JP2002279752A - Aluminum alloy plate for shutter of recording medium case - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy plate for a shutter of a recording medium case, satisfying the characteristics including lightness, rigidity, scratch resistance, punching and bending workability which are required for the aluminum alloy plate for the shutter. SOLUTION: A chromate coating film and a synthetic resin coating film are provided on the surface to be an outer surface of the shutter of an aluminum alloy substrate. The aluminum alloy substrate contains 2.2-2.8 mass% Mg, 0.35-0.55 mass% Mn, 0.1-0.4 mass% Fe and the rest consisting of aluminum and inevitable impurities. The chromate coating film has 50 mg/m<2> thickness expressed by chromium deposit. The synthetic resin coating film has 0.5-3 μm film thickness. The total aluminum alloy substrate has 300-350 MPa tensile strength.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suitable as a material for a shutter provided in a case for storing a recording medium such as a magnetic disk such as a flexible (floppy (registered trademark)) disk and an optical disk such as an MO disk and a mini disk. In particular, the present invention relates to an aluminum alloy plate for a shutter of a recording medium case having excellent punching workability and bending workability.

[0002]

2. Description of the Related Art In a magnetic disk such as a flexible (floppy) disk and an optical disk such as an MO disk and a mini disk, information is recorded in a synthetic resin case 2 as shown in FIG. A recording medium 3, such as a magnetic disk or an optical disk (recording disk), is stored. When writing or reading information, the recording medium 3 in the case 2
The magnetic head or the optical head is brought close to the magnetic disk or the optical disk medium 3 for reading and writing. Therefore, these cases 2 are provided with openings (windows) as windows for disposing the magnetic head or the optical head close to the recording medium 3, and the shutter 1 is provided for opening and closing the openings. Have been.

[0003] The shutter 1 has a perspective view of FIG.
As shown in the cross-sectional view of FIG. 2, the cross-sectional shape is a U-shaped plate, and the case 2 is sandwiched between the pair of surfaces.
By sliding by being guided by the guide groove provided in the case 2, the window is opened at a position where the window of the case 2 and the window 4 of the shutter 1 are aligned, and the window of the case 2 is always closed. I have to.

[0004] The function required of the shutter is to open and close when necessary and to protect the magnetic surface.
Further, since the shutter slides while being guided on the case, it is necessary that the shutter be lightweight and have high rigidity. As a material for the shutter, a material made of stainless steel or a synthetic resin such as polystyrene or ABS (acrylonitrile-butadiene-styrene copolymer) has been used. However, stainless steel shutters
Relatively heavy, fingerprints tend to be formed when the surface is touched by hand, and the appearance is likely to deteriorate. In addition, polystyrene and ABS shutters have low rigidity, are easily charged,
It is harmful to the magnetic surface because dust and dirt tend to adhere.

[0005] Therefore, in recent years, a lightweight and rigid aluminum alloy plate has been used as a shutter material instead of stainless steel and synthetic resin.

When an aluminum alloy plate is used for a shutter, if the aluminum alloy plate is exposed on the surface of the shutter, the surface has low lubricity and low surface hardness, so that the wear resistance is insufficient. In each manufacturing process, such as processing to the shutter, transporting the processed product, assembling into the case, and final inspection of the magnetic disk and optical disk products, the aluminum alloy plate surface is easily scratched and harmful wear powder is likely to appear on the magnetic surface. Become. In addition, the appearance of the shutter significantly impairs the appearance of the shutter. And this problem is not only in the manufacturing process, but also in the contact between shutters in carrying,
Furthermore, it is caused by contact with mechanical parts at the time of insertion / removal of a read / write device such as a word processor and a personal computer in use.

For this reason, various techniques have been proposed for preventing scratches on the aluminum alloy plate for the shutter and for improving the adhesiveness of the UV curable ink. For example, in JP-A-3-73479 and JP-A-6-346178, an acrylic-based,
It has been proposed to coat a synthetic resin selected from the group consisting of acrylic ester, epoxy and urethane. It has also been proposed to provide a surface hardened coating on the surface of an aluminum alloy plate in order to improve abrasion resistance (JP-A-6-68638). Still further, there has been proposed an aluminum alloy plate provided with an anodized film on its surface (Japanese Patent Application Laid-Open Nos. 6-111516 and 6-162710).

