JP2002008850A - Self-luminous device and electric appliance using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a self-luminous device and an electric appliance provided with it capable of enhancing a light taking-out efficiency of a light-emitting device, particularly an EL element. SOLUTION: A light taking-out efficiency can be enhanced by providing a light scattering body 108 formed by etching a transparent film on a substrate 101. A fine processing of pitch becomes possible by forming the light scattering body 108 by etching the transparent film. The self-luminous device high in luminous efficiency can thus be provided by forming the light scattering body 108.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to an element structure that improves the efficiency of extracting light emitted inside a device when planar light emission is extracted by flowing a current through the device. Note that the self-luminous device of the present invention uses an organic electroluminescent display (OELD: Organic EL Displ.) Using an organic light-emitting element (light-emitting element) as a self-luminous element.
ay) or an organic light emitting diode (OLED)
t Emitting Diode).

[0002]

2. Description of the Related Art Light emitted from a self-luminous device is extracted as planar light emission into the atmosphere. However, a substrate located at the interface between the self-luminous device and the atmosphere cannot be extracted from the substrate because its shape is a flat plate. There is not much light and its extraction efficiency is 2
0 to 50%.

[0003]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a light-emitting element, particularly an EL element, is formed by forming an uneven light scatterer on a surface opposite to a substrate. It is an object of the present invention to improve the light extraction efficiency generated in the above. Further, a transparent film on the substrate is formed by etching as a light scatterer to enable fine processing of the pitch. It is another object of the present invention to provide a self-luminous device with higher luminous efficiency by forming a light scatterer having a fine pitch.

[0004]

According to the present invention, a shape used for improving light extraction efficiency is shown in FIG.
This will be described with reference to FIG.

FIG. 1A shows an example in which the present invention is applied to an active matrix type self-luminous device. 1
Reference numeral 01 denotes a substrate made of an insulator.
A current control TFT 102 is formed. The drain region of the current controlling TFT 102 is electrically connected to the pixel electrode 103. (It is also possible to connect to the source region.) Here, the pixel electrode 103 is an anode, and the pixel electrode 103 is a transparent conductive film to emit light from the pixel electrode 103 side of the EL element 106. It is formed with.

Further, an EL layer 1 is formed on the pixel electrode 103.
04 is formed, and a cathode 105 is formed on the EL layer 104. Thus, an EL element 106 including the pixel electrode 103, the EL layer 104, and the cathode 105 is formed.

In the self-luminous device having the above-described shape, irregularities are formed on the back surface of the substrate 101, that is, on the surface on which the TFT is not formed. The light scatterer 108
Is indicated by 107, and an enlarged view of 107 is shown.

By forming the light scatterer 108, the angle of incidence from the light scatterer 108 into the atmosphere 109 can be prevented from exceeding the critical angle, so that the light is totally reflected and confined in the light scatterer. E
Light extraction efficiency from the L element 106 can be improved. Note that the light scatterer is formed by etching a transparent film made of a transparent material. Note that a transparent film in this specification refers to a film that is transparent to visible light.

The enlarged view of 107 shown in FIG. 1B shows how light passing through the substrate 101 passes through the light scatterer 108 and is emitted to the atmosphere. FIG. 1 (B)
Light scatterers 108a, 108b, 108c, 1
08d and 108e are each formed in a dot shape, and are referred to as light scatterers 108 in this specification. Note that FIG. 1C is a perspective view of a surface on which the light scatterer 108 is formed.

In the present invention, the light emitted from the EL element 106 enters the substrate 101, and then enters the light scatterer 108.
Incident on.

The refraction of light is determined by the angle of incident light (incident angle) and the refractive index of the medium, as shown in FIG.
Further, this relationship obeys the following equation (Snell's law). That is, in medium 1 (201) having a refractive index of n ₁ , θ ₁
When the light (incident light) incident at an angle of 2 enters the medium 2 (202) having a refractive index of n ₂ ,

[0012]

(Equation 1)

Light (refracted light) having an angle θ ₂ that satisfies the above condition is obtained. Incidentally, the refractive light angle theta ₂ is the incident angle theta ₁ such that 90 ° of the critical angle. When the incident angle θ ₁ with respect to the medium 2 becomes larger than the critical angle, the light is totally reflected. That is, light is confined in the medium 1 .

Further, the following formula (Fresnel's law) holds for the energy reflectance (R) and transmittance (T).

[0015]

(Equation 2)

[0016]

[Formula 3] T = 1−R

That is, if the refractive index of the substrate 101 is different from the refractive index of the light scatterer 108, a reflection component is generated.

When light is emitted from the light scatterer 108 having a refractive index of 1.45 to 1.60 into the atmosphere 109 having a refractive index of 1 as shown in FIG. When light is emitted from a medium having a large refractive index to a medium having a small refractive index, the reflectance increases. Further, when the incident angle is larger than the critical angle, the light is totally reflected. That is, the shape of the light scatterer 108 may be such that the incident angle becomes small.

From the above, according to the present invention, the shape of the light scatterer is made uneven so that the angle of incidence into the atmosphere is reduced, and more light is scattered so as to be easily extracted into the atmosphere. did.

In the present invention, since irregular irregularities formed by etching become the light scatterers 108, there is the advantage that the shape does not need to be precisely unified and the fabrication is easy.

The present invention can be used for many self-luminous devices, but is particularly affected by the efficiency of light utilization.
An EL element using an L material is very effective because the power consumption and the life of the EL element can be reduced.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail in the following embodiments.

