JP2016157799A - El display device and manufacturing method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an EL display device whose luminescence characteristic is maintained.SOLUTION: The EL display device includes a display portion including pixels. The pixels include an EL element including a luminescent layer containing a host and at least two kinds of dopants. The at least two kinds of dopants have different concentration distribution relative to the host. The at least two kinds of dopants include a first dopant and a second dopant. The first dopant has the concentration distribution in which the concentration decreases gradually in a first direction and the second dopant has the concentration distribution in which the concentration increases gradually in the first direction.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a display device having a pixel composed of a light emitting element such as an electroluminescence (EL) element. In particular, the present invention relates to an organic EL display device using an organic EL material as a light emitting material.

  An electroluminescence (hereinafter also referred to as “EL”) element is known as a light-emitting element utilizing an electroluminescence phenomenon. The EL element can emit light with various wavelengths by selecting a light emitting material constituting the light emitting layer, and its application to a display device or a lighting fixture is being promoted. In particular, an organic EL element using an organic material as a light emitting material has attracted attention.

  In an organic EL display device in which an organic EL element is applied to a display device, an organic EL element as a light emitting element and a switching element for controlling light emission of the organic EL element are provided in each pixel arranged in a matrix on a substrate. Is provided. Then, by controlling on / off of the switching element for each pixel, it is possible to display an arbitrary image as the entire display region.

  The light emission color of the organic EL element can be varied depending on the type of EL material used for the light emitting layer of the EL element. For example, various emission colors can be realized depending on the type of EL material (host) that is the main component of the light emitting layer and the type of EL material (dopant) that is the subcomponent of the light emitting layer. In particular, in recent years, development of organic EL elements that enable white light emission with high color purity has been progressing.

  In order to realize white light emission in an organic EL element, there are known a structure in which light emitting layers emitting light of RGB colors are laminated, or a structure in which a light emitting layer emitting blue light and a light emitting layer emitting yellow light are laminated ( Patent Document 1). In particular, a structure in which a light emitting layer that emits blue light and a light emitting layer that emits yellow light is stacked, is attracting attention because the number of stacked layers can be reduced as compared to the case where light emitting layers of RGB colors are stacked.

JP 2005-285708 A

  In forming a light emitting layer that emits yellow light, it is possible to widen the color gamut by adding dopants that emit light of different colors to the host. In this case, in order to cause each dopant to emit light in different regions, it is preferable to sandwich a layer containing almost no dopant (that is, a layer substantially composed of only the host) between the regions.

  FIG. 10 is a diagram illustrating an example of an EL element in which a light emitting layer emitting blue light and a light emitting layer emitting yellow light are stacked. 10, in order from the bottom of the drawing, a pixel electrode (anode) 11, a first charge transport layer 12, a first light-emitting layer 13, a second charge transport layer 14, a second light-emitting layer 15, a third charge transport layer 16, A common electrode (cathode) 17 is stacked. Here, a light emitting layer that emits yellow light is shown as the first light emitting layer 13, and a light emitting layer that emits blue light is shown as the second light emitting layer 15.

  In the example shown in FIG. 10, the first charge transport layer 12 includes a hole injection layer and a hole transport layer. The second charge transport layer 14 includes a hole injection layer, a hole transport layer, a charge generation layer, an electron injection layer, and an electron transport layer. The third charge transport layer 16 includes an electron injection layer and an electron transport layer.

  Here, the first light emitting layer 13 that emits yellow light has a three-layer structure. The first layer is a layer in which a first dopant is added to the host (hereinafter referred to as “first light-emitting region”) 13a, and the second layer is a layer composed only of the host (hereinafter referred to as “undoped region”). The third layer is a layer (hereinafter referred to as “second light emitting region”) 13c in which a second dopant is added to the host.

  As described above, with such a structure, the first light emitting region 13a and the second light emitting region 13c can emit light of different colors, and yellow with a wide color gamut can be expressed. For example, a dopant that emits yellow-green light and a dopant that emits yellow light can be used as the first dopant and the second dopant, respectively.

  Here, the trial process up to the present invention by the inventors will be described. FIG. 11 is a diagram schematically showing a method for forming a light emitting layer. The inventors used the light emitting layer forming method using in-line vapor deposition shown in FIG. 11 in order to obtain the laminated structure shown in FIG. Note that “in-line deposition” refers to continuous deposition in each chamber arranged in series without opening to the atmosphere when depositing different materials from a plurality of deposition sources.

  In the forming method shown in FIG. 11, first, the substrate 24 is moved in the direction of the arrow above the first vapor deposition source 21a, the second vapor deposition source 22a, and the third vapor deposition source 23a, and a dopant (here, the first dopant) 21b, A layer in which the first host 22b and the second host 23b are mixed, that is, the first light emitting region 13a is formed.

