CN115279858A - Adhesive composition - Google Patents

Abstract

The adhesive composition of the present invention provides an adhesive composition which has excellent flexibility of an uncured coating film, and is excellent in heat resistance of a wet solder and peel strength at high temperatures as an adhesive for a flexible printed wiring board. The adhesive composition of the invention comprises a polyester having a glass transition temperature or melting point of greater than 80 ℃ and a polyisocyanate.

Description

adhesive composition

technical field

The present invention relates to an adhesive composition. In more detail, it is related with the adhesive composition which is excellent in the flexibility of an uncured coating film, and is excellent in the heat resistance of humidified solder as an adhesive agent for flexible printed wiring boards, and the peel strength at high temperature.

Background technique

Flexible printed circuit board (FPC) refers to a substrate on which a thin and flexible insulating film such as polyimide is bonded to a conductive metal such as copper foil with an adhesive, and a circuit is formed on it. . Unlike rigid substrates, since they are very thin and flexible, they can be used in small spaces or curved movable parts of electronic devices, so they are used in many everyday electronic devices such as personal computers and smartphones. In recent years, many FPCs are mounted on automobiles, so adhesives are required to have high-temperature adhesiveness.

Polyester is widely used as a raw material for resin compositions used in coating agents, inks, and adhesives, and is usually composed of polyvalent carboxylic acids and polyhydric alcohols. Since the flexibility and molecular weight can be freely controlled by the selection and combination of polycarboxylic acids and polyhydric alcohols, it is widely used in various applications including coating agent applications and adhesive applications.

Polyester has excellent adhesiveness (peel strength) to metals including copper, and is used in an adhesive for FPC in combination with a curing agent.

(eg, Patent Document 1).

prior art literature

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 9-125043

Contents of the invention

The problem to be solved by the invention

However, the polyester resin described in Patent Document 1 is composed only of a polyester resin having a glass transition temperature (Tg) as low as 80° C. or lower, and thus has insufficient peel strength at high temperatures.

The present invention has been accomplished against the background of the above-mentioned problems of the prior art. That is, an object of the present invention is to provide an adhesive that is excellent in flexibility of an uncured coating film (B stage), and is excellent in humidity solder heat resistance and peel strength at high temperature as an adhesive for flexible printed wiring boards. combination.

means to solve the problem

As a result of intensive studies, the inventors of the present invention found that the above-mentioned problems can be solved by the following means, and completed the present invention.

That is, the present invention has the following configurations.

An adhesive composition comprising polyester (A1) and polyisocyanate (B) having a glass transition temperature or a melting point higher than 80°C.

The adhesive composition described above preferably further contains a polyester (A2) having a glass transition temperature of 0° C. or lower and a melting point of 80° C. or lower or amorphous.

It is preferable that content of the said polyester (A2) is 10 mass parts or more and 100 mass parts or less with respect to 100 mass parts of polyester (A1) of the said adhesive composition.

It is preferable that content of the said adhesive composition is 0.1 mass parts or more and 10 mass parts or less with respect to 100 mass parts of total amounts of polyester (A1) and polyester (A2).

The above-mentioned adhesive composition is suitably used for flexible printed wiring boards.

The effect of the invention

The adhesive composition of the present invention has excellent flexibility of an uncured coating film, and is excellent in humidity solder heat resistance and high-temperature peel strength as an adhesive for FPC.

Detailed ways

Hereinafter, one embodiment of the present invention will be described in detail below. However, the present invention is not limited thereto, and may be implemented with various modifications added within the range already described.

<polyester (A1)>

The adhesive composition of the present invention contains polyester (A1) having a glass transition temperature or a melting point higher than 80°C. By using a polyester (A1) having a glass transition temperature (Tg) or a melting point (Tm) higher than 80° C., the humidity solder heat resistance and the peel strength at high temperatures can be improved.

