JP2000090719A - Surface light source device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To emit illumination light from a light source forward,
Provided is a surface light source device capable of reflecting external light incident from the front and emitting the light forward. A light guide having one end face formed as an incident end face and a front face formed in a stepped surface, a light source disposed on a side of the light guide, and the light guide. And a reflection plate 6a provided on the back side of the light source 3. The illumination light from the light source 3 is
The light is introduced into the light guide 1 from the incident end face 1a, emitted from the plurality of step surfaces 2b on the front surface of the light guide 1, and external light incident from the front of the light guide 1 is transmitted to the light guide 1. The reflected light of the external light which enters from the plurality of stepped surfaces 2a on the front surface, exits to the rear surface, is reflected by the reflection plate 6a and is incident on the light guide 1 from the back surface is reflected by the plurality of light guides 1 From the step surface 2a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface light source device having both a function of emitting illumination light from a light source forward and a function of reflecting external light incident from the front and emitting the light forward. .

[0002]

2. Description of the Related Art As a surface light source device used as a backlight of a display device provided with a non-light emitting type display body which controls transmission of light incident from the outside such as a liquid crystal display element, for example, a side light type is used. There is something called.

Conventionally, this side light type surface light source device takes in light from an end face and emits the light to the front side, and illumination light arranged on the side of the end face that takes in the light from the light guide plate. And a light source that emits light. The light source includes a straight tube fluorescent lamp or a neon tube, an EL (electroluminescence) illuminant,
An LED array or the like in which EDs (light emitting diodes) are arranged is used.

Generally, a flat transparent plate made of acrylic resin or the like is used for the light guide plate, at least one end surface of which is an incident end surface for receiving illumination light from the light source, and the entire front surface is formed. , And an emission surface of the light taken in from the incident end surface.

The light guide plate receives illumination light from the light source from the incident end face, and reflects the illumination light in the longitudinal direction of the light guide plate while totally reflecting the illumination light at the interface between the front and back surfaces of the light guide plate and the outside air (air). And emits forward from almost the entire area of the front surface.

[0006]

By the way, a display device using a surface light source device as a backlight always performs a transmissive display using illumination light from the surface light source device, and a display device such as natural light or indoor light. There is a so-called two-way display type that performs both a reflective display using external light and a transmissive display using illumination light from the surface light source device.

When the external light of sufficient brightness can be obtained, the two-way display device performs a reflection type display using the external light without emitting the illumination light from the surface light source device, and the brightness of the external light is increased. When the surface light source device is not enough, the illumination light is emitted from the surface light source device, and the reflection type display using the external light and the transmission type display using the light from the surface light source device are simultaneously performed, so that the reflection is performed. The transmissive display compensates for the lack of screen luminance due to the mold display, and performs transmissive display using light from the surface light source device when external light cannot be obtained. The device can perform display under an environment of any brightness, and it is not necessary to emit illumination light from the surface light source device when external light with sufficient external light is obtained. Therefore, always use a surface light source device As compared with performing transmissive display using illumination light, it has the advantage that power consumption is small.

However, in the conventional surface light source device, illumination light from a light source arranged on the side of the light guide plate is taken into the light guide plate from its incident end face, and the illumination light is emitted forward from the front surface of the light guide plate. For example, in order to configure the above-described two-way display device, a semi-transmissive reflector is disposed on the back of a non-light-emitting display such as a liquid crystal display element, and behind the transflective plate. The surface light source device had to be arranged.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a surface light source device capable of emitting illumination light from a light source forward and reflecting external light incident from the front to emit the light forward. .

[0010]

According to the surface light source device of the present invention, at least one end surface is an incident end surface, and the front surface has a stepped surface having a plurality of step surfaces and a plurality of step surfaces connecting these step surfaces. Light, which takes in the illumination light from the incident end face and emits the light from the plurality of step faces, takes in the external light incident from the front from the plurality of step faces, emits the light to the rear face, and emits the light from the back face. A light guide that emits illumination light from the plurality of stepped surfaces, a light source that is disposed on a side of the light guide, and emits illumination light toward the incident end face of the light guide, and a back surface of the light guide. And a reflecting means for reflecting the external light emitted to the back surface of the light guide.

That is, in the surface light source device according to the present invention, the illumination light from the light source is taken into the light guide from its incident end face and emitted from a plurality of step surfaces on the front surface of the light guide, and the light guide is provided. External light incident from the front of the light body is taken in from a plurality of step surfaces on the front surface of the light guide and emitted to the rear surface, and the external light reflected by the reflection means and incident on the light guide from the rear surface is input. The reflected light is emitted from the plurality of step surfaces of the light guide, and according to the surface light source device, the illumination light from the light source is emitted forward,
External light incident from the front can be reflected and emitted forward.

Therefore, according to this surface light source device, when external light with sufficient brightness is obtained, only the reflected light of the external light is emitted without turning on the light source, and the brightness of the external light is insufficient. Sometimes, the light source is turned on to emit both reflected light of external light and illumination light from the light source to compensate for the lack of luminance of the reflected light of external light by the illumination, and that no external light is obtained. In some cases, illumination light from the light source can be emitted.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, a surface light source device according to the present invention has a staircase having at least one end surface serving as an incident end surface, a front surface having a plurality of step surfaces, and a plurality of step surfaces connecting these step surfaces. It is formed on a shape surface, and takes in the illumination light from the incident end surface and emits the light from the plurality of step surfaces, fetches the external light incident from the front from the plurality of step surfaces and emits the light to the back surface, and from the back surface. A light guide that emits incident light from the plurality of step surfaces; a light source that is disposed on a side of the light guide and emits illumination light toward the incident end surface of the light guide; Reflecting means for reflecting the external light emitted to the back of the light guide, the illumination light from the light source being taken into the light guide from the incident end face thereof, and It is emitted from a plurality of step surfaces on the front of the light body. External light incident from the front of the light guide is taken in from a plurality of step surfaces on the front of the light guide and emitted to the back, reflected by the reflection means and incident on the light guide from the back. The reflected light of the external light is emitted from the plurality of step surfaces of the light guide. According to this surface light source device, the illumination light from the light source is emitted forward, and from the front. Since the incident external light can be reflected and emitted forward, when external light of sufficient brightness can be obtained, only the reflected light of the external light is emitted without turning on the light source and the brightness of the external light is increased. When the light is insufficient, the light source is turned on to emit both the reflected light of the external light and the illumination light from the light source to compensate for the lack of luminance of the reflected light of the external light by the illumination. When it is not possible to emit the illumination light from the light source Kill.

