JP4967423B2 - LIGHT EMITTING DEVICE AND ELECTRONIC DEVICE - Google Patents

Description

  The present invention relates to a light emitting device and an electronic apparatus.

2. Description of the Related Art In recent years, light emitting devices including a plurality of electroluminescence (hereinafter referred to as EL) elements as means for displaying information have been proposed in electronic devices such as notebook computers, mobile phones, and electronic notebooks. In an EL element, an EL layer (light emitting layer) is disposed between a pair of electrodes facing each other.

In the field of EL devices, it is known to arrange a light emitting layer between reflecting layers to resonate light of a specific wavelength by reflection and amplify the intensity of the light of the specific wavelength. For example, in Patent Document 1, a translucent reflective film made of a dielectric formed on the entire surface of a glass substrate, a spacer made of SiO ₂ formed thereon, a transparent electrode formed thereon, An EL device having a hole injection layer formed on the substrate, a light emitting layer formed thereon, and a reflective electrode formed thereon is disclosed. This light emitting layer is formed of a common material in all pixels and emits white light. However, in order to make the target output color different, the thickness of the transparent electrode or the thickness of the SiO ₂ spacer is It depends on the output color. Therefore,
Even when the light emitting layer is formed from the same white light emitting material, output colors of R (red), G (green), and B (blue) can be obtained.

Further, in Patent Document 2, an organic layer including a light emitting layer formed of a different material for each of R, G, and B light emitting elements and a translucent reflective layer are disposed between the reflective electrode and the transparent electrode. A display device is disclosed. The translucent reflective layer has the same structure for all light emitting layers,
For the purpose of improving the color purity of the output color, the organic layer including the R light emitting layer has a thickness suitable for the resonance of the R light, and the organic layer including the G light emitting layer is the resonance of the G light. The organic layer including the light emitting layer for B light has a thickness suitable for resonance of B light. Accordingly, light with high color purity can be emitted, and thereby the color reproducibility of the display device can be improved.

Further, Patent Document 3 discloses a display device in which an organic layer including a light emitting layer and a transparent conductive layer are disposed between a reflective electrode and a semitransparent electrode. In this display device, the transparent conductive layer overlapping the R light organic layer has a thickness suitable for R light resonance, and the transparent conductive layer overlapping the G light organic layer has a thickness suitable for G light resonance. The transparent conductive layer that overlaps the organic layer of B light has a thickness suitable for resonance of B light.

Japanese Patent No. 2797883 International Publication No. 01/039554 Pamphlet JP-A-2005-116516

In the technique described in Patent Document 1, the thickness of the transparent electrode or the thickness of the SiO ₂ spacer varies depending on the target output color. However, as described above, in this technique in which the semitransparent reflective film, the spacer, the transparent electrode, the hole injection layer, the light emitting layer, and the reflective electrode are laminated in this order on the substrate, the portion overlapping the edge of each transparent electrode Then, since the hole injection layer, the light emitting layer, and the reflective electrode, which are the elements of the resonance structure, are easily bent (a step is likely to be formed), the thickness of each of these layers is larger than that at the center of the transparent electrode. Tend to be small. Further, the transparent electrode itself has a constant thickness at the center, but tends to be unstable in the vicinity of the edge. In the resonant structure, the wavelength of light emitted from the resonant structure varies depending on the optical distance between the reflecting layers. Therefore, if there is such a variation in layer thickness, not only the target output light wavelength but also A lot of light of other wavelengths is output. In other words, the target color is mixed with other colors.

In the technique described in Patent Document 2 or Patent Document 3, it is considered that the reflective electrode is a pixel electrode corresponding to each light emitting dot, and a layer that is an element of a resonance structure in a portion overlapping the edge of each reflective electrode, For example, it is considered that the thickness of each of these layers tends to be smaller than the portion overlapping the center of the reflective electrode because the organic layer is easily bent (a step is likely to occur). Therefore, in the same manner as the technique described in Patent Document 1, it is considered that not only the desired output light wavelength but also a large amount of light having other wavelengths is output.

Accordingly, the present invention provides a light emitting device capable of improving the purity of the target light color and an electronic apparatus using the light emitting device.

The light emitting device according to the present invention includes a light reflecting layer having light reflectivity provided on a substrate, a dielectric layer provided so as to cover the light reflecting layer, and light provided on the dielectric layer. A light emitted from the light-emitting layer, comprising: a pixel electrode having transparency; a light-emitting layer provided on the pixel electrode; and a counter electrode having semi-transmissive and semi-reflective properties provided on the light-emitting layer. At least a part of which is resonated between the light reflection layer and the counter electrode, and the pixel electrode has an area larger than the area of the light reflection layer so as to cover the light reflection layer in plan view. And an insulating layer is not provided between an end portion of the pixel electrode and the light emitting layer.
The light emitting device according to the present invention includes a light reflecting layer having light reflectivity provided on a substrate, a dielectric layer provided so as to cover the light reflecting layer, and light provided on the dielectric layer. A transparent pixel electrode, a light emitting layer provided on the pixel electrode, and a semi-transparent semi-reflective counter electrode provided on the light emitting layer, the pixel electrode in plan view It has an area larger than the area of the light reflection layer so as to cover the light reflection layer, and no insulating layer is provided between the end of the pixel electrode and the light emitting layer. It is characterized by.
The light emitting device according to the present invention includes a substrate, a plurality of light reflecting layers provided on the substrate, a transparent dielectric layer provided so as to cover the light reflecting layer, and each of the plurality of light reflecting layers. And each of the plurality of light emitting elements is provided on a side opposite to the substrate with respect to the pixel electrodes. A translucent counter electrode and a light emitting layer interposed between the pixel electrode and the counter electrode, and light emitted from the light emitting layer is emitted through the counter electrode; The color of the first light emitted through the counter electrode included in one light emitting element is the second light emitted through the counter electrode included in the second light emitting element among the plurality of light emitting elements. The color of the pixel electrode is different from the color of the light reflection layer corresponding to the pixel electrode. The pixel electrode has a larger area than the light reflecting layer, and the thickness of the pixel electrode included in the first light emitting element is different from the thickness of the pixel electrode included in the second light emitting element. Features.

