CN107009698B

CN107009698B - Small electronic device case, method for molding same, and aluminum alloy rolled laminated sheet material for small electronic device case

Info

Publication number: CN107009698B
Application number: CN201610947840.8A
Authority: CN
Inventors: 竹内雅规
Original assignee: Showa Denko Packaging Co Ltd
Current assignee: Lishennoco Packaging Co ltd
Priority date: 2015-10-27
Filing date: 2016-10-25
Publication date: 2020-07-31
Anticipated expiration: 2036-10-25
Also published as: TW201718899A; JP6832102B2; JP2017081149A; CN107009698A; KR20170049410A; TWI657148B; KR102500876B1

Abstract

The present invention relates to a small electronic device case, a method of molding the same, and an aluminum alloy rolled laminated sheet material for use in the small electronic device case. Provided is a small-sized electronic device case which can be efficiently molded at low cost by drawing, is less likely to cause molding failure, does not cause damage to the surface by molding, and has excellent appearance. An aluminum alloy rolled laminated sheet material for forming a small electronic device case by drawing is composed of an aluminum alloy rolled sheet material having a 0.2% yield strength of 200MPa or more and a covering material laminated on at least one of both surfaces of the aluminum alloy rolled sheet material. The covering material is formed of any one of a synthetic resin film and a laminate in which synthetic resin films are laminated on both surfaces of a metal foil. The rolled aluminum alloy sheet has a fibrous crystal structure extending in a direction perpendicular to the thickness direction.

Description

Small electronic device case, method for molding same, and aluminum alloy rolled laminated sheet material for small electronic device case

Technical Field

The present invention relates to a housing for a small electronic device such as a tablet personal computer terminal, a portable communication terminal device, a notebook computer, a mobile phone, a portable music device, and a digital camera, a method for molding the housing, and an aluminum alloy rolled laminated sheet used as a molding material for the housing.

Background

Conventionally, as a case of a small electronic device, a case formed by cutting (cutting the entire surface) a thick plate-shaped aluminum alloy extruded material is known (for example, see patent document 1 below).

The housing is suitable for use as a housing for small electronic devices because of its excellent appearance, precision and strength.

Further, generally, drawing is widely performed as a means for forming a product having a predetermined shape from a metal plate material such as an aluminum alloy plate material.

[ Prior art documents ]

[ patent document ]

[ patent document 1] Japanese patent laid-open No. 2012-246555 (JP2012-246555A)

Disclosure of Invention

Problems to be solved by the invention

However, in the case of a small-sized electronic device case molded by cutting, it takes a long time to cut a material, so that the manufacturing efficiency is low, and a large amount of cutting chips are generated along with the cutting, and a large amount of energy is required to recover the cutting chips, resulting in a problem of high cost.

On the other hand, in the case of drawing, since the forming is performed in a short time, the manufacturing efficiency is excellent, and the manufacturing can be performed at low cost because no chips are generated in association with the working. However, the small electronic device case generally has a substantially square bottom wall in plan view and a side wall rising from a peripheral edge of the bottom wall. When a case of such a form is formed by drawing, cracks are likely to be generated at corner portions of the side walls, and the forming is likely to be poor.

In the case of drawing, the surface of the metal plate material is in sliding contact with the die, and therefore damage may occur on the surface of the molded product, thereby impairing the appearance of the product.

The purpose of the present invention is to provide a small-sized electronic device case that can be efficiently molded at low cost by drawing, is less likely to suffer from molding defects, does not cause surface damage due to molding, and has excellent appearance.

Means for solving the problems

To achieve the above object, the present invention is constituted by the following embodiments.

1) An aluminum alloy rolled laminated plate material for a small electronic device case, which is an aluminum alloy rolled laminated plate material for forming a small electronic device case by drawing, is composed of an aluminum alloy rolled plate material having a 0.2% yield strength of 200MPa or more and a covering material laminated on at least one of both surfaces of the aluminum alloy rolled plate material, the covering material being formed of one of a synthetic resin film and a laminate in which synthetic resin films are laminated on both surfaces of a metal foil.

2) The rolled aluminum alloy laminated sheet for a small electronic device case of 1) above, wherein the rolled aluminum alloy sheet has a fibrous crystal structure extending in a direction perpendicular to a thickness direction.

3) The aluminum alloy rolled laminated plate for a small electronic device case of the above 1) or 2), wherein the aluminum alloy rolled plate is formed of any 1 aluminum alloy of the following alloys: an Al-Mn-Mg alloy containing 0.2 to 0.7 mass% of Mnand 2.0 to 5.0 mass% of Mgand the balance of Al and unavoidable impurities; an Al-Si-Mg alloy containing 0.2 to 0.8 mass% of Si, 0.4 to 1.2 mass% of Mgand the balance of Al and unavoidable impurities; and an Al-Zn-Mg alloy containing 4.0 to 6.5 mass% of Zns, 0.5 to 3.0 mass% of Mgs, and the balance of Al and unavoidable impurities.

4) The aluminum alloy rolled laminated sheet material for a small electronic device case of any one of the above 1) to 3), wherein the thickness of the covering material is 0.05 times to 1.5 times the thickness of the aluminum alloy rolled sheet material.

5) The aluminum alloy rolled laminated sheet for a small electronic device case of any one of the above 1) to 4), wherein the aluminum alloy rolled sheet has a thickness of 0.5mm to 3.5 mm.

6) The aluminum alloy rolled laminated sheet material for a small-sized electronic device case of any one of the above 1) to 5), wherein a covering material formed of a polyester resin film or a polyamide resin film having a thickness of 50 μm to 100 μm is laminated on a surface which becomes an outer surface of the small-sized electronic device case among both surfaces of the aluminum alloy rolled sheet material.

