JP2010282899A - Organic EL device and manufacturing method thereof - Google Patents

Abstract

An organic EL device having an organic layer with a uniform film thickness and a high aperture ratio even when a bank is formed by photolithography.
An organic EL device of the present invention covers a substrate, a pixel electrode disposed on the substrate, an organic layer disposed on the pixel electrode, a part of the pixel electrode, and the organic layer. A forward-tapered bank that defines an arrangement region of the first electrode and a counter electrode disposed on the organic layer. When the taper angle at the lower end of the taper surface of the bank is α and the maximum taper angle of the bank closer to the counter electrode than the organic layer is β, β <α.
[Selection] Figure 3

Description

  The present invention relates to an organic EL device and a manufacturing method thereof.

  The organic EL device has an anode and a negative electrode, and an organic layer that emits light between the electrodes. Electroluminescent organic layer materials can be broadly classified into combinations of low-molecular organic compounds (host material and dopant material) and high-molecular organic compounds. Examples of the polymer organic compound that emits electroluminescence include polyphenylene vinylene called PPV and derivatives thereof.

  An organic layer made of an organic compound can be driven at a relatively low voltage, consumes little power, and is easy to cope with a large display panel. An organic layer using an organic compound as a material can be manufactured by a coating method such as an inkjet method.

  When the organic layer is formed by a coating method such as an ink jet method, it is necessary to prevent ink from penetrating into adjacent pixels that emit light of other colors.

  In order to prevent ink from penetrating into adjacent pixels that emit light of other colors, a technique is known in which a partition (bank) is formed and ink containing an organic EL material is dropped in a region defined by the bank. Yes. By accurately applying the ink in the area defined by the bank, it is possible to prevent the ink from entering the adjacent pixels that emit light of other colors.

  Such a bank can be formed by photolithography. A method for forming a bank by photolithography includes a step of forming a photosensitive resin film on a substrate, a step of exposing and developing the photosensitive resin film, and a step of baking the developed resin film (for example, Patent Document 1). reference).

  FIG. 1 shows a cross section of an organic EL device that has already been proposed (see, for example, Patent Document 1). As shown in FIG. 1, an organic EL device 10 disclosed in Patent Document 1 includes a substrate 11, an anode 13 disposed on the substrate 11, an organic layer 15 disposed on the anode 13, and an anode 13. And a bank 17 that covers a part and defines an arrangement region of the organic layer 15. The bank 17 is a bank formed by a photolithography method.

  As shown in FIG. 1, when the bank 17 is formed by photolithography, the bank 17 has a forward taper shape. Further, when the bank 17 is formed by a photolithography method, the elastic modulus of the resin constituting the bank 17 may be reduced by the high temperature during the baking process, and the skirt of the bank 17 may spread on the anode 13. In particular, when the bank is formed of a resin having a low glass transition temperature and a low elastic modulus (for example, a fluorine-containing resin), the skirt of the bank tends to spread on the anode.

JP 2006-004743 A

  However, as shown in FIG. 1, when the skirt of the bank spreads on the anode, the taper angle at the lower end of the taper surface of the bank becomes small. When the taper angle at the lower end of the taper surface of the bank is decreased, the film thickness of the organic layer applied and formed on the anode may become non-uniform (see Comparative Examples 1 and 2). If the thickness of the organic layer is not uniform, uneven light emission may occur in the organic EL device or the life of the organic EL device may be shortened.

  Further, when the bank skirt spreads on the anode, the light emission area (aperture ratio) may be reduced (see FIG. 4).

  The present invention has been made in view of the above points, and provides an organic EL device having an organic layer with a uniform film thickness and a high aperture ratio even when a bank is formed by photolithography. With the goal.

  The present inventor has found that it is possible to prevent the bottom of the bank from spreading on the anode during the baking process in the photolithography method by re-exposing the developed resin film, and has further studied and completed the invention.

That is, the first of the present invention relates to the following organic EL device.
[1] A substrate, a pixel electrode disposed on the substrate, an organic layer disposed on the pixel electrode, a forward tapered shape that covers a part of the pixel electrode and defines a region in which the organic layer is disposed A counter electrode disposed on the organic layer, wherein the taper angle of the lower end of the taper surface of the bank is α, and the counter electrode side of the organic layer is closer to the counter electrode side. An organic EL device in which β <α, where β is the maximum bank taper angle.
[2] The organic EL device according to [1], wherein the bank includes a fluorine-containing resin.
[3] The organic EL device according to [1] or [2], wherein the bank has a glass transition temperature of 130 to 170 ° C.
[4] The organic EL device according to any one of [1] to [3], wherein α is 40 to 60 °.

