JP7657744B2 - Highly heat-resistant coating composition - Google Patents

Description

The present invention relates to a highly heat-resistant coating composition.

In recent years, as electronic devices have become more sophisticated, the performance of the electronic components used has become noticeably higher. In particular, surface coatings are being used more and more to physically and chemically protect the component materials in order to improve their reliability. In the past, materials that had both functionality and stability over time were used, but the level of functionality required has become much higher due to the recent increase in the functionality of electronic devices. For this reason, component materials have been specialized for high performance, and stability over time has been imparted through surface coatings, etc. However, even when imparting the same properties to electronic components, coatings must be made using different methods and materials depending on the environment, shape, and manufacturing method in which the components are used, and coating materials and methods that correspond to the various required properties must be prepared. However, at present, there are not enough methods or coating materials that meet the requirements of each component.

One coating that remains problematic is thick-film coating, which requires high heat resistance. In particular, there is a demand for hole-filling coatings that cover and flatten the unevenness of the substrate, and coating materials that do not deteriorate even at high temperatures of around 400°C. Silicone-based coating materials, which are generally said to have higher heat resistance than organic coating materials, have a heat resistance of around 250°C, so silicone resin coatings have traditionally been used as heat-resistant coatings (see, for example, Patent Document 1). However, recent electronic components sometimes require high heat resistance of 300 to 400°C, and traditional silicone resin-based coating materials cannot meet this requirement.

To solve this problem, a method has been proposed in which silicone resin, which is more heat-resistant than organic resins, is baked at high temperatures to perform a process similar to that used for baking paint with acrylic resins and melamine resins (Patent Document 2). It has been reported that this method improves the heat resistance of the coating film at 400°C, but the film thickness is significantly reduced during baking due to the curing shrinkage of the coating film and the volatilization of the coating film components, making it difficult to use it as a hole-filling coating to fill unevenness in a substrate. For hole-filling applications, it is necessary to maintain the film thickness at the time of application even during curing and high-temperature heating.

On the other hand, inorganic coating materials such as sol-gel glass have high heat resistance of nearly 1,000°C, and can be formed into films by wet processes or dry processes such as CVD, so that different manufacturing methods can be used depending on the substrate (Patent Document 3). However, inorganic coating agents shrink significantly when cured, and if the film thickness is increased, cracks and peeling occur during curing due to shrinkage stress, so they can basically only be used with a film thickness of 1 μm or less. In the case of chemical protection of surfaces, a thin film coating of 1 μm or less can be expected to be sufficiently effective, but it cannot be used for filling and flattening the unevenness of the surface of parts such as semiconductor trenches. To solve this problem, many methods have been reported for adding inorganic fillers to inorganic coating materials, similar to the above-mentioned method of increasing the heat resistance of silicone resins, but the film thickness is thin, at only a few μm, and it cannot be used to cover unevenness.

A method using polysilazane as another inorganic coating material has also been proposed (Patent Document 4). Like sol-gel glass, polysilazane can form a glass film by wet coating, and has a high film density and excellent heat resistance compared to sol-gel glass. In addition, sol-gel glass cannot be exposed to high temperatures because components such as water and alcohol tend to remain in the film, which expand at high temperatures and cause the film to burst. On the other hand, polysilazane has a small molecular size of the detached components and is unlikely to remain in the film, so there is no concern about film bursting even at high temperatures. However, inorganic polysilazanes that form silica glass after curing are difficult to form thick films, like sol-gel glass, and organic group-modified polysilazanes that contain a large amount of organic groups have little curing shrinkage and can be formed into thick films, but have the problem of low bond strength after curing and poor durability at high temperatures.

Due to these issues, there is a demand for a coating composition that is durable at high temperatures of around 400°C and can form a thick film that can cover the unevenness of the substrate.

JP 2005-206761 A Japanese Patent Application Publication No. 6-001847 Japanese Patent Application Publication No. 11-043782 JP 2014-191841 A

The present invention was made in consideration of the above circumstances, and aims to provide a coating composition that has high heat resistance and is less prone to film loss at high temperatures, yet can be used to form thick films.

（式中、Ｒ^１は炭素数１～６の脂肪族炭化水素基、炭素数６～１２の芳香族炭化水素基から選ばれる基であり、ポリシラザン化合物中でＲ^１は同一であっても異なっていてもよい。）

（式中、Ｒ^２は炭素数１～６の脂肪族炭化水素基、炭素数６～１２の芳香族炭化水素基から選ばれる基であり、ポリシラザン化合物中でＲ^２は同一であっても異なっていてもよい。） In order to achieve the above object, the present invention provides
The present invention provides a highly heat-resistant coating composition comprising the following component (A) and component (B):
(A) a polysilazane compound containing a structure represented by the following general formula (A-1) and/or a structure represented by the following general formula (A-2), in which the total amount of the structure represented by the general formula (A-1) and the structure represented by the general formula (A-2) is 50 to 100 mass % relative to the entire polysilazane compound; (B) an inorganic filler having a melting point and decomposition temperature of 400° C. or higher.

