CH711819A2 - Cladding element with temperature sensor. - Google Patents

Abstract

The present invention relates to a thermochromic element (10) comprising a thermochromic layer (11) composed of a binder and a thermochromic pigment chosen to react at a specific temperature so that said pigment passes from a first color to a second color when said specific temperature is reached, characterized in that said thermochromic layer has a thermally conductive layer, and is protected by an optically transparent layer protecting it from physical and chemical degradation.

Description

Description: [0001] The present invention relates to a thermochromic element comprising a thermochromic layer composed of a binder and a thermochromic pigment chosen to react at a specific temperature so that said pigment passes from a first color to a second color when said specific temperature is reached.

BACKGROUND

There are known portable objects such as bracelets that use thermochromic pigments for temperature sensor type applications or purely decorative applications. One technology used is Leuco technology. The operation of the Leuco systems is maintained well known and widely used in inks and paints but also in bulk in plastics; the pigment is actually a micro-capsule containing three components: a pH-sensitive dye (iono-chromism), usually of the class of spyrolactone, a weak acid functioning as the color developer, it is usually bisphenol A, and a co-solvent of the class of low melting fatty acids, amides or alcohols.

It is the melting point of the co-solvent which determines the transition threshold of the colored form to the colorless form of the dye.

A disadvantage of this system is its high sensitivity to ultraviolet (UV) which results, therefore, a rapid degradation of the pigment if exposure to ultraviolet radiation is greater than more than ten hours continuously .

To solve this problem, it is envisaged to use additives inhibiting the degradation of the ultraviolet dye such as ultraviolet absorbers on the basis of titanium oxides, cerium or zinc are known and it is accepted that they can be used in the formulation of the painting or thermochromic ink.

However, the disadvantage of these ultraviolet absorbers is that they have a high refractive index and therefore a high light scattering power resulting in opacification of the system.

A known variant is the use of submicron particles and good dispersion thereof to improve the optical qualities.

Another alternative is the use of phenolic type organic particles such as hydoxybenzophenone or lignin.

The use of all these additives complicates the formulation and disrupts the achievement of a good functional, aesthetic and resistant result.

A last alternative is the use of nanoparticles composed of spin transition complexes. The thermochromic effect of these nanoparticles is described in patent application US2008 / 0311401. They also have good ultraviolet stability. However, some nanoparticles have, depending on the complexes used, the disadvantage of a more or less significant memory effect which does not allow, for a temperature sensor application, a reliable indication of the temperature.

SUMMARY OF THE INVENTION

The invention relates to a cladding element that overcomes the aforementioned drawbacks of the prior art by providing a portable object capable of providing a temperature change indication in a readable and reliable manner.

For this purpose, the invention consists of a thermochromic element comprising a thermochromic layer composed of a binder and a thermo-chromic pigment chosen to react at a specific temperature so that said pigment passes from a first color to a second color when said specific temperature is reached, characterized in that the thermochromic element further comprises a support layer on which the thermochromic layer is deposited and a protective layer resistant to ultraviolet rays covering the thermochromic layer and the support layer.

This invention makes it possible to have the thermochromic layer which is protected from UV by the protective layer but which has a good reactivity to temperature changes via the support layer.

In a first advantageous embodiment, the support layer has a thermal conductivity greater than 100 W.rrf1.K_1. This layer makes it possible to have a good reactivity for the color change during a variation of temperature.

In a second advantageous embodiment, the thermochromic layer is of the hard lacquer type consisting of a binder in which the pigment is mixed, this binder being chosen from the family of acrylics, copolymers of acrylics or polyurethanes, a polycarboxylic acid salt type dispersant, a benzoate type plasticizer, a solvent selected from the family of glycols or esters.

In a third advantageous embodiment, the thermochromic layer (11) is of the flexible lacquer type consisting of a binder in which the pigment is mixed, said binder being selected from the family of silicones or polyurethanes.

In a fourth advantageous embodiment, the thermochromic layer is of the ink type consisting of a binder selected from the family of acrylics or polyurethanes or silicones; a polycarboxylic acid salt-type dispersant or anti-flocculant, a sulfonamide-type plasticizer and adhesion promoter and a solvent selected from the family of glycols or esters.

In a fifth advantageous embodiment, the protective layer is selected from the list comprising: sapphire, acrylic charged with diamond nano and graphene in the form of lacquer or other, a thin layer of nanodiamond.

In another advantageous embodiment, the protective layer has a thermal conductivity of at least greater than 10 W.rrf1.K_1.

