JPH10186360A - Surface light source device and liquid crystal display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source device capable of being used as a light source emitting light from a surface light source and also as a reflection light source reflecting outer light as the light source. SOLUTION: A scattering control film 20 consisting of plural light transmission parts 21 and reflection films 22 held among boundaries of these light transmission parts is provided on the outgoing surface of an EL element 10 being a surface light source. Then, among incident light on the light transmission parts 21 of the scattering control film 20 by being emitted from the EL element 10, incident light in the vertical direction are made to straightly advance to be emitted and incident light in an oblique direction is made to be scattered by reflections at the reflection films 22 to be emitted and, also, among incident outer light from the outside, incident outer light in the vertical direction is made to straightly advance to be reflected at the back side electrode 13 of the EL element 10 to be emitted and incident outer light in the oblique direction is made to be scattered by the reflections at the reflection films 22 to be emitted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a surface light source device and a liquid crystal display device using the same.

[0002]

2. Description of the Related Art A surface light source device is used, for example, for a backlight of a liquid crystal display element in a liquid crystal display device. Conventionally, this surface light source device includes an LE (electroluminescence) element, a light guide plate made of a transparent plate, and a light source lamp arranged to face the end face thereof, and the light from the light source lamp is guided by the light guide plate. A light guide plate type surface light source that emits light from the surface thereof, and outputs the light emitted from the surface light source to the light emission surface (the surface in the case of the LE element, the surface of the light guide plate in the case of the light guide plate type). A device provided with a diffusion plate for emitting light that is diffused and has a substantially uniform luminance distribution is used.

[0003]

However, the above-mentioned conventional surface light source device only has a function as a light source for emitting light from the surface light source, and natural light or indoor illumination light entering the surface light source device from its surface. However, it does not have a function as a so-called reflection light source that reflects external light such as the above as light source light.

[0004] This is because external light incident on the surface light source device from its surface is diffused by a diffusion plate disposed on the exit surface of the surface light source, and only a small amount enters the surface light source. Even if the electrode on the back side of the LE element as the light source is a metal electrode that reflects light, or even if the back surface of the light guide plate in a light guide plate type surface light source is a reflective surface, the light reflected by that surface Since the amount of light is small, reflected light with sufficient luminance as a light source cannot be obtained.

[0005] Therefore, the liquid crystal display device using the above-mentioned conventional surface light source device as a backlight can perform only a transmissive display using light from the backlight. Note that if a transflective plate is disposed between the liquid crystal display element and the backlight, a so-called transmissive display using light from the backlight and a reflective display using external light can be performed. Although the transflective plate can be used as a two-way display device, since the transflective plate has a low light transmittance and a low reflectivity, the display is considerably improved in both transmissive display and reflective display. It will be dark.

The present invention provides a surface light source device which can be used both as a light source for emitting light from a surface light source and as a reflection light source for reflecting external light to produce light source light. It is an object of the present invention to provide a liquid crystal display device using a surface light source device and having both functions of a transmissive display and a reflective display.

[0007]

A surface light source device according to the present invention includes a surface light source and a scattering control member disposed on a light emission surface of the surface light source, and the scattering control member controls the surface light source. Of the light emitted and incident on the scattering control member from its back surface, light incident at a predetermined angle range goes straight without reflection, and light incident at an angle other than the angle range is reflected and scattered. And, of the light incident on the surface of the scattering control member, the light that travels straight without reflecting the light incident at a predetermined angle range, and reflects and scatters the light incident at an angle other than the angle range. It is characterized by having characteristics.

According to this surface light source device, of the light emitted from the surface light source and incident on the scattering control member from the back surface thereof, the light incident within a predetermined angle range goes straight to the surface of the scattering control member. And the light incident at an angle other than the angle range is reflected or scattered and exits to the surface.

Further, of the light incident on the scattering control member from its front surface, the light incident within a predetermined angle range travels straight through the scattering control member and exits to the back surface of the scattering control member. The light incident at an angle of? Is reflected or scattered, and of the light, light directed toward the surface of the scattering control member is emitted to the surface.

In this case, the light traveling straight through the scattering control member and emitted to the back surface enters the surface light source. If the surface light source has a light reflecting member, the light emitted to the back surface is reflected. Is reflected, and the light travels straight through the scattering control member, or is reflected or scattered and emitted to the surface, similarly to the light emitted from the surface light source.

Therefore, according to the surface light source device of the present invention, it can be used both as a light source for emitting light from a surface light source and as a reflection light source for reflecting external light to be a light source.

In addition, according to this surface light source device, of the light emitted from the surface light source and incident on the scattering control member from the back surface, the light incident within a predetermined angle range goes straight to the scattering control member. Since the light emitted to the surface and incident at an angle other than the angle range is reflected or scattered and emitted to the surface, the brightness of the emitted light in the direction in which light traveling straight through the scattering control member is emitted is high, and An emission angle range in which emission light with sufficient luminance is obtained is wide, and light with a good luminance distribution can be emitted.Also, when used as a reflection light source, light is scattered by the scattering control member. It is possible to emit light with an appropriate luminance distribution.

A liquid crystal display device according to the present invention comprises a liquid crystal display element and the surface light source device disposed behind the liquid crystal display element. That is, the liquid crystal display device uses the surface light source device as a backlight of a liquid crystal display element. According to the liquid crystal display device, the surface light source device is used as a light source that emits light from the surface light source. However, since it can also be used as a reflection light source that reflects external light and becomes light source light, it can have both functions of a transmission type display and a reflection type display.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The surface light source device according to the present invention, as described above, of the light emitted from the rear surface, of the light emitted from the surface light source, makes the light incident within a predetermined angle range go straight. The light incident at an angle other than the angle range is reflected and scattered, and among the light incident from the surface, the light incident at a predetermined angle range is caused to travel straight without being reflected, and at an angle other than the angle range. By providing a scattering control member having an optical property of reflecting and scattering incident light, it can be used as a light source that emits light from a surface light source or as a reflection light source that reflects external light and becomes light source light. It is something that can be done.

In this surface light source device, for example, the scattering control members are respectively arranged adjacent to each other,
A plurality of transparent light guides each having a parallel interface, and a reflective thin film disposed on each of the boundaries of these light guides and having a flat surface having reflective surfaces on both sides, wherein the reflective thin film is An optical film having an intersecting front and back surface, and if a scattering control member made of the optical film is used, of light incident on the light guide portion from the back surface, includes a direction along the film surface of the reflective thin film. Light that enters within a predetermined angle range goes straight without reflection,
The light incident at an angle other than the angle range is reflected and scattered, and of the light incident from the surface of the scattering control member, without reflecting the light incident at a predetermined angle range including the direction. It is possible to travel straight and reflect and scatter light incident at an angle other than the above angle range.

Further, as described above, the liquid crystal display device of the present invention can be used as a light source that emits light from a surface light source behind a liquid crystal display element, or as a reflection light source that reflects external light and becomes light source light. By arranging the surface light source device that can also be used, both functions of a transmission type display and a reflection type display are provided.

