Emission device, surface light source device, display and light flux control member

Abstract

A display has a member irradiated by a surface light source device comprising a light diffusion member and emission device. The emission device is provided with a light flux control member having a recess and light control emission face which is configurated so as to satisfy Conditions 1 and 2 in a range at least covering a half-intensity-angular-range. light emitting element(s) may be sealed. Condition 1 is that relation θ5/θ1>1 is satisfied except for light emitted from a light emitting element toward within an angular-neighbourhood of a standard optical axis of the emission device, and Condition 2 is that value of θ5/θ1 decreases gradually according to increasing of θ1, where θ1 is an emission angle of any light at being emitted from the light emitting element, and θ5 is an emission angle of that light of θ1 at then being emitted from the light control emission face of the light flux control member.

Description

• • where θ1<δ1.
    θ3=tan⁻¹ {(sin θ5−n·sin θ1)/(cos θ5−n·cos θ1)},  (Formula 2)
  • where n is refractive index of light flux control member.

Such calculated angle θ3 decreases gradually according to increasing of θ1 until θ1=δ2 is satisfied from an angular neighbourhood of optical axis L as shown by curve 16 in FIG. 6. In a range of θ1>δ2, θ3 increases gradually according to increasing of θ1. If θ1=δ2, θ3=θ1.

General operations light flux control member 5 having light control emission face 6 are as follows.

As illustrated in FIGS. 2 and 3, light beam H generally representing emission from light emitting element 4 enters into light flux control member 5, then traveling within light flux control member 5 and reaches light control emission face 6 to be emitted toward an ambient medium (air) according to Snell's Law.

This emission from light control emission face 5 in accordance with the present invention occurs more uniformly toward an illumination range, and broader and smoother angular expansion is realized as compared with a case of emission from conventional hemisphere light flux control member 23. In other words, locally strong emission toward just above portion of light emitting element 4.

(Example of First Mode)

In the next place, an example of emission device 29 employing light flux control member 5 of first mode is described by referring to FIGS. 1 to 4. Shapes and others of first and second emission face regions 6a, 6b are designed depending on various factors such as the followings.

(a): Emission characteristics of light emitting element 4, especially, angular extension represented by half-intensity-angular-range.

(b): Thickness d of light flux control member 5 along a direction of optical axis L, especially, distance d1 from emission portion 4a of light emitting element 4 to light control emission face 6 along a direction of optical axis L.

(c): Arrangement pitch p of light emitting element 4.

(d): Outer diameter Do of light flux control member 5.

(e): Distance L1 from light control emission face 6 to light diffusion member 7 along a direction of optical axis L.

(f): Refractive index n of light flux control member 5.

(g): Configuration of incidence concave face (Configuration of concave surface provided by recess 10).

(h): Refractive index n of medium (air or sealing material) through which light of light emitting element 4 transmits before impinging on light flux control member 5.

According to an example, light flux control member 5 has a hemisphere-like recess, being made of transparent resin of refractive index n=1.49, with L1=13.89 mm, p=24.25 mm, d=3.31 mm, d1=2.11 mm and Do=7.85 mm. Medium between light flux control member 5 and light emitting element 4 has the same refractive index as that of light flux control member 5.

This light flux control member 5 has first and second emission face regions 6a, 6b which form a connection portion at which angle θ1 satisfies θ1=δ2=16°. In addition, second and third emission face regions 6b, 6c form a connection portion at which angle θ1 satisfies θ1=δ1=85°. It can be said that third emission face region 6c is provided by rotating tangent of second emission face regions 6b by 360° around optical axis L.

A range of θ1≤δ2 corresponds to first emission face region 6a and range of δ2≤θ1≤δ1 corresponds to second emission face region 6b, and range of δ1≤θ1 corresponds to third emission face region 6c, in FIG. 4B.

It is noted that, if sealing material 9 has refractive index substantially the same as that of light flux control member 5, light beam H from light emitting element 4 reaches light control emission face 6 without undergoing refraction. For instance, if sealing material 9 is made of the same transparent resin or glass, this is realized.

However, the present invention is not limited by this mode. Sealing material 9 may have refractive index different from that of light flux control member 5. It is noted that absence of sealing material 9 air occupies a gap between light emitting element 4 and light flux control member 5.

