JPH04236270A - Electrically conductive coating material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to conductive coating materials used in conductive pastes, conductive paints, magnetic shield paints, etc. used in the formation of electronic circuit electrodes and wiring conductors.

0002

[Prior Art] For example, in a plasma display, an electrode (cathode) is printed on the glass back plate side, a transparent electrode (anode) is formed on the cover plate side facing the cathode, and a space between the two electrodes is formed. A voltage is applied to the battery to cause it to discharge and develop color.

[0003] In order to form the above-mentioned electrode on the back plate side, a thick film printing layer is formed on the surface of the back plate by screen printing or the like with a conductive paste in which metal powder is dispersed in a vehicle which is a synthetic resin solution, and after drying. A method of firing in the atmosphere to form a conductive fired film has been adopted.

Conventionally, Ni powder has been used in the conductive paste, but as mentioned above, there is a problem in that the Ni oxidizes during firing in the atmosphere and the fired film loses its conductivity. In order to prevent this, a conductive paste in which B powder is added to Ni powder has been provided (Japanese Patent Publication No. 16041/1986).

[0005] In the thick film printed layer made of the conductive paste, the B powder is selectively oxidized to B2O3 by firing in the atmosphere, and as a result, oxidation of the Ni powder is prevented.

[0006]

[Problems to be Solved by the Invention] However, in the conventional conductive paste described above, if the particle size of the Ni powder is large, the printability when printing a thick film printing layer deteriorates, and the Ni particles in the fired film deteriorate. The packing density is small and the conductivity is reduced. On the other hand, when the particle size of the Ni powder is small, the packing density of the Ni particles in the fired film increases, but as a result of the increased total surface area of the Ni particles, the Ni particles are easily oxidized during firing despite the presence of the B powder. Become.

[0007]

[Means for Solving the Problems] As a means for solving the above conventional problems, the present invention consists of Ni powder, B powder, glass frit, and a vehicle, and the Ni powder is a coarse powder with an average particle size of 3 μm or more. and fine powder with an average particle size of 2 μm or less in a weight ratio of 30:70 to 80:20, and 10 to 70% by weight of the coarse powder is flaky coarse powder with an average particle size of 3 μm or more. , the B powder is contained in a range of 2.0 to 10 parts by weight when the total of Ni powder and B powder is 100 parts by weight to provide a conductive coating material.

The present invention will be explained in detail below. The Ni powder used in the present invention is a mixture of coarse powder with an average particle size of 3 μm or more and fine powder with an average particle size of 2 μm or less, and the mixing ratio of the coarse powder and fine powder in the mixture is 30:70 to 8.
0:20, and 10 to 70% by weight of the coarse powder is flake-like coarse powder with an average particle size of 3 μm or more. Further, the B powder is contained in an amount of 2.0 to 10 parts by weight when the total of Ni powder and B powder is 100 parts by weight.

That is, the coarse powder is 30% by weight in the Ni powder.
Below, if the fine powder is contained in a proportion of 70% by weight or more, the total surface area of the Ni powder becomes large, and oxidation of the Ni powder tends to occur during firing even in the presence of the B powder; When the coarse powder is contained in the proportion of 80% by weight or more, that is, the fine powder is contained in the proportion of 20% by weight or less,
The printability of the conductive coating material deteriorates, and the packing density of the Ni powder in the thick film printing layer that is formed becomes small, making it impossible to obtain good conductivity. Furthermore, if the amount of flaky coarse powder with an average particle size of 3 μm or more in the coarse powder is less than 10% by weight, the conductivity of the thick film printing layer to be formed will be insufficient, and the flaky coarse powder will not have sufficient conductivity. When the amount exceeds 70% by weight, it becomes difficult to obtain good printability even if the total amount of the coarse powder is 80% by weight or less.

Furthermore, if the B powder is contained in a proportion of 2.0 parts by weight or less, the effect of preventing the oxidation of the Ni powder by the B powder will not be sufficient, while if it is contained in a proportion of 10 parts by weight or more, a thick film printed layer will be formed. conductivity deteriorates. The B powder is preferably contained in an amount of 5 parts by weight or less.

The glass frit used in the present invention is 55
It is desirable to have a softening point of 0°C or lower. The reason is that the temperature at which the B powder is activated is from 550°C.
Therefore, since the firing temperature of the thick film printing layer is also set at 550°C or higher, the softening point of the glass frit is preferably 550°C or lower in order to sufficiently soften the glass frit during firing. However, if the glass frit has a softening point of 400° C. or lower, the softening of the glass frit during firing may cause significant deformation of the thick film print layer, and the heat resistance of the thick film print layer may also decrease. The glass frit usually contains 5 to 15 parts by weight when the total of Ni powder and B powder is 100 parts by weight.
It is added in a range of parts by weight. The reason is that glass frit serves as a binder for Ni powder, and if the amount added is less than 5 parts by weight, the binder effect is small.
On the other hand, if the amount added is 15 parts by weight or more, the Ni powder will be diluted and the conductivity will be adversely affected.

The vehicle of the present invention is a synthetic resin solution,
Synthetic resins used include cellulose derivatives such as methylcellulose, ethylcellulose, methoxycellulose, ethoxycellulose, and carboxymethylcellulose;
In addition, it is desirable to select synthetic resins such as acrylic resins and urethane resins that do not leave carbon in the thick film printing layer when fired. As the solvent for dissolving the synthetic resin, it is desirable to select a reducing high-boiling organic solvent having a hydroxyl group such as ethylene glycol, propylene glycol, glycerin, pentaerythritol, or terpineol.

The conductive coating material of the present invention is prepared by kneading the above components using a kneading machine such as a three-roll mill, a ball mill, or an attriter, and is usually applied to a substrate such as glass, ceramic, or plastic by screen printing, spraying, etc. It is applied to a film thickness of 10 to 30 μm,
As described above, the B powder is fired at a temperature of 550° C. or higher, which activates the B powder. However, if the firing temperature is 650°C or higher, oxidation of the Ni powder may occur even in the presence of the B powder, so the preferred firing temperature is 550°C to 650°C. Firing is performed in the atmosphere. By firing, the solvent and synthetic resin constituting the vehicle are volatilized, and the glass frit is melted to form a matrix in which Ni powder is dispersed. Then, the B powder becomes B2O3 and is mixed into the matrix. In this way, an electrically conductive and magnetically shielding fired film is formed on the surface of the base material.

[0014]

[Operation] The conductive coating material of the present invention is thick-film printed on a substrate by screen printing, for example, as a conductive paste. At this time, the coarse powder with an average particle size of 3 μm or more in the Ni powder accounts for 80% by weight or less. Furthermore, since the flake-like coarse powder with an average particle diameter of 3 μm or more is contained in the coarse powder in an amount of 70% by weight or less, the printability is not deteriorated. In addition, in the formed thick film printing layer, since the fine powder with an average particle size of 2 μm or less in the Ni powder is mixed at a mixing ratio of 70% by weight or less, the total surface area of the Ni powder does not become excessive, and the Ni powder is removed during firing. oxidation is less likely to occur. However, the fine powder is Ni
The powder contains 20% by weight or more of the fine powder, and the fine powder fills the gaps between the coarse powders, and the coarse powder contains 10% by weight or more of the flaky coarse powder, and the foil The flaky coarse powder has good mutual contact, and as a result, the packing density of the Ni powder in the resulting conductive fired film becomes high, resulting in good conductivity.

On the other hand, since B is contained in an amount of 2.0 parts by weight or more when the total of Ni powder and B powder in the thick film printed layer is 100 parts by weight, the thick film printed layer is baked in the atmosphere. When this happens, it is selectively oxidized to become B2O3, which prevents the oxidation of the Ni powder. However, since the amount of B powder is 10 parts by weight or less, the conductivity of the resulting conductive fired film is not inhibited by the B powder.

