Note: Descriptions are shown in the official language in which they were submitted.
PHN. 7737~
, ~ ' KTS/WJM/JEL~.
7-7-1975.
~Method of etching a pattern n glass".
The invention relates to a ~ethod of etching
a pattern in glass and to products manufactured by this
method.
United States Patent 3,489,6Z4 describes such
a method in which first via a pyrolysable tin compound
at an increased temperature a uniform layer of tin oxide
and then a layer of an etch-resist material adapted to be
modified by light are deposited on the glass surface~ the
latter layer is exposed to light and then developed so
that a coating according to the negative of a pattern
desired in the glass is left, and finally the uncovered
glass surface is exposed to the action of an etchant
which contains h~drofluoric acid.
The tin oxide is deposited by heating the
glass to a temperature between 400~ and the so~tening
temperature of the glass and then spraying a liluid of
dissolved pyrolysable tin compound on to the glass. This
tin oxide, which is of a complex structure in which a
chemical bond to the glass plays a part, ensures as an
intermediate layer that the light-modifiable etch- resist
layer adheres to the glass surface, for none of the usual
photosensitive resists has sufficient adherence to glass.
Positive and negative photoresists are available, i.e.
resists which are soluble in a given reagent and become
insoluble after exposure and resists which are insoluble
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- PHN. 7737-
~ 7-7-1975.
in a reag-nt and become soluble in it after exposure
respectively. Removing the soluble portions of the resist
in the suitable solvent is referred to as developing.
After development the glass remains covered,
via a tin oxide layer, with the exposed etch resist layer
in the areas outside the pattern to be etched. The glass
in the pattern parts is coated with a layer of tin oxide
which first must ba removed. For this purpose the tin
oxide is for so~e time maintained in contact with an acid
solution under strongly reducing conditions, for example
a HCl solution containing ~inc powder in contact with the
tin oxide.
In practice the adherence of the etch-resist
material to the tin oxide is found to be Fomparatively
poor; hence the end result often leaves much to be desired.
The present invention provides a method the
result of which is of appre~iably higher quality. In
addition the method has further advantages over the above-
described method.
The method of etching a pattern in glass by
depositing first~ via a pyro~ysable metal compound at an
increased temperature, a uniform metal of a metal oxide
and then a layer of a light-modifiable etch-resist mate-
rial on to the glass surface, e~posing the latter layer
to light and then developing it so that an etchant-re-
sistant coating according to the negative of a desired
pattern in the glass i9 left, and subjecting the uncovered
3L5~
glass surface to the action of an etchant which contains
hydro~luoric acid, according to the invention is character-
ized in that the glass sur~ace is brought into contact
with a pyrolysable titanium compound at a temperature
between loO C and 240C.
The titanium dioxide, which in this manner is
deposited at a far lower temperature than the tin oxide
in the known method, has an amorphous structure and is an
excellent adherence-intermediary for the etch-resist
material. In view of de~ormation o~ the glass the lower
temperature is ~ar more attractive.
The titanium dioxide is slowly dissolved in
the etchant containing hydrofluoric acid. Because the
layer of titanium dioxide need only be very thin ~at
most 0.1 /um) and moreover is slightly porous, it can
be removed comparatively rapidly. However, the di~erence
in rate of the solution also results in that no under-
etching takes place. In any case, in the method accord-
ing to the invention, the additional processing step
required in the method using tin oxide is dispensed with.
The pyrolysable titanium compound which can be
used in the method according to the invention can be
selected from organotitanium compound~ such as titanium
acetylacetonate or isopropyltitanate. To obtain increased
e ~ ng depths the glass pre~erably ~irst is subjected to
a roughening treatment as described in Canadian Patent 1,000,131
PHN. 7737.
7-7-1975.
The uses of the etche~ product obtained by the
method according to the invention may be of various natu-
res, such as a stereotype for printing methods, a master
for information recorded by optical means or an anode
pl~te for a display panel.
The invention will now be illustrated by
Examples.
Exam~
A sheet of soda-lime glass i5 ultrasonically
cleaned for 5 minutes in a bath containing
1 l of ~l2S04 and
35 ml of a saturated R2Cr207 solution in H20,
and subsequently rinsed for 1 minute in flowing de-ionized
water. The sheet then is cleaned for 5 minutes in isopro-
---15 panol vapour. After cooling the plate is pulled up from
a 5 ~ by weight solution of titanium acetylacetonate
in isopropanol at a rate of 2.5 cm/min. The sheet is
dried at 220C for 10 minutes and then by pulling up coat-
ed with a photoresist which is commercially available
under the trade name Shipley AZ 1350H. The photoresist
is dried at 70C for 10 minutes and then exposed for 1
minute behind a negative by a high-pressure mercury
vapour lamp (type HPR 125W) at a distance of 30 cm. The
exposed photoresist is dissolved (developed) with Shipley
. ,~........... ~ ~AZ developer (duration 2 m:inutes) 9 rinsed and dried. The
glass sheet locally covered with photoresist is after-
dried in an oven at 120C for 5 minutes~ The glass then
.
~ rr~le~n~r~c
is etched by immersing it in an aqueous HF solution. The
etching depth is determined by the time of treatment and
the concentration of the HF solution. The etching rates
for various concentrations are
10 % HF 1-5 /um/min.
20 % HF 5 /um/min.
30 % HF 10 /um/min.
40 % HF 30 /um/min.
The method described enables patterns 20 /um deep to be
etched. The underetching factor is 0.5. The etching depth
has been measured with a Talysurf 10*.
If patterns of greater depth are to be etched,
the photoresist must have better adherence to the glass.
Then a method as described in Canaclian Patent 1,000,131
is used. The soda-lime glass then first is mechanically
roughened by a mechanical grinding operation using silicon
carbide powder (SiC) having a grain coarseness of 44
(grain 240 according to FEPA standard) and then for 10
seconds chemically treated with 10 % HF solution, rinsed
and dried. Subsequently an amorphous TiO2 layer and a
photoresist are deposited in the manner described in
Example I. After this treatment patterns at least 200 /um
deep can be etched. The underetching factor remains 0.5.
Example III.
A sheet o~ a borosilicate glass is cleaned
* TrNdemark 6 -
PHN. 7737.
9 7-7-1975.
and provided with an amorphous layer of TiO2 and a photo-
resist coating in the manner described in Example I.
When etching with 40 % HF the depth as a function of
time is
1 minute 12 /um.
2 minutes 17 /um.
3 minutes 21 /um.
Using a pretreatment as described in Example I the maximum
etching depth is 8 /um whereas using a pretreatment as
described in Example II the etching depth is indefinite.
The underetching factor is 0.5,
Example IV.
A quartz sheet is pretreated in the manner des-
cribed in Example I. When etching in 40 % HF the following
depths are obtained as functions of etching time
1 minute 4 /um.
2 minutes 6 /um.
3 minutes 8 /um.
With a pretreatment as described in Example I the maximum
etching depth is 3 /um whereas with a pretreatment as
described in Example II the etching depth is indefinite.
The underetching factor is 0.5.