According to the present invention, the light emitted from the light emitting layer reciprocates between the light reflecting layer and the translucent counter electrode of each light emitting element, thereby amplifying the intensity of light of a specific wavelength. That is, each light emitting element, the dielectric layer, and the light reflecting layer constitute a resonance structure, that is, a microcavity. To resonate the light,
The optical distance of the optical path in the resonance structure is set to be proportional to the wavelength of light to be resonated.
Therefore, the pixel electrode has a thickness corresponding to the color of the emitted light from the counter electrode, and the resonance structure has an optical distance suitable for the color of the emitted light with respect to each light emitting element. In the place where it overlaps with the edge of each pixel electrode, the light emitting layer and the counter electrode which are the elements of the resonance structure are easily bent (
Therefore, the thickness of each of the light emitting layer and the counter electrode tends to be smaller than the portion overlapping the center of the pixel electrode. Also, the pixel electrode itself has a constant thickness at the center, but tends to be non-uniform in the vicinity of the edge. However, according to the present invention, each of the pixel electrodes of the light emitting element has a larger area than the light reflection layer so as to overlap the entire light reflection layer that overlaps the pixel electrode. Therefore, light reciprocating between the light reflecting layer and the translucent counter electrode of each light emitting element does not pass through the edge of the pixel electrode and the portion overlapping with this edge. That is, the edge of the pixel electrode and the portion overlapping the edge are excluded from the resonance structure, and the portion where the optical distance is steady can be used as the resonance structure. In this way, the possibility that light of other wavelengths is mixed with light of the target wavelength is reduced, and the purity of the target color can be improved.

Preferably, the pixel electrode includes a first layer and a second layer stacked on the first layer, and the first layer includes the light reflecting layer in a plan view. The second layer has an area larger than the area of the light reflection layer so as to cover, and the second layer covers an area larger than the area of the first layer so as to cover the first layer in plan view. It is characterized by having.
Preferably, the pixel electrode included in at least one of the first light-emitting element and the second light-emitting element is formed by stacking a plurality of layers made of the same material, and the first of the plurality of layers is a first layer. When the layer and the second layer are compared, the first layer is provided between the second layer and the substrate, and the second layer is the entire first layer. It has a larger area than the first layer so as to cover it.
As described above, in order to resonate light, the optical distance of the optical path in the resonance structure is set to be proportional to the wavelength of light to be resonated. Accordingly, the pixel electrode of the light-emitting element whose emission light has a longer peak wavelength than the other light-emitting elements is thicker than the pixel electrode of the other light-emitting elements. That is, the pixel electrode of the light emitting element that emits R light is thicker than the pixel electrode of the light emitting element that emits G light, and the pixel electrode of the light emitting element that emits G light is larger than the pixel electrode of the light emitting element that emits B light. Also thick. If such a thick pixel electrode is formed of a plurality of layers of the same material, any of those layers can be formed in the same process as the pixel electrode (or a layer in it) of another light emitting element. Manufacturing time can be shortened. Of such a thick pixel electrode, the layer farther from the substrate has a larger area than the nearer layer so as to cover the entire layer of the pixel electrode closer to the substrate. Compared with the case where the thickness is smaller than that of the nearer layer, it is possible to reduce a portion where the thickness is not uniform near the edge of the pixel electrode. Therefore, the possibility that light of other wavelengths is mixed with light of the target wavelength is further reduced, and the purity of the target color can be improved.

Preferably, the pixel electrode includes a third layer stacked on the second layer, and the second layer covers the second layer in a plan view. It has an area larger than the area of the layer.
Preferably, the pixel electrode included in the first light emitting element that emits the first light is formed by stacking two layers made of the same material, and the second light that emits the second light. The pixel electrode included in the light emitting element is formed by stacking three layers made of the same material, and emits third light having a color different from both the color of the first light and the color of the second light. The pixel electrode included in the third light emitting element is a single layer, the color of the first light is green, the color of the second light is red, and the color of the third light is It is blue.
According to this structure, one of the pixel electrodes of the light emitting element that emits R light and one of the pixel electrodes of the light emitting element that emits G light have the same process as the pixel electrode of the light emitting element that emits B light. The other layer of the pixel electrode of the light emitting element that emits R light can be formed in the same process as the other layer of the pixel electrode of the light emitting element that emits G light. Accordingly, the manufacturing time can be shortened.

Preferably, in the light emitting device, a protective substrate is provided on the counter electrode so as to face the substrate, and the protective substrate transmits a color filter that transmits light emitted from the light emitting layer; A first light-shielding layer, wherein the first light-shielding layer and the light reflecting layer have a planarly overlapping portion.
Preferably, the light-emitting device further includes a light-shielding film disposed on the opposite side of the substrate with the light-emitting element interposed therebetween, and the light-shielding film includes a plurality of lights that transmit light emitted from the light-emitting element. A transmission part is formed, and one light reflection layer of the plurality of light reflection layers is larger than the one light transmission part so as to overlap the entire one light transmission part of the plurality of light transmission parts. Has an area. In this configuration, the light emitted from the light emitting element passes through the light transmission part formed in the light shielding film.
Since the light transmission part is smaller than the light reflection layer overlapped therewith, the light reflected by the edge of the light reflection layer or the light passing through the part overlapping the edge of the light reflection layer may pass through the light transmission part. It is suppressed. Moreover, even if the light that has passed through the edge of the pixel electrode and the portion that overlaps the edge of the pixel electrode is reflected by the light reflection layer, such light is suppressed from passing through the light transmission portion.

Further, a second light shielding layer is provided between the substrate and the light reflecting layer, and the second light shielding layer and the light reflecting layer have a portion overlapping in a plane. To do.
Furthermore, it is preferable that a light shielding layer is disposed below the light reflecting layer, and a thin film transistor for driving the light emitting element is disposed under the light shielding layer. In this configuration, the thin film transistor disposed at a position closer to the substrate than the light reflecting layer is covered by the light shielding layer disposed at a position closer to the thin film transistor than the light reflecting layer. Accordingly, external light or light emission of the light-emitting element is suppressed from reaching the thin film transistor, and a photocurrent is prevented from flowing through the thin film transistor to cause the thin film transistor to malfunction.

