JP7473813B2 - Film-coated metal foil and method for producing film-coated metal foil - Google Patents

Description

The present invention relates to a film-coated metal foil and a method for manufacturing the film-coated metal foil.

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 manufactured on flexible substrates, they will not break even if dropped, and they can be developed into new fields that take advantage of their light weight and flexibility (for example, new fields such as wearable devices).

Conventionally, resin substrates such as polyimide resin substrates and polyethylene naphthalate (PEN) resin substrates have been considered as flexible substrates. However, resin substrates have poor gas barrier properties, which allows moisture to penetrate to electronic devices, degrading their performance.

Metal foils are also being considered as flexible substrates. Metal foils have high gas barrier properties and can prevent moisture from penetrating into electronic devices.
On the other hand, the surface of the metal foil has low flatness due to the presence of rolling marks, scratches, etc. Therefore, in order to use the metal foil as a flexible substrate, it is necessary to coat the surface of the metal foil with a film that provides insulation and flatness.
However, outgassing due to trace amounts of residue contained in the film can degrade the characteristics of electronic devices.

As a metal foil to be applied to a flexible substrate, for example, a film-coated metal foil using a film-forming coating liquid as disclosed in Patent Documents 1 to 3 is known.

Specifically, Patent Document 1 discloses a film-forming coating liquid in which "0.1 to 1 mol of acetic acid and 0.005 to 0.05 mol of organotin are added as catalysts to 1 mol of phenyltrialkoxysilane in an organic solvent, hydrolysis is performed with 2 to 4 mol of water, and the organic solvent is distilled off under reduced pressure at a temperature of 160°C to 210°C to obtain a resin, which is then dissolved in an aromatic hydrocarbon solvent."

Patent Document 2 also discloses a coating liquid for forming a flattening film, which is prepared by mixing alcohol, phenyltrialkoxysilane, acetic acid, organotin, one or more metal alkoxides selected from Ti, Zr, Nb, and Ta, and distilling the mixture under reduced pressure at a temperature of 80°C to 130°C to obtain a condensation reaction product, dissolving the product in an organic solvent, and removing the water by heating under reflux to produce a phenylsilsesquioxane ladder polymer, wherein the amount of the metal alkoxide is 0.005 to 0.05 per mole of phenyltrialkoxysilane, and the viscosity at 25°C when the solid content is 30 mass% is 3.5 mPa·s to 35 mPa·s.

Patent Document 3 also discloses "a coating liquid for forming a flattening film that contains phenyl silsesquioxane that is soluble in an organic solvent, the viscosity of which is 2.5 mPa·s to 35 mPa·s when the solids concentration of the phenyl silsesquioxane is 30 mass %, and the content of alkoxy groups bonded to Si in the phenyl silsesquioxane is 0 to 5% relative to Si."

International Publication No. WO2016/076399 JP 2019-99775 A International Publication No. WO/2020/067467

The coating liquid for forming a planarizing film in Patent Document 1 is a coating liquid that is moisture resistant and can form a planarizing film in which the generation of alcohol is suppressed even in a high-temperature, high-humidity environment. As a result, Patent Document 1 can improve the life of an electronic device that includes a metal foil with a planarizing film.

The coating liquids for forming the planarizing film in Patent Documents 2 and 3 are coating liquids that can obtain planarizing films with excellent moisture resistance so as not to adversely affect organic semiconductors that are sensitive to moisture. As a result, Patent Documents 2 and 3 can improve the lifespan of electronic devices that include metal foils with planarizing films.

However, due to recent demands, there is a demand for film-coated metal foils that can further improve the lifespan of electronic devices.

The objective of the present invention is to provide a film-coated metal foil that can improve the lifespan of electronic devices, and a method for manufacturing the film-coated metal foil.

Means for solving the above problems include the following aspects.
＜1＞
Metal foil;
a film formed on at least one surface of the metal foil, the film being composed of a phenylsiloxane polymer in which the ratio of alkoxy groups to all Si bonds is 2.5% or less and the ratio of Q nuclei to all Si nuclei is 5.5% or more and 15.0% or less;
The film-coated metal foil has a film-coated metal foil having a film-coated metal foil.
＜2＞
the ratio of alkoxy groups to the total bonds of the Si is 1.5% or less,
The film-coated metal foil according to <1>, wherein the ratio of Q nuclei to all Si nuclei is 7.0% or more and 15.0% or less.
＜3＞
A step of preparing a coating solution for forming a film, the coating solution including an organic solvent and a hydrolysis/dehydration/condensation reaction product of a phenyltrialkoxysilane, the ratio of alkoxy groups to all bonds of Si being 0 to 20%, dissolved in the organic solvent;
a step of applying the coating liquid onto at least one surface of a metal foil, drying the coating liquid to form a dried film of the coating liquid, and then heat-treating the dried film at a temperature of 380 to 450° C. in an oxygen-containing inert gas atmosphere with an oxygen concentration y that satisfies the following formulas (1) to (4), where x (%) is a ratio of alkoxy groups to all bonds of Si in the hydrolysis/dehydration/condensation reaction product of the phenyltrialkoxysilane, and y (ppm by volume) is an oxygen concentration, thereby forming a film composed of a phenylsiloxane polymer;
A method for producing a film-coated metal foil having the above structure.
Formula (1): _yA ≦y≦ _yB
Formula (2): _yA = ^x2 + 50
Formula (3): y _B = 8x ² + 300
Formula (4): x = 0 to 20

The present invention provides a film-coated metal foil that can improve the life of electronic devices, and a method for manufacturing the film-coated metal foil.

FIG. 2 is an explanatory diagram for explaining the structures of T ¹ , T ² , and T ³ in phenylsilsesquioxane or phenylsiloxane. FIG. 2 is a schematic diagram showing an example of a film-forming apparatus applied to the "film-forming step" in the method for producing a film-coated metal foil according to the present embodiment. FIG. 1 is a schematic partial cross-sectional view showing an example of a film-coated metal foil according to an embodiment of the present invention. FIG. 1 is a schematic diagram of a phenylsilsesquioxane ladder polymer. FIG. 2 is a schematic diagram of a phenylsiloxane polymer in which the structure of a phenylsilsesquioxane ladder polymer is changed by heat treatment.

Hereinafter, an embodiment of the present invention will be described as an example.
In this specification, a numerical range expressed using "to" means a range that includes the numerical values before and after "to" as the lower and upper limits.
In a numerical range described in stages, the upper limit value described in a certain numerical range may be replaced with the upper limit value of another numerical range described in stages, and the lower limit value described in a certain numerical range may be replaced with the lower limit value of another numerical range described in stages.
In a numerical range, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the examples.
The term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved.

<Metal foil with film>
The film-coated metal foil according to this embodiment has a metal foil and a film provided on at least one surface of the metal foil.
The film is a film composed of a phenylsiloxane polymer in which the ratio of alkoxy groups to all Si bonds is 2.5% or less, and the ratio of Q nuclei to all Si nuclei is 5.5% or more and 15.0% or less.

The film-coated metal foil of this embodiment can improve the lifespan of electronic devices. The reason for this is presumed to be as follows.

In a film made of phenylsiloxane polymer, if the proportion of alkoxy groups in the polymer is high, the alkoxy groups in the film will be hydrolyzed over time by moisture in the air. This will produce alcohol that reduces the performance of electronic devices, shortening their lifespan.

On the other hand, ideally, when a dry film composed of a phenylsilsesquioxane ladder polymer is heat-treated, the phenyl group is not eliminated and no Q nuclei are generated. Phenylsiloxane polymers with few Q nuclei have almost no crosslinking points and are therefore soluble in organic solvents. Therefore, by washing the film-coated metal foil with an organic solvent before device fabrication, the film composed of the phenylsiloxane polymer becomes easily peeled off, shortening the life of the electronic device. In addition, the film composed of the phenylsiloxane polymer dissolves in alcohol generated by hydrolysis of the alkoxy group, shortening the life of the electronic device.
Conversely, a film composed of a phenylsiloxane polymer in which Q nuclei are present in excess has low flexibility and is prone to cracking when bent, shortening the life of the electronic device.

In contrast, by using a film made of a phenylsiloxane polymer in which the ratio of alkoxy groups to all Si bonds is reduced to 2.5% or less, the production of alcohol caused by hydrolysis of the alkoxy groups is suppressed.
Furthermore, by forming a film composed of a phenylsiloxane polymer in which the ratio of Q nuclei to all Si nuclei is adjusted to 5.5% or more and 15.0% or less, peeling of the film due to organic solvents is suppressed, the flexibility of the film is ensured, and cracks are suppressed.

Therefore, it is speculated that the film-coated metal foil according to this embodiment can improve the lifespan of electronic devices.

The details of the film-coated metal foil according to this embodiment are described below.

