JP2012054091A - Multicolor display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multicolor display device which has a light load in manufacturing a substrate of the display device and high throughput in manufacturing the device, while having an excellent view angle characteristic.SOLUTION: Transparent conductive layers 25 and 26 composing a reflection electrode layer are formed with two kinds of different thicknesses, which is common to all pixels, so that regions 40 and 41 each having a different optical distance are set inside the pixel of each luminescent color. Furthermore, for a green pixel (or blue pixel), the areal ratio between the regions 40 and 41 having different optical distances is determined so that the view angle color shift relative to white display becomes minimum. And also, the blue pixel (or green pixel) is set so that the region of optical distance having the less view angle color shift for a blue monochrome (or green monochrome) has a larger area, and the red pixel is set so that the region of optical distance having the less view angle color shift for a red monochrome has a larger area.

Description

  The present invention relates to a display device using an organic light-emitting element (organic electroluminescence (EL) element) that emits light by applying a voltage to an organic compound layer including a light-emitting layer, and in particular, exhibits two or more different emission colors. The present invention relates to a multicolor display device including an organic light emitting element.

  The organic light emitting device includes an organic compound layer including a light emitting layer between an anode and a cathode. In the following description, the organic light emitting element may be simply referred to as “light emitting element” or “element”.

  FIG. 15 is a schematic view showing a laminated structure of a general organic light emitting device. In FIG. 15, the organic light emitting device includes a reflective layer 2, an anode (transparent conductive layer) 3, a hole transport layer 4, a light emitting layer 5, an electron transport layer 6, an electron injection layer 7, and a semitransparent layer on a substrate 1. 8 and a cathode (transparent electrode) 9 are sequentially provided. By passing a current through the organic light emitting element, the holes injected from the anode 9 and the electrons injected from the cathode 3 are recombined in the light emitting layer 5. The light emitting material of the light emitting layer 5 is excited by the energy generated during the recombination, and when the light emitting material returns to the ground state, the energy is emitted as light to emit light.

  In such an organic light emitting device, a part of light emission is reflected. As a result, an optical interference effect in which light of a specific wavelength resonates and is strengthened inside the organic light-emitting element appears remarkably.

  Specifically, a resonator structure is configured between the reflective layer 2 on the substrate 1 and the reflective interface of the translucent layer 8. Here, the optical distance between the reflective layer 2 and the reflective interface of the translucent layer 8 is L, the resonance wavelength is λ, the angle at which light emitted from the element is visually recognized is θ (0 ° when viewed directly facing the element) ). Further, when the sum of phase shifts when light is reflected by the upper and lower electrodes 3 and 9 is φ (rad) and the order of optical interference is m, the relationship satisfying the following formula (1) is satisfied between the parameters. If there is, a strengthening of light emission due to resonance occurs.

  That is, when the maximum peak wavelength of the emission spectrum (PL spectrum) generated by photoexcitation of the light emitting layer 5 is combined with the resonance wavelength, the intensity of the maximum peak wavelength of the emission spectrum emitted from the device can be increased. Hereinafter, in order to distinguish from the “PL spectrum”, the emission spectrum emitted from the element is referred to as “EL spectrum”.

    λ = 2L cos θ / (m−φ / 2π) (m is a positive integer) (1)

  In Expression (1), the optical distance L is the sum of values (nd products) obtained by multiplying the refractive index (n) and the film thickness (d) of each layer. In addition, when light emission is actually reflected by each electrode, the sum φ of the phase shift changes depending on the combination of the electrode material and the organic material constituting the reflective interface. The refractive index (n) of each layer can be measured using, for example, a spectroscopic ellipsometer.

  From the equation (1), the maximum peak wavelength (resonance wavelength) λ for strengthening varies with the optical distance L. Further, when the angle (viewing angle) θ viewed with respect to the element increases, the cos θ value decreases and the resonance wavelength λ shifts to the short wavelength side. Therefore, when the viewing angle for observing the element having the optical distance L is increased, the resonance wavelength shifts from the maximum peak wavelength of the emission spectrum (PL spectrum) of the light emitting layer, and as a result, the maximum peak wavelength of the EL spectrum. Can not be strengthened. In addition, the maximum peak wavelength is weakened, and there is a problem that it appears darker as the viewing angle increases.

  Furthermore, when the viewing angle increases, the resonance wavelength λ shifts to the short wavelength side (blue shift) as the cos θ value decreases, so that the color of the light emitting element appears to change.

  In view of this, an organic light emitting device has been proposed in which a portion having a different optical distance is provided in one light emitting device, and light emission having different viewing angle characteristics is combined to average and mitigate characteristic changes due to viewing angles (for example, patents). Reference 1). This patent document 1 discloses a green light emitting element in which the optical distance inside the light emitting element is changed, for example, the resonance wavelength and the order at a viewing angle of 0 degree are set to 510 nm / m = 2 and 570 nm / m = 1, respectively. Has been. In addition, an organic light emitting device is disclosed in which the area ratio of regions having different optical distances is optimized in one light emitting device to reduce the viewing angle dependency. Furthermore, an electroluminescence panel using these organic light emitting elements as light emitting pixels is disclosed.

JP 2006-32327 A (paragraph number [0036], FIG. 1)

  However, the organic light-emitting element constituting the electroluminescence panel of Patent Document 1 optimizes the optical distance in the pixel and the area ratio of regions having different optical distances so as to reduce the viewing angle dependency for each color. ing.

  As described above, in the organic light emitting device, a resonator structure is formed between the reflective layer on the substrate and the reflective interface of the semitransparent layer thereabove. However, since the light emitting layer that emits light is provided between the reflective layer and the translucent layer, the optical distance related to the resonance of light emission is mainly the optical distance from the light emitting layer to the reflective layer. Two types of optical distances from the reflective layer to the reflective interface of the translucent layer are affected. The optical characteristics of the organic light emitting element can be adjusted by these two kinds of parameters.

  Therefore, in a display device including a plurality of organic light emitting elements of light emission colors, it is preferable to optimize the light emission characteristics individually for each color if there are at least two types of optical characteristic adjustment parameters for each color.

