JPS60246071A - Magnetic disk cartridge - Google Patents

Abstract

PURPOSE:To obtain a magnetic disk cartridge which excels in thermal stability, shock resistance, etc. by using a hard polyvinyl chloride sheet having low temperature side peak higher than a high temperature side peak in case two heat absorption peaks of a differential thermal analysis exist in a specific temperature range where one or two said peaks exist normally. CONSTITUTION:An oblong material 4 of a heat resistant hard polyvinyl chloride sheet having a low temperature side peak higher than a high temperature side peak is used in case two heat absorption peaks of a differential thermal analysis exist within a 60- 105 deg.C range. The said hard polyvinyl chloride is obtained by processing a copolymer of No.405 post-chlorinated polyvinyl [made of SUMITOMO Bakelite Company, polyvinyle chloride, (metha)acrylic acid ester, etc. for a prescribed period of time in a range of (Tg-40) deg.C-Tg with the glass transition temperature set at Tg( deg.C)]. A cleaning sheet 3 of unwoven fabric of polypropylene, etc. is put on said polyvinyl sheet and partially unified with thermal fusing. Then this laminated sheet is folded at a point near a folding line 6 with heating, and edge parts 5 and 5'' are folded with heat fusing. A magnetic disk 2 is put into a hollow part, and an edge part 5' is folded and fixed with a paste agent. Thus it is possible to obtain a cartridge which excels in the size stability at a high temperature, the impact resistance at a low temperature, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic disk cartridge, and more particularly to a magnetic disk cartridge having improved thermal stability, one-dimensional stability, and impact resistance at low temperatures.

BACKGROUND OF THE INVENTION Magnetic disks have recently attracted attention as magnetic recording media for use in devices such as word processors and microcomputers, and are being produced in large quantities. This magnetic disk is normally used by being rotatably housed in a cartridge having at least an opening for externally driving and rotating the disk and an opening for recording and reproducing.

Such cartridges are usually made from polyvinyl chloride sheets, but conventional cartridges suffer from poor quality characteristics at high or low temperatures. As the usage of magnetic disks expands, this drawback becomes more apparent, and improvements are desired.

For example, magnetic disks are increasingly being used at high temperatures of 60° or higher, but conventional cartridges are subject to large thermal deformations such as elongation and warping, and such thermal deformation affects the normal operation of magnetic disk recording and reproducing devices. Not only is it difficult to install and remove the disc, but the disc is held in an eccentric state in the recording/reproducing device, causing problems such as incorrect tracking and other problems.

Furthermore, when a magnetic disk is handled in an atmosphere with a low temperature of KO'0 or below, the cartridge housing the magnetic disk becomes brittle, its impact resistance decreases, and even a small impact can damage the cartridge. Breakage is often a problem. For this reason, in the past, in order to improve the impact resistance strength in cold weather, various low molecular weight compounds called cold impact agents, flexible high molecular weight compounds, etc. were blended into polyvinyl chloride. Measures have been taken to copolymerize or graft various polymers, such as vinyl acetate and acrylic esters, to these materials. However, even with these measures, the cold impact strength has not been sufficiently improved. Furthermore, these countermeasures have the effect of deteriorating the physical properties at high temperatures.

In order to improve the physical properties at high temperatures, there are methods to use large amounts of post-chlorinated polyvinyl chloride, low-temperature polymerization polyvinyl chloride, etc., but these methods not only increase costs but also reduce the impact properties at cold temperatures. Become.

As described above, there is an antinomic relationship between improving physical properties at high temperatures and improving physical properties at low temperatures, and it is difficult to satisfy both at the same time, and so far there has been no solution that has been able to satisfy both.

Purpose of the Invention The present inventors have worked hard to solve the problems of the prior art and develop a cartridge, that is, a magnetic disk cartridge, that has physical properties that do not cause problems in recording and reproducing over a wide temperature range. As a result of research, we have arrived at the present invention.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a magnetic disk cartridge having improved thermal stability, dimensional stability, and impact resistance at low temperatures.

Structure and Effects of the Invention An object of the present invention is to provide a magnetic disk car or trille made of a synthetic resin sheet, in which the synthetic resin sheet has one or two endothermic peaks in the temperature range of 60 to 105°0 in differential thermal analysis. If there are two, this can be achieved by a magnetic disk cartridge characterized by being a hard polyvinyl chloride sheet in which the peak on the low temperature side is larger than the peak on the high temperature side. These 5 endothermic peaks are presumed to be endothermic peaks corresponding to what is usually called the glass transition endothermic peak. Also, the magnitude of the endothermic peak means the magnitude of the endothermic amount (Joule/Il).

This magnetic disk car) IJ Tsuji has high deformation resistance and dimensional stability at high temperatures, and does not warp or stretch.

It is characterized by little change in shape such as deformation, and, which is difficult to predict based on conventional technical knowledge, it also has high impact resistance at cold temperatures of 0°0 or below, which is much lower than the glass transition temperature. It has the characteristic of being greatly improved in width.