2nd of this invention is related with the manufacturing method of the organic EL device shown below.
[5] preparing a substrate on which the pixel electrode is disposed; forming a negative photosensitive resin film on the substrate; exposing and developing the photosensitive resin film; Exposing at least a portion; re-exposing the developed resin film; baking the re-exposed resin film to form a bank; and forming an organic layer in a region defined by the bank. Applying an ink containing a layer material to form an organic layer, and a method of manufacturing an organic EL device.
[6] The glass transition temperature of the resin film before the re-exposure is 100 to 120 ° C., and the glass transition temperature of the resin film after the re-exposure is 130 to 170 ° C. Manufacturing method of organic EL device.
[7] The method for producing an organic EL device according to [5] or [6], wherein the baking is performed at 200 to 240 ° C. for 50 to 70 minutes.

  According to the present invention, by controlling the shape of the bank, the thickness of the organic layer formed in the region defined by the bank can be made uniform, the organic EL device having a large light emitting area and a long lifetime. Can be provided.

Cross-sectional view of a conventional organic EL device The figure which shows the manufacturing method of the organic EL device of this invention Sectional view of the organic EL device of the present invention Cross-sectional view of a conventional organic EL device The figure which shows the result of the experimental example The figure which shows the result of the experimental example The figure which shows the result of Example 1 The figure which shows the result of the comparative example 1 The figure which shows the result of the comparative example 2

1. About the organic EL device of the present invention The organic EL device of the present invention covers a substrate, a pixel electrode disposed on the substrate, an organic layer disposed on the pixel electrode, a part of the pixel electrode, And a bank that defines an arrangement area.

  The organic EL device of the present invention is characterized by the shape of the bank, but other configurations of the organic EL device of the present invention may be the same as those of known organic EL devices as long as the effects of the present invention are not impaired.

  For example, the organic EL device of the present invention may be either a bottom emission type (a type in which light is extracted through a pixel electrode and a substrate) or a top emission type (a type in which light is extracted through a counter electrode and a sealing film).

The material of the substrate differs depending on whether the organic EL device of the present invention is a bottom emission type or a top emission type. Since the substrate is required to be transparent when the organic EL device is a bottom emission type, examples of the substrate material include PET (polyethylene terephthalate), PEN (polyethylene naphthalate), and PI (polyimide). Transparent resin and glass are included.
On the other hand, when the organic EL device is a top emission type, the substrate does not need to be transparent, and therefore the material of the substrate is arbitrary as long as it is an insulator.

The pixel electrode is a conductive member disposed on the substrate. In an organic EL display panel, the pixel electrode normally functions as an anode, but can also function as a cathode. The material of the pixel electrode differs depending on whether the organic EL device of the present invention is a bottom emission type or a top emission type. When the organic EL device is a bottom emission type, the pixel electrode is required to be transparent. Examples of the pixel electrode material include ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), and tin oxide. Is included.
On the other hand, when the organic EL device is a top emission type, the pixel electrode is required to have light reflectivity, and examples of the material of the pixel electrode include APC alloy (silver, palladium, copper alloy) and ARA (silver, Rubidium, gold alloy), MoCr (molybdenum and chromium alloy), NiCr (nickel and chromium alloy), and the like. The thickness of the pixel electrode is typically 100-500 nm and can be about 150 nm.

  The pixel electrode may be connected to the drain electrode of the driving TFT. When the organic EL device of the present invention is a bottom emission type, the drive TFT and the organic EL device are usually arranged on the same plane. On the other hand, when the organic EL device of the present invention is a top emission type, the organic EL device is usually disposed on the driving TFT.

  The organic layer is a layer that includes at least an organic light emitting layer and is applied and formed in a region defined by a bank described later. The thickness of the organic layer is preferably about 60 to 300 nm (for example, 200 nm). Here, the thickness of the organic layer means the distance from the bottom surface of the organic layer on the pixel electrode to the top surface of the organic layer on the pixel electrode.

  The organic light emitting material contained in the organic light emitting layer may be a low molecular organic light emitting material or a polymer organic light emitting material, but is preferably a polymer organic light emitting material. This is because an organic light emitting layer containing a polymer organic light emitting material is easy to form by coating. Examples of the polymer organic light-emitting material include polyphenylene vinylene and derivatives thereof, polyacetylene and derivatives thereof, polyphenylene and derivatives thereof, polyparaphenylene ethylene and derivatives thereof, poly 3 -Hexylthiophene (Poly 3-hexyl thiophene (P3HT)) and derivatives thereof, polyfluorene (Polyfluorene (PF)) and derivatives thereof, and the like are included.

  The organic layer may further have an electron block layer, an electron transport layer, and the like. A hole injection layer may be disposed between the pixel electrode and the organic layer.

