JP2018073668A - Surface light source element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source element having a sheet-like light control member capable of obtaining high uniform luminance characteristics.SOLUTION: A surface light source element comprises: a plurality of punctiform light sources 1; and a light control member in which a plurality of lenses 21 are disposed at random, and the plurality of lenses 21 are constituted of a reference lens and a similar shape lens. The cross-sectional shape of the reference lens 21 in the X axis direction is composed of (2 N+1) different gradient regions Nto Nexpressed by D, H, X; the cross-sectional shape of the reference lens in the Y axis direction is composed of (2 N+1) different gradient regions Nto Nexpressed by D, H, Y; and the ratio of a largest value and a minimal value of the sum of the intensity of the outgoing radiation light the Z axis direction corresponding to three periods of the punctiform light source 1 adjacent in the X axis direction and the Y axis direction is 0.8 or more, where the length of the punctiform light source 1 in the X axis direction and the Y axis direction corresponding to one period is D,D, the distance between the punctiform light source 1 and the light control member is H, and the position coordinates in the X axis direction and the Y axis direction with the center position of the arbitrarily selected the punctiform light source 1 as the origin is defined as X and Y.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a surface light source element composed of a plurality of point light sources and a sheet-like light control member, and is particularly large in size, such as a lighting signage device and a liquid crystal display device that require high front luminance and luminance uniformity. The present invention relates to a direct-type surface light source element used in the above.

The performance required for the surface light source element of the direct type includes high front luminance, luminance uniformity, thinning, and low power consumption. Among them, the luminance uniformity is particularly important in the application of observing the irradiation surface of an image display device, an illumination signboard, etc., by eliminating the light / dark difference in the screen due to the light source image.
A general direct type surface light source element includes a light source, a reflection plate, a diffusion plate, and a diffusion sheet. A method of using a point light source such as a light emitting diode (LED) which consumes less power than a linear light source such as a fluorescent lamp and does not use mercury as a light source, and uses the LED as a surface light source element arranged in a plane. Has been proposed (Non-Patent Document 1). However, when the point light source is arranged in a plane, the light and dark difference due to the light source image is generated two-dimensionally. Furthermore, since the light emission of the LED is highly directional, it is possible to obtain higher luminance uniformity than using a linear light source. It becomes difficult. Various proposals have been made to solve this problem.

  For example, a method has been proposed in which the directivity of light emission is reduced by giving a unique shape to an LED package (Patent Document 1). However, the use of a package is not preferable because the thinning of the surface light source element is hindered.

  In addition, a method of providing a light guide unit to make the light emission of the LED light source uniform is also proposed. However, it is not preferable because the weight increase and productivity of the surface light source element are reduced (Patent Document 2).

  On the other hand, a method has also been proposed in which a pattern is provided on a diffusion plate in which fine particles for diffusing light are dispersed in accordance with the arrangement of LED light sources (Patent Document 3). However, since it requires precise alignment with the LED light source, it is not preferable because productivity decreases.

  Furthermore, a method of making the front luminance uniform using a macro lens obtained from the arrangement period of the LED light source and the distance from the LED light source to the diffusion plate has been proposed (Patent Document 4). However, if one type of microlens is regularly arranged in a plane with a short period, the emitted light is diffracted, and it is difficult to obtain high luminance uniformity.

JP 2005-340750 A JP 2005-327682 A JP 2005-38643 A International Publication No. 2008/029911

“Flat-Paneldisplay 2004 Practice”, Nikkei Business Publications, Japan, December 26, 2013, p. 170

  In the present invention, it is a surface light source element of a direct type, which does not hinder thinning, does not require strict alignment with an LED light source, does not change the optical design of the light control member with an increase in size, and is highly uniform. It is an object of the present invention to provide a surface light source element having a sheet-like light control member that can obtain excellent luminance characteristics.

A first aspect according to the present invention includes:
One of the normal lines of the XY plane parallel to the X axis and the Y axis orthogonal to the X axis is the Z axis direction, and at least a plurality of point light sources and one sheet or film A light control member,
The plurality of point light sources are periodically arranged in the X-axis and Y-axis directions in a virtual plane parallel to the XY plane, the light control member is parallel to the XY plane, and A plurality of lenses are randomly arranged on the surface of the point light source in the Z-axis direction, and the light control member mainly emits light, and the plurality of lenses includes at least one type of reference lens and its similar shape lens. Consists of
The reference lens is
Of the plurality of point light sources, the length D _X of one cycle of the X-axis _direction, the length of one period of the Y-axis direction D _Y,
When the center position of the arbitrarily selected point light source is the origin, the position coordinate in the X-axis direction is X, and the position coordinate in the Y-axis direction is Y,
In a virtual plane parallel to the XZ plane parallel to the X axis and the Z axis,
A function that represents the distance between the selected point light source and the light control member as H, and the intensity of the emitted light in the Z-axis direction of the exit surface at the position X of the light incident on the light control member from the selected point light source. Is fX (X),
g _X (X) = f _X (X−D _X ) + f _X (X) + f _X (X + D _X )
In the range of −D _X / 2 ≦ X ≦ D _X / 2,
In g _X (X) is the minimum value of _{g X (X) min} and the maximum value _g X _(X) ratio of _{max g X (X) min /} g X (X) max is 0.8 or more Yes,
The minimum value X _min of _{X is in} the range of −3.0D _X ≦ X _min ≦ −0.5D _X , and the maximum value X _{max of} X is in the range of 0.5D _X ≦ X _max ≦ 3.0D _X , (X _min and X _max are the coordinates of both ends where the value of f _X (X) is attenuated around the arbitrarily selected point light source where X = 0 and becomes substantially 0),
The cross-sectional shape of the reference lens in the X-axis direction is composed of (2N _X +1) different regions −N _{X to} N _X represented by the following formula,
δ _X = (X _max −X _min ) / (2N _X +1)
X _i = i × δ _X
α _Xi = tan ⁻¹ (X _i / H)
β _Xi = sin ⁻¹ {(1 / n) sin α _Xi }
γ _Xi = sin ⁻¹ {(1 / n _s ) sin α _Xi }
_{a Xi αf X (X + T} × tanγ Xi) × cosΦ Xi × cosβ Xi / {I i (α Xi) × cos (α Xi) × cos (Φ Xi -β Xi)}
Φ _Xi = tan ⁻¹ {(n × sin β _Xi ) / (n × cos β _Xi −1)}
N _X : natural number
i: integer from -N _X to N _X
n: Refractive index of the lens portion of the light control member
n _s : refractive index of the base material of the light control member
a _Xi : width of region i in the X-axis direction
Φ _Xi : Inclination with respect to the exit surface of region i
T: Thickness from the incident surface of the light control member to the bottom of the lens unit
I _i (α _Xi ): intensity of light emitted per unit angle in the direction of α _Xi along the X-axis direction from an arbitrarily selected point light source, and
Intensity of emitted light in the Z-axis direction of the exit surface at the position Y of light incident on the light control member from the selected point light source in a virtual plane parallel to the YZ plane parallel to the Y-axis and Z-axis Let f _Y (Y) be a function that represents
g _Y (Y) = f _Y (Y−D _Y ) + f _Y (Y) + f _Y (Y + D _Y )
In the range of −D _Y / 2 ≦ Y ≦ D _Y / 2,
In _{g Y (Y) g Y (} Y) is the minimum value _min and the ratio _g Y _(Y) and _g Y _{(X) max} is the maximum value min / g _{Y (Y) max} is 0.8 or more Yes,
Minimum value _{Y min} Y is in the range of _{-3.0D Y ≦ Y min ≦ -0.5D Y} , maximum value _{Y max} Y is in the range of 0.5 D _Y ≦ _{Y max} ≦ 3.0D _Y, (Y _min and Y _max are the coordinates of both ends where the value of f ₂ (Y) is attenuated around the arbitrarily selected point light source where Y = 0 and becomes substantially 0),
The surface light source element is characterized in that the cross-sectional shape of the reference lens in the Y-axis direction includes (2N _Y +1) different regions −N _{Y to} N _Y expressed by the following formula.
δ _Y = (Y _max −Y _min ) / (2N _Y +1)
Y _j = j × δ _Y
α _Yj = tan ⁻¹ (Y _j / H)
β _Yj = sin ⁻¹ {(1 / n) sin α _Yj }
γ _Yj = sin ⁻¹ {(1 / n _s ) sin α _Yj }
_{a Yj αf Y (Y j +} T × tanγ Yj) × cosΦ Yj × cosβ Yj / {I j (α Yj) × cos (α Yj) × cos (Φ Yj -β Yj)}
Φ _Yj = tan ⁻¹ {(n × sin β _Yj ) / (n × cos β _Yj −1)}
N _Y : Natural number
j: integer from -N _Y to N _Y
a _Yj : the width of the region j in the Y-axis direction
Φ _Yj : slope of region j with respect to the exit surface
I _j (α _Yj ) is the intensity of light emitted per unit angle in the direction of αY _j along the Y-axis direction from an arbitrarily selected point light source.

