Glass-ceramic plate comprising a liquid-retaining bead

Abstract

A glass-ceramic plate for a cooking device includes a first main face to be in contact with liquids, a second main face and an edge, a liquid-retaining bead fastened to and in contact with the first main face, wherein the retaining bead surrounds a region of the first main face so as to form a liquid-retaining reservoir, and includes at least two hydrophobic sub-beads inscribed within one another and separated by hydrophilic zones, a width of the hydrophilic zone between two consecutive sub-beads is throughout at least greater than 500 μm and less than a threshold value, the threshold value being defined so that, when a liquid is present in the hydrophilic zone, a variation in the retention time or volume of the liquid before overflowing, relative to a same liquid present in a hydrophilic zone, the width of which is greater than the value, is less than 5%.

Claims

1. A glass-ceramic plate for a cooking device comprising: a first main face configured to be in contact with liquids when the plate is in the process of being used, a second main face and an edge, a liquid-retaining bead fastened to and in contact with said first main face, wherein said retaining bead: surrounds at least one region of said first main face so as to form a liquid-retaining reservoir, and comprises at least two hydrophobic sub-beads inscribed within one another and separated by at least one hydrophilic zone, a width of the at least one hydrophilic zone between two consecutive sub-beads is at least greater than 500 μm and less than a threshold value, said threshold value being defined so that, when a liquid flows in the hydrophilic zone, a variation between (a) a retention time or volume of said liquid before said liquid overflows from the hydrophilic zone, and (b) a retention time or volume of a same liquid before said same liquid overflows from a hydrophilic zone having a width greater than said value, is less than 5%.

2. The glass-ceramic plate as claimed in claim 1, wherein the threshold value is at most 2.5 cm, the width of the at least one hydrophilic zone between two consecutive sub-beads being throughout between 500 μm and 2.5 cm.

3. The glass-ceramic plate as claimed in claim 1, wherein, when the hydrophobic sub-beads are in contact with water, the hysteresis H of the contact angle between said hydrophobic sub-beads and the water is greater than or equal to 20°, said hysteresis H of the contact angle being defined as the difference between the advancing angle θa and the receding angle θr the water on said hydrophobic sub-beads.

4. The glass-ceramic plate as claimed in claim 3, wherein said advancing angle is between 108 and 120°.

5. The glass-ceramic plate as claimed in claim 4, wherein said advancing angle is between 110 and 120°.

6. The glass-ceramic plate as claimed in claim 3, wherein, when the hydrophobic sub-beads are in contact with water, the hysteresis H of the contact angle between said hydrophobic sub-beads and the water is greater than or equal to 30°.

7. The glass-ceramic plate as claimed in claim 1, wherein the width of the hydrophobic sub-beads is between 5 mm and 20 mm.

8. The glass-ceramic plate as claimed in claim 7, wherein the width of the hydrophobic sub-beads is between 10 mm and 15 mm.

9. The glass-ceramic plate as claimed in claim 1, wherein a value of the roughness parameter, Ra, of the hydrophobic sub-beads is between 1 and 10 μm.

10. The glass-ceramic plate as claimed in claim 1, wherein a value of the peak-to-valley parameter, Rz, of the hydrophobic sub-beads is between 5 and 50 μm.

11. The glass-ceramic plate as claimed in claim 1, wherein a width of the retaining bead is between 2 cm and 6 cm.

12. The glass-ceramic plate as claimed in claim 1, wherein the retaining bead is placed at at most 3 cm from the edge of said glass-ceramic plate.

13. The glass-ceramic plate as claimed in claim 1, wherein a surface area of the region of the glass-ceramic plate surrounded by at least one retaining bead represents at least 60% of the surface area of the main face of the glass-ceramic plate.

14. The glass-ceramic plate as claimed in claim 1, wherein the hydrophobic sub-beads comprise one or more organic or inorganic compounds, the surface tension of which is at most 20 mN.Math.m.sup.−1.

