KR102749883B1 - Profile evaluation method of ink composition and manufacturing method of organic light emitting device comprising same - Google Patents

Abstract

The present invention relates to an ink composition profile evaluation method including a first step of discharging an ink composition including one or more solvents onto a substrate; a second step of spraying a first solvent having the lowest evaporation rate or the highest evaporation temperature among the solvents onto the substrate or its surroundings; a third step of forming vapor of the first solvent through drying and forming an ink film; and a fourth step of observing a profile of the formed ink film, and a method for manufacturing an organic light-emitting device including the ink composition profile evaluation method.

Description

PROFILE EVALUATION METHOD OF INK COMPOSITION AND MANUFACTURING METHOD OF ORGANIC LIGHT EMITTING DEVICE COMPRISING SAME

The present invention relates to a method for evaluating the profile of an ink composition and a method for manufacturing an organic light-emitting device comprising the same.

In the past, the deposition process was mainly used to manufacture organic light-emitting devices. However, there is a problem that a lot of material loss occurs when manufacturing organic light-emitting devices using the deposition process. To solve this problem, a technology for manufacturing devices through a solution process that can increase production efficiency by reducing material loss is being developed, and the development of materials that can be used in the solution process is required.

Materials used in organic light-emitting devices for solution processes must have the following properties:

First, it must be possible to form a storable homogeneous solution. In the case of commercialized deposition process materials, they have good crystallinity and do not dissolve well in the solution, or even if a solution is formed, crystals are easily caught, so the concentration gradient of the solution changes depending on the storage period, or there is a high possibility of forming a defective element.

Second, the material used in the solution process must have excellent coating properties so that a film of uniform thickness can be formed without voids or clumping when forming the film, and excellent current efficiency and excellent life characteristics are required when manufacturing organic light-emitting devices.

Japanese Patent Publication No. 1998-073709

Recently, organic light-emitting devices using solution processes instead of conventional deposition processes are being developed to reduce process costs. Among the solution processes, the inkjet printing process is being studied the most, as it can minimize material consumption and has the advantage of being able to create precise patterns in a non-contact manner because it discharges fine drops.

In order to form an ink film using an inkjet process, ink is ejected onto a hydrophobic bank substrate and vacuum dried. After vacuum drying, it is important to make the profile of the ink film flat, but this profile is greatly affected by the surrounding environment. In other words, if an experiment is conducted on a small scale in a lab, the problem of a difference occurs between the profile of a mass-produced unit and the profile of a mass-produced unit. To solve this problem, an evaluation method that can simulate the ink profile that has gone through the drying process of a mass-produced scale is required.

Therefore, the present invention aims to provide a profile evaluation method capable of simulating a pilot scale even at a lab scale.

One embodiment of the present invention

A first step of discharging an ink composition including one or more solvents onto a substrate;

A second step of spraying the first solvent having the lowest evaporation rate or the highest evaporation temperature among the above solvents onto the substrate or its surroundings;

A third step of forming vapor of the first solvent through drying; and

Step 4: observing the profile of the ink film formed after drying;

A method for evaluating an ink composition profile including:

Another embodiment of the present specification provides an ink composition profile evaluation method, wherein the third step further includes a heat treatment step.

Another embodiment of the present specification provides a method for manufacturing an organic light-emitting device, comprising the ink composition profile evaluation method.

When controlling the ink film profile of the edge by dummy jetting ink around the pixel emission area of the substrate as in the conventional method for simulating the ink profile of mass production size, a problem occurs in which the profile of mass production conditions cannot be sufficiently reproduced when the amount of solvent is insufficient.

In this specification, the profile of mass production conditions can be reproduced by using a method of spraying a solvent having the lowest evaporation rate or the highest evaporation temperature among the ink solvents onto a substrate or its surroundings.