  Next, the substrate 24 on which the first light emitting region 13a is formed is moved in the direction of the arrow above the second vapor deposition source 22a and the third vapor deposition source 23a, and only the first host 22b and the second host 23b are mixed. A layer, that is, an undoped region 13b is formed.

  Finally, the substrate 24 on which the undoped region 13b is formed is moved in the direction of the arrow above the first vapor deposition source 21a, the second vapor deposition source 22a, and the third vapor deposition source 23a, and a dopant (here, a second dopant). 21b, a layer in which the first host 22b and the second host 23b are mixed, that is, the second light emitting region 13c is formed.

  Through the above forming method, the first light emitting layer 13 having the laminated structure shown in FIG. 10 is formed. During the vapor deposition, the dopant, the first host, and the second host are not uniformly mixed, and each formed layer is formed. Concentration distribution occurred in the inside.

  FIG. 12 is a diagram showing a concentration distribution when the first light emitting region 13a is formed by in-line vapor deposition shown in FIG. In FIG. 12, curves 25 and 26 indicate the dopant concentration and the second host concentration, respectively. Note that the dopant concentration and the second host concentration shown in FIG. 12 are each normalized by the concentration of the first host. That is, the ratio with respect to the density | concentration of a 1st host is shown.

  As is apparent from FIG. 12, the dopant has a peak concentration (maximum value) near one end of the first light emitting region 13a, and the second host has a peak concentration (maximum value) near the other end of the first light emitting region 13a. ). Therefore, the present inventors improved the in-line deposition method in order to eliminate such a concentration distribution.

  FIG. 13 is a diagram schematically showing an improved method for forming a light emitting layer. In the forming method shown in FIG. 13, the vapor deposition sources 21a and 23a are inclined toward the vapor deposition source 22a and vapor deposition is performed in that state. Thus, it has been found that the dopant, the first host, and the second host are mixed uniformly without a concentration distribution, and the first light emitting region 13a with improved lifetime and light emission efficiency can be formed.

  However, in the forming method shown in FIG. 13, it is necessary to accurately adjust the angle at which the vapor deposition source 21a and the vapor deposition source 23a are inclined, and there is a problem that it takes a very long time to replace the vapor deposition source. Further, in order to obtain the structure shown in FIG. 10, it is necessary to prepare a large number of vapor deposition sources, which has been a factor in increasing the manufacturing cost.

  Further, when the tilt of the vapor deposition source is deviated, the concentration distribution of the dopant and the second host in the first light emitting region 13a is changed, and there is a problem that the life as the light emitting layer and the light emission efficiency are affected.

  An object of the present invention is to provide an EL display device having excellent light emission characteristics.

  An object of the present invention is to provide a method for manufacturing an EL display device with high productivity.

  The present invention is based on the technical idea completely opposite to the idea of eliminating the concentration distribution by vapor deposition as described above. Rather, the concentration distribution by vapor deposition is positively utilized, and the concentration distribution of the dopant is shown in FIG. To achieve the structure.

  One embodiment of the present invention is an EL display device including a display portion including a plurality of pixels, the plurality of pixels including an organic EL element having a light-emitting layer including a host and at least two types of dopants. The at least two dopants have different concentration distributions with respect to the host. The at least two kinds of dopants include a first dopant and a second dopant, the first dopant has a concentration distribution that gradually decreases in a first direction, and the second dopant is: It may have a concentration distribution in which the concentration gradually increases in the first direction. The first dopant may have a peak concentration near one end on the pixel electrode side, and the second dopant may have a peak concentration near the other end on the common electrode side.

  According to one embodiment of the present invention, a pixel electrode is formed over an insulating surface, a light-emitting layer including a host and at least two kinds of dopants is formed over the pixel electrode, and the at least two kinds of dopants are different from the host. Forming a concentration distribution, and forming a common electrode on the light emitting layer. The at least two kinds of dopants include a first dopant having a concentration distribution in which the concentration gradually decreases in the first direction, and a second concentration distribution in which the concentration gradually increases in the first direction. A dopant may be included. The light emitting layer may be formed such that the peak concentration of the first dopant is located near one end on the pixel electrode side and the peak concentration of the second dopant is located near the other end on the common electrode side. .

  In one embodiment of the present invention, a pixel electrode is formed over an insulating surface, and a light-emitting layer is formed on the pixel electrode by in-line deposition in the order of a first dopant, a host, and a second dopant. Forming a common electrode. On the light emitting layer, another light emitting layer that emits a color complementary to the color emitted from the light emitting layer may be formed. Further, a charge transport layer may be further formed before and after forming the light emitting layer and the other light emitting layer.

