Process for the manufacture of reflecting glass and the product thereof

A process for the manufacture of reflecting glass comprises implantation of ions of selected metal elements under selected conditions of temperature, energy and dosage in a glass substrate to obtain a product which has characteristics of light reflection and transmission rendering it suitable for advantageous use in the fields of vehicles and building construction.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention refers to a process for the manufacture of reflecting 
glass, particularly suited for use in the field of vehicles as a rear view 
mirror and/or side window and in the field of building construction for 
external glazing and/or non-opaque mirrors. 
The present invention also refers to a reflecting glass obtained using said 
process. 
2. Description of the Prior Art 
Methods of manufacture of sheets of glass capable of being advantageously 
employed in the above mentioned fields and for the applications specified 
are known in the state of the art. 
In general a glass made by said methods, at wavelengths comprised between 
350 nm and 750 nm reflects a rate from 20% to 50% of the incident light in 
a perpendicular direction, and transmits, at the same wavelengths, a rate 
from 15% to 70% of the incident light. 
Most recent are methods teaching a glass with those characteristics is 
produced by coating the surface of the glass to be in contact with the 
external environment, with at least one layer of dielectric material (in 
general a metal oxide). 
The coating is obtained using the known method of vacuum cathodic 
sputtering, hereinafter called physical deposition, or using another known 
method consisting in the immersion of the glass in various chemical 
solutions, and successively the promotion of precipitation onto said glass 
of chemical substances, which method will hereinafter be called chemical 
deposition. 
The product obtained according to the manufacturing methods mentioned 
hereinabove has several drawbacks: the coating is, in fact, exposed during 
its working life to atmospheric agents, as the deposition is carried out 
on the outer surface of the glass, and this causes deterioration and wear. 
In particular, in the case of deposition of layers using the physical 
method, the coating, while showing a resistance and endurance in line with 
the user specifications prescribed by the authorities of the USA and the 
EEC, has a shorter life than that produced using the chemical method. 
On the other hand, the latter method is more expensive than the physical 
one, due to the complexity of its realization. 
There is furthermore known in the state of the art, and this forms the 
object of European published patent application number 0318440, a process 
for changing the refraction index value in one or more layers of a sheet 
of glass, consisting in a suitable use of the ionic implantation method. 
This method permits the formation of a homogeneous and continuous layer of 
a substance under the surface of the glass, by inserting into the 
molecular structure of the glass itself the ions of a selected element, at 
selected chosen conditions of glass temperature and ion dosages. 
In particular, in the cited patent application, the ions of the elements 
argon, xenon, krypton, neon, helium, nitrogen or carbon were chosen which, 
when inserted into the molecular structure of the glass, at a certain 
depth, vary the refraction index of the same. 
The use of this process gives the reflecting glass characteristics of 
notable duration and resistance to atmospheric agents, as the implanted 
layer is buried within the glass itself. 
SUMMARY OF THE INVENTION 
An object of the present invention is therefore to provide a process for 
the manufacture of reflecting glass which, using the implantation of ions 
of several chemical elements, suitably chosen, into a glass substrate, 
provides said substrate with the desired reflection characteristics. 
A further object of the present invention is to provide a reflecting glass 
having reflection rates of incident light in a perpendicular direction 
comprised within a desired range of rates. 
A further object of the present invention is to provide a glass having a 
transmission rate of incident light comprised within a desired range of 
rates. 
The above objects have been obtained according to the present invention by 
means of implantation of ions of one of the following elements: silver, 
copper, gold, gallium, zinc or tantalum, into a sheet of transparent 
commercial glass, heated to a selected temperature and using selected 
doses of implanted ions. 
In particular, in the case of implantation of the ions of the elements 
silver, gold, and copper the glass substrate is heated to a temperature 
from 100.degree. C. to 200.degree. C., the implantation dose is comprised 
between 4E16 and E17, and the power is 10 to 60 KeV. 
In the case of implantation of the ions of gallium and zinc the glass 
substrate is heated to a temperature from 30.degree. C. to 40.degree. C. 
and the implantation takes place using doses comprised between 5E16 and 
E17, and using a power from 10 to 60 KeV. 
In the case of implantation of tantalum ions the glass substrate is heated 
to a temperature from 100.degree. C. to 200.degree. C. and the 
implantation takes place using a dose comprised between 5E16 and E17 and a 
power 50 to 150 KeV. 
The glass thus obtained reflects at wavelengths comprised between 350 nm 
and 750 nm a rate from 20% to 50% of the incident light in a perpendicular 
direction and transmits, at the same wavelengths, a rate comprised between 
15% and 70% of the incident light. 
In all cases the same implantation process can be repeated a number of 
times, in order to modify a suitable number of layers and thus obtain the 
desired light reflection and transmission rates. 
An object of the present invention is therefore a process for the 
manufacture of reflecting glass, particularly suited for use in the field 
of vehicles as a rear view mirror and/or side window and in the field of 
building construction as external glazing and/or non-opaque mirrors, in 
which a sheet of glass is heated and at least one layer of a chemical 
element is formed by implantation of ions of said element in the glass 
substrate at the desired depth under the glass surface, characterized in 
that said element is selected from the group consisting of silver, gold, 
copper, gallium, zinc and tantalum, so that the sheet of glass shows a 
reflection rate from 20 to 50% and a transmission rate from 15 to 70% of 
incident light in a perpendicular direction at a range of wavelength from 
350 to 750 nm.

The characteristics of the invention will be more clearly seen on 
consideration of the following examples of embodiment of the invention. 
EXAMPLE 1 
Silver ions were implanted in a sheet of transparent commercial glass, 
suitable to be used in building construction and in automobiles, heated to 
a temperature of 140.degree. C. measured within the mass of the glass 
itself. 
The implantation power was 60 KeV and the dose of ions was 5E16 ions per 
cm.sup.2. After heat treatment of the glass at approximately 200.degree. 
C., light reflection was measured in the glass equivalent to 50% of 
incident light in a normal direction and light transmission of 20% at a 
wavelength of 450 nm. 
In the widest range comprised between 350 nm and 750 nm a minimum 
reflection rate equivalent to 20% and a maximum reflection rate equivalent 
to 50% of the incident light in a perpendicular direction were measured, 
along with a minimum transmission rate equivalent to 18% and a maximum 
transmission rate equivalent to 70%. 
EXAMPLE 2 
Gallium ions were implanted in a sheet of transparent commercial glass, 
suitable to be used in building construction and in automobiles, heated to 
a temperature of 37.degree. C. The implantation power was 60 KeV and the 
dose of ions was E17 ions per cm.sup.2. 
A light reflection was measured in the glass equivalent to 50% of incident 
light in a perpendicular direction and a transmission rate equivalent to 
30% at a wavelength of 450 nm. 
In the widest range comprised between 350 nm and 750 nm reflection rates of 
incident light in a normal direction comprised between 37% and 50% and 
light transmission rates comprised between 15% and 50% were measured. 
EXAMPLE 3 
Tantalum ions were implanted in a sheet of transparent commercial glass, 
suitable to be used in building construction and in automobiles, heated to 
a temperature of 150.degree. C. The implantation power was 100 KeV and the 
dose of ions was 7.5E16 ions per cm.sup.2. 
A light reflection was measured in the glass equivalent to 35% of incident 
light in a perpendicular direction and a light transmission equivalent to 
40% at a wavelength of 450 nm. 
Reflection rates of the incident light in a perpendicular direction from 
27% to 35% and light transmission rates from 30% to 50% were measured in 
the broader range from 350 to 750 nm.