Clock with display and illumination device

Abstract

We provide a clock equipped with a display lighting device that makes ITO tracks unnoticeable even under specific lighting conditions. [Solution] A clock comprising a display unit, a glass 6 positioned above the display unit and having a useful area (9) through which the user of the clock can view the display unit, and a lighting device positioned below the glass 6 and comprising at least one electroluminescent unit 14a, wherein at least one electroluminescent unit 14a is electrically powered from peripheral contact zones 30a to 30d superimposed on the edge of the glass 6 via conductor pads 22g to 22j made of a transparent conductor material, the conductor pads 22g to 22j cover the entire useful area except for gaps 26a to 26d separating the conductor plates in at least the useful area, each gap separating two adjacent conductor areas, and these gaps are not perceptible to the user of the clock at a distance of about 30 cm in normal ambient light.

Description

Technical Field

[0001] The present invention generally relates to the field of timepieces having at least an analog or digital display of the current time and a lighting device for this display. More specifically, the present invention relates to an active lighting device, that is, a device comprising at least one light source powered by an electric energy source, in particular using a control device.

Background Art

[0002] In order to make an analog display readable in a dark or black environment (i.e., a space not illuminated by an external light source), several active lighting devices (active lighting devices, in contrast to passive lighting devices, particularly the arrangement of phosphorescent materials on the dial and / or the hands) have already been proposed. In particular, International Publication No. 02 / 23637 describes a timepiece comprising an analog display and a light-emitting diode (also called "LED" from the initials of "Light Emitting Diode") arranged at the center of the lower surface of the watch glass. The LED is electrically powered from the periphery of the glass by two straight tracks made of a transparent conductive material made of indium tin oxide (a mixture of indium oxide and tin oxide, also called ITO). The advantage of such a lighting device is that the light-emitting diode has small dimensions and its presence can be made unobtrusive or hardly perceptible to the user, especially when aligned with the axis of the hands of the analog display. However, the lighting device described in the aforementioned document has two drawbacks. First, the distance between the periphery of the glass and the center of the glass is relatively long. Therefore, the two straight conductor tracks are narrow and have a fairly high resistance, which limits the value of the current that can be supplied to the LED and thus the amount of light that can be emitted at a given voltage. Second, the ITO tracks have good transparency, but are in a state where they can be seen when the glass is slightly darkened. The user can notice the ITO tracks under certain lighting conditions, which is aesthetically undesirable and may even mean that the glass has manufacturing problems. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 02 / 23637 [Overview of the project] [Problems that the invention aims to solve]

[0004] As described above in the technical background, the present invention aims to improve upon two problems faced in the prior art. [Means for solving the problem]

[0005] For this purpose, the present invention relates to a clock comprising a display unit, a glass positioned above the display unit and having a useful area through which the user of the clock can view the display unit, and a lighting device comprising at least one electroluminescent unit positioned below the glass and above the display unit, wherein the electroluminescent unit is formed from at least one light source, in particular an LED or OLED (an acronym for "Organic Light Emitting Diode"). The at least one electroluminescent unit is electrically powered from a peripheral contact zone positioned axially overlapping outside the useful area via a conductive pad made of a transparent conductive material, the conductive pad covers at least the entire lower part of the useful area of ​​the glass, except for gaps separating the two conductive pads in the case of a single electroluminescent unit having only two power contacts, and except for a plurality of gaps separating the conductive pads in the case of an electroluminescent unit having at least three power contacts or a plurality of electroluminescent units. A notable feature is that each gap separates two adjacent conductive pads, and that the gap is so wide that it is barely perceptible or preferably imperceptible to a watch user with normal vision in normal ambient light, and the width of the gap is less than 200 micrometers (200 μm) for each of the multiple gaps.

[0006] In a preferred embodiment relating to an electroluminescent unit or a plurality of electroluminescent units having at least three power contacts, each individual conductive pad, each electrically connected to a single power contact associated with a single light source, is configured to have substantially the same electrical resistance between its respective peripheral contact zone and the respective power contact of the electroluminescent unit or the plurality of electroluminescent units.

