JP2013157424A - Organic el panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic EL panel capable of expressing arbitrary design without deteriorating appearance during non-emission.SOLUTION: An organic EL panel 10 includes an organic EL element formed on a support substrate 11, the organic EL element being formed by at least laminating organic light emitting layers 14b, 14c and an electron injection layer 14e between an anode 12 and a cathode 15. The electron injection layer is formed so as to express arbitrary design. The electron injection layer 14e is also formed to have a dot shape where dot size and/or dot density is partially different.

Description

  The present invention relates to an organic EL (Electro Luminescence) panel.

  Conventionally, an organic EL element known as a self-luminous element formed of an organic material is, for example, a first electrode made of ITO (Indium Tin Oxide) or the like serving as an anode, an organic layer having at least a light emitting layer, and a cathode. A non-translucent second electrode made of aluminum (Al) or the like is sequentially laminated (for example, see Patent Document 1).

  Such an organic EL element emits light by injecting holes from the first electrode and injecting electrons from the second electrode, and the holes and electrons recombine in the light emitting layer. In addition to being employed in displays, organic EL elements have also been developed as surface-emitting lighting in recent years. Furthermore, since a highly light-reflective material is mainly used for the cathode, an organic EL element is formed on a light-transmitting substrate as disclosed in Patent Document 2 or the like to form a self-luminous mirror. Is also known.

JP 59-194393 A JP 2000-41807 A

  As a simple method for expressing a design in an organic EL panel using an organic EL element, a method is known in which an insulating film is formed between both electrodes and a light emitting portion is formed in an arbitrary shape (see Patent Document 2). ).

  However, in the method of defining the shape of the light emitting part by forming an insulating film between both electrodes, the boundary between the light emitting part and the non-light emitting part is noticeable at the time of non-light emission due to the color and film thickness of the insulating film, and the appearance is impaired. There was a problem. Such a problem becomes a problem particularly when an organic EL panel is used as a mirror because the appearance of the mirror surface is not uniform when no light is emitted. However, as used in high-definition displays, the method of arranging light-emitting parts in a matrix is expensive, including the manufacturing process and drive method, and should be used for simple displays and lighting. I can't.

  Therefore, the present invention has been made in view of this problem, and an object thereof is to provide an organic EL panel capable of expressing an arbitrary design without impairing the appearance when no light is emitted.

In order to solve the above-described problems, the present invention provides an organic EL panel in which an organic EL element formed by laminating at least an organic light emitting layer and an electron injection layer between an anode and a cathode is formed on a support substrate. Because
The electron injection layer is formed so as to form a predetermined design.

  In addition, the electron injection layer is formed in a halftone dot shape having partially different sizes and / or densities.

Further, a voltage is applied between the anode and the cathode so that the light emission luminance of the portion where the electron injection layer is not formed is 20 cd / m ² or less.

  According to the present invention, it is possible to express an arbitrary design without impairing the appearance when no light is emitted.

1 is a schematic cross-sectional view showing an organic EL panel that is an embodiment of the present invention. The figure which shows the light emission surface of an organic electroluminescent panel same as the above. The figure which shows the luminance-voltage characteristic and current density-voltage characteristic of the 1st area | region and 2nd area | region in Example 1 of this invention. The figure which shows the luminance-voltage characteristic and current density-voltage characteristic of the 1st area | region and 2nd area | region in Example 2 of this invention.

  Hereinafter, embodiments in which the present invention is applied to an organic EL panel will be described with reference to the accompanying drawings.

  FIG. 1 is a diagram showing an organic EL panel 10 according to an embodiment of the present invention. As shown in FIG. 1A, the organic EL panel 10 includes a support substrate 11, a first electrode 12 that is a transparent electrode, an insulating film 13, an organic layer 14, and a second electrode 15 that is a reflective electrode. The sealing member 16 is mainly configured. A laminated body composed of each part formed on the support substrate 11 constitutes an organic EL element. The organic EL element emits light when a voltage is applied between both electrodes, and the light L emitted from the organic EL element is emitted to the outside from the surface (the surface on the viewer side) of the support substrate 11 that is the light emitting surface. That is, the organic EL panel 10 is a bottom emission type organic EL panel.

