JP3359093B2 - Conductive paste and translucent conductive film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive paste and a light-transmitting conductive film used for forming a light-transmitting electrode such as an electroluminescence (EL) light-emitting device.

[0002]

2. Description of the Related Art Conventional electroluminescence (E)
L) As a conductive paste used for forming a light-transmitting electrode such as a light-emitting element, indium-tin oxide (ITO) ultra-fine powder as a conductive filler may be dispersed in a solvent in which a resin is dissolved, or phosphorus. There is one in which flaky ITO powder is dispersed in a solvent in which a resin is dissolved.

In the organic dispersion type EL device, a zinc sulfide (ZnS) layer as a light emitting layer is formed on a substrate by screen printing or blade coating, and a conductive paste is applied thereon by screen printing or the like to form a light-transmitting conductive layer. A film is formed.

[0004] In a conductive paste using ITO ultrafine powder as a conductive filler, it is necessary to use a large amount of conductive filler with respect to the resin in order to obtain conductivity. This light-transmitting conductive film has a thickness of 2 to 3 μm in order to obtain light transmittance.
It is said that the thickness is preferably about m.

[0005] The zinc sulfide layer, which is the light emitting layer, has a size of several tens of μm of zinc sulfide particles, so that the printing surface has irregularities. When the conductive paste is applied, the thickness of the conductive paste is reduced by the irregularities on the surface of the zinc sulfide layer. Is not uniform, and a portion of 1 μm or less or a portion of 5 μm or more is generated, and a conductive film of 2 to 3 μm cannot be uniformly formed on the entire surface, and there is a problem that a thin portion is cracked and resistance increases.

In a conductive paste in which flaky ITO powder is dispersed in a solvent in which a resin is dissolved, conductivity can be obtained by using a small amount of a conductive filler with respect to the resin. Even so, sufficient light transmittance is obtained, and unevenness on the surface of the zinc sulfide layer does not cause much problem. However, there is a problem that the resistance of the film is not sufficient.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a conductive paste and a light-transmitting conductive film which provide sufficient conductivity and light transmittance.

[0008]

Means for solving the problems of the present invention are as follows: a resin having a major axis of 5 to 100 in a solvent thereof;
It contains acicular indium-tin oxide fine powder having a major axis to minor axis ratio of 10 μm or more , and acicular indium-tin oxide.
When the weight ratio of the material fine powder: resin is 60:40 to 80:20
What is claimed is: 1. A conductive paste comprising: a conductive paste; and a light-transmitting conductive film comprising a needle-like indium-tin oxide fine powder and a resin, wherein the needle-like indium-tin oxide fine powder has a major diameter of 5 to 10.
At 0 μm, the ratio of the major axis to the minor axis is 10 or more, the specific resistance of the film is 1.0 Ω · cm or less, and the volume content of the acicular indium-tin oxide fine powder in the film is 25% by volume or less. A light-transmitting conductive film is characterized in that:

[0009]

The acicular indium-tin oxide fine powder used in the present invention is prepared, for example, by adding tin tetrachloride hydrate to a solution obtained by dissolving indium metal in nitric acid, and heating and concentrating the mixture with stirring. The slurry is concentrated until a thick slurry is formed. A large amount of water is added to the slurry, followed by filtration. The acicular powder obtained by the filtration is washed, dried, and calcined at about 700 ° C. for about 30 minutes.

This acicular indium-tin oxide fine powder is
With a major axis of 5 μm or more and an aspect ratio of 5 or more, an aspect ratio of about 30 can be obtained depending on the tin compound to be added and the concentration conditions. The specific resistance when the powder is formed into a pellet by applying a pressure of 100 kgf / cm ² (hereinafter referred to as powder resistance) is about 0.03 Ω · cm.