(Metal foil)
The metal foil is not particularly limited, and examples thereof include aluminum foil, copper foil, titanium foil, stainless steel foil, etc. Among these, stainless steel foil is preferred. Stainless steel foil is suitable as a flexible substrate for electronic devices because it is easy to manufacture industrially at low cost and is less likely to break.
The stainless steel foil may be any of austenitic, ferritic, and martensitic stainless steel foils, with austenitic or ferritic stainless steel foils being preferred from the viewpoint of application to flexible substrates.
The thickness of the metal foil is not particularly limited, and may be, for example, 10 μm to 100 μm.

When using stainless steel foil, since stainless steel foil has a low reflectance (reflectance 60%), a reflective film may be formed on at least one surface of the stainless steel foil (specifically, the surface on which the film is to be formed).
When a top-emission organic EL lighting device, organic EL display, etc. is manufactured as an electronic device using a transparent lower electrode, light is repeatedly reflected on the surface of the stainless steel foil. If the reflectance of the stainless steel foil is about 60%, a lot of light is lost and the efficiency of the device decreases. In contrast, if a reflective film (for example, with 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, and the efficiency of the device is significantly improved. For example, types of reflective films having a high reflectance of about 95% include pure Al, Al alloys, pure Ag, and Ag alloys. Examples of Al alloys include Al-Si and Al-Nd alloys. Examples of Ag alloys include alloys such as Ag-Nd and Ag-In. The reflective film can be formed by a sputtering method or the like.

An insulating film may be provided on at least one surface of the metal foil (specifically, the surface on which the film is formed). By using a metal foil coated with an insulating film, the insulating properties of the metal foil after film formation are more highly and reliably achieved. The type of insulating film is not particularly limited, and examples thereof include metal oxides (silica, alumina, etc.), inorganic salts (aluminum phosphate, calcium phosphate, etc.), and heat-resistant resins (polyimide, polytetrafluoroethylene, etc.).
The insulating coating of metal oxide can be formed by a method such as sputtering, vapor deposition, CVD, etc. The insulating coating of inorganic salt can be formed by a coating method such as a roll coater or spray.
The heat-resistant resin insulating coating can be formed by a coating method such as a comma coater, a die coater, or a spray.

(Coating Liquid)
The film is formed by heat treating a dried film of a film-forming coating liquid (hereinafter also referred to as "coating liquid").
The coating solution contains a phenylsilsesquioxane ladder polymer (hereinafter, also simply referred to as "phenylsilsesquioxane") as a hydrolysis/dehydration/condensation reaction product of phenyltrialkoxysilane (see FIG. 4). The dried film of the coating solution is a film composed of phenylsilsesquioxane.

In order to investigate the molecular structure of phenylsilsesquioxane, ²⁹ Si NMR and ¹³ C NMR measurements are performed using NMR measurement devices "ECZ-600" and "ECA-400" (both manufactured by JEOL RESONANCE Co., Ltd.). A sample solution prepared by adding an appropriate amount of a toluene solution containing 30 mass% phenylsilsesquioxane to the inner tube of a double sample tube for NMR measurement, and heavy benzene (C ₆ D ₆ ) as a lock solvent to the outer tube, is used for the measurement. As the chemical shift standard, tetramethylsilane is set to 0.0 ppm for ²⁹ Si, and the methyl group carbon of the solvent toluene is set to 20.43 ppm for ¹³ C. In the ²⁹ Si NMR spectrum, peaks of T ¹ , T ² and T ³ are observed at −67.5, −72.1 and −77.9 ppm, respectively, and from the peak area ratio, the abundance ratios of T ¹ , T ² and T ³ are calculated to be 8.6 mol %, 29.9 mol % and 61.5 mol %, respectively.

Figure 1 shows the structures of ^T1 , ^T2 , and ^T3 in phenylsilsesquioxane. From the ^13C 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 ratios of each component are calculated to be 388.2 mol%, 2.0 mol%, 100 mol%, and 13.1 mol%, respectively. Calculations are made so that the mol% of Si-Ph is 100.
In addition, when a peak is buried in the background in the NMR spectrum and is not observed, the corresponding component is considered not to be present.

In the case of Si in ^T3 , all three ethoxy groups have undergone hydrolysis and condensation reactions to form Si-O-Si bonds. On the other hand, in ^T2 and ^T1 , terminal groups that have not undergone condensation remain. For one mole of Si, ^T1 has two moles of terminal groups, and ^T2 has one mole of terminal groups. Si has four bonds, one of which is bonded to a phenyl group. The remaining three bonds are either Si-O-Si bonds or terminal groups. If the total Si is 100, the number of Si-O-Si bonds is 3 x 61.5 + 2 x 29.9 + 8.6 = 253.2, and the number of terminal groups is 2 x 8.6 + 29.9 = 47.1. From this, it can be calculated that of the total bonds of Si, phenyl groups make up 25%, Si-O-Si bonds make up 75 x 253.2/(253.2 + 47.1) = 63.3%, and terminal groups make up 11.8%.

As shown by ¹³ C NMR, there are two types of terminal groups, Si-OH groups and Si-OEt groups. When Si is 1, T ¹ has two terminal groups and T ² has one terminal group. If the ratio of Si-OEt groups is a and the ratio of Si-OH groups is 1-a, when Si is 100, the ethoxy groups in the coating liquid are 2×8.6×a+29.9×a=47.1a. Since the number of phenyl groups and Si is the same in all of T ¹ , T ² , and T ³ , when Si is 100, there are also 100 phenyl groups. On the other hand, since it is known from ¹³ C that the ratio (molar ratio) of phenyl groups to ethoxy groups is 100:13.1, a is 0.277. Therefore, the breakdown of the above 11.8% terminal groups is 3.3% Si-OEt groups and 8.5% Si-OH groups.
The content of Si-OEt groups relative to all silicon bonds in the phenylsilsesquioxane measured as above can be estimated to be 3.3%.

The phenylsilsesquioxane ladder polymer is a polymer whose main chain structure is composed of Si—O bonds, and has a ladder structure represented by [(RSiO _1.5 ) _n ] in which at least some of the R's have phenyl groups.

Whether the phenylsilsesquioxane ladder polymer has a ladder structure can be confirmed by the following measurement.
First, although a phenylsilsesquioxane ladder polymer was synthesized in the study by Brown et al., it is not possible to define a phenylsilsesquioxane polymer as a polymer having a ladder structure, and it is necessary to estimate whether the polymer has a ladder structure based on experimental facts. Specifically, for example, the following is true.
A toluene solution containing 30% by weight of phenylsilsesquioxane is prepared.
Next, a toluene solution containing 30% by mass of phenylsilsesquioxane is analyzed by gel permeation chromatography (GPC) to determine the weight average molecular weight in terms of styrene. It is confirmed whether the weight average molecular weight is 5,000 to 100,000 and whether the phenylsilsesquioxane has solubility in organic solvents.
Next, a toluene solution containing 30% by mass of phenylsilsesquioxane is placed on a hot plate heated to 150° C. to evaporate the solvent, and it is confirmed whether the polymer exhibits spinnability.
Next, it is confirmed whether or not the infrared absorption spectrum shows a double peak attributable to siloxane bonds near 1100 cm ⁻¹ .
If the analyzed phenylsilsesquioxane polymer has a weight average molecular weight of 5,000 to 100,000, is soluble in an organic solvent, exhibits spinnability, and exhibits a double peak derived from siloxane bonds, the phenylsilsesquioxane polymer is estimated to be a polymer having a ladder structure.

(film)
The film is provided on at least one surface of the metal foil. That is, the film may be provided on both rolled surfaces of the metal foil, or may be provided only on one rolled surface. Electronic device elements (e.g., organic EL lighting elements) are generally often fabricated only on one surface of a substrate. Therefore, the film may be provided only on one surface of the metal foil.

The film is composed of a phenylsiloxane polymer (hereinafter also simply referred to as "phenylsiloxane"). Specifically, the film is a phenylsiloxane film. However, the phenylsiloxane film may contain impurities such as one or more metal elements selected from Sn, Al, Ti, Zr, Nb, and Ta in a total amount of 2 mass% or less.

Here, the film is obtained by coating the coating liquid, drying, and heat treatment. The coating liquid contains a phenylsilsesquioxane ladder polymer represented by [(RSiO _1.5 ) _n ] as a hydrolysis dehydration condensation reaction product of phenyltrialkoxysilane, but by heat treatment of the dried film of the coating liquid, the phenylsilsesquioxane ladder polymer undergoes thermal decomposition of the phenyl group, the Q nucleus increases, and the phenylsilsesquioxane ladder structure is no longer formed, and the phenylsilsesquioxane polymer is converted to a phenylsiloxane polymer that cannot be represented by [(RSiO _1.5 ) _n ]. As a result, the film composed of the phenylsiloxane polymer loses its solubility in organic solvents (see FIG. 5).

