JPH0762591A - Tin-plated steel sheet for three-piece can excellent in print vividness and film adhesion - Google Patents

Abstract

PURPOSE:To provide a tin-plated steel sheet for a film-laminated three-piece can excellent in print vividness and further in film adhesion to the outer and inner faces of the can. CONSTITUTION:This tin-plated steel sheet has the tin coating weight of 0.5-2.0g/m<2> on one side with the areal ratio of the region, where the glossiness Gs in all facial directions is controlled to >=250%, the ratio of the glossiness Gs (C) in the width direction to the glossiness Gs (L) in the longitudinal direction to >=0.4 and the ratio of X-ray energy intensity of tin I (Sn) to that of iron I (Fe) measured simultaneously with an X-ray microanalyzer to >=20, adjusted to 5-80%. A nickel-contg. layer with the coating nickel weight controlled to 0.01-0.5g/m<2> is formed under the tin plating film.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a can container, and more particularly to a steel plate for a three-piece can in which can bodies are joined by welding, and more specifically, a film obtained by laminating films in place of conventional painting and printing. The present invention relates to a tin-plated steel sheet for laminated three-piece cans.

2. Description of the Related Art Looking at a can container from the viewpoint of the can manufacturing process,
There are roughly two types. The first is a can with the can bottom and can body integrated into one, and the canopy is wrapped around it. It is usually called a two-piece can. A typical can is a DI can (Draw) that is manufactured by drawing and ironing. and Ironi
ng can) and a DrD can (Dr.
aw and Redrow can) and the like. The other is a body and canopy wrapped around the body, which is usually called a three-piece can.
Welding cans are available, but currently adhesive cans and welding cans are the mainstream. As materials for three-piece cans, tin-based materials that are tin-plated and chromated on steel sheets, nickel-plated materials that are nickel-plated and chromated on steel sheets, and double-layer coatings of metallic chromium and hydrated chromium oxide on steel sheets. Used tin-free steel materials and others. In the case of can barrels made of these materials, in most cases, the inner surface of the can is painted from the viewpoint of content retention (corrosion resistance), and the outer surface of the can is printed with a trademark design to show the content. ing. In particular, from the viewpoint of the clarity of the print design, it is usually common to print the trademark design on the outer surface of the can after coating with a white pigmented paint. As a material for a can, a material obtained by laminating a film on a steel plate other than the above-mentioned plated steel plate has been conventionally studied. For example, JP-A-58-82717 and JP-A-62-22
As can be seen in Japanese Patent No. 7642, conventionally, it has been mainly used for two-piece cans such as squeezed cans and squeezed and ironed cans, 18 liter cans and can lids, but in recent years, three-piece cans have been studied. For example, as can be seen in Japanese Unexamined Patent Publication No. 5-112361 and Japanese Unexamined Patent Publication No. 5-131607, a can body having both inner and outer surfaces laminated is proposed.
As described above, in the case of a steel sheet having a film laminated on both the inner and outer surfaces, direct lamination of the film on the steel sheet has been studied from the viewpoint of reducing the can cost. In this case, it is necessary to have both the print clarity on the outer surface and the film adhesion on the inner and outer surfaces at the same time, but it is difficult to cope with the conventional steel sheet and improvement is necessary.

As described above, in the field of three-piece cans, from the viewpoint of reducing the cost of the cans, studies have been made to cope with the use of a steel plate in which a film is directly laminated on the inner and outer steel plates. In view of these technical trends, the present invention provides a steel sheet having both print clarity and adhesion, such as ensuring print clarity and adhesion on the outer surface and securing adhesion on the inner surface. It is intended.

According to the present invention, a tin plating layer having a tin deposition amount on one side of 0.5 to 2.0 g / m ² and a nickel deposition amount of 0.01 to 0.5 g / m ^{2 on} the lower layer thereof. ^{2 has} a nickel-containing plating layer, the gloss Gs in all surface directions is 250% or more, and the gloss in the longitudinal direction of the steel sheet (Gs
(L)) and gloss ratio in the width direction (Gs (C)), Cs
(C) / Gs (L) is 0.4 or more, and the area of the site where I (Sn) / I (Fe) is 20 or more, the ratio of the X-ray energy intensities of tin and iron measured simultaneously by an X-ray microanalyzer. The subject matter is a tin-plated steel sheet for a three-piece can, which is excellent in print clarity and film adhesion and is characterized by a rate of 5 to 80%.

