KR100964561B1 - Conductive adhesive composition - Google Patents

Abstract

PURPOSE: An acryl conductive adhesive composition is provided to effectively improve conductivity and adhesion by having graphene with a conductive filler. CONSTITUTION: A conductive adhesive composition contains 100.0 weight parts of acrylic adhesive, 0.1-15 weight parts of graphene powder, and 0.1-10 weight parts of cross-linking agent. The composition further contains 0.001-30 weight parts of fatty acid having 5 or more carbon atoms. The cross-linking agent is a compound having two or more epoxy groups, isocyanate groups, amine groups, or aziridine groups. A method for adding fatty acid to the composition comprises a step of dispersing graphene in 20-200 times of solvent, a step of adding fatty acid having 5 or more fatty acid, a step of stirring strongly, and a step of treating the surface of the graphene.

Description

Conductive Adhesive Composition

The present invention relates to a conductive adhesive composition, in particular a conductive adhesive composition containing graphene, and an adhesive protective film coated on the base film.

Electronic components or devices are attached with a protective film to minimize surface damage during transportation, storage and assembly. The protective film should be provided with conductivity so as not to damage the device caused by the generation of static electricity.

Substances added to impart conductivity to the pressure-sensitive adhesive include surfactants, conductive polymers, and the like. However, the surfactant has a disadvantage that the antistatic function is reduced when the humidity is low, and the degree of conductivity provision is not large. In addition, the conductive polymer is poor in compatibility with the pressure-sensitive adhesive has a problem that it is not easy to effectively improve the conductivity. In addition, conductive fillers such as metal fibers, metal flakes, carbon black, graphite, and the like may be added, but most of them may cause a weakening of adhesive strength or miscibility with the adhesive.

Since the conductive filler has a larger surface area as the particle size decreases, a higher conductivity improvement effect can be obtained when the same amount is added. Accordingly, researches actively using nano-sized conductive materials such as carbon nanotubes have been actively conducted. However, carbon nanotubes also have a problem that it is not easy to be uniformly dispersed due to poor compatibility with the pressure-sensitive adhesive.

The present invention is to provide an acrylic conductive pressure-sensitive adhesive composition effectively expressing conductivity and adhesion.

In addition, the present invention is to provide an adhesive protective film having good conductivity and excellent adhesion.

The present inventors have observed that the use of graphene as the conductive filler can effectively improve the conductivity of the pressure-sensitive adhesive, and can also improve the adhesion by the surface treatment of the graphene to complete the contents of the present invention.

According to the present invention, 100 parts by weight of the acrylic pressure-sensitive adhesive; 0.1 to 15 parts by weight of graphene powder; And 0.1 to 10 parts by weight of the crosslinking agent is provided.

In addition, according to the present invention, 100 parts by weight of the acrylic pressure-sensitive adhesive; 0.1 to 15 parts by weight of graphene powder; 0.001 to 30 parts by weight of fatty acid having 5 or more carbon atoms; And 0.1 to 10 parts by weight of the crosslinking agent is provided.

In addition, according to the present invention, there is provided a protective film for an electronic component coated with the conductive adhesive composition on a base film.

The compositional component ratio in the conductive adhesive composition is based on solids, and the solvents and dispersions used in the preparation of the composition are considered to be completely evaporated (dried) to the final adhesive sheet or film.

The acrylic pressure-sensitive adhesive is prepared by radical polymerization in a solvent with an acrylic monomer as a main component. Acrylic monomers are mainly composed of condensates of aliphatic alcohols such as 2-ethylhexyl acrylate, butyl acrylate and acrylic acid or methacrylic acid, which have a glass transition temperature of less than room temperature. do. In addition, a vinyl compound having a carboxylic acid group, for example, acrylic acid, methacrylic acid, itaconic acid, and the like are copolymerized together to give a synergistic effect to adhesion and provide a crosslinking point for increasing heat resistance. The vinyl compound having a carboxylic acid group is used in the range of 1 to 20% by weight. When the amount is less than this, heat resistance and adhesive strength decrease, and in excessive cases, the glass transition temperature of the pressure-sensitive adhesive increases to decrease the adhesive strength. Some vinyl-based monomers, such as other vinyl acetates, can be copolymerized, and their amount is less than 40 weight percent. As the polymerization initiator, a peroxide such as benzoyl peroxide, an azo compound such as 2,2'-azobisisobutyronitrile (AIBN), or the like can be used. Other compounds capable of generating radicals or a combination thereof can also be used.