(Example of Second Mode)

FIG. 7 shows emission device 29 employing light flux control member 5 of second mode in accordance with the present invention. This light flux control member 5 is generally the same as that of first mode except structure for engaging with light emitting element 4.

As shown in FIG. 7, light flux control member 5 is suitable for a case where LED 19 has a rectangular cross section and light emitting face 17. Rectangular recess 18 formed at a center portion on the back side contacts with rectangular light emitting face 17. Light flux control member 5 has flat portion 11 on the back side. Flat portion 11 is stuck and fixed to mounting substrate 12 for light emitting element 4 and recess 18 is stuck and fixed to light emitting surface 17.

Light flux control member 5 of this mode structured as above-described has functions generally the same as those of light flux control member 5 of first mode.

It is noted that, although FIG. 7 shows that sealing material 9 sealing light emitting element 4 (LED 19) has a rectangular cross section, this does not limit the scope of the present invention. For instance, LED 19 may shaped like hemisphere or others.

(Example of Third Mode)

FIG. 8 shows light flux control member 5 of third mode in accordance with the present invention. This light flux control member 5 is generally the same as that of first mode except structure for engaging with light emitting element 4.

As shown in FIG. 8, light flux control member 5 of third mode has a hemisphere-like incidence surface (concave surface of recess 23) 20 engaging with light emitting element 4 with a gap. Incidence surface 20 is formed on the upper side with respect to reference line C in FIG. 8.

Hemisphere-like incidence surface 20 has cylinder-like LED-accommodation-portion 21 engaging with light emitting element 4 with a gap on the lower side in FIG. 8.

Light emitting element 4 is stuck and fixed to substrate 22. On the other hand, light flux control member 5 has flat portion 11 on the lower side and flat portion 11 is stuck and fixed to 22 after light emitting element 4 is accommodated in LED-accommodation-portion 21 and positioned at a predetermined location by an action like applying capping to light emitting element 4.

Light flux control member 5 structured as above-described causes light of light emitting element 4 to enter into light flux control member 5 through hemisphere-like incidence surface 20 after transmitting through an air layer. After propagating in light flux control member 5, emission from light control emission face 6 occurs.

In this mode, light control is performed under consideration of conditions such as difference of the air layer and light flux control member 5, and the concave configuration of incidence face.

Light flux control member 5 of this mode has functions generally the same as those of light flux control member 5 of first mode.

It is noted that the above-described second and third modes may be modified by using only light emitting element 4 instead of LED 19.

Emission device 29 employing light flux control member 5 of first or second mode may be modified as to omit sealing material 9.

Alternatively, sealing material 9 may be used as light flux control member 5. Sealing material 9 may be stuck and fixed to light flux control member 5 or contacted with light flux control member 5 without sticking and fixing.

(Other Modes)

Other modifications such as followings are allowed.

(1): Matting may be applied to light control emission face 6 of light flux control member 5 of the above-described first, second or third mode so that light is diffused on emitting from light control emission face 6.

(2): Light flux control member 5 of the above-described first or second mode may be made of material containing light diffusible articles such as silicone articles or titanium oxide articles.

<Light Diffusion Member>

FIGS. 9a to 9f are side views of light diffusion members 7 in accordance with to first to sixth examples, respectively.

Each light diffusion member 7 is a sheet-like or plate-like member made of light well-permeable resin such as PMMA (polymethyl methacrylate) or PC (polycarbonate), having an area size generally equal to that of member 3 to be illuminated such as LCD panel, advertising display panel.

Light diffusion member 6 shown in FIG. 9A employs sheet-like base material 7a to both faces of which processing for giving light diffusion ability, such as emboss-processing or bead-processing, is applied. Thus both faces of light diffusion member 7 are provided with fine uneven configurations 7b.

Light diffusion member 7 shown in FIG. 9B employs sheet-like base material 7a to both faces of which processing for giving light diffusion ability, such as emboss-processing or bead-processing, is applied. Thus both faces of light diffusion member 7 are provided with fine uneven configurations 7b. In addition, light diffusive material 7c is dispersed within base material 7a.

Light diffusion member 7 shown in FIG. 9C employs sheet-like base material 7a to only an inner face of which processing for giving light diffusion ability, such as emboss-processing or bead-processing, is applied to form a fine uneven configuration 7b. It is noted that the inner face of light diffusion member 7 is a face directed to light flux control member 4. In addition, other face of light diffusion member 7 is provided with a great number of repeated prismatic projections 7d extending along a direction perpendicular to the paper surface.

