JPH0278540A - Black surface treatment steel plate - Google Patents

Abstract

PURPOSE:To realize high-grade external appearance by a method wherein a black inorganic film and a resin film layer, which is produced by dispersing the specified amount of black fine particles in resin and has the specified thickness, are produced on steel plate or plated steel plate. CONSTITUTION:Black inorganic film mainly consists of black compound such as hydrated oxide or sulfide of Fe, Ni, Co, Mn, Mo, Cr, Cu, Bi, V or the like and is obtained by heat treatment, chemical oxidation in solution, electrical anodic oxidation, cathodic electrolytic deposition or the like or consists of hydrated oxide or composite component of hydrated oxide and metal. The bonded amount of the film is controlled to be 0.1-3.0g/m<2>. Further, the bonded amount of the resin film layer, in which black fine particles are dispersed, is set to be 3mum or less. The film is produced by hardening water-soluble, water- dispersible or solvent-soluble organic polymeric compound. As the black fine particle to be dispersed in the resin, carbon black having particle diameter of 50-200nm can be used. As a result, new type steel plate, the reflectance of which is low and which has gloss-controlled external appearance and is excellent in workability and corrosion resistance, can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a black surface-treated steel sheet used for members requiring screening.

(Prior art) By introducing a pre-coated steel plate to a product that has been pre-treated and painted after press-forming a steel plate, the pre-treatment and painting that were performed in the customer process can be omitted. There is an active movement toward the use of pre-painted steel sheets to obtain high-quality products at low cost.In order to meet these demands, pre-painted steel sheets have traditionally been used, but with thorough cost reduction and high-grade Due to problems with appearance, weldability, and handling scratches, there has been an increasing demand for inorganic colored steel sheets.

There is a strong need for a black color tone, and the above-mentioned resistance to fingerprints, processability, chemical resistance, and corrosion resistance are also required.

Conventional blackening methods commonly use stainless steel, steel sheets, and copper, but galvanized steel sheets are suitable for this purpose from the viewpoint of cost and corrosion resistance, so the conventional technology for blackening them will be described below. .

The method disclosed in Japanese Unexamined Patent Publication No. 143594/1984 is a process for producing a black steel sheet, which is characterized by subjecting a steel sheet made of an alloy of ferrous elements and zinc to an anodic electrolytic treatment in an aqueous solution containing anions such as NO3- and 504'-. It's the manufacturing method. This publication states from page 2, lower right column, line 7 to page 3, upper left column, line 12, that it is desirable to have a coating with a chromate coating and/or a transparent organic resin applied on the above-mentioned black coating from the viewpoint of corrosion resistance and other aspects. ing.

The method disclosed in JP-A-58-151491 uses Co.

After electroplating in a zinc plating bath containing Ni and Mo, an inorganic black film is formed by anodic electrolysis treatment in an aqueous solution containing NH4'', and further coated with a silicate film if necessary. There are 7 characteristics.

Moreover, in Japanese Patent Application Laid-open No. 60-200996, N[-Zn
A method for forming a black zinc alloy plating film containing 15% or more Ni by cathodic electrolysis in an alloy plating bath is disclosed.

However, these methods have problems in terms of manufacturing, and cannot be said to satisfy the performance required by the market. For example, in terms of production, the method of remelting plating is disadvantageous in terms of cost, and requires measures against drainage and water, and is limited to alloy plating. Although cathodic treatment can solve the above problem, it has the problem of easily causing unevenness. More importantly,
Processing wide steel strips at high speeds causes various problems in appearance (color unevenness, color tone), resulting in lower yields.

In addition, in terms of quality, there are issues as described below.

[Problem to be solved by the invention]

As mentioned above, inorganic black surface treated steel sheets have been put into practical use.
Demand is increasing, but the following improvements are needed in terms of performance. In other words, ■Since it has been used for parts close to the outer panel from interior panels, it is necessary to have a more stable color tone, uniform appearance, and high-quality black appearance with controlled gloss. Due to demand, properties with better conductivity are required, and low reflectance properties are required from office equipment that uses light.

In conventional technology, for performance reasons such as corrosion resistance, the upper layer is coated with an insulating clear organic resin or silicate film with a thickness of 1 to 3 μm, so conductivity under pressure such as welding is not ensured. However, it was insufficient in terms of conductivity under low pressure, such as in electronic equipment.