In this liquid crystal display device, it is desirable that the surface light source device has a light reflecting member, and if the surface light source has a light reflecting means, the surface light source device is provided with a light reflecting member. Of the external light that enters from the front surface, transmits through the liquid crystal display element, and enters the scattering control member of the surface light source device, the light that goes straight through the scattering control member and exits to the back surface also reflects the reflection. In this case, a bright display can be obtained by efficiently using incident external light even in a reflective display.

[0018]

1 is a sectional view of a surface light source device according to a first embodiment of the present invention, in which hatching is omitted. The surface light source device 1 of this embodiment uses an EL (electroluminescence) element 10 as a surface light source, and has a scattering control member 20 disposed on the light emission surface of the EL element 10.

First, the EL element 10 will be described.
This EL element body 10 is made of a transparent substrate 11 made of glass.
An organic EL in which an electroluminescent layer 14 made of a conductive polymer is interposed between a transparent emission electrode 12 formed on one surface of the substrate and a back electrode 13 facing the emission electrode 12.
The emission-side electrode 12 is an anode, and the back-side electrode 13 is a cathode.

The emission-side electrode 12 is made of ITO or IZnXO, and the back-side electrode 13 is made of Mg-, which has a small work function of injecting electrons into the electroluminescent layer 14.
It is formed of a Mg-based alloy such as an In alloy or a Mg-Ag alloy.

However, since the Mg-based alloy has high reactivity, the back-side electrode 13 made of the Mg-based alloy may be degraded by reacting with moisture in the air or oxidized by reacting with oxygen. .

For this reason, in this embodiment, as shown in FIG. 1, the periphery of the EL element 10 is covered with a highly airtight resin film 15 from the entire back surface to the lower surface of the transparent substrate 11, and Is completely shielded from the air.

FIG. 1 shows the electroluminescent layer 14 as one layer. The electroluminescent layer 14 has a two-layer structure in which a hole transport layer is laminated on the anode side of the electron transporting luminescent layer. Alternatively, it has a three-layer structure in which a hole transport layer is stacked on the anode side and an electron transport layer is stacked on the cathode side with the light emitting layer interposed therebetween.

For example, when the electroluminescent layer 14 has a three-layer structure, the light-emitting layer is made of DPVBi {4,4'-bis (2,2-diphenylvinylene) biphenyl} and BCz
VBi @ 4,4'-bis (2-carbazolevinylene)
96% by weight of DPVBi and BCzV
Bi is formed of a polymer material mixed at a ratio of 4% by weight,
The hole transport layer is composed of α-NPD ｛N, N′-di (α-naphthyl) -N, N′-diphenyl-1,1′-biphenyl-
4,4′-diamine}, and the electron transport layer is made of Alq
3 {aluminum tris (8-hydroxyquinoline)}.

The refractive index on the emission side of the electroluminescent layer 14, that is, the refractive index of the hole transport layer made of α-NPD is 1.40.
To 1.80, and the output side electrode (ITO or I
ZnXO) 12 has a refractive index of about 2.00, and the transparent substrate (glass) 1 has a refractive index of 1.45 to 1.80.

The EL element 10 has an emission side electrode 12
When a voltage (DC voltage) is applied between the first electrode 12 and the back electrode 13 to drive the light emission, when a voltage is applied between the two electrodes 12 and 13, the emission electrode (anode) is applied to the electroluminescent layer 14. Holes are injected from 12 and electrons are injected from the back electrode (cathode) 13, and recombination of the injected holes and electrons generates singlet excitons to emit light.

The light emitted by the singlet exciton is
The light enters the emission-side electrode 12 from the electroluminescent layer 14, further passes through the transparent substrate 11, and exits to the surface thereof. The light emitted from the singlet exciton includes light traveling toward the back surface of the electroluminescent layer 14, but the light is reflected by the back electrode 13.

It should be noted that the electroluminescent layer 14 is formed of the DPV.
In the case of a three-layer structure in which a light-emitting layer composed of Bi and BCz VBi, a hole transport layer composed of α-NPD, and an electron transport layer composed of Alq3, light emitted from the electroluminescent layer 14 is visible. It is light of a wavelength component that includes all the wavelengths in the optical band, but has a slightly larger amount of light in the blue wavelength range, and thus has a bluish color.

Therefore, in this embodiment, a suitable amount of a red fluorescent substance and a green fluorescent substance are dispersed in the light emitting layer of the electroluminescent layer 14 or the hole transport layer on the emission side, and a part of the emitted light is emitted. Is absorbed by the fluorescent substance to generate red and green fluorescence, so that the color of light emitted from the EL element 10 is made closer to white.

Next, the scattering control member 20 will be described. FIG. 2 is a perspective view of the scattering control member 20. This scattering control member 20 is disposed adjacent to each other, a plurality of transparent light guide portions 21 each having a parallel boundary surface, and both surfaces disposed at the boundaries of these light guide portions 21, respectively. A reflective thin film (hereinafter, referred to as a reflective film) 22 composed of a flat surface having reflectivity; and an optical film having front and back surfaces where the reflective thin film 22 intersects. Hereinafter, the scattering control member 20 is referred to as a scattering control film.

That is, the scattering control film 20
Between the boundaries of the plurality of light guides 21 arranged along the plane direction,
In other words, both surfaces are sandwiched between the respective side surfaces of the adjacent light guide portion 21, and both surfaces are formed of the reflection films 22 each of which is a mirror surface or a light scattering surface. In parallel with a plane along a predetermined direction (a rising plane that intersects the film plane at a predetermined angle). The reflection film 22 is formed of a material having high reflection efficiency such as a silver vapor deposition film, an aluminum vapor deposition film, and a white diffusion film.

In the scattering control film 20 of this embodiment, the reflection film 22 is located on a surface along a direction perpendicular to the film surface, and extends along any of the width directions of the scattering control film 20 in the vertical and horizontal directions. The flat linear reflection films 22 have a louver shape in which the reflection films 22 are arranged in parallel with each other at intervals corresponding to the width of the light guide portion 21.

This louver-like scattering control film 20
For example, a transparent resin layer having a thickness corresponding to the width of the light guide portion 21 and the reflection film 22 are alternately laminated, and the laminated glock is formed on a cut surface perpendicular to the thickness direction (lamination direction). It is manufactured by a method of slicing the film along a film, and a transparent support sheet 23 for reinforcement is provided on each of the front and back surfaces.

The light guide 21 of the scattering control film 20 and the support sheet 23 have a refractive index of the EL element 1
0 (the transparent substrate 11 in this embodiment).
The support sheet 23 is welded to the front and back surfaces of the light guide portion 21 or is bonded by an adhesive having the same refractive index. .

The refractive index of the emission side substrate of the EL element 10, that is, the refractive index of the transparent substrate 11 made of glass is 1.
The resin having a refractive index of about 45 to 1.80, which is almost the same or close to that, includes PET (polyethylene terephthalate), PES (polyether sulfone), PC (polycarbonate) and the like. Has a refractive index of 1.40 to 1.60.