A second aspect of the present invention is the surface light source element of the first aspect,
Regions −N _{X to} N _X representing the cross-sectional shape in the X-axis direction of the reference lens are arranged in the order of the position coordinates of the X-axis,
And,
The surface light source element is characterized in that regions -N _{Y to} N _Y representing the cross-sectional shape of the reference lens in the Y-axis direction are arranged in the order of the position coordinates of the Y-axis.

A third aspect according to the present invention is the surface light source element according to the first or second aspect,
The cross-sectional shape of the reference lens in the X-axis direction is a shape that approximates the shape of at least one pair of two adjacent regions out of (2N _X +1) different regions with a curve,
And,
A surface light source characterized in that the cross-sectional shape of the reference lens in the Y-axis direction is a shape obtained by approximating the shape of at least one pair of two adjacent regions with a curve among (2N _Y +1) different regions of inclination. element.

The 4th aspect which concerns on this invention is a surface light source element of the said 1st-3rd aspect, Comprising:
In the XZ plane of the light control member, the ratio of the light emitted within an angle of 30 degrees with respect to the Z-axis direction is 50% or more of the light emitted in the Z-axis direction in the XZ plane,
And,
In the YZ plane of the light control member, the ratio of the light emitted within an angle of 30 degrees with respect to the Z-axis direction is 50% or more of the light emitted in the Z-axis direction of the YZ plane. A surface light source element.

A fifth aspect according to the present invention is the surface light source element according to the first to fourth aspects,
A surface obtained by dividing an area of a flat portion other than a plurality of lenses formed mainly on a light emitting side of the light control member by an area of the light control member is 1.0% or less. Light source element.

The effects of the present invention will be described in detail below.
In the present invention, the period of a plurality of point light sources, the distance from the light source to the light control member, the intensity per unit angle of the point light source, the substrate thickness of the light control member, and the substrate of the light control member The shape of at least one kind of reference lens is obtained from the refractive index and the refractive index of the lens of the light control member. And this invention provides the light control member which arrange | positioned the reference | standard lens and the similar shape lens which has a shape similar to the said reference | standard lens at random. The reference lens has a uniform property that similarly controls the direction in which the incident light is emitted at all points on the incident surface of the light control member. It is not necessary to align the position. Further, it is possible to obtain luminance uniformity by making the intensity distribution of the emitted light in the Z-axis direction constant. Furthermore, the combined functions of the light control member, such as brightness uniformity and brightness enhancement effect, make it possible to eliminate or reduce the use of other functional optical films, which is advantageous for productivity and thickness reduction. In addition, an image display device with high luminance and high luminance uniformity can be obtained by arranging a transmissive display device on the exit surface side of these surface light source elements.

  The surface light source element provided by the present invention is a surface light source element having an emission surface parallel to the XY plane, and the surface light source element includes a plurality of point light sources and a sheet-like light control member. And high luminance and luminance uniformity in the Z-axis direction can be obtained by the light control member.

  The light control member provided in the surface light source element provided by the present invention obtains luminance uniformity in the Z-axis direction by making the intensity distribution of the emitted light in the Z-axis direction substantially constant on the emission surface.

A first aspect according to the present invention includes:
By arranging the plurality of point light sources and the light control member in parallel, the distance from the point light source to the light control member becomes uniform, so that each point light source enters the light control member. The light intensity distribution is uniform. Furthermore, since the arrangement of the point light sources is periodic along the X-axis direction and the Y-axis direction, the entire intensity distribution of incident light is in the X-axis direction and the Y-axis direction, which are the arrangement directions of the point light sources. Therefore, it is easy to improve luminance uniformity.

Light from the plurality of point light sources is incident on the surface of the light control member on which light is mainly incident. The light control member has the length of one cycle along the X-axis direction of the plurality of point light sources as D _X , the center position of the arbitrarily selected point light source as the origin, and the position coordinates in the X-axis direction as X , A function representing the intensity of the outgoing light in the Z-axis direction of X on the outgoing surface of the light control member is defined as f _X (X),
When
In the range of −D _X / 2 ≦ X ≦ D _X / 2,
is the minimum value of _{g X (X) g X (} X) min and _g X (X) is the maximum value _g X _(X) ratio of _{max g} X of _{(X) min / g X (} X) max is It is 0.8 or more.

Further, the light control member is configured such that the length of one cycle along the Y-axis direction of the plurality of point light sources is D _Y , the center position of the arbitrarily selected point light source is the origin, and the position coordinates in the Y-axis direction Is Y, and a function representing the intensity of the emitted light in the Z-axis direction of Y on the exit surface of the light control member is f _Y (Y),
When
In the range of −D _Y / 2 ≦ Y ≦ D _Y / 2,
g _Y (Y) is the minimum value of _{g Y (Y) min} and _g Y is the maximum value of _{(Y) g Y (X)} max and the ratio _{g Y (Y) min / g} Y (Y) max is It is 0.8 or more.

  One period along the X-axis or Y-axis of the plurality of point light sources refers to a unit of arrangement of light sources arranged repeatedly in the X-axis direction or the Y-axis direction. The X-axis direction or the Y-axis The array of point light sources is reproduced by repeating this unit, including all elements relating to the intensity, relative position, and luminance uniformity of each light source along the direction. However, the arrangement in the X-axis direction and the arrangement in the Y-axis direction may be independent from each other.