15. The glass-ceramic plate as claimed in claim 1, wherein the hydrophobic sub-beads comprise one or more organic compounds chosen from polysiloxanes, organosiloxanes, fluorosiloxanes, fluorocarbons, fluoropolymers, fluorosilanes and a mixture thereof.

16. The glass-ceramic plate as claimed in claim 1, wherein the at least one hydrophilic zone is formed by the surface of the glass-ceramic plate that has not undergone any surface treatment.

17. The glass-ceramic plate as claimed in claim 1, wherein the at least one hydrophilic zone comprises one or more hydrophilic coatings deposited on one or more regions of the surface of the glass-ceramic plate.

18. The glass-ceramic plate as claimed in claim 1, wherein an entire region of the first main face of the glass-ceramic plate that separates the at least two hydrophobic sub-beads is formed solely by the at least one hydrophilic zone.

19. A cooking device comprising a glass-ceramic plate as claimed in claim 1.

20. The cooking device as claimed in claim 19, further comprising a control unit, wherein the control unit is not within the region(s) of the glass-ceramic plate defined by the retaining bead.

Description

(1) The advantages of the invention are illustrated by the figures and examples described below.

(2) FIG. 1 is a schematic representation of a glass-ceramic plate according to a first embodiment of the invention.

(3) FIG. 2 is a schematic representation of a glass-ceramic plate according to a second embodiment of the invention.

(4) FIG. 3 is a schematic representation of a cross section along the plane A of the detail III from FIG. 1.

(5) FIG. 4 is a schematic representation of a cross section along the plane B of the detail IV from FIG. 2.

(6) FIG. 5 is a schematic representation of a glass-ceramic plate according to a third embodiment of the invention.

(7) FIG. 6 is a schematic representation of a cooking device comprising a glass-ceramic plate according to a fourth embodiment of the invention.

(8) FIG. 1 represents a glass-ceramic plate 100 according to a first embodiment of the invention. It comprises a main face 101 liable to be in contact with the liquids when it is in the process of being used. For purely illustrative purposes, zones 102 of the face of the glass-ceramic plate under which heating elements may be located when the glass-ceramic plate is used in a cooking device are also represented. The glass-ceramic plate comprises a single liquid-retaining bead 103 which surrounds a region 104 of the main face 101 of the plate liable to be in contact with the liquids. The retaining bead 103 is located in the vicinity of the periphery of the glass-ceramic plate and surrounds zones 102 of the face of the glass-ceramic plate under which heating elements may be located when the glass-ceramic plate is used in a cooking device. The liquid-retaining bead comprises two hydrophobic sub-beads 103a-103b separated by a hydrophilic zone 303. The alternation of the hydrophobic sub-beads and of the hydrophilic zone is represented in FIG. 3 which corresponds to a cross section through the detail III along the plane A.

(9) FIG. 2 represents a glass-ceramic plate 100 according to a second embodiment of the invention. It comprises a main face 101 liable to be in contact with the liquids when it is in the process of being used. Zones 102 of the face of the glass-ceramic plate under which heating elements may be located when the glass-ceramic plate is used in a cooking device are also represented. The glass-ceramic plate comprises a single liquid-retaining bead 201 which surrounds a region 104 of the main face 101 of the plate liable to be in contact with the liquids. The retaining bead 201 is located in the vicinity of the periphery of the glass-ceramic plate and surrounds zones 102 of the face of the glass-ceramic plate under which heating elements may be located when the glass-ceramic plate is used in a cooking device. The liquid-retaining bead comprises three hydrophobic sub-beads 201a-201c separated by hydrophilic zones 401 and 402. The alternation of the hydrophobic sub-beads and of the hydrophilic zones is represented in FIG. 4 which corresponds to a cross section through the detail IV along the plane B.

(10) A cross section of the detail III along the plane A from FIG. 1 is represented in FIG. 3. The glass-ceramic plate 100 comprises a first main face 101, a second main face 302 and an edge 301. The main face 101 is liable to be in contact with liquids when the plate is in the process of being used. The retaining bead 103 is fastened to and in contact with the main face 101 liable to be in contact with liquids. It comprises two hydrophobic sub-beads 103a-103b separated by a hydrophilic zone 303. The two consecutive sub-beads may be irregularly or regularly spaced. The width of the hydrophobic zone is throughout between 500 μm and 2.5 cm, in particular between 500 μm and 1.2 cm, or even between 700 μm and 1.2 cm. The width of the hydrophobic sub-beads may advantageously be between 5 mm and 20 mm, in particular between 7 mm and 18 mm, or even between 10 mm and 15 mm.