The function of the present invention will be described in detail below. Although the trademark design is printed with colored ink on the outer surface of the can, white ink is also often printed together from the viewpoint of the clarity of the design. If the whiteness of the white printed portion is not sufficiently secured, the clarity of the entire design cannot be secured. In order to secure the print clarity, that is, the whiteness of the white ink portion, it is an important factor to coat the steel plate surface with a metal having a high spectral reflectance and also to increase the glossiness. It was clarified by the study of the present inventors. Usually, the color tone of a metal is basically determined by the spectral reflectance of the metal itself, and for example, the degree of whiteness appears whiter when the spectral reflectance in the wavelength range of 400 to 700 nm is higher. As a result of investigating the metal having a high spectral reflectance, it has been clarified that tin is a metal having a relatively high spectral reflectance among the plated metals currently used as steel plates for containers. Therefore, the present invention applies a tin-plated steel sheet. Further, in the case of the same metal, generally, the one having a large surface roughness and a low glossiness is diffusely reflected and thus appears white, and the one having a small surface roughness and a high glossiness is rather black due to its high regular reflectance. However, as in the present invention, when the printed film is laminated on the surface that contacts the outer surface of the can, the opposite is true, and the higher the glossiness, the better the print clarity. In the present invention, the gloss values Gs in all the surface directions are set to 250% or more. Here, the glossiness Gs refers to the specular glossiness defined by JIS Z 8741, and as a commercially available device, for example, a haze-gloss reflectometer manufactured by Vic-Gardner, Gs (60 °) The measured value is used as the gloss value. The reason why the glossiness Gs is limited to 250% or more in all the surface directions is as follows. The difference in gloss in the surface direction subtly affects the color condition when printing films are laminated. Also, depending on the viewing direction, the difference in the clarity of the print design will appear, and the product value will be impaired. Therefore, it is necessary to limit the gloss level Gs in order to secure the gloss in all the surface directions above a certain level. When the gloss level Gs is less than 250%, the whiteness is not sufficiently secured, so Gs is set to 250% or more. In particular, when the amount of white ink attached is small or when the amount of white pigment contained in the film is small, the effect of the steel sheet used becomes noticeable, and a higher glossiness is required. As the surface gloss, the gloss Gs is preferably 300% or more. Next, the longitudinal glossiness (Gs (L)) and the transverse glossiness (Gs
The reason for setting the ratio (C)) and Gs (C) / Gs (L) to 0.4 or more is basically the same reason as described above.
When Gs (C) / Gs (L) is less than 0.4, the whiteness varies depending on the viewing direction, and the clearness of the print design varies, which is not preferable. Although the judgment of whiteness varies slightly depending on the viewer, it can be measured by the L * value measured by a colorimeter such as Minolta spectrocolorimeter CM-1000, and the higher the L * value, the whiter. The L * value is preferably 73 or more. Next, regarding the tin-plated film, the ratio of the X-ray energy intensities of tin and iron simultaneously measured by the X-ray microanalyzer of the present invention, the area ratio of the site where I (Sn) / I (Fe) is 20 or more is 5 to 5. The reason for limiting to 80% will be described. From the viewpoint of printing image clarity on the outer surface of the can, it is advantageous to have a high glossiness, and in the case of tin-plated steel sheet, one of the means to increase the glossiness is to increase the tin deposition amount and the tin deposition state. There is a smoothing method. However, in the case of a tin-plated steel sheet on which films are laminated, if the amount of deposited tin is increased and the tin deposition state is smoothed, problems may occur in terms of film adhesion. That is, since the temperature becomes equal to or higher than the melting point of tin due to heat during welding or baking during repair coating of the welded portion, if the molten portion of tin is large, the film is not fixed and the film shrinks. Therefore, management of the molten portion of tin is important in terms of both glossiness and adhesion. I (Sn) / I in the present invention
