WO2008012575A1

WO2008012575A1 - Hand held apparatus for activating thermal medium and suitable thermal medium

Info

Publication number: WO2008012575A1
Application number: PCT/GB2007/050432
Authority: WO
Inventors: Robert Charles Lewis Day; John Philip Stanton; Clive Lawrence Ayling
Original assignee: The Technology Partnership Plc
Priority date: 2006-07-25
Filing date: 2007-07-23
Publication date: 2008-01-31
Also published as: GB0614698D0

Abstract

A hand held apparatus (10) for activating thermal medium (13), the apparatus comprising a main body (11) shaped so that it can be held by a user and having a nib (17) for contacting the thermal medium (13) in use, a heating element (17) in or on the main body (11) for directing heat towards the thermal medium (13), and means (spring loaded contact switch 32) for determining whether or not the heating element (17) should be activated.

Description

HAND HELD APPARATUS FOR ACTIVATING THERMAL MEDIUM AND SUITABLE THERMAL MEDIUM

This invention relates to a hand held apparatus for activating thermal medium and also to the thermal medium itself.

We use the term "Thermal paper" here to mean any medium which has the capability to be selectively marked using the application of heat. For example most receipts are printed using thermal paper. Typically the medium consists of a paper substrate and a coating, at least one layer of which contains chemicals whose function is activated by the application of heat. The function of the chemicals is to change permanently from no colour to a colour. Typically the colour used is black, however thermally-activated chemical formulations that produce colours such as pink, red, green, blue and orange are also known. Typically the coatings are applied over areas of the medium (many millimetres in size, normally coating the entirety of one face of the medium) and they are activated by "thermal printheads" (although other power sources such as light sources can be used). Thermal printheads have heater elements that can be digitally selected to heat the medium directly in contact with the element. The size of the heater element is typically 40-250 microns in width and is usually very much smaller than the size of the medium that is coated with the thermally activate-able chemicals.

In addition, it is known from our earlier British patent application No. GB 0610094.5 to provide a medium with an array of pixels of different heat activatable colourants in a predetermined pattern, the different pixels being selectively activated to produce images not previously defined on the medium. In this way, a thermal printer or the like can, when supplied with suitable instructions as to which pixels to activate, display any colour image on the medium.

It would be useful to be able to activate thermal paper using a pen. However there is a problem with placing the necessary heater elements] into a pen in that the pen does not know whether it is contact with suitable medium or not. A pen which was always on (or a pen which was activated by a method that did not detect exclusively the presence of the correct type of medium) could cause damage to other materials through trying to "write" on these materials. If the material was human skin then harm could be caused.

Accordingly, the present invention provides a hand held apparatus for activating thermal medium, the apparatus comprising: a main body shaped so that it can be held by a user and having a nib for contacting the thermal medium in use, a heating element in or on the main body for directing heat towards the thermal medium; and means for determining whether or not the heating element should be activated.

This is known as a "Picture Pen".

The determining means may sense the presence of either the thermal medium itself or a support means on which the thermal medium is to be placed in use. The determining means may determine whether or not the nib or heating element is within a predetermined distance of the thermal medium. The determining means may include one or more sensors in or on the main body for determining whether or not the nib is in contact with the thermal medium. The determining means may include one or more sensors in or on the main body for detecting either fluorescence or magnetism. The heating element is preferably in a nib of the pen. The apparatus may further comprise a sensor for obtaining information from the thermal medium concerning the colour which will be revealed when the pen is in any particular position on the medium. The heating element is preferably only operable when the nib is in contact with the thermal medium.

The apparatus may also include a further sensor for sensing a colour on a surface and means for determining which pixels on a suitable thermal medium should be activated to reproduce that colour transferring that colour on to a suitable thermal medium.

One or more additional heating element may be provided. If so, the apparatus may further comprise means for selectively activating one or more of the heating elements in order to generate a desired pattern on a thermal medium.

