GB2381080A

GB2381080A - Method of resizing and resealing a LCD employing a clamp

Info

Publication number: GB2381080A
Application number: GB0222237A
Authority: GB
Inventors: Peter Martin Bartholomew; Andrew Timothy Hake Harwood; Nigel John Tebbitt
Original assignee: Smiths Group PLC
Current assignee: Smiths Group PLC
Priority date: 2001-10-18
Filing date: 2002-09-25
Publication date: 2003-04-23
Anticipated expiration: 2022-09-25
Also published as: GB2381080B; GB0125039D0; GB0222237D0

Abstract

A liquid crystal display having associated circuits 7 and 8 attached with it is cut from a rectangular shape to a square shape. It is first clamped between two bars 11 and 12 extending alongside the proposed line of cut 16. The display and its associated circuit 7 is then cut, such as a rotating cutting wheel 20 or a water and abrasive cutting jet. The unwanted portion 17 of the display is disposed of and a seal 19 is applied along the cut edge 18 of the retained portion 14, while it is still clamped. The cut part of the circuit 7 is protected by applying an electrically-insulating coating to it.

Description

DISPLAY MANUFACTURE This invention relates to display manufacture or re-sizing.

The invention is more particularly concerned with altering the size of electronic displays such as a liquid crystal displays (LCDs).

Electronic displays, such as LCDs, are being increasingly used in aircraft, in place of cathode ray tube displays and electromechanical instruments. Usually, these displays are custom made to the particular size and shape required for a particular application. This makes the displays relatively expensive. By contrast, LCDs used in commercial products, such as laptop computers, are considerably cheaper and can provide a very high quality display. The problem with such commercial LCDs, however, is that they are only available in a restricted range of sizes.

GB 2330423 and US 6204906 describe methods by which conventional, commercial LCDs can be cut to a desired size and sealed along the cut edge to produce a display that can be used in aircraft or other applications. Various techniques are described in these documents for cutting, such as by using a scribing tool or a diamond cutting wheel. Although these techniques can produce working displays of the desired size, the cutting process sometimes causes stress damage in the region of the cut, which can cause discoloration of the display towards the edge. Because of this, the yield of usable displays is less than desired.

It is an object of the present invention to provide alternative methods of manufacturing displays.

According to a first aspect of the present invention there is provided a method of resizing a display including the steps of providing a generally planar display of a first size, cutting the display along a line to separate it into first and second regions, and sealing the cut edge of the first region, the first region of the display being clamped adjacent the line along substantially the length of the line during the cutting.

Preferably the display remains clamped during the sealing of the cut edge. The display may be cut using a rotating cutting wheel or by fluid cutting. The display preferably has at least one associated circuit attached therewith, the circuit being cut. An electrically-insulative coating is preferably applied to the cut edge of the circuit. The display and circuit are preferably cut by the same technique. The display may be clamped in a jig that is locatable and removable from cutting apparatus used to form the cut.

According to a second aspect of the present invention there is provided a method of re-sizing a display including the steps of providing a generally planar display of a first size, cutting the display along a line to separate it into first and second regions, and sealing the cut edge of the first region, the cutting being performed by directing a jet of fluid onto the display.

The display preferably has at least one associated circuit attached therewith, both the display and the circuit being cut by the fluid jet. The fluid cutting may be carried out with a mixture of water and an abrasive.

According to a third aspect of the present invention there is provided a method of resizing a display including the steps of providing a generally planar display of a first size and having at least one associated circuit attached therewith, cutting the display and circuit along a line to separate both the display and circuit into first and second regions, applying an electrically insulative coating to the cut edge of the circuit, and sealing the cut edge of the display.

The display is preferably a liquid crystal display. The display may be cut from a rectangular shape to a substantially square shape. The display may have polarizing filters on opposite surfaces, the display being cut with the polarizing filters in position. The method may include the subsequent step of bonding a glass plate to at least one surface of the cut display. The glass plate may have an anti-reflection coating and or alternatively it may incorporate a heater.

According to a fourth aspect of the present invention there is provided a display resized by a method according to the above first, second or third aspect of the invention.

According to a fifth aspect of the present invention there is provided apparatus for use in a method according to the above first, second or third aspect of the invention.

According to a sixth aspect of the present invention there is provided a display resized using apparatus according to the above fifth aspect of the invention.

A method of manufacture of a display and a display made by the method, according to the present invention, will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a simplified plan view of a conventional display; Figure 2 is a sectional side elevation view of the display of Figure 1 along the line II-II ; Figure 3 is a plan view illustrating a step in the method of re-sizing ; Figure 4 is a sectional side elevation view along the line IV-IV of the method step shown in Figure 3; and Figure 5 is a sectional side elevation view of a part of the display showing a subsequent step in the method.

With reference first to Figures 1 and 2, a conventional active matrix liquid crystal display (AMLCD) 1 is provided of rectangular shape, being 10. 4 inches (264 mm) in diameter. The display 1 is available from NEC as part number NC8060BC26-17. The display has an upper and lower plate 2 and 3 of borosilicate glass separated around their edges by a

spacer frame 4 to form a gap 5 between the plates. The gap 5 is filled with a liquid crystal material 6 containing polymer beads (not shown), which act as spacers to maintain the separation of the two plates 2 and 3 away from the edges. Transparent electrodes (not shown) and conductive tracks are deposited on the facing surfaces of the two plates 2 and 3 so that a voltage can be applied across regions of the liquid crystal material 6, to disrupt its molecular arrangement and alter its optical properties. Connection to the electrodes is made by flexirigid circuit boards 7 and 8 attached along edges of the display, including various column and row driver electronics. Two polymer polarizing filters 9 and 10 are attached to the upper and lower surfaces of the plates 2 and 3, the axes of polarization of the filters being crossed so that light is blocked from passing through the display except in regions where a voltage is applied across the liquid crystal material 6. As so far described, the display is conventional.

With reference to Figures 3 and 4 the method of the present invention involves cutting the display shown in Figures 1 and 2 to alter its shape and, in particular, to provide a display that is square.

The display is clamped by clamping apparatus having two bars 11 and 12 of Paxolin (a resin bonded paper/cotton laminate). The display is clamped between the two bars 11 and 12, which extend beyond the lower edge of the display at one end and beyond the upper edge of the display and the circuit board 7 at its other end. The clamping bars 11 and 12 could be made of other relatively compliant materials such as PTFE. Bolts 13 at opposite ends of the bars 11 and 12 enable the clamping force to be exerted between the two bars in an adjustable manner. The clamping force should be sufficient to grip the plates 2 and 3 firmly but should not be so high as to compress the polymer spacer beads within the liquid crystal material 6.

The bars 11 and 12 are located to extend along the right-hand edge of that part of the display that is to be retained, that is, the left-hand portion 14 of the display, with the right-hand edge 15 of the bars extending parallel to and closely adjacent to the cut line 16 that is to be formed subsequently. The clamping bars 11 and 12 also support the circuit board 7 along one edge of the display.

The next step is to cut through the display along the cut line 16 in order to divide it into left-hand and right-hand portions 14 and 17 respectively, the right-hand portion being disposed of. The cutting can be carried out in various different ways. One preferred cutting technique is to use a rotating cutting wheel 20 such as an electroplated nickel/diamond cutting wheel 20 that is 0.6 mm thick and 125 mm in diameter. The wheel 20 is fitted to a conventional horizontal milling machine, indicated generally as 21, the wheel being rotated at 900 rpm and irrigated with distilled water. The clamped display 1 is held horizontally and several cutting passes are made relative to the wheel 20 along the cut line 16 on one side of the display at a speed of about 175 mm/minute. Each cut pass removes a depth of glass of approximately 0.05mm and this is repeated until the thickness of the upper plate 2 is reduced to about 0.035 mm in the cut. The display 1 is then turned over, while still being clamped, and the same cutting procedure is carried out on the lower plate 3. The display is thoroughly dried, using a compressed air line, with special attention to the region of the cut line 16. The left-hand portion 14 of the display is then separated from the right-hand portion 17 by bending the two portions along the cut line 16 so that the display fractures along this line. The right-hand portion 17 of the display is disposed of. With the left-hand portion 14 of the display still clamped by the bars 11 and 12, the exposed, cut edge 18 of the left-hand portion is then sealed by applying an edge sealing fillet 19 of an epoxy adhesive, such as Araldite

Rapid. The seal 19 should be applied as quickly as possible to avoid air ingress into the display; it has been found that satisfactory results are produced if the seal is applied within about one minute of cutting. The display remains clamped until the adhesive 19 has fully cured-this may be accelerated by placing the clamped display in an oven at elevated temperature.

The circuit board 7 along the upper edge of the display may be cut by a different technique either before or after the glass plates 2 and 3 are cut. Alternatively, the circuit board 7 may be cut using the same technique as that for cutting the glass plates 2 and 3 at the same time simply by extending the length of the cut. Depending on the layout of tracks on the circuit board 7, it may be necessary to cut the circuit board at a different location from the plates and the cut may need to be of a more complex shape than a straight line. Because the circuit boards 7 have multiple layers, the cutting will usually expose conductive tracks at the cut edge. After cutting, the cutting residues are cleaned off and an electrically insulative polymer coating is applied over the edge to prevent shorting and environmental damage to the exposed track ends, such as from moisture.

It has been found that it is not necessary to remove the polarizing filters 9 and 10 before cutting because these are cut through cleanly by the cutting wheel 20.

After re-sizing by cutting and sealing the display it can be modified in other ways. It can, for example, be made more rugged by bonding an additional glass plate to its upper and or alternatively to its lower surface. The glass plates may already have either anti-reflection or heating surfaces applied prior to laminating to the AMLCD.

It has been found that clamping the display during the cutting operation substantially reduces the extent of damage to the display in the region of the cut edge and enables improved yields to be obtained. The re-sizing method can be used with any similar display having column/row drivers laid out in such a manner that they still address the remaining portion of the display after cutting.

Various alternative apparatus and techniques could be used to cut the glass plates.

One preferred technique is to use a water jet. In this technique, a conventional water jet cutting machine is used and an olivine abrasive is included in the cutting water to make the cutting quicker. A cutting speed of 750 mm/minute is achieved and, because the jet cuts through both plates, there is no need to invert the display. Immediately after cutting, the cut edge of the glass panel is dried using a paper towel before an epoxy adhesive sealing bead is applied in the manner described above. As above, the display is clamped during the cutting and sealing operations.

Surprisingly, it has been found that this water jet technique can be used to produce a cut with very little water penetration between the two glass plates providing that care is taken to allow the water to flow away from the cut edge. For example, the cut edge of the display should be spaced sufficiently from the collecting bath and other surfaces to reduce splashing.

The amount of water penetration may be further reduced by angling the water jet so that it is directed away from the usable part of the display. The water jet cutting technique has advantages in that it is quicker than mechanical machining and laser techniques. Also, the water jet can cut through the circuit board readily as well as the glass plates, avoiding the

need for a separate cutting operation. It also enables greater flexibility in the shape of the cut, that is, it need not be a straight line but could be curved or have bends. This could be an advantage if it were necessary for the cut to have a complex shape to separate and retain specific parts of the circuit boards. It will be appreciated that other fluids could be used instead of water.

Preferably, the clamping bars form a part of a cassette or jig having locating lugs for positioning on the cutting machine. In this way, the cassette containing the display can be removed from the cutting machine after cutting and the display edge sealed while it is outside the machine, making the cutting machine available for the next display.

Claims

CLAIMS 1. A method of re-sizing a display including the steps of providing a generally planar display of a first size, cutting the display along a line to separate it into first and second regions, and sealing the cut edge of the first region, wherein the first region of the display is clamped adjacent the line along substantially the length of the line during the cutting.
2. A method according to Claim 1, wherein the display remains clamped during sealing of the cut edge.
3. A method according to Claim 1 or 2, wherein the display is cut using a rotating cutting wheel.
4. A method according to Claim 1 or 2, wherein the display is cut by fluid cutting.
5. A method according to any one of the preceding claims, wherein the display has at least one associated circuit attached therewith, and wherein the circuit is cut.
6. A method according to Claim 5, wherein an electrically-insulative coating is applied to coat the cut edge of the circuit.
7. A method according to Claim 5 or 6, wherein the display and circuit are cut by the same technique.

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8. A method according to any one of the preceding claims, wherein the display is clamped in a jig that is locatable with and removable from cutting apparatus used to form the cut.
9. A method of re-sizing a display including the steps of providing a generally planar display of a first size, cutting the display along a line to separate it into first and second regions, and sealing the cut edge of the first region, wherein the cutting is performed by directing a jet of fluid onto the display.
10. A method according to Claim 9, wherein the display has at least one associated circuit

I attached therewith, and wherein both the display and circuit are cut by the fluid jet.
11. A method according to Claim 4,9 or 10, wherein the fluid cutting is carried out with a mixture of water and an abrasive.
12. A method of re-sizing a display including the steps of providing a generally planar display of a first size and having at least one associated circuit attached therewith, cutting the display and circuit along a line to separate both the display and circuit into first and second regions, applying an electrically insulative coating to the cut edge of the circuit, and sealing the cut edge of the display.
13. A method according to any one of the preceding claims, wherein the display is a liquid crystal display.

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14. A method according to any one of the preceding claims, wherein the display is cut from a rectangular shape to a substantially square shape.
15. A method according to any one of the preceding claims, wherein the display has polarizing filters on opposite surfaces, and wherein the display is cut with the polarizing filters in position.
16. A method according to any one of the preceding claims including the subsequent step of bonding a glass plate to at least one surface of the cut display.
17. A method according to Claim 16, wherein the glass plate has an anti-reflection coating.
18. A method according to Claim 16 or 17, wherein the glass plate incorporates a heater.
19. A method substantially as hereinbefore described with reference to the accompanying drawings.
20. A display resized by a method according to any one of the preceding claims.
21. Apparatus for use in a method according to any one of Claims 1 to 19.

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22. Apparatus substantially as hereinbefore described with reference to the accompanying drawings.
23. A display resized using apparatus according to Claim 21 or 22.
24. A resized display substantially as hereinbefore described with reference to the accompanying drawings.
25. Any novel and inventive feature or combination of features as hereinbefore described.