KR102575657B1 - Surface treatment and metal pattern formation method on polymer film substrate - Google Patents

Abstract

The present invention relates to a method for surface treatment and metal pattern formation on a polymer film substrate, and more particularly, to a surface-modified polymer film having excellent chemical bonding between catalytic ions and a substrate by subjecting a polymer film substrate to a wet surface treatment followed by a plasma dry treatment. It relates to a method for surface treatment and metal pattern formation on a polymer film substrate to produce a catalyst electrode pattern having excellent durability and adhesion on the polymer film.

Description

Surface treatment and metal pattern formation method on polymer film substrate {SURFACE TREATMENT AND METAL PATTERN FORMATION METHOD ON POLYMER FILM SUBSTRATE}

The present invention relates to a method for surface treatment and metal pattern formation on a polymer film substrate, and more particularly, to a surface-modified polymer film having excellent chemical bonding between catalytic ions and a substrate by subjecting a polymer film substrate to a wet surface treatment followed by a plasma dry treatment. It relates to a method for surface treatment and metal pattern formation on a polymer film substrate to produce a catalyst electrode pattern having excellent durability and adhesion on the polymer film.

Recently, flexible displays, flexible digital signage, flexible electronic devices, etc. have been developed using flexible substrates, and are increasingly being used.

In forming an electronic circuit on a flexible substrate, as a technology for forming a metal circuit pattern on a polymer film used as a dielectric for a flexible circuit board and a package, a metal film is deposited on the polymer film and a photoresist process is used to form a constant A method of manufacturing a pattern by forming a circuit pattern of the form and etching a metal is generally used. This photoresist process has disadvantages in that most of the chemicals are thrown away because electrode materials are applied to the entire surface of the substrate and then removed except for the electrode portion, resulting in high cost and large amount of wastewater.

In the case of using a printing technique using ink or catalyst ink, since only a desired electrode area is printed, the process complexity is lower than that of thin films and photoresists, and electrodes can be formed with a low-cost process. In the case of a printing process, adhesion with a polymer film is very important, and when a functional ink is printed on a flexible substrate such as a polymer substrate and the substrate is bent, if the adhesion of the metal is low, peeling or cracking may occur.

In the case of a printing process using ink or catalyst ink, it is necessary to form appropriate conditions on the surface of the polymer substrate. In particular, the polymer film, which is the basis of flexible devices, does not have a polar group on its surface, and its adhesive strength with electrodes is weakened due to low surface energy, poor wettability, and low adhesiveness. need this

In the case of polymer materials, they are physically and chemically hindered in the catalyst treatment and plating process due to low wetting characteristics and contamination of additives generated during processing, and as a result, the adhesion between polymer and metal is very low.

In order to solve this problem, many surface treatment techniques have been performed, and representatively, a method of inducing chemical bonding of polar groups on the surface of a polymer using an alkali solution such as potassium hydroxide or sodium hydroxide and increasing the surface area by surface irregularities is used.

However, although the wet surface treatment technology enables rapid surface treatment and has high adhesion between the electrode and the substrate, it is not easy to control the surface characteristics, and there are disadvantages in that various surface characteristics are exhibited depending on the type and manufacturer of the polymer resin film.

In order to improve the hydrophilicity, water repellency, and adhesiveness of polymer films, there is a film surface modification technology with dry methods such as plasma, ion beam, UV, and O ₃ that react with gas, and suitable surface treatment to improve the electrodeposition rate with catalyst ink need.

Republic of Korea Patent Registration No. 10-1220327 Republic of Korea Patent Publication No. 10-2010-0027526 Republic of Korea Patent Publication No. 10-2017-0132990 Republic of Korea Patent Publication No. 10-2016-0146187

The present invention is to meet the above needs, to prepare a surface-modified polymer film having excellent chemical bonding between catalytic ions and the substrate by subjecting a polymer film substrate to a wet surface treatment followed by a plasma dry treatment, durability and adhesion to the polymer film Its purpose is to provide a method for surface treatment and metal pattern formation on a polymer film substrate to form this excellent catalytic electrode pattern.

