JPS6056097A - Surface-treated steel sheet having superior adhesive strength - Google Patents

Abstract

PURPOSE:To provide superior adhesive strength to a steel sheet by successively forming a metallic Cr layer, a nonmetallic Cr layer and a very thin layer of a phenol compound having a hydroxymethyl group or a polycondensation product thereof bonded to the nonmetallic Cr layer on the steel sheet. CONSTITUTION:A surface-treated steel sheet is composed of a steel sheet 1 manufactured by cold rolling, a metallic Cr layer 2 on the sheet 1, a nonmetallic Cr layer 3 on the layer 2, and a very thin layer 4 of a phenol compound having a hydroxymethyl group or a polycondensation product thereof bonded to the layer 3 on the layer 3. The thickness of the layer 4 is 1-100Angstrom . The layer 2 is coated by 6-360mg/m<2> when expressed in terms of Cr. The layer 3 is made of chromium oxide or chromium oxide hydrate, and it is coated by 1-60mg/m<2> when expressed in terms of Cr.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a surface-treated steel sheet with excellent adhesion, and more specifically, the present invention relates to a surface-treated steel sheet with excellent adhesion. The present invention relates to a surface-treated steel sheet with excellent adhesion, characterized by comprising a chromium-containing coating layer selected from the group chromium-containing coating layer and an ultra-thin layer of a hydroxymethyl group-containing phenol or its polycondensate bonded to the surface of the chromium-containing coating layer. .

Instead of expensive tin plating, Nine Free Steel forms a layer of metallic chromium, non-metallic chromium, or a combination of these on the steel base by subjecting the surface of the steel plate to electrolytic chromic acid treatment. Due to its excellent corrosion resistance, paint adhesion, and economic efficiency, it has come to be widely used as a packaging material for various beverage cans and other cans.

However, due to its coating layer, tin free steel (TFS) cannot be soldered like tinplate, so to join the edges of the steel material, a material such as polyamide is required. Both end edges are overlapped with a thermoplastic adhesive, and the can body is formed by thermal bonding. During this thermal bonding, the adhesive strength between the TFS surface and the adhesive is not necessarily high even at the initial stage (there is a tendency for the adhesive to deteriorate significantly over time. In order to solve this problem, we have developed Generally, a method is employed in which an adhesive primer such as epoxy-phenol resin is applied to the substrate, baked, and then thermally bonded with a thermoplastic resin adhesive through this adhesive primer layer.

However, epoxy-phenol paints are relatively expensive and can be used in the form of TFS coatings.
There is also the troublesome process of having to provide it on the material. Furthermore, since the above-mentioned paint must be applied in the form of an organic solvent solution, solvent costs and energy costs for baking are required, and the release of organic solvents into the atmosphere is not allowed, so after-sales care is required to prevent this. - Pollution prevention facilities such as burners are required.

Such strong adhesion between thermoplastic resin and metal materials is also strongly desired in applications such as film-laminated TFs steel sheets that replace conventional coated steel sheets, and the above-mentioned drawbacks also apply in this case. will occur.

Furthermore, in adhesive structures and coating structures of TFS materials and thermoplastic resins, there is a constant demand to maintain the adhesive force or adhesion between them at a high level even after a long period of time.

According to the present invention, by providing a thin layer treated with a phenol containing a VC hydroxymethyl group on the surface of the TFS material, the adhesive strength or adhesion between the aforementioned resin layer and the TFS material is improved both initially and after time. It was found that there was a very significant improvement.

The invention will be explained in detail below.

In FIG. 1 showing a preferred example of a surface-treated steel sheet according to the present invention, this surface-treated steel sheet includes a steel sheet substrate 1 produced by cold rolling, a metal chromium layer 2 on the steel sheet substrate, and a metal chromium layer 2 on the metal chromium layer. It consists of a nonmetallic chromium layer 6 and an extremely thin layer 4 of hydroxymethyl group-containing phenols or polycondensates thereof bonded on the nonmetallic chromium layer.

The surface-treated steel sheet of the present invention is characterized in that a coating layer 4 of a hydroxymethyl group-containing phenol or its polycondensate is present on the chromium-containing M layer 2゜6, and this coating layer 4 is a chromium-containing coating layer. and this coating layer 4.
is an order of magnitude thinner layer than conventional resin coatings, for example 1
It has a remarkable feature in that it exists in the form of an extremely thin layer of 1 to 100 angstroms, particularly 1 to 60 angstroms.