In another advantageous embodiment, the support layer is made of a material in the form of a thin layer, of sheets or solid selected from the list comprising: anodized aluminum, copper, gold alloys, silver alloys, aluminum / silicon carbide alloys, thin layers of nano-diamonds, thin layers of graphite or graphene.

In another advantageous embodiment, the thermochromic element further comprises a substrate on which the different layers are arranged to form an insert.

In another advantageous embodiment, the thermochromic element further comprises at least one intermediate layer arranged under the thermochromic layer.

In another advantageous embodiment, the intermediate layer is a luminescent layer combining lanthanide doped alkaline earth type phosphor pigments and / or pigments and fluorescent dyes.

The invention also relates to a cladding element of a portable object comprising a frame made of a first material, said cladding element further comprising at least one device responsive to temperature variations, characterized in that said device responsive to temperature variations is formed of at least one thermochromic element according to the invention.

In another advantageous embodiment, the device responsive to temperature variations is a temperature sensor provided with a plurality of thermochromic elements, each thermochromic element reacting to a specific temperature of its own.

In another advantageous embodiment, the thermochromic elements all have the same first color.

In another advantageous embodiment, the thermochromic elements all have the same second color.

In another advantageous embodiment, the thermochromic elements are designed so that their second color allows a gradient when they have all passed from the first color to the second color.

In another advantageous embodiment, the covering element comprises at least one recess arranged so that at least one thermochromic element can be placed there.

The invention further relates to a portable object comprising a housing formed by a middle part closed by a bottom and an ice, said portable object also comprises a bracelet, characterized in that it further comprises at least one element of dressing invention selected from the list comprising the middle part, the ice, the bezel, the dial, the bracelet, the clasp.

BRIEF DESCRIPTION OF THE FIGURES

The advantages of such a dressing element will become clear from reading the description which follows and the examination of the drawings which illustrate it by way of example and in which: FIGS. 1 and 2 show schematically a timepiece according to the present invention; figs. 3 and 4 schematically represent a thermochromic element according to the present invention; fig. Figure 5 schematically shows a first embodiment according to the present invention; fig. 6 schematically shows a second embodiment according to the present invention; fig. 7 schematically shows a variant of the first embodiment of the thermochromic element according to the present invention; fig. 8 schematically shows a variant of the second embodiment of the thermochromic element according to the present invention; figs. 9 to 16 show a temperature sensor and its variants using the thermochromic element according to the present invention;

DETAILED DESCRIPTION

The present invention relates to a cladding element 1 of a timepiece or shows 100.

The timepiece 100, visible in FIGS. 1 and 2, is for example a wristwatch and comprises a housing 102. This housing is formed by a middle part 104 closed by a bottom 106 and a mirror 108 to see a bezel 114. The timepiece may comprise a dial 109 and display means 109a. The timepiece also comprises control means 116. The timepiece also comprises a bracelet 110. The latter is fixed to the middle part via two pairs of horns 112. The bracelet may consist of two strands, each strand being attached to a pair of horns and connected to the other strand via a clasp.

This dressing element may be for example a bracelet 110, a middle part 104, a bezel 114, a mirror 108, a pusher or a crown 116, a dial 109 of the timepiece. This covering element can be made of a metallic or ceramic material or plastic type.

This cladding element 1 is arranged to carry a thermochromic element 10. Such a thermochromic element 10 is an element capable of changing color depending on the temperature. A thermochromic element 10 generally comprises a thermochromic pigment that reacts with temperature to change its color.

Advantageously according to the invention, the thermochromic element 10 is composed of at least three different compounds, in the form of layers and superimposed on each other as shown in FIGS. 3 and 4. These at least three compounds are used to obtain a thermochromic element having a good life and good efficiency.

The first compound is a compound called A which is characterized as being in the form of a thermochromic layer 11. This thermochromic layer 11 is composed of thermochromic pigments such as a pigment called leuco c i.e., a microcapsule containing a pH change sensitive dye (iono-chromism), generally of the class of spyrolactones, a weak acid functioning as the color developer, generally bisphenol A, and a co-solvent of the class of fatty acids with low melting points, usually amides or alcohols.

It may also be a pigment using spin transition technology.

The second compound is a compound called B which is characterized as being a protective layer 12. Such a protective layer 12 consists of a layer resistant to at least ultraviolet rays. This transparent layer may be a layer made of nano-diamond and / or graphene-filled acrylic having good transparency and improved thermal conductivity or a thin layer of nano-diamond.

Preferably, this layer of compound B has a thermal conductivity of greater than 10 W m -1 K -1.

The thickness of this layer of compound B varies between 10 pm and 0.1 mm.

This advantageous arrangement allows to protect the compound A, that is to say the compound comprising the thermochromic pigment, ultraviolet and therefore to improve the longevity of the thermochromic element since the layer of compound B will absorb some of the ultraviolet rays.

