JP2007090251A - Method and apparatus for forming thin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating method and a coating apparatus capable of easily uniformly forming a pattern at a desired film thickness in a necessary position on a substrate for a device having a first electrode layer formed thereon. <P>SOLUTION: The coating apparatus is provided for coating a substrate for a device of which a first electrode layer has a pattern preformed in a predetermined circuit form thereon, and the coating apparatus comprises an ultrasonic spray nozzle in its upper portion, a pattern mask covering a surface of the substrate for a device, and an electrical field-type mechanism mounted on the substrate for a device or a side mounting the substrate for a device. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for forming a functional thin film for forming an element such as an organic electroluminescent element, and a thin film forming apparatus used therefor.

A general method for forming a functional thin film such as a hole transport layer on an organic electroluminescent element is for an organic electroluminescent element in which an ITO thin film as a first electrode layer is patterned in a predetermined circuit shape in advance. This is a method of obtaining a patterned functional thin film by applying an organic material for a hole injection layer to a substrate using a spin coater, slit coater, etc., drying, and then irradiating a laser to remove unnecessary portions. .

Thus, in the method of removing the organic thin film by irradiating the laser, the hole injection layer existing on the ITO thin film formed as the anode circuit is also removed, so that the ITO thin film is damaged or coated. There was a risk of dust adhering to the hole transport layer thin film.
When the ITO thin film was scratched or dust adhered, there was no cleaning process and no repair process, resulting in defects. Moreover, when forming the coating film of one hole transport layer, there exist an application | coating process and a removal process, there are many production processes, and it has influenced production efficiency.

In order to solve such problems, a printing method such as a screen printing method, an inkjet method, and a spray printing method through a coating pattern mask have been proposed (see Patent Documents 1 to 3).
All of the above proposals are improvements mainly aimed at reducing the amount of hole transport material used.
For example, when the hole transport layer is formed by the screen printing method, the screen plate network is transferred, the film thickness becomes nonuniform, and the light emission becomes nonuniform.
In addition, the ink jet method has no problem with the pattern accuracy of the hole transport layer, but the problem due to the clogging with the discharge liquid discharged from the nozzle must be solved.

Furthermore, the spray method using the coating pattern mask described in Patent Documents 1 to 3 is a coating method using a low flow rate two-fluid nozzle or the like, and the coating liquid is urged by compressed air or nitrogen at the tip of the nozzle. Because it atomizes well, it is not possible to form a thin film that maintains a uniform film thickness due to slight changes in the airflow caused by the movement of the spray nozzle and clogging of the solid part of the coating liquid to the nozzle tip. There was a problem such as defective light emission.
JP 2001-232251 A JP 2001-237070 A JP 2003-347049 A

  It is an object of the present invention to provide a thin film forming method and a thin film forming apparatus capable of forming a pattern uniformly and easily in a desired film thickness at a required location on an element substrate on which a first electrode layer is formed. To do.

In the present invention, the first electrode layer is applied to the element substrate having a pattern formed in advance in a predetermined circuit shape by atomizing the coating liquid with an ultrasonic spray nozzle through a pattern mask covering the surface, It is a thin film formation method characterized by forming a functional thin film.
Further, the present invention is an apparatus for forming a thin film on an element substrate in which a pattern of the first electrode layer is previously formed in a predetermined circuit shape, and an ultrasonic spray nozzle is provided on an upper portion of the element substrate. A thin film forming apparatus comprising a pattern mask covering a surface and provided with an electric field forming mechanism on the element substrate or on the element substrate installation side.

As described above, by using the ultrasonic spray nozzle, it is possible to form a thin film with a desired film thickness uniformly and with high production efficiency.
Also, by installing an ultrasonic spray nozzle equipped with an ultrasonic receiving terminal, a coating liquid injection port, and a compressed gas injection port, dry compressed air and inert gas can be injected from the compressed gas injection port, Dry compressed air can be selected for a coating solution that is not easily altered, and an inert gas can be selected for a coating solution that is easily altered.

  The present invention provides a thin film in which at least one functional layer of a device substrate having a first electrode layer formed on a substrate is applied and formed by atomizing a coating liquid with a spray nozzle. A thin film forming apparatus equipped with an ultrasonic nozzle having an ultrasonic receiving terminal, a coating liquid injection port, and a compressed gas injection port.

As described above, by installing the ultrasonic spray nozzle including the ultrasonic receiving terminal, the coating liquid injection port, and the compressed gas injection port, a thin film can be formed uniformly with a desired film thickness and with high production efficiency. It becomes like this.
Examples of the gas injected from the compressed gas inlet include dry compressed air and inert gas, and dry compressed air can be selected for a coating solution that is difficult to change, and an inert gas can be selected for a coating solution that is easily changed. it can.
Moreover, what is necessary is just to set a gas flow rate so that the atomized coating liquid may fall on the board | substrate which wants to apply | coat uniformly.

