WO2020067467A1 - Planarized film-forming application liquid, method for producing planarized film-forming application liquid, metallic foil provided with planarized film, method for producing metallic foil provided with planarized film - Google Patents

Abstract

This planarized film-forming application liquid contains phenylsilsesquioxane which is soluble in an organic solvent, wherein the planarized film-forming application liquid has a viscosity of 2.5-35 mPa·s when the solid concentration of the phenylsilsesquioxane is 30 mass%, and the amount of alkoxy groups bound to Si in the phenylsilsesquioxane is 0-5% with respect to Si.

Description

Coating liquid for forming flattening film, method for manufacturing coating liquid for forming flattening film, metal foil with flattening film, and manufacturing method for metal foil with flattening film

The present disclosure relates to a coating liquid for forming a flattening film, a method for manufacturing a coating liquid for forming a flattening film, a metal foil coil with a flattening film, and a method for manufacturing a metal foil coil with a flattening film.

フ レ キ シ ブ ル Flexible substrates are required for electronic devices such as electronic paper, organic EL displays, organic EL lighting, and solar cells. If these electronic devices are fabricated on a flexible substrate, they will not break even when dropped, and new applications utilizing light weight and flexibility can be developed.

樹脂 Conventionally, resin substrates and glass substrates have been studied as flexible substrates. In addition to these, application of metal foil is being studied. The surface of the metal foil has lower flatness than the surface of the glass substrate due to the presence of rolling streaks and scratches. For this reason, in order to apply a metal foil as a flexible substrate, it is necessary to cover the surface of the metal foil with a flattening film and flatten it to the same level as the surface of the glass substrate. Providing this flattening film also leads to imparting insulation to the metal foil.

プ ロ セ ス Process temperatures for producing electronic devices differ depending on the type and constituent materials of the electronic device. For example, when a TFT liquid crystal display of amorphous silicon or low-temperature polysilicon (LTPS) is formed, a process temperature of about 300 ° C. to 400 ° C. is required. Therefore, the insulating film covering the metal foil is required to have heat resistance that can withstand up to 400 ° C.

Examples of the film material for coating the metal foil include an inorganic / organic hybrid material. As an insulating film made of an inorganic-organic hybrid material, an organic-modified silica film is typical. Since the organic-modified silica film contains an organic group, it is more flexible than an inorganic film. For this reason, the film thickness can be increased. The organic modified silica film has a main skeleton formed of an inorganic skeleton of Si—O.
Therefore, the heat resistance of the organically modified silica film is determined by the decomposition temperature of the organic group modifying the main skeleton.
If a methyl group or a phenyl group is selected as the organic group, the organically modified silica film can secure heat resistance of about 400 ° C. In particular, the silica film modified with a phenyl group has its Si—O main skeleton hydrolyzed even at high temperature and high humidity (for example, at 85 ° C. and 85% RH environment acceleration test) due to the high hydrophobicity of the phenyl group. Difficult and excellent in moisture resistance. For this reason, a metal foil coated with a phenyl group-modified silica film is preferable as a substrate for an electronic device.

材料 Materials for forming the organically modified silica film are disclosed, for example, in Patent Documents 1 to 5. Patent Documents 3 to 5 disclose coating liquids for forming an organically modified silica film covering a metal foil.

Patent Document 1: Japanese Patent Application Laid-Open No. 2008-81736 Patent Document 2: Japanese Patent Application Laid-Open No. 2003-226755 Patent Document 3: International Patent Application Publication No. WO 2016/076399 Patent Document 4: Japanese Patent Application Publication No. 2018-123192 Patent Document 5: Japanese Patent Application Publication No. 2018-062582

で は In Patent Document 3, a phenylsiloxane ladder polymer is produced by distilling a solution containing phenyltrialkoxysilane hydrolyzed in an organic solvent under reduced pressure. Then, it is dissolved in toluene or the like to synthesize a coating solution. In this method, the alkoxy groups that could not be completely hydrolyzed and the alcohol that could not be completely removed by distillation under reduced pressure remain in the coating solution as they are. As a flexible substrate, for example, when a metal foil with a flattening film provided on a metal foil with a flattening film made of an organic-modified silica film disclosed in Patent Document 3 is applied to an electronic device, the life of the electronic device element is reduced. It turns out that there are cases. This phenomenon is considered to be due to the alkoxy groups remaining in the organically modified silica film. If the amount of the alkoxy group remaining in the coating liquid is large, the alkoxy group remains in the film after being applied to the metal foil and thermally cured. It is expected that the alkoxy group contained in the film will be hydrolyzed over time with atmospheric moisture or the like, thereby producing alcohol which degrades the performance of the electronic device element. In addition, there is also a problem that alcohol contained in the coating liquid is likely to lead to a repellent film defect at the time of coating.

塗布 Further, the coating solution by the synthesis method described in Patent Documents 4 and 5 is synthesized by the same process as the coating solution of Patent Document 3. Therefore, in an electronic device manufactured on a substrate flattened with a coating liquid described in Patent Documents 4 and 5, the lifetime of the electronic device element may be shortened by alcohol generated by hydrolysis of an alkoxy group.

An object of the present disclosure is to provide a coating solution for forming a flattening film, a method for manufacturing a coating solution for forming a flattening film, and a flattening film, which can provide a flattening film in which generation of alcohol is suppressed even in a high-temperature and high-humidity environment An object of the present invention is to provide a method for producing a metal foil with a passivation film and a metal foil with a flattening film.

具体 Specific means for solving the above problems include the following aspects.

[1]
An organic solvent that is immiscible with water, and a phenylsilsesquioxane soluble in the organic solvent, a coating liquid for forming a flattening film,
The viscosity of the coating liquid when the solid concentration of the phenylsilsesquioxane is 30% by mass and the liquid temperature is 25 ° C. is 2.5 mPa · s to 35 mPa · s,
The content of the alkoxy group bonded to Si in the phenylsilsesquioxane is 0 to 5% based on all the bonds of Si.
Coating liquid for forming flattening film.
[2]
The alkoxy group bonded to Si in the phenylsilsesquioxane is at least one selected from the group consisting of a methoxy group, an ethoxy group, and a propoxy group,
The coating liquid for forming a flattening film according to [1].
[3]
The content of the alcohol with respect to Si in the phenylsilsesquioxane is 0 to 2.5 mol%,
The coating liquid for forming a flattening film according to [1] or [2].
[4]
The phenylsilsesquioxane,
Alcohol, phenyl trialkoxysilane, acetic acid, organotin, and water in an amount of 4.2 to 14 times the molar amount of 1 mole of the phenyl trialkoxysilane are mixed and hydrolyzed. Process and
A step of producing a dehydration-condensation reaction product containing phenylsilsesquioxane, obtained by distilling off the alcohol under reduced pressure,
Dissolving the dehydration-condensation reaction product in a water-immiscible organic solvent, while heating and refluxing at a temperature equal to or higher than the boiling point of the water-immiscible organic solvent, further dehydration condensation reaction to increase the molecular weight,
Is a compound obtained at least through
The coating liquid for forming a flattening film according to any one of [1] to [3].
[5]
Alcohol, phenyl trialkoxysilane, acetic acid, organotin, and water in an amount of 4.2 to 14 mole times based on 1 mole of the phenyl trialkoxysilane are mixed and hydrolyzed. Process and
Proceeding the dehydration condensation reaction by distilling off the alcohol under reduced pressure to produce a dehydration condensation reaction product containing phenylsilsesquioxane,
Dissolving the dehydration-condensation reaction product in a water-immiscible organic solvent, while heating and refluxing at a temperature equal to or higher than the boiling point of the water-immiscible organic solvent, further dehydration condensation reaction to increase the molecular weight,
Having,
A method for producing a coating liquid for forming a flattening film.
[6]
When the solid content of the phenylsilsesquioxane is 30% by mass and the liquid temperature is 25 ° C., the viscosity of the coating solution is 2.5 mPa · s to 35 mPa · s. The content of the alkoxy group bonded to Si is 0 to 5% based on all the bonds of Si;
The method for producing a coating liquid for forming a flattening film according to [5], wherein the coating liquid for forming a flattening film is manufactured.
[7]
The amount of the acetic acid is 0.1 mol to 1 mol with respect to 1 mol of the phenyl trialkoxysilane, and the amount of the organotin is 0.005 mol to 0 mol with respect to 1 mol of the phenyl trialkoxysilane. 0.05 moles,
The method for producing a coating liquid for forming a flattening film according to [5] or [6].
[8]
Metal foil,
A flattening film provided on at least one surface of the metal foil, the flattening film comprising a cured product of the coating solution for forming a flattening film according to any one of [1] to [4];
Having,
Metal foil with flattening film.
[9]
The metal foil is a stainless steel foil,
The metal foil with a flattening film according to [8].
[10]
A step of applying the coating liquid for forming a flattening film according to any one of [1] to [4] to at least one surface of the metal foil;
A step of reflowing and curing the applied coating liquid for forming a flattening film in a temperature range of 300 ° C. to 450 ° C. in an inert gas atmosphere to form a flattening film;
Having,
A method for producing a metal foil with a flattening film.