The third compound called compound C is in the form of a support layer 13 having a thermal conductivity of at least greater than 100 W.rrr1.K_1. The support layer 13 formed by the compound was then deposited between the covering element 1 and the layer 11 of compound A containing the thermochromic pigments, this compound A being covered by the compound B. It is specified that the The film formed by this layer C has a surface slightly larger than the films formed by the compounds A and B, so that the conductive layer is in direct contact with the external medium and can drive the variations with the greatest efficiency. temperatures experienced.

This compound C may be chosen to be transparent or opaque depending on the material of the cladding element. Indeed, for a covering element such as ice, that is to say transparent, a transparent compound C will be used.

For this compound C, one will choose a material from the following list: anodized aluminum, gold, silver or one of their alloys, thin layer of nano diamonds deposited for example by a sol-gel process.

The thickness of this layer 13 of compound C varies between 10 and 5 mm so as to allow a greater or lesser energy transmission and / or fast.

This layer 13 made with the compound C is used to thermally conduct the heat of the cladding element and therefore to allow good reactivity in the color change of the thermo-chromic element of the layer A.

In a first embodiment, the thermochromic element 10 is made by superposition of layers. For this, the various layers 11, 12, 13 of respective compounds A, B and C are in the form of layers with a thickness of 10 to 100 μm, so that the thermochromic element is in the form of a silkscreen as shown in fig. 5.

As such, the layer of compound A, which is the layer containing the thermochromic pigments may be a layer deposited uniformly by spray or soaking or screen printing or stamping.

The layer of compound B, which is the protective layer is a layer deposited by screen printing methods, buffering or by spraying methods or dipping to obtain a homogeneous layer. In a first form, the layer of compound B will be of the hard lacquer type and will consist of a binder in which the anti-UV agents and other additives are mixed, this binder may be derived from the family of acrylics or copolymers of acrylics for high scratch and UV resistance or polyurethane binder for high abrasion resistance, polycarboxylic acid salt dispersant, benzoate plasticizer, glycol or ester solvent and others additives as anti-UV agents for polyurethane in order to avoid degradation of the polymer, or touch agents (waxes, paraffins, etc.) making it possible to improve the haptic properties.

In a second form, the layer of compound B will be of the flexible lacquer type and consist of a binder in which the anti-UV agents and other additives are mixed. This binder may be derived from the family of silicones or polyurethanes.

According to a third form, the layer of compound B will be of the ink type and consist of a binder of the family of acrylics for high UV resistance and high transparency or family of polyurethanes for high resistance to abrasion or a silicone ink for flexible substrates; a polycarboxylic acid salt-type dispersant or anti-flocculant, a sulfonamide type plasticizer and adhesion promoter and a glycol or ester type solvent.

The layer of compound C which is the layer allowing better thermal conductivity, may be a thin layer of nano-diamonds deposited by sol-gel or a thin layer of copper, gold or silver, carbon or similar deposited by a PVD or PECVD treatment.

In a second embodiment, the thermochromic element 10 is formed by superposition of layers to form an insert chip as shown in FIG. 6. For this, the various layers of compound A, B are in the form of so-called thick layers, that is to say that the layers themselves support the opposite of an ink or lacquer which must to be deposited on a substrate. The layer C may be thick or thin.

As such, the layer of compound A is then in the form of a flexible or hard material. It is assembled by overmoulding, gluing, riveting, screwing or any other mechanico-chemical means with the other layers. It is produced by injection or overmolding. The layer may be of the thermoplastic type such as, for example, a resin of the acrylonitrile butadiene styrene, polyamide or methyl polymethacrylate type, thermosetting such as an epoxy or acrylic resin, or thermoplastic elastomer such as, for example, a polyurethane type resin. This resin will be premixed with the thermochromic pigments and a dispersing agent and compatibilizer type modified / graft copolymers, a plasticizer of benzoate or sulfonamide type.

The layer may also be of the vulcanized elastomer type, by over-molding or compression injection, such as, for example, an elastomeric resin of nitrile butadiene or hydrogenated nitrile butadiene or elastomeric fluoropolymer, or silicone type, a vulcanization process adapted to the selected resin using additional elements such as sulfur and vulcanization accelerators such as thiurams or peroxides and its derivatives, optional coupling agents (silane type).

For the layer of compound C, it can be envisaged that it is in the form of a metal alloy of high thermal conductivity (copper alloy for example). In this case, this compound C will be assembled with the other layers. It is also possible that compound C is produced by plasma treatment on the lower and longitudinal surfaces.

