JP2000082269A - Information recording cartridge and magnetic disk cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an information recording cartridge such as a magnetic disk cartridge, and optical disk cartridge having a highly reliable recording/ reproducing characteristic. SOLUTION: This information recording cartridge is provided with cartridge cases 1 and 4 and a recording medium 3 housed in these cartridge cases 1 and 4. In this case, each of the cartridge cases 1 and 4 is made of a composition containing styrol plastic where a part of styrene is substituted by α- methylstyrene and rubber material, which are uniformly dispersed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording cartridge such as a magnetic disk cartridge and an optical disk cartridge, and more particularly to a highly reliable information recording cartridge even at high temperatures.

[0002]

2. Description of the Related Art Recently, the use environment of a magnetic disk has become widespread not only indoors such as offices but also outdoors or in automobiles with the spread of equipment using magnetic disks. Therefore, the performance of the magnetic disk is required to be strict.

That is, for example, when a car is parked outdoors in the summer, the temperature inside the car may reach 80 ° C. or higher,
When a magnetic disk and its use equipment are mounted in a vehicle, the magnetic disk is also required to withstand the high temperatures described above. Even at low temperatures, low-temperature characteristics are required with the use of magnetic disks and equipment used in extremely cold regions.

For these reasons, the temperature and humidity characteristics were previously set at 4 to 53 ° C. and 8 to 90% RH in product design, but recently, at −40 to 85 ° C. and 8 to 9% RH.
The setting condition is 5% RH, and the upper limit and lower limit of the temperature and the upper limit of the humidity are expanded, which is a severe condition.

The expansion and contraction of the flexible magnetic disk due to temperature and humidity are mainly affected by the temperature and humidity characteristics of the base film. As a base film of this flexible magnetic disk, for example, a polyethylene terephthalate (PET) film is used, and this base film is biaxially stretched in advance. A magnetic layer having a predetermined thickness is formed on the base film that has been subjected to this treatment to form a wide raw film, and a flexible magnetic disk having a predetermined size is punched from the raw film.

[0006]

However, if a magnetic disk cartridge incorporating such a flexible magnetic disk is left under high-temperature and high-humidity conditions, the output fluctuates significantly during signal reproduction, resulting in poor reliability. There's a problem.

In order to solve such a problem, an invention described in Japanese Patent Application Laid-Open No. 63-261587 has been proposed. In this proposal, a flexible magnetic disk and a center core adhered thereto are separately heat-treated. The conditions of the heat treatment are as follows.
0 ° C., humidity 20-80% RH, heat treatment time 12
-100 hours, or a temperature of 60-90 ° C, a humidity of 50-80% RH, and a heat treatment time of 48-72 hours.

As described above, by increasing the humidity during the heat treatment, the processing temperature is lowered and the processing time is shortened.
Increasing the humidity undesirably makes the flexible magnetic disk easier to deform.

An ABS resin is usually used for a cartridge case of a conventional magnetic disk cartridge or optical disk cartridge. However, this ABS resin does not always have good heat resistance. For example, the ABS resin is left at a high temperature as described above, and there is a problem that the cartridge case is thermally deformed. The thermal deformation of the cartridge case not only affects the appearance but also directly affects the recording and reproducing characteristics.

That is, in the case of a magnetic disk cartridge, the cartridge case is deformed into an irregular shape such as a waveform due to heat, and a magnetic disk cartridge having a space in the cartridge case of, for example, 3.5 inches is about 1.
Due to the extremely small width of 5 mm, the magnetic disk is locally strongly pressed against the cleaning sheet attached to the inner surface of the cartridge case. For this reason, the rotational torque of the magnetic disk becomes large, causing a problem that a predetermined rotational speed cannot be obtained or that the magnetic disk does not rotate at all.

Further, when the cartridge case is deformed to the middle bulge, the magnetic disk does not come into contact with the cleaning sheet, so that the essential recording area of the magnetic disk is not cleaned, causing an error.