Figure 1 illustrates a profile that may appear in an ink film.
Figure 2 illustrates a step of spraying a first solvent around a substrate.
Figure 3 illustrates the vacuum drying profiles of decahydronaphtalene, 1-MON (1-methoxynaphthalene), ethyl 4-ethoxybenzoate, and EMB (ethy 4-methoxybenzoate).
Figure 4 shows a pressure-time graph of vacuum conditions depending on the presence or absence of DEP (diethyl phthalate) vapor.
Figure 5 illustrates a cross-section of the formed ink film.
Figure 6 illustrates an ink film profile measured using an optical profiler.
Figure 7 is a graph showing the X-axis and Y-axis cross-sections of an ink film profile measured using an optical profiler.

In order to manufacture an organic light-emitting element using an inkjet process, a hydrophobic bank substrate is required. The bank substrate prevents ink from falling on areas other than the pixel area. An organic light-emitting element manufactured using an inkjet process ejects ink droplets onto a substrate divided into banks, and goes through a drying process in which the solvent is evaporated under high vacuum conditions. Afterwards, the residual solvent is removed and the ink film is stabilized through heat treatment. In order to uniformly light-emits within the pixel, it is important to form a flat ink film, as shown in Fig. 1. In order to form a flat ink film, the solvent included in the ink composition must be selected appropriately. Mainly, ink having a mixed solvent composition is manufactured rather than a single solvent composition, and the ink film profile is controlled. Therefore, it is important to manufacture an optimal ink through profile evaluation.

Ink profile evaluation includes a step of discharging ink onto a pixel portion of a substrate on which a bank is formed, a step of vacuum drying under high vacuum conditions, and a step of observing the profile of the ink film formed within the bank with an optical profiler after heat treatment. At this time, the size of the substrate used is a small size of a lab scale (e.g., 50x50, 40x40, 100x100 mm), but a problem has arisen in which the ink film profile does not match the pilot evaluation of an actual mass production size. It is thought that this occurs because the ink drying process is greatly affected by the surrounding environment, and the environments of the lab-scale evaluation and the mass production-scale evaluation are different from each other. Therefore, a lab-scale evaluation method that directly replicates the evaluation results of the mass production size is required.

The inventors of the present invention have focused on the fact that the biggest difference between mass production and lab evaluation is the difference in the size of the equipment or substrate used. Accordingly, the amount of ink discharged on the substrate is different, and the amount of vapor formed during drying is different, resulting in different drying film profiles. Therefore, in lab evaluation, a method of artificially forming vapor was applied to produce vapor at the mass production level, and evaluation was conducted.

The following describes this specification in more detail.

One embodiment of this specification is

A first step of discharging an ink composition including one or more solvents onto a substrate;

A second step of spraying the first solvent having the lowest evaporation rate or the highest evaporation temperature among the above solvents onto the substrate or its surroundings;

A third step of forming vapor of the first solvent through drying; and

Step 4: observing the profile of the ink film formed after drying;

A method for evaluating an ink composition profile including:

[Step 1]

The above first step is a step of discharging an ink composition including one or more solvents onto a substrate.

According to one embodiment of the present specification, the substrate is a bank substrate including a bank. Since the bank substrate is provided with hydrophobicity, it has the effect of preventing ink from falling on a portion other than a pixel portion.

According to one embodiment of the present specification, the ink composition includes one or more solvents and includes a functional material. At this time, a solvent having a high boiling point of 180° C. or higher can be used as the solvent. For example, a solvent capable of dissolving the functional material, such as a hydrocarbon solvent, an ester solvent, an ether solvent, a glycol ether solvent, or an alcohol solvent, can be used, and preferably, an ester solvent, a hydrocarbon solvent, or an aromatic ether can be used, but is not limited thereto.

As the functional material, a commonly used material for organic light-emitting devices can be used. For example, an amine compound or a carbazole compound can be used, but is not limited thereto.

According to one embodiment of the present specification, the ink composition may further include an additive including a surfactant or a polymer material. In this case, the surfactant or additive may be made of a material commonly used in the art.

According to one embodiment of the present specification, the amount of the solvent used may be determined according to the reaction conditions of the ink composition, etc. For example, the solvent may be included in an amount of 90 to 99.5 parts by weight based on 100 parts by weight of the total composition of the functional material and the solvent.