7) The aluminum alloy rolled laminated sheet material for a small-sized electronic device case of any one of the above 1) to 6), wherein a covering material formed of a polyethylene resin film, a polypropylene resin film or a polyamide resin film having a thickness of 10 μm to 100 μm is laminated on a surface which becomes an inner surface of the small-sized electronic device case, among both surfaces of the aluminum alloy rolled sheet material.

8) A small electronic device case with a covering material, which is obtained by drawing the rolled aluminum alloy laminated plate material for a small electronic device case of any one of the above 1) to 7), wherein at least one of the inner and outer surfaces is covered with a covering material formed of a synthetic resin film or a laminate.

9) A small-sized electronic device case obtained by removing a covering material covering at least one of the inner and outer surfaces after drawing the rolled aluminum alloy laminated plate material for a small-sized electronic device case of any one of the above 1) to 7).

10) The small-sized electronic device case of the above 9) having a bottom wall and a side wall rising from a peripheral edge of the bottom wall, wherein a height of the side wall is 0.5mm to 25mm, and an angle of the side wall with respect to the bottom wall is 90 ° to 150 °.

11) A method of molding a small electronic device case, comprising subjecting the rolled aluminum alloy laminated sheet for a small electronic device case of any one of the above 1) to 7) to drawing.

ADVANTAGEOUS EFFECTS OF INVENTION

The rolled aluminum alloy laminated plate material for a housing of a small electronic device according to 1) above uses a material having a 0.2% proof stress (hereinafter referred to as "proof stress") of 200MPa or more as the rolled aluminum alloy plate material used as the material of the housing, and thus can secure a desired housing strength.

Further, according to the rolled aluminum alloy laminated plate material of the above 1), since the covering material having a small frictional resistance, which is formed of the synthetic resin film or the laminate in which the synthetic resin film is laminated on both surfaces of the metal foil, is laminated on at least one of both surfaces of the rolled aluminum alloy plate material, the occurrence of the molding failure is suppressed without generating wrinkles in the side wall of the case molded by the drawing work or cracks in the corner portion of the side wall, and not only the occurrence of the molding failure is prevented, but also the damage to the surface of the case due to the contact with the die can be prevented without impairing the appearance of the case.

According to the rolled aluminum alloy laminated plate material for a small electronic device case of the above 2), since the rolled aluminum alloy plate material has a fibrous crystal structure extending in a direction perpendicular to the thickness direction, the plate material strength with respect to bending becomes high, and molding defects such as wrinkles and cracks are less likely to occur.

The rolled aluminum alloy laminated sheet for a small-sized electronic device case according to the above 3), which is formed of 1 aluminum alloy of the Al — Mn — Mg alloy, the Al — Si — Mg alloy, and the Al — Zn — Mg alloy having the above respective compositions, can be favorably formed by drawing, and can provide a case having high precision and strength and excellent appearance.

The aluminum alloy rolled laminated sheet material for a small electronic device case according to the above 4), since the thickness of the covering material is 0.05 times to 1.5 times the thickness of the aluminum alloy rolled sheet material, the following problems can be avoided.

That is, if the thickness of the covering material is less than 0.05 times the thickness of the rolled aluminum alloy plate material, the covering material is broken and damaged at the position where the molded article and the die are in contact with each other. On the other hand, even if the thickness of the covering material is more than 1.5 times the thickness of the rolled aluminum alloy sheet material, no more preferable effect is obtained, and only the cost is increased.

The aluminum alloy rolled laminated sheet for a small electronic device case according to the above 5), the aluminum alloy rolled sheet having a thickness of 0.5mm to 3.5mm, so that the following problems can be avoided.

That is, if the thickness of the rolled aluminum alloy sheet is less than 0.5mm, the strength of the final product is insufficient. On the other hand, if the thickness of the rolled aluminum alloy sheet is more than 3.5mm, the radius of curvature (R) at the bent portion or corner portion becomes too large.

The aluminum alloy rolled laminated sheet material for a small electronic device case according to the above 6) can obtain the following effects. That is, when the aluminum alloy rolled laminate sheet is subjected to drawing processing to form a small electronic device case, a surface of the two surfaces of the sheet, which is an outer surface of the small electronic device case, is partially drawn by a die, and when a polyester resin film or a polyamide resin film having a thickness of 50 μm to 100 μm is used as a covering material covering the surface, the die is not broken by the drawing, so that damage to the surface of a molded product can be reliably avoided, an increase in cost due to an excessively large film thickness can be suppressed, and the film can be prevented from being lifted or peeled from a bent molded portion of the case due to an excessively large film rigidity.

The aluminum alloy rolled laminated sheet material for a small electronic device case according to the above 7) can obtain the following effects. That is, when the aluminum alloy rolled laminate sheet is subjected to drawing processing to form a small electronic device case, the surface of the two surfaces of the sheet which becomes the inner surface of the small electronic device case is not drawn by the die, but a curved portion is generated in the concave direction, and therefore, if a polyethylene resin film, a polypropylene resin film, or a polyamide resin film having a thickness of 10 μm to 100 μm is used as a covering material covering the surface, it is possible to avoid a situation in which the film is excessively rigid and lifted or peeled from the curved portion of the case, and it is possible to avoid a situation in which the curvature radius (R) of the curved portion of the case becomes large and a sharp shape cannot be obtained.

According to the small-sized electronic device case with a covering material of the above 8), not only can the aluminum alloy rolled sheet material by drawing be favorably molded, but also the surface is not damaged at the time of molding, and therefore, a case with high precision and high strength and a beautiful appearance can be obtained.

