JPH05177168A - Painted metal plate with excellent weather resistance - Google Patents

Abstract

(57) [Summary] [Purpose] To improve the weather resistance of dyed coated steel sheets. [Structure] A clear second coating layer having low dyeability is provided on the first coating layer containing a dye. [Effect] The color change after exposure to the atmosphere is greatly improved, and the life of the coated steel sheet is significantly extended.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
For example, the present invention relates to a colored steel sheet having excellent weather resistance, which is suitable for use as a coated steel sheet for household appliances such as refrigerators and microwave ovens or indoor building materials, and is particularly applicable as a refrigerator door material or interior building material for which design is required. .. In the following,
A coated steel plate will be described as an example of the coated metal plate.

[0002]

2. Description of the Related Art The purpose of coating a steel sheet is to improve the appearance of the steel sheet and to improve the corrosion resistance. Corrosion resistance is also considered to be a secondary aesthetic as long as it is not a structural member. In recent years, design patterns and high image clarity are also required for home appliances and interior building materials against the backdrop of upscale and individualized living environments, and high designability is required. It started to come.

The applicant of the present invention has already filed a patent application as Japanese Patent Application Laid-Open No. 3-1114824 for dyeing a coated steel sheet, and for a method of forming a pattern using the same, Japanese Patent Application Laid-Open No. 3-234526 and It was proposed in Japanese Patent Application No. 2-137621. Dyes usually have the advantage of easily obtaining a bright hue as compared with the inorganic pigments used for coated steel sheets, but have the disadvantage of poor weather resistance.

Further, according to the coloring method by dyeing of a coated steel sheet disclosed in Japanese Patent Laid-Open No. 2-270545, when a pattern is formed by a printing method or the like, the sharpness is deteriorated, but the dyeing has a high sharpness. Can be maintained. As described above, the coloring method by dyeing has an advantage that the hue is vivid and the image clarity is maintained, but has a disadvantage that the weather resistance is poor.

[0005]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a dye-colored coated metal plate or a coated metal plate having a patterned pattern formed with a dye, which has improved weather resistance.

[0006]

Therefore, the present inventors have
In order to achieve such an object, various investigations have been conducted on causes of deterioration of the dyed coating film, and the following findings have been obtained. When a coating film is formed by coating->drying-> curing and then immersed in a dyeing solution for dyeing, dye molecules are extracted into the coating film. The dye molecules are molecularly dispersed, that is, dissolved in the coating film.

[0007] Dye molecules easily penetrate into the coating film because they are low molecular weight substances having a molecular weight of about several hundreds, but conversely diffuse with time in the coating film and sublimate from the surface of the coating film. In order to suppress the sublimation phenomenon from the coating film surface, it is effective to provide a barrier coating film layer for suppressing the diffusion of the dye.

However, since the dye is also extracted in this barrier coating layer, it is necessary that the barrier coating layer is a layer in which the dye is difficult to extract. Thus, the gist of the present invention is that, in a coated metal plate having a coating film containing a dye, the dyeing property is lower on the first coating film layer containing the dye and further lower than the first coating film layer. A coated metal plate having excellent weather resistance, characterized in that a substantially transparent second coating layer is provided as a barrier coating layer.

[0009]

Next, the operation of the present invention will be specifically described. As already mentioned, according to the present invention, one of the causes of the poor weatherability of the dyed coated metal sheet is due to the sublimation phenomenon of the dye, and thus on the dyed first coating layer. By providing the transparent second coating film layer, the diffusion of the dye is suppressed to improve the weather resistance. In addition,
If this second coating layer, that is, the barrier coating layer, is not substantially transparent, a beautiful dyed surface cannot be seen.

The dyeing step is to extract dye molecules dispersed in water by a surfactant or the like into the coating film. Such migration occurs when the dye molecules are dissolved and present in the coating film.
It is considered that it is more stable in terms of free energy than it is dispersed in water. Therefore, the greater the solubility of the dye in the resin, the easier it is to dye, that is, the greater the color change during the equilibration time, but of course,
This easiness of dyeing differs depending on the type of coating resin.

In the present specification, this easiness of dyeing is referred to as "dyeability", and specifically, when the dyeing treatment is carried out at the same dye type, dye concentration and temperature for the same time. In addition, "a coating film having a large ΔE has high dyeability".
ΔE is an index of color change before and after the dyeing process.