On the other hand, in the case of an optical disk cartridge,
When the optical disk cartridge is inserted into the recording / reproducing apparatus, a part of the cartridge case comes into contact with a reference position regulating member provided in the apparatus, thereby positioning the optical disk cartridge in the apparatus in the vertical direction. The vertical distance between the reference position regulating member and the optical head (a beam spot formed by irradiating a beam from the optical head) is kept constant by mechanical coupling.

Therefore, as described above, when the cartridge case in which the cartridge case has been thermally deformed (particularly, the portion in contact with the reference position regulating member is deformed in a concave or convex shape) is inserted into the recording / reproducing apparatus and positioned, the optical disk cartridge is positioned. The position of the beam spot with respect to the recording film is shifted in the vertical direction (optical axis direction) by the amount of deformation of the cartridge case.

If such a shift occurs during signal recording, the recording power applied to the recording film becomes insufficient, and desired recording pits cannot be formed. Further, if such a deviation occurs during signal reproduction, the reproducing power applied to the recording film becomes insufficient, so that not only does the S / N decrease, but when the deviation amount is large, a problem of crosstalk occurs. Reliability decreases. Particularly, in order to realize high-density recording on an optical disk, the track interval is inevitably narrower than ever, so that the displacement of the beam spot with respect to the recording film becomes an important problem.

An object of the present invention is to provide a highly reliable information recording cartridge, such as a magnetic disk cartridge or an optical disk cartridge, which solves the disadvantages of the prior art.

[0016]

In order to achieve the above object, a first aspect of the present invention is to provide a cartridge case and a recording medium such as a magnetic disk or an optical disk housed in the cartridge case. In an information recording cartridge such as a magnetic disk cartridge or an optical disk cartridge, the cartridge case is
It is characterized by being molded with a composition in which a styrene resin in which a part of styrene is substituted by α-methylstyrene and a rubber substance are uniformly dispersed.

According to a second aspect of the present invention, there is provided a cartridge case, and a flexible magnetic disk having a magnetic layer formed on a base film and rotatably housed in the cartridge case. In the magnetic disk cartridge, the flexible magnetic disk may be used in an environment where the temperature is 85 ° C. and the humidity is 40% RH.
The maximum heat shrinkage when left for a period of time is 0 to 30 μm, and the cartridge case converts a part of styrene into α-
It is characterized by being molded with a composition in which a styrene-based resin substituted with methylstyrene and a rubber substance are uniformly dispersed.

In the present invention, the temperature of 85 ° C. for obtaining the maximum heat shrinkage of the flexible magnetic disk is based on the upper limit temperature (85 ° C.) of the setting condition in the product design of the information recording cartridge as described above. Things.

[0019]

Embodiments of the present invention will now be described with reference to the drawings. 1 is an exploded perspective view of a magnetic disk cartridge according to this embodiment, FIG. 2 is an enlarged sectional view of a magnetic disk used in the magnetic disk cartridge, and FIG. 3 is a schematic configuration showing a process for processing a raw film. FIG.

As shown in FIG. 1, the magnetic disk cartridge includes an upper case 1, an upper cleaning sheet 2 adhered to an inner surface of the upper case 1, a flexible magnetic disk 3,
Lower cleaning sheet 5 attached to the inner surface of lower case 4
, A lower case 4 and a shutter 6.

The shutter 6 is for opening and closing a head insertion opening 7 formed in the upper case 1 and the lower case 4, and has an opening 8 having substantially the same size as the head insertion opening 7. On the inner surfaces of the upper case 1 and the lower case 4, a substantially circular concave portion 9 (only the lower case 4 is shown) for attaching the upper cleaning sheet 2 and the lower cleaning sheet 5 to predetermined positions is formed. . A hub 10 made of a thin metal plate such as a stainless steel plate is fixed to the center of the magnetic disk 3.

The upper cleaning sheet 2 and the lower cleaning sheet 5 are made of the same material as the cleaning sheet 50 used in another embodiment described later.

The magnetic disk 3 is, as shown in FIG.
It is composed of a base film 11 having a thickness of 30 to 75 μm and a magnetic layer 12 having a thickness of 0.5 to 4 μm applied on the surface thereof (in the present embodiment, both sides but sometimes one side). .

As the base film, for example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), aromatic polyamide, polyimide and the like are used.