In the present invention, the aspect ratio of the acicular indium-tin oxide fine powder is set to 5 or more in order to obtain conductivity by using a small amount of the resin. If the aspect ratio is 5 or less, it is impossible to achieve a specific resistance of the film of 1.0 Ω · cm or less when the volume content of the conductive filler of the light-transmitting conductive film is 25% or less. The aspect ratio is preferably higher, and more preferably 10 or more.

In the present invention, the major axis of the acicular indium-tin oxide fine powder is set to 5 μm or more because the larger the major axis, the smaller the number of contacts between particles and the lower the resistance of the film. For example, when used in a dispersion type EL, the phosphor layer on the coating surface uses zinc sulfide particles having a diameter of 5 to 30 μm, and thus has irregularities of about several μm on its surface, but has a long diameter of 5 μm.
If the thickness is at least μm, the contact between the acicular particles will be maintained and the necessary conductivity will be obtained even if such irregularities are present.

However, when the major axis is 100 μm or more,
In general, it is difficult to pass through the screen mesh at the time of screen printing, which may hinder printing.
Those having a long diameter of 00 μm or less are preferred. However, this does not apply when a coarse screen having a mesh size of 100 mesh or less is used. In the conductive paste of the present invention, a relatively large filler is used, but a line having a width of about 200 μm can be screen-printed.

As the resin used in the present invention, a thermoplastic resin, a thermosetting resin, an ultraviolet curable resin, or the like similar to the resin used for the conventional light-transmitting conductive film is used. The weight ratio of the acicular indium-tin oxide fine powder and the resin in the paste is
Acicular indium-tin oxide fine powder: resin = 60: 40-
80:20 is good. If the amount of the resin is more than 60:40, the resistance of the light-transmitting conductive film becomes too high. If the amount of the resin is less than 80:20, the strength of the light-transmitting conductive film decreases and the resistance also increases.

The resistance of the resulting light-transmitting conductive film also differs slightly depending on the substrate on which the conductive paste is applied. For example, a film having a lower resistance is generally obtained by applying the film to a polyester film than when applying the film to a glass.

When the light-transmitting conductive film of the present invention is compared with a conventional conductive film using an ultrafine ITO powder as a conductive filler, the present invention shows that a fine powder of acicular indium-tin oxide having a high aspect ratio is used. Since it is used as a conductive filler, the optimal weight ratio of the acicular indium-tin oxide fine powder to the resin is 60:40 to 80:20, preferably 65:40.
35-70: 30, whereas conventional ITO
In the case of using ultrafine powder, the weight ratio of ITO: resin is 8
It is about 5:15 to 90:10. Therefore, in the present invention, the volume content of the acicular indium-tin oxide fine powder in the light-transmitting conductive film is set to 25% or less and 1.0 Ω · cm.
The following specific resistance can be obtained. In the present invention, the conductive film can be made thicker than before, so that the surface resistance can be reduced.

When the optical characteristics of the translucent conductive film of the present invention are compared with those of a conventional film using ultrafine ITO powder, the film of the present invention has a very high haze value of about 90%, and thus the scattering of light is small. Large, so the measured total light transmission is 50-80
% And low. However, for example, when used as a light-transmitting conductive film of an EL element, the light transmittance does not simply reflect the EL luminance. In the light-transmitting conductive film of the present invention, the light transmittance is low because not a large amount of light is absorbed but a large amount of incident light is scattered by a high haze.
When considering the luminance of the element, absorption of light of the ITO particles becomes more problematic than scattering light.

It is considered that the smaller the amount of acicular indium-tin oxide fine powder present in the film, the smaller the light absorption. Therefore, the light-transmitting conductive film of the present invention, which can form a low-resistance light-transmitting conductive film with a small amount of acicular indium-tin oxide fine powder, can obtain high luminance despite low measured light transmittance. Can be.

