JPH10189237A - Surface light emitting body and liqiud crystal display device using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve luminescence distribution of emission light by increasing luminescence of light to be emitted in a predetermined direction as a surface light emitting body employing an EL element and widening an emission angle range in which the emission light of sufficient luminescence can be obtained. SOLUTION: An emission face of an EL element 10 is provided with a luminescence distribution control member 20 consisting of a plurality of transparent parts 21 arrayed along a plane direction and a scattering reflection membrane 22 sandwiched between these transparent parts 21, the light incident toward a diagonal direction, of the light emitting the EL element and incident to the transparent parts 21 of the luminescence distribution control member 20 is advanced straight and emitted, and the light emitted toward the diagonal direction is scattered by the scattering reflection membrane 22 and is emitted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a surface light emitting device using an electroluminescent device (hereinafter, referred to as an EL device) and a liquid crystal display device using the same.

[0002]

2. Description of the Related Art An EL element used as a surface light emitter is:
For example, it is used for a backlight of a liquid crystal display element in a liquid crystal display device. FIG. 7 is a cross-sectional view of a conventional EL element with hatching omitted, and here, what is called an organic EL element is shown. This organic EL element
An electroluminescent layer 4 made of an organic material is interposed between a transparent emission electrode 2 formed on one surface of a transparent substrate 1 made of glass and a back electrode 3 facing the emission electrode 2. The emission side electrode 2 is an anode,
The back electrode 3 is a cathode.

The emission side electrode 2 is made of ITO (indium tin oxide) or indium zinc oxide, and has high transmittance in a visible light wavelength region. The back electrode 3 is made of a Mg-based alloy (Mg-In) having a small work function from the viewpoint of injecting electrons into the electroluminescent layer 4.
Alloy or Mg-Ag alloy).

Although the electroluminescent layer 4 is shown as one layer in the figure, the electroluminescent layer 4 is generally a two-layer structure in which a hole transport layer is laminated on the anode side of an electron transporting luminescent layer, or 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.

The organic EL element is driven to emit light by applying a voltage (DC voltage) between the emission side electrode 2 and the back side electrode 3, and a voltage is applied between the electrodes 2 and 3. Then, holes are injected from the emission-side electrode (anode) 2 and electrons are injected from the back-side electrode (cathode) 3 into the electroluminescent layer 4, and a singlet exciton is generated by recombination of the injected holes and the electrons. Generates and emits light.

[0006] Light from the singlet exciton is incident on the emission electrode 2 from the electroluminescent layer 4, passes through the transparent substrate 1, and exits to the surface thereof. The light emitted from the singlet exciton includes light traveling toward the back surface of the electroluminescent layer 4, but the light is reflected by the back electrode 3.

Looking at the light emission path from one point of the electroluminescent layer 4 in the EL element, light from this point radiates in various directions as shown by arrows in FIG. Light traveling in a direction perpendicular to the emission surface (the surface of the substrate 1) (along a direction perpendicular to the emission surface) does not cause refraction or reflection at the interface between the layers of the EL element and the interface between the emission surface and the outside air. Transmits and exits in the vertical direction.

On the other hand, the radiation emitted in the oblique direction is obliquely incident on the interface between the respective layers, so that the light is refracted or reflected at the interface. This is because the refractive index on the emission side of the electroluminescent layer 4, for example, the refractive index of the hole transport layer in the electroluminescent layer having a three-layer structure is 1.40 to 1.80, and the refractive index of the emission side electrode 2 is ITO. Is about 2.00, the refractive index of the transparent substrate (glass) 1 is 1.45 to 1.80, the refractive index of air as outside air is about 1.0008, and the refractive index of an adjacent layer is This is because they are different from each other.

For this reason, the radiated light traveling in the oblique direction first enters the interface A between the electroluminescent layer 4 and the emission-side electrode 2, and of the light, the total reflection critical angle to the interface A is smaller than the critical angle. Light incident at an incident angle is refracted at the interface A and is incident on the emission electrode 2, and 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 repeats the reflection at the back electrode 3 and the reflection at the interface A and the lateral end face of the electroluminescent layer 4 so as to form a zigzag in the electroluminescent layer 4. Refraction proceeds, and in the process, light incident on 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 2.

The light incident on the emission-side electrode 2 passes through the emission-side electrode 2 and is incident on the interface B with the transparent substrate 1. Light incident at a smaller incident angle is refracted at the interface B and enters the transparent substrate 1, and light incident at an incident angle larger than the critical angle for total reflection is totally reflected at the interface B.

Part of the light totally reflected at the interface B is partially reflected at the interface A with the electroluminescent layer 4 and at the interface B.
And the reflection at the lateral end face of the emission-side electrode 2 is repeated, and the light is refracted in the emission-side electrode 2 in a zigzag manner, and the light is incident on the interface B at an incident angle smaller than the critical angle for total reflection. Light passes through the interface B and enters the transparent substrate 1.

