KR101081320B1 - Conductive paste composition - Google Patents

Abstract

The present invention prevents pattern roll drying by using a binder having a low Tg, and uses a binder having a high Tg to provide excellent print quality and mass productivity (continuous printing), and excludes or applies a small amount of a solvent having a low boiling point below 200 ° C. In addition, it is suitable for gravure offset printing because it is not possible to dry even in the fine line width of a large pattern including the solvent having a high boiling point of more than 200 ° C and high boiling point of more than 200 ° C, and is particularly suitable for gravure offset printing. Provided is a conductive paste composition capable of forming a fine pattern.

Conductive paste, conductive line, printing

Description

Conductive Paste Composition {CONDUCTIVE PASTE COMPOSITION}

The present invention relates to a conductive paste composition and a conductive line produced using the same, and more particularly to a conductive paste composition particularly suitable for gravure offset printing.

In recent years, plasma display panels (hereinafter referred to as PDPs) have been used in various fields because of their fast response speed and easy enlargement as compared with liquid crystal panels. Conventionally, as a method of forming an electrode on such a PDP, the patterning method of the electrode material using the screen printing method has been generally used. However, the conventional screen printing method requires a high degree of skill, and the viscosity is low when screen printing is performed, so that the paste can flow down on the substrate, and the accuracy of the screen is reduced. It is difficult to obtain a large screen pattern with a precision. In addition, the conventional screen printing method has a drawback that short-circuit or disconnection due to the screen when printing, the use thereof is gradually reduced.

On the other hand, in recent years, the photolithography method using the photosensitive resin composition was developed in order to form the high precision electrode circuit suitable for a large area. This uses a photosensitive resin composition in which fine conductive powder is dispersed to form a uniform thick film through a printing method, expose the formed thick film using a mask having a desired shape, and then implement a necessary pattern using an alkaline developer. It is a way.

However, when the pattern is formed using the photolithography method as described above, reprocessing of the material removed during the development process is required to reduce the manufacturing cost, and many discussions have been made.

In order to solve the above problems, researches on a method of directly forming a desired pattern on a substrate, such as an inkjet printing method or a gravure offset printing method, which are widely used in the conventional printing industry, are being conducted.

In the conventional conductive paste composition, when the pattern is formed using an inkjet printing method or a gravure offset printing method, in particular, a gravure offset printing method, a large amount of residue remains on the blanket due to the characteristics of the components of the conventional conductive paste composition. As a result, the number of continuous prints is remarkably dropped, and there are many problems in the straightness of the pattern or the gravure offset printing may not be possible at all.

In order to solve the above problems, the present invention is suitable for a gravure offset printing method capable of directly forming a fine pattern, and improves productivity by reducing process steps and reducing the amount of coating materials as compared with the conventional photolithography method. In addition, it is possible to reduce waste liquids such as aqueous alkali solution used during development, and to provide an electrically conductive paste composition that can improve environmental problems.

In addition, in the process of forming a pattern using the gravure offset printing method of the present invention, it is possible to provide a conductive paste which is excellent in print quality and mass productivity (number of continuous prints), and enables continuous printing even at a fine line width of a large pattern. For the purpose of

As a means for achieving the above object, the present invention provides a conductive powder, a Tg (glass transition temperature) of 0 ° C or less, a low Tg binder, a Tg of 50 ° C or more, a high Tg binder, high boiling point of 200 ℃ or more Provided is a conductive paste composition comprising a solvent. In the case of such a component, as a critically significant content, 65 to 88% by weight of the conductive powder, 1 to 3% by weight of low Tg binder, 3 to 12% by weight of high Tg binder, high boiling point solvent It provides a conductive paste composition comprising 4 to 20% by weight.