(11) FIG. 4 represents a cross section along the plane B of the detail IV from FIG. 2. The glass-ceramic plate 100 comprises a first main face 101, a second main face 302 and an edge 301. The main face 101 is liable to be in contact with liquids when the plate is in the process of being used. The retaining bead 201 is fastened to and in contact with the main face 101 liable to be in contact with liquids. It comprises three hydrophobic sub-beads 201a-201c separated alternately by two hydrophilic zones 401 and 402. The three consecutive sub-beads may be irregularly or regularly spaced. The width of the hydrophobic zones is throughout between 500 μm and 2.5 cm, in particular between 500 μm and 1.2 cm, or even between 700 μm and 1.2 cm. The width of the hydrophobic sub-beads may advantageously be between 5 mm and 20 mm, in particular between 7 mm and 18 mm, or even between 10 mm and 15 mm.

(12) FIG. 5 represents a glass-ceramic plate 100 according to a third embodiment. The glass-ceramic plate comprises a face 101 liable to be in contact with the liquids when the plate is in the process of being used. Zones 102 of the face of the glass-ceramic plate under which heating elements may be located when the glass-ceramic plate is used in a cooking device are also represented. The glass-ceramic plate comprises one two liquid-retaining beads 501 and 502 which surround two regions 503 and 504 of the face of the plate liable to be in contact with the liquids. The retaining beads surround zones 102 of the face of the glass-ceramic plate under which heating elements may be located when the glass-ceramic plate is used in a cooking device. Each liquid-retaining bead 501 and 502 comprises two hydrophobic sub-beads 501a-501b and 502a-502b respectively separated by hydrophilic zones 505 and 506.

(13) A cooking device 600 comprising a glass-ceramic plate according to a variant of the first embodiment of the invention from FIG. 1 is represented in a top view in FIG. 6. The glass-ceramic plate 100 comprising a main face 101 liable to be in contact with the liquids when the plate is in the process of being used. For purely illustrative purposes, zones 102 of the face of the glass-ceramic plate under which heating elements may be located when the glass-ceramic plate is used in a cooking device are also represented. The glass-ceramic plate comprises a single liquid-retaining bead 103 which surrounds a region 104 of the main face 101 of the plate liable to be in contact with the liquids. The retaining bead 103 is located in the vicinity of the periphery of the glass-ceramic plate and surrounds zones 102 of the face of the glass-ceramic plate under which heating elements may be located. The liquid-retaining bead comprises two hydrophobic sub-beads 103a-103b separated by a hydrophilic zone 303. The cooking device comprises a display unit 601 and two control units 602. The display 601 and control 602 units are not within the region 104 defined by the retaining bead 103.

EXAMPLES

(14) In order to illustrate the technical effect obtained by the invention, two examples of glass-ceramic plate according to the invention are compared to two examples of glass-ceramic plate provided with a retaining device or system according to the prior art.

(15) The glass-ceramic plate used in the examples is a commercially available lithium aluminosilicate glass-ceramic plate.

(16) In the examples according to the invention, a retaining bead comprising two hydrophobic sub-beads is fastened to and in contact with the face of two glass-ceramic plates according to the arrangement illustrated in FIG. 1. For each of the glass-ceramic plates, the width of each of the hydrophobic sub-beads and the width of the hydrophilic zone separating them are reported in table 1 (examples 1 and 2). The hydrophilic zone is formed by the surface of the glass-ceramic plate that has not undergone any treatment.

