JPH05147155A - Organic composite coated steel plate excellent in discrimination properties - Google Patents

Abstract

PURPOSE:To obtain an org. composite coated steel plate capable of being widely utilized in various fields including a car body because the good discrimination properties due to a color sensor can be imparted without damaging excellent corrosion resistance, electrodepotition coating properties, water-resistant secondary adhesion and weldability. CONSTITUTION:In an org. composite coated steel plate, a chromate film containing Cr<6+> in an amount of 70% or less of a total Cr amount is provided on the surface of a galvanized or zinc alloy-plated steel plate in an adhesion amount of 5-500 mg/m<2> as Cr and planar aggregates with a mean primary particle size of 5-60nm, a mean thickness of 0.2-2mum and a mean diameter of 5-300mum are formed to the upper layer of the chromate film. Further, a resin composite layer containing almost uniformly dispersed silica, phthalocyanine pigment being color pigment and an org. polymeric resin is provided on the surface of the steel plate in a dry wt. of 0.1-3 g/m<2>.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic composite coated steel sheet which is excellent in press workability, cationic electrodeposition coating property, spot weldability, corrosion resistance, etc. ..

[0002]

2. Description of the Related Art In response to the strong social demand for high corrosion resistance of automobile bodies, the application of surface-treated steel sheets having zinc or zinc alloy plating on the surface of cold-rolled steel sheets has been expanding in recent years. ..

Examples of these surface-treated steel sheets include hot-dip galvanized steel sheets, alloyed hot-dip galvanized steel sheets, electrogalvanized steel sheets, and electrogalvanized alloy-plated steel sheets. However, even higher corrosion resistance has been required in the bag structure portion and the bending portion (hemming portion) of the inner plate of the vehicle body where the coating performed after the vehicle body assembly is not sufficiently spread.
As a steel sheet for automobiles which can be used for such purposes, for example, JP-A-57-108292 and JP-A-58-2.
No. 24174, JP-A No. 63-22637, etc., propose an organic composite coated steel sheet in which a chromate and an organic polymer resin layer are formed on a zinc or zinc alloy plated steel sheet. In these organic composite coated steel sheets,
Many proposals are still made today for further improvement in press workability, cationic electrodeposition coating property, spot weldability, corrosion resistance and the like.

By the way, in a processing and assembly line of an automobile manufacturing plant, a surface-treated steel sheet such as an organic composite coated steel sheet, a cold-rolled steel sheet, or even a surface-treated steel sheet having a different coating weight is used depending on the use site or destination. It is normal to use a mixture of these. Therefore, using the steel sheet as originally designed without confusion leads to important quality control. For this purpose, use of a photoelectric sensor utilizing the difference in light reflection intensity between a cold-rolled steel sheet and a surface-treated steel sheet such as an organic composite coated steel sheet has been put into practical use as an automatic identification means. If only two types of steel plates having different light reflection intensities are mixed, the purpose can be achieved even by using a relatively inexpensive photoelectric sensor. However,
In the case where the same type of surface-treated steel sheet is different only in the coating weight, the light reflection intensity does not change, and therefore the above method cannot be applied. A method of positively changing the glossiness of an organic composite-coated steel sheet by incorporating an additive into an organic resin is disclosed in Japanese Patent Laid-Open No. 3-1244.
Although proposed in Japanese Patent Laid-Open No. 36, the discrimination is insufficient only by the light reflection intensity when the type of plating used increases.

[0005]

The present invention has been made to solve these problems in the prior art.
For example, if there is a difference in color tone of the organic composite-coated steel sheet depending on the type of plating and the difference in coating weight, it is possible to automatically identify using a color sensor. Further, even when a person makes a judgment, there is an advantage that it is possible to prevent confusion such as a mistake in the applied steel sheet due to a clear difference in color tone.

From this point of view, the present invention is mainly aimed at giving a color tone to the organic composite coated steel sheet, but the organic composite coated steel sheet as a steel sheet for automobile bodies is press workable and cationic electrodeposition coatable. In addition to being excellent in spot weldability and corrosion resistance, there is no deterioration in powdering resistance, slidability, chromium elution resistance, water secondary adhesion, etc. even if a coloring pigment is added. An object of the present invention is to provide an organic composite-coated steel sheet having excellent distinguishability, in which a coloring pigment is not eluted during alkali degreasing to contaminate the degreasing liquid.

