GB2086575A - Temperature-responsive screen to detect temperature anomalies of the skin - Google Patents

Abstract

Thermographic screen to display temperature variations at the skin surface comprising a supporting plate A, and a thermosensitive composite layer Al carried on said support plate and composed of sequential layers of microencapsulated liquid crystal formulations carried in a binder. Each formulation has a different range of temperature sensitivity. The composite layer is prepared by silk printing sequentially successive formulations on to a support plate A and covering with a film A2. <IMAGE>

Description

SPECIFICATION Thermographic screen to detect temperature anomalies at the skin This invention relates to a screen of the type used to detect thermographically anomalous conditions at the skin surface of a human. These may be indicative of malfunction. More specifically, the invention provides a screen particularly designed to detect possible malformations of the human breast, such as cysts, adenomas, mastitis, etc.

The object of the invention is to provide a screen with an extended useful temperature range by means of which any person may scan the thermal topography of her own breast as a cursory test against the onset or incipience of certain anomalous conditions, possibly of a serious nature.

In particular the invention provides one with the means to determine the thermal distribution in the breast in order to ascertain the presence or absence of an asymmetric or altered thermal status, usually determined by neoplastic conditions, thereby to make one aware of the need for prompt medical assistance to avoid the progress of the condition and its consequences.

The prior art teaches certain structures to detect thermal observations or changes at the skin surface but, in, general discloses support structures which carry or are laminated with a single liquid crystal formulation. Thus, for example, U.S. Patent No.

4,101,696 teaches a structure composed of a polymer support sheet, a specially structured black layer, and a layer of microencapsulated liquid crystals applied with a coating knife. U.S. Patent No.

3,620,889 teaches encapsulation of a liquid crystal formulation in a heat cured resin to control the opacity of the material. U.S. Patent No.3,830,224 shows packages of liquid crystal formulations secured to a brassiere garment. In U.S. Patent No.

3,619,254, a liquid crystal formulation is printed by silk screen, letter press, or other printing, spraying or brushing techniques onto a sheet of material for thermometer sensing.

Those patents which do deal with extended range structures using more than one liquid crystal formulation, approach the problem by ganging together a number of discrete liquid crystal structures or elements, U.S. Patent No. 4,060,654 describes a sandwich composite screen made up of a stack of sheets carrying separate liquid crystal formulations. U.S.

Patent No. 4.030,482 describes a rigid support with superimposed non-adjacent temperature range numerical displays, for use as a thermometer. The non-adjacent temperature display range is necessary to make the numbers readable. U.S. Patent NO.

3,847,139 teaches spraying an encapsulated liquid crystal formulation onto a stretchable substrate in the form of a brassiere type garment. When a second layer is provided, it is separated from the first layer by the stretchable substrate.

A second approach is to have each liquid crystal formulation in a separate area on the support, for example to form a thermometer as in U.S. Patent No.

4,220,680 wherein adjacent areas carry liquid crystal formulations with overlapping temperature ranges.

A similar arrangement is shown in U.S. Patent No.

4,190,058 for the detection of breast cancer, but does not use liquid crystals as sensors.

A device for stretching and holding liquid crystal sheets is shown in U.S. Patent No. 4,079,529.

The screen according to the invention consists of a plate of transparent flexible material and having one of its surfaces provided with a heat sensitive layer of liquid crystals held in place by a suitable bonding material. By placing the screen in contact with the part of the breast to be scanned, the heat of said part affects the liquid crystals and different coloring is imparted to the plate as a function of the temperature of said parts, revealing the altered or anomalous area. The liquid crystal layer is a composite of several layers of separately applied encapsulated liquid crystal formulations. Formulation methods are known, for example from U.S. Patent No. 3,620,889.

By providing a mixture of formulations on the same screen, an extended temperature range of use for the screen is possible. The liquid crystal mixtures are preferably composed of cholesteryl chloride (CCI), cholesteryl carbonate (CC) and cholesteryl nonaonate (CN) in various proportions to give an extended temperature range topographic display of about 4.5 C, with color changes from red to blue.

