JPH0734032A - Composition for hard coat - Google Patents

Abstract

PURPOSE:To obtain a composition for hard coats, capable of forming a film having a high hardness and flexibility and excellent in pot life. CONSTITUTION:This composition for hard coats is obtained by blending a tetraethoxysilane oligomer wit <=1% monomer content in a solvent or a dispersing medium.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a composition for hard coat.

[0002]

2. Description of the Related Art Resin, silicone and inorganic coatings are used as a means for preventing scratches from forming a hard thin film on the surface of glass, resin or metal, preventing erosion of various chemicals, and preventing gas permeation such as moisture and air.

[0003]

Among these coating materials, the resin thin film is flexible but easily scratched. Although the silicone thin film has water repellency, it is easily scratched. On the other hand, although the inorganic thin film is not easily scratched, it is brittle and difficult to form a uniform thin film. In particular, tetraethoxysilane oligomer is used as the inorganic hard coat composition, but the hardness of the thin film is insufficient and the storage stability as the hard coat composition is difficult, and mass production is difficult. .

[0004]

Therefore, the present inventors have
As a result of repeated intensive studies in view of the above-mentioned problems, surprisingly, the composition blended in the tetraethoxysilane / oligomer solvent or dispersion medium in which the amount of the monomer is suppressed to a certain level or less has good storage stability, and by using this In addition, they have found that they are excellent in hardness and flexibility and can form an ultrathin coating film, and have reached the present invention.

That is, the gist of the present invention resides in a hard coat composition obtained by blending a tetraethoxysilane oligomer having a monomer content of 1% or less with a solvent or a dispersion medium. Hereinafter, the present invention will be described in detail. First, as the tetraethoxysilane oligomer in the present invention, a partial hydrolyzate of tetraethoxysilane is used.

The hydrolysis reaction itself can be carried out by a known method, for example, by adding a predetermined amount of water to the above tetraethoxysilane in the presence of an acid catalyst and distilling off the by-produced alcohol, usually at room temperature. The reaction is performed at about -100 ° C. By this reaction, ethoxysilane is hydrolyzed, and further, a liquid silicate oligomer having an average of 2 or more hydroxyl groups (usually an average degree of polymerization of about 2 to 8, preferably 3 to 6) is obtained as a hydrolyzate by a condensation reaction. The degree of hydrolysis can be appropriately adjusted depending on the amount of water used, but in the present invention, it is usually selected from about 40 to 90%, preferably about 60 to 80%.

The tetraethoxysilane thus obtained
The oligomer usually contains about 2 to 10% of the monomer. If this monomer is contained, the storage stability of the composition liquid for hard coat is lacking, the viscosity increases during storage, and it becomes difficult to form a thin film, so the monomer content is 1% or less, preferably 0.3% or less. This monomer removal is carried out by flash distillation, vacuum distillation, etc.

As the solvent used in the present invention, alcohols or glycol derivatives, hydrocarbons, esters, ketones and ethers may be used alone or in admixture of two or more. Specific examples of alcohols include methanol, ethanol, isopropyl alcohol, n-butanol, isobutanol, and octanol.
Examples of the glycol derivative include ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono n-propyl ether, ethylene glycol mono n-butyl ether and the like.

Hydrocarbons include benzene, kerosene,
Toluene, xylene, etc. can be used, and as esters,
Methyl acetate, ethyl acetate, butyl acetate, methyl acetoacetate, ethyl acetoacetate and the like can be used. Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and acetylacetone, and ethers such as ethyl ether, butyl ether, methyl cellosolve, ethyl cellosolve, dioxane, furan and tetrahydrofuran can be used.

As the dispersion medium, for example, a water-surfactant system is suitable, and as the surfactant, anionic, cationic or nonionic ones are generally used. The anionic surfactants include carboxylates, sulfonates, sulfates, phosphates, etc., and the cationics include organic or inorganic acid salts of primary to tertiary amines, quaternary ammonium salts, Polyoxyethylene alkylamine salts and the like, and further nonionic ones include sorbitan dialkyl esters, ethylene glycol condensates of sorbitan alkyl esters, aliphatic alcohol polyethylene glycol condensates, alkylphenol polyethylene glycol condensates, polypropylene glycol polyethylene glycol condensates. And so on.