According to the present disclosure, even in a high-temperature and high-humidity environment, a flattening film in which the generation of alcohol is suppressed can be obtained, a coating solution for forming a flattening film, a method for manufacturing a coating solution for forming a flattening film, and flattening. A method for producing a metal foil with a passivation film and a metal foil with a flattening film is provided.

Is an explanatory view illustrating the structure of T ^1, T ^2, and T ³ in the phenyl silsesquioxane. 1 is a schematic diagram illustrating an example of a film forming apparatus applied to manufacture a metal foil with a planarizing film according to the present disclosure. 1 is a schematic partial cross-sectional view illustrating an example of a metal foil with a flattening film according to the present disclosure.

Hereinafter, an example of a preferred embodiment of the present disclosure will be described.
In the present disclosure, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit and an upper limit.
In the numerical ranges described stepwise, an upper limit or a lower limit described in a certain numerical range may be replaced with an upper limit or a lower limit of another numerical range described in a stepwise manner.
In the numerical ranges, the upper limit or the lower limit described in a certain numerical range may be replaced with the value shown in the embodiment.
The amount of each component in the composition means the total amount of the plurality of substances present in the composition, unless otherwise specified, when there are a plurality of substances corresponding to each component in the composition.
The term “step” is included in the term as well as an independent step, even if it cannot be clearly distinguished from other steps as long as the intended purpose of the step is achieved.

<Coating liquid for forming flattening film>
The coating liquid for forming a flattening film according to the present disclosure is a coating liquid for forming a flattening film containing an organic solvent immiscible with water and phenylsilsesquioxane soluble in the organic solvent.
In the coating liquid for forming a flattening film according to the present disclosure, the viscosity of the coating liquid when the solid content concentration of phenylsilsesquioxane is 30% by mass and the liquid temperature is 25 ° C. is 2.5 mPa · s to 35 mPa. S, and the content of the alkoxy group bonded to Si in the phenylsilsesquioxane is 0 to 5% based on all the bonds of Si.

に お い て In the present disclosure, phenylsilsesquioxane is a compound that is soluble in a water-immiscible organic solvent. A phenylsilsesquioxane that is soluble in a water-immiscible organic solvent is a phenylsilsesquioxane that is soluble in a water-immiscible organic solvent at 25 ° C. that is 70% by mass or more. Represents Sun.

In the coating liquid for forming a flattening film according to the present disclosure, for example, phenylsilsesquioxane is used in an amount of alcohol, phenyltrialkoxysilane, acetic acid, organic tin, and 1 mol of phenyltrialkoxysilane. After mixing and hydrolyzing 2 to 14 times by mole of water, the alcohol is distilled off under reduced pressure, and the resulting dehydration-condensation reaction containing phenylsilsesquioxane is not mixed with water. The compound is preferably a compound which is dissolved in an organic solvent and heated and refluxed at a temperature equal to or higher than the boiling point of the organic solvent immiscible with water, and further dehydration-condensed to further increase the molecular weight.
A dehydration-condensation reaction product containing phenylsilsesquioxane is obtained by hydrolyzing phenyltrialkoxysilane in a mixed solution containing alcohol, phenyltrialkoxysilane, acetic acid, organotin, and water, and then hydrolyzing the phenyltrialkoxysilane. Obtained by a dehydration condensation reaction of alkoxysilane.

Here, conventionally, for example, phenylsilsesquioxane produced by hydrolyzing phenyltrialkoxysilane has been known as a material for the organically modified silica film. Phenylsilsesquioxane is a polymer whose main chain skeleton is composed of Si—O bonds, and has a structure represented by [(RSiO _1.5 ) _n ] having a phenyl group in at least a part of R. The structure of this polymer depends on the catalyst and the synthesis conditions, and cage, ladder, and random structures are known.

For example, Patent Literature 1 discloses a ladder type in which, after hydrolyzing a silane compound, an organic solvent that generates an azeotropic compound with water is added, heated to reflux, and then water is removed by azeotropic distillation. A method for producing polysilsesquioxane is disclosed.
Patent Document 2 discloses that a thermoplastic polyphenylsilsesquioxane having a ladder-type structure is obtained by hydrolyzing phenyl trialkoxysilane with an acid and then proceeding with a condensation reaction using a basic catalyst. It has been disclosed.

However, Patent Documents 1 and 2 disclose only the production of ladder-type silsesquioxane. Since the main purpose of the coating liquid for forming a flattening film of the present disclosure is to obtain a flattening film in which the generation of alcohol is suppressed, the technique is different from those disclosed in these documents.

On the other hand, Patent Document 3 discloses a coating liquid for forming a flattening film in which phenylsilsesquioxane is formed using phenyltrialkoxysilane, and the phenylsilsesquioxane is dissolved in an aromatic hydrocarbon-based solvent.

塗布 The coating liquid for forming a supported film disclosed in Patent Document 3 is obtained, for example, as follows. First, phenyl trialkoxysilane is hydrolyzed in alcohol using acetic acid and organotin as catalysts. Thereafter, the mixture is refluxed at 80 ° C. for 3 hours under a nitrogen stream, and phenylsilsesquioxane obtained by distillation under reduced pressure at a temperature of 160 ° C. to 210 ° C. is dissolved in toluene. When phenylsilsesquioxane is dissolved in toluene, a polymer having a high molecular weight of tens of thousands in terms of styrene is obtained. This polymer is considered to have a ladder structure because of its spinnability and reflow properties. After dissolving in toluene and performing steps such as filtration, a coating liquid for forming a flattening film containing phenylsilsesquioxane is obtained.

In order to flatten the surface of a metal foil on which rolling streaks or the like are present, it is effective to use the reflow property of phenylsilsesquioxane having a ladder-type structure. By using the coating liquid for forming a flattening film containing phenylsilsesquioxane disclosed in Patent Document 3, it is possible to provide a flattening film on a metal foil. In particular, the coating liquid for forming a flattening film disclosed in Patent Document 3 is useful in that a flattening film can be provided by a Roll-to-Roll process, so that it can be cured in a short time.

The coating liquid for forming a flattening film obtained as described above is applied on a metal foil, dried at 20 ° C. to 150 ° C., and heat-treated at 400 ° C. to produce a metal foil with a flattening film. I do. Then, an organic EL lighting element is provided as a flexible device element on the flattening film of the metal foil with the flattening film, and sealed with a glass cap. However, it was found that the lifetime of the organic EL lighting element was shortened when left in a high temperature and high humidity environment.

調査 The investigation of the fabricated metal foil with a flattening film was proceeded. As a result, an alkoxy group remained in the flattening film. Therefore, in the conventional coating liquid for forming a flattening film, an alkoxy group bonded to Si present in phenylsilsesquioxane (that is, an alkoxy group bonded to Si in phenylsilsesquioxane; It is considered that OR--R and R are alkyl groups) in a relatively large amount.

The flexible substrate is sealed with a sealing material and provided to a flexible device. However, even when the flexible substrate is sealed, a small amount of moisture (water vapor) infiltrates. In particular, in a high-temperature and high-humidity environment, it is considered that the intrusion of moisture becomes remarkable. Even when an organic EL lighting element is provided on a flattening film of a metal foil with a flattening film and sealed with a sealing material, infiltration of moisture becomes remarkable under a high-temperature and high-humidity environment. Groups (eg, ethoxy groups) hydrolyze. Thereby, alcohol (eg, ethanol) may be produced. Some components constituting the organic EL lighting element are soluble in alcohol. Therefore, when a flattening film is formed using a conventional coating liquid for forming a flattening film containing phenylsilsesquioxane, it is expected that device deterioration due to the influence of alcohol generated due to the alkoxy group will occur.

