GB2280049A

GB2280049A - Display dial

Info

Publication number: GB2280049A
Application number: GB9413934A
Authority: GB
Inventors: Kazuhiro Iwama; Yukio Tajima
Original assignee: Seikosha KK
Current assignee: Seikosha KK
Priority date: 1993-07-13
Filing date: 1994-07-11
Publication date: 1995-01-18
Anticipated expiration: 2014-07-11
Also published as: GB9413934D0; CN1047005C; HK1004015A1; JP2824732B2; CN1103491A; JPH0777585A; GB2280049B

Abstract

The display, for example a timepiece, can be viewed in the dark by using a photophorescent ink. The phosphorescent ink 11 is coated on the rear surface of a transparent plate 10 and indices 12 such as figures, symbols or gradations are formed on the transparent plate 10 with a shading ink having a color different from that of the phosphorescent ink. In a bright environment, the phosphorescent ink 11 receives and stores light therein so that the dark-colored indices 12 shows up on the white surface of the plate from the front side and the user can read time through the indices 12 indicated by the hands. Further, in a dark environment, the phosphorescent ink 11 emits light due to the energy stored therein whereby the indices 12 shows up on the bright surface of the plate as they throw their shades on the plate surface. <IMAGE>

Description

DISPLAY DIAL The present invention relates to a display dial, for example for a timepiece, coated with a phosphorescent ink and which enables the display by the display device to be easily viewed at night or in the dark.

Previously a so called internal illumination type display dial incorporating a display dial surface illuminating lamp in its casing to enable a display to be identified in the dark has been provided.

Alternatively, a display dial has been provided which has indices such as figures, symbols or gradations, including, for example, in the case of a timepiece, time-indicating gradations or figures formed on the front surface thereof and coated with a selfilluminating fluorescent or phosphorescent ink, which emits light in the dark due to the energy stored while the dial plate is in the light Where the fluorescent or phosphorescent ink is used, it has been usual that each of the indices is formed as an aperture letter.

As shown in Figures 21 and 22, an index (b) in the form of an aperture letter is made up of a fluorescent ink portion or phosphorescent ink portion (bl) and an ink portion (b2) surrounding the former portion on the front surface of an opaque plate (a) made of a metal.

The index (b) can be identified by both the portions (bl) and (b2) in the light, and in the dark it can be identified by the fluorescent or phosphorescent ink applied to the aperture portion (bl).

However, the internal illumination type display has the disadvantages that its structure is complicated and requires a great number of parts, resulting in an increase in the cost. Further, the display using a self luminous ink has also had the problem that the amount of ink used is subject to legal restrictions, i.e., laws relating to the prevention of radiation sickness due to a radioisotope, so that an overall coating of the ink is not possible and a sufficient degree of brightness for the identification of the display cannot be obtained.

Further, when indices are formed on the front surface of the plate by using a fluorescent or phosphorescent ink, the coating of the ink becomes thick so that the front surface of the plate becomes irregular and the surface is not flat. Therefore, where the indicating needle is moved on the front surface of the plate so as to indicate each of the indices, there has been a danger that the indicating needle touches the index forming a projection thereby stopping the needle. This problem is especially acute in thin timepieces or watches, where the clearance between the surface of the dial plate and the front cover is too small for each of the hands to rotate.

Further, a display dial using a fluorescent or phosphorescent ink has always provided a negative display i.e. a bright display on a dark background.

The present invention therefore seeks to provide a display dial coated with a phosphorescent ink which allows the user to identify the display with ease even in the dark.

The present invention also seeks to provide a display dial coated with a phosphorescent ink which allows the user to identify the display even in the dark and which has a smooth display surface thereby reducing the thickness of the display.

According to the present invention, there is provided a display dial comprising a transparent plate whose rear surface is at least partially coated with a phosphorescent ink and having at least one index mark visible when viewed from the front of the display dial, and defined by shading ink applied to the transparent plate in contrast with the phosphorescent ink.