The functions g _X (X) and g _Y (Y) are functions representing the sum of the intensity of emitted light in the Z-axis direction for three periods of adjacent point light sources in the X-axis direction and the Y-axis direction, respectively. In a configuration in which only the same type of point light sources are arranged at equal intervals, the sum is obtained for three adjacent point light sources. The range of −D _X / 2 ≦ X ≦ D _X / 2 and the range of −D _Y / 2 ≦ Y ≦ D _Y / 2 are the X-axis direction and Y-axis, respectively, with an arbitrarily selected point light source as the origin. By representing one period of the direction and realizing high luminance in the range of one period of the array of point light sources, it is possible to obtain luminance uniformity over the entire emission surface of the surface light source element.

Since the light intensity of the point light source is inversely proportional to the distance, the influence of the light from a distant light source is small. Therefore, by setting the functions g _X (X) and g _Y (Y) taking into consideration only the intensity of the emitted light from the adjacent point light sources having three cycles, the intensity of the emitted light in the Z-axis direction is reduced. It is possible to control and to obtain luminance uniformity in the Z-axis direction. g _X is the minimum of _{(X) g X (X)} min and the maximum value _{g X (X) max} and the ratio _{g X (X) min / g} X (X) max of 0.8 or more, and and _{g Y (Y) g Y (} Y) is the minimum value _min and a maximum value _{g Y (Y) max} ratio of _{g Y (Y) min / g} Y (Y) max of at least 0.8 As a result, the intensity distribution of the emitted light in the Z-axis direction at any position on the emission surface of the surface light source element becomes substantially constant, and luminance uniformity can be obtained.

f _X (X) and f _Y (Y) do not need to be line-symmetric with respect to the origin at the center position, and do not need to have the same distribution.

Furthermore, a method for calculating the shape of the reference lens for making the intensity distribution of the emitted light in the Z-axis direction substantially uniform has been found.
That is, in the present invention, the minimum value X _min of _{X is in} the range of −3.0D _X ≦ X _min ≦ −0.5D _X , and the maximum value X _max is 0.5D _X ≦ X _max ≦ 3.0D _X The cross-sectional shape of the reference lens in the X-axis direction is composed of (2N _X +1) different regions −N _{X to} N _X represented by the following formulas (3) to (9), and minimum value _{Y min} Y is in the range of _{-3.0D Y ≦ Y min ≦ -0.5D Y} , maximum value _{Y max} is in the range of 0.5 D _Y ≦ _{Y max} ≦ 3.0D _Y, the reference The cross-sectional shape of the lens in the Y-axis direction is characterized by comprising (2N _Y +1) different regions −N _{Y to} N _Y expressed by the following formulas (10) to (16).

N _X : natural number
i: integer from -N _X to N _X
n: Refractive index of the convex portion of the light control member
n _s : refractive index of the base material of the light control member
a _Xi : width of region i in the X-axis direction
Φ _Xi : Inclination with respect to the exit surface of region i
T: Thickness from the incident surface of the light control member to the bottom of the convex portion
I _i (a _Xi ): intensity of light emitted per unit angle in the direction of a _Xi along the X-axis direction from an arbitrarily selected point light source

N _Y : Natural number
j: integer from -N _Y to N _Y
a _Yj : the width of the region j in the Y-axis direction
Φ _Yj : slope of region j with respect to the exit surface
I _j (α _Yj): where the intensity of light emitted optionally terms like light source that was selected unit angle per the direction of the alpha _Yj along the Y-axis _{direction, α Xi, β Xi, γ} Xi, Φ Xi, Angles such as α _Yj , β _Yj , γ _Yj , and Φ _Yj all have absolute values of less than 90 °, and the clockwise angle with respect to the reference line is positive and the counterclockwise angle is negative.

First, equation (8) will be described with reference to FIG.
X _min and X _max are the coordinates of both ends when f _X (X) = 0 substantially when the position coordinates of the arbitrarily selected point light source are used as the origin. When X _{min to} X _max are equally divided by (2N _X +1), the width δ _{X of} each divided element is expressed by Expression (3). At this time, the center coordinate X _i of an arbitrary element is expressed by Expression (4). The incident angle α _Xi from the point light source at the position of X = 0 to the light control member of the coordinate X _i is expressed by the equation (5) with respect to the normal direction of the incident surface.

The light emitted from the point light source enters the light control member at X = X _i , is refracted at an angle γ _{Xi represented} by Expression (7) with respect to the normal direction, and travels into the light control member. When the bottom of the reference lens is reached, the light is refracted again and proceeds to the inside of the reference lens at an angle β _{Xi represented} by the equation (6). Note that the refractive index of the base material and the reference lens constituting the light control member may be the same. In this case, light is not refracted at the bottom of the reference lens, and γ _Xi = β _Xi . Of the light traveling inside the reference lens, only the light that has reached the inclined surface with the inclination Φ _Xi with respect to the emission surface represented by the equation (9) travels in the Z-axis direction.

The length of the slope of the region i occupied by the slope of the inclination Φ _Xi is b _Xi, and the length of projection from the slope of the region i in the direction perpendicular to the light ray direction in the reference lens is e _Xi , the X-axis direction And the angle ξ _Xi formed by the angle of the slope of the region i in the cross section parallel to the normal direction of the principal surface of the reference lens with respect to the angle perpendicular to the light ray direction in the reference lens is Φ _Xi −β _Xi So
It becomes.

In addition, when the length of the projection onto the plane parallel to the incident surface of the area i occupied by the slope of the angle Φ _Xi , that is, the width of the area i in the X-axis direction is a _Xi ,
It is.

From equation (17) and equation (18),
It becomes.
Here, when the width of the reference lens in the X-axis direction, that is, the sum of a _Xi is P _X , of the light that is incident on the base material of the light control member at the angle α _Xi and is directed to the reference lens, The ratio is e _Xi / (P _X × cos β _Xi ).

Here, the relationship between the incident angle to the light control member and the incident intensity will be described with reference to FIG. Considering the minute angle Δθ centering on the incident angle θ from the point light source to the light control member, when Δθ is sufficiently small, the equations (20), (21), and (22) are established.
Therefore,
That is, since V is proportional to 1 / cos ² θ, the intensity of incident light per unit area, that is, the illuminance, is I (θ) × cos, where I (θ) is the intensity of emitted light within Δθ from the light source. ² Proportional to θ.

On the other hand, as shown in FIG. 3, the angle Δα _Xi in which the light source at the coordinate X _i is viewed is proportional to cos α _Xi . Since the intensity of incident light per unit area is proportional to I (θ) × cos ² θ, the intensity of light per unit area and unit angle incident on coordinates X _i is proportional to I _X (α _Xi ) × cos α _Xi . To do. That is, the ratio of the intensity per unit angle of the light incident on the reference lens at the coordinate X _i with respect to the intensity per unit angle of the light incident on the reference lens at the point where X = 0 from the point light source is I _X (Α _Xi ) × cos α _Xi .
Therefore, the light emitted in the Z-axis direction is
I _X (α _Xi ) × cos α _Xi × {e _Xi / (P _X × cos β _Xi )}
_{= A Xi / cosΦ Xi × cos} (Φ Xi -β Xi) × I X (α Xi) × cosα Xi / (P X × cosβ Xi)
It is.

Since the light incident on the coordinate X _i is emitted to the coordinate (X _i + T × tan γ _Xi ) when the thickness of the base material of the light control member is T, the intensity of the emitted light in the Z-axis direction at that time The distribution is f _X (X _i + T × tan γ _Xi ).
Therefore, the intensity of the emitted light in the Z-axis direction is proportional to the emission intensity of the point light source and the emission ratio in the Z-axis direction.
It is.
Therefore,
It becomes.

