JPH09175839A - Method for forming coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a brittle coating film having poor flexibility without generating cracks by bonding a specific resin sheet to a substrate using a specific adhesive, applying a coating material to the laminate, hardening the coating layer and successively peeling the resin sheet and the coating film from the substrate. SOLUTION: A heat-resistant resin sheet having excellent peelability from a coating film and having a thickness of preferably about 0.1-1.0mm (preferably a fluororesin sheet) is bonded to a substrate (e.g. a glass plate) using a low- solvent or solventless heat-resistant adhesive having high adhesive force (e.g. two-pack solventless quick-drying epoxy adhesive), the laminate is coated with a coating material (e.g. a back-protecting coating for mirror) to a film thickness of about 20-80μm in cured state, the coating layer is cured, the resin sheet is peeled off from the substrate and finally the coating film is peeled off from the resin sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION When measuring certain physical properties of a paint film after curing of various paints applied to a substrate, for example, physical properties such as dynamic / static viscoelasticity, gas permeability and water absorption Although it is necessary to form the coating film in the form of a film, the present invention relates to a film forming method for a baking type coating film having such a case that it is particularly poor in flexibility and brittle.

[0002]

2. Description of the Related Art Conventionally, in order to form a paint film in the form of a film for measuring the above-mentioned physical properties, for example, a paint is applied to a resin sheet having good releasability such as polyethylene or polypropylene. A method is known in which a coating film obtained by drying is peeled off from a sheet to form a film. In this case, if a resin having a softening point of 200 ° C. or lower such as polyethylene or polypropylene is used for the sheet, in the case of a baking-type paint, the sheet may be deformed by heat during welding, or a problem such as welding may occur, resulting in a good coating film. Hard to get. Further, when a decorative coating film is applied to the base material, the heating behavior of the paint is affected by the heat capacity and thermal conductivity of the base material, but when the above resin sheet is used as a substitute for the base material, Have different thermophysical properties, the heating behavior of the paint also differs, and therefore the curing state also changes, so it is difficult to obtain the physical properties of the paint film in line with actual operation in terms of temperature control.

In addition to this, there is an example of forming a film directly from a paint by forming a film with a specific resin composition. For example, JP-A-1-297432 discloses a film formed at a specific decomposition / softening temperature or higher. There is disclosed a film-form phenol resin obtained by film-forming and heat-treating a phenol resin in which a hard powder having a particle size or less is dispersed by an appropriate means. That is, if a film-like paint coating is prepared in advance and adhered to a substrate, the film can be formed efficiently without the need for steps such as coating, drying, and curing on the substrate. Is. However, it is premised that it is a flexible paint film, as in the decorative paint film,
In the case of a coating film which is inherently poor in flexibility and brittle, it is difficult to form a film in advance.

The present invention solves the above-mentioned problems and provides a film forming method for a coating film which is particularly poor in flexibility and brittle. Further, according to the present invention, it is also possible to measure the physical property values of the film obtained under various baking and curing conditions (e.g., temperature rising conditions, time, etc.), and find the optimum curing conditions conversely from the optimum physical property values. it can.

[0005]

Means for Solving the Problems The present invention provides 1) a base material which is a resin sheet having heat resistance and good releasability from a coating film, and which has a low solvent amount or a solvent-free type and has heat resistance and high adhesiveness. Adhesion through, then apply paint on it, cure to form a paint film, and then peel off the resin film from the base material, then the paint film from the resin sheet, in order to form the paint film, 2) Film formation of the paint film In the method, the resin sheet is a fluororesin sheet.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the manufacture of a mirror, for example, a silver film and a copper film are formed on a glass substrate by a usual method such as a chemical plating method, and a backing coating material is applied on the copper film. Then, the film is formed by heating and curing to complete the mirror.

When a film is formed to measure the dynamic / static viscoelasticity, gas permeability, water absorption, etc. of the paint film, the paint film is firmly adhered to the copper film and the film itself. Since it is poor in flexibility and brittle, it is difficult to form a film without cracking only the coating film, and peeling off a part of the copper film without adhering,
Therefore, it is impossible to obtain accurate physical and physical properties such as dynamic / static viscoelasticity, gas permeability and water absorption.

Further, as described above, it is possible to apply a paint to a sheet of a resin having good releasability such as polyethylene and cure it to form a film, and peel the film to form a film. Thermophysical properties are different from resin sheets, so even if they are heated under the same heating conditions,
The heating behavior of the coating itself differs, and the curing status also changes. Therefore, when the various physical properties of the paint film are measured, it is not possible to obtain the physical properties of the film that match the actual manufacturing and operating conditions, which is meaningless.