(In the formula, R ¹ is a group selected from an aliphatic hydrocarbon group having 1 to 6 carbon atoms and an aromatic hydrocarbon group having 6 to 12 carbon atoms, and in the polysilazane compound, R ¹ may be the same or different.)

(In the formula, ^R2 is a group selected from an aliphatic hydrocarbon group having 1 to 6 carbon atoms and an aromatic hydrocarbon group having 6 to 12 carbon atoms, and in the polysilazane compound, ^R2 may be the same or different.)

Such a coating composition will have little film loss at high temperatures and will be highly heat-resistant and capable of being made into a thick film.

In addition, R ¹ in the general formula (A-1) is preferably a methyl group.

If this is the case, the polysilazane compound will have excellent stability and workability.

In addition, R ² in the general formula (A-2) is preferably a methyl group.

If this is the case, the curing speed and film properties after curing of the highly heat-resistant coating composition of the present invention will be excellent.

It is also preferable that the component (B) is selected from silica, alumina, zinc oxide, and titanium oxide.

Such a material has excellent wettability and dispersibility with the polysilazane compound.

It is also preferable that the average particle size of the (B) component is within the range of 5 to 100 nm.

Within this range, the dispersibility of the polysilazane compound is good, and the transparency of the coating film is improved.

It is also preferable that the amount of the (B) component is 50 to 500 parts by mass per 100 parts by mass of the (A) component.

Within this range, the crack resistance and heat resistance of the coating composition are fully exhibited, and the coating composition is easy to work with and apply.

As described above, the highly heat-resistant coating composition of the present invention is a composition that contains a polysilazane compound containing a certain amount or more of a specific structure and an inorganic filler, and it is possible to obtain a coating composition that has the characteristics of being able to apply a thick film (can be made thicker) at high temperatures of about 400°C with little film loss.

As mentioned above, there was a need to provide a coating composition that is durable at high temperatures of about 400°C and can form a thick film that can cover the irregularities of the substrate.

As a result of intensive research aimed at solving the above problems, the inventors discovered that by using a polysilazane compound containing a certain amount or more of a specific structure, durability at high temperatures of about 400°C can be improved and a thick film capable of covering the unevenness of a substrate can be formed, which led to the creation of the present invention.

（式中、Ｒ^１は炭素数１～６の脂肪族炭化水素基、炭素数６～１２の芳香族炭化水素基から選ばれる基であり、ポリシラザン化合物中でＲ^１は同一であっても異なっていてもよい。）

（式中、Ｒ^２は炭素数１～６の脂肪族炭化水素基、炭素数６～１２の芳香族炭化水素基から選ばれる基であり、ポリシラザン化合物中でＲ^２は同一であっても異なっていてもよい。） That is, the present invention provides:
The highly heat-resistant coating composition comprises the following component (A) and component (B):
(A) a polysilazane compound containing a structure represented by the following general formula (A-1) and/or a structure represented by the following general formula (A-2), in which the total amount of the structure represented by the general formula (A-1) and the structure represented by the general formula (A-2) is 50 to 100 mass % relative to the entire polysilazane compound; (B) an inorganic filler having a melting point and decomposition temperature of 400° C. or higher.

(In the formula, R ¹ is a group selected from an aliphatic hydrocarbon group having 1 to 6 carbon atoms and an aromatic hydrocarbon group having 6 to 12 carbon atoms, and in the polysilazane compound, R ¹ may be the same or different.)

(In the formula, ^R2 is a group selected from an aliphatic hydrocarbon group having 1 to 6 carbon atoms and an aromatic hydrocarbon group having 6 to 12 carbon atoms, and in the polysilazane compound, ^R2 may be the same or different.)

The present invention is described in detail below, but is not limited to these.

[(A) Polysilazane compound]
The polysilazane compound used in the coating composition of the present invention is characterized in that it contains a specific structure represented by the following general formula (A-1) and/or the following general formula (A-2) in a certain amount or more relative to the entire polysilazane compound.

（式中、Ｒ^１は炭素数１～６の脂肪族炭化水素基、炭素数６～１２の芳香族炭化水素基から選ばれる基であり、ポリシラザン化合物中でＲ^１は同一であっても異なっていてもよい。） (Polysilazane Structure (A-1))
The polysilazane structure (A-1) is a structure represented by the following general formula (A-1).