In the phenylsiloxane, the ratio of alkoxy groups to all silicon bonds is 2.5% or less.
By keeping the proportion of alkoxy groups at 2.5% or less, the generation of alcohol due to hydrolysis of the alkoxy groups in the film is suppressed, thereby improving the element life of the electronic device.
The proportion of alkoxy groups is preferably 2.0% or less, 1.6% or less, 1.4% or less, 1.2% or less, 1.0% or less, or 0.5% or less. The proportion of alkoxy groups is most preferably 0%.

The alkoxy group may be at least one selected from the group consisting of a methoxy group, an ethoxy group, and a propoxy group. The alkoxy group is preferably an ethoxy group.

The proportion of alkoxy groups is the amount of alkoxy groups bonded to silicon in the phenylsiloxane, and is the amount of alkoxy groups relative to the total number of bonds to silicon. In other words, the proportion of alkoxy groups is the amount of -Si-O-R groups (R: methyl, ethyl, propyl, etc.) bonded to silicon in the phenylsiloxane (relative to the total number of bonds to silicon).

The proportion of alkoxy groups (i.e., the content of alkoxy groups bonded to Si) is a value measured by NMR. Specifically, it is measured as follows.
When a phenyltrialkoxysilane other than phenyltriethoxysilane is used as the raw material, or when a solvent other than toluene is used, the peak positions in the NMR spectrum will differ, but the measurement and calculation methods will be similar.

To investigate the molecular structure of phenylsiloxane, ²⁹ Si NMR and ¹³ C NMR measurements are performed using NMR measurement devices "AVANCE400" and "AVANCE400 III" (both manufactured by Bruker Corporation), respectively. The film alone is cut out from the film-coated metal foil and filled into a 7 mm diameter sample tube for NMR measurement, and the measurements are performed. The sample rotation speed is 6 kHz for ²⁹ Si NMR and 13 kHz for ¹³ C NMR. The chemical shift standard is -9.66 ppm for hexamethylcyclotrisiloxane for ²⁹ Si, and 17.35 ppm for the methyl group of hexamethylbenzene for ¹³ C. In the ²⁹ Si NMR spectrum, peaks of T ¹ , T ² and T ³ are observed at −67.5, −72.1 and −77.9 ppm, respectively, and from the peak area ratio, the abundance ratios of T ¹ , T ² and T ³ are calculated to be 8.6 mol %, 29.9 mol % and 61.5 mol %, respectively.

Figure 1 shows the structures of ^T1 , ^T2 , and ^T3 in phenylsiloxane. From the ^13C 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 to be 388.2 mol%, 2.0 mol%, 100 mol%, and 13.1 mol%, respectively. The calculations are made so that the mol% of Si-Ph is 100.
In addition, when a peak is buried in the background in the NMR spectrum and is not observed, the corresponding component is considered not to be present.

In the case of Si in ^T3 , all three ethoxy groups have undergone hydrolysis and condensation reactions to form Si-O-Si bonds. On the other hand, in ^T2 and ^T1 , terminal groups that have not undergone condensation remain. For one mole of Si, ^T1 has two moles of terminal groups, and ^T2 has one mole of terminal groups. Si has four bonds, one of which is bonded to a phenyl group. The remaining three bonds are either Si-O-Si bonds or terminal groups. If the total Si is 100, the number of Si-O-Si bonds is 3 x 61.5 + 2 x 29.9 + 8.6 = 253.2, and the number of terminal groups is 2 x 8.6 + 29.9 = 47.1. From this, it can be calculated that of the total bonds of Si, phenyl groups make up 25%, Si-O-Si bonds make up 75 x 253.2/(253.2 + 47.1) = 63.3%, and terminal groups make up 11.8%.

As shown by ¹³ C NMR, there are two types of terminal groups, Si-OH groups and Si-OEt groups. When Si is 1, T ¹ has two terminal groups and T ² has one terminal group. If the ratio of Si-OEt groups is a and the ratio of Si-OH groups is 1-a, when Si is 100, the ethoxy groups in the coating liquid are 2×8.6×a+29.9×a=47.1a. Since the number of phenyl groups and Si is the same in all of T ¹ , T ² , and T ³ , when Si is 100, there are also 100 phenyl groups. On the other hand, since it is known from ¹³ C that the ratio (molar ratio) of phenyl groups to ethoxy groups is 100:13.1, a is 0.277. Therefore, the breakdown of the above 11.8% terminal groups is 3.3% Si-OEt groups and 8.5% Si-OH groups.
The content of Si-OEt groups relative to all silicon bonds in the phenylsiloxane measured as above can be estimated to be 3.3%.

In the phenylsiloxane polymer, the ratio of Q nuclei to all Si nuclei is 5.5% or more and 15.0% or less.
Phenylsiloxane polymer is a polysiloxane compound, and the Si core as a basic structure includes M core ( _{R3SiO1 /2} ), D core ( _{R2SiO2 /2} ), T core (RSiO3 _/2 ) and Q core (SiO4 _/2 ). Here, R represents a substituent such as a phenyl group. The M core, D core, T core and Q core are also called M unit, D unit, T unit and Q unit.
The total Si nuclei include M nuclei, D nuclei, T nuclei and Q nuclei, and the ratio of these Q nuclei is the ratio to these M nuclei, D nuclei, T nuclei and Q nuclei.

By making the ratio of Q nuclei 5.5% or more, peeling of the film due to organic solvents is suppressed.
By setting the ratio of Q nuclei to 15.0% or less, the flexibility of the film is ensured and cracks are suppressed.
Therefore, by setting the proportion of Q nuclei within the above range, the life span of electronic devices can be improved. The proportion of Q nuclei is preferably 7.0% or more and 15.0% or less, and more preferably 9.0% or more and 12.0% or less.

The proportion of Q nuclei is a value measured as follows.
²⁹ Si NMR was measured using an NMR measurement device "AVANCE 400III" (both manufactured by Bruker). The film was cut out from the film-coated metal foil and filled into a 7 mm diameter sample tube for NMR measurement. The sample rotation speed was 6 kHz. Hexamethylcyclotrisiloxane was used as the chemical shift standard at -9.66 ppm. ²⁹ Si In the NMR spectrum, the peaks of T1, T2, and T3 are observed at -68 ppm, -71 ppm, and -77 ppm, respectively, and the peak of Q nucleus is observed at -107 ppm. From the peak area ratio, the abundance ratios of T1, T2, and T3 are calculated to be 9.91 mol%, 5.53 mol%, and 38.71 mol%, respectively. From the peak areas of the spin side bands of T nucleus and Q nucleus observed at 75, 0 ppm, -150 ppm, and -230 ppm in addition to T1, T2, and T3, respectively, the proportion of Q nucleus is calculated as the peak area of Q nucleus/(the sum of T1+T2+T3+the spin side bands of T nucleus+the peak area of Q nucleus).

<Method of manufacturing film-coated metal foil>
The method for producing the film-coated metal foil according to the present embodiment includes, for example, the following two methods.

(1) When the "hydrolysis, dehydration, and condensation reaction product of phenyltrialkoxysilane" contained in the coating liquid for film formation does not contain Q nuclei, when the dried film after the coating liquid for film formation is applied to the metal foil and then heat-treated, the oxygen concentration in the inert gas atmosphere is controlled according to the ratio of alkoxy in the "hydrolysis, dehydration, and condensation reaction product of phenyltrialkoxysilane", and Q nuclei are generated by thermal decomposition of the phenyl group during the heat treatment in the inert gas atmosphere, thereby forming a film composed of a phenylsiloxane polymer having a predetermined ratio of Q nuclei (hereinafter referred to as the manufacturing method for film-coated metal foil according to the first embodiment).

(2) When producing a coating solution for film formation, a method is used in which, in addition to phenyltriethoxysilane, a tetraalkoxysilane having a Q nucleus is used to produce a coating solution for film formation that contains a "hydrolysis/dehydration/condensation reaction product of phenyltrialkoxysilane" having a predetermined Q nucleus (hereinafter referred to as the method for producing a film-coated metal foil according to the second embodiment).

First Embodiment
Hereinafter, the method for producing the film-coated metal foil according to the first embodiment will be described.
The method for producing a film-coated metal foil according to the first embodiment includes the steps of:
A step of preparing a coating solution for forming a film, the coating solution including an organic solvent and a hydrolysis/dehydration/condensation reaction product of a phenyltrialkoxysilane, the ratio of alkoxy groups to all bonds of Si being 0 to 20%, dissolved in the organic solvent;
a step of applying the coating liquid onto at least one surface of a metal foil, drying the coating liquid to form a dried film of the coating liquid, and then heat-treating the dried film to form a film composed of a phenylsiloxane polymer;
has.

