JP2000113705A - Surface light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source device capable of emitting the illuminating light from a light source forward, and capable of reflecting the outside light entering from the front and emitting it forward. SOLUTION: This device is provided with a light guide body 1 emitting the light taken in from an incident end face 1a from a front face, a light control plate 3 arranged in front of the light guide body 1, and having a step-shaped face 6 composed of plural step faces 6a provided with reflecting films 7 and plural stepped faces 6b joining the step faces 6a, and a light source 2 arranged on the side of the light guide body 1, and emitting the illuminating light toward the incident end face 1a of the light guide body 1. Here, the illuminating light emitted from the light source 2 is taken in from the incident end face 1a of the light guide body 1, to be emitted forward from the front face of the light guide body 1 through the respective stepped faces 6b of the light control plate 3. Further, the outside light entering from the front is reflected by the reflecting films 7 of the respective step faces 6a of the light control plate 3, to be emitted forward.

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 sidelight type surface light source device is disposed at a side of a light guide which takes in light from an end face and emits the light to the front side, and an end face which takes in light of the light guide. And a light source for emitting illumination 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.

In general, a flat transparent plate made of an acrylic resin or the like is used for the light guide, at least one end surface of which is an incident end surface for receiving illumination light from the light source. Is an emission surface of the light taken in from the incident end surface.

The light guide takes in the illumination light from the light source from the incident end face, and totally reflects the illumination light at the interface between the front and back surfaces of the light guide and the outside air (air), while taking the illumination light into the light guide. The light is guided in the longitudinal direction, and is emitted 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 in any brightness environment, and it is not necessary to emit illumination light from the surface light source device when external light of sufficient brightness is obtained. The illumination light from the light source device As compared with performing the transmissive display and use, it has the advantage that power consumption is small.

However, in the conventional surface light source device, illumination light from a light source disposed on the side of the light guide is taken into the light guide from its incident end face, and the illumination light is received from the front surface of the light guide. For example, in order to constitute 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 device, and the transflective plate is provided. Has to be arranged behind the surface light source device.

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 present invention, there is provided a surface light source device, wherein at least one end surface is an incident end surface, and a light guide for emitting illumination light taken in from the incident end surface from the front surface;
A light control device disposed on the front side of the light guide, having a step-shaped surface including a plurality of step surfaces and a plurality of step surfaces connecting these step surfaces, and a reflection film provided on each of the step surfaces; A plate 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 the illumination light emitted by the light source is emitted from the incident end face of the light guide. The light is taken in and emitted forward from the front surface of the light guide through each step surface of the light control plate, and external light incident from the front is reflected by the reflection film on each step surface of the light control plate and emitted forward. It is characterized by the following.

That is, in the surface light source device of the present invention, the illumination light from the light source is taken into the light guide from the incident end face thereof, and emitted from the plurality of step surfaces of the light control plate from the front surface of the light guide. External light incident from the front of the light control board,
The light is reflected by the reflection film on each step surface of the light control plate and is emitted forward. According to this surface light source device, the illumination light from the light source can be emitted forward, and at the same time, the light is incident from the front. External light can be reflected and emitted forward.

For this reason, according to this surface light source device, when external light of sufficient brightness is obtained, only the reflected light of external light is emitted without turning on the light source, and the brightness of the external light is insufficient. When turning on, the light source is turned on, and both the reflected light of the external light and the illumination light from the light source are emitted to compensate for the lack of luminance of the reflected light of the external light with the illumination light, and the external light is not obtained. In some cases, illumination light from the light source can be emitted.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the surface light source device of the present invention has at least one end surface as an incident end surface, and emits illumination light taken in from the incident end surface from the front surface, and the light guide. A light control plate arranged on the front side of the body, having a step-shaped surface consisting of a plurality of step surfaces and a plurality of step surfaces connecting these step surfaces, and a reflection film provided on each of the step 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. The illumination light emitted by the light source is taken in from the incident end face of the light guide and guided. The light was emitted forward from the front surface of the light body through each step surface of the light control plate, and external light incident from the front was reflected by the reflection film on each step surface of the light control plate and emitted forward. According to this surface light source device, external light with sufficient brightness can be obtained. When light is emitted, only the reflected light of the external light is emitted without turning on the light source, and when the brightness of the external light is insufficient, the light source is turned on and both the reflected light of the external light and the illumination light from the light source are emitted. To compensate for the lack of brightness of the reflected light of the external light with the illumination light, and when the external light cannot be obtained,
Illumination light from the light source can be emitted.

