JPH07196986A - Composition for coating - Google Patents

Abstract

PURPOSE:To obtain a coating composition, capable of providing a dense ceramic film excellent in heat, abrasion and corrosion resistances, etc., according to the baking at low temperatures by adding metallic fine particles to a coating solution consisting essentially of a polysilazane having a specified structure. CONSTITUTION:This composition is obtained by adding metallic fine particles (preferably independent dispersed superfine particles of Ag having 50-100Angstrom particle diameter) in an amount of preferably 0.05-5 pts. wt. based on 100 pts. wt. polysilazane to a coating solution consisting essentially of the polysilazane, having a main skeleton composed of a unit expressed by the formula (R<1> to R<3> each is H, an alkyl, an alkenyl, etc., with the proviso that at least one of R<1> to R<3> is H) and having 100-50000 number-average molecular weight. Furthermore, methylene chloride, ethyl ether, etc., are preferred as a solvent used in the polysilazane coating solution. The solvent is preferably used so as to afford 3-50 wt.% solid concentration in the coating solution.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a coating composition containing polysilazane as an essential component and capable of forming a coating film having excellent heat resistance, abrasion resistance and corrosion resistance.

[0002]

2. Description of the Related Art Organic paints are not sufficient for obtaining high heat resistance, wear resistance and corrosion resistance, and ceramic coatings are used. Conventionally, as a method of forming a ceramic coating, PVD (sputtering method, etc.),
Known are CVD, sol-gel method, polytitanocarbosilane-based paint, poly (dicyl) silazane-based paint, polysilazane-based paint, polymetallosilazane-based paint, and the like.

[0003]

The above-mentioned ceramics-based coating methods are known, but all have problems. That is, the PVD and CVD methods are expensive. In the sol-gel method, the required firing temperature is as high as 500 ° C or higher. Low-temperature baking (4
The surface strength at 00 ° C. or lower) is insufficient. Those using a poly (disyl) silazane-based polymer are difficult to apply and cracks occur. Polysilazane and polymetallosilazane coatings can be fired at 200 to 500 ° C, but firing at less than 300 ° C does not necessarily give good film quality.

Therefore, the present invention solves the problems in the prior art as described above, and by baking at a low temperature (150 ° C. to 350 ° C.), a dense coating film having excellent heat resistance, abrasion resistance and corrosion resistance and no cracks is formed. It is an object of the present invention to provide a coating composition to be given and a construction method thereof, and in particular, to make it possible to coat electronic parts, plastics and the like, which has hitherto been impossible due to the feature of low temperature firing.

[0005]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned problems, the present inventors have found that a coating liquid containing polysilazane as a main component is added with metal fine particles to form a coating film with air. It has been found that the curing reaction is promoted when firing in a medium, and a good coating is formed at a firing temperature lower than conventional ones.

Thus, according to the present invention, the general formula (I):

[0007]

[Chemical 2]

(However, R ¹ , R ² and R ³ are each independently a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, or a group other than these groups in which the group directly bonded to silicon is carbon. , An alkylsilyl group, an alkylamino group, an alkoxy group or a metal atom, provided that at least one of R ¹ , R ² and R ³ is a hydrogen atom). There is provided a coating composition comprising fine particles of metal added to a coating solution containing polysilazane having an average molecular weight of 100 to 50,000 as a main component.

The polysilazane to be used may be any polysilazane having at least a Si--H bond or an N--H bond in the molecule. Not only polysilazane alone but also a copolymer of polysilazane and another polymer or polysilazane and other It can also be used as a mixture with the compound of. The polysilazanes to be used include those having a chain structure, a cyclic structure, or a crosslinked structure, or those having a plurality of these structures simultaneously in the molecule, and these can be used alone or in a mixture.

Typical examples of the polysilazane to be used are as follows, but the polysilazane is not limited thereto. Perhydropolysilazane is preferred. General formula (I)
Wherein R ¹ , R ² and R ³ have a hydrogen atom is perhydropolysilazane, and the production method thereof is, for example, Japanese Patent Publication No. 63-16325, D. Seyferth et al. Communicat.
ion of Am. Cer. Soc., C-13, January 1983. What is obtained by these methods is a mixture of polymers having various structures, but basically contains a chain portion and a cyclic portion in the molecule,

[0011]

[Chemical 3]

It can be represented by the chemical formula: An example of the structure of perhydropolysilazane is as follows.