  The electron blocking layer has a role of blocking the penetration of electrons into the hole injection layer and a role of efficiently transporting holes to the organic light emitting layer, and is a layer made of, for example, a polyaniline material. The thickness of the electron blocking layer is usually 5 nm or more and 150 nm or less, preferably 10 nm or more and 50 nm or less (for example, about 20 nm).

  In addition, the hole injection layer and the electron blocking layer may be omitted as long as holes can be efficiently transported from the pixel electrode to the organic light emitting layer.

  The bank is a barrier that defines the arrangement area of the organic layer. The height of the bank (distance between the bottom surface of the bank and the top surface of the bank) is 0.1 μm to 2 μm, and particularly preferably 0.8 μm to 1.2 μm. When the bank height is 2 μm or more, a counter electrode described later may be divided by the bank. Further, when the height of the bank is 0.8 μm or less, there is a possibility that ink applied in an area defined by the bank leaks from the bank.

  The bank of the present invention is preferably forward tapered. Further, the present invention is characterized by the shape of the taper surface of the bank. The shape of the taper surface of the bank will be described in detail in “3.

  The bank in the present invention contains a resin. Examples of the resin included in the bank include cresol-novolak resin, polyvinylphenol resin, acrylic resin, methacrylic resin, and combinations thereof. Further, since the bank defines a region to which the ink containing the organic light emitting material is applied as described above, it is preferable that the bank has low wettability. In order to reduce the wettability of the bank, the bank may be plasma-treated with fluorine gas, or a liquid repellent may be contained in the resin material of the bank. Since the plasma treatment may adversely affect the members of the organic EL device, it may be preferable to include a liquid repellent in the resin material of the bank.

  Examples of the liquid repellent include fluorine compounds such as vinylidene fluoride, vinyl fluoride, and ethylene trifluoride, and fluorine-containing polymers.

Examples of the resin material of the bank include a negative photosensitive resin composition described in JP-A No. 2005-166645, specifically, a fluorine-containing polymer, an alkali-soluble photosensitive resin, a crosslinking agent, a radical An initiator and a light absorber are included. Here, the fluorine-containing polymer has a group represented by Formula 1 and an ethylenic double bond; and both the alkali-soluble photosensitive resin and the crosslinking agent have an ethylenic double bond. Photocured.
-CFXR ^f ... Formula 1 (In Formula 1, X represents a hydrogen atom or a fluorine atom, and R ^f represents an alkyl group having 20 or less carbon atoms in which at least one of the fluorine atom or the hydrogen atom is substituted with a fluorine atom. .)

  A resin bank manufactured by photolithography generally needs to be fired. This is because the rinsing liquid used in the development process is removed by baking, and the shape of the bank becomes a forward taper. The firing temperature is often higher than about 200 ° C., and if the glass transition temperature of the resin constituting the bank is excessively low, the shape change of the bank during firing becomes large (for example, “the skirt of the bank widens”). Therefore, a desired bank shape may not be obtained.

  Therefore, the glass transition temperature of the bank (the glass transition temperature of the resin constituting the bank) is preferably, for example, 130 ° C. or higher, and the upper limit is not particularly limited, but is preferably 180 ° C. or lower. Moreover, it is preferable that the elastic modulus at the time of high temperature (for example, 200 degreeC) of resin which comprises a bank is high. This is because the shape of the bank prevents “the skirt of the bank from spreading” in the firing process. The glass transition temperature and elastic modulus of the bank can be measured by using a rigid pendulum type physical property test apparatus such as RPT-3000w (manufactured by A & D).

  As described above, the bank of the present invention can be manufactured by photolithography. The present inventor has found that the resin patterned by photolithography does not have a sufficiently high glass transition temperature; if the patterned resin is baked, a desired bank shape may not be obtained. I found some things, for example, the bank's skirt expanded. In particular, if the resin constituting the bank is a resin containing a fluorine compound or a fluorine-containing polymer (hereinafter also simply referred to as “fluorine-based resin”), this problem tends to become significant. This is because the glass transition temperature of a fluororesin is generally lower than the glass transition temperature of a non-fluorine resin.

  Therefore, as described later (2. Manufacturing method of organic EL device of the present invention), it is preferable that the resin patterned by photolithography is exposed again and then baked to obtain a bank.

  The organic EL device of the present invention has a counter electrode on the organic layer. The counter electrode is a conductive member disposed on the organic layer. In the organic EL display panel, the counter electrode normally functions as a cathode, but can also function as an anode. The material of the counter electrode differs depending on whether the organic EL device is a bottom emission type or a top emission type. When the organic EL device is a top emission type, the counter electrode needs to be transparent. Therefore, the material of the counter electrode is preferably an ITO electrode or an IZO electrode.

