JPWO2013105534A1 - Thin film forming method and thin film forming apparatus - Google Patents

Abstract

Provided are a thin film forming method and a thin film forming apparatus having high productivity by suppressing interlayer mixing between stacked organic layers.
The thin film forming apparatus 100 is formed by a second film forming unit B that forms an organic layer on a substrate by applying or spraying a solution in which an organic material is dissolved or dispersed in a solvent by a wet process. The first film forming means A for forming an organic layer made of the same organic material as that of the organic layer on the upper or lower layer of the organic layer to be formed by a trace solvent coating method. The thin film forming apparatus 100 can form an organic layer with the first film forming unit A and form an organic layer with the second film forming unit B on the organic layer. Moreover, the thin film forming apparatus 100 can form an organic layer on the organic layer formed by the second film forming unit B by the first film forming unit A.

Description

  The present invention relates to a thin film forming method and a thin film forming apparatus.

  Formation of an organic thin film is indispensable for the manufacture of organic EL (Electro Luminescence) elements, solar cells, and the like. As a method for forming a thin film, a spray method called a wet process, a spin coating method, a casting method, a slot method, an ink jet method, a printing method and the like are used in addition to a vapor deposition method.

  In recent years, a film forming method based on a wet process has attracted attention because it does not require a vacuum process and can simplify continuous production. Among the wet processes, the spray method is a highly productive method capable of forming a large area in a short time (see, for example, Patent Document 1).

JP 2010-226087 A

However, it is generally known that an organic EL element manufactured by a wet process does not provide sufficient performance in terms of element performance, particularly a light emission lifetime, compared to an organic EL element manufactured by a vapor deposition method. .
This is because when the organic layers having different organic materials are stacked, the lower organic layer is dissolved by the upper solvent or the upper solvent penetrates into the lower layer, so that the organic material is between the upper layer and the lower layer. It is thought that this is caused by the mixing of layers and the occurrence of interlayer mixing called mixing.

  The subject of this invention is suppressing the interlayer mixing between the laminated | stacked organic layers, and providing the thin film formation method and thin film formation apparatus with high productivity.

According to the invention of claim 1,
In a thin film forming method of forming an organic layer on a substrate by applying or spraying a solution in which an organic material is dissolved or dispersed in a solvent by a wet process,
A thin film forming method is provided in which an organic layer made of the same organic material as the organic layer is formed on an upper layer or a lower layer of the organic layer by a trace solvent coating method.

According to invention of Claim 2,
2. The thin film forming method according to claim 1, wherein in forming the organic layer by the trace solvent coating method, a voltage is applied to a solution of the organic material, and the charged solution is sprayed on the substrate to form the organic layer. .

According to invention of Claim 3,
The thin film formation method according to claim 1, wherein in forming the organic layer by the micro solvent application method, an aerosol of a solution of an organic material is formed, the aerosol is heated and sprayed on a substrate, and the organic layer is formed. Is done.

According to invention of Claim 4,
2. The organic layer is formed by forming an organic layer in a supercritical fluid obtained by pressurizing and heating a gas and spraying the organic material on a substrate in the formation of the organic layer by the trace solvent coating method. A method for forming a thin film is provided.

According to the invention of claim 5,
In the formation of the organic layer by the wet process, the thin film forming method according to any one of claims 1 to 4, wherein the organic layer is formed on the substrate by spraying a solution of an organic material by a spray method. .

According to the invention of claim 6,
The thin film forming method according to any one of claims 1 to 5, wherein a film thickness of the organic layer formed by the trace solvent coating method is in a range of 1 to 10 nm.

According to the invention of claim 7,
The organic layer formed by the trace solvent coating method and the wet process is a light emitting layer of an organic EL element,
The thin film forming method according to claim 1, wherein the upper layer or the lower layer of the light emitting layer is a hole transport layer or an electron transport layer.

According to the invention described in claim 8,
A second film forming means for applying or spraying a solution in which an organic material is dissolved or dispersed in a solvent by a wet process to form an organic layer on the substrate;
A first film forming means for forming an organic layer made of the same organic material as the organic layer on an upper layer or a lower layer of the organic layer formed by the second film forming means by a trace solvent coating method;
Is provided.

  According to the present invention, an organic layer can be formed by a wet process, and high productivity can be obtained. And since the organic layer is formed on the upper layer or the lower layer of the organic layer formed by the wet process by a small amount of solvent coating method, there is little action of the solvent between other adjacent organic layers, and between the stacked organic layers Interlayer mixing of organic materials can be suppressed. Accordingly, it is possible to provide a thin film forming method and a thin film forming apparatus with high productivity by suppressing interlayer mixing between the stacked organic layers.

It is a schematic block diagram of the thin film forming apparatus which concerns on this Embodiment. It is a figure explaining the basic principle of ESD method. It is a figure which shows the example of the auxiliary | assistant means provided in order to form a uniform organic layer. It is a figure which shows the example of the interlayer mixing produced by lamination | stacking of a light emitting layer and a positive hole transport layer. It is a figure which shows the light emitting layer formed by the 2nd film-forming means, and the light emitting layer formed in the lower layer by the 1st film-forming means. It is a figure which shows the light emitting layer formed by the 2nd film-forming means, and the light emitting layer formed by the 1st film-forming means on the upper layer and the lower layer. The schematic block diagram of the 1st film-forming means which forms an organic layer by ESDUS method is shown. The schematic block diagram of the 1st film-forming means which forms an organic layer with a supercritical spray method is shown.

  Hereinafter, embodiments of a thin film forming method and a thin film forming apparatus of the present invention will be described with reference to the drawings.

