JP3322204B2 - Multicolor light-emitting organic electroluminescent device and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multicolor light-emitting organic EL device used for an organic electroluminescence (hereinafter, referred to as "EL") display and a method for producing the same.

[0002]

2. Description of the Related Art An applied voltage of 1 by Tang et al.
A stacked EL device capable of obtaining a high luminance of 1000 cd / m ² or more at 0 V is reported (Appl. Phys. Lett. 51, 913 (198)
7)) Since then, organic EL devices have been actively studied for practical use. The organic EL element is a thin-film spontaneous light-emitting element, and has low driving voltage, high resolution, and high visibility.
It has features not found in other systems, and is expected to be applied to flat panel displays. When the application of the organic EL element to a display is considered, multicolor display is indispensable in order to expand the application.

As a method of multicolor display, there are a method of sequentially patterning three primary color EL elements and disposing them on a plane, and a method of providing three primary color (red, green and blue) color filters on a white light emitting element. Conceivable.

[0004] However, patterning of the three primary color EL elements reduces the efficiency of the elements and requires a very complicated process, which makes mass production difficult. In addition, no material has been found that can produce color with good color purity, especially in red, and it has not been put to practical use. On the other hand, in the color filter method, a white light-emitting element capable of stably obtaining sufficient luminance has not yet been obtained, and has not yet been put to practical use.

Therefore, in recent years, a color conversion method has been developed in which a fluorescent material that absorbs light in an emission range of an organic EL element and emits fluorescence in a visible light range is used as a filter (hereinafter referred to as a “color conversion filter”). JP-A-3-152897 and JP-A-5-258860. Since the emission color of the light-emitting element is not limited to white, an organic light-emitting element having higher luminance can be used as a light source. In a color conversion method using a blue light-emitting organic EL element, the conversion efficiency to a long wavelength is 60% or more. .

[0006]

One of the points to be noted when manufacturing a display by the color conversion method is the distance between the color conversion filter and the organic EL element. As the distance increases, the emission of light from adjacent pixels tends to leak, and the viewing angle characteristics deteriorate. Accordingly, the shorter the distance between the color conversion filter and the organic EL element, the better the viewing angle characteristics, so that it can be said that it is desirable to form the organic EL layer directly on the upper surface of the color conversion filter. However, according to the study of the present inventors, organic E
Fluorescent materials used to convert L emission into light of a desired wavelength are very weak to light of a specific wavelength, or to moisture, heat, organic solvents, etc., and their functions are easily lost due to these effects. It turned out to be. Therefore, when the organic EL element layer is formed on the upper surface of the color conversion filter, various restrictions occur.

When a color conversion filter is created,
Due to the difference in the conversion efficiency of the fluorescent material corresponding to each color, in order to balance the colors, the thickness of the dye layer of each color is not uniform, and a step occurs in the color conversion filter on the glass substrate 1 as shown in FIG. . According to the experiments performed by the present inventors, in particular, the conversion material for red has lower efficiency than other colors (green and blue), and a film thickness of several tens μm (green: 4 to 10 μm, blue: about 0 to 5 μm), and it was also found that a step was generated at least about 10 μm. When the organic EL element layer is formed directly on this step, disconnection of the electrode and unevenness of the thickness of the organic light emitting layer are apt to occur, and stable light emission from the organic light emitting layer cannot be obtained.

As a means for solving these problems, a thin film glass plate is bonded on a color conversion filter, and an organic EL
A method of forming an element layer is disclosed (Japanese Patent Laid-Open No. 8-2).
No. 79394). However, there is a limit to thinning the glass plate, and a distance of at least about 100 μm exists between the color conversion filter and the organic EL element layer.
This causes a narrow viewing angle. Further, it is very difficult to cope with an increase in the area due to the problem of machining accuracy and the problem of insufficient mechanical strength of glass.

The present invention has been made in view of the above-mentioned problems, and has a superior viewing angle characteristic, and does not substantially deteriorate a fluorescent material in a manufacturing process. The purpose is to provide.