Solution Contents of the polymer when the polymerized acrylic pressure-sensitive adhesive solution is prepared and the pressure-sensitive adhesive composition is coated on the base film. That is, it is preferable to use the solids content in the range of 10 to 70 percent. If the content is less than this, it takes a long time to remove the solvent after coating the pressure-sensitive adhesive, the viscosity is too low may cause a problem flowing down after coating on the film. If the content is more than this range, the viscosity is too high, the coating is not easy to occur.

In the present invention, the graphene is preferably dispersed in a medium and mixed with the pressure-sensitive adhesive. Graphene is produced by swelling and peeling the layers constituting the graphite oxide by heating the graphite oxide to a high temperature instantaneously. That is, when graphite oxide is instantaneously heated to a high temperature of 300 ° C. or higher, gaseous products such as carbon dioxide generated by reduction and decomposition of functional groups on the surface generated by oxidation are vaporized instantaneously, and each layer of graphite oxide is peeled off to remove the graphite, That is, graphene is made. The degree of peeling varies depending on the degree of oxidation of the graphite oxide used for peeling, and the degree of peeling may be improved by further ultrasonication. As the polar groups attached to the graphite oxide decompose and decompose, carbon dioxide is generated and some polar groups remain polarized and serve to improve dispersion in the composition. Graphene is a structure in which carbon nanotubes are laid out in a flat state, and thus have high conductivity corresponding to carbon nanotubes, excellent mechanical properties, and long horizontal and vertical lengths compared to thickness, and thus have a very large surface area. Even small additions can achieve significant improvements in conductivity and mechanical properties. Graphene is inexpensive to produce if graphite is used as a raw material. Graphene prepared from graphite oxide can be judged to have a greater degree of peeling as the X-ray diffraction peak of graphite at 2θ = 26.5 ° and the X-ray diffraction peak of graphite oxide at 2θ = 13 ° are minimized. . The surface area of the exfoliated graphite is in the range of 10 to 3000 m ² / g, and the larger the surface area, the greater the conductivity enhancement effect when uniformly dispersed in the same amount, but relatively uniform dispersion tends to be difficult.

The graphite oxide is prepared by oxidizing graphite powder using nitric acid, NaClO ₃ , KClO ₃ , KMnO ₄ , or other oxidizing agents alone or in combination, and may be prepared by oxidizing by electrochemical method. The ratio of the number of carbon / oxygen in the graphite oxide powder may be in the range of 1 to 20/1 but may be smaller or larger than this depending on the degree of oxidation. Graphite oxide powder usually has peaks around 2θ = 13 ° in wide-angle X-ray diffraction analysis because the distance between layers is about 7Å, but the values may vary depending on the degree of oxidation and absorption of moisture.

In the present invention, the fatty acid having 5 or more carbon atoms is a compound having a carboxylic acid group attached to an aromatic, aliphatic, or alicyclic compound having 5 or more carbon atoms. As the fatty acid has more aromatic structure, physical adsorption on the graphene surface is easier, which is advantageous for improving the adhesive force, which is the purpose of the present patent. Representative aromatic carboxylic acid structure fatty acids include pyrenecarboxylic acid, pyreneacetic acid, pyrenebutyric acid and the like. Aliphatic fatty acids include stearic acid and lauric acid. Fatty acid is suitably used in the range of 0.1 to 200 parts per 100 parts of graphene, less than this is not noticeable adhesion improvement effect, more than this is insignificant additional adhesion improvement effect.