Regarding reflectance, a clear coat containing matte silica has been proposed, but there is a problem that there is a balance between the thickness of the coating film and the size of the silica particles, making it impossible to achieve both gloss and scratch resistance. Particularly in copiers, low reflectance is strongly desired because high reflectance causes problems in copying accuracy.

Regarding production, as mentioned above, the conventional method blackens a large amount of wide steel strip, so it is necessary to maintain a stable and uniform color tone even when the plating composition, flow rate, and liquid composition fluctuates. It was necessary to reduce the speed and increase the frequency of liquid replacement, which was accompanied by the problem of reduced yield.

[Means to solve the problem]

The black surface-treated steel sheet of the present invention is as follows.

■ It is characterized by having a black inorganic coating on a steel plate or a plated steel plate, and further having a resin coating layer with a thickness of 0.1 to 3.0 μm in which black fine particles are dispersed in 15 to 40 parts per 100 parts of the resin. Black surface treated steel plate.

■ Has a black inorganic coating on steel plate or plated steel plate,
Furthermore, a chromate coating with a chromium deposition amount of 10 to 200 B/m2 and black fine particles of 15 to 4
A black surface-treated steel sheet characterized by having a resin coating layer having a thickness of 0.1 to 3.0 μm in which 0.0 μm is dispersed.

(2) The black surface-treated steel sheet described in (1) above, wherein carbon black having a particle size of 50 to 200 nm is used as the black fine particles.

(2) The black surface-treated steel sheet described in (1) above, wherein carbon black having a particle size of 50 to 200 rv+ is used as the black fine particles.

■ A black inorganic film is deposited by cathodic electrolytic treatment.
The black surface-treated steel sheet according to (1) above, which is composed of a compound whose main component is one or more hydrated oxides of Co, Ni, Cr, Cu, and Zn.

■ A black inorganic film is deposited by cathodic electrolytic treatment.
The black surface-treated steel sheet according to (1) above, which is composed of a compound whose main component is one or more hydrated oxides of Co, Ni, Cr, Cu, and Zn.

[For production]

A schematic diagram of the coating structure of the black surface-treated steel sheet of the present invention is shown in FIG. FIG. 1(A) is a schematic diagram of a black surface-treated steel plate corresponding to the above-mentioned ■, ■, and ■, and FIG.
FIG. 3 is a schematic diagram of black surface-treated steel sheets corresponding to (1) and (2). In the figure, a is a steel plate or a plated steel plate, b is a black inorganic coating, C is a chromate coating, and d is a resin coating in which black fine particles are dispersed.

Normally, in order to obtain a black appearance with one coat, it is necessary to apply a high concentration of black pigment and a thick coating film. With a thin film of 0.2 to 3μ, which is the aim of inorganic black steel sheets, it is extremely difficult to achieve the desired properties in terms of the degree of coloration and uniformity.For thick films, the characteristics of the organic resin itself governs the product performance, so the desired properties cannot be achieved. For example, weldability, scratch resistance, fingerprint resistance, etc. deteriorate. By controlling the thickness of the organic phase and fat to 3 μm or less, excellent properties can be obtained due to the combined effect with the inorganic coating including the underlying plating. The present invention has a black inorganic coating (
The problems of the conventional method are solved by forming a black organic resin coating (d) after applying a chromate coating (c) to the upper layer (b) and the upper layer if necessary.

That is, the lower black inorganic coating must have a uniform colored appearance when the upper organic coating layer is transparent. As a result, productivity and yield decrease. However, it has been found that by making the upper layer a slightly blackish coating (actually a thin film, with a light gray tone due to its low concentration), the color tone of the lower inorganic coating can be largely tolerated. As mentioned above, since the upper black-based coating is a thin film, color unevenness occurs by itself, but this is repaired by the lower black inorganic coating, and a uniform appearance can be achieved by the action of both layers. In the present invention, it is desirable that the blackness (indicated by the L value for boat fishing) of the upper layer coating is lighter in tone (higher L value) than the black inorganic coating of the lower layer. That is, it is desirable that the L value of both layers is 20 or less for the lower black inorganic coating layer and 20 to 3o for the upper coating layer when coated on a white plate such as electrogalvanized plate. .