For this reason, according to the 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. It can be configured without using a transflective plate.

In the surface light source device of the present invention, reflection of external light incident from the front and the external light reflected from the reflection film of the light control plate and emitted from each step surface is provided on the front side of the light control plate. It is desirable to dispose an optical member that transmits light and emits illumination light emitted from each of the step surfaces of the light control plate forward in a predetermined direction.

With this configuration, the illumination light emitted from the step surface of the light control plate is turned forward in a predetermined direction by the optical member, so that the illumination light is emitted in a predetermined direction. Can be done.

In this case, the optical member is a transparent plate having a flat front surface and a back surface facing the front surface of the light guide, and the light is emitted from the step surface of the light control plate to the back surface. It is preferable to form a plurality of projecting incident portions having an incident surface for capturing the illumination light and a refraction surface for refracting the light captured from the incident surface in a front direction. Almost all of the illumination light emitted from the plurality of step surfaces of the light control plate 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, the light emitted from the plurality of step surfaces of the light control plate and incident on the 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, so that illumination light having a high luminance distribution in a predetermined direction (for example, a front direction) can be emitted from the front surface of the optical member, and the step surface of the light control plate. The reflected light of the external light reflected by the reflection film can also be emitted forward of the optical member as light having a high luminance 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 formed by a plurality of steps of the light control plate. It is more desirable to adopt a configuration in which the input / output surface faces the surface.

According to the optical member having such a configuration, external light incident on the optical member from the front surface can be emitted to the rear surface of the optical member from the incident portion and the incident / exit surface therebetween. The reflected light of the external light reflected by the reflection film on the step surface of the control plate can be taken into the optical member from the incident portion and the entrance / exit surface, and can be emitted forward from the front surface of the optical member. Can be converted into 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 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 film on the stepped surface is determined. It is desirable that the luminance control condition of the illumination light by the illumination luminance control means be 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. By doing so, even in the environment where external light of sufficient brightness can be obtained, when only the reflected light of external light is emitted without turning on the light source,
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 light, Further, even when the illumination light is emitted from the light source in an environment where external light cannot be obtained, it is possible to emit light having a brightness suitable for the environmental illuminance in accordance with the illuminance of the environment.

[0022]

1 and 2 show an embodiment of the present invention. FIG. 1 is a sectional view of a surface light source device, and FIG. 2 is a cross-sectional view in which a part of the surface light source device is enlarged.

The surface light source device of this embodiment comprises a light guide 1,
A light source 2 disposed on the side of the light guide 1, a light control plate 3 disposed on the front side of the light guide 1, and an optical member 4 disposed on the front side of the light control plate 3 And

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 taking in light from the light source 2, and the thickness before and after the end surface 1a is closer to the incident end surface 1a. From the other side to the other end side. A reflector 5 is attached to the back of the light guide 1.

The light control plate 3 is a transparent plate made of an acrylic resin or the like, and is provided so as to be opposed to the front surface of the light guide 1 with a slight gap therebetween. The light control plate 3 has a shape extending while sequentially forming a step from the incident end face 1a side of the light guide 1 toward the other end side,
That is, it is formed in the shape of a step having a fine pitch having a plurality of step surfaces 6a parallel to each other and a plurality of step surfaces 6b connecting these step surfaces 6a.

Each step surface 6a of the light control plate 3 is substantially parallel to the back surface of the light guide 1 and has a horizontally long flat surface along the width direction of the light guide 1 (the length direction of the incident end face 1a). Has become. On the front surface of the step surface 6a, a reflective film 7 of high reflectivity made of aluminum, silver, or the like is provided over the entire area of the step surface 6a by vapor deposition or the like. An external light reflecting portion is provided.

Each step surface 6b of the light control plate 3 is a rising surface of a very small height substantially parallel to the incident end surface 1a of the light guide 1, and these step surfaces 6b respectively emit illumination light. Department.

The light guide 1 includes a light source 2 disposed on the side thereof.
Is received from the incident end surface 1a and emitted from the front surface. The illumination light emitted from the front surface of the light guide 1 is emitted from each step surface 6b of the light control plate 3. The light source 2 includes the light guide 1
The illumination light is emitted toward the incident end face 1a of the
A luminous body 8 such as a straight tube fluorescent lamp or a neon tube, an EL (electroluminescence) luminous body, an LED array in which a plurality of LEDs (light emitting diodes) are arranged, and a reflector 9 for reflecting radiated light from the luminous body 8 It consists of The light source 2 is arranged on the side of the light guide 1 so as to face the incident end face 1a.

