JP2016030394A - Impact absorption film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an impact absorption film in which the impact absorption capability is not deteriorated, or the degree of the deterioration is suppressed, even when subjected to consecutive impacts.SOLUTION: An impact absorption film comprises a laminate essentially composed of only: A) a first stretchable film having a tensile strength 10% modulus of 0.15 to 0.5 N/10 mm and a stretchability of returning to its original length when the tensile force is released; and B) a foam having a thickness of 0.05 mm or more and 0.5 mm or less and in which a sheet composed of only said foam has a repulsive stress measured when several of such sheets are overlapped to a thickness of 1 cm and is compressed to a thickness of 50%, of 0.02 MPa or more and 3.0 MPa or less.SELECTED DRAWING: None

Description

  The present invention relates to an impact absorbing film, and more particularly to an impact absorbing film for protecting display panels, electronic circuits, batteries, and the like of products such as smartphones, tablet terminals, and notebook computers.

  Products such as smartphones and tablet terminals need to be provided with a material that absorbs impact so that the display panel does not break when impacted by dropping or the like.

For example, Patent Document 1 discloses that an impact absorbing layer that protects a display panel or the like from impact is made of a pressure-sensitive adhesive, acrylic, urethane, urethane acrylate, silicone, or rubber.
Patent Document 2 discloses a structure in which a synthetic resin film made of polyethylene terephthalate and a foam sheet made of a polyolefin resin and laminated with a foam sheet having shock absorption are integrated.

Special table 2010-515783. JP2010-82808.

  However, products such as smartphones and tablet terminals are desired to be thinner and lighter, and materials that absorb shocks are desired to be thinner and lighter. In response to this requirement, when the thickness of the shock absorbing layer of Patent Document 1 or the thickness of the foamed sheet having the shock absorbing property of Patent Document 2 is reduced, when the impact is continuously applied, It has been found that the shock absorbing layer or the foamed sheet of Patent Document 2 continues to be crushed by a continuous shock, and there is a problem that the shock absorption is deteriorated.

An object of the present invention is to solve the problems of the prior art described above.
Specifically, an object of the present invention is to provide an impact-absorbing film having characteristics capable of withstanding continuous impact even when the thickness of the impact-absorbing layer is reduced.
More specifically, an object of the present invention is to provide an impact-absorbing film in which the impact-absorbing property is not deteriorated or the degree of deterioration is suppressed even when subjected to a continuous impact.

The inventors have found the following invention.
<1> a laminate; an impact-absorbing film comprising:
The laminate is
A) Tensile strength 10% modulus is 0.15 to 0.5 N / 10 mm, preferably 0.2 to 0.45 N / 10 mm, and has elasticity to return to the original length when the tensile force is lost. A first stretch film;
B) A foam having a thickness of 0.05 mm or more and 0.5 mm or less, preferably 0.08 mm or more and 0.3 mm or less, and a plurality of sheets made of only the foam are stacked to a thickness of 1 cm. The repulsion stress of the sheet measured when compressed to a thickness of 50% is 0.02 MPa to 3.0 MPa, preferably 0.02 MPa to 1.0 MPa, more preferably 0.02 MPa to 0.3 MPa. Foam;
The shock-absorbing film essentially consisting of only the above.

<2> a laminate; an impact-absorbing film comprising:
The laminate is
A) Tensile strength 10% modulus is 0.15 to 0.5 N / 10 mm, preferably 0.2 to 0.45 N / 10 mm, and has elasticity to return to the original length when the tensile force is lost. A first stretch film;
B) A foam having a thickness of 0.05 mm or more and 0.5 mm or less, preferably 0.08 mm or more and 0.3 mm or less, and a plurality of sheets made of only the foam are stacked to a thickness of 1 cm. The repulsion stress of the sheet measured when compressed to a thickness of 50% is 0.02 MPa to 3.0 MPa, preferably 0.02 MPa to 1.0 MPa, more preferably 0.02 MPa to 0.3 MPa. Foam;
A ′) may be the same as or different from A) above, the tensile strength 10% modulus is 0.15 to 0.5 N / 10 mm, preferably 0.2 to 0.45 N / 10 mm, and there is no tension force A second stretchable film having a stretchability that returns to its original length when hit;
The impact-absorbing film as described above, wherein the laminate is essentially composed of only a laminate, and B) a foam is disposed between A) the stretchable film and A ′) the stretchable film.