Light diffusion member 7 shown in FIG. 9D is the same as one shown in FIG. 9C except that light diffusive material 7c is dispersed within base material 7a.

In the same manner as the case of FIG. 9C, processing such as emboss-processing or bead-processing is applied to one face directed to light flux control member 4 to form a fine uneven configuration 7b. The other face of light diffusion member 7 is provided with a great number of repeated prismatic projections 7d extending along a direction perpendicular to the paper surface. Each of prismatic projections 7d shown in FIGS. 9C and 9D is shaped like triangle, for instance, like isosceles triangle.

Light diffusion member 7 shown in FIG. 9E employs sheet-like base material 7a on an emission side face of which circular-cone-like projections 7e for are formed to cause light transmitted through base material 7a to be diffused.

Light diffusion member 7 shown in FIG. 9F employs sheet-like base material 7a on an emission side face of which pyramid-like (such as triangle-pyramid-like, quadrangle-pyramid-like or hexangle-pyramid-like) projections 7f for are formed to cause light transmitted through base material 7a to be diffused.

Every light diffusion member 7 as above transmits and diffuses light emitted from light control emission face 6 of light flux control member 5, causing member 3 to be illuminated uniformly.

It is noted that every light diffusion member 7 as above may be mounted on an inner face directed to light flux control member 5 of member 3 to be illuminated, or alternatively, may be interposed between light flux control member 5 and member 3 to be illuminated, with being separated from member 3.

<Emission Intensity from Light Diffusion Member>

FIG. 10 is a diagram illustrating distributions of emission intensity from light diffusion member 7, together with an emission intensity distribution of an example for comparison (Prior Art 4).

(Case of Single LED Arrangement)

In FIG. 10, curve A shows a distribution of emission intensity in a case where light flux control member 5 in accordance with the present invention is disposed, giving light intensity of one light emitting element 4 after transmitting through light flux control member 5 and light diffusion member 7. Curve B shows a distribution of emission intensity in the prior art case of FIG. 15 where light flux control member 123 is disposed, giving light intensity of one LED 124 after transmitting through light flux control member 123 and light diffusion member 126.

Comparing curve A (using light flux control member 5) with curve B (using light flux control member 123), the followings are understood.

That is, Curve A shows a gently rising mountain-like changing while Curve B shows a sharp rising in the vicinity of optical axis L. Curve A gives smaller intensities in the vicinity of optical axis L as compared with Curve B, but giving grater intensities in positions far from optical axis L as compared with Curve B.

This tells that light flux control member 5 in accordance with the present invention provides more uniformly distributed illumination as compared with the prior art.

(Case of Multi-LED Arrangement)

In FIG. 10, curve C shows a distribution of emission intensity in a case where light flux control members 5 in accordance with the present invention are disposed corresponding to a plurality of light emitting elements 4, giving light intensity of light emitting elements 4 after transmitting through light flux control members 5 and light diffusion member 7 (See FIGS. 1 and 2).

In FIG. 10, Curve D shows a distribution of emission intensity in the prior art case of FIG. 15 where light flux control members 123 corresponding to a plurality of LEDs 124 are disposed, giving light intensity of one LEDs 124 after transmitting through light flux control members 123 and light diffusion member 126.

Comparing curve C (using light flux control members 5) with curve D (using light flux control members 123), the followings are understood.

That is, Curve D shows a striking wave/-like repeating brightness unevenness corresponding to discretely arranged LEDs 124. To the contrary, Curve C hardly shows such a striking brightness unevenness.

This is supposed to be brought by two facts. One fact is that light from each light emitting element 4 is free from locally strong emission toward a direction along optical axis L and spread widely, as Curve A shows. Another fact is that light beams from light emitting elements 4 adjacent to each other are mixed mutually well, with the result a small bright unevenness is realized on an emission face side of light diffusion ] member 7.

As described above, the present invention can provide uniform and well-mixed illumination as shown in FIG. 10.

Well-mixed illumination enables high quality illumination to be realized even if a plurality of light emitting elements 4, such as white light emitting LEDs), have different intensities or emission tones. For example, even if some emit remarkably yellowish light and others emit slightly yellowish light, uniformly yellowish illumination is obtained.

