JP3480178B2 - Painted metal plate surface protection film or sheet, and coated metal plate with surface protection film or sheet - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface protective film (including a sheet, the same applies hereinafter) which is attached for the purpose of protecting the surface of a coated metal plate, and the surface protective film is attached. The present invention relates to a coated metal plate.

[0002]

2. Description of the Related Art Conventionally, a metal plate used for household electric appliances, indoor appliances, etc. is generally coated for the purpose of imparting an aesthetic appearance and preventing corrosion. In recent years, household electric appliances and the like have been diversified and upscaled, and high-gloss appearances are preferred in refrigerators, washing machines, microwave ovens, and the like, while conversely low-gloss in audio / visual equipment and the like. Adjustments are desired. The surface of the metal plate that is required to have aesthetic properties is called a decorative surface, and the surface on the back side is called a non-decorative surface.

To impart aesthetics, it is common to apply a coating to the decorative surface of a metal plate, and such a coated metal plate (hereinafter also referred to as a pre-coated metal plate) is generally continuously coated. In many cases, a surface protection film is attached to the decorative surface of the above-mentioned coated metal plate in order to prevent scratches during the cutting process performed by the user or the construction process performed by the user.

[0004]

However, the film for protecting the surface of a coated metal plate is not limited to any one as long as it has a protective function, and a film suitable for the type of coating film on the coated metal plate is not used. Then, the film floats or, conversely, causes problems such as difficulty in peeling and adhesive residue due to excessive adhesion of the film. That is, if the adhesive strength is too small, the adhesion will be insufficient, and thus the surface protection film will float immediately after the attachment, while if the adhesion is too large, it will be difficult to peel off the surface protection film. Moreover, there is a problem that the adhesive of the surface protection film is transferred to the decorative surface of the coated steel sheet.

Generally, the adhesive strength of the surface protection film is usually 30 to 100 g / 25 mm immediately after the film is attached.
The degree is the best, and the adhesive strength after a long time is 300
It is necessary to be g / 25mm or less, 300g / 25
If the thickness is more than mm, there is a problem that peeling becomes difficult, or the film may be broken at the time of peeling.

Although it is necessary to make the adhesive force suitable as described above, it is difficult for the pressure-sensitive adhesive contained in the surface protection film to follow irregularities on the surface, especially for a coated metal plate surface having a large surface roughness. Therefore, it is not easy to bond them together, and the adhesion to the coated steel plate surface is poor. Also, when laminating at room temperature, even if laminating with a high laminating pressure, it is easy to peel off from the surface of the coated metal plate due to the spring back force of the film base material, and it does not play a role as a surface protection film. There is.

[0007] Therefore, as a countermeasure against the above problem, it is considered to take measures to add a tackifier or the like to the pressure-sensitive adhesive or to increase the thickness of the pressure-sensitive adhesive layer for the purpose of further improving the adhesiveness. However, in this case, as described above, the coated metal plate and the film become too close to each other and peeling becomes difficult, and the peeling work takes time, and if peeled quickly, adhesive residue may occur, The problem that the film breaks occurs. Further, when the surface protective film is peeled off from the coated metal plate after a long time has passed, there is a problem that glue marks are likely to remain. The coated metal plate with the problems as described above lacks suitability as an outer plate material for home electric appliances,
Due to the loss of commercial value, effective solutions to the above problems are urgently needed.

The present invention has been made in view of the above circumstances, and is a film for protecting the surface of a coated metal plate which does not cause the film to float, the film to be difficult to peel off, or the adhesive traces to remain. A coated metal plate surface protection film that allows the adhesive to easily follow the surface irregularities of even a heavily coated metal plate and easily peel off without leaving a glue mark even after a long period of time. It is an object of the present invention to provide a coated metal plate having the film for surface protection.

[0009]

The coated metal plate surface protection film according to the first aspect of the present invention has a pressure-sensitive adhesive layer on at least one surface of a thermoplastic resin film, and the pressure-sensitive adhesive layer has a thickness of 3 to 3. 30 μm, glass transition temperature is −30 to 30 ° C., thickness (Y) and glass transition temperature (Z) of the pressure-sensitive adhesive layer are contact angles (X) of distilled water droplets to the coating film of the coated metal plate. On the other hand, the gist is to satisfy the relationship of the following equation (1).