[0010]

Means for Solving the Problems To solve the above problems, the present invention is as follows. (1) An organic EL element in which an organic light-emitting layer that emits light by injecting electric charges is provided on a layer in which a plurality of different phosphor layers are separated in a plane on a transparent support substrate,
A multicolor light-emitting organic EL element, wherein the phosphor layer and the organic EL element are arranged so that each of the phosphor layers can absorb light emitted from the organic light-emitting layer and emit light; between the the layer organic light-emitting layer, the as a protective layer of the fluorescent material layer, the number-average molecular weight 50,000～500,0
A cross-linked urethane resin using a urethane resin of No. 00 ,
A multicolor light emitting EL device comprising at least two layers, a hard coat layer having gas barrier properties and hardness capable of withstanding the formation of the EL device.

(2) In the multicolor light-emitting EL device, one of the phosphor layers is a multicolor light-emitting organic EL device in which a color filter for adjusting the emission color and color purity from the organic light-emitting layer is replaced. is there.

[0012] (3) In the multi-color light emitting EL elements, before
The crosslinked urethane resin has a number average molecular weight of 50,000.
A number average molecular weight of 1,000 to 30,000 containing an isocyanate group of 10 to 30% by weight to a urethane resin of up to 500,000.
This is a multicolor light emitting organic EL device in which a film made of a resin formed by adding 100,000 crosslinking agents is used as a protective layer of the phosphor layer.

[0013] (4) In the multi-color light emitting EL elements of the (3), the multi-additive amount of the crosslinking agent having an isocyanate group is in the range of 1 to 50% by weight relative to the solid content of the <br/> urethane resin It is a color light emitting organic EL device.

(5) In the multicolor light emitting EL device, the protective layer of the phosphor layer is a multicolor light emitting organic EL device containing 0.1 to 10% by weight of an ultraviolet absorber.

(6) In the multicolor light emitting EL device, the hard coat layer is a visible light transmitting resin layer or an inorganic oxide layer having a pencil hardness of 2H or more.

(7) In the multicolor light-emitting device according to the above (5) or (6), the hard coat layer is formed on the upper surface of the protective layer of the phosphor layer and cured by ultraviolet or visible light. It is a multicolor light emitting organic EL element which is a curable resin.

(8) In the method of manufacturing a multicolor light emitting EL device, an organic EL device layer is formed sequentially on the upper surface of the hard coat layer. .

According to the present invention, it is possible to maintain the color conversion function of the color conversion filter, achieve flattening of the color steps with a bonding layer having a minimum film thickness, and directly form a color on the hard coat layer. By forming the organic EL element, it is possible to provide a color display element having a short distance between the color conversion filter and the organic EL layer, that is, a high viewing angle characteristic. Further, the formation of the protective layer and the hard coat layer is very simple because a general method of forming a resin thin film such as a coating method can be applied, and also corresponds to an increase in the area of the display element. be able to.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings. FIG. 1 is a cross-sectional view of a typical element structure showing an embodiment of the invention, which is transparent and stable (from room temperature to 150 ° C.).
(A component that degrades the phosphor material and the organic EL element is not generated in the range of ° C.) On the supporting substrate 1 such as a glass substrate, red,
Phosphor dye layers 2 to 4 provided for blue and green colors, a protective layer 5 for these dye layers, a hard coat layer 6 having gas barrier properties, and an organic EL element layer 7 directly provided on the upper surface thereof
Consists of

The color conversion filter has a structure in which a red dye layer 2, a green dye layer 3, and a blue dye layer 4 are disposed on a plane of a supporting substrate 1 so as to be separated in a plane. There is no particular limitation on the method of forming each phosphor dye filter, and for example, photolithography, micellar electrolysis, or the like can be used. In the present invention, any one of the phosphor layers may be replaced with a color filter for making the color of emitted light from the organic light emitting layer and the color purity uniform.