<3> In the above <1> or <2>, A) The first stretchable film has a thickness of 3 to 50 μm, preferably 3 to 40 μm.
<4> In the above item <2> or <3>, A) the first elastic film and A ′) the second elastic film each independently have a thickness of 3 to 50 μm, preferably 3 to 40 μm. It is good to be.
<5> In any one of the above items <1> to <4>, the laminate may have a thickness of 0.053 mm to 0.6 mm.

<6> In any one of the above items <1> to <5>, A) the first stretchable film and A ′) the second stretchable film are each independently made of polyurethane resin, acrylic resin, and silicone resin. It is good to have at least 1 sort (s) chosen from the group which consists of. In particular, A) the first stretchable film and A ′) the second stretchable film are preferably formed from a polyurethane resin.
<7> In any one of the above items <1> to <6>, B) the foam is formed by including at least one resin selected from the group consisting of a polyolefin resin, a polyurethane resin, and an acrylic resin. Good. In particular, B) the foam may be formed from a polyolefin resin (eg, polyethylene resin, polypropylene resin) or an acrylic resin, preferably an acrylic resin.

According to the present invention, the above-mentioned problems of the prior art can be solved.
Specifically, according to the present invention, it is possible to provide an impact-absorbing film having characteristics that can withstand continuous impacts even when the thickness of the impact-absorbing layer is reduced.
More specifically, according to the present invention, it is possible to provide an impact-absorbing film in which the impact absorbability is not deteriorated or the degree of deterioration is suppressed even when subjected to continuous impact.

It is a figure which shows the outline of the point impact test machine 1 used for the Example of this application.

Hereinafter, the invention described in the present application will be described in detail.
The present application is a shock absorbing film having a laminate as a first aspect,
The laminate is
A) Tensile strength 10% modulus is 0.15 to 0.5 N / 10 mm, preferably 0.2 to 0.45 N / 10 mm, and has elasticity to return to the original length when the tensile force is lost. A first stretch film;
B) A foam having a thickness of 0.05 mm or more and 0.5 mm or less, preferably 0.08 mm or more and 0.3 mm or less, wherein a plurality of sheets made only of the foam are stacked to a thickness of 1 cm and a thickness of 50% A foam having a repulsive stress of 0.02 MPa to 3.0 MPa, preferably 0.02 MPa to 1.0 MPa, more preferably 0.02 MPa to 0.3 MPa, as measured when compressed into a sheet;
An impact-absorbing film consisting essentially of only is provided.

The present application is a shock absorbing film having a laminate as a second aspect,
The laminate is
A) Tensile strength 10% modulus is 0.15 to 0.5 N / 10 mm, preferably 0.2 to 0.45 N / 10 mm, and has elasticity to return to the original length when the tensile force is lost. A first stretchable film; and B) a foam having a thickness of 0.05 mm or more and 0.5 mm or less, preferably 0.08 mm or more and 0.3 mm or less, and a plurality of sheets made of only the foam are stacked. The sheet has a repulsive stress of 0.02 MPa to 3.0 MPa, preferably 0.02 MPa to 1.0 MPa, more preferably 0.02 MPa to 0, as measured when the thickness is 1 cm and the thickness is compressed to 50%. A foam of 3 MPa or less;
A ′) Tensile strength 10% modulus, which may be the same as or different from A) above, is 0.15 to 0.5 N / 10 mm, preferably 0.2 to 0.45 N / 10 mm, and pulling force A second stretchable film having a stretchability that returns to its original length when there is no more;
The impact-absorbing film according to claim 1, wherein the laminate consists essentially of A and the laminate is provided with B) a foam between A) a stretchable film and A ′) a stretchable film.

Hereinafter, a 1st aspect and a 2nd aspect are demonstrated in detail in order. However, the description of the common parts of the first and second aspects is omitted.
<Shock absorbing film of the first aspect>
The shock-absorbing film provided as the first aspect of the present application has a laminate, and the laminate essentially consists of only A) a first stretchable film; and B) a foam.
Here, “consisting essentially of only A); and B); may have other components other than component A) and component B), but the other components are those of the shock absorbing film. This means that the types and amounts of the other components are limited to such an extent that the characteristics are not adversely affected. The types and amounts of other components will be described later.

