JPH05202314A - Optically curable coating composition, its cured coating film and its formation - Google Patents

Abstract

PURPOSE:To obtain an optically curable coating composition suitable for a hard coating agent, providing a cured material having excellent curability, high hardness and scratch resistance, comprising a silane hydrolyzate, a colloidal metal oxide and an aluminum compound. CONSTITUTION:(A) 100 pts.wt. hydrolyzate of a silane (preferably 3- acryloxypropyltrialkoxysilane) of the formula (R<1> is H or methyl; R<2> is substituted or nonsubstituted bifunctional hydrocarbon group; R<3> is substituted or nonsubstituted monofunctional hydrocarbon group; R<4> is monofunctional group or hetero atom-containing monofunctional organic group; (a) is 0 or 1) or co-hydrolyzate of the silane and other hydrolyzable silane is blended with (B) 30-150 pts.wt. calculated as sol solid content of a colloidal metal oxide (e.g. colloidal silica) and (C) 0.01-2 pts.wt. aluminum compound to give a composition. The composition is irradiated with light rays, cured, heated before or after the light irradiation and remaining silanol groups are condensed to give a cured coating film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is easily cured by irradiation with light for a short period of time, has high hardness and is excellent in scratch resistance, abrasion resistance, solvent resistance and moisture resistance, and various base materials. The present invention relates to a photocurable coating composition useful as a hard coating agent, which gives a cured product exhibiting excellent adhesiveness to, a cured film thereof, and a method for forming the cured film.

[0002]

BACKGROUND OF THE INVENTION Generally, plastic products, such as polymethylmethacrylate,
Polystyrene, polycarbonate, polyvinyl chloride, A
BS resins are used in various applications because of their excellent lightness, workability, and impact resistance, but these plastic products have low surface hardness, are easily scratched, and have excellent solvent resistance and weather resistance. Since it is scarce, it was difficult to use it in fields requiring abrasion resistance and exterior applications (building materials, vehicle window materials, etc.). Therefore, in order to solve the above problems, a hard coating agent was applied to the surface of the plastic substrate,
The method of hardening and protecting is adopted.

As a coating agent capable of forming the hard film, a heat-curable silicone hard coating agent and an ultraviolet-curable acrylic hard coating agent are mainly used.

However, this heat-curable silicone-based hard coating agent has a drawback in that productivity is poor because it requires a long period of time for curing and that the substrate is easily deformed by the heat applied during curing. ..

On the other hand, the ultraviolet-curable acrylic hard coating agent is superior in economical efficiency and productivity to the silicone hard coating agent, and in recent years, this type has been drawing attention. However, this ultraviolet-curable acrylic hard coating agent has a problem that the cured film is inferior in abrasion resistance, weather resistance, chemical resistance, etc., and is difficult to use for optical materials and exterior applications.

On the other hand, various kinds of UV-curable silicone type hard coating agents have been conventionally known. For example, a hard film is formed by ring-opening polymerization of an epoxy group-containing silane hydrolyzate using a photolysis catalyst of an onium salt. A method for obtaining the above is proposed in Japanese Examined Patent Publication No. 63-65115. However, this method is susceptible to photodegradation due to the effect of residual hydroxyl groups, and is not suitable for exterior applications (building materials, vehicle window materials, etc.).

[0007] Further, JP-A-59-204669 also discloses a methacryloxysilane hydrolyzate, a photopolymerization initiator,
A composition consisting of a polyfunctional acrylate and a hydrophobic colloidal silica has been proposed, but this composition has poor adhesion to a plastic substrate, and therefore must be coated with a primer and is hydrolyzed by methacryloxysilane. Since the silanol groups of the product remain, there is a drawback that the moisture resistance is poor.

Further, as a method for improving the adhesion to a plastic substrate, a composition comprising a methacryloxysilane hydrolyzate obtained by removing water from the system, a photopolymerization initiator, a polyfunctional acrylate and an organic solvent-dispersed silica sol is particularly preferable. Kaisho 6
Although it has been proposed in JP-A-2-256874, this composition has excellent adhesion, but since the silanol group remains, and the polyfunctional acrylate compound is considerably contained, the weather resistance of the cured film is high. There is a problem that the scratch resistance is significantly inferior to that of the heat-curing type silicone hard coating agent.

