JPH0422984B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for producing a plastic molded product having a metal thin film coating layer, and more specifically, a method for manufacturing a plastic molded product having a metal thin film coating layer, which does not generate cracks and has high brightness. The purpose is to provide a plastic molded product with a surface.

(Prior art) Conventionally, plastic molded products having a metal thin film have been obtained by forming a metal thin film on the surface of the plastic molded product by methods such as vacuum evaporation, hot stamping, plating, etc. Since this method can only use metals with relatively low melting points, such as aluminum, tin, and antimony, products with excellent surface properties cannot be obtained, and hot stamping and plating methods are complicated in terms of process. It wasn't economical. A sputtering method has been developed as a method to solve these problems, but the metal thin film produced by this method is prone to cracks due to its relationship with the base material, and also has difficulty adhesion to the top coat layer provided on its surface. It had poor performance and was difficult to put into practical use.

(Means for Solving the Problems) As a result of intensive research in order to solve the above-mentioned drawbacks of the conventional technology, the inventor of the present invention found that when forming a metal thin film on a plastic molded product by sputtering,
By providing a specific base coat, sputtering metal on the base coat layer under specific conditions, and then providing a specific top coat layer on the formed metal thin film, cracks in the metal thin film do not occur, and metal The present invention was completed based on the discovery that it is possible to provide a plastic molded product that has good adhesion between the thin film and the top coat layer and retains excellent shine semi-permanently.

That is, the present invention provides the following methods: (a) Applying an ultraviolet curable acrylic resin base coat paint to the surface of a plastic molded product on which a metal thin film coating layer is to be formed, and curing it with ultraviolet rays to form a base coat layer having a pencil hardness of H or higher. (b) Vacuum degree 1×10 ^-3 to 6×10 ^-5 Torr, argon pressure 5×10 ^-3 to 1×10 ^-4 Torr, voltage 200 to 600V,
Various alloys such as metals such as chromium and nickel, brass, and stainless steel are heated by sputtering at a current density of 20 to 500 A/ ^m2 .
(c) forming a thin film with a thickness of 2000 Å on the above base coat layer; (c) applying an ultraviolet curable acrylic resin top coat paint containing a reactive alkoxysilane compound and having an acid value of 5 to 50 on the surface of the above metal thin film; Apply,
A method for producing a plastic molded product having a metal thin film coating layer, comprising the steps of curing with ultraviolet rays.

To explain the present invention in detail, if the material of the plastic molded product used in the method of the present invention has a large coefficient of thermal expansion, it will be difficult to form a metal thin film or use it.
The metal thin film causes cracks. Therefore, it is desirable that the coefficient of thermal expansion be small, and practically it is preferably 20×10 ^-5 cm/cm/°C.

Specifically, particularly preferred materials for plastic molded products include polyester resin, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-styrene, acrylic resin, polycarbonate resin, PVC, etc., or materials coated or laminated with these materials. Can be mentioned.

The ultraviolet curable acrylic resin composition used to form the base coat in the present invention is a known material, and consists of an ultraviolet curable acrylic resin, a sensitizer, and other optional components.

Typical examples of UV-curable acrylic resins include relatively low molecular weight polyester (meth)acrylate resins that have radically polymerizable unsaturated double bonds in their molecular structures, and polyether (meth)acrylate resins.
Acrylate resins, acrylic (meth)acrylate resins, epoxy (meth)acrylate resins, urethane (meth)acrylate resins, oligomers or prepolymers such as (meth)acrylates of polyfunctional compounds such as polyhydric alcohols, and styrene, methylstyrene, Including addition polymerizable compounds such as divinylbenzene and (meth)acrylic acid ester,
It contains these components alone or as a mixture.

In the present invention, about 5 to 100 of these ultraviolet curable acrylic or oligomer resins are used.
It is desirable to use trifunctional or higher functional poly(meth)acrylates such as tri(meth)acrylate, sorbitol triglycidyl(meth)acrylate, etc., in which the weight percent, preferably about 30% by weight or more, of such poly(meth)acrylates. When the amount of acrylate or the like is less than 5% by weight, it is not possible to form a film with sufficient surface hardness, and it is not possible to prevent the occurrence of cracks in the metal thin film.

In addition, the necessary sensitizer is a compound that generates free radicals by the energy of ultraviolet rays,
Examples include carbonyl compounds such as benzoin, benzophenone, or their esters, organic peroxides such as benzoyl peroxide, azo compounds such as azobisisobutyronitrile, and sulfur compounds such as diphenyl disulfide.

Other optional ingredients include small amounts of organic solvents, coloring agents such as dyes and pigments, wax, and various other additives.

Such UV-curable acrylic resin base coat paints are applied to the surface of degreased plastic moldings using conventional methods such as brush painting, spray painting, dip painting, curtain flow coating, roll painting, etc. It is cured by irradiating it with ultraviolet light using a lamp, xenon lamp, etc.

The dry film thickness of the UV-curable acrylic resin base coat paint is usually 1 to 50 μm, preferably 3 to 50 μm.
Approximately 30 μm is appropriate.

The base coat layer obtained in this way has a hardness of H or higher (according to the measurement method based on JIS KB5400) in order to prevent cracks from occurring in the metal film.
Particularly preferably, it needs to be 2H or more.

In the method of the present invention, the UV-curable acrylic resin base coat paint is particularly used for cold energy drying, which does not cause deterioration or damage to the plastic molded product, smooths the surface of the plastic molded product, and makes it possible to form a thin metal film on the plastic molded product. This is to alleviate the stress between them and improve the adhesion between the plastic molded product and the metal thin film.

Next, a metal thin film of a metal such as chromium or an alloy such as stainless steel is formed on the surface of the base coat layer by sputtering.

A method for forming a metal thin film is, for example, using a DC dipole magnetron sputtering device, using a metal such as chromium or an alloy such as stainless steel as a cathode target, and vacuuming at 1×10 ^-3 to 6×10 ^-5 Torr. After filling the bell jar with argon gas and setting the argon pressure to 5 × 10 ^-3 to 1 × 10 ^-4 Torr, a voltage of 200 to 600 V and a current density of 20 to 20
A discharge is caused at 500 Å/m ² .

Argon ions generated by the discharge impact a metal such as chromium or an alloy such as stainless steel of the cathode target to release metal atoms such as chromium or stainless steel. These metal atoms travel straight through the bell gear, reach the surface of the base coat layer, and condense to form a thin metal film on the surface of the base coat layer.

As a condition for sputtering, the voltage between the two poles is
A sputtering phenomenon occurs when the voltage is set to 200 to 600V. If the voltage is below 200V, sputtering will not occur even if it is discharged;
When the following happens, various industrial difficulties appear.

In addition, the appropriate current density is 20 to 500 A/ ^m2 ; below this range, the spatter phenomenon will not occur; on the other hand, above this range, the plastic molded product may be deformed due to temperature rise, or the metal thin film may be cracked. This is not preferable because it tends to occur.

Further, a metal thin film that is less likely to cause cracks can be obtained at a vacuum degree of 1×10 ^-3 to 6×10 ^-5 Torr and an argon pressure of 5×10 ^-3 to 1×10 ^-4 Torr.

If the degree of vacuum and argon pressure are outside this range,
Even if sputtering does not occur or a thin metal film is formed, cracks are likely to occur.

The thickness of the metal thin film in the present invention is usually 300~
2000 Å is appropriate. If it is less than that, a shiny metal film cannot be obtained.

A top coat layer is then formed on the metal thin film formed as described above, and the basic composition of this top coat top coat paint is the same as that of the base coat-like paint described above. It is necessary that the acid value is controlled within the range of 5 to 50. Such acid value control can be easily performed when producing an ultraviolet curable acrylic resin using (meth)acrylic acid. By using an ultraviolet curable acrylic resin having an acid value within this range, a top coat layer can be formed which has excellent adhesion to metal thin films and the like, as well as excellent mechanical and chemical properties.

A second feature is that such top coating agents contain a reactive alkoxysilane compound in an amount of 0.1 to 5% by weight based on the acrylic resin.

Preferred examples of such reactive alkoxysilanes include aminoalkoxysilanes such as N-(2-aminoethyl)3-aminopropylmethyldimethoxysilane and 3-aminopropyltributoxysilane, and 3-glycidoxypropylmethyldimethoxysilane. Epoxyalkoxysilane such as silane, 3
-Chloroalkoxysilanes such as chloropropylmethyldimethoxysilane, alkoxysilanes containing vinyl groups or methacryloxy groups such as vinyltris(2-methoxyethoxy)silane, and 3-methacryloxypropyltrimethoxysilane, and among these, particularly preferred are These include amino, epoxy, and other materials that are highly reactive with the acid part of UV-curable acrylic resin.
It is an alkoxysilane containing a mercapto group,
Moreover, from the viewpoint of stability, those having a large molecular weight are preferable.

By adding such a reactive alkoxysilane in the amount within the above range, the reactive alkoxysilane acts on both the metal surface and the ultraviolet curable acrylic resin, resulting in excellent formation of the metal surface and the top coat layer. Provides adhesion.

The method of applying and drying the top coat agent as described above is the same as that for forming the base coat layer, and it is preferable to form a top coat layer with a thickness of about 1 to 50 .mu.m, preferably about 5 to 20 .mu.m.

(Function/Effect) In the method of the present invention, by adopting the above configuration, that is, by forming a layer having a pencil hardness of H or higher as a base coat layer, it is possible to In addition, by sputtering under specific conditions, a glittering layer with low crack occurrence is formed, and a top coat layer with good adhesion to the metal layer is formed using a specific top coat agent. is formed, the above-mentioned drawbacks of the prior art are overcome, and a plastic molded product with excellent brightness and long-term surface durability is provided.

(Example) Next, the present invention will be explained in more detail by giving examples and reference examples. Note that "%" or "%" in the text is based on weight.

Example 1 The following base coat paint was applied to a corona discharge treated polyester film (thickness: 50 μm) to create a base coat layer.

Bifunctional urethane acrylate (molecular weight 1000~
1500) 50 parts average trifunctional polyester acrylate (molecular weight
500-1600) 40 parts Dipentaerythritol hexaacrylate 10 parts Isobutyl acetate 50 parts Bendiphenone 3 parts Benzyl dimethyl ketanol 2 parts Apply this paint with a gravure ketal roll coater to approx.
After coating to a thickness of 3 μm and drying the solvent, the film was cured using a 160 W/cm high pressure mercury lamp 15 cm at a conveyor speed of 20 m/min, and the pencil hardness of the film obtained was 3H.

Next, the above base coat was coated with a vacuum degree of 1×10 ^-4 Torr using a sputtering device manufactured by Tokuda Vacuum Co., Ltd.
Argon pressure 8×10 ^-4 Torr, voltage 500V, current density
Chromium spatter film ( ^thickness
1000 Å) was formed.

Next, the following top coat paint was applied onto the above sputtered thin film to prepare a top coat.

Bifunctional urethane acrylate (molecular weight 1000~
1500) 50 parts trimethylolpropane triacrylate 20 parts 1,6-hexanediol diacrylate 10 parts bis(methacryloxyethyl) phosphate
4 parts methyl isobutyl ketone 20 parts ethyl acetate 20 parts 2-hydroxy-2-methyl-triphenylpropan-1-one 4 parts 3-mercaptopylpyrotrimethoxysilane 2 parts Silicone leveling agent Byk-300 0.3 parts (acid value =30) Apply this paint to approximately 4μm using a gravure roll coater.
After drying the solvent, cure it under a 80W/cm high-pressure mercury lamp for 15cm at a conveyor speed of 10m/min.It has a pencil hardness of 3H, has an adhesion of 1mm, cross-cut cellophane tape, and has good durability and peelability of 100/100. I was able to create a film with beautiful chrome sputtering.

Reference example 2 The pencil hardness of the base coat in Example 1
In the case of HB, many fine cracks were generated in the sputtered film after the top coat was cured.

In the top coat shape of Example 1, 3-
When a paint excluding mercaptopropyltrimethoxysilane was used, the top coat had a 20/100 adhesion test, indicating poor adhesion.