  The support substrate 11 is a rectangular substrate made of translucent non-alkali glass, for example. Other glass substrates such as alkali glass may be used, and the glass thickness is not particularly limited. On the support substrate 11, a first electrode 12, an insulating film 13, an organic layer 14, and a second electrode 15 are sequentially stacked.

The first electrode 12 serves as an anode for injecting holes, and a transparent conductive material such as ITO or AZO is formed on the support substrate 11 with a film thickness of 50 to 500 nm by means such as sputtering or vacuum deposition. And a transparent electrode formed by patterning into a predetermined shape by means such as photolithography. The surface of the first electrode 12 is subjected to a surface treatment such as UV / O ₃ treatment or plasma treatment.

  The insulating film 13 covers the peripheral region of the support substrate 11 including the edge of the first electrode 12. For example, a polyimide-based or phenol-based insulating material is formed in a layer shape by means such as a spin coat method, and a photolithography method. And patterning to a desired shape. In the present embodiment, the insulating film 13 does not delimit the shape of the light emitting part, but merely for preventing a short circuit between the electrodes 12 and 15 in the peripheral region.

  The organic layer 14 is formed of a multilayer including at least an organic light emitting layer made of an organic material, and is formed on the first electrode 12. In this embodiment, as shown in FIG. 1B, the hole injection transport layer 14a, the first light emitting layer 14b, the second light emitting layer 14c, the electron transport layer 14d, and the electrons are sequentially formed from the first electrode 12 side. The injection layer 14e is formed by laminating sequentially.

  The hole injecting and transporting layer 14a has a function of taking holes from the first electrode 12 and transmitting them to the first light emitting layer 14b. For example, a hole transporting organic material such as an amine compound is deposited by means such as vapor deposition. It is formed in a layer shape with a film thickness of about 15 to 40 nm. The hole injecting and transporting layer 14a has a glass transition temperature of 130 ° C. or higher and an energy gap of about 3.1 eV.

  The first light emitting layer 14b is made of an organic material, for example, a thin film layer in which a fluorescent material having a fluoranthene skeleton or a pentacene skeleton that emits orange light is formed into a layer having a film thickness of 5 nm or less by means such as vapor deposition. As the first light emitting layer 14b, a phosphorescent material or a heat delay fluorescent material may be used in addition to a fluorescent material, or a mixed layer of a host material and a light emitting dopant may be used.

The 2nd light emitting layer 14c consists of a mixed layer with a film thickness of 15-60 nm which mixed host material and the light emission dopant by means, such as co-evaporation.
The host material can transport holes and electrons, and has a function of causing the luminescent dopant to emit light by recombination of holes and electrons in the molecule. The host material has an energy gap of about 3.3 eV and a glass transition temperature of about 120 ° C. Specifically, it consists of an anthracene derivative, for example.
The light-emitting dopant has a function of emitting light in response to recombination of holes and electrons, and is made of an organic material that exhibits a predetermined emission color different from that of the first light-emitting layer 14b. In this embodiment, for example, a fluorescent material made of styrylamine or an amine-substituted styrylamine compound that emits blue light is used in a doping amount that does not cause concentration quenching. In addition to the fluorescent material, a phosphorescent material or a thermally delayed fluorescent material may be used as the light emitting dopant.

The electron transport layer 14d has a function of transmitting electrons to the second light-emitting layer 14c. For example, an electron transport material made of aluminum quinoline (Alq ₃ ), a triazine compound, or the like is formed into a layer having a thickness of about 8 to 30 nm. It is formed.

  The electron injection layer 14e has a function of taking electrons from the second electrode 15. For example, lithium fluoride (LiF) or lithium quinoline (Liq) is formed in a halftone dot shape with a film thickness of about 1 nm by means such as vapor deposition. It will be. Here, as a method for forming the electron injection layer 14e in a dot pattern, in the vapor deposition method, a material to be the electron injection layer 14e is vapor-deposited on the support substrate 11 through a vapor deposition mask having a dot-shaped opening. Moreover, the electron injection layer 14e is formed so that the predetermined design defined by the pattern of the opening part of the said vapor deposition mask may be comprised as a whole. Here, the “design” specifically represents a number, a character, a figure, a pattern, an image, a character, or a combination thereof when viewed from the light emitting surface side of the organic EL panel 10. The halftone dot electron injection layer 14e forms a predetermined design means that the design is drawn by the electron injection layer 14e which is a halftone dot. The dot-like electron injection layer 14e is formed so that the size and / or density thereof is partially different. That is, gradation (shading) is applied to the design formed by the dot-shaped electron injection layer 14e by the AM screening method for changing the dot size, the FM screening method for changing the dot density, or the hybrid screening method using both in combination. Is given. The vapor deposition mask used for the formation of the electron injection layer 14e is manufactured by appropriately selecting a processing method according to the definition of the design formed by the electron injection layer 14e. When the design is relatively rough (resolution is low), the dot-shaped openings are formed by laser processing on SUS304 serving as a base material to produce a laser metal mask. Further, in order to increase the resolution of the design, a photomask is used to form the dot-shaped openings in SUS304 by etching, thereby producing an etching metal mask. The opening that can be formed with an etching metal mask is square and has a side of about 100 μm. As a mask that further refines the design, there is an active metal mask using Ni as a base material. For example, if an active metal mask is used, the openings are formed as a square opening having a side of 52 μm, a square opening having a side of 36 μm, and a square opening having a side of 24 μm. It is possible to partially change the size of the electron-injecting layer 14e and apply high-definition shading to the design by the AM screening method.

  The second electrode 15 serves as a cathode for injecting electrons. On the electron injection layer 14e or the electron transport layer 14d, for example, Al, magnesium (Mg), cobalt (Co), Li, gold (Au), copper ( This is a reflective electrode made of a conductive film in which a low-resistance conductive material such as Cu) or zinc (Zn) is formed into a layer having a thickness of 50 to 200 nm by means such as sputtering or vacuum deposition.

  The sealing member 16 is made of, for example, a glass material, and is formed into a concave shape by an appropriate method such as molding, sandblasting, cutting, or etching. The sealing member 16 is hermetically disposed on the support substrate 11 via an adhesive 17 made of, for example, an ultraviolet curable epoxy resin, and the organic EL element is sealed. A hygroscopic agent (not shown) is disposed in a sealing space formed by the support substrate 11 and the sealing member 16. The sealing member 16 may have a flat plate shape. In this case, the sealing member 16 is disposed on the support substrate 11 via a spacer.

  As described above, the organic EL panel 10 is configured. Note that well-known contents such as routing wirings and terminals formed on the support substrate 11 and connected to the first electrode 12 or the second electrode 15 are omitted as appropriate for the sake of simplicity.

FIG. 2 is a front view showing the light emitting surface of the organic EL panel 10. In the present embodiment, when viewed from the light emitting surface of the organic EL panel 10, a first region A1 where the electron injection layer 14e is formed and a second region A2 where the electron injection layer 14e is not formed are formed.
In the organic EL element, when the electron injection layer 14e is formed and when the electron injection layer 14e is not formed, the current does not flow easily when the electron injection layer 14e is not formed as compared with the case where the electron injection layer 14e is formed. The light emission luminance is greatly different when the same voltage is applied. As a result of intensive studies, the inventor of the present application has found that an arbitrary design can be expressed by forming only the electron injection layer 14e into a predetermined shape using this characteristic.
That is, the first region A1 in which the electron injection layer 14e is formed is a portion with high current efficiency, so that the light emission luminance is high, and the second region A2 in which the electron injection layer 14e is not formed is a portion with low current efficiency. Since the light is not emitted or the light emission luminance is extremely low, the viewer is given a predetermined design drawn by light emission of the halftone dot first region A1 due to the luminance difference between the two regions A1 and A2 (in FIG. 2, the numeral “1”). )). Strictly speaking, since the second region A2 also exhibits a certain amount of light emission depending on the applied voltage value, in order for the viewer to see the design well, the applied voltage value is the light emission luminance of the first region A1. In the case of about 1000 cd / m ² , it is desirable that the light emission luminance of the second region A2 be a value that is 20 cd / m ² or less.
Furthermore, in this embodiment, the electron injection layer 14e is formed in a halftone dot shape, and the electron injection layer 14e is formed so that the size and / or density thereof is partially different. In FIG. 2, the number “1” is formed so that the density of the electron injection layer 14 e is the highest and the density of the electron injection layer 14 e gradually decreases upward. This makes it possible to express gradation (shading) in the design by partially varying the luminance. Although FIG. 2 shows an example in which only the density of the electron injection layer 14e is partially changed for convenience, the electron injection layer 14e in which the size of the electron injection layer 14e is partially changed as described above. The size and density may be partially changed. Moreover, in this embodiment, when gradation is not expressed, the electron injection layer 14e may be formed in a segment shape forming a design singly or in combination. Further, if the design can be visually recognized by the luminance difference (light / dark), a dot-like electron injection layer 14e may be formed around the number “1” as a background in FIG. In this case, the size and / or density of the surrounding electron injection layer 14e is sufficiently smaller than the electron injection layer 14e inside the numeral “1”.

  According to this embodiment, the first electrode 12, the hole injection transport layer 14 a, the first light emitting layer 14 b, the second light emitting layer 14 c, the electron transport layer 14 d, and the electron injection that are stacked on the support substrate 11. An arbitrary design can be expressed by a simple method of forming only the electron injection layer 14e out of the layer 14e and the second electrode 15 so as to form a predetermined design. Further, since the electron injection layer 14e is a thin film of about 1 nm, the boundary portion between the first region A1 and the second region A2 is visible to the viewer when no light is emitted as in the method of defining the light emission shape by the insulating film. It will not be done. Therefore, the organic EL panel 10 can be used as a simple display or illumination when emitting light, and the second electrode 15 without a pattern can be visually recognized when not emitting light, so that the entire surface can be used as a mirror surface. Further, the electron injection layer 14e is formed only in the peripheral portion of the light emitting surface of the organic EL panel 10, and the electron injection layer 14e is not formed in the central portion, or the second electrode 15 is formed on the support substrate 11 adjacent to the organic EL element. The organic EL panel 10 can be a mirror having illumination having an arbitrary design, for example, by providing a mirror surface portion in which the light-reflective material to be formed is formed in layers.

  The above description exemplifies the present invention, and it goes without saying that various changes and modifications can be made without departing from the scope of the invention. The laminated structure of the organic EL element in the present invention is not limited to this embodiment, and the hole injection layer and the hole transport layer may be formed from the first electrode 12 side instead of the hole injection transport layer 14a. Alternatively, the light emitting layer may be a single layer, or a plurality of electron transport layers may be formed.

  Next, the effects of the present invention will be specifically described with reference to examples.

First, the first electrode 12 was formed by forming ITO with a film thickness of 145 nm on the support substrate 11 made of a glass material by a sputtering method.
Next, a hole transporting material HT1 was formed as a hole injecting and transporting layer 14a on the first electrode 12 with a film thickness of 30 nm by vacuum deposition without being exposed to the atmosphere. The hole transporting material HT1 has a glass transition temperature Tg = 132 ° C., Ip = 5.4 eV, and μh = 4 × 10 ⁻⁴ cm ² / Vs.
Next, a fluorescent material AD1 exhibiting orange light emission was formed as a first light emitting layer 14b on the hole injecting and transporting layer 14a with a film thickness of 1 nm by vacuum deposition. The fluorescent material AD1 has Eg (energy gap) = 2.0 eV, Ip (ionization potential) = 5.2 eV, and a glass transition temperature Tg = 156 ° C.
Next, a mixed layer of a host material EM1 and a fluorescent dopant BD1 exhibiting blue-green light emission is contained as a second light-emitting layer 14c on the first light-emitting layer 14b at a weight percent ratio of EM1: BD1 = 40: 2. The film was formed by co-evaporation to a film thickness of 40 nm. The host material EM1 has Ip = 5.9 eV, Ea (LUMO energy, that is, electron affinity) = 2.9 eV, μe (electron mobility) = 3 × 10 ⁻³ cm ² / Vs, μh (hole mobility) = 2 × 10 ⁻³ cm ² / Vs, glass transition temperature Tg = 130 ° C. The fluorescent dopant BD1 has Eg = 2.7 eV, Ip = 5.6 eV, and a glass transition temperature Tg = 200 ° C.
Next, as the electron transport layer 14d, the electron transport material ET1 that is a triazine derivative was formed with a film thickness of 20 nm on the second light emitting layer 14c by vacuum deposition. The electron transport material ET1 has Ip = 6.0 eV, Ea = 3.0 eV, μe = 4 × 10 ⁻⁴ cm ² / Vs, and a glass transition temperature Tg = 136 ° C.
Next, LiF was formed on the electron transport layer 14d as the electron injection layer 14e with a film thickness of 1 nm by a vacuum deposition method. At this time, using the vapor deposition mask having the dot-like pattern of openings, the electron injection layer 14e has a halftone dot shape with an aperture ratio (area of the entire electron injection layer 14e / area of the entire light emitting surface) of 30%. In addition to being formed, the entire electron injection layer 14e was formed to form a predetermined design.
Next, Al was formed as a second electrode 15 on the electron injection layer 14e with a film thickness of 100 nm by vacuum deposition.
Thereafter, the sealing member 16 coated with a hygroscopic agent was then placed on the support substrate 11 and sealed to produce an organic EL panel as Example 1.
Example 1 is a mirror surface when not energized and the boundary line is not visually recognized. When a voltage is applied and energized, the design of the first region A1 by white light emission can be visually recognized, and the emission luminance is 1000 cd / m ² . The power consumption at the time was 12.9 mW / cm ² .