By dispersing conductive fine particles, the electrical resistance of the upper coating layer, which has been a problem in the past, can be lowered, and black surface-treated steel sheets with excellent conductivity can be obtained at a high yield under low pressure. In addition, the particle diameter and content of the black fine particles are important for reducing the reflectance.

For the upper layer coating, coating d consisting of black fine particles dispersed in an organic resin was used as shown in Fig. 1(A).
In the case of B), chromate coating is applied as an intermediate layer to improve adhesion and corrosion resistance. In the case of FIG. 1(^), it is desirable that the lower black inorganic coating contains chromium oxide. This will be discussed later.

The details of each coating will be described below.

The base metal of the present invention is a steel plate or a plated steel plate. The plated steel sheet is galvanized, Fe, Go.

These are electrically and hot-dip galvanized steel sheets plated with alloys of metals such as Ni, -^u, and Sn and zinc, tin plated, aluminum plated, copper plated, etc. Average roughness (Ra) is the roughness of the surface of a steel plate.
By adjusting the thickness to 1μ or more, preferably 1.2 to 2.0μ, the gloss of the product can be lowered and a high-class appearance image can be imparted. From the viewpoint of scratch resistance and corrosion resistance, the base steel plate is preferably a hard zinc alloy plated steel plate.

Next, the black inorganic coating must contain a black compound as a main component and have excellent adhesion. These coatings are made of Fe,
Ni, Co, Mn, Mo, Cr, Cu, B
It is mainly composed of hydrated oxides and sulfides such as I and V, and is obtained by heat treatment, chemical dissolution oxidation, electrical anodic oxidation, cathodic electrolytic deposition, etc. These coatings are composed of a hydrated oxide or a composite component of a hydrated oxide and a metal. Figure 2 shows Zn2ゝ, Ni'' and NO
The powder obtained by peeling off the black inorganic coating cathodically deposited on a steel plate in an aqueous solution of No. 3- is qualitatively analyzed by X-ray diffraction. Metallic zinc and hydrated oxide N1(OH)z have been detected.

Since the coating is composed of an inorganic compound, it is desirable to control the coating amount to 0.1 to 3.0 g/+o'' in terms of black tone and adhesion. It is effective as a remedy for uneven appearance, which is a drawback of the cathodic electrolytic treatment method, which is superior in terms of efficiency, productivity, and versatility.

It is necessary to consider the amount of the resin coating layer in which black fine particles are dispersed so as not to cause any harm to the appearance, weldability, etc., and the amount of adhesion is 3 μm or less, preferably 1.5 μm or less. Further, the minimum thickness for imparting uniformity of appearance, stabilization of color tone, corrosion resistance and scratch resistance as described above, and for immobilizing black fine particles is 0.1 μm, preferably 0.5 μm, which is the optimum thickness in the present invention. The film thickness range is 0.5 to 1.5 μm.

Resin (organic polymer) is a film made by coating a water-soluble, water-dispersible, or solvent-soluble organic polymer compound with a hardening agent added if necessary, and hardening it by baking, or a coating film cured by ultraviolet rays, or an inorganic or organic polymer. It is a film obtained by coating a composite polymer containing a compound with a hardening agent if necessary and hardening it by baking, etc. The compound to be composited is preferably a fine oxide such as silica, titania, alumina, or zirconia. organic metals such as sol, mica, talc, phosphate, 1-urate, chromate inorganic compounds, fatty acid soaps, fatty acid esters, organic compounds of plastic particles, silane coupling agents, titanium coupling agents, etc. There are compounds. Furthermore, as described later,
Since the thickness of the guard coat is thin, the compound to be compounded is preferably as fine particles as possible (1 to 100r+m),
It must be uniformly dispersed in the resin.

