JP2013250001A - Drying device and drying method for coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To previously raise a temperature of a substrate before drying by condensation, so that temperature unevenness in a costing film surface during drying can be reduced, and uniformity of drying can be improved.SOLUTION: A drying device 1 for a coating film has a condensation drying device B and a condensation plate 11 faced to a coating film on a substrate f1, and condenses vapor of a solvent from the coating film by the condensation plate 11, for drying. Further, the drying device 1 for the coating film has a heating device A disposed after coating of the coating film and during up to drying by the condensation drying device B, and preliminary heating the substrate f1 and the coating film.

Description

  The present invention relates to a coating film drying apparatus and a drying method.

  As a method for forming an organic thin film in an organic electroluminescence (EL) element or an organic thin film solar cell, a vacuum process is not required and continuous production is easy. Attention has been focused on application methods by wet processes such as spraying and printing. However, according to the wet process, drying unevenness may occur in the step of drying the coating film, and it is difficult to obtain a uniform film thickness. One of the factors is that a highly volatile organic solvent is used as a solvent for the coating solution in order to increase the solubility.

  Conventionally, as a drying method capable of uniform drying, a drying method in which a condensing plate faces a coating film surface and a solvent in the coating film is condensed by the condensing plate has been disclosed (for example, see Patent Document 1). According to this drying method, precise drying is possible by controlling the distance between the condenser plate and the coating film and the respective surface temperatures without using convection.

According to Patent Document 1, there is a description that the substrate is heated by the heating drum and the solvent is evaporated from the coating film, but the layout of the heating drum itself is likely to be restricted because the equipment of the heating drum itself is large.
On the other hand, in order to heat with the compact equipment without impairing the quality of the substrate, a method of increasing the drying efficiency after coating by preheating the substrate before coating is disclosed (for example, Patent Document 2). reference).

Special table 2003-524847 JP 2003-170102 A

  However, if the substrate is heated before coating, wrinkles may occur on the substrate, and coating unevenness is likely to occur due to the influence of the wrinkles. As a result, drying unevenness was likely to occur, and there was no guarantee that film thickness uniformity required for electronic devices such as organic EL elements could be obtained.

  An object of the present invention is to improve the uniformity of drying of a coating film.

According to the invention of claim 1,
A condensing plate that faces the coating film on the substrate, condensing the solvent vapor from the coating film by the condensing plate, and drying,
A heating device that is disposed between the application of the coating film and the drying by the condensation drying device, and preliminarily heats the substrate and the coating film;
An apparatus for drying a coating film is provided.

According to invention of Claim 2,
The coating film drying apparatus according to claim 1, wherein the heating device heats the substrate and the coating film by infrared radiation heat.

According to invention of Claim 3,
The coating film drying apparatus according to claim 1, wherein the coating film after being heated by the heating device has a viscosity of 5 mPa · s or less.

According to invention of Claim 4,
The amount of the solvent dried by the condensation drying device is in the range of 10 to 80% by volume with respect to the total volume of the solvent contained in the coating film. The coating film according to any one of claims 1 to 3. A drying device is provided.

According to the invention of claim 5,
In the drying method of the coating film, the coating film on the substrate and the condensing plate face each other, the vapor of the solvent from the coating film is condensed by the condensing plate, and dried.
There is provided a method for drying a coating film, which includes a step of preheating the substrate and the coating film after coating the coating film and before drying by the condensation.

  According to the present invention, before drying by condensation, the temperature of the substrate is raised in advance to reduce temperature unevenness in the coating film surface during drying, and the uniformity of drying can be improved.

The example of the production line where the drying apparatus of the coating film which concerns on this Embodiment was used is shown. It is the front view of the condensation drying apparatus of FIG. 1 seen from the conveyance direction of the board | substrate.

  Embodiments of a coating film drying apparatus and drying method of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of a production line in which a coating film drying apparatus 1 according to the present embodiment is used.
In the production line shown in FIG. 1, an organic layer coating solution is applied by a coating device 3 on a substrate f <b> 1 held and transported by rollers 22 and 23, and the coating film is dried by a drying device 1.
In addition, you may install the drying apparatus for post-processing after the drying apparatus 1 for the purpose of the removal of a residual solvent, etc. The drying method is not particularly limited. For example, solid heat transfer drying such as hot air, infrared rays and plane heating, internal heat generation drying using microwaves, vacuum drying, supercritical drying, ultrasonic drying, etc. Known methods such as gas drying such as system drying, moisture absorption drying, cooling drying, and condensation drying can be selected.