[Embodiment 1] In this embodiment, an example in which the present invention is applied to an active matrix type self-luminous device that transmits light to the pixel electrode side will be described. First, as shown in FIG.
01, a transparent film is formed on the back surface. As a transparent material for forming a transparent film, a film made of an organic resin such as polycarbonate, acrylic resin, polyimide, polyamide, or BCB (benzocyclobutene), a film made of indium oxide, tin oxide, or zinc oxide, or a compound film obtained by combining these is used. .

Next, the transparent film is etched to form a light scatterer 302 as shown in FIG. FIG. 4 shows the light scatterer 302 formed at this time.
This will be described with reference to FIG. Note that FIG. 4A shows the light scatterer 302 formed in a trapezoidal shape. Further, since the same symbols as those used in FIG. 3 are used here, it is preferable to correspond each time.

FIG. 4A is a view showing a state in which the light scatterer 302 formed on the back surface of the substrate in FIG.
(A) shows the structure which turned upside down. Then, it is assumed that the light emitted from the EL element on the TFT side as viewed from the substrate 301 is emitted to the light scatterer 302 at an incident angle θ1 as shown in FIG. Here, when the refractive index of the substrate 301 is n1 and the refractive index of the light scatterer 302 is n2,
When the relationship of n1> n2 is satisfied, the light is transmitted to the light scatterer 30.
2 at an angle of θ2.

On the other hand, if the relationship of n1 <n2 holds,
The light exits the light scatterer 302 at an angle of θ2 ′. That is, the relationship of θ2> θ2 ′ holds, and the emission angle of light emitted from a portion having a small refractive index to a portion having a large refractive index becomes small.

However, when the light is extracted from the light scatterer 302 into the atmosphere, the light is emitted from a medium having a large refractive index to a medium having a small refractive index, so that the emission angle is increased and the reflectance is also increased. It becomes difficult to emit light. Thus, as shown in FIG. 4A, the angles θ3 and θ4 formed by the light scatterer 302a and the substrate which is an insulator are limited. In the present invention, the shape is such that the light extraction efficiency of light emitted in the normal direction of the substrate with the highest extraction efficiency does not decrease, and θ
3 and θ4 are formed so as to be 60 degrees or more.
However, θ3 and θ4 do not necessarily have to be formed at the same angle.

Further, in order to prevent the image from being blurred, the pitch of the light scatterers 302a is set so that the length W1 of the contact portion with the substrate is not more than 1/2 of the pixel pitch. Further, it is better to shorten the length W2 of the trapezoidal upper bottom portion so that light can be more easily extracted. It is most preferable that W2 = 0.

Further, in order to form the light scatterer 302 so that the angles of θ3 and θ4 are 60 degrees or more, the thickness H of the transparent film is H ≧ H with respect to the pitch (W1) of the light scatterer a302. It is preferable that the relationship be W1.

Further, in the present invention, it is not necessary to form an accurate shape using a mold or the like or to smooth the surface, and fine irregularities are formed on the light emitting side on the back surface of the substrate. Just do it.

As described above, the light scatterer 302 is formed on the back surface of the substrate 301. Also, FIGS. 4B to 4G
Shows a pattern that can be formed as the light scatterer 302. FIG. 4B is an example in which a rectangular light scatterer is provided on the back surface of the substrate with a space therebetween. FIG. 4C shows an example in which the light scatterers completely cover the substrate and are provided without leaving a space between the light scatterers. FIG. 4D shows an example in which an inversely tapered light scatterer is formed on the back surface of the substrate.
In FIG. 4E, a hemispherical light scatterer is formed on the back surface of the substrate. Further, FIG. 4F shows an elliptical light scatterer, and FIG. 4G shows an example in which a triangular light scatterer is formed when viewed from the cross section.

The light scatterers shown in FIG. 4 may be provided with an interval between the light scatterers or may be provided such that the light scatterers overlap each other.

After the light scatterer 302 is formed on the back surface of the substrate 301, p-channel TFTs 303 and 304 are formed by a known method on the substrate 301 having an insulating film formed on the surface. In this embodiment, a planar type TFT is taken as an example, but the TFT structure is not limited. That is, an inverted staggered TFT may be used.

Next, p-channel type TFTs 303 and 304
Pixel electrodes 305, 3 electrically connected to each of
06 is formed. EL is used as the pixel electrodes 305 and 306.
A material having a high work function is used to function as an anode of the element. Therefore, in this embodiment, as a light-transmitting material (or a transparent material) that is transparent to visible light, an oxide conductive film (a film made of indium oxide, tin oxide, or zinc oxide, or a compound film obtained by combining these). Is used.
Gallium may be added to this oxide conductive film (FIG. 3).
(B)).

Next, banks 307 and 308 are formed of a resin film so as to surround the ends of the pixel electrodes 305 and 306, and an EL layer 309 is formed thereon. In this embodiment, the bank 30
7 and 308 are formed of an acrylic film, and the EL layer 309 is formed by spin coating. As a material of the EL layer 309, polyfluorene, which is a high-molecular organic material, is used. Of course, chromaticity control may be performed by adding a fluorescent substance to polyfluorene (FIG. 3C).

Next, a cathode is formed using a light-shielding material. In this embodiment, an alloy film is formed to a thickness of 300 nm by co-evaporation of aluminum and lithium as the cathode 311, and a silicon nitride film is formed thereon as a passivation film 312 by a sputtering method. It is also effective to stack a carbon film, specifically, a DLC (diamond-like carbon) film on this.

As described above, the self-luminous device having the structure shown in FIG. 3D is completed. Thereafter, the EL element may be sealed with resin or the EL element may be sealed in a closed space so that the EL element does not come into contact with the outside air.

Embodiment 2 In this embodiment, an example in which the present invention is applied to an active matrix type self-luminous device that reflects light on the pixel electrode side will be described. First, as shown in FIG. 5, n-channel TFTs 502 and 503 are formed by a known method on a substrate 501 on which an insulating film is formed on the surface. In this embodiment, a planar type TFT is taken as an example, but the TFT structure is not limited. That is, an inverted staggered TFT may be used.