The features of the present invention for achieving the above object are,

A wet surface treatment step of immersing the polymer film substrate in an alkali solution to convert the hydrophobic surface into a hydrophilic surface by forming fine curves having polar groups on the surface of the polymer film substrate; a drying step of drying the polymer film substrate on which fine curves having polar groups are formed; a dry surface treatment step of dry-processing the surface of the polymer film substrate by atmospheric pressure plasma method to improve printability by lowering the contact angle of the surface of the dried polymer film substrate and improving surface roughness; and a catalyst electrode forming step of forming a catalyst electrode by printing the catalyst ink composition on the surface of the polymer film substrate and then depositing and reducing the catalyst ink composition in a reducing agent.

Here, the polymer film substrate is a transparent polyimide (CPI: Colorless Polyimide) film.

Here also, the alkali solution is KOH, NaOH, NH ₄ OH solution alone or in combination.

Here again, the catalyst ink composition includes a palladium salt, an ammonium salt and a stabilizer.

Here again, the reducing agent is any one selected from NaBH ₄ , HCOOH, C4H ₅ O ₆ , N ₂ H ₄ .

Here again, the catalyst electrode has a particle size of 40 nm or less.

According to the surface treatment and metal pattern formation method on the polymer film substrate of the present invention configured as described above, a polymer film having high wear and tensile strength is immersed in an alkali solution, dried, and the dried film is subjected to plasma dry treatment to form a polymer film. Bonding between the polymer film and catalytic ions is formed through chemical bonding through the surface treatment, so that catalyst particles can be uniformly distributed, the bonding force is relatively excellent, and a catalyst electrode with low electrical resistance can be obtained.

In addition, according to the present invention, since a relatively large number of polar groups exist on the surface of the polymer film substrate, the bonding strength between the catalyst and the electroless plating metal can be remarkably increased.

In addition, according to the present invention, it is possible to improve the deterioration of the adhesion between the polymer film and the metal, which is a disadvantage of the printing process, has excellent durability, and can prevent peeling of the metal pattern even when bent or bent.

1 is a process chart for explaining a method of surface treatment and metal pattern formation on a polymer film substrate according to the present invention.
2 is a chemical formula showing changes in the chemical structure of a transparent polyamide film substrate surface-treated with a KOH solution according to the present invention.
3 is an image showing a contact angle change before and after KOH solution surface treatment and plasma surface treatment of a transparent polyimide film substrate according to Examples and Comparative Examples of the present invention.
Figure 4 is a three-dimensional image of the surface of the transparent polyamide film substrate according to the KOH concentration according to Examples and Comparative Examples of the present invention ((a) before surface treatment, (b) 1M, (c) 3M, (d) 5M) am.
5 is a graph comparing bond strength of O functional groups of surface treatment with KOH solution alone, plasma surface treatment after KOH solution surface treatment, and plasma surface treatment only surface treatment samples of transparent polyimide film substrates according to Examples and Comparative Examples of the present invention. .
6 is a graph showing the comparison of OH functional group strength of KOH solution-only surface treatment, plasma surface treatment after KOH solution surface treatment, and plasma surface treatment alone surface treatment samples of transparent polyimide film substrates according to Examples and Comparative Examples of the present invention.
7 is a graph showing a comparison of the concentrations of O and N atoms in samples subjected to KOH solution alone surface treatment, plasma surface treatment after KOH solution surface treatment, and plasma surface treatment alone according to Examples and Comparative Examples of the present invention. am.
8 is a graph comparing the intensity of oxygen atoms in an O 1s orbit before and after plasma surface treatment of a transparent polyimide film substrate according to Examples and Comparative Examples of the present invention.
9 is a SEM photograph of catalyst particles attached to a transparent polyimide film substrate by reduction depending on whether or not the plasma treatment of the present invention is performed.
10 is a photograph of a catalyst electrode formed on a transparent polyimide film substrate according to the present invention.

Hereinafter, a method of surface treatment and metal pattern formation on a polymer film substrate according to the present invention will be described in detail with reference to the accompanying drawings.

In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted. In addition, terms to be described later are terms defined in consideration of functions in the present invention, which may vary according to the intention or custom of a user or operator. Therefore, the definition should be made based on the contents throughout this specification.

1 is a process chart for explaining a method of surface treatment and metal pattern formation on a polymer film substrate according to the present invention.