<Surface Light Source Device and Display for Color Illuminations>

FIGS. 11A and 11B illustrate color-emission type surface light source device 2 and display 1 using the same to which the present invention is applicable. FIG. 11A is a plan view, with a member to be illuminated and light diffusion member being not shown and FIG. 11B is a cross section view along X4-X4 in FIG. 11A.

As illustrated, light emitting elements 4R, 4G and 4B emitting light of colors R, G and B are disposed alternately. Light from these light emitting elements is emitted from light control emission face 6 of light flux control member 5 to irradiate member 3 to be irradiated after transmitting through light diffusion member 7.

Not only in a case all light emitting elements 4R, 4G and 4B are lighted on, but also in a case any of light emitting elements 4R, ones 4G and 4B are lighted on, light of each light emitting element can reach far positions over adjacent ones, being mixed well there. This brings a uniform brightness.

It is noted that emission device 29 in accordance with the present invention has third emission face region 6c at which two or more emission devices 29 are connected with each other. If pitch of LED 19 or light emitting element 4 is small, this makes assembling for obtaining surface light source device 2 easy.

If large emission device 29 is produced, one light flux control member may be assembled from a plurality of blocks each of which corresponds to one light emitting element 4.

Further, although above description handles cases optical axis L of light from light emitting element 4 accord a normal direction as shown in FIG. 3, this does not limit the scope of the present invention,

For example, the present invention can be applied to cases where optical axis L of light from light emitting element 4 is slightly different from a normal direction due to unevenness in quality of light emitting element 4 or assembling errors of components including light emitting element 4, allowing to provide generally the same functions as those of embodiments described above.

Claims

1. An emission device comprising a light flux control member provided with a recess and an light control emission face, and a light emitting element accommodated in said recess, said light emitting element emits light which is emitted from said light control emission face after travelling within said light flux control member,

wherein said light control emission face is configured so as to satisfy the following Conditions 1 and 2 for at least light which is emitted toward within a half-intensity-angular-range around a maximum-intensity-emission-direction from said light emitting element;

Condition 1: Relation θ5/θ1>1 is satisfied except for light emitted toward within an angular-neighborhood of a standard optical axis of said emission device;

Condition 2: Value of θ5/θ1 decreases gradually according to increasing of θ1;

2. The emission device in accordance with claim 1, wherein said recess provides a concave surface which is in contact with an light emitting surface of said light emitting element.

3. The emission device in accordance with claim 1, wherein said recess provides a concave surface and a gap is formed between said concave surface and an light emitting surface of said light emitting element.

4. The emission device in accordance with claim 1, 2 or 3, wherein said light control emission face includes a first emission face region crossing with said standard optical axis and a second emission face region extending around said first emission face region, said first and second emission face regions having a connecting portion in which a point of inflection exists.

5. A surface light source device comprising an emission device and a light diffusion member which diffuses and transmits light from said emission device,

wherein said emission device is an emission device in accordance with claim 1, 2 or 3.

6. A surface light source device comprising an emission device and a light diffusion member which diffuses and transmits light from said emission device,

wherein said emission device is an emission device in accordance with claim 4.

7. The surface light source device comprising an emission device and a light diffusion member which diffuses and transmits light from said emission device,

wherein said emission device is an emission device in accordance with claim 5.

8. The surface light source device comprising an emission device and a light diffusion member which diffuses and transmits light from said emission device,

wherein said emission device is an emission device in accordance with claim 6.

9. The emission device in accordance with claim 1, wherein said light emitting element is sealed by a sealing material so that light emitted from said light emitting element impinges on said light flux control member after transmitting through said sealing material.

10. The emission device in accordance with claim 9, wherein said recess provides a concave surface which is in contact with an outer surface of said sealing material.

11. The emission device in accordance with claim 9, wherein said recess provides a concave surface and a gap is formed between said concave surface and an outer surface of said sealing material.

12. The emission device in accordance with claim 9, 10 or 11, wherein said light control emission face includes a first emission face region crossing with said standard optical axis and a second emission face region extending around said first emission face region, said first and second emission face regions having a connecting portion in which a point of inflection exists.

13. The surface light source device comprising an emission device and a light diffusion member which diffuses and transmits light from said emission device,

wherein said emission device is an emission device in accordance with claim 9, 10 or 11.

