JP3338966B2 - Coating solution for forming transparent conductive film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a coating solution for forming a transparent conductive film. More specifically, the present invention relates to a coating liquid that is applied on a substrate such as glass or ceramics and is suitable for forming a transparent conductive film.

[0002]

2. Description of the Related Art A transparent conductive film is, for example, a display tube such as a liquid crystal display, a transparent electrode such as a touch panel or a solar cell, a cloud protection for a window such as a frozen showcase or a transparent heating element for preventing a swimsuit, an infrared reflection film, Used for antistatic.

As a transparent conductive film used for such a purpose, there has been known a method of forming a conductive film by applying a solution of an organic or inorganic metal compound to a substrate and heating and firing the solution. This method can be realized by simple steps of pattern printing, drying, and baking if a printing method is used for applying a solution, and a conductive film of any shape can be formed over a large area on a substrate.

[0004]

As a coating solution used in this method, for example, a coating solution for forming a transparent conductive film containing indium nitrate, an organotin compound, hexylene glycol, acetic acid and / or acetic anhydride (particularly, Kaihei 4-25576
No. 8). This coating liquid has a viscosity of 50 to 1
It is possible to use flexographic printing which requires 100 to 200 cps, or spin coating or gravure printing which requires 50 to 100 cps, but requires a coating viscosity of 50,000 to 300,000 cp. The film cannot be formed by lithographic printing, letterpress printing requiring 10,000 to 80,000 cp, or screen printing requiring 500 to 1,000 cp.

Japanese Patent Publication No. 63-25448 discloses a mixture of an indium compound, a tin compound for adjusting a resistance value, nitrocellulose as a viscous agent, and butylsolve, butylcarbitol, benzylacetate and dimethylphthalate as solvents. A high-viscosity transparent conductive film-forming paste obtained by adding a solvent is disclosed. This paste uses Cellsorb, which dissolves nitrocellulose well, or carbitols to improve screen printability and life characteristics.
The addition amount of the viscous agent is as high as 13 to 17% by weight, and therefore, there is a disadvantage that the thermal decomposition property is deteriorated at the time of firing, and the conductivity or transparency of the formed film is reduced.

It is an object of the present invention to provide a coating film having at least high viscosity characteristics capable of forming a film by screen printing, exhibiting good conductivity, having excellent mechanical strength and light transmittance, and having small in-plane variation. An object of the present invention is to provide a coating solution for forming a transparent conductive film.

[0007]

In order to achieve the above object, the coating liquid for forming a transparent conductive film according to the present invention comprises:
A coating liquid for forming a transparent conductive film in which indium acetylacetone and organotin are dissolved in a solvent and a viscous agent is added, wherein the solvent is an alkylphenol and / or alkenylphenol, a dibasic acid ester and / or acetic acid. Benzyl, and the viscosity agent is hydroxypropylcellulose, the amount of which is not more than 5% by weight.

[0008] The content of indium acetylacetone and organotin is 7% by weight to 40% by weight.

[0009] The organic tin is tin acetylacetone.

[0010] The addition amount of the alkylphenol and / or alkenylphenol is 40% by weight or less.

Further, the composition further contains a diluent, and the diluent is an organic solvent that lowers the viscosity of the coating solution.

[0012]

[Action] Indium acetylacetone (AcAcIn)
Is the general formula

(Equation 1) It is a compound shown by these. As the organic tin, tin acetylacetone is particularly preferable.

Hydroxypropyl cellulose has the general formula

(Equation 2) It is a compound shown by these.

Examples of the alkylphenol and / or alkenylphenol include cresols, p-tert-butylphenol, octylphenol, nonylphenol and cashew nut shell liquid [3 pentadecadesil phenol].

The dibasic acid ester has the general formula

(Equation 3) It is a compound shown by these.

Particularly, high boiling solvents (distillation range 196 to 22)
Glutaric acid which is 5 ℃)

(Equation 4) Is preferred.

The present inventors have found that a mixed solvent of alkylphenol and / or alkenylphenol and a dibasic ester or a mixed solvent of alkylphenol and / or alkenylphenol and benzyl acetate can convert indium acetylacetone and organotin very well. It was found that when dissolved and hydroxypropylcellulose was added to these mixed solvents, the viscosity increased when the amount of hydroxypropylcellulose added was 5% by weight or less. Further, since the amount of the cellulose added is small, it is easily thermally decomposed at the time of baking after coating. Therefore, a film having high transparency and high conductivity can be obtained.