The method of adding a fatty acid to the adhesive composition is preferably, after dispersing the graphene in a solvent of 20 to 200 times by weight, the fatty acid is added and then vigorously stirred to add the surface after the graphene is surface treated. In this case, by applying energy by irradiating ultrasonic waves, the amount of fatty acids attached to the surface of the graphene may be increased. The treatment time is preferably about 10 minutes to 2 hours.

The crosslinker reacts with the carboxylic acid of the pressure-sensitive adhesive to form a crosslink, thereby increasing heat resistance of the pressure-sensitive adhesive and also removing the pressure-sensitive adhesive component upon removal of the pressure-sensitive adhesive sheet or pressure-sensitive adhesive film. Such crosslinking agents are preferably compounds having two or more epoxy groups, isocyanate groups, amine groups, aziridine groups and the like in the molecule. For example N, N, N ', N'- tetraglycidyl - m - xylene, Boutique amine (N, N, N', N'-tetraglycidyl- m -xylenediamine), iso-butylated melamine (iso- butylated melamine), polyfunctional aziridine, and the like. In addition, compounds such as aluminum acetylacetonate, which uses metal chelate bonds for crosslinking, may also be used.

In the present invention, the pressure-sensitive adhesive composition is prepared by mixing the acrylic pressure-sensitive adhesive solution, the graphene dispersion or the dispersion obtained by surface treatment of the graphene with a fatty acid and a crosslinking agent, and then evaporating the solvent. When the solvent is removed, the temperature is preferably maintained at 100 ° C. or higher so that a reaction between the carboxylic acid group of the pressure-sensitive adhesive and the crosslinking agent occurs.

The conductive adhesive composition of the present invention is preferably coated on the base film and can be used for the protective film of the electronic component. The base film is generally a polymer film, for example, a polyethylene film or a polyester film. The back side of this protective film may further have a release film removed at the time of use.

According to the present invention, while the conductivity is effectively improved by the graphene, it is possible to prepare an acrylic pressure-sensitive adhesive composition with improved adhesion.

The following examples illustrate the invention in detail. However, the scope of the present invention should not be construed as being limited to these examples.

Production Example

Each component of an electroconductive adhesive composition is manufactured as follows.

Preparation of Acrylic Adhesive

144 g of ethyl acetate, 68 g of toluene, and 3.3 g of itaconic acid were added to the reactor and heated to 70 ° C. 100 g of a mixture of 210 g of 2-ethylhexyl acrylate, 134 g of butyl acrylate, 44 g of vinyl acetate, 9.0 g of acrylic acid, and 0.56 g of benzoyl peroxide was first introduced into the reactor and the rest was about 1 hour and 30 minutes. Feed slowly over. After the addition was completed, the reaction was carried out for about 1 hour, and then a solution of 0.16 g of 2,2'-azobisisobutyronitrile was added to 12 g of toluene, followed by further 3 hours of reaction. After the reaction, 252 g of toluene and 123 g of methanol were further added to prepare 1000 g of a pressure-sensitive adhesive solution having a solid content of 40 weight percent.

Preparation of Graphene

Into a 500 mL reactor equipped with a stirrer, a thermometer, etc., 5 g of graphite powder (Hyundai Cooma Co., Ltd. HC-908, average particle size of 8 μm) and 100 mL of fuming nitric acid were added and stirred while maintaining at 0 ° C., followed by 40 g of potassium chlorate. Was slowly added over 2 hours, and the graphite was oxidized while stirring at room temperature for 24 hours. The oxidized graphite was filtered off and washed with distilled water until the pH was about 6. The filtered graphite oxide was dried for 2 days at 50 ° C. in vacuum, then crushed and passed through 100 mesh. The elemental analysis showed that the atomic composition was C ₁₀ O _{3 .55} H _{1 . It} was ₃₂ .

The dried graphite oxide prepared by the above method was put in a quartz tube, flowed with nitrogen gas, and then put into an electric furnace at 1100 ° C. for 1 minute to obtain graphene in which each layer of graphite was thinly thin. The atomic composition of graphene was C ₁₀ O _0.76 H _0.91 and the apparent volume was 320 cm ³ / g.