An electronic apparatus according to the present invention includes the light-emitting device according to the present invention as a display unit, for example. According to such an electronic device, display with high color purity of output light can be realized. As such an electronic device, a personal computer, a cellular phone, a portable information terminal, or the like in which a light-emitting device is applied to a display device is applicable.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In these drawings, the ratio of dimensions of each layer and each member is appropriately different from the actual one.

<Light emitting device>
FIG. 1 is a cross-sectional view showing a part of a full-color light emitting device 10 according to an embodiment of the present invention. The light-emitting device 10 includes an organic EL element, that is, an OLED (organic light emitti) as a large number of light-emitting elements 12R, 12G, and 12B arranged in a matrix on a substrate 14.
ng diode) element. In the figure, three light emitting elements 12R, 1
Only 2G and 12B are illustrated.

As the substrate 14, in addition to a glass substrate, a silicon substrate, a quartz substrate, a ceramic substrate,
Various known substrates such as a metal substrate, a plastic substrate, and a plastic film substrate can be used. On the substrate 14, a plurality of thin film transistors (TFTs) 16 for driving the light emitting elements 12R, 12G, and 12B and various wirings (not shown) for driving the light emitting elements are arranged. Although not shown in detail, the TFT 16 and these wirings are formed on the substrate 14 by a known method.

The TFT 16 is covered with an insulating layer 18 formed on the substrate 14. The insulating layer 18 is formed of an insulator such as silicon oxide. The insulating layer 18 may be composed of a plurality of layers formed of the same or different materials.

A light shielding layer 20 is disposed so as to cover the TFT 16. The light shielding layer 20 prevents light from the upper side in FIG. 1 (for example, external light or light emitted from the light emitting element) from reaching the TFT 16. The light shielding layer 20 can be formed from a metal, for example. As such a metal,
There are aluminum, chromium, silver, tantalum and so on. The light shielding layer 20 may have a high light reflectance. This is because even if light from above in FIG. 1 is reflected by the light shielding layer 20, the reflected light is not emitted outside by the black matrix (light shielding film 40) described later.

The insulating layer 18 described above is interposed between the light shielding layer 20 and the TFT 16, and the insulating layer 18 also overlaps the light shielding layer 20. In FIG. 1, a light reflection layer 22 is formed on the insulating layer 18. The light reflecting layer 22 is made of a material having high reflectivity, for example, aluminum, silver, or an alloy containing one or both of them, and the upper surface thereof is smooth. Light reflection layer 22
Are disposed under each of the light emitting elements 12R, 12G, and 12B.

A transparent dielectric layer 24 is formed on the insulating layer 18 so as to cover each of the light reflecting layers 22. The dielectric layer 24 may be formed of a transparent inorganic dielectric such as silicon nitride, silicon oxide, or silicon oxynitride, or may be formed of a transparent organic dielectric such as an acrylic resin. . In FIG. 1, one dielectric layer 24 is disposed for each of the light emitting elements 12R, 12G, and 12B. However, one dielectric layer 24 common to these light emitting elements may be disposed.

A plurality of light emitting elements 12R, 12G, and 1 are provided at positions overlapping the light reflecting layer 22 on the dielectric layer 24.
2B is formed. In the following description, the subscripts R, G, and B attached to the symbols represent the colors of light emitted by the light emitting elements, that is, red, green, and blue, respectively, and may be omitted as appropriate.

The light emitting element 12 is a dot visually recognized from the outside. Each of the light emitting elements 12 includes a transparent pixel electrode 26, a translucent counter electrode 36 that is farther from the dielectric layer 24 than the pixel electrode 26 and faces the pixel electrode 26, and between the pixel electrode 26 and the counter electrode 36. And a light emitting layer 32 interposed therebetween. One pixel electrode 26 is provided for each of the light emitting elements 12, while one counter electrode 36 common to the plurality of light emitting elements 12 is provided. In this embodiment, the pixel electrode 2
6 is an anode and the counter electrode 36 is a cathode. Conversely, the pixel electrode 26 may be a cathode and the counter electrode 36 may be an anode.

The pixel electrodes 26R, 26G, and 26B are made of, for example, ITO (indium tin oxide) or IZO.
(Indium zinc oxide) or an oxidized conductive material having optical transparency such as ZnO ₂ . The thickness of the pixel electrode 26 varies depending on the color of light emitted from the light emitting elements 12R, 12G, and 12B. This will be described later in more detail.

Each of the pixel electrodes 26 is connected to a TFT 16 directly below in FIG. 1 through a through hole (not shown). The through hole passes through the dielectric layer 24, the insulating layer 18 and the light shielding layer 20 and reaches the TFT 16.

A hole transport layer 30 is disposed between the pixel electrode 26 serving as an anode and the light emitting layer 32. On the other hand, an electron transport layer 34 is interposed between the counter electrode 36 serving as a cathode and the light emitting layer 32. In addition to these, a hole injection layer, an electron block layer, an electron injection layer, and a hole block layer may be formed as components of the light emitting element 12.

The counter electrode 36 is formed of a material having a low work function so that electrons can be easily injected. Although not shown in detail, for example, the counter electrode 36 is formed of a calcium layer and an aluminum layer. The one near the electron transport layer 34 is a very thin second counter electrode layer made of calcium, and the one far from the electron transport layer 34 is made of aluminum and is a thicker first counter electrode layer. The counter electrode 36 is a half mirror. That is, a part of the light irradiated here is transmitted and the other part is reflected. Therefore, the emitted light resulting from the light emission in the light emitting layer 32 is emitted to the outside through the counter electrode 36. That is, the light emitting device 10 is a top emission type in which light is emitted to the side opposite to the substrate 14.

The hole transport layer 30, the light emitting layer 32, the electron transport layer 34, and the counter electrode 36 are formed of any one of the light emitting elements 1.
The same applies to 2R, 12G, and 12B, each of which has a uniform thickness. The light emitting layer 32 emits white light, that is, light having a wide wavelength band, by the combination of holes and electrons inside the light emitting layer 32. The light emitting layer 32 is of a low molecular type and can be formed, for example, by vapor deposition.
Although the light emitting layer 32 may be a single layer, it is often difficult to manufacture a light emitting layer that emits light having a strong energy over a wide wavelength band. For example, a light emitting material that emits blue light and light emission that emits orange light. It may be a combination of a plurality of light emitting layers, such as a combination of materials. Thus, although the light emitting layer 32 emits white light, the light emitting element 12R emits red light, the light emitting element 12G emits green light, and the light emitting element 12B emits blue light by a resonance structure described later. discharge.

A black matrix, that is, a light shielding film 40 is bonded to the counter electrode 36 by a transparent adhesive 38 which is a transparent resin, for example, an epoxy resin. However, in order to protect the light emitting layer 32 and the like from air or moisture and to improve the life of the light emitting element 12, the transmittance of air such as silicon nitride is low between the counter electrode 36 and the transparent adhesive 38. You may arrange | position the sealing layer (not shown) formed from the inorganic material.

The light shielding film 40 is disposed on one side of a transparent protective plate 42 made of glass or plastic. The light shielding film 40 is formed of a resin containing a black pigment, a metal (for example, titanium or chromium) or an oxide thereof. The light shielding film 40 is formed with a plurality of apertures, that is, light transmission portions, and light emitted from the light emitting element 12 is emitted upward through the light transmission portion. In each of the light transmission portions of the light shielding film 40, the color filters 44R, 44G, or 4
4B is arranged. Each of the color filters transmits more light having a peak wavelength of the emitted light of the light emitting element superimposed thereon than light having a peak wavelength of the other light emitting elements. For example, the color filter 44R transmits light having a peak wavelength (red light) emitted from the light emitting element 12R more than green or blue light. These color filters 44R, 44G, and 44B are surrounded and shielded from each other by a light-shielding film 40 that blocks light in order to prevent color mixing between the color filters.

Next, the optical resonance structure will be described. According to this embodiment, the light emitted from the light emitting layer 32 reciprocates between the light reflecting layer 22 and the translucent counter electrode 36 of each of the light emitting elements 12R, 12G, and 12B. The intensity is amplified. Therefore, although the light emitting layer 32 itself emits white light, the light emitting element 12R emits red light having a long wavelength, the light emitting element 12G emits green light, and the light emitting element 12B emits blue light having a short wavelength. discharge. That is, each of the light emitting elements 12R, 12G, and 12B, the dielectric layer 24, and the light reflecting layer 22 constitute a resonance structure, that is, a microcavity. In order to resonate the light, the optical distance of the optical path in the resonance structure is set to be proportional to the wavelength of the light to be resonated. Therefore, the pixel electrodes 26R, 26G, 26B
Has a thickness corresponding to the color of the light emitted from the counter electrode 36, and each light emitting element 12R, 12G.
, 12B, the resonant structure has an optical distance suitable for the color of the emitted light.

Specifically, the pixel electrode 26 of the light emitting element in which the peak wavelength of emitted light is longer than the other light emitting elements is thicker than the pixel electrode 26 of the other light emitting elements. That is, the light emitting element 12 that emits R light.
The R pixel electrode 26R is thicker than the pixel electrode 26G of the light emitting element 12G that emits G light.
The pixel electrode 26G of the light emitting element 12G that emits light is thicker than the pixel electrode 26B of the light emitting element 12B that emits B light.

The thickest pixel electrode 26R has three layers of the same material. That is, the first pixel electrode layer 28a
The second pixel electrode layer 28b and the third pixel electrode layer 28c are stacked.
The second thickest pixel electrode 26G has two layers of the same material. That is, the second pixel electrode layer 2
8b and the third pixel electrode layer 28c are stacked. Thinnest pixel electrode 26
B has a single layer, that is, a third pixel electrode layer 28c.

The ordinal numbers (first to third) of the pixel electrode layer indicate the order of formation. That is, among the pixel electrode layers, the first pixel electrode layer 28a of the pixel electrode 26R is formed first.

Thereafter, the second pixel electrode layer 28b of the pixel electrodes 26R and 26G is simultaneously formed in the same process. In the pixel electrode 26R, the second pixel electrode layer 28b covers the first pixel electrode layer 28a,
In the pixel electrode 26G, the second pixel electrode layer 28b is directly formed on the dielectric layer 24. However, the second pixel electrode layers 28b of the pixel electrodes 26R and 26G have the same thickness. However, the term “thickness” here means the thickness where the thickness is constant, and excludes the thickness near the edge of the pixel electrode layer where the thickness is unstable.

Finally, the third pixel electrode layer 28c of the pixel electrodes 26R, 26G, and 26B is simultaneously formed in the same process. In the pixel electrodes 26R and 26G, the third pixel electrode layer 28c covers the second pixel electrode layer 28b, and in the pixel electrode 26B, the third pixel electrode layer 28c is directly formed on the dielectric layer 24, but the pixel electrode 26R , 26G, and 26B have the same thickness. However, the term “thickness” here means the thickness where the thickness is constant, and excludes the thickness near the edge of the pixel electrode layer where the thickness is unstable.

Individual layers of the pixel electrode 26 are formed by sputtering, CVD (chemical vapor deposition).
) Or other known various film forming techniques. For patterning each layer, for example, a photolithography technique and an etching technique are used.
The dielectric layer 24 is a material that can withstand a developer and an etchant used in photolithography. Even if the light reflecting layer 22 is formed of a material that is easily exposed to the developer and the etchant, the dielectric layer 24 reflects the light. Layer 22 can be protected.

As described above, if the thick pixel electrode 26 is formed of a plurality of layers of the same material, any one of these layers is formed in the same process as the pixel electrode 26 (or a layer therein) of another light emitting element. Manufacturing time can be shortened. That is, the third pixel electrode layer 28c of the pixel electrode 26R of the light emitting element 12R that emits R light and the third pixel electrode layer 28c of the pixel electrode 26G of the light emitting element 12G that emits G light have B light. The second pixel electrode layer 28b in the pixel electrode 26R of the light emitting element 12R that emits R light emits G light. Pixel electrode 2 of element 12G
6G can be formed in the same process as the second pixel electrode layer 28b.