し た We considered to proceed with heat treatment to reduce the alkoxy groups in the planarization film. However, even if heat treatment is performed on the metal foil with a flattening film, the heat treatment cannot be reduced to a level that suppresses a reduction in the life of the organic EL lighting element. For example, a heat-treated product A obtained by performing a heat treatment at 400 ° C. for 10 minutes and a heat-treated product B obtained by performing a heat treatment at 400 ° C. for 150 minutes on the metal foil with a flattening film obtained as described above are manufactured. did. Then, an organic EL lighting element was formed on the flattening film of each processed product, and an environmental acceleration test was performed under high temperature and high humidity conditions. As a result, the life of the device was short regardless of which heat-treated product was used. Analysis of heat-treated product A and heat-treated product B revealed that the alkoxy group remained in the planarized film in each of the heat-treated products. Thus, it has been found that it is difficult to sufficiently reduce the alkoxy groups in the flattening film by the heat treatment of the metal foil with the flattening film. Therefore, in the phenylsilsesquioxane contained in the coating liquid for forming a flattening film, it is required to reduce the alkoxy groups sufficiently.

In this regard, phenyltrialkoxysilanes produced by the synthesis methods described in Patent Documents 4 and 5 also have a large amount of alkoxy groups remaining. Therefore, the alkoxy group remains in the flattening film using phenyl trialkoxysilane formed by the synthesis method described in Patent Documents 4 and 5, and the device life is shortened.

On the other hand, according to the coating liquid for forming a flattening film of the present disclosure, the amount of the alkoxy group bonded to Si in the phenylsilsesquioxane is sufficiently reduced to a level that suppresses the performance deterioration of the organic semiconductor. I have. That is, when the content of the alkoxy group is 0 to 5% of the total bonds of Si, the device life is improved.

Therefore, in the flattening film obtained by using the coating solution for forming a flattening film of the present disclosure, no alkoxy group is present, or even if an alkoxy group is present, the amount thereof is small. For this reason, even in a high-temperature and high-humidity environment, generation of alcohol in the flattening film is suppressed. As a result, it is possible to suppress a reduction in the life of the flexible device element.

Hereinafter, each material constituting the coating liquid for forming a flattening film of the present disclosure will be described.

The coating liquid for forming a planarizing film according to the present disclosure includes an organic solvent that is immiscible with water, and phenylsilsesquioxane that is soluble in the organic solvent.
The coating liquid for forming a flattening film according to the present disclosure is, for example, mixed with a predetermined material (mixed with alcohol, phenyl trialkoxysilane, acetic acid, organotin, and water) and hydrolyzed. It is obtained by dissolving a dehydration-condensation reaction product obtained by distillation under reduced pressure in an organic solvent immiscible with water.

(Organic solvent immiscible with water)
Examples of the organic solvent immiscible with water include aromatic hydrocarbons, ketones, and ethers. For example, specifically, aromatic hydrocarbons such as toluene, xylene (o-xylene, m-xylene, p-xylene), trimethylbenzene; MEK (methyl ethyl ketone), MIBK (methyl isobutyl ketone), cyclohexanone, cyclopentane Ketones such as nonone; ethers such as diethyl ether and diisopropyl ether; and cyclic aliphatic hydrocarbons such as cyclopentane, cyclohexane and methylcyclohexane. The organic solvents may be used alone or in combination of two or more.

Here, in the present disclosure, the “organic solvent immiscible with water” is a concept including an organic solvent having low miscibility with water, and represents an organic solvent having a solubility in water of 300 g / L or less. The solubility in water indicates the weight of an organic solvent soluble in 1 L of water at 25 ° C. in units of g / L. The organic solvent that is immiscible with water is ideally an organic solvent having a solubility in water at 25 ° C. of 30 g / L or less.

(Phenyl trialkoxysilane)
The phenyl trialkoxysilane is not particularly limited. For example, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltripropoxysilane (phenyltri-n-propoxysilane, phenyltri-iso-propoxysilane), phenyltributoxysilane (phenyltri-n-butoxysilane, phenyltri-silane) sec-butoxysilane, phenyltri-tert-butoxysilane) and the like. Of these, phenyltriethoxysilane is preferred from the viewpoint of being industrially mass-produced and easily available.

(alcohol)
Alcohol is used when hydrolyzing phenyl trialkoxysilane. The alcohol is not particularly limited, and examples thereof include methanol, ethanol, propanol (n-propanol, iso-propanol), and butanol (n-butanol, iso-butanol).

(Acetic acid and organic tin)
Acetic acid and organotin are each catalysts. Acetic acid is a catalyst that promotes hydrolysis. Organotin is a catalyst that promotes phenyltrialkoxysilane and its dehydration-condensation reaction after hydrolysis.

Examples of the organic tin include dibutyltin diacetate, bis (acetoxydibutyltin) oxide, dibutyltinbisacetylacetonate, monobutylester dibutyltinbismaleate, monobutylester dioctyltinbismaleate, and bis (lauroxydibutyltin) oxide. . Among these, dibutyltin diacetate and dibutyltin bisacetylacetonate are particularly preferable as the organic tin.

(water)
The water is not particularly limited, and includes, for example, distilled water, ion-exchanged water, ultrafiltration water, pure water and the like.

(Characteristics of coating liquid for forming flattening film)
The coating liquid for forming a flattening film according to the present disclosure has the following characteristics.

-Viscosity of coating liquid-
The viscosity of the coating liquid for forming a flattening film according to the present disclosure is 2.5 mPa · s to 35 mPa · s. However, the viscosity of the coating liquid is the viscosity of the coating liquid when the solid content concentration of phenylsilsesquioxane is 30% by mass and the liquid temperature is 25 ° C.
When the solid content concentration is 30% by mass and the viscosity at a temperature of 25 ° C. is in this range, it is preferable from the viewpoint of coating properties when forming a flattening film and from the viewpoint of storage stability. When the viscosity is less than 2.5 mPa · s, the weight average molecular weight in terms of styrene of phenylsilsesquioxane is low, which is generally less than 5000. Therefore, even if the solid content concentration is increased, the viscosity cannot be increased, resulting in poor coatability. Therefore, a desired film thickness cannot be obtained. Further, a rapid dehydration / condensation reaction occurs due to the heat treatment, which causes a large volume shrinkage, so that the flattening film is easily cracked. When the viscosity exceeds 35 mPa · s, the weight average molecular weight in terms of styrene of the phenylsilsesquioxane becomes a high molecular weight generally exceeding 100,000. For this reason, gelation easily proceeds, the storage life of the coating solution is shortened, and the storage stability is reduced. On the other hand, if the viscosity is too high, the film thickness becomes non-uniform, and cracks tend to occur from the thick film portion.

測定 The method of measuring the viscosity of the coating liquid for forming a flattening film is as follows. First, the solid content concentration of phenylsilsesquioxane in the coating liquid for forming a flattening film is adjusted to 30% by mass, and the liquid temperature of the coating liquid is adjusted to 25 ° C. Next, the viscosity of the coating liquid whose solid content concentration and liquid temperature have been adjusted is measured using a VISCOMATE @ VM-10A vibrating viscometer manufactured by CBC Corporation.

As a result of analyzing the coating liquid for forming a flattening film of the present disclosure by gel permeation chromatography (GPC), the weight average molecular weight in terms of styrene of phenylsilsesquioxane was 5,000 to 100,000. When evaporating the organic solvent on a hot plate heated to 150 ° C. and evaporating the liquid with a glass rod, the phenylsilsesquioxane can be confirmed to exhibit spinnability. . In addition, when the infrared absorption spectrum (IR) of phenylsilsesquioxane was measured, a double peak derived from a siloxane bond was shown at a wavenumber of about 1100 cm ^-1 .

From these facts, it is presumed that phenylsilsesquioxane contained in the coating liquid for forming a flattening film of the present disclosure has a ladder-type structure. That is, phenylsilsesquioxane is presumed to have a ladder structure in the following points.
1) it is dissolved in an organic solvent,
2) phenylsilsesquioxane having a weight average molecular weight in terms of styrene of 5,000 to 100,000;
3) The point where phenylsilsesquioxane after evaporating the organic solvent exhibits spinnability. 4) The point where IR shows a double peak derived from a siloxane bond at a wavenumber of about 1100 cm ^-1 .

<Content of alkoxy group bonded to Si>
In the coating liquid for forming a planarizing film according to the present disclosure, the content of the alkoxy group bonded to Si in phenylsilsesquioxane is 0 to 5% based on all the bonds of Si. That is, the amount of -Si-OR groups (R: methyl group, ethyl group, propyl group, etc.) bonded to Si in the phenylsilsesquioxane is 5% or less (total bonds to Si). When the content of the alkoxy group is 5% or less, generation of alcohol is suppressed even when a flattening film is formed on the metal foil substrate. The smaller the content of the alkoxy group, the more preferable. Therefore, in the coating liquid for forming a flattening film according to the present disclosure, the lower limit of the content of the alkoxy group bonded to Si in phenylsilsesquioxane is 0%. The upper limit of the content of the alkoxy group may be 3% or less, 2% or less, or 1% or less. The alkoxy group may be at least one selected from the group consisting of a methoxy group, an ethoxy group, and a propoxy group, depending on the phenyl trialkoxysilane used. The alkoxy group may be an ethoxy group.