In the film-forming process, the ratio of alkoxy groups to all Si bonds in the hydrolysis/dehydration/condensation reaction product of phenyltrialkoxysilane is x (%), and the oxygen concentration is y (ppm by volume). The dried film is heat-treated at a temperature of 380 to 450°C in an inert gas atmosphere containing oxygen, with the oxygen concentration y satisfying the following formulas (1) to (4), to form a film composed of a phenylsiloxane polymer.

Formula (1): _yA ≦y≦ _yB
Formula (2): _yA = ^x2 + 50
Formula (3): y _B = 8x ² + 300
Formula (4): x = 0 to 20

The method for producing a film-coated metal foil according to the first embodiment can produce a film-coated metal foil having a film composed of a phenylsiloxane polymer in which the ratio of alkoxy groups to all Si bonds is 1.5% or less, and the ratio of Q nuclei to all Si nuclei is 7.0% or more and 15.0% or less. In other words, a film-coated metal foil that can improve the lifespan of electronic devices can be produced. The reasons for this are as follows.

First, the inventors obtained the following findings.
The molecular structure of the phenylsilsesquioxane ladder polymer, which is a product of hydrolysis, dehydration, and condensation reaction of phenyltrialkoxysilane contained in the coating solution, does not change during the drying process, but changes during the heat treatment process. During the heat treatment process, the phenylsilsesquioxane ladder polymer changes to a structure containing Q nuclei due to thermal decomposition of the phenyl groups, becoming a phenylsiloxane polymer (see FIG. 5).
The generation of Q nuclei in phenylsilsesquioxane ladder polymer is greatly affected by the presence of organotin and the oxygen concentration during heat treatment. The lower the oxygen concentration during heat treatment, the easier it is for Q nuclei to be generated, and the number of Q nuclei increases. When the oxygen concentration is less than 50 ppm, Q nuclei are difficult to generate. On the other hand, when the oxygen concentration during heat treatment is increased, the organic group (such as butyl group) bonded to the organotin is decomposed, and the organotin forms a Sn=O bond, so that the function of promoting the detachment of the phenyl group is lost, and Q nuclei are difficult to generate. Generally, the higher the oxygen concentration during heating, the easier it is for organic groups to be decomposed, so the higher the oxygen concentration, the more the decomposition of alkoxy groups is promoted.

In addition, if the temperature during heat treatment is low, the decomposition of the phenyl group does not progress, making it difficult for the Q nucleus to be generated. On the other hand, if the temperature during heat treatment is high, the decomposition of the phenyl group progresses, making it easier for the Q nucleus to be generated.

And if there are too many alkoxy groups in the hydrolysis-dehydration-condensation reaction product of phenyltrialkoxysilane in the coating solution for film formation, the film shrinks too much due to the elimination of the alkoxy groups, causing cracks in the film.

The inventors therefore investigated the heat treatment conditions for forming a film composed of a phenylsiloxane polymer with a low proportion of alkoxy groups and a proportion of Q nuclei within a specified range. As a result, the inventors discovered that a film composed of the desired phenylsiloxane polymer can be formed by heat treating a dried film at a temperature of 380 to 450°C in an inert gas atmosphere containing oxygen with an oxygen concentration y that satisfies the above formulas (1) to (4).

Below, we will explain in detail each step of the manufacturing method for the film-coated metal foil according to the first embodiment.

--Process of preparing a coating solution for film formation--
In the step of preparing a coating liquid for forming a film, a hydrolysis/dehydration/condensation reaction product of a phenyltrialkoxysilane is generated, and a coating liquid for forming a film is prepared, the coating liquid containing the hydrolysis/dehydration/condensation reaction product of the phenyltrialkoxysilane, which is soluble in the organic solvent and has an alkoxy group ratio of 0 to 20% relative to the total bonds of Si.

The method for producing the coating solution for film formation is not particularly limited. For example,
a step of mixing phenyltrialkoxysilane, alcohol, acetic acid, organotin and water to hydrolyze the phenyltrialkoxysilane to produce a hydrolysis product of the phenyltrialkoxysilane (hereinafter referred to as the "hydrolysis step");
a step of distilling off the alcohol under reduced pressure to dehydrate and condense the hydrolysis product of the phenyltrialkoxysilane to produce a dehydration and condensation reaction product of the phenyltrialkoxysilane (hereinafter referred to as the "concentration step");
and a step of dissolving the dehydration-condensation reaction product of phenyltrialkoxysilane in a water-immiscible organic solvent, and further promoting the dehydration-condensation reaction of the dehydration-condensation reaction product of phenylsilsesquioxane while heating and refluxing at a temperature equal to or higher than the boiling point of the water-immiscible organic solvent, thereby polymerizing the dehydration-condensation reaction product of phenyltrialkoxysilane (hereinafter referred to as the "polymerization step").

--Hydrolysis step--
The hydrolysis step is preferably carried out by mixing organotin, acid and water with phenyltrialkoxysilane in alcohol. For example, it may be carried out as follows. First, a mixed solution is prepared by mixing alcohol and phenyltrialkoxysilane. Next, organotin and acid are mixed with this mixed solution, and water is further mixed to carry out hydrolysis of phenyltrialkoxysilane. A mixed solution of alcohol, phenyltrialkoxysilane and organotin may be mixed with acid and further mixed with water. A first mixed solution of alcohol, phenyltrialkoxysilane and organotin may be mixed with a second mixed solution of acid and water to carry out hydrolysis. In order to promote the hydrolysis reaction, reflux may be carried out at about 80° C. under a nitrogen stream.

From the viewpoint of promoting the hydrolysis of phenyltrialkoxysilane, the amount of acid is preferably in the range of 0.1 mol to 1 mol per mol of phenyltrialkoxysilane. When the amount of acid per mol of phenyltrialkoxysilane is 0.1 mol or more, the phenylsilsesquioxane is polymerized. If the amount of acid exceeds 1 mol, the effect of polymerizing the phenylsilsesquioxane is saturated.

The amount of organotin is preferably 0.005 to 0.05 mol per mole of phenyltrialkoxysilane in order to promote the polycondensation reaction of phenylsilsesquioxane. If the amount of organotin per mole of phenyltrialkoxysilane is 0.005 mol or more, the condensation reaction of phenylsilsesquioxane during heat treatment after application to the metal foil is promoted. In addition, the film is less likely to crack. If the amount is 0.05 mol or less, gelation of phenylsilsesquioxane is less likely to occur during the hydrolysis stage before vacuum distillation.

Here, the components used in the hydrolysis step will be described.
The phenyltrialkoxysilane is not particularly limited. Examples thereof include phenyltrimethoxysilane, phenyltriethoxysilane, phenyltripropoxysilane (phenyltri-n-propoxysilane, phenyltri-iso-propoxysilane), phenyltributoxysilane (phenyltri-n-butoxysilane, phenyltri-sec-butoxysilane, phenyltri-tert-butoxysilane), and the like. Among these, phenyltriethoxysilane is preferred from the viewpoint of being industrially mass-produced and easily available.

The amount of water used for hydrolysis is 2 to 20 moles per mole of phenyltrialkoxysilane, from the viewpoint of controlling the ratio of alkoxy groups to all bonds of Si in the hydrolysis/dehydration/condensation reaction product of phenyltrialkoxysilane to 0 to 20%, and the preferred amount of water is 6 to 12 moles.
When phenyltrialkoxysilane is hydrolyzed in alcohol using acid and organotin as catalyst, adding water in an amount of 6 to 12 moles per mole of phenyltrialkoxysilane makes it easier to reduce the alkoxy groups at the hydrolysis stage. Since the hydrolysis reaction is an equilibrium reaction with the alcohol addition reaction, a certain amount of alkoxy groups remains. Then, in the next concentration step, when the alcohol is distilled off under reduced pressure, the alcohol with a high vapor pressure is removed from the system preferentially over water. Therefore, it is considered that the equilibrium reaction between the hydrolysis reaction and the alcohol addition reaction is shifted, the hydrolysis proceeds further, and the alkoxy groups are further reduced.

The alcohol is used when hydrolyzing the phenyltrialkoxysilane. There is no particular limitation on the alcohol, and examples of the alcohol include methanol, ethanol, propanol (n-propanol, iso-propanol), and butanol (n-butanol, iso-butanol).

The acid and organotin are catalysts. The acid is a catalyst that promotes hydrolysis. The organotin is a catalyst that promotes phenyltrialkoxysilane and the dehydration condensation reaction after hydrolysis.

The acid includes acetic acid, hydrochloric acid, nitric acid, formic acid, etc., with acetic acid being preferred.
Examples of the organotin include dibutyltin diacetate, bis(acetoxydibutyltin)oxide, dibutyltin bisacetylacetonate, dibutyltin bismaleic acid monobutyl ester, dioctyltin bismaleic acid monobutyl ester, bis(lauroxydibutyltin)oxide, etc. Among these, dibutyltin diacetate and dibutyltin bisacetylacetonate are particularly preferred as the organotin.

The water is not particularly limited, but examples include distilled water, ion-exchanged water, ultrafiltered water, and pure water.

--Concentration process--
In the concentration step, the alcohol is distilled off under reduced pressure, and the hydrolysis product of phenyltrialkoxysilane is dehydrated and condensed to produce a dehydration and condensation reaction product of phenyltrialkoxysilane. 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 120° C. under reduced pressure. In the concentration step, a dehydration and condensation reaction product is obtained in which almost 100% hydrolyzed phenyltrialkoxysilane is partially dehydrated and condensed.

It is preferable to adjust the temperature, degree of vacuum, and time to advance the dehydration condensation reaction of the partial dehydration condensation reaction product. Specifically, it is preferable to adjust the weight of the dehydration condensation reaction product to be 1.04 to 1.11 times the molecular weight of the product (i.e., C ₆ H ₅ SiO _3/2 ) obtained when 1 mole of phenyltrialkoxysilane is completely dehydration condensed, which is 129.

In the concentration step, the alcohol is almost completely removed at the end of the step, resulting in a state close to no solvent, so that if the hydrolyzed molecules collide with each other, dehydration condensation is likely to proceed even if there is steric hindrance. Therefore, oligomers containing a large amount of the above-mentioned T ¹ and T ² (see FIG. 1) are likely to be produced. If such oligomers undergo dehydration condensation, undesirable reactions will occur in the high molecular weight step. For this reason, it is preferable that the oligomers are not large 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 C ₆ H ₅ SiO _3/2 (129), it can be considered that the monomer, dimer, and oligomer of the hydrolyzed product of phenyltrialkoxysilane are mixed.

--Molecular weight increasing process--
In the polymerizing step, the dehydration-condensation reaction product of the phenyltrialkoxysilane is dissolved in a water-immiscible organic solvent, and the dehydration-condensation reaction of the phenylsilsesquioxane is further promoted by heating and refluxing at a temperature equal to or higher than the boiling point of the water-immiscible organic solvent.
In the high molecular weight step, it is preferable to dissolve the dehydration condensation reaction product of the phenyltrialkoxysilane obtained in the concentration step (i.e., the partial dehydration condensation reaction product) in a water-immiscible organic solvent so that the solid content concentration is 30% by mass to 80% by mass. It is also preferable to reflux for 3 hours to 30 hours at a temperature equal to or higher than the boiling point of the water-immiscible organic solvent. It is preferable to carry out the heating and refluxing while removing alcohol together with water using a Dean-Stark trap, thereby allowing the dehydration condensation reaction between the partial dehydration condensation reaction products to proceed.
In this case, if the partial dehydration condensation reaction product is an oligomer containing a large amount of ^T1 and ^T2 , the dehydration condensation reaction between such oligomers will result in a random structure phenylsilsesquioxane that is insoluble in an organic solvent that is not miscible with water. In order to form a ladder structure of phenylsilsesquioxane in the high molecular weight process, it is considered ideal to sequentially add monomers or dimers to an oligomer that does not contain a silanol group inside by a dehydration condensation reaction. For this purpose, it is preferable to control the state of the partial dehydration condensation reaction product in the previous concentration process.

Here, the "organic solvent immiscible with water" corresponds to an organic solvent that dissolves the hydrolysis/dehydration/condensation reaction product of phenyltrialkoxysilane in the film-forming coating liquid.
Examples of the organic solvent include aromatic hydrocarbons, ketones, and ethers. Specific examples include aromatic hydrocarbons such as toluene, xylene (o-xylene, m-xylene, p-xylene), and trimethylbenzene; ketones such as MEK (methyl ethyl ketone), MIBK (methyl isobutyl ketone), cyclohexanone, and cyclopentanone; ethers such as diethyl ether and diisopropyl ether; and cyclic aliphatic hydrocarbons such as cyclopentane, cyclohexane, and methylcyclohexane. One type of organic solvent may be used alone, or two or more types may be used in combination.

The term "water-immiscible organic solvent" includes organic solvents that are poorly miscible with water, and refers to organic solvents whose solubility in water is 300 g/L or less. Solubility in water is the weight of the organic solvent that dissolves in 1 L of water at 25°C, expressed in g/L. Ideally, the organic solvent that is immiscible with water is one whose solubility in water at 25°C is 30 g/L or less.

Through the above steps, a film-forming coating liquid is obtained, which contains an organic solvent and a hydrolysis/dehydration/condensation reaction product of a phenyltrialkoxysilane, which is soluble in the organic solvent and has an alkoxy group ratio of 0 to 20% relative to the total Si bonds.
Here, the "ratio of alkoxy groups to all Si bonds" in the hydrolysis/dehydration/condensation reaction product of phenyltrialkoxysilane is a value measured in the same manner as the "ratio of alkoxy groups to all Si bonds" in phenylsilsesquioxane.

The method for producing the film-forming coating liquid is not limited to the above-mentioned method.
For example, the method for producing the coating liquid for film formation may employ the methods for producing the coating liquid for film formation described in the above-mentioned Patent Documents 1 to 3.

-Membrane forming process-
In the film-forming process, a film-forming coating liquid is applied to at least one surface of a metal foil and dried to form a dry film, and the dry film is then heat-treated to form a film composed of a phenylsiloxane polymer.

Here, when the ratio of alkoxy groups to all Si bonds in the hydrolysis, dehydration, and condensation reaction product of phenyltrialkoxysilane is x (%) and the oxygen concentration is y (ppm by volume), if the dried film is heat-treated in an oxygen-containing inert gas atmosphere (e.g., a nitrogen gas atmosphere) where the oxygen concentration y is less than _yA (equation (2): _yA = ^x2 + 50), the oxygen concentration will be too low, and depending on the ratio of alkoxy groups in the "hydrolysis, dehydration, and condensation reaction product of phenyltrialkoxysilane" in the coating liquid, the ratio of alkoxy groups in the generated phenylsiloxane polymer may exceed 2.5%.
On the other hand, when the dried film is heat-treated in an inert gas atmosphere (e.g., a nitrogen gas atmosphere) containing oxygen with an oxygen concentration exceeding _yA ( _yB = ^8x2 + 300 in formula (3)), the oxygen concentration is too high and the proportion of Q nuclei in the phenylsiloxane polymer produced is less than 5.5%.
Therefore, the oxygen concentration y during the heat treatment is set to satisfy the formula (1): _yA ≦y≦ _yB .
However, if the alkoxy group of the hydrolysis/dehydration/condensation reaction product of phenyltrialkoxysilane in the film-forming coating liquid is too large, the film shrinkage caused by the elimination of the alkoxy group becomes too large, causing the film to crack. Therefore, the ratio of the alkoxy group of the hydrolysis/dehydration/condensation reaction product of phenyltrialkoxysilane is set to satisfy formula (4): x = 0 to 20.

If the heat treatment temperature is less than 380° C., the decomposition of the phenyl groups does not proceed, and the proportion of Q nuclei in the resulting phenylsiloxane polymer is less than 5.5%.
On the other hand, if the temperature during the heat treatment is higher than 450° C., the decomposition of the phenyl groups will proceed excessively, and the proportion of Q nuclei in the resulting phenylsiloxane polymer will exceed 15.0%.
Therefore, the temperature during the heat treatment is set to 380 to 450° C. The preferable temperature during the heat treatment is 410 to 450° C.

An example of the film-forming process will be described below with reference to FIG. 2. FIG. 2 is a schematic diagram showing an example of a film-forming device that is applied to the "film-forming process" in the method for producing a film-coated metal foil according to this embodiment.

This film forming apparatus represents a continuous film forming apparatus for providing a film on one side of a metal foil by a roll to roll process. The film forming apparatus 100 shown in Fig. 2 includes a coil unwinding section 12 that unwinds the metal foil wound into a coil shape, a coating section 22 that contains a film forming coating liquid 22A and applies the film forming coating liquid 22A to form a coating film, a drying section 24 that dries the coating film of the film forming coating liquid 22A to form a dry film, a heat treatment section 26 that heat-treats the dried film of the film forming coating liquid 22A and then heat-cures it, a cooling section 28 (first cooling body 28A, second cooling body 28B) that cools the film-coated metal foil after the heat treatment, and a coil winding section 14 that winds up the film-coated metal foil after the heat treatment.
In the drying section 24 and the heat treatment section 26, the support rolls that support the metal foil are arranged so as not to come into contact with the film surface (dried film surface and cured film surface) on which the electronic devices are formed.

The film forming apparatus 100 is equipped with tensioning rolls 32A and 32B to prevent wrinkles and the like from occurring during transport. Tensioning roll 32A is provided upstream of the coating section 22 in the metal foil transport direction, stabilizing the transport of the metal foil. Tensioning roll 32B is provided downstream of the heat treatment section 26 and upstream of the coil winding section 14, stabilizing the transport of the film-coated metal foil.