[Thin film forming equipment]
FIG. 1 shows a main configuration of a thin film forming apparatus 100 according to an embodiment of the present invention.
As shown in FIG. 1, the thin film forming apparatus 100 includes a first film forming unit A and a second film forming unit B, and forms an organic layer made of an organic material on a substrate T.
The substrate T is an object to be formed, and may be a substrate made of a flexible material such as a glass substrate or a resin film, or some layer may already be formed on these substrates. .

  The thin film forming apparatus 100 shown in FIG. 1 forms an organic layer made of the same organic material on the same substrate T by the first film forming unit A and the second film forming unit B. A transport unit may be provided between the second film forming units B, and the substrate T may be automatically transported according to the order in which the organic layers are formed. The operator may transfer the substrate T and place it on the first film forming means A or the second film forming means B.

[Organic materials]
The organic material can be selected according to the organic layer to be formed.
For example, the organic EL element is configured by laminating an anode, a hole transport layer, a light emitting layer, an electron transport layer, a cathode, and the like in this order. In addition, a hole injection layer, an electron injection layer, and the like may be provided between the anode and the light emitting layer and between the cathode and the light emitting layer as necessary.
Examples of organic materials for the hole transport layer include triazole derivatives, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, styryl. Examples thereof include conductive polymer oligomers such as anthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline copolymers, 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 thin film forming apparatus 100 can form an organic layer in manufacturing solar cells, transistors, memories, sensors, and the like. Examples of such an organic material include pentacene, naphthalene and the like in addition to a conductive polymer such as polythiophene.

For the preparation of the organic material solution, a solvent capable of dissolving or dispersing the organic material is used. In film formation, the smaller the droplet of the solution, the more uniform and smooth the organic layer can be formed. Therefore, a solvent having high solubility in an organic material is preferable.
From such a viewpoint, depending on the selected organic material, examples of usable solvents include pure water, alcohols such as 2-ethoxyethanol and 2-methoxyethanol, chloroform, methylene chloride, tetrachloroethylene, dichloroethane, tetrahydrofuran and the like. Halogen series, aromatic hydrocarbon series such as xylene, toluene, hexane, cyclohexylbenzene and anisole, ketone series such as acetone and methyl ethyl ketone, ester series such as acetic acid, methyl acetate, ethyl acetate, butyl acetate and acetonitrile, diethyl ether And dimethyl sulfoxide.

  As the organic material solution, the same solution may be used for the first film forming unit A and the second film forming unit B. Further, according to each of the first film forming means A and the second film forming means B, the concentration of the organic material or a different solvent is selected, and the solutions for the first film forming means A and the second film forming means B are selected. It may be prepared. For example, the solvent for the first film forming means A is a solvent having a high vapor pressure under an assumed environmental temperature because the more easily the solvent is volatilized, the more the droplets are dried when sprayed. Is preferred.

[First film forming means]
The first film forming means according to the present invention forms the organic layer by a trace solvent coating method.
The “trace solvent coating method” in the present invention is to form droplets by spraying a solution obtained by dissolving and / or dispersing an organic material in a solvent, volatilizing and concentrating the solvent in the droplets, Depositing concentrated droplets on a substrate or on a thin film provided on the substrate. Specific examples of the trace solvent coating method include an ESD (Electro Spray Deposition) method, an ESDUS (Evaporative Spray Deposition from Ultra-dilute Solution) method, and a supercritical spray method.

The first film forming means A in FIG. 1 is an embodiment of a first film forming means for forming an organic layer by a trace solvent coating method, and forms an organic layer by an ESD method.
Specifically, the first film forming unit A applies a voltage to a solution in which an organic material is dissolved or dispersed in a solvent, sprays the charged solution, and forms an organic layer on the substrate T.

With reference to FIG. 2, the basic principle of film formation by the ESD method will be described.
As shown in FIG. 2, according to the ESD method, a power source 32 applies a voltage between a capillary 31 filled with an organic material solution and a support 34. Specifically, a positive voltage is applied to the capillary 31 and a negative voltage is applied to the support 34. As a result, the solution 33 in the capillary 31 is charged with positive polarity, and the substrate 35 placed on the support 34 is charged with negative polarity. Instead of applying a negative voltage, the support 34 may be grounded, or the polarity for charging the solution 33 and the support 34 may be reversed. In this state, the solution 33 delivered from the capillary 31 is repelled by the Coulomb force and split into droplets having a positive charge. Since the solvent in the solution 33 is volatilized by the splitting and the charge density is increased by the volatilization, the droplet is further repelled and repeats the splitting. The droplets which are finely divided by repeating the division are attracted to the negative polarity substrate 35 and adhere to the substrate 35 to form an organic layer. Since the solvent is almost volatilized before reaching the substrate 35, there is almost no solvent in the formed organic layer, and a dry organic layer is formed.

  For example, as shown in FIG. 1, the first film forming unit A includes a control unit 11, voltage application units 12 a and 12 b, a solution supply unit 13, a capillary 14, an electrode 15, and a support 16.

  The control unit 11 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a non-volatile memory such as a hard disk, and the like, and reads and executes a control program stored in the non-volatile memory, thereby The operation of each part of the film means A is controlled. For example, the control unit 11 controls the voltage applied by the voltage application units 12 a and 12 b, the liquid supply speed at which the solution supply unit 13 supplies liquid to the capillary 14, and the like.

  The voltage application unit 12 a applies a voltage to the electrode 15 provided in the capillary 14, and the voltage application unit 12 b applies a voltage to the support 16 of the substrate T, and the solution sprayed by the capillary 14 and the substrate T Are charged to opposite polarities. The support 16 is made of a conductor such as metal. Either the solution or the substrate T may be charged to any polarity, but if the solution is charged with a positive polarity and the substrate T is charged with a negative polarity, the voltage application unit 12a applies a positive voltage to the electrode 15. The voltage application unit 12 b applies a negative voltage to the support 16.