The (Fe) measurement is performed by a computer-controlled X-ray microanalyzer such as CMA (Computer aidde).
d MicroAnalyzer), the data obtained by simultaneously measuring a plurality of elements is image-processed by a computer, and I (Sn) /
The area ratio of I (Fe) is 20 times or more is calculated. Ratio of X-ray energy intensities of tin and iron, I (Sn) /
I (Fe) indicates a molten portion of tin, and I (Sn) / I (Fe) is 20 or more in area ratio less than 5%. The degree is insufficient. On the other hand, when it exceeds 80%, on the contrary, the glossiness is sufficient, but the adhesion is insufficient. The balance of I (Sn) / I (Fe) is important in order to simultaneously secure the glossiness and the adhesiveness, and preferably 10 to 70%. Next, the tin deposition amount will be described. The amount of tin deposited according to the present invention is limited to 0.5 to 2.0 g / m ² on one side. When the lower limit of the amount of adhesion is less than 0.5 g / m ² , the surface roughness of the steel sheet before plating is large, and it is difficult to obtain a mirror-like gloss, and high-speed weldability is not obtained when the body is made by the welding method. It becomes a problem. On the other hand, when the upper limit of 2.0 g / m ² is exceeded, the molten portion of tin increases and the adhesion cannot be secured. In the present invention, after tin plating, tin is heated and melted by reflow treatment, then cooled, and further subjected to chromate treatment. Reflow heat melting is an important step to increase the gloss of plated tin, and it is necessary to completely heat and melt tin after plating, but if too much alloy tin is produced at the same time, weldability and processing It is necessary to heat and melt in a short time because there is a risk that the property will be impaired. In addition, in order to melt the tin on a smooth surface for a short time in a short time, it is an effective method to heat-melt by using a flux such as phenolsulfonic acid after tin plating. In the present invention, it is desirable to form a Ni-containing plating layer having a nickel deposition amount of 0.01 to 0.5 g / m ² under the tin plating film. For Ni-containing lower layer plating, not only Ni alone but also Fe-Ni, Fe-
Ni-Sn alloy or the like may be applied. These alloys
It contributes to smoothing the surface by heating and melting tin, and at the same time has the effect of suppressing the formation of tin alloy. Such action is particularly effective when a small tin coating weight, Ni deposition amount can not be obtained the effects thereof is less than 0.01 g / m ^2, alloying exceeds 0.5 g / m ² It becomes too difficult to secure the glossiness. The amount of deposited nickel is preferably 0.015 to 0.3 g / m ² . Further, the main requirement of the steel sheet of the present invention is the surface roughness of the plating original sheet. The surface roughness of the steel sheet before plating is preferably Ra 0.35 μm or less in all the surface directions, and the surface roughness difference in the in-plane direction is preferably Ra 0.20 μm or less. The reason for this is
When Ra exceeds 0.35 μm, 0.5 to 2.0 g / m
^This is because even if the tin adhesion amount is limited to 2 and heated and melted, especially when the tin adhesion amount is small, it is difficult to secure the whiteness that is the gist of the present invention due to the influence of the roughness of the steel plate before plating. . or,
Unless the difference in surface roughness in the in-plane direction is Ra 0.20 μm or less, the difference between the gloss in the longitudinal direction and the gloss in the width direction of the steel sheet described above becomes noticeable, and the degree of whiteness depending on the viewing direction is further improved. The sharpness is different, which is not preferable. The surface roughness of the steel sheet before plating is preferably Ra0.
30 μm or less, surface roughness difference in the in-plane direction is Ra 0.15 μ
m or less is preferable. Further, in the present invention, the above tin plating,
After heat-melting treatment, tin plating (Sn
A chemical conversion treatment such as a chromate treatment called CDC treatment, which is used as a chemical conversion treatment for plated steel sheets), or a chromium / chromate treatment which is a film made of metal chromium / hydrated chromium oxide, is performed. This chemical conversion treatment is extremely effective in terms of securing adhesion, but if it is large, it causes a decrease in glossiness, so
It is necessary to find out the balance between glossiness and adhesion. Hereinafter, the effects of the present invention will be specifically shown in Examples.