An advantage of this embodiment is that it allows to have thermochromic elements that can be machined to the final shape of the temperature sensor. They are easily manipulated and can be reported to components by assembly.

This embodiment may be associated with recesses 15 arranged on the trim element 10, these recesses 15 serving as a housing for the thermochromic elements 10 in the form of inserts.

In a variant of the first embodiment, it may be provided that the different layers of the thermochromic element are deposited on a support 14 as shown in FIG. 7, the support 14 is then placed in a recess of the housing element serving as housing.

In a variant of the first and second embodiments, it may be envisaged that the thermochromic element is composed of a mixture of thin layers and thick layers. As such, it is possible that the layers of compound A and compound C are so-called thick layers. This configuration makes it possible to have the layers of compounds A and C forming a kind of shell enclosing the thermochromic compound.

Another example would be to have the layer of compound C in the form of a thick layer on which the layers of compound A and compound B are arranged. These layers of compound B and compound A are so-called thin layers. This makes it possible to have a thermochromic element easier to handle than a thermochromic element made only with thin layers.

In a variant of the first and second embodiments, it can be provided that at least one intermediate layer 16 is arranged between the layer of compound A and the layer of compound C as shown in FIG. 8. Such a layer 16 may be used to obtain an additional effect. An advantageous example is the use of a luminescent, phosphorescent or fluorescent layer, to provide readability in case of low light exposure.

Of course, it may be expected to have other types of intermediate layers such as a pearlescent layer, metallized or colored to provide an additional effect.

This thermochromic element 10 is then used in different applications. A first application consists of a temperature sensor 200 which allows the visualization of a temperature scale. For this, the temperature sensor 200 comprises a plurality of thermochromic elements 10, each of them comprising a pigment reacting at a specific temperature. Therefore, each thermochromic element 10 changes color when a specific temperature is reached.

In order to have a temperature scale, it will be ensured that the specific temperatures of the thermochromic elements 10 are increasing or decreasing. Thus, when the wearer carrying the portable object undergoes temperature variations, the thermochromic elements 10 change color as and when they allow a visual indication that is easy to interpret. These thermochromic elements 10 may be glued to each other or spaced apart.

In a preferred embodiment, the various thermochromic elements 10 composing the temperature scale all have a first color, ie a color at rest, identical. It is understood that at a reference temperature, all the thermochromic elements 10 have the same color.

In another preferred embodiment, the various thermochromic elements 10 composing the temperature scale all have a second color, ie a color when their specific threshold is reached, identical. It is understood that at the maximum measurable temperature, all the thermochromic elements 10 will have the same color.

In another preferred embodiment, the various thermochromic elements 10 composing the temperature scale all have a first identical color but are made so that they do not all have a second identical color to allow a gradient. More specifically, the thermochromic elements 10 are designed so that, when they form a temperature scale, the first color changing thermochromic elements have a second lighter color than the color changing thermochromic elements. Lastly. For example, the first thermochromic elements 10 turn yellow and the last ones turn red. This allows a double indication: not only does the user know that the temperature increases because the number of thermochromic elements 10 changing color increases but he also knows that it is approaching a maximum temperature because the color varies and becomes darker and darker.

It will therefore be understood here that the thermochromic pigment is of the reversible type. This means that when the pigment reaches or exceeds a specific temperature threshold, it changes color from a first color to a second color. But it also means that when the temperature goes below the specific threshold, the pigment passes from the second color to the first color.

It may be provided that the thermochromic elements of the temperature sensor are arranged on the bezel or the ice of the watch and extend on the bezel in a circular arc from the 3H position of the hour turn. at the 6H position of the hour circle or the 9H position of the hour circle at the 12H position of the hour circle as shown in FIGS. 9 and 10.

It is also possible that the temperature sensor extends on the middle as shown in FIG. 11 or the wristband of the watch as shown in fig. 12 to 16.

In a first case visible in FIG. 12, the bracelet 110 consists of two bracelet strands 110a, each strand being attached to a pair of horns 112 and connected to the other strand via a clasp 111. Preferably, the strap strands 110a are made of rubber or plastic.

In a second case visible in FIG. 13, the bracelet is metal or ceramic and then consists of a plurality of links 110b attached to each other by means of pins. This makes it possible to have links 110b which can pivot relative to each other.

In both cases, the thermochromic elements can be screen printed or be in the form of inserts and be arranged in recesses on the bracelet.