An example of the composition of the magnetic paint for forming the magnetic layer 12 is as follows.

Composition example of magnetic paint 100 parts by weight of Co-containing γ-Fe ₂ O ₃ 19 parts by weight of nitrocellulose 12 parts by weight of polyurethane 12 parts by weight of fine alumina particles 16 parts by weight of carbon black 6 parts by weight of oleyl oleate 1 part by weight of butyl cellosolve stearate 200 parts by weight of cyclohexane 200 parts by weight of toluene This composition was mixed and dispersed in a ball mill for 72 hours, and then 8 parts by weight of a trifunctional isocyanate crosslinking agent was added.
The dispersion was further dispersed for 1 hour to obtain a magnetic paint.

This magnetic paint was applied on a wide base film, dried, and calendered to form a magnetic layer having a predetermined thickness to obtain a wide original film.

FIG. 3 is a schematic structural view showing the steps for processing the raw film. The raw film 13 manufactured and wound into a roll as described above is fed out by a feed roll 14 and introduced into a heater box 16 through a preheating roll 15.

The heater box 16 has an inlet 1 at the lower side.
7 is provided with an outlet 18 on the upper side, between which a film passage 19 is formed. This film passage 19
A damper 20 is disposed on both sides of the substrate, and a ceramic heater 21 is further disposed outside the damper 20.

The raw film 13 is placed in the heater box 1
In the state where external force such as tension is not applied as much as possible, the raw film temperature is 90 ° C. or more,
The running raw film 13 is heated by the heater box 16 so that the temperature is preferably raised to 95 ° C. or more and the humidity is less than 20% RH, preferably less than 10% RH. The upper limit of the temperature treatment is preferably about 250 ° C.

The heat-treated raw film 13 is passed through a cooler box 22 adjacent to the heater box 16 and cooled by a cooling gas 23 (for example, dry air from which dust has been removed) flowing in the cooler box 22. The use of the cooler box 22 to return the raw film 13 to a temperature close to room temperature is not always influenced by the cooling state depending on the season, the climate, and the like.
In order to stabilize the quality.

The raw film 13 thus cooled to near normal temperature is fed into the slitter 24, and the raw film 13 is cut into a predetermined width by a cutter. Although a number of rollers, cutters and the like are provided in the slitter 24, they are not shown because the drawing is complicated. The film cut into a predetermined width by the slitter 24 is sent to the next step (not shown) to be punched into a disk shape.
0 is fixed by, for example, an adhesive, and the magnetic disk 3 is obtained.

A 75 μm-thick polyethylene terephthalate film is used as a base film, and a magnetic layer having a thickness of 1 μm is formed on both sides using the above-described magnetic paint to form a raw film 13. Then, the raw film 13 is heat-treated under the conditions described below, slitted, and then punched into a 3.5-inch disk 25.

FIG. 4 is a diagram showing the longitudinal direction and the lateral direction of the raw film 13. The arrow MD in the figure is the longitudinal direction of the raw film 13, and the elongation in this direction is the largest at the stage of film production. It is. The arrow TD in the figure is a short direction orthogonal to the longitudinal direction MD, and the degree of elongation is smaller than that in the longitudinal direction MD. The disk 25 is continuously and efficiently punched from the raw film 13.

The amount of heat shrinkage when each sample disk thus punched was left at 85 ° C. and 40% RH for 96 hours (4 days) was measured, and the results are shown in FIG.

In the figure, the horizontal axis shows the temperature during the heat treatment of the raw film, and the vertical axis shows the heat shrinkage as a negative value. The humidity during the heat treatment of the raw film was less than 10% RH, and the heat treatment time was 2 hours. The black circles in the figure indicate the heat shrinkage in the longitudinal direction (MD) of the raw film, and the white circles indicate the heat shrinkage in the transverse direction (TD) of the raw film (actually, a positive value, slightly expanding due to heat). ) Are shown.