The above-mentioned polyester (A1) is composed of a chemical structure that can be obtained by polycondensation of a polycarboxylic acid component or a polycarboxylic acid ester component and a polyhydric alcohol component, wherein the polycarboxylic acid component or polycarboxylic acid ester component and the polyhydric alcohol component are respectively composed of Composition of 1 or more selected ingredients.

It does not restrict|limit as a polyhydric carboxylic acid component which comprises the said polyester (A1), The following polyhydric carboxylic acid, these ester, and polyhydric carboxylic acid anhydride can be used. Specifically, examples of the polyvalent carboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, naphthalene dicarboxylic acid, tetrahydrophthalic acid, methyltetrahydrophthalic acid, adipic acid, and Acid, sebacic acid, dimer acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, fumaric acid, maleic acid, dimethyl isophthalate-5-sulfonic acid Sodium, trimellitic acid or pyromellitic acid and their esters. Examples of the polyvalent carboxylic acid anhydride include phthalic anhydride, tetrahydrophthalic anhydride, succinic anhydride, trimellitic anhydride, pyromellitic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, Hydrogenated naphthalene dicarboxylic acid, etc. In particular, aromatic polyhydric carboxylic acid components such as naphthalene dicarboxylic acid and terephthalic acid are preferable. By using an aromatic polyhydric carboxylic acid, Tg becomes high and the peel strength in high temperature can be improved.

The polyhydric alcohol constituting the polyester (A1) is not particularly limited, and ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexane Diol, 1-methyl-1,8-octanediol, 2-methyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-ethyl -2-n-propyl-1,3-propanediol, 2,2-di-n-propyl-1,3-propanediol, 2-n-butyl-2-ethyl-1,3-propanediol, 2,2-di n-Butyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 1,4-cyclohexanedimethanol, tri Cyclodecane dimethanol, polytetramethylene glycol, polypropylene glycol and other polyalkylene ether glycols, glycerin, trimethylolpropane, trimethylolethane, pentaerythritol, α-methylglucose, mannitol , sorbitol, and diol components such as dimer glycol, among these, 1 type or 2 or more types can be used. In particular, polyhydric alcohols such as ethylene glycol, 1,2-propanediol, and 1,3-propanediol that do not have a long-chain alkyl group, or alicyclic alcohols such as 1,4-cyclohexanedimethanol and tricyclodecanedimethanol are preferred. family of polyols. By using these polyhydric alcohols, Tg becomes high, and the peel strength in high temperature can be improved.

In the polyester (A1), a trivalent or higher polyvalent carboxylic acid component and/or a trivalent or higher polyhydric alcohol component may also be copolymerized. Examples of polyhydric carboxylic acid components having three or more valences include trimellitic acid, pyromellitic acid, benzophenone tetracarboxylic acid, trimellitic acid, trimellitic anhydride (TMA), and pyromellitic anhydride (PMDA). Aromatic carboxylic acids, aliphatic carboxylic acids such as 1,2,3,4-butanetetracarboxylic acid, and the like can be used alone or in combination of two or more. Examples of the trivalent or higher polyhydric alcohol component include glycerin, trimethylolpropane, trimethylolethane, pentaerythritol, α-methylglucose, mannitol, and sorbitol, and one of these can be used. or 2 or more.

Lactone and lactam may also be copolymerized with the polyester (A1). For example, ε-caprolactone, ε-caprolactam can be used.

As a method of polycondensation reaction for producing the above-mentioned polyester (A1), there are, for example: 1) heating a polycarboxylic acid and a polyhydric alcohol in the presence of a known catalyst, and performing a polyhydric alcohol removal and polycondensation reaction through a dehydration esterification step method; 2) heating the alcohol ester body of polycarboxylic acid and polyhydric alcohol in the presence of a known catalyst, and carrying out the method of polyhydric alcohol removal and polycondensation reaction through transesterification; 3) the method of performing depolymerization; etc. In the methods of 1) and 2) above, part or all of the acid component may be replaced with an acid anhydride.