In the film forming apparatus 100, first, the film forming coating liquid is applied. The metal foil wound around a core is attached to the coil unwinding section 12. Next, the metal foil is unwound from the coil unwinding section 12 in the direction of arrow A. The metal foil passes through tensioning roll 32A, whereby the transport is stabilized, and the metal foil is sent to the coating section 22, which contains the film forming coating liquid 22A. In the coating section 22, the coating roll applies the film forming coating liquid 22A to one side of the metal foil, forming a coating film of the film forming coating liquid 22A.

Next, in the film forming apparatus 100, after coating, the film-coated metal foil is wound up after drying, heat treatment, and cooling. The metal foil on which the coating film of the film-forming coating liquid 22A has been formed is sent to the drying section 24. In the drying section 24, the solvent and moisture contained in the coating film are removed, and the coating film becomes a dry film. The metal foil on which the dry film of the film-forming coating liquid 22A has been formed is sent from the drying section 24 to a heat treatment section 26.
In the heat treatment section 26, the dried film is heat-treated to flatten the surface of the dried film. Then, the heat treatment is followed by crosslinking of the polymer to form a three-dimensional network structure, resulting in a cured film. The metal foil on which the cured film (i.e., film) of the film-forming coating liquid 22A is formed is sent from the heat treatment section 26 to the cooling section 28. In the cooling section 28, cold air is blown from the cooling body 28A arranged on the side on which the cured film is provided and the cooling body 28B arranged on the opposite side (i.e., the metal foil side) to cool the film. After cooling, the film-coated metal foil is sent from the cooling section 28 to the coil winding section 14. The film-coated metal foil passes through the tension-imparting roll 32A, so that the transport is stabilized. The film-coated metal foil is then transported in the direction of arrow A and wound around a core in the coil winding section 14.

Through the above steps, a film-coated metal foil as shown in FIG. 3 is obtained. FIG. 3 shows a portion of the film-coated metal foil, and is a schematic partial cross-sectional view showing the film-coated metal foil according to this embodiment. The film-coated metal foil 300 shown in FIG. 3 comprises a metal foil (metal foil) 302 and a film 304 provided on one side of the metal foil 302.

An example of preferred conditions for the film-forming process is described below. In the following description, reference symbols are omitted.

The metal foil conveying speed (sheet passing speed) is not particularly limited, and is, for example, about 1 m/min to 20 m/min. The faster the conveying speed, the higher the productivity.

In the coating section, the method of coating the film-forming coating liquid onto the surface of the metal foil is not particularly limited. Examples of coating methods include various coating methods (spin coating, casting, microgravure coating, gravure coating, bar coating, roll coating, wire bar coating, dip coating, slit coating, capillary coating, spray coating, nozzle coating, etc.), various printing methods (gravure printing, screen printing, flexographic printing, offset printing, reverse printing, inkjet printing, etc.), etc.

After coating on the metal foil, the coating film on the metal foil is dried in the drying section to remove the solvent and moisture from the coating film, forming a dry film. The drying process 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 section may be air or an inert gas atmosphere (e.g., nitrogen gas atmosphere). If the drying temperature is higher than the synthesis temperature of phenylsilsesquioxane by vacuum distillation, the ladder-type structure of phenylsilsesquioxane may soften. For this reason, the drying temperature is preferably lower than the synthesis temperature of phenylsilsesquioxane. In the dried film, the phenylsilsesquioxane is entangled and appears to have a network structure, and the film appears to be hardened. However, when the molecular movement becomes active due to thermal vibration, the phenylsilsesquioxane becomes loose and exhibits fluidity.

The metal foil with the dry film sent out from the drying section is heat-treated in the heat treatment section.
This heat treatment is performed on the dried film in an inert gas atmosphere (e.g., a nitrogen gas atmosphere) containing oxygen with an oxygen concentration that satisfies the above formulas (1) to (4) at a temperature of 380 to 450° C. However, the heat treatment time is 30 to 1800 seconds.
In the heat treatment, the oxygen concentration in the inert gas atmosphere can be controlled, for example, by the amount of inert gas injected into the heat treatment section (heat treatment furnace or the like) and the number of revolutions of the exhaust fan.
The heat treatment also has two purposes: (1) to melt and soften (i.e., heat treat) the phenylsilsesquioxane that forms the dried film, thereby flattening the surface of the film, and (2) to proceed with crosslinking of the polymer following the heat treatment, thereby forming a three-dimensional network structure and hardening the film.

Reflow is a phenomenon that occurs in a temperature range higher than the synthesis temperature of phenylsilsesquioxane by vacuum distillation, but lower than the temperature at which three-dimensional cross-linking progresses and the dried film begins to harden. There is no need to employ a special heat treatment process for reflow. Reflow occurs during the process of raising the temperature to the heat treatment temperature by heat treatment, and the film hardens due to cross-linking. As mentioned above, heat treatment changes phenylsilsesquioxane into a phenylsiloxane polymer.

To effectively flatten the surface of the metal foil, it is best to perform the heat treatment in a nearly horizontal state, as in the heat treatment section 26 of the film-forming apparatus 100 shown in Figure 2. Since film hardening is the formation of a network structure through a cross-linking reaction, once the film hardens, it rarely reflows again.

To cool the metal foil after heat treatment, cold air may be blown from a cooling body. In the film-forming device 100 shown in FIG. 2, cold air is blown from both sides of the metal foil with the cured film, but it may also be blown from one side of the cured film. The temperature of the cold air may be room temperature (e.g., 25°C).

After cooling, when the metal foil with the film is wound around the core, a protective film may be attached to the film surface to protect the film, and interleaf paper may be inserted to prevent scratches. In addition, in the film-forming device 100 shown in FIG. 2, drying and heat treatment are performed consecutively, but drying and heat treatment may be performed separately. For example, after the metal foil with the dried film is wound into a coil, the dried film may be hardened by performing only heat treatment again. In this case, two types of equipment, one for drying treatment and one for heat treatment, are installed. Performing drying and heat treatment separately has the advantage that the optimum threading speed can be set for each treatment.

Second Embodiment
Hereinafter, the method for producing a film-coated metal foil according to the second embodiment will be described.
The method for producing a film-coated metal foil according to the second embodiment is a method in which the generation of the Q nuclei shown in Fig. 5 occurs not by thermal decomposition of a phenyl group but by adding a tetraalkoxysilane.
The method for producing a film-coated metal foil according to the second embodiment includes, for example,
A step of preparing a coating solution for forming a film, the coating solution including an organic solvent and a hydrolysis/dehydration/condensation reaction product of a phenyltrialkoxysilane, the hydrolysis/dehydration/condensation reaction product being soluble in the organic solvent and having a ratio of alkoxy groups to all bonds of Si of 0 to 20% and a ratio of Q nuclei to all Si nuclei of 1.0% or more and 5.0% or less;
A step of applying a coating liquid onto at least one surface of a metal foil, drying the coating liquid to form a dried film of the coating liquid, and then heat-treating the dried film to form a film composed of a phenylsiloxane polymer;
has.

In the process of preparing a coating liquid for forming a film, for example, phenyltrialkoxysilane, a tetraalkoxysilane having a Q nucleus, alcohol, acetic acid, organotin, and water are mixed together to hydrolyze the phenyltrialkoxysilane, thereby generating a hydrolysis product of the phenyltrialkoxysilane.
Thereafter, similarly to the first embodiment, a concentration step and a polymerizing step are carried out to obtain a film-forming coating liquid containing a hydrolysis/dehydration/condensation reaction product of a phenyltrialkoxysilane in which the ratio of alkoxy groups to all Si bonds is 0 to 20% and the ratio of Q nuclei to all Si nuclei is 1.0% or more and 5.0% or less.

Examples of the tetraalkoxysilane include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane, with tetraethoxysilane being preferred.
The molar ratio of the tetraalkoxysilane having a Q nucleus to the phenyltrialkoxysilane is preferably, for example, 1.0 to 5.0 mol %.
When the molar ratio of tetraalkoxysilane is 1.0 to 5.0 mol %, it becomes easier to obtain a hydrolysis, dehydration, and condensation reaction product of phenyltrialkoxysilane in which the proportion of Q nuclei among all Si nuclei is 1.0% or more and 5.0% or less.

The film forming step is carried out in the same manner as the film forming step in the first embodiment.
However, the second embodiment is not limited to the heat treatment conditions of the first embodiment (i.e., the oxygen concentration of the inert gas during the heat treatment and the heat treatment temperature). In the second embodiment, for example, when the ratio of alkoxy groups to all bonds of Si in the coating liquid is 2% and the ratio of Q nuclei to all Si nuclei is 4.9%, the dried film of the coating liquid for film formation is heat treated at a temperature of 300 to 450° C. in an inert gas atmosphere with an oxygen concentration of 500 ppm or more (volume basis).