【Example】

(Example 1) A cold-rolled steel sheet having a surface roughness shown in Table 1 (sheet thickness: 0.19 mm) is subjected to lower layer plating and upper layer plating under the same conditions shown in Table 1 to form a two-layer plating, and then heated and melted. The treatment (reflow treatment) was performed using flux, and then chromate treatment was performed. And the glossiness Gs of the obtained plated steel sheet and the area ratio with I (Sn) / I (Fe) of 20 or more were measured. The results are shown in Table 2. Next, a printing film for lamination was gravure-printed on a biaxially stretched polyester resin film having a thickness of 15 μm with a trademark design using four colored inks and white ink, and after drying, a dry thickness of 2.3 μm was applied on the ink surface. A urethane adhesive was applied and prepared. Then, the plated steel sheet was heated with a heating roll to laminate the printing films. A 250 ml juice can barrel was made by the welding method so that the film laminated surface of the printed film laminated steel sheet thus obtained was the outer surface of the can, and the welded portion was repair-painted, and the highest temperature reached (local area of the repair-painted portion). (Temperature) 250 degreeC, it dried and the welding can body was obtained. And
While observing the outer surface of the can body, the L * value was measured for the whiteness of the white ink portion, and the film shrinkage width was measured by optical microscope observation. The results are shown in Table 2. The outer surface of the can body of the can body obtained from the steel sheet of the present invention had good gloss and no color unevenness, and the visual clarity of the design was better than the existing three-piece cans as a result of visual observation. Also,
Both whiteness and film shrinkage were good without problems. Furthermore, the can body obtained from the steel sheet of the present invention was necked-in, the canopy was wrapped around one end, the contents were filled, and the canopy was wrapped up and sealed. After the retort treatment for minutes, the appearance change and sealing property of the film were examined. As a result, the film had a good appearance without any change in adhesion, gloss, color unevenness, sealing property and the like. On the other hand, looking at the outer surface of the can body obtained from Comparative Steel Sheet 1 to Comparative Steel Sheet 4, the can body obtained from Comparative Steel Sheet 1 has poor overall image clarity and is printed as compared to the current can. The appearance was inferior. Further, the can body obtained from the comparative steel plate 2 had good gloss and no color unevenness, and the visual clarity of the design was better than that of the existing three-piece can according to the result of visual observation. As described above, the shrinkage width of the film is large, which is a practical problem. The can body obtained from the comparative steel plate 3 had L * of the white ink portion as shown in Table 2.
Although the value and the shrinkage width of the film are at a practical level, the clarity of the print design differs depending on the viewing direction, and there was a problem as a product. The can body obtained from the comparative steel plate 4 had poor image clarity as a whole, and the printing appearance was inferior to the current can. (Example 2) Using the steel sheets of the present invention steel sheets 1 to 8 and comparative steel sheets 1 to 4 used in Example 1, the steel sheets were heated by a heating roll system to obtain a urethane-based adhesive having a dry thickness of 2.5 µm. The coated transparent film of biaxially stretched polyester resin having a thickness of 15 μm was laminated. The transparent film-laminated steel sheet thus obtained was manufactured according to the procedure of Example 1, a welding can barrel was manufactured, a repair coating for the welded portion was performed, and drying was performed so that the film surface became the inner surface. The film shrinkage width was measured by an optical microscope as in Example 1. The measurement results of the film shrinkage width are shown in Table 2. The results were the same as in Example 1. Furthermore, the can body was necked in, the canopy was wrapped around one end, coffee was filled, and the lid was wrapped around and sealed, and then retorted at 125 ° C for 30 minutes to obtain film adhesion. As a result of examining the sealing property, the corrosion resistance and the like, the can body obtained from the steel sheet of the present invention had no problem in film adhesion and sealing property and had no corrosion resistance. On the other hand, the cans obtained from the comparative steel plate 1, the comparative steel plate 3 and the comparative steel plate 4 had no problem in terms of film adhesion and sealing property and had no problem in corrosion resistance, but they were obtained from the comparative steel plate 2. The can body was inferior in corrosion resistance, and corrosion was observed especially near the flange processed part.
As described above, the can body obtained from the steel sheet of the present invention has an excellent print appearance on the outer surface, in particular, the clarity of the trademark design, and is better than the current can body. In addition, the inner surface of the can also shows good corrosion resistance, which is good. On the other hand, a can body obtained from a steel plate outside the scope of the present invention has a large film shrinkage when the outer surface has a good printed appearance, and has a problem in corrosion resistance particularly on the inner surface. When the film shrinkage is good, there is a problem in the printed appearance on the outer surface, which is not preferable in practice.

[Table 1]

[Table 2]

Industrial Applicability When the steel sheet of the present invention is applied as a means for obtaining a three-piece can by laminating a printing film on the outer surface and a transparent film on the inner surface, it guarantees the following many advantages as compared with the conventional steel sheet. Is. (1) It is possible to omit the white coat and the size coat which have been conventionally performed by applying a printing base coating film. (2) It is possible to perform continuous coating printing using coil products at a high speed with a wide width, and it is possible to secure productivity that is at least twice as high as that of a cutting plate coating line. (3) Since it is not necessary to pass the line through a large number of times, the finishing period can be shortened. (4) Since it is handled as a coil product, it has an advantage that even if the material plate is made extremely thin, it does not cause a big problem in operation. As described above, it is possible to solve the labor-saving due to the omission of the steps, the manufacturing problem for the cost reduction of the conventional three-piece can, and the like. (5) In addition, compared to the current external printing cans, the depth of printing allows the trademark design to be more vivid, and it is possible to supply three-piece cans that are compatible with the diversification and upsizing of consumers.
The inner surface of the can has higher corrosion resistance than the conventional coating. (6) Further, since it can be used for conventional paint cans as well, it can be used in a wide range, and thus has great economic and social significance.

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[Procedure amendment]

[Submission date] June 2, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Detailed explanation of the invention

[Correction method] Change

[Correction content]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a can container, and more particularly to a steel plate for a three-piece can in which can bodies are joined by welding, and more specifically, a film obtained by laminating films in place of conventional painting and printing. The present invention relates to a tin-plated steel sheet for laminated three-piece cans.