When producing the above-mentioned polyester (A1), existing known polymerization catalysts can be used, such as titanium compounds such as tetra-n-butyl titanate, tetraisopropyl titanate, titanium oxide acetylacetonate, antimony trioxide, tributoxy Antimony compounds such as base antimony, germanium compounds such as germanium oxide and tetra-n-butoxygermanium, and acetates of magnesium, iron, zinc, manganese, cobalt, aluminum, etc. can be used. These catalysts may be used alone or in combination of two or more.

As a method of increasing the acid value of the above-mentioned polyester (A1), for example, there are: (1) after the polycondensation reaction is completed, adding a polyhydric carboxylic acid with a trivalent or higher value and/or a polyvalent carboxylic acid anhydride with a trivalent or higher value to make it react ( (2) during the polycondensation reaction, through the effects of heat, oxygen, water, etc., intentionally carry out resin modification; and other methods, these methods can be carried out arbitrarily. The polycarboxylic acid anhydride used in the acid addition in the above-mentioned acid addition method is not particularly limited, and examples thereof include phthalic anhydride, tetrahydrophthalic anhydride, succinic anhydride, maleic anhydride, trimellitic anhydride, Pyrellitic anhydride, hexahydrophthalic anhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride , ethylene glycol dianhydrotrimellitate, and the like, and these can be used alone or in combination of two or more.

The acid value of the polyester (A1) is preferably 200 eq/10 ⁶ g or less, more preferably 100 eq/10 ⁶ g or less, still more preferably 50 eq/10 ⁶ g or less, particularly preferably 30 eq/10 ⁶ g or less, most preferably It is below 20eq/10 ⁶ g. By setting the resin acid value within the above range, effects of favorable pot life, substrate adhesiveness, and crosslinkability improvement can be expected. In addition, the lower the acid value, the more hygroscopicity can be suppressed, and the heat resistance of humidified solder can be improved.

It is preferable that the number average molecular weight of the said polyester (A1) is 5,000 or more and 100,000 or less. More preferably, it is 10000 or more. Moreover, it is more preferably 50,000 or less. When the number average molecular weight is within the above-mentioned range, handling at the time of dissolution in a solvent is easy, and since it has a high cohesive force after curing, excellent peel strength can be exhibited.

In order to make the Tg or Tm of the polyester exceed 80° C., it can be achieved, for example, by introducing rigid structures such as aromatic compounds and alicyclic compounds, or by increasing the concentration of ester bonds.

<polyester (A2)>

The adhesive composition of the present invention preferably further contains an amorphous polyester (A2) having a Tg of 0°C or lower and a melting point of 80°C or lower. By containing the polyester (A2) whose Tg is 0 degreeC or less and whose melting point is 80 degreeC or less or is amorphous, flexibility can be imparted to an uncured coating film, and humidification solder heat resistance can be imparted. The Tg of the polyester (A2) is preferably -10°C or lower.

In addition, the term "amorphous" refers to one that does not show a melting peak in the measurement of the melting point described later.

It is preferable that content of the said polyester (A2) is 10 mass parts or more and 100 mass parts or less with respect to 100 mass parts of polyester (A1) whose Tg or Tm exceeds 80 degreeC. More preferably, it is 25 mass parts or more. Furthermore, it is more preferably 70 parts by mass or less. By making content of polyester (A2) into the said range, it will be excellent in the flexibility of an uncured coating film, the peeling strength in high temperature, and humidified solder heat resistance.

The acid value of the polyester (A2) is preferably 200 eq/10 ⁶ g or less, more preferably 100 eq/10 ⁶ g or less, still more preferably 50 eq/10 ⁶ g or less, particularly preferably 30 eq/10 ⁶ g or less, most preferably It is below 20eq/10 ⁶ g. By setting the resin acid value within the above range, effects of favorable pot life, substrate adhesiveness, and crosslinkability improvement can be expected. In addition, the lower the acid value, the more hygroscopicity can be suppressed, and the heat resistance of humidified solder can be improved.