Graphene  Preparation of Dispersion

According to the embodiment, 1 to 5 g of graphene powder were added to 100 wt. Times of ethyl acetate, and then ultrasonic waves were added at room temperature for 2 hours to obtain a graphene dispersion.

Surface treatment Graphene  Preparation of Dispersion

4 g of graphene powder was dispersed in 400 g of ethyl acetate for use in Examples 6 to 12, 0.04 to 0.60 g of pyrenebutyric acid was added thereto, and surface treatment was performed by adding ultrasonic wave at room temperature for 2 hours. The prepared graphene dispersion was obtained.

Comparative example  One

250 g of the pressure-sensitive adhesive solution prepared in the above preparation (100 g on a solid basis) and 3 g of a crosslinking agent, N, N, N ', N'-tetraglycidyl- m -xylenediaamine, were stirred and mixed at 1500 rpm for 10 minutes. Then, after pouring the mixed solution on the release paper, and dried at 120 ℃ 35 minutes to obtain a pressure-sensitive adhesive composition film of 75 μm, it was pressed on a polyethylene terephthalate (PET) film and then removed the release paper, the pressure-sensitive adhesive composition to PET film This coated protective film was prepared.

The coated adhesive surface resistance was measured by the surface resistance meter (ST-3) of Simco, Japan.

Adhesion was measured by attaching a 1 cm wide protective film to stainless steel, pressing 10 times with a 666 g roller, and peeling 180 ° at 200 mm / min with an Oriental tensile tester (OTU-2). The physical properties are summarized in Table 1.

Example  One

250 g of the pressure-sensitive adhesive solution prepared in the preparation example (100 g on a solids basis), 3 g of N, N, N ', N'-tetraglycidyl- m -xylenediaamine as a crosslinking agent and 101 g of a graphene dispersion (based on graphene) 1 g) was stirred at 1500 rpm for 10 minutes, mixed, poured onto a release paper, and then dried at 120 ° C. for 35 minutes to obtain a 75 μm-thick pressure-sensitive adhesive composition film, which was then pressed onto a polyethylene terephthalate (PET) film. After removing the release paper, a protective film coated with a pressure-sensitive adhesive composition on a PET film was prepared.

Coated adhesive surface resistance was measured by Simco, Japan's Surface Resistance Meter (ST-3). Adhesion was measured by attaching a protective film of 1 cm width to stainless steel, pressing it ten times with a 666 g roller, and then using a tensile tester (OTU-) of Oriental. It measured while peeling 180 degrees at 200 mm / min in 2). The physical properties are summarized in Table 1.

Example  2 ~ 5

The graphene dispersion prepared in the above Preparation Example was carried out as in Example 1` except that the graphene dispersion was changed to 2 to 5g, respectively. The composition ratio of the composition (based on the solid matter except the solvent) and its physical properties are summarized in Table 1.

Example  6

250 g of the pressure-sensitive adhesive solution prepared in the above preparation (100 g on a solids basis), 3 g of N, N, N ', N'-tetraglycidyl- m -xylenediaamine and 4 g of graphene, which are crosslinking agents, 400 g of ethyl After dispersing in acetate and adding 0.04 g of pyrenebutyric acid and stirring 404.04 g of the surface-treated graphene dispersion at 1500 rpm for 10 minutes, the mixture was poured onto a release paper, dried at 120 ° C. for 35 minutes, and then dried to a thickness of 75 A pressure-sensitive adhesive composition film was obtained, which was pressed onto a polyethylene terephthalate (PET) film to be transferred, and then the release paper was removed to prepare a protective film coated with the adhesive composition on a PET film.

The coated adhesive surface resistance was measured by the surface resistance meter (ST-3) of Simco, Japan.

Adhesion was measured by attaching a protective film having a width of 1 cm to stainless steel, pressing 10 times with a 666 g roller, and peeling 180 ° at 200 mm / min with an Oriental tensile tester (OTU-2). The physical properties of the composition are summarized in Table 2.