Further, the method disclosed in Japanese Patent Application Laid-Open No. 6-68638, in which a surface hardened coating is provided on the surface of an aluminum alloy plate, is excellent in abrasion resistance and is prevented from being flawed, but the aluminum alloy plate is bent by 90 °. Processing, Figure 3
When processing into a shutter having a U-shape in cross section as shown in FIG. 5, cracks occur in the film at the 90 ° bending inner corners 5 and the film peels off, thereby causing harmful dust and dust on the magnetic surface. Is more likely to occur.

In the method disclosed in JP-A-6-111516 and JP-A-6-162710 in which an anodic oxide film is provided on the surface of an aluminum alloy plate, the film is cracked at the above-mentioned 90 ° bending inner corner 5, In addition, the peeling of the film easily causes dust and dust harmful to the magnetic surface. Also, the surface of the anodic oxide film tends to produce interference colors,
There are also cosmetic problems. Further, since anodized film processing requiring stable power and processing time is performed, there is a problem that manufacturing cost is increased.

[0010]

The aluminum alloy for a shutter is disclosed in, for example, Japanese Patent No. 2925891 and Japanese Patent No. 2925 for the purpose of obtaining high rigidity.
954, Mg: 3.0 to 6.0% by mass
And an aluminum alloy containing aluminum and unavoidable impurities in the balance. Mg is an important element for obtaining strength. In this case, since the amount of Mg added is too large and the strength is too high, the blade of a processing tool (cutting edge) is used during punching when forming a shutter. Since the abrasion of the tip is promoted, and the tip of the blade is worn out after continuous molding, and sagging occurs (R increases), there is a problem that burrs are easily generated on the punched shutter end face. If burrs are generated on the punched shutter end surface, there is a problem that the burrs damage other shutter surfaces during the subsequent assembling process, and the appearance is impaired.

[0011] The applicant of the present application has coated a surface of an aluminum alloy plate with a polyester resin having higher hardness and higher abrasion resistance than other resins such as acrylic resin, acrylic epoxy resin, urethane resin and the like. Has proposed an aluminum alloy plate for a shutter in which a chromate film is provided to improve the adhesion of the polyester resin (Japanese Patent Application No. Hei 8-8).
220228). Further, in order to improve the lubricity of the resin film on the surface of the aluminum alloy plate, polymer PE (polyethylene) wax is contained in the resin film having a pencil hardness of 5H or more.
An aluminum alloy plate for a shutter containing a lubricant such as PTEF wax and fluorine-based wax has been proposed (Japanese Patent Application No. 9-36569).

Furthermore, in order to improve the solvent solubility and hardness of the resin film on the surface of the aluminum alloy plate, an aluminum alloy plate for a shutter in which a specific polymer vinyl compound contains a metal chelate compound has been proposed. Nippon 9
-232335).

Further, in order to prevent scratches, an aluminum alloy plate for a shutter in which a thermosetting resin film containing inorganic fine particles having a specific average particle size and a lubricant is provided on the surface of the aluminum alloy plate has been proposed. 9-305381
issue).

Furthermore, in order to improve the adhesiveness of the UV curable ink, an aluminum alloy plate for a shutter in which a polyester urethane-based resin film having an acrylate group as a functional group is provided on the surface of the aluminum alloy plate has been proposed (Japanese Patent Application No. 2002-313,197). Hei 10-197412).

However, in the prior invention proposed by the present applicant, not only the characteristics such as lightness and rigidity required as an aluminum alloy plate for a shutter, but also all of the workability such as punching and bending. However, it cannot be said that these characteristics are satisfied, and further improvement of each characteristic is desired.

The present invention has been made in view of the above-mentioned problems, and is directed to a recording medium case which satisfies all the characteristics of lightness, rigidity, punching workability, and bending workability required for an aluminum alloy plate for a shutter. An object of the present invention is to provide an aluminum alloy plate for a shutter.

[0017]

According to the present invention, an aluminum alloy plate for a shutter of a recording medium case according to the present invention comprises Mg: 2.2.
And 2.8% by mass, Mn: 0.35 to 0.55% by mass, Fe: 0.1 to 0.4% by mass, the balance being an aluminum alloy substrate having a composition of aluminum and unavoidable impurities. The aluminum alloy substrate is provided as a first layer on at least the surface of the recording medium case on the outer surface side of the shutter, and has a chromium adhesion amount of 5 to 50
mg / m ² of a chromate film, a synthetic resin film provided as a second layer on a surface on the outer surface side of the shutter,
And the total tensile strength is 300 to 350 MPa.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The aluminum alloy plate for a shutter of a recording medium case according to the present invention has an aluminum alloy substrate and a chromate film as a first layer formed on at least a surface of the aluminum alloy substrate on the outer surface side of the shutter of the recording medium case. A synthetic resin film is formed as a second layer on the film.