It is preferable that the number average molecular weight of the said polyester (A2) is 5,000 or more and 100,000 or less. It is more preferably 10,000 or more, still more preferably 20,000 or more, and particularly preferably 25,000 or more. When the number average molecular weight is more than the above-mentioned value, the density|concentration of a polar group falls relatively, and hygroscopicity can be suppressed, and the heat resistance of humidified solder can be improved. In addition, the number average molecular weight is more preferably 50,000 or less. When the number average molecular weight is not more than the above value, handling at the time of dissolving in a solvent is easy, cohesion force is maintained even before curing, and flexibility of an uncured coating film is exhibited.

In order to make the glass transition temperature of the polyester below 0°C and the melting point below 80°C or be amorphous, for example, by copolymerizing monomer components with long-chain alkyl groups, or by copolymerizing monomers with asymmetric structures ingredients to destroy the crystallinity.

<Polyisocyanate (B)>

The adhesive composition of this invention contains polyisocyanate (B). The polyisocyanate (B) used in the present invention is not particularly limited as long as it is an isocyanate compound that reacts with a polyester resin and is cured.

Examples of the polyisocyanate (B) include aromatic or aliphatic diisocyanate compounds, trivalent or higher polyisocyanate compounds, and the like. These isocyanate compounds may be any of low-molecular compounds and high-molecular compounds. For example, aliphatic diisocyanate such as tetramethylene diisocyanate and hexamethylene diisocyanate, aromatic diisocyanate such as toluene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, hydrogenated diphenyl Alicyclic diisocyanates such as methane diisocyanate, hydrogenated xylylene diisocyanate, dimer acid diisocyanate, and isophorone diisocyanate, or trimers of these isocyanate compounds. In addition, the above-mentioned isocyanate compound is reacted with low-molecular-weight active hydrogen compounds such as ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitol, ethylenediamine, monoethanolamine, diethanolamine, and triethanolamine. Compounds containing terminal isocyanate groups were obtained. Furthermore, a terminal isocyanate group-containing compound obtained by reacting an excess of the above-mentioned isocyanate compound with various polyester polyols, polyether polyols, and polyamide-based high-molecular active hydrogen compounds may be mentioned. These isocyanate compounds can be used alone or in combination of two or more. Among these, trimers of hexamethylene diisocyanate compounds are particularly preferred.

In the adhesive composition of this invention, it is preferable that content of polyisocyanate (B) is 0.1 mass part or more and 10 mass parts or less with respect to a total of 100 mass parts of polyester (A1) and polyester (A2). More preferably, it is 5 parts by mass or less. Moreover, it is more preferably 1 part by mass or more. By making content of a polyisocyanate (B) into the said range, the peel strength outstanding in high temperature can be exhibited.

In addition, in the present invention, inorganic flame retardants such as organic phosphorus compounds, zinc oxide, zinc sulfate, aluminum hydroxide, and barium hydroxide can be appropriately blended within the range that does not impair the characteristics of the adhesive composition of the present invention. Leveling agents, dyes, pigments and other coloring agents.

Example

Hereinafter, the present invention will be specifically described with reference to examples. In addition, in this Example and a comparative example, abbreviation "part" means a mass part.

(1) Determination of the composition of polyester

Using a 400 MHz ¹ H-nuclear magnetic resonance spectrometer (hereinafter, it may be abbreviated as NMR), the molar ratio of the polyvalent carboxylic acid component and the polyhydric alcohol component constituting the polyester was quantified. Deuterochloroform was used as solvent. In addition, when the acid value of polyester is increased by acid post-addition, the total of acid components other than the acid component used for acid post-addition is set to 100 mol%, and the molar ratio of each component is calculated.