Therefore, by applying the phosphorescent ink to the rear surface of the transparent plate, the thickness of the coating of the ink can be accommodated on the rear surface of the plate so that the front surface of the plate is flat. Therefore, when the plate is used as a display dial, even when each of the hands touches the front surface of the plate, the movement of the hand is not hindered.

In this context, the "rear surface" of the transparent plate is the side of the transparent plate opposite the side from which the display is viewed.

For a better understanding of the present invention, and to show how it may be brought into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 shows a front view of a timepiece using a dial plate according to a first embodiment of the present invention.

Figure 2 shows a front view of the dial plate shown in Figure 1.

Figure 3 shows a partially enlarged sectional view taken along the line A-A in Figure 2.

Figure 4 shows a partially enlarged sectional view of a dial plate according to a second embodiment of the present invention.

Figure 5 shows a partially enlarged front view of a dial plate according to a third embodiment of the present invention.

Figure 6 shows a partially enlarged sectional view of a dial plate according to a fourth embodiment of the present invention.

Figure 7 shows a partially enlarged sectional view of a dial plate according to a fifth embodiment of the present invention.

Figure 8 shows a partially enlarged sectional view of a dial plate according to a sixth embodiment of the present invention.

Figure 9 shows a partially enlarged sectional view of a dial plate according to a seventh embodiment of the present invention.

Figure 10 shows a front view of a time piece using a dial plate according to an eighth embodiment of the present invention.

Figure 11 shows a front view of the dial plate shown in Figure 10.

Figure 12 shows an enlarged sectional view taken along the line B-B in Figure 11.

Figure 13 shows a partially enlarged sectional view of a dial plate according to a ninth embodiment of the present invention.

Figure 14 shows a front view of a timepiece using a dial plate according to a tenth embodiment of the present invention.

Figure 15 shows a front view of the dial plate shown in Figure 14.

Figure 16 shows an enlarged sectional view taken along the line C-C in Figure 15.

Figure 17 shows a partially enlarged sectional view of a dial plate according to an eleventh embodiment of the present invention.

Figure 18 shows a front view of a dial plate according to a twelfth embodiment of the present invention.

Figure 19 shows a partially enlarged sectional view of a dial plate according to a thirteenth embodiment of the present invention.

Figure 20 shows a partially enlarged sectional view of a dial plate according to a fourteenth embodiment of the present invention.

Figure 21 shows a partially enlarged sectional view of a prior art example of a dial plate.

Figure 22 shows a sectional view of an essential portion of the dial plate of Figure 21.

Embodiments of the present invention will now be described by referring to the accompanying drawings.

Figures 1 through to 3 shows a display dial coated with a phosphorescent ink according to a first embodiment of the present invention. This embodiment is essentially useful when the display dial is used as a dial plate for a timepiece. That is, the dial plate 1, as an example of the display dial coated with the phosphorescent ink, is arranged on a time display section formed on the front surface of a casing 15 of the timepiece. On the upper portion of the casing 15 there is provided a vertically movable snooze button 16. An hour hand 17, a minute hand 18 and an alarm hand 19 are provided so as to rotate freely around the dial plate by means of a movement within the casing 15.

The structure of the dial plate 1 will now be described.

The dial plate 1 comprises a trar'parent plate 10, for example made of Mayler, acryl, polyester, vinyl chloride, with its rear surface entirely coated with a phosphorescent ink 11 (Figure 3).

The phosphorescent ink 11 consists of a zinc sulfi::e/coeeer mix (ZnS : Cu, zilch produces a ligt green luminescence) which is mixed with a molding natural material in a ratio of 0.5 - 5% with respect to the latter. A sufficiently long persistence characteristic or luminous characteristic can be obtained depending on the mixing ratio of the phosphorescent ink and mixing ratio of the phosphorescent ink and the molding material in the manufacturing met H . Further, it is possible to cause the ink to anit light and blue light, too.On the surface of the plate 10 there are formed indices 12 such as figures, symbols or gradations depicted with a dark (e.g. black) shading ink different in color from the phosphorescent ink 11 and forming a high contrast theeeto an the front surface of the plate 10 preferably in a symmetrical or complementary hue or a hue close thereto, by silk screen printing. Consequently, although the indices 12 coated with the shading ink are formed on the front surface of the plate 10, since the indices 12 are small in thickness and almost flat, the rotation of each of the hands is not hindered.