The materials and their thicknesses in a specific example of a resonant structure are as follows. The materials and values listed herein are described for purposes of illustration and are not intended to limit the invention. The dielectric layer 24 can be formed to a thickness of 30 nm with silicon nitride (refractive index 1.8). The first pixel electrode layer 28a can be formed with a thickness of 30 nm from ITO (refractive index 1.95). The second pixel electrode layer 28b can be formed with a thickness of 35 nm from ITO. The third pixel electrode layer 28c can be formed with a thickness of 30 nm from ITO. Accordingly, the pixel electrode 26R has a thickness of 95 nm, the pixel electrode 26G has a thickness of 65 nm,
The pixel electrode 26B has a thickness of 30 nm. However, the term “thickness” here means the thickness where the thickness is constant, and excludes the thickness near the edge of the pixel electrode layer where the thickness is unstable.

FIG. 2A is a plan view of one pixel 50 of the light emitting device 10. As shown in the figure, one pixel 50 is provided with three light emitting elements 12R, 12G, and 12B having different emission lights.

FIG. 2B is a plan view of one pixel of the light emitting device 10 in which the light shielding film 40, the light shielding layer 20, the TFT 16, and the above wiring are omitted. As shown in FIGS. 1 and 2B, the pixel electrode 2
Each of 6 has an area larger than that of the light reflection layer 22 so as to overlap the entire light reflection layer 22 that overlaps the light reflection layer 22. Of the layers constituting the pixel electrode 26, the layer closest to the substrate 14 (
The pixel electrode 26R has a first pixel electrode layer 28a, and the pixel electrode 26G has a second pixel electrode layer 28.
b. In the pixel electrode 26B, the third pixel electrode layer 28c) has a larger area than the light reflecting layer 22 so as to overlap the entire light reflecting layer 22 which overlaps the third pixel electrode layer 28c).

As shown in FIG. 1, the hole transport layer 30, the light emitting layer 32, the electron transport layer 34, and the counter electrode 36, which are elements of the resonance structure, are easily bent at portions where they overlap the edges of the individual pixel electrodes 26 (steps are different). Therefore, the thickness of each of these layers tends to be smaller than the portion overlapping the center of the pixel electrode 26. Also, the pixel electrode 26 itself has a constant thickness at the center, but tends to be non-uniform in the vicinity of the edge. However, according to this embodiment, each of the pixel electrodes 26 of the light emitting elements 12R, 12G, and 12B has a larger area than the light reflecting layer 22 so as to overlap the entire light reflecting layer 22 that overlaps the pixel electrode 26. Have. Therefore, the light reciprocating between the light reflecting layer 22 and the translucent counter electrode 36 of each light emitting element 12R, 12G, 12B does not pass through the edge of the pixel electrode 26 and the portion overlapping the edge. That is, the edge of the pixel electrode 26 and a portion overlapping with the edge are excluded from the resonance structure, and a portion having a constant optical distance can be used as the resonance structure. In this way, the possibility that light of other wavelengths is mixed with light of the target wavelength is reduced, and the purity of the target color can be improved.

As shown in FIGS. 1 and 2B, among the pixel electrodes 26R formed from a plurality of layers, the third pixel electrode layer 28c far from the substrate 14 is closer to the substrate 14 than this. The second pixel electrode layer 28b has an area larger than the second pixel electrode layer 28b so as to cover the entire pixel electrode layer 28b.
The pixel electrode layer 28b has a larger area than the first pixel electrode layer 28a so as to cover the entire first pixel electrode layer 28a closer to the substrate 14 than this. Further, among the pixel electrodes 26G formed from a plurality of layers, the third pixel electrode layer 28c far from the substrate 14 is the substrate 1 than this.
4 has an area larger than that of the second pixel electrode layer 28b so as to cover the entire second pixel electrode layer 28b close to 4. Thus, the layer farther from the substrate 14 in the thick pixel electrode 26 is
Since the pixel electrode 26 has a larger area than the nearer layer so as to cover the entire layer nearer to the substrate 14, the pixel electrode 26 has a larger area than the nearer layer than the substrate 14. A portion where the thickness is not uniform in the vicinity of the edge of the electrode 26 can be reduced. Therefore, the possibility that light of other wavelengths is mixed with light of the target wavelength is further reduced, and the purity of the target color can be improved.

Furthermore, as shown in FIG. 1 and FIG. 2B, each of the light reflection layers 22 overlaps with any one of the light transmission portions (the color filters 44 are disposed) formed in the light shielding film 40. Thus, it has an area larger than this light transmission part. That is, since the light transmission part is smaller than the light reflection layer 22 that overlaps the light transmission part, the light beam visible from the outside is defined by the light transmission part of the light shielding film 40, and the edge part of the resonance structure is hidden by the light shielding film 40. Therefore, the light that is reflected at the edge of the light reflecting layer 22 or passes through the portion that overlaps the edge of the light reflecting layer 22 is suppressed from passing through the light transmitting portion. Further, even if light that has passed through the edge of the pixel electrode 26 and a portion that overlaps the edge of the pixel electrode 26 is reflected by the light reflection layer 22, such light is suppressed from passing through the light transmission portion. In this way, it is possible to prevent the luminance and chromaticity variations within one light emitting element from being visually recognized. Moreover, since the light transmission part of the light shielding film 40 is smaller than the light reflection layer 22 that overlaps the light transmission part 40, the directivity of the light beam emitted to the outside can be increased.

As described above, each of the light emitting elements 12R, 12G, and 12B constitutes a resonance structure. In the resonance structure, light of a specific wavelength is emitted from the counter electrode 36 so that light of a specific wavelength is amplified and light of other wavelengths is attenuated. In the resonance structure, the external light is transmitted with a very large amount of light having a specific wavelength and hardly reflected, and the light with other wavelengths is reflected without being transmitted so much. That is, when light having the peak wavelength of the light emitted from the light emitting element is irradiated to the resonance structure from the outside, the light is hardly reflected. Such an event is described in Patent Document 2, for example.