The present invention solves the above problems, and the embodiments of the present invention will be described below with reference to examples of mirrors. In the present invention, the substrate basically means a material to which a paint is applied, and the mirror means a structure of glass plate \ silver film \ copper film. In the case of a mirror, the thickness of the glass plate is 5-10 mm
However, the total thickness of silver and copper films is 100
It is as small as about nm (by the way, it is about 50 to 70 to 80 μm even in the backing coating film), so the heating behavior of the glass plate dominates the heating behavior of the paint in the usual heating furnace, and the silver film or copper film Can be ignored. In such a case, only the glass plate can be adopted as the base material, and the silver film and the copper film can be omitted.

As the resin sheet which is heat resistant and has a good peelability from the coating film, a fluororesin sheet such as ethylene tetrafluoride resin, polyfluoroalkoxy resin, polyvinyl fluoride resin, polyvinylidene fluoride resin, polychlorinated trifluoride is used. A sheet of ethylene resin or the like, particularly a tetrafluoroethylene resin can be preferably used. Although the thickness of the resin sheet is not specified, it is preferably about 0.1 to 1.0 mm, particularly about 0.3 mm. If it exceeds 1.0 mm, it may affect the heating behavior of the paint film, which may be different from the heating during actual manufacturing and operation, and the peelability when peeling from the substrate after film formation is poor.

When the above-mentioned fluororesin sheet is used as the resin sheet, the fluororesin has insufficient adhesiveness with the adhesive and may peel off from the glass plate during the heating process. Peeling can be prevented by rubbing with a file-like material in advance or chemically etching to make it a rough surface and to cause an anchoring action.

As the adhesive for adhering the resin sheet to the base material, an adhesive having a softening point of 200 ° C. or higher, that is, an epoxy adhesive, which is a synthetic polymer having excellent coatability, adhesiveness and high temperature stability, is used. Heat resistance of acrylic, polyvinyl alcohol, urethane, melamine, polyvinyl acetal, urea, phenol, resorcinol, polyester, polyaromatic, natural rubber, asphalt, cellulose derivative, etc. A highly adhesive adhesive may be used. On the other hand, an adhesive having a low softening point made of a thermoplastic polymer cannot be adopted. Incidentally, in the above, when the adhesive is solvent-rich, the resin sheet may swell due to the volatilization of the solvent during heating, and therefore the paint may be distorted.Therefore, it is necessary to select one having a small amount of solvent of less than 50 wt%. Especially, a solventless type quick-drying two-component epoxy adhesive is recommended. The adhesive may be applied to the glass plate as thin as several tens of μm.

The coating material is applied onto the resin sheet by, for example, a method suitable for actual operation such as a flow coating method, a roller coating method, a brush coating method, a spray coating method, a spin coating method, a doctor blade method and the like. For example, in the case of mirror backing paints, talc, calcium carbonate, barium sulfate, titanium oxide, filling / coloring agents such as rouge, zinc flower, lead sulfate, lead carbonate, lead are used in vehicles such as mirror back coatings. A mixture of anti-corrosion pigments such as red is adopted, and a paint in which the above raw materials are dissolved and dispersed in a solvent is applied.
The film thickness after curing is about 20 to 80 μm.

After the backing coating material is applied, it is dried and heat-cured by the usual heating means used in actual operation. For example, in the manufacture of mirrors, it is customary to bake at 100 to 200 ° C. for 2 to 10 minutes as appropriate.

After further curing, the resin sheet is first peeled off from the substrate, and then the paint film is peeled off from the resin sheet, whereby a paint film can be obtained.

[0016]

[Examples and Comparative Examples] The following examples and comparative examples are compared,
Specific examples of mirror manufacturing will be described in detail, but the present invention is not limited thereto.

[Preliminary Test Example 1] On a glass plate of 50 cm × 25 cm × 5 mm (thickness), a laminated film having a thickness of several tens of nm including a silver film and a copper film was formed by an ordinary chemical plating method. Further, the back coating material as described above was applied onto the copper film by the doctor blade method, taking into consideration the film thickness of the cured film to be 50 μm.

A thermocouple is set in advance so that the temperatures of the front surface and the back surface (side surface of the copper film) [both of the width and length of the film] of the sample can be detected.
The sample was carried into an electric heating furnace whose temperature was set to 200 ° C. in advance, and the temperature rising situation was investigated for 10 minutes.

[Preliminary Test Example 2] Preliminary Test Example 1 A glass plate having the same size as above was thinly coated with a solventless type quick-drying two-component epoxy adhesive without forming a silver film and a copper film. A 0.3 mm thick tetrafluoroethylene resin sheet was adhered on top. The surface of the tetrafluoroethylene resin sheet to be bonded with the epoxy adhesive was previously rubbed with a 1000-mesh paper file to form a rough surface.