1 is a diagram illustrating an overall configuration of an EL display device according to a first embodiment. It is a figure which shows the pixel part of the EL display apparatus which concerns on 1st Embodiment. It is a figure which shows the cross section of the pixel part of the EL display apparatus which concerns on 1st Embodiment. It is a figure which shows the cross section of the EL element of the EL display apparatus which concerns on 1st Embodiment. It is a figure which shows the formation method of the light emitting layer of the EL display apparatus which concerns on 1st Embodiment. In the EL display device according to the first embodiment, it is a diagram illustrating a dopant concentration distribution in a first light emitting layer constituting an EL element. It is a figure which shows the manufacturing method of the pixel part of the EL display apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows the manufacturing method of the pixel part of the EL display apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows the formation method of the light emitting layer of the EL display apparatus which concerns on 3rd Embodiment. It is a figure which shows the cross section of the EL element of EL display apparatus. It is a figure which shows the formation method of the light emitting layer of EL display apparatus. In an EL display device, it is a figure which shows the dopant and the density | concentration distribution of the 2nd host in the 1st light emission area | region which comprises an EL element. It is a figure which shows the formation method of the light emitting layer of EL display apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention can be implemented in various modes without departing from the gist thereof, and is not construed as being limited to the description of the embodiments exemplified below.

  Further, in order to make the explanation clearer, the drawings may be schematically represented with respect to the width, thickness, shape, and the like of each part as compared with the actual embodiment, but are merely examples, and the interpretation of the present invention. It is not intended to limit. In addition, in the present specification and each drawing, elements having the same functions as those described with reference to the previous drawings may be denoted by the same reference numerals and redundant description may be omitted.

(First embodiment)
<Configuration of display device>
FIG. 1 is a diagram showing an overall configuration of an organic EL display device 100 according to the first embodiment of the present invention. The organic EL display device 100 includes a pixel portion (display area) 102, a scanning line driving circuit 103, a data line driving circuit 104, and a driver IC 105 formed on a substrate 101. The driver IC functions as a control unit that provides signals to the scanning line driving circuit 103 and the data line driving circuit 104.

  Note that the data line driving circuit 104 may be included in the driver IC 105. Although FIG. 1 shows an example in which the driver IC 105 is integrally formed on the substrate 101, it may be separately arranged on the substrate 101 in the form of an IC chip. Further, a form in which the driver IC 105 is provided in an FPC (Flexible Printed Circuits) and externally attached may be employed.

  A plurality of pixels are arranged in a matrix in the pixel portion 102 shown in FIG. A data signal corresponding to image data is given to each pixel from the data line driving circuit 104. By providing these data signals to the pixel electrodes through transistors provided in the respective pixels, screen display corresponding to the image data can be performed. As the transistor, typically, a thin film transistor can be used. However, not only the thin film transistor but any element having a current control function may be used.

  FIG. 2 is a diagram showing a configuration of the pixel portion 102 in the organic EL display device 100 shown in FIG. In this embodiment, the pixel 201 is a pixel that emits white light and is provided with a thin film transistor 202. As will be described later, a color filter corresponding to each RGB color is provided corresponding to each pixel, and various colors can be expressed by controlling each pixel 201 on / off using the thin film transistor 202.

  In the present embodiment, an example is shown in which all pixels emit white light and color display is performed using a color filter. However, the present invention is not limited to this, and 4 (white (W) or yellow (Y) is added to RGB). The pixel 201 can also be configured with two subpixels. In this case, it is preferable to apply the present invention to white or yellow pixels.

  In addition, an example in which pixels corresponding to the same color are arranged in stripes is shown as the pixel arrangement, but other arrangements such as a delta arrangement, a Bayer arrangement, or a pen tile structure may be used.

  FIG. 3 is a diagram illustrating a cross-sectional configuration of the pixel 201 illustrated in FIG. 2 taken along line III-III ′. In FIG. 3, an insulating layer made of an inorganic material such as silicon oxide, silicon nitride, or aluminum oxide is provided as a base layer 302 over a first substrate 301, and a thin film transistor 303 is formed thereover.

  As the first substrate 301, a glass substrate, a quartz substrate, or a flexible substrate (polyimide, polyethylene terephthalate, polyethylene naphthalate, or other bendable substrate) can be used. In the case where the first substrate 301 does not need to have a light-transmitting property, a metal substrate, a ceramic substrate, or a semiconductor substrate can be used.

  The thin film transistor 303 may be formed by a known method. The structure of the thin film transistor 303 may be a top gate type or a bottom gate type. In the organic EL display device 100 of the present embodiment, the first insulating layer 304 is provided so as to cover the thin film transistor 303, and the unevenness caused by the thin film transistor 303 is flattened. As the first insulating layer 304, a resin material is preferably used. For example, known organic materials such as polyimide, polyamide, acrylic, and epoxy can be used. As long as the planarization effect is achieved, an inorganic material such as silicon oxide may be used instead of the organic material, or a stacked structure of an organic material and an inorganic material may be used.