At this time, the n-channel TFTs 502, 5
03, the drain wiring is connected to the pixel electrodes 504, 5
Used as 05. In the case of this embodiment, the pixel electrode 504,
Since it is necessary to reflect light emission at 505, the pixel electrode 5
A highly reflective metal film is used for 04 and 505. Further, a metal film containing a material having a low work function is used because the metal film also functions as a cathode of the EL element. In this embodiment,
An alloy film containing aluminum and lithium is used (FIG. 5)
(A)).

Next, banks 506 and 507 are formed of a resin film so as to surround the ends of the pixel electrodes 504 and 505, and an EL layer 508 is formed thereon. In this embodiment, the bank 50
6 and 507 are formed of an acrylic film, and the EL layer 508 is formed by an evaporation method. As a material of the EL layer 508, Alq ₃ (tris-8-quinolinolato aluminum complex) which is a low molecular weight organic material is used. Of course, chromaticity control may be performed by adding a fluorescent substance to Alq ₃ (FIG. 5).
(B)).

Next, an anode 510 is formed to a thickness of 300 nm as an oxide conductive film obtained by adding gallium oxide to zinc oxide, and a silicon nitride film is formed thereon as a passivation film 511 by a sputtering method. This has a carbon film,
Specifically, it is also effective to laminate a DLC (diamond-like carbon) film (FIG. 5C).

Next, as shown in FIG. 5D, a sealing film made of an organic resin is formed. At this time, the sealing film is formed so that the EL element does not come into contact with the outside air.

Further, a sealing substrate 513 is formed on the sealing film 512.
Is provided. At this time, the sealing substrate 513 is provided so that the EL element does not come into contact with outside air by forming a sealing film and a series of processing.

Next, a transparent film is formed on the sealing substrate. As a transparent material for forming a transparent film, polycarbonate, acrylic resin, polyimide, polyamide, BC
A film made of an organic resin such as B (benzocyclobutene), indium oxide, tin oxide, or zinc oxide, or a compound film obtained by combining these is used. Further, in order to form the light scatterers 514 so that the angles θ3 and θ4 are 60 degrees or more, the thickness (H) of the transparent film is H ≧ W1 with respect to the pitch (W1) of the light scatterers. Preferably, they are in a relationship. By etching this transparent film, FIG.
A light scatterer 514 as shown in FIG.

Further, it is not always necessary to provide a sealing film formed of an organic resin film as shown in this embodiment.
The element may be sealed in a closed space. Note that light is difficult to extract when emitted from a medium having a high refractive index to a medium having a low refractive index. In this case, the light scattering member 514 is disposed on the interface between the passivation film 511 and the sealed space, that is, on the passivation film 511. Should be provided.

The self-luminous device thus obtained has a higher light extraction efficiency than the conventional self-luminous device because the light scatterer is provided on the surface from which light is finally emitted as compared with the normal sealing structure. Obtainable. Thus, the voltage for driving the EL element can be reduced, and the life of the EL element can be extended.

The structure of this embodiment can be implemented in combination with any structure of the first embodiment.

[Embodiment 3] In Embodiments 1 and 2,
While an example in which the present invention is applied to a planar TFT is shown, in this embodiment, a structure in which the present invention is applied to an inverted staggered TFT is shown in FIG. 6A shows a structure of an active matrix self-luminous device that transmits light to the pixel electrode side, and FIG. 6B shows a structure of an active matrix self-luminous device that reflects light at the pixel electrode side. Is shown.

In FIG. 6, reference numeral 601 denotes a substrate, and 602 denotes a substrate.
This is a p-channel TFT used in FIG.
Numeral 03 denotes an n-channel TFT used in FIG. These have a structure in which a gate electrode is formed over a substrate 601, and a source region, a drain region, and a channel formation region are formed over the gate electrode with a gate insulating film interposed therebetween. 605 is a pixel electrode, and 605 is formed with a bank for partitioning between pixel electrodes. An EL layer 606 is formed over the pixel electrode 605, and a cathode 607 and a passivation film 608 are formed over the EL layer 606.

FIG. 6A shows a structure in which light is transmitted to the pixel electrode side.
9 are provided. Further, FIG. 6B shows a structure in which light is reflected on the pixel electrode side; therefore, the light scatterer is used for the sealing film 610 and the sealing substrate 611 on the passivation film 608.
Formed on a sealing structure made of

It should be noted that the inverted staggered TFT structure is easier to fabricate than the planar type TFT, so that the number of masks can be reduced. Further, since the gate insulating film and the channel formation region can be formed continuously, there is an advantage that the interface can be formed without contamination.

The configuration of this embodiment can be implemented by freely combining with any of the configurations of the first and second embodiments.

[Embodiment 4] In this embodiment, an example in which the present invention is applied to a passive matrix type self-luminous device that emits light through a substrate will be described.

First, a transparent film is formed on the back surface of the substrate 701. As a transparent material for forming a transparent film, a film made of an organic resin such as polycarbonate, acrylic resin, polyimide, polyamide, or BCB (benzocyclobutene), a film made of indium oxide, tin oxide, or zinc oxide, or a compound film obtained by combining these is used. . Also,
In order to form the light scatterers so that the angles of θ3 and θ4 are 60 degrees or more, the thickness (H) of the transparent film has a relationship of H ≧ W1 with the pitch (W1) of the light scatterers. Is preferred.

By etching this transparent film, a trapezoidal light scatterer 702 as shown in FIG. 7A is formed. At the time of etching, it is necessary to prevent the transparent film from being excessively etched and exposing the substrate 701 to the surface. This is because if the substrate is exposed on the surface, the light scatterer 702 does not sufficiently refract light.