  On the other hand, when the organic EL device is a bottom emission type, the counter electrode does not need to be transparent. Therefore, the material of the counter electrode is not particularly limited as long as it is conductive, and includes, for example, barium (Ba), barium oxide (BaO), aluminum (Al), and the like.

  For example, an electron injection layer made of barium (Ba), lithium fluoride (LiF), or the like may be disposed between the counter electrode and the organic layer.

  A cover material (sealing material) may be further provided on the counter electrode to seal the organic EL device. The cover material prevents entry of moisture and oxygen.

  The organic EL device of the present invention can function as an organic EL element of an organic EL display panel. Therefore, an organic EL display panel can be configured by arranging the organic EL devices of the present invention in a matrix. The organic EL display panel configured by arranging the organic EL devices of the present invention in a matrix is preferably an active matrix type. In an active matrix type organic EL display panel, a plurality of organic EL elements (preferably all organic EL elements) separated by a bank share one counter electrode. This is because the bank of the present invention is less likely to divide the counter electrode (formed by a sputtering method or the like), and easily produces a counter electrode shared by all organic EL elements of the organic EL display panel (described later).

2. Production Method of Organic EL Device of the Present Invention The organic EL display panel of the present invention can be produced by any method as long as the effects of the present invention are not impaired.

An example of a preferred production method is
1) a first step of preparing a substrate on which pixel electrodes are arranged;
2) a second step of forming a negative photosensitive resin film on the substrate;
3) a third step of exposing and developing the photosensitive resin film;
4) a fourth step of exposing the developed resin film again;
5) a fifth step of baking the exposed resin film again;
6) A sixth step of forming an organic layer by applying an ink containing an organic layer material in an area defined by the bank;
And 7) a seventh step of forming a counter electrode on the organic layer.

  Unlike the conventional organic EL device manufacturing method, the organic EL device manufacturing method of the present invention includes 4) a fourth step of exposing the developed resin film again. Hereinafter, each step will be described in detail.

  1) In the first step, a substrate on which pixel electrodes are arranged is prepared. In order to form a pixel electrode on a substrate, an electrode material for the pixel electrode may be deposited or sputtered. A hole injection layer may be patterned on the pixel electrode.

  2) In the second step, a negative photosensitive resin film is formed on the substrate. For example, a negative photosensitive resin composition is applied onto a substrate by a coating method such as spin coating, and then baked at 80 to 120 ° C. for 1 to 3 minutes to form a resin film.

  The photosensitive resin composition includes a binder resin, a monomer, a photopolymerization initiator, and the like, and may include the liquid repellent described above.

  Examples of the binder resin include phenol-novolak resin, polyvinyl phenol resin, acrylic resin, and methacrylic resin.

  Examples of monomers include (meth) acrylic acid and its salts, (meth) acrylic acid, esters, (meth) acrylamides, maleic anhydride, maleic acid esters, itaconic acid esters, styrenes, vinyl ethers, vinyl esters , N-vinyl heterocycles, allyl ethers, allyl esters, and derivatives thereof.

  Examples of photopolymerization initiators include benzophenone compounds such as benzophenone, 4,4′-bis (dimethylamino) benzophenone, and 4,4′-bis (diethylamino) benzophenone; 1-hydroxycyclohexylacetophenone and 2,2-dimethoxy- Acetophenone derivatives such as 2-phenylacetophenone and 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one; thioxanthone, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 2- Thioxanthone derivatives such as chlorothioxanthone; anthraquinone derivatives such as 2-methylanthraquinone, 2-ethylanthraquinone, 2-t-butylanthraquinone, chloroanthraquinone; benzoin methyl ether and benzoin ethyl Benzoin ether derivatives such as ether and benzoin phenyl ether; acyl phosphine derivatives of phenyl bis- (2,4,6-trimethylbenzoyl) -phosphine oxide; 2- (o-chlorophenyl) -4,5-bis (4 ′ Lophine isomers such as -methylphenyl) imidazolyl dimer; N-aryl glycines such as N-phenylglycine; Organic azides such as 4,4'-diazidochalcone; 3,3 ', 4,4'- Tetra (tert-butylperoxycarboxy) benzophenone; quinonediazide group-containing compounds are included.

  3) In the third step, the photosensitive resin film is exposed and developed. A part of the pixel electrode is exposed by developing the photosensitive resin film. In the third step, the photosensitive resin film is selectively irradiated with light using a mask or the like in the region to be left, and the photosensitive resin film in the region not irradiated with light is developed with a developer such as TMAH. Can be removed. Thereby, the pixel electrode (or hole injection layer) arranged on the substrate is exposed.