[0016] The glass frit melts during firing and becomes Ni.
The powder is coated to prevent direct contact with air to prevent oxidation of the Ni powder, and in the conductive fired film, a matrix in which the Ni powder is dispersed is formed to serve as a binder for the Ni powder.

[0017]

[Example] A coarse powder with an average particle size of 11.5 μm produced by the atomization method as a coarse powder in Ni powder, and a coarse powder with an average particle diameter of 16 μm produced by crushing the coarse powder with an attritor.
．． Using a flaky coarse powder of 4 μm and a fine powder with an average particle size of 0.8 μm produced by a wet reduction method as a fine powder, B
An amorphous type powder with an average particle size of 0.7 μm was used. Furthermore, as a glass frit, the softening point is 44.
A temperature of 0° C. was used, and a terpineol solution of ethyl cellulose was used as the vehicle.

The above components were mixed in the composition shown in Table 1 and kneaded in a three-roll mill to form conductive paste sample N.
o. 1~No. 10 was prepared. In the same manner, the above components were mixed and kneaded with the composition shown in Table 2, and a comparison conductive paste sample ratio No. 1 was obtained. 1~No. 6 was prepared.

[Table 1]

[Table 2]

[0019] The above sample No. 1~No. 10 and ratio no. 1 to ratio No. 6 uses a #200 polyester fiber screen on the surface of the glass substrate with a width of 5 mm and a length of 2
61 after being printed on a 0 mm strip and drying at 200°C.
Firing was performed in the atmosphere at 0°C for 10 minutes three times, and after each firing, the surface resistance value (mΩ/□) of the fired film was measured using the four-probe method (Kyowa Riken Resistance Measuring Instrument 705RL). The surface condition of the fired film was visually judged. Note that the thickness of the fired film was 20 μm. The results are shown in Tables 3 and 4.

[Table 3]

[Table 4]

According to Table 3, sample No. of the present invention. 1
~No. No. 10 showed a stable low resistance value regardless of the number of firings, and No. 8~No. 9, there is little change in conductivity depending on the amount of B powder, but in Table 4, ratio 1 containing 70% by weight or more of fine powder shows a high resistance value as a result of oxidation of the Ni powder, and the resistance value increases depending on the number of firings. Ratio 2, which contains 80% by weight or more of coarse powder, similarly shows an unstable high resistance value depending on the number of firings, and Ratio 3, which contains 10% by weight or less of flaky coarse powder in the coarse powder, shows a high resistance value. Invention sample no. The resistance value is slightly higher than that of No. 4, and the resistance value fluctuates slightly depending on the number of firings. However, when ratio 4 contains 70% by weight or more of flaky coarse powder, the resistance value is high and the surface smoothness of the fired film becomes poor. In ratio 5 containing 2 parts by weight or less of B powder, most of the Ni powder is oxidized and becomes non-conductive, and in ratio 6 containing 10 parts by weight or more of B powder, a high resistance value is unstable depending on the number of firings.

[0021]

[Effects of the Invention] Therefore, in the coating film made of the conductive coating material of the present invention, oxidation of the Ni powder is prevented even when fired, and a fired film exhibiting good conductivity can be obtained. Furthermore, even after repeated firing, the conductivity is stable with little change, and furthermore, when the amount of B powder added is in the range of 2.0 to 10 parts by weight, the conductivity of the fired film obtained can be changed even by changing the amount of B powder added. becomes less. Such characteristics are particularly useful as a material for forming electrodes of plasma displays, which are subjected to repeated firing.

Claims (1)

[Claims] Claim 1: Consisting of Ni powder, B powder, glass frit, and vehicle, the Ni powder has an average particle size of 3 μm.
It is a mixture in which the weight ratio of the above coarse powder and fine powder with an average particle size of 2 μm or less is 30:70 to 80:20, and 10 to 70% by weight of the coarse powder is in the form of flakes with an average particle size of 3 μm or more. A conductive coating material which is a coarse powder, and the B powder is contained in a range of 2.0 to 10 parts by weight when the total of Ni powder and B powder is 100 parts by weight.