The coating solution according to the present invention is a transparent and uniform solution containing the above components. Such a solution can be obtained, for example, by stirring these components at 60 to 200 ° C for 0.5 to 12 hours.

Table 1 shows the results of a variation test of p-tert-butylphenol and hydroxypropylcellulose.

[0020]

[Table 1]

Table 2 shows the ultimate saturated viscosity of the coating solution depending on the type of phenol.

[0022]

[Table 2] AcAcIn 11.4 AcAcSn 0.6 hydroxypropylcellulose y phenol derivative 20.0 DBE 68-y Production conditions 120 ° C × 3 hrs

The viscosity of the coating solution obtained by the present invention is as follows:
Despite the small amount of hydroxypropylcellulose, which is a viscosity agent, being 5% by weight or less, depending on the combination with phenols, it is 120 to 300 kcps / 25.
C. to reach high viscosities, such as C.degree.
H ₂ OH, -CHO, and a phenolic OH group on the benzene nucleus is believed to be due to cause chemical reactions.

Phenols may be added in excess of 40% by weight or hydroxypropyl cellulose may be added in an amount of 5% by weight.
Excessive addition results in poor film properties. The reason for this is that a gel-like substance is generated due to a cross-linking reaction between each other, and is applied on a glass substrate by a method such as printing, and the temperature is 400 ° C to 620 ° C.
This is probably because when burned at ℃, the incineration trace of the gel-like material forms relatively coarse and inhomogeneous voids, causing irregular reflection of light and inferior optical characteristics.

The coating liquid for forming a transparent conductive film of the present invention obtained by blending the above components has a high viscosity which is at least as high as the viscosity required for screen printing and suitable for a printing method.

Regarding the viscosity of the coating solution, in the case of screen printing, when the viscosity of the coating solution becomes low, such as 200 cps / 25 ° C., the coating solution flows to the back side from between the meshes when the coating solution is returned. As a result, a flow-down phenomenon that causes printing failure occurs, and the film thickness increases. For reference, Table 3 shows the viscosity of the coating liquid when ethyl cellulose [N200] was used. The viscosity of the coating liquid when using ethylcellulose [N200] is approximately 1/100 or less when using hydroxypropylcellulose.

[0027]

[Table 3]

The present invention is based on the chemical reaction between hydroxypropylcellulose and phenols, so that a high-viscosity coating solution can be obtained despite the relatively small amount of hydroxypropylcellulose added. As described above, a delicate and fine transparent conductive film pattern having an arbitrary shape can be formed on a substrate by using a printing method that requires a high viscosity of a coating solution.

Moreover, the coating liquid obtained by the present invention has a satisfactory leaking property to the substrate, and the solvent used has a high boiling point and a low evaporation rate, so that the viscosity stability during the coating operation and the leveling after coating are high. Thus, a transparent conductive film having good properties and thus having extremely small in-plane variations such as film thickness and flexural modulus can be obtained.

The coating film is generally dried by holding the substrate coated with the coating solution at a temperature of 80 to 160 ° C. for 10 to 60 minutes. And raising the temperature to 400 to 620 ° C.

FIG. 1 shows AcAcIn + AcA in the coating solution.
cSn content and sheet resistance (R) as film properties,
The relationship between the total light transmittance (LT) and the haze value (H) was shown. According to FIG. 1, when the (AcAcIn + AcAcSn) amount is 6% or less, the sheet resistance does not decrease,
% Is preferable. The practical upper limit is 40%. The composition of ingredients and production conditions
This is as shown in the figure.

The solubility of AcAcIn in a solvent is limited because, when it is added in excess, the undissolved portion present in a heterogeneously dispersed state makes the In / Sn concentration in the fired film non-uniform. It is thought that the optical characteristics are inferior.

FIG. 2 shows (AcAcSn / Ac) of the printed baked film.
(AcIn + AcAcSn) × 100% and the film characteristics are shown. With an increase in the amount of AcAcSn, the film is colored blue, and the degree increases. The decrease in the optical characteristics with the AcAcSn amount is due to this coloring. The composition of the components and the manufacturing conditions are shown in the figure.

According to FIG. 2, the AcAcSn amount is 5
% By weight is optimal, and the organic tins other than AcAcSn show the same tendency. Table 4 shows the relationship between the difference in the material composition of the coating liquid and the characteristics of the fired film. Table 4 shows that the smaller the amount of hydroxypropylcellulose and / or the amount of para-tert-butylphenol, the better the conductivity of the fired film.