(17) In order to produce the examples of glass-ceramic plate according to the prior art, a retaining bead comprising only a single hydrophobic sub-bead is fastened to and in contact with the face of two glass-ceramic plates according to the same arrangement illustrated in FIG. 1 (examples 3 and 4). Examples 3 and 4 are comparative examples. In order to avoid any experimental bias linked to the resizing of the retaining beads, the width of the sub-beads was adapted so that the surface area covered by the sub-beads and the surface area of the region surrounded by the retaining bead are identical to those of examples 1 and 2.

(18) In the four examples, the surface area of the region (104) surrounded by the retaining bead is identical.

(19) The hydrophobic sub-beads are based on fluorinated trichlorosilane. They were deposited by evaporation under reduced pressure (chemical vapor deposition). During the deposition, the regions of the glass-ceramic plate outside of the hydrophobic sub-beads were protected using a mask that is impermeable to the fluorinated compounds.

(20) The retention performance of each glass-ceramic plate was evaluated by pouring water into the center of the regions surrounded by the retaining bead with an average flow rate of 2.4 to 2.5 ml/s. This flow rate is representative of the flow rate of a liquid overflowing from a cooking container.

(21) The maximum volume retained and the maximum retention time before overflowing beyond the retaining beads were measured. The results are reported in table 1.

(22) The comparison of examples 1 and 2 according to the invention and of comparative examples 3 and 4 according to the prior art shows that a glass-ceramic plate according to the invention enables a gain of 7% to 8% in the volume of liquid retained and the retention time before overflowing.

(23) TABLE-US-00001 TABLE 1 Example Example Example 3 Example 4 1 2 (comparative) (comparative) Number of hydrophobic 2 2 1 1 sub-beads Width of the hydrophobic 1 1 1.81 1.57 sub-beads (cm) Width of the hydrophilic 1 2 — — zones (cm) Time before overflowing 47 46 43 44 (s) Maximum volume before 112 113 105 105 overflowing (ml)

(24) Three examples of glass-ceramic plates according to the invention were produced with hydrophobic sub-beads comprising different hydrophobic compounds. Some of these compounds are commercially available.

(25) In each example, the same type of glass-ceramic plate is used and the surface area of the region (104) surrounded by the retaining bead is identical. The glass-ceramic plate is of lithium aluminosilicate type. It representative of the glass-ceramic plates commercially available.

(26) Table 2 indicates, for each example, the trade name of the hydrophobic compound used for the sub-beads, the type of compound, the values of contact angle θc, advancing angle θa, receding angle θc, and of hysteresis H.

(27) The contact angles, advancing angle and receding angle were measured using a DSA100 goniometer sold by Krüss.

(28) In example 5, the hydrophobic sub-beads are based on silicone (Diamon fusion ultra (DFI)). They were deposited in two goes by means of a spray or wiping (chemical liquid deposition).

(29) In example 6, the hydrophobic sub-beads are based on silica and fluorosilane (SiF7E). They were deposited according to the protocol comprising the following steps: depositing a solution of hydrolyzed TEOS at 0.3% by weight in isopropanol at pH 2 by spraying (chemical liquid deposition), drying for a time of 5 minutes, depositing a solution of SiF7E in isopropanol at pH 2 by spraying or wiping (chemical liquid deposition), drying for 15 minutes.

(30) In example 7, the hydrophobic sub-beads are based on the product Nanofilm ABW.

(31) The retention performance of each glass-ceramic plate was evaluated by pouring water into the center of the region surrounded by the retaining bead and by measuring the maximum height, h, of the film of retained liquid and the maximum retention time before overflowing beyond the bead.

(32) Under static conditions, the water is deposited slowly, care being taken to minimize the movements of the liquid, and the height of the film of water formed is measured continually until there is overflowing beyond the retaining bead.

(33) Under dynamic conditions, the water is poured with a flow rate representative of the flow rate of a liquid overflowing from a cooking container, and the height of the film of water formed and the time are measured continually until there is overflowing beyond the retaining bead. The measurements were carried out for three flow rate values: 1.8 ml/s (flow rate 1), 2.3 ml/s (flow rate 2) and 2.7 ml/s (flow rate 3).

(34) The maximum values measured are given in table 2.