In the present invention, the protective layer 5 of the color conversion filter has high transparency and adhesion, for example, 400 to 700 n.
It is preferable that the transmittance be 50% or more in the range of m and that a film can be formed on the color conversion filter in the order of μm. Further, a material that does not dissolve the materials of the phosphor layers 2 to 4 of the color conversion filter is used. As a preferable material of the protective layer 5, use of a cross-linked urethane resin, an olefin resin, an acrylic resin, an epoxy resin, a melamine resin, a phenol resin, an alkyd resin, an ester resin, an amide resin, or the like. Can be.

In particular, a cross-linked urethane-based resin has no effect on the underlayer, has good transparency, and is preferred as a protective layer. If such a resin has too low a molecular weight, the color conversion filter may be dissolved or the fluorescent dye itself in the color conversion filter may be deactivated. On the other hand, when the molecular weight is too high, preparation of the coating liquid becomes difficult. Therefore, the number average molecular weight is 50,0.
Urethane resins of 00 to 500,000 are particularly preferred.
Crosslinking of the urethane resin is performed by adding a crosslinking agent having an isocyanate group. The crosslinking agent to be added is preferably a high molecular compound containing 10 to 30% by weight of isocyanate groups and having a number average molecular weight in the range of 1,000 to 100,000. When the amount of isocyanate groups is small, the chemical resistance and hardness of the formed film become insufficient, and when the amount of isocyanate groups is too large, the reaction proceeds rapidly, and as a result, the film is not transparent, which contains many bubbles in the film. Will be.
Further, if the molecular weight is too low, there is a possibility that the color conversion filter as a base may be adversely affected as in the case of the urethane resin.

The coating method of the protective layer 5 is not particularly limited, and a usual spin coating method, roll coating method, casting method and the like can be used. The curing method is also not particularly limited, and heat curing, moisture curing, chemical curing, light curing, or a combination of these methods can be used.
However, in the case of the thermosetting method, the deterioration of the fluorescent material is taken into account.
It is desirable to carry out at a temperature up to about 0 ° C. In the case of the photo-curing method, it is desirable to carry out with visible light in consideration of the deterioration of the fluorescent material.

Next, the hard coat layer 6 according to the present invention has a barrier property against a gas and an organic solvent, has high transparency, and has a
The hardness is such that a thin film can be formed on the order of μm and can withstand the formation of the anode. Preferably, a material having a film hardness of 2H or more may be used, and a polymer material, an inorganic oxide, or the like can be used. In particular, a photocurable resin such as polyester acrylate, polyurethane acrylate, epoxy acrylate, polyether acrylate, oligoacrylate, alkyd acrylate, and polyol acrylate, or a combination of heat and light curable resin can provide a good film in a short curing time. Therefore, it is preferable. Ultraviolet or visible light can be used as light for photocuring. Ultraviolet light has high energy and is more suitable for curing resins than visible light. However, ultraviolet light may deactivate the functions of the phosphor layers 2 to 4 of the color conversion filter. When the hard coat layer 6 is cured by the method described above, it is preferable that the protective film 5 contains an ultraviolet absorber as necessary. When adding an ultraviolet absorber, it is important not to impair the transparency of the protective film 5. According to the experiments of the present inventors, it slightly varies depending on the type of the ultraviolet absorber,
When the content of the ultraviolet absorber in the protective film 5 is about 0.1 to 1
It was found that the hard coat layer 6 could be cured with ultraviolet light at 0% by weight without impairing the properties of the color conversion filter and the transparency of the protective film.

Organic EL directly formed on hard coat layer
The element layer 7 preferably emits light in the region from the near ultraviolet region to the visible region (blue-green). Specific layer configurations include (1) anode (transparent electrode) / organic light emitting layer / cathode (electrode) (2) anode (transparent electrode) / hole injection layer / organic light emitting layer / cathode (electrode) (3) Anode (transparent electrode) / organic light emitting layer / electron injection layer / cathode (electrode) (4) anode (transparent electrode) / hole injection layer / organic light emitting layer / electron injection layer / cathode (electrode) Japanese Unexamined Patent Publication No. Hei.
114487, JP-A-5-94876, JP-A-5-948
No. 94877, JP-A-5-125360, JP-A-5-125360
No. 134430, JP-A-6-200242, JP-A-6-2002
JP-A-234969, JP-A-7-11245, JP-A-7-11245
It can be formed by a known method disclosed in a publication such as -11246.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. Example 1 A multicolor organic EL device schematically shown in FIG. 1 was manufactured by the following forming process as an example.