Further, according to the small-sized electronic device case with a cover material of the above 8), since the surface of the case is covered with the cover material, it is possible to prevent the surface from being damaged during storage, transportation, and the like.

According to the small-sized electronic device case of the above 9), not only can the aluminum alloy rolled sheet material by drawing be favorably molded, but also the surface is not damaged at the time of molding, storage, and transportation, and therefore, a case having high precision and high strength and a beautiful appearance can be obtained.

The small electronic device case according to 10) above, the height of the side wall is 0.5mm to 25mm, and the angle of the side wall with respect to the bottom wall is 150 °, so that the following problems can be avoided.

That is, if the height of the side wall is less than 0.5mm, the number of cut portions increases in the subsequent process. On the other hand, if the height of the side wall is larger than 25mm, the thickness of the small electronic device becomes large, which is not preferable.

Further, if the angle of the side wall with respect to the bottom wall is less than 90 °, that is, the side wall is inclined inward, wrinkles are generated at the corner portions, and the processing becomes difficult. On the other hand, if the angle of the side wall with respect to the bottom wall is larger than 150 °, the depth of the case becomes shallow, and the accommodation volume of the components of the small electronic device becomes small.

The method for molding a small-sized electronic device case according to 11) above can efficiently mold a small-sized electronic device case having high precision and high strength and a beautiful appearance at low cost by drawing.

Drawings

Fig. 1 is a partially enlarged sectional view showing a layer structure of an aluminum alloy rolled laminate sheet for a small electronic device case according to the present invention.

Fig. 2 is a vertical sectional view sequentially showing a step of forming a small electronic device case by drawing the same plate material.

Fig. 3 is a perspective view of a small electronic device case according to the present invention.

FIG. 4 is a perspective view showing a cross-sectional direction in a case where a rolled aluminum alloy sheet material is subjected to bending processing to observe a fibrous crystal structure in the cross section.

FIG. 5 is a photomicrograph of a cross section (cross-sectional direction with respect to the rolling direction: 90 ℃ C.) of a bent material (inner arc radius: 0mm) of the same rolled aluminum alloy sheet material.

FIG. 6 is a photomicrograph of a cross section (cross-sectional direction with respect to the rolling direction: 90 ℃ C.) of a bent material (inner arc radius: 0.4mm) of the same rolled aluminum alloy sheet.

FIG. 7 is a photomicrograph of a cross section (cross-sectional direction with respect to the rolling direction: 0 ℃ C.) of a bent material (inner arc radius: 0mm) of the same rolled aluminum alloy sheet.

FIG. 8 is a photomicrograph of a cross section (cross-sectional direction with respect to the rolling direction: 0 ℃ C.) of a bent material (inner arc radius: 0.4mm) of the same rolled aluminum alloy sheet.

Description of the reference numerals

(1): rolled laminated aluminum alloy sheet

(2): aluminum alloy rolled sheet

(3)(4): coating material

(30)(40): synthetic resin film

(31)(41): metal foil

(32)(33)(42)(43): synthetic resin film

(5): fixed female die

(6): movable male die

(20): small electronic equipment casing

(21): bottom wall

(22): side wall

(22a) The method comprises the following steps Corner portion (of side wall)

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to fig. 1 to 8.

Fig. 1 shows a layer structure of an aluminum alloy rolled laminate sheet 1 for a small electronic device case according to the present invention.

As shown in the figure, an aluminum alloy rolled laminated plate material 1 used for a small electronic device case is composed of an aluminum alloy rolled plate material 2 and covering

materials

3, 4 laminated on both surfaces of the aluminum alloy rolled plate material 2.

As the rolled aluminum alloy sheet 2, an aluminum alloy sheet having a 0.2% yield strength of 200MPa or more, preferably 250MPa or more, and more preferably 300MPa or more can be used. Thereby, a desired strength of the case can be obtained. The rolled aluminum alloy sheet 2 preferably has an elongation at break of 5% or more and 20% or less. This improves the formability of the drawing. Herein, "0.2% yield strength" and "elongation at break" were measured by a tensile test in a direction parallel to the rolling direction using a No. 5 test piece specified in JIS Z2241-2011.

The rolled aluminum alloy sheet material 2 has a fibrous crystal structure extending in a direction perpendicular to the thickness direction.

The fibrous crystal structure is formed by hot rolling the homogenized aluminum alloy ingot, heat treating the aluminum alloy ingot under predetermined conditions, and then cold rolling the aluminum alloy ingot. The above heat treatment is carried out by holding at 200 to 400 ℃ for 1 hour or more. By the above heat treatment, Mg can be made₂Si is finely and uniformly precipitated, and the processing strain existing in the rolled material can be reduced. By performing the subsequent cold working to work-harden the aluminum alloy sheet, a high-strength rolled aluminum alloy sheet can be obtained within a range that does not impair the subsequent formability.

The conditions for the homogenization treatment of the aluminum alloy ingot are not particularly limited, but the homogenization treatment is preferably carried out at 500 ℃ or higher for 2 hours or longer according to a conventional method.

In the hot rolling, in any rolling (Japanese: パス) step, the same effect as in quenching can be obtained by lowering the temperature during rolling under predetermined temperature conditions. Therefore, the temperature of the material before rolling is required to be 350 ℃ to 440 ℃ so as to maintain the solid solution state of Mg and Si. In order to set the finish rolling temperature to the above-mentioned temperature range of 200 ℃ to 400 ℃, forced cooling such as high-pressure shower water cooling may be immediately performed at the time of finish hot rolling. In order to obtain the quenching effect, the cooling rate between the rolling passes is set to 50 ℃/min or more, the finish rolling temperature is set to 250 ℃ to 340 ℃, the rolling speed of the rolling passes is set to 50 m/min or more, and the thickness of the finish plate is set to 10mm or less.