(In the formula, R ¹ is a group selected from an aliphatic hydrocarbon group having 1 to 6 carbon atoms and an aromatic hydrocarbon group having 6 to 12 carbon atoms, and in the polysilazane compound, R ¹ may be the same or different.)

R ¹ in the above general formula (A-1) may be, for example, a methyl group, an ethyl group, a phenyl group, etc., and may be the same or different within the molecule. Among them, a methyl group is preferable from the viewpoint of the stability and workability of the generated polymer. Hereinafter, the part of the component (A) consisting of the above polysilazane structure (A-1) will be referred to as the component (A-1).

（式中、Ｒ^２は炭素数１～６の脂肪族炭化水素基、炭素数６～１２の芳香族炭化水素基から選ばれる基であり、ポリシラザン化合物中でＲ^２は同一であっても異なっていてもよい。） (Polysilazane Structure (A-2))
The polysilazane structure (A-2) is a structure represented by the following general formula (A-2).

(In the formula, ^R2 is a group selected from an aliphatic hydrocarbon group having 1 to 6 carbon atoms and an aromatic hydrocarbon group having 6 to 12 carbon atoms, and in the polysilazane compound, ^R2 may be the same or different.)

^R2 in the above general formula (A-2) may be, for example, a methyl group, an ethyl group, a phenyl group, etc., and may be the same or different within the molecule. Among them, a methyl group is preferable from the viewpoint of the curing speed and the film properties after curing. Hereinafter, the part of the component (A) consisting of the above polysilazane structure (A-2) will be referred to as the component (A-2).

（式中、Ｒ^３は炭素数１～６の脂肪族炭化水素基、炭素数６～１２の芳香族炭化水素基から選ばれる基であり、ポリシラザン化合物中でＲ^３は同一であっても異なっていてもよい。Ｒ^４は水素原子、炭素数１～６の脂肪族炭化水素基、炭素数６～１２の芳香族炭化水素基から選ばれる基であり、ポリシラザン化合物中でＲ^４は同一であっても異なっていてもよい。） (Other polysilazane structures)
The polysilazane compound of component (A) may also contain, as another polysilazane structure, a moiety (component (A-3)) consisting of a structure represented by the following general formula (A-3) (polysilazane structure (A-3)) other than the above components (A-1) and (A-2).

(In the formula, R ³ is a group selected from an aliphatic hydrocarbon group having 1 to 6 carbon atoms and an aromatic hydrocarbon group having 6 to 12 carbon atoms, and in the polysilazane compound, R ³ may be the same or different. R ⁴ is a group selected from a hydrogen atom, an aliphatic hydrocarbon group having 1 to 6 carbon atoms, and an aromatic hydrocarbon group having 6 to 12 carbon atoms, and in the polysilazane compound, R ⁴ may be the same or different.)

Examples of R ³ in the above general formula (A-3) include methyl, ethyl, and phenyl groups, and may be the same or different within the molecule. Among these, a methyl group is preferable from the viewpoint of stability over time and film properties after curing. Furthermore, examples of R ⁴ in the above general formula (A-3) include hydrogen atoms, methyl, ethyl, and propyl groups, and may be the same or different within the molecule. Among these, a hydrogen atom is preferable from the viewpoint of curing speed and removal of elimination components during curing.

In the present invention, taking into consideration the balance between workability, curing speed, and cured product properties, the total of components (A-1) and (A-2) must be 50 to 100% by mass relative to 100% by mass of the polysilazane compound. This range is preferable because it provides good workability during application and good crack resistance and heat resistance of the cured coating film.

In addition, component (A-1) or component (A-2) may be used alone. The ratio of components (A-1) and (A-2) is arbitrary.

If the total of components (A-1) and (A-2) is less than this ratio, the stability of the polymer will be too high or too low, resulting in an inappropriate curing speed and a clean coating film. This is inappropriate. In addition, the above structure contributes greatly to the hardness of the cured coating film, so outside the above range, appropriate hardness will not be obtained.

Since the total of the (A-1) and (A-2) components is 50 to 100% by mass relative to 100% by mass of the polysilazane compound, the (A-3) component can be 0 to 50% by mass relative to 100% by mass of the polysilazane compound.

In addition, the content of component (A) is preferably 15% by mass or more based on the entire high heat-resistant coating composition of the present invention. Component (A-1) and component (A-2) can form a uniform, hard coating film after curing, but at the same time, they also have flexibility against stress. A soft coating film has weak bonds between the coating film components, and the bonds break and volatilize at high temperatures, making the coating film prone to film loss. On the other hand, a hard coating film cannot keep up with the thermal expansion of the substrate and coating film components at high temperatures, making it prone to cracking and peeling. In the present invention, by combining coating hardness and flexibility, it is possible to obtain both of the contradictory properties of film loss at high temperatures and prevention of cracking.