[0019]

【Example】

Example 1 As shown in FIG. 1, the major axis manufactured by the applicant was 5 μm or more, the aspect ratio was 5 or more, the powder resistance was 0.03 Ω · cm, and the tin content was 2.
6% by weight of acicular indium-tin oxide fine powder (hereinafter referred to as IT
O powder) and a resin solution were mixed in the composition of Paste 1 in Table 1, mixed and stirred well, and then filtered through a 200-mesh stainless steel wire mesh to obtain a conductive paste.

The obtained conductive paste is 75 × 75 ×
A 1.1 mm soda-lime glass plate and a 100 μm-thick polyester film (Lumirror T type, manufactured by Toray Industries, Inc.) on a 200-mesh screen plate to a size of 4 × 5 cm. Printing was performed, and drying and curing were performed at 120 ° C. for 20 minutes to obtain a light-transmitting conductive film. FIG. 2 shows a photomicrograph (× 2000) of the translucent conductive film obtained on the polyester film.

The thickness, surface resistance, total light transmittance, haze value, and weight of the film (glass plate only) of the obtained film were measured.
Since the film has irregularities on the surface, the film thickness was read from the measurement chart in units of 0.5 μm. The weight of the polyester film was not measured because the weight changed due to moisture absorption or the like. The specific resistance of the film was determined from the film thickness and the surface resistance, and the ITO powder volume content was determined from the weight, the film thickness, and the paste composition of the conductive film.

Specific resistance of the film (Ω · cm) = surface resistance (Ω /
□) × film thickness (10 ⁻⁴ cm) ITO powder volume content (%) = film weight (g) × ΔITO
(G) / [ITO (g) + resin (g)]｝ × ｛1/7.
2 (specific gravity of ITO g / cm ³ )} × {1 / [4 × 5 (area cm ² ) × film thickness (10 ⁻⁴ cm)]} × 100

The film thickness is measured by a surface roughness measuring device manufactured by Tokyo Seimitsu Co., Ltd.
The surface resistance was measured using Surfcom 900A (trade name) and the Loresta MCP-T400 (trade name, manufactured by Mitsubishi Yuka Co., Ltd.). The total light transmittance and the haze value were measured together with the glass plate of the substrate and the polyester film using a direct reading haze computer HGM-ZDP manufactured by Suga Test Machine Co., Ltd.

Example 2 A conductive paste and a light-transmitting conductive film were obtained in the same manner as in Example 1 except that the composition of the paste was Paste 2 shown in Table 1. FIG. 3 shows a photomicrograph of 2000 times of the translucent conductive film obtained on the polyester film. The same measurement as in Example 1 was performed, and the obtained results are shown in Table 2.

Example 3 A conductive paste and a light-transmitting conductive film were obtained in the same manner as in Example 1, except that the composition of the paste was Paste 3 in Table 1. FIG. 4 shows a 2000 × microscopic photograph of the translucent conductive film obtained on the polyester film. The same measurement as in Example 1 was performed, and the obtained results are shown in Table 2.

Example 4 A conductive paste and a light-transmitting conductive film were obtained in the same manner as in Example 1, except that the composition of the paste was Paste 4 in Table 1. FIG. 5 shows a 2,000-fold micrograph of the translucent conductive film obtained on the polyester film. The same measurement as in Example 1 was performed, and the obtained results are shown in Table 2.

Example 5 A conductive paste and a light-transmitting conductive film were obtained in the same manner as in Example 1 except that the composition of the paste was Paste 5 shown in Table 1. FIG. 6 shows a photomicrograph of 2000 times of the translucent conductive film obtained on the polyester film. The same measurement as in Example 1 was performed, and the obtained results are shown in Table 2.

Example 6 FIG. 7 having a tin content of 2.6% by weight and a dust resistance of 0.03 Ω · cm.
A conductive paste and a light-transmitting conductive film were obtained in the same manner as in Example 1, except that the ITO powder shown in Table 1 was used and the paste composition was changed to the composition of Paste 6 in Table 1. FIG. 8 shows a photomicrograph at 2000 times of the translucent conductive film obtained on the polyester film. The same measurement as in Example 1 was performed, and the obtained results are shown in Table 2.