Here, the sum of aXi can make the width of the reference lens PX,
It becomes.

In the formula (25) _{P X} is the formula (8) is satisfied except the order constant expressions (26).
The cross-sectional shape of the reference lens is a shape composed of a region i having a width a _Xi that satisfies the relationship of Expression (8). As already known, since the proportional reduction optical system exhibits almost the same directivity characteristics, the width of the reference lens can be freely selected.

Next, equation (9) will be described.
FIG. 4 shows the principle of directing light in the Z-axis direction by the light control member used in the surface light source element of the present invention. From the point light source, light incident at the light control member at an angle alpha _Xi refractive index n _s is refracted at the incident surface of the light control member, passes through the interior of the light control member is refracted at the exit surface-side lens And exit to the exit surface side. At this time, the emitted light is emitted in the Z-axis direction when the inclination of the lens is a desirable angle Φ _Xi . In the present invention, the intensity distribution of outgoing light in the Z-axis direction can be adjusted by adjusting the ratio of the angle Φ _{Xi in} consideration of the distribution of α _Xi based on the arrangement and the intensity of incident light.

The lens inclination Φ _Xi for deflecting the light emitted from the light control member in the Z-axis direction is determined by the refractive index of the lens and the incident angle of the light to the light control member. The incident angle is α _Xi , the angle formed by the light that is refracted at the incident surface and passes through the inside of the lens with respect to the normal of the incident surface is β _Xi , and the light that travels inside the lens is the normal of the exit side slope of the lens Ε _Xi , the light is refracted at the exit slope, ω _{Xi is} the angle formed with respect to the normal of the slope of the light toward the exit surface, and the refractive index of the lens is n. At this time, the angle of the inclined surface of the lens where the light emitted from the lens travels in the Z-axis direction is defined as Φ _Xi .

At this time, the following relationship is established.
From Equation (27) and Equation (28),
Dividing both sides of equation (29) by cosΦXi
Therefore, Φ _Xi is expressed by the following equation.
From Equation (6) and Equation (9),

α _Xi , n, and Φ _Xi have the relationship shown in Expression (29) ″, and light having an incident angle α _Xi can be emitted in the Z-axis direction by the refractive index n of the lens and the inclination Φ _Xi of the inclined surface of the lens. By satisfying Expression (9) for each region i of the lens portion, light incident on the light control member at an angle α _Xi can be emitted from the lens region i in the Z-axis direction.

  Since the same theory can be applied to the cross-sectional shape in the X-axis direction and the cross-sectional shape in the Y-axis direction of the reference lens, equations (10) to (16) can be similarly derived.

  As the reference lens, one type of lens whose cross-sectional shape in the X-axis direction conforms to Equations (8) and (9) and whose cross-sectional shape in the Y-axis direction conforms to Equations (15) and (16) may be used. Two types of lenses that follow only the X-axis direction and only the Y-axis direction may be used as the reference lens.

  The plurality of lenses arranged on the light exit surface of the light control member uses at least one kind of reference lens similar in shape. As already known, since the proportional reduction optical system exhibits almost the same directivity characteristic, even if a similar lens of the reference lens is arranged on the light control member, the same diffusion characteristic as that of the reference lens is exhibited. Furthermore, the use of a plurality of similar shaped lenses can reduce the influence of diffracted light, which is advantageous for uniforming the luminance in the Z-axis direction.

  On the light exit surface of the light control member, at least one kind of reference lens having a similar shape is randomly arranged. Random arrangement is an arrangement method in which a plurality of types of similar-shaped lenses are arranged so as not to overlap each other, and then the gaps between the lenses are filled with other similar-shaped lenses. Since there is no periodicity in lens arrangement, the influence of diffracted light can be reduced, which is advantageous for uniforming the luminance in the Z-axis direction.

A second aspect according to the present invention is the surface light source element according to the first aspect, in which the regions -N _{X to} N _X representing the cross-sectional shape of the reference lens in the X-axis direction are arranged in the order of the X-axis position coordinates. In addition, the surface light source element is characterized in that the areas -N _{Y to} N _Y representing the cross-sectional shape of the reference lens in the Y-axis direction are arranged in the order of the position coordinates of the Y-axis.
At this time, there is no inflection point between the cross-sectional shape in the X-axis direction and the cross-sectional shape in the Y-axis direction of the reference lens, and the reference lens is substantially convex. When there are many inflection points, the light reaches the region on another convex part before reaching the region on the desired convex part, and the direction of the light beam is changed by reflection or refraction, and the light emission direction is controlled. May be difficult. Further, since the shape having no inflection point is simpler than the shape having the inflection point, it is easy to shape and is advantageous in production.

A third aspect according to the present invention is the surface light source element according to the first or second aspect, wherein the cross-sectional shape in the X-axis direction of the reference lens is at least one of (2N _X +1) regions having different inclinations. It is a shape that approximates the shape of two adjacent regions of the set by a curve, and the cross-sectional shape of the reference lens in the Y-axis direction is (2N _Y +1) at least one set of adjacent regions having different inclinations The surface light source element is characterized in that the shape of two regions is approximated by a curve.
The reference lens in the first invention is composed of (2N _X +1) angle Φ _Xi slopes, but the reference lens in the third invention approximates the shape of at least one set of two adjacent regions by a curve. The reference lens of the first invention is composed of (2N _Y +1) inclined surfaces with an angle Φ _Yj , and the reference lens of the third invention has at least one pair of two adjacent lenses. The shape which approximated the shape of the area | region with the curve is shown.
By approximating with a curve, the intensity distribution of outgoing light in the Z-axis direction and the angular distribution of outgoing light become smoother, which is desirable. In addition, since it is easier to form, it is advantageous in production and desirable. Furthermore, since the joint portion in the region is not sharp, it is difficult for damage to occur. Therefore, a change in the light emission direction due to the breakage of the joint portion in the region and unnecessary scattering are unlikely to occur, which is desirable.

The 4th aspect which concerns on this invention is a surface light source element in any one of the 1st-3rd aspect, Comprising: In the said light control member, in an XZ plane, within 30 degrees of angles with respect to Z-axis direction The ratio of the emitted light is 50% or more of the total emitted light in the XZ plane, and the ratio of the light emitted within an angle of 30 degrees with respect to the Z-axis direction in the YZ plane is Y−. The surface light source element is characterized by being 50% or more of the total emitted light in the Z plane. Since the surface light source element has a relatively large ratio of emission in the Z-axis direction, it is possible to efficiently obtain bright illumination in applications such as a television and a personal computer monitor that mainly observe the emission surface from the front direction. Further, in the light control member, the ratio of light emitted within a range of an angle of 30 degrees or less with respect to the Z axis direction in the cross section of the XZ plane, and the angle with respect to the Z axis direction in the cross section of the YZ plane. The ratio of the light emitted in the range of 30 degrees or less can be adjusted by the angle of the inclined surface of the reference lens. The angle of the inclined surface of the reference lens can be adjusted by the width of X _{max to} X _{min and} the width of Y _max to Y _min .

A fifth aspect according to the present invention is the surface light source element according to any one of the first to fourth aspects, wherein a void ratio obtained by dividing an area other than the area of the similar lens of the reference lens by the area of the light control member. It is a surface light source element characterized by being 1.0% or less.
When the porosity of the lens in the light control member is 1.0% or more, the emitted light traveling in the Z-axis direction decreases, leading to a decrease in luminance uniformity. Therefore, reducing the gap is advantageous for improving the luminance uniformity.