As is apparent from this figure, although the dimensional change in the transverse direction (TD) of the raw film is scarcely observed, heat shrinkage in the longitudinal direction (MD) is conspicuous, and the amount of heat shrinkage is low at the heat treatment temperature. Is more remarkable. By the way, heat treatment temperature is 65 ℃
In the case of (sample A in the figure), the heat shrinkage in the longitudinal direction (MD) is as large as 100 μm, and in the case of 80 ° C. (sample B in the figure), the heat shrinkage is 77 μm and in the case of 85 ° C. The heat shrinkage of the sample C) is 50 μm. However, when the heat treatment temperature is 9
If the temperature is 0 ° C. or more (samples D, E, and F in the figure), the heat shrinkage can be suppressed to 30 μm or less.
If the temperature is 5 ° C. or more (samples E and F in the figure), the heat shrinkage is 10
μm or less. If this amount of heat shrinkage is absent, there is nothing to do with it, so the lower limit of the amount of heat shrinkage is 0 μm.

Regarding the dimensional change in the transverse direction (TD) of the raw film, a film having a large amount of heat shrinkage in the longitudinal direction (MD) tends to expand due to the shrinkage. The sample having a small heat shrinkage, that is, the sample having a heat shrinkage of 30 μm or less (samples D, E, and F) has the short direction (T
There is almost no dimensional change in D), indicating that the dimensional stability of the disk is good.

Table 1 below shows each of the samples A to A shown in FIG.
5 is a table summarizing the results of measuring the output level of F. This output level was measured at 23 ° C. and 50% RH using a 3.5-inch 2M byte magnetic disk drive.
The signal is recorded under the condition (1), and the average output (initial output) of one round of the track is measured under the same condition.
After leaving the disk and the drive device under an environment of 85 ° C. and 40% RH for 24 hours, the recording signal was read out, the minimum output among the outputs of one track was calculated, and the ratio was shown by the ratio to the initial output. .

Table 1 Sample disk output level (%) A 52 B 34 C 40 D 92 E 98 F 96 As can be seen from this table, the sample disks A to C have output level fluctuations in tests under high temperature and high humidity. Is large, but the sample disks D to F according to the present invention (the heat shrinkage is 30
.mu.m or less) has little fluctuation in the output level even in the severe test as described above, and has high reliability.

FIGS. 6 to 8 are views showing another example of the heat treatment method. FIG. 6 is a plan view of the magazine, FIG. 7 is a side view of the magazine, and FIG. It is a schematic plan view showing the state where it was placed.

As shown in FIGS. 6 and 7, the magazine 30 is formed of a heat-resistant synthetic resin.
And a pin 32 erected at the center thereof. A magnetic disk 3 having a predetermined size is punched from a wide original film, and the punched magnetic disks 3 are inserted into pins 32 of a magazine 30 as shown in FIG.

As shown in FIG. 8, the magazine 30 holding a large number of magnetic disks 3 stacked on each other is
3 and placed sequentially. This heat treatment shelf 3
A heater 34 is disposed outside the heater 3, and the heat treatment temperature is controlled by the amount of electricity supplied to the heater 34. As such a heat treatment apparatus, a commercially available blower type high temperature bath can be used. Although the heat treatment conditions are almost the same as those in the above-described embodiment, it is preferable that the heat treatment time is longer than that in the above-described embodiment because a large number of magnetic disks 3 are heat-treated.

In the case of this embodiment, the magnetic disk 3 is placed in a horizontal position so that no external force is applied to the magnetic disk 3 during the heat treatment. After the heat treatment in this manner, a hub is attached to the center of the magnetic disk 3 according to a conventional method.

9 to 14 are views for explaining a magnetic disk cartridge according to another embodiment of the present invention. FIG. 9 is an exploded perspective view of the disk cartridge, and FIG. 10 shows a cleaning sheet in an upper case. FIG. 11 is a bottom view showing a state in which the cleaning sheet is attached, FIG. 11 is a plan view showing a state in which a cleaning sheet is attached to the lower case, and FIG. 13 is an enlarged sectional view of the vicinity of the elastic piece of the magnetic disk cartridge, and FIG. 14 is an enlarged sectional view of the cleaning sheet.

The magnetic disk cartridge mainly comprises a cartridge case 41, a magnetic disk 42 rotatably housed therein, and a shutter 43 movably supported by the cartridge case 41.