Example 7 A conductive paste and a light-transmitting conductive film were obtained in the same manner as in Example 1 except that the ITO powder used in Example 6 was used and the paste composition was changed to the composition of Paste 7 in Table 1. . Example 1
The same measurement as described above was performed, and the obtained results are shown in Table 2.

Example 8 The procedure of Example 1 was repeated except that the UV-curable resin shown in Table 1 was used as the resin, the ITO powder used in Example 6 was used, and the paste composition was changed to the composition of paste 8 in Table 1. Thus, a conductive paste and a light-transmitting conductive film were obtained. The same measurement as in Example 1 was performed, and the obtained results are shown in Table 2. The curing of the film
Metal highland lamp M01 manufactured by igrafik
-L212, Irradiator (cold mirror type) UE011-
201C, power supply unit UB01.51-3A / BM-E
2. Illuminance 150m using heat ray cut filter
The test was performed in a nitrogen gas at W / cm ² for 20 seconds.

Example 9 The paste 9 shown in Table 1 was prepared using the ITO powder used in Example 1.
A conductive paste and a light-transmitting conductive film were obtained in the same manner as in Example 1, except that the composition was changed as follows. The same measurement as in Example 1 was performed, and the obtained results are shown in Table 2.

Example 10 The conductive paste obtained in Example 3 was 3.3 lines / m
FIG. 9 shows a 100-fold micrograph of a line pattern of the light-transmitting conductive film obtained by screen-printing the m-th line in the same manner as in Example 1.

Example 11 Using the conductive paste obtained in Example 6, an organic dispersion type E
L was prototyped. First, barium titanate paste (TU-K manufactured by Tohoku Kako Co., Ltd.) was used as an insulating layer (dielectric layer) on the aluminum-deposited surface of a polyester film having a thickness of 100 μm, an area of 4 × 5 cm, 0.95 Ω / □, and aluminum deposited on one side. 217) was printed to a size of 4 × 5 cm using a 200 mesh screen and dried.

On the insulating layer, a zinc sulfide paste (TU-219, manufactured by Tohoku Kako Co., Ltd.) was printed twice using a 200 mesh screen to a size of 4 × 5 cm and dried. The conductive paste of Example 6 was printed thereon in a size of 3 × 4 cm using a 200-mesh screen.
After drying for 0 minutes, a light-transmitting conductive film was formed.

A lead wire for voltage application was connected to one end of the translucent conductive film, a lead wire for resistance measurement was connected to the other end, and a lead wire for voltage application was connected to one end of the aluminum deposition surface of the polyester film. 4 × 5c on both sides of these laminates
Then, an end of the lead wire was exposed to the outside from both sides thereof, wrapped with a 5 × 6 cm fluorine film, and subjected to moisture-proof lamination to produce an EL element.

The resistance between the lead wire for voltage loading and the lead wire for resistance measurement connected to both ends of the light-transmitting conductive film is measured, and the surface resistance of the light-transmitting conductive film is measured. A pseudo trapezoidal wave voltage of 106 V, 800 Hz was applied between a voltage loading lead wire connected to one end of the conductive film and a voltage loading lead wire connected to one end of the polyester film deposition surface, and EL was applied. The device was allowed to emit light, and the luminance was measured. The luminance was measured with a luminance meter (trade name: BM-8, manufactured by Topcon Corporation). Table 3 shows the results.

Example 12 An EL element was prepared in the same manner as in Example 11 except that the paste of Example 9 was used, and the same measurement was performed. Table 3 shows the results.

Comparative Example 1 The same ITO powder as in Example 1 was used, and the paste 10 shown in Table 1 was used.
A conductive paste was prepared in the same manner as in Example 1 except that the composition was changed to obtain a light-transmitting conductive film. The same measurement as in Example 1 was performed, and the obtained results are shown in Table 2.