In cold rolling, the reduction ratio is set to 30% or more in order to obtain a predetermined strength by work hardening. The preferable reduction ratio is 50% or more.

Further, the alloy sheet after cold rolling may be subjected to final annealing at a temperature of 130 to 150 ℃ as required. By performing the heat treatment at a low temperature, age hardening can be performed to further improve the strength and the elongation. In addition, the present invention has an effect of stabilizing various mechanical properties.

As the rolled aluminum alloy sheet material 2, an aluminum alloy sheet material formed of any of the following aluminum alloys is suitably used.

i) An Al-Mn-Mg alloy containing 0.2 to 0.7 mass% of Mn, 2.0 to 5.0 mass% of Mg2, and the balance of Al and unavoidable impurities

ii) an Al-Si-Mg alloy containing 0.2 to 0.8 mass% of Si and 0.4 to 1.2 mass% of Mgand the balance of Al and unavoidable impurities

iii) an Al-Zn-Mg alloy containing 4.0 to 6.5 mass% of Zns, 0.5 to 3.0 mass% of Mgs, and the balance of Al and unavoidable impurities

Examples of the alloy of i) include an aluminum alloy containing 0.4 mass% or less of si, 0.4 to 0.6 mass% of mn, 4.0 to 4.9 mass% of mg, 0.4 mass% or less of fe, 0.05 to 0.25 mass% of cr, and 0.25 mass% or less of zns, with the balance being Al and unavoidable impurities.

Examples of the alloy of ii) include an aluminum alloy containing 0.2 to 0.6 mass% of si, 0.45 to 0.9 mass% of mgs, not more than 0.35 mass% of fe0.1 mass% of crs, not more than 0.1 mass% of zns, and the balance of Al and unavoidable impurities.

Examples of the alloy of iii) include an aluminum alloy containing 0.4 mass% or less of si, 2.1 to 2.9 mass% of mgs, 0.5 mass% or less of fe0.5 mass% or less of cus, 1.2 to 2.0 mass% of mns, 0.3 mass% or less of crs, 0.18 to 0.28 mass% of crs, 5.1 to 6.1 mass% of zns, and the balance of Al and inevitable impurities.

Among them, the rolled aluminum alloy sheet 2 made of an aluminum alloy containing 0.2 to 0.6 mass% of si, 0.45 to 0.9 mass% of mgs, not more than 0.35 mass% of fe0.1 mass% of cr0.1 mass% or less of zns, and the balance of Al and inevitable impurities is particularly suitable as a molding material for a housing of a small electronic device.

In addition, the thickness of the rolled aluminum alloy sheet material 2 to be used may be appropriately set depending on the molding conditions, the size of the housing as a molded article, and the like, and is preferably 0.5mm to 3.5mm, more preferably 0.8mm to 1.2 mm.

The

coating materials

3 and 4 are used for: the formability of the aluminum alloy rolled sheet 2 in drawing is improved; in addition to reducing the use of a lubricant during molding, the surface of the plate 2 is prevented from being damaged during molding, and the surface of the shell is protected after the shell is molded, for example, during storage and transportation.

As the

coating materials

3 and 4, there are cases where: as shown in fig. 1(a), in the case of using the

laminated bodies

3, 4 in which the

synthetic resin films

32, 33, 42, 43 are laminated on both surfaces of the metal foils 31, 41; and a case where

synthetic resin films

30 and 40 are used as shown in fig. 1 (b).

As the metal foils 31, 41 constituting the

laminated bodies

3, 4 of the covering material, the rolled aluminum alloy laminated plate material 1 for a small electronic device case of embodiment 1 shown in fig. 1(a) includes aluminum foil, stainless steel foil, and copper foil. Examples of the

synthetic resin films

32, 33, 42, and 43 of the

laminated bodies

3 and 4 include an unstretched polypropylene resin film (CPP), a polyethylene terephthalate resin film (PET), a nylon resin film (Ny), a polyimide resin film (PI), a polyethylene resin film (PE), and stretched films thereof. The metal foils 31 and 41 and the

synthetic resin films

32, 33, 42 and 43 can be laminated using an adhesive layer (not shown) formed of a polyester urethane resin (PAUR), an acrylic resin, an acid-modified polyolefin resin (APO), or the like, and a curing agent, for example.

As the aluminum alloy rolled laminate sheet 1 for a small electronic device case of the 2 nd embodiment shown in fig. 1(b), for example, any one of a polypropylene resin film, a polyester resin film, a polyamide resin film, a polyimide resin film, a polyethylene resin film, preferably a biaxially stretched polyethylene terephthalate resin film (PET), a biaxially stretched nylon resin film (ONy), a polyethylene resin film, a biaxially stretched polyamide resin film, a biaxially stretched polypropylene resin film (OPP), an unstretched polypropylene resin film (CPP), and an unstretched nylon resin film (CNy) can be used for the

synthetic resin films

30 and 40 constituting the covering

materials

3 and 4.

Further, it is preferable to use a synthetic resin film 30 having a thickness of 10 μm to 200 μm for the covering material 3 laminated on the surface (lower surface in fig. 1(b)) which becomes the outer surface of the small electronic device case out of both surfaces of the rolled aluminum alloy sheet material 2, and to use a synthetic resin film 40 having a thickness of 10 μm to 100 μm for the covering material 4 laminated on the surface (upper surface in fig. 1(b)) which becomes the inner surface of the small electronic device case.