The scattering control film 20 has an emission surface of the EL element 10 and an EL element 1
0 is provided in close contact with the emission surface (surface of the transparent substrate 11). In this example, the scattering control film 2 was used.
0 is substantially the same as one of the refractive index of the light guide portion 21 and the support sheet 23 and the refractive index of the transparent substrate 11 of the EL element 10, or has a refractive index between both refractive indexes, not shown. It is bonded to the EL element 10 with an adhesive.

The surface light emitter emits light from the electroluminescent layer 14 of the EL element 10 and exits to the surface of the EL element 10 through the scattering control film 20 in the direction of the emission substrate. It was done.

First, the path of light emitted from the electroluminescent layer 14 of the EL element 10 to the surface of the EL element will be described with respect to light from one point of the electroluminescent layer 14. FIG. Light is emitted in various directions as indicated by solid arrows. Among them, light traveling in a predetermined angle range including a direction substantially perpendicular to the emission surface of the EL element 10 is emitted by the electroluminescent layer 14 and the emission side electrode 12. Through the interface A and the interface B between the emission side electrode 12 and the transparent substrate 11 without causing refraction or reflection, and emits the light perpendicular to the EL element surface.

On the other hand, radiation emitted obliquely at an angle other than the above-mentioned angle range is obliquely incident on each of the interfaces A and B, but the refractive indices of the electroluminescent layer 14, the emission electrode 12 and the transparent substrate 11 are changed. Is the value described above, and the refractive indices of the adjacent layers are different from each other. Therefore, the radiated light traveling in the oblique direction is refracted or reflected at the interfaces A and B.

That is, the radiated light traveling in the oblique direction first enters the interface A between the electroluminescent layer 14 and the emission-side electrode 12, and the incident angle of the light with respect to the interface A is smaller than the critical angle for total reflection. The light incident at the interface A is refracted at the interface A and is incident on the emission-side electrode 12, and the light incident at an incident angle larger than the critical angle for total reflection is totally reflected at the interface A.

The light totally reflected at the interface A is reflected by the back electrode 13 and also reflected at the interface A and the end face of the electroluminescent layer 14 and refracted in the electroluminescent layer 14 in a zigzag manner. In the process, light that has entered the interface A at an incident angle smaller than the critical angle for total reflection passes through the interface A and enters the emission-side electrode 12.

The light incident on the output side electrode 12 passes through the output side electrode 12 and is incident on the interface B with the transparent substrate 11. Light incident at a smaller incident angle is refracted at the interface B and is incident on the transparent substrate 11, and light incident at an incident angle larger than the critical angle for total reflection is totally reflected at the interface B.

A part of the light totally reflected at the interface B is totally reflected at the interface A with the electroluminescent layer 14 and also reflected at the interface B and the end face of the emission electrode 12 so as to be reflected at the emission electrode. 12 is refracted in a zigzag manner, and of the light, the light incident on the interface B at an angle of incidence smaller than the critical angle for total reflection passes through the interface B and is incident on the transparent substrate 11.

The other light totally reflected at the interface B is
The electroluminescent layer 1 transmits through the interface A with the electroluminescent layer 14 and
4, the light is refracted in the electroluminescent layer 14 in a zigzag manner in the same manner as the light totally reflected at the interface A, and proceeds in the process at an incident angle smaller than the total reflection critical angle at the interface A. The incident light is transmitted through the interface A and is incident on the emission-side electrode 2, and the light incident on the interface B with the emission-side electrode 2 at an incident angle smaller than the critical angle for total reflection is transmitted through the interface B. The light enters the transparent substrate 11.

Then, from the emission side electrode 12 to the transparent substrate 11
Is transmitted through the transparent substrate 11 and is emitted to the front surface thereof, and is incident on the light guide portion 21 of the scattering control film 20 from the back surface.

In this case, in this embodiment, the refractive index of the light guide 21 and the support sheet 23 of the scattering control film 20 is set to the refractive index of the emission side substrate of the EL element 10 (the transparent substrate 1).
The refractive index of the scattering control film 20 and the refractive index of the light guide 21 and the support sheet 23 and the transparent substrate 1 of the EL element 10
1 is bonded to the EL element 10 with an adhesive (not shown) having a refractive index substantially equal to one of the refractive indices 1 or between the two. Most of the light incident on the interface C with the scattering control film 20 passes through the interface C without being largely refracted and totally reflected, regardless of the angle of incidence on the interface C. Incident on the light guide 21 of the scattering control film 20.

As shown in FIG. 1, while the light totally reflected at the interfaces A and B travels while refracting the electroluminescent layer 14 and the emission electrode 12, a part of the light is emitted. 2 and the light emitted from the end face of the electroluminescent layer 4 to form leakage light, the amount of leakage of which is extremely small.
As described above, most of the light incident on the interface C is totally reflected without being totally reflected, regardless of the angle of incidence on the interface C between the transparent substrate 11 and the scattering control film 20.
Is transmitted to the light guide section 21 of the scattering control film 20, so that the light emitted in the electroluminescent layer 14 of the EL element 10 before exiting the LE element 10 has a very small light loss.

Next, the emission path of light emitted from the EL device 10 and incident on each light guide 21 of the scattering control film 20 will be described. , The reflection film 22 at the boundary between the light guide portions 21
Light incident at an incident angle within a predetermined angle range including the direction along the axis, that is, light incident at an inclination angle within a predetermined angle range centered on a direction perpendicular to the film surface of the scattering control film 20, The light travels straight through the light section 21 and enters the interface D between the surface of the scattering control film 20 and the outside air.

On the other hand, light incident on the light guide section 21 at an incident angle other than the above angle range, that is, light incident from a direction obliquely greatly inclined with respect to the film surface of the scattering control film 20, Are transmitted obliquely to the light guide portions 2
The light is incident on the reflection film 22 at the boundary of No. 1 and is reflected and scattered on the reflection surface (mirror surface or scattering surface).

The light transmitted obliquely through the light guide 21 includes light incident on the light guide 21 without being incident on the reflection film 22 like light incident at an incident angle within the predetermined angle range. There is also light that reaches the surface of the surface D, and the light enters the interface D without being scattered by reflection.

The predetermined angle range will be described.
FIG. 3 shows a case where the light incident on the light guide 21 when the reflection film 22 of the scattering control film 20 is on a surface along a direction perpendicular to the film surface as in this embodiment.
FIG. 4 is a view for explaining a range of an incident angle of light which goes straight in and enters the interface D with the outside air, as shown in FIG.
The pitch of the reflection film 22 of the scattering control film 20 (the width of the light guide 21) is P, the thickness of the light guide 21 is d, and the center of the back surface of the light guide 21 (the middle point in the width direction) is perpendicular to the center. Assuming that the incident angle of the light incident from one direction and the incident angle of the light incident from the other direction on the line are + ψ and −ψ, respectively, the light incident on the light guide 21 is And the range of the incident angle of light that enters the interface D with the outside air by going straight through is represented by the following equation.