The molecular weight of the polysilazane compound is not particularly specified, but from the viewpoint of workability such as curing speed and viscosity, it is preferable that the weight average molecular weight is within the range of 500 to 500,000. A weight average molecular weight of 500 or more is preferable because curing proceeds quickly and the coating film becomes non-tacky, while a weight average molecular weight of 500,000 or less is preferable because it has an easy-to-handle viscosity and there is no risk of curing during use. The weight average molecular weight was measured using a GPC (gel permeation chromatography) device according to the following method.

[Measurement conditions]
Developing solvent: tetrahydrofuran (THF)
Flow rate: 0.6mL/min
Detector: UV detector Column: TSK Guardcolumn SuperH-L
TSKgel SuperMultipore HZ-M
(4.6mm I.D. x 15cm x 4)
(Both manufactured by Tosoh Corporation)
Column temperature: 40°C
Sample injection volume: 20 μL (THF solution with a concentration of 0.5% by weight)

(B) Inorganic Filler There are no particular limitations on the inorganic filler used in the present invention, so long as it has a melting point and decomposition temperature of 400° C. or higher. In the present invention, in order to satisfy the heat resistance at temperatures of 250 to 400° C., which silicone resin cannot meet, the inorganic filler used must not dissolve or decompose in this temperature range.

The melting point and decomposition temperature of the inorganic filler can be measured from the weight change and heat change using thermogravimetric differential thermal analysis (TG-DTA).

Examples of the inorganic filler that meets these conditions include metals such as aluminum, silicon, titanium, manganese, iron, cobalt, nickel, copper, zinc, zirconium, palladium, silver, and tungsten; metal oxides such as aluminum oxide (alumina), silicon oxide (silica, silica glass), titanium oxide, iron oxide, copper oxide, zinc oxide, and zirconium oxide; and metal nitrides such as boron nitride, aluminum nitride, and silicon nitride. Among these, silica, alumina, zinc oxide, and titanium oxide, which have excellent wettability and dispersibility with polysilazane, are preferred, and nanosilica (silica with an average particle size of 100 nm or less), which tends to give a transparent coating film in terms of refractive index, is even more preferred.

The inorganic filler preferably has a small average particle size, specifically within the range of 5 to 100 nm. If it is within this range, it will have good dispersibility in the polysilazane compound, and the transparency of the coating film will also be improved.

The inorganic filler average particle size is a volume-based average particle size, and can be measured using a laser diffraction/scattering particle size distribution measuring device.

The amount of the inorganic filler (component (B)) added is preferably within the range of 50 to 500 parts by mass per 100 parts by mass of the polysilazane compound (component (A)). If it is 50 parts by mass or more, the crack resistance and heat resistance of the coating composition are fully exhibited, and if it is 500 parts by mass or less, the workability is good and coating is easy.

[Other additives]
If necessary, a curing catalyst, a diluting solvent, etc. may be added to the coating composition of the present invention.

There are no particular limitations on the curing catalyst, so long as it has the effect of accelerating the curing reaction of the polysilazane compound.

Specific examples of the curing catalyst include organic acids such as carboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, linoleic acid, linoleic acid, oleic acid, and oxalic acid, hydroxycarboxylic acids such as malic acid and citric acid, d-block elements belonging to the fourth period of the periodic table such as titanium, manganese, cobalt, nickel, and zinc, platinum group elements such as ruthenium, rhodium, palladium, osmium, iridium, and platinum, and amphoteric elements such as aluminum, tin, and zinc, or compounds containing these elements. Among these, palladium acetate and palladium propionate are preferred because they promote the curing reaction with the addition of small amounts and are soluble in solvents.

The mixing ratio with the polysilazane compound is not particularly limited as it varies depending on the composition of the polysilazane compound and the type of the curing catalyst added, but in the case of palladium acetate, it is preferable that it is within the range of 0.01 to 2 parts by mass per 100 parts by mass of the polysilazane compound. If it is within this range, it has an excellent balance between curing speed and workability when used as a coating material.

The dilution solvent may be used to improve workability during coating. Examples of the dilution solvent include alkane compounds such as n-hexane, n-octane, and n-nonane; alkene compounds such as 1-octene, 1-nonene, and 1-decene; cycloalkane compounds such as cyclohexane, methylcyclohexane, and dimethylcyclohexane; ester compounds such as n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, isoamyl acetate, and ethyl caproate; and ether compounds such as diethyl ether, dibutyl ether, and ethylene glycol diethyl ether. Naphthene-based solvents such as Exxol DSP145/160 can also be used as the dilution solvent.

The dilution solvent may be used to adjust the viscosity of the composition or to improve wettability to the substrate, but it is preferable that the non-volatile content of the polysilazane compound does not fall below 50% by mass. If the non-volatile content is 50% by mass or more, the dilution solvent is less likely to remain in the cured product, and voids and discoloration are less likely to occur when exposed to high temperatures, which is preferable.