That is, for the barrier coating layer having a low dyeability,
Dye does not easily migrate from the dyed layer. However, when the dyeability of the barrier coating layer is high, migration of dye, that is, extraction into the barrier coating layer proceeds, and the dye sublimates from the surface of the barrier coating layer.

The cause of insufficient weather resistance of the dyed coated metal plate is deterioration of the dye by ultraviolet rays. Against this, it is effective to provide a barrier coating layer, but when sunlight or the like is directly irradiated,
An ultraviolet absorber, a transparent inorganic pigment, etc. can be mixed in the barrier coating layer.

Further, the transparency of the coating film is determined by the difference in the refractive index between the contained pigment and the coating resin. When the difference in refractive index is large, the reflectance at the resin / pigment interface increases, so
Transparency decreases. That is, the concealing property is improved.
Therefore, although it is of course related to the thickness of the barrier coating layer, normally, if the coating thickness is 20 μm or less,
The difference in refractive index between the added inorganic pigment and the resin is 0.5 or less, and if the addition concentration is about 1 to 50% by weight, the transparency can be sufficiently maintained.

Examples of the inorganic pigments mentioned here include pigments such as calcium carbonate and glass flakes.
Further, when the addition amount is large, the amount of ultraviolet rays which penetrates the barrier coating film layer and reaches the dyeing layer is reduced, but the workability of the coating film is often deteriorated, so that it is necessary to appropriately balance the amount.

As a matter of course, the present invention relates to the dyed coating film and the upper layer thereof, that is, the cover coat, and the type of the steel plate, that is, whether or not any plating is applied, or the primer for the surface treatment is described. Need not be limited. Further, whether or not the dyed coating layer is two-dimensionally uniform (monochromatic) is not limited at all.

Next, the specific structure of the coated steel sheet according to the present invention will be described. In the present invention, the coated metal plate,
Using various plated steel plates, aluminum plates, stainless steel plates, etc. as base metal, with or without base treatment such as zinc phosphate treatment or chromate treatment, or applying one or more layers of various resin-based paints or various resins It includes those obtained by laminating a system film and then performing a dyeing treatment.

In the present invention, the types of base metal plate, base treatment and coating resin are not limited. It can be appropriately selected according to the purpose.

The dyeing solution is not particularly limited, and may be a commercially available one used for dyeing fibers such as disperse dyes and metal-containing dyes, and may be appropriately selected according to the type of resin coating layer of the metal plate to be colored. Just select it.

In producing the coated steel sheet according to the present invention, a cold rolled steel sheet or a plated steel sheet is used as a base material,
If necessary, this is subjected to chromate treatment and / or phosphate treatment, and then coated or laminated to form a resin coating layer. For example, the coated steel sheet may be obtained by forming a coating film by a conventional method such as roll coating, dip coating, spray coating, or electrodeposition coating, and curing the coating film by baking if necessary. ..

The laminated steel plate can be obtained by directly heat-bonding a film formed in advance or a film extruded on a steel plate at the time of lamination to the steel plate or heat-bonding it with an adhesive. Appropriate surface modification treatment such as corona discharge treatment may be performed in order to enhance the dye receptivity, that is, the dyeability.

Examples of the organic resin include polyester-based, acrylic-based, epoxy-based, urethane-based, melamine-based, vinyl chloride-based, vinyldene chloride-based, butyral-based resins and the like, which are generally used for producing paints or laminated films. The type is not limited as long as it can be dyed. The resin used may be either a thermosetting resin or a thermoplastic resin. As described above, even a thermosetting film can be colored by dyeing.

The organic resin coating layer may be either a transparent coating or a colored opaque coating, but it is preferable to consider so that a beautiful color can be obtained by dyeing. White or light opaque coatings are usually preferred.

The dye used for dyeing is a metal-containing complex salt dye,
Any acid dye, cationic dye or the like can be used as long as it is suitable for dyeing an organic resin, and may be appropriately selected depending on the type of the resin coating layer to be dyed and the desired color.

The dyeing may be carried out so that the entire surface of the coated steel sheet is colored, or the colored portion may be partially provided in an island shape. The dyeing method can be carried out by applying a dyeing method of cloth or thermoplastic fimeul. For example, when dyeing the entire surface, it is generally convenient to carry out the dipping method.
For partial dyeing, a method of dyeing by a stencil dyeing method using a mold (mask) can be adopted.

