Note: Descriptions are shown in the official language in which they were submitted.
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L BA_GRO~JND OF T~:IE INVENTION
This invention relates to magne-tic tape cassettes.
In general, a signal recording and reproduclng
magnetic tape is wound, in endless form or in reel form, on
5 reels and is incorporated in a plastic case, so that the
magnetic tape is protected from the touch of an external
member or hands as much as possible except when the case
is loaded in a signal recording or xeproducing device.
The aforementioned case is fabricated by combining
a pair of upper and lower half cases, and is called a
cassette. Depending on the uses and sizes, cassettes are
divided into compact cassettes, microcassettes, video
cassettes, etc.
The cassette is excellent in portability and
mobility, and can be stored stably in an atmosphere in which
the temperature and humidity are variable to some extent.
The ranges of temperature and humidity which the cassette
undergoes during storage or the use have increased with new
and varied uses of cassettes. Among temperature and
humidity, the former seriously affects the cassette and
the magnetic tape. Therefore, it is essential to provide a
countermeasure against temperature.
At excessively high temperatures the cassette may
be permanently deformed and the magnetic characteristics
of the tape may deteriorate. When the magnetic tape is
heated, the output level of the recorded signals will de-
crease. Such a phenomenon is called "heat demagnetization".
Also, if the magnetic tape when wound in reel form is heated,
recorded signals which are recorded at a high level on the
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tape are transferxed to or traced over the other portion of
the tape which is wound inside or outside the portion having
the high level of recorded signals thereon. As a result, when
the signals are being reproduced, the transferred signal
will adversely affect the reproduction of the original sig-
nals. In the case of a magnetic tape employing a denatured
cobalt magnetic material, the coercive force Hc thereof is
dependent upon temperature and if the tape is excessively
heated, the anti-magnetic force thereof is lowered and the
high frequency characteristic thereof deteriorates. When
the magnetic tape is provided with a support base of poly-
ethylene terephthalate (PET) excessive heat can cause the
tape to shrink longitudinally. Therefore, excessive heat
can adversely a~fect a magnetic tape cassette in a number
; 15 of ways which would render the tape cassette substantially
useless.
A conventional cassette cannot in~orm the user of
the occurrence oE such problems vi~ually directly (or through
color change) so that the user can take countermeasures.
Furthermore,- the conventional cassette cannot inform the user
of the range of usage temperatures through color change.
~UMMARY OF THE INV~NTION
Accordingly, the object of this invention is to
provide a magnetic tape cassette in which the abo~e-described
v 25 difficulties are eliminate, so that the magnetic tape can
be stably stored and used.
The foregoiny object and other objects of the
invention have been achieved by the provision of a magnetic
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1 cassette -tape which includes a temperature indicating
member which is bonded to a surface of a cassette half or
included in the half ~tself.
BRIEF DESCRIPTION OF THE DRAWINGS
.
Fig. 1 is a plan view of a magnetic tape cassette
according to this invention; and
Fig. 2 is a sectional view showing essential
components of the cassette according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Fig. 1 is a plan view showing one example of a
magnetic tape cassette according to one embodiment of the
invention, for recording and reproducing audio slgnals.
The cassette has a temperature indicating member 6 which
is bonded to a corner of the upper surface 2 of a half 1
: 15 which is relatively flat e~cept for a pair of hub holes 3
and 4 and a window member S.
The temperature indicating member 6, as shown in
Fig. 2, comprises a support 7 and a film layer 8 formed on
the surface of the support 7 by coating with a coating
solution which is prepared by dispersing temperature in
dicating pigment in a binder. The temperature indicating
member 6 is bonded to the upper surface 2 with an adhesive
which is suitably determined from the relation between the
materials of the half 1 and the support 7.
The temperature indicating pigment may be of the
reversible or non-reversible type, and the grain size rnay
preferably be 30 ~ or less,
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1 Examples of suitable reversible temperature
indicating pigments are Ag2HgI4, Cu2HyI4, and a solid
solution of the mixture of Ag2HgI4 and Cu2HgI4. "Reversible
thermopaints" R-4, R-5, R-6, R-7, R-13, R-15 and R-17
manufactured by Rikagaku Kenkyusho are commercially
available for use as such reversible temperature indicating
pigments.
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The properties of the "reversible thermopaints" are
as indicated in the following table:
Table 1
color High
Low temperature changetemperature
- No. color temperature color Remarks
R-4Reddish yellow 40C ReddishOrange at about
orange 35C
R-5 Yellow 50C Yellowish Reddish yellow
orange at about 45C
R-6 Bright 60C Dark brown- Dark red at about
yellowish red purple 55C
R-7 Red 70C Dark brown- Dark red at about
purple 60C
R-13 Yellow 130C Yellow-
orange
R-15Lemon-yellow- 150C Yellow
green
R-17 - Lemon-yellow- 170C Yellow
green
Examples of suitable non-reversible temperature indicat-
ing pigments are [Cu~Pyr)2] ~CNsJ2~ CoI2 2C6H12N4 1OH2O,
[Cr~NH3)5Cl]Cz04, NiC12-2C6H12N4rlOH20, 2PbC03~Pb~OH32, CoKP04-
H O CdCO NH4VO3, NH4MnP2O7 and Cd~OH)2.
thermopaints #S, ~-7, #8, #9, #11, #13, #14, #16, #18, #20,
#22, #25, #27, #29, #31, #33, #36, #41, #44 and #45 manufactured
10- by Rikagaku Kenkyusho are commercially available for use as
such non-reversible temperature indicating pigments.