Therefore, according to this surface light source device, for example, a two-way display device that displays both a reflection type display using external light and a transmission type display using illumination light from the surface light source device is provided in half. It can be configured without using a transmission reflection plate.

In the surface light source device according to the present invention, the external light incident on the front side of the light guide from the front and the external light reflected by the reflecting means and emitted from the plurality of step surfaces of the light guide. It is preferable to dispose an optical member that transmits the reflected light and emits illumination light emitted from a plurality of step surfaces of the light guide forward in a predetermined direction.

With this configuration, the illumination light emitted from the plurality of step surfaces of the light guide can be turned forward in a predetermined direction by the optical member. Light can be emitted in a predetermined direction.

In this case, the optical member is formed of a transparent plate having a flat front surface and a rear surface facing the front surface of the light guide, and the rear surface is provided with the step surface of the light guide. It is preferable that a plurality of projection-like incident portions having an incident surface for capturing illumination light emitted from the lens and a refraction surface for refracting the light captured from the incident surface in the front direction are formed, With such a configuration, almost all of the illumination light emitted from the plurality of step surfaces of the light guide can be taken into the optical member without waste, and can be emitted forward from the front surface.

Further, by configuring the optical member as described above, light emitted from a plurality of step surfaces of the light guide and incident on a plurality of incident portions of the optical member from the incident surface can be transmitted to the optical member. The light is refracted by the refraction surface and condensed in a predetermined direction, and illumination light having a high luminance distribution in a predetermined direction (for example, front direction) can be emitted from the front surface of the optical member, and is reflected by the reflection unit. Thus, the reflected light of the external light emitted from the plurality of stepped surfaces of the light guide can also be emitted forward of the optical member as light having a high brightness distribution in a predetermined direction (for example, the front direction).

Further, the optical member is provided with the plurality of incident portions at intervals, and a region between the adjacent incident portions on the back surface of the optical member is provided with the plurality of incident portions of the light guide. It is more desirable to adopt a configuration in which the input / output surface faces the step surface.

According to the optical member having such a configuration, external light incident on the optical member from the front surface is emitted to the rear surface of the optical member from the incident portion and the entrance / exit surface therebetween, and the reflection means is provided. The reflected light of external light reflected by the light guide and emitted from the plurality of step surfaces of the light guide is taken into the optical member from the incident portion and the input / output surface, and emitted forward from the front surface of the optical member. In addition, the reflected light can be light having a luminance distribution with a higher luminance in a predetermined direction (for example, the front direction).

Further, in this surface light source device, the light source is provided with an illumination brightness control means for controlling the brightness of the illumination light emitted from the light source, and the reflectance of the external light by the reflection means and the illumination brightness are controlled. It is preferable that the brightness control condition of the illumination light by the control means is set such that the brightness of the light emitted in front of the surface light source device falls within a predetermined brightness range according to the illuminance of the external environment. By doing so, even when emitting only reflected light of external light without turning on the light source in an environment where external light of sufficient brightness is obtained,
When the light source is turned on in an environment where the brightness of the external light is insufficient, and both the reflected light of the external light and the illumination light from the light source are emitted to compensate for the insufficient luminance of the reflected light of the external light by the illumination. Also, when illuminating light from the light source is emitted in an environment where external light cannot be obtained, it is possible to emit light having a brightness suitable for the illuminance of the environment according to the illuminance of the environment.

[0022]

1 and 2 show an embodiment of the present invention. FIG. 1 is a side view of a surface light source device, and FIG. 2 is an enlarged view of a front plate and a part of an optical member of the surface light source device. is there.
The surface light source device of this embodiment includes a light guide 1 and the light guide 1.
, A light source 3 disposed on the back side of the light guide 1, and an optical member 7 disposed on the front side of the light guide 1.

The light guide 1 is a transparent plate made of an acrylic resin or the like, and one end surface thereof is an incident end surface 1a for receiving light from the light source 3. In addition, this light guide 1
A plurality of parallel step surfaces 2a formed so as to be gradually lowered from the incident end surface 1a side to the other end side (narrowing the gap with the back surface of the light guide 1); The stepped surface 2a is formed on a stepped surface 2 having a minute pitch and composed of a plurality of stepped surfaces 2b connecting the stepped surfaces 2a, and the back surface is a flat surface.

The plurality of step surfaces 2a are substantially parallel to the back surface of the light guide 1 and in the width direction of the light guide 1 (incident end surface 1a).
(Longitudinal direction), and these step surfaces 2a are external light incident / exit surfaces, respectively.

The plurality of step surfaces 2b are rising surfaces of extremely small height substantially parallel to the incident end surface 1a, and these step surfaces 2b are emission surfaces of illumination light.