According to one embodiment of the present specification, the first step is carried out under room temperature and normal pressure conditions. At this time, the process of discharging the ink composition can be carried out using Uni jet equipment (UJ-300 model).

[Step 2]

The second step is a step of spraying the first solvent having the lowest evaporation rate or the highest evaporation temperature among the solvents of the first step onto the substrate or its surroundings.

In this specification, the lowest evaporation rate or the slowest evaporation temperature means having the characteristics of a high boiling point and low vapor pressure.

In the past, ink was jetted onto a dummy area around the pixel emission area of the substrate to control the ink film profile at the edge (dummy jetting). However, among the solvents contained in the ink, the one that has the greatest influence on the ink profile is the solvent component that evaporates last. The amount during dummy jetting was about 10 ^-7 ml to 10 ^-5 ml, which is not sufficient to reproduce the environment of an actual mass production scale, and thus the problem occurred that the profile of the mass production conditions could not be sufficiently reproduced with dummy jetting alone. In addition, when a mixed solvent of ink was used, the same problem occurred that the profile of the mass production conditions could not be sufficiently reproduced because the ratio of the solvent that evaporates last was not sufficient.

Therefore, in this specification, a method of spraying a first solvent having the lowest evaporation rate or the highest evaporation temperature among the solvents of the ink onto a substrate or its surroundings is used.

According to one embodiment of the present specification, the first solvent is a solvent having the lowest evaporation rate or the slowest evaporation temperature among the solvents in the first step, and has the characteristics of a high boiling point and low vapor pressure.

According to one embodiment of the present specification, the first solvent must be a solvent that has a low vapor pressure and thus evaporates slowly even under vacuum. If the solvent of the first step is a single solvent, the single solvent is added as is to the substrate or its surroundings, and if the solvent of the first step is a mixed solvent, one of the solvents that evaporates most slowly is added to the substrate or its surroundings.

According to one embodiment of the present specification, any solvent that can be used as the first solvent is an inkjet processable solvent and can dissolve an organic light-emitting device material well. Preferably, esters, hydrocarbons, alcohols, or ethers can be used, and more preferably, diethyl phthalate, dimethyl phthalate, ethyl 4-methoxy benzoate, ethyl 4-ethoxy benzoate, benzyl benzoate, ethyl biphenyl, 1-ethylnaphthalene, or triethylene glycol monobutyl ether can be used, but is not limited thereto.

According to one embodiment of the present specification, the amount of the first solvent added in the second step may vary depending on the capacity of the pump. The amount of vapor of the first solvent should be sufficiently large, but if too much is added, the solvent is not sufficiently dried, so it should be added according to the pump capacity. For example, the first solvent may be added in an amount of 0.05 ml to 5 ml, preferably 0.05 ml to 1 ml, more preferably 0.1 ml to 1 ml, and even more preferably 0.1 ml. At this time, the pumping speed for Air based on the turbo pump is 665 ℓ/s, and the chamber capacity is 7 ℓ.

According to one embodiment of the present specification, the first solvent of the second step can be added in an amount of 7.5 X 10 ^-6 % to 7.5 X 10 ^-4 % based on air of the pump capacity.

According to one embodiment of the present specification, the amount of the first solvent in the second step is an amount that continues to evaporate for more than 100 seconds in the drying step and is completely evaporated within 30 minutes. This can be confirmed by measuring the vacuum drying profile of the solvent itself. The measurement of the vacuum drying profile can use a pumping system equipped with a dry pump (DUO 10M) and a turbo pump (HiPace 700), and is performed at room temperature.

According to one embodiment of the present specification, a first solvent having high boiling point and low vapor pressure characteristics is selected and sprayed on a substrate or its surroundings. For example, as shown in Fig. 2, the substrate may be placed in the center of an empty petri dish, and the solvent may be sprayed only on the edges of the petri dish and then dried. However, the present invention is not limited thereto, and any method may be used, such as spraying the solvent directly on the substrate or around the substrate so that vapor can be formed around the substrate.