Accordingly, in a bright environment like daytime, since the phosphorescent ink 11 presents a faint light green color close to white, the dark colored indices 12 show up on the front surface of the dial plate so that the indices 12 are identified by the viewer as a positive display.

Further, in a dark envirwtnt like night time, the phosphorescent ink 11 emits light due to the energy stored when it was in the bright envi=rlnt ,so that the indices 12 iKW up on the front surface of the bright dial plate as they throw their shadows on the plate and are identified by the viewer also as a positive display.

Moreover, the dial plate shines brightly, the hour hand 17, minute hand 18 and alarm hand 19 are illuminated brightly to enable the position of each hand to be identified even in a dark envinxwent.

Fig. 4 shows a dial plate 2 according to a second embodiment of the present invention. As shown, like the first embodiment, an index 22 such as a figure formed on the rear surface of the plate 20 with a shading ink 21 of a color (e.g. black) different from that of a phosphorescent ink 21.

Further, the phosphorescent ink 21 capable of emitting the green light as in the first embodiment is coated on the entire rear surface of the dial plate so as to cover the index 22. Consequently, the surface of the plate 20 is quite flat and the rotation of each hand is not hindered.

The display operation of this display dial is the same as that of the first embodiment.

Fig. 5 shows a dial plate 3 according to a third embodiment of the present invention wherein the indices 12 and 22 shown in Figs. 3 and 4 are each provided in the form of a syn,bol 32 having an aperture portion.

The symbol 32 is formed on the upper surface of the transparent plate 30 but it may be formed on the rear surface of the plate 30. As the rear surface of the plate 30 is coated with a phosphorescent ink 31 as described above, the central portion of the symbol 32 is occupied by a phosphorescent ink 31.

Therefore, in a bright enVirOt like daytime, the index made up of the aperture symbol 32 with the shading ink and the phosphorescent ink of a faint light green color close to white are identified by the viewer as a positive display.

In a dark erdronlst like night time , the phosphorescent ink 31 emits light due to the energy stored when it was in a bright environment whereby the aperture symbol 32 shews up on the front surface of the dial plate in the form of its shadow so that the symbol 32 is identified as a positive display.

Fig. 6 shows a dial plate 4 according to a fourth embodiment of the present invention. As shown, an aperture syrttl 42 as an index is formed on the front surface of a transparent plate 40 by means of silk screen printing using an ink different in color from a phosphorescent ink 41 to be applied. In this case, the ink is not always required to be light-shielding. At the rear surface of the plate 40 there lies a dark frame (not shown) and the color of this frame is made use of as the color of the dial plate 4.As this dial plate 4 becomes itself a dark background, the aperture sy*ol 42 is formed with an ink of a color (e.g. white) close to the color of the phosphorescent ink 41 and the rear surface of the dial plate 40 is coated with the ink 41 only at a portion corresponding to the aperture portion of the 5pio1. On the upper surface of the plate 40 there is formed an aperture symbol 42 but since the symbol 42 is thin and almost flat, the rotation of each hand is not hindered.

In a bright envirament like the daytime, as the phosphorescent ink 41 presents a light green color close to white, the bright color aperture symbol 42 shows up on the dark-colored front surface of the dial plate as an index so that the index is identified by the viewer as a negative display.

In a dark envircrMT'nt such as the nighttime, phosphorescent ink 41 emits light by the energy stored when it was in a bright environient so that the phosphorescent ink 41 ixws up on the dark dial plate from the front as an index and the index is identified by the viewer as a negative display as in the case when it is in the daytime.