  The voltage (V) to be applied can be appropriately set according to the distance Da from the spray port of the capillary 14 to the substrate T and the relationship with the spray amount of the solution. Although it does not specifically limit as a voltage to apply, Preferably it exists in the range of 5-20 kV, More preferably, it exists in the range of 10-15 kV.

The solution supply unit 13 stores an organic material solution and sends the solution to the capillary 14. The flow rate of the solution to be fed and the liquid feeding speed can be set as appropriate.
The viscosity of the solution used by the first film forming means A is preferably 100 mPa · s or less, more preferably 5 mPa · s or less. The viscosity is a value measured according to JIS Z 8803 using a viscometer DV-II + Pro (manufactured by Brookfield) at 25 ° C.
The solid concentration of the solution used by the first film forming means A is preferably 2.00% by mass or less, and preferably in the range of 0.01 to 1.00% by mass.

  The capillary 14 sends out the organic material solution supplied from the solution supply unit 13 from the spray port at the tip. An electrode 15 formed in a linear shape is installed in the tube of the capillary 14, and the solution in the capillary 14 is sent out in a charged state by the voltage applied to the electrode 15. As shown in FIG. 2, the solution repeats splitting by repulsion, is sprayed as fine particle droplets, and reaches the substrate T.

  The capillary 14 can be made of a conductor such as metal. One capillary 14 may be provided as shown in FIG. 1, or a plurality of capillaries 14 may be provided to increase productivity.

  The inner diameter of the spray port of the capillary 14 can be appropriately set according to the flow rate of the solution, the desired size of the droplet, and the like. Although it does not specifically limit as an internal diameter, The inside of the range of 10-300 micrometers is preferable, More preferably, it exists in the range of 30-50 micrometers.

  The distance Da from the spray port of the capillary 14 to the film formation surface of the substrate T can be appropriately set to a distance at which the volatilization of the solvent from the solution becomes good. As the distance Da increases, the solvent volatilizes and the droplets easily dry. However, since the droplets are widely distributed and the film formation area is enlarged, it takes time to form a desired film thickness. From such a tendency, the distance Da is not particularly limited, but is preferably in the range of 3 to 20 cm, more preferably in the range of 5 to 10 cm.

[Second film forming means]
The second film forming means according to the present invention is not particularly limited as long as a solution in which an organic material is dissolved or dispersed in a solvent can be applied or sprayed by a wet process to form an organic layer on the substrate. As a wet process, a known spin coating method, slot coating method, wire bar method, ink jet method and the like can be selected in addition to a spray method that is preferably used without actively heating a solution of an organic material. .

The second film forming means B in FIG. 1 is an embodiment of the second film forming means for forming an organic layer by a wet process, and forms the organic layer by a spray method.
Specifically, the second film forming unit B sprays a solution in which an organic material is dissolved or dispersed in a solvent by a spray method to form an organic layer on the substrate T.
For example, as shown in FIG. 1, the second film forming unit B includes a control unit 21, a solution supply unit 22, a nozzle 23, a drive unit 24, a support 25, and the like.

  The control unit 21 includes a CPU, a RAM, a non-volatile memory, and the like, and controls the operation of each unit of the second film forming unit B by reading and executing a control program stored in the non-volatile memory. For example, the control unit 21 controls the amount of solution fed to the nozzle 23 by the solution supply unit 22 and the driving of the nozzle 23 by the driving unit 24.

The solution supply unit 22 stores an organic material solution and sends the solution to the nozzle 23. The liquid feeding flow rate and the like can be set as appropriate.
As a liquid feeding method of the solution supply unit 22, a known method can be used, and examples thereof include pressure liquid feeding, syringe pump liquid feeding, tube liquid feeding, and the like. An optimal liquid feeding method can be selected according to the required liquid feeding amount, liquid feeding accuracy, solid content concentration, viscosity, cost, and the like. Of these, pressure liquid feeding is preferable because it is easy to control the liquid feeding amount and the liquid feeding accuracy.

  The solution used by the second film forming means B is for the purpose of controlling the coating range, and for the purpose of suppressing the liquid flow accompanying the surface tension gradient after adhering to the substrate T (for example, the liquid flow causing a phenomenon called coffee ring). Depending on the case, a surfactant or a plurality of solvents may be mixed. 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 T, 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 nozzle 23 sprays the solution of the organic material supplied from the solution supply unit 22 from the spray port.
As a method for spraying the solution, a known method can be used, and is not particularly limited, and examples thereof include an ultrasonic method, a two-fluid method, and a rotary method in which the solution is atomized using an ultrasonic vibrator.

  The distance Db from the spray port of the nozzle 23 to the film formation surface of the substrate T may be appropriately set according to the amount of solution fed, the solid content concentration, and the like. By the time the solution sprayed from the nozzle 23 reaches the substrate T, the solvent gradually evaporates, but the solid content concentration of the organic material increases and the viscosity of the solution increases. The larger the distance Db, the more the solution diffuses and the productivity increases. However, the solvent easily evaporates and the solid content concentration increases, so the wettability on the substrate T decreases and uniform film formation becomes difficult. Become.

The drive unit 24 includes a drive source such as a motor, and drives the movement of the nozzle 23. The nozzle 23 is moved in one direction by the drive unit 24, and the relative position with respect to the substrate T varies.
The driving unit 24 may drive the support 25 of the substrate T instead of the nozzle 23 to move the position of the substrate T relative to the nozzle 23.
Further, a free span may be used instead of the support body 25.