Therefore, it is difficult to say that the above-mentioned UV-curable silicone type hard coating agent has sufficiently satisfactory properties as a coating agent, and therefore, the development of a photocurable coating composition which gives a cured film excellent in various properties. Was desired.

The present invention has been made in order to meet the above-mentioned demands. It is easily cured by light irradiation for a short time, has good adhesiveness to various substrates, especially plastics, and has high hardness, scratch resistance and abrasion resistance. It is an object of the present invention to provide a photocurable coating composition that provides a cured film having good properties, solvent resistance, and moisture resistance, a cured film thereof, and a method for forming the same.

[0011]

Means and Actions for Solving the Problems As a result of intensive studies to achieve the above object, the present inventor has found that a hydrolysis product of silane represented by the following general formula (1) or this silane and other hydrolysis products. By using a co-hydrolysis product with a decomposable silane, a colloidal metal oxide, and an aluminum compound in combination, it is possible to easily cure by light irradiation for a short time, particularly ultraviolet irradiation, and at the time of light irradiation. Most of the silanol groups remaining in the hydrolysis product of the silane due to heat crosslink in the condensation reaction, and in order to complete the condensation of such silanol groups, heat treatment is performed before or after light irradiation. It was found that this is effective. The cured film thus cured has high hardness and excellent scratch resistance, abrasion resistance, solvent resistance, and moisture resistance, and also has excellent adhesiveness to various base materials, especially plastics. Shows,
Therefore, the above-mentioned composition was found to be useful as a hard coating agent and the like, and the present invention has been completed.

[0012]

[Chemical 2](However, in the formula R¹ Is hydrogen or a methyl group, R²Is replaced or non-
Substituted divalent hydrocarbon group, R³Is a substituted or unsubstituted monovalent carbon
Hydrogenated group, R^FourIs a monovalent hydrocarbon group or a hetero atom-containing
The monovalent organic group, a is 0 or 1. )

Therefore, the present invention provides (1) a hydrolysis product of the silane represented by the above general formula (1) or a cohydrolysis product of the silane of the general formula (1) and another hydrolyzable silane. , (2) colloidal metal oxide, (3) a photocurable coating composition containing an aluminum compound, a cured film thereof, and before curing the composition by light irradiation. Alternatively, there is provided a method for forming a cured film, in which the composition is subsequently heated to condense residual silanol groups.

The present invention will be described in more detail below. The first essential component of the present invention is a hydrolysis product of a silane represented by the following general formula (1) or a co-product of the silane and another hydrolyzable silane. It is a hydrolysis product and is the main component when the composition of the present invention is radically polymerized by light irradiation to form a cured film. In the present invention, the hydrolysis product and the co-hydrolysis product may be a partial hydrolysis product or a total hydrolysis product.

[0015]

[Chemical 3](However, in the formula R¹ Is hydrogen or a methyl group, R²Is replaced or non-
Substituted divalent hydrocarbon group, R³Is a substituted or unsubstituted monovalent carbon
Hydrogenated group, R^FourIs a monovalent hydrocarbon group or a hetero atom-containing
The monovalent organic group, a is 0 or 1. )

Where R in the formula¹ Is a hydrogen atom or a methyl group
Is. Also, R² Is a substituted or unsubstituted divalent hydrocarbon group
And preferably has 1 to 6 carbon atoms, especially 1 to 3 carbon atoms.
For example, methylene group, ethylene group, trimethylene
Examples include alkylene groups such as groups. R³ Is replaced or not
A substituted monovalent hydrocarbon group, preferably having 1 to 1 carbon atoms
0, especially 1 to 6, such as methyl, ethyl
Alkyl group such as vinyl group and butyl group, allyl group such as phenyl group
Groups and their hydrogen atoms are halogen atoms, cyano groups, etc.
And a trifluoroalkyl group substituted by. Change
And R^Four Is a monovalent hydrocarbon group or a monovalent hydrocarbon containing a hetero atom.
Machine base, preferably having 1 to 10 carbon atoms, especially 1 to 4 carbon atoms
Such as methyl group, ethyl group, isopropyl group
Alkyl group such as vinyl group, butyl group, vinyl group, isopropene
Alkenyl group such as nyl group, methoxyethyl group, ethoxy
Examples include ethyl group, methoxypropyl group, and acetyl group.
Be done. In addition, a is 0 or 1.

Specific examples of the silane of the above formula (1) include 3-acryloxypropyltrimethoxysilane, 3-acryloxypropyltriethoxysilane and 3
-Acryloxypropylmethyldimethoxysilane, 3-
Acryloxypropylmethyldiethoxysilane, 3-acryloxypropylethyldimethoxysilane, 3-acryloxypropylethyldiethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropyl Methyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropylethyldimethoxysilane, 3-methacryloxypropylethyldiethoxysilane and the like are exemplified, and particularly 3
-Acryloxypropyltrialkoxysilane and 3-methacryloxypropyltrialkoxysilane are preferred. Even if one of the above silanes is used alone, 2
You may use it in mixture of 2 or more types.

Other hydrolyzable silanes that are co-hydrolyzed with the silane of the above formula (1) include, for example, tetramethoxysilane, tetraethoxysilane, methylpolysilicate, ethylpolysilicate, methyltrimethoxysilane and methyltrisilane. Ethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3
-Glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-chloropropyltrimethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, 2-perfluoroalkylethyltrimethoxysilane And the like, and one of these may be used alone or two or more of them may be used in combination.

Hydrolysis of the (meth) acrylic silane of the above formula (1) or co-hydrolysis of the (meth) acrylic silane of the above formula (1) with other hydrolyzable silanes results in the addition of acid to these silanes. It can be generally carried out by acting an aqueous solution, for example, a dilute aqueous acid solution such as hydrochloric acid or acetic acid.
In this case, as described above, the hydrolyzate and the co-hydrolyzate may be a partial hydrolyzate or a total hydrolyzate. The above reaction is preferably performed in the presence of an organic solvent such as a lower aliphatic alcohol in terms of stability of the coating liquid.

In the present invention, the above formula (1) is used as the first component.
Even if the hydrolysis product of the (meth) acryl-based silane alone is used, a film having sufficient properties can be obtained. However, when the silane of the above formula (1) and the above other hydrolyzable silane are used, By using a hydrolysis product, it is possible to further increase the hardness of the film, impart adhesion, impart flexibility, and enhance heat resistance and weather resistance. in this case,
The weight ratio of the silane of the formula (1) to the other silane is 100: 0 to 50:50, and particularly 100: 0 to 70: 3.
It is preferably 0.

Next, the second essential component, the colloidal metal oxide, is a component that imparts abrasion resistance to the cured film. As the colloidal metal oxide, the metal oxide is dispersed in an organic solvent or water and has an average particle size of 1 to 100 mμ, particularly 3
Colloidal metal oxides having a colloidal size of up to 20 mμ are preferred, and among them, colloidal metal oxides dispersed in an organic solvent in view of compatibility in the system of the composition of the present invention and stabilized under neutral or basic conditions. A thing is used suitably. Average particle size is 1mμ
If the colloidal metal oxide of less than 100 is used, the surface hardness may not be increased, and if it exceeds 100 mμ, the transparency of the film may be lost.

Specific examples of such colloidal metal oxides include one or more of colloidal silica, colloidal titania, colloidal antimony oxide, colloidal tin oxide and colloidal tungsten oxide. be able to. As the colloidal metal oxide, particularly economically inexpensive colloidal silica is preferably used, but in order to match the refractive index of the composition with the refractive index of the plastic substrate, titania sol, antimony oxide sol,
A tin oxide sol or the like can be added, and a single sol, a mixed sol, a mixed crystal sol or the like can be added according to the refractive index within a range that does not impair the effects of the present invention. As the mixed crystal sol, for example, antimony oxide / silica sol, titania / silica sol, cerium oxide / titania sol, iron oxide / titania sol, antimony oxide / titania sol, tungsten oxide / tin oxide sol and the like can be used.

The amount of the above colloidal metal oxide compounded is preferably 30 to 150 parts, especially 50 to 100 parts, as a sol solid component, relative to 100 parts (parts by weight, hereinafter the same) of the first component, If it is less than 30 parts, the abrasion resistance of the coating may be insufficient, and if it exceeds 150 parts, the coating may become too brittle and the adhesion to the substrate may be poor.

Further, in the present invention, it is preferable to add a photopolymerization initiator in order to cure the silane hydrolysis product as the first component with ultraviolet rays. Specific examples of the photopolymerization initiator include benzoin, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 2-hydroxy. −
2-Methyl-1-phenylpropan-1-one, benzophenone, 4,4′-bis (dimethylamino) benzophenone, 4-trimethylsilylbenzophenone, 4-trimethylsilyl-4′-dimethylaminobenzophenone and the like are exemplified, and these 1 The seeds may be used alone or in combination of two or more. Of these, it is particularly preferable to use a liquid compound in view of compatibility with the first and second components.

In this case, the composition of the present invention can be cured by irradiating with an electron beam instead of ultraviolet rays, and when irradiating with an electron beam, a good cured film can be obtained without adding a photopolymerization initiator. Although it can be formed, when the photopolymerization initiator is blended, the blending amount is 0.
It is preferably from 0.1 to 20 parts, particularly preferably from 0.1 to 10 parts. If the blending amount is less than 0.01 part, the sensitizing action is poor, and tack may remain on the coating film, and if it exceeds 20 parts, the coating film becomes soft and the storage stability of the coating solution deteriorates. There are cases.

The aluminum compound as the third essential component of the present invention accelerates the condensation reaction of the silanol groups remaining in the hydrolysis product of the silane as the first component.

The aluminum compound is preferably one which does not impair the photosensitizing property of the above-mentioned photopolymerization initiator, and a Lewis acid such as aluminum chloride, aluminum perchlorate or aluminum chelate is particularly effective.

Specific examples of the aluminum compound include the following compounds, and one of these may be used alone or two or more of them may be used in combination.

[0029]

[Chemical 4]

Further, the composition of the present invention contains, in addition to the above-mentioned aluminum compound, silanol group condensation accelerators such as sodium acetate, trimethylammonium hydroxide,
Tetramethylammonium hydroxide, tetramethylammonium acetate, tetrabutylphosphonium hydroxide, zinc octylate, sodium hexafluoroantimonate, aluminum triisopropoxide, aluminum triisobutoxide, etc. are required within a range that does not impair the effects of the present invention. It can be optionally added according to.

Here, in the present invention, the silanol remaining in the first component is utilized by utilizing the heat generated during light irradiation, particularly ultraviolet irradiation, or by slightly heating before or after light (ultraviolet) irradiation. The group can be condensed to siloxane, and in order to effectively promote the siloxane formation, post-curing the composition of the present invention at 50 to 100 ° C. for about 1 to 20 minutes after UV irradiation. It is possible to obtain a film having high hardness, excellent wear resistance, and scratch resistance, and in particular, a film excellent in adhesion, water resistance, weather resistance, etc., because silanol groups do not remain in the film. However, the condensation accelerator more effectively promotes the condensation of silanol groups.

The content of the condensation accelerator is preferably 0.01 to 2 parts, particularly 0.05 to 1 part, relative to 100 parts of the first component. If it exceeds 2 parts, the storage stability of the coating solution may be deteriorated.

The composition of the present invention preferably contains an epoxy compound as a component capable of improving the adhesion to the plastic substrate and reacting with the silanol group in the first component. In this case, the epoxy compound is not particularly limited as long as it is a liquid compound, for example, a polycondensate of bisphenol A and epichlorohydrin, diglycidyl ether, phenylglycidyl ether, glycidyl esters, novolac type epoxy resin, cyclohexene oxide group-containing ether. , Cyclohexene oxide group-containing ester and the like can be used.