D = P / 2 tan (θ / 2) That is, for example, the pitch P of the reflection film 22 is 100 μm.
m, and when the thickness d of the light guide 21 is 572 μm, light incident on the center of the back surface of the light guide 21 from one direction and the other with respect to a vertical line is reflected by the surface of the light guide 21. Membrane 22
Is incident on the light guide section 21 at + 境 = +
5 °, light incident at an incident angle of −ψ = −5 °, and therefore, of the light incident on the center of the back surface of the light guide 21,
Light incident in an angle range of ± 5 ° around the vertical line, that is, an angle range of less than 10 ° including a direction along the film surface of the reflective film 22 travels straight through the light guide portion 21 to control scattering. When the light enters the interface D between the surface of the film 20 and the outside air,
Light incident at an angle range greater than 0 ° is reflected by the reflection film 22.
Is incident on and reflected and scattered.

The scattered light reflected by the reflection film 22 travels in the light guide 21 in various directions, and the light directed to the surface of the light guide 21 is incident on the interface D. Further, light traveling in other directions does not directly enter the interface D, but most of the light enters the other reflection film 22 and is scattered again by reflection. Is incident on the interface D.

Therefore, most of the light that has entered the light guide portion 21 enters the interface D between the surface of the scattering control film 20 and the outside air, either directly or after repeating scattering by reflection.

Then, of the light incident on the interface D,
Light incident on the interface D at an incident angle smaller than the critical angle for total reflection passes through the interface D and exits from the surface light source device 1.

That is, of the light incident on the interface D at an incident angle smaller than the critical angle for total reflection, the light incident perpendicularly on the interface D is not refracted on the interface D but in the vertical direction. The light emitted and incident from a direction inclined with respect to the vertical direction is incident on the interface D at an angle with respect to the interface D, and the refractive index between the light guide 21 and the support sheet 23 and the outside air (air). The light is refracted according to the difference and emitted in that direction.

The light incident on the interface D at an angle of incidence larger than the critical angle for total reflection is totally reflected at the interface D. Since scattering by reflection is repeated, these lights finally enter the interface D at an incident angle smaller than the critical angle of total reflection, and pass through the interface D and exit.

Most of the emitted light is refracted at the interface D according to the angle of incidence with respect to the interface D and the refractive index difference between the light guide 21 and the outside air (air), and exits in that direction. However, in the process of repeating the scattering due to the reflection, light is generated in a direction perpendicular to the interface D, and the light is emitted in the vertical direction without being refracted at the interface D. The luminance of the light emitted in the direction perpendicular to the surface of the scattering control film 20 is further increased by being superimposed on the amount of light emitted in the vertical direction.

As described above, according to the surface light source device 1,
Of the light emitted from the EL element 10 and incident on the back surface of the scattering control film 20, the light incident at an angle within a predetermined range from a direction perpendicular to the film surface goes straight and exits to the front surface, and the angle Since light incident at an angle out of the range is scattered by reflection and emitted to the surface, the intensity of emitted light in a direction perpendicular to the surface of the scattering control film 20 is high,
In addition, it is possible to emit light with a good luminance distribution (luminance distribution with respect to the emission angle of the emitted light) with a wide emission angle range in which emitted light with sufficient luminance can be obtained.

Further, according to the surface light source device 1, the EL
Each light guide 2 of the scattering control film 20 is emitted by emitting the element 10.
1, the light that travels at an incident angle larger than the critical angle for total reflection toward the interface D between the surface of the light guide 21 and the outside air, which is the final exit surface, is scattered by reflection to change the direction. In other words, since the light finally enters the interface D at an incident angle smaller than the critical angle for total reflection and passes through the interface D and exits, the exit efficiency of the light incident on the scattering control film 20 from the EL element 10 is increased. be able to.

FIG. 4 shows the luminance distribution of the light emitted from the surface light source device 1, the luminance distribution in the case of only the EL element 10 as the surface light source, and the luminance distribution of the scattering control film 20 on the emission surface of the EL element 10. FIG. 9 is a diagram showing a comparison with a luminance distribution when a diffusion plate is arranged instead, in which a solid line is a luminance distribution with respect to an emission angle of the surface light source device 1 of the above embodiment, and a broken line is an EL element 10.
The dashed-dotted line indicates the luminance distribution with respect to the emission angle when the diffusion plate is disposed on the emission surface of the EL element 10.

The luminance distribution shown in FIG. 4 is perpendicular to the exit surface (the surface of the scattering control film 20) of the surface light source device 1 of the above embodiment, and the light guide 21 and the reflection film 22 of the scattering control film 20. Is a luminance distribution with respect to an emission angle on a surface along a direction orthogonal to the length direction of the light emitting device. In the drawing, + θ is one of the directions perpendicular to the emission surface (the direction of the emission angle θ = 0 °). The outgoing angle of light emitted in the direction, -θ is the outgoing angle of light emitted in the opposite direction to the perpendicular direction.

As shown in FIG. 4, the luminance distribution in the case of using only the EL element 10 shows that the luminance of light emitted in the front direction (the direction perpendicular to the emission surface) is high, but the emission angle increases. The distribution has a strong directivity in which the luminance sharply decreases, and therefore, the emission angle range in which high-luminance emission light is obtained is narrow.

The luminance distribution when the diffusion plate is arranged on the exit surface of the EL element 10 is almost uniform, but the light emitted from the EL element in the front angle direction with a high luminance exits from the EL element. Is also diffused, so that the luminance of light emitted in the front direction is considerably lower than that of the conventional EL element.

In comparison with the above, the luminance distribution of the surface light source device 1 of the above embodiment has a higher luminance of light emitted in the front direction, and has a wider emission angle range in which emitted light of sufficient luminance can be obtained.
That is, in addition to the straight light that passes through the scattering control film 20 vertically and exits to the surface, the scattering control film 20
Of the light scattered by reflection at the interface with the outside air D
Since the light that is perpendicularly incident on the EL device 10 is also emitted in the vertical direction, the brightness of the light emitted in the front direction is even higher than in the case where only the EL element 10 is used.

The surface light source device 1 of the above embodiment uses, as the EL element 10, an organic EL element having an electroluminescent layer 14 made of a conductive polymer. Since the transmittance of the light of No. 14 is high, the emitted light can be efficiently emitted.

Further, in the organic EL device, since the electroluminescent layer 14 is made of a conductive polymer, a defective light emission called a dark spot occurs at the interface between the emission electrode 12 and the electroluminescent layer 14. When this dark spot occurs, the brightness distribution of the light emitted from the EL element 10 has a partial decrease in brightness corresponding to the location where the dark spot occurs. Is emitted with a luminance distribution in which the drop in luminance has been eliminated by scattering. Therefore, according to the surface light source device 1, even if a dark spot unique to an organic EL element is generated in the EL element 10, In addition, it is possible to emit light having a good luminance distribution without a partial decrease in luminance.

Further, in the surface light source device 1, since the scattering control film 10 is disposed on the emission surface of the LE element 10 which is a surface light source, not only the light source for emitting light from the surface light source but also It can also be used as a reflection light source that reflects external light, such as natural light or indoor illumination light, to be used as light source light.

