WO1992016889A1

WO1992016889A1 - Writing surfaces and keyboardless computers

Info

Publication number: WO1992016889A1
Application number: PCT/GB1992/000460
Authority: WO
Inventors: Stephen Randall
Original assignee: Eden Group Ltd
Current assignee: Eden Group Ltd
Priority date: 1991-03-15
Filing date: 1992-03-16
Publication date: 1992-10-01
Anticipated expiration: 1993-09-15
Also published as: KR940011654B1; KR920018565A; GB9105518D0

Abstract

Keyboardless computers generally comprise a stylus that is used to contact a glass plate, the glass plate constituting the writing surface. The tactile qualities of this arrangement are not good. This invention discloses coating the glass layer with a plastics film, such as a polycarbonate film, to improve tactile quality, as well as solve other disadvantages associated with the prior art.

Description

Writing surfaces and kevboardless computers

Field of the Invention

This invention relates to writing surfaces, and in particular to writing surfaces suitable for keyboardless computers. In addition, this invention relates to keyboardless computers utilising such writing surfaces.

The term 'keyboardless computer' used herein refers to a computer in which the user can communicate with the computer without a keyboard, using, for example, a stylus and digitising tablet. In a typical keyboardless computer, graphical information, such as handwriting, can be input using a stylus co-operating with a digitising pad or mat that itself overlies, underlies or is integral with a display screen, commonly a LCD type screen. What is displayed on the screen when the stylus is moved over it therefore corresponds to what would be displayed if the stylus were a pen and the screen paper. A typical example of such a keyboardless computer is the Sony Palmtop (Trade Marks) notebook computer. The term 'keyboardless computer' will be appreciated to include within its ambit devices known in the art as 'pen computers'.

The term also refers to a touch screen computer, i.e one in which pointing to and selecting objects that are displayed on a screen, actions commonly hitherto achieved using a mouse or trackball, can be achieved by touching a stylus or finger to the portion of the screen overlying the object to be selected.

The term 'writing surface' refers to the surface of the screen of a keyboardless computer to which the stylus or finger is applied when inputting, for example, graphical information. It is the surface on which a stylus in such a system might be said to write.

Description of the Prior Art

Commonly, keyboardless computers have a glass top plate overlying a LCD screen. This is desirable for a variety of reasons. For example, it distributes a localised force, such as that from a stylus being pressed onto the writing surface, and can thereby reduce the interference rings or disfunctioning that would otherwise result from altering the LCD internal plate separation.

One disadvantage of having a top plate is, however, that it introduces an extra thickness of glass between the writing surface, i.e. the top of the glass plate, and the perceived location of the image, which is within the LCD itself. It will be appreciated that there is a need to toughen the glass top plate, for example by chemically treating it and forming it relatively thickly, so that it is less likely to shatter or break. Noticeable parallax problems may result, however. Overall, the impression of the stylus and screen being like pen and paper is weakened and the familiarity and user friendliness of the device reduced. A further disadvantage of having a top plate is that if it breaks then shards of glass can easily cut the user's hands.

A further problem with glass top plates is that they do not have good tactile qualities. It will be appreciated that keyboardless computers are often designed to be attractive to those either without keyboard skills or to those who would rather not use such skills. For a product to appeal to such persons, it is particularly advantageous if, when the user writes with a stylus on the writing surface, the 'feel^* is as pleasing as possible.

The present generation of such keyboardless computers may be regarded as particularly inadequate in this respect. When a user is running a stylus along a glass plate as the writing surface, the perceived 'feel' is much smoother and harder than that of pressing a pen or pencil on paper. Consequently, this again detracts from the aim of getting as paper-like an interface as possible. In some devices, the stylus has to have a brass tip end to provide good electrical contact with an electrically conductive writing surface such as indium tin oxide. The 'feel' of this stylus is particularly unsatisfactory.

One solution to the problem of giving a writing surface better tactile qualities is to texture the glass top plate, for instance by acid etching it. The problem with this is that it is both expensive and leads to degrading excessively the sharpness of the display.

