This invention relates to a method of marking or writing upon a substrate,
and subsequently removing the markings when required, and also to apparatus for
enabling the method to be put into effect.
Erasable marking systems are well known. One such system employs
a pen having a solvent-based ink which may be erased by wiping or dabbing with
solvent carried on a cloth or pad. The solvent used is often water, for health
and safety reasons and because it is readily available. Dry-wipe marking systems,
using ink formed from a pigment carried in a solvent which evaporates completely
after use, are also known. Provided a suitable substrate is used, markings made
with a dry-wipe pen may be wiped away without the use of any solvent.
One problem with erasable marking systems is that of ensuring that
the marking remains until it is required to remove it. Using water-soluble or
dry-wipe inks, a marking may be erased or smudged accidentally by touching it with
a dry or damp finger, for example. Where the item to be marked is an article which
may be handled frequently the problem of accidentally erasing the markings may
be particularly troublesome. One situation where this problem may be apparent is
in the marking of video cassettes because it is common to record and re-record
on the same cassette many times. A labelling system for marking such items is disclosed
in Patent Specification No. GB 2118135 and entails writing upon an impermeable
substrate label with a pen containing either a water-soluble or a waterproof ink
and then wiping the writing away using water or an organic solvent as appropriate.
When water-soluble ink is used for the purpose, the writing may easily be smudged
if the labelled tape is handled with damp or sweaty hands. Waterproof inks are
less convenient to use in this application than water-soluble inks because the
solvent must be dispensed on to a suitable wiping article when it is required
to remove the writing and the dispensing, use and subsequent disposal of the solvent
can create potential health problems or a fire hazard.
It is an object of the present invention to overcome some at least
of the foregoing problems.
According to the invention, a method of erasably marking a substrate
and subsequently erasing said marking comprises marking with a waterproof ink
on the substrate, said substrate having a surface which is smooth and impermeable
to said ink, and subsequently removing said marking by rubbing with a non-abrasive
Apparatus according to the invention for enabling an article to be
erasably marked with ink and subsequently erasing said marking comprises a pen
containing a waterproof ink, a surface which is smooth, impermeable and able to
be marked with said pen and a non-abrasive eraser.
The pen preferably delivers "indelible" or waterproof ink and is
preferably a felt-tip or fibre-tip pen. Examples of suitable commercially available
pens include the "STAEDTLER LUMOCOLOR 317", "EDDING 142M" permanent OHP marker
and the "BEROL PERMANENT LABELLING PEN" and other similar pens which are sold
as permanent, indelible or waterproof marking pens.
The substrate which is marked upon has a surface which is smooth
and impermeable to the ink used in the pen. That is to say, the surface should
not absorb or be etched by any component of the ink to any significant extent.
The surface should have physical and chemical properties which enable it to be
wetted by and to bond to the ink sufficiently for it to be clearly written upon
by the pen. The markings, when dry, should not be easily removable on contact
with wet or dry skin. The surface should be selected to bond to the ink sufficiently
weakly for the markings to be removable by rubbing with an eraser. The substrate
may be transparent, opaque or translucent. The substrate is preferably a plastics
film and most preferably is either oriented polypropylene or oriented polyester
film or a gloss-finished polyvinyl chloride film. An unfilled high-gloss film
may have a surface which is generally smoother than a film which contains particles
of a filler material.
The non-abrasive eraser is preferably a block eraser of the type
sold for erasing pencil markings. Non-abrasive in this context means that the eraser
does not abrade the impermeable surface on which the erasable markings are formed
to any significant degree. If the permeable surface were to be abraded then ink
would be trapped within the small irregularities or scratches on the surface and
that ink would be difficult to remove without recourse to wiping with a solvent.
One example of a suitable block eraser is the "STAEDTLER MARS PLASTIC ERASER"
although many suitable erasers exist, which, typically, are made from vinyl compounds.
The eraser may be used dry but for removal of certain markings, especially where
the markings are relatively old, it is advantageous to moisten the eraser or the
marked surface to achieve a faster, more complete removal of the markings.
The impermeable surface, which is preferably a plastics film, may
form part of a laminate structure. The laminate preferably includes an opaque layer,
which may be paper, board or opaque film or a layer of an opaque ink printed upon
the under-surface of the impermeable markable substrate, so that writing etc.
which is marked on the surface can be clearly seen. It is preferred that where
such a laminate and a pen are provided together as a 'kit', the colour of the
ink contrasts with that of the opaque layer so that the markings of the pen are
clearly visible. In certain forms, the laminate structure may include an adhesive
layer on its lower surface so that the surface may be adhered to an article such
as a video tape for example, for labelling purposes.