First, the hydroxymethyl group-substituted phenols (hereinafter sometimes referred to as surface treatment agents) used in the present invention have a chemical property of having both a phenolic hydroxyl group and a hydroxymethyl group on the nuclear carbon atom. .

However, when this hydroxymethyl group-substituted phenol is provided in the form of an extremely thin layer bonded to the chromium-containing coating layer,
The adhesive strength between the resin layer and TFS, particularly the adhesive strength over time, is significantly improved. Generally, the tendency of the joint between the thermoplastic resin layer and the metal material to deteriorate over time can be evaluated by immersing the laminate in a dilute aqueous solution of citric acid at high temperature.

Electrolytic chromic acid treated steel sheet (Tin-free steel (T)
The can body joint, which is made by applying a known epoxy-phenolic resin primer to FS) and thermally bonding it with nylon adhesive tape, has an initial adhesive strength of 6 to 7 ky15 length. In the above-mentioned aging adhesion deterioration acceleration test, after 96 hours of immersion, the adhesive strength was 1.1.
It is observed that the weight decreases to the order of 1.3 kg and 15 tongs. In contrast, according to the present invention, heated TF
The can body joint, which was formed by treating the surface of the S plate with salichenin ((J-oxybenzyl alcohol) to form a thin layer and then bonding them together using a nylon adhesive, showed similar adhesive strength at the initial stage.) 4.4 to 4.5 ky15i even after immersion in citric acid solution for 96 hours.
It has become clear that the adhesive strength is maintained by as much as 1000 ml, and that the formation of an extremely thin layer of hydroxymethyl group-substituted phenols brings about a significant improvement in the tendency for adhesive deterioration over time.

It is also extremely important for the surface treatment agent used in the present invention to have both a nuclear-substituted hydroxymethyl group and a phenolic hydroxyl group in terms of initial adhesive strength and adhesive strength over time. For example, when a metal surface is treated with a compound having only phenolic hydroxyl groups, such as valaclesol or carbolic acid, in a high-temperature gas phase, the initial adhesive strength of the resulting adhesive image is quite low. It is recognized that high initial adhesive strength and high adhesive strength retention over time can be obtained only by using a surface treatment agent having a hydroxymethyl group in addition to the fusilic hydroxyl group.

That is, both the phenolic hydroxyl group and the hydroxymethyl functional group of the surface treatment agent used in the present invention are useful for forming a strong bond with the chromium-containing coating layer and adhesion or adhesion to the thermoplastic resin such as nylon. It is understood that

In the present invention, it is also extremely important that the hydroxymethyl group-containing phenol or its polycondensate be chemically bonded to the chromium-containing coating layer. In other words, if a hydroxymethyl group-containing phenol is simply spray-coated onto a chromium-containing coating layer and then heated to a high temperature afterwards, the resin layer will remain strong even if it is thermally melted on this treated layer. For example, by applying a hydroxymethyl group-containing phenol in the gas phase to a chromium-containing coating layer maintained at a high temperature, a strong adhesive bond can be formed between the molten resin layer and the chromium-containing coating layer. The importance of forming a chemical bond between the hydroxymethyl group-containing phenol and the chromium-containing coating layer is understood since it allows the formation of a durable adhesive bond. Although the details of this chemical bond have not yet been fully clarified, the surface of the chromium-containing coating layer always has an oxygen formation (Qx
oLation structure and Cr-0-Cr oholation structure exist, and furthermore, the former oxide structure is desirable for water resistance, and the latter oholation structure is desirable for adhesion. However, the surface-treated steel sheet of the present invention exhibits exceptionally high water-resistant adhesive strength. It is recognized that chemical bonding of phenols has occurred.

Furthermore, a remarkable feature of the present invention is that the hydroxymethyl group-containing phenols or their polycondensates are present in a layer that is an order of magnitude thinner than in conventional coatings. Conventionally, the thickness of the resin layer applied in the form of a coating film is generally 1 to 1.
00 microns, and it is technically difficult to reduce this thickness to less than 1 micron. On the other hand, the layer of hydroxymethyl group-containing phenols or their polycondensates in the present invention is only provided with a thickness of the order of 10 nm, which increases the adhesive strength or adhesion between the TFS material and the resin layer. It will be clear that the present invention has many advantages in terms of processing agent cost, processing operation cost, etc.