In another case visible in FIGS. 14 to 16, the cladding element is the clasp 111 that is to say the clasp of the bracelet. Such a folding clasp is generally composed of three parts 111a, 111b, 111c as spars hinged relative to each other. Two of these parts are attached to a link or a strand. These parts

Claims (18)

component folding clasp 111 are then designed to articulate so that they can stack, these three parts 111a, 111b, 111c then only one. This configuration makes it possible to enlarge the length of the bracelet momentarily for attachment to the wrist of the user. For some models of folding clasp, one of the parts serves as the main part 111a because it is this part that hosts the other two parts 111b, 111c; this part 111a said principal is the visible part of the outside. From the outside, the user sees a part in the form of a metal plate on which indications such as the name of the mark can be engraved. The present invention uses this surface for the arrangement of the temperature sensor. The thermochromic elements 1 are therefore disposed on this surface of the central portion 111a of the folding clasp. It will be understood that various modifications and / or improvements and / or combinations obvious to those skilled in the art can be made to the various embodiments of the invention described above without departing from the scope of the invention defined by the appended claims. claims A thermochromic element (10) comprising a thermochromic layer (11) composed of a binder and a thermochromic pigment chosen to react at a specific temperature so that said pigment passes from a first color to a second color when said specific temperature is reached, characterized in that the thermochromic element further comprises a support layer (13) on which the thermochromic layer (11) is deposited and a protective layer (12) resistant to ultraviolet radiation covering the thermochromic layer and the support layer. 2. thermochromic element according to claim 1, characterized in that the thermochromic layer (11) is of the hard lacquer type consisting of a binder in which the pigment is mixed, this binder chosen from the family of acrylics, copolymers of acrylics or polyurethanes, a dispersant of the polycarboxylic acid salt type, a benzoate plasticizer, a solvent chosen from the family of glycols or esters. Thermochromic element according to claim 1, characterized in that the thermochromic layer (11) is of the flexible lacquer type consisting of a binder in which the pigment is mixed, said binder being chosen from the family of silicones or polyurethanes. 4. thermochromic element according to claim 1, characterized in that the thermochromic layer (11) is of the ink type consisting of a binder selected from the family of acrylics or polyurethanes or silicones, a dispersant or an anti-flocculant agent of the polycarboxylic acid salt type, a plasticizer and a sulfonamide-type adhesion promoter and a solvent chosen from the family of glycols or esters. 5. thermochromic element according to one of claims 1 to 4, characterized in that the protective layer (12) is selected from the list comprising: sapphire glass, acrylic glass nanodiamant loaded and graphene, a thin layer of nanodiamond , an acrylic lacquer loaded with nanodiamond and graphene charge. 6. thermochromic element according to one of claims 1 to 5, characterized in that the protective layer (12) has a thermal conductivity at least greater than 10 W.irf1.K "1. Thermochromic element according to claim 2, characterized in that the support layer (13) has a thermal conductivity greater than 100 W.rrf1.K "1. 8. thermochromic element according to claim 1, characterized in that the support layer (13) is made of a material selected from the list comprising: anodized aluminum, copper, gold alloys, alloys silver, aluminum / silicon carbide alloys, nanodiamond thin films, graphite thin films, graphene. 9. thermochromic element according to one of the preceding claims, characterized in that it further comprises a substrate (14) on which the various layers are arranged to form an insert. 10. Thermochromic element according to one of the preceding claims, characterized in that it further comprises at least one intermediate layer (16) arranged under the thermochromic layer. Thermochromic element according to one of the preceding claims, characterized in that the intermediate layer (16) is a phosphor layer. 12. A covering element (10) of a portable object (100) comprising a frame made of a first material, said covering element further comprising at least one device responsive to temperature variations (200), characterized in that said device responsive to temperature changes is formed of at least one thermochromic element (10) according to one of claims 1 to 12. 13. cladding element (10) according to claim 12, characterized in that the device responsive to temperature changes (200) is a temperature sensor provided with a plurality of thermochromic elements, each thermochromic element reacting to a specific temperature of its own. 14. Cladding element according to claim 13, characterized in that said thermochromic elements (10) all have the same first color. 15. A cladding element according to claim 13, characterized in that said thermochromic elements (10) all have the same second color. 16. A cladding element according to claim 13, characterized in that said thermochromic elements (10) are designed so that their second color allows a gradient when they have all passed from the first color to the second color . 17. A cladding element according to one of claims 12 to 16, characterized in that it comprises at least one recess (15) arranged for at least one thermochromic element (10) to be able to to place. 18. 18. Portable object comprising a housing (102) formed by a middle part (104) closed by a bottom (106) and an ice (108), said portable object also comprises a bracelet (110), characterized in that it further comprises at least one dressing element according to one of claims 1 to 17 selected from the list comprising the middle part, the ice, the bezel, the dial, the bracelet, the clasp.