The content of the alkoxy group bonded to Si is a value measured by NMR. Specifically, it is measured as follows.

For the NMR measurement, phenylsilsesquioxane was synthesized from phenyltriethoxysilane as a raw material in a toluene solvent, and the coating liquid for forming a flattening film according to the present disclosure prepared by adjusting the solid content concentration of phenylsilsesquioxane to 30% by mass was used. An example will be described.
When phenyltrialkoxysilane other than phenyltriethoxysilane is used as a raw material, or when a solvent other than toluene is used, the peak positions of NMR spectra and the like are different, but the concepts of measurement and calculation are the same.

In order to investigate the molecular structure of phenylsilsesquioxane in the coating solution, ²⁹ Si NMR was measured using NMR measuring apparatuses “ECZ-600” and “ECA-400” (both manufactured by JEOL RESONANCE Co., Ltd.). And ¹³ C NMR measurement. A sample solution prepared by adding an appropriate amount of heavy benzene (C ₆ D ₆ ) as a lock solvent to the outer tube and a proper amount of heavy benzene (C ₆ D ₆ ) to the outer tube is used for the measurement. As a chemical shift standard, tetramethylsilane is set to 0.0 ppm in ²⁹ Si, and the methyl group carbon of toluene of the solvent is set to 20.43 ppm in ¹³ C. In ²⁹ Si NMR spectra, -67.5, -72.1, the -77.9Ppm, respectively ^T 1, ^{T 2,} and the peak of ^{T 3} was ^{observed, T 1, T 2, T} 3 from the peak area ratio Are calculated as 8.6 mol%, 29.9 mol%, and 61.5 mol%, respectively.

FIG. 1 shows the structures of T ¹ , T ² , and T ³ in phenylsilsesquioxane. ^{From the 13} C NMR spectrum, the presence of toluene, ethanol, Si-Ph groups, and Si-OEt groups is indicated by peaks at 20.4 ppm, 57.1 ppm, 133.7 ppm, and 58.1 ppm. From the peak area ratio, the abundance ratio of each component is calculated as 388.2 mol%, 2.0 mol%, 100 mol%, and 13.1 mol%, respectively. It is calculated so that the mol% of Si-Ph becomes 100.
In the case where the peak is buried in the background and no peak is observed in the NMR spectrum, it is considered that the corresponding component does not exist.

In Si of T ³ , all three ethoxy groups undergo a hydrolysis and condensation reaction to form a Si—O—Si bond. On the other hand, at T ² and T ¹ , a terminal group that has not undergone a condensation reaction remains. Relative to 1 mol of Si, ^{T 1} is 2 moles of end groups, ^{T 2} are 1 mol possess end groups. Si has four bonds, one of which has a phenyl group bonded thereto. The remaining three bonds are Si—O—Si bonds or end groups. Assuming that the total Si is 100, the number of Si—O—Si bonds is 3 × 61.5 + 2 × 29.9 + 8.6 = 253.2, and the terminal group is 2 × 8.6 + 29.9 = 47.1. From this, the phenyl group is 25% of all the bonds of Si, the Si—O—Si bond is 75 × 253.2 / (253.2 + 47.1) = 63.3%, and the terminal group is 11.8%. Can be calculated.

As shown by ¹³ C NMR, the terminal groups are of two types: a Si—OH group and a Si—OEt group. When Si is 1, T ¹ has ^two terminal groups and T ² has one terminal group. Assuming that the ratio of the Si—OEt group is a and the ratio of the Si—OH group is 1−a, when Si is 100, the ethoxy group in the coating solution is 2 × 8.6 × a + 29.9 × a = 47. .1a. In any of T ¹ , T ² , and T ³ , the number of phenyl groups and Si are the same, and therefore, when Si is 100, there are 100 phenyl groups. On the other hand, from ¹³ C, the abundance ratio (molar ratio) of the phenyl group to the ethoxy group is known to be 100: 13.1, so a is 0.277. Therefore, the breakdown of 11.8% of the terminal groups is 3.3% of Si—OEt groups and 8.5% of Si—OH groups.
The content of the Si-OEt group with respect to all the bonds of Si of the phenylsilsesquioxane in the coating solution measured as described above can be estimated to be 3.3%.

-Alcohol content of coating liquid-
In the coating liquid for forming a flattening film according to the present disclosure, the content of alcohol with respect to Si in phenylsilsesquioxane is preferably 0 to 2.5 mol%.
When the alcohol content is 2.5 mol% or less, poor coating (voids, uneven coating, etc.) is suppressed. From the viewpoint of coating failure control, the smaller the amount of alcohol in the coating solution, the better. Therefore, the upper limit of the alcohol content is more preferably 1.5 mol% or less, and further preferably 0.5 mol% or less. The alcohol content is most preferably 0 mol% (that is, it is most preferable that the coating solution does not contain alcohol).

Examples of a method for producing a coating liquid having an alcohol content within the above range include a method for producing a coating liquid for forming a flattening film (method for producing phenyltrialkoxysilane) described later.
When phenyl trialkoxysilane is produced by the synthesis methods described in Patent Documents 3 to 5, a certain amount of alcohol remains in the coating solution.
Here, the alcohol is exemplified by methanol, ethanol, and propanol.

The alcohol content is measured by a ¹³ C NMR spectrum.
For example, the content of ethanol as an alcohol is calculated to be 2.0 mol%, based on the peak area ratio of 57.1 ppm and 133.7 ppm in ¹³ C NMR measurement, where the Si-Ph group is 100 mol%. You. Solids contained in the coating liquid of the present disclosure is ideally phenyl silsesquioxane, namely from those represented as PhSi [theta] _3/2, ethanol when the Si in the coating liquid was 100 mol% The content is 2.0 mol%.
The content of alcohol other than ethanol is also calculated from the peak area ratio in ¹³ C NMR measurement.

<Production method of coating liquid for forming flattening film>
Next, an example of a preferable manufacturing method for obtaining the coating liquid for forming a flattening film of the present disclosure will be described.
The method for producing a coating liquid for forming a planarizing film according to the present disclosure includes the following steps.
A step of mixing an alcohol, phenyl trialkoxysilane, acetic acid, organotin, and water in an amount of 4.2 to 14 times by mole to 1 mole of the phenyl trialkoxysilane to perform hydrolysis. (Hydrolysis step).
A step of evaporating the alcohol under reduced pressure to advance the dehydration condensation reaction to generate a dehydration condensation reaction product containing phenylsilsesquioxane (concentration step).
A step of dissolving the dehydration-condensation product in an organic solvent immiscible with water and heating and refluxing at a temperature equal to or higher than the boiling point of the organic solvent immiscible with water, and further advancing the dehydration-condensation reaction to increase the molecular weight (polymerization step) .

(Hydrolysis step)
In the hydrolysis step, it is preferable to carry out hydrolysis by mixing organotin, acetic acid, and water with respect to phenyl trialkoxysilane in alcohol. For example, it may be performed as follows. First, a mixed solution of alcohol and phenyl trialkoxysilane is prepared. Next, organotin and acetic acid are mixed with this mixed solution, and water is further mixed to hydrolyze phenyltrialkoxysilane. A mixture of alcohol, phenyl trialkoxysilane, and organotin may be mixed with acetic acid and further mixed with water. The hydrolysis may be performed by mixing a first mixed solution in which alcohol, phenyl trialkoxysilane, and organotin are mixed, and a second mixed solution in which acetic acid and water are mixed. Reflux may be performed at about 80 ° C. under a nitrogen stream to promote the hydrolysis reaction.

From the viewpoint of promoting the hydrolysis of phenyltrialkoxysilane, the amount of acetic acid is preferably in the range of 0.1 mol to 1 mol based on 1 mol of phenyltrialkoxysilane. When the amount of acetic acid is 0.1 mol or more per 1 mol of phenyltrialkoxysilane, the molecular weight of phenylsilsesquioxane increases. Even if the amount of acetic acid exceeds 1 mol, the effect of increasing the molecular weight is saturated.

The amount of the organotin is preferably 0.005 mol to 0.05 mol per 1 mol of phenyltrialkoxysilane from the viewpoint of accelerating the polycondensation reaction of phenylsilsesquioxane. When the amount of the organotin is 1 mol or more per 1 mol of the phenyl trialkoxysilane, the condensation reaction of the phenylsilsesquioxane during the heat treatment after the application on the metal foil is promoted. In addition, cracks hardly occur in the flattening film. When the amount is less than 0.05 mol, gelation of phenylsilsesquioxane hardly occurs at the stage of hydrolysis before distillation under reduced pressure.