Next, the substrate 701 shown in FIG. 7A is turned upside down and the surface of the substrate 701 is directed upward.
It is shown in (B). Then, after forming an insulating film on the surface of the substrate 701, the anode 703 is formed over the insulating film. In this embodiment, an oxide conductive film including a compound of indium oxide and tin oxide is used as the anode 703 (FIG. 7B).

The anode 703 is formed in a strip shape in a direction parallel to the paper surface, and is arranged in a stripe shape in a direction perpendicular to the paper surface. This structure is similar to that of a known passive matrix self-luminous device.

Next, the partition wall 7 is perpendicular to the anode 703.
04 is formed. The partition 704 is provided for separating a metal film serving as a cathode. In this embodiment, a two-layer resin film is used and processed so as to form a T-shape. Such a structure can be obtained by performing etching under the condition that the etching rate of the lower layer is higher than that of the upper layer.

Next, an EL layer 705 is formed. In this embodiment, the EL layer 705 is formed by an evaporation method. EL layer 70
As the material of No. 5, Alq ₃ (tris-8-quinolinolato aluminum complex) which is a low molecular weight organic material is used. Of course, chromaticity control may be performed by adding a fluorescent substance to Alq ₃ .

Next, as the cathode 707, an alloy film formed by co-evaporation of aluminum and lithium is formed to a thickness of 300 nm. At this time, the cathode 707 is separated along the partition 704, is formed in a strip shape toward the back of the paper, and is formed in a stripe shape. Further, a resin film is formed thereon as a passivation film 708 by an inkjet method or a printing method. To this, a carbon film, specifically DLC
It is also effective to laminate a (diamond-like carbon) film.

As described above, the self-luminous device having the structure shown in FIG. 7C is completed. Thereafter, the EL element may be sealed with resin so that the EL element does not come into contact with the outside air.

The self-luminous device thus obtained has a light-scattering body provided on the light-emitting surface as compared with a normal sealing structure, so that a higher light extraction efficiency can be obtained as compared with the conventional self-luminous device. Accordingly, the voltage for driving the EL element can be lower than usual, and thus the life of the EL element can be extended.

The structure of this embodiment can be implemented in combination with any of the structures of the first to third embodiments.

[Embodiment 5] In this embodiment, an example in which the present invention is applied to a passive matrix type self-luminous device which emits light upward from a substrate will be described. First, a cathode 802 is formed over a substrate 801 on which an insulating film is formed. In this embodiment, an electrode having a structure in which an MgAg film (a metal film in which magnesium and silver are co-evaporated) is stacked on an aluminum film is used as the cathode 802. (FIG. 8A)

The cathode 802 is formed in a strip shape in a direction parallel to the paper surface, and is arranged in a stripe shape in a direction perpendicular to the paper surface.

Next, the partition walls 8 are perpendicular to the cathode 802.
03 is formed. A partition 803 is provided for separating an oxide conductive film serving as an anode. In this embodiment, a two-layer resin film is used and processed so as to form a T-shape. Such a structure can be obtained by performing etching under the condition that the etching rate of the lower layer is higher than that of the upper layer.

Next, an EL layer 804 is formed. In this embodiment, the EL layer 804 is formed by an evaporation method. EL layer 80
As material No. 4, Alq ₃ (aluminum quinolylato complex) which is a low molecular weight organic material is used. Of course, chromaticity control may be performed by adding a fluorescent substance to Alq ₃ .

Next, an oxide conductive film made of a compound of indium oxide and zinc oxide was used as the anode 806 for 300 nm.
Formed to a thickness of At this time, the anode 806 is
Is separated along, is formed in a belt shape toward the back of the paper,
They are formed side by side in stripes. Further, a resin film is formed thereon as a passivation film 807 by an inkjet method or a printing method. It is also effective to stack a carbon film, specifically, a DLC (diamond-like carbon) film on this.

After the structure shown in FIG. 8B is formed as described above, the EL element is protected from contact with the outside air.
A sealing film 808 is formed by sealing the element with a resin. Further, a sealing substrate 809 is provided over the sealing film 808.

Next, a transparent film is formed on the sealing substrate 809. As a material for forming a transparent film, polycarbonate, acrylic resin, polyimide, polyamide, B
A film made of an organic resin such as CB (benzocyclobutene), indium oxide, tin oxide, or zinc oxide, or a compound film obtained by combining these is used. Further, in order to form the light scatterers so that the angles of θ3 and θ4 are 60 degrees or more, the thickness (H) of the transparent film is related to the pitch (W1) of the light scatterers by H ≧ W1. It is preferred that This transparent film is etched to obtain FIG.
A light scatterer 810 shown in FIG.

As described above, by forming the light scatterer 810 having a fine structure on the surface from which light is emitted, light generated from the EL element can be more efficiently extracted.

Further, it is not always necessary to provide a sealing film formed of an organic resin film as shown in this embodiment.
The element may be sealed in a closed space. Note that light is difficult to extract when emitted from a medium having a high refractive index to a medium having a low refractive index. In this case, a light scatterer is placed on the interface between the passivation film 807 and the sealed space, that is, on the passivation film 807. The sealing substrate 809 is provided over the sealed space.

In the self-luminous device thus obtained, a light scattering body is provided on the surface from which light is finally emitted as compared with the ordinary sealing structure, so that the light extraction efficiency is higher than that of the conventional self-luminous device. Can be enhanced. Accordingly, the voltage for driving the EL element can be lower than usual, and thus the life of the EL element can be extended.

The structure of this embodiment can be implemented in combination with any of the structures of the first to fourth embodiments.