[0007]

In order to solve the above-mentioned problems, the present invention provides that Cr ⁶⁺ is 70% or less with respect to the total Cr amount on the surface of a zinc- or zinc-based alloy-plated steel sheet, and the adhesion amount is Has a chromate film of 5 to 500 mg / m ² in terms of Cr, and an organic composite-coated steel sheet having a resin composite layer mainly containing silica, a color pigment and an organic polymer resin as an upper layer of the chromate film. The average primary particle diameter of the silica is 5 to 60 nm, and the silica forms a planar aggregate having an average thickness of 0.2 to 2 μm and an average diameter of 5 to 300 μm in the resin composite layer. The planar aggregates of silica are substantially evenly distributed on the steel plate surface, and the coloring pigment is at least one selected from phthalocyanine-based pigments, and the amount of the resin composite layer deposited is a dry weight. Then .1～
An organic composite-coated steel sheet excellent in distinctiveness, which is characterized in that it is 3 g / m ² .

The content of the phthalocyanine pigment in the resin composite layer is preferably 1 to 10% by weight.

The content of silica in the resin composite layer is 1
It is preferably from 0 to 50% by weight.

The organic polymer resin of the resin composite layer is preferably a resin based on an epichlorohydrin-bisphenol A type epoxy resin having a number average molecular weight of 2000 or more.

The silica has an average particle diameter of 0.05 to 2 μm.
m is preferably an organic solvent-dispersed silica sol.

Preferably, the silica is a hydrophobic fumed silica.

The present invention will be described in detail below.

The material of the organic composite coated steel sheet of the present invention is zinc
Alternatively, it is a zinc alloy plated steel sheet. Subs applied to steel sheets
For lead or zinc alloy plating, pure zinc plating, Z
Binary alloy alloy such as n-Ni, Zn-Fe, Zn-Cr
, Zn-Ni-Cr, Zn-Co-Cr, etc.
Gold plating, Zn-SiO₂, Zn-Co-Cr-Al ₂
O₃It is also possible to use composite dispersion plating such as. This
These plating methods are electroplating, hot dipping, vapor phase
It may be applied by the method of plating.

The organic composite coated steel sheet of the present invention is made of these zinc
Or, on the surface of zinc-based alloy plated steel sheet,
Improves adhesion with the coalesced layer and also imparts high corrosion resistance.
Therefore, it has a chromate film. Chrome
The amount of chromate deposited on the coating film is 5 in terms of Cr.
500 mg / m², Preferably 10 to 150 mg / m ²
Is. In the organic composite coated steel sheet of the present invention,
Chromate adhesion on the coating is 5 mg / m²Less than
To obtain good corrosion resistance and water resistant secondary adhesion
I can't. Also, the amount of chromate deposited is 500 mg / m
²If it exceeds the limit, chromium elution occurs, which is not environmentally favorable.
Yes. In the present invention, the chromate film is a coating type chrome.
Method, electrolytic chromate method, reactive chromate method, etc.
It may be formed by the shifting method.

The amount of Cr ⁶⁺ in the chromate film is 70% or less based on the total amount of Cr. If the amount of Cr ⁶⁺ in the chromate film exceeds 70% of the total amount of Cr, the chromium elution resistance during alkaline degreasing deteriorates, which is not preferable.

In the organic composite-coated steel sheet of the present invention, a resin composite layer containing silica, a color pigment and an organic polymer resin is provided on the chromate film. The organic polymer resin contained in this resin composite layer is not particularly limited, but an epoxy resin, an acrylic resin, a polyethylene resin, an alkyd resin, a urethane resin or the like is exemplified, and particularly, JP-A-2-25833.
No. 5 and JP-A-3-130141 proposed epichlorohydrin having a number average molecular weight of 2000 or more.
Using a resin composition based on a bisphenol A type epoxy resin is more desirable from the viewpoint of toughness and corrosion resistance.

Next, the color pigment will be described. Color pigments are roughly classified into inorganic pigments and organic pigments. The inorganic pigment is
Generally, since the particle size is large and the coloring power is poor, a large amount of pigment must be added for coloring. Most of the film thickness of the thin film type organic composite coated steel sheet aimed at by the present invention is 2 μm or less, so that if the average particle diameter of the pigment exceeds this, there is a problem that powdering resistance and press workability are deteriorated.