The present invention will be described in more detail below with reference to examples. However, these examples do not limit the present invention.

Example A
In Example A, a film-coated metal foil was produced using a film-forming coating liquid in which the hydrolysis, dehydration, and condensation reaction product of phenyltrialkoxysilane did not contain a Q nucleus.

In accordance with Table 1, phenyltriethoxysilane, 0.01 molar equivalent of organotin per molar equivalent of phenyltriethoxysilane, 9 molar equivalents of alcohol (ethanol) per molar equivalent of phenyltriethoxysilane, and the amounts of acid catalyst and water shown in Table 1 (molar equivalents per molar equivalent of phenyltriethoxysilane) were mixed as raw materials in a 1 L flask to give a total volume of 0.7 L.
In Table 1, the abbreviations in the column "Type of organotin" are as follows.
"Sn-1": dibutyltin diacetonate "Sn-2": dibutyltin bisacetylacetonate

After preparation, the raw materials were stirred and mixed with a magnetic stirrer for 15 minutes, and then refluxed under a nitrogen stream at 80° C. for 3 hours to promote hydrolysis of phenyltriethoxysilane.
Thereafter, using a rotary evaporator, the oil bath temperature was set to 120° C. and the alcohol, water and acetic acid were distilled off under reduced pressure to obtain a condensation reaction product of phenyltriethoxysilane.
Then, toluene was added as a water-immiscible organic solvent in an amount equal to the weight of the condensation reaction product of phenyltriethoxysilane to dissolve the condensation reaction product. At this point, the condensation reaction product was dissolved with a solid concentration of 50 mass %.
This 1 L flask was connected to a reflux condenser equipped with a Dean-Stark trap and heated under reflux, and the dehydration-condensation reaction of the condensation reaction product was further advanced to increase the molecular weight of the dehydration-condensation reaction product of phenyltriethoxysilane.
After heating under reflux, toluene was added as a water-immiscible organic solvent to dilute the mixture to a solid content of 30% by mass, and a filter having a pore size of 5 μm was placed in the mixture to perform filtration under reduced pressure.
Through the above steps, a film-forming coating solution was obtained containing a hydrolysis, dehydration, and condensation reaction product of phenyltriethoxysilane having the proportion of ethoxy groups shown in Table 1 (represented as "amount of alkoxy groups in coating solution" in the table).

Next, the obtained coating solution was passed through a filter with a pore size of 0.5 μm, and then spin-coated onto a stainless steel foil. The stainless steel foil used was SUS304MW (milk white finish) with a size of 120 mm x 120 mm x 0.05 mm manufactured by Nippon Steel Chemical & Material Co., Ltd. The rotation speed of the spin coater was set so that the film thickness was 3.0 μm.
After spin coating, the coating film was dried in an oven at 80° C. for 1 minute to obtain a stainless steel foil with a dried film. It was confirmed by ¹³ C NMR and ²⁹ SI NMR that the proportion of Q nuclei and the proportion of ethoxy groups in the hydrolysis/dehydration/condensation reaction product of phenyltriethoxysilane were unchanged between the coating liquid and the dried film.
The obtained stainless steel foil with the dry film was heat-treated in a roll-to-roll heat treatment furnace. The heat treatment was performed by attaching the stainless steel foil with the dry film to a lead coil and passing the foil through the heat treatment furnace at a sheet passing speed of 1.0 m/min. The heat treatment furnace had a heating section of 5 m in length, and the heat treatment time was 5 minutes based on the sheet passing speed. The temperature in the heat treatment furnace was set to 420°C.
The oxygen concentration during the heat treatment was controlled to the concentration shown in Table 1 by adjusting the amount of nitrogen injected into the heat treatment furnace and the rotation speed of the exhaust fan.
Table 1 also shows y _A in formula (2) (represented in the table as "oxygen concentration lower limit y _A ") and y _B in formula (3) (represented in the table as "oxygen concentration upper limit y _B ").

Through the above steps, a stainless steel foil with a membrane was obtained.

First, the proportion of ethoxy groups in the phenylsiloxane polymer of the film (represented as "alkoxy group amount" in the table) and the proportion of Q nuclei (represented as "Q/Si" in the table) were examined for the stainless steel foil with the film according to the method described above. However, in Comparative Example 9, the film could not be recovered due to significant peeling, and analysis was not possible.

Next, the stainless steel foil with the film was cut into a 30 mm square, and then attached to a glass plate of the same size and 0.7 mm thick with a slight adhesive sheet.
Next, an organic EL light-emitting device with the structure of Ag(100)/ _MoO3 (5)/αNPD(140)/ _Alq3 (30)/DPB:Liq(45)/Al(1.5)/Ag(25) was formed on the film-attached stainless steel foil and sealed with a glass cap. The numbers in () for the device structure indicate the film thickness, in nm. The size of the light-emitting area of the device is 2 mm square.
Incidentally, 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, a voltage of 4.5 V was applied to the organic EL device to cause it to emit light, and the initial state of the light-emitting surface was observed with an optical microscope.
Next, the organic EL light-emitting device was stored in a thermohygrostat at 40°C and 90% RH for 40 hours, and then 4.5 V was applied again to observe the light-emitting surface and measure the shrinkage of the light-emitting surface from the cathode side. If the shrinkage was greater than 10 μm, it was judged as B (good), and if it was 10 μm or less, it was judged as A (very good). The results are shown in the "Shrinkage (μm) after storage at 40°C and 90% RH for 40 hours" column.
If the shrinkage width is less than 10 μm, it is difficult to read the width with a microscope. Therefore, for A, which has a relatively long element life, the organic EL light-emitting element was stored separately in a constant temperature and humidity chamber at 85° C. and 85% RH for 40 hours, and then 4.5 V was applied to observe the light-emitting surface and measure the shrinkage width of the light-emitting surface from the cathode side. If this shrinkage width exceeds 50 μm, it was judged to be A (very good), and if it is 50 μm or less, it was judged to be S (very good). The results are shown in the column "Shrinkage width (μm) after storage at 85° C. and 85% RH for 40 hours."

The above results show that in this embodiment, the amount of shrinkage of the light-emitting surface of the element after storage in a thermo-hygrostat is smaller than in the comparative example. Therefore, it can be seen that the film-coated metal foil of this embodiment can improve the lifespan of electronic devices.

Example B
In Example B, a metal foil with a film was produced using a film-forming coating solution in which a hydrolysis/dehydration/condensation reaction product of phenyltrialkoxysilane contained a Q nucleus, using a combination of phenyltrialkoxysilane and tetraalkoxysilane.

In accordance with Table 2, phenyltrialkoxysilane, a tetraalkoxysilane in the amount shown in Table 2 (molar equivalent relative to 1 equivalent of phenyltrialkoxysilane), 0.01 molar equivalent of organotin relative to 1 molar equivalent of phenyltrialkoxysilane, 9 molar equivalents of alcohol (ethanol when phenyltriethoxysilane was used, methanol when phenyltrimethoxysilane was used) relative to 1 molar equivalent of the alkoxy group of the phenylalkoxysilane, and an acid catalyst and water in the amounts shown in Table 2 (molar equivalent relative to 1 equivalent of phenyltrialkoxysilane) were mixed and prepared in a 1 L flask until the total amount became 0.7 L.
In Table 2, the abbreviations in the columns "Type of tetraalkoxysilane" and "Type of organotin" are as follows.
"TEOS": tetraethoxysilane "TMOS": tetramethoxysilane "Sn-1": dibutyltin diacetonate "Sn-2": dibutyltin bisacetylacetonate

After preparation, the raw materials were stirred and mixed with a magnetic stirrer for 15 minutes, and then refluxed under a nitrogen stream at 80° C. for 3 hours to promote hydrolysis.
Thereafter, the alcohol was distilled off under reduced pressure using a rotary evaporator with the oil bath temperature set to 120° C., to obtain a condensation reaction product of phenyltrialkoxysilane.
Then, toluene was added as a water-immiscible organic solvent in an amount equal to the weight of the condensation reaction product of phenyltrialkoxysilane to dissolve the condensation reaction product. At this point, the condensation reaction product was dissolved with a solid concentration of 50 mass %.
This 1 L flask was connected to a reflux condenser equipped with a Dean-Stark trap and heated under reflux, and the dehydration-condensation reaction of the condensation reaction product was further advanced to increase the molecular weight of the dehydration-condensation reaction product of phenyltrialkoxysilane.
After heating under reflux, toluene was added as a water-immiscible organic solvent to dilute the mixture to a solid content of 30% by mass, and a filter having a pore size of 5 μm was placed in the mixture to perform filtration under reduced pressure.