The apparatus may further comprises means for determining whether an individual pixel should be activated in order to produce a preselected colour and/or pattern. This may include a biassing means for biassing the nib away from a contact such that, upon pressure between the thermal medium and the nib, a contact switch is closed to enable the heating element to be activated.

A means of measuring travel of the nib across the medium may be provided and may include one of an encoder wheel, sensing means by IR or RF for detecting features on the medium, or direct sensing of some or all of the pixels.

The invention also provides an image creating system comprising: an apparatus according to any one of the preceding claims; and a pallette on which a thermal medium is provided.

The pallette may include colour and/or image selection means operable by a user to determine the colour or image that the pen will generate when moved across the thermal medium. The pen may be electronically connected to the pallette. The colour and/or image selection means preferably include one or more colours or images which can be sensed by the pen. The colour and/or image selection means may include one or more buttons or switches for selecting a desired colour or image.

The thermal medium typically comprises a substrate and at least one thermally activatable region on the substrate including at least one hidden image made up of pixels of thermally activatable coating in one or more colours which, on the application of heat to the thermally activatable region, is revealed.

The substrate may have at least one visible pre-printed image thereon.

If the medium is imaged using thermally-activatable colour formers, then the application of heat via a thermal pen would selectively reveal the hidden image. The revealed image could be an image taken from life though the use of a camera or an artificial image such as a cartoon. This image is preferably pre-printed onto the media using thermally activatable colour former pixels of at least one colour, but usually three distinct colours, using conventional flexographic, offset or gravure printing. The process of revealing the hidden image, using a pen, could provide entertainment and thus the components could comprise an attractive toy.

In addition, there is an application in which the ability of the pen to sense the presence of thermally-activatable coatings would be of additional benefit: in patent application GB 0610094.5, we teach a medium with small pixels of different colour formers which could be activated to produce images not previously defined in the pattern of colour-formers. In a preferred embodiment of the present invention, it is important that a thermal pen not only detect that the appropriate medium is present, but that also it sense information that allows it to deduce which tint of colour former is instantaneously available for activation. A method for doing this, as a sophistication of the more general method described, is described below.

In addition we describe a concept for medium to be used with this pen in which the medium contains a mix of hidden thermally-activatable images and un-hidden preprinted images in order that new children's activities such as modifying images, colouring-in outlines and learning tasks, also other activities such as games, quizzes and lottery tickets and the like can be constructed. As this system uses a medium that is a composite of two printing methods it is branded as a "Composite Picture Pen".

In addition, we describe a concept for a pen similar to that in the Picture Pen in which the pen selectively activates its heating elements according to pre-programmed patterns. The image created is therefore a printed swath of pattern. We disclose methods for the user to select these patterns. As this pen is of particular attraction when using medium with a largely plain pattern and in which the user is largely controlling the final appearance of the image this system is branded as a "Freestyle thermal pen". In addition we describe a further development of this pen concept in which the pen, or pen and palette system contains:

A thermal heater element, or a multitude of thermal elements such as those found in a standard thermal printhead.

A sensor for detecting the presence of each tint of colour-forming pixels present in the appropriately constructed thermal medium and means to decide if this pixel should be activated or not in order to produce the selected colour and/or pattern.

This pen can use the medium described in our earlier patent application GB 0610094.5 modified in that the colour former ink used to create the medium must also contain a respective florescent identifier in order that the hidden tint of each pixel can be identified by the pen using one or more suitable sensors. The user is then free to draw freehand in any process colour and/or use pre-programmed patterns or even narrow stored "photographic" images. Thus, this system is branded as a "Freestyle photo thermal pen". In addition we describe a useful user interface for a toy based on the pen, or pen and palette system described above consisting of either:

A sensing functionality in which the pen can sense a colour and then mark appropriately constructed thermal medium with a colour approximating to this colour; And/or

A sensing functionality in which the pen can sense coded markings as it is passed over them, which then modify the function of the pen when it writes on appropriately constructed thermal medium. And/or A palette for such a pen and palette system which contains a printed image of selectable colours and coded marks that can be scanned to activate functions of the pen. Picture Pen The pen typically has a means of activating a small area of the thermal medium.