<< A) First Stretchable Film >>
A) The first stretchable film is
Tensile strength 10% modulus is 0.15 to 0.5 N / 10 mm, preferably 0.2 to 0.45 N / 10 mm, and has elasticity to return to the original length when the tensile force is lost.
In the present application, the tensile strength is a value measured by a method based on JIS K 7161.
A) The first stretchable film has a stretchability that returns to its original length when the pulling force is lost. Here, “return to the original length” means to return to a length in the range of 100 ± 5% compared to the original length.
A) The 1st elastic film has these characteristics, and can have the characteristic desired for this application by using it in combination with the below-mentioned B) foam.

  A) The first stretchable film depends on the thinness, hardness, impact absorbability, etc. required for the final product, but the thickness is 3-50 μm, preferably 3-40 μm, more preferably 5-30 μm. There should be.

A) The first stretchable film has at least one selected from the group consisting of polyurethane resin, acrylic resin, and silicone resin, although it depends on the thinness, hardness, impact absorbability, etc. required for the final product. It is good to form.
In particular, A) the first stretchable film is preferably formed from a polyurethane resin.

<< B) Foam >>
B) The foam is a foam having a thickness of 0.05 mm to 0.5 mm, preferably 0.08 mm to 0.3 mm. It fully meets the above-mentioned demands for reduction in thickness and weight.
The foam has the following repulsive stress. That is, the sheet has a repulsive stress of 0.02 MPa or more and 3.0 MPa or less, preferably 0.02 MPa or more and 1.0.0 MPa or more when measured by compressing a plurality of sheets made of only a foam to a thickness of 1 cm and a thickness of 50%. 0 MPa or less, more preferably 0.02 MPa or more and 0.3 MPa or less. Here, the reason why a plurality of sheets are stacked to a thickness of 1 cm is that repulsive stress cannot be measured as a single foam sheet. Here, the “repulsive stress” is a value measured by superposing a plurality of sheets with a thickness of 1 cm.
B) The foam has these characteristics, and can have the characteristics desired for the present application by using it in combination with the above-mentioned A) first stretchable film.

B) The foam is formed by including at least one resin selected from the group A consisting of a polyolefin resin, a polyurethane resin, and an acrylic resin, depending on the thinness required for the final product, impact absorption, and the like. It is better. “Formed with at least one type of resin” means that two or three types may be selected from the group A and formed from a mixture of the selected types.
In particular, the B) foam may be formed from a polyolefin resin (eg, polyethylene resin, polypropylene resin) or an acrylic resin, preferably an acrylic resin.

<< Laminated body of the first aspect >>
The impact-absorbing film of a 1st aspect has a laminated body (laminated body of a 1st aspect) which consists only of A) 1st elastic film; and B) foam.
As described above, the laminate of the first aspect may have other components other than the component A) and the component B), but the other components do not adversely affect the characteristics of the shock absorbing film. In addition, the types and amounts of the other components are limited.

Examples of other components include, but are not limited to, an adhesive for bonding.
Examples of the amount of other components include, but are not limited to, about 30 μm in terms of thickness.

  The laminated body according to the first aspect may have a thickness of 0.053 mm to 0.6 mm.

The shock absorbing film of the first aspect has the laminate of the first aspect. In a certain aspect, the impact-absorbing film of the first aspect may consist essentially of the laminate of the first aspect or only the laminate of the first aspect. “Consisting essentially of the laminate of the first embodiment” may contain components other than the laminate of the first embodiment, but the components do not adversely affect the properties of the laminate, Means type and quantity.
The impact absorbing film of the first aspect may have a layer other than the laminate of the first aspect. Examples of the layer other than the laminate of the first aspect include, but are not limited to, an adhesive layer provided on any surface of the laminate.

  The impact-absorbing film of the first aspect can be used to protect display panels, batteries, circuit components and the like of products such as smartphones, tablet terminals, and notebook computers.