The substrate f1 is a coating object. As the substrate f1, a base material made of a flexible material such as a metal, a glass substrate or a resin film, or a base material support when the base material itself is coated is used. Some organic layers may already be formed on the substrate f1.
The substrate f1 is sent out to the coating device 3 by the unwinder 21 and wound by the winder 24 after coating and drying.

  In addition to wet processes such as spin coating, casting, ink-jet, spraying, and printing, the coating apparatus 3 is a slot method using a slit-type die coater, an ESD (Electro Spray Deposition) method, ESDUS. Apply the coating solution by the Evaporative Spray Deposition from Ultra-ditule Solution method. If the coating liquid containing a solvent can be apply | coated, the coating method of the coating device 3 will not be specifically limited.

  As a method of coating on the substrate f1 that is continuously transported, a post-weighing type in which an application liquid is applied in excess of the amount necessary to form a coating film having a required film thickness, and then the excess is removed. A pre-weighing type in which a coating solution is applied in a necessary amount is known. Any coating method can be applied, but the pre-weighing type is preferable from the viewpoints of high accuracy of coating, high speed, thin film, improved coating film quality, suitability for lamination, and the like. Moreover, a closed system is preferable from the viewpoints of suppressing the exposure of the coating liquid, suppressing the change in concentration, maintaining the cleanliness, and preventing the contamination of foreign matters. Therefore, among the above coating methods, a slot method using a slit type die coater, a spray method, and an ink jet method are preferable.

The coating solution can be prepared by dissolving or dispersing an organic material in a solvent.
In the case of an organic EL device in which organic layers such as a hole transport layer, a light-emitting layer, and an electron transport layer are sequentially stacked between an anode and a cathode, examples of organic materials for the hole transport layer include triazole derivatives, oxazole derivatives, and oxazines. Azole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline-based co-weights Examples thereof include conductive polymer oligomers such as coalescence and thiophene oligomers.

The organic material for the light emitting layer may be a low molecular compound having no repeating unit, a high molecular compound having a repeating unit, or a low molecular compound having a polymerizable group such as a vinyl group or an epoxy group.
Specifically, compounds having a basic skeleton such as carbazole derivatives, triarylamine derivatives, aromatic borane derivatives, nitrogen-containing heterocyclic compounds, thiophene derivatives, furan derivatives, oligoarylene compounds, and carboline derivatives as organic materials for the light-emitting layer And diazacarbazole derivatives (herein, diazacarbazole derivatives are derivatives in which at least one carbon atom of the hydrocarbon ring constituting the carboline ring of the carboline derivative is substituted with a nitrogen atom).
Moreover, a phosphorescent compound is also mentioned as an organic material of a light emitting layer. The phosphorescent compound is a complex compound containing a group 8 to group 10 metal in the periodic table of elements, and examples thereof include iridium compounds, osmium compounds, platinum compounds, and rare earth complexes.

  Examples of the organic material for the electron transport layer include nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyrandioxide derivatives, carbodiimides, fluorenylidenemethane derivatives, anthraquinodimethane, anthrone derivatives, oxadiazole derivatives, and the like.

  In addition to the organic EL element, the coating apparatus 3 can form organic layers such as a solar cell, a transistor, a memory, and a sensor. Examples of such an organic material include conductive polymers such as polythiophene, pentacene, naphthalene derivatives, and the like.

  The solvent used in the coating solution depends on the organic material that is a solute. For example, pure water, alcohols such as 2-ethoxyethanol and 2-methoxyethanol, and halogens such as chloroform, methylene chloride, tetrachloroethylene, dichloroethane, and tetrahydrofuran System, aromatic hydrocarbons such as xylene, toluene, hexane, cyclohexylbenzene, anisole, ketones such as acetone, methyl ethyl ketone, esters such as acetic acid, methyl acetate, ethyl acetate, butyl acetate, normal propyl acetate, acetonitrile, Examples include diethyl ether and dimethyl sulfoxide.