[0035]

[Table 4]

FIG. 3 shows the effect of the firing temperature on the film characteristics. FIG. 3 shows the film characteristics of Samples 1 and 2 having the composition shown in FIG. From FIG. 3, it is understood that the film characteristics are more excellent as the temperature is increased.

The method of applying the coating liquid for forming a conductive film obtained by the present invention is not particularly limited, and any of conventionally known methods such as a dipping method, a spin coating method, and a printing method can be used.

The coating solution of the present invention can reduce the viscosity. For example, an organic solvent such as isophorone, acetylacetone, terpineol, ethylene brassate, or butylcyclohexyl acetate may be used alone and / or as a mixture, and this may be appropriately added as a diluent. Thereby, spin coating, spray coating, bar coating and blade coating can be formed.

[0039]

EXAMPLES The present invention will be described in detail with reference to the following Examples, but the present invention is not limited by these Examples.

Example 1 As a dibasic acid ester,
To 64 gr of a high boiling point solvent (DBE (manufactured by DuPont Japan)), 20 gr of para-tert-butylphenol was added and dissolved with stirring at room temperature for 10 minutes. Then, 4 gr of hydroxypropylcellulose was added, and 6
The mixture was dissolved with stirring at 0 ° C. for 1 hour to obtain a viscous liquid. To this viscous liquid was added 0.6 gr of AcAcSn and finally 11.4 g.
rAcAcIn was added, the temperature was raised to 160 ° C. while stirring, and the temperature was maintained for 1 hour. 500m while still hot
Using an esh screen, suction filtration and 80 kcps
/ 25 ° C. to obtain a coating solution for forming a conductive film.

100, 150, 200, 250, 270
The obtained coating liquid was screen-printed in a 5 cm square on a substrate obtained by cutting a general-purpose blue plate glass (thickness: 3 mm) into a 10 cm square as a window glass or the like using a mask of 300 mesh and 300 mm.

After drying at 120 ° C. for 10 minutes, it is put into a firing furnace,
The temperature was raised from room temperature to 500 ° C. over about 80 minutes, and kept as it was for 10 minutes. Next, 30 minutes later, when the furnace temperature became 300 ° C. or lower, the furnace was taken out to obtain a conductive film.

For the obtained conductive film, the sheet resistance was measured by a four-terminal method, the total light transmittance (LT) and the haze value (H) were measured by a haze meter, the hardness was measured by a pencil hardness meter, and the film thickness was measured by surface roughness. Each was measured with a total. Table 5 shows the results.

[0044]

[Table 5]

(Example 2) In 64 gr of benzyl acetate, 2
0 gr of para-tert-butylphenol was added and dissolved with stirring at room temperature for 10 minutes. Next, 4 gr of hydroxypropylcellulose was added and dissolved with stirring at 60 ° C. for 1 hour to obtain a viscous liquid. Add 0. 0 to this viscous liquid.
6gr of AcAcSn and 11.4gr of AcAcIn were added, the temperature was raised to 160 ° C with stirring, and the temperature was maintained for 1 hour. While still hot, a 500 mesh screen was used and suction filtration was performed to obtain a 24 kcps / 25 ° C. coating liquid for conductive film formation.

Printing, drying and baking were performed in the same manner as in Example 1 using masks of 270 mesh and 150 mesh to obtain a conductive film. Table 6 shows the properties of the obtained conductive film.

[0047]

[Table 6]

Example 3 The conductive film forming coating solution obtained in Example 1 was printed and dried in the same manner as in Example 1 using a 270 mesh mask. Then in oxygen 45 minutes
The temperature was raised to 20 ° C. After reaching this temperature, nitrogen was introduced, and when the inside of the furnace became a nitrogen atmosphere, the temperature was raised again and
Baking was performed at 00 ° C. for 10 minutes.

After cooling for about 4 hours, the furnace temperature was set to 150
Table 7 shows the properties of the fired film taken out after the temperature reached ℃.

[0050]

[Table 7]

(Example 4) 20 gr is added to 64 gr of DBE.
Of octylphenol was added and dissolved with stirring at room temperature for 10 minutes. Next, 4 gr of hydroxypropylcellulose was added and dissolved with stirring at 60 ° C. for 1 hour to obtain a viscous liquid. To this viscous liquid, 0.6 gr of AcAcSn and 11.4 gr of AcAcIn were added and stirred.
The temperature was raised to 0 ° C. and kept for 1 hour. While still hot, the viscous liquid was subjected to suction filtration using a 500 mesh screen to obtain a coating liquid for forming a conductive film at 150 kcps / 25 ° C. Next, the coating liquid obtained using a 270 mesh mask was printed, dried, and fired in the same manner as in Example 1 to form a transparent conductive film on the substrate. Table 8 shows the characteristics of the conductive film.