The surface may have non-erasable markings upon it such as a border,
grid, words or graphics. Those markings may be printed or etched upon the surface
or, more preferably where the surface is a clear plastics film, they may be printed
on the reverse of the film or on a separate layer located beneath the surface,
e.g. on an opaque layer of a laminate structure. In one preferred form of the
invention, the impermeable surface is the upper surface of a clear film laminated
to or overlaying an opaque layer, which may be an opaque film, paper or board
for example, upon which is printed a grid pattern. The grid is preferably an alphanumeric
grid. The grid is preferably printed in reverse i.e. so that the background is
relatively dark and the alphanumeric grid lighter in colour. By selecting a pen
having ink of a similar colour to the background of the grid, selected parts of
the grid may be overwritten by the pen, leaving the remainder of the grid visible
to form letters or numbers. This form of the invention is particularly preferred
for providing labels for video cassettes and for labelling the spine of video
cassette cases because words or numbers formed from such a grid are usually neater
and therefore more acceptable to someone who wishes to display his collection of
tapes than a handwritten label. By providing an alphanumeric grid printed on or
beneath an impermeable surface located on the spine of cardboard or plastics video
cassette cases and designing the surrounding area of the video case in an appropriate
manner, it is possible to achieve a high standard of presentation for the video
cassette case, whilst retaining the versatility of being able to erase and re-mark
the label or box when the contents of the tape are changed.
The application of the method and apparatus of the present invention
to video cassette cases or sleeves may take different forms, depending in part
on the material of which the case or sleeve is made. In the case of cases or sleeves
made of paper or card, the whole case or sleeve may be formed as a laminate for
marking according to the invention or its spine may bear a laminated label attached
to it. When the case or sleeve is formed in a plastics material, it may be formed
as a whole in the desired impermeable markable material or as a laminate or the
material may be adhered in the form of a label. In another form, the case or sleeve
may be moulded in a suitable plastics material such as polypropylene with one
or more areas formed with a gloss surface to receive the identity markings. As
one alternative, the markable substrate may be attached to the spine of the case
or sleeve by welding, gluing or clips.
A further form of the invention comprises one or more laminated sheets
of which the top layer is a smooth impermeable clear film and having an opaque
layer which is optionally printed with an alphanumeric grid and, preferably, other
markings such as a list of numbers. This sheet or sheets may then be used as an
index to record information pertaining to the contents of a number of video cassettes.
In a preferred form, the sheets are adapted to be placed into a binder which is
itself adapted to fit neatly into a video cassette sleeve and preferably also
adapted to hold a waterproof pen and non-abrasive eraser, for example in a loop
or pocket secured to the binder. The binder may then be stored together with the
video tapes about which information is contained therein.
Some examples of other suitable uses for this form or any other form
of the invention are camcorder and audio cassette labelling, insert cards for
tape cassettes, name and address recording systems, e.g. for personal organisers,
and computer disk labels.
One example of an end-use of the present invention will now be further
described with reference to the accompanying drawing, which is a perspective view
of a video cassette in a case.
The drawing shows a video cassette 10 partially inserted into a video
cassette sleeve 11. The sleeve 11 is made of a cardboard base layer laminated
to a top layer of a clear impermeable plastics film. Areas 12 of the cardboard
are printed with an alphanumeric grid. The grid is formed in white on a black
background so that if a white part of the grid is overwritten in black, that part
is no longer clearly visible. The remainder of the cardboard may be printed with
an attractive design. By marking the film over the alphanumeric grid with a pen
delivering waterproof ink so as to cover selected parts of the grid, a word, words
or numerals may be formed so as to indicate the contents of the tape contained
within the sleeve. When it is required to change the words or numerals so formed,
for example when the tape has been re-recorded, the markings may be removed by
rubbing with a non-abrasive eraser and different letters may be formed on the
grid by remarking the area 12 with the pen.
The sleeve 11 may alternatively simply have a clear area, perhaps
surrounded by a decorative border, in which a user may write words or numbers
with a waterproof pen.
The back spine 13 of the video cassette may itself have a label which
is a laminate structure having at its top layer a clear impermeable film. That
label preferably comprises an alphanumeric grid printed on an opaque layer of the
laminate. The label may then be marked upon and erased in the manner described