The black fine particles to be dispersed in the resin are most preferably Carpump or Rack. The particle size is selected depending on the desired color tone and gloss, and commercially available carbon black with a particle size of 50 to 200 nm can be used. Although fine carbon black with a particle size of less than 50r++n has excellent blackening ability, it has no effect on reducing gloss, and rather increases gloss, so a particle size of 0 has the opposite effect on reducing gloss, which is the objective of the present invention. is 200
If it exceeds nm, it is difficult to obtain a uniform appearance, carbon black in the paint tends to precipitate, and the scratch resistance further deteriorates. Practically speaking, a commercially available product in which carbon black is dispersed can be used as a dispersion. The particle size of carbon black can be measured and controlled using a spectroscopic analyzer that uses laser scattered light. The amount to be added is such that the weight ratio (carbon black/resin) to the resin is 15/100 or more from the viewpoint of reflectance, color tone and uniformity of appearance, and electrical conductivity. A preferred weight ratio is 20/100 or more. If it is less than 157,100, it is difficult to recognize the difference from the clear resin, and the ability to reduce gloss is weak. Also, if the absorption rate of carbon black is too high, secondary agglomeration of carbon black will cause carbon black! The sludge protrudes through the resin coating, making the surface rough, causing scratches and powdering, and deteriorating adhesion and corrosion resistance. For these reasons, the weight ratio to the resin is (15-40)/loo, preferably (20-30)
7100.

In addition to carbon black, black fine particles such as Fe and C
o, Nt, Cu, Mn, Mo, ^11. Sn
Oxides, sulfides, carbides, etc., and black metal fine powder can be used.

In the present invention, by preferably incorporating a chromium oxide into the black inorganic coating, the chromate coating can be omitted as shown in FIG. 1(A), and the resin in which black fine particles are dispersed can be directly applied.

As a method for incorporating chromium oxide into the black inorganic coating layer, there is a method of adding Cr'' to a black cathode treatment bath.

As the chromate treatment, coating-drying type coating chromate, reaction chromate using dipping or spraying followed by washing with water, and electrolytic chromate can be applied. The coating chromate is a water-soluble compound of Cr and Cr, preferably chromic anhydride (Crys) or a reducing agent, and CS”/Cr”=0.
．． After applying an aqueous solution of chromic acid partially reduced to 1 to 0.5, or a complex chromate treatment solution containing silica sol, phosphoric acid, an organic polymer compound, etc. on the black film, the temperature is immediately forced to 60 to 100°C. Obtained by drying.

The reactive chromate can be obtained by using a commercially available treatment solution consisting of a chromic acid compound and an anionic compound. Further, electrolytic chromate can be obtained by cathodic electrolysis in an aqueous chromic acid solution containing 9110, 5 to 5 chromic acid and anion as main components, followed by washing with water.

The adhesion amount is 10-200IIIg/l1 by crtM calculation.
12.

If it exceeds 200 mg/m2, problems such as deterioration of adhesion due to cohesive failure of the chromate film itself and contamination of the welding electrode will occur. Below 10 mg/m2, the effect of chromate (
Corrosion resistance, adhesion) are insufficient.

(Example) Hereinafter, the present invention will be explained with reference to Examples. The terms and evaluation methods in Examples are as follows.

1) Black appearance L value: Lightness (JIS Z 11370 standard) L≦20 is required for black. Desirably ≦ 15°G Value: 60°-60° with a black glass plate as standard value 90.1
Gloss was measured at a 60° angle.

The reflectance was measured at two angles of 45 degrees with the mirror surface set to 1000.

Appearance uniformity: The appearance after coating with the resin film was visually evaluated.

5: No unevenness at all, 4: Mild unevenness that does not pose a problem for practical use, 3: Line-like unevenness is observed, 2: Unevenness is clearly observed, 1: Severe unevenness.

Conductivity: The surface of the black steel plate was measured using a commercially available two-probe portapull surface resistance meter (Loresta FP, Mitsubishi Yuka Co., Ltd.), and the spring pressure was 6.5 kg.
/c+n', and the unit is resistance (Ω).

Appearance color tone: Visual evaluation: N: Normal black, R: Black with red, B...
・Black with a bluish tinge.

2) I-layer properties: After drawing Eriracene 10rnI11, it was peeled off with Sellotape (registered trademark), and the peeled area was evaluated as a percentage (%).

○...No peeling observed 0%△...Peeling (dots) Less than 1%X...Peeling 1! I 5% or more 3) Scratch Resistance A two-nickel coin was rubbed once under a constant load, and the degree of scratches was evaluated.

5... Hardly noticeable, 4... Slightly noticeable scratches, 3... Clear scratches left, 2... 1 m
A scar with a width of m remains, or a scar with a width of 1...2a+m or more remains.

4) Corrosion resistance: Time until 5% white rust occurs in JIS Z-2371 continuous salt spray test (expressed as i(rs)).