  A pixel electrode 305 is provided over the first insulating layer 304. The pixel electrode 305 is connected to the thin film transistor 303 through a contact hole formed in the first insulating layer 304. In the organic EL display device 100 of the present embodiment, the pixel electrode 305 functions as an anode that constitutes the organic EL element.

  The pixel electrode 305 is configured differently depending on whether it is a top emission type or a bottom emission type. For example, in the case of the top emission type, a metal film having a high reflectance is used as the pixel electrode 305, or a work function such as an indium oxide-based transparent conductive film (for example, ITO) or a zinc oxide-based transparent conductive film (for example, IZO, ZnO) is used. A stacked structure of a high transparent conductive film and a metal film may be used. Conversely, in the case of the bottom emission type, the above-described transparent conductive film may be used as the pixel electrode 305. In the present embodiment, a top emission type organic EL display device will be described as an example.

  Between adjacent pixel electrodes 305, a bank 306 is disposed as shown in FIG. The bank 306 is provided so as to cover the end (edge) of each pixel electrode 306, and as a result, functions as a member that partitions each pixel. Note that the bank 306 may function not only to cover the end portion of the pixel electrode 306 but also to function as a filler that fills the concave portion caused by the contact hole.

  In the present embodiment, a known resin material such as polyimide, polyamide, acrylic, epoxy, or siloxane can be used for the bank 306. FIG. 3 shows an example in which a bank having a curved outline is formed in a cross section including the top of the bank 306 (cross section cut along a plane perpendicular to the main surface of the pixel electrode). It is not necessary to limit the shape, and it may be trapezoidal.

  An electroluminescent layer (EL layer) 307 is provided on the pixel electrode 305 and the bank 306. The EL layer 307 has at least a light emitting layer and functions as a light emitting portion of the organic EL element. In addition to the light-emitting layer, the EL layer 307 can also include various charge transport layers such as an electron injection layer, an electron transport layer, a hole injection layer, and a hole transport layer. Details of the EL layer will be described later.

  In the present embodiment, as described above, an EL layer 307 that emits white light is provided, and color separation is performed using a color filter. A known structure or a known material can be used for the EL layer 307, and the EL layer 307 is not particularly limited to the configuration of this embodiment. Further, the EL layer 307 may be formed only on each pixel electrode 305. That is, it may be formed separately for each pixel without being formed on the bank 306.

  On the EL layer 307, a common electrode 308 that functions as a cathode of the organic EL element is provided. Since the organic EL display device 100 of this embodiment is a top emission type, an MgAg thin film or a transparent conductive film (ITO or IZO) is used as the common electrode 308. The common electrode 308 is provided on the entire surface of the pixel portion 102 across the pixels.

  In this embodiment, an EL element 309 is configured by the pixel electrode 305, the EL layer 307, and the common electrode 308. Further, an insulating film 310 is provided to protect the EL element 309 from external moisture and the like. As the insulating film 310, it is preferable to use a dense inorganic insulating film such as a silicon nitride film.

  The first substrate 301 to the insulating film 310 described above are collectively referred to as an array substrate in this embodiment.

  On the array substrate, a sealing substrate is provided via a filler (fill material) 311 that functions as an adhesive and a protective material. As the filler 311, a known resin material such as polyimide, polyamide, acrylic, epoxy, or siloxane can be used. On the other hand, as long as sufficient sealing at the peripheral portion of the substrate and maintaining the gap between the first substrate and the second substrate can be realized, hollow sealing can be performed without using the filler 311.

  In the present embodiment, the “sealing substrate” is a color filter corresponding to each of the RGB colors provided on the second substrate 312 and the main surface of the second substrate 312 (the surface facing the first substrate 301). 313R, 313G, and 313B, and a black matrix 314 provided in a gap between the color filters.

  However, the structure of the sealing substrate is not limited to this, and the black matrix 314 may be omitted. If the EL layer 307 is provided separately for each color of RGBW, the color filter can be omitted from the sealing substrate. Further, if the color filter is omitted or formed on the first substrate 301 side, the sealing substrate itself can be omitted.

  Here, details of the EL element 309 in the organic EL display device 100 of the present embodiment will be described.

  FIG. 4 is a diagram showing a cross section of the EL element 309 of the organic EL display device 100 of the present embodiment. 4, in order from the bottom of the drawing, a pixel electrode (anode) 305, a first charge transport layer 401, a first light-emitting layer 402, a second charge transport layer 403, a second light-emitting layer 404, a third charge transport layer 405, The common electrode (cathode) 308 is laminated. In this embodiment, the first light-emitting layer 402 is a light-emitting layer that emits yellow light, and the second light-emitting layer 404 is a light-emitting layer that emits blue light. Note that the present invention is not limited to this configuration, and the positions of the first light emitting layer 402 and the second light emitting layer 404 may be reversed.