The incident angle α _Xi of the light from the point light source on the plane parallel to the X axis and perpendicular to the Y axis, the slope Φ _Xi of the slope of the region i in the lens part, and the width a _{Xi of} the region i in the X axis direction It is a figure which shows the relationship. It is a figure which shows the relationship between the incident angle of light to a light control member, and incident intensity. It is a figure which shows angle (DELTA) (alpha) _Xi which anticipates the point light source in the point of the coordinate Xi in the cross section parallel to a X-axis and orthogonal to a Y-axis. It is a figure which shows the principle which deflects light to a front direction with the surface light source element of this invention. It is a figure which shows a suitable example of the surface light source element of this invention. It is a figure which shows intensity distribution of the emitted light from a point light source to a Z-axis direction in the cross section parallel to a X-axis and orthogonal to a Y-axis. It is a figure which shows the relationship between the position of the point light source in the plane parallel to the X-axis, and orthogonal to the Y-axis of the surface light source element of FIG. It is a figure which shows an example of the intensity distribution to the X-axis direction of the emitted light to the Z-axis direction of the light from one point light source in the cross section parallel to a X-axis and orthogonal to a Y-axis. And _f X (X) of the surface light source device shown in FIG. 8 is a diagram showing a _g X (X) corresponding thereto. It is a figure which shows the relationship between the angle of an emitted light, and intensity | strength by the difference in the arrangement | positioning method of the lens shown in Example 1 and Comparative Example 1. FIG.

Embodiment 1
Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiment. In addition, for clarity of explanation, the following description and drawings are simplified as appropriate.
An example of the surface light source element according to Embodiment 1 of the present invention is shown in FIG.
One of the normal lines of the XY plane parallel to the X axis and the Y axis perpendicular to the X axis is defined as the Z axis direction, and at least a plurality of point light sources 1 parallel to the XY plane and one sheet A sheet-like light control member is provided, the plurality of point light sources 1 are periodically arranged in the X-axis and Y-axis directions in a virtual plane parallel to the XY plane, and the light control member is X- A plurality of similarities of the reference lens 21 is a surface light source element arranged in parallel to the Y plane and in the Z-axis direction of the plurality of point light sources 1 and on the surface of the light control member that mainly emits light. This is a surface light source element in which the shape lenses 21 are randomly arranged.

Although there is no restriction | limiting in particular as the point light source 1 of this invention, LED etc. can be used. Examples of the LED include white LEDs, red, blue, and green LEDs, and the like. For example, only white is used, and each color LED is periodically arranged. In addition, a plurality of light sources having the same color may be arranged within one period according to the color required on the emission surface. The plurality of point light sources 1 X-axis direction and the Y-axis direction of the periodic D _X, D _Y is shorter is the luminance uniformity is good, since the high brightness obtained desirable. However, if the period is too short, the number of the point light sources 1 increases, resulting in an increase in power consumption and a problem of heat generation. The periods D _X and D _Y are preferably 7 mm to 70 mm. More desirably, the thickness is 15 mm to 50 mm.

  FIG. 6 is a diagram showing the intensity of emitted light in the Z-axis direction on the XZ plane and the position of the point light source 1 when the point light sources 1 are arranged. As shown here, in a surface light source element having an array of a plurality of point light sources 1, the intensity of the emitted light in the Z-axis direction is the portion directly above each point light source 1, the portion directly above, The adjacent point light sources 1 and the intermediate position portions of the point light sources 1 are greatly different. This indicates that in the surface light source element of the present invention, the intensity of the incident light on the surface on which the light is mainly incident on the light control member is greatly different between the portion directly above the respective point light sources 1 and the obliquely upper portion. ing. The difference in strength is the same in the YZ plane.

  FIG. 7 is a diagram showing the relationship between the position of the point light source 1 and the intensity of emitted light in the Z-axis direction on the XZ plane of the surface light source element shown in FIG. A similar intensity distribution is shown even in a cross section parallel to the Y-Z plane. Thus, in the surface light source element of the present invention, the intensity distribution of the emitted light in the Z-axis direction is substantially constant, so that the luminance in the Z-axis direction is Uniformity is obtained.

In FIG. 8, Z X direction in the XZ plane by light from any one point light source 1 of the surface light source element of the present invention in which D _X = 30 mm and the point light sources 1 are arranged in the X axis direction. An example of intensity distribution of the emitted light to is shown. The outgoing light in the Z-axis direction by the light from one point light source 1 is in the range of X _{min to} X _max . In the case of gradually decreasing attenuation as shown in FIG. 8, for example, the value of X when the value of f _X (X) is 1/100 of the maximum value can be substituted. The values of f _X (X) for determining X _min and X _max are preferably the same, and if it is 1/20 or less of the maximum value, there is no problem and 1/100 is more desirable. In FIG. 8, X _min = −3D _X , X _max = 3D _X , and f _X (X _min ) = f _X (X _max ), which is 1/100 or less of the maximum value of f _X (X). Since the intensity of the emitted light in the Z-axis direction of the surface light source element obtained from such a distribution is not strictly determined only by the sum of the point light sources 1 for three adjacent periods, g _X (X) is constant. It is preferable that g _X (X) in the vicinity of X = 0 is slightly higher than that in the vicinity. Similarly, in the YZ plane, it is desirable that g _Y (Y) in the vicinity of Y = 0 is slightly higher than that in the vicinity.

_Further, the _{g X (X) min} is the minimum value of _g X (X), the ratio of _{g X (X) max} is the maximum _{value, g X (X) min /} g X (X) max is 0. made uniform brightness along the X-axis direction when 8 or more, _{and, g} Y and _{g Y (Y) min} is the minimum value of _{(Y), g Y (Y} ) and _max is the maximum value When the ratio g _Y (Y) _min / g _Y (Y) _max is 0.8 or more, the luminance is uniform along the Y-axis direction, so that a surface light source element with high luminance uniformity is obtained. It is done. g _{X (X)} values for _min / g _{X (X) max} and _{g Y (Y) min / g} Y (Y) max is more preferably 0.85 or more, a high uniformity of more luminance in this case A surface light source element can be obtained, and when a transmissive liquid crystal panel or the like is arranged in the Z-axis direction of the emission surface of the surface light source element to obtain an image display device, high screen quality can be obtained. In order to obtain a higher screen quality, 0.90 or more is desirable.

FIG. 9 shows g _X (X) of the surface light source element obtained from f _X (X) shown in FIG. If g _X (X) is constant in a range of −D _X / 2 ≦ X ≦ D _X / 2, which is one cycle of the point light source 1, high luminance uniformity can be obtained in the Z-axis direction. When X _min and X _max are optimum, light with high energy in the vicinity of the point light source 1 is deflected to the front, and therefore the luminance in the Z-axis direction becomes higher. The same applies to the YZ plane.