The exposure amount in the third step is appropriately selected depending on the composition of the photosensitive resin, and is, for example, 50 to 300 mJ / cm ² . The exposure time in the third step is also appropriately selected depending on the composition of the photosensitive resin. For example, when the illuminance of the lamp is 20 mW / cm ^2, it is 2.5 to 15 seconds.

  The resin film after exposure and development may not have a sufficiently high glass transition temperature. For example, the glass transition temperature of the resin film after development may be 120 ° C. or lower. When a resin film having a low glass transition temperature is baked, elasticity may be lowered in a baking process (baking temperature is 200 ° C., for example), and the bottom of the bank may be widened.

  However, since the present invention exposes the developed resin film again in the fourth step described later, the glass transition temperature of the developed resin film may be low, for example, 100 to 120 ° C .; The elastic modulus at the film baking temperature (for example, 200 ° C.) may also be low. Therefore, the photosensitive resin composition of the present invention can be a fluororesin that tends to decrease the glass transition temperature.

  4) In the fourth step, the developed resin film is exposed again. As described above, the present invention is characterized in that the photosensitive resin film is developed and then exposed again (hereinafter also simply referred to as “re-exposure”). Unlike the third step, no mask is required for the exposure in this step. By reexposing the resin film in the fourth step, the glass transition temperature and the elastic modulus of the resin film can be improved. Although the mechanism is not necessarily clear, the resin material that has not been sufficiently photopolymerized and photocured in the exposure in the third step is further photopolymerized and photocured in the fourth step.

The glass transition temperature of the resin film is preferably increased to 130 to 170 ° C. by re-exposure in this step; and the elastic modulus at 200 ° C. is also preferably increased. Specifically, the exposure amount in the fourth step is 50 to 400 mJ / cm ² , and the exposure time is ^2.5 to 20 seconds when the lamp illuminance is 20 mW / cm ² , for example.

  In the conventional bank formation method by photolithography, a resin film having a low glass transition temperature and a low elastic modulus after baking is baked, so that it is difficult to control the shape of the bank to be formed, and the bank base is a pixel electrode. There was a problem of spreading up. However, in the present invention, the glass transition temperature and elastic modulus of the resin film are increased by re-exposure before baking (fifth step), so that the shape of the bank can be controlled, and the skirt of the formed bank is placed on the pixel electrode. Can be prevented (see FIG. 3).

  5) In the fifth step, the reexposed resin film is baked to form a bank. The rinse liquid used in the development process is removed by baking, and the shape of the bank becomes a forward tapered shape. The firing temperature is, for example, 200-240 ° C .; the firing time is, for example, 50-70 minutes.

  In the present invention, since the resin film is re-exposed in the fourth step and the glass transition temperature and the elastic modulus at 200 ° C. of the resin film are increased, the skirt of the bank does not spread on the pixel electrode in the baking step. Thereby, in the present invention, a bank having a forward taper shape and a relatively large taper angle at the bottom is obtained (see FIG. 3). In the present invention, the taper angle at the top of the bank is relatively small (see FIG. 3). The bank shape will be described in detail in “3. Bank shape”.

  6) In the sixth step, an organic layer is formed by applying ink containing an organic layer material such as an organic light-emitting material in the region defined by the bank formed in the fifth step. As described above, the organic layer formed by drying the ink applied in the region defined by the bank having a relatively large taper angle at the bottom has a uniform thickness (see Example 1).

  7) In the seventh step, a counter electrode is formed on the organic layer. The counter electrode is preferably formed by a sputtering method or the like. As described above, in the present invention, since the taper angle of the upper part of the bank is small, the counter electrode is not easily divided by the bank. Therefore, the present invention is advantageous for manufacturing an active matrix organic EL display panel in which all organic EL elements share one counter electrode.

  Thus, according to the method for manufacturing an organic EL device of the present invention, the shape of the bank can be controlled even when the bank is formed from a resin having a low glass transition temperature and a low elastic modulus (for example, a fluororesin). Accordingly, the film thickness of the organic layer formed in the region defined by the bank can be made uniform, and an organic EL device having a large light emitting area and a long lifetime can be manufactured.

3. As described above, in the present invention, the bank has a forward tapered shape. Furthermore, the present invention is characterized in that the taper angle at the bottom of the bank is relatively large; the taper angle at the top of the bank is relatively small. Here, the “taper angle at the bottom of the bank” means the taper angle at the lower end of the bank and the taper surface, and the “taper angle at the top of the bank” means the taper angle of the bank on the counter electrode side from the organic layer. Means the maximum value of. Therefore, when the taper angle at the bottom of the bank is α and the taper angle at the top of the bank is β, the following relational expression “β <α” is satisfied.

