GB2195664A

GB2195664A - Article exhibiting a golden colour

Info

Publication number: GB2195664A
Application number: GB08720330A
Authority: GB
Inventors: Kouji Hirose; Hitoshi Ito; Kazuhito Yoshida
Original assignee: Seikosha KK
Current assignee: Seikosha KK
Priority date: 1986-09-02
Filing date: 1987-08-28
Publication date: 1988-04-13
Anticipated expiration: 2007-08-28
Also published as: JPH0461071B2; SG51193G; DE3728836A1; GB2195664B; JPS6362863A; HK67693A; DE3728836C2; GB8720330D0; CH676856A5

Description

1 1 10 GB2195664A 1

SPECIFICATION

Article exhibiting a golden colour This invention relates to articles exhibiting a 70 golden colour. The articles may, for example, be spectacle frames, stationery, personal orna ments, accessories, etc.

It is known that nitrides such as titanium nitride or tantalum nitride exhibit a golden col our under certain conditions and they have been utilised as a substitute for expensive gold plating to provide the exterior of articles with a decorative appearance. It is known to apply a coating of a nitride such as of titan ium or tantalum on an article by sputtering, vapour deposition or ion plating, titanium metal or tantalum metal in a nitrogen atmos phere.

The tone or colour of the nitride formed is greatly dependent on the pressure of the gas in the nitrogen atmosphere when forming a nitride of, for example, titanium or tantalum. Particularly, the range of gas pressure to pro- vide a golden colour is extremely limited. Accordingly, it has been necessary to control the partial pressure of the nitrogen gas with a high accuracy in order to obtain a golden colour of high quality with good reproducibility.

However, it is extremely difficult to adopt the process to industrial mass production.

In view of the above, to obtain a beautiful golden colour with good reproducibility, it has been proposed in Japanese Patent Application No. 59(1984)-26664 that a hard layer of golden colour comprising titanium nitride or tantalum nitride is formed and then a coating of gold or gold alloy is formed on the layer. Although a beautiful golden colour can be ob- tained by this technique, this is due to the brightness of the gold coating on the surface of the titanium nitride or tantalum nitride layer. The gold coating is extremely thin in view of the cost of gold and accordingly it is easily abraded. However, since the layer of titanium nitride or tantalum nitride underlying the gold coating also exhibits a golden colour to some extent, if the gold coating is abraded, the abrasions are not particularly noticable. How- ever, production is troublesome and cost is increased by the fact that gold is used.

The present invention seeks to provide an article exhibiting a golden colour at a reduced cost without using expensive gold. The pre- sent invention also seeks to provide an article exhibiting a golden colour with good reproducibility and by a process that is adapted to mass production.

Although the present invention is primarily directed to any novel integer or step, or combination of integers or steps, herein disclosed and/or as shown in the accompanying drawings, nevertheless, according to one particular aspect of the present invention to which, however, the invention is in no way restricted, there is provided an article exhibiting a golden colour having formed on at least part of the surface thereof a composite membrane composed of a nitride of at least one element of group 1Va of the periodic table and a nitride of at least one element of group Va and/or group Via of the periodic table.

In one embodiment the composite membrane consists of titanium nitride and tantalum nitride, the ingredient ratio of tantalum being 5 to 75% by weight.

In another embodiment the composite membrane consists of zirconium nitride and tantalum nitride, the ingredient ratio of tantalum be- ing 3 to 68% by weight.

Preferably the composite membrane is formed by vapour deposition, sputtering or ion plating.

Preferably the article is composed of a syn- thetic resin, metal or ceramic material, and a primer coating on which the composite membrane is formed. The primer coating may be of nickel or chromium.

The composite membrane may be formed in a nitrogen-containing atmosphere at a pressure in the range (2.5-4.0) x 10-2 Pa or in the range (3.0-4.5) x 10-2 Pa.

The invention is illustrated, merely by way of example, in the accompanying drawings, in which:- Figure 1 is a graph showing the difference of tone for a composite membrane of an article according to the present invention of titanium nitride and tantalum nitride, a pure gold sputtered membrane and a conventional titanium nitride sputtered membrane; Figure 2 is a graph showing the relationship between the tantalum ingredient ratio constituting a factor for determining the tone of the composite membrane as described in Example 1 and the saturation C; Figure 3 is a graph showing the difference of tone for a composite membrane of an article according to the present invention of zir- conium nitride and tantalum nitride, a pure gold sputtered membrane and a conventional zirconium nitride sputtered membrane; and Figure 4 is a graph showing the relationship between the tantalum ingredient ratio consti- tuting a factor for determining the tone of the composite membrane as described in Example 3 and saturation C.