[0013]

[Chemical 4]

In the general formula (I), R ¹ and R ² are hydrogen atoms,
A method for producing polysilazane having a methyl group in R ³ is described in D.
Seyferth et al. Polym. Prepr., Am. Chem. Soc., Div. Po
lym. Chem., 25 , 10 (1984). The polysilazane obtained by this method has a repeating unit of −
(SiH ₂ NCH ₃₎ - is a chain polymer and a cyclic polymer, either no cross-linked structure.

In the general formula (I), R ¹ and R ³ are hydrogen atoms,
A method for producing a polyorgano (hydro) silazane having an organic group in R ² is described in D. Seyferth et al., Polym. Prepr., Am. Chem.
Soc., Div. Polym. Chem., 25 , 10 (1984), JP-A-6
1-89230 and 62-156135. The polysilazane obtained by these methods, - (R ² SiHNH) - as a repeating unit, and which mainly polymerization degree having a cyclic structure 3~5 (R ³ SiHNH) _X [(R ² SiH) _1.5 N ]
_Some have the chain structure and the ring structure at the same time in the molecule represented by the chemical formula of _1-X (0.4 <x <1).

In the general formula (I), polysilazane having a hydrogen atom at R ¹ and an organic group at R ² and R ³ , and R ¹ and R ²
An organic group for R ³ and a hydrogen atom for R ³ is — (R ¹ R ²
SiNR ³ ) -is a repeating unit and the degree of polymerization is mainly 3
It has a cyclic structure of ~ 5. The polysilazane used is
As described above, it has a main skeleton composed of the unit represented by the general formula (I), but the unit represented by the general formula (I) may be cyclized as is clear from the above. When the moiety serves as a terminal group and such cyclization does not occur, the terminal of the main skeleton can be a group similar to R ¹ , R ² and R ³ or hydrogen.

Among the polyorgano (hydro) silazanes are D. Seyferth et al. Communication of Am. Cer. Soc., C.
-132, July 1984. has a crosslinked structure in the molecule. An example is as follows.

[0018]

[Chemical 5]

Further, polysilazane (R ¹ Si (NH) _x ) having a crosslinked structure obtained by ammonia decomposition of R ¹ SiX ₃ (X: halogen) as reported in JP-A-49-69717, or R ¹ SiX ₃ and R ²
Polysilazane having the following structure obtained by co-ammonia decomposition of ₂ SiX ₂ can also be used as a starting material.

[0020]

[Chemical 6]

Further, a polymetallosilazane containing a metal atom as shown in the following structure (in the formula, M which is a side chain metal atom may be crosslinked) can also be used as a starting material.

[0022]

[Chemical 7]

Further, polysiloxazane as reported in JP-A-62-195024, JP-A-2-8443.
Borosilazanes as reported in JP-A No. 6-63
81122, JP-A-63-191832, JP-A-2
Polymetallosilazanes as reported in JP-A-77427, JP-A-1-138108 and JP-A-1-13810.
7, JP-A-1-203429, JP-A-1-2034
No. 30, JP-A-4-63833, and Japanese Patent Application No. 3-3201.
No. 67, modified polysilazane, JP-A-2-175726, JP-A-1-138107, JP-A-5-86200, JP-A-5-331293, and JP-A-3-31326. The copolymerized polysilazane as described above can also be preferably used.

The polysilazane used has a number average molecular weight of from 100 to 50,000, more preferably from 500 to 10,000.
It is 0. If the molecular weight is too small, the yield during firing will be low,
On the other hand, if the molecular weight is too large, the stability of the solution is low and a sound film cannot be obtained. The present invention is characterized by adding fine metal particles to the coating solution containing polysilazane as a main component as described above. By adding fine metal particles, the curing and ceramization temperature of polysilazane can be lowered by about 100 to 150 ° C. The applicant has disclosed that polysilazane can be reacted with a specific organic compound to form a modified polysilazane to lower the ceramization temperature (Japanese Patent Application No. 4-3).
No. 9595, No. 4-272020, etc.), it was found in the present invention that similar effects can be obtained only by adding metal fine particles.

Compared with the case where polysilazane is modified with an organic compound, when the metal fine particles are added, the coating solution is stable, the obtained film is relatively dense, and the cost is relatively low. There is. The reason why the coating solution is stable is that the metal fine particles do not react with polysilazane to change its structure. However, when the independent dispersion ultrafine particles described later are added, since the dispersion liquid is a high boiling point alcohol, this acts as a stabilizer, and the coating liquid becomes more stable than the powdered additive product.

