JP3476364B2 - Aluminum material for disk shutter - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suitable for use as a material for a disk shutter provided in a case of a magnetic disk or an optical disk and has scratch resistance, processability, solvent resistance, and UV curable ink. The present invention relates to an aluminum material for a disk shutter having excellent printability.

[0002]

2. Description of the Related Art For magnetic disks such as flexible (floppy) disks, optical disks such as MO disks and mini disks, information is stored 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. And write information,
Alternatively, when reading, the recording medium 3 in this case 2
A magnetic head or an optical head is brought close to the magnetic disk or the optical disk medium 3 to read or write. Therefore, these cases 2 are provided with an opening (window) as a window for disposing the magnetic head or the optical head close to the recording medium 3, and the shutter 1 for opening and closing the opening is provided. Has been.

This shutter 1 is shown in the perspective view of FIG. 2 and FIG.
As shown in the cross-sectional view of FIG. 1, the plate member has a U-shaped cross section, and the case 2 is sandwiched between the pair of surfaces,
The window is opened at a position where the window portion of the case 2 and the window portion 4 of the shutter 1 are aligned by being guided and slid by the guide groove provided in the case 2, and the window portion of the case 2 is normally closed. I have to.

The function required of this disk shutter (hereinafter, simply referred to as "shutter") is to open and close when necessary to protect the magnetic surface. Further, since the shutter slides while being guided on the case, it needs to be lightweight and have high rigidity. As a material for the shutter, stainless steel or synthetic resin such as polystyrene or ABS has been conventionally used.
However, the stainless steel shutter is relatively heavy, and when the surface is touched with a finger, fingerprints are easily attached to the shutter, which impairs the appearance. Also, polystyrene and ABS shutters
It has low rigidity, is easily charged with electricity, and is easily attached with dust and dust, which is harmful to the magnetic surface.

Further, these stainless steels and synthetic resins such as polystyrene and ABS have poor adhesion to UV-curable ink used for printing shutters, and modification of corona discharge or the like to improve this adhesion. It requires treatment and increases the manufacturing cost. The UV curable ink is used for printing to display the manufacturer name, product type, etc. on the surface of the disk shutter.

Therefore, in recent years, in place of these stainless steel and synthetic resin, a lightweight and rigid aluminum material (in the present invention, aluminum or aluminum alloy material is referred to as aluminum material; "Al material" is used.

[0007]

However, when an Al material is used for a shutter, the bare Al material surface has poor lubricity and low hardness, resulting in insufficient wear resistance. In each manufacturing process such as transportation of processed products, assembly into a case, final inspection of magnetic disk and optical disk products, the Al material is apt to have flaws on the surface, and Al wear powder, which is harmful to the magnetic surface, is easily generated. Furthermore, the appearance of the shutter will be significantly impaired due to the occurrence of flaws. This Al material has a problem of scratches on the surface not only in the manufacturing process but also in contact with mechanical parts when inserting and removing a floppy disk or the like into a recording / reading device such as a personal computer or a word processor. It is also caused by the contact of each other. As described above, when the Al material is used for the shutter, flaws on the shutter pose a problem.

Furthermore, the surface of the bare Al material has a low adhesion to the UV-curable ink used for printing the shutter, which causes a problem of printability that the printed ink is easily peeled off.

Therefore, in order to prevent the Al material for the shutter from being scratched and to improve the adhesion of the UV curable ink,
(A) A method for coating a synthetic resin selected from acrylic, acrylic ethylene, epoxy, and urethane on the surface of an Al material (see JP-A-3-73479 and JP-A-6-346178) is proposed. ing.
However, even with the coating of these synthetic resins, the abrasion resistance is insufficient and the scratch resistance cannot be improved. Therefore, in order to improve the abrasion resistance, a surface hardening coating method for the surface of the (b) Al material (Japanese Patent Laid-Open No. 6-242242). -68638),
(C) A method for forming an anodized film on the surface of an Al material (see JP-A-6-111516 and JP-A-6-162710) has been proposed.