FIG. 3A shows the luminance-voltage (L) in the first region A1 where the electron injection layer 14e is formed in Example 1 and the second region A2 where the electron injection layer 14e is not formed. -V) characteristics, and FIG. 3B shows the current density-voltage (J-V) characteristics in the first region A1 and the second region in the first embodiment. In measuring the luminance or current density, the organic EL element having the same stacked structure as the first region A1 (that is, the electron injection layer 14e is formed) and the same stacked structure as the second region A2. An organic EL element (that is, the electron injection layer 14e is not formed) was produced, and the luminance or current density was measured. In FIG. 3, the characteristic indicating the first region A1 is expressed as “with electron injection layer”, and the characteristic indicating the second region A2 is expressed as “without electron injection layer”. In the first region A1, a current of 10 mA / cm ² flows at an applied voltage of 4.2 V, and the light emission luminance is 1000 cd / m ² , whereas in the second region A2, 0 is applied at an applied voltage of 4.2 V. A current of 0.1 mA / cm ² flowed, and the light emission luminance was 4 cd / cm ² . According to this result, the luminance difference between the first region A1 and the second region A2 is 250 times, and it is possible to express an arbitrary design by making only the electron injection layer 14e a predetermined shape. It is clear from FIG. Further, it can be seen that the second region A2 has a lower current flowing than the first region A1. Moreover, although the said evaporation mask which has the said dot-shaped opening part tends to produce the said opening part clogging, since Example 1 is only used for film-forming of the electron injection layer 14e of about 1 nm, 1 sheet preparation At times, the material deposited on the mask was relatively small, and the deposition mask could be stably produced without causing clogging. Although it depends on the size of the opening, it is possible to continuously produce 100 sheets if it is assumed that the deposited film thickness is changed to 0.1 μm.

In Example 2, the organic light emitting layer was a single layer consisting of only the second light emitting layer 14c.
First, the first electrode 12 was formed by forming ITO with a film thickness of 145 nm on the support substrate 11 made of a glass material by a sputtering method.
Next, a hole transporting material HT1 was formed as a hole injecting and transporting layer 14a on the first electrode 12 with a film thickness of 80 nm by vacuum deposition without being exposed to the atmosphere.
Next, a mixed layer of a host material EM1 and a fluorescent dopant BD1 exhibiting blue-green light emission is contained as a second light emitting layer 14c on the hole injecting and transporting layer 14a at a wt% ratio of EM1: BD1 = 40: 2. The film was formed by co-evaporation to a film thickness of 40 nm.
Next, Alq ₃ was formed as an electron transport layer 14d on the second light-emitting layer 14c to a thickness of 20 nm by vacuum deposition.
Next, LiF was formed on the electron transport layer 14d as the electron injection layer 14e with a film thickness of 1 nm by a vacuum deposition method. At this time, using the vapor deposition mask having the dot-like pattern of openings, the electron injection layer 14e is formed in a dot shape with an aperture ratio (area of the electron injection layer 14e / area of the entire light emitting surface) of 30%. In addition, the entire electron injection layer 14e was formed to form a predetermined design.
Next, Al was formed as a second electrode 15 on the electron injection layer 14e with a film thickness of 100 nm by vacuum deposition.
Thereafter, the sealing member 16 coated with a hygroscopic agent was then placed on the support substrate 11 and sealed to produce an organic EL panel as Example 2.
In Example 2, the mirror surface is not visible when no current is applied, and the boundary line is not visually recognized. When a voltage is applied and the current is applied, the design of the first region A1 by blue-green light emission can be visually recognized, and the emission luminance is 1000 cd / m ² . In some cases, power consumption was 24.4 mW / cm ² .