In Jthis embodiment, the casing behind the plate 40 is described as having a dark color, it may have a bright color. In that case, however, the dial plate 4 presents a bright background,the aperture qytol 42 is coated with a shading ink of a color (e.g. black) different from that of the phosphorescent ink 41.

In this case, in a bright environment such as the daytime, since the phosphorescent ink 41 presents a light green color close to white, the bright color aperture symbol 42 shows up on the front surface of the dark plate as an index and the index is identified by the viewer as a positive display.

In the above case, in a bright em,irnn' such as the daytime, since the phosphorescent ink 41 presents a light green color close to white, the bright-colored aperture syritol 42 shows up on the dial plate from the front as an index so that the index is identified by the viewer as a positive display.

On the other hand, in a dark errvirorment such as the night time, the phosphorescent ink 41 emits light by the energy stored in the daytime so that the phosphorescent ink 41 shins up on the dark-colored dial plate from the front and the ink 41 is identified by the viewer as a negative display contrary to the situation in the daytime.

Fig. 7 shows a dial plate 5 according to a fifth embodiment of the present invention. The dial plate 5 comprises a transparent plate 50 which is provided with an aperture syiol 52 on the rear surface thereof. The aperture syntol 52 is formed such that,like the fourth embodiment, where the color of the casing at the back of the plate 50 is dark in color, the aperture symbol 52 is depicted with an ink of a color (e.g. white) close to the color of the phosphorescent ink while where the color of the casing is bright, the aperture syrbol 52 is depicted with an ink (e.g.

black) different from the color of the phosphorescent ink.

Further, the phosphorescent ink 51 is coated only to the portion of the rear surface of the plate 50 corresponding to the aperture portion. Therefore, the front surface of the plate 50 is quite flat so that the movement of each hand is not hindered and the display by this display dial is the same as that of the fourth embodiment.

Fig. 8 shows a dial plate 6 according to a 6th embodiment of the present invention. The dial plate 6 comprises a transparent plate 60 which is provided on the front surface thereof with an aperture tyrol 62 depicted with a dark colored (e.g. black) shading ink with the area outside the ybol (numeric figure or letter ) is coated with a bright-colored ink 60a different from the phosphorescent ink 61. The rear surface of the transparent plate 60 is coated with the phosphorescent ink 61. Therefore, the front surface of the plate 60 is quite flat and the rotation of each of the hands is not hindered.

In a bright environeent such as the daytime, since the phosphorescent ink 61 presents a light green color close to white, the dark-colored aperture syiol 62 different in color from the aperture ink 61 shows up on the surface of the dial plate from the front as an index so that the phosphorescent ink 61 is identified as a negative display.

Fig. 9 shows a dial plate 7 according to a seventh embodiment of the present invention. The dial plate comprises a transparent plate 70 whose rear surface is provided with an aperture-sptel 72 depicted with a dark-colored ink different in color from the phosphorescent ink 71 and the area outside the aperture syol 72 (numeric figure or letter ) is coated with a bright-colored ink 70a. Consequently, the front surface of the plate 70 is quite flat and the rotation of each of the hands is not hindered. The display operation of this display panel is the same as that of the sixth embodiment.

Figs. 10 through 12 show a dial plate 8 according to an eighth embodiment of the present invention. The dial plate 8 comprises a transparent plate 80 whose rear surface is coated with a dark-colored ink 81 different in color from a phosphorescent ink used leaving, as an aperture portion 81a, the portion to become an index such as a figure. The rear surface of the plate 80 is coated with the phosphorescent ink 82 in corresponding to the aperture portion 81a. Of an hour hand 87, a minute hand 88 and an alarm hand 89 rotatable over the dial plate 8, the hour and minute hands 87 and 88 have their top end surfaces coated with a phosphorescent ink thereby forming luminous portions 87a and 88a, respectively.

The timepiece case and snooze button are substantially the same as those of Fig. 1 so that they are designated by the same reference numerals.

