JPH08281200A - Coating of polysilazane solution - Google Patents

Abstract

PURPOSE: To obtain a polysilazane coating film having uniformity and smooth ness capable of being permitted as an SiO2 ceramics film after ceramic forming treatment by moving an infiltrative member infiltrated with a polysilazane soln. along a plate-shaped surface to be coated held to an inclined state under predetermined pressure. CONSTITUTION: When a coating film of a polysilazane soln. is formed on a surface 20 to be coated extending in a flat plate shape, the surface 20 to be coated is held so as to be inclined with respect to a horizontal surface and an infiltrative member holder 10 infiltrated with the polysilazane soln. is moved in an almost horizontal direction while pressed to the surface 20 to be coated. At this time, the soln. infiltration amt. into the holder 10 is set to such a degree that a part of the soln. 21 bled from the holder 10 at the time of the movement of the holder 10 drips from the moving region of the holder 10 to flow. By repeating the movement of the holder 10 while a moving axis is successively shifted downward, the polysilazane soln. is applied to the surface 20 to be coated. A felt material is used as the holder 10 and the viscosity of the polysilazane soln. is set to 1-10 centipoise.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for coating a polysilazane solution.

[0002]

_2. Description of the Related Art A method has been developed for coating a surface of a substrate with ceramics which substantially consists of a SiO ₂ film. For example, in Japanese Patent Application No. 5-318188 by the present applicant, a coating composition containing a specific polysilazane is applied, heat-treated, and then exposed to a steam atmosphere, and / or
Alternatively, a method is disclosed in which a plastic film is coated with a SiO ₂ ceramic at a low temperature of 150 ° C. or lower by performing a step of immersing in an aqueous solution containing an acid catalyst or a base catalyst. Also, in Japanese Patent Application No. 6-236881 filed by the applicant of the present invention, a method of forming a polysilazane film on a substrate and then contacting it with an aqueous solution of a silicate ester so that the SiO ₂ ceramics can be coated at room temperature is disclosed. Has been done.

In these methods, it is necessary to apply a polysilazane solution to a substrate, but as a method for applying a polysilazane solution to a surface having a large area, spray coating, electrostatic coating, roller coating, brush Paint coating, flow coating,
Etc. are known.

[0004]

However, spray coating, electrostatic coating and flow coating have the drawback that the rate of adhesion to the coated area is low. Further, in the electrostatic coating method, since a high voltage is applied to the spray gun portion, the solvent of the polysilazane solution is limited from the viewpoint of preventing discharge. The brush coating method has problems such as deterioration of film quality due to hair loss and traces of brush streaks left when the drying speed of the solution solvent is high. further,
In the flow coating method, the coating thickness gradually increases from the upper side to the lower side of the surface to be coated, so that a uniform polysilazane coating cannot be obtained. The SiO ₂ -based ceramic coating obtained by converting such an inhomogeneous polysilazane coating into a ceramic has poor properties such as uniformity, smoothness, and optical characteristics. Therefore, the desired uniformity when applying the polysilazane solution,
A method that can easily obtain smoothness is desired.

[0005]

According to the present invention, the above-mentioned problems are (1) a method of coating a polysilazane solution on a flat surface to be coated, wherein the surface to be coated is inclined with respect to a horizontal plane. Then, the impregnating member impregnated with the polysilazane solution is moved in a substantially horizontal direction while being pressed against the surface to be coated, and the solution impregnation amount in the impregnating member is set to the above value when the impregnating member moves. Part of the solution exuding from the impregnating member is made to flow downward below the moving region of the impregnating member, and polysilazane is applied to the surface to be coated by repeating the moving while shifting the moving axis sequentially downward. It is solved by a coating method of a polysilazane solution characterized by coating.

The preferred embodiments of the present invention are listed below. (2) The method according to item (1), wherein the impregnating member is a felt material. (3) The polysilazane solution has a viscosity of 1 to 10 centipoise at a coating temperature, (1)
Alternatively, the method described in (2). (4) The polysilazane is represented by the following general formula (I):

[0007]

Embedded image

(In the above formula, 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 which is directly bonded to silicon. Represents an alkylsilyl group, an alkylamino group, and an alkoxy group.
At least one of R ¹ , R ² and R ³ is a hydrogen atom.) The method according to item (4), which is a polysilazane having a main skeleton composed of a unit represented by the formula: and having a number average molecular weight of 100 to 50,000.

According to the coating method of the present invention, the polysilazane solution dripping below the inclined surface to be coated is applied together with the solution that is newly exuded by the next movement of the impregnating member (particularly the felt material). Therefore, the uniformity that is acceptable as a SiO ₂ ceramics film after ceramization treatment,
At the same time as obtaining a polysilazane coating film having smoothness,
The yield is improved because the amount of polysilazane solution used is minimized.

The method of the present invention is particularly useful for coating a polysilazane solution having a low viscosity and fast solvent drying. The term "low viscosity" or "low viscosity" as used herein means that the viscosity of the polysilazane solution at the coating temperature is in the range of 1 to 100 centipoise.

The polysilazane used in the polysilazane solution to which the method of the present invention is preferably applied may be any polysilazane having at least Si-H bond or N-H bond in the molecule, not to mention polysilazane alone. Also, a copolymer of polysilazane and another polymer or a mixture of polysilazane and another compound can be used. Suitable polysilazanes 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. Representative examples of the polysilazane that is preferably used include, but are not limited to, the following.

[0012]

Embedded image

(In the above formula, 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, which is directly bonded to silicon. Represents an alkylsilyl group, an alkylamino group, and an alkoxy group.
At least one of R ¹ , R ² and R ³ is a hydrogen atom), and has a main skeleton composed of a unit represented by the formula: polysilazane having a number average molecular weight of 100 to 50,000.

From the viewpoint of increasing the hardness (denseness) of the obtained coating film, perhydropolysilazane in which R ¹ , R ² and R ³ are all hydrogen atoms in the above general formula (I) is preferable.
Organopolysilazane in which at least one of R ¹ , R ² and R ³ is an organic group (provided that at least one must be a hydrogen atom) is preferable from the viewpoint of increasing the flexibility of the obtained coating film. These polysilazanes and their production methods are described, for example, in Japanese Examined Patent Publication No. 63-16325, D. S.
eyferth et al. Communication of Am. Cer. Soc., C-13, Jan
uary 1983., D. Seyferth et al. Polym. Prepr., Am. Che
See m. Soc., Div. Polym. Chem., 25 , 10 (1984), JP 61-89230 A, JP 62-156135 A, and the like.

In the present invention, the following low temperature ceramics are further provided.
Mixed polysilazane can be preferably used
It For example, Japanese Patent Application No. 5-35604 filed by the applicant of the present application
The acetylacetonato complex addition po
Lisilazane can be mentioned. This modified polysilazane is
As polysilazane represented by the general formula (I) and a metal
An alloy containing nickel, platinum, palladium or aluminum
Acetyl obtained by reacting a cetylacetonato complex
Acetonato complex / polysilazane weight ratio 0.00000
Within the range of 1 to 2 and the number average molecular weight is about 200 to 500,000
It is an acetylacetonato complex-added polysilazane. the above
The acetylacetonato complex containing the metal of
Generated by acid dissociation from ton (2,4-pentadione)
Anion acac^-Is a complex coordinated to a metal atom,
Generally, the formula (CH₃COCHCOCH ₃)_nM [in the formula, M
Represents an n-valent metal].

The polysilazane which can be preferably used according to the present invention is not practical when the molecular weight is too low and the yield at the time of ceramization after coating is low. On the other hand, if the molecular weight is too high, the stability of the solution is low and a sound polysilazane coating film cannot be obtained. For these reasons, the molecular weight of the polysilazane used is a number average molecular weight with a lower limit of 100, preferably 5
00. The upper limit is 50,000, preferably 10,000.
Is.

The method of the present invention is particularly useful when using a polysilazane solvent which dries quickly after coating. For example,
As a solvent for preparing the polysilazane solution as described above, a hydrocarbon solvent of aliphatic hydrocarbon, alicyclic hydrocarbon, aromatic hydrocarbon, halogenated methane, halogenated ethane, halogenated carbonized halogenated benzene, etc. Ethers such as hydrogen, aliphatic ether and alicyclic ether, specifically, methylene chloride, chloroform, carbon tetrachloride, bromoform, ethylene chloride, ethylidene chloride, trichloroethane, halogenated hydrocarbons such as tetrachloroethane, ethyl ether. , Isopropyl ether, ethyl butyl ether, butyl ether, 1,2-dioxyethane, dioxane, dimethyldioxane, tetrahydrofuran,
Ethers such as tetrahydropyran, hydrocarbons such as pentanehexane, isohexane, methylpentane, heptane, isoheptane, octane, isooctane, cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, benzene, toluene, xylene, ethylbenzene and the like. .

According to the present invention, the concentration of the polysilazane dissolved in the solvent as described above may be any as long as the viscosity at the coating temperature is in the range of 1 to 100 centipoise, preferably 1 to 60 centipoise. It can be the concentration. For example, when xylene is used as a solvent,
A solution containing 65% by weight, preferably 5 to 58% by weight of polysilazane can be suitably used.

According to the present invention, the impregnable member is impregnated with the polysilazane solution as described above. This impregnable member is
Any material can be used as long as it can be impregnated with and retain a desired amount of the polysilazane solution, but it is preferable that the polysilazane coating film can be provided with uniformity and smoothness which are acceptable as a coating film. As a material for such an impregnable member,
Felt materials, sponge materials, and the like can be mentioned. Among them, the reason why the felt materials are preferable is that they have excellent liquid retention, are less likely to foam, and have no fibers falling out.

According to the present invention, the impregnating member containing the polysilazane solution is moved in a substantially horizontal direction while being pressed against the surface to be coated which is held so as to be inclined with respect to the horizontal plane, to apply the solution. In the simplest mode, a flat impregnating member such as a felt material is folded in two and sandwiched by a clip of a holder with a handle, and manually moved horizontally. The movement in the horizontal direction may be relative, and the impregnating member may be moved, the surface to be coated may be moved, or both may be combined.

When the impregnating member is pressed against the surface to be coated, a part of the polysilazane solution exuding from the impregnating member is allowed to hang down below the horizontally moving region of the impregnating member so that the impregnating member is allowed to flow downward. Control the amount of solution to be impregnated into. In practice, it is sufficient that the impregnating member can naturally hold the solution when the impregnating member is immersed in the polysilazane solution immediately before coating and taken out from the solution. Alternatively, it can be continuously performed by a continuous supply means (for example, by continuously supplying the polysilazane solution from another polysilazane solution tank through the impregnating member holder) according to the coating amount.

The pressure for pressing is not particularly limited as long as the polysilazane solution adheres evenly to the surface to be coated without fading when the impregnating member is moved in a substantially horizontal direction. However, whichever pressure is applied, it is preferable to keep the pressure constant in order to obtain a coating film having a uniform thickness. By doing so, a uniform polysilazane coating film is formed in the horizontal moving region of the impregnating member.

According to the present invention, after the impregnating member is moved in a substantially horizontal direction, in order to apply the downwardly flowing polysilazane solution, the moving axis thereof is shifted downward and the horizontal movement is repeated. At this time, the moving direction may be the same as the previous direction or the opposite direction. The width at the time of shifting downward can be arbitrarily set within a range in which the upper edge of the next moving region of the impregnating member is not below the lower edge of the previous moving region. Preferably, the impregnating member is moved so that the lower edge of the coated area and the upper edge of the next coated area slightly overlap, and the polysilazane solution portion that drooped earlier is applied. By moving the coating areas so as to slightly overlap each other in this manner, it is possible to reliably apply the drooped portion. In this way, the portion of the polysilazane solution that drooped in a certain horizontal moving step is applied by the impregnating member in the next horizontal moving step, and a uniform coating area gradually extends downward.

The material having the surface to be coated is not particularly limited,
For example, glass and various plastic materials are included. Examples of the plastic material include polycarbonate, polymethyl methacrylate, polyether sulfide, polyester, polypropylene, polyethylene terephthalate, and the like. The area and thickness of the surface to be coated are not particularly limited, and those having any area and thickness according to the application can be adopted.

During coating, the surface to be coated is held by being tilted, and its tilt angle θ is arbitrarily set within the range of 0 ° <θ <90 °, depending on the liquid viscosity and the bp of the solvent. Can be set. A preferable inclination angle θ is 30 ° <θ <90 °, and a more preferable inclination angle θ is 45 ° <θ <90 °.

The dry thickness of the coating film obtained by moving the impregnating member impregnated with the polysilazane solution once in the substantially horizontal direction is preferably 0.1 to 2.0 μm, more preferably 0.1 to 1. It is in the range of 0 μm. This film thickness can be controlled by changing the polysilazane concentration in the solution. For example, the film thickness can be increased by increasing the solid content concentration (decreasing the solvent concentration).