According to one embodiment of the present specification, in order to select the first solvent, the vacuum drying profile of the solvent itself is checked. For example, 0.1 to 0.2 ml of each solvent is placed in a container and placed in a vacuum device to obtain the vacuum drying profile of the solvent itself. Then, by checking the section where the solvent evaporates in the graph (the section where the slope is different from the bare state), the solvent that evaporates the slowest can be identified. For example, in the vacuum drying profiles of decahydronaphtalene, 1-MON (1-methoxynaphthalene), ethyl 4-ethoxybenzoate, and EMB (ethyl 4-methoxybenzoate) in FIG. 3, the section where the slope differs from the bare state is the evaporation section of each solvent, so among the solvents, ethyl 4-ethoxybenzoate, which has the section where the slope differs the latest, becomes the first solvent.

The measurement of the above vacuum drying profile can be performed using a pumping system equipped with a dry pump (DUO 10M) and a turbo pump (HiPace 700) at room temperature.

[Step 3]

The third step is a step of forming vapor of the first solvent through drying and forming an ink film.

In this specification, a first solvent among solvents used in ink is sprayed onto a substrate or its surroundings, so that a large amount of vapor of the first solvent is artificially formed when drying.

According to one embodiment of the present specification, in the third step, vapor of the first solvent is formed through drying, and the ink composition is dried under the formed vapor of the first solvent to form an ink film.

According to one embodiment of the present specification, the drying step is performed under a vacuum. At this time, the vacuum level may be performed while maintaining 10 ^-4 torr to 10 ^-6 torr or a commonly used range. Since the vacuum level of the drying step may vary when the amount of the sample increases, the boiling point is high, or the sample evaporates, it is not limited to the above range.

According to one embodiment of the present specification, the drying step is performed for 5 minutes to 1 hour, and preferably for 5 minutes to 30 minutes.

According to one embodiment of the present specification, the third step further includes a heat treatment step.

In one embodiment of the present specification, the temperature of the heat treatment step is 85° C. to 250° C., in one embodiment, it may be 100° C. to 250° C., and in another embodiment, it may be 150° C. to 220° C.

In one embodiment of the present specification, the heat treatment step may be performed for 5 minutes to 1 hour, preferably 20 minutes to 40 minutes.

FIG. 4 illustrates a pressure-time graph of vacuum conditions depending on the presence or absence of DEP (diethyl phthalate) vapor. As shown in FIG. 4, when a solvent having high boiling point and low vapor pressure characteristics is used as the first solvent to form vapor, the pressure value of the vacuum graph changes, and accordingly, the profile of the ink film also changes. In this case, since a sufficient amount of first solvent vapor is formed, simulation of mass production drying conditions becomes possible.

[Step 4]

The fourth step is the step of observing the profile of the ink film formed after drying.

According to one embodiment of the present specification, the step of observing the profile of the formed ink film can be performed using an optical profiler.

According to one embodiment of the present specification, the profile of the ink film formed after the first to third steps is consistent with the profile of the ink film formed in a mass production size.

According to one embodiment of the present specification, the ink film can be formed to a thickness of 30 nm to 200 nm, preferably 50 nm to 150 nm.

According to one embodiment of the present specification, the ink composition is for an organic light-emitting device.

According to one embodiment of the present specification, the ink composition profile evaluation method is a method of predicting an ink composition profile of a mass production size in a lab size.

According to one embodiment of the present specification, the ink composition profile evaluation method can be used in the manufacture of an organic light-emitting device.

One embodiment of the present specification provides a method for manufacturing an organic light-emitting device, comprising the ink composition profile evaluation method described above.

According to one embodiment of the present specification, the method for manufacturing the organic light-emitting device includes a method of selecting an ink composition for an organic light-emitting device by measuring the film flatness of a formed ink film.

In one embodiment of the present specification, the film flatness of the ink film can be measured to select an appropriate ink composition for an organic light-emitting element. The method for measuring the film flatness is as follows.

<Measurement of the flatness of the membrane>

After jetting the ink composition onto the ITO substrate on which the bank is formed, vacuum drying (10 ^-6 torr) is performed for 15 minutes. After heat treatment on a 220 ℃ hot plate for 30 minutes, the film is observed through an optical microscope to determine whether the film is well formed, and the film thickness is measured using an OP (Optical Profiler).