The reason why the metal fine particles lower the ceramization temperature is considered to be the action as a metal oxidation catalyst or dehydrogenation catalyst. In particular, the effect of independent dispersed ultrafine particles of Ag is great, and this is due to the fact that Ag ₂ O or A
It is considered that gO acts as an oxidant by the following reaction. 2Ag ₂ O-- → 4Ag + O ₂ (> 160 ° C.) 2AgO-- →→ 2Ag + O ₂ (> 100 ° C) The fine metal particles to be used are not particularly limited, but Au, Ag,
Pd and Ni are preferable, and Ag is particularly preferable.

The particle size of the fine metal particles is preferably smaller than 0.5 μm, more preferably 0.1 μm or less, and 0.1.
More preferably, it is smaller than 05 μm. If the particle size of the metal fine particles is large, the effect as a catalyst is small and the particles settle in the solution, which is not preferable. In particular, the particle size is 50-100Å (0.005-0.01)
(μm) ultrafine particles such as Au, Ag, and Pd dispersed in a dispersion liquid such as a high-boiling alcohol such as α-terpineol remains as a dispersion liquid (10 to 70 wt% concentration),
Alternatively, it suffices to add a dispersion liquid diluted with a solvent such as xylene as a coating liquid, and stir with a stirrer for about 10 to 60 minutes. As with general fine particles, a ball mill or ultrasonic dispersion is used to further disperse It is very suitable because it does not need to be uniformly dispersed.

The amount of the fine metal particles added is preferably 0.01 to 10 parts by weight, more preferably 0.05 to 5 parts by weight, based on 100 parts by weight of polysilazane. If the addition amount is too small, there is no effect. On the other hand, if the addition amount is too large, the agglomerated portion of the metal fine particles becomes a film defect, which is not preferable. As mentioned above, the fine metal particles should be uniformly dispersed in the polysilazane coating solution. As a method for uniformly dispersing, in the case of a dispersion liquid of independently dispersed ultrafine particles, stirring with a stirrer is sufficient, but in the case of general metal fine particles, in a silazane solution to which a commercially available dispersant is added in advance, if necessary. Ball mill,
By mixing and dispersing with a vibration mill etc. to make a uniform coating liquid.

Examples of the solvent include aliphatic hydrocarbons, alicyclic hydrocarbons, hydrocarbon solvents of aromatic hydrocarbons, halogenated hydrocarbons such as halogenated methane, halogenated ethane and halogenated benzene, aliphatic ethers, and fats. Ethers such as cyclic ethers can be used. Preferred solvents are halogenated hydrocarbons such as methylene chloride, chloroform, carbon tetrachloride, bromoform, ethylene chloride, ethylidene chloride, trichloroethane and tetrachloroethane, ethyl ether,
Ethers such as isopropyl ether, ethylbutyl ether, butyl ether, 1,2-dioxyethane, dioxane, dimethyldioxane, tetrahydrofuran, tetrahydropyran, pentanehexane, isohexane, methylpentane, heptane, isoheptane, octane, isooctane, cyclopentane, methylcyclopentane And hydrocarbons such as cyclohexane, methylcyclohexane, benzene, toluene, xylene and ethylbenzene.

When these solvents are used, two or more kinds of solvents may be mixed in order to adjust the solubility of polysilazane and the evaporation rate of the solvent. The amount (ratio) of the solvent used is selected according to the coating method used so as to improve workability, and is also selected according to the required film thickness, and also depends on the average molecular weight of polysilazane, the molecular weight distribution and its structure. Can be mixed up to about 99% by weight, and preferably has a solid content concentration of 3 to 50.
It is possible to mix in the range of% by weight.

Further, in the present invention, a suitable filler may be added if necessary. Examples of the filler include fine powders of oxide-based inorganic materials such as silica, alumina, zirconia, and mica, or non-oxide-based inorganic materials such as silicon carbide and silicon nitride. Depending on the application, it is also possible to add metal powders such as aluminum, zinc and copper. More specifically, examples of fillers include silica-based materials such as silica sand, quartz, novaculite, and diatomaceous earth: synthetic amorphous silica: kaolinite, mica, talc, wollastonite, asbestos, calcium silicate, aluminum silicate. Silicates such as: glass powder, glass spheres, hollow glass spheres, glass flakes, glass spheres such as foam glass spheres: boron nitride, boron carbide, aluminum nitride, aluminum carbide, silicon nitride, silicon carbide, titanium boride, nitride Non-oxide inorganic substances such as titanium and titanium carbide: calcium carbonate: zinc oxide, alumina, magnesia, titanium oxide, beryllium oxide and other metal oxides: barium sulfate, molybdenum disulfide,
Tungsten disulfide, carbon fluoride, and other inorganic substances: metal powders such as aluminum, bronze, lead, stainless steel, zinc: carbon black, coke, graphite, pyrolytic carbon, carbon bodies such as hollow carbon spheres, and the like.

These fillers have various shapes such as needle-like shape (including whiskers), granular shape, and scale-like shape, either alone or in 2 pieces.
A mixture of two or more species can be used. Further, it is desirable that the particle size of these fillers is smaller than the film thickness that can be applied at one time. The addition amount of the filler is in the range of 0.05 parts by weight to 10 parts by weight with respect to 1 part by weight of polysilazane, and the particularly preferable addition amount is in the range of 0.2 parts by weight to 3 parts by weight. Further, the surface of the filler may be surface-treated by a coupling agent treatment, vapor deposition, plating or the like for use.

The coating composition may contain various pigments, leveling agents, defoaming agents, antistatic agents, ultraviolet absorbers, pH adjusters, dispersants, surface modifiers, plasticizers, and drying accelerators, if necessary. Alternatively, anti-flow agents may be added. According to the invention,
Similarly, in the coating method using the coating composition as described above, the coating composition is repeatedly applied to the substrate once or twice or more and then fired to obtain a silicon-nitrogen-oxygen-metal element system or The coating film is made of silicon-nitrogen-oxygen-carbon-metal element ceramics.

The base on which the coating composition is applied is not particularly limited and may be any of metal, ceramics, plastics and the like. As a coating means for coating, a usual coating method, that is, dipping, roll coating, bar coating, brush coating, spray coating, flow coating or the like is used. Further, if the substrate is sanded, degreased, and surface-treated with various blasts before coating, the adhesion performance of the coating composition is improved.

After coating by such a method and sufficiently dried, it is heated and baked. By this firing, the metal fine particle-containing polysilazane is crosslinked, condensed, or, depending on the firing atmosphere, oxidized and hydrolyzed to be hardened to form a tough coating. The firing conditions differ depending on the molecular weight and structure of polysilazane. The heating rate is not particularly limited,
A slow temperature rising rate of 0.5 to 10 ° C./min is preferable. The preferred firing temperature is in the range of 250 ° C to 350 ° C. The firing atmosphere may be oxygen, air, or an inert gas, but the air is more preferable. Oxidation of polysilazane added with fine metal particles by hydrolysis in air or hydrolysis by water vapor coexisting in the air proceeds,
At the low firing temperature as described above, Si—O bond or Si
It is possible to form a tough coating mainly composed of -N bond.

Depending on the type of polysilazane containing fine metal particles to be coated, conversion into ceramics may be incomplete under limited firing conditions. In this case, the coating film after firing may be treated at a temperature of less than 150 ° C. Hold for a long time,
It is possible to improve the properties of the coating film. In this case, the holding atmosphere is preferably air, and more preferably wet air having an increased water vapor pressure. The holding time is not particularly limited, but 10 minutes or more and 30 days or less is practically appropriate. The holding temperature is not particularly limited, but 0 ° C or higher and lower than 150 ° C is actually suitable. Although it is naturally effective to keep the temperature at 150 ° C. or higher, the heating operation at 150 ° C. or higher is defined as “baking” in the text.

By this holding in air, the oxidation of the polysilazane containing the fine metal particles or the hydrolysis by the water vapor coexisting in the air further progresses, the conversion to ceramics is completed, and the properties are further improved and the toughness is improved. It becomes possible to form a coating film. According to the above method, the firing temperature can be lowered and various problems caused by the high firing temperature can be alleviated.

[0038]

[Production of raw material perhydropolysilazane]

Gas injection tube into a four-necked flask with an internal volume of 1 liter,
A mechanical stirrer and dewar condenser were installed. After replacing the inside of the reactor with deoxygenated dry nitrogen, put 490 ml of degassed dry pyridine in a four-necked flask,
This was ice-cooled. Next, 51.6 g of dichlorosilane was added to produce a white solid adduct (SiH ₂ Cl · 2C ₅ H ₅
N) was produced. The reaction mixture is ice-cooled and, with stirring,
51.0 g of purified ammonia was bubbled through the sodium hydroxide tube and the activated carbon tube to heat.

After the reaction was completed, the reaction mixture was centrifuged, washed with dry pyridine, and then filtered under a nitrogen atmosphere to obtain 850 ml of a filtrate. The solvent was removed from the filtrate (5 ml) by distillation, and 0.1 g of a resinous solid perhydropolysilazane was obtained. The number average molecular weight of the obtained polymer was measured by the freezing point depression method (solvent: dry benzene),
It was 893. IR (infrared absorption) spectrum (solvent:
Concentration of dry o-xylene; perhydropolysilazane: 1
0.2 g / l) is the wave number (cm ⁻¹ ) 3340 (apparent extinction coefficient ε = 0.5571 g ⁻¹ cm ⁻¹ ), and N of 1175.
H-based absorption; SiH-based absorption of 2160 (ε = 3.14); SiH and SiNSi of 1024-820
Showed absorption based on. ^{The 1} H NMR (proton nuclear magnetic resonance) spectra (60 MHz, solvent CDCl ₃ / reference material TMS) all show broad absorption. That is,
δ 4.8 and 4.4 (br., SiH); 1.5 (b
r. , NH) absorption was observed.

[0040] Example Tonen made perhydropolysilazane (Type-1, PHP
S-1: 0.75 g of ultrafine Ag dispersion liquid (manufactured by Vacuum Metallurgical Co., Ltd., 10 wt% α-terpineol solution, in 100 g of a 15 wt% xylene solution having a number average molecular weight Mn≈800)
Particle size; 50 to 100Å) was added and stirred at room temperature for 60 minutes.

Using this solution as a coating solution, a silicon wafer having a diameter of 4 inches and a thickness of 0.5 mm was coated with a spin coater (1500 rpm, 20 seconds). This coating film was heated at 350 ° C. for 1 hour in the air (heated at 10 ° C./minute) to obtain a ceramic coating having a film thickness of 5600 Å. When the degree of progress of ceramization was evaluated by IR, S
The iH residual rate was 0 (%), and the SiO / SiN ratio was 40.

Comparative Example On the other hand, a coating solution of perhydropolysilazane containing no ultrafine Ag dispersion was applied and evaluated by the same process. SiH residual ratio = 10 (%), SiO / S
The iN ratio was 2.3. Next, these baked coatings are
% Hydrofluoric acid (manufactured by Daikin Industries, Ltd.) and 1763 ml of 61% nitric acid (manufactured by Kosou Chemical Co., Ltd.), the etching rates were 1057 Å / min and 2013 Å / in Example 1 and Comparative Example 1, respectively. It was a minute.

When the coating liquid of Example 1 was placed in a glass bottle with a polypropylene cap and allowed to stand at room temperature, it did not gel even after 3 months (the coating liquid of Comparative Example 1 gelled).

[0044]

EFFECTS OF THE INVENTION According to the present invention, a coating having excellent heat resistance, abrasion resistance, corrosion resistance and good adhesion to a substrate can be obtained by firing at a low temperature which has never been seen before. Moreover, the coating solution is stable and inexpensive, and the obtained ceramic film is dense. The composition of the present invention is suitable as a surface protective agent for not only metals and ceramics but also plastic materials unsuitable for high temperature treatment and electronic parts. In particular, hard coating agents for plastics, coating agents for suppressing gas permeation of synthetic resin films and containers, protective films and insulating films for semiconductors, that is, passivation films, interlayer insulating films, chip coat films, etc.
It can also be used as a semiconductor sealant, an undercoat film or an alignment film of a liquid crystal display.

[Brief description of drawings]

FIG. 1 is an IR spectrum diagram for evaluating ceramics of Examples.

FIG. 2 is an IR spectrum diagram for evaluating the ceramic of Comparative Example 1.

Claims (2)

[Claims] 1. Mainly represented by the general formula (I): (However, R ¹ , R ² and R ³ are each independently a hydrogen atom,
An alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, or a group other than these groups in which the group directly bonded to silicon is carbon, an alkylsilyl group, an alkylamino group, and an alkoxy group. However, at least one of R ¹ , R ² and R ³ is a hydrogen atom. ) A coating composition, wherein fine particles of metal are added to a coating solution containing polysilazane as a main component and having a main skeleton composed of a unit represented by the formula (1) and having a number average molecular weight of 100 to 50,000. 2. The coating composition according to claim 1, wherein the metal is at least one of Au, Ag, Pd and Ni.