In this specification, the above-mentioned thickness is determined by Electron Spectroscopy for Chemical/L/-Analysis (Electron 5pactrozcopy
for Chemical Analysis! is, hereinafter simply referred to as ESCA), by measuring the intensity of the 15 photoelectron spectra of carbon, which is a constituent element of the treated metal surface treatment film, to make a relative comparison with a standard sample made by vapor-depositing carbon. Then, X defined by the following formula was taken as the film thickness. In addition, since there was an organic substance previously attached to the gold maple surface material, a blank test was conducted, the thickness of the organic substance was subtracted, and the subtracted value was taken as the treated thickness.

X; Thickness σ of organic substance; Spectral intensity h of vapor-deposited carbon; Spectral intensity of sample In the present invention, a TFS material, which is known per se, is used as the steel plate substrate having the chromium-containing coating layer. TFS
Known materials include a steel plate substrate such as a rolled steel plate and a chromium-containing coating layer selected from the group consisting of metallic chromium, nonmetallic chromium, and combinations thereof applied to the surface of the steel plate substrate. The chromium-containing coating layer is 6 to 3601n9/m", especially 10 to 250n9/m" in terms of chromium.
A trap having a coating amount in the range of /77Lt is easy for general trapping, but of course there is no need to be limited to this, and other traps can also be used. In addition, the chromium-containing coating layer has particularly excellent corrosion resistance, consisting of a metallic chromium layer on the steel plate substrate and a non-metallic chromium layer (chromium oxide and/or hydrated chromium oxide layer) on the metallic chromium layer. , and the metallic chromium layer is 0 to 6001n9/m", especially 10 to 2
Film thickness in the range of 00 me/m", non-metallic chromium layer is 1 to 60 m97 m" in terms of chromium, especially 5 to 4Q1n
Those having a film thickness in the range of 9/m'' are most preferably used.

The chromium-containing coating layer is generally made of chromic anhydride; and sulfuric acid,
Using an aqueous bath containing complexes such as borofluorides and fluorosilicates, chlorine ions such as chloride ions, various organic acids, alcohols, and cations such as sodium and calcium, a steel plate substrate is immersed as a cathode, The electrolytic treatment is carried out, and if necessary, the electrolytically treated product is immersed in this aqueous bath under non-electrolytic conditions or immersed in a second aqueous bath containing chromic anhydride for second-stage electrolysis. It is formed by processing and even electroless immersion. In some cases, depending on the treatment bath selected, the formation can be achieved even by performing only electroless immersion.

The TFS material used can vary widely from thin materials like foils to thick sheets, but generally has a thickness of 0.01 to 0.5 mrx, particularly 10 to 100 mrx for foils, and 0.10 to 0.10 mrx for sheets. It is best to select and use one with an appropriate thickness from the 0.60 mm range depending on the purpose.

Suitable examples of hydroxymethyl group-containing phenols used for treating the surface of the chromium-containing coating layer include, but are not limited to, the following.

In the general formula, R is a hydrogen atom, an alkyl group, a hydroxyl group, or a phenyl group, R is an integer from 1 to 6, and the door is an integer from 1 to 6.
Hydroxymethyl-substituted phenols represented by an integer of , where the sum of n+m does not exceed 5.

In the above formula (1), hydroxymethyl is preferably bonded to the ortho or para position with respect to the phenolic hydroxyl group.

For example, saligenin, O-hydroxymethyl-P-cresol, P-hydroxymethyl-〇-cresol, O-
Hydroxymethyl-pt-7' tylphenol, O-
Hydroxymethyl-P-phenylphenol, di(0-
hydroxymethyl)-p-cresol, 2,4-dihydroxymethyl-〇-cresol, 2,4-dimethyl-6
- Mono- or dimethylolated products of hydroxymethylphenol, resorcinol, catechol or hydroquinone.

In the general formula, R1 represents a direct bond or a divalent bridging group, each of R' and m' is an integer up to 2 including zero, and n
The sum of '-1-m' is an integer of 1 or more, and rings A and B may be substituted with an alkyl group or a halogen atom, a hydroxymethyl-substituted trinuclear phenol represented by: In the above formula (2), suitable examples of the bridging group R1 are a methylene group, a methyleneoxymethylene group (-C-o-C
(-), ethylidene group, 2,2-pro1 yellow atom (-5-), sulfonyl group (-5-), and i1-mino group (-NH-).