The other light totally reflected at the interface B is
The light passes through the interface A with the electroluminescent layer 4 and returns to the electroluminescent layer 4, and the light is refracted zigzag in the electroluminescent layer 4 like the light totally reflected at the interface A, and travels there. In the process, light incident on the interface A at an incident angle smaller than the critical angle for total reflection passes through the interface A and is incident on the emission-side electrode 2,
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 passes through the interface B and enters the transparent substrate 1.

Further, the light incident on the transparent substrate 1 from the emission-side electrode 2 passes through the transparent substrate 1 and is incident on the interface C between the surface thereof and the outside air (air). Light incident at an incident angle smaller than the critical angle for total reflection is refracted at the interface C and emitted, and light incident at an incident angle larger than the critical angle for total reflection is totally reflected at the interface C.

Part of the light totally reflected at the interface C is totally reflected at the interface B with the emission-side electrode 2 and at the interface A.
And the reflection at the lateral end surface of the transparent substrate 1 is repeated, and the light is refracted in a zigzag manner in the transparent substrate 1 and proceeds. Of the light, the light incident on the interface C at an incident angle smaller than the critical angle for total reflection is considered. The light exits through the interface C.

The other light totally reflected at the interface C is
The light passes through the interface B with the emission-side electrode 2 and returns to the emission-side electrode 2, or further transmits through the interface A with the electroluminescence layer 4 and returns to the electroluminescence layer 4. The light exits the electrode 2 or the electroluminescent layer 4 and refracts in a zigzag manner.
Light incident on the interfaces A and B at an incident angle smaller than the critical angle for total reflection is incident on the transparent substrate 1 again, and of the light, the light is smaller than the critical angle for total reflection with respect to the interface C with the outside air. Light incident at an incident angle is emitted.

That is, in the above EL device, the light enters the interface A between the electroluminescent layer 4 and the emission side electrode 2 and the interface B between the emission side electrode 2 and the transparent substrate 1 at an incident angle smaller than the critical angle for total reflection. Thus, light that has passed through these interfaces A and B and that has entered the interface C between the surface of the transparent substrate 1 and the outside air, which is the emission surface, at an angle of incidence smaller than the critical angle for total reflection becomes emission light.

The other light is totally reflected at any one of the interfaces A, B, and C. However, as described above, these lights are transmitted through the electroluminescent layer 4, the emission-side electrode 2, and the transparent substrate 1. The light proceeds while being refracted. In the process, a part of the light is emitted from the emission-side electrode 2, the electroluminescent layer 4, and the end face of the transparent substrate 1, and becomes a leaked light.

Therefore, the light finally emitted to the exit surface is the light that enters the interface C between the exit surface and the outside air at an incident angle smaller than the critical angle for total reflection, and as shown in FIG.
The angle of the light emitted from the electroluminescent layer 4 with respect to the vertical direction (direction along the perpendicular to the emission surface) at the interface A with the emission side electrode 2 is defined as the incident angle α, and the angle between the emission side electrode 2 and the transparent substrate 1 at the interface. Of the transparent substrate 1 with respect to the vertical direction
Assuming that the angle with respect to the vertical direction at the interface C between the air and the outside air is the incident angle γ, and the angle from the emission surface to the vertical direction is the emission angle δ, the light finally emitted from the emission surface, that is, the emission angle δ is 90 The light in the range smaller than ° is the light of the light emitted from the electroluminescent layer 4 that is incident on the interfaces A, B, and C at the following incident angles α, β, and γ.

Here, for example, the refractive index of the electroluminescent layer 4 is 1.60, the refractive index of the emission side electrode 2 is 2.00, the refractive index of the transparent substrate 1 is 1.45, and the refractive index of the outside air is 1.
0008, the incident angles α, β, and γ on the interfaces A, B, and C where the emission angle δ is δ ≦ 90 ° are α ≦ 38.7 ° β
≦ 30.0 ° γ ≦ 43.6 °, and among the light incident on the exit surface (the interface C between the surface of the transparent substrate 1 and the outside air), the incident angle γ with respect to the exit surface is smaller than 43.6 °. Is the emitted light.

[0021]

However, the above conventional E
The L element has high luminance of light emitted in the front direction, that is, the direction perpendicular to the emission surface (light with an emission angle δ = 0 °), but its luminance sharply decreases as the emission angle δ increases. Therefore, there is a problem that the luminance distribution of the emitted light is a distribution having a high directivity, and therefore, the emission angle range where high-luminance emitted light can be obtained is narrow.

The EL element is used for, for example, a backlight of a liquid crystal display element in a liquid crystal display device. However, in the above-mentioned conventional EL element, the luminance distribution of emitted light has a strong directivity distribution. In a liquid crystal display device using the EL element as the backlight, the screen becomes considerably dark when the display is observed from an oblique direction with respect to a direction perpendicular to the emission surface, so that the display can be observed with sufficient brightness. There is a problem that the angle range is narrow.

Therefore, conventionally, it has been considered that the light emitted from the EL element is diffused by a diffusion plate to make the luminance distribution of the emitted light substantially uniform. Since the emitted light in the range is also diffused and its luminance is reduced, the luminance of the light emitted in a predetermined direction (for example, the front direction) cannot be increased.