The dyeing time is appropriately determined depending on the type of resin and the type of dye. The number of times of dyeing is not limited to once, and it is possible to form multiple colors by performing dyeing twice or more. In that case, it is preferable to select the dyeing order in consideration of the decolorizing property in the next dyeing step.

According to the present invention, after forming such a dyeing layer, a film having a poorer dyeability than that is provided as a barrier film. As such a second film, the following paint is used. You can

For example, a polyester coating layer having a higher melamine content than the first coating layer or a polyester resin-based coating layer having a high OH value, even if the melamine content is about the same, has a higher crosslinking density than the first coating layer. The higher one has the effect of reducing the dyeability. The dyeing property of the second film may be lower than that of the first film.

The coating means may be the same as that for the first coating layer. As described above, if necessary, an ultraviolet absorber, a transparent inorganic pigment, etc. may be added. The thickness of the barrier coating layer is not particularly limited, but in order to achieve its purpose, it is preferably about 5 to 10 μm.

Although a saturated polyester-based coating material may be applied as a clear layer to the uppermost layer as a protective layer even in the past, they improve weather resistance as compared with the barrier coating layer in the present invention. The difference is that a clear layer having a high effect is provided. For example, when the first layer and the second layer have opposite configurations, the dramatic weather resistance improving effect is not exhibited. Next, the present invention will be described more specifically by way of its examples.

[0031]

【Example】

Example 1 A hot dip galvanized steel sheet (60 g / m ² attached amount) was subjected to a conventional zinc phosphate treatment, and then a white epoxy type primer 5 μm and a high molecular weight polyester type paint 15 μm
A coated steel sheet A coated with m and a coated steel sheet B coated with 15 μm of a white acrylic paint on the primer and the above-mentioned base treatment were prepared. The baking conditions for each coating are 210 ° C
× 60 seconds, 230 ℃ × 90 seconds.

Next, the coated steel sheets A and B were immersed for 5 minutes in boiling water containing 10 g / l of a Villian Pink disperse dye (trade name: Terasil ^™ , manufactured by Ciba Geigy) for dyeing treatment.

The color difference at that time is ΔE as compared with that before dyeing.
At 50 and 8 respectively. The coated steel sheet A has higher dyeability than the coated steel sheet B. After the dyeing treatment, the coated steel sheet A contained no coloring pigment, that is, 15 μm of a clear high molecular weight polyester paint was applied to form a sample-1 while the coated steel sheet B was coated.
A clear acrylic paint of 15 μm was applied on top of the above to give Sample-2. Each sample was exposed to the atmosphere indoors for one year to see the color change. The color difference between the initial and post-exposure is ΔE of 5 and 1.
It was 5.

Example 2 A clear acrylic paint was applied to a coated steel sheet A, which had been subjected to the same dyeing treatment as in Example 1, to a thickness of 15 μm, and the obtained Sample-3 was subjected to the same indoor exposure. The color difference between the initial and post-exposure was 0.5.

Comparative Example 1 The coated steel sheets A and B obtained in Example 1 were exposed indoors for one year. A considerable color change was observed at that time, and the color difference ΔE was 10 and 3 as compared with that immediately after dyeing.

(Comparative Example 2) In this example, in order to confirm that the degree of discoloration due to exposure of the clear coating film was small, only the clear coating was applied to the coated steel sheets A and B without dyeing, and Samples -4 and-respectively. Got 5.

When the same indoor exposure was carried out for these, it was found that the color change was ΔE <0.1, and the discoloration of the clear coating film itself was very small. Therefore, it can be seen that the change in ΔE due to the above exposure is all the color change in the dyed layer.

As described above, the weather resistance is better when the clear layer is applied on the dyed layer even when the resin composition of the upper layer is a resin layer which is hard to be dyed, even if it is of the same quality. It can be seen that is dramatically improved.

[0039]

Since the present invention is constructed as described above, it is possible to improve the weather resistance of the coated metal sheet provided with the dyed layer.

Claims (1)

[Claims] 1. A coated metal plate having a coating film containing a dye, wherein a substantially transparent first metal layer having a dyeability lower than that of the first coating film layer containing the dye. A coated metal plate with excellent weather resistance characterized by having two coating layers.