For example, trinuclear derivatives derived from mono-, di- or trimerol compounds of bisphenols such as bisphenol A1 and bisphenol F, and heptaenols such as p-rusol, P-ethylphenol, P-butylphenol, and 0-cresol. body methylolate.

In addition, oxymethyl derivatives of naphthols, such as 2-hydroxymethyl-1-naphthol and 2,4-dihydroxymethyl-1-naphthol, may also be used. Of course, methylolated products of trinuclear phenonyls can also be used for the purpose of the present invention, but when the number of benzene rings in the phenols used increases, it is necessary to chemically bond them to the surface of the chromium-containing coating layer in the form of an ultra-thin layer. Since this becomes difficult, it is desirable to use compounds up to the trinuclear form.

Particularly suitable hydroxymethyl-substituted phenols for the purposes of the present invention are those having a molecular weight of 124 to 620, in particular 124 to 260, in particular one hydroxymethyl substituted in the ortho or para position to the phenolic hydroxyl group. Mononuclear or trinuclear phenol having a group and another substituent at the remaining ortho or para position is preferred in terms of adhesion and surface treatment workability.

In order to apply this hydroxymethyl group-containing phenol in the form of an ultra-thin layer and chemically bonded to the chromium-containing coating layer, it is possible to A method is generally employed in which a hydroxymethyl group-containing phenol is applied in the gas phase.

That is, by applying hydroxymethyl-substituted phenols in the gas phase to the surface of the TFS material maintained at high temperature, a strong bond is formed between the organically treated coating layer and the chromium-containing coating layer, and the thermoplastic resin is It is possible to increase the initial adhesion force and the adhesion force over time between the layer and TFS. For example, when applying hydroxymethyl-substituted phenols in liquid form to the surface of a metal composite by spray coating, it is possible to increase the adhesion force between the layer and TFS. Only about half or less of the adhesion strength can be obtained compared to the treated case. Furthermore, if the temperature of the TFS material is too low, it will also be difficult to form strong chemical bonds.

During this surface treatment, the surface of the metal material is heated at a temperature of 150°C or higher, particularly at a temperature of 180 to 600°C, most preferably at a temperature of 2°C.
The treatment with hydroxymethyl-substituted phenols is preferably carried out while maintaining the temperature at 00 to 250°C. If this temperature is lower than the above range, the degree of improvement in adhesion will be lower than if it is within the above range. The specific temperature conditions used vary depending on the type of hydroxymethyl-substituted phenol, and higher temperatures are preferably used for high molecular weight phenols.

Various means can be used to cause hydroxymethyl-substituted phenols to act on the surface of the TFS material in the gas phase. In the simplest method, a hydroxymethyl-substituted phenol is placed in a hot atmosphere to generate a vapor of the compound, and the TFS material is exposed to this vapor-filled atmosphere.

Of course, hydroxymethyl-substituted phenols can be used alone or in combination of two or more kinds, and this compound may be supplied in the above-mentioned high-temperature atmosphere in a lump form, that is, in an undiluted state, or it can be supplied with water or an organic solvent, etc. It may be supplied in a diluted state such as a solution, emulsion, or suspension.

Furthermore, it may be supported on a carrier such as an inorganic pigment, filler, various gel particles, glass beads, etc., and supplied to the atmosphere in a state where the surface area is increased. In short, it should be understood that any shape and composition of hydroxymethyl-substituted phenols that can generate vapor can be used in the present invention. For example, a coating solution applied to one side of a TFS plate or TFS foil contains hydroxymethyl-substituted phenols, and this single-sided coated metal plate is placed in a high temperature atmosphere in large numbers at small intervals. By arranging them side by side, it becomes possible to treat the surface of the metal material opposite to the coating surface with the vapor of the hydroxymethyl-substituted phenol.

This process can be carried out either batchwise or continuously.

For example, a coiled or sheet-shaped TFS foil or TFS plate can be continuously fed into a tunnel type heat treatment furnace and treated with steam, or a fixed amount of TFS can be fed into a tunnel type heat treatment furnace.
Processing can also be carried out by introducing the material into a processing furnace, sealing the processing furnace, and then filling the processing furnace with steam.

In any of these cases, hot air containing vapor of hydroxymethyl-substituted phenols is prepared inside or outside the processing furnace, and this hot air is circulated within the processing furnace.
Steam treatment may also be used.