In this case, the external light that enters the surface light source device 1 from the surface thereof as shown by the broken arrow in FIG. 1 first enters the interface D between the surface of the scattering control film 20 and the outside air.
Of the light, the light incident on the interface D at an incident angle smaller than the critical angle for total reflection passes through the interface D and enters each light guide 21 of the scattering control film 20.

The path of the external light incident on these light guides 21 takes different paths according to the angle of incidence on the light guides 21, although the path is not shown. External light incident at an incident angle within a predetermined angle range including the direction along the reflective film 22, that is, light incident at an inclination angle within a predetermined angle range around a direction perpendicular to the film surface of the scattering control film 20 Goes straight through the light guide section 21 and
The light enters the interface C with the E element 10.

The light incident on the interface C has a refractive index of the light guide 21 and the support sheet 23 of the scattering control film 20 that is equal to the refractive index of the emission side substrate of the EL element 10 (the transparent substrate 11).
Of the light guide 21 and the supporting sheet 23 and the refractive index of the transparent substrate 11 of the EL element 10. An EL element 10 is provided by an adhesive (not shown) having the same or a refractive index between the two.
Most of the light passes through the interface C and enters the LE element 10 regardless of the angle of incidence on the interface C.

On the other hand, the external light incident on the light guide section 21 at an incident angle other than the above angle range, that is, the scattering control film 20
The light incident from the direction greatly inclined obliquely to the film surface passes through the light guide portion 21 and enters the reflection film 22 at the boundary between the light guide portions 21, and the reflection surface (mirror surface or (Scattering surface).

The light reflected and scattered by the reflection film 22 travels in various directions in the light guide 21, and the light traveling toward the back surface of the light guide 21 is transmitted to the interface C with the LE element 10. And most of the light passes through the interface C and enters the LE element 10.

The light traveling in the other direction is transmitted to the light guide section 21.
The light is repeatedly scattered by reflection between the reflection films 22 at the interfaces on both sides of the light guide, and the light traveling toward the back surface of the light guide 21 is incident on the LE element 10 as described above, and is directed toward the surface of the light guide 21. That is, the light returning in the first incident direction of the external light enters the interface D with the outside air.

Then, of the light incident on the interface D,
Light incident on the interface D at an incident angle greater than the critical angle for total reflection is totally reflected at the interface D, but light incident at an incident angle smaller than the critical angle for total reflection is transmitted through the interface D. And emit.

The direction in which the light exits depends on the angle of incidence on the interface D. Light incident perpendicular to the interface D exits in the vertical direction without being refracted at the interface D,
Light incident from a direction inclined with respect to the vertical direction is
At the interface D, the light is refracted in accordance with the angle of incidence with respect to the interface D and the refractive index difference between the light guide 21 and the support sheet 23 and the outside air, and is emitted in that direction.

The light totally reflected at the interface D is incident on the reflection film 22 in the reflection direction, and is again scattered by reflection. Of the light, the light traveling to the back surface of the light guide 21 is L.
Light incident on the E element 10 and traveling toward the surface of the light guide portion 21 (light returning in the first incident direction of external light) is incident on the interface D with the outside air, and the interface D of the light is critically reflected by the total reflection. Light incident at an incident angle smaller than the angle passes through the interface D and exits in each direction as described above.

That is, the scattering control film 20
Of the light emitted from the LE element 10 as a surface light source and incident on the scattering control film 20 from the back surface thereof, the light incident at a predetermined angle range is made to travel straight without being reflected, and at an angle other than the angle range. The incident light is reflected and scattered, and among the light incident on the scattering control film 20 from its surface, the light incident in a predetermined angle range is made to travel straight without being reflected, and at an angle other than the angle range. It has optical characteristics of reflecting and scattering incident light, and therefore, the EL element 10
Not only as described above, but also, among the external light incident on each light guide portion 21 of the scattering control film 20 from the surface thereof, the light incident at an angle out of the predetermined angle range is reflected. And the light is scattered, and of the light, the light directed toward the surface of the scattering control film 20 can be emitted to the surface.

Of the external light incident on each light guide portion 21 of the scattering control film 20 from its front surface, the light that enters the light guide portion 21 in the above-described predetermined angle range and travels straight through the light guide portion 21 to the rear surface side is considered. Of the light that has been repeatedly scattered by reflection in the scattering control film 20, most of the light that travels toward the back surface of the light guide unit 21 passes through the interface C with the LE element 10 and enters the LE element 10 as described above. However, the light is reflected by the back electrode 13 of the LE element 10 and returned to the scattering control film 20, and, like the light emitted from the EL element 10 described above, travels straight through the scattering control film 20, or
Alternatively, the light is scattered by reflection and emitted to the surface.

Therefore, according to the above-mentioned surface light source device, it can be used as a light source for emitting light from the EL element 10 which is a surface light source, or as a reflection light source that reflects external light and becomes light source light.

Further, according to this surface light source device, the E
Of the light emitted from the L element 10 and incident on the back surface of the scattering control film 20, the light incident within a predetermined angle range goes straight and exits to the surface of the scattering control film 20 and has an angle other than the angle range. The incident light is scattered by reflection and emitted to the surface, so that the emitted light in the direction in which the light that has traveled straight through the scattering control film 20 is emitted has high luminance, and the emitted light has sufficient luminance. A wide angular range, it is possible to emit light having a good luminance distribution as shown by the solid line in FIG. 3, and also when used as a reflection light source, the light is scattered and reflected by the scattering control film 20. Light with a good luminance distribution can be emitted.

FIG. 5 is a sectional view of a surface light source device according to a second embodiment of the present invention, in which hatching is omitted. In the surface light source device 1 of this embodiment, the transparent substrate of the EL element 10 which is a surface light source is also used as the scattering control film 20.
The basic structure of the L element 10 and the structure of the scattering control film 20 are the same as in the first embodiment.

However, in this embodiment, the refractive index of the light guide 21 and the support sheet 23 of the scattering control film 20 is changed to the refractive index on the emission side of the EL element 10 (the electroluminescent layer 14).
Is a three-layer structure, it is formed of a transparent resin having a value substantially equal to or close to the refractive index of the hole transport layer which is the layer on the emission side.

According to the surface light source device 1 of this embodiment, the EL
The light emitted from the element 10 and incident on the interface with the scattering control film 20 has any angle of incidence,
Since the light is transmitted through the interface and enters the light guide portion 21 of the scattering control film 20 without being totally reflected, the total reflection in the process in which the light emitted from the electroluminescent layer 14 of the EL element 10 exits the EL element 10 is As shown by the solid arrow in FIG. 5, the light emission path mostly occurs at the interface between the electroluminescent layer 14 and the emission-side electrode 12, and at the interface between the EL element 10 and the scattering control film 20. Very slight. Therefore E
Since light leakage due to total reflection in the L element 10 is almost only leakage from the end face of the electroluminescent layer 14, it is necessary to further increase the amount of light emitted from the EL element 10 as compared with the first embodiment. it can.