(2) Determination of glass transition temperature and melting point

The measurement was performed using a differential scanning calorimeter (SII company, DSC-200). 5 mg of polyester was put into an aluminum lidded container, sealed, and cooled to -50°C using liquid nitrogen. Then, increase the temperature to 150°C at a rate of 20°C/min. In the endothermic curve obtained during the heating process, the extension line of the baseline before the endothermic peak appears (below the glass transition temperature) and the endothermic peak The temperature at the intersection point of the tangent line (the tangent line with the largest slope from the rising section of the peak to the apex of the peak) was taken as the glass transition temperature (Tg, unit: °C).

In addition, in the same endothermic curve, the temperature at the apex of the crystal melting peak was taken as the melting point (Tm, unit: °C).

(3) Determination of number average molecular weight

A polyester sample was dissolved and/or diluted in tetrahydrofuran so that the resin concentration was about 0.5% by weight, filtered through a polytetrafluoroethylene membrane filter with a pore size of 0.5 μm, and used as a measurement sample. Molecular weight was determined by gel permeation chromatography (GPC) with tetrahydrofuran as mobile phase and differential refractometer as detector. The flow rate was 1 mL/min, and the column temperature was 30°C. KF-802, 804L, and 806L manufactured by Showa Denko were used as columns. Molecular weight standards use monodisperse polystyrene.

(4) Determination of acid value

0.2 g of a polyester sample was dissolved in 40 ml of chloroform, and titrated with a 0.01N potassium hydroxide ethanol solution to obtain the equivalent per 10 ⁶ g of polyester (eq/10 ⁶ g). Phenolphthalein was used as an indicator.

Hereinafter, the production example of the adhesive composition containing the polyester of this invention and the polyester which is a comparative example, and polyisocyanate is shown.

Production example of polyester (a1)

In a reaction vessel equipped with a mixer, a condenser, and a thermometer, add 359 parts of terephthalic acid, 58 parts of dimethyl 2,6-naphthalene dicarboxylate, 67 parts of ethylene glycol, 189 parts of propylene glycol, trimethylolpropane 5 parts of tetrabutyl orthotitanate as a catalyst in an amount of 0.03 mol% relative to the total acid components were heated from 160° C. to 220° C. over 4 hours, and the esterification reaction was carried out while passing through the dehydration step. Then, the pressure in the system was reduced to 5 mmHg over 20 minutes, and the temperature was further raised to 250° C. to perform a polycondensation reaction step. Then, the pressure was reduced to 0.3 mmHg or less, and the polycondensation reaction was performed for 60 minutes, and then it was taken out. As a result of compositional analysis by NMR of the obtained polyester (a1), in molar ratio, terephthalic acid/2,6-naphthalene dicarboxylic acid/ethylene glycol/propylene glycol/trimethylolpropane= 90/10/27/72/1 [molar ratio]. In addition, the glass transition temperature was 89°C. The results are shown in Table 1.

Production example of polyester (a2) to (a11)

Polyesters (a2) to (a11) were synthesized by changing the types and compounding ratios of raw materials according to the production example of polyester (a1). Moreover, in polyester (a2), after completion|finish of a polymerization reaction, ε-caprolactone was further added, it was made to react at 200 degreeC for 30 minutes, and post-addition was implemented. Moreover, trimellitic anhydride was further added to polyester (a3) after completion|finish of a polymerization reaction, it was made to react at 230 degreeC for 30 minutes, and acid post-addition was implemented. Table 1 shows the composition analysis value, melting point (Tm) and glass transition temperature (Tg) of each polyester. In addition, PTMG 1000 is polytetramethylene ether glycol (average molecular weight 1000). In addition, in Table 1, the case where the melting point (Tm) was not observed is represented by "-".

Example 1

80 parts (solid content) of polyester (a1) dissolved in toluene with a solid content concentration of 50% and 20 parts (solid content) of polyester (a2) with a solid content concentration of 50% dissolved in toluene were mixed as polyisocyanate 2 parts of SUMIDUR N3300 (SUMIDUR N3300, manufactured by Sumika Covestro Urethane Co., Ltd.) were used to prepare an adhesive composition. For the obtained adhesive composition, various evaluations of peel strength, humidified solder heat resistance, and flexibility of the uncured coating film were implemented. The results are shown in Table 2.

