AU622297B2

AU622297B2 - Compact cassette having at least one substantially rectangular support liner and support liner for this cassette

Info

Publication number: AU622297B2
Application number: AU52207/90A
Authority: AU
Inventors: Juergen Ahlers; Klaus Manzke
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 1989-03-28
Filing date: 1990-03-27
Publication date: 1992-04-02
Anticipated expiration: 2010-03-27
Also published as: EP0390023B1; CN1020980C; EP0390023A1; JPH02285571A; ZA902340B; DE8903787U1; CN1047413A; AU5220790A; DE59008328D1

Description

COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952-69 COMPLETE SPECIFICATION

(ORIGINAL)

Form Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: S' Priority 'Related Art ,Name of Applicant Address of Applicant BASF AKTIENGESELLSCHAFT 6700 Ludwigshafen, Federal Republic of Germany klaus manzke and JUERGEN AHLERS WATERMARK PATENT TRADEMARK ATTORNEYS.

LOCKED BAG NO. 5, HAWTHORN, VICTORIA 3122, AUSTRALIA Actual Inventor Address for Service Complete Specification for the invention entitled: COMPACT CASSETTE HAVING AT LEAST ONE SUBSTANTIALLY RECTANGULAR SUPPORT LINER AND SUPPORT LINER FOR THIS CASSETTE The following statement is a full description of this invention, including the best method of performing it known to O.Z. 0050/40677 Compact cassette having at least one substantially recttangular support liner and support liner for this cassette The present invention relates to a compact cassette having at least one substantially rectangular plastic support liner which is arranged above and/or below the V tape rolls and essentially covers these over their area and which has at least one longitudinal bend for elastic support of the tape rolls, and a support liner for this cassette.

It is known that, in compact cassettes (corresponding to DIN 45,516), support liners can be used as means for irtiroving the roll support and the friction properties during rewind and playback. These liners can fee* 15 be provided with bends and beads for roll support and for reducing the contact areas.

I: As a rule, these support liners consist of (aliphatic, nonaromatic) polyester material, or more precisely of polyethylene terephthalate having low heat stability.

It is an object of the present invention to pro- "'fl vide a compact cassette and support liners for this cassette, which, in the form of a liner having a longitudinal bend, continue to function even after storage at a temperature of about 85'C, in particular under the longterm influence of a temperature of about 85 0

C.

We have found that this object is achieved by a compact cassette having at least one substantially rectangular plastic support liner which is arranged above and/or below the tape rolls and essentially covers these over their area and which has at least one longitudinal bend for elastic support of the tape rolls, wherein the elastic deflectionskof the liner, based on the deflections of 50 Am thick liner, under a load of from about 1.5 to about 3.6 where \thie liner has not been exposed to a temperature of about 851C (deflection &f and oe* L1 p (pond) 1 cN (centiNewton] 2 O.Z. 0050/40677 N)the liner has been exposed to a temperature of about 0 C (deflection AfN), ;1 have increased by mer tYha a factor ofk 2 ;ie AfN AfV 2.

As a result, the compact cassettes remain fully Soperational in respect of the support liners contained therein, particularly in motor vehicles and also in other areas involving temporary or long-term exposure to high temperatures.

The present invention also relates to a support Sliner itself having the properties according to the Iinvention, and said liner may advantageously be transi, parent.

In further mechanical embodiments, the compact S '15 cassette may be provided with liners having a central longitudinal bend or may have two or more longitudinal I bends parallel to the central longitudinal axis. The iK liner may furthermore have one or two transverse Sbends.

The liner should consist of a plastic material having a glass transition temperature of not less than 0 C. The novel support liner can be produced from such a plastic material without difficulties and, with appropriate further selection of material, the loss of elasticity can be even further reduced.. Specifically, the liner material may consist of a polyethersulfone or of a polysulfone, both of which have a high glass transition temperature of TG 170 0 C and are therefore very suitable for compact cassettes resistant to high temperatures.

j 30 However, it is also possible to use blends or copolymers of polyethersulfones and polysulfones with the same advantages. It is also advantageous to use a polyetherimide as the liner material.