According to one embodiment of the present specification, an ink composition having a |H ₉₀ -H _C | / H _C value of less than 0.25 can be selected as an ink composition for an organic light-emitting device. When the |H ₉₀ -H _C | / H _C value is less than 0.25, it has excellent flatness and is therefore suitable as an ink for an organic light-emitting device.

In this specification, the Hc refers to the height of the center of the ink layer in FIG. 5 below, and the H ₉₀ refers to the height at a position 90% of the length from the center of the ink layer to the bank wall. That is, if the x-axis length of the pixel is 100 in total, Hc refers to the height at a position of 50, and H ₉₀ refers to the height at a position of 5 or 95.

Hereinafter, in order to specifically explain this specification, examples will be given and described in detail. However, the examples according to this specification may be modified in various different forms, and the scope of this specification is not construed as being limited to the examples described below. The examples of this specification are provided to more completely explain this specification to a person having average knowledge in the art.

Example 1

An ink composition was prepared by dissolving the following compound 1 and chemical formula A (weight ratio 9:1) in EMB (ethyl4-methoxybenzoate) at a concentration of 1 wt%. After stirring so that the compound 1 and chemical formula A were sufficiently dissolved, the ink composition was injected into UJ300 equipment (Uniget), and ink was discharged under 10 to 14 drop conditions on a substrate on which a hydrophobic bank was formed. Next, 0.1 ml of the first solvent was applied to the edge of the petri dish, and the substrate was placed at the center of the petri dish. The petri dish with the substrate placed thereon was placed in a vacuum equipment, and vacuum drying was performed for 20 minutes to form vapor of the first solvent, and the ink was vacuum-dried under the vapor of the first solvent. Thereafter, a heat treatment step was performed at 200° C. for 30 minutes to form an ink film with a thickness of 100 nm. Next, the ink film formed as described above was observed with an optical profiler to measure the ink film profile.

The compounds used in the examples are as follows.

[Chemical Formula A]

[Compound 1]

Examples 2 to 8 and Comparative Examples 1 to 13

The same method as Example 1 was used except that the compounds described in Table 1 below were used as the solvent of the ink composition and the first solvent in the example.

Functional materials menstruum First solvent
(vapor) Profile Match Example 1 Compound 1+Chemical Formula A EMB(ethyl4-methoxybenzoate) EMB agreement Example 2 Compound 1+Chemical Formula A DBO(dibutyl oxalate)+EMB EMB agreement Example 3 Compound 1+Chemical Formula A DBO+EMB+DEP(diethylphtalate) DEP agreement Example 4 Compound 1+Chemical Formula A 1-MON(1-methoxynaphthalene) 1-MON agreement Example 5 Compound 1+Chemical Formula A DPGDME(dipropylene glycol dimethyl ehter) + 1-MON 1-MON agreement Example 6 Compound 1+Chemical Formula A Decahydronaphthalene + EMB EMB agreement Example 7 Compound 1+Chemical Formula A Phenylacetaldehyde dimethylacetal + EMB EMB agreement Example 8 Compound 1+Chemical Formula A 1,3-dimethoxybenzene + EEB (ethyl 4-ethoxybenzoate) EEB agreement Comparative Example 1 Compound 1+Chemical Formula A EMB No Vapor inconsistency Comparative Example 2 Compound 1+Chemical Formula A EMB DEP inconsistency Comparative Example 3 Compound 1+Chemical Formula A DBO + EMB DBO inconsistency Comparative Example 4 Compound 1+Chemical Formula A DBO + EMB + DEP DBO+EMB+DEP inconsistency Comparative Example 5 Compound 1+Chemical Formula A DBO + EMB + DEP BzB inconsistency Comparative Example 6 Compound 1+Chemical Formula A 1-MON No Vapor inconsistency Comparative Example 7 Compound 1+Chemical Formula A DPGDME + 1-MON No Vapor inconsistency Comparative Example 8 Compound 1+Chemical Formula A DPGDME + 1-MON DPGDME inconsistency Comparative Example 9 Compound 1+Chemical Formula A Decahydronaphthalene + EMB No Vapor inconsistency Comparative Example 10 Compound 1+Chemical Formula A Phenylacetaldehyde dimethylacetal + EMB No Vapor inconsistency Comparative Example 11 Compound 1+Chemical Formula A 1,3-dimethoxybenzene + EEB No Vapor inconsistency Comparative Example 12 Compound 1+Chemical Formula A DBO + EMB Ink (dummy jetting) inconsistency Comparative Example 13 Compound 1+Chemical Formula A DBO + EMB EMB(dummy jetting) inconsistency