5) Particle size of carbon black: Measured using a commercially available laser scattering spectrometer "Coulter Model N4 (Nikikaki)", and the average value for the particle size was adopted.

Example 1 Zinc-lead nickel alloy plated steel sheet (Ni content 11%,
Plating amount 20 g/lrr", average roughness 1.6μ), Zn"50 g/42, Nl"70 g/It
, Cr3" 1 g/fL and NO" 4 g/11.
As a cathode in an aqueous solution containing 5o32-0.7g/It,
Current density: 30^/da+2, current flow: 40 coron/dm
2. After forming a black inorganic film with a coating amount of 0.9 g/m" by electrolysis, carbon black with a particle size of 10 to 50 nm and a vertical diameter of 50 to 200 nm) was added to resin 10
An acrylic resin emulsion dispersed at a ratio of 0 to 0 to 0, 0, 15, 20, 30, 40 was coated with a dry film thickness of 1±0.1 μm using a roll coater, and baked at a board temperature of 120°C. The Cr content in the black inorganic coating was 25 mg/m2. Table 1 shows the evaluation results.

No. 1 is a comparative example that does not contain black fine particles, exhibits a black appearance with uneven streaks and a reddish tone, and has a G value of 27.
It had a shiny appearance. No. 2 is an example black surface-treated steel sheet in which 15 carbon black was added to 100 resin, and No. 5 below was an example black surface-treated steel sheet in which 40 carbon black was added to 100 resin. No
The best results were obtained by adding 15 to 30 carbon blacks of No., 2 and No. 4.

In No. 5, there was a tendency for the scratch resistance to deteriorate slightly.

Example 2 Zinc-nickel alloy electroplated steel sheet (Ni12%.

Plating amount 20 g/1tr2. After forming a black inorganic film mainly composed of nickel oxide with an adhesion amount of 0.8 g/m2 on a surface with an average roughness of 1.5μ) by cathodic treatment, a liquid of CrQs-10 g/i was applied to a squeezing roll. After coating with the aim of achieving a Cr adhesion of 50 mg/m'' and drying, a resin solution containing colloidal silica and a commercially available polyolefin acrylic emulsion was coated with a primary particle size of 10 to 50 nI (
Carbon black with a particle size of 50 to 200 nm was added to resin 1.
0,1,5,10,15°20.30.4 for 00
It was coated with a roll coater and baked at a plate temperature of 120°C.

The film thickness is aimed at 1μm, and the actual result is 1± from 51 analysis results.
It was 0.1 μm. About the obtained results 2 Figure 3 shows the uniformity of appearance and scratch resistance, Figure 4 shows the gloss and brightness,
Figure 5 shows the surface electrical resistance values.

In the case of the comparative example containing no carbon black, the appearance shown in FIG. 2 was a reddish black color tone with unevenness, but this was improved by adding carbon black. Although the effect of reducing appearance unevenness was observed at a carbon black/resin ratio of 5/100, it did not disappear completely, and a perfect appearance was obtained at a carbon black/resin ratio of 307,100. The scratch resistance shown in Figure 3 is carbon black content of 40/100.
It was in good condition with only visible scratches. or,
The gloss and reflectance in Figure 4 are reduced by the addition of carbon black, resulting in a semi-gloss high-grade appearance with low reflectance r G: 17
~20'' was obtained. Moreover, the brightness was also lowered by adding carbon black, and a normal black color tone was obtained. The conductivity shown in FIG. 5 tends to decrease with the addition of carbon black, and a carbon black/resin composition of 157,100 or higher showed a low resistance value (Ω from 0.05 to 1). In addition, with regard to corrosion resistance, all samples showed good results, with no white rust occurring after 168 hours. Adhesion was good with no peeling due to Erichsen processing.

Example 3 Zinc-nickel alloy plating @ steel plate (Ni 12%, plating 4
x 20 g/rn2. After forming a black inorganic film by electrolyzing the average roughness L, Sμ) in an aqueous solution of nitrate and phosphoric acid as a cathode, electrolytic chromate treatment was performed as a cathode in a solution consisting of chromic anhydride and sulfuric acid bath, and after washing with water. Carbon glass with a primary particle size of 50 to 70 nm is added to resin 1.
The dry coating thickness of the urethane-modified acrylic resin emulsion in which 20% of the 00% was dispersed was Q, l, 0.5, 1
．． It was coated with a target thickness of 0, 1.5, 2.0, and 3.0μ and baked at a board temperature of 120°C. For a film thickness of 1.0 μm, the amount of electrolytic chromate film deposited is 0 to 120 mg as Cr.
Samples were prepared by changing /ln2. Further, as a comparative example, samples No. 13 coated with a resin film not containing carbon black were prepared. The results are shown in Table 2.

No. 7 is an example in which electrolytic chromate was not performed, No.
, 8 to 12 are 15 when the amount of electrolytic chromate attached is Cr.
．． This is an example in which the carbon black-containing resin film was coated with a thickness of 1±0.1 μm by changing the carbon black to 30, 50, 80, and 120ff1g/m2, and excellent performance was obtained in terms of appearance, L and G values, adhesion, etc. Corrosion resistance improved in proportion to the amount of Cr deposited.

Comparative Example No. 13 had a black appearance with a slightly uneven reddish gloss.

Nos. 14 to 18 are examples in which the thickness of the resin film containing carbon black was varied from 0.12 μm to 3.0 μm, and No. 14, which has a thin film thickness, is slightly lacking in unevenness erasing and color tone correction effects. However, other performances were good. Samples No. 17 and 113 with thick films tend to have higher gloss but lower reflectance.

The most preferable results were obtained for No. 15 and 16 O, F+ to 1.5 μm.

Example 4 A cold-rolled steel sheet (CR), a hot-dip galvanized steel sheet (GI), and a hot-dip zinc-aluminum alloy coated steel sheet (2^) whose average roughness of the original sheet was adjusted to 1.5 to 1.7μ were Zn”50.
g/IL, Ni"70 g/11, CS" o, sg
/It and NO3-4g/11, SOs'-0,
Cathodic electrolytic treatment (40A/IL) in an acidic aqueous solution containing 8g/IL
dffi2.40 coron/dm') L, adhesion amount 0.
After attaching 8g/m2 black film (L value 16-18), Na2Cr20y/H2S04=5010.5g
/j2 pl = 2.0 cathodic electrolytic treatment (5
A/dI112.20 fl:/da2). Cr
The amount of adhesion is 90 to 1100ff in total with Cr in plating.
I/l was 112.

Next, carbon black (particle size 50~'l 00 n+
) was coated with an acrylic emulsion with a resin ratio of 20/100 on a dry housing with a target of 1.5μ, and the plate temperature reached 120t.
Burnt with. For comparison, a coating film made of resin alone was also tested. The film thickness of the resin was calculated from the gravimetric method (specific gravity: 1.2).

No. 19.20 shown in Table 3 shows the effect of adding carbon black, and No. 20- had better appearance uniformity, gloss (G value), and reflectance than No. 19. Ta. No. 21.22 is an example of hot-dip galvanized steel sheet.
, No. 22 has better uniformity and scratch resistance, and lower reflectance and gloss than No. 21. No. 23, No. 24 are examples of hot-dip zinc-aluminum alloy plating, N0123
Compared to No. 24, the reflectance gloss was lower, and it showed excellent results in terms of scratch resistance and appearance.

Example 5 After performing black treatment and chromate treatment on a 10% Ni-Zn alloy plated steel sheet in the same manner as in Example 4, silver oxide, nickel sulfide, iron oxide, and carbide with a particle size of around 100 r+m were added as black fine particles. 20 to 100 resin
The added epoxy resin was applied to a thickness of 3μ, and the plate was baked at a temperature of 150°C. Appearance uniformity is 4 points in each case, and L value is 1 in each case.
It was 6.0.14.0°17.0.17.0. A low gloss product with a reflectance of 6 to 9 and a gloss of 11 to 13 was obtained.

Example 6 After performing black treatment and chromate treatment on a 10% Ni-Zn alloy plated steel plate in the same manner as in Example 4, the average particle size of the black particles was 5 nm.