Further, a backing coating composition similar to that in Preliminary Test Example 1 was applied thereon by the same procedure as in Preliminary Test Example 1. Also in this sample, a thermocouple for temperature detection is set on the front surface and the back surface (side surface of the resin sheet) in the same manner as in Preliminary Test Example 1.
The temperature rise situation was investigated and compared.

[Results of temperature rising test] The results are as follows, and there is no difference in the heating behavior of the backing coating film in the preliminary test examples 1 and 2. That is, even when the paint film is formed on the copper film of the mirror, on the other hand, the film formation of the silver film and the copper film on the glass plate is omitted, and the paint film is formed by interposing the adhesive and the resin sheet. It can be seen that almost the same temperature rise situation is exhibited, and therefore it is judged that the curing state is also the same. Based on this, the configurations of the preliminary test example 2 were also adopted for the examples and comparative examples described later, and comparative examinations were carried out. Preliminary test example 1 Preliminary test example 2 Coating surface, coating back surface, coating surface, coating back surface Temperature after heating 2.5 minutes (° C) 91 85 90 90 87 〃 5.0 〃 125 123 123 124 122 〃 7.5 〃 149 147 149 148 〃 10.0 〃 166 164 166 166

Example 1 A glass plate having the same size as in Preliminary Test Example 2 was thinly coated with a solventless type quick-drying two-component epoxy adhesive in the same manner as in Preliminary Test Example 2, and a thickness of 0.3 m was applied thereon.
An m 4 tetrafluoroethylene resin sheet was adhered. Also,
The surface of the tetrafluoroethylene resin sheet to be adhered to the epoxy adhesive was previously rubbed with a 1000-mesh paper file to form a rough surface. Further, a backing coating composition similar to that of Preliminary Test Example 2 was applied on the coating film by the doctor blade method, taking into consideration that the film thickness of the cured film was 50 μm. This sample in advance
It was carried into an electric heating furnace whose temperature was set at 200 ° C, baked and cured for 6 minutes, cooled, and then examined for paint film peeling properties.

Example 2 A sample was prepared in the same manner as in Example 1 except that a polyvinylidene fluoride resin sheet (forming a rough surface on the adhesive bonding surface) was used as the resin sheet, and an electric heating furnace was used as in Example 1. After heating, baking and curing for 6 minutes and cooling,
The peelability of the paint film was investigated.

[Comparative Example 1] A sample was prepared in the same manner as in Example 1 except that a polyethylene resin sheet was used as the resin sheet, heated in an electric heating furnace in the same manner as in Example 1, and taken out after 6 minutes. However, since the polyethylene resin sheet was melted and deformed, the subsequent peeling test was omitted.

[Comparative Example 2] A sample was prepared in the same manner as in Example 1 except that a vinyl chloride-based adhesive was used as the adhesive, heated in an electric heating furnace in the same manner as in Example 1, and after 6 minutes, the sample was removed. When it was taken out, the adhesive softened and the tetrafluoroethylene resin sheet was peeled and deformed from the glass plate. Therefore, the subsequent peel test was omitted.

Comparative Example 3 A sample was prepared in the same manner as in Example 1 except that an epoxy adhesive consisting of 1 part by weight of epoxy adhesive resin: 1 part by weight of xylene solvent was used as the adhesive.
After heating in an electric heating furnace in the same manner as in Example 1 and taking out the sample after 6 minutes, a large number of swelling (0.5 to 1 cmφ) of the tetrafluoroethylene resin sheet, which is considered to be caused by the volatilization of the solvent, was generated. Therefore, the subsequent peel test was omitted.

[Removability of coating film] The resin sheet was peeled from the glass plate by hand, and then the paint film was peeled from the resin sheet, and the possibility of peeling and the presence of cracks were examined. Example 1 Example 2 Comparative Examples 1 to 3 Resin sheet Good peeling, no crack Good peeling, no cracking Not performed Paint coating Good peeling, no cracking Good peeling, no cracking Not performed As described above, according to the example, The peelability is also good, and a good film without cracks can be obtained.

[0028]

INDUSTRIAL APPLICABILITY According to the present invention, it is particularly suitable for forming a film of a coating film which is brittle and brittle.

Claims (2)

[Claims] 1. A resin sheet having heat resistance and good peelability from a coating film is adhered to a substrate through a low solvent amount or solventless type heat-resistant and high-adhesive adhesive, and the coating material is applied thereon. A method for forming a film of a paint film, comprising the steps of: after curing and forming the paint film, the resin sheet is peeled off from the base material, and then the paint film is peeled off from the resin sheet. 2. The method for forming a coating film according to claim 1, wherein the resin sheet is a fluororesin sheet.