The amount of the epoxy compound compounded is 10 parts of the first component.
It is preferably 20 parts or less with respect to 0 part, and if it exceeds 20 parts, the coating may become soft or the weather resistance may be poor.

The composition of the present invention may contain other components such as trimethylolpropane-tri- (meth) acrylate and pentaerythritol-tetra- (meth) acrylate for improving the adhesion to the substrate and the curability. , A polyfunctional (meth) acrylate such as ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, etc. can be added, and the compounding amount thereof hinders the effect of the present invention. It can be a normal amount within the range not included.

Further, as an optional component, a weather resistance improver such as an ultraviolet absorber, a silicone-modified polyether leveling agent, a thickener, a colorant, an antistatic agent and the like can be added alone or in combination.

The composition of the present invention can be adjusted in viscosity with an organic solvent for the purpose of improving workability during coating. The organic solvent preferably has good compatibility with the composition and does not attack the surface of the plastic substrate, specifically, methanol, ethanol, isopropanol, isobutanol, methyl cellosolve, ethyl cellosolve, butyl. Cellosolve, cellosolve acetate,
Examples include diacetone alcohol and the like.

The photocurable coating composition of the present invention is applied on the surface of a substrate such as plastic and then cured by irradiation with ultraviolet rays or electron beams to form a film.
Especially when applied to a plastic substrate having poor adhesion, the composition of the present invention may be applied and cured after forming a primer layer on the surface of the substrate in advance. For example, when polycarbonate or the like is used as a plastic substrate, good adhesiveness can be obtained by applying an acrylic primer layer to this and then applying and curing the composition of the present invention.

As a method for applying the composition of the present invention, a usual method such as flow coating, dip coating, spray coating and spin coating can be applied, and usually 0.5 to 5 is applied to the surface of the substrate.
It is preferably applied to a thickness of μm. After application,
Ultraviolet rays or electron beams are irradiated from a light source such as a high pressure mercury lamp, the irradiation amount is 20 to 200 W / cm ² , and the irradiation time is 5 to 5.
It is desirable to set it to 600 seconds. After the light irradiation, the cured film can be formed by subsequently performing heating (post-cure) for a short time as described above.

[0040]

The photocurable coating composition of the present invention is easily cured by irradiation with light for a short time to have high hardness and scratch resistance,
It gives a cured product that is excellent in abrasion resistance, solvent resistance, and moisture resistance, and also has excellent adhesion to various substrates. Therefore,
The composition of the present invention can be effectively used as a hard coating agent or the like for exterior applications (building materials, vehicle window materials, etc.) and optical materials.

[0041]

EXAMPLES 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.

[Example 1] 17.0 g of 3-acryloxypropyltrimethoxysilane and 2 of isobutyl alcohol
To 7.0 g of the mixture, 4.2 g of 0.1 N dilute hydrochloric acid was added to 5
It dripped at 10 degreeC over 4 hours, and then MA-ST20
After adding 26.5 g (manufactured by Nissan Kagaku Kogyo Co., Ltd., average particle diameter 10 mμ of neutral methanol silica sol, nonvolatile content 30%), the mixture was aged at room temperature for 4 hours. To this, 0.2 g of 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one [Darocur 1116 (manufactured by Merck & Co., a photopolymerization initiator)] and 0.1 g of AlCl ₃ .6H ₂ O were added.
g, Epicoat 827 (Okaka Shell Epoxy Co., Ltd., epoxy resin) 0.6 g, isobutyl alcohol 26.5 g
Was added and filtered to prepare coating agent-1.

Example 2 A coating agent-2 was prepared in the same manner as in Example 1 except that 18.0 g of 3-methacryloxypropyltrimethoxysilane was used in place of 3-acryloxypropyltrimethoxysilane of Example 1. Was prepared.