Through the above steps, a film-forming coating solution was obtained, containing a hydrolysis, dehydration, and condensation reaction product of phenyltrialkoxysilane having the ratio of alkoxy groups shown in Table 2 (represented as "amount of alkoxy groups in the coating solution" in the table) and the ratio of Q nuclei to all Si nuclei (represented as "Q/Si in the coating solution" in the table).
In Comparative Example 10, the amount of tetraalkoxysilane having a Q nucleus was too large, so that the hydrolysis/dehydration/condensation reaction product of phenyltrialkoxysilane gelled, and a coating liquid could not be obtained.

Then, using the obtained flattening coating liquid, a stainless steel foil with a film was obtained in the same manner as in Example A, except that the heat treatment conditions shown in Table 2 were used.
In Example B, it was also confirmed by ¹³ C NMR and ²⁹ SI NMR that the proportion of Q nuclei and the proportion of alkoxy groups in the hydrolysis/dehydration/condensation reaction product of phenyltrialkoxysilane were unchanged between the coating solution and the dried film.

First, the proportion of methoxy or ethoxy groups in the phenylsiloxane polymer of the film (represented as "alkoxy group amount" in the table) and the proportion of Q nuclei (represented as "Q/Si" in the table) were examined for the stainless steel foil with the film according to the method described above.

Next, the stainless steel foil with the film was cut into a 30 mm square, and then attached to a glass plate of the same size and 0.7 mm thick with a slight adhesive sheet.
Next, an organic EL light-emitting device with the structure of Ag(100)/ _MoO3 (5)/αNPD(140)/ _Alq3 (30)/DPB:Liq(45)/Al(1.5)/Ag(25) was formed on the film-attached stainless steel foil and sealed with a glass cap. The numbers in () for the device structure indicate the film thickness, in nm. The size of the light-emitting area of the device is 2 mm square.
Incidentally, 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 For Comparative Example 11 in which cracks occurred in the film, there was no point in carrying out element evaluation, so an element was not produced.

Next, a voltage of 4.5 V was applied to the organic EL device to cause it to emit light, and the initial state of the light-emitting surface was observed with an optical microscope.
Next, the organic EL light-emitting device was stored in a thermohygrostat at 40°C and 90% RH for 40 hours, and then 4.5 V was applied again to observe the light-emitting surface and measure the shrinkage of the light-emitting surface from the cathode side. If the shrinkage was greater than 10 μm, it was judged as B (good), and if it was 10 μm or less, it was judged as A (very good). The results are shown in the "Shrinkage (μm) after storage at 40°C and 90% RH for 40 hours" column.
If the shrinkage width is less than 10 μm, it is difficult to read the width with a microscope. Therefore, for A, which has a relatively long element life, the organic EL light-emitting element was stored separately in a constant temperature and humidity chamber at 85° C. and 85% RH for 40 hours, and then 4.5 V was applied to observe the light-emitting surface and measure the shrinkage width of the light-emitting surface from the cathode side. If this shrinkage width exceeds 50 μm, it was judged to be A (very good), and if it is 50 μm or less, it was judged to be S (very good). The results are shown in the column "Shrinkage width (μm) after storage at 85° C. and 85% RH for 40 hours."

From the above results, in this embodiment, when a film-attached metal foil is manufactured using a film-forming coating solution in which the hydrolysis/dehydration/condensation reaction product of phenyltrialkoxysilane is previously containing Q nuclei, even if the heat treatment is performed under oxygen concentration conditions that do not satisfy the above conditions (1) to (3), the shrinkage of the light-emitting surface of the element is small after storage in a thermo-hygrostat. Therefore, it is found that the film-attached metal foil of this embodiment can improve the life of electronic devices.
In Comparative Example 10, the amount of tetraalkoxysilane having a Q core was too large, so that the coating liquid gelled.
In Comparative Example 11, the amount of tetraalkoxysilane having Q nuclei was too large, so that the proportion of Q nuclei in the phenylsiloxane polymer of the film also increased, causing cracks in the film.

Example C
In Example C, the heat treatment temperature for the dried film of the film-forming coating solution was changed to produce a film-coated metal foil.

First, the same film-forming coating solution as in Experiment No. 4 of Example A (Example 3) was obtained.
The obtained coating solution for film formation was used to obtain a film-coated stainless steel foil in the same manner as in Example A, except that the heat treatment conditions shown in Table 3 were used.
In Example C, it was also confirmed by ¹³ C NMR and ²⁹ SI NMR that the proportion of Q nuclei and the proportion of alkoxy groups in the hydrolysis/dehydration/condensation reaction product of phenyltrialkoxysilane were unchanged between the coating solution and the dried film.

First, the proportion of ethoxy groups in the phenylsiloxane polymer of the film (represented as "alkoxy group amount" in the table) and the proportion of Q nuclei (represented as "Q/Si" in the table) of the stainless steel foil with the film were investigated using the method described above.

Next, the stainless steel foil with the film was cut into a 30 mm square, and then attached to a glass plate of the same size and 0.7 mm thick with a slight adhesive sheet.
Next, an organic EL light-emitting device with the structure of Ag(100)/ _MoO3 (5)/αNPD(140)/ _Alq3 (30)/DPB:Liq(45)/Al(1.5)/Ag(25) was formed on the film-attached stainless steel foil and sealed with a glass cap. The numbers in () for the device structure indicate the film thickness, in nm. The size of the light-emitting area of the device is 2 mm square.
Incidentally, 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 Note that for Comparative Example 14 in which cracks occurred in the film, there was no point in carrying out element evaluation, so an element was not produced.

Next, a voltage of 4.5 V was applied to the organic EL device to cause it to emit light, and the initial state of the light-emitting surface was observed with an optical microscope.
Next, the organic EL light-emitting device was stored in a thermohygrostat at 40°C and 90% RH for 40 hours, and then 4.5 V was applied again to observe the light-emitting surface and measure the shrinkage of the light-emitting surface from the cathode side. If the shrinkage was greater than 10 μm, it was judged as B (good), and if it was 10 μm or less, it was judged as A (very good). The results are shown in the "Shrinkage (μm) after storage at 40°C and 90% RH for 40 hours" column.
If the shrinkage width is less than 10 μm, it is difficult to read the width with a microscope. Therefore, for A, which has a relatively long element life, the organic EL light-emitting element was stored separately in a constant temperature and humidity chamber at 85° C. and 85% RH for 40 hours, and then 4.5 V was applied to observe the light-emitting surface and measure the shrinkage width of the light-emitting surface from the cathode side. If this shrinkage width exceeds 50 μm, it was judged to be A (very good), and if it is 50 μm or less, it was judged to be S (very good). The results are shown in the column "Shrinkage width (μm) after storage at 85° C. and 85% RH for 40 hours."

The above results show that in this embodiment, in which the film-coated metal foil was produced at a heat treatment temperature in the range of 380 to 450°C, the amount of shrinkage of the light-emitting surface of the element after storage in a thermo-hygrostat was smaller than in the comparative example. Therefore, it can be seen that the film-coated metal foil of this embodiment can improve the lifespan of electronic devices.

12 Coil unwinding section 14 Coil winding section 22 Coating section 22A Film-forming coating liquid 24 Drying section 26 Heat treatment section 28 Cooling section 28A First cooling body 28B Second cooling body

Claims (3)

Metal foil;
a film formed on at least one surface of the metal foil, the film being composed of a phenylsiloxane polymer in which the ratio of alkoxy groups to all Si bonds is 2.5% or less and the ratio of Q nuclei to all Si nuclei is 5.5% or more and 15.0% or less;
The film-coated metal foil has a film-coated metal foil having a film-coated metal foil. the ratio of alkoxy groups to the total bonds of the Si is 1.5% or less,
The film-coated metal foil according to claim 1 , wherein the ratio of Q nuclei to all the Si nuclei is 7.0% or more and 15.0% or less. A step of preparing a coating solution for forming a film, the coating solution including an organic solvent and a hydrolysis/dehydration/condensation reaction product of a phenyltrialkoxysilane, the ratio of alkoxy groups to all bonds of Si being 0 to 20%, dissolved in the organic solvent;
a step of applying the coating liquid onto at least one surface of a metal foil, drying the coating liquid to form a dried film of the coating liquid, and then heat-treating the dried film at a temperature of 380 to 450° C. in an oxygen-containing inert gas atmosphere with an oxygen concentration y that satisfies the following formulas (1) to (4), where x (%) is a ratio of alkoxy groups to all bonds of Si in the hydrolysis/dehydration/condensation reaction product of the phenyltrialkoxysilane, and y (ppm by volume) is an oxygen concentration, thereby forming a film composed of a phenylsiloxane polymer;
A method for producing a film-coated metal foil having the above structure.
Formula (1): _yA ≦y≦ _yB
Formula (2): _yA = ^x2 + 50
Formula (3): y _B = 8x ² + 300
Formula (4): x = 0 to 20

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