More preferably, in addition to the above components, a metal oxide and a glass frit are further included, and the solvent is a high boiling point solvent having a boiling point of 200 ° C. or higher, or a high boiling point solvent having a boiling point of 200 ° C. or higher and a low boiling point solvent having a boiling point of less than 200 ° C. It provides a conductive paste composition, characterized in that the mixture of. In the case of such a component, as a critically significant content, 65 to 88% by weight of the conductive powder, 1 to 3% by weight of low Tg binder, 3 to 12% by weight of high Tg binder, high boiling point solvent It provides a conductive paste composition comprising 4 to 20% by weight, 2 to 13% by weight of metal oxide, 1.5 to 6.5% by weight of glass frit, and 0.01 to 3% by weight of low boiling point solvent having a boiling point of less than 200 ° C.

The conductive paste composition having the above characteristics is particularly suitable for the gravure offset printing method, and when printing through the gravure offset printing method, the number of continuous prints (repeating printing and a predetermined amount on the blanket after the set process) The number of sheets printed until the residue remains, and the composition remaining on the blanket without transferring to the substrate during the Set process is more than 15% of the initial average line width of the blanket when observed with an optical microscope. Until the number of prints) is 100 or more, and the average line width is 25 µm or less.

In addition, when a conductive line having a width of 20 μm is formed through a gravure offset printing method, the pattern has a straightness of a pattern having a standard deviation of 2 or less in width.

The present invention also provides a conductive line manufactured by forming a pattern using the conductive paste composition and a display device having the conductive line.

Hereinafter, the present invention will be described in more detail. The following description is intended to assist in the understanding of the present invention by describing specific or optimal examples, so that there may be definite or limited expressions, but it is not intended to limit the scope of rights defined by the claims.

Conductive paste composition according to an embodiment of the present invention, the conductive powder, Tg (glass transition temperature) is 0 ℃ or less, low Tg binder, Tg is 50 ℃ or more, high Tg binder, high boiling point of 200 ℃ or more It characterized by comprising a solvent. In addition, other components may be added and are not limited. The detailed description of each component is as follows.

1) conductive powder

As a material which can be used as a conductive fine pattern, a metal powder having excellent electrical conductivity is preferable, and as a material that can be commonly used as an electrode, silver (Ag), gold (Au), platinum (Pt), rhodium (Rh) and palladium are typically used. At least one conductive metal powder selected from the group consisting of (Pd), nickel (Ni), aluminum (Al), and copper (Cu) may be used.

The content of the conductive metal powder may be used in a preferred range of 65 to 88% by weight. Although the content of the conventional conductive metal powder was determined based on the conductivity mainly, the present invention further studies the content threshold suitable for the offset printing process. As a result, when the content is less than 65%, the viscosity of the paste composition is so low that spreading can often occur on the substrate, unless there is another means to increase the viscosity, on the contrary, when the content exceeds 88% by weight, the composition rises in viscosity and especially Dispersion is difficult, there is a problem that the print quality may be reduced during the offset process.

2) Low Tg Binder Resin

The binder resin is set to be transferred from a gravure roll to a blanket roll in an offset process and to a substrate (such as a glass substrate) from a blanket roll. It is good to use the one that exhibits excellent ability. It was found that it is particularly important to use a binder resin having a low Tg in order to prevent such pattern roll drying to improve transfer characteristics.

The binder resin having a low Tg that can be used preferably has a Tg (glass transition temperature) of 0 ° C or less, and particularly preferably in the range of -60 to 0 ° C. Acrylic resins, polyester resins, urethane resins, and the like, and preferably, carboxyl group-containing monomers such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, clotonic acid, itaconic acid and citraconic acid; Hydroxyl group-containing monomers such as (meth) acrylic acid-2-hydroxyethyl, (meth) acrylic acid-2-hydroxypropyl, and (meth) acrylic acid-3-hydroxypropyl; Methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, n-lauryl (meth) acrylate, benzyl (meth) acrylate, glycidyl (meth) acrylate, iso-octyl acrylate, acrylic monomers such as iso-dodecyl (meth) acrylate; Copolymers polymerized with at least one monomer selected from the group such as polystyrene, poly (meth) acrylate, poly (meth) acrylic acid ester monomer, and the like are possible.