Example 3 17.0 g of 3-methacryloxypropyltrimethoxysilane and 6.5 g of 3-glycidoxypropyltrimethoxysilane were added with 5.8 g of 0.05N dilute hydrochloric acid at 5 to 10 ° C. for 4 hours. After the dropping, the coating agent-3 was prepared in the same manner as in Example 1 except that the Epicoat 827 was not added.

Example 4 Example 4 was repeated except that the sun colloid AMT-130S (manufactured by Nissan Kagaku Kogyo Co., Ltd., antimony oxide sol having an average particle size of 15 m, non-volatile content 30%) was used instead of MA-ST20 of Example 1. A coating agent-4 was prepared in the same manner as in Example 1.

Example 5 In place of 17.0 g of 3-methacryloxypropyltrimethoxysilane and 6.5 g of 3-glycidoxypropyltrimethoxysilane of Example 3, 3 g was used.
-Acryloxypropyltrimethoxysilane 16.0
g, and coating agent-5 was prepared in the same manner as in Example 3 except that 3.4 g of tetramethoxysilane was used.

[Comparative Example 1] A coating agent-6 was prepared in the same manner as in Example 1 except that AlCl ₃ .6H ₂ O was not added.

Coating agents-1 to 6 obtained in Examples 1 to 5 and Comparative Example 1 were coated on a polymethylmethacrylate extruded flat plate with a bar coater (No. 20), air-dried for 10 minutes, and then 80 W / The test pieces 1 to 6 were irradiated with ultraviolet rays from a distance of 8 cm with a high pressure mercury lamp of cm 2 for 30 seconds, and then heated at 80 ° C. for 5 minutes to be cured.
It was created. These films were evaluated by the following methods. The stability of the coating liquid was also evaluated by the following method. The results are shown in Tables 1 and 2.

Hardness: Evaluated by a pencil hardness test according to JIS-K-5400. Adhesiveness: Cross-cutting was performed with a knife at intervals of 1 mm in length and width with a knife, a cellotape (manufactured by Nichiban Co., Ltd.) peeling test was performed, and remaining squares were counted. Scratch resistance: about 500 using # 0000 steel wool
The film was rubbed 10 times with a load of g, and the scratched state was visually evaluated according to the following criteria. ◯: Almost no scratches Δ: Slight scratches ×: Many scratches Abrasion resistance: Taber abrasion test (CS-10 abrasive paper, 50
The haze (%) of the film after 0 g, 20 times) was measured with a haze meter. Solvent resistance: Xylene was impregnated and the film was rubbed 100 times with absorbent cotton, and the appearance state was visually judged according to the following criteria. ◯: No abnormality Δ: Slight peeling of the coating X: Peeling of the coating entirely Moisture resistance: Adhesion after immersion in pure water at room temperature for 1 week was evaluated by a cellophane tape peeling test. Liquid stability: The liquid state after the coating liquid was left at room temperature for 2 weeks was visually evaluated.

[0050]

[Table 1]

From the results shown in Table 1, the photocurable coating compositions (Examples 1 to 5) of the present invention have good liquid stability, high hardness, adhesion, scratch resistance and abrasion resistance. It was confirmed that a film having excellent solvent resistance and moisture resistance was provided.

Claims (3)

[Claims] 1. A sila represented by the following general formula (1):
Hydrolysis product of silane or silane of this general formula (1) and others
A product of co-hydrolysis with a hydrolyzable silane,(However, in the formula R¹ Is hydrogen or a methyl group, R²Is replaced or non-
Substituted divalent hydrocarbon group, R³Is a substituted or unsubstituted monovalent carbon
Hydrogenated group, R^FourIs a monovalent hydrocarbon group or a hetero atom-containing
The monovalent organic group, a is 0 or 1. ) (2) Colloidal
Metal oxide and (3) aluminum compound
A photocurable coating composition comprising: 2. A cured film obtained by curing the composition of claim 1. 3. The composition according to claim 1 is irradiated with light to be cured, and the composition is heated before or after the irradiation with light,
A method for forming a cured film by condensing residual silanol groups.