From the viewpoint of controlling the content of the alkoxy group bonded to Si in the phenylsilsesquioxane to 5% or less with respect to all the bonds of Si, the amount of water used for the hydrolysis is 1 mole of phenyltrialkoxysilane. On the other hand, the molar ratio is 4.2 to 14 times. The preferred amount of water is 4.5 to 13.5 moles. In the method for producing a coating for forming a flat film according to the present disclosure, when phenyltrialkoxysilane is hydrolyzed in an alcohol using acetic acid and organotin as a catalyst, water is added to 4 moles of phenyltrialkoxysilane per mole. By adding 2 to 14 mole times, it becomes easy to reduce the number of alkoxy groups at the stage of hydrolysis. Since the hydrolysis reaction is an equilibrium reaction with the alcohol addition reaction, a certain amount of alkoxy group remains. Thereafter, in the subsequent step of producing a dehydration condensation reaction product, when alcohol is distilled off under reduced pressure, alcohol having a high vapor pressure is removed from the system with priority over water. Therefore, it is considered that the equilibrium reaction between the hydrolysis reaction and the alcohol addition reaction is deviated, and the hydrolysis proceeds more easily, so that the alkoxy group can be more easily reduced.

When the phenyl trialkoxysilane is hydrolyzed by the synthesis methods described in Patent Documents 3 to 5, water is used excessively (water is used in an amount of 4.2 mol times or more with respect to 1 mol of phenyl trialkoxysilane). Then, an excessive amount of the random condensate is generated, and it becomes cloudy.

(Concentration process)
In the concentration step, the alcohol is distilled off under reduced pressure, and the dehydration condensation reaction proceeds to generate a dehydration condensation reaction product containing phenylsilsesquioxane. In the concentration step, it is preferable to distill off the alcohol while heating the solution containing the hydrolyzed phenyltrialkoxysilane to a temperature of 30 ° C. to 90 ° C. under reduced pressure. In the concentration step, a product obtained by partially dehydrating and condensing phenyltrialkoxysilane that has been hydrolyzed almost 100% is obtained.

It is preferable that the temperature, the degree of reduced pressure, and the time of the partial dehydration condensation reaction be adjusted to advance the dehydration condensation reaction. Specifically, with respect to the molecular weight 129 of the product (that is, C ₆ H ₅ SiO _3/2 ) obtained when 1 mol of phenyl trialkoxysilane is completely dehydrated and condensed, It is preferable to adjust the weight to be 1.04 times to 1.11 times.

In the concentration step, at the time of completion, the alcohol is almost removed and the state becomes almost solventless. Therefore, if the hydrolyzed molecules collide with each other, dehydration condensation easily proceeds even if there is steric hindrance. Therefore, an oligomer containing a large amount of the aforementioned T ¹ and T ² (see FIG. 1) is likely to be generated. When such oligomers are dehydrated and condensed, an undesirable reaction occurs in the step of increasing the molecular weight. For this reason, it is preferable that the oligomer does not become a large oligomer in the concentration step. For example, when the average molecular weight of the dehydration-condensation reaction product is 1.04 to 1.11 times the average molecular weight of 129 of C ₆ H ₅ SiO _3/2 , the monomer of the hydrolyzate of phenyl trialkoxysilane , And a mixture of a dimer and an oligomer.

(High molecular weight process)
In the step of increasing the molecular weight, it is preferable to dissolve the partial dehydration-condensation reaction product in an organic solvent immiscible with water so that the solid content concentration is 30% by mass to 80% by mass. Further, it is preferable that the reflux time is 3 hours to 30 hours at a temperature not lower than the boiling point of the organic solvent immiscible with water. The heating and refluxing is preferably performed while removing alcohol together with water using a Dean-Stark trap, so that a partial dehydration / condensation reaction between dehydration / condensation products proceeds.
At this time, when the partial dehydration condensation product is an oligomer containing a large amount of T ¹ and T ² , the phenyl having a random structure insoluble in an organic solvent immiscible with water due to the dehydration condensation reaction between such oligomers. It becomes silsesquioxane. In order to form a ladder-type structure of phenylsilsesquioxane in the high molecular weight process, a monomer or a dimer is sequentially added to an oligomer having no silanol group by a dehydration condensation reaction. Considered to be ideal. For this purpose, it is preferable to control the state of a partial dehydration-condensation reaction product in the concentration step which is the preceding step.

Through the above steps, the coating liquid for forming a flattening film according to the present disclosure is obtained.

<Metal foil with flattening film and manufacturing method thereof>
Next, the metal foil with a flattening film of the present disclosure will be described together with a method for manufacturing the same.
The metal foil with a flattening film according to the present disclosure has a metal foil and a flattening film provided on at least one surface of the metal foil and obtained by curing the coating liquid for forming a flattening film according to the present disclosure.
Further, an example of a preferable manufacturing method for obtaining the metal foil with a flattening film according to the present disclosure includes the following steps.
A step of applying the coating liquid for forming a flattening film of the present disclosure to at least one surface of the metal foil (coating step).
After reflow and film curing in a temperature range of 300 ° C. to 450 ° C. in an inert gas atmosphere, a winding step (winding step).

金属 In the metal foil with a flattening film, the flattening film is provided on at least one surface of the metal foil. That is, the flattening film may be provided on both sides of the rolled surface of the metal foil, or may be provided only on one side of the rolled surface. In general, electronic device elements (for example, organic EL lighting elements) are often manufactured only on one side of a substrate. Therefore, the flattening film may be provided only on one side of the metal foil.

Since the metal foil is thinned by rolling, streaks are observed in the rolling direction. In addition, there are flaws elongated in the rolling direction due to inclusions included in the original molten metal, foreign matters caught in the rolling rolls, and the like. The size of the flaw is, for example, often about several tens μm in width and about 1 mm to several mm in length.

表面 The surface roughness of the metal foil differs between the direction parallel to the rolling streaks and the direction perpendicular to the rolling streaks, and the vertical direction has a larger surface roughness. Therefore, for the purpose of improving the flatness of the metal foil by covering the flattening film, attention is paid to the vertical direction in which the surface roughness is the largest. Specifically, the surface roughness was measured at a measurement length of 1.25 mm with a stylus type roughness meter at 10 or more points perpendicular to the rolling direction of the metal foil, that is, in the width direction of the metal foil, and the average value was measured. Is adopted.

The relationship between the surface roughness of the metal foil with a flattening film and the characteristics of the organic EL element as a flexible device element formed thereon was examined in detail. As a result, it was found that the flatness of the film surface was important in reducing the leak current of the organic EL element. If the arithmetic average roughness Ra in the direction perpendicular to the rolling direction of the surface of the metal foil with a flattening film is 30 nm or less, the leak current of the organic EL light emitting element is set to a practical level of 1E-4 A / m ² or less. be able to.

The leak current of the device is formed by forming a lower electrode, a light emitting portion, and an upper electrode of the device in this order on a flattened film of phenylsilsesquioxane to produce a device, and applying 3 V between the lower electrode and the upper electrode. It is determined by dividing the current when a voltage is applied by the element area. The light emitting section is composed of a plurality of layers, and the total thickness is about 100 nm to 150 nm. When the surface of the film is rough, a portion where the distance between the lower electrode and the upper electrode is short is formed, and the leak current of the element increases. When Ra of the metal foil with a flattening film exceeds 30 nm, an element having a large leak current exceeding 1E-4 A / m ² is obtained. As a result, phenomena such as a reduction in the efficiency of the element and a short circuit occur. A more preferable range of Ra is 20 nm or less, and further preferably 15 nm or less. By setting Ra within this range, a smaller leak current can be obtained. The arithmetic average roughness Ra in the direction perpendicular to the rolling direction of the surface of the metal foil with a flattening film is preferably as small as possible, and the lower limit of Ra is not limited. Ra may be, for example, 0.5 nm or more.

絶 縁 An insulating coating may be provided on at least one surface of the metal foil. By using the metal foil coated with the insulating film, the insulating property of the metal foil after the formation of the flattening film becomes higher and more reliable. The type of the insulating coating is not particularly limited, and examples thereof include metal oxides (silica, alumina, and the like), inorganic salts (aluminum phosphate, calcium phosphate, and the like), and heat-resistant resins (polyimide, polytetrafluoroethylene, and the like). The insulating film made of a metal oxide can be formed by, for example, a method such as sputtering, vapor deposition, or CVD. The inorganic salt insulating film can be formed by a coating method such as a roll coater or a spray. The insulating film of the heat-resistant resin can be formed by a coating method such as a comma coater, a die coater, and a spray.