First, with respect to the aluminum alloy substrate of the present invention, reasons for adding the components of the alloy and reasons for limiting the composition will be described.

Mg content of aluminum alloy substrate: 2.
2 to 2.8% by mass Mg is an essential component in the present invention because it has the effect of promoting work hardening when cold rolling an aluminum alloy sheet and improving the material strength. However, M
If the content of g is less than 2.2% by mass, a sufficient strength improving effect cannot be obtained, and the rigidity of the shutter becomes insufficient. For example, when the recording medium case is dropped, the shutter is deformed and easily comes off. Is generated. On the other hand, if Mg is added excessively, the strength is too high, so that during the punching process when forming the shutter, the abrasion of the blade tip of the processing tool (cutting blade) is promoted, and after continuous molding, the blade tip wears. Since sagging occurs (R increases), there is a problem that burrs are likely to occur on the punched shutter end surface. Therefore, the upper limit of the amount of added Mg is 2.80% by mass.
Need to be regulated. Therefore, the added amount of Mg is set in the range of 2.2 to 2.8% by mass.

Mn content of aluminum alloy substrate: 0.
Addition of 35 to 0.55% by mass Mn improves the cuttability at the time of punching.
In the present invention, Mn is contained as an essential component because it has an effect on the generation of -Fe-Mn-based crystals and the improvement of the material strength of the aluminum alloy substrate. Al-Fe-Mn
The generation of system crystallized material improves the cutting performance of the aluminum alloy plate, and reduces the load on the cutting tool edge during punching.This reduces wear on the cutting tool edge and reduces the tip of the cutting edge after continuous forming. Burrs are prevented from being generated on the punched shutter end surface. In order for the effect of improving the cutting property to appear, it is necessary to add at least 0.35% by mass of Mn. However, Mn was 0.55% by mass.
If added in excess, the number of giant crystallized substances and the number of crystallized substances will increase, the formability will decrease, and cracks will occur in the bent part when bending the shutter into a U-shape. Problem arises. Therefore, the added amount of Mn is 0.3
The range is 5 to 0.55% by mass.

The Fe content of the aluminum alloy substrate: 0.
Addition of 1 to 0.4 mass% Fe improves the cuttability at the time of punching.
-It has a great effect on the generation of Fe-Mn-based crystals and the refinement of crystal grains for improving the formability of the aluminum alloy substrate. The crystal grains are refined as the amount of Fe added increases. However, if the added amount of Fe is less than 0.1% by mass, the effect is not recognized. If the added amount exceeds 0.4% by mass, the number of giant crystallized substances and the number of crystallized substances increase. This leads to a reduction in moldability. Therefore, the added amount of Fe is set in the range of 0.1 to 0.4% by mass.

On the surface of the aluminum alloy substrate having such a limited composition, a chromate film of 5 to 50 mg / m ^{2 in} terms of the amount of chromium is provided as a first layer,
As the layer, for example, a synthetic resin film having the following composition is provided.
The synthetic resin film has an acrylate-modified polyester urethane-based resin, and has an average particle diameter of 1 to 100 parts by weight of the acrylate-modified polyester-urethane-based resin.
It has 5 to 20 parts by weight of inorganic fine particles of 0 μm or less and 0.5 to 3 parts by weight of a polyethylene oxide-based lubricant. Then, the synthetic resin film is coated with 0.5 to 3 μm.
By providing a film thickness of m, characteristics excellent in punching workability, bending workability, scratch resistance, printability and solvent solubility are obtained. However, the composition and thickness of the synthetic resin film are not limited to the above, and a synthetic resin film having another composition and thickness may be provided.

By providing a chromate film of 5 to 50 mg / m ^{2 in} terms of the amount of chromium deposited as a first layer on the surface of the aluminum alloy substrate, the interlayer adhesion between the aluminum alloy substrate and the synthetic resin film provided as the second layer is improved. This has the effect of improving the quality of the film, making it less likely to cause peeling due to cracking of the film during bending, and also less likely to cause flaws on the material surface.

Next, each component of the synthetic resin film provided as the second layer in this embodiment will be described.