In preparing the composition of the present invention, a dispersion of the inorganic filler (B) can be used. A solvent such as anisole may also be added to the composition of the present invention.

The present invention is a coating composition that is durable at high temperatures of about 400°C and can form a thick film that can cover the unevenness of the substrate.

Methods for applying the highly heat-resistant coating composition of the present invention include, for example, roll coating methods using a chamber doctor coater, single-roll kiss coater, reverse kiss coater, bar coater, reverse roll coater, forward rotation roll coater, blade coater, knife coater, etc., spin coating methods, dispensing methods, dipping methods, spraying methods, transfer methods, slit coating methods, etc.

There are no particular limitations on the substrate to which the coating is applied, but examples include highly heat-resistant organic synthetic resins such as polyimide resin (PI) and bismaleimide resin (BMI), metals such as aluminum, silicon, iron, nickel, copper, silver, and gold, oxides such as alumina, silica, titanium oxide, and zinc oxide, and nitrides such as boron nitride, aluminum nitride, silicon nitride, and gallium nitride. The substrate surface may have irregularities.

The thickness of the coating film varies depending on the difference in linear expansion coefficient with the substrate and the temperature to which it is exposed, but is generally 0.1 to 100 μm, preferably 0.5 to 50 μm, in terms of cured film thickness. The composition of the present invention can form a thick film that can cover the unevenness of the substrate.

As a coating method, it is preferable to form an uncured coating film of the polysilazane compound by applying it to a substrate by any method, and then heat and dry the coating. This step is intended to completely remove the solvent and low molecular weight components contained in the coating, but is not necessarily required if the coating does not contain a solvent.

The heating and drying temperature is usually in the range of room temperature (25°C) to 300°C, preferably 70°C to 150°C. Preferred methods for the heating and drying process include heat treatment, microwave treatment, and infrared treatment. Curing proceeds even at room temperature, but curing can be accelerated by heating.

The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples. In the following examples, parts indicate parts by mass. The weight average molecular weight of component (A), the melting point and decomposition temperature of component (B), and the average particle size were measured by the above-mentioned methods.

[Synthesis Example A]
378 g of methyltrichlorosilane and 326 g of dimethyldichlorosilane were added as halogenated silane raw materials to 4,000 g of pyridine, and ammonia gas was blown into the liquid at 1.0 L/min for 430 minutes to cause a reaction. At this time, white ammonium chloride salt was generated and removed by filtration. The filtrate was heated at 100° C. under a reduced pressure of about 800 Pa to distill off pyridine, thereby obtaining polysilazane compound A. The weight-average molecular weight of this polysilazane compound was measured and found to be 2,700. In addition, in 100% by mass of this polysilazane, the (A-1) component was 50% by mass, the (A-2) component was 0% by mass, and the (A-3) component was 50% by mass.

[Synthesis Example B]
529 g of methyltrichlorosilane and 196 g of dimethyldichlorosilane were added as halogenated silane raw materials to 4,000 g of pyridine, and ammonia gas was blown into the liquid at 1.0 L/min for 460 minutes to cause a reaction. At this time, white ammonium chloride salt was generated and removed by filtration. The filtrate was heated at 100° C. under a reduced pressure of about 800 Pa to distill off pyridine, thereby obtaining polysilazane compound B. The weight average molecular weight of this polysilazane compound was measured and found to be 3,800. In addition, in 100% by mass of this polysilazane, the (A-1) component was 70% by mass, the (A-2) component was 0% by mass, and the (A-3) component was 30% by mass.

[Synthesis Example C]
582 g of monomethyldichlorosilane was added to 4,000 g of pyridine as a halogenated silane raw material, and ammonia gas was blown into the liquid at 1.0 L/min for 400 minutes to cause a reaction. At this time, white ammonium chloride salt was generated and removed by filtration. The filtrate was heated at 100° C. under a reduced pressure of about 800 Pa to distill off pyridine, thereby obtaining polysilazane compound C. The weight-average molecular weight of this polysilazane compound was measured and found to be 1,200. In addition, in 100 parts by mass of this polysilazane, the components (A-1) and (A-3) were 0% by mass, and the component (A-2) was 100% by mass.

[Synthesis example D] (for comparison)
227 g of methyltrichlorosilane and 456 g of dimethyldichlorosilane were added as halogenated silane raw materials to 4,000 g of pyridine, and ammonia gas was blown into the liquid at 1.0 L/min for 430 minutes to cause a reaction. At this time, white ammonium chloride salt was generated and removed by filtration. The filtrate was heated at 100° C. under a reduced pressure of about 800 Pa to distill off pyridine, thereby obtaining polysilazane compound D. The weight-average molecular weight of this polysilazane compound was measured and found to be 1,700. In addition, in 100% by mass of this polysilazane, the (A-1) component was 30% by mass, the (A-2) component was 0% by mass, and the (A-3) component was 70% by mass.