[0010]

[Equation 3]

X: Contact angle (degree) of distilled water droplets to the coating film of the coated metal plate Y: Thickness of adhesive layer (μm) Z: Glass transition temperature (° C)

Further, the film for protecting a surface of a coated metal plate according to the second aspect of the present invention has a pressure-sensitive adhesive layer on at least one surface of the thermoplastic resin film, and the pressure-sensitive adhesive layer has a thickness of 3 to 30.
μm, the glass transition temperature is −30 to 30 ° C., and the thickness (Y) and the glass transition temperature (Z) of the pressure-sensitive adhesive layer correspond to the center line average roughness (A) of the coating film of the coated metal plate. On the other hand, the gist is to satisfy the relationship of the following expression (2).

[0013]

[Equation 4]

A: Center line average roughness [Ra] (μm) of the coated metal plate Y: Thickness of the adhesive layer (μm) Z: Glass transition temperature (° C.)

The pressure-sensitive adhesive layer may be provided on at least one side of the film, or may be linear, dotted, or
It may be provided partially such as in an island shape or only in the ear portion of the film. In addition, it is a gist that the coated metal plate with a surface protection film according to the present invention is a coated metal plate to which the surface protection film of the first and second inventions is attached.

In each of the above inventions, the thickness and glass transition temperature (hereinafter sometimes referred to as Tg) of the pressure-sensitive adhesive layer provided on one surface of the film, and the contact angle or the center of the coating film of the coated metal plate The above problem was solved by focusing on the line average roughness (hereinafter sometimes referred to as Ra) and using a simple method combining them.

In the first aspect of the present invention, the surface condition of the coated metal plate is grasped by the contact angle of the distilled water droplets to the coating film, and the contact angle of the distilled water droplets with the thickness of the adhesive layer and the glass transition temperature are By defining the pressure-sensitive adhesive layer in a related manner, a surface protective film that can be favorably attached was obtained.

On the other hand, in the second aspect of the invention, the surface condition of the coated metal plate is grasped by Ra, and the pressure-sensitive adhesive layer is defined from the relationship between the Ra and the thickness of the pressure-sensitive adhesive layer and the glass transition temperature. A film for surface protection that can be attached to was obtained.

As described above, the thickness of the adhesive layer is 3 to 30.
The reason is that when the thickness of the pressure-sensitive adhesive layer exceeds 30 μm, the adhesive layer is likely to be over-adhered to the adherend and peeling is difficult, and the adhesive may remain when peeled. If the thickness of the pressure-sensitive adhesive layer is less than 3 μm, the pressure-sensitive adhesive force is often insufficient, and the film floats immediately after the surface protection film is attached, and the film is naturally peeled off.

As mentioned above, the glass transition temperature of the pressure-sensitive adhesive is -30 ° C to 30 ° C. If the Tg is less than -30 ° C, the pressure-sensitive adhesive is too soft, and therefore, for example, it may adhere to the decorative surface of the precoated metal plate and cause reverse contamination. On the other hand, if the Tg is higher than 30 ° C, the pressure-sensitive adhesive layer is hard. This is because the adhesive strength is reduced and the adhesive strength is reduced, and sufficient adhesive strength is not exhibited.

Next, the above formulas (1) and (2) will be described.
FIG. 1 is a graph showing the relationship between the surface roughness of the decorative surface and the adhesive force when a colored steel plate is used as the coated metal plate. As the surface protection film, film: polyethylene, adhesive layer: acrylic Is used. In addition, ○ (A-13
50) and ● (L-2250) are surface protection films having different thicknesses of the adhesive layer.

As can be seen from FIG. 1, the surface condition of the coated metal plate is such that the smoother it is, the better the tackiness is, and the rougher it is, the lower the tackiness is. A low gloss has a large surface roughness, and a low gloss has a low adhesive strength (Fig. 2 [graph showing the relationship between the gloss and the adhesive strength]).
reference).

FIG. 3 shows the surface roughness (R
(a: center line average roughness) and adhesive force, a high-process coating material is used as a coating film, ◯ indicates film adhesive force, and ● indicates coating film gloss. As can be seen from FIG. 3, the larger the Ra of the coating surface (decorative surface), the lower the film adhesive force, and conversely, the smaller the Ra, the higher the film adhesive force. That is, when a film is attached, the tackiness varies depending on the surface roughness and glossiness of the adherend.

Further, the film adhesive strength depends on the type of paint applied to the coated metal plate. The adhesive strength is low in the case of highly processed paint or high hardness type paint, and is low in the case of balanced paint. Is high (see FIG. 4).

The relationship between the type of paint and the adhesive strength is as follows.
It can also be explained by the contact angle of water droplets, and the contact angle of water droplets changes when the type of paint changes, and the smaller the contact angle, the greater the interfacial energy and the greater the adhesive force (see FIG. 5).