Referring to FIG. 1, the method of surface treatment and metal pattern formation on a polymer film substrate according to the present invention includes a wet surface treatment process (S10), a dry process (S20), a dry surface treatment process (S30), and catalyst electrode formation. It consists of a process (S40).

《Wet surface treatment process-S10》

First, a wet surface treatment is performed by immersing the polymer film substrate in an alkali solution to convert the hydrophobic surface into a hydrophilic surface by forming fine curves having polar groups on the surface of the polymer film substrate. The polymer film substrate applied to the present invention is preferably a fluorine-containing transparent polyimide (CPI: Colorless Polyimide) film.

At this time, it is preferable to use a transparent polyimide film immersed in a 1-3M alkaline solution and surface-treated for 10 to 30 minutes because Pd particles are uniformly dispersed and bonded to the transparent polyimide film. A KOH, NaOH or NH4OH solution may be used as the alkali solution, and these alkali solutions may be used alone or in combination.

As the concentration of the alkali solution increases to more than the maximum M (molar) concentration or as the treatment time becomes longer than the maximum value, an irregular surface is formed and the surface roughness increases, resulting in a decrease in bonding strength, so it is preferable to maintain the above range.

First, the wet surface treatment of the transparent polyimide film substrate shows the following surface characteristics. By forming fine curves with polar groups on the surface of the transparent polyimide film substrate, the hydrophobic surface is converted to a hydrophilic surface to improve the adhesion of the catalyst ink composition and the adhesion to the plating layer during electroless plating. was optimized.

Transparent polyimide film is a polymer material that is in the spotlight as a material with excellent thermal stability, chemical resistance and mechanical strength, and its application to the field of flexible printed circuit boards is expanding. However, since there is no polar group on the surface, there is a disadvantage in that the adhesive strength with metal or polymer material is lowered.

In order to improve these disadvantages, the present invention forms polar groups through wet surface treatment and dry surface treatment.

The characteristics of the transparent polyimide film substrate subjected to surface treatment for printing ink according to the present invention are shown in FIG. 2.

2 is a chemical formula showing changes in the chemical structure of a polyimide film substrate surface-treated with a KOH solution according to the present invention.

The transparent polyimide film substrate undergoes a surface reaction with an alkali solution, KOH solution, and the imide ring is opened by hydrolysis to generate a polar group.

《Drying Process-S20》

The surface-treated transparent polyimide film substrate is dried at room temperature.

《Dry surface treatment process-S30》

In order to increase the generation of polar oxygen groups that can chemically bond with Pd ²⁺ ions on the surface of the dried transparent polyimide film substrate and to improve printability by lowering the contact angle, it is necessary to perform chemical treatment and plasma surface treatment in parallel. there is.

Plasma surface treatment of the transparent polyimide film substrate decreased the contact angle from 70° to 22~35°, slightly increased the surface roughness, and greatly improved the printing characteristics of the substrate.

《Catalyst Electrode Process-S40》

First, the catalyst ink composition in the present invention is composed of a palladium salt, an ammonium salt, and a stabilizer. In the preparation of the catalyst ink composition, the catalyst ink is prepared by stirring the palladium salt and the ammonium salt in a solvent for 30 minutes to 2 hours, and the catalyst ink is stable. It is prepared by adding an agent and then filtering.

The catalyst ink may be prepared, for example, through the following method. When PdCl ₂ and NH ₄ Cl are added to pure water (H ₂ O) and stirred for about 1 hour to dissolve them, PdCl ₂ does not dissociate into Pd ²⁺ ions and Cl ^- ions in the solution, and PdCl ₂ 1M ( mol) to form a PdCl ₂ (H ₂ O) ₂ complex containing 2M water molecules.

[Scheme 1]

PdCl ₂ + 2NH ₄ Cl + 2H ₂ O → PdCl ₂ (H ₂ O) ₂ + 2NH ₃ + 2HCl

Then, a palladium catalyst ink can be prepared by adding 35% H ₂ O ₂ and 2-propanol as a stabilizer and filtering. The prepared palladium catalyst ink is preferably stored in a refrigerator.

In the present invention, the palladium salt serves as a precursor of the palladium complex, PdCl ₂ , PdSO ₄ , Pd(NO ₃ ) ₂ , K ₂ [PdCl ₄ ], [Pd(NH ₃ ) ₄ Cl ₂ ], [Pd( NH ₃ ) ₂ (NO ₂ ) ₂ ] and the like may be used alone or in a mixed form.