This method could be a narrow (0.1 mm - 10mm) thermal printhead of similar construction to those commonly used in thermal label printers. The method could be one or more individually activatable resistance wires comprising or closely attached to the nib of the pen. The pen further requires a sensor to detect the presence of the correct medium as this prevents marking, damage or injury being caused by attempting to write with a heater elements] on incorrect surfaces and objects such as human skin. The sensor could detect a characteristic of the medium which had been specifically added to the medium to make it discernibly different from other common materials. For example the medium could have a transparent coating of a chemical that has magnetic qualities, IR absorbent qualities or UV fluorescent qualities. The sensor would be appropriate to the known identifier of the medium.

A preferred embodiment of the system includes a fluorescing component within the colour-forming inks used. In this embodiment the pen has a UV or blue source (typically a UV or blue LED) and one or more optical detectors to detect the presence of fluorescence. The detection of each new pixel causes the sensors to produce a pulse which the electronics can use to trigger the production of one or more bursts of energy to the heater elements]. In this way the power to the heater element is matched to the demand for printing and the heater element is never heated unless in contact with the appropriate medium.

The CMOS array used in an optical mouse in an example of a sensor that may be used to identify when the firing pulses should be used, the firing pulses being controlled to be spaced appropriately on the medium as the pen is moved about. If this CMOS array chip is selected to the type which outputs the raw CMOS values (related to light received in each segment of its array) then, by synchronising the CMOS scanning to the UV or blue light source the same sensor can be used to detect the presence of the medium and the accurate placement of each fluorescing pixel.

The sensor may work in concert with a contact sensor (e.g. a micro-switch) to identify when the appropriate medium was in sufficient contact (and pressure) with the nib. Composite Picture Pen

It is clear that a number of exciting product ideas are enabled by the use of this system in conjunction with appropriate medium containing some areas which have been printed normally. For example, a child could be entertained by colouring in areas of an image previously printed using only line art. A child could reveal letters on a page using pen strokes to learn how to write. A quiz or raffle ticket could have hidden information revealed by use of the composite picture pen.

Freestyle pen

In its simplest form, the medium is a coated thermal paper of the standard type and the pen has an array of heater elements which it activates in a time-dependent pattern, so that if the pen is moving in correct contact with the medium, then a pattern is formed on the medium. Selection of the pattern can be made using a simple button arrangement on the pen. The size of the pattern in one direction depends on how fast the pen is moved over the medium.

A more complex situation is where the pen has a means of measuring travel across the medium. For example: an encoder wheel, sensing means by IR, RF etc to features on a palette containing the medium, or direct sensing of some or all of the pixels. In this situation the size of the pattern in the direction of travel is no longer dependent on the speed of movement of the pen and it is practical, for example, to print a pattern that is read as a line of text.

In the situation where the pen is detecting some or all pixels, this can be achieved easily by adding a fluorescent agent into the ink containing the thermally activated colour former[s] that is used to print the pixels. A UV source in the pen (or guided from a source outside the pen to the pen via an optical cable) can cause the pixel under the pen to fluoresce - an action which can be detected easily by an optical sensor mounted on the pen. The flickering of this fluorescence as the pen moves over the medium can be used as an encoder to control the speed of pattern formation. The patterns produced by the description above would have the colour of whatever colour formers were printed in the pixels that were activated. The pen has no way of knowing which colours these are. Thus for a medium coated in monochrome blue colour-former the image would be blue. For a medium printed in a plaid pattern of colour formers, the patterns produced would be plaid. Freestyle photo pen