On the other hand, since the organic pigment has a smaller particle size and a larger coloring power than the inorganic pigment, it can be colored in a small amount and is advantageous in terms of powdering resistance and press workability. However, azo pigments that are widely used as organic pigments have poor heat resistance, as can be inferred from their chemical structure,
When the resin composite layer is used for baking at a high temperature of about 160 ° C. as in the present invention, stable identification by a color sensor becomes difficult. Also, acid dye lake pigments,
Basic dye lake pigment or alkali blue pigment is
When it is used in applications where it is inferior in water resistance and alkali resistance and is subjected to alkaline degreasing and the like, decolorization of the steel sheet and elution of the pigment into the degreasing liquid occur, which is also not suitable.

As described above, the performance of the organic pigment varies greatly depending on the chemical structure. In the present invention, an organic pigment is used as the color pigment contained in the resin composite layer. This organic pigment is required to have excellent heat resistance, alkali resistance, acid resistance, solvent resistance, water resistance, tinting strength, etc. from the intended use, and the azo pigments and lake pigments described above are not suitable for this purpose. is there. For blue or green coloring, a phthalocyanine pigment is preferably applied. Phthalocyanine-based pigments have very good performance because they have chemical stability due to their high electron density and the presence of highly conjugated π-electron system.

Specific examples of the phthalocyanine pigment include phthalocyanine green, polychlorobrom copper phthalocyanine, metal-free phthalocyanine blue, phthalocyanine blue, and fast sky blue.

Next, based on concrete experimental facts, the lid is
The distinctiveness of the cyanine pigment will be described. Remove cold rolled steel sheet
After pickling oil and pickling, the average Ni content is 12% by weight and the basis weight is 2
0 g / m ²Zn-Ni plating of
Made Chromium reduction rate of about 50 on the surface of this plated steel sheet
% Of chromate treatment solution using a roll coater.
After baking, baking in an electric furnace at a maximum temperature of 130 ° C
Chromate treatment was carried out. Chromate adhesion amount is 5
0 mg / m²And Furthermore, the upper layer of the chromate treatment layer
Epoxy resin with a number average molecular weight of 3750, ethyl cello
Silica sol dispersed in sorb (average primary particle size 10
nm, average secondary particle size 0.4 μm) and phthalocyanine
Green, and the silica content in the solid content is 40% by weight.
Fix and adjust the blending amount of phthalocyanine green to 1 to 15
It changes in the range of wt% and the rest becomes epoxy resin.
In addition, the solid content of the paint is 15% by weight.
Phthalocyanine green
Various paints having different contents of were prepared. This phthaloshi
Various paints with different content of Anine Green
After coating the plated steel sheet using a bar coater,
Baking is performed in the furnace so that the maximum temperature reaches 160 ° C.
Thus, an organic composite coated steel sheet was produced. Organic composite coated steel sheet
Adhesion amount of resin composite layer is 0.7 g / m²And

In the resin composite layer of the obtained organic composite-coated steel sheet, silica is aggregated in the form of a sheet having an average thickness of 0.2 to 2 μm and an average diameter of 5 to 300 μm. It was distributed almost uniformly on the steel plate surface. The identifiability of the organic composite coated steel sheet obtained in this way is HOYA
-SCHOTT color sensor HCS1080
It evaluated using. FIG. 1 shows the evaluation results of green distinguishability of an organic composite-coated steel sheet having a resin composite layer produced by using phthalocyanine green as a color pigment. When the blending amount of phthalocyanine green in the resin composite layer was 1% by weight or more, it was possible to obtain the output value required for green color identification. This is the reason why the lower limit of the color pigment in the resin composite layer is set to 1% by weight. From this point of view, the larger the blending amount is, the higher the output value is. However, when the blending amount of the above-mentioned coloring pigment exceeds 10% by weight, deterioration in the adhesiveness with the electrodeposition coating material was confirmed. did.