According to the present invention, as a surface light emitter using an EL element, the luminance of light emitted in a predetermined direction is increased, and the emission angle range in which emitted light with sufficient luminance is obtained is widened to increase the emission angle. It is an object of the present invention to provide a device capable of improving the luminance distribution and to provide a liquid crystal display device using the surface light emitter.

[0025]

Means for Solving the Problems The surface illuminator of the present invention comprises:
Of the incident light from the back surface opposite to the emission surface, the light incident in the predetermined direction on the emission surface of the EL element goes straight and exits to the surface, and the light incident in the other direction is scattered. And a brightness distribution control member having a characteristic of emitting light to the surface is provided.

That is, the surface light emitter of the present invention emits light from the EL element and emits the light to the surface through the luminance distribution control member.
According to this surface light emitter, of the light emitted from the EL element and incident on the luminance distribution control member from the back surface, the light incident in a predetermined direction goes straight and exits to the front surface, and is emitted in the other direction. Since the light incident toward the surface is scattered and emitted to the surface, the brightness of the emitted light in the predetermined direction is increased, and the emission angle range in which the emitted light having sufficient brightness is obtained is widened. Can be improved.

Further, in the liquid crystal display device of the present invention, the surface illuminant is disposed as a backlight behind the liquid crystal display element, and the surface illuminant has a luminance of light emitted in a predetermined direction. The liquid crystal display device according to the present invention has a high emission angle and a wide emission angle range in which emission light of sufficient luminance can be obtained. Can be widened in an angle range that can be observed with sufficient brightness.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the surface illuminator of the present invention has a structure in which light incident on a light emitting surface of an EL element from a back surface opposed to the light emitting surface in a predetermined direction. Is emitted straight to the surface, the light incident in the other direction is scattered, and by providing a brightness distribution control member having a characteristic of emitting the light to the surface, the brightness of the emitted light in a predetermined direction is reduced. The brightness distribution of the emitted light is improved by increasing the emission angle range in which the emitted light can be obtained with sufficient brightness.

In the surface light emitter of the present invention, the brightness distribution control member comprises a plurality of transparent portions arranged along the surface direction and a scattering reflection film sandwiched between side surfaces of these transparent portions. It is preferable that the scattering reflection film is on a surface along the predetermined direction, and if the luminance distribution control member has such a configuration, a predetermined portion of light incident on the transparent portion from the back surface thereof is used. The light incident in one direction is made to go straight, and the light incident in another direction can be scattered by the scattering reflection film.

Preferably, the brightness distribution control member is provided with its back surface in close contact with the emission surface of the EL element.
Further, it is preferable that the refractive index of the transparent portion is substantially the same as or close to the refractive index on the emission side of the EL element.

As described above, the back surface of the brightness distribution control member is in close contact with the emission surface of the EL element, and the refractive index of the transparent portion is substantially equal to or close to the refractive index of the emission side of the EL element. If so, the light emitted from the EL element efficiently enters the brightness distribution control member, so that the light emitted from the EL element can be emitted with high efficiency to obtain higher brightness emitted light.

The EL element may be an organic EL element. In this case, when a dark spot peculiar to the organic EL element is generated, the luminance distribution of light emitted from the EL element corresponds to the location where the dark spot is generated. However, the light emitted to the surface of the brightness distribution control member becomes light having a brightness distribution in which the brightness drop has been eliminated by scattering, so that a dark spot is generated in the EL element. Even so, it is possible to emit light having a good luminance distribution without a partial decrease in luminance.

This is particularly effective in a liquid crystal display device using the surface light emitter as a backlight. According to this liquid crystal display device, even if a dark spot is generated in the EL element of the surface light emitter, the liquid crystal display device can be used. Since light having a luminance distribution in which a drop in luminance has been eliminated enters the display element, a high-quality image can be displayed without a decrease in luminance of a pixel corresponding to the location where the dark spot occurs.

[0034]

FIG. 1 is a sectional view of a surface light emitter according to a first embodiment of the present invention, in which hatching is omitted. In this surface light emitter, of the incident light from the back surface opposite to the emission surface, the light incident in a predetermined direction on the emission surface of the EL element 10 goes straight and emits to the front surface, and in the other direction. A luminance distribution control member 20 having a characteristic that light incident toward the surface is scattered and emitted to the surface is provided.

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 element in which an electroluminescent layer 14 made of an organic material is interposed between a transparent emission electrode 12 formed on one surface of the first electrode and a rear 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 output side electrode 12 is made of ITO or indium zinc oxide, and the back side electrode 13 is made of a Mg-In alloy or M
It is formed of a Mg-based alloy such as a g-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. .

Therefore, 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.

Although 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 composed 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 of the layer 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. Is about 2.00 for ITO, 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 from the singlet exciton enters the emission electrode 12 from the electroluminescent layer 14 and further passes through the transparent substrate 11 and exits to the surface. 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 provided with 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 the light emitted from the EL element 10 approaches white.