Depending on the purpose of controlling the application range and the purpose of controlling the liquid flow accompanying the surface tension gradient after application (for example, the liquid flow causing a phenomenon called coffee ring) A solvent can be contained.
Examples of the surfactant include an anionic or nonionic surfactant from the viewpoint of the influence of moisture contained in the solvent, leveling properties, wettability to the substrate f1, and the like. Specifically, surfactants listed in International Publication No. 08/146661, JP-A-2-41308, etc., such as fluorine-containing activator, can be used.

The thickness of the coating film can be appropriately selected depending on the function required for the organic layer and the solubility or dispersibility of the organic material. As the film thickness is larger, drying unevenness due to flow is more likely to occur, and the usefulness of the drying apparatus 1 capable of uniform drying is greater.
Specifically, the thickness of the coating film is preferably in the range of 1 to 90 μm.

Similarly to the film thickness, the viscosity of the coating film can be appropriately selected depending on the function required for the organic layer and the solubility or dispersibility of the organic material. As the viscosity is smaller, drying unevenness due to flow tends to occur, and the usefulness of the drying apparatus 1 capable of uniform drying is great.
Specifically, the viscosity of the coating film is preferably in the range of 0.3 to 100 mPa · s, and more preferably in the range of 0.5 to 10 mPa · s.

[Drying equipment]
The coating film drying apparatus 1 includes a condensation drying apparatus B as shown in FIG. 1, and the coating film on the substrate f1 is dried by the condensation drying apparatus B. Further, the drying device 1 includes a heating device A, and the substrate f1 is preliminarily heated by the heating device A before being dried by the condensing drying device B.

  The drying apparatus 1 is preferably installed immediately after the coating apparatus 3 so that it can be dried immediately after the coating film. During the period from the coating to drying, there is an influence of the surrounding airflow and natural convection generated in the drying apparatus 1, but drying immediately after the coating can prevent drying unevenness due to the influence of the airflow. Although it depends on the conveyance speed, the time from the coating film to drying is preferably within 30 seconds, and more preferably within 10 seconds. In addition, between the coating device 3 and the drying device 1, a blocking plate that blocks the surrounding airflow is provided, or a rectifying plate that rectifies the surrounding airflow and a rectifying fan are provided so that no airflow is generated on the coating film. You can also.

[Heating device]
The heating device A is disposed after the coating film is applied by the coating device 3 and before drying by the condensation drying device B. The heating device A heats the substrate f1 and the coating film. As shown in FIG. 1, the heating device A may be disposed so as to face the coating film on the substrate f1, or may be disposed so as to face the substrate f1. By heating the substrate and the coating film in advance, the temperature unevenness in the coating film surface can be reduced when the condensation drying apparatus B is dried, and the uniformity of drying of the coating film can be improved. Further, in the condensation drying apparatus B, the solvent is easily evaporated from the coating film, and the drying efficiency is improved.

The heating device A can use convection and radiation as a heating method. In the case of convection, heating can be performed by blowing hot air on the coating film on the substrate f1 with a dryer.
From the viewpoint of increasing the uniformity of drying, it is preferable that the heating device A includes the infrared heater 51 and the substrate f1 and the coating film are heated by radiant heat from the infrared heater 51.

The infrared wavelength of the infrared heater 51 can be selected according to the absorption wavelength of the heating target.
For example, the absorption wavelength of ITO (Indium Tin Oxide) is 1.50 μm or more, the absorption wavelength of polyethylene terephthalate is around 8.0, 6.0, 3.3, 2.9 μm, the absorption wavelength of polyethylene naphthalate Is known to be around 8.0, 3.3 μm. Further, it is known that the absorption wavelength of normal propyl acetate used as a solvent is around 8.0, 6.0, 3.3, 2.9 μm.
Polyethylene terephthalate has relatively little absorption around 2.9 μm compared to normal propyl acetate, and if the solvent is selectively heated, the infrared heater 51 has a maximum energy wavelength in the range of 2.50 to 4.00 μm. It is preferable to radiate infrared light having a medium wavelength.

  The infrared heater 51 may be spherical or line-shaped. As described above, when radiating short wavelength infrared rays together with medium wavelengths, short wavelength infrared heaters 51 and medium wavelength infrared heaters 51 are alternately arranged to simultaneously radiate infrared rays of respective wavelengths.