Elements of group Va of the periodic table such as vanadium, niobium or tantalum, when applied by reactive sputtering together with elements of group 1Va of the periodic table such as titanium, zirconium or hafnium, act as a buffer to the reaction system in which the group 1Va elements react with nitrogen. Accordingly, upon forming a nitride of a group 1Va element that actually exhibits a golden col,,our, the effect of fluctuation of the nitrogen partial pressure on the tone or colour can be moderated.

Further, elements of group Via of the per- 2 GB2195664A 2 iodic table such as chromium, molybdenum or tungsten act similarly to moderate the effect of the fluctuation of the nitrogen partial pres sure on the tone. In this case, they also act to dilute the tone thereby enabling paler tones 70 to be produced.

Since an article according to the present in vention exhibits a golden colour identical to that of gold itself stably with no substantial effect due to fluctuation of nitrogen partial pressure in the reaction atmosphere, the pro cess is well suited to industrial mass pro duction at a reduced cost. In addition, the tone of the golden colour can be determined depending on the ratio of the group Va ele ment or group Via element relative to the group 1Va element and this ratio can be con trolled extremely easily. Accordingly, it is pos sible to select the tone of the golden colour optionally over a wide range.

EXAMPLES

EXAMPLE 1

This example illustrates a composite mem brane comprising a nitride of titanium and a 90 nitride of tantalum.

After placing an article made of ABS resin into a sputtering device and reducing the pres sure to about (1.0-2.0) X 10-3 Pa, nitrogen gas was injected to a pressure of 3.0 x 10-2 Pa and then argon gas was added to increase the pressure of the gas mixture to 6.Ox 10-1 Pa. Shutters were disposed on both titanium metal and tantalum metal targets and reactive sputtering was conducted for 7 minutes at a high frequency output of 8 Watts/cm2 while fully opening the shutter on the titanium metal target and opening the shutter to about one third on the tantalum metal target. As a result, a composite membrane comprising titanium ni tride and tantalum nitride with an ingredient ratio of tantalum being 45% by weight was coated on the ABS resin article to a thickness of 0.15 micron. In this case, since the coating was applied by means of sputtering, the tem perature at which the membrane was formed could be controlled to be less than 70'C and thus deformation, etc.. of the article did not take place.

The composite membrane thus formed exhibited a metallic appearance and a glossy and decorative golden colour. Further, the composite membrane had the same degree of hardness and close bondability as that of titanium nitride alone and showed improved corrosion resistance to that of titanium nitride alone since it had a more dense texture.

While the golden colour of the composite membrane is determined by the ingredient ra- tio of tantalum, temperature and the partial pressure of the nitrogen gas during sputtering, since tantalum acts as a buffer in the reaction between nitrogen and titanium and also contributes to the reaction with nitrogen, the effect of fluctuation in the partial pressure of the nitrogen gas is reduced upon forming the titanium nitride which actually causes the go]den colour and, as a result, the effect on the tone is decreased.

However, the partial pressure of nitrogen gas under which the titanium nitride itself exhibits a golden colour is at least 2.5 x 10-2 Pa. Further, if the partial pressure goes higher than 4.Ox 10-2 Pa, the composite membrane itself becomes extremely fragile thereby causing an actual problem with respect to resistance to cracking. Accordingly, a suitable range for the partial pressure of the nitrogen gas is (2.5-4.0x 10-2 Pa.

The graph of Fig. 1 shows a difference of the colour tone for the composite membrane of titanium nitride and tantalum nitride of an article according to the present invention, a pure gold sputtered membrane and a conven- tional titanium nitride sputtered membrane. In this case, the tone is expressed by measuring L, a, b for each of the membranes by way of an L, a, b chromaticity diagram by using a light source C and a chromaticity meter and by plotting lightness L, saturation W=V(a 2 + b2), and hue H=tan-'(b/a). It can be seen from the graph that the tone of the composite membrane of an article according to the present invention is excellent as compared with the conventional titanium nitride sputtered membrane both for lightness and saturation and it is approximately equal with the pure gold sputtered membrane for hue.