In this example, the medium is printed with colour formers formulated into an ink appropriate for the type of printing used (gravure, flexographic etc) and one or more additional components are added into each colour of ink in order to produce a different characteristic that can be sensed by a pen. For example, if the red colour former had red phosphor components added to it, then it could be sensed by a fluorescence sensor on the pen. Likewise another colour former (say the blue colour former) could have another colour of phosphor added to it (say blue or orange phosphor). The sensing system would require multiple sensors in order to detect the multiple responses produced by the multiplicity of colour formers used. For example a fluorescence sensor that used one blue or UV LED to activate the fluorescence could have three optical sensors, each masked by a colour filter in order to identify only fluorescence of the right colour. In one embodiment of this, a CMOS array can be used to detect the light emitted by fluorescence, segments of the array being filtered to let through only the wavelengths of light from each type of pixel on the medium. By synchronising the light source (UV or blue) that causes the fluorescence to the scanning frequency of the optical sensor (e.g. CMOS array) it is possible to cancel out the effect of the ambient light on the sensor readings and thus get good imaging of the pixels against their background.

It is also possible to construct a system in which the patterns have colours selected by the pen and not the medium: the medium is printed with colour formers formulated into an ink appropriate for the type of printing used (gravure, flexographic etc) and one or more additional components are added into each colour of ink in order to produce a different characteristic that can be sensed by a pen. For example if the red colour former had red phosphor components added to it, then it could be sensed by a fluorescence sensor on the pen. Likewise another colour former (say the blue colour former) could have another colour of phosphor added to it (say blue phosphor). The pattern of these pixels is as described in our previous patent application. The sensing system, within or attached to the pen, contains multiple sensors in order to detect the multiple responses produced by the multiplicity of colour formers used (for example there could be three optical sensors, each masked by a colour filter (RGB) in order to identify only fluorescence of the right colour.

As the pen can identify the hidden colour of the colour formers passing under the nib, it is possible for the pen to selectively activate those colours that it requires to generate a user-selected process colour and/or a pattern. Thus the Freestyle Photo Pen, with correct media, can be used to create lines and patterns in a great many process colours, as selected by the user.

How to create a user interface for the selection of colours and other functions such as pattern creation

A button or other simple on/off user interface can switch the pen from 'writing mode to 'sensing mode'. In this sensing mode, the pen can use its optical colour sensors to detect the colour of a target area or to read a code (such as a bar code) when the pen is scanned over the code. Alternatively, to improve readability, the pen can use its UV source to activate and thus permit detection of the colour of fluorescent items printed on a permanent palette.

For example, the colour 'mauve' can be selected by touching the pen nib on a mauve-coloured area of the palette. Any subsequent use of the pen in 'writing' mode will activate the appropriate ratio of colour-forming pixels to produce the process colour mauve. The algorithm used can be similar to this:

1. Sensing/writing mode switch is set to 'sense'

2. The pen nib is touched against the mauve icon on the palette and RGB sensors on the pen detect the colour 'mauve'.

3. Sensing/writing mode switch is set to 'write'

4. Three software buffers are set up ("R", "G" and "B") each containing an initial number corresponding to the ratio of red green and blue in the colour mauve.

5. As the pen is moved over the medium, and the hidden colours of each passing pixel is detected, the pixels are heated and the appropriate buffers are decremented. Once a buffer is emptied, further pixels of that colour are not heated. Once all the buffers are emptied, then they are all refilled to their initial levels for mauve.

It is obvious that other algorithms can be used to improve the randomisation and averaging of pixel tints to produce the desired process colour, however the principle is shown here.

By scanning the pen along a code when in 'sense' mode the time-response of the sensors can identify which code has been selected. Preferably the codes look similar to the function that they code for. E.g. a code to tell the pen to write using a sequence of arrows could look like a sequence of arrows.

Combinations of codes can be used to further adjust the pattern that is to be printed. For example: one code may code for Red, another for footprints, another for large, another for inverse printing, etc. Various examples of the present invention are now described with reference to the accompanying drawings, in which:

Figures 1 A to C show different stages in the activation of a medium having a hidden image;

Figures 2A and 2B illustrate the use of a pen to uncover a hidden image; Figure 3 illustrates different patterns which could be created using the freestyle pen;

Figure 4 shows one possible form of pen for use in the present invention;

Figure 5 shows a close-up view of the nib of the pen of Figure 4;

Figure 6 illustrates a pen and pallette combination; Figure 7 illustrates one example of a contact switch for use with the invention; and

Figure 8a and 8b show a range of movement of the pen of the invention over which it should be operable.