  Such a change in the optical distance can be adjusted by changing the film thickness and material of the transparent conductive layer on the reflective layer, each organic compound layer, and the semitransparent layer on the organic compound layer. In the organic light-emitting device described in Patent Document 1, the optical distance is adjusted by adjusting the film thickness of the transparent electrode provided on the substrate side of the device to two types and adjusting the light-emitting area. Therefore, for example, when an RGB three-color full-color panel is to be realized by the technique of Patent Document 1, at least six types of transparent electrodes having different thicknesses are required for one panel.

  In order to change the film thickness of the transparent electrode in one pixel in this way, for example, a technique such as photolithography is used, but at that time, the number of photolithography processes corresponding to the number of types of film thickness to be manufactured is required. It becomes.

  Therefore, when the organic light-emitting element described in Patent Document 1 is applied as a light-emitting pixel of a multicolor display device, there is a problem that a load for manufacturing a substrate for the display device is increased and throughput of manufacturing the multicolor display device is reduced. there were.

  Furthermore, Patent Document 1 improves the viewing angle characteristics of the chromaticity of each color of RGB, and does not necessarily improve the viewing angle characteristics of the chromaticity of a color (for example, white) synthesized with RGB. The RGB composite color is determined by each chromaticity and luminance of RGB, and even if the chromaticity change is small, if the luminance change is different for each RGB, the viewing angle characteristics of the composite color are deteriorated. Conversely, even if the chromaticity change is large for each color, it is possible to improve the viewing angle characteristics of the chromaticity of the composite color by adjusting the luminance change.

  An object of the present invention is to provide a multicolor display device that can reduce the substrate manufacturing load of the display device and increase the throughput of device manufacturing while providing good viewing angle characteristics. To do.

  The configuration of the present invention made to achieve the above object is as follows.

That is, in the multicolor display device according to the present invention, a plurality of pixels composed of multicolor organic light emitting elements including at least R (red), G (green), and B (blue) are arranged on a substrate, The organic light emitting device is a multicolor display device having an organic compound layer including a light emitting layer between a reflective electrode layer and a translucent electrode layer,
The transparent conductive layer constituting the reflective electrode layer has two different thicknesses in common for all the pixels so that regions having different optical distances are set inside each light emitting color pixel,
Further, for the green pixel (or blue pixel), the area ratio of the regions having different optical distances is determined so that the viewing angle color shift with respect to the white display is minimized,
In blue pixels (or green pixels), the area of the optical distance region with a small viewing angle color shift of blue single color (or green single color) is large, and in the red pixels, the area of the optical distance region with a small viewing angle color shift of red single color is large. The multicolor display device is characterized by being set to be large.

  According to the present invention, since the thickness of the transparent conductive layer constituting the reflective electrode layer is formed in two different thicknesses in all the pixels on the display device, the number of processes is larger than that of the conventional display device. Less.

  In addition, for green pixels (or blue pixels), the area ratio of the regions having different optical distances is determined so that the viewing angle color shift with respect to white display is minimized. Furthermore, in blue pixels (or green pixels), the area of the optical distance region with a small viewing angle color shift of blue single color (or green single color) is large, and in the red pixels, the area of the optical distance region with a small viewing angle color shift of red single color. Is set to be large. Therefore, there is an excellent effect that it is possible to realize a multicolor display device having a good viewing angle characteristic, reducing the load for manufacturing a substrate of the display device, and having a high device manufacturing throughput.

It is a schematic diagram which shows the laminated structure of one Embodiment of the multicolor display apparatus which concerns on this invention. It is explanatory drawing which shows the chromaticity change characteristic by the viewing angle of a green light emission pixel. It is explanatory drawing which shows the chromaticity change characteristic by the viewing angle of a blue light emission pixel. It is explanatory drawing which shows chromaticity variation | change_quantity (delta) xy when the area ratios of the area | region where the transparent conductive layer film thickness differs in a green pixel are each varied. It is explanatory drawing which shows the relationship between the area ratio similar to a green pixel, and the chromaticity variation | change_quantity (delta) xy of synthetic light in a blue light emitting pixel. It is explanatory drawing which shows the relationship between the area ratio similar to a green pixel, and the chromaticity variation | change_quantity (delta) xy of synthetic light in a red light emitting pixel. It is explanatory drawing which shows the resonance wavelength change by the viewing angle of m = 2 and 1 in the green light emission pixel of 10 nm of transparent conductive layers. It is explanatory drawing which shows the resonant wavelength change by the viewing angle of m = 3 and 2 in the case of the transparent conductive layer 125nm. It is explanatory drawing which shows the chromaticity change characteristic by the viewing angle of the green light emission pixel in the display apparatus whose thickness of a transparent conductive layer is 24 nm and 165 nm. It is explanatory drawing which shows chromaticity variation | change_quantity (delta) xy when the area ratios of the area | region where the transparent conductive layer film thickness differs in the green pixel in a display apparatus with thickness 24nm and 165nm of a transparent conductive layer differ, respectively. It is explanatory drawing which shows the relationship between the area ratio similar to a green pixel, and the chromaticity variation | change_quantity (delta) xy of synthetic light in the blue light emission pixel in the display apparatus whose thickness of a transparent conductive layer is 24 nm and 165 nm. It is the schematic which shows an example of the pixel arrangement | positioning of the multi-color display apparatus of this embodiment. It is a figure which shows an example of pixel arrangement | positioning of the multi-color display apparatus of this embodiment. It is a figure which shows an example of pixel arrangement | positioning of the multi-color display apparatus of this embodiment. It is a schematic diagram which shows the laminated structure of a general organic light emitting element.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. For convenience of explanation, each layer is shown in a recognizable size in the drawing, and the scale of the drawing is different from the actual one. In addition, well-known or publicly known techniques in the technical field are applied to portions that are not particularly illustrated or described in the present specification.

  FIG. 1 is a schematic diagram showing a laminated structure of an embodiment of a multicolor display device according to the present invention. In FIG. 1, when layers having the same name have a two-layer structure, for convenience of explanation, the two layers are denoted by reference symbols A and B.