[0002]

2. Description of the Related Art Looking at a can container from the viewpoint of the can manufacturing process,
There are roughly two types. The first is a can with the can bottom and can body integrated into one, and the canopy is wrapped around it. It is usually called a two-piece can. A typical can is a DI can (Draw) that is manufactured by drawing and ironing. and Ironi
ng can) and a DrD can (Dr.
aw and Redrow can) and the like.

The other is a body and a canopy wrapped around the body, which is usually called a three-piece can. Typical cans are solder cans, adhesive cans, and welding cans. Cans and welded cans are the mainstream. As materials for three-piece cans, tin-based materials that are tin-plated and chromated on steel sheets, nickel-plated materials that are nickel-plated and chromated on steel sheets, and double-layer coatings of metallic chromium and hydrated chromium oxide on steel sheets. Used tin-free steel materials and others.

In the case of a can body using these materials, in most cases, the inner surface of the can is coated from the viewpoint of content retention (corrosion resistance), and the outer surface of the can is a trademark design for indicating the content. It is printed. In particular, from the viewpoint of the clarity of the print design, it is usually common to print the trademark design on the outer surface of the can after coating with a white pigmented paint.

As a material for a can, in addition to the above-mentioned plated steel sheet, a material obtained by laminating a film on a steel sheet has been conventionally studied. For example, as seen in JP-A-58-82717 and JP-A-62-227642, two-piece cans such as squeezed cans and squeezed and squeezed cans, 18-liter cans, and can lids have been conventionally used. However, in recent years, three-piece cans have been considered. For example, JP-A-5-112361 and JP-A-5-131607.
As can be seen in Japanese Patent Laid-Open Publication No. JP-A-2003-264, there is proposed a can body laminated on both the inside and outside.

As described above, in the case of a steel sheet having a film laminated on both the inner and outer surfaces, it has been considered to laminate the film directly on the steel sheet from the viewpoint of reducing the cost of the can. In this case, it is necessary to have both the print clarity on the outer surface and the film adhesion on the inner and outer surfaces at the same time, but it is difficult to cope with the conventional steel sheet and improvement is necessary.

[0007]

As described above, in the field of three-piece cans, from the viewpoint of reducing the cost of the cans, studies have been made to cope with the use of a steel plate in which a film is directly laminated on the inner and outer steel plates. In view of these technical trends, the present invention provides a steel sheet having both print clarity and adhesion, such as ensuring print clarity and adhesion on the outer surface and securing adhesion on the inner surface. It is intended.

[0008]

According to the present invention, a tin plating layer having a tin deposition amount on one side of 0.5 to 2.0 g / m ² and a nickel deposition amount of 0.01 to 0.5 g / m ^{2 on} the lower layer thereof. ^{2 has} a nickel-containing plating layer, the gloss Gs in all surface directions is 250% or more, and the gloss in the longitudinal direction of the steel sheet (Gs
(L)) and gloss ratio in the width direction (Gs (C)), Cs
(C) / Gs (L) is 0.4 or more, and the area of the site where I (Sn) / I (Fe) is 20 or more, the ratio of the X-ray energy intensities of tin and iron measured simultaneously by an X-ray microanalyzer. The subject matter is a tin-plated steel sheet for a three-piece can, which is excellent in print clarity and film adhesion and is characterized by a rate of 5 to 80%.

[0009]

The function of the present invention will be described in detail below. Although the trademark design is printed with colored ink on the outer surface of the can, white ink is also often printed together from the viewpoint of the clarity of the design. If the whiteness of the white printed portion is not sufficiently secured, the clarity of the entire design cannot be secured.

In order to secure the clearness of printing, that is, the whiteness of the white ink portion, it is important to coat the steel sheet surface with a metal having a high spectral reflectance and to increase the glossiness at the same time. It was revealed by the examination of the present inventors that it is a factor. Usually, the color tone of a metal is basically determined by the spectral reflectance of the metal itself, and for example, the degree of whiteness is a wavelength of 40
Higher spectral reflectance in the range of 0 to 700 nm looks whiter. As a result of examining this metal having high spectral reflectance, tin is one of the plated metals currently used as steel plates for containers.
It was revealed that the metal has a relatively high spectral reflectance. Therefore, the present invention applies a tin-plated steel sheet.