As described above, the adhesive force of the film to the coated metal plate is affected by the water droplet contact angle and Ra of the coating film. Therefore, the present inventors paid attention to these contact angles and Ra,
The thickness and Tg of the pressure-sensitive adhesive layer so that (1) or (2) is satisfied.
It was found that the film can be applied well if The contact angle of the coating film on the coated metal plate is represented by the contact angle of distilled water drops when distilled water is dropped on the surface of the coating film.

The contact angle and Ra both represent the state of the coating film surface, but these differ from the viewpoint of how to grasp the surface state of the coating film.
The above Ra represents the height and spacing of the surface irregularities,
The value of Ra changes depending on the type of coating film and the type of original plate. On the other hand, the contact angle represents the wettability and gloss of the coating film surface, and the value of the contact angle is related only to the type of coating film.

Regarding the correlation between the contact angle value and the Ra value,
When the original plate of the coated metal plate is a certain type and the coating film is variously changed, there is a correlation between the two, but when the coating film is a certain type and various original plates are used, , And found that the correlation was not so great.

These contact angles and Ra are both related to the adherability of the surface protective film. Regardless of which way of grasping the adhesive, the adhesive can be regulated so that the film can be adhered well. I found that I can do it.

When the contact angle or Ra of the coating film of the coated metal plate is large, or when the thickness of the pressure-sensitive adhesive layer is thin, the adhesive force becomes low as described above, and the film may peel off. On the other hand, when Tg is high, the pressure-sensitive adhesive layer is hardened and the pressure-sensitive adhesive force is lowered, so that sufficient pressure-sensitive adhesive force cannot be exhibited. On the other hand, when Tg is low, sufficient adhesive strength can be obtained, but since the adhesive layer is too soft, there is a risk that it will adhere to the decorative surface of the precoated metal sheet and cause reverse contamination.

The contact angle or Ra of the coating film on the coated metal plate
When the value is small or the thickness of the pressure-sensitive adhesive layer is large, the adhesive strength becomes high as described above, and adhesive residue of the pressure-sensitive adhesive may occur.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION When the above three parameters X, Y and Z satisfy the relation of the above formula (1), a good adhesion state of the surface protection film can be obtained on the coated metal plate. To be In addition, the above three parameters A, Y, Z are
Even when the relationship of the above formula (2) is satisfied, a good stuck state can be obtained. Equation (3) below is a modification of Equation (1).

[0033]

[Equation 5]

The contact angle of the coating film of the coated metal plate is a value determined by the gloss desired for household electric appliances and the like, and if the glass transition temperature of the adhesive to be used is determined, the above formula (3) is used. It is possible to determine the thickness of the pressure-sensitive adhesive layer. Also, equation (4) below is a modification of equation (2).

[0035]

[Equation 6]

Similarly, Ra of the coating film of the coated metal plate is a value determined by the original plate and the coating film of the coated metal plate desired for household electric appliances and the like, and the glass transition temperature of the adhesive used is determined. For example, the thickness of the pressure-sensitive adhesive layer can be determined using the above formula (4).

The pressure-sensitive adhesive layer may be any one that can be generally used as a surface protective film, and examples thereof include natural rubber-based, acrylic-based, polyisobutylene, styrene-isobutylene-styrene copolymer, and styrene-. Examples thereof include butylene-styrene copolymer.

Examples of the film provided with the pressure-sensitive adhesive include homopolymers such as polyethylene, polyvinyl chloride, high-density polyethylene and polypropylene, and copolymers containing these as the main components. The thickness is preferably 5 to 60 μm. , And more preferably 10 to 40 μm. The film may be a single layer or multiple layers, and may be printed if necessary. The surface protection film may be provided with a release film on the surface having the adhesive layer.

As the original plate of the coated metal sheet, cold rolled steel sheet, hot-dip galvanized steel sheet, electrogalvanized steel sheet, galvannealed steel sheet, aluminum sheet, stainless steel sheet, copper sheet, copper-plated steel sheet, tin-plated steel sheet and the like can be mentioned. As a paint to be applied to these metal plates, polyester-based paint,
Epoxy paints and the like can be mentioned, and the kind is not particularly limited.

In order to improve the adhesion between the metal plate which is the original plate and the coating film, it is desirable to carry out a known metal surface treatment. Examples of these known surface treatment methods include phosphate surface treatment and chromate surface treatment. Moreover, you may add a softening agent, a ultraviolet absorber, an antioxidant, etc. to a pressure sensitive adhesive as needed.

The method of providing the pressure-sensitive adhesive layer on one surface of the film may be any method, for example, a method of coextruding the film and the pressure-sensitive adhesive to laminate the film and the pressure-sensitive adhesive layer.