Next, the brightness distribution control member 20 will be described. FIG. 2 is a perspective view of the brightness distribution control member 20. The brightness distribution control member 20 includes a plurality of transparent portions 21 arranged along the surface direction, and a scattering reflection film 22 sandwiched between the side surfaces of the transparent portions 21 and having both surfaces.
And the scattering reflection film 2
2 is on a plane along a predetermined direction. Hereinafter, the brightness distribution control member 20 is referred to as a brightness distribution control film.

The scattering / reflecting film 22 may be a reflective microcrystalline film of an inorganic metal such as aluminum or silver, an organic metal containing a polyacetylene derivative, a titanium oxide, or the like.
A diffusible film made of a sintered body of a metal oxide such as zinc oxide, aluminum oxide, and magnesium oxide is used.

In the brightness distribution control film 20, the scattering reflection film 22 is on a surface along a direction perpendicular to the film surface.
A linear scattered reflection film 22 along any one of the width directions in the vertical and horizontal directions has a louver shape in which they are arranged in parallel with each other at intervals corresponding to the width of the transparent portion 21.

The louver-like brightness distribution control film 20 is formed by alternately laminating a transparent resin layer having a thickness corresponding to the width of the transparent portion 21 and the scattering / reflection film 22. Can be manufactured by a method of slicing into a film along a cut surface perpendicular to the thickness direction (laminating direction).

The transparent portion 21 of the brightness distribution control film 20 has a refractive index substantially equal to or close to the refractive index on the emission side of the EL element 10 (the refractive index of the transparent substrate 11 in this embodiment). It is made of a certain transparent resin.

The refractive index of the emission side of the EL element 10, that is, the refractive index of the transparent substrate 11 made of glass is 1.45 to 1.45.
The transparent resin having a refractive index of about 1.80, which is almost the same as or close to that, is PET (polyethylene terephthalate), PES (polyether sulfone),
PC (polycarbonate) and the like, and the refractive index of these resins is 1.40 to 1.60.

The brightness distribution control film 20
Indicates that the back surface of the film is EL
It is provided in close contact with the emission surface of the element 10 (the surface of the transparent substrate 11). In this embodiment, the brightness distribution control film 20 is provided with the refractive index of the transparent portion 21 and the EL element 1.
0 is substantially the same as one of the refractive indices of the transparent substrate 11,
Alternatively, it is adhered to the EL element 10 by a transparent adhesive (not shown) having a refractive index between both the refractive indices.

The above-mentioned surface light emitter emits light emitted from the electroluminescent layer 14 of the EL element 10 and emitted to the surface of the EL element 10 through the brightness distribution control film 20.

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 the light from one point of the electroluminescent layer 14. FIG. Light is emitted in various directions as indicated by arrows, and light traveling in a direction perpendicular to the emission surface of the EL element 10 (a direction perpendicular to the emission surface) is emitted from the electroluminescent layer 14 and the emission side. The light passes through the interface A ′ between the electrode 12 and the interface B ′ between the emission-side electrode 12 and the transparent substrate 11 without refraction or reflection, and is emitted perpendicular to the EL element surface.

On the other hand, the radiation emitted in the oblique direction is obliquely incident on each of the interfaces A 'and B'.
4 and the refractive index of the emission side electrode 12 and the transparent substrate 11 are as described above, and the refractive indices of the adjacent layers are different from each other. Is refracted or reflected.

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 light is smaller than the total reflection critical angle with respect to the interface A'. Light incident at an incident angle is refracted at the interface A 'and enters the emission-side electrode 12, and 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 by 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 incident on the interface A ′ at an incident angle smaller than the critical angle for total reflection is applied to the interface A ′.
And enters the emission side electrode 2.

The light incident on the emission-side electrode 12 passes through the emission-side electrode 12 and is incident on the interface B ′ with the transparent substrate 11. Light incident at an incident angle smaller than the critical reflection angle is refracted at the interface B 'and enters 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 at the lateral end face of the interface B ′ and the emission side electrode 12. Is repeated in a zigzag manner in the emission-side electrode 12, and of the light, the light incident on the interface B ′ at an incident angle smaller than the critical angle for total reflection passes through the interface B ′ and becomes transparent. The light enters the substrate 11.

The other light totally reflected at the interface B 'passes through the interface A' with the electroluminescent layer 14 and returns to the electroluminescent layer 14, but the light is totally reflected at the interface A '. Like the reflected light, the light is refracted in the electroluminescent layer 14 in a zigzag manner, and in the process, light incident on the interface A ′ at an incident angle smaller than the critical angle for total reflection passes through the interface A ′ and is emitted. Incident on the side electrode 2, of which the interface B ′ with the emission side electrode 2
At an incident angle smaller than the critical angle for total reflection passes through the interface B ′ and enters the transparent substrate 11.

Then, the light-emitting side electrode 12 to the transparent substrate 11
The light incident on the transparent substrate 11 passes through the transparent substrate 11 and exits to the surface thereof.
From the back side.