The metal foil is not particularly limited, and examples thereof include an aluminum foil, a copper foil, a titanium foil, and a stainless steel foil. Among these, stainless steel foil is preferable. Stainless steel foil is suitable as a flexible substrate for electronic devices from the viewpoint that it is industrially easy to manufacture at low cost and hardly breaks. When a stainless steel foil is used, the reflectivity of the stainless steel foil is low (the reflectivity is 60%), so that a reflective film may be formed on at least one surface of the stainless steel foil. The stainless steel foil may be any of austenitic, ferrite and martensitic stainless steel foils. From the viewpoint of application to a flexible substrate, an austenitic or ferritic stainless steel foil is preferable. The thickness of the metal foil is not particularly limited, and may be, for example, 10 μm to 100 μm.

(4) When an organic EL lighting, an organic EL display or the like of top emission is manufactured using a transparent lower electrode as an electronic device, light is repeatedly reflected on the surface of the stainless steel foil. If the reflectance of the stainless steel foil is about 60%, much light is lost and the efficiency of the device is reduced. On the other hand, when a reflective film (for example, a reflectance of about 95%) is formed on the surface of the stainless steel foil, most of the light is reflected by the reflective film, so that the efficiency of the device is significantly improved. For example, examples of the type of the reflective film having a high reflectance of about 95% include pure Al, an Al alloy, pure Ag, and an Ag alloy. Examples of the Al alloy include Al-Si and Al-Nd alloys. Ag alloys include alloys such as Ag-Nd and Ag-In. The reflection film can be formed by a sputtering method or the like.

膜厚 The thickness of the flattening film is preferably 2.0 μm to 5.0 μm from the viewpoint of flattening the film and suppressing cracks. When the thickness of the flattening film is 2.0 μm or more, it is easy to cover the unevenness of the metal foil. From the viewpoint of covering the unevenness of the metal foil, the thickness of the flattening film is preferably 2.5 μm or more. On the other hand, when the thickness of the flattening film is 5 μm or less, cracking of the flattening film is suppressed. Further, not only cracks during film formation but also cracks when the stainless steel foil covered with the flattening film is bent as a flexible substrate are suppressed. In light of crack suppression and the like, the thickness of the flattening film is more preferably equal to or less than 4.5 μm, and still more preferably equal to or less than 4.0 μm.

Here, an example of a preferable manufacturing method for obtaining the metal foil with a planarizing film of the present disclosure will be described with reference to FIG. FIG. 2 is a schematic diagram illustrating an example of a film forming apparatus applied to manufacture the metal foil with a flattening film according to the present disclosure. This film forming apparatus represents a continuous film forming apparatus for providing a flattening film on one side of a metal foil by a Roll to Roll process. The film forming apparatus 100 shown in FIG. 2 contains a coil unwinding unit 12 that unwinds a metal foil wound in a coil shape and a coating liquid 22A for forming a flattening film according to the present disclosure. A coating unit 22 for forming a coating film by applying the liquid 22A, a drying unit 24 for drying the coating film of the coating liquid 22A for forming a flattening film to form a dry film, and drying the coating liquid 22A for forming a flattening film. A heat treatment section 26 for thermally curing the film after reflow, a cooling section 28 (first cooling body 28A, second cooling body 28B) for cooling the metal foil with a flattening film after the heat treatment, and a flattening film after the heat treatment And a coil winding unit 14 for winding the attached metal foil. In the drying unit 24 and the heat treatment unit 26, the support roll supporting the metal foil is arranged so as not to contact the film surface (the dried film surface and the cured film surface) on the electronic device formation side. Further, the film forming apparatus 100 includes a tension applying roll 32A and a tension applying roll 32B so that wrinkles and the like do not occur when the film is conveyed. The tension applying roll 32 </ b> A is provided on the upstream side of the application unit 22 in the metal foil transport direction, and stabilizes the transport of the metal foil. The tension applying roll 32B is provided on the downstream side of the heat treatment unit 26 and on the upstream side of the coil winding unit 14, and stabilizes the transport of the metal foil with the flattening film.

(Coating process)
First, the application step will be described. The application step is a step of applying the coating liquid for forming a flattening film according to the present disclosure. First, the metal foil wound around the core is attached to the coil unwinding section 12. Next, the metal foil is unwound from the coil unwinding unit 12 in the direction of arrow A. The transport of the metal foil is stabilized by passing through the tension applying roll 32A, and the metal foil is sent to the coating unit 22 in which the coating liquid 22A for forming a flattening film of the present disclosure is stored. In the application section 22, the coating roll applies the flattening film forming coating liquid 22A to one surface of the metal foil to form a coating film of the flattening film forming coating liquid 22A.

(Winding process)
Next, the winding step will be described. The winding step is a step of winding after drying, heat treatment, and cooling after application. The metal foil provided with the coating film of the coating liquid 22A for forming a flattening film is sent to the drying unit 24. In the drying unit 24, the solvent and moisture contained in the coating film are removed, and the coating film becomes a dried film. The metal foil on which the dried film of the coating liquid 22A for forming a flattening film is formed is sent from the drying unit 24 to the heat treatment unit 26. In the heat treatment section 26, the surface of the dried film is flattened by being reflowed. Then, the cross-linking of the polymer is advanced following the reflow to form a cured film in which a three-dimensional network structure is formed. The metal foil on which the cured film of the coating liquid 22A for forming a flattening film (that is, the flattening film) is formed is sent from the heat treatment unit 26 to the cooling unit 28. In the cooling unit 28, cool air is blown from a cooling body 28 </ b> A arranged on the surface side where the cured film is provided and a cooling body 28 </ b> B arranged on the opposite surface side (that is, the metal foil surface side) to be cooled. You. Then, after cooling, the metal foil with the flattening film is sent from the cooling unit 28 to the coil winding unit 14. The transport of the metal foil with the flattening film is stabilized by passing through the tension applying roll 32A. Then, the metal foil with the flattening film is transported in the direction of arrow A, and is wound around the core by the coil winding unit 14.

Through the above steps, a metal foil with a flattening film of the present disclosure as shown in FIG. 3 is obtained. FIG. 3 is a schematic partial cross-sectional view showing a part of the metal foil with a flattening film, showing the metal foil with a flattening film according to the present disclosure. The metal foil 300 with a flattening film shown in FIG. 3 includes a metal foil (metal foil) 302 and a flattening film 304 provided on one surface of the metal foil 302.

Hereinafter, an example of a preferred method of manufacturing the metal foil with a flattening film according to the present disclosure will be further described. In the following description, reference numerals are omitted.

搬 送 The transport speed (sheet passing speed) of the metal foil is not particularly limited, and is, for example, about 1 m / min to 20 m / min. The higher the transfer speed, the higher the productivity.

(4) The method of applying the coating liquid for forming a flattening film to the surface of the metal foil in the coating section is not particularly limited. Examples of the coating method include various coating methods (spin coating method, casting method, microgravure coating method, gravure coating method, bar coating method, roll coating method, wire bar coating method, dip coating method, slit coating method, capillary coating method) Method, spray coating method, nozzle coating method, etc.) and various printing methods (gravure printing method, screen printing method, flexographic printing method, offset printing method, reverse printing method, inkjet printing method, etc.).

(4) After coating on the metal foil, the drying section dries the coating film on the metal foil and removes the solvent and moisture from the coating film to form a dried film. The drying treatment is preferably performed at a temperature of 20 ° C to 150 ° C. The drying time is preferably about 0.5 to 2 minutes. The atmosphere in the drying unit may be the air or an inert gas atmosphere (for example, a nitrogen gas atmosphere). If the drying temperature is higher than the synthesis temperature of phenylsilsesquioxane by distillation under reduced pressure, the ladder-type structure of phenylsilsesquioxane may be softened. For this reason, the drying temperature is preferably lower than the synthesis temperature of phenylsilsesquioxane. In the dried film, the phenylsilsesquioxane is entangled and apparently has a network structure, so that the film is hardened. However, when the movement of the molecule becomes active due to the thermal vibration, the phenylsilsesquioxane is released and becomes fluid.

金属 The metal foil with a dried film sent from the drying unit is heat-treated in the heat treatment unit. The heat treatment has the following two purposes. (1) melt-softening (ie, reflow) the phenylsilsesquioxane forming the dried film to flatten the surface of the film; (2) proceeding with crosslinking of the polymer following reflow to form a three-dimensional network structure And curing the film.

Reflow is a temperature range higher than the synthesis temperature of phenylsilsesquioxane by distillation under reduced pressure, and occurs within a temperature range lower than the temperature at which the dry film begins to cure due to the progress of three-dimensional crosslinking. It is. It is not necessary to employ a special heat treatment process for reflow. When the heat treatment temperature is in the range of 300 ° C. to 450 ° C., reflow occurs in the process of raising the temperature to the heat treatment temperature, and film curing by crosslinking proceeds.