  The taper angle α at the bottom of the bank is preferably 40 to 60 °. By increasing the taper angle α at the bottom of the bank, the thickness of the organic layer to be applied can be made uniform (see Example 1). In addition, since the bottom of the bank (the lower end of the bank) does not spread on the pixel electrode, the aperture ratio of the organic EL device is increased (see FIG. 3).

  On the other hand, the taper angle β at the top of the bank is preferably 10 to 40 °. This is because the counter electrode formed by sputtering or vapor deposition can be prevented from being cut by the bank by making the taper angle β at the top of the bank relatively small.

  Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a diagram showing a flow of a method for manufacturing an organic EL device of the present invention. As shown in FIG. 2, the manufacturing method of the organic EL device of the present invention is as follows.
1) a first step of preparing a substrate 101 on which a pixel electrode 103 is arranged (FIG. 2A);
2) a second step of forming a negative photosensitive resin film 106 on the substrate (FIG. 2B);
3) a third step of exposing and developing the photosensitive resin film 106 through the mask 110 (FIGS. 2C and 2D);
4) a fourth step of exposing the developed resin film 106 again (FIG. 2E);
5) A fifth step of baking the exposed resin film 106 to form the bank 107 (FIG. 2F),
6) A sixth step of forming the organic layer 105 by applying the ink 104 containing the organic layer material in the region defined by the bank 107 (FIG. 2G);
7) A seventh step of forming the counter electrode 109 on the organic layer 105 (FIG. 2H) is included.

  FIG. 3A shows a cross-sectional view of an organic EL device manufactured by the manufacturing method shown in FIG. As shown in FIG. 3A, the organic EL device 100 of the present invention includes a substrate 101, a pixel electrode 103, an organic layer 105, a bank 107, and a counter electrode 109.

  The organic EL device 100 is characterized by the shape of the bank 107. Hereinafter, the shape of the bank 107 will be mainly described.

  FIG. 3B is an enlarged view of the square X in FIG. 3A. As shown in FIG. 3, the taper angle at the bottom of the bank 107 is relatively large; the taper angle at the top of the bank 107 is relatively small. More specifically, the taper angle α at the lower end of the taper surface of the bank 107 is larger than the maximum taper angle β of the bank 107 closer to the counter electrode 109 than the organic layer 105. α is preferably 40 to 60 °, and β is preferably 10 to 40 °.

  Thus, in the present invention, since the taper angle at the bottom of the bank is large, an organic layer having a uniform thickness can be obtained. Further, since the taper angle at the top of the bank is small, the counter electrode is prevented from being divided by the bank 107. Furthermore, the aperture ratio A of the organic EL device 100 can be increased by preventing the bottom of the bank from spreading on the pixel electrode.

  On the other hand, in the conventional organic EL device 200 as shown in FIG. 4, since the taper angle at the bottom of the bank 207 is small, the organic layer formed by applying ink in the region defined by the bank 207. The film thickness becomes non-uniform. Further, since the taper angle at the top of the bank 207 is increased, the counter electrode 109 ′ formed by the vapor deposition method may be divided as shown in FIG. 4. Furthermore, since the skirt of the bank 207 extends over the pixel electrode 103, the aperture ratio A 'of the organic EL device 200 is low.

[Experimental Example 1]
In Experimental Examples 1 to 5, the following experiment was performed to show that the glass transition temperature and the elastic modulus of the resin film are increased by re-exposure.

(Sample preparation)
In Experimental Example 1, three sample resins for measurement were prepared. Each sample was prepared in the following steps.

  A negative photosensitive resin (an acrylic resin containing a fluorine compound) is spin-coated on a glass substrate of 25 mm × 25 mm, and the spin-coated resin composition is baked at 100 ° for 2 minutes to be photosensitive. A resin film (thickness: 1.3 μm) was formed.

Next, the resin film was exposed. The exposure illuminance was 20 mW / cm ² ; the exposure dose was 200 mJ / cm ² ; and the exposure time was 10 seconds.

Furthermore, the resin film was re-exposed to prepare a sample resin for measurement. The illuminance for re-exposure was 20 mW / cm ² ; the exposure amount was 100 mJ / cm ² ; and the exposure time was 5 seconds.

[Experiment 2]
A sample resin for measurement was prepared in the same manner as in Experimental Example 1 except that the exposure amount in re-exposure was 300 mJ / cm ² .

[Experiment 3]
A sample resin for measurement was prepared in the same manner as in Experimental Example 1 except that the exposure amount in re-exposure was 500 mJ / cm ² .
[Experimental Example 4]
A sample resin for measurement was prepared in the same manner as in Experimental Example 1 except that the exposure amount in the re-exposure was 1000 mJ / cm ² .

[Experimental Example 5]
A measurement sample resin was prepared in the same manner as in Experimental Example 1 except that the step of re-exposure was omitted.