One advantageous version of the screen is adapted for thermographic examination of both breasts. This embodiment includes a flexible material support provided with two zones which hold thermosensitive layers spaced for simultaneous application to both breasts. The ends of the flexible support are provided with suitably shaped hollows forming extensions or wings which, when held firmly in the armpits, ensure correct positioning of the screen on the breasts during the thermographic test.

In order to protect the thermally sensitive layer, it is covered with a fine transparent film, which is also thermally conductive. This prevents abrasive damage to the crystal and allows the cleaning, and disinfecting of the layer, when conditions of use require it.

The invention will now be described in detail, in conjunction with the annexed drawings, which illustrate, by way of example, some advantageous forms of embodiment of the screen according to the invention. In the drawings: Figure 1 is a cross section on an enlarged scale of a simplified version of the screen.

Figure 2 shows the use of a version of the screen for simultaneous thermographic examination of both breasts.

Figure 3 is an elevated view of the screen of Figure 2.

Figure 4 is a detailed cross section, on an enlarged scale, of the screen shown in Figure 3.

Figure 5, illustrates in the conventional manner the thermographic image of a breast obtained with the screen according to the invention, in which the differently colored areas are identified with different dash patterns.

With reference to Figure 1 in the drawing, the thermographic screen shown consists of a flexible transparent plate A of non-toxic, anti-allergic material having thermal properties similar to those of the human skin. One of the surfaces of said plate is provided with a composite layer Al of liquid crystals held in a suitable binder to ensure adequate flexibility, and adhesion of said layer to said plate A. The flexible plate thus obtained can be conveniently applied and made to adhere to the breast by applying an adequate pressure without deforming or damaging the crystals permanently.

For protection during use the liquid crystals compositelayer Al is covered by a thin film A2 of a transparent, thermoconductive material. The plate A is thus effectively protected during use and cleaning or disinfecting of the screen.

Depending on the thermal field explored in each case, and the chromatic intensity to be achieved, cholesteric and/or smetic and/or nematic crystals, in the proper proportions, are used for layers.

It is thus possible to obtain a range of colors that may vary more or less intensely within the temperature range of 25 to 48 C, from black to dark blue and successively red, brown, yellow and green. The preferred range for use on human breasts is 290C to 33.5 C. To obtain a topographical display discernible by the human eye and over this 4.50C range requires the use of two separate liquid crystals formulations, sequentially applied to a flexible plate support material as will be discussed below.

With reference to Figures 2 through 4, the screen shown consists of a support S of suitable flexible material, for example, cloth, paper, etc., which forms a strip provided at its ends with suitably shaped hollows S1 which form wings S2, conveniently engageable with the armpits of the user.

If required, the extremities of said wings S2 can be provided on their rear surfaces with zones S4 which may in turn be provided with self adhesive strips to secure screen S in position during the thermographic scan test.

In the preferred embodiment shown, supporting strips S consist of two overlapping elements S and S', the mid part of which is provided with two square apertures S3 with means to hold the edges of a flexible plate A, which closes said apertures. In a second embodiment, the supporting strip may consist of one element only and, in this case, flexible plates A are secured to the edges of apertures S3 either by adhesive or welding or also by securing a frame to the edge of each aperture S3. Flexible plate A is transparent and its lower face, coming into contact with one of the breasts, is provided with composite layer Al consisting of sequential layers of liquid crystal formulations microencapsulated and suspended in suitable binding material.Each formu lation has a different range of thermal sensitivities which enables it to change color in a given temperature range between 250C and 480C most preferably 290C to 33.5 C.

When a liquid crystal layer Al according to the invention, is exposed to the required temperature range a color change more or less intensely starting from black, to dark blue and successively red, brown, yellow and green is sensible to the human eye.

In view of the fact that plates A having thermosensitive layers Al, are flexible, it is most preferred to form screen S as a single piece of transparent, flexible material and apply to said screen, in the appropriate positions, the two zones of crystals Al.