Although the surface light source device 1 of the first and second embodiments uses the EL element 20 as the surface light source, the surface light source is not limited to the EL element. .

FIG. 6 is a sectional view of a surface light source device according to a third embodiment of the present invention, in which hatching is omitted. One surface or both end surfaces (a light source plate 10a) of a light guide plate 16 is used as the surface light source 10a. The light source 18 is arranged so as to face one end face in the drawing, and a scattering control film 20 is provided on the light emission surface.

The light guide plate 16 is made of a transparent plate such as an acrylic resin plate, and a reflective film (mirror surface or scattering surface) 16a is provided on the back surface and on the peripheral surface other than the light intake end surface facing the light source 18. Is formed. The light source 1
Reference numeral 7 denotes, for example, a straight tubular fluorescent lamp having a length extending over the entire end face of the light guide plate 16, and a reflector 18 is provided behind the fluorescent lamp.

The surface light source 10a emits light from the light source 18 to the surface through the light guide plate 16, and the light from the light source 18 is taken into the light guide plate 16 from its end face. The light is guided through 16 and exits from the surface.

The scattering control film 20 used in the surface light source device 1 of this embodiment is basically the same as that of the first and second embodiments, and the description thereof is the same as that of the drawings. Is omitted.

However, in this embodiment, the light guide 21 and the support sheet 23 of the scattering control film 20 are formed of a transparent resin having a refractive index substantially equal to or close to the refractive index of the light guide plate 16. .

Also in the surface light source device 1 of this embodiment, since the above-mentioned scattering control film 20 is disposed on the light emitting surface (the surface of the light guide plate 16) of the surface light source 10a, the light from the surface light source 10a is provided. As well as a reflection light source that reflects external light to produce light source light.

In the first and second embodiments,
As the scattering control film 20, one having the reflection film 22 on a surface along a direction perpendicular to the film surface is used, but the scattering reflection surface of the reflection film 22 may be an inclined surface.

FIG. 7 is a cross-sectional view showing another example of the scattering control film 20 in which a part of the scattering control film 20 is omitted from hatching. The film surface of the reflection film (reflection film whose both surfaces are mirror surfaces or scattering surfaces) 22 provided at the boundary is inclined obliquely with respect to the film surface.

When such a scattering control film 20 is used, of the light emitted from the surface light source and incident on each light guide portion 21 of the scattering control film 20 from the back as shown by the solid arrow in FIG. Light incident in a predetermined angle range including a direction along the film surface of the film 22 travels straight without being scattered by reflection in the light guide portion 21 and exits to the surface of the scattering control film 20, and the angle range Light incident at an angle other than the above is scattered by reflection on the reflection film 22 and finally emitted to the surface.

Therefore, according to the surface light source device using the scattering control film 20 shown in FIG. 7, the brightness of the emitted light in the direction inclined obliquely to the direction perpendicular to the emission surface is high and sufficient. It is possible to emit light having a luminance distribution with a wide emission angle range in which emission light with high luminance can be obtained.

The external light enters each light guide portion 21 of the scattering control film 20 from its surface as shown by a broken arrow in FIG. The light that has entered at a predetermined angle range including the direction that has entered the light guide portion 21 travels straight without being scattered by reflection in the light guide portion 21 and exits to the back surface of the scattering control film 20. The light is scattered by the reflection on the reflection film 22, and of the light, the light directed to the surface of the scattering control film 20 is emitted to the surface.

In this case, the light that has traveled straight through the light guide section 21 and emitted to the rear surface is incident on the surface light source. If the surface light source had light reflecting means, it was emitted to the rear surface. Light is reflected, and the light travels straight through the scattering control member or is scattered by reflection and emitted to the surface, similarly to the light emitted from the surface light source.

For this reason, the surface light source device using the scattering control film 20 shown in FIG. 7 is used not only as a light source for emitting light from a surface light source but also as a reflection light source for reflecting external light to be a light source light. can do.

Further, in the first to third embodiments, as the scattering control member provided on the emission surface of the surface light source, linear reflection films 22 are arranged in parallel with each other at intervals corresponding to the width of the light guide 21. Although the louver-shaped scattering control film 20 is used, the scattering control member may be a transparent film in which a reflective film is provided in a lattice shape, and a short-length reflective film may be provided in the transparent film in the longitudinal direction. Also, one provided at an appropriate pitch in the width direction may be used.

FIG. 8 is a perspective view showing a modification of the scattering control member. This scattering control member has two louver-like scattering control films 20 used in the above embodiment, and the length of each of the reflection films 22. The directions are perpendicular to each other and are superimposed. In this example, two scattering control films 2 were used.
0 are bonded to each other, and a support sheet 23 is bonded to the outer surface of each of the scattering control films 20.

When such a scattering control member is used, since the reflection film 22 is provided substantially in a lattice shape, the incident light is scattered in two directions orthogonal to each other. Can be made distributions as shown in FIG.

The scattering control member is provided in each of the light guide sections 21.
The light is not limited to the one provided with the reflection film 22 at the boundary of the light, and the light that is emitted from the surface light source and incident on the scattering control member from the back surface of the light is made to travel straight without reflecting the light incident at a predetermined angle range. Reflecting and scattering light incident at an angle other than the angle range, and of the external light incident from the surface of the scattering control member, the light incident at a predetermined angle range travels straight without reflection. However, any material having an optical characteristic of reflecting and scattering light incident at an angle other than the above angle range may be used.

Next, a liquid crystal display device using the surface light source device 1 will be described. FIG. 9 is a side view showing an embodiment of the liquid crystal display device. In the liquid crystal display device, the above-described surface light source device 1 is disposed behind a liquid crystal display element 30 as a backlight.

The liquid crystal display element 30 is, for example, a simple matrix or active matrix type ECB.
(Birefringence effect) type liquid crystal display element, frame-shaped sealing material 3
3, a pair of transparent electrode forming substrates 31 and 3
A liquid crystal layer in which liquid crystal molecules are aligned in a predetermined alignment state (for example, a twist alignment state) is provided between the two, and polarizing plates 34 and 35 are arranged on the outer surfaces of the substrates 31 and 32, respectively.

The ECB type liquid crystal display element 30 obtains colored light by utilizing the birefringence function of the liquid crystal layer and the polarizing action of the polarizing plates 34, 35. The linearly polarized light is converted into elliptically polarized light having different polarization states in the respective wavelengths due to the birefringence action of the liquid crystal during the transmission through the liquid crystal layer, and the light is converted to the other polarizing plate 35.
And the light that has passed through the other polarizing plate 35 becomes colored light having a color corresponding to the ratio of the light intensities of the respective wavelength lights constituting the light.

That is, the ECB type liquid crystal display element 30
Is to obtain colored light without using a color filter. Therefore, since light is not absorbed by the color filter, light transmittance can be increased and a bright color display can be obtained.