<The manufacturing method of the impact-absorbing film of a 1st aspect>
The impact-absorbing film of the first aspect can be manufactured by the following method, for example, but is not limited thereto.
For example, B) a foam is first prepared, and the B) foam is coated with the first stretchable film precursor that becomes A) the first stretchable film to form the laminate of the first aspect. Form. Thereafter, an impact-absorbing film having the laminate, consisting essentially of the laminate, or consisting only of the laminate can be obtained.
In addition, for example, A) a first stretchable film is first prepared, and B) a precursor that becomes a foam is applied to the A) first stretchable film to form the laminate of the first aspect. To do. Thereafter, an impact-absorbing film having the laminate, consisting essentially of the laminate, or consisting only of the laminate can be obtained.
Further, for example, A) the first stretchable film and B) the foam are separately prepared, and the laminate of the first aspect is formed by bonding or the like via an adhesive or the like. . Thereafter, an impact-absorbing film having the laminate, consisting essentially of the laminate, or consisting only of the laminate can be obtained.

<Shock absorbing film of the second aspect>
The impact-absorbing film of the second aspect has A ′) a second elastic film, and the laminate of the second aspect is B) foamed between A) the elastic film and A ′) the elastic film. Although the point by which a body is arrange | positioned differs, since it is the same as that of the impact-absorbing film of a 1st aspect except that, said difference point is demonstrated hereafter.

<< A ') Second stretchable film >>
A ′) The second stretchable film may be the same as or different from A) the first stretchable film, and A) has the same characteristics as the first stretchable film.
In other words, A ′) the second stretchable film has a characteristic that the tensile strength 10% modulus is 0.15 to 0.5 N / 10 mm, preferably 0.2 to 0.45 N / 10 mm.

In addition, A ′) the second stretchable film has a stretchability that returns to its original length when the pulling force is lost.
Further, A ′) the second stretchable film depends on the thinness, hardness, impact absorbability and the like required for the final product, but the thickness is 3 to 50 μm, preferably 3 to 40 μm, more preferably 5 It is good that it is ˜30 μm.
A ′) The second stretchable film depends on the thinness, hardness, impact absorbability, etc. required for the final product, but at least one selected from the group consisting of polyurethane resins, acrylic resins, and silicone resins. It is good to have.
In particular, A ′) the second stretchable film is preferably formed from a polyurethane resin.

<< Laminated body of second aspect >>
As described above, the laminate of the second aspect has a structure in which B) a foam is disposed between A) the first stretchable film and A ′) the second stretchable film.

<The manufacturing method of the impact-absorbing film of a 2nd aspect>
The impact-absorbing film of the second aspect can be manufactured, for example, by the following method, but is not limited thereto.
For example, A) a first stretchable film is first prepared, and B) a foam is laminated on the A) first stretchable film. In addition, about this lamination | stacking method, it can carry out similarly to <the manufacturing method of the impact-absorbing film of a 1st aspect>. A ′) a second stretchable film is laminated on the B) foam of the obtained laminate. In this lamination method, A ′) a second stretchable film is formed by applying a precursor of a second stretchable film to be a second stretchable film on B) a foam. Thus, the laminate of the second aspect is obtained. Alternatively, A ′) a second stretchable film is prepared separately, and A ′) the second stretchable film is bonded to the foamed body via an adhesive or the like, so that the second The laminate of the aspect is formed.
Thereafter, the impact-absorbing film of the second aspect, which has the laminate of the second aspect obtained, consists essentially of the laminate, or consists only of the laminate, can be obtained.
Note that the impact-absorbing film of the second aspect also has the same uses as the impact-absorbing film of the first aspect.
Hereinafter, although the present invention is explained in full detail using the following examples, the present invention is not limited to the following examples.

An acrylic foam was first prepared, and then polyurethane having elasticity was formed on the acrylic foam, thereby obtaining a shock absorbing film A-1 that was a laminate.
Specifically, an acrylic foam having a thickness of 0.12 mm (ISR-ACF-TH manufactured by Iwatani Corporation) was used as the foam.
Coating the urethane foam surface (Y-210B, manufactured by Dainichi Seika) with dimethylformamide (DMF) diluted with dimethylformamide (DMF) to a viscosity of 500 mPa · s, using the Mayer bar No. 8 on the surface of the acrylic foam. Then, it was placed in an oven at 100 ° C. for 3 minutes to dry, and a 10 μm film of urethane was formed on the surface of the foam.