Further, in the case of the same metal, generally, the one having a large surface roughness and a low glossiness is diffusely reflected and thus appears white.
Those with a small surface roughness and a high glossiness look rather black due to the high regular reflectance. However, as in the present invention, when the printed film is laminated on the surface that contacts the outer surface of the can, the opposite is true, and the higher the glossiness, the better the print clarity. In the present invention, the glossiness Gs in all surface directions is 2
50% or more.

Here, the gloss level Gs is JIS Z 87.
The specular glossiness defined by No. 41, which is a commercially available device, for example, a haze-gloss reflectometer manufactured by Vic-Gardner Co., Ltd., in which the measured value at Gs (60 °) is used as the glossiness value. is there. The reason why the glossiness Gs is limited to 250% or more in all the surface directions is as follows.

The difference in gloss in the surface direction slightly affects the color condition when printing films are laminated. Also, depending on the viewing direction, the difference in the clarity of the print design will appear, and the product value will be impaired. Therefore, in order to ensure that the gloss in all surface directions is above a certain level, the glossiness Gs
Need to be limited. When the gloss level Gs is less than 250%, the whiteness is not sufficiently secured, so Gs is set to 250% or more.

In particular, when the amount of white ink adhered is small or the amount of white pigment contained in the film is small, the effect of the steel sheet used becomes remarkable, so that a higher glossiness is required. As the surface gloss, the gloss Gs is preferably 3
00% or more is good. Next, the glossiness (G
The ratio of s (L)) to the gloss in the width direction (Gs (C)), Gs
The reason why (C) / Gs (L) is set to 0.4 or more is basically the same reason as described above. Gs (C) / Gs
When (L) is less than 0.4, the whiteness varies depending on the viewing direction, and the clearness of the print design varies, which is not preferable.

Although the judgment of whiteness is slightly different depending on the viewer, it can be measured by the L * value measured by a colorimeter such as the Minolta spectrocolorimeter CM-1000. The higher the L * value, the whiter the image. . The L * value is preferably 73 or more. Next, regarding the tin-plated film, the ratio of the X-ray energy intensities of tin and iron simultaneously measured by the X-ray microanalyzer of the present invention, the area ratio of the site where I (Sn) / I (Fe) is 20 or more is 5 to 5. The reason for limiting to 80% will be described.

From the standpoint of printing clarity on the outer surface of the can, it is advantageous that the glossiness is high. In the case of a tin-plated steel sheet, one of the means for increasing the glossiness is to increase the tin deposition amount and increase the tin content. There is a method to smooth the adhered state. However, in the case of a tin-plated steel sheet on which films are laminated, if the amount of deposited tin is increased and the tin deposition state is smoothed, problems may occur in terms of film adhesion.

That is, since the temperature becomes higher than the melting point of tin due to heat during welding or baking for repair coating of the welded portion, if the molten portion of tin is large, the film is not fixed and the film shrinks. Therefore, management of the molten portion of tin is important in terms of both glossiness and adhesion. I (Sn) / I in the present invention
The (Fe) measurement is performed by a computer-controlled X-ray microanalyzer such as CMA (Computer aidde).
d MicroAnalyzer), the data obtained by simultaneously measuring a plurality of elements is image-processed by a computer, and I (Sn) /
The area ratio of I (Fe) is 20 times or more is calculated. Ratio of X-ray energy intensities of tin and iron, I (Sn) /
I (Fe) indicates a molten portion of tin, and I (Sn) / I (Fe) is 20 or more in area ratio less than 5%. The degree is insufficient. On the other hand, when it exceeds 80%, on the contrary, the glossiness is sufficient, but the adhesion is insufficient.

The balance of I (Sn) / I (Fe) is important in order to satisfy both glossiness and adhesion.
It is preferably 10 to 70%. Next, the tin deposition amount will be described. The amount of tin deposited according to the present invention is 0.5 to 2.0 on one side.
Limited to g / m ² . When the lower limit of the amount of adhesion is less than 0.5 g / m ² , the surface roughness of the steel sheet before plating is large, and it is difficult to obtain a mirror-like gloss, and high-speed weldability is not obtained when the body is made by the welding method. It becomes a problem. On the other hand, when the upper limit of 2.0 g / m ² is exceeded, the molten portion of tin increases and the adhesion cannot be secured.

In the present invention, after tin plating, tin is heated and melted by reflow treatment, then cooled, and chromate treatment is further applied. Reflow heat melting is an important step to increase the gloss of plated tin, and it is necessary to completely heat and melt tin after plating, but if too much alloy tin is produced at the same time, weldability and processing It is necessary to heat and melt in a short time because there is a risk that the property will be impaired.