Figure 1 A-C illustrate how a medium 1 containing an image printed with thermally activatable colour formers is, when not activated, substantially blank as shown in Figure 1A and, in Figure 1 B, a thermal pen according to the invention has been drawn across the centre of the hidden image to reveal a portion 2 of that image. Continual use of the pen in contact with the medium will subsequently reveal the whole of the image 3, as shown in Figure 1 C. Figure 2A illustrates the simplest use of the pen in the standard mode, in which the user draws the pen across the medium 1 to reveal the hidden image 3 beneath. Figure 2B illustrates that the colours displayed are made up of a combination of activated pixels 4 in an appropriately selected ratio of tinted pixels.

Figure 3 illustrates that the pen 10 of the present invention can be utilised to create predetermined patterns when drawn across a thermally activatable medium 1 .

These predetermined patterns can be selected by the use of switches, dials or similar or by use of scanning codes, images or similar such as those shown on the palette described with reference to Figure 6.

In Figure 4, one example of a pen in accordance with the invention is disclosed. The pen 10 has a main body 1 1 having a nib 12 which, in use, is intended to contact the upper surface of a thermal medium 13. The medium 13 is provided with individual pixels 14 of heat activatable colourant, either in a predetermined image, or in an seemingly random array of different colours in order that, upon suitable activation, an image can be produced. The main body 1 1 contains a power supply such as batteries 15 and has control electronics 16 for ensuring the correct operation of the device. A thermal printhead 17 is also located in the nib for directing heat towards the pixels 14 on the medium 13. The printhead is controlled by the electronics 16, such that, depending upon the mode in which the pen is operating, either all or only selected pixels are activated. In addition, the electronics 16 can ensure that the heater does not get "left on" when the pen is not being used and also that the heater printhead will not function unless the nib 12 is in contact with a suitable thermal medium.

As shown more clearly in Figure 5, the nib 12 is provided with a light guide and lens 18 and a UV LED and optical sensors 19. The light guide and lens 18 and the UV LED and optical sensors 19 are used to sense the presence of the thermal medium rather than other surfaces, thereby permitting the printhead 17 to be operated only when in contact with a suitable thermal medium. In addition, the sensors act to detect the different coatings and/or phosphors applied to the individual pixels.

Figure 6 illustrates a combination of the pen 10 and a colour palette 20 linked via an umbilical 21 , containing items such as power cables, optical fibre(s) etc. The provision of the pallette 20 means that various components, such as the batteries and control electronics can be removed from the pen, thereby reducing the weight of the pen. In addition, a pallette of colours 22 can be provided or a series of patterns 23, which the user can scan using the pen such that, when the pen is then activated on the thermal medium, the desired pattern or colour is displayed on the medium. In addition, the palette may be provided with a stock of suitable thermal medium

13 and a housing 24 for the various components removed from the pen 10.

Figure 7 shows one example of a nib 12 having an outer sleeve 30 which defines a cavity 31 in which a contact switch 32 is mounted. A heat sink 33 on which the thermal printhead 17 is mounted is supported by a biassing means 34 such as a spring mounted around the contact switch 32 such that, in the normal at rest position, the heat sink is spaced from the end of the contact switch. When the print head is placed in contact with a thermal medium 13, the print head and heat sink are urged against the force of the spring into contact with contact switch 32 such that activation of the printhead 17 can occur. When in contact with a hard surface, such as a desk, on which the medium would sit, the switch will be depressed as the user pushes down on the printhead to draw and only when the switch is so depressed will the printhead be activated and so heat up.