Embodiment 6 Next, an example in which the present invention is applied to a front light will be described. FIG. 9 is a diagram showing a configuration of the front light. 9A and 9B are cross-sectional views of the front light, and FIG. 9C is a rear perspective view of the light guide plate 901.

As shown in FIG. 9A, a light source 902 is disposed on a side surface 901 a of a light guide plate 901, and a reflector 903 is provided behind the light source 902. Also,
A light scatterer 904 is provided in contact with the lower surface of the light guide plate 901.

The light guide plate 901 is a flat plate made of a transparent material in the shape of a rectangular parallelepiped, and has a rectangular shape in which the shorter side is extremely shorter than the longer side. The material of the light guide plate 901 has a visible light transmittance (total light transmittance) of 80%, preferably 85% or more, and the incident light of the light guide plate 901 increases as the refractive index becomes larger than ^21/2. 90 degrees light on the side 90
This is because the light can be refracted at 1a and guided inside the light guide plate 901. In this embodiment, the refractive index is 1.4 to
Use a material that is in the range of 1.7.

As such a transparent material, a material such as quartz, glass or plastic can be used. As the plastic, materials such as methacrylic resin, polycarbonate, polyarylate, AS resin (acrylotrile, styrene polymer) and MS resin (methyl methacrylate, styrene polymer) can be used alone or as a mixture.

The light source 902 includes a cold cathode tube or an LED.
Are arranged along the side surface 901 a of the light guide plate 901. Further, two light sources may be provided to face each other along the side surface 902b.

Next, the light scatterer 904 is formed by forming a transparent film on the light guide plate 901 and then etching it. As a transparent material for forming a transparent film, polycarbonate, acrylic resin, polyimide, polyamide, BCB
A film made of an organic resin such as (benzocyclobutene), indium oxide, tin oxide, or zinc oxide, or a compound film obtained by combining these is used. The thickness (H) of the film is H ≧ W1 with respect to the pitch (W1) of the light scatterers.
It is preferable that the relationship be as follows.

By providing the front light formed as described above between the liquid crystal panel (LCD) 905 and the user, a liquid crystal display with high light extraction efficiency can be obtained.

In this embodiment, the light is reflected on the side surface of the light scatterer, and then the liquid crystal panel is irradiated.
The angle of incidence on the liquid crystal panel can be reduced. As a result, the component of the light that vertically illuminates the pixel electrode of the liquid crystal panel increases, so that the light can be used efficiently.

FIG. 9C is a cross-sectional view of the trapezoid obtained when the light scatterer 904 is cut in the direction of xx ′. The acute angle of the trapezoidal light scatterer 904 is θ. ₅ ,
When θ ₆ is set, these angles are preferably larger. When θ ₅ and θ ₆ are increased, emitted light can be easily collected from the front light toward the liquid crystal panel. Note that θ ₅ and θ ₆ need not be the same angle, and may be different.

In this embodiment, the light guide plate 901 is used.
After a new transparent film was formed thereon, this was etched to form a light scattering body 904. The light guide plate 901 surface (the liquid crystal panel side) was directly etched to obtain a structure as shown in FIG. May be formed.

[Embodiment 7] Next, an example in which the present invention is applied to a backlight will be described. FIG. 10 is a diagram illustrating a configuration of a backlight. FIG. 10A is a cross-sectional view of the backlight, and FIG. 10B is a perspective view of the backlight.

As shown in FIG. 10A, the light guide plate 1001
A light source 1002 is disposed on a side surface 1001a of the light source 1001, and a reflector 1003 is provided behind the light source 1002. Further, the light scatterer 1 contacts the upper surface of the light guide plate 1001.
004 is provided.

Thus, the light emitted from the light source 1002 irradiates the liquid crystal panel (LCD) 1005 after passing through the light scatterer 1004 from the light guide plate 1001.

The light source 1002 uses a cold cathode tube or an LED as in the case of the front light, and is arranged along the side surface 1001 a of the light guide plate 1001. Also,
Two light sources may be provided to face each other along the side surface 1002b.

In this embodiment, the light guide plate 100
After a new transparent film was formed on the light guide plate 1001, the light scatterer 1004 was formed by etching the transparent film.
The light guide plate 1102 having a structure as shown in FIG. 11B may be directly formed by etching itself.

[Embodiment 8] In this embodiment, when the self-luminous device of the present invention is implemented by digital driving, in what region the current control TFT is driven in a region having voltage-current characteristics will be described.

In the EL element, even if the applied voltage changes even slightly, the current flowing through the EL element greatly changes exponentially. From another viewpoint, even when the magnitude of the current flowing through the EL element changes, the voltage value applied to the EL element does not change much. The luminance of the EL element increases almost directly in proportion to the current flowing through the EL element. Therefore, rather than controlling the magnitude (voltage value) of the voltage applied to the EL element to control the luminance of the EL element, the EL element is controlled by controlling the magnitude (current value) of the current flowing through the EL element. It is better to control the brightness of the TFT
And the luminance of the EL element can be easily controlled.

Referring to FIG. FIG.
In the pixel of the EL display of the present invention shown in (A), only the components of the current control TFT 108 and the EL element 110 are shown. In FIG. 12 (B),
The current controlling TFTs 108 and E shown in FIG.
4 shows a voltage-current characteristic of the L element 110. Incidentally graph of voltage-current characteristics of the current controlling TFT 108 shown in FIG. 12, for V _DS is a voltage between the source region and the drain region, it indicates the magnitude of the current flowing through the drain of the current controlling TFT 108, FIG. Reference numeral 12 denotes a current control TFT 10
8 shows a plurality of graphs having different values of V _GS which is a voltage between the source region and the gate electrode.