The covering material 3 laminated on the surface (lower surface in fig. 1(b)) which becomes the outer surface of the small electronic device case, of the both surfaces of the rolled aluminum alloy sheet material 2, is preferably composed of a polyester resin film or a polyamide resin film having a thickness of 50 to 100 μm, and more preferably composed of a biaxially stretched polyethylene terephthalate resin film (PET), a biaxially stretched polyethylene naphthalate resin film (PEN), or a biaxially stretched nylon 6 resin film (ONy)30 having a thickness of 50 to 100 μm. For the above-mentioned film 30, those having a tensile strength of 180MPa to 330MPa and a tensile elongation at break of 80% to 180% can be suitably used. Among them, the film 30 having a ratio of MD/TD of tensile strength or tensile elongation at break in the range of 0.8 to 1.2 can be suitably used.

The covering material 4 laminated on the surface (upper surface in fig. 1(b)) which is the inner surface of the small electronic device case out of the two surfaces of the rolled aluminum alloy sheet material 2 is preferably made of a polyethylene resin film, a polypropylene resin film or a polyamide resin film having a thickness of 10 to 100 μm (more preferably 20 to 80 μm), and more preferably made of an unstretched polyethylene resin film, an unstretched polypropylene resin film (CPP), a stretched polypropylene resin film (OPP) or a stretched nylon resin film (ONy) 40. For the above-mentioned film 40, those having a Young's modulus of 30MPa to 400MPa are suitably used.

The covering material may be laminated on at least one of the two surfaces of the rolled aluminum alloy sheet material 2, more specifically, on the surface constituting the outer surface of the case, but from the viewpoint of improving the formability and protecting the surface of the case during and after forming, it is preferable to laminate the covering material on both surfaces of the rolled aluminum alloy sheet material 2 as shown in fig. 1.

When the clad materials are laminated on both surfaces of the rolled aluminum alloy sheet material 2, the 2 kinds of clad materials to be laminated on the respective surfaces may be the same or different in material/thickness.

It should be noted that when the bending strength of the rolled aluminum alloy plate material 2 is small and the thickness is small, the

synthetic resin films

30 and 40 may be used as the covering material (see fig. 1(b)), but when the bending strength of the rolled aluminum alloy plate material 2 is large and the thickness is large, the synthetic resin film used as the covering material may be broken at the time of drawing and wrinkles may be generated on the surface of the molded product, and therefore, the covering material is preferably constituted by the laminated body 3 and 4 (see fig. 1 (a)).

In consideration of the necessity of removing the covering

materials

3 and 4 from the surface after the case is molded, it is preferable that the covering

materials

3 and 4 are laminated on the surface of the rolled aluminum alloy sheet material 2 via the

adhesive layers

34 and 44 as shown in fig. 1. For the

adhesive layers

34 and 44, for example, a urethane adhesive, an acrylic adhesive, or a rubber adhesive is used. The adhesion of the

adhesive layers

34, 44 to the rolled aluminum alloy sheet 2 is preferably 0.5N/25mm to 15N/25mm (more preferably 1N/25mm to 10N/25 mm). Herein, "adhesive force" is according to JIS Z0237: 2000. adhesion as represented by 180 ° peel adhesion. If the adhesive strength of the

adhesive layers

34 and 44 is less than 0.5N/25mm, the covering

materials

3 and 4 are liable to be unintentionally peeled off from the rolled aluminum alloy sheet material 2 before the case is formed, for example, when the rolled aluminum alloy laminated sheet material 1 is handled, whereas if the adhesive strength of the

adhesive layers

34 and 44 is more than 15N/25mm, workability in peeling and removing the covering

materials

3 and 4 after the case is formed is lowered, and moreover, there is a possibility that a part of the adhesive remains on the surface of the case and a trouble occurs in polishing or the like in a subsequent step.

The thickness of the covering

materials

3, 4 is preferably 0.05 to 1.5 times the thickness of the rolled aluminum alloy sheet material 2, and more preferably 0.2 to 1.0 times the thickness of the rolled aluminum alloy sheet material 2.

Fig. 2 shows a process of forming a small electronic device case by drawing the rolled aluminum alloy laminated sheet material 1.

First, a rolled aluminum alloy laminated plate 1 cut into a substantially square shape with a predetermined size is set on the upper surface of a fixed female die (die) 5 on the lower side of a die (see fig. 2 (a)). Here, it is preferable that a lubricant made of, for example, a silicone-based lubricant, a mineral oil, or a synthetic petroleum-based lubricant is applied in advance to at least the lower surface that becomes the outer side of the case, that is, the surface of the lower covering material 3, of the upper and lower surfaces of the rolled aluminum alloy laminated sheet material 1, whereby the formability can be further improved.

When the movable punch (punch) 6 on the upper side of the die is lowered, the portion other than the peripheral edge portion of the rolled aluminum alloy laminated plate material 1 is pressed downward by the tip end portion of the punch 6, whereby the straight portion of the peripheral edge portion can be bent upward and the corner portion of the peripheral edge portion can be drawn (see fig. 2 (b)). At this time, since both surfaces of the rolled aluminum alloy sheet material 2 are coated with the

coating materials

3 and 4, the occurrence of wrinkles can be suppressed, and as a result, cracks are not generated. Further, since the surface of the rolled aluminum alloy sheet 2 is not in direct contact with the female die 5 and the male die 6, it is not abraded and damaged.

Thereby, the small electronic device case 20 with the covering

materials

3 and 4 is obtained. Since the surface of the small electronic device case 20 is covered with the covering

materials

3 and 4, it is possible to maintain a beautiful state without being damaged by contact with another object, for example, during storage or transportation.

Fig. 3 shows a small electronic device housing 20. The housing 20 is obtained as follows: the

covers

3 and 4 are peeled off from the inner and outer surfaces of the small electronic device case 20 with the

covers

3 and 4, and then partially cut to be finally molded (japanese laid-in molding), and the surface is further subjected to alumite (alumite) treatment.

The small electronic device case 20 is composed of a bottom wall 21 having a substantially square shape in plan view, and 4 side walls 22 rising from 4 sides of the bottom wall 21. The ends of adjacent side walls 22 are continuous with each other, and the bottom wall 21 is surrounded by 4 side walls 22.

The height of the side wall 22 (in other words, the molding height) is 0.5mm to 25mm, preferably 1mm to 15mm, and more preferably 2mm to 10 mm.

The angle of the side wall 22 with respect to the bottom wall 21 is 90 ° to 150 ° (about 90 ° in the illustrated case), preferably 90 ° to 120 °, and more preferably 90 ° to 100 °.

The bottom wall 21 and the side wall 22 are rounded at their boundary portions (japanese: アール), and the side wall 22 is also rounded at its corner portions 22 a. In these circular arc portions, the fibrous crystalline structure extends along the circular arc.

The fibrous crystal structure can be confirmed by observing the cross section of the rolled aluminum alloy sheet 2 or the cross section of the case 20 after the aluminum alloy sheet 2 is drawn and molded by using a polarization microscope.

Preferably, the fibrous crystalline structure is observed in a cross section obtained by cutting the rolled aluminum alloy sheet material in any direction such as 0 °, 90 °, 45 °, 135 ° with respect to the rolling direction. The same can be observed in the bent portion and the corner portion.

Specifically, for example, as shown in fig. 4(a) and (b), an aluminum alloy rolled sheet material 2 having a thickness of 0.25mm is bent so that the inner circular radius is 0mm or 0.4mm, and a cross section obtained by cutting the bent material in a direction (Y) at 90 ° (right angle) or 0 ° (parallel) with respect to the rolling direction (X) is observed with a polarization microscope. From the photomicrographs of fig. 5 to 8, it is seen that, in any one of the cross sections of 0mm in the inner arc radius, 90 ° (fig. 5) in the cross-sectional direction with respect to the rolling direction, 0.4mm in the inner arc radius, 90 ° (fig. 6) in the cross-sectional direction with respect to the rolling direction, 0mm in the inner arc radius, 0 ° (fig. 7) in the cross-sectional direction with respect to the rolling direction, and 0.4mm in the inner arc radius, 0 ° (fig. 8) in the cross-sectional direction with respect to the rolling direction, the fibrous crystalline structure extends along the arc in the direction perpendicular to the thickness direction of the sheet material.

[ examples ]

Next, specific examples of the present invention will be explained. The present invention is not limited to these examples.

< example 1>

An aluminum alloy ingot containing 0.2 to 0.6 mass% of Si, 0.45 to 0.9 mass% of Mg0.35 mass% or less of Fe0.35 mass% or less, 0.1 mass% or less of Cr0, and 0.1 mass% or less of Zn0.1 mass% with the balance being Al and inevitable impurities is homogenized at 580 ℃ for 10 hours, then surface-cut, preheated at 500 ℃ to start hot rolling. The final pass start temperature of the hot rolling was set at 400 ℃, and the steel sheet was cooled at a rate of 80 ℃/min after the rolling. Thereafter, the heat treatment was carried out at 240 ℃ for 4 hours. Thereafter, cold rolling was performed at a reduction ratio of 86%. Thus, a rolled aluminum alloy sheet having a 0.2% yield strength of 310MPa and an elongation at break of 7% and a thickness of 1mm was obtained.

The cross section of the plate was observed by an optical microscope and a polarizer, and as a result, a fibrous crystal structure extending in a direction perpendicular to the thickness direction was observed.

A laminate which is laminated as a covering material on the lower surface of a rolled aluminum alloy plate material constituting the outer surface of a small-sized electronic device case via a pressure-sensitive adhesive layer formed of an acrylic pressure-sensitive adhesive, the laminate comprising: an unstretched polypropylene resin film having a thickness of 30 μm was laminated on one surface of an aluminum foil having a thickness of 120 μm via an adhesive layer composed of a polyester urethane resin and 1, 6-hexamethylene diisocyanate, and an unstretched polypropylene resin film having a thickness of 200 μm was laminated on the other surface thereof via an adhesive layer.

Further, a nylon resin film having a thickness of 30 μm as a covering material was laminated on the upper surface of the rolled aluminum alloy plate material constituting the inner surface of the small electronic device case via an adhesive layer formed of an acrylic adhesive.

The rolled aluminum alloy laminated plate thus obtained was cut into a substantially square shape having a longitudinal length of 150mm, a transverse length of 82mm and a corner portion arc radius of 14.5mm, to prepare a molding material of example 1.

< example 2>

An aluminum alloy ingot containing Si at most 0.4 mass%, Mn at 0.4 to 0.6 mass%, Mg4.0 to 4.9 mass%, Fe0.4 mass%, Cr0.05 to 0.25 mass%, and Zn0.25 mass% or less, with the balance being Al and unavoidable impurities, is homogenized at 580 ℃ for 10 hours, then subjected to surface cutting, preheated at 500 ℃ to start hot rolling. The final pass start temperature of the hot rolling was set at 400 ℃, and the steel sheet was cooled at a rate of 80 ℃/min after the rolling. Thereafter, the heat treatment was carried out at 240 ℃ for 4 hours. Thereafter, the steel sheet was cold-rolled at a reduction ratio of 79%, and then subjected to final annealing at 130 ℃ for 4 hours. Thus, a rolled aluminum alloy sheet having a 0.2% yield strength of 210MPa and an elongation at break of 7% and a thickness of 1.5mm was obtained.

Nylon resin films having a thickness of 90 μm as covering materials were laminated on both upper and lower surfaces of the rolled aluminum alloy sheet via pressure-sensitive adhesive layers made of acrylic pressure-sensitive adhesives.

The rolled aluminum alloy laminated plate thus obtained was cut into a substantially square shape having a longitudinal length of 150mm, a transverse length of 82mm and a corner portion arc radius of 14.5mm, to prepare a molding material of example 2.

< example 3>

An aluminum alloy cast ingot containing 0.4 mass% or less of si, 2.1 to 2.9 mass% of mgs, 0.5 mass% or less of fe0, 1.2 to 2.0 mass% of cus, 0.3 mass% or less of mns, 0.18 to 0.28 mass% of crs, 5.1 to 6.1 mass% of zns, and the balance of Al and inevitable impurities was rolled in the same steps and conditions as in example 2, whereby a rolled aluminum alloy sheet having a 0.2% yield strength of 550MPa and an elongation at break of 9% and a thickness of 1.5mm was obtained.

A nylon resin film having a thickness of 90 μm as a covering material was laminated on the lower surface of a rolled aluminum alloy sheet material constituting the outer surface of a small electronic device case via an adhesive layer formed of an acrylic adhesive.

The rolled aluminum alloy laminated plate thus obtained was cut into a substantially square shape having a longitudinal length of 150mm, a transverse length of 82mm and a corner portion arc radius of 14.5mm, to prepare a molding material of example 3.

< example 4>

The same rolled aluminum alloy sheet as in example 1 was prepared.

The rolled aluminum alloy laminated plate thus obtained was cut into a substantially square shape having a longitudinal length of 150mm, a transverse length of 82mm and a corner portion arc radius of 14.5mm, to prepare a molding material of example 4.

< comparative example 1>

An aluminum alloy extruded sheet having a thickness of 2mm and a 0.2% proof stress of 230MPa and an elongation at break of 14%, which sheet is formed of an aluminum alloy containing not more than 0.4% by mass of Si, 0.4 to 1.0% by mass of Mn4.0 to 4.9% by mass of Mg4.0 to 4.9%, not more than 0.4% by mass of Fe0.4%, 0.05 to 0.25% by mass of Cr0.25%, and not more than 0.25% by mass of Zn0.25% with the balance being Al and inevitable impurities, is prepared. The sheet material is an extrusion-molded sheet material and does not have a fibrous crystal structure extending in a direction perpendicular to the thickness direction.

On both upper and lower surfaces of the aluminum alloy extruded sheet, a nylon resin film having a thickness of 90 μm as a covering material was laminated via adhesive layers formed of an acrylic adhesive.

The aluminum alloy extruded laminate sheet thus obtained was cut into a substantially square shape having a longitudinal length of 150mm, a transverse length of 82mm and a corner portion arc radius of 14.5mm, to prepare a molding material of comparative example 1.

< comparative example 2>

An aluminum alloy extruded sheet having a 0.2% yield strength of 510MPa and an elongation at break of 11% and a thickness of 1.5mm, which is formed of an aluminum alloy containing 0.4% by mass or less of Si, 2.1 to 2.9% by mass of Mg2.1, 0.5% by mass or less of Fe0.5, 1.2 to 2.0% by mass of Cu1, 2.3% by mass or less of Mn0.3, 0.18 to 0.28% by mass of Cr0.1 to 6.1% by mass of Zn5.1, and the balance being Al and unavoidable impurities, is prepared. The sheet material is an extrusion-molded sheet material and does not have a fibrous crystal structure extending in a direction perpendicular to the thickness direction.

The aluminum alloy extruded plate was cut into a substantially square shape having a longitudinal length of 150mm, a transverse length of 82mm and a corner portion arc radius of 14.5mm, to prepare a molding material of comparative example 2.

< comparative example 3>

An aluminum alloy ingot containing 0.2 to 0.6 mass% of Si, 0.45 to 0.9 mass% of Mg0.35, Fe0.35 or less, Cr0.1 or less, Zn0.1 or less, and the balance of Al and inevitable impurities is homogenized at 580 ℃ for 10 hours, then subjected to surface cutting, preheated at 500 ℃ to start hot rolling. The final pass start temperature of the hot rolling was set at 400 ℃, and the steel sheet was cooled at a rate of 80 ℃/min after the rolling. Thereafter, the heat treatment was carried out at 240 ℃ for 4 hours. Thereafter, the steel sheet was cold-rolled at a reduction ratio of 57%, and then heat-treated at 250 ℃ for 2 hours. Thus, a rolled aluminum alloy sheet having a 0.2% yield strength of 150MPa and an elongation at break of 14% and a thickness of 3mm was obtained. The sheet material is a sheet material which has been subjected to a natural aging treatment after cold rolling, and does not have a fibrous crystal structure extending in a direction perpendicular to the thickness direction.

On both upper and lower surfaces of the rolled aluminum alloy sheet, a nylon resin film having a thickness of 30 μm as a covering material was laminated via an adhesive layer formed of an acrylic adhesive.

The rolled aluminum alloy laminated plate thus obtained was cut into a substantially square shape having a longitudinal length of 150mm, a transverse length of 82mm and a corner portion arc radius of 14.5mm, to prepare a molding material of comparative example 3.

< comparative example 4>

A rolled aluminum alloy sheet having a thickness of 2mm and a 0.2% yield strength of 145MPa and an elongation at break of 12%, which is formed from an aluminum alloy containing 0.2 to 0.6% by mass of Si, 0.45 to 0.9% by mass of Mg0.45, Fe0.35 or less, Cr0.1 or less, Zn0.1 or less and the balance Al and unavoidable impurities, is prepared. The sheet material was cold-rolled (reduction ratio: 33%) into an extruded sheet material, and had no fibrous crystal structure extending in a direction perpendicular to the thickness direction.