However, there are problems in each of the techniques for preventing the Al material for the shutter from being scratched and improving the adhesion of the UV curable ink. That is, in the method (a) of coating the Al alloy surface with the synthetic resin, when the synthetic resin is cured to increase the surface hardness of the coating in order to prevent flaws, the coating formation process (curing reaction process) And functional groups in synthetic resin (eg, highly reactive carboxyl group, hydroxyl group, etc. in synthetic resin selected from acrylic type, acrylic ethylene type, epoxy type, and urethane type)
Is consumed, and the functional group that binds to the UV curable ink is lost, so that the adhesion of the UV curable ink becomes low and the printed ink easily peels off. On the other hand, if a large amount of functional groups are left in the synthetic resin in order to improve the adhesion of the UV curable ink during the film formation process, the curing of the synthetic resin will be insufficient and the surface hardness will be low to prevent scratches. I can't. Moreover,
1.1.1. After press working of the Al material on the shutter. -The synthetic resin coated during the ultrasonic cleaning process using an organic solvent such as trichlorethylene elutes.

Furthermore, in the surface hardening coating method (b) on the surface of the Al material, the surface hardening coating film (anodizing coating film) has excellent wear resistance and prevents scratches, but When the shutter is bent to form a shutter having a U-shaped cross section shown in FIG. 3, the resin film is cracked and peeled off in the inside of the 90 ° bend 5 to cause magnetic properties. Dust and dust that are harmful to the surface will be generated. Furthermore, since the number of functional groups to which the UV curable ink binds is insufficient in the surface-cured coating film, the adhesion of the UV curable ink becomes low, and the printed ink easily peels off. Occurs.

Further, in the method of forming an anodized film on the surface of the Al material in (c), the anodized film has excellent wear resistance,
Although scratches are prevented and the adhesion of the UV curable ink is improved by the anchor effect of the holes existing on the surface of the film, the film is cracked inside the 90 ° bend and the film is peeled off. Dust and dust, which are harmful to the magnetic surface, are easily generated.

On the other hand, the applicants have filed Japanese Patent Application No. 8-22.
According to Japanese Patent No. 0228, a surface of an Al material is coated with a polyester resin having higher hardness and higher abrasion resistance than an acrylic resin, an acrylic epoxy resin, a urethane resin or the like, and a chromate film is provided as a lower layer. We have proposed an Al plate material for shutters with improved adhesion of polyester resin. In addition, in order to improve the lubricity of the resin film on the surface of the Al material, an Al plate material for shutters in which a resin film having a pencil hardness of 5H or more contains a lubricant such as high molecular weight PE wax, PTEF wax and fluorine-based wax , 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 Al material, an Al plate material for a shutter in which a specific polymer vinyl compound contains a metal chelate compound is disclosed in Japanese Patent Application No. 9-2323.
No. 35 gazette.

However, in the prior inventions proposed by these applicants, not only the lightness and rigidity required for the Al material for shutters, but also the scratch resistance, the workability such as press working and bending, There is still room for improvement in that it has all of a plurality of properties such as solvent solubility and printability, and that each property is superior.

The present invention has been made in view of such circumstances, and its purpose is not only light weight and rigidity required for an Al material for a disk shutter, but also scratch resistance and press working. The present invention provides an Al material for a disk shutter, which has all of a plurality of properties such as workability such as bending and bending, solvent solubility resistance, and printability, and has excellent printability of UV curable ink.

In order to achieve this object, the gist of the present invention is an aluminum material for a disk shutter, comprising a chromate coating on the surface of an Al material, and a polyester-based urethane resin coating on the upper surface thereof. The polyester-based urethane resin film has a molecular weight of 20 with an acrylate group represented by the chemical formula of —CH═CH ₂ as a functional group.
1 or more per 000, and 200-250 ℃
It is dried at a temperature and its dry film weight is 50
It is 0 to 3000 mg / m 2 . In the present invention, a coating film of Al material surface, -CH = CH ₂
The greatest feature is that it is composed of a polyester-based urethane resin having an acrylate group represented by the following chemical formula. With this configuration, the adhesion between the UV-curable ink printed (laminated) on the polyester urethane resin film and the film is improved.

That is, when the UV-curable ink laminated (printed) on the polyester urethane resin film having an acrylate group is irradiated with ultraviolet rays (UV) to cure the UV-curable ink, Due to the catalytic action of the photopolymerization initiator, the acrylate group in the UV curable ink becomes a radical and the acrylate group in the film also becomes a radical. The acrylate group in the UV curable ink that has become these radicals and the acrylate group in the film are firmly bonded to each other, the adhesion of the UV curable ink is improved, and an aluminum material for a disk shutter having excellent printability is obtained. Obtainable.

The UV curable ink and its curing mechanism will be further described. The UV curable ink is composed of a urethane acrylate-based or epoxy acrylate-based oligomer having an acrylate group, a photopolymerization initiator, and a pigment. To cure the UV curable ink, light energy (hν) due to ultraviolet (UV) irradiation is required. As shown below, when light energy (hν) is applied to the UV curable ink, the acrylate group of the oligomer having an acrylate group forms a radical by the catalytic action of the photopolymerization initiator (see Formula 1). Next, the radicals bond with each other (see Formula 2) to cure.

[0019]

[Chemical 1]

The present invention is characterized in that an acrylate group represented by the chemical formula of —CH═CH ₂ is newly added to a polyester urethane resin. Furthermore, since this film does not contain a photopolymerization initiator, even if light energy is applied to the film, the acrylate groups in the film do not bond with each other. Therefore, the acrylate group in this film is bonded only to the acrylate group in the UV curable ink, which effectively acts on the adhesion between the film and the UV curable ink. Since this acrylate group is not included in conventional acrylic, acrylic ethylene, epoxy, urethane, or other synthetic resins, the adhesion between the synthetic resin film and the UV curable ink cannot be improved. .

In addition to this, the polyester-based urethane resin has very high strength because the isocyanate bond in the polymer is very strong and flexible, and
Shows very good stretchability. Since the resin strength is high, the surface hardness of the coating is high, and the scratch resistance during the shutter manufacturing process, the transporting process, or during use is improved.
Also, since the resin stretchability is excellent, even during bending
It does not cause cracks in the coating and does not generate dust or dirt that is harmful to the magnetic surface of the disk. Furthermore, the isocyanate bond has excellent chemical resistance, and 1.1.1. -Even in the ultrasonic solvent cleaning step using an organic solvent such as trichlorethylene, the film does not elute and the solvent solubility is excellent.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The significance of each requirement in the Al material for a disk shutter of the present invention will be described more specifically below. First, the chromate film is provided on the upper surface of the Al material of the disk shutter Al material so that the upper polyester-based urethane resin film does not peel off even when the shutter material is subjected to severe processing such as bending. As described above, the polyester-based urethane film is interposed in order to improve the adhesion between the surface of the Al material and the adhesion between the urethane-based urethane film and the surface of the Al material. Further, the coating amount on the surface of the Al material is preferably 5 to 30 mg / m ^{2 in} terms of Cr amount. Coating amount is 5 in terms of Cr amount
If it is less than mg / m ² , the chromate film on the surface of the Al material becomes non-uniform, and the polyester urethane resin film and Al
The effect of improving the adhesion to the material surface is lost. On the other hand, when the coating amount exceeds 30 mg / m ^{2 in} terms of Cr amount, the chromate film is likely to be cracked when the shutter material is bent, and on the contrary, harmful dust is likely to be generated on the magnetic surface.

As the kind of the chromate film, a general alkali-chromate type, chromate type, chromium phosphate type and a coating type chromate type in which a resin and chromic acid are mixed can be appropriately used. . However, in consideration of various characteristics required for the Al material in the present invention, particularly adhesion and processability, chromate-based Cr (OH) ₂ .HCrO ₃ and acrylic resin by coating type chromate treatment, or chromate phosphate. Treated chromium phosphate is preferred. These chromate films can be applied by known methods, and the coating type chromate film can be applied by the roll coating method, and the phosphoric acid chromate film can be applied by the dipping method or the spray method.

The polyester-based urethane resin coated on the chromate film to form the polyester-based urethane resin film may have one or more acrylate groups represented by the chemical formula of —CH═CH ₂ as a functional group per 20,000 molecular weight. is necessary. This polyester urethane resin has the following chemical structure.