From the viewpoint of improving the uniformity of drying by the condensation drying apparatus B, the viscosity of the coating film after heating by the heating apparatus A is preferably 5 mPa · s or less.
As the viscosity of the coating film increases, drying unevenness due to flow decreases. By heating to a viscosity of 5 mPa · s or less, drying unevenness in the condensing dryer B is suppressed and drying uniformity is further improved. be able to.

The heating conditions can be appropriately selected in consideration of the effect of heating on the drying unevenness of the coating film, the deformation of the substrate f1, and the like. For example, the surface temperature of the coating film by heating can be selected within a range of 20 to 200 ° C. The distance between the infrared heater 51 and the coating film can be selected within a range of 1 to 500 mm.
In order to alleviate the heating, ceramics may be disposed between the infrared heater 51 and the coating film, or the infrared heater 51 may be air-cooled or water-cooled.

[Condensation drying equipment]
FIG. 2 is a front view of the inside of the condensing and drying apparatus B viewed from the conveyance direction y of the substrate f1.
As shown in FIGS. 1 and 2, the condensing and drying apparatus B includes a condensing plate 11 facing the coating film f2 on the substrate f1, and condenses the vapor of the solvent from the coating film f2 by the condensing plate 11 to dry it. To do. The condensing plate 11 may be fixedly arranged or may be transported by a roller.
In addition, the condensing and drying apparatus B includes a heating device 12 that heats the substrate f1 in order to promote evaporation of the solvent. The heating method is not particularly limited, and examples thereof include heating methods such as heating by hot air (heating gas), infrared rays, UV, and plane heating, and internal heating using electric resistance by microwaves.

  The material of the condenser plate 11 is not particularly limited, but is preferably a solvent absorber. By being an absorbent material, the condensing plate 11 absorbs the solvent condensed on the condensing surface 11a, the solvent can be discharged from the condensing surface 11a, and further condensation of the solvent can be promoted. The condensing surface 11a refers to the surface of the condensing plate 11 that faces the coating film surface f2a and condenses the solvent from the coating film f2. The coating film surface f2a is the surface of the coating film f2.

  Examples of such absorbent materials include porous materials, high silica zeolite, activated carbon, and the like. Further, the condensing plate 11 can be configured by bonding a sheet made of an absorbent material to a resin film, an aluminum material, or the like. For example, a solvent absorbing material described in JP-A-2005-232308, a resin film including a solvent-absorbing layer described in JP-A-2003-191598, and the like can be used as the condensing plate 11.

Moreover, it is preferable to use a material with a large heat capacity from the viewpoint of preventing condensation from slowing down. In order to condense the solvent, it is necessary to maintain the condensing surface 11a at a lower temperature than the coating film surface f2a. By using the condensing plate 11 having a large heat capacity, even when radiant heat is generated from the coating film f2 by the heating of the heating device 12, the temperature rise of the condensing surface 11a due to the radiant heat can be suppressed, and the slowing of condensation can be prevented.
Specifically, the heat capacity is preferably 2700 kJ / m ³ · K or more, and the larger the better.

  Examples of the material having such a heat capacity include zirconia, cast iron, alumina, and the like, and can be appropriately selected in consideration of workability and thermal conductivity. In particular, the condenser plate 11 is required to have a certain degree of thermal conductivity from the ease of temperature control, and the higher the thermal conductivity, the easier it is to shift the temperature of the condenser plate 11 to a steady state at a desired temperature.

  The condensing plate 11 can have a plurality of slits in the condensing surface 11a in order to discharge the condensed solvent from the condensing surface 11a and promote further condensation. The direction in which the slit is formed may be either the width direction x or the conveyance direction y. The solvent condensed on the condensing surface 11a by the capillary force of the slit is transported to the end in the width direction x or the transport direction y and discharged.

  The condensing plate 11 may be arranged to be inclined with respect to the substrate f1, and the solvent condensed on the condensing surface 11a may be discharged along the inclined condensing surface 11a by gravity. For example, it can be installed such that the distance between the condensation surface 11a and the coating film surface f2a increases from one end to the other end in the width direction x.

  When the slit is provided, a side plate hanging from the side surface of the condensing plate 11 or a container for collecting the solvent can be installed to collect the solvent discharged by the slit.