In a bright emEhcnllt such as the daytime, since the phosphorescent ink 82 presents a light green color close to white, the phosphorescent ink 82 shows up on the dark-colored dial plate 8 from the front as a bright- colored index so that the index is identified by the viewer as a negative display.

In a dark rdwonEnt such as the night time, the phosphorescent ink 82 emits light by the energy stored when it was in a bright emtrnal5t, so that the phosphorescent ink 82 shows up on the dark-colored dial plate as an index and the ink 82 is identified by the viewer as a negative display.

In this case, since the dial plate is dark-colored, the time is identified from the positions of the luminous portions 87a and 88a of the hour and minute hands, respectively.

In this embodinent, the area outside the aperture portion 81a of figure or letter on the rear surface of the plate 80 is painted with the dark-colored ink 81 different in color fran the phaSSxresxnt ink. Alternatively, it may be painted with a bright-colored ink different in color from the phosphorescent ink and in that case, the dial plate 8 becomes a bright ground.

In a bright environeent such as the daytime, the phosphorescent ink 82 presents a light green color close to white, the ink 82 shows up on the bright colored dial plate 8 from the front as an index so that the index is identified by the viewer as a positive display.

On the other hand, in a dark enV rnalft such as the nighttime, the phosphorescent ink 82 emits light stored when it was in a bright envlnxrrnt , so that the phosphorescent ink 82 shows up on the dark-colored dial plate from the front and the phosphorescent ink 82 is identified by the viewer as a negative display.

Fig. 13 shows a ninth embodiment of the present invention. A dial plate 9 comprises a transparent plate 90 whose front surface is coated with an ink 91 different in color from a phosphorescent ink used, leaving an aperture portion 91a for forming an index such as a figure. The portion of the rear surface of the plate 90 corresponding to the aperture portion 91a is coated with the phosphorescent ink 92. The coating of the ink 91 different in color from the phosphorescent ink is thin and almost flat, so that rotation of each of the hands is not hindered. The display operation of the display dial is the same as in the case of the eighth embodiment.

Figs. 14 through 16 show a tenth embodiment of the present invention. A dial plate 1F comprises a transparent plate 10F whose front surface is provided with indices 12F such as figures or gradations formed by silk screen printing using a dark shading ink different in color from a phosphorescent ink. Further, the rear surface of the plate 10F has phosphorescent ink coatings llF corresponding to the indices 12F, respectively. In the instant embodiment, the phosphorescent ink coatings llF are not entirely but partially formed to provide a circular ring. Consequently, although the indices 12F are formed on the front surface of the plate 10F using the shading ink but since the indices are thin and almost flat, the rotation of each of the hands is not hindered.Of an hour hand 17F, a minute hand 18F and an alarm hand 19F, the hour and minute hands 17F and 18F have the top ends thereof coated with the phosphorescent ink by printing thereby forming luminous portions 17Fa and 18Fa, respectively. The timepiece case and snooze button are substantially the same as in Fig. 1 so that they are designated by the same reference numerals.

In a bright enviDxTent such as the daytime, the phosphorescent ink llF presents a light green color close to white so that each of the dark-colored indices 12F shows up on the surface of the dial plate from the front and it is identified by the viewer as a positive display.

On the other hand, in a dark env. such as the night time, the phosphorescent ink llF emits light by the energy stored therein when it is in a bright envinonent so that the indices 12F show up on the brightly shining ringlike portion on the dial plate throwing their shadows on the plate and the indices 12F are also identified by the viewer as a positive display. Further, since the ringlike portion is luminous, the hour hand 17F, minute hand 18F and alarm hand 19F are illuminated brightly thereby allowing the positions of the hands to be identified.

Fig. 17 shows a dial plate 1G according to an eleventh embodiment of the present invention. The dial plate 1G comprises a transparent plate 10G whose rear surface is provided with indices 12G such as figures depicted with a dark-colored shading ink as in the case of the tenth embodiment. Further, the rear surface of the plate 10G has phosphorescent ink coatings llG in a ringlike form covering the indices 12G as in the case of the tenth embodiment.