In both the first film formation means A and the second film formation means B, turbulent flow due to the air flow is generated during the spraying process, which may hinder uniform film formation. Auxiliary means may be provided.
For example, as an auxiliary means, as shown in FIG. 3, a shielding plate 61 may be provided around the capillary 14 or nozzle 23 and the substrate T to shield the airflow entering between the capillary 14 or nozzle 23 and the substrate T. As another auxiliary means, a rectifying plate 62 such as a slit or a punch plate is provided around the spray port of the capillary 14 or the nozzle 23, and the direction in which the solution is sprayed from the air flow that has entered between the capillary 14 or the nozzle 23 and the substrate T is provided. May be rectified. Alternatively, instead of the rectifying plate 62, a fan or the like may be installed to blow air for rectification. Further, as an auxiliary means, a fan 63 for blowing accompanying air from the capillary 14 or the nozzle 23 toward the substrate T may be installed.

A mask may be provided between the capillary 14 or the nozzle 23 and the substrate T. A configuration may be adopted in which a plurality of masks can be exchanged depending on the application.
The material and thickness of the mask are not particularly limited, but it is preferable to use a porous mask or a highly hygroscopic mask in order to prevent dripping.

[Thin film formation method]
A thin film forming method when the thin film forming apparatus 100 of FIG. 1 forms an organic layer will be described.
In this thin film forming method, a solution in which an organic material is dissolved or dispersed in a solvent is applied by a wet process to form an organic layer on a substrate, and an upper layer or a lower layer of the organic layer is formed from the same organic material as the organic layer. The organic layer to be formed is formed by a trace solvent coating method.

When an organic layer made of the same organic material is formed below the organic layer formed by the wet process by a trace solvent coating method, first, the substrate T is placed on the support 16 of the first film forming means A. The first film forming means A applies an organic material solution used for forming the organic layer to form the organic layer on the substrate T.
The film thickness of the organic layer formed by the first film forming means A is preferably 1 nm or more and 10 nm or less. When the film thickness is 1 nm or more, inter-layer mixing is unlikely to occur with another organic layer that is adjacent to the organic layer formed by the first film forming unit A and has a different organic material. On the other hand, when the film thickness is 10 nm or less, the film formation time is short and the productivity is improved.

After forming the organic layer by the first film forming means A, a drying process may be performed.
The drying method is not particularly limited. Solid heat transfer drying such as hot air, infrared rays, and plane heating, internal heat generation drying such as microwaves, vacuum non-drying, supercritical drying, ultrasonic drying, and other non-heating drying, hygroscopic drying A known method such as gas drying such as cooling drying or condensation drying can be selected.

Next, the substrate T is placed on the support 25 of the second film forming means B.
The second film forming unit B applies the same organic material solution as the first film forming unit A on the organic layer formed on the substrate T by the first film forming unit A to form an organic layer.
After the organic layer is formed by the second film forming means B, a drying process may be performed.

  When an organic layer made of the same organic material is formed on the upper layer of the organic layer formed by the wet process by a trace solvent coating method, the substrate T is transferred from the second film forming means B to the first film forming means A and supported. Install on the body 16. The first film forming means A applies a solution of the same organic material as the organic layer formed by the second film forming means B, and the same organic material is applied onto the organic layer formed by the second film forming means B. An organic layer is formed.

In this way, the organic layer formed by the first film forming unit A and the second film forming unit B can suppress interlayer mixing with other organic layers having different organic materials.
Interlayer mixing will be described using an organic EL element as an example.
For example, when an anode, a hole transport layer, and a light emitting layer are stacked in this order on a resin substrate, light is emitted only by the second film forming means B having high productivity on the hole transport layer L1 as shown in FIG. Layer L22 is formed. In this case, although the productivity of the light emitting layer L22 is high, as shown in FIG. 4, interlayer mixing tends to occur between the light emitting layer L22 and the hole transport layer L1 below the light emitting layer L22. The light emitting layer L22 formed by the wet process by the second film forming means B is in a wet state with a considerable amount of solvent remaining in the organic layer, although a little amount of solvent is volatilized during film formation. The hole transport layer L1 is dissolved in the remaining solvent, the organic material in the light emitting layer L22 is eluted in the solvent in the hole transport layer L1, or the lower layer organic material is in a low viscosity solution state. Infiltrate into the interstices between the molecules, causing inter-layer mixing. When the same solvent is used for the light emitting layer L22 and the hole transport layer L1, the action of the solvents is large, and interlayer mixing is more likely to occur.

Interlayer mixing is likely to occur when the organic material has a low molecular weight. This is because the organic material is likely to elute into other organic layers as compared with the case of a high molecular weight. Here, the low molecular weight organic material means a low molecular compound having no repeating unit, and generally has a weight average molecular weight of 5000 or less, preferably 3000 or less, more preferably 2000 or less.
Interlayer mixing is particularly likely to occur between the light emitting layer and the hole transport layer or electron transport layer. This is because the same solvent is likely to be used for the light emitting layer and the hole transport layer or the electron transport layer, and a low molecular organic material is often used as the light emitting layer. This is probably because a polymer having a relatively large molecular weight is often used, and the gap between the low molecular weight organic materials of the light emitting layer is likely to be formed.

  On the other hand, when the light emitting layer is formed by the above-described thin film forming method, as shown in FIG. 5A, the first layer between the hole transport layer L1 and the light emitting layer L22 formed by the second film forming unit B is 1 The light emitting layer L21 formed by the film forming means A is interposed. Since the light emitting layer L21 is formed by the ESD method, the light emitting layer L21 has no or almost no solvent and is in a dry state. Even if the same solvent is used for the hole transport layer L1 and the light emitting layer L21, the solvent that acts on the hole transport layer L1 is removed, so that no interlayer mixing occurs. Rather than forming all the light emitting layers by the first film forming means A, the light emitting layer L22 is formed by the highly productive second film forming means B using the light emitting layer L21 in which interlayer mixing does not occur as a barrier layer. Thus, the productivity of the entire light emitting layer (the light emitting layer L21 and the light emitting layer L22) can be improved.