In this case, in this embodiment, the refractive index of the transparent portion 21 of the luminance distribution control film 20 is set to
The refractive index of the transparent portion 21 and the refractive index of the transparent portion 21 are set to be substantially the same as or close to the refractive index of the light-emitting side (the refractive index of the transparent substrate 11).
Since the transparent substrate 11 is bonded to the EL element 10 with a transparent adhesive (not shown) having a refractive index substantially equal to one of the refractive indices of the transparent substrate 11 or a refractive index between the two.
The light incident on the interface C ′ between the surface of the element 10 and the brightness distribution control film 20 passes through the interface C ′ without being totally reflected, regardless of the angle of incidence. Transparent part 21 of brightness distribution control film 20
Incident on.

Next, a description will be given of an emission path of light incident on the transparent portion 21 of the brightness distribution control film 20. Of the light incident on the transparent portion 21 from the back surface thereof, That is, light (light emitted perpendicularly from the EL element 10) incident in a direction perpendicular to the film surface of the luminance distribution control film 20 goes straight through the transparent portion 21 and is perpendicular to the surface of the luminance distribution control film 20. Emit.

On the other hand, light incident on the transparent portion 21 in the other direction, that is, light obliquely incident on the film surface of the brightness distribution control film 20, is transmitted obliquely through the transparent portion 21 and has a side surface. And is scattered on the scattering reflection surface.

Some of the light obliquely transmitted through the transparent portion 21 reaches the surface of the transparent portion 21 as it is without being incident on the scattering reflection film 22, and the light is not scattered but has a brightness distribution. The light is emitted to the surface of the control film 20. The emitted light is refracted at an interface D ′ between the surface of the transparent portion 21 and the outside air according to an incident angle with respect to the interface D ′ and a refractive index difference between the transparent portion 21 and the outside air (air),
Light is emitted in that direction.

The light scattered by the scattering reflection film 22 travels in the transparent portion 21 in various directions, and the light directed to the surface of the transparent portion 21 enters the interface D 'with the outside air.

Although the light traveling in the other direction does not directly enter the interface D ', most of the light enters the scattering reflection film 22 on the opposite side and is scattered again. Since light traveling toward the surface of the transparent portion 21 is incident on the interface D ', most of the light incident on the transparent portion 21 is incident on the interface D'.

Of the light incident on the interface D 'between the surface of the transparent portion 21 and the outside air, the light incident on the interface D' at an incident angle smaller than the critical angle for total reflection is the interface D '. And is emitted to the surface of the brightness distribution control film 20. The outgoing light is incident on the interface D ′ at an angle of incidence with respect to the interface D ′, and between the transparent portion 21 and the outside air
The light is refracted according to the difference in refractive index between the two and exits in that direction.

The light incident on the interface D 'at an incident angle larger than the critical angle for total reflection is totally reflected at the interface D', but the light is incident on the scattering reflection film 22 in the reflection direction and again. Since the light is scattered, these lights finally enter the interface D 'at an incident angle smaller than the critical angle for total reflection, pass through the interface D', and exit to the surface of the brightness distribution control film 20.

As described above, according to the above-mentioned surface light emitter, EL
Of the light emitted from the element 10 and incident on the brightness distribution control film 20 from the back surface, the light incident in the vertical direction goes straight and exits to the front surface, and the light incident in the other direction is scattered. In order to emit the light to the surface, it is possible to improve the luminance distribution of the emitted light by increasing the luminance of the emitted light in the vertical direction and widening the emission angle range in which the emitted light with sufficient luminance can be obtained. it can.

The light scattered by the brightness distribution control film 20 includes the brightness distribution control film 20.
Some light is incident perpendicular to the interface D 'between the surface of
Since the light is emitted vertically without being refracted at the interface D ′, the brightness of the emitted light in the vertical direction is higher than the brightness of the straight light that is transmitted vertically through the brightness distribution control film 20 and emitted to the surface. Will be even higher.

Further, according to the above-described surface light emitter, each transparent portion 2 of the luminance distribution control film 20 is emitted from the EL element 10.
Out of the light incident on 1, the light traveling at an incident angle larger than the total reflection critical angle toward the interface D ′ between the surface of the transparent portion 21 and the outside air, which is the final exit surface, is scattered and changes direction, Since the light 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 emission efficiency of the light incident on the brightness distribution control film 20 from the EL element 10 is increased. can do.

Further, in the conventional EL device, as shown in FIG. 7, the light totally reflected at each of the interfaces A, B, and C refracts the electroluminescent layer 4, the emission-side electrode 2, and the transparent substrate 1. In the process, a part of the light is emitted from the emission-side electrode 2, the electroluminescent layer 4, and the end face of the transparent substrate 1 and becomes a leaked light. Although it is large and thus the emission light amount is considerably smaller than the light emission energy in the electroluminescent layer 4, according to the surface light emitter, light loss in the process of emitting the EL element 10 is also small.

That is, in the above-mentioned surface light emitter, FIG.
As shown in FIG. 5, in the process in which 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 transmitted to the emission electrode 2 and the electroluminescent layer. 4 and the light emitted from the end face of the transparent substrate 1 to become leaked light. As described above, the light incident on the transparent substrate 11 has an incident angle with respect to the interface C ′ between the transparent substrate 11 and the brightness distribution control film 20. Even at such an angle, most of the light passes through the interface C 'without being totally reflected and enters the transparent portion 21 of the luminance distribution control film 20, so that the light is transmitted from the end face of the transparent substrate like a conventional EL element. Almost no light leakage.

