In applications such as the fabrication of AMLCDs (active matrix liquid crystal displays), significant cost savings are possible if the relatively costly photolithographic production steps used for applying layers to substrates are replaced by either high quality printing of resist onto the substrate to form a mask prior to etching or by direct printing of precursors which may subsequently be treated or cured to give conducting, insulating or semiconducting layers.

Offset lithographical techniques such as gravure offset printing use a cliche that is patterned with recessed portions or grooves, these corresponding to features required in a layer to be applied to a substrate. United States patent application publication US-A-2003/0081095 describes an example of the use of gravure offset printing in the fabrication of an LCD device. An illustration of the process of gravure offset printing is provided in Figures 1 to 3.

Referring firstly to Figure 1, a cliche 1 having a series of generally rectangular recessed portions 2 in its upper surface is depicted. In a preliminary stage in the printing process, the recesses 2 are filled with a material 3 that is to be applied as a layer onto a substrate. The material 3 may be any of a number of functional materials, such as a precursor, an ink or a resist material. Surplus material 4 is removed from the cliche surface using a doctor blade 5 in a doctoring process, the blade being passed over the surface of the cliche 1 to remove material 4 that is not within a recess 2. Immediately after the doctoring process, the upper surface of the material 3 should be level with the surface of the cliche 1, as illustrated in Figure 2.

In a further stage, a blanket roller 6 is applied to the cliche 1, as depicted by Figure 3. The blanket roller 6 is a cylindrical roller having a

covering of a material such as silicone. The blanket roller 6 is rolled over the surface of the cliche 1 and some of the photoresist material 3 from the filled recesses 2 is thus transferred to the surface of the blanket roller 6. The transferred photoresist material forms portions 7 on the blanket roller surface, the position and shape of these corresponding to the position and shape of recesses 2 on the cliche 1.

In a final step depicted in Figure 4 the blanket roller 6 is rolled over the surface of a substrate 8. Portions of photoresist material 7 that were transferred to the blanket roller 6 from the cliche 1 are now deposited onto the substrate 8 to form printed features 9 on the substrate surface. The position of the photoresist material on the blanket roller 6 before it was deposited onto the substrate 8 is shown at 7A, and the material remaining to be deposited is shown at 7.

A normal line pattern printed using conventional offset lithography on paper is produced as a series of dots which are so closely spaced that the eye resolves them into a single line. Although this technique is satisfactory for printing on paper, it is not suitable for line definition as part of an active matrix process. Here, it is important that linear features truly are linear.

It has been found that where long linear features defined on a cliché extend perpendicularly to the doctor blade 5, the features are not always properly filled with material 7. This results from the doctor blade 5 being unsupported for substantial portions of its length, which causes some distortion of the doctor blade and/or the cliché 1. The resulting cliche fill is illustrated in Figure 5, with the surface of the cliché 1 given by a dotted line 10. When a feature is not properly filled with material, the blanket roller 6 is less likely to collect the material from the recesses in the cliché 1 which forms the feature.

This can result in a degradation of the printing quality of the pattern.

A way of addressing this is disclosed in JP-A-07-128520 and JP-A-11- 320816. Each of these documents discloses the angling of a doctor blade used in a printing process. However, it is often neither desirable nor feasible to angle a doctor blade used in certain printing processes.

According to a first aspect of the present invention, there is provided a cliche usable for defining a print pattern in which an approximately linear feature of the print pattern extending between two points is provided with at least two spaced deviations from a straight line connecting the two points by an amount greater than a width of the feature in the vicinity of the deviation.

According to a second aspect of the present invention, there is provided a cliche configured to define a print pattern, the print pattern including a number of features each having a width, in which at least one of said features is an approximately linear feature extending between first and second points on the cliche, the first and second points being intercepted by a straight line, wherein the feature is provided with at least two deviations from the straight line spaced from each other, each of the deviations extending from the straight line by an amount greater than the width of the feature in the vicinity of the respective deviation.

A cliché so constructed can provide better support for a doctor blade when passing over the linear feature than can a cliche with a linear feature without such deviations.

Advantageously, the feature has deviations at substantially regular intervals along its length. This provides a convenient arrangement in which a feature can extend for a substantial length whilst not allowing the doctor blade to be unsupported for any substantial length as it passes over the feature. The feature can have a generally zig-zag shape for a substantial part of its length, although there are numerous other feature shapes which can provide sufficient doctor blade support.

The invention also relates to a substrate having printed thereon a pattern from a cliché as described above. The invention further relates to a substrate having thereon a pattern formed by using a mask or precursor pattern from a cliche as described above.

A third aspect of the invention provides a substrate having a pattern printed thereon, or a pattern thereon formed using a printed mask or precursor pattern, in which an approximately linear feature of the pattern extending between two points is provided with at least two spaced deviations from a

straight line connecting the two points by an amount greater than a width of the feature in the vicinity of the deviation.

The invention also relates to a display including any of the substrates described above.

A fourth aspect of the invention provides a method of forming a pattern on a substrate, the method comprising: filling features in a cliché with material; and transferring the material from the cliché to the substrate via a blanket, in which at least one approximately linear feature extending between two points is provided with at least two spaced deviations from a straight line connecting the two points by an amount greater than a width of the feature in the vicinity of the deviation.

When the filling step comprises passing a doctor blade across the cliché in a direction perpendicular to the straight line, the doctor blade can be supported sufficiently to avoid an undesirable amount of distortion of the cliche or the doctor blade.

Advantageously, the feature has deviations at substantially regular intervals for a substantial part of its length. The feature can have a generally zig-zag shape for a substantial portion of its length.

The invention also relates to a substrate produced using a method as described above.

For a better understanding of the invention, embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is an illustration of a step in the process of gravure offset printing involving applying material to a cliché ; Figure 2 is an illustration of material in narrow recesses of a cliche after doctoring; Figure 3 is an illustration of a step in the process of gravure offset printing involving transferring material from a cliche to a blanket roller;

Figure 4 is an illustration of a step in the process of gravure offset printing involving transferring material to be printed from a blanket roller to a substrate; Figure 5 is an illustration of material in a wide recess of a cliche after doctoring; Figures 6 and 7 illustrate alternative cliches according to the invention having shaped linear features; Figure 8 illustrates a cliche having extended linear features not constructed according to the invention; Figures 9 and 10 illustrate cliches according to the invention and having a pattern corresponding to the pattern on the Figure 8 cliche ; Figure 11 is a flow chart illustrating a process of printing on a substrate according to the invention; and Figure 12 illustrates a substrate provided by the Figure 9 process.

Figure 6 illustrates part of a cliche 1 in plan view. It will be appreciated that the cliche is much larger than the part illustrated, although it is not necessary to illustrate the entire cliche to explain the invention. The cliche 1 has associated with it a direction, indicated by the arrow A, in which a doctor blades is passed when features formed on the surface of the cliche 1 are to be filled with ink, or with any other material. Formed on the upper surface of the cliche 1 are first and second linear features 20,21. These features 20.21 are formed in the same direction as the direction of passing of the doctor blade 5, so their shape is not critical. When the doctor blade 5 is passed over these linear features 20,21, the blade is supported for a significant fraction of its length in the region of the features, so there is not any significant distortion of the blade nor the cliche 1. The cliche 1 also has formed on its upper surface first to sixth linear features 22 to 27. These features 22 to 27 extend beyond the part of the cliche 1 which is illustrated in the Figure. The features 22 to 27 extend substantially perpendicularly to the direction A of the passing of the doctor blade. Each of the features 22 to 27 is approximately linear, but includes a number of deviations.

The feature 22 can be seen to be comprise a channel having a width W and being formed in a regular zig-zag pattern having a period P and height H.

The height H of the deviations exceeds the width W of the feature 22. In this way, a doctor blade 5 being passed in the direction A over the feature 22 is supported at at least one position in every period P of the zig-zag pattern. For example, the position of the doctor blade at one moment in time as it is passed in the direction A is illustrated by the dotted line B. Here, it will be seen that the doctor blade would be supported by lands 29,30, 31 and 32, which fall on alternate sides of the feature 22. Because the width W of the feature 22 is less than the height H of the zig-zag pattern, the doctor blade of the position B always is supported by at least some of the lands 29 to 32, whichever side of the line B it happens to be at at a given moment in time.

The feature 22 can be envisaged as running in an approximately straight line between any two points on the line B. Such points are labelled at point 1 and point 2. The feature 22 is linear except for the deviations which are the features of the zig-zag pattern.

The period P and the height H of the feature 22 together determine the maximum length of the doctor blade which is unsupported by the surface of the cliche 1 at any particular point as it is passed in the direction A. For example, it can be envisaged that if the height H is fractionally greater than the width W, then the doctor blade will at most have an unsupported length fractionally less than the period P of the zig-zag pattern. In the example illustrated in Figure 6, however, the height H of the zig-zag pattern is approximately one and a half times the width W of the feature 22. In this case, the doctor blade is unsupported for a maximum distance approximately three-quarters of the period P of the zig-zag pattern.

The features 24,25, 26 and 27 are included for the purposes of illustration. These features 24 to 27 have substantially the same arrangement as that of the feature 22, although the zig-zags thereof have a greater period and also an increased height. However, the effect is the same, namely that a doctor blade 5 passing in the direction A is supported at at least one portion in every period P. The total length of the features 24 to 27 for a given straight

line distance can be the same as the total length of the feature 22 for the same distance. However, because the features 24 to 27 have an increased height H, they are wider in the direction A so potentially utilise more area on the cliché 1.

The feature 23 is not provided as a zig-zag, but instead as a curved oscillating wave, such as a sine wave. Again, the height H of the oscillations is greater than the width W of the feature 23. The effect of the feature 23 is substantially the same as that of the feature 22. In particular, it allows the doctor blade to be supported at at least one position in every period P as it is passed in the direction A, whilst allowing the feature 23 to extend substantially perpendicularly to the passing of the doctor blade.

Alternative configurations of features are illustrated in Figure 7. Here, a feature 30 has the shape of a generally square waveform. Again, the height H of the oscillations is greater than the width W of the feature 30. Here, instead of the doctor blade being supported at least once in every period P of the oscillations, the blade is unsupported for a distance equal to the period P plus the width W of the feature whilst the doctor blade is passing over a peak or a trough of the feature 30. Accordingly, it may be desirable to provide a reduced period P of the square wave pattern of the feature 30, compared to the zig-zag pattern of the feature 22 and the sine wave pattern of the feature 23, to result in the same degree of filling of the feature.

A feature 31 is provided with a substantially linear form for most of its length. At regular intervals, discrete deviations 32,33 are provided, and it is these deviations which allow the doctor blade 5 to be supported at regular intervals along its length. Again, the height H of the deviations is greater than the width W of the feature 33. Also, again it is the period P, which equals the distance between the peaks of successive deviations 32,33, which determines the maximum length of the doctor blade which is unsupported at any one time.

An alternative shape of feature is illustrated by way of the feature 34 in Figure 7. Here a zig-zag is illustrated, although the angle of deviance from the direction A is different for successive links of the zig-zag pattern. For example, the leg illustrated at 35 is placed at an angle 61 from the direction A which is

less than an angle 62 from the direction A by which an adjacent leg 36 is formed. A successive leg 37 is formed parallel to the leg 35.

It will be appreciated by the person skilled in the art that there are numerous other patterns and feature shapes which can be used.

Figure 8 illustrates a part cliche 40 having extended linear features not constructed according to the invention. Here, a pattern 41 comprises a plurality of fingers 42 extending from a first linear feature 43, and a second plurality of fingers 44 extending from a second linear feature 45. The first linear feature 43 includes a step 46, but still includes quite lengthy grooves extending perpendicularly to a doctor blade passing direction 47. The second linear feature 45 comprises a single groove extending entirely perpendicularly to the doctor blade passing direction 47. The pattern 41 is a level of an In Plane Switching design. A TFT would be sited in the bottom left corner of the pattern 41 as shown.

Clearly, a doctor blade (not shown) being passed in the direction 47 would be unsupported for the entire length of the second linear feature 45 whilst crossing it, as well as for a significant distance on two separate occasions while crossing the first linear feature 43. This would be likely to result in distortion of the doctor blade and/or the cliche 40, and could degrade the quality of a resulting print pattern.

This would be substantially ameliorated by the corresponding part cliche 48 according to the invention shown in Figure 9. Here, a pattern 49 includes the first and second linear features 43 and 45. Each of the first and second linear features 43 and 45 includes plural deviations, indicated at 50. Thus, a doctor blade being passed over the cliche 48 is supported at least at intervals corresponding to the distance between adjacent fingers 42,44.

In Figure 10, a cliché 51 comprises plural ones of the pattern 49.

Figure 11 illustrates the printing of a pattern on a substrate 8 according to one aspect of the invention. At step S1, a cliché 1 is formed with zig-zag features 22,23 thereon. It is only features that extend in an approximately linear direction across the direction A of the passing of the doctor blade which need to be formed with intermittent deviations. However, features extending in

other directions can also be formed with intermediate deviations, especially since this might allow flexibility in which directions the doctor blade can be passed. At step S2, the cliche 1 is inked, by passing a doctor blade 5 preceded by ink material 4 in a direction perpendicular to the direction of the zig-zag features 22,23. At step S3, a blanket 6 is rolled over the cliche 3, thereby transferring ink from the features onto the blankets. At step S4, the blanket is rolled onto a substrate 8, thereby placing the ink 4 from the blanket 6 onto the substrate 8 to provide a pattern the same as that on the cliche 1.

Reference is made to Figures 1,3 and 4 and the associated description for further details of the steps S2 to S4.

The substrate resulting from the above process applied using the part cliche 1 of Figure 6 is illustrated in Figure 12. Here, it can be seen that the substrate 60 has the same pattern as the cliche 1, and in particular the features 22 to 27 are provided in the same size and at the same positions.

The invention is not limited to the gravure offset printing process described. Many other printing techniques may be used, although the invention is seen as particularly relevant to offset litho generated patterns.

From reading the present disclosure, other variations and modifications will be apparent to persons skilled in the art. Such variations and modifications may involve equivalent and other features which are already known in the design, manufacture and use of printed substrates and which may be used instead of or in addition to features already described herein.

The invention is not limited to the fabrication of AMLCDs. It may also be applied to any other printed layers on substrates. The choice of printed material, cliche material and substrate material would be influenced by the particular application. The printed material is not limited to ink or resist, but could for example be a precursor, such as an ITO precursor, which is subsequently cured to form a metal layer.

Although offset printing techniques have primarily been described in this application, the invention is applicable to other printing techniques.