In the reference lens 21, the arrangement order of the regions −N _{X to} N _X is not necessarily along the X axis. However, in this case, an inflection point exists in the convex portion having a cross-sectional shape in the X-axis direction of the reference lens 21 depending on the order of arrangement of the regions, and the angle Φ _Xi that deflects the light incident at the angle α _Xi to the front surface Before reaching the reference lens 21, it reaches a slope of another angle, the light beam direction changes due to refraction or reflection, does not reach the slope of angle Φ _Xi , or reaches the slope of angle Φ _Xi at an undesired angle. As a result, it is difficult to control the light emission direction, and the performance may be insufficient. When the regions of −N _{X to} N _X are arranged in the order of the position coordinates of the X axis, the shape of the convex portion usually has no inflection point, and the entire reference lens 21 has a substantially convex shape. Such a reference lens 21 is advantageous in that light normally does not change due to reflection or refraction when light reaches a region on a desired convex portion, and the light direction can be easily controlled.

In the reference lens 21, the arrangement order of the regions −N _{Y to} N _Y is not necessarily along the Y axis. However, in this case, an inflection point exists in the convex portion having a cross-sectional shape in the Y-axis direction of the reference lens 21 depending on the arrangement order of the regions, and the angle Φ _Yj that deflects the light incident at the angle α _Yj to the front surface before reaching the reference lens 21 to reach the slopes of different angle, refraction or the beam direction changes by the reflection, it does not reach the slant angle [Phi _Yj, or angle reaches the slope angle [Phi _Yj undesirable As a result, it is difficult to control the light emission direction, and the performance may be insufficient. When the areas of -N _{Y to} N _Y are arranged in the order of the position coordinates of the X axis, the shape of the convex portion usually has no inflection point, and the entire reference lens 21 has a substantially convex shape. Such a reference lens 21 is advantageous in that light normally does not change due to reflection or refraction when light reaches a region on a desired convex portion, and the light direction can be easily controlled.

The width _{a Xi} in the X-axis direction of each region i of the reference lens 21 is proportional to _{f X (X i + T ×} tanβ Xi) × cosΦ Xi × cosβ Xi / {cosα Xi × cos (Φ Xi -β Xi)} This is a feature of the surface light source element of the present invention, but the preferred width may be slightly shifted due to the influence of the height from the bottom of the lens portion to the surface, but there is no significant influence. The same applies to the width a _{Yj in the} Y-axis direction.

  Although it is desirable that the thickness T of the substrate 2 of the light control member is thin, in the surface light source element of the present invention which is a direct type, since a space is provided between the light source and the light control member, it is disposed on the most light source side. It is desirable that the light control member has a thickness that does not cause bending or deformation. The light control member arranged closest to the light source differs depending on the size of the surface light source element, but the thickness is preferably 0.5 to 5 mm. If it is thinner than this, the light control member will be bent or deformed, the point light source 1 will come into contact with the light control member, and the appearance quality will deteriorate. If it is thicker than this, the surface light source element becomes thick and the weight also increases. More desirably, it is 1-4 mm, More preferably, it is 1.5-2.5 mm. In this range, the strength is maintained, and it is possible to suppress an increase in manufacturing cost due to an increase in the amount of base material used per main surface area.

Further, N _X and N _Y that determine the number of regions into which the reference lens 21 is divided are desirably 2 or more. When N _X and / or N _Y is large, the convex portion of the cross-sectional shape of the reference lens 21 in the X-axis direction and / or the cross-sectional shape of the reference lens 21 in the Y-axis direction has a complicated shape having a large number of inclinations. When the number of inclinations is large, the outgoing light in the front direction can be accurately controlled, and the intensity distribution of the outgoing light in the front direction is highly uniform. From the viewpoint of accuracy, N _X and N _Y are preferably large, but if they are too large, the shape becomes complicated and it is difficult to manufacture. From the viewpoint of ease of production, N _X and N _Y are preferably 100 or less, and more preferably 10 or less.

  In the cross-sectional shape of the reference lens 21 in the X-axis direction and / or the cross-sectional shape of the reference lens 21 in the Y-axis direction, the shape of at least one pair of adjacent regions that form the convex portions may be approximated by a curve. Furthermore, the shape of three or more adjacent regions may be approximated by a curve, and the shape of the entire convex portion may be approximated by a curve. When the shape of many areas is approximated by a curve, the shape of adjacent areas such as smoothing the intensity distribution of outgoing light in the Z-axis direction and the angular distribution of outgoing light, being easy to shape, and not easily damaged are curved. The effect of approximating with is more desirable and desirable. The method for approximating the curve is not particularly limited, and the generally well-known least square method, spline interpolation method, Lagrange interpolation method, and the like can be used. For the approximation, at least one point is selected from the approximated areas, and is usually larger than the number of approximated areas. For example, it is possible to select both ends of a plurality of continuous regions and contact points of each region. Further, the midpoint of each region can also be used for approximation.

  In the XZ plane, the proportion of light emitted within an angle of 30 degrees with respect to the Z axis direction is 50% or more of the light emitted in the Z axis direction on the XZ plane, and in the YZ plane, When the proportion of light emitted within an angle of 30 degrees with respect to the Z-axis direction is 50% or more of the light emitted in the Z-axis direction on the YZ plane, a surface light source element having high brightness in the Z-axis direction is obtained. can get. In a display device such as a personal computer monitor that requires high luminance, this value is more preferably 60% or more, and more preferably 80% or more. On the other hand, for a display device that requires a wide viewing angle, such as an illumination signboard, if the rate of emission in the Z-axis direction is too high, light is directed only in the Z-axis direction and the viewing angle is not desirable. Therefore, when used for a lighting signboard or the like, this value is desirably 60% to 80%.

A longer distance H between the point light source 1 and the light control member is desirable because of high luminance uniformity. However, if the length is too long, the thickness of the entire apparatus increases, which is not preferable. The distance H between the point light source 1 and the light control member is preferably 5 mm to 50 mm. More desirably, the thickness is 10 mm to 30 mm. Further, the ratio of the point light source 1 to the period, D _X / H, D _Y / H is preferably 0.5 to 3, and more preferably 1 to 2.

  The width of the similar-shaped lens 21 of the reference lens 21 is desirably 1 μm to 300 μm. If it is larger than 300 μm, the pattern itself is visually recognized from the exit surface and the appearance quality is lowered. If it is smaller than 1 μm, it is difficult to form a lens shape. More preferably, it is 5 μm to 100 μm. Usually, when the diameter is smaller than 30 μm, the appearance quality is deteriorated due to the diffraction phenomenon. However, since the plurality of similar shaped lenses 21 are randomly arranged in the surface light source element of the present invention, it is possible to suppress the deterioration of the appearance quality due to the diffraction phenomenon. .

  Although there is no restriction | limiting in particular as a manufacturing method of the light control member of this invention, The shaping | molding which uses extrusion molding, injection molding, and ultraviolet curable resin is mentioned. However, when the lens 21 is provided, a suitable molding method may be selected in consideration of the size of the lens 21, the shape of the lens 21, mass productivity, and the like. Extrusion molding is suitable when the main surface is large.

  As a material for the light control member, any optically transparent material can be used. For example, methacrylic resin, polystyrene resin, polycarbonate resin, cycloolefin resin, methacryl-styrene copolymer resin, cycloolefin-alkene copolymer resin and the like can be mentioned.

  In order to use more light, a reflector or the like may be used on the −Z axis side of the light source. By using the reflector, the light emitted from the light source to the −Z-axis side and the light emitted from the light control member to the −Z-axis side can be directed to the Z-axis side, so that more light can be used and the luminance is high. It is possible to obtain

  The reflecting plate has a function of reflecting light emitted from the light source to the −Z axis side in the front direction. A reflectance of 95% or more is desirable because of high light utilization efficiency. Examples of the material of the reflecting plate include metal foils such as aluminum, silver, and stainless steel, white coating, and foamed PET resin. In order to increase the light utilization efficiency, it is desirable that the material has a high reflectance. This includes silver, foamed PET, and the like. In order to improve luminance uniformity, the material is preferably diffusely reflected. This includes foamed PET and the like.