It is well known to laminate glass sheets together where splintering of shards of glass have to be avoided for safety reasons. Generally, this is achieved by laminating one or two separate sheets together, the lamination being between the internal surface of each sheet. Obiect of the Invention

The object of the invention is to provide a writing surface for a keyboardless computer that does not suffer some or all of the above defects.

Statement of the Invention

In accordance with a first aspect of the present invention, a writing surface for a keyboardless computer comprises a substantially translucent plastics film laminated onto an underlying structure. This surface is much less likely to crack or shatter than an untreated glass top plate and is therefore far safer. Consequently, the underlying structure can be made thinner than it would be if it were untreated material, typically glass in the present generation of devices, thus reducing the problems associated with thick prior art glass writing surfaces. Further, if the underlying sheet does shatter, the plastics film will retain the shattered material in place, preventing shards of material from cutting the user's hands.

Additionally, by providing for a plastics material to be the uppermost surface, the tactile feel is greatly improved as compared to plain glass.

Preferably, the plastics film is a low gloss film. A high gloss film is one that has a high^' specular reflectivity as compared to diffuse reflectivity. This is due to the surface of a high gloss film being flatter than a low gloss film; because it is flatter, image degradation is less with a high gloss film than a low gloss one. Surprisingly, it has been found that in practice a lower gloss film is preferable to a higher gloss film because the former degrades the image enough to smooth out the pixels. This is highly desirable. Preferably, the writing surface is spaced from an underlying display to optimise the perceived smoothness of any displayed image. This is desirable since the perceived-smoothness of the image, i.e. the extent to which adjacent pixels of the display appear to merge into one another, varies with the distance of the plastics film from the image. If the plastics film is too close, then the individual pixels are too clearly visible. If the plastics film is too far away, then the image is too blurred and the thickness of the device becomes excessive. Preferably, the plastics film is one that can take ink. An inkable film is particularly useful as it allows an area of the writing surface to be marked up with, for example a function key, whereby touching that area of the writing surface with the stylus would initiate that function. In this way, both commonly used functions can be assigned specific key areas on the writing surface and the surface marked up accordingly, or the user can customise the writing surface to his own requirements by marking the surface with only those functions that would be commonly required by him and programming the computer appropriately.

In a preferred embodiment, the plastics film is a polycarbonate film. Polycarbonate is a particularly appropriate since polycarbonate films may have a number of physical properties that make them suitable for use in a writing surface, e.g high tensile and tear strength, high light transmissivity, good chemical and abrasion resistance. Additionally, polycarbonates can be readily bondable to various materials, including glass where glass is the desired choice of material for the underlying structure, as it will be in the present generation of writing surfaces. Preferably, the bonding agent is a free flowing adhesive coated onto both sides of a laminar carrier.

After considerable tests, a nylon tipped stylus co-operating with polycarbonate surface has also been shown to approximate most nearly to the tactile feel of pencil on paper.

Preferably, the polycarbonate is Lexan Martec (Regd. Trade Marks) HP Graphic film from GE Plastics. This is an especially suitable choice since it satisfies most of the before mentioned desirable qualities of a polycarbonate. A Lexan Martec film such as Martec HP12S is desirable where a low gloss film is needed.

The choice of other suitable plastics, including other polycarbonate films, is within the compass of those skilled in these arts and within, therefore, the ambit of the present invention.

Generally, the underlying structure will be a thin glass sheet overlying a display such as a LCD, with a digitiser provided under the LCD.

Advantageously, the underlying structure may instead be the upper plate of the LCD. This embodiment not only provides the desired tactility, but also minimises the distance between the writing surface and the perceived location of the LCD image, thus reducing parallax errors and providing a more paper-like interface than prior art approaches. In such an embodiment, the digitiser may again be placed underneath the LCD. In this embodiment, it may however be necessary to provide for the upper plate of the LCD to be strengthened or otherwise modified to reduce the likelihood of the LCD plate separation altering when pressure is applied to it and leading to image distortion.