The time required for treatment in the gas phase with hydroxymethyl-substituted phenols varies depending on the concentration and temperature of the vapor in the gas phase, but it is sufficient as long as it is sufficient to form a coating layer with the thickness described above. Any time can be taken depending on the processing temperature and vapor concentration conditions. The thickness of this coating layer is extremely thin, and on the other hand, there is no particular advantage in forming a coating layer thicker than the above-mentioned range, so there is no particular advantage in making this treatment time longer than 10 minutes. , which is economically disadvantageous.

In the treated steel sheet of the present invention, the hydroxymethy/L/substituted phenols used in the treatment usually exist in the form of a thin layer directly bonded to the chromium-containing coating layer. However, these hydroxymethyl-substituted phenols may also exist in a polycondensed form, and especially when multiple hydroxymethyl groups are present in the phenol, they tend to exist in a polycondensed form. .

The surface-treated steel sheet of the present invention exhibits extremely strong adhesive strength to many thermoplastic resins, such as polyamides, polyesters, acid-modified polyolefins, acrylic resins, vinyl resins, polycarbonates, etc. Therefore, it is advantageously used in the production of resin-coated steel sheets and adhesive structures made of resin.

Incidentally, chromium-treated steel sheets are usually commercially coated with oiling using various oils such as diocter cebakut and cottonseed oil. In the present invention, the layer consisting of hydroxymethylphenols or their polycondensates is
It may be formed on this oil layer, or it may be formed on a chromium-treated layer after the oil layer has been removed by degreasing. Furthermore, it will be obvious to those skilled in the art that the ultra-thin layer made of hydroxymethylphenols or polycondensates thereof can be applied with the oil agent for various purposes.

The invention is illustrated by the following example.

Example 1゜Tin-free steel (Toyo Kohan Co., Ltd., Itotsubu) with a thickness of 0.17 nm having a surface characteristic in which the amount of metallic chromium is 112M97m2 and the amount of non-metallic PM is 14m9/rrL2 in terms of chromium. 0), and the surface was coated with P-cresol dimethylol compound (-nuclear body), 1
, 1'-dihydroxy-2,2'-dihydroxymethyl-4,4'-dimethyl-diphenylmethane (trinuclear substance) purification reagents (with purity levels of 99% or higher) were deposited using the following method. That is, the diameter is approximately 15cIrL and the height is 15G.
1 g of the reagent was placed in the bottom of a metal container with a lid, and at the same time, the above tin-free steel supported using a glass holder was placed, the lid was put on, and the container was heated at 200°C for 10 minutes.
Heating was performed for 1 minute.

Thereafter, the T-shaped beer strength was measured by thermocompression bonding the treated tin-free steel pieces using a polyamide adhesive (80 μm thick nylon 12 film made by Toshi), and the results shown in Table 1 were obtained.

Table-1 Example 2゜Metal chromium amount 102〃ν/m2, non-metallic chromium 12 instead of high top ■ made by Toyo Kohan Co., Ltd. in Example 1
The process was carried out in the same manner as in Example 1 except for using Cansuper manufactured by Nippon Steel Corporation, which has a surface of 100 m2/m2.

The results are shown in Table-2.

Table-2 Example 6゜Example 1 using the tin-free steel in Example 1
dimethylolated product of P-cresol (-nuclear body A
f, Ir, :168), heating temperature was applied using the same method as in Example 1, vapor deposition was performed for 10 minutes each, and the adhesive strength was measured in the same manner as in Example 1.

The results are shown in Table-6.

Example 4゜Example 1 using the tin-free steel in Example 1
The same method as in Example 1 was used using the dimethylol compound of P-cresol in , except that the amount of the dimethylol compound previously added to the bottom of the metal container was increased or decreased, and the deposition was repeated and repeated treatments were performed. Samples were prepared with different coating thicknesses, and the T-shaped beer strength was measured.

Table 4 shows the results.

Example 5. and Comparative Example 1゜ K as in Example 1, but metal chromium 1t108Tn9/
A dimethylolated product of P-cresol (-nuclear body) was prepared using tin-free steel (Hydotsuno 9 manufactured by Toyo Kohan Co., Ltd.) with a thickness of 0.201 tuB and a surface characteristic of m2 nonmetallic chromium content i 6 rl'9/g. , al, y: 168)
Vapor deposition was performed at 200° C. for 10 minutes using a vacuum cleaner.