In order to melt the tin on the surface to a certain extent and in a short time, it is an effective method to heat and melt by using a flux such as phenolsulfonic acid after tin plating. In the present invention, it is desirable to form a Ni-containing plating layer having a nickel deposition amount of 0.01 to 0.5 g / m ² under the tin plating film.

For the Ni-containing lower layer plating, not only Ni alone but also Fe-Ni, Fe-Ni-Sn alloy or the like may be applied. These alloys contribute to the surface smoothing by heating and melting tin, and at the same time have the effect of suppressing the formation of tin alloy. This effect is particularly effective when the amount of deposited tin is small, but the amount of deposited Ni is 0.01 g.
If it is less than / m ² , the effect is not obtained, and 0.5 g / m
^If it exceeds ² , alloying will proceed too much and it will be difficult to secure the glossiness. Nickel deposition amount 0.015 to 0.3 g / m
² is preferred.

Further, the main requirement of the steel sheet of the present invention is the surface roughness of the original plating plate. The surface roughness of the steel sheet before plating is preferably Ra 0.35 μm or less in all the surface directions, and the surface roughness difference in the in-plane direction is preferably Ra 0.20 μm or less. The reason for this is that if Ra exceeds 0.35 μm, even if the tin deposition amount is limited to 0.5 to 2.0 g / m ² and the material is melted by heating, especially when the tin deposition amount is small, the roughness of the steel sheet before plating is This is because it is difficult to secure the whiteness, which is the main purpose of the present invention, due to the influence of the degree.

Further, the difference in surface roughness in the in-plane direction is Ra 0.2.
If the thickness is not 0 μm or less, the above-mentioned difference in gloss between the longitudinal direction and the transverse direction of the steel sheet becomes remarkable, and the degree of whiteness depending on the viewing direction and the sharpness of the print design are not preferable, which is not preferable. The surface roughness of the steel sheet before plating is preferably Ra 0.30 μm or less in all the surface directions and Ra 0.15 μm or less in the surface roughness difference in the in-plane direction.

Further, in the present invention, after the above tin plating and heat-melting treatment, a chromate treatment called CDC treatment, which is conventionally used as a chemical conversion treatment of tinplate (Sn plated steel sheet), as a chemical conversion treatment, metal chromium / water. A chemical conversion treatment such as chromium / chromate treatment, which is a film made of Japanese chromium oxide. This chemical conversion treatment is extremely effective in securing adhesiveness, but if it is too large, it causes a decrease in glossiness, so it is necessary to determine the balance between glossiness and adhesion.

The effects of the present invention will be specifically shown in the following examples.

[0026]

Example 1 A cold-rolled steel sheet (sheet thickness: 0.19 mm) having the surface roughness shown in Table 1 is subjected to the lower layer plating and the upper layer plating under the conditions shown in Table 1 to form a double layer plating. Then, heating and melting treatment (reflow treatment) was performed using a flux, and then chromate treatment was performed.

Then, the gloss Gs of the obtained plated steel sheet
And the area ratio of I (Sn) / I (Fe) of 20 or more was measured. The results are shown in Table 2. Next, a printing film for lamination was gravure-printed on a biaxially stretched polyester resin film having a thickness of 15 μm with a trademark design using four colored inks and white ink, and after drying, a dry thickness of 2.3 μm was applied on the ink surface. A urethane adhesive was applied and prepared. Then, the plated steel sheet was heated with a heating roll to laminate the printing films.

A 250 ml juice can barrel was made by the welding method so that the film laminated surface of the thus obtained printed film laminated steel sheet became the outer surface of the can, and the welded portion was repair-painted to obtain the maximum attainable temperature (repair coating). (Local temperature of part) at 250 ° C. to obtain a welded can body. Then, while observing the outer surface of the can body, the L * value was measured for the whiteness of the white ink portion, and the film shrinkage width was measured by optical microscope observation. The results are shown in Table 2.

The outer surface of the can body of the can body obtained from the steel sheet of the present invention has good gloss and no color unevenness, and the visual clarity of the design is better than that of the existing three-piece can according to the result of visual observation. It was Further, the whiteness film shrinkage was good without any problem. Further, the can body obtained from the steel sheet of the present invention was necked-in, the canopy was wrapped around one end, the contents were filled, and the canopy was wrapped up and sealed.
As a result of conducting retort treatment for 30 minutes and examining the appearance change and sealing property of the film, it was found that the film had a good appearance without any change in adhesion, gloss, color unevenness, sealing property and the like.

On the other hand, looking at the outer surface of the can body obtained from Comparative Steel Sheet 1 to Comparative Steel Sheet 4, the can body obtained from Comparative Steel Sheet 1 has a poor overall image clarity and the current cans. The print appearance was inferior to that of. Further, the can body obtained from the comparative steel plate 2 had good gloss and no color unevenness, and the visual clarity of the design was better than that of the existing three-piece can according to the result of visual observation. As described above, the shrinkage width of the film is large, which is a practical problem.