The condensing plate 11 may be subjected to a surface treatment on the condensing surface 11a.
For example, the condensation surface 11a can be subjected to a water repellent treatment or a hydrophilic treatment in order to prevent contamination or to efficiently discharge the condensed solvent.
As the water repellent treatment, as described in JP-A-2005-343016 and JP-A-2000-254582, a water-repellent material such as a silane compound having a fluoroalkyl group, an alkyl group or the like is used as a flow coating method. And a treatment applied by a dip coating method or the like. In addition, as described in JP-A-2005-23122, a honeycomb structure or pillar structure film manufactured using a polymer having a polyfluoroalkyl group having water and oil repellency is applied to the condensation surface. May be.
Examples of other surface treatment include rubbing treatment to prevent drying unevenness. Moreover, in order to improve wettability, the condensation surface 11a can also be finished rough.
In addition, the solvent on the condensation surface 11a may be discharged by a mechanical force such as a belt, a wipe, or a pump.

The drying speed of the condensing dryer B can be controlled by adjusting the temperature Tc of the condensing surface 11a and the temperature Th (Th> Tc) of the coating film surface f2a.
The temperature control method of the condensing plate 11 is not particularly limited. For example, heating by heat transfer such as hot air (heating gas), infrared rays, UV, and plane heating, heating methods such as internal heating using electric resistance by microwaves, The temperature Tc can be controlled in combination with cooling methods such as cooling using a refrigerant, air cooling using air blowing, and electrical cooling using a Peltier element.
Moreover, if necessary, the temperature Th of the coating film surface f2a can be controlled by using the cooling device according to the above-described cooling method in combination with the heating device 12.

  The temperature Tc of the condensing surface 11a may be higher or lower than room temperature as long as it is lower than the temperature Th of the coating film surface f2a, but is preferably in the range of 5 to 30 ° C, and in the range of 10 to 20 ° C. It is more preferable that By controlling within the above range, an increase in cost required for heating can be suppressed. Further, uniform temperature control of the entire condensation surface 11a is facilitated, and drying unevenness due to temperature unevenness and film thickness unevenness of the coating film f2 are easily suppressed. From the same viewpoint, the temperature unevenness in the condensing surface 11a is preferably within 2 ° C.

In order to prevent substances other than the solvent such as moisture in the atmosphere from condensing on the condensation surface 11a, it is preferable to lower the dew point of the atmosphere or reduce the pressure between the condensation surface 11a and the coating film surface f2a.
In addition, in order to prevent the solvent from condensing in a member of the condensing drying apparatus B other than the condensing plate 11, such as a housing, the temperature of the member other than the condensing plate 11 may be adjusted to be equal to or higher than the temperature Tc of the condensing surface 11a. preferable.

  The temperature Th of the coating film surface f2a may be higher or lower than room temperature as long as it is higher than the temperature Tc of the condensing surface 11a, but is preferably within a range of 30 to 100 ° C, and within a range of 30 to 70 ° C. It is more preferable that By setting it as 30 degreeC or more, it is easy to suppress that the water | moisture content etc. in air | atmosphere other than a solvent condense, and drying efficiency falls. By setting the temperature to 100 ° C. or lower, it is easy to suppress an increase in cost due to a high temperature and a conveyance failure due to the modification of the substrate f1. In addition, uniform temperature control of the entire substrate f1 is facilitated, and drying unevenness due to temperature unevenness, and consequently film thickness unevenness of the coating film f2, can be easily suppressed. From the same viewpoint, the temperature unevenness in the coating film surface f2a is preferably within 2 ° C.

  The drying speed of the condensing dryer B can also be controlled by adjusting the distance d between the condensing surface 11a and the coating film surface f2a. As the distance d is smaller, the solvent is more easily condensed and the drying speed is increased, but is preferably in the range of 0.1 to 10 mm, and more preferably in the range of 0.1 to 4 mm. By setting the thickness to 0.1 mm or more, it is easy to avoid contact between the coating film f2 and the condensing plate 11 due to flapping of the substrate f1, and it is possible to reduce the cost associated with high accuracy of the arrangement of the condensing plate 11. Moreover, it is easy to avoid adhesion of the condensed solvent to the coating film f2, and drying unevenness due to adhesion can be suppressed. Moreover, by being within 10 mm, the influence of the surrounding convection can be reduced, drying unevenness can be prevented, the drying speed can be increased, and productivity can be improved.