However, in another preferred embodiment, the underlying structure comprises the top plate of the LCD but there is a digitiser positioned between the plastics film and the underlying structure. The digitiser may then comprise a grid of translucent electrically conductive pathways defining one co-ordinate axis, overlaid by a further such grid defining a mutually orthogonal axis, there being a translucent, electrically insulating layer separating the two grids. Conveniently, at least one of these grid may be formed on a surface of the plastics film. This is desirable since it lowers production costs. In addition, the digitiser suffers much lower noise levels since it is further from the CPU.

In another aspect of the invention, there is a keyboardless computer comprising a writing surface in accordance with the first aspect of the invention. .

Brief Description of the Drawings

The invention will now be described with reference to the accompanying drawings, in which:

Figure 1 shows a schematic cross section through the writing surface together with the underlying LCD screen and digitiser for a typical prior art keyboardless computer,

Figure 2 shows a schematic cross section through a writing surface in accordance with the present invention, together with the underlying LCD screen and digitiser in which the digitiser is positioned above the LCD;

Figure 3 shows a schematic cross section through a writing surface in accordance with the present invention, together with the underlying LCD screen and digitiser in which the digitiser is positioned below the LCD. Figure 4 shows a schematic cross section through a writing surface in accordance with the present invention, together with the underlying LCD screen and digitiser in which the digitiser is positioned between the polycarbonate film and the LCD.

Figure 5 shows a keyboardless computer in accordance with the present invention, incorporating a digitiser below the LCD.

Detailed Description

Referring now to the prior art arrangement shown in Figure 1, a LCD is shown with lower glass plate 1 separated from an upper glass plate 3 by liquid crystal material 2. A digitising network 4 is shown overlying a glass plate 5. The digitising network 4 comprises an electrically conductive film formed from Indium Tin Oxide (ITO). The detailed structure of such a combined LCD and ITO digitiser is well known in this field and will not be described further here.

A glass plate 5 overlies the LCD upper plate 3 and provides the required degree of protection for the underlying structures. The upper surface of the glass plate 5 is sputter coated with a thin layer 4 of ITO and therefore constitutes a writing surface. When a user wishes to write something to a keyboardless computer incorporating such a combination LCD and digitiser, he writes on the writing surface of the glass plate 5 with a stylus (not shown) that co-operates with the ITO layer, allowing an indication of the contact position to be provided. However, the tactile quality of the glass writing surface as felt when using a stylus in no way approximates to that of paper. In some prior art systems, the stylus has to be provided with a brass tip to ensure adequate electrical contact. The feel of the brass tipped stylus on ITO coated glass is not at all like a pen or pencil on paper and is therefore not that satisfactory. Further, the stylus may not be that easily controlled as it may slip over the writing surface. The conventional solution is to texture the glass, for instance by acid etching it, but this has the severe drawback of being both expensive and leading to excessively degrading the sharpness of the screen image.

Referring now to the inventive embodiment shown in Figure 2, there is again shown a LCD comprising a lower glass plate 1 and an upper glass plate 3 with liquid crystal material 2 between the two plates. A digitising network 4 is incorporated into the upper glass plate 3. A polycarbonate graphic film 6, such as Lexan Martec (Regd. Trade Marks), manufactured by GE Plastics, is laminated to the upper surface of the upper glass plate 3 to form a writing surface. Commonly, this bonding is achieved using a water soluble, optically clear, free flowing adhesive coating each surface of a laminar modified acrylic sheet approximately 12 microns thick. The method of applying such a carrier backed adhesive is well known in the laminating arts and will not be further described here. A carrier backed with free flowing adhesive has been found necessary since the film 6 can move very slightly with respect to the glass plate 3 at temperature extremes; the carrier allows for independent movement of the film 6 from the plate 3, obviating the problems with bubbling that otherwise would result.