  In the multicolor display device exemplified in this embodiment, a plurality of light emitting pixels made of multicolor organic light emitting elements including at least R (red), G (green), and B (blue) are arranged on a substrate 20. This is a top emission type active matrix display device. Specifically, the multicolor display device of the present embodiment includes RGB light emitting pixels, and the organic light emitting element of each light emitting color includes an organic compound layer including a light emitting layer between a reflective electrode layer and a translucent electrode layer. Is formed. In the following description, although simply referred to as “pixel” or “light emitting pixel”, a set of three colors of RGB is a main pixel, and each light emitting pixel of R, G, and B is a sub pixel.

  As shown in FIG. 1, a TFT drive circuit 21, a planarizing film 22, a contact hole 23, a reflective layer 24, and a transparent conductive layer A25 are provided on a substrate 20. The transparent conductive layer A25 is formed to have a common film thickness for each of the RGB light emitting pixels (sub-pixels). Further, a transparent conductive layer B26 having a film thickness common to the respective light emitting pixels is formed in a partial region on the transparent conductive layer A25 of each light emitting pixel. The reflective layer 24 and the transparent conductive layers A25 and B26 constitute the reflective electrode layer.

  On the transparent conductive layer A25 and the transparent conductive layer B26, a hole transport layer A27 having a common film thickness for each RGB light emitting pixel and a hole transport layer B28 having a different film thickness for each light emitting pixel are formed. Has been. That is, the total film thickness of the hole transport layers A27 and B28 is individually set for each emission color. In the present invention, the hole transport layer B28 may have a common film thickness for each emission color. Further, the hole transport layer B28 may be configured not to be provided depending on the emission color.

  On the hole transport layer B28 having different thicknesses, a red light emitting layer 29, a green light emitting layer 30, and a blue light emitting layer 31 are formed for each RGB light emitting pixel. Further, the light emitting layers 29, 30, and 31 having different emission colors of RGB are set to individual film thicknesses.

  On each light emitting layer 29, 30, 31, an electron transport layer 32 and an electron injection layer 33 are formed in common for each light emitting pixel. On the electron injection layer 33, an electrode A34 and an electrode B35 constituting the translucent electrode layer are formed.

  An element isolation film 36 that separates the colors is formed between the RGB light emitting pixels. A sealing member 38 is formed on the thus formed multicolor light emitting element via a sealing space 37 filled with dry nitrogen.

  In this multicolor organic light emitting device, a current is passed using the transparent conductive layer A25 and the transparent conductive layer B26 as an anode and the electrode A34 and the electrode B35 as a cathode. Then, the holes injected from the transparent conductive layer A25 and the transparent conductive layer B26 to the hole transport layer A27 and the hole transport layer B28 and the electrons injected from the electrode A34 and the electrode B35 to the electron injection layer 33 are each color. The light emitting layers 29, 30, and 31 are moved to recombine. The light-emitting material of the light-emitting layers 29, 30, and 31 is excited by the energy generated during the recombination, and when the light-emitting material returns to the ground state, energy is emitted as light, and the device emits light. The light emitted at this time is emitted to the outside of the element through the electrode A34 and the electrode B35.

  In the multicolor display device of the present embodiment, a plurality of such multicolor organic light emitting elements are arranged on the substrate 20 in a matrix. Although the board | substrate 20 is not specifically limited, A metal, ceramics, glass, quartz, etc. are used. In addition, by using a flexible sheet such as a plastic sheet as the substrate 20, a flexible display device can be formed.

  As the reflective layer 24, a layer made of a material having a reflectance in the wavelength range of visible light at the interface with the transparent conductive layer A25 of at least 50% or more, preferably 80% or more is desirable. Examples of materials that satisfy this condition include metals such as aluminum, silver, and chromium, and alloys thereof. The reflective layer 24 does not need to be made of a conductive member such as metal, and an insulating member such as a dielectric multilayer mirror can be used as the reflective layer.

  As the transparent conductive layer A25 and the transparent conductive layer B26, for example, a metal oxide conductive film, specifically, an indium tin oxide (ITO) film, an indium zinc oxide (IZO (trademark)) film, or the like is used. Although it can, it is not limited to these. The term “transparent” means having a transmittance of 70% to 100% with respect to visible light. As conditions for the transparent conductive layer A25 and the transparent conductive layer B26 that satisfy transparency, the transparent conductive layer A25 and the transparent conductive layer have an extinction coefficient κ of 0.05 or less, preferably 0.01 or less. This is preferable from the viewpoint of suppressing attenuation of light emitted by B26.

  The transparent conductive layer A25 and the transparent conductive layer B26 can be formed by sputtering, for example, but are not limited thereto. In addition, forming only the transparent conductive layer A25 in a part of the inside of the light emitting pixel and forming the transparent conductive layer A25 and the transparent conductive layer B26 in the other area uses, for example, a general-purpose photolithography method. It is possible to cope with it. If necessary, an insulating resin member may be provided in the stepped portion of the transparent conductive layer A25 and the transparent conductive layer B26. By comprising in this way, it can avoid that the transparent conductive layer and electrode A34 of a light emitting element short-circuit at a level | step-difference part.

  The organic compounds used for the hole transport layers A27 and B28, the red light emitting layer 29, the green light emitting layer 30, the blue light emitting layer 31, the electron transport layer 32, and the electron injection layer 33 are composed of a low molecular material or a polymer material. However, it may be composed of both, and is not particularly limited. Moreover, a well-known material can be used as needed.

  In FIG. 1, an organic compound layer of a five-layer type (hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer) is illustrated. Without being limited thereto, the organic compound layer is a single layer type (light emitting layer), two layer type (hole transport layer / light emitting layer), three layer type (hole transport layer / light emitting layer / electron transport layer), four layers. Any configuration of the type (hole injection layer / hole transport layer / light emitting layer / electron injection layer) may be used. The number of organic compound layers and the stacking order are appropriately determined depending on the configuration of the electrodes.

  The organic compound layer is generally formed by a known coating method (for example, spin coating, dipping, casting method, ink jet method, etc.) after being dissolved in a vacuum deposition method, ionization deposition method, sputtering, plasma, or an appropriate solvent. .