FIG. 3 shows a reflection spectrum of the resonance structure formed by each of the light emitting elements 12R, 12G, and 12B in the embodiment. Resonant structure materials and their thicknesses are as in the above example, and the graph of FIG. 3 was obtained by simulation. In FIG. 3, the solid line indicates the light emitting element 12R.
, The reflection spectrum of the resonance structure of the light emitting element 12G,
The thin broken line represents the reflection spectrum of the resonance structure of the light emitting element 12B.

As apparent from FIG. 3, in the resonance structure of the light emitting element 12 </ b> R, light of red wavelength is hardly reflected, and light of other wavelengths is reflected more. In the resonance structure of the light emitting element 12G, light of green wavelength was hardly reflected, and light of other wavelengths was reflected more. In the resonance structure of the light emitting element 12B, light of blue wavelength is hardly reflected, and light of other wavelengths is reflected more.
As described above, in the resonance structure, when light having a wavelength that is enhanced by internal light emission is irradiated from the outside, the light is hardly reflected. That is, it was confirmed that when the light having the peak wavelength of the light emitted from the light emitting element is irradiated on the resonance structure from the outside, it is hardly reflected.

FIG. 4 shows transmission spectra of the color filters 44R, 44G, and 44B used in the embodiment. In FIG. 4, the solid line represents the transmission spectrum of the color filter 44R, the thick broken line represents the transmission spectrum of the color filter 44G, and the thin broken line represents the transmission spectrum of the color filter 44B.

As apparent from FIG. 4, the color filter 44 </ b> R has the light emitting element 12 with which it overlaps.
The light having the peak wavelength of R emitted light, that is, red light is transmitted more than the light having the peak wavelength of emitted light of other light emitting elements 12G and 12B, that is, green and blue light. The color filter 44G transmits light having a peak wavelength of light emitted from the light emitting element 12G on which it overlaps, that is, green light, more than light having a peak wavelength of light emitted from the other light emitting elements 12R and 12B, that is, red and blue light. Let The color filter 44B transmits more light having a peak wavelength of light emitted from the light emitting element 12B on which the color filter 44B overlaps, that is, blue light, than light having a peak wavelength of light emitted from the other light emitting elements 12R and 12G, that is, red and green light. Let As described above, each of the color filters 44 transmits more light having a peak wavelength of the light emitted from the corresponding light emitting element than light having other wavelengths, so that the purity of the target color can be improved. .

In addition, as described above with reference to FIG. 3, in the resonance structure, when light having a peak wavelength of emitted light is irradiated from the outside, this is hardly reflected. By superimposing a color filter on such a resonance structure, the light emitting device 10 can suppress the reflection of external light and increase the contrast. Specifically, the color filter 44R transmits light having a red wavelength out of external light and absorbs light having another wavelength, so that the red external light can reach the light emitting element 12R. However, since the resonance structure of the light emitting element 12R transmits red light remarkably and hardly reflects, the red light hardly travels from the light emitting element 12R to the color filter 44R. As a result, even if the color filter 44R is irradiated with external light, light of any wavelength is slightly reflected. Similarly, the color filter 44G transmits light having a green wavelength out of external light and absorbs light having other wavelengths, and the resonance structure of the light emitting element 12G hardly reflects green light. Even if it is irradiated, light of any wavelength is slightly reflected. Similarly, the color filter 44B transmits light having a blue wavelength out of external light and absorbs light having other wavelengths, and the resonance structure of the light emitting element 12B hardly reflects blue light. Even if it is irradiated, light of any wavelength is slightly reflected.

As shown in FIG. 1, in this embodiment, at a position closer to the substrate 14 than the light reflecting layer 22,
A TFT 16 for driving the light emitting element 12 is disposed, and a light shielding layer 20 covering the TFT 16 is disposed at a position closer to the TFT 16 than the light reflecting layer 22. In this configuration, the light reflecting layer 2
TFT 16 arranged at a position closer to the substrate 14 than 2 is TFT 16 than the light reflection layer 22.
It is covered with the light shielding layer 20 disposed at a position closer to the surface. Accordingly, the external light or the light emission of the light emitting element 12 is suppressed from reaching the TFT 16, and the photocurrent flows to the TFT 16, and the TFT
16 is prevented from malfunctioning.

In the embodiment shown in FIG. 1, the light shielding layer 20 does not overlap the central portion of each light reflecting layer 22, but the light shielding layer 20 may overlap the entire light reflecting layer 22.

The dielectric layer 24 having the above-described resonance structure is preferably formed from a transparent dielectric having a refractive index lower than that of the pixel electrode 26. If the refractive index of the material of the dielectric layer 24 is higher than that of the pixel electrode 26, out of the optical distance (the sum of the product of the refractive index and the thickness) from the light emitting position of the light emitting layer 32 to the light reflecting layer 22. The ratio of the optical distance of the dielectric layer 24 increases, and the pixel electrodes 26R, 26G, 26
The thickness of B must be reduced. On the contrary, the refractive index of the material of the dielectric layer 24 is the pixel electrode 2.
When it is lower than 6, the thickness of the pixel electrodes 26R, 26G, and 26B can be increased, and the pixel electrodes can be easily manufactured. From such a viewpoint, when the pixel electrode 26 is formed of ITO, for example, the material of the dielectric layer 24 is preferably silicon nitride, silicon oxide, silicon oxynitride, or acrylic resin. However, such a refractive index condition is not an absolute reference, and a material having a relatively high refractive index such as titanium oxide may be used for the dielectric layer 24.

As described above, in this embodiment, each of the pixel electrodes 26 has an area larger than that of the light reflection layer 22, and a light transmission portion (color filter 44) in which each of the light reflection layers 22 is formed in the light shielding film 40. It is possible to improve the purity of the target color. A simulation was conducted to confirm this effect.
The materials of the resonance structure and their thicknesses in the simulation were as in the above specific example. 5 and 6 show the results obtained by the simulation.

FIG. 5 shows a spectrum of light that has resonated in the resonance structure and transmitted through the counter electrode 36 due to light emission in the light emitting layer 32, that is, a spectrum of light that has not transmitted through the color filter 44 in the embodiment. In FIG. 5, the solid line is the spectrum of the emitted light from the resonance structure of the light emitting element 12R, the thick broken line is the spectrum of the emitted light from the resonance structure of the light emitting element 12G, and the thin broken line is the spectrum of the emitted light from the resonance structure of the light emitting element 12B. Represents.