These surfactants are generally used in an amount of 0.1 to 5% with respect to the above-mentioned oligomer. When dispersing (emulsifying), an appropriate amount of water is used and a homomixer or colloid is used. A known method such as a mill or ultrasonic wave can be used. The compounding amount of the tetraethoxysilane oligomer is preferably 50 to 400 parts by weight, more preferably 100 to 250 parts by weight, based on 100 parts by weight.

If the amount is less than 50 parts by weight, cracks are likely to occur in the coating film, which is not preferable, and if it exceeds 400 parts by weight, the thickness of the coating film becomes extremely thin. The compounding method is generally to mix the tetraethoxysilane oligomer with the predetermined solvent or dispersion medium at room temperature. A curing catalyst is added as needed. Hydrochloric acid and nitric acid are used as curing catalysts. Tetraethoxysilane oligomer 100 is added
It is selected from about 0.1 to 1 part by weight based on parts by weight.

The hard coat composition of the present invention thus obtained is formed into a film on a substrate of polymer, metal, ceramic or the like by an impregnation method, a spin coater method, a spray method or the like. After being left as a solvent removal treatment at room temperature for 1 to 10 minutes, it is heat-cured at 100 ° C. or higher. The heating furnace may be a general-purpose furnace such as a gas furnace or an electric furnace. The hard coat according to the present invention is particularly suitable for forming a thin film having a thickness of 3 μm or less, further 1 μm or less. Three
If it exceeds μm, the resulting hard coat is likely to cause cracks in the ultrathin coating film. The hard coat composition of the present invention has a feature that the bot life in a liquid is 2 weeks or more, film formation is possible without thickening, the coating film hardness after film formation is high, and the film is also flexible.

[0014]

EXAMPLES The present invention will be described in more detail below with reference to examples. Parts and% are parts by weight and% by weight, unless otherwise specified. Example 1 500 equipped with stirrer, reflux condenser and thermometer
Tetraethoxysilane 2 in a round bottom flask in 3 ml
After adding 34 gr and 74 gr of methanol and mixing,
22.2 gr of 0.05% hydrochloric acid was added, and the internal temperature was 65 ° C, and 2
The hydrolysis reaction was performed for a time.

Then replace the condenser with an extraction tube,
The internal temperature was raised to 170 ° C., extraction was performed with methanol, and the mixture was further heated at 150 ° C. for 3 hours for condensation. In this way, a hydrolyzate was obtained. The degree of polymerization was 3 to 6 and the hydroxyl group was 10 or more. The amount of monomer in the tetraethoxysilane oligomer was 5%. Continue to 150
A jacket heated to ˜170 ° C. is boiled with tetraethoxysilane oligomer and the vaporized monomer is discharged out of the system together with an inert gas. The amount of monomer in the tetraethoxysilane oligomer thus obtained is 0.2%.
Met.

The tetraethoxysilane thus obtained
100 parts by weight of ethanol was added as a solvent to 100 parts by weight of the oligomer. Then, 1 cc of nitric acid was added as a curing catalyst. The viscosity of this hard coat composition liquid was about 1 to 2 cps without any change in viscosity after one month. A glass substrate was impregnated with this composition liquid for hard coat for 1 minute, pulled up at a pulling rate of 180 mm / min, subjected to solvent removal treatment at room temperature for 5 minutes, and then heat-cured at 100 ° C. for 30 minutes in an electric furnace. The obtained coating film thickness is 0.5 μm and the pencil hardness is 4
H was obtained.

Comparative Example 1 After obtaining a hydrolyzate by the same operation as in Example 1, the monomer was not removed. This hydrolyzate increased its viscosity remarkably thereafter, and after three days, it became several hundred cps and film formation was impossible.

[0018]

According to the present invention, a hard coat composition having excellent storage stability and high hardness and flexibility even after film formation can be obtained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuyuki Matsuzoe 2-5-2 Marunouchi, Chiyoda-ku, Tokyo Sanryo Kasei Co., Ltd.

Claims (1)

[Claims] 1. A hard coat composition comprising a tetraethoxysilane oligomer having a monomer content of 1% or less in a solvent or a dispersion medium.