Fusion glass (143 × 11) is used as the glass substrate 1 on which the color conversion filter is formed.
Color filter blue material (manufactured by Fuji Hunt Electronics Technology Co., Ltd.):
After the color mosaic CB-7001) was applied by spin coating, patterning was performed by photolithography to obtain a line pattern of the blue dye layer 4 with a 2 mm line and a 5.5 mm gap. Next, coumarin 6 (manufactured by Aldrich) / polyvinyl chloride resin was printed on the substrate by using a screen printing method, baked at 150 ° C., and a 2 mm line of the green dye layer 3 , a 5.5 mm gap, and a film thickness of 12 μm.
m line pattern was obtained. Further, Rhodamine 6G (manufactured by Aldrich) / polyvinyl chloride resin is printed on the substrate by a screen printing method, baked at 100 ° C., and a red dye layer 2 of 2 mm line, 5.5 mm gap, and film thickness of 3 mm.
A 0 μm line pattern was obtained.

[0028]Formation of protective layer Urethane resin (S-720Q, manufactured by Hodogaya Chemical Co., Ltd.)
To isocyanate-based crosslinking agent (Nippon PolyurethaneIndustry
Spin-coated with the addition of A2020)
Apply to the top of the color conversion filter by the method and air dry for 5 hours
Then, vacuum drying is performed at 60 ° C. to form a protective layer having a thickness of 7 μm.
Was.

Formation of Hard Coat Layer A visible curable resin (manufactured by Ardel: VLC15) is applied to the upper surface of the protective layer by a spin coat method, and the energy intensity is 60 mW / with a high-pressure mercury lamp equipped with a filter for cutting a wavelength of 400 nm or less. Irradiation with light of cm ² was performed for 6 minutes to form a hard coat layer having a thickness of 3 μm.

Formation of Organic EL Layer (Anode, Organic Layer, Cathode) FIG. 2 is a schematic diagram (cross section) of the layer structure of the organic EL element layer 7 manufactured in this embodiment. The organic EL element layer formed on the upper surface of the color conversion filter had a six-layer structure of transparent electrode 8 / hole injection layer 9 / hole transport layer 10 / light emitting layer 11 / electron injection layer 12 / cathode 13.

First, the transparent electrode 8 (IT) was formed on the upper surface of the protective layer film attached on the color conversion filter by sputtering.
O) was formed over the entire surface. Patterning is performed by applying a resist agent (OFPR-800, manufactured by Tokyo Ohka Co., Ltd.) on ITO, and then performing photolithography, and performing 2 mm line printing.
A stripe pattern having a pitch of 0.5 mm and a thickness of 100 nm was obtained.

Next, the substrate was mounted in a resistance heating evaporation apparatus, and a hole injection layer 9, a hole transport layer 10, a light emitting layer 11, and an electron injection layer 12 were sequentially formed without breaking vacuum. During film formation, the pressure in the vacuum chamber was reduced to 1 × 10 ⁻⁴ Pa. The hole injection layer 9 has the following formula: Copper phthalocyanine (CuPc) represented by
Laminated. The hole transport layer 10 has the following formula: 4,4'-bis [N- (1-naphthyl) -N represented by
-Phenylamino] biphenyl (α-NPD)
m. The light emitting layer 11 has the following formula: 4,4'-bis (2,2-diphenylvinyl) biphenyl (DPVBi) represented by the following formula was laminated to a thickness of 30 nm. The electron injection layer 12 has the following formula: 20 nm of aluminum chelate (Alq) was laminated.

Thereafter, the substrate is taken out of the vacuum chamber,
Attach a mask that can obtain a stripe pattern of 2 mm line and 0.5 mm gap perpendicular to the ITO line,
After being newly installed in the resistance heating evaporation apparatus, 200 nm of Mg / Ag (10: 1 weight ratio) was formed as the cathode 13.