Comparative Example 2 The conductive paste of Example 3 was subjected to a strong dispersing treatment using a three-roll mill, and the ITO powder was broken and the aspect ratio was 5
The following paste containing a large amount of ITO powder was prepared. Using this paste, a light-transmitting conductive film was obtained in the same manner as in Example 1. FIG. 10 shows a photomicrograph of 2000 times of the translucent conductive film obtained on the polyester film. The same measurement as in Example 1 was performed, and the obtained results are shown in Table 2.

Comparative Example 3 A conductive paste having a composition of paste 11 in Table 1 in which an ultrafine ITO powder having an average particle size of 0.03 μm was dispersed as a conductive filler in an acrylic resin and a solvent (trade name: X- 101) is a 75 × 75 × 1.1 mm thick soda-lime glass and a 100 μm thick, 75 × 75
mm polyester film (Lumirror T type manufactured by Toray Industries Co., Ltd.) was printed on a screen of 300 mesh in a size of 4 × 5 cm. A light conductive film was obtained. 10,000 of the translucent conductive film on the obtained polyester film
A magnification micrograph is shown in FIG. The same measurement as in Example 1 was performed. Table 2 shows the results.

[0041]

[Table 1] Paste composition Ingredients wt% ITO powder / resin weight ratio ─────────────────────────────────── Paste 1 ITO powder 40.0 Acrylic resin A 10.0 80:20 (manufactured by Soken Chemical Co., trade name Thermolac M-45C) Solvent A Isophorone 50.0 ───────────────────── Paste 2 ITO powder 30.5 Acrylic resin A 13.0 70:30 Solvent A 56.5 ────────ペ ー ス ト Paste 3 ITO powder 29.0 Acrylic resin A 14.0 67.5: 32.5 Solvent A 57 2.0 ペ ー ス ト Paste 4 ITO powder 27.7 Acrylic tree A 14.9 65:35 Solvent A 57.4 ペ ー ス ト Paste 5 ITO Powder 27.0 Acrylic resin A 18.0 60:40 Solvent A 55.0──────────────────────────────── Paste 6 ITO powder 29.4 Acrylic resin B 14.1 67.5: 32.5 (Dianal BR-80 manufactured by Mitsubishi Rayon Co., Ltd.) Solvent A 56.5 ──────────────────────── Paste 7 ITO powder 39.8 Acrylic thermosetting resin 19.1 67.5: 32.5 (Kansai Paint (Magicallon No.1000, product name) Solvent A 41.1 ペ ー ス ト Paste 8 IT Powder 34.2 Vinyl ester resin 13.7 (manufactured by Showa Polymer Co., Ltd., trade name: Lipoxy VR-77) Trimethylolpropane triacrylate 8.0 2-hydroxy-2-methyl-1-phenyl-propanone-1 1.160 : 40 Solvent A 43.0 ─────────────────────────────────── Paste 9 ITO powder 30.5 High Dielectric thermoplastic resin 15.5 67:33 (Cyanoresin CR-S manufactured by Shin-Etsu Chemical Co., Ltd.) Solvent γ-butyrolactone 53.0 Paste 10 ITO powder 21.5 Resin A 21.5 50:50 Solvent A 57.0ペ ー ス ト Paste 11 ITO fine powder 29.0 Resin A 6.9 88:12 Solvent A 42.7───────────────────────────────────

[0042]