(4) In order to effectively flatten the surface of the metal foil, it is preferable to perform the heat treatment in a nearly horizontal state as in the heat treatment unit 26 of the film forming apparatus 100 shown in FIG. Since film curing is a network structure formation by a crosslinking reaction, once the film is cured, it hardly reflows again. When the heat treatment temperature is lower than 300 ° C., the crosslinking does not proceed sufficiently, and a reactive group such as a silanol group remains in the film, resulting in insufficient insulation. In addition, if moisture adsorbed to silanol groups or the like during the production of the organic electronic device is desorbed, the device is adversely affected, which is not suitable. If the heat treatment temperature is higher than 450 ° C., volumetric shrinkage due to thermal decomposition of the phenyl group occurs and cracks easily occur, which is not suitable. A more preferred heat treatment temperature is from 360 ° C to 420 ° C.

(4) The dry heat treatment is performed while flowing an inert gas so that the phenyl group is not easily thermally decomposed. In the case of a continuous film forming apparatus, a slight amount of air is brought in when the substrate enters the heat treatment furnace. In the present disclosure, phenylsilsesquioxane does not affect the film properties even if about 1% of the air is mixed.

冷却 Cooling after heat treatment may be performed by blowing cool air from a cooling body. In the film forming apparatus 100 shown in FIG. 2, the metal foil with the hardened film is sprayed from both sides, but may be sprayed from one side of the hardened film side. The temperature of the cold air may be room temperature (for example, 25 ° C.).

After cooling, when winding the metal foil with the flattening film around the core, a protective film may be stuck on the flattening film surface to protect the flattening film, and an interleaf paper is inserted to prevent scratches. May be. Further, in the film forming apparatus 100 shown in FIG. 2, the drying and the heat treatment are performed continuously, but the drying and the heat treatment may be performed independently. For example, after winding the metal foil with the dry film into a coil, only the heat treatment may be performed again to cure the dry film. In this case, two types of equipment, a drying treatment equipment and a heat treatment equipment, are installed. When the drying and the heat treatment are performed independently, there is an advantage that each processing can be set to an optimum passing speed.

実 施 Examples will be described below, but the present disclosure is not limited to these examples. In the following description, “parts” and “%” are all based on mass unless otherwise specified.

<Examples 1 to 8, Comparative Examples 1 to 5>
The mixing ratio and the manufacturing conditions of each example were carried out according to the conditions described in Table 1.
First, using a 1 L flask, the ingredients were blended so as to have the blending ratio shown in Table 1, and the raw materials were blended so that the total amount was 0.7 L.
After the preparation, the raw materials were stirred and mixed with a magnetic stirrer for 15 minutes, and refluxed at 80 ° C. for 3 hours under a nitrogen stream to promote hydrolysis. The results of the visual observation in the flask after the reflux are described in the column of “Properties of Hydrolyzed Solution”.

Thereafter, using a rotary evaporator, the temperature of the oil bath was set to 80 ° C., and the solvent was distilled off under reduced pressure to obtain a condensation reaction product.
Thereafter, an organic solvent immiscible with water was added in an amount equivalent to the weight of the condensation reaction product to dissolve the condensation reaction product. At this point, the condensation reaction product is dissolved at a solid concentration of 50% by mass.
The 1 L flask was connected to a reflux condenser equipped with a Dean-Stark trap, and heated to reflux. Table 1 shows the set temperature of the oil bath and the reflux time during heating and reflux.
After heating under reflux, an organic solvent immiscible with water was added to dilute the solid content to 30% by mass, and a filter having a pore size of 5 μm was set, followed by filtration under reduced pressure.
The viscosity of the coating solution at a solid concentration of 30% by mass was measured at 25 ° C. using a VISCOMATE VM-10A vibrating viscometer manufactured by CBC Corporation.

The yield was determined from the theoretical amount when the obtained filtrate and the raw material phenyltrialkoxysilane were subjected to a 100% condensation reaction and dissolved in the coating solution. The results are shown in the column of "Yield at 30% dilution". The yield was rated A (very good) for 93% or more, B (good) for less than 85% and less than 85%, and C (bad) for less than 85%.
Further, ²⁹ Si NMR and ¹³ C NMR measurements were performed on the coating solution, and the ratio of the alkoxy group to the total bond of Si and the ratio of the alcohol to Si (mol%) were determined by the above-described methods.

<Comparative Examples 6 and 7>
Comparative Examples 6 and 7 were carried out in accordance with the conditions shown in Table 1 with respect to the mixing ratio and the production conditions of each example.
Comparative Example 6 is an example synthesized according to Patent Document 3. Comparative Example 7 is an example in which the amount of water is increased based on the process of Patent Document 3. In Comparative Example 7, when only water was increased, turbidity was likely to be generated during hydrolysis. Therefore, ethanol was also added so as to easily occur after uniform hydrolysis.
First, using a 1 L flask, each component was blended so as to have a blend ratio shown in Table 1, and raw materials were blended so that the total amount was 0.7 L.
After the preparation, the raw materials were stirred and mixed with a magnetic stirrer for 15 minutes, and refluxed at 80 ° C. for 3 hours under a nitrogen stream to promote hydrolysis. The results of the visual observation in the flask after the reflux are described in the column of “Properties of Hydrolyzed Solution”.

Thereafter, using a rotary evaporator, the temperature of the oil bath was set at 180 ° C., and the solvent was distilled off under reduced pressure until fluidity disappeared, to obtain a condensation reaction product. The time until the fluidity disappeared was 20 minutes.
Thereafter, toluene was added to dilute the solid content concentration to 30% by mass, and a filter having a pore size of 5 μm was set, followed by filtration under reduced pressure.
The viscosity of the coating solution at a solid concentration of 30% by mass, the yield at a dilution of 30% by mass, the ratio of the alkoxy group to the total bond of Si, and the ratio of the alcohol to Si (mol%) were as in Examples 1 to 8. It was determined in the same manner as in Comparative Examples 1 to 5.

に お い て In all Examples and Comparative Examples, the obtained coating solution was spin-coated on a stainless steel foil through a filter having a pore size of 0.5 μm. As the stainless steel foil, SUS304MW (milk white finish) of 150 mm × 150 mm × 0.05 mm manufactured by Nippon Steel Chemical & Materials Co., Ltd. was used. The number of revolutions of the spin coater was set so that the film thickness became 3.0 μm. After spin coating, drying was performed in an oven at 80 ° C. for 1 minute, and then heat treatment was performed in a heat treatment furnace at 400 ° C. for 10 minutes to obtain a stainless steel foil with a flattening film in each example.

After the stainless steel foil with the flattening film is cut into a 50 mm square, it is attached to a glass plate of the same size and a thickness of 0.7 mm with a slightly adhesive sheet, and Ag (100) / MoO ₃ (5) / αNPD (140) / Alq 3 (30 ) / DPB: An organic EL light emitting element was formed with a configuration of Liq (45) / Al (1.5) / Ag (25) and sealed with a glass cap. Numerical values in parentheses in the element configuration indicate film thickness, and the unit is nm. The size of the light emitting region of the device is 2 mm square. αNPD, Alq3, DPB, and Liq are as shown below.
αNPD: (bis [N- (1-naphthyl) -N-phenyl] benzidine)
Alq3: (tris (8-hydroxyquinolinato) aluminum DPB: 1,4-dipyrenylbenzene Liq: 8-hydroxyquinolinolato-lithium

Next, the initial state of the light emitting surface was observed with an optical microscope in a state where 4.5 V was applied to the element to emit light. Next, the device was stored in a thermo-hygrostat at 60 ° C. and a relative humidity of 90% RH for 40 hours, then 4.5 V was applied again to observe the light emitting surface, and the shrinkage width of the light emitting surface from the cathode side was measured. . When the shrinkage width exceeded 50 μm, it was determined as C (impossible), when it was 50 μm or less, B (good), and when it was 20 μm or less, it was determined as A (very good). Those having cracks on the substrate are excluded from the evaluation because there is no point in performing element evaluation. The results are described in the column of “Shrinkage width after storage at 60 ° C. and 90% RH for 40 hours”.

Next, applicability (average number of repelling defects within 100 mm square) of the obtained coating liquid was evaluated as follows.
Four sides of three 150 mm × 150 mm spin-coated film-formed products were cut off by 25 mm each to obtain a size of 100 × 100 mm. They were observed with an optical microscope having a magnification of 100 times, and the occurrence frequency of repelling defects was examined. A (very good) if the number of repelling defects averaged over three is less than one per 100 mm square, B (good) if more than one and less than three, and C (if more than three) No). Those having cracks on the substrate did not function as a film in the first place, and were therefore excluded from the evaluation.