(Measurement)
The glass transition temperature of the prepared sample resin was measured. For the measurement of the glass transition temperature, RPT-3000w (manufactured by A & D), which is a rigid pendulum type physical property test apparatus, was used. FRB100 was used for the pendulum, and RBP040 was used for the pipe. The measurement temperature was room temperature to 300 ° C., and the rate of temperature increase was 5 ° C./min. The measurement result of the sample prepared in Experimental Example 1 is shown in FIG. 5A, the measurement result of the sample prepared in Experimental Example 2 is shown in FIG. 5B, the measurement result of the sample prepared in Experimental Example 3 is shown in FIG. The measurement result of the sample prepared is shown in FIG. 6A, and the measurement result of the sample prepared in Experimental Example 5 is shown in FIG. 6B.

  The horizontal axis of the graphs shown in FIGS. 5 and 6 indicates temperature, and the vertical axis indicates logarithmic decay rate. The temperature Tg at the peak of the logarithmic decay rate indicates the glass transition temperature of the sample resin. The magnitude of the logarithmic decay rate represents the degree of decrease in the viscosity (elastic modulus) of the sample resin during heating. Therefore, a large logarithmic decay rate of the resin means that the elastic modulus of the resin is lowered during heating. On the other hand, a low logarithmic decay rate of the resin means that the elastic modulus of the resin does not decrease much even during heating. Table 1 shows the glass transition temperature Tg and the maximum value P of the logarithmic decay rate of the sample resins prepared in Experimental Examples 1 to 5 derived from the graphs shown in FIGS. 5 and 6.

As shown in Table 1, the glass transition temperature of the resin film was higher in Experimental Examples 1 to 4 having the re-exposure step than in Experimental Example 5 having no re-exposure step. Moreover, the maximum value of the logarithmic decay rate decreased as the exposure amount in re-exposure increased. That is, as the resin sample with a larger exposure amount in re-exposure, the elastic modulus did not decrease much during heating, and the elastic modulus during heating increased.
This result suggests that the glass transition temperature of the resin film can be increased by exposing the resin film again after the development of the photosensitive resin film in the bank forming method by the photolithography method. In addition, as described above, the logarithmic decay rate represents a decrease in the elastic modulus of the sample resin. Therefore, the maximum value of the logarithmic decay rate is reduced by re-exposure. Suggests that

  Hereinafter, the organic EL device of the present invention will be described with reference to examples. Also, the following examples do not limit the scope of the present invention.

[Example 1]
In Example 1, the following experiment was conducted to show that the film thickness of the organic layer in the organic EL device of the present invention is uniform.

  A reflective pixel electrode was patterned by forming a 150 nm thick Al alloy film on a 6-inch glass substrate by sputtering and etching. Thereafter, a tungsten oxide film having a thickness of 50 nm was formed on the reflective pixel electrode by sputtering, and the hole injection layer was patterned by etching.

  Thereafter, a negative photosensitive resin composition (an acrylic resin containing a fluorine compound) is spin-coated on a glass substrate on which the reflective pixel electrode and the hole injection layer are patterned, and the spin-coated resin composition is 100%. A photosensitive resin film (thickness: 1.3 μm) was formed by baking at 2 ° C. for 2 minutes.

Next, the photosensitive resin film was exposed and developed through a mask to pattern the resin film. The illuminance for exposure was 20 mW / cm ² ; the exposure dose was 200 mJ / cm ² ; and the exposure time was 10 seconds. The exposed resin film was immersed in 0.2% TMAH for 40 seconds, then rinsed with pure water for 60 seconds and developed to obtain a patterned resin film.

Next, the developed resin film was further reexposed. The illuminance for re-exposure was 20 mW / cm ² ; the exposure amount was 100 mJ / cm ² ; and the exposure time was 5 seconds.

  Finally, the reexposed resin film was baked to form a bank. The firing temperature was 220 ° C., and the baking time was 1 hour. The shape of the bank 107 formed by such a method is shown in FIG. 7A. As shown in FIG. 7A, in the bank 107 formed by the method of the first embodiment, the skirt does not spread on the pixel electrode, the taper angle at the bottom of the bank is large, and the taper angle at the top of the bank is small.

  Subsequently, an electron block layer (thickness 20 to 50 nm) was formed by dropping a material solution of an electron block layer containing a polyaniline derivative and anisole onto an application region defined by the bank by an ink jet method, and drying and baking. . Finally, an organic light emitting layer (thickness of 50 to 150 nm) is formed on the electron blocking layer by dropping a material liquid of an organic light emitting layer containing a polyfluorene derivative and anisole by an ink jet method, followed by drying and baking. A model of the organic EL device of the present invention was produced.