These zones are then protected with transparent film A2 which is made to adhere to said layer thus allowing good thermic contact, whilst the epidermic contact surfaces can be easily and properly cleaned and disinfected.

In order to obtain the extended 4.5 C range of temperature responsive display, two different base formulations of liquid crystals are microencapsulated and sequentially printed onto the support material. In the preferred embodiment, a first formulation covers approximately the range of 290 to 31 C and a second formulation covers the range of 31"two 33.5 C. Two separate formulations are necessary because the maximum range detectable by human eye for each formulation is about 2.5 C as the liquid crystals change from red to blue. When the first formulation passes the blue color stage, the second formulation commences changing from red to blue.

The two base formulations are sequentially applied to form layer Al, and allowed to flow together during the drying step discussed below so that the observable color change pattern appears continuous and it is possible to distinguish temperature variations across a 4.5 C range.

The proportions of liquid crystals necessary for tailoring each formulation to an appropriate range can easily be determined by those skilled in the art.

Usually, various amounts of cholesteryl chloride, cholesteryl carbonate and cholesteryl nonanate, in appropriate proportions, are melted together. The melted material is then microencapsulated by usual procedures to be converted into particles in the range of from about 10 to about 30 microns. It is important that the preponderance of particles be within the range of 10 to 30 microns in order that a uniform layer will be maintained on the final product when it is flexed or stretched.

The small particles of liquid crystals are coated with a polymeric material to complete the microencapsulation process. Suitable procedures are wellknown in the art, see for example "Methods of Preparing Microcapsules: Coacervation, or phase separation", Pharmaceutical Technology International, October 1979 pages 51-56, and references cited therein.

After the microencapsulating process is completed, the microcapsules are concentrated by filtration and thereafter a suitable binding agent is added to obtain a final viscosity of 200 to 300 cps. It is this material which is applied to the flexible support.

It is very important that the microcapsules containing the liquid crystals have a good elastic coating in order that they be sufficiently robust to withstand the silk screen printing process and mechanical actions during normal handling operations.

As noted above, because of the limitations of the human eye, any particular liquid crystal formulation is restricted to indexing a range of 2.5 C. To obtain the desired 4.5 C range, the present invention uses two formulations having adjacent ranges which coverthe desired absolute temperature range. In order to apply the two formulations to a flexible support, a silk screen printing method is used.

Commercially available equipment is used for this purpose although care should be taken that the mesh of the silk screen is large enough to permit the encapsulated liquid crystals to pass through without damage. Any usual commercially available binder can be used. The preferred support on which the formulations are silk screen printed is a flexible clear polymeric material such as polyethylene terephthalate. These materials should be treted on one side with agents to allow them to accept aqueous base inks. This will allow printing thereon with the aqueous suspension of microencapsulated liquid crystals.

The support material can be in the form of one by two meter sheet on which the liquid crystal formulations are applied. This can later be cut for use.

Each formulation is separately printed on the support material. Preferably, the liquid crystals are applied in sequential layers in such a manner that the layer containing crystals having a temperature variation display range closest to that expected to be found normally on the skin surface, in use will be closest to the skin surface. Thus, the first layer on the clear substrate will contain liquid crystals with a temperature range change furthest from that normally to be expected. The last layer will contain a formulation of crystals closesttothat normally expected and finally, a black background layer is added. The final black layer may be any usual material employed in the artto make liquid crystal layer colors more visible.

After the liquid crystals have been applied to the support sheet, they must be dried. This drying process is effected by supporting the flexible support material in a horizontal position and drying it with warm air.

The drying step is preferably carried out under mild conditions with warm air (approximately 45 50 C) and over an extended period of time of several hours. This reduces the possibility of altering the characteristics of the crystals with respect to their temperature and color changes and allows the separate layers of microcapsules to settle gently together to form an integrated matrix. The result is a substantially monolithic light sensitive layer having an extended temperature range continuous display.