The content of the binder having a low Tg is 3 to 11% by weight, and when the coating composition is applied on the substrate, an appropriate viscosity is shown, and a weight average molecular weight (Mw) of 1,000 to 100,000 may be used.

3) High Tg Binder

In the present invention, when using a binder having a high Tg of more than 50 ℃ Tg 3 to 12% by weight in combination with a binder resin with a low Tg was found that the continuous printing ability during the offset printing operation greatly improved. Preferably it is Tg in the range of 50-150 degreeC. In addition, in the content, when the binder with a high Tg is less than 3%, the effect of continuous printing capability and the print shape may be deteriorated, and the print quality may be deteriorated. On the contrary, when the binder having a high Tg is used in excess of 12% by weight, the doctoring ( There is a problem that print quality deteriorates due to drying of pattern rolls during doctoring). Examples of the binder include epoxy, cellulose-based, and the like, but are not limited thereto, and one or more kinds thereof may be used.

4) solvent

Solvents are used to prepare dispersions containing the compositions described above, and organic solvents commonly used in the art are possible. The content of the solvent is not limited but is in the range of 4 to 20% by weight. Solvents that can be used are trimethyl pentamediol monoisobutyrate (TMP), butyl carbitol (BC), butyl cellosolve (BC), butyl carbitol acetate (BCA), terpinol isomer, terpine Organic solvents such as theol, toluene, texanol, Ether, and Glycol can be used. The content of such a solvent is 4 to 30 parts by weight so that the conductive paste composition has a viscosity of 100 to 100,000 cP, preferably 1,000 to 50,000 cP so that printing can be easily performed.

It is preferable to use 4-20 weight% of high boiling point solvents with a boiling point of 200 degreeC or more in a composition preferably. If the amount of high boiling point solvent is less than 4%, pattern roll drying may occur and print quality may be a problem. In addition, in order to prevent drying of the pattern roll, it is more preferable that a high boiling point solvent having a boiling point of 250 ° C. or more is contained in 13 to 50% by weight of the 200 ° C. high boiling point solvent.

In addition, when a low boiling point solvent having a boiling point of less than 200 ° C. is added in the above solvents, it may help in the three step of the gravure offset process, but may cause problems in print quality due to drying of the pattern roll during doctoring. It is advisable to avoid use as much as possible and, if used, to use within 3% by weight or less of the composition.

As another embodiment of the present invention, in addition to the components of the composition, a metal oxide, glass frit may be further included. In the case of having such a composition, as a critically significant content, 65 to 88% by weight of the conductive powder, 1 to 3% by weight of a low Tg binder, 3 to 12% by weight of a high Tg binder, and a high boiling point solvent, based on 100 weight of the total composition 4 to 17% by weight, metal oxides 2 to 13% by weight, glass frit 1.5 to 6.5% by weight, a low boiling point solvent having a boiling point of less than 200 ℃ or provides a conductive paste composition characterized in that it comprises 3% by weight or less. Components overlapping with the components of the above-described embodiment will be omitted, and then the components will be described.

5) metal oxides

In the conductive paste composition of the present invention, a metal oxide may be added to adjust contrast as necessary, and the amount of the metal oxide used is 2 to 13% by weight of the total composition. If the content is less than 2% by weight, the formed pattern may not exhibit blackness, and when the content exceeds 13% by weight, light transmittance is lowered, pattern resolution is lowered, and electrical conductivity is lowered. Examples of the metal oxide include Co ₂ O ₃ , Co ₃ O ₄ , MnO, MnO ₂ , Cr ₂ O ₃ , and at least one of them is used.

6) glass frit

The conductive paste composition of the present invention may further include a glass frit, and the glass frit contains lead oxide, bismuth oxide, zinc oxide and the like having a softening point of 300 to 500 ° C for low temperature firing (470 to 600 ° C). It is good to select and use at least 1 type from them.

The glass frit is 1.5 to 6.5% by weight of the total composition. If the content is less than 1.5%, the adhesion between the pattern and the substrate after firing is not easy, and if the content exceeds 6.5% by weight, the content of the conductive material or the organic binder is relatively low, and the conductivity and the pattern formability may be reduced.

In addition, various additives may be further added. As an example, a dispersant can be mentioned. Dispersants are used to enhance the dispersion stability of the composition and to prevent aggregation or precipitation from occurring. Dispersants that can be used include compounds having affinity polar groups such as carboxyl groups, hydroxyl groups, and acid esters, acid-containing compounds such as high molecular compounds, for example, phosphate esters, copolymers containing acid groups, and hydroxyl group-containing polycarboxylic acids. Esters, polysiloxanes, salts of long chain polyamino-amides and acid esters, and the like.

The content of the dispersant depends on the content and type of fine powder and is used at 0.5 to 3.0 parts by weight. In addition to the above composition, a polymerization inhibitor and an antioxidant for improving the preservation of the coating composition, an antifoaming agent for reducing bubbles in the paste, a leveling agent for improving the flatness of the film during printing, and a thixotropic agent for giving thixotropic properties may be further added.

The conductive paste composition according to the present invention can be particularly suitably used for the gravure offset printing method due to the organic combination between the components. As shown in the following examples, in the case of forming a pattern by printing through the gravure offset printing method with the conductive paste composition of the present invention, the number of continuous prints (repeated printing to a predetermined amount on the blanket after the Set process) The number of sheets printed until the remaining residues remained, which was not transferred to the substrate during the set process, and the composition remained on the blanket exceeded 15% of the initial average line width of the blanket when observed with an optical microscope. It can be seen that the number of prints until remaining) is 100 or more, and the average line width is 25 μm or less, and when a 20 μm wide conductive line is formed by gravure offset printing, the standard deviation of the conductive line width is It can be seen that the following properties are very suitable for gravure offset printing.

The present invention also provides a conductive line produced by forming a pattern using the conductive paste composition described above. The method of forming the pattern is not limited, but a method of printing the pattern directly on the substrate, such as gravure offset printing, inkjet printing, or imprinting, is preferable. Since the printing method is well known, a detailed description thereof will be omitted.

The present invention also provides a display device having the conductive line. The display device is not limited to PDP, LCD, OLED, and the like, and the conductive line may be an electrode provided in the display device, an electrode of an electromagnetic shielding mesh filter, or the like.

The conductive paste composition according to the present invention is mixed with a binder having a low Tg and a binder having a high Tg, so that the printing quality and mass productivity (number of continuous prints) are excellent, and a solvent having a low boiling point below 200 ° C. or a small amount is applied. This product is especially suitable for gravure offset printing, as it can be continuously printed because it does not dry even in the fine line width of large patterns, including solvent having high boiling point above 200 ℃ and high boiling point above 250 ℃. Patterns can be formed.

Hereinafter, the present invention will be described in more detail based on the following Examples and Comparative Examples. However, the following examples are not intended to limit the invention only.

 Examples 1-2, Comparative Examples 1-2

Preparation of Paste Composition

To prepare a paste using the compositions of Table 1 as follows.

1) An organic compound composed of a binder, a solvent, and an additive is put together in a mixer to prepare a vehicle mixed well by stirring.

2) While stirring the vehicle of 1), glass frit, metal powder and metal oxide are gradually added in order to combine.

3) The combined paste composition of 2 is mechanically mixed using a 3-roll mill.

4) Filtering removes impurities such as large particles and dust.

According to the paste manufacturing method, the compositions of Examples 1 and 2 and Comparative Examples 1 and 2 shown in Table 1 are blended.

Table 1

Example 1 Example 2 Comparative Example 1 Comparative Example 2 Conductive powder 75 75 75 75 Metal oxide 5 5 5 5 Glass frit 3 3 3 3 Low Tg Binder 7 7 7 7 High Tg Binder 3 2 3 0 additive One One One One Low boiling point solvent having a boiling point of 200 ° C or lower 0 0 4 3 High boiling point solvent with boiling point above 200 ℃
(High boiling point solvent having boiling point of 250 degrees Celsius or more) 6
(3) 7
(2) 2 6
(3)

(Numbers in weight percent)

Gravure offset printing evaluation of printing characteristics, minimum line width, and pattern straightness was performed using the printing paste compositions prepared in Examples 1 and 2 and Comparative Examples 1 and 2, and the results are shown in FIG. 1 and Table 2 below. .

The number of continuous prints is the number of sheets printed repeatedly until a predetermined amount of residues remain on the blanket after the set process, and remain on the blanket without being transferred to the substrate during the set process. The number of prints until the composition remained more than 15% of the initial average line width of the blanket when observed with an optical microscope,

"○" means no printing composition remaining during the set process, and "×" means the case where the excess of the printing composition remains on the blanket during the set process and pattern transfer is impossible on the substrate. The minimum line width measured the minimum size of the pattern that can be formed by gravure offset printing. In addition, the pattern straightness observed the degree of linearity of the pattern formed on the substrate after printing with an optical microscope, and the linearity of the pattern was less than 1.5. , The standard deviation is 1.5 ~ 2.5 △, the standard deviation is represented by 이상 when 2.5 or more.

[Table 2]

Example 1 Example 2 Comparative Example 1 Comparative Example 2 Remarks Number of Continuous Prints 130 sheets 120 sheets 40 sheets 10 sheets Printing characteristics ○ ○ ○ ○ Average line width 21 20 14 28 Design value: 30㎛ Pattern Straightness ○ ○ △ X

As can be seen in Table 2 and FIG. 1, the examples show that the number of continuous prints is more than 100 compared to the comparative example, and the pattern straightness is also very excellent.

1 is a photograph showing the gravure offset printing after using the printing paste composition prepared according to Examples 1 and 2 and Comparative Examples 1 and 2 of the present invention.

Claims (8)

As an electrically conductive paste composition containing electroconductive powder, a binder, and a solvent, The solvent is a high boiling point solvent having a boiling point of 200 ° C. or more, or a mixture of a high boiling point solvent having a boiling point of 200 ° C. or more and a low boiling point solvent having a boiling point of less than 200 ° C., 4 to 20% by weight of the high boiling point solvent, a low boiling point solvent having a boiling point of less than 200 ℃ relative to 100 weight of the total composition, or less than 3% by weight, The low boiling point solvent, the low boiling point solvent / high boiling point solvent = 1/10 weight ratio or less, The high-boiling solvent is a conductive paste composition containing 13 to 50% by weight of the high boiling point solvent of 250 ℃ or more of the high boiling point solvent. The method of claim 1, further comprising a metal oxide and a glass frit, wherein the binder is mixed with a binder having a low Tg with a Tg (glass transition temperature) of 0 ° C. or less and a binder having a high Tg of 50 ° C. or more. Electroconductive paste composition characterized by the above-mentioned. The method according to claim 2, wherein the conductive powder is 65 to 88% by weight of the total composition, 1 to 3% by weight of the low Tg binder, 3 to 12% by weight of the high Tg binder, 2 to 13% by weight of the metal oxide, glass frit Conductive paste composition comprising 1.5 to 6.5% by weight. delete According to any one of claims 1 to 3, when printing through the gravure offset printing method, when the number of continuous prints (repeated printing to leave a predetermined amount of residue on the blanket after the Set process) The number of sheets printed up to and including the composition remaining on the blanket and not transferred to the substrate during the set process until the remaining amount exceeds 15% of the initial average line width of the blanket when observed by optical microscope The number of printed sheets) is 100 sheets or more, and the average line width is 25 micrometers or less, The electrically conductive paste composition characterized by the above-mentioned. The conductive paste composition according to any one of claims 1 to 3, wherein the standard deviation of the conductive line width is 2 or less when forming a conductive line having a width of 20 탆 through gravure offset printing. The conductive line manufactured by forming a pattern using the electrically conductive paste composition of any one of Claims 1-3. Display device provided with the conductive line of Claim 7.

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