  The ultrasonic spray nozzle used for this invention should just be able to atomize a coating liquid uniformly in the front-end | tip part of a spray nozzle, and is not influenced by the shape etc. of a nozzle.

  And it is the thin film formation apparatus which connected the ultrasonic transmitter which can transmit an ultrasonic wave of 15-130 KHz to the said ultrasonic spray nozzle main body.

By connecting the ultrasonic transmitter to the ultrasonic spray nozzle, the ultrasonic transmitter can transmit an ultrasonic wavelength signal to the ultrasonic spray nozzle and vibrate it to atomize the coating liquid.
In order to atomize the coating liquid well at the tip of the ultrasonic spray nozzle, the wavelength of a good ultrasonic wave is in the range of 15 to 130 KHz, and the relationship between the liquid properties such as the viscosity and molecular weight of the coating liquid and the ultrasonic spray nozzle. It is desirable to adjust to match the wavelength.
However, in the case of a wavelength not included in the wavelength region of 15 to 130 KHz, good atomization may not be formed. The ultrasonic transmitter may be either a fixed frequency type or a frequency variable type, and a manufacturer recommended ultrasonic transmitter optimized for the characteristics of the ultrasonic spray nozzle may be used.

In the thin film forming method of the present invention, the coating liquid is fogged by an ultrasonic spray nozzle through a pattern mask covering the surface of the element substrate having the first electrode layer formed on the substrate, on the first electrode layer. This is a method for forming a thin film to be applied.
Here, by providing a liquid feed pump capable of adjusting a precise flow rate (hereinafter referred to as a precision flow rate liquid feed pump), the coating liquid can be stably supplied.

This precision flow rate pump is a pump that sends a coating solution to an ultrasonic spray nozzle connected to an ultrasonic transmitter. It delivers a constant amount of coating solution at a constant speed and is stable at the tip of the ultrasonic spray nozzle. Thus, the coating liquid can be stably atomized.
The type of pump that can be used here is to send a certain amount of chemical at a constant speed. Reciprocating pumps such as pistons, plungers, diaphragm pumps, rotary pumps such as gears, dividers, screws, rope pumps, etc. And centrifugal pumps such as turbines and volute pumps, and syringe pumps.
In addition, a syringe pump can be used when a small amount of coating liquid is to be sent in a constant amount without pulsating flow, and two or more plunger pumps that are operated to reduce the pulsating flow when a certain amount of liquid is to be sent in a constant amount. Use a system that combines.

  The structure capable of forming an electric field on the element substrate side means means for increasing the difference in electric field between the electrode part and the insulating part, for example, a structure for controlling the electric field by static electricity or an already formed substrate. Examples include a structure in which an electric current is supplied to the electrode to control the electric field.

  In addition, the thin film forming apparatus of the present invention further includes a trap mechanism that can collect chemicals and solvents scattered below the element substrate, and a duct and a tank that can collect unnecessary coating and cleaning liquids. Yes.

The duct with a trap mechanism that can collect the solvent scattered below the element substrate is a cooling function that takes into account the case where the organic solvent of the coating liquid to be sprayed is volatilized from the spray nozzle. A duct having a structure having a function of liquefying and recovering a volatile solvent or the like by using a trap tube equipped with a scrubber or adsorbing and removing the volatile solvent using a scrubber.

  In addition, the tank that can collect the unnecessary coating liquid and cleaning liquid is a tank that has a function to collect the coating liquid sprayed on the substrate other than the element substrate and the cleaning liquid inside the device housing and the spray body. is there.

The thin film forming apparatus of the present invention further includes a substrate holder that can hold the element substrate without distortion, thereby enabling stable thin film formation.
The substrate holder is made of a rigid material such as a metal plate that matches the size of the element substrate.

  Then, when applying the coating liquid by atomizing with an ultrasonic spray nozzle, pattern formation can be easily performed by providing a mask holding part for holding a pattern mask covering the surface of the element substrate on the element substrate holder. It becomes.

  By holding the pattern mask with this mask holding portion, it becomes possible to accurately fix a mask for forming a desired pattern on the element substrate between the ultrasonic spray nozzle and the element substrate. The element substrate can be sequentially applied by retracting the element substrate at the time of mounting and also having an element for removing or cleaning the coating liquid applied on the mask.

  The ultrasonic spray nozzle is attached to an XY robot installed on the upper part of the element substrate, and can move in accordance with the movement of the XY robot.