The light guide 1 receives illumination light from a light source 3 disposed on its side from the incident end face 1a and emits the light from the plurality of stepped faces 2b, and also filters external light incident from the front. The light from the plurality of step surfaces 2a is emitted to the back surface, and the light incident from the back surface is reflected by the plurality of step surfaces 2a.
Emitted from

The light source 3 is a light incident end face 1 of the light guide 1.
a light-emitting body 4 such as a straight fluorescent lamp or a neon tube, an EL (electroluminescence) light-emitting body, an LED array in which a plurality of LEDs (light-emitting diodes) are arranged, and the like; A reflector 5 reflects the light emitted from the light emitter 4. The light source 3 is arranged on the side of the light guide 1 so as to face the incident end face 1a.

The reflecting means 6 provided on the back side of the light guide 1 is composed of a mirror-reflecting plate 6a having a high reflectivity. It is arranged close to the back of the body 1.

On the other hand, the optical member 7 disposed on the front side of the light guide plate 1 is reflected by the external light incident from the front thereof and the reflection plate 6a (reflecting means 6) so as to reflect the light guide 1
Having a characteristic that the reflected light of the external light emitted from the plurality of step surfaces 2a is transmitted, and the illumination light emitted from the plurality of step surfaces 2b of the light guide 1 is emitted forward in a predetermined direction. I have.

The optical member 7 is a transparent plate made of an acrylic resin or the like having substantially the same width as the light guide 1 and having a flat front surface and a back surface facing the front surface of the light guide 1. In addition, a plurality of incident portions 8 for taking in illumination light emitted from the plurality of step surfaces 2b of the light guide 1 are integrally provided on the back surface thereof.

Each of the plurality of incident portions 8 is formed in the shape of a horizontally long projection extending over the entire width of the optical member 7, and the optical member 8 is arranged in the longitudinal direction of the plurality of incident portions 8 on the back surface thereof. Are substantially parallel to the length direction of the plurality of step surfaces 2 b of the light guide 1, and the apexes of the plurality of incident portions 8 are arranged so as to approach or contact the plurality of step surfaces 2 a of the light guide 1. ing.

The plurality of incident portions 8 formed on the back surface of the optical member 7 have a triangular cross-sectional shape, and oppose the step surface 2b of the light guide 1 on both side surfaces thereof. One side surface is an incident surface 8a for taking in the illumination light emitted from the step surface 2b of the light guide 1, and the other side surface is a refraction for refracting the illumination light taken in from the incident surface 8a toward the front. Surface 8b.

The incident surface 8a has an inclination substantially parallel to or close to the step surface 2b of the light guide 1 and an angle with respect to the step surface 2a of the light guide 1 (an angle in a direction facing the step surface 2b). ) Does not exceed 90 °, and the angle between the refracting surface 8 b and the normal to the front surface of the optical member 7 is:
This is an inclined surface having an inclination angle larger than the angle between the incident surface 8a and the normal.

The more desirable shape of the incident portion 8 is such that the incident surface 8a is inclined by 5 to 15 degrees with respect to the normal to the step surface 2b of the light guide 1, and the refracting surface 8b Has a shape inclined by 20 to 50 degrees in a direction opposite to the incident surface 8a with respect to the normal line.

Further, the plurality of incident portions 8 are provided at a constant pitch with an interval therebetween, and a region between the adjacent incident portions 8 on the back surface of the optical member 7. Are input / output surfaces 9 facing the plurality of step surfaces 2a of the light guide 1.

The input / output surface 9 is provided on the step surface 2 of the light guide 1.
is a surface that is almost parallel to a or has a slope close to it,
External light incident on the optical member 7 from the front thereof and the plurality of step surfaces 2a of the light guide 1 reflected by the reflection plate 6a.
This is a surface through which the reflected light of the external light emitted from the light transmitting portion is transmitted.

Further, the plurality of incident portions 8 are provided at a pitch smaller than the pitch of each step surface 2b of the light guide 1, and therefore, the plurality of step surfaces 2b of the light guide 1 are provided.
Are always opposed to at least one incident portion 8 of the optical member 7.

In this surface light source device, as shown in FIG. 1, the light source 3 is provided with an illumination brightness control means 10 for controlling the brightness of the illumination light emitted from the light source 3.

The illumination luminance control means 10 includes an illuminance detector 11 for measuring the illuminance of an external environment (the use environment of the surface light source device), and the light source 3 based on the environmental illuminance measured by the illuminance detector 11. And a means for controlling the luminance of the illumination light emitted by the light-emitting body 4. The means for controlling the luminance of the illumination light includes a luminance adjustment circuit 12 and a light source lighting circuit 13.

The illuminance detector 11 adjusts the light receiving surface to the front surface (the optical member 7) of the surface light source device so as to measure the same environmental illuminance as the illuminance of external light incident on the surface light source device from the front.
And the front surface of the lens).

Further, the brightness adjusting circuit 12 adjusts the brightness of the illumination light emitted from the light source 3 based on the environmental illuminance measured by the illuminance detector 11 to the intensity of the emitted light emitted in front of the surface light source device. The light source lighting circuit 13 adjusts the luminous body 4 of the light source 3 according to the luminance value from the luminance adjustment circuit 12 so that the luminance falls within a predetermined luminance range according to the ambient illuminance. It is driven so as to emit illumination light having the increased brightness.

In this surface light source device, the reflectance of the external light by the reflection plate 6a and the brightness control condition of the illumination light by the illumination brightness control means 10 are determined by the light emitted to the front of the surface light source device. Is set so as to fall within a predetermined luminance range according to the illuminance of the external environment.

In the surface light source device, the illumination light from the light source 3 is guided by the light guide plate 1 and emitted from the plurality of stepped surfaces 2b on the front surface of the light guide plate 1, and the external light incident from the front is reflected by the light guide plate 1. The light is reflected by the plate 6a and emitted forward, and the light source 3 is turned on when the reflected light of external light incident from the front alone cannot provide emitted light of sufficient luminance.

That is, this surface light source device emits only the reflected light of the external light without turning on the light source 3 when the external light of sufficient brightness is obtained, and when the brightness of the external light is insufficient. Turns on the light source 3 so that the reflected light of external light and the light source 3
The illumination makes up for the lack of brightness of the reflected light of the external light by emitting both of the illumination light from the light source, and emits the light from the light source 3 when the external light cannot be obtained.

First, the emission path of the illumination light from the light source 3 will be described. Illumination light from the light source 3 is incident on the light guide 1 as shown by a solid line in FIG. 1 and FIG. 1a, and is guided in the light guide 1 in the length direction.

Then, of the illuminating light guided in the light guide 1 in the longitudinal direction thereof, light directed directly to any one of the plurality of step surfaces 2b on the front surface of the light guide is the step surface 2b.
Out of the light guide 1 toward the front side.

Light other than the light directly traveling to the step surface 2b, ie, the light traveling toward the plurality of step surfaces 2a on the front surface of the light guide and the light traveling toward the back surface of the light guide 1, Step surface 2a and outside air (air layer between light guide 1 and optical member 7)
Due to the total reflection at the interface with the light guide and the interface between the back surface of the light guide and the outside air (the air layer between the light guide 1 and the reflection plate 6a). The light is changed in direction while being guided by the light source, enters one of the plurality of step surfaces 2b, and exits from the step surface 2b.

In the light traveling inside the light guide 1 toward the rear surface, the light enters the interface between the light guide rear surface and the outside air at an incident angle smaller than the total reflection critical angle (nearly perpendicular). There is also light, and the light passes through the interface and leaks to the back surface of the light guide 1. The leak light is reflected by the reflector 6a disposed close to the back surface of the light guide 1 and becomes light. The light enters the light body 1 again from its rear surface.

The direction of the re-incident light changes due to total reflection at the interface between the step surface 2a on the front surface of the light guide and the outside air and total reflection at the interface between the back surface of the light guide and the outside air. 2b
Emitted from any of.

Some of the light guided inside the light guide 1 is incident on the interface between the step surface 2a on the front surface of the light guide plate and the outside air at an angle of incidence smaller than the critical angle for total reflection. Is emitted from the step surface 2a to the front of the light guide plate 1 through the interface.

Therefore, the light guide 1 has its incident end face 1
Most of the illumination light taken from a is emitted to the front of the light guide plate 1 without waste. The illumination light emitted in front of the light guide 1 is applied to the optical member 7 disposed on the front side of the light guide 1, to a plurality of incident portions 21 on the back side, and to the first side of the first side. The light enters from the optical interface 21a.

At this time, the plurality of step surfaces 2 of the light guide 1
b is at least one of 7 of the optical members,
Most of the light emitted from the plurality of stepped surfaces 2b of the light guide 1 is incident on any one of the incident portions 7 of the optical member 7 without waste because the light incident portions 8 always face the two incident portions 8.

As described above, among the illumination light emitted in front of the light guide 1, there is light emitted from the stepped surface 2 a as described above. The light enters the incidence part 7.

As shown in FIG. 2, some of the light emitted from the plurality of stepped surfaces 2b of the light guide 1 is emitted toward the next stepped surface 2a. The optical member 7 is reflected at the interface between the next step surface 2a and the outside air.
Incident on the incident portion 8 of the light source.

Light incident on the plurality of incident portions 8 of the optical member 7 is taken into the incident portions 8 from the incident surfaces 8a of the incident portions 8, and the interface between the refraction surface 8b on the opposite side and the outside air. The light is totally reflected and changes its direction toward the front surface of the optical member 7, passes through the optical member 7, and exits from the front surface.

Therefore, the illuminating light emitted forward from the front surface of the optical member 7 enters the plurality of incident portions 8 from the incident surface 8a, and the refracting surface 8b on the opposite side (interface with outside air).
This is light having a luminance distribution with a high luminance in a predetermined direction, which is refracted by and condensed in a predetermined direction.

In this embodiment, the refracting surface 8 of the incident portion 8
b, the direction of the light refracted by the refraction surface 8b is
It is set so as to be in the front direction (direction near the normal to the front surface of the optical member 7), so that the illumination light emitted to the front surface of the optical member 7 has directivity with high brightness in the front direction. It is the light of the distribution.

The emission direction of the illumination light emitted to the front surface of the optical member 7 is a direction corresponding to the inclination angle of the refraction surface 8b of the incident portion 8, and the inclination angle of the refraction surface 8b is Is closer to the front when it is within a range of 20 to 50 degrees with respect to the normal to the front.

Next, the outgoing path of the external light entering from the front will be described. The path of the external light entering from the front is placed on the front side of the optical member 7 as shown by the broken line in FIGS. From the optical member 7, and exits from the plurality of incident portions 8 on the rear surface and the incident / exit surface 9 between them to the rear side.

Since the external light is incident at various angles of incidence, among the external light incident from the front surface of the optical member 7 toward the incident section 8, the incident surface 8a and the incident surface 8a of the incident section 8 are included. Some light is incident on the interface between the refraction surface 8b and the outside air (the air layer between the light guide 1 and the optical member 7) at an incident angle larger than the critical angle for total reflection, and is totally reflected at the interface. The light that has been subjected to the total reflection critical angle at the interface between the incident surface 8a and the outside air is:
The light was incident on the interface between the refracting surface 8b on the opposite side and the outside air at an incident angle smaller than the critical angle for total reflection, transmitted through this interface, emitted to the back side, and totally reflected on the interface between the refracting surface 8b and the outside air. The light is incident on the interface between the opposite incident surface 8a and the outside air at an incident angle smaller than the critical angle for total reflection, passes through this interface, and exits to the back side. Therefore, most of the external light incident from the front surface of the optical member 7 is emitted to the rear surface side of the optical member 7 without waste.

Most of the external light emitted to the back side of the optical member 7 is taken into the light guide 1 from the plurality of step surfaces 2 a of the light guide 1 and transmitted through the light guide 1. And exits to the back.

Then, the light emitted to the back of the light guide 1 is reflected by a reflector 6 a arranged opposite to the back of the light guide 1, and the reflected light is reflected by the light guide 1. The light is taken in from the rear surface, passes through the light guide 1, and exits forward from the plurality of step surfaces 2 a on the front surface, and the optical member 7 has a plurality of incident portions 8 on the rear surface and an input / output surface 9 therebetween. Incident from

At this time, as described above, the incident portion 8 has the incident surface 8a on one side thereof connected to the step surface 5 of the front plate 4.
b is a surface that is almost parallel to b or has a slope close to it,
Since the opposite refracting surface 8b is an inclined surface having an angle formed by a normal to the front surface of the optical member 7 and a larger angle than the angle formed by the incident surface 8a and the normal, the light guide is formed. Most of the reflected light emitted from the plurality of step surfaces 2a of the body 7 is provided on the optical member 7 by a refraction surface 8b having a large inclination angle of the incident portion 8 and an incident / exit surface between the plurality of incident portions 8. 9 and taken in.

Then, of the reflected light taken into the optical member 7 from the refraction surface 8b and the entrance / exit surface 9 of the incident portion 8, the light directly traveling to the front surface of the optical member 7 is transmitted through the optical member 7. Of the light emitted from the front surface and directed toward the opposite incident surface 8a of the light taken in from the refraction surface 8b of the incident portion 8, is totally reflected at the interface between the incident surface 8a and the outside air. The direction is changed, and the light is emitted from the front surface of the optical member 7 by changing the direction from the refraction surface 8b and the entrance / exit surface 9 to a direction close to the direction of light directly traveling toward the front surface of the optical member 7.

Therefore, in this surface light source optical device, external light incident from the front is also emitted forward almost without waste. In addition, the reflected light of the external light emitted forward from the front surface (the front surface of the optical member 7) of the surface light source optical device is high-luminance light in which the external light incident at various incident angles is collected. The reflected light of the external light is also light having a luminance distribution in which the luminance of light emitted in a predetermined direction (for example, the front direction) is high.

As described above, this surface light source device has a stepped surface 2 having one end face as the incident end face 1a, a front face having a plurality of step faces 2a and a plurality of step faces 2b connecting these step faces 2a. The illumination light is taken in from the incident end face 1a and emitted from the plurality of step faces 2b, and the external light incident from the front is taken in from the plurality of step faces 2a and emitted to the back, and A light guide 1 for emitting light incident from the plurality of stepped surfaces 2a, and a light guide 1 disposed on a side of the light guide 1 and the incident end face 1 of the light guide 1.
a light source 3 for emitting illumination light toward the light guide 1; and a reflecting plate 6a provided on the back side of the light guide 1 and reflecting the external light emitted to the back of the light guide 1. Illumination light from the light guide 3 is taken into the light guide 1 from its incident end face 1a and emitted from a plurality of step surfaces 2a on the front surface of the light guide 1, and external light entering from the front of the light guide 1 To
The reflected light of the external light, which is taken in from the plurality of stepped surfaces 2a on the front surface of the light guide 1 and emitted to the back surface, is reflected by the reflection plate 6a and enters the light guide 1 from the back surface, is transmitted through the light guide. According to this surface light source device, the illumination light from the light source 3 is emitted forward, and the external light incident from the front is reflected by the surface light source device. Can be emitted forward.

Further, in the surface light source device of the above embodiment, external light incident from the front and the plurality of stepped surfaces 2a of the light guide 1 are reflected by the reflection plate 6a on the front side of the light guide plate 1. The optical member 7 that transmits the reflected light of the emitted external light and emits the illumination light emitted from the plurality of stepped surfaces 2b of the light guide 1 forward in a predetermined direction is disposed. The illuminating light emitted from the plurality of step surfaces 2a of the optical body 1 can be changed in a predetermined direction by the optical member 7 and emitted forward, so that the illuminating light can be emitted in a predetermined direction. it can.

In the above embodiment, the optical member 7
Is formed of a transparent plate having a front surface formed of a flat surface and a back surface facing the front surface of the light guide 1, and an incident light for taking in illumination light emitted from the stepped surface 2 b of the light guide 1 on the back surface. Since a plurality of projecting incident portions 8 having a surface 8a and a refracting surface 8b for refracting light taken in from the incident surface 8a in the front direction are formed, a plurality of step surfaces of the light guide 1 are formed. Most of the illumination light emitted from 2b can be taken into the optical member 7 without waste, and emitted forward from the front surface.

Further, in this surface light source device, since the optical member 7 has the above-described configuration, the light is emitted from the plurality of step surfaces 2b of the light guide 1 and the plurality of incident portions 8 of the optical member 7 is emitted. The light incident from the incident surface 8a is refracted by the refracting surface 8b and condensed in a predetermined direction, and illumination light having a high luminance distribution from the front surface of the optical member 7 in a predetermined direction (for example, the front direction). And the reflected light of external light reflected by the reflection plate 6a and emitted from the plurality of step surfaces 2a of the light guide 1 also has high brightness in a predetermined direction (for example, in the front direction). The light can be emitted in front of the optical member 7 as light having a distribution.

Further, in the above embodiment, the optical member 7
The plurality of incident portions 8 are provided at intervals, and a region between the adjacent incident portions 8 on the rear surface of the optical member 7 is
Since the light guide 1 is configured so as to have the incident / exit surface 9 facing the plurality of step surfaces 2a, external light incident on the optical member 7 from the front surface is transmitted to the incident portion 8 and the incident / exit portion therebetween. The reflected light of external light which is emitted from the surface 9 to the back surface of the optical member 7 and is reflected by the reflection plate 6a and emitted from the plurality of stepped surfaces 2a of the light guide 1 is reflected by the incident portion 8 and the incident / emitted light. Taking in the optical member 7 from the surface 9,
The light can be emitted forward from the front surface of the optical member 7, and the reflected light can be converted into light having a higher luminance in a predetermined direction (for example, the front direction).

Further, in the above-mentioned surface light source device, the light source 3 is provided with an illumination brightness control means 10 for controlling the brightness of the illumination light emitted from the light source 3, so that the reflectance of the external light by the reflection plate 6a is improved. The luminance control condition of the illumination light by the illumination luminance control means 10 is set such that the luminance of the light emitted in front of the surface light source device is within a predetermined luminance range according to the illuminance of the external environment. Therefore, in an environment in a wide illuminance range from low illuminance to high illuminance, light having a luminance suitable for the environmental illuminance can be emitted.

That is, the preferable luminance of the emitted light emitted from the surface light source device depends on the illuminance of the external environment. Even if the emitted light has the same luminance, the emitted light may be too dazzling or too dark depending on the illuminance of the environment. .

For this reason, in this embodiment, even in an environment of high illuminance exceeding 100,000 lux, such as under direct sunlight in summer, for example, the reflecting plate 6a is provided so as to obtain light of suitable brightness that is not too dazzling. The reflectance is set to be somewhat lower, and the emission luminance by both the reflected light of the external light reflected by the reflection plate 6a and the illumination light from the light source 3 (however, the ambient illuminance is almost 0 lux) In such a case, the luminance of the illumination light emitted from the light source 3 is controlled by the illumination luminance control means 10 according to the environmental illuminance so that the emission luminance only by the illumination light) becomes a suitable luminance according to the environmental illuminance. I am trying to do it.

Therefore, according to the surface light source device described above, even when only the reflected light of the external light is emitted without turning on the light source 3 in an environment where the external light with sufficient brightness can be obtained, the brightness of the external light can be reduced. When the light source 3 is turned on in an insufficient environment to emit both the reflected light of the external light and the illumination light from the light source 3 to compensate for the lack of brightness of the reflected light of the external light by the illumination, Even when illuminating light from the light source is emitted in an environment where light cannot be obtained, it is possible to emit light having a luminance suitable for the environmental illuminance in accordance with the illuminance of the environment.

Further, in the above-mentioned surface light source device, in an environment where external light of sufficient brightness can be obtained, light having a luminance suitable for environmental illuminance can be emitted only by reflected light of external light without turning on the light source 3. In the environment where the brightness of the external light is insufficient, the light source 3 is turned on, and both the reflected light of the external light and the illumination light from the light source 3 are emitted, so that the reflected light of the external light is reduced. Even when the insufficient illumination is compensated for by the illumination, the luminance of the illumination light emitted from the light source 3 is adjusted so that the emission luminance by both the reflected light of the external light and the illumination light becomes a luminance suitable for environmental illuminance. Since the control is sufficient, the power consumption of the light source 3 may be small.

The above-mentioned surface light source device is used, for example, in a two-way display device which displays both a reflection type display using external light and a transmission type display using illumination light from the surface light source device. According to this surface light source device, the illumination light from the light source 3 can be emitted forward, and external light incident from the front can be reflected and emitted forward, so that 2
The way display device can be configured without using a transflective plate.

That is, when a two-way display device is constructed using the above-mentioned surface light source device, the liquid crystal display element is provided on the front side of the surface light source device as shown by a virtual line (two-dot chain line) in FIG. It is only necessary to arrange a non-light emitting type display 14 such as.

Since the two-way display device does not require a transflective plate, a bright image can be displayed by efficiently using both the illumination light from the surface light source device and the external light incident from the front. .

That is, in the two-way display device using the transflective plate, the illumination light from the surface light source device transmits through the transflective plate at a transmittance according to the reflection / transmission characteristics of the transflective plate. The external light incident on the display body from the rear surface thereof and from the front of the display body transmits through the semi-transmissive reflection plate at a reflectance according to the reflection / transmission characteristics of the semi-transmissive reflection plate. Since the light enters the display body from the back, neither the illumination light from the surface light source device nor the external light entering from the front can be used efficiently.

On the other hand, in the two-way display device using the surface light source device of the above embodiment, the surface light source device theoretically emits light from the light source 3 with almost 100% emission efficiency. Also, external light incident from the front is reflected with a reflection efficiency of almost 100%, and furthermore, since a semi-transmissive reflector is not required, both the illumination light from the surface light source device and the external light incident from the front are efficient. By using this, a bright image can be displayed.

In the two-way display device, the surface light source device has a high luminance in a predetermined direction from the front surface of the optical member 7 for both the illumination light from the light source 3 and the reflected light of the external light incident from the front. In order to emit as light of brightness distribution, a predetermined direction,
For example, a display with high luminance in the front direction can be obtained.

Further, the surface light source device has the light source 3 provided with an illumination brightness control means 10 for controlling the brightness of the illumination light emitted from the light source 3, and the reflectance of the external light by the reflecting plate 6a, The luminance control condition of the illumination light by the illumination luminance control means 10 is set such that the luminance of the light emitted in front of the surface light source device falls within a predetermined luminance range according to the illuminance of the external environment. Therefore, the two-way display device using this surface light source device can obtain a display having a screen luminance suitable for the environmental illuminance in a usage environment in a wide illuminance range from low illuminance to high illuminance.

In the two-way display device, external light incident from the front passes through the display 14 and enters the surface light source device, and light emitted from the surface light source device (external light is obtained). In the environment, the reflected light of the external light or both the reflected light of the external light and the illumination light from the light source 3, and the illumination light from the light source 3 in the environment where the external light cannot be obtained, pass through the display body 14. Since the light is emitted forward, the screen luminance is determined by the reflectance of external light by the reflector 6 a of the surface light source device, the luminance of illumination light from the light source 3, and the transmittance of the display 14.

Therefore, when the surface light source device is used in a two-way display device, the reflectivity of external light by the reflector 6a and the luminance control condition of the illumination light by the illumination luminance control means 10 are set to the screen luminance. May be set to be a predetermined luminance range according to the illuminance of the external environment.

That is, the suitable screen luminance according to the environmental illuminance is, for example, 20 to 200 nits at an ambient illuminance of 50 lux such as a street lamp at night, as in a room when the daytime or nighttime indoor lighting is turned on. 30-300 nits at 1000 lux of ambient illuminance, 30,000 like a shade on a sunny day
Lux ambient illuminance is 400-4000 nits.

Therefore, when the surface light source device is used in a two-way display device, the luminance of the illumination light from the light source 3 is controlled by the illumination luminance control means 10 so that the screen luminance with respect to the environmental illuminance is 50 lux. 20-200 nits, 30-300 nits at 1000 lux ambient illuminance,
What is necessary is just to control according to environmental illuminance so that it may become the brightness | luminance represented by the quadratic function which respectively satisfies the range of 400-4000 nits in environmental illuminance of 30,000 lux.

In FIG. 1, for convenience, the step-shaped surface 2 of the light guide 1, the plurality of entrances 8 of the optical member 7, and the entrance / exit surface 9 therebetween are greatly enlarged. When a dot matrix type liquid crystal display element is used for the light emitting type display body 10, the pitch of the incident portion 8 of the optical member 7 is set substantially equal to or smaller than the pixel pitch of the liquid crystal display element. The step surface 2b of the step-shaped surface 2 of the light guide 1 according to the pitch of the incident portion 8 of the member 7
It is preferable to set the pitch of the reflected light of the external light and the illumination light from the light source 3 to all the pixel portions of the liquid crystal display element. Images can be displayed.

The surface light source device is not limited to a two-way display device, and can be widely used, for example, as an illumination panel that uses light from a light source disposed laterally and external light incident from the front. it can.

In the above embodiment, the external light incident on the front side of the light guide plate 1 from the front and the external light reflected by the reflector 6a and emitted from the plurality of step surfaces 2a of the light guide 1 are described. An optical member that transmits the reflected light and emits the illumination light emitted from the plurality of stepped surfaces 2b of the light guide 1 forward in a predetermined direction is disposed, but the emission direction of the illumination light is The optical member 7 may be omitted when the direction of inclination may be large with respect to the normal line of the front surface of the optical member 1.

In the above embodiment, the reflection plate 6a is arranged on the back side of the light guide plate 1 so as to be close to the back surface, but this reflection plate 6a is attached to the back surface of the light guide plate 1. The external light reflection means 6 provided on the back side of the light guide 1 is not limited to the reflection plate 6a, and a reflection film made of, for example, aluminum or silver is deposited on the back of the light guide 1. Alternatively, it may be formed by film formation.

Further, in the above embodiment, one end face of the light guide plate 1 is used as the incident end face. However, the light guide plate 1 has, for example, the end faces at both ends as the incident end faces, and the front face as the middle of the light guide from both ends. It may be a symmetrical shape formed on a stair-shaped surface that gradually decreases toward the portion, with a middle portion in the length direction interposed therebetween.

When a light guide having such a configuration is used,
Light sources may be arranged on both sides of the incident end faces at both ends of the light guide plate, and the optical member 7 arranged on the front side of the light guide is symmetrical with respect to the left and right sides of the middle part in the length direction. What is necessary is just to form in a shape.

[0093]

According to the surface light source device of the present invention, at least one end surface is an incident end surface, and the front surface is formed as a step-shaped surface having a plurality of step surfaces and a plurality of step surfaces connecting these step surfaces. Taking in the illumination light from the incident end face and emitting from the plurality of step faces, and taking in the external light incident from the front from the plurality of step faces and emitting to the rear face,
A light guide that emits light incident from the back surface from the plurality of step surfaces, and a light source that is disposed on a side of the light guide and emits illumination light toward the incident end surface of the light guide, A reflection unit that is provided on the back side of the light guide and reflects the external light emitted to the back of the light guide, and irradiates the illumination light from the light source to the light guide from its incident end face. The light is emitted from a plurality of step surfaces on the front surface of the light guide,
External light incident from the front of the light guide is taken in from a plurality of step surfaces on the front of the light guide and emitted to the back, and reflected by the reflection means and incident on the light guide from the back. The reflected light of the external light is emitted from the plurality of step surfaces of the light guide. According to this surface light source device, the illumination light from the light source is emitted forward and is incident from the front. When the external light with sufficient brightness is obtained, only the reflected light of the external light is emitted without turning on the light source, and the brightness of the external light is increased. Is insufficient, the light source is turned on to emit both the reflected light of the external light and the illumination light from the light source to compensate for the lack of luminance of the reflected light of the external light by the illumination. When not obtained, it is possible to emit illumination light from the light source .

For this reason, according to this surface light source device, for example, a two-way display device that performs both a reflective display using external light and a transmissive display using illumination light from the surface light source device can be used as a half-display device. It can be configured without using a transmission reflection plate.

In the surface light source device of the present invention, the external light incident on the front side of the light guide from the front and the external light reflected by the reflecting means and emitted from the plurality of step surfaces of the light guide. It is desirable to arrange an optical member that transmits the reflected light of the light guide and emits the illumination light emitted from the plurality of step surfaces of the light guide forward in a predetermined direction, and in this case, the light guide Since the illumination light emitted from the plurality of step surfaces can be changed in a predetermined direction by the optical member and emitted forward, the illumination light can be emitted in a predetermined direction.

In this case, the optical member is made of a transparent plate having a flat front surface and a back surface facing the front surface of the light guide, and the rear surface is provided with the step surface of the light guide. It is preferable that a plurality of projection-like incident portions having an incident surface for capturing illumination light emitted from the lens and a refraction surface for refracting the light captured from the incident surface in the front direction are formed, With such a configuration, almost all of the illumination light emitted from the plurality of step surfaces of the light guide can be taken into the optical member without waste, and can be emitted forward from the front surface.

Further, by configuring the optical member as described above, light emitted from a plurality of step surfaces of the light guide and incident on a plurality of incident portions of the optical member from the incident surface can be reflected by the optical member. The light is refracted by the refraction surface and condensed in a predetermined direction, and illumination light having a high luminance distribution in a predetermined direction (for example, front direction) can be emitted from the front surface of the optical member, and is reflected by the reflection unit. Thus, the reflected light of the external light emitted from the plurality of stepped surfaces of the light guide can also be emitted forward of the optical member as light having a high brightness distribution in a predetermined direction (for example, the front direction).

Further, in the optical member, the plurality of incident portions are provided at intervals, and a region between the adjacent incident portions on the back surface of the optical member is divided into the plurality of light guides. It is more preferable that the input / output surface is configured to face the stepped surface. According to the optical member having such a configuration, external light incident on the optical member from the front surface is transmitted to the incident portion and the input / output portion therebetween. While being emitted from the emission surface to the back surface of the optical member, the reflected light of external light reflected by the reflection means and emitted from the plurality of step surfaces of the light guide is transmitted from the incident portion and the input / output surface to the optical member. The light can be taken in and emitted forward from the front surface of the optical member, and the reflected light can be light having a higher luminance distribution in a predetermined direction (for example, the front direction).

Further, in this surface light source device, the light source is provided with illumination luminance control means for controlling the luminance of illumination light emitted from the light source, and the reflectance of the external light by the reflection means and the illumination luminance It is preferable that the brightness control condition of the illumination light by the control means is set such that the brightness of the light emitted in front of the surface light source device falls within a predetermined brightness range according to the illuminance of the external environment. By doing so, even when emitting only reflected light of external light without turning on the light source in an environment where external light of sufficient brightness is obtained,
When the light source is turned on in an environment where the brightness of the external light is insufficient, and both the reflected light of the external light and the illumination light from the light source are emitted to compensate for the insufficient luminance of the reflected light of the external light by the illumination. Also, when illuminating light from the light source is emitted in an environment where external light cannot be obtained, it is possible to emit light having a brightness suitable for the illuminance of the environment according to the illuminance of the environment.

[Brief description of the drawings]

FIG. 1 is a side view of a surface light source device according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a part of a front plate and an optical member of the surface light source device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Light guide 1a ... Entrance end surface 2 ... Stepped surface 2a ... Step surface 2b ... Step surface 6 ... Reflection means 6a ... Reflector 7 ... Optical member 8 ... Incident part 8a ... Incident surface 8b ... Refraction surface 9 ... Incoming / outgoing surface

Claims (5)

[Claims] At least one end surface is an incident end surface, and a front surface is formed as a step-shaped surface including a plurality of step surfaces and a plurality of step surfaces connecting these step surfaces, and illumination light is transmitted from said incident end surface. A light guide that captures and emits light from the plurality of step surfaces, captures external light incident from the front from the plurality of step surfaces, emits the light to the back surface, and emits light incident from the back surface from the plurality of step surfaces. And a light source that is disposed on the side of the light guide and emits illumination light toward the incident end face of the light guide, and is provided on the back side of the light guide and on the back side of the light guide. Reflecting means for reflecting the emitted external light. 2. A front surface of the light guide, through which external light incident from the front and reflected light of the external light reflected by the reflection means and emitted from the plurality of step surfaces of the light guide are transmitted. 2. The surface light source device according to claim 1, wherein an optical member that emits illumination light emitted from the plurality of step surfaces of the light guide toward a predetermined direction and forward is disposed. 3. The optical member according to claim 1, wherein the optical member comprises a flat front surface,
The light guide is made of a transparent plate having a back surface facing the front surface, and on the back surface, an incident surface for taking in illumination light emitted from the step surface of the light guide, and a light taken in from the incident surface. The surface light source device according to claim 2, wherein a plurality of projecting incident portions having a refraction surface for refracting the light in the front direction are formed. 4. The plurality of incident portions are provided at intervals, and a region between the adjacent incident portions on the back surface of the optical member is the plurality of stepped surfaces of the light guide. The surface light source device according to claim 3, wherein the surface light source device has an input / output surface facing the light source. 5. The illumination device according to claim 1, wherein the light source includes illumination brightness control means for controlling the brightness of illumination light emitted from the light source, and the reflectance of the external light by the reflection means and the illumination light by the illumination brightness control means. The brightness control condition is set such that the brightness of light emitted in front of the surface light source device falls within a predetermined brightness range according to the illuminance of an external environment. 5. The surface light source device according to any one of 4.