In the present invention, the ammonium salt serves to form a PdCl ₂ (H ₂ O) ₂ complex by dissolving the palladium salt in water, and NH ₄ Cl, (NH ₄ ) ₂ SO ₄ , (NH ₄ ) ₂ CO ₃ , NH ₄ NO ₃ and the like may be used alone or in combination, and the amount of the ammonium salt is preferably 50 to 200 parts by weight based on 100 parts by weight of the palladium salt. When using less than 50 parts by weight, it is difficult to dissolve the palladium salt in water, making it impossible to form a PdCl ₂ (H ₂ O) ₂ complex. When using more than 200 parts by weight, storage stability of the PdCl ₂ (H ₂ O) ₂ complex It is good to maintain the above range because there is a problem of lowering.

In the present invention, the stabilizer increases the stability of the solution by preventing metal precipitation (preventing Pd (II) from being precipitated as metal), and has a surface tension value lower than the surface tension value of water of 72.00 mN / m and a low viscosity. It has a role of facilitating inkjet printing by giving, and H ₂ O ₂ , propanol, isopropanol, butanol, methanol, etc. may be used alone or in combination. The amount of the stabilizer is preferably used in an amount of 2,000 to 6,000 parts by weight based on 100 parts by weight of the palladium salt. When using less than 2,000 parts by weight, there is a problem that the PdCl ₂ (H ₂ O) ₂ complex is precipitated as Pd(0) metal particles during the storage process, and inkjet printing is difficult due to increased surface tension and viscosity, and in excess of 6,000 parts by weight, When using PdCl ₂ (H ₂ O) ₂ The concentration of the complex is low, so it cannot act as a catalytic nucleus after reduction, so it is better to maintain the above range because there is a problem in that a metal circuit cannot be formed through electroless plating.

It is preferable to use pure water, distilled water, ion-exchanged water, etc. as the solvent, and it is preferable to use 10,000 to 150,000 parts by weight based on 100 parts by weight of the palladium salt. When less than 10,000 parts by weight is used, the concentration of the PdCl ₂ (H ₂ O) ₂ complex increases, reducing the bonding strength between the substrate and the metal circuit layer during electroless plating, and excessively increasing the consumption of catalyst ink. When used in excess of parts by weight, the concentration of the PdCl ₂ (H ₂ O) ₂ complex is low, making it difficult to form a Pd(0) catalyst electrode on the substrate.

After printing the catalyst ink composition prepared as described above on a plasma-treated transparent polyimide film substrate, it is reduced.

At this time, reduction may be performed by a chemical method using NaBH4, HCOOH, C4H5O6, N2H4, etc. as a reducing agent, but is not limited thereto. It is preferably reduced by precipitating in a 0.1 M NaBH4 solution at 50° C. for 5 minutes.

When catalyst ink is printed on the surface of the surface-treated transparent polyimide film and reduced, Pd ²⁺ ions are bonded to polar groups formed on the surface of the transparent polyamide film substrate, and a catalyst electrode is created. At this time, the catalyst electrode is preferably formed with a particle size of 40 nm or less capable of electroless plating.

Hereinafter, the present invention will be described in detail by examples.

<Example 1: Preparation of Palladium Catalyst Ink>

4 g of PdCl ₂ and 4 g of NH ₄ Cl were put into 2400 ml of pure water as a solvent and stirred for 1 hour to prepare a palladium catalyst ink. Thereafter, 15 ml of 35% H ₂ O ₂ and 125 g of 2-propanol were added as a stabilizer and filtered to prepare a palladium catalyst ink.

The prepared palladium catalyst ink was stored in a refrigerator at about 4°C.

<Example 2: Wet Surface Treatment of Transparent Polyimide Film Substrate>

A transparent polyimide film (Kolon Industries, CPI film) with a size of 50 × 80 mm was washed in distilled water for 30 minutes, immersed in 1M, 3M, 5M, and 7M KOH solutions for 10 minutes, 30 minutes, and 40 minutes, and then washed with distilled water. Wet surface treatment was completed by washing and drying at room temperature.