[Synthesis example E] (for comparison)
582 g of dimethyldichlorosilane was added to 4,000 g of pyridine as a halogenated silane raw material, and ammonia gas was blown into the liquid at 1.0 L/min for 400 minutes to cause a reaction. At this time, white ammonium chloride salt was generated and removed by filtration. The filtrate was heated at 100° C. under a reduced pressure of about 800 Pa to distill off pyridine, thereby obtaining polysilazane compound E. The weight-average molecular weight of this polysilazane compound was measured and found to be 960. In addition, in 100% by mass of this polysilazane, the components (A-1) and (A-2) were 0% by mass, and the component (A-3) was 100% by mass.

[Example 1]
70 parts of the polysilazane compound A obtained in Synthesis Example A, 30 parts of anisole, 0.2 parts of palladium acetate, and 525 parts of a silica filler toluene dispersion (TOL-ST: manufactured by Nissan Chemical Industries, Ltd., particle size 10 to 15 nm, non-volatile content 40% by mass) were mixed to obtain an intermediate liquid a. This intermediate liquid a was dried under reduced pressure with an evaporator to remove the solvent, and then diluted with Exxol DSP145/160 (manufactured by Exxon Mobil Corp.) so that the non-volatile content was 70% by mass to obtain a coating liquid a. This coating liquid a was applied to a silicon wafer having a thickness of 0.65 mm with a spin coater so that the coating thickness after curing was 20 μm, and the coating was cured by heating at 150 ° C. for 3 hours. When the appearance after curing was checked, no appearance defects were observed. Thereafter, a heat resistance test was performed at 400 ° C. for 3 hours, and the appearance after the heat resistance test was checked again, and there was no change compared to before the test.

[Example 2]
70 parts of the polysilazane compound B obtained in Synthesis Example B, 30 parts of anisole, 0.2 parts of palladium acetate, and 525 parts of a silica filler toluene dispersion (TOL-ST: manufactured by Nissan Chemical Industries, Ltd., particle size 10-15 nm, non-volatile content 40% by mass) were mixed to obtain an intermediate liquid b. This intermediate liquid b was dried under reduced pressure with an evaporator to remove the solvent, and then diluted with Exxol DSP145/160 (manufactured by Exxon Mobil Corp.) so that the non-volatile content was 70% by mass to obtain a coating liquid b. This coating liquid b was applied to a silicon wafer having a thickness of 0.65 mm with a spin coater so that the coating thickness after curing was 20 μm, and the coating was cured by heating at 150 ° C. for 3 hours. When the appearance after curing was checked, no appearance defects were observed. Thereafter, a heat resistance test was performed at 400 ° C. for 3 hours, and the appearance after the heat resistance test was checked again, and there was no change compared to before the test.

[Example 3]
70 parts of the polysilazane compound C obtained in Synthesis Example C, 30 parts of anisole, 0.2 parts of palladium acetate, and 525 parts of a silica filler toluene dispersion (TOL-ST: manufactured by Nissan Chemical Industries, Ltd., particle size 10-15 nm, non-volatile content 40% by mass) were mixed to obtain intermediate liquid c. This intermediate liquid c was dried under reduced pressure with an evaporator to remove the solvent, and then diluted with Exxol DSP145/160 (manufactured by Exxon Mobil Corp.) so that the non-volatile content was 70% by mass to obtain coating liquid c. This coating liquid c was applied to a silicon wafer having a thickness of 0.65 mm with a spin coater so that the coating thickness after curing was 20 μm, and the coating was cured by heating at 150 ° C. for 3 hours. When the appearance after curing was checked, no appearance defects were observed. Thereafter, a heat resistance test was performed at 400 ° C. for 3 hours, and the appearance after the heat resistance test was checked again, and there was no change compared to before the test.

[Example 4]
70 parts of the polysilazane compound A obtained in Synthesis Example A, 30 parts of anisole, 0.2 parts of palladium acetate, and 70 parts of zinc oxide (Panatetra: manufactured by Panasonic Corporation, particle size 20 to 40 μm) were mixed to obtain intermediate liquid d. This intermediate liquid d was dried under reduced pressure using an evaporator to distill off the solvent, and then diluted with Exxol DSP145/160 (manufactured by Exxon Mobil Corporation) so that the non-volatile content was 80 mass% to obtain coating liquid d. This coating liquid d was applied to a silicon wafer with a thickness of 0.65 mm using a spin coater so that the coating thickness after curing was 20 μm, and was heated at 150 ° C for 3 hours to be cured. When the appearance after curing was checked, no appearance defects were found. Thereafter, a heat resistance test was performed at 400 ° C for 3 hours, and the appearance after the heat resistance test was checked again, and there was no change compared to before the test.