  The first charge transport layer 401 includes a hole injection layer and a hole transport layer. However, the hole injection layer or the hole transport layer can be omitted. Further, a plurality of transport layers may be stacked.

  The second charge transport layer 403 includes a hole injection layer, a hole transport layer, a charge generation layer, an electron injection layer, and an electron transport layer. The charge generation layer plays a role of generating holes and electrons. The holes generated here go to the second light emitting layer 404 through the hole injection layer and the hole transport layer. Further, the electrons generated here travel to the first light emitting layer 402 through the electron injection layer and the electron transport layer.

  The third charge transport layer 405 includes an electron injection layer and an electron transport layer. However, the electron injection layer or the electron transport layer can be omitted. Further, a plurality of transport layers may be stacked.

  In the present embodiment, as described above, the first light-emitting layer 402 that emits yellow light is configured with a three-layer structure. Specifically, a layer (first light-emitting region) in which a first dopant is added to a host is provided as a first layer, and a layer substantially composed of only a host (undoped region) as a second layer. And a layer (second light emitting region) in which a second dopant is added to the host is provided as a third layer. In the present embodiment, the second light emitting layer 404 uses a known blue light emitting material.

  Here, the organic EL display device 100 of the present embodiment uses the method of tilting the vapor deposition source described with reference to FIG. 13 when the first light emitting layer 402 includes the first light emitting region, the undoped region, and the second light emitting region. Without forming the light emitting layer. Specifically, as shown in FIG. 5, the first vapor deposition source 501a, the second vapor deposition source 502a, and the third vapor deposition source 503a are arranged without inclining, and the substrate 504 passes therethrough.

  At this time, the first dopant 501b is diffused from the first vapor deposition source 501a, the host 502b is diffused from the second vapor deposition source 502a, and the second dopant 503b is diffused from the third vapor deposition source 503a. The first dopant 501b and the second dopant 503b are dopants that emit light of different colors.

  In the present embodiment, a dopant that emits yellow-green light is used as the first dopant 501b, and a dopant that emits yellow light is used as the second dopant 503b. However, the present invention is not limited to this. For example, the order of adding the first dopant 501b and the second dopant 503b may be reversed. Further, the host 502b is not limited to one type, and two or more types of hosts can be included.

  As described with reference to FIGS. 11 and 12, when the light emitting layer is formed by arranging the three vapor deposition sources without tilting, the concentration of the light emitting material is biased inside the light emitting layer. That is, in the material diffused from the vapor deposition source arranged first with respect to the traveling direction of the substrate and the material diffused from the vapor deposition source arranged last, the concentration distribution inside the light emitting layer is almost symmetrical, The position of the maximum value (peak concentration) is the opposite position.

  In the present embodiment, contrary to the above-described trial process of the present inventors, the above phenomenon is used positively, the dopant concentration is intentionally biased inside the first light emitting layer 402, and light emission is different for each dopant. Form a region. Here, FIG. 6 shows a specific configuration of the first light emitting layer 402 in the organic EL display device 100 of the present embodiment.

  FIG. 6 is a diagram showing a dopant concentration distribution in the first light emitting layer 402 constituting the EL element 309 in the organic EL display device according to the first embodiment. A curve 601 indicates the concentration distribution of the first dopant 501b that emits yellow-green light, and a curve 602 indicates the concentration distribution of the second dopant 503b that emits yellow light. Note that the concentration of the first dopant 501b and the concentration of the second dopant 503b shown in FIG. 6 are normalized by the concentration of the host 502b, respectively. That is, the relative ratio with respect to the density | concentration of the host 502b is shown.

  As shown in FIG. 6, the first dopant 501b has a peak concentration (maximum value) in the vicinity of one end on the pixel electrode side, and is directed in the direction from the pixel electrode toward the common electrode (hereinafter referred to as “first direction”). The concentration distribution gradually decreases. On the contrary, the second dopant 503b has a peak concentration (maximum value) in the vicinity of the other end on the common electrode side, and has a concentration distribution in which the concentration gradually increases in the first direction. Note that “near” here means that when normalized by the film thickness of the first light-emitting layer 402 (when the film thickness of the first light-emitting layer 402 is “1”), The range is within 0.3 (typically within 0.2) from the interface with the layer.

  As a result, in the first light emitting layer 402, the first light emitting region 402a in which the first dopant 501b is mainly added to the host 502b and the second light emitting region 402a in which the second dopant 503b is mainly added to the host 502b. A light emitting region 402b is formed. Furthermore, a region where the concentration of the first dopant 501b and the second dopant 503b is sufficiently low between the first light emitting region 402a and the second light emitting region 402b, that is, an undoped region configured substantially only by the host 502b. 402c is formed. In the undoped region 402c, it is desirable that the concentration of the first dopant 501b and the second dopant 503b is 15% or less (preferably 10% or less).