<Example 3: Dry Surface Treatment of Transparent Polyimide Film Substrate>

The transparent polyimide film subjected to the wet surface treatment in Example 2 was subjected to dry surface treatment using an atmospheric pressure plasma treatment machine. At this time, the atmospheric pressure plasma treatment machine used PVR 650 of API Co., Ltd., input power 220V, input frequency 50/80Hz, input current 15A, output power 15kV, output current 0.1A, air pressure 0.14MPa, surface treatment conditions: room temperature, normal pressure treated for 5 minutes.

<Example 4: Reduction after Printing with Palladium Catalyst Ink>

The palladium catalyst ink prepared in Example 1 was injected into an HP Deskjet Printer (D1560), printed on the transparent polyimide film substrate of Example 3 with a line width of 300 mm, and then reduced in a 0.1M NaBH4 solution at 50 ° C for 5 minutes ( Reduction) to prepare a catalyst electrode, washed with distilled water, and dried at room temperature.

《Experimental Example 1: Measurement of contact angle of transparent polyimide film according to wet treatment and wet/dry treatment》

In order to examine the change in contact angle according to the characteristics of the polyimide film, an experiment was performed with a wet-processed transparent polyimide film substrate and a wet-processed and then dry-processed transparent polyimide film substrate.

The contact angle of the transparent polyimide film substrate was measured by the sessile drop method using a Phoenix 300 from SEO.

contact angle change measurement sample Example 2
Contact angle (°) Example 3
Contact angle (°) One 66.68 22.35 2 71.02 22.46 3 74.75 22.83

3 shows the change in contact angle of a transparent polyimide film substrate subjected to wet surface treatment (rear surface before treatment in FIG. 3) and dry surface treatment (rear surface after treatment in FIG. 3) after wet surface treatment according to the present invention.

As shown in Table 1 and FIG. 3, in the case of Example 2 in which only wet surface treatment was performed, the CPI film exhibited a contact angle in the range of 66.68 to 74.75 ° (rear surface before treatment in FIG. 3) with low wettability, indicating that it had a surface unsuitable for printing. Able to know. However, in the case of Example 3, in which dry plasma surface treatment was performed after wet surface treatment, a contact angle in the range of 22.35 to 22.83 ° (rear side after treatment in FIG. 3) with sufficient wettability was obtained, indicating that a surface suitable for printing catalyst ink was formed. there is.

《Experimental Example 2: Measuring the surface state of a transparent polyimide film substrate》

An experiment was conducted to measure the surface state of the transparent polyimide film substrate according to Example 2. Figure 4 is a three-dimensional image of the surface of the transparent polyamide film substrate according to the KOH concentration according to Examples and Comparative Examples of the present invention ((a) before surface treatment, (b) 1M, (c) 3M, (d) 5M) am.

In FIG. 4, in the low-concentration KOH solution in the range of 1M and 3M, there are generally uniformly etched marks. As a result of measuring the surface state of the polyimide film substrate before surface treatment, the average roughness (Ra) was 1.530 nm as shown in (a). As shown in (b), the surface treated with 1M potassium hydroxide (KOH) solution has uniform curves with an average roughness (Ra) of 2.454 nm, and the surface treated with 3M KOH solution as shown in (c) It can be confirmed that the average roughness (Ra) of the surface is 3.261 nm, and the waviness is uniformly present.

《Experimental Example 3: Results of O functional group and OH radical bond strength of transparent polyimide film substrate》

5 is a graph comparing the strength of O functional groups of KOH solution alone surface treatment, plasma surface treatment after KOH solution surface treatment, and plasma surface treatment alone surface treatment samples of transparent polyimide film substrates according to Examples and Comparative Examples of the present invention, 6 is a graph comparing the intensity of OH radicals of KOH solution alone surface treatment, plasma surface treatment after KOH solution surface treatment, and plasma surface treatment only surface treatment samples of transparent polyimide film substrates according to Examples and Comparative Examples of the present invention.

As shown in FIG. 5, it can be seen that in the sample subjected to chemical treatment and plasma treatment, the most functional group (Oxygen Functional Group) capable of chemical bonding with Pd(II) ions is present on the surface of the transparent polyimide film substrate. . This indicates that the printability of the catalyst ink and the uniform pattern of the electrode can be formed by increasing the strength of the chemical bond with the catalyst ion.