Therefore, according to the above-mentioned surface emitting device, E
The L element 10 is emitted, and the luminance distribution control film 20
The amount of light that passes through and emits light is drastically increased (at least twice or more) as compared with the amount of light emitted from a conventional EL element, so that high-luminance emitted light can be obtained.

FIG. 3 is a diagram showing the luminance distribution of the light emitted from the surface light emitter in comparison with the luminance distribution of the conventional EL element and the luminance distribution when a diffusion plate is arranged on the exit surface of the EL element. , The solid line is the luminance distribution of the surface light emitter of the above embodiment, the broken line is the luminance distribution of the conventional EL element, and the dashed line is the conventional EL element.
4 shows a luminance distribution when a diffusion plate is arranged on an emission surface of the element.

The brightness distribution of the surface light emitter shown in FIG. 3 is perpendicular to the emission surface of the surface light emitter (the surface of the brightness distribution control film 20), and the transparent portion 21 and the scattering reflection of the brightness distribution control film 20. It is a luminance distribution on a surface along a direction orthogonal to the length direction of the film 22. In the drawing, + θ is one direction with respect to a direction perpendicular to the emission surface (direction of emission angle θ = 0 °). Is the emission angle of the light emitted in a direction opposite to the perpendicular direction.

As shown in FIG. 3, according to the luminance distribution of the conventional EL element, the luminance of light emitted in the front direction (the direction perpendicular to the exit surface) is high, but the luminance is increased as the exit angle increases. Is sharply reduced, and the directivity distribution is strong. 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 emission surface of the conventional EL element is almost uniform,
Since light emitted from the EL element in a high-luminance emission angle range is also diffused, 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 emitter of the above embodiment is such that the luminance of emitted light in the front direction is higher and the emission angle range over which emitted light of sufficient luminance can be obtained is wider. Moreover, in addition to the straight light that is transmitted vertically through the brightness distribution control film 20 and exits to the surface, of the light scattered by the brightness distribution control film 20, the light that is vertically incident on the interface D ′ with the outside air is also vertical. Therefore, the brightness of the light emitted in the front direction is higher than that of the conventional EL element.

Further, the surface luminous body of the above embodiment has the EL
An electroluminescent layer 14 made of a conductive polymer is used as the element 10.
Since the organic EL element has a high light transmittance of the electroluminescent layer 14, the emitted light can be emitted efficiently.

Further, in the organic EL element, since the electroluminescent layer 14 is made of an organic material, a defective light emission called a dark spot is formed at the interface between the electroluminescent layer 14 and the emission-side electrode 12 made of a metal material. 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, but the brightness distribution control film The light emitted to the surface of the light emitting device 20 is light having a luminance distribution in which the drop in the luminance has been eliminated by scattering.
Even if a dark spot peculiar to the L element occurs, the light becomes a light having a luminance distribution in which the drop in luminance is eliminated.
Even if a dark spot occurs at 0, light with a good luminance distribution without a partial drop in luminance can be emitted.

FIG. 4 is a sectional view of a surface light emitter according to a second embodiment of the present invention, in which hatching is omitted. In the surface light emitter of this embodiment, the transparent substrate of the EL element 10 is also used as the luminance distribution control film 20, and the basic structure of the EL element 10 and the structure of the luminance distribution control film 20 are the same as those of the first embodiment. This is the same as the embodiment.

However, in this embodiment, the transparent portion 21 of the brightness distribution control film 20 is provided with a refractive index of the EL element 1
It is formed of a transparent resin having a refractive index substantially equal to or close to the refractive index of the emission side of 0 (when the electroluminescent layer 14 has a three-layer structure, the refractive index of the hole transport layer which is the layer on the emission side). ing.

According to the surface light emitter of this embodiment, the light emitted from the EL element 10, that is, the light incident on the interface between the EL element 10 and the luminance distribution control film 20, is incident at any angle. Even if there is light, the light emitted from the electroluminescent layer 14 of the EL element 10 exits the EL element 10 because the light is transmitted through the interface and enters the transparent portion 21 of the brightness distribution control film 20 without being totally reflected. Is generated only at the interface between the electroluminescent layer 14 and the emission-side electrode 12, as shown by the arrow in FIG. Since only leakage from the end face of the light emitting layer 14 occurs, the amount of emitted light can be further increased as compared with the first embodiment.

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

When such a luminance distribution control film is used, of the light emitted from the EL element and incident on the luminance distribution control film from the back surface, the light incident in the direction along the scattering reflection film 22 goes straight. As a result, the light emitted in the other direction is scattered and emitted to the surface, so that the brightness of the emitted light in the oblique direction is increased, and the emitted light with sufficient brightness is obtained. The angular distribution can be widened to improve the luminance distribution of the emitted light.