In the ECB type liquid crystal display element 30, the birefringence of the liquid crystal changes depending on the alignment state of the liquid crystal molecules according to the voltage applied between the electrodes of the two substrates 31, 32.
Since the polarization state of each wavelength light incident on the other polarizing plate changes accordingly, the color of the colored light is changed by controlling the applied voltage, and a plurality of colors are displayed on the same pixel,
A multi-color image such as a full-color image can be displayed.

In this embodiment, the surface light source device 1 of the first embodiment shown in FIG. 1 is used as the backlight. The description of the configuration of the surface light source device 1 is omitted by attaching the same reference numerals to the drawings.

That is, in this liquid crystal display device, the surface light source device 1 is disposed as a backlight, and the surface light source device 1 is provided on the emission surface of an EL element 10 which is a surface light source.
Of the light emitted from the element 10, the light emitted in a predetermined angle range is made to go straight without reflection, and the light emitted in an angle other than the angle range is reflected and scattered,
Among the external light incident from the surface, a light scattering control film having an optical property of causing light incident at a predetermined angle range to travel straight without reflecting, and reflecting and scattering light incident at an angle other than the angle range. 20 are provided.

This liquid crystal display device has the liquid crystal display element 3
Since the surface light source device 1 can be used both as a light source that emits light from the EL element 10 and a reflection light source that reflects external light and becomes light source light, It can have both functions of the pattern display and the reflection type display.

The scattering control film 20 of the surface light source device 1 has a characteristic of, for example, traveling straight without reflecting light incident at an incident angle within a predetermined angle range including a direction perpendicular to the film surface. When the surface light source device 1 is turned on and the display of the liquid crystal display device is observed, the EL element 10 is emitted and the scattering control film 2 is turned on.
Of the light incident on 0, light emitted in a predetermined angle range travels straight without being reflected and scattered, and light emitted in angles other than the angle range is scattered by reflection and is directed in the front direction (to the display surface). The light emitted in a wide angle range (including the vertical direction) has a high brightness of light emitted in the front direction, and has a wide emission angle range in which emitted light of sufficient brightness can be obtained. The light can be incident on the element 30.

When the display is observed by using the external light incident on the liquid crystal display device, the scattering control film 20 of the surface light source device 1 causes the external light incident from the surface to have a predetermined angle range. In this case, the incident light is made to travel straight without being reflected, and the incident light is reflected and scattered at an angle other than the above-mentioned angle range. Therefore, of the light transmitted through the liquid crystal display element 30 and incident on the scattering control film 20,
Light incident within a predetermined angle range from a direction parallel to the film surface of the reflection film 22 travels straight through the scattering control film 20 and is incident on the EL element 10, and the light is incident on the back electrode 13 of the EL element 10.
And is incident on the liquid crystal display element 30 from the scattering control film 20. External light incident outside the angle range is reflected and scattered by the reflection film 20 of the scattering control film 20, and is incident on the liquid crystal display element 30.

Therefore, when the surface light source device 1 is turned on for observation, the scattering control film 20 of the surface light source device 1 improves the front luminance of light emitted from the EL element 10 and reduces the luminance distribution. It functions as an optical element for flattening, and functions as an illuminated liquid crystal display device with a high front luminance and a wide viewing angle for obtaining a bright display.

When observation is performed using external light, the scattering control film 20 of the surface light source device 1 functions as a reflection member for reflecting external light, and the back electrode 13 of the EL element 10 functions as a reflection film. In this case as well, it functions as a reflection-type liquid crystal display device having a high front luminance and a wide viewing angle for obtaining a bright display.

That is, The above-mentioned liquid crystal display device uses the above-mentioned surface light source device 1 for its backlight, and reflects light by the scattering control film 20 of this surface light source device 1 and the back electrode 13 of the EL element 10 which is a light emitting source. Therefore, without driving the EL element 10 to emit light, it is also possible to display by reflecting external light incident from the surface (emission surface) of the liquid crystal display element 30 as shown by a broken arrow in FIG. Therefore, it can be used as a so-called two-way display device capable of performing both a transmissive display using light from the surface light source device 1 and a reflective display using external light.

In this case, the surface light source device 1 of the above embodiment is
Since an organic EL element having a high light transmittance of the electroluminescent layer 14 is used for the EL element 10 as a light emitting source,
Not only can the emitted light be emitted efficiently, but also in the case of performing a reflective display, the incident external light can be efficiently reflected to obtain a bright display.

The EL element 10 may generate a dark spot peculiar to the organic EL element in some cases. Even in such a case, light emitted from the surface light emitter (light emitted to the surface of the scattering control member) is Since light having a luminance distribution in which the drop in luminance has been eliminated by scattering is obtained, light having a good luminance distribution without a partial drop in luminance is incident on the liquid crystal display element 30 to display a high-quality image. Can be.

Further, in this liquid crystal display device, since the ECB type liquid crystal display element for obtaining colored light without using a color filter is used as the liquid crystal display element 30, it is sufficient for a reflective display using external light. A bright color image can be displayed.

Further, the ECB type liquid crystal display element 30
Since colored light is obtained by utilizing the birefringence function of the liquid crystal layer and the polarizing action of the polarizing plates 34 and 35, a full-color image is displayed by, for example, changing the color of each pixel to red, green, and blue. In this case, not all display colors can be obtained with high color purity, but the ECB type liquid crystal display element 30 itself emits a fluorescent substance that emits fluorescence of a color corresponding to a color for which high color purity is difficult to obtain. By adding to the electroluminescent layer 14, a color image with good color balance can be displayed.

In the liquid crystal display device of the above embodiment, as shown in FIG. 9, the surface light source device 1 is arranged such that the surface (outgoing surface) of the scattering control film 20 is provided on the back surface (incident surface) of the liquid crystal display element 30. The surface light source device 1
May be arranged such that the front surface of the scattering control film 20 is adhered to the back surface of the liquid crystal display element 30 as in the other embodiment shown in FIG.
The support sheet 23 on the 0 surface may be omitted.

Although the liquid crystal display element 30 used in the liquid crystal display device of the above embodiment is of the ECB type, the liquid crystal display element 30 may display a color image using a color filter. Good.

[0122]

The surface light source device according to the present invention comprises a surface light source and a scattering control member disposed on the light exit surface of the surface light source, and the scattering control member emits the surface light source to emit light. Of the light incident on the back surface of the scattering control member, the light incident at a predetermined angle range is made to travel straight without reflection, and the light incident at an angle other than the angle range is reflected and scattered, and the scattering is performed. Among the light incident on the control member from its surface, it has an optical property of causing light incident at a predetermined angle range to travel straight without reflection, and reflecting and scattering light incident at an angle other than the angle range. Therefore, it can be used as a light source that emits light from a surface light source, or as a reflection light source that reflects external light to generate light as source light.