  As the electron injection layer 33, for example, a commonly used electron injection material such as lithium fluoride, alkali metal, or alkaline earth metal can be used. Alternatively, the electron-injecting layer 33 may be formed by adding an alkali metal, an alkaline earth metal, or a compound thereof to the electron-transporting organic compound material in an amount of 0.1% to several tens of percent. At this time, it is preferable to set the film thickness of the electron injection layer 33 to about 10 to 100 nm because film formation damage of the electrode A34 and the electrode B35 to be formed thereafter can be reduced.

  The electrode A34 and the electrode B35 are required to have light transmittance in order to extract the light emitted from the light emitting layers 29, 30, and 31 to the outside of the element. Further, it is preferable to apply a thin film metal electrode to the electrode A34 so as to be a semitransparent electrode layer because a resonator structure is formed with the reflective layer 24 provided on the substrate side. In the present embodiment, a configuration in which the electrode A34 is a semitransparent electrode layer is employed, and a plurality of light transmission layers and light emitting layers 29, 30, and 31 are provided between the reflective layer 24 and the semitransparent electrode layer A34. When a metal thin film is used as the electrode A34, it is desirable that the film thickness is 5 nm to 30 nm, preferably 5 nm to 20 nm, from the viewpoint of transmittance. Further, the electrode A34 may have a two-layer structure of a metal oxide conductive film and a metal thin film.

  Further, as the electrode B35, a metal oxide conductive film can be used similarly to the transparent conductive layer A25 and the transparent conductive layer B26. In the case of using a metal oxide conductive film, the thickness of the electrode B35 is preferably set in the range of 10 nm to 1000 nm, preferably 30 nm to 300 nm, from the viewpoint of sheet resistance and transmittance of the electrode. If sufficient resistance is obtained with the electrode A34, the electrode B35 is not essential. These electrodes A34 and B35 can be formed by a known method such as sputtering. A layer such as an optical adjustment layer may be formed on the electrode A34 and the electrode B35.

  Instead of sealing by sealing a gas with a material such as glass or metal, sealing may be performed by directly covering and sealing with an inorganic material or an organic material, or a multilayer film thereof. The sealing member 38 is provided for the purpose of protecting the element from oxygen and moisture in the external environment. For example, glass, a gas impermeable film, a metal, or the like can be used. Further, in order to improve the moisture proof performance, a hygroscopic material (not shown) may be disposed in the sealed space 37.

  Further, instead of filling the sealed space 37 between the sealing member 38 and the organic light emitting element with dry nitrogen, a protective film may be formed directly on the element. As this protective film, for example, a metal nitride film such as silicon nitride or silicon nitride oxide, a metal oxide film such as tantalum oxide, a diamond thin film, a resin film, or the like can be used as a single film or a plurality of films. . In this case, a thinner organic light emitting device is obtained, which is particularly preferable.

  The transparent conductive layers A25 and B26 in FIG. Alternatively, the transparent conductive layers A25 and B26 may be reversed in order, and the underlying transparent conductive layer B26 may be an insulating transparent film. In this case, the holes from the anode side are supplied by the transparent conductive layer A25 located above.

  Next, the light emission characteristics of the multicolor display device according to the present invention will be described. Table 1 below shows the film thickness of each layer constituting the multicolor display device of this embodiment.

  In the multicolor display device of this embodiment, the transparent conductive layer is formed in each light emitting pixel in two thicknesses of 10 nm and 125 nm (10 + 115 nm). The film thicknesses of the hole transport layer B and the light emitting layer are changed for each emission color, but the film thicknesses of the other hole transport layer A, electron transport layer, electron injection layer, electrode A and electrode B are as follows: It is common regardless of the emission color. Moreover, the organic compound layer and the electrode to be formed are formed with the same film thickness for each emission color on the transparent conductive layer. Therefore, there are three types of RGB individual film thicknesses, additional transparent conductive layer film thicknesses, and film thicknesses for each color common layer as the degree of freedom of optical characteristic adjustment, and there are a total of five types of optical characteristic adjustment parameters for the display device. .

  In each light emitting pixel, a region having a different thickness of the transparent conductive layer is formed. Therefore, in a region where the transparent conductive layer is thick and a thin region in the pixel, between the reflective layer and the electrode A and the electrode B, The optical distance of the formed resonator structure is different. Therefore, the resonance wavelength λ shown by the above-described equation (1) changes, and the light emission characteristics generated from the thick and thin regions of the transparent conductive layer in each light emitting pixel are different.

  Table 2 below shows the chromaticity of light emission in the respective regions where the transparent conductive layer is 10 nm and 125 nm in each color light emitting pixel. As shown in Table 2, since the optical distance of the resonator structure varies depending on the film thickness of the transparent conductive layer and the resonance wavelength changes, the light emission chromaticity of each region in the light emitting pixel varies.

By the way, although depending on the resolution, one light emitting pixel is as small as about 190 μm in the case of a 3 inch diagonal display device with QVGA resolution and about 95 μm in the case of display device with VGA resolution. Therefore, the light emission characteristics visually recognized from one light emitting pixel are equivalent to those obtained by combining the light emission characteristics of the respective regions. The combined chromaticity (x, y) in each light emitting pixel is as follows when the chromaticity coordinates and the brightness are (x ₁ , y ₁ , Y ₁ ) and (x ₂ , y ₂ , Y ₂ ), respectively. It is calculated | required by the formula of Formula 1.

  Table 3 below shows the combined chromaticity of each color light emitting pixel when the light emission characteristics of each region in each color light emitting pixel are combined at an area ratio of 1: 1 in the pixel.

  As shown in Table 3, the composite characteristic of each light emitting pixel is determined by the light emission characteristic in each region inside each light emitting pixel.

  FIG. 2 is an explanatory diagram showing chromaticity change characteristics depending on the viewing angle (0 to 85 °) of the green light emitting pixel. In the region of the transparent conductive layer 10 nm, the chromaticity changes in the left direction on the chromaticity diagram as the viewing angle is tilted from the front chromaticity coordinates (0.265, 0.680). On the other hand, in the region of the transparent conductive layer 125 nm, the chromaticity changes counterclockwise on the chromaticity diagram from the front chromaticity coordinates (0.177, 0.734). Further, the synthesized chromaticity obtained by synthesizing them 1: 1 changes from the chromaticity coordinates (0.230, 0.702) to the left in the chromaticity diagram.