Table 2 Example Paste substrate Coating film physical properties Composition Film thickness ITO Surface resistance Film specific resistance Total light Haze value (μm) Volume content (Ω / □) (Ω · cm) Transmittance (%) Rate (%) (% 1 1 Glass 7.5 19.7 630 0.47 40.1 92.8 PET 6.5 405 0.26 44.3 92.6 2 2 Glass 6.0 17.5 383 0.23 58.7 92.8 PET 6.0 342 0.21 59.4 92.8 3 3 Glass 6.0 17.6 410 0.25 62.5 92.6 PET 6.0 405 0.24 64.3 92.7 4 4 Glass 5.0 16.5 486 0.24 64.2 92.8 PET 5.0 468 0.23 65.8 92.7 5 5 Glass 5.5 15.0 1500 0.83 70.3 92.6 PET 5.5 1100 0.61 72.1 92.5 66 Glass 5.0 15.8 347 0.17 77.1 82.2 PET 7.0 147 0.10 73.0 90.7 77 Glass 9.0 19.8 189 0.17 63.7 91.2 PET 14.0 176 0.25 61.6 92.0 8 8 Glass 8.0 16.9 140 0.11 50.5 92.2 PET 8.0 145 0.12 52.0 92.0 99 Glass 6.0 16.2 490 0.29 60.4 92.7 PET 6.0 410 0.25 65.3 92.6 ────────────── ──────────── ──────── Comparative Example 1 10 Glass ^{5.0 12.3 1.5 × 10 4 7.5 78.0} 91.5 PET 6.0 1.1 × 10 4 6.6 79.0 91.6 2 3 Glass 4.0 21.1 4820 1.93 70.5 92.5 PET 4.5 3870 1.74 70.0 92.7 3 11 Glass 1.9 43.4 630 0.12 80.7 9.3 PET 2.5 520 0.13 78.5 10.6 ─────────────────────────────────── Glass is a glass plate And PET represents a polyester film.

[0043]

Table 3 Translucent conductive film Surface resistance (Ω / □) EL luminance (conductive paste) (Cd / m ² ) Example 11 ITO powder film 188 198 (Paste 6) Example 12 ITO powder film 720 212 (Paste 9)

[0044]

According to the present invention, it is possible to provide a conductive paste and a light-transmitting conductive film having sufficient conductivity and light transmittance.

[Brief description of the drawings]

FIG. 1 is a micrograph showing the crystal structure of acicular indium-tin oxide fine powder used in Example 1.

FIG. 2 is a photomicrograph of the translucent conductive film obtained in Example 1.

FIG. 3 is a photomicrograph of the translucent conductive film obtained in Example 2.

FIG. 4 is a photomicrograph of the translucent conductive film obtained in Example 3.

FIG. 5 is a photomicrograph of the translucent conductive film obtained in Example 4.

FIG. 6 is a photomicrograph of the translucent conductive film obtained in Example 5.

FIG. 7 is a micrograph showing the crystal structure of the acicular indium-tin oxide fine powder used in Example 6.

FIG. 8 is a photomicrograph of the translucent conductive film obtained in Example 6.

FIG. 9 is a photomicrograph of a line pattern of the translucent conductive film obtained in Example 10.

FIG. 10 is a photomicrograph of the translucent conductive film obtained in Comparative Example 2.

FIG. 11 is a photomicrograph of a translucent conductive film obtained in Comparative Example 3.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-295110 (JP, A) JP-A-4-282508 (JP, A) JP-A-3-24188 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01B 1/22 H01B 1/00 H01B 5/14 H05K 1/09

Claims (2)

(57) [Claims] 1. A resin having a major axis of 5 to 100 in a resin and a solvent thereof.
It contains acicular indium-tin oxide fine powder having a major axis to minor axis ratio of 10 μm or more , and acicular indium-tin oxide.
When the weight ratio of the material fine powder: resin is 60:40 to 80:20
A conductive paste , characterized in that there is a conductive paste. 2. A needle indium - a light-transmitting conductive film made of tin oxide fine powder and a resin, acicular indium - tin
The oxide fine powder has a major axis of 5 to 100 μm and a major axis with respect to the minor axis.
And a ratio of 10 or more, the specific resistance of the film is 1.0 [Omega] · cm or less, and acicular indium in the film - the volume content of the tin oxide fine powder is permeable to equal to or less than 25 volume% Photoconductive film.