Consequently, the surface of the plate 10G is quite flat and so the rotation of the hands is not hindered. The display of the display dial is the same as in the case of the tenth embodiment.

Although the phosphorescent inks llF and llG according to the tenth and eleventh eildin=ts are of a ring-like form, the present invention is not always limited thereto and it goes without saying that these ink coatings may be applied in any shape such as circular or square only if they lie in correspondence to the indices 12F and 12G, respectively.

In the tenth and eleventh embodiments, nothing is coated inside and outside of each of the annular portions of the plates lOF and lOG so that the color of the casing 15 shows up On the contrary, when the color of the abovedescribed areas are desired to be differentiated from that of the casing, a shading ink different in color from the casing may be applied on the front and rear surfaces of the plates lOF and lOG at positions inside and outside the annular portions, respectively. In this case, the indices coated with a shading ink are identified by the viewer as a positive display even in a bright envinol7nt such as the daytime or in a dark atmosphere such as the nighttime.

Fig. 18 shows a dial plate 1H according to a twelfth embodiment of the present invention. The dial plate 1H comprises a transparent plate 10H which is provided wth indices 12H such as figures formed by using a dark shading ink as in the case of the tenth embodiment. The position at which the indices 12H are formed is described to be on the front surface of the transparent plate 10H but it may be on the rear surface thereof. Further, a phosphorescent ink llH same as that in the tenth embodiment is applied to the rear surface of the plate 10H such that a plurality of circular phosphorescent ink coatings 11H are formed in correspondence to the indices 12H, respectively.

In a bright envinrnwt such as the daytime, the phosphorescent ink 11 presents a light green color close to white so that the dark-colored indices 12H show up on the surface of the dial plate and are identified by the viewer as a positive display.

Further, in a dark envircnrent such as the night time, the phosphorescent ink emits light due to the energy stored therein when it is in a bright envircient so that the indices 12 show up on the surface of the dial plate throwing their shades on that surface and the indices 12H are identified by the viewer as a positive display.

In the twelfth embodiment, since the portion outside the circular phosphorescent ink coatings 11H separated from one another in correspondence to the indices 12G on the plate 10H is not coated with any ink, the color of the casing 15 comes up as it is and in this case, the indices formed with the shading ink are identified by the viewer as a positive display even in a bright envicnFrt such as the daytime or in a dark environment such as the night time.

Fig. 19 shows a dial plate 1I according to a thirteenth embodiment of the present invention wherein the index 12F of Fig. 16 or the index 12G of Fig. 17 is represented in the form of an aperture symbol 32I. Although the aperture symbol 32I is formed on the front surface of a transparent plate 301 it may be formed on the rear surface thereof. As already described, since an annular phophorescent ink coating 31I is provided on the rear surface of the plate 30 I at the position corresponding to the aperture symbol 32I, the central portion of the aperture symbol 32I is occupied by the phosphorescent ink coating 31I.

In a bright environment such as the daytime, the index made up of the aperture Symbol 32 1 depicted with a shading ink and the phosphorescent ink 311 which is light-green close to white is identified by the viewer as a positive display. In a dark -envinlTrrt such as the night tiie, the phosphorescent ink coating 31I emits light by the energy stored therein when it is in a brightenviroanent so that the aperture letter 32I comes up to the bright annular surface throwing its shadow thereon and the aperture syiol 32 1 is also identified by the viewer as a positive display.

In the thirteenth embodiment, since the inside and outside of the annular phosphorescent ink coating 31I corresponding to each of the aperture symbols 32I formed on the plate 301 are not coated with any ink, the color of the casing 15 shows up as it is. On the other hand, where the above-mentioned inside and outside portions are desired to have a different color from the casing, the front and rear surfaces of the plate 30I may be coated with a shading ink having a color different from that of tho casing.In that case, the indices with the shading ink are identified by the viewer as a positive display both in a bright ewzonlYt such as the daytime and in a dark erwiwiiint such as the night- tine.