[0007] In certain modifications, a common conductor pad for multiple power contacts is configured to have a lower electrical resistance than the individual conductor pads. [Brief explanation of the drawing]

[0008] The present invention will be described in more detail below with reference to the attached drawings, which are provided as non-limiting examples. [Figure 1] This is a schematic cross-sectional view of a clock according to a first embodiment of the present invention. [Figure 2] This is a plan view of a first modification of the first embodiment, showing the portion of the lighting device located beneath the clock glass. [Figure 3A] This is a plan view of a second modification of the first embodiment, showing the portion of the lighting device located beneath the clock glass. [Figure 3B] This is a plan view of a third modification of the first embodiment, showing the portion of the lighting device located beneath the clock glass. [Figure 4] This is a schematic cross-sectional view of a clock according to a second embodiment of the present invention. [Figure 5] This is a plan view of the first modified example of the second embodiment, showing the portion of the lighting device located beneath the clock glass. [Figure 6] This is a plan view of a second modification of the second embodiment, showing the portion of the lighting device located beneath the clock glass. [Modes for carrying out the invention]

[0009] Referring to Figures 1 to 3B, a first embodiment of the clock according to the present invention will be described below.

[0010] Generally, the watch 2 comprises a case 4, a movement 10, an analog display unit 12, a glass 6 positioned above the analog display unit, and a lighting device. The lighting device comprises at least one electroluminescent unit, such as an LED or OLED, positioned below the glass and above the analog display unit. The glass 6 has a useful area 9 superimposed on the inside of the upper opening 9a of the case 4, and the wearer of the watch can view the analog display unit 12 through the useful area 9. In particular, the case 4 is formed by a middle case 4a, a bezel 4b, and a case back 4c. The analog display unit 12 comprises a pair of hands and a dial 11.

[0011] In the first modified example shown in Figure 2, the electroluminescent unit is an LED 14 positioned in a structured layer 16 of conductive material deposited on the lower surface 8 of the glass 6, and this conductive layer 16 covers almost the entire usable area 9 of the glass in the case for the wearer of the watch. In the illustrated modified example, the conductive layer 16 covers almost the entire lower surface 8 of the glass. The conductive layer 16 is structured to form conductive pads for supplying power to the LED 14 or, in other modified examples described below, to an LED or OLED provided. More specifically, the LED 14 is electrically supplied via two power contacts 24 positioned on the LED on the same side as the conductive layer 16, and via two conductive pads 22a and 22b made of transparent conductive material, from two peripheral contact zones 20a and 20b located outside the usable area 9, i.e., along the perimeter 7 of the glass, overlapping axially. These conductive pads cover at least the entire lower part of the usable area 9 of the glass 6, except for a gap 26 separating only the two conductive pads 22a and 22b. These two conductive pads (which can also be called "electrodes") each extend to approximately half of the usable area 9.

[0012] Currently, there are extremely small electroluminescent light sources, miniature light sources that are barely perceptible or imperceptible to the naked eye. These miniature light sources are very small (<500 μm). Two main types, LEDs and OLEDs, are well known; the latter are very small and can be manufactured directly on transparent substrates. LEDs are generally less than 1 millimeter in size and advantageously less than 500 μm on each side, so that they are not easily visible when the LED is turned off. In certain modifications, they can be as small as 150 × 100 μm. 2 A mini LED with the following dimensions was selected, meaning it has sides less than 200 μm, which is practically imperceptible to a user with normal vision at approximately 30 cm. The size is practically 100 × 100 μm. 2 The following mini-LEDs are preferred, and such mini-LEDs are imperceptible to a watch user with normal vision at a distance of approximately 30 cm, in other words, invisible to the naked eye. The mini-LEDs may be blue, green, yellow, or red, but may also be white. To manufacture a white LED, a phosphorescent material can be deposited on a blue LED to convert the blue light into yellow light. The mixture of residual blue light from the LED and the yellow light produced by the phosphorescent material is perceived by the eye as white light.

[0013] Advantageously, the transparent conductive pads 22a and 22b are structured by photolithography of a thin transparent conductive layer 16 made of a transparent conductive oxide, or by printing silver nanostructures. Common examples of transparent conductive oxides include indium tin oxide (ITO) or indium zinc oxide (referred to as IZO from the acronym "Indium Zinc Oxide"). Other techniques and other transparent conductive materials for forming transparent conductive pads can be conceived by those skilled in the art.

[0014] The electrical connection between the power contacts 24 on the LED 14 and the transparent conductor pads 22a and 22b can be made in various ways. For example, isotropic or anisotropic conductive adhesive or eutectic solder can be used. In the case of isotropic conductive adhesive, especially those based on silver particles, two separate very small beads of adhesive each ensure adhesion of the LED to the substrate and electrical conductivity between the surface / contact pad or contact stud called the power contact on the LED and the transparent conductor pads 22a and 22b. In the case of anisotropic conductive adhesive, especially one made of gold microbeads, a single extended adhesive surface beneath the LED 14 ensures only adhesion of the LED to the substrate and electrical conductivity along an axis perpendicular to the underside 8 of the glass 6 between the power contacts 24 on the LED and the transparent conductor pads 22a and 22b. In the figures, the power contacts 24 are schematically drawn as continuous lines so that they are clearly visible and easily recognizable, but it should be noted that they are located beneath the LED substrate and are therefore hidden by this substrate in the various views from below shown in the plan view.

[0015] In eutectic soldering, i.e., soldering low-melting-point alloys, the power contacts 24 on the LED are pre-covered with an alloy layer, specifically made of Au / Sn, and the relative zones on the conductor layer (substrate) are covered with a metal layer, specifically made of gold (Au). During the soldering process, the LED contacts are rubbed and heated on the substrate so that the contact surfaces melt. After cooling, the LEDs are firmly soldered to the substrate, forming good contacts with low electrical resistance. This process results in lower contact resistance and higher bonding strength compared to conductive adhesives, but requires more extensive pre-treatment of the LED contacts and the substrate.

[0016] In FIG. 2, the two peripheral contact zones 20a and 20b extend radially from the two conductor pads 22a and 22b. These are made of the same transparent conductor material as the conductor pads by structuring the conductor layer 16 and are separated from each other by a gap 26. In practice, since the peripheral contact zones are located axially outside the useful area 9 of the glass 6 and outside the opening 9a in the plane of the glass, along the periphery 7 of the glass, there is no difference between the two peripheral contact zones and the two conductor pads, except that the electrical connectors 36 between the power supply circuit 34 and the peripheral contact zones 20a and 20b are not visible to the user of the clock.

[0017] The ITO or IZO conductor pads are transparent, but they are slightly colored to change the reflection of light at the lower surface 8 of the glass 6, especially in the case of a sapphire-made lower surface, compared to the part of this lower surface without such a conductor layer, so it should be noted that the zones with such a conductor layer in the glass 6 can be visually distinguished from the parts without it. Furthermore, there is a slight difference in height at the edge of each conductor pad, and a thin line can be seen by the user of the clock. According to the invention, generally, the width of the gap 26 is such that it is advantageously hardly perceptible or preferably imperceptible to a user of the clock with normal vision in normal ambient light at about 30 cm. One advantage of having a more extensive contact area is that the conductor pads are thinner than in the case of essentially narrow conductor tracks, but maintain better conductivity than such conductor tracks. The thinner conductor layer for the conductor pads means better transparency and also lower visibility of the periphery on the conductor pads.

[0018] The "gap" is understood to mean a small space or slit separating two material zones between two material zones. In order to make the contrast between the conductor pad and the substrate, i.e., the glass 6, as inconspicuous as possible, the gap 26 (or rather, space / slit) between two conductor pads is preferably as narrow as possible while ensuring electrical insulation between these conductor pads. For example, by structuring the ITO layer using photolithography, a very narrow gap of about 10 μm can be formed between two conductor pads.

[0019] Generally, the width of the gap is less than 200 micrometers (200 μm). In an advantageous variant, the width is less than 100 micrometers (100 μm). In a preferred variant, the width is less than 50 micrometers (50 μm).

[0020] The transparent conductor pads 22a, 22b are connected to the power supply circuit 34 by at least one connector. In the variant of FIG. 2, a cylindrical spring-biased connector 36 is shown that enables a single transparent conductor pad to be connected to the power supply circuit. In a first variant, two connectors 36 are provided, one for each of the two transparent conductor pads. In an alternative variant, the electrical connection is made by an anisotropic elastomer conductor (Zebra (registered trademark)) arranged in one of the two peripheral zones through which the gap 26 passes. In order to ensure that the electrical connection means between the power supply circuit 34 and the peripheral contact zones 20a and 20b are not visible to the user of the watch, the connector 36 is arranged behind the flange 38 forming the display space of the watch 2.

[0021] Figures 3A and 3B show a second and third modification. In these two modifications, the electroluminescent unit 14a is formed by three LEDs arranged on the same support, the three LEDs having a common anode or cathode and each having an individual cathode or anode, so that the electroluminescent unit 14a has four power contacts 24. This electroluminescent unit 14a is designed to provide white light by three LEDs (mini-LEDs) that produce red, green, and blue light, respectively. In another modification, two LEDs can be provided, one emitting blue light and the other emitting yellow light. By powering the three LEDs separately, the color of the illumination can be adjusted as needed to obtain a specific white light.

[0022] In Figure 3A, unit 14a is electrically powered via four conductor pads 22c-22f made of transparent conductive material that cover the entire useful area 9 of the glass in the watch, except for four gaps 26b-26d that separate the conductor pads in pairs, i.e., each separating two adjacent conductor pads, from four peripheral contact zones 20c-20f located at the edge of the glass 6. Here again, the width of each gap is such that it is substantially imperceptible, preferably imperceptible, to the user of the watch at a distance of about 30 cm in normal ambient light. The various advantageous width ranges described above also apply to all other modifications. In this second modification, each transparent conductor pad extends substantially over a quarter of the underside of the glass, and this modification is advantageous when only one LED is activated at a time. Thus, there are four identical conductor pads 22c-22f. The peripheral contact zones 20c-20f extending the conductor pads are spaced apart along the periphery of the glass. This imposes certain disadvantages on the electrical connectors to the power circuits, as they must be positioned along the periphery of the glass over angular distances exceeding 180°. Specifically, four cylindrical spring-biased connectors 36 can be provided, spaced apart along the periphery of the glass or in pairs on either side of the gap, or two diametrically opposite anisotropic elastomer conductors can be provided, each covering a gap, i.e., gaps 26a and 26c or gaps 26b and 26d.

[0023] The third modification shown in Figure 3B allows for improvements over the aforementioned shortcomings of the second modification. The peripheral contact zones 30a to 30d on the conductor pads 22g to 22j are arranged side by side on the same local connection sector 29, in this example the connection sector 29 extends over less than 1 / 8 of the perimeter 7 of the glass, and the peripheral contact zones are arranged in a line. In a typical modification, the connection sector extends over less than 1 / 8 of the perimeter 7. To achieve homogeneity of light radiated between the LEDs and maximum overall power, the pattern for structuring the conductor pads 16 is made such that each individual electrode / individual conductor pad, each electrically connected to a single power contact 24 specific to a single LED, has substantially the same electrical resistance between the power contact and its respective peripheral contact zone. In Figure 3B, the individual conductor pads are labeled 22h to 22j. A common conductor pad 22g connected to the power contact 24 on a common electroluminescent unit 14a for the three LEDs is configured such that each has a lower electrical resistance than the individual conductor pads associated with a single LED. In the second modification, as shown in Figure 3A, all conductor pads are similar and have the same electrical resistance. In the second modification, it should be noted that the common conductor pad may have a lower electrical resistance by structuring the conductor layer 16 such that, for example, the common conductor pad extends over a larger angular distance (150° in detail) and the three individual conductor pads extend over the same smaller angular distance (i.e., 70°).

[0024] The light source is positioned to radiate toward the dial 11, but also partially radiates outward, which is unsightly and could dazzle the wearer. In fact, this direct upward radiation is generally stronger than the light reflected by the dial, hindering the readability of the display. One solution is to add an opaque, optionally reflective cover between the outside of the glass and the electroluminescent unit (particularly the LED).

[0025] Several configurations can be considered for using a cover to block the light emitted toward the user by the electroluminescent unit. Advantageously, the cover is made either on the side of the glass bottom surface 8, directly on this bottom surface, or between the transparent conductive layer 16 and the electroluminescent unit / LED. In the latter case, the cover must ensure both the desired optical opacity and electrical conductivity for powering the electroluminescent unit / LED. Two embodiments are possible: The cover is made of structured black resin with openings filled with conductive material that allow electrical contact to be made between the transparent electrodes and the power contacts of the electroluminescent unit. The cover is made from an opaque anisotropic conductive adhesive used to mount and electrically connect the electroluminescent unit, which includes conductive metal beads incorporated into a resin that has been made optically opaque by the addition of a non-conductive absorbing pigment, for example.

[0026] A second embodiment is described below with reference to Figures 4 to 6. Similar elements and reference numerals in the first embodiment that have already been described will not be described again in detail here. Figures 5 and 6 show plan views of a first and second modification of a part of the lighting device according to the second embodiment of the present invention, which is positioned under the glass of a clock.

[0027] This second embodiment differs from the first embodiment in two essential features. Firstly, several electroluminescent units 14b, spaced apart from each other, are positioned beneath the glass 6 within a useful area 9 formed by an opening 9a in the bezel 4b of the case 4. Secondly, the electroluminescent units 14b are placed on a transparent substrate 44 separate from the watch glass, and the transparent substrate 44 is bonded beneath the watch glass with a layer of transparent adhesive 50. Advantageously, OLED technology is used to fabricate the electroluminescent units / light sources 14b, and each of the electroluminescent units / light sources 14b has a micrometer-sized light-emitting surface that is imperceptible to the naked eye at approximately 30 cm. Preferably, when viewed in plan view, each OLED 14b is substantially 100 × 100 μm 2The transparent substrate 44 has the following surface area. The transparent substrate 44 can be made of glass, sapphire, PC, PMMA, or other transparent polymers. It should be noted that in another modification, the light source is located on the side of the analog display unit 12 below the transparent substrate 44.

[0028] Unlike LEDs (possible variations) which are generally manufactured in a preliminary step and then brought in and mounted on the glass 6 or an additional transparent substrate 44, OLEDs are manufactured directly on the underside of the glass 6 8 (possible variations), or on an additional transparent substrate 44 that covers the entire useful area 9 of the glass, as shown in Figure 4. In the case of OLEDs, the light-emitting surface is obtained by structuring the functional layers (anode, organic layer, cathode) that form each OLED. In the first step, transparent conductor pads 22g (common conductor pad) and 22h~22k (individual conductor pads) in the first variation, and transparent conductor pads 22p (common conductor pad) and 22n (individual conductor pads) in the second variation are deposited on the transparent substrate 44, respectively. In the second step, the anode on the OLED 14b is created on the respective contact zones on the individual conductor pads 22h~22k. In the third step, an organic layer is deposited on the anode, and in the fourth step, the cathode is deposited on the organic layer, with a portion of each extending beyond the respective organic layer and covering the contact zone on the common conductor pad 22g. Finally, as in the conventional case, a protective layer made of, for example, glass, covers the OLED.

[0029] According to the present invention, similar to the first embodiment, the electroluminescent unit 14b is electrically powered from peripheral contact zones 30a to 30e in the first modification and peripheral contact zones 30a to 30n in the second modification, respectively, via conductive pads 22g to 22k, conductive pads 22p and 22n made of transparent conductive material on the transparent substrate 44. The peripheral contact zones 30a to 30e and peripheral contact zones 30a and 30n are preferably arranged in a line within the same connection sector 29 located on the periphery of the transparent substrate 44, outside the useful area of ​​the glass 6 in the axial projection, and are located in a limited angular sector. The conductive pads cover at least the entire lower part of the useful area 9 of the glass 6, except for gaps 28 separating these conductive pads. Each gap separates two adjacent conductive pads and has a width such that, in normal ambient light, the gap 28 is not perceptible to the user of the watch observing the display. The advantageous and preferred ranges of value for the gap width described above also apply to the second embodiment.

[0030] Preferably, in order to achieve luminescence homogeneity between light sources (i.e., OLEDs 14b) and maximum overall illumination power, the transparent conductor pads within the conductor layer 16 covering the transparent substrate 44 are structured to achieve substantially equal low electrical resistance between the peripheral contact zone and each power contact of the OLEDs 14b compared to individual conductor pads. This is made possible by the transparent conductor pads extending at least overall over the entire surface area formed by the useful region 9 of the glass 6, except for the gap 28. Furthermore, as already shown, this advantageous characteristic makes it possible to conceal the presence of conductor electrodes extending facing the lower surface 8 of the glass, at least within the useful region 9 in the axial projection, if the gap is very narrow and almost imperceptible to the naked eye, preferably completely imperceptible. This makes the illumination device according to the present invention very inconspicuous. It should be understood that the expression "useful region of the glass" refers to a cylindrical space having an axial direction and an outer circumference formed by the opening 9a of the bezel 4b of the case 4.

[0031] The common conductor pads 22g and 22p connected to each of the multiple power contacts on the OLED are configured to have lower electrical resistance than the individual conductor pads 22h, 22k, and 22n, respectively, between these power contacts and the surrounding contact zone 30a. This is because the current flowing through these common conductor pads is greater in order to collect multiple currents from the individual conductor pads.

[0032] The cathode is preferably made of an opaque material that prevents the OLED from emitting light axially through the glass 6. Advantageously, the cathode is reflective. It is important that each cathode covers a very small area of ​​the common conductive pad beyond the organic layer and is not visible. To minimize the size of the cathode, the contact zone on the common conductive pad 22g is positioned as close as possible to the light-emitting zone on the OLED around the light-generating organic layer. As in the first embodiment, an opaque and optionally reflective cover may be provided above each OLED, these covers being deposited, for example, on the underside 8 of the glass facing the OLED. When assembling the glass 6 with the transparent substrate 44 using adhesive 50, care must be taken to align the cover approximately point-aligned with the OLED, and in alternative versions using LEDs instead of OLEDs, approximately point-aligned with the LEDs.

[0033] Preferably, the electrical connection between the peripheral contact zones, which are arranged in a straight line, and the power supply circuit 34 is made using a flexible circuit board 48.

[0034] In the first modification (Figure 5), the lighting device comprises four light sources 14b (each an electroluminescent unit formed by a single OLED or LED) arranged at regular intervals in the angular direction, with two adjacent light sources having an angular distance between them equal to 90°. A common conductor pad 22g occupies the central zone on the transparent substrate 44 and the connector zone from this central zone to the peripheral contact zone 30a, while the individual conductor pads extend around the central zone. In the second modification (Figure 6), the lighting device comprises twelve light sources 14b, each light source positioned above the different digits 1 through 12 indicating the time on the dial. A common conductor pad 22p occupies the peripheral zone and substantially the inner diameter zone on the transparent substrate 44, while the individual conductor pads 22n spread out in a fan shape from the contact zone 30n. In this second modification, which has a relatively large number of distinct light sources 14b, the transparent substrate 44 comprises an outer projection 45 where the connection sector 29 is located.

[0035] The illumination device according to the present invention can also be used as a "front light" system in the case of a watch equipped with a purely reflective digital display (also called an "electronic display"), thus enabling the reading of information when there is insufficient light on such a digital display. This type of digital / electronic display in a watch, particularly an energy-efficient LCD display, provides better contrast and readability in daylight than a similar digital display with a backlight system. This is because, in the latter case, the digital display must be semi-transparent to allow the backlight to reach the observer, and therefore has inferior optical quality in daylight. The present invention is particularly suitable for structures forming various display zones, especially digital displays covered with decorative structures, and an illumination device comprising multiple LEDs or OLEDs is positioned in front of these display zones to illuminate these zones locally, simultaneously, or selectively.

Claims

1. A clock (2, 42) comprising a display unit (12), a glass (6) positioned above the display unit and having a useful area (9) through which the user of the clock can view the display unit, and a lighting device comprising at least one electroluminescent unit (14, 14a, 14b) positioned below the glass and above the display unit, wherein the electroluminescent unit is formed by at least one light source, in particular an LED or OLED, and the at least one electroluminescent unit is positioned axially overlapping outside the useful area via conductive pads (22a, 22b, 22c-22f, 22g-22j, 22g-22k, 22p, 22n) made of a transparent conductive material, and peripheral contact zones (20a, 20b, 20c-20f, 30 A clock characterized in that it is electrically powered from a-30d, 30a-30e, 30a, 30n), and the conductor pads cover at least the entire lower part of the useful area of ​​the glass, except for a gap (26) separating two conductor pads (22a, 22b) in the case of a single electroluminescent unit (14) having only two power contacts, and except for a plurality of gaps (26a-26d, 28) separating the conductor pads in the case of an electroluminescent unit (14a) having at least three power contacts or a plurality of electroluminescent units (14b), and each gap (26, 26a-26d, 28) separates two adjacent conductor pads and has a width of less than 200 micrometers (200 μm) or substantially equal to 200 micrometers (200 μm).

2. The clock according to claim 1, characterized in that the width is less than 100 micrometers (100 μm).

3. The clock according to claim 1, characterized in that the width is less than 50 micrometers (50 μm).

4. The clock according to any one of claims 1 to 3, characterized in that, in the case of a single electroluminescent device (14) having only the two power contacts, the two conductor pads (22a, 22b) each extend to approximately half of the useful area (9) of the glass.

5. The clock according to any one of claims 1 to 3, characterized in that, in the case of an electroluminescent unit (14a) or a plurality of electroluminescent units (14b) having at least three power contacts, each individual conductor pad (22d to 22f, 22h to 22j, 22h to 22k) of the conductor pads is configured to have substantially the same electrical resistance between its respective peripheral contact zone (20d to 20f, 30b to 30d, 30b to 30e, 30n) and each power contact of the electroluminescent unit or the plurality of electroluminescent units, and each individual conductor pad is electrically connected to a single power contact associated with a single light source.

6. The clock according to claim 5, characterized in that a common conductor pad (22c, 22g, 22p) is configured to have a lower electrical resistance than the individual conductor pads, and the common conductor pad is connected to a plurality of power contacts and / or associated with a plurality of light sources (14b) connected to the same power contacts.

7. The clock according to claim 5, characterized in that the peripheral contact zones are arranged at intervals along the periphery of the glass.

8. The clock according to claim 5, characterized in that the peripheral contact zone is arranged in a single connection sector (29) that extends over less than one-quarter of the perimeter (7), preferably less than one-eighth of the perimeter, and the peripheral contact zone is arranged in a row.

9. The clock according to any one of claims 1 to 3, characterized in that the conductor pad is formed by a structured conductor layer (16) deposited on the lower surface (8) of the glass (6), and the at least one electroluminescent unit (14, 14a) is attached to the conductor pad.

10. The clock according to any one of claims 1 to 3, characterized in that the conductor pad is formed by a structured conductor layer (16) deposited on the upper surface of a transparent substrate (44), the at least one electroluminescent unit (14b) is attached to the conductor pad, and the transparent substrate is bonded to the lower surface (8) of the glass (6) and covers the at least one electroluminescent unit.

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