The overall evaluation in Table 1 was based on the following criteria.
A: Yield, shrinkage width, and applicability are all judged as A. B: At least one of yield, shrinkage width, and applicability is judged as B, and the rest is judged as A. C: Yield, shrinkage width, One or more of the applicability could not be evaluated or evaluated as C

 

塗布 Since the amount of the alkoxy group relative to Si was small and the viscosity of the coating solution was in an appropriate range, the coating solutions of Examples 1 to 8 obtained good results.

On the other hand, in the coating liquid of Comparative Example 1, both the hydrolysis reaction and the dehydration condensation reaction were insufficient because the amount of water added was too small. For this reason, the molecular weight of the condensation reaction product was small, and the viscosity at the time of 30 mass% dilution was also low. Also, the ratio of the alkoxy group to Si was high. It was shown that the shrinkage width after storage in a thermo-hygrostat for 40 hours was large, and the element was deteriorated early. In addition, since the residual amount of alcohol was large, the frequency of occurrence of repelling defects was high.

(4) Since acetic acid was not added to the coating liquid of Comparative Example 2, there was no effect of promoting hydrolysis by acid, and both the hydrolysis reaction and the dehydration condensation reaction were insufficient. For this reason, the molecular weight of the condensation reaction product was small, and the viscosity at the time of dilution by 30% by mass was low. Also, the ratio of the alkoxy group to Si was high. It was shown that the shrinkage width after storage in a thermo-hygrostat for 40 hours was large, and the element was deteriorated early. In addition, since the residual amount of alcohol was large, the frequency of occurrence of repelling defects was high.

(4) The coating liquid of Comparative Example 3 had an acid catalyst and water was added in a sufficient amount, but the condensation reaction did not proceed sufficiently because no organotin was added. For this reason, the molecular weight of the condensation reaction product was small, and the viscosity at the time of 30 mass% dilution was very low. A rapid dehydration-condensation reaction occurred in the heat treatment step after the spin coating, causing a large volume shrinkage, thereby causing cracks in the film and making it impossible to prototype the device. Since a sound film could not be obtained, the applicability could not be evaluated.

塗布 In the coating solution of Comparative Example 4, as in Comparative Example 1, the amount of water added was too small, and both the hydrolysis reaction and the dehydration condensation reaction were insufficient. Since the viscosity of the solvent immiscible with water was high, the viscosity of the coating solution was within an appropriate range, but the ratio of the alkoxy group to Si was high. It was shown that the shrinkage width after storage in a thermo-hygrostat for 40 hours was large, and the element was deteriorated early. Since cyclohexanone having a high boiling point was used, the removal of ethanol was progressing, and the content of alcohol was within an allowable range.

(4) In the coating liquid of Comparative Example 5, the amount of water added was slightly large, and the viscosity of the coating liquid at the time of 30% by mass dilution was too high. For this reason, it was not possible to form a film having a uniform film thickness by spin coating, cracks occurred from the thick film portion, and it was not possible to make a prototype of the device and to evaluate applicability. Since the amount of water at the time of synthesizing the coating liquid was large, the hydrolysis was in progress and the content of the alkoxy group was small. Since a cyclohexanone solvent having a high boiling point was used, the removal of ethanol proceeded and was not detected by NMR.

エ タ ノ ー ル Ethanol and water were removed from the coating liquid of Comparative Example 6 by distillation at 180 ° C. under reduced pressure. However, the amount of water was small, so that hydrolysis did not proceed completely and many ethoxy groups remained. Further, a small amount of water and ethanol also remained after the distillation under reduced pressure. Since water and ethanol remaining after the distillation under reduced pressure remain after being dissolved in toluene, the content of ethanol was large and repelling defects were large. Since the solvent was distilled off under reduced pressure at a high temperature of 180 ° C., the solubility in toluene was lowered, and the yield was lowered. It was shown that the ratio of the alkoxy group to Si was high, and the degree of shrinkage after storage in a thermo-hygrostat for 40 hours was large, and the element was deteriorated early.

The coating solution of Comparative Example 7 was subjected to hydrolysis by increasing the amount of water compared to the coating solution of Comparative Example 6, but after evaporating under reduced pressure at 180 ° C., it was tried to dissolve in toluene. A large amount of insolubles was generated, and the liquid became cloudy. It is presumed that when a large amount of water was added and distilled off under reduced pressure at a high temperature, more random condensates were insoluble in toluene than in the ladder polymer. More than half of the distillate under reduced pressure did not dissolve and could not be filtered under reduced pressure due to clogging, and the coating liquid and the film could not be evaluated.

The disclosure of Japanese Patent Application No. 2018-182233 is incorporated herein by reference in its entirety.
All documents, patent applications, and technical standards mentioned herein are to the same extent as if each individual document, patent application, and technical standard were specifically and individually stated to be incorporated by reference. Incorporated herein by reference.

Claims (10)

1. An organic solvent that is immiscible with water, and a phenylsilsesquioxane soluble in the organic solvent, a coating liquid for forming a flattening film,
   The viscosity of the coating liquid when the solid concentration of the phenylsilsesquioxane is 30% by mass and the liquid temperature is 25 ° C. is 2.5 mPa · s to 35 mPa · s,
   The content of the alkoxy group bonded to Si in the phenylsilsesquioxane is 0 to 5% based on all the bonds of Si.
   Coating liquid for forming flattening film.
2. The alkoxy group bonded to Si in the phenylsilsesquioxane is at least one selected from the group consisting of a methoxy group, an ethoxy group, and a propoxy group,
   The coating liquid for forming a flattening film according to claim 1.
3. The content of the alcohol with respect to Si in the phenylsilsesquioxane is 0 to 2.5 mol%,
   The coating liquid for forming a flattening film according to claim 1 or 2.
4. The phenylsilsesquioxane,
   Alcohol, phenyl trialkoxysilane, acetic acid, organotin, and water in an amount of 4.2 to 14 mole times based on 1 mole of the phenyl trialkoxysilane are mixed and hydrolyzed. Process and
   A step of producing a dehydration-condensation reaction product containing phenylsilsesquioxane, obtained by distilling off the alcohol under reduced pressure,
   Dissolving the dehydration-condensation reaction product in a water-immiscible organic solvent, while heating and refluxing at a temperature equal to or higher than the boiling point of the water-immiscible organic solvent, further dehydration condensation reaction to increase the molecular weight,
   Is a compound obtained at least through
   The coating liquid for forming a flattening film according to any one of claims 1 to 3.
5. Alcohol, phenyl trialkoxysilane, acetic acid, organotin, and water in an amount of 4.2 to 14 mole times based on 1 mole of the phenyl trialkoxysilane are mixed and hydrolyzed. Process and
   Proceeding the dehydration condensation reaction by distilling off the alcohol under reduced pressure to produce a dehydration condensation reaction product containing phenylsilsesquioxane,
   Dissolving the dehydration-condensation reaction product in a water-immiscible organic solvent, while heating and refluxing at a temperature equal to or higher than the boiling point of the water-immiscible organic solvent, further dehydration condensation reaction to increase the molecular weight,
   Having,
   A method for producing a coating liquid for forming a flattening film.
6. When the solid content of the phenylsilsesquioxane is 30% by mass and the liquid temperature is 25 ° C., the viscosity of the coating solution is 2.5 mPa · s to 35 mPa · s. The content of the alkoxy group bonded to Si is 0 to 5% based on all the bonds of Si;
   The method for producing a coating liquid for forming a flattening film according to claim 5, wherein the coating liquid for forming a flattening film is produced.
7. The amount of the acetic acid is 0.1 mol to 1 mol with respect to 1 mol of the phenyl trialkoxysilane, and the amount of the organotin is 0.005 mol to 0 mol with respect to 1 mol of the phenyl trialkoxysilane. 0.05 moles,
   A method for producing the coating liquid for forming a flattening film according to claim 5.
8. Metal foil,
   A flattening film which is provided on at least one surface of the metal foil and is made of a cured product of the coating solution for forming a flattening film according to any one of claims 1 to 4.
   Having,
   Metal foil with flattening film.
9. The metal foil is a stainless steel foil,
   A metal foil with a flattening film according to claim 8.
10. A step of applying the coating liquid for forming a flattening film according to any one of claims 1 to 4 to at least one surface of the metal foil;
    A step of reflowing and curing the applied coating liquid for forming a flattening film in a temperature range of 300 ° C. to 450 ° C. in an inert gas atmosphere to form a flattening film;
    Having,
    A method for producing a metal foil with a flattening film.

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