In the above-mentioned specific examples, an organic solvent-dispersed silica sol having a cohesive property was used as the silica constituting the resin composite layer. As silica in paint, n-
The results of the same experiment using silica sol (average particle size 10 nm) uniformly dispersed in propyl cellosolve are also plotted in FIG. 1, but the output value was significantly reduced. Even in this case, when observed with the naked eye, a clear green color tone was recognized, but it was difficult to detect with a color sensor.
When the cause was examined, when the uniformly dispersed silica sol was used (● in FIG. 1), since the surface of the resin composite layer had a high glossiness, specular reflection light from the surface of the resin composite layer was transmitted from the chromate layer. It was found that the intensity was stronger than that of the reflected light (including the light transmitted through the resin composite layer as a signal), making it difficult to detect information regarding the color tone inside the resin composite layer.

When a cohesive organic solvent-dispersed silica sol is used as the silica constituting the resin composite layer, the gloss of the surface of the resin composite layer is low and the light reflected from the surface of the resin composite layer is weak. Therefore, the reflected light from the chromate layer containing the transmitted light inside the resin composite layer as a signal becomes relatively strong, and the information about the color tone inside the resin composite layer can be easily detected. For the same purpose, when hydrophobic fumed silica was used as the silica constituting the resin composite layer, agglomeration inside the resin composite layer was clearly observed, and a cohesive organic solvent-dispersed silica sol was used. It was possible to detect almost the same signal as when there was.

From the above results, the content of the color pigment in the dry coating film is set to 1 to 10% by weight. When the content of the color pigment is less than 1% by weight, sufficient distinguishability cannot be obtained, and when it exceeds 10% by weight, the adhesion after coating is deteriorated, which is not preferable.

Regarding silica, the average primary particle diameter is 5 to 60 nm, and the silica is aggregated in the resin composite layer in a plane shape having an average thickness of 0.2 to 2 μm and an average diameter of 5 to 300 μm. The silica surface aggregates should be distributed almost uniformly on the steel plate surface. Any silica having such a structure can be applied. The silica having such a structure has an average aggregate particle diameter of 0.0
Preferable examples are organic solvent-dispersed silica sols having a thickness of 5 to 2 μm and hydrophobic fumed silica.

Furthermore, the amount of silica in the resin composite layer is preferably 10 to 50% by weight. When the amount of silica is less than 10% by weight, the ability to stably hold a Zn-based corrosion product formed when exposed to a corrosive environment is insufficient, and high corrosion resistance cannot be obtained. Further, if the amount of silica exceeds 50% by weight, the compatibility with the resin product decreases and it becomes difficult to apply it as a paint on a steel sheet, which is not preferable.

[0029]

EXAMPLES The present invention will be described in more detail with reference to Examples of the present invention.

(Example) After degreasing and pickling cold-rolled steel sheet, average
Ni content is 12% by weight and basis weight is 20 g / m ²Zn
-Ni plating was performed to produce a plated steel sheet. Got
Chromate with a chromium reduction rate of 50% on the surface of plated steel sheet
After coating the treatment liquid using a roll coater, use an electric furnace
Chromate by baking at the maximum temperature of 130
Processed. Table 4 shows the amount of chromate deposited. further
On the upper layer, the resin shown in Table 1, the silica shown in Table 2, and
And the coloring pigments shown in Table 3 are blended appropriately and the organic solvent (ethylen
Glycol monobutyl ether, propylene glycol
Rumonomethyl ether acetate and aromatic petroleum
The mixed resin composite liquid prepared by
The maximum temperature reached by the electric furnace is 1 after coating with a heater.
Baking to 60 ° C to form a resin composite layer
It was Siri of resin composite layer formed on the surface of plated steel sheet
F content, organic coating amount, and content of coloring pigment are shown in Table 4.
You

(Observation of Surface Shape) When the surface of the steel sheet coated with the mixed solution containing silica E and silica F shown in Table 2 was observed, each silica had an average thickness of 0.2 to 2 μm.
m, and the average diameter was 5 to 300 μm. Further, on the surface of the steel sheet coated with the resin composite solution containing silica G in Table 2, silica was uniformly dispersed in the resin composite layer.