It is preferable that the amount of solvent dried by the condensing dryer B is in the range of 10 to 80% by volume with respect to the total volume of the solvent contained in the coating film f2.
Although the solvent evaporates and is dried by preheating the heating device A, the entire drying process is performed by drying the solvent within the above range by the condensing drying device B that is superior in drying uniformity to the heating device A. As a result, the uniformity of drying can be improved.

[Drying method]
The coating film drying method by the coating film drying apparatus 1 includes a step of preliminarily heating the substrate f1 and the coating film f2 by the heating apparatus A after the coating process by the coating apparatus 3, and a heating and condensation drying apparatus B after the heating. Then, the coating film f2 on the substrate f1 and the condensing plate 11 are made to face each other, the vapor of the solvent from the coating film f2 is condensed by the condensing plate 11 and dried.

  Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

[Prototype of drying device K1]
Condensation drying with the same configuration as the condensation drying apparatus B shown in FIGS. 1 and 2 using an aluminum member (length in the width direction 0.4 m, length in the conveyance direction 2.0 m, thickness 10 mm) as a condensing plate A device was made. Next, a plurality of infrared heaters BSG500 / 300 (manufactured by Heraeus Co., Ltd., maximum energy wavelength 2.50 μm) were arranged in the transport direction to prepare a heating device. As shown in FIG. 1, the produced heating device is disposed so as to face the coating film on the substrate immediately after the coating device, and the condensation drying device is disposed immediately after the heating device, so as to dry the coating film. Prototype K1.

[Prototype of drying device K3]
In the trial production of the drying device K1, instead of a heating device using an infrared heater, a dryer having an air nozzle DX-300 (manufactured by Kikuchi Co., Ltd.) was arranged, and a drying device K3 was prototyped. The dryer can select hot air temperature and wind speed.

[Production of Organic EL Element 1]
On a substrate of polyethylene terephthalate film (manufactured by Teijin-DuPont, length 0.33 m in the width direction, length 40 m in the transport direction, thickness 100 μm), an ITO film having a thickness of 100 nm is used as an anode using a sputtering apparatus. Formed.

  Further, a solution obtained by diluting Baytron P Al 4083 (poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate), Bayer Co.) to 70% with pure water under the same coating conditions as those of the light emitting layer to be described later is used. Coating was performed by a coating method to form a hole injection layer having a length of 0.3 m in the width direction. After coating, the substrate was dried at a surface temperature of 80 ° C. for 1 hour. It was 30 nm when it apply | coated on the conditions prepared on the board | substrate prepared separately and the film thickness of the formed positive hole injection layer was measured.

This substrate was transferred to a glove box under a nitrogen atmosphere in accordance with JIS B 9920, the measured cleanliness was class 100, the dew point temperature was −80 ° C. or lower, and the oxygen concentration was 0.8 ppm. Next, the following hole transport layer coating solution is prepared and coated on the substrate in the glove box by the slot coating method under the same coating conditions as those of the light emitting layer described later. A hole transport layer was formed. After coating, the substrate was dried by heating at a surface temperature of 80 ° C. for 30 minutes. It was 20 nm when it apply | coated on the board | substrate prepared separately on the same conditions and the film thickness of the formed positive hole transport layer was measured.
(Hole transport layer coating solution)
Monochlorobenzene 100.0g
ADS254BE (Poly- (N, N′-bis (4-butylphenyl) -N, N′-bis (phenyl) benzidine, manufactured by American Die Source)) 0.5 g

Subsequently, the following light emitting layer coating liquid was prepared under nitrogen atmosphere. The coating solution had a solid content concentration of 0.01% by mass and a viscosity of 0.6 mPa · s. The viscosity was measured in an environment at a temperature of 25 ° C. using a viscometer DV-II + Pro (manufactured by Brookfield) in accordance with JIS Z 8803.
(Light emitting layer coating solution)
Normal propyl acetate 10.00000g
H-A 0.1000g
D-A 0.0110 g
D-B 0.0002g
D-C 0.0002g

The organic materials HA, DA, DB, and DC represent the following compounds.

The prepared light emitting layer coating solution was applied onto a substrate by a slot coating method using a slit type die coater. The length of the slit type die coater in the width direction was 0.17 m, and the slit interval was 100 μm. The application conditions are as follows.
(Application conditions)
Application speed: 10 m / min
Environmental temperature during application: 25 ° C
Applied length in width direction: 0.1m
Applied length in transport direction: 40.0m
Wet film thickness: 4μm
The coating speed was measured with a laser Doppler velocimeter LV203.
Moreover, the wet film thickness was computed by the following formula.
Wet film thickness = supply amount of coating solution / (length in the width direction applied x coating speed)

A prototype drying device K1 was placed at a position immediately after application of the slit type die coater, and was dried by the drying device K1 immediately after the application. The heating conditions of the heating device and the drying conditions of the condensation drying device are as follows.
(Heating condition of heating device)
Temperature of coating film surface during heating: 120 ° C
Distance between infrared heater and coating film surface: 20mm
(Condensation drying equipment drying conditions)
Condensing surface temperature Tc: 20 ° C.
Temperature Th of coating film surface: 25 ° C.
Distance between condensation surface and coating film surface: 2.00 mm

When the viscosity of the coating film after heating by the heating device was determined as follows, it was 0.5 mPa · s.
The same coating solution as the coating solution used for the light emitting layer is put in a container and heated at 120 ° C. which is the same as the temperature of the coating film surface during the above heating. ). The temperature of the coating film surface was measured with a digital radiation temperature sensor FT-H10 (manufactured by Keyence Corporation).
Moreover, the film thickness of the coating film was measured using LT-9000 (manufactured by Keyence Corporation) immediately after coating and before and after condensation drying. From the measured film thickness, the drying amount (volume%) by condensation drying according to the following formula: Was found to be 70% by volume.
Drying amount by condensation drying (volume%) = (film thickness immediately before condensation drying−film thickness immediately after condensation drying) / film thickness immediately after coating

Next, the following electron transport layer coating solution was prepared under a nitrogen atmosphere.
(Coating liquid for electron transport layer)
2,2,3,3-tetrafluoro-1-propanol 100.00 g
ET-A 0.75g
ET-A represents the following compound.

  The prepared coating solution for the electron transport layer was coated under the same coating conditions as those for the light emitting layer, and was dried by heating at a substrate surface temperature of 80 ° C. for 30 minutes to form an electron transport layer. The film thickness was 40 nm when it apply | coated on the conditions prepared on the board | substrate prepared separately and the film thickness of the formed electron carrying layer was measured.

When the electron transport layer was formed, the substrate was moved to the vapor deposition machine without being exposed to the atmosphere, and the pressure was reduced to 4 × 10 ⁻⁴ Pa. Note that potassium fluoride and aluminum were each placed in a tantalum resistance heating boat and attached to a vapor deposition machine.
First, a resistance heating boat containing potassium fluoride was energized and heated to form a 3 nm electron injection layer made of potassium fluoride on the substrate. Next, a resistance heating boat containing aluminum was energized and heated to form a cathode having a thickness of 100 nm made of aluminum at a deposition rate of 1 to 2 nm / s.

  A glove box having a cleanliness of class 100, a dew point temperature of -80 ° C. or less, and an oxygen concentration of 0.8 ppm measured in accordance with JIS B9920 in a nitrogen atmosphere without exposing the substrate on which the cathode is formed to the atmosphere. Moved to. In the glove box, it sealed with the glass sealing can which attached the barium oxide which is a water catching agent, and the organic EL element 1 was obtained. Barium oxide, a water-absorbing agent, is a high-purity barium oxide powder manufactured by Aldrich, which is attached to a glass sealing can with a fluorine-based semipermeable membrane (Microtex S-NTF8031Q, manufactured by Nitto Denko) with an adhesive. The attached one was prepared and used in advance. For adhesion between the sealing can and the organic EL element 1, an ultraviolet curable adhesive was used, and both were adhered by irradiating ultraviolet rays to produce a sealing element.

[Production of organic EL elements 2 to 5]
In the production of the organic EL element 1, the distance between the condensing plate and the substrate of the condensing drying device of the drying device K1 and the temperature difference between the condensing surface and the coating film surface are adjusted, and the drying amount by the condensing drying device is shown in Table 1 below. Organic EL elements 2 to 5 were produced in the same manner as the organic EL element 1 except that the organic EL elements 1 and 2 were changed.

[Production of organic EL elements 6 to 9]
In the production of the organic EL element 1, propylene glycol monomethyl ether acetate and propylene glycol monomethyl ether-dispersed silica sol are added to the coating solution of the light emitting layer, and the addition amount is adjusted, and the viscosity of the coating film after heating is shown in Table 1 below. Organic EL elements 6 to 9 were produced in the same manner as the organic EL element 1 except that the differences were shown.

[Production of Organic EL Element 10]
In the production of the organic EL element 1, the organic EL element 10 was produced in the same manner as the organic EL element 1 except that the drying device K3 was used instead of the drying device K1 for drying the light emitting layer. The heating conditions of the dryer of the drying device K3 are as follows.
(Dryer heating conditions)
Wind speed: 1.5m / s
Hot air temperature: 120 ° C

[Production of Organic EL Element 11]
Separate the dryer and the condensing dryer used for the drying device K3, arrange the dryer just before the coating device to heat the substrate before coating the light emitting layer coating solution, and place the condensing drying device just after the coating device. Then, an organic EL element 11 was produced in the same manner as the organic EL element 1 except that the light emitting layer was dried. The drying conditions of the dryer are as follows.
(Dryer drying conditions)
Wind speed: 1.5m / s
Hot air temperature: 120 ° C

<Evaluation>
[Dryness uniformity]
Since the luminance of the organic EL element has a correlation with the film thickness of the light emitting layer, and the film thickness of the light emitting layer has a correlation with the uniformity of drying, the luminance of each of the organic EL elements 1 to 11 is measured. The variation was evaluated as the uniformity of the light emitting layer thickness, that is, the uniformity of drying. First, using a luminance meter CS2000 (manufactured by Konica Minolta Sensing Co., Ltd.), the luminance of each of the organic EL elements 1 to 11 was measured at 300 points by changing the position in the transport direction at intervals of 0.01 m in the width direction. Among the 300 measured values, the maximum luminance value, the minimum luminance value, and the average luminance value were obtained, and the luminance variation was obtained by the following equation.
Variation in luminance = {(maximum luminance value−minimum luminance value) / average luminance} × 100

From the obtained variation in luminance, the uniformity of drying was evaluated as follows.
(Double-circle): The dispersion | variation in a brightness | luminance is less than 0.5, and it has performed very uniform drying.
A: The variation in luminance is 0.5 or more and less than 1.0, and uniform drying is achieved.
(Triangle | delta): The dispersion | variation in brightness | luminance is 1.0 or more and less than 5.0, and although the dispersion | variation is seen in a film thickness, it has dried uniformly as much as it is practical.
X: The variation in luminance is 5.0 or more, and it cannot be uniformly dried.

Table 1 below shows the evaluation results.

  As shown in Table 1, according to the organic EL elements 1 to 10 according to the examples, high drying uniformity is obtained. On the other hand, according to the organic EL element 11 which concerns on a comparative example, it is estimated that the film thickness nonuniformity of the coating film had arisen by the heating before application | coating, and it turns out that it cannot be dried uniformly also by subsequent condensation drying.

DESCRIPTION OF SYMBOLS 1 Coating film drying apparatus A Heating apparatus 51 Infrared heater B Condensation drying apparatus 11 Condensing plate 11a Condensing surface 12 Heating apparatus 3 Coating apparatus f1 Substrate f2 Coating film f2a Coating film surface

Claims (5)

A condensing plate that faces the coating film on the substrate, condensing the solvent vapor from the coating film by the condensing plate, and drying,
A heating device that is disposed between the application of the coating film and the drying by the condensation drying device, and preliminarily heats the substrate and the coating film;
A coating film drying apparatus comprising:   The coating film drying apparatus according to claim 1, wherein the heating device heats the substrate and the coating film with infrared radiation heat.   The apparatus for drying a coating film according to claim 1 or 2, wherein the viscosity of the coating film after being heated by the heating device is 5 mPa · s or less.   The amount of the solvent dried by the condensation drying device is in the range of 10 to 80% by volume with respect to the total volume of the solvent contained in the coating film. The coating film according to any one of claims 1 to 3. Drying equipment. In the drying method of the coating film, the coating film on the substrate and the condensing plate face each other, the vapor of the solvent from the coating film is condensed by the condensing plate, and dried.
A method for drying a coating film, comprising: a step of preheating the substrate and the coating film after coating the coating film and before drying by the condensation.

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