As shown in FIG. 12A, the EL element 1
The voltage applied between the pixel electrode 10 and the counter electrode 111 is V
_EL , terminal 2601 connected to power supply line and EL element 1
10 voltage applied between the opposing electrodes 111 of the V _T.
Note V _T is the value is fixed by the potential of the power supply line. The voltage between the source region and the drain region of the current control TFT 108 is V _DS , the voltage between the wiring 2602 connected to the gate electrode of the current control TFT 108 and the source region, that is, the gate electrode and the source of the current control TFT 108 The voltage between the regions is V _GS .

The current control TFT 108 is an n-channel type T
Either FT or p-channel TFT may be used.

The current control TFT 108 and the EL element 110 are connected in series. Therefore, the current values flowing through both elements (the current control TFT 108 and the EL element 110) are the same. Therefore, the current controlling TFT 108 and the EL element 110 shown in FIG. 12A are driven at the intersection (operating point) of the graph showing the voltage-current characteristics of both elements. In FIG. 12B, _VEL is a voltage between the potential of the counter electrode 111 and the potential at the operating point. V _DS is a voltage between the potential at the terminal 2601 of the current control TFT 108 and the potential at the operating point. In other words, V _T is equal to the sum of V _EL and V _DS.

Here, the case where V _GS is changed will be considered. As can be seen from FIG. 12 (B), the current control TF
As | V _GS −V _TH | of T108 increases, in other words, as | V _GS |
The value of the current flowing through the FT 108 increases. V _TH is a threshold voltage of the current control TFT 108. Therefore, as can be seen from FIG. 12B, as | V _GS | increases, the current value flowing through the EL element 110 at the operating point naturally increases. The luminance of the EL element 110 is
It increases in proportion to the value of the current flowing through zero.

When the value of the current flowing through the EL element 110 increases as | V _GS | increases, the value of V _EL also increases in accordance with the current value. And the size of the V _T is definite by the potential of the power supply line, the V _EL increases, correspondingly V _DS becomes smaller.

As shown in FIG. 12B, the voltage-current characteristics of the current controlling TFT are divided into two regions according to the values of V _GS and V _DS . The region where | V _GS −V _TH | <| V _DS | is the saturation region, and the region where | V _GS −V _TH |> | V _DS | is the linear region.

The following equation 4 holds in the saturation region. Note that I _DS is a current value flowing through the channel forming region of the current control TFT 108. Β = μC ₀ W / L, μ is the mobility of the current controlling TFT 108, C ₀ is the gate capacitance per unit area, and W / L is the ratio of the channel width W to the channel length L of the channel formation region. .

[0099]

[Equation 4] _{I DS = β (V GS -V} TH) 2/2

In the linear region, the following expression 5 holds.

[0101]

[Formula 5] _{I DS = β {(V GS} -V TH) V DS -V DS 2/2}

As can be seen from Equation 4, the current value hardly changes with V _DS in the saturation region, and the current value is determined only by V _GS .

On the other hand, as can be seen from Equation 5, in the linear region, the current value is determined by V _DS and V _GS . As | V _GS | increases, the current control TFT 108 operates in the linear region. And _VEL gradually increases. Thus, by an amount corresponding to V _EL is increased, V _DS becomes smaller. In the linear region, the amount of current decreases as V _DS decreases. Therefore, even when | V _GS | is increased, the current value becomes difficult to increase. | V _GS | = ∞
, The current value = I _MAX . That is, | V _GS |
No matter how large, I _MAX or more current does not flow.
Here, I _MAX is a current value flowing through the EL element 110 when V _EL = V _T.

By controlling the magnitude of | V _GS | in this manner, the operating point can be set to a saturation region or a linear region.

It is desirable that all the current control TFTs have ideally the same characteristics. However, in practice, the threshold V _TH and the mobility μ are different between the individual current control TFTs. Often. And each current control T
When FT and the threshold V _TH and the mobility μ are different from each other, as can be seen from Equation 4 and Equation 5, the value of the current flowing through the channel formation region of the current controlling TFT108 any value of V _GS the same becomes different .

FIG. 13 shows the current-voltage characteristics of the current controlling TFT in which the threshold value V _TH and the mobility μ are shifted. Solid line 270
1 is a graph of an ideal current-voltage characteristic.
703 is a current-voltage characteristic of the current controlling TFT when the threshold value V _TH and the mobility μ are different from ideal values. Graphs of current-voltage characteristics 2702, 27
03 deviates from the graph 2701 of the current-voltage characteristic having the ideal characteristic by the same current value ΔI ₁ in the saturation region, and the operating point 270 of the graph 2702 of the current-voltage characteristic
5 is in the saturation region, and the operating point 2706 of the current-voltage characteristic graph 2703 is in the linear region. In that case,
The difference between the current value at the operating point 2704 of the graph 2701 of the current-voltage characteristic having the ideal characteristic and the current value at the operating point 2705 and the current value at the operating point 2706 are ΔI ₂ ,
Assuming ΔI ₃ , the operating point 2706 in the linear region is smaller than the operating point 2705 in the saturated region.

Therefore, in the case of using the digital driving method shown in the present invention, the current control TFT and the EL element are driven so that the operating point exists in the linear region. It is possible to perform gradation display in which luminance unevenness of the EL element is suppressed.

In the case of the conventional analog drive, | V _GS
It is preferable to drive the current control TFT and the EL element such that the operating point exists in a saturation region where the current value can be controlled only by |.

As a summary of the above operation analysis, FIG. 14 shows a graph of the current value with respect to the gate voltage | V _GS | of the current controlling TFT. When | V _GS | is increased and becomes larger than the absolute value | V _th | of the threshold voltage of the current control TFT, the current control TFT becomes conductive and current starts flowing. In this specification, | V _GS | at this time is referred to as a lighting start voltage. When | V _GS | is further increased, | V _GS | becomes a value that satisfies | V _GS −V _th | = | V _DS | Area. As | V _GS | is further increased, the current value increases, and finally the current value saturates. At that time, | V _GS | = ∞.