  As described above, in the present embodiment, a light emitting layer composed of two different light emitting regions and an undoped region between them can be formed by utilizing the uneven concentration distribution of the dopant by in-line deposition. Then, an organic EL display device including such a light emitting layer can be provided by a highly productive method without performing precise adjustment of tilting the evaporation source.

  In addition, the organic EL display device 100 of the present embodiment emits yellow light from the first light-emitting layer 402 having a three-layer structure in which the undoped region 403c is provided between the first light-emitting region 402a and the second light-emitting region 402b. Since it has as a layer, it can have a wide color gamut and excellent emission characteristics.

  Hereinafter, the manufacturing process of the organic EL display device 100 of the present embodiment having the above-described configuration will be described with reference to FIGS.

<Manufacturing method of display device>
First, as shown in FIG. 7A, a base layer 302 is formed on a first substrate 301, and a thin film transistor (TFT) 303 is formed thereon by a known method. Then, the first insulating layer 304 is formed so as to flatten the unevenness generated by the formation of the thin film transistor 303.

  As the first substrate 301, a glass substrate, a quartz substrate, a flexible substrate (polyimide, polyethylene terephthalate, polyethylene naphthalate or other bendable substrate) or the like can be used. In the case where the first substrate 301 does not need to have a light-transmitting property, a metal substrate, a ceramic substrate, or a semiconductor substrate can be used.

  As the base layer 302, typically, a silicon oxide insulating film, a silicon nitride insulating film, or a stacked film thereof can be used. The base layer 302 has a function of preventing entry of contaminants from the first substrate 301 and relaxing stress generated by expansion and contraction of the first substrate 301.

  In this embodiment, an example in which a top gate TFT is formed as the thin film transistor 303 is shown, but a bottom gate TFT may be used.

  The first insulating layer 304 may be formed by applying a known resin material such as polyimide, polyamide, acrylic, epoxy, or siloxane, and then curing the applied resin material with light or heat. The thickness of the first insulating layer 304 may be sufficient to flatten the unevenness caused by the thin film transistor 303. Typically, the thickness may be 1 to 3 μm, but is not limited thereto.

  Next, as shown in FIG. 7B, after a contact hole reaching the thin film transistor 303 is formed in the first insulating layer 304, a pixel electrode 305 is formed by a known method. In this embodiment, after forming a laminated film of ITO (Indium Tin Oxide) and an aluminum film by a known sputtering method, the pixel film 305 is formed by patterning the laminated film by a known photolithography. The pixel electrode 305 is patterned so as to correspond to positions corresponding to a plurality of pixels, respectively.

  Next, a bank 306 made of a resin material is formed. In this embodiment, the bank 306 is formed by applying a photocurable resin. Regarding the formation of the bank 306, the shape is not particularly limited, and may be trapezoidal or semicircular. In forming the bank 306, any of known photolithography, printing, and solution coating methods may be used.

  Next, as illustrated in FIG. 8A, an EL layer 307 is formed over the pixel electrode 305 and the bank 306. In this embodiment, the EL layer 307 is a white light emitting portion, and is formed in common for all pixels. Therefore, the manufacturing process can be simplified and a manufacturing process with high productivity can be constructed.

  In the present embodiment, the stacked structure described with reference to FIG. 4 is used as the structure of the EL layer 307. That is, the EL layer 307 in this embodiment is an example of a stacked structure including the first charge transport layer 401, the first light emitting layer 402, the second charge transport layer 403, the second light emitting layer 404, and the third charge transport layer 405. To do.

  In the present embodiment, the first light-emitting layer 402 is formed by in-line deposition described with reference to FIG. That is, as shown in FIG. 5, the first deposition source 501a for depositing the first dopant 501b emitting yellow-green, the second deposition source 502a for depositing the host 502b, and the first emission source emitting yellow. The first light emitting layer 402 is formed by sequentially arranging the third vapor deposition source 503a for vapor deposition of the two dopants 503b and performing in-line vapor deposition.

  Accordingly, the first light emitting layer 402 having the undoped region 402c between the first light emitting region 402a and the second light emitting region 402b described with reference to FIG. 6 can be formed. In this case, the first light emitting layer 402 can be formed by in-line vapor deposition as usual without adjusting the vapor deposition source with high accuracy. Furthermore, the first light-emitting layer 402 including the first light-emitting region 402a, the second light-emitting region 402b, and the undoped region 402c can be formed by one-time in-line vapor deposition using the uneven concentration distribution by in-line vapor deposition. Therefore, according to the present embodiment, the number of vapor deposition sources can be reduced to reduce the manufacturing cost, and a method for manufacturing an EL display device with high productivity can be provided.