FIG. 4A shows the luminance-voltage (L) in the first region A1 where the electron injection layer 14e is formed in Example 2 and the second region A2 where the electron injection layer 14e is not formed. FIG. 4B shows the current density-voltage (JV) characteristics in the first region A1 and the second region in Example 2. FIG. In measuring the luminance or current density, the organic EL element having the same stacked structure as the first region A1 (that is, the electron injection layer 14e is formed) and the same stacked structure as the second region A2. An organic EL element (that is, the electron injection layer 14e is not formed) was produced, and the luminance or current density was measured. In FIG. 4, the characteristic indicating the first region A1 is expressed as “with electron injection layer”, and the characteristic indicating the second region A2 is expressed as “without electron injection layer”. In the first region A1, a current of 9.3 mA / cm ² flows at a voltage of 7V and the light emission luminance is 1000 cd / m ² , whereas in the second region A2, a current of 1 mA / cm ² is applied at a voltage of 7V. The flow emission luminance was 20 cd / cm ² . According to such a result, the luminance difference between the first region A1 and the second region A2 is 50 times, and it is possible to express any design by making only the electron injection layer 14e a predetermined shape. It is clear from FIG. Further, it can be seen that the second region A2 has a lower current flowing than the first region A1.

(Comparative Example 1)
Comparative Example 1 was carried out in the same manner as in Example 1 except that the electron injection layer 14e was formed on the entire surface of the electron transport layer 14d without using a vapor deposition mask having a dot-like opening pattern when forming the electron injection layer 14e. An organic EL panel was prepared.
In Comparative Example 1, when a voltage was applied and energized, the entire surface emitted white light, and the power consumption was 42.0 mW / cm ² when the light emission luminance was 1000 cd / m ² . Thus, it can be seen that Example 1 consumes less power than Comparative Example 1 and can emit light with low power. This is because, in Example 1, the electron injection layer 14e was formed in a halftone dot shape so as to form a predetermined design, so that the electron injection layer 14e was not formed as shown in FIG. This is due to the occurrence of a location with a small amount of flowing current.

(Comparative Example 2)
Comparative Example 1 was performed in the same manner as in Example 2 except that the electron injection layer 14e was formed on the entire surface of the electron transport layer 14d without using a vapor deposition mask having a dot-like opening pattern when forming the electron injection layer 14e. An organic EL panel was prepared.
In Comparative Example 1, when a voltage was applied and energized, the entire surface emitted white light, and the power consumption was 65.0 mW / cm ² when the light emission luminance was 1000 cd / m ² . Thus, it can be seen that Example 2 consumes less power than Comparative Example 2 and can emit light with low power. As in Example 1, in Example 2, the electron injection layer 14e is formed in a dot pattern and has a predetermined design, and as shown in FIG. 4B, the electron injection layer 14e is formed. This is because 14e is not formed and there is a portion where the flowing current is small.

  The present invention is suitable for an organic EL panel that expresses an arbitrary design.

10 Organic EL Panel 11 Support Substrate 12 First Electrode (Anode)
14 Organic layer 14a Hole injection transport layer 14b First light emitting layer (organic light emitting layer)
14c Second light emitting layer (organic light emitting layer)
14d Electron transport layer 14e Electron injection layer 15 Second electrode (cathode)
A1 first area A2 second area

Claims (3)

An organic EL panel in which an organic EL element formed by laminating at least an organic light emitting layer and an electron injection layer between an anode and a cathode is formed on a support substrate,
An organic EL panel, wherein the electron injection layer is formed so as to form a predetermined design. 2. The organic EL panel according to claim 1, wherein the electron injection layer is formed in a halftone dot shape partially different in size and / or density. 3. The organic material according to claim 1, wherein a voltage is applied between the anode and the cathode so that a light emission luminance in a region where the electron injection layer is not formed is 20 cd / m ² or less. EL panel.

Images