It is also possible to use aromatic polyesters formed from an aromatic dicarboxylic acid and an aromatic diol (dihydroxy compound), for example from terephthalic acid and bisphenol A or an alcohol having a higher (R7A4.

TVrO<

-I~U~

3 O.Z. 0050/40677 functionality, which polyesters have a TG 100 0 C and therefore possess better heat stability than the aliphatic polyesters (TG 70°C) which usually consist of polyi ethylene terephthalate. Polycarbonate films, which are usually used for electrical insulation purposes and have I a glass transition temperature of 150 C, for example Makrofol" (registered trade mark of Bayer Aktiengesellschaft, Leverkusen, Germany), can also be used.

A polyarylether ketone film whose glass transition temperature is about 170 0 C can also advantageously be Sused for the novel cassette and/or support liners.

i Where they can be chemically prepared, mixed forms and/or copolymers of the claimed materials may also be used, as well as all other film materials which have 15 not been listed here but are ruitable for the purposes of the present invention.

i Illustrative Examples i Support liners having different longitudinal and i transverse bends were produced, ie. the bends were produced by cold forming and had the following forms: 1. 1 central longitudinal bend I 2. 2 parallel longitudinal bends about 1.5 cm apart S3. 1 central longitudinal bend and two transverse bends isymmetric with respect to the central transverse axis and about 3 cm apart.

SIn the stress-free state, a base height of about 7 cm was measured for all embodiments to All films had the same thickness of 50 um (micrometers), and the same contour and surface area before pro- V 30 duction of the bends.

H^J From the materials stated above and in the m- claims, the following were selected: Polyester (polyethylene terephthalate) Polycarbonate Polysulfone (Ultrason* S from BASF Aktiengesellschaft, Ludwigshafen, Germany) The glass transition temperature TG is 185 0

C.

A> 4 O.Z. 0050/40677 There is also an Ultrason" E from BASF Aktiengesellschaft which chemically is a polyethersulfone and has a glass transition temperature TG of 210 0

C.

Registered trade mark of BASF Aktiengesellschaft The stated plastics polysulfone, polyethersulfone and polyetherimide may be represented schematically by the following structures: CH 0 Polysulf one Ultrasons S) CH 0 0 Polyethersulfone Ultrasone E) 0 CH 0 0 Polyetherimide D-o i N N T 0 0 films of each material A-C and with each bend V form were subjected to loads of from 1.2 p to 3.6 p in succession using weights, before long-term exposure to heat (as will be described below) and after this exposure, and the height"a" from the load surface f to the bend was measured in mm. The 5 values for a film material having a certain bend form were averaged and the difference Af between this value (fm) and the height fmax of the film from which the load had been removed was calculated: fmax-fm Af.

The bend forms are shown schematically in the drawing, and the results of the measurements are plotted as spring characteristics in graphs I to III.

Long-term exposure to heat The process of heat exposure consists of the following sequence of steps to which the cassettes and liners are subjected, and is based on the Ford test for compact cassettes, which originates from the United States of America: Starting temperature 23'C and uncontrolled humidity, 5 O.Z. 0050/40677 on average 50% humidity.

i- Heating of the cassettes to 85 0 C in the course of hours.

Storage of the cassettes at 85 0 C for 8 hours.

Cooling of the cassettes to 23 0 C in the course of hours.

Residence time of 2 hours at 23 0

C.

Then carrying out the measurements.

During storage at high temperatures, the cassettes stand vertically on the front of the cassette Si housing on a perforated metal sheet in an oven, so that the two support liners contained in the cassette are treated completely identically.