FIG. 6 shows a spectrum of light further transmitted through the color filter 44 in the embodiment. The used color filter 44 has the transmission characteristics shown in FIG. In FIG. 6, the solid line is the spectrum of light emitted from the resonance structure of the light emitting element 12R and transmitted through the color filter 44R, and the thick broken line is the spectrum of light emitted from the resonance structure of the light emitting element 12G and transmitted through the color filter 44G. A broken line represents a spectrum of light emitted from the resonance structure of the light emitting element 12B and transmitted through the color filter 44B. The intensity of the vertical axis in FIGS. 5 and 6 indicates the intensity of the peak of the emitted light from the resonance structure of the light emitting element 12B that does not transmit the color filter 44B.
It is standardized as 0%.

NTS of light emitted from the resonance structure of the light emitting element 12R and transmitted through the color filter 44R
C (National Television Standards Committee) color coordinates are (0.666, 0.32)
7) The color coordinates of the light emitted from the resonance structure of the light emitting element 12G and transmitted through the color filter 44G are (0.229, 0.682), and are emitted from the resonance structure of the light emitting element 12B and transmitted through the color filter 44B. The color coordinates of the light were (0.133, 0.086). As a result, the NTSC ratio was calculated to be 100.5%.

For comparison, a comparative example in which the embodiment is modified as shown in FIG. 7 is assumed. In the comparative example of FIG. 7, the area of the third pixel electrode layer 28 c of the pixel electrodes 26 R, 26 G, and 26 B is the light reflecting layer 2.
The third pixel electrode layer 28 c just overlaps the light reflection layer 22. Other features are the same as in the embodiment of FIG. In the comparative example of FIG. 7, the area of the third pixel electrode layer 28c, which is the outermost of the layers constituting the pixel electrode, is equal to the area of the light reflecting layer 22, so that the pixel electrode 26R having the three-layer structure and the two-layer structure A portion having a non-uniform thickness near the edge of the pixel electrode 26 </ b> G overlaps the light reflecting layer 22. Therefore, the light reciprocating between the light reflecting layer 22 and the translucent counter electrode 36 of each light emitting element 12R, 12G passes through the edge of the pixel electrode 26 and the portion overlapping with this edge. That is, the edge of the pixel electrode 26 and a portion overlapping the edge are included in the resonance structure, and a portion where the optical distance is unstable is used as the resonance structure. In this way, light of other wavelengths is mixed with light of the target wavelength.

About this comparative example, it simulated similarly to the above. 8 and 9 show the results obtained by the simulation.

FIG. 8 shows a spectrum of light that has resonated in the resonance structure and transmitted through the counter electrode 36 due to light emission in the light emitting layer 32, that is, a spectrum of light that has not transmitted through the color filter 44 in the comparative example of FIG. . In FIG. 8, the solid line represents the spectrum of the emitted light from the resonance structure of the light emitting element 12R, the thick broken line represents the spectrum of the emitted light from the resonance structure of the light emitting element 12G, and the thin broken line represents the spectrum of the emitted light from the resonance structure of the light emitting element 12B. Represents.

As is clear from comparison between FIG. 5 and FIG. 8, the spectrum of the emitted light from the resonant structure of the light emitting element 12B is the same in the embodiment and the comparative example, but from the resonant structure of the light emitting element 12G in the comparative example. The blue component had more influence on the spectrum of emitted light. This is because the pixel electrode 26
This is because a portion where the thickness of B is unstable, particularly a portion suitable for resonance of the blue wavelength, was included in the resonance structure. In addition, the blue component and the green component have more influence on the spectrum of the emitted light from the resonance structure of the light emitting element 12R in the comparative example. This is because the portion where the thickness of the pixel electrode 26B is unstable, in particular, the portion suitable for the resonance of the blue wavelength and the portion suitable for the resonance of the green wavelength are included in the resonance structure. Thus, in the comparative example, the purity of the color obtained is inferior to that of the embodiment.

FIG. 9 shows a spectrum of light further transmitted through the color filter 44 in the comparative example of FIG. In FIG. 9, the solid line is the spectrum of light emitted from the resonance structure of the light emitting element 12R and transmitted through the color filter 44R, and the thick broken line is the spectrum of light emitted from the resonance structure of the light emitting element 12G and transmitted through the color filter 44G. A broken line represents a spectrum of light emitted from the resonance structure of the light emitting element 12B and transmitted through the color filter 44B. 8 and 9
The intensity of the vertical axis is normalized with the intensity of the peak of emitted light from the resonant structure of the light emitting element 12B not transmitting the color filter 44B as 100%. The use of the color filter made the color purity defect seen in FIG. 8 less noticeable, but the NTSC ratio was inferior to the embodiment and was calculated to be 85.6%.

<Modification>
The illustrated light emitting device uses an organic EL element, that is, an OLED element as a light emitting element.
It is not intended to limit the scope of the present invention to OLED elements, but inorganic EL elements, light emitting diodes or other suitable light emitting elements may be used. Further, the details of the structure of the exemplified light emitting device are specifically described in order to facilitate understanding of the present invention, and are not intended to limit the present invention, and may have other structures.

Although the illustrated light emitting device uses an OLED element having a low molecular type light emitting layer, an OLED element having a polymer type light emitting layer may be used in the present invention.

The illustrated light emitting device extracts light having a target wavelength from the white light emitted from the light emitting layer common to the light emitting elements to the outside by the resonance structure. However, in the present invention, a light emitting layer that emits R, G, and B light may be used, and each light emitting element may have any one of R, G, and B light emitting layers. Also in this case, the optical distance of the resonant structure is designed to amplify the light emitted by the light emitting layer of the corresponding light emitting element, so that the pixel electrodes having different thicknesses are the same as described above with respect to the embodiment. Is used.

<Electronic equipment>
Next, an electronic apparatus using the light emitting device according to the present invention will be described. FIG. 10 is a perspective view showing the configuration of a mobile personal computer that employs the light-emitting device 10 described above as a display device. The personal computer 2000 includes a light emitting device 10 as a display device and a main body 2010. The main body 2010 is provided with a power switch 2001 and a keyboard 2002.