As can be seen from FIG. 14, | V _GS | ≦ | V _th
In the region of |, almost no current flows. | V _th | ≦ |
The region where V _GS | ≦ A is a saturation region, and the current value changes depending on | V _GS |. The region where A ≦ | V _GS | is a linear region, and the current flowing through the EL element is | V _GS | and |
V _DS | changes the current value.

The self-luminous device of the present invention is driven digitally.
When implementing | V_GS| ≦ | V _th| Area and A ≦
｜ V_GSIt is preferable to use the linear region of |. Note that
The embodiment is based on the self-luminous devices shown in the first to third embodiments.
They can be freely combined.

[Embodiment 9] In the self-luminous device of the present invention, by using an EL material capable of utilizing phosphorescence from a triplet exciton for emission, external light emission quantum efficiency can be remarkably improved. Thus, low power consumption, long life, and light weight of the EL element can be achieved. Here, a report is shown in which the triplet exciton is used to improve the external emission quantum efficiency. (T.Tsutsui, C.Adachi, S.Saito, Photochem
ical Processes in Organized Molecular Systems, ed.
K. Honda, (Elsevier Sci. Pub., Tokyo, 1991) p. 437.) The molecular formula of the EL material (coumarin dye) reported by the above article is shown below.

[0113]

Embedded image

(MABaldo, DFO'Brien, Y. You, A. Shou
stikov, S. Sibley, METhompson, SRForrest, Natur
e 395 (1998) p.151.) The molecular formula of the EL material (Pt complex) reported by the above paper is shown below.

[0115]

Embedded image

(MABaldo, S. Lamansky, PEBurrrows,
METhompson, SRForrest, Appl.Phys.Lett., 75 (199
9) p.4.) (T.Tsutsui, M.-J.Yang, M.Yahiro, K.Nakamura, T.Wat
anabe, T.tsuji, Y.Fukuda, T.Wakimoto, S.Mayaguchi,
Jpn. Appl. Phys., 38 (12B) (1999) L1502.) The molecular formula of the EL material (Ir complex) reported by the above paper is shown below.

[0117]

Embedded image

As described above, if the phosphorescence emission from the triplet exciton can be used, it is possible to realize an external emission quantum efficiency three to four times higher than that in the case of using the fluorescence emission from the singlet exciton in principle. . Note that the configuration of this embodiment is the same as that of Embodiments 1 to
The self-luminous device described in Embodiment 5 can be implemented in any combination.

[Embodiment 10] A self-luminous device formed by carrying out the present invention is of a self-luminous type, so that it has better visibility in a bright place than a liquid crystal display device and has a wide viewing angle. Therefore, it can be used as a display portion of various electric appliances. For example, to watch a TV broadcast or the like on a large screen, an E of 30 inches or more (typically, 40 inches or more) of diagonal is used.
The self-luminous device of the present invention may be used as a display unit of an L display (a display in which the self-luminous device is incorporated in a housing).

The EL display includes all displays for displaying information, such as displays for personal computers, displays for receiving TV broadcasts, and displays for displaying advertisements. In addition, the self-luminous device of the present invention can be used as a display portion of various electric appliances.

Examples of the electric appliance of the present invention include a video camera, a digital camera, a goggle type display (head mounted display), a navigation system, a sound reproducing device (car audio, audio component, etc.), a notebook personal computer, a game, and the like. Devices, personal digital assistants (mobile computers, mobile phones,
An image reproducing apparatus provided with a recording medium (specifically, a digital video disc (D
VD) and the like, which reproduces a recording medium and has a display capable of displaying the image. In particular, it is desirable to use a self-luminous device for a portable information terminal, which is often viewed from an oblique direction, because importance is attached to a wide viewing angle.

Further, these electric appliances may be equipped with a sensor such as an optical sensor capable of controlling the brightness according to the surrounding brightness in order to reduce power consumption.
At this time, it is preferable that the contrast of the brightness of the self-luminous device with respect to the surrounding brightness is 100 to 150. Hereinafter, specific examples of these electric appliances are shown in FIGS.

FIG. 15A shows an EL display.
A housing 2001, a support base 2002, a display portion 2003, and the like are included. The present invention can be used for the display portion 2003. E
Since the L display is a self-luminous type, it does not require a backlight and can be a display portion thinner than a liquid crystal display.

FIG. 15B shows a video camera, which includes a main body 2101, a display section 2102, an audio input section 2103, operation switches 2104, a battery 2105, and an image receiving section 210.
6 and so on. The self-luminous device of the present invention can be used for the display portion 2102.

FIG. 15C shows a part (one side on the right) of the head-mounted EL display, which includes a main body 2201, a signal cable 2202, a head fixing band 2203, and a display section a.
(2204), optical system 2205, display unit b (2206)
And so on. The present invention can be used for the display portion a (2204) or the display portion b (2206).

FIG. 15D shows an image reproducing apparatus (specifically, a DVD reproducing apparatus) provided with a recording medium.
1, recording medium (DVD or the like) 2302, operation switch 23
03, a display unit (a) 2304, a display unit (b) 2305, and the like. The display unit (a) mainly displays image information, and the display unit (b) mainly displays character information. The self-luminous device of the present invention can be used for these display units (a) and (b). Note that the image reproducing device provided with the recording medium includes a home game machine and the like.

FIG. 15E shows a portable computer, which includes a main body 2401, a camera section 2402, an image receiving section 2403, operation switches 2404, a display section 2405, and the like. The self-luminous device of the present invention can be used for the display portion 2405.