In addition, according to the surface light source device of the present invention,
Of the light emitted from the surface light source and incident on the scattering control member from its back surface, light incident on a predetermined angle range goes straight and exits on the surface of the scattering control member and enters at an angle other than the angle range. The reflected light is reflected or scattered and emitted to the surface, so that the emission light in the direction in which the light that has traveled straight through the scattering control member is emitted has a high luminance, and the emission angle range in which the emitted light with sufficient luminance is obtained. Light with a wide and good luminance distribution can be emitted, and also when used as a reflection light source, light with a good luminance distribution can be emitted due to light scattering by the scattering control member.

In this surface light source device, for example, the scattering control members are respectively arranged adjacent to each other,
A plurality of transparent light guides each having a parallel interface, and a reflective thin film disposed on each of the boundaries of these light guides and having a flat surface having reflective surfaces on both sides, wherein the reflective thin film is An optical film having an intersecting front and back surface, and if a scattering control member made of the optical film is used, of light incident on the light guide portion from the back surface, includes a direction along the film surface of the reflective thin film. Light that enters within a predetermined angle range goes straight without reflection,
The light incident at an angle other than the angle range is reflected and scattered, and of the light incident from the surface of the scattering control member, without reflecting the light incident at a predetermined angle range including the direction. It is possible to travel straight and reflect and scatter light incident at an angle other than the above angle range.

It is desirable that the back surface of the scattering control member is provided in close contact with the exit surface of the surface light source, and the refractive index of the light guide portion is substantially the same as the refractive index of the exit side of the surface light source. Or a value close to it. By doing so, the light emitted from the surface light source is efficiently incident on the scattering control member, so that the light emitted from the surface light source can be emitted with high efficiency, and emitted light with higher luminance can be obtained.

The surface light source may be, for example, an organic EL element. In this case, when a dark spot peculiar to the organic EL element is generated, the luminance distribution of the light emitted from the EL element is located at the location where the dark spot is generated. Correspondingly, a partial decrease in luminance occurs, but the light emitted to the surface of the scattering control member has a luminance distribution in which the decrease in luminance has been eliminated by scattering.

Further, in the liquid crystal display device of the present invention, the surface light source device is disposed behind a liquid crystal display element.
The surface light source device is configured such that, out of the light emitted from the surface light source, the light emitted from the surface light source travels straight without reflecting, and the light emitted at an angle other than the angle range. Is reflected and scattered, and of the external light incident from the outside, the light incident at a predetermined angle range is made to travel straight without reflection, and the light incident at an angle other than the angle range is reflected and scattered. A scattering control member having optical characteristics is provided.

According to the liquid crystal display device of the present invention, the surface light source device disposed as a backlight behind the liquid crystal display element has high luminance of light emitted in a predetermined direction.
In addition, since the emission angle range in which emission light with sufficient brightness is obtained emits light with a wide brightness distribution, according to this liquid crystal display device, a decrease in the brightness of the screen when the display is observed from an oblique direction is reduced. Thus, the angle range in which the display can be observed with sufficient brightness can be widened.

Further, in the liquid crystal display device of the present invention, the above-mentioned surface light source device is disposed behind a liquid crystal display element. This surface light source device has a light exiting from the surface light source on an exit surface of the surface light source. Among them, the light emitted in a predetermined angle range goes straight without reflection, the light emitted in an angle other than the angle range is reflected and scattered, and the external light incident from the outside is determined in advance. A scattering control member having an optical characteristic of causing light incident in an angle range to travel straight without being reflected and reflecting and scattering light incident at an angle other than the angle range is provided.

Therefore, when the liquid crystal display device of the present invention is observed with the surface light source device turned on, as described above, of the light emitted from the surface light source and incident on the scattering control member, Light emitted in a predetermined angle range travels straight without being reflected and is emitted, and light emitted at angles other than the angle range is scattered and emitted by reflection, so that the brightness of light emitted in a predetermined direction is high. In addition, it is possible to make light with a luminance distribution having a wide emission angle range from which light with sufficient luminance can be obtained enter the liquid crystal display element.

In the case of observation using external light incident on the liquid crystal display device, the scattering control member of the surface light source device is
Of the incident external light, the light incident at a predetermined angle range is made to travel straight without being reflected, and the light incident at an angle other than the angle range is reflected and scattered. Of the light incident from the device,
The light incident in the angle range is transmitted as it is, reflected by the reflection member of the surface light source, and emitted to the observer side,
Light incident outside the angle range is reflected and scattered by the scattering control member and is emitted again to the observer side.

Therefore, when the surface light source device is turned on for observation, the scattering control member increases the luminance of light emitted from the surface light source in a predetermined direction and flattens the luminance distribution. Acting as an element, when observing by using external light, the scattering control member and the reflecting member of the surface light source act as a reflecting film, so that in any of the observations, bright observation is performed in a wide observation angle range. can do.

[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, in which hatching is omitted.

FIG. 2 is a perspective view of a scattering control film used in the surface light source device.

FIG. 3 is a view for explaining a range of an incident angle of light that is incident on a light guide portion of the scattering control film and travels straight through the light guide portion and is incident on an interface with outside air.

FIG. 4 shows the luminance distribution of the emitted light of the surface light source device, the luminance distribution when only an EL element is used, and the luminance distribution when a diffusion plate is arranged instead of a scattering control film on the exit surface of the EL element. FIG.

FIG. 5 is a sectional view of a surface light source device according to a second embodiment of the present invention, in which hatching is omitted.

FIG. 6 is a sectional view of a surface light source device according to a third embodiment of the present invention, in which hatching is omitted.

FIG. 7 is a cross-sectional view showing another example of the scattering control unit film, in which a part of the film is omitted from hatching.

FIG. 8 is a perspective view showing a modification of the scattering control member.

FIG. 9 is a side view showing one embodiment of the liquid crystal display device of the present invention.

FIG. 10 is a side view showing another embodiment of the liquid crystal display device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Surface light source device 10 ... EL element (surface light source) 11 ... Transparent substrate 12 ... Outgoing side electrode 13 ... Back side electrode 14 ... Electroluminescent layer 1a ... Surface light source 16 ... Light guide plate 17 ... Light source 20 ... Scattering control film 21 ... Conduction Optical part 22 ... Reflective film 30 ... Liquid crystal display element

Claims (3)

[Claims] 1. A surface light source, and a scattering control member disposed on a light emission surface of the surface light source, wherein the scattering control member emits the surface light source and enters the scattering control member from a back surface thereof. Of the light to be emitted, the light incident at a predetermined angle range is made to travel straight without being reflected, and the light incident at an angle other than the angle range is reflected and scattered, and is incident on the scattering control member from the surface thereof. A surface light source device having an optical characteristic of causing light incident on a predetermined angle range of light to travel straight without being reflected, and reflecting and scattering light incident on an angle other than the angle range. 2. The scattering control member according to claim 1, wherein said plurality of scattering control members are arranged adjacent to each other, and each of said plurality of transparent light guides has a parallel boundary surface. And a reflective thin film formed of a flat surface having reflectivity, wherein the reflective thin film is made of an optical film having front and back surfaces intersecting with each other.
A surface light source device according to claim 1. 3. A liquid crystal display device comprising a liquid crystal display element and the surface light source device according to claim 1 disposed behind the liquid crystal display element.