  When the light control member is not disposed closest to the light source, the thickness of the light control member may be set in consideration of the strength, productivity, and the like of the light control member itself. When used as a normal surface light source element, the vicinity of the end surface is fixed together with the light control member arranged closest to the light source, so that even a thin sheet is less likely to be bent. Therefore, the light control member that is not closest to the light source can be made thinner than the light control member that is closest to the light source. The light control member that is not closest to the light source is preferably thin in order to reduce the thickness of the entire apparatus. Although the thickness varies depending on the size of the surface light source element, the thickness is preferably 0.05 mm to 1 mm. If it is thinner than this, the strength of the light control member itself is lowered, and the quality is lowered due to deformation or the like. On the other hand, if it is thicker than this, the surface light source element becomes thick and the weight also increases. Furthermore, in order to prevent the light control member from being deformed by heat and to obtain high productivity by extrusion molding or the like, 0.1 mm to 0.7 mm is desirable, and 0.2 mm to 0.5 mm is further desirable.

  In addition, a transparent support substrate made of resin, glass, or the like may be provided on the light source side of the light control member. By disposing the support substrate, the light control member can be supported even if the light control member is thinned, for example, from 0.1 mm to 1 mm. By reducing the thickness of the light control member, molding by extrusion molding or the like is further facilitated, and productivity is improved. In addition, it becomes easy to support the light control member that becomes increasingly difficult as the surface light source element becomes larger. Although there is no restriction | limiting in particular in the thickness of the said support substrate, Usually, it is 1 mm to 5 mm, and it is still more desirable that it is the range of 2 mm to 4 mm normally from the balance of weight reduction and intensity | strength.

There is no problem even if the support substrate is made of several kinds of plates having different refractive indexes, for example, when the support substrate is used and when the support substrate and the light control member are joined. In this case, aXi can be obtained by deriving an expression corresponding to Expression (8) in accordance with the idea described so far.
However, when the variation of the refractive index is within 90%, the refractive index can be approximated according to the ratio of the plate thicknesses to derive the equation (8). For example, when the support substrate portion is composed of three plates with refractive indexes n ′, n ″, n ′ ″ and plate thicknesses T ′, T ″, T ′ ″, respectively, n is (n It can be approximated by a value of “× T” + n ″ × T ″ + n ′ ″ · × T ′ ″) / T.

  The light control member of the present invention can be used for light sources other than the plurality of point light sources 1. For example, by using it for a single point light source 1, it is possible to obtain uniform and high brightness in a wider range. In addition, the light control member included in the surface light source element of the present invention includes a plurality of linear light sources arranged in a virtual plane parallel to the XY plane, parallel to the X-axis direction and along the Y-axis, or the Y-axis It is possible to control the direction of light rays from a plurality of linear light sources arranged in parallel to the direction and along the X axis, and high luminance uniformity can be realized. As these linear light sources, it is also possible to use a linear light source configured by linearly arranging point light sources 1 such as fluorescent lamps or LEDs at narrow intervals.

  Further, the image display device of the present invention is realized by providing a transmissive display device on a surface light source element, and a transmissive liquid crystal panel or the like can be given as the display device. As a result, an image display device having a high luminance on the display surface and excellent luminance uniformity can be obtained.

  Examples of the present invention will be described below, but the present invention is not limited thereto.

The brightness uniformity of the surface light source element shown in FIG. 5 was analyzed using lighting design analysis software LightTools (registered trademark). In the point light source 1, the upper surface of a cylinder having a height of 0.5 mm and a diameter of 0.8 mm was used as a light emitting part, and the angular characteristics of light emission were set to Lambertian distribution. The coordinates (X, Y) of the point light source 1 = (D _X / 2, D _Y / 2), (−D _X / 2, D _Y / 2), (D _X / 2, −D _Y / 2), (−D _X / 2, D _Y / 2), and arranged such that the upper surface side of each light source is in the Z-axis direction. A reflecting plate that diffusely reflects is disposed on the lower surface side of the point light source 1, and an incident surface of the light control member is disposed at a position 25 mm away from the reflecting plate. The light control member is assumed to be a general optical resin having a refractive index of 1.5. The shape of the reference lens 21 was determined by designating the intensity distribution f _X (X) in the X-axis direction and the intensity distribution f _Y (Y) in the Y-axis direction of the light emitted from the light control member in the Z-axis direction. The similar shape lens 21 of the reference lens 21 is randomly arranged in the range of −D _X / 2 ≦ X ≦ D _X / 2, −D _Y , / 2 ≦ Y ≦ D _Y / 2 on the exit surface of the light control member. The luminance L (X, Y) in the Z-axis direction was analyzed by simulation. The ratio of the maximum luminance to the minimum luminance R _X = L _XMAX / L _XMIN from the maximum value L _XMAX and minimum value L _XMIN of the luminance L _X in the X-axis direction was used as an index of luminance uniformity. Similarly, the ratio RY = L _YMAX / L _YMIN of the maximum luminance and the minimum luminance from the maximum value L _YMAX and the minimum value L _YMIN of the luminance LY in the Y-axis direction was used as an index of luminance uniformity.

  Next, using the diffractive optical element design analysis software DiffractMOD (registered trademark), the effect of suppressing the occurrence of the diffraction phenomenon was analyzed when the arrangement method of the plural kinds of similar-shaped lenses 21 was arranged randomly and periodically. The light source was incident in a direction perpendicular to the incident surface of the light control member using TM polarized light having a wavelength of 550 nm. In order to obtain the relationship between the emission angle and intensity of the emitted light in the XZ plane, a light control member in which one type of a reference lens 21 having a width of 15 μm and a similar lens 21 having a width of 7.5 μm is randomly arranged is analyzed by simulation. did.

Table 1 shows the values of R _X and R _Y obtained in Examples and Comparative Examples and analysis conditions.

In Example 1 and Comparative Example 1, the reference lens 21 in the light control member is a case where the contour line of the cross-sectional shape in the X-axis direction and the contour line of the cross-sectional shape in the Y-axis direction are curves, and the calculation result by LightTools Then, the luminance uniformity in the Z-axis direction is as high as R _X = 0.92 and R _Y = 0.88. On the other hand, in the arrangement method, in Example 1, one type of the reference lens 21 and one type of the similar shape lens 21 were randomly arranged, whereas in Comparative Example 1, one type of reference lens was periodically arranged. FIG. 10 shows the relationship of the intensity distribution with respect to the angle of light emitted from the light control member. The emission angle 0 degree direction was defined to be the Z-axis direction. In Comparative Example 1, diffracted light was generated in the directions of −15 °, 0 °, and + 15 ° to reduce the luminance uniformity. However, since Example 1 hardly generated diffracted light, the luminance uniformity was high. I understand.

  In Example 2 and Comparative Example 2, the X-axis direction cross-sectional outline and the Y-axis cross-sectional outline of the reference lens in the light control member are straight lines. Even when the outline of the reference lens is not approximated, diffracted light is not generated by randomly arranging the lens arrangement method with similar-shaped lenses, and high luminance uniformity is obtained.