[Example 5]
70 parts of the polysilazane compound A obtained in Synthesis Example A, 30 parts of anisole, 0.2 parts of palladium acetate, and 88 parts of a silica filler toluene dispersion (TOL-ST: manufactured by Nissan Chemical Industries, Ltd., particle size 10 to 15 nm, non-volatile content 40% by mass) were mixed to obtain an intermediate liquid e. This intermediate liquid e was dried under reduced pressure with an evaporator to remove the solvent, and then diluted with Exxol DSP145/160 (manufactured by Exxon Mobil Corp.) so that the non-volatile content was 70% by mass to obtain a coating liquid e. This coating liquid e was applied to a silicon wafer having a thickness of 0.65 mm with a spin coater so that the coating thickness after curing was 20 μm, and the coating was cured by heating at 150 ° C. for 3 hours. When the appearance after curing was checked, no appearance defects were observed. Thereafter, a heat resistance test was performed at 400 ° C. for 3 hours, and the appearance after the heat resistance test was checked again, and there was no change compared to before the test.

[Example 6]
70 parts of the polysilazane compound A obtained in Synthesis Example A, 30 parts of anisole, 0.2 parts of palladium acetate, and 875 parts of a silica filler toluene dispersion (TOL-ST: manufactured by Nissan Chemical Industries, Ltd., particle size 10 to 15 nm, non-volatile content 40% by mass) were mixed to obtain an intermediate liquid f. This intermediate liquid f was dried under reduced pressure with an evaporator to remove the solvent, and then diluted with Exxol DSP145/160 (manufactured by Exxon Mobil Corp.) so that the non-volatile content was 70% by mass to obtain a coating liquid f. This coating liquid f was applied to a silicon wafer having a thickness of 0.65 mm with a spin coater so that the coating thickness after curing was 20 μm, and the coating was cured by heating at 150 ° C. for 3 hours. When the appearance after curing was checked, no appearance defects were observed. Thereafter, a heat resistance test was performed at 400 ° C. for 3 hours, and the appearance after the heat resistance test was checked again, and there was no change compared to before the test.

[Comparative Example 1]
70 parts of the polysilazane compound D obtained in Synthesis Example D, 30 parts of anisole, 0.2 parts of palladium acetate, and 525 parts of a silica filler toluene dispersion (TOL-ST: manufactured by Nissan Chemical Industries, Ltd., particle size 10-15 nm, non-volatile content 40% by mass) were mixed to obtain an intermediate liquid g. This intermediate liquid g was dried under reduced pressure using an evaporator to remove the solvent, and then diluted with Exxol DSP145/160 (manufactured by Exxon Mobil Corp.) so that the non-volatile content was 70% by mass to obtain a coating liquid g. This coating liquid g was applied to a silicon wafer having a thickness of 0.65 mm using a spin coater so that the coating thickness after curing was 20 μm, and the coating was cured by heating at 150 ° C. for 3 hours. When the appearance after curing was checked, no appearance defects were found. Thereafter, a heat resistance test was performed at 400 ° C. for 3 hours, and when the appearance after the heat resistance test was checked again, cracks were found to have occurred in the coating film.

[Comparative Example 2]
70 parts of the polysilazane compound E obtained in Synthesis Example E, 30 parts of anisole, 0.2 parts of palladium acetate, and 525 parts of a silica filler toluene dispersion (TOL-ST: manufactured by Nissan Chemical Industries, Ltd., particle size 10 to 15 nm, non-volatile content 40% by mass) were mixed to obtain an intermediate liquid h. This intermediate liquid h was dried under reduced pressure using an evaporator to remove the solvent, and then diluted with Exxol DSP145/160 (manufactured by Exxon Mobil Corp.) so that the non-volatile content was 70% by mass to obtain a coating liquid h. This coating liquid h was applied to a silicon wafer having a thickness of 0.65 mm using a spin coater so that the coating thickness after curing was 20 μm, and the wafer was heated at 150 ° C. for 3 hours to cure, but did not cure. Thereafter, a heat resistance test was performed at 400 ° C. for 3 hours, and the appearance after the heat resistance test was checked again, and the coating thickness was found to have significantly decreased.

[Comparative Example 3]
70 parts of the polysilazane compound A obtained in Synthesis Example A, 30 parts of anisole, 0.2 parts of palladium acetate, and 210 parts of zinc carbonate (manufactured by Kanto Chemical Co., Ltd.) were mixed to obtain intermediate liquid i. This intermediate liquid i was dried under reduced pressure using an evaporator to remove the solvent, and then diluted with Exxol DSP145/160 (manufactured by Exxon Mobil Corp.) so that the non-volatile content was 70% by mass to obtain coating liquid i. This coating liquid i was applied to a silicon wafer having a thickness of 0.65 mm using a spin coater so that the coating thickness after curing was 20 μm, and was heated at 150 ° C for 3 hours to be cured. When the appearance after curing was confirmed, voids were generated on the front surface of the coating film. Thereafter, a heat resistance test was performed at 400 ° C for 3 hours, and the appearance after the heat resistance test was confirmed again, and more voids were generated compared to before the test.

[Comparative Example 4]
70 parts of the polysilazane compound A obtained in Synthesis Example A, 30 parts of anisole, and 0.2 parts of palladium acetate were mixed to obtain intermediate liquid j. This intermediate liquid j was dried under reduced pressure using an evaporator to remove the solvent, and then diluted with Exxol DSP145/160 (manufactured by Exxon Mobil) so that the non-volatile content was 70% by mass to obtain coating liquid j. This coating liquid j was applied to a silicon wafer having a thickness of 0.65 mm using a spin coater so that the coating thickness after curing was 20 μm, and was heated at 150 ° C for 3 hours to be cured. When the appearance after curing was checked, no appearance defects were found. Thereafter, a heat resistance test was performed at 400 ° C for 3 hours, and when the appearance after the heat resistance test was checked again, cracks were found to have occurred in the coating film.

[Heat resistance test]
A heat resistance test was carried out on the coating samples prepared in the examples and comparative examples. The test conditions were to raise the temperature from room temperature to 400°C at 10°C/min, hold for 3 hours, and then naturally cool to room temperature. When the temperature returned to room temperature, the appearance was observed. Note that if the difference (Q-P)/Q between the film thickness P after the heat resistance test and the film thickness Q after coating was 5% or less, it was considered as no change.

The examples and comparative examples are shown in the following Table 1. The melting point and decomposition temperature of the filler are indicated with "(decomposition)" for the decomposition temperature, and only the numerical value for the melting point is shown.

In Examples 1 to 6 and Comparative Examples 1 and 4, no poor appearance occurred after curing. On the other hand, in Comparative Example 2, the coating did not cure even after heating at 150°C. This is presumably because the polysilazane compound used does not contain any of the (A-1) or (A-2) components, making it difficult to form three-dimensional bonds compared to the structure specified in this invention. Also, in Comparative Example 3, voids occurred after curing. This is thought to be because the decomposition temperature of the filler used is low, and it decomposed at the curing treatment temperature and generated bubbles. Furthermore, the effect was even more noticeable during the heat resistance test at 400°C.

In the appearance after the heat resistance test, almost no change was observed compared to before the test in Examples 1 to 6, whereas changes in appearance occurred in Comparative Examples 1 to 4. It is believed that in Comparative Examples 1 and 2, the (A-1) and (A-2) components specified in the present invention were less than 50 mass% of the total polysilazane compound, and therefore sufficient heat resistance was not achieved. Also, in Comparative Example 4, no filler was added, so the cure shrinkage stress of the polysilazane resin was large, and the stress due to the difference in linear expansion coefficient between the substrate and the coating film at high temperatures was further added, which is thought to have caused cracks.

From these findings, it can be said that the highly heat-resistant coating material of the present invention is stable even at high temperatures of 400°C and is resistant to cracks and film loss.

The present invention is not limited to the above-described embodiment. The above-described embodiment is merely an example, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits similar effects is included within the technical scope of the present invention.

Claims (5)

A highly heat-resistant coating composition comprising the following component (A) and component (B):
(A) a polysilazane compound containing a structure represented by the following general formula (A-1), wherein the structure represented by the general formula (A-1) accounts for 50 to 100 mass % of the entire polysilazane compound; (B) an inorganic filler having a melting point and decomposition temperature of 400° C. or higher;

(In the formula, R ¹ is a group selected from an aliphatic hydrocarbon group having 1 to 6 carbon atoms and an aromatic hydrocarbon group having 6 to 12 carbon atoms, and in the polysilazane compound, R ¹ may be the same or different.) 2. The highly heat-resistant coating composition according to claim 1, wherein R ¹ in the general formula (A-1) is a methyl group. 3. The highly heat-resistant coating composition according to claim 1, wherein the component (B) is selected from the group consisting of silica, alumina, zinc oxide and titanium oxide. 4. The highly heat-resistant coating composition according to claim 1 , wherein the average particle size of the component (B) is within the range of 5 to 100 nm. 5. The highly heat-resistant coating composition according to claim 1 , wherein the component (B) is contained in an amount of 50 to 500 parts by mass per 100 parts by mass of the component (A).