Fig. 20 shows a dial plate 1J according to a fourteenth embodiment of the present invention wherein the index 12H shown in Fig. 18 is represented by an aperture letter 32J depicted with a dark-colored shading ink as in the case of the tenth embodiment. Although the aperture symbol 32 J is formed on the front surface of a transparent plate 30J, it may be formed on the rear surface thereof. As already described, since the rear surface of the plate 30J has a plurality of circular phosphorescent coatings 31J separated from one another so as to correspond to aperture symbols 32J, respectively, the central portion of each of the aperture letters 32 is occupied by each of the phosphorescent ink coatings 31J. The display operation of this display dial is the same as the embodiment 13.

In the fourteenth embodiment, since the outside of the ringlike phosphorescent ink coating 31J corresponding to each of the aperture letters 32J formed on the plate 30J is not coated with any ink, the color of the casing 15 shows up as it is. On the contrary, where the above-mentioned outside portion is desired to have a different color from the casing, the front or rear surface of the plate 30J at the outside of each phosphorescent ink coating 31J may be coated with a shading ink having a color different from that of the casing.

In that case, the indices depicted with the shading ink are identified by the viewer as a positive display both in a bright envirormylt such as the daytime and in a dark environrrrent such as the night-time, Thus, the display dial with a phosphorescent ink according to the present invention comprises a transparent plate whose rear surface is provided with a thick phosphorescent ink coating, the front surface of the transparent plate is free from irregularities so that the identification of display can be made quite easily even in a dark envinonrnt. Further, since the front surface of the transparent plate is flat, the movement of each display hand is not hindered so that the clearance between the front surface and each hand can be reduced resulting in the size-reduction of the apparatus. Further, by the provision of a phosphorescent ink coating over the entire rear surface of the transparent plate, the identification of display can be made without the necessity of forming a luminous portion on each of the display hands thereby contributing more effectively to the thickness-reduction of the apparatus.

Further, the use of a phosphorescent ink enables a positive display to be made even in the dark.

Claims

1. A display dial comprising a transparent plate whose rear surface is at least partially coated with a phosphorescent ink and having at least one index mark visible when viewed from the front of the display dial and defined by shading ink applied to the transparent plate in contrast with the phosphorescent ink.

2. A display dial as claimed in claim 1 wherein the shading ink is applied to the front surface of the transparent plate.

3. A display dial as claimed in claim 1 herein the shading ink is applied to the rear surface of the transparent plate.

4. A display dial as claimed in any preceding claim wherein for the or each index mark, shading ink defines an aperture through which the phosphorescent ink is visible, to form that index mark.

5. A display dial as claimed in one of claims 14 wherein the or each index mark corresponds to an individual and separate phosphorescent ink marking.

6. A display dial as claimed in one of claims 14 wherein the phosphorescent ink is applied to substantially the whole rear surface of the transparent plate.

7. A display dial as claimed in one of claims 14 wherein the phosphorescent ink is applied in an annular ring to the rear surface of the transparent plate.

8. A display dial as claimed in any preceding claim wherein the transparent plate has a further contrasting ink applied to it where the index mark has not been applied.

9. A display dial substantially as shown in one of Figures 1-3, 4, 5, 6, 7, 8, 9, 10-12, 13, 14-16, 17, 18, 19 or 20 of the accompanying drawings.

10. A display dial coated with a phosphorescent ink, comprising a transparent plate whose front or rear surface is coated with an ink different in color from said phosphorescent ink leaving, as an aperture portion, a portion where an index such as a figure or symbol is formed, the rear surface of said plate being coated with said phosphorescent ink at a portion corresponding to said aperture portion.

11. A display dial as claimed in any preceding claim wherein the transparent plate is made of an acrylic polymer, a polyester, e.g. Mylar, or polyvinylchloride.

12. A timepiece including a display dial as claimed in any preceding claim.

13. A timepiece as claimed in claim 10 wherein the minute and the hour hand carry phosphorescent marks.