(Distinguishability) Using a color sensor HCS 1080 manufactured by HOYA-SCHOTT Co., Ltd., the R, G, B values were measured at an extraction angle of 70 ° to evaluate the distinguishability.
The evaluation was performed according to the following criteria. ◎: Stable identification is possible △: Identification is unstable ×: Identification is not possible

(Corrosion resistance) A combined cycle corrosion test in which the following steps to 1 cycle are repeated was repeated until red rust was generated, and the number of cycles when red rust was generated was used as an index of bare corrosion resistance. Salt spray 4 hours 5% NaCl solution 35 ° C Dry 2 hours 60 ° C Wet 2 hours 95% RH 50 ° C

(Phosphate Treatment, Chromium Elution Resistance, Decolorization) Normal alkali degreasing is carried out, followed by phosphate treatment (Nippon Parkerizing Co., Ltd. Valbond L3020 1
It was immersed for 20 seconds). The elution amount of chromium of each sample obtained here before and after the phosphate treatment step was measured. The chromium deposition amount was measured by fluorescent X-ray analysis, and the difference between before and after was used as the chromium elution amount and evaluated according to the following criteria. ◎: 1mg / m ² or less 〇: 1-2 mg / m less than ² △: ^2~5mg / m ² less ×: more than 5 mg / m ² was also evaluated bleaching properties at this time based on the following criteria. ⊚: No bleaching ◯: Almost no bleaching Δ: Slightly bleaching ×: Almost all bleaching results are shown in Table 4.

(Water-resistant secondary adhesion) Power Top U-600 (manufactured by Nippon Paint Co., Ltd.) was applied to the phosphate-treated sample by applying an electrodeposition voltage of 250 V, a bath temperature of 28 ° C. for 180 seconds.
Was electrodeposited and baked at 170 ° C. for 20 minutes. The sample after the electrodeposition coating was further spray-coated with an automotive topcoat paint. A water resistance secondary adhesion test was performed using each of the samples thus obtained. 40 ° C for each sample
It was immersed in warm water for 240 hours. On the surface of each sample taken out, using a cutter knife, 100 at 2 mm intervals
A checkerboard-like scratch was made on each piece, and a peeling test was performed using cellophane tape. The evaluation was performed by measuring the number of peeled grids. ⊚: No peeling ◯: Peeling number 1 or less Δ: Peeling number 2 to 10 x: Peeling number 11 or more Table 4 shows the test results.

(Electrodeposition coating property) A sample treated with phosphate was electrocoated with Power Top U-600 (manufactured by Nippon Paint Co., Ltd.) by applying an electrodeposition voltage of 90 V, a bath temperature of 28 ° C. for 180 seconds. It was baked at 170 ° C. for 20 minutes. Then, the appearance (number of gas pinholes) was evaluated according to the following criteria. ◎: 0 pcs / cm ² 〇: 1 to 6 pcs / cm ² △: 7 to 10 pcs / cm ² ×: 11 pcs / cm ² or more

(Welding property) Using a welding tip made of Al ₂ O ₃ dispersed copper alloy having a tip diameter of 6 mmφ, a pressure of 200 kgf,
Continuous welding was performed at a welding current of 9 kA and a welding time of 10 cycles, and the number of continuous welding points until the nugget diameter fell below the reference diameter was measured and evaluated according to the following criteria. ◎: 3000 points or more ○: 2000 to 2999 points △: 1000 to 1999 points ×: Less than 1000 points

As shown in Table 4 below, according to the organic composite coated steel sheet of the present invention, corrosion resistance, adhesion, paintability,
It is understood that the distinguishability by the color sensor can be obtained without impairing the performance such as weldability.

[0039]

[0040]

[0041]

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

The organic composite-coated steel sheet of the present invention can provide excellent corrosion resistance, electrodeposition coatability, water-resistant secondary adhesion, and good distinguishability in a color sensor without impairing weldability. It can be widely used for automobile bodies and so on, and its industrial value is extremely high.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a blending amount of phthalocyanine green in a resin composite layer and a green discriminating property in an organic composite-coated steel sheet.

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[Procedure amendment]

[Submission date] February 4, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0019

[Correction method] Change

[Correction content]

On the other hand, since the organic pigment has a smaller particle size and a larger coloring power than the inorganic pigment, it can be colored in a small amount and is advantageous in terms of powdering resistance and press workability. However, azo pigments that are widely used as organic pigments have poor heat resistance, as can be inferred from their chemical structure,
When the resin composite layer is used for baking at a high temperature of about 160 ° C. as in the present invention, stable identification by a color sensor becomes difficult. Also, acid dye lake pigments,
Basic dye-based lake pigments are poor in water resistance and alkali resistance, and when used in applications where alkaline degreasing and the like are performed, decolorization of steel sheets and elution of the pigments into the degreasing liquid occur,
This is also not suitable.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0030

[Correction method] Change

[Correction content]

(Example) After degreasing and pickling a cold-rolled steel sheet, Zn having an average Ni content of 12% by weight and a basis weight of 20 g / m ²
-Ni plating was performed to produce a plated steel sheet. A chromate treatment solution having a chromium reduction rate of 50% was applied to the surface of the obtained plated steel sheet using a roll coater, and then baked in an electric furnace at a maximum attainable temperature of 130 ° C. to perform chromate treatment. Table 4 shows the amount of chromate deposited. Further, the resin shown in Table 1, the silica shown in Table 2, and the coloring pigment shown in Table 3 are appropriately blended in the upper layer and added to an organic solvent (ethylene glycol monobutyl ether, propylene glycol monomethyl ether acetate and aromatic petroleum naphtha). The mixed liquid prepared by dispersion was applied using a bar coater, and then baked in an electric furnace so that the maximum temperature reached was 160 ° C. to form a resin composite layer. Silica content of the resin composite layer formed on the surface of the plated steel sheet,
Table 4 shows the amount of the organic coating film and the content of the coloring pigment.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0031

[Correction method] Change

[Correction content]

(Observation of Surface Shape) When the surface of the steel sheet coated with the mixed solution containing silica E and silica F shown in Table 2 was observed, each silica had an average thickness of 0.2 to 2 μm.
m, and the average diameter was 5 to 300 μm. Further, on the surface of the steel sheet coated with the mixed solution containing silica G in Table 2, silica was uniformly dispersed in the resin composite layer.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0041

[Correction method] Change

[Correction content]

[0041]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location C25D 5/26 F (72) Inventor Ryoichi Mukai 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Stock Company Technical Research Division (72) Inventor Mori Tonobu Kawasaki, Chiba City, Chiba Prefecture 1 Kawasaki Steel Co., Ltd.Technical Research Division (72) Inventor Hideo Ohgishi 1 Kawasaki Town, Chiba City Kawasaki Steel Co., Ltd. (72) Inventor Hiroyuki Tanabe 8-15 Asahi-cho, Nishinasuno-cho, Nasu-gun, Tochigi Prefecture 72-72 (72) Inventor Masanori Nagai 1926-9, thin leaf, Otawara-shi, Tochigi Prefecture (72) Osamu Ogawa 3-1172-4 Shimonagata, Nishinasuno Town, Nasu District, Tochigi Prefecture

Claims (6)

[Claims] 1. A chromate film having a Cr ⁶⁺ content of 70% or less based on the total Cr content and an adhesion amount of 5 to 500 mg / m ² in terms of Cr on the surface of a zinc or zinc-based alloy plated steel sheet. An organic composite-coated steel sheet having a resin composite layer containing silica, a color pigment and an organic polymer resin as an upper layer of the chromate film, wherein the average primary particle diameter of the silica is 5 to 60 nm. The silica forms a sheet-like aggregate having an average thickness of 0.2 to 2 μm and an average diameter of 5 to 300 μm in the resin composite layer, and the sheet-like aggregate of the silica is almost on the steel plate surface. The color pigment is evenly distributed, and the color pigment is at least one selected from phthalocyanine-based pigments, and the amount of the resin composite layer deposited is 0.1 to 0.1 in terms of dry weight.
An organic composite coated steel sheet excellent in distinctiveness, which is characterized in that it is 3 g / m ² . 2. The organic composite-coated steel sheet excellent in distinguishability according to claim 1, wherein the content of the phthalocyanine-based pigment in the resin composite layer is 1 to 10% by weight. 3. The content of silica in the resin composite layer is 1
It is 0 to 50 weight%, The organic-composite coated steel plate excellent in the distinguishability in any one of Claim 1 and 2. 4. The distinguishability according to claim 1, wherein the organic polymer resin of the resin composite layer is a resin based on an epichlorohydrin-bisphenol A type epoxy resin having a number average molecular weight of 2000 or more. Excellent organic composite coated steel sheet. 5. The silica has an average particle size of 0.05 to 2 μm.
The organic composite-coated steel sheet excellent in distinguishability according to any one of claims 1 to 4, which is an organic solvent-dispersed silica sol of m. 6. The organic composite-coated steel sheet excellent in distinguishability according to claim 1, wherein the silica is a hydrophobic fumed silica.