The polysilazane coating film having the desired homogeneity thus obtained may optionally be subjected to a drying step, a firing step, or a heat treatment followed by a humidification step and / or an acid catalyst or a base. By performing the step of immersing in a catalyst-containing aqueous solution, it is possible to convert the ceramics to substantially SiO ₂ . For the ceramicization of such polysilazane, refer to Japanese Patent Application No. 5-318188 cited above. Further, as another method of ceramization treatment, as described in Japanese Patent Application No. 6-236881 cited above, the polysilazane coating film is brought into contact with an aqueous solution of silicate ester to remove SiO ₂ from room temperature. It can also be converted into ceramics. After being made into ceramic in this way, the coating may be subjected to a washing step and / or a drying step, if desired.

The method of the present invention will now be further described with reference to the figures. FIG. 1 shows an example of an impregnable member holder 10 that can be used in the method of the present invention. The holder 10 has a clip 12 for fastening the impregnable member 11 and a handle 13. In a preferred embodiment, the impregnating member 11 is a non-woven felt sheet folded in two.

FIG. 2 illustrates a coating method of the polysilazane solution according to the present invention. The surface 20 to be coated is shown in FIG.
As shown in (a), it is inclined at an angle of 0 ° <θ <90 ° with respect to the horizontal plane. As shown in FIG. 2 (b), the impregnating member 11 soaked with the polysilazane solution is applied to the surface 20 to be coated by the holder 10 at a constant pressure so as to exude the solution.
Move it almost horizontally while pressing it against. After the impregnating member has moved, a part of the solution 21 flows downward due to gravity. After that, as shown in FIG. 3, the impregnating member is moved so that the lower edge of the area coated in FIG. The area is smeared with freshly leaching solution. By moving so as to slightly overlap with each other, it is possible to reliably apply the previously drooping portion.

[0030]

Example: Tonen perhydropolysilazane Type-1
A 20% xylene solution of (PHPS-1; number average molecular weight 900) was prepared. By adding 20 g of a 0.5% xylene solution of palladium acetate to 50 g of this solution,
A low temperature curable polysilazane solution containing palladium was prepared. The viscosity of this solution was 2 cps. As the impregnating member, a piece of felt cloth having a weight of 1 g and having a xylene resistance of 5 cm × 5 cm × thickness of 0.5 cm was folded in two and sandwiched between clips of a holder with a handle. A glass plate having a length of 30 cm and a width of 30 cm was held at an angle of 75 ° with respect to the horizontal plane. The felt cloth was impregnated with the polysilazane solution by immersing it in the previously prepared polysilazane solution.

A felt cloth impregnated with the polysilazane solution is applied to the upper end portion of the glass plate while holding the handle by hand, and the felt cloth is soaked by the polysilazane solution exuded during the movement and hung down the glass plate. While pressing it with a constant pressure so that it droops, it was moved at a speed of 10 cm / sec in the substantially horizontal direction to the opposite side end. Then, once the felt cloth is separated from the glass plate and the polysilazane solution is not re-immersed, it is below the starting point,
The felt cloth was placed at a position where the moving axis was shifted so as to overlap with the previous coating area by about 1 cm, and the felt cloth was similarly moved in the same direction. In this way, the felt cloth is repeatedly moved to coat the desired position on the glass plate, and then 250 ° C. in air.
It was baked for 1 hour. The ceramic film thus obtained was uniform, and no trace of brush streaks was visually observed.

[0032]

According to the coating method of the present invention, a polysilazane coating film having an acceptable uniformity and smoothness as a SiO ₂ ceramic coating after ceramization treatment can be obtained, and the amount of the polysilazane solution used is minimized. It's done.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of an impregnable member holder that can be used in the method of the present invention.

FIG. 2 is a side view (a) and a front view (b) showing a coating method of a polysilazane solution according to the present invention.

FIG. 3 is a front view showing a method for applying a polysilazane solution according to the present invention.

[Explanation of symbols]

 10 ... Impregnating member holder 11 ... Impregnating member 12 ... Clip 13 ... Handle 20 ... Surface to be coated

Claims (1)

[Claims] 1. A method of applying a polysilazane solution onto a flat surface to be coated, wherein the surface to be coated is held inclined with respect to a horizontal plane, and the impregnating member impregnated with the polysilazane solution is used as the impregnating member. While being pressed against the surface to be coated, it is moved in a substantially horizontal direction.
A part of the solution exuding from the impregnating member during the movement of the impregnating member is set to a level below the moving region of the impregnating member, and the movement is repeated while sequentially shifting the moving axis downward. The polysilazane solution is applied onto the surface to be coated by the method described above.