The cartridge case 41 includes an upper case 41a.
And a lower case 41b, which are injection-molded with the following materials.

An opening 44 for inserting a rotary drive shaft is formed substantially at the center of the lower case 41b, and a rectangular magnetic head insertion opening 45 is provided near the opening 44. Similarly, the magnetic head insertion opening 45 is provided in the upper case 41a. Is provided. In the vicinity of the front surfaces of the upper case 41a and the lower case 41b, as shown in FIG. 9, recesses 46 are formed slightly lower in order to regulate the movement range of the shutter 43, and the head 46 is located at an intermediate position between the recesses 46. An insertion slot 45 is provided.

As shown in FIG. 11, counterbore-shaped recesses 47 are formed on the inner surface of the upper case 41a and on both left and right sides of the magnetic head insertion slot 45, respectively. The vertical width W1 of the concave portion 47 is substantially equal to the longitudinal width (vertical width) W2 of the magnetic head insertion slot 45, and the horizontal width W3 of the concave portion 47 is the width (horizontal width) in the direction orthogonal to the longitudinal direction of the magnetic head insertion slot 45. W4 is regulated to 0.3 times or more, preferably 0.5 to 1.5 times.

A large number of linearly extending projections 48 are provided on the upper case 41a on the upstream side of the magnetic head insertion slot 45 in the disk rotation direction, and two projections 48 on both sides are slightly higher than the projections 48 on the inner side. ing.

The magnetic disk 4 is provided on the inner surface of the upper case 41a.
An arc-shaped restricting rib 49 for restricting the storage position of No. 2 protrudes, a part of which passes through the end of the concave portion 47, and the restricting rib 49 also serves as a reinforcing member around the concave portion 47.

A substantially C-shaped cleaning sheet 50 is inserted inside the regulating rib 49. The width W5 of the opening 51 provided at a position corresponding to the magnetic head insertion port 45 of the cleaning sheet 50 is
Is slightly larger than the width W4. By mounting the cleaning sheet 50 on the inner surface of the upper case 41a, the recess 47 and the projection 48 are also covered, and the peripheral portion of the cleaning sheet 50 is ultrasonically welded to the upper case 41a. Since the concave portion 47 of the upper case 41a has a sufficient width, the edge of the opening 51 in the cleaning sheet 50 can be subjected to ultrasonic welding 52 in the concave portion 47 as shown in FIG.

As shown in FIGS. 11 and 13, a ridge support 53 and a ridge 54 for preventing sticking are provided on the inner surface of the lower case 41b and at a position substantially opposite to the protrusion 48 of the upper case 41a. ing. The base 56 of the elastic piece 55 formed by bending the plastic sheet is
It is fixed to the inner surface of 1b and in the vicinity of the support portion 53 by an appropriate means such as adhesion or heat fusion. The free end 57 of the elastic piece 55 is supported by the support portion 53, and the inclined state thereof is maintained.

A regulating rib 49 is also provided on the inner surface of the lower case 41b, and a cleaning sheet 50 is arranged on the inner surface of the regulating rib 49. The width W5 of the opening 51 provided at a position corresponding to the magnetic head insertion opening 45 of the cleaning sheet 50.
Is designed to be slightly larger than the width W4 of the magnetic head insertion opening 45. By placing the cleaning sheet 50 inside the lower case 41b as shown in FIG.
The elastic piece 55 is covered, and the peripheral portion of the cleaning sheet 50 is ultrasonically welded 52 to the lower case 41b, but the ultrasonic weld 52 is omitted near the elastic piece 55.

When a magnetic disk cartridge is assembled by combining the upper case 41a and the lower case 41b,
As shown in FIG. 13, the lower case 41b is
The cleaning sheet 50 is partially lifted from the magnetic disk 4 by the projection 48 provided on the upper case 41a.
2 is elastically held between the upper and lower cleaning sheets 50 and 50. Then, as the magnetic disk 42 rotates, the disk surface is cleaned by the cleaning sheet 50.