The resulting laminate provides an exposed upper surface that has particularly appropriate tactile qualities, i.e it is pleasing to run a stylus over it, in particular a stylus with a nylon tip. Further, it has a number of physical properties that make it suitable for use in a writing surface, e.g high tensile and tear strength, high light transmissivity, good chemical and abrasion resistance. Lexan Martec HP12S is the preferred choice of polycarbonate film as it has relatively low gloss levels.

Referring now to the inventive embodiment shown in Figure 3, there is again shown a LCD comprising a lower glass plate 1 and an upper glass plate 3 with liquid crystal material 2 between the two plates. A thin glass plate 5 overlies the upper glass plate 3. The digitising network 4 is in this embodiment positioned below the lower glass plate

1. The Lexan Martec HP12S polycarbonate graphic film 6 is laminated to the upper surface of the thin glass plate 5 to form the writing surface as described above. In practice, it has been found that the thin glass plate 5 should have a thickness of about lmm with this choice of film. This combination is both safe and provides an excellent screen image. Further details of this embodiment arc found in Figure 5. The thin glass plate 5 is chemically treated to strengthen it using conventional techniques. Typically, strengthening treatment for only 2 hours is needed in this embodiment, whereas 4 hours of treatment is more commonly required. The requirement for a shorter time is possible because of the presence of the plastics film.

Referring now to Figure 4, there is again shown a LCD comprising a lower glass plate 1 and an upper glass plate 3 with liquid crystal material 2 between the two plates. The digitising network 4 is in this embodiment positioned above the upper glass plate 1 but below the Lexan Martec polycarbonate graphic film 6. In this case, the digitising network is formed by sputtering an electrically conductive but optically transparent grid of Indium'Tin Oxide (ITO) onto the lower surface of the polycarbonate film 6. This grid defines one of the co-ordinate axes against which the position of the stylus held by the user will be measured. There are a variety of other methods of introducing an electrically conductive grid onto the lower surface of the film 6, for instance, printing with electrically conductive ink. The grid is separated from a further grid, defining a mutually orthogonal axis,by a thin layer of translucent Mylar. On the lower surface of the Mylar is sputtered the second ITO grid. Again, there are different approaches to the choice of insulating layer and different techniques for getting a conductive grid onto that insulating layer. It will be appreciated that the selection of an appropriate insulating layer and choice of conducting materials and the manner of their application are matters within the knowledge of those skilled in these arts.

Referring now to Figure 5, a display means 30, preferably comprising a LCD type display, is shown forming part of a keyboardless computer . The input means for the computer comprises an electromagnetic induction digitising mat or tablet 20 underlying the display 30, together with an electromagnetic stylus 40. The digitising mat 20 comprises an electrically conducting grid with conductors running parallel to an X-axis, overlaying a similar grid with conductors running parallel to a Y-axis. The stylus 40 comprises an energisable coil which can be excited with alternating current. The amplitude of the voltages induced in the conductive grids provide an indication of the position of the stylus relative to the Cartesian co-ordinate system defined by the X and

Y axes. The detailed operation of this form of digitiser is well known in this field. Further reference may be made, for example, to US 4570033. Using this digitising system, the user can easily and naturally input graphical information for storage and subsequent, although nearly immediate, display by the apparatus.

It will be appreciated that a variety of components, e.g. a power supply, is necessary for the functioning of the apparatus and will have to be present in the apparatus but these are not expressly detailed here in the interests of brevity and clarity. The stylus 40 is touching the Lexan Martec HP12S graphic film 6 laminated onto the upper surface of the upper glass plate of the LCD 30. Electrical signals indicative of the position (X Y Co-ordinates) at which it contacts the writing surface are supplied to an A to D converter 11 feeding a data path or system bus 15. A CPU 12 is connected for bi-directional data flow to the bus 15, as is a RAM 17. A ROM 18 is also connected to bus 15, being programmed with the operating system for the apparatus, including various telecommunications procedures. CPU 12 provides all control signals via bus 15. RAM 17 stores the user input RAM 17 may be an EEPROM or magnetic bubble memory. CPU 12 may be a microprocessor such as the 80286 manufactured by Intel Corporation. In addition there is provided a data modem 19 connected to bus 15 for sending and receiving serial data information. A display driver 14 is connected to bus 15 and drives the display 20.