<Evaluation by point impact test>
The impact value was measured by applying a plurality of impacts with a point impact tester 1 schematically shown in FIG.
The point impact tester 1 schematically shown in FIG. 1 will be described in detail. In this example, the impact value was measured by applying a plurality of impacts using the point impact tester 1 schematically shown in FIG.
The point impact test machine 1 includes a measuring unit 2 for setting a sample and measuring impact, and a 13.7 g iron ball 3.
The measuring unit 2 mainly includes a metal plate 6 having a stage 5 (not shown in the drawing) on which the sample X is placed, an impact sensor 7 installed below the metal plate 6, and the metal plate 6 and the impact sensor 7. It consists of a supporting base 8.
In the measurement of the present example, the sample X was fixed on the stage 5 using the double-sided tape 9, and the iron ball 3 was arranged so that the lower end of the iron ball 3 was 20 cm above the stage 5, and then the iron ball 3 Is allowed to fall freely and collide with the sample X. The impact value at the time of collision is detected by the impact sensor 7, and the value is set as the impact value.
Multiple impacts were measured over time. Specifically, one measurement and the next measurement were performed within about 5 seconds.
Table 1 shows the types of foam, the thickness of the foam, the thickness of the urethane layer, and the 10% modulus value of the urethane layer, as well as the evaluation by the point impact test (first and fifth times). In addition, Comparative Example A is a result (first time and fifth time) of performing a point impact test in a state without a sample.

(Example 2)
In Example 1, the impact-absorbing film A-2 was obtained in the same manner as in Example 1 except that the thickness of the urethane obtained was changed to 30 μm instead of 10 μm by changing the coating amount of the urethane paint.

(Comparative Example 1 and Comparative Example 2)
In Example 1, the application amount of the urethane paint was changed to be Comparative Example 1 and Comparative Example 2.
In Comparative Example 1, the coating amount of the urethane paint was zero, that is, the film C-1 was obtained without applying the urethane paint.
Moreover, the comparative example 2 obtained film C-2 like Example 1 except the thickness of the urethane obtained having been 5 micrometers instead of 10 micrometers.
Similarly to Example 1, the impact absorbing film A-2 (Example 2), the films C-1 (Comparative Example 1), and C-2 (Comparative Example 2) were evaluated by the point impact test (first and 5th). Table 1 shows the type of foam, the thickness of the foam, the thickness of the urethane layer, and the 10% modulus value of the urethane layer.

(Example 3)
In Example 1, shock absorbing film A-3 was prepared in the same manner as in Example 1 except that a 0.2 mm polyethylene foam (XLIM WF Sekisui Chemical Co., Ltd.) was used instead of the 0.12 mm acrylic foam. Obtained.
Example 4
In Example 3, an impact absorbing film A-4 was obtained in the same manner as in Example 3 except that the amount of urethane coating was changed and the thickness of the obtained urethane was changed to 30 μm instead of 10 μm.

(Comparative Example 3 and Comparative Example 4)
In Example 3, the amount of urethane coating applied was changed to be Comparative Example 3 and Comparative Example 4.
In Comparative Example 3, the coating amount of the urethane paint was zero, that is, the film C-3 was obtained without applying the urethane paint.
Moreover, the comparative example 4 obtained film C-4 similarly to Example 3 except the thickness of the urethane obtained having been 5 micrometers instead of 10 micrometers.

  Similarly to Example 1, the impact absorbing films A-3 (Example 3) and A-4 (Example 4) and the films C-3 (Comparative Example 3) and C-4 (Comparative Example 4) Table 1 shows the types of foam, the thickness of the foam, the thickness of the urethane layer, and the 10% modulus value of the urethane layer, as well as the evaluation by the point impact test (first and fifth times).

(Example 5)
In Example 1, an impact absorbing film A-5 was obtained in the same manner as in Example 1 except that a 0.2 mm polypropylene foam (SCF406, manufactured by Nitto Denko Corporation) was used instead of the 0.12 mm acrylic foam. .
(Example 6)
In Example 5, an impact absorbing film A-6 was obtained in the same manner as in Example 5 except that the amount of urethane coating was changed and the thickness of the obtained urethane was changed to 30 μm instead of 10 μm.

(Comparative Example 5 and Comparative Example 6)
In Example 5, the amount of urethane paint applied was changed to Comparative Example 5 and Comparative Example 6.
In Comparative Example 5, the coating amount of the urethane paint was zero, that is, the film C-5 was obtained without applying the urethane paint.
Moreover, the comparative example 6 obtained film C-6 like Example 5 except the thickness of the urethane obtained having been 5 micrometers instead of 10 micrometers.