It has been found that essentially all of the water should be removed from the liquid crystal layers before the layer is sealed with a final protective sheet of polymeric material. Residual water trapped in contact with the crystals will tend to degrade the liquid crystals with time, causing a change in their temperature-color characteristics. Dryness can be determined by visual inspection as is usual in the art.

The final protective layer, as noted above, is a thin sheet of polymeric material, preferably cellulose acetate or other similar material, of about 20 micron thickness. Normally the flexible support on which the liquid crystals are printed will be of about 100 micron thickness polyethylene terephthalate. The result will be a reasonably flexible structure between which the liquid crystal layers are supported.

Testing the range of color change for the liquid crystal layers should be done to ensure no changes occured during processing. This is preferably accomplished by carefully heating a test sample to the desired temperature range and visually confirming that the expected color changes occur.

It will be understood that the specification and examples are illustrative but not limitative of the present invention and that other embodiments within the spirit and scope of the invention will suggest themselves to those skilled in the art.

Claims (13)

1. Thermographic screen to display temperature variations at the skin surface comprising: a flexible supporting plate; and a monolithic thermosensitive layer carried on said support plate and composed of two substantially co-extensive and sequentially applied microencapsulated liquid crystal formulations carried in a binder, the display temperature range of each said formulation being adjacent the other to give an extended temperature range continuous display.

2. Screen according to claim 1, wherein said binder for the liquid crystal layer is flexible and its thermal properties are similar to those of the skin.

3. Screen as claimed in claim 1 wherein the liquid crystals of the thermosensitive layer are cholesteric and/or smectic and/or nematic type and that the three types may be mixed in suitable proportions to provide different colorings at different body temperatures in the range of 30 to 420C.

4. Screen as claimed in claim 1 further comprising a thin, transparent, thermally conductive sheet of flexible material securely applied to the thermosensitive layer to protect said layer and to allow disinfection of the screen.

5. Screen as claimed in claims 1 or 4 further comprising a support of flexible material, provided with two apertures and a second said supporting plate, said support being operable to hold one of said support plates in each said aperture to allow the simultaneous application of the two plates simultaneously to skin covering both breasts on a patient, so that temperature variations over the breasts can be visually compared.

6. Screen as claimed in claim 5, wherein said flexible support includes, at its two ends, suitably shaped hollows forming wings operable to ensure correct positioning of the screen on the breasts during the thermographic examination, when held under the armpits of the user.

7. Screen as claimed in claim 6 wherein the ends of said wings are provided with self adhesive zones.

8. Screen as claimed in claim 1 or claim 4 wherein said support plate includes two zones carrying said thermosensitive layer, said zones being spaced apart a predetermined distance to permit simultaneous application of said zones to the breasts of a patient.

9. In a method for making a thermographic screen of the type carrying liquid crystals and operable to display temperature variation, the steps comprising: applying, by silk screen printing, a first layer of encapsulated liquid crystals having a first display temperature range, to a flexible support; and thereafter applying, by silk screen printing, a second layer of encapsulated liquid crystals having a second display temperature range adjacent said first display temperature range.

10. The method of claim 9 further comprising the steps of drying said layers with warm air for several hours and until dry, and thereafter applying a film of protective material.

11. A thermographic screen for providing a continuous color display indexing the temperature variations across both breasts of a patient simultaneously for comparison, comprising; an elongated flexible support member having portions spaced apart and operable to cover the areas of both breasts to be compared, and supported on the portions of said support member, a monolithicthermosensitive layer carried on said support plate and composed of two substantially co-extensive and sequentially applied microencapsulated liquid crystal formulations carried in a binder, the display temperature range of each said formulation being adjacent the other to give an extended temperature range continuous display, and a thin transparent, thermally conductive sheet of flexible material securely applied to the thermosensitive layer to protect said layer.

12. A thermographic screen constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

13. A method of making a thermographic screen, such method being substantially as hereinbefore described with reference to the accompanying drawings.