Acrylate-modified polyester urethane
The resin polyester urethane-based resin has a high proportion of an aliphatic component in the molecule of the polyester portion, and further has a two-dimensional ester bond, so that it is a linear high molecular weight resin, and thus exhibits high elongation characteristics. Due to this effect, cracking and peeling of the film at the bent portion during bending are suppressed. Furthermore, urethane bonds are relatively strong as compared with other resin bonds, and exhibit high strength due to intermolecular interaction between urethane bonds. Due to this effect, the hardness of the film is increased, and the surface of the material is hardly flawed, and the coated synthetic resin film is hardly eluted in the solvent washing step.

Inorganic fine particles As the inorganic fine particles, one or more selected from colloidal silica, talc, mica and the like can be used. These substances have relatively high hardness, and by including these substances in the synthetic resin film, the surface hardness of the material is further increased, and there is an effect that scratches are less likely to occur. I do not care.

By adding a lubricant to the polyethylene oxide-based lubricant synthetic resin film, the lubricity of the material surface is improved. The improvement in lubricity of the material surface has the effect of making it difficult for scratches to occur on the material surface, and also reduces the load on the cutting tool edge during punching. This has the effect of suppressing the occurrence of burrs on the punched shutter end surface due to the sag.

Examples of the lubricant include synthetic compound lubricants such as polyethylene oxide type, microcrystalline type, polytetrafluoroethylene type and fluorine type, and oil and fat type lubricants such as lanolin and carnauba wax. It is preferable to use a polyethylene oxide-based lubricant having excellent lubricity and high strength because the molecular structure is a straight-chain structure from the viewpoint that scratches are less likely to occur.

The reasons for limiting the numerical values of the chromate film provided as the first layer and the synthetic resin film provided as the second layer will be described below.

Chromium adhesion amount of chromate film: 5 to 5
By providing a chromate film as the first layer on the surface of the 0 mg / m ² aluminum alloy plate, the interlayer adhesion between the aluminum alloy plate and the synthetic resin film provided as the second layer is improved, and peeling due to cracking of the film during bending. The effect of reducing the occurrence of scratches on the material surface as well as the effect of reducing the occurrence of scratches is small, but when the amount of chromium is less than 5 mg / m ² , the effect is hardly recognized. On the other hand, when the chromium adhesion amount is more than 50 mg / m ² , a crack occurs in the chromate film itself during bending, and a crack also occurs in the synthetic resin film starting therefrom.
Further, there is a problem that peeling occurs at the site where the crack has occurred. Therefore, the amount of chromium deposited on the chromate film is 5 to 5
The range is 0 mg / m ² .

The thickness of the synthetic resin film: By providing the above-mentioned synthetic resin film on a 0.5 to 3 μm aluminum alloy plate, the effect of making the surface of the material less prone to flaws can be obtained. If the thickness is less than 0.5 μm, this effect is less likely to be exhibited. On the other hand, when the thickness of the synthetic resin film is greater than 3 μm, the internal stress of the formed film becomes too high, and the adhesion of the film is reduced. Then, when the adhesion of the film is reduced, there is a problem that the film is easily peeled at the bent portion. Therefore, the thickness of the synthetic resin film is preferably in the range of 0.5 to 3 μm.

Tensile strength of aluminum alloy plate: 300
Itaru 350MPa Furthermore, this way aluminum alloy plate overall tensile strength formed in a range of 300 to 350MPa.
If the tensile strength is less than 300 MPa, the rigidity of the shutter becomes insufficient, and there is a problem that the shutter is deformed at the time of forming the shutter, assembling the recording medium case, and using the recording medium case. On the other hand, if the tensile strength is higher than 350 MPa, the strength is too high, which promotes abrasion of the blade tip of the processing tool (cutting edge) during punching when forming the shutter, and after continuous forming. Since the blade tip sags (R increases) due to wear, there is a problem that burrs are likely to occur on the punched shutter end face. Further, if burrs are generated on the punched shutter end surface, the burrs may damage other shutter surfaces during the subsequent assembling process, resulting in a problem that the appearance is impaired.

Next, a method of manufacturing the aluminum alloy plate configured as described above will be described. First, the above composition (Mg: 2.2 to 2.8% by mass, Mn: 0.35
The aluminum alloy is melted so as to have a composition of 0.5 to 0.55% by mass and Fe: 0.1 to 0.4% by mass, with the balance being aluminum and unavoidable impurities. . Then, for example, at a temperature of 500 ° C., 4
Perform time homogenization. Next, for the ingot subjected to homogenization, hot rolling or hot rolling and cold rolling are performed,
Roll to a predetermined thickness. Thereafter, the rolled plate was heated to 350 ° C.
Intermediate annealing at the above temperature, the final rolling reduction is 20 to 90
% Cold rolling.

Thereafter, stabilization processing, distortion correction, and the like are performed as necessary. Next, as a pre-coating treatment, the oil and oxide film on the surface of the aluminum alloy plate are removed by alkali degreasing and acid treatment.

The obtained aluminum alloy plate is used as an aluminum alloy substrate described in the claims, and a chromate film of 5 to 50 mg / m ^{2 in} terms of chromium adhesion is provided as a first layer on the surface of the aluminum alloy substrate. Thereafter, as the second layer, for example, an acrylate-modified polyester urethane-based resin, inorganic fine particles having an average particle diameter of 10 μm or less (5 to 20 parts by weight based on 100 parts by weight of the acrylate-modified polyester urethane resin), and polyethylene oxide -Based lubricant (0.5 to 3 parts per 100 parts by weight of acrylate-modified polyester urethane resin)
(Parts by weight) is applied to the surface of an aluminum alloy plate by, for example, a roll coating method so that the film thickness after drying is 0.5 to 3 μm.
By heating and drying at 5 ° C. or lower for 5 to 30 seconds, a synthetic resin film is formed on the chromate film.

[0037]

Next, the characteristics of the examples of the present invention will be described in comparison with comparative examples which are out of the scope of the present invention.

An aluminum alloy having a composition shown in Table 1 below was melted by a conventional method, and was cast into an ingot by continuous casting.
Next, the ingot was homogenized at a temperature of 510 ° C. for 4 hours, and then hot-rolled to obtain a sheet having a sheet thickness of 2.8 mm.
Next, after rolling to a thickness of 1 mm by cold rolling,
Intermediate annealing was performed at a temperature of 20 ° C. After that, the plate thickness 0.1
The final cold rolling was performed to 8 mm, and in some cases, annealing was performed after the final cold rolling to perform a stabilization treatment. In Examples 1 to 4, the compositions fall within the range defined in the claims of the present invention, and in Comparative Examples 1 to 6, the compositions fall outside the claims of the present invention. Comparative Examples 7 and 8
The composition is the same as in Example 1.

[0039]

[Table 1]

Table 2 below shows the chromate film and the resin formed on the surface of the obtained aluminum alloy plate. Alkaline degrease the plate material obtained as described above,
In Examples 1 to 4 and Comparative Examples 1 to 6, a chromate film was formed as a first layer by a phosphoric acid chromate treatment so as to be 20 mg / m ^{2 in} terms of a chromium adhesion amount, and then a second layer was formed as shown in the following table. A test material coated with a synthetic resin film was obtained by applying a paint having the composition shown in FIG. 2 by a roll coating method so that the film thickness after drying was 1 μm, and drying by heating at a temperature of 200 ° C. Comparative Examples 7 and 8
Is different from those of the other examples and comparative examples in that the amount of the first layer chromate film deposited is different from that of the other examples and comparative examples, and the forming method is performed by coating. The conditions for forming the second layer are the same as those of the other examples. Also,
The coating conditions were the same as in the other examples and comparative examples.

[0041]

[Table 2]

With respect to the obtained test materials, the following measurements were respectively performed to evaluate the overall tensile strength, punching workability, and bending workability. The measurement results and evaluation are shown in Table 3 below.

[0043]

[Table 3]

The total tensile strength was determined by preparing a JIS No. 5 test piece and performing a tensile test.

Regarding the punching workability, a continuous cutting test was conducted under the conditions shown in FIG.
And the amount of burrs were measured. In the continuous cutting test, a low viscosity volatile press oil AF was used as the press oil.
2A (made by Idemitsu Kosan Co., Ltd.), and the amount of oil applied was 1 g /
It was m ^2. The material of the cutting tool (cutting blade) is SK
Using D11 (JIS), the clearance of the cutting edge is 20
It was set to μm. Further, the processing speed was 300 cm / min, the stroke length was 3 mm, and the cutting length was 30 mm. The cutting edge tip shape (R) is measured using a shape measuring device (SED36).
D: Measured with Kosaka Laboratory; stylus R = 2 μm). In addition, the amount of burrs was measured from the projection to the tip of the burr shown in FIG. The number of continuous cutting operations was 200,000 shots.
The cutting edge shape (R) and the amount of burrs after 10,000 shots were measured.

Regarding the product rigidity, the obtained test material was processed into the shape shown in FIG. 2 to obtain a shutter, and the shutter incorporated in the flexible disk case shown in FIG. The height of the flexible disk shown in FIG. 1 was evaluated by dropping the corners of the case so as to collide with the floor. The evaluation was performed for each test material by n = 10, and the number of shutters deformed and coming out of the case was counted.