[0052]

[Table 8]

(Example 5) 20 gr is added to 64 gr of DBE.
Of nonylphenol was added with 4 gr of hydroxypropylcellulose and dissolved at 60 ° C. for 1 hour to obtain a viscous liquid. Then 0.6 gr of AcAcSn and 11.4 g
In the same manner as in Example 4 except that rAcAcIn was added, a coating film for forming a conductive film at 200 kcps / 25 ° C. was obtained. Next, the coating liquid obtained using the masks of 150, 200 and 270 mesh was printed, dried and dried in the same manner as in Example 1.
By firing, a transparent conductive film was formed on the substrate. 150mes
A fine crack was generated in the fired film using the mask of h. Table 9 shows the characteristics of the conductive film according to 200 and 270 mesh.

[0054]

[Table 9]

Example 6 20 gr is added to 64 gr of DBE.
Cashew nut shell liquid (3pentodedecency)
lphenol) was added with 4 gr of hydroxypropylcellulose and dissolved at 60 ° C for 1 hour to obtain a viscous liquid. Then 0.6 gr of AcAcSn and 11.4 g
In the same manner as in Example 1 except that rAcAcIn was added, a 300 kcps / 25 ° C. coating liquid for forming a conductive film was obtained. Next, 200, 250, 270 and 300 mesh
Using the mask described above, the obtained coating solution was printed and dried in the same manner as in Example 1, and baked at 500 ° C. for 1 hour to form a transparent conductive film on the substrate. Fine cracks were generated in the fired films using the masks of 200 and 250 mesh.
Table 10 shows the properties of the conductive film.

[0056]

[Table 10]

(Example 7) 5 gr of paratertiary butylphenol was added to 87 gr of DBE, and 1 gr of DBE was added.
Dissolve with stirring at room temperature for 0 minutes. Next, 1 gr of hydroxypropylcellulose was added and dissolved at 60 ° C. for 1 hour to obtain 0.3 gr of AcAcSn and 6.7 gr of Ac.
AcIn was added. After dissolving with stirring at 160 ° C. for 1 hour, the solution was suction-filtered with a 500 mesh screen while the solution was still hot to obtain a coating solution for forming a conductive film of 140 kcps / 25 ° C. Table 11 shows the viscosity when this coating solution was diluted with acetylacetone.

[0058]

[Table 11]

On the other hand, a blue plate glass (LT91.6%, H0.0%) having a size of 15 cm × 20 cm and a thickness of 2 mmt was placed in an oven at 80 ° C. for 20 minutes, heated, taken out of the furnace, and the glass plate was spun. 300 rpm with coater
, And 8 g of a coating liquid / acetylacetone = 60/40 diluent was applied instantaneously thereon, and the rotation was continued for 2 minutes after the application. Then, it was baked at 500 ° C. for 10 minutes in the same manner as in Example 1 to form a transparent conductive film. The formation of the conductive film was performed similarly at a rotation speed of 200 rpm. Table 12 shows the properties of the obtained conductive film.

[0060]

[Table 12]

Example 8 180 was added to 270 gr of DBE.
Add gr. para-tert-butylphenol and add 1
Dissolve with stirring at room temperature for 0 minutes. Next, 13 gr of hydroxypropylcellulose was added and dissolved with stirring at 60 ° C. for 1 hour to obtain a viscous liquid. 2. Add this viscous liquid to
1 gr of monobutyltin triacetate and finally 47.
5 gr of AcAcIn was added, the temperature was raised to 160 ° C. with stirring, and the temperature was maintained for 1 hour.

While still hot, the viscous liquid was filtered off with suction using a 500 mesh screen, and 16 kcps / 25 ° C.
A coating liquid for forming a conductive film was obtained.

On the other hand, 10
The coating solution obtained on a blue glass substrate of cm × 10 cm × 0.3 cm was screen-printed.

After drying at 120 ° C. for 10 minutes, it is placed in a firing furnace,
The temperature was raised from room temperature to 550 ° C. over about 90 minutes and maintained for 20 minutes. Then, after 30 minutes, when the furnace temperature was lowered to 300 ° C. or less, the furnace was taken out to obtain a conductive film.

Table 13 shows the characteristics of the obtained conductive film.

[0066]

[Table 13]

(Example 9) 32 kcp in the same manner as in Example 8 except that 3.9 gr of di-n-butoxytin was used in place of 2.1 gr of monobutyltin triacetate.
A coating solution for forming a conductive film having a s / 25 ° C. was obtained.

The characteristics of the conductive film obtained by printing, drying and firing in the same manner as in Example 8 were as shown in Table 14.

[0069]

[Table 14]

Example 10 Except that 2.5 gr of tin octylate was used in place of 2.1 gr of monobutyltin triacetate, the procedure was the same as in Example 8 except that 25 kcps /
A coating film for forming a conductive film at 25 ° C. was obtained.

Table 15 shows the characteristics of the conductive film obtained by printing, drying and firing in the same manner as in Example 8.

[0072]

[Table 15]

Comparative Example 1 Instead of 2.1 gr of monobutyltin triacetate, 1.3 gr of tin chloride SnCl _2.
Except that 2H ₂ O was used, 2
A coating solution for forming a conductive film at 5 kcps / 25 ° C. was obtained.

Table 16 shows the properties of the conductive film obtained by printing, drying and firing in the same manner as in Example 8.

[0075]

[Table 16]

Comparative Example 2 26.33 g of benzyl acetate
r, terpineol 42.33 gr, isophorone 9.1
2.94 gr of hydroxypropylcellulose was added to a mixed solution of 5 gr and 9.14 gr of acetylacetone,
The mixture was heated and dissolved at 160 ° C. for 8 hours with stirring to obtain a viscous liquid.

To this viscous liquid, 9.60 gr of indium octylate and 0.51 gr of tin octylate were added, and a coating solution for forming a conductive film of 1.8 kcps / 25 ° C. was obtained in the same manner as in Example 8. .

Table 17 shows the characteristics of the conductive film obtained by printing, drying and firing in the same manner as in Example 8.

[0079]

[Table 17]

As is clear from the comparison between the examples and the comparative examples, the conductive films according to the comparative examples are all inferior in total light transmittance and haze value and large in resistance value. While the resistance value is large, the coating liquid of the present invention is such that the conductive film obtained with high viscosity has a small resistance value, and the total light transmittance and the haze value are both excellent. It has been demonstrated that a practical transparent conductive film can be formed by spin coating using a diluent.

[0081]

As described above, the coating solution for forming a conductive film of the present invention has a high viscosity and a small resistance value. For example, a transparent conductive film having excellent film characteristics can be formed, and in particular, a transparent conductive film fine pattern of any shape can be formed on a substrate by simple steps of pattern printing, drying, and baking.

Further, firing at a low firing temperature is possible, and the obtained conductive film has good conductivity, mechanical strength,
Since it has excellent optical properties and small in-plane variation, it can be widely used for transparent electrodes and antistatic films of touch panels and display devices.

[Brief description of the drawings]

FIG. 1 is a view showing the relationship between the amount of [AcAcIn + AcAcSn] and the sheet resistance of a fired film.

FIG. 2 (AcAcSn) / (AcAcI) of a printed baked film
It is a figure which shows the relationship between n) * 100% and a film characteristic.

FIG. 3 is a diagram illustrating the effect of the firing temperature of a coating film on film characteristics.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hirotoshi Koizumi 7-9-4 Nishigotanda, Shinagawa-ku, Tokyo Tohoku Kako Co., Ltd. (56) References JP-A-61-9471 (JP, A) 57-199105 (JP, A) JP-B 63-19044 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01B 13/00 H01B 5/14 C09D 5/24

Claims (5)

(57) [Claims] 1. A coating solution for forming a transparent conductive film obtained by dissolving indium acetylacetone and organotin in a solvent and adding a viscous agent, wherein the solvent is an alkylphenol and / or alkenylphenol, and a dibasic acid. A coating liquid for forming a transparent conductive film, wherein the coating liquid is an ester and / or benzyl acetate, the viscous agent is hydroxypropylcellulose, and the added amount is 5% by weight or less. 2. The coating liquid for forming a transparent conductive film according to claim 1, wherein the contents of indium acetylacetone and organotin are 7% by weight to 40% by weight. 3. The coating liquid for forming a transparent conductive film according to claim 1, wherein the organic tin is tin acetylacetone. 4. The coating liquid for forming a transparent conductive film according to claim 1, wherein the addition amount of the alkylphenol and / or the alkenylphenol is 40% by weight or less. 5. The coating liquid for forming a transparent conductive film according to claim 1, further comprising a diluent, wherein the diluent is an organic solvent that reduces the viscosity of the coating liquid. A coating liquid for forming a transparent conductive film, comprising: