GB2267252A

GB2267252A - Label with liquid crystal polymer.

Info

Publication number: GB2267252A
Application number: GB9210957A
Authority: GB
Inventors: Leslie Charles Laycock
Original assignee: GEC Marconi Ltd; Marconi Co Ltd
Current assignee: BAE Systems Electronics Ltd
Priority date: 1992-05-22
Filing date: 1992-05-22
Publication date: 1993-12-01
Also published as: GB9210957D0

Abstract

A data storage arrangement for providing information on a body in holographically coded form, comprising a label incorporating, as the holographic storage medium, a liquid crystal polymer. The polymer may be in the form of a film having a thickness of 3-10 mu m consisting of a polyacrylate or polysiloxane. The film may be supported on a sheet of polyethylene terephthalate (PET) having a thickness of 75-100 mu m.

Description

DATA STORAGE ARRANGEMENTS This invention relates to data storage arrangements, and more especially to such arrangements for use in providing information on bodies for identification or other purposes. For example the information may be applied to a label arranged to be attached to a component used in a manufacturing environment. Recently a system has been developed in which data is holographically stored on a label which is then used to identify the component to which it is attached.

Such "holotags", as they are commonly referred to, offer several advantages over conventional bar-code identification systems. Thus, they possess greater storage capacity and security, are more tolerant to damage and obscuration, and have the capability of being remotely interrogated.

Such a system as used hitherto uses as its holographic storage medium a special paper, known as Digital Paper. However, such paper suffers from the disadvantage that it is a write once/read many times medium, so that it is not possible to update any data initially recorded.

An object of the present invention is to provide a data storage arrangement which permits such updating.

According, therefore, to the invention a data storage arrangement for providing information on a body, comprises a label incorporating, as a holographic storage medium, a liquid crystal polymer.

A liquid crystal polymer (LCP) is an organic material that has liquid crystalline molecules bonded on to a polymer backbone.

Within a certain temperature range the crystalline side chains self-align in a nematic, cholesteric or smectic arrangement. Above the liquid crystal (LC) phase the LCP becomes an isotropic liquid at the clearing point, Tc, and below the LC phase the LCP becomes a glassy solid at the glass transition temperature, Tg, which can freeze the molecules into alignment of the LC phase. In the glassy phase information can be stored in the LCP, for example as a hologram, by thermo-optical means. However by applying an electric field across the LCP whilst cooling from the isotropic phase the stored information can be erased.

The use of a liquid crystal polymer (LCP) as the storage medium thus has the advantage that data stored thereon is capable of being erasable, and consequently updatable.

The LCP, which may be in the form of a polyacrylate or a polysiloxane, is conveniently in the form of a film applied to a suitable substrate designed to be attached to a respective body, and in some cases may be protected by an overlying, optically transparent cover layer. The substrate is conveniently formed of polyethyleneterephthalate (PET), preferably having a thickness of the order of 75 to lOO > um.

In order to produce sufficient bifringement changes to enable holographic storage properties to be obtained the LCP film needs to be at least a few microns thick and preferably has a thickness of around 3-10/um; with such films both intensity and phase holograms may be produced. The film may be applied to the substrate in any convenient manner, for example by depositing the film as a coating on a substrate in the form of a continuously travelling strip.

One form of data storage label in accordance with the invention will now be described by way of example.

The label comprises a backing sheet of polyethyleneterephthalate (PET) having a thickness of approximately 100 sum, on which is deposited a film of a liquid crystal polymer, such as that designated ATR 39 supplied by Akzo International Research B.V. of Arnhem, Netherlands, the film having a thickness of the order of 3 to 5,us.

The film may be formed by applying the polymer in solution in a suitable solvent to the backing sheet, or by any other suitable coating technique. Following the coating process the coated backing sheet is heated above the glass transition temperature, and subsequently cooled into the glassy liquid crystal phase, in which state information can be stored in it as a hologram. An improvement in quality may be achieved by carrying out the heating cooling cycle several times.

The label may be attached to a component used in a manufacturing process, the data written into it giving information identifyng the component, and possibly to identify particular tasks which a machine tool or robot is required to perform on the component. The label, however, has the property that by heating and cooling, whilst at the same time applying an electric field across it, the stored information can be erased, and the information updated. This is of advantage, for example, where the component needs to undergo several processing stages, as, following one operational process fresh information detailing a subsequent operation or destination can be written into the label.

Such a label may also be used to advantage on a container vehicle for storing information about a route and destination of the vehicle, which information can be erased and fresh information written into it for a subsequent journey. However it is clear that a label in accordance with the invention can have many other useful applications.

Claims

-1. A data storage arrangement comprising a label incorporating, as a holographic storage medium, a liquid crystal polymer.
2. A data storage arrangement according to Claim 1 wherein the label comprises a substrate carrying the holographic storage medium in the form of a film.
3. A data storage arrangement according to Claim 2 herein the film has a thickness of between 3 and 10 Am.
4. A data storage arrangement according to Claim 3 wherein the film consists of a polyacrylate or a polysiloxane.
5. A data storage arrangement according to Claim 2, 3 or 4 wherein the substrate comprises a sheet of polyethyleneterephthalate having a thickness of between 75 and 100 Am.
6. A component employed in a manufacturing process carrying a data storage label having, as a holographic storage medium, a liquid crystal polymer.
7. A container vehicle carrying a data storage label having, as a holographic storage medium, a liquid crystal polymer.
8. A data storage arrangement comprising a label carrying a holographic storage medium substantially as hereinbefore described by way of example.