The can body obtained from the comparative steel plate 3 has the L * value of the white ink portion and the shrinkage width of the film at the practical level as shown in Table 2, but the clearness of the print design in the viewing direction. Differently, there was a problem as a product. The can body obtained from the comparative steel plate 4 had poor image clarity as a whole, and the printing appearance was inferior to the current can.

(Example 2) Using the steel sheets of the present invention steel sheets 1 to 8 and comparative steel sheets 1 to 4 used in Example 1, the steel sheets were heated by a heating roll method to obtain a urethane-based coating having a dry thickness of 2.5 µm. A 15 μm thick transparent film of biaxially stretched polyester resin coated with an adhesive was laminated. The transparent film-laminated steel sheet thus obtained was manufactured according to the procedure of Example 1, a welding can barrel was manufactured, a repair coating for the welded portion was performed, and drying was performed so that the film surface became the inner surface.

The shrinkage width of the film was measured by observation with an optical microscope as in Example 1. The measurement results of the film shrinkage width are shown in Table 2. The results were the same as in Example 1. Furthermore, the can body was necked in, the canopy was wrapped around one end, coffee was filled, and the lid was wrapped around and sealed, and then retorted at 125 ° C for 30 minutes to obtain film adhesion. As a result of examining the sealing property, the corrosion resistance and the like, the can body obtained from the steel sheet of the present invention had no problem in film adhesion and sealing property and had no corrosion resistance.

On the other hand, the can bodies obtained from the comparative steel plate 1, the comparative steel plate 3 and the comparative steel plate 4 had no problem in film adhesion and sealing property and had no problem in corrosion resistance. The cans obtained from No. 1 had inferior corrosion resistance, and corrosion was observed especially near the flange processed part. As described above, the can body obtained from the steel sheet of the present invention has an excellent print appearance on the outer surface, in particular, the clarity of the trademark design, and is better than the current can body. In addition, the inner surface of the can also shows good corrosion resistance, which is good.

On the other hand, a can body obtained from a steel plate outside the scope of the present invention has a large film shrinkage when the printed appearance of the outer surface is good, and has a problem in corrosion resistance particularly on the inner surface. or,
When the film shrinkage is good, there is a problem in the printed appearance on the outer surface, which is not preferable in practice.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

Industrial Applicability When the steel sheet of the present invention is applied as a means for obtaining a three-piece can by laminating a printing film on the outer surface and a transparent film on the inner surface, it guarantees the following many advantages as compared with the conventional steel sheet. Is. (1) It is possible to omit the white coat and the size coat which have been conventionally performed by applying a printing base coating film.

(2) The continuous coating printing using the coil product can be performed at a high speed with a wide width, and the productivity can be secured more than twice as much as that of the cutting plate coating line. (3) Since it is not necessary to pass the line through a large number of times, the finishing period can be shortened. (4) Since it is handled as a coil product, it has an advantage that even if the material plate is made extremely thin, it does not cause a big problem in operation.

As described above, it is possible to solve the labor-saving due to the omission of the steps and the manufacturing problem for the cost reduction of the conventional three-piece can at once. (5) In addition, compared to the current external printing cans, the depth of printing allows the trademark design to be more vivid, and it is possible to supply three-piece cans that are compatible with the diversification and upsizing of consumers.
The inner surface of the can has higher corrosion resistance than the conventional coating.

(6) Further, since it can be used for a conventional paint can, of course, it can be used in a wide range, so that it has great economic and social significance.

Claims (2)

[Claims] 1. The amount of tin deposited on one surface is 0.5 to 2.0 g / m.
^It has a tin-plated film of ² , the gloss Gs in all surface directions is 250% or more, and the gloss in the longitudinal direction of the steel sheet (Gs
(L)) and gloss ratio in the width direction (Gs (C)), Cs
(C) / Gs (L) is 0.4 or more, and the area of the site where I (Sn) / I (Fe) is 20 or more, the ratio of the X-ray energy intensities of tin and iron measured simultaneously by an X-ray microanalyzer. A tin-plated steel sheet for a three-piece can having excellent image clarity and film adhesion, which is characterized by a rate of 5 to 80%. 2. The print image clarity and film adhesion according to claim 1, further comprising a nickel-containing plating layer having a nickel deposition amount of 0.01 to 0.5 g / m ² under the tin plating film. Excellent tin-plated steel sheet for three-piece cans.