The amount of change in chromaticity due to the viewing angle of the synthesized light is evaluated by the amount of change in chromaticity δxy calculated from the following formula 2. The chromaticity change amount δxy indicates the chromaticity when the apparatus is observed from the front and the change amount of chromaticity when the apparatus is observed from the viewing angle of 50 degrees. In the following formula 2, (x ₀ , y ₀ ) is chromaticity when the apparatus is observed from the front, and (x ₅₀ , y ₅₀ ) is chromaticity when the apparatus is observed from a viewing angle of 50 degrees.

  FIG. 3 is an explanatory diagram showing the chromaticity change characteristic depending on the viewing angle of the blue light emitting pixel. The blue light emitting pixel, together with the green light emitting pixel, has a large influence of the viewing angle color shift on the white display of the display device. It can be seen that the chromaticity change characteristic of the blue light-emitting pixel changes upward as if drawing an arc from the lower left.

  FIG. 4 is an explanatory diagram showing the chromaticity change amount δxy when the area ratios of the regions having different transparent conductive layer thicknesses in the green pixel are made different. As shown in the chromaticity change curve of FIG. 4, it is possible to adjust the viewing angle characteristics of the synthesized light, that is, the light emitting pixels, by adjusting the area ratio of the regions having different transparent conductive layer thicknesses. Further, the amount of change in chromaticity of the combined light with the adjusted area ratio is set to be smaller than 0.085 and 0.164 of each chromaticity change when the transparent conductive layer has an area ratio of 10 nm and 125 nm as 100%. be able to.

  FIG. 5 is an explanatory diagram showing the relationship between the area ratio similar to that of the green pixel and the chromaticity change amount δxy of the combined light in the blue light emitting pixel. As shown in FIG. 5, in the blue pixel, the chromaticity change amount δxy increases uniformly as the area ratio of the transparent conductive layer of 125 nm increases.

  In this way, it is possible to adjust the change in the emission color depending on the viewing angle by changing the area ratio of regions having different optical distances. Therefore, this area ratio was taken as a parameter for adjusting the optical characteristics of the display device, and the display device of this embodiment obtained a total of six types of adjustment parameters, including the five adjustment parameters based on the film thickness.

By the way, the multicolor display device as in the present embodiment is mainly used as a display of a television, a mobile phone, a digital camera, a video camera, or the like. In such usages, rather than using each light-emitting pixel alone to display the primary color, the light from each color light-emitting pixel is additively mixed to display, for example, an intermediate color such as white or skin color. Is common. For example, the chromaticity (x, y) of the combined light emission obtained by additively mixing three colors of RGB is the light emission chromaticity and brightness of each light emitting pixel, R (x ₁ , y ₁ , Y ₁ ), G (x ₂ ), respectively. , Y ₂ , Y ₂ ), B (x ₃ , y ₃ , Y ₃ )

  As described above, in the multicolor display device of this embodiment, the viewing angle color shift during white display is reduced by using six types of adjustment parameters. More specifically, the viewing angle color misregistration of white display is reduced by adjusting the area ratio of the two different transparent conductive layer thicknesses, the individual color layers, the common color layer thicknesses, and the regions having different optical distances in each light emitting pixel. .

  In this embodiment, the green light-emitting pixel is set to an area ratio that reduces the total viewing angle color shift of the light-emitting pixels by combining light emission from the two regions. Further, for the blue light emitting pixel, when the chromaticity change amount δxy of the transparent conductive layer 10 nm is smaller than that of the transparent conductive layer 125 nm and the area ratio of the transparent conductive layer 10 nm is set to be large, the total viewing angle color shift of the blue light emitting pixel is reduced. it can. Therefore, the transparent conductive layer is set so as to increase the area of 10 nm.

  The area ratio is not necessarily set so that the viewing angle color shift for each emission color is minimized, and the area ratio is selected from the viewpoint of reducing the viewing angle color shift of white display of the display device.

  In the present embodiment, the area ratios of the transparent conductive layers of 10 nm and 125 nm are set as shown in Table 4 below within each color light emitting pixel.

  At this time, the luminance ratio of each color light emitting pixel is set to red: green: blue = 27.8: 64.4: 7.8, and when the display device is viewed from the front, white corresponding to a color temperature of 6500 k is displayed. Adjusted to display. The individual color layers and the area ratio of red are adjusted so that the change in chromaticity of the viewing angle in white display is minimized, and thus the viewing angle characteristics of the chromaticity of a single red color are not minimized as described above. When this display device calculates the color shift amount up to a viewing angle of 50 degrees as a change amount δu′v ′ in the u′v ′ color space, it shows a very small value of 0.0009 (in Example 1 described later). (See Table 10).

  In general, since the color change amount δu′v ′ allowed in the u′v ′ space is about 0.02, the display apparatus according to the present embodiment can significantly suppress color misregistration in the viewing angle, and has a favorable viewing angle. It can be said that the display device has characteristics.

In addition, δu′v ′ is calculated by the following formula 4. In Equation 4, (u ′ ₀ , v ′ ₀ ) is the chromaticity in the u′v ′ color space when the apparatus is observed from the front, and (u ′ ₅₀ , v ′ ₅₀ ) is the viewing angle of 50 degrees. It is chromaticity when observed from.

  In addition, the setting of the viewing angle color shift like the green pixel of this embodiment can be applied to the light emitting pixels of other colors by adjusting the optical distance and the area ratio. However, the luminance ratio at the time of white display is higher for green light emitting pixels than for pixels of other colors. For this reason, the viewing angle characteristics of the green light-emitting pixels have a great influence on the viewing angle characteristics of the entire display device, and thus it is particularly preferable to set the green pixels to such a setting.