Claims

What is claimed is:

1. A writing surface, arranged to be contacted by a stylus of a keyboardless computer, comprising: a substantially translucent plastics film having an upper and a lower surface; a structure arranged under the lower surface of the film; the film being laminated onto the structure at the lower surface and forming at the upper surface a surface to be contacted by the stylus.

2. A writing surface as claimed in Claim 1 wherein the the plastics film is a low gloss film.

3. A writing surface as claimed in Claim 1 wherein the plastics film is spaced from an underlying display to optimise the perceived smoothness of any displayed image.

4. A writing surface as claimed in Claim 1 wherein the plastics film is one that can take ink.

5. A writing surface as claimed in Claim 1 wherein the plastics film is a polycarbonate film.

6. A writing surface as claimed in Claim 5 wherein the polycarbonate film is Lexan Martec.

7. A writing surface as claimed in Claim 6 wherein the polycarbonate film is Lexan

Martec HP12S.

8. A writing surface as claimed in Claim 1 wherein the underlying structure comprises a glass sheet overlying a display.

9. A writing surface as claimed in Claim 1 wherein the plastics film is laminated directly onto the upper plate of a LCD.

10. A.writing surface as claimed in Claim 1 wherein there is provided a digitiser positioned between the plastics film and the underlying structure, the digitiser comprising a grid of translucent electrically conductive pathways defining one co¬ ordinate axis, overlaid by a further such grid defining a mutually oπhogonal axis, there being a translucent, electrically insulating layer separating the two grids.

11. A writing surface as claimed in Claim 10 wherein at least one said grid is formed on a surface of the polycarbonate film.

12. A writing surface as claimed in Claim 11 wherein the grid is of electrically conductive ink.

13. A writing surface as claimed in Claim 1 wherein the film is laminated to the underlying structure by a free flowing adhesive.

14. Aieeyboardless computer comprising a stylus for contacting a writing surface, wherein the writing surface is arranged to be contacted by the stylus, and comprises a substantially translucent plastics film having an upper and a lower surface, a structure arranged under the lower surface of the film, the film being laminated onto the structure at the lower surface and forming at the upper surface a surface to be contacted by the stylus.

15. A keyboardless computer as claimed in Claim 14 wherein the the plastics film is a low gloss film.

16. A keyboardless computer as claimed in Claim 14 wherein the plastics film is spaced from an underlying display to optimise the perceived smoothness of any displayed image.

17. A keyboardless computer as claimed in Claim 14 wherein the plastics film is one that can take ink.

18. A keyboardless computer as claimed in Claim 14 wherein the plastics film is a polycarbonate film.

19. A keyboardless computer as claimed in Claim 18 wherein the polycarbonate film is Lexan Martec.

20. A keyboardless computer as claimed in Claim 19 wherein the polycarbonate film is Lexan Martec HP12S.

21. A "keyboardless computer as claimed in Claim 14 wherein the underlying structure comprises a glass sheet overlying a display.

22. A keyboardless computer as claimed in Claim 14 wherein the plastics film is laminated directly onto the upper plate of a LCD.

23. A keyboardless computer as claimed in Claim 14 wherein there is provided a digitiser positioned between the plastics film and the underlying structure, the digitiser comprising a grid of translucent electrically conductive pathways defining one co¬ ordinate axis, overlaid by a further such grid defining a mutually orthogonal axis, there being a translucent, electrically insulating layer separating the two grids.

24. A keyboardless computer as claimed in Claim 23 wherein at least one said grid is formed on a surface of the polycarbonate film.

25. A keyboardless computer as claimed in Claim 24 wherein the grid is of electrically conductive ink.

26. A keyboardless computer as claimed in Claim 14 wherein the film is laminated to the underlying structure by a free flowing adhesive.