Example  7-12

Except for using the surface-treated graphene dispersion prepared by adding 0.08 to 0.60 g of pyrene butyric acid, respectively, it was carried out as in Example 6. The composition ratio of the composition (based on solid matter except solvent) and its physical properties are summarized in Table 2.

Example  13

250g of the pressure-sensitive adhesive solution prepared in the preparation example (100g on a solids basis), 3g of N, N, N ', N'-tetraglycidyl- m -xylenediaamine as a crosslinking agent and 404g of a graphene dispersion (based on graphene) 4 g) was stirred and mixed at 1500 rpm for 10 minutes, and then 0.04 g of pyrenebutyric acid was further added, and stirred and mixed at 1500 rpm for 10 minutes. The mixed solution was poured on a release paper, dried at 120 ° C. for 35 minutes, and then dried. A 75 μm pressure-sensitive adhesive composition film was obtained, and the resultant was pressed onto a polyethylene terephthalate (PET) film, and then release paper was removed to prepare a protective film coated with a pressure-sensitive adhesive composition on a PET film.

The coated adhesive surface resistance was measured by the surface resistance meter (ST-3) of Simco, Japan.

Adhesion was measured by attaching a 1 cm wide protective film to stainless steel, pressing 10 times with a 666 g roller, and peeling 180 ° at 200 mm / min with an Oriental tensile tester (OTU-2). The physical properties of the composition are summarized in Table 3.

Example  14-16

The same procedure as in Example 13 was carried out except that the weight of pyrenebutyric acid was added differently. Table 3 shows the composition ratio (based on solid matter except solvent) and the physical properties of the composition.

Analysis

In Comparative Example 1 and Examples 1 to 5 of Table 1 it can be seen that the surface resistance is significantly reduced as the graphene content increases in the pressure-sensitive adhesive composition, which shows that the graphene effectively improves the conductivity of the pressure-sensitive adhesive. However, it can be seen that the adhesion decreases with increasing graphene content.

In Examples 6 to 12 of Table 2, when using graphene surface-treated with pyrenebutyric acid, surface resistance was similar to that of untreated graphene (Example 4), but the adhesion was increased. Can be. This adhesion improvement effect can be seen in Example 6 that even if the graphene is treated with a small amount of pyrene butyric acid. This is because the aromatic carboxylic acid containing at least one aromatic ring such as hydrocarbon carboxylic acid, in particular pyrenebutyric acid, is adsorbed to the graphene due to its similarity to the graphene structure (flat polyaromatic ring structure) and expresses particularly high adhesion by such adsorption. Estimate.

However, in Examples 13 to 16, in which graphene was first mixed with the adhesive, followed by pyrenebutyric acid, the surface resistance values were similarly reduced, but no improvement in adhesion was observed. These results show that when pyrenbutyric acid is well adsorbed on the surface of the graphene by the same method as the ultrasonic mixing, it is possible to express an adhesion improving effect.

Table 1. Adhesive composition and physical properties

Table 2. Adhesive Composition and Physical Properties

Table 3. Adhesive Composition and Physical Properties

Claims (6)

100 parts by weight of an acrylic adhesive; 0.1 to 15 parts by weight of graphene powder; And 0.1 to 10 parts by weight of a crosslinking agent. The conductive pressure-sensitive adhesive composition of claim 1, further comprising 0.001 to 30 parts by weight of a fatty acid having 5 or more carbon atoms. The conductive adhesive composition according to claim 1 or 2, wherein the crosslinking agent is a compound having two or more epoxy groups, isocyanate groups, amine groups or aziridine groups in the molecule. The method of claim 2, wherein the fatty acid is added to the adhesive composition, and the graphene is dispersed in 20 to 200 times the solvent, and then, the fatty acid having 5 or more carbon atoms is added and vigorously stirred to surface-treat the graphene. Conductive adhesive composition to be added The conductive adhesive composition according to claim 4, wherein the fatty acid having 5 or more carbon atoms is an aromatic fatty acid and an ultrasonic wave is applied when the aromatic fatty acid is added. The protective film for electronic parts according to claim 2, wherein the conductive adhesive composition of claim 2 is coated on a base film.