The hard polyvinyl monochloride in the present invention is analyzed by differential thermal analysis (equipment: DuPont 910 differential thermal analyzer: temperature rise 10'
60' when measured at a nitrogen flow rate of 48 d/min)
1 or 2 endothermic peaks in the O~105'0(1) range
If there are two numbers, it is hard polyvinyl chloride whose low temperature peak is larger than the high temperature peak.

When the above two endothermic peaks are shown, the low temperature peak is 0.7
It is preferably at least 1.0 joule/g, more preferably at least 1.0 joule/g. When such an endothermic peak is exhibited, mechanical properties at low temperatures are particularly excellent. Further, a material having one endothermic peak is not only preferable in terms of the above-mentioned physical properties, but also has advantages such as ease of bending, and is therefore preferable.

At this time, the magnitude of the endothermic peak is preferably 0.5 joules/g or more, more preferably 1.0 joules/11 or more.

The hard polyvinyl chloride in the present invention is not particularly limited as long as it has the above endothermic peak characteristics. For example, so-called polyvinyl chloride.

Polyvinyl chloride polymerized at low or medium temperatures, or post-chlorinated polyvinyl chloride alone or in combination, or reactive monomers such as vinyl acetate, acrylic esters, methacrylic esters, vinyl ether maleic derivatives, vinylidene chloride. . Among these, polyvinyl chloride, post-chlorinated polyvinyl chloride, or a mixture thereof is particularly preferred.

Such hard polyvinyl chloride may be a chlorinated polyolefin or an ethylene copolymer, if desired.

Acrylic acid or methacrylic acid polymers may be blended, and various additives such as stabilizers, plasticizers, pigments, etc. may be blended. Stabilizers include inorganic acid salts (e.g. basic lead carbonate, etc.) as heat stabilizers.
.

Metal soaps (e.g. barium stearate, calcium stearate, etc.), organotin compounds (e.g. dibutyltin laurate, etc.), phenol crocodile conductors, benzophenone derivatives, salicylic aS conductors, etc. as anti-oxidation inhibitors or deterioration due to ultraviolet rays, and epoxy compounds. , sulfur compounds, phosphorus compounds, etc.

In the present invention, a rigid polyvinyl chloride sheet exhibiting 5 differential thermal analysis peaks is obtained when a normal polyvinyl chloride sheet is expressed as the glass transition temperature of the polyvinyl chloride (TgC'O).
Tg -40) 'O to Tg temperature range for a specified time,
Easily obtained by heat treatment. More preferably, the heat treatment is performed at (Tg -40) 0 to (Tg -lo) "0. The gloss treatment time is at least 1 hour, more preferably 3 hours or more, and even more preferably 5 hours or more. Heat treatment reduces the endothermic peak to 60-105
This situation will be further explained by taking Sumitomo Bakelite's φ405 heat-resistant polyvinyl chloride (post-chlorinated polyvinyl chloride, degree of polymerization 62Q, degree of chlorination 66CH) as an example. .

This heat-resistant polyvinyl chloride exhibits an absorption curve indicated by symbol A in FIG. 1, with an endothermic peak of 109°C and an endothermic amount of 2.5 J/g. When this heat-resistant polyvinyl chloride is heat-treated at 60°0 for 24 hours, it becomes an absorption curve shown by symbol B, with an endothermic peak of 106'O and an endothermic amount of 1.6 Joule/y. The afterheating curve is shown by symbol C, with an endothermic peak of 95°0 and an endothermic amount of 1.5 joules/g.

In order to achieve the object of the present invention, this heat-resistant polyvinyl chloride is preferably heat-treated at 70°C for 24 hours.

The magnetic disk car 1 to the ring of the present invention is characterized in that it is made from the above-mentioned hard polyvinyl chloride sheet, and its structure can be of a structure known per se. 2 to 4 are shown as examples of this structure □ A magnetic disk cartridge 1 is normally lined with a cleaning sheet 3 and forms a space for rotatably housing a magnetic disk 2 punched into a donut shape. The cleaning sheet 3 is usually made of a nonwoven fabric such as a nonwoven fabric made of polypropylene fibers and rayon fibers, and the sheet 3 is fixed to the sheet material 4 by partially heat-sealing it. . This cleaning sheet 3 comes to be interposed between the magnetic disk 2 and the cartridge l.

The magnetic disk 2 is formed by forming a magnetic recording layer on one or both sides of a synthetic resin base film having flexibility and elasticity, such as polyester film, etc., and is usually manufactured by punching it into a donut shape. The through hole 7 in the center of the magnetic disk 2 is a hole that engages with the rotary drive shaft of the recording/reproducing device, and the magnetic guide 7-1. A recording track of a predetermined width is formed on the button 8.