In the above-described embodiment, the electroluminescent layer 14 is a layer in which a fluorescent substance emitting red fluorescence and a fluorescent substance emitting green fluorescence are contained in a dispersed state in a light emitting layer emitting blue light. However, the present invention is not limited to this.For example, a dot-shaped light emitting layer that emits red light, a dot light emitting layer that emits green light, and a dot light emitting layer that emits blue light are alternately formed. Alternatively, the color of the light emitted from the EL element 10 may be white.

Further, in the above embodiment, as a brightness distribution control member provided on the emission surface of the EL element 10, a louver shape in which linear scattering reflection films 22 are arranged in parallel at intervals corresponding to the width of the transparent portion 21. Brightness distribution control film 20
However, the brightness distribution control member, even in the case where a scattering reflection film is provided in a transparent film in a lattice shape, a scattering reflection film having a short length in the transparent film is suitable for the vertical width direction and the horizontal width direction. It may be provided at a pitch.

FIG. 5 is a perspective view showing a modified example of the luminance distribution control member. This luminance distribution control member is composed of two louver-like luminance distribution control films 20 used in the above embodiment, and each of the scattering reflection films. 22 are overlapped with each other so that their length directions are orthogonal to each other.

By using such a luminance distribution control member,
Since the scattering reflection film 22 is provided in a lattice shape, the incident light is scattered in two directions orthogonal to each other. Therefore, the luminance distribution of the outgoing light in the two directions should be as shown in FIG. it can.

The brightness distribution control member is not limited to the one in which a scattering reflection film is provided in a transparent film, but the light incident from a rear surface in a predetermined direction goes straight to the front surface. The light may be of any type as long as it has the characteristic of emitting light to the surface and scattering light incident in another direction and emitting the light to the surface.

Next, a liquid crystal display device using the above-mentioned surface light emitter will be described. FIG. 6 is a side view showing an embodiment of the liquid crystal display device. In the liquid crystal display device, the above-described surface light emitter is disposed behind a liquid crystal display element 30 as a backlight 36 thereof.

The liquid crystal display element 30 is a simple matrix or active matrix type ECB (birefringence effect) type liquid crystal display element, and a pair of transparent electrode forming substrates 31 and 32 joined via a frame-shaped sealing material 33. Between,
The liquid crystal molecules are in a predetermined alignment state (for example, a twist alignment state)
And a liquid crystal layer oriented on the substrates 31 and 3.
2, polarizing plates 34 and 35 are arranged on the outer surface, 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 and 35. The linearly polarized light is converted into elliptically polarized light having different polarization states due to the birefringence of the liquid crystal in the process of transmitting through the liquid crystal layer, and the light is incident on the other polarizing plate, and the other polarized light is emitted. The light transmitted through the plate becomes colored light having a color corresponding to the ratio of the light intensity of each wavelength light 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 backlight 36 uses the surface light emitter of the first embodiment shown in FIG. The description of the configuration of the surface light emitter will be omitted by attaching the same reference numerals to the drawings.

This liquid crystal display device has its liquid crystal display element 3
As the backlight 36 of 0, a surface luminous body having high emission light in a predetermined direction and a wide emission angle range capable of obtaining emission light of sufficient luminance as described above is used. The decrease in the brightness of the screen when obliquely viewed is reduced, and the angle range in which the display can be observed with sufficient brightness can be widened.

Moreover, in the above-mentioned surface light emitter, the amount of light emitted from the EL element 10 and further transmitted through the luminance distribution control film 20 is significantly larger than the amount of light emitted from the conventional EL element. Therefore, high-luminance light is applied to the liquid crystal display element 3.
0, and a high-luminance image can be displayed.

The liquid crystal display device uses the above-mentioned surface light emitter for the backlight 36, and can reflect light on the back electrode 13 of the EL element 10 which is the light source of the surface light emitter. Therefore, without driving the EL element 10 to emit light, external light (natural light or room illumination light) incident from the emission surface side of the liquid crystal display element 30 is reflected by the back electrode 13 of the EL element 10 as shown by a broken line in FIG. It is also possible to display as a so-called two-way display device capable of performing both a transmission type display using light from the backlight 36 and a reflection type display using external light. can do.

In this case, the surface luminous body of the above embodiment is EL
Since the organic EL element having a high light transmittance of the electroluminescent layer 14 is used for the element 10, not only can the emitted light be efficiently emitted, but also the reflection type display can be performed. The reflected external light is efficiently reflected by the back electrode 13 to obtain a bright display.

Further, the brightness distribution control film 20 of the surface luminous body is provided such that each of the scattering / reflection films 22 is provided in the form of a lattice so as to correspond to each of the rows and columns of each pixel of the liquid crystal display element 30. If a black mask corresponding to the lattice-shaped scattering reflection film 22 is provided in the liquid crystal display element 30,
The display flicker due to the light reflection of the scattering reflection film 22 itself can be prevented, and the light emitted from the EL element 10 can efficiently enter each pixel of the liquid crystal display element 30.

The EL element 10 may generate a dark spot peculiar to the organic EL element in some cases. Even in such a case, the light emitted from the surface light emitter (the light emitted to the surface of the brightness distribution control member) is not changed. Since light having a luminance distribution in which the drop in luminance has been eliminated due to 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. be able to.