FIG. 12 is a diagram showing a state of use of the magnetic disk cartridge. In FIG. 12, reference numeral 58 denotes a magnetic head.
As shown in FIG.
It has a layer structure. That is, a disk-side nonwoven fabric layer 59 facing the magnetic disk 42, a case-side nonwoven fabric layer 60 facing the cartridge case 41, and an intermediate nonwoven fabric layer 61 connecting the disk-side nonwoven fabric layer 59 and the case-side nonwoven fabric layer 60. Have.

The disc-side nonwoven fabric layer 59 and the case-side nonwoven fabric layer 60 are both made of rayon fiber alone, so that there is no distinction between front and back. As the rayon fiber, viscose rayon, cuprammonium rayon, acetate rayon and the like are used. Rayon fiber (stable) has a tensile strength of about 2.5 to 3.1
g / D, elongation is about 16-22%, elongation modulus (at 3% elongation) is about 55-80%, and specific gravity is about 1.50-1.52.

The intermediate nonwoven fabric layer 61 is composed of a mixed fiber layer of rayon fiber and polyamide fiber. The mixing ratio of rayon fiber to polyamide fiber (rayon fiber / polyamide fiber) is appropriately selected in the range of about 1/9 to 9/1, and particularly preferably in the range of 3/7 to 7/3.

The polyamide fiber is a fiber using a polycondensate of adipic acid and hexamethylenediamine as a raw material monomer. Polyamide fiber has a tensile strength of about 4.5 to 7.5.
g / D, elongation is about 25-60%, elongation modulus (at 3% elongation) is about 95-100%, and specific gravity is about 1.14.

The cleaning sheet 50 may be made of rayon fiber alone, but as in the present embodiment, an intermediate nonwoven fabric made of a nonwoven fabric containing thermoplastic fibers between the disk-side nonwoven layer 59 and the case-side nonwoven layer 60 as in the present embodiment. Layer 61
Is provided, it is possible to satisfactorily heat seal with the cartridge case.

The intermediate nonwoven fabric layer 61 is preferably made of various thermoplastic fibers such as polyethylene terephthalate, polyethylene, polypropylene, polystyrene, polyvinyl chloride, and acrylic resin, in addition to the mixture of rayon fiber and polyamide fiber as described above. Can be used. Particularly, as described above, the disk-side nonwoven fabric layer 59 and the case-side nonwoven fabric layer 60
Since rayon fiber is used for both layers 5
Considering the compatibility with 9, 60, the intermediate nonwoven fabric layer 61 is preferably composed of a mixed fiber layer containing rayon fibers.

The basis weight of the cleaning sheet 50 is
Although not particularly limited, about 20 to 50 g / m ² is suitable. The basis weight here is 50 × 50c.
This is a value obtained by measuring the weight of five samples of m and taking the average value.

The thickness of the cleaning sheet 50 is 150
３００300 μm is appropriate. Specific physical properties of the cleaning sheet 50 according to the embodiment are as follows.

Table 2 Weight per unit area 43 (g / m ² ) Thickness 220 (μm) Tensile strength Vertical direction 5.50 (kg / 5 cm) Tensile strength Horizontal direction 1.10 (kg / 5 cm) Charge decay time (temperature 20) Humidity 65 ° C) 0.6 (sec) Surface electric resistance 9 × 10 ¹⁰ (Ω) Coefficient of friction against magnetic disk 1 The cleaning sheet 50 has a three-layer structure as described above. When the magnetic disk cartridge is assembled by the
All of the fibers that come into contact with the cleaning sheet 50 may not be rayon fibers, and only a part of the thermoplastic fibers in the intermediate nonwoven fabric layer 61 may be entangled with each other.
And may come into contact with the magnetic disk 42. However, even in this case, the ratio of the thermoplastic fibers in contact with the magnetic disk 42 is about 10% or less, and substantially all of the fibers in contact with the magnetic disk 42 are rayon fibers.

In this embodiment, the case of a cleaning sheet having a three-layer structure has been described. In addition, for example, a nonwoven fabric made of rayon fiber alone, rayon fiber and other fibers (eg, polyethylene terephthalate fiber, acrylic fiber, polypropylene fiber, polyamide fiber) And the like can also be used.