On the other hand, the optical member 4 disposed on the front side of the light control plate 3 transmits external light incident from the front thereof and transmits illumination light emitted from each step surface 6b of the light control plate 3 to a predetermined level. It has the characteristic of emitting light forward in the direction.

The optical member 4 has a flat front surface and a rear surface opposite to the front surface of the light control plate 3.
A transparent plate made of an acrylic resin or the like having substantially the same width as the light guide 1, and a plurality of incident portions 10 for taking in illumination light emitted from the plurality of step surfaces 6 b of the light control plate 3 on the back surface thereof. Are provided integrally.

Each of the plurality of incident portions 10 is formed in a horizontally long projection shape that extends over the entire width of the optical member 4. The top of each of the light incident portions 10 is lighted such that the length direction of the light incident portions 10 on the rear surface thereof is substantially parallel to the length direction of the plurality of step surfaces 6 b of the light control plate 3. The control plate 3 is arranged so as to approach or contact each step surface 6a.

The plurality of incident portions 10 formed on the back surface of the optical member 4 have a triangular cross-section, and one of two side surfaces of the incident portion 10 that faces the stepped surface 6b of the light control plate 3 has:
The incident surface 10a takes in the illumination light emitted from the step surface 6b of the light control plate 3, and the other side surface is a refraction surface 10b for refracting the illumination light taken in from the incident surface 10a toward the front. .

The incident surface 10a has an inclination substantially parallel to or close to the step surface 6b of the light control plate 3, and has an angle with respect to the step surface 6a (an angle in a direction facing the step surface 6b).
Does not exceed 90 °, and the refracting surface 10b has a larger angle between the front surface of the light control plate 3 and a perpendicular to the perpendicular than the angle between the incident surface 10a and the perpendicular. It has an inclined surface.

The more desirable shape of the incident portion 10 is such that the incident surface 10a is inclined by 5 to 15 degrees with respect to the perpendicular to the direction facing the step surface 6b of the light control plate 3, and the refracting surface 10b is The shape is inclined by 20 to 50 degrees in a direction opposite to the incident surface 10a with respect to a vertical line.

Further, the plurality of incident portions 10 are provided at a constant pitch with an interval therebetween, and a region between the adjacent incident portions 10 on the back surface of the optical member 4. Are the entrance / exit surfaces 11 facing the plurality of step surfaces 6a of the light control plate 31.

The entrance / exit surface 11 is provided on the step surface 6 of the light control plate 3.
a surface that is substantially parallel to or has a slope close to it,
This is a surface through which external light entering the optical member 4 from the front is transmitted.

Furthermore, the plurality of incident portions 10 are provided at a pitch smaller than the pitch of each stepped surface 6b of the light control plate 3, so that the plurality of stepped surfaces 6b of the light control plate 3 are provided.
Have a relationship in which each of them always faces at least one incident portion 10 of the optical member 4.

In this surface light source device, as shown in FIG. 1, the light source 2 is provided with an illumination brightness control means 20 for controlling the brightness of the illumination light emitted from the light source 2.

The illumination luminance control means 20 includes an illuminance detector 21 for measuring the illuminance of an external environment (the use environment of the surface light source device), and the light source 2 based on the environmental illuminance measured by the illuminance detector 21. The means for controlling the luminance of the illumination light emitted by the light-emitting body 8 includes a luminance adjustment circuit 22 and a light source lighting circuit 23.

The illuminance detector 21 adjusts the light receiving surface to the front surface (the optical member 4) of the surface light source device so as to measure the same environmental illuminance as the illuminance of the external light entering the surface light source device from the front.
Is preferably arranged substantially in parallel with the front surface of the optical disk.

The luminance adjusting circuit 22 adjusts the luminance of the illumination light emitted from the light source 2 based on the environmental illuminance measured by the illuminance detector 21 to the intensity of the emitted light emitted in front of the surface light source device. The light source lighting circuit 23 adjusts the luminous body 8 of the light source 2 in accordance with the luminance value from the luminance adjustment circuit 22 so that the luminance falls within a predetermined luminance range according to the ambient illuminance. It is driven so as to emit illumination light of increased brightness.

In this surface light source device, the reflectance of external light on the stepped surface 6a of the light control plate 3 and the luminance control condition of the illumination light by the illumination luminance control means 20 are determined according to the surface light source device. The luminance of the light emitted forward is set so as to be 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 2 is guided by the light guide 1 and emitted from the front surface of the light guide 1 through the plurality of step surfaces 6b of the light control plate 3, and the light is emitted from the front. The external light incident from the front is reflected by the reflection film 7 on the stepped surface 6a of the light control plate 3 and emitted forward, and the light source 2 has sufficient luminance only with the reflected external light incident from the front. Lights when no outgoing light is obtained.

In other words, this surface light source device emits only the reflected light of the external light without turning on the light source 2 when the external light of sufficient brightness is obtained. Turns on the light source 2 to emit both the reflected light of the external light and the illumination light from the light source 2 to compensate for the lack of brightness of the reflected light of the external light with the illumination light, and obtain the external light. When there is no light, the light from the light source 2 is emitted.

The illumination light path from the light source 2 will be described. Illumination light from the light source 2 is taken into the light guide 1 from its incident end face 1a as shown by a solid line in FIGS. It is guided in the light guide 1 in its length direction.

The illumination light guided in the light guide 1 in the length direction thereof is emitted directly from the front surface of the light guide 1 or is reflected by the reflection plate 5 on the back surface of the light guide 1. From the front surface of the light guide 1, or total reflection at the interface between the front surface of the light guide 1 and the outside air (the air layer between the light guide 1 and the light control plate 3) or the light guide The light is emitted from the front surface of the light guide 1 by repeating reflection on the reflection plate 5 on the back surface of the light guide 1.

Then, of the illumination light emitted from the front surface of the light guide 1, the light going directly to the step surface 6 b of the light control plate 3 is emitted from the step surface 6 b to the front surface side of the light control plate 3. In addition, light other than light directly traveling to the step surface 6b, that is,
The light traveling toward the step surface 6a of the light control plate 3 is reflected by the step surface 6a.
The light reflected by the reflective film 7a, and further reflected by the interface between the outside air (the air layer between the light guide 1 and the light control plate 3) and the front surface of the light guide 1, the plurality of light control plates 3 Light is emitted from any of the step surfaces 6b. Therefore, most of the illuminating light taken into the light guide 1 from the incident end face 1a is efficiently transmitted to the light control plate 3
Exits in front of.

The illumination light emitted in front of the light control plate 3 is applied to an optical member 4 disposed on the front side of the light control plate 3.
A plurality of incident portions 10 on the back surface of the
a.

At this time, each of the plurality of step surfaces 6 b of the light control plate 3 is at least one of the optical members 4.
Most of the light emitted from the plurality of stepped surfaces 6b of the light control plate 3 is incident on any one of the incident portions 10 of the optical member 4 without waste since the light incident portions 10 are always opposed to the two incident portions 10.

The light incident on the plurality of incident portions 10 of the optical member 4 is refracted by a refracting surface 10b on the opposite side from the incident surface 10a.
The light is totally reflected at the interface between the refraction surface 10b and the outside air, changes its direction toward the front surface of the optical member 4, passes through the optical member 4, and exits from the front surface.

For this reason, the illuminating light emitted from the front surface of the optical member 4 to the front thereof enters the plurality of incident portions 10 from the incident surface 10a, and is incident on the opposite refracting surface 10b (interface with outside air). The light is refracted and condensed in a predetermined direction, and has a luminance distribution with high luminance in the predetermined direction.

In this embodiment, the inclination angle of the refraction surface 10b of the incident portion 10 is set such that the direction of the light refracted by the refraction surface 10b is the front direction (the direction substantially along the perpendicular to the front surface of the optical member 4). Therefore, the illumination light emitted to the front surface of the optical member 4 has a directivity distribution with high brightness in the front direction.

The emission direction of the illumination light emitted to the front surface of the optical member 4 is a direction corresponding to the inclination angle of the refraction surface 10b of the incident part 10, and the inclination angle of the refraction surface 10b is Becomes closer to the front when the angle is within a range of 20 to 50 degrees with respect to a perpendicular line perpendicular to the front of the camera.

Next, the outgoing path of the external light entering from the front will be described. The external light entering from the front enters the optical member 4 from the front as shown by a broken line in FIGS. The light passes through the optical member 4 and exits from the plurality of incident portions 10 on the rear surface and the entrance / exit surface 11 therebetween 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 4, the light directed to the incident section 10 includes the incident surfaces 10 a and 10 a of the incident section 10. Some light is incident on the interface between the refraction surface 10b and the outside air (air layer between the light control plate 3 and the optical member 4) at an incident angle larger than the critical angle for total reflection, and is totally reflected at the interface. The light totally reflected at the interface between the incident surface 10a and the outside air is incident on the interface between the opposite refraction surface 10b 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. The light totally reflected at the interface between the refraction surface 10b and the outside air is incident on the interface between the opposite incidence surface 10a and the outside air at an incidence angle smaller than the critical angle of total reflection, passes through this interface, and goes to the back side. Emit. Therefore, most of the external light incident from the front surface of the optical member 4 is emitted to the rear surface side of the optical member 4 without waste.

External light emitted to the back side of the optical member 4 is reflected by the reflection films 7 on the plurality of step surfaces 6a of the light control plate 3, and the reflected light is transmitted to the optical member 4 by a plurality of incident portions on the back surface. The light enters from the entrance / exit surface 11 and the entrance / exit surface 11 therebetween.

At this time, as described above, the incident portion 10 has the incident surface 10a on one side thereof formed on the step surface 6 of the light control plate 3.
b is substantially parallel to or has a slope close thereto, and the angle formed between the front surface of the optical member 4 and the perpendicular perpendicular to the opposite refracting surface 10b is smaller than the angle formed between the incident surface 10a and the perpendicular. Is also an inclined surface having a large inclination angle, most of the light reflected and emitted by the plurality of step surfaces 6 a of the light control plate 3 is incident on the optical member 4 by the incident portion 1.
Refracting surface 10b having a large inclination angle of 0 and a plurality of incident portions 1
It is taken in from the entrance / exit surface 11 between 0.

Then, the incidence part 10 is
Of the reflected light taken in from the refraction surface 10b and the entrance / exit surface 11, the light heading directly to the front surface of the optical member 4 passes through the optical member 4 and exits from the front surface. Of the light taken in from the refraction surface 10b, the light traveling toward the opposite incident surface 10a is the incident surface 10a.
The direction is changed by total reflection at the interface between
The light exits from the front surface of the optical member 4 while changing its direction to a direction close to the direction of light from the input / output surface 11b and the front surface of the optical member 4 directly.

Therefore, in this surface light source optical device,
External light incident from the front can also be emitted forward with little waste. Moreover, the reflected light of the external light emitted from the front surface of the surface light source optical device (the front surface of the optical member 4) 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 at least one end face as the incident end face 1a, and the light guide 1 for emitting the illumination light taken in from the incident end face 1a from the front face;
A stepped surface 6 is disposed on the front side of the light guide 1 and includes a plurality of step surfaces 6a and a plurality of step surfaces 6b connecting the step surfaces 6a. 7
And a light source 2 disposed on a side of the light guide 1 and emitting illumination light toward the incident end face 1a of the light guide 1. The light source 2 is The emitted illumination light is taken in from the incident end surface 1a of the light guide 1 and emitted forward from the front surface of the light guide 1 through each stepped surface 6b of the light control plate 3, and the external light incident from the front is reflected by the light. The light is reflected by the reflection film 7 on each step surface 6a of the control plate 3 and emitted forward. Therefore, according to this surface light source device, the illumination light from the light source 2 can be emitted forward. At the same time, external light incident from the front can be reflected and emitted forward.

In addition, the surface light source device of the above embodiment transmits the reflected light that enters from the front of the light control plate 3 disposed on the front side of the light guide 1 and is reflected by the step surface 6a, thereby transmitting a plurality of step surfaces. 6
b, the optical member 4 for emitting the illumination light of the light source 2 emitted from the light source 2 toward the predetermined direction and forward is provided.
The illumination light emitted from the plurality of step surfaces 6b can be changed in a predetermined direction by the optical member 4 and emitted forward.

In the above embodiment, the optical member 4
Is a transparent plate having a flat front surface and a back surface opposite to the front surface of the light control plate 3, and on the back surface, an incident surface 10a for taking in illumination light emitted from the step surface 6b of the light control plate 3. Since a plurality of projecting incident portions 10 having a refracting surface 10b for refracting light taken in from the incident surface 10a in the front direction are formed, the light exits from the plurality of step surfaces 6b of the light control plate 3. Most of the illuminating light to be taken can be taken into the optical member 4 without waste and emitted forward from the front surface.

Further, in this surface light source device, since the optical member 4 has the above-described structure, the light control plate 3
The light emitted from the plurality of step surfaces 6b and incident on the plurality of incident portions 10 of the optical member 4 from the incident surface 10a is refracted by the refraction surface 10b and collected in a predetermined direction,
A predetermined direction (for example, the front direction) from the front surface of the optical member 4
The illumination light having a high luminance distribution can be emitted, and the reflected light of external light reflected by the reflection film 7 on the step surface 6a and emitted from the step surface 6a also has a predetermined direction (for example, the front direction). The light can be emitted forward of the optical member 4 as light having a high luminance distribution.

Further, in the above embodiment, the optical member 4
The plurality of incident portions 10 are provided at intervals, and a region between the adjacent incident portions 10 on the back surface of the optical member 4 faces the plurality of step surfaces 6 a of the light control plate 3. Since the light input / output surface 11 is employed, external light incident on the optical member 4 from the front surface is emitted from the incident portion 10 and the input / output surface 11 therebetween to the rear side of the optical member 4, The reflected light of the external light reflected and emitted by the reflection film 7 on the step surface 6a of the control plate 3 is taken into the optical member 4 from the incident part 10 and the entrance / exit surface 11, and is directed forward from the front surface of the optical member 4. Can be emitted,
The reflected light can be light having a luminance distribution with a higher luminance in a predetermined direction (for example, the front direction).

In the surface light source device described above, the light source 2 is provided with an illumination brightness control means 20 for controlling the brightness of the illumination light emitted from the light source 2, and the external light is reflected by the reflection film 7 on the stepped surface 6a. The reflectance and the luminance control condition of the illumination light by the illumination luminance control means 20 are 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 of a wide illuminance range from low illuminance to high illuminance, it is possible to emit light having a luminance suitable for the environmental illuminance.

That is, the preferable brightness of the emitted light emitted from the surface light source device depends on the illuminance of the external environment. Even if the brightness of the emitted light is the same, 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 stepped surface 6a is formed so that emitted light of suitable brightness that is not too dazzling can be obtained. The reflectance of the reflective film 7 is set to a somewhat lower value, and the luminance of the light emitted by both the reflected light of the external light reflected by the reflective film 7 and the illumination light from the light source 2 (however, the ambient illuminance is almost 0) Lux, the luminance of the illumination light emitted from the light source 2 is adjusted in accordance with the environmental illuminance so that the emission luminance only by the illumination light becomes a suitable luminance in accordance with the environmental illuminance. 20.

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 2 in an environment where the external light of sufficient brightness can be obtained, the brightness of the external light can be reduced. When the light source 2 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 2 to compensate for the lack of luminance of the reflected light of the external light with the illumination light, When the illumination light from the light source is emitted in an environment where the light intensity is not obtained, it is possible to emit light having a luminance suitable for the environmental illuminance in accordance with the illuminance of the environment.

Further, the above-mentioned surface light source device emits light having a luminance suitable for the ambient illuminance only by reflected light of the external light without turning on the light source 2 in an environment where external light of sufficient brightness can be obtained. The light source 2 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 2 are emitted. Even when the shortage is compensated for by the illumination light, the luminance of the illumination light emitted from the light source 2 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 2 is small.

The above-mentioned surface light source device can be used, for example, in 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. According to this surface light source device, the illumination light from the light source 2 is emitted forward,
Since external light incident from the front can be reflected and emitted forward, the two-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, a liquid crystal display device or the like is provided on the front side of the surface light source device as shown by a virtual line (two-dot chain line) in FIG. Is disposed.

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 passes 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 the light from the light source 2 with an emission efficiency of nearly 100%. In addition, external light incident from the front can be reflected with a reflection efficiency of nearly 100%. Further, since a semi-transmissive reflector is not required, the illumination light from the surface light source device can also be reflected from the front. A bright image can be displayed by efficiently using external light incident from the light source.

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 4 for both the illumination light from the light source 2 and the reflected light of 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, in the surface light source device, the light source 2 is provided with an illumination brightness control means 20 for controlling the brightness of the illumination light emitted from the light source 2, and the external light reflectance and the external light The luminance control condition of the illumination light by the illumination luminance control means 20 is set such that the luminance of the light emitted in front of the surface light source device becomes a predetermined luminance range according to the illuminance of the external environment. Therefore, the two-way display device using the 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 24 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 2, and the illumination light from the light source 2 in an environment where the external light cannot be obtained, pass through the display body 24 and Since the light is emitted forward, the screen luminance is determined by the reflectance of external light by the reflection film 7 of the surface light source device, the luminance of illumination light from the light source 2, 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 reflection film 7 and the luminance control condition of the illumination light by the illumination luminance control means 20 are determined by the screen luminance. May be set to be a predetermined luminance range according to the illuminance of the external environment.

That is, a 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, such 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 2 is controlled by the illumination luminance control means 20 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, the stepped surface 6 of the light control plate 3, the plurality of incident portions 10 of the optical member 4, and the entrance / exit surface 11 therebetween are shown in a greatly enlarged manner for convenience. When a dot matrix type liquid crystal display element is used for the light emitting type display 24, the incident portion 10 of the optical member 4 is used.
Is substantially equal to or smaller than the pixel pitch of the liquid crystal display element, and the height of the stepped surface 6b of the step-shaped surface 6 of the light control plate 3 is changed according to the pitch of the incident portion 10 of the optical member 4. It is preferable to set the pitch, and by doing so, the reflected light of the external light and the illumination light from the light source 2 are made incident on all the pixel portions of the liquid crystal display element, and a good image without chipping of pixels is obtained. Can be displayed.

The above-mentioned surface light source device is not limited to a two-way display device, and can be widely used as, for example, an illumination panel using light from a light source arranged on the side and external light incident from the front. it can.

In the first embodiment, the front surface and the back surface of the light control plate 3 are stepped, and the reflection film 7 is provided on the step surface 6a of the step surface 6 on the front surface. As shown in FIG. 3 as a second embodiment,
The rear surface of the light control plate 3 is a smooth surface, and only the front surface is a step-shaped step surface 6 composed of a plurality of step surfaces 6a parallel to each other and a plurality of step surfaces 6b connecting these step surfaces 6a. A reflection film 7 for reflecting external light may be provided on the step surface 6a of the surface 6, or as shown in FIG. 4 as a third embodiment, the front surface of the light control plate 3 is made a smooth surface, and A stepped surface 6 having a plurality of parallel step surfaces 6a and a plurality of step surfaces 6b connecting the step surfaces 6a is formed. The step surface 6a of the step surface 6 has a reflection film 7 for reflecting external light. May be provided.

In each of the above-described embodiments, the external light incident from the front and the light reflected by the reflection film 7 on the step surface 6a are transmitted to the front side of the light control plate 3, and the light emitted from the step surface 6b. The optical member 4 that emits light forward in a predetermined direction is disposed. However, when the emission direction of the illumination light may be a direction that is greatly inclined with respect to a perpendicular perpendicular to the front surface of the light control plate 3, The optical member 4 may be omitted.

Further, in each of the above embodiments, the light guide 1
The reflector 5 is provided on the back surface of the light guide 1. However, the reflector 5 is omitted, and instead of the reflector 5, a diffusely reflecting substance that diffuses and reflects light inside the light guide 1 is contained. It is also possible to provide diffusion dots for diffusing light on the back surface by printing or the like.

[0086]

According to the surface light source device of the present invention, at least one end face is an incident end face, and a light guide for emitting illumination light taken in from the incident end face from the front face, and the light guide body is arranged on the front face side of the light guide body. A light control plate having a step-shaped surface composed of a plurality of step surfaces and a plurality of step surfaces connecting these step surfaces, and a light control plate provided with a reflection film on each of the step surfaces; And a light source that emits illumination light toward the incident end face of the light guide. The illumination light emitted by the light source is taken in from the incident end face of the light guide, and the light is emitted from the front face of the light guide. While emitting light forward through each step surface of the control plate,
External light incident from the front is reflected by the reflection film on each step surface of the light control plate and is emitted forward,
According to this surface light source device, when external light of sufficient brightness is obtained, only the reflected light of the external light is emitted without turning on the light source, and when the brightness of the external light is insufficient, the light source is used. Turn on and 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 light,
When external light cannot be obtained, illumination light from the light source can be emitted.

For this reason, 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. It can be configured without using a transflective plate.