FIG. 15F shows a personal computer, which includes a main body 2501, a housing 2502, a display portion 2503,
A keyboard 2504 and the like are included. The self-luminous device of the present invention can be used for the display portion 2503.

If the emission luminance of the organic EL material increases in the future, it becomes possible to enlarge and project the light including the output image information with a lens or the like and use it for a front-type or rear-type projector.

[0130] Further, the above-mentioned electric appliances are available on the Internet or C
Information distributed through an electronic communication line such as an ATV (cable television) is frequently displayed, and in particular, opportunities to display moving image information are increasing. Since the response speed of the organic EL material is very high, the self-luminous device is preferable for displaying a moving image. Therefore, it is extremely effective to use the self-luminous device of the present invention for clearing the contour between pixels as a display portion of an electric appliance.

In the self-luminous device, since the light emitting portion consumes power, it is desirable to display information so that the light emitting portion is reduced as much as possible. Therefore, portable information terminals,
In particular, when a self-light-emitting device is used for a display portion mainly including character information such as a mobile phone or a sound reproducing device, it is desirable to drive the non-light-emitting portion as a background so that character information is formed by a light-emitting portion.

FIG. 16A shows a portable telephone, which includes a main body 2601, an audio output unit 2602, and an audio input unit 260.
3, including a display unit 2604, operation switches 2605, and an antenna 2606. The self-luminous device of the present invention has a display portion 2604.
Can be used. Note that the display portion 2604 can display power of the mobile phone by displaying white characters on a black background.

FIG. 16B shows a sound reproducing device, specifically, an audio for vehicle, which includes a main body 2701, a display portion 2702, and operation switches 2703 and 2704. The self-luminous device of the present invention can be used for the display portion 2702. In this embodiment, the in-vehicle audio is shown, but the present invention may be applied to a portable or home-use audio reproducing apparatus. Note that the display portion 2704 can suppress power consumption by displaying white characters on a black background. This is particularly effective in a portable sound reproducing device.

As described above, the applicable range of the present invention is extremely wide, and the present invention can be used for electric appliances in various fields. In addition, the electric appliance of this embodiment may use the self-luminous device having any configuration shown in the first to eighth embodiments.

[0135]

According to the present invention, by providing a light scatterer on an insulator, light extraction efficiency of a light emitting element, particularly, an EL element can be improved. Furthermore, by etching a transparent film to form a light scatterer, fine processing of the pitch becomes possible. As described above, by forming a light scatterer with a fine pitch, a self-luminous device with high luminous efficiency can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a light scatterer of the present invention.

FIG. 2 is an explanatory diagram of light refraction.

FIG. 3 is a diagram in which the present invention is applied to an active matrix type TFT.

FIG. 4 is a diagram showing details of a light scatterer.

FIG. 5 is a diagram in which the present invention is applied to an active matrix type TFT.

FIG. 6 is a diagram in which the present invention is applied to an inverted staggered active matrix type TFT.

FIG. 7 is a diagram in which the present invention is applied to a passive matrix type TFT.

FIG. 8 is a diagram in which the present invention is applied to a passive matrix type TFT.

FIG. 9 is a diagram in which the present invention is used for a front light.

FIG. 10 is a diagram in which the present invention is used for a backlight.

FIG. 11 is a diagram in which the present invention is used for a front light and a backlight.

12A and 12B are diagrams illustrating a configuration of connection between an EL element and a current control TFT, and a diagram illustrating voltage-current characteristics of the EL element and a current control TFT.

FIG. 13 is a diagram showing voltage-current characteristics of an EL element and a current control TFT.

FIG. 14 is a diagram showing a relationship between a gate voltage and a drain current of a current control TFT.

FIG. 15 illustrates an example of an electric appliance.

FIG. 16 illustrates an example of an electric appliance.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05B 33/22 H05B 33/22 Z

Claims (13)

[Claims] 1. A self-luminous device, wherein an insulator is interposed between a light emitting element and a light scatterer. 2. A TFT formed on an insulator, a first electrode electrically connected to the TFT, an EL layer formed on the first electrode, and a TFT formed on the EL layer. A light emitting device having a second electrode, wherein a light scatterer is formed on the opposite side of the first electrode via the insulator. 3. The self-luminous device according to claim 2, wherein said first electrode is an anode, and said second electrode is a cathode. 4. A self-luminous device according to claim 2, wherein said first electrode is made of a light-transmitting material, and said second electrode is made of a light-shielding material. 5. A self-luminous device having a first electrode formed on an insulator, an EL layer formed on the first electrode, and a second electrode formed on the EL layer. And a light-scattering body is formed on the opposite side of the first electrode via the insulator. 6. The self-luminous device according to claim 5, wherein said first electrode is an anode, and said second electrode is a cathode. 7. The self-luminous device according to claim 5, wherein said first electrode is made of a light-transmitting material, and said second electrode is made of a light-shielding material. 8. The self-luminous device according to claim 1, wherein the light scatterer is formed of a light-transmitting material. 9. The light scatterer according to claim 1, wherein the light scatterer is polycarbonate, polyimide,
A self-luminous device comprising BCB, indium oxide, or tin oxide. 10. The light-scattering body according to claim 1, wherein a thickness (H) of the light-scattering body has a relationship of H ≧ W1 with a pitch (W1) of the light-scattering body. A light-emitting device having a thickness. 11. The self-luminous device according to claim 1, wherein the pixel pitch is at least twice the pitch of the light scatterers. 12. The method according to claim 1, wherein the angle between the light scatterer and the insulator is 60.
A self-luminous device characterized by being at least 180 ° and less than 180 °. 13. An electric appliance using the self-luminous device according to any one of claims 1 to 12.