Reference Example 3 In Example 1, when bis(methacryloxyglycidyl) phosphate was removed and the acid value was set to 5 or less in the formation of the top coat, the adhesion test showed that the top coat was 0/100 and had poor adhesion.

Example 2 The following base coat paint was applied to an ABS molded article to create a top coat layer.

Bifunctional epoxy acrylate (molecular weight 600-1000)
50 parts pentaerythritol triacrylate 40 parts benzophenone 2 parts 1-hydroxycyclohexyl ketone 3 parts n-hexane 30 parts isopropyl alcohol 20 parts ethyl acetate 20 parts xylene 30 parts methyl cellosolp 30 parts butyl cellosolp 30 parts Apply this paint to approximately 10 μm using air spray. After drying the solvent, it was cured for 5 seconds under a high-pressure mercury lamp of 80 W/cm while rotating at 15 cm to obtain a base coat layer with a pencil hardness of H.

The above base coat layer was coated with a sputtering device manufactured by Tokuda Vacuum Co., Ltd. at a vacuum level of 8 x 10 ^-5 Torr, an argon pressure of 8 x 10 ^-4 Torr, a voltage of 400 V, and a current density.
Nickel sputtered film ( ¹⁵⁰⁰
Å) was formed.

The following top coat paint was applied onto the nickel spatter thin film to form a top coat layer.

Bifunctional epoxy acrylate (molecular weight 600-1000)
30 parts bifunctional polyether acrylate (molecular weight 1000~
1400) 30 parts hydroxyvalic acid neopentyl glycol diacrylate 15 parts diethoxyacetophenone 3 parts benzoin isobutyl ether 1 part acrylic diacrylate (molecular weight 500, acid value 150)
5 parts 3-aminopropyltributoxysilane 2 parts ethyl acetate 20 parts isopropyl alcohol 20 parts ethyl cellosolve 30 parts metolysobutyl ketone 30 parts toluene 30 parts Shin-Etsu Silicone KF-69 0.2 parts (acid value 12) The above paint was air sprayed. Apply to approximately 8μm,
After drying the solvent, it was cured by irradiating it for 6 seconds while rotating under a mercury lamp under a high pressure of 80W/cm for 6 seconds.The pencil hardness was 3H, and the adhesion was 100/100 in a 1mm width cross-cut Sellotape peel test, indicating good durability. An ABS molded product with a beautiful nickel spatter film was obtained.

Reference Example 4 When the hardness of the base coat of Example 2 was F, several cracks occurred after the top coat was formed.

Reference Example 5 When forming the top coat of Example 2 without using a silane compound, the adhesion of the top coat layer was 40/100 in a peel test and 40/100 in a moisture resistance test (60°C, 95% RH, 12 hours). It was 0/100.

Reference Example 6 When the top coat of Example 2 was formed without using acrylic diacrylate, the adhesion was insufficient.

Claims (1)

[Claims] 1(a) A base coat having a pencil hardness of H or higher by applying an ultraviolet curable acrylic resin base coat paint to the surface of a plastic molded product on which a metal thin film coating layer is to be formed and curing it with ultraviolet light. Step of forming a layer, (b) degree of vacuum 1 × 10 ^-3 to 6 × 10 ^-5 Torr, argon pressure 5 × 10 ^-3 to 1 × 10 ^-4 Torr, voltage 200 to 600 V,
Various alloys such as metals such as chromium and nickel, brass, and stainless steel are heated by sputtering at a current density of 20 to 500 A/ ^m2 .
(c) forming a thin film with a thickness of 2000 Å on the above base coat layer; (c) applying an ultraviolet curable acrylic resin top coat paint containing a reactive alkoxysilane compound and having an acid value of 5 to 50 on the surface of the above metal thin film; Apply,
A method for producing a plastic molded product having a metal thin film coating layer, comprising the step of curing with ultraviolet rays. 2. The method according to claim 1, wherein the UV-curable acrylic resin base coat paint and top coat paint contain 5% by weight or more of a trifunctional or higher functional component.