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

Further, the ECB type liquid crystal display element 30 is
Since colored light is obtained by utilizing the birefringence of the liquid crystal layer and the polarization of the polarizing plates 34 and 35, for example, the color of each pixel is changed to red, green, and blue to display a full-color image. However, not all display colors can be obtained with high color purity, but a fluorescent substance that emits fluorescence of a color corresponding to a color in which high color purity is difficult to obtain with the ECB type liquid crystal display element 30 is used as the electric field of the EL element 10. If added to the light emitting layer 14, a color image with good color balance can be displayed.

The liquid crystal display element 30 used in the liquid crystal display device of the above embodiment is of the ECB type. However, in the case of a display device exclusively used for a transmission type using light from a surface illuminant which is a backlight 36. The liquid crystal display element 30 may display a color image using a color filter.

[0108]

According to the surface emitting body of the present invention, of the incident light from the back surface opposite to the exit surface of the EL element,
A brightness distribution control member having a characteristic that light incident in a predetermined direction travels straight and emits to the surface, and light incident in another direction is scattered and emitted to the surface is provided. From, to increase the brightness of the light emitted in a predetermined direction,
In addition, the emission angle range in which emission light with sufficient luminance can be obtained is widened, and the luminance distribution of the emission light can be improved.

In the surface light emitter of the present invention, the brightness distribution control member comprises a plurality of transparent portions arranged along the surface direction and a scattering reflection film sandwiched between the side surfaces of these transparent portions. It is preferable that the scattering reflection film is on a surface along the predetermined direction, and if the luminance distribution control member has such a configuration, a predetermined portion of light incident on the transparent portion from the back surface thereof is used. The light incident in one direction is made to go straight, and the light incident in another direction can be scattered by the scattering reflection film.

It is preferable that the brightness distribution control member is provided with its back surface in close contact with the emission surface of the EL element.
Further, it is preferable that the refractive index of the transparent portion is substantially the same as or close to the refractive index on the emission side of the EL element.
With this configuration, since the light emitted from the EL element efficiently enters the luminance distribution control member, the light emitted from the EL element can be emitted with high efficiency to obtain higher luminance emitted light.

The EL element may be an organic EL element. In this case, when a dark spot peculiar to the organic EL element is generated, the luminance distribution of light emitted from the EL element corresponds to the location where the dark spot is generated. As a result, a partial drop in brightness occurs, but the light emitted to the surface of the brightness distribution control member becomes light having a brightness distribution in which the drop in brightness has been eliminated by scattering.

Further, in the liquid crystal display device of the present invention, the surface illuminant is disposed as a backlight behind the liquid crystal display element, and the surface illuminant has a luminance of light emitted in a predetermined direction. The liquid crystal display device according to the present invention has a high emission angle and a wide emission angle range in which emission light of sufficient luminance can be obtained. Can be widened in an angle range that can be observed with sufficient brightness.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a surface light emitter according to a first embodiment of the present invention, in which hatching is omitted.

FIG. 2 is a perspective view of a brightness distribution control member used for the surface light emitter.

FIG. 3 is a graph showing the luminance distribution of light emitted from the surface light emitter according to the conventional E;
The figure which shows in comparison with the brightness | luminance distribution of the L element, and the brightness | luminance distribution at the time of arrange | positioning a diffusing plate in the emission surface of the EL element.

FIG. 4 is a sectional view of a surface light emitter according to a second embodiment of the present invention, in which hatching is omitted.

FIG. 5 is a perspective view showing a modification of the luminance distribution control member.

FIG. 6 is a side view showing one embodiment of the liquid crystal display device of the present invention.

FIG. 7 is a cross-sectional view of a conventional EL element with hatching omitted.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... EL element 11 ... Transparent substrate 12 ... Emitting side electrode 13 ... Back side electrode 14 ... Electroluminescent layer 20 ... Brightness distribution control member 21 ... Transparent part 22 ... Scattering reflective film 30 ... Liquid crystal display element 36 ... Backlight (surface emitting body) )

Claims (6)

[Claims] 1. A light incident on a light emitting surface of an electroluminescent element from a back surface facing the light emitting surface in a predetermined direction, goes straight to a front surface, and is emitted to the other surface. A surface light-emitting body provided with a brightness distribution control member having a characteristic that light incident on the surface is scattered and emitted to the surface. 2. The brightness distribution control member comprises a plurality of transparent portions arranged in a plane direction and a scattering reflection film sandwiched between side surfaces of the transparent portions. The surface light emitter according to claim 1, wherein the surface light emitter is on a surface along the predetermined direction. 3. The surface illuminator according to claim 2, wherein a back surface of said brightness distribution control member is in close contact with an emission surface of said electroluminescence element. 4. The surface emitting device according to claim 3, wherein the refractive index of the transparent portion of the brightness distribution controlling member is substantially the same as or close to the refractive index of the emission side of the electroluminescence element. body. 5. The surface light emitting device according to claim 1, wherein said electroluminescent element is an organic electroluminescent element. 6. A liquid crystal display device comprising a liquid crystal display element and the surface light emitter according to claim 1 disposed behind the liquid crystal display element.