Embodiment 2～14, comparative example 1～4

According to Example 1, the types and compounding ratios of raw materials were changed as shown in Table 2 to prepare adhesive compositions, and various evaluations were performed. The results are shown in Table 2.

Peel strength (adhesiveness)

In such a way that the thickness after drying becomes 25 μm, the adhesive composition prepared in each of the above examples was applied to a polyimide film (manufactured by Kaneka Co., Ltd., Apical (registered trademark)) with a thickness of 12.5 μm, and dried at 140 °C for 3 minutes. The thus obtained adhesive film (B-stage product) was bonded to a rolled copper foil (manufactured by JX Metal Co., Ltd., BHY series) with a thickness of 18 μm. Bonding was carried out by pressing at 160° C. and 2 MPa for 30 seconds under a pressure of 2 MPa so that the glossy surface of the rolled copper foil came into contact with the adhesive layer, and bonded. Next, it heat-processed at 170 degreeC for 3 hours, it hardened|cured, and the sample for peeling strength evaluation was obtained. Regarding the peel strength, the film was pulled at 125° C., and a 180° peel test was performed at a tensile speed of 50 mm/min to measure the peel strength. This test represents the bond strength at 125°C.

<Evaluation criteria>

○: 0.3N/mm or more

△: 0.1N/mm or more and less than 0.3N/mm

×: 0.1N/mm or less

Humidified Solder Heat Resistance

Samples were prepared by the same method as for the above peel strength evaluation. The sample was cut out to a size of 2.0cm×2.0cm, absorbed moisture for 2 days at 40°C and 80% temperature and humidity, floated in a molten solder bath at 260°C, and measured the time until swelling occurred.

<Evaluation criteria>

○: No swelling for more than 60 seconds

△: There is swelling within 30 seconds or more and less than 60 seconds

×: There is swelling within less than 30 seconds

Softness of uncured film

In such a way that the thickness after drying becomes 25 μm, the adhesive composition prepared in each of the above examples was applied to a polyimide film (manufactured by Kaneka Co., Ltd., Apical (registered trademark)) with a thickness of 12.5 μm, and dried at 140 °C for 3 minutes. When the thus-obtained adhesive film (B-stage product) was bent by 90°, whether cracks occurred in the coating film was checked and evaluated.

<Evaluation criteria>

○: No cracks

△: There are creases

×: Cracked

[Table 2]

Industrial availability

The adhesive composition of the present invention is excellent in the flexibility of the uncured coating film, the heat resistance of humidified solder, and the peel strength at high temperature. Therefore, it is suitable for the adhesive composition of FPC exposed to high temperature, such as FPC for automobiles.

Claims (5)

1. An adhesive composition comprising a polyester (A1) having a glass transition temperature or melting point of more than 80 ℃ and a polyisocyanate (B).

2. The adhesive composition according to claim 1, further comprising a polyester (A2) having a glass transition temperature of 0 ℃ or lower and a melting point of 80 ℃ or lower or being amorphous.

3. The adhesive composition according to claim 2, wherein the content of the polyester (A2) is 10 parts by mass or more and 100 parts by mass or more with respect to 100 parts by mass of the polyester (A1).

4. The adhesive composition according to any one of claims 1 to 3, wherein when the adhesive composition does not contain the polyester (A2), the polyisocyanate (B) is contained in an amount of 0.1 to 10 parts by mass per 100 parts by mass of the polyester (A1); when the adhesive composition contains the polyester (A2), the polyisocyanate (B) is contained in an amount of 0.1 to 10 parts by mass based on 100 parts by mass of the total amount of the polyester (A1) and the polyester (A2).

5. The adhesive composition according to any one of claims 1 to 4, which is used for a flexible printed wiring board.