In the surface light source device according to the present invention, reflection of external light entering from the front and the external light reflected from the reflection film of the light control plate and emitted from each step surface is provided on the front side of the light control plate. It is desirable to dispose an optical member that transmits light and emits illumination light emitted from each of the step surfaces of the light control plate forward in a predetermined direction.

In this manner, the illumination light emitted from the step surface of the light control plate is turned forward in a predetermined direction by the optical member, so that the illumination light is emitted in a predetermined direction. Can be done.

In this case, the optical member is a transparent plate having a flat front surface and a back surface facing the front surface of the light guide, and the light is emitted from the step surface of the light control plate to the back surface. It is preferable to form a plurality of projecting incident portions having an incident surface for capturing the illumination light and a refraction surface for refracting the light captured from the incident surface in a front direction. Almost all of the illumination light emitted from the plurality of step surfaces of the light control plate 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 the plurality of step surfaces of the light control plate and incident on the 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, so that illumination light having a high luminance distribution in a predetermined direction (for example, a front direction) can be emitted from the front surface of the optical member, and the step surface of the light control plate. The reflected light of the external light reflected by the reflection film can also be emitted forward of the optical member as light having a high luminance 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 a plurality of steps of the light control plate. It is more desirable to adopt a configuration in which the input / output surface faces the surface.

According to the optical member having such a configuration, external light incident on the optical member from the front surface can be emitted to the rear surface of the optical member from the incident portion and the incident / exit surface therebetween. The reflected light of the external light reflected by the reflection film on the step surface of the control plate can be taken into the optical member from the incident portion and the entrance / exit surface, and can be emitted forward from the front surface of the optical member. Can be converted into light having a higher luminance distribution in a predetermined direction (for example, the front direction).

In this surface light source device, the light source is provided with illumination brightness control means for controlling the brightness of the illumination light emitted from the light source. It is desirable that the luminance control condition of the illumination light by the illumination luminance control means be 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. By doing so, even in the environment where external light of sufficient brightness can be obtained, when only the reflected light of external light is emitted without turning on the light source,
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 light, Further, even when the illumination light is emitted from the light source in an environment where external light cannot be obtained, it is possible to emit light having a brightness suitable for the environmental illuminance in accordance with the illuminance of the environment.

[Brief description of the drawings]

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

FIG. 2 is an enlarged sectional view showing a part of the surface light source device.

FIG. 3 is a side view of a surface light source device according to a second embodiment of the present invention.

FIG. 4 is a sectional view of a surface light source device according to a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Light guide 1a ... Incident end surface 2 ... Light source 3 ... Light control plate 4 ... Optical member 6 ... Step formation surface 6a ... Step surface 6b ... Step surface 7 ... Reflection film 10 ... Incident part 10a ... Incident surface 10b ... Refraction surface 11: input / output surface 20: illumination brightness control means

Claims (5)

[Claims] 1. A light guide body having at least one end face serving as an incident end face, for emitting illumination light taken in from the incidence end face from the front face, and a plurality of stepped faces and a plurality of step faces arranged on the front face side of the light guide body. A light control plate having a stair-shaped surface consisting of a plurality of step surfaces connecting the step surfaces, and a reflection film provided on each of the step surfaces, disposed on a side of the light guide, And a light source that emits illumination light toward the incident end face.The illumination light emitted by the light source is taken in from the incident end face of the light guide, and from the front face of the light guide through each step surface of the light control plate. A surface light source device which emits light forward and reflects external light incident from the front with reflection films on each step surface of the light control plate and emits the light forward. 2. An external light, which is incident on the front surface of the light control plate and which is reflected by the reflection film of the light control plate and emitted from each step surface, transmits the external light and transmits light. The surface light source device according to claim 1, wherein an optical member that emits illumination light emitted from each of the step surfaces of the control plate 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 control plate 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 control plate, and a light taken in from this incident surface in a front direction. The surface light source device according to claim 2, wherein a plurality of projecting incident portions having a refracting surface for refracting the light are formed. 4. The plurality of incident portions are provided at intervals, and a region between adjacent ones of the incident portions on the back surface of the optical member is the plurality of stepped surfaces of the light control plate. 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 system 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 external light by the reflection film and the illumination light by the illumination brightness control means. The luminance control condition is set such that the luminance of light emitted in front of the surface light source device falls within a predetermined luminance range according to the illuminance of an external environment. 5. The surface light source device according to any one of 4.