Further, the graph of Fig. 2 was prepared by plotting saturation C, tantalum ingredient ratio (% by weight) and the sputtering temper- ature constituting the determining factors for the tone. In the graph, when the tones are classified under each of the conditions based on the saturation C, they can be divided into zones I to IV, in which the regions of the zones 11 and III are effective regions for obtaining decorative golden hard composite membranes and the ingredient ratio of tantalum is 5 to 75% by weight within a sputtering temperature range of 50'C to 300'C.

Further, in the sputtering process described above, tantalum metal is more reactive with oxygen as compared with the titanium metal, has a gettering effect to oxygen as impurity gas in the vacuum atmosphere and can prevent undesired effects of oxygen on the tone.

EXAMPLE 2

This example illustrates a composite membrane of an article according to the present invention comprising a nitride of titanium and a nitride of chromium.

Under the same conditions as those in Example 1, reactive sputtering was conducted for 7 minutes at a high frequency output of 8 Watt/cm2 while fully opening a shutter on a 3 GB2195664A 3 titanium metal target and opening a shutter to one-third on a chromium metal target. As a result, a composite membrane comprising titanium nitride and chromium nitride with the chromium ingredient ratio of 28% by weight was coated to a thickness of 0. 15 micron on an article made of ABS resin. The composite membrane containing chromium nitride had a metallic appearance and exhibited a glossy pale golden colour.

EXAMPLE 3

This example illustrates a composite membrane of an article according to the present invention comprising a nitride of zirconium and a nitride of tantalum.

After placing an article made of ABS resin in a sputtering device and reducing the pressure to about (1.0-2.0) x 10-3 Pa, nitrogen gas was injected to a pressure of 3.5 x 10-2 Pa and then argon gas was added to increase the pressure of the gas mixture to 6.Ox 10-1 Pa. Shutters were disposed on both of zircon ium metal and tantalum metal targets and re active sputtering was conducted for 7 minutes 90 at a high frequency output of 6.3 Watts/CM2 while fully opening the shutter on the zircon ium metal target at 8 Watts/CM2 and opening the shutter to about one-third on the tantalum metal target. As a result, composite mem brane comprising zirconium nitride and tanta lum nitride with the tantalum ingredient ratio of 36% by weight was coated on the ABS resin article to a thickness of 0.15 micron. In this case, since the coating was applied by means of sputtering, the temperature at which the membrane was formed could be controlled to be less than 7WC and thus deforation, etc.

of the article did not take place.

The composite membrane thus formed exhibited a metallic appearance and a glossy and decorative golden colour. Further, the composite membrane had the same degree of hardness and close bondability as that of zircon- ium nitride alone and showed more excellent corrosion resistance than zirconium nitride alone since it had a more dense texture.

While the golden colour of the composite membrane is determined by the ingredient ra- tio of tantalum, the temperature and the partial pressure of the nitrogen gas, since tanta lum acts as a buffer in the reaction between nitrogen and zirconium and also contributes to the reaction with nitrogen, the effect of fluctu- ation in the partial pressure of the nitrogen gas is reduced upon forming the zirconium ni tride which actually causes the golden colour and the effect on tone is decreased as a re sult.

However, the partial pressure of nitrogen gas under which the zirconium nitride itself exhibits a golden colour is at least 3.Ox 10-2 Pa. Further, if the pressure goes higher than 4.5 x 10-2 Pa, the composite membrane itself becomes extremely fragile thereby causing an actual problem with respect to resistance to cracking. Accordingly, a suitable range for the partial pressure of the nitrogen gas is (3.0-4.5) x 10-2 Pa.

The graph of Fig. 3 shows the difference in the tone for the composite membrane of zirconium nitride and tantalum nitride of an article according to the present invention, a pure gold sputtered membrane and a conventional zirconium nitride sputtered membrane in the same manner as in Fig. 1. It can be seen from the graph that the tone of the composite membrane is excellent as compared with the conventional zirconium nitride sputtered mem- brane both with respect to lightness and saturation. It can also be seen that it is approximately equal with respect to the hue of the pure gold sputtered membrane.