50-nm, 100nm, 200nm, 5
Carbon black of 00 nm was added to the acrylic emulsion in an amount of 25% to 100% of the resin, and the dispersed aqueous emulsion was coated with a dry film thickness of 1.5 μm, and baked at a plate temperature of 120°C. Regarding the appearance, streaks occurred in the sample to which 50 nm of carbon black was added, but the other samples were good. The L values were all in the range of 14 to 15, and a sufficient black appearance was obtained. The reflectance decreases in inverse proportion to the particle size, and when the particle size is 5r+n+ (reflectance 27), 50nI1
1 (25), 100nm 100n, 200r+m (9)
Met. Gloss (G value) decreases in inverse proportion to particle size, becoming semi-gloss, particle size 5nm (G 30.0), 50n
m(19,9), 100nm(17,1),
200nm (16,5), 500nm (15,
2). The scratch resistance of the 50σnm carbon black-added resin was 2 points, which was inferior to other carbon blacks (4 to 5 points).

Example 7 An aqueous solution containing 80 g/JZ of sodium nitrate and 30 g/λ of phosphoric acid was sprayed on a Ni-Zn alloy plated steel sheet containing 12% Ni (fabric weight 25 g/m2) for 5 seconds, and then washed with water and treated with chromic acid-sulfuric acid. After electrolysis as a cathode in a chromate solution of It was baked at a temperature of 150°C. L
A high-grade, low-reflectance black steel plate with a value of 16, a gloss of 19, and a reflectance of 8.2 was obtained. In addition, the electrical conductivity was 50 to 500Ω.

[Effects of the Invention] The black surface-treated steel sheet of the present invention has a low reflectance, a gloss-controlled appearance, excellent workability, and corrosion resistance, and is a new steel sheet that has strong resistance to scratches, compared to conventional coated steel sheets. It can be used in various fields, contributing to higher quality products and lower costs.

In addition, a wide range of processing conditions can be applied to manufacturing, and high-speed, short-time processing is possible, so processing can be performed within a conventional electroplating line, and manufacturing can be performed at low cost.

In particular, color unevenness can be reduced when blackening wide steel strips, improving product yield. In addition, the gloss can be controlled by the particle size and content of black fine particles added to the resin.
Gloss, semi-gloss and matte finishes are available.

[Brief explanation of the drawing]

Fig. 1 is a schematic cross-sectional view of the black surface-treated steel sheet of the present invention, and Fig. 8 (8) is an example without chromate coating;
) is a diagram showing an example of chromating; Figure 2 is a diagram showing the results of X-ray diffraction of a black inorganic film deposited by cathodic electrolysis from an acidic aqueous solution of Zn'', Ni'' and No3-; Figure 3 is a diagram showing the results of X-ray diffraction A diagram showing the relationship between the carbon black content in the resin coating and the appearance and scratch resistance ratings, Figure 4 shows the reflectance,
FIG. 5 is a diagram showing the relationship between gloss (G) and lightness (L) and carbon black/resin ratio, and FIG. 5 is a diagram showing the relationship between the amount of carbon black added and conductivity. Agent Patent attorney Masamitsu Akizawa and 1 other person Fig. 7i1 (A) CB) Fig. 2 2θ Fig. 3 π5 Fig. Hishima 1 tai 1

Claims (6)

[Claims] (1) It is characterized by having a black inorganic coating on a steel plate or a plated steel plate, and further having a resin coating layer with a thickness of 0.1 to 3.0 μm in which black fine particles are dispersed in 15 to 40 parts per 100 parts of the resin. Black surface treated steel plate. (2) Having a black inorganic coating on a steel plate or a plated steel plate, and a chromate coating with a chromium adhesion amount of 10 to 200 mg/m^2, and black fine particles at a ratio of 15% to 100% resin.
A black surface-treated steel sheet characterized by having a resin coating layer having a thickness of 0.1 to 3.0 μm and having a thickness of 0.1 to 3.0 μm dispersed therein. (3) The black surface-treated steel sheet according to claim 1, wherein carbon black having a particle size of 50 to 200 nm is used as the black fine particles. (4) The black surface-treated steel sheet according to claim 2, wherein carbon black having a particle size of 50 to 200 nm is used as the black fine particles. (5) The black color according to claim 1, wherein the black inorganic coating is composed of a compound whose main component is one or more hydrated oxides of Fe, Co, Ni, Cr, Cu, and Zn precipitated by cathodic electrolytic treatment. Surface treated steel plate. (6) The black color according to claim 2, wherein the black inorganic film is composed of a compound whose main component is a hydrated oxide of one or more of Fe, Co, Ni, Cr, Cu, and Zn precipitated by cathodic electrolytic treatment. Surface treated steel plate.