[0042]

【Example】

<Experiment on the First Invention> 25 as a film substrate
Using a polyester film (melting point 235 ° C.) of μm,
Various acrylic pressure-sensitive adhesives having Tg as shown in the following Table 1 were applied to this in a thickness (Y) shown in Table 1 to prepare a surface protective film.

As the metal plate, a steel plate having a thickness of 0.6 mm was used, electrogalvanized so that the amount of zinc deposited was 20 g / m ² , alkali degreasing treatment was performed, and then chromate treatment was performed. After that, a polyester primer is applied and baked so that the dry film thickness becomes 5 μm, and further, a paint in which silica as a matting agent is added to the polyester top coating is applied so that the dry film thickness becomes 15 μm. It was applied and baked on to prepare a coated steel sheet. Different contact angles on the decorative surface can be produced by changing the amount of silica added. A surface protection film was pressed onto each of the various coated steel plates with a pressing roll of 2 kg at 23 ° C. and attached to the decorative surface (Experimental Example No. 1-
twenty five).

The Tg of the adhesive is a heat flux type differential scanning calorimeter (manufactured by Seiko Denshi Kogyo: Model SSC 5200 DSC 220).
Was measured under the following conditions. Sample amount: Approx. 10 mg Heating rate: 10 ° C / min. Heating range: -50 to 200 ° C Standard substance: Alumina Sample container: Aluminum, closed type atmosphere: Nitrogen gas, 30 ml / min. Refrigerant: Liquid nitrogen

The thickness of the pressure-sensitive adhesive layer was measured by a gravimetric method.
In this method, first, xylene is used to dissolve the pressure-sensitive adhesive layer, the adhesion amount of the pressure-sensitive adhesive layer per unit area is calculated from the weight difference before and after the removal, and the size of the test piece, and the coating is performed based on the specific gravity of the pressure-sensitive adhesive after drying. It is to convert the film thickness. The contact angle of the decorative surface of the coated steel sheet was determined by the drop method (using distilled water) using a contact angle meter.

The adhesive strength of the surface protection film was measured under the following conditions using an Orientec universal tester UCT-1T. Peeling speed: 0.2m / min Temperature: 25 ° C Film width: 25mm Film peeling angle: 180 °

These experimental examples were subjected to a 180 ° angle constant speed peel strength test (pulling speed: 100 mm / min) to give an initial adhesive force (23 ° C.) and an adhesive force at room temperature with no load (2).
3 ° C x 30 days), and high temperature aging adhesion under no load (5
(0 ° C. × 10 days) was measured. In addition, the presence or absence of floating of the protective film, the change in appearance of the coating film after the film was peeled off, and the presence or absence of adhesive residue were visually observed. The results are also shown in Table 1.

[0048]

[Table 1]

As can be seen from Table 1, the thickness of the adhesive is 3 to.
Those having a thickness of 30 μm and a Tg in the range of −30 to 30 ° C. and satisfying the formula (1) have no peeling or floating of the surface protective film, and have a makeup even after the surface protective film is peeled off. There was no adhesive residue on the surface (Experimental Example Nos. 1 to 16).

However, those which do not satisfy the thickness and Tg of the adhesive and the formula (1) (Experimental Examples Nos. 17 to 23), and the thickness and Tg of the adhesive do not satisfy the formula (1). The ones (Experimental Example Nos. 24 and 25) were peeled and floated on the surface protection film,
Alternatively, adhesive residue was generated when peeled off.

<Experiment on Second Present Invention> In the same manner as described above, a 25 μm polyester film (melting point 235 ° C.) was used as a film substrate and the Tg as shown in Table 2 was used.
Various acrylic pressure-sensitive adhesives having a thickness of (Y) shown in Table 2 were applied to produce a surface protection film.

As the metal plate, a steel plate having a thickness of 0.6 mm was used. A galvanized steel plate obtained by electrogalvanizing one side of the above steel plate so that the zinc adhesion amount was 20 g / m ² , and the zinc adhesion amount 45 g / m ^2. As described above, two types of plated steel sheets each having one surface of the above steel sheet subjected to galvannealing were prepared as original plates, and alkali degreasing treatment was performed on these, and then chromate treatment was performed. In Table 2, the original plate indicated by GA is a galvannealed steel sheet, and the original plate indicated by EG is an electrogalvanized steel sheet.