Next, the material of the cartridge case will be described. The cartridge case according to the present invention is formed of a composition in which a styrene-based resin in which a part of styrene is substituted with α-methylstyrene and a rubber substance are uniformly dispersed.

Examples of the styrene resin include polystyrene and a copolymer of styrene and acrylonitrile (A
(S resin: acrylonitrile content: 20 to 30% by weight), a copolymer of acrylonitrile, butadiene, and styrene (ABS resin).

The ABS resin is classified into a blend type and a graft type. The blend type ABS resin is obtained by mixing a predetermined amount of nitrile rubber (NBR) with a copolymer of styrene and acrylonitrile (AS resin). On the other hand, the graft type ABS resin is obtained by copolymerizing styrene and acrylonitrile in the presence of polybutadiene. At this time, since the polybutadiene has a form in which a styrene-acrylonitrile copolymer is partially graft-polymerized, it has particularly excellent impact resistance.

It is preferable that the content of α-methylstyrene in the above-mentioned styrene resin is regulated in the range of 20 to 60% by weight. α-methylstyrene content of 2
When the content is less than 0% by weight, the effect of improving heat resistance is insufficient. On the other hand, when the content of α-methylstyrene exceeds 60% by weight, the cartridge case tends to be mechanically brittle. It is not preferable to form such a thin wall.

Examples of the rubber substance include diene rubbers such as butadiene rubber, styrene-butadiene rubber, isoprene rubber, acrylonitrile-butadiene rubber, chloroprene, butyl rubber, ethylene-propylene rubber, acrylic rubber, and chlorosulfonated polyethylene rubber. Olefin rubber, fluorine rubber, silicone rubber, urethane rubber, and the like.

FIG. 15 is an explanatory diagram when the present invention is applied to an optical disk cartridge. As shown in the figure, the optical disc cartridge includes a cartridge case 71,
It mainly comprises an optical disk 72 rotatably housed therein and a shutter 73 slidably supported by the cartridge case 71.

In the drawing, 74 is a head access port, and 75 is a shutter holding plate. The cartridge case 7
No. 1 is formed of a composition in which a styrene-based resin in which a part of styrene is substituted with α-methylstyrene and a rubber substance are uniformly dispersed as described above.

[0073]

According to the present invention, a cartridge case (3.5) molded from a composition in which a styrene resin in which a part of styrene is substituted by α-methylstyrene and a rubber substance are uniformly dispersed.
Inches) and a cartridge case (same size) molded with a conventional ABS resin was measured under the conditions of 85 ° C. and 40% RH for 96 hours (4 days). The warpage of the conventional cartridge case was 0.97 mm, whereas that of the present invention was only 0.04 mm. The amount of warpage of the cartridge case was measured by a shape measuring instrument manufactured by Kosaka Laboratory.

According to a first aspect of the present invention, as described above, in an information recording cartridge including a cartridge case and a recording medium housed in the cartridge case, the cartridge case contains a part of styrene. α
-Characterized by being molded with a composition in which a styrene resin substituted with methylstyrene and a rubber substance are uniformly dispersed. As a result, the heat resistance and moldability of the cartridge case can be improved, and from this, it is possible to provide an information recording cartridge having high recording and reproduction characteristics.

According to a fourth aspect of the present invention, as described above, a cartridge case and a disk-shaped flexible magnetic recording medium rotatably housed in the cartridge case with a magnetic layer formed on a base film are provided. In the magnetic disk cartridge provided, the flexible magnetic recording medium has a maximum heat shrinkage of 30 μm or less when left in an environment of a temperature of 85 ° C. and a humidity of 40% RH for 96 hours. It is characterized by being molded with a composition in which a styrene resin in which a part of styrene is substituted by α-methylstyrene and a rubber substance are uniformly dispersed. By using a cartridge case excellent in heat resistance and moldability in combination with a disk-shaped flexible magnetic recording medium excellent in dimensional stability, both the cartridge case and the flexible magnetic recording medium are not thermally deformed. A high magnetic disk cartridge can be provided.