  In Comparative Example 3, the luminance uniformity of the reference lens is low. This is because if a plurality of similar-shaped lenses are randomly arranged, diffracted light is suppressed, but there is no effect of significantly increasing the luminance uniformity of the reference lens. It is not preferable.

DESCRIPTION OF SYMBOLS 1 Point light source 2 The board | substrate which comprises a light control member 21 The reference | standard lens arrange | positioned at the output surface of the light control member, and its similar shape lens L1 The light ray L2 light control member which makes it inject into the position Xi of a light control member from a point light source Rays passing through the lens of

Claims (5)

One of the normal lines of the XY plane parallel to the X axis and the Y axis orthogonal to the X axis is the Z axis direction, and at least a plurality of point light sources and one sheet or film A light control member,
The plurality of point light sources are periodically arranged in the X-axis and Y-axis directions in a virtual plane parallel to the XY plane, the light control member is parallel to the XY plane, and A plurality of lenses are randomly arranged on the surface of the point light source in the Z-axis direction, and the light control member mainly emits light, and the plurality of lenses includes at least one type of reference lens and its similar shape lens. Consists of
The reference lens is
Of the plurality of point light sources, the length D _X of one cycle of the X-axis _direction, the length of one period of the Y-axis direction D _Y,
When the center position of the arbitrarily selected point light source is the origin, the position coordinate in the X-axis direction is X, and the position coordinate in the Y-axis direction is Y,
In a virtual plane parallel to the XZ plane parallel to the X axis and the Z axis,
A function that represents the distance between the selected point light source and the light control member as H, and the intensity of the emitted light in the Z-axis direction of the exit surface at the position X of the light incident on the light control member from the selected point light source. Is f _X (X),
g _X (X) = f _X (X−D _X ) + f _X (X) + f _X (X + D _X )
In the range of −D _X / 2 ≦ X ≦ D _X / 2,
In g _X (X) is the minimum value of _{g X (X) min} and the maximum value _g X _(X) ratio of _{max g X (X) min /} g X (X) max is 0.8 or more Yes,
The minimum value X _min of _{X is in} the range of −3.0D _X ≦ X _min ≦ −0.5D _X , and the maximum value X _{max of} X is in the range of 0.5D _X ≦ X _max ≦ 3.0D _X , (X _min and X _max are the coordinates of both ends where the value of f _X (X) is attenuated around the arbitrarily selected point light source where X = 0 and becomes substantially 0),
The cross-sectional shape of the reference lens in the X-axis direction is composed of (2N _X +1) different regions −N _{X to} N _X represented by the following formula,
δ _X = (X _max −X _min ) / (2N _X +1)
X _i = i × δ _X
α _Xi = tan ⁻¹ (X _i / H)
β _Xi = sin ⁻¹ ((1 / n) sin α _Xi )
γ _Xi = sin ⁻¹ ((1 / n _s ) sin α _Xi )
_{a Xi αf X (X + T} × tanγ Xi) × cosΦ Xi × cosβ Xi / {I i (α Xi) × cos (α Xi) × cos (Φ Xi -β Xi)}
Φ _Xi = tan ⁻¹ ((n × sin β _Xi ) / (n × cos β _Xi −1))
(However, N _X : natural number
i: integer from -N _X to N _X
n: Refractive index of the lens portion of the light control member
n _s : refractive index of the base material of the light control member
a _Xi : width of region i in the X-axis direction
Φ _Xi : Inclination with respect to the exit surface of region i
T: Thickness from the incident surface of the light control member to the bottom of the lens unit
I _i (α _Xi ): intensity of light emitted per unit angle in the direction of α _Xi along the X-axis direction from an arbitrarily selected point light source)
And,
Intensity of emitted light in the Z-axis direction of the exit surface at the position Y of light incident on the light control member from the selected point light source in a virtual plane parallel to the YZ plane parallel to the Y-axis and Z-axis Let f _Y (Y) be a function that represents
g _Y (Y) = f _Y (Y−D _Y ) + f _Y (Y) + f _Y (Y + D _Y )
In the range of −D _Y / 2 ≦ Y ≦ D _Y / 2,
In _{g Y (Y) g Y (} Y) is the minimum value _min and the ratio _g Y _(Y) and _g Y _{(X) max} is the maximum value min / g _{Y (Y) max} is 0.8 or more Yes,
Minimum value _{Y min} Y is in the range of _{-3.0D Y ≦ Y min ≦ -0.5D Y} , maximum value _{Y max} Y is in the range of 0.5 D _Y ≦ _{Y max} ≦ 3.0D _Y, (Y _min and Y _max are the coordinates of both ends where the value of f _Y (Y) is attenuated around the arbitrarily selected point-like light source where Y = 0 and becomes substantially 0),
A surface light source element characterized in that the cross-sectional shape of the reference lens in the Y-axis direction includes (2N _Y +1) different regions −N _{Y to} N _Y expressed by the following formula.
δ _Y = (Y _max −Y _min ) / (2N _Y +1)
Y _j = j × δ _Y
α _Yj = tan ⁻¹ (Y _j / H)
β _Yj = sin ⁻¹ ((1 / n) sin α _Yj )
γ _Yj = sin ⁻¹ ((1 / n _s ) sin α _Yj )
_{a Yj αf Y (Y j +} T × tanγ Yj) × cosΦ Yj × cosβ Yj / {I j (α Yj) × cos (α Yj) × cos (Φ Yj -β Yj)}
Φ _Yj = tan ⁻¹ ((n × sin β _Yj ) / (n × cos β _Yj −1))
(However, N _Y : natural number
j: integer from -N _Y to N _Y
a _Yj : the width of the region j in the Y-axis direction
Φ _Yj : slope of region j with respect to the exit surface
I _j (α _Yj ) is the intensity of light emitted per unit angle in the direction of α _Yj along the Y-axis direction from an arbitrarily selected point light source) The surface light source element according to claim 1,
Regions −N _{X to} N _X representing the cross-sectional shape in the X-axis direction of the reference lens are arranged in the order of the position coordinates of the X-axis,
And,
A surface light source element, wherein regions -N _{Y to} N _Y representing a cross-sectional shape of the reference lens in the Y-axis direction are arranged in the order of the position coordinates of the Y-axis. The surface light source element according to claim 1 or 2,
The cross-sectional shape of the reference lens in the X-axis direction is a shape that approximates the shape of at least one pair of two adjacent regions out of (2N _X +1) different regions with a curve,
And,
A surface light source characterized in that the cross-sectional shape of the reference lens in the Y-axis direction is a shape obtained by approximating the shape of at least one pair of two adjacent regions with a curve among (2N _Y +1) different regions of inclination. element. The surface light source element according to claim 1,
In the XZ plane of the light control member, the ratio of the light emitted within an angle of 30 degrees with respect to the Z-axis direction is 50% or more of the light emitted in the Z-axis direction in the XZ plane,
And,
In the YZ plane of the light control member, the ratio of the light emitted within an angle of 30 degrees with respect to the Z-axis direction is 50% or more of the light emitted in the Z-axis direction of the YZ plane. A surface light source element. The surface light source element according to any one of claims 1 to 4,
A surface obtained by dividing an area of a flat portion other than a plurality of lenses formed mainly on a light emitting side of the light control member by an area of the light control member is 1.0% or less. Light source element.