  In the present embodiment, all layers other than the first light emitting layer 402 are formed by vapor deposition. Since the EL layer is very sensitive to moisture, it is desirable that the EL layer be not exposed to the outside air as much as possible. Therefore, as long as the first light-emitting layer 402 is formed by in-line vapor deposition, it is preferable to form other layers using in-line vapor deposition. Thereby, it is also possible to laminate | stack all the layers continuously, without making outside air contact. Of course, it is not necessary to limit to such a method, and you may use together other well-known methods, such as an inkjet method, as needed.

  As described above, the first charge transport layer 401, the first light-emitting layer 402, the second charge transport layer 403, the second light-emitting layer 404, and the third charge transport layer 405 are formed on the pixel electrode 305 by using an in-line vapor deposition method. An EL layer 307 is formed.

  Next, as shown in FIG. 8B, a common electrode 308 that functions as a cathode of the organic EL element is formed. In this embodiment, as the common electrode 308, an ITO film or an IZO film formed by a sputtering method is used. Of course, another transparent conductive film may be used, or a metal film such as MgAg may be used. After that, an insulating film 309 including a silicon nitride film is formed as a protective film. At this time, it is desirable that the common electrode 308 and the insulating film 309 be continuously formed without being exposed to the outside air.

  Finally, a sealing substrate provided with a known color filter 313R, 313G, 313B and a black matrix 314 made of a resin containing a metal film or a black pigment on a second substrate 312 is prepared, and a filler 311 is prepared. To the array substrate. Thus, the organic EL display device 100 shown in FIG. 3 is completed.

(Second Embodiment)
In the first embodiment described above, a light emitting layer that emits yellow light is used as the first light emitting layer 402 and a light emitting layer that emits blue light is used as the second light emitting layer 404 in order to form an EL layer that emits white light. An example is shown. However, the present invention can also be implemented in a combination of different light emitting layers. In addition, it has the same structure as the organic EL display device 100 according to the first embodiment except that the combination of emission colors of the light emitting layers is different.

  According to this embodiment, for example, a light emitting layer that emits red light may be used as the first light emitting layer 402, and a light emitting layer that emits blue green light may be used as the second light emitting layer 404. In this case, the in-line deposition described in the first embodiment can be applied to the formation of the second light emitting layer 404. For example, a first dopant 501b that emits blue light and a second dopant 503b that emits green light may be added to the host 502b. Of course, the order of depositing the first dopant 501b and the second dopant 502b is arbitrary.

  Alternatively, a light-emitting layer that emits red-green light may be used as the first light-emitting layer 402, and a light-emitting layer that emits blue light may be used as the second light-emitting layer 404. In this case, in-line deposition described in the first embodiment is applied to the formation of the first light emitting layer 402, and for example, a first dopant 501b that emits red light and a second dopant 503b that emits green light are added to the host 502b. do it. Also in this case, the order of depositing the first dopant 501b and the second dopant 502b is arbitrary.

  As described above, in this embodiment, a white light-emitting EL element is formed using the first light-emitting layer and the second light-emitting layer that emits light having a color complementary to the light emission color of the first light-emitting layer. To do. The light emitting layer having the structure described in the first embodiment can be applied to either the first light emitting layer or the second light emitting layer.

(Third embodiment)
FIG. 9 is a diagram showing a method for forming a light emitting layer of an organic EL display device according to the third embodiment of the present invention. The difference from the first embodiment is that the third embodiment uses two types of materials as the host. Other configurations are the same as those of the organic EL display device 100 according to the first embodiment.

  In the present embodiment, instead of the second vapor deposition source 502a in FIG. 5, a vapor deposition source 901a and a vapor deposition source 902a are used as the second vapor deposition source for the host. The deposition source 901a diffuses the first host 901b, and the deposition source 902a diffuses the second host 902b. In this embodiment, the vapor deposition sources 901a and 902a are arranged adjacent to each other so that a wide area 903b in which two types of hosts are mixed can be secured. Thereby, two types of host materials are deposited on the host itself without concentration distribution, and adverse effects due to the concentration distribution of the host material can be eliminated.

  Note that although an example in which the vapor deposition sources 901a and 902a are arranged adjacent to each other is shown in the present embodiment, a region 903b in which different host materials are mixed may be formed by inclining both of them toward each other.

  In the present embodiment, an example in which two different types of host materials are used has been described, but it is also possible to use three or more types of host materials. Even in that case, it is possible to deposit a plurality of host materials without concentration distribution by arranging a plurality of deposition sources closely.

  The embodiments described above as the embodiments of the present invention can be implemented in appropriate combination as long as they do not contradict each other. Also, those in which those skilled in the art appropriately added, deleted, or changed the design based on the display device of each embodiment, or those in which the process was added, omitted, or changed in conditions are also included in the present invention. As long as the gist is provided, it is included in the scope of the present invention.

  In addition, even for other operational effects different from the operational effects brought about by the aspects of the above-described embodiments, those that are apparent from the description of the present specification, or that can be easily predicted by those skilled in the art, Of course, it is understood that the present invention provides.