The same effect can be obtained not only in the lower layer of the light emitting layer L22 formed by the second film forming means B but also in the case where the light emitting layer L21 formed by the first film forming means A is provided in the upper layer.
For example, as shown in FIG. 5B, when the light emitting layer L21 is formed by the first film forming unit A on the light emitting layer L22 formed by the second film forming unit B, the electron transport formed on the light emitting layer L21 is performed. Interlayer mixing with the layer L3 can be suppressed.
In this way, in the lower layer and the upper layer, an organic layer in which no solvent remains as a barrier layer is formed at the boundary with other organic layers by the first film forming means A, so that inter-layer mixing with the other organic layers is performed. Can be suppressed.

[Other Embodiments]
If film formation by a trace solvent coating method is possible, instead of the first film formation means A using the ESD method, the first film formation means using the ESDUS method and the first film formation using the supercritical spray method are used. Membrane means can also be used.

  In the ESDUS method, an aerosol of a solution in which an organic material is dissolved or dispersed in a solvent is formed, and the aerosol is heated and sprayed to form an organic layer on a substrate. One of the features of the ESDUS method is that a thin film can be formed even if the organic material in the solution has a very low concentration.

FIG. 6 is a schematic configuration diagram of the first film forming means C using the ESDUS method.
As shown in FIG. 6, the first film forming means C includes, for example, a gas supply unit 41, a solution supply unit 42, an aerosol formation unit 43, chambers 44a and 44b, a heating unit 45, a support 46, and the like. Yes.

The gas supply unit 41 provides the carrier gas to the aerosol forming unit 43. As the carrier gas, a gas such as nitrogen, argon, helium, or air can be used.
The solution supply unit 42 stores an organic material solution and sends the solution to the aerosol forming unit 43.

  The aerosol forming unit 43 forms an aerosol that floats in the carrier gas as a solution of the supplied organic material as liquid particles. The aerosol forming means is not particularly limited, and an aerosol may be used as the aerosol forming portion 43 by mixing the solution and the carrier gas, and then spraying at high speed to form an aerosol. Moreover, as the aerosol formation part 43, you may atomize a solution using an ultrasonic transducer | vibrator, and may make it aerosol in a carrier gas.

The aerosol forming unit 43 sprays the formed aerosol into the chamber 44a.
The sprayed aerosol is transported by the transport gas and passes through the chamber 44a heated by the heating unit 45, whereby the solvent in the aerosol is vaporized and fine particles of the organic material are generated. The fine particles of the organic material are further transported into the chamber 44b by the transport gas, and adhere to the substrate T provided on the support 46 in the chamber 44a, thereby forming an organic layer.

  In the ESDUS method, as in the ESD method, the aerosol and the substrate T may be charged with opposite characteristics to spray the aerosol. In this case, fine particles can be formed by repulsion of charges.

  The supercritical spray method is represented by RESS (Rapid Expansion of Supercritical Solution) method, PGSS (Particles from Gas Saturated Solution) method, etc. This is a method of rapidly expanding and depositing dissolved solutes as fine particles from the difference in solubility (supersaturation) accompanying expansion.

  The first film forming means using the supercritical spray method dissolves and sprays an organic material in a supercritical fluid obtained by pressurizing and heating a gas to form an organic layer on the substrate. Since the supercritical fluid used as the solvent for the organic material is vaporized at the time of spraying, an organic layer containing no solvent can be formed.

FIG. 7 is a schematic configuration diagram of the first film forming means E using the supercritical spray method.
As shown in FIG. 7, the first film forming means E includes, for example, a gas supply unit 51, a cooler 52, a pressure pump 53, a preheater 54, a solute dissolution cell 55, a nozzle 56, a support 57, a valve V, and the like. It is prepared for.

  The gas supply unit 51 supplies a gas that causes a phase change to the supercritical fluid. The gas can be appropriately selected according to the organic material that is a solute. Examples of gases that can be used include carbon dioxide (critical temperature 31 ° C., critical pressure 7.38 MPa), ethane (critical temperature 32 ° C., critical pressure 4.88 MPa), water (critical temperature 374 ° C., critical pressure 22.06 MPa), Examples include propane (critical temperature 97 ° C., critical pressure 4.25 MPa), ethylene, alcohol and the like. In consideration of cost and environmental load, water, carbon dioxide, and alcohol are preferably used.

  The gas supplied from the gas supply unit 51 is cooled and liquefied by the cooler 52, and then pressurized by the pressurizing pump 53 and further heated by the preheater 54 to change into a supercritical fluid. Here, pressurization of gas means pressurization above the critical pressure of gas, and heating of gas means heating above the critical temperature. Specifically, pressurization of 1 MPa or more and heating of 27 ° C. or more are performed.

  When the solute dissolution cell 55 is filled with an organic material that is a solute and the supercritical fluid passes through the solute dissolution cell 55, the solute is dissolved in the supercritical fluid at the solute dissolution temperature and pressure. In order to maintain the state of the supercritical fluid, the solute dissolution cell 55 after the preheater 54, piping to the nozzle 56, and the like are installed in a constant temperature bath 58 at a constant temperature. The nozzle 56 is heated to a temperature higher than the solute dissolution temperature in order to prevent the supercritical fluid from expanding before spraying.

The supercritical fluid in which the solute is dissolved is delivered from the nozzle 56 and, when placed under atmospheric pressure, is separated into vapor phase carbon dioxide and solute clusters, and the solute is precipitated as fine particles and sprayed onto the substrate T. The
The support 57 may incorporate a heater and heat the substrate T. By heating the substrate T, the adhesion of the sprayed solute to the substrate T is improved, and densification of the solute is promoted on the substrate T.

  Valves V are provided at various locations on the path of carbon dioxide gas and supercritical fluid, and the valves V are opened and closed at a predetermined timing. Moreover, a pressure gauge and a thermometer (not shown) are provided in the solute dissolution cell, and the pressure and temperature in the solute dissolution cell are managed.

The inner diameter of the spray port of the nozzle 56 can be set as appropriate, but is usually in the range of 1 to 100 μm.
The distance De from the spray port of the nozzle 56 to the film formation surface of the substrate T can be appropriately set according to the delivery amount from the nozzle 56, the delivery speed, and the like. In general, the larger the distance De, the larger the particle size of the solute fine particles and the smaller the film formation area. Although distance De is not specifically limited, From such a tendency, Preferably it exists in the range of 0.1-10.0 cm, More preferably, it exists in the range of 1-5 cm.

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

<Preparation of organic EL element 11>
A substrate (NA45, manufactured by NH Techno Glass Co., Ltd.) having a film thickness of 100 nm of ITO (Indium Tin Oxide) as an anode was patterned on a 20 × 20 × 0.7 mm glass substrate. Then, it ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and further UV ozone cleaning was performed for 5 minutes.
Next, a solution was prepared by diluting Baytron P Al 4083 (poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT / PSS), Bayer) to 70% with pure water. A film of the prepared solution was formed on the cleaned substrate under the conditions of a rotation speed of 3000 rpm and a film formation time of 30 sec by spin coating. Thereafter, the substrate was dried at a surface temperature of 200 ° C. for 1 hour to provide a hole injection layer having a thickness of 30 nm.

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. The following hole transport layer solution was prepared, and film formation was performed in a glove box with a spin coater at a rotation speed of 1500 rpm and a film formation time of 30 sec. This substrate was dried by heating at a substrate surface temperature of 150 ° C. for 30 minutes to provide a hole transport layer. It was 20 nm when it formed into a film on the conditions with the board | substrate prepared separately, and the film thickness of the formed positive hole transport layer was measured.
(Hole transport layer solution)
Monochlorobenzene 100.0g
Poly- (N, N′-bis (4-butylphenyl) -N, N′-bis (phenyl) benzidine) (ADS254BE, manufactured by American Die Source) 0.5 g

Next, the following light emitting layer solutions a1 and b1 were prepared under a nitrogen atmosphere. The light-emitting layer solution a1 had a solid content concentration of 0.01% by mass and a viscosity of 0.6 mPa · s. The solid content concentration of the light emitting layer solution b1 was 1.00% by mass. The viscosity was measured at a temperature of 25 ° C. using a viscometer DV-II + Pro (manufactured by Brookfield) in accordance with JIS Z 8803.
(Luminescent layer solution a1)
Butyl acetate 100.000g
H-A 0.1000g
D-A 0.0110 g
D-B 0.0002g
D-C 0.0002g

(Light emitting layer solution b1)
Butyl acetate 10.00000g
Organic material HA 0.1A g
Organic material DA 0.0110g
Organic material D-B 0.0002g
Organic material DC 0.002g

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

Like the first film forming means A shown in FIG. 1, a film forming apparatus using the ESD method was prototyped and filled with the light emitting layer solution a1. Under the following ESD deposition conditions, a film was formed on a substrate on which a hole transport layer was formed under nitrogen gas to form a light emitting layer. Film formation was performed under the same conditions on a separately prepared substrate, and the thickness of the formed light emitting layer was measured to be 10 nm.
(ESD deposition conditions)
Inner diameter of capillary spray port: 40 μm
Liquid feeding speed to capillary: 10 μl / min
Distance from spray port to substrate Da: 5 cm
Voltage applied between capillary and substrate: 15 kV
Spraying time: 240 sec

Further, as a second film forming means B shown in FIG. 1, a film forming apparatus using a spray method was made as a prototype. A liquid feed pump using air pressure was used for the solution supply part of the prototype film forming apparatus. The film-forming apparatus was filled with the light-emitting layer solution b1, and a light-emitting layer was formed on the light-emitting layer formed by the ESD method under nitrogen gas according to the film forming conditions of the following spray method. Thereafter, the substrate was dried at a surface temperature of 120 ° C. Film formation was performed under the same conditions on a separately prepared substrate, and the thickness of the formed light emitting layer was measured to be 50 nm.
(Spray deposition conditions)
Spray flow rate from nozzle: 1.50 g / min
Air pressure during liquid feeding: 0.1 MPa
Nozzle movement speed: 0.5 m / sec
Distance Db from nozzle nozzle to substrate Db: 5cm

Next, the following electron transport layer solution was prepared under a nitrogen atmosphere.
(Electron transport layer solution)
2,2,3,3-tetrafluoro-1-propanol 100.00 g
0.75g of organic material ET-A
The organic material ET-A represents the following compound.

  The prepared electron transport layer solution was formed under the same spray method film formation conditions as those for the light emitting layer using a prototype film formation apparatus using a spray method. Thereafter, the substrate was heated and dried at a surface temperature of 120 ° C. for 30 minutes to form an electron transport layer. When a film was formed under the same conditions on a separately prepared substrate and the film thickness of the formed electron transport layer was measured, the film thickness was 40 nm.

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 / sec.

  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 11 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 the adhesion between the sealing can and the organic EL element, an ultraviolet curable adhesive was used, and both were adhered by irradiating with ultraviolet rays to produce a sealing element.

<Production of organic EL elements 12 to 16>
In the production of the organic EL element 11, the organic EL elements 12 to 16 were prepared in the same manner as the organic EL element 11 except that the film formation conditions of the ESD method and the spray method were changed as shown in Tables 1 and 2. Produced. Tables 1 and 2 below show the film thickness of the light emitting layer formed by the ESD method of the organic EL elements 12 to 16 and the film thickness of the light emitting layer formed by the spray method.

<Preparation of organic EL element 17>
In the production of the organic EL element 11, the light emitting layer solution a1 is changed to the light emitting layer solution a2 having the following composition, the light emitting layer solution b1 is changed to the light emitting layer solution b2 having the following composition, and the film formation conditions of the ESD method and the spray method are changed. The organic EL element 17 was produced in the same manner as the organic EL element 11 except that the changes were made as shown in Tables 1 and 2. The solid content concentration of the light emitting layer solution a2 was 0.01% by mass, the viscosity was 0.6 mPa · s, and the solid content concentration of the light emitting layer solution b2 was 1.00% by mass.

(Luminescent layer solution a2)
THF (tetrahydrofuran) 1000.0 g
MEH-PPV (methoxyethyl hexoxypolyphenylene vinylene) 0.1 g
(Luminescent layer solution b2)
THF (tetrahydrofuran) 10.0 g
MEH-PPV (methoxyethyl hexoxypolyphenylene vinylene) 0.1 g

<Preparation of organic EL element 18>
As a first film forming means E shown in FIG. 7, a film forming apparatus using a supercritical spray method was prototyped.
In the production of the organic EL element 11, the prototype film forming apparatus using the ESD method is replaced with the prototype film forming apparatus using the supercritical spray method. An organic EL element except that a light emitting layer is formed using the same organic materials HA, DA, DB, and DC as a1, and the film formation conditions of the spray method are changed as shown in Table 2. In the same manner as in Example 11, an organic EL element 18 was produced. The film thickness of the light emitting layer formed by the supercritical spray method of the organic EL element 18 was 10 nm.

(Supercritical spray deposition conditions)
Supercritical fluid gas: Carbon dioxide Inner diameter of nozzle: 50 μm
Supercritical fluid feed rate: 10 μl / min
Supercritical fluid spraying time: 100 sec
Distance Deter from nozzle nozzle to substrate De: 3cm

In the prototype film forming apparatus using the supercritical spray method, four solute dissolution cells 551 to 554 were prepared. In each of the solute dissolution cells 551 to 554, as shown below, the same organic materials HA, DA, DB, and DC as the luminescent layer solution a1 were put as solutes.
Solute dissolution cell 551: HA
Solute dissolution cell 552: DA
Solute dissolution cell 553: DB
Solute dissolution cell 554: DC
The weight concentration of each organic material was adjusted to the following ratio.
H-A: D-A = 1.000: 0.110
H-A: D-B = 1.000: 0.002
H-A: D-C = 1.000: 0.002

<Preparation of organic EL element 19>
In the production of the organic EL element 11, the film formation conditions of the ESD method are changed as shown in Table 1, and instead of a prototype film formation apparatus using a spray method, a commercially available spin coater is used, and a spin coat method is used. Thus, an organic EL element 19 was produced in the same manner as the organic EL element 11 except that the light emitting layer solution b1 was formed.
The film forming conditions of the spin coating method are as follows.
(Spin coating method)
Spin coater: MS-A200 (Mikasa Co., Ltd.)
Rotation speed: 2000rpm
Solution application time: 30 sec

<Preparation of organic EL element 20>
In the production of the organic EL element 11, the organic EL element 20 was produced in the same manner as the organic EL element 11 except that the film formation conditions of the ESD method and the spray method were changed as shown in Tables 1 and 2. . The film thickness of the light emitting layer formed by the ESD method of the organic EL element 20 was 2 nm, and the film thickness of the light emitting layer formed by the spray method was 58 nm.

<Preparation of organic EL element 21>
As a first film forming means C shown in FIG. 6, a film forming apparatus using the ESDUS method was prototyped.
In the production of the organic EL element 11, the prototype film forming apparatus using the ESD method is replaced with the prototype film forming apparatus using the ESDUS method, and the light emitting layer solution a1 is applied under the following film forming conditions of the ESDUS method. Then, an organic EL element 21 was produced in the same manner as the organic EL element 11 except that the film formation conditions of the spray method were changed as shown in Table 2 below.
(Deposition conditions for ESDUS method)
Aerosol heating temperature: 85 ° C
Distance from chamber opening to substrate: 10 mm
Carrier gas: Nitrogen gas

<Preparation of organic EL element 31>
In the production of the organic EL element 11, the light emitting layer is not formed by the prototype film forming apparatus using the ESD method, but only by the film formation of the light emitting layer solution b1 by the prototype film forming apparatus using the spray method. An organic EL element 31 was produced in the same manner as the organic EL element 11 except that the light emitting layer was formed. The film thickness of the light emitting layer of the organic EL element 31 was 60 nm.

<Production of Organic EL Element 32>
In the production of the organic EL element 11, the light emitting layer is not formed by the prototype film forming apparatus using the spray method, and light is emitted only by the film formation of the light emitting layer solution a1 by the prototype film forming apparatus using the ESD method. An organic EL element 32 was produced in the same manner as the organic EL element 11 except that the layer was formed. The thickness of the light emitting layer of the organic EL element 32 was 60 nm.

<Preparation of organic EL element 33>
In the production of the organic EL element 31, the light emitting layer solution b1 was replaced with the light emitting layer solution b2 in the same manner as the organic EL element 21 except that the light emitting layer was formed by a prototype film forming apparatus using a spray method. An organic EL element 33 was produced. The light emitting layer of the organic EL element 33 had a film thickness of 60 nm.

<Evaluation>
The following items were evaluated for the produced organic EL elements 11 to 21 and 31 to 33.
Productivity In the production of the organic EL elements 11 to 21 and 31 to 33, the time required for forming the entire light emitting layer (not including the drying step) was measured, and rank evaluation was performed as follows. For example, in the case of the organic EL element 11, the total time of the time required for forming the light emitting layer using the ESD method and the time required for forming the light emitting layer using the spray method is an object of rank evaluation. It is.
○: Deposition time <4 min
Δ: 4 min ≦ film formation time <10 min
X: 10 min ≦ deposition time Δ, ○ is an acceptable rank.

-Luminous lifetime A current was applied to each of the organic EL elements 11 to 21 and 31 to 33 so that the front luminance was 1000 cd / m ^2, and the organic EL elements were continuously driven. The time required for the front luminance to reach 500 cd / m ^{2 which} was half the initial luminance was measured as the half-life. The measured value of the half-life of the organic EL element 11 was set to 100, and the light emission lifetimes of the organic EL elements 11 to 21 and 31 to 33 were obtained by the following formula.
Luminescence life of each organic EL element = (half life of each organic EL element) / (half life of organic EL element 11)

The obtained light emission lifetime was ranked as follows.
○: 0.9 <light emission life Δ: 0.5 <light emission life ≦ 0.9
×: Luminescence life ≦ 0.5
The rank of △ and ○ is set as the pass rank.

Interlayer mixing Using a scanning X-ray photoelectron spectrometer PHI 5000 (manufactured by ULVAC-PHI), the interlayer mixing amount was measured by the following method.
(1) On the glass substrate, only the light emitting layer is formed to a thickness of 40 nm in the same manner as the light emitting layers of the organic EL elements 11 to 21 and 31 to 33.
(2) After film formation, sputtering is performed using a scanning X-ray photoelectron spectrometer PHI 5000 until the glass component of the substrate is detected by Ar gas cluster ions. The film thickness can be estimated from the sputtering time t at that time.
(3) A light emitting layer is formed on the substrate formed up to the hole transport layer under the same conditions as in (1) above.
(4) Sputtering is performed in the same manner as (2) above, but at this time, the hole transport layer is sputtered for a sputtering time t or longer.
(5) In the hole transport layer, if there is a specific material that is not contained in the organic material of the hole transport layer but is contained in the organic material of the light-emitting layer, the amount represents the interlayer mixing amount. For example, in the case of the organic EL element 11, Ir (iridium) is mentioned as a material specific only to the organic material of the light emitting layer. The Ir amount peculiar to the light emitting layer in the hole transport layer is measured, and the measured value is obtained as the interlayer mixing amount. Further, sputtering is performed until Ir specific to the light emitting layer is not measured, and the thickness of the interlayer mixture is estimated from the sputtering time t at that time.

Focusing on the film thickness in which interlayer mixing occurred between the light emitting layer and the hole transport layer, rank evaluation was performed as follows.
○: Film thickness <2 nm
Δ: 2 nm ≦ film thickness <5 nm
X: Rank of 5 nm ≦ film thickness Δ and ◯ is an allowable range.

Table 2 below shows the evaluation results.
In addition, about the organic EL element 32, since it is assumed that interlayer mixing hardly arises, evaluation of interlayer mixing was abbreviate | omitted.

As can be seen from Tables 1 and 2, the organic EL elements 11 to 21 according to the examples have high productivity, and excellent light emission lifetime is obtained by suppressing interlayer mixing.
On the other hand, in the organic EL elements 31 and 33 in which the light emitting layer is formed only by the wet process, interlayer mixing occurs at 5 nm or more, and a sufficient light emission life cannot be obtained. Moreover, although the organic EL element 32 in which the light emitting layer is formed only by the ESD method can obtain a good light emission lifetime, it takes a considerable time to form a film and the productivity is lowered.

  The present invention can be used for thin film formation technology and can be applied to the formation of organic layers in the manufacture of organic EL elements, solar cells, transistors, memories, sensors, for example.

T Substrate A First film forming means 12a, 12b Voltage application section 13 Solution supply section 14 Capillary 15 Electrode 16 Support B Second film formation means 22 Solution supply section 23 Nozzle 25 Support body C First film formation means (other implementations) Form)
41 Gas supply part 42 Solution supply part 43 Aerosol formation part E 1st film-forming means (other embodiment)
51 Gas Supply Unit 53 Pressurizing Pump 54 Preheater 55 Solute Melting Cell 56 Nozzle

Claims (8)

In a thin film forming method of forming an organic layer on a substrate by applying or spraying a solution in which an organic material is dissolved or dispersed in a solvent by a wet process,
The thin film formation method which forms the organic layer which consists of the same organic material as the said organic layer in the upper layer or lower layer of the said organic layer with a trace solvent coating method.   2. The method of forming a thin film according to claim 1, wherein in forming the organic layer by the trace solvent coating method, a voltage is applied to the solution of the organic material, and the charged solution is sprayed on the substrate to form the organic layer.   The thin film formation method according to claim 1, wherein in forming the organic layer by the trace solvent coating method, an aerosol of a solution of an organic material is formed, and the aerosol is heated and sprayed on a substrate to form the organic layer.   2. The organic layer is formed by forming an organic layer in a supercritical fluid obtained by pressurizing and heating a gas and spraying the organic material on a substrate in the formation of the organic layer by the trace solvent coating method. Thin film forming method.   5. The thin film forming method according to claim 1, wherein in forming the organic layer by the wet process, a solution of an organic material is sprayed by a spray method to form the organic layer on the substrate.   The thin film forming method according to claim 1, wherein a film thickness of the organic layer formed by the trace solvent coating method is in a range of 1 to 10 nm. The organic layer formed by the trace solvent coating method and the wet process is a light emitting layer of an organic EL element,
The thin film forming method according to claim 1, wherein the upper layer or the lower layer of the light emitting layer is a hole transport layer or an electron transport layer. A second film forming means for applying or spraying a solution in which an organic material is dissolved or dispersed in a solvent by a wet process to form an organic layer on the substrate;
A first film forming means for forming an organic layer made of the same organic material as the organic layer on an upper layer or a lower layer of the organic layer formed by the second film forming means by a trace solvent coating method;
A thin film forming apparatus comprising:

Images