1! Graphs I to III show the spring characteristics 15 K/ 4 the average difference of the measured values, of support liners having a bend height of 7.0 cm before the i! I t measurement and uniform thickness of 50 Mm and identical areas, said characteristics being before or before/after 11 characteristics. Without exception, the bends were produced not thermally but mechanically. The means for measuring the initial height"a"from the support surface F to the highest film bend (cf. diagram in Graph I) consisted of a balance-like apparatus on which the weights V were placed and the deflections were measured with an Si 25 accuracy of 0.1 mm. The response limit for applied loads r| was 1 pond (i cN).

Graph I shows the before spring characteristics of the following liners VAI Polyethylene terephthalate (PETP) liner having 1 I 30 central longitudinal bend VA2 PETP liner having 2 parallel longitudinal bends cm apart VA3 PETP liner having 1 central longitudinal bend and 2 transverse bends symmetrically with respect to the central transverse axis and 3 cm apart.

After exposure to heat, all PETP liners were virtually completely flat and no spring deflection under -6 O.Z. 0050/40677 load was any longer present or measurable. This radical change in the properties of the liner material, which is caused by freezing of the molecular chains of the plastic, even occurs on exposure to heat for less than 8 hours and begins roughly on reaching the glass transition temperature of PETP, at TG 70 0

C.

This Graph I was plotted to demonstrate the prior art, in order to show how the conventional support liners present in virtually all compact cassettes on the market today behave under the action of heat. They are without exception ineffective as support liners in the sense that spring forces can be exerted.

Graph II shows the before/after spring characteristics of the following liners VB1 Polycarbonate support liner having 1 central longirI tudinal bend NB1 VB2 Polycarbonate support liner having 2 parallel longitudinal bends 1.5 cm apart j 20 NB2 VB3 Polycarbonate support liner having 1 central longitudinal bend and 2 transverse bends symmetrically with respect to the central transverse axis and 3 cm apart NB3 The letter V denotes the curves before exposure to heat and the letter N denotes the curves after exposure to heat.

The maximum value of Afv/AfN is 1.33.

Graph III shows the before/after spring characteristics AgL j of the following liners: VC1 Polysulfone support liner having 1 central longitudinal bend NC1 VC2 Polysulfone support liner having 2 parallel longitudinal bends symmetrically with respect to the central longitudinal axis and 1.5 cm apart _I I 7 O.Z. 0050/40677 NC2 VC3 Polysulfone support liner having 1 central longitudinal bend and 2 transverse bends symmetrically with respect to the central transverse axis and 3 cm apart NC3 In Graph III, the maximum value of Afv/fN is 1.60.

The start of the applied force range was chosen as 1.5 pond to take into account the minimum response force of 1 pond but nevertheless to obtain reliable measurements.

The maximum tolerance of 25% was imposed at the maximum value Afv/AfN in Graphs II and III, giving the 15 maximum value of 2.0 claimed.

In addition to the stated film materials which are also suitable for use in compact cassettes because the said materials are transparent, all other film materials having a glass transition temperature TG 85 0 C can also be used according to the invention. These include in particular the aromatic polyester films having TG L 100°C.

'i The novel liners are provided with the abovementioned bends in order to provide the necessary guidii 25 ance and support for the tape and the tape roll in the cassette and, by reducing the contact areas, to improve the friction properties (by reducing and keeping constant the frictional forces and forces due to electrostatic ii charge). Through the use of the novel liners, expensive tape guidance means, such as guide levers, etc. can be dispensed with.

In the compact cassette, an internal height of about 0.6 cm is available for each support liner, and the liner can display its spring properties in this height.

On average, the novel liners exert forces of from about p to about 2.5 p, preferably about 2 p, on the tape rolls. Forces of this magnitude are sufficient for 8 O.Z. 0050/40677 proper functioning of the cassette in the record/playback and rewind modes. According to the invention, it is now ensured that, even in the case of long-term exposure of the cassettes and/or liners to heat, the spring characteristics are essentially retained after exposure to j heat, with slightly larger deflections after exposure to heat, in a range less than or equal to twice the deflections before exposure to heat.