DESCRIPTION OF SYMBOLS 100 Organic EL display device 102 Pixel part 103 Scan line drive circuit 104 Data line drive circuit 105 Driver IC
201 Pixel 202 Thin Film Transistor 301 First Substrate 302 Underlayer 303 Thin Film Transistor (TFT)
304 First insulating layer 305 Pixel electrode (anode)
306 Bank 307 EL layer 308 Common electrode (cathode)
309 EL element 310 Insulating film 311 Filler 312 Second substrate 313R Color filter corresponding to R (red) 313G Color filter corresponding to G (green) 313B Color filter corresponding to B (blue) 314 Black matrix 401 First charge Transport layer 402 First light-emitting layer 403 Second charge-transport layer 404 Second light-emitting layer 405 Third charge-transport layer 501a First deposition source 502a Second deposition source 503a Third deposition source 501b First dopant 502b Host 503b Second dopant 504 Substrate 402a First light emitting region 402b Second light emitting region 402c Undoped region 601 and 602 Curve showing concentration distribution

Claims (20)

An EL display device including a display unit including a plurality of pixels,
The plurality of pixels include an EL element having a light emitting layer including a host and at least two kinds of dopants,
The EL display device, wherein the at least two kinds of dopants have different concentration distributions with respect to the host. The at least two kinds of dopants include a first dopant and a second dopant,
The first dopant has a concentration distribution in which the concentration gradually decreases in the first direction, and the second dopant has a concentration distribution in which the concentration gradually increases in the first direction. The EL display device described in 1.   The EL display device according to claim 2, wherein the first dopant has a peak concentration in the vicinity of one end on the pixel electrode side, and the second dopant has a peak concentration in the vicinity of the other end on the common electrode side.   3. The EL display device according to claim 2, wherein the light emitting layer has a region where the concentration of the first dopant and the second dopant with respect to the host is 15% or less.   The EL display device according to claim 1, wherein the at least two kinds of dopants include a dopant that emits yellow light and a dopant that emits yellow-green light.   The EL display device according to claim 1, wherein the at least two kinds of dopants include a dopant that emits blue light and a dopant that emits green light.   The EL display device according to claim 1, wherein the at least two kinds of dopants include a dopant that emits red light and a dopant that emits green light.   2. The EL display device according to claim 1, wherein the EL element includes the light emitting layer and another light emitting layer that emits light having a color complementary to a light emission color of the light emitting layer. Forming a pixel electrode on the insulating surface;
Forming a light emitting layer including a host and at least two kinds of dopants on the pixel electrode so that the at least two kinds of dopants have different concentration distributions with respect to the host;
Forming a common electrode on the light emitting layer,
Manufacturing method of EL display device.   The at least two kinds of dopants include a first dopant having a concentration distribution in which the concentration gradually decreases in the first direction, and a second concentration distribution in which the concentration gradually increases in the first direction. The method for manufacturing an EL display device according to claim 9, wherein a dopant is contained.   The light emitting layer is formed so that the peak concentration of the first dopant is located near one end on the pixel electrode side and the peak concentration of the second dopant is located near the other end on the common electrode side. The manufacturing method of EL display apparatus as described in 1 ..   11. The method for manufacturing an EL display device according to claim 10, wherein the light emitting layer is formed so as to have a region in which both the concentration of the first dopant and the second dopant are 15% or less with respect to the host.   The method for manufacturing an EL display device according to claim 9, wherein the at least two kinds of dopants include a dopant that emits yellow light and a dopant that emits yellow-green light.   The method of manufacturing an EL display device according to claim 9, wherein the at least two kinds of dopants include a dopant that emits blue light and a dopant that emits green light.   The method of manufacturing an EL display device according to claim 9, wherein the at least two kinds of dopants include a dopant that emits red light and a dopant that emits green light.   The method for manufacturing an EL display device according to claim 9, further comprising forming another light emitting layer that emits light having a color complementary to a light emission color of the light emitting layer on the pixel electrode.   The method for manufacturing an EL display device according to claim 10, wherein when forming the light emitting layer on the pixel electrode, in-line deposition is performed in which deposition sources are arranged in the order of the first dopant, the host, and the second dopant. Forming a pixel electrode on the insulating surface;
A light emitting layer is formed on the pixel electrode by performing in-line deposition in the order of the first dopant, the host, and the second dopant,
Forming a common electrode on the light emitting layer,
Manufacturing method of EL display device.   The method for manufacturing an EL display device according to claim 18, further comprising: forming another light emitting layer that emits a color complementary to a color emitted from the light emitting layer on the light emitting layer. The method for manufacturing an EL display device according to claim 19, wherein a charge transport layer is further formed before and after forming the light emitting layer and the other light emitting layer.

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