How to determine if the ink film profile matches

In the profile of the ink film, the X-axis cross-section means a short-axis profile measured by an optical profiler. For example, if the optical profile of the ink film is measured, a profile such as that in Fig. 6 can be obtained, and by indicating the line intersecting the central axis as a cross-section, the X-axis cross-section graph and the Y-axis cross-section graph of Fig. 7 can be obtained. Accordingly, the X-axis and Y-axis cross-sections obtained by measuring the lap profile and the mass-production profile, respectively, are plotted as graphs to measure whether the lap profile and the mass-production profile match.

If the profile shapes of the X-axis and Y-axis cross sections of the wrap profile and the mass-produced profile are all the same, the wrap size can be judged to be a direct reproduction of the mass-produced size. If the mass-produced profile and the wrap profile are compared and the basic shapes of the right and left edges and the center are the same, it is judged to be a match. At this time, it must be observed under the same thickness, and if the shape of any one of the X-axis and Y-axis profiles is different, or if the graph shape of any one of the right and left edges and the center is different, it is judged to be a mismatch.

In Examples 1 to 8, the vapor was formed using the first solvent, which is the solvent that evaporates the slowest among the solvents, and in Comparative Examples 1 to 11, the vapor was formed by not spraying the first solvent on the substrate or spraying the solvent that evaporates the slowest on the substrate. In addition, in Comparative Examples 12 and 13, the vapor was formed by dummy jetting ink or the solvent that evaporates the slowest.

As a result, in Comparative Examples 1 to 13, the shapes of the mass-produced ink film profile and the lab ink film profile did not match, but in Examples 1 to 8, the shapes of the mass-produced ink film profile and the lab ink film profile matched.

Claims (11)

A first step of discharging an ink composition including one or more solvents onto a substrate;
A second step of spraying the first solvent having the lowest evaporation rate or the highest evaporation temperature among the above solvents onto the substrate or its surroundings;
A third step of forming vapor of the first solvent through drying and forming an ink film; and
A fourth step of observing the profile of the ink film formed above;
A method for evaluating an ink composition profile comprising: In claim 1,
A method for evaluating an ink composition profile, wherein the amount of the first solvent in the second step is such that evaporation continues for 100 seconds or longer in the drying step and is completely evaporated within 30 minutes. In claim 1,
A method for evaluating an ink composition profile, wherein the first solvent is an ester, a hydrocarbon, an alcohol or an isotherm. A method for evaluating an ink composition profile according to claim 1, wherein the amount of the first solvent in the second step is 0.05 ml to 1 ml. A method for evaluating an ink composition profile according to claim 1, wherein the substrate is a bank substrate including a bank. A method for evaluating an ink composition profile according to claim 1, wherein the third step is performed under a vacuum. A method for evaluating an ink composition profile according to claim 1, wherein the third step is performed for 5 minutes to 1 hour. A method for evaluating an ink composition profile according to claim 1, wherein the third step further includes a heat treatment step. A method for evaluating an ink composition profile according to claim 1, wherein the ink composition is for an organic light-emitting device. A method for manufacturing an organic light-emitting device, comprising a method for evaluating an ink composition profile according to any one of claims 1 to 9. A method for manufacturing an organic light-emitting device according to claim 10, wherein the ink composition profile evaluation method includes a method for selecting an ink composition for an organic light-emitting device by measuring the film flatness of a formed ink film.