  By attaching the ultrasonic spray nozzle to the XY robot in this way, it is possible to move the XY robot in front, back, left and right along the movement of the XY robot, stabilizing the atomized coating liquid. Therefore, spraying can be performed so that a desired thickness can be formed.

  Here, one ultrasonic spray nozzle to be mounted on the XY robot may be mounted, or several units may be arranged and mounted in a row.

A mechanism in which several ultrasonic spray nozzles are arranged and mounted on the XY robot in a row and applied to the element substrate is suitable as an apparatus corresponding to an increase in the area of the substrate.
Also, unlike the case where one ultrasonic spray nozzle is installed, several ultrasonic spray nozzles are mounted on the robot arm at equal intervals, and the robot arm moves back and forth to stabilize the atomized coating liquid. Therefore, spraying can be performed so that a desired thickness can be formed.

  Applying at least one of the functional layers to a device substrate having a pattern formed in advance in a predetermined circuit pattern on the substrate by using an apparatus for atomizing a chemical solution with an ultrasonic nozzle. It is suitable for forming a hole injection layer as a functional layer to be formed.

  This thin film forming apparatus is not limited to the production of organic EL elements, but can be used in the production of thin films for elements and apparatuses other than organic EL elements.

  The thin film forming apparatus is not limited to the thin film formation of the element substrate. For example, the thin film forming apparatus can be applied to a metal substrate such as glass or aluminum, or a plastic substrate such as acrylic, polyester polyethylene, or polystyrene. Can do.

  Furthermore, the thin film forming apparatus may have a structure that can be connected to an exhaust unit, a drying hot plate required as part of the coating film forming process, or another unit such as an oven or an ultraviolet washer. Further, a transfer robot may be attached.

  Hereinafter, an embodiment will be described with reference to the drawings. In addition, this invention is not limited by this embodiment.

An embodiment of the present invention will be described with reference to FIG. FIG. 1 is an explanatory view schematically showing the configuration of a thin film forming apparatus.

  As shown in FIG. 1, the configuration of the thin film forming apparatus 1 according to the present invention includes an ultrasonic spray nozzle 2 attached to a robot arm 6, a holder 7 that can hold a pattern mask and an element substrate 8, and an exhaust duct 4. Thus, a desired pattern coating can be performed on the element substrate 8 via a pattern mask.

  The ultrasonic spray nozzle 2 includes an ultrasonic receiving terminal, a coating liquid injection port, and a compressed gas injection port, which are connected to the ultrasonic transmitter 3, the precision flow rate liquid feeding pump 9, and the compressed gas regulator, respectively. By properly controlling the flow rate of the coating solution and the gas flow rate, a desired coating solution can be sprayed.

  The precision flow rate liquid feeding pump 9 is connected to the coating liquid tank 5 so that the coating liquid is continuously supplied and continuous coating is possible.

  The exhaust duct is equipped with a trap mechanism that collects the mist of the coating liquid, and a tank that collects a cleaning liquid that is used for cleaning the deposits such as the atomized coating liquid.

  There are various techniques for holding the pattern mask and the element substrate 8, and the holding method is not limited as long as the substrate is fixed and the substrate can be held so as not to be distorted.

  The number of ultrasonic spray nozzles may be appropriately selected depending on the substrate size, coating tact, coating accuracy, and the like, and the driving of the robot arm can be appropriately selected depending on the number of spray nozzles.

  The ultrasonic spray nozzle of the thin film forming apparatus shown in FIG. 1 has, for example, a coating liquid inlet 10 and a compressed gas inlet 12 at the base end of the nozzle body, as shown in FIG. And the coating liquid coating outlet 20 and the compressed gas coating outlet 22 are comprised in the front-end | tip part.

  An example using the above embodiment will be described below.

A hole transport material solution having a solid content adjusted to 0.4% by weight was placed in the coating liquid tank 5, and piped from the coating liquid tank to the ultrasonic spray nozzle 2 via a precision flow rate liquid feeding pump 9.
At that time, the flow rate of the precision flow rate pump was set to 5.0 mL / min.
Moreover, it piped from the piping of dry compressed air to the ultrasonic spray nozzle through the regulator.
At that time, the pressure of the regulator was set to 0.01 MPa. The operating speed of the robot arm 6 to which the ultrasonic spray nozzle is attached was set to 200 mL / min, the ultrasonic spray pitch was set to 30 mm, and the ultrasonic spray nozzle distance from the substrate was set to 40 mm.

  On the holder 7 capable of holding the element substrate, the element forming substrate on which the 200 mm × 200 mm pattern mask, the 200 mm × 200 mm ITO electrode and the insulating film pattern were formed was fixed in this order. The distance between the pattern mask and the element substrate was 0.2 mm.