In the rectangular sheet material 4, there are magnetic disks 2 in two square parts separated by the center bending line (broken line 6).
A drive opening 8 corresponding to the through hole 7 and having a larger diameter than the through hole 7 and exposing the peripheral portion of the through hole 70, and a recording/reproducing opening for the magnetic head to access across the recording track of the disk 2. A starting point detection hole 10 is provided for detecting the starting point of the track in the circumferential direction of the disk 2, thereby determining the starting point of the radial movement of the disk 2, and for correctly tracking the magnetic head.

In this way, the rectangular sheet element 4 with the cleaning sheet 3 fused to one side is folded along the center bending line 6 with the cleaning sheet 3 inside, and the magnetic disk 2 is inserted into the formed hollow part. Each laminating edge 5
, 5', and 5' are bent and heat-sealed to the outer surface of the other square portion of the sheet body 4 to make a disk containing the magnetic disk 2.

The magnetic disk cartridge of the present invention is made of a hard polyvinyl chloride sheet that exhibits a specific endothermic peak, has excellent thermal stability, has little thermal deformation such as elongation or warping at high temperatures, and has excellent recording and playback characteristics of the magnetic disk it accommodates. It has the advantage of being highly stabilized and also has high impact resistance in cold weather.

Example The present invention will be further explained below with reference to Examples.

Example 1 and Comparative Examples 1 and 2 Heat-resistant polyvinyl chloride (manufactured by Sumitomo Bakelite Co., Ltd. $405:
Post-chlorinated polyvinyl chloride, degree of polymerization 620, degree of chlorination 60
'%) sea) at 60°0 for 24 hours and at 70°0 for 24 hours.
Each was heat-treated for 4 hours. those that are not heat treated,
The endothermic curve of the heat-treated material in differential thermal analysis was as shown in Figure 1.

A rectangular sheet material 4 having the shape shown in FIG. 4 is made from each sheet, and a cleaning sheet 3 made of a nonwoven fabric made of polypropylene fibers and rayon fibers and having the shape shown in FIG. 4 is layered thereon.

The two were integrated by partial heat fusion treatment.

Thereafter, the rectangular sheet material 4 near the center bending line 6 was heated with a heater and then bent so that the Y-lining sheet 3 was on the inside. Furthermore, the bonding edges 5, 5' of the sheet material were bent and heat-sealed in the same manner. A magnetic disk 2 formed by overlaying a magnetic layer on a polyethylene terephthalate film was inserted into the formed hollow portion, and the bonding edge 5' was further bent and fixed with glue.

The dimensional stability and heat deformation resistance of the obtained disk at high temperatures were determined by checking the presence or absence of deformation after storing it at 60゛0 for 144 hours.
The criterion was determined as to whether or not the disk could pass through a slit of a predetermined width (2.41 m) by free fall. Those that passed the test were considered to have passed the test, and those that did not pass the test were considered to have failed.

The impact resistance at low temperatures was determined by cooling to -s'o and dropping a 500 g steel ball from above 30 nm onto a magnetic disk cartridge, and determining whether or not a crank was generated due to the impact of the drop.

Furthermore, the aesthetic appearance of the bent portion, which is strongly emphasized by users when commercializing magnetic disk cartridges, was evaluated by a visual test.

The results are shown in Table 1.

Example 2 Polyvinyl chloride [degree of polymerization = 700: stabilizer (dibutyl tin malate type) content: 10 pHR: filler (carbon black) content: 15 pHR] with a thickness of 210 microns
The sheet was heat treated at 60°C for 48 hours.

Differential thermal analysis was performed on the sample before heat treatment (untreated product) and the sample subjected to the heat treatment (heat-treated product). The results are shown in FIG.

At the 6th meter, the symbol is the endothermic curve of the untreated product, and the endothermic peak is 70°0 (endothermic amount 0.46 joules/1 liter and 8
There are two at 1°0 (endothermic amount 1.46 joules/g). Symbol E is the endothermic curve of the heat-treated product, and the endothermic peak is go
'o (endothermic amount 2.9 joules/f).

Using these, discs were prepared in the same manner as in Example 1, and the same characteristics were evaluated. The results are shown in Table 2.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an endothermic curve in differential thermal analysis. FIG. 2 is a front view of the magnetic disk cartridge, FIG. 3 is a sectional view taken along line II, and FIG. 4 is a developed view of the magnetic disk cartridge. FIG. 5 is a diagram showing an endothermic curve in differential thermal analysis. 1: Magnetic disk cartridge. 2; Magnetic disk. 3; Cleaning sheet. ,, JfA force it sheet number, Dou 9. 5.5', 5': Edge. 6: Bending part. 7: Penetration of M1 Qi disk. 8: Cartridge opening. 9=Cartridge opening. 10: Detection hole of cartridge. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] In a magnetic disk cartridge made of a synthetic resin sheet, the synthetic resin sheet has one or two endothermic peaks in the temperature range of 60 to 105'O in differential thermal analysis, and when there are two peaks, the peak on the low temperature side is on the high temperature side. A magnetic disk cartridge characterized by being a sheet of hard polyvinyl chloride that is more dog than peak.