[Comparative Example 1]
A model of an organic EL device was produced in the same manner as in Example 1 except that the step of performing re-exposure was omitted. The shape of the bank 207 formed by the method of Comparative Example 1 is shown in FIG. 8A. As shown in FIG. 8A, the skirt of the bank 207 formed by the method of Comparative Example 1 extends over the pixel electrode 103, the taper angle at the bottom of the bank is small, and the taper angle at the top of the bank is large.

[Comparative Example 2]
A model of an organic EL device was produced in the same manner as in Example 1 except that the step of re-exposure was omitted and the exposure amount in the development process was set to 300 mJ / cm ² . The shape of the bank 307 formed by the method of Comparative Example 2 is shown in FIG. 9A. As shown in FIG. 9A, the skirt of the bank 307 formed by the method of the comparative example 2 spreads on the pixel electrode 103 as compared with the skirt of the bank 107 of the first embodiment. Compared to the 207 hem, it does not spread. This is probably because the glass transition temperature of the resin film before firing increased in Comparative Example 2 because the exposure amount of the photosensitive resin film was larger than in Comparative Example 1.

  The film thickness distribution of the organic light emitting layer of the models of Example 1, Comparative Example 1 and Comparative Example 2 was measured. For measurement of the film thickness distribution, an atomic force microscope (AFM) apparatus AS-7B-W (AUTO) manufactured by Takano Corporation was used. FIG. 7B shows the measurement result of Example 1, FIG. 8B shows the measurement result of Comparative Example 1, and FIG. 9B shows the measurement result of Comparative Example 2.

[Study on bank shape]
In Example 1 including the re-exposure step, the taper angle at the lower part of the bank was increased, and the taper angle at the upper part of the bank was decreased. On the other hand, in Comparative Example 1 having no re-exposure step, the bottom of the bank was widened, the taper angle at the lower part of the bank was reduced, and the taper angle at the upper part of the bank was increased. Further, in Comparative Example 2 that does not have a re-exposure step and the exposure amount during development is increased, the taper angle at the lower part of the bank is smaller than that in Example 1, and the taper angle at the upper part of the bank is smaller. It became bigger. This result suggests that the shape of the bank can be controlled by adding a re-exposure step rather than increasing the exposure amount during development. That is, it is suggested that the taper angle at the lower part of the bank can be increased and the taper angle at the upper part of the bank can be reduced by re-exposure.

[Consideration of organic layer thickness]
As shown in FIG. 8B, the film thickness of the organic layer of Comparative Example 1 varied in the range of 25 to 125 μm. Moreover, the film thickness of the organic layer of Comparative Example 2 varied in the range of 50 to 125 μm as shown in FIG. 9B. Furthermore, the film thickness of the organic layer of Example 1 varied in the range of 100 to 110 μm as shown in FIG. 7B. Thus, the greater the taper angle at the bottom of the bank, the more uniform the film thickness of the organic layer. This result suggests that an organic layer having a uniform film thickness can be formed by increasing the taper angle at the bottom of the bank.

  The organic EL device of the present invention can be applied to, for example, an organic EL display (such as a monitor of an information equipment terminal such as a large-screen TV and a mobile phone).

100, 200 Organic EL device 101 Substrate 103 Pixel electrode 104 Ink 105 Organic layer 107, 207, 307 Bank 109 Counter electrode 110 Mask

Claims (7)

A substrate, a pixel electrode disposed on the substrate, an organic layer disposed on the pixel electrode, a forward tapered bank covering a part of the pixel electrode and defining a region in which the organic layer is disposed; An organic EL device having a counter electrode disposed on the organic layer,
The taper angle of the lower end of the taper surface of the bank is α,
When the maximum taper angle of the bank closer to the counter electrode than the organic layer is β,
An organic EL device in which β <α.   The organic EL device according to claim 1, wherein the bank includes a fluorine-containing resin.   2. The organic EL device according to claim 1, wherein the bank has a glass transition temperature of 130 to 170 ° C. 3.   The organic EL device according to claim 1, wherein α is 40 to 60 °. Preparing a substrate on which pixel electrodes are disposed;
Forming a negative photosensitive resin film on the substrate;
Exposing and developing the photosensitive resin film to expose at least a portion of the pixel electrode;
Re-exposing the developed resin film;
Firing the re-exposed resin film to form a bank;
Applying an ink containing an organic layer material in a region defined by the bank to form an organic layer;
The manufacturing method of the organic EL device which has this. The glass transition temperature of the resin film before re-exposure is 100 to 120 ° C.,
The method for producing an organic EL device according to claim 5, wherein a glass transition temperature of the repellent film after the re-exposure is 130 to 170 ° C.   The said baking is a manufacturing method of the organic EL device of Claim 5 performed at 200-240 degreeC for 50 to 70 minutes.

Images