The ultrasonic transmitter 3 was operated, and then the precision flow rate pump was operated to start feeding the coating liquid.
When the atomization of the coating liquid from the ultrasonic spray nozzle was stabilized, the robot arm was operated to draw a trajectory as shown in FIG. 2 to coat the hole transport material.
Then, after the entire surface of the pattern mask and the device substrate was coated, only the device substrate was placed in an oven and dried at 120 ° C. for 10 minutes. A desired pattern of a hole transport material layer having a film thickness of 400 ± 20 angstroms was obtained on the device substrate.

<Comparative Example 1>
A hole transport material solution having a solid content adjusted to 0.4% was placed in a coating liquid tank, and piped from the coating liquid tank to a two-fluid spray nozzle via a precision flow rate liquid feeding pump. At that time, the flow rate of the precision flow rate pump was set to 8.0 mL / min.
Moreover, it piped from the piping of dry compressed air to the 2 fluid spray nozzle through the regulator.
At that time, the pressure of the regulator was set to 2.00 MPa. The operating speed of the robot arm to which the ultrasonic spray nozzle was attached was set to 200 mL / min, the 2-fluid spray pitch was set to 25 mm, and the 2-fluid spray nozzle distance from the substrate was set to 40 mm.

  On the holder 7 capable of holding the element substrate, the substrate was fixed in the order of the substrate on which the pattern mask for 200 mm × 200 mm, the ITO electrode of 200 mm × 200 mm and the insulating film pattern were formed. The distance between the pattern mask and the substrate was 0.2 mm.

The precision flow rate pump was turned on to start feeding the coating solution. When the atomization of the coating solution was stabilized, the robot arm was operated so as to draw a trajectory as shown in FIG. 2 to coat the hole transport material.
After the entire surface of the pattern mask and the substrate was coated, only the substrate was placed in an oven and dried at 120 ° C. for 10 minutes. A hole transport material layer having a film thickness of 400 ± 70 Å was obtained in a desired pattern.

<Comparative example 2>
A hole transport material was coated on a substrate on which an ITO electrode of 200 mm × 200 mm and an insulating film pattern were formed by a spin coater. The spin-coated substrate was placed in an oven and dried at 120 ° C. for 5 minutes. A hole transport material layer having a film thickness of 400 ± 15 Å was obtained. The unnecessary portion of the formed hole transport material layer was irradiated with a laser and removed to obtain a desired pattern.

An organic EL layer was formed on the substrates prepared in Examples, Comparative Example 1 and Comparative Example 2, and a cathode was formed and sealed to form an organic EL element.

The formed organic EL element was evaluated for lighting. The evaluation results are shown in Table 1.

  As is clear from Table 1, according to the lighting evaluation of the organic EL element, the organic EL element in which the hole transport layer was formed using the thin film forming apparatus according to the present invention was lit without any problem of unevenness or short circuit. In addition, when the thin film forming apparatus according to the present invention is used, the number of current processes can be reduced.

Explanatory drawing which shows an example of the thin film forming apparatus of this invention. Explanatory drawing which shows the movement state of an ultrasonic spray nozzle. Cross-sectional explanatory drawing which shows an example of an ultrasonic spray nozzle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Thin film formation apparatus 2 ... Ultrasonic spray nozzle 3 ... Ultrasonic transmitter 4 ... Exhaust duct 5 ... Coating liquid pump 6 ... Robot arm 7 ... Holder 8 ...・ Element substrate 9: Precision flow rate pump

Claims (8)

A functional thin film is formed by spraying a coating solution with an ultrasonic spray nozzle and applying it to a device substrate on which a first electrode layer has been previously patterned in a predetermined circuit shape through a pattern mask that covers the surface. A method for forming a thin film, comprising: 2. The thin film forming method according to claim 1, wherein an electric field is formed on the element substrate side. The first electrode layer is an apparatus for applying to a device substrate in which a pattern is formed in a predetermined circuit shape in advance, and includes an ultrasonic spray nozzle on the upper portion, a pattern mask that covers the surface of the device substrate, An electric field forming mechanism is provided on the element substrate or on the element substrate installation side. The thin film forming apparatus according to claim 3, wherein an ultrasonic transmitter is connected to the nozzle body of the spray nozzle. 5. The thin film forming apparatus according to claim 3, wherein the spray nozzle includes an ultrasonic receiving terminal, a coating liquid injection port, and a compressed gas injection port. 6. The thin film forming apparatus according to claim 3, further comprising a trap mechanism capable of collecting a coating solution and a solvent scattered below the element substrate.   The thin film forming apparatus according to claim 3, wherein the ultrasonic spray nozzle is mounted on an XY robot.   The thin film forming apparatus according to claim 7, wherein a plurality of ultrasonic spray nozzles are mounted in a line on an XY robot.

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