On the other hand, an epoxyphenol paint with good adhesion (patent pending, described in Japanese Patent Application No. 55-69012) was applied to the same tin-free steel to a film thickness of 5 μm.
Baking was performed at ℃ for 10 minutes.

Both were bonded in the same manner as in Example 1 and held at 90° C. in a citric acid solution for 0.4 hours, after which changes in adhesive strength were measured.

Table 5 shows the changes in T-shaped beer strength.

Single W5wm Example 6. Comparative Example 2: A chromic acid-treated nickel-plated steel plate (product name: Canwell) manufactured by Shinsei Iron Co., Ltd. with a plate thickness of 0.2'4 toi was used, and saligenin was applied to the surface in a vapor phase using the method of Example 1. . The film thickness was 10.7 Ao.

This sample and a sample that had not been subjected to vapor phase coating of salignin were thermally bonded using the same adhesive as in Example 1, and then held at 90°C in a 0.4% citric acid solution.
Table 6 shows the measurement results of the T-shaped beer strength, which investigated the state of adhesive strength deterioration over time.

Example Z and Comparative Example 6 A low carbon copper plate with a plate thickness of 0.22 m was degreased and pickled, then washed with water, and a 6%
It was immersed in chromic anhydride at 25° C. for 5 seconds, washed with water, and dried. The surface of this board was coated with zarigenin in a vapor phase using the method of Example 1. The film thickness was 29.7 Ao. This sample and a sample that had not been vapor-phase coated with saligenin were thermally bonded using the same adhesive as in Example 1, and then held at 90°C in a 0.4 cicitric acid solution to deteriorate the adhesive strength over time. I checked the condition. Table 7 shows the measurement results of the T-shaped beer strength.

Example 8. and Comparative Example 4. Maleic acid-modified borizolopyrene (manufactured by Toyo Ink Manufacturing Co., Ltd., trade name Liosene M4) as an adhesive film for thermocompression bonding.
The same experiment as in Example 7 and Comparative Example 6 was carried out except that a cold specimen (with a thickness of 40 μrn) was used. The results are shown in Table-8.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the surface-treated steel sheet of the present invention. Reference numeral 1 indicates a copper plate substrate, 2 indicates a metallic chromium layer, 3 indicates a non-metallic chromium layer, and 4 indicates a layer treated with hydroxymethyl-substituted phenols.

Claims (7)

[Claims] (1) Steel plate substrate, metallic chromium applied to the steel plate substrate surface,
It is characterized by comprising a chromium-containing coating layer selected from the group consisting of non-metallic chromium and combinations thereof, and an ultra-thin layer of hydroxymethyl group-containing phenols or polycondensates thereof bonded to the surface of the chromium-containing coating layer. Surface-treated steel plate with excellent adhesion. (2) The surface-treated steel sheet according to claim 1, wherein the ultra-thin layer of the phenol or its polycondensate has a thickness of 1 to 100 angstroms. (3) The chromium coating layer is 6 to 660 m in terms of chromium.
The surface-treated steel sheet according to claim 1, which has a coating amount of y/m2. (4) The chromium coating layer is formed on the steel plate substrate from O to 300%.
The surface-treated steel sheet according to claim 1, comprising a metallic chromium layer of m9/m2 and a non-metallic chromium layer of 1 to 60 m/rIL2 in terms of metallic chromium on the metallic chromium layer. (5) The hydroxymethyl-substituted phenol is 12
The surface-treated steel sheet according to claim 1, which has a molecular weight of 4 to 6,200. (6) In the general formula of the hydroxymethyl-substituted phenols, R is a hydrogen atom, an alkyl group, a hydroxyl group, or a phenyl group, R is an integer of 1 to 6, and m is an integer of 1 to 6. , n0m, the sum of which does not exceed 5. The surface-treated steel sheet according to claim 1, wherein the sum of n0m does not exceed 5. (7) In the general formula of the hydroxymethyl-substituted phenols, R3 represents a direct bond or a divalent bridging group, each of n/ and m' is an integer up to 2 including zero, and R3 represents a direct bond or a divalent bridging group; The sum of 10 m' is an integer of 1 or more, and rings A and B may be substituted with an alkyl group, which is a hydroxymethyl-substituted trinuclear phenol represented by Surface treated steel plate.