  Furthermore, the optical constant of each layer constituting each pixel changes steeply in the vicinity of the blue wave height wavelength. Therefore, in the blue light-emitting pixel, when the viewing angle is changed, the optical distance of the resonator structure is also greatly changed as compared with the other light-emitting color pixels, and the characteristic variation due to the viewing angle is large. Therefore, the blue light emitting pixels may be set so that the total pixel color shift is reduced as in the green light emitting pixels of the present embodiment.

  FIG. 6 is an explanatory diagram showing the relationship between the area ratio of red pixels and δxy. The area ratio of the regions having different optical distances in the red pixel is determined for the purpose of adjusting the change in the viewing angle chromaticity in the white display of the display device, and does not optimize the viewing angle characteristics of the red pixel single color. That is, as shown in FIG. 6, δxy is not necessarily minimized in the red pixel because of the balance between the color shift of the green pixel and the blue pixel.

  Note that the change in the area ratio of each color light emitting pixel can be simultaneously performed in a photolithography process in which different regions of the transparent conductive layer are formed inside the pixel. Therefore, two adjustment parameters can be increased by adding one process without adding a special process, which is preferable.

  Further, without changing the area ratio inside the transparent conductive layer and the light emitting pixel as in the present embodiment, for example, the organic compound layer is changed in film thickness other than the hole transport layer B28 and the light emitting layer for each emission color. It is also possible to increase the adjustment parameters. However, since, for example, mask vapor deposition or the like is required for the number of necessary parameters, it becomes a problem from the viewpoint of the throughput of manufacturing the display device.

  Here, in this embodiment, the film thicknesses of 10 nm and 125 nm are selected as the transparent conductive layer in order to apply optical interference conditions of different orders. That is, in the above-described formula (1), the wavelength λ strengthened by the optical interference effect inside the element is the optical distance L, the viewing angle θ (0 ° when facing the element), and the phase at the light reflection interface. It is determined by the structural parameters of the element such as the shift sum φ and the order m of the optical interference. These optical constants can be measured using, for example, a spectroscopic ellipsometer.

The phase shift φ at the reflection interface is defined as a material on the light incident side of the two layers forming the interface, medium I, and the other material as medium II, and the optical constants (n ₁ , If k ₁ ) and (n ₂ , k ₂ ), they can be expressed by the following relational expression (2).

φ = tan ⁻¹ (2n ₁ k ₂ / (n ₁ ² −n ₂ ² −k ₂ ² )) (2)

  In the multicolor display device of the present embodiment, for example, the refractive index of each layer is the organic compound layer 1.85, the light transmission layer (transparent conductive layer) 1.92, the refractive index of the anode 0.12, and the extinction coefficient 3. 46. In this case, the resonance wavelength of optical interference generated between the light emitting region inside the light emitting layer and the anode is calculated from the relational expression (1) using the film thickness shown in Table 1. The resonance wavelength of the light transmission layer (transparent conductive layer) having a thickness of 10 nm is shown in Table 5 below, and the resonance wavelength of 125 nm in thickness is shown in Table 6 below.

  In the calculation of the resonance wavelength in Table 5 and Table 6 below, the light emitting region inside the light emitting layer is the light emitting layer center in the red light emitting pixel, and the light emitting layer-electron transport layer interface in the green and blue light emitting pixels. And the optical distance between the anode and the anode.

  From Tables 5 and 6, the resonance wavelength of optical interference varies depending on the thickness of each organic compound layer, the transparent conductive layer, the order of optical interference, and the viewing angle.

  The m = 2 condition in Table 5 and the m = 3 condition in Table 6 have a resonance wavelength difference of about 18 to 67 nm, which is a substantially equivalent optical interference condition.

  In this embodiment, the thickness of the organic compound layer is the same except for the hole transport layer B, but the thickness of the transparent conductive layer is set so that the order of optical interference is different and the resonance wavelength is equal. Set.

  Also consider the change in resonant wavelength with viewing angle. The change in resonance wavelength varies depending on the thickness of the transparent conductive layer. For example, FIG. 7 shows a change in resonance wavelength according to a viewing angle of m = 2 and 1 in a green light emitting pixel having a transparent conductive layer of 10 nm. Similarly, FIG. 8 shows the change in resonance wavelength depending on the viewing angle of m = 3 and 2 when the transparent conductive layer is 125 nm.

  In the front of the apparatus, the resonance wavelength at 491 nm (FIG. 7 m = 2 condition) and 473 nm (FIG. 8 m = 3 condition) shifts to a short wavelength as the viewing angle changes. In both cases, in the viewing angle region of about 30 degrees or more, the resonance wavelength is shorter than the visible wavelength region. Further, in the region where the viewing angle is 30 degrees or more, the resonance wavelength in the m = 1 condition (FIG. 7) and m = 2 condition (FIG. 8), which is lower than the front, is in the green wavelength region (500 to 600 nm). It will overlap. Therefore, in the region up to a viewing angle of 30 degrees, the chromaticity depends on the resonance wavelength change under a higher order condition, and in the region of 30 degrees or more, the chromaticity depends on the resonance wavelength change in a lower order condition than the front. Changes.

  The influence of the resonance wavelength having a lower order than the front is more pronounced when the transparent conductive layer is 125 nm, and the chromaticity change of the transparent conductive layer 125 nm shown in FIG. This is caused by a combination of interference conditions.

  On the other hand, in the case of the transparent conductive layer of 10 nm, the influence of the interference condition having a lower order than the front is slight, and the change in chromaticity mainly shifts the resonance wavelength under the condition of m = 2 to the short wavelength side with the viewing angle. Due to influence. Therefore, FIG. 2 shows a state in which the chromaticity changes uniformly from right to left.

  Therefore, the chromaticity of the synthesized light obtained by mixing the element of the transparent conductive layer 10 nm and the element of the transparent conductive layer 125 nm is a mixture of two kinds of elements, each of which changes in chromaticity in approximately opposite directions depending on the viewing angle. Therefore, the chromaticity change as a composite color can be reduced.

  Further, the film thickness of the transparent conductive layer may be any combination other than 10 nm and 125 nm as long as the resonance wavelength satisfies the above relationship. However, in order to reduce the chromaticity of the synthesized light obtained by mixing the two types of elements, it is effective if the combination is such that the two types of elements change in approximately opposite directions depending on the viewing angle. . Therefore, although it is difficult to limit the numerical value, the transparent conductive layer is preferably 10 nm to 200 nm from the viewpoints of manufacturability and miniaturization.

  For example, even with a laminated structure as shown in Table 7 below, characteristics equivalent to the above can be obtained.

  The area ratio of the light emitting pixels of each light emitting color of the display device having such a stacked structure is shown in Table 8 below. The chromaticity of each light emitting color of this display device and the amount of white color deviation δu′v ′ at a viewing angle of 50 degrees are shown in Table 8 below. Each is shown in Table 9 below.

  Further, FIG. 9 is an explanatory diagram showing changes in chromaticity when the viewing angle is changed in the range of 0 to 80 degrees in the green light emitting pixel of the display device when the film thickness of the transparent conductive layer is 24 nm and 165 nm. . As shown in FIG. 9, a display device having a transparent conductive layer thickness of 24 nm and 165 nm can exhibit a change in chromaticity of the composite color due to the same effect as a display device having a transparent conductive layer thickness of 10 nm and 125 nm. It can be made smaller. That is, as shown in Table 7 and FIG. 9, the same tendency is shown even if the film thickness and level difference of the transparent conductive layer are different.

  FIG. 10 is an explanatory diagram showing the characteristics of the area ratio and chromaticity change amount δxy of the green light emitting pixels of the display device having the laminated structure shown in Table 7. FIG. 11 is an explanatory diagram showing the characteristics of the area ratio and chromaticity change amount δxy of the blue light emitting pixels of the display device having the laminated structure shown in Table 7. As shown in FIGS. 10 and 11, the characteristic of the chromaticity change amount δxy appears in the same tendency even when the film thickness and the step (difference in film thickness) of the transparent conductive layer are different.

  12 to 14 are schematic views illustrating pixel arrangements of the multicolor display device of this embodiment. In these drawings, reference numeral 40 denotes a portion of the optical region A in a region having a different optical distance, and reference numeral 41 denotes a portion of the optical region B in a region having a different optical distance.

  The arrangement of the regions 40 and 41 having different optical distances inside the light emitting pixels is not particularly limited. As shown in FIG. 12, the regions 40 and 41 having different optical distances are arranged with the same area ratio and the same arrangement regardless of the light emitting pixels. May be.

  Further, it is more preferable that the regions having different optical distances are arranged so as to avoid moiré and unevenness. As an appropriate arrangement, for example, the regions 40 and 41 having different optical distances shown in FIG. 13 have main pixel units having a plurality of emission colors (the same pixel area ratio and arrangement between adjacent pixels of the same color). It is preferable to change the mutual positions of the regions 40 and 41 alternately (staggered) in units of RGB (main pixel unit consisting of three colors). Furthermore, the areas 40 and 41 having different optical distances shown in FIG. 14 are arranged in the same positions in the area ratio and the arrangement of adjacent pixels of the same color, while the sub-pixels of different emission colors have the mutual positions of the areas 40 and 41. Is preferably changed alternately (staggered).

  As described above, in the multicolor display device of this embodiment, the thickness of the transparent conductive layers A25 and B25 constituting the reflective electrode layer is set to two different thicknesses (10 nm) in all the pixels on the display device. , 125 nm). Therefore, the number of processes is reduced as compared with the conventional display device.

  Further, the area ratio of the regions 40 and 41 having different optical distances is determined so that the viewing angle color shift with respect to the white display is minimized with respect to the green pixel (or blue pixel). Furthermore, in blue pixels (or green pixels), the area of the optical distance region with a small viewing angle color shift of blue single color (or green single color) is large, and in the red pixels, the area of the optical distance region with a small viewing angle color shift of red single color. Is set to be large. Therefore, it is possible to reduce a load for manufacturing a substrate of the display device, realize a multi-color display device having high device manufacturing throughput and good viewing angle characteristics.

  Further, as shown in FIGS. 13 and 14, by alternately arranging two types of regions 40 and 41 having different optical distances in adjacent pixels, the viewing angle characteristics of the chromaticity of the composite color can be improved, and the image quality is good. A multi-color display device can be realized.

  The preferred embodiment of the present invention has been described above. However, this is merely an example for explaining the present invention, and various embodiments different from the above-described embodiment may be implemented without departing from the gist of the present invention. Can do.

  For example, in the above embodiment, an example of the configuration in which the anode is formed on the substrate 20 has been shown. However, the cathode may be configured in the order of the cathode, the organic compound layer, and the anode from the substrate side. There is no limit.

  Hereinafter, although an Example is given and the multicolor display device concerning the present invention is explained still in detail, the present invention is not limited to these Examples.

<Example 1>
In Example 1, a multicolor display device having the configuration shown in FIG. 1 was produced by the following steps.

  As a support, a TFT drive circuit 21 made of low-temperature polysilicon was formed on a glass substrate 20, a planarizing layer 22 made of acrylic resin was formed thereon, and a contact hole 23 was formed by a photolithography technique.

  On top of this, an aluminum alloy (AlNd) film having a thickness of 150 nm was formed as a reflective layer 24 by sputtering, and patterned.

  Next, ITO was formed into a film having a thickness of 10 nm as the transparent conductive layer A25 by sputtering, and was patterned for each pixel. Subsequently, an ITO film having a thickness of 115 nm is formed as the transparent conductive layer B26 by sputtering, so that the ITO thickness in a part of the pixel is 10 nm and the ITO thickness in the other area is 125 nm. And patterning. At this time, the patterning was performed so that the area ratio of the ITO thickness inside the pixel was 10 nm and 125 nm was the area ratio described in Table 4 above.

  Thereafter, an element isolation film 36 was formed using an acrylic resin. This was ultrasonically washed with isopropyl alcohol (IPA), then boiled and dried. Further, after UV / ozone cleaning, an organic compound is deposited by vacuum deposition.

In forming the organic compound layer, first, a compound represented by the chemical formula of the following chemical formula 1 was formed as a hole transport layer A27 in a film thickness of 118 nm in common for all pixels. The degree of vacuum during the film formation was 1 × 10 ⁻⁴ Pa, and the film formation rate was 0.2 nm / sec.