  Similarly to Example 1, the impact absorbing films A-5 (Example 5) and A-6 (Example 6) and the films C-5 (Comparative Example 5) and C-6 (Comparative Example 6) Table 1 shows the types of foam, the thickness of the foam, the thickness of the urethane layer, and the 10% modulus value of the urethane layer, as well as the evaluation by the point impact test (first and fifth times).

Table 1 shows the following.
Comparative Examples 1 to 6 do not have a urethane layer which is a stretchable film (Comparative Examples 1, 3 and 5), or even if it has a urethane layer, its 10% modulus value is a predetermined value, specifically Specifically, 0.2 N / 10 mm or more is not achieved. Therefore, when the same materials are used for the foams, the comparative examples 1 and 2 and the examples 1 and 2 are compared specifically, the comparative examples 3 and 4 and the examples 3 and 4 are compared with the comparative example. Comparing 5 and 6 with Examples 5 and 6, in Comparative Examples 1 to 6, both the first and second impact values are higher than the control example. From this, it can be seen that each of the impact absorbing films of Examples 1 to 6 is more excellent as an impact absorbing film than the films of Comparative Examples 1 to 6 as a control.
Moreover, the impact absorption films A-1, A-2, A-4, and A-6 of Example 1, Example 2, Example 4, and Example 6 are the same as the first impact value. It is the same, and it can be seen that the shock absorption does not deteriorate even when subjected to continuous impact. In addition, also about the impact-absorbing film A-3 of Example 3, and the impact-absorbing film A-5 of Example 5, the comparative example 3 or 4 from which the impact value of the 5th time becomes a control, or 1 of Comparative Example 5 or 6 It can be seen that the shock absorption is maintained even when subjected to continuous impacts, which is lower than the impact values of the first and fifth times.

Claims (7)

A shock absorbing film having a laminate;
The laminate is
A) a first elastic film having a tensile strength of 10% modulus of 0.15 to 0.5 N / 10 mm and having elasticity that returns to its original length when the tensile force is lost; and B) thickness Is a foam of 0.05 mm or more and 0.5 mm or less, and the sheet has a repulsive stress of 0. 0 when a plurality of sheets made of only the foam are stacked to a thickness of 1 cm and compressed to a thickness of 50%. A foam of 02 MPa to 3.0 MPa;
The shock-absorbing film essentially consisting of only the above. A shock absorbing film having a laminate;
The laminate is
A) A first elastic film having a tensile strength of 10% modulus of 0.15 to 0.5 N / 10 mm and having elasticity that returns to the original length when the tensile force is lost;
B) A foam having a thickness of 0.05 mm or more and 0.5 mm or less, wherein a plurality of sheets made of only the foam are stacked to have a thickness of 1 cm and measured when compressed to a thickness of 50%. Foam having a repulsion stress of 0.02 MPa or more and 3.0 MPa or less; and A ′) The same or different from A) above, the tensile strength 10% modulus is 0.15 to 0.5 N / 10 mm A second elastic film that has elasticity and returns to its original length when the tension is lost;
The impact-absorbing film as described above, wherein the laminate is essentially composed of only the A, and B) foam is disposed between the A) stretchable film and the A ′) stretchable film.   The impact-absorbing film according to claim 1 or 2, wherein the A) first stretchable film has a thickness of 3 to 50 µm.   4. The impact absorbing film according to claim 2, wherein the A) first elastic film and the A ′) second elastic film each independently have a thickness of 3 to 50 μm. 5.   The impact-absorbing film according to any one of claims 1 to 4, wherein the laminate has a thickness of 0.053 to 0.6 mm.   The A) first stretchable film and the A ′) second stretchable film are each independently formed of at least one selected from the group consisting of a polyurethane resin, an acrylic resin, and a silicone resin. It is better. The impact-absorbing film according to any one of claims 1 to 5, wherein the impact-absorbing film is formed having at least one selected from the group consisting of:   The impact-absorbing film according to any one of claims 1 to 6, wherein the foam (B) has at least one resin selected from the group consisting of a polyolefin resin, a polyurethane resin, and an acrylic resin.

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