Regarding the bending workability, a 90 ° -0R bending test was performed using the plate thickness of the test material as a bending radius, and the bending portion was determined to be 5 mm.
Observation was made with a stereoscopic microscope at a magnification of 0 to 200 times, and evaluation was made based on the state of cracks in the bent portion. With respect to the evaluation, those without cracks were evaluated as ○, those with minute cracks as Δ, and those with large cracks as X.

As shown in Table 3, Example 1 is within the scope of the present invention, and the overall tensile strength is in the range of 300 to 350 MPa. There was no change in the tip shape (R), and no increase in burrs was observed. Further, even in the drop impact test, the shutter is not deformed and detached from the case, and has sufficient product rigidity. In Comparative Example 1, although the composition was within the range of the present invention, the heating temperature of the stabilization treatment was high, so the overall tensile strength was 200 MPa, which was low outside the range of the present invention, and the punching workability was good. However, the shutter deformed and came off in the drop impact test, and the product rigidity was insufficient. In Comparative Example 2, since the overall tensile strength was too high at 380 MPa, the product rigidity was good, but the punching workability was poor, and an increase in the cutting edge shape (R) was observed in continuous cutting. Accordingly, an increase in burrs is also observed. In Comparative Example 3, the total tensile strength was as low as 290 MPa, the product stiffness was insufficient, and the generation of Al-Fe-Mn-based crystallization that improved the cuttability even in the composition was insufficient. The cutting performance is poor, and an increase in the cutting edge shape (R) is observed in continuous cutting, and an increase in burrs is also observed. In Comparative Example 4, the overall tensile strength was 170 MPa, which was out of the range of the present invention, and although the punching workability was good, the shutter was deformed in the drop impact test and came off, resulting in insufficient product rigidity. In Comparative Example 5, since the amount of added Mn was excessive, the number of giant crystallized substances and the number of crystallized substances increased, and the formability was reduced. Cracks occur and bending workability becomes insufficient. In Comparative Example 6, since the amount of Fe added was excessive, the number of giant crystallized substances and the number of crystallized substances increased, and the formability was reduced. Cracks occur and bending workability becomes insufficient. Comparative Example 7 has too little chromate film.
In bending workability, minute cracks occur in the bent portion, and the bending workability becomes insufficient. In Comparative Example 8, since the amount of the chromate film was excessive, minute cracks were generated in the bent portion in bending workability, and bending workability was insufficient.

[0049]

As described in detail above, according to the present invention,
An aluminum alloy plate for a shutter excellent in both punching workability and bending workability can be obtained. For this reason, when this aluminum alloy plate is formed into a shutter of a recording medium case, it has excellent punching workability and bending workability, and also has excellent scratch resistance, solvent solubility resistance, and printability. Thus, a resin-coated aluminum alloy plate suitable for a shutter of a recording medium case can be obtained.

[Brief description of the drawings]

FIG. 1 is a front view showing a flexible disk as a recording medium.

FIG. 2 is a perspective view showing a shutter used in the case of the flexible disk.

FIG. 3 is a sectional view of the shutter.

FIG. 4 is a diagram illustrating test conditions of an example of the present invention.

[Explanation of symbols]

 1: shutter 2: case 3: recording medium 4: window 5: inner corner

Continued on the front page F term (reference) 4K026 AA09 AA22 BA01 BA06 BA07 BA12 BB04 BB09 BB10 CA39 DA16 EB08 4K044 AA06 AB02 BA15 BA21 BB03 BC01 BC05 CA16 CA53

Claims (1)

[Claims] An aluminum alloy plate for a shutter of a recording medium case used for a shutter for opening and closing a recording head window provided in a case for accommodating a recording medium.
g: 2.2 to 2.8% by mass, Mn: 0.35 to 0.
55% by mass, Fe: 0.1 to 0.4% by mass,
An aluminum alloy substrate having a composition consisting of aluminum and unavoidable impurities, and at least 5 equivalent to the amount of chromium adhered, provided as a first layer on at least the surface of the aluminum alloy substrate on the outer side of the shutter of the recording medium case.
Or a chromate film of 50 mg / m ^2, has a synthetic resin film provided as the second layer on the surface serving as the shutter outer surface, the overall tensile strength of 300 to 350M
An aluminum alloy plate for a shutter of a recording medium case, which is Pa.