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The properties of the "non-reversible ther~opaints"
are as indicated in Table 2:
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Table 2
color
Original change
No. color temperature Change color Remarks
SPale Pink 50C Bright blue
7Pale Pink 70C Pale purple
8. Pale Pink 80C Bright purple
9 Pinlc white 90C Bright purple
11 Pale green 110C Bright bluish Yellowish gray
purple at about 70C
13 Purplish 130C Dim bluish
pink purple
14 Bluish green 140¢ Pale red-purple
16 Bright 160C Gray-black
greenish
blue
18 Red-purple 180C Brown-black
20 Pale yellow- 200C Bright bluish
orange purple
.:
22 White 220C Gray-black Pale pink at about
180C
25 Pale yellow- 250C Bright brown Pale yellow-brown
green at about 210C
27 Pale yellow- 270C Pale blue-
orange purple
29 Pale pink 290C Black ~ale purple at
about 170C
31 Bright blu- 310C Brown black
ish gray
color
Original change
No. colortemperature Change color Remarks
33 Pale blue~ 330C Gray-black
green
36 White 360C Orange Gray-white at
about 290C
41 Blue 410C Brown white
44 White 440C Pale yellow- Bluish white at
brown about 210C and
bluish black at
about 310C
Purple 450C White
For the reversible temperature indicating pigments
mentioned above, methyl methacrylate-vinyl acetate (1 : 1)
- copolymer resin varnish is preferably employed as the binder.
For the non-reversible temperature indicating pigments, ethyl
cellulose lacquer is preferably employed as the binder in the
case where the color change temperature is 200C or below9 and
silicone varnish is preferably employed as the binder in the
case where the color change temperature is 200C or higher.
Examples of the above-described support are a plastic
sheet of polyethyline terephthalate, cellulose triacetate,
vinyl chloride, polycarbonate or the like; paper, synthetic
paper, metal foil or the like.
As is apparent from the above description, in the
cassette according to the invention, a temperature indicating
member 6 whose color is freely changed by the ambient temper-
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ature is bonded to the upper surface 2 of the half 1, which
can be readily seen. Therefore, the deformation of the
cassette and deterioration in the magnetic characteristic of
the magnetic tape therein due to overheating of the cassette
can be detected early. Thus, the cassette can be used at any
place and under any operating condition.
It is often impossible to observe the temperature
indicating member when the cassette is stored; however, the
highest temperature the cassette has been exposed to can be
detected later. Similarly, in the case where it is--impossible
to observe the temperature indicating member during the use of
the cassette, the highest temperature the cassette has under-
gone can be detected later by merely observing the color
change.
In the case of Fig. 1, only one temperature indicating
member 6 is bonded to the surface of the cassette; however,
a plurality of temperature indicating members may be bonded
to the surface, for example at differing temperature character-
istics, or the temperature indicating members may be bonded to
both the "A" surface and/or the "B" sur-face of the cassette
~alf.
In the temperature indicating member shown in Fig. 2,
the film layer 8 is formed on the support 7; however, the
i,nvention is not limited thereto or thereby. That is~ the
aforementioned pigment may be mixed with the material which
forms the half 1. The same effect can be obtained by directly
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coating the surface of the hal-f with the "thermopaint".
The novel effects of the cassette will be clarified
by describing a number of concrete examples.
Example 1
,
The following materials were kneaded by allowing them
to pass through two heated rolls:
Styrol resin (manufactured by Asahi Dau Co.) for
fabricating a cassette: 100 parts by wt.
Cu2HgI4 (average particle size 4 ~): 2 parts by wt.
The resultant red mixture was melted by heat, to
mold a cassette half, and a complete cassette half was prepared
by incorporating a magnetic tape therein. The cassette half
was placed on the dash board of a vehicle in the sun, with the
windows closed. In forty minutes after the casstte half was
placed, it was observed that the color had changed from red into
brown-purple. In this case, the surface temperature of the
dash board was 67C. Judging from the properties of the tem-
perature indicating pigment Cu2HgI4, the color change into brown-
purple meant that the surface temperature of the cassette half
zo had exceeded 70C.
Example 2
The cassette half was coated with reversible thermo-
paint ~7 manufactured by Rikagaku Kenkyusho and held at a
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sunny place in a vehicle. In forty minutes, it was observed
that the color had changed from pale pink into pale purple.
The temperature in the vehicle was 67C in this experiment.
Concrete Example 3
The reversible thermopaint #7 manu-factured by the
Rikagaku Kenkyusho was applied to a PET base 23 ~ in thickness,
or the support, to a thickness of lS ~, to prepare the temper-
ature indicating member. The temperature indicating member
thus prepared was bonded to the cassette half, and the cassette
half was held at a sunny place in the vehicle. In forty
minutes, it was observed that the color was changed from pale
pink into pale purple. In this experiment, the temperature
in the vehicle was 67C
Concrete ~xample 4
A non-reversible temperature indicating pigment CoKPO4
H2O and ethyl cellulose lacquer were mixed in the ratio 1 : 1,
and the resultant mixture was applied to an ordinary cassette
half. After being dried, the cassette was placed in a constant
temperature oven in an atmosphere of 150C. In ten minutes,
it was observed that the color was changed from rose to blue.
At the same time, the cassette half was taken out of the constant
temperature oven, and it was found that the cassette half was
deformed. Judging from the properties of the pigment used, the
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color change to blue meant that the cassette half was subjected
to a temperature of 140C or higher.
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