As shown in FIG. 6, OH radicals capable of chemically bonding with Pd(II) ions formed by the functional group ring opening reaction of the transparent polyimide film in an alkaline solution are the transparent polyimide film of Example 3 It can be confirmed that it is most present on the substrate surface.

《Experimental Example 4: Results of Comparing Concentrations of O and N Atoms in Transparent Polyimide Film Substrate》

7 is a graph showing a comparison of concentrations of O and N atoms in surface treatment with KOH solution alone, plasma surface treatment after KOH solution surface treatment, and plasma surface treatment alone according to Examples and Comparative Examples of the present invention. am.

As shown in FIG. 7 , it can be confirmed that most of the oxygen and nitrogen polar groups forming a chemical bond with Pd(II) ions and a hydrophilic surface are present on the surface of the transparent polyimide film substrate of Example 3.

<<Experimental Example 5: Results of Comparison of Intensities of Oxygen Atoms in O 1s Orbitals of Transparent Polyimide Film Substrates>>

8 is a graph comparing the intensity of oxygen atoms in an O 1s orbit before and after plasma surface treatment of a transparent polyimide film substrate according to Examples and Comparative Examples of the present invention.

As shown in FIG. 8, it can be seen that the number of oxygen polar groups forming a chemical bond with Pd(II) ions and a hydrophilic surface rapidly increases on the surface of the transparent polyimide film substrate of Example 3.

《Experimental Example 6: Analysis of contact angle and shape of Pd(0) particles of transparent polyimide film according to wet treatment and wet/dry treatment》

FIG. 9 is a SEM photograph showing the attachment of catalyst particles to a transparent polyimide film substrate by reduction depending on whether or not the plasma treatment of the present invention is performed.

The shapes of the Pd(0) particles bonded to the transparent polyimide film substrates of Examples 2 and 3 were analyzed by FE SEM (Philips, XL-30S FEG) and are shown in FIG. 9 .

After printing Pd(II) catalyst ink on a transparent polyimide film substrate subjected to chemical treatment and plasma surface treatment in Example 3 and reducing it, SEM images of observing Pd(0) catalyst particles are (a) 1M KOH solution, ( b) The contact angle of the 3M KOH solution is about 23°, and the Pd(II) catalyst ink is printed on the transparent polyimide film substrate subjected to only the chemical treatment of Example 2, and the Pd(0) catalyst particles are observed after reduction. SEM image Through (c) 1M KOH solution, (d) 3M KOH solution, the contact angle is about 67°.

10 is a photograph of a catalyst electrode formed on a transparent polyimide film substrate according to the present invention, confirming that a catalyst electrode having a thickness of 5 to 8 μm is uniformly formed. A circuit electrode having excellent electrical conductivity and electrical resistance can be formed.

The present invention can be variously modified and can take various forms, and in the detailed description of the invention, only specific embodiments thereof have been described. However, it should be understood that the present invention is not limited to the particular forms mentioned in the detailed description, but rather it is understood to include all modifications, equivalents and substitutes within the spirit and scope of the present invention as defined by the appended claims. It should be.

Claims (6)

A polymer film substrate, which is a fluorine-containing transparent polyimide (CPI: Colorless Polyimide) film, is immersed in an alkali solution of KOH, NaOH, or NH4OH alone or mixed, and the imide ring is opened by hydrolysis to form a polar group on the surface. a wet surface treatment step of converting a hydrophobic surface into a hydrophilic surface by forming fine curves;
a drying step of drying the polymer film substrate formed with fine curves having polar groups;
A dry surface treatment step of dry-treating the surface of the polymer film substrate by atmospheric pressure plasma method to lower the contact angle of the surface of the dried polymer film substrate to 22 to 35 ° and improve surface roughness to improve printability; and
After printing a catalyst ink composition containing a palladium salt, an ammonium salt, and a stabilizer on the surface of the polymer film substrate, it is reduced by immersion in a reducing agent selected from NaBH ₄ , HCOOH, C4H ₅ O ₆ , and N ₂ H ₄ A method of surface treatment and metal pattern formation on a polymer film substrate, characterized in that it consists of a catalyst electrode forming step of forming a catalyst electrode having a particle size of 40 nm or less. delete delete delete delete delete