As described above, the present invention according to claims 2 and 5 is characterized in that the styrene resin is a graft type ABS resin in which a part of styrene is substituted with α-methylstyrene. is there. When the graft type ABS resin is used, the impact resistance of the cartridge case can be improved.

As described above, the present invention according to claims 3 and 6 has a content of α-methylstyrene of 20 to 6
It is characterized in that it is restricted to a range of 0% by weight. When the content of α-methylstyrene is regulated in this way, the effect of improving the heat resistance is assured and the thin-wall moldability is improved.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a magnetic disk cartridge according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a magnetic disk used in the magnetic disk cartridge.

FIG. 3 is a schematic configuration diagram showing a process for processing an original film.

FIG. 4 is a diagram for explaining a longitudinal direction and a lateral direction of an original film.

FIG. 5 is a characteristic diagram showing the relationship between the heat treatment temperature of the raw film and the amount of heat shrinkage of the disc when the disc is stored after heat treatment.

FIG. 6 is a plan view of a magazine used for heat treatment.

FIG. 7 is a side view of the magazine.

FIG. 8 is a schematic plan view showing a state where the magazine is placed on a heat treatment shelf.

FIG. 9 is an exploded perspective view of a magnetic disk cartridge according to another embodiment of the present invention.

FIG. 10 is a bottom view showing a state in which a cleaning sheet is attached to an upper case.

FIG. 11 is a plan view showing a state in which a cleaning sheet is attached to a lower case.

FIG. 12 is an enlarged cross-sectional view of the vicinity of a magnetic head insertion slot showing a usage pattern of the magnetic disk cartridge.

FIG. 13 is an enlarged sectional view of the vicinity of an elastic piece of the magnetic disk cartridge.

FIG. 14 is an enlarged sectional view of a cleaning sheet used in the magnetic disk cartridge.

FIG. 15 is a plan view of an optical disc cartridge according to still another embodiment of the present invention.

[Explanation of symbols]

 1, 41b Upper case 3, 42 Magnetic disk 4, 41a Lower case 11 Base film 12 Magnetic layer 13 Raw film 30 Magazine 41, 71 Cartridge case 72 Optical disk

 ──────────────────────────────────────────────────続 き Continued on the front page (31) Priority claim number Japanese Patent Application No. 2-129164 (32) Priority date May 21, 1990 (May 21, 1990) (33) Priority claim country Japan (JP) (72) Inventor Akira Katami 1-88 Ushitora, Ibaraki-shi, Osaka Prefecture Within Hitachi Maxell Co., Ltd. (72) Inventor Shinichiro Oda 1-1-88 Ushitora, Ibaraki-shi, Osaka Prefecture Within Hitachi Maxell Co.

Claims (6)

[Claims] 1. An information recording cartridge comprising a cartridge case and a recording medium housed in the cartridge case, wherein the cartridge case is made of a styrene-based resin in which a part of styrene is replaced with α-methylstyrene. An information recording cartridge formed of a composition in which a rubber substance is uniformly dispersed. 2. The information recording cartridge according to claim 1, wherein the styrene resin is a graft-type acrylonitrile-butadiene-styrene copolymer in which a part of styrene is substituted with α-methylstyrene. Information recording cartridge. 3. The information recording cartridge according to claim 1, wherein the content of the α-methylstyrene is regulated in a range of 20 to 60% by weight. 4. A magnetic disk cartridge comprising: a cartridge case; and a flexible magnetic disk having a magnetic layer formed on a base film and rotatably housed in the cartridge case, wherein the flexible magnetic disk has A maximum heat shrinkage of 0 to 30 μm when left in an environment of 85 ° C. and a humidity of 40% RH for 96 hours; A magnetic disk cartridge formed of a composition in which a rubber material is uniformly dispersed. 5. The magnetic disk cartridge according to claim 4, wherein the styrene resin is a graft-type acrylonitrile-butadiene-styrene copolymer in which a part of styrene is substituted with α-methylstyrene. Magnetic disk cartridge. 6. The magnetic disk cartridge according to claim 5, wherein the content of the α-methylstyrene is 20 to
A magnetic disk cartridge which is regulated to a range of 60% by weight.