Further, the graph shown in Fig. 4 was pre- pared by plotting the saturation C with respect to the tantalum ingredient ratio (% by weight) and the sputtering temperature constituting the determination factors for the tone. In the graph, when the tones are classified under each of the conditions based on the saturation C, they can be divided into zones I to JV, in which the regions of zones 11 and III are effective regions for obtaining a decorative golden composite membrane and the ingredi- ent ratio of tantalum is 3 to 68% by weight within a sputtering temperature range of 500C to 3000C.

Further, in the sputtering process, the tantalum metal is more reactive with oxygen as compared with zirconium metal, has a gettering effect to oxygen as impurity in the vacuum atmosphere and can prevent undesired effects of oxygen on the tone.

EXAMPLE 4

This example illustrates a composite membrane of an article according to the present invention comprising a nitride of zirconium and a nitride of chromium.

Under the same conditions as those in Example 1, reactive sputtering was conducted for 7 minutes at a high frequency output of 6.3 Watts/CM2 while fully opening a shutter on a titanium metal target at 8 Watts/CM2 opening a shutter to one-third on a chromium metal target. As a result, a composite membrane comprising zirconium nitride and chromium nitride with the chromium ingredient ratio of 20% by weight was coated to a thickness of 0. 15 micron on an article made of ABS resin. The composite membrane containing chromium had a metallic appearance and exhibited a glossy pale golden colour.

Although the above examples employ a sputtering technique as an example, similar golden composite membranes can be formed also by means of vapour deposition and ion plating techniques. Both with vapour deposition and ion plating, when an electron beam is employed as the evaporation source, two 4 GB2195664A 4 electron guns and two crucibles are disposed in one device and vapour deposition or ion plating is conducted for group lVa elements independently at an appropriate evaporation rate in a nitrogen atmosphere to form the composite membrane. In the case of using one electron gun and crucible a composite material previously formulated to an appropriate ingredient ratio is place in the crucible and evaporated.

The article on which the composite membrane is formed may be of, for example, resin, metal or ceramic material and a primer coating such as of nickel or chromium may be formed on the article by means of, for example, plating and, then the composite membrane described above may be formed thereover. Alternatively, it is also possible to apply a primer coating of metal such as chromium, nickel-chromium or nickel on the article by means of sputtering, vapour deposition or ion plating and, thereafter, applying the composite membrane.

The primer coating has the aim of improving the close bonclability and/or, particularly in the case where the article is of metal, improving corrosion resistance.

Claims

1. An article exhibiting a golden colour having formed on at least part of the surface thereof a composite membrane composed of a nitride of at least one element of group 1Va of the periodic table and a nitride of at least one element of group Va and/or group Via of the periodic table.

2. An article as claimed in claim 1 in which the composite membrane consists of titanium nitride and tantalum nitride, the ingredient ratio of tantalum being 5 to 75% by weight.

3. An article as claimed in claim 1 in which the composite membrane consists of zirconium nitride and tantalum nitride, the ingredient ratio of tantalum being 3 to 68% by weight.

4. An article as claimed in any preceding claim in which the composite membrane is formed by vapour deposition, sputtering or ion plating.

5. An article as claimed in any preceding claim composed of a synthetic resin, metal or ceramic material, and a primer coating on which the composite membrane is formed.

6. An article as claimed in claim 5 in which the primer coating is of nickel or chromium.

7. An article as claimed in any preceding claim in which the composite membrane is formed in a nitrogen-containing atmosphere at a pressure in the range (2.5-4.0) x 10-2 Pa or in the range (3.0-4.5)x 10-2 Pa.

8. An article exhibiting a golden colour substantially as herein described with reference to and as shown in the accompanying drawings.

9. Any novel integer or step, or combina- tion of integers or steps, hereinbefore de- scribed and/or as shown in the accompanying drawings, irrespective of whether the present claim is within the scope of or relates to the same, or a different, invention from that of the preceding claims.

10. An article exhibiting a golden colour in which a composite membrane comprises of a nitride of at least one of elements belonging to group Wa and a nitride of at least one of elements belonging to group Va or Via of the periodical table is formed on the surface thereof.

Published 1988 at The Patent Office, State House, 66/71 HighHolborn, London WC 1 R 4TP. Further copies may be obtained from The Patent Office, Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Burgess & Son (Abingdon) Ltd. Con. 1/87.