FIG. 11 shows a configuration of a mobile phone to which the light emitting device 10 according to the embodiment is applied. The cellular phone 3000 includes a plurality of operation buttons 3001, scroll buttons 3002, and the light emitting device 10 as a display device. By operating the scroll button 3002, the screen displayed on the light emitting device 10 is scrolled.

FIG. 12 shows a personal digital assistant (PDA: Personal) to which the light emitting device 10 according to the embodiment is applied.
The structure of Digital Assistant) is shown. The information portable terminal 4000 includes a plurality of operation buttons 400.
1 and a power switch 4002 and a light emitting device 10 as a display device. When the power switch 4002 is operated, various types of information such as an address book and a schedule book are displayed on the light emitting device 10.

Electronic devices to which the light emitting device according to the present invention is applied include digital still cameras, televisions, video cameras, car navigation devices, pagers, electronic notebooks, electronic papers, calculators, in addition to those shown in FIGS. , Word processor, workstation,
Examples include a video phone, a POS terminal, a printer, a scanner, a copying machine, a video player, and a device equipped with a touch panel.

1 is a cross-sectional view illustrating a part of a full-color light emitting device according to an embodiment of the present invention. FIG. 2A is a plan view of one pixel of the light emitting device of FIG. 1, and FIG. 2B is a plan view of one pixel of the light emitting device of FIG. 1 with some components omitted. 2 is a graph showing a reflection spectrum of a resonance structure formed by each light emitting element in the light emitting device of FIG. 1. It is a graph which shows the transmission spectrum of the color filter used with the light-emitting device of FIG. 2 is a graph showing a spectrum of light that is resonated in a resonance structure due to light emission in a light emitting layer in the light emitting device of FIG. 1 but is not transmitted through a color filter. 2 is a graph showing a spectrum of light that resonates in a resonance structure due to light emission in a light emitting layer in the light emitting device of FIG. 1 and further passes through a color filter. It is sectional drawing which shows a part of light-emitting device of a comparative example. FIG. 8 is a graph showing a spectrum of light that is resonated in a resonance structure due to light emission in a light emitting layer in the light emitting device of FIG. 7 but is not transmitted through a color filter. 8 is a graph showing a spectrum of light that resonates in a resonance structure due to light emission in the light emitting layer in the light emitting device of FIG. 7 and further passes through a color filter. It is a perspective view which shows the specific form of the electronic device which concerns on this invention. It is a perspective view which shows the specific form of the electronic device which concerns on this invention. It is a perspective view which shows the specific form of the electronic device which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Light emitting device, 12R, 12G, 12B ... Light emitting element, 14 ... Substrate, 16 ... Thin film transistor (TFT), 18 ... Insulating layer, 20 ... Light-shielding layer, 22 ... Light reflecting layer, 24 ... Dielectric layer, 2
6R, 26G, 26B ... pixel electrode, 28a ... first pixel electrode layer, 28b ... second pixel electrode layer, 28c ... third pixel electrode layer, 30 ... hole transport layer, 32 ... light emitting layer, 34 ... Electron transport layer,
36 ... Counter electrode, 38 ... Transparent adhesive, 40 ... Light-shielding film, 42 ... Protection plate, 44R, 44G, 4
4B ... Color filter, 50 ... Pixel.

Claims (10)

A light reflecting layer having light reflectivity provided on the substrate;
A dielectric layer provided to cover the light reflecting layer;
A light-transmissive pixel electrode provided on the dielectric layer;
A light emitting layer provided on the pixel electrode;
A counter electrode having transflective properties provided on the light emitting layer,
At least a portion of the light emitted from the light emitting layer resonates between the light reflecting layer and the counter electrode;
The pixel electrode has an area larger than an area of the light reflection layer so as to cover the light reflection layer in a plan view;
A light-emitting device, wherein an insulating layer is not provided between an end portion of the pixel electrode and the light-emitting layer. The pixel electrode includes a first layer and a second layer stacked on the first layer,
In plan view, the first layer has an area larger than the area of the light reflection layer so as to cover the light reflection layer,
2. The light emitting device according to claim 1, wherein the second layer has an area larger than an area of the first layer so as to cover the first layer in a plan view. . The pixel electrode has a third layer stacked on the second layer,
3. The light emitting device according to claim 2, wherein the third layer has an area larger than an area of the second layer so as to cover the second layer in a plan view. . A protective substrate is provided on the counter electrode so as to face the substrate.
The protective substrate includes a color filter that transmits light emitted from the light emitting layer, and a first light shielding layer,
4. The light emitting device according to claim 1, wherein the first light shielding layer and the light reflection layer have a planarly overlapping portion. 5. A second light shielding layer is provided between the substrate and the light reflecting layer;
5. The light emitting device according to claim 1, wherein the second light shielding layer and the light reflection layer have a planarly overlapping portion.   A transistor electrically connected to the pixel electrode is provided between the second light shielding layer and the substrate so as to overlap the second light shielding layer in a plan view. The light emitting device according to claim 5. The pixel electrode includes a first pixel electrode and a second pixel electrode,
The light reflecting layer has a first light reflecting layer and a second light reflecting layer,
A first light emitting element having the first pixel electrode, the light emitting layer and the counter electrode provided at a position corresponding to the first light reflecting layer; and a position corresponding to the second light reflecting layer. A second light emitting element having the second pixel electrode, the light emitting layer and the counter electrode provided,
The light emitting device according to claim 1, wherein a film thickness of the first pixel electrode is different from a film thickness of the second pixel electrode. The pixel electrode has a third pixel electrode;
The light reflecting layer has a third light reflecting layer,
A third light emitting element including the third pixel electrode, the light emitting layer, and the counter electrode provided at a position corresponding to the third light reflecting layer;
The light emitting device according to claim 7, wherein a film thickness of the third pixel electrode is different from a film thickness of the first pixel electrode and the second pixel electrode.   The light emitting device according to claim 1, wherein the light emitted from the light emitting layer is emitted from the counter electrode side.   An electronic device comprising the light emitting device according to any one of claims 1 to 9.

Images