The rolled aluminum alloy laminated plate thus obtained was cut into a substantially square shape having a longitudinal length of 150mm, a transverse length of 82mm and a corner portion arc radius of 14.5mm, to prepare a molding material of comparative example 4.

< Molding of Small electronic device case >

The molding materials of examples 1 to 4 and comparative examples 1 to 4 were subjected to drawing using a drawing apparatus shown in fig. 2, and thereby molded into a small-sized electronic device case having a vertical length of 140.5mm, a horizontal length of 70.5mm, a side wall height (molding height) of 7mm, and a side wall corner portion arc radius of 2 mm. The side walls are at an angle of 90 deg. relative to the bottom wall.

As a result of visual observation of each of the molded cases, no wrinkles or cracks were generated at the corner portions of the side walls, and no damage was observed on the outer surfaces of the side walls due to contact with the lower mold in the cases formed from the molding materials of examples 1 to 4.

On the other hand, in the case formed of the molding materials of comparative examples 1 to 4, wrinkles and cracks were generated at the corner portions of the side walls. In addition, in the case of the cases formed of the molding materials of comparative examples 1, 3 and 4, although no damage was observed on the outer surfaces of their side walls, damage due to contact with the lower mold was formed on the outer surfaces of the side walls of the case formed of comparative example 2.

Industrial applicability

The present invention can be suitably applied to molding of housings of small electronic devices such as tablet personal computer terminals, portable communication terminal devices, notebook computers, mobile phones, portable music devices, and digital cameras.

Claims

1. An aluminum alloy rolled laminated plate material for a small-sized electronic device case, which is an aluminum alloy rolled laminated plate material for forming a small-sized electronic device case by drawing, the aluminum alloy rolled laminated plate material for a small-sized electronic device case being composed of an aluminum alloy rolled plate material having a 0.2% yield strength of 200MPa or more and a covering material laminated on at least one of both surfaces of the aluminum alloy rolled plate material via an adhesive layer, the covering material being formed of one of a synthetic resin film and a laminated body in which the synthetic resin film is laminated on both surfaces of a metal foil, the adhesive layer having an adhesive force of 0.5N/25mm to 15N/25mm with respect to the aluminum alloy rolled plate material, wherein, after forming the small-sized electronic device case by drawing, the covering material is peeled off from the aluminum alloy rolled plate material and removed,

the rolled aluminum alloy sheet material has a fibrous crystal structure extending in a direction perpendicular to the thickness direction, and is formed from any 1 of the following alloys, in any cross section obtained by cutting the sheet material in any direction with respect to the rolling direction: an Al-Mn-Mg alloy containing 0.2 to 0.7 mass% of Mnand 2.0 to 5.0 mass% of Mgand the balance of Al and unavoidable impurities; an Al-Si-Mg alloy containing 0.2 to 0.8 mass% of Si, 0.4 to 1.2 mass% of Mgand the balance of Al and unavoidable impurities; and an Al-Zn-Mg alloy containing 4.0 to 6.5 mass% of Zns, 0.5 to 3.0 mass% of Mgs, and the balance of Al and unavoidable impurities.

2. The aluminum alloy rolled laminated sheet for a small electronic device case as claimed in claim 1, wherein the thickness of the covering material is 0.05 times to 1.5 times the thickness of the aluminum alloy rolled sheet.

3. The aluminum alloy rolled laminated sheet for a small electronic device case as claimed in claim 1, wherein the aluminum alloy rolled sheet has a thickness of 0.5mm to 3.5 mm.

4. The rolled aluminum alloy laminated plate material for a small electronic device case according to claim 1, wherein a covering material formed of a polyester resin film or a polyamide resin film having a thickness of 50 μm to 100 μm is laminated on a surface which becomes an outer surface of the small electronic device case, of both surfaces of the rolled aluminum alloy plate material, via an adhesive layer.

5. The rolled aluminum alloy laminated plate material for a small electronic device case according to claim 1, wherein a covering material formed of a polyester resin film or a polyamide resin film having a thickness of 50 μm to 100 μm is laminated on a surface which becomes an outer surface of the small electronic device case, of both surfaces of the rolled aluminum alloy plate material, via an adhesive layer.

6. The rolled aluminum alloy laminated plate material for a small electronic device casing according to claim 1, wherein a covering material formed of a polyethylene resin film, a polypropylene resin film or a polyamide resin film having a thickness of 10 μm to 100 μm is laminated on a surface which becomes an inner surface of the small electronic device casing, among both surfaces of the rolled aluminum alloy plate material, via an adhesive layer.

7. A small electronic device case with a covering material, which is obtained by drawing the rolled aluminum alloy laminated plate material for a small electronic device case according to any one of claims 1 to 6, and at least one of the inner and outer surfaces of which is covered with a covering material formed of a synthetic resin film or a laminate.

8. A small electronic device case obtained by removing a covering material covering at least one of the inner and outer surfaces after subjecting the rolled aluminum alloy laminated plate material for a small electronic device case described in any one of claims 1 to 6 to drawing.

9. A small electronic device housing as claimed in claim 8, having a bottom wall and a side wall rising at a peripheral edge of the bottom wall, the side wall having a height of 0.5mm to 25mm and an angle of 90 ° to 150 ° with respect to the bottom wall.

10. A method of molding a small electronic device case, comprising subjecting the rolled aluminum alloy laminated sheet for a small electronic device case as defined in any one of claims 1 to 6 to drawing.