  Next, using a shadow mask, the compound [I] represented by the chemical formula of the following chemical formula 1 is used as the hole transport layer B28 for each of the red, green, and blue light-emitting pixels with a film thickness of 135 nm, 52 nm, and 8 nm, respectively. The film was formed.

  Thereafter, using a shadow mask, a red light emitting layer 29, a green light emitting layer 30, and a blue light emitting layer 31 were formed to a thickness of 30 nm, 40 nm, and 24 nm, respectively. As the red light emitting layer 29, a light emitting material showing a PL spectrum having a maximum peak wavelength of 620 nm and a half width of 97 nm was used. As the green light emitting layer 30, a light emitting material showing a PL spectrum having a maximum peak wavelength of 525 nm and a half width of 68 nm was used. As the blue light emitting layer 31, a light emitting material showing a PL spectrum having a maximum peak wavelength of 460 nm and a half width of 45 nm was used.

Further, as the common electron transport layer 32, bathophenanthroline (Bphen) was formed to a thickness of 20 nm by a vacuum deposition method. The degree of vacuum during vapor deposition was 1 × 10 ⁻⁴ Pa, and the film formation rate was 0.2 nm / sec.

Next, as a common electron injection layer 33, Bphen and Cs ₂ CO ₃ were co-evaporated (weight ratio 90:10) to form a film with a thickness of 28 nm. The degree of vacuum during vapor deposition was 3 × 10 ⁻⁴ Pa, and the film formation rate was 0.2 nm / sec.

Thereafter, a silver film having a thickness of 12 nm was formed as an electrode A34 common to each pixel. The degree of vacuum during vapor deposition was 2 × 10 ⁻⁴ Pa, and the film formation rate was 0.2 nm / sec.

Subsequently, the substrate on which the electrodes A34 were formed was moved to a sputtering apparatus while maintaining a vacuum, and an ITO film having a thickness of 50 nm was formed as an electrode B35. Thereafter, the substrate was filled with dry nitrogen. The UV curable resin was applied to the periphery of the substrate with a seal dispenser. Then, a concave glass plate (sealing member 38) having a thickness of 0.7 mm in which a portion corresponding to the organic light emitting element was dug to a depth of 0.3 mm was covered from above the substrate. The peripheral resin portion on the substrate was irradiated with ultraviolet rays, and the substrate and the glass plate were brought into close contact with each other by curing the resin to obtain a display device. Note that FIG. 1 does not show the UV curable resin.

  Table 10 below shows the emission chromaticity of each color of the display device obtained as described above and the white color shift amount δu′v ′ at a viewing angle of 50 degrees.

<Comparative Example 1>
In Comparative Example 1, the film thickness of the transparent conductive layer provided on the reflective layer 24 was uniformly 10 nm over the entire surface inside the light emitting pixel. Other than that was carried out similarly to Example 1, and produced the multicolor display device.

  Table 11 below shows the film thickness of each layer of the element of Comparative Example 1. Note that the thicknesses of the hole transport layer A27 and the hole transport layer B28 are adjusted in order to make the emission chromaticity of each color substantially coincide with that of the display device of Example 1 on the front surface of the display device.

  Further, Table 12 below shows the emission chromaticity of each color of the multicolor display device of Comparative Example 1 obtained as described above and the white color shift amount δu′v ′ at a viewing angle of 50 degrees.

  From Tables 10 and 12, the multicolor display device of Example 1 is significantly less in the amount of white color shift δu′v ′ due to the viewing angle than the multicolor display device of Comparative Example 1. It was found that it exhibits luminescent properties.

  The display device according to the present invention can be applied to various uses such as illumination, a display of an electronic device, and a backlight for the display device. Examples of the display of the electronic device include a television receiver, a display of a personal computer, a rear display unit of an imaging device, a display unit of a mobile phone, a display unit of a portable game machine, and the like. Other examples include a display unit of a portable music player, a display unit of a personal digital assistant (PDA), a display unit of a car navigation system, and the like.

  20 substrate, 24 reflective layer, 25 transparent conductive layer A, 26 transparent conductive layer B, 27 hole transport layer A, 28 hole transport layer B, 29 red light emitting layer, 30 green light emitting layer, 31 blue light emitting layer, 32 electrons Transport layer, 33 Electron injection layer, 34 Electrode A, 35 Electrode B, 40 region (part of optical distance A), 41 region (part of optical distance B)

Claims (5)

A plurality of pixels composed of multicolor organic light emitting elements including at least R (red), G (green), and B (blue) are disposed on a substrate, and the organic light emitting element includes a reflective electrode layer and a semitransparent electrode. A multicolor display device having an organic compound layer including a light emitting layer between the layers,
The transparent conductive layer constituting the reflective electrode layer has two different thicknesses in common for all the pixels so that regions having different optical distances are set inside each light emitting color pixel,
Further, for the green pixel (or blue pixel), the area ratio of the regions having different optical distances is determined so that the viewing angle color shift with respect to the white display is minimized,
In blue pixels (or green pixels), the area of the optical distance region with a small viewing angle color shift of blue single color (or green single color) is large, and in the red pixels, the area of the optical distance region with a small viewing angle color shift of red single color is large. A multicolor display device characterized by being set to be large.   2. The multicolor display device according to claim 1, wherein the thickness of the light emitting layer and the thickness of the hole transport layer constituting the organic compound layer are individually set for each emission color.   3. The multicolor display device according to claim 1, wherein the regions having different optical distances are arranged with the same area ratio and the same arrangement regardless of pixels. 4.   The regions having different optical distances alternately change the mutual positions of the regions having different optical distances in units of RGB pixels while maintaining the same area ratio and arrangement of adjacent pixels of the same color. Item 3. The multicolor display device according to Item 1 or 2.   The regions having different optical distances alternately change the mutual positions of the regions having different optical distances between pixels of different emission colors while maintaining the same area ratio and arrangement of adjacent pixels of the same color. The multicolor display device according to claim 1 or 2.

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