(35) The examples show that a hysteresis value, H, of greater than or equal to 20° increases the values of the maximum height of the film retained and the retention time before overflowing under dynamic conditions compared to static conditions. The retention times are in particular 2 to 4 times higher, especially when the flow rate is high.

(36) The comparison of examples 5 and 7 on the one hand, and of examples 7 and 8 on the other hand, shows that a high hysteresis value, in particular of greater than 30, allows longer retention times.

(37) The comparison of examples 6 and 7 shows that, for similar advancing angle values, an increase in the hysteresis value allows longer retention times.

(38) TABLE-US-00002 TABLE 2 Example Example Example 5 6 7 Trade name of the hydrophobic compound of the sub-beads Diamon Nanofilm fusion ultra ABW (DFI) (Ferro) Type of compound silica and silicone SiF7E — Static h (mm) 3.4 4.4 4.1 Dynamic Flow rate h (mm) 4.2 4.6 4.6 1 Time (s) 19.9 10.1 17.7 Flow rate h (mm) 4.9 5.3 5 2 Time (s) 13.2 11.2 14.9 Flow rate h (mm) 5 5.8 5.6 3 Time (s) 9.7 9.8 13.7 Contact angles θ 105 114 108 θa 108 120 117 θr 80 87 68 Hysteresis H 20 33 49

(39) Four other comparative examples, examples 8, 9, 10 and 11 were also carried out in order to illustrate the technical effect of the invention. In these examples, a retaining bead comprising two hydrophobic sub-beads is fastened to and in contact with the face of two glass-ceramic plates according to the arrangement illustrated in FIG. 1. For each of the glass-ceramic plates, the width of each of the hydrophobic sub-beads and the width of the hydrophilic zone separating them are reported in table 1. In examples 8, 9, the width of the hydrophilic zone between two consecutive sub-beads is inside the range 500 μm-2.5 cm. In examples 10 and 11, the width of the hydrophilic zone is outside of this range. The hydrophilic zone is formed by the surface of the glass-ceramic plate that has not undergone any treatment. For comparison purposes, the surface area of the hydrophilic zone (303) surrounded by the two sub-beads is identical for all the examples 8, 9, 10 and 11.

(40) The hydrophobic sub-beads are based on fluorinated trichlorosilane. They were deposited by evaporation under reduced pressure (chemical vapor deposition). During the deposition, the regions of the glass-ceramic plate outside of the hydrophobic sub-beads were protected using a mask that is impermeable to the fluorinated compounds.

(41) The retention performance of each glass-ceramic plate was evaluated by pouring water into the center of the hydrophilic zones defined by the consecutive sub-beads of the retaining bead with an average flow rate of 2.4 to 2.5 ml/s. This flow rate is representative of the flow rate of a liquid overflowing from a cooking container.

(42) The volume retained and the maximum retention time before overflowing beyond the hydrophilic zone were measured. The results are reported in table 3.

(43) The comparison of the results of examples 8 and 9 according to the invention with that of example 10 shows that a glass-ceramic plate according to the invention enables a gain of 23% for example 8 and of 40% for example 9 in the volume of liquid retained before overflowing from the hydrophilic zone compared to a plate comprising a retaining bead comprising two consecutive sub-beads defining a hydrophilic zone width of 0.4 cm. Compared to the volume retained in example 9, the gain is 3% for comparative example 11 comprising a retaining bead with two consecutive sub-beads defining a hydrophilic zone width of greater than 2.5 cm. The gain in volume and in time are more particularly elevated when the width of the hydrophilic zone is between 500 μm and 2.5 cm, and more particularly between 0.5 cm and 2.5 cm.

(44) TABLE-US-00003 TABLE 3 Example Example Example Example 11 8 9 10 (comparative) Number of hydrophobic 2 2 2 2 sub-beads Width of the 1 1 1 1 hydrophobic sub-beads (cm) Width of the hydrophilic 1 2 0.4 3 zones (cm) Time before 27.1 30.5 21.7 31.6 overflowing from the hydrophilic zone (s) Volume before 66.4 75.4 53.9 77.3 overflowing from the hydrophilic zone (ml)