example 6, no diffusion sheet was disposed. The other configuration was the same as that of Example 5 to configure the lighting device.
The evaluation results of the 1/2 beam angle and the total luminous flux in Comparative Example 6 are shown in Table 3 below.
In Comparative Example 6, the front glare and the oblique glare are felt strongly, and the 1/2 beam angle is as wide as 120 °, so that it does not have practically good characteristics as an illumination device such as a downlight. I understood.

  The present application includes a Japanese patent application filed with the Japan Patent Office on December 10, 2009 (Japanese Patent Application No. 2009-280597), and a Japanese patent application filed with the Japan Patent Office on January 20, 2010 (Japanese Patent Application No. 2010-010334), Japanese patent application filed with the Japan Patent Office on April 7, 2010 (Japanese Patent Application No. 2010-088826), Japanese Patent Application filed with the Japan Patent Office on October 29, 2010 (Japanese Patent Application No. 2010-244605), the contents of which are incorporated herein by reference.

  The illuminating device of the present invention has industrial applicability as various illuminating devices used for the purpose of illuminating an object such as a base light, a downlight, a ceiling light, and an in-vehicle illumination in a house or office.

11 Point light source 12 Diffusion sheet 13 Frame 14 Substrate

Claims (15)

A point light source,
A diffusion sheet provided in the direction of light emission from the point light source;
Comprising
The diffusion sheet has a light incident surface on which light from the point light source is incident and a light exit surface from which light from the point light source is emitted, and an uneven structure is formed on the light incident surface and / or the light exit surface. And
In the diffusion sheet, when light is incident in a direction perpendicular to the surface of the diffusion sheet on which the concavo-convex structure is formed, the diffusion angle of the emitted light is one of the diffusion angles in the plane of the diffusion sheet. It has the characteristic that it increases according to the distance from the minimum position in one change pattern,
A light distribution with the horizontal axis representing the absolute value A of the angle between the normal direction of the light exit surface of the diffusion sheet and the direction of the light beam emitted from the light exit surface, and the light intensity B of the light exiting from the diffusion sheet as the vertical axis In the characteristic diagram, as the absolute value A of the angle increases, the luminous intensity B decreases ,
The illumination device in which the ratio of the total luminous flux of the illuminating device in which the diffusion sheet is arranged on the light output side of the point light source is 90% or more with respect to the total luminous flux value of the light directly emitted from the point light source . A point light source,
A diffusion sheet provided in the direction of light emission from the point light source;
Comprising
The diffusion sheet has a light incident surface on which light from the point light source is incident and a light exit surface from which light from the point light source is emitted, and an uneven structure is formed on the light incident surface and / or the light output surface. And
In the diffusion sheet, when light is incident in a direction perpendicular to the surface of the diffusion sheet on which the concavo-convex structure is formed, the diffusion angle of the emitted light is one of the diffusion angles in the plane of the diffusion sheet. It has the characteristic that it increases according to the distance from the minimum position in one change pattern,
A light distribution with the horizontal axis representing the absolute value A of the angle between the normal direction of the light exit surface of the diffusion sheet and the direction of the light beam emitted from the light exit surface, and the light intensity B of the light exiting from the diffusion sheet as the vertical axis In the characteristic diagram,
A first angle region in which the luminous intensity B increases as the absolute value A of the angle increases;
A second angle region in which the luminous intensity B decreases as the absolute value A of the angle increases;
Have
The illuminating device in which the difference between the minimum luminous intensity and the maximum luminous intensity in the first angle region in which the luminous intensity B increases is 5% or less of the luminous intensity in the vertical direction of the light exit surface of the diffusion sheet. The diffusion angle is minimum in the vicinity of the intersection of the diffusion sheet and a perpendicular drawn from the point light source to the diffusion sheet,
The illumination device according to claim 1 or 2, wherein a difference between a minimum value and a maximum value of the diffusion angle in the surface of the diffusion sheet is in a range of 30 ° to 90 °.   The illumination device according to any one of claims 1 to 3, wherein a diffusion angle of the diffusion sheet is in a range of 0.1 ° to 100 °.   The illumination device according to any one of claims 1 to 4, wherein a minimum value of a diffusion angle of the diffusion sheet is in a range of 0.1 ° to 30 °.   The illuminating device according to any one of claims 1 to 5, wherein a diffusion angle of the diffusion sheet periodically changes in a specific direction within a plane of the diffusion sheet.   The illuminating device according to any one of claims 1 to 6, wherein the diffusion angle changes concentrically around an intersection of a perpendicular drawn from the point light source to the diffusion sheet and the diffusion sheet. .   The illuminating device according to any one of claims 1 to 6, wherein the diffusion angle is changed to a concentric polygonal shape centering on an intersection of a perpendicular drawn from the point light source to the diffusion sheet and the diffusion sheet. . The total light flux value of the light emitted directly from the point light source, any one of claims 2 to 8 ratio of total flux of the lighting device a diffusion sheet disposed on the light outgoing side of the point light source is 90% or more The lighting device according to one item. In the light distribution characteristic diagram,
For the maximum luminous intensity value in the range where the absolute value A of the angle is 0 ° or more and less than 40 °,
The lighting device according to any one of claims 1 to 9, wherein a ratio of luminous intensity in a range where the absolute value A of the angle is 40 ° to 60 ° is in a range of 10% to 70%. A plurality of the point light sources are arranged on the substrate,
The illuminating device according to any one of claims 1 to 10, wherein a distance between the substrate surface and the diffusion sheet is smaller than a shortest arrangement interval between the plurality of point light sources.   The lighting device according to any one of claims 1 to 11, further comprising a reflecting member and / or a light shielding member.   The lighting device according to claim 12, wherein the reflecting member is disposed on the substrate surface.   The lighting device according to any one of claims 1 to 13, wherein the lighting device is arranged so as to irradiate a floor from a ceiling.   The illuminating device according to any one of claims 1 to 13, wherein the illuminating device is attached to an exterior of a vehicle and arranged so that light is emitted to the periphery of the vehicle.

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