Example 2 A benzotriazole ultraviolet absorber (Tinuvi manufactured by Ciba-Geigy) was added to a mixture of urethane and a crosslinking agent shown in Example 1.
n326) was added to the upper surface of the color conversion filter shown in Example 1 by a spin coating method,
Under the conditions shown in Example 1, a protective layer having a thickness of 7 μm was obtained.

Next, an ultraviolet curable resin (V259PA manufactured by Nippon Steel Chemical Co., Ltd.) is applied to the upper surface of the protective layer by spin coating, and the energy intensity is 100 mW / c by a high pressure mercury lamp.
m ² light was irradiated for 30 seconds to obtain a hard coat layer having a thickness of 3 μm. Thereafter, an organic EL element layer (anode, organic layer, cathode) was formed on the upper surface of the hard coat layer in the same manner as in Example 1.

Example 3 An ultraviolet-curable resin (manufactured by Nippon Steel Chemical Co., Ltd.) was applied to the upper surface of the color conversion filter whose surface was protected by the protective layer shown in Example 1.
V259PA) was applied by a spin coating method, and irradiated with light having an energy intensity of 100 mW / cm ² for 30 seconds using a high-pressure mercury lamp to obtain a 3 μm-thick hard coat layer. Thereafter, an organic EL element layer (anode, organic layer, cathode) was formed on the upper surface of the hard coat layer in the same manner as in Example 1.

[0037] Comparative Example Example 1 shows color conversion filter top into visible curable resin (Ardel made: VLC15) was applied by spin coating at a high pressure mercury lamp fitted with a filter to cut wavelengths below 400nm Energy intensity 60mW / cm
Light ² was irradiated for 6 minutes to form a hard coat layer having a thickness of 3 μm. Thereafter, an organic EL element layer (anode, organic layer, cathode) was formed on the upper surface of the hard coat layer in the same manner as in Example 1.

Evaluation The above four elements (Example 1, Example 2, Example 3, Comparative Example)
Table 1 below summarizes the evaluation results. The evaluation method and results of each item will be described after Table 1.

[0039]

[Table 1]

Evaluation 1: Protective Layer Thickness The height from the surface of the transparent support substrate 1 to the surface of the hard coat layer 6 as shown in FIG. As shown in Table 1, in each of the methods, the protective layer of the fluorescent material could be formed with a very thin film thickness.

[0041]Evaluation 2: Leveling performance (filter stage
difference) Using a surface roughness meter (Nihon Vacuum Technology)
(DEKTAK IIA). The present invention
According to the embodiment, the height distribution of the hard code layer surface is ±
It was as good as 1 μm or less. On the other hand, by applying resin
The height distribution of the hard code layer surface of the formed comparative example is ±
It was 5 μm or more.

Evaluation 3: Viewing Angle When the organic EL element emits monochromatic light, the angle up to the angle at which light emission leaks to the adjacent phosphor layer of another color is defined as the viewing angle. Was evaluated. All the elements had a viewing angle of 60 ° or more on both the left and right sides, and it was found that there was no practical problem.

Evaluation 4: Device Life FIG. 4 is a plot of the change over time of the dark spot size in each of the examples and comparative example 2. The device was stored under a nitrogen stream, and the state of growth of a dark spot in the light emitting portion (2 mm square) was observed with an optical microscope. No growth of dark spots was observed in each example, and it was found that the device was stable without deterioration.

Evaluation 5: Influence on Fluorescent Material CIE when each element was stored under a nitrogen stream and emitted monochromatic light
Table 2 below shows the results of evaluation based on changes in color coordinates.

[0045]

[Table 2]

From the results shown in Table 2, in Examples 1 and 2, the fluorescent material was protected by the protective layer and the hard coat layer, so that the fluorescent material functioned stably after forming the organic EL device. It was confirmed that. On the other hand, in the comparative example in which the hard coat layer was directly formed, a decrease in the characteristics was considered, which is considered to be because the fluorescent dye layer for red color conversion was damaged. Also, in Example 3 in which no ultraviolet absorber was added to the protective layer when using the ultraviolet-curable resin for the hard coat layer, a slight decrease in the properties was observed, but slightly lower than that of the comparative example. .

[0047]

As described above, according to the present invention, it is possible to easily and inexpensively manufacture a color display element having excellent viewing angle characteristics and emission life. In addition, when the hard coat layer 6 is cured with ultraviolet light, the function of the color conversion filter can be prevented from being deteriorated by including an ultraviolet absorber in the protective film 5.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an example of a multicolor light emitting organic EL device of the present invention using a color conversion filter protected by a protective layer and a hard coat layer.

FIG. 2 is a schematic sectional view showing a layer structure of an organic EL element layer used in Examples and Comparative Examples of the present invention.

FIG. 3 is a graph showing a growth state of a light-emitting part dark spot when the color display elements shown in Examples and Comparative Examples are stored under a nitrogen stream.

FIG. 4 is a schematic sectional view of a color conversion filter.

[Explanation of symbols]

 Reference Signs List 1 transparent support substrate 2 red dye layer 3 green dye layer 4 blue dye layer 5 protective layer 6 hard coat layer 7 organic EL layer 8 transparent electrode 9 hole injection layer 10 hole transport layer 11 organic light emitting layer 12 electron injection layer 13 electrode

Continuation of the front page (56) References JP 8-279394 (JP, A) JP 8-78158 (JP, A) JP 8-222369 (JP, A) JP 5-258860 (JP) , A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05B 33/00-33/28 C08G 18/00-18/87 C08G 71/00-71/04

Claims (8)

(57) [Claims] 1. A method according to claim 1, further comprising the steps of:
Charge is injected onto a layer on which multiple phosphor layers are arranged
Electr with organic light emitting layer that emits light
A luminescent element, wherein each of the phosphor layers is
Before absorbing the light emitted from the organic light emitting layer and emitting light,
A phosphor layer and the organic electroluminescent element;
Multicolor light-emitting organic electroluminescent device provided with
In the device, between the phosphor layer and the organic light emitting layer, the phosphor layer
With a protective layerNumber average molecular weight 50,000-500,
-Type urethane resin using 000 urethane resin
Withstand the formation of the electroluminescent element.
Hard coat layer with high gas barrier properties and hardness
A multi-color light emitting element characterized by having at least two layers.
Castroluminescence element. 2. The multicolor light-emitting organic electroluminescent device according to claim 1, wherein one of the phosphor layers is replaced with a color filter for adjusting the color purity and the color emitted from the organic light-emitting layer. 3. The urethane resin having a number average molecular weight of 50,000 to 500,000 , wherein the crosslinked urethane resin is
2. A protective layer of the phosphor layer, wherein a film made of a resin formed by adding a crosslinking agent having a number average molecular weight of 1,000 to 100,000 containing 10 to 30% by weight of isocyanate groups is used. Multicolor light-emitting organic electroluminescence device. 4. The multicolor light-emitting organic electroluminescent device according to claim 3, wherein the amount of the crosslinking agent having an isocyanate group is in the range of 1 to 50% by weight based on the solid content of the urethane resin. 5. The phosphor layer according to claim 1, wherein the protective layer has a thickness of 0.1 to 10.
The multicolor light-emitting organic electroluminescent device according to any one of claims 1 to 4, wherein the multicolor light-emitting organic electroluminescent device contains an ultraviolet absorber in a percentage by weight. 6. The multicolor light emitting organic electroluminescent device according to claim 1, wherein the hard coat layer is a visible light transmitting resin layer or an inorganic oxide layer having a pencil hardness of 2H or more. 7. The multicolor light-emitting organic electroluminescent device according to claim 5, wherein the hard coat layer is formed on a top surface of the protective layer of the phosphor layer and is a photocurable resin which is cured by light in an ultraviolet or visible region. Luminescent element. 8. The method for producing a multicolor light-emitting organic electroluminescent element according to claim 1, wherein the organic electroluminescent element layer is formed successively on the upper surface of the hard coat layer. A method for producing a multicolor light-emitting organic electroluminescent device, which is characterized in that: