JPH06150604A - Disk cartridge - Google Patents

Abstract

PURPOSE:To decrease warpage and to increase impact resistance strength by using a resin formed by adding an elastomer to polybutyrene terephthalate(PBT) as a material of a shutter. CONSTITUTION:Polycarbonate is usually used for the materials of a shell 1 and slider 5. The resin formed by adding 5 to 40wt.% elastomer to 95 to 60wt.% PBT having the small warpage but the low impact resistance strength is used for the material of the shutter 3, by which elasticity is increased and the impact resistance strength is increased. The elastomer having >=100% and <=500% elongation is used as the elastomer to be added in such a case. The shutter 3 formed by using such resin has sufficient hardness, the high impact resistance strength and low hygroscopicity and, therefore, the warpage arising from an environmental change is small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disc cartridge in which an opening window of a shell containing a disc is covered with a resin shutter.

[0002]

2. Description of the Related Art Conventionally, as shown in FIGS.
In a disk cartridge (hereinafter also referred to as a cartridge) such as a ROM, a write-once optical disk, a rewritable magneto-optical disk, and a floppy disk, in order to protect the disk such as the magneto-optical disk 2 housed in the shell 1,
The opening window 4 of the shell 1 can be opened and closed by the shutter 3. The shutter 3 is opened and closed by a disk drive device in which a cartridge is inserted, and the disk drive device performs writing and reading on the magneto-optical disk 2. A slider 5 is fixed to the shutter 3, and the slider 5 is slid on the peripheral edge of the shell 1 to open and close the opening window 4 by the shutter 3.

It is known that a shutter made of metal and a shutter made of resin are known as the shutter 3. The shutter made of metal is hard to crack and has high strength, but it is difficult to return to the original state when it is deformed by dropping the cartridge or the like.
Further, the metal shutter easily abrades the shell 1 due to friction, which hinders reading and writing of information on the magneto-optical disk 2. Furthermore, the manufacturing cost of metal shutters is high,
It is also not preferable in terms of weight saving of the cartridge. For this reason, a resin shutter may be used.

However, the resin shutter has a smaller impact strength than the metal shutter and is liable to be cracked when the cartridge is dropped. Further, a resin shutter generally causes a warpage with time due to a change in temperature and humidity in a use environment. So, regarding the resin shutter,
In order to solve these problems, the shape and material of the shutter have been studied, but the material and shape that have solved both problems of impact strength and prevention of warpage are not known. As a shutter material, polyacetal (PO
M), polybutylene terephthalate (PBT), polypropylene (PP) and the like are used, but POM is apt to warp with time, PBT and PP are easily cracked, and there is a problem in impact strength.

[0005]

The object of the present invention is to provide excellent impact resistance,
It is an object of the present invention to provide a shutter that takes advantage of the original advantages of a resin shutter that is less likely to warp over time, is lighter in weight, less expensive, and less contaminated by abrasion powder.

[0006]

According to the present invention, there is provided a disk cartridge comprising a resin shell for accommodating a disk and having an opening window formed therein, and a resin shutter for opening and closing the opening window of the shell. Of polybutylene terephthalate to 95-60 wt% and elongation of 10
5-40 wt% of 0% or more and 500% or less elastomer
It is characterized in that it is formed of an added resin material.
The growth here is based on ASTM (American Society for Testi
ng Materials) D638. In addition to the magneto-optical disk shown in the embodiment, the type of disk is a CD-ROM, a write-once optical disk, a floppy disk, or the like. In this specification, the total amount of polybutylene terephthalate and elastomer is 100 wt.
The addition amount is shown as%.

[0007]

According to the disk cartridge having the above structure,
Warpage with time due to environmental changes is small. This is because polybutylene terephthalate has low hygroscopicity and is originally a material that is less likely to warp due to environmental changes, and the added elastomer has an elongation of 100 to 500% and an addition amount of 5 to 5.
This is because in the range of 40 wt%, the increase in warpage due to the addition of the elastomer is small. Next, plain polybutylene terephthalate has a low impact strength, and when the cartridge is dropped, cracking or the like occurs. On the other hand, the added elastomer increases the elasticity of the shutter and the impact strength. In order to have both impact strength and less warpage, the elastomer has an elongation of 100% or more and 500% or less, and the addition amount is 5 to 5.
It is necessary to set it to 40 wt% (the total amount of the shutter is 100%). With these configurations, it is possible to obtain a shutter for a disk cartridge that has excellent impact resistance strength and has less warpage.

[0008]

【Example】

[0009]

Example 1 The cartridge shown in FIGS. 1 and 2 is used as a magneto-optical disk cartridge, and the shell 1 is made of polycarbonate (PC) and the slider 5 is made of polycarbonate, and polybutylene terephthalate (P) is used.
Based on BT, resin shutter 3 (thickness 0.3 m
m) was produced. Five kinds of materials shown in Table 1 are prepared as materials for the resin shutter 3, and the shutter 3 is formed by injection molding.
Was produced. These materials are based on PBT (80 wt%), vinyl chloride resin elastomer, ethylene propylene copolymer elastomer, styrene butadiene copolymer elastomer, urethane rubber A, urethane rubber B
Is added in an amount of 20 wt%. Also, as a comparative example, a shutter of PBT alone was manufactured. Using the above six types of shutters A to F, the following evaluation test was performed on the optical disk cartridge of FIG. Warp : The shutter 3 when each of the above optical disk cartridges was left in a high temperature and high humidity (31.8 ° C., 90% RH) atmosphere for 24 hours and then taken out to a normal temperature and normal humidity (26 ° C., 60% RH) atmosphere The rising of the end portion of the shell 1 from the surface of the shell 1 was measured and used as the warp. Drop strength : When each of the above optical disk cartridges was dropped from a height of 760 mm onto a vinyl-covered (0.2 mm) concrete floor surface, the deformation and cracking of the shutter 3 was examined by itself.

The results for warpage and drop strength are shown in Table 1. No warpage occurs with the shutter F of the PBT alone,
The drop test causes cracking. It is considered that the warpage does not occur because PBT is an exceptionally low hygroscopic substance and has a small hygroscopic amount during the high temperature and high humidity test.
It is considered that the cracks occur because the PBT alone lacks elasticity and cannot absorb the impact when dropped. Next, the shutter A to which the vinyl chloride resin elastomer having an elongation of 90% was added also showed the same result as the shutter F to which the elastomer was not added, and cracking occurred in the drop test. It is considered that this is because when the elongation was 90%, sufficient elasticity could not be imparted to the base PBT. Therefore, the elongation needs to be 100% or more, and preferably 120% or more. On the contrary, in the shutter E to which the elastomer (urethane rubber B) having a large elongation of 550% was added, cracks did not occur, but the hardness decreased, and scratches were likely to occur when the surface of the shutter 3 was rubbed with a cloth or the like. . Therefore, the growth is 5
It is necessary to set it to 00% or less. Next, the permissible limit for warpage is generally 0.5 mm or less. The shutters in Table 1 all satisfy the allowable range regarding the warp. From these facts, the elastomer to be added has elongation (ASTM
D638) is 100 to 500%, more preferably 12
0 to 500%.

[0011]

[Table 1] PBT + 20 wt% elastomer shutter results Shutter added elastomer Elongation (%) Warp Drop strength (α) (mm) A * Vinyl chloride resin elastomer 90 0.1 Crack generation B Ethylene propylene elastomer 150 0.1 No abnormality C Styrene butadiene rubber 300 0.2 No abnormality D Urethane rubber A 480 0.3 No abnormality E * Urethane rubber B 550 0.2 Hardness decrease F * 0 cracking * is a comparative example, elongation is when external force is applied The length is L1, the length in the natural state is L0, and the value of n in L1 = (1 + n) L0 is measured according to ASTM D638. The same applies hereinafter.

[0012]

Example 2 In order to clarify the amount of the elastomer to be added, with respect to the shutter 3 to which the ethylene propylene copolymer elastomer and the urethane rubber A were respectively added, the addition amount was changed as shown in Tables 2 and 3, and The drop strength was evaluated.

As is clear from Tables 2 and 3, even if the type of elastomer added to PBT is changed, the amount added is 3w.
At t%, the shutter 3 cracked in the drop test. On the other hand, when the addition amount was 7 wt% (Table 3) or 9 wt% (Table 2), cracking did not occur and warpage was small at about 0.1 mm. Therefore, the amount of addition is required to be 5 wt% or more. Conversely, if the amount of elastomer added is large (45 wt% in Table 2 or 43 in Table 3)
wt%), and a warp of 0.6 to 0.7 mm occurred due to environmental changes. This is because the water absorption of the added elastomer is PBT.
It is considered that this is because the effect of deformation due to moisture absorption of the elastomer increases as the amount of addition increases. Therefore, the addition amount is set to 40 wt% or less. And taking these results together, the elastomer has an elongation of 100-
When the amount is 500% (more preferably 120 to 500%), the added amount is 5 to 40% by weight.

[0014]

[Table 2] Addition amount of PBT + ethylene propylene elastomer (wt%) Warp (mm) Drop strength 3 * 0.1 Crack generation 9 0.1 No abnormality 20 0.1 No abnormality 37 0.3 No abnormality 45 * 0.6 No abnormality * is a comparative example, and the total amount of PBT and elastomer is 100 wt%.

[0015]

[Table 3] Addition amount of PBT + urethane rubber A (wt%) Warp (mm) Drop strength 3 * 0.1 Crack generation 7 0.1 No abnormality 20 0.3 No abnormality 38 0.3 No abnormality 43 * 0.7 No abnormality * is a comparative example, and the total amount of PBT and elastomer is 100 wt%.

In any of the shutters shown in Tables 1 to 3, this tendency becomes remarkable as the amount of elastomer increases and the warp increases and the elongation increases. Therefore, Table 4 shows the relationship between the product of the elongation of the elastomer and the amount of addition of the warp after the experience in a high temperature and high humidity atmosphere. As is clear from Table 4, in the shutter 3 in which the product of elongation and addition amount is 1350 to 3360, the warpage is 0.1 mm, but this product is 55
In the shutter 3 of 50 or 6000, the warp is 0.2 to 0.3.
reach mm. Therefore, in order to suppress the warpage to about 0.1 mm or less, it is preferable to set the product of the addition amount in wt% unit and the elongation in% unit to 1000 to 4000.

[0017]

[Table 4] Optimal conditions for warpage Elastomer addition amount Elongation x addition amount Warpage (%) (wt%) (mm) Ethylene propylene elastomer 150 9 1350 0.1 Same as 20 3000 3000 Same as 37 5550 0. 3 Styrene Butadiene Elastomer 300 20 6000 0.2 Urethane Rubber A 480 7 3360 0.1 Same as 20 9600 0.3 Same as 38 38240 0.3 * Repeat only Examples from Table 1 to Table 3.

[0018]

According to the disk cartridge of the present invention,
Polybutylene terephthalate 95 to 60 wt% with 5 to 40 wt% of elastomer with elongation of 100 to 500% is used, and it has high impact resistance and does not cause cracking or deformation at the time of dropping. A shutter for a disc cartridge having a small warp is obtained. This shutter has sufficient hardness, is free from scratches at the time of use, is inexpensive and lightweight, and has the original characteristics of a resin shutter that generates little abrasion powder due to friction with the shell.

[Brief description of drawings]

FIG. 1 is a front view of a magneto-optical disk cartridge according to an embodiment.

FIG. 2 shows a magneto-optical disk cartridge of an embodiment,
Front view with shutter open

[Explanation of symbols]

 1 Shell 2 Magneto-optical disk 3 Shutter 4 Opening window 5 Slider

Claims (1)

[Claims] 1. A disk cartridge comprising a resin shell for accommodating a disk and having an opening window formed therein, and a resin shutter for opening and closing the opening window of the shell, wherein the shutter is made of polybutylene. Terephthalate 95 ~
Elastomer having elongation of 100% or more and 500% or less defined by ASTM D638 to 60 wt% is 5 to 40 w.
A disk cartridge comprising a resin material containing t%.