14. The surface light source device comprising an emission device and a light diffusion member which diffuses and transmits light from said emission device,

wherein said emission device is an emission device in accordance with claim 12.

15. The surface light source device comprising an emission device and a light diffusion member which diffuses and transmits light from said emission device,

wherein said emission device is an emission device in accordance with claim 13.

16. The surface light source device comprising an emission device and a light diffusion member which diffuses and transmits light from said emission device,

wherein said emission device is an emission device in accordance with claim 14.

17. A light flux control member provided with a recess for accommodating a light emitting element, comprising:

a light control emission face for causing light coming from said light emitting element after travelling within said light flux control member to be emitted,

wherein said light control emission face is configured so as to satisfy the following Conditions 1 and 2 for at least light which is emitted toward within a half-intensity-angular-range around a maximum-intensity-emission-direction from said light emitting element;

Condition 1: Relation θ5/θ1 >1 is satisfied except for light emitted toward within an angular-neighborhood of a standard optical axis of said light flux control member;

Condition 2: Value of θ5/θ1 decreases gradually according to increasing of θ1;

18. The light flux control member in accordance with claim 17, wherein said recess is a recess for accommodating a light emitting element together with a sealing material that seals said light emitting element.

19. A surface light source device comprising:

an emission device unit comprising a substrate and emission devices disposed on said substrate, each of said emission devices including a light emitting element and a light flux control member for controlling a light distribution of light emitted from said light emitting element; and

a diffuser disposed over said emission device unit,

wherein said light flux control member includes a light incidence surface on which light emitted from said light emitting element is incident, and an light control emission face which emits light incident on said incidence surface,

said light control emission face is configured so as to satisfy the following Conditions 1 and 2 for at least light which is emitted toward within a half-intensity-angular-range around a maximum-intensity-emission-direction from said light emitting element, and thereby the at least light which is emitted toward within said half-intensity-angular-range around said maximum-intensity-emission-direction from said light emitting element is expanded smoothly;

Condition 1: Relation θ5/θ1>1 is satisfied except for light emitted toward within an angular-neighborhood of a standard optical axis of said emission device;

Condition 2: Value of θ5/θ1 decreases gradually according to increasing of θ1;

where θ1 is an emission angle of any light at being emitted from said light emitting element, and θ5 is an emission angle of that light of θ1 at then being emitted from said light control emission face of said light flux control member,

said emission devices are disposed on said substrate at predetermined intervals so that light from said emission devices adjacent to each other are mixed,

said diffuser is disposed over said emission device unit such that light from said emission devices adjacent to each other are mixed between said emission devices and said diffuser, and

said light emitted from said emission device is directly applied to the diffuser and does not travel through another element disposed between said emission device and said diffuser.

20. The surface light source device in accordance with claim 19, wherein said light control emission face has a substantially circular shape when viewed along said standard optical axis.

21. The surface light source device in accordance with claim 19, wherein said light control emission face includes a first emission face region existing within a predetermined range from said standard optical axis and a second emission face region extending around said first emission face region, said first emission face region having a concave shape being shaped like a partially removed sphere, said first emission face region and second emission face region having a connecting portion in which a point of inflection exists.

22. The surface light source device in accordance with claim 21, wherein θ3 decreases gradually according to increasing of θ1 in said first emission face region, and θ3 increases gradually according to increasing of θ1 in said second emission face region, where θ3 is an angle between a line perpendicular to said standard optical axis and a line being a tangent of said light control emission face at a pass position at which that light of θ1 is emitted from said light control emission face.

23. The surface light source device in accordance with claim 19, wherein a gap is formed between said light incidence surface and a light emitting surface of said light emitting element.

24. The surface light source device in accordance with claim 19, wherein said light emitting element is sealed by a sealing material.

25. The surface light source device in accordance with claim 24, wherein a gap is formed between said light incidence surface and an outer surface of said sealing material.

26. The surface light source device in accordance with claim 19, wherein said emission devices are disposed on said substrate at predetermined intervals such that light from said emission devices adjacent to each other across said emission device are mixed between said emission devices and said diffuser.

27. The emission device to be used in said surface light source device in accordance with claim 19.

28. A display comprising:

said surface light source device in accordance with claim 19; and

a display member to be irradiated with light emitted from said surface light source device.