A compact cassete is produced with substantially rectangular plastic support liner(s) between tape roll(s) and cassette wall(s), having at least one longitudinal bend, and the deflections of the support liners in a defined load range should be not more than a factor of 2 greater in I the case of exposure to heat at 85 0 C compared with no S ''15 exposure to heat. Film materials having glass transition j temperatures equal to or greater than 85 0 C may be used, for example films of polysulfone, polyethersulfone, i polycarbonate, polyarylether ketones, polyetherimide, aromatic polyesters and/or blends and/or copolymers thereof.

i i i

Claims

1. A compact cassette having at least one substantially rectangular plastic support liner which is arranged above and/or below the tape rolls and essentially covers these t over their area and which has at least one longitudinal bend for elastic support of the tape rolls, wherein the elastic deflections (Af) of the liner under a load of from 1.5 to 36 p, where V) the liner has not been exposed to a temperature of about 850C (deflection AfV) and Si N) the liner has been exposed to a temperature of about 85oC (deflection AfN), have increased by a factor of not more than 2, i.e. AfN Afv 2, wherein Afv is the deflection in case V) and AfN is the deflection in case N).

2. A compact cassette as claimed in claim 1, wherein the liner(s) has or have a central longitudinal bend. S'3. A compact cassette as claimed in claim 1, wherein the liner(s) has or have longitudinal bends parallel to the longitudinal central axis of the cassette. i* A 9 O.Z. 0050/40677 II I: r Tg-HLAIMS DEFINIG THE INVENTION ARE AS FOLLOWS- 1. A compact cassette having at least one substantial rectangular plastic support liner which is arranged bove and/or below the tape rolls and essentially cov s these over their area and which has at least one ngitudinal bend for elastic support of the tape roll wherein the elastic deflections (Af) of the liner under a load of from about 1.5 to about 3.6 p, wher V) the liner has not been expo d to a temperature of about 85 0 C and N) the liner has been exp ed to a temperature of about 0 C, have increased by a f ctor of not more than 2: AfN: Afv s 2, wherein Afv is the deflection in case V) and af, is the deflection in ose N). 2. A c pact cassette as claimed in claim 1, wherein the line has or have a central longitudinal bend.

3. /A compact cassette as claimed in claim 1, wherein th liner(s) has or have longitudinal bends parallel to he cntral axis.

4. A compact cassette as claimed in claim 1, wherein the liner(s) has or have one central longitudinal bend and two transverse bends.

A compact cassette as claimed in claim 1 and one or more of claims 2 to 4, wherein the liner consists of a plastic material having a glass transition temperature TG a 85 0 C.

6. A compact cassette as claimed in claim 5, wherein the liner consists of a polysulfone.

7. A compact cassette as claimed in claim 5, wherein the liner consists of a polyethersulfone.

8. A compact cassette as claimed in claim 5, wherein the liner consists of a blend of a polysulfone and a polyethersulfone.

9. A compact cassette as claimed in claim 5, wherein the liner consists of a copolymer of a polysulfone or of a polyethersulfone.

10. A compact cassette as claimed in claim 5, wherein RA( /TC\ T1 O<$j 10 O.Z. 0050/40677 the liner consists of a polyetherimide.

11. A compact cassette as claimed in claim 5, wherein the liner consists of an aromatic polyester formed from an aromatic dicarboxylic acid and an aromatic diol.

12. A compact cassette as claimed in claim 11, wherein the liner consists of an aromatic polyester formed from terephthalic acid and bisphenol A.

13. A compact cassette as claimed in claim 5, wherein the liner consists of a polycarbonate.

14. A compact cassette as claimed in claim 5, wherein the liner consists of a polyarylether ketone.

A support liner for a compact cassette as claimed in one or more of claims 1 to 14.

16. A support liner as claimed in claim 15, wherein said liner is transparent. DATED THIS 26th day of March, 1990 BASF AKTIENGESELLSCHAFT WATERMARK PATENT TRADEMARK ATTORNEYS, 2nd Floor, The Atrium, 290 Burwood Road, HAWTHORN. VICTORIA 3122.