[0025]

[Chemical 2]

As described above, having an acrylate group as a functional group is necessary to improve the adhesion between the surface of the polyester type urethane resin film and the UV curable ink, but the number of acrylate groups is the molecular weight. 2000
When the number is less than 1 per 0, the UV curable ink is laminated on the film and forms a radical when irradiated with ultraviolet rays (UV), and similarly binds to an acrylate group in the UV curable ink that has formed the radical. The number of acrylate groups in the film is insufficient, sufficient adhesion cannot be obtained between the film surface and the UV curable ink, and the ink tends to peel off after printing. The upper limit is 1 acrylate group per 1000 molecular weight. The reason for this is that if the amount of acrylate group added is further increased, the formed film becomes brittle and tends to be depressed, so that the occurrence of foreign matter due to peeling of the film and the dissolution of the film in the trichlene cleaning step tend to occur. This may occur.

This polyester type urethane resin film is
It is necessary to apply a dry coating weight of 500 to 3000 mg / m ² . If the coating amount of the polyester-based urethane resin film is less than 500 mg / m ² , the surface of the Al material cannot be uniformly covered with the film, and the effect of improving the adhesiveness of the UV curable ink is obtained in the part not covered with the film. And the printability becomes insufficient. If the surface coating is too thin, the surface of the Al material of the base material is likely to come into contact with other Al materials or other equipment parts, and the surface of the Al material is likely to be flawed. On the other hand, when the coating amount of the polyester-based urethane resin film exceeds 3000 mg / m ² , the abrasion powder of the Al material generated during punching press working and the excess surface resin film component are mixed with the working press oil. It becomes sludge. The processing press oil in the sludge state causes the clearance of the mold to be clogged, and adversely affects the shape and surface properties of the product Al material for shutters.

The coating or coating of the polyester urethane resin film of the present invention having the above-mentioned structure on an Al plate can be carried out by a known Al coating process. That is,
After subjecting the material Al plate or coil to pretreatment such as alkaline degreasing, etching, or washing with water as necessary,
The above chromate treatment is performed. And, -CH =
Known coating methods such as air spraying, electrostatic coating, dip coating, roll coating, TFS coating, and electrodeposition coating of a polyester-based urethane resin liquid having one or more acrylate groups represented by the chemical formula of CH ₂ as a functional group per 20,000 molecular weight. Thus, the surface of the material Al plate or the coil on which the chromate film is provided is coated. The Al plate or coil coated with the polyester urethane resin film liquid is then dried by a conventional method.

The drying temperature for forming a film after applying this polyester-based urethane resin liquid is in order to exhibit the characteristics of the polyester-based urethane resin film.
A temperature range of 200-250 ° C is preferred. The drying temperature is
If the temperature is less than 200 ° C., the thermosetting reaction amount of the resin is insufficient, the curing of the polyester urethane resin is insufficient, the hardness of the film is increased, and the effect of improving the scratch resistance is lost, and
Solvent resistance is not exhibited. On the other hand, the drying temperature is 25
If the temperature exceeds 0 ° C, the polyester-based urethane resin will be thermally decomposed and the coating will become brittle, so during processing such as bending, the coating will be cracked at the processed portion, and dust and dirt that is harmful to the magnetic surface will occur. There is also the problem of being easier to do.

The Al material for a shutter of the present invention manufactured by the above steps is subjected to forming processing such as press working and bending from an Al plate or coil shape precoated with the polyester urethane resin film, After that, the surface of the Al material for the shutter is printed with UV curable ink and cured, and finally the shutter is formed. The shutter is assembled into a case to form the flexible disk shown in FIG.

The shape of the material Al material used in the present invention may be a plate manufactured by rolling or the like, or a mold material manufactured by extrusion or the like as long as it can be finally processed into a shutter. It doesn't matter, but the shutter thickness is 0.185
Considering that it is a thin plate of about mm and the coating work such as the chromate treatment and the polyester-based urethane resin coating, it is manufactured by hot rolling and cold rolling in terms of shape accuracy, productivity and manufacturing cost. It is preferably a plate material.

Further, the characteristic of the material Al material used in the present invention is 350 N from the strength or rigidity required for the shutter.
/ Mm ² or more tensile strength and 280 N / mm ² or more proof stress, and because it is processed into a shutter, it has excellent press workability and bendability, and also has excellent corrosion resistance. preferable. Therefore, as the type of Al material, JIS 5000-series Al alloy, and particularly H38 material of JIS 5182 Al alloy is preferable as the Al alloy having high strength and excellent workability and corrosion resistance.
Other than this, an Al alloy such as JIS 5052 can be used as an Al alloy having similar characteristics.

[0033]

[Example] JIS 5182 A having a plate thickness of 0.185 mm
After degreasing the H38 material of the 1-alloy with alkali, washing with water, and drying, a chromate film as the first layer (underlayer) and a polyester-based urethane resin film as the second layer (upper layer) are provided under the conditions shown in Table 1. It was As shown in Table 1, in each example, the type and coating amount of chromate or polyester-based urethane resin, the number of acrylate groups in the polyester-based urethane resin film, the drying temperature of the polyester-based urethane resin, etc. We carry out various changes. In Table 1, the chromate is a coating type chromate in each example, but the invention example No. Only 2 is used by changing the type of chromate phosphate and chromate.
Then, the Al alloy plate provided with the chromate film and the polyester-based urethane resin film is processed into a shutter material by press working and 90 ° bending, and various characteristics of these shutter materials, scratch resistance, bending workability, and resistance to bending. Table 1 also shows the results of the solvent solubility and UV curable ink printability tested and evaluated.

[0034]

[Table 1]

With regard to specific test conditions, as to the scratch resistance, the pencil hardness is JIS K5400 pencil hardness test, and the dynamic friction coefficient is 3/16 inch steel ball by a Bowden adhesion sliding tester. Load 1000g
It was determined by sliding under the conditions of f and sliding speed of 4 mm / sec. In addition, the number of defects is 3 for the shutter material.
0 pieces were packed in a box of 150 mm length × 250 mm width × 50 mm height and shaken for 30 seconds to measure the number of flaws in 30 samples.

Regarding bending workability, 90
° 90 ° when bending is performed under the condition that the inner diameter is 0 mm
Observing the inner surface of the bend, ○: No cracks were found in the resin film, ○: Small cracks were found in the resin film, but peeling of the film was not observed, △: Cracks were found in the resin film Then, the case where harmful film peeling was observed on the magnetic surface was evaluated as x.

Further, regarding the resistance to solvent dissolution, the shutter material sample is 1.1.1. The resin film elution amount was determined after immersion in trichlorethylene for 6 minutes while using ultrasonic waves.

Regarding the UV curable ink printability (adhesion), urethane acrylic UV is used on the surface of the shutter material.
A curable ink (RIG BLAK No. 10, manufactured by Seiko Advance) was used as a mesh No. After screen printing using a 270 silk screen, UV curing is performed with a UV irradiation device (manufactured by Eye Graphic) under the condition of 80 W / cm ² × 3 seconds, and a cross-cut (1 mm) cross cut is printed on the printed part. The peeling test was performed with cellophane tape, and the peeled state of the ink in the printed part was observed. The ink remaining part (non-peeled part) in 100 grids I counted the number.

As is clear from Table 1, Invention Example No. 1 to
No. 12 has a hardness as high as 5H or more and a dynamic friction coefficient of 0.07.
It is as low as or less, and the number of defects is less than or equal to 8 and 9
There is no peeling of the resin film even in the 0 ° bending process, there is almost no elution of the resin film, and there is no cross-cut peeling. Therefore, scratch resistance, bending workability, solvent solubility resistance,
It can be seen that the UV curable ink has excellent printability. Among the invention examples, No. 3 having a relatively low chromate film amount. 11 and relatively high chromate coating amount N
o. In Nos. 12 and 11, all of the coatings have minute cracks in the 90 ° bending process (evaluation Δ), which is inferior to the other invention examples.

On the other hand, as is apparent from Table 1, Comparative Example No. Nos. 13 to 20 are inferior to the invention examples in any of scratch resistance, bending workability, solvent solubility resistance, and UV curable ink printability. More specifically, Comparative Example No. No. 13 is UV, because the number of acrylate groups contained in the polyester-based urethane resin film is too small and is less than the lower limit of the range specified in the present invention.
Since the number of acrylate groups bonded to the acrylate group in the curable ink becomes insufficient and the ink adhesion decreases, the UV curable ink printability is poor. Comparative Example N
o. In the case of No. 14, the dry film weight is too small, falling below the lower limit of the range specified in the present invention, so that the scratch resistance is inferior and the printability of the UV curable ink is inferior. Comparative Example No. No. 15 has a drying temperature that is too low for forming a polyester-based urethane resin film, insufficient curing of the polyester-based urethane resin film, low hardness of the film, low scratch resistance, and low solvent solubility. Become. Comparative Example N
o. No. 16 has a drying temperature that is too high for forming the polyester-based urethane resin film, thermal decomposition of the polyester-based urethane resin occurs, and the film becomes brittle, which causes cracks in the film in the bent portion and is harmful to the magnetic surface. The bending workability is inferior, as the peeling of the film is observed.

Comparative Example No. No. 17 uses a polyepoxy resin, and because the film is not sufficiently cured, it has good UV-curable ink printability, but has low film hardness and poor scratch resistance, and is also resistant to solvent dissolution. The sex is also inferior. Comparative Example No. No. 18 uses a polyacrylic resin, the film is sufficiently cured, the scratch resistance, solvent resistance and solubility are excellent, but the UV curable ink printability is inferior.

Comparative Example No. No. 19 is an example using water glass. Reference numeral 20 denotes a film that has been anodized, and both of the films are cracked and peeled off at the inner surface of the 90 ° bending work, and fine particles harmful to the magnetic surface are produced. Comparative Example No. No. 21 is an example of no treatment, and has low scratch resistance and low UV-curable ink printability.

From the above examples, the Al material for a disk shutter of the present invention is excellent in all of scratch resistance, bending workability, solvent solubility resistance, and UV curable ink printability, and is flexible (floppy). It can be seen that it can be suitably used as a member of a disk shutter provided in a case of a magnetic disk such as a disk, an MO (magneto-optical disk) and an optical disk such as a mini disk.

[0044]

According to the present invention, it is possible to provide an aluminum material for a disk shutter which is excellent in printability of UV curable ink, and is excellent in scratch resistance, processability and solvent dissolution resistance. You can By improving the printability of UV curable ink, improving the aesthetics of the disk shutter, maintaining the commercial value for a long time, and improving the scratch resistance,
This makes it possible to extend the life of the disc shutter and improve its reliability. Further, by using the aluminum material of these disc shutters, the weight reduction and the thickness reduction of the disc shutters are promoted, and the disc shutters having stable quality can be manufactured by improving the workability and the solvent dissolution resistance. .

[Brief description of drawings]

FIG. 1 is an explanatory view showing a schematic view of a flexible (floppy) disk showing a portion where a shutter is used.

FIG. 2 is a perspective view of a shutter.

FIG. 3 is a sectional view of a shutter.

[Explanation of symbols]

1 shutter 2 cases 3 recording discs 4 windows 5 90 ° bending inner part

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-9-207296 (JP, A) JP-A-9-187886 (JP, A) JP-A-6-346178 (JP, A) JP-A-8- 306155 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G11B 23/03 605 G11B 23/033 601

Claims (5)

(57) [Claims] 1. A disk shutter aluminum material comprising a chromate film formed on the surface of aluminum or an aluminum alloy material and a polyester urethane resin film formed on the surface thereof, wherein the polyester urethane resin film is --CH. = CH ₂ containing one or more acrylate groups represented by the chemical formula per molecular weight of 20,000 as a functional group, and dried at a temperature of 200 to 250 ° C.
The dry film weight is 500 to 3000 mg.
Aluminum material for disk shutters, characterized in that it is / m2 . 2. The chromate film is a coating type chromate.
Treatment or chromate phosphate treatment, C
The amount is 5 to 30 mg / m2 in terms of r.
The aluminum material for the disk shutter according to [4]. 3. The disk shutter is a recording disk
Open and close the recording head window provided in the case
The disc shutter according to claim 1 or 2, which is a shutter.
Aluminum material for tta. 4. The aluminum material is 350 N / mm2.
Has the above tensile strength and proof stress of 280 N / mm2 or more
The aluminum alloy material according to any one of claims 1 to 3.
The aluminum material for the disk shutter described. 5. The aluminum material is JIS 5182.
The disk according to claim 4, wherein the disk is an Al alloy H38 material.
Aluminum material for shutters.