Diamond bearing microscopic certificate of appraisal

A diamond with an inscription comprises a diamond gem structure having an outer surface cut and polished into a specific shape and a microscopic inscription formed at a specific position on the outer surface of the diamond gem structure. The inscription has a pattern indicating the results of expert appraisal of the diamond gem structure. The inscription may be formed by a method including cleaning a selected portion of the stone surface, depositing a layer of metal thereon, coating the metal with a photoresist film, producing thereon a photo impression by using a mask, developing the impression, etching away the uncoated metal portions and then removing the photoresist.

BACKGROUND OF THE INVENTION 
The present invention relates generally to diamonds with inscriptions and 
more particularly to diamond gems bearing inscriptions certifying and 
guaranteeing particulars such as the gem quality and the number of carats 
of the diamond gem structure. This invention concerns gems of diamonds, 
that is, diamonds of value which have been cut and polished, but for the 
sake of brevity these gems will hereinafter be referred to simply as 
"diamonds". 
In general, it has been customary in the lapidary trade to provide 
diamonds, for ornamental use and the like for commercial transactions upon 
completion of cutting and polishing, with certificates of appraisal or 
written expert opinions on which are recorded particulars such as the 
numbers of carats, color grades, and presence or absence of defects 
(flaws) of the diamonds in order to certify and guarantee the gem quality 
thereof. 
However, since a certificate of appraisal of this kind and the diamond 
described and certified thereby are separate objects, there is the risk of 
loss of the certificate, which therefore requires care in the custody 
thereof. If the certificate should be lost or destroyed, a troublesome 
appraisal would again become necessary, and a certificate of appraisal 
must be made anew. 
Furthermore, there are instances of forgery of, appraisal certificates. For 
this reason, great care must be exercised during a transaction in judging 
whether or not each certificate is correct and genuine. Because these 
appraisal certificates are thus separate from their respective diamonds, 
it cannot be said that they are completely reliable. For this reason, it 
is a fact of reality in the present state of the trade that an appraisal 
certificate is verified by again carrying out the above mentioned 
troublesome appraisal particularly during a transaction for a high-priced 
diamond. 
Furthermore, while properties such as color grade and flaws of a diamond 
can be readily appraised even when it is in a mounted state on an object 
such as a ring, the weight in carats of the diamond cannot be determined. 
For this reason, in a case where a party insists on a reappraisal of the 
weight of such a diamond, it must be detached from its setting, which 
ordinarily means the destruction of the setting. 
SUMMARY OF THE INVENTION 
Accordingly, it is a general object of the present invention to provide 
novel and useful diamonds with inscriptions which solve the above 
described problems. 
Another and more specific object of the invention is to provide diamonds 
having inscriptions provided directly thereon and certifying the gem 
quality. By this provision according to the invention, the inscriptions 
take the place of certificates of appraisal, which may henceforth become 
unnecessary and be dispensed with. Since the inscriptions certifying gem 
quality are provided integrally with their respective diamonds, there is 
no longer any possibility of undesirable occurrences such as loss or 
forgery of conventional certificates of appraisals separate from their 
diamonds. Moreover, there is no longer any necessity of verification of 
correspondence between a diamond and its appraisal certificate. 
Furthermore, there is no necessity of dismounting a diamond from a setting 
such as a ring to reappraise its carat value 
Still another object of the invention is to provide diamonds provided with 
the above mentioned inscriptions without any impairment whatsoever of the 
gem quality and commercial value of the diamonds for ornamental use. 
Other objects and further features of the invention will be apparent from 
the following detailed description with respect to preferred embodiments 
of the invention when read in conjunction with the accompanying drawings.

DETAILED DESCRIPTION 
A brilliant cut diamond, which will be taken as one example of a diamond on 
which an inscription is to be formed in accordance with the present 
invention, has a shape as indicated in FIGS. 1 and 2. The diamond has a 
structure 10 that comprises a crown 11, a girdle 12, and a pavilion 13. 
The crown 11 has a table surface 14, star facets 15, bezel facets 16, and 
crown girdle facets 17. The pavilion 13 has pavilion girdle facets 18, 
pavilion facets 19, and a culet 20. These surfaces are cut and polished 
surfaces. 
In a first embodiment of the invention, an inscription is formed on the 
culet 20 of the diamond. 
As a first step in this inscription forming process, a photomask 30 of a 
pattern as shown in FIG. 3, for example, is formed by an ordinary 
photographic technique or photo-etching technique. This photomask 30 is 
designed to indicate an inscription comprising marks 31, numerals 32, and 
the like representing necessary appraisal particulars of the diamond such 
as carat number, color grade, and presence or absence of flaws, which have 
resulted from an appraisal. In this connection, the pattern of the 
photomask 30 is of a size which is a magnification of, for example, 
approximately 2,000 times that of the inscription to be formed. 
On one hand, the diamond 10 on which the inscription is to be formed is 
placed with its culet 20 above and its table 14 below in a case 40. Next, 
a resin 41 is poured into the case 40 to a level at which the culet 20 is 
slightly covered thereby to fix the diamond 10 embeddedly in the resin 41. 
The upper surface of the resin 41 is thereafter ground thereby to expose 
the culet 20 of the diamond 10 as indicated in FIG. 5(A). Then, as 
indicated in FIG. 5(B), a layer 42 of a metal which does not readily 
deteriorate, such as chromium, is formed by a process such as evaporation 
deposition on the culet 20. Prior to this step, the surface of the culet 
20 should be cleaned in order to obtain intimate and secure adhesion of 
the metal layer 42 to this culet surface 20 of the diamond 10. 
On this metal layer 42, a photoresist such as AZ-1350 (trade name) is 
applied as a coating to form a photoresist film 43 as shown in FIG. 5(C). 
Then, by means of an optical system (not shown) at an intermediate point 
of which the aforementioned photomask 30 is mounted, the pattern of the 
photomask 30 is reduced in size, for example to 1/2,000 and projected on 
this photoresist layer 43 thereby to effect photographic exposure. 
Thereafter, as indicated in FIG. 5(D), developing is carried out, and 
parts of the photoresist are removed in accordance with the printed 
pattern. Next, parts of the metal layer 42 which have been exposed by the 
removal of the photoresist are removed by an film etching process as 
indicated in FIG. 5(E). The remaining photoresist 43 is thereafter 
removed. 
Finally, the resin 41 is melted by heating, and the diamond thus released 
is taken out, whereupon a diamond 10a bearing on its culet surface 20 an 
inscription 44 constituted by the remaining parts of the metal layer 42 in 
a pattern in accordance with the pattern of the mask 30 is obtained. 
The size of the pattern of the inscription 44 formed in the above described 
manner (see FIG. 5(F)) is of the order of 0.1 mm. in diameter, for 
example. On one hand, the diameter of the culet 20 is of the order of 0.2 
to 0.3 mm., for example. Therefore, there is ample space on the culet 20 
for forming an inscription. Furthermore, since the inscription is very 
minute as mentioned above, it cannot impair the original ornamental beauty 
or value of the diamond. 
When the inscription 44 formed as described above is to be read, it is read 
directly by means of optical magnifying means such as a microscope in the 
case where the diamond 10a is not mounted on another object such as a ring 
setting. In the case where the diamond 10a is mounted on a ring setting or 
the like, the inscription is read by placing the objective lens of a 
microscope in a position to confront the table 14 of the diamond. 
In the above described embodiment of the invention, the culet 20 is very 
small, being of the order of 0.2 to 0.3 mm., for example. Furthermore, the 
photomask 30 is placed in the aforementioned optical system for 
photographic exposure at a position separated from the culet 20 of the 
diamond. For these reasons, it is difficult to focus the pattern of the 
photomask 30 accurately on the culet, whereby fine adjustment is required. 
Thus, there arises the problem of troublesome work. 
This problem has been solved by a second embodiment of the invention as 
described below, in which an inscription is formed on the surface of the 
table 14 of the diamond 10. 
In the formation of the inscription, a mask 50, as shown in FIG. 8, having 
a pattern corresponding to the result of an appraisal is first prepared 
similarly as in the case of the pattern shown in FIG. 3. The pattern of 
the mask to be used in the instant embodiment of the invention, however, 
is of the same size (for example, a diameter of 0.1 mm.) as the 
inscription to be formed. 
On one hand, the diamond 10 on which the inscription is to be formed is 
placed with its culet 20 below and its table 14 above in the case 40 and 
is embeddedly set in the case 40 by pouring the resin 41 thereinto as 
shown in FIG. 7. Then, after the table 14 has been made clean, a layer 42 
of a metal such as chromium is deposited by evaporation on the table 14 
similarly as in the preceding embodiment of the invention, and a 
photoresist film 43 is further formed thereon by application as a coating. 
Then, as indicated in FIG. 8, a mask 50 having the above mentioned pattern 
is placed in intimate contact on the photoresist film 43. With the mask 50 
in this state, light is projected thereonto to carry out exposure, 
whereupon only the parts of the photoresist film 43 corresponding to the 
pattern of the mask 50 are exposed to light. The mask 50 is then removed, 
and thereafter the steps of development of the photoresist film 43, the 
etching of the metal layer 42, the removal of the photoresist, and 
succeeding steps are carried out similarly as in the preceding embodiment 
of the invention. As a result, a diamond 10b having an inscription 51 
formed on the table 14 thereof as shown in FIG. 6 is obtained. 
In accordance with the instant embodiment of the invention, the inscription 
can be formed at almost any position since the surface of the table 14 is 
wide. Furthermore, since it is sufficient merely to place the mask 51 in 
intimate contact with the photoresist film 43, the work of adjusting the 
position of the mask at the time of photographic exposure, as in the 
preceding embodiment of the invention, is not necessary, whereby the work 
of forming the inscription is greatly facilitated. 
While the inscription 51 on the table 14 in FIG. 6 is shown in a greatly 
enlarged state, it is actually very small, being of the order of 0.1 mm. 
and thereby being almost imperceptible by naked eye. Therefore, this 
inscription 51 cannot impair the aesthetic value of the diamond for 
ornamental purposes. 
When the inscription 51 is to be read, it can be readily pin-pointed by 
scanning the surface of the table 14 with lowered magnification of a 
microscope of the order of 100 times thereby to widen the field of vision. 
In accordance with the present invention, the surfaces on which the 
inscription is formed need not be limited to the culet and table of the 
diamond as in the embodiments of the invention described above but may be 
any other facet. Furthermore, instead of embeddedly setting the diamond 10 
in a resin 41 for the purpose of holding the same, the diamond may be held 
by clamping it at its girdle 12 part. 
Further, this invention is not limited to these embodiments but various 
variations and modifications may be made without departing from the scope 
and spirit of the invention.