Figures 8a and 8b illustrate the sort of range of movement of the pen over which it must operate in order to enable many users, each of whom will have a different writing style, to use the pen. Although these figures illustrate a range of movement, the range of movement over which the pen should be operable should be as great as possible and certainly may include the pen being vertical in the orientation shown in figure 8a, or even beyond the vertical, and may also include angels of tilt of the pen as shown in figure 8b outside of the ranges shown.

In order to achieve this, the printhead component of the pen requires mechanical articulation and its mechanism must enable the printhead to fully contact the medium and remain within the optimum limits of printing angle as the pen is dragged by the user across the printing surface. The articulation must allow the printhead's orientation to stay within the limits of successful printing.

One possible way of articulating the head is shown in figure 7, such that the printhead is on a floating heat sink 33. This is enclosed in a sleeve 30 with a ledge 25 to prevent the heat sink 33 from falling out. This does, however, allow the printhead itself to be exposed outside of the sleeve 30 and to be able to contact the thermal medium in use. The spring 34 inside the sleeve 30 biasses the printhead 17 out of the sleeve, whilst also providing a reaction force necessary to align the head parallel with the surface 13 on which the pen is to be used.

Claims

1 . A hand held apparatus for activating thermal medium, the apparatus comprising: a main body shaped so that it can be held by a user and having a nib for contacting the thermal medium in use, a heating element in or on the main body for directing heat towards the thermal medium; and means for determining whether or not the heating element should be activated.

2. An apparatus according to claim 1 , wherein the determining means senses the presence of either the thermal medium itself or a support means on which the thermal medium is to be placed in use.

3. An apparatus according to claim 1 or claim 2, wherein the determining means determines whether or not the nib or heating element is within a predetermined distance of the thermal medium.

4. An apparatus according to any one of the preceding claims, wherein the determining means includes one or more sensors in or on the main body for determining whether or not the nib is in contact with the thermal medium.

5. An apparatus according to any one of the preceding claims, wherein the determining means includes one or more sensors in or on the main body for detecting either fluorescence or magnetism.

6. An apparatus according to any one of the preceding claims, wherein the heat element is in the nib.

7. An apparatus according to any one of the preceding claims, further comprising a sensor for obtaining information from the thermal medium concerning the colour which will be revealed when the pen is in any particular position on the medium.

8. An apparatus according to any one of the preceding claims, wherein the heating element is only operable when the nib is in contact with the thermal medium.

9. An apparatus according to any one of the preceding claims, further comprising a further sensor for sensing a colour on a surface and means for determining which pixels on a suitable thermal medium should be activated to reproduce that colour transferring that colour on to a suitable thermal medium.

10. An apparatus according to any one of the preceding claims, further comprising one or more additional heating elements in or on the main body.

1 1. An apparatus according to claim 10, wherein the apparatus further comprises means for selectively activating one or more of the heating elements in order to generate a desired pattern on a thermal medium.

12. An apparatus according to any one of the preceding claims, further comprising a means for determining whether an individual pixel should be activated in order to produce a preselected colour and/or pattern.

13. An apparatus according to claim 12, wherein the means includes a biassing means for biassing the nib away from a contact such that, upon pressure between the thermal medium and the nib, a contact switch is closed to enable the heating element to be activated.

14. An apparatus according to any one of the preceding claims, further comprising a means of measuring travel of the nib across the medium.

15. An apparatus according to claim 14, wherein the means includes one of: an encoder wheel, sensing means by IR or RF for detecting features on the medium, or direct sensing of some or all of the pixels.

16. An image creating system comprising: an apparatus according to any one of the preceding claims; and a pallette on which a thermal medium is provided.

17. A system according to claim 16, wherein the pallette includes colour and/or image selection means operable by a user to determine the colour or image that the pen will generate when moved across the thermal medium.

18. A system according to either claim 16 or claim 17, wherein the pen is electronically connected to the pallette.

19. A system according to any one of claims 16 to 18, wherein the colour and/or image selection means include one or more colours or images which can be sensed by the pen.

20. A system according to any one of claims 16 to 19, wherein the colour and/or image selection means include one or more buttons or switches for selecting a desired colour or image.