Thereafter, a polyester primer is applied and baked so that the dry film thickness becomes 5 μm, and further silica (SiO ₂ , particle size 3 μm) as a matting agent and / or acrylic organic beads (particle size) 2 to 4 .mu.m) of a polyester-based top coating composition was applied and baked on the polyester-based primer so that the dry film thickness was 15 .mu.m, thus producing a coated steel sheet. It should be noted that coated steel sheets having various center line average roughnesses (Ra) on the decorative surface were manufactured by changing the addition amount of the silica and the acrylic organic beads (referred to as acrylic beads in Table 2). did. A surface protection film was pressed onto each of the various coated steel plates with a pressing roll of 2 kg at 23 ° C. and attached to the decorative surface (Experimental Examples No. 26 to 46).

The Tg of the pressure-sensitive adhesive, the thickness of the pressure-sensitive adhesive layer, and the adhesive strength of the surface protective film were measured in the same manner as described above. The center line average roughness (Ra) of the decorative surface of the coated steel sheet was measured using a surface roughness measuring instrument (manufactured by Tokyo Seimitsu Co., Ltd.) to measure a length of 25.
It was measured under the measurement conditions of 4 mm and a cutoff of 0.8 mm.

These experimental examples were subjected to a 180 ° angle constant speed peel strength test (pulling speed 100 mm / min) to give an initial adhesive force (23 ° C.) and an adhesive force at room temperature with no load (2).
3 ° C x 30 days), and high temperature aging adhesion under no load (5
(0 ° C. × 10 days) was measured. In addition, the presence or absence of floating of the protective film, the change in appearance of the coating film after the film was peeled off, and the presence or absence of adhesive residue were visually observed. The results are also shown in Tables 2 and 3.

[0056]

[Table 2]

[0057]

[Table 3]

As can be seen from Tables 2 and 3, the adhesive having a thickness of 3 to 30 μm and a Tg in the range of −30 to 30 ° C. and satisfying the formula (2) is used for surface protection. There was no peeling or floating of the film, and there was no adhesive residue on the decorative surface even after peeling the surface protection film (Experimental Example No. 26).
~ 38).

However, those which do not satisfy the thickness and Tg of the adhesive and the formula (2) (Experimental Examples No. 39 to 44), and the thickness and Tg of the adhesive do not satisfy the formula (2). The ones (Experimental Example No. 45, 46) were peeled or floated on the surface protection film,
Alternatively, adhesive residue was generated when peeled off.

[0060]

As described above, according to the present invention, not only those having a small surface roughness but also precoated metal sheets having a large surface roughness can be easily followed by the pressure-sensitive adhesive to cause the film floating or peeling. It is possible to obtain a surface-protective film and a coated steel sheet with a surface-protective film that can be easily peeled off without leaving a trace of glue even after a long period of time. Therefore, it is possible to meet high demands in various fields such as construction and home appliances.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the adhesive strength of a color steel plate to a surface protection film and the surface roughness.

FIG. 2 is a graph showing the relationship between the adhesive strength of a color steel plate to a surface protection film and the glossiness.

FIG. 3 is a graph showing the relationship between Ra of a coating film and the adhesive force of a film.

FIG. 4 is a graph showing the relationship between paint type and film adhesion.

FIG. 5 is a graph showing the relationship between the type of paint and the contact angle.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-194080 (JP, A) JP-A-3-124783 (JP, A) JP-A-5-98223 (JP, A) JP-A-7- 216324 (JP, A) JP-A-5-247420 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B32B 1/00-35/00 C09J 7/02 C23C 26/00

Claims (3)

(57) [Claims] 1. A surface protective film or sheet for a coated metal plate, wherein the surface protective film or sheet has a pressure-sensitive adhesive layer on at least one surface of the thermoplastic resin film or sheet, and the pressure-sensitive adhesive layer has a thickness. Is 3 to 30 μm, the glass transition temperature is −30 to 30 ° C., and the thickness of the adhesive layer (Y: μ
m) and the glass transition temperature (Z: ° C.) satisfy the relationship of the following expression (1) with respect to the contact angle (X: degree) of the distilled water water drop with respect to the coating film of the coated metal plate. Painted metal plate surface protection film or sheet. [Equation 1] 2. A surface protective film or sheet for a coated metal plate, wherein the surface protective film or sheet has a pressure-sensitive adhesive layer on at least one side of the thermoplastic resin film or sheet, and the pressure-sensitive adhesive layer has a thickness. Is 3 to 30 μm, the glass transition temperature is −30 to 30 ° C., and the thickness of the adhesive layer (Y: μ
m) and the glass transition temperature (Z: ° C.) with respect to the center line average roughness (A: μm) of the coating film of the coated metal plate,
A film or sheet for protecting the surface of a painted metal plate, which satisfies the relationship of (2). [Equation 2] 3. A coated metal plate with a